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.

October 8, 1999 -- Vol. 3 Number 41

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

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Contents of This Issue:

1. Evolving Trends in Pediatric Poisoning
2. Morphological Innovation and Developmental Genetics
3. Evolutionary Consequences of Niche Construction
4. On Interplanetary Biotic Transfer
5. A Continuing Feud Concerning Nanobacteria
6. On Density Functional Theory in Materials Science
7. Rock-Dating Errors: An Update

In Focus: On the Neuronal Synapse as a Micro-Unit

Correction: On Education Physicians Concerning... (SW 3/#40)

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1. EVOLVING TRENDS IN PEDIATRIC POISONING
Despite the many educational programs aimed at prevention,
exposure to a poison is still the most common cause of nonfatal
childhood accidents in the home. Poisoning can occur by many
routes, including oral ingestion, absorption through the skin,
and infiltration of the eyes (ocular installation). In the US,
more than 1 million children younger than 6 years experience
toxic exposure annually, making poisoning a major and persistent
cause of injury-related *morbidity. Significant advances have
been made in the prevention and treatment of pediatric poisoning
in the past 5 decades: in the 1940s, childhood poisonings were
responsible for an estimated 500 deaths per year and were
attributed primarily to household products; in 1972, the number
of pediatric poisoning deaths in the US was 216; in 1997, the
number of pediatric poisoning deaths in the US was 25. ... ...
E.L. Liebelt and C.D. DeAngelis (Johns Hopkins University, US)
present a review of evolving trends in pediatric poisoning, with
a focus on epidemiology, prevention, and treatment. The authors
make the following points:
     1) Concerning human toxic exposures and fatalities, children
younger than 6 years have persistently accounted for 50 to 60
percent of these exposures. Cosmetics and personal care products,
plants, and cough and cold preparations have consistently been
the top 5 categories for pediatric poison exposures in the last
10 years.
     2) More than half of the poison fatalities in children
younger than 6 years are caused by non-pharmaceutical and
household products. The authors tabulate the following non-
pharmaceutical and household products toxic in children:
... ... Alcohols: beverage ethanol, methanol (windshield wiper
fluid), ethylene glycol (antifreeze).
... ... Caustic agents: alkalis (drain and oven cleaners, perm
relaxers, Clinitest tablets); acids (toilet bowl cleaners, anti-
rust compounds).
... ... Food-flavoring additives: methylsalicylate (Oil of
Wintergreen) [*Note #1].
... ... Hydrocarbons: kerosene, lamp oil, mineral seal oil
(furniture polish), mineral spirits (paint thinner), naphtha
(lighter fluid).
... ... Industrial chemicals: methylene chloride (paint
stripper), selenious acid (gun bluing), zinc chloride (soldering
flux).
... ... Nail products: acetonitrile (sculptured nail remover),
methacrylic acid (artificial nail primer), nitromethane
(artificial nail remover).
... ... Pesticides and/or insecticides: organophosphates,
lindane, paraquat.
     3) Pharmaceutical products responsible for significant
morbidity and mortality in young children have included the
following: iron supplements, tricyclic antidepressants,
cardiovascular medications (calcium channel blockers, beta-
blockers), oral hypoglycemic agents, narcotic analgesics, and
antimalarials (chloroquine). Iron supplements continue to be one
of the leading causes of poisoning deaths due to pharmaceutical
products in children younger than 6 years.
     4) The US Consumer Product Safety Commission estimates that
child-resistant packaging for aspirin and oral prescription
medications has saved the lives of approximately 800 children
since requirements went into effect in the mid 1970s.
     5) The authors conclude: "In the past 40 years,
extraordinary advances have been made in the prevention and
treatment of poisonings in young children. Future challenges
include further development and funding of poison information
centers, clinical and basic science research, development of
regional poison treatment centers, and the continued training of
health professionals dedicated to clinical toxicology."
-----------
Editor's note: This review by Liebelt and DeAngelis does not
consider pediatric lead poisoning, although lead poisoning is
usually designated a significant source of pediatric toxic
exposure. In the related background material below, we have
included two reports on lead poisoning from previous issues of
SW.]
-----------
E.L. Liebelt and C.D. DeAngelis: Evolving trends and treatment
advances in pediatric poisoning.
(J. Amer. Med. Assoc. 22/29 Sep 99 282:1113)
QY: Erica L. Liebelt [eliebelt@welch.jhu.edu]
-----------
Text Notes:
... ... *morbidity: In general, this refers to a diseased state;
in particular, the term refers to the ratio of the diseased to
the well in a community.
... ... *Note #1: Death has been reported from ingestion of less
than 1 teaspoon of methyl salicylate (Oil of Wintergreen) in a
young child. Any internal exposure in quantity to methyl
salicylate (found in liniments and in solutions used in hot
vaporizers) is potentially lethal.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 8Oct99
-------------------
Related Background:
A DANGEROUS NEW SOURCE OF ENVIRONMENTAL LEAD
There is ample evidence that the developing nervous system of a
child is highly sensitive to a number of toxic substances, the
effects of which are various encephalopathies (brain disorders)
[*Note #1]. One environmental toxic substance of considerable
importance in this context is lead, an urban environmental
contaminant that in the past few decades has become a focus of
public awareness. The classical sources of urban environmental
lead contamination are the gasoline exhaust fumes of motor
vehicles and lead-based paints, but recently another important
source of such contamination has become apparent. ... ... Howard
W. Mielke (Xavier University New Orleans, US) presents a review
of the problem of lead in inner cities with emphasis on the newly
recognized danger of lead contamination of inner city soil and
dust. The author makes the following points: 1) Since the 1920s,
millions of US children have been quietly poisoned by lead, and
thousands of deaths are attributed to this over the long term. 2)
Although childhood lead exposure in the US has diminished during
the past 2 decades, the problem has not been solved. Instead, the
demographics has shifted. 3) Over 50 percent (and perhaps even 70
percent) of children living in the inner city of New Orleans and
Philadelphia have blood lead levels above the current guideline
of 10 micrograms per deciliter [*Note #2]. In contrast, in the
concrete "jungle" of Manhattan, where very little of the soil is
exposed and almost all apartments and housing contain lead-based
paints, only between 5 and 7 percent of children under the age of
6 have been reported to have blood-lead levels of 10 micrograms
per deciliter or higher. It is of significance that in Brooklyn,
across the river from Manhattan, where yards containing soil are
common, the percentage of affected children is several times
higher than in Manhattan. 4) The serious of the problem has been
recognized by the US Centers for Disease Control and Prevention
since the early 1990s, which has called pediatric lead poisoning
"entirely preventable". 5) The author suggests that effective
prevention assumes an accurate identification of the
environmental reservoirs of lead, and that current policies to
reduce lead exposure are based on the assumption that the
greatest lead hazard comes from lead-based paints [*Note #3].
Most lead-based have now been removed from the market, and
parents have been instructed to guard their children from eating
paint flakes. However, for children, paint is now neither the
most abundant nor the most accessible source of lead. The common
problem is lead dust in the environment, with the soil a giant
reservoir of tiny particles of lead. The greatest risk for
exposure of inner city children is in the yards around houses and
to a lesser extent in public playgrounds. 6) The author suggests
that an accurate and complete appreciation of the distribution of
lead in the environment can help shape policies that more
effectively protect the health of children. The author concludes:
"It took nearly 10 decades for lead to accumulate to its current
levels in urban areas. With judicious planning, the problem can
be resolved in much less time."
-----------
Howard W. Mielke: Lead in inner cities.
(American Scientist Jan/Feb 1999 87:62)
QY: Howard W. Mielke 
-----------
Text Notes:
... ... *Note #1: There is much data concerning certain
syndromes, e.g., fetal alcohol syndrome, lead poisoning, etc. One
research problem is that effects of low levels of environmental
toxins on the developing nervous system can be subtle and not
detected unless specific rather than general behavioral measures
are applied.
... ... *Note #2: There is hardly a consensus concerning
acceptable levels of lead in the whole blood of children. Some
clinicians consider the danger point to be in the region of 50
micrograms per deciliter whole blood; other clinicians consider
anything above 10 micrograms per deciliter as a cause for alarm.
In terms of low-level effects on the developing central nervous
system, general concentration cut-off points are perhaps
arbitrary, since there is considerable individual variation in
toxic susceptibility.
... ... *Note #3: In the US, lead was used in residential paint
between 1884 and 1978, and leaded paint remains on the walls of
many old buildings.
-------------------
Summary & Notes by SCIENCE-WEEK  15Jan99
-------------------
Related Background:
PRENATAL LEAD EXPOSURE AND POSTNATAL LEAD TOXICITY
Lead is a highly toxic metal, especially in children, but
unfortunately the incidence of lead poisoning in metropolitan
slums remains high due to past widespread use of lead based
paints and lead water pipes. There are also other sources that
contribute to dangerous concentrations in the environment. In
children, concentrations of lead in the range 40 micrograms per
deciliter, and probably as low as 10 micrograms per deciliter,
will produce definite serious cognitive deficits. Higher blood
concentrations produce encephalopathies that are both malignant
and difficult to treat. In the past, the focus has been on the
exposure of young children to environmental lead, since children
are the most vulnerable and environmental lead the apparent
primary source. Now William H. Bowen et al (University of Roch-
ester, US) present evidence that in rats toxic concentrations of
lead can pass from mother to offspring when mother rats are
drinking water that produces blood lead levels of only 40 micro-
grams per deciliter, with transmission evidently occurring via
blood to the fetus and via milk to the postnatal rat pup.
Evidently one consequence in these lead-exposed rat pups is a
high incidence of dental caries. Bowen's group is a dental
research group, and they apparently became interested in the
problem after considering that although dental caries in children
has shown a marked drop in prevalence in the U.S., about 80 per
cent of the cases that still occur are occurring in only about
20% of the children -- those that live in inner cities, where
lead exposures can still be relatively high. Metropolitan
children are thus faced with another source of lead poisoning --
lead of maternal origin.
QY: W. Bowen, University of Rochester (716) 275-3221
(Nature Medicine September 1997) (Science-Week 12 Sep 97)


