ScienceWeek

SCIENCEWEEK

New Books & Miscellany in the Sciences

July 4, 2003

Vol. 7 - Number 27C

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Contents:

1. Sizes of Plants and Animals
2. The 1918-1919 Influenza Epidemic Virus
3. Cosmic Rays, Clouds, and Climate
4. Atomic and Molecular Electron Affinities
5. On the Reality of Objects in Physics
6. On the Brains of Mice and Humans
7. New Books

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1. SIZES OF PLANTS AND ANIMALS

The following points are made by John Damuth (Proc. Nat. Acad.
Sci. 2001 98:2113):

1) The relationship of body size to the anatomical,
physiological, behavioral, and ecological characteristics of
animals has long been a focus of interest in zoology. As one
considers animal species of different sizes, regular, predictable
changes are seen in the relative proportions of the body's organs
and the relative rates of physiological processes such as
metabolism and growth. Students of zoology are familiar with
these scaling relationships (also called "allometries") and many
of their ecological and adaptive implications. For example, the
relative scaling of metabolism versus that of the volume of the
digestive tract affects the potential diets of herbivorous
mammals, which in turn influences their social behavior. 

2) Plant biology, on the other hand, does not have a long history
of investigation of issues involving the scaling of physiological
processes versus body-size, despite a wealth of detailed data on
plant morphology and function. This situation is perhaps because
plants are seen to exhibit degrees of modular construction,
indeterminate growth, and variety of form greater than those
shown by animals, so the idea of a plant species even having a
"body size" strikes some as problematical. Nevertheless, plant
species do have characteristic shapes and sizes and span 20
orders of magnitude in body mass. Niklas's 1994 book on plant
allometry has been described fairly as the first attempt to
provide a unified treatment of plant form and function from an
allometric perspective. However, until even more recently, the
scaling of such basic processes as metabolism and growth had
remained undocumented for a representative sample of plant
species. New analyses reveal that growth scales among plants in
the same way that it does among animals, and further underscores
the growing realization that the same scaling rules may apply to
both animals and plants, and for much the same reasons. 

3) Growth rates, or rates of production of new biomass, are of
fundamental importance in linking physiological processes to
adaptively important features such as reproductive rates and
other life history variables. Among animal species, rates of
biomass production and growth are proportional to metabolic rate,
which scales as the 3/4 power of body mass (M). This
proportionality, where organismal growth rate scales as M^(0.75),
makes intuitive sense. Cells should divide or otherwise do work
at rates roughly proportional to the rates at which they are
supplied with energy. Across different species, these rates
should be the rates of metabolism, less the energy used for
physiological maintenance and ecological demands, and energy lost
as heat. Previous work has strongly suggested that plant nutrient
flux used for photosynthesis scales as M^(0.75). This result
implies that plant growth rates should also scale as M^(0.75), a
value confirmed by Niklas and Enquist (2001). Further emphasizing
this connection between plant metabolic processes and growth
rates is the additional demonstration that the anatomical
measures of an individual's photosynthetic pigment volume (and
thus its presumed ability to obtain energy) also scale as
M^(0.75). 

Related Material:

DINOSAURS, DRAGONS, AND DWARFS: THE EVOLUTION OF MAXIMAL BODY
SIZE

The following points are made by G.P. Burness et al (Proc. Nat.
Acad. Sci. 2001 98:14518):

1) The size and taxonomic affiliation of the largest locally
present species ("top species") of terrestrial vertebrate vary
greatly among faunas, raising many unsolved questions. Why are
the top species on continents bigger than those on even the
largest islands, bigger in turn than those on small islands? Why
are the top mammals marsupials on Australia but placentals on the
other continents? Why is the world's largest extant lizard (the
Komodo dragon) native to a modest-sized Indonesian island, of all
unlikely places? Why is the top herbivore larger than the top
carnivore at most sites? Why were the largest dinosaurs bigger
than any modern terrestrial species?

