ScienceWeek

SCIENCE-WEEK

A Weekly Digest of the News of Science

September 11, 1998

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What is the path? There is no path.
-- Niels Bohr (1885-1962)

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Contents of This Issue:

1. On Free Internet Access to Traditional Journals
2. On the Evolution of Galaxies in a Changing Universe
3. On Globular Star Clusters
4. On the Future of Carbon Nanotube Chemistry
5. Experimental Coaxial Nanocables
6. Molecular Biology: On the Workings of the Ribosome
7. On Honeybee Social Behavior, Genes, and the Environment
8. Significance of Estrogen for Male Bone Mass
9. Effects of Methylmercury Exposure from Fish Consumption
10. Sunlight Exposure and the Risk of Eye Lens Opacities

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1. ON FREE INTERNET ACCESS TO TRADITIONAL JOURNALS
Thomas J. Walker (University of Florida, US) presents an analysis
of current problems involving the production costs and
subscription prices of scientific journals, the author making the
following points: 1) On the Web, publishers are now beginning to
charge for access to journal articles online through
subscriptions, site licenses, and "pay-per-view" plans. These
toll-gate approaches are an extension of the current economic
structure of scientific publishing and are being developed
largely by the organizations that benefit most from that economic
structure. On the other hand, many of those who do the research
and write the articles do not share these economic interests, nor
do many of the scientific societies to which they belong. 2) Some
scientific societies currently finance publishing through per-
page charges that are paid by authors or their grants or
institutions. Such charges now help hold down subscription
prices, and in the future similar charges might finance free
access. 3) The 1970s witnessed the beginning of extraordinary
increases in the real prices of science journals. Whereas the
costs of scholarly publishing in general closely followed the
Consumer Price Index, the average prices of science and technical
journals markedly diverged upward, so that by 1996 the relative
increase in the prices of scientific journals was an order of
magnitude greater than the relative increase in the prices of
scientific books. 4) In the past decade, research libraries have
spent more than twice what they spent in 1986 to purchase 7
percent fewer titles. Every year libraries must cancel journal
subscriptions in order to continue to receive other journals that
are increasingly costly. And publishers often raise subscription
prices as their subscriber base shrinks, creating a feedback loop
that worsens the situation. 5) Unfortunately, rather than ending
the journals crisis for libraries, the beginning of Web access to
traditional journals may have intensified it. Publishers now
offer licenses to electronic versions as add-ons to regular
subscriptions, in most cases with a substantial increase in
subscription price. 6) The author suggests that the economics of
electronic publication are so favorable that scientific societies
should be able to finance free access to all their articles from
page charges to authors who want their articles immediately
posted, and that the Florida Entomological Society is now doing
just that. 7) The author further suggests that if scientific
societies acknowledge that their mission is to serve members,
they should realize that restricting access to refereed research
results, when free access has finally become affordable, is
counter to that mission. The author concludes: "Free access to
traditional journals is affordable and achievable... Taking
action now can secure an information highway where toll gates do
not limit access to the literature of science."
QY: Thomas J. Walker 
(American Scientist Sep/Oct 1998) (Science-Week 11 Sep 98)

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Related Background:

A CHEAPER CHEMISTRY JOURNAL AT US$2300 PER YEAR
The US Association of Research Libraries is an affiliation of 81
libraries with a stated combined annual purchasing power of
approximately US$500 million. The association has a unit called
the Scholarly Publishing and Academic Resources Coalition
(SPARC), the ostensible purpose of the unit to seek ways and
agreements to reduce the cost of scientific journal subscriptions
to libraries. At the present time, the apparent modus operandi in
much of scientific journal publishing is to publish highly
specialized journals for a captive market (university and
corporate research libraries) and charge for these journals as
much as the market will bear. The publisher Elsevier, for
example, charges US$8000 per year for a subscription to its
weekly organic chemistry journal *Tetrahedron*, and US$5073 per
year for its journal *Neuroscience*. SPARC is now reported to
have an agreement from the American Chemical Society to publish a
new biweekly journal next year called *Organic Chemistry
Letters*, the subscription price to be US$2300 per year, with the
81 libraries of the association committed to subscriptions. This
proposed new chemical journal at US$2300 per year is now being
touted as a happy "solution" to the problem of journal prices. At
the indicated subscription price, the annual guaranteed revenue
to the American Chemical Society from this new journal will begin
at US$186,300 per year. Of course, the same revenue could be
generated from this new organic chemistry journal by providing it
online to 10,000 organic chemists worldwide at a subscription
price of less than US$20 per year, but then one loses the
commercial advantage of a solid captive market that will also
provide easily increased revenues in the future. The evident
focus is information concentrated via relatively few library
subscriptions rather than information widely disseminated via
personal subscriptions. Sooner or later, it seems, the libraries,
the scientific societies, and the scientific community in general
will need to decide unequivocally whether the purpose of the
publishing of scientific journals by scientific societies is to
disseminate the results of scientific research as widely as
possible or to generate revenues with commercial publishing as
the model.
(Chem. & Eng. News 6 Jul 98) (Science 3 Jul 98 281:21)
(Science-Week 24 Jul 98)

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Related Background:

