Tuesday, August 24, 2010

STONE AGE REMAINS ARE BRITAIN'S EARLIEST HOUSE

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Archaeologists working on Stone Age remains at a site in North Yorkshire say it contains Britain's earliest surviving house.

The team from the Universities of Manchester and York reveal today that the home dates to at least 8,500 BC - when Britain was part of continental Europe.

The research has been made possible by a grant from the Natural Environment Research Council, early excavation funding from the British Academy, and from English Heritage who are about to schedule the site as a National Monument . The Vale of Pickering Research Trust has also provided support for the excavation works.

The research team unearthed the 3.5 metres circular structure next to an ancient lake at Star Carr, near Scarborough, a site comparable in archaeological importance to Stonehenge.

The team are currently excavating a large wooden platform next to the lake, made of timbers which have been split and hewn. The platform is the earliest evidence of carpentry in Europe.

A large tree trunk has also been uncovered by the team. Despite being 11,000 years old it is well preserved with its bark still intact.

The house predates what was previously Britain's oldest known dwelling at Howick, Northumberland, by at least 500 years.

Dr Chantal Conneller and Barry Taylor from The University of Manchester with Dr Nicky Milner from the University of York have been working at Star Carr since 2004.

The house, which was first excavated by the team two years ago, had post holes around a central hollow which would have been filled with organic matter such as reeds, and possibly a fireplace.

Universities and Science Minister, David Willetts, said: “This exciting discovery marries world-class research with the lives of our ancestors. It brings out the similarities and differences between modern life and the ancient past in a fascinating way, and will change our perceptions for ever. I congratulate the research team and look forward to their future discoveries.”

The site was inhabited by hunter gatherers from just after the last ice age, for a period of between 200 and 500 years.

According to the team, they migrated from an area now under the North Sea, hunting animals including deer, wild boar, elk and enormous wild cattle known as auroch.

Though they did not cultivate the land, the inhabitants did burn part of the landscape to encourage animals to eat shoots and they also kept domesticated dogs.

Dr Milner said: "This is a sensational discovery and tells us so much about the people who lived at this time.

"From this excavation, we gain a vivid picture of how these people lived. For example, it looks like the house may have been rebuilt at various stages.

“It is also likely there was more than one house and lots of people lived here.

“The platform is made of hewn and split timbers; the earliest evidence of this type of carpentry in Europe. And the artefacts of antler, particularly the antler head-dresses, are intriguing as they suggest ritual activities.”

Dr Conneller said: "This changes our ideas of the lives of the first settlers to move back into Britain after the end of the last Ice Age.

"We used to think they moved around a lot and left little evidence. Now we know they built large structures and were very attached to particular places in the landscape."

Barry Taylor added: "The ancient lake is a hugely important archaeological landscape many miles across.

“To an inexperienced eye, the area looks unremarkable - just a series of little rises in the landscape.

"But using special techniques I have been able to reconstruct the landscape as it was then.

"The peaty nature of the landscape has enabled the preservation of many treasures including the paddle of a boat, the tips of arrows and red deer skull tops which were worn as masks.

"But the peat is drying out, so it's a race against time to continue the work before the archaeological finds decay."

English Heritage recently entered into a management agreement with the farmers who own the land at Star Carr to help protect the archaeological remains.

Keith Emerick, English Heritage Inspector of Ancient Monuments, explained:

“We are grateful to the landowners for entering into this far reaching agreement.

“Star Carr is internationally important, but the precious remains are very fragile.

“A new excavation currently underway will tell us more about their state of preservation and will help us decide whether a larger scale dig is necessary to recover information before it is lost for ever.”

(Photo: Alan Sorrell)

The University of Manchester

INDONESIAN ICE FIELD MAY BE GONE IN A MATTER OF YEARS, CORE MAY CONTAIN SECRETS OF PACIFIC EL NINO EVENTS

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Glaciologists who drilled through an ice cap perched precariously on the edge of a 16,000-foot-high Indonesian mountain ridge say that the ice field could vanish within in the next few years, another victim of global climate change.

The Ohio State University researchers, supported by a National Science Foundation grant and the Freeport-McMoRan mining company and collaborating with Meteorological, Climatological and Geophysical Agency (BMKG) Indonesia and Columbia University, drilled three ice cores, two to bedrock, from the peak’s rapidly shrinking ice caps.

