October 27, 2006, 4:34 AM CT

Cracking The Stellar Evolution

Using 3D models run on some of the fastest computers in the world, Laboratory physicists have created a mathematical code that cracks a mystery surrounding stellar evolution.

For years, physicists have theorized that low-mass stars (about one to two times the size of our sun) produce great amounts of helium 3 (³He). When they exhaust the hydrogen in their cores to become red giants, most of their makeup is ejected, substantially enriching the universe in this light isotope of helium.

This enrichment conflicts with the Big Bang predictions. Researchers theorized that stars destroy this ³He by assuming that nearly all stars were rapidly rotating, but even this failed to bring the evolution results into agreement with the Big Bang.

Now, by modeling a red giant with a fully 3D hydrodynamic code, LLNL scientists identified the mechanism of how and where low-mass stars destroy the ³He that they produce during evolution.

They observed that ³He burning in a region just outside of the helium core, previously believed to be stable, creates conditions that drive this newly discovered mixing mechanism.

Bubbles of material, slightly enriched in hydrogen and substantially depleted in ³He, float to the surface of the star and are replaced by ³He-rich material for additional burning. In this way the stars destroy their excess ³He, without assuming any additional conditions (like rapid rotation).........

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October 26, 2006, 5:05 AM CT

200-million-year-old Baby Galaxies

Astronomers have taken amazing pictures of two of the most distant galaxies ever seen. The ultradeep images, taken at infrared wavelengths, confirm for the first time that these celestial cherubs are real. The researchers* are now able to weigh galaxies and determine their age at earlier times than ever before, providing important clues about the evolutionary origins of galaxies like our Milky Way. The work appears in the October 1 issue of Astrophysical Journal Letters.

Carnegie Fellow Ivo Labbe, along with Rychard Bouwens and Garth Illingworth of the UCO/Lick Observatory at the University of California, Santa Cruz, and Marijn Franx of the Leiden Observatory, examined galaxies in the Hubble Ultra Deep Field (HUDF) using the sensitive Infrared Array Camera (IRAC) aboard NASA's Spitzer Space Telescope. The HUDF, scanned by NASA's Hubble Space Telescope in late 2003, remains the deepest view ever taken at visible and near-infrared wavelengths.

The two galaxies are seen when the universe was just a baby-700 million years after the Big Bang, or five percent of the universe's current age. They belong to a precious small sample of similarly ancient galaxies, discovered two years ago by Bouwens, Illingworth, and Franx and analyzed in-depth in Nature last month. The relative deficit of such far-away luminous sources indicates that this early period is when galaxies were rapidly building up from a very small number of stars to the massive galaxies we see at later times.........

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October 26, 2006, 4:56 AM CT

Pollinators Help One-third Of Crop Production

Pollinators such as bees, birds and bats affect 35 percent of the world's crop production, increasing the output of 87 of the leading food crops worldwide, finds a new study published recently (Wednesday, Oct. 25), in the Proceedings of the Royal Society B: Biological Sciences and co-authored by a conservation biologist at the University of California, Berkeley.

The study is the first global estimate of crop production that is reliant upon animal pollination. It comes one week after a National Research Council (NRC) report detailed the troubling decline in populations of key North American pollinators, which help spread the pollen needed for fertilization of such crops as fruits, vegetables, nuts,.

Of particular concern in the NRC report was the decline of the honey bee, a species introduced from Europe and a critical pollinator for California's almond industry. The report pointed out that it takes about 1.4 million colonies of honey bees to pollinate 550,000 acres of this state's almond trees.

In an effort to better understand how dependent crop production is upon pollinators worldwide, an international research team led by Alexandra-Maria Klein, an agroecologist from the University of Goettingen in Germany, conducted an extensive review of scientific studies from 200 countries and for 115 of the leading global crops.........

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October 26, 2006, 4:51 AM CT

Nuclear Receptors In Bee Genome

Susan Fahrbach, a Wake Forest University biologist, is among the more than 170 scientists who helped decode the honey bee genome. She contributed to the article on the bee genome sequence that appears in the Oct. 26 issue of Nature.

Her piece of the puzzle -- analyzing the nuclear hormone receptors found in the bee genome -- also appears in the current issue of Insect Molecular Biology.

