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ScienceWeek
SCIENCE-WEEK
A Weekly Email Digest of the News of Science
A journal devoted to the improvement of communication
between the scientific disciplines, and between scientists,
science educators, and science policy-makers.
May 4, 2001 -- Vol. 5 Number 18
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False facts are highly injurious to the progress
of science, for they often long endure; but false
views, if supported by some evidence, do little harm,
as everyone takes a salutary pleasure in proving
their falseness.
-- Charles Darwin (1809-1882)
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=-=-=-=-=-=-=-=-=
Section 1
=-=-=-=-=-=-=-=-=
Contents of this Issue (Full reports in Section 2):
1. SCIENCE POLICY:
FURTHER DEVELOPMENTS IN GERMAN SCIENTIFIC FRAUD CASE
The four-year-old Herrmann-Brach scientific fraud scandal in
Germany, involving the publication of 94 papers containing
alleged falsified data or data manipulation, the papers published
between 1988 and 1992, has now spread to the head of the
department in which the Herrmann laboratory was located. Roland
Mertelsmann, a well-known cancer researcher, and the head of the
Department of Oncology and Hematology at the University of
Freiburg, has been publicly criticized by an investigative panel
for failing to detect the alleged data falsification and data
manipulation that occurred in his department. Mertelsmann, in
fact, was listed as co-author in 58 of the Herrmann papers. This
recent investigative panel, headed by Albin Eser, director of the
Max Planck Institute for Foreign and International Criminal Law,
also cited Mertelsmann for "serious irregularities" in two
Mertelsmann papers not related to Herrmann.
(Robert Koenig: Science 9 Mar 01 291:1876)
2. NEUROBIOLOGY: ON THE FUNCTIONS OF BRAIN GLIAL CELLS
A diversity of glial cell types exist in the central nervous
system, each type with apparent distinct functions. The glial
cells called "oligodendrocytes" form myelin, the tight segmented
wrappings of lipid-rich membrane layers that coat nerve-cell
axons, the myelin serving as segmented electrical insulation the
speeds up the propagation of action potentials along the nerve
axon. The glial cells called "astrocytes" ensheath synapses, but
the function of astrocytes is largely undefined. Many reports
indicate that astrocytes contain ion channels, both ligand-gated
and voltage-gated, and astrocytes have been proposed to have the
general function of clearing neurotransmitters and ions away from
the synapse. However, recent groundbreaking studies of the
identity and function of ion channels in astrocytes suggest that
these glial cells have a more direct and active role in synapse
function.
(M.K. Temburni and M.H. Jacob:
Proc. Natl. Acad. Sci. US 27 Mar 01 98:3631)
3. ECOLOGY: CLIMATE AND THE DECLINE OF AMPHIBIANS
Amphibian populations have exhibited widespread declines and
extinctions in recent decades. Although climatic changes,
increased exposure to ultraviolet-B radiation, and increased
prevalence of disease have all been implicated at particular
localities, the importance of global environmental change remains
unclear. Researchers now report that pathogen outbreaks in
amphibian populations in the western US are linked to climate-
induced changes in UVB exposure. Using long-term observational
data and a field experiment, the authors examined patterns among
interannual variability in precipitation, UVB exposure, and
infection by a pathogenic oomycete, Saprolegnia ferax. The
authors suggest their findings indicate that climate-induced
reductions in water depth at egg-laying (oviposition) sites have
caused high mortality of embryos by increasing the exposure of
embryos to UVB radiation and consequently increasing the
vulnerability of the embryos to infection.
(J.M. Kiesecker et al: Nature 5 Apr 01 410:681)
4. ASTROPHYSICS: ON THE ORIGIN OF COMETS
At a basic level, a comet is simply a collection of silicate dust
and a smattering of organic molecules coated with ice made
primarily of water. Some of the ice-coated grains may have been
present in the giant molecular cloud that partly collapsed to
form the solar nebula, but other ice-coated grains must have
formed in the solar nebula itself. In general, it is believed
that comets begin to form by an accreting "snowball" effect in
which the icy dust grains stick together to form fractal-like
aggregates. According to current models, this process begins at
some considerable distance from the center of the solar nebula,
perhaps as far as 100 AU away from the center. Aggregates
accumulate into compact boulder-sized snowballs (cometesimals),
continue to grow by the accretion of dust and ice grains, as well
as by merging with other aggregates in their path, and in due
course (10,000 to 100,000 years), this pile of rubble becomes a
comet, perhaps 10 to 20 kilometers in diameter.
(Joseph A. Nuth III: American Scientist May-June 2001 89:228)
5. EXPERIMENTAL PHYSICS:
VERIFICATION OF NEGATIVE REFRACTIVE INDEX MATERIALS
Researchers report experimental scattering data at microwave
frequencies on a structured metamaterial that exhibits a
frequency band where the effective index of refraction is
negative. The material consists of a 2-dimensional array of
repeated unit cells of copper strips and split ring resonators on
interlocking strips of standard circuit board material. By
measuring the scattering angle of the transmitted beam through a
prism fabricated from this material, the authors determined the
effective refractive index appropriate to Snell's law. The
authors suggest their experiments directly confirm the
predictions of Maxwell's equations that the refractive index is
given by the negative square root of the product of permittivity
and permeability for the frequencies where both the permittivity
and permeability are negative. The authors suggest that any
material that exhibits the property of negative refractive index,
a property not observed in naturally occurring materials, will
have a variety of practical applications, such as beam steerers,
modulators, band-pass filters, and lenses permitting wavelength
point source focusing.
(R.A. Shelby et al: Science 6 Apr 01 292:77)
6. GENERAL PHYSICS: ON THE VALUES OF THE FUNDAMENTAL CONSTANTS
The values of the fundamental constants are determined by a broad
range of experimental measurements and theoretical calculations
involving many fields of physics and measurement science
(metrology). The best value of even a single constant is likely
to be determined by an indirect chain of information based on
seemingly unrelated phenomena. For example, the value of the mass
of the electron in kilograms is based mainly on the combined
information from experiments that involve classical mechanical
and electromagnetic measurements, the highest precision optical
laser spectroscopy, experiments involving trapped electrons, and
condensed matter quantum phenomena, together with condensed
matter theory and extensive calculations in quantum
electrodynamics. The basic approach to finding a self-consistent
set of values for the fundamental constants is to identify the
critical experiments, determine the theoretical expressions as
functions of the fundamental constants that make predictions for
the measured quantities, and adjust the value of the constants to
achieve the best match between theory and experiment.
(P.J. Mohr and B.N. Taylor: Physics Today March 2001)
7. IN FOCUS: ON GOEDEL'S THEOREM
=-=-=-=-=-=-=-=-=
Section 2
=-=-=-=-=-=-=-=-=
1. SCIENCE POLICY:
FURTHER DEVELOPMENTS IN GERMAN SCIENTIFIC FRAUD CASE
[Editor's note: The lengthy collation of background material
appended to this report may give an impression of fraud rampant
in science. There are many views on this question. Our own view
is that approximately 1 in 1000 published papers contain
fabricated or unethically manipulated data. Each case, however,
deserves serious attention and study, since one of the important
bases of the scientific enterprise involves a necessary division
of labor, the mutual dependence of laboratories on the validity
of their reported research. The public, of course, is often
shocked and titillated by scientific fraud, the shock based on
the false notion that scientists are somehow a superhuman group
adhering to superhuman ethics, a ridiculous idea indeed.
Scientists laugh, cry, shudder, catch diseases, sweat at their
jobs like everyone else -- and some of them cheat. Scientific
fraud is not to be condoned or excused or treated lightly, but it
is also not a rational basis for any attack against scientists or
against the entire scientific enterprise.]
------------------------------------------
The four-year-old Herrmann-Brach scientific fraud scandal in
Germany, involving the publication of 94 papers containing
alleged falsified data or data manipulation (see related
background material below), the papers published between 1988 and
1992, has now spread to the head of the department in which the
Herrmann laboratory was located. Roland Mertelsmann, a well-known
cancer researcher, and the head of the Department of Oncology and
Hematology at the University of Freiburg, has been publicly
criticized by an investigative panel for failing to detect the
alleged data falsification and data manipulation that occurred in
his department. Mertelsmann, in fact, was listed as co-author in
58 of the Herrmann papers. This recent investigative panel,
headed by Albin Eser, director of the Max Planck Institute for
Foreign and International Criminal Law, also cited Mertelsmann
for "serious irregularities" in two Mertelsmann papers not
related to Herrmann: a September 1994 paper in the journal
_Blood_, and an August 1995 paper in the _New England Journal of
Medicine_. The panel has evidently found that some data in these
papers, which report on clinical trials of cancer treatments,
were presented to give an impression of being "more complete and
consistent than was actually the case." Mertelsmann has called
the inquiry unfair and has indicated he will mount a vigorous
defense.
-----------
Robert Koenig: Fallout from German fraud case continues.
(Science 9 Mar 01 291:1876)
QY: Robert Koenig: editors@sciencemag.org
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Summary by SCIENCE-WEEK http://scienceweek.com 4May01
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Related Background:
RESEARCH FRAUD SCANDAL IN GERMANY: AN UPDATE
What has been called in Germany and elsewhere "Germany's biggest
ever scientific fraud" is apparently still without closure. The
essence of the case (details are provided in the attached
background material) is the involvement of 2 molecular
biologists, Marion Brach and Friedhelm Herrmann (who both worked
and lived together during their scientific collaboration at
Harvard, Freiburg, and Berlin), in an alleged systematic
fabrication of data in 37 publications over a 9 year period
ending in 1996. It is now nearly 2 years after the affair was
first revealed, but no case has yet been brought to court.
Prosecutors in Germany are evidently finding it more difficult
than expected to bring charges against the two scientists
involved, both of whom achieved full professorships on the basis
of the apparently fraudulent research reports. After being
dismissed as full professor at the University of Lubeck in 1997
(she assumed the post in 1996), Brach evidently left Germany and
she is now reported to be working in New York. Herrmann resigned
his professorship at the University of Ulm and now works in
private medical practice in Munich. Herrmann continues to deny
any involvement in misconduct, and says the failure to bring
charges against him is proof of his innocence. Meanwhile
Germany's main university research funding agency, Deutsche
Forschungsgemeinschaft, has set up a task force to determine the
"full extent of any scientific damage" caused by the alleged
fraudulent publications.