2. MORPHOLOGICAL INNOVATION AND DEVELOPMENTAL GENETICS
A central question in both developmental and evolutionary biology
is this: How do the actions of individual genes contribute to the
complex morphologies of animals and plants? ... ... C.R Marshall
et al (3 authors at 3 installations, US) present a short review
of current research on this question, the authors making the
following points:
     1) Over the past two decades, developmental biologists have
made great strides in understanding embryonic pattern formation
at the genetic, molecular, and cellular levels. Much of this
progress has occurred as a result of the remarkable success of
studies of pattern formation in model living systems such as the
fruit fly Drosophila melanogaster [*Note #1]. Identification of
genes that play major roles in setting up the body plan, followed
by the discovery that many of these genes are *well-conserved
even between different phyla, has also led to a renaissance in
the investigation of the links between evolution and development.
     2) A number of comparative studies aimed at examining the
evolution of body morphology have focused on a well-characterized
set of genes termed the "homeotic genes" ("Hox genes"). In a wide
range of phyla, the Hox genes are known to play a major role in
specifying regional identity along the anterior-posterior axis of
the bodies of animals, and the potential role of these genes in
altering body plan patterning during evolution was recognized
soon after their characterization [*Note #2].
     3) An important question concerns the number of genes
involved in differences between species and the sizes of their
effects. Does the evolution of diverse animal and plant forms
typically result, for example, from the action of many genes of
small effect, or from a few genes of large effect? Historically,
evolutionists have favored the first view. Indeed, traditional
quantitative genetic theory largely rests on the so-called
"infinitesimal assumption", i.e., the assumption that morphologic
change involves many factors of very small effect each.
     4) However, recent quantitative trait locus (QTL) analyses
have called this infinitesimal-assumption view into question. QTL
analysis, a fusion of molecular and quantitative genetics, allows
genetic dissection of morphological differences between pairs of
*crossable taxa. By producing hybrids which carry random
combinations of chromosome regions from two taxa (where species
identity of regions is inferred from molecular markers), and by
scoring the mean distribution of a trait, one can map, count, and
estimate the effects of genes underlying the trait studied. Such
analyses routinely reveal that morphological differences involve
a modest number of chromosome regions of substantial effect. 
     5) In summary, it appears that the distribution of gene
effects underlying morphological evolution may be highly
*leptokurtic: whereas many genes of small effect may be involved,
a few factors of large effect might account for most of the
morphologic differences between taxa.
-----------
C.R. Marshall et al: Morphological innovation and developmental
genetics.
(Proc. Natl. Acad. Sci. US 31 Aug 99 96:9995)
QY: Charles R. Marshall [marshall@harvard.edu]
-----------
Text Notes:
... ... *Note #1: Concerning the laboratory use of the fruit fly
Drosophila melanogaster in developmental biology, the biologist
Robert E. Kohler has pointed out that although the fact has been
overlooked by most historians of science, the chief advantage of
Drosophila initially was that it was an excellent organism for
student projects. A number of organisms now important in
molecular biology were first common in laboratories because of
their long-standing utility in teaching classical biology.
... ... *well-conserved: In this context, the term "well-
conserved" refers to a gene or complex of genes maintained
throughout evolution across diverse phyla.
... ... *Note #2: For more on Hox genes, see the background
material below.
... ... *crossable taxa: In general, a "taxon" is a grouping
defined in terms of shared similar characters, and "crossable
taxa" are different taxa which can be mated to produce hybrids.
... ... *leptokurtic: In statistics, a "leptokurtic distribution"
is a distribution in which the ratio of the fourth moment to the
square of the second moment is greater than 3. The ratio is 3 for
a normal distribution. In general, a leptokurtic distribution
exhibits a heavier concentration around the mean than a normal
distribution; i.e., the distribution is more peaked. In
statistics, the term "kurtosis" refers to the peakedness of a
distribution.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 8Oct99
-------------------
Related Background:
ZEBRAFISH AND VERTEBRATE GENOME EVOLUTION
To an engineer with open eyes, the assemblage of parts that
constitute a living organism is an engineering marvel. The
exterior anatomy of an insect, for example, involves a complex
arrangement of numerous parts with specific mechanical and
sensory functions, and this assemblage is replicated with great
precision in the production of each generation. In an ordinary
manufacturing plant, the various parts of a machine are usually
manufactured independently of each other and then the finished
parts assembled according to an external grand plan to produce
the final manufactured product. In a biological organism,
however, the "manufacturing" scheme is quite different: In the
first place, the "grand plan" is internal and not external: each
cell of the organism carries the "grand plan" -- the genome --
with specific parts of the plan activated in each cell type, and
the activation/inactivation of specific parts of the genome
differentially dynamic in various cell types during the
developmental process. Secondly, during development of the
embryo, body parts are developed in parallel, in tandem, in
sequence, with an intricate network of control loops, until
finally the complete developed product emerges in toto as a
functioning entity. How is this biological development and
assembly process orchestrated? One of the most spectacular
findings of this decade has been that flies and mice use the same
genes for specifying embryonic developmental regions along the
anterior-posterior axis of the body. In general, "homeotic" genes
are genes that control development, and "homeogenes" are the
subset of homeotic genes that contain "homeoboxes". A "homeobox"
is a part of a gene encoding a protein "homeodomain", a protein
domain that binds to DNA. (The protein functions as one of a
number of "*transcription factors".) The DNA-binding homeodomain
consists of approximately 60 amino acids, and these homeodomain
motifs are apparently involved in orchestrating the development
of a wide range of organisms. "Hox" genes are a subset of
homeogenes, the Hox genes encoding proteins (and protein
homeodomains) that determine positional cell differentiation and
development. Mutations in Hox genes result in the conversion of
one body part into another: for example, in the fruit fly
Drosophila, a specific Hox mutation results in a leg appearing
where an antenna usually appears. There are clusters of Hox genes
in the genome: e.g., 1 Hox cluster in *nematode worms, 2 Hox
clusters in the fruit fly Drosophila, 4 Hox clusters in
vertebrates. Since mammals have more clusters of Hox genes than
lower forms, it has been thought that Hox cluster duplication
facilitated the evolution of the vertebrate body plans.
... ... A. Amores et al (13 authors at 7 installations, US CA)
now report that *zebrafish (Danio verio) have 7 Hox clusters.
Thus, *teleosts, the most species-rich group of vertebrates,
appear to have more copies of these developmental regulatory
genes than do mammals, despite less complexity in the anterior-
posterior axis. The authors report that *phylogenetic analysis
and *genetic mapping suggest a *chromosome doubling event,
probably by whole genome duplication, after the *divergence of
*ray-finned and lobe-finned fishes, but before the teleost
*radiation. The authors state: "The conclusion that the genetic
complexity of Hox clusters in teleost fish has exceeded that of
mammals for more than 100 million years calls into question the
concept of a tight linkage of Hox cluster number and
morphological complexity along the body axis."
-----------
A. Amores et al: Zebrafish Hox clusters and vertebrate genome
evolution.
(Science 27 Nov 98 282:1711)
QY: John H. Postlethwait, Univ. of Oregon Eugene 541-346-1000.
-----------
Text Notes:
... ... *transcription factors: Transcription is the process by
which the genetic information in DNA is converted into RNA, and
transcription factors are a class of DNA-binding proteins that
regulate RNA transcription.
... ... *nematode worms: An abundant and ubiquitous phylum of
unsegmented roundworms.
... ... *zebrafish: A common tropical aquarium species.
... ... *teleosts: In general, this refers to any of the bony
fish, the most advanced in terms of evolution and the largest
group of fish. Besides the calcified internal skeleton, the most
obvious uniform characteristic of the teleost fish is their tail,
with upper and lower halves of about equal size, whereas in
cartilaginous fish the tail has two lobes of unequal size. Almost
all sport, commercial, and ornamental fish are teleosts.
... ... *phylogenetic analysis: In general, an analysis of
evolutionary history.
... ... *genetic mapping: (chromosome mapping; linkage mapping)
In general, elucidation of the linear arrangement of genes on a
*chromosome or of sites within a gene. 
... ... *chromosome: In cells with chromosomes, the
chromosomes are the physical structure into which DNA is
organized and on which genes are carried.
... ... *divergence: In this context, the acquisition of
dissimilar characteristics by related organisms in unlike
environments.
... ... *ray-finned and lobe-finned fishes: Actinopterygii and
Crossopterygii.
... ... *radiation: In this context, the term "radiation" refers
to the spread of a group of biological entities into new
environments with consequent diversification.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 22Jan99