RESEARCH LIBRARIES UNITING AGAINST JOURNAL PRICES
Several decades ago, a number of commercial publishers discovered
a paradigm for financial success: Found a new specialized
scientific journal, recruit an editorial board of specialists,
encourage high volume submission of papers with only cursory peer
review, inform research libraries they must carry the journal
because the specialty is important and because of the volume of
publications, and finally, over a period of years, gradually
increase the price of the journal several thousand per cent with
no fear of rejection by the captive library market. Other
publishers have used similar tactics in the publication of
scientific monographs and collections of papers: there are now on
the market a number of such books offered at a price of as much
as US$1 a page, the publisher's blurb more or less informing the
research library that without this item on your shelves your
library is not serious. The publishers say they cannot publish
research journals and monographs in the absence of maximum profit
to shareholders, and the research librarians say they can no
longer afford to maintain their libraries current in what is
being published. Scientific publishers are now giants of
industry, with the merger of Reed Elsevier and Wolters Kluwer
apparently about to produce a company with US$6 billion in
revenues publishing 1500 scientific and medical journals.
[Editor's note: The proposed merger fell apart.] For a time
it was hoped that electronic publishing of journals would
ameliorate the problem of library budgets, since the production
cost of electronic publication is only a small fraction of the
cost of print publication. But it seems the publishers are not
about to allow electronic publication to substantially reduce
their revenues: most journals now available separately in
electronic form do not charge much less for the electronic form
than they do for the printed form, and other journals may be
available in electronic form, but the electronic form is only an
adjunct to the printed form, and the electronic form is not
available as an independent publication. There may be a 90%
reduction in production cost for the electronic form, but there
is certainly not a 90% reduction in journal costs for the
research library. Now the libraries are apparently in revolt, and
a number of European libraries, particularly Dutch and German
libraries, are banding together to refuse electronic journal
subscription prices that are more than 80% of print subscription
prices. Alex Klugkist, chair of a consultative body of 15 Dutch
scientific libraries says, "We're fed up."
(Science 28 Nov 97) (Science-Week 19 Dec 97)

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Related Background:

CHEMIST CITES CRISIS IN DISTRIBUTION OF SCIENTIFIC INFORMATION
Alexandru T. Balaban, Professor of Organic Chemistry at the
University of Bucharest, argues that current methods of
distributing scientific information have caused critical
hardship to research workers in most countries of the world. In
Romania, for example, the only complete collection of *Chemical
Abstracts* exists in the capital city, Bucharest, although
universities and chemical research institutes are located in
five other cities. Balaban cites the paradox: Quality scientific
information is being produced, but only a tiny fraction of the
potential users can afford to buy and use this information. For
example, the Houben-Weyl *Methoden der organischen Chemie*,
important for any research in chemical synthesis, has more than
50 volumes with each volume priced at approximately $2000.
Recent volumes are practically unavailable, and many libraries
have stopped subscribing to the well-known Gmelin and Beilstein
series as well. Balaban concludes that a completely new approach
to the dissemination of scientific information is badly needed,
perhaps an approach utilizing the current interconnections
available via the Internet.
(American Scientist June 1997) (Science-Week 8 May 97)


2. ON THE EVOLUTION OF GALAXIES IN A CHANGING UNIVERSE
In a detailed review of research in this century concerning the
evolution of galaxies, Alan Dressler (Carnegie Observatories
Pasadena, US) makes the following points: 1) When the century
opened, most astronomers assumed the Universe was eternal and
basically changeless, its general structure immutable. In 1915,
with the publication of Einstein's general theory of relativity,
there were implications of the cosmic role of gravity, but these
implications were for the most part ignored. Indeed, even after
1924 and the proof by *Edwin Hubble (1889-1953) that the spiral
nebulae are other galaxies at vast distances, astronomers were
slow to recognize the implications of the new observations. 2)
The first big step in changing the view of the cosmos was the
construction by *George Ellery Hale (1868-1938) of the 100-inch
Hooker reflector on Mount Wilson (US), a project completed in
1918. This was the telescope used by Hubble and his colleagues to
reveal the large-scale organization of the Universe into
galaxies, the vast size of the Universe, and the expansion of the
Universe. *George Lemaitre (1894-1966) soon proposed that the
expansion of the Universe implied a dense explosive birth of the
Universe at a specific finite time in the past (the event that
came to be called the Big Bang). 3) An even greater telescope was
needed, and again George Hale led the way in the building of the
200-inch reflector on Palomar Mountain (US), that instrument
finally completed in 1948. The 200-inch telescope produced the
first observations of galaxy evolution -- the first evidence that
galaxies observed at high *redshift are unlike galaxies closer to
us in time. An even greater accomplishment of the 200-inch
telescope was a series of observations concerning the spectra of
*quasars, and the evidence for their immense distances and
luminosities. Theorists eventually proposed that quasars were
*black holes of 100 million solar-masses or more. It is now clear
that most galaxies with a central bulge, including our own
Galaxy, harbor massive black holes at their cores. 4) In 1961,
Allan Sandage published a landmark paper outlining the
possibility of testing cosmological models with the 200-inch
telescope, and over the next two decades Sandage devoted himself
to this project. Unfortunately, the underlying premise of the
project -- that the brightest galaxy in every galactic cluster
has about the same true luminosity -- was demonstrated by
*Beatrice Tinsley (1941-1981) to be untenable. 5) In the fall of
1977, at a Yale University (US) conference on the evolution of
galaxies, Harvey Butcher and Augustus Oemler presented their
evidence for relatively young star-forming galaxies. This
evidence, which implied strong galaxy evolution during relatively
recent cosmic time, met with controversy and skepticism. 6) In
the 1980s, observations by various groups proved that Butcher and
Oemler were correct, and it was now understood that these
relatively young galaxies were often producing new stars in huge
bursts. These bursting galaxies are evidently spirals with a more
disheveled appearance than is common today, and in their twisted
and distorted disks huge numbers of stars were recently born. 7)
During the past 2 years, among the most interesting results of
various observations with various instruments is the formulation
of the so-called Madau diagram (popularized by Piero Madau) that
plots the Universe-wide rate of star formation from early times
to today, spanning almost the whole history of the cosmos. The
rate of star formation apparently rose rapidly in the first few
billion years, the peak rate at about 5 or 6 billion years later
at redshifts of 1 to 2. (Our Sun apparently formed at a time
corresponding approximately to redshift = 0.5.) The author
concludes: "Our generations are fortunate to live to see one of
the great mysteries of where we came from in process of being
solved."
QY: Alan Dressler, Carnegie Observatories, Pasadena, Ca. US.
(Sky & Telescope October 1998) (Science-Week 11 Sep 98)

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Related Background:

