ScienceWeek

SCIENCE-WEEK

A Weekly Email Digest of the News of Science

A journal devoted to the improvement of communication
between the scientific disciplines, and between scientists,
science educators, and science policy-makers.

January 19, 2000 -- Vol. 5 Number 3

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Should we force science down the throats of those
who have no taste for it? Is it our duty to drag
them kicking and screaming into the 21st century?
I am afraid that it is.
-- George Porter

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Section 1
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Contents of this Issue (Full reports in Section 2):

1. COSMOLOGY: CONFIRMATION OF BIG-BANG MODEL PREDICTION OF
INCREASED BACKGROUND RADIATION TEMPERATURE AT HIGH REDSHIFT
The existence of the cosmic microwave background radiation is a
fundamental prediction of hot Big Bang cosmology, and the
background temperature should increase with increasing redshift.
At the present time (redshift z = 0), the temperature has been
determined with high precision to be 2.726 +- 0.010 degrees
kelvin. Researchers now report the detection of absorption lines
from the first and second fine-structure energy levels of neutral
carbon atoms in an isolated cloud of gas at redshift z = 2.3371.
The authors suggest their data indicate the cosmic microwave
background radiation was indeed warmer in the past: they find
that the cosmic microwave background temperature at z = 2.3371 is
between 6.0 and 14 degrees kelvin, and they point out this is in
accord with the temperature of 9.1 degrees kelvin predicted by
hot Big Bang cosmology. (Nature 21/28 Dec 00 408:931)

2. ASTROPHYSICS: DISCOVERY OF A NEW KIND OF BLACK HOLE
Astrophysicists have categorized black holes into 3 types:
ordinary stellar black holes; supermassive black holes of unknown
origin; and Hawking mini black holes of microscopic dimensions.
Now a Japanese-British-US collaboration using the Chandra X-Ray
Observatory has in press a report of the first strong evidence of
a middleweight black hole, the object an x-ray source 500 light
years off galactic center in the galaxy M82. Luminosity
measurements imply an Eddington lower mass limit of 500 to 900
solar masses for this object, which suggests the object is an
intermediate-mass black hole. (Physics Today November 2000)

3. QUANTUM PHYSICS: KONDO PHYSICS IN CARBON NANOTUBES
Researchers report that electrically-contacted single-walled
carbon nanotubes can serve as powerful probes of Kondo physics,
demonstrating the universality of the Kondo effect. Arising in
the prototypical case from the interaction between a localized
impurity magnetic moment and delocalized electrons in a metallic
host, the Kondo effect has been used to explain enhanced low-
temperature scattering from magnetic impurities in metals, and
also occurs in transport through semiconductor quantum dots. The
far greater tunability of quantum dots (in this case, nanotubes)
compared with atomic impurities makes new classes of Kondo-like
effects accessible to study. (Nature 16 Nov 00 408:342)

4. BIOCHEMISTRY: ON THE PUZZLES OF HYPERTHERMOPHILES
Evolution gives no clue as to how life can thrive near and above
100 degrees centigrade. Most microbes, and all eukaryotic cells,
cannot survive at temperatures much above 50 degrees centigrade
because of the general instability of biological molecules. The
3-dimensional structure of most enzymes and other proteins are
lost at temperatures much above 70 degrees centigrade, and the
double-helical structure of DNA has a comparable lack of
stability in _in vitro_ studies. There are also a wide variety of
ubiquitous metabolites that are rapidly hydrolyzed at
temperatures above 90 degrees centigrade. How do
hyperthermophilic cells circumvent these problems?
(Proc. Natl. Acad. Sci. US 21 Nov 00 97:12961)

5. CELL BIOLOGY: TELOMERES AND THE FATE OF BIOLOGICAL CELLS
A new way to link telomeres to cellular senescence is proposed.
The central concept is that the telomere is a dynamic
nucleoprotein complex that can switch stochastically between two
states, capped and uncapped. Capping is functionally defined as
preserving the physical integrity of the telomere, allowing cell
division to proceed. However, regulated uncapping occurs normally
in dividing cells, with the crucial property of a functional
telomere being a high probability that it will rapidly switch
back to a capped state. Left uncorrected too long, the uncapped
state elicits cell-cycle arrest or other responses.
(Nature 2 Nov 00 408:53)

6. PUBLIC HEALTH:
THE BURDEN OF DISEASE IN INDIA FROM INDOOR AIR POLLUTION
In India, air pollution has become a major concern in recent
years both because it is now clear that large parts of the Indian
urban population are exposed to some of the highest pollutant
levels in the world, and also because new studies around the
world on the health effects of air pollution have increased
confidence in estimates of the risks posed by air pollution
exposures. The situation in China and a number of other
developing countries is similar. In a new report, conservative
estimates indicate that some 400,000 to 500,000 premature deaths
can be attributed annually to the use of biomass fuels in these
population groups. (Proc. Natl. Acad. Sci. US 21 Nov 00 97:13286)

7. IN FOCUS: ON ELECTRICITY AND NEUROPHYSIOLOGY

8. FROM THE SCIENCEWEEK ARCHIVE: 
MATHEMATICS: ON KURT GODEL AND THE LIMITS OF LOGIC

9. BOOK NOTICES: NEUROSCIENCE; THEORETICAL PHYSICS

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Section 2
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1. COSMOLOGY: CONFIRMATION OF BIG-BANG MODEL PREDICTION OF
INCREASED BACKGROUND RADIATION TEMPERATURE AT HIGH REDSHIFT
     What is known as the "cosmic microwave background radiation"
was discovered accidentally in 1964, when A.A. Penzius and R.
Wilson, measuring noise that might interfere with satellite
communications, noted a mysterious signal that was soon
interpreted to be the microwave background radiation originating
in the Big Bang. In 1978, Penzius and Wilson received the Nobel
Prize in Physics for this discovery. The cosmic microwave
background is black-body radiation (the emission radiation of a
perfect absorber of radiation) at a present temperature of 2.73
degrees Kelvin, and has an almost equal intensity in all
directions in space. The Big Bang theory is the general
cosmological model that proposes that all matter and radiation in
the universe originated in an explosion at a finite time in the
past, and the "hot Big Bang" model proposes that the present
Universe has cooled from an intensely hot initial state.
     "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. As observers of redshift, we are by definition at redshift
z = 0.
     In spectroscopy, the term "fine structure" refers to the
splitting of the main spectral lines of an atom into two or more
components, each component representing a slightly different
wavelength. In general, fine structure is produced when an atom
emits light in making the transition from one energy state to
another. The split lines, which are called the "fine structure"
of the main lines, arise from the interaction of the orbital
motion of an electron with the quantum mechanical "spin" of that
electron ("spin-orbit coupling"): in essence, the spinning
electron interacts with the magnetic field produced by the
rotation of the electron about the atomic nucleus, and this
interaction generates the fine structure of the spectrum.
     Given the hot Big Bang model, which proposes an intensely
hot beginning for the Universe, and the cosmic microwave
background radiation, which shows the present Universe with a
background temperature of 2.73 degrees kelvin, one can state the
following: If it is true that the Universe was intensely hot in
the beginning and has now cooled, then at some time in the past
the cosmic microwave background radiation must have had a higher
temperature than 2.73 degrees kelvin. Can we detect, even
indirectly, such a higher-temperature background radiation?
... ... R. Srianand et al (3 authors at 3 installations, IN FR
DE) now report measurements of the cosmic microwave background
radiation temperature at a redshift of 2.34. The authors make the
following points:
     1) The authors point out that the existence of the cosmic
microwave background radiation is a fundamental prediction of hot
Big Bang cosmology, and the background temperature should
increase with increasing redshift. At the present time (redshift
z = 0), the temperature has been determined with high precision
to be 2.726 +- 0.010 degrees kelvin. In principle, the background
temperature can be determined using measurements of the relative
populations of atomic fine-structure levels, which are excited by
the background radiation. But all previous measurements have
achieved only upper limits, thus still formally permitting the
background radiation temperature to be constant with increasing
redshift.
     2) The authors report the detection of absorption lines from
the first and second fine-structure energy levels of neutral
carbon atoms in an isolated cloud of gas at redshift z = 2.3371.
The authors report they also detected absorption due to several
rotational transitions of molecular hydrogen, and fine-structure
lines of singly ionized carbon. The authors suggest these
constraints enable them to determine that the background
radiation was indeed warmer in the past: they find that the
cosmic microwave background temperature at z = 2.3371 is between
6.0 and 14 degrees kelvin, and they point out this is in accord
with the temperature of 9.1 degrees kelvin predicted by hot Big
Bang cosmology.
-----------
R. Srianand et al: The cosmic microwave background radiation
temperature at a redshift of 2.34.
(Nature 21/28 Dec 00 408:931)
QY: R. Srianand: anand@iucaa.ernet.in
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Summary by SCIENCE-WEEK http://scienceweek.com 19Jan01
For more information: http://scienceweek.com/swfr.htm

