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SCIENCE-WEEK

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A journal devoted to the improvement of communication
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science educators, and science policy makers.

February 5, 1999 -- Vol. 3 Number 6

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The first part of the human story is simple:
We rose out of the primeval muck to peer at the stars.
The second part of the story has yet to be written.
-- Anonymous

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Contents of This Issue:

1. On Cosmological Antigravity
2. On the Universality of Turbulence
3. On Molecular Conservation Genetics
4. On the Genome Sequence of the Nematode C. Elegans
5. Nitric Oxide Function in Skeletal Muscle
6. Aspirin and Increased Risk of Hemorrhagic Stroke

Following the main text: Notices, subscription information,
editorial contacts, etc.

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1. ON COSMOLOGICAL ANTIGRAVITY
The branch of physics called "cosmology" deals with the structure
and evolution of the Universe, and during the past few years it
has become apparent that this field may be facing one of its most
significant transitions. In all the sciences, it is common for
observations to conflict with theory, with a resultant refinement
and even abandonment of old theory for new theory. Indeed, a case
can be made that this is the essence of science, and the basis
for the continued improvement in our understanding of natural
phenomena. In cosmology, a serious theoretical reformulation is
apparently imminent. At this point in its history, the science of
cosmology is evidently in the throes of a major overhaul of
theoretical constructs, an overhaul produced by mounting evidence
relevant for considerations of the structure of the Universe.
Central to these considerations are the distinctions between the
geometries of a "flat" (uncurved; infinite in both extent and
lifetime), "closed" (spherical; finite in both extent and
lifetime), and "open" (*hyperbolic; infinite and expanding
forever) Universe. An important quantity is the Omega parameter,
defined as the ratio of the density of matter (or energy) in the
Universe to the theoretical density required for flatness. An
Omega with a value of greater than 1 implies a closed Universe; a
value less than 1 implies an open Universe; a value equal to 1
implies a flat Universe. The problem for the past 60 years has
thus been to obtain an estimate of the mass density of the
Universe from observations. The current standard conception is
that the geometry of the Universe is flat. Recently, however, new
data have apparently indicated that the entire scheme upon which
models of the structure of the Universe are based may need
serious revision, and such revision may in turn force revision of
certain areas of fundamental physics. ... ... Lawrence M. Krauss
(Case Western Reserve University, US) presents a review of the
problem, the author making the following points: 1) The standard
cosmology of the 1980s, postulating a flat Universe dominated by
matter, is dead. The Universe is either open or filled with an
energy of unknown origin. 2) Although the visible contents of the
Cosmos are clearly not enough to make the Universe flat, analysis
of celestial dynamics indicates there is far more matter than we
can observe, with most of the material in galaxies and assemblies
of galaxies invisible to telescopes... An overwhelming body of
evidence now implies that even the unseen matter is not enough to
produce a flat Universe... If the Universe is open, the current
*inflationary theory of the evolution of the Universe immediately
following the *Big Bang must be modified or discarded. If the
Universe is indeed flat, the Universe must be composed largely of
an "ethereal" form of energy that inhabits empty space ("*vacuum
energy"). 2) The existence of vacuum energy is implied by quantum
mechanics and demonstrated experimentally by the *Casimir effect.
Physicists have thus corroborated the theory put forth by Dirac
(and later by Feynman, Schwinger, and Tomonaga) that space is
filled with fleeting "virtual particles". 3) The author
distinguishes 4 types of matter: a) visible matter, which is
ordinary matter composed mainly of protons and neutrons, and
which forms stars, dust, and gas; b) *baryonic dark matter, which
is ordinary matter too dim to be observed; c) nonbaryonic dark
matter, which consists of exotic particles such as "*axions",
*neutrinos with mass, or *weakly interacting massive particles;
d) cosmological dark matter, which consists of vacuum energy. 4)
Concerning the approximate quantitative contributions to the
dimensionless Omega parameter, the author presents the following:
visible matter 0.01; baryonic dark matter 0.05; nonbaryonic dark
matter 0.3; vacuum energy 0.6. The author states that of the 2
apparent alternatives, an open Universe or a flat Universe filled
with vacuum energy, "either scenario will require a dramatic new
understanding of physics."
-----------
Lawrence M. Krauss: Cosmological antigravity.
(Scientific American January 1999)
QY: L.M. Krauss, Case Western Reserve University 216-368-2000