... ... *Edwin Hubble (1889-1953): Hubble first studied law
before switching to astronomy at the age of 25. He began his work
at the Mount Wilson Observatory with the 100-inch telescope at
the age of 30. In 1941, at the age of 52, he tried to join the US
Army to fight the Nazis, but he was persuaded that he could do
more in war-related research. 
... ... *George Ellery Hale (1868-1938): Hale is best known for
his work building large-telescopes (and for obtaining the funds
for the Yerkes Observatory, named after the street-car magnate
Charles Tyson Yerkes), but already at the age of 21 he invented
the spectroheliograph, a device that made it possible to
photograph the light of a single spectral line of the sun, and he
made several ground-breaking observations with this instrument.
... ... *George Lemaitre (1894-1966): Lemaitre began his
professional life as a civil engineer, then at 21 he switched to
physics and mathematics. He also became a Roman Catholic priest
at the age of 22. After obtaining his PhD at the Massachusetts
Institute of Technology in 1927, he settled in Belgium as a
professor of astrophysics at the University of Louvain. At the
time of his death, he was president of the Pontifical Academy of
Sciences at Rome. Lemaitre's theoretical ideas concerning the
origin of the Universe were published in 1927, when he was 31,
but the paper was largely unnoticed until the astrophysicist
Arthur Eddington (1882-1944) called attention to it much later.
... ... *redshift: Redshift (symbol: z) is a lengthening of the
wavelengths of electromagnetic radiation from a source caused
either by the movement of the source (Doppler effect) or by the
expansion of the universe (cosmological redshift). Redshift is
defined as the change in wavelength of a particular spectral line
divided by the unshifted wavelength of that line. Large redshifts
imply large radial velocities (which imply large distances,
according to current cosmological theory), but at redshifts
greater than about 0.2 there is a relativistic divergence from a
linear relation. A redshift of 4.0 corresponds to an object
receding with a radial velocity 92% that of the velocity of
light. The largest astrophysical redshifts so far observed are of
the order of z = 4.9.
... ... *quasars: (quasi-stellar objects). Extremely luminous
sources radiating energy over the entire spectrum from x-rays to
radio waves, and which are apparently the oldest and most distant
objects in the universe.
... ... *black holes: If the terminal stages of star death leave
a remnant star mass greater than 3 solar-masses, the ultimate
gravitational collapse will produce a black hole, a relativistic
singularity. A black hole is a localized region of space from
which neither matter nor radiation can escape. The "trapping"
occurs because the requisite escape velocity, which can be
calculated from the relevant equations, exceeds the velocity of
light and is therefore unattainable. Another view of a black hole
is that it is a mass that has collapsed to such a small volume
that its gravity prevents the escape of all radiation. Space and
time essentially have no meaning in a black hole. The boundary of
the black hole is called the "event horizon", because any event
within the boundary is invisible outside, the invisibility
resulting from the fact that no radiation can escape to be
detected. The radius of the black hole depends upon how much
matter has fallen into the region; it is called the "Schwarzchild
radius", and it is usually a few kilometers. However, massive
black holes are possible and are thought to be the source of
quasars. If quasars indeed involve black holes, the radiation is
from material just outside the black hole, and not from anything
within it. Nothing inside a black hole can get out of it.
... ... *Beatrice Tinsley (1941-1981): During her short life,
Tinsley managed to be a force in astronomy from her first entry
into the field. At the age of 25, an unknown graduate student at
the University of Texas, she rose before an audience about to
hear Allan Sandage and publicly challenged his idea that giant
elliptical galaxies exhibited luminosities constant enough to be
used as "standard candles" to estimate distances. She proved her
point by the age of 36, and the variability of galaxy
luminosities became the consensus view. It was Tinsley who co-
hosted the 1977 Yale conference that set the course of galaxy-
evolution studies. She died 4 years later of cancer. Near the
end, she wrote the following: "Let me be like Bach, creating
fugues; till suddenly the pen will move no more."


3. ON GLOBULAR STAR CLUSTERS
A galactic halo, such as that associated with our own Galaxy, is
a spheroidal distribution of old stars and globular clusters of
old stars surrounding the galaxy. In the case of our own Galaxy,
the galactic halo has a radius of approximately 50,000 light
years. The globular clusters of old stars are near-spherical
clusters containing from 10^(5) to 10^(7) stars in gravitational
association and moving en masse. They are found in our own
Galaxy, and also in other galaxies, and the consensus is that
such globular clusters are at least 10 billion years old.
... ... S. George Djorgovski reviews current research concerning
globular clusters, and makes the following points: 1) The oldest
star systems known, globular clusters witnessed the birth of our
Galaxy, and they now serve as laboratories for theories of
stellar dynamics and evolution. 2) The apparent simplicity of
globular clusters has enticed astronomers to construct
mathematical models of such systems, and early attempts at
modeling arrived at a basically correct picture: globular
clusters are collections of stars held together by their
aggregate gravity. The members of a cluster move randomly like
molecules of a gas, with Newtonian gravity causing the
interactions that maintain the cluster. 3) The first successful
dynamical models of globular clusters were independently
developed in the early 1960s by Michie, King, and Henon. The
Michie and King models, based on a premise of random interactions
between cluster stars, were quite successful, predicting cluster
structures in excellent agreement with observations available at
that time, and these models are still tenable even with the
superior data now being gathered. The Henon model, which was
developed at the same time as the Michie and King models, was of
a different kind, the Henon simulations predicting that globular
clusters would fall in upon themselves in a process called
"gravothermal catastrophe", or core collapse. Henon's models were
mostly disregarded for more than 20 years, but theoretical
investigations in the 1980s essentially confirmed and extended
Henon's ideas. At the present time, the consensus is that the
models of Michie, King, and Henon explain different aspects of
globular cluster dynamics: globular cluster cores do collapse,
but the collapse is arrested by the presence of one or more *hard
binary star systems that provide energy to counter the collapse.
4) As members of the larger galaxy, globular star clusters are
subject to so-called *gravitational "tidal" shocks, and these
shocks can be effective in hastening the dissolution of clusters.
The 150 or so globular clusters surviving today in our own Galaxy
are probably just a small fraction of those that once populated
the galactic halo. 5) In a globular star cluster, many millions
of stars may occupy a relatively small volume of space, and under
such conditions physical interactions and collisions of stars can
and do occur, with some stars merging, outer envelopes in other
stars stripped away, in other cases close binaries forming, etc.
The result may be a profound effect on stellar evolution, and the
evidence for unusual stellar populations in many clusters is
indeed strong and abundant.
QY: S. George Djorgovski, Calif. Inst. of Technology 818-395-6811
(Sky & Telescope October 1998) (Science-Week 11 Sep 98)

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Related Background:

... ... *hard binary star systems: This refers to binary star
systems with binding energies larger than the average among stars
in the cluster.
... ... *gravitational "tidal" shocks: The essential idea here is
that the gravitational field in a galaxy is not uniform, and as
clusters of stars pass through nonuniformities, gravitational
interactions within the cluster can be severely disrupted.