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2. ASTROPHYSICS: DISCOVERY OF A NEW KIND OF BLACK HOLE
     The death of supermassive stars must result in collapse,
since no known force can resist gravity in such stars once their
nuclear energy sources are exhausted. For the most massive stars,
the result of this inevitable collapse is the "*black hole", at
the present time the most exotic astronomical object in the
Universe. In recent years, astrophysicists have come to
distinguish ordinary black holes and supermassive black holes,
and these latter objects now reign as the supreme cosmic exotica,
with masses 1 million to nearly 10 billion times the mass of the
Sun, and an origin completely unknown but apparently non-stellar.
An ordinary black hole of stellar origin is expected to have a
mass of a few solar masses with a diameter of only a few
kilometers. In addition to supermassive black holes and stellar-
origin black holes, Stephen Hawking has postulated the existence
of "mini black holes", objects in the mass range 10^(-19) solar-
masses and with radii of 10^(-10) meters. (The mass of the Sun is
approximately 2 x 10^(30) kilograms.)
     The center of our own Galaxy is apparently a supermassive
black hole, and observations indicate that supermassive black
hole growth and galaxy formation in general are closely linked.
     An important theoretical concept in astrophysics is the so-
called "Eddington limit", named after Arthur S. Eddington (1882-
1944), and which is the theoretical upper limit to the luminosity
of a star of given mass, at which limit the outward force of
radiation on the stellar surface just balances the inward force
of gravity. Stars with a greater luminosity would be blown apart
by their own radiation. The Eddington limit for the Sun is 30,000
times its actual luminosity. In this context, what is important
is that the maximum mass of star set by the Eddington limit is
approximately 120 solar masses, so that if, on the basis of
observations or calculations, the mass of some object appears to
be greater than 120 solar masses, then that object cannot be a
star and is assumed to be a black hole.
     In astronomy, an "x-ray source" is any of a class of cosmic
objects that emit radiation at x-ray wavelengths. Since the
atmosphere of the Earth is an efficient absorber of x-rays,
devices to detect x-ray sources must be carried high above the
atmosphere by spacecraft. Advances in instrumentation and
improved observation techniques have led to the discovery of an
increasing number of x-ray sources, and at present thousands of
x-ray sources have been detected. A major type of x-ray source is
apparently the black hole, x-ray emissions arising from the
rapidly spinning accretion disk of hot gases surrounding the
black hole. These accretion disks become a high-energy emission
source and emit x-rays.
     In 1999, the unmanned satellite called the "Chandra X-Ray
Observatory was launched. This instrument was formerly called the
Advanced X-ray Astrophysics Facility, but it was renamed in honor
of the astrophysicist Subrahmanyan Chandrasekhar (1910-1995). The
Chandra instrument is equipped with a nested array of mirrors to
focus x-rays on two cameras that can produce highly detailed
images or high-resolution spectra of sources of x-ray emissions.
... ... Bertram Schwarzschild (Physics Today, US) reviews some
recent observational work by astrophysicists, Schwarzschild
making the following points:
     1) A Japanese-British-US collaboration using the Chandra X-
Ray Observatory has in press (H. Matsumoto et al: Astrophys. J.
Lett.) a report of the first strong evidence of a middleweight
black hole, the object an x-ray source 500 light years off
galactic center in the galaxy M82. Luminosity measurements imply
an Eddington lower mass limit of 500 to 900 solar masses for this
object, which suggests the object is an intermediate-mass black
hole.
     2) The upper mass limit, which has been calculated at 10^(5)
solar-masses, is considered more problematic: The apparent off-
center location of this black hole (500 light years from the M82
galactic center) is what provides the best upper limit of its
mass. In 1975, J. Ostriker and S. Tremaine formulated a relation
between the mass of a celestial object and the rate at which
"dynamical friction" (random gravitational encounters) would
cause the object to migrate toward the center of its galaxy, with
the heaviest objects migrating fastest. From the M82 x-ray source
off-center position and the measured dispersion of stellar
velocities in the galaxy, Philip Kaaret et al (Harvard-
Smithsonian Center for Astrophysics, US) have calculated that the
mass of this source must be less than 10^(5) solar-masses, if it
is nearly as old [10^(10) years] as the galaxy itself. Anything
more massive would have long since settled in at the dynamic
center of the galaxy. But if the object is only a billion years
old, its mass could be as large as 10^(6) solar masses.
     3) Schwarzschild suggests that the evidence for an accreting
intermediate-mass black hole in the M82 galaxy is strong, and if
such objects are as abundant as a recent survey of nearby
galaxies has suggested, "they may soon teach us much about how
galaxies form."
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Betram Schwarzschild: Chandra X-Ray Observatory examines a new
kind of black hole.
(Physics Today November 2000)
QY: Bertram Schwarzschild: pt@aip.org
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Text Notes:
... ... *black hole: A black hole is a space-time *singularity
predicted by Einstein's general theory of relativity, and an
object that, because of its essentially infinite gravitational
field, accretes external matter into itself. Once matter has
disappeared into a black hole, only three original properties can
be ascertained: the total mass, the net electric charge, and the
total angular momentum. (So-called "black-hole emissions" are
really emissions of matter immediately outside the black hole.)
Since all black holes must have mass, there are 4 possible types
of black hole, each type derived from the general relativity
equations: a) a "Schwarzschild black hole" (first derived 1916)
has no charge and no angular momentum; b) a "Reissner-Nordstrom"
black hole (first derived 1918) has charge but no angular
momentum; c) a "Kerr black hole" (first derived 1963) has angular
momentum but no charge; d) a "Kerr-Newman black hole" (first
derived 1965) has both charge and angular momentum. It is
currently believed that real black holes are almost certainly
rotating and have very little electric charge, so that the Kerr
solution should be the most applicable. [Editor's note: the
Schwarzschild of the Schwarzschild black hole is Karl
Schwarzschild (1873-1916). K. Schwarzschild was the first to
provide a solution of the complex partial differential equations
by which the general theory of relativity is expressed
mathematically. K. Schwarzschild also introduced the idea of what
is now called the "Schwarzschild radius": when a star is
contracting under the effect of gravity, at a particular radius
(Schwarzschild radius) the gravitational potential will become
infinite, and an object will have to travel at the velocity of
light to escape from the gravitational field of the star. The
value of the Schwarzschild radius depends on the mass of the
body: if the body reaches a radius less than its Schwarzschild
radius, nothing, including light, will be able to escape from
it. In the 1960s, John Archibald Wheeler coined the term "black
hole" for such an object.
... ... *singularity: In this context, the term "singularity"
refers to a mathematical singularity, in general a point at which
a function takes on infinite values.
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Summary & Notes by SCIENCE-WEEK http://scienceweek.com 19Jan01
For more information: http://scienceweek.com/swfr.htm
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Related Background:
ASTROPHYSICS: BLACK HOLES AS EMPIRICAL OBJECTS
During the life of a star, two opposing forces control the
star's equilibrium: the gravitational force, which drives the
collapse of the star's mass inward to the center of gravity, and
the counteracting outward pressure derived from the nuclear
fusion reactions in the star's core. When the nuclear fuel burns
out, the star begins its death and gravitational collapse
occurs. If the terminal stages of star death (during which large
amounts of stellar material are blown away) 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
"Schwarzschild radius", and it is usually a few kilometers.
However, massive black holes are possible and are thought to be
the source of quasars (quasi-stellar objects), which are
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. 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. Other massive black
holes, closer to us than quasars, are apparently the centers of
galaxies, both *galaxies with active centers and galaxies with
dormant centers.
... ... R.Blandford and N. Gehrels (2 installations, US) present
a review of current research on black holes, with a focus on
observable phenomena. The authors make the following points:
     1) The term "black hole" was introduced in a lecture by John
Wheeler in 1968, and used to describe a new view of gravitational
collapse, a shift in perspective from that of an observer at
infinity, for whom the black hole is a limiting case and never
forms, to a description of a black hole in terms of the fate of
matter falling into it as the matter crosses the event horizon.
     2) Energy is the key to understanding astrophysical black
holes. For the past three decades, it has become well established
theoretically that black holes can be voracious monsters
devouring all that they encounter. Some black holes are extremely
luminous and easily outshine their stellar and galactic
counterparts that rely on nuclear, as opposed to gravitational,
energy for their power. Since the late 1970s, it has been well
understood that black holes are most likely to be detected in
stellar *binary systems of approximately 10 solar-masses (i.e.,
10 times the mass of the Sun, whose mass is approximately 2 x
10^(30) kilograms), and in galactic nuclei with masses of the
order of 10^(6) to 10^(9) solar masses.
     3) The archetype of the stellar black hole is Cygnus X-1, a
powerful x-ray source varying so rapidly that it must be a
compact star. Only 3 types of compact stars are known: *white
dwarfs, *neutron stars, and black holes. But theory indicates
that of compact stars only black holes can have masses greater
than 3 solar-masses. Since application of Kepler's laws to Cygnus
X-1 in 1971 resulted in an estimated mass of 8 solar-masses, this
object was established as a black hole.
     4) For black holes in active galactic nuclei, dynamical
investigations beginning in the late 1970s, established that
galaxies, such as the giant *elliptical galaxy M87 in the Virgo
Cluster, contain central dark masses (3 x 10^(9) solar-masses in
the case of M87) that appeared to be too compact to be a central
cluster of stars. In 1995, M. Miyoshi et al were able to measure
the orbital speed of the gaseous disk around the nucleus of the
nearby spiral galaxy NGC 4258. The authors demonstrated that the
gas speed obeys Kepler's laws, and that the gaseous disk is
warped. Since the calculated mass and size of the central object
are 4 x 10^(7) solar-masses and half a light year, respectively,
the consensus is that the central object is definitely a black
hole.
     5) Concerning our own Galaxy, measurements of motions and
velocities of individual stars in orbit around the center of the
Galaxy indicate the mass of our own black hole has a value of 2.6
x 10^(6) solar-masses.
     6) The authors suggest that at the present time we have 15
mass estimates for black holes in the nuclei of nearby galaxies
that are quite secure. It appears that the majority of nearby
luminous galaxies now contain dormant black holes. However,
during earlier epochs, when the black holes were supplied with
gaseous fuel at a much higher rate, they were able to outshine
their host galaxies, in some cases by factors of thousands. These
ancient objects are the quasars, which we can spot from distances
so large that many of them emitted the light we see now when the
Universe was less than 10 percent of its present age.
     7) In summary, the authors note: "The past five years have
seen a remarkable gain in the sophistication of black hole
observations with telescopes that span the entire electromagnetic
spectrum. No longer is there any serious debate as to whether
black holes exist. We know that they must be quite common, and we
can now study them in increasing detail."
-----------
R. Blandford and N. Gehrels: Revisiting the black hole.
(Physics Today June 1999)
QY: Roger Blandford, Calif. Institute of Technology 818-395-6811.
-----------
Text Notes:
... ... *galaxies with active centers: Active galactic nuclei are
central regions of galaxies in which considerable energy is
apparently generated by processes other than those operating in
ordinary stars. The energy may result from the accretion of
material into a massive black hole situated at the core of the
galaxy.
... ... *binary systems: Binary stars are a pair of stars
revolving around a common center of mass under the influence of
their mutual gravitational attraction, and apparently the
majority of stars in the universe are binaries and not singlets.
In some cases the binary system is resolvable into two
components, and in other cases the presence of a second star is
inferred by perturbations in the motion or emitted radiation of
the first star. If the binaries are close enough, they may share
stellar material, and this results in a particular kind of
stellar evolution.
... ... *white dwarfs: White dwarf stars are extremely dense
and compact stars that have undergone gravitational collapse.
They are the final stage in the evolution of low-mass stars after
they have lost their outer layers. White dwarf stars are
approximately the size of Earth, but with a mass approximately
that of the Sun.
... ... *neutron stars: If, following its terminal stages, the
remnant mass of a star is between 1.4 and 2 to 3 solar masses,
the star will collapse into a neutron star, a body with a radius
of 10 to 15 kilometers, with a core so dense that its component
protons and electrons have merged into neutrons.
... ... *elliptical galaxy: In 1925, the astronomer Edwin Hubble
introduced a classification scheme for galaxies that is now
widely used. The scheme has 3 main types of galaxy: elliptical,
spiral, and barred spiral, and each is further divided into
morphological subtypes. Elliptical galaxies are apparently
composed of old stars, contain little dust, are the central
dominant galaxies in rich clusters, and many are powerful sources
of radio wavelength radiation. The size of elliptic galaxies
ranges from dwarf ellipticals [10^(8) stars] to supergiant
ellipticals [10^(13) stars]. Elliptical galaxies are believed to
be a stage in the evolution of galaxies, and different
cosmological models make specific predictions about the number of
elliptical galaxies as a function of redshift. In principle,
therefore, observations of elliptical galaxies can be used to
discriminate between models.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 10Sep99
For more information: http://scienceweek.com/swfr.htm

