April 10, 2007, 5:58 PM CT

Coral Reef Tells The History Of Soil Erosion

Coral reefs, like tree rings, are natural archives of climate change. But oceanic corals also provide a faithful account of how people make use of land through history, says Robert B. Dunbar of Stanford University.

According to a research findings published in the Feb. 22 issue of Geophysical Research Letters, Dunbar and his colleagues used coral samples from the Indian Ocean to create a 300-year record of soil erosion in Kenya, the longest land-use archive ever obtained in corals. A chemical analysis of the corals revealed that Kenya has been losing valuable topsoil since the early 1900s, when British settlers began farming the region.

"We found that soil erosion in Kenya increased dramatically after World War I, coinciding with British colonialism and a series of large-scale agricultural experiments that provoked a dramatic change in human use of the landscape," said Dunbar, a professor of geological and environmental sciences. "Today, the Kenyan landscape continues to lose topsoil to the Indian Ocean, primarily because of human pressure".

Erosion is a serious threat, he noted, because the loss of fertile soil often is accompanied by a decrease in food production. According to one recent study, soil erosion is a global problem that has caused widespread damage to agriculture and animal husbandry, placing about 2.6 billion people at risk of famine. "This is particularly worrisome in East and sub-Saharan Africa, where per capita food production has declined for the last half-century," Dunbar said......... Posted by: Beverly      Read more         Source

April 9, 2007, 11:06 PM CT

Blending in, Not Fighting Back

Biomedical engineers are constantly coming up with ways to repair the human body, replacing defective and worn out parts with plastic, titanium, and ceramic substitutes - but the body does not always accept such substitutes seamlessly. Engineers from Brown and Purdue universities have observed that simply changing the surface texture of implants can dramatically change the way cells colonize a wide variety of materials.

Two recent experiments have focused on the materials used in stents - those springy little cylinders that hold open once-clogged arteries - and artificial blood vessels. Currently only about 30 percent of small diameter blood vessel grafts (less than 6 mm diameter) last more than five years, and up to 20 percent of stents need to be replaced because the artery walls thicken in and around them in a process known as restenosis. Drug-coated stents were introduced years ago as one way to combat this problem, but concerns have surfaced recently about increased clotting.

Instead of using chemistry to fight the body's response to such foreign materials, Thomas Webster, an associate professor of engineering, and Karen Haberstroh, an assistant professor of engineering, thought maybe they could use physical structure to allow the foreign materials to blend in better. "What we're trying to do is fundamentally different," says Webster. "We're trying to find materials that the body accepts, rather than develop drugs or develop materials that will kill a cell - no matter if it kills a bad cell or a good cell. We're trying to find materials that accept good cells, as opposed to killing off bad cells"......... Posted by: Beverly      Read more         Source

April 3, 2007, 10:49 PM CT

How Lead Exposure Produces Learning Deficits

A study of young adult rats by researchers from the Johns Hopkins Bloomberg School of Public Health provides evidence that explains exactly how exposure to lead during brain development produces learning deficits. The study shows that exposure to levels of lead that are similar to those measured in lead-intoxicated children reduces the birth and survival of new neurons (neurogenesis) in the brain. Lead also alters the normal development of newly born neurons in a part of the brain (hippocampus) known to be important for learning and memory. The study is published in the March 30, 2007, issue of Neuroscience.

"There was a dogma in neuroscience that you were born with all the neurons you would ever have, but that thinking has changed dramatically in the last 20 years," said Tomás R. Guilarte, PhD, senior author of the study and professor of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health. "The exciting idea is that scientists have discovered ways to increase the number of new neurons, and this may facilitate learning in the hippocampus portion of the brain".

The researchers studied young adult rats, using a group of lead-treated and non-treated (control) rats. When they examined the brains of lead-exposed rats, they found that fewer neurons were born and those neurons that were born survived for a shorter amount of time and had abnormal development......... Posted by: Beverly      Read more         Source

April 3, 2007, 10:39 PM CT

Financial Risks Of Nuclear Power Plants

Berkeley -- Enticed by the gleam of government subsidies, many companies are rushing to invest in nuclear power, expecting that new technology and safer reactors will make them as good an investment as other types of power plants.

A new study appearing in the April 1 issue of the journal Environmental Science and Technology notes, however, that the country's history of unexpected cost overruns when building nuclear plants should sound a cautionary note for power companies that nuclear power may not be financially attractive.