They hope these new cores will provide a long-term record of the El Nino-Southern Oscillation (ENSO) phenomenon that dominates climate variability in the tropics.

“We were able to bring back three cores from these glaciers, one 30 meters (98.4 feet) long, one 32 meters (105 feet) long and the third 26 meters (85 feet) long,” explained Lonnie Thompson, Distinguished University Professor in the School of Earth Sciences and a senior researcher with Ohio State’s Byrd Polar Research Center.

While the cores are relatively short compared to those retrieved during some of Thompson’s previous 57 expeditions, “We won’t know what history they contain until we do the analyses.” A short 50-meter core previously drilled in 2000 through ice fields atop Mount Kilimanjaro in Africa yielded an 11,700-year history of climate.

This project is largely focused on capturing a record of ENSO. Last year, Thompson’s team drilled through an ice cap atop Hualcán, a mountain in the Peruvian Andes on the eastern side of the Pacific Ocean.

From there, they brought back a 189-meter (620-foot) and a 195-meter (640-foot) core (to bedrock) from which they are reconstructing a high-resolution climate record going back over 500 years. The Hualcán record should complement the more recent part of their 19,000-year record recovered from nearby Huascarán in 1993.

This year’s effort focused on several small and rare ice fields almost due west of the Andes on the other side of the Pacific – near a mountain called Puncak Jaya. Along with the ice core, the team collected rainwater samples from locations ranging in elevation from sea level up to the site of the glacier.

Coupled with weather data garnered from 11 weather stations operated by Freeport-McMoRan, the isotopic composition of the rainwater samples will help the team interpret the climate history locked in the ice cores.

The relative abundances of the stable isotopes of oxygen and hydrogen provide a proxy for temperature, while concentrations of different chemical species preserved in the ice reveal changes in the atmosphere such as those occurring during major volcanic eruptions.

Elevated dust content in the ice may signal increased drought while the presence of specific organic compounds may reflect increased fire activity (forest burning).

Radioactivity from atomic bomb tests in the 1950s and 1960s provide time markers that help date the cores. However, cores recently collected from Himalayan ice fields lacked these radioactive layers indicating the glaciers are now losing mass from the surface down, destroying the time markers.

The drill site itself was hazardous. “The area was riddled with crevasses and lacked any substantial snowfall,” Thompson said. This meant that the team had to wear crampons – pointed metal cleats on their boots – to maneuver on the ice. Daily rainstorms in the area, complete with lightning, increased the risks at the drill site.

The expedition was stalled almost before it began when a pallet containing the ice core drills was missing from the equipment delivered to the drill site. Inquiries with the shipping company failed to uncover the missing pieces SO Freeport-McMoRan offered their own machine shop to fabricate a new drill. While that effort got underway, Thompson, Freeport liaison Scott Hanna and researcher Dwi Susanto of Columbia University flew back to Jakarta and eventually found the lost equipment inside the shipper’s warehouse.

Near the end, the project came close to catastrophe again at the end when members of a local native tribe, after failing in their attempt to reach the ice core drilling site, broke into the freezer facility where the cores were stored, intent on destroying them. Company officials, fearing the worst, had secretly transported the ice to another facility for safekeeping a few hours earlier.

Four local tribes claim the ice fields as their own, Thompson said. “They believe that the ice is their god’s skull, that the mountains are its arms and legs and that we were drilling into the skull to steal their memories,” he said. “In their religion they are a part of nature, and by extension they are a part of the ice, so if it disappears, a part of their souls will also be lost.”

Several days later, at a public forum arranged by Freeport-McMoRan, Thompson addressed over 100 tribal members and Freeport employees to explain the importance of the project to understanding local to global climate changes. After 4.5 hours of discussion, the local people agreed to allow the ice cores to be returned to Ohio State for analysis.

Thompson said that the project could never have been done without the aid of Freeport-McMoRan which provided aircraft and helicopter support, provided cooks and food for the drill camp, and long-term storage of the ice cores and safe transport of the ice from Papua back to Jakarta.

“They provided hundreds of thousands of dollars worth of support to the project. And the result is that these cores are in the best possible condition of any core we’ve ever brought out of the field,” Thompson said.