-----------
A. Abbott: German scientists may escape fraud trial.
(Nature 8 Oct 98 395:532)
QY: Alison Abbot: a.abbott@nature.com
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 6Nov98
-------------------
Related Background:
GERMAN RESEARCHER ADMITS FRAUD AND CHARGES ACADEMIC COVER-UP
Producing another chapter in the scientific fraud case that has
caused an apparent sensation in Germany, Marion A. Brach, one of
the accused scientists, has published a letter in the journal
*Nature* in which she points out the following: 1) She has
confessed to falsifying scientific papers; 2) she has resigned
her position as a full professor at the University of Lubeck; 3)
she does not believe further victimization is appropriate; 4) she
has concluded that the various German investigating commissions
met only with the intention of limiting damage to the German
academic community rather than with the intention of discovering
the full extent of culpability; 5) the German government has
reneged on its legal agreement to provide her with severance pay
following her early confession and resignation; 6) official
bodies have found it expedient to imply that she was the major or
only culprit in the affair.
QY: Marion A. Brach, c/o Walter F. Kalthoff, Pacellistr. 14,
D-80333, Muenchen, DE.
(Nature 2 Apr 98) (Science-Week 17 Apr 98)
-------------------
Related Background:
MORE DEVELOPMENTS IN GERMAN SCIENTIFIC FRAUD CASE
The scientific fraud case that has been shocking the German
intellectual community these past months, and which is claimed to
be the worst case of scientific fraud in that country since 1945,
continues to be a public spectacle. The scandal involves two
German molecular biologists, Marion Brach (who has resigned as a
Professor at Lubeck University), and Friedhelm Herrmann (a
suspended Professor at Ulm University). Brach has admitted
falsifying published data while she worked under the supervision
of Herrmann at the Max Delbruck Center for Molecular Medicine a
few years ago. Herrmann claims he is only a clinician and had
nothing to do with the laboratory bench work. Herrmann is a
prominent hematologist and a leading genetic therapy researcher.
The two biologists had worked together for some time, and each
received professorships on the basis of that work. (Herrmann's
salary was apparently US$278,000 per year). Now it has been
announced that Herrmann is suing various academic investigators
in the case for DM10 million (US5.6 million) in compensation for
damage to his career. In addition, there is now a claim by a new
investigation team that the two accused researchers also
published falsified data earlier in their careers.
(Nature 11 Sep 97) (Science-Week 26 Sep 97)
-------------------
AN UPROAR OVER SCIENTIFIC FRAUD IN GERMANY
The German scientific community was rocked by scandal this
spring, and the resulting repercussions are apparently not yet
complete. The brouhaha involves two German molecular biologists,
Marion Brach (recently resigned as a Professor at Lubeck
University), and Friedhelm Herrmann (a suspended Professor at Ulm
University). Brach has admitted falsifying published data while
she worked under the supervision of Herrmann at the Max Delbruck
Center for Molecular Medicine a few years ago. Herrmann claims he
is only a clinician and had nothing to do with the laboratory
bench work. Herrmann is a prominent hematologist and a leading
genetic therapy researcher. The two biologists have worked
together for some time, and each received professorships on the
basis of that work. All of that work is now being investigated,
and the German government has established a commission of
international scientific experts to discuss research standards
and the procedures for scientific oversight in German and
internationally. (Science 11 Jul 97) (Science-Week 18 Jul 97)
-------------------
Related Background:
ABDERHALDEN'S FRAUD REVISITED
Last year was not a good year for German biological and medical
science, since 1997 was marked by a major fraud scandal involving
two full professors apparently involved in the fabrication of
data published in dozens of scientific papers during a 9-year
period. That story is not yet finished (see background material
below). Now from Germany comes the publication of a "commentary"
by two scientists, U. Deichmann and B. Muller-Hill, the
commentary revisiting what has come to be considered the
fraudulent career of German scientist Emil Abderhalden
(1877-1950). Abderhalden was a biochemist involved in designing
tests for various clinical disease entities, the tests involving
what he called "defense enzymes" (Abwehrfermente), enzymes which
he claimed to have identified, and which according to his
analyses were specific proteases produced when humans were
challenged by foreign proteins. During the years 1912 to 1950,
Abderhalden enjoyed the status of one of the most eminent
scientists in Germany, was professor of physiology and
physiological chemistry at Halle University, president of the
oldest German academy of science (the Leopoldina), editor of
several journals, and author of several books and more than 1000
research papers -- and all of this notwithstanding, the consensus
today is that nearly all of his research on the so-called
"defense enzymes" was completely fraudulent, with scores of
colleagues and underlings either explicitly or implicitly
colluding in the fraud over a period of decades. It is an ugly
story with political tangents (e.g., Joseph Mengele, the
notorious Auschwitz doctor, was one of Abderhalden's proteges).
In their commentary, Deichmann and Muller-Hill conclude: "The
elite of today [the biomedical elite in Germany] are loyal
students of the old elite, and they have learned and internalized
the old values. Has medical, clinical science in Germany today
really changed that much? We doubt it. The Brach-Herrmann-
Mertelsmann affair provides a brief glimpse into the abyss of
medical science in Germany. Will it be soon forgotten by the
German medical elite, or will there be real change in the spirit
of true science?" [Editor's note: Roland Mertelsmann, Professor
Herrmann's department head, was co-author of 25 suspected papers
produced by Herrmann, but has pleaded non-involvement in the
research.]
QY: Ute Deichmann, Institute of Genetics, Cologne University,
Weyertal 121, 50931, Koeln, DE.
(Nature 14 May 98 393:109) (Science-Week 5 Jun 98)
-------------------
Related Background:
DATA ON BIO EFFECTS OF ELECTROMAGNETIC FIELDS FOUND FRAUDULENT
The US Office of Research Integrity has reported intentional
falsification and fabrication of data by a biochemist studying
the effects of ambient electromagnetic fields (power lines and
home appliances) on biological cells. The researcher is Robert P.
Liburdy, formerly of the Lawrence Berkeley National Laboratory
(US). Liburdy has agreed to request retraction of his published
papers. Liburdy's findings were apparently among the first to
offer a plausible mechanism for a possible link between EMF
exposure and cancer or other diseases. In 1992, in two papers of
which he was the sole author, Liburdy published evidence that
EMFs increase the flow of calcium into lymphocytes. At that time,
the papers produced much interest because there are known
mechanisms by means of which calcium signaling could conceivably
lead to cancer. Liburdy had been awarded more than US$3.3 million
in federal grants for his EMF research. The current consensus
among researchers is that scientific evidence that EMF exposure
poses any health risk is weak, and that research by a number of
independent laboratories has failed to demonstrate any consistent
pattern. (Science 2 Jul 99) (Science-Week 7 Jul 99)
-------------------
Related Background:
SCIENCE AND SOCIETY: A NEW SCIENTIFIC FRAUD SCANDAL -- IN FRANCE
There is often an element of farce in detected scientific
fraud, since in hindsight it usually seems ludicrous that the
perpetrator or perpetrators of the fraud expected to get away
with it. But farce aside, there are serious aspects to scientific
fraud, first the damage to the ideals of the scientific
community, and second (and perhaps more important), the damage
caused to other scientists by the fraud provoking costly
strategic decisions based on the faked evidence.
The coelacanth is a primitive *teleost fish that apparently
first appeared in the *Devonian Period, with the most recent
fossil specimens dating from the *Cretaceous Period. The group
was assumed to be extinct, but a living specimen was caught in
1938 in the mouth of the Chalumna River in South Africa and named
Latimeria chalumnae. The 1938 specimen was 2 meters in length and
weighed 40 kilograms. More specimens have since been caught, all
off the coast of South Africa and near the island of Madagascar
(Comoros archipelago) in the Indian Ocean.
In July 1998, M.V. Erdmann et al reported the capture and
observation of a live coelacanth specimen near the island of
Manado Tua (north Sulawesi) in Indonesia (see related background
material below), and the find was quickly published in the
journal _Nature_ and recognized as of considerable importance. In
the published article, a photograph of the captured coelacanth
appeared, a lateral view of the complete fish.
Several months ago (Spring 2000), three French scientists
(Bernard Seret, Laurent Pouyaud, and George Serre), one of whom
(Seret) is an ichthyologist at the Museum National d'Histoire
Naturelle de Paris (FR), submitted to the journal _Nature_ an
article claiming a prior discovery in 1995 of a coelacanth in
Indonesian waters (thus preempting the 1998 discovery of M.V.
Erdmann et al), the Seret et al submitted article including a
photograph of their captured fish. The French group stated they
were unable to register their specimen in 1995 because it failed
to reach the museum to which it had been sent. They state they
photographed the fish at the time, then lost the photograph while
moving house, and only found the photograph again this year.
In addition to the question of priority of discovery, the
scientific implications of the findings of the French team were
that it would extend the distribution of living coelacanths,
since the French fish was stated to have been caught more than
2000 kilometers from the spot where Erdmann et al found the 1998
specimen, which suggests a larger distribution of the fish in the
Indo-West Pacific region.
What happened was that staff people at _Nature_ noticed that
the photograph submitted by B. Seret et al a few months ago and
the photograph by M.V. Erdmann et all previously published two
years ago were virtually identical. The Seret et al paper was
refused by _Nature_, and the French photograph has now been
denounced as an outright fake. Apparently what was done was to
use computer graphics software to simply cut and paste the 1998
Erdmann et all fish into another photograph, moving the
coelacanth onto a table with two other ordinary fish as though
all three fish were in the same catch. When presented with the
hard evidence that the two coelacanth photos are identical, the
Seret et al response was that the picture was "taken by a friend
who later died and whose widow gave it to Serre before moving
abroad." In the 13 July 2000 _Nature_ issue in reference below,
the apparently faked photo and the original photo published in
1998 by Erdmann et all appear side by side for comparison.
Again, aside from the farcical aspects here (clipping a
photograph of an unusual object from a journal article and using
the clipped photograph to fake another photograph submitted as
"evidence" in another article sent to the very same journal), it
should be recognized that a bit more cleverness with computer
software might have made the fake unrecognizable as such, and
steered coelacanth specialists onto a false trail for decades.
That is not amusing.
Commenting on this affair in a recent letter, M.V. Erdmann
and R.I. Caldwell (University of California Berkeley, US),
Erdmann the discoverer of the 1998 coelacanth, state: "The
Indonesians and Comorans are rightfully proud of efforts in their
two countries to preserve these rare and very special fish. What
pride can we in the Western scientific community take in this
affair?"