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3. QUANTUM PHYSICS: KONDO PHYSICS IN CARBON NANOTUBES
     The "Kondo effect", first explained by the theoretical
physicist Jun Kondo, is observed when magnetic ions occur as
dilute impurities in nonmagnetic crystals. If the host crystal is
a metal (e.g., copper), the magnetic impurities (e.g., iron)
contribute to the electrical resistivity, with the conduction
electrons scattered by the magnetic impurity. The scattering is
strong at low temperatures, and increases slightly as temperature
decreases, an anomalous resistivity-temperature relation. The
effect essentially results from the interactions between the
localized spins of the magnetic impurities and the free electrons
involved in conduction. There is a characteristic temperature,
called the "Kondo temperature", which depends on the impurity and
on the host crystal, the resistivity increasing at low
temperature, starting near the Kondo temperature. The Kondo
temperature of the system iron-in-copper is 24 degrees kelvin.
Nearly all transition metal atoms are found as magnetic
impurities in copper or gold, and each system has a different
Kondo temperature, which varies from 1000 degrees kelvin to a
fraction of 1 degree kelvin.
     Fullerenes are large molecules composed entirely of carbon,
with the chemical formula C(n), where n is any even number from
20 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-wall and single-wall versions, with single-
wall nanotubes having a diameter of approximately 1 nanometer and
multi-wall versions having diameters of the order of 10 to 30
nanometers. There have been rapid developments in understanding
the chemistry and physics of carbon nanotubes, and there is much
excitement in both the materials science and electronics
communities concerning possible applications of these unique
structures.
     In general, the term "quantum dot" refers to an artificial
atom. As realized in the laboratory, quantum dots are small
electrically conducting regions, typically less than 1 micron in
diameter, that contain from one to a few thousand electrons.
Because of the small volume, the electron energies within the dot
are quantized, and the behavior of the quantum dot is
intermediate between that of an atom and that of a classical
macroscopic object.
     Electron transport in conductors is usually well described
by so-called "Fermi-liquid theory", which assumes that the energy
states of the electrons near the *Fermi level are not
qualitatively altered by Coulomb interactions. In one-dimensional
systems, however, even weak Coulomb interactions cause strong
perturbations, and the resulting system, known as a "Luttinger
liquid" (after Joaquim Luttinger, who did major work on such
systems in the 1950s) is predicted to be distinctly different
from its 2- and 3-dimensional counterparts.
     Single-walled carbon nanotubes are model systems for the
study of 1-dimensional electron transport, and according to
theoretical predictions, such systems should be very sensitive to
Coulomb repulsion and become insulators at low temperatures.
However, researchers have demonstrated that it is possible to
create superconducting junctions when carbon nanotubes are
connected to superconducting contacts, a phenomenon called
"proximity-induced superconductivity". In the case of nanotubes,
the junction properties are apparently related to its highly 1-
dimensional character, and such junctions may have potential
applications as thermal detectors of weak infrared radiation
(bolometers).
     In this context, the term "ballistic" (as opposed to the
term "diffusive") refers to the passage of electrons through a
conductor whose length is less than the mean free path of
electrons in the conductor, with the result that most of the
electrons pass through the conductor without scattering.
... ... J. Nygard et al (3 authors at 2 installations, DK UK)
present a report on Kondo physics in carbon nanotubes, the
authors making the following points:
     1) The authors point out that the connection of electrical
leads to wire-like molecules is a logical step in the development
of molecular electronics, but such a system also allows studies
of fundamental physics. For example, metallic carbon nanotubes
are essentially quantum wires that have been found to act as 1-
dimensional quantum dots, Luttinger liquids, proximity-induced
superconductors, and ballistic and diffusive 1-dimensional
metals.
     2) The authors report that electrically-contacted single-
walled carbon nanotubes can serve as powerful probes of Kondo
physics, demonstrating the universality of the Kondo effect.
Arising in the prototypical case from the interaction between a
localized impurity magnetic moment and delocalized electrons in a
metallic host, the Kondo effect has been used to explain enhanced
low-temperature scattering from magnetic impurities in metals,
and also occurs in transport through semiconductor quantum dots.
The far greater tunability of quantum dots (in this case,
nanotubes) compared with atomic impurities makes new classes of
Kondo-like effects accessible to study. The nanotube devices used
by the authors differ from previous systems in which Kondo
effects have been observed in that they are 1-dimensional quantum
dots with 3-dimensional metal (gold) reservoirs. This allows
observations of Kondo effects for very large electron numbers in
the quantum dot, numbers estimated as of the order of tens of
thousands.
-----------
J. Nygard et al: Kondo physics in carbon nanotubes.
(Nature 16 Nov 00 408:342)
QY: David Henry Cobden: d.h.cobden@warwick.ac.uk
-----------
Text Notes:
... ... *Fermi level: The "Fermi level" is the energy level at
which there is an 0.5 probability of finding an electron.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 19Jan01
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
A TUNABLE KONDO EFFECT IN QUANTUM DOTS
Quantum dots are small electrically conducting regions, typically
less than 1 micron in diameter, that contain from one to a few
thousand electrons. Because of the small volume, the electron
energies within the dot are quantized, and the behavior of the
quantum dot is intermediate between that of an atom and that of a
classical macroscopic object. Such intermediate systems are
called "mesoscopic" systems, and in the past several years great
attention has been devoted to the physics of such systems, since
they apparently can provide insights into quantum systems in
general. The electronic states in quantum dots can be probed by
transport when a small *tunnel coupling is allowed between the
dot and nearby source and drain leads. ... ... Cronenwett et al
(3 authors at 2 installations, NL US) report the realization of a
tunable *Kondo effect in small quantum dots, with the capability
of switching a dot from a Kondo system to non-Kondo system as the
number of electrons on the dot is changed from odd to even. The
*Kondo temperature can be tuned by means of a gate voltage as a
single-particle energy state nears the *Fermi energy.
Measurements of the temperature and magnetic field dependence of
a *Coulomb-blockaded dot show good agreement with prediction of
both equilibrium and nonequilibrium Kondo effects.
QY: Sara M. Cronenwatt, Stanford University 415-723-0830.
(Science 24 Jul 98 281:540) (Science-Week 14 Aug 98)
-------------------
Related Background:
... ... *tunnel coupling: This refers to tunneling, 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.
... ... *Kondo effect: 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.
... ... *Kondo temperature: The temperature at which the Kondo
effect predominates.
... ... *Fermi energy: The average energy of electrons in a
metal.
... ... *Coulomb-blockaded: This refers to an effective blockade
of quantum mechanical tunneling produced by specific energy
barrier constraints.
-------------------
Related Background:
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.
 ... ... 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: mkastner@mit.edu
(Nature 8 Jan 98) (Science-Week 23 Jan 98)
For more information: http://scienceweek.com/swfr.htm