The ice fields near Punkak Jaya are tiny. Together they total barely 1.7 square kilometers (0.6 square miles), an area very similar to the current 1.8 square kilometers (0.7 square miles) on the summit of Mount Kilimanjaro in Africa. An analysis of the first of the cores is expected by December, the researchers said.

(Photo: Thomas Nash)

Ohio State University

RESEARCHERS SUCCESSFULLY TEST NEW ALTERNATIVE TO TRADITIONAL SEMICONDUCTORS

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Researchers at Ohio State University have demonstrated the first plastic computer memory device that utilizes the spin of electrons to read and write data.

An alternative to traditional microelectronics, so-called “spintronics” could store more data in less space, process data faster, and consume less power.

In the August 2010 issue of the journal Nature Materials, Arthur J. Epstein and colleagues describe how they created a prototype plastic spintronic device using techniques found in the mainstream computer industry today.

At this point, the device is little more than a thin strip of dark blue organic-based magnet layered with a metallic ferromagnet and connected to two electrical leads. (A ferromagnet is a magnet made of ferrous metal such as iron. Common household refrigerator magnets are ferromagnets.) Still, the researchers successfully recorded data on it and retrieved the data by controlling the spins of the electrons with a magnetic field.

Epstein, Distinguished University Professor of physics and chemistry and director of the Institute for Magnetic and Electronic Polymers at Ohio State, described the material as a hybrid of a semiconductor that is made from organic materials and a special magnetic polymer semiconductor. As such, it is a bridge between today’s computers and the all-polymer, spintronic computers that he and his partners hope to enable in the future.

Normal electronics encode computer data based on a binary code of ones and zeros, depending on whether an electron is present in a void within the material. But researchers have long known that electrons can be polarized to orient in particular directions, like a bar magnet. They refer to this orientation as spin -- either “spin up” or “spin down” -- and have been working on a way to store data using spin. The resulting electronics, dubbed spintronics, would effectively let computers store and transfer twice as much data per electron.

But higher data density is only part of the story.

“Spintronics is often just seen as a way to get more information out of an electron, but really it’s about moving to the next generation of electronics,” Epstein said. “We could solve many of the problems facing computers today by using spintronics.”

Typical circuit boards use a lot of energy. Moving electrons through them creates heat, and it takes a lot of energy to cool them. Chip makers are limited in how closely they can pack circuits together to avoid overheating.

Flipping the spin of an electron requires less energy, and produces hardly any heat at all, he explained. That means that spintronic devices could run on smaller batteries. If they were made out of plastic, they would also be light and flexible.

“We would love to take portable electronics to a spin platform,” Epstein said. “Think about soldiers in the field who have to carry heavy battery packs, or even civilian ‘road warriors’ commuting to meetings. If we had a lighter weight spintronic device which operates itself at a lower energy cost, and if we could make it on a flexible polymer display, soldiers and other users could just roll it up and carry it. We see this portable technology as a powerful platform for helping people.”

The magnetic polymer semiconductor in this study, vanadium tetracyanoethanide, is the first organic-based magnet that operates above room temperature. It was developed by Epstein and his long-standing collaborator Joel S. Miller of the University of Utah.
Postdoctoral researcher Jung-Woo Yoo called the new material an important milestone in spintronic research.

“Our main achievement is that we applied this polymer-based magnet semiconductor as a spin polarizer -- meaning we could save data (spin up and down) on it using a tiny magnetic field -- and a spin detector -- meaning we could read the data back,” he said. “Now we are closer to constructing a device from all-organic material.”

In the prototype device, electrons pass into the polymer, and a magnetic field orients them as spin up or spin down. The electrons can then pass into the conventional magnetic layer, but only if the spin of electrons there are oriented in the same way. If they are not, the resistance is too high for the electrons to pass. So the researchers were able to read spin data from their device based on whether the resistance was high or low.

Collaborators at the University of Wisconsin-Madison prepared a sample of conventional magnetic film, and Yoo and his Ohio State colleagues layered it together with the organic magnet to make a working device.

