January 12, 2007, 5:04 AM CT

Soil Nutrients Shape Tropical Forests

Tropical forests are among the most diverse plant communities on earth, and researchers have labored for decades to identify the ecological and evolutionary processes that created and maintain them. A key question is whether all tree species are equivalent in their use of resources - water, light and nutrients - or whether each species has its own niche.

A large-scale study by scientists at the University of Illinois at Urbana-Champaign and eight other institutions sheds some light on the issue. It indicates that nutrients in the soil can strongly influence the distribution of trees in tropical forests. The finding, published this week in the Proceedings of the National Academy of Sciences, challenges the theory that at local scales tree distributions in a forest simply reflect patterns of seed dispersal, said James W. Dalling, a U. of I. professor of plant biology and a principal researcher on the study.

The study reviewed three sites: two lowland forests, in central Panama and eastern Ecuador, and a mountain forest in southern Colombia. The scientists plotted every tree and mapped the distribution of soil nutrients on a total of 100 hectares (247 acres) at the sites. The study included 1,400 tree species and more than 500,000 trees.

The scientists compared distribution maps of 10 essential plant nutrients in the soils to species maps of all trees more than 1 centimeter in diameter. Each of the sites was very different, but at each the scientists found evidence that soil composition significantly influenced where certain tree species grew: The spatial distributions of 36 to 51 percent of the tree species showed strong associations with soil nutrient distributions.........

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January 12, 2007, 4:59 AM CT

Bilingualism Has Protective Effect On Dementia

Canadian scientists have found astonishing evidence that the lifelong use of two languages can help delay the onset of dementia symptoms by four years compared to people who are monolingual.

There has been much interest and growing scientific literature examining how lifestyle factors such as physical activity, education and social engagement may help build "cognitive reserve" in later years of life. Cognitive reserve refers to enhanced neural plasticity, compensatory use of alternative brain regions, and enriched brain vasculature, all of which are thought to provide a general protective function against the onset of dementia symptoms.

Now scientists with the Rotman Research Institute at the Baycrest Research Centre for Aging and the Brain have found the first evidence that another lifestyle factor, bilingualism, may help delay dementia symptoms. The study is published in the February 2007 issue of Neuropsychologia (Vol.45, No.2).

"We are pretty dazzled by the results," says principal investigator Ellen Bialystok, Ph.D., whose research team at Baycrest included psychologist Dr. Fergus Craik, a world authority on age-related changes in memory processes, and neurologist Dr. Morris Freedman, an eminent authority on understanding the mechanisms underlying cognitive impairment due to diseases such as Alzheimer's.........

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January 12, 2007, 4:52 AM CT

Travelers need to know more about diarrhea

Most people heading off to a sunny winter vacation in a foreign country know something about how to avoid a nasty case of travellers' diarrhea, but they don't know everything they should, according to a University of Alberta study.

A survey of 104 vacationers boarding flights for Mexico revealed that their general level of knowledge about the prevention of this condition was generally adequate; however, there were still some things they needed to know more about.

Of the travellers, surveyed as they boarded flights from the Calgary International Airport in March and April of 2005, more than 80 per cent knew that foods such as salad, partially cooked beef or chicken and ice cubes posed high risks for the illness. But only 47 per cent knew that chlorinated water is not always safe to drink, due to the resistance to chlorination among microorganisms such as Cryptosporidium. And while 96 per cent of the respondents knew that travellers' diarrhea could be contracted from bacteria, only 43 per cent knew that viruses could also be a cause. As well, only 55.8 per cent realized that hand-washing was an effective way to help ward off the sickness and 25 per cent of those surveyed wrongly identified fungi as sources of the diarrhea.

"The study showed that while these respondents are aware of the condition, they may not be aware of some important factors in avoiding and treating travellers' diarrhea," said Julie Johnson, lead author of the study and a PhD student in the Departments of Public Health Sciences and Agricultural, Food and Nutritional Science at the University of Alberta in Edmonton, Canada.........

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January 11, 2007, 9:22 PM CT

Spread Of Modern Humans Occurred Later

The spread of modern humans out of Africa occurred 40,000 to 50,000 years later than previously thought, as per scientists including one Texas A&M University anthropologist.

Ted Goebel, associate director of the Center for the Study of the First Americans at Texas A&M, is the author of the paper titled "The Missing Years for Modern Humans" that appears in the Jan. 12 (Friday) issue of Science.