-----------
H. McCabe and J. Wright: Tangled tale of a lost, stolen and
disputed coelacanth.
(Nature 13 Jul 00 406:114)
QY: H. McCabe editors@nature.com
-----------
M.V. Erdmann and R.I. Caldwell: How new technology put a
coelacanth among the heirs of Piltdown Man.
(Nature 27 Jul 00 406:343)
QY: Mark V. Erdmann, Univ. of Calif. Berkeley 510-642-6000.
-----------
Text Notes:
... ... *teleost: In general, this refers to any of the bony
fish, the most advanced in terms of evolution and the largest
group of fish. Besides the calcified internal skeleton, the most
obvious uniform characteristic of the teleost fish is their tail,
with upper and lower halves of about equal size, whereas in
cartilaginous fish the tail has two lobes of unequal size. Almost
all sport, commercial, and ornamental fish are teleosts.
... ... *Devonian Period: From approximately 400 million to 345
million years ago. Sometimes called the Age of the Sea, since
more of the Earth was underwater than is now.
... ... *Cretaceous Period: The geological period ranging
approximately from 146 million years ago to 65 million years ago.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 25Aug00
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
SCIENTIFIC FRAUD: AN IMPORTANT CASE IN PLANT BIOLOGY
Here is an interesting case of scientific fraud, albeit with the
appearance of an opera surrounding a farce:
1) A laboratory invents a new important technology which is
validated by other laboratories and becomes widely used.
2) The inventing laboratory then proceeds to apply the
technology to a particular problem. In the course of the
application, one of the laboratory researchers apparently
fabricates data to achieve important results, and a number of
"co-authors" in the laboratory join with the fabricating
researcher to publish the results in a series of papers in
various leading international journals.
3) Ultimately, the results cannot be replicated by others,
the results are considered fabrications, and the group leader of
the laboratory and the fabricating researcher are forced to
resign. The co-author fabricating researcher is identified as a
"technician" (see the related background report below).
4) A research team led by the head of the department that
housed the laboratory takes on the task of determining which
published papers are suspect, and reports that 10 papers in
various leading journals (Science, Nature, EMBO Journal, Proc.
Natl. Acad. Sci. US, etc.), published between 1992 and 1998,
probably contain serious fabrications.
5) The former group leader and the involved laboratory
researcher-technician both refuse to comment on the case.
6) Two of the 10 papers have already been retracted by other
co-authors, but there are apparently no plans by any co-authors
to retract the other papers.
7) The editors of the various leading journals say they have
no plans to retract the remaining published papers themselves,
but will wait for retractions by the authors. The journal editors
have evidently been criticized because at least some of the
fabrications might have been detected by proper review of the
papers when they were originally submitted.
The laboratory in question is part of the Max Planck
Institute for Plant Breeding Research in Cologne, DE. The group
leader of the laboratory was Richard Walden, who resigned in
1998, and who is apparently now working in a laboratory in the
UK. The implicated "technician" is Inge Czaja. The research
involved a new technique to study the actions of plant genes
(activation T-DNA tagging), a validated technique now widely used
in plant biology. The investigating team consisted of researchers
at the Cologne institute and colleagues from other European
laboratories, the team led by Jeff Schell, head of the department
containing the fabricating laboratory. The investigation report
concerning the 10 suspected fraudulent papers was recently
published in the March 1999 issue of _Plant Journal_. Alan Jones
(University of North Carolina, Chapel Hill US), a researcher in
the field, is quoted as saying: "I can no longer believe any
parts of the data in any parts of the papers... When the papers
came out, I was extremely enthusiastic." Jones states that the
discovery of the fabrications will have a "negative effect on the
field" because major conclusions were drawn from the papers.
-----------
Michael Balter: Data in key papers cannot be reproduced.
(Science 26 Mar 99 283:1987)
QY: Michael Balter: science_editors@aaas.org
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 4Jun99
-------------------
Related Background:
KAROLINSKA INSTITUTE ACCUSES ONE OF ITS RESEARCHERS OF FRAUD
The Karolinska Institute in Sweden is the group that is usually
responsible for awarding the Nobel Prize in Physiology and
Medicine each year. Now, after a delay of apparently 6 months,
the Institute has announced that one of its researchers, Ulf
Lonn, has "most probably" committed scientific fraud involving 20
papers published in the last decade. The conclusion is evidently
based on the recommendation of an independent investigating
panel. Lonn is a specialist in gene amplification in breast and
bladder cancer, and it is alleged his publications included
manipulated data. Lonn has denied the charges. (Nature 28 Aug 97)
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 5Sep97
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
ON FRAUD IN SCIENCE
There are two prevalent myths concerning scientific fraud: The
first myth states that since most scientific experiments are
replicated by other laboratories, science is self-correcting
because the discovery of fraud involving the fabrication of data
is inevitable. The second myth is that scientific papers
involving fabrication of data are extremely rare, with only a few
fraudulent papers published in any one year. Concerning the first
myth, it is not true that all or even most published experiments
are sooner or later replicated. What is true is that research
results that are of apparent great significance will probably be
replicated, but not other research results. These days, in the
front lines of fast-moving fields in science, few laboratory
heads are inclined to waste precious manpower and funds simply
replicating the work of others: the most successful research
strategy is to assume the relevant published product of other
laboratories is honest and take the next step, or better yet the
step after that, in the push to solve a hot problem. Concerning
the second myth, the evidence that exists suggests the number of
scientific papers involving fabricated data published each year
may involve hundreds and perhaps thousands of publications. For
example, the Office of Research Integrity of the US National
Institutes of Health (NIH) found that between 1993 and 1997, 61
researchers receiving its grants were involved in the fabrication
of data. The total number of NIH grants during the same period
was approximately 150,000. These figures produce a fabrication
rate for published papers of 0.0004, assuming each research grant
produced on average the same number of papers. This fabrication
rate concerns the biomedical sciences in the US (the area with
which NIH is concerned), but there is no evidence of a lower rate
in other areas of science. In 1998, the top 5600 scientific
journals published approximately 1 million articles, and it is
estimated this is approximately one-tenth of the total world
output. Considering only the top 1 million publications and
applying the fabrication rate derived from the NIH evidence, we
find the expected number of publications each year in all
scientific fields involving fabricated data is approximately 400
papers for the top 5600 journals, and perhaps as much as 10 times
that if all scientific journals are considered. It is certainly
true that these estimates involve some assumptions; it is also
true that a small fabrication rate applied to a large number of
published articles will yield a significant number of fraudulent
publications. In general, the idea that only a few fraudulent
scientific papers are published each year is probably a complete
fallacy. ... ... Alison Abbott (_Nature_) presents an extensive
review of official handling of the problem of scientific
misconduct (especially the problem of scientific fraud), the
author making the following points: 1) Although the incidence of
proven scientific fraud remains low, several high-profile cases
have convinced the research community of the need for effective
action, in particular by enforcing codes of good laboratory
practice. 2) The extent of scientific misconduct of the
"fabrication-falsification-plagiarism" type is hotly debated in
both the US and Europe. Some scientists fear that publicized
cases are merely the tip of an iceberg. Others remain convinced
that the overall incidence remains low, and even those with
direct experience of misconduct cases are often optimistic. 3) In
one survey, published in _American Scientist_ in 1993, between 6
and 9 percent of respondents said they were personally aware of
results that had been plagiarized or fabricated within their
faculties. 4) Many journal editors believe that breaches of the
traditional ethics of scientific publication are increasing, but
few editors are confident of how they should react. 5) Last year,
two foundations in Germany set up a project to determine how many
of the 550 journal papers and 80-odd book chapters written by two
German cancer researchers, Friedhelm Herrmann and Marion Brach
(see SW background material below), and some of their former
colleagues, included apparently fabricated data. Investigating
committees have already identified 58 papers by Herrmann and
Brach that involve apparently fabricated data, but investigation
of the publications is only 20 percent finished. The
investigation will take months to complete, and the intention is
to publish the results in an international journal.
-----------
Alison Abbott: Science comes to terms with the lessons of fraud.
(Nature 4 Mar 99 398:13)
Alison Abbott: a.abbott@nature.com
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 30Apr99
For more information: http://scienceweek.com/swfr.htm
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
2. NEUROBIOLOGY: ON THE FUNCTIONS OF BRAIN GLIAL CELLS
"Synapses" are effectively transmission junctions between
nerve cells, and like transmission junctions in electronic
circuits, they are the places where information is transmitted
from one modulation domain to another. In general, nerve cells
have a single long extension (the "axon") that propagates the
electrical output (the action potential) of the cell. The term
"synapse" refers to the junction between the terminal of a
neuron's axon and another neuron. When studying the synapse, the
first neuron is called the "presynaptic" neuron, and the second
neuron is called the "postsynaptic" neuron. Synaptic transmission
in the central nervous system is mediated by the release of
neurotransmitter substances into the junction (into the synaptic
cleft) and the subsequent activation of postsynaptic receptors,
with this activation of receptors either inhibiting or provoking
the excitation of the postsynaptic neuron.
In general, nerve cells in the central and peripheral
nervous systems of mammals (including humans) are surrounded by
satellite cells that play various roles in neural function. In
the central nervous system, these satellite cells are called
"neuroglial cells" (glial cells), and they constitute
approximately one-half of the volume of the human brain and
greatly outnumber neurons in the brain. Neurons and glial cells
in the brain are densely packed together, their surface membranes
separated from each other by fluid-filled extracellular spaces
approximately 20 nanometers wide. Glial cell membranes, like
those of neurons, contain channels for ions, receptors for
transmitter substances, ion transport pumps, and amino-acid
transporters. In addition, many glial cells are linked to each
other by low-resistance junctions that permit direct passage of
ions and small molecules. Glial cells usually have more negative
resting potentials than neurons, but glial cells do not generate
action potentials.
So-called "astrocytes" (astroglia, macroglia) are the
largest glial cells, with many extensions radiating outward like
a starburst, and at least one of their functions is apparently to
maintain the so-called "blood-brain barrier" effectively
separating neural tissue from blood. As will be seen below, other
important functions of astrocytes are now apparent.