"For energy security and carbon emission concerns, nuclear power is very much back on the national and international agenda," said study co-author Dan Kammen, UC Berkeley professor of energy and resources and of public policy. "To evaluate nuclear power's future, it is critical that we understand what the costs and the risks of this technology have been. To this point, it has been very difficult to obtain an accurate set of costs from the U. S. fleet of nuclear power plants".

The study, conducted by a research team from Georgetown University, Stanford University and UC Berkeley, analyzes the costs of electricity from existing U.S. nuclear reactors and discusses the possibility for cost "surprises" in new energy technologies, including next-generation nuclear power......... Posted by: Beverly      Read more         Source

April 2, 2007, 10:22 PM CT

Breakthrough Points To Hydrogen-powered Vehicles

Researchers at the U.S. Department of Energy's Argonne National Laboratory have developed an advanced concept in nanoscale catalyst engineering - a combination of experiments and simulations that will bring polymer electrolyte membrane fuel cells for hydrogen-powered vehicles closer to massive commercialization.

The results of their findings identify a clear trend in the behavior of extended and nanoscale surfaces of platinum-bimetallic alloy. Additionally, the techniques and concepts derived from the research program are expected to make overarching contributions to other areas of science well beyond the focus on electrocatalysis.

The Argonne researchers, Nenad Markovic and Vojislav Stamenkovic, published related results last month in Science and this month in Nature Materials on the behavior of single-crystal and polycrystalline platinum alloy surfaces. The researchers discovered that the nanosegregated platinum-nickel alloy surface has unique catalytic properties, opening up important new directions for the development of active and stable practical cathode catalysts in fuel cells.

These scientific accomplishments together provide a solid foundation for the development of hydrogen-powered vehicles, as basic research brings value to society today by helping to lay the foundation for tomorrow's technological breakthroughs. "Understanding catalysis is a grand challenge of nanoscience that is now coming within reach," said George Crabtree, director of Argonne's Materials Science Division. "The systematic work that Voya and Nenad are doing is a major step toward transforming catalysis from an empirical art to a fundamental science"......... Posted by: Beverly      Read more         Source

April 1, 2007, 9:28 PM CT

Sleep quantity affects morning testosterone levels

The testosterone levels of healthy men decline as they get older. As sleep quality and quantity typically decrease with age, objectively measured differences in the amount of sleep a healthy older man gets can affect his level of testosterone in the morning, as per a research studyreported in the April 1st issue of the journal SLEEP.

The study, conducted by Plamen Penev, MD, PhD, of the University of Chicago, focused on 12 healthy men between the ages of 64 and 74. Three morning blood samples were pooled for the measurement of total and free testosterone. In addition to overnight laboratory polysomnography, wrist activity monitoring for six-to-nine days were used to determine the amount of nighttime sleep of the participants in everyday life settings.

The main outcome levels were total sleep time and morning testosterone levels. Analyses revealed that the amount of nighttime sleep measured by polysomnography was an independent predictor of the subjects morning total and free testosterone levels.

"The results of the study raise the possibility that older men who obtain less actual sleep during the night have lower blood testosterone levels in the morning," said Penev. "Eventhough the findings suggest that how long a person sleeps may be an indicator of age-related changes in important hormone signals in the body, future studies are needed to determine the importance of these relationships for the health of elderly adults"......... Posted by: Beverly      Read more         Source

April 1, 2007, 9:08 PM CT

Right angles are all wrong for tree frog adhesion

Tree frogs have the unique ability to stick to smooth surfaces even when they are tilted well beyond the vertical - some small tree frogs can even adhere when completely upside down. Conversely when walking or jumping they can detach their toe pads easily. Researchers from the University of Glasgow will present insights into how this fascinating ability is controlled at the Society for Experimental Biologys Annual Meeting in Glasgow, UK.

The toe pads of tree frogs are coated with a thin mucus which adhere to surfaces by wet adhesion, like wet tissue paper sticking to glass. The process by which they detach their toe pads is called peeling and is akin to us removing a sticking plaster from ourselves, explains Dr Jon Barnes, head of the research group, We were keen to understand why a tree frog on an overhanging surface didnt simply peel off rather than adhere.