3. EVOLUTIONARY CONSEQUENCES OF NICHE CONSTRUCTION
In ecology, the term "ecosystem" refers to a functioning unit of
nature that combines biotic communities and the abiotic
environment with which they interact, and the term "niche" refers
to the physical location of an organism and the function of an
organism within an ecosystem. There is an increasing recognition
that all organisms modify their environments, a process called
"niche construction" (also called "ecosystem engineering"). Such
modifications can have profound effects on the distribution and
abundance of organisms, the influence of *keystone species, the
control of energy and material flows, migrating species residence
and return times, *ecosystem resilience, and specific *trophic
relationships. But the consequences of environmental modification
by organisms are not restricted to ecology, and organisms can
affect both their own and each other's evolution by modifying
sources of natural selection in their environments.
... ... K.N. Laland et al (3 authors at 3 installations, UK US)
present an analysis of the evolutionary consequences of niche
construction using a *population genetics model that extends
earlier analyses by allowing resource distributions to be
influenced both by niche construction and by independent
processes of renewal and depletion. The authors report their
analysis confirms that niche construction can be a potent
evolutionary agent by generating selection that leads to the
fixation of otherwise deleterious *alleles, supporting stable
*polymorphisms where none are expected, eliminating what would
otherwise be stable polymorphisms, and generating unusual
evolutionary dynamics. The authors suggest that even small
amounts of niche construction, or niche construction that only
weakly affects resource dynamics, can significantly alter both
ecological and evolutionary patterns. The authors conclude:
"Unlike standard evolutionary theory, the present approach is
equally applicable to both population-community ecology and
ecosystem-level ecology, which may eventually make it easier to
reconcile these two ecological subdisciplines under the rubric of
an extended evolutionary theory that includes niche
construction."
-----------
K.N. Laland et al: Evolutionary consequences of niche
construction and their implications for ecology.
(Proc. Natl. Acad. Sci. US 31 Aug 99 96:10242)
QY: K.N. Laland [knl1001@hermes.cam.ac.uk]
-----------
Text Notes:
... ... *keystone species: In this context, the term "keystone
species" refers to organisms that play dominant roles in an
ecosystem, affecting many other organisms. For example, the
removal of a keystone predator from an ecosystem usually causes a
reduction of species diversity among its former prey.
... ... *ecosystem resilience: The "resilience" of an ecosystem
is the ability of the ecosystem to return to its original or
steady-state condition after a disturbance.
... ... *trophic relationships: In general, the term "trophic"
refers to nutrition or food. (The term should not be confused
with "tropic" [from "tropism"; e.g., a "tropic" response], which
refers to an involuntary or reflex turning by a cell, plant, or
animal in response to a stimulus.)
... ... *population genetics model: In general, "population
genetics" is the study of the genetic composition of populations.
Population geneticists attempt to estimate gene frequencies and
detect the selective influences that determine these gene
frequencies in natural populations. Mathematical models in
population genetics examine the interaction of factors such as
selection, population size, mutation, and migration on the
fixation and loss of linked and unlinked genes.
... ... *alleles: (allelomorph) An "allele" is one of two or more
forms of a given gene that control a particular characteristic,
with the alternative forms occupying corresponding loci on
homologous chromosomes. Different alleles usually produce
different characteristics in an organism, e.g., brown versus blue
eyes.
... ... *polymorphisms: In this context, the term "polymorphism"
refers to the existence of more than one form or type in a
species, beyond simple gender differences. For example, social
insects such as honeybees (with queens, drones, and workers)
demonstrate polymorphisms.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 8Oct99
-------------------
Related Background:
EVOLUTION: ADAPTIVE RADIATION IN A HETEROGENEOUS ENVIRONMENT
The term "adaptive radiation" refers to the rapid evolution of
one or a few forms into many different species that occupy
different habitats within a new geographical area. The marsupial
radiation in Australia illustrates the process: when marsupials
were protected from competition with placental mammals by the
isolation of the continent, the process led to an entire array of
species with widely divergent functions, from herbivores to
carnivores. ... ... Rainey and Travisano (University of Oxford,
UK) report an investigation of the role of ecological opportunity
and competition in driving the genetic diversification associated
with adaptive radiation. The form studied was the common aerobic
bacterium Pseudomonas fluorescens, which evolves rapidly under
novel environmental conditions to generate a large repertoire of
mutants. As bacteria reproduce asexually, identical populations
can be established from a single genotype, and all subsequent
variation is therefore generated de novo by mutation. The authors
report that when provided with ecological opportunity, identical
populations of P. fluorescens diversify morphologically, but when
ecological opportunity is restricted, there is no such
divergence. In spatially structured environments, the evolution
of variant forms follows a predictable sequence, with competition
among the newly evolved niche-specialists apparently maintaining
this variation. The authors suggest their results demonstrate
that the elementary processes of mutation and selection alone are
sufficient to promote rapid proliferation of new designs, and
that their results support the theory that trade-offs in
competitive ability drive adaptive radiation.
QY: Paul B. Rainey 
(Nature 2 Jul 98 394:69) (Science-Week 31 Jul 98)