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

4. BIOCHEMISTRY: ON THE PUZZLES OF HYPERTHERMOPHILES
     In this context, the term "geothermal" refers to the escape
of heat from the interior of the Earth into the Earth's surface,
and the term "hydrothermal" refers to hot solutions rising from 
cooling molten rock (magma). "Hydrothermal vents" are hot springs
occurring in volcanic regions of the ocean floor. The heavy-metal
ions and hydrogen sulfide dissolved in the overheated vent fluid
precipitate as metal sulfides as soon as contact with seawater
cools the fluid. This reaction produces the characteristic
underwater black "smoke" plume, with a vent "smoker chimney"
building up from precipitated materials, mostly gypsum and
sulfides.
     "Plate tectonics" is the modern theory that unifies many of
the features and characteristics of continental drift and sea
floor spreading into a coherent model. Continental drift is the
slow movement of the Earth's land masses, a shifting across the
underlying molten material. Sea-floor spreading is the process
whereby sea floor is continuously created as the crustal plates
move apart, and continuously destroyed where the plates push
against each other. The term "mid-ocean(ic) ridge" refers to a
topographic feature of a tectonic spreading center between
diverging oceanic plates. New crustal material is formed by
upswelling magma (molten material from which rock forms) as the
plates diverge.
     In general, bacteria have adapted to a wide range of
temperatures, with the range of temperature over which optimal
growth can occur in any one species spanning approximately 20
degrees centigrade; the range over which any growth at all takes
place usually spans approximately 40 to 50 degrees centigrade.
     Bacteria that grow at temperatures of less than 15 degrees
centigrade are called "psychrophiles". Obligate psychrophiles,
which have been isolated from Arctic and Antarctic ocean waters
and sediments, have optimum growth temperatures of approximately
10 degrees centigrade and do not survive if exposed to 20 degrees
centigrade.
     The term "mesophilic bacteria" refers to those bacteria in
which optimum growth occurs between 20 and 45 degrees centigrade;
such bacteria can usually grow in or survive temperatures between
10 and 50 degrees centigrade, and all animal pathogens are in
this group.
     So-called "thermophilic bacteria" are the only organisms
that can grow at temperatures higher than 60 degrees centigrade.
Such temperatures are encountered in rotting compost piles, hot
springs, and oceanic geothermal vents. In the runoff of a hot
spring, various thermophiles are found near the source where the
temperature has fallen to approximately 70 degrees centigrade. An
example is the species Thermus aquaticus, which has an optimum
temperature for growth of 70 degrees centigrade, and a maximum
temperature for growth of 79 degrees centigrade.
     In the mid-1980s, researchers discovered bacteria in
nutrient-rich, extremely hot hydrothermal vents in the deep sea
floor. For example, the bacteria in the genus Pyrodictium thrive
in the temperature range 80 to 110 degrees centigrade,
temperatures at which the water remains liquid only because of
the extremely high pressure.
... ... R.A. Zierenberg et al (3 authors at 3 installations, US)
present a review of current research on life in extreme
environments such as hydrothermal vents, the authors making the
following points concerning current puzzles in this area:
     1) The authors point out that eruption of volcanic rocks at
mid-ocean ridges is the major mechanism by which heat is lost
from the interior of the Earth. Approximately one-third of the
heat is removed from the sea-floor spreading centers by
convective circulation of sea water, and the magnitude of this
heat loss requires that the entire volume of the oceans
circulates through the mid-ocean ridges in approximately 10
million years. Seawater interaction with volcanic rocks at near
400 degrees centigrade results in substantial chemical flux and
makes an important contribution to buffering the composition of
some elements in sea water. Sea-floor hydrothermal vents support
ecosystems with enormous biomass and productivity compared with
that observed elsewhere in the deep oceans. What is the energy
source that fuels these oases of life and what adaptations allow
them to exist in these extreme environments?
     2) Although there is a potential abundance of chemical
energy at hydrothermal vents, deep-sea hydrothermal biological
communities have had to adapt to extreme conditions to exploit
this resource. Of particular interest are the hyperthermophiles,
which are defined as microorganisms able to grow at 90 degrees
centigrade and above. Approximately 20 different types of such
organisms are now known. They have been found both within the
walls of black smoker chimneys and where the hydrothermal vent
fluids mix with the surrounding seawater. Classifications of the
hyperthermophiles has provided new insights into the evolution
and the origin of life. All but two of the hyperthermophilic
genera are classified by *ribosomal RNA analysis as "Archaea"
(formerly Archaebacteria), which are the second domain of
prokaryotic life, in addition to the bacteria. By these
phylogenetic analyses, the hyperthermophilic archaea types and
the two hyperthermophilic bacteria types are the most slowly
evolving within their domains, suggesting that life may have
first evolved when the Earth was much hotter than it is now. Such
a thesis is very controversial, the thesis suggesting that extant
life forms are largely the result of temperature adaptations to
lower (below hyperthermophilic) temperatures.
     3) Evolution gives no clue, however, as to how life can
thrive near and above 100 degrees centigrade. Most microbes, and
all *eukaryotic cells, cannot survive at temperatures much above
50 degrees centigrade because of the general instability of
biological molecules. The 3-dimensional structure of most enzymes
and other proteins are lost at temperatures much above 70 degrees
centigrade, and the double-helical structure of DNA has a
comparable lack of stability in _in vitro_ studies. There are
also a wide variety of ubiquitous metabolites that are rapidly
hydrolyzed at temperatures above 90 degrees centigrade. How do
hyperthermophilic cells circumvent these problems?
     4) Although there are some examples of modified pathways and
unusual enzymes in hyperthermophiles, in general the biochemistry
of these organisms closely resembles that of the mesophilic
world. Yet, most enzymes from hyperthermophiles are extremely
stable at high temperatures, showing optimal catalytic activity
above 100 degrees centigrade with virtually no activity at
ambient temperature. These enzymes contain exactly the same 20
amino acids as enzymes from conventional organisms, so why are
they so stable? Sequence comparisons of analogous proteins from
hyperthermophilic and conventional organisms are essentially
identical, so the enormous amount of sequence information now
becoming available will be of little use in elucidating
stabilizing mechanisms. Comparisons must be made at the level of
3-dimensional structures, yet even then, there are no gross
structural differences between hyperthermophilic proteins and
their mesophilic counterparts, and both forms are stabilized by
the same noncovalent interactions. The number and extent of such
interactions is generally only slightly higher in the
hyperthermophilic versions, so extended protein stability at 100
degrees centigrade appears to be the result of very subtle,
synergistic, and cooperative intramolecular interactions.
Moreover, different types of hyperthermophilic proteins seem to
have unique solutions to the problem. A general mechanism by
which any conventional protein could be made stable and
functional at temperatures above 100 degrees centigrade may not
be forthcoming.
-----------
R.A. Zierenberg: Life in extreme environments: Hydrothermal
vents.
(Proc. Natl. Acad. Sci. US 21 Nov 00 97:12961)
QY: Robert A. Zierenberg: Univ. of California Davis 530-752-1863.
-----------
Text Notes:
... ... *ribosomal RNA: A ribosome (not to be confused with
riboZYME) is a small particle, a complex of various ribonucleic
acid component subunits and proteins that functions as the site
of protein synthesis. The tripartite kingdom proposal (Archaea,
Bacteria, Eukarya) of Woese and others is primarily based on gene
sequence analysis of particular ribosomal RNA fractions.
... ... *eukaryotic cells: In general, a eukaryotic cell is any
biological cell containing internal membrane-bound organelles
such as a nucleus.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 19Jan01
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
EVIDENCE AGAINST A HYPERTHERMOPHILIC COMMON LIFE ANCESTOR
An apparent feature of genome sequences is the presence of traces
of extremely ancient evolutionary events, including perhaps the
very first steps of life on Earth. In the late 1970s, by
sequencing small-subunit *ribosomal RNA (rRNA) genes from various
*eukaryotic and prokaryotic species, Woese and colleagues
constructed for the first time a comprehensive picture of the
"universal tree of life". This work gave rise to conjectures
about the nature of the "most recent common ancestor" of extant
life forms. A hot *auxotrophic origin of life was hypothesized,
consistent with conjectures about the former temperature of
Earth. This scenario was later endorsed by numerous authors and
reached the status of a working hypothesis for the early
evolution of life on Earth. Some researchers, however, have
repeatedly criticized this view, arguing that present-day
*hyperthermophily may be a derived state. Resolution of the
question is considered to be dependent on molecular data, but the
molecular data are obscured by numerous nucleotide base
substitution events that have occurred during billions of years
of *diverging evolution. One approach is to construct realistic
models of molecular evolutionary processes in order to
discriminate between molecular evolutionary signals and noise.
... ... N. Galtier et al (3 authors at 3 installations, FR US)
present a modeling approach to the question of the "most recent
common ancestor". The authors consider the fact that the
nucleotide guanine + cytosine (G + C) content of ribosomal RNA
sequences is apparently strongly correlated with the optimal
growth temperature of prokaryotes. The authors propose that this
property allows inference of the environmental temperature of the
common ancestor to all life forms from knowledge of the G + C
content of the ribosomal RNA sequences of the supposed common
ancestor. The authors devised a model of sequence evolution,
assuming varying G + C content among lineages and unequal
substitution rates among genome sites, the purpose of the model
to estimate ancestral nucleotide base compositions. The authors
applied the model to ribosomal RNA sequences of various species
representing the major apparent lineages of life. The authors
report the inferred G + C content of the common ancestor to
extant life forms appears incompatible with survival at high
temperature, and they suggest this finding challenges the widely
accepted hyperthermophilic origin of life hypothesis. Concerning
extant hyperthermophilic species, the authors suggest these forms
evolved from mesophilic organisms via adaptation to high
temperatures. The authors state: "The hypothesis of a hot origin
of life cannot be ruled out (it may have preceded the "most
recent common ancestor"), but no support from rRNA sequences can
be claimed for it."
-----------
N. Galtier et al: A nonhyperthermophilic common ancestor to
extant life forms.
(Science 8 Jan 99 283:220)
QY: Nicolas Galtier, University C. Bernard, Lyon 1, FR.
-----------
Text Notes:
... ... *ribosomal RNA: A ribosome (not to be confused with
riboZYME) is a small particle, a complex of various ribonucleic
acid component subunits and proteins that functions as the site
of protein synthesis.
... ... *eukaryotic and prokaryotic species: Eukaryotes are cells
(and organisms consisting of such cells) that contain
intracellular membrane-bound compartments such as a nucleus
(membrane-bound "organelles"). Prokaryotes are cells (e.g.,
bacteria) without such compartments.
... ... *auxotrophic: An "auxotrophe" is a mutant species
variety, usually a microorganism, that will proliferate only when
its growth medium contains certain specific nutrients not
required by the wild-type (non-mutated) members of the species. 
... ... *hyperthermophily: In general, hyperthermophiles are 
microorganisms whose optimal growth temperature lies above 80
degrees centigrade.
... ... *diverging evolution: In this context, "divergence" is
the acquisition of dissimilar characteristics by related 
organisms in unlike environments.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 2Apr99
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
COMPLETE GENOME OF A HYPERTHERMOPHILIC BACTERIUM
In evolutionary biology, the term "divergence" refers to the
manifestation of new genetic characteristics in a subpopulation
of a species when the subpopulation has become separated from the
larger population by physical barriers -- new genetic
characteristics appearing as the organism adapts to new
conditions. Thermophiles are microorganisms that thrive under
conditions of high temperature such as those in hot springs and
deep ocean vents. "E. coli" refers to the bacterium Escherichia
coli, a rod- shaped intestinal organism that has been used
extensively in research.
... ... Deckert et al (15 authors at 4 installations, US DE)
report the complete genome sequence of Aquifex aeolicus. The
organism is apparently one of the earliest to diverge, and is one
of the most thermophilic bacteria known. It can grow on hydrogen,
oxygen, carbon dioxide, and mineral salts, and at 95 deg C. The
complete genome is one-third the size of the E. coli genome, with
1,551,335 DNA base pairs. The authors suggest that the large
number of diverse genome sequences of various biological
organisms that will become available in the future will allow
more detailed correlation of global genomic properties with
particular physiologies.
QY: Ronald V. Swanson: rswanson@diversa.com
(Nature 26 Mar 98) (Science-Week 10 Apr 98)
For more information: http://scienceweek.com/swfr.htm