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Editor's note: In addition to the related background material
below, see the following SW Focus Reports:
-----
"Cosmology: Dark Matter"
[http://scienceweek.com/swfr010.htm]
-----
"Cosmology: Models and Extrapolations"
[http://scienceweek.com/swfr020.htm]
-----
"Theoretical Physics: String Theory"
[http://scienceweek.com/swfr035.htm]
-----
Also, the report in the 22 Jan 99 issue of SW: "Astrophysics: On
Accelerating Cosmic Expansion".
-----------
Text Notes:
... ... *hyperbolic: This is a negative curvature, like the
surface of a saddle, and it is sometimes called a "saddle"
Universe. In such a geometry, the sum of the angles of a triangle
is less than 180 degrees. In a spherical (closed) geometry, the
sum of angles is more than 180 degrees; in a flat geometry, the
sum of angles is exactly 180 degrees.
... ... *inflationary theory: The inflationary model, first
proposed by Alan Guth in 1980, proposes that quantum
fluctuations in the time period 10^(-35) to 10^(-32) seconds
after time zero were quickly amplified into large density
variations during the "inflationary" 10^(50) expansion of the
universe in that time frame.
... ... *Big Bang: 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.
... ... *vacuum energy: The idea of "vacuum energy" is considered
by some theorists to be embodied in Einstein's relativity
equations as the so-called "*cosmological constant". Unlike
ordinary forms of mass and energy, the Einstein vacuum energy
adds gravity that is repulsive and can drive the Universe apart
at ever increasing speeds. At the level of quantum mechanics, the
existence of vacuum energy is based on considerations of zero-
point energy and the fact that according to quantum mechanics
nothing of interest (including a vacuum) can have zero energy. In
a vacuum, quantum fluctuations of a field produce a minimum
energy (zero-point energy), and through the relation of energy
and mass, it is possible to associate this vacuum energy with the
existence of "virtual particles", particles whose duration of
existence and non-existence is of the order of quantum
fluctuations.
... ... *cosmological constant: A mathematical term introduced by
Einstein into the equations of general relativity, the purpose to
obtain a solution of the equations corresponding to a "static
Universe" (i.e., flat Universe). The term describes a pressure
(if positive) or a tension (if negative) which can cause the
Universe to expand or contract even in the absence of any matter
("vacuum energy"). When the expansion of the Universe was
discovered, Einstein apparently began to regard the introduction
of this term as a mistake, and he described the cosmological
constant as the "greatest mistake of my life". But the term has
reappeared as the proposed source of apparent accelerated cosmic
expansion.
... ... *Casimir effect: This is the force between 2 macroscopic
conducting surfaces in a volume that contains only an
electromagnetic field (i.e., an electromagnetic field in a
vacuum). The zero-point energy of the electric field depends,
according to quantum mechanics, on the types of vibrations of the
field (mode frequencies), which in turn depend on the boundary
conditions on the field. This zero-point energy leads to a force
between the plates. The existence of this force was theoretically
predicted by H.B.G. Casimir and detected experimentally by M.J.
Sparnay in 1958. Both the sign and magnitude of the Casimir
effect depend on the geometry of the surfaces.
... ... *baryonic dark matter: A baryon is a nuclear particle,
e.g., a proton, built from 3 quarks (fundamental particles that
combine to make up protons, neutrons, and mesons).
... ... *axions:  A hypothetical elementary particle of very low
mass and zero charge, and one of the candidates for dark matter
in the Universe.
... ... *neutrinos with mass: An electrically neutral elementary
particle until recently considered to be always without mass.
... ... *weakly interacting massive particles: (WIMPS) This
refers to a hypothetical elementary particle that is a candidate
for cosmic dark matter, a stable neutral particle, somewhat
heavier than the neutron, that interacts only weakly with
ordinary matter.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 5Feb99
-------------------
Related Background:
COSMOLOGY: OPEN, CLOSED, OR FLAT UNIVERSE?
Marc Kamionkowski (Columbia University, US) reviews current
research in cosmology, making the following points: 1) Determin-
ation of the geometry of the universe has been a central goal of
cosmology ever since Hubble discovered its expansion 75 years
ago. 2) The central question is whether the universe is a multi-
dimensional equivalent of a 2-dimensional surface ("flat"), a
sphere ("closed"), or a saddle ("open"). The geometry, in the
context of current theory and observations, determines whether
the universe will expand forever or eventually collapse. 3) Until
now, most astronomers have pursued the geometry by attempting to
measure the mass density of the universe. According to general
relativity, if the density is equal to, larger than, or smaller
than a critical density fixed by the expansion rate, then the