As a test, the researchers exposed the material to a magnetic field that varied in strength over time. To determine whether the material recorded the magnetic pattern and functioned as a good spin injector/detector, they measured the electric current passing through the two magnetic layers. This method is similar to the way computers read and write data to a magnetic hard drive today.

The results, Yoo said, were “textbook” -- they retrieved the magnetic data in its entirety, exactly as they stored it.

The patented technology should transfer easily to industry, he added.
“Any place that makes computer chips could do this. Plus, in this case, we made the device at room temperature, and the process is very eco-friendly.”

(Photo: OSU)

Ohio State University

COUCH POTATOES OF THE ANIMAL KINGDOM

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In a study involving the first-ever daily energy expenditure measurements in apes, a researcher from Washington University in St. Louis and his team have determined that orangutans living in a large indoor/outdoor habitat used less energy, relative to body mass, than nearly any eutherian mammal ever measured, including sedentary humans.

All this despite activity levels similar to orangutans in the wild.

“It’s like finding a sloth in your family tree,” says Herman Pontzer, PhD, assistant professor of anthropology in Arts & Sciences and lead author of the study. “It’s remarkably low energy use.”

The research will be published online the week of Aug. 2 in the early edition of the Proceedings of the National Academy of Sciences.

Pontzer and his team spent two weeks studying daily energy expenditure of orangutans in the Great Ape Trust, a 230-acre campus in Des Moines, Iowa.

The study revealed an extremely low rate of energy use not previously observed in primates, but consistent with slow growth and low rate of reproduction in orangutans.

Pontzer suggests this may be an evolutionary response to severe food shortages in the orangutan’s native Southeast Asian rainforests. The rainforests of Borneo and Sumatra are highly random environments that often experience crashes in the availability of ripe fruit, the food on which orangutans depend.

The study suggests that orangutans have adapted over time by becoming consummate low-energy specialists, decreasing their daily energy needs to avoid starvation in food-poor times.

Pontzer thinks this research also may shed light on the evolved energy use of other primates, as well as human foragers. He plans to expand the study.

(Photo: Wikipedia Commons)

Washington University in St. Louis

AN ANCIENT EARTH LIKE OURS

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An international team of scientists including Mark Williams and Jan Zalasiewicz of the Geology Department of the University of Leicester, and led by Dr. Thijs Vandenbroucke, formerly of Leicester and now at the University of Lille 1 (France), has reconstructed the Earth’s climate belts of the late Ordovician Period, between 460 and 445 million years ago.

The findings have been published online in the Proceedings of the National Academy of Sciences of the USA – and show that these ancient climate belts were surprisingly like those of the present.

The researchers state: “The world of the ancient past had been thought by scientists to differ from ours in many respects, including having carbon dioxide levels much higher – over twenty times as high – than those of the present. However, it is very hard to deduce carbon dioxide levels with any accuracy from such ancient rocks, and it was known that there was a paradox, for the late Ordovician was known to include a brief, intense glaciation – something difficult to envisage in a world with high levels of greenhouse gases. “

The team of scientists looked at the global distribution of common, but mysterious fossils called chitinozoans – probably the egg-cases of extinct planktonic animals – before and during this Ordovician glaciation. They found a pattern that revealed the position of ancient climate belts, including such features as the polar front, which separates cold polar waters from more temperate ones at lower latitudes. The position of these climate belts changed as the Earth entered the Ordovician glaciation – but in a pattern very similar to that which happened in oceans much more recently, as they adjusted to the glacial and interglacial phases of our current (and ongoing) Ice Age.

This ‘modern-looking’ pattern suggests that those ancient carbon dioxide levels could not have been as high as previously thought, but were more modest, at about five times current levels (they would have had to be somewhat higher than today’s, because the sun in those far-off times shone less brightly).

“These ancient, but modern-looking oceans emphasise the stability of Earth’s atmosphere and climate through deep time – and show the current man-made rise in greenhouse gas levels to be an even more striking phenomenon than was thought,” the researchers conclude.

(Photo: University Leicester)

University of Leicester

GONDWANA SUPERCONTINENT UNDERWENT MASSIVE SHIFT DURING CAMBRIAN EXPLOSION

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The Gondwana supercontinent underwent a 60-degree rotation across Earth’s surface during the Early Cambrian period, according to new evidence uncovered by a team of Yale University geologists.

