May 7, 2002
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Editor: Josh Chamot
Contents of this News Tip:
Determines How Humans are Related to Fruit Flies and
The most comprehensive genetic study of evolutionary
relationships among those animals whose genes have
been completely sequenced - the human, the fruit fly,
and the nematode worm - has determined that the human
species is more closely related to the fruit fly than
to the nematode.
"We compared 100 genes that are common among these
three species - the largest data set ever used to
address this question - and obtained a result that
is unambiguous," says S. Blair Hedges, an evolutionary
biologist at Penn State University.
Hedges and his colleagues overturn a popular hypothesis
that was based primarily on the study of a single
gene. The research team, comprising scientists from
Penn State and Japan, was funded by the National Science
Foundation (NSF). Two of these species represent much
larger groups of animals, with humans representing
vertebrates and the fruit fly representing arthropods.
The study impacts any field that is concerned with
the inheritance of traits in major groups of animals,
Hedges says. The results - expected to affect the
content of biology textbooks - have important implications
for research in fields such as medicine and developmental
biology. The results of the study were published in
the web-based journal BMC Evolutionary Biology.
The researchers tapped into the wealth of data now
available in the completely sequenced genomes of the
three species. The nematode and fruit fly are among
the most widely used model organisms in medical and
genetics research because they can be bred easily
and produce new generations quickly.
"A lot of our understanding of human medicine is based
on these species because we can do experiments with
them that you wouldn't do with humans," Hedges says.
Scientists' understanding of how the species are related
will determine how to reconstruct their histories
and whether a mutational change is interpreted as
relatively recent or ancient. [Cheryl Dybas]
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Produce Long Nanotube Strands
Researchers have developed a simplified method for
making continuous, hair-like strands of carbon nanotubes
as long as eight inches. This breakthrough, reported
in the May 3 issue of Science, is a first step toward
creating such products as microcables for electrical
devices or electrochemical actuators for artificial
NSF-supported researcher Pulickel Ajayan and colleagues
at Rensselaer Polytechnic Institute in Troy, New York,
collaborated with others at Tsinghua University in
Beijing, China. They found that chemical vapor deposition,
a widely used technique for growing nanotubes, can
produce long strands when a sulfur-containing compound
and hydrogen are added to the process.
Because chemical vapor deposition is already used to
make nanotubes, it would be easily adaptable and more
efficient for synthesizing long strands than previous,
more complex methods of producing the fibers.
"Carbon nanotubes are generally microns in length,
which is not long enough for any practical purpose,"
said Ajayan. "We have created strands with nearly
aligned nanotubes that are as long as 20 centimeters.
The nanotubes are well ordered in these structures
and are self-assembled during the growth process,
which means we don't end up with an unusable lump
that looks like cooked spaghetti." [Amber Jones]
For images, see: http://www.rpi.edu/dept/NewsComm/sub/Pressimgs/SEM/SEMimage.jpg
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Expedition Finds Microbial Life Beneath the Seafloor
A team of scientists from seven nations has recently
returned from the first seafloor drilling expedition
dedicated to the study of life beneath the ocean bottom.
The Ocean Drilling Program (ODP) drill ship JOIDES
Resolution, funded in part by NSF, left San Diego,
California, in late January and returned to Valparaiso,
Chile, at the end of March. Shipboard scientists worked
over Pacific Ocean water depths ranging from 150 to
5,300 meters, and drilled into sediments and the underlying
rocky crust. Sediments ranged in temperature from
0°C to 25°C, and in age from zero to almost 40 million
years. The sites were selected to represent the range
of subsurface environments that exists throughout
most of the world's oceans.
"This research cruise taught us a great deal about
life in a place we haven't looked before," remarked
Steven D'Hondt of the University of Rhode Island Graduate
School of Oceanography, one of the expedition co-chief
Earlier studies of marine sediments had found microbes
to be ubiquitous in deep-sea sediments. However, almost
nothing was known about the nature of the microbes,
the extent of their activity and their relationships
to life on Earth's surface.
The recent expedition found evidence of active microbial
life in all the marine sediments that researchers
explored. Scientists discovered that the microbial
life is fueled by several sources: chemicals that
sink down from the overlying ocean, chemicals released
by the degradation of the surrounding sediment, or
chemicals that bubble up from the underlying rocky
crust. Wherever microbial life relies on degradation
of the sediment that surrounds it, the organisms depend
on conditions that prevailed when the sediment was
deposited, often millions of years ago.
The microbes will be studied further to document the
genetic relationships between the life forms of Earth's
subsurface and surface realms. The recovered sediments
and fluids will also be studied to determine how biogeochemical
processes deep beneath the seafloor affect Earth's
surface. [Cheryl Dybas]
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Imagery Seeks New Insights into Breaking Wave Dynamics
To surfers, breaking waves represent the thrill and
challenge at the core of their sport. To scientists
who study interactions between the air and the sea,
breaking waves represent a different kind of thrill
A NSF-funded study led by scientist Ken Melville of
Scripps Institution of Oceanography at the University
of California, San Diego, has provided unprecedented
insight into the dynamics involved in breaking waves.
The study advances the science of important processes
associated with the waves, including ocean wave height
limits, generation of currents and surface mixing.
"One of the most important functions of breaking waves
is to transfer momentum from the wind to ocean currents,"
said Melville. "Wave breaking also is vital to air-sea
exchange processes such as heat and gas transfer,
which may have a profound effect on weather and climate."
In the past, wave breaking has been tracked by so-called
"whitecap coverage," in which still or video imagery
was used to statically identify ocean whitecaps and
the corresponding surface covered by breaking waves.
But those measurements suffered because they failed
to account for the motion of the breaking waves, an
aspect critical for understanding an array of air-sea
For the new study (part of the Shoaling Waves Experiment,
or SHOWEX), Melville and Peter Matusov (also of Scripps)
used high-tech instrumentation aboard a light aircraft
to obtain detailed image sequences of breaking waves.
The equipment included an airborne video system and
differential global positioning system technology
to precisely characterize breaking processes.
The results of the study not only demonstrate that
researchers can accurately measure breaking waves
with remote imaging techniques, but also describe
aspects of wave growth and decay in unique detail.
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