Goebel's paper is one of three reported in the current issue of Science dealing with the origins and dispersals of modern humans during the Ice Age. A fourth paper appeared in a prior issue of the journal.

The other papers are written by human paleontologist Frederick Grine of Stony Brook University, geneticist Annamaria Olivieri from the University of Pavia in Italy, and archeologists Michael Anikovich and Andre Sinitsyn of the Russian Academy of Science and John Hoffecker of the University of Colorado.

"All of them have one thing in common," says Goebel of the papers. "They are all trying to investigate and demonstrate when it was that modern humans evolved in Africa, left Africa and colonized different areas of the Old World".

Prior theories held that modern humans spread from Africa 100,000 years ago. New data, however, suggest that their migration occurred only 50,000 to 60,000 years ago, Goebel argues. Additionally, the spread of modern humans in eastern Europe and Russia occurred earlier than previously thought notes Goebel.........

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January 11, 2007, 7:51 PM CT

Fixing The Nitrogen Balance

Scientists in the US have observed that, reassuringly, the global nitrogen cycles can be more easily balanced out than previously thought, as sources and sinks of usable nitrogen are geographically close and respond to each other in rapid feedback.

Conventional wisdom in biogeochemistry suggested that most of the nitrogen fixation in the oceans was going on in the Atlantic, where the supply of iron, mandatory by the nitrogenase enzyme, is more plentiful. However, the evidence also suggested that most of the loss of fixed nitrogen (denitrification) occurred in the Pacific. With such a vast distance between producers and consumers, the equilibrium between the two processes might have taken millennia to adjust to changes in environmental conditions, such as the current climate change.

Curtis Deutsch from the University of Washington at Seattle, together with colleagues from four other institutions across the US, has developed a new way of analysing the existing data on nitrogen cycles, based on the parameter P*, which describes the relative excess or lack of phosphate ions with respect to the predicted ratio between N and P consumption (normally 16:1).

Deutsch and his colleagues now conclude that inhabitants of the Pacific Ocean are responsible for around two thirds of the total nitrogen fixation that occurs annually in the oceans (estimated to be 140 million tons). The Atlantic contributes less than 20 per cent. Thus, the sources and sinks of usable nitrogen are geographically closer than anticipated. Furthermore, the analysis suggests that the supply of iron from the continents is not the limiting factor for nitrogenase activity. Instead, it looks as though nitrogen fixation is encouraged by a shortage of nitrate in a negative feedback loop, which stabilises the overall nitrogen balance of our planet.........

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January 11, 2007, 6:33 PM CT

Greetings From The Bottom Of The World

In May 2003, astronaut Don Pettit returned home from his five-month stay aboard the International Space Station. Living in isolated conditions in an extreme environment, he spent much of his time conducting scientific research.

Now, he's doing it again, but this time he's not leaving the planet.

Pettit is currently in Antarctica on a scientific expedition to look for meteorites. Even though he's still on Earth, the trip will have a lot in common with his ISS stay as part of the Expedition 6 crew. So in addition to the search for meteorites, Pettit will be using his background for another mission -- learning more about how Antarctica can prepare astronauts to travel to the moon and Mars.

"This is an opportunity that appeals to the heart of any explorer, whether an Earth explorer or space explorer," he said. "To be able to go off on a frontier, a place where one's normal intuition no longer applies, is the essence of exploration. When in such a place, new discoveries abound, to be found simply by opening your eyes. And to be able to participate in some meaningful way with other scientific missions and gain the experience for space exploration presents an exceptional opportunity."

"Antarctica is a great match for either lunar or Martian training analogs," he said. "Antarctica has both Mars and moon analogs, depending on where you go on the continent. If you go to the dry valleys, places in Antarctica that have no snow, you have as close to a Mars environment on Earth as you can get. If you stay on the ice sheets, you have more like a lunar setting where the geographic contrast is self-similar without the rich resources that we are use to on a planetary surface (like Earth and Mars). Where we will be going is the ice sheets, and this should be more akin to a lunar analog setting."........

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January 11, 2007, 6:27 PM CT

How to Swallow A Thermometer

From the football turf to high above the Earth, heat exhaustion can be life-threatening. Now the same type of "thermometer pill" that astronaut John Glenn swallowed as part of space shuttle medical experiments is also helping athletes to beat the heat.

Just as an engine overheats on a hot day, heat exhaustion -- or hyperthermia -- occurs when the body retains too much heat due to extreme environmental conditions or increased internal heat production. This is particularly dangerous among football players. Athletes may train when the heat index is above 100 degree F, all while wearing heavy pads that not only retain heat, but also increase their body weight.

