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 26, 2001 -- Vol. 5 Number 4

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We measure things. We spend countless dull hours
measuring the swing of a pendulum, the heat of an acid,
the twitch of a muscle. But only with these measurements
in hand can we begin our dialogue with the Cosmos.
-- Anonymous

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

1. ECOLOGY: A CRITICISM OF CURRENT ECOLOGICAL THEORY
Much "theoretical" environmental and ecological science is
necessarily based on laboratory experiments carried out under
very controlled conditions. But little effort goes into
extrapolating the results of these studies to the outside world.
Despite the urgent need for properly tested predictive models in
ecological and environmental science, such models are extremely
rare. Although the scientific literature teems with mathematical
models, these are almost never applied and tested by formal
"blind" predictions of the real world behavior of environmental
systems. (Nature 16 Nov 00 408:293)

2. EVOLUTIONARY BIOLOGY:
A POSSIBLE CASE OF REPEATED SYMPATRIC SPECIATION
A species of vertebrate gives rise to another species on average
once every few million years, a time-scale that makes the study
of speciation particularly difficult. "Sympatric speciation", a
controversial concept, refers to speciation in which populations
inhabiting the same geographic range become somehow
reproductively isolated, with a resultant gene pool isolation and
ultimate species divergence. A new study just published provides
evidence for an apparent case of speciation in cichlid fishes
from Nicaragua, with the evidence suggesting the occurrence of
sympatric speciation. (Nature 16 Nov 00 408:298)

3. MEDICAL BIOLOGY:
ON THE BIOLOGY OF ALLERGY AND ALLERGIC DISEASES
The marked increase in the prevalence of atopic disease in
western Europe, the US, and Australasia during recent years
indicates the importance of environmental influences, and it is
possible that a Western lifestyle accounts for the increase in
prevalence. One hypothesis is that in Western countries the
developing immune system is deprived of the microbial antigens
that stimulate type 1 T-helper cells, because the environment is
relatively clean and the use of antibiotics for minor illnesses
in early life is widespread. Epidemiological studies apparently
seaport this theory. (New England J. Med. 4 Jan 01 344:30)

4. ASTROPHYSICS: WHITE DWARF STARS AND DARK MATTER
An unexpected current conclusion of a recent survey is that dark
objects in our Galaxy typically have masses near 0.5 solar-
masses. Had these objects been ordinary stars, they would have
been detected long ago by their own light. Their relative mass
and dimness leaves only one possibility: the dark objects can
only be white dwarf stars. The current estimate is that up to 50
percent of the mass of the dark Galactic halo is in the form of
old white dwarf stars. If this interpretation is correct, not
only are white dwarf stars common, but they also outnumber
ordinary stars 5 to 1. (American Scientist Nov/Dec 200 88:498)

5. PARTICLE PHYSICS: THE SEARCH FOR THE HIGGS BOSON
Searches for the Higgs boson have occurred at ever higher
energies since the late 1970s, and possible evidence for its
existence was recently obtained at the European Center for
Particle Physics (CERN). The evidence so far indicates that the
Higgs boson is a very massive particle, heavier than all known
elementary particles except possibly the top quark. There are
indications of the direct production of a Higgs boson near 115
Gev, a mass-energy which would be in a agreement with recent
indirect evidence that such a particle should have a mass less
than approximately twice that of the Z particle.
(Science 12 Jan 00 291:259)

6. CONDENSED-MATTER SCIENCE:
ON THE PROBLEM OF THE NATURE OF LIQUIDS
Understanding the structure of simple liquids is a fundamental
unsolved problem in the mathematical and physical sciences.
Attempts to describe liquids as disordered crystals have all
failed, and descriptions of liquids as dense gases (fluids)
remain too complex. The best approach so far, although far from
complete, has been to describe liquids as dense packings of
tetrahedral building blocks. A new report provides the first
direct evidence for polytetrahedral structures in a monoatomic
liquid trapped at a solid interface.
(Nature 14 Dec 00 408:781)

7. IN FOCUS: ON THE HISTORY OF THE PHYSICS OF LIGHT

8. FROM THE SCIENCEWEEK ARCHIVE:
FETAL EFFECTS OF EXPOSURE TO ORGANIC SOLVENTS DURING PREGNANCY

9. BOOK NOTICES:

10. CORRECTION: ISSUE OF 19 JANUARY 2001


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Section 2
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1. ECOLOGY: A CRITICISM OF CURRENT ECOLOGICAL THEORY
The term "ecology" derives from the Greek "oikos", meaning house,
and ecology literally means the study of the house. It is the
branch of biology that studies the relationships among living
organisms and between organisms and their environments. In recent
years, ecological considerations have acquired certain direct
political aspects whenever and wherever human civilization has an
impact on non-human populations of living systems. But with or
without political ramifications, ecology is a complex and
important science that utilizes data and constructs from many
other disciplines.
... ... Jim Smith (Center for Ecology and Hydrology Dorchester,
UK) presents a critique of current theoretical research in
ecology, the author making the following points:
     1) The author suggests that issues concerning hypothesis
testing are particularly relevant for the environmental and
ecological sciences, since the complexity of environmental
systems often limits our ability to test hypotheses
quantitatively. Much "theoretical" environmental and ecological
science is necessarily based on laboratory experiments carried
out under very controlled conditions. But little effort goes into
extrapolating the results of these studies to the outside world.
The assumptions relevant to the laboratory often do not hold in a
real, complex environment, and the models are therefore only very
weakly predictive. Of course there is a place for detailed
studies of environmental processes, but (the author suggests)
such studies will not constitute useful scientific theory until
they can be used to make predictions in the real world.
     2) The author suggests the most pressing environmental
problems require scientists to predict the effects of man-made
changes. We need, for example, to predict the density and
distribution of artificially introduced species; to evaluate the
impact on an ecosystem of a road-building program; or to assess
the consequences of pollution. Despite the urgent need for
properly tested predictive models in ecological and
environmental science, such models are extremely rare. Although
the scientific literature teems with mathematical models, these
are almost never applied and tested by formal "blind" predictions
of the real world behavior of environmental systems.
     3) The author suggests that, faced with a complex
environment, ecological and environmental scientists have
responded by developing ever more intricate and detailed
techniques and models. Yet, ironically, simple, semi-empirical
relationships are usually a much better guide to the behavior of
environmental systems. The author concludes: "Perhaps ecological
and environmental scientists should concentrate less on
theoretical explanation and more on finding applied solutions to
humankind's environmental problems."
-----------
Jim Smith: Nice work -- but is it science?
(Nature 16 Nov 00 408:293)
QY: Jim Smith: Center for Ecology and Hydrology, Dorchester,
Dorset DT@ 8ZD (UK)
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Summary by SCIENCE-WEEK http://scienceweek.com 26Jan01
For more information: http://scienceweek.com/swfr.htm