4. ON INTERPLANETARY BIOTIC TRANSFER
The techniques and data available to any generation in science
differ more or less from the techniques and data available to the
generation that preceded it. And so it makes sense for each
generation to reexamine important still-unanswered questions in
terms of possibilities. One such question concerns the origin of
life on Earth: Did life originate here on Earth, or did "living"
entities arrive here from elsewhere as the result of one or more
natural cosmic processes? What are the possibilities to be
reasonably considered, now that several decades of modern
astronomy, astrophysics, and space exploration have occurred? In
general, the term "panspermia" is the name given to the idea that
life was introduced on Earth from elsewhere in the Universe. This
is a classical notion, fostered by the chemist Svante A.
Arrhenius (1859-1927) in the early part of the 20th century
[*Note #1].
... ... Paul Davies (Imperial College London, UK) presents a
review of current ideas concerning the seeding from elsewhere of
life on Earth, the author making the following points:
     1) In recent years, several experiments have been performed
to test the viability of bacteria and viruses under space
conditions. In one of these experiments, the bacterial species
Bacillus subtilis was maintained nearly 6 years in space aboard
the NASA Long Duration Exposure Facility, and a series of filters
were used to determine separately the effects of vacuum, solar
radiation, and cosmic rays. Another experiment simulated the
effect of 250 years of space exposure in the laboratory. The
results of these experiments indicate that microbes cope
relatively easily with the cold and the vacuum, in effect
becoming freeze-dried and this acting as a preservative. Some
bacteria form *spores under these conditions. In general, under
harsh conditions such as these, microbes apparently go into
suspended animation, their metabolism ceases, and they merely
remain inert until circumstances improve.
     2) The most lethal form of radiation in interplanetary space
is the ultraviolet radiation of the Sun. This radiation, however,
can be screened by a thin layer of material, and it has been
pointed out that cool *red giant stars spew out large quantities
of carbon, and that space-faring bacteria in such a star system
might therefore become coated in soot and be shielded from the
worst of the ultraviolet radiation.
     3) Another harmful radiation in space is galactic *cosmic
radiation, the collection of high-energy subatomic particles that
arises from the deeps of space. It is expected that over time the
cumulative effects of such radiation would prove deadly to living
systems. However it is possible to imagine scenarios in which
microbes are at least partially shielded even from this
ubiquitous hazard. In general, the long-term survival of bacteria
or other microbes in space might occur because of rock-shielding
from cosmic rays. A thin film of carbon affords protection from
ultraviolet light, but a thick mantle of rock is needed to shield
organisms from high-energy cosmic rays. Since this form of
radiation creates a cascade of secondary particles upon impact,
microbes embedded in small rocks would actually suffer higher
radiation doses than those exposed directly to space. It has been
estimated that for adequate shielding from cosmic radiation, the
enclosing rock must be approximately 1 meter across.
-----------
Paul Davies: Interplanetary infestations.
(Sky & Telescope September 1999)
QY: Paul Davies, Imperial College London, UK.
-----------
Text Notes:
... ... *Note #1: As the author points out, the physicist William
Kelvin (1824-1907), in a lecture at a meeting of the British
Association in Edinburgh in 1871, speculated that from time to
time an astronomical body might strike a planet with enough force
to blast debris into space, and that as a result "many great and
small fragments carrying seed and living plants and animals would
undoubtedly be scattered through space... If at the present
instant no life existed upon this Earth, one such stone falling
on it might... lead to its becoming covered with vegetation."
... ... *spores: Only certain bacterial species form spores,
which are specialized cell structures that may allow survival in
extreme environments. In general, under conditions of nutritional
depletion, each bacterium forms a single internal spore that is
liberated when the mother cell undergoes destruction (autolysis).
The spore is a resting system, highly resistant to desiccation,
heat, and chemical agents; when returned to favorable nutritional
conditions and activated, the spore germinates to produce a
single bacterium.
... ... *red giant stars: A "red giant star" is a star in a late
stage of evolution, having exhausted the hydrogen fuel in its
core. It has a surface temperature of less than 4700 degrees
Kelvin and a diameter 10 to 100 times that of the Sun.
... ... *cosmic radiation: Cosmic rays are highly energetic
particles moving at close to the speed of light and continuously
bombarding the Earth's atmosphere from all directions. The
energies of the particles are enormous and range from 10^(8) to
over 10^(19) electronvolts. The term "highest energy cosmic rays"
refers to cosmic rays with energies of the order of 10^(20)
electronvolts or greater, apparently from extra-galactic sources,
but the origins are not clear.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 8Oct99