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Related Background:

ON THE FORMATION OF STAR CLUSTERS
Elmegreen and Efremov (2 installations, US RU) review current
views concerning the formation of star clusters. Star clusters in
a spiral galaxy such as the Milky Way are found in the halo and
the disk. The Milky Way's halo contains about 200 globular
clusters that appear to be as old as the Galaxy itself
(approximately 13 billion years). In contrast, the Galactic disk
contains younger star groups arranged in open clusters,
associations, and complexes. The authors suggest that all star
clusters, regardless of age and appearance, can be explained by
the same basic mechanism: the structuring of star-forming gas
into a hierarchical distribution of clouds by the actions of
turbulence and gravity. A third influence is involved in
"triggered" star formation, a mode of star birth that follows the
direct compression of gas by an outside source such as hot young
stars or supernovas. These outside sources can move gas around,
leading to the formation of new gas clouds out of low-density
material, or to fast collapse and star formation inside pre-
existing clouds. Many examples of apparent triggered star
formation exist in our Galaxy and other nearby galaxies.
QY: Bruce Elmegreen, IBM T.J. Watson Research Cntr, PO Box 218,
Yorktown Heights, NY US.
(American Scientist May/Jun 1998) (Science-Week 1 May 98)

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Related Background:

ON THE BIRTH OF STAR CLUSTERS
A star cluster is a group of stars whose members are close enough
to each other to be physically associated, and the current
consensus is that the stars in a cluster formed together. A
globular cluster is a spherically symmetrical and compact cluster
of stars, the cluster containing from several tens of thousands
to perhaps a million stars, and as in clusters in general, these
stars are thought to share a common origin. The Hubble Space
Telescope, named after the astronomer Edwin Hubble (1889-1953),
was launched from a space shuttle in 1990 into a 600-kilometer
low-Earth orbit and has been providing extensive imaging and
spectroscopic observations critical for the development of
astronomy and astrophysics. The new information has concerned hot
stars, stellar chromospheres and coronas, the interstellar
medium, galaxies and galactic clusters, quasars, etc. -- all of
it information uncorrupted by the Earth's atmosphere, which is
the problem for ground based telescopes. ... ... Meylan and
Brandl (2 installations, DE US), in a review of the birth of star
clusters, focus on the nebula NGC 2070 (also known as 30 Doradus
or the "Tarantula Nebula"), and note that it is now known that
this nebula in the nearby galaxy called the Large Magellanic
Cloud is an exceptionally massive and luminous concentration of
ionized hydrogen (showing an "H II" region in the spectrum) where
thousands of stars are in the process of being born, and that
recent observations by the Hubble Space Telescope indicate that
in NGC 2070 the birth of a globular star cluster may be
occurring.
QY: Georges Meylan, European Southern Observatory, Garching DE
(Sky & Telescope March 1998) (Science-Week 30 Jan 98)


4. ON THE FUTURE OF CARBON NANOTUBE CHEMISTRY
Fullerenes are large molecules composed entirely of carbon, with
the chemical formula C(sub n), where n is any even number from 32
to over 100. They apparently have the structure of a hollow
spheroidal cage with a surface network of carbon atoms connected
in hexagonal and pentagonal rings. Carbon nanotubes are similar
to fullerenes, except their shape is tubular. They were first
discovered by Sumio Iijima (NEC Laboratories, JP) in 1991, they
come in both multi-walled and single-walled versions, and they
have diameters of the order of 10 to 30 nanometers.
... ... Robert F. Service (*Science*, US) reviews the reasons for
current excitement concerning nanotubes and recent research in
the field, and makes the following points: 1) Carbon nanotubes
are stronger than steel; lightweight; able to withstand repeated
bending, buckling, and twisting; can conduct electricity as well
as copper, or semiconduct like silicon; and they transport heat
better than any other known material. 2) The possible important
applications of carbon nanotubes include superstrong cables,
wires for microscale electronic devices, charge storage devices
in batteries, and microscale electron guns for flat-screen
television. 3) The key to the potential applications of carbon
nanotubes lies in the unique structure of carbon nanotubes and in
the possible defects in that structure that confer special
properties. The structure itself depends on the unique properties
of carbon. Under intense pressure, carbon atoms form bonds with 4
neighboring atoms to produce diamond. Under special conditions,
however, sheet-like carbon structures involving 3-bonded carbon
can be formed (graphite), and with still further specialization
of conditions,  these sheets organize into spherical (fullerene)
or tubular (nanotube) arrays. One critical aspect of the 3-bonded
carbon array is that the nature of the bonding produces a cloud
of unpaired electrons floating above and below the sheet, and
these electrons are mobile enough to make the material a good
electrical conductor. The importance of defects in this context
is that specifically designed defects in the carbon arrays can
alter the physical properties of these arrays, including the
electrical properties -- all in a controlled manner. It has
recently been reported, for example, that single-walled carbon
nanotubes can function not only as conductors but also as
semiconductors, depending on the conditions, which is of
considerable significance for the possible use of carbon
nanotubes as semiconductor switches in computer devices. It has
also been possible to form hybrid carbon nanotubes such that one
end of the tube behaves as a metallic conductor while the other
end of the tube behaves as a semiconductor, and such tubes have
the potential to act as molecular diodes, devices that allow
electric current to flow in one direction, from a semiconductor
to a metal but not in reverse. 4) Perhaps of greatest interest is
the recent demonstration by Heer et al (Georgia Institute of
Technology, US), confirming theoretical predictions, that carbon
nanotubes can carry current at room temperature with essentially
no resistance. The mechanism for this involves so-called
"ballistic transport", which refers to the passage of electrons
through a semiconductor whose length is less than the mean free
path of electrons in the system, so that most of the electrons
pass through the semiconductor without scattering. 5) At the
present time, one critical aspect of carbon nanotube research is
that before the mentioned potential applications can be achieved,
the technology of carbon nanotube production must be improved so
that carbon nanotubes are available in bulk quantities for
materials research and development. At the present time, single-
walled carbon nanotubes are commercially available for
approximately US$200 per gram. This price needs to be severely
reduced by technological advances before these new structures can
be fully developed for practical use.
QY: Robert F. Service 
(Science 14 Aug 98 281:940) (Science-Week 11 Sep 98)

