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ScienceWeek
SCIENCE-WEEK - Part 1/3
A Free Weekly Digest of the News of Science
January 23, 1997
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"It took a million years to move from counting
pebbles to the elaborations of quantum mechanics.
Certainly this was an arduous migration of the
multitude -- not a private party of physicists,
but the Long March of the entire human race."
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Contents of This Issue:
Part 1:
1. A Problematic Double Standard in Bioethics
2. AIDS Research in Poor Countries: Bioethics Revisited
3. Another View of the Swiss Gene Technology Referendum
4. Biology Funding vs. Physics Funding: Unease Expressed
5. US Space Agency to Organize an Astrobiology Institute
Part 2:
6. Further Evidence for a Planet Orbiting Star 51 Pegasi
7. On the Evolution of String Theory to Membrane Theory
8. Theoretical Implications of Neutrino Deficits
9. Surface Self-Trapping of Electrons
10. Kondo Effect in a Single Electron Transistor
11. Unimolecular Reactions Activated by Black-Body Radiation
12. A New Method for Synthesis of Nanowires
13. Control of Polymer Shape in Synthetic Self-Assembly Systems
14. On the Origins of Birds and Bird-Flight
Part 3:
15. Therapod Dinosaurs and the Origin of Feathers
16. A Caspase Involvement in Oogenesis Apoptosis
17. Analysis of Decoding of Intracellular Calcium Oscillations
18. On the Specificity of Individual Olfactory Receptors
19. Evidence for Protein Assembly Errors in Alzheimer's Disease
20. Long Term Effects of Physiological Response to Stress
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1. A PROBLEMATIC DOUBLE STANDARD IN BIOETHICS
During the past year, a schism of sorts has developed among
bioethicists and people concerned with bioethics. The particular
focus has been the protocols of AIDS research in so-called
developing countries, but the issue concerns more than AIDS, and
indeed pertains to any clinical research involving human subjects
in such regions. The problem is essentially as follows: Consider
two countries A and B. A is rich and B is poor, and in both
countries, the same serious lethal disease is rampant. A drug
treatment exists, affordable by the government of the rich
country but not affordable by the government of the poor country.
In the rich country, research guidelines prohibit protocols that
involve withholding drug treatment from patients diagnosed with
the disease; in the poor country, since the drug is unavailable,
no such guidelines exist. Some clinical researchers in the poor
country wish to focus on assessment of locally available
treatment methods, particularly preventive methods involving
vaccines, but the country is too poor for these research efforts.
The rich country is also interested in vaccine research, but such
research is now difficult to do in the rich country because the
ethical requirements of drug treatment in the rich country have
"contaminated" the patient population so that it is difficult if
not impossible to assess the effectiveness of a vaccine. Research
teams from the rich country therefore collaborate with research
teams in the poor country to carry out the relevant vaccine
research in the poor country, the protocol involving the
withholding of the life-saving drug treatment from the control
patient group with the rationalization that the drug is not
available in the poor country anyway. Such, it appears, is the
ethical problem now facing the international medical research
community. Are clinical researchers to do their research with
human patients with two standards of ethics, one standard for
rich countries and another standard for poor countries? One has
the feeling this is one of those questions whose answer one way
or the other will be a defining moment in the history of bio-
ethics. In a family, if one member is ill, the members of the
family usually pool resources. The same occurs in a group, a
tribe, or a country. But it does not yet occur on an internat-
ional scale, which means patients in poor countries are denied
access to life-saving drugs because they do not have the requis-
ite cash to pay for the pills they need. Pills -- not hospitals
or expensive machines or expensive facilities for state-of-the-
art surgery. This is people dying for lack of a pill that exists
in plenty in one place but not in another place. The editors of
the New England Journal of Medicine not long ago condemned
research protocols based on such disparities, but there are
clinicians in both rich and poor countries who say a double
standard is indeed required if any progress is to be made.... ...
E. Mbidde (Makerere Univ., UG), in an editorial in the journal
Science, calls for a double standard and states that "a
discussion of ethical principles in biomedical research that
ignores the socioeconomic heterogeneity of society is not ethical
and not worth holding", and that the International Ethical
Guidelines for Biomedical Research Involving Human Subjects, in
place since 1993, will in their present form "delay development
of badly needed vaccines and treatment regimens." QY: Edward
Mbidde, Uganda Cancer Institute, Makerere University, UG (Science
9 Jan 98) (cf. SW report #2 below)
2. AIDS RESEARCH IN POOR COUNTRIES: BIOETHICS REVISITED
B. Bloom (Albert Einstein College of Medicine, US), in a review
of international ethical issues in research in AIDS vaccines, the
review appearing in the same issue of Science as the editorial
mentioned in the previous report, concludes it is necessary to
clarify the existing guidelines to make clear what is attainable
for implementation in developing countries whose health care
resources are severely constrained. The author mentions only in
passing the editorial in the New England Journal of Medicine last
year that began the public discussion.
QY: Barry R. Bloom (Science 9 Jan 98)
-------------------
Related Background:
NADER GROUP CALLS AIDS TRIALS UNETHICAL
Ralph Nader's Public Citizen's Organization has charged that
international AIDS therapy trials in developing countries are
unethical. The basis of the accusation is that patients given
placebos rather than the drug AZT are compromised by not re-
ceiving the most effective treatment for the disease. Health
officials state that on the contrary the studies are ethical
and are vital for international treatment of the AIDS epidemic.
Nader held a press conference on 22 April.
(Science-Week 1 May 97)
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ETHICAL DILEMMAS IN THIRD WORLD CLINICAL RESEARCH
It is not often that a leading scientific journal publishes an
eight page front article and in the same issue of the journal
also publishes eight pages of editorial matter most of which
calls the front article an example of unethical research. But
that is exactly what happened last week in connection with a
study of drug therapy against tuberculosis in patients already
infected with HIV. The reported study, by Christopher C. Whalen
et al (Case Western Reserve University, US; other installations
in US and UG), took place in Uganda, and included a placebo group
of HIV infected individuals who were not given any anti-tubercul-
osis drug therapy at all (the drugs isoniazid, rifampin, pyrazin-
amide) even though these drugs have been shown in other studies
to have preventive action against tuberculosis in people who
carry tuberculosis antibodies. In the editorial matter, presented
in three separate pieces by 5 physicians, Marcia Angell, the
Executive Editor of the journal, calls into question the ethics
of the Whalen study. It appears the justification of the Whalen
study by its authors was the desire to glean definitive data con-
cerning the expected effectiveness of the known anti-tuberculosis
drugs in HIV infected patients in both the U.S. and Africa.