The honey bee was chosen to have its genome sequenced because of its dual importance to agriculture and medicine. The well-known pollination activities of honey bees add billions of dollars of value to U.S. crops every year, but bees are also used in the laboratory to study issues correlation to human health such as immunity, longevity and diseases of the X chromosome. In addition, brain researchers are interested in the honey bee's complex social life and their ability to communicate the location of flowers to other members of the hive.

Fahrbach, Reynolds Professor of Developmental Neuroscience, and her co-scientists at Wake Forest and the University of Illinois, searched the genome sequence to find all of the nuclear receptors encoded in the bee genome. They observed that the same nuclear receptors that control the development of the nervous system during the early.........

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October 24, 2006, 8:52 PM CT

Early Bronze Age Mortuary Complex Discovered

An ancient, untouched Syrian tomb that wowed the archaeological world on its discovery by Johns Hopkins University researchers nearly six years ago has revealed another secret: It is not alone.

The tomb, which was filled with human and animal remains, gold and silver treasures and unbroken artifacts dating back to the third millennium B.C., is actually one of at least eight located near each other in Umm el-Marra, archaeologist Glenn Schwartz said. That northern Syrian city is believed to be the site of ancient Tuba, one of Syria's first cities and the capital of a small kingdom, said Schwartz, the Whiting Professor of Archaeology in the Department of Near Eastern studies at Johns Hopkins.

The newly discovered tombs contain signs of the ritual sacrifice of humans and animals, including the skeletons of infants and decapitated donkeys, as well as puppy bones, Schwartz said. "Given these discoveries, it's likely that the tomb complex is a royal cemetery," he said.

"Animal sacrifices were certainly a big part of this culture in that offerings of sheep and other animals are given to the gods to eat and also given to deceased royal ancestors," Schwartz said. He and his team have dubbed this site the Acropolis Center mortuary complex.

The tombs are located about 35 miles east of the site of Aleppo, the main city and dominant center in the region dating at least as far back as 2000 B.C., Schwartz said. Though the tomb complex is much less showy than the famous one from the same period at Ur in Mesopotamia, which is now Iraq, the Umm el-Marra complex is the only known one in Syria from this time period.........

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October 24, 2006, 8:45 PM CT

A Supersolid Not Quite So Super?

A deceptively simple experiment, recently published in the journal Science, has moved physics one step closer to explaining the odd behavior of supersolid helium. The unusual state of matter - in which a portion of the atoms are able to flow through a solid crystal with no resistance - was predicted as early as 1969 but not observed until recently.

In 2004, Eunsong Kim and Moses Chan from Penn State University published the first experimental evidence that the predicted behavior could actually be demonstrated in the laboratory. In the last two years, a flurry of papers attempted to clarify under what conditions the behavior emerges. So when Humphrey Maris, a professor of physics at Brown University, visited colleagues Satoshi Sasaki and Sebastien Balibar at l'Ecole Normale Superieure in Paris, they decided they needed to plan an experiment that could shed some new light on the problem.

"We were trying to think of an easy way to do something on superfluid solids," said Maris. "The idea of something flowing through something solid is pretty weird, isn't it? That's what we like about it".

Maris and company hatched an elegant plan that uses kitchen table physics to examine the behavior of this strange new state of matter. To understand how they probed the phenomenon, try this simple experiment. Fill a drinking straw with water and cover it with your finger. Place it in a glass of water. As long as your finger seals the straw, the water won't flow out into the cup. As soon as you release your finger, it does. The water doesn't flow out of the straw until you open a path that allows air to replace it.........

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October 24, 2006, 8:19 PM CT

Amazon River Reversed Flow

Ask any South American dinosaur which way the Amazon River flows and she would have told you east-to-west, the opposite of today. That's the surprising conclusion of scientists studying ancient mineral grains buried in the Amazon Basin.

The once westward roll of what is now the world's largest river was caused by a long-gone highland near what today is the river's mouth. That highland was created by the breaking away of South America from Africa and the creation of the Atlantic Ocean during the Cretaceous Period, 65 to 145 million years ago. Later, when the Andes rose up on the western side of South America, the river had no choice but to drain into the new ocean.

"It just happened in a way that the current Amazon could take advantage of where an old river and ocean basin used to sit," said geologist Russell Mapes, a doctoral candidate at the University of North Carolina in Chapel Hill.

Prior Brazilian and U.S. scientists have proposed smaller scale reversals and splits in the Amazon Basin, but nothing on the scale of the entire basin, said Mapes.

