Physics in Canada La Physique au Canada

Transcription

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Vol. 64 No. 3
JULY-SEPTEMBER (SUMMER) 2008
JUILLET À SEPTEMBRE (ÉTÉ) 2008
Physics in Canada
La Physique au Canada
FEATURING :
Serving the Canadian
physics community
since 1945 /
Servont la communauté
de physique
depuis 1945
What Journalism Can Teach Us About Science Promotion /
Ce que le journalisme peut nous enseigner au sujet de la promotion des sciences
Is Faith the Enemy of Science?, My Encounter with Gerhard Herzberg in Wartime Saskatoon,
The Universe as an Inside-Out Star, The Future of TRIUMF, Interviews with four of our
medal winners / Entrevues avec quatre de nos médaillés, and more ....
PLUS:
Extended abstracts by the winners of the 2008 Best Student Presentation Competitions at the CAP
Annual Congress / Résumés étendus des gagnants des compétitions meilleures présentations par un(e)
étudiant(e) au Congrès de l’ACP
Canadian Association
of Physicists /
Association canadienne
des physiciens et
physiciennes
www.cap.ca
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PHYSICS IN CANADA
LA PHYSIQUE AU CANADA
Canadian Association
of Physicists
Association canadienne des
physiciens et physiciennes
www.cap.ca
Vol. 64 No. 3 (July-September (Summer) 2008 / juillet à septembre (été) 2008)
97
Editorial - “What Journalism can Teach us about Science Promotion”,
DE FOND
ARTICLES
FEATURES
by B. Joós, P.Phys.
98
Éditorial - “Ce que le journalisme peut nous enseigner au sujet de la
promotion des sciences”, par B. Joós, phys.
103
107
111
119
123
Is Faith the Enemy of Science?, by Richard MacKenzie
My Encounter with Gerhard Herzberg in Wartime Saskatoon, by Lynn Trainor
The Universe as an Inside-Out Star, by Mitch Crowe, Adam Moss and Douglas Scott
Building a Vision for the Future of TRIUMF, by Nigel Lockyer and Timothy Meyer
Génération expérimentale de faisceaux Bessel-Gauss spatiotemporels,
par Michaël Dallaire et al.
126 Block Copolymer Lamella: Simple Experiments and Complex Physics,
by Andrew Croll et al.
129
132
135
138
Friction Measurements on Living Cells, by Marc-Antoni Goulet et al.
Magnetic Fields from Heterotic Cosmic Strings, by Rhiannon Gwyn et al.
Taking Control of the Flagellar Motor, by Mathieu Gauthier et al.
Écriture de structures photoniques à l’aide de faisceaux Bessel,
par Véronique Zambon et al.
141 Viscoelastic Properties of Poly(Vinyl Alcohol) Nanofibres and Hydrogels
EDUCATION
ÉDUCATION
Measured by Atomic Force Microscopy, by N. Yang et al.
145 Resource Comparison of Canadian
Physics Departments, by Robert Brooks
149 Factors Affecting Student Drop Out
From the University Introductory
Physics Course, including the anomaly of the Ontario double cohort,
by Alan Slavin
Advertising Rates and Specifications (effective January 2008) can be found on the PiC website
(www.cap.ca - Physics in Canada).
Les tarifs publicitaires et dimensions (en vigueur depuis janvier 2008) se trouvent sur le site internet de
La Physique au Canada (www.cap.ca - La Physique au Canada).
Cover / Couverture :
Left: Various images relating to the 2008 CAP
Congress
at
Laval
University.
Right: Fig. 3 from the article by V. Zambon (pg. 138).
A gauche: Plusieurs photos reliées au Congrès de
l’ACP 2008 qui a eu lieu à
l’Université Laval.
A droite: Fig. 3 de l’article par
V. Zambon (pg. 138).
LA PHYSIQUE AU CANADA / Vol. 64, No. 3 ( juillet. à septembre (été) 2008 ) C i
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Comments Regarding “On the Nature of
Science”
102 Comments by Lawrence Krauss on “Is
Faith the Enemy of Science?”
122 Best Student Presentations at 2008
Congress
DEPARTMENTS
DÉPARTEMENTS
The Journal of the Canadian Association of
Physicists
La revue de l'Association canadienne des physiciens et physiciennes
ISSN 0031-9147
EDITORIAL BOARD / COMITÉ DE RÉDACTION
Editor / Rédacteur en chef
Béla Joós, PPhys
144 Departmental, Sustaining, and CorporateInstitutional Members / Membres départementaux, de soutien, et corportifs-institutionnels
Physics Department, University of Ottawa
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Ottawa, Ontario K1N 6N5
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Associate Editor / Rédactrice associée
Managing / Administration
Francine M. Ford
c/o CAP/ACP; E-mail: [email protected]
Book Review Editor / Rédacteur à la critique de livres
155 CAP News / Informations de l’ACP
161 In Memoriam - Lynn Trainor
162 News, Congratulations, Call for
Nominations / Informations, Félicitations,
et Appel de candidatures
166 2008 Medals and Awards - including four
interviews / Médailles
quatre entrevues
et prix 2008 - avec
195 Books Received - Book Reviews /
Livres reçus - Critiques de livres
197 Ads / Publicités
Canadian Association of Physicists (CAP)
Association canadienne des physiciens et physiciennes (ACP)
The Canadian Association of Physicists was founded in 1945 as a non-profit association
representing the interests of Canadian physicists. The CAP is a broadly-based national
network of physicists in working in Canadian educational, industrial, and research settings. We are a strong and effective advocacy group for support of, and excellence in,
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une association à but non-lucratif représentant les intérêts des physicien(ne)s
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milieux canadiens de l'éducation, de l'industrie et de la recherche. Nous constituons un
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ceux qui poursuivent leur carrière en physique et dans l'enseignement de la physique.
Vous pouvez trouver les renseignements concernant les nombreuses activités de l’ACP à
http://www.cap.ca. Les formulaires d’adhésion sont aussi disponibles dans la rubrique
“Adhésion” sur ce site.
II
PHYSICS IN CANADA
LA PHYSIQUE AU CANADA
C PHYSICS
IN
CANADA / VOL. 64, NO. 3 ( July-Sept. (Summer) 2008 )
Richard Hodgson, PPhys
c/o CAP / ACP
Suite.Bur. 112, Imm. McDonald Bldg., Univ. of / d' Ottawa,
150 Louis Pasteur, Ottawa, Ontario K1N 6N5
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National Research Council (M-36)
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8/18/2008
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Page 97
ÉDITORIAL
WHAT JOURNALISM CAN TEACH US ABOUT
SCIENCE PROMOTION
he CAP made a significant gesture at its last
Congress, which was a first for the Association. It
gave one of its awards, the CAP-COMP Peter
Kirkby Medal for outstanding service to the
Canadian Physics community to Peter Calamai, the national
science reporter for The Toronto Star. Peter Calamai is not a
research scientist and has not directly contributed to the promotion of our professional organizations, either the CAP or
COMP. Giving Peter Calamai the prize was a recognition of
the positive press that he gave to physics and science in general during a career of more than 40 years, nearly 15 of those
years as a science reporter. I interviewed Peter Calamai in
Quebec City on Tuesday June 10th 2008, a few hours before
he was presented with the prize: a 45 minute interview that
appears in this issue, only slightly edited. He reveals in this
interview his motivations and his perspective on science journalism. I found it an eye-opener. The following quote, late in
the interview, sums up his relationship with science and scientists:
T
“I don’t want to be seen as a handmaiden. A lot of people say
‘you have a very important role, you’re helping us get our
story out to the public’. I may incidentally help put the story
out to the public but that’s not why I’m doing it. I’m doing it
because you’re a good story. My job is to exploit scientists,
to make them into stuff that gets people to read our newspapers so that we can sell advertising.” [See top of first column,
page 173 of this issue].
Few scientists in history have been able to reach the public at
large directly. Feynman is the most striking example here in
North America. Even Einstein’s famous quotes had more to
do with human affairs and, although there are a few related to
physical theory, he did not try to teach the general public the
physics he discovered. So we rely mainly on journalists to
reach the greater public. What Peter Calamai teaches us is
that we have to play by the rules of journalism if we want the
communication to be effective. As sympathetic as the journalist may be to scientists, only stories of general interest, whose
relevance and achievement can be expressed in non mathematical terms with simple underlying concepts, will find their
way into the paper or broadcast. Peter Calamai teaches us also
about timing and the fickleness of news. Important scientific
discoveries should be promoted when there is little else happening, such as around the Christmas holidays. And as
Preston Manning taught us about politicians (Physics in
Canada, July-Aug. 2006), the “hook”, the connection, is
always human. Journalists, like politicians, are not usually
scientists, nor are their constituents, and they are mainly
interested in the human dimension of the story. So an effort
has to be made to make the link to human experience and
societal needs. He also discussed the challenge of bringing
science policy issues on the public stage in Canada.
Acquiring journalistic skills is one step in our apprenticeship
in communication. It not only helps us reach the public at
large but teaches us how to communicate with colleagues in
different fields, an essential skill in selling our research projects to granting councils. Recently I happened to listen to an
instalment of the CBC Radio I show The age of persuasion
which explores the countless ways marketers permeate our
life, from media, art, and language, to politics, religion, and
fashion. It made me think that we have a lot to learn in terms
of communication. We are trained to communicate with our
audience, which consists mostly of our peers. Our focus is a
clear exposition of the science that we do. The quality of presentations that we hear has considerably improved over the
years, not only thanks to technology, but also due to a greater
awareness of communication techniques. We have come a
long way. But advertisers, and sales people, have very sophisticated approaches, and there is a lot that they could teach us,
especially at the multi-sensory level (relating concepts with
sound, colour, touch and, possibly even smell). Our physics
audience is mostly cerebral in its approach, but it is still
human. How to take advantage of our many senses to increase
the interest in physical topics is still unknown to most of us.
Maybe it is because of the influence of journalists that we
thought about presenting some of our award winners through
interviews. The interviews are long, because they go beyond
introducing the award winners. They gave us a chance to do
some journalism, trying to present their work in simple terms.
The first interview is Peter Calamai’s itself (p.169-173).
Peter Calamai carried out the two following ones: those of
Carl Svensson (p.186-189), the CAP Herzberg medallist, and
Adam Sarty (p.177-182), the Physics Teaching medal winner,
so that I had a chance to see an experienced journalist at work
before I carried out the last interview, in French, with
Louis Taillefer (p.191-193) who, after winning the CAP
Herzberg medal and the CAP Brockhouse medal a few years
ago, has been awarded the CAP Medal of Achievement this
year. Your feedback on these interviews is both welcome and
will be appreciated. Next year, we hope to have additional
volunteers to carry them out, or we may evolve from interviews to another form of reporting. PiC-PaC has only begun
its journey as a magazine.
B. Joós, P.Phys.
Editor, Physics in Canada
Comments of readers on this editorial are more than welcome.
The contents of this journal, including the views expressed above, do not necessarily represent the
views or policies of the Canadian Association of Physicists. Le contenu de cette revue, ainsi que les
opinions exprimées ci-dessus, ne représentent pas nécessairement les opinions et les politiques de
l’Association canadienne des physiciens et des physiciennes.
Béla Joós is a
Professor of Physics
at the University of
Ottawa. He has
been a member of
the Editorial Board of
Physics in Canada
since January 1985
and took over as
Editor in June 2006.
Béla Joós est professeur de physique
à l’Université
d’Ottawa. Il est
membre du Comité
de rédaction de la
Physique au Canada
depuis 1985, et est
devenu rédacteur en
juin 2006.
LA PHYSIQUE AU CANADA / Vol. 64, No. 3 ( juillet. à septembre (été) 2008 ) C 97
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EDITORIAL
CE
QUE LE JOURNALISME PEUT NOUS ENSEIGNER AU SUJET
DE LA PROMOTION DES SCIENCES
L
'ACP a fait un geste significatif, une première pour elle,
à son dernier congrès. Elle a décerné l'un de ses prix, la
médaille Peter Kirkby de l'ACP-OCMP pour services
exceptionnels à la collectivité canadienne de la
physique, au journaliste scientifique national au Toronto Star,
Peter Calamai. Celui-ci n'est pas un chercheur et n'a pas contribué directement à promouvoir nos organismes professionnels,
l'ACP ou l'Organisation canadienne des physiciens médicaux
(OCMP). Par ce prix, elle a reconnu l'excellente presse qu'il a
faite à la physique et à la science en général en plus de 40 ans de
carrière, dont près de 15 à titre de journaliste scientifique. J'ai
interviewé Peter Calamai à Québec, le mardi 10 juin 2008,
quelques heures avant qu'il reçoive le prix. Voir le texte presque
intégral de l'entrevue de 45 minutes dans le présent numéro.
Dans cette entrevue, il expose ce qui le pousse à agir ainsi et son
optique sur le journalisme scientifique. Ce fut pour moi une
révélation. L'extrait suivant, tiré de la fin de l'entrevue, résume
la relation de Peter Calamai avec la science et les scientifiques :
" Je ne veux pas être perçu comme servant. Bien des gens disent : 'vous jouez un rôle fort important; vous nous aidez à exposer nos travaux au public'. Au fait, j'aide peut-être à exposer vos
travaux; ce n'est toutefois pas dans ce but que je le fais, mais
parce que c'est un bon sujet d'article. Mon travail est d'exploiter
les scientifiques, d'en tirer des articles qui incitent les gens à lire
nos journaux pour que nous puissions vendre des réclames. "
[Voir haut de la première colonne, page 173 de ce numéro.]
Dans l'histoire, peu de scientifiques ont pu toucher directement
le grand public. Feynman est l'exemple le plus frappant en
Amérique du Nord. Même les déclarations célèbres d'Einstein
étaient plus liées à l'aspect humain et, même si quelques-unes
ont trait à la théorie de la physique, il n'a pas essayé d'enseigner
au grand public ce qu'il a découvert en physique. Aussi comptons-nous principalement sur les journalistes pour atteindre le
grand public. L'enseignement de Peter Calamai est qu'il nous
faut respecter les règles du journalisme pour que porte la communication. Quelle que soit la sympathie du journaliste à l'endroit des scientifiques, seuls pourront être imprimés ou diffusés
les articles d'intérêt général dont la pertinence et l'apport peuvent
s'exprimer en termes non mathématiques par des notions de base
simples. Peter Calamai nous instruit aussi quant au moment et au
caractère changeant des nouvelles. Les découvertes scientifiques
importantes doivent être annoncées quand il ne se passe pas
grand-chose d'autre, comme dans le temps des Fêtes. Et, comme
Preston Manning nous l'a enseigné au sujet des politiciens (La
Physique au Canada, juillet-août 2006), le " lien " est toujours
humain. Comme les politiciens, les journalistes ne sont généralement pas des scientifiques, au même titre que leurs électeurs, et
ils s'intéressent surtout à la dimension humaine des articles.
Aussi faut-il faire un effort pour faire des liens avec l'expérience
humaine et avec les besoins de la société. Peter Calamai a aussi
exposé la difficulté qu'il y a à porter les questions de politique
scientifique sur la place publique au Canada.
98 C PHYSICS
IN
L'acquisition de compétences en journalisme est un volet de
notre apprentissage de la communication. Non seulement nous
aide-t-elle à atteindre le grand public, mais elle nous montre
comment communiquer avec les collègues d'autres disciplines,
ce qui est essentiel pour faire accepter nos projets de recherche
par les conseils subventionnaires. Il y a quelque temps, j'écoutais
un épisode de l'émission de CBC Radio One, The age of persuasion, qui inventorie les innombrables moyens par lesquels les
responsables du marketing pénètrent notre vie, soit les médias,
l'art et la langue ainsi que la politique, la religion et la mode.
Cela m'a fait voir que nous avons beaucoup à apprendre en
matière de communication. Nous sommes formés à communiquer avec notre auditoire, qui se compose surtout de pairs. Notre
premier souci est d'exposer clairement nos travaux scientifiques.
La qualité des exposés que nous entendons s'est sensiblement
améliorée au fil des ans, grâce non seulement à la technologie,
mais aussi à une meilleure connaissance des méthodes de communication. Nous revenons de loin. Mais annonceurs et spécialistes de la vente ont des méthodes très subtiles et pourraient nous
en apprendre beaucoup, surtout au niveau multisensoriel (reliant
les notions au son, à la couleur, au toucher et peut-être même à
l'odorat). En physique, notre auditoire a surtout une approche
cérébrale qui demeure toutefois humaine. La plupart d'entre
nous ignore encore comment tirer parti de bien des sens pour
accroître l’interêt des sujets touchant la physique.
C'est peut-être grâce à l'influence des journalistes que nous
avons pensé à présenter certains de nos lauréats au moyen d'entrevues. Celles-ci sont longues parce qu'on ne se contente pas de
présenter les lauréats. Elles nous donnent la chance de faire du
journalisme, d'essayer d'exposer leurs travaux en termes simples. La première entrevue est celle-là même de Peter Calamai
(p.169-173) qui a effectué les suivantes, celles de Carl Svensson
(p.186-189), lauréat de la médaille Herzberg de l'ACP, et
d'Adam Sarty (p.177-182), lauréat de la médaille en enseignement de la physique, ce qui m'a donné la chance de voir un journaliste chevronné à l'œuvre avant de mener la dernière entrevue,
en français, avec Louis Taillefer (p.191-193). Celui-ci, lauréat il
y a quelques années des médailles Herzberg et Brockhouse de
l'ACP, s'est vu décerner cette année la Médaille de l'ACP pour
contributions exceptionnelles. Nous vous saurions gré de nous
faire savoir ce que vous pensez de ces entrevues. L'an prochain,
nous espérons avoir d'autres volontaires pour les mener ou nous
pourrions passer des entrevues à une autre forme de reportages.
PiC-PaC ne vient que de commencer son cheminement comme
magazine.
B. Joós, phys.
Rédacteur en chef, La Physique au Canada
Les commentaires de nos lecteurs au sujet de cet éditorial sont
bienvenus.
NOTE: Le genre masculin n’a été utilisé que pour alléger le
texte.
8/18/2008
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Page 99
OPINION
COMMENTS REGARDING "ON
THE
O
n the Nature of Science [1] presents many valid
points regarding the epistemology and practice
of science in the 21st century, but there are several important incongruities.
umented observations of other parties are admissible.
Should less reliable observations (not repeatable but documented by others) have the same epistemological status
as repeatable experiments?
Three axioms presupposed by the scientific method are
realism (the existence of objective reality), the existence
of observable natural laws, and the constancy of observable natural law [2]. Rather than depend on provability of
these axioms, science depends on the fact that they have
not been objectively falsified.
The author describes the three-legged stool of scientific
error correction as experimental care, reproducible experiment, and peer review. Like Occam's razor, peer review
is a temporal expedient for judging scientific work at a
given time. Peer review serves the temporal interests of
publishers, funding agencies, and employers. The ultimate arbiter of scientific validity is repeatable experiment
alone.
Occam's razor and related appeals to simplicity are epistemological preferences, not general principles of science.
The general principle of science is that theories (or models) of natural law must be consistent with repeatable
experimental observations. This principle rests upon the
unproven axioms mentioned above. Occam's razor supports, but does not prove, these axioms.
In addition, Occam's razor fails to acknowledge that if
multiple models of natural law make exactly the same
testable predictions, they are equivalent and there is no
need for parsimony to choose one that is preferred. For
example, Newtonian, Hamiltonian, and Lagrangian classical mechanics are equivalent. Which one of the three
would be preferred by Occam's razor? Is this a justification for saying the other two are wrong? Likewise, how
would advocates of simplicity principles arbitrate between
wave and matrix formulations of quantum mechanics?
Defining science broadly as internally consistent and logical models supported by observation removes the requirement of repeatable experiment and broadens the realm of
applicability from questions of natural law to questions of
history and nearly every other question the human mind
can devise. More importantly, it contains the implicit presupposition that observations that are limited in scope,
audience, and duration are equally reliable as experimental observations that are repeatable a large number of
times by any audience that bothers to exercise sufficient
experimental care. One also wonders to what degree doc-
OF
SCIENCE"
The three-legged stool of historical inquiry includes physical evidence (and scientific analysis thereof), documentary evidence, and eyewitness testimony [3]. When considering historical facts of legal significance, one is hard
pressed to find many criminal convictions based only on
scientific evidence without corroborating documentary or
eyewitness testimony. The legal system recognizes that
the availability and quality of evidence degrades with
time. Increasing entropy guarantees that historical questions cannot be repeatedly tested as many times and by as
many independent parties as questions of natural law.
Because models of natural law can be repeatedly tested by
any audience that exercises sufficient experimental care,
the reliability (or even the identity) of sources is less
important in questions of natural law than in historical
matters. Few scientists would object to acceptance of a
new theory or even an anonymous experimental result if it
was repeatable by independent sources. In contrast, the
reliability of sources is critical in the believability of historical theories. For example, if those collecting evidence
at a crime scene are found to be careless or dishonest in
their handling of evidence, the prosecution stands very little chance of gaining a conviction based on the evidence
collected, and the procedure simply cannot be repeated in
a manner that counteracts the unreliability of the original
sources.
OPINION
There are many examples where Occam's razor would
have picked the wrong theory given the available data.
Simplicity principles are useful philosophical preferences
for choosing a more likely theory from among several possibilities that are each consistent with available data.
However, anyone invoking Occam's razor to support a scientific preference should be aware that future experiments
may well falsify the model currently favored by Occam's
razor. One accurate observation of a white crow falsifies
the theory that "all crows are black." Likewise, a single
instance of Occam's razor picking a wrong theory falsifies
the razor as a general principle.
NATURE
The author shifts from a relatively narrow definition of
science as reproducible experiment to "anything that can
be observed" in order to make the case that supernatural
Amy Courtney, PhD
Department of Physics,
United States Military Academy,
West Point, NY 10996
Michael Courtney, PhD
Ballistics Testing Group,
P.O. Box 24, West Point NY 10996
[email protected]
[email protected]
8/18/2008
2:10 PM
Page 100
OPINION
claims can be investigated scientifically. However, this ignores the
presupposition of constancy of natural law that underpins the
demand of experimental repeatability as the ultimate arbiter in science. Since science presupposes the constancy of natural law in the
demand of experimental repeatability, supernatural claims cannot be
falsified scientifically without creating a circular argument. (In
addition, most supernatural claims concern specific historical
events rather than repeatable phenomena.) The objectivity of science rests in experimental repeatability.
Defining science as "observationally constrained model building" is
barely more specific than defining science as "what scientists do."
How far is this from defining sound science as "what scientists say"
(with appropriate homage to peer review)? At this point, is science
really a powerful, objective epistemology for exploring natural law,
or have we merely replaced one set of authorities (the Catholic
Church of the Middle Ages) with another (the scientists of the 21st
century)?
We must not replace experimental repeatability with peer-reviewed
observations as the ultimate arbiter of scientific validity. Only
repeatable experimental results qualify as scientific observations.
Observations of physical and documentary evidence of historical
events do not warrant equal status with repeatable experiments.
Evolution as a model of natural history is widely accepted because
many expectations have been fulfilled by later discoveries of preexisting evidence. (Such later discoveries are better described as
fulfilled expectations than specific predictions akin to Einstein's
prediction of the bending of light by gravitation.) As a scientific theory of ongoing biological processes, evolution would be strengthened by more direct future observations of speciation in higher
organisms via the expected mechanisms of natural selection.
"Predictive power" as an arbiter of science means the ability to predict the future course of systems under study, not merely the ability
to predict future discoveries of pre-existing historical evidence.
Valid models of natural law do not merely predict future discoveries of pre-existing evidence; they predict observations of future
events.
Does failing to make an epistemological distinction between natural history and natural law really serve the interests of science?
Does replacing the demand for predicting results of repeatable
experiment with the much broader "observable support" better prepare today's student to become tomorrow's scientist?
Science needs objective criteria to rank the value of predictions and
observations without the appeals to authority inherent in peer
review or "scientific consensus." Observations that are experimentally repeatable should rank higher than historical observations
whose repeatability is limited by increasing entropy. Specific predictions regarding future events should rank higher than expectations of future discoveries of pre-existing evidence. Thus, the science of natural law is inherently more objective than scientific
descriptions of natural history.
What is the benefit of pretending that science provides the same
high levels of certainty in historical theories of origins (species, universe, solar system) as the more objectively and repeatably testable
quantum electrodynamics and classical mechanics (within their
well-established areas of applicability)?
In conclusion, parsimony and failure to distinguish history from science can conspire to produce unwarranted levels of certainty. For
example, consider an innocent man whose blood is found at a murder scene. In the absence of observable exculpatory evidence, the
Jennings definition of science would seem to demand his conviction, regardless of plausible alternate explanations that might be
offered, since alternate explanations are likely more complex than
the theory that the defendant is guilty.
References:
1.
2.
3.
BK Jennings, “On the Nature of Science”, Physics in Canada,
63(1) 2007.
One might attempt to reformulate a scientific method without presupposing natural law, but the presupposition of natural law is a
common feature of the scientific method in epistemologies from
Bacon to Feynman. Novum Organum, F Bacon, 1620. The
Character of Physical Law, R Feynman, 1965. The Feynman
Lectures on Physics, Vol. I, R Feynman, R Leighton, M Sands,
1963.
M Courtney, A Courtney, Epistemological Distinctions Between
Science and History, http://arxiv.org/ftp/arxiv/papers/0803/
0803.4245.pdf
REPLY TO COMMENTS REGARDING "ON
SCIENCE"
THE
T
he article "On the Nature of Science" presented a simple
but subtle description of the scientific method with wide
applicability. It was meant to be descriptive, not prescriptive or axiomatic 1. It was based on the idea that science is
model building not recreating reality. The idea of model building
eliminates the assumption of realism. The scientific method, as outlined in the article, neither assumes nor implies realism. Model
building, as the fundamental concept behind science, does not rely
on the existence of "natural laws' either but only on the existence of
correlations in the observations which science then attempts to
model.
100 C PHYSICS
IN
NATURE
OF
B.K. Jennings,
TRIUMF,
4004 Wesbrook Mall,
Vancouver, BC V6T 2A3
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OPINION
The scientific method is the building of models that are tested
against observations. The article repeatedly makes the point that in
science it is the observations that are the ultimate authority not peer
review or other possible authorities. The constraining observations
can be used in two different ways. They can either be used to influence the construction of the model or they can be used to test the
model after it has been constructed. This is the difference between
curve fitting (postdiction) and making real predictions. This distinction is crucial. It is relatively easy to describe observations that are
already known. It is much more difficult to predict observations that
are not yet been made or whose results are not yet known to the
model builder. Predictions are the real test of a model.
Epistemologically, it does not matter if the observation refers to a
process that happens in the future or a process that occurred in the
past. The only important distinction is between predictions and
postdictions.
Repeatability is a key aspect of the scientific method, but it is not
without its pitfalls and subtleties. It is easy to repeat an experiment
and, due to systemic errors, make the same mistake over and over
again. Repeatability does not, of itself, guarantee correctness.
Repeatability is subtle in another way. Consider the location of
Jupiter in the night sky. Repeated observations will give different
locations due the daily, yearly and other real or apparent motions of
the planet. A simple interpretation of repeatability fails in this case;
however, since the models predict the variation, the motion can be
studied using model construction and testing against observations.
Repeatability must be interpreted within the context of a model.
Repeatability is just a special case of the more general idea of testing predictions against observations. It is the predictions that must
be able to be repeatedly confirmed not the individual observations
themselves. That observations are repeatable, if indeed they are, is
a prediction of many if not most of the models that we work with in
science. As the example of Jupiter illustrates, it is not absolute.
Within the context of model building and testing against observation, the distinction between "natural law" and "natural history" as
defined in the Comment is neither useful nor significant. In both
cases one constructs models, makes predictions, and tests these predictions against observations, most critically, against observations
that have not influenced the formation of the model. While models
involving history may have less possibility for testing, this is a matter of practice and not principle. Even tests of "natural law" may in
some cases not be possible. For example, if quantum gravitational
effects only have observational consequences near the Planck scale,
then tests of quantum gravity will be practically excluded.
Occam's razor is used to distinguish between equivalent models, i.e.
models that make the same predictions for all observables. This is
the only principle that would eliminate the Omphalas Hypothesis
and its cousin Last Thursdayism. In this regard its application is
ubiquitous; additional assumptions are automatically discarded, frequently without conscious thought. Occam's razor can and does lead
to errors when applied to models that can in principle be distinguished observationally but not with the currently available data.
Even in this case, it can be useful in refining tentative models for
further testing.
Peer review is an important part of the scientific process; however,
it is not an incantation that magically guarantees a result is correct.
Contrary to the implication of the Comment, peer review is not the
setting up of a new high priesthood but rather replaces it. In science
there is no human who serves as the ultimate authority thus when
decisions have to be made some process is required. The decisions
are referred to the peers of the person involved, as these people are
the ones most likely to have the ability to judge correctly. Is this
process perfect? No. Is there a better process? Perhaps, but no one
seems to know what it is.
Peer review plays another very important role unrelated to "the temporal interests of publishers, funding agencies, and employers".
This is as a check on the validity of one's work. Errors are commonplace. Running one's work past experts is simply prudent. They are
in the best position to spot errors and mistakes. Perhaps the authors
of the Comment have never made a mistake but I find this peer
review exceptionally useful. The article "On the Nature of Science"
had much peer review both before and after it was submitted for
publication. Even this reply has been subject to review by my peers
before I sent it to the editor.
The concept of the supernatural is not well defined. The Vikings or
ancient Greeks would have regarded lightening as supernatural,
resulting from the actions of the Gods. What is frequently regarded as supernatural, for example the healing of sickness by anointing,
if it actually occurs would be repeatable and could be studied by
even the restrictive scientific method presented in the Comment. All
observations can be treated on an equal footing with no distinction
made between natural and supernatural. The distinction, if one
wishes to make it, comes purely through the models used to
describe the observations. Is mental illness due to daemons (supernatural) or chemical imbalance (natural)?
"Observationally constrained model building" is much more than
saying science is what scientists do. As previously pointed out, the
idea of model building decouples science from the assumption of
realism. The scientific method outlined in the paper could be used
by a "mind in a vat" and is even consistent with solipsism. In the
both cases it might be sterile, but it could be done. By saying
"observationally constrained" we are putting the emphasis on observation as the final arbiter and not on any human agency.
The Comment says: "One also wonders to what degree documented
observations of other parties are admissible." As a theorist I rely
entirely on "documented observations of other parties". My experimental colleagues would gladly tell you that if I did an experiment,
that would, indeed, not be science. But seriously, modern science
would grind to a halt if "documented observations of other parties"
were excluded or not used.
In conclusion, there are two main differences of opinion between
myself and the authors of the Comment. First they regard the scientific method as of limited applicability whereas I regard it as applicable to most if not all areas of human knowledge. Second they are
committed to realism whereas my view of science is based firmly
on instrumentalism.
1. For a more axiomatic treatment see B.K. Jennings, The Scientific Method,
arXiv:0707.1719v1 [physics.hist-ph]
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OPINION
COMMENTS BY LAWRENCE KRAUSS
ON “IS FAITH THE ENEMY OF SCIENCE?”
W
OPINION
hen Richard MacKenzie contacted me some
time ago asking for the slides of my presentation at the CAP annual meeting, I had no
idea that he was planning such a comprehensive, and cogent, reflection on my remarks. After reading
the substance of his paper, I find myself with little to disagree with. The chief disagreement we may have, if
indeed we have one, is primarily semantic. It is based on
the definition of the three key words, “faith”, “ignorance”
and “enemy”.
Let me begin by explaining what I meant by the word
“enemy”. I take an operational view of this word. An
enemy is someone to either be avoided or vanquished.
I have had several interesting discussions with
Richard Dawkins, some of them quite public and available
on YouTube, on this issue. I have asked Richard if his
recent purpose is to destroy faith or teach science, and he
has indicated that destroying faith at the moment is a higher priority. I accept that argument, however for me the latter purpose, teaching science, is higher priority. (At least
it certainly was in the context of a lecture on the teaching
of science!). And since I therefore view that vanquishing
ignorance is a higher priority for a teacher, this makes
ignorance the enemy.
Now, let’s talk about ignorance for a bit. There is nothing
evil about ignorance. I always make a big point of stating
that when I describe some viewpoint as being based on
ignorance it is not a pejorative statement, but meant as a
statement of fact. Thus, for example, when I say that
President Bush’s statement about evolution vs intelligent
design that “Both sides should be taught, so students know
what the debate is all about.”, I argue that is a statement of
ignorance, because he doesn’t know there is no scientific
debate at the current time. It is not a stupid statement. If
there were such a debate, it would be worth teaching students about it. (I should add that I don’t take a moralistic
view of the term “enemy” either. Enemies need not be
evil. They are simply enemies.)
Lawrence M. Krauss
<[email protected]>,
Foundation Professor,
Director, Origins Initiative,
Co-Director, Cosmology Initiative
School of Earth and Space
Exploration and Physics Department
Arizona State University
P.O. Box 871404
Tempe, AZ U.S.A. 85287-1404
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Finally, the most emotionally charged word of all, “faith”.
Richard takes this to mean an unsubstantiated belief,
which is not a bad definition. But he then interprets religious faith as being the same as faith in the precepts of
organized religion. If this were true, I agree that science
and religious faith are generally incompatible. There is
nothing about the universe that science has unveiled that
supports the notion of a God interested in human affairs,
and many of the stories in the Bible, for example, are not
empirically true. However, having a kind of general faith
in order and purpose to the Universe is not so obviously
unscientific, and while I don’t view this faith as particularly well founded, I also don’t view it as particularly
destructive.
But, just for the purposes of discussion, what about doctrinal faith by religious scientists? Even if it is inconsistent
with science, is this something that we need to vanquish?
I doubt we can, and I don’t see trying to do so as the highest priority.
First, I see the existence of conventionally religious scientists as merely a clear example of the fact that humans can
hold fast to two inconsistent ideas at the same time. This
is not a fact worth extolling, but it is simply something that
we cannot do much about. Humans are not completely
logical beings. As I have said elsewhere, most of us need
to convince ourselves of 10 impossible things before
breakfast in order to face the day. Perhaps the world
would be a better place if human nature was completely
logical, but it isn’t. Should we therefore place our highest
priority on vanquishing this aspect of human nature? I
remain unconvinced.
Second, as long as someone’s religious faith does not get
in the way of their learning about nature, their ability to
assess empirical data, and to predict the results of future
experiments, then I view it as no more obstructionist than
the faith they may have that money can’t buy happiness,
or that marriage produces happiness ever after, or that the
Canadiens will win the Stanley Cup. Naïve, perhaps.
Maybe even based on ignorance. But not necessarily
counterproductive.
Prof. Lawrence M. Krauss is an internationally known theoretical physicist with wide research interests, including the interface between elementary particle physics and cosmology, where his studies include the
early universe, the nature of dark matter, general relativity and neutrino
astrophysics. He has investigated questions ranging from the nature of
exploding stars to issues of the origin of all mass in the universe. He
has been involved for some time in issues of science and society and has
helped spearhead national efforts to educate the public about science,
ensure sound public policy , and defend science against attacks at a variety of levels. He has helped lead a national effort to defend the teaching
of evolution in the public schools.
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ARTICLE DE FOND
IS FAITH THE ENEMY OF SCIENCE?
BY
RICHARD MACKENZIE
S
ome readers of this article may have seen
Lawrence Krauss' entertaining and thought-provoking plenary talk at the 2007 CAP congress in
Saskatoon. They may remember that the first
individual to raise a hand during the question period did so
in an almost-Horshackian fashion [1], and that he bluntly
asserted that he disagreed strongly with the following
statement made by Krauss on the challenge of teaching
science to the public:
Faith is not the enemy.
Ignorance is the enemy.
That brazen individual was me, and I would like to explain
why I disagree with this statement B to the point where
I would be inclined to go so far as to interchange the
words "faith" and "ignorance."
Let us recall that Krauss' talk, entitled "Selling Science to
Unwilling Buyers," concerned itself with how to teach science to the general public B the unwilling buyer B by discussing applications of science which interest the buyer,
rather than more traditional "bottom-up" approaches to
teaching science which might themselves be partly
responsible for the preconception that science is boring in
the first place. Krauss talked about the current (and
abysmal) state of scientific illiteracy in the US, its underlying causes, and how to improve the situation. In giving
such a talk to an audience of physicists, Krauss was to a
large extent preaching to the converted, and I myself was
entirely in agreement with everything he said, except for
the above quote, which I found surprisingly discordant
with the rest of his talk.
Let me begin with working definitions for the two key
terms in the discussion, "science" and "faith."
Science is the study of natural phenomena in order to
understand and explain the world around us. This can be
with the ultimate goal of serving humanity with such technological advancements as the wheel, agriculture and television (presumably reality TV was not foreseen by those
SUMMARY
In this article, inspired by Lawrence Krauss'
plenary talk at the 2007 CAP congress, the
relation between faith and science is examined.
who imagined that television would improve the human
condition), or it can simply be for the sake of understanding how the world around us works.
Byron Jennings [2] went into far greater detail on the
nature of science than I intend to do here, but the fundamental tool of science is the scientific method: making
careful observations or performing controlled experiments, developing a theory which explains the results,
making predictions from the theory, and putting the theory to the test with further observations. While this is no
doubt a simplistic view of how scientists do science, and
there are surely many notable exceptions, it is probably an
accurate representation of the way the majority of scientists work.
By "faith" I mean the unsubstantiated belief in something.
Now, "unsubstantiated" is somewhat subjective and not a
binary concept, but let us not get too distracted by pedantic details. The "something" can be just about anything:
that the Montreal Canadiens are going to win the Stanley
Cup, that all matter and energy is made up of tiny, vibrating strings, or that there is a benevolent higher power who
loves us and is watching over us, but who regularly tests
our faith by throwing cataclysmic events at us which leave
hundreds of thousands of us dead or in despair. (These are
of course minor inconveniences compared to the Sun's
evolution towards a red giant that awaits us in a few billion years or so.)
These three examples illustrate the breadth of the term
faith (or my definition of it, at least). Belief that the
Canadiens are going to win the Stanley Cup is not a statement about reality today, but about a future reality. There
may be some measure of justification for holding this
belief, and the justification may be compelling or not, so
this is perhaps not the greatest example of unsubstantiated
belief. But ultimately the Canadiens will either win the
Stanley Cup or not, leaving the believer either gloating
because s/he knew something the rest of us didn't, or quietly forgetting that s/he had ever held that belief in the first
place.
Richard MacKenzie
<richard.mackenzie@
umontreal.ca>,
Physique des particules, Université de
Montréal, C.P. 6128,
Succursale
Centreville, Montréal
QC H3C 3J7
Belief in string theory, in contrast, is a statement about an
ongoing, for all intents and purposes eternal, reality.
Matter either is or is not made of strings; as far as I know,
no one believes that this description came into being last
week, or that it will no longer be valid next week.
Is belief in string theory unsubstantiated? Again, this is a
tricky point. Some have argued for a much stronger state-
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IS FAITH THE ENEMY OF SCIENCE? (MACKENZIE)
ment: that string theory is not only unsubstantiated but
untestable B that it will always be unsubstantiated. This point
of view is often portrayed as "demoting" string theory to
"mere" religion or philosophy. I will argue against both points
(although I will fall far short of the opposing view held by a
certain Canadian theoretical physicist who, tongue in cheek,
drops a pencil to "prove" the validity of string theory).
First, while there is no direct evidence for string theory, there
are legitimate scientific reasons for taking it seriously as a
description of the world around us. The fact that it is a quantum theory of gravity makes it worth consideration, in spite of
a few minor remaining hurdles to overcome such as explaining
the observed dimensionality of space-time.
Second, even if sceptics consider the preceding argument a bit
thin, string theory is certainly not fundamentally untestable.
Eventually string theory will presumably make actual predictions (if this were not the case, then I would agree with its
demotion to religion or philosophy), and its validity will either
be supported by or contradicted by future observations or
experiments. In the former case, string theory will not have
been proven to be the correct description of reality, but its credibility will take a giant leap upward, leaving many erstwhile
sceptics scrambling to understand why string theorists draw
what to the untrained eye appear to be bagels on the blackboard
and describe them as compactified AdS geometries. In the latter case, string theory must be rejected, or modified in such a
way as to bring it into agreement with the "offending" observations or experiments.
The third example of faith is quite different. Like the second,
it is a statement about an eternal reality; however (as far as
I can see, at least) it is not a belief that will one day be tested
(unless, of course, the higher power sends an indisputable sign
our way). This being the case, it is perhaps the gold standard
in unsubstantiated belief. I imagine it is this type of faith B
whether you call it religious faith, belief in God, or whatever B
that Krauss had in mind in his talk, and that most of us associate with the word "faith" in any case, so I will restrict myself to
this definition of faith in what follows.
What, then, is the relation between faith and science? Put simply, in my mind they are diametrically opposed to one another.
The cornerstone of faith is blind, unquestioning acceptance;
that of science is observation and scrutiny B and the willingness
to accept that a cherished belief is wrong if it conflicts with
observation. It's hard to imagine two world-views more different than that.
I get a powerful illustration of the contrast between the two
when (as happens every few months or so) the Jehovah's
Witnesses come to my door to promote their religion. I am perhaps in a minority in that I actually enjoy talking to them; the
conversation is always very civil and respectful, although to
date they have not succeeded in enlightening me (nor I them).
At some point, I get around to telling my visitors that I would
104 C PHYSICS
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be only too happy to believe in God, but that, despite considerable reflection, I can't think of a single reason why I should. To
them, all the proof I could possibly need is in the Bible, whose
many predictions have all come true with absolute precision.
(I was once offered the following example: that the world will
be filled with misery and evil.) After they have assured me that
they stand by every word in the Bible (since, after all, it is the
word of God), I question them about the fact that the Universe
is known to be billions of years old and not thousands… and
the back-pedaling begins: the word of God is a moving target.
The reason I bring this up is that I feel I am merely being a scientist and not an atheist when I tell my proselytizing visitors
that I need a reason to believe in God. The origin of the
Universe is as much a mystery to me as to anyone, and maybe
it was created by a Creator… but that is about as far as my minimalist, scientific philosophy will allow me to go without further evidence. To evoke a well-defined, precise notion of God
(a humanized notion, if you will) who created the Universe,
life, and man in His own image is a huge, unsubstantiated
extrapolation that is grotesquely unjustified, nicely illustrated
by Bertrand Russell's celestial teapot analogy [3] and, more
recently and in a lighter vein, by the Flying Spaghetti
Monster [4]. I owe it to myself as a scientist to try to minimize
the number of assumptions I make in my philosophy of life,
just as almost any scientist does in formulating an explanation
for any observable phenomenon. Creator? Maybe. God who,
though omnipotent, waited 15 billion years before having a
son, according to one widespread religion? I don't think so.
Recently, I was told by a colleague that he believes in God but
that he separates this side of his philosophy from the scientist
side. Although our conversation went in a different direction,
it occurred to me that he might quantify his philosophy of life
by a point in a plane whose axes are "scientificity" and "faith"
or "religiosity." If the origin is neutral on both counts, I would
guess that he would place himself somewhere in the first quadrant, given that he is rather scientific and obviously at least
somewhat religious.
In my opinion, only one dimension is necessary, with science
to the right, say, and faith to the left. The more a person is a
true scientist, the less willing s/he is to accept notions as true
without a reason for accepting them, so the less inclined s/he is
towards unsubstantiated belief B faith. So already we see that
faith and science are antagonistic.
But to what extent is faith the enemy of science? That is a
trickier point. Does faith obstruct scientists from doing science? Seemingly not; clearly there is no shortage of religious
scientists who do good, respectable science, although the combination strikes me as having at least a degree of internal inconsistency. But I would argue that the overwhelming majority of
modern science is far from the arena of potential conflict. It
simply doesn't matter how strong the researcher's faith is when
s/he is removing atoms from the surface of a solid with a laser
or studying magnetic currents in the Sun. Science is so incred-
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IS FAITH THE ENEMY OF SCIENCE? (MACKENZIE)AA
ibly specialized that a student can get a PhD in particle physics
without having a clue what supersymmetry is, to say nothing of
worrying about how, and for what purpose (if any), the
Universe was created.
Indeed, we can go a step farther and observe that even the arena
of potential conflict B studying the origin of the Universe, say
B is not in conflict with faith, per se (although it is obviously in
conflict with a literal interpretation of the Bible). We are back
to the observation that religion B faith B is not falsifiable
because any scientific observation can simply be argued to be
just what God had wanted. In a recent series of articles [5], Don
Page argued (among other things) that a current idea in cosmology, the multiverse, like Darwinian evolution, should not be
perceived as a threat to Christian theology, although both are
widely perceived as such. Given this "non-falsifiability escape
clause," Page's conclusion strikes me as rather self-evident,
although it depends to a great extent on how malleable the theology is, or in other words on how narrowly Christian theology is defined. I personally have a hard time reconciling evolution and even a single Universe (to say nothing of a multiverse)
in which our planet is about as remarkable as a grain of sand on
a beach, on the one hand, with the idea that humanity is any
more important to God than dinosaurs, say, or amoeba, or life
elsewhere in the Universe, on the other. Given that the importance to God of humanity seems to be a cornerstone of
Christian theology, I think I would feel quite threatened indeed
if I adhered to such a theology..
The bottom line is that direct observation shows that faith does
not obstruct scientists from doing science. That said, there are
many who portray themselves as scientists who, due to their
faith, are doing a brand of science which is an indignity to the
word. I have in mind particularly those whose principal goal
in science is to advance a faith-based agenda. One must wonder whether these individuals, who probably have a reasonable
amount of scientific talent, might not be doing respectable science if their scientificity had not been stronger, or their religiosity weaker.
Does faith obstruct non-scientists from learning science?
I would argue that it does, for several reasons.
First, there is the issue of what is taught in schools, how it is
taught, and by whom. Well-known are the efforts of fundamentalist Christian groups to prevent the teaching of evolution
in U.S. schools, and failing that, to advance intelligent design
(a close cousin of creationism) as a competing scientific theory which, as such, deserves equal class time B in spite of overwhelming scientific evidence for one and none for the
other.("None for the other" is a gross misstatement, in fact,
because it implies there could in principle be evidence for it.
But creation is by its very nature not a science because it is not
falsifiable by observation.) Battles are regularly fought on this
issue (and not just in the U.S., by the way: the subject of the
teaching of creationism in schools has been in the news in the
U.K. and in Canada recently). Science has usually maintained
the upper hand, fortunately, but the war goes on.
Second, organizations such as the Seattle-based Discovery
Institute and the John Templeton Foundation (both of which
have deep pockets) are engaged in a different, more indirect
and therefore more dangerous campaign in the "war" against
science: to blur the distinction between religion and science.
The Discovery Institute is a Christian-based organization with
various offshoots, two of which are the Center for Science and
Culture and the Biologic Institute. These are pretty scientific
sounding names, so one would assume these institutes are
engaged in some sort of scientific thinking or research. But
their main mission is to advance the notion of intelligent design
as a serious scientific theory in competition with evolution.
The non-scientific public runs the risk of falling into the carefully-laid trap of associating creationism with science. Further
on down the road (if the Discovery Institute gets its way),
school boards, voters, and elected representatives at all levels
of government will be unsure about what is and isn't science.
If you think this is fearmongering or an overstatement of the
facts, just take a look at the man in the White House at the time
of this writing [6].
The Templeton Foundation's slogan is "Supporting science B
investing in the big questions." While it has in the past funded
activities of the Discovery Institute, to its credit it has more
recently distanced itself from intelligent design and from the
Discovery Institute itself. Nonetheless, its main thrust can be
described as blurring the line between science and religion. The
Foundation's flagship offering is a prize whose value is adjusted so that it beats out the Nobel Prize financially (thereby gaining publicity, and probably credibility in the eyes of the dollardazed public), for "progress toward research or discoveries
about spiritual realities." Early winners include Mother
Theresa and Billy Graham, but the prizes have been more
recently been frequently awarded to scientists, including physicists such as Paul Davies and Freeman Dyson.
The third B and in my mind the most important but the least
quantifiable and therefore the most contentious B way in which
faith gets in the way of non-scientists learning science goes
back to the antagonistic relation between faith and science. The
blind acceptance that is the hallmark of faith could, if not confined to the arena of one's theology (indeed, why should it be
so confined?), compromise one's ability to think critically, a
key ingredient in scientific thinking. I think that in all aspects
of life, science and non-science, we must be guided by critical
thinking and common sense. (The latter is a tricky issue, as
exemplified in the expression "One man's common sense is
another's nonsense." I have in mind a sort of intuition or judgment guided by the sort of analytical, scientific thinking we
hope to foster in our students.) This has always been the case,
but perhaps it is true now more than ever, given the quantity of
demonstrable nonsense on the internet just a click or two of the
mouse away. A healthy amount of scepticism helps us evaluate whether we should believe what we hear or read. Blindly
accepting authority is not a very good guideline because an
authority can be found to advance virtually any side of any
issue, big (whether or not humanity is responsible for global
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IS FAITH THE ENEMY OF SCIENCE? (MACKENZIE)
warming), small (whether one should stretch before exercise or
afterwards), and everything in between.
Before I accept an idea as valid, it must be scrutinized, or
undergo the "common sense test." Should I believe that distant
stars and planets have some bearing on my daily life? After
thinking about this question for some time, I cannot conceive
of a known mechanism for them to do so, so I am doubtful, to
say the least: astrology has failed the common sense test.
Failing this test is not a proof that an idea is false, of course, but
it does place the "burden of proof" on the idea. All religions
I can think of fail spectacularly, because even if they are not in
direct conflict with scientific observations (the best-known
example of this, perhaps, being the Bible), they place great
importance on phenomena which have never been observed
under controlled conditions (for example, the various [and
mutually incompatible] notions of an afterlife found in many
common religions).
If one is to adhere to such a system of belief, a sort of Pandora's
box is opened. One might as well believe that certain people
have the ability to read fortunes, that water (labelled as homeopathic medicine) can cure virtually any illness, that we will be
reincarnated after death in a form determined by our behaviour
in this life, and so on and so forth. As scientists, we may
chuckle at these beliefs, yet they are quite widespread, and are
symptomatic of a non-scientific world-view, or, equivalently,
of an impaired ability to use the common sense test. This incapacity, in my mind, is a great impediment to understanding the
world around us and is an impediment to learning science.
Krauss gave several examples of scientific illiteracy in the
U.S., which would be amusing if they were not true. The most
spectacular of these was that only about 50% of respondents in
a recent survey realized that the Earth goes around the Sun in
about a year. Although I don't know if such a test has been
done, it would be interesting to see if there was a correlation
between religiosity and the answer given for this question.
What of ignorance, which according to Krauss is the enemy of
science? Krauss may well have had a more colloquial interpretation of ignorance as a stubborn refusal to accept new ideas,
but ignorance actually means a lack of knowledge. In my mind,
if the goal is to educate the public, then in a sense Krauss is
correct: ignorance is the enemy. However, I am inclined to
think that an open-minded but ignorant person, rather than
being the enemy, is exactly where the most progress can be
made in educating the public, so rather than viewing ignorance
as the enemy, I would view it as a primary target, where
resources can most effectively be used. It is much easier to
write on the clean slate of an ignorant but open-minded person
than to have to first erase preconceived notions that run counter to the criticality needed to develop a scientific understanding of the world around us.
In summary, I have argued that faith and science represent
antagonistic world-views: blind acceptance is the cornerstone
of faith, and is diametrically opposed to the open-minded scepticism of a scientific world-view. I believe that faith can indeed
impede non-scientists from learning science, both indirectly (in
terms of the choice of school curricula) and directly (since faith
by its very nature and definition runs counter to a scientific
way of thinking).
Stevie Wonder said it as well as anybody: "When you believe
in things that you don't understand, then you suffer.
Superstition ain't the way."
REFERENCES
1.
2.
3.
4.
5.
6.
Arnold Horshack was a character on the 1970s television sit-com "Welcome Back, Kotter." See http://en.wikipedia.org/
wiki/Welcome_Back_Kotter for details.
B.K. Jennings, "On The Nature Of Science," Physics in Canada , 63 (7), (2007).
B. Russell, "Is There A God?," in J. Slater and P. Köllner, eds., The Collected Papers of Bertrand Russell, vol. 11 (Routledge, 1997).
Reprinted at http://www.cfpf.org.uk/ articles/religion/br/br_god.html .
See http://www.venganza.org .
D. Page, arXiv:0801.0245,arXiv:0801.0246,arXiv:0801.0247.
See for instance http://www.nytimes.com/2005/08/03/politics/03bush.html
106 C PHYSICS
IN
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ARTICLE DE FOND
MY ENCOUNTER WITH GERHARD HERZBERG
IN WARTIME SASKATOON
LYNN E.H. TRAINOR
BY
I
n 1935 the very distinguished scientist, Dr. Gerhard
Herzberg, joined the staff of the Physics Department
of the University of Saskatchewan in Saskatoon. The
detailed story of how Dr. Herzberg lost his academic
post in Darmstadt, Germany, during the Nazi years
because his wife (also a scientist) was
a Jew and how they sought safe haven
in Saskatoon, has been eloquently
told by Boris Stoicheff in his book
Gerhard Herzberg: An Illustrious
Life in Science (Ottawa: NRC Press,
2002). Dr. Herzberg was indeed
illustrious and became a leading
spectroscopist of his time. His
research in atomic and molecular
spectroscopy began in Darmstadt,
continued in Saskatoon, and culminated with his work in Ottawa at the
National Research Council. He
received the Nobel Prize in
Chemistry in 1971. His books on
atomic and molecular spectroscopy
are classics in these fields.