Angell states: "An essential condition for a randomized clinical
trial comparing two treatments for a disease is that there be no
good reason for thinking one is better than the other." Everyone
apparently agrees that the study could not possibly have been
carried out in the U.S. because it would be prohibited by current
U.S. regulations. These prohibitions evidently do not exist in
Uganda. (New England J. Med. 18 Sep 97)
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HEAD OF NIH COMMENTS ON CLINICAL STUDIES IN THIRD WORLD
There is evidently a flap brewing concerning U.S. management of
clinical studies of diseases in developing countries in which
placebo groups are used as controls, the placebo groups receiving
no medication at all, even if such medication is available and
known to have therapeutic value. Such placebo studies in the U.S.
are not allowed, but they are allowed in many developing countr-
ies, and in the September 18th issue of the respected New England
Journal of Medicine a paper reporting such a study in Uganda by a
U.S. managed research team of the clinical effectiveness of three
anti-tuberculosis drugs in HIV infected Ugandans was published.
In the same issue of the journal, as many pages as the report
were devoted by the journal to editorial criticism of the ethics
involved. Now Harold Varmus, head of the U.S. National Institutes
of Health, which was involved in the Uganda study, and David
Satcher of the U.S. Centers for Disease Control and Prevention,
which was also involved in the Uganda study, have an article in
that journal defending such studies in developing countries. The
crux of the Varmus-Satcher position is apparently as follows:
"The most compelling reason to use a placebo controlled study is
that it provides definitive answers to questions about the safety
and value of an intervention in the setting in which the study is
performed, and these answers are the point of the research." One
wishes Varmus and Satcher would have in the very next sentence
considered why, despite this "compelling" reason, such placebo
studies are not permitted in the U.S. The evident answer is that
in the U.S., the "compelling" reason has not been found compell-
ing enough. So that is the fundamental question: Why the applic-
ation of one ethical standard in the U.S. and another ethical
standard in Uganda? And this is the question addressed by the
editorial matter in the 18th September issue of the journal. The
New England Journal of Medicine has announced it will later
publish responses to the Varmus-Satcher article by Marcia Angell,
Executive Editor of the journal, who with others previously
criticized the reported Uganda study. (Our first report of the
Uganda study is in the SCIENCE-WEEK/SCIENCE-REPORT issue of 26
Sep 1997) QY: H. Varmus, National Institutes of Health, Bethesda
MD 20892-0148 US (New England J. Med. 2 Oct 97)
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ESTIMATED 20 MILLION INFECTED WITH AIDS IN SUB-SAHARAN AFRICA
There is perhaps too much of a tendency in many quarters to think
of a plague only as a state of affairs in which people drop dead
in expensive restaurants and get hauled away in trucks containing
piles of bodies. Our current plague, although not as dramatic as
some plagues of the past, is no less an international calamity.
The United Nations AIDS Program recently released a report
containing the following:
-- In 1997, 5.8 million people worldwide were newly infected with
HIV.
-- The number of new HIV infections this year rose 9% over 1996.
-- The total number of infected adults is now a little under 30
million, about 1% of the world's adult population.
-- This year, the total number of people infected with HIV
increased by 13%
-- More than 20 million people in sub-Saharan Africa are infected
with HIV, which is 7% of that adult population.
-- This year, 2.3 million people worldwide will have died of
AIDS, the consequent stage of HIV infection.
-- In South and Southeast Asia, 6 million people are infected
with HIV.
-- In Latin America, 1.3 million people are infected with HIV.
-- In North America, 860,000 people are infected with HIV.
-- In Western Europe, 150,000 people are infected with HIV.
(Nature 27 Nov 97)
3. ANOTHER VIEW OF THE SWISS GENE TECHNOLOGY REFERENDUM
F. Cavalli (Ospidale San Giovanni Bellinzona, CH), a member of
the Swiss Parliament, in a letter to the journal Science,
responds to the recent editorial by Nobel Laureate Rolf M.
Zinkernagel concerning the coming Swiss referendum on a
constitutional prohibition of gene manipulation. Cavalli suggests
that Zinkernagel and others have made an erroneous assessment of
the current situation in Switzerland, and that there is distrust
throughout Europe "of giant companies whose solicitude for their
shareholders appears to outweigh their concern for their
thousands of workers."QY: Franco Cavalli, Ospidale San Giovanni,
6500 Bellinzona, CH (Science 9 Jan 98)
-------------------
Related Background:
ON THE SWISS CONSTITUTIONAL PROHIBITION OF GENE MANIPULATION
There is an interesting science policy development brewing in
Switzerland. A policy formulation called the Gene Protection
Initiative has come into existence, and it will be voted on in a
national referendum in 1998. This initiative, if approved by the
public referendum, will result in a constitutional prohibition of
gene manipulation, prohibition of the use and patenting of gene-
modified animals (including worms and flies), and prohibition of
the cultivation of gene-modified plants. The Swiss scientific
community says that if the referendum is passed it will cause the
end of Swiss biotechnology and molecular biology. Both houses of
the Swiss parliament have voted against the Initiative, agreeing
with the scientists and the Swiss industrial biotechnology
community that passing the referendum will produce a disaster. At
the present time it is not clear how the public will vote. Those
supporting the initiative claim that gene-modified plants cause
allergies, that science is one step away from the creation of
super-monsters, that scientists lack ethics, morals, and a sense
of responsibility, and that scientists have let the public down
on too many occasions. So they say gene technology must be banned
from Switzerland, and they hope the rest of the world will follow
suit. In an editorial in the journal Science, Rolf M. Zinkernagel
(Institute for Experimental Immunology, Univ. of Zurich, CH) is
optimistic that the good sense of the Swiss public will prevail
and that the Gene Protection Initiative will be defeated in the
referendum, but he points out that scientists must play their
part in dispelling the negative image of science and scientists,
and they must educate the public concerning the beneficial
applications of modern science. (Science 14 Nov 97)
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MOVEMENTS IN UK AND EU TO BAN TRANSGENIC ANIMAL RESEARCH
There are movements underway in Britain and Europe to ban or