universe is flat, open, or closed, respectively. 4) Another
possibility is to look directly at the predicted observational
effects of a curved (open or closed) universe versus a flat
universe, and in particular at the angular power spectrum of the
cosmic microwave background. The authors suggest that in the near
future a new generation of experiments will provide substantial
advances in these observations, enabling more definitive
statements about the geometry of the universe, and that these
results will in turn provide clues to the new particle physics
required to understand the inflation phase following the Big Bang
origin of the universe.
QY: Marc Kamionkowski (kamion@phys.columbia.edu)
(Science 29 May 98 280:1397) (Science-Week 19 Jun 98)
-------------------
Related Background:
ON THE NATURE OF DARK MATTER
Joel R. Primack (University of California Santa Cruz, US)
presents a commentary on a paper by E. Gawiser and J. Silk
(University of California Berkeley, US) ((Science 29 May 98
280:1405), Primack making the following points: 1) One of the
fundamental issues facing cosmologists concerns the evidence that
observable matter in the universe makes up only a fraction of
what is needed to explain the properties of the universe. A large
portion of matter in the universe must therefore be unobserved,
or "dark matter". 2) In current cosmology, "hot" dark matter is
defined as particles that were still moving at nearly the speed
of light at about a year after the big bang. "Cold" dark matter
is defined as particles that were moving sluggishly at that time.
Neutrinos are the standard example of hot dark matter, although
other more exotic possibilities have been discussed. 3) Gawiser
and Silk (ref. cited above) conclude that of all the currently
popular cosmological models, the only one whose predictions agree
with the data on the cosmic microwave background anisotropies and
the large-scale distribution of galaxies is the cold + hot dark
matter model, with 70% of the matter cold dark, 20% hot dark, and
10% ordinary matter (baryonic). 3) There are 3 species of
neutrinos, and there are mounting astrophysical and laboratory
data suggesting that neutrinos oscillate from one species to
another, which can only happen if they have nonzero mass. As
dark-matter candidates, neutrinos are entities with masses that
may be 10^(-5) of the mass of the electron, but with an expected
density more than 8 orders of magnitude greater than the density
of electrons and protons in the universe. Neutrinos, therefore,
can provide a substantial fraction of dark matter. 4) The success
of the cold + hot dark matter model in fitting the cosmic
microwave background and galaxy distribution data indicates that
this type of model should be investigated in more detail.
QY: Joel R. Primack (joel@physics.ucsc.edu)
(Science 29 May 98 280:1398) (Science-Week 19 Jun 98)
-------------------
Related Background:
A GRAVITATIONAL DIFFUSION MODEL WITHOUT DARK MATTER
R.J. Britten (California Institute of Technology, US) presents a
model that without dark matter quantitatively describes the flat
rotation curves of galaxies and the mass-to-light ratios of
clusters of galaxies. The hypothesis is that the agent of
gravitational force is propagated as if it were scattered with a
mean free path of about 5 kiloparsecs. As a result, the force
between moderately distant masses separated by more than the mean
free path diminishes as the inverse first power of the distance,
following diffusion equations, and describes the flat rotation
curves of galaxies. The force between masses separated by 
(Chem. & Eng. News 29 Jun 98) (Science-Week 24 Jul 98)
-------------------
Related Background:
... ... *nitric oxide: The gas nitric oxide is the prime member
of an entirely new class of neurotransmitters discovered only in
the 1990s. In the brain, the enzyme that synthesizes nitric oxide
(nitric oxide synthase) is localized in discrete populations of
neurons. In the peripheral autonomic nervous system, the enzyme
occurs in neurons that regulate the adrenal medulla, the
posterior pituitary, and the smooth muscle cells of the intestine
involved in *peristalsis. In all of these systems, nitric oxide
acts as a neurotransmitter released as a consequence of neural
activity. Nitric oxide has also been implicated as a messenger in
the response of macrophages (immune system cells) to cancer cells
and invading bacteria. It is also released from *endothelium in
response to acetylcholine and other vasodilators, with a
resultant relaxation of blood vessels. And, as noted in the
report, it is involved in penile erection. Nitric oxide is a free
radical with a half-life of only a few seconds, and its
concentration in tissues is difficult to establish
quantitatively. It should not be confused with nitrous oxide
("laughing gas"), which is an analgesic gas used as an auxiliary
in anesthesia in dentistry and surgery.
... ... *peristalsis: This refers to the regulated waves of
alternating contraction and relaxation of the intestine that move
its contents onward.
... ... *endothelium: A layer of flat cells lining blood vessels,
lymphatic vessels, the heart, etc.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 24Jul98