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2. EVOLUTIONARY BIOLOGY:
A POSSIBLE CASE OF REPEATED SYMPATRIC SPECIATION
     "Speciation" is the splitting of a species into two or more
species, and in general there are two types: a) "horizontal
speciation" (horizontal evolution; cladogenesis) refers to
speciation in which daughter species coexist in time; and b)
"vertical speciation" (vertical evolution; phyletic evolution)
refers to speciation which involves a transformation (usually
gradual) from one species to another without an increase in
species number.
     The term "allopatric speciation" refers to the development
of distinct species via differentiation of populations in
geographic isolation.
     The term "sympatric speciation" refers to speciation in
which populations inhabiting (at least in part) the same
geographic range become somehow reproductively isolated, with a
resultant gene pool isolation and ultimate species divergence.
This type of speciation is controversial, since many evolutionary
biologists do not accept the reality of the process.
     "Cichlid fishes" are a group of more than 600 species of
fishes of the family Chichlidae (order Perciformes), many of
which are popular aquarium fishes (e.g., angelfish). Cichlids are
primarily freshwater fishes and are found in tropical America,
Africa and Madagascar, and southern Asia. The majority of cichlid
species are African, and are found in great diversity in the
major African lakes. (The order Perciformes, of which the
cichlids are one family, includes some of the most important game
and food fishes (e.g., tunas, mackerels, marlins, perches, sea
basses).
... ... Mark Kirkpatrick (University of Texas Austin, US)
presents a commentary on new evidence of possible sympatric
speciation in cichlids, the author making the following points:
     1) The author points out that a species of vertebrate gives
rise to another species on average once every few million years,
a time-scale that makes the study of speciation particularly
difficult. A new study just published (A.B. Wilson et al: Proc.
Roy. Soc. Lond. B 267:2133 2000) provides evidence for an
apparent case of speciation in cichlid fishes from Nicaragua,
with the evidence suggesting the occurrence of sympatric
speciation.
     2) Concerning the cichlid fishes, the author (Kirkpatrick)
points out that the cichlids are particularly attractive for
speciation studies, with 700 cichlid species remarkable for their
diverse colors, shapes, sizes, and behaviors (which include
complex courtship and parental care). Cichlids can speciate
rapidly: the 300 species in Lake Victoria (east Africa) may have
descended from a single ancestral cichlid in only the past 12,400
years. Further, these fish may be prone to sympatric speciation.
A remarkable case involves cichlids from isolated crater lakes in
Cameroon, with genetic data demonstrating that 9 species living
in Lake Bermin are each other's closest relatives, implying that
they speciated in that lake. The lake is only 0.6 kilometers in
surface area and 14.5 meters deep, making it implausible that
geographic barriers were involved.
     3) The noted evolutionary biologist Ernst Mayr (1904- ) has
proposed that speciation can occur only when geographical
barriers enforce non-random mating while species are emerging
(allopatric speciation). Mayr's view became the orthodoxy in
evolutionary biology for many years, but there is now growing
evidence that sympatric speciation can occur in certain
circumstances. The author (Kirkpatrick) suggests the study by
Wilson et al breaks new ground by providing the first example of
replicated sympatric speciation: one species splitting in two
several times independently. "If confirmed, these natural
replicates would offer a unique opportunity to identify the
factors that trigger sympatric speciation." [*Note #1]
-----------
Mark Kirkpatrick: Fish found in flagrante delicto.
(Nature 16 Nov 00 408:298)
QY: Mark Kirkpatrick: kirkp@mail.utexas.edu
-----------
Text Notes:
... ... *Note #1: The following is an excerpt from a recent SW
report (5 Jan 01): In biology, the term "species" has had a
history filled with controversy, since the term essentially
involves categorizations of living systems, and such
categorizations can range from the subjective to the objective,
but with objective categorizations heavily dependent on extant
knowledge of biological systems. Both present and past biological
systems show an extreme diversity of form and function, and thus
far no single definition of the term "species" has been accepted
as universally useful. The current general view among biologists
is to consider a species to be a group of organisms that resemble
each other and that are generally able to interbreed and produce
fertile offspring. This is the so-called "biological species
concept", derived from Georges Buffon (1707-1788) and others, the
concept defining a species as a sexually interbreeding or
potentially interbreeding group of individuals normally separated
from other species by the absence of genetic exchange, i.e., by
"reproductive isolation". In contrast to this is the
"evolutionary species concept", championed by George Gaylord
Simpson (1902-1984), an influential paleontologist who proposed
the idea that species be defined in terms of differences that are
not dependent on sexual isolation but rather on their
evolutionary isolation, of which sexual isolation is only one
aspect. In Simpson's words: "An evolutionary species is a lineage
(an ancestor-dependent sequence of populations) evolving
separately from others and with its own unitary evolutionary role
and tendencies." Neither concept of species can be universally
applied to all biological systems. Some organisms, for example,
exhibit asexual reproduction, which makes irrelevant the idea of
reproductive isolation as defining speciation. Similarly, the
application of the evolutionary species concept depends on
extensive knowledge of lineages, and detailed lineages are not
always apparent.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 26Jan01
For more information: http://scienceweek.com/swfr.htm 