2) A useful starting point is the observation of Marquet and
Taper (1998), based on three data sets (Great Basin mountaintops,
Sea of Cortez islands, and the continents), that the size of a
landmass's top mammal increases with the landmass's area. To
explain this pattern, they noted that populations numbering less
than some minimum number of individuals are at high risk of
extinction, but larger individuals require more food and hence
larger home ranges, thus only large land masses can support at
least the necessary minimum number of individuals of larger-
bodied species. If this reasoning were correct, one might expect
body size of the top species also to depend on other correlates
of food requirements and population densities, such as trophic
level and metabolic rate. Hence the authors assembled a data set
consisting of the top terrestrial herbivores and carnivores on 25
oceanic islands and the 5 continents to test 3 quantitative
predictions:

a) Within a trophic level, body mass of the top species will
increase with land area, with a slope predictable from the slope
of the relation between body mass and home range area.

b) For a given land area, the top herbivore will be larger than
the top carnivore by a factor predictable from the greater
amounts of food available to herbivores than to carnivores.

c) Within a trophic level and for a given area of landmass, top
species that are ectotherms will be larger than ones that are
endotherms, by a factor predictable from ectotherms' lower food
requirements.

3) The authors point out that on reflection, one can think of
other factors likely to perturb these predictions, such as
environmental productivity, over-water dispersal, evolutionary
times required for body size changes, and changing landmass area
with geological time. Indeed, the database of the authors does
suggest effects of these other factors. The authors point out
they propose their three predictions not because they expect them
always to be correct, but because they expect them to describe
broad patterns that must be understood in order to be able to
detect and interpret deviations from those patterns.

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2. THE 1918-1919 INFLUENZA EPIDEMIC VIRUS

The following points are made by Joshua Lederberg (Proc. Nat.
Acad. Sci. 2001 98:2115):

1) The 1918-1919 pandemic of H1N1 virus influenza was the
greatest acute plague of the 20th century. Incurring over 20
million human fatalities, however, was not a good strategy for
sustaining the evolutionary fitness of the virus, because it is
no longer extant; whereas, say, measles and chickenpox remain
with us with no evidence of remarkable genetic change, although
this may become more evident if they were to face total or near
eradication through vaccination programs.

2) The folly of flu virulence remains our chagrin, because the
threat always looms over us that this family of viruses, endemic
in birds, again may generate human-lethal gene reassortments. We
had valid scares about that contingency with the appearance of
H5N1 variant flu in Hong Kong just 3 years ago. Influenza can be
regarded as a zoonosis prevalent in birds, many of them world
travelers, with occasional outbreaks in humans and other animals
mainly rooted in nature's own experiments in genetic engineering.

3) Special importance is attached to reassortments between bird-
and human-adapted strains most likely to occur in habitats with
close contact between birds, e.g., ducks, humans, and swine (as a
mixing reservoir). For these reasons, high urgency attaches to
efforts to resurrect genetic information about the singularities
of H1N1-1918. The intact virus is nowhere to be found, but
genomic fragments can still be detected sensitively and
diagnosed. Exemplifying the latest technical advances in the use
of DNA amplification, reverse-transcriptase-PCR (RT-PCR), Jeffery
Taubenberger and his associates at the Armed Forces Institute of
Pathology initiated the tour de force of recovering sequences of
flu from paraffin-embedded pathological specimens preserved since
1918 in the AFIP collections (Science 1997 275:1793). These
sources then were augmented by samples from frozen remains of an
Inuit woman who succumbed to the flu in 1918 and was buried in
permafrost at Brevig Mission on the Seward Peninsula of Alaska's
western coast, not far from the Bering Strait. This nameless
woman has left an indelible mark on world medical history.