So-called "oligodendrocytes" (oligodendroglia) are glial
cells characterized by sheet-like processes that are wrapped
around individual neuron axons to form the myelin sheath of nerve
fibers in the central nervous system. (The myelin sheath of a
nerve fiber is effectively a periodically interrupted insulation
which increases the propagation velocity of nerve impulses.)
Although neuroglial cells in the brain have been known and
categorized since the 19th century, until recently their various
involvements in the functioning of neurons in the brain have been
unclear and enigmatic. The earliest idea, first proposed in the
19th century, was that glial cells in the brain existed simply to
"hold up" the neurons of the brain ("stutzfunktion"). By the
middle of the 20th century, neuroglia were believed to have
important but still unspecified metabolic roles. During the last
decade, the work of many laboratories has provided a more
detailed accounting of the involvements of neuroglia in the
activity of neurons, and there have been a number of surprises.
... ... M.K. Temburni and M.H. Jacob (Tufts University, US)
present a commentary on recent research on newly revealed
functions of glial cells in the brain, the authors making the
following points:
1) The authors point out that a diversity of glial cell
types exist in the central nervous system, each type with
apparent distinct functions. The glial cells called
"oligodendrocytes" form myelin, the tight segmented wrappings of
lipid-rich membrane layers that coat nerve-cell axons, the myelin
serving as segmented electrical insulation the speeds up the
propagation of action potentials along the nerve axon. The glial
cells called "astrocytes" ensheath synapses, but the function of
astrocytes is largely undefined. Many reports indicate that
astrocytes contain ion channels, both *ligand-gated and voltage-
gated, and astrocytes have been proposed to have the general
function of clearing neurotransmitters and ions away from the
synapse. However, recent groundbreaking studies of the identity
and function of ion channels in astrocytes suggest that these
glial cells have a more direct and active role in synapse
function (e.g., G. Sharma and S. Vijayaraghavan: Proc. Natl.
Acad. Sci. US 2001 98:4148; E. Ullian et al: Science 2001
291:657)
2) The present apparent scheme of astrocyte-neuron
intercellular signalling is essentially as follows: Action
potential firing in the neuron induces a) neurotransmitter
release from the presynaptic terminal; b) receptor activation of
adjacent astrocytes; c) increases in intracellular calcium ions
in the astrocytes; d) calcium-dependent neurotransmitter release
from the astrocytes; and e) the activation of neighboring neurons
and potentiation of interneuronal synaptic transmission. In
addition, astrocyte-derived soluble *neurotrophic factors are
also likely to affect CNS synapse function.
3) The authors point out that the key question is what is
the functional significance of receptor activation and increases
in intracellular calcium ion levels in these non-neuronal cells?
Recent studies have demonstrated that activation of a specific
type of functional transmitter receptor (glutamate receptors) in
astrocytes produces an increase in intracellular calcium ion
levels and the calcium-dependent release of glutamate, which is
the major excitatory neurotransmitter in the vertebrate central
nervous system. In cell-culture preparations, the glial-released
glutamate activates neighboring neurons. In this way, astrocytes
apparently enhance interneuronal synaptic transmission: such
astrocyte responses can be initiated by neurotransmitter released
from the neuronal presynaptic terminal. Altogether, these studies
demonstrate that there is activity-dependent rapid intercellular
signaling between astrocytes and neurons (at least in vitro) and
that this signaling modulates interneuronal synaptic activity.
4) A recent study [Ullian et al, see related background
material below] demonstrates another new and unexpected glial
cell function: astrocytes profoundly increase synapse number and
are required for the maintenance of synapses in vitro. The
authors suggest this effect is likely related, at least in part,
to the capability of astrocytes to increase synaptic activity.
5) The authors conclude: "It is now clear that detailed
knowledge of the conversation between astrocytes and neurons will
be essential for understanding the development of the nervous
system and its responses during learning, struggles with injury,
and changes with aging."
-----------
M.K. Temburni and M.H. Jacob: New functions for glia in the
brain.
(Proc. Natl. Acad. Sci. US 27 Mar 01 98:3631)
QY: Michele H. Jacob: michele.jacob@tufts.edu
-----------
Text Notes:
... ... *ligand-gated and voltage-gated: Most biological ion
channels are selective, allowing only ions of a certain type to
pass, and an individual cell has ion channels with various ion
selectivities. The selectivity of an ion channel can be "gated",
the channel effectively opened or closed, and ion channels are
said to "voltage-gated" or "ligand-gated", depending on how the
change in selectivity is provoked. The term "voltage-gated"
refers to the opening or closing of an ion channel by changes in
the electrical potential across the membrane, while the term
"ligand-gated" refers to opening and closing of an ion channel by
interactions between ligands and membrane receptors.
... ... *neurotrophic factors: A general term for molecules that
promote the growth and survival of neurons.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 4May01
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
NEUROBIOLOGY: CONTROL OF SYNAPSE NUMBER BY NEUROGLIA
... In this context, the term "plasticity" refers to that
ability of neurons (or synapses) to modify behavior as the result
of past inputs. Currently, most neurobiologists believe that the
plasticity of synapses is an important component of learning and
memory in the mammalian brain.
... ... E.M. Ullian et al (4 authors at Stanford University, US)
now report analyses by histological, electrophysiological, and
optical techniques that indicate that in preparations of cultured
nerve cells (retinal ganglion cells) few synapses form in the
absence of glial cells, and that the few synapses that do form
are functionally immature. The presence of astrocytes increases
the number of mature functional synapses on central nervous
system neurons by 7-fold, and astrocytes are required for
maintenance of synapses in vitro. The authors also demonstrate
that in vivo most synapses are generated concurrently with the
development of glial cells. The authors suggest these data a)
demonstrate a previously unknown function for glial cells in
inducing and stabilizing central nervous system synapses; b)
demonstrate that the number of synapses on central nervous system
neurons can be profoundly regulated by non-neuronal signals; and
c) raise the possibility that glial cells may actively
participate in synaptic plasticity.
-----------
E.M. Ullian et al: Control of synapse number by glia.
(Science 26 Jan 01 291:657)
QY: Erik M. Ullian: emu@stanford.edu
-----------
Text Notes:
... ... *Note #1: In general, nerve cells have a single long
extension (the "axon") that propagates the electrical output (the
*action potential) of the cell. The general input extensions of
nerve cells are called "dendrites", and they may be extensively
branched. Dendrites generally receive input and axons generally
propagate output, but the electrical architecture of most neurons
is complicated, and in many types of nerve cells activation of
the axon produces electrical activity that not only propagates
down the axon but also propagates backward through the cell body
and dendrites. The term "synapse" refers to the junction between
the terminal of a neuron's axon and another neuron (or muscle
cell, if the synapse is a neuromuscular junction), and the number
of synapses on any neuron may range from a few to thousands, the
junctions scattered over the dendrites and cell body of the post-
synaptic nerve cell. The general scheme of neural network
activity is that output propagated along an axon ultimately
causes secretion of a "transmitter substance" at the termination
of that axon, the transmitter substance diffusing into the
synaptic junction to interact with the surface membrane of the
post-synaptic neuron, the result a production of excitation or
inhibition of the post-synaptic neuron, depending on the type of
transmitter substance.
... ... *action potential: (nerve impulses) In general,
transient pulses (e.g., 1 millisecond) of reversed membrane
potential propagated over the long extensions of neurons (axons).
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 16Feb01
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
NEUROBIOLOGY:
ON DIRECT INVOLVEMENT OF BRAIN GLIA IN INFORMATION NETWORKS
In the middle of the 19th century, the anatomist Rudolf
Virchow (1821-1902) recognized that cells in the brain could be
categorized into two distinct groups: a) neurons (nerve cells),
and b) a far more numerous group of cells that appear to surround
the neurons and fill the spaces between them. Virchow called this
second category of cell the "neuroglia", or "nerve glue", the
idea being that one of the functions of these cells is to hold
the neurons in place ("stutzfunktion"). Although this gluing
function of neuroglia (glia; glial cells) was long ago abandoned
for lack of evidence, the name of these cells has survived.
Glial cells are in turn subdivided into several classes
based on their appearance in the microscope. In the central
nervous system, the two main types of glial cells are the
"astrocytes" and the "oligodendrocytes". Astrocytes have a star-
like appearance, with numerous long processes radiating out from
a central cell body; the oligodendrocytes also have a central
cell body, but with radial arms that tend to be shorter and more
branched than those of the astrocytes.
Because glia do not generate *action potentials and do not
have *axons, they were initially thought incapable of propagating
neural impulses. In recent years, however, calcium-imaging
studies have demonstrated that astrocytes are capable of
propagating cellular signals as waves of intracellular calcium
changes that spread from astrocyte to astrocyte. Furthermore,
calcium waves through astrocyte networks have been shown to
influence the activity of adjacent neurons and modulate *synaptic
transmission.
Glutamate, the anion of glutamic acid (one of the amino acid
components of proteins), is an *excitatory neurotransmitter
substance of considerable importance in the brain, and there is
increasing evidence that glutamate released by astrocytes may
affect the behavior of nerve cells and thus provide a link
between propagated astrocyte events and propagated neuronal
events.
The term "flash photolysis" refers to a technique for
producing intracellular changes in calcium ion concentration, the
technique based on the use of "calcium cage" molecules which are
taken up by biological cells, the caged calcium subsequently
released by exposure of the cells to a short-duration (e.g.
several nanoseconds) laser pulse.
... ... V. Parpura and P.G. Haydon (Iowa State University, US)
present a study of glutamate release by astrocytes, the authors
making the following points:
1) The authors point out that astrocytes can release
glutamate in a calcium-dependent manner and consequently signal
to adjacent neurons. Whether this glutamate release pathway is
used during physiological signaling or is involved only under
pathophysiological conditions is not clear. One reason for this
lack of understanding is the limited knowledge concerning the
levels of calcium necessary to stimulate release from astrocytes,
and how these levels compare with the range of physiological
calcium levels in these cells.
2) The authors report they used flash photolysis to raise
internal calcium in astrocytes, while monitoring astrocytic
calcium levels and glutamate. The changes in astrocytes caused
slow inward electrical currents in single neurons grown on micro-
islands of astrocytes in a tissue culture preparation.