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3. MEDICAL BIOLOGY:
ON THE BIOLOGY OF ALLERGY AND ALLERGIC DISEASES
     The term "allergy" refers to a hypersensitive reaction by
the body to foreign substances (antigens) that in similar amounts
and circumstances are harmless within the bodies of people who do
not manifest such a reaction. Antigens that provoke an allergic
reaction are called "allergens", and these include various
pollens, drugs, lints, bacteria, foods, dyes and other chemicals.
     The term "antibodies" refers to proteins produced by the
immune system, these proteins binding to and destroying or
neutralizing antigens. Lymphocytes (lymph cells, lympho-
leukocytes) are a type of leukocyte (white blood cell) involved
in the immune response. There are two classes of such
lymphocytes: 1) the "B-cells", which after a cascade of immune
system events involving a specific antigen change into
proliferating specific antibody producing blood-plasma cells; 2)
the "T-cells", one subclass of which (cytotoxic T-cells)
interacts directly with foreign invaders such as bacteria and
viruses, while the other subclass of T-cells (helper T-cells) is
involved in the proliferation of antibody-specific B-cells.
     There are several types of allergic reactions. So-called
"type 1 reactions" include hay fever, insect venom allergy, and
asthma, and they involve a class of antibodies known as
immunoglobulin E (IgE). IgE molecules are bound to *mast cells,
which are located in loose connective tissue. When enough antigen
has bound with the IgE antibodies, the mast cells release
granules of *histamine and *heparin, and produce other substances
such as *leukotrienes. These chemicals dilate blood vessels and
constrict bronchial air passages. Histamine is apparently
responsible for the visible symptoms of an allergic attack: e.g.,
running nose, wheezing, and tissue swelling. The predisposition
of a person to type 1 allergic reactions is apparently
genetically determined.
... ... A.B. Kay (Imperial College School of Medicine London, UK)
presents a review of allergy and allergic diseases, the author
making the following points concerning the biology of allergy:
     1) The author points out that the term "allergy" was
introduced in 1906 by Clemens P. Pirquet [von Cesenatico] (1874-
1929), who used the term to describe both protective immunity and
hypersensitivity reactions, but over time, the term has come to
be used exclusively for hypersensitivity reactions. The term
"atopy" (from the Greek _atopos_, meaning out of place) is often
used to describe IgE-mediated diseases. Persons with atopy have a
hereditary predisposition to produce IgE antibodies against
common environmental allergens and have one or more "atopic
diseases": allergic rhinitis, asthma, or atopic eczema. Some
allergic diseases, such as *contact dermatitis and
*hypersensitivity pneumonitis, develop via IgE-independent
mechanisms and can be considered non-atopic allergic conditions.
     2) The author points out that everyone inhales aero-
allergens derived from pollen, house-dust mites, and cat dander.
In general, adults and children without atopy mount a low-grade
immune response to these aero-allergens, producing several types
of immunoglobulin antibodies, but not IgE antibodies. Persons
with atopy, by contrast, have an exaggerated immune response to
these aero-allergens, the response characterized by the
production of allergen-specific IgE antibodies, and such persons
have elevated serum levels of IgE antibodies and positive
reactions to extracts of common aero-allergens in skin-prick
tests. In general, the immunopathological hallmark of allergic
disease is the infiltration of affected tissue by a specific type
(type 2) of T-helper cells. The types of T-helper cells are
distinguished on the basis of the types of *cytokines they
produce when activated.
     3) In utero, T cells of the fetus are primed by common
environmental allergens that cross the placenta, with the immune
response of virtually all newborn infants dominated by type 2 T-
helper cells. It has been proposed that during subsequent
development the normal (i.e., non-atopic) infant's immune system
shifts in favor of a type 1 T-helper cell-mediated response to
inhaled allergens, whereas in the potentially atopic infant there
is a further increase in type 2 T-helper cells that were primed
in utero. Microbes are probably the chief stimuli of protective
type 1 T-helper cell immunity.
     4) The author suggests the marked increase in the prevalence
of atopic disease in western Europe, the US, and Australasia
during recent years indicates the importance of environmental
influences. An informative example is the change in the incidence
of seasonal allergic rhinitis and asthma after the reunification
of Germany. These disorders were less common in East Germany than
in West Germany before reunification, whereas since
reunification, the prevalence of atopy and hay fever, but not
asthma, has increased among children who spent their early
childhood in East Germany. The author suggests this phenomenon
raises the possibility that a Western lifestyle accounts for the
increase in prevalence. Perhaps in Western countries the
developing immune system is deprived of the microbial antigens
that stimulate type 1 T-helper cells, because the environment is
relatively clean and the use of antibiotics for minor illnesses
in early life is widespread. The author suggests the results of
epidemiological studies seaport this theory.
-----------
A.B. Kay: Allergy and Allergic diseases.
(New England J. Med. 4 Jan 01 344:30)
QY: A.B. Kay: Imperial College School of Medicine, National Heart
and Lung Institute, London (UK).
-----------
Text Notes:
... ... *mast cells: Mast cells are white blood cells
(leukocytes) containing dense granules of various substances,
with mast cells often associated with connective tissue.
... ... *histamine: A local hormone that acts as a powerful
stimulant of gastric secretion, constriction of bronchial smooth
muscle, and dilation of blood vessels.
... ... *heparin: The heparins are polymers of O- and N-linked
sulfated glucosamines and hexuronic acids (iduronic and
glucouronic) joined by glycoside linkages, and they are the
most acidic organic acids in the human body. When administered as
pharmacological agents, the heparins have anticoagulant
activity, but they are not ordinarily present in blood, and their
normal function has been a mystery. Mast cells are one of the two
types of cells (the other type being basophils) that synthesize
heparin.
... ... *leukotrienes: In general, a "leukotriene" is a member of
a family of pharmacologically active substances derived from
polyunsaturated fatty acids (especially from arachidonic acid),
some of which contain a peptide moiety based on cysteine. The
leukotrienes are classified as "local hormones", i.e., hormones
that are not stored, but which are synthesized in response to
specific stimuli. They are formally derived from eicosanoic acid
and contain a set of 3 conjugated double bonds (thus the suffix
"triene").
... ... *contact dermatitis: In general, a skin rash resulting
from exposure to either an irritating (e.g., an acid) or allergic
substance.
... ... *hypersensitivity pneumonitis: A chronic progressive form
of pneumonia resulting from exposure to any of a variety of
antigens.
... ... *cytokines: In general, a cytokine is any substance that
promotes cell growth and cell division.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 26Jan01
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
MEDICAL BIOLOGY:
ON THE PRESENT WORLD EPIDEMIC OF ALLERGIC DISEASES
     The term "antigen" refers to any substance that elicits an
immune response, and an individual who is overreactive to an
antigen that is tolerated by most others is said to be "allergic"
(hypersensitive). When an allergic reaction occurs, there is
usually some tissue injury, and the antigens that induce an
allergic reaction are called "allergens". Common allergens
include certain foods, antibiotics, vitamins, drugs, vaccines,
insect and snake venoms, cosmetics, plant chemicals, pollens,
dust, molds, iodine-containing dyes, etc. 
     Asthma is a chronic *inflammatory disorder that produces
*sporadic narrowing of the airways. Attacks are brought on by
spasms of *smooth muscle in the walls of the smaller *bronchi and
bronchioles, causing the passageways to close partially or
completely (bronchoconstriction). Symptoms include periods of
coughing, difficult breathing, and wheezing that may abate
spontaneously or with treatment. The patient has trouble
inhaling, and air may be trapped in the *alveoli during
expiration. The airways of people with asthma are hypersensitive
to a variety of stimuli that normally do not trigger
bronchoconstriction in people without asthma. Sometimes the
trigger is an allergen, such as pollen, house dust mites,, molds,
or a particular food.
     In the US, approximately 12 million people have asthma. From
1982 to 1992, the US prevalence of asthma increased from 34.7 to
49.4 per 1000. The death rate due to asthma increased by 40
percent, from 13.4 to 18.8 per million, with the death rate 5
times higher for blacks than for whites. Asthma is currently the
leading cause of hospitalization for children, and the primary
chronic condition causing school absenteeism.
... ... A recent journal supplement presents 6 papers reviewing
current research concerning allergy and asthma. Stephen T.
Holgate (University of Southampton, UK) reviews the current
epidemic of allergy and asthma, the author making the following
points:
     1) Our knowledge of allergy has evolved slowly, beginning
with the description by John Bostock of catarrus aestivus (hay
fever) (1819), the recognition by Charles Blackley of pollen
grains as causative agents (1873), the discovery of a
transferable tissue-sensitizing factor in the serum by Frausnitz
and Kuestner (1921), and the identification of this factor as an
*immunoglobulin subclass (immunoglobulin E; IgE) by two separate
laboratories (Johanssen and Ishizaka) in 1967.
     2) The past 30 years have witnessed a spectacular increase
in our knowledge of the cellular and molecular mechanisms of
allergic disease, and this has been paralleled by the rising
trends in the incidence and health impacts of these diseases
worldwide. Whereas in Bostock's and Blakeley's time hay fever was
a rare disorder restricted to the privileged class, at present
almost half the population of the West exhibits sensitization to
one or more environmental allergens. In countries such as the UK
and Australia, this translates to 1 in 4 children under the age
of 14 years having asthma, and 1 in 5 children under the age of
14 years having *eczema. Added to this is the occurrence of
serious allergic disorders caused by new allergens such as nuts,
soya, and latex.
     3) The author suggests that allergic diseases, such as
asthma, *rhinitis, eczema, and food allergies, are reaching
epidemic proportions in both the developed and developing world,
and that key factors driving these rising trends are apparently
increased exposure to sensitizing allergens and reduced
stimulation of the immune system during the critical periods of
development. In allergic disease, there is a polarization of *T-
lymphocyte responses, and enhanced secretion of *cytokines
involved in regulation of various immune system cells, and this
ultimately leads to inflammation and disease.
     4) The author suggests that although genetic factors may
explain at least part of the wide intercountry differences in
allergic disease incidence, they do not explain the rising
disease trends. The current consensus hypothesis is that higher
standards of hygiene deprive the developing immune response of
important signals during the period from the fetus to up to 5
years after birth, signals important for immune system
development. This hygiene hypothesis "best accommodates the link
between allergy and social class, the urban to rural gradient,
infant diet, over-use of antibiotics and the East to West
gradient of disease."
     5) The author concludes: "The recognition that most atopic
disorders [allergic disorders] have their origins in childhood,
are increasing in incidence in developed and developing countries
and have strong links to the environment suggests that solutions
to stop the epidemic are more likely to come from public health
than pharmacological interventions."
-----------
Stephen T. Holgate: The epidemic of allergy and asthma.
(Nature 25 Nov 99 402supp:B2)
QY: Stephen T. Holgate [sth@soton.ac.uk]
-----------
Text Notes:
... ... *inflammatory disorder: In general, inflammation is a
fundamental pathologic process consisting of a dynamic complex of
cellular and chemical reactions occurring in affected blood
vessels and adjacent tissues in response to an injury or abnormal
stimulation caused by physical, chemical, or biological agents.
... ... *sporadic: In this context, the term "sporadic" refers to
a reversible phenomenon (e.g., asthmatic attack) that occurs
irregularly.
... ... *smooth muscle: Smooth muscle was originally
differentiated from striated muscle on the basis of microscopic
appearance, but there are important other differences both
functional and molecular. In general smooth muscle is
specialized for slow sustained contractions such as those
involved in the control of the diameters of blood vessels.
... ... *bronchi and bronchioles: A "bronchus" is one of the two
subdivisions of the trachea that serve as airways to and from the
lungs, and a "bronchiole" is one of the approximately 6
generations of linear branches of the bronchi.
... ... *alveoli: In general, an "alveolus" is a small cavity or
socket, and in this context, a [pulmonary] alveolus is one of the
thin-walled sac-like terminal dilations of the respiratory
bronchioles and alveolar ducts across which gas exchange occurs
between alveolar air and the pulmonary capillaries.
... ... *immunoglobulin: The immunoglobulins are a large
glycoprotein category that includes antibodies as a subset. In
general, an "antibody" is a protein molecule produced by the
immune system of vertebrate organisms, the molecule designed to
specifically interact with a particular antigen.
... ... *eczema: In general, an inflammatory conditions of the
skin.
... ... *rhinitis: (nasal catarrh) In general, inflammation of
the nasal mucous membranes.
... ... *T-lymphocyte: (T-cells) Lymphocytes (lymph cells,
lympho-leukocytes) are a type of leukocyte (white blood cell)
involved in the immune response. T-lymphocytes are lymphocytes
that mature in the thymus gland.
... ... *cytokines: A cytokine is any substance that promotes
cell growth and cell division. Cytokines mediate many functions
of the immune system.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 25Feb00
For more information: http://scienceweek.com/swfr.htm