rigidly control the use of transgenic animals in biological
research. In the UK there are calls for a commission of inquiry
to investigate the welfare of transgenic animals. A recent survey
supported by the European Commission into public attitudes to
biotechnology evidently showed most respondents in EU countries
consider the creation of transgenic animals for research and for
organ transplantation to be morally unacceptable. In Switzerland,
Swiss scientists have issued a warning that biomedical research
in universities will be seriously harmed if a referendum to be
held next year to restrict genetic engineering (including a ban
on the use of transgenic animals) wins approval. An irony is that
surveys in Switzerland have shown that although three-quarters of
the population is against field trials of genetically modified
organisms, novel food, and cloning, a majority are in favor of
medical applications of technology. The apparent view of most
biologists about this matter is not complicated. The feeling
among biologists is that after centuries of arduous struggle by
thousands of biological researchers to understand fundamental
principles and apply them in medicine to alleviate suffering and
extend life, we are now, at the end of the 20th century, at the
threshold of the most important applications of basic biological
science to human health and the control of human disease. Genetic
engineering and the use of transgenic animals are absolutely
essential to extend molecular biology and apply it expeditiously
to human clinical medicine. It is indeed ironic that the same
people who call for a halt to transgenic animal research expect
the ultimate in scientific expertise when they or their children
are victims of disease or other biological misfortunes. It is sad
to have a public uneducated about these matters; it is even
sadder that many politicians deem it wisdom to follow the public
mood rather than lead it. (Nature 24 Jul 97)
4. BIOLOGY FUNDING VS. PHYSICS FUNDING: UNEASE EXPRESSED
The journal Nature, in a recent editorial, criticizes US
President Bill Clinton for asserting that the next 50 years will
be "very likely characterized predominantly as the age of
biology." The journal also criticizes the emphasis on the news of
biology, "trumpeted by the media worldwide". Politicians ought to
understand, Nature says, that the results of physics "have a way
of unobtrusively and unpredictably invigorating apparently
unrelated disciplines and technologies, even to a revolutionary
extent..." Ergo, support for the physical sciences continues to
be in the best interests of society. (Nature 8 Jan 98)
-------------------
Related Background:
ON FASHIONS IN SCIENCE AND TECHNOLOGY
Rolf Landauer (IBM Corp., US), in a review of fashions in science
and technology, points out both the negative and positive aspects
of such fashions in general, and in particular in his own field,
condensed matter physics. Among other problems, Landauer notes:
1) Fashions in science and technology draw attention away from
other deserving areas. 2) Funding agencies make an apparently
sensible initial decision to support a particular exploratory
scientific path, but they too easily become emotionally tied to
their choice. 3) The competition for grants and employment causes
public relations activities to have an increasing greater role in
the practice of science. 4) Whereas in the past judgments in an
institution about the quality of a colleague's work were based on
an assumed understanding of that work, at present promotions
depend on the ability to get funding, citation index scores,
etc., and in-house evaluations often are less important than
external evaluations. 5) These days a single publication is lost
in the deluge of papers, and the only way to be heard in the
scientific community is to repeatedly publish essentially the
same information over and over again. This produces a large
publication volume per researcher, which in turn forces other
researchers to do the same if they want to advance in status in
their installations and in their field. As any working scientist
is aware, these are only some of the problems inherent in the
present structure of professional science. Landauer suggests that
fashions in science have a mostly negative impact, and that more
serious debate is needed about how fashions affect professional
science and the training of new scientists. QY: Rolf Landauer,
Thomas J. Watson Research Center, IBM Corp., Yorktown Hts, NY US
(Physics Today December 1997)
5. US SPACE AGENCY TO ORGANIZE AN ASTROBIOLOGY INSTITUTE
In places where elephants are known, there is usually a saying
that when the elephant walks it is wise to listen. Now the US
National Aeronautics and Space Administration, an entity with
enormous physical and financial resources at its disposal, has
announced its intent to organize an astrobiology institute. An
"avalanche" of proposals are expected to be received by the end
of this month from research groups that wish to join the effort.
The scope of research at the new Astrobiology Institute will
range from investigation of the origins of life on Earth, through
the evolution of terrestrial ecosystems, to the search for extra-
terrestrial life. The idea, in essence, is to create a new field:
astrobiology. Funding for the first year will be approximately
US$7 million, then US$8 million the next year, and US$10 million
after that. (Nature 8 Jan 98)
-------------------
Related Background:
A FUNDING CRISIS IN PALEONTOLOGY
Paleontology is one of those scientific disciplines whose subject
matter is often of more interest to the public than the discipl-
ine itself. People, especially small children, are fascinated by
dinosaurs but not particularly interested in paleontology or
paleontologists. So museums will pay considerable sums for
dinosaur fossils because such fossils attract museum visitors,
while the paleontologists who find and study the fossils find it
difficult to obtain funds for their research. Paleontology, in
fact, is considered a threatened discipline by paleontologists,
due simply to human mortality: there is hardly any money to train
new paleontologists while the old paleontologists are dying out.
Even the oil industry, in its current downsizing mode, has elim-
inated the jobs of many paleontologists who made their mark in
the oil industry by analysis of microfossils to determine if an
oil field is worth exploring. ARCO, for example, slashed the
number of its paleontologists from 98 to 10. The number of full
professors in the field is now over 300, while the number of
lecturers and assistant professors is now a little over 50. In a
recent letter to the journal Science, M. Lee (Univ of Sydney, AU)
addresses the plight of paleontology and points out the irony of
the recent acquisition by the Field Museum of Chicago (US) of a
well-preserved fossil of T. Rex for US$7.6 million, a sum that
"could have provided the entire discipline of paleontology with a
much-needed shot in the arm for almost a decade."
