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May 7, 2002

For more information on these science news and feature story tips, contact the public information officer listed at (703) 292-8070. Editor: Josh Chamot

Gene Study Determines How Humans are Related to Fruit Flies and Nematode Worms

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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Scientists 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 muscles.

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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Ocean Drilling 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 0C to 25C, 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 scientists.

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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High-Tech 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 and challenge.

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 interactions.

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. [Cheryl Dybas]

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