To investigate this, scientists measured adhesive and frictional forces simultaneously on individual toe pads of Whites tree frogs (Family Hylidae), while varying the surface angle. It was found that the change from adhesion to peeling is a gradual process, with adhesive forces weakening at angles above 90. Thus frogs maintain a grip by keeping the angle of their toes with respect to a surface at a low value, and detach when this angle increases beyond 90. By examining the behaviour of the frogs researchers were able to correlate this observation with how the animals positioned their legs - they spread their legs out sideways to minimise the angle between their feet and the surface......... Posted by: Beverly      Read more         Source

April 1, 2007, 8:53 PM CT

Getting dirty may lift your mood

Treatment of mice with a friendly bacteria, normally found in the soil, altered their behavior in a way similar to that produced by antidepressant drugs, reports research published in the latest issue of Neuroscience.

These findings, identified by researchers at the University of Bristol and colleagues at University College London, aid the understanding of why an imbalance in the immune system leaves some individuals vulnerable to mood disorders like depression.

Dr Chris Lowry, lead author on the paper from Bristol University, said: "These studies help us understand how the body communicates with the brain and why a healthy immune system is important for maintaining mental health. They also leave us wondering if we shouldnt all be spending more time playing in the dirt".

Interest in the project arose after human cancer patients being treated with the bacteria Mycobacterium vaccae unexpectedly reported increases in their quality of life. Lowry and his colleagues reasoned that this effect could be caused by activation of neurons in the brain that contained serotonin.

When the team looked closely at the brains of mice, they found that treatment with M. vaccae activated a group of neurons that produce the brain chemical serotonin. The lack of serotonin in the brain is thought to cause depression in people, thus M. vaccaes effects on the behavior of mice may be due to increasing the release of serotonin in parts of the brain that regulate mood......... Posted by: Beverly      Read more         Source

March 29, 2007, 10:33 PM CT

Nanotubes Could Improve Thermal Management

As the electronics industry continues to churn out smaller and slimmer portable devices, manufacturers have been challenged to find new ways to combat the persistent problem of thermal management. New research published in the March 19 issue of Applied Physics Letters suggests that carbon nanotubes may soon be integrated into ever-shrinking cell phones, digital audio players, and personal digital assistants to help ensure the equipment does not overheat, malfunction, or fail.

The chips inside an electronic device give off heat as a byproduct of power consumption when the object is on or being used. To reduce high temperatures, heat sinks - finned devices made of conductive metal such as aluminum or copper - are attached to the back of the chips to "pull" thermal energy away from the microprocessor and transfer it into the surrounding air. Fans or fluids are sometimes used to improve the cooling process, but they increase the device weight, size, and bulk.

Using microfin structures made of aligned multiwalled carbon nanotube arrays mounted to the back of silicon chips, researchers from Rensselaer Polytechnic Institute and the University of Oulu in Finland have proven that nanotubes can dissipate chip heat as effectively as copper - the best known, but most costly, material for thermal management applications. And the nanotubes are more flexible, resilient, and 10 times lighter than any other cooling material available......... Posted by: Beverly      Read more         Source

March 28, 2007, 10:16 PM CT

Tangle Under Turbulence

Picture the flow of water over a rock. At very low speeds, the water looks like a smooth sheet skimming the rock's surface. As the water rushes faster, the flow turns into turbulent, roiling whitewater that can overturn your raft.

Turbulence is important in virtually all phenomena involving fluid flow, such as air and gas mixing in an engine, ocean waves breaking on a cliff and air whipping across the surface of a vehicle. However, a comprehensive description of turbulent fluid motion remains one of physics' major unsolved problems.

Now, in a paper would be published in an upcoming issue of Physical Review Letters, MIT scientists report that they have visualized for the first time a convoluted tangle underlying turbulence. This work may ultimately help engineers design better planes, cars, submarines and engines.

Scientists have long suspected that there's a hidden but coherent structure underlying turbulence's messy complexity, but there has been no objective way of identifying it, said MIT research group leader George Haller, professor of mechanical engineering, who also heads Morgan Stanley's Mathematical Modeling Center in Hungary.

"The fluid mechanics community has not reached a consensus even on an objective definition of a vortex, or whirlpool effect, let alone the definition of structures forming turbulence. The mathematical techniques we have developed give a systematic way to identify the material building blocks of a turbulent flow," Haller said......... Posted by: Beverly      Read more         Source