QY: Michael S. Y. Lee
(Science 14 Nov 97)
(continued in Part 2)
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
SCIENCE-WEEK - Part 2/3
A Free Weekly Digest of the News of Science
January 23, 1998
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Contents of Part 2:
6. Further Evidence for a Planet Orbiting Star 51 Pegasi
7. On the Evolution of String Theory to Membrane Theory
8. Theoretical Implications of Neutrino Deficits
9. Surface Self-Trapping of Electrons
10. Kondo Effect in a Single Electron Transistor
11. Unimolecular Reactions Activated by Black-Body Radiation
12. A New Method for Synthesis of Nanowires
13. Control of Polymer Shape in Synthetic Self-Assembly Systems
14. On the Origins of Birds and Bird-Flight
----------------------------------------------------------------
6. FURTHER EVIDENCE FOR A PLANET ORBITING STAR 51 PEGASI
Doppler-shift is an observed change in spectrum frequencies when
the source of the spectrum or the observer move either toward or
away from each other. In astronomy, radial velocity is the
velocity of a star along the line of sight of an observer,
determined by measuring the Doppler-shift in the star's spectrum,
and periodic perturbations of an observed stellar Doppler-shift
have in some cases been interpreted as evidence for the existence
of a massive object orbiting the star. A massive planet around
the star 51 Pegasi was reported last year by Meyor and Queloz,
but a subsequent paper by D. Gray challenged their interpretation
of the data on the basis of spectral line-shape oscillations that
would indicate the Doppler-shift perturbations originated in the
stellar surface. ... ... D. Gray (Univ. of Western Ontario, CA)
now reports that recent new monitoring of 51 Pegasi showed an
absence of his previously published spectral line-shape
oscillations that previously called into question the Doppler-
shift data as indicating an orbiting planet. The author suggests
his previous results were noise, and that these new results,
together with other high-precision measurements by other
researchers, indicate the planet hypothesis as the best
explanation for the radial-velocity perturbations. (cf. con-
tiguous paper by Hatzes et al). QY: David F. Gray
(Nature 8 Jan 98)
-------------------
Related Background:
GIANT PLANET EVIDENCE CONFOUNDS SOLAR SYSTEM THEORISTS
Until recently, speculations and theories about planets orbiting
other stars than our sun have depended on our own solar system as
the guiding model. But during the past two years, astronomers
have been able to gather information about nine such planets, and
the evidence is apparently not in harmony with expectations. The
three variables that are evidently making trouble for theorists
are planet size, proximity to the parent star, and orbital
eccentricity. For example, the planet orbiting the star 51 Pegasi
is large enough to have about half the mass of Jupiter, but seems
to be orbiting the star at a radius of one-sixth the radius of
Mercury's to our sun. This is a puzzle, although there appears to
be still controversy about whether this planet is actually a
planet. Others of the discovered planets are apparently in highly
eccentric and unexplained orbits. So the theorists are busy
revising models for planet formation, establishment of orbits,
planetary orbital drift, and so on. The major difficulty is that
there are no direct observations of these discovered planets --
their existence is proposed to explain perturbations in the
behavior of their parent stars. Stephen Lubow of the Space
Telescope Science Institute (Baltimore MD US) says of the recent
observations: "It's been a revolution." (Science 30 May)
7. ON THE EVOLUTION OF STRING THEORY TO MEMBRANE THEORY
In particle physics, string theory is a theory of elementary
particles based on the idea that the fundamental entities are not
point-like particles but finite lines (strings), or closed loops
formed by strings, the strings one-dimensional curves with zero
thickness and lengths (or loop diameters) of the order of the
Planck length of 10^(-35) meters. The fundamental forces comprise
the gravitational force, the electromagnetic force, the nuclear
strong force, and the nuclear weak force, and the "grand unified
theories" are theories that aim to provide a mathematical frame-
work in which the electromagnetic forces, strong forces, and weak
forces emerge as parts of a single unified force, with the three
forces related by symmetry. Supersymmetry is an aspect of an
extension of the grand unified theories, an attempt to unify all
the four fundamental forces, i.e., linking gravitation to the
electromagnetic force, the strong force, and the weak force
through a supersymmetry scheme, and superstrings are strings in
this scheme that obey supersymmetry. Membrane theory (M-theory)
is a recent extension of string theory in which the fundamental
physical entities are considered as surfaces in a many-dimens-
ional space (membranes) rather than as lines or loop elements
(open or closed strings). Given all of the above, some caution is
necessary: the translation of a highly abstract mathematical
model of physical reality into non-mathematical language is often
an exercise of limited usefulness, and in this case in particul-
ar, we are presenting only the ghost of the theoretical scheme.
String theory was originally invented in the 1960s as a theory of
the strong force, became overshadowed by the strong force theory
of gluons and quarks, then had a revival in the 1980s -- but with
the history more dependent on new work than on fashion.
... ... M. Duff (Texas A & M Univ., US), who is active in string
theory and membrane theory, in a review of various aspects of the
history and essentials of string theory and membrane theory,
suggests that future historians may judge the 20th century as "a
time when theorists were like children playing on the seashore,
diverting themselves with the smoother pebbles or prettier shells
of superstrings, while the great ocean of M-theory lay
undiscovered before them." QY: Michael J. Duff, Texas A & M
Univ., Dept. Physics 409-847-9451
(Scientific American February 1998)
8. THEORETICAL IMPLICATIONS OF NEUTRINO DEFICITS
Leptons are a class of point-like fundamental particles showing
no internal structure and no involvement with the strong forces.
There are 6 leptons: the electron, the muon, the massive tau
lepton, and a specific neutrino associated with each of the
former (3 neutrino "flavors"). An antilepton is an anti-particle
of a lepton, for example an antineutrino (an anti-particle of a
neutrino) or a positron (an anti-particle of an electron). The
term "lepton-number" refers to a conserved quantum number equal
to the number of leptons minus the number of antileptons in a
system, with the lepton-number conservation laws separately
individualized for each flavor. Neutrinos have zero charge,
possibly zero mass, and an angular momentum factor (spin) of 1/2.
Various processes produce neutrinos: stellar nuclear reactions,
reactions occurring during supernova explosions, cosmic ray
collisions with matter, etc., and installations have been
constructed to measure the flux of neutrinos impacting Earth. To
avoid contamination by cosmic rays, such installations are deep
underground. One such installation is the Kamioka mine in Japan,
which houses the Kamiokande detector, an emplacement of a large
volume of ultrapure water. One of the best sources of neutrinos
should be the nuclear reactions in our own Sun. At the present
time, the fluxes of neutrinos measured by various detector
installations have been no more than 60% of that predicted by
theory, particularly in the case of solar neutrinos, and the
deficits are a puzzle. One possibility is that since current
detectors measure only one lepton flavor, the deficits may be a
result of neutrinos oscillating (converting) from one flavor to
another, which would imply neutrinos have mass. Another
possibility is that there is something wrong with the current
theory of stellar nuclear reactions or with the current theory of
fundamental particles. ... ... F. Wilczek (Instit. for Advanced
Study Princeton, US), reviewing discussions at a recent neutrino
conference (Santa Barbara, Calif. US, 2-6 Dec 97), notes the
anomalies and contradictions produced by current neutrino
research, particularly the anomalies in cosmic ray neutrino
flavor ratios reported by the SuperKamiokande detector, and
suggests that it seems probable the separate laws of lepton-
number conservation will soon fall.