At the University of Saskatchewan
Dr. Herzberg, still an enemy alien,
became involved in explosives
research for the Government of
Canada. He was invited by Professor
George Wright of the University of
Toronto to undertake spectroscopic
analyses of new explosives that
Prof. Wright had invented.
Dr.
Herzberg responded by bringing his
spectroscopic genius to bear on the
problem.
an important prelude to my long career of physics teaching and research at several Canadian universities.
I had grown up as the third of four boys on a family farm
near the small town of Chamberlain, Saskatchewan during
the so-called dirty thirties. My
parents started farming in 1929
but only had their first paying
crop in 1942. These years were
characterized by worldwide economic depression, and by
drought, dust storms and
grasshopper plagues on the
Canadian prairies. For me,
these years represented a period
of isolation and poverty,
divorced from intellectual stimulation, even from high school
experience. I studied alone at
home through grades 8 to 12,
achieving matriculation at age
16. That might well have ended
my educational career, but for
circumstances related to the
Second World War.
My father had noted an
announcement in the Winnipeg
Free Press that the head of the
Canadian
Armed
Forces,
General
Andrew
G.L.
McNaughton, was establishing
university entrance scholarships
Dr. Herzberg on the steps of the Physics for promising students going
Department at the University of Saskatchewan. into engineering and science
(Photo provided by U. Sask. archives.)
programmes at Canadian universities. Part of the requirement for a scholarship was enrollment in the Reserve
This short essay describes my remarkable encounter with
Officers Training Corps. General McNaughton was preDr. Herzberg during my undergraduate years in the honscient in the belief that future wars would be dominated by
ours physics programme at Saskatchewan, which formed
scientific and engineering achievements, so that Canadian
youth training to be officers should preferably have science or engineering backgrounds.
SUMMARY
This short essay describes my remarkable
encounter with Dr. Herzberg during my
undergraduate years in the honours physics
programme at Saskatchewan.
Lynn E.H. Trainor
Emeritus Professor,
Department of
Physics, University of
Toronto, 60 St.
George St., Toronto
M5S 1A7, Ontario,
Canada
[NOTE: Since the submission of this article,
Dr. Trainor has passed
away -- see page 161
for In Memoriam.]
My father encouraged me to apply for a McNaughton
scholarship. At first I resisted because I felt that there
would be many students with high school education who
would be ahead of me in the competition. But he insisted
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MY ENCOUNTER WITH G. HERZBERG .... (TRAINOR)
and so I applied and won a scholarship! I was able to enter the
University of Saskatchewan in the fall of 1942, an event much
beyond my wildest dreams! Once in university, I was able to
finance myself through National Research Council scholarships and university teaching assistantships. I entered the honours physics programme at Saskatchewan and there the present
tale begins.
I shall never forget the influence that Dr. Herzberg had on us
students in the Physics Department at Saskatchewan.
Suddenly the little-known prairie city was transformed into a
place that the whole world knew. A new age of scientific discovery and the excitement of pursuing a scientific career had
arrived locally. I can still recall, in my mind's eye, what a towering figure Dr. Herzberg was C not towering in size, but in
stature and personality. As naïve young students, we knew that
we had been blessed with the privilege of taking classes and of
studying under this giant of science, out here in remote
Saskatchewan, with its cold winters and academic isolation.
We were suddenly and auspiciously brought into contact with
the real magic of science. I first perceived the wonderful and
exciting world of quantum theory from the remarkable and
concise little book Atomic Spectra and Atomic Structure written by Dr. Herzberg. It was a prize possession of mine over the
years.
We students were all deeply influenced by
Dr. Herzberg's admonition that "Scientific research is ten percent inspiration and ninety percent perspiration" C a bit of
realism to season the academic excitement of his students.
Dr. Herzberg in his office at the University of Saskatchewan.
(Photo provided by U. Sask. archives.)
Of course I revered Professor Herzberg as did all the physics
students at Saskatchewan, and already in my second year a circumstance developed which brought me into close association
with him. Dr. Herzberg went to the Department Head,
Dr. E.L. Harrington, to ask whom he would recommend from
among the undergraduate students to act as his assistant.
Fortunately, Dr. Harrington suggested me. And so I began
working as an assistant to Dr. Herzberg in his research on
explosives.
108 C PHYSICS
IN
What an opportunity! I was thrilled, but at the same time my
excitement was muted because I knew he was doing secret
work under enemy alien status and could not really share much
with me about the physics of our work together. My first task
under his direction was to prepare charges of picric acid for the
explosives research. By this time he already had a sod shack
constructed and the spectroscope mounted ready for action, a
Rube Goldberg feat to which we will return a little further
on ….
For this first assignment Dr. Herzberg gave me a work table in
the hot and dark attic of the physics building, together with a
thick piece of safety glass behind which to prepare charges of
picric acid (picric acid had been the explosive of choice in the
First World War). I was also equipped with an equal arm balance for measuring small weights accurately, a supply of powdered picric acid, a quantity of glass test tubes of standard laboratory quality, and a hard rubber rod for packing the picric
acid into the glass tubes. My assignment was to measure out
10-gram samples of picric acid with the equal arm balance and
to pack these samples, one at a time, into each test tube until
100 grams had been packed, proceeding in this way to prepare
one test tube at a time. I worked behind the protective glass
plate wearing safety goggles. (It was known that picric acid is
not easily exploded through mechanical means alone, so the
danger of an explosion during preparations was very small.
Nonetheless we proceeded with caution.)
I was sternly warned by Dr. Herzberg that the utmost care was
to be exercised to ensure that all tubes would be identical in
size and preparation. So I proceeded to prepare test tube after
test tube in this fashion, sweating under safety goggles in the
confining atmosphere of the physics department attic.
Naturally, I did not write home to my parents telling them of
my work with explosives. My mother would certainly not have
approved, if she had known.
Well, things went along as smoothly as one might have expected, until Dr. Herzberg visited me in the lab unexpectedly after
a week or two of my preparations. By this time I had collected quite a few packed test tubes, each containing ten 10-gram
samples of picric acid. I had proceeded with great care because
I wanted to do the work well, and I was conscious that
Dr. Herzberg was quite a serious and exacting scientist. Also it
was an opportunity to demonstrate my promise as a budding
young scientist.
Now you could tell by looking at the glass tubes that I had
packed ten of the10-gram samples into each tube, because there
was a thin interface mark between the layers of picric acid and
you just had to count the number of layers. However, this was
my first experience working with a relentless and exacting scientist, because after checking that each tube had indeed the
appropriate ten layers, he proceeded to compare the heights of
the picric acid columns in several different tubes, two at a time.
Chagrin! Chagrin! They did not match! This circumstance led
to the following severe conversation:
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MY ENCOUNTER WITH G. HERZBERG .... (TRAINOR)AA
Herzberg: "Trainor, did you measure out the 10-gram samples carefully before packing?"
Trainor:
"Yes sir. I was extraordinarily careful with the
weighing process!"
Herzberg: "Did you pack them in the same way each time?"
Trainor:
"Yes sir. To the best of my ability, I packed each
sample firmly in the same way."
Herzberg: "But you could not have proceeded properly
because as you can see for yourself the heights of
the picric acid columns are not the same in each
test tube."
Trainor:
"But sir, it couldn't be, because I did everything as
instructed and as carefully as possible."
Now for a few words on the programme itself. Dr. Herzberg's
first task was to determine how to make a movie of the flash
which accompanied an explosion (over the duration of the
flash), a movie that would show how the light energy is distributed over the frequency spectrum, from the infrared through
the visible to the ultra-violet frequencies. The instrument that
does this is a combination of a spectroscope and a rotating mirror camera. One has to initiate and contain the explosion in
such a way as to protect the spectroscope from harm.
Somehow the explosion chamber has to be isolated from the
spectroscope, except for the light flash itself. This is where the
Rube Goldberg shack mentioned above comes in, and I will
now describe its construction.
That was the end of the conversation. He left me abruptly and
I was sorely crushed. What could have gone wrong? I really
had proceeded with the utmost care and caution! I was devastated. My short life as a physicist was over. How could I face
Dr. Herzberg again? How could I face Dr. Harrington who had
recommended me from among all the undergraduate physics
students?
Dr. Herzberg's plan was to construct a two-room shack in the
open field behind the physics building and at a safe distance
from it. The "shack" was not to be an ordinary shack, but one
built with bags of soil to form thick and massive outer walls, as
well as a partition between the two rooms. These walls were
strong enough to withstand the power of the explosives used in
the experiment. One room would house the spectroscopic
equipment, protected from harm by the partition; the second
room would house the explosive charge mounted suitably on a
light wooden support. One had to arrange things so that the
spectroscope could "see" the flash from the explosion through
a lens mounted in a small aperture in the heavy wall separating
the explosive and the spectroscope. This aperture was made
small enough so that the force of explosion would not penetrate
significantly into the spectroscope chamber, but the flash could
be focussed on the spectroscope through a lens mounted in the
Shortly after my work hour started the next day, Dr. Herzberg
came in again to the lab. I was still mystified and frightened,
but prepared to be fired on the spot. He spoke to me in his
usual gruff voice:
Herzberg: "Trainor, I must apologize to you. I have checked
with the chemists as to the accuracy of the diameters of those chemical test tubes. They told me they
were not standardized at all
and could easily vary in
diameter by 5%." [The 5%
variation in the diameters
would translate into a 10%
variation in the lengths of
the columns of picric acid
charges in the chemical
tubes.]
I felt liberated! Moreover he went on to
say, "I believe you when you say that all
samples were prepared with diligence
and care." Suddenly the sun seemed to
shine brighter on my physics career.
But I had learned something of the
importance of examining all aspects of
an issue in a scientific venture.
Dr. Herzberg and I proceeded to work
together on the explosives programme
in the "Rube Goldberg" shack behind
the physics building with quiet efficiency for several weeks, eventually to be
joined by George Walker and his bugle,
as elaborated below. The relationship
between all three of us was very pleasant and harmonious.
The explosion causes the roof of the sod hut to blow off. (Photograph provided courtesy of R. Pywell,
University of Saskatchewn; it appeared in an article published in a Saskatchewan newspaper in August 1949.)
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MY ENCOUNTER WITH G. HERZBERG .... (TRAINOR)
aperture itself so that a movie image could be formed on suitable film in the rotating mirror camera associated with the
spectroscope.
One last piece of constructive genius remains to be described.
A light-proof roof for the sod hut was necessary to screen outside light from entering the shack while the spectroscope was
taking the movie pictures of the flash from the short-lived
explosion. This important detail was accomplished by making
a roof with pieces of tar paper, held in place by several long
planks, which could be recovered after the explosion blew
them off.
This scheme had the advantage of dissipating the force of the
explosion upward and outward through the loose fitting roof.
Finally, it was arranged that the explosive charge would be
activated through a fuse which itself was activated by an electrical charge, controlled by a switch at a safe distance mounted
on the back wall of the physics building.
The procedure consisted of preparing the spectroscopic film for
exposure and setting up the explosive charge on a light wooden frame aimed at the aperture access to the spectroscope.
When the switch at the physics building was closed, the explosion would occur and the spectral movie recorded before the
roof had time to blow off, sending tar paper and planks flying.
This method had the advantage that for the next explosion one
had only to refit the roof with fresh tar paper using the same
planks now recovered. It was both a simple and an ingenious
arrangement, both hallmarks of good science.
At first, Dr. Herzberg examined the spectra obtained from
explosions of various charge sizes using the picric acid tubes
which I had prepared. He wanted to compare the picric acid
spectra with the spectra of newly developed explosives, in particular, an explosive called RDX. The RDX was shipped to
him in cylinders of about 2 inches in diameter and perhaps a
metre in length. In practice, one could begin with short pieces
of RDX, and gradually increase the lengths to get larger explosions as desired. The RDX explosives were much more pow-
110 C PHYSICS
IN
erful than the picric acid ones, and the sound from their firing
soon became a nuisance to campus life. In particular, the
chemists complained that when blasts were set off without
warning students and staff dropped expensive glassware, and
they asked that some warning system be devised before another charge was about to be set off.
This problem was solved when George Walker joined
Dr. Herzberg's scientific team. George, or Russell as he preferred to be called, had been a bugler in the army, and we
arranged that he would play the Last Post just prior to closing
the switch that initiated the next blast. This caper of Russell's
seemed to satisfy the chemists and others on the campus who
had concerns, so Dr. Herzberg's work could proceed without
further interruption.
Dr. Herzberg left the University of Saskatchewan in 1945 for
Yerkes Observatory in the U.S. but he returned to Canada in
1948 to create a spectroscopy laboratory at the National
Research Council in Ottawa and to become, in 1949, the director of the Physics Division at NRC. Dr. Herzberg played a
leadership role in the development of science in Canada until
his retirement in 1994 at the age of ninety. I went on to get my
Ph.D. in theoretical physics and, over my career at various
Canadian universities, I had the pleasure of a number of contacts with Dr. Herzberg. Whenever I met him whether in
Ottawa or elsewhere Dr. Herzberg was always very cordial and
we recalled with pleasant nostalgia those early days in
Saskatoon during the war years when I assisted him with his
research on explosives and when he gave new life to physics
research at the University of Saskatchewan.
ACKNOWLEDGEMENTS
I first met Dr. Herzberg's son Paul when I was a professor at
Queen's in the 1950s and he was an undergraduate student
there. We have maintained a close friendship since then and
I thank Paul for his help in editing this piece of scientific history.
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ARTICLE DE FOND
THE UNIVERSE AS AN INSIDE-OUT STAR
BY
MITCH CROWE, ADAM MOSS AND DOUGLAS SCOTT
MBology’ (or CMB-Cosmology), the study
of temperature fluctuations in the Cosmic
Microwave Background (CMB [1]), and
Helioseismology, the study of acoustic
oscillations on the surface of the Sun [2], are two fields of
much experimental and theoretical interest today. In the
last decade, our knowledge of both areas has increased
dramatically through an active ground and space-based
observational programme. This has led to substantial
improvement in the quantification of models for both the
early Universe and the interior of the Sun, and hence given
us a deeper understanding of the underlying physics.
‘C
waves in the early Universe and solar interior is of great
importance, since they can be used to study the insides of
objects that are otherwise unreachable.
These two areas are vastly different in terms of scale.
Firstly, consider the difference in physical size.
Cosmology B literally ‘the study of the whole Universe’ B
encompasses scales so vast as to make even our own
Galaxy seem minuscule. The study of solar oscillations,
on the other hand, is constrained to an object barely 100
Earths in diameter B virtually non-existent on a cosmological map. We can also consider the vast temporal disparity
between the two fields. The photons we observe from the
Sun describe it as it was about 8 minutes ago, while CMB
photons give an imprint of the Universe as it was more
than 13 billion years ago.
THE CMB AND HELIOSEISMOLOGY
Although the Sun and CMB are very different in terms of
scale, the underlying physics enabling us to understand
them is essentially the same B the physics of sound waves
resonating in a cavity. Acoustic waves are a common
everyday physical phenomenon, and every undergraduate
learns about the use of standing sound waves to understand the interior of a cavity. Probing the same kinds of
SUMMARY
Acoustic modes can be used to study the
physics of the interior of a cavity, and this is
especially useful when the inside region is
inaccessible. Many astrophysicists use such
sound waves as an essential tool in their
research. Here we focus on two separate
sub-fields in which oscillations on the surface of a sphere are studied B CMBology
and Helioseismology B the surface being
either the solar or cosmic photosphere. Both
research areas use the language of spherical
harmonics, as well as sharing many close
similarities in the underlying physics.
However, there are also many fundamental
differences, which we explain in this pedagogical article.
In this article we will compare the physics of these 2 astrophysical arenas: CMB anisotropies and helioseismology.
Both use similar language, talking about acoustic modes,
the photosphere and spherical harmonics, and hence it
should come as no surprise that there are very close physical analogues that can be drawn1. However, as we will
see, this is only possible if one thinks about the Universe
as an inside-out version of a star.
Standard Cosmological Model
All current cosmological data point towards the Hot Big
Bang picture, in which the early Universe was full of relativistic particles (baryons and electrons) and radiation,
along with components of dark matter and dark energy.
This extremely dense and hot Universe evolved by
expanding and cooling B as does an expanding gas. Most
of the initial energy was in radiation, which drove the
expansion according to the equations of General
Relativity. Because of the expansion, radiation from earlier times reaches us with stretched wavelengths, and it is
natural to use the observed redshift, z, as a label for the
epoch we are observing B z increases monotonically as we
look farther away and back to earlier times.
The immensely high temperatures meant that photons B
whose energy distributions well approximated a blackbody spectrum B were originally energetic enough to keep
the atoms ionized. The primordial gas, then, must have
been optically thick, due to the high cross-section for
Thomson scattering of the free electrons. Photons and
baryons were said to be ‘coupled’ during this era; the continuous scattering off one another linked their temperature
and fluid properties.
As the Universe cooled, the rate of expansion fell due to
the overall gravitational attraction of matter. A number of
important epochs occurred as particle interaction rates fell
below the expansion rate. One example is the formation of
the light elements at a temperature of around 1 MeV (redshift of several billion), as the conversion between neutrons and protons froze out. This gave a helium mass fraction of around 25%, in fairly close agreement with the
value in the solar interior today.
Mitch Crowe, Adam
Moss <adammoss@
phas.ubc.ca> and
Douglas Scott
<[email protected].
ca>, Department of
Physics and
Astronomy, University
of British Columbia,
Vancouver, British
Columbia, V6T 1Z1,
Canada
1. The earliest analogy of the CMB last-scattering surface, the shell
from which photons last scatter, to a cosmic photosphere goes back
at least as far as 1982 [3].
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THE UNIVERSE AS AN INSIDE-OUT STAR (CROWE ET AL.)
As the Universe continued to cool, the ratio of the energy density in massive particles relative to radiation increased, until the
epoch of matter-radiation equality was reached. At a redshift
several times smaller than this (z 1000), very few photons
were energetic enough to ionize hydrogen, and so electrons
were captured by protons, leading to an optically thin universe
B a process referred to as cosmological recombination.
Photons, having been freed from their electron captors traveled
unhindered through a mostly empty space until they are seen
today as the CMB. The probability for a photon last scattering
with an electron peaks at z 1100, and so we call this the ‘last
scattering surface’.
Photons that last scattered at this epoch are seen today with a
remarkably pure black-body distribution at a cool temperature
of about 2.7 K. At a redshift of 1100 this means that recombination occurred at a temperature of about 3000 K. This cosmic
photosphere is seen at an age of around 400,000 years, while
the age of the Universe today is about 14 billion years.
The background radiation, as seen by any observer, is remarkably isotropic, but contains the signatures of primordial structure in the form of temperature anisotropies on the order of one
part in 105. It is these anisotropies that are of most interest to
cosmologists, as their measurement promises to constrain the
many otherwise free parameters in theoretical models of the
evolution of the Universe. Moreover, they are caused by the
small fluctuations in density that grows in contrast to become
the rich structure (galaxies, stars, people) that we see today.
Standard Solar Model
Not unlike the CMB, the solar surface is mostly uniform. When
we observe the Sun, we see photons escaping from the solar
photosphere, the energy distribution of which is crudely that of
a black-body with an effective temperature T 5800 K.
Because of its brightness and angular extent on our sky, solar
temperature anisotropies were witnessed long before scientific
explanation could be provided for them. Sunspots were first
noted by Galileo and could be seen with a tool as simple as a
pin-hole camera. However, these large solar ‘blemishes’ are
very localized on the solar surface, as well as being transient,
and as such do not contribute much to the overall variance of
angular anisotropies; in CMB language, sunspots are localized
highly non-Gaussian cold spots with amplitude ΔT / T 0.1.
The configuration of the solar interior can be inferred by applying the standard equations of stellar structure, which derive
from the principles of thermal and hydrostatic equilibrium.
These are complicated by details of energy generation through
nuclear processes and energy transport by radiation and convection. The convective zone is confined to the outer 30% of
the solar radius, where no radiative transport occurs. Energy
generation is driven by the conversion of hydrogen to helium
at similar temperatures to what was achieved in the Universe
when the primordial helium was formed.
It is the acoustic oscillations B anisotropies discovered in 1960
by observing Doppler shifts in absorption lines due to the phys-
112 C PHYSICS
IN
ical movements of atoms in the photosphere B that are of greatest interest to helioseismologists. These oscillations, composed
of various pressure modes or ‘p-modes’, are waves sustained
by a radial pressure gradient; they are sound waves trapped in
the solar interior. The principle underlying helioseismology is
that the various acoustic modes provide different information
about the solar interior. In particular, modes characterized by
different numbers of radial nodes penetrate to different depths
within the Sun, providing a series of probes allowing one to
determine the radially dependent physics of the Sun. For example, by measuring the dispersion relation of a mode, one can
estimate the average sound speed it experiences. Using several
modes, and knowing their penetration depths, a helioseismologist can determine the functional form of the solar sound speed
with respect to radius. Such tests can be used to both confirm
and to constrain parameters within the Standard Solar Model,
including determining the interior composition and rotation
rate.
The Universe as an inside-out star
Some similarities between the Sun and the Universe should
already be apparent. Consider, for instance, that an observation
of either the CMB or the Sun collects photons originating from
a spherical surface, and describing a nearly uniform blackbody spectrum. In the Sun the photosphere is the surface where
gas density has increased sufficiently for photons to be strongly scattered, and its radius is usually defined as R , which is
around 700,000 km. In the CMB the last scattering surface has
a distance from the Big Bang that is given by the recombination time multiplied by the speed of light. However, the CMB
sky surrounds us, and when we look out towards the cosmic
photosphere it is like looking into the surface of a star.
In contrast, the Sun is localized on our sky. That is to say, one
can point a finger at the centre of the Sun with the knowledge
that it is entirely contained within some finite radius of that
point (at a given time). This is not possible for the CMB last
scattering surface, where every observer (potentially in quite
different parts of the Universe) has their own last scattering
surface. This is because in the uniformly expanding Universe
everything is moving away from everything else B thus there is
no true centre of the universal expansion or, rather, every point
can be considered to be the centre. So every observer sees the
early Universe photons arriving from all directions in a spherical shell around them. We are at the centre of a space in which
the cosmic photosphere surrounds us, as if the surface of the
star had been wrapped all round us. The centre of this ‘star’ is
then located in the very early Universe, well beyond the distance of the last scattering surface, and this centre (the position
of the ‘Big Bang’ if you like) is in every direction as we look
out, into the ‘cosmic star’.
The Solar and Cosmic photospheres are therefore quite analogous to each other. It is the fluctuations over each of these
spheres that are of most interest, since they probe the nature of
the acoustic cavities. Helioseismologists and cosmologists use
the same mathematical tools to describe these acoustic modes,
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THE UNIVERSE AS AN INSIDE-OUT STAR (CROWE ET AL.)AA
this spherical surface. For the Sun
(or any other star)
the photosphere is
also defined by the
region where τ ∼ 1,
but the source of
opacity is much
more complicated,
including
lines
from heavy elements and HB ion
scattering.
But
there is a more sigFig. 1 Illustration of the Y m harmonics used to expand the temperature fluctuations of the CMB and velocity fluctua- nificant distinctions on the solar surface. In the left panel of four harmonics, we show the real component of: Y 2 1 (top-left), Y 2 2 tion, coming from
(top-right), Y 10 5 (bottom-left) and Y 10 10 (bottom-right). Cosmologists are interested in the amplitude of these the vastly different
modes, while helioseismologists study their variation with time. Helioseismologists also decompose modes in the p h o t o n - t o - a t o m
third (radial) dimension, as shown on the right.
ratio B approximately 1 billion for
namely the spherical harmonics. Any angular function f (θ,φ)
the Universe, but less than one billionth for the solar surface!
can be expanded in terms of spherical harmonics by
Hence the temperature at which the Universe went from plas∞
ma to neutral is determined by when the photons allowed the
f ( θ, φ ) = ∑ ∑ a mY m ( θ, φ ).
(1)
atoms to recombine, and this determines the last-scattering sur=0 −
face. But the photosphere of the Sun is mainly determined by
Several of these modes are illustrated in Fig 1. Roughly speakwhere the density has fallen off. So it is much more like an
ing, the
index describes the angular extent of features,
actual edge to the solar material than in the case of the
180o/ , while m characterizes the azimuthal dependence.
Universe, where the density is slowly varying, but the ionizaCosmologists are mainly interested in the power spectrum of
tion changes.
a ms, while helioseismologists study their time dependence.
The fact that the Universe is like an inside-out star means there
One might then ask why the cosmic recombination temperature
is also another important difference to keep clear. The spheriturns out to be within a factor of 2 of the temperature of the
cal harmonics describing anisotropies in the Sun and the CMB
must be projected from a different centre in each case B helioseismologists use the centre of the Sun as the origin, while cosmologists use the observer’s position as the centre.
The scales and ‘inside-out’ geometry are illustrated in Fig. 2.
The other major difference is the colossal distance of the cosmic photosphere on which we see the CMB anisotropies. At a
redshift of around 1100, the last scattering surface is about
14 Gpc away from us (a bit more than the light travel time in
14 billion years, because it has been expanding during that
interval). This is about 1017 times the scale of a Sun-like star.
So the Universe is exactly like a star, except that it is completely turned inside-out, and 100 quadrillion times bigger!
Surface of last scattering and the photosphere
The reason why the inside-out star is an attractive analogy for
the CMB is that we observe photons emerging from the cosmic
photosphere. This last-scattering surface is a shell defined by
the distance from us in which there is a significant probability
for the photons to have suffered their last scattering event. We
see to where the optical depth τ is around unity, with τ entirely
due to Thomson scattering off free electrons. The last scattering surface is therefore defined by the epoch at which the
Universe went from being a plasma to a neutral gas; the time
since this epoch, coupled with the finite speed of light, defines
Fig. 2
Geometry and length scales of the Sun versus the comic
inside-out star.
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solar surface. The answer is that partly this was just a coincidence. But the fact that the order of magnitude is similar is not
surprising, since this comes basically from the temperature at
which atoms get ionized. So, despite the chemistry being different, this is ~eV in both cases.
Another important feature for the CMB is acoustic damping,
which is related to the thickness of the last scattering surface.
This turns out to be approximately Δ z / z 0.1, which leads to
a smearing of the anisotropies at an angular scale which is
about 10 times smaller than the causal scale at the last scattering epoch, corresponding to
1000, as can be seen in Fig. 3.
Similarly, in the Sun the optical depth does not drop instantaneously, although it much more abrupt than for the CMB. The
thickness of the solar photosphere is a few hundred km or
around 0.001 R3. This means that the damping for solar modes
is at an angular scale about 100 times higher in than for the
CMB.
PHYSICS OF SOUND WAVES
Acoustic modes
A crucial property of both CMB and solar fluctuations is that
their amplitude is small. As a result, the equations which
describe them can be solved by linear perturbation theory, such
that a set of initial conditions can be evolved forward in time
exactly to predict the final observed oscillation spectrum (particularly in the cosmic case), greatly simplifying the comparison of theory with observations.
Both the fluids in the solar interior and early Universe are characterized by several variables, each with an average value and
a small perturbation which varies with both time and position
B the energy density ρ, pressure P (related by an equation of
state P = P (ρ,T )) and local velocity υ. A continuity equation
enforces conservation of mass, Euler’s equation determines the
motion of the fluid, and Poisson’s equation describes the
response of the fluid to gravity. The full cosmological equations are relativistic generalizations of these, but the physics is
the same.
In order to understand acoustic waves it is sufficient to initially ignore gravity and consider a density perturbation in each
fluid. The cosmological fluid is adiabatic, a natural outcome of
inflationary initial conditions, and this is also an excellent
approximation in most of the solar interior. This means that one
can ignore heat exchange between fluid elements B only compression increases the temperature, and expansion cools it. In
both cases, the resulting continuity and Euler equations then
describe a simple oscillator
a
(2)
δ + δ + c s2 k 2 δ = 0,
a
where δ / δρ / ρ, δρ . ρ and an overdot denotes the time
derivative. The scale factor a(t) describes the cosmological
expansion, and is related to redshift by a = (1 + z)B1 B this term
is zero in the solar case. We have written this equation in
114 C PHYSICS
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Fourier space, where k = 2π / λ is the wavenumber of the
mode. Neglecting the expansion term, the solutions to this
equation are plane acoustic waves oscillating at the sound
speed, defined through c2s = dP / d ρ. In a relativistic cosmological fluid c2s = c2 / 3, where c is the speed of light. In the solar
interior the sound speed varies as a function of radius, and for
G, where kB is
an ideal gas we would just have c2s = kBT/m
Boltzmann’s constant and m
G is the average particle mass. In the
standard model of the Sun the values range from about 6 kms B1
near the solar surface to about 500 kms B1 near the solar core.
Equation (2) has several important consequences [4]. The dispersion relation of the waves, given by ω = csk, means that spatial and temporal modes are related by a constant in the cosmological fluid B i.e. a wave with twice the wavelength has twice
the oscillation timescale, which turns out to be crucial for
understanding the observed CMB acoustic spectrum. In the
solar interior, the oscillation equations must be combined with
boundary conditions at the surface. Coupled with the fact that
the sound speed varies as a function of depth, this leads to
refraction of waves in the solar interior. High frequency modes
are trapped near the surface, while low frequency modes penetrate closer to the core. This means that observation of oscillations as a function of frequency can be used to probe the interior.
Since the oscillations in density in equation (2) also involve
oscillations in velocity, then there may be more than one physically observable effect. The velocities will be 90o out of phase,
since the velocity maxima and minima occur at the zeros of the
density oscillations. For the Sun it is usually the time-varying
Doppler shifts of the velocity oscillations that are observed
directly (although there are also luminosity variations observable from the lowest multipole modes). For the CMB the
amplitudes of the standing waves are frozen at the last scattering epoch B the main effect is from the density variations,
although there is a sub-dominant contribution from the velocities.
Another important property of the acoustic modes is that they
are irrotational. This means that the fluid velocity is in the
direction of the wavevector k. The cosmological fluid is dominated by irrotational modes, which are the primary source of
anisotropy in the CMB. However, inflationary initial conditions also predict a small fraction of rotational modes, which
are seeded by gravitational waves. The most characteristic
effect of these is through their effect on the pattern of CMB
polarization in which (through analogy with curl in electromagnetism) they are usually referred to as ‘B-modes’. These
have not yet been detected, but are one of the main motivations
for future CMB missions. In the Sun there is some evidence for
‘r-modes’ in the photosphere, which are similar to the Rossby
waves seen in the Earth’s atmosphere and oceans. These are
driven by the Sun’s rotation. So, although there is a very loose
analogy with the CMB ‘B-modes’, there is also a very fundamental difference B there are extremely strict limits on the rotation of the Universe, coming from the non-observations of spiral-like patterns in the CMB anisotropies.
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Cosmological oscillations
Inflationary cosmology predicts that quantum fluctuations created in the very early Universe seeded gravitational fluctuations within the primordial plasma. The introduction of gravity
means that pressure and gravity are now two competing forces.
The gravitational instability imposed on these perturbations,
along with the counter-acting radiation pressure from the energetic and numerically dense photons (still highly coupled to the
baryons) leads to acoustic oscillations within this early plasma.
After recombination, the photons’ restoring radiation pressure
no longer drives these oscillations and the perturbations in
structure are frozen-out as the CMB is released. On the largest
scales we simply see a reflection of the initial conditions in the
gravitational potential. This is the main physical effect for
angles larger than that subtended by the causal length at lastscattering, which corresponds to about 2o on the sky (about the
width of your thumb held at arm’s length, or coincidentally
about 4 times the diameter of the Sun).
On smaller scales, the temperature fluctuations are due to the
density and velocity variations in the oscillating plasma at the
time of last scattering. One observes these as a ‘fundamental’
mode, together with a series of harmonic overtones in angular
scale on the sky. This occurs because of the approximately constant sound speed within the plasma up to decoupling. There
therefore exists a scale, which at last scattering had suffered
maximal compression B so CMB photons have a maximum
temperature variance at this angular scale. This fundamental
mode for the CMB is the angle subtended by the ‘sound horizon’ at last scattering, i.e. the maximum distance sound could
propagate since the initial fluctuations were laid down. This
corresponds to an angular scale of around half a degree on the
Fig. 3
sky, or
220. We observe a set of harmonic overtones at
220 (2n + 1), corresponding to the modes which have
undergone further oscillations to reach maximal compression,
and we observe peaks at
440 (n + 1), corresponding to maximal rarefaction modes (with n = 0,1,… in each case).
These features are most easily seen by plotting the variance of
CMB temperature against angular scale on the sky, or more
precisely by plotting power versus multipole for spherical harmonics. In the left panel of Fig. 3, we show the anisotropy
power spectrum for current observational data. The conventional quantity, which is plotted as power, is a scaled version of
C = |a m|2 , where the angled brackets mean an average over
all possible realizations of each mode, and each m is equivalent
(since there are no preferred directions in the Universe). We see
a clear detection of the first, second and third acoustic peaks.
This coherence of the CMB power spectrum only occurs
because the initial conditions are ‘synchronized’. This happens
naturally in inflationary models for the initial perturbations
when modes start oscillating at very early times and over
almost arbitrarily large scales (even those which are apparently acausal). This synchronization means that each cosmological Fourier mode has the same temporal phase. In the acoustic
cavity analogy this means that the modes have a node at t = 0
(with the fundamental and harmonics having nodes or antinodes at the recombination time). This is just like the radial
modes in the Sun, which all have a node at the centre and at the
surface. However, for the Sun the distance and epoch are not
tied together as they are for cosmological distance and lookback time. The sound waves in the Sun may all have a node at
the centre, but they are excited at different (and random) times.
In the left panel, we show the CMB power spectrum as measured by the latest data from the WMAP [5], BOOMERANG [6], VSA [7],
QUAD [8], CBI [9] and ACBAR [10] experiments. In the right panel, we show oscillation modes of the solar surface, made using a representative example of SOHO [11] MDI data. The prominent ridges correspond to different radial modes, while the low frequency structure
is ‘noise’ below the sound speed. The same diagram for the CMB would consist of a single line, ω % , but with an extremely small coefficient, so that it would lie almost along the x-axis.
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Inflationary initial conditions with amplitude about 1 part in
105 appear to provide an excellent fit to today’s cosmological
perturbations B they are approximately scale invariant in gravitational potential, are adiabatic in nature and maximally random (i.e. have Gaussian statistics, with no phase correlations
between modes). This means that the power-spectrum contains
all useful cosmological information. Of course this is manifestly not true for the Sun, or indeed any object where one can
meaningfully point at specific features.
Solar oscillations
In the CMB, the oscillation modes are mainly acoustic in
nature. In the Sun the modes are acoustic (‘p-modes’), gravity
(‘g-modes’) and surface waves (‘f-modes’). Acoustic oscillations are driven by pressure variations, whereas g-modes are
driven by buoyancy of fluid parcels (gravity provides the
restoring force). Surface waves arise from discontinuities in
density along the surface and propagate along these discontinuities. Neither gravity nor surface waves are possible in the
CMB at linear order, due to the isotropy of temperature at
zeroth order.
In solar models spherical symmetry and boundary conditions at
the surface are enforced. This leads to a set of discrete oscillation frequencies ωn m, where and m are the degree and order
of spherical harmonics, and n is the radial node number. These
frequencies are independent of m for a spherically symmetric
non-rotating star. However, if the star is rotating (as is usually
the case), this splits the frequencies, in a similar fashion to the
Zeeman or Stark effects for spectral lines. The +m modes travel at a different speed around the star than the Bm modes. Thus
observations of this splitting over many different multiplets
enable reconstruction of the solar interior rotation.
In the Sun the period of acoustic oscillation is dependent on the
radial node number n. When a helioseismologist talks about the
‘fundamental’, what is meant is the radial mode that has a node
at the centre and an anti-node at the surface. The harmonics are
then the radial modes with extra numbers of nodes. Each of
these radial modes can have a whole set of angular harmonics
with different (and m). The frequencies can be estimated from
the time taken for a sound wave to travel one horizontal wavelength, which gives w ~ cs / R (for a wave propagating at
depth R). The fundamental node (n = 0) has a period of
~1 hour, coming approximately from the free-fall time
(Gρ) B1/2. Typical observed modes have n = 20-30, with a period of ~5 minutes. However, there is not really a fundamental
angular mode for the Sun in the way that there is for the CMB
(although see Section on ‘A power spectrum of the Sun’).
Since the solar oscillation timescale is much (much!) shorter
than the cosmological timescale, helioseismologists have a
more powerful signature of acoustics in the Sun than the
acoustic peaks frozen onto the CMB B they can observe the
actual oscillations and measure their frequencies directly,
instead of simply inferring the oscillations from a harmonic
116 C PHYSICS
IN
imprint. These observations can be captured in an - ν plot,
where the angular frequencies are plotted against the temporal
frequencies, as shown in Fig. 3. The ridges in this plot correspond to node number B the ridge with lowest temporal frequency corresponds to the fundamental mode. Since modes
with small n probe deeper into the solar interior, they can be
used to constrain radially dependent properties.
Two key effects in the Sun prevent us from seeing coherent
acoustic modes like we observe in the CMB. Firstly the modes
are probably generated by turbulent eddies in the convection
zone, so that there is stochastic forcing of the oscillations, with
random temporal phases. And secondly the very long lifetime
of a star compared with its typical mode timescale
(ωT3 ~ 1015) ensures that even if initial conditions were synchronized like for the Universe, stochastic excitation would
almost immediately lead to loss of coherence.
To summarize, in Table 1 we contrast some of the features of
the Universe with those of the Sun.
TABLE 1
SUMMARY OF SIMILARITIES AND DIFFERENCES BETWEEN
CMBOLOGY AND HELIOSEISMOLOGY
Observation and interpretation of oscillations
At present, the instrument that has produced the most sensitive
full-sky maps of the CMB is the Wilkinson Microwave
Anisotropy Probe (WMAP) [5]. For the Sun, the analogous
instrument is the Michelson Doppler Imager (MDI) on board
the Solar and Heliospheric Observatory (SOHO) [11].
WMAP measures temperature differences on the sky with an
instrument located at the L2 Lagrange point of the Earth-Sun
system, which lies about 1.5 million km on the opposite side of
the Earth from the Sun. WMAP has an angular resolution of
0.22o, which means it can measure anisotropies up to ~ 800.
MDI measures the Doppler shifts of the gas in the solar photosphere on a spacecraft located at the L1 Lagrange point, which
lies at the same distance from the Earth as L2, but on the Sun
side. MDI has an angular resolution of about 0.0006o when
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observing the full solar disk, such that the pixel resolution on
the solar surface is around R3/500. However, since the Sun is
not an inside-out star, the origin for the spherical harmonic
coordinate system is the solar centre, and this means that MDI
can measure anisotropies out to ~ 1000. This is coincidentally similar to the WMAP resolution.
The solar oscillation spectrum in Fig. 3 was produced using
11 hours of nearly continuous high-resolution MDI solar
dopplergrams, consisting of one-minute integrations.
Helioseismologists studying such data have access to several
years of uninterrupted dopplergrams, but the basic information
is evident using this limited data set.
The information extracted from the modes has a different form
for each of the 2 fields we are comparing. In cosmology one
makes a CMB map, extracts the power spectrum of
anisotropies and typically uses a least-squares routine to fit a
cosmological model to the data. It is remarkable that only
6 parameters (within a simple isotropic, homogeneous framework) are needed to provide an excellent fit to WMAP data. In
helioseismology, fitting to the acoustic frequencies are often
computed using direct inversion techniques on the data. These
are then used to tune the solar model, where the ‘parameters’
include some unknown radial functions.
A POWER SPECTRUM OF THE SUN
CMBologists learn about the Universe from the CMB power
spectrum, because it contains almost all the useful information,
together with the fact that the linear perturbation theory is
remarkably simple. In contrast, the full theory for the amplitudes of helioseismic modes would have to be non-linear, and
hence is far from simple. Because of this, the amplitude information of solar modes is often set aside in order to focus on the
frequencies.
Nevertheless, we can ask what the mode power spectrum
would look like for the Sun, in analogy with the CMB C s. In
the solar -ν plot (Fig. 3) the ridges are p-modes with different
radial mode number, n, while the signal at lower temporal frequencies is dominated by convective and other noise effects.
This is mainly from convective granulation and supergranulation motions, and although these are interesting in their own
right, they will obscure the acoustic oscillations. We therefore
remove this low (temporal) frequency signal from the MDI
data before attempting to make a power spectrum. We do this
by cutting out everything in -ν that would lie below the surface sound speed (following [12]), which is the lowest speed at
which acoustic modes can propagate in the interior.
We can make an order of magnitude conversion to temperature
using a blackbody model for the luminosity: L = 4πR2σT4eff ,
where σ is the Stefan-Boltzmann constant. If for simplicity we
take L as constant over any oscillation, then ΔT/T V/2ωR3,
where V is an average of the velocity integrated over time, and
Fig. 4
Comparison of CMB and solar power spectra.
ω is the measured oscillation frequency. Performing this scaling to ‘temperature units’, integrating MDI data over all frequencies, and correcting for some instrumental efficiency
effects, gives the curve shown in Fig. 4. Remarkably, the CMB
power spectrum needs only to be scaled up by about an order
of magnitude in order to be comparable. This means that in
terms of ΔT/T amplitude the two power spectra are within
about a factor of three, although of course the shapes of the
2 curves are quite different.
CONCLUSIONS
We have shown interesting analogies between the fields of
CMBology and helioseismology. One could contrast more features B for example looking at the polarization information or
comparing details of how the Sun and the Universe have
changed over time. However, we have probably carried this
analogy far enough to be useful in understanding more of the
physics of both the CMB and the Sun.
As a final remark, we note that as well as learning about the
Sun through its acoustic structure, astrophysicists are also
beginning to learn about the interiors of other stars B the science of Asteroseismology. For example, since 2003 the
microsatellite MOST [13] has been studying low angular degree
modes in many nearby stars. If there is a further analogy to be
drawn here, it may be that each of these stars is like a separate
inside-out universe, and Asteroseismology is like studying the
multiverse!
ACKNOWLEDGMENTS
This research was supported by the Natural Sciences and
Engineering Research Council of Canada. We thank Chris
Cameron, Mark Halpern, Jaymie Matthews and Jim Zibin for
very useful conversations.
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REFERENCES
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
See e.g. Scott D., Smoot G.F., ‘Cosmic Microwave Background Mini-review’, in Yao W.-M. et al., ‘The Review of Particle Physics’,
J. Phys. G33, 1 [astro-ph/0601307], (2006), and 2007 web update at http://pdg.lbl.gov/
See e.g. Christensen-Dalsgaard J., ‘Helioseismology’, Rev. Mod. Phys., 74, 1073-1129 [astro-ph/0207403], (2003).
Hogan, C.J., Kaiser, N. Rees M.J., ‘Interpretation of anisotropy in the cosmic microwave background’, Philosophical Transactions of
the Royal Society of London, 307, 97-110, (1982).
Further discussion of the physics of CMB acoustic oscillations can be found in: Scott D., White M., ‘Echoes of Gravity’, Gen. Rel.
Grav., 27, 1023-1030 [astro-ph/9505102], (1995); Hu W., Sugiyama N., Silk J., ‘The Physics of Microwave Background
Anisotropies’, Nature, 386, 37-43 [astro-ph/9604166], (1997); Hu W., White, ‘The Cosmic Symphony’, Sci. American, 290, 44-53,
(2004). The web-page of Mark Whittle also has some interesting visuals and sound files on ‘Big Bang Acoustics’: http://www.astro.virginia.edu/ dmw8f/
See http://map.gsfc.nasa.gov/
See http://www.astro.caltech.edu/ lgg/boomerang_front.htm
See http://www.jb.man.ac.uk/research/cmb/vsa/
See http://www.stanford.edu/ schurch/quad.html
See http://www.astro.caltech.edu/ tjp/CBI/
See http://cosmology.berkeley.edu/group/swlh/acbar/
See http://sohowww.nascom.nasa.gov/
D. Georgobiani, J. Zhao and A. .G. Kosovichev, ‘Local Helioseismology and Correlation Tracking Analysis of Surface Structures in
Realistic Simulations of Solar Convection’, Astrophys. J., 657, 1157-1161, (2007).
See http://www.astro.ubc.ca/MOST/
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ARTICLE DE FOND
BUILDING A VISION
BY
FOR THE
FUTURE
OF
TRIUMF*
NIGEL S. LOCKYER AND TIMOTHY I. MEYER
T
he world economy is increasingly based on
knowledge as a driver of productivity. For the
foreseeable future, scientific discoveries and technological innovation will be the most powerful
engine for economic growth. Excellence in these areas
derives from substantial investments in state-of-art technical infrastructure and from the talents of highly skilled,
highly educated individuals. However, success and leadership in a knowledge economy requires much more. The
knowledge must be relevant and timely. TRIUMF,
Canada’s national laboratory for particle and nuclear
physics, is poised to help Canada be a leader in the science-and-technology knowledge economy.
TRIUMF is owned and operated as a joint venture by a
consortium of Canadian universities via a contribution
through the National Research Council Canada with building capital funds provided by the Government of British
Columbia. TRIUMF’s operations are supported in fiveyear funding increments. The present performance period
completes March 31, 2010. The forthcoming Five-Year
Plan reviews recent accomplishments, proposes a plan for
2010–2015, and summarizes the resource needs. In the
context of the laboratory’s mission, TRIUMF’s five-year
planning process has identified targeted opportunities that
are ripe for exploitation: they build on TRIUMF’s successes, play to Canadian strengths, and promise high-impact
results.
TRIUMF’s vision for the next decade brings together university, industrial, and international partners in three priority areas with the promise of true competitive advantage
(see Figure 1). The vision includes providing leadership
in the transforming field of nuclear medicine, building a
new superconducting accelerator for generating not-yetdiscovered heavy isotopes at Canada’s world-class isotope
beam facility, and participating fully in the international
Large Hadron Collider (LHC) project at CERN. All three
areas have potential for significant scientific, economic,
and societal impact.
SUMMARY
TRIUMF’s five-year planning process has
identified targeted opportunities that are ripe
for exploitation: they build on TRIUMF’s successes, play to Canadian strengths, and
promise high-impact results. The proposed
plan for 2010-2015 is summarized in this article.
Fig. 1
The TRIUMF Five-Year Plan in schematic form. The
proposed strategic initiatives will draw on TRIUMF’s
established partners and scientific expertise and will be
supported by new capital investments.
TRIUMF has been involved with Canada’s innovations in
nuclear medicine and at the forefront of this field for
decades: from one of the first PET scanners in the country
to study of the underlying biological mechanisms of
Parkinson’s disease to a 30-year partnership with MDS
Nordion for the production and distribution of 15% of
Canada’s medical isotopes. Nuclear medicine is undergoing a revolution and has great potential for dramatically
improving health care for all Canadians. TRIUMF’s work
to design “tracer” molecules or drugs and label them with
radioactive medical isotopes allows researchers to image
their location in the body with high precision. This breakthrough capability is penetrating into every area of disease
screening. It will soon be possible to image—and pinpoint—disease metabolism or cancerous tumour construction using positron-emission tomography (PET) imaging.
Monitoring tumour metabolism during cancer therapy or
even just monitoring where a drug goes in the body, will
transform medicine and treatment models. Canadians will
be able to access this high level of screening through PET
scans and a ready supply of medical isotopes connected to
various types of “designer” molecules. As radiotracerlabelled designer molecules and drugs become more spe-
Nigel S. Lockyer is
Director of TRIUMF.
Timothy.I. Meyer
<[email protected]>
is Head of Strategic
Planning and
Communications at
TRIUMF, 4004
Wesbrook Mall,
Vancouver BC
V6T 2A3
* Avant la mi-septembre 2008, une version française de l'article sera
disponible sur le site http://www.cap.ca/pic/pic-f.html (numéro de
juil.-sept. 2008).
8/18/2008
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... FUTURE OF TRIUMF (LOCKYER AND MEYER)
Fig. 2
Measurements of the two-neutron separation energy (S2n)
made at TRIUMF in late 2007 using the TITAN experiment
(right-most measurement in the figure). The S2n can be
derived from nuclear binding energies B via S2n(A,Z) =
B(A,Z) - B(A-2,Z), where A and Z denotes the mass and atomic number of the nucleus. These measurements not only show
that the world average AME 03 (“Atomic Mass Evaluation
2003”, G. Audi, A.H. Wapstra, C. Thibault, Nucl. Phys. A 729
337 (2003)) was inaccurate, but they also dramatically
improve the overall precision. The new weighted S2n is
shown as the upper grey band and in the detailed inset.
cific and target metabolic activity in the body more precisely,
the demand for these life saving technologies will soar. The
day will come soon when every hospital in Canada will insist
upon the ability to deliver a single-patient dose of a specific
radiotracer quickly and easily.
Medical isotopes produced with cyclotrons are typically complementary to those produced with nuclear reactors with the
former focusing on shorter-lived isotopes for PET and the latter focusing on those for SPECT. However, the capability for
producing 99Mo with an accelerator, for instance, is presently
being investigated by TRIUMF and a team of radiochemical
experts.
Fig. 3
Leading international rare-isotope beam facilities around the
world. The proposed US FRIB facility has not yet been sited.
science fiction could have imagined. TRIUMF brokered the
international partnership that has put Canadian scientists as
integral collaborators in the LHC project. The Canadian contributions to the accelerator, detector, and data centre are recognized throughout the international particle-physics community
as a measure of Canadian excellence (see Figure 4). The LHC
Tier-1 Data Centre provides Canada access to the technology
of global grid-computing in a leadership role. The accelerator,
detector, and computing systems are all working, commissioned and ready for data while Canadian graduate students are
preparing for discovery.
TRIUMF has a superb international reputation not just as a
subatomic physics laboratory but also as a laboratory that partners successfully with industry. Transferring technology to
Canadian business is a major goal of the 2010-2015 Five-Year
TRIUMF is home to a world-class rare-isotope beam facility,
ISAC. It is arguably one of the premier centres in the world,
and for specific species of beams, the best (see Figure 2). This
branch of nuclear physics has the potential to reach the scientific holy grail of a single unified theory of nuclei. The proposed expansion of TRIUMF’s isotope-beam facilities has the
potential for a triple impact: doubling the productivity of the
existing infrastructure and equipment, enabling a scientific
home run in the field of fundamental physics for Canada, and
studying the next generation of medical isotopes. The
European Union, France, Germany, Japan, and the US are all
seeking new major accelerator projects in this area; worldwide
investment exceeds $4 billion. TRIUMF has a lead position in
this pack and with the right investment, could become the top
institution in this field for a decade and beyond (see Figure 3).
The LHC project is expected to begin taking data in 2008-2009
and could fundamentally change the way we think about our
world. It may discover properties of space and time that only
120 C PHYSICS
IN
Fig. 4
The ATLAS detector at CERN’s Large Hadron Collider.
8/18/2008
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... FUTURE OF TRIUMF (LOCKYER AND MEYER)AA
pany, to transfer high technology. In early 2008, the team
announced the first “Made in Canada” superconducting radiofrequency cavity—only five other companies in the world have
this capability in what will become a globally competitive market.
This plan is bold: it calls for an investment of $328 million
from the Government of Canada over 2010-2015. This plan
takes full advantage of discovery potential, impact on society,
state-of-the-art technical infrastructure, a highly talented pool
of scientists, engineers, technicians, entrepreneurs, and graduate and undergraduate students.
Fig. 5
History of TRIUMF-driven investments, separated by source,
in five-year periods, including provincial contributions and
federal investments by NRC, CIHR, NSERC, and CFI. The
private-sector category totals activity directly attributed to
TRIUMF’s programs, such as sales of medical isotopes by
MDS Nordion using cyclotrons developed by TRIUMF.
Plan (see Figure 5). TRIUMF is known internationally for its
work with MDS Nordion, a global health and life-science company, with which it received the NSERC 2004 Synergy Award.
Another TRIUMF-inspired company, D-Pace, was awarded the
2007 Synergy Award. In 2008, TRIUMF received a National
Centres of Excellence award to create a commercialization
partner, AAPS, Inc. TRIUMF recently partnered with PAVAC
Industries, Inc., a small Canadian electron-beam welding com-
The full plan will be printed in late summer 2008 as a standalone report. Its preparation has taken a tremendous effort from
many sectors of the broader community for which we are grateful. From the earlier discussions more than two years ago to
the prioritization process undertaken by the all-university
Policy and Planning Advisory Committee to the individual
contributions, reviews, and suggestions, the Five-Year Plan
report is truly a group-consensus document. We had the privilege of presenting the plan to the CAP community at the June
2008 Congress at a special evening session.
The report proposal will be reviewed by an international committee of experts this fall and then formally transmitted to the
government in early 2009. It is our hope that the plan is as
inspiring and exciting to the Canadian scientific community as
it is for us.