3) The authors suggest that with their approach they have
demonstrated that modest changes of astrocyte calcium (from 84 to
140 nanomoles) result in substantial glutamate-dependent
("glutamatergic") currents in neighboring neurons. Since various
neurotransmitters (e.g., glutamate, norepinephrine, dopamine) all
raise calcium in astrocytes to levels exceeding 1.8 micromolar,
the authors suggest their quantitative studies also demonstrate
that the astrocytic glutamate release pathway is engaged at
physiological levels of internal calcium. "Consequently, the
calcium-dependent release of glutamate from astrocytes functions
within an appropriate range of astrocytic calcium levels to be
used as a signaling pathway within the functional nervous
system."
... ... In a commentary on the above work, Joseph J. LoTurco
(University of Connecticut Storrs, US) states: "The most
challenging and important questions to be addressed in the future
relate to specifying exactly what aspects of neural processing
are determined and shaped by glia. For example, do they
participate in *synaptic plasticity, or do they shape *receptive
fields? Ultimately, experiments will have to be designed in which
glia are selectively removed from or silenced in central nervous
system circuits. Answers to these and other questions will likely
reshape our view of neural circuits in the next century from
exclusively neuronal to glial/neuronal circuits."
-----------
V. Parpura and P.G. Haydon: Physiological astrocytic calcium
levels stimulate glutamate release to modulate adjacent neurons.
(Proc. Natl. Acad. Sci. US 18 Jul 00 97:8629)
QY: Vladimir Parpura: vlad@iastate.edu
-----------
Joseph J. LoTurco: Neural circuits in the 21 century: Synaptic
networks of neurons and glia.
(Proc. Natl. Acad. Sci. US 18 Jul 00 97:8196)
QY: Joseph J. LoTurco: LoTurco@oracle.prib.uconn.edu
-----------
Text Notes:
... ... *action potentials: See main report.
... ... *axons: See main report.
... ... *synaptic transmission: See main report.
... ... *excitatory neurotransmitter substance: See main report.
... ... *synaptic plasticity: See previous reports.
... ... *receptive fields: In all higher animals, each array of
sensory receptors constituting a sensory organ projects activity
to a corresponding array of neurons in the central nervous
system. In many cases, both the sensory receptor array and the
central nervous system neuron array are more or less two
dimensional. The term "receptive fields", in this context, refers
to groups of neurons in the central nervous system receiving
direct or indirect isomorphic input from corresponding sensory
receptors in the periphery. (The term "receptive field" is also
used to describe an array of receptors in a sense organ.)
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 25Aug00
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
A SPECIFIC GLIAL-NEURONAL SIGNALING PATHWAY
... ... L-L. Yuan and B. Ganetzky (University of Wisconsin
Madison, US) now report that in the fruit fly Drosophila a
specific gene (axotactin) encodes a member of the *neurexin
protein superfamily, the protein secreted by glia and
subsequently localized to *axonal tracts. Null mutation (i.e.,
elimination of the gene by mutation) caused temperature sensitive
paralysis and a corresponding blockade of axonal conduction. The
authors suggest that the protein expressed by this gene (the
protein denoted as AXO) appears to be a component of a glial-
neuronal signaling mechanism that helps to determine the membrane
electrical properties of target axons.
-----------
L-L. Yuan and B. Ganetzky: A glial-neuronal signaling pathway
revealed by mutations in a neurexin-related protein.
(Science 26 Feb 99 283:1343)
QY: Barry Ganetzky: ganetzky@facstaff.wisc.edu
-----------
Text Notes:
... ... *neurexin protein superfamily: Neurexins are a family of
neuronal cell surface proteins with apparent roles in cell
adhesion and intercellular signaling. Three distinct genes
encoding neurexins have been identified in vertebrates. The
neurexins have been grouped with several other proteins into a
"superfamily". In general, in this context, a "superfamily" is
any group of genes and their cognate proteins that can be related
by sequence homology.
... ... *axonal tracts: Axons transmitting information to distal
regions are usually grouped, and in the central nervous system
the groupings are called "tracts".
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 14May99
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
SECRETION OF GLUTAMATE BY BRAIN ASTROCYTES
Glial cells are more numerous than neurons in the brain, but
their function has been generally characterized as "metabolic" or
"supportive", without much discussion of details, and more is
known about peripheral glial cells than glial cells in the
central nervous system. Astrocytes are the largest glial cells,
with many extensions radiating outward like a starburst, and at
least one of their functions is apparently to maintain the so-
called "blood-brain barrier" effectively separating neural tissue
from blood. ... Kainic acid, an algal neurotoxin, is a structural
analogue of glutamate, and it has been extensively used in
research, since at high concentrations it selectively destroys
glutamate receptor neurons (glutaminergic neurons). Glutamate is
known to act on 3 classes of receptors, one of them called the
kainate receptor because at low concentrations of kainic acid the
action of glutamate on this receptor is enhanced. The chemistry
of this kainate receptor is not yet well-characterized, mainly
because selective ligands for it are not known. Another class of
glutamate receptor is the AMPA receptor [AMPA = (RS)-alpha-amino-
3-hydroxy-5-methyl-4-isoxazoleproprionic acid], and the third is
NMDA (N-methyl-D-aspartate). These 3 receptors are ionotropic,
i.e., their activation produces changes in membrane ion
permeability. According to another and more recent scheme of
glutamate receptor classification, one receptor type is
AMPA/kainate (ionotropic), another receptor type is NMDA
(ionotropic), and a third receptor type is a slow-acting receptor
type coupled to G-proteins and called metabotropic receptors.
(The G-proteins are membrane-bound proteins that act as
transducers between messenger molecules interacting with the cell
surface and the intracellular messenger system). Prostaglandins
are fatty acids secreted by cells that have hormone-like actions
in the immediate vicinity, and one circumstance that produces
their release is tissue injury.
... ... Bezzi et al (8 authors at 2 installations, IT) report
that coactivation of the AMPA/kainate and metabotropic glutamate
receptors on astrocytes stimulates these cells to release
glutamate through a calcium-dependent process mediated by
prostaglandins. The authors suggest their results reveal a new
pathway of regulated transmitter release from astrocytes, and
that interactions between neurons and astrocytes may play a
critical role in synaptic plasticity and neurotoxicity. They also
suggest that the prostaglandin-mediated glutamate release from
astrocytes may be involved in the pathophysiology of various
brain diseases and injuries.
-----------
QY: Andrea Volterra: andrea.volterra@unimi.it
(Nature 15 Jan 98) (Science-Week 30 Jan 98)
For more information: http://scienceweek.com/swfr.htm
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 4May01
For more information: http://scienceweek.com/swfr.htm
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
3. ECOLOGY: CLIMATE AND THE DECLINE OF AMPHIBIANS
A growing number of researchers have proposed the
possibility that the recent global decline of amphibian
populations may be caused by increasing amounts of ultraviolet-B
radiation (UVB; UV-B) reaching the Earth's surface. Populations
of amphibians in widely scattered locations have been drastically
reduced in the last decade, and some of these species (such as
the golden toad of Costa Rica) have recently become extinct.
While no single cause for these declines has been identified, the
fact that the declines have occurred in undisturbed areas and
throughout the world has prompted considerations of global
phenomena.
The categorizations of ultraviolet radiation (UV) differ in
physics and biology. In physics, UV radiation is traditionally
divided into 4 regions: near UV (400-300 nanometers); middle UV
(300-200 nanometers); far UV (200-100 nanometers); extreme UV
(below 100 nanometers). In biology, there are two categorizations
of UV: a) The 3 conventional divisions are: near UV (400-315
nanometers), which is absorbed relatively poorly by organisms;
actinic UV (315-200 nanometers), which is absorbed most readily
by organic matter and which has the greatest effect on biological
systems; vacuum UV (less than 200 nanometers, which is absorbed
by most substances. b) The second type of categorization of UV in
biology is based on the interaction of UV radiation with
biological materials: UVA (400-315 nanometers) ("black light");
UVB (315-280) nanometers), responsible for the most marked
effects on organisms; UVC (280-100 nanometers), which does not
reach the Earth's surface.
Ultraviolet radiation is produced by high-temperature
surfaces (e.g., the Sun) in a continuous spectrum, and as a
discrete spectrum of wavelengths by atomic excitation in a
gaseous discharge tube. Most of the UV radiation in sunlight is
absorbed by oxygen in Earth's atmosphere, the oxygen that forms
the ozone layer of the lower stratosphere. Of the UV that does
reach the surface of the Earth, approximately 99 percent is UVA
radiation; when the ozone layer becomes thin, more UVB radiation
reaches the Earth's surface and may have hazardous effects on
organisms.
In general, ultraviolet radiation, especially UVB radiation,
is a potent mutation-producing agent (mutagen), since nucleic
acids (both DNA and RNA) absorb light in the UV region, with the
pyrimidine bases thymine and cytosine especially reactive. UV
radiation causes the hydration of cytosine by the insertion of a
water molecule ring at a C=C bond, whereas it disrupts the C=C
bonds in thymine and generates thymine dimers.
The term "El Nino" refers to an aperiodic intermittent (2 to
10 years) flow of unusually warm surface water along the western
coast of South America, the flow capable of causing abnormally
high rainfall in usually dry areas and severe local ecosystem
dislocations -- what is termed an El Nino "event". El Ninos are
regional phenomena, but they have global consequences. The name
"El Nino" ("The Child") arose because the phenomenon usually
occurs around Christmas. In 1986, M.A. Cane and S.A. Zebiak
proposed a model for making forecasts of El Nino several seasons
ahead by applying Newton's equations of motion and the laws of
thermodynamics to the dynamics of the ocean and atmosphere of the
tropical Pacific.
The term "Southern Oscillation" (SO) refers to a coherent
interannual fluctuation of atmospheric pressure over the tropical
Indo-Pacific region. The El Nino/Southern Oscillation phenomenon
(called ENSO), the interaction between El Nino and the Southern
Oscillation, is the strongest source of natural variability in
Earth's climate system. Although ENSO originates in the tropical
latitudes of the Pacific Ocean, its climate impact is felt
globally. Variations in major rainfall systems that are
attributed to ENSO range from droughts in Indonesia and Australia
to storms and flooding in Ecuador and the US. The crucial role
of the interaction between the ocean and the atmosphere in the
tropical Pacific was first postulated in 1969 by Jacob Bjerknes
(1897-1975), and the development of quantitative models has
progressed during the past 3 decades. The essence of the current
Bjerknes hypothesis, as it is called, is that ENSO arises as a
coupled cycle in which anomalies in sea surface temperature in
the Pacific cause the trade winds to strengthen or slacken and,
in turn, drive the changes in ocean circulation that produce
anomalous sea surface temperatures. Ocean-atmosphere feedback can
amplify perturbations in either the equatorial sea surface
temperature or what is called the Walker Circulation -- the
thermodynamic circulation of air parallel to the equator.