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

5. CELL BIOLOGY: TELOMERES AND THE FATE OF BIOLOGICAL CELLS
     A major distinction between bacteria (prokaryotes) and
higher organisms consisting of cells with a nucleus (eukaryotes)
is the arrangement of the genome: in general, genomes are
circular in prokaryotes, whereas in eukaryotes genomes are
collections of linear molecules called "chromosomes". Although a
linear architecture has its benefits, it also presents certain
specific problems. For example, the free ends of DNA molecules
are unstable: they degrade chemically and undergo recombination
much more often than their circular counterparts. Another problem
is that DNA polymerase, the enzyme responsible for replicating
the nuclear genome during cell proliferation, has difficulty
copying the very ends of DNA molecules, so that without special
precautions the end molecular sequences of DNA tend to be lost in
the copies. To solve this problem, eukaryotic cells cap their
chromosomes at both ends with specialized structures (specific
DNA sequences) called "telomeres". Since telomeres are not
replicated by DNA polymerase, and since because of the nature of
the replication process telomeres will shorten at each cell
division, an enzyme called "telomerase" exists to maintain the
telomeres. Telomerase adds telomere sequences onto each
chromosome at each cell division.
     Most mammalian non-germ cell tissues (somatic tissues) lack
telomerase, so it has been proposed that telomere shortening
could be a "clock" that eventually stops cells from further
divisions. When, for example, human *fibroblasts are cultured,
they can divide only a certain number of times, their telomeres
shortening with each division. But if these cells are made to
express telomerase, they can continue dividing indefinitely.
     There is no correlation, however, between telomere length
and the life span of an animal (e.g., humans have much shorter
telomeres than mice), nor is there a correlation between human
telomere length and the age of an individual. Telomerase-
deficient mice do not show profound aging defects. But studies of
normal human and nonhuman cells that are naturally immortal
(e.g., germ cells) have demonstrated that the telomeres of such
cells appear to be stable with time. There is thus the suggestion
that telomerase activity is generally absent in normal mortal
cells, which as a consequence experience replicative telomere
shortening, while telomerase activity in immortal cells exists.
In addition, telomerase activity is also generally found in
cancer cells.
... ... Elizabeth H. Blackburn (University of California San
Francisco, US) now presents a new model of telomere function, the
author making the following points:
     1) The author points out that recent work in several
biological systems has revealed a more complex relationship than
previously realized between telomere length and cell
proliferative capacity. The author proposes a new way to link
telomeres to cellular senescence, with the central concept that
the telomere is a dynamic nucleoprotein complex that can switch
stochastically between two states: capped and uncapped. "Capping"
is functionally defined as preserving the physical integrity of
the telomere, allowing cell division to proceed. But regulated
"uncapping" occurs normally in dividing cells, with the crucial
property that a functional telomere then has a high probability
that it will switch back to a capped state. Left uncorrected too
long, the uncapped state elicits *cell-cycle arrest or other
responses. The author states: "Crucially, this probabilistic
model identifies telomere capping status, as opposed to telomere
length alone, as the important property relevant to telomere
function." [Editor's note: "telomere capping" should be
distinguished from "chromosome capping": chromosome capping
involves capping of the ends of the chromosome by telomeres;
telomere capping involves capping of the telomere by an apparent
protein capping complex.]
     2) The author suggests that quantitative examinations, on a
cell by cell basis, of normal human and mouse somatic cells in
culture have demonstrated that these cells exist in two states:
a) cells that are in the cell-cycle; and b) cells that have
exited the cell-cycle. Even from the very beginning of *tissue
culture passaging, cells are stochastically dropping out of the
cycling population. They do so with ever-increasing frequency
until the population as a whole ceases to double. Notably, even
late in the passaging, any cells still in the cycling state are
cycling as fast as those early in the passaging. Thus, the only
difference between early and late passages is the frequency of
cycling versus non-cycling cells; those cycling cells that are
"old" by virtue of their passage number are not significantly
different from the cycling cells early in the passaging.
     3) The author concludes: "Increasingly, investigations into
a variety of biological processes point to the view that
stochastic stabilization of one of two functionally different
physical states can underlie many seemingly deterministic
phenomena in biology. The stochastic behavior of telomeres and
cells provide another example of this."
-----------
Elizabeth H. Blackburn: Telomere states and cell fates.
(Nature 2 Nov 00 408:53)
QY: Elizabeth H. Blackburn: telomer@itsa.ucsf.edu
-----------
Text Notes:
... ... *fibroblasts: Fibroblasts are a type of connective tissue
cell, secreting structural proteins such as collagen, the
proteins forming a matrix in which the fibroblasts become
embedded. These cells can be easily obtained from skin, and they
can be easily cultured outside the body.
... ... *cell-cycle arrest: In this context, the term "cell
cycle" refers to the entire life history of a single cell from
mitosis to mitosis, including the sequence of intervening phases
(stages).
... ... *tissue culture passaging: In this context, the term
"passage" refers to a replication of cells in culture, with each
passage referring to a single replication.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 19Jan01
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
TELOMERASE ACTIVITY AND IMMORTAL CELLS
Tumors arise as the end product of a multistep process involving
successive rounds of mutation, selection, and *clonal expansion.
One obstacle to the completion of tumor development may be the
limited number of replication cycles apparently allowed normal
human cells. In vitro, normal human cells exhibit a limited
replicative potential, eventually succumbing to "senescence".
Premalignant cell populations evolving in vivo may exhaust this
apparent allotment of doublings before the population progresses
to a malignancy, and when that happens such progression to a
malignancy will only occur if the "replication clock" is
disrupted by the cells acquiring replicative immortality. 
Telomeres are defined ends of chromosomes that contain specific
repeated DNA sequences. They are apparently essential for normal
chromosome replication, and since their length shortens a bit
with each replication, they are believed to be involved in the
aging of the cell. Telomerase is an enzyme that repairs damage to
telomeres, and it is thought by some that cancerous cells may
have mutant telomerase, the mutant enzyme conferring immortality
on the cancer cell. In addition to cell "senescence", there is a
phenomenon called "crisis" (proliferative crisis), which
essentially involves the following: Certain viral or biochemical
interventions in human cell cultures can overcome cell
senescence, typically by causing 20 to 30 extra population
doublings, but at the end of this extended lifespan, there is a
decline and death of the culture in 4 to 6 weeks, which has been
termed "crisis" (proliferative crisis). Cell culture crisis has
been proposed to be the result of telomeric shortening.
... ... C.M. Counter et al (8 authors at 4 installations, US CA)
now report that ectopic expression (i.e., "abnormal" expression)
of the telomerase catalytic subunit (human telomerase *reverse
transcriptase) and subsequent activation of telomerase can allow
post-senescent cells to proliferate beyond crisis. The authors
also report that alteration of the *carboxyl terminus of human
telomerase reverse transcriptase does not affect telomerase
enzymatic activity but does impede the ability of this enzyme to
maintain telomeres, and cells expressing this mutant enzyme fail
to undergo immortalization. The authors state: "Our results
formally demonstrate that acquisition of human telomerase reverse
transcriptase expression is sufficient to immortalize human cells
and [thus our results] validate the role of telomerase in
rescuing cells from crisis."