TRIUMF LABORATORY APPOINTS INTERNATIONALLY RENOWNED PHYSICIST
TO TOP CANADIAN SCIENTIFIC POST -Lia Merminga joins world-leading physics research laboratory as Chief of Accelerator Division
On June 17, 2008, TRIUMF, Canada's national laboratory for particle and nuclear physics, announced the
appointment of Lia Merminga as the new Head of its Accelerator Division. This role is one of Canada's most senior scientific posts. With over twenty years of experience in accelerator physics, Merminga is a well respected
and preeminent physicist in the international scientific and research community.
Merminga is widely recognized for expertise in identifying problems and solutions associated with the push for
higher energy, higher quality accelerator beams, and developing concepts for new accelerators. Merminga has
also been recognized for maintaining and establishing collaborative teams for sophisticated national and international projects. At TRIUMF, she will be leading the Accelerator Division, which is the foundation of TRIUMF's
scientific excellence in nuclear physics and life-sciences technology.
Previously, Merminga worked as the Director of the Centre for Advanced Studies of Accelerators (CASA) at the
Thomas Jefferson National Accelerator Facility (Jefferson Lab) in Virginia, USA. Merminga was also responsible for establishing practices that supported and helped expand Jefferson Lab's strong program of mentorship and
training.
For more information, contact :
Timothy Meyer, Strategic Planning and Communications, TRIUMF
604-222-7674
[email protected]
July08-final-to-trigraphic-v4.qxp
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Page 122
BEST STUDENT COMPETITION WINNERS AT 2008 CONGRESS
STUDENT COMPETITIONS / COMPÉTITIONS ÉTUDIANTES
CONGRATULATIONS
(SEE EXTENDED ABSTRACTS OF SEVERAL WINNERS ON PAGES 123-143 PLUS PHOTOS ON PAGE 194 /
VOIR RÉSUMÉS DE PLUSIEURS GAGNANTS AUX PAGES 123-143 ET PHOTOGRAPHIES À LA PAGE 194)
The Canadian Association of Physicists has established these
awards to recognize student members giving the best oral and
poster research presentations at the annual CAP Congress. Up to
three awards in each category, each consisting of a certificate of
recognition and a prize of $300, will be made each year. In addition, a number of CAP Divisions offer prizes for the best student
presentations at the divisional level.
L'Association canadienne des physiciens et physiciennes a créé
ces prix afin de récompenser les membres étudiants auteurs des
meilleures communications au congrès annuel. Elle décernera
tous les ans un maximum de trois prix dans chaque catégorie,
chacun consistant d’un certificat de mérite et d’une somme de
300 $. De plus, plusieurs divisions offrent des prix pour leurs
meilleures présentations étudiantes.
Eligibility, selection procedure, and selection criteria for the competitions are available through the Congress website each year.
The full list of winners, including divisional prize winners and
honourable mentions, can be found on the CAP website, under
medals/awards.
Admissibilité, modalités et critères de sélection pour les prix sont
sur le site web de l’ACP. Le liste complète des gagnants et mentions honorables, incluant les prix aux niveaux divisionnels, se
trouvent sur le site internet de l’ACP, sous la rubrique
médailles/prix.
CAP AWARDS - POSTERS
NSERC AWARDS - BEST POSTERS BY FEMALE STUDENTS
Poster prizes included a certificate of recognition and a cash
award of $300 for top three placements. Book prizes generously donated by Pearson Education Canada were awarded to
each of the seven finalists.
NSERC poster prizes included a certificate of recognition and
a cash award of $300 .
PLACEMENT
NAME/AFFILIATION
PLACEMENT
NAME/AFFILIATION
First
Mathieu Gauthier, Université Laval
First
Véronique Zambon, Université Laval
Second
Véronique Zambon, Université Laval
Second
Nan Yang, Univ. of Western Ontario
Third
Antoine Allard, Université Laval
Honourable Mentions:
Philip Desautels, University of Saskatchewan; Harold Dehez, Université Laval; and Olivier LandenCardinal, Université Montreal
CAP AWARDS - ORAL PRESENTATIONS
NSERC AWARDS - BEST TALKS BY FEMALE STUDENTS
Oral prizes included a certificate of recognition and a cash
award of $300 for top three placements. Book prizes generously donated by John Wiley & Sons Limited were awarded
to each of the ten finalists.
NSERC oral prizes included a certificate of recognition and a
cash award of $300.
PLACEMENT
NAME/AFFILIATION
PLACEMENT
NAME/AFFILIATION
First
Michaël Dallaire, Université Laval
First
Jennifer Godfrey, Simon Fraser U.
Second
Andrew Croll, McMaster University
Second
Rhiannon Gwyn, McGill University
Third
Marc-Antoni Goulet, McMaster U.
Honourable Mentions:
Ahdiyeh Delfan Abazari, University of Calgary; Jonathan Ziprick, University of Manitoba; and
Ryan MacLellan, Queen's University. David Tessier, University of Windsor and Sayf Gamudi
Elgriw, University of Saskatchewan, were invited to participate in the finals but were unable to
attend.
Thanks to our generous sponsors / Merci à nos commanditaires généreux :
Pearson Education Canada
John Wiley & Sons Limited
and/et NSERC/CRSNG
and to the CAP’s Past President at that time, Dr. Melanie Campbell of the University of Waterloo, for her
efforts in organizing this event. Our thanks are also extended to all of the judges and competitors.
122 C PHYSICS
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ARTICLE DE FOND
The winners of the 2008 CAP Best Student Presentation Competitions at the CAP Annual Congress,
2008 June 8-11, in Quebec City, Quebec are listed on page 122. The extended abstracts of those
winners of the CAP and NSERC prizes who submitted them for publication are reproduced below. Ed.
GÉNÉRATION EXPÉRIMENTALE
GAUSS SPATIOTEMPORELS
PAR
DE FAISCEAUX
BESSEL-
MICHAËL DALLAIRE, NATHALIE MCCARTHY ET MICHEL PICHÉ
I
l n’est pas dans la nature des faisceaux laser de conserver leur taille et leur durée sur de très grandes distances de propagation, car la lumière est soumise aux
lois physiques de la diffraction et de la dispersion. On
peut cependant jouer d’astuce pour atténuer (et parfois
même compenser complètement) l’effet de ces lois en
combinant les effets non-linéaires à la dispersion et la diffraction pour obtenir notamment les solitons, ou encore en
structurant adéquatement le champ transversal pour
obtenir un faisceau Bessel quasi-invariant.
faisceaux Bessel transversaux, qui ont été proposés par
Durnin et al. en 1987 [3,4]. La figure 1a présente la distribution en intensité d’un faisceau Bessel transversal. On
obtient une telle distribution en intensité en faisant interférer une multitude d’ondes planes uniformes dont les
vecteurs d’onde sont disposés sur un cône d’angle 2θ.
L’équation suivante représente la distribution en intensité
du faisceau Bessel transversal:
Un nouveau type de paquet d’onde quasi-invariant appelé
faisceau Bessel spatiotemporel a récemment été proposé [1,2]. La distribution d’intensité de ce nouveau faisceau possède la propriété de ne pas subir les effets de la
dispersion ni de la diffraction. Cependant, il est impossible de générer expérimentalement une fonction de Bessel
pure étant donné les dimensions infinies de cette dernière.
Pour contourner ce problème, on a recours à une
enveloppe gaussienne, qui induit une légère variation de la
distribution du champ lors de la propagation, d’où le qualificatif de faisceau quasi-invariant. La section qui suit
présente les notions de base relatives aux faisceaux Bessel
et Bessel-Gauss spatiotemporels. La troisième section est
consacrée au montage utilisé pour générer expérimentalement ces faisceaux et les résultats expérimentaux sont
présentés à la dernière section.
où J0 est la fonction de Bessel de première espèce d’ordre
zéro, β0(=2π/λ0) est le nombre d’onde, α = β0θ est la composante transversale du nombre d’onde, et A0 est l’amplitude du champ. L’éq. (1) est indépendante de la distance
de propagation z, indiquant que ce faisceau serait parfaitement invariant.
FAISCEAUX BESSEL ET BESSEL-GAUSS
SPATIOTEMPORELS
Afin de bien comprendre la nature des faisceaux Bessel
spatiotemporels, il convient d’aborder en premier lieu les
RÉSUMÉ
On présente les éléments théoriques fondamentaux relatifs à de nouveaux faisceaux
invariants, le montage expérimental permettant leur génération ainsi que les résultats
confirmant leur synthèse.
2
2
I (r ) = A0 J 0 (β0 θr ) = A0 J 0 (αr ) , avec r = x 2 + y 2 (1)
Les anneaux du faisceau Bessel spatiotemporel ne se
situent pas dans le plan transversal à l’axe de propagation,
mais plutôt dans le plan
espace-temps (soit dans le
plan x-z) tel que présenté à
la figure 1b. Dans une telle
configuration, les anneaux
concentriques se déplacent
le long de l’axe z, d’où un
train d’ondes sur l’axe
optique et une distribution
spatiale au centre de l’impulsion correspondant à la
fonction de Bessel. Pour
décrire une telle distribution de champ, on définit
une variable radiale spatiotemporelle telle que:
ρ = x 2 − T / β0 β 2 ,
avec T = t - z / νg
(2)
où t est le temps, νg
représente la vitesse de
groupe, et β2 est le
Fig. 1
Distribution d'intensité
pour a) un faisceau
Bessel transversal et
b) un faisceau Bessel
spatiotemporel.
Michaël Dallaire
<michael.dallaire.1@
ulaval.ca>, Nathalie
McCarthy
<nathalie.mccarthy@
phy.ulaval.ca>,
Michel Piché
<mpiche@
phy.ulaval.ca>,
Centre d'optique,
photonique et laser
(COPL),
Département de
physique, de génie
physique et d'optique, Université
Laval, QC, Canada
G1V 0A6
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GÉNÉRATION EXPÉRIMENTALE ... (DALLAIRE ET AL.)
paramètre de dispersion du milieu de propagation, qui doit être
négatif pour que le rayon ρ soit réel pour toute valeur de x et de
T.
Comme la fonction de Bessel est une fonction infinie, on en
limite les dimensions spatiales et temporelles à l’aide d’une
enveloppe gaussienne spatiotemporelle. L’équation représentant la distribution du champ d’un faisceau Bessel-Gauss spatiotemporel (BGST) à l’étranglement (z = 0) est la suivante:
⎡
u BG (ρ, z = 0) = A0 exp ⎢ −
ρ2 ⎤
J
2 ⎥ 0
⎣ wst ⎦
(
aρ
)
(3)
où wst représente la taille spatiotemporelle de l’enveloppe
gaussienne et a est un paramètre de modulation permettant
d’ajuster la dimension des anneaux. La présence de l’enveloppe gaussienne induit une variation de la distribution du
champ lors de la propagation, telle que présentée à la figure 2.
Fig. 2
que la séparation temporelle provient de la
dispersion du milieu de
propagation. Ainsi, on
doit sélectionner les
fréquences
optiques
appropriées en fonction
de la position x, tel que
présenté à la figure 3.
Cette figure représente
donc le masque à utiliser
dans un modeleur spaFig. 3 Masque en réflexion utilisé
tiotemporel d’impuldans le modeleur d'impulsions; ce dernier doit
sions.
effectuer la transformée
de Fourier spatiale et temporelle des impulsions.
Le montage présenté à la figure 4 a été conçu dans le but de
générer un faisceau BGST à l’étranglement en effectuant la
Représentation de l'évolution du faisceau BGST le long de
l'axe de propagation.
La distribution du champ avant l’étranglement peut être vue
comme une multitude d’impulsions gaussiennes, distribuées
sur un anneau, qui convergent spatialement et temporellement
vers un centre commun qui se déplace à la vitesse de groupe.
Dès que les impulsions sont suffisamment rapprochées pour
interférer, les anneaux de la fonction de Bessel deviennent visibles, jusqu’à atteindre un maximum de contraste à l’étranglement (z = 0). Il est à noter que la taille des anneaux reste la
même aussi longtemps que ces derniers sont visibles. Ainsi, la
distance de Rayleigh d’un faisceau BGST est beaucoup plus
longue que celle associée à un faisceau gaussien ayant la taille
du lobe central du faisceau BGST, d’où le qualificatif de faisceau quasi-invariant. Si on laisse propager le faisceau BGST
au-delà de l’étranglement, les diverses impulsions gaussiennes
se séparent graduellement, de sorte qu’à partir d’une certaine
distance de propagation, ces dernières sont trop éloignées les
unes des autres pour interférer et il ne subsiste qu’un anneau
divergent.
Fig. 4
Modeleur d'impulsions spatiotemporel permettant de générer
des faisceaux BGST à l'étranglement.
Fig. 5
Traces d'autocorrélation expérimentale et théorique d'un faisceau BGST [1].
MONTAGE EXPÉRIMENTAL
C’est dans la distribution du champ après (ou avant) l’étranglement que réside la clé pour générer un faisceau BGST. Dans le
champ lointain, on obtient la transformée de Fourier spatiale et
temporelle du faisceau. En effet, la distribution annulaire du
champ est constituée de toutes les impulsions gaussiennes
séparées spatialement et temporellement. La séparation spatiale provient de la divergence naturelle des impulsions alors
124 C PHYSICS
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GÉNÉRATION EXPÉRIMENTALE ... (DALLAIRE ET AL.)AA
Fig. 6
Profils spatiaux a) théorique et b) expérimental obtenus à
l'étranglement d'un faisceau BGST.
transformée de Fourier du masque dans les domaines spatial et
temporel de façon indépendante. Une impulsion incidente,
émise par un laser femtoseconde Ti:saphir à une longueur
d’onde centrale de 800 nm, est dispersée spatialement par un
réseau. Le masque réfléchissant sélectionne les fréquences
adéquates en fonction de la position x et le réseau en effectue
la transformée de Fourier temporelle. La propagation s’effectue
ensuite jusqu’à une lentille cylindrique (#2) qui effectue la
transformée de Fourier spatiale. Ainsi, au plan focal de cette
lentille, on obtient la distribution en intensité correspondant au
faisceau BGST recherché.
Fig. 7
Spectre résolu spatialement: a) modèle théorique et
b) données expérimentales.
fonction de Bessel ne sont pas d’intensité nulle, tel qu’on peut
le voir sur les figures 6a et 6b.
De plus, on peut visualiser le faisceau BGST comme étant
constitué de trains d’impulsions dont la structure temporelle
varie selon la position x. Ainsi, on obtient une distribution
spectrale qui dépend de la position transversale, tel qu’illustré
à la fig. 7a. L’imagerie du spectre résolu spatialement présenté
à la fig. 7b, obtenue à l’aide d’un réseau et d’une caméra CCD,
concorde bien avec le modèle théorique.
CONCLUSION
RÉSULTATS EXPÉRIMENTAUX
Afin de vérifier si les faisceaux BGST produits expérimentalement correspondent au modèle théorique, on doit analyser la
structure spatiale et temporelle des impulsions générées, ce qui
ne peut se faire simultanément avec les diagnostics conventionnels d’analyse d’impulsions laser. La structure temporelle,
présentée à la figure 5 (tirée de [1]), a été obtenue à l’aide d’un
autocorrélateur de construction maison. Il est important de
noter que les autocorrélateurs n’ont aucune résolution spatiale;
la trace obtenue est donc la convolution temporelle de l’impulsion intégrée sur toute son étendue spatiale. En tenant compte
de ces considérations expérimentales, les résultats obtenus correspondent bien au modèle théorique.
L’analyse du profil spatial, présenté à la figure 6, permet également de constater un excellent accord avec le modèle
théorique. En imageant spatialement le faisceau à l’aide d’une
caméra CCD (figure 6b), on obtient un profil présentant une
distribution en intensité s’apparentant à une fonction de Bessel
altérée, étant donné que l’intégration se fait sur tous les
anneaux spatiotemporels. Il en découle ainsi que les zéros de la
L’approche présentée à la section 3, qui consiste à modeler une
impulsion femtoseconde dans les domaines spatial et temporel
de façon indépendante à l’aide d’un masque annulaire unique,
donne des résultats expérimentaux qui sont en bon accord avec
le modèle théorique, validant ainsi la notion de faisceau spatiotemporel quasi-invariant. L’impact de certains paramètres,
tels l’épaisseur de l’anneau, l’étendue spectrale utilisée et la
longueur focale de la lentille #2, devra être investigué afin de
valider davantage le modèle théorique. De plus, la propagation
quasi-invariante reste à être testée en présence de dispersion
anomale.
REMERCIEMENTS
Ces recherches sont appuyées financièrement par le Conseil de
recherche en sciences naturelles et en génie du Canada
(CRSNG), le Fond québécois de la recherche sur la nature et
les technologies (FQRNT) et l’Institut canadien pour les innovations en photonique (ICIP/CIPI).
RÉFÉRENCES
1.
2.
3.
4.
M. Dallaire, N. McCarthy, M. Piché, “Spatiotemporal Bessel beams”, Proc. SPIE, Vol. 6796, 67963O (2007)
M. Dallaire, M. Piché, and N. McCarthy, “Analysis and Generation of Spatiotemporal Bessel Beams,” Frontiers in Optics, OSA
Technical Digest, Optical Society of America, paper FWC2 (2007)
J. Durnin, “Exact solutions for nondiffracting beams. I. The scalar theory,” Journal of the Optical Society of America A (Optics and
Image Science) 4(4), 651-654 (1987)
J. Durnin, J.J. Miceli and J.H. Eberly, “Diffraction-free beams,” Physics Review Letters 58, 1499-1501 (1987)
8/18/2008
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FEATURE ARTICLE
BLOCK COPOLYMER LAMELLA: SIMPLE EXPERIMENTS
AND COMPLEX PHYSICS
BY
ANDREW B. CROLL, AN-CHANG SHI, KARI DANOLKI-VERESS, AND MARK W. MATSEN
P
olymers are molecules of exceptional aspect ratio.
The simplest are linear chains made of many
repeated molecular units known as monomers.
Often the number of monomers polymerized to
form a chain is so high that the aspect ratio can easily
exceed 106. As one might expect, this results in extremely
flexible molecules which form a tangled mass when in the
equilibrium fluid state (the melt), much like a pot of
cooked spaghetti noodles. The unique properties of this
disordered material leads to the ubiquity of polymers in
both industry and Nature [1].
In a melt one might then expect to find the physics governing the material behavior to be described directly by
the exceptionally large length of the molecules.
Remarkably this is not the case, as one must also account
for the conformational entropy of these flexible molecules. In fact, if one considers a generalized chain made up
of N segments of size a, where there is no longer any correlation between a segment at location n and n+1, the
result is a random walk [1-3]. In this description the most
relevant length is that of the end-to-end distance, Ree,
which, for a linear chain, is proportional to the radius of
gyration, Rg = a(N/6)0.5 (see fig. 1).
Andrew B. Croll
<crollab@mcmaster.
ca>, An-Chang Shi
Kari Dalnoki-Veress
<dalnoki@mcmaster.
ca>, Brockhouse
Institute for Materials
Research and the
Department of
Physics & Astronomy,
McMaster University,
Hamilton, ON
L8S 4M1
and Mark W. Matsen
<M.W.Matsen@
reading.ac.uk>,
Department of
Mathematics,
University of
Reading, Reading,
RG6 6AF, UK
While there are many novel polymer architectures that are
routinely synthesized by organic chemists, of these complex molecules block copolymers are likely the most studied. The simplest type of block copolymer is the diblock,
a molecule where two chemically distinct chains, A and B,
are joined together. As with any mixture of A and B molecules, diblock copolymer melts can be found in one of
two states – mixed or phase separated. In the mixed state
a diblock copolymer is not very different from that of an
ordinary homopolymer; the molecular size is well
described by the radius of gyration. When the interaction
between A and B becomes larger, micro-phase separation
takes place. That is, the molecules phase separate but the
126 C PHYSICS
SUMMARY
Here we describe an experiment that allows
characterization of the length scale of pattern formation in symmetric diblock copolymers. This experiment can lead to a deeper
understanding of these complex polymeric
materials.
IN
Fig. 1. Schematic representation of a Gaussian polymer chain.
The magnified insets show the various levels of structure B the monomer, and the well defined bond angles
between adjacent monomers. In the top right a simulated polymer chain is shown, the end to end vector (which
is proportional to Rg) is a grey arrow.
domains of A and B can only grow to molecular dimensions. The lengthscale is frustrated by the connectivity of
A and B which results in a nanostructured material.
The state of the material can be described by χN, where χ
is the Flory-Huggins interaction parameter that characterizes the A-B interaction. The Flory-Huggins parameter is
most easily understood as a combination of the enthalpic
interaction between A and B as well as an entropic contribution due to the localization of the A-B interface. χ is
therefore related to temperature in the phenomenological
form χ = C1/T + C2, where C1 is the enthalpic part, and C2
is the entropic part [3].
The resulting nanostructures have much in common with
those formed by lipids, containing micellular like, cylindrical and lamellar ordered regions. In the case of diblock
copolymers the morphology of the resultant structures is
determined by f, the ratio of the lengths of A and B. If both
blocks have the same length, the resulting structure will
resist curvature and will form long ranged lamellar (layered) order. In the ordered state diblocks must accommodate the entropy associated with the A and B chains as well
as the usual enthalpic interactions. It is this conflict
between chemical difference and entropy that govern the
final dimensions of the spontaneously formed nanoscopic
patterns (see fig. 2).
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BLOCK COPOLYMER LAMELLA ... (CROLL ET AL.)AA
In this work we
describe a simple
experimental
technique
for
measuring the
spacing of the
lamellar domains
formed by a symmetric diblock
copolymer melt.
This technique
yields unparalled
resolution
in
measurement of
the response of
the domains to
Fig. 2 Schematic diblock copolymer phase
changes in temdiagram showing the location of the
four most common phases. The perature, which
largest central region (nearly sym- allows for a very
metric molecules, above χN~10.5) simple measureof the
shows lamellar order. As the mole- ment
cules become less symmetric the Flory-Huggins
phase changes to hexagonally packed i n t e r a c t i o n
cylinders and then to face centered parameter
(χ).
cubic spheres. Below the curve the We also analyze
diblock remains in its isotropic disor- the dynamics of
dered phase [1,4].
the
molecular
motion, and show
that it is consistent with both our interpretation of the static
measure and current self-consistent field theory (SCFT).
In a typical experiment a thin diblock film is created by spincasting poly (styrene – 2-vinyl pyridine) (Polymer Source,
Montreal) from toluene solution on electronics grade silicon
wafers (University Wafer, U.S.A.) that have been cleaned by
super-critical carbon dioxide gas (Applied Surface
Technologies, U.S.A.) and UV-ozone treatment. Films of different thickness can be created by changing the weight percentage of the toluene solution or by manipulation of the angular
speed of the spin coater. A sample is then placed on a hot-stage
(Linkam Scientific, U.K.) which is purged with dry nitrogen
gas. The sample is then raised above the glass transition of the
diblock (~100ºC) and allowed to equilibrate.
The thin films are not likely to be commensurate with an integer number of lamella; hence the surface must break up into an
incomplete layer in order to accommodate the lamellar
microstructure [5]. For example, a film that is initially slightly
thicker than n lamella, will (upon heating above the glass transition) form n complete lamella, but the surface will be decorated by several ‘islands’ one lamella thick (see fig. 3).
Likewise, a film slightly thinner than n lamella will form n-1
complete lamella and a surface layer decorated with ‘holes’
1 lamella deep upon equilibration. These surface structures
provide an excellent window on the internal spacing of the
material.
The total area of the islands on a sample is a direct result of the
lamellar spacing. Consider a sample which has islands on its
surface in equilibrium at some low temperature. At low temperature entropy is less important than the enthalpic cost of the
interface between the A and B blocks, hence the molecular configurations will be extended away from the interfaceB they will
be tall and thin. At a higher temperature entropy is favoured at
the cost of more A-B interactions and a broader A-B interface
B the molecules will now be short and fat. Since volume is conserved as the temperature changes (note that thermal expansion
is very small in comparison with the effect discussed here and
can be ignored), the islands must increase in area as the temperature increases. Hence by simply observing a change in
area, we can accurately measure a change in lamellar thickness.
Fig. 3
Typical experimental data. Inset shows a film of n=4 with
islands on its surface at 140ºC (bottom left) and at 195ºC
(top right). Both images are 53x53 μm2.
Figure 3 shows a plot of lamellar thickness as a function of
temperature for a typical experiment. Here we have taken into
account the total sample thickness (the number of lamella
amplify the effect on the surface), the type of surface structure
(holes respond oppositely to islands) and have conserved volume. For example, the lamellar thickness is given by
L (T ) nA + na (T0 )
=
L (T0 ) nA + na (T )
Where the L is the lamellar thickness, n is the number of complete lamella in the film, A is the area of the microscope field
of view and a(T) is the area of the surface layer at a particular
temperature. With an external measure of the lamellar thickness at the reference temperature T0 (we use atomic force
microscopy) the result is an absolute measurement of lamellar
thickness. The quality of this data is important because it
allows the resolution necessary to determine that the lamellar
spacing does not depend on the proximity to a surface, and that
there is no difference between surface structures (islands or
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BLOCK COPOLYMER LAMELLA ... (CROLL ET AL.)
in good agreement with other more complex measurements [6,7,8]. Our experiment, however, offers the advantage of
a simple ‘in house’ measurement relying only on an optical
microscope.
Fig. 4. Area of surface layer as a function of time. The sample is
quenched from 180ºC to the temperature indicated above the
curve. The solid line is a fit to the function described in the
text, with additional instrumental drift taken into account.
holes) [6]. We also note that the thickness resolution would be
exceptionally difficult to achieve by atomic force microscopy
alone.
Currently the most accurate modeling of diblock copolymer
systems rely on the use of mean field theory. Here the conformations of a single chain are considered in a background field
created by all the other molecules in the material (see the article by A-C. Shi in [1]). Numerical implementations are highly
accurate and can easily predict the pattern spacing of a diblock
copolymer melt.
The data in figure 3 is fit by a quadratic approximation of the
self-consistent field theory lamellar thickness predictions [6].
The theory has one free parameter, and the results we obtain are
In order to verify our measurements we consider the dynamics
of the transition from one temperature to another. Once a sample has been quenched, molecules must move from one layer to
another in order for the system to relax to a new equilibrium
thickness. This molecular motion will be slowed by viscosity
and by the energy cost of moving an A block through an
unfavourable layer of B or vice versa. The data follows an
exponential relaxation of the area [6]. This relaxation curve is
shown as solid lines in figure 4. The time constant of the relaxation can be understood as a hopping of molecules from one
lamella to another and calculated from knowledge of viscosity,
our measured χ and SCFT. The agreement between theory and
experiment is excellent [6].
In conclusion, we have used a very simple optical technique to
measure the Flory-Huggins interaction parameter of a diblock
copolymer near its order-disorder transition. We verify our
understanding by considering the dynamics of the transition.
This technique opens the door for simple, accurate, measurement of internal structure of a diblock copolymer subjected to
any number of perturbations (phase transition, confinement,
polydispersity, nanoparticle-inclusions, etc.), which will
undoubtedly lead to a deeper understanding of the physics of
these materials.
ACKNOWLEDGEMENT
This work was supported in part by NSERC and the ACS
PRF which are gratefully acknowledged. ABC expresses his
gratitude to the NSERC Canadian Graduate Scholarship program for his funding.
REFERENCE
1.
2.
3.
4.
5.
6.
7.
8.
M. D’Iorio, G. Slater (ed.), Physics In Canada – La Physique au Canada, 59, (2003).
P.G. de Gennes, Scaling Concepts in Polymer Physics, Cornell University Press, 1979.
G. Strobl, The Physics of Polymers, Springer, 1997.
M.W. Matsen, M. Schick, “Stable and unstable phases of a diblock copolymer melt”, Phys. Rev. Lett., 72, 2260 (1994).
B. Collin, et. al., “Ordering of copolymer thin films as revealed by atomic force microscopy”, Macromolecules, 25, 1621 (1992).
A.B. Croll, et. al., “Kinetics of layer-hopping in a diblock copolymer lamellar phase”, submitted Physics Review Letters, (2008).
K.H. Dai, E.J. Kramer, “Determining the temperature-dependent Flory interaction parameter for strongly immiscible polymers from
block copolymer segregation measurements”, Polymer, 35, 157 (1994).
M.F. Schulz, et. al., “Phase behavior of polystyrene-poly(2-vinylpyridine) diblock copolymers”, Macromolecules, 29, 2857 (1996).
128 C PHYSICS
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ARTICLE DE FOND
FRICTION MEASUREMENTS
BY
ON
LIVING CELLS
MARC-ANTONI GOULET, MARIE-JOSÉE COLBERT AND KARI DALNOKI-VERESS
T
he phenomenon of biological adhesion is a necessary precursor to the formation of multi-cellular
organisms. Without adhesion, life would not have
evolved beyond the single-celled ‘primordial
soup’. Although micron sized objects do adhere to each
other due to colloidal interactions, these interactions are
isotropic in nature and therefore insufficient for a living
organism which needs to ‘choose’ its surroundings in
order to survive. In addition to the non-specific colloidal
interaction, living cells have various specific adhesion
mechanisms which enable them to bond preferentially to a
certain substrate or other cells. Studying the dynamics of
this active process is one of the ultimate goals of our
research and is relevant to the biomedical industry for
applications such as implant technology, where cellular
adhesion is essential to the success of the implant.
Although several experiments have studied the detachment force of a cell adhered to a substrate, few have
looked into the dynamics of bond formation in the first
place. An experiment performed by Goetz et al. involves
imaging a neutrophil rolling over endothelial tissue [1]. By
varying the shear stress applied by the viscous medium
they obtain different binding rates. In our measurements
we study the dynamics of adhesion as a living cell slides
across a substrate using a specially forged micropipette.
The micropipette technique used in this project was largely inspired by previous work from the groups of Evans,
Brochard-Wyart and several others [2-5]. Generally, their
experiments used micropipettes to manipulate and apply a
specific suction pressure to cells or vesicles. From the
variable pressure they are able to determine the surface
tension and adhesion energy. In our experiments we use
the micropipettes not only to manipulate the cells but also
as cantilevers to perform force measurements in much the
same way as the cantilever on an atomic force microscope [6]. This technique, similar to that used by Francis
et al. [7], provides a direct method of measuring force
without making any assumptions about the cell itself.
Fig. 1
Schematic of experimental setup.
In order to fully characterize the friction, we need to know
both the normal and shearing force between the cell and
substrate [8]. Here we use a very thin and flexible
micropipette to measure only the shearing force. The
micropipette is pulled to a length of about 1.5 cm and
outer diameter of 15 Fm. The pipette, filled with water, is
inserted into an open chamber containing the HeLa cells
as shown in Fig. 1. By controlling the height of a water
column connected to the micropipette, we create a gentle
suction pressure to hold the cell in place. The cell,
attached to the pipette, is manoeuvred into position next to
the substrate with a micro manipulator. The substrate is
mounted on a translation stage controlled by a computer.
For studying simple friction, we use a clean silicon substrate. With the use of the computer the substrate is pushed
into the cell, thereby compressing it slightly. Once the cell
and substrate are in contact, the substrate is moved parallel to the cell’s contact area, shearing it, and deflecting the
cantilever by a measurable friction force. Images of the
entire process are captured with an optical microscope.
Marc-Antoni Goulet
<gouletmf@
mcmaster.ca>,
Marie-Josée Colbert
<colberm@
mcmaster.ca>, and
Kari Dalnoki-Veress
<dalnoki@
mcmaster.ca>,
Department of
Physics and
Astronomy, McMaster
University, ON,
Canada, L8S 4M1
SUMMARY
A specially forged micropipette is used as a
cantilever to measure the friction force
applied to a living HeLa cell sliding along a
substrate.
Fig. 2
Optical images of a HeLa cell on a silicon substrate at
rest (left), and on a substrate moving upwards (right).
The mirror image of the micropipette and cell is due to
the reflective silicon substrate.
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FRICTION MEASUREMENTS ... (GOULET ET AL.)
and the cell begins to slide with respect to the substrate, relaxing to the steady state configuration corresponding to its kinetic friction value (B). When the substrate motion stops, the cell
relaxes further to another steady state value of static friction
(C). This process is then repeated in the opposite direction (D).
These trends are indeed observed in real measurements as
shown in Fig. 5. The most notable difference is the sharpness
of the static friction peak which is primarily due to the high
velocity of substrate motion. Using the calibration values
obtained for the micropipette the pipette position can be converted to a force measurement as shown in Fig. 5.
Fig. 3
Optical images of micropipette being deflected downwards
by the increasing weight of a water droplet.
To calibrate each the cantilever we apply a known force and
measure the deflection. In our approach we use the weight of a
water droplet and measure the deflection of the micropipette as
shown in Fig. 3. By tracking the position of the pipette and
volume of the droplet, we can use the known density of water
to plot the weight as a function of displacement. From the slope
the spring constant of the cantilever is obtained.
Fig. 5
Fig. 4
Schematic of pipette motion during friction experiment.
Although living cells are very complex objects, when looking
on the scale of the entire cell they behave much like soft materials in response to a physical deformation. Based on other
friction studies [9] of soft materials, we expect to see behavior
similar to that depicted in Fig. 4. As the substrate begins to
move, it shears the cell and drags the micropipette along to a
point of maximum static friction (A). At a maximum deflection the force on the cell is large enough to overcome adhesion
Pipette position and force vs. time for a substrate moving
100 μm at 0.7 μm/s.
The micropipette technique demonstrated here is a versatile
tool for measuring the shearing force applied to micron-sized
soft materials. Moreover, the non-invasive approach makes it
especially suitable for studying living cells. A variety of
improvements can also be made such as introducing a right
angle into the cantilever to measure the normal force and friction force simultaneously [7]. Coating the substrate with various materials provides opportunities for studying specific
adhesion interactions and the dynamics of friction of living
cells.
ACKNOWLEDGEMENTS
The authors thank Prof. Cecile Fradin for valuable discussions.
Financial support from NSERC and the ACS PRF are gratefully acknowledged.
REFERENCES
1.
2.
3.
4.
D.J. Goetz et. al., “Dynamics of Neutrophil rolling Over Stimulated Endothelium in Vitro”, Biophysical Journal, 66, 2202-2209
(1994).
E. Evans, “Analysis of adhesion of large vesicles to surfaces.”, Biophys J., 31, 425 (1980).
E. Evans, et al., “Detachment of agglutinin-bonded red blood cells. I. Forces to rupture molecular-point attachments.”, Biophys J.,
59, 849 (1991).
E. Evans, et al., “Sensitive force technique to probe molecular adhesion and structural linkages at biological interfaces.”, Biophys J.,
65, 2580 (1995).
130 C PHYSICS
IN
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FRICTION MEASUREMENTS ... (GOULET ET AL.)AA
5.
6.
7.
8.
9.
F. Brochard-Wyart, P.-G. De Gennes, “Détachement des vésicules adhesives.”, C. R. Physique, 4, 281 (2003).
M.-J. Colbert, et. al., “Measurement of the adhesion and elasticity of single cells using a novel micropipette-based technique”, to be
published, (2008).
G.W. Francis et. al., “Direct measurement of cell detachment force on single cells using a new electrochemical method”, Journal of
Cell Science, 87, 519-523 (1987).
M.-A. Goulet, et. al., “Friction measurements on living HeLa cells”, to be published, (2008).
T. Baumberger, C. Carroll, O. Ronsin, “Self-Healing Slip Pulses along a Gel/Glass Interface”, Phys. Rev. Lett., 88 (7), 0755091
(2002).
8/18/2008
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FEATURE ARTICLE
MAGNETIC FIELDS
BY
FROM
HETEROTIC COSMIC STRINGS
RHIANNON GWYN, STEPHON ALEXANDER, ROBERT BRANDENBERGER AND KESHAV DASGUPTA
S
TRING THEORY AND THE EARLY
UNIVERSE
This article discusses an attempt [1] to solve an
astrophysical problem using string theory. If string theory
is correct, it should hold at the very highest energies. We
can’t reach energies high enough to produce strings directly in our colliders, but we live in the remnants of a huge
once-off high-energy experiment: the universe. As shown
in Figure 1, we can extrapolate backwards from today’s
expanding and cooling to a hot and dense early universe in
which physics should be described by string theory.
It remains possible that a surviving macroscopic string
might be observed directly, but it is more likely that only
indirect evidence of this regime remains, waiting to be
decoded. A stringy origin for galactic magnetic fields is
one possible indirect cosmological application.
GALACTIC MAGNETIC FIELDS
Let us begin with the crime scene: our galaxy today. The
gaseous disc of the galaxy is known to contain a general
toroidal magnetic field with a strength of a few microgauss and which is furthermore coherent on scales of up to
a megaparsec [2-4]. That such a field is necessary for confinement of cosmic rays was first argued by Fermi [5], but
it also has crucial roles to play in stellar formation and the
dynamics of pulsars and white dwarfs [3].
Rhiannon Gwyn a
<[email protected]
.mcgill.ca>,
Stephon Alexander b
Robert
Brandenberger a
<[email protected].
mcgill.ca> and
Keshav Dasgupta a
<keshav@hep.
physics.mcgill.ca>,
a Department of
Physics, McGill
University, Montreal,
Quebec, H3A 2T8;
b Department of
Physics, Penn State
University, University
Park, PA 16802-6300
These fields have been observed elsewhere and are
believed to be ubiquitous in galaxies and galactic clusters.
In spiral galaxies like our own the coherence scale is comparable to that of the galactic disc [6]. There are no contemporary sources for these fields, and they cannot be primordial since their decay time is two orders of magnitude
less than the galactic lifetime of 1010 years [7]. Primordial
fields are fields that would have been present at the time
of galactic formation, condensing along with matter from
the gas clouds which collapsed to form galaxies. This
132 C PHYSICS
SUMMARY
If right, string theory should describe the
earliest universe. What cosmological fingerprints might survive? One possibility is
galactic magnetic fields descending indirectly from cosmic strings.
IN
Fig. 1
A brief history of the universe, with the big bang on the
left and our current universe on the right. Taken from
http://map.gsfc.nasa.gov/media/060915/index.html
(NASA/WMAP).
implies the existence of a mechanism for continual regeneration of galactic magnetic fields.
THE DYNAMO MECHANISM
The likeliest suspect is the dynamo mechanism. Turbulent
motions in the interstellar medium are rendered cyclonic
by the non-uniform rotation of the gaseous disc of the
galaxy. The so-called αω dynamo that results has been
shown to be responsible for regeneration and amplification of the magnetic field of the galaxy [7-10], and functions as shown schematically in Figure 2.
Any poloidal field (in
the meriodonal plane
B see diagram) that
is present will give
rise to azimuthal field
lines Bφ because of
the non-uniform rotation. At the same time
the cyclonic cell
shown will raise,
twist and distort the
azimuthal field line
into a loop with nonvanishing projection
in the meriodonal
plane, thus generating
a (dashed) poloidal
field line.
Fig. 2
A cyclonic cell.
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MAGNETIC FIELDS ... (GWYN ET AL.)AA
Thus we have an explanation for the continued generation of
galactic magnetic fields, but the relevant hydromagnetic equation contains no source term, or weapon. The dynamo still
requires seed primordial fields to amplify. These fields would
have been amplified during galaxy formation as well, so their
amplitude at the time of galaxy formation can be found to be
~ 10 −20 G. Furthermore, they should be coherent at the time of
galaxy formation. For a fundamental process to be responsible
for these seed fields, this coherence is a nontrivial condition,
since galaxies form at very late times from a particle physics
perspective. Structures on galactic scales can start to form at
teq, the time of equal
matter and radiation.
The relevant scale λgal is
approximately given by
the Hubble radius at this
time, H −1(teq), as shown
in Figure 3. Typical particle physics processes
will create magnetic
fields whose coherence
length is limited by
H −1(tpp ). A particle
physics solution that
scales
appropriately
until at least teq (with
H −1(t), or linearly in t) Fig. 3 The coherence problem.
is given by cosmic
strings [1].
COSMIC STRINGS
As the universe cooled, it underwent phase transitions in which
new vacua became available. Boundaries between different domains could have formed in the universe as different regions
cooled into different vacua, just as in a ferromagnet with
regions of different spin alignment bordering one another.
These boundaries are configurations of energy which are topologically stable, where the topology in question is that of the
vacuum manifold. They are called topological defects.
Depending on the topology of the manifold, defects of different dimensions can form. It is when an axial or cylindrical symmetry is broken that a linelike defect or cosmic string forms,
because the vacuum manifold is not simply connected. These
can be macroscopic, and are called cosmic strings. Thus cosmic strings are not fundamental strings, but topological defects
formed during phase transitions undergone as the universe
cooled [11-13].
During a phase transition, a network of strings will form, characterised by a parameter ξ which gives both the typical stringstring distance and the typical curvature radius of the strings.
Both infinitely long strings (strings with curvature radius larger than the horizon) and loops will be formed, since the long
strings can intercommute and form loops. A sufficiently small
loop will decay away via gravitational radiation, but the rate at
which strings can chop each other off into loops is limited by
the speed of light. What results is a scaling solution in which
the string properties, such as ξ (t), are all proportional to
the time passed [11,12]. This has been confirmed by simulations [14-18] and implies that if cosmic strings can produce magnetic fields they will be coherent over galactic scales at the
time of galaxy formation, thus solving our problem.
STRING THEORY EMBEDDING
Pion strings (which arise from chiral symmetry breaking in
QCD) are cosmic strings that possess the right coupling to electromagnetism to give rise to magnetic fields. The resulting
fields have been shown to be of the required strength and
coherence to serve as seed galactic fields [19, 20].
We have shown that this mechanism can be embedded in a
string theory setting [1], using so-called heterotic cosmic
strings. These are cosmic strings arising from suitably wrapped
five-dimensional M5-branes in the eleven-dimensional M-theory of which string theory (which exists in ten dimensions) is a
low-energy limit. The M5-branes are wrapped on 4 dimensions
to give rise to 1-dimensional objects (strings) in our 3 + 1dimensional world, which are identified with strings in heterotic string theory. This higher-dimensional construction is necessary to stabilise the strings, so that they can become macroscopic, or cosmic [21,22]. Charged modes propagate along the
heterotic string, making it possible to use the same coupling to
electromagnetism as in the pion string case.
Thus cosmic strings arising from string theory could have produced magnetic fields coherent on the scales required to serve
as primordial seeds of the galactic magnetic fields observed
today. This would by no means constitute a proof of string theory, but is an interesting application of it to the “real-world”
physics it might underlie.
REFERENCES
1.
2.
3.
4.
5.
6.
7.
S.H. Alexander, R.H. Brandenberger, K. Dasgupta and R. Gwyn, “Magnetic fields from heterotic cosmic strings”, soon to appear.
E.N. Parker, Cosmical Magnetic Fields: Their Origin and Their Activity, Clarendon Press, Oxford, 1979.
M.S. Turner and L.M. Widrow, “Inflation Produced, Large Scale Magnetic Fields”, Phys. Rev. D 37, 2743 (1988).
R. Beck, A. Brandenburg, D. Moss, A. Shukurov and D. Sokoloff, “Galactic Magnetism: Recent developments and perspectives”,
Ann. Rev. Astron. Astrophys. 34, 155 (1996).
E. Fermi, “On the Origin of the Cosmic Radiation”, Phys. Rev. 75, 1169 (1949).
L.M. Widrow, “Origin of Galactic and Extragalactic Magnetic Fields”, Rev. Mod. Phys. 74, 775 (2003) [arXiv:astro-ph/0207240].
E.N. Parker, “The Generation of Magnetic Fields in Astrophysical Bodies III. Turbulent Diffusion of Fields and Efficient Dynamos”,
Astrophys. J. 163, 279 (1971).
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MAGNETIC FIELDS ... (GWYN ET AL.)
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
E.N. Parker, “Hydromagnetic Dynamo Models”, Astrophys. J. 122, 293 (1955).
E.N. Parker, “The Generation of Magnetic Fields in Astrophysical Bodies I. The Dynamo Equations”, Astrophys. J. 162, 665 (1970).
E.N. Parker, “The Generation of Magnetic Fields in Astrophysical Bodies II. The Galactic Field”, Astrophys. J. 163, 255 (1971).
A. Vilenkin and E.P.S. Shellard, Cosmic Strings and Other Topological Defects, Cambridge University Press, 1994.
M.B. Hindmarsh and T.W.B. Kibble, “Cosmic strings”, Rept. Prog. Phys. 58, 477 (1995) [arXiv:hep-ph/9411342].
R.H. Brandenberger, “Topological defects and structure formation”, Int. J. Mod. Phys. A 9, 2117 (1994) [arXiv:astro-ph/9310041].
A. Albrecht and N. Turok, “Evolution Of Cosmic Strings”, Phys. Rev. Lett. 54, 1868 (1985).
A. Albrecht and N. Turok, “Evolution Of Cosmic String Networks”, Phys. Rev. D 40, 973 (1989).
D.P. Bennett and F.R. Bouchet, “Evidence For A Scaling Solution In Cosmic String Evolution”, Phys. Rev. Lett. 60, 257 (1988).
D.P. Bennett and F.R. Bouchet, “High Resolution Simulations of Cosmic String Evolution. 1. Network Evolution”, Phys. Rev. D 41,
2408 (1990).
B. Allen and E.P.S. Shellard, “Cosmic String Evolution: A Numerical Simulation”, Phys. Rev. Lett. 64, 119 (1990).
R.H. Brandenberger and X.M. Zhang, “Anomalous global strings and primordial magnetic fields”, Phys. Rev. D 59, 081301 (1999)
[arXiv:hep-ph/9808306].
D.B. Kaplan and A. Manohar, “Anomalous Vortices and Electromagnetism”, Nucl. Phys. B 302, 280 (1988).
K. Becker, M. Becker and A. Krause, “Heterotic cosmic strings”, Phys. Rev. D 74, 045023 (2006) [arXiv:hep-th/0510066].
E.J. Copeland, R.C. Myers and J. Polchinski, “Cosmic F- and D-strings”, JHEP 0406, 013 (2004) [arXiv:hep-th/0312067].
134 C PHYSICS
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ARTICLE DE FOND
TAKING CONTROL OF
BY
THE
FLAGELLAR MOTOR
MATHIEU GAUTHIER, DANY TRUCHON AND SIMON RAINVILLE
M
otility, the ability to move around in one’s
A great deal is known about the bacterial flagellum [6-9].
environment, is critical for most living cells.
Yet many important questions remain unanswered. The
Like most other swimming bacteria,
details of how the torque is generated are still unknown,
Escherichia coli (E. coli in short) swims by
and so is the mechanism by which the motor manages to
rotating helical filaments that can be up to 10 μm long [1].
shift abruptly from one direction of rotation to the other.
The body of E. coli (about 1μm in
This system is extremely rich, with
diameter by 2μm long) is randomly
new aspects continually being discovered with an average of about
covered, and its study is a very
4 filaments [2]. Each one is driven
active area of current research.
at its base by a rotary motor called
the bacterial flagellar motor (as
MOTIVATION AND EXPERillustrated in Fig. 1). The energy
IMENTAL SETUP
source for this amazing machine of
The bacterial flagellar motor is a
nanoscopic dimensions is the profairly complex machine; it is made
ton flux across the membrane [3].
of ~ 20 different kinds of proteins,
The work that can be done by a
and it requires 40-50 genes for its
proton diffusing from the outside to
expression, assembly and control [8].
the inside of the cell is called the
Furthermore, it needs to be embedprotonmotive force (a combination
ded in the multiple layers of the bacof the electrical potential and pH
difference across the membrane). Fig. 1 Schematic representation of the bacterial terial membrane to assemble and
function properly. That explains
E. coli’s flagellar motors can spin at
flagellar motor. The bacterium E. coli
a speed of up to ~350Hz in either
has many flagella randomly distributed why, unlike many other molecular
the counterclockwise or the clockon its body. At the base of each filament, motors, it has not been studied in
a rotary motor of ~ 45nm in diameter is vitro, that is, in an artificial system
wise direction. This allows the cell
imbedded in the three layers of the bac- outside of the living cell. As spectacto perform a random walk in three
terium’s membrane. The filament is ular studies of linear motors have
dimensions. In a process called
linked to the motor by a flexible hook clearly demonstrated, an in vitro syschemotaxis, receptors on the surthat allows the filament to rotate about tem provides the essential control
face of the cell detect the concenan arbitrary axis. The moving parts of over experimental parameters to
tration of molecules of interest
the flagellum (the rotor) are colored in
achieve the precise study of the
(sugars, amino acids, etc.) and,
dark grey. The different rings that anchor
motor’s physical and chemical charthrough a remarkably simple chain
the motor in the membrane and the
of biochemical components, they
torque generating units (the stator) are in acteristics. For example, the stepcontrol the probability that a motor
light grey. Protons power the motor by ping behavior of kinesin, myosin
diffusing through the torque generating and dynein has been resolved in
reverses its direction of rotation
units where their protonmotive force is vitro using optical traps, thus providand that the cell changes its trajecconverted into torque.
ing much information about these
tory [4,5]. If the cell is swimming
motors’ mechanochemical cycles
towards a source of nutrients, the
and working mechanisms [10-12]. Our
probability for a change of trajectogoal is therefore to develop an in vitro system to study the
ry is decreased. By biasing its random walk, E. coli activeflagellar motor.
ly finds favourable regions in its environment.
SUMMARY
Progress towards the development of an in
vitro system to study the bacterial flagellar
motor using an adaptation of the patchclamp technique and laser nanosurgery.
Our in vitro assay improves upon a previous attempt by
Fung and Berg [13]. As illustrated in Fig. 2, the system
consists of a filamentous E. coli bacterium (~75μm long)
partly squeezed inside a glass micropipette. The
micropipette is fabricated so that a constriction with an
inner diameter of around 1μm (matching the outer diameter of the bacteria we study) is present near its tip. Outside
the micropipette, the rotation of one (or many) flagellar
Mathieu Gauthier
<mathieu.gauthier.5
@ulaval.ca>, Dany
Truchon <dany.
[email protected]>,
Simon Rainville
<simon.rainville@
phy.ulaval.ca>, Center
for Optics, Photonics
and Lasers;
Department of
Physics, Engineering
Physics and Optics,
Université Laval, QC,
Canada, G1V 0A6
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... FLAGELLAR MOTOR (GAUTHIER ET AL.)
Fig. 2
The in vitro assay. a) Diagram of our in vitro assay showing
the tip of the micropipette with a filamentous bacterium
squeezed in the constriction. To artificially power the motor,
an electrical voltage is applied between one electrode backinserted in the micropipette and a second electrode placed in
the bath; b) Brightfield image of a typical micropipette with
a bacterium in the constriction; c) Still frame from a movie
showing fluorescently labelled filaments whose rotation is
under the control of an external voltage. Scale bars are 10μm.
motors can be monitored. Compromising the cell membrane
inside the micropipette creates the artificial assay we are looking for by giving us complete electrical and physical access to
the inside of the cell. This opens the door to easy labelling of
internal components of the flagellar motor and allows us to
expose the motor to known concentrations of various molecules that affect the motor’s behaviour. Moreover, the application of a voltage between the inside and outside of the
micropipette changes the electrical potential that powers the
motor, thereby modifying its rotation speed.
To achieve the localized damage to the cell membrane that our
in vitro assay requires, we use the process of laser ablation with
ultrashort laser pulses. When laser pulses from a femtosecond
laser are tightly-focused on the part of the bacterium that is
located inside the micropipette, a submicrometer-sized hole is
vaporized in the wall of the bacterium. The ablation occurs
when plasma is produced at the focal spot by a highly non-linear process which allows for an ablation diameter below the
diffraction limit (< 300nm) [14-17]. Very little energy is actually
deposited in the medium and, thus, thermal damage to the surrounding biological structures is minimal. In practice, to
achieve the desired ablation, we use around 100 pulses from an
attenuated NIR femtosecond laser (790nm, 60fs pulse duration,
10kHz repetition rate, ~10nJ per pulse) focused with an 1.3 NA
objective. We have experimentally characterized the hole made
by the laser pulses by directly imaging pierced bacteria using a
scanning electron microscope. Holes in the membrane of about
200nm in diameter were observed.
Our experimental setup, based on a modified Olympus IX71
inverted microscope, is shown schematically in Fig. 3. The
femtosecond laser pulses used for ablation are inserted in the
optical axis of the microscope with a dichroic mirror and
focused on the sample with the same objective that is used for
imaging. A typical sequence of events for setting up an in vitro
assay is as follows. A selected bacterium is partly sucked into
the micropipette by applying negative pressure via a large
syringe. Once in place, the rotation of the bacterium’s filaments
is confirmed using fluorescence imaging. A standard patch-
136 C PHYSICS
IN
clamp amplifier is used to
control the electrical voltage
across the bacterium’s membrane and to measure the current flowing between the electrodes (providing a measure of
electrical resistance). A voltage of about -75mV is applied
before (and during) the laser
ablation to avoid defunctionalisation of some to the motors’
proteins [18]. A mechanical
shutter is then opened for
10ms to allow a burst of femtosecond laser pulses into the
microscope and perform laser
ablation of a small portion of
the cell membrane inside the
micropipette. Finally, we vary
the applied voltage in order to
confirm we have control over
the proton-motive force that
powers the motors.
Fig. 3
The experimental setup.
The femtosecond laser
pulses are introduced in
the optical axis of our
inverted microscope
with a dichroic mirror
(DM) and then focused
on the sample with a
100x high NA objective. The same objective is used to image
the specimen in bright
field or epifluorescence
microscopy onto a CCD
camera.