Although the oscillatory aspect of ENSO behavior is now
understood reasonably well, the irregularity of the observed
cycle is a subject of active research.
The term "oomycete" refers to a group of water molds and
related organisms, the oomycetes producing motile cells that
include parasites. Of the water molds, the genus Saprolegnia
includes parasitic species that cause diseases of fish and fish
eggs. Although oomycetes are often called "fungi", the cell walls
of oomycetes are chemically quite different than the cell walls
of most fungi.
... ... J.M. Kiesecker et al (3 authors at 2 installations, US)
present a report of analysis and experiment on the causes of
amphibian population declines, the authors making the following
points:
1) The authors point out that amphibian populations have
exhibited widespread declines and extinctions in recent decades.
Although climatic changes, increased exposure to ultraviolet-B
radiation, and increased prevalence of disease have all been
implicated at particular localities, the importance of global
environmental change remains unclear.
2) The authors report that pathogen outbreaks in amphibian
populations in the western US are linked to climate-induced
changes in UVB exposure. Using long-term observational data and a
field experiment, the authors examined patterns among interannual
variability in precipitation, UVB exposure, and infection by a
pathogenic oomycete, Saprolegnia ferax. The authors suggest their
findings indicate that climate-induced reductions in water depth
at egg-laying (oviposition) sites have caused high mortality of
embryos by increasing the exposure of embryos to UVB radiation
and consequently increasing the vulnerability of the embryos to
infection.
3) The authors suggest that precipitation, and thus water
depth/UVB exposure, is strongly linked to El Nino/Southern
Oscillation cycles, underscoring the role of large-scale climatic
patterns involving the tropical Pacific. Elevated sea-surface
temperatures in this region since the mid-1970s, which have
affected the climate over much of the world, could be the
precursor for pathogen-mediated amphibian declines in many
regions.
... ... In a commentary on this work, J. Alan Pounds (Tropical
Science Center Puntarenas, CR) states: "During the 1990s, there
was controversy over whether the [amphibian population] declines
were real, or simply a consequence of natural population
fluctuations and direct human disturbances such as habitat
destruction. Meanwhile, a separate debate focused on climate
change and its relationship to greenhouse-gas emission. Today,
there is little doubt that both phenomena -- amphibian declines
and global warming -- are real. If there is indeed a link between
the two, as the work of Kiesecker et al suggests, there is
clearly a need for a rapid transition to cleaner energy sources
if we are to avoid staggering losses of biodiversity."
-----------
J.M. Kiesecker et al: Complex causes of amphibian population
declines.
(Nature 5 Apr 01 410:681)
QY: Joseph M. Kiesecker: jmk23@psu.edu
-----------
J. Alan Pounds: Climate and amphibian declines.
(Nature 5 Apr 01 410:639)
QY: J. Alan Pounds: goldtoad@sol.racsa.cr
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 4May01
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
PUBLIC HEALTH: EXPECTED CONSEQUENCES OF GLOBAL WARMING
Climate change produced by global warming is expected to result
in melting ice caps, rising sea levels, torrential floods,
devastating droughts, and severe harvest failures. What are often
not considered in discussions of global warming are the effects
of global warming on public health.
... ... Pim Martens (University of Maastricht, NL) presents a
review of the expected effects of global warming on public
health, the author making the following points:
1) Concerning heat stress: The author suggests that perhaps
the most immediate consequence of increasing global temperatures
will be a rise in the number of heat waves and heat-related
illnesses. Such temperature extremes can, for example, increase
the sensitivity of asthmatics to their condition. There will also
be an increasing number of deaths from heat stress brought about
by high ambient temperatures lasting days on end. On the other
hand, the milder winters associated with global warming will
offer a better chance of survival for at-risk groups such as the
elderly during the coldest months. Research into the effect of a
gradual temperature increase has revealed that we can expect a
decline in mortality from cardiovascular and pulmonary disease in
the winter. Whether the milder winters could offset the mortality
during the summer heat waves is not clear.
2) Concerning malaria: The spread of this disease is limited
by conditions that favor the disease vector (the malarial
mosquito Anopheles) and the protozoan parasite (Plasmodium). The
malarial mosquito is most comfortable at temperatures of
approximately 20 to 30 degrees centigrade and at a relative
humidity of at least 60 percent. Also, the malaria parasite
develops more rapidly inside the mosquito as the temperature
rises, and the development ceases entirely below approximately 15
degrees centigrade. Increased rainfall and increased surface
water, expected to result from global warming, will produce more
breeding grounds for the mosquito. Malaria currently kills 1 to 2
million people each year.
3) Concerning schistosomiasis (bilharzia): The enormous
expanse of irrigation systems in many tropical countries has
doubled the incidence of this disease in the past 50 years. There
are some estimates that nearly 200 million people are infected
worldwide. The disease is caused by a parasitic worm (a
trematode; also called a "fluke"; a type of flatworm) whose eggs
enter the water supply by way of human urine or feces. Infected
water snails serve as hosts for the parasites while they develop
into free-swimming "mini-worms" (larvae; cercaria). The circle
closes when a larva penetrates the skin of a human who comes in
contact with the contaminated water. The development of the
parasite and the population of the host snails are both governed
by the ambient temperature, with warm waters favoring their
growth. Also, the warmer the ambient temperature, the more often
people come into contact with water. In places where the disease
is endemic, it is known that the number of infected snails
declines sharply during the winter months. A temperature rise of
only a few degrees will ensure that this disease is transmitted
throughout the year. It is estimated that currently worldwide
approximately 500 million people are at risk of infection by this
pathogen.
4) Concerning dengue: Like malaria, this disease is
transmitted by mosquitoes (Aedes aegypti, which also transmits
yellow fever), but the pathogen is a virus (dengue virus, a
flavivirus). The dengue virus is currently restricted to the
tropics, approximately between latitudes 30 degrees south and 20
degrees north. Temperature affects the development of both the
mosquito and the virus as well as the frequency of mosquito
bites. A warmer climate may increase not only the elevations
above sea level at which the disease occurs, but also its
northern and southern ranges. Dengue hemorrhagic fever, a severe
form of the disease, has a mortality of 6 to 30 percent, with
most deaths occurring in infants less than 1 year old.
5) Concerning various water-borne diseases: Changes in the
amount of precipitation will accompany the temperature changes to
a warmer Earth. Many disease-causing organisms require water for
survival, and increases in rainfall and flooding will encourage
the wider distribution of such pathogens, with higher
temperatures increasing the chances of pathogen survival. Various
bacteria (e.g., Salmonella and Shigella), viruses (e.g.,
rotavirus), protozoa (e.g., Giardia and Cryptosporidium) can
cause diarrhea, which kills more than 3 million children every
year.
6) In general, many factors will interact with a changing
climate in a nonlinear way, so their effects on human health are
extremely difficult to quantify. Despite the uncertainties, there
are increasing indications that a changed global climate may be a
major factor in the global distribution of many diseases.
-----------
Pim Martens: How will climate change affect human health?
(American Scientist Nov/Dec 1999 87:534)
QY: Pim Martens: p.martens@icis.unimaas.nl
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 21Jan00
For more information: http://scienceweek.com/swfr.htm
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4. ASTROPHYSICS: ON THE ORIGIN OF COMETS
Composed of ice and dust, comets are relatively small
objects in orbit around the Sun. They are believed to exist in
large numbers in regions beyond the planets (the *Oort Cloud and
the *Kuiper Belt), where they are perturbed by the gravitational
influence of passing stars into new orbits that bring them into
the inner Solar System. When a comet is far from the Sun, its
nucleus is frozen solid and shines only by reflected light; as
the nucleus nears the Sun, its temperature increases and it
releases gas and dust.
Like certain meteorites, comets are apparently vestiges of
the origin of the Solar System, with comets believed to be icy
*planetesimal remainders from the formation of the outer planets.
The total population of the Oort Cloud and Kuiper belt may be
10^(12) objects, with a combined mass greater than the Earth. The
main component of cometary ice is apparently frozen water, plus
some methane, carbon monoxide, and carbon dioxide. Also detected
in comets are formaldehyde, hydrogen cyanide, and methyl cyanide.
All of these molecules, detected by spectroscopy, are also found
in interstellar nebulae similar to the original "solar nebula"
(see below) from which the Sun was formed.
The current consensus view of the origin of the Solar System
proposes that its formation began with the gravitational collapse
of part of an interstellar cloud of gas and dust, the cloud with
an initial mass only 10 to 20 percent larger than the present
mass of the Sun and approximately spherical in shape. As the
cloud revolved about the Galactic center, its collapse caused it
to rotate, the speed of rotation increasing as the cloud
contracted, the increase in accordance with the conservation of
angular momentum. As the cloud contracted, it flattened to form a
disk around a central condensation, this configuration called the
"solar nebula". As gas and dust were pulled in toward the central
condensation, potential energy was converted to kinetic energy
and the temperature of the material rose until ultimately the
temperature became great enough in the interior of the
condensation for nuclear reactions to begin and give birth to a
star -- our Sun. Meanwhile, the material of the rotating disk
collided, coalesced, and gradually formed larger and larger
objects by accretion.
A chondrule is a small rounded particle embedded in certain
meteorites (chondrites). Chondrules are usually approximately 1
millimeter or less in diameter and consist for the most part of
the silicate minerals olivine and pyroxene. From textural and
chemical relationships, it is apparent that chondrules were
formed at high temperatures as dispersed molten droplets, which
subsequently solidified and aggregated into chondrite masses.
This process evidently occurred in the solar nebula before the
accretion of the planets. However, how the chondrules were melted
is not understood. It is believed that dust particles already in
existence were melted by high-energy events such as high-velocity
collisions, the melts splashed about as droplets that quickly
cooled and crystallized. In general, it is believed that the
formation of chondrules required temperatures of approximately
1500 kelvins.