Related Material:

ON THE INFLUENZA PANDEMIC OF 1918

The following points are made by Robert G. Webster (Science 2001
293:1773):

Two influenza outbreaks in the 20th century challenge current
beliefs about patterns of influenza virulence. The "Spanish flu"
pandemic of 1918, rather than sparing young healthy adults,
killed millions in the prime of life. The pandemic wiped out
entire villages at opposite ends of the Earth and depressed world
population growth for 10 years. In 1997, a lethal avian influenza
virus was transmitted directly to humans from chickens in Hong
Kong: 6 of 18 clinically diagnosed human cases were fatal, and
again, many of the victims were young adults. Both of these
outbreaks suggest the emergence of highly virulent influenza
variants. Unfortunately, until the basis of influenza virulence
is understood, the human population will be defenseless against
similar outbreaks in the future. The virulence of a virus is
defined by its comparative capacity to produce disease in a host.
The 1918 Spanish flu virus was extremely virulent: it killed 10
times as many persons in the US as did the 1957 Asian flu and
approximately 20 times as many people as the 1968 Hong Kong flu.
The human population is most vulnerable to influenza viruses that
have new antigenic properties. It now takes approximately 6
months to prepare an appropriate vaccine. Although advances in
reverse genetics will shorten this time, several months will
still be needed to prepare a vaccine, and during the period
between the detection of a pandemic strain and the availability
of a vaccine, antiviral drugs will be essential. It is gravely
disquieting that no action has yet been taken to create strategic
stockpiles of such antiviral drugs.

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3. COSMIC RAYS, CLOUDS, AND CLIMATE

The following points are made by K. S. Carslaw et al (Science
2002 298:1732):

1) The correlation between cosmic rays and Earth's cloud cover
over a solar cycle, first reported by Svensmark and Friis-
Christensen in 1997, was hailed by some as the missing piece in
the puzzle of understanding how the Sun could influence climate
change. The intensity of cosmic rays varies globally by about 15%
over a solar cycle because of changes in the strength of the
solar wind, which carries a weak magnetic field into the
heliosphere, partially shielding Earth from low-energy galactic
charged particles. Although long suspected of having some
influence on atmospheric processes, the correlation between
cosmic rays and global cloudiness was to some researchers the
clearest indication that such a link might exist.

2) Changes in cloud cover are important because clouds exert a
strong control over Earth's radiative balance. Since the original
observation, improved satellite data have become available and
the cosmic ray-cloud effect seems to be present in low-altitude
clouds. Because low clouds exert a large net cooling effect on
the climate, this determines the sign of the possible cosmic ray-
cloud effect: More cosmic rays are associated with more low
clouds and lower temperatures. The observed variation of low
clouds by about 1.7% absolute corresponds to a change in Earth's
radiation budget of about 1 Wm^(-2) between solar maximum and
minimum. This change in energy input to the lower atmosphere is
highly significant when compared, for example, with the estimated
radiative forcing of 1.4 Wm^(-2) from anthropogenic CO2
emissions.

3) In summary: It has been proposed that Earth's climate could be
affected by changes in cloudiness caused by variations in the
intensity of galactic cosmic rays in the atmosphere. This
proposal stems from an observed correlation between cosmic ray
intensity and Earth's average cloud cover over the course of one
solar cycle. Some scientists question the reliability of the
observations, whereas others, who accept them as reliable,
suggest that the correlation may be caused by other physical
phenomena with decadal periods or by a response to volcanic
activity or El Nino. Nevertheless, the observation has raised the
intriguing possibility that a cosmic ray-cloud interaction may
help explain how a relatively small change in solar output can
produce much larger changes in Earth's climate. Physical
mechanisms have been proposed to explain how cosmic rays could
affect clouds, but they need to be investigated further if the
observation is to become more than just another correlation among
geophysical variables.

Related Material:

ON COSMIC RAYS

Radio, X-ray and gamma-ray astronomy have resulted in many
discoveries which can only be interpreted in terms of the
presence of large fluxes of relativistic particles in galaxies.
In parallel with these developments, cosmic ray studies opened up
new areas of astrophysical importance through direct observation
of high energy particles at the top of the atmosphere and in the
environment of the Earth from satellites and, for the very
highest energy cosmic rays, from the surface of the Earth by the
large air-shower arrays.