QY: Frank Wilczek (Nature 8 Jan 98)
9. SURFACE SELF-TRAPPING OF ELECTRONS
Delocalized (conducting) electrons are electrons that are
effectively spatially uncoupled and free to move as charge
carriers in one or more dimensions in a system, and phonons are
virtual particles associated with crystal thermal vibrations.
Polarons are electrons associated with phonons in lattice
deformations, the polaron itself behaving as a virtual particle.
So-called "large" polarons are polarons involving lattice
deformations extending over several unit cells, and "small"
polarons are polarons involving electron self-trapping (i.e., the
trapping of an electron by deforming lattice polarization that
the electron has itself induced). Photoelectrons are electrons
emitted from a surface exposed to light, and photoelectron
spectroscopy is an instrumental method for analyzing the energies
of photoelectrons resulting from the bombardment of matter with
ultraviolet or x-ray radiation. The term "potential barrier"
refers to an energy barrier opposing the movement of a particle
through a region, and "tunneling" is a quantum mechanical
phenomenon involving an effective penetration of an energy
barrier resulting from the width of the barrier being less than
the wavelength of the particle. ... ... Ge et al (6 authors at
Univ. of California Berkeley, US) report a study using photo-
electron spectroscopy of two-dimensional small-polaron formation
at ultrathin adsorbed alkane layers on a silver surface. Optical
excitation apparently creates interfacial electrons in quasi-free
states for motion parallel to the interface, and these initially
delocalized electrons self-trap as small polarons within a few
hundred femtoseconds, then decay back to the metal within
picoseconds by tunneling through the adsorption layer potential
barrier. The authors suggest their theoretical analysis of the
system may contribute to the fundamental picture of electron
behavior in weakly bonded solids.
QY: C.B. Harris (Science 9 Jan 98)
10. KONDO EFFECT IN A SINGLE ELECTRON TRANSISTOR
A transistor is essentially a semiconductor device in which it is
possible to control voltage or current in such a way as to
achieve gain or switching action, and a single-electron
transistor is a transistor of extremely small dimensions isolated
from its leads by potential barriers narrow enough to permit
electron tunneling, with a minute electron source that is
essentially a droplet of electrons. A single-electron transistor
switches on and off with the addition of each electron, in
contrast with the ordinary transistor which sustains a switched-
on state given a flow of added electrons. This quantized behavior
of the single-electron transistor is due to its dimensions, the
electron droplet essentially behaving as an artificial atom. The
Kondo effect is a large anomalous increase in the resistance of
certain dilute alloys of magnetic materials in nonmagnetic hosts
as the temperature is lowered. In general, the Kondo effect
occurs when an impurity atom with an unpaired electron is placed
in a metal, producing an interaction of localized electrons with
delocalized electrons. ... ... Goldhaber-Gordon et al (6 authors
at 2 installations, US IL) report measurements on single-electron
transistors smaller than those previously made, and which exhibit
all of the predicted aspects of the Kondo effect in such systems.
The authors suggest the increased functionality of single
electron transistors may eventually be technologically important.
QY: M.A. Kastner (Nature 8 Jan 98)
11. UNIMOLECULAR REACTIONS ACTIVATED BY BLACK-BODY RADIATION
Unimolecular reactions are reactions in which a single molecule
decomposes into two or more molecules (or atoms), and a classical
unimolecular process is one in which the rate of the unimolecular
decomposition is apparently dependent only on the amount of
reactant molecule present. In physics, a black-body is an ideal
body that absorbs all radiation and reflects none of it, and
black-body radiation is the emission of radiant energy that would
occur from a black-body at a fixed temperature and with a
spectral energy distribution described by Planck's black-body
radiation equation. In 1919, Perrin proposed that unimolecular
reactions were activated by black-body radiation from the
reaction vessel, but the radiation hypothesis was rejected by
Langmuir (and by most physicists) on the grounds that the
activation energies were too high to be provided by ambient
radiation, given the spectrum absorption characteristics of
molecules that exhibited unimolecular dissociation. The consensus
then formed that bimolecular collisions were involved, and with
some subsequent supporting evidence for this, the black body
radiation hypothesis was essentially forgotten. ... ... Dunbar
and McMahon (at 2 installations, US CA), in a review of unimol-
ecular reactions activated by ambient black body radiation,
present the evidence that after nearly 80 years of rejection,
Perrin's original radiation hypothesis is a viable mechanism for
the activation of unimolecular reactions under certain specific
conditions involving molecular infrared absorption. The authors
suggest that the ambient black body radiation activation
mechanism is a major addition to the field of chemical kinetics,
with particularly promising applications to cluster ions and
large biomolecule ions. QY: R.C. Dunbar
(Science 9 Jan 98)
12. A NEW METHOD FOR SYNTHESIS OF NANOWIRES
Nanowires (and nanotubes) are nanoscale [of the order of 10^(-9)
meters] structures that are effectively one-dimensional, and such
structures have great potential importance in many applications
ranging from probe microscopy to nanoelectronics. There are a
number of methods of producing one-dimensional nanoscale
structures, but so far none of them has allowed enough control of
structure parameters to be satisfactory. Vapor-liquid-solid
growth is a method of forming crystalline wire-like structures
with a liquid metal cluster or catalyst acting as the energetic-
ally favored site for absorption of gas-phase reactants. What
happens is that the cluster supersaturates and grows a one-
dimensional structure of the material, and the lower diameter
limit of the grown one-dimensional structure is apparently the
diameter of the liquid metal cluster starting locus. In the
context of this report, the term "laser ablation cluster
formation" refers to the use of a laser to reduce (ablate) a
cluster to nanoscale dimensions. ... ... Morales and Lieber
(Harvard Univ., US) report a method combining laser ablation
cluster formation and vapor-liquid-solid growth to synthesize
semiconductor nanowires, the laser ablation used to prepare
catalyst clusters that define the size of wires produced. The
authors suggest that well-established phase diagrams can be used
to predict catalyst materials and growth conditions for the
controlled preparation of crystalline nanowires of many different
materials. QY: Charles M. Lieber
(Science 9 Jan 98)
13. CONTROL OF POLYMER SHAPE IN SYNTHETIC SELF-ASSEMBLY SYSTEMS
In general, the term "polymer conformation" refers to the higher
order structure of polymers, and one goal of synthetic polymer
chemistry is to define the conditions producing various types of
conformations, since in many cases both the physical properties
and reactivity of polymers is conformation dependent. In polymer
chemistry, "quasi-equivalent" building blocks are chemically
identical subunits that self-control their shape by switching
between different conformational states during the process of
self-assembly. The significance of quasi-equivalent units is
perhaps most apparent in the comparative supramolecular struct-
ures of icosohedral-shaped versus rod-shaped viruses.