-----------
C.M. Counter et al: Dissociation among in vitro telomerase
activity, telomere maintenance, and cellular immortalization.
(Proc. Natl. Acad. Sci. US 8 Dec 98 95:14723)
QY: Robert A. Weinberg: weinberg@wi.mit.edu
-----------
Text Notes:
... ... *clonal expansion: In this context, the term "clonal
expansion" refers to the replicative production of a population
of cells from a single originating parent cell.
... ... *reverse transcriptase: Transcription is the process by
which genetic information in DNA is converted into RNA, and
*reverse transcription, involving the enzyme reverse
transcriptase, is the synthesis of complementary DNA from an RNA
template. (Note: The terminological convention in biochemistry is
to identify an enzyme by use of the suffix "-ase")
... ... *carboxyl terminus: In general, since all proteins (and
all enzymes are proteins) are linear polymers consisting of amino
acid subunits connected by peptide bonds, one terminus of the
linear polymer is a carboxyl residue and the other terminus is an
amino residue.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 29Jan99
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
CELLULAR AGING: DONOR AGE AND CELLULAR REPLICATION LIFESPAN
Fibroblasts are a type of connective tissue cell, secreting
structural proteins such as collagen, the proteins forming a
matrix in which the fibroblasts become embedded. These cells can
be easily obtained from skin, and they can be easily cultured
outside the body. Normal human fibroblasts have a finite
replicative lifespan in vitro (i.e., they divide a finite number
of times), and this has been postulated to be a cellular
manifestation of aging of the human organism. Several studies
have indeed shown an inverse relationship between donor age (the
age of the persons from which cultured cells are derived) and
fibroblast culture replicative lifespan. But in all cases the
correlation was weak, and with few exceptions the health status
of the donors was unknown. Thus, the relationship between the
replicative lifespan and the age of the donor from which the
cells are derived has remained equivocal (*Note #1).
... ... V.J. Cristofalo et al now report a study of the
replicative lifespan of 124 skin fibroblast cell lines
established from donors of different ages. All donors were
medically examined and were declared "healthy" (according to
Baltimore Longitudinal Study of Aging protocols) at the time the
biopsies were taken. The authors report that both long- and
short-lived cell lines were observed in all age groups, but no
significant correlation between the proliferative potential of
the cell lines and donor age was found. A comparison of multiple
cell lines established from the same donors at different ages
also failed to reveal any significant trends between
proliferative potential and donor age. The authors suggest their
results clearly indicate that if health status and biopsy
conditions are controlled, the replicative lifespan of
fibroblasts in culture does not correlate with donor age.
-----------
V.J. Cristofalo et al (5 authors at 2 installations, US)
Relationship between donor age and the replicative lifespan of
human cells in culture: A reevaluation.
(Proc. Natl. Acad. Sci. US 1 Sep 98 95:10614)
QY: Vincent J. Cristofalo, Center for Gerontological Research,
Allegheny University of the Health Sciences, Philadelphia, PA
19129 US.
-------------------
... ... *Note #1: The possibility that the process of cell aging
and death is under genetic control was first suggested by Leonard
Hayflick in 1961. Hayflick reported that normal human fibroblasts
apparently have an intrinsic limit to the number of times they
can proliferate, with human fibroblasts removed from an embryo
and grown in culture dividing approximately 50 times before they
deteriorate and die. In contrast, human fibroblasts removed from
adults multiply only 15 to 30 times before dying. Also,
fibroblasts removed from young children suffering from Werner's
syndrome (a rare disease that causes premature aging) divide only
2 to 10 times in culture. Further evidence for a relationship
between aging and the replicative capacity of cells was provided
by the discovery that the number of replications in culture is
apparently related to the lifespan of organism. For example,
cultured cells of the Galapagos tortoise, whose maximum life span
is approximately 175 years, divide more than 100 times in
culture, whereas cells from the mouse, whose maximum life
expectancy is only a few years, divide fewer than 30 times in
culture. The correlation roughly holds for other species as well.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 16Oct98
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
BIOLOGY OF AGING: ON TELOMERES AND REPLICATIVE SENESCENCE
... ... In a review of cell senescence, the aging of cell
cultures, and the immortalization of mammalian cells, John
M. Sedivy (Brown University, US) makes the following points: 1)
Finite replicative lifespan (senescence) of mammalian cells in
culture is a phenomenon that has generated much curiosity since
its description. The obvious significance of senescence to
organismal aging and the development of cancer has engendered a
long-lasting and lively debate about its mechanisms. 2) Three
classical observations are usually cited to argue that in vitro
replicative senescence is a phenomenon with biological
significance: a) the correlation of in vitro lifespan with the
age of the donor; b) the correlation of in vitro lifespan with
the average life expectancy of species; and, c) the reduced in
vitro lifespan of cells from patients afflicted with premature
aging syndromes. 3) Two major theories have been used to explain
limited replicative capacity. The first hypothesis invokes the
gradual accumulation of mutations, and the second hypothesis
invokes the existence of a molecular clock (or clocks) that can
keep track of cell divisions. The second theory is now believed
to be generally true. 4) It is known that cell senescence can be
overcome, because many cell lines in common laboratory use are
quite obviously immortal. Rodent cells can overcome senescence
spontaneously. Human, chicken, bovine, and horse cells rarely, if
ever, immortalize spontaneously. 5) Certain viral or biochemical
interventions in human cell cultures can overcome cell
senescence, typically by causing 20 to 30 extra population
doublings. At the end of this extended lifespan, there is a
decline and death of the culture in 4 to 6 weeks, which has been
termed "crisis". Senescent cells, on the other hand, can be
maintained in vitro in a viable non-proliferative state for very
long periods of time (reports of from 4 to 6 months, and up to 2
years). 6) The author suggests it is amazing that in spite of
very long periods of apparent "immortality", the senescent
program in cells remains intact in cells in which senescence has
been overridden, so that on removal of the overriding agent, the
program is capable of establishing rapid growth arrest. 7) The
current prevailing hypothesis for the nature of the molecular
clock involved in cell senescence is the attrition of telomeres.
*Germ cells, and some key *stem cells, are known to express
telomerase catalytic activity, whereas the majority of somatic
cells lack it. Murine (mouse) embryonic stem cells express
telomerase and are functionally immortal, and elimination of
telomerase eventually results in loss of proliferation. 8) The
author proposes that immortalization of human cells requires a
bypass of both cell senescence and crisis, whereas in rodent
cells cell crisis does not exist and culture lifespan is limited
only by senescence. 9) Evidence indicates that, at least in human
cells, telomere length appears to be linked critically to the
triggering of senescence. The author suggests that although it
remains to be rigorously demonstrated, this strongly implies that
activation of telomerase can result in one-step immortalization.
In conclusion, the author states the two most significant
questions in this field: a) Does cell senescence limit organismal
lifespan? And, b) Is telomerase expression necessary for cancer
progression in vivo?
QY: John M. Sedivy: john_sedivy@brown.edu
(Proc. Natl. Acad. Sci. US 4 Aug 98 95:9078)
(Science-Week 4 Sep 98)
-------------------
Related Background:
... ... *Germ cells: Any cell from which gametes (sperm cells and
egg cells) are derived. All other cells are called "somatic"
cells.
... ... *stem cells: In general, a stem cell is any precursor
cell, a form prior to cell differentiation. E.g., stem cells in
bone marrow that give rise to blood cells.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 4Sep98
For more information: http://scienceweek.com/swfr.htm