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4. ASTROPHYSICS: WHITE DWARF STARS AND DARK MATTER
A "white dwarf star" is an intrinsically faint star with a very
small radius and high density. The mass of a typical white dwarf
star is approximately 0.7 solar-masses, and the average radius is
approximately 8000 kilometers. This produces a mean density of 6
x 10^(5) grams per cubic centimeter, or 10 tons per cubic inch.
Surface temperatures of white dwarf stars are between 4000 and
85,000 degrees kelvin, and brightness ranges from 10^(-4) to 10
times that of the Sun. White dwarf stars are composed largely of
helium and carbon or heavier elements. It is believed that white
dwarf stars are the final stage in the evolution of relatively
low-mass stars after they have lost their outer layers and
undergone gravitational collapse [*Note #1].
... ... S.D. Kawaler and M. Dahlstrom (Iowa State University, US)
present a review of current research on white dwarf stars, the
authors making the following points:
     1) The authors point out that there are apparently large
numbers of white dwarf stars present in our Galaxy, with the
total number unknown because such stars are too small and too dim
to be easily observed. White dwarfs, in fact, were only
identified as a distinct class of stars less than 100 years ago,
and almost all of the catalogued white dwarf stars lie within our
neighborhood, with nearly half the number of known white dwarf
stars found within 75 light-years of our Sun.
     2) At the enormous interior densities of white dwarf stars,
the self-gravity of the star is too strong to be balanced by
ordinary gas pressure, and the only force keeping the star from
total destruction is the behavior of electrons: According to the
Pauli exclusion principle, no two electrons in the same system
can share the same quantum numbers, and therefore no two
electrons can share the same quantum state. The gravity of a
white dwarf star compresses the electrons to the point where they
cannot be any closer, and this "electron degeneracy pressure"
stabilizes the star at an incredibly high density: one million
times that of water. No substance on Earth has a density anywhere
close to this. The densest terrestrial material, pure iridium,
has a density 22.65 times that of water; gold is at 19.3; iron is
at 7.9 times that of water.
     3) Measurements of the rotation of our Galaxy indicate there
is 10 times more matter in the Galaxy than can be accounted for
by the stars, gas nebulae, and other visible matter. This "dark
matter" apparently comprises between 90 and 99 percent of the
entire Universe. In our Galaxy, the distribution of dark matter
is presumed to be in a spherical region called the "dark halo",
the region extending far beyond the visible disk of the Milky
Way.
     4) The actual composition of dark matter is unknown, but
most of it must be ordinary matter too faint to detect and at the
same time widespread in the Cosmos. One attempt to identify dark
matter, with the assumption that such matter involves stellar-
mass objects, is the Massive Compact Halo Object (MACHO) survey.
The idea is that when massive dark objects drift through space
and come between Earth and a more distant star, the gravity of
the massive dark object will cause the light from the distant
star to brighten according to the theory of "*gravitational
lensing", which is derived from Einstein's theory of general
relativity. By observing the change in the brightness of the
star, the MACHO project can determine the mass of the intervening
dark object.
     5) An unexpected current conclusion of the MACHO survey is
that dark objects typically have masses near 0.5 solar-masses.
Had these objects been ordinary stars, they would have been
detected long ago by their own light. Their relative mass and
dimness leaves only one possibility: the dark objects can only be
white dwarf stars. The current estimate, based on the MACHO
survey, is that up to 50 percent of the mass of the dark Galactic
halo is in the form of old white dwarf stars. If this
interpretation is correct, not only are white dwarf stars common,
but they also outnumber ordinary stars 5 to 1.
-----------
S.D. Kawaler and M. Dahlstrom: White dwarf stars.
(American Scientist Nov/Dec 200 88:498)
QY: Steven D. Kawaler: sdk@iastate.edu
-----------
Text Notes:
... ... *Note #1: See related background material below.
... ... *gravitational lensing: See related background material
below.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 26Jan01
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
ASTROPHYSICS: AN EXTREMELY COOL WHITE DWARF STAR
One of the great achievements of astrophysics during the second
half of the 20th century was a detailed theoretical approach to
the birth and death of stars. The sequence of events during the
death of a star, when its fuel is exhausted, involves a radical
alteration of the internal structure of the star, including a
blow-off of many of its outer layers. According to the current
view of stellar evolution, the remnant mass after the outer-
region blow-off determines the ultimate fate of the star. If the
remnant mass is greater than 1.44 solar masses (the Chandrasekhar
limit for a star with no hydrogen content; the limit varies
slightly, depending on star composition and star rotation), the
star, which in any case can no longer support itself against the
inward pull of its own gravity, collapses into either a *neutron
star or a black hole. If, however, the remnant mass is less than
the Chandrasekhar limit, the star also undergoes gravitational
collapse, but it collapses into a so-called "white dwarf star", a
relatively cool and extremely dense star about the size of Earth
but with a mass approximately that of the Sun.
... ... S.T. Hodgkin et al (6 authors at 5 installations, UK US
ES) now report the accidental discovery of what is apparently the
coolest white dwarf yet identified, the authors making the
following points:
     1) The authors point out that white dwarf stars cool
gradually over billions of years, and it has been suggested they
make up much of the so-called "dark matter" in the halo of our
Galaxy. Although extremely cool white dwarfs have proved
difficult to detect because of both their low luminosity and
their expected similarity in color to other classes of dwarf
stars, recent models have suggested that white dwarfs may be much
more blue in color than previously supposed. The authors suggest
this may indicate that earlier searches for Galactic halo white
dwarfs may have been looking for the wrong kinds of objects.
     2) The authors report an infrared spectrum of an extremely
cool white dwarf, the spectrum consistent with the new models of
white dwarf color. The authors determined the temperature of this
star to be 3500 +- 200 degrees kelvin, "making it the coolest
known white dwarf." The authors suggest the kinematics of this
star indicate that it is in the halo of our Galaxy, and the
density of such objects, as implied by the serendipitous
discovery of this star, is "consistent with white dwarfs
dominating the dark matter in the halo."
-----------
S.T. Hodgkin et al: Infrared spectrum of an extremely cool white
dwarf star.
(Nature 6 Jan 00 403:57)
QY: S.T. Hodgkin: sth@ast.cam.ac.uk
-----------
Text Notes:
... ... *neutron star or a black hole: The important
consideration here is the competition between two forces: a) the
enormous inward pull of gravity produced by the mass of the star;
and b) the repulsive forces between the constituents of atoms. In
an ordinary star, the radiation pressure produced by the burning
of the core of the star is enough to counteract the inward
gravitational force and keep the star from collapsing; in a star
that has exhausted its fuel, such radiation pressure is severely
reduced and the star begins a gravitational collapse due to its
enormous mass. But how far will the collapse proceed? 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. The average density of a neutron star is
10^(15) grams per cubic centimeter, and the weight of an object
on the surface of a neutron star would be 10^(11) its weight on
the surface of the Earth. Neutron stars apparently have an outer
shell of iron, but it is iron like no Earth iron, an iron of 4
orders of magnitude greater density. On the other hand, if the
terminal stages of star death leave a remnant star mass greater
than 3 solar-masses, the ultimate gravitational collapse will
produce a black hole, a relativistic singularity. A black hole is
a localized region of space from which neither matter nor
radiation can escape. The "trapping" occurs because the requisite
escape velocity, which can be calculated from the relevant
equations, exceeds the velocity of light and is therefore
unattainable. 
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 12May00
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
WHITE DWARF STARS AND GRAVITATIONAL MICROLENSING
Gravitational lensing is the bending of light and other radiation
by a massive gravitational entity such as a star, a black hole, a
galaxy, or a cluster of galaxies. The effect is predicted by
Einstein's theory of relativity and was first detected during a
total solar eclipse by Eddington in 1919. Large-scale
gravitational lensing causes multiple images of an object, the
type and arrangement of the images determined by the specifics of
the lensing entity. Gravitational "microlensing" is a small-scale
lensing effect, the gravitational field of the lensing object not
strong enough to form distinct images of the background source,
but instead causing an apparent brightening of the source. Stars
are expected to vary in brightness in a characteristic manner if
low-mass stars pass in front of them, and this effect has been
detected in the Large Magellanic Cloud and in the central bulge
of our Galaxy. The Magellanic Clouds are two comparatively small
and irregular galaxies close to our own galaxy, visible by the
naked-eye but observable only in the southern hemisphere, and
named after Ferdinand Magellan, who first recorded them in 1519.
The Large Magellanic Cloud has a diameter of approximately 10,000
*parsecs, and lies at a distance of approximately 50,000 parsecs
from Earth. The analysis of gravitational microlensing events of
stars in the Large Magellanic Cloud indicates the masses of the
lensing objects are in the range 0.3 to 0.8 solar-masses, which
suggests they might be old *white-dwarf stars. ... ... In an
analysis of white dwarf stars as possible sources of
gravitational microlensing events in the Large Magellanic Cloud,
Brad Hansen points out that 1) if white dwarfs exist in abundance
in the *halo of our Galaxy, this would apparently have profound
implications for our understanding of the early generations of
stars in the Universe; 2) previous attempts to theoretically
constrain the contribution of white dwarfs to microlensing
indicated they can account for only a small fraction of the
events, but these estimates relied on models of white dwarf
cooling that may be inadequate for the oldest white dwarfs. The
author presents cooling models proposed as appropriate for very
old white dwarfs, and using these models, the author reports that
the widely held idea that old white dwarfs are red applies only
to those with a helium atmosphere. Old white dwarfs with hydrogen
atmospheres, which could be a considerable fraction of the total
population of old white dwarfs, will appear blue, with colors
similar to those of the faint blue sources in the *Hubble Deep
Field. The author suggests that observational searches for the
population of microlensing objects should therefore look for
faint blue objects, rather than for faint red objects.
-----------
Brad M.S. Hansen (University of Toronto, CA): Old and blue white-
dwarf stars as a detectable source of microlensing events.
(Nature 27 Aug 98 394:860) 
QY: Brad M.S. Hansen: hansen@cita.utoronto.ca
-----------
Text Notes:
... ... *parsecs: 1 parsec equals 3.262 light-years, or 30.86 x
10^(12) kilometers.
... ... *white-dwarf stars: These are extremely dense and compact
stars that have undergone gravitational collapse after nuclear
fusion burn-out in their centers. They are the final stage in the
evolution of low-mass stars after such stars have lost their
outer layers. The white dwarfs are about the size of Earth, but
with a mass about that of the Sun.
... ... *halo: A galactic halo, such as that associated with our
own Galaxy, is a spheroidal distribution of old stars and
globular clusters of old stars surrounding the galaxy. In the
case of our own Galaxy, the galactic halo has a radius of
approximately 50,000 light years.
... ... *Hubble Deep Field: The orbiting Hubble Space Telescope
has the ability to discern images of galaxies too faint to be
picked up by planet-based and other orbital telescopes. After the
Hubble Space Telescope was repaired in 1993, one of the projects
begun with this instrument was the Hubble Deep Field Project,
which involves long-exposure detection of radiation received from
a relatively small area of the sky, the long-exposure providing
information concerning "deep" objects, i.e., objects extremely
distant from the instrument (in this case, beyond our local
Universe).
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 18Sep98
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
STUDY OF A PULSATING WHITE DWARF STAR
White dwarfs are the final phase in the evolution of low mass
stars. The stars from which they originate can be up to 8 solar
masses, but they lose 90% of their mass during star death, and
the remaining mass contracts until they have diameters only 1%
that of the sun. Most dead stars are white dwarfs, approximately
the size of the Earth, with masses approximately the mass of the
sun. This of course means an enormous density, 0.1 to 100 tons
per cubic centimeter, resulting from a terminal star the size and
mass of the sun collapsing to Earth-size. In a white dwarf, the
ordinary atomic structure has broken down completely, with
electrons and nuclei compacted tightly together by the
gravitational force. The luminosity of white dwarfs is low, and
they gradually cool to become cold and dark objects. Many white
dwarfs have been identified, the first of them the dark companion
of the star Sirius. It is estimated that in our galaxy alone the
number of white dwarf stars is of the order of 10^(10). Don
Winget et al (University of Texas Austin, US; Universidade
Federal do Rio do Sul, BR) report that a study of the white dwarf
star BPM 37093 indicates this particular pulsating white dwarf is
massive enough (about twice the white dwarf average) to have a
crystalline interior despite its apparent relatively high surface
temperature of over 11,000 degrees Celsius. But more evidence is
needed to sort out effects that could mimic indicators of
crystallization, and observations next year by the Hubble Space
Telescope of this star are planned.
QY: D. Winget, Univ. Texas Austin (512) 471-3350
(Astrophys. J. 1 Oct 97) (Science-Week 31 Oct 97)
For more information: http://scienceweek.com/swfr.htm