6. ASPIRIN AND INCREASED RISK OF HEMORRHAGIC STROKE
Aspirin was introduced as an analgesic (a drug against pain) and
antipyretic (a drug against fever) almost a century ago, but it
is only during the past 2 decades that attention has been focused
on the therapeutic effect of aspirin on cardiovascular disease
[*Note #1]. In this context, the term "myocardial infarction"
refers to a sudden insufficiency of the blood supply to the
heart, and the term "stroke" refers to a sudden development of
focal neurological deficits usually related to impaired cerebral
blood supply (cerebrovascular stroke). Of cerebrovascular
strokes, there are in general 2 categories, ischemic strokes and
hemorrhagic strokes. The term "ischemic stroke" refers to a
stroke caused by blockage of a blood vessel (ischemia), the
blockage involving a blood clot, a mass of bacteria, or in
general any mechanical obstruction -- any of these termed an
"embolus" (producing an "embolism"). A "thrombus" (producing a
"thrombosis") is a particular type of embolus, one involving a
blood clot. The second category of stroke, "hemorrhagic stroke",
refers to a stroke caused by sudden localized bleeding
(hemorrhaging) that can result, for example, from a break in a
thinned arterial wall (aneurism) or breakdown of a capillary bed.
A number of large randomized controlled clinical trials have
demonstrated that aspirin treatment reduces the risk of
myocardial infarction and ischemic stroke among patients with a
wide range of preexisting cardiovascular diseases. A smaller body
of data suggests that aspirin treatment reduces the risk of
nonfatal myocardial infarction in healthy persons, and aspirin is
now widely used for primary and secondary prevention of
cardiovascular disease in the general US population. ... ... J.
He et al (4 authors at 2 installations, US) now report a "meta-
analysis" review of the medical literature, the purpose of which
was to estimate the risk of hemorrhagic stroke associated with
aspirin treatment. The study consisted of analysis of 16 aspirin
trials involving 55,462 participants. The authors report that
aspirin use was associated with an absolute risk reduction in
myocardial infarction of 137 events per 10,000 persons, and in
ischemic stroke, an absolute risk reduction of 39 events per
10,000 persons. However, the authors report that aspirin
treatment was also associated with an absolute risk increase in
hemorrhagic stroke of 12 events per 10,000 persons. The authors
suggest these results indicate that aspirin therapy increases the
risk of hemorrhagic stroke, but they also suggest that the
overall benefit of aspirin use on myocardial infarction and
ischemic stroke may outweigh, in most populations, the adverse
effects of aspirin on risk of hemorrhagic stroke.
-----------
J. He et al: Aspirin and risk of hemorrhagic stroke.
(J. Amer. Med. Assoc. 9 Dec 98 280:1930)
QY: Jiang He [jhe@mailhost.tsc.tulane.edu]
-----------
Text Notes:
... ... *Note #1: The name "aspirin" derives from "Spirsaure",
the German word for salicylic acid, but aspirin itself is
acetylsalicylic acid, which was first introduced into medicine by
Dreser in 1899. The antipyretic properties of the salicylates
were apparently known to the ancients via Willow bark (Salix
alba), and a glycoside extract called salicin was first
discovered by Leroux in 1827.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 5Feb99


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