5. A CONTINUING FEUD CONCERNING NANOBACTERIA
     Ultimately, the labeling of a system as "living" or
"nonliving" is an anthropocentric question and perhaps not of
paramount importance in the effort to unravel the workings of
nature. But labels and the categories they name do have utility:
in particular, labels and categories do help us conceptually
organize the enormous variety that nature presents to us. During
the past few years, there has been a strong debate in progress
concerning the use of the label "nanobacteria" to characterize
certain inclusions found in samples of Martian rock, and also
recently in kidney stones. (For details, see the related
background material appended below.)
     These nanobacterial entities are extremely small, an order
of magnitude smaller than the systems biologists classify as
"bacteria", but not smaller than a number of small viruses. Are
these entities bacteria? Biologists do not use the term
"bacteria" loosely, and the defining parameter of bacteria is not
size. For example, there are protozoa, which as a group consists
of organisms considerably more complex structurally and
dynamically than bacteria, that are smaller than certain
bacteria. There are also fungi that are smaller than certain
bacteria. In biology, structure and dynamics are the criteria for
differentiating bacteria, protozoa, fungi, and viruses -- not
size. Biologists, for example, never use the term "microbacteria"
to characterize living systems which are not bacteria but which
are smaller than bacteria. Again, the term "bacteria" puts no
constraint on the size of a system, except that the system must
be at least large enough to contain those molecular entities and
structures that differentiate bacteria from other known living
forms.
     So when several years ago a group of NASA space researchers
announced to the world in a press conference that they had
discovered "nannobacteria" (their first spelling of the term) in
a Martian rock, and that these inclusions were of the order of 20
to 50 nanometers in diameter, a host of biologists rose up to
complain (and even effectively shout) that these inclusions could
not be "bacteria" because they were simply too small as systems
to include the molecular and structural repertoires known to
exist in bacteria, which repertoires differentiate bacteria from
viruses, protozoa, fungi, etc. To provide an analogy that might
be helpful in understanding the uproar among biologists, if a
team of sociologists would call a press conference to announce to
the world that a group of six people holding hands in a closed
loop would thenceforth be called by them a "benzene ring", and
they would further announce their intent to seek the financial
support of various funding agencies for research in chemistry --
given such a scenario, one might understand a few thousand
chemists rising to their feet to shout that a benzene ring is
much more than six entities joined in a closed loop. "Never
mind," the sociologists reply: "We know chemistry when we see
it."
     Considering the use of labels, one wonders whether to label
this affair as out of Harold Pinter or Groucho Marx. Certainly,
at the outset, it would have been advisable to have called the
Martian rock inclusions something other than "nannobacteria".
     Apparently, rather than dissipate, the debate has now become
more structured. A Finnish scientist has now formally requested
the University of Kuopio to investigate the work of one of its
senior researchers, Olavi Kajander, the accuser charging that
Kajander is making misleading but widely publicized claims that
he has discovered a new form of life, known as "nanobacteria".
This has some international ramifications, since Kajander is now
formally associated with the NASA Institute of Astrobiology, a
"virtual institute" involving 11 research centers in the US, and
collaborating with David McKay of the Johnson Space Center in
Texas on Mars rock research (details of the work of both Kajander
and McKay is included in the related background material below).
     In brief, Kajander claims that he has identified DNA in
nanobacteria. Jouni Issakainen (Turku University, FI), the
Finnish scientist (mycologist) who is requesting investigation,
says this cannot be substantiated because controls were not
shown, and because Kajander increased the normal concentration of
a DNA stain by an order of magnitude, as well as increasing the
reaction time. Under these conditions, says Issakainen, the stain
can become nonspecific.
     Kajander, in turn, states: "In fact, I don't care whether
nanobacteria have genetic material or not -- we have shown that
they are automatically replicating particles that produce
apatite, and that they are involved in disease. And I want to
cure disease."
     Apparently despite the controversy, the medical and
scientific sections of the Academy of Finland have continued to
support Kajander's work. Reviewers of a US$120,000 (FM706,000) 3-
year grant application for work on nanobacteria "combining
microbiology, geology, and astrobiology" recommended rejection,
but the grant was approved after the publication of Kajander's
paper in the _Proceedings of the National Academy of Sciences
US_, and evidently funded with money from the Academy's "risk
fund". An academy spokesman states: "Although we recognize that
there are no solid elements of a scientific basis, the academy
decided to take a risk with the work."
-----------
Alison Abbott: Battle lines drawn between "nanobacteria"
researchers.
(Nature 9 Sep 99 401:105)
QY: Alison Abbott [nature@nature.com]
-------------------
Summary by SCIENCE-WEEK [http://scienceweek.com] 8Oct99
-------------------
Related Background:
THE MARTIAN METEORITE MICROBES CONTROVERSY: AN UPDATE
In 1984, a 1.9 kilogram meteorite the size of a potato
(designated ALH84001) was found in Antarctica, and because of its
chemical composition the consensus is that this meteorite (and a
dozen similar meteorites) originated from the planet Mars. The
basis for the consensus is the detailed quantitative
correspondence of the trapped gases in the meteorites to Martian
atmospheric gases, and the specific distributions of oxygen
isotopes. In 1996 a group of researchers, D. McKay et al
(National Aeronautics and Space Administration Johnson Space
Center, US; Stanford University, US) reported they had concluded
that unusual characteristics of the meteorite ALH84001 can be
most reasonably interpreted as vestiges of ancient Martian
bacterial life. In particular, the authors noted the presence of
tubules 20 to 40 nanometers in diameter (called by some
"nannobacteria"), and they proposed these structures were
fossilized bacteria or parts of microorganisms. The report was
first delivered at a press conference in August 1996 (published
as a paper 9 days later) and provoked considerable media
attention and controversy when it appeared. The controversy has
continued, with many biologists objecting to the interpretation
of the rock data, and in particular objecting to the idea of
"bacteria" 20 to 40 nanometers in diameter.
... ... Allan Treiman (National Aeronautics and Space
Administration, US) presents a review and update of the ALH84001
meteorite controversy, the author making the following points: 1)
Early hopes for a fast resolution of the controversy concerning
meteorite ALH84001 have evaporated: no agreement has emerged on
whether or not the meteorite ever contained Martian life. 2)
There is no disagreement that ALH84001 formed on Mars
approximately 4.5 billion years ago, that the meteorite was
probably ejected into space approximately 16 million years ago by
an asteroid impact, that the meteorite fell in Antarctica 13,000
years ago, and that the meteorite remained in Antarctica until
found on the ice in 1984. 3) ALH84001 is an igneous rock (i.e., a
rock congealed from a molten mass) that apparently crystallized
slowly from molten lava and which contains globules of carbonate
minerals scattered along fractures. All the evidence for life is
in the carbonate globules or their rims. 4) The 4 lines of
evidence originally proposed by the McKay group were a) the
presence in the meteorite of carbon compounds (polycyclic
aromatic hydrocarbons) suggestive of decayed organic matter; b)
the presence in the meteorite of unusual small crystals of
magnetite (an iron oxide) matching identical crystals believed to
be produced only by Earth bacteria; c) the presence in the
meteorite of apparently incompatible minerals (e.g., iron-sulfide
and iron-oxide) close together whose proximity would suggest
organic action if the rock were from Earth; and d) the presence
in the meteorite of bacteria-shaped formations. 5) The author
[Treiman] suggests that a) The polycyclic aromatic hydrocarbons
may or may not be Martian, and if they are, they may or may not
be related to life. b) The magnetite crystals are indeed Martian,
but there is evidence that some of these crystals formed without
life and the origin of the others remains unclear. c) The mineral
associations in the carbonate globules do not prove life, but
also do not exclude it. d) The bacteria-shaped objects in
ALH84001 are not fossil bacteria but could be fossils of bacteria
fragments. (McKay's group now agrees that the objects are too
small to be fossil microbes.) 6) The author concludes: "McKay's
original hypothesis (as expressed in the 1996 paper) depended on
all four lines of evidence working together... The evidence has
not been verified, so the hypothesis has not succeeded... Despite
world attention, significant spending, and the work of the best
laboratories on Earth, the question [of life on Mars] is
unresolved."
-----------
Allan Treiman: Microbes in a Martian meteorite?
(Sky & Telescope April 1999)
QY: Allan Treiman [treiman@lpi.jsc.nasa.gov]
-------------------
Related Background:
NANOBACTERIA AND PATHOGENIC EXTRACELLULAR CALCIFICATION
The formation of discrete and organized inorganic crystalline
structures within macromolecular extracellular matrices is a
widespread biological phenomenon generally referred to as
biomineralization. Mammalian bone and dental enamel are examples
of biomineralization involving *apatite minerals, but the
molecular basis of such mineralization remains largely unknown.
Recently, bacteria have been implicated as factors in
biogeochemical cycles for mineral formation in aqueous sediments.
The principle constituent of modern *authigenic phosphate
minerals in marine sediments is carbonate apatite. Microorganisms
are capable of depositing apatite in sea water, and they can
segregate Ca from Mg and actively nucleate carbonate apatite by
means of specific *oligopeptides under conditions of pH < 8.5 and
an Mg/Ca concentration ratio of greater than 0.1. Such conditions
are also present in the human body. ... ... Kajander and
Ciftcioglu (University of Kuopio, FI) report a study of biogenic
apatite production by "nanobacteria", identified by the authors
as "the *smallest cell-walled bacteria, only recently discovered
in human and cow blood and commercial cell culture serum." The
authors report that nanobacteria can act as crystallization
centers for the formation of biogenic apatite structures, and
that nanobacteria can produce apatite in media mimicking tissue
fluids and *glomerular filtrate, and provide a unique model for
in vitro studies of calcification. The authors suggest that
nanobacteria may play a key role in the formation of all kidney
stones, and they report they have found nanobacteria in all 30
human kidney stones that they have screened. The authors suggest
their findings are of concern in medicine because nanobacterial
*bacteremia occurs in humans, and nanobacterial crystallization
centers might initiate pathological calcification.
QY: E. Olavi Kajander 
(Proc. Natl. Acad. Sci. US 7 Jul 98 95:8274)
(Science-Week 7 Aug 98)
-------------------
Related Background:
... ... *apatite minerals: A group of phosphate-containing
minerals. 
... ... *authigenic phosphate minerals: Authigenic minerals
(authigenes) are minerals that came into existence with or after
the formation of the rock of which they constitute a part. The
principal constituent of modern authigenic phosphate minerals in 
marine sediments is carbonate (hydroxy)fluorapatite:
Ca(sub10)(PO(sub4))(sub6-x)(CO(sub3))(subx)(F,OH)(sub2+x).
... ... *oligopeptides: A peptide composed of no more than 10
amino acids.
... ... *smallest cell-walled bacteria: The electron micrographs
in this report show various forms with diameters 0.2 to 0.5
microns. See related reports below concerning the reported size
of nanobacteria.
... ... *glomerular filtrate: A glomerulus is a tuft-like
structure composed of blood vessel capillaries or nerve fibers,
and in this context, a glomerulus is a blood vessel capillary
structure and part of the nephron, the fundamental filtration
unit of the kidney. The filtrate from kidney glomeruli consists
of small solute molecules filtered under pressure from blood.
... ... *bacteremia: This is a general term referring to the
presence of bacteria in blood.
-------------------
Related Background:
EVIDENCE THAT MARTIAN METEORITE AMINO ACIDS ARE CONTAMINANTS
As the subunits that compose protein polymers in living systems,
the detection of certain amino acids in a material is often
interpreted as indicating a possible biological origin. The
meteorite ALH84001, along with a number of other discovered
meteorites, has a composition that suggests it was apparently
ejected from the surface of Mars, and during the past year it has
been proposed that microanalysis of this meteorite indicates the
possible presence of bio-organics and biogenic fossils. This
proposal, however, has met with considerable controversy, and the
controversy is still in full force. ... ... Bada et al (4 authors
at 3 installations, US) now report that the amino acids present
in a sample of the ALH84001 meteorite appear to be terrestrial in
origin and similar to those found in the ice where the meteorite
was discovered, although the possibility remains that minute
amounts of endogenous amino acids are preserved in the meteorite.
The authors suggest that radiocarbon studies (cf. contiguous
report: Jull et al, Science 279:366 1998), coupled with their own
amino acid results, indicate that major and minor organic
constituents in the Martian meteorites are contaminants.
QY: Jeffrey L. Bada 
(Science 16 Jan 98) (Science-Week 30 Jan 98)
-------------------
Related Background:
AN ARGUMENT FOR RELIC LIFE ON MARS
... ... Gibson et al (National Aeronautics and Space
Administration Houston, US; University of Georgia, US), the
group including some of the authors of the 1996 McKay report, in
a review of the evidence for relic life on Mars, consider the
ALH84001 meteorite not only the strongest evidence for Martian
relic life, but also for the possibility of present Martian
microbial life. The authors are hopeful that in 2005 a "sample
return" mission will be launched to robotically collect Martian
rocks and soil and return them to Earth.
QY: Everett K. Gibson 
(Scientific American December 1997) (Science-Week 28 Nov 97)
-------------------
Related Background:
EVIDENCE AGAINST NANOFOSSILS IN MARTIAN METEORITE
The term "nanofossils" (originally spelled "nannofossils" by the
group that introduced the term) refers to elongated microscopic
forms found in the Martian meteorite ALH84001. Several groups in
the space and geology communities have proposed these forms are
fossilized bacteria, but most biologists have rejected the idea
on the basis that the forms are too small to be bacteria and
should not be classified as such. Bradley et al (3 installations,
US) now report that new analysis of material from the ALH84001
meteorite indicates the majority of the elongated microscopic
forms can be resolved as either emergent substrate layers or
magnetite whiskers, rather than biogenic nanofossils. Their
report is followed by a response from McKay et al (3
installations, US CA), some of the original proponents of the
nanofossil idea, and in their response McKay et al say the
artifact possibilities mentioned by Bradley et al are already
known to them, but are not related to their own observations.
They add that living bacteria as small as 70 nanometers in
diameter have been observed in mammalian blood, and that soil
bacteria as small as 80 nanometers have also been observed. The
references for these bacterial forms are one unpublished paper
and two recently published papers in Proc. Soc. Photo-Opt.
Instrum. Eng. 3111:420,429 (1997). It is evident that the
nanofossil controversy has not yet been resolved.
QY: J.P. Bradley, Georgia Inst. Technol. 404-894-2000; David S.
McKay 
(Nature 4 Dec 97) (Science-Week 26 Dec 97)
-------------------
Related Background:
A CONTROVERSY CONCERNING MINIMUM POSSIBLE DIMENSIONS OF BACTERIA
Apart from their heuristic significance, scientific controversies
can be either amusing or irritating. In recent months, a
controversy between some geologists and many biologists has
developed, and it is apparently irritating the biologists. The
issue concerns the minimum possible dimensions of bacteria. The
geologists are led by Robert L. Folk (University of Texas, Austin
TX US), and they have proposed that certain microscopic entities
found in the Martian meteorite ALH84001 are fossils of what they
term "nannobacteria" (their own unique spelling of the prefix
nano-), which they say are similar to those found in Earth
travertine and limestone rocks, and which have dimensions of 30
to 50 nanometers. This has caused a furor among biologists, whose
understanding of bacteria and life forms in general is that the
smallest dimensions possible for a life form with a bounding
plasma membrane is about 200 nanometers. In fact no membrane-
bound bacterium with dimensions less than 340 nanometers has ever
been identified, and one can make simple calculations that a 50
nanometer bacterium would not have enough internal volume to
sustain its chemistry. Folk published papers on the subject in
several geological journals in 1996, starting the debate, and in
the Letters section of the 20 June 1997 issue of *Science* the
debate continues, and this week it is being reported in the
popular media as a "debate about life on earth". What evidently
irritates biologists is the apparent misunderstanding by these
geologists of experimental methods in biology. Characterizations
of "living" vs. "non-living" by biologists are made on the basis
of experimental laboratory replicability of an organism, and not
on the basis of the visible structure of an entity. Which means
the geologists involved need to attempt to culture their
Earth-rock entities, and which means decisions that the Martian
meteorite's so-called "nannobacteria fossils" are actually such
will require demonstration of cultured entities with those
dimensions. Biologists are not unwilling to admit the existence
of new species of life forms, of which they have already
recognized several million entities, but they argue that one does
not classify pieces of rock as a life form on the basis of
structure alone.
(New York Times 29 Jul 97) (Science-Week 1 Aug 97)