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

5. PARTICLE PHYSICS: THE SEARCH FOR THE HIGGS BOSON
     The current "Standard Model" in particle physics is
essentially a combination of two theories into a single framework
to describe all interactions of subatomic particles, except those
interactions due to gravity. The two theories are a)
"*electroweak theory", which describes interactions via the
electromagnetic force and the "*nuclear weak force", and b)
*quantum chromodynamics, which is the theory of the *strong
nuclear force. Both of these theories describe the interactions
between particles in terms of the exchange of intermediate
"messenger" particles that have one unit of intrinsic angular
momentum ("spin"). In addition to these force-carrying particles,
the Standard Model encompasses two families of subatomic
particles that comprise matter and that have spins of one-half
unit. These particles are the *quarks and the *leptons, of which
there are 6 varieties ("flavors") of each, related in pairs in
three "generations" of increasing mass. Ordinary matter is built
from the lightest generation; heavier types of quark and lepton
have been discovered in studies of high-energy particle
interactions.
     According to current physics, all particles in nature are
either fermions or bosons, with fermions (always elementary
particles) having half-integer spin (spin-states characterized by
half-integer multiples of Planck's constant divided by 2ã), and
bosons (all other particles) having integer spin (spin-states
characterized by integer multiples of Planck's constant divided
by 2ã). In general, bosons are particles that obey *Bose-Einstein
statistics, and they include photons, *pi mesons, all nuclei
having an even number of particles, and all particles with
integer or zero spin.
     In theory, there are 6 types of quarks, the so-called "top
quark" the most massive and with an electric charge of +2/3. In
1995, two independent groups reported they had found the top
quark, and they established the mass of the top quark as
approximately 176 billion electron volts (176 Gev).
     The "Z particle" is an electrically neutral carrier of the
weak nuclear force that acts upon all known subatomic particles.
The mass of the Z particle (93 GeV) is approximately 100 times
the mass of the proton, and it has a lifetime of only 10^(-25)
seconds. The Z particle is essentially the neutral partner of the
related electrically-charged "W particle". The W particle has
either positive or negative charge, both with a mass of 83 GeV.
Direct evidence for both Z and W particles was obtained in 1983.
     In general, the "Higgs particle" (named after Peter Higgs,
who proposed the particle in 1964, is the carrier of an all-
pervading fundamental field ("Higgs field") hypothesized to endow
elementary particles with mass via interactions of the field with
the elementary particles. The idea is that the variety of masses
of elementary particles arises because the different particles
have different strengths of interaction with the Higgs field. The
Higgs field is without direction (scalar), and the Higgs
particle, which "carries" the Higgs field (the particle
corresponding to perturbations in the Higgs field), is a spin-
zero particle with a non-zero mass. Since it is spin-zero, the
Higgs particle is thus a boson, and so it called the "Higgs
boson."
... ... M. Riordan et al (Stanford Linear Accelerator Center, US)
present a review on current research on the Higgs boson, the
authors making the following points:
     1) The authors point out that a critical requirement of the
Standard Model is a means to endow elementary particles with the
property of mass. According to the Higgs mechanism, particle
masses are the result of an invisible energy field (Higgs field)
that permeates space and confers inertia upon most elementary
particles. Without such an all-pervasive ethereal medium, the
elementary particles would remain forever massless like the
photon -- "racing about at light speed and never coalescing into
galaxies, stars, planets, and people."
     2) According to the wave-particle duality of quantum
mechanics, the Higgs field should become manifest as a spinless
particle called the "Higgs boson", which corresponds to
disturbances in the field. Searches for this object have occurred
at ever higher energies since the late 1970s, and possible
evidence for its existence was recently obtained at the European
Center for Particle Physics (CERN). New searches are about to
begin on the recently upgraded Tevatron collider at the Fermi
National Accelerator Laboratory (US).
     3) The authors point out that the evidence so far indicates
that the Higgs boson is a very massive particle, heavier than all
known elementary particles except possibly the top quark. There
are indications of the direct production of a Higgs boson near
115 Gev, a mass-energy which would be in a agreement with recent
indirect evidence that such a particle should have a mass less
than approximately twice that of the Z particle.
     4) The authors conclude: "The advanced linear electron-
positron colliders now being designed in Germany, Japan, and the
United States are ideally suited for detailed studies of such a
relatively light Higgs boson."
-----------
M. Riordan et al: The search for the Higgs boson.
(Science 12 Jan 00 291:259)
QY: Michael Riordan: michael@slac.stanford.edu
-----------
Text Notes:
... ... *electroweak theory: In 1979, Sheldon Glashow, Abdus
Salam, and Steven Weinberg shared the Nobel Prize in Physics for
their formulation of electroweak theory, which is essentially the
mathematical unification of the electromagnetic force and the
nuclear weak force.
... ... *nuclear weak force: The nuclear weak interactions are
the interactions involved in radioactive decay.
... ... *quantum chromodynamics: Quantum chromodynamics (QCD) is
a theory that describes the strong interaction (strong nuclear
force) in terms of quarks and antiquarks and the exchange of
massless "gluons" between them. The "chromo-" in chromodynamics
derives from the use of designated "color" attributes of quarks,
the various "colors" labels for various quark properties.
... ... *strong nuclear force: The current view among nuclear
physicists is as follows: each nucleus contains a population of
protons and neutrons, collectively known as nucleons, as well as
a host of other particles that bind the nucleons together. Each
nucleon, in turn, is made up of three quarks bound by what is
called the strong nuclear force.
... ... *quarks: A quark is a hypothetical fundamental particle,
having charges whose magnitudes are one-third or two-thirds of
the electron charge, and from which the elementary particles may
in theory be constructed.
... ... *leptons: A class of elementary particles. Although they
are affected by electromagnetic and gravitational forces, apart
from that they are involved only with weak interactions, acted
upon by weak forces but not by strong forces, as opposed to
quarks, which are acted upon by strong forces but not by weak
forces. One further difference between leptons and quarks is that
leptons can be isolated as single particles, whereas quarks
apparently cannot. The leptons include the electron, the muon,
the tau, and their associated neutrinos. The mass of the tau is
approximately 3484 times the mass of the electron; the mass of
the muon is intermediate.
... ... *Bose-Einstein statistics: Bose-Einstein statistics is
the statistical mechanics of a system of indistinguishable
particles for which there is no restriction on the number of
particles that may simultaneously exist in the same quantum
energy state. Particles that obey Bose-Einstein statistics are
called "bosons".
... ... *pi mesons: (pions) Pi mesons are subatomic particles
with masses approximately 270 times the mass of the electron.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 26Jan01
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
PARTICLE PHYSICS: AN EXCHANGE CONCERNING RELEVANCE
     In general, "reductionism" is the idea that macroscopic
phenomena can be explained in terms of microscopic entities
and/or events, but the specific meaning of the term depends upon
context and the conceptual identification within a particular
science of levels of understanding. In biology in general, for
example, "reductionism" is the term applied to attempts to
explain biological phenomena in the language of physics and
chemistry. In neurobiology, the term "reductionism" may be
applied to attempts to explain human cognitive behavior in terms
of the behavior of nerve cells and their connections. In
evolutionary biology, the term "reductionism" may be applied to
attempts to explain the dynamics of evolution in terms of
molecular genetics. In physics and chemistry, the term
"reductionism" may be applied to attempts to explain the
macroscopic behavior of physical or chemical systems in terms of
events at the level of atomic phenomena. Also in physics, the
term "reductionism" may be applied to attempts to explain both
the macroscopic behavior of a physical system and/or the
microscopic atomic behavior of the entities of the system in
terms of events at the still more microscopic level of
fundamental particles and fundamental forces.
     The various sciences are split by scientists (not by nature)
into various levels of explanation, with researchers working at
the various levels using various techniques and concepts.
Ordinarily, in the practice of science, the working scientist
does not spend much time cogitating about whether a general
reductionist approach is useful or not useful, philosophically
valid or not valid, or whatever. The attitude essentially is that
here is a house, I choose to study in detail the nature of the
bricks, you choose to study in detail the nature of the
construction of the house, I enjoy what I'm doing, you enjoy what
you're doing, and each of us is making some contribution to a
general understanding of the nature of the entity "house". This
division of labor has been quite fruitful in science, and there
is never much of a problem concerning the existence of various
levels of investigation until the person who studies bricks says
that what he or she is doing is more important than what the
person who studies the construction of the house does, or when
the person studying the construction of the house says it is the
study of the construction of the house that is more important
than the study of bricks. From the standpoint of "nature", from
the perspective of the giant star *Betelguese, for example, a
relatively nearby stupendous and violent supergiant star
apparently 400 to 500 times the diameter of our Sun, any serious
bickering on the planet Earth about the relative merits of