The evidence for the Amazon's ancient switcheroo comes in the form of tiny crystals of a mineral called zircon, as well as telltale signs of the river flow direction captured in the structure of old river sediments.........

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October 24, 2006, 7:20 PM CT

New Theory For Mass Extinctions

A new theory on just what causes Earth's worst mass extinctions may help settle the endless scientific dust-up on the matter. Whether you favor meteor impacts, volcanic eruptions, cosmic rays, epidemics, or some other cause for the worst mass extinction events in Earth's history, no single cause has ever satisfied all researchers all the time for any extinction event. That may be because big extinctions aren't simple events.

The new Press/Pulse theory gets around the controversy by rejecting the all-or-nothing approach to mass extinction, calling instead on a combination of deadly sudden catastrophes - "pulses" - with longer, steadier pressures on species - "presses".

"What we wanted to do is move away from the idiosyncratic approach to extinction mechanisms and look for what these intervals had in common. If you have A and B you will get a mass extinction," said Ian West, a 2006 graduate of Hobart and William Smith Colleges in Geneva, NY.

West and Hobart and William Colleges paleontology professor Nan Crystal Arens are scheduled to present their work on the Press/Pulse theory on Wednesday, 25 October, at the Annual Meeting of the Geological Society of America in Philadelphia.

Using databases that chart genera of marine organisms and their extinctions through the fossil record, West and Arens divided the last 488 million years of geologic history into four groups: times of suspected impact events (Pulses), times of massive volcanic eruptions (Presses), times when neither Presses nor Pulses occurred, and times when Press and Pulse coincided. They compared average extinction rates in geologic stages in each of these groups.........

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October 24, 2006, 7:12 PM CT

Trotting With Emus To Walk With Dinosaurs

One way to make sense of 165-million-year-old dino tracks may be to hang out with emus, say paleontologists studying thousands of dinosaur footprints at the Red Gulch Dinosaur Tracksite in northern Wyoming. Because they are about the same size, walk on two legs and have similar feet, emus turn out to be the best modern version of the enigmatic reptiles that once trotted along a long-lost coastline in the Middle Jurassic.

"We don't have any documented dinosaur bones and teeth from that period in North America, except for some very scrappy material from Mexico," said Brent Breithaupt, curator and director of the University of Wyoming's Geological Museum in Laramie, Wyo. That makes it very hard to connect the tracks to a particular dinosaur. And of course, "We unfortunately can't go out and see walking dinosaurs today. Or can we?".

After scouring the dinosaur fossil record in other parts of the world and deciding that a human-sized, meat-eating dinosaur (theropod) fit the bill for the tracks at Red Gulch, Breithaupt and colleagues and students did something unusual. Instead of speculating about what the dinosaurs were doing, they went hunting for a modern analog animal they could study to help decipher the tracks.

Large flightless birds are the most logical choice and are, along with all birds today, believed to be descended from dinosaurs. But not all of those alive today are good choices or easy to work with. Ostriches are two-toed and have an attitude problem, so that ruled them out, says Breithaupt. Rheas have three toes, but are "like working with a bunch of kindergarteners on too much sugar," he said.........

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October 24, 2006, 7:05 PM CT

Cougar Predation Key To Ecosystem Health

The general disappearance of cougars from a portion of Zion National Park in the past 70 years has allowed deer populations to dramatically increase, leading to severe ecological damage, loss of cottonwood trees, eroding streambanks, and declining biodiversity.

This "trophic cascade" of environmental degradation, all linked to the decline of a major predator, has been shown in a new study to affect a broad range of terrestrial and aquatic species, according to scientists from Oregon State University.

The research was just published in the journal Biological Conservation and, like recent studies outlining similar ecological ripple effects following the disappearance of wolves in the American West may cause land managers to reconsider the importance of predatory species in how ecosystems function.

The findings are consistent, researchers say, with predictions made more than half a century ago by the famed naturalist Aldo Leopold, often considered the father of wildlife ecology.

"When park development caused cougar to begin leaving Zion Canyon in the 1930s, it allowed much higher levels of deer browsing," said Robert Beschta, an OSU professor emeritus of forest hydrology. "That set in motion a long cascade of changes that resulted in the loss of most cottonwoods along the streambanks and heavy bank erosion".........

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