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6. PUBLIC HEALTH:
THE BURDEN OF DISEASE IN INDIA FROM INDOOR AIR POLLUTION
     In India, air pollution has become a major concern in recent
years both because it is now clear that large parts of the Indian
urban population are exposed to some of the highest pollutant
levels in the world, and also because new studies around the
world on the health effects of air pollution have increased
confidence in estimates of the risks posed by air pollution
exposures. The situation in China and a number of other
developing countries is similar.
     The 1991 National Census in India included for the first
time a question about the primary household fuel used, and the
data reflected that approximately 95 percent of the rural
population of India still relies primarily on biomass fuels
(dung, crop residues, and wood), with a small fraction of the
population (2 percent) using coal. Nationwide (urban and rural
populations together), approximately 81 percent of all households
rely on biomass fuels and coal (78 percent and 3 percent,
respectively). Unfortunately, such fuels are substantially more
polluting per meal cooked than the liquid and gaseous fuels
further up on the "energy ladder".
... ... Kirk R. Smith (University of California Berkeley, US)
presents a report that evaluates the total burden of disease in
India from indoor air pollution, the author making the following
points:
     1) In the author's study, attributable risks are calculated
in reference to the demographic conditions and patterns of each
disease in India. Sufficient evidence is available to estimate
risks most confidently for acute respiratory infections, chronic
obstructive pulmonary disease, and lung cancer. Estimates for
tuberculosis, asthma, and blindness are of intermediate
confidence. Estimates for heart disease have the lowest
confidence. Insufficient quantitative evidence is currently
available to estimate the impact on adverse pregnancy outcomes
(e.g., low birthweight and stillbirth).
     2) The author reports that the resulting conservative
estimates indicate that some 400,000 to 500,000 premature deaths
can be attributed annually to the use of biomass fuels in these
population groups.
     3) The author concludes: "The estimates made here should be
viewed as tentative. They rely on distressingly few studies and
many untested assumptions. Their alarming scale, however, argues
for additional efforts to understand and ameliorate the
conditions that lead to such severe pollution levels in the
village and urban slum homes of India and elsewhere in the Third
World. At the very least, they call for a serious effort to
conduct the medical and abatement research that would pin down
more accurately the impact of the pollution and effective ways to
reduce it. Over the next decade, millions of lives may depend on
it."
-----------
Kirk R. Smith: National burden of disease in India from indoor
air pollution.
(Proc. Natl. Acad. Sci. US 21 Nov 00 97:13286)
QY: Kirk R. Smith: krksmith@uclink4.berkeley.edu
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 19Jan01
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
ON HEALTH IMPACTS OF DOMESTIC COAL USE IN CHINA
The coals burned in the US generally contain low to modest
concentrations of hazardous air pollutant elements, and many
coal-burning utilities use sophisticated pollution control
systems that efficiently reduce the emissions. Such is not the
case in many developing countries, especially in homes where coal
is used for heating and cooking. Domestic use of coal can present
serious human health problems because the coals generally are
mined locally with little regard to their composition, and the
coals are commonly burned in poorly vented or unvented stoves,
directly exposing residents to the emissions. Thus, domestic coal
combustion has had profound adverse effects on the health of
millions of people worldwide. In China alone, several hundred
millions of people commonly burn raw coal in unvented stoves that
permeate their homes with high levels of toxic metals and organic
compounds. ... ... R.B. Finkelman et al (2 installations, US CN)
present a review of the health impacts of domestic coal use in
China, the authors making the following points:
     1) At least 3000 people in Guizhou Province in southwest
China are suffering from severe *arsenic poisoning. The primary
source of the arsenic appears to be consumption of chili peppers
dried over fires fueled with high-arsenic coal. Coal samples in
the region were found to contain up to 35,000 parts per million
(ppm) arsenic. Chili peppers dried over high-arsenic coal fires
adsorb 500 ppm arsenic on average.
     2) More than 10 million people in Guizhou Province and
surrounding areas suffer from dental and skeletal *fluorosis. The
excess fluorine is caused by eating corn dried over burning
briquettes made from high-fluorine coals and high-fluorine clay
binders.
     3) Polycyclic aromatic hydrocarbons formed during coal
combustion are believed to cause or contribute to the high
incidence of esophageal and lung cancers in parts of China.
Esophageal cancer is a fatal cancer and the fourth-leading cause
of cancer death in China. Parts of Henan Province in north-
central China have some of the highest rates of esophageal cancer
in the world, with cumulative death rates of over 20 percent by
age 75 for both sexes.
     4) Domestic coal consumption also has caused selenium
poisoning and possibly mercury poisoning. Nearly 500 cases of
human selenosis (excess selenium) have been reported in southwest
China, the disease attributed to the use of selenium-rich
carbonaceous shales. The use of combustion ash as a soil
amendment results in selenium uptake by crops. Concerning
mercury, chemical analysis of a coal sample used in Guizhou
Province indicates a mercury concentration of 55 ppm, which is
approximately 200 times the average mercury concentration in US
coals.
     5) The authors suggest that better knowledge of coal quality
parameters may help to reduce some of these health problems.
Information on concentrations and distributions of potentially
toxic elements in coal may help delineate areas of coal deposit
to be avoided. Information on the modes of occurrence of toxic
elements and the textural relations of the minerals and *macerals
in coal may help predict the behavior of the potentially toxic
components during coal combustion.
-----------
R.B. Finkelman et al: Health impacts of domestic coal use in
China.
(Proc. Natl. Acad. Sci. US 30 Mar 99 96:3427)
QY: Robert B. Finkelman: rbf@usgs.gov
-----------
Text Notes:
... ... *arsenic poisoning: Typical consequences of chronic
arsenic poisoning are hyperpigmentation (flushed appearance,
freckles), hyperkeratosis (scaly lesions on the skin), Bowen's
disease (dark precancerous lesions of the skin), and squamous
cell carcinoma.
... ... *fluorosis: Typical consequences of fluorosis (excess
fluorine) include mottling of tooth enamel, osteosclerosis,
limited movement of the joints, severe bone deformations of the
limbs, spinal curvature.
... ... *macerals: In general, "macerals" are the microscopic
organic constituents found in coal.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 23Jul99
-------------------
Related Background:
IN BRIEF: FINE PARTICLE AIR POLLUTION AND URBAN MORTALITY
J.M. Samet et al (5 authors Johns Hopkins University, US)
assessed the effects of 5 major outdoor-air pollutants on daily
mortality rates in 20 of the largest cities and metropolitan
areas in the US from 1987 to 1994. The pollutants were
particulate matter less than 10 microns in *aerodynamic diameter,
ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide. The
authors report they found consistent evidence that the level of
particulate matter less than 10 microns in aerodynamic diameter
is associated with the rate of death from all causes and from
cardiovascular and respiratory illnesses. Weaker evidence
indicated that increases in ozone levels increased the relative
rates of death during the summer, when ozone levels are highest,
but not during the winter. Levels of the other pollutants were
not significantly related to the mortality rate. The authors
conclude: "There is consistent evidence that the levels of fine
particulate matter in the air are associated with the risk of
death from all causes and from cardiovascular and respiratory
illnesses. These findings strengthen the rationale for
controlling the levels of respirable particles in outdoor air."
-----------
J.M. Samet et al: Fine particulate air pollution and mortality in
20 US cities 1987-1994.
(New England J. Med. 14 Dec 00 343:1742)
QY: Jonathan M. Samet: jsamet@jhsph.edu
-----------
Text Notes:
... ... *aerodynamic diameter: In this context, the term
"aerodynamic diameter" is defined as the diameter of a unit-
density sphere that has the same settling velocity in gas as the
particle of interest.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 15Dec00
For more information: http://scienceweek.com/swfr.htm