various levels of understanding in science begins to smack of
farce. But science is a human enterprise, and occasionally the
bickering about reductionism and levels of understanding does get
serious and does occupy attention.
     In 1996, in a most prestigious physics journal (_Reviews of
Modern Physics_), the physicist Robert Cahn stated that particle
physics is essential to the understanding of our everyday world,
that "particle physicists construct accelerators kilometers in
circumference and detectors the size of basketball pavilions not
ultimately to find the *t-quark or the *Higgs boson, but because
that is the only way to learn why our everyday world is the way
it is... Given the masses of the quarks and *leptons, and nine
other closely related quantities, [the current theory of particle
interaction] can account in principle for all the phenomena in
our daily lives."
     In July 1998, in the journal _Physics Today_, Pablo Jensen,
a condensed matter physicist, took issue with Cahn's views and
suggested that Cahn's "reductionist vision seems to be shared by
many other particle physicists." Stating that he wished to
"reopen a debate in the physics community," Jensen made the
following points: 1) The reductionist ideas of Cahn and other
reductionist particle physicists are wrong: even if we knew all
the "fundamental" laws, we could not say anything useful about
our everyday world. Our everyday world is irremediably
macroscopic, and macroscopic concepts are needed to understand
it. 2) Contrary to the pretensions of particle physicists,
science is organized in decoupled layers, each with its own
elementary entities or concepts, which generally are not simply
derived from those of the lower level but constructed in creative
efforts... Particle physics is practically irrelevant to
understanding our everyday world... "If we learned tomorrow that
previous results and analysis had overlooked certain systematic
errors, and that the t-quark mass is near 195 *GeV and not 175
GeV, it is particle physics that would have to adjust to remain
in agreement with the rest of physics, and not vice versa." 3)
Considering, for example, the property of *chirality of large
molecules (e.g., a sugar or any biological molecule), for all
practical purposes, such molecules do not show the symmetry
expected from the fundamental laws  -- in this case, quantum
mechanics. 4) In the study of phase transitions, there are
characteristics of such transitions that apparently depend on the
collective behavior of the system and are not determined by the
microscopic interactions. 5) Each level of complexity must be
studied with its own instruments, and requires the invention of
new concepts adapted to describe and understand its behavior...
Intermediate concepts such as *entropy, *dissipative structures,
cells, genes, etc., cannot be simply "deduced" from the
fundamental laws: such concepts are said to be "emergent" because
they arise at high levels of complexity and must be invented at
those levels to deal with specific situations... These emergent
concepts are as real and as fundamental as the concepts and
particles introduced by particle physicists. The author
concludes: "By all means let us each study our chosen "layer" of
reality, whether it involves quarks or convective cells. But let
us also remember that each layer is just one part of the greater
whole. Accounting for all the phenomena in our daily lives *in
principle* is entirely different from accounting for them in
actuality."
     In the November 1998 issue of _Physics Today_, Robert Cahn
presents a rebuttal to the critique of Pablo Jensen, the author
making the following points: 1) The empirical parameters of the
*Standard Model of particle physics shape the most familiar
aspects of our physical surroundings... Given *these parameters,
the Standard Model, which subsumes the Maxwell and Schroedinger
equations, determines all the fundamental processes of
*electroweak and strong interactions. Changes in the basic
parameters would produce worlds quite different from our own. 2)
The stuff of daily life is made just of electrons and the
lightest quarks. However, we cannot understand these particles by
themselves, because they are intimately connected to others
accessible only in high energy collisions. 3) Concerning the
supposed irrelevance of particle physics, constructs that embody
the essential physical features of complex systems are
indispensable, but their success is not a reason for abandoning
the search for basic physical laws. 4) Nature is not neatly
partitioned into autonomous layers, as Jensen suggests. On the
contrary, the macroscopic makes manifest the microscopic... The
gross properties of the materials around us, their color,
conductivity, and strength, reflect the details of their quantum
mechanical states. Likewise the structure of atoms reflects
divisions in the subatomic world... "Only by willfully closing
our eyes can we miss the connection between the fundamental
interactions and their manifestations that surround us." The
author concludes: "We particle physicists share with all
physicists the goal of explaining the world. We differ by asking
ever more basic questions. Like young children who relentlessly
insist, Why?, particle physicists ask, Why is there light? Why
are electrons light and protons heavy? Why are there electrons or
protons, anyway? 'Just because' and 'Who cares?' will not satisfy
the curious child, nor should they satisfy us."
     The same issue of the journal includes a number of letters
on the subject from other physicists, and in one of these letters
Paul Roman suggests that perhaps the motivation for the debate is
that the physics research "grant pie is shrinking while the
number of pie-hungry individuals is still increasing." Perhaps
that is so, and perhaps that is also the motivation behind
debates concerning the reductionist approach in other sciences.
But perhaps such motivations are also part of science as a human
enterprise. Meanwhile, the enormous furnace of Betelguese
continues to roar.
-----------
R.N. Cahn (Lawrence Berkeley Natl. Lab., US)
(Rev. Mod. Phys. 1996 68:951)
QY: Robert N. Cahn, Lawrence Berkeley National Laboratory,
Berkeley, CA US
----------
P. Jensen (Claude Bernard University, FR)
Particle physics and our everyday world.
(Physics Today July 1998)
QY: Pablo Jensen, Claude Bernard University, Villeurbanne FR)
----------
R.N. Cahn (Lawrence Berkeley Natl. Lab., US)
"Particle physics and our everyday world": A reply
(Physics Today November 1998)
QY: Robert N. Cahn, Lawrence Berkeley National Laboratory,
Berkeley, CA US
-----------
Text Notes:
... ... *Betelguese: Also known as Alpha Orionis. It is the 10th
brightest star in the sky, with a luminosity 5000 times that of
the Sun, with an estimated distance of 400 light years. Some
astronomers believe its distance is 1400 light years, which would
make its luminosity 50,000 times that of the Sun. The star is a
variable, its size swelling and contracting with a period of
several years.
... ... *t-quark: (top-quark) A quark is a hypothetical
fundamental particle, having charges whose magnitudes are
one-third or two-thirds of the electron charge, and from which
the elementary particles may in theory be constructed. A t-quark
is one of the types of quarks and has an electrical charge of
+2/3.
... ... *Higgs boson: Higgs fields (named after Peter W. Higgs,
University of Edinburgh, UK) constitute a set of fundamental
theoretical fields that induce spontaneous symmetry breaking. In 
general, spontaneous symmetry breaking occurs in systems whose
underlying symmetry state is unstable. A Higgs particle is
associated with a Higgs field in the same way that a photon is
associated with the electromagnetic field. Higgs bosons are
massive mesons whose existence is predicted by certain theories.
Mesons are apparently composed of quark and anti-quark pairs;
they are produced by various high-energy interactions and decay
into stable particles.
... ... *leptons: Leptons are a class of point-like fundamental
particles showing no internal structure and no involvement with
the strong forces. There are 6 leptons: the electron, the muon,
the massive tau lepton, and a specific neutrino associated with
each of the former (3 neutrino "flavors").
... ... *GeV: (Gev) Also written as Bev, a billion electronvolts.
An electronvolt is defined as the energy acquired by an electron
falling freely through a potential difference of one volt, and is
equal to 1.6022 x 10^(-19) joule.
... ... *chirality: In chemistry, chirality is a property of
certain asymmetric molecules, the property being that the mirror
images of the molecules cannot be superimposed one on the other
while facing in the same direction.
... ... *entropy: A measure of disorder in a system. 
... ... *dissipative structures: In general, a dissipative system
is a system that loses energy by conversion of energy into heat.
... ... *Standard Model: In particle physics, the *Standard Model
is a theoretical framework whose basic idea is that all the
visible matter in the universe can be described in terms of the
elementary particles leptons and quarks and the forces acting
between them.
... ... *these parameters: The parameters referred to here are
the masses of the quarks, the masses of the charged leptons, the
strength of 3 forces, 4 numbers that describe the weak
transformations of one quark type into another, the mass of the
*W boson, and the mass of the Higgs boson.
... ... *W boson: Very massive charged particles (+ or -) that
convey part of the weak force between leptons and *hadrons. Bose-
Einstein statistics is the statistical mechanics of a system of
indistinguishable particles for which there is no restriction on
the number of particles that may simultaneously exist in the same
quantum energy state. Bosons are particles that obey Bose-
Einstein statistics, and they include photons, *pi mesons, all
nuclei having an even number of particles, and all particles with
integer *spin.
... ... *pi mesons: (pions) Pi mesons are subatomic particles
with masses approximately 270 times the mass of the electron.
... ... *spin: In quantum mechanics, "spin" is the intrinsic
angular momentum of a subatomic particle. 
... ... *hadrons: Hadrons are particles with internal structure,
e.g., neutrons and protons.
... ... *electroweak and strong interactions: The fundamental
forces comprise the gravitational force, the electromagnetic
force, the nuclear strong force, and the nuclear weak force. The
electroweak interactions comprise the electromagnetic and nuclear
weak interactions, the latter involved in radioactive decay
processes.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 13Nov98
For more information: http://scienceweek.com/swfr.htm