6. ON DENSITY FUNCTIONAL THEORY IN MATERIALS SCIENCE
The current method of choice in many applications of quantum
mechanics to certain systems of interest in chemistry and
condensed matter physics is an approach call "density functional
theory", an approach first developed by Walter Kohn, Pierre
Hohenberg, and Lu Sham in the 1960s and later. The name "density
functional theory" derives from the connection (predicted by the
theory) 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.
... ... Jerzy Bernhole (North Carolina State University, US)
reviews the application of density functional theory to materials
science, the author making the following points:
     1) We are entering an era in which high-performance
computing allows predictive simulations of complex materials to
be made from information concerning their individual atoms. At
the present time, for example, the properties of new and
artificially structured materials can be predicted and explained
entirely by computations using atomic numbers as the only input.
     2) Methods for computing the properties of materials can be
divided into two classes: a) those that do not use any
empirically or experimentally derived quantities, and b) those
that do use such quantities. The former methods are often called
"ab initio methods" or "first-principle methods", while the
latter methods are called empirical or "semi-empirical". The ab
initio methods are particularly useful in predicting the
properties of new materials or new complex material structures,
and for predicting trends across a wide range of materials. The
semi-empirical methods excel at interpolating and extrapolating
from known properties. Density functional theory is an ab initio
method.
     3) The binding in molecules and solids is due to Coulomb
forces between electrons and nuclei. The exact solution of the
full many-body Schrodinger equation describing a material is not
possible, but one can make accurate approximations of the ground
state of a system, and such approximations, based on density
functional theory, are now widely used in condensed-matter
physics, and have had an important impact on chemistry. 
     4) Because electronic structure calculations are
computationally demanding, progress in the field depends on both
advances in theoretical methods and advances in computer
technology. For simple materials, e.g., silicon with only two
atoms in a periodically repeated unit cell, the computational
effort required has now become so modest that the calculations
can be carried out on any contemporary personal computer. In
contrast, understanding the growth and properties of silicon
devices requires calculating the characteristics of silicon
surfaces, and the required computational effort becomes
significantly greater. The largest ab initio calculations usually
explicitly include only valence electrons in the calculation, and
the calculations use atomic numbers as the only input. Ab initio
calculations have long been useful in explaining experimental
results and providing unique insights, and recent advances make
it possible to predict the properties of materials with complex
atomic arrangements, predictions that would have been
prohibitively expensive only a few years ago.
     5) Density functional theory has known drawbacks. For
example, it is not successful in describing properties that
involve excited states, such as bandgaps of semiconductors and
insulators. This limitation is not surprising, since density
functional theory is an approach for obtaining the total energy
of only the ground state. To obtain the energies of excited
states, one needs a many-body theory that properly takes into
account the nonlocal interactions between electrons.
     6) Concerning future prospects, the author states: "Progress
in materials simulation is accelerating while also becoming more
important. The rapid increase in the speed of computers is likely
to continue unabated for at least the next decade, and possibly
significantly longer. The algorithmic progress, stimulated by the
interest and advances in the field, is even more robust... It is
already possible to predict many properties reliably, and in some
cases the theoretical input has stimulated important experimental
discoveries."
-----------
Jerzy Bernhole: Computational materials science: The era of
applied quantum mechanics.
(Physics Today September 1999)
QY: Jerzy Bernhole, Dept. of Physics, North Carolina State
University 919-515-2434.
-------------------
Summary by SCIENCE-WEEK [http://scienceweek.com] 8Oct99