... ... Percec et al (6 authors at 3 installations, US UK DE) now
report a general method for the control of polymer conformation
through the self-assembly of quasi-equivalent monodendritic
(branched) side-groups attached to flexible backbones, with the
production of either spherical or cylindrical polymers controlled
by the degree of polymerization. The authors suggest their
strategy will provide new approaches to the rational design of
organized supramolecular materials, expanding the synthetic and
technological uses of dendritic building blocks. QY: V. Percec
(Nature 8 Jan 98)
14. ON THE ORIGINS OF BIRDS AND BIRD-FLIGHT
In paleontology, the theropods are dinosaurs with four or fewer
toes on the hind feet, a suborder of bipedal reptiles that first
appeared in the Upper Triassic period (about 215 million years
ago) and culminated in the Upper Cretaceous period (about 70
million years ago). A difficult problem in paleontology has been
the tracing of the evolution of birds, with most paleontologists
believing birds evolved from dinosaurs. The first feathered bird-
like fossils are classified as Archeopteryx and were found in
Upper Jurassic deposits dating at about 150 million years ago,
but unfortunately there are no feathered intermediates yet dis-
covered between these fossils and any dinosaur ancestors. Birds
are rather unique in several aspects: feathers, toothless beaks,
hollow bones, perching feet, etc., with a combination of skeletal
features unknown in other living animals. ... ... Padian and
Chiappe (2 installations, US), in a review of extant data and the
controversies concerning the evolution of birds, conclude there
is no reasonable doubt that all groups of birds, living and
extinct, are descended from small meat-eating therapods, and that
"in fact, living birds are nothing less than small, feathered,
short-tailed therapod dinosaurs." QY: Kevin Padian, Univ. of
Calif. Berkeley, Dept. Integ. Biol. 510-642-5130 (Scientific
American February 1998)
(continued in Part 3)
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
SCIENCE-WEEK - Part 3/3
A Free Weekly Digest of the News of Science
January 23, 1998
----------------------------------------------------------------
Contents of Part 3:
15. Therapod Dinosaurs and the Origin of Feathers
16. A Caspase Involvement in Oogenesis Apoptosis
17. Analysis of Decoding of Intracellular Calcium Oscillations
18. On the Specificity of Individual Olfactory Receptors
19. Evidence for Protein Assembly Errors in Alzheimer's Disease
20. Long Term Effects of Physiological Response to Stress
----------------------------------------------------------------
15. THERAPOD DINOSAURS AND THE ORIGIN OF FEATHERS
Chen et al (3 authors at 3 installations, CN) describe two nearly
complete skeletons of a small therapod dinosaur, Sinosauropteryx.
The specimen has the longest tail of any known therapod, a 3-
fingered hand dominated by the first finger, and integumentary
structures that could be related to the origin of feathers. The
larger specimen has stomach contents and two eggs in the abdomen.
The authors suggest the integumentary structures indicate that
avian feathers may have evolved from simpler branched structures
appearing in non-avian therapod dinosaurs, possibly for insulat-
ion. QY: Pei-ji Chen
(Nature 8 Jan 98)
-------------------
Related Background:
FOSSIL EVIDENCE LINKS BIRDS AND DINOSAURS
Most paleontologists agree that birds are descendants of
dinosaurs, but the precise linkage is still to be determined,
and many questions remain. Now paleontologist Fernando Novas
(Museo Argentino de Ciencias Naturales, Buenos Aires AR) has
unveiled a reconstruction of a 90 million year old fossil of a
meat-eating dinosaur found in Argentina, the most birdlike
dinosaur ever discovered. The fossil's structure provides a link
between dinosaurs and birds, and will help explain how dinosaur
limbs evolved into bird wings. The creature was almost four feet
tall at the hip, and nearly seven feet long. It has been named
Unenlagia comahiensis. (Nature 22 May 97)
-------------------
NEW FOSSIL EVIDENCE FUELS BIRD-DINOSAUR LINKAGE DEBATE
Paleobiologists continue to debate whether birds evolved from
dinosaurs or from earlier reptiles. This week Jose L. Sanz et al
(Autonomous University of Madrid ES, Smithsonian Institution,
Washington DC US, University of Barcelona ES) report the
discovery, in the Pyrenees of northern Spain, of a well-preserved
nestling bird dating from approximately 135 million years ago,
the specimen the earliest hatchling bird yet discovered,
apparently existing only 10 million years after Archaeopteryx,
considered the first undisputed bird. The hatchling is reported
to show a mix of primitive and advanced features, and is the
second claimed bird-dinosaur link in two weeks. Those who dispute
the bird-dinosaur link, however, say the hatchling provides no
evidence one way or the other. But partisans on both sides of the
issue admit this is an important find because it is indeed a
hatchling. (Science 6 Jun 97)
16. A CASPASE INVOLVEMENT IN OOGENESIS APOPTOSIS
Oocytes are egg cells, and in invertebrates, "nurse cells" are
accessory cells connected to oocytes by cytoplasmic bridges that
allow nutrients to be directly transferred to the oocyte. The
cytoskeleton of biological cells is the quasi-rigid matrix that
among other things determines cell shape. Proteases are a class
of enzymes that hydrolyze proteins, splitting them into various
groups of subunits, with the sites of hydrolysis dependent on the
particular enzyme and the protein substrate, and a caspase is a
type of protease. Apoptosis is programmed cell death produced by
control mechanisms designed to destroy defective cells, or cells
that must necessarily be discarded in the embryological develop-
ment of tissues. ... ... McCall and Stellar (Massachusetts
Instit. of Technol., US) report that loss of function of the
Drosophila gene dcp-1, which encodes a caspase, causes female
sterility by inhibiting the transfer of cytoplasm to oocytes by
nurse cells, the nurse cells being apparently defective in the
cytoskeletal reorganization and nuclear breakdown that normally
accompany this process. The authors suggest their results
demonstrate that scheduled apoptosis of nurse cells is a
necessary event in oocyte development. QY: Hermann Steller, Mass.