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6. CONDENSED-MATTER SCIENCE:
ON THE PROBLEM OF THE NATURE OF LIQUIDS
     Gases, at least in the ideal approximation approached at
high temperatures and low densities, are characterized by
complete randomness on the molecular scale. The ideal crystal, on
the other hand, is nature's most orderly arrangement. Since the
extremes of perfect chaos and perfect harmony are both relatively
simple to treat mathematically, the theories of gases and
crystals are at respectively advanced stages. Liquids, however,
representing a peculiar compromise between order and disorder,
have so far defied a comprehensive theoretical treatment.
     A solid is crystalline if it has long-range order: once the
positions of an atom and its neighbors are known at one point,
the place of each atom is known precisely throughout the crystal.
Most liquids lack long-range order, although many liquids have
short-range order. "Short range" is defined as the first- or
second-nearest neighbors of an atom. However, at distances many
atoms away, the positions of the atoms become uncorrelated.
Fluids such as water have short-range order but lack long-range
order. Certain liquids may have short-range order in one
direction and long-range order in another direction: these
comprise the "liquid crystals". Solid crystals have both short-
range order and long-range order. Amorphous solids have short-
range order but not long-range order.
     In this context, the term "symmetry" refers to a precise
correspondence between two halves of an entity with respect to
both size and shape. An entity has an "n-fold axis of symmetry"
if rotation around this axis through an angle of 360 degrees
divided by (n) produces an arrangement indistinguishable from the
original. The water molecule, for example, has a two-fold axis of
symmetry. In general, five-fold symmetry axes are forbidden in
ordinary crystals, while other axes, such as four-fold and six-
fold axes, are allowed. The reason is that long-range order
(translational periodicity), which is characteristic of crystal
lattices, cannot be present in structures with five-fold
symmetry.
... ... Frans Spaepen (Harvard University, US) presents a
commentary on some recent research on the structure of liquids,
the author making the following points:
     1) The author points out that understanding the structure of
simple liquids is a fundamental unsolved problem in the
mathematical and physical sciences. Attempts to describe liquids
as disordered crystals have all failed, and descriptions of
liquids as dense gases (fluids) remain too complex. The best
approach so far, although far from complete, has been to describe
liquids as dense packings of tetrahedral building blocks.
     2) A complete picture of the short-range order in a liquid
requires knowledge not only of the number and length of the
bonds, but also of their directions. The atomic structure of a
liquid changes over space and time, so conventional scattering
experiments using x-rays or electron or neutron provide only
directionally averaged information -- specifically the
distribution of interatomic distances. Such data has favored a
polytetrahedral model.
     3) The author points out that finding a simple structural
description of liquids, such as "periodicity" for crystals or
"sparsity" for gases, is a persistent challenge in condensed-
matter science. It is now accepted that a liquid is not a heavily
defective crystal or a random assembly of microcrystals, but a
well-defined phase in its own right. This was demonstrated most
dramatically in the late 1940s when it was shown that many simple
liquids could be supercooled far below their freezing points
without crystallization occurring. This is possible only if the
liquid structure is fundamentally different from that of a
crystal.
     4) The author calls attention to recent work by H. Reichert
et al (Nature 408:839 2000), who report the first direct evidence
for polytetrahedral structures in a monoatomic liquid trapped at
a solid interface. Reichert et al have apparently captured some
of the polytetrahedral configurations in liquid lead by aligning
the configurations against a crystalline silicon wall. They
observed the characteristic five-fold symmetry of the bonds from
the scattering of totally internally reflected x-rays, which are
sensitive only to the structure of the interface.
     5) The author (Spaepen) comments: "The experiment by
Reichert et al suggests that studying polytetrahedral structures
and their defects is a promising route toward understanding the
structure of liquids... The x-ray technique developed by Reichert
et al is a useful tool for the direct structural investigation of
a variety of crystal-melt interfaces."
-----------
Frans Spaepen: Five-fold symmetry in liquids.
(Nature 14 Dec 00 408:781)
QY: Frans Spaepen: spaepen@deas.harvard.edu
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 26Jan01
For more information: http://scienceweek.com/swfr.htm