7. ROCK-DATING ERRORS: AN UPDATE
It sometimes happens in science that an accepted and widely-used
technique is eventually called into question by the discovery of
contaminating factors that skew the data in one direction or
another. Science moves on, but individual scientists have only a
short existence, and their careers are often banged up on the
reefs of such technical controversies. We are presenting here
what is apparently the concluding episode in one such
controversy, a controversy we reported in SW a year ago. Last
week, following a lengthy investigation by a faculty committee,
Arizona State University (US) officials reported they have
concluded that Ronald Dorn, Professor of Geography at the
university, did not commit scientific misconduct in collecting
and preparing rock varnish samples for carbon dating (see the
appended background material). The university investigation found
the evidence did not support allegations that Dorn added coal and
charcoal to rock varnish samples to hit pre-determined "target
dates". Some researchers in the field had charged that coal and
charcoal do not occur in nature together near rock surfaces, and
so must have been added by Dorn. But the university statement
points out that researchers other than Dorn have published papers
demonstrating that coal-like and charcoal-like materials do
indeed occur together, and the university's own investigation
also found these materials together naturally in rock varnish. In
summary, the misconduct allegations against Ronald Dorn have been
dismissed by the provost of his university.
-----------
Nancy Tribbensee: ASU provost dismisses misconduct allegations
following investigation.
(ASU Press Release 1 Oct 99)
QY: Nancy Neff, Arizona State University, 480-965-4836.
-------------------
Summary by SCIENCE-WEEK [http://scienceweek.com] 8Oct99
-------------------
Related Background:
GEOLOGY: A SHARP CONTROVERSY CONCERNING A ROCK-DATING METHOD
The geology community is evidently in the midst of an apparent
scandal concerning the rock-dating data produced by a prominent
researcher. The elements of the story are as follows: 1) Data
from Ronald Dorn (Arizona State University Tempe, US) concerning
hundreds of petroglyphs, stone tools, and rock surfaces around
the world are in question. 2) These data were produced by a
method of dating the organic material in rock varnish samples
(see below). It is being reported that rock varnish samples
processed by Dorn contain microscopic granules of coal and
charcoal, which it is said render the dating results meaningless,
with implications for such debates as the peopling of the
Americas. 3) The carbon granules evidently do not appear in
samples processed by other researchers, and it said the US
National Science Foundation and Arizona State University are
reviewing the possibility of misconduct. 4) Dorn is reported to
acknowledge that his technique is flawed and produces "ambiguous"
results. But he says the suggestion of tampering is "utterly
false" and that the carbon granules are naturally occurring. 5)
The technique in question involves accelerator mass spectrometry
radiocarbon analysis, one of several rock-surface dating methods
pioneered since the 1980s by Dorn. The method assumes that
microscopic quantities of carbon-rich organic material become
trapped in and beneath a thin layer of natural varnish on the
rock surface. Although some specialists have doubted the trapped
material can be accurately dated, Dorn has argued since 1986 that
the material holds measurable quantities of radioactive carbon-
14, which decays at a known rate. To date a rock, Dorn scrapes
the varnish and material beneath the varnish, extracts the
organic material with acid, then sends samples to various
accelerator mass spectrometry facilities. This controversy is
apparently serious enough so that many geologists are now
considering rock-varnish dating in general of significantly
reduced utility. A technical commentary by Beck et al (7 authors
at 4 installations, US CH) has been published to alert the
geology community to the problem.
QY: David Malakoff 
QY: W. Beck, University of Arizona 520-621-2211.
(Science 26 Jun 98 280:2132) (Science-Week 17 Jul 98)