As a quality measure, the electrical resistance between the
bacterium’s membrane and the
glass of the micropipette is
continuously monitored and
Table 1 shows the typical
resistance measured at various
stages of an experiment. The
electrical seal between the cell and the micropipette is judged
to be good when the resistance remains high after laser ablation
(compared to when both ends of the cell are pierced).
TABLE 1
ELECTRICAL RESISTANCE BETWEEN
THE TWO ELECTRODES IN VARIOUS SITUATIONS
For the experiments reported here, we have used the E. coli
strain HCB1661 (provided by H.C. Berg). That strain contains
a mutated filament protein FliCT236C in which a cysteine was
introduced by site directed mutagenesis. This allows specific
labelling of the filaments with Alexa Fluor 546 C5-maleimide
(Invitrogen, A10258) that is used to visualize the rotation of the
motor with fluorescence microscopy. Cells are grown to midexponential phase in Tryptone Broth containing 50μg/ml
cefalexin, a β-lactam antibiotic that suppresses septation. After
incubating with the fluorophores for a few hours, cells are
washed and resuspended in motility buffer (10mM potassium
phosphate, 0,1mM EDTA, 10mM lactic acid, pH 7,0).
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... FLAGELLAR MOTOR (GAUTHIER ET AL.)AA
EXPERIMENTAL RESULTS AND WORK IN
PROGRESS
Our experimental results using the in vitro assay are still preliminary, but show unambiguously that we can take control of
the flagellar motor. We have recorded many sequences of
images like the one shown in Fig. 3c) while alternating the
applied voltage between 0 and about -75mV. These movies
clearly show that turning the applied voltage on and off results
in restarting or stopping the flagellar motors. We found that the
assay is stable for at least 15 minutes. Beyond that time, the
electrical seal around the cell is decreasing (as observed
in [13]) and this compromises our control over the flagellar
motors. To increase the electrical seal resistance and the lifetime of a cell preparation, we are trying to embed the tip of the
micropipette (with the bacterium) in a partly cured RTV silicone bubble [19].
To provide us with a quantitative measure of the filaments’
rotation speed (which should be around 100Hz), we are buying
a faster and more sensitive camera. Another serious limitation
of the current setup is photobleaching of our fluorescent probe
which limits us to a few minutes of continuous observation. To
circumvent this problem, novel methods to monitor the rotation
of the motor are being implemented (use of quantum dots, gold
nanoparticles, etc.). The small size of these probes will allow
us to study the regime where the load on the motor is near zero,
a regime that has been a lot less studied experimentally, and to
investigate the stepping behaviour of this motor [20].
CONCLUSION
In summary, we have recently made significant progress
towards the development of an in vitro assay to study the bacterial flagellar motor. The system consists of a filamentous cell
squeezed into a custom-made micropipette. A stable hole is
punched in the cell membrane inside the micropipette using a
burst of femtosecond laser pulses. By varying an external voltage applied between the inside and the outside of the
micropipette, we have been able to stop and restart the flagellar motors located outside of the micropipette. For these preliminary results, the rotation of the motors was observed using
video microscopy of fluorescently labelled filaments. By providing physical access to the inside of the cell and control of
the motors’ energy source, this assay opens the door to many
new experiments. We are confident that it will enable us to
probe in more details the working mechanisms of the bacterial
flagellar motor and possibly other membrane-bound systems
that are difficult to isolate.
ACKNOWLEDGMENTS
We are indebted to Howard C. Berg and members of his laboratory at Harvard University for their support (NIH grant number AI016478). This project was begun by S.R. as a postdoctoral fellow in his laboratory (in collaboration with Aravinthan
Samuel). Funding for this work is provided by Natural
Sciences and Engineering Research Council of Canada
(NSERC) and Fond Québécois de la Recherche sur la Nature et
les Technologies (FQRNT).
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8/18/2008
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FEATURE ARTICLE
ÉCRITURE
DE STRUCTURES PHOTONIQUES À L’AIDE DE
FAISCEAUX BESSEL
PAR
VÉRONIQUE ZAMBON, NATHALIE MCCARTHY ET MICHEL PICHÉ
D
Véronique Zambon
<veronique.zambon.1
@ulaval.ca>,
Nathalie McCarthy
<nathalie.mccarthy@
phy.ulaval.ca> and
Michel Piché
<michel.piche@
phy.ulaval.ca>,
COPL, Département
de physique, de
génie physique et
d’optique,
Université Laval,
Québec, Canada,
G1V 0A6
urant la dernière décennie, il a été observé que
la focalisation d’impulsions femtoseconde peut
altérer de façon permanente l’indice de réfraction dans différents types de verre. Ce changement d’indice est attribué à la densification locale du verre
ainsi qu’à la formation de défauts suite à la déposition
d’énergie causée par l’absorption multiphotonique en
champ laser intense. Un tel phénomène rend possible le
modelage de l’indice de réfraction d’un matériau selon un
motif tridimensionnel déterminé; cette technique fut utilisée pour fabriquer différents composants photoniques
tels des guides d’ondes [1], des coupleurs [2] et des
cristaux photoniques [3]. Ces composants ont été fabriqués avec des faisceaux gaussiens focalisés par une
lentille. Les faisceaux Bessel ultra-rapides, obtenus par la
focalisation avec un axicon, constituent une alternative
intéressante pour la fabrication de structures et composants photoniques. Un axicon [4] est une lentille de
forme conique qui permet d’obtenir un faisceau optique
dont le profil transversal du champ électrique est décrit par
une fonction de Bessel d’ordre 0. Le profil de tels faisceaux Bessel est caractérisé par un lobe central étroit avec
un diamètre de quelques micromètres qui demeure invariant sur des distances de l’ordre du centimètre. Par la
focalisation, à l’aide d’un axicon, d’impulsions femtoseconde dans du verre de silice, nous avons induit un
changement positif d’indice de réfraction le long de la
ligne focale de l’axicon; cette ligne correspond à la distance sur laquelle le profil du faisceau Bessel est invariant.
Dans cet article, nous allons décrire comment nous avons
utilisé cette technique pour fabriquer différents types de
guides d’ondes optiques dans du verre de silice.
FOCALISATION AVEC UN AXICON
Les axicons sont des miroirs ou lentilles de forme conique.
Un faisceau Bessel d’ordre zéro J0(k(n−1)r tan α) serait
obtenu par la transmission d’une onde plane uniforme à
travers un axicon réfractif de dimensions infinies. Bien
entendu, cette condition n’est pas physiquement réali-
I (r , z ) = 2πk (tan 2 α )(n − 1) 2 zI 0e − 2( n −1)
2
z 2 tan 2 α w02
× J 02 (k (n − 1)r tan α )
(1)
où r et z sont les coordonnées radiale et longitudinale
respectivement, I0 est l’intensité au centre du faisceau
gaussien incident sur l’axe, w0 est la taille du faisceau incident, k est le nombre d’onde (k = 2π/λ), n est l’indice de
réfraction et α, l’angle de l’axicon (voir figure 1). L’angle
de propagation β des rayons est simplement calculé par la
loi de Snell :
β = arcsin(n sin (α)) - α.
(2)
La profondeur de champ L du faisceau Bessel fondamental ainsi produit et la position radiale r0 du premier zéro de
la distribution transversale de l’intensité dépendent des
paramètres de l’axicon et sont données par :
L = w0 tan (90o - (arcsin(n sin (α)) - α))
r0 = 2.4048 / [ k (n - 1) tan α ].
(3)
(4)
Les axicons produisent des faisceaux Bessel avec une
grande profondeur de champ comparativement aux faisceaux gaussiens focalisés par une lentille. L’intensité est
cependant moins concentrée lors de la focalisation avec un
axicon. En effet, l’axicon permet de limiter l’intensité de
RÉSUMÉ
Des guides d’ondes optiques ont été inscrits
dans le verre de silice en focalisant des
impulsions femtoseconde à l’aide d’un axicon.
138 C PHYSICS
sable. Par contre, il est possible d’obtenir un faisceau se
comportant comme un faisceau Bessel d’ordre zéro sur
une distance de propagation finie. En pratique, on utilise
un faisceau gaussien collimé pour illuminer un axicon. La
distribution d’intensité produite par un faisceau gaussien
collimé traversant un axicon peut être calculée avec l’intégrale de Huygens-Fresnel en faisant intervenir l’approximation de la phase stationnaire [5]. L’intensité du profil
du faisceau focalisé par un axicon est donnée, près de
l’axe, par l’expression:
IN
Fig. 1
(a) Focalisation avec un axicon. (b) Profil transversal du
faisceau Bessel fondamental.
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... STRUCTURES PHOTONIQUES ... (ZAMBON ET AL.)AA
Fig. 2
Techniques couramment utilisées pour l’inscription de guides d’ondes avec des faisceaux gaussiens
focalisés par un objectif de microscope : (a) écriture parallèle; (b) écriture perpendiculaire.
(c) Inscription de guides d’ondes à l’aide de faisceaux gaussiens focalisés par un axicon.
la tache focale à une valeur beaucoup plus faible qu’avec une
lentille, évitant ainsi le bris du matériau dans lequel est focalisé un faisceau laser de haute puissance.
METHODES D’INSCRIPTION DE GUIDES
D’ONDES
L’inscription de guides d’ondes dans du verre à l’aide de lasers
femtoseconde repose généralement sur l’utilisation de faisceaux gaussiens focalisés par une lentille ou un objectif de
microscope. L’indice de réfraction est ainsi modifié dans un
volume confiné autour du point focal. La fabrication d’un
guide d’ondes est réalisée en translatant parallèlement ou perpendiculairement l’échantillon par rapport au faisceau incident
(figures 2a et 2b). L’écriture parallèle est limitée par la distance de travail de la lentille alors que l’écriture perpendiculaire produit des guides d’ondes elliptiques et biréfringents à
moins d’utiliser un faisceau avec un astigmatisme approprié.
L’approche que nous avons développée consiste à utiliser un
axicon pour focaliser les impulsions femtoseconde à l’intérieur
de l’échantillon de verre (figure 2c). L’indice de réfraction est
modifié le long de la mince ligne focale de l’axicon sans avoir
besoin de translater l’échantillon pour obtenir des guides d’ondes cylindriques. En translatant l’échantillon de verre à une
vitesse constante durant le processus d’inscription, il est possible d’induire une variation d’indice de réfraction le long d’un
mince plan de façon à produire des guides d’ondes plans.
Les axicons produisent des faisceaux Bessel avec une
grande profondeur de champ et un lobe central étroit et intense;
ce lobe central est entouré d’anneaux concentriques d’intensité
beaucoup plus faible. Les interactions non-linéaires qui conduisent à l’altération permanente de l’indice de réfraction dans
le verre se produisent majoritairement dans le lobe central et
sont négligeables dans les anneaux du faisceau Bessel. La
focalisation avec un axicon pour l’inscription de guide d’ondes
a l’avantage de distribuer le foyer sur une ligne (> 1cm) d’une
largeur de quelques micromètres; cette propriété permet d’utiliser toute la puissance disponible de sources laser femtoseconde commerciales opérant à une cadence d’émission de l’ordre du kHz. De plus, puisque le faisceau Bessel possède une
symétrie circulaire, des guides d’ondes cylindriques sans
biréfringence détectable sont attendus. Une autre propriété
intéressante des faisceaux Bessel est leur particularité à se
régénérer après une perturbation locale [6]. En effet, si l’on
considère géométriquement
l’effet d’un obstacle sur l’axe
optique, on observe une
reconstruction du faisceau à
une certaine distance au-delà
de l’obstacle. Cette particularité provient du fait que le
faisceau Bessel est construit à
partir de l’interférence de
toutes les parties du faisceau
incident qui sont réfractées
par l’axicon à un angle β.
RÉSULTATS EXPÉRIMENTAUX
Trois différentes sources laser femtoseconde ont été utilisées
pour l’inscription des guides d’ondes : deux chaînes laser
Ti:saphir de cadences d’émission de 1 kHz et 5 kHz, où les
impulsions sont amplifiées par la méthode de dérive de
fréquence (CPA pour chirped pulse amplification) ainsi qu’un
amplificateur paramétrique optique (APO) pompé par une
chaîne Ti:saphir fonctionnant à 100 Hz. Les chaînes laser
Ti:saphir émettent à une longueur d’onde centrale de 800 nm
alors que l’APO peut être accordé de 1200 à 1500 nm tout en
conservant une énergie par impulsion de l’ordre du millijoule.
Les impulsions femtoseconde sont focalisées à l’aide d’un axicon dans l’échantillon de verre. Les axicons que nous avons
utilisés sont fabriqués à partir de verre SiO2 ou de BK7 et possèdent des angles α de 5°, 10° et 20°. Nous avons utilisé deux
différents types de verre pour inscrire des guides d’ondes :
SiO2 et BK7. Toutefois, une altération permanente de l’indice
de réfraction menant à la formation de guides d’ondes n’a pu
être observée que dans le SiO2.
Des guides d’ondes de bonne qualité ont été obtenus avec
l’APO et les chaînes Ti:saphir. Pour caractériser les guides
d’ondes, un laser à He-Ne émettant un faisceau gaussien à
633 nm est couplé à l’intérieur des guides d’ondes à l’aide d’un
objectif de microscope de 10x. L’image en champ lointain du
faisceau transmis est observée sur un écran. La distribution
d’intensité en champ proche est obtenue en imageant le faisceau à la sortie du guide d’ondes sur une caméra CCD.
La figure 3 illustre les distributions en champ lointain des faisceaux couplés à la sortie de deux guides d’ondes, l’un cylindrique et l’autre plan. Le mode couplé ainsi que la section
transversale des guides d’ondes sont aussi montrés. Les franges
d’interférence des images en champ lointain représentent l’interférence entre le faisceau couplé et le faisceau direct. Le
mode fondamental LP01 se propage dans le guide d’ondes
cylindrique. L’efficacité de couplage augmente avec le nombre
de tirs (c’est-à-dire le temps d’inscription pour la fabrication du
guide d’ondes), mais au-delà d’un certain nombre de tirs, le
guide d’ondes devient multimode. Si le temps d’inscription est
trop long, il y a une dégradation de la qualité du guide d’ondes.
Lors de la fabrication des guides d’ondes plans, la vitesse de
translation pendant l’inscription va influencer directement
l’altération d’indice de réfraction. C’est avec une vitesse de
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... STRUCTURES PHOTONIQUES ... (ZAMBON ET AL.)
du faisceau couplé à la sortie de guides cylindriques
est la même que celle du faisceau incident ; les
guides produits sont exempts de biréfringence, conséquence de la symétrie circulaire du faisceau Bessel.
CONCLUSION
Fig. 3
Image en champ proche, mode couplé et section transversale (a) d’un guide
cylindrique (b) d’un guide plan. Le guide cylindrique a été inscrit à une
longueur d’onde de 1300 nm après 3000 tirs avec des impulsions d’énergie
de 0.66 mJ en utilisant une axicon de 10° en SiO2. Le guide d’ondes plan a
été inscrit à une longueur d’onde de 800 nm à une vitesse de translation de
30 μm/s avec des impulsions de 0.5 mJ à une cadence d’émission de 5 kHz
et en utilisant un axicon de 10° en BK7.
30 Fm/s que nous avons obtenu le meilleur confinement du
faisceau à l’intérieur du guide d’ondes. Le diamètre des guides
d’ondes cylindriques est typiquement de 5 Fm. En mesurant la
divergence du faisceau couplé dans le champ lointain, nous
avons pu évaluer un changement d’indice de l’ordre de 1x10-3.
De plus, en imageant la face de sortie du guide d’ondes de 1 cm
de longueur sur une caméra CCD, nous avons évalué l’efficacité de couplage entre 60 et 70%. À l’aide d’une lame demionde et d’un polariseur, nous avons vérifié que la polarisation
Les faisceaux Bessel ultra-rapides, générés par la
focalisation d’impulsions femtoseconde avec un axicon, présentent plusieurs avantages comparativement
aux techniques directes d’inscription de guides d’ondes, dont l’utilisation de toute la puissance disponible
de systèmes commerciaux opérant à quelques kHz
sans causer de bris dans le matériau où on focalise le
faisceau. La méthode que nous avons développée est
simple et efficace. Les guides d’ondes cylindriques
ainsi fabriqués présentent de faibles pertes et ne possèdent aucune biréfringence détectable. Des travaux
futurs visent la fabrication de dispositifs photoniques
tels des coupleurs.
REMERCIEMENTS
Ce travail a été financé par le Conseil de recherches
en sciences naturelles et en génie du Canada
(CRSNG), le Fond québécois de la recherche sur la nature et
les technologies (FQRNT) ainsi que l’Institut canadien pour les
innovations en photonique (ICIP/CIPI). Nous remercions
INRS-EMT et ALLS pour l’utilisation de leurs équipements et
pour leur assistance lors de nos expériences.
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IN
July08-to-trigraphic-final.qxp
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ARTICLE DE FOND
VISCOELASTIC PROPERTIES OF POLY (VINYL ALCOHOL)
NANOFIBRES AND HYDROGELS MEASURED BY ATOMIC
FORCE MICROSCOPY
BY
NAN YANG, JOHN R.
DE
BRUYN AND JEFFREY L. HUTTER
C
haracterizing the mechanical properties of soft
materials is important for a range of applications
such as wound dressings, vascular grafts, tissue
scaffolds and sensors [1–4]. Because these materials are viscoelastic, they not only store elastic energy
when deformed, but also dissipate energy like a viscous
fluid.
Traditionally the viscoelastic properties of a material are
determined from measurements of the shear modulus G,
which is defined as the ratio of shear stress to strain. G can
be written as G = GN + GO, where GN is the elastic (storage) modulus and GO is the viscous (loss) modulus. If an
oscillatory shear strain with a small amplitude γ0 and frequency ω is applied, the resultant shear stress τ is given by
τ (t) = γ0 [GN (ω) sin (ωt ) + GO (ω) cos (ωt)],
(1)
function of position. Mahaffy et al. extended this method
to allow frequency-dependent measurements [8] by applying a vertical oscillation to the sample and measuring the
amplitude of the cantilever deflection.
Here we present an alternative approach, in which we add
an oscillatory signal to the feedback electronics of the
AFM and measure the amplitude of the resultant oscillation of the scanner. The advantages of this technique over
conventional methods are that the measurements can be
done in normal imaging mode, the set-up and analysis are
simpler, and the excitation frequency can be easily controlled, allowing the frequency dependence of the viscoelastic properties to be measured.
To test this technique, we measured the viscoelastic properties of two materials composed of poly(vinyl alcohol)
(PVA): electrospun nanofibres and PVA/water hydrogels.
where both GN and GO are functions of frequency.
This kind of measurement has been used successfully for
homogenous bulk materials, but does not allow for local
measurements of viscoelastic properties in inhomogeneous systems or in systems with nanometer length scales.
The atomic force microscope (AFM) has previously been
used to measure the local mechanical properties of soft
samples, including bone marrow [5], gelatine [6,7], polyacrylamide gels [8], platelets and living cells [8,9]. One
common technique, known as the force-spectrum
method [10], is to displace the sample vertically through a
known distance while measuring the resulting deflection
of the AFM cantilever. The difference between these two
distances is equal to the deformation of the material surface and can be used to calculate the elastic properties of
the sample. By measuring force spectra at several locations on a grid, a force-volume (FV) image is obtained,
and the mechanical properties can be determined as a
MODIFICATION OF AFM ELECTRONICS
The function of the AFM feedback electronics is to maintain a constant cantilever deflection y(t) by adjusting the
height z(t) of the scanner when the tip moves across the
surface of a rough sample. We modified the feedback loop
by adding a small sinusoidal voltage to the deflection signal of the AFM through a circuit consisting of an adder
and inverter, resulting in an apparent additional deflection
of Sqeiωt, where S (in units of nm/V) is a calibration factor
and the amplitude q is ~ 0.1 V. This causes the scanner to
move up and down to compensate for this apparent deflection. This resultant oscillatory motion of the scanner can
be detected by a lock-in amplifier. In our experiment, a
digital lock-in amplifier implemented in LabView was
used to detect the amplitude and phase of the scanner
motion. Maps of the amplitude and phase response were
conveniently recorded as images alongside the conventional AFM height image.
Nan Yang
John R. de Bruyn
<[email protected]>
and Jeffrey L. Hutter
Department of
Physics and
Astronomy, University
of Western Ontario,
London, Ontario,
Canada, N6A 3K7
ANALYSIS AND RESULTS
SUMMARY
We describe a technique for investigating
viscoelasticity using atomic force microscopy and use it to measure the properties
of poly(vinyl alcohol) nanofibres and hydrogels.
Frequency dependent mechanical modulus of PVA
nanofibres
As a first test of this technique, we produced PVA nanofibres by electrospinning from an aqueous solution onto a
grid, as shown schematically in Fig. 1. The deformation δ
of such a suspended fibre in response to a force applied at
position x is linear in the applied force F and is given by
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VISCOELASTIC PROPERTIES ... (YANG ET AL.)
3
δ=
F ⎡ x( L − x) ⎤
= CF ,
3IE ⎢⎣ L ⎥⎦
(2)
where L is the length of the fibre, I its area moment of inertia,
and E its Young’s modulus. The compliance C of the fibre thus
depends on position x of the measurement.
The
bending
force
of the
cantilever
is
related to its
deflection y(t) by
Hooke’s
law:
F = –ky (t). The
fibre de-formation is δ = z (t) –
Fig. 1 Suspended fibre of length L deflected y (t), allowing
by a vertical force F at point x.
the
Young’s
modulus to be
determined from the slope dy/dz of the force spectrum, as has
previously been shown[10].
When we apply our oscillatory technique to suspended PVA
nanofibres, the resultant oscillation of the scanner is
z(t) = qS (1 + Ck)ei(ωt+π) = z0ei(ωt+ϕ) ,
(3)
where k is the force constant of the AFM cantilever. We measure the amplitude z0 and phase ϕ (relative to the external oscillatory signal) using the lock-in amplifier. As expected, z0
changes with position along the fibre while the phase is constant. By fitting z0 as a function of x to the model of eq. (2), we
can determine the Young’s modulus E of the fibre.
Fig. 2 shows AFM images of (a) height and (b) oscillation
amplitude for a fibre of diameter 137 nm and length 3.50 μm
suspended across a gap. The oscillation amplitude is larger in
the middle of the fibre where it is freely suspended than where
it is supported by the substrate. The data corresponding to
Fig. 2(b) are plotted in Fig. 3. The circles are the oscillation
amplitude z0 from all pixels within 50 nm of the midline of the
fibre, with distance from the midline indicated by the size of
the circle. The solid curve is the best fit to the clamped-beam
model represented by eq. (2). From this fit, we extract a
Young’s modulus for this fibre of 4.04 ± 0.06 GPa, which is in
agreement with
the value of
4.3 ± 0.2
GPa
that we obtain
from the traditional FV technique.
The oscillation
technique allows
the viscoelastic
properties
of
fibres to be investigated as a function of frequency.
Fig. 4 shows the
frequency
dependent modulus of a PVA
nanofibre with
suspended length
of 4.15 μm and
diameter
of
179 nm. When
the
frequency
increases from
500 Hz to 1000
Hz, the modulus
increases. It is
noteworthy that a
straight line fit to
the oscillatory
data extrapolates
to zero-frequency
within
experimental uncertainty to the value
measured with
the
traditional
force-volume
technique.
Fig. 3
Oscillation amplitude (circles) for
positions along the suspended fibre
shown in Fig. 2. The solid curve is the
best fit to Eq. (2).
Fig. 4
Young’s modulus (squares) of a PVA
fibre as determined by the oscillatory
method plotted as a function of excitation frequency. The circle is the
Young’s modulus derived from the FV
technique. The dashed line is a fit to
the oscillatory data only.
VISCOELASTICITY OF PVA HYDROGELS
PVA hydrogels were created from 12 wt% PVA solutions by
freeze/thaw cycling, as described previously[4]. A polystyrene
bead of diameter 8 μm was glued to the end of an AFM cantilever. The deformation δ of a viscoelastic surface due to such
a spherical contact is described by the Hertz model[11,12] as
F=
Fig. 2
142 C PHYSICS
AFM images of (a) height and (b) oscillation amplitude
for a fibre of suspended length 3.50 μm and diameter
137 nm. The solid line in (b) is the centerline of the
fibre.
IN
4
KR1/ 2 δ3 / 2 ,
3
(4)
where R is the radius of the bead, and K is E/(1B ν 2 ) where ν
is the Poisson ratio. K will in general be complex, reflecting
both viscous and elastic contributions to the complex modulus
E, and be a function of frequency ω. When an oscillatory signal qeiωt is added to the deflection of AFM cantilever, the force
can be expanded around an average deformation δ0 as
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VISCOELASTIC PROPERTIES ... (YANG ET AL.)AA
4
K 0 δ30 / 2 R1/ 2 + 2 K * R1/ 2 δ10/ 2 δ* .
(5)
3
The second term is the time dependent oscillation
force and δ* is the oscillatory deformation of the surface about the average deformation. The resultant
time-dependent oscillatory movement of AFM scanner is
F=
z * (t ) = z0 ei ( ωt + ϕ) = qS (1 +
k
1/ 2
1/ 2
2 K * R δ0
)ei ( ωt + π ) ,
(6)
where z0 is the amplitude and ϕ is the phase delay of
the scanner compared with the external oscillation
qeiωt. By comparing this amplitude with that obtained
on a rigid substrate, we can determine the complex
modulus K*= E(ω)/(1B ν 2 ), and thus E(ω), as a function of the frequency of the applied oscillation.
Fig. 5
Fig. 5 is a plot of the frequency-dependent complex
Young’s modulus of a PVA hydrogel subjected to
four thermal cycles during fabrication. We see that the mechanical response at low frequency is dominated by the storage
modulus and at high frequency by the loss modulus. We performed this test at different points on the surface of the same
hydrogel and found that although the moduli had the same
trend with frequency, the magnitudes varied by 24%. This indicates that PVA hydrogel is inhomogeneous, which is consistent
with previous reports [4].
CONCLUSIONS
Frequency-dependent mechanical properties of PVA nanofibres
and PVA hydrogels were measured using an AFM with modi-
fied feedback electronics. We found
that the modulus of the PVA fibres
increased with frequency, and
extrapolating the data to zero frequency produced values in good
agreement with measurements
made using the static method. This
shows that static measurements are
not sufficient to fully characterize
the mechanical properties of PVA
nanofibres. Viscoelastic effects are
even more evident in PVA hydrogels. Our results for the frequency
Complex Young’s modulus of a dependence of the complex moduPVA hydrogel as a function of lus show that the storage modulus
frequency. Squares: storage dominates the viscoelastic response
modulus EN; triangles: loss of these materials at low frequency,
modulus EO; filled circles: mag- while the loss modulus dominates at
nitude of the complex modulus. high frequency. This technique was
easy to implement by adding an
oscillatory voltage to the feedback
loop of the AFM with an external circuit. The main advantages
of this technique over conventional techniques for using the
AFM to measure mechanical properties are that it can be done
in imaging mode, simplifying the set-up and analysis, and that
the excitation frequency can be easily varied.
ACKNOWLEDGEMENTS
We acknowledge K. Wong for preparation and SEM imaging of
the nanofibres, NSERC for research funding and the Centre for
Chemical Physics, UWO, for travel support.
REFERENCES
1.
A.L. Yarin, S. Koombhongse, D.H. Reneker, “Bending instability in electrospinning of nanofibers”, J. Appl. Phys., 89, 3018
(2001).
2. L. Huang, K. Nagapundi, E.L. Chaikof, “Engineered collagen–PEO nanofibers and fabrics”, J. Biomater. Sci. Polym. Ed., 12,
979 (2001).
3. A. Theron, E. Zussman, A.L. Yarin, “Electrostatic field-assisted alignment of electrospun nanofibres”, Nanotechnology, 12,
384 (2001).
4. L.E. Millon, M.P. Nieh, J.L. Hutter, W.K. Wan, “SANS Characterization of an Anisotropic Poly(vinyl alcohol) Hydrogel with
Vascular Applications”, Macromolecules, 40, 3655 (2007).
5. N.J. Tao, S.M. Lindsay, S. Lees, “Measuring the microelastic properties of biological material”, Biophys. J., 63, 1165 (1992).
6. M. Radmacher, M. Fritz, P.K. Hansma, “Imaging soft samples with the atomic force microscope: gelatin in water and
propanol”, Biophys. J., 69, 264 (1995).
7. J. Domke, M. Radmacher, “Measuring the Elastic Properties of Thin Polymer Films with the Atomic Force Microscope”,
Langmuir, 14, 3320 (1998).
8. R.E. Mahaffy, C.K. Shih, F.C. MacKintosh, J. Käs, “Scanning Probe-Based Frequency-Dependent Microrheology of Polymer
Gels and Biological Cells”, Phys. Rev. Lett., 85, 880 (2000).
9. M. Radmacher, M. Fritz, C.M. Kacher, J.P. Cleveland, P.K. Hansma, “Measuring the viscoelastic properties of human platelets
with the atomic force microscope ”, Biophys. J., 70, 556 (1996).
10. G. Guhados, W.K. Wan, J.L. Hutter, “Measurement of the Elastic Modulus of Single Bacterial Cellulose Fibers Using Atomic
Force Microscopy”, Langmuir, 21, 6642 (2005).
11. I.N. Sneddon, “The relation between load and penetration in the axisymmetric boussinesq problem for a punch of arbitrary profile”, Int. J. Eng. Sci., 3, 47 (1965).
12. K.L. Johnson, K. Kendall, A.D. Roberts, “Surface Energy and the Contact of Elastic Solids”, Proc. Roy. Soc. Lond. A, 324, 301
(1971).
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DEPARTMENTAL MEMBERS / MEMBRES DÉPARTMENTAUX
- Physics Departments / Départements de physique (as at 2008 August 1 / au
1er
août 2008)
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(as at 2008 August 1 / au 1er août 2008)
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144 C PHYSICS
IN
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ENSEIGNEMENT
RESOURCE COMPARISON
PHYSICS DEPARTMENTS
BY
OF
CANADIAN
ROBERT L. BROOKS
S
hortly after becoming chair a few years ago, our
administration commenced an exercise in “strategic planning” which could be cynically looked at
as, which units can we cut and by how much?
The details of this exercise are unimportant as every institution goes through these challenges from time to time and
invariably physics departments wind up being compared
to ones in the arts, social sciences or the veterinary college. But if a colleague leaves a physics department it will
rarely be to join one of these comparison departments.
Rather she would go to some other physics department
and the relevant issue is not how our teaching loads compare with those in History but how do they compare with
our competition? With these thoughts in mind, at the
annual chair’s meeting of the CAP in 2006, I suggested
conducting a poll and presented a number of questions
I thought would be interesting to have answered. The
other chairs seemed to be in agreement. They made some
suggestions for changes and additions to my suggested list
of questions, and promised they would reply to an electronic poll when queried. I used a survey from our central campus computing facility which proved more problematic than I might have anticipated. Several respondents had to submit more than once. I did have a lot to
learn about surveys and wound up having to do a lot of
manual compilation for a number of reasons which would
be nice to minimize if this were done again.
er response would be desirable. Part of the reason for
writing this article is to stimulate enough interest in the
results to do it again but better. One important category
that I expressly did not ask was the level of external grant
support received by the departments. Some years ago,
when most grants were individual ones, that number had
much better validity than it has today. Compounding the
difficulty is that grant support of departments and universities themselves, has become a bragging issue. The way
money is apportioned in fact can differ by a large degree
from the way it is apportioned by bean counters. The official value used by the university for a given department
often counts money being spent on the other side of the
country and the relevance of the figure to the department’s
bottom line is dependent on the allocation for distributing
overheads and indirect costs, which themselves differ
wildly among institutions. I wanted to try to use numbers
that had meaning for comparison purposes and while the
importance of external grants cannot be overstated I felt
the numbers I would receive would have little value for
comparison.
Ultimately, nineteen physics departments responded and
I promised the chairs that if I got twenty or more responses I would write up the results. My original idea was that
only those who responded would see the results and the
incentive for participating was reception of the final
spread sheet. I then promised that if the results were written up they would be done in a summary manner so that
the results of any individual department would remain
unknown. A number of chairs have commented to me that
doing this survey on an ongoing basis would be worthwhile and if it were to be done even one more time a larg-
Robert L. Brooks
<rbrooks@uoguelph.
ca>, Professor and
Past Chair of
Physics, University of
Guelph, Guelph,
Ontario N1G 2W1.
SUMMARY
The results of a survey among 19 physics
departments in Canada are presented comparing enrolments, staffing and teaching
requirements.
Fig. 1
Survey sent to physics departments across Canada.
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RESOURCE COMPARISON ... (BROOKS)
THE PARTICIPANTS
I did get a very reasonable cross-section of Canadian
physics departments. In fact, I received a reply from at
least one in every province. Eight were from smaller institutions, the kind Macleans would call primarily undergraduate. The rest were from larger ones, and interestingly, my first cut as to which was which contained one in
each category that belonged in the other. My first attempt
to define “smaller” used the number of faculty and the
number of undergraduate physics students but when
I looked at the number of graduate physics students I realized I had made a mistake. So the demarcation between
smaller department and larger department is whether there
are fewer than 15 physics graduate students or more than
30. No respondent had a graduate enrolment between
those numbers. One consequence is that one member of
the “larger” group had fewer faculty than a member of the
“smaller” group but the replies to the other questions were
consistent with the groups determined by graduate enrolments.
tion of the first year class goes on to second year in
physics and that judgment could then be used. The number of graduate students is much easier to determine but
you can note that the distinction between the mean and the
median is quite large. Four universities with large graduate programs responded which caused those numbers to
skew.
STAFF SUPPORT
While the questionnaire asked for responses relating to a
number of categories of staff support, I shall limit Table 2
to just clerical, undergraduate laboratories, and total.
TABLE 2
Departmental Staffing
TABLE 1
Overview of the Participants
Table 1 shows the ”demographics” of the participating
universities. Because samples of 8 and 11 are small,
I have given the range, mean and median of the replies
which should enable the reader to get a good idea of the
validity (or lack) of the responses and of my comments
relating to them. It is not a good idea to try to guess which
university gave which response. The questionnaire, which
is reproduced in a box within this article, also contained a
page of explanatory material which is not reproduced.
There I commented on the difficulty of even giving the
number of faculty. There are CRC’s, special research
chairs, joint-appointed faculty, contractually limited and
sessional appointments and any number of complications
that make counting bodies difficult. Basically, I left that
up to the chairs with a few suggestions from me. We all
know who we think of as faculty (the phone list?). They
were free to comment or to ask me my opinion.
The number of undergraduates was not easy to determine.
The question called for majors and often students in first
year have not declared. History might dictate what frac-
146 C PHYSICS
IN
That the smaller universities would have 3 to 4 staff members in support of their efforts with half of that in the
undergraduate labs is not a surprise. That most of the
smaller schools exist with a single secretary, who must be
a true Jack of all Trades, shows how lean we have become
in our modern times. One question I wanted to answer
was whether staffing of the larger departments scaled with
the number of faculty or the student enrolments as I compiled them. I can imagine all of the chairs who read this
smiling to themselves and thinking that staffing levels correlate with nothing but historical accidents. My data can’t
confirm that but do indicate that there is no correlation
between staffing and faculty numbers or student enrolments. One would look for the ratio under consideration
to be nearly constant among the universities but in fact it
differs by over a factor of three among the universities for
each of the three categories. One cannot forget that faculty grants are not included. The fact that many grants
demand accountability might explain at least some of the
wide range of staffing levels seen in this survey.
One further comment worth making is that several departments share staff resources among other units in their faculty or college. Since nearly all of the staff numbers are
small (median of 13), if even a few positions are shared it
makes a noticeable difference on the graph shown on the
next page.
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RESOURCE COMPARISON ... (BROOKS)AA
For example, on its web site, the University of Guelph
claims 17,484 full time undergraduate and graduate students and 830 faculty. The ratio of 21.1 would then be the
norm for that university and departmental comparisons
could be made with that value in mind. At the University
of Victoria the ratio is 24.7 while at Trent it is 25.9. These
are the only ones I checked. I would have thought that a
number in the low 20’s would be rather normal for both
large and small universities so it seems noteworthy that
Table 3 above shows a significant difference between
them. That is almost certainly related to large universities
having large first year physics classes in large lecture halls
while small institutions do not enjoy that advantage of
scale. (What they enjoy is a more personal learning environment for their students!)
Fig. 2
Staff ratios for larger physics departments
TEACHING
Teaching comparisons (Table 3) were certainly among the
most important reasons for performing this survey. That
the smaller universities teach more (4.4) than the larger
ones (2.8) was expected. That teaching requirements
within a single cohort would be so similar was unexpected. But first a few comments on the data.
TABLE 3
Teaching Duties
The first number in the table is the student to faculty ratio.
To understand how this was obtained you have to imagine
taking the total student enrolment at a university and
dividing by the total faculty. That would give an institutional student to faculty ratio. Administrators are then
interested in whether a given department falls above or
below that value. Some departments do a lot of teaching,
some do a lot of research, some have an equal emphasis on
both. Some disciplines attract students from nearly the
entire campus and do a lot of service teaching (mathematics) while others typically don’t (engineering). If one
takes the count of all of the students being taught in all of
the (semester) courses offered by a department, then
divides by 10 (as the usual full time load for a student is
five courses per semester), and then divides by the number
of faculty in the department, one obtains the number in the
table. This is the department’s number which should be
comparable to the university’s number obtained as
described above.
The numbers of 17 or 12 for student to faculty ratios are
significantly lower than the university averages but one
might expect this since our discipline is physics. The
range for both the large and small universities is quite
large so there are exceptions to this generality. Are the
largest universities so “fat” with researchers that they have
the smallest ratios? In general, the answer is no, as 3 of
the 4 largest have a ratio at or above the median value of
17. My conclusion, after looking at all of the data, is that
the student to faculty ratio must be determined by the
amount of service teaching performed by the department
since it in no way correlates with the number of physics
undergraduates.
The teaching loads for physics departments are more similar within a category than any other number compiled.
The average teaching load is 4.4 semester courses for the
smaller departments and 2.8 for the larger ones. I also
asked for the minimum teaching load and did specify that
it was to be the “normal” minimum but I suspect several
chairs did not know what I meant. To clarify the intent,
I first need to describe the distinction between a variable
and fixed teaching load. Many departments today allow
their faculty to choose the amount of teaching (within
some specified range) they want to perform and the question relating to minimum teaching was asking for the
value at the low end of the range. If the teaching load
were fixed, this question would have no meaning.
All but four departments said they used a variable teaching load but for those four with fixed amounts of teaching
(two from large schools and two from small) a “normal”
minimum would have no meaning since everyone has the
same teaching to perform. Of course, there are the exceptions relating to research chairs, administrators, and so on.
Those exceptions tend to lower the average and so it is
easy to understand the results from one of the large departments that said its teaching load was fixed at 3 and had an
average load of 2.8. The minimum teaching category is
meaningful only for those with variable teaching loads.
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RESOURCE COMPARISON ... (BROOKS)
For such departments, with some faculty teaching four or
even six semester courses, the average teaching can be
larger than the minimum even though there are chairs and
administrators teaching less than the minimum. Hence,
the average teaching load was higher than the minimum
for a bit more than half of the departments but lower for
most of the rest.
Among the 11 larger departments there was a correlation
of average teaching load with faculty numbers. The six
largest departments by faculty number had an average
teaching load of 2.4 semester courses while the five smaller departments averaged 3.2. There was no such (anti)correlation among the 8 smaller departments. I suspect this
statistic claims the obvious: research intensiveness cannot
be performed by faculty with large teaching loads. But
even here one has to realize that one of the six largest
departments is the one mentioned previously with a fixed
teaching load of 3 semester courses and an average of 2.8.
One further question asked in the survey was the fraction
of courses not taught by faculty (ranged from 0 to 36%)
and whether one could buy out teaching. Three of the
larger departments with a higher than median student to
faculty ratio had the lowest values for their average teaching but also had the largest fraction of courses not taught
by faculty ($ 30%). One of the larger departments had the
highest student to faculty ratio of all departments, had the
highest average teaching load and had a small fraction
(11%) of courses not taught by faculty. These numbers all
make sense and reflect differing philosophies among university administrators. There is enormous pressure today
to have faculty in front of all classes and to treat teaching
on an equal footing with research for promotion and
tenure. I suspect the variations seen in this survey reflect
the degree to which various administrations encourage
such an agenda.
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These issues are connected to the notion of teaching faculty. The survey did not gather any direct information on
this question and the matter is complicated by whether
contractually limited term appointments are or are not
considered faculty. Even as librarians often have a different salary grid from faculty, in some institutions lecturers
have a different grid from normal faculty. This survey did
not address this issue but a future one might. Of course
regular faculty, specializing in teaching, are becoming
more common even at the larger universities and the fact
that most respondents had an average teaching load higher than the minimum might indicate widespread adoption
of this practice.
CONCLUSION
I have tried to summarize the results of a survey taken last
year (2007) among chairs and heads of physics departments in Canada. With a total sample size of 19 it might
be difficult to defend the results as statistically significant
but they did come from a broad cross-section of departments by both size and geography. The respondents were
each given the detailed results of the survey which could
be used to argue for increased resources should their relative position be unfavourable. I also asked the respondents to point out any errors in the detailed tables that
I had compiled. This article first described the demographics of the respondents and then summarized the
results by separating the returns into “smaller” and “larger” departments and has looked at both staff complements
and teaching requirements.
ACKNOWLEDGMENTS
Thanks are extended to E. McFarland, E. Poisson and
R. Thompson for suggestions after reading a preliminary
version of this manuscript.
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ENSEIGNEMENT
FACTORS AFFECTING STUDENT DROP OUT FROM
THE UNIVERSITY INTRODUCTORY PHYSICS COURSE,
INCLUDING THE ANOMALY OF THE
BY
ONTARIO DOUBLE COHORT
ALAN SLAVIN
T
his article uses data from Ontario and the twosemester, introductory course at Trent University
(Physics 100) to discuss a number of possible factors affecting the student drop-out rate including
the following: academic preparation from high school,
student motivation and work habits, changes in highschool assessment practices, high-school grade inflation,
gender balance, living in residence, and working together
on assignments. One must remember that these data show
correlations, not causal relationships, but they can still be
used for guidance in improving student performance. The
paper has two major components. The first is a review of
the drop-out rate from the 1980's to the present with a discussion of the probable factors affecting it. The second
component gives the results of a recent student survey that
explores potential reasons for dropping the course at the
present time. This article is an abridged, updated version
of a recent paper in the Canadian Journal of Physics,
which contains most of the original figures and data [1].
There have been many studies on the retention of students
at university in general, with the general conclusion being
that students who are well integrated both socially and
intellectually into college or university life are more likely to remain in university than those who are not well integrated. Reference [2] (p.82) even concludes "For most
departures, leaving has little to do with the inability to
meet formal academic requirements." However, no studies were found that focussed on physics. One meta-study
on the retention of women and minorities in science courses concluded that retention improves for students placed in
cooperative learning environments [3].
SUMMARY
The drop-out rate from the introductory
physics course at university may be a better
indicator of average student success than
the final course average, as many students
who are performing poorly drop out and so
are not counted in that average. This article
discusses a number of possible factors
affecting the student drop-out rate.
The data used was taken primarily from years when
I taught the Trent course. The course material was essentially the same over this period and the average of incoming students to Trent varied by only 1.2% since 1993, the
period for which this number was easily available. The
course serves both life-science and physical-science students, and so requires only algebra for the solution of
problems although it uses calculus as necessary for derivation of formulae. The course was taught primarily as a traditional lecture course with regular assignments and labs
until 1997, after which it has used the Peer Instruction [4]
approach for the "lecture" component, with the students
being required to read, before each class, the material that
would have previously been provided in the lecture. The
"lecture" is used primarily to develop the student's conceptual understanding using concept-intensive, multiple
choice questions which are discussed by the students in
small groups and then voted on, followed by clarification
by the instructor if the voting shows it is necessary. The
solution of numerical problems is developed in a separate
tutorial session, followed by assignments submitted for
marking.
The course drop-out rate has been calculated as the fraction of students per year who were present at the first term
test in early November but subsequently drop the course;
this avoids counting the significant number of students
who adjust their courses at the beginning of the school
year. The drop-out rate is important both as a measure of
the difficulty or relevance of the course compared to others at a university, and as one indication of the success of
measures taken to improve teaching. Even when taught
primarily by the same instructor, the drop-out rate of students from the first-year university physics course at Trent
University increased from about 8% in the 1980's to over
25% since 1999. (Ref. [1], Table 1). This included a rapid
doubling of the drop-out rate from about 12% to over 25%
between about 1995 and 1999.
Alan Slavin
Department of
Physics and
Astronomy, Trent
University,
Peterborough, ON
K9J 7B8
The major exception to this upwards trend occurred for the
Ontario "double-cohort" when high school was reduced
from five to four years, with the final-year courses being
re-labelled from OAC (Ontario Academic Credit) to 4U.
However, 22% of the first 4U students stayed at high
school for a 5th year [5] for various reasons: to avoid the
competition for university places, improve their grades, or
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FACTORS AFFECTING STUDENT DROPOUT ... (A. SLAVIN)
take elective courses that they missed because of the more
compressed 4U schedule. Because of the large number of
students who stayed for this extra year, the major part of
the double-cohort phenomenon at universities really
extended over two years: 2003-04 and 2004-05. The dropout rate for these years fell back to about 9% before
rebounding to 27% in 2005-06. A similar decrease in this
rate for the double-cohort years has been observed at
Brock University and the University of Guelph and so was
probably widespread, although the rebound was not as
dramatic at these two universities as at Trent. This data
raises three important questions: why did the drop-out rate
increased so dramatically at Trent between 1981 and the
present; what can be done about the increased drop rate;
and why did this rate decrease by a factor of three during
the double-cohort years, and then rebound? The final
question will be discussed first.
EFFECT OF THE DOUBLE-COHORT
The "double-cohort" was expected to nearly double the
number of students seeking to enter university in
September 2003. It was widely believed that there would
not be enough places at university for all of these students,
so that the pressure to do well in high school to obtain a
place at university was extremely high for these students.
In the end, the Ontario government put enough extra funding into the system to guarantee a university place for
every qualified student, but it was not obvious that this
would be possible even towards the end of 2002-03, and
there was considerable anxiety within this group of students.
In the absence of student exit surveys that spanned the
period from before 2003-05 to after, the best one can do is
speculate as to the reason for the dramatic decrease in the
drop rate during the double-cohort years. The most likely
reason is that the double-cohort students were highly motivated by the competition to garner a university position at
a time when it seemed certain that there would not be
enough to go around. Therefore they developed a work
ethic and work habits that remained with them into university: they stayed up-to-date in their university studies and
so were less likely to drop out. This suggestion is supported by anecdotal evidence from high-school teachers that
these students were much more concerned about performance than students immediately prior to 2003-04. It is also
supported by the anomalously high average grade for high
school students applying to universities in 2003 (Ref. [1],
Fig. 1). While one could argue that the increased retention in 2003-04 was because the best students entered university that year, this cannot apply to the second year of
the double cohort which also had a low drop-out rate. This
raises the question whether the increase in the drop-out
rate since 1988 was due to gradual erosion in the student
motivation, work ethic and work habits over the years. If
this is the case, as is supported by data discussed in the following section, then the evidence from the double-cohort
150 C PHYSICS
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class shows that this trend can be reversed, and reversed
within a very short time, by changing the attitudes of highschool students. The question of how to do this is beyond
the scope of this article.
POSSIBLE CAUSES OF THE INCREASE IN
THE DROP-OUT RATE
Grade inflation
One possible cause of the increase in the drop-out rate
with time is grade inflation. If the average high-school
grade has been increasing over the years, one must ask if
we are seeing weaker students even though the effective
entrance standard has not changed much. Specific examples of grade inflation in high schools are well documented; for example, see the Appendix of Ref. [6]. However,
no published time-sequence data could be found. The
Ontario Ministry of Education has only just started to collect centralized data on its students, although limited
information on this issue, reported below, is available
from the Ontario Universities' Application Centre
(OUAC) from 1998 onwards. This data (Ref. [1], Fig.1)
shows an almost linear increase of 0.23% per year in the
average high-school grade of Ontario students applying to
Ontario universities since 1998. If this rate were constant
over the period 1981 to 2006 of this drop-out study, this
would represent an overall grade inflation of almost 6% in
this time period.
It is necessary to go to individual schools to obtain any
data before 1998. Ontario designated students with
Honours Graduation Diplomas from grade 13, with finalyear average of at least 80%, as Ontario Scholars since
about 1962. The results from a local high school, taken
from the graduation ceremony booklet for each year [7],
show that the percentage of these eligible students who
were awarded Ontario Scholarships was about 6% from
1962 to 1967 when exams were set and graded by the
province. Grade inflation began when individual schools
took over this responsibility, with the number of Ontario
Scholars increasing, on average, about 1% a year from
1968, reaching 31% in 1988. The school system was
revised in 1989 with the elimination of grade 13 and its
replacement by Ontario Academic Credits; students with
at least 6 OAC credits and an average of about 65% were
eligible for university entrance. It was then possible for a
student to complete high school in four years, but most
continued to take five. From 1990 onwards, all secondary
school graduates, both university- and college-bound,
were eligible for Ontario Scholarships. This increased the
eligible pool of students by almost three times but the
average grade in the expanded group was obviously lower
than previously, as the percentage of students gaining
Ontario Scholarships fell from 31% in 1988 to 17% in
1990. However, the inflationary trend continued at
approximately the same rate as previously, with 32% of
grade 12 students again receiving Ontario Scholarships by
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FACTORS AFFECTING STUDENT DROPOUT ... (A. SLAVIN)IA
2007. The move to a 4-year school system in 2003
showed no significant perturbation in this inflation rate.
There is no reason to think that the trend in the data from
this one high school is not roughly representative of the
entire province
this credentialism B the desire for a credential rather than
the desire to learn B has been the main cause of the
increase in postsecondary participation rate (fraction of
high-school students continuing to postsecondary education) in the last 20 years.
Therefore, there is clear evidence of grade inflation; the 6fold increase in the percentage of students with 80% averages between 1962 and 1988, and the similar rate of
increase since 1988, is too large to be attributed to students
being more capable.
In Ontario, the participation rate seems to have been augmented by the Ministry of Education's policies to increase
the percentage of students graduating from high school.
These policies include one [11] beginning in 2000 that
greatly restricts the ability of teachers to deduct marks for
lateness of assignments as long as they are eventually submitted (reference [12] is an example of one school board’s
implementation of this policy). A second policy is a "credit recovery" program started in 2004-05 [13] that allows
students with a grade in the 40's to obtain a pass by repeating just the failed components of the course. There were
good reasons for these changes, and the high school completion rate has increased from 68% in 2004 to 75% in
2007 [14]. However, there is concern that this is allowing
more marginal students to attend university and may have
contributed to the very high drop-out rate in recent years.
However, the minimum average required for Ontario university entrance has also increased, from 60% in the mid
1960's to an official 65% today while the de facto minimum entrance requirement is now about 70%. Therefore,
it might be argued that this increase in entrance standards
has largely compensated for grade inflation. However,
there is strong evidence that the average high school student entering university today is, indeed, weaker than in
the past. For example, the average grade on the same
chemistry test administered to incoming chemistry students at one Ontario university fell from 64% in 1978 to
48% in 1996 [8], and the performance of our Physics 100
class on an identical first test was 66% in 1996 and 50%
in 2006. Moreover, four of the five lowest grades on the
first test in this course have occurred in 2003 to 2006, with
the lowest in 2006. The recent drop in performance was
not restricted to my course; our mathematics department
reported similar drops in performance, as has Brock
University for their mathematics and physics students [9].
It is argued elsewhere [10] that much of the decline in performance since the double cohort is related to an increased
reliance on rote memorization over analytical ability that
seems to have accompanied the new, more content-intensive, primary and secondary curriculum introduced in
Ontario in 1997 and 1998. However, the students already
in high school at the time of implementation of this new
curriculum remained with the previous curriculum until
they graduated in 2003, so this cannot explain the rapid
doubling in the drop-out rate between 1995 and 1999.
To try to explain this rapid rise we turn to the analysis of
Côté and Allahar [6] who argue that a large percentage of
students are now going to university, not because they
have any desire to learn, but only for the credential
required for a job. These "disengaged" students do not
have the motivation, and often not the work habits, to succeed at university. Côté and Allahar blame the increased
numbers of such students on the decline in the number of
good jobs accessible with only a high school diploma,
which began in the late 1970's. Governments, as a result,
have publicized widely that a university degree is needed
for the rewarding jobs of the future. This has become a
self-fulfilling prophecy as more employers, just because
university graduates are available, now require this credential for jobs that previously were handled by someone
with a high school education. Côté and Allahar state that
The full-time university participation rate of students age
17 -19 doubled in Ontario from 9% in 1997-98 to 19% in
2005-06 [15]. Ontario is the only province to show this
very rapid increase, so it seems likely that the Ministry's
attempts to increase graduation rates are at least partly
responsible. If we accept that most of the increase in
Ontario's participation rate is being driven by a combination of credentialism and the Ministry's change in assessment policies, then much of the recent rapid rise in the
drop-out rate from our Physics 100 is likely due to these
causes. That is, many students are lacking the academic
preparation, motivation or study habits to keep up with the
rapid pace of a university course.