... ... Joseph A. Nuth III (NASA Goddard Space Flight Center, US)
presents a review of recent studies of the origin of comets, the
author making the following points:
1) The author points out that comets are apparently the most
primitive bodies in the Solar System, with some of the material
inside a comet believed to be preserved in nearly the same state
the material was in when the Solar System was just forming and
before the Sun and the planets were fully constituted. The author
suggests each comet is effectively a "grab bag" sample of the
building blocks present in the solar nebula at the time the comet
was formed, approximately 4.5 billion years ago. Although the
nebular material may have undergone considerable processing
before incorporation into the comet, very little has been altered
since.
2) The author points out that at a basic level, a comet is
simply a collection of silicate dust and a smattering of organic
molecules coated with ice made primarily of water. Some of the
ice-coated grains may have been present in the giant *molecular
cloud that partly collapsed to form the solar nebula, but other
ice-coated grains must have formed in the solar nebula itself. In
general, it is believed that comets begin to form by an accreting
"snowball" effect in which the icy dust grains stick together to
form fractal-like aggregates. According to current models, this
process begins at some considerable distance from the center of
the solar nebula, perhaps as far as 100 astronomical units (AU)
away from the center. (As an indication of scale, Pluto is 40 AU
from the Sun; the distance from the Earth to the Sun is 1 AU) At
this stage, the movements of the dust grains and small aggregates
are coupled to the movements of the ambient nebular gas. Over
time, however, as the aggregates accumulate into compact boulder-
sized snowballs (cometesimals), they are slowed down by drag in
the ambient gas, and they begin to drift inward as their orbits
decay. As the cometesimals fall closer to the center of the solar
nebula, they continue to grow by the accretion of dust and ice
grains, as well as by merging with other aggregates in their
path. In due course (10,000 to 100,000 years), this pile of
rubble becomes a comet, perhaps 10 to 20 kilometers in diameter,
the comet containing a collection of materials from a wide swath
of its orbital radius.
3) The author suggests that strong convection ("winds") in
the solar nebula may have been responsible for the mixing of
"hot" and "cold" components found in both meteorites and comets.
Meteorites contain calcium-aluminum-rich inclusions (formed at
approximately 2000 kelvins) and chondrules (formed at
approximately 1650 kelvins), which were created near the proto-
Sun and then blown several astronomical units away into the
asteroid region between Mars and Jupiter, where they were
embedded in a matrix of temperature-sensitive carbon-based "cold"
components. The "hot" component in comets -- tiny grains of
annealed silicate dust (olivine) -- would be vaporized at
approximately 1600 kelvins, suggesting that this component never
reached the innermost region of the accretion disk before it was
transported out beyond the orbit of Pluto, where it was mixed
with ices and unheated silicate dust ("cold" components).
Vigorous convection in the accretion disk may have contributed to
the transport of materials.
4) In summary, the view of the author is that comets are not
simply collections of unaltered presolar grains and ices formed
in the precollapse molecular cloud, but are instead aggregates of
materials representative of the building blocks then present in
the nebula at the time of their accretion.
-----------
Joseph A. Nuth III: How were the comets made?
(American Scientist May-June 2001 89:228)
QY: Joseph A. Nuth III: u1jan@lepvax.gsfc.nasa.gov
-----------
Text Notes:
... ... *Oort Cloud: The Oort cloud is an apparent spherical
shell of comets 10,000 to 100,000 astronomical units (AU) from
the Sun and the proposed source of comets that orbit the Sun. The
cloud is at the extreme edge of the Sun's influence, halfway to
the nearest star, and it is believed that when the cloud is
perturbed by passing stars, comets may be sent into a solar
orbit. The size and structure of the Oort cloud have been deduced
from statistical studies of the orbits of comets; there is no
direct evidence for the cloud's existence. Approximately 900
comets are known. The cloud is named after Jan Hendrik Oort
(1900-1992). Oort first proposed the existence of the cloud in
1950. In 1927, Oort calculated the mass and size of the Galaxy,
and the distance of the Sun from its center, from the observed
movements of the stars around the center.
... ... *Kuiper Belt: In 1951 the astronomer Gerard P. Kuiper
(1905-1973) postulated the existence of a belt of objects beyond
the orbit of Pluto. Both the existence and nature of the objects
were matters of speculation for decades, until finally in 1992
Jewitt and Luu identified the first Kuiper object. The current
estimate is that as many as 10^(8) objects larger than 10
kilometers in diameter may exist in what is called the "Kuiper
belt", a disc that hugs the plane of the planetary system and
lies between 35 and 1000 *AU from the Sun. Observations to date
have yielded some 55 trans-Neptune bodies with radii on the order
of 100 km or larger, and Pluto is considered by some astronomers
to be a member of this population.
... ... *planetesimal: Planetesimals are bodies with dimensions
of 10^(-3) to 10^(3) meters that are believed to form planets by
a process of accretion. The term "accretion" refers to an
aggregation, an increase in the mass of a body by the addition of
smaller bodies that collide and adhere to it, provided the
relative velocities are low enough for coalescence. As the mass
of the agglomerate increases, so does the rate of accretion, and
this accretion process is believed to generally occur in the form
of a disk. A stellar accretion disk is a swarm of dust grains
that evolve into planetesimals and then planets.
... ... *molecular cloud: In this context, the term "molecular
cloud" refers to a cool and dense region of interstellar matter
within which atoms tend to be combined into molecules. Such
clouds are composed principally of molecular hydrogen, with
between 300 to 2000 molecules per cubic centimeter. Such clouds
also contain an admixture of "cosmic dust" comprising
approximately 1 percent of the mass, with gas temperatures
between 10 and 20 degrees kelvin.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 4May01
For more information: http://scienceweek.com/swfr.htm
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5. EXPERIMENTAL PHYSICS:
VERIFICATION OF NEGATIVE REFRACTIVE INDEX MATERIALS
In physics, the term "refraction" refers to the change in
direction of a wave passing from one medium to another, the
change occurring when the wave velocity differs in the two media.
Given the velocity-difference condition, there is only one
instance when there is no change in wave direction, and that is
when the incidence of the wave is exactly perpendicular to the
interface between the media. The phenomenon of refraction is
exhibited by any wave, including light waves, sound waves, water
waves, etc., and the major quantitative details were worked out
in 1621 by Willebrord Snell (1580-1626). The electromagnetic
waves that constitute light are thus refracted when crossing the
boundary from one transparent medium to another, if the wave
velocities in the two media differ and the incident light strikes
the interface at an angle different from the perpendicular. But
all waves in the electromagnetic spectrum can exhibit refraction,
including all waves from the shortest waves to waves in the
microwave and radio region.
In this context, the term "refractive index" (refractive
constant) takes two forms: a) The "absolute refractive index" of
a medium is the ratio of the velocity of electromagnetic
radiation in free space to the velocity of the radiation in the
medium. b) The "relative refractive index" is the ratio of the
velocity of electromagnetic radiation in one medium to that in an
adjacent medium. In general, the refractive index varies with
wavelength, and the usual method is to standardize by denoting
the refractive index as related to the wavelength of the sodium D
line.
... ... R.A. Shelby et al (3 authors at University of California
San Diego, US) present a report of an experimental verification
of a negative index of refraction, the authors making the
following points:
1) The authors point out that refraction is perhaps one of
the most basic of electromagnetic phenomena, whereby when a beam
of radiation is incident on an interface between two materials at
an arbitrary angle, the direction of propagation of the
transmitted beam is altered by an amount related to the indices
of refraction of the two materials. Snell's law, arrived at by
requiring that the phase of the incident and transmitted beams be
the same everywhere at the interface, provides the quantitative
relation between the incident and refractive angles (the angles
measured from the refraction interface normal) and the indices of
refraction of the media. The law takes the form
(a)sin(A) = (b)sin(B), where (a) and (b) are the refractive
indices of media 1 and 2, respectively, and (A) and (B) are the
refractive angles in media 1 and 2, respectively. A refracted ray
is thus bent toward the normal (but never emerges on the same
side of the normal as the incident rays) upon entering a
naturally occurring material from air, as most materials have an
index of refraction greater than 1.
2) The authors point out that refraction forms the basis of
lenses and imaging, as any finite section of material with a
refractive index differing from that of its environment will
alter the direction of incoming rays that are not normal to the
interface. Lenses can thus be designed to focus and steer
radiation for a wide range of applications and are of use over a
large range of wavelengths. Although all known naturally
occurring materials exhibit positive indices of refraction, the
possibility of materials with negative refractive index has been
explored theoretically, and the conclusion has been that such
materials would not violate any fundamental physical laws.
3) The authors report experimental scattering data at
microwave frequencies on a structured metamaterial that exhibits
a frequency band where the effective index of refraction is
negative. The material consists of a 2-dimensional array of
repeated unit cells of copper strips and split ring resonators on
interlocking strips of standard circuit board material. By
measuring the scattering angle of the transmitted beam through a
prism fabricated from this material, the authors determined the
effective refractive index appropriate to Snell's law. The
authors suggest their experiments directly confirm the
predictions of Maxwell's equations that the refractive index is
given by the negative square root of the product of *permittivity
and *permeability for the frequencies where both the permittivity
and permeability are negative.
4) The authors conclude: "The use of *photonic crystals as
negative refractive materials is intriguing and may offer the
means of extending the phenomenon we report here to optical
wavelengths. Any material that exhibits the property of negative
refractive index, a property not observed in naturally occurring
materials, will have a variety of practical applications, such as
beam steerers, modulators, band-pass filters, and lenses
permitting wavelength point source focusing."
-----------
R.A. Shelby et al: Experimental verification of a negative index
of refraction.
(Science 6 Apr 01 292:77)
QY: R.A. Shelby: Department of Physics, University of California
San Diego, La Jolla, CA 92093-0350 (US).
-----------
Text Notes:
... ... *permittivity: In general, in this context, the term
"permittivity" (dielectric constant) refers to the ratio of the
electric displacement in a medium to the intensity of the
electric field producing the displacement.
... ... *permeability: In general, in this context, the term
"permeability" refers to the ratio, in a substance, of the
magnetic flux density to the external magnetic field strength.
The relative permeability of a substance is given by the ratio of
the permeability of the substance to the permeability of free
space.