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

IN FOCUS: ON THE NEURONAL SYNAPSE AS A MICRO-UNIT
[Editor's note: In general, nerve cells have a single long
extension (the "axon") that propagates the electrical output (the
action potential) of the cell. The term "synapse" refers to the
junction between the terminal of a neuron's axon and another
neuron. When studying the synapse, the first neuron is called the
"presynaptic" neuron, and the second neuron is called the
"postsynaptic" neuron. As is demonstrated by the following text,
the task of delineating the microcircuitry of the human brain,
and the workings of the units of this circuitry, is one of the
most formidable projects in reverse engineering ever undertaken
by science.]
-----------
"In addition to its ability to mediate specific functions, an
important property of the synapse is its small size. The area of
contact has a diameter of 0.5 to 2.0 microns, and the presynaptic
terminal (bouton) has a diameter that characteristically is only
slightly larger. These small sizes mean that large numbers of
synapses can be packed into the limited space available within
the brain. For example, in the cat visual cortex, 1 cubic
millimeter of grey matter contains approximately 50,000 neurons,
each of which gives rise on average to some 6000 synapses, making
a total of 300 million synapses... Given an approximate density
of 100,000 neurons below 1 square millimeter of cortical grey
matter in primates, and assuming that the cortical area of one
hemisphere in the human is approximately 100,000 square
millimeters, there must be 10 billion cells in the human cortex
and 60 trillion synapses. In humans, these packing densities can
be as large as 1 billion synapses per cubic millimeter of
cortical tissue... Like the national debt, these numbers are so
large that they lose meaning. The important point is that the
number of synapses in the brain is several orders of magnitude
larger than the number of neurons, providing a rich substrate for
the construction of microcircuits within the packed confines of
the brain. During early development, an exuberance of synapses is
generated throughout the nervous system. During this time,
synapses are very dynamic and appear and disappear rapidly. When
the animal reaches maturity, the final synaptic density is half
the density present earlier on (yet the size of the brain has
usually expanded considerably."
-----------
G.M. Shepherd and C. Koch: Introduction to Synaptic Circuits
in: Gordon M. Shepherd (ed.)_The Synaptic Organization of the
Brain_. (Oxford University Press, New York 1998, p.6)

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

CORRECTION: On Education Physicians Concerning... (SW 3/#40)

In the sentence: "The authors received data from 122 US medical
schools (98.6 percent of the total medical schools in the US)."
The percentage "98.6" is what appears in the paper by Ferry et
al, but the correct percentage is 96.8.

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

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