-------------------

Related Background:

A SINGLE-WALL CARBON NANOTUBE ROOM-TEMPERATURE TRANSISTOR
Carbon nanotubes are similar to fullerenes, except their shape is
tubular. They were first discovered by Sumio Iijima (NEC
Laboratories, JP) in 1991, they come in both multi-walled and
single-walled versions, and they have diameters of the order of
10 to 30 nanometers. The use of individual molecules as
functional electronic devices was first proposed by Aviram and
Ratner in 1974. Since then, molecular electronics has attracted
much interest, particularly because it could lead to conceptually
new miniaturization strategies in the electronics and computer
industry. But the realization of single-molecule devices has
remained a challenge, largely owing to difficulties in achieving
electrical contact to individual molecules. Recent advances in
nanotechnology, however, have resulted in electrical measurements
on single nano-scale molecules. ... ... Tans et al (3 authors at
Delft University of Technology, NL) report the fabrication of a
field-effect transistor -- a 3-terminal switching device -- that
consists of one semiconducting single-wall carbon nanotube
connected to 2 metal electrodes. By applying a voltage to a gate
electrode, the nanotube can be switched from a conducting to an
insulating state. The device operates at room temperature,
thereby meeting an important requirement for potential practical
applications. Electrical measurements on the nanotube transistor
indicate that its operation characteristics can be qualitatively
described by the semi-classical band-bending models currently
used for traditional semiconductor devices, an unexpected result.
The authors suggest the fabrication of this 3-terminal switching
device at the level of a single molecule represents an important
step towards molecular electronics.
QY: Cees Dekker (dekker@qt.tn.tudelft.nl)
(Nature 7 May 98 393:49) (Science-Week 29 May 98)

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Related Background:

ELASTICITY, STRENGTH, AND TOUGHNESS OF NANO-STRUCTURES
There has been much excitement in recent years concerning the
possible applications of so-called "nano-structures". Carbon
nanotubes are similar to fullerenes, except their shape is
tubular. They were first discovered by Sumio Iijima (NEC
Laboratories, JP) in 1991, they come in both multi-walled and
single-walled versions, and they have diameters of the order of
10 to 30 nanometers. They may be the strongest materials ever
produced, and depending on their geometry, their electrical
behavior can be that of a metal, a semiconductor, or an
insulator. Nanorods are similar to nanotubes, except they are
solid rather than hollow. Atomic force microscopy is a method of
mapping surface atomic structure by measuring the force acting on
the tip of a sharply pointed probe as it is moved over the
surface. Eric W. Wong et al (Harvard University, US) have now
used atomic force microscopy to determine the mechanical
properties of individual structurally isolated silicon carbide
nanorods and multi-wall carbon nanotubes pinned at one end. The
authors found carbon nanotubes to have particularly high energy-
absorbing capability, and they suggest that both nanorods and
nanotubes should have great potential in mechanical applications.
QY: Charles M. Lieber 
(Science 26 Sep 97) (Science-Report 17 Oct 97)

-------------------

Related Background:

CONDUCTIVITY ENHANCEMENT IN METAL-DOPED CARBON NANOTUBES
As we have indicated in earlier reports, carbon nanotubes are
graphite-like sheets of hexagonally bonded carbon rolled up into
tubes of nanometer dimensions. They can now be synthesized as
single-walled or multi-walled tubes with specific diameters, and
the chemists who work with these molecular structures believe
they will eventually revolutionize a number of technologies. This
week R. S. Lee et al (University of Pennsylvania US; Rice
University, Houston TX) report that doping of single-walled
carbon nanotubes with bromine and potassium produces what are
essentially synthetic metals. In a second paper by an associated
group, A. M Rao et al (various installations in US, JP) report
that examination of metal-doped nanotube bundles using Raman
scattering indicates charge transfer mechanisms are responsible
for the metal-like behavior. R. E. Smalley (Rice University, TX),
who received the Nobel Prize in Chemistry for his work with
fullerenes (spherical carbon structures related to the nanotubes)
is associated with both groups, and one of the authors of both
papers. Now that nanotube synthesis is apparently maturing, we
can expect a flood of new reports on their electrical properties
under various conditions.
(Nature 17 Jul 97) (Science-Week 25 Jul 97)

-------------------

Related Background:

VARIABLE ELECTRONIC PROPERTIES OF MOLECULAR CARBON NANOTUBES
Fullerenes ... were discovered by Richard E. Smalley, who
received the Nobel Prize in Chemistry for the discovery in 1996.
Carbon nanotubes are similar to fullerenes, except their shape is
tubular. They were first discovered by Sumio Iijima (NEC
Laboratories, JP) in 1991, they come in both multi-walled and
single-walled versions, and they have diameters of the order of
10 to 30 nanometers. They may be the strongest materials ever
produced, and depending on their geometry, their electrical
behavior can be that of a metal, a semiconductor, or an
insulator. Richard E. Smalley, the discover of fullerenes, is at
Rice University (TX US), and a recent workshop sponsored by Rice
and the U.S. Office of Naval Research was devoted to carbon
nanotubes. Smalley is convinced that carbon nanotubes have the
potential to change the future of humanity, and apparently the
chemists working with these new molecular forms are in agreement
with him, and consider the chemistry of carbon nanotubes as the
first step to a science of molecular devices.
(Chem. & Eng. News 30 June) (Science-Week 10 Jul 97)
 