Finally, significant grade inflation is also happening at
Canadian universities with, for example, the percentage of
A's and B's in first-year courses in seven universities sampled [16] increasing from 48.2% to 53.3% from 1973-4 to
1993-94. Evidence shows a continuation of grade inflation to the present [Ref. [6], pp.196-197]. This data is supported by a recent Statistics Canada survey [17], that
reports that 69% of age 24-26 Canadian postsecondary
students in 2005, who had not yet graduated, had obtained
first-year averages in the A and B range. For comparison,
the average end-of-year grade in Trent's Physics 100 is
also recorded in Table 1 of Ref. [1]. There has been no
grade inflation in this course over this time.
We now turn to other possible causes of the increase in
drop-out rate.
Background preparation in mathematics and
physics
A second possible cause of the increasing drop-out rate
could be changing mathematics or physics preparation of
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students over the years. We have regularly surveyed
Trent's Physics 100 class at the start of each year, including a question on what advanced high-school mathematics
and physics courses they have taken. We no longer have
all of these records, but the results available are given in
Table 1 of Ref. [1] [18]. These surveys were done at the
start of the year and some students will have dropped the
course before the first test, so that the group replying to
this survey and that writing the first test were slightly different. Nevertheless, the data is informative. The fraction
of students with high-school calculus has remained fairly
steady at just over 90% from the late 1980's to the present.
The percentage taking the final-year algebra course was
also roughly constant at about 77%. The percentage of
students with the final-year high-school physics course
has been fairly constant at about 80% (with an unexplained exception of the 71% in 1988-89), except for
2004-05, 05-06 and 06-07 when this dropped to 66%, 72%
and 63%, respectively. It is unfortunate that we are missing this data for the double-cohort years, but it is clear that
the general increase in drop-out rate since the 1980's is not
caused by a decrease in the number of students taking
high-school physics or mathematics. Nevertheless, given
the results presented in section 4 of this paper, it seems
likely that the very high drop-out rates in the last three
years is partially a reflection of the lack of physics preparation.
To investigate further the low percentage of recent Trent
students without 4U/OAC physics, Trent's statistician used
the OUAC data to determine the percentage of Ontario
applicants to Ontario universities who have taken the
final-year physics course at high school. The results are
shown in Fig. 1 which also includes, for comparison, the
ratio for British Columbia of the number of students who
have taken the senior physics course to the number who
have taken a senior English course [19]. As applicants to
BC universities are all required to take English, this ratio
is close to the percentage of students taking the senior
physics course. The percentage of applicants from
Ontario high schools taking the 4U/OAC physics has
decreased dramatically recently, by almost a quarter from
35% in to 27% in 2006, whereas the corresponding percentage in British Columbia is essentially constant. At the
same time, the absolute number of Ontario applicants with
OAC/4U physics has stayed steady over this period. The
number of students in our Physics 100 has increased from
about 55 to 75 over the last decade. If other Ontario universities have seen similar increases in enrolments, then it
follows from Fig. 1 that a smaller percentage of our
Physics 100 students have OAC/4U physics than previously, and it is not surprising that the drop-out rate has
risen recently.
Gender effects
Another possibility is that the increase in the drop-out rate
could be related to the increasing participation of female
students at the university level. The percentage of female
students in our Physics 100, and their drop-out rate relative to the males, are given in Table 1 of Ref. [1]. There
has not been a significant increase in the percentage of
female students taking this course over the years, although
there has been a significant increase in the percentage of
females continuing to a major in physics. Moreover, there
is no obvious difference in the percentage of males and
females that have dropped the course, although these percentages fluctuate greatly from year to year, so gender
does not appear to be a significant factor.
Other systemic effects are of potentially greater importance to the drop-out rate in Ontario including, for example, the general move from full-year high-school courses
to semestering that began in the early 1970's, which
increased the class time from about 50 minutes to 75 minutes but reduced the amount of material covered; 75 minutes was too long for continuous teaching so some class
time was allotted to homework. Nevertheless, the most
important result of the drop-out data from the 1980's to the
present is that, in spite of all the system changes since
1981, the drop-out rate in the double-cohort years 20032005 actually fell back to the level of the 1980's. The
main conclusion seems to be that changes in the motivation, work ethic and work habits of high school students is
the main culprit here, and this can be reversed if the external motivation is high enough.
POSSIBLE INFLUENCES ON THE DROPOUT RATE FOR CURRENT STUDENTS
Fig. 1
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Percentage of students entering university from 19992006 who took senior high-school physics.
Even if the abilities and attitudes of student graduating
from high school cannot be changed, it may be possible to
reduce the drop-out rate in other ways, such as by requiring different high school courses or by changing student
habits once they do arrive at university. We carried out a
survey in Physics 100 in March of 2005-06, to try to
determine which of a variety of potential causes might
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FACTORS AFFECTING STUDENT DROPOUT ... (A. SLAVIN)IA
contribute to the current drop-out rate, including (1) hours
per week working (to pay for their education), (2) long
commuting times, (3) a culture of dropping out in high
school and in university, (4) years off after high school,
(5) high-school physics background, (6) high-school math
background, (7) whether or not a student lived in residence, and (8) whether or not students worked on assignments with their peers. Either high school calculus or
algebra is a prerequisite for the course, although university calculus is a prerequisite for subsequent physics courses. As with most introductory physics courses at the university level, it covers all the high school physics material
again but at a much faster rate. Therefore, although it is
recommended, high school physics is not a prerequisite
for this course, to allow students to obtain the university
physics they may require for their programs even if they
did not take it in high school.
The drop-out rate for those students who stayed in the
course (the Stays) as compared to those who dropped it
(the Drops) showed no significant dependence on commuting time, number of years off between high school and
university, or hours of outside work either in high school
or at university. There also is no statistical indication that
the Drops had a higher culture of dropping high-school
courses than the Stays, although the Drops had a much
higher average number of other university courses
dropped, 0.88 compared to 0.18 for the Stays. Of course,
this could just mean that the Drops were weaker students
and therefore had difficulty with more than their physics
courses. Both groups knew comparable numbers of other
students who were dropping courses.
However, there is a very strong dependence between the
number of Drops and the lack of high-school physics, with
82% of Drops not having high-school physics, compared
to only 29% of the Stays. This parallels results at the
University of Guelph [20], and at the University of
Calgary [21]. In the latter case the drop rate was four times
as high in an introductory course specifically designed for
students without the final-year high-school physics course
than in the sister course for students with high-school
physics. This finding is counter to the general conclusion
by Tinto, who claimed that (Ref. [2], p. 82), "Voluntary
departure appears to be the result more of what goes on
after entry into the institution than of what may have
occurred beforehand." The fast pace of a university
course may not allow the time to develop the required conceptual and analytical skills if students have not already
started to develop them in a high-school physics course.
Alternatively, the much larger drop rate for students who
have not previously taken physics may be due to preselection: students who had already found physics difficult at
the high-school level may not even try it at university.
There is a weak indication that the probability of staying
in the course is improved by taking high-school calculus
but, rather surprisingly, there is a much weaker dependence on taking Algebra and Geometry, or the Finite Math
(OAC) or Data Management (4U) courses which included
some statistics.
Students living in residence also had a significantly higher chance of staying in the course: 64% of the Stays lived
in residence, compared to only 18% of the Drops.
Similarly, students who work with others on assignments
(82% of the Stays vs. 44% of the Drops) have a much
higher probability of staying in the course than those who
do not. The results for these last two groups are consistent
with other studies (e.g. [2]) that show that students who
are well integrated into university life socially and intellectually are more likely to complete their degrees. They
feel fulfilled by their studies, they know that their problems are not unique to them, and they have a support
group of their academic peers that helps develop their selfconfidence. In addition, those who work in physics study
groups are more likely to obtain a better understanding of
the material.
CONCLUSIONS
The main conclusions that can be drawn from the above
data are the following:
1. The Ontario double-cohort results suggest that a major
contributor to the increasing drop-out rate from the
introductory physics course is deteriorating work ethic
and work habits of the students. If so, it seems possible to change these dramatically over the four years of
high school, given adequate external motivation.
2. These results raise the question of how much other
interesting data can be mined from the double-cohort
years. This will be more difficult now that these students have graduated and dispersed.
3. Students, physics teachers and high-school guidance
counsellors should be informed of the great importance
of taking high-school physics if there is any chance of
the student requiring a university course in the subject,
even if there is no formal prerequisite for high-school
physics. On the suggestion of myself and other members of the CAP Division of Physics Education, the
past Chair of CAP (Canadian Association of
Physicists), Louis Marchildon, sent such a letter [22] to
all ministries of education in Canada (except for
Quebec, because of its very different pre-university
system), asking them to forward the letter to all of its
high school principals and guidance counsellors. Only
a few did this.
4. Students entering university, especially those who are
living off-residence, should be made aware of the
importance to their academic success of integrating
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Page 154
fully into university life, including the development of
a peer support group. In Physics, this may be most
effectively accomplished by working on assignments
and studying with other physics students.
5. The coupling of credentialism B as a major motivator
for a university degree B with significant high-school
grade inflation has resulted in a greatly increased postsecondary participation rate in Ontario that appears to
have increased the percentage of weaker and unmotivated students, and may be the primary cause of the
large increase in drop-out rate over the years. This may
have been aggravated by recent changes in high-school
assessment policies.
ACKNOWLEDGEMENTS
Thanks to D.J. Kennett and A.M. Young of Trent
University for advice on the statistical analysis, R. Wortis
and R. Shiell of Trent for providing some of the data in
Table 1 and for useful discussions, D. Giles for assistance
with OUAC data, and Peterborough Collegiate and
Vocational School for access to their commencement
booklets. S. Bose of Brock University, E. McFarland and
J. O'Meara of the University of Guelph, and R. Thompson
of the University of Calgary kindly provided data from
their institutions. John MacMillan-Jones gave valuable
input on changes to the high-school physics curriculum
over this period.
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Ontario Ministry of Education, The Ontario Curriculum, Grades 9-12: Program Planning and Assessment, (2000).
(http://www.edu.gov.on.ca/eng/curriculum/secondary/progplan912curr.pdf)
Bluewater District School Board, Chelsey, ON.
Assessment for Learning: Policy to Practice, (2003).
(http://www.bwdsb.on.ca/Assessment/Downloads/Assessment_Learning_CD.pdf?FCItemID=S02C56305)
G. Zegarac and R. Franz, Secondary School Reform in Ontario and the role of Research, Evaluation, and Indicator Data,
(2007). (http://edu.gov.on.ca/eng/research/SSreform.pdf)
Toronto Star, Feb. 28, 2008.
D. Hango and P. de Broucker, Statistics Canada, (2007). Catalogue no. 81-595-MIE No. 058.
P. Angling and R. Ming, Canadian Public Policy/Analyse de Politique 26, 361-368 (2000).
D. Shaienks and T. Gluszynski, Statistics Canada, 2007. Catalogue no. 81-595-MIE No. 059.
Attempts were also made to obtain this information from data supplied by the Ontario Universities Application Centre
(OUAC) for the period 1995 B 2006. However, this gave information on typically only half the students in the course, as
the OUAC data references only Ontario high-school credits, and it appears that not all these records are complete.
M. Coombes, Kwantlen University College B.C. (personal communication).
J. O'Meara and E. McFarland, University of Guelph (personal communication).
R. Thompson, University of Calgary (personal communication).
http://www.cap.ca/news/briefs/High-School-Physics.pdf
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BUREAU DE L’ACP
CAP NEWS / INFORMATIONS DE L’ACP
CAP 2007-08 Report, by L. Marchildon, President
Rapport de l'ACP pour 2007-08, par L. Marchildon, président
This report is a summary of the accomplishments of the Canadian Association of Physicists
in 2007-08, of our challenges and of our specific goals to further promote Canadian physics.
With a highly dedicated but very small staff, the
CAP could not function without the support of a
large number of volunteers, Executives,
Councillors and Friends in the first place but
also many individual members involved in various committees or specific tasks. Witnessing
that level of dedication first hand has been an
extraordinary experience, and I thank everyone for their
help and commitment.
Ce rapport résume les réalisations de
l'Association canadienne des physiciens et
physiciennes en 2007-08, nos défis ainsi que
nos objectifs pour promouvoir davantage la
physique canadienne.
Avec un personnel dévoué mais très restreint,
l'ACP ne pourrait fonctionner sans l'appui d'un
grand nombre de bénévoles, les membres de
l'Exécutif, du Conseil et les Amis en premier
lieu, mais aussi plusieurs membres individuels
oeuvrant dans différents comités ou à des tâches spécifiques. Avoir observé de près un tel niveau d'engagement a été une expérience extraordinaire, et je remercie chacun de son aide et de son dévouement.
Conseil de l'ACP 2007-08 CAP Council
Division Chairs/Chefs de division
Canadian Geophysical Union/Union géophysique canadienne, Gary T. Jarvis, York University
Atmospheric and Space Physics/Physique atmosphérique et de l'espace,
Thayyil Jayachandran, University of New Brunswick
Atomic and Molecular Physics and Photon Interactions/Physique atomique et moléculaire et d'interactions avec les photons,
Dennis Tokaryk, University of New Brunswick
Condensed Matter and Materials Physics/Physique de la matière condensée et des matériaux,
Alexander Moewes, University of Saskatchewan
History of Physics/Histoire de la physique, Walter Davidson, National Research Council
Industrial and Applied Physics/ Physique industrielle et appliquée, Andrzej Kotlicki, University of British Columbia
Instrumentation and Measurement Physics/Physique des instruments et mesures, Kirk Michaelian, CANMET
Medical and Biological Physics/Physique médicale et biologique, Apichart Linhananta, Lakehead University
Nuclear Physics/Physique nucléaire, Malcolm Butler, St. Mary's University
Optics and Photonics/Optique et photonique, Pandurang Ashrit, Université de Moncton
Particle Physics/Physique des particules, Roger Moore, University of Alberta
Physics Education/Enseignement de la physique, Robert Thompson, University of Calgary
Plasma Physics/Physique des plasmas, Jordan Morelli, Queen's University
BUREAU DE L’ACP
*President/Président, Louis Marchildon, Université du Québec à Trois-Rivières
*Past President/Présidente sortante, Melanie C. W. Campbell, University of Waterloo
*Vice-President/Vice-présidente, Shelley A. Page, University of Manitoba
*Vice-President Elect/Vice-président désigné, Robert Mann, University of Waterloo
*Secretary-Treasurer/Secrétaire-trésorier, Richard Hemingway, Carleton University
Director-Affiliate Members/Directrice-membres affiliés, Hélène St-Jean, Cégep d'Ahuntsic
Director-Student Members (CUPC)/Directeur-membres étudiants (CCÉP), Braden Brinkman, Simon Fraser University
Director-Corporate Members/Directeur-membres corporatifs, Andranik Sarkissian, Plasmionique Inc.
*Director-Professional Affairs/Directeur-affaires professionnelles, Ewart Blackmore, TRIUMF
*Director-Academic Affairs/Directeur-affaires académiques, Bruce Gaulin, McMaster University
*Director-International Affairs/Directeur-affaires internationales, Gordon Drake, University of Windsor
*Director-Communications/Directeur-communications, Bill Whelan, University of Prince Edward Island
*Executive Director/Directrice exécutive, Francine M. Ford
(* Members of CAP Executive Committee/Membres du comité exécutif de l'ACP)
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CAP OFFICE
Surface Science/Science des surfaces, Keith Griffiths, University of Western Ontario
Theoretical Physics/Physique théorique, Richard MacKenzie, Université de Montréal
Regional Councillors/Conseillers régionaux
British Columbia and Yukon: David Broun, Simon Fraser University and Stan Yen, TRIUMF
Alberta and Northwest Territories: Andrew Yau, University of Calgary and Adriana Predoi-Cross, University of Lethbridge
Saskatchewan and Manitoba: Byron Southern, University of Manitoba and Randy Lewis, University of Regina
Ontario - Southwest: Chitra Rangan, University of Windsor and Ragnar Dworschak, AECL
Ontario - Central and North: Eduardo Galiano-Riveros, Laurentian University and Clarence Virtue, Laurentian University
Ontario - East: Jean-Marc Noel, RMC
Québec - Nord et ouest: Victor Zacek, Université de Montréal et Andreas Warburton, McGill University
Québec - Sud et est: Christian Lupien, Université de Sherbrooke et René Roy, Université Laval
New Brunswick and Newfoundland: David Hornidge, Mount Allison and Li-Hong Xu, University of New Brunswick
Nova Scotia and Prince Edward Island: Sheldon Opps, University of Prince Edward Island and
Roby Austin, St. Mary's University
Councillors at Large/Conseillers généraux
Mick Lord, Canadian Nuclear Safety Commission
Adrian Buzatu, McGill University
CAP OFFICE
Editor-Canadian Journal of Physics/Directeur scientifique-Revue canadienne de physique,
Michael Steinitz, St. Francis Xavier University
Editor-Physics in Canada/Rédacteur-La Physique au Canada, Béla Joós, Université d'Ottawa
Chair-Science Policy Committee/Directeur-comité de politique scientifique, Eric C. Svensson, Chalk River
156 C PHYSICS
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CAP Initiatives during 2007-08 include:
Les initiatives de l'ACP en 2007-08 incluent:
The Annual Congress coinciding with Quebec City's 400th
anniversary and drawing more than 640 participants, featuring
C Outstanding physics done in Canada: Plenary talks by
R. Laflamme, N. Lockyer, A. McDonald and all medal
recipients
C More than 60 technical sessions
C A session on the commercialization of innovation
C A memorial session for Roger Lessard
C Joint activities with NSERC
C A special CAP/HPCS session
C Student competitions - record attendance > 140
C The teachers' workshop
Le congrès annuel coïncidant avec le 400e anniversaire de
Québec et rassemblant plus de 640 participants, avec
A number of papers and letters expressing the CAP's position on matters of science policy:
C Position Papers on NSERC International Review of the
Discovery Grants Program and GSC Structure; the outcome of the international review was very positive
C Letter to the Minister of Industry about NRC layoffs
C Position Paper on the Transfer of Federal NonRegulatory Laboratories
C Letter to the Prime Minister about advice to Government
on science and technology matters
C Brief to the Standing Committee on Industry, Science
and Technology about big science projects and science
advice to Government
Plusieurs documents et lettres exprimant la position de
l'ACP sur des questions de politique scientifique:
C Opinion sur l'examen international du programme de
subventions à la découverte du CRSNG et la structure
des CSS; l'examen international a été très positif
C Lettre au ministre de l'Industrie sur les mises à pied au
CNRC
C Opinion sur le transfert des laboratoires fédéraux à vocation non réglementaire
C Lettre au Premier ministre au sujet des conseils au gouvernement en science et technologie
C Avis au Comité permanent de l'industrie, de la science et
de la technologie au sujet des grands projets scientifiques
et des conseils au gouvernement
The third Canada-America-Mexico Graduate Physics
Conference, held at McGill University 8-11 August and
drawing more than 115 students from the three countries.
La troisième conférence d'étudiants diplômés du Canada,
des États-Unis et du Mexique, qui a attiré plus de 115 participants des trois pays à l'Université McGill.
Theory Canada 4 Meeting.
La conférence Théorie Canada 4.
C La reconnaissance de la physique remarquable faite au
Canada: des conférences plénières de R. Laflamme, N.
Lockyer, A. McDonald et tous les médaillés
C Plus de 60 sessions techniques
C Une session sur la commercialisation de l'innovation
C Une session commémorative pour Roger Lessard
C Des activités conjointes avec le CRSNG
C Une session spéciale ACP/HPCS
C Les concours étudiants - record de participation > 140
C L'atelier des enseignants
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BUREAU DE L’ACP
A new fast track for professional certification.
Une nouvelle voie rapide pour la certification professionnelle.
Development of a new website, and a new interface for proposing and selecting medal candidates online.
Le développement d'un nouveau site web, et une nouvelle
interface pour la proposition et la sélection en ligne de
médaillés.
Addressing issues in education:
C Letter to tri-council Presidents regarding research in science education
C Working to increase enrolments in High School physics
courses
C Establishing a High School teaching award
Des gestes concrets en éducation:
C Lettre aux présidents des trois conseils à propos de la
recherche en enseignement des sciences
C Soutien de l'enseignement secondaire en physique
Financial Report
Bilan financier
With the recent closure of the books for the 2007 financial
year, we can report on the status of the finances of the CAP.
The CAP finances are mainly organised in two separate
funds, the General Fund and the Educational Trust Fund.
The General Fund is now in a surplus situation with revenues exceeding expenses by $34,488 (compared to a large
deficit of $41,097 for the previous fiscal year). However,
the Educational Trust Fund continues, for the 4th consecutive year, to run a deficit. This year it was $5,618, even
larger than the deficit of $4,535 the previous fiscal year.
Les livres sont fermés pour l'année financière 2007, et nous
pouvons faire le bilan des finances de l'ACP. Celles-ci sont
principalement réparties en deux fonds, le fonds général et
le fonds d'éducation. Le fonds général affiche maintenant
un surplus, l'excédent des revenus sur les dépenses s'élevant
à 34 488 $ (comparé à un important déficit de 41 097 $ l'an
dernier). Cependant, le fonds d'éducation est déficitaire
pour la 4e année consécutive. Le déficit de cette année est
de 5 618 $, supérieur à celui de 4 535 $ pour l'année précédente.
In the Educational Trust Fund, income is derived mainly
from donations by members and by corporate members
together with some small interest income from the Fund.
Expenses go towards high school and university prizes, to
the CAP lecture tour, to support the Canadian
Undergraduate Physics Conference, and to the Canadawide science fair and physics Olympiad. For 2007 (2006)
the income was $16,839 ($17,162) versus expenses of
$22,457 ($21,696). For 2008, the CAP Council and
Executive encourage more contributions from members
and corporations. In the interim, they have approved the
reduction of amounts for prizes for high schools and universities, stopped the support of the Virtual Science Fair, and
waived the administration fee in an attempt to balance the
budget. Nevertheless, some creative thinking will be needed by the ETF Trustees.
Les revenus du fonds d'éducation proviennent surtout de
dons des membres individuels et corporatifs, ainsi que d'intérêts modestes générés par le fonds. Les dépenses couvrent les prix scolaires et universitaires, la tournée de conférenciers de l'ACP et le soutien de la Conférence canadienne des étudiants de premier cycle, de l'expo-sciences pancanadienne et de l'Olympiade de physique. En 2007 (2006)
les revenus atteignaient 16 839 $ (17 162 $) en comparaison de dépenses de 22 457 $ (21 696 $). En 2008, le
Conseil et l'Exécutif de l'ACP encouragent les membres et
les corporations à contribuer davantage. Entre temps, ils
ont approuvé la diminution des prix pour les écoles secondaires et les universités, ont interrompu le soutien de l'expo-sciences virtuelle et ont éliminé les frais de gestion dans
le but d'équilibrer le budget. Malgré tout, les fiduciaires du
fonds devront réfléchir à la situation.
The General Fund has made a remarkable recovery!
Income comes from a variety of sources, but the bulk
income comes from membership fees and from the Annual
Congress (see graph on income). The 2007 Congress
returned a much larger income than expected ($63,462 versus $35,000) and the membership fee income increased
from $150,726 in 2006 to $174,019 in 2007. Additionally,
a small profit of $7,084 has been returned by Physics in
Canada. The total income for the General Fund amounted
to $331,791 whereas the expenses were $297,303.
Expenses support the salaries and benefits of the CAP
office staff, bank charges, office rent, insurance and supplies, telephone and fax, postage, legal and audit charges,
printing, translation, travel, computer, database and website
charges, and miscellaneous charges. With such a positive
situation we are able to repay $15,000 to the Congress
Averaging Fund that was taken the year before to offset the
2006 Congress shortfall. Additionally, we are able to pay
Le fonds général a, par contre, remarquablement récupéré.
Les revenus proviennent de plusieurs sources, mais la plus
grande partie vient des frais d'adhésion et du congrès annuel
(voir la figure sur les revenus). Le congrès de 2007 a produit un revenu beaucoup plus important que prévu (63 462
$ vs 35 000 $) et les revenus des frais d'adhésion sont
passés de 150 726 $ en 2006 à 174 019 $ en 2007. De plus,
La Physique au Canada a réalisé un profit de 7 084 $. Les
revenus totaux du fonds général ont atteint 331 791 $, tandis que les dépenses se sont élevées à 297 303 $. Les
dépenses couvrent les salaires et bénéfices du personnel de
bureau de l'ACP, les frais bancaires, la location, les assurances et les fournitures de bureau, la poste, le téléphone et
la télécopie, les frais légaux et de vérification, l'impression,
la traduction, les voyages, les frais informatiques et
quelques autres. Nous pouvons ainsi rembourser au fonds
d'équilibrage du congrès le montant de 15 000 $ pris l'an
dernier pour renflouer le congrès de 2006. De plus, nous
C Prix de l'enseignement secondaire
BUREAU DE L’ACP
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CAP OFFICE
CAP OFFICE
158 C PHYSICS
IN
the $10,000 Minasu database upgrade without taking the
monies from the General Reserve Fund.
avons pu payer 10 000 $ pour la mise à jour de la base de
données Minasu sans retirer d'argent du fonds de réserve.
On a number of minor issues: Membership fees for 2008
have been increased by 1.7%, representing the average
monthly CPI increase over the period September 2006 August 2007. The CAP holds a number of long-term GICs
(total value $308,641) and, at maturity, these are being systematically renegotiated to provide more income for the
General Fund. Finally, since the Graduate Student
Conference at McGill in 2007 (CAM2007) returned a net
profit of $15,175, this is now held in the Educational Trust
Fund for future conferences in this series.
Quelques points mineurs: Les frais d'adhésion pour 2008
ont été augmentés de 1.7%, ce qui représente l'augmentation du coût de la vie de septembre 2006 à août 2007.
L'ACP détient quelques dépôts à terme (d'une valeur totale
de 308 641 $) qui, lorsqu'ils viennent à échéance, sont renégociés pour augmenter les revenus du Fonds général.
Enfin, étant donné que la conférence des étudiants diplômés
qui a eu lieu à McGill en 2007 (CAM2007) a fait un profit
net de 15 175 $, ce montant a été versé au Fonds d'éducation pour les conférences futures de cette série.
Membership
L'adhésion
Renewal and enhancement of our membership is the most
crucial issue faced by our organization. Partly because of
changes in our database, membership declined to a longtime low in 2005 and has been slowly recovering, thanks to
concerted efforts by the CAP office, VP Elects, Friends and
Councillors of CAP. Individual membership data over the
past five years are shown in the graph on Membership
Statistics.
L'accroissement du nombre de membres et le renouvellement constituent le problème le plus crucial auquel nous
faisons face. En partie à cause de problèmes avec la base
de données, le nombre de membres a connu un creux en
2005 et remonte lentement, grâce aux efforts concertés du
bureau de l'ACP, des VP désignés, des amis et conseillers
de l'ACP. Les données sur les membres individuels au
cours des cinq dernières années sont indiquées à la figure
sur les statistiques d'adhésion.
This year a Powerpoint slide show promoting membership
in CAP was developed, which most Friends showed in their
respective departments and/or places of employment.
Friends were also asked to review their membership lists to
see which inactive members should be removed, so that
recruitment campaigns could be better targeted. In the short
run, membership could possibly be increased by one or two
hundred if we could simply get lapsed members to renew
on time. In the longer run, membership could be more than
doubled if all eligible Canadian physicists joined the CAP.
There is nothing like personal contact to achieve this aim.
Cette année, un diaporama Powerpoint encourageant l'adhésion à l'ACP a été développé, et la plupart des amis l'ont
présenté dans leur département ou lieu de travail. On a
aussi demandé aux amis de revoir les listes de membres
pour retirer les membres inactifs, de manière à mieux
diriger les campagnes de recrutement. À court terme, on
pourrait ajouter cent ou deux cents membres si les gens
renouvelaient leur adhésion à temps. À plus long terme, on
pourrait plus que doubler le nombre de membres si tous les
physiciens canadiens se joignaient à l'ACP. Il n'y a rien
comme le contact personnel pour y arriver.
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BUREAU DE L’ACP
Activités courantes:
Science policy
C Lobbying activities through CCR and PAGSE
C Strong relationship with NSERC (liaison committee and
partnership at Congress)
C Special sessions at Congress
C Science policy committee
Politique scientifique
C Pression politique à travers le CCR et PAGSE
C Solide relation avec le CRSNG (comité de liaison et
partenariat au congrès)
C Sessions spéciales au congrès
C Comité de politique scientifique
Professional issues
C Annual Congress
C Professional certification and stamp
C Professional exam written by senior undergrads and grads
C Monitoring of engineering acts
C Cooperation with APS and EPS
C Canadian National IUPAP Liaison Committee
C Links with Physics depts. and Chairs' meeting
C Flexible structure for institutional/corporate
members
C Awards and Medals
Affaires professionnelles
C Congrès annuel
C Certification professionnelle et timbre
C Examen professionnel offert aux universités
C Surveillance des chartes de génie
C Coopération avec l'APS et l'EPS
C Comité de liaison avec l'UIPPA
C Liens avec les départements et réunion de directeurs
C Structure flexible pour membres institutionnels/corporatifs
C Médailles et distinctions
Communications
C Physics in Canada
C CAP News
C Art of Physics competition
Communications
C La Physique au Canada
C Bulletin d'information
C Concours l'Art de la physique
Web based services
C Member services interface
C Careers page and employment opportunities
C Membership application and renewal
C Science Policy information
C Division reports
C and more!
Services sur le web
C Interface des services aux membres
C Page des carrières et offres d'emploi
C Adhésion et renouvellement
C Information sur la politique scientifique
C Rapports des divisions
C et plus!
Education
C CAP lecture tour
C High School and University prize exams
C Support of CUPC and CUPJ
C Canada-wide Science Fair and Physics Olympiad
Éducation
C Tournée de conférenciers de l'ACP
C Concours pré-universitaire et universitaire
C Soutien de la CCÉP et du JCÉP
C Expo-sciences pancanadienne et Olympiade de physique
BUREAU DE L’ACP
Ongoing activities:
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CAP OFFICE
En 2008-09, nous voulons
Increasing membership
C Regular members and students
C Corporate/institutional
Accroître le nombre de membres
C Membres réguliers et étudiants
C Corporatifs/institutionnels
Improving web based services
C New web site
C PiC articles on line
Améliorer les services sur le web
C Nouveau site web
C Articles de PaC en ligne
Working with new committees on
C Student affairs
C Science policy
C Communications
Travailler avec les nouveaux comités
C Affaires étudiantes
C Politique scientifique
C Communications
Rationalizing CAP office operations and specifying staff
responsibilities better for more efficient use of our staff.
Rationaliser les opérations du bureau de l'ACP et mieux
décrire les responsabilités des employés pour rendre leur
travail plus efficace.
CAP OFFICE
During 2008-09, we are working towards:
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IN MEMORIAM
LYNN EMMET HOMER TRAINOR - (1921-2008)
Lynn Trainor, Professor Emeritus of
Physics at the University of Toronto,
died on April 30, 2008, at age 86. A
long time faculty member of the
Department of Physics (1963 - 87),
Lynn played an important role in the
early development of theoretical
physics in Canada in the period 1955
–1970. While starting his career in
theoretical nuclear physics, Lynn
developed wide intellectual interests,
and concentrated on theoretical biology in the last part of his
career. He was also well known for his tireless efforts on
public issues.
At Saskatoon, Lynn and his fellow physics students were
inspired by the presence of Gerhard Herzberg, who had
escaped from Nazi Germany in 1935. Lynn has written a
beautiful account of being Herzberg’s assistant while he was
an undergraduate (it appears in this issue of Physics in
Canada).
Lynn went on to complete his Ph.D. at the University of
Minnesota in 1951 in theoretical nuclear physics. As often
happens in physics, the first paper Lynn published in 1952 in
the Physical Review (based on his thesis) was one of his
most influential. Its importance was quickly realized and led
to what are now called isotopic spin selection rules in nuclear
transitions.
In the 1950s, theoretical physics was just starting to be an
accepted part of Physics Departments in Canada – previously it had been viewed as a branch of mathematics. Lynn held
faculty positions at Queen’s University and the University of
Alberta before coming to U of T as a full professor in 1963.
He played an active role in the CAP and its Theoretical
Physics Division, and was the founder and first Director of
the Theoretical Physics Institute at Edmonton created in
1961. Lynn and Jan Van Kranendonk, as senior faculty members, built up a strong theoretical physics group at U of T in
the late 1960s and early 1970s.
Even before Lynn switched to theoretical biology in the late
1970s, he had widened his research interests. He and his students wrote significant papers on group theory, many-body
techniques, statistical mechanics, Bose-Einstein condensation, and problems in the interpretation of quantum theory.
Probably Lynn’s greatest impact was as a wise and stimulating mentor of young students and post-doctoral fellows. He
In the last decade before taking mandatory retirement in
1987, Lynn developed a vigorous research program in theoretical biology. While he attracted many talented graduate
students, the Department of Physics did not feel that this initiative was central to its mission at the time. This did not
deter Lynn! He wrote and edited several well received books
in this area, was cross-appointed to the Faculty of Medicine,
developed an active collaboration with other researchers
around the world, and continued his thinking on biological
problems almost to the day he died.
Beginning with his early activities in the 1960s on behalf of
the CAP and theoretical physics, Lynn was always an
activist, increasingly concerned with wider public questions.
From 1970 on, Lynn was the Chair of the North York Board
of Education for several terms. This post strengthened his
interest in learning difficulties of children as well as in medical problems arising from environmental effects, which
acted as a stimulus to Lynn’s shift to research in theoretical
biology. He was an active participant in Science for Peace, as
well as many organizations related to health and education
issues.
Lynn held a strong belief that one had to balance the rigorous
standards of proof that applied in physics research with an
openness to new ideas in uncharted areas. This independent
attitude sometimes led Lynn to support ideas, on the grounds
that one should keep an open mind, that were quite controversial. This openness also made him successful as a supportive research supervisor. At the memorial service held at
U of T on May 13, many people from the University and the
wider public spoke about Lynn as an inspiration to their
lives, emphasizing how he was willing to engage them on
scientific questions as an equal. Shining examples were the
tributes by people who had attended the continuing studies
evening courses which Lynn gave for many years after retiring. He would choose a recent physics-related best seller and
patiently lead his adult students through
the science at a level they could underAllan Griffin,
Department
stand. Lynn’s educational fervour sets
of Physics,
an example for all professional scienUniversity
tists.
of Toronto,
I would like to thank David Rowe,
Sam Wong, Derek Paul, John Valleau,
Charlie Trainor, and Anne Trainor for
their contributions.
IN MEMORIAM
After his high school education, spent studying on the family farm in Saskatchewan, and two years as a public school
teacher, Lynn began his studies at the University of
Saskatchewan in 1942. With Lynn’s strong aversion to all
things military, he must have chuckled when he recalled that
he got a chance of going to University after receiving a special scholarship sponsored by the Canadian Armed Forces to
increase the number of science graduates in Canada. His isolated life in his early years produced a life-long passion for
education and learning about things, and the desire to share
this with others.
was willing to strike out in new directions with his young coworkers, learning as he went along. To quote Michael
Revzen, who was Lynn’s first Ph.D. student at the University
of Alberta: “Lynn would encourage his students to follow
novel ideas, but insisted that these ideas be buttressed with
clear arguments. He had a very gentle yet cutting sense of
humour.” Mark Wise, a leading high-energy theorist at
Caltech, co-authored with Lynn several important papers as
an undergraduate and a book based on a second year undergraduate course on theoretical physics. Remembering the
1970s Mark says, “Lynn was a deep scientist but even more
was a marvellous human being. He was patient and caring,
and had a huge impact on my life and career.”
Toronto ON
M5T 2N2
<[email protected].
ca>,
8/18/2008
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Page 162
NEWS
NSERC PUBLISHES RESULTS OF THE
GRANT SELECTION COMMITTEE (GSC)
STRUCTURE REVIEW
LE CRSNG PUBLIE LES RÉSULTATS DE
L’EXAMEN DE LA STRUCTURE DES COMITÉS
On June 10, 2008, NSERC published the recommendations
[http://www.nserc.gc.ca/about/GSC_final_report_e.pdf] of its
Grant Selection Committee (GSC) Structure Review Advisory
Committee. Chaired by Dr. Adel Sedra, Dean of Engineering at the
University of Waterloo, the Committee [http://www.nserc.gc.ca/
about/GSC_advisory_comm_e.asp] was charged with an in-depth
investigation of the challenges facing the Discovery Grants peer
review system, specifically the rapid emergence of new areas, proposals that cross traditional boundaries and the growing workload
faced by many GSCs.
Le 10 juin, 2008, le CRSNG a publié les recommandations
[http://www.crsng.gc.ca/about/GSC_final_report_f.pdf] de son
Comité consultatif sur l’examen de la structure des comités de
sélection des subventions (CSS). Présidé par Adel Sedra, doyen de
la Faculté de génie à l’University of Waterloo, le Comité consultatif [http://www.crsng.gc.ca/about/GSC_advisory_comm_f.asp]
était chargé d’effectuer un examen approfondi des défis auxquels
est confronté le système d’évaluation par les pairs des demandes
de subvention à la découverte, notamment l’émergence rapide de
nouveaux domaines de recherche, la croissance de la recherche
chevauchant plusieurs disciplines et l’augmentation de la charge
de travail de nombreux comités.
NEWS
Key among the report recommendations is that NSERC adopt a
Conference Model for the review of applications. The new Model
would be developed from a system that four GSCs have already
implemented successfully. Its primary advantage is its much more
flexible and dynamic approach to grant review, allowing the system to adapt quickly to changes in the research environment and to
accommodate proposals that cross disciplines.
The report of the Advisory Committee made other recommendations including:
• separation of scientific evaluation and funding recommendations;
• "binning" of proposals based on scientific/engineering merit,
without reference to prior grants; and
• "cost of research" to replace "need for funds" as a factor in the
award amount.
"We heard from many researchers about their perception of the
strengths of the current system, so we were very conscious of the
need to build on these positive features," said Dr. Sedra. "What we
recommend is not quite a complete re-design—there are many
evolutionary elements—but it is also not just a fine tuning."
Isabelle Blain, NSERC's Vice President of Research Grants and
Scholarships, said that NSERC's Committee on Research Grants
(CORG) and the Discovery Grant Program Management have
accepted in principle the Review Committee's main recommendations, and that NSERC is now developing and refining the processes in order to implement the new structure for the 2010 Discovery
Grant Competition.
The decision was supported by NSERC President Dr Suzanne
Fortier. "The GSC Structure Review Committee has provided an
exceptionally valuable service to the natural sciences and engineering research community and to NSERC. Our capacity to recognize and support excellence is critical to our vision of making
Canada a nation of discoverers and innovators. These new measures will assure us, and our funders, that our peer review systems
are evolving to accommodate changes in the research environment
and that we will continue to have the rigour and the ability to evaluate excellent proposals."
The new model and processes will be subjected to further extensive focus testing and proving over the summer and fall.
The GSC Structure Review is the second major review of the
Discovery Grants Program released recently. Last month, NSERC
published the Report of the International Review Committee
[http://www.crsng.gc.ca/about/PDF/international_review_e.pdf]
This Report endorsed the philosophy of the Program and the quality of the research and training it supports.
162 C PHYSICS
IN
DE SÉLECTION DES SUBVENTIONS
Une des recommandations importantes du rapport porte sur
l’adoption d’un modèle de conférence par le CRSNG pour l’évaluation des demandes. Le nouveau modèle serait élaboré à partir
d’un système que quatre CSS ont déjà mis en oeuvre avec succès.
Son principal avantage réside dans son approche beaucoup plus
souple et dynamique de l’évaluation des demandes de subvention,
ce qui permet au système de s’adapter rapidement aux changements dans les domaines de recherche et de prendre en charge les
propositions qui chevauchent plusieurs disciplines.
Le Comité consultatif a formulé d’autres recommandations,
notamment les suivantes :
• séparer l’évaluation scientifique des recommandations de
financement;
• classer les demandes dans des « catégories » en fonction du
mérite en sciences ou en génie, sans tenir compte des subventions
précédentes;
• le remplacement du « besoin de fonds » par les « coûts de la
recherche » comme critère de sélection.
« De nombreux chercheurs nous ont fait part de leur perception des
points forts du système actuel, et nous sommes donc très conscients du besoin de faire fond sur ces caractéristiques positives, a
affirmé M. Sedra. Ce que nous recommandons n’est pas tout à fait
une restructuration complète – il y a de nombreux éléments évolutifs – mais il ne s’agit pas non plus de modifications mineures. »
Isabelle Blain, vice-présidente de la Direction des subventions de
recherche et bourses, a indiqué que le Comité des subventions de
recherche du CRSNG et les responsables du Programme de subventions à la découverte ont accepté en principe les principales
recommandations du Comité consultatif. Elle a également ajouté
que le CRSNG élabore et peaufine maintenant les processus nécessaires afin de mettre en oeuvre la nouvelle structure pour le concours de subventions à la découverte de 2010.
La décision a été appuyée par Suzanne Fortier, présidente du
CRSNG, qui a affirmé que « le Comité consultatif sur l’examen de
la structure des comités de sélection des subventions a rendu un
service exceptionnellement précieux à la communauté des
chercheurs en sciences naturelles et en génie, et au CRSNG. Notre
capacité de reconnaître et d’appuyer l’excellence est essentielle à
la réalisation de notre vision de faire du Canada un pays de découvreurs et d’innovateurs. Ces nouvelles mesures nous assureront,
ainsi qu’à nos bailleurs de fonds, que notre système d’évaluation
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FÉLICITATIONS
Au cours de l’été et de l’automne, le nouveau modèle et les processus détaillés feront l’objet de vastes essais auprès de groupes de
consultation.
L’examen de la structure des CSS est le second examen important
du Programme de subventions à la découverte qui a été diffusé
récemment. Le mois dernier, le CRSNG a publié le Rapport du
Comité d’examen international du Programme de subventions à la
découverte [http://www.crsng.gc.ca/about/PDF/international_
review_f.pdf]. Ce rapport a corroboré la philosophie du programme et la qualité de la recherche et de la formation qu’il
appuie.
For more information / Pour le plus amples renseignements :
Arnet Sheppard
Senior Advisor to the Director /
Conseiller principal auprès de la directrice
NSERC / CRSNG
613-995-5997
[email protected]
PAUL CORKUM APPOINTED CANADA
RESEARCH CHAIR AT THE UNIVERSITY
OF OTTAWA
On June 10, 2008, the University of Ottawa
announced the appointment of Paul Corkum as
a Canada Research Chair. Paul Corkum, a full
professor in the Department of Physics and a
researcher at the National Research Council of
Canada, is one of the world’s leading specialists in lasers and their applications. For over 30
years, he has been developing and advancing
concepts needed to understand how intense
laser-light pulses can be used to study the
structure of matter. He is the father of the attosecond pulse, which
is so fast that it allowed him to capture the first image of an electron orbiting an atom. His research, which has uncovered a new
source of light and innovative means of observing and controlling
molecules, atoms and even subatomic particles, could spawn new
materials and tools in the health-care sector.
The Canada Research Chairs Program supports researchers who
are internationally recognized as leaders in natural science, engineering, health sciences or the humanities. The recognition allows
them to conduct groundbreaking research, to supervise students
and to share their discoveries with a variety of audiences.
FÉLICITATIONS
par les pairs évolue pour s’adapter aux changements dans le milieu
de la recherche et que nous continuerons d’avoir la capacité et la
rigueur requises pour évaluer d’excellentes propositions ».
CALLING ALL ARTISTS
NOUS LANÇONS UN APPEL À T OUS LES ARTISTES
CONTEST FOR NEW LOGO FOR PHYSICS IN CANADA IS UNDERWAY
The Editorial Board is inviting all CAP members, friends, or colleagues to submit designs for a new PiC-PaC logo
which should fit well in the upper left hand corner of the front cover of each issue, and integrate well on any of the
PiC covers.
The deadline for submission is Nov. 1st 2008.
The winning entry will be featured on the 2009 January-March issue and the photograph and bio of the submitter
will be published in the issue. The winner will receive an “Art of Physics” t-shirt and, if applicable, a one-year
membership in the CAP.
UN CONCOURS POUR UN NOUVEAU LOGO DE PIC-PAC EST EN COURS
Le Comité de rédaction invite tous les membres de l’ACP, amis, et collègues à soumettre des croquis de logos PiCPaC pour remplacer celui qui se trouve au coin en haut à gauche de la couverture. Le logo devrait bien s’intégrer
dans ce coin supérieur gauche quelque soit la conception de la page couverture.
La date de soumission des croquis est le 1er novembre 2008.
Le croquis choisi figurera dans le numéro de Jan/mars 2009 avec une photographie et une courte biographie de
l’artiste. Le gagnant recevra un T-shirt « Art de la physique » et si, pertinent, une adhésion d’un an à l’ACP.
8/18/2008
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NEWS
CALL FOR NOMINATIONS / APPEL DE CANDIDATURES
CAP MEDALS / MÉDAILLES DE L’ACP
The following medals will be awarded in 2009:
CAP MEDAL FOR LIFETIME ACHIEVEMENT
IN PHYSICS
CAP HERZBERG MEDAL
CAP (UNDERGRADUATE) TEACHING MEDAL
CAP BROCKHOUSE MEDAL (CONDENSED MATTER & MATERIALS PHYSICS)
CAP/CRM PRIZE IN THEORETICAL AND MATHEMATICAL PHYSICS
CAP MEDAL FOR OUTSTANDING ACHIEVEMENT IN INDUSTRIAL AND
APPLIED PHYSICS
Information and nomination forms can be found on the CAP`s website - http://www.cap.ca
(Deadline: 10 January 2009)
Les médailles suivantes seront décernées en 2008 :
MÉDAILLE
DE L’ACP POUR CONTRIBUTIONS EXCEPTIONNELLES
DE CARRIÈRE EN PHYSIQUE
MÉDAILLE HERZBERG DE L’ACP
MÉDAILLE POUR L’EXCELLENCE EN ENSEIGNEMENT DE LA PHYSIQUE
MÉDAILLE BROCKHOUSE (MATIÈRE CONDENSÉE ET MATÉRIAUX)
PRIX ACP/CRM DE PHYSIQUE THÉORIQUE ET MATHÉMATIQUE
MÉDAILLE POUR DES RÉALISATIONS EXCEPTIONNELLES EN PHYSIQUE
INDUSTRIELLE ET APPLIQUÉE
Renseignements et formulaires de nominations pourront être trouvés
au site internet de l’ACP -- http://www.cap.ca
(Date d’echéance : 10 janvier 2009)
IUPAP SPONSORSHIP OF INTERNATIONAL CONFERENCES
PARRAINAGE DE CONFÉRENCES INTERNATIONALES PAR L’UIPPA
Each year IUPAP sponsors from 20 to 30 international conferences and awards
grants to some of them. Conference organizers desiring IUPAP’s sponsorship
should communicate with the appropriate international Commission which will
then make recommendations to the IUPAP Executive Council. April of the year
preceding the proposed conference is the target date by which applications
should be submitted to Commissions. Potential organizers of conferences to
be held in Canada, during 2010 or early 2011 should obtain the support of the
Canadian National IUPAP Liaison Committee (CNILC). In order for this to occur,
the relevant information must be sent to the address below by February 28,
2009.
Chaque année, l’UIPPA parraine de vingt à trente conférences internationales et
accorde des subventions à certaines d’entre elles. Les organisateurs de conférences qui souhaitent obtenir le parrainage de l’UIPPA doivent communiquer
avec la Commission internationale appropriée, laquelle fera des recommendations
au Conseil excutif de l’UIPPA. Les demandes de parrainage doivent être
présentées aux commissions au plus tard le mois d’avril de l’année précédant la conférence proposée. Les éventuels organisateurs de conférences
devant avoir lieu au Canada en 2010 ou au début de 2011 devraient obtenir l’appui
du Comité national canadien de liaison avec l’UIPPA. Pour ce faire, ils doivent lui
faire parvenir l’information nécessaire à l’adresse indiquée ci-dessous, d’ici le 28
février 2009.
It should be noted that conditions for IUPAP sponsorship that the conference registration fee should not exceed the upper limit set by IUPAP each year (see
IUPAP web site) and that circulars, other announcements, and the proceedings of
the confrerence contain the following statement:
Il est important de noter que l’UIPPA ne parraine que les conférences respectant
certaines conditions -- les frais d’inscription à le conférence ne doivent pas excéder
le montant maximal fixé par l’UIPPA (information sur le site internet d’UIPPA) et les
circulaires, les autres annonces, ainsi que les actes de la conférence doivent comporter l’énoncé suivant:
“To secure IUPAP sponsorship, the organizers have provided assurance that
(Conference name) will be conducted in accordance with IUPAP principles as
stated in the ICSU Document “Universality of Science” (sixth edition 1989)
regarding the free circulation of scientists for international purposes. In particular,
no bona fide scientist will be excluded from participation on the grounds of national origin, nationalitiy, or political considerations unrelated to science.”
“To secure IUPAP sponsorship, the organizers have provided assurance that
(Conference name) will be conducted in accordance with IUPAP principles as stated in the ICSU Document “Universality of Science” (sixth edition 1989) regarding
the free circulation of scientists for international purposes. In particular, no bona
fide scientist will be excluded from participation on the grounds of national origin,
nationalitiy, or political considerations unrelated to science.”
Application forms and additional information can be obtained from the IUPAP
website: http://www.iupap.org or from the Secretary of the Canadian National
IUPAP Liaison Committee :
Pour obtenir des formules de demande et toute autre information, il suffit de visiter
le site suivant : http://www.iupap.org ou de s’addresser au secrétaire du Comité
national canadien de liaison avec l’UIPPA :
P. Hawrylak
Institute for Microstructural Sciences
National Research Council of Canada (M-50)
Ottawa, Ontario K1A 0R6
P. Hawrylak
Institut des sciences et des microstructures
Conseil national de recherches Canada (M-50)
Ottawa, Ontario K1A 0R6
Tel: (613) 993-9389
Fax: (613) 990-0202
E-mail: [email protected]
Télphone : (613) 993-9389
Télécopieur : (613) 990-0202
Courrier électronique : [email protected]
PROFESSIONAL CERTIFICATION PROFESSIONNELLE
Details regarding the certification process, as well
as all forms required to apply for certification, can
be found in the "Professional Certification" section
of http://www.cap.ca.
164 C PHYSICS
IN
L'information relative au processus de certification,
ainsi que les formulaires requis, sont disponibles
sous la rubrique "Certification professionnelle" du
site Internet de l'ACP qui se lit ainsi :
http://www.cap.ca.
8/18/2008
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Page 165
TACHES VOLONTAIRES
CALL FOR NOMINATIONS-SUGGESTIONS / APPEL DE CANDIDATURES
CANADIAN NATIONAL IUPAP LIAISON COMMITTEE
Nominations are invited to fill two positions (terms ending Dec.31/08) on the Canadian National IUPAP Liaison Committee
(CNILC) for a term of three years commencing January 1, 2009 (ending Dec.31/11). Although there are no restrictions on who
is nominated, efforts will be made to ensure that there is a broad representation on the Committee covering the areas of geographic location, physics sub-discipline, and language requirements. The final decision remains with the CNILC Secretariat.
The current members of the Committee are:
G.W.F. Drake (Chair)
P. Hawrylak (Secretary)
E. Hessels (term ends Dec.31/08)
C. Gale (term ends Dec.31/08)
to be announced (term ends Dec.31/10) to be announced (term ends Dec.31/10)
Ex-officio IUPAP Commission members (Sept.2005 to Sept.2008) are:
J.-C. Kieffer
(Plasma Physics)
P. Hawrylak
S.P. Goldman
(Physics Education)
J. Dilling
H. Couchman
(Computational Physics)
B.D. Gaulin
C. Rangan
(Quantum Electronics)
W.T.H. van Oers
R. Thompson
(Atomic. Mol. and Opt. Physics)
M. Freeman
D. Pinard (observer)
L. Marleau (term ended Dec.31/09)
(Semiconductors)
(Symbols, Units, Nomenclature...)
(Struct. & Dynamics of Cond.Matt.)
(Nuclear Physics)
(Magnetism)
Ex-officio CNILC Members:
A. Astbury (President of IUPAP)
Formal letters of nomination, that include the nominee’s curriculum vitae and a brief description of the nominee’s involvement
in international activities, must be sent to the Executive Director of the Canadian Association of Physicists, Suite 112,
McDonald Building, 150 Louis Pasteur Avenue, Ottawa, Ontario, K1N 6N5, by 2008 November 30.
For further information, please contact Dr. P. Hawrylak, CNILC Secretary, Institute for Microstructural Sciences, NRC (M-50),
Ottawa. Tel: (613) 993-9389; Fax: (613) 990-0202; E-mail: [email protected]. Detailed reports on IUPAP matters can be found at http://www.iupap.org.
NOTE: All the IUPAP Commissions are soliciting nominations for the newly created IUPAP Young Scientist Prizes.
For the IUPAP Commission on Semiconductors (C8), please consult http://iupap-ysp.nrc.ca for further details.
For other Commissions, please check with the Commission Chairs.