Inst. of Technology, Dept. Biol., 617-253-4738 (Science 9 Jan
98)
-------------------
Related Background:
PROTEASES AS MEDIATORS OF APOPTOSIS
... Actin is a structural protein present in all cells as a
constituent of the cell cytoskeleton, and gelsolin is a protein
that breaks actin filaments and causes a gel-sol conversion -- a
conversion of a gelatin-like system to a solution (liquid)
system. This type of conversion is ordinary in certain cell types
under certain conditions, but it is also seen in apoptosis
(programmed cell death) when the cytoskeleton is destroyed and
the cytoplasm liquified. ... ... Srinivas Kothakota et al (11
authors at 3 installations, US) report that the protein gelsolin
is the primary substrate for the caspase-3 protease family that
has been implicated in apoptosis. Gelsolin cleavage products
cause multiple cell types to round up, detach from the cell
culture plate, and undergo nuclear fragmentation. Cells isolated
from genetically engineered mice lacking gelsolin showed marked
delays in apoptosis onset following apoptosis induction, while
wild-type cells did not show these delays. The authors suggest
that cleaved gelsolin may be one of the physiological effectors
that produce morphological changes during apoptosis. QY: David J.
Kwiatkowski
(Science 10 Oct 1997)
17. ANALYSIS OF DECODING OF INTRACELLULAR CALCIUM OSCILLATIONS
The calcium ion [Ca(2+)], although present in relatively small
concentrations, is ubiquitous in all living cells, and usually
involved in an important way in many aspects of cell function,
particularly in nerve and muscle cells. Local calcium concentrat-
ions can change markedly and rapidly in living cells, and such
changes are called "calcium spikes". A kinase is an enzyme that
catalyzes the transfer of a phosphate group from one compound to
another. Calmodulin is a Ca(2+) binding protein that mediates
many of the regulatory effects of calcium ions in eukaryotic
cells (cells with nuclei), and a calmodulin-dependent protein
kinase is a protein kinase activated by Ca(2+)-calmodulin and in
turn catalyzing the phosphorylation of various target proteins.
Pulse perfusion is a method of rapidly changing ambient concentr-
ations by controlled delivery of fluid pulses in vitro to living
cells or chemical reactants. The term "synaptic plasticity"
refers to the changeability of neuronal synaptic connections,
usually as a result of ongoing neural activity.
... ... De Koninck and Shulman (Stanford Univ., US) report that
rapid pulse perfusion (called "superfusion" by the authors) with
Ca(2+) ions of an immobilized calcium-and-calmodulin-dependent
protein kinase (CaM kinase II) in vitro indicates the enzyme can
decode the frequency of calcium spikes into distinct amounts of
kinase activity. The authors suggest this allows specificity in
the activation of the enzyme by distinct cellular stimuli and may
underlie its pivotal role in activity-dependent forms of
synaptic plasticity. QY: Howard Schulman
(Science 9 Jan 98)
18. ON THE SPECIFICITY OF INDIVIDUAL OLFACTORY RECEPTORS
The adenoviruses are DNA-containing viruses with an outer protein
coat shaped like an icosahedron, and a recombinant adenovirus is
an adenovirus whose genome has been modified by the introduction
of foreign genetic material. The common cold virus is an
adenovirus. In general, the term "gene expression" includes any
gene activity, but particularly an activity that produces the
synthesis or activation of a specific protein. Olfactory
receptors are protein receptors on the surfaces of olfactory
neurons that are involved in the binding of odorant ligands, the
binding then producing a series of events that result in the
nerve cell sending a signal to the central nervous system.
... ... Zhao et al (6 authors at 3 installations, US JP) report
the use of a recombinant adenovirus to drive the expression of a
particular olfactory receptor gene in an increased number of
sensory neurons in rat olfactory epithelium. The method involved
infecting the olfactory cells with the adenovirus. Electrophys-
iological recording indicates that increased expression of a
single gene produces a greater sensory sensitivity to a small
subset of odorants. The authors suggest their method, coupled
with introduced mutations, can lead to a detailed understanding
of the relation between gene sequence, protein structure, and
ligand-binding specificity in membrane-bound receptors.
QY: Stuart Firestein, Columbia University, US 212-854-1754
(Science 9 Jan 98)
19. EVIDENCE FOR PROTEIN ASSEMBLY ERRORS IN ALZHEIMER'S DISEASE
Post-mortem tissue analysis of Alzheimer's disease patients and
Down syndrome patients reveals anomalous protein deposits (beta-
amyloid protein) in brain nerve cells. Most researchers believe
these deposits are in some way related to the etiology of these
disease entities. Beta-amyloid precursor protein is a protein of
unknown function, but one of its cleavage products is the beta-
amyloid protein found in the Alzheimer's disease and Down
syndrome "plaques" (in this context: deposits). Ubiquitin-B
protein is a "disposal" protein that marks faulty proteins for
degradation and disposal in the cell, and this protein is also
common in Alzheimer's plaques. In the context of this report, the
term "carboxyl terminus" refers to the carboxyl moiety end of a
protein (the other terminus possessing an amino moiety). Trans-
cription is the process whereby the DNA code is transcribed into
an RNA code, and a transcript mutation is some aberration in this
process. The term "reading frame" refers to a specific permutat-
ion of nucleotide triplets in DNA as "framed" by a preceding
start triplet (start codon), and one type of transcript mutation
is "frameshift" mutation, an error involving a shift of the
reading frame so that the wrong triplet codons are transcribed.