Gondwana made up the southern half of Pangaea, the giant supercontinent that constituted the Earth’s landmass before it broke up into the separate continents we see today. The study, which appears in the August issue of the journal Geology, has implications for the environmental conditions that existed at a crucial period in Earth’s evolutionary history called the Cambrian explosion, when most of the major groups of complex animals rapidly appeared.

The team studied the paleomagnetic record of the Amadeus Basin in central Australia, which was part of the Gondwana precursor supercontinent. Based on the directions of the ancient rock’s magnetization, they discovered that the entire Gondwana landmass underwent a rapid 60-degree rotational shift, with some regions attaining a speed of at least 16 (+12/-8) cm/year, about 525 million years ago. By comparison, the fastest shifts we see today are at speeds of about four cm/year.

This was the first large-scale rotation that Gondwana underwent after forming, said Ross Mitchell, a Yale graduate student and author of the study. The shift could either be the result of plate tectonics (the individual motion of continental plates with respect to one another) or “true polar wander,” in which the Earth’s solid land mass (down to the liquid outer core almost 3,000 km deep) rotates together with respect to the planet’s rotational axis, changing the location of the geographic poles, Mitchell said.

The debate about the role of true polar wander versus plate tectonics in defining the motions of Earth’s continents has been going on in the scientific community for decades, as more and more evidence is gathered, Mitchell said.

In this case, Mitchell and his team suggest that the rates of Gondwana’s motion exceed those of “normal” plate tectonics as derived from the record of the past few hundred million years. “If true polar wander caused the shift, that makes sense. If the shift was due to plate tectonics, we’d have to come up with some pretty novel explanations.”

Whatever the cause, the massive shift had some major consequences. As a result of the rotation, the area that is now Brazil would have rapidly moved from close to the southern pole toward the tropics. Such large movements of landmass would have affected environmental factors such as carbon concentrations and ocean levels, Mitchell said.

“There were dramatic environmental changes taking place during the Early Cambrian, right at the same time as Gondwana was undergoing this massive shift,” he said. “Apart from our understanding of plate tectonics and true polar wander, this could have had huge implications for the Cambrian explosion of animal life at that time.”

(Photo: Ross Mitchell/Yale University)

Yale University

CHARCOAL TAKES SOME HEAT OFF GLOBAL WARMING

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As much as 12 percent of the world's human-caused greenhouse gas emissions could be sustainably offset by producing biochar, a charcoal-like substance made from plants and other organic materials. That's more than what could be offset if the same plants and materials were burned to generate energy, concludes a study published in the journal Nature Communications.

"These calculations show that biochar can play a significant role in the solution for the planet's climate change challenge," said study co-author Jim Amonette, a soil chemist at the Department of Energy's Pacific Northwest National Laboratory. "Biochar offers one of the few ways we can create power while decreasing carbon dioxide levels in the atmosphere. And it improves food production in the world's poorest regions by increasing soil fertility. It's an amazing tool."

The study is the most thorough and comprehensive analysis to date on the global potential of biochar. The carbon-packed substance was first suggested as a way to counteract climate change in 1993. Scientists and policymakers have given it increasing attention in the past few years. The study was conducted by Dominic Woolf and Alayne Street-Perrott of Swansea University in Wales, U.K., Johannes Lehmann of Cornell University in Ithaca, N.Y., Stephen Joseph of the University of New South Wales, Australia, and Amonette.

Biochar is made by decomposing biomass like plants, wood and other organic materials at high temperature in a process called slow pyrolysis. Normally, biomass breaks down and releases its carbon into the atmosphere within a decade or two. But biochar is more stable and can hold onto its carbon for hundreds or even thousands of years, keeping greenhouse gases like carbon dioxide out of the air longer. Other biochar benefits include: improving soils by increasing their ability to retain water and nutrients; decreasing nitrous oxide and methane emissions from the soil into which it is tilled; and, during the slow pyrolysis process, producing some bio-based gas and oil that can offset emissions from fossil fuels.

Making biochar sustainably requires heating mostly residual biomass with modern technologies that recover energy created during biochar's production and eliminate the emissions of methane and nitrous oxide, the study also noted.