CAP COUNCIL / CONSEIL DE L’ACP
Are you interested in having a voice in the management of
the CAP? Do you want to help define the priorities of your
association? Volunteers for the following 2009-2010
Council positions are now being sought:
*Vice-President Elect (Presidential line)
*Secretary-Treasurer (3-year term)
*Director of Professional Affairs (3-year term)
*Director of Academic Affairs (3-year term)
*Director of Communications (3-year term)
Councillor-at-Large (2-year term)
Regional Councillors (2-year term)
Vous voulez avoir voix au chapitre dans la direction de l’ACP?
Vous désirez définir les priorités de votre association? Nous
sommes présentement à la recherche de personnes voulant
se proposer comme candidat(e)s aux postes suivants à
combler au Conseil 2008-2009:
*Vice-Président Élu (ligne présidentiel)
*Secretaire-Tresorier (3-années)
*Directeur des affaires professionnelles (3-années)
*Directeur des affaires académique (3-années)
*Directeur de communications (3-années)
Conseiller général, étudiants gradués (2-années)
Conseillers régional (2-années)
A brief call for suggestions and a description of the roles
and responsibilties of CAP Council members, can be found
on the CAP’s website at http://www.cap.ca or by contacting
the CAP office at 613-562-5614 or by email at
[email protected].
Si vous voulez voir un formulaire d’appel de candidatures et
une description du rôle et des responsabilités des membres
du Conseil de l’ACP, veuillez consulter les pages internet de
l’ACP à l’URL www.cap.ca ou contacter le bureau de l’ACP à
613-562-5614 ou par courriel à [email protected].
Deadline for the submission of expressions of interest is
2008 November 30.
L’échéance pour la présentation des candidatures a été fixée
au 30 novembre 2008.
* Executive Committee position
* Position sur le Comité exécutif
8/18/2008
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Page 166
2008 MEDALS AND AWARDS
THE CAP-INO MEDAL FOR OUTSTANDING ACHIEVEMENT
IN APPLIED PHOTONICS
LA MÉDAILLE DE L'ACP-INO POUR CONTRIBUTIONS
EXCEPTIONNELLES EN PHOTONIQUE APPLIQUÉE
A
leading physicist and researcher, Dr. Jacques
Beaulieu has had a decisive influence on
Canadian laser history with the development of
a brand new type of high power gas laser called
the CO2-TEA laser which stands for Transverse Excitation
at Atmospheric pressure laser. In the late 1960s, there was
intense competition with teams in Europe and the US
striving to increase the operating pressure of pulsed CO2
lasers to produce a
compact, efficient
The CAP-INO Medal for
high power laser
source for applica- Outstanding Achievement in
tions such as rang- Applied Photonics is awarding and material ed to Jacques Beaulieu
processing.
Dr. (retired), for the invention of
Beaulieu
devel- the transversely-excited
oped a solution that atmospheric carbon dioxide
was both elegant in laser as well as his work in
its simplicity and system performance modelfar reaching in its ing.
impact.
Nine
patents were eventually filed on various aspects of the new laser. Dr Beaulieu came up with a
new concept of using a double discharge, the first discharge leading to pre-ionization of the gas and the second
discharge leading to pumping the population inversion.
The main benefits from that laser were its operation at
atmospheric pressure leading to broadening of absorption
lines and large energy density storage allowing faster
amplification of the signal. This in turn led to its gainswitch operation on a submicrosecond time scale.
This low cost table-top mega-watt peak power pulsed laser
was recognized around the globe as a technological revolution for laser processing as well as for plasma generation
and studies. Apart from its intended uses, the laser had a
major impact on University Research around the world
166 C PHYSICS
IN
and expanded the knowledge of areas such as plasma
physics, spectroscopy, material processing, and photochemistry. A typical PhD project went from 90% laser
design and 10% Science to 90% Science activities and
10% laser design. It also triggered collaborative activities
between Defence Research Establishment - Valcartier,
National Research Council, Institut de Recherche
d’Hydro-Québec, INRS-Energy and Université Laval for
the development of
new applications.
La médaille de l'ACP-INO
pour contributions exceptionnelles en photonique
appliquée est décernée à
Jacques Beaulieu (retraité),
pour l'invention du laser au
dioxyde de carbone atmosphérique et à excitations
transverses, et ses travaux
de modélisation de performance des systèmes.
The scientific market for TEA lasers
was sufficient to
nurture
start-up
companies such as
Lumonics
which
then went on to
develop the major
commercial application for TEA lasers
inlaser marking. The
success of this application allowed Lumonics to become a major global force
in Industrial Lasers. The transverse excitation method has
afterwards been applied to chemical lasers and to excimer
lasers which resulted in a variety of new applications of
these lasers. Overall these developments have helped
shape the Canadian laser and laser application industries
during several decades from 1970 to 2000.
While at DREV, Dr. Beaulieu was also very active on
other significant projects such as Low Level Air Defense
which resulted in the establishment of Oerlikon in Canada
and NATO Anti-Air Weapon System which resulted in the
creation of Wescam. After his retirement from DREV in
1991, he continued his activities as a consultant involved
in defence system projects and in the medical field.
Recipient of the 2008
Medal / Récipiendaire
de la médaille de 2008:
The importance and impact of his work has been demonstrated by the numerous other awards he has received from
many organizations including being nominated as Grand
chevalier de l’Ordre National du Québec and Officer of
the Order of Canada.
Dr. Jacques
Beaulieu
Dr. Robert Corriveau
Canadian Institute for Photonic Innovation
Institut canadien pour les innovations en photonique
8/18/2008
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Page 167
MÉDAILLES 2008 - ACP/INO (BEAULIEU)
RESPONSE
BY
JACQUES BEAULIEU
Fifty five years ago when I started my postgraduate work at
McGill University, the main choices then were between
Nuclear Physics research and Microwave research at the
Eaton Lab under the direction of Gar Woonton, which was the
option I chose. Optics was then considered a mature technology with little prospect of significant technical progress.
In 1958, Townes and
Shallow announced "I am honored and flatthe discovery of the tered to have been nomM A S E R inated for this award. I
(Microwave
consider this to repreAmplification by
Stimulated Emission sents also a recognition
of Radiation). This of the excellent collabowas an interesting ration I have received
innovation but it from my colleagues of
could hardly com- the Defense Research
pete with simple
Establishment Valcartier,
radio tubes or transistors and the trav- the Physics department
eling wave tube for of Laval University and
general applications. the accomplishments of
Its
unexpected INO in the field of
impact was that this Photonics."
technique was translated to the field of
Optics by the invention of the LASER less then two years
later. This invention was a new concept that transformed the
technology of Optics into that of Photonics.
The LASER provided coherent light sources instead of using
incoherent visible sources obtained from the natural spontaneous broadband emission of hot sources such as light bulbs
or electric arcs in different gases. When DREV’s optical
experts duplicated the original LASER device, they were perplexed about the way its radiation pattern behaved. At that
time I was developing new types of resonators for microwave
spectroscopy and when I was shown the strange radiation pattern I said spontaneously that it was resonating in the TM01
mode, and added how to modify the laser mirrors to correct
this. Shortly after a new phenomena was reported called a Pi
Pulse generated by a short laser pulse illumination. This was
a quantum inertia effect which I had already used in the
development of a microwave “Transient Effect Spectrometer”
and for which a mathematical model had been developed.
That led me to reoriented my career towards the study of
coherent Optics, which was to become the field of Photonics.
For many applications, it was found that the original Patel
CO2 gas laser had a very much higher efficiency than solid
state lasers. However for military applications they were too
big. Some “experts” had calculated that a laser powerful
enough to be used as a LIDAR would be too large to fit in a
large transport aircraft. From the performance of the original
laser, to produce pulses with peak powers of one megawatt,
required for useful range performance, would need lasers of
more than 50 meters long. At that time, we had just discovered the TEA laser principle and an early prototype less than
one meter long was generating 2 megawatts per pulse. Within
a year a better version of this technique was generating
impulses of the order of 20 megawatts per meter.
The Transverse Excitation technique was also applied to
chemical laser, and achieved comparable performances. But
a new technique called Gas Dynamics lasers received more
attention south of the
border, because of its
« Je suis honoré et flatté possibilities for Laser
Weapons. A version of
d’avoir été nommé pour
the more modest elecce prix. Je considère
trically pumped chemque ceci représente
ical laser was develaussi la reconnaissance
oped by Lumonics in
de l’excellente collabora- Ottawa which found
tion que j’ai reçue de
many applications in
mes collègues du Centre micromachining and
other
commercial
de Recherches pour la
applications. But the
Défense de Valcartier, et
etching of glass was
du département de
most efficient when
Physique de l’Université
using the CO2 laser
and Coca-Cola was a
Laval et des réalisations
de l’INO dans le domaine major customer for the
Lumonics laser as it is
de la Photonique. »
used to etch the production code number
on the bottles as they moved along on the production belt at
the manufacturing plants.
After the creation of the INO, the Photonics technology
exploded. Diode lasers became cheap coherent sources in the
visible and near-IR, and fiber optics was extensively used to
play the same role as the waveguide technology did in the
radar developments 50 years ago. The fiber light guides could
be made to execute the same functions as the earlier
microwave components such as waveguides, coupler, circulator, magic Tee, polarization control, delay lines, signal couplers, etc. The main difference with microwave systems is
that the dimensions are reduced by a factor of the order 500,
so that the volume and weight are reduced by many 6 to 7
orders of magnitude.
LAURÉATS ET PRIX DE 2008
I am honoured to have been selected for Outstanding
Achievements in Applied Photonics. This honor is to be
shared with many colleagues the Defense Research
Establishment Valcartier (specially Paul Pace and Georges
Fournier) where most of my work was carried out and with
the team of Laval University of the Physics department that
participated in the evaluation and improvements of many
laser innovations, and INO that are now leaders in fiber
Optics technology and applications. I thank Robert Corriveau
for nominating me.
The R&D emphasis is now focused on the processing of
images to extract more object information than can be done
by a human operator. This means that autonomous systems
can perform a variety of functions completely autonomously,
which is the basic requirement for the development of
autonomous robotic systems.
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2:14 PM
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THE CAP-COMP PETER KIRKBY MEMORIAL MEDAL FOR
OUTSTANDING SERVICE TO CANADIAN PHYSICS / LA MÉDAILLE
COMMÉMORATIVE PETER KIRKBY DE L'ACP-OCPM POUR
SERVICES EXCEPTIONNELS À LA PHYSIQUE AU CANADA
P
eter Calamai is a true friend of Canadian physics
and is one of those who have made a real difference in Canadian science literacy and Canadian
science policy. He is a shining example of a truth
that we have been too slow to assimilate, i.e. that physics
students who choose not to follow a career in physics are
not a sign of failure on our part (or theirs), but people who
may bring their analytical skills (which we hope we have
augmented through
our teaching), to
The CAP-COMP Peter Kirkby
bear on problems
Memorial Medal for
of great importance
outside of the pro- Outstanding Service to
fession of scientific Canadian Physics is awarded to Peter Calamai, National
discovery.
Science Reporter for The
Peter
graduated Toronto Star, for his exemfrom
McMaster plary communication of sciUniversity in 1965 ence to the public, for his
with a B.Sc. in dedication to the promotion
Physics in and of science through the
worked as corremedia, and for his advocacy
spondent and editor
for science in Canada.
with the Southam
newspaper company for 30 years. He
is a three-time winner of the National Newspaper Award,
Canada's highest print journalism honour, and is currently
an Adjunct Research Professor at the School of Journalism
and Communication at Carleton University.
Peter is retiring as the Ottawa-based national science
reporter for the Toronto Star, Canada’s largest circulation
daily newspaper. He is a founder of the Canadian Science
Writers’ Association, past member of advisory boards to
Environment Canada and NSERC, and served on the
board of the Canadian Language and Literacy Research
Network.
Mr. Peter Calamai
168 C PHYSICS
IN
Peter Calamai’s byline was always a pointer to wellresearched and insightful information on both science and
science policy of immediate interest and utility to the
Canadian public in times when such information was often
sorely lacking from other sources.
Peter has always been generous with his time, making
time for late-night dinner meetings with the CAP executive, giving knowledgeable advice on
La médaille commémorative
how to navigate the
Peter Kirkby de l'ACP-OCPM shoals of parliament
pour services exceptionnels in lobbying for scià la physique au Canada est entific
research,
décernée à Peter Calamai,
energy policy, and
National Science Reporter
higher education.
He also made it a
pour le Toronto Star, pour
sa façon exemplaire de com- point to frequently
muniquer la science au pub- ask for referrals to
expert physicists
lic, pour son dévouement à
who might provide
présenter la science à trabackground inforvers les médias et pour sa
mation for a forthpromotion de la science au
coming article.
Canada.
As particular examples, physicists would be well advised to commend to
their friends the articles Peter wrote on January 19th and
February 25th about events at Chalk River. They are models of clear statement of analyses presented by competent
experts in a manner accessible and persuasive to any interested citizen.
His writing has always been engaging, insightful and factually correct, making reading that truly helped members
of the Canadian public to see and understand the questions
of science and science policy that would affect their lives
and those of their children.
His spare-time quasi-scientific pursuits include conchology (shell collecting) with specialization in the cowry
(Cyprae), ornithology, astronomy and the genetic engineering of tomatoes. His pseudo-scientific studies revolve
around Sherlock Holmes, and he has authored several new
Holmes adventures, which make very enjoyable reading.
Dr. Michael Steinitz
St. Francis Xavier University
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2:14 PM
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MÉDAILLES 2008 - KIRKBY (CALAMAI)
INTERVIEW WITH PETER CALAMAI, JUNE 10, 2008,
QUEBEC CITY (BY B. JOÓS, PIC EDITOR)
B.J. : We were very pleased to give you the prize.
PC – Because that’s fiction, that’s not …
P.C.: I must ask Gordon (Drake) what the prize was awarded
for. I gather it was not for a particular thing but for a body of
work.
BJ – There are also people who do history writing, a lot of
research, massive research….
PC – So what do
you want to know?
BJ – Well, first of
all, it’s your experience with science
because you, yourself, started as a
physicist?
"When I squeaked out of
McMaster University
four decades ago with a
B.Sc. in physics, it was
beyond my wildest
dreams that some day I
might be so handsomely
honoured by real physicists. I'll still be pinching myself on June 10."
PC – I graduated
in
physics
at
McMaster in 1965,
but never worked in
physics. I thought
I was going to do
work in physics, but
I got involved with
the student newspaper at the university and it was far more exciting than my
physics labs.
BJ – So, you like writing…
PC – No journalist actually likes writing. Journalists all like
reporting. It’s the difference between doing field research and
then having to write your notes afterwards. I don’t know anybody who does field research and then likes writing the
papers afterwards C they do it because they have to. Almost
all journalists do reporting because they’re inquisitive,
because they have an intense curiosity about things and a
short attention span. You know, a week would be a long time
for most journalists to work on a story. The undesirable part
is writing; the desirable part is having written. When you finish, it doesn’t matter whether it gets published or not C it’s
almost, not quite, inconsequential. That’s not always the
truth, but almost all reporters C and I’m talking here about
newspapers and print reporters/magazine reporters C get the
satisfaction of gathering the material, out of being able to
shape it into a narrative, into a story that has some sort of
structure, so that the reader, who knows nothing about the
issue, is able to sort of follow it, whether it’s a five letter article or a 2500 word article. When they finish writing, they
look back in admiration to what a wonderful job they did in
writing it, but the actual writing for most people is sheer
agony.
BJ – I see. It’s quite different from being a writer whose passion is getting up in the morning and putting in a few hours of
writing.
PC – But that’s a much longer time frame, usually they’re
working for years. There are certainly journalists who write
books and spend a couple of years doing it. That’s not me,
but there are people who do it.
BJ – Your investigative journalism at the student paper, was it
on science or was it just about…
PC – No, it was about all sorts of things. I eventually became
the editor, so we would
do things about univer« À mon départ de
sity funding policies,
l’Université McMaster il y university expansion
a 40 ans, avec en poche
policy, and governance
of the university and,
un B.Sc. en physique,
of course, the endless
même dans mes rêves
articles about how stules plus fous, je ne parpid the people on the
venais pas à croire qu’un student council were: a
jour je pourrais être hon- staple of all student
oré si généreusement par newspapers C they
always think people
de vrais physiciens. Je
who go into student
n’en croirai toujours pas
politics are stupid.
mes yeux le 10 juin. »
BJ – So your driving
curiosity was humani-
ty, human affairs…
PC – It always is. Even when you are talking about science,
what you’re talking about is the field of human endeavour. It
is not so much the τ lepton, for instance, that is the interesting thing for reporters (I’m not talking about physicists). It’s
the fact that physicists are tackling this, that they’re using different techniques to try to get into it, that they go through
thought experiments to devise how they’re actually going to
run the physical experiment C it’s the quest aspect, and that’s
human nature C that’s what makes it interesting. It also happens to be 4 billion dollars buried underground underneath
the French-Swiss border, having taken 12 years to design, and
the engineers from twelve different countries who come
together and it all fits within millimeters. That’s wonderful.
That’s also good, but it’s why people are doing this, what is it
they’re trying to find out and what kind of people are driven
to do that sort of thing C that is what is interesting.
BJ: Yes, it had to do with your promotion of science. The
citation doesn’t go into details. It is not only because you’ve
been writing credible and factual articles, but also because of
your good relationship with scientists, teaching us the importance of communicating with the general public and politicians.
BJ – So, from the student paper, you went on to …?
PC – I graduated and went directly to the Hamilton Spectator
as a general assignment reporter. I’d worked there in the
summer to make tuition, I’d worked mostly as a photographer
and then became a photographer/reporter, what used to be
called, in the quaint old days, a 2-way man, a wonderful term.
I loved it. And I went in and became police reporter, and you
know, outdoors reporter and labour reporter and urban renewal reporter. That took a period of 3 years from 66 to 69, and
one day the phone rang and Charles Lynch, who is the chief
of Southam News C the Hamilton Spectator was a Southam
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2008 MEDALS - KIRKBY (CALAMAI)
paper just as the Ottawa Citizen used to be a Southam paper,
so were 1400 papers in Canada, that was the largest group C
Lynch said how would you like to come and work in the
Ottawa bureau, the parliamentary bureau of Ottawa. My wife
had just signed a teaching contract, so I said I had to check
with her, she said yes, because going to that job meant that we
could get foreign postings. We were both interested in traveling.
BJ – Is she a journalist also?
PC – No, she’s a teacher, a high school teacher, but she was
interested in foreign postings and going overseas. When I got
to Ottawa, in 1969, I discovered that the man I was replacing
C there were four reporters who covered the federal government C had done science and environment, and anything that
had numbers in it. Basically, his share of the federal government departments were the ones that are now called the science-based departments: Natural Resources; Energy, Mines
and Resources; Health Canada … so that became my responsibility. So I became a science reporter in 69, and from 69 to
73 I was the science reporter for Southam, based in Ottawa,
going all the way across the country, going to Stockholm for
the environment conference, going down to Cape Canaveral
for the Apollo program, the end of the Apollo program,
Apollo 16, and then I got my first foreign posting which was
England in 73 and became a general correspondent, again
covering everything that was in my territory, whether it was
science or the disappearance of the village pub or whatever.
I did that for 4 years and went from there to Vancouver for 2
years, went from there to Africa for 3 years, came back into
the fellowship of the University of Toronto and Massey
College for 1 year, came back to Ottawa for 5 years, and in
the middle of that went to the University of Regina and was a
Visiting Professor for a year (1985-86), then went to
Washington to go to the White House bureau for Southam. It
was a 4 year posting, but after 2 years I got offered a job as
the editorial page editor in charge of the opinion pages of The
Ottawa Citizen. It seemed like a good idea at the time, and
for 5 and a half years, from 1990 to 1996, it was a very good
job and I liked it a lot, and then Conrad Black bought the
Southam company. And Conrad Black and I, ideologically,
are just not on the same planet.
BJ – He was imposing his ideology to the Editorial Board?
PC – He was the owner and I had no problem with the owner
saying he wanted the editorial pages to reflect his point of
view; however, I never even got to have that conversation
with him because various things I’d done had got up his nose,
and he fired me. I was fired along with the editor of the
Montreal Gazette, who also got up his nose and that was in
96. I freelanced for 2 years and, in 98, Toronto Star hired me
as the science correspondent. I did science from 69 to 73 and
now after a 25 year gap, started it again in 98.
BJ – So the Toronto Star always had a tradition of reporting
on science?
PC – Toronto Star always had a staff of science writers for
30 years at least. I’ve known many of them.
BJ – So how do you choose your stories in science?
PC – Well, it depends on who you work for. It differs from
paper to paper, from outlet to outlet. The ones that are chosen for CBC’s Quirks and Quarks are not the same ones that
I choose. We have different audiences – Q&Q is a science
show, is listened to by people who are predisposed to be inter-
170 C PHYSICS
IN
ested in science stories. It’s like a boutique in that sense. We
used to have a page that was called “Science” in the Star. We
still have one on Saturdays. I wrote for it a lot, but I always
was of mixed emotions because I thought that if it said “science” on the top, there would be all sorts of people that would
turn the page and never start to read it. I would much rather
have an article in the sports section, in the entertainment section or the general news section, because the readership is
higher C the percentage of people that will look at the page at
all is higher than if it is on a science page.
BJ – You spread them around.
PC – Well, I don’t have the choice, but I’m telling you where
I try to go, but it’s not my decision.
BJ – But how do you choose a story?
PC – Let’s talk about how I choose it for the Toronto Star. It
is not the same rule everywhere. What you want to anticipate
is a really big story because the Toronto Star wants to have its
name on the really big stories. So, if you have the results
from SNO…
BJ – You want it to be syndicated …
PC – No, no, in the Star, we don’t want to run a wire service
story from Canadian Press or Associated Press or even the
New York Times. We look for a really big story, like the mapping of the human genome, the first results from SNO, the
Challenger launch C the really big story, the front page main
story on the front page. The Phoenix Mars Lander is not a
front page main story; it is back inside the paper, but some
other Mars stories are. You always try to make sure you
anticipate those and offer them up to the various editors of the
paper before they even ask for them. You know they will want
them.
BJ – So you keep an eye on the wire service?
PC – Most cases, not on the wire. In most cases, you’re keeping an eye on major academic journals. I see Science on
Friday, along with every other registered subscriber ahead of
time. I get Nature ahead of time. I get PNAS. I get
Proceedings of the Royal Society. Then you’re looking
through them for published papers. You’re also trying to keep
your ears open for conferences that are being held where
results may be announced before they’re actually published.
Of course, you’re monitoring what other people are writing
about. I do it by going to a thing called the Knight Science
Journalism Tracker out of MIT and they look at everything
around so that I don’t have to do that, they do it all. The news
wires are not particularly good. I mean, I would find more
stories in the Daily Telegraph in London than I would find in
Reuters, just for an example. I would probably find more stories in New Scientist than I would find in Reuters. They just
have more people reporting on them. So you look at all those
areas and, in my case, what I’m looking for is a Canadian
story. If I can choose between an American story and a
Canadian story of equal scientific merit, I will always take the
Canadian story because the American story will get reported.
The New York Times will report it, the Washington Post will
report it, the Associated Press will report it, but the chances of
the Canadian story being reported are slimmer C by a wire
agency, it is not going to happen. I am automatically biased
towards stories involving people in southern Ontario, because
over 90% of the Star readership is centralized in and around
the Greater Toronto area. I want to write stories about people
whom readers know, if possible. So, that’s the check list: is
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BJ – When this Frenchman tried to jump from 25 miles high
in North Battleford, Saskatchewan, a few weeks ago…
PC – There’s no science in that story, there is technology, but
no science. We have lots of people to do that. There’s no
point in my doing this story that a general assignment reporter
or even one of our feature writers can do just as well and
maybe even better than I can. Because that story is largely a
writing story, you don’t have to have any special scientific
expertise. But when the Canadian nuclear safety commission
decides that AECL shouldn’t restart the NRU reactor at Chalk
River, it becomes…
BJ – You wrote about that?
PC – Wrote a lot about it. So did the political reporters. They
wrote about the political side of it, but I wrote articles about
the technology side of it and the background. I had attended
almost all of the CNSC hearings, so I had all those documents. So there, I had something to contribute to the story
that an ordinary beat reporter, or general assignment reporter
as we call them, couldn’t have contributed. I could make a
value-added contribution to this story. The equation that
I always go through is “do I have something that allows me to
do this story better than a general assignment reporter C do
I know some of the people involved; do I know where to find
some of the information; do I understand the difference
between the alpha, beta, and gamma ray radiations, so that I
don’t have to fumble around trying to remember which one
really matters C that sort of thing. If I do, well then, I don’t
know, I put my hand up, send in what’s called a skedline in
the morning saying I’m proposing to file this story, here’s a
30 word definition, 30 word précis of what’s it’s going to be
about C it’s going to be this long, and I think you can find this
sort of artwork to go with it, illustrations or photos. And
that’s it. It’s all done in about 35 words maximum. That goes
into a meeting in which editors basically say we have this
much space in the paper, we have all these other things happening, there is just no space for this Calamai story. He may
think this is the most important thing since sliced bread, but
there’s not much space for it or maybe we can find space for
it, which is the worst answer, then you go do all the work and
it might not get in the paper. You would much rather they say
no, good story, but in tomorrow’s paper. It’s the luck of the
draw. I can’t remember what it was about, but I remember I
sweated bullets over this story, which I thought was very
important and the Queen Mother died. Four pages were automatically taken right out of the paper; everything else got
crunched like that, and my story was ... gone. News is a very
perishable commodity. If a story looks newsworthy today, by
tomorrow, it might not be newsworthy for several reasons.
One, somebody else may have already published it and we are
not going to publish it a day later C even though we knew
about it at the same time as those people. If we didn’t get into
the paper at the same time as them or on air at the same time
as them, it looks like we’re just following up on their story.
Our self-esteem and reputation won’t allow us to look like
we’re following up on somebody’s story, or it may just be old
because then the story has moved on. What the prime minister said 2 days ago about Linda Keen, is not news 2 days later
because the story has evolved. There’s been a next day story
and a next day story. So you either get it in while it’s still hot
news or you forget it and go on to the follow up story and then
the follow-up story.
BJ – But there are other reports which are longer and more
exhaustive and take some time. Does the Toronto Star publish those, or do you do those?
PC – All the time, of course.
BJ – But that’s different. Those don’t have a timeliness as
much as ….
PC – But you still have to …in the Toronto Star. It isn’t the
same for all papers, but in the Toronto Star you still have to
have a peg. There has to be a reason why you’re doing a story
about gravitational waves now. Why didn’t you do it 3
months ago, or 3 months from now.
BJ – For instance, the new big accelerator, is it commissioned?
PC – No, it hasn’t started yet. I’ve already written 2 stories
about it, and I’ll write some more about it.
BJ – When they actually turn on the power?
PC – I’ll probably write an injection around the beginning of
September C first electrons injected into the ring gives me a
peg. The story can appear on the Saturday, saying next week
they will inject. But the way I manage to do stories on gravitational waves and all sorts of other things, was ... back in
2005, in the year of physics, I proposed to the Star a series C
which is still there on the web, you can see it C on what I call
Einstein’s legacy. What are the research projects that people
are still working on today that basically you can say were
born with Einstein’s brain: Bose-Einstein condensation, gravitational waves, the gravity B probe, the most expensive satellite ever put into orbit, looking for frame dragging ... the peg
was the annus mirabilis. It’s the anniversary of Einstein, it’s
the year of physics, so we can run an 8-part series (it was
actually more, we got Clifford Will to write an article) but the
peg was the year of Einstein, so there was a reason to do it.
They would not have found space for those stories in 2006.
We have to understand the most important thing, in reporting,
whether you’re reporting politics, or sports, or the environment, or science is not that the newspaper has the money to
send you to Quebec city or 3 weeks up on the CCGS
Amundsen in the arctic, is that they’ll make the space available or the air time available. People think, oh it cost a lot of
money for Calamai to travel around and go to conferences,
that is true. But it costs a lot, lot more to publish the articles
in the paper because it’s foregone revenue. My article takes
the space of an ad that would have brought in how much
money? Or takes the space of another story. A big newspaper like the Star, it may be that as much as one out of every 4
stories written on any day do not get printed, don’t get in the
paper, ever. They’re dead, they’re gone.
it really important scientifically?, yes; is it a Canadian story?,
even better; does it involve somebody from York or Ryerson
or Waterloo or McMaster, or anywhere where the readership
is?, even better. But that doesn’t mean that, if it’s a marginal
story you write about it just because it involves somebody
from the Perimeter Institute. I think I’ve written very very
few stories about research from people at the Perimeter
Institute because there hasn’t been a lot of published material
that actually has shaken up the whole area. There were a couple of things C one by Lee Smolin, one by Fontini C but,
other than that, not that much yet. Other things that the
Perimeter Institute do, like their Einstein Fest, or their lecturer series C I went up there and spent 2 days when they had
the high school physics teachers in to help them find new
ways of teaching the new physics, if you will. That’s a good
story, not a news story but a feature story.
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BJ. They do not even go on the web?
PC – No. Some papers do that, but we don’t. The struggle all
the time is to try to be able to find stories that fit all of the criteria that I ran through C that you could find an editor (an editor, not the Editor necessarily) who is committed to try and
find you space in the paper. Maybe in the end he may not be
able to deliver, but at least he’s going to go in and fight for
that space with all the other people who are fighting for that
space, because it’s limited. There are only four stories on the
front page of the Toronto Star on any one day. To get a story
on the front page of the Toronto Star, and only one of those is
discretionary; the other three are basically decided by what
the big international news story of the day is, what the big
national story of the day is, and what the big local story of the
day is. So there is one discretionary one you might be able to
get a science story put in (if it’s not already the biggest story
of the day).
BJ – What attracts you to science? Do you think you have a
bias or not about different kinds of stories?
PC – I have a dual standard; but first is, can I get it in the
paper. There may be things that are very interesting but I will
never get it in the paper. Mathematics is very, very hard to
get in the paper. It has to do with the fact that not many people think the way mathematicians do and most people who
enter journalism were never very good at math C that’s why
they became Arts graduates, Humanities graduates. Mixed
fractions throw them into frenzies. They say they don’t have
the math gene, but what they have is a math phobia. So math
stories are a very hard sale, and the only decent mathematic
article I had in the paper in the last year, was from Queen’s
University Profs A. Herzberg and R. Murty, who did a nice
little piece of work on optimizing solutions for Sudoku, the
little nine square thing that my wife does all the time, where
you have to put the numbers in the square. So it was pure
math but it was applied to Sudoku, and therefore I knew there
was a peg. And I could write about it. In the end, they were
published in the American Mathematical Society. So it made
a good story. The math stories are a hard sale. I’m always
interested in stories that sort of are a twist, a reversal of what
you would have thought. One of the climate change stories
that I wrote that got the most feedback from readers was when
I found a study of a guy at Waterloo on how good the climate
change would be for golf courses in Canada, expand their
year, etc., and I only wrote about 400 words about it, a short
little story. People were so mad, wait a minute, this is climate
modeling, I’ve written tons about climate weather before and
all of a sudden, you’re angry because this climate model says
golf courses will flourish. You want everything to be doom
and gloom. So it’s nice to get counter-intuitive stories and
there are always lots in science. It is hard to write stories
about the Large Hadron Collider and the physics when it gets
that rarefied. It was hard enough the other day to talk about
CP violation. If I can’t get my head around it, how will I get
my reader’s head around it? It requires a whole bunch of
prior knowledge, and since newspaper articles are getter
shorter and shorter, it’s very hard to put all of the background
information you need to explain to people who really aren’t
sure what a molecule is, much less a boson, and have any
space left for the news C to do the remedial education, which
is what we’re talking about here, and then get space left for
what’s new. If you don’t do the remedial education, they
don’t have a way of knowing how this news fits in. So you
have to do both in 500 words, which is extremely difficult to
do. Some topics are just self-eliminated because you can’t
172 C PHYSICS
IN
find a way to deal with them in the amount of space that
you’re going to have available. For example, I’ve been struggling for 3 weeks to write an article about what happens in the
artic with mercury and bromine C mercury depletion events.
It is very complicated… chemical kinetics is extremely complicated ... and I just can’t get my head around how I can
explain this to people who don’t remember anything of high
school chemistry. Some subjects select themselves out. I
love paleo-. Put the word paleo- in front of anything: paleobiology, paleo-anthology. It is always good. I could write a
dinosaur story a week and get it into the paper. You can probably write a black hole story almost every week, but I get
bored by yet another story about a big black hole eating something else, and I have pretty much given up on writing the
gene of the week story because it’s getting repetitive now…
yet another gene is discovered that affects this particular disease. Of course none of these diseases are single gene diseases, therefore we do not really know much more than when
we started, because you do not know how many genes are
involved to start with. Some things you initially write about
in a great burst of enthusiasm and you think this will go somewhere. Then you find that it really isn’t going anywhere and
you give up. There’s absolutely no shortage … this last year
has been an anomaly, because I was off work with my hip surgery for 3 months. In a standard year, I would normally publish somewhere between 120 and 140 articles. If you remove
holidays, that basically means roughly 2.5 articles a week.
Some weeks will be four, some weeks will be 1, some weeks
will be 5. I’ve had weeks that I’ve had 7 articles. When I
used to go to the AAAS meetings, I used to do 2 articles a day
back in the 1970’s. They were held between Christmas and
New Year then. There was no other news. The papers were
thick with ads, boxing day ads. They had all this space to fill.
There was no news from Parliament. All the institutional
news dried out. There wasn’t much police news. Now they
hold the AAAS in February when there is tons of other news.
So I have to really fight. I write one a day. That is enough. If
I write two, they ask which is the important one. I have to
make my own selection. So far this strategy has worked. I got
four stories from the 2007 AAAS on the front page, and three
from the 2008 meetings.
BJ – How do you view your role in science? Scientists are
always concerned about their image because they know that,
in the long term, their funding depends upon the general population believing that science is important, but another aspect
is politicians believing that it’s good for the economy. So do
you feel that you have a role to play in promoting science?
PC – My business card says national science reporter. I try
always to describe myself as a reporter whose beat is science
and I make that distinction because sport reporters too often
start to identify with the sport that they cover and sometimes
with the team that they cover, and become cheerleaders for
that team. You hear every year that the Maple Leafs have a
chance to win the Stanley Cup. You do not want to start the
year saying that they will not amount to much. So you make
it believable. Same thing with the political reporters. They
identify with the people in politics. Political reporters go into
politics, they go work for ministers, identify with them and
there’s a real danger to that in my view. I try desperately not
to be a scientist manqué, the way other people are sport manqué, or political manqué. You guys are my meat, as it were.
I look at you as the source of stories, what to write about. I
write about you as fairly and honestly as possible, not with
detachment. You see scientists as people. You don’t want to
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BJ – What about NSERC underfunding?
PC – Somebody could do a story on it in the Canadian
Geographic maybe. Somebody can certainly write about it in
Research Money Newsletter. Most people do not care about
NSERC being underfunded unless it becomes a crisis.
BJ – This brings me to “brain drain”.
PC – When it came to the brain drain, I wrote about it. That
is what I wrote about when I wanted to do a piece on the
Canada Research Chairs. I wrote it as a “brain drain reversed”
story, because I knew both editors and readers would be interested in “brain drain”. They wanted me to promote the idea
that other countries are copying the Canada Research Chair
program. Now we are going ahead with even more highly
prestigious ten chairs, the Vanier chair. Most people do not
care about that. But what they do care about is that we managed to bring back Canadians from abroad; we managed to
stop people from going abroad; and we managed to steal people from other countries. So we have “brain retain”, “brain
retrieve”, and “brain gain”. We got all three. This was worth
writing about, but the endless briefs, cater vaulting, and disputed statistics about how many people were actually lost was
not a story. It did not have any heart to it. There was no core
to it as a science story. It became a political story. You are not
doing enough to stop the brain drain. You are responsible for
Canada slipping to the x spot among developing countries.
The government’s promise that Canada increase its science
funding to be in the top five in the world in terms of per capita funding of science. If you walked out in the streets of
Ottawa, or Quebec City and asked people; “Did the
Government of Canada set a target for where we should be on
science spending?” Nobody would know. So why would I
write about something nobody cared enough to store in their
excess baggage. The Government of Canada sure worked
hard to promote it. It is not an issue, not even in the bottom of
my list. The scientific community would love to have me
write about that dull policy stuff. Science policy in the
Toronto Star and in most daily newspapers is a non starter B
in Research Money, fine; in Science and Nature, fine; but not
for a mass market newspaper. Even Quarks and Quirks barely mentioned that A. Carty’s position as Science Advisor had
been terminated. They did put it on their website.
BJ – The public want an interesting science story.
PC – Yes. The politics of science, if you will. One of the
problems is that we’re not big enough.. If we were the size of
the U.S., we could have the equivalent of the Federation of
American scientists who run a well equipped and big
Washington office with really good in depth research and
people assigned to all the key senate committees and they’re
there all the time. We would generate something like Daniel
Greenberg who, for 20 years or so, wrote about the politics of
science in Washington for Science Magazine or books and
became quite popular. The New York Times scientist team B
the 9 people who write science B has someone based in
Washington. And they’re based there to do the science policy story, but we’re not big enough to have that…We do not
have the differentiation in readership to whom you can
appeal. 1% of the American public is 3 million people. Daniel
Greenberg’s newsletter was readership supported. There’s
not the volume or the interest in Canada to do that. You can
make the argument that they do publish those sorts of things
in Sweden a lot, in Denmark a fair amount, and in Norway
more or less, but they’re different countries. They have lively science policy communities. Canada does not have that.
BJ – Your community of science journalists is small, I presume? Do you interact with the others? .
PC – We interact in the sense that we compete. It burns me
to no end when Margaret Munroe gets a story based on documents released under access of information about people
getting NSERC grants and spending it on hubcaps. We do not
get the fraud stories told often enough in Canada, so we
assume that there is no fraud. But I do not believe that. We
may not have the egregious stories as in the U.S. , but human
nature being what it is, there have to be some. We all interact
and have a Canadian Science Writers Association of 500
members. Somewhere around 45 are staff reporters, in newspapers, radio and television, and organizations such as universities. When I started in 69, there were more than that,
more newspapers. The Hamilton Spectator no longer has a
science reporter with MacMaster University, Waterloo, and
Perimeter at its doorstep. All of those papers that had science
reporters have fired them, or they have retired. A large number of science writers are freelancers.
continue the stereotype of people in white lab coats; you want
to try to avoid that or, even worse, as people staring at computer screens. I don’t want to be seen as a handmaiden. A lot
of people say you have a very important role. You’re helping
us get our story out to the public. I may incidentally help put
the story out to the public but that’s not why I’m doing it. I’m
doing it because you’re a good story. My job is to exploit scientists, to make them into stuff that gets people to read our
newspapers so that we can sell advertising. And that’s the
formula. The newspaper is a vehicle to sell readers to advertisers. We, the people who actually work on the news, have
nothing to do with the advertising department at all, but the
business model which pays our salary, and sends us to various places, depends on advertisers. No newspaper in Canada
is reader supported, some in Europe are, but not in Canada
because our cover price is too low B you can’t support it with
a dollar for a paper. So I always have to keep in mind that my
job is to write things that enough people will want to read that
they continue to buy the paper, subscribe to the paper. It has
to have popular appeal. That precludes being a promoter for
the scientists. There are a lot of things that the scientists
would like you to write about that have no popular appeal.
Some do. I just finished talking to Art Macdonald about the
new things that they are going to do with SNOLAB, and they
definitely have popular appeal. I was out this morning at an
INRS lab where they are planning to build a whole experimental river 200 km north of Quebec City, channelized, with
gauges and all. It would be a phenomenal story. They would
like to have the thing publicized. That is fine. I would like to
write about it. It is a great story. We have a receptor-capacitor. A lot of times scientists would like me to write about
things that I know I cannot do a story that the editors will put
in the paper and the readers will read.
BJ – Thank you.
PC – A final word. A major difference between someone
reporting science and politics, for instance, is that we are
always reporting good news. After spending a lifetime, 25
years in my case, reporting terrible news, war, deaths and
destruction, politicians saying stupid things and arguing a lot,
you finally get a chance to write a story where everybody
feels good. The scientists want to talk about their discoveries.
They want the exposure. They are not running down some
corridor on Parliament Building trying to escape you.
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THE CAP-CRM PRIZE IN THEORETICAL AND
MATHEMATICAL PHYSICS
LE PRIX ACP-CRM DE
PHYSIQUE
THÉORIQUE ET MATHÉMATIQUE
P
rofessor Richard Cleve is an outstanding computer scientist whose work at the boundary of physics,
mathematics and computer science has transcended computer science to achieve broad impact on
the physics of quantum information. He has made seminal
contributions to the field of quantum information science,
described briefly below, and he has been instrumental in
building Canada’s research effort in this emerging area.
Quantum information science aims to The CAP-CRM Prize in
devise more effi- Theoretical and
cient ways to solve Mathematical Physics is
information pro- awarded to Richard Cleve,
cessing tasks than University of Waterloo, for
are possible with fundamental results in quanclassical informa- tum information theory,
tion processing. In
including the structure of
order to compare
quantum algorithms and the
their relative efficiencies, it is foundations of quantum
important to quan- communication complexity.
tify the resources
required for certain
tasks.
Professor
Cleve showed how quantum algorithms can be broken into
a series of fundamental blocks that quantify the resources
used by a quantum processor.
Transistors comprise universal gates for classical computing; in 1995 Cleve and colleagues showed that in the
quantum world, any unitary transformation on an arbitrary
number of bits could be implemented by a circuit containing one and two quantum bit (qubit) gates. Today, most
physical implementations of quantum computer prototypes employ this key result. In later work, Cleve and colleagues described methods, called lower bounds, for estimating the minimum amount of resources required in
some models of quantum information processing. These
tools are critical to understanding not only the distinction
between classical and quantum algorithms, but also for
Dr. Richard Cleve
174 C PHYSICS
IN
establishing the limits of the efficiency of quantum algorithms.
Quantum mechanical theory makes counterintuitive predictions with philosophical implications that physicists
have been struggling with for 75 years. An example is the
famous Einstein-Podolsky-Rosen (EPR) paradox, which
predicted that paired particles would demonstrate behaviour counterintuitive to our sense of classical reality. These
counterintuitive preLe Prix ACP-CRM de
dictions were encapphysique théorique et math- sulated by John
ématique est décerné à
Bell, who showed
that if quantum
Richard Cleve, Université
de Waterloo, pour ses résul- mechanics is valid
with the EPR states,
tats fondamentaux en
it would violate the
théorie de l'informatique
Bell inequalities,
quantique, y compris la
thereby turning a
structure des algorithmes
qualitative differquantiques et les fondeence into a quantitaments de la complexité des tive one. This was a
communications quankey step towards
tiques.
understanding the
importance of quantum mechanics to information processing.
In a similar fashion, Cleve gave a quantitative analysis of
the breakdown of the local hidden variable model for communication. In 1997, Cleve and colleagues showed that in
the presence of entanglement it is possible to reduce the
cost of communication drastically for certain sets of protocols. This was the first evidence that quantum information can reduce the communication complexity of a problem; in so doing, Cleve single-handedly created the nowflourishing field at the intersection of physics and computer science—quantum communication complexity.
Quantum computation first came to widespread attention
in 1994, when Peter Shor discovered an efficient algorithm using quantum computers to factor large numbers
that were products of primes. This implied the ability to
break many public key cryptographic systems with quantum computers, (when they were created). It was one of
the first indications of the potential power of quantum
information, and sparked an intense research effort to find
quantum algorithms and techniques able to beat classical
ones.
Cleve has contributed to several such quantum algorithms
and showed how they can be understood in terms of interference. More recently, he has examined the random walk
8/18/2008
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MÉDAILLES 2008 - ACP/CRM (CLEVE)
paradigm. Classical random walks have been used in computer science and physics for decades. In physics, for
example, they can give an unbiased sample of states in
simulations of systems where the state space is too large to
investigate in detail. Cleve and colleagues showed examples in the black box model where quantum information
techniques yield an exponential speed-up over classical
algorithms. This was a breakthrough, since previous quantum algorithms had always used the quantum Fourier
transform to achieve a speed-up.
RESPONSE
BY
In 2004, Cleve joined the nascent Institute for Quantum
Computing at the University of Waterloo, where he holds
the Chair in Quantum Information. Also in 2004, he joined
the Perimeter Institute for Theoretical Physics as a
research associate. Professor Cleve is a founding editor of
the journal Quantum Information and Computation, and is
a team leader in QuantumWorks, an NSERC innovation
platform that brings together academia, government and
industry to develop quantum information processing in
Canada.
Raymond Laflamme
IQC/University of Waterloo
RICHARD CLEVE
This prize is an enormous honour and surprise for me,
especially considering how distinguished the previous
winners are.
Broadly speaking “quantum information” and “quantum
computing” refer to information processing in models that
incorporate quantum mechanical effects. One of the beautiful underlying
ideas is that these "It is a great honour to
quantum mechani- receive this award,
cal effects can be which implicitly recogexploited by a
nizes the work of many
“quantum computer” to perform physicists and computer
feats that are qual- scientists, in an area
itatively different where there is a rich
from what is possi- interplay between these
ble on any “classi- disciplines."
cal
computer”.
Although the problem of implementing large-scale quantum computers appears daunting, there are many compelling reasons to expect that this will eventually be possible. If, on the other hand, it should turn out that there is
a fundamental reason why this cannot be done, the repercussions may be more extreme, as this would mean that
textbook quantum mechanics is in some sense false.
I’ve been something of a Jack-of-several-trades (and master of none!) in this field. Among the areas that I’ve
worked in are quantum nonlocality and communication
complexity—which can both be thought of in terms of
algorithms that are spread out among spatially distributed
processors. A feature of these areas that I have found to be
particularly pleasing is the rich interplay that arises
between concepts in theoretical computer science and
physics. For example, computer scientists in the late 1980s
were considering complexity classes that we now know
are intimately related to the ideas behind the Bell inequalities, which were formulated back in the late 1960s.
I believe that the foundations of computer science cannot
be understood in purely mathematical terms that are
divorced from the laws of physics. This view is not that
widespread in the broad community of computer scientists, but I think this will change.
I would like to say how wonderful the atmosphere is in
Canada for pursuing
« C’est un grand honneur research in quantum
information processde recevoir ce prix, qui
ing. I find this primareconnaît implicitement
rily due to the presle travail de nombreux
ence of very talented
physiciens et informatiresearchers—many of
ciens, dans un domaine
whom I have had the
où il y a une interaction
privilege of working
féconde entre ces disciwith. There are severplines. »
al lively research
groups across the
country, in places such as Calgary, Montréal, Sherbrooke,
Toronto, Vancouver, and of course here in Waterloo. We
have several local and national institutional structures that
support interactions and collaborations, and are a magnet
for other participants from around the world.
Finally, I am grateful to many colleagues. A partial list
includes: Charles Bennett, Dominic Berry, Alexandre
Blais, Gilles Brassard, Harry Buhrman, Andrew Childs,
Isaac Chuang, Claude Crépeau, David DiVincenzo, Artur
Ekert, Joseph Emerson, Eddie Farhi, Richard Jozsa,
Dmitry Gavinsky, Sevag Gharibian, Daniel Gottesman,
Patrick Hayden, Peter Høyer, Rahul Jain, Raymond
Laflamme, Debbie Leung, Hoi-Kwong Lo, Alex Lvovsky,
Serge Massar, Michele Mosca, Ashwin Nayak, Michael
Nielsen, Barry Sanders, William Slofstra, Aephraim
Steinberg, Alain Tapp, Ben Toner, Falk Unger, Sarvagya
Upadhyay, John Watrous, Avi Wigderson, Ronald de Wolf,
and David Yonge-Mallo.
Cleve has been instrumental in building Canada’s research
effort in quantum information science. After a Post-doctoral Fellowship at Berkeley, he joined the University of
Calgary in 1990, built a strong reputation, attracted other
outstanding researchers to Calgary, and was named
University Professor. In 2002, he was instrumental in
establishing the quantum information program at the
Canadian Institute for Advanced Research as a Founding
Fellow.
8/18/2008
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THE CAP MEDAL FOR EXCELLENCE IN TEACHING
LA MÉDAILLE DE L'ACP POUR L'EXCELLENCE
EN
ENSEIGNEMENT DE LA PHYSIQUE
W
hen Adam Sarty returned to Canada in 2000,
he made it clear that he wanted to be in an
environment where teaching would be valued. He wanted an environment where the
balance between teaching and research could be found so
that he could pursue both his passions as a university professor. Since that time, Adam has worked to improve the
quality of physics teaching at Saint Mary’s, and through
that the quality of
teaching on camThe CAP Medal for
pus. He has also
Excellence in Teaching is
worked with colleagues in the awarded to Adam James
Atlantic region and Sarty, St. Mary's University,
across
Canada for inspiring his students to
sharing
experi- love learning physics, sucences and mentor- cessfully implementing innoing implementation vative teaching technologies
of new teaching and sharing the beauty of
technologies.
the discipline, through his
dedication to physics educa-
An example of this
tion.
is his dedication to
the "pre-med" firstyear
physics
course, making it
as engaging and
approachable as possible: this is a course taken by nonphysicists/non-engineers, and is the road to "de-mystify"
physics for the non-specialist university student. As such,
all the various approaches he has brought to the course are
all means to that end. As part of this effort, Adam was
instrumental in the preparation of a “Physics
Demonstration Website” (www.ap.smu.ca/demos).
Teachers can use the online videos to demonstrate key
principles to students or as a resource for new physics
demonstration ideas – should the teacher have the time
and equipment on hand.
Second is his dedication to community outreach, particularly engaging school-aged children in the region; this is
Dr. Adam J. Sarty
176 C PHYSICS
IN
manifest in all of his school shows, his current involvement with the Discovery Center, and special events on
campus. Furthermore, Adam takes his love and passion for
physics to the parks and streets where people live. He has
run “Adam Sarty Physics Shows” in his own driveway, at
neighborhood barbeques, and they have been a popular
auction prize at various university fundraisers. His goal is
to excite children (and their parents) about physics and
how it impacts their
everyday lives. The
La Médaille de l'ACP pour
demonstrations do
l'excellence en enseignenot have to be comment de la physique est
plicated to do this –
décernée à Adam Sarty,
they have to be releUniversité St. Mary’s, pour
vant. In fact, simavoir inspiré ses étudiants à plicity is often the
key to success. The
aimer apprendre la
goals here are not
physique, pour avoir mis
just to engage peosur pied avec succès de
ple in a future study
nouvelles technologies
of physics, but to
d'enseignement et pour
raise their awareness
avoir fait partager la beauté
that physics matters
de la discipline, à travers
and that it is not
son dévouement à l'ensomething mysteriseignement de la physique. ous beyond the
publics’ reach.
Adam is on the board of the Discovery Centre, and a
champion of their grade 5 science film festival. His work
has been recognized at Saint Mary’s through the awarding
of both the Reverend Stewart Medal for Excellence in
Teaching (2005) and the Geraldine Thomas award for
Educational Leadership (2008). He has also been the university teaching scholar for the 2007-08 academic year,
working to help faculty on the effective use of “clicker”
technology in the classroom.
In summarizing these activities, it may seem like this is all
Adam does! However, this is not the case. Adam is a leading researcher in experimental nuclear physics, with an
active research program based at a national laboratory in
Newport News VA. This research effort, combined with
his teaching and administrative duties at Saint Mary’s,
would not seem to leave much free time in Adam’s schedule. For him, however, teaching and physics education.
The research is diminished in value if the excitement of
his work cannot be shared with others.
Dr. Malcolm Butler
St. Mary’s University
8/18/2008
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MÉDAILLES 2008 - ENSEIGNEMENT (SARTY)
INTERVIEW WITH ADAM SARTY, JUNE 10, 2008, QUEBEC
CITY (BY P. CALAMAI AND B. JOÓS)
PC –
Did you know a great teacher of physics at some
point in your life?
AS –
My high school physics teacher was the wrestling
coach …
PC –
The wrestling coach!
PC –
Where was this?
AS –
That was in Saskatoon. I went to Evan Hardy
Collegiate in Saskatoon.
PC –
What was
the teacher’s name?
AS –
Norman
Stonehouse. I don’t
know if he is still
there. My 25 year
high school reunion
is in two weeks but
I can’t go because I
am going to be in
Italy at a research
conference. I had to
make
a
tough
choice.
PC –
W h a t
inspired you about
Stonehouse’s
demonstrations?
“I am humbled and honoured to receive this
Medal, and would like to
share the recognition
with my 'team': my wife
and children, my
Department and Dean,
and SMU's instructional
development office - all
have taught me, guided
me, and supported me
in my physics teaching."
AS –
I
think
just the show – it was fun. I was always one of the geeky
guys, that was good at math and good at science, and then to
have this physics course in high school being taught by “not
a nerd”. He was the wrestling coach, he wasn’t a nerd, and
he was doing all this crazy stuff in class that everybody loved
and so it humanized it for me right from the very beginning.
Of course, when I went into university, I went into engineering even though I loved physics because engineering was
where my family and I would get a job, and my brother was
an engineer, so it seemed a natural choice. So I could hear the
same thing – my brother was an engineer; you are good at
math and science - you should do what he did.
PC –
Was this at U of Sask?
AS –
U of Sask, yes. But I went quickly into engineering physics. I discovered that it existed and went into it to
realize that I was not an engineer, but a physicist.