Frameshift mutations can be produced by corrupting insertions or
deletions of nucleotides in the genome. ... ... Van Leeuwen et al
(13 authors at 4 installations, NL) report that the character-
istic protein deposits in the cerebral cortex of Alzheimer's
disease and Down syndrome patients contain forms of beta-amyloid
precursor protein and ubiquitin-B protein that are aberrant in
the carboxyl terminus (i.e., they are +1 frameshift mutation
proteins). The authors suggest this type of transcript mutation
may be an important factor in the widespread nonfamilial (i.e.,
of no apparent familial genetic etiology) early- and late-onset
forms of Alzheimer's disease, and that dinucleotide deletion at
the transcript level may underlie a number of neurodegenerative
pathologies. QY: Fred W. van Leeuwen
(Science 9 Jan 98)
20. LONG TERM EFFECTS OF PHYSIOLOGICAL RESPONSE TO STRESS
Consider three people forming a group at a party, two of the
people talking and the third listening. At some point in the
conversation a sentence is uttered, a sentence quite insignif-
icant for the two people talking, but a sentence that may be of
strong significance for the person listening. The listening
person blushes. What has happened is that the blood vessel
capillary beds in the face have enlarged, the capillary lumens
controlled by the autonomic nervous system, which in this case is
receiving certain stress signals from the central nervous system,
which in turn has received and interpreted sensory input from the
ears: i.e., the words of the two talking people produce a
physiological response in the listening person. If we consider
the various aspects of the response of the human organism to
external stimuli, then one significant aspect is the response to
stress, particularly psychological stress. An extreme physical
threat in war, for example, is a psychological stress that easily
produces severe physiological responses. Less dramatic, but
potentially as important, are the non-lethal psychological
stresses experienced by many people either acutely or in chronic
circumstances. The physiological responses to these stresses are
attempts of the organism to protect itself and restore equilibr-
ium, but it has been recognized for most of this century that the
physiological systems activated by stress can also damage the
body. The capillary enlargement involved in blushing is trivial;
a suppression of the immune system by psychological stress is not
trivial at all. ... ... B. McEwen (Rockefeller Univ., US), in a
review of the protective and damaging effects of stress mediators
(the physiological systems activated by stress), introduces the
term "allostatic load" as the long term effect of the physiolog-
ical response to stress. Allostasis -- stability achieved through
change -- is critical to survival, and involves the autonomic
nervous system, the hypothalamic-pituitary-adrenal axis, and the
cardiovascular, metabolic, and immune systems -- which can be
called "allostatic systems". Chronic overactivity or underactiv-
ity of these allostatic systems produces the allostatic load --
the wear and tear -- resulting from allostasis. QY: Bruce S.
McEwen, Rockefeller University, 1230 York Avenue, New York, NY
10021 US (New England J. Med. 15 Jan 98)
-------------------
Related Background:
CUMULATIVE MEDICAL IMPACT OF SUSTAINED ECONOMIC HARDSHIP Although
it has been generally recognized that a correlation exists
between economic hardship and health, the existing data is a
result of correlation studies at one particular time, and
apparently no studies have been reported to show a correlation of
poor health with sustained economic hardship in individuals.
... ... Lynch et al (3 authors at 2 installations, US), in a
study of 1100 people with a median age of 65 years in 1994, with
income information collected in 1965, 1974, and 1983, now report
that after adjustment for age and sex, there is a significant
association between sustained poverty level and all measures of
functioning except social isolation. The authors conclude that
sustained economic hardship leads to poorer physical, psycholog-
ical, and cognitive functioning, and they suggest that increases
in economic inequality that push large proportions of the popul-
ation into low-income groups may have serious short-term and
long-term health consequences. QY: John W. Lynch, Univ. of Mich-
igan, Dept. of Epidemiology 313-764-7433
(New England J. Med. 25 Dec 97)
---------------------------------------------
BOOK NOTES
R.L. Fleischer: TRACKS TO INNOVATION
Nuclear Tracks in Science and Technology
Springer, 1998, 208p, US49.95
An account of the discovery and applications of the latent tracks
in materials produced by energetic charged particles. Applicat-
ions to geology, materials science, archeology, art history,
etc., are discussed with only a minimal knowledge of physics
required of the reader.
H. Flyvbjerg et al (eds.): PHYSICS OF BIOLOGICAL SYSTEMS
From Molecules to Species
Springer, 1997, 366p, US89.95
Nucleic acids, proteins, membranes, microtubules, neurons,
sensory signal processing, micro- and macro-scale evolution. This
is a useful introduction for graduate students in physics
contemplating research in biological physics. The articles are by
researchers in the various fields.
A. Isihara: ELECTRON LIQUIDS
Second Edition
Springer, 1998, 352p, US65
Discusses newly discovered electronic phenomena with an emphasis
on electron correlations. High temperature superconductivity,
quantized Hall effect, crystallization and stability of matter,
etc.
L. Jacak, P. Hawrylak, A. Wojs: QUANTUM DOTS
Springer, 1998, 184p, US44.95
Basic structure and production of quantum dots, internal
properties, electronic structure, response to light, physical
effects in dots, theoretical models, computational methods,
future applications.
L. Sipes, C. McQueen, A. Gandolfi (eds.):
COMPREHENSIVE TOXICOLOGY
Pergamon, 1997, 8000p, US3402, cdrom US4252
13 print volumes that will most likely be out of date before any
of the volumes is completely utilized. With the CDROM at over
US$4200 and 125% more costly than the print edition, this is
certainly a counter-example to any hypothesis suggesting
electronic publication of scientific material will reduce costs
to researchers and libraries. 50,000 references, most including
their abstracts -- which means approximately 5 abstracts to a
page, which means a good portion of the text is merely an
abstract compendium. A rather expensive luxury for any library
that already carries Chemical Abstracts, and a fiscal
impossibility for most other libraries.
John R. Taylor: AN INTRODUCTION TO ERROR ANALYSIS
Second Edition
The Study of Uncertainties in Physical Measurements
University Science Books, 1997, 327p, US44.50
An undergraduate text. A introduction to understanding and
estimating random uncertainties in physical measurements.
Reporting and using uncertainties, propagation of errors,
statistical analyses and the normal distribution, criteria for
rejecting data, weighted averages, least-squares fitting,
correlation and three-dimensional distributions. Numerous worked
examples relevant to physics. Recommended for all physics
students, and for students in other sciences with an interest in
quantitative measurements.
---------------------------------------------
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