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7. IN FOCUS: ON THE HISTORY OF THE PHYSICS OF LIGHT
"The revival of the wave theory of light, begun by Thomas Young
(1773-1829), is one of the most important features of the history
of the 19th century. Young pointed out that the dividing of a
beam of light into a refracted ray at the interface between two
mediums was to be expected from the wave theory but had not been
satisfactorily explained on the corpuscular theory. In 1801, he
presented to the Royal Society a paper 'On the Theory of Light
and Colors', in which he proposed the principle of the
interference of two wave trains as an explanation of Newton's
rings and the colors of thin plates. From Newton's measurements
of the thickness of the air layers necessary to produce the
several colors, Young was enabled to compute wavelengths. In
subsequent papers, he described the interference fringes which he
had observed by placing hairs on silk threads in front of a
narrow slit illuminated from the rear; he announced the change of
phase on reflection; he explained diffraction bands by the
principle of interference; and he showed that the spacing of
these bands gave values of the wavelength agreeing with those
obtained from Newton's rings and that, therefore, both phenomena
must be due to a common cause... But the dogmatic spirit in
regard to scientific matters was not yet dead. Young's paper
aroused a storm of protest, even of derision and abuse. He was
attacked not by the church, as was Galileo, but by some of his
scientific, or, more probably, pseudoscientific contemporaries.
His chief assailant was Henry Brougham, afterward Lord Chancellor
of England, who 'reviewed' Young's papers in the _Edinburgh
Review_. The nature of Brougham's attack is indicated by the
following quotation: 'We wish to raise our feeble voice against
innovations that can have no other effect than to check the
progress of science and renew all those wild phantoms of the
imagination which Bacon and Newton put to flight from her temple.
We wish to recall philosophers to the strict and severe methods
of investigation.' Although Young replied at length in a
privately published pamphlet, it was a long time before public
opinion was willing to receive his theories with an open mind."
-----------
F.K. Richtmyer et al: Introduction to Modern Physics (5th ed.)
(McGraw-Hill, New York 1955, p.33)
[Editor's note: Thomas Young (1773-1829) was an infant prodigy
who matured into an adult prodigy. At Cambridge, he was called
"Phenomenon Young". He studied and practiced medicine, but failed
at it because of the apparent absence of a "suave bedside
manner". But while still a medical student, he was the first to
discover the manner in which the lens of the eye changes shape
(accommodation) in focusing on objects at differing distances.
And it was Thomas Young who, in 1801, explained astigmatism as
resulting from irregularities in the curvature of the cornea. The
early rejection of Young's wave theory of light by his British
contemporaries was due more to chauvinism than to reason: the
particle theory of light was essentially British; the wave theory
of light was essentially French. At the age of 41, Young
abandoned both medicine and physics and devoted himself to an
analysis of the Rosetta Stone. In 1818, he produced a classic
paper on Egypt that laid the groundwork for the later definitive
analysis of the Rosetta Stone by Jean Francois Champollion (1790-
1832).]

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8. FROM THE SCIENCEWEEK ARCHIVE:
FETAL EFFECTS OF EXPOSURE TO ORGANIC SOLVENTS DURING PREGNANCY
Biological membranes are essentially lipid barriers with a
secondary population of attached or embedded proteins. Organic
solvents are particularly potent in their chemical action on
biological systems because they readily and quickly pass through
lipid domains such as biological membranes, including membranes
of the skin, the digestive tract, and the respiratory system.
Many women of child-bearing age are occupationally exposed to
organic solvents, and since fetal tissue is even more vulnerable
to such solvents than adult tissue, the question of the effects
on the fetus of occupational exposure of the mother to organic
solvents is of some significance. The most important women-
dominated occupations with potential chemical exposures are
health care professions and work tasks in the clothing and
textile industries, all of which involve exposures to organic
solvents. Many industrial solvents are teratogenic (i.e., capable
of producing a malformed fetus) in laboratory animals, and there
are reports of limb and central nervous system defects in mice,
marked developmental toxic effects and retardation of skeletal
growth in rats, and congenital malformations in rabbits. However,
the animal studies typically use high doses of single solvents
and a variety of routes of administration. In the human
occupational setting, exposure usually occurs to a multitude of
solvents at much lower doses by inhalation, making extrapolations
from animals to humans problematic.
... ... S. Khattak et al (6 authors at University of Toronto, CA)
now report a study to evaluate pregnancy and fetal outcome
following maternal occupational exposure to organic solvents. The
study involved 125 pregnant women who were exposed occupationally
to organic solvents and seen during the first trimester between
1987 and 1996, and 125 matched controls. The organic solvents to
which the women were occupationally exposed included aliphatic
and aromatic hydrocarbons, phenols, trichloroethylene, xylene,
vinyl chloride, acetone, and related compounds. These women
worked in the following occupations (number of women): factory
worker (37), laboratory technician (21), artist (16), printing
industry (14), chemist (13), painter (8), office worker (4), car
cleaning service (3), veterinary technician (3), orthotist (2),
funeral home service (2), carpenter (1), social worker (1). Only
women known individually to be exposed to organic solvents were
in the above groupings. The authors tabulated the occurrence of
major congenital malformations in the infants delivered by these
women. The authors report that significantly more major
malformations occurred among fetuses of women exposed to organic
solvents than matched controls (13 vs. 1). In other words, 10.4
percent of the women in the organic-solvent-exposed group
produced a malformed fetus, as opposed to 0.8 percent of the
women in the control group. 12 of the 13 malformations occurred
among the 75 women who had symptoms of exposure during their
exposure, while no malformations occurred among the exposed women
who did not exhibit symptoms during their exposure. The authors
conclude that occupational exposure to organic solvents during
pregnancy is associated with an increased risk of major fetal
malformations, and that this risk appears to be increased among
women who report symptoms associated with organic solvent
exposure. The authors suggest that exposure of women to organic
solvents should be minimized during pregnancy, and that "health
care professionals who counsel families of reproductive age
should inform their patients that some types of employment may
influence reproductive outcomes."
-----------
S. Khattak et al: Pregnancy outcome following gestational
exposure to organic solvents.
(J. Amer. Med. Assoc. 24/31 Mar 99 281:1106)
QY: Gideon Koren, The Hospital for Sick Children, 555 University
Avenue, Toronto, Ontario CA M5G 1X8.
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 30Jul99
For more information: http://scienceweek.com/swfr.htm

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9. BOOK NOTICES:

John Ziman: Real Science: What is It, and What it Means.
Cambridge University Press, 2000. 412pp. Hardcover. US$39.95
"In sum this is an important book about the practice of science
from someone who has been there... Must be read by anyone who
wants to understand modern science as it is practiced. -- Times
Higher Education Supplement.
For more information or to order this book:
http://www.amazon.com/exec/obidos/ASIN/052177229X/scienceweek

J.R. Matthews et al: Successful Scientific Writing (2nd Edition).
Cambridge University Press, 2000. 256pp. US$20.95
"Compulsory reading for all biomedical science undergraduates and
postgraduate students and all others likely to have to write or
edit scientific reports." -- Times Higher Education Supplement.
For more information or to order this book:
http://www.amazon.com/exec/obidos/ASIN/0521789621/scienceweek

George W. Barlow: The Cichlid Fishes: Nature's Grand Experiment
in Evolution.
Perseus Publishing, 2000. 351pp. Hardcover. US$28
A very readable account of the explosive diversification of
cichlid fishes in the three great lakes of East Africa.
"Overall... a lively read in natural history for general readers
and professionals alike. Behaviorists, ichthyologists, and
evolutionary biologists will find... [the] book a stimulating and
controversial work that deserves discussion and scrutiny."
-- Amy McCune (Cornell University).
For more information or to order this book:
http://www.amazon.com/exec/obidos/ASIN/0738203769/scienceweek

Pat Shipman: The Man Who Found the Missing Link: Eugene Dubois
and His Lifelong Quest to Prove Darwin Right.
Simon & Schuster, 2001, 514pp. Hardcover. US$28.
A full-scale biography of a paleontologist by a paleontologist
who writes "without sacrificing the complexities of the issues
that energize and sometimes divide scientists."
For more information or to order this book:
http://www.amazon.com/exec/obidos/ASIN/068485581X/scienceweek

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10. CORRECTION: ISSUE OF 19 JANUARY 2001
In the issue of 19 January 2001, Report #2, Note on
"Schwarzschild radius", the phrase

when a star is contracting under the influence of gravity, it
attains a particular radius then the gravitational potential will
be infinite...

should read:

when a star is contracting under the influence of gravity, at a
particular radius (Schwarzschild radius) the gravitational
potential will be infinite...

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The first issue of SCIENCE-WEEK appeared May 1, 1997, and it has
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