5. EXPERIMENTAL COAXIAL NANOCABLES
Zhang et al (4 authors at 2 installations, JP FR) report the
synthesis of multi-element nanotubes comprising multiple phases,
with diameters of a few tens of nanometers and lengths up to 50
microns. The experimentally determined structure consists of a
silicon carbide core, an amorphous silicon oxide intermediate
layer, and graphite outer shells made of boron nitride and carbon
layers separated in a radial direction. The structure resembles
a
coaxial nanocable with a semiconductor-insulator-metal (or
semiconductor-insulator-semiconductor) geometry, and the authors
suggest this may have applications in nanoscale electronic
devices that can take advantage of this self-organization
mechanism for multi-element nanotube formation. The authors
further suggest that although many details are still unknown, it
is evident that the phases formed are all controlled by chemical
reactions, and that self-organization of nanocables with
different components is possible by changing the starting
materials. The electronic properties of the nanocable can
therefore be tailored by combining various nanowires and
nanotubes.
QY: Y. Zhang 
(Science 14 Aug 98 281:973) (Science-Week 11 Sep 98)


6. MOLECULAR BIOLOGY: ON THE WORKINGS OF THE RIBOSOME
A ribosome (not to be confused with riboZYME) is a small particle
found in all living cells, a complex of various ribonucleic acid
component subunits and proteins that functions as the site of
protein synthesis. Each ribosome particle is approximately 30
nanometers in diameter, and each particle essentially functions
as a translating unit, translating RNA sequence code into a
protein polymer sequence. ... ... Joachim Frank (State University
of New York Albany, US) presents a review of current
understanding of ribosome function and structure, the author
making the following points: 1) Although it is important to know
the structure of the ribosome at atomic resolutions, this goal is
still quite remote, since even one of the simplest ribosomes,
that of the bacterium Escherichia coli, is made up of more than
50 components, mostly proteins plus 3 large RNA molecules.
Ribosomes of higher organisms are even more complex and have more
components. 2) It is now believed that all important functions of
the ribosome actively involve the ribosomal RNAs as major
players, whereas the ribosomal proteins act either as structural
"glue" or as "helpers" that promote specific binding reactions.
This represents a complete reversal of the long-held view that
the proteins of the ribosome perform all the important tasks. 3)
The translation from the nucleotides of messenger RNA (mRNA) to
the amino acids in the protein polypeptide chain is accomplished
at the ribosome with the help of an adaptor molecule called
"transfer RNA" (tRNA). The molecule tRNA exists in 20 varieties,
each variety specifically designed to accommodate only one of the
20 amino acids at one end of the tRNA molecule, and each tRNA
molecule also carries a specific *anticodon at the other end of
the molecule that recognizes only the *codon on mRNA specifying
that particular amino acid. Each tRNA molecule thus acts as a
physical code-link between an mRNA codon for an amino acid and
that specific amino acid, the assembly of the protein polymer
involving the sequential selection of amino acids from the
ambient amino acid pool. 4) The author reviews an application of
the technique of cryo-electron microscopy to the determination of
ribosome structure, the application involving methods of "single-
particle reconstruction" developed by the author. Cryo-electron
microscopy provides a means to image macromolecules in a "close-
to-native" conformation by freezing the molecules rapidly in
liquid ethane at -196 degrees Celsius. The technique was first
developed in the 1970s by Glaeser et al, and then perfected early
in the 1980s by Dubochet et al. The method of single-particle
reconstruction essentially involves the idea that in principle
the 3-dimensional geometry of a macromolecule can be
reconstructed from its projections on a 2-dimensional surface,
provided the molecule occurs in a range of orientations and
provided these orientations are known. The author reviews in
detail what is known concerning the workings of the ribosome
during protein synthesis as amplified by recent data involving
the application of cryo-electron microscopy coupled with
techniques of single-particle geometric reconstruction.
QY: Joachim Frank, Wadsworth Center, Howard Hughes Medical
Institute, PO Box 509, Albany, NY 12201-0509 US.
(American Scientist Sep/Oct 1998 86:428) (Science-Week 11 Sep 98)

-------------------

Related Background:

... ... *codon and anticodon: A codon is the coding unit of
messenger RNA, comprising a triplet of nucleotides that pairs
with a corresponding triplet (anticodon) of transfer RNA. The
term "codon" is also in more general use as the basic genetic
coding unit, a triplet of nucleotides in DNA.


7. ON HONEYBEE SOCIAL BEHAVIOR, GENES, AND THE ENVIRONMENT
The so-called social insects live in societies that rival human
societies in complexity and internal cohesion. Honey bees, for
example, apparently always follow 3 rules: a) they live in
colonies with overlapping generations; b) they care cooperatively
for offspring other than their own; and, c) they maintain a
reproductive division of labor. ... ... In a review of research
(much of it from the author's own laboratory) concerning the
genetic and environmental factors responsible for honey bee
behavior, Gene E. Robinson (University of Illinois Urbana-
Champaign, US) makes the following points: 1) Genes do not play
an exclusive role in regulating behavior: biologists have long
realized that behavior is influenced by genes, the environment,
and interactions between the two. 2) Genes never act alone. They
must operate in an environment where they code for proteins that
participate in many systems in an organism, with these systems in
turn influencing the expression of genes. Consequently,
biologists must take a broad approach in assessing the impact of
any gene. 3) The research group of the author uses the Western
honey bee, Apis mellifera. Honey bees pass through different life
stages as they age, and their behavioral responses to
environmental and social stimuli change in predictable ways.
Although worker bees go through a consistent path of behavioral
development, this path is not rigidly determined. Bees can
accelerate, retard, or even reverse their behavioral development
in response to changing environmental and colony conditions. 4)
Experimental evidence indicates that *juvenile hormone, one of
the most important hormones influencing insect development, helps
time the pace of behavioral maturation in honey bees. The rate of
endocrine-mediated behavioral development is influenced by
inhibitory social interactions. Older bees inhibit the behavioral
development of younger bees: the rate of behavioral development
is negatively correlated with the proportion of older bees in a
colony. Inhibitory social interactions that influence the rate of
behavioral development involve chemical communication between
colony members. 5) Evidence from the laboratory of the author in
1993 indicated the so-called mushroom bodies in the bee brain are
involved in the behavioral changes occurring during maturation,
the volume of the bodies increasing, and the volume increase
associated with an increase in synapses with neurons from brain
regions devoted to sensory input. The author suggests this was
the first report of brain plasticity in an invertebrate. 6) The
author suggests that, in general, two-way interactions between
the nervous system and the genome contribute fundamentally to the
control of social behavior. Information about social conditions
that is acquired by the nervous system is likely to induce
changes in genomic function that in turn produce adaptive
modifications of the structure and function of the nervous
system. 7) The author proposes a new research initiative called
"sociogenomics", defined as a "wide-ranging approach to identify
genes that influence social behavior, determining the influence
of these genes on underlying neural and endocrine mechanisms, and
exploring the effects of the environment -- particularly the
social environment --  on gene action."
QY: Gene E. Robinson, Dept. of Entomology, Univ. of Illinois
Urbana-Champaign 217-333-3090.
(American Scientist Sep/Oct 1998 86:456)
(Science-Week 11 Sep 98)