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7. IN FOCUS: ON ELECTRICITY AND NEUROPHYSIOLOGY
"The development of our present-day concepts of nerve activity
has depended very largely on improvements in electrical and
electronic techniques. If one goes back to the 18th century, one
finds that even in the early days of the history of electricity
our knowledge of it was closely interwoven with studies of nerve
and muscle. Long before the announcement of the laws of [G.S.]
Ohm [1787-1854] and [M.] Faraday [1791-1867], before the
invention of galvanometers and other sensitive recording
instruments, Luigi Galvani [1737-1798] had discovered a form of
electric discharge which he believed to be due to the production
of electric currents by living nerve and muscle tissue. His
interpretation was soon challenged by Alessandro Volta [1745-
1827], who showed that the electromotive force in most of
Galvani's experiments originated at the contact points between
tissues and metals. The famous dispute between Galvani and Volta
proved to be the impetus for a whole stream of experiments and
ideas -- in physiology as well as physics and physical chemistry
-- which have continued to grow and develop ever since. For many
years, the twitch that one observes when a brief current is
discharged through the isolated nerve-muscle preparation of a
frog was the most sensitive detector for short lasting electric
pulses. By the middle of the 19th century, [C.] Matteucci [?-?]
and [Emil] Du Bois-Reymond [1818-1896) had discovered with the
help of slow but sensitive galvanometers that nerves and muscles
are capable of generating electromotive forces themselves."
-----------
Bernard Katz: _Nerve, Muscle, and Synapse_
(McGraw-Hill, 1966, p.11)
[Editor's note: Bernard Katz (1911- ) received the Nobel Prize in
Physiology and Medicine in 1970 for his work on the unit-packet
("quantum") release at synapses of the neurotransmitter
acetylcholine. Concerning Galvani and Volta, their story has
become a much discussed paradigm in the history of science,
because it illustrates accidental discovery (Galvani), progress
gained through an initially wrong theory (animal electricity),
later insight into fundamentals (two metals and an electrolyte),
and the giving up of nonessentials (animal tissues) to achieve
definite progress (Volta and the battery).]
-------------------
SCIENCE-WEEK http://scienceweek.com 19Jan01
For more information: http://scienceweek.com/swfr.htm

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8. FROM THE SCIENCEWEEK ARCHIVE:
MATHEMATICS: ON KURT GODEL AND THE LIMITS OF LOGIC
The mathematician Kurt Godel (1906-1978), brilliant and
individualistic and psychiatrically self-destructive, appears in
the history of 20th century science like some character invented
by a novelist. Godel was a Viennese physics student who switched
to mathematics; participated as a youth in the famous *Vienna
Circle of philosophers; met and became bonded to an older
nightclub dancer when he was a student; published at the age of
25 a thesis that forever changed the field of mathematics;
escaped from Nazi Germany in 1940 by travelling across Asia with
the nightclub dancer (whom he had now married); settled at the
Institute for Advanced Study at Princeton, where apparently
everyone agreed that Godel was brilliant but slightly crazy; was
chaperoned by Einstein in daily walks apparently designed by
Einstein to calm Godel and keep him working; and then, finally,
in 1978, refusing to eat because he believed people were trying
to poison him, Godel died of starvation. Science, after all, is a
human enterprise, and every human enterprise has its human
stories. Concerning the contributions of Godel to mathematics,
John W. Dawson Jr (Pennsylvania State University, US) presents a
biographical essay on Godel, the author making the following
points:
     1) The story of Godel's life and work is that of a
persistent quest for rationality in all things, pursued against a
background of recurrent mental instability.
     2) Godel proved that the mathematical methods in place since
the time of Euclid were inadequate for discovering all that is
true about the natural numbers. His discovery undercut the
foundations on which mathematics had been built through the ages
up to the 20th century, stimulated thinkers to seek alternatives,
and generated a lively philosophical debate about the nature of
truth. Godel's innovative techniques, which could readily be
applied to algorithms for computation, also laid the foundation
for modern computer science.
     3) In his famous 1931 "incompleteness theorem" paper, Godel
demonstrated that there exists some statement that is true of the
natural numbers that must fail to be provable. That is, objects
that obey the axioms of number theory, but fail to behave like
the natural numbers in some other respects, do exist.
     4) The concepts and methods Godel introduced in his
"incompleteness" paper are central to the discipline of
*recursion theory, which underlies all of modern computer
science. Extensions of his ideas have allowed the derivation of
several other results concerning the limits of computational
procedures. One result is the unsolvability of the so-called
"halting problem" -- that of deciding, for an arbitrary computer
with an arbitrary input, whether the computer will eventually
halt and produce an output rather than becoming stuck in infinite
loop. Another result is the demonstration that no computer
program that does not alter a computer's operating system can
detect all programs (e.g., computer viruses) that do.
     5) Godel published remarkably few papers during his lifetime
-- fewer than any other great mathematician except *Bernhard
Riemann -- but the impact of Godel's papers has been enormous,
and his work has affected virtually every branch of modern logic.
-----------
John W. Dawson Jr.: Godel and the limits of logic.
(Scientific American June 1999)
QY: John W. Dawson Jr., Dept. of Mathematics, Pennsylvania State
University York 814-863-8461.
-----------
Text Notes:
... ... *Vienna Circle of philosophers: (Vienna School) A
philosophical school of philosophers in Vienna in the 1920s,
inspired by the physicist-philosopher Ernst Mach (1838-1916). The
group is considered responsible for the branch of philosophy
called "logical positivism", and included Ludwig Wittgenstein
(1889-1951) and Rudolf Carnap (1891-1970). The essential approach
of logical positivism was to dismiss most "metaphysics" as
meaningless answers to pseudoproblems, and to focus on the
foundations of knowledge, scientific method, logic, and
semantics. Although Godel is often considered a member of the
Vienna Circle, from a philosophical standpoint he was a Platonist
rather than a logical positivist: Godel believed the objects of
true knowledge are ideas, particularly universals.
... ... *recursion theory: In this context, the theory of
iterative processes in computation.
... ... *Bernhard Riemann: Georg Friedrich Bernhard Riemann
(1826-1866). Many mathematicians consider Riemann's influence on
the course of modern mathematics to be unparalleled. Almost all
of his short number of papers were and remain important. He died
of tuberculosis before his 40th birthday.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 23Jul99

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9. BOOK NOTICES:

NEUROSCIENCE:
Eric R. Kandel et al: Principles of Neural Science (4th edition).
McGraw-Hill, 2000, 1414 pp., Hardcover, US$85
Considered by many in the field to be the "bible" of
neuroscience, this is currently the most authoritative
introduction to the brain, its structure, function, development,
and control of behavior available today in a single volume. The
principal author, E.R. Kandel, is a recent Nobel Prize winner in
Physiology and Medicine for his work in neuroscience. In 63
chapters, the book presents both a comprehensive summary of the
state of neuroscience and a full discussion of historical issues
in the study of the brain. Neuroanatomy, cell and molecular
mechanisms, mechanisms of signaling, and development are
thoroughly described in the context of the cognitive approaches
to behavior, with an emphasis on the examination of behavior at
the level of individual nerve cells, the area of research of the
principal author. The text is thoroughly revised, with new
full-color illustrations. Highly recommended as a principal
reference work for anyone interested in neuroscience.
For more information or to order this book:
http://www.amazon.com/exec/obidos/ASIN/0838577016/scienceweek

THEORETICAL PHYSICS:
Max Jammer: Concepts of Mass in Contemporary Physics and
Philosophy.
Princeton University Press, 2000, 180 pp., Hardcover, US$39.50
(Amazon price: US$31.60)
Mass is a fundamental concept in physics, a quantitative measure
of inertia, the resistance that a body of matter offers to a
change in its speed or position on the application of a force.
But should inertial mass be viewed as a theoretical or an
observational concept? Max Jammer is a physicist who over the
past four decades has produced a series of monographs on the
philosophical aspects of various fundamental concepts in physics.
This book is a unique assemblage of a number of diverse topics
concerning the concept of mass in modern physics: inertial mass,
relativistic mass, the mass-energy relation, gravitational mass,
and the nature and origin of mass. Jonathan Bain (Polytechnic
University Brooklyn, US) says the following concerning this new
Jammer monograph: "Physicists and philosophers of science will
both benefit greatly from the book. It provides an invaluable
source and commentary on the relevant contemporary literature.
While the minimal use of technical exposition makes the book very
readable to the nonspecialist, enough mathematical detail is
provided to satisfy the curiosity of the expert." (Physics Today)
For more information or to order this book:
http://www.amazon.com/exec/obidos/ASIN/069101017X/scienceweek

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The first issue of SCIENCE-WEEK appeared May 1, 1997, and it has
been published regularly each week since that date. SW is
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