Cosmic radiation (what we would now call cosmic rays) was
discovered as long ago as 1912 by Victor Hess (1883-1964), but
the astrophysical understanding of the origin and propagation of
these particles had to await the 1960s when cosmic ray particle
detectors were flown in satellites. These observations
established many crucial facts about the particles detected in
the cosmic radiation. First of all, the energy spectra of the
particles are almost exactly the same as the typical spectrum of
high-energy particles inferred to be present in both Galactic and
extragalactic nonthermal radio sources. Observations indicate
that the cosmic ray particles observed at the top of the
atmosphere are only part of a population of high-energy particles
pervading the whole Galaxy.

Subsequent satellite observatories have determined the chemical
composition and detailed energy spectra of cosmic ray nuclei.
Remarkably, the chemical composition of the cosmic rays is
similar to the abundances of the elements in the Sun, although
there are some variations in the abundances at the higher
energies. These observations provide evidence on the chemical
composition of the cosmic rays as they left their sources and
also about the modifications which could have taken place during
propagation from their sources to the Earth. These observations
are very important for high energy astrophysics because they are
the only particles which we can detect which have traversed a
considerable distance through the interstellar medium and which
were accelerated in events such as supernovae and possibly
pulsars in the relatively recent past, probably within the last
10^(7) years.

At the very highest energies, cosmic rays are detected by large
air-shower arrays on the surface of the Earth. The arrival rate
of the most energetic particles is very low indeed, but particles
with energies up to about 10^(20) eV have been detected. One
important puzzle is the origin of these very high energy
particles. Their arrival directions seem to be reasonably
isotropic and, at these very high energies, these should not be
significantly influenced by the magnetic field in our own Galaxy.

Adapted from: Paul Davies (Ed.): The New Physics. Cambridge
University Press 1989.

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4. ATOMIC AND MOLECULAR ELECTRON AFFINITIES

The following points are made by J.C. Rienstra-Kiracofe et al
(Chem. Rev. 2002 102:231):

1) The energy difference between an uncharged species and its
negative ion, referred to as an "electron affinity" (EA), is an
important property of atoms and molecules. Negative ions, or
anions, result from neutral molecules (often radicals) binding an
additional electron. The importance and utility of EAs extend
well beyond the regime of gas-phase ion chemistry. Indeed, there
are many areas of pure chemistry, materials science, and
environmental chemistry where the properties of negative ions and
radicals are important. A survey of recent examples illustrates
the diversity of areas in which electron affinities play a role:
silicon and quantum dot (nanocrystal) semiconductor chemistry,
Schottky diodes, molecular clusters, fullerene chemistry,
interstellar chemistry, polymer photoluminescence,
microelectronics, flat panel displays, and even hypotheses
regarding the shuttle glow phenomenon.

2) Furthermore, the stabilities of free radicals and anions are
of great importance in the determination of biochemical pathways
for electron transfer, photosynthesis, oxidative phosphorylation,
and oxidative stress. Recent examples here include the binding of
type 1 human immunodeficiency virus (HIV-1) to nucleic acids,
toxin chemistry, photosynthesis, electron transfer in biological
systems, and electron attachment to nucleic acid bases 

3) Such examples demonstrate the importance of electron
affinities in chemistry. Clearly, the magnitudes of the electron
binding energies are of great interest. The experimental
measurement and/or theoretical determination of these energetic
quantities is an important task.

4) Photoelectric techniques are currently the most accurate and
reliable experimental methods for measuring electron affinities,
and density functional theory is perhaps the only widely
applicable and easily employed theoretical method in use today
which achieves satisfactory accuracy (within 0.2 eV) in the
prediction of EAs for large molecules (with no elements of point
group symmetry), by which we mean molecules with more than 50
first-row atoms C, N, and O.