8. SIGNIFICANCE OF ESTROGEN FOR MALE BONE MASS
In humans, during childhood and young adulthood, the skeleton
accrues virtually all the bone mineral it will ever have. Since
the aging process is associated with bone loss, the more bone
mass one gains in the formative years, the less likely the
increased bone resorption and decreased bone formation will
result in *osteoporosis. Thus, the failure to achieve optimal
peak bone mass is a pathogenic mechanism in osteoporosis. The sex
steroids are critically important in helping to establish peak
bone mass for both sexes. Girls with *estrogen deficiency do not
achieve optimal peak bone mass. Similarly, achievement of peak
bone mass is compromised in boys with *hypogonadism and in boys
whose puberty is delayed. To clearly demonstrate the importance
of estrogens in establishing peak bone mass in growing males, it
is important to show that replacement of estrogen, in the setting
of lifelong estrogen deficiency, leads to restoration of bone
mass. ... ... Bilezikian et al (4 authors at 2 installations, US)
report the results of a study in which a young man with severe
*aromatase deficiency was treated with *conjugated estrogen for 3
years. The authors report that bone mass in the patient increased
dramatically at all sites. The patient reported no side effects
from estrogen therapy. He did not gain weight, did not develop
*gynecomastia, or have mood disturbances. He had no change in
libido or sexual orientation. The authors suggest this case
illustrates the essential role of estrogens in skeletal
development in males. From this and other studies, they conclude
that estrogen is essential for the establishment of peak bone
mass in growing boys, as well as for the maintenance of bone mass
in adult men.
QY: John P. Bilezikian, Columbia Univ. 212-854-1754.
(New England J. Med. 27 Aug 98 339:599)
(Science-Week 11 Sep 98)

-------------------

Related Background:

... ... *estrogen: Hormones are signaling molecules secreted into
the blood stream by endocrine cells and acting on target cells
that possess receptors for the hormone. Estrogen is a collective
term for the female hormones, the most powerful of which is
estradiol. They control female secondary sexual characteristics,
and prepare and maintain the uterine lining.
... ... *osteoporosis: This is a generalized progressive
diminution in bone tissue mass per unit volume causing skeletal
weakness. The ratio of mineral to organic elements is unchanged
in the remaining morphologically normal bone. Bone resorption is
increased, while bone formation may be normal or defective. The
major clinical manifestations of osteoporosis are bone fractures.
... ... *hypogonadism: In general, this is inadequate gonadal
function. In this context, hypogonadism in prepubertal males
produces an altered body form characterized by a short trunk and
long limbs.
... ... *aromatase: An enzyme which can convert testosterone into
estrogen. It is evidently of considerable developmental
importance in many species.
... ... *conjugated estrogen: An amorphous preparation of
naturally occurring water-soluble forms of mixed estrogens
obtained from the urine of pregnant mares. The principal estrogen
present is sodium estrone sulfate.
... ... *gynecomastia: Excessive development of the male mammary
glands.

-------------------

Related Background:

ESTROGEN: BOTH A MALE AND FEMALE HORMONE
... Estrogen affects the growth, differentiation, and function of
peripheral tissues of the reproductive system, including the
mammary gland, uterus, vagina, and ovary. Estrogens also play an
important role in bone maintenance and exert cardioprotective
effects. In the brain, estrogens modulate physiological
parameters important for regulating procreation, including
reproductive behavior, *gonadotropin production and release from
the pituitary, and mood. ... ... Kuiper et al (3 installations,
SE) review recent research on estrogen as a hormone, and the
authors make the following points: 1) As the so-called female sex
hormone, estrogen is best known for its critical role in
influencing female secondary sexual characteristics, reproductive
cycle, fertility, and maintenance of pregnancy. Less well known
are the important actions of estrogen in male tissues such as the
prostate, testis, and *epididymis. 2) Estrogens are essential for
the normal development of bone tissue in the male, in addition to
their well-known role in female bone. 3) The recent unexpected
discovery of a second estrogen receptor protein (*ER-beta) has
advanced understanding of the mechanisms underlying estrogen
signaling. The authors suggest the challenge is to use this
knowledge for the development of the next generation of drugs
targeted to the estrogen receptor.
QY: George G.J.M Kuiper, Karolinska Institute Huddinge, SE.
(Science & Medicine Jul/Aug 1998) (Science-Week 31 Jul 98)

-------------------

Related Background:

... ... *estradiol: 1,3,5(10)-estratriene-3,17beta-diol.
C(sub18)H(sub24)O(sub2). This is the natural hormone -- present
in pure form in the urine of pregnant mares and in the ovaries of
pigs.
... ... *gonadotropin: (gonadotrophin, gonadotrophic hormone)
Refers to a group of hormones capable of promoting growth and
function of the gonads.
... ... *epididymis: An elongated structure connected to the
surface of the testis, it stores and matures sperm cells.
... ... *ER-beta: The first discovered estrogen receptor (ER) has
now been renamed ER-alpha. Both receptors apparently consist of
several functional domains: a transcription activation domain, a
central DNA-binding domain, an estrogen-binding domain. The
second estrogen receptor was first cloned in 1995.