PC –
Did you already know at that point whether you
were an experimentalist?
AS –
Oh yes, I was for sure an experimentalist. I think I
could have done theory but I was at a place where, after second year, I got to do a student internship with the engineer at
PC –
That wasn’t the lab that then became part of the
cyclotron?
AS –
It has now become the synchrotron light source, the
Canadian Light Source (CLS). The accelerator that I worked
on for my thesis became the injector into the CLS. My thesis
advisor was Dennis Skopik, who is the guy who worked with
Bancroft to make the synchrotron light facility exist ... I got
all of my thesis work done when we had a new upgrade to that
nuclear physics facility, and then that upgraded facility ran for
a few years after I left before it changed into its current incarnation as the CLS.
« Je suis honoré de
recevoir cette médaille
en toute humilité et
j’aimerais partager cette
reconnaissance avec
mon ‘équipe’, ma femme
et mes enfants, mon
département et mon
doyen et le bureau de
perfectionnement pédagogique de l’Université
Saint Mary’s – tous m’ont
appris et guidé et m’ont
appuyé dans l’enseignement de la physique »
PC –
When did
you do your PhD?
AS –
I finished
at the end of ’92… fall
of ’92 I finished.
PC –
Tell
me
how you got to Saint
Mary’s from there.
AS –
So, after I
finished in the Fall of
1992, I did a three-year
postdoc at the MIT
Laboratory for Nuclear
Science, and worked
with Bill Bertozzi, who
is still there, and that
took me to laboratories
in a few different
places; one at MIT, one
in Germany, one in
Virginia which is the big national lab – now Jefferson Lab. I
got a faculty position in 1995 at Florida State University –
that was the best option that was available when I was looking. I stayed there for five years and, at the end of five years,
we had two children and my wife and I decided that we wanted to come back to Canada. I already had enough experience
by then to realize that I really loved teaching and that it was
hard at a big research university because the emphasis was on
getting more time into research. Even though I had really
great teaching mentors at Florida State, the emphasis was still
clearly on doing the research. The Dean of Science called me
in, in 1999, because he found out that I was spending time
going to inner-city schools doing science shows and he said
that this was admirable but wasting my talent … that I should
be “teaching teachers”. He gave me the names of a couple of
other people on the faculty who were involved with teaching
teachers’ programs and said “you should do that”, and get
your research done. That was one of the issues. So, when we
looked to come back to Canada, I looked for a place that valued teaching. There was a job available at Saint Mary’s that
entertained someone that did what I do and was good at teaching and that’s where we ended up.
AS –
… and he was fantastic! I think all of my interest
in doing demonstrations and things comes from this guy – he
would lie on a bed of nails; he would have people then walk
on top of him, he would break bricks with his hands. He was
crazy and that was really fun.
the nuclear physics lab in Saskatoon. So I was already in with
the nuts and bolts of a nuclear physics lab and that was what
I wanted to do. I could have done the theory I guess, but …
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2008 MEDALS - TEACHING (SARTY)
PC –
What did you do with the inner city school kids?
AS –
I just did science shows, which is what I still do.
PC –
Bang, bang, bang?
AS –
Well I try to convince people I am not doing magic
shows. What I do is take a whole host of demonstrations that
I use in my first year university class that demonstrate everyday phenomena but are not what people would predict is
going to happen. Kids love that. Then I have a chance to talk
about the science behind why they have just seen that, and to
talk about how we learn science. I do that from all levels –
from pre-school up to grade 12.
PC –
Can I have a couple of “for instances”?
AS –
The one that they get the biggest bang out of is
when I talk to them about air pressure and, especially with
kids, that they have to “believe” that air is real. We tell them
it is real but they can’t see it. How do they know it is real?
I say we have to make a measurement to prove it is real and I
talk about how everything should have some weight; there is
so much air above us, it should be really heavy, and then I try
to explain why we aren’t crushed. I take a big can – probably
a 15 litre solvent can that I get from the chemistry department
– that is very solid, and I hold it up and say that this is like
your body – there is air on the outside pushing in, and there is
air on the inside pushing out so there is a balance of these big
forces. If I could remove the air from the inside, you would
see the effect of heavy air; so I hook it up to a vacuum pump,
suck the air out, and, after about a minute, a huge crush.
BJ –
Weren’t you nervous about going to a university
where the course workload was so heavy?
AS –
Yes, when I went to Saint-Mary’s it was three
courses per semester.
BJ –
What was left for research?
AS –
Um…
BJ –
There is a choice there to be made?
AS –
There was a choice and so I realized that I had to
convince my research community that I wasn’t retiring,
because they thought I was, and I convinced them that it was
possible to do research – that the department that I was going
to had some very active astrophysics researchers and it was a
matter of balance. I was able to do it by involving a lot of
undergraduate students, during the summers, and so most of
my research was done during the four months of summer.
Since that time Saint Mary’s has made a move, and now the
standard load for me has been two courses per semester
which is almost even with a research-level university, so it
has been possible, but when I went there my choice was …
my research: I would do what I could, but my priority would
be my teaching. Now I think I have a pretty even balance. I
have been able to keep up both ends.
BJ –
So you took a risk?
AS –
I took a risk, knowing that I was comfortable with
the risk.
PC –
Are two courses enough to satisfy your teaching
bug?
AS –
Yes. Two is still enough. I am actually quite happy
doing one per semester, which I got to do last semester
because I was the Teaching Scholar, which was a new program we have at Saint Mary’s ... which, oddly enough, gave
178 C PHYSICS
IN
me teaching relief. It was to pursue an educational initiative
campus-wide, but to do that takes time and so you need some
break. I ended up teaching only one course per semester. I
taught my introductory physics course, but I was able to completely revamp the introductory physics course because it was
the only one that I was doing. I was able to be a lot more
innovative because I was teaching only one. So it is not really the number of courses that dictates whether the university
cares about teaching, it is what they allow you to do.
BJ –
How much technical support are you getting for
your teaching, because the problem facing faculty in many
universities is the lack of technical support – you have to find
the software, you have to find the demonstration setups, you
have to get people to help you to do those demonstrations?
You can’t just do everything.
AS –
Yes, so I had great support. We have departmental
technicians; we only have eleven faculty in our department,
and we have two technicians – an astronomy and a physics
technician – and between the two of them, there is enough IT
support and enough physics demonstration-like technical
capability support that it has been possible to do it. Not
everything is as good as it could be if there was lots more
money around, that’s for sure, but I don’t think it always takes
all of the money.
PC –
Tell me about the campus-wide initiative.
AS –
So what I did this year with that Teaching Scholar
program was a “faculty awareness” campaign on clickers.
PC –
What are clickers? They are used in classes, right?
Where they vote?
AS –
Yes. So I worked with an accounting professor a
few years ago to standardize across campus one brand of
clickers. What that allowed us to do was to put, in every
classroom that seated about 50 people or more, a receiver so
that an instructor could use clickers if they wanted to.
PC –
You were in favour of clickers.
AS –
Yes, so I brought them with this accounting professor to campus. I’ll give a history. In 2000, while I was still in
Florida State, I applied for an internal instructional development grant and received one of three that the campus gave out
for about $10,000, and I got the first set of clickers for Florida
State’s campus. I never got to use them because, as soon as
they arrived, I moved to Saint Mary’s. Since my departure,
they were used by my physics department and now at Florida
State they are campus-wide because of that initiative, and I’ve
been told have about 10,000 clickers a year sold on campus.
That started with my buying that one kit, and I have effectively now done the same thing at Saint Mary’s. In 2001, I got
enough money to buy one kit for my own class and I have
convinced the rest of campus in the years since then that it
was a worthy initiative to try to have available across campus.
After I had done that, I realized that just getting the tool available was not enough because people would try it and they
would have limited success. What faculty needed was help
and support to know how to use it – what the pedagogical
implications were. So my job last year, as Teaching Scholar,
was to try to go to every department (I got to many, not all)
and give a presentation on how to use this technology in a
best practice kind of way – what was involved, and what it
meant for their teaching. Then I had a regional symposium in
April where I had people from around Atlantic Canada come
– we had about 60 people from 10 different institutions come
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together – and spend the day talking about best practices in
clickers. I had a guest speaker from Colorado, Doug Duncan,
come up and give the keynote and that was a major success.
It really convinced a lot of people about the worth of clickers
… interestingly enough Doug Duncan’s first slide in the
keynote is one that I agree with – that “it is not about the
clickers”. The clicker is an avenue to use a different pedagogical technique that changes how you run your classroom and
that’s the key point.
BJ –
Do you use a “stick” with it, because I have heard
that some people actually record all of the answers and give
them bonus points for participation?
BJ –
AS –
Human nature is still what it is. You have to give
an incentive for students to participate.
It gives a voice to the students basically.
PC –
it?
The pedagogical bottom line is interchange? Is that
AS –
Yes, so that the students are interactively engaging
with the material in real time, and then you are challenging
them to think, and then you are using the information that
they are telling you about what they understand to decide
what to do next – to decide whether they need to talk to each
other more, to help explain it to each other, or that you have
to present the material in a new way. If they clearly don’t have
the answer, you have to figure out why.
PC –
So this is using a modern technology to go back to
what actually happened in the classrooms in the 1960’s when
class sizes were small enough and this could actually happen.
AS –
Exactly. With ten people you could have this discussion easily, like around the table. This is a discussion that
would happen naturally, yes.
PC –
There used to be ten people in my engineering
physics class, just to take an example, in 1961.
AS –
There were ten in mine in 1985.
PC –
So you had those discussions. They were just part
of the parcel.
AS –
Although this is a bit better.
PC –
Why? I haven’t actually seen one in action.
AS –
There were shy people in my engineering physics
class who wouldn’t speak at all but, with this, they have a
voice. I have had student feedback from shy students who
thank me, saying that “I don’t participate in any of my other
classes, but your clicker allows me to tell you what I think”.
PC –
They are anonymous are they?
AS –
I know. The instructor has a spreadsheet that
knows, but, during class, it is anonymous.
BJ –
Human nature is still …
PC –
You mentioned something about a class size of 50 I
think earlier, didn’t you? The cutoff point where you start …
AS –
Yes, we put it in every class that seats 50 or more.
PC –
So in a class size of 20 there is not much point.
AS –
There could be. I haven’t used it in that small of a
class but others have, and say that there is benefit for it. For
me, the big benefit is in the bigger classes.
PC –
So tell me how it works in your introductory
physics class. I would be interested to know that. Some
examples of where, because you are using it, you have actually changed the way in which you have structured the course,
and the way in which the course actually rolls out is different
as well.
AS –
Yes, the biggest change is what I did this year
because I adopted a relatively new textbook on the market by
a guy named Randy Knight, who has written a textbook that
is based on trying to implement what has been learned in
physics education research over the last 10 or 15 years – and
the biggest thing there is you are supposed to not lecture. As
much as possible, don’t lecture – but discuss example problems and have the students work on the example problems
right then and there, and you then use the clickers to find out
how they are doing while answering those problems. You use
the responses to decide what needs to be discussed to solve
the problem. So in a class where I am about to do a demonstration – I set up a demonstration and I ask a clicker question
related to what they think is going to happen. They answer
the question – there are a couple of ways to do it – the way
Eric Mazur does it (he talked about it here today) he would
have them answer on their own and then see the distribution,
and then they would turn and talk with their neighbours and
have a few minute discussion to convince each other of the
right answer, and then they vote again, and you see how the
answers change. Now they have already done a lot of learning and the person at the front of the classroom, the instructor, for that last 10 minutes hasn’t done anything except walk
around to see what is going on so that, at the end of it all, they
can talk about it. In my class, I haven’t been quite so brave.
BJ –
AS –
It gives a voice to the students, but means that you
have to prepare your class in a way to listen to their voice.
Most standard presentations of a lecture don’t allow for any
input from the students. You have to change the way you
teach and how you think about your class in order to use that
input, because if they are going to tell you what they think,
you had better be ready to use it – otherwise they are going to
realize that it is a token, and if it is a token, they are not going
to be very happy ... so there is a lot involved. That was a lot
of my discussions this year. There were faculty saying “well
won’t this mean a little more work for me?” Yes. “Won’t this
mean I can’t cover as much material because it slows you
down?” Yes. Understanding that this is all good ... that it is
better to talk about less in class if it is understood better, and
it’s okay that you have to change how you prepare your lectures to account for what they are going to tell you.
AS –
That is one of my best-practice suggestions that
I have been promoting: that there needs to be some grade,
somehow, associated with using that technique otherwise the
students won’t do it, and there is good reason …
That would make it even slower, no?
AS –
That would make it even slower, and that is why
I have been tentative. What I do is ... I set it up. I ask the
question. I have them talk immediately – you know, “while
you are answering the question talk to your neighbours” – and
they all talk, trying to work out this question, and they will
talk to whoever they can see around them. They vote on the
answer. You look at the results. They have now had an active
chance to think about a problem, give an answer; and then
I revert back to kind of a lecture mode where I explain why
they might have picked the wrong answer they did, where
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their mistake in reasoning was, and then try to show them the
right way. Then I do the demonstration and prove, with physical observation, that that was reality ... and, by and large, that
is how all of my classes go. So every day there are two to five
of those kinds of questions, and the lecturing is explaining
what is behind each of the demonstrations or the examples.
PC –
What was the topic of the class?
PC –
Is the rigour in examining the different pedagogies
for teaching using clickers or not using clickers as rigorous as
it is in your own area of research in physics?
AS –
For my study? I picked special relativity because I
needed a topic that the students walking in probably didn’t
know anything about. My pool of students was introductory
psychology students who did this to get bonus points in their
intro psych class (that is the standard pool of students for
many psych studies). I needed it to be new to them, but yet
not mathematically challenging at all because this would be
students who don’t have a math background.
AS –
It is getting there. It is harder. There are so many
variables…
PC –
Oh, so they weren’t enrolled in introductory
physics?
PC –
AS –
No, these were all students enrolled in the psychology class and we put on a psychology study. Every university does this, where the psych department has available, every
term, psych studies that students in intro psych classes can
sign up for to get bonus points. There are enough intro psych
classes that you can populate many studies, with 100 student
each, with this pool of students.
I don’t know where you get the control.
AS –
So, I have actually been involved with some
research of my own, but before I tell you that, let me tell you
that there are lots of data out there. People who have studied,
you know, numerous courses at numerous institutions, some
using a clicker and some not, and some using some other
interactive engagement technique and some not, and to try to
measure the difference in performance of these students
based on some standardized diagnostic test. So that’s out
there, but I looked at that information with a psychologist at
my university (Bob Konopasky) who got interested in clickers because he used to teach after me and he would always
come into class as I was asking these questions (because I
would always go late!) and he thought it was very interesting
to see because he thought it was a lot like watching an evangelical preacher on TV; that, instead of saying “amen”, they
would all click in. He thought this was a gimmick to get them
engaged and so….
PC –
Well, it is!
AS –
… and so we got talking! We decided we wanted
to do some research to see if it is a gimmick or if it really is
an effective educational tool. When we looked at these studies, it was hard to isolate the clicker with so many things
going on. So we tried to design our own studies. We have
done a few now over the years. We haven’t got any of it published; we have talked about it at conferences but we haven’t
yet published it. We are trying to be rigorous to control the
variables/ One of the latest ones we have done (I talked a little bit about it this morning) was: two lectures, identical content, each given to 100 students (different students each time).
The only thing that is different: in one lecture, I asked clicker questions and had them vote on the answers and, in the
other one, there was just slides that gave them the factual
information. At the end of it all, they go through the material, I give them a test of the material they have just heard, and
then I give them a subjective evaluation on how they felt
about the whole process. Our data shows, from this first
study, that there was no difference in content retention; they
tested out, statistically, identically the same B but, I covered
less material in the clickers group because it took more time
to do it. What they covered the same was retained the same.
The subjective evaluation said that the people who used clickers substantially enjoyed the process more; off the charts –
really enjoyed it more. Now we are trying to progress beyond
that tier. But that was our first attempt to control all of the
variables and be rigorous like we would in my nuclear
physics research, for example, but it is so hard – there are so
many variables – and we immediately identified variables
that we didn’t control well enough and tried to account for
that. There is a lot of physics education research being out
there that is rigorous – as rigorous as you can be with human
beings, I think.
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PC –
So, is it important for students to enjoy learning or
is it just important for them to learn? Because what you said
is that, in the first method, they might learn more because
they cover more material.
AS –
Yes, maybe, okay. There are some limitations to
that. For instance, in the context of that study, I would focus
on the fact that there was no difference in retention, and
enjoying it more, I think, is important. I think one of the reasons I have gotten consistently high teaching evaluations
across my career is because the students always enjoy the
experience. When I have tried to measure, in a standard
device, whether they have learned as much as they should, I
have been a bit shocked that maybe they haven’t been learning as much as I thought they were. That was the topic of Eric
Mazur’s talk this morning – that he had the same experience.
I did change some things last year and proved, with measurement, that they learned more when I changed a few things to
do it better, to let them think more in class. But enjoying it is
always important because how much effort the students put
into the course outside of my class depends on whether it is
an enjoyable class or not. Whether they show up to my class
depends on whether they find it an enjoyable experience to be
in my class and, if they are not there, they are going to have
a hard time learning.
PC –
So, would you draw an analogy with your wrestling
coach who lay down on the bed of nails – you enjoyed?
AS –
Right, and so I think, right from the beginning
when I started to teach, I didn’t know anything about teaching. I was lucky enough to have people at Florida State share
with me. One of the professors, a guy named Hon-Kie Ng, let
me sit in the back of his class – an intro physics class – the
whole year and just experience it as a student, which I did.
That was great because a lot of people wouldn’t like that
(having another faculty member watching every one of their
lectures) B that is kind of intimidating. So I had enough people sharing with me what they did ... but at the back of my
mind was – I wanted it to be fun, because that is what I
remembered from high school, is that physics was fun, and I
didn’t want that to go. I always wanted my students to enjoy,
and I always figured that, if they enjoyed it, they were learning more. Turns out it is not quite so simple but they did definitely like it. I have kept the enjoyment but now, hopefully,
I have learned how to get the learning tacked onto that too.
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PC –
What does it cost to equip a class of 50?
AS –
It costs one receiver, and that one receiver …
PC –
The clicker is not…
BJ –
The students pay for the clickers.
BJ –
So it is peanuts in the budget.
AS –
Right. So to get 50 classrooms outfitted took one
grant and we were done and now it is there.
PC –
How do you spell the name of the fellow who let
you sit in the back of his class?
AS –
Hon-Kie Ng.
I am deeply indebted to him for
doing that. It was a struggle for him because he didn’t get
great course evaluations. But, because he was very passionate about teaching, he did a lot of things off line that the students didn’t realize he was doing to structure the course and
to provide web resources back in the early days of web. He
really wanted to do a good job teaching but his style in class
– he was not a charismatic presenter – and the students, therefore, did not respond well in his course evaluations. But he
was so passionate about what he did that he wanted feedback
from me too, so he was helping me and I was helping him,
and so it was a very good relationship.
AS –
Right, so it’s the same. When I was in engineering
physics we had labs every day. We went 8:30 to 5:00 every
day.
PC –
So they tell me that they have got a full schedule…
But they don’t. What may be is that they are all working.
AS –
Yes, there is a big difference, especially at Saint
Mary’s. Because we are an urban university, the majority of
our students are working at least 20 hours a week, and they
have to.
PC –
A lot of them have no choice. I think that is what
the overload is. It is not that there is too much course material; it is that there is too little time. It is a different thing.
AS –
I have been very sensitive to that. Right from the
inception of using the web in the late 90s when it became feasible, I made the course material available for them after class
because I know that, in my courses, there are many students
who miss my class, not because they don’t want to be there,
but because they have to work. I have been able to put
enough material available online, and to respond to them by
e-mail that they can still function in the course without being
so much present in the class.
PC –
What are the resources you put online?
AS –
I have everything online. The lecture, the audio
version of my lecture, and the text …
PC –
Of course, you don’t do a lecture …
BJ –
But often these teachers get long-term appreciation.
AS –
Well, I still do. I try to get away without it, but
everything I say in class is put up there on an MP3 file, text
translation, as poor as it might be, is there. The software I use
B “Viascribe”, available through the Atlantic Centre for
Students with Disabilities as part of a consortium at Saint
Mary’s B is linked to the powerpoint slide that was on the
screen at the time. So they can load it up, click on the slide
that they want to hear me talking about and it will jump to that
part of the audio on the text translation and they can listen to
that five minute part of class and close it up.
AS –
Which he did, I think, in the end.
PC –
BJ –
Years later, people remember that, although this
person was dull, they got a very good education from him.
AS –
Yes, because he structured his course so well, students did, in the end, I think, come back to appreciate that.
BJ –
There is one thing that I wanted to ask you at the
lecture was – that although students don’t learn any better in
courses where they enjoy themselves, it may have a positive
impact on the enrolment in follow-up physics courses. Do
you observe this effect?
AS –
They talk about it, but they don’t do it. There are a
lot of students who say “that was really nice; I would like to
take more physics” but they don’t. I think that is the structure
of our program. The students have very little freedom. The
requirements are so strict so that hasn’t been an impact. In
Florida State it was, I think. My recitation section was always
full and the other section wasn’t. So we saw the impact there.
So then they see the scroll …
AS –
They see the scroll of the text, yes. They see all that
with the slides. That’s a bit painful – to listen to a whole lecture – but some of my students tell me they have done it.
When they miss a class they listen to the whole thing. I
would find that painfully boring because you can’t see what I
am doing, I don’t video it – maybe that is the next step. You
can’t see what I am doing and you can’t see what I am writing on the board, but I am talking about what I am writing, so
they get some of that. But I post everything. There are solutions to problems; the homework is on line.
AS –
The students buy it at the bookstore and the model
that we have is that the clicker can cost them as little as five
dollars. If they buy a new one, it can actually cost them as little as zero because one of the textbook companies, Pearson,
will, for no extra charge, bundle a coupon in with their textbook that, if a student buys a new clicker from the bookstore,
whatever the brand, just send that in to Pearson and Pearson
will rebate the whole cost of the clicker, because they are
encouraging use of that technology, no matter which company. Otherwise the student buys the clicker for $20. They can
sell it back to the store during book buy-back time for half
price, or $10, so then that cost them $10. If they buy a used
clicker, they buy it for $15, then they still sell it back for $10,
so it cost them $5. So, from the student’s point of view, it cost
them somewhere between zero and $20 to get the clicker.
From the institutional side, we need that receiver. The receiver the company will sell to you for varying costs depending
on how many you are getting so I got them for something like
$150 or $200 each.
PC –
I hear people keep saying the students have a full
schedule. My first year at McMaster in 1960, I had forty
hours a week; five labs every afternoon for three hours, and a
full morning of lectures. I don’t know how many students
carry that sort of workload now-a-days, I mean they are lucky
if they get to 25.
PC –
So can you get statistics on unique hits to know
what sections, what pages are being read.
AS –
I use WebCT. It is a course management software
package which allows some of that. The main thing that
WebCT allows is password protection so that only students
enrolled in the course see the material, so it is not publicly
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available, and then I can post their grades. I upload a spreadsheet and the students only see their line of the spreadsheet so
they know what their grades are. With that you can track a
little bit of the hits.
PC –
So how much extra work does all that take?
AS –
Well, if you do a little bit at a time it’s not too much
… right now I couldn’t imagine teaching without it. But the
first time that you do any component it takes time, so I try to
do one component per year as I am adding things in.
BJ –
I guess that covers it, huh?
AS –
So the one thing that isn’t recorded here that I want
to make sure that it gets recorded here because I put it in my
response and said it in my talk: I just want to make sure that
the biggest inspiration for my teaching (aside from my high
school physics teacher) over the last 19 years, has been my
wife. My wife is a phenomenal teacher …
BJ –
Diane MacKenzie?
AS –
Yes. She is a professor now of Occupational
Therapy. She was an occupational therapist, director of her
182 C PHYSICS
IN
clinic, when we were in Florida; and when we moved back to
Canada she chose to start teaching, thinking she would just do
a little bit of it. Then she was so good at it that, you know,
she quickly became full time and quickly became an award
winning teacher.
BJ –
Where? At a college?
AS –
At Dalhousie University, in the Faculty of Health
Professions. And so, since she has done that, the quality of
my teaching has improved tremendously because we talk,
every day, about university students, about the challenges that
we face. The amazing thing to me has been how similar it is
between her students, doing something completely different
than physics, and mine. That has encouraged me, over the
last eight years, since she has been doing that, and we have
been in Halifax, for me to talk more broadly to other disciplines and to become involved in inter-disciplinary teaching
efforts. I think that has been driven by my home life. I wanted to make sure that that was captured in this interview.
BJ –
You are very lucky.
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MÉDAILLES ET PRIX 2008
THE CAP/DCMMP BROCKHOUSE MEDAL
(FOR OUTSTANDING EXPERIMENTAL OR THEORETICAL CONTRIBUTIONS
TO
CONDENSED MATTER AND MATERIALS PHYSICS)
LA MÉDAILLE ACP/DPMCM BROCKHOUSE
(POUR L'EXCELLENCE
DANS LE DOMAINE DE LA RECHERCHE THÉORIQUE OU
EXPÉRIMENTALE EN PHYSIQUE DE LA MATIÈRE CONDENSÉE ET DES MATÉRIAUX)
Brewer recognized the opportunity that TRIUMF offered
of a thousand-fold increase in muon production over that
of previous facilities in the world. Three major complementary subfields of materials research emerged directly
from nuclear and particle physics: 1) neutron physics
using reactors and, more recently also, from proton-accelerator-driven spallation neutron sources; 2) photon light
sources which have been synchrotron based; 3) μSR facilities at meson factories. When he came to UBC Brewer
worked at first with Professor Donald Fleming. While
Brewer focused on the condensed matter applications,
Fleming explored fundamental chemical reactions using
positive muons as very light hydrogen ion: Fleming
gained great distinction for this work. Right from the
beginning of his μSR work Brewer had important international collaborations, particularly with the University of
Tokyo group led by Toshimitsu Yamazaki and Ken
Nagamine. (The TRIUMF μSR work helped Yamazaki
earn a very rare honour: the Imperial Medal given by the
Emperor of Japan).
Under Brewer’s guidance μSR became a valuable tool for
the measurement of magnetic field distributions in macroscopic samples. For example, he personally recognized
immediately the opportunity to study high-temperature
superconductors with μSR. This gave fascinating and
valuable information about the vortex lattice in a superconductor: it was found that the vortex cores were magnetic in the underdoped region close to the antiferromagnetic
boundary.
La Médaille Brockhouse est Similarly μSR prodécernée à Jess Brewer,
vided a method to
study very weak
Université de la Colombieantiferromagnetism
Britannique, pour reconand also other
naître son travail de piostrongly correlated
nnier dans le développematerials such as
ment de la relaxation de
“heavy
fermion”
spin muonique et de techsuperconductors in
niques reliées, qui a conduit which both antiferà la création d'un important romagnetism and
nouveau champ en
superconductivity
physique des matériaux.
occur. These subjects have become
central to condensed matter physics.
Brewer was personally responsible for the development of
important techniques with which μSR has prospered. He
recognized the importance of building the first surface
muon beamline which became the standard at all of the
world’s μSR facilities. For the surface muon beamline
muons emerging from the surface of a target are completely polarized and their electron contamination is easily
removed. He led the development of the important technique of muon-level-crossing-resonance This technique
has been enormously successful, for example, in determining the structure of muonium (μ+e-) in semiconductors for
which the muonium acts like hydrogen, altering the electrical activity.
P
rofessor Jess Brewer is a wide ranging intellectual who created and developed, at TRIUMF in
Vancouver, an important subfield of condensed
matter physics: Muon Spin Rotation/Relaxation
(μSR). He obtained his Ph.D. at Berkeley in 1972, under
the tutelage of Professor Kenneth Crowe, and they appreciated the new research opportunities which would be possible at the TRIUMF meson factory, then being built, to
use intense beams
of low energy The CAP/DCMMP
muons for materi- Brockhouse Medal is
als science. Arriv- awarded to Jess Brewer,
ing in Vancouver, University of British
in 1973, with a Columbia, in recognition of
truckload of mag- his pioneering work to
nets shipped from develop muon spin relaxBerkeley to build a
ation and related techspecial
muon
niques, leading to the crebeamline at TRIUMF, Brewer has ation of an important new
spent 35 years in field in materials physics.
creating and establishing μSR, now a
flourishing contributor to materials science. He, and Alex
Schenck at the sister meson factory, PSI, in Switzerland,
were the pioneers of this field.
Dr. Jess Brewer
8/18/2008
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2008 MEDALS - BROCKHOUSE (BREWER)
Jess Brewer has been an intellectual leader with broad
vision. He has inspired ideas and stimulated an international group of collaborators. His vision has been a key
factor in the successful development of μSR. With his
broad view he has inspired many students and has even
published science fiction (not in his physics publications!)
RESPONSE
BY
In 1957, a property of elementary particles that would once
have been pure fantasy (forbidden by the "known laws of
physics") became science fiction (possible but not yet practical): parity nonconservation in the weak
interaction. In the "I am proud to accept
very first experiments the 2008 Brockhouse
confirming this effect,
it was recognized that Medal on behalf of the
it would provide μSR users community of
beams of highly spin- TRIUMF, to whom all
polarized
muons credit is due; for the
which would subse- past 30 years I've had
quently
broadcast
their polarization in a the privilege of working
shower of high energy with and for them on a
positrons, providing a wonderful science fictechnique analogous tion dream that came
to NMR but ten to true."
twelve orders of magnitude more sensitive.
This "science fiction" technique was developed in the following decades into a useful tool by a generation of physicists
who used it to perform the most delicate tests of quantum
electrodynamics. Sometimes unintentionally, they left a legacy of solutions to "systematic problems" which because fields
of study in their own right: muon depolarization, muonium
chemistry and muons as microscopic probes of magnetism
and superconductivity. I arrived on the scene in 1970 as a
graduate student bent upon acquiring credibility as a science
fiction author. Naturally, the fledgling μSR technique was
irresistible for me.
In the following decade, the advent of "meson factories" like
TRIUMF and the low energy, 100% polarized "surface muon
beam" gave improvements of stopping luminosity that
allowed μSR studies to progress from kilogram-sized to milligram-sized samples, a crucial step toward broader applicability in condensed matter research. In the decades that followed, my colleagues and I developed, invented or stumbled
upon many new uses for and techniques of μSR, including
spin rotators, level crossing resonance and lineshape analysis
in type II superconductors. There are now hundreds of scien-
IN
Erich Vogt
TRIUMF
JESS BREWER
I am deeply honoured to receive the Brockhouse Medal, joining the ranks of previous winners to whom I have always
looked up in admiration. It is especially rewarding that the
citation specifies my contributions to μSR (muon spin rotation/relaxation/resonance), the suite of experimental techniques to which I have devoted my scientific career so far,
and for whose advancement I remain an enthusiastic advocate.
184 C PHYSICS
We are very proud that he has been awarded the
Brockhouse Medal by the Canadian Association of
Physicists.
tists capitalizing upon these Canadian investments and breaking new ground in condensed matter physics, materials science and chemistry. There has never been a lull in the
onslaught of new applications, and I do not expect one in the
foreseeable future.
There are presently four major μSR facilities in the world:
TRIUMF in Canada, PSI in Switzerland, ISIS in the U.K. and
J-PARC in Japan (just coming on line now). Of these, only
PSI and TRIUMF have the CW muon beams that give the
highest possible resolution. In spite of a much higher intensity at PSI, TRIUMF has remained a key contributor to
progress in μSR,
thanks to its emphasis upon innovation
« Je suis fier d’accepter
and flexibility. It is
la médaille Brockhouse
my fondest hope that
de 2008 au nom des utilthis
commitment
isateurs μSR de la collec- will persist.
tivité de TRIUMF, à qui
revient tout le mérite;
depuis 30 ans, j’ai eu le
privilège de travailler
avec et pour eux à un
merveilleux rêve de science-fiction devenu réalité »
Like most emerging
disciplines, especially those requiring
major facilities, μSR
is the creation of a
large community of
talented, hard-working researchers and
inspired administrators. One person is
entitled to only a tiny fraction of credit for its success. If any
role of mine has been important, it is probably that of head
cheerleader -- and that has been an easy one because there has
been so much to cheer about. Thanking individuals is like
washing a white ceiling: once you start, there is no stopping.
So I will mention only the person who did most of the work
for which I receive credit: my beloved wife and helpmate, Pat
Sparkes.
One presumption in which I will indulge is to offer advice for
younger generations on "how to succeed in science": Find
something that fascinates you so much that your obsession
will outlive your frustration. Take chances. Give away your
best ideas, to make room for new ones to form. Help your
competition succeed. Do things just for fun. Tell everything
you know. Try to understand everything, but never underestimate the creative potential of ignorance. Above all, cultivate your sense of humour; you will need it most when all
else fails.
That's about it.
8/18/2008
2:14 PM
Page 185
THE CAP HERZBERG MEDAL
(FOR
OUTSTANDING ACHIEVEMENT BY A PHYSICIST AGED
40
OR LESS)
LA MÉDAILLE HERZBERG
(POUR
DE L’ACP
CONTRIBUTIONS EXCEPTIONNELLES PAR UN PHYSICIEN DE
T
At 36 Svensson has beams.
already cut a wide
and impressive swath through physics. As a graduate student at McMaster University he chose to pursue one of the
most important problems in the field of nuclear physics:
the superdeformed bands with their energy levels of almost
mesmerizing regularity - one of the most astonishing phenomena in the quantum mechanics of small systems. He
found that they existed not only in heavy nuclei, where they
had first been discovered, but also in medium weight nuclei
where there was greater opportunity to achieve a theoretical
understanding. As a result of the international attention
which this work attracted the world was open to him and he
chose to continue the study of these superdeformed bands
in a postdoctoral year at Berkeley. Then Svensson made a
fateful decision: he turned down several prestigious international opportunities to return to a post in Canada, at the
University of Guelph.
Svensson immediately led Guelph to become a leading
institution in a new field of physics, developing a major
program at ISAC, the new radioactive beam facility at TRIUMF, in Vancouver. Around the world the highest priority
in nuclear physics now focuses on rare isotope facilities
such as ISAC. It is one of the leading Rare Isotope Beam
(RIB) facilities in the world and it promises to provide
world leadership for the pursuit of nuclear structure (for
OU MOINS)
exotic nuclei far from the valley of stability), for nuclear
astrophysics and for the study of fundamental symmetries.
Svensson is the principal investigator for the TIGRESS collaboration at ISAC which involves 84 researchers from 16
institutions in Canada, France and the United Kingdom and
for which he has received almost $ 10 M from Canadian
sources alone. TIGRESS has just finished its first experimental measurements. At Guelph Svensson has built a
solid base for this leadership of this program.
Svensson clearly has a strong vision for where he is going.
While leading the
initial efforts of
La Médaille Herzberg est
TIGRESS
for
décernée à Carl Svensson,
nuclear physics and
Université de Guelph, pour
nuclear astrophysics
son leadership solide et ses he has also formulated a proposal to
réalisations majeures en
build a new state-ofphysique nucléaire expérithe-art, high efficienmentale, y compris des
cy γ-ray spectromemesures qui améliorent
ter (GRIFFIN) for
beaucoup la compréhenthe
search
for
sion des états de moment
Electric
Dipole
Moments (EDM) in
cinétique élevé dans des
the odd-mass radon
noyaux moyens et des
nuclei, produced by
mesures physiques fondaISAC, which are parmentales qui utilisent des
ticularly suited for
faisceaux radioactifs.
this purpose. It may
be a long shot, but
the discovery of the EDM would be a strong candidate for
the Nobel Prize. Svensson has shown that where he leads,
discovery follows. For his accomplishments and his vision
he was, earlier this year, awarded one of the six Steacie
Awards in science by NSERC. We are very fortunate that
he returned to Canada and became one of our leaders and
we are proud to have him join the ranks of the distinguished
young Canadians who have achieved the Herzberg Medal.
Perhaps we should analyze that Ottawa River water!.
Erich Vogt
TRIUMF
here appears to be something in the water of the
Ottawa River that nurtures the development of
outstanding leaders in Canadian physics. Eighty
years ago Allan Bromley grew up near Deep
River and rose to prominence. Almost half a century later
Carl Svensson was born and raised in Deep River and has
already at a very young age achieved great distinction
which now includes the Herzberg Medal of the Canadian
Association of Physicists. He manifests many of the fine
qualities and flare for science which characterized
Bromley: great depth of knowledge in physics and excellent judgment about
the most important
problems at its The CAP Herzberg Medal is
frontier; impres- awarded to Carl Svensson,
sive technical skills University of Guelph, for his
and energy to pur- strong leadership and major
sue his goals; accomplishments in experiinnate leadership mental nuclear physics,
qualities
which
including measurements
place him at the
head of the large that improve significantly
teams needed to the understanding of high
organize successful angular momentum states in
efforts at large medium weight nuclei and
international user fundamental physics measfacilities.
urements using radioactive
40 ANS
Dr. Carl Svensson
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2008 MEDALS - HERZBERG (SVENSSON)
INTERVIEW WITH CARL SVENSSON, JUNE 10, 2008,
QUEBEC CITY (BY P. CALAMAI AND B. JOÓS)
PC –
I want to start a little bit back at the beginning and
find out how you got into this area of research in the first place.
CS –
Oh, serendipity I guess. Like everything … there is
a background. I grew up in Deep River, Ontario. My father is
a physicist at the Chalk River labs so there is obviously some
background there. But I actually went off to university as an
undergraduate to do genetics and biochemistry. After the first
year, which was a general year of natural sciences I decided …
BJ –
That was the good old days when there was a common one year of science.
CS –
So we all did everything in the first year and I decided that I liked physics best.
PC –
Which university was it?
CS –
McMaster
PC –
What year?
CS –
1990 I started as an undergrad.
PC –
Was there
was somebody in particular in the physics
department?
"It is a tremendous honour to be awarded the
2008 Herzberg Medal of
the Canadian
Association of
Physicists. It recognizes the dedication and
achievements of a large
team of scientists who
have come together to
make this research possible."
CS –
The
first
year course was actually taught by several
instructors, but it certainly didn’t take long
in the second year
when I had Jim
Waddington as a professor for electricity
and magnetism. There was an immediate connection. I
worked for him as an undergraduate on a thesis in nuclear
physics and that is really, as much as anything else, what led
me here.
PC –
What is it that appealed to you about the physics
over the genetics and biology or over chemistry or anything
else?
CS –
It is a different mode of approaching problems I
think. One in which there are fewer, if you like, things to memorize and more things to deduce. I think in retrospect it was a
good choice. I am much better suited to the latter than the former.
BJ –
Your father was already a physicist.
CS –
My father was already a physicist.
BJ –
He was a very active in the community, so had that
already shaped your vision of a profession at the time?
CS –
It really hadn’t. I think I can, looking back, conclude
that I was probably going to do science B some kind of science
B from as far back as I can remember. There is no doubt that
Deep River’s atmosphere had a physics lean to it. Nonetheless,
as I said, I had made a fairly clear decision – as well as you can
make such decisions by the end of high school – that I was
186 C PHYSICS
IN
heading for genetics. But certainly having a physicist as a
father I was familiar with the context of research in general,
probably more so than most undergraduates.
PC –
You made the point that reasoning through deduction
rather than rote appealed to you more. Is that because you
were a chess player on the side?
CS –
I was actually a chess player on the side, at least during my undergraduate days, but I think it is simply that different people like to learn in different ways. Perhaps there is
some connection between those things.
PC –
I didn’t make the connection. Did you say that
because you had done work with Waddington, that is why you
ended up in this very particular field?
CS –
There
is
certainly a direct
« C’est un immense hon- connection there. I
neur de me voir attribuer did a senior underla médaille Herzberg de
graduate thesis project
with
Jim
2008 par l’Association
Waddington. I loved
canadienne des physieverything about that
ciens et physiciennes.
project and the
Cette médaille reconnaît
research
environment and I stayed on
le dévouement et les
and did my PhD at
réalisations d’une vaste
McMaster with Jim.
équipe de scientifiques
At the end of my
qui se sont réunis pour
undergraduate
degree, there were
rendre possible cette
many aspects of
recherche »
physics that I found
tremendously exciting. Like many others I suspect, I might have very easily found
myself in a different field. A lot depends on the specific individuals you interact with at key points in your career.
BJ –
The subject matter itself was’nt the key point?
CS –
The subject matter is tremendously exciting, but so
are other fields of physics.
BJ –
So what motivates you? Is it the fundamental forces
of the universe? Is it the big questions? Some people go into
particle astrophysics because they want the answer to everything, and many select condensed matter physics because they
love problem solving.
CS –
Nuclear physics is nice in that it has both of those
aspects to it. Much of my current interest is in what you might
call the big problems, big questions. One of our programs is
studying CP violation, trying to understand why the universe is
mostly made of matter and not a balance of matter and antimatter. That usually gets lumped under the category of fundamental physics. On the other hand, with the same experimental device, we are also studying the structure of the nuclear
quantum many-body system, which actually shares many more
similarities with condensed matter physics than it does with
high energy particle physics, so it certainly has both aspects.
We are also looking at the structures of nuclei that haven’t been
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MÉDAILLES 2008 - HERZBERG (SVENSSON)
studied to date. They have direct implications for our understanding, again, of some big questions – how the chemical elements are synthesized in astrophysical explosions, in supernovae. This process involves many reactions on unstable nuclei
which haven’t been available to study before. You put together the whole group of these experiments to understand the
structure of the nucleus and its astrophysical implications.
PC –
Do you keep in mind when you are working in an
area B this is something which in my lifetime we should be able
to make some considerable progress in?
PC –
But over the course of say, five years, do you vary
between pessimism and optimism?
CS –
The experiments tend to be long term programs and
new information certainly comes in. We are impacted, for
example, by the recent results from SNO and the study of neutrino oscillations. We are looking for effects involving quarks,
but you can also accomplish the same matter-anti-matter asymmetry involving leptons. So as other groups refine measurements of their parameters, maybe it looks more or less
favourable that the explanation to this problem lies with the
leptons or the quarks. So there are new ideas, new flavours, all
the time, but, quite frankly, none of us know where the answer
is until we do the experiments. Theorists can change direction
relatively quickly. In this business, experimentalists make a
long term commitment to the set up and execution of a program.
BJ –
Does your work rely on competing theories or is it
something that has its own driving force?
CS –
There are many, many models. As an experimentalist, I like to stay focused on the bottom line. We are searching
for what is called an electric dipole moment. If the only interactions in nature are the ones we know about – the strong
nuclear interaction, gravitation, and the electro-weak interaction – this moment is many orders of magnitude smaller than
current experimental sensitivity for all particles. So it is a
property that, for all practical purposes, is zero if all that exists
is the currently known physics. So if you measure it, you are
guaranteed that you have found a signature of new physics.
Now, if you succeed in doing that, then there are many potential models, all of which extend the current suite of physical
PC –
Was there some point where you knew you wanted
to be an experimentalist as opposed to a theorist?
CS –
In thinking back, that was fairly clear to me early on
in my undergraduate career.
PC –
There is a longer term commitment to being an
experimentalist. You have to start with an experiment and keep
following it through whereas as a theorist you can use, to use
your term, the flavour of the day, right?
CS –
Well, I certainly don’t want to belittle the efforts of
my theory colleagues who devote enormous effort to developing models of new physics, but they can obviously change
direction more quickly. We build fairly complicated instruments that take many years to construct, and once you start
building it is difficult to change what it is that you are building.
PC –
Different personalities are involved, whether or not
it is fair to make generalizations about personalities who
become theorists and those who become experimentalists. Did
you take motorcycles apart in your youth?
CS –
I did not actually take motorcycles apart, but yes,
fairly early on in physics I was always interested in experiments and I took all the lab courses I could.
BJ –
Do you see now a change in the new generation
which is brought up on video games and everything is software
and intuitive? Are they ready for the labs the ones you take on
in undergrad and summer projects?
CS –
Certainly yes. We have an excellent group of students working with our group. There are certainly different
personality types; those who are natural with their hands and
those who are more natural with the computer. What you mention is, however, certainly an issue in our field, maybe even
more than some others. We do most of our experiments at TRIUMF in Vancouver. We go there to set up and run our experiments. Because of the requirement to travel to a major accelerator facility, students sometimes do not get the opportunity
that they historically would have had to have their own lab
space where they can, if you like, ‘play’, and really get to know
the system. We have to go to a major facility like TRIUMF to
run our experiments. Beam time is highly oversubscribed and
in limited supply. You have to get it right the first time.
Because of this environment, my colleagues and I have recognized the need for formal training which, historically, would
probably have happened along the way because students would
have been in the lab more.
CS –
Certainly, we all lay our bets to some extent and I
guess most of us don’t bet very well or else we would all work
on whatever the next Nobel prize is going to be in. Discovery
is obviously not very easy to predict but, in this problem of
studying CP violation B looking for new effects which would
break time-reversal symmetry – we at least have the empirical
evidence that the universe out there is made up mostly of matter and it is not made up of equal amounts of matter and antimatter. We simply can’t explain that given our current understanding of physics. We know that there has to be something
new out there and each generation of experiments gets more
and more sensitive and then you ask yourself if your next step
is going to be the one. You always hope it is or you would
probably not expend the enormous effort required to mount
such experiments. There is, however, a theoretical context that
we work within. There are many theoretical models which
attempt to explain this imbalance and each makes a prediction
about the size of the effects that we should see in these experiments. In fact, experiments are already in a regime where they
eliminate many of those theories; in other words, some theories
predict effects of a size that are now excluded by experiments.
So there is reason to be hopeful that the next step may be the
one where you make a discovery …
interactions, which can have this effect. So then you would
have to say, okay, we’ve discovered it, but what implications
does our value have for each of the postulated theories which
might explain it. Then things get more complicated. Each of
those theories has many parameters, and the measurable may
be a function of many of those parameters. You exclude certain possibilities and others will remain. It’s a nul experiment
if you like. If you measure anything that is non-zero, you are
guaranteed to have a smoking gun for new physics. Then you
get to the next level and ask, what is this new physics?
PC –
I was struck by the fact that here you are in Guelph
but your experiment basically is in the campus of UBC, right?
BJ –
A suitcase physicist is what we used to call them.
CS –
That is right.
PC –
Typically you go out for how long?
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CS –
I am back and forth frequently. It varies. At times I
am out to TRIUMF for a couple of weeks and other times for
a couple days.
PC –
Are these round-the-clock sessions?
CS –
When we are running we run 24 hours a day and usually have several people on shift all the time. Each person has
their own specific expertise so when subsystem x breaks, it is
person x who gets the call to make it work again. There is a
fairly sizable groups of collaborators involved.
PC –
10 to 15?
CS –
In that ballpark. It is not 100s as it is often is in high
energy physics, but it is also not one or two as it often is in
many fields of physics. We are looking at a scale of approximately 20 people for a typical experiment.
PC –
Do you ever see anything while you are actually
there or is it only when you come back and analyze the data
later that you see things?
CS –
We certainly see things when we are running. Beam
time at a facility like TRIUMF is precious, so we basically analyze the data in real time as it comes in. In fact, many of the
interesting results you see right away. You still come home
and spend two years refining your analysis and tightening
things up. In the end, you usually wind up with a number
which differs from the one that you had the first night by about
5% and a much more refined estimate of its uncertainty, but in
a large class of our experiments you basically know that you
have a result before the experiment is done.
PC –
So is there an eureka moment to some of these
experiments?
CS –
Certainly. There are not many times when people
actually run around the lab naked, shouting in Greek, but there
are certainly cases where you see things very quickly while
running the experiment. We basically do as much as we can in
real time and then there is the next level of analysis that takes
a bit more computer work off line.
PC –
Let me see if I understand what you said about this
CP violation. The reason that it is interesting is that it should
not exist. It is not explained by the current theory.
CS –
Physicists like symmetries. We use them to guide
our theories. Now, we should be a bit careful in talking about
this CP violation. CP violation certainly does exist. It is
known to exist.
BJ –
The Nobel prize was given for it.
CS –
and it has been measured very accurately. But, to
our current knowledge, all of the known CP violation comes
from a single parameter in the standard model of particle
physics – a complex phase in the so-called CKM quark-mixing
matrix. It has been measured well and it is not sufficient to
explain the imbalance between matter and anti-matter in the
universe. One of the conditions for generating that imbalance
is thus a new source of CP violation. So, looking out at the universe and seeing that it is mostly matter tells you right away
that there has to be another source of CP violation, that we
don’t yet know about, which was sufficient in magnitude to
have generated a matter/anti-matter imbalance in the early universe.
PC –
So you are searching for the thing that isn’t there in
the sense that no one has yet found it.
188 C PHYSICS
IN
CS –
No one has ever measured a non-zero particle electric dipole moment, and the predicted values with the currently known CP violation of the standard model are many orders
of magnitude smaller than current experimental sensitivity. So,
if you believe that the current standard model encompasses all
of elementary particle physics then we are indeed searching for
something that isn’t there, or at least something that we won’t
be able to measure any time soon. We generally view this as a
positive, in that if you do measure something there are no complicated questions about standard model backgrounds and you
can be sure that you have a signature of new physics. Then,
of course, you would have to decide on what new physics you
have. Basically all of the models of physics that go beyond the
standard model – things called super-symmetry, or models in
which you have multiple Higgs particles, or models in which
you have both left and right handed weakly interacting particles B all generate this kind of CP violation and time reversal
violation. Each of those models has a set of parameters that
determines how large the violation will be. One of the interesting motivations for our work is that many of the favoured models predict electric dipole moments that are approximately the
same size as current experimental sensitivity. So, if you believe
those theories, you are going to measure one soon, and if you
don’t measure one soon, you rule out some of the favoured
models of the new physics.
PC –
So either way if you get an answer it is going to be
new physics.
CS –
Either way you have an impact. Obviously a discovery would be more exciting than ruling out some particular
subclass of models, but even a nul measurement has impact. If
you like, we would be restricting the theorist’s playground and
we experimentalists consider that a good thing. You cannot
propose models that predict electric dipole moments larger
than have already been ruled out by experiments. So, there is
impact either way. Obviously, we would prefer the discovery
….
PC –
How old are you?
CS –
36
PC –
How long have you been at Guelph?
CS –
7 years – since January 2001. I guess that makes 7
and ½ years.
PC –
And you came there from?
CS –
I did my PhD at McMaster. I graduated in 1998. I
then spent two years in Berkeley as a postdoc.
BJ –
Quickly, a personal question. Are you a driven person or is this just something that you do naturally?
CS –
This is a hard question to answer. We certainly work
hard and I want to stress that in what we do a lot of people
work hard. This requires a team of people to all dedicate large
amounts of time to make it all come together. We are developing sophisticated instrumentation and different people have
different expertise and there is a lot of teamwork involved. We
have a really great team working on our experiments at Guelph
and at TRIUMF. Everybody is deeply excited by the science
and the motivation lets us get far more out of the team than the
sum of its individual parts. The TIGRESS spectrometer that
we are building, which was generously funded by NSERC, was
funded over a period of six years, so we have been building this
instrument for almost six years now. It takes some focus and
ongoing refocus to keep that on track and put it all together.
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But certainly the science is what keeps us going. That is what
motivates us to do this.
PC –
In my mind, when you talked about the electric
dipole it reminded me of a famous British childhood nursery
rhyme which starts off as:
Yesterday upon the stair
I saw a man who wasn’t there
He wasn’t there again today
I wish that man would go away
The electric dipole moment is the man upon the stair.
CS –
But we don’t want him to go away. We wish him to
be there tomorrow. We would like to see a man who is there,
just very small.
BJ / PC – Thank you Carl for taking the time to be with us
today.
EXCEPTIONNELLES À LA PHYSIQUE
L
e professeur Taillefer est un scientifique de
renommée internationale. Il a obtenu son BSc de
l'Université McGill et son PhD de l'Université
Cambridge. Après cinq ans au CNRS à Grenoble,
France, il revint au
Canada dn 1992, là The CAP Medal for
où il a effectué la Achievement in Physics is
majorité de ses awarded to Louis Taillefer,
brillants travaux, Université de Sherbrooke,
d'abord à McGill, for his strong leadership in
puis à Toronto et condensed matter research,
maintenant
à resulting in the discovery of
S h e r b r o o k e . multi-component superconMalgré le fait qu'il ductivity, the first observed
ne soit que dans la
violation of the Wiedemannquarantaine, Louis
Franz universal ratio of
Taillefer est un des
scientifiques les charge and heat conductiviplus cités dans son ties, and an experimental
domaine. Il a gagné breakthrough in high-temles prix les plus perature superconductors,
prestigieux.
where quantum oscillations
were discovered.
Matériaux quantiques
Les matériaux où le comportement collectif des électrons
se manifestent de manière inattendue et souvent remarquable, sont connus sous le nom de maétriaux quantiques.
Le professeur Taillefer explore la frontière de ce domaine.
Il est détenteur de la chaire de recherché du Canada en
matériaux quantiques et directeur du programme correspondant de l'Institut canadien de recherches avancées.