5) Atoms represent the simplest chemical systems from which a
discussion of electron affinities can begin. The electron
affinity, EA, of an atom A can be defined as the difference
between the total energies of the ground states of A and its
negative ion A-. Note that the electron affinity is positive for
systems in which the neutral atom lies energetically above the
anion. Time scales must be considered when the stability of the
negative ion is discussed. In general, anions of atoms with
positive EAs exist sufficiently long enough to play a role in
chemical reactions and allow for straightforward, direct
experimental investigations. Anions of atoms with negative
electron affinities do not exist for any chemically significant
time period (typically only a few picoseconds) and thus are
usually of less interest to chemists.

Notes:

For many theoretical investigations concerning atoms, the current
method of choice is "density functional theory", due to Kohn,
Hohenberg, and Sham. Its name comes from its predicted connection
between the total ground state electronic energy of a system and
the electronic charge density. The theory was first proposed in
1964, and has since been useful as a simplifying alternative to
more rigorous but intractable many-electron wavefunction
calculations. In general, in density functional theory, it is the
electron density which is the fundamental variable: the ground
state of a system is defined by that electron density
distribution which minimizes the total energy. In this approach,
once the ground state electron density is known, all other ground
state properties (lattice constants, cohesive energies, etc.)
follow, at least in principle. In mathematics, a "functional" is
a function whose value depends on the set of all values of
another function. In density functional theory, the ground state
properties of a system are functionals of the ground state
electron density function.

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5. ON THE REALITY OF OBJECTS IN PHYSICS

When we say that a thing is real we are simply expressing a sort
of respect. We mean that the thing must be taken seriously
because it can affect us in ways that are not entirely in our
control and because we cannot learn about it without making an
effort that goes beyond our own imagination. This much is true
for instance of the chair on which I sit (to take a favorite
example of philosophers) and does not so much constitute evidence
that the chair is real but is rather just what we _mean_ when we
say that the chair is real. As a physicist I perceive scientific
explanations and laws as things that are what they are and cannot
be made up as I go along, so my relation to these laws is not so
different from my relation to my chair, and I therefore accord
the laws of nature (to which our present laws are an
approximation) the honor of being real. This impression is
reinforced when it turns out that some law of nature is not what
we thought it was, an experience similar to finding that a chair
is not in place when one sits down. But I have to admit that my
willingness to grant the title of 'real' is a little like Lloyd
George's willingness to grant titles of nobility; it is a measure
of how little difference I think the title makes.

Adapted from: Steven Weinberg: Dreams of a Final Theory. Pantheon
Books, New York 1992.

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6. ON THE BRAINS OF MICE AND HUMANS

No category of cell, no particular type of circuit is specific to
the human cerebral cortex. The components of our cerebral
machinery derive from a stock very similar, if not identical, to
that of the mouse. The major event in the evolution of the
mammalian brain is the expansion of the neocortex. This growth is
accompanied by an increase in the total number of neurons, and
thus in the number and complexity of the operations which the
cortex can perform. The number of cellular elements per unit of
surface area has not changed. The cortical thickness varies, but
much less than its surface area. On average, the cortex of man is
only three times thicker than that of the mouse, although the
increase is not uniform in all layers... The more the surface
area of the cortex expands, the more the number of neurons
capable of establishing association connections increases... This
translates, finally, into an increase in the mean number of
connections per neuron, with a consequent burgeoning of the
dendritic and axonal trees, reaching a maximum in man.
Nevertheless, the increase in the mean number of synapses per
neuron is not directly proportional to the increase in cortical
area. Far from it. The density of synapses per cubic millimeter
of cortex is of the same order in the rat as in man... At the
levels of both the macroscopic anatomy of the cortex and its
microscopic architecture, no sudden qualitative reorganization
marks the passage from the "animal" brain to the human brain.
There is, on the contrary, a continuous _quantitative_ evolution
in the total number of neurons, the diversity of areas, the
number of possible connections between neurons, and, therefore,
the complexity of the neuronal networks that make up the cerebral
machine.