Heat exhaustion can turn to heatstroke, causing the body's heat-regulating mechanisms to falter and fail. Ultimately this can lead to brain damage, organ damage, and eventually death. Heatstroke is the third leading cause of death among athletes in the United States.

Astronauts working in space face a similar threat. During activities such as spacewalks, astronauts may perform strenuous activity that causes a rapid rise in body temperature. A space suit is insulated against external temperature extremes because the side facing the sun can heat to 250 degree F, and the side facing deep space can plunge to -250 degree F. The danger of overheating comes from within as astronauts release body heat and humidity inside the suits, potentially causing heat illnesses.........

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January 11, 2007, 5:04 AM CT

High school physics enrollment record high

More U.S. high-school students are taking physics than ever before, and the number of physics bachelor's degree recipients in the nation has increased 31 percent since 2000, as per new data presented today by the American Institute of Physics (AIP). In addition, physics bachelor's degree recipients are eight times more likely to go on to earn any kind of PhD than those with non-physics bachelor's, the new data show. Michael Neuschatz, senior research associate at AIP's Statistical Research Center, will present these new data in a physics education symposium entitled --"Overcoming Gravity"-- at this week's joint meeting of the American Association of Physics Teachers (AAPT) and the American Astronomical Society in Seattle.

"Good physics education is the backbone of a first-class workforce in science, technology, engineering, and mathematics," said Toufiq Hakim, AAPT's Executive Director, who organized the "Overcoming Gravity" session. "The future of U.S. economic competitiveness hinges on strong science education in our country".

Presenting new data that encourage this outlook, Neuschatz will show that enrollment in high school physics classes is up and likely to continue increasing. The data show more than 30 percent of high school seniors have taken physics classes, more than ever before. This percentage has been rising steadily since the mid-1980s.........

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January 11, 2007, 4:57 AM CT

Light Echo From The Milky Way's Black Hole

Like cold case investigators, astronomers have used NASA's Chandra X-ray Observatory to uncover evidence of a powerful outburst from the giant black hole at the Milky Way's center.

A light echo was produced when X-ray light generated by gas falling into the Milky Way's supermassive black hole, known as Sagittarius A* (pronounced "A-star"), was reflected off gas clouds near the black hole. While the primary X-rays from the outburst would have reached Earth about 50 years ago, the reflected X-rays took a longer path and arrived in time to be recorded by Chandra.

"This dramatic event happened before we had satellites in space that could detect it," said Michael Muno of the California Institute of Technology in Pasadena. "So, it's remarkable that we can use Chandra to dig into the past and see this monster black hole's capacity for destruction".

Previously, scientists have used Chandra to directly detect smaller and more recent outbursts from the black hole. This latest outburst revealed by the X-ray echo was about 1,000 times brighter and lasted well over 1,000 times longer than any of the recent outbursts observed by Chandra.

Theory predicts that an outburst from Sagittarius A* would cause X-ray emission from the clouds to vary in both intensity and shape. Muno and his team found these changes for the first time, thus ruling out other interpretations. The latest results corroborate other independent, but indirect, evidence for light echoes generated by the black hole in the more distant past.........

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January 10, 2007, 10:01 PM CT

Homer's Ithaca Possibly Found

Results of geologic tests released on January 9, 2007, by British businessman Robert Bittlestone, Cambridge classicist James Diggle, and University of Edinburgh geologist John Underhill suggest further evidence to support the hypothesis that Homer's Ithaca can be found on western Kefalonia as published in the January 2007 issue of Geotimes magazine, published by the American Geological Institute (AGI).

This hypothesis, fully explained in Geotimes, suggests that the western peninsula of the modern-day Greek island Kefalonia, called Paliki, was a separate island 3,000 years ago. Landslides and rockfalls from earthquakes filled in the valley between Kefalonia and Paliki, thus disguising the ancient landscape that was described by Homer in the Odyssey.

Underhill and his colleagues have conducted extensive geological and geophysical studies on the southern end of the isthmus between Kefalonia and Paliki where the team drilled a 122-meter borehole. The team never encountered bedrock but instead bored through unconsolidated rockfall and landside material even below sea level. The absence of bedrock and presence of very young marine fossils in the reworked borehole sediments confirm that rockfalls and landslides could have filled in the ancient sea channel to create the isthmus between the once separate islands. If this hypothesis holds true, Paliki likely matches Homer's description of Ithaca.........

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