Pioneering research & recent breakthroughs
Louis Taillefer is internationally known for his innovative
experimental research on quantum materials. He pioneered the use of heat transport at ultra-low temperature to
determine the symmetry of the superconducting state,
probe critical behaviour at quantum phase transitions, and
elucidate the nature of excited states in magnetic insulators. He was the first to directly measure the giant electron masses of heavy-fermion metals. He discovered the
first instance of multi-component superconductivity and
the first violation of
La Médaille de l'ACP pour
the
Wiedemanncontributions exceptionFranz law B the
nelles à la physique est
physical law that
décernée à Louis Taillefer,
determines the universal
ratio
of
Université de Sherbrooke,
charge and heat conpour son leadership solide
ductivities of a
dans la recherche en
metal at absolute
matière condensée, qui a
zero.
conduit à la découverte de
la supraconductivité à
plusieurs composantes, à la
première observation d'une
violation du rapport universel de Wiedemann-Franz
des conductivités de charge
et de chaleur, et à une percée expérimentale dans les
supraconducteurs à haute
température, où des oscillations quantiques ont été
découvertes.
In March 2007,
Taillefer's
team
made a far-reaching
breakthrough: the
first observation of
quantum
oscillations in a high-temperature superconductor. Taillefer's
discovery is thought
to hold one of the
keys to that enigma.
This experimental
THE CAP MEDAL FOR ACHIEVEMENT IN PHYSICS
LA MÉDAILLE DE L'ACP POUR CONTRIBUTIONS
Dr. Louis Taillefer
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tour de force by Taillefer and his collaborators in Toulouse
and at the University of British Columbia required a lownoise measurement of the Hall resistance at low temperature (~ 1 K) up to the highest available fields (60 Tesla) on
the very best single crystals. The observed Shubnikov-de
Haas oscillations provide unambiguous proof that underdoped cuprates have a well-defined closed Fermi surface,
in contrast to what has been suggested by photoemission
experiments for a decade. This is causing a paradigm shift
in the field.
Taillefer is now leading the most exciting and promising
developments in the highly competitive field of high-temperature superconductivity. This comes after 20 years of
major contributions to the field of superconductivity and
correlated electron physics, many of them after he
returned to Canada from Europe fifteen year ago in 1992.
To name a few: phenomenological theory of spin fluctuations in magnetic metals (1985); first direct measurement
of quasiparticle mass in heavy-fermion metals (19871988); discovery of multi-component superconductivity
(1988-1989); discovery of universal conduction in superconductors (1997); first observation of a violation of the
Wiedemann-Franz law (2001); discovery of a new quantum critical point (2003); first observation of anisotropic
quantum criticality (2007).
Awards
Taillefer's achievements in research have been recognized
by major awards, including an Alfred P. Sloan Fellowship
at age 32, an E.W.R. Steacie Memorial Fellowship from
NSERC at age 38, and the prestigious Prix Marie-Victorin
from the Québec Government at age 44. The latter is the
top career prize in science and engineering in Québec and
Taillefer is the youngest recipient of all 29 laureates since
1977. He was nominated to the Academy of Sciences of
Canada in 2007.
Leadership
Taillefer's contribution to collaborative research in Canada
has been outstanding. In 1998, he was appointed by the
Canadian Institute for Advanced Research (CIFAR) as the
youngest director of one of their programs, on
Superconductivity (1998-2003), where he displayed
190 C PHYSICS
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exceptional leadership, securing two renewed mandates
for a broadened program on Quantum Materials, (20032008) and (2009-2014), which now brings together 40
Canadian and 11 international scientists and their students/postdocs. It is probably fair to say that no other network of researchers in the world has had as much cumulative impact on the field of high-temperature superconductivity as the CIFAR Superconductivity / Quantum
Materials program. With colleagues at McGill University
and Université de Montréal, Taillefer was also involved in
the creation (in 2003) and direction (from 2005 to 2007)
of the largest Québec-funded research network in science
and engineering, the Regroupement Québécois sur les
Matériaux de Pointe (RQMP). Taillefer's exceptional ability as a speaker has made him a prime guest at public
events.
L'impact scientifique de Louis Taillefer est vraiment
exceptionnel et son leadership dans la direction de collaborations de recherches nationales est remarquable. Sa
feuille de route des derniers vingt ans contient une série de
découvertes majeures et plusieurs percées scientifiques
récentes. Ce sont les deux critères principaux pour la
Médaille de l'ACP pour contributions exceptionnelles de
carrière à la physique. Grâce à sa personnalité charismatique et sa jeunesse, il représente parfaitement la recherche
canadienne et québécoise à l'échelle internationale et il est
un modèle inspirant pour les jeunes scientifiques. Les
réussites et les talents de ce scientifique au plus haut
niveau international dans son domaine, font de Louis
Taillefer un récipiendaire particulièrement méritant de la
Médaille de l'ACP pour contributions exceptionnelles de
carrière à la physique.
André-Marie Tremblay M.S.R.C.
Professeur, département de physique
Chaire de recherche du Canada en physique de la matière
condensée, niveau I
Membre du programme de matériaux quantiques de
l'Institut canadien de recherches avancées
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ENTREVUE AVEC LOUIS TAILLEFER,
QUÉBEC (PAR B. JOÓS)
BJ – Tes intérêts en science et en physique plus précisément
ont commencé quand?
LT – Mon intérêt pour la physique est venu avec la recherche.
Je n’avais pas un intérêt marqué pour la physique avant d’arriver au doctorat.
LT – Oui, ça allait, mais je n’étais pas passionné par la
physique. J’étais un peu comme beaucoup de jeunes qui ne
savent pas nécessairement ce qu’ils veulent faire ni pourquoi.
D’ailleurs, au Cégep, j’avais pris une année de congé, j’ai travaillé sur une ferme toute une année parce que je ne voyais pas
pourquoi j’allais à l’école. J’étais très bon académiquement,
mais je n’étais pas motivé. Mes passions étaient à l’extérieur.
Je suis allé à
McGill en Mining
Engineering parce "I am moved by the supque je n’avais port I receive through
aucune idée quoi this award from the
faire mais après
deux semaines, je Canadian community of
me
suis
rendu physicists. This support
compte que je ne has made all the differsuis
pas
un ence for me, in making
ingénieur, j’ai donc
transféré en géo- Canada the best place in
physique, j’ai fait un the world for deep,
an en géophysique, ambitious, long-term,
et j’ai vu que ce qui collaborative research."
m’intéressait
le
plus en géophysique
c’était la physique.
Surtout parce que
j’étais intéressé aux
questions fondamentales plus qu’aux questions pratiques.
Après ça, j’ai fait mon bac en physique. J’ai aimé ca en grande
partie parce que j’avais des bons amis en classe … J’ai eu du
plaisir et j’ai fait mon bac et j’avais des bonnes notes. Après
ça, je ne savais pas trop que faire. J’ai postulé à toutes sortes
d’endroits, et mon frère, lui il voulait aller faire des maths à
Cambridge et je me suis dit que cela m’intéresse, moi aussi je
veux aller en Europe. Je ne suis pas allé à Cambridge pour faire
un doctorat, je suis allé à Cambridge parce que j’avais envie
d’être en Europe. Mais je suis tombé sur quelqu’un qui m’a
vraiment inspiré, Gilbert Lonzarich.
LT – Gil était un mentor au vrai sens du mot. C’est lui qui m’a
donné le feu sacré de la recherche, puis c’est quand j’ai vu ce
qu’est la recherche que j’ai vraiment accroché. Je me décris
d’abord et avant tout comme un chercheur, pas comme un
physicien. C’est-à-dire, que moi j’aurais fait de la recherche
dans d’autres disciplines. Je pense que c’est le processus de la
recherche qui me passionne. Beaucoup de gens ont une compréhension de la physique plus grande, plus profonde que la
mienne. Moi, ce que j’aime et où je pense que j’ai une certaine
abilité c’est la recherche.
BJ – Est-ce que devenir expérimentateur était un choix naturel
pour toi ?
10
JUIN,
2008,
LT – Je sais maintenant que pour moi le grand plaisir c’est la
découverte expérimentale. Elle me donne un très grand plaisir
que je ne retrouverais pas dans la recherche théorique.
Autrement dit, pour moi, ca ne vient pas de ma tête, ca vient du
monde extérieur. C’est le monde qui me parle. Ce n’est pas moi
qui invente ou qui conçoit quelque chose pour l’expliquer. Ce
qui me fascine, ce n’est pas tant d’expliquer les phénomènes
que de les découvrir. C’est la découverte, en fait. Donc,
recherche et découverte. La découverte, je trouve, est la chose
la plus excitante qui soit. Pour d’autres l’obsession est de comprendre. Ceci dit, j’aimerais bien comprendre comment ca
marche un supraconducteur à haute température !
BJ – Et donc, après Cambridge ?
LT – Après, je suis allé faire un postdoc à Grenoble, puis j’ai
eu un poste au CRNS, à Grenoble, qui est un grand centre de
matière
condensée.
« Je suis ému par le sou- Cela a été une période
excitante. C’est là que
tien que me procure ce
j’ai vraiment comprix de la collectivité
mencé à travailler en
supraconductivité.
canadienne des physi-
ciens. Ce soutien a été
toute la différence pour
moi, faisant du Canada le
meilleur endroit du
monde entier pour la
recherche en collaboration, poussée et
ambitieuse, menée à long
terme. »
BJ – Alors, avec
Lonzarich ce n’était pas
la supraconductivité ?
Parce ce que lui est
devenu assez visible en
supraconductivité…
LT – Oui mais plus tard,
A l’époque, ce qui l’intéressait, c’était le magnétisme. Eventuellement il a démontré que
le magnétisme peut
causer la supraconductivité…mais ca s’est venu beaucoup plus
tard. Vers la fin de mon doctorat, j’ai fait des cristaux, j’ai fabriqué mes propres cristaux. Je les appelle mes « Christmas
crystals » parce que c’était à Noël 1985. J’étais tout seul dans
le labo. J’ai fait des cristaux de UPt3, qui se sont avérés être les
meilleurs cristaux qui avaient jamais été faits et qui m’ont permis de voir les oscillations quantiques dans les fermions lourds
pour la première fois. Une découverte très excitante. Il faut
savoir que dans les oscillations quantiques, il y a deux facteurs
exponentiels dans l’amplitude : un qui fait intervenir la masse
effective m*, qui est de la forme exp(- m*T / B), et l’autre qui
fait intervenir la qualit des ééchantillons, de la forme exp(- π
r / l ), où r est le rayon de l’orbite de cyclotron et l est le libre
parcours moyen de l’électron. Alors, plus la masse est élevée,
plus il faut que la température T soit basse. Dans les fermions
lourds, c’est énorme comme effet, puisque les masses effectives sont 10 fois la masse de l’électron, me. Alors c’est un
défit fou de voir les oscillations quantiques et cela demandait,
en autre, de très bons échantillons, avec de longs libres parcours moyens. Avec ces cristaux, j’ai été le premier avoir les
oscillations quantiques, et j’ai pu mesurer des masses de
m* = 90 me. ... Je disais à Gil que j’étais chanceux. Lui, Gil
ne croyait pas à la chance, il disait que ce n’était pas la chance.
Moi, vraiment, je ne croyais pas que ce que je faisais était
quelque chose de spécial, et je me trouvais extrêmement
chanceux.
BJ – Mais tu as quand même décidé de faire de la physique,
plutôt que quelque chose d’autre?
LE
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BJ – Mais c’était propre. Bon échantillon ça veut dire d’abors
propre, pur…
LT – Dans ce cas là, ça veut dire pur, parce que UPt3 pousse
d’une manière ordonnée naturellement. Dans le cas des
cuprates, propre c’est une chose, mais en plus il faut que le
matériau soit ordonnée, c’est autre chose. Ce qui nous a permis de voir les oscillations quantiques dans YBCO l’année
dernière c’est la grande qualité des cristaux fabriqués à UBC,
non seulement leur pureté mais, en particulier, le fait que les
atomes d’oxygène sont distribués de façon ordonnée.
BJ – Donc après, tu n’es pas resté longtemps à Grenoble au
CNRS.
LT – Pas très longtemps. Ils m’ont offert un poste permanent
au CNRS, j’avais à peu près 30 ans (1988). Mais, ce que j’ai
découvert, c’est qu’ils ne me donnaient aucun moyen pour être
indépendant : pas de subvention, pas de labo. Il fallait être dans
un groupe avec un Directeur de recherche. Cela ne me plaisait
pas. Ce n’était pas la façon de lancer sa carrière en tant que
jeune. J’avais mes idées et je voulais les suivre moi-même. Et
je me suis rendu compte que le système français était mal
conçu et eux mêmes s’en sont rendus compte par la suite et il
y a eu des grandes réformes au CNRS parce que les jeunes partaient. Tous les jeunes s’en allaient, parce qu’ils ne voulaient
pas être sous la gouverne de quelqu’un ...
l’Université de Toronto, il promettait des postes, des fonds
pour monter un labo, c’était vraiment le fun. Après cela ça
c’est rétabli au Québec. Donc ce fut une coïncidence de certaines frustrations personnelles que mon domaine n’allait pas
être prioritaire à McGill et des situations d’un contexte financier difficile. Mais, après ça Toronto…
BJ – Une situation de famille ?
LT – Oui, l’éducation de mes enfants.
BJ – Et Sherbrooke c’est une université avec une tradition dans
les systèmes corrélés théorique et expérimentale.
LT – Oui, en fait, il y avait un gros groupe et aussi, en fait, au
délà de la question de l’affinité du sujet, il y a aussi une attitude
très collaborative à Sherbrooke. C’est un petit département et
ce serait du suicide de ne pas se mettre ensemble. Mais j’aime
ça, on travaille ensemble, on a des projets conjoints, il y a un
esprit de collectivité très fort. Donc, je suis très heureux à
Sherbrooke.
BJ – Les haut-T c ont été découverts en 1986. Quand as-tu
commencé à travailler sur les haut-T c ?
LT – Il y a plusieurs éléments, mais une chose à quoi je suis
particulièrement sensible, et cela dépend peut-être des disciplines, mais dans ma discipline, mon domaine de physique,
c’est l’approche collaborative de la recherche.
LT – Je me suis joins aux haut-T c quand je suis revenu au
Canada en 1992, parce que j’ai vu ce que le groupe de UBC
faisait et je me suis dit que cela m’intéressait. Bien sur j’ai
suivi l’évolution de la discipline depuis le début avec intérêt
mais je n’étais pas là-dedans. Je travaillais sur les fermions
lourds qui étaient des supraconducteurs aussi, donc le
phénomène de la supraconductivité m’intéressait mais en 92
quand j’ai vu qu’ils faisaient des cristaux à UBC, ils m’ont
invité à joindre le programme de l’ICRA (Institut canadien de
recherches avancées). Je leur ai dit que je savais faire des
mesures de transport de chaleur, et on a commencé une collaboration. Je dirais que notre première contribution significative
au domaine des haut T c, celle qui se démarque vraiment c’était
l’observation de « la conduction universelle de la chaleur ».
C’est une propriété des supraconducteurs de type d.
BJ – Égal à égal.
BJ – « Universelle », dans quel sens ?
LT – Non de travailler ensemble. Au lieu d’être compétitif,
parce que dans un domaine, très vite, il faut décider si l’on va
travailler ensemble ou l’un contre l’autre. Au Canada, dans le
domaine de la supra, c’est vraiment parti dans une direction de
collaboration et moi, cela me convient et j’aime ça. Je prends
plaisir au jeu de la compétition au niveau international, mais
j’aime bien travailler au sein d’une équipe. Notre équipe contre votre équipe à la limite. Mais il faut qu’il y ait une collaboration et que l’on travaille ensemble. Je ne suis pas un solitaire
dans ma recherche.
LT – Universelle dans le sens que la conductivité thermique ne
dépend pas de la concentration des impuretés. C’est une propriété vraiment singulière des supraconducteurs d-wave.
Donc, je suis venu au Canada et depuis ce temps là, j’ai découvert à quel point le système canadien est bien. Je trouve que
c’est le meilleur système pour faire de la recherche. Je le compare aux Etats-Unis, et à la France…
BJ – Est-ce à cause du CRSNG… ou à cause du milieu
académique ?
BJ – Au Canada, tu as fait plusieurs institutions, McGill,
Toronto et ensuite Sherbrooke. Est-ce-que c’était pour garder
ta liberté ou pour les opportunités, …
LT – Ce qui m’a fait quitter McGill pour aller à Toronto, ce
sont des raisons professionnelles, et ce qui m’a fait quitter
Toronto, c’était une raison personnelle. Donc, c’était très différent. A McGill, il y avait deux raisons pour lesquelles je n’étais pas satisfait comme « Assistant Professor » après 4-5 ans.
La première c’est qu’il n’y avait pas de volonté de construire
un groupe de recherche dans mon domaine. La supraconductivité n’était pas une priorité. J’ai compris que ça allait être difficile d’avoir une équipe. Je vais être isolé, et j’ai trouvé cela
difficile à accepter. C’était la raison principale, l’autre raison c’était l’époque. En 1997 au Québec le financement de la
recherche et des universités n’était pas très bon. En Ontario
cela allait mieux. Quand finalement j’ai postulé pour
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BJ – Ce n’est pas observé dans un supra ordinaire ?
LT – Non, voilà, c’est ça.
BJ – Le courant total est affecté ?
LT – C’est plus facile de penser en terme du courant de chaleur,
car la résistivité est zéro. Les paires de Cooper sont des bosons
qui, une fois formées, ne transportent aucune entropie, donc
pas de chaleur. Ce qui transporte la chaleur ce sont les paires
brisées, les excitations, qu’on appelle des quasi-particules.
Dans un supra s-wave, la population de ces quasi-particules va
exponentiellement vers zéro à basse température. Il y a un gap
pour les excitations. Donc, à basse température, il n’y a aucun
transport de chaleur. Un supraconducteur est un solide étrange,
c’est le meilleur conducteur de charge, mais c’est un isolant de
chaleur. Cela ne conduit aucune chaleur sauf par les phonons.
BJ – C’est différent dans les Haut-T c ?
LT – Alors, c’est différent dans un supraconducteur de type dwave parce que il y a des zéros dans le gap. Le gap s’annule à
certains points et à ces points là, il y a des excitations d’énergie
nulle, donc en fait, jusqu’à T=0, il y a des excitations fermioniques, les quasi-particules, qui transportent de la chaleur, et ils
vont la transporter d’autant mieux s’il y a moins d’impuretés
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comme n’importe quel porteur de charge ou de chaleur, sauf
que le nombre de ces quasi-particules est proportionnel à la
densité d’impuretés. C’est-à-dire que le point où se trouve le
gap nul s’élargit avec l’addition d’impuretés. Plus on met d’impuretés, plus on expose la surface de Fermi, plus il y a de quasiparticules qui peuvent porter, mais leur libre parcours moyen
est d’autant plus court. Les deux effets se compensent exactement.
BJ – Cela maintient le courant de chaleur constant.
BJ – On ne connaît toujours pas le principe de cette supraconductivité.
LT – C’est ça, on ne connaît pas le mécanisme de pairing, mais
on connaît la symétrie complètement, absolument. Notre résultat on l’a obtenu en 1997, je dirais que c’est une preuve du dwave. On ne peut pas avoir cette propriété sans avoir le dwave. Ce n’est pas la première preuve de symétrie « d-wave ».
La première démonstration expérimentale de d-wave est venue
du groupe de Walter Hardy et Doug Bonn à UBC. C’était la
mesure de la longueur de pénétration du champ magnétique en
1993. Nous sommes venus quatre ans après, mais notre observation était une confirmation très forte que l’on avait affaire à
un d-wave. C’était sans doute le résultat le plus important de
ma période McGill. Mais la grande question de mécanisme de
pairing reste ouverte.
BJ – Dans ton colloque aujourd’hui tu parlais de votre découverte spectaculaire [1] de la surface de Fermi dans les haut-T c
à petit dopage de trous où l’état supra est supprimé par un
champ magnétique intense [2]. Ce qui m’a vraiment frappé dans
cette présentation, c’est que j’avais l’impression de retourner
30 ans en arrière dans mon cours d’état solide où on parlait
d’oscillations Shubnikhov-de-Haas, et de l’effet Hall dans l’étude des surfaces de Fermi des métaux et semiconducteurs.
LT – C’est en effet de la fermiologie tout à fait classique. Une
surface de Fermi cylindrique fermée, des petites poches en 2d.
Combinant les résultats de l’oscillation quantique avec l’effet
Hall qui est négatif, on sait que ce sont des poches d’électrons,
et non pas des poches de trous. Une surprise totale ! On connait sa masse précisément. On connait son aire. On a son libre
parcours moyen. Mais on ne sait pas d’où vient cette poche
d’électrons dans un matériau dopé aux trous ! C’est spectaculaire, totalement inattendu. Le côté génial de la découverte ...
On a soumis notre article à Nature le 4 avril et il a été accepté
le 18 avril. Des huit cent articles soumis en 2007, ce fut celui
qui fut accepté le plus rapidement. Il fut publié en mai. Ce qui
est impressionnant, c’est que cela a été reproduit par un groupe
américain avant que cela ne paraisse. Cela donne ce sentiment
(c’est la théorie de Gil (Lonzarich)) que les découvertes
arrivent simultanément. Il y a un côté psychologique. Si tu sais
que quelque chose a été mesuré, il y en a qui sont instantanément prêts à le répéter. Le laboratoire des hauts champs américain l’a reproduit mais dans un autre matériau. C’est moins
propre mais les oscillations sont là. C’est bien parce que tout
résultat spectaculaire doit être reproduit pour être assimilé.
BJ – Des nouveaux supra qui contiennent du fer viennent
d’être découverts. Cela donne l’impression que nous n’avons
pas fini d’être surpris. Comment vois-tu l’avenir en supra ?
BJ – En conclusion, tu es très positif pour l’avenir, tu es juste
en mi-carrière ?
LT – J’en ai encore pour un bout de temps.
BJ – Comment vois-tu la recherche au Canada? Il y a ces nouveaux programmes du Fonds canadien de l’innovation, des
Chaires de recherche du Canada, du CRSNG.
LT – J’en ai beaucoup bénéficié.
BJ – Ils rendu l’environnement de recherche au Canada beaucoup plus excitant.
LT – Oui, absolument. Quand on met tous ces programmes
ensemble, le CRSNG à mon avis, c’est la base fondamentale
qui donne le ton à tout le reste. J’ai énormément de respect
pour le CRSNG. Je me trouve chanceux de travailler dans un
pays qui gère ses fonds de recherches ainsi.
BJ – Tu dois être content que la revue internationale du
CRSNG soit revenue avec un rapport positif.
LT – Oui, très positif, très content. Puis, après ça, il y a tous les
autres mécanismes qui ont été mis en place, et dans un esprit
de respect de la collaboration mais aussi en même temps, de
belles ambitions. Alors oui je suis très optimiste. Je suis confiant dans l’avenir du Canada. Je ne veux pas aller nulle part
ailleurs. Une des choses qui me donnent un grand plaisir c’est
de travailler avec les jeunes. C’est pour cela que j’aime travailler à l’université où on est toujours en contact avec des
jeunes.
BJ – Énergies nouvelles, nouvelles idées.
LT – Oui, ouverture d’esprit complète, questionnements, pas
d’idées préconçues, car au coeur des découvertes il y a l’intuition. Bingo, à un moment donné cela marche. Cette intuition,
comment cela se développe-t-elle? C’est une question fascinante. L’éducation y est certes pour quelque chose, mais cela
prend une attitude de respect des idées folles, un encouragement à imaginer, à explorer. Et c’est chez les jeunes que cela
s’optimise, voilà ce que je pense.
LT – Exactement. Donc, on peut multiplier par un facteur 10
le nombre d’impuretés, cela ne change pas la conductivité thermique, d’où le nom de conductivité universelle qui caractérise
le matériau. Cela avait été prédit théoriquement par Patrick
Lee, à MIT en 1990 mais n’avait jamais été observé. C’est une
propriété des « d-wave ».
LT – Moi ce que j’adore de ça, encore une fois, (ceci est arrivé
en janvier, février 2008) c’est impossible de prédire ce qui va
se passer, il y a toujours des surprises comme cela qui apparaissent, mais c’est clair que cela va être très intéressant de voir le
développement de la compréhension dans ce domaine. On en
connaît déjà beaucoup. Cela fait vingt ans que l’on étudie la
question. Il y a maintenant cette nouvelle famille avec de nouveaux régimes de comportements et d’essayer de voir, en fait,
est-ce-que c’est le même mécanisme qui fait que ça marche
mieux dans un ou moins bien dans l’autre matériau. La comparaison est extremement utile, alors on a toute suite nommé
un membre dans notre programme de l’ICRA qui est un des
chercheurs chinois les plus actifs dans le domaine. C’est un
domaine, en passant, qui est dominé à 90% par la Chine. Pour
l’instant !
BJ – Merci
[1] Nicolas Doiron-Leyraud, Cyril Proust, David LeBoeuf, Julien Levallois, JeanBaptiste Bonnemaison, Ruixing Liang, D. A. Bonn, W. N. Hardy, and Louis
Taillefer, Quantum oscillations and the Fermi surface in an underdoped high-Tc
superconductor, Nature, 447 (31 mai 2007), pp 565-568 (2007).
[2] Dans les haut-Tc, la phase supraconductrice est observée sur un intervalle de
dopage de trous, formant une région en forme de cloche dans un diagramme de
phase T vs dopage (voir [1]). A fort dopage le matériau dans la phase supra a une
grande surface de Fermi. A petit dopage la surface de Fermi apparaît déconnectée, faite de petits arcs. L’équipe de Louis Taillefer et ses collaborateurs de
Toulouse et de l’Université de Colombie britannique ont montré que si la phase
supraconductrice est supprimée à l’aide d’un fort champ magnétique, la surface
de Fermi du matériau à petit dopage révèle des petites poches fermées typiques
d’un métal simple.
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2008 MEDALS AND PRIZES
2008 BEST STUDENT PRESENTATION COMPETITION
The 2008 Best Student Presentation Competition was organized by the CAP’s Past President at the time,
Dr. Melanie Campbell of the University of Waterloo. Congratulations to all of the winners and honourable mentions in the CAP’s Best student presentation competition at the 2008 CAP Congress (see
pages 122 - 143 for list of winners and extended abstracts).
Winners of the divisional, CAP, and NSERC best poster presentations were presented with their awards on June 10th at the 2008
banquet at Laval University, Quebec City.
Winners of the divisional best oral presentations were presented
with their awards on June 10th at the 2008 banquet at Laval
University, Quebec City. The oral finalists were announced as well.
2008 CANADA-WIDE SCIENCE FAIR
The 46th Annual Canada-Wide Science Fair, held May 2008 in Ottawa, Ontario, was once again a resounding success! Over $150,000 in cash, scholarships,and other prizes were won bythe participating students. This year, the
CAP sponsored an award for the best physics projects in the senior category. The prizes consist of a cash award
of $1,000 plus a CAP plaque commemorating their achievement. The winners of the 2008 CAP prize was :
Dynamic Testing of Strength and Vibration Properties of Hardwoods
This project examined the relationships within and between the strength and vibration properties of hardwoods by dynamically testing the modulus of elasticity, impact surface hardness,
logarithmic decrement, and speed of sound in four hardwood species. New equipment was
designed and constructed by the exhibitor to do the testing, and extensive use was made of
mathematics and graphing to correlate and determine the various relationships.
A thank you from our winner
Thank you for supporting the Canada-Wide Science Fair and its participants by sponsoring the CAP
Physics Prize that I received along with the Senior Gold Medal in Physical and Mathematical Sciences for
my project. In it I explored and compared dynamic and static methods of determining the density, modulus
of elasticity, impact surface hardness (a property and testing method I developed), logarithmic decrement,
and speed of sound in fifteen samples of each of four species of hardwoods. I also examined the relationships between these properties.
Alice Jourmel
Grade 11/Secondary V
Frances Kelsey Secondary
Duncan, BC
I benefitted greatly from being able to present my project at the regional and national levels. At the CWSF
in Ottawa I had the opportunity to share my work with professional scientists and engineers, with finalists
who had similar interests, with students on school tours, and with both VIP visitors and ordinary citizens. I
was glad of the chance to have my project examined by professionals in the field I wish to enter, and to
demonstrate my enthusiasm for science and engineering to those not directly involved (or not involved yet)
in these areas.
There were many other engaging, interesting, and just plain fun activities in which I took part in Ottawa,
and I have no doubt that my participation in this and past CWSF’s has opened doors for me. For instance,
this summer I will be attending the Shad Valley program at the University of Calgary and then participate in the Marine Plants and Algae
Summer Youth forum at the Bamfield Marine Sciences Centre, on the west coast of Vancouver Island; I’m certain my science fair participation
and awards contributed significantly to my acceptance in these programs. And especially, the money will help me continue my education!
Attending the CWSF has affirmed my desire to pursue a career in either science or engineering, and your generosity has made it easier for me
to achieve my goal of a post-secondary education. Thank you once again for your support - it is greatly appreciated.
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LIVRES
BOOK REVIEW POLICY
Books may be requested from the Book Review Editor, Richard Hodgson, by using the online book request form at http://www.cap.ca.
CAP members are given the first opportunity to request books. Requests from non-members will only be considered one month after the distribution date of
the issue of Physics in Canada in which the book was published as being available (e.g. a book listed in the January/February issue of Physics in Canada will
be made available to non-members at the end of March).
The Book Review Editor reserves the right to limit the number of books provided to reviewers each year. He also reserves the right to modify any submitted
review for style and clarity. When rewording is required, the Book Review Editor will endeavour to preserve the intended meaning and, in so doing, may find
it necessary to consult the reviewer. Reviewers submit a 300-500 word review for publication in PiC and posting on the website; however, they can choose to
submit a longer review for the website together with the shorter one for PiC.
LA POLITIQUE POUR LA CRITIQUE DE LIVRES
Si vous voulez faire l’évaluation critique d’un ouvrage, veuillez entrer en contact avec le responsable de la critique de livres, Richard Hodgson, en utilisant le
formulaire de demande électronique à http://www.cap.ca.
Les membres de l'ACP auront priorité pour les demandes de livres. Les demandes des non-membres ne seront examinées qu'un mois après la date de distribution du numéro de la Physique au Canada dans lequel le livre aura été déclaré disponible (p. ex., un livre figurant dans le numéro de janvier-février de la
Physique au Canada sera mis à la disposition des non-membres à la fin de mars).
Le Directeur de la critique de livres se réserve le droit de limiter le nombre de livres confiés chaque année aux examinateurs. Il se réserve, en outre, le droit de
modifier toute critique présentée afin d'en améliorer le style et la clarté. S'il lui faut reformuler une critique, il s'efforcera de conserver le sens voulu par l'auteur
de la critique et, à cette fin, il pourra juger nécessaire de le consulter. Les critiques de 300 à 500 mots seront publiées dans la revue et affichées sur le web;
cependant les auteurs peuvent opter d’écrire une plus longue version pour le web et une version abrégée pour la PaC.
BOOKS RECEIVED / LIVRES REÇUS
The following books have been received for review. Readers are
invited to write reviews, in English or French, of books of interest to
them. Books may be requested from the book review editor,
Richard Hodgson by using the online request form at
http://www.cap.ca.
Les livres suivants nous sont parvenus aux fins de critique. Celle-ci
peut être faite en anglais ou en français. Si vous êtes intéressé(e)s à
nous communiquer une revue critique sur un ouvrage en particulier, veuillez vous mettre en rapport avec le responsable de la critique
des livres, Richard Hodgson par internet à http://www.cap.ca.
A list of ALL books available for review, books out for review, and
copies of book reviews published since 2000 are available on-line B
see the PiC Online section of the CAP's website :
http://www.cap.ca.
Il est possible de trouver électroniquement une liste de livres
disponibles pour la revue critique, une liste de livres en voie de
révision, ainsi que des exemplaires de critiques de livres publiés
depuis l'an 2000, en consultant la rubrique "PiC Électronique" de la
page Web de l'ACP : www.cap.ca.
GENERAL INTEREST
UNDERGRADUATE TEXTS
EINSTEIN: HIS LIFE AND UNIVERSE, Walter Isaacson, Simon &
Schuster Canada, 2007; pp. 675; ISBN: 978-0-743-3264730 (hc); Price:
$38.99.
AN INTRODUCTION TO THERMODYNAMICS AND STATISTICAL
MECHANICS, SECOND EDITION, Keith Stowe, Cambridge University
Press, 2007; pp. 555; ISBN: 978-0-521-86557-9 (hc); Price: $70.00.
MEETING THE UNIVERSE HALFWAY: QUANTUM PHYSICS AND THE
ENTANGLEMENT OF MATTER AND MEANING, Karen Barad, Duke
University Press, 2007; pp. 524; ISBN: 978-0-8223-3917-5 (pbk); Price:
$27.95.
DISSOCIATIVE RECOMBINATION OF MOLECULAR IONS, Mats Larsson
and Ann E. Orel, Cambridge University Press, 2008; pp. 376; ISBN:
978-0-521-82819-2 (hc); Price: $150.00.
THE FORMATION OF THE SOLAR SYSTEM: THEORIES OLD AND NEW,
Michael Woolfson, World Scientific Publishing Co., 2007; pp. 318;
ISBN: 978-186-0948244-P512 (hc); Price: $78.00.
THE LEGACY OF ALBERT EINSTEIN; A COLLECTION OF ESSAYS IN
CELEBRATION OF THE YEAR OF PHYSICS, Spenta R. Wadia, World
Scientific Publishing Co., 2007; pp. 260; ISBN: 978-981-270-480-1
(pbk); 978-981-270-049-0 (hc); Price: $54/$98.
THE QUANTUM TEN: A STORY OF PASSION, TRAGEDY, AMBITION AND
SCIENCE, Sheilla Jones, Thomas Allen Publishers, 2008; pp. 304;
ISBN: 978-0-887-623318 (hc); Price: 29.95.
INTRODUCTION TO ELEMENTARY PARTICLE PHYSICS, Alessandro
Bettini, Cambridge University Press, 2008; pp. 423; ISBN: 978-0-52188021-3 (hc); Price: $70.00.
METHODS IN HELIO- AND ASTEROSEISMOLOGY, Frank P. Pijpers,
World Scientific Publishing Co., 2007; pp. 306; ISBN: 978-1-860947551 (hc); Price: $85.00.
METHODS IN MOLECULAR BIOPHYSICS: STRUCTURE, DYNAMICS,
FUNCTION, Igor N. Serdyuk, Nathan R. Zaccai, Joseph Zaccai,
Cambridge University Press, 2007; pp. 1120; ISBN: 978-0-521-815246 (hc); Price: $99.00.
MODERN MANY-PARTICLE PHYSICS, 2ND EDITION, Enrico Lipparini,
World Scientific Publishing Co., 2008; pp. 575; ISBN: 978-9-812709325 (pbk); Price: 65.00.
8/18/2008
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BOOKS
QUANTUM MECHANICS: ITS EARLY DEVELOPMENT AND THE ROAD TO
ENTANGLEMENT, Edward G. Steward with a contribution by Sara M.
McMurry, World Scientific Publishing Co., 2008; pp. 245; ISBN: 9781-860-949784 (pbk); Price: 55.00.
NUMERICAL RECIPES SOURCE CODE CD-ROM 3RD EDITION: THE ART
OF SCIENTIFIC COMPUTING, W.H. Press, S.A. Teukolsky,
W.T. Vetterling & B.P. Flannery, Cambridge University Press, 2007;
pp. n/a; ISBN: 978-0-521-70685-8 (CD); Price: $80.00.
STATISTICAL MECHANICS MADE SIMPLE, 2ND EDITION, Daniel C. Mattis
and Robert H. Swendsen, World Scientific Publishing Co., 2008; pp.
335; ISBN: 978-9-812-779090 (pbk); Price: 42.00.
PARTICLE DETECTORS, SECOND EDITION, Claus Grupen and Boris
Shwartz, Cambridge University Press, 2008; pp. 649; ISBN: 978-0521-840064 (hc); Price: 160.00.
SUPERSYMMETRY IN PARTICLE PHYSICS: AN ELEMENTARY
INTRODUCTION, Ian Aitchison, Cambridge University Press, 2007;
pp. 218; ISBN: 978-0-521-88023-7 (hc); Price: $65.00.
STATISTICAL MECHANICS OF NONEQUILIBRIUM LIQUIDS, Denis Evans
and Gary Morriss, Cambridge University Press, 2008; pp. 308; ISBN:
978-0-521-85791-8; Price: $140.00.
GRADUATE TEXTS
AND PROCEEDINGS
BEYOND THE MECHANICAL UNIVERSE: FROM ELECTRICITY TO MODERN
PHYSICS, R.P. Olenick, T.M. Apostol, D.L. Goostein, Cambridge
University Press, 2008; pp. 565; ISBN: 978-0-521-71591-1 (pbk); Price:
$75.00.
COMPOSITE FERMIONS, Jainendra Jain, Cambridge University Press,
2007; pp. 539; ISBN: 978-0-521-86232-5 (hc); Price: $95.00.
ELECTOWEAK THEORY, Emmanuel A. Paschos, Cambridge University
ELECTRODYNAMICS OF METAMATERIALS, Andrey K. Sarychev and
Vladimir M. Shalaev, World Scientific Publishing Co., 2007; pp. 247;
ISBN: 978-981-0242459-4366; Price: $50.00.
EXTENDED DEFECTS IN SEMICONDUCTORS: ELECTRONIC PROPERTIES,
DEVICE EFFECTS AND STRUCTURES, D.B. Holt, B.G. Yacobi, Cambridge
University Press, 2007; pp. 631; ISBN: 978-0-521-81934-3 (hc); Price:
$160.00.
STATISTICAL PHYSICS OF FIELDS, Mehran Kardar, Cambridge
$75.00.
STATISTICAL PHYSICS OF PARTICLES, Mehran Kardar, Cambridge
$75.00.
SYMMETRY AND CONDENSED MATTER PHYSICS: A COMPUTATIONAL
APPROACH, M. El-Batanouny and F. Wooten, Cambridge University
THE MECHANICAL UNIVERSE: MECHANICS AND HEAT, ADVANCED
EDITION, S.C. Frautschi, R.P. Olenick, T.M. Apostol and D.L.
Goodstein, Cambridge University Press, 2008; pp. 577; ISBN: 978-0521-71590-4 (pbk); Price: $75.00.
TOPOLOGICAL FOUNDATIONS OF ELECTROMAGNETISM, Terence W.
Barrett, World Scientific Publishing Co., 2008; pp. 181; ISBN: 978-9812-779960 (hc); Price: 69.00.
MULTIVALUED FIELDS IN CONDENSED MATTER, ELECTROMAGNETISM
AND GRAVITATION, Hagen Kleinert, World Scientific Publishing Co.,
2008; pp. 480; ISBN: 978-9-812-791719 (pbk); Price: 38.00.
BOOK REVIEWS / CRITIQUES DE LIVRES
Book reviews for the following books have been received and posted to the Physics in Canada section of the CAP’s website :
http://www.cap.ca. Review summaries submitted by the reviewer are included; in some cases a more detailed review can be seen at the url
listed with the book details.
Des revues critiques ont été reçues pour les livres suivants et ont été affichées dans la section “La Physique au Canada” de la page web de
l’ACP : http://www.cap.ca .
LARGE-SCALE ATMOSPHERE-OCEAN DYNAMICS II: GEOMETRIC METHODS AND
MODELS, John Norbury and Ian Roulstone,
Cambridge University Press, 2002; pp. 384;
ISBN: 0-521-80757-3; Price: US$80 (hc).
[Review posted 7/29/2008; To read the detailed
review, please see http://www.cap.ca/brms/
reviews/Rev776_614.pdf ]
Ce second volume, d’une série de deux, ce veux
une mise à jour dans le domaine des mathématiques et de la modélisation géométrique, spécifiquement conçue pour la météorologie et
l’océanographie dynamique. Les sujets présentés
intéresseront les étudiants gradués et experts
dans le domaine. Ce volume est le résultat d’un
atelier tenu en 1996 dans le cadre du programme
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Mathematics of Atmosphere and Ocean
Dynamics de l’Institut Isaac Newton de
l’Université de Cambridge. Le volume permet
d’identifier clairement le fait qu’il existe
plusieurs façons d’écrire les équations qui
décrivent les phénomènes des fluides. Les différentes façons dépendent du choix des variables
utilisées, que ce soit Lagrangienne ou
Eulérienne, c’est différentes façons occasionnent
différentes sortes de structures Hamiltonienne.
Même si, à l’origine l’utilisation de la seconde loi
de Newton, la conservation de la masse et de
l’entropie à valeur constante, est utilisés, il existe
différents développements possibles des contraintes en tant que tel, occasionnant différentes
analyses possibles des phénomènes des fluides,
notamment l’analyse de leur stabilité. Une autre
conséquence du développement des différentes
formes de contraintes possibles est la formation
de différentes expressions d’énergie qui sont
décrites dans ce volume. Même si les hypothèses
utilisées ici pour décrire les différents modèles ne
sont pas sévères, le prix inévitable à payer est
que la formulation dynamique de ces modèles est
inévitablement plus compliquée. Il sera alors très
utile de se référer continuellement aux divers
articles mentionnés, à la fin de chaque chapitre
du volume, de façon a obtenir une version plus
complète et plus accessible des diverses méthodes et modèles géométriques.
André April
Environnement Canada
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LIVRES
PROBLEMES DE PHYSIQUE COMMENTÉS,
H. Lumbroso, Masson, 1993; pp. 472; ISBN: 2225-83994-8; Price: . [Review posted 7/29/2008;
To read the detailed review, please see http://
www.cap.ca/brms/reviews/Rev175_613.pdf ]
«Problèmes de physique commentés» est le premier d’une série de deux tomes destinés aux étudiants français du premier cycle de l’enseignement supérieur ou encore aux étudiants des classes préparatoires aux grandes écoles. Les problèmes sont intéressants et ils sont abordés avec
une certaine élégance donnant l’impression
qu’ils sont, somme toute, très simples. Les énoncés sont clairs et la résolution est méthodique.
Les lois et les principes physiques sont clairement cités et mis en pratique et la résolution
mathématique est assez complète.
Les quatorze chapitres du recueil sont regroupés
en six thèmes soit la mécanique du point, la relativité, l’électrocinétique, l’électromagnétisme,
l’optique puis les problèmes généraux. La résolution des problèmes inclut une courte explication théorique et est le plus souvent suivie de
commentaires où le sujet est approfondi. Les
chapitres de problèmes commentés sont complétés à la fin par un chapitre de problèmes sans
solution. Les problèmes sont tridimensionnels
(coordonnées cartésiennes et polaires) et le
niveau mathématique est plutôt avancé : on
utilise les nombres complexes, le calcul
matriciel, le calcul différentiel et intégral en passant par la résolution d’équations différentielles
et le calcul du gradient, du rotationnel et de la
divergence.
«Problèmes de physique commentés» est un
recueil de problème intéressant. Il pourrait être
utile aux professeurs et aux démontrateurs (T.A.)
qui désirent bonifier leur banque de problèmes à
résoudre en classe, ou encore, aux étudiants du
BSc spécialisé en physique qui désirent un outil
de référence autre que leur manuel de cours.
Hélène St-Jean
Collège Ahuntsic
TRENTE
LIVRES DE PHYSIQUE QUI ONT
CHANGÉ LE MONDE, Jean-Jacques Samueli et
Jean-Claude Boudenot, Ellipses, 2007; pp. 575;
ISBN: 2729833765 (hbk); Price: 39 Euros.
[Review posted 6/23/2008; To read the detailed
review, please see http://www.cap.ca/brms/
reviews/Rev905_624.pdf ]
Comme son titre l'indique, cet imposant volume
en histoire des sciences présente chronologiquement 30 livres de physique qui ont changé le
monde et notre vie quotidienne, depuis le 16e siècle jusqu'en 1915, allant de Galilée à Einstein.
L'ouvrage débute avec la présentation de l'ouvrage De Magnete, datant de 1600, publié par
William Gilbert, considéré comme "le père du
magnétisme". Le physicien expérimenté reconnaîtra ses auteurs "classiques", faisant tous l'objet
d'un chapitre entier: Galilée, Newton, Benjamin
Franklin, Volta, Ampère, Ohm, Faraday, Joule,
Planck, et les Curie. Parmi les titres étudiés, on
retiendra les livres de Torricelli sur le baromètre,
celui de Boyle sur les mesures de l'air, et le
mémoire d'Henri Poincaré intitulé "Sur la
dynamique de l'électron", paru en 1905.
Ce "livre sur les livres" est très bien conçu et
organisé logiquement: chaque chapitre correspond à un titre présenté en suivant les mêmes
étapes: courte biographie de l'auteur ou de l'inventeur, présentation de son livre le plus influent,
analyse de ses théories et réception critique de
son oeuvre au moment de sa sortie et ultérieurement. De plus, on retrouve pour chaque "classique" une reproduction en facsimilé de la couverture d'origine de la première édition et
quelques extraits traduits en français. Cet apport
me paraît le plus original, puisqu'on découvre
dans chaque cas de cinq à six pages tirées de
chaque livre, avec la mise en contexte fournie par
Jean-Jacques Samueli et Jean-Claude Boudenot.
On peut ainsi lire à la source des écrits fondateurs
qui sont trop souvent cités de manière indirecte,
en dehors de leur contexte initial.
Les deux auteurs sont des physiciens de formation et non historiens; s'ils expliquent l'influence
de chaque livre choisi, ils en reprennent également certaines des démonstrations les plus innovatrices en utilisant souvent des formules mathématiques complexes. Les textes de Jean-Jacques
Samueli et Jean-Claude Boudenot sont en outre
très précis et bien écrits; les auteurs ont également inclus des extraits de quelques discours
d'époque, dont certains très beaux (je pense à
ceux d'Henri Poincaré, p. 511).
Il ne s'agit donc pas d'un ouvrage d'initiation à la
physique classique ou de vulgarisation scientifique qui serait destiné aux enfants, mais bien
d'un livre savant et dense qui traite éloquemment
de physique et d'histoire des sciences. J'estime
que cet excellent Trente livres de physique qui
ont changé le monde de Jean-Jacques Samueli et
Jean-Claude Boudenot servira d'abord aux
chercheurs et aux universitaires dans le domaine
des sciences exactes et de toutes les branches de
la physique, car il étudie non seulement la vie des
"grands hommes de science" des siècles précédents, mais il situe en des termes scientifiques (et
non anecdotiques) l'essentiel de la contribution
de chacun. La somme de renseignements offerte
par ce livre est immense, et je crois que même le
physicien le plus accompli apprendra énormément en lisant ce livre admirable, tout comme les
didacticiens des mathématiques, les historiens et
les sociologues des sciences.
Yves Laberge
Université Laval
HIGH LATITUDE IONOSPHERE-MAGNETOSPHERE
RESEARCH OPPORTUNITIES:
The Institute of Space and Atmospheric Studies (ISAS) at the University of
Saskatchewan seeks a full time Professional Research Associate and a PostDoctoral Fellow for its ionospheric/space weather research groups in the study
of high latitude radar data. The applicants will need a good working knowledge
of ionospheric/atmospheric radars, their data acquisition process, and the scientific problems that can be studied with such systems. The successful applicants will be expected to investigate polar cap dynamics and electro¬dynamics, and to assess the role of the polar cap in the coupling between the solar
wind and the magnetosphere-ionosphere-thermosphere system. A tool of
choice for these studies will be two new PolarDARN HF radars operating in
the Canadian polar region. The radars are used in conjunction with satellite
observations when possible, and with a wide array of ground-based instruments
in the polar cap and elsewhere. There will be opportunities to work on data
acquired with the US-built AMISR incoherent scatter radar, the SuperDARN
chain of HF radars, and with the instrument array from the Canadian GeoSpace Monitoring (CGSM) program.
A doctoral degree with at least 2 years of postdoctoral research experience in
ionospheric radar studies will be required for the Research Associate position.
The successful candidate should be able to demonstrate an ability to design
experiments, engage in independent research, and have a capability to publish
the results in refereed journals. Salary will be commensurate with experience.
Please send a statement of interests, experience, and curriculum vitae including the names and addresses of three references to:
Prof. J-P St. Maurice by email at [email protected] or
by post at
Prof St. Maurice, ISAS,
University of Saskatchewan,
116 Science Place, Saskatoon, SK S7N 5E2, Canada.
The University of Saskatchewan is committed to Employment Equity. Members of
Designated Groups (women, aboriginal people, people with disabilities and visible minorities) are encouraged to self-identify on their applications. All qualified
candidates are encouraged to apply; however, Canadians and permanent residents will be given priority for the Research Associate position.
Applications will be considered until the positions are filled.
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EMPLOYMENT OPPORTUNITIES
DEPARTMENT OF PHYSICS
Three-Year Contractually Limited Assistant Professor
The Department of Physics at the University of Guelph invites applications for a three-year Contractually Limited Assistant Professor position
with an emphasis on teaching. The Guelph Physics Department has 18 faculty and offers strong programs in teaching and research to the Ph.D.
level. The graduate and research programs are enhanced by participation in the Guelph-Waterloo Physics Institute (GWPI) and the Biophysics
Interdepartmental Group (BIG). Guelph faculty members collaborate with many off-campus research facilities including the Canadian Light Source
and TRIUMF. Experimental and theoretical research areas include biophysics, soft and hard condensed matter, gravitational, subatomic, and
atomic and molecular physics. For more information, see the Department’s web site at http://www.physics.uoguelph.ca.
Responsibilities of this position include teaching six physics courses per year, along with significant involvement in undergraduate program
development or laboratory development and some administrative duties and scholarly activities in physics education. It is a full-year appointment
with a three-year duration having a start date no later than January 1, 2009.
The successful candidate will have a Ph.D. in physics and will have demonstrated exceptional strength in teaching. To apply, submit a letter of
application, curriculum vitae, teaching dossier, publications list, and names and addresses of three professional references to: Leonid Brown,
Acting Chair, Department of Physics, University of Guelph, Guelph, Ontario N1G 2W1.
Consideration of applications will begin September 15, 2008, but applications will be accepted until the position is filled.
All qualified candidates are encouraged to apply; however, Canadian citizens and permanent residents of Canada will be given priority.
The University of Guelph is committed to an Employment Equity Program that includes special measures
to achieve diversity among its faculty and staff. We, therefore, particularly encourage applications from
qualified aboriginal Canadians, persons with disabilities, and members of visible minorities and women.
The appointment is subject to final budgetary approval.
Faculty Position, Experimental Astroparticle Physics
The Department of Physics, University of Alberta
(www.phys.ualberta.ca) invites applications for a tenure-track
faculty position in experimental astroparticle physics, as part of our
expansion into the areas of direct detection of dark matter, searches
for neutrinoless double beta decay, and measurements of neutrino
oscillations and properties, by exploiting the new Sudbury Neutrino
Observatory Laboratory (SNOLAB). We primarily seek candidates at
the Assistant Professor level, but exceptional candidates at a more
senior level will be considered.
Applicants must have a Ph.D. in experimental astroparticle physics,
particle physics or nuclear physics, outstanding promise in research,
and be committed to teaching. The successful candidate will be
expected to build a strong research program, supervise graduate
students and teach at the undergraduate and graduate levels.
The Department of Physics has approximately 40 faculty and
130 graduate students, with research interests in particle physics,
astrophysics, condensed matter physics and geophysics. Our particle
physics group includes members with research interests in astroparticle
physics, collider physics, particle and nuclear astrophysics and the
standard model, and we are expanding in both experimental and
theoretical particle physics. The Department has excellent electronics,
machine shop and computational facilities and staff, and access to high
performance computational infrastructure (see www.westgrid.ca).
Initiatives by the Governments of Alberta and Canada provide
exceptional opportunities for additional funding to establish new
research programs at the University of Alberta. See, for example,
www.albertaingenuity.ca, www.gov.ab.ca/sra, www.icore.ca, and
www.innovation.ca for further information.
The application should include a curriculum vitae, a research
plan, and a description of teaching experience and interests. The
applicant must also arrange to have at least three confidential letters of
reference sent to the address below on or before November 1, 2008.
Consideration of applications will begin by that date and continue until
the position is filled. The start date for this position is July 1, 2009.
Interested applicants may apply to:
Particle Physics Search & Selection Committee
Dr. John Beamish, Chair
Department of Physic
University of Alberta
Edmonton, Alberta, Canada, T6G 2G7
Fax: (780) 492-0714
All qualified candidates are encouraged to apply; however, Canadians and permanent residents will be given priority. If suitable Canadian citizens and
permanent residents cannot be found, other individuals will be considered. The University of Alberta hires on the basis of merit. We are committed to the
principle of equity in employment. We welcome diversity and encourage applications from all qualified women and men, including persons with disabilities,
members of visible minorities, and Aboriginal persons.
198 C PHYSICS
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2:15 PM
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ALL UNDELIVERABLE
COPIES
IN
CANADA
/ TOUTE
CORRESPONDANCE
NE POUVANT
ETRE
LIVREE
AU
CANADA
should be
returned
to /
devra être
retournée
à:
Canadian
Association of
Physicists/
l’Association
canadienne
des
physiciens et
physiciennes
Suite/bur. 112
Imm. McDonald
Bldg.
Univ. of/
d’Ottawa,
150 Louis
Pasteur,
Ottawa,
Ontario
K1N 6N5
Canadian Publications Product Sales Agreement No.
40036324 / Numéro de convention pour les envois de
publications canadiennes : 40036324

Physics in Canada La Physique au Canada

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