Adapted from: Jean-Pierre Changeux: Neuronal Man: The Biology of
Mind. Oxford University Press 1985.

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7. NEW BOOKS

Bolt of Fate: Benjamin Franklin and His Electric Kite Hoax. Tom
Tucker. Public Affairs 2003, 297pp. With his famous kite
experiment, Franklin is said to have proved that lightning and
electricity were identical. The author argues that Franklin never
flew the famous kite at all, and that Franklin was an
enthusiastic hoaxer. More information at:
http://www.amazon.com/exec/obidos/ASIN/1891620703/scienceweek

Win-Win Ecology: How the Earth's Species Can Survive in the Midst
of Human Enterprise. Michael L. Rosenzweig. Oxford University
Press 2003, 221 pp. A non-specialist argument for an ecology that
involves sharing of habitats with other species. The author is a
biologist at Stanford University. More information at:
http://www.amazon.com/exec/obidos/ASIN/0195156048/scienceweek

A Shortcut Through Time: The Path to the Quantum Computer. George
Johnson. Knopf 2003, 221 pp. A non-specialist account of quantum
computers and their importance for future technology. The author
is a theoretical physicist at the Massachusetts Institute of
Technology. More information at:
http://www.amazon.com/exec/obidos/ASIN/0375411933/scienceweek

Sex Ratios: Concepts and Research Methods. Ian C. Hardy (Ed.).
Cambridge University Press 2002, 438 pp. "A very valuable book
that will be indispensable for anyone working in this field and
be of great interest to all evolutionary biologists." -- Science.
More information at:
http://www.amazon.com/exec/obidos/ASIN/0521665787/scienceweek

Life on a Young Planet: The First Three Billion Years of
Evolution on Earth. Andrew H. Knoll. Princeton University Press
2003, 304pp. An account of early Earth by a noted paleontologist-
geobiologist. "Expresses better than most the bumptious vitality
and sheer fun of open-minded research." -- Science. More
information at:
http://www.amazon.com/exec/obidos/ASIN/0691009783/scienceweek

The Man Who Flattened the Earth: Marpertuis and the Sciences in
the Enlightenment. Mary Terrall. University of Chicago Press
2002, 408pp. "One of the better studies of the problems and
opportunities of the 18th century scientific career under the
conditions of absolutism." -- Science. More information at:
http://www.amazon.com/exec/obidos/ASIN/0226793605/scienceweek

The History of Organ and Cell Transplantation. N.S. Hakim and
V.E. Papalois (Eds.). Imperial College Press 2003, 444pp. Each
chapter is by a specialist in transplantation of the kidney,
liver, pancreas, intestine, lung, heart, skin, or bone marrow.
More information at:
http://www.amazon.com/exec/obidos/ASIN/1860942091/scienceweek

Properties of Amorphous Carbon. S.R. Silva (Ed.). IEE 2003,
367pp. An encyclopedic coverage of the subject, including
discussion of microstructure, hydrogen content and nitrogen
content, band structure and density of states, defects, optical
properties, mechanical, thermal and surface properties,
conduction and doping. More information at:
http://www.amazon.com/exec/obidos/ASIN/0852969619/scienceweek

Uncertain Science Uncertain World. H.N. Pollack. Cambridge
University Press 2003, 243pp. A discussion of contradictions and
uncertainties inherent in the problems such as global warming,
radioactive waste disposal, and earthquake prediction. More
information at:
http://www.amazon.com/exec/obidos/ASIN/0521781884/scienceweek

Chaos and Transport in Fluids and Plasmas. V. Stefan (Ed.). The
Stefan University Press 2003, 227pp. Comprises 16 selected papers
from the conference held in La Jolla, California in 2000.
Discussions of stratified fluids, dynamics of molecular chains,
turbulence, transport in dusty plasmas, chaotic dynamics,
superfluidity and complex systems. More information at:
http://www.amazon.com/exec/obidos/ASIN/1889545309/scienceweek

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