9. EFFECTS OF METHYLMERCURY EXPOSURE FROM FISH CONSUMPTION
Inorganic mercury discharged into lakes, rivers, and oceans is
converted to methylmercury by microorganisms and then bio-
accumulated up the aquatic food chain. Concern about the
potential public health threat from methylmercury arose in the US
in the early 1970s when elevated concentrations were found in
fish in the Great Lakes. At present, recreational fishing in the
US is restricted in many states, and US Food and Drug
Administration guidelines regulate interstate commerce of fish
because of their methylmercury content. A dose-response analysis
has suggested that fetal developmental effects of methylmercury
may occur at maternal hair concentrations as low as 10 ppm,
although there is considerable uncertainty in this estimate. The
average methylmercury hair concentration in the US is at present
1 ppm or less. ... ... Davidson et al (12 authors at 4 install-
ations, US SC SE) report a study of human neurodevelopmental
consequences of exposure to methylmercury from eating fish, the
study consisting of measurement of prenatal and postnatal
methylmercury exposure and 6 standard age-appropriate
neurodevelopmental tests in a total of 711 mother-child pairs in
the Republic of Seychelles, an archipelago in the Indian Ocean
where 85 percent of the population consumes ocean fish daily. The
authors report the mean maternal hair total mercury level was 6.8
ppm, and the mean child hair total mercury level at age 66 months
was 6.5 ppm. The authors report no adverse outcomes at 66 months
were associated with either prenatal or postnatal methylmercury
exposure. The authors suggest results from this study are
relevant for the US and other countries with similar dietary
intake of fish. The major source of methylmercury in Seychelles
is ocean fish, and the average fish methylmercury levels in the
Seychelles islands are similar to those on the US market. The
authors suggest the methylmercury levels of the Seychelles
population is 10 to 20 times higher than in the US because the
Seychelles population consumes more fish, not because they eat a
few fish with abnormally high levels of methylmercury. Thus, the
authors suggest, any potential adverse effects of methylmercury
in fish should be detected in the Seychelles long before such
effects would be seen in the US. The authors suggest their
results for children at 66 months of age strongly support their
previous findings at younger ages, and also support the
observations of other investigators that it would be inadvisable
to forgo the health benefits of fish consumption to protect
against a small risk of adverse effect at the levels of
methylmercury found in ocean fish on the US market.... ... In a
companion editorial comment in the same journal, Kathryn R.
Mahaffey (Environmental Protection Agency, US) points out that
defining the level of exposure for neurodevelopmental toxic
effects is influenced by the types of tests used as the end
points for neurological assessment. Traditional measurements of
child development were the basis of the conclusion by Davidson et
al that no effects were observed following in utero methylmercury
exposures. But use of additional tests designed to identify
subclinical neurocognitive function might provide an expanded
understanding of methylmercury effects. Mahaffey states: "Until
these data are available, current findings from the Seychelles
cohort must be regarded as interim." Mahaffey concludes:
"Advisories that recommend restrictions of fish consumption for
women of child-bearing age because of mercury contamination
should be followed carefully."
QY: Philip W. Davidson 
QY: Kathryn R. Mahaffey 
(J. Amer. Med. Assoc. 26 Aug 98 280:701,737)
(Science-Week 11 Sep 98)


10. SUNLIGHT EXPOSURE AND THE RISK OF EYE LENS OPACITIES
Despite advances in surgical procedures and targeted programs,
*cataract remains the leading cause of visual loss worldwide. In
the US, for example, cataract surgery is responsible for 12
percent of the Medicare budget (data for 1991). Exposure to *UV-B
radiation in sunlight has been shown to increase the risk of
cataract formation in high-risk occupational groups, but the risk
to the general population has not yet been quantified.
... ... West et al (7 authors at Johns Hopkins University, US)
report a study to determine the ocular exposure to UV-B radiation
in sunlight for a population of older persons, and to determine
the association between UV-B radiation and lens opacities. The
research group consisted of a total of 2520 community-dwelling 65
to 84 year old adults in Salisbury, Maryland (US) from 1993 to
1995. The study involves detailed quantitative assessment of all
apparently relevant factors, including the correlation variables.
The authors report that the odds of lens opacity increased with
increasing ocular exposure to UV-B (odds ratio = 1.10). Analysis
of the ocular dose by each age group after the age of 30 years
(based on questionnaires concerning past subject job history)
showed no vulnerable age group, suggesting damage is based on
cumulative exposure. The authors suggest their results add to the
growing body of knowledge that indicates even low levels of UV-B
radiation can harm the lens of the eye. The authors suggest
measures to avoid ocular exposure to UV-B radiation are simple:
the wearing of plastic glasses or sunglasses confers excellent
protection, and the mere wearing of a hat with a brim decreases
ocular exposure by 30 to 50 percent. The authors conclude: "These
measures should be part of any public health program to increase
awareness of sun damage and avoid unhealthy consequences."
QY: Sheila K. West 
(J. Amer. Med. Assoc. 26 Aug 98 280:714)
(Science-Week 11 Sep 98)

-------------------

Related Background:

... ... *cataract: In general, cataract is any developmental or
degenerative opacity of the lens of the eye. The cause of
degenerative cataract may be aging, exposure to x-rays, heat from
infrared exposure, systemic disease (e.g., diabetes mellitus),
various inflammations of the internal eye, and systemic
medication (e.g., corticosteroids).
... ... *UV-B radiation: In medical science, the ultraviolet part
of the spectrum is partitioned into 3 regions: UV-A is radiation
of wavelength 320-400 nanometers, causing skin tanning but only
weakly sunburn producing or carcinogenic; UV-B is radiation of
wavelength 290-320 nanometers, most effectively causing sunburn
and tanning, and carcinogenic for fair skin; UV-C is radiation of
wavelength 200-290 nanometers, and this radiation does not reach
the surface of the Earth from sunlight. UV-C radiation produced
by mercury arc lamps is germicidal, causes sunburn, and may cause
photokeratitis (light-induced inflammation of the cornea).

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