... ... *photonic crystals: In general, "photonic crystals" are
crystals with a lattice that diffracts visible light. Since the
wavelength of visible light is much longer than the wavelength of
x-rays, in order for diffraction of visible light to occur, the
distances between atoms in a photonic crystal must be much
greater than in an ordinary crystal.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 4May01
For more information: http://scienceweek.com/swfr.htm
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6. GENERAL PHYSICS: ON THE VALUES OF THE FUNDAMENTAL CONSTANTS
In physics, the term "fundamental constants" (universal
constants) refers in general to those constants that do not
change throughout the Universe. For example, the charge on an
electron, the speed of light in a vacuum, the Planck constant,
the gravitational constant, are some of the constants considered
as "fundamental constants".
In 1931, the physicist F.K. Richtmyer (d. 1939), author of a
textbook well-known to an entire generation of physics students,
remarked: "Why should one wish to make measurements with ever
increasing precision? Because the whole history of physics proves
that a new discovery is quite likely to be found lurking in the
next decimal place." The essential basis for this view is that
accurate values of the fundamental constants are required for the
critical comparison of theory with experiment, and it is only
such comparisons that enable our understanding of the physical
world to advance. A closely related idea is that by comparing the
numerical values of the same fundamental constants obtained from
experiments in the different fields of physics, the self-
consistency of the basic theories of physics can be tested.
... ... P.J. Mohr and B.N. Taylor (National Institute of
Standards and Technology, US) present a review of current
determinations and adjustments of the fundamental constants, the
authors making the following points:
1) The authors point out that the values of the fundamental
constants are determined by a broad range of experimental
measurements and theoretical calculations involving many fields
of physics and measurement science (metrology). The best value of
even a single constant is likely to be determined by an indirect
chain of information based on seemingly unrelated phenomena. For
example, the value of the mass of the electron in kilograms is
based mainly on the combined information from experiments that
involve classical mechanical and electromagnetic measurements,
the highest precision optical laser spectroscopy, experiments
involving trapped electrons, and condensed matter quantum
phenomena, together with condensed matter theory and extensive
calculations in quantum electrodynamics.
2) Two additional features of the values of the fundamental
constants are not evident from a table of numbers: a) The numbers
form a tightly linked set -- very few of the values are
independent of the others. In general, a change in a single item
of the data on which the constants are based will change many of
the values. b) The numbers are based only on the information
available at a particular time. Therefore, the recommended values
change over time, and the type of information from which the
values are obtained changes as well. For example, in the distant
past, the charge of the electron was determined by the classic
oil-drop experiment, but that method is no longer competitive.
Now the electron charge is determined indirectly from other
constants.
3) The author points out that the basic approach to finding
a self-consistent set of values for the fundamental constants is
to identify the critical experiments, determine the theoretical
expressions as functions of the fundamental constants that make
predictions for the measured quantities, and adjust the value of
the constants to achieve the best match between theory and
experiment. The idea of making systematic study of potentially
relevant experimental and theoretical information in order to
produce a set of self-consistent values of the constants dates
back to Raymond T. Birge, who published such a study in 1929 as
the very first article in what is now the _Reviews of Modern
Physics_. The Task Group on Fundamental Constants, established by
the Committee on Data for Science and Technology in 1969, has
published three sets of recommended values of the fundamental
constants, one set in 1973, one set in 1986-1987, and the latest
in 1999-2000. The most recent set is termed the "1998 recommended
values", because it is based on the information available as of
31 December 1998.
-----------
P.J. Mohr and B.N. Taylor: Adjusting the values of the
fundamental constants.
(Physics Today March 2001)
QY: Peter J. Mohr, National Institute of Standards and
Technology, Gaithersburg, MD (US)
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 4May01
For more information: http://scienceweek.com/swfr.htm
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7. IN FOCUS: ON GOEDEL'S THEOREM
"The bedrock upon which the edifice of mathematics rests is
the notion of proof. Unlike areas such as the law, where
arguments can be won by force of personality alone, in
mathematics an argument succeeds only by producing a logically
consistent set of steps leading from a primitive axiom to the
statement whose proof is desired. Such a set of deductive steps
is called a _proof sequence_, with the final statement in the
sequence termed a _theorem_. We're all familiar with such a setup
from the elementary geometry of Euclid, which we grappled with in
secondary school. In Euclid's view of the world, the axioms are
'self-evident' truths, such as 'Two points determine a straight
line' and the infamous parallel postulate, 'Through a given point
one and only one line may be drawn that is parallel to a given
line.' From a handful of such statements whose truth is accepted
without proof, one can use the tools of deductive logic to derive
a plenitude of theorems about the properties of triangles,
circles, and other geometric objects.
"In the early part of this century, the famed German
mathematician David Hilbert [1862-1943] believed that all of
mathematics -- arithmetic, geometry, analysis -- could be framed
within a logical system that would enable us to prove or disprove
_any_ statement you cared to make about mathematical objects. In
other words, any assertion was either true or false, and which of
these was the case could be determined in a finite number of
deductive steps. Hilbert's dream of a unified framework within
which to encompass all of mathematics was shattered in 1931, when
the Austrian logician Kurt Goedel [1906-1978] published a paper
in which he showed that this could not possibly be the case.
Goedel proved that for any consistent logical system strong
enough to talk about the relationships between whole numbers
(arithmetic), there must necessarily exist statements about
numbers that could be neither proved nor disproved using the
tools of that logical framework. Here by 'consistency' we mean a
system in which a statement and its negation cannot both be
proved true., which is the minimal requirement for the system to
be useful in separating fact from fiction.
"Goedel actually proved even more. He showed that there must
exist a statement about numbers that is unprovable within the
rules of the logical system -- but that can be seen to be
actually true by looking at the statement from _outside_ the
system. Goedel accomplished this logical sleight-of-hand by
inventing a clever way to code any statement about numbers using
numbers themselves. He then coded the self-referential statement
'This statement is unprovable' using his numerical scheme,
thereby creating an assertion about numbers that is logically
true -- but cannot be seen to be true using the proof machinery
of the logical system itself. One way to describe this
'incompleteness' result is to say that Goedel proved that truth
is bigger than proof."
-----------
John L. Casti: _Paradigms Regained: A Further Exploration of the
Mysteries of Modern Science_
(Perennial, New York 2001, p.126)
http://www.amazon.com/exec/obidos/ASIN/0380731711/scienceweek
-------------------
SCIENCE-WEEK http://scienceweek.com 4May01
-------------------
Related Background:
MATHEMATICS: ON KURT GOEDEL AND THE LIMITS OF LOGIC
The mathematician Kurt Goedel (1906-1978), brilliant and
individualistic and psychiatrically self-destructive, appears in
the history of 20th century science like some character invented
by a novelist. Goedel was a Viennese physics student who switched
to mathematics; participated as a youth in the famous *Vienna
Circle of philosophers; met and became bonded to an older
nightclub dancer when he was a student; published at the age of
25 a thesis that forever changed the field of mathematics;
escaped from Nazi Germany in 1940 by travelling across Asia with
the nightclub dancer (whom he had now married); settled at the
Institute for Advanced Study at Princeton, where apparently
everyone agreed that Goedel was brilliant but slightly crazy; was
chaperoned by Einstein in daily walks apparently designed by
Einstein to calm Goedel and keep him working; and then, finally,
in 1978, refusing to eat because he believed people were trying
to poison him, Goedel died of starvation. Science, after all, is
a human enterprise, and every human enterprise has its human
stories. Concerning the contributions of Goedel to mathematics,
John W. Dawson Jr (Pennsylvania State University, US) presents a
biographical essay on Goedel, the author making the following
points:
1) The story of Goedel's life and work is that of a
persistent quest for rationality in all things, pursued against a
background of recurrent mental instability.
2) Goedel proved that the mathematical methods in place
since the time of Euclid were inadequate for discovering all that
is true about the natural numbers. His discovery undercut the
foundations on which mathematics had been built through the ages
up to the 20th century, stimulated thinkers to seek alternatives,
and generated a lively philosophical debate about the nature of
truth. Goedel's innovative techniques, which could readily be
applied to algorithms for computation, also laid the foundation
for modern computer science.
3) In his famous 1931 "incompleteness theorem" paper, Goedel
demonstrated that there exists some statement that is true of the
natural numbers that must fail to be provable. That is, objects
that obey the axioms of number theory, but fail to behave like
the natural numbers in some other respects, do exist.
4) The concepts and methods Goedel introduced in his
"incompleteness" paper are central to the discipline of
*recursion theory, which underlies all of modern computer
science. Extensions of his ideas have allowed the derivation of
several other results concerning the limits of computational
procedures. One result is the unsolvability of the so-called
"halting problem" -- that of deciding, for an arbitrary computer
with an arbitrary input, whether the computer will eventually
halt and produce an output rather than becoming stuck in infinite
loop. Another result is the demonstration that no computer
program that does not alter a computer's operating system can
detect all programs (e.g., computer viruses) that do.
5) Goedel published remarkably few papers during his
lifetime -- fewer than any other great mathematician except
*Bernhard Riemann -- but the impact of Goedel's papers has been
enormous, and his work has affected virtually every branch of
modern logic.
-----------
John W. Dawson Jr.: Goedel and the limits of logic.
(Scientific American June 1999)
QY: John W. Dawson Jr., Dept. of Mathematics, Pennsylvania State
University York 814-863-8461.
-----------
Text Notes:
... ... *Vienna Circle of philosophers: (Vienna School) A
philosophical school of philosophers in Vienna in the 1920s,
inspired by the physicist-philosopher Ernst Mach (1838-1916). The
group is considered responsible for the branch of philosophy
called "logical positivism", and included Ludwig Wittgenstein
(1889-1951) and Rudolf Carnap (1891-1970). The essential approach
of logical positivism was to dismiss most "metaphysics" as
meaningless answers to pseudoproblems, and to focus on the
foundations of knowledge, scientific method, logic, and
semantics. Although Goedel is often considered a member of the
Vienna Circle, from a philosophical standpoint he was a Platonist
rather than a logical positivist: Goedel believed the objects of
true knowledge are ideas, particularly universals.
... ... *recursion theory: In this context, the theory of
iterative processes in computation.
... ... *Bernhard Riemann: Georg Friedrich Bernhard Riemann
(1826-1866). Many mathematicians consider Riemann's influence on
the course of modern mathematics to be unparalleled. Almost all
of his short number of papers were and remain important. He died
of tuberculosis before his 40th birthday.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 23Jul99
For more information: http://scienceweek.com/swfr.htm
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The first issue of SCIENCE-WEEK appeared May 1, 1997, and it has
been published regularly each week since that date. SW is
designed to cross existing conceptual and linguistic barriers
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