For their study, the researchers looked to the world's sources of biomass that aren't already being used by humans as food. For example, they considered the world's supply of corn leaves and stalks, rice husks, livestock manure and yard trimmings, to name a few. The researchers then calculated the carbon content of that biomass and how much of each source could realistically be used for biochar production.

With this information, they developed a mathematical model that could account for three possible scenarios. In one, the maximum possible amount of biochar was made by using all sustainably available biomass. Another scenario involved a minimal amount of biomass being converted into biochar, while the third offered a middle course. The maximum scenario required significant changes to the way the entire planet manages biomass, while the minimal scenario limited biochar production to using biomass residues and wastes that are readily available with few changes to current practices.

Amonette and his colleagues found that the maximum scenario could offset up to the equivalent of 1.8 petagrams — or 1.8 billion metric tons — of carbon emissions annually and a total of 130 billion metric tons throughout in the first 100 years. Avoided emissions include the greenhouse gases carbon dioxide, methane and nitrous oxide. The estimated annual maximum offset is 12 percent of the 15.4 billion metric tons of greenhouse gas emissions that human activity adds to the atmosphere each year. Researchers also calculated that the minimal scenario could sequester just under 1 billion metric tons annually and 65 billion metric tons during the same period.

But to achieve any of these offsets is no small task, Amonette noted.

"This can't be accomplished with half-hearted measures," Amonette said. "Using biochar to reduce greenhouse gas emissions at these levels is an ambitious project that requires significant commitments from the general public and government. We will need to change the way we value the carbon in biomass."

Experiencing the full benefits of biochar will take time. The researchers' model shows it will take several decades to ramp up biochar production to its maximum possible level. Greenhouse gas offsets would continue past the century mark, but Amonette and colleagues just calculated for the first 100 years.

Instead of making biochar, biomass can also be burned to produce bioenergy from heat. Researchers found that burning the same amount of biomass used in their maximum biochar scenario would offset 107 billion metric tons of carbon emissions during the first century. The bioenergy offset, while substantial, was 23 billion metric tons less than the offset from biochar. Researchers attributed this difference to a positive feedback from the addition of biochar to soils. By improving soil conditions, biochar increases plant growth and therefore creates more biomass for biochar productions. Adding biochar to soils can also decrease nitrous oxide and methane emissions that are naturally released from soil.

However, Amonette and his co-authors wrote that a flexible approach including the production of biochar in some areas and bioenergy in others would create optimal greenhouse gas offsets. Their study showed that biochar would be most beneficial if it were tilled into the planet's poorest soils, such as those in the tropics and the Southeastern United States.

Those soils, which have lost their ability to hold onto nutrients during thousands of years of weathering, would become more fertile with the extra water and nutrients the biochar would help retain. Richer soils would increase the crop and biomass growth — and future biochar sources — in those areas. Adding biochar to the most infertile cropland would offset greenhouse gases by 60 percent more than if bioenergy were made using the same amount of biomass from that location, the researchers found.

On the other hand, the authors wrote that bioenergy production could be better suited for areas that already have rich soils — such as the Midwest — and that also rely on coal for energy. Their analysis showed that bioenergy production on fertile soils would offset the greenhouse gas emissions of coal-fired power plants by 16 to 22 percent more than biochar in the same situation.

The study also shows how sustainable practices can make the biochar that creates these offsets.

"The scientific community has been split on biochar," Amonette acknowledged. "Some think it'll ruin biodiversity and require large biomass plantations. But our research shows that won't be the case if the right approach is taken."

The authors' estimates of avoided emissions were developed by assuming no agricultural or previously unmanaged lands will be converted for biomass crop production. Other sustainability criteria included leaving enough biomass residue on the soil to prevent erosion, not using crop residues currently eaten by livestock, not adding biochar made from treated building materials to agricultural soils and requiring that only modern pyrolysis technologies — those that fully recover energy released during the process and eliminate soot, methane and nitrous oxide emissions — be used for biochar production.

"Roughly half of biochar's climate-mitigation potential is due to its carbon storage abilities," Amonette said. "The rest depends on the efficient recovery of the energy created during pyrolysis and the positive feedback achieved when biochar is added to soil. All of these are needed for biochar to reach its full sustainable potential."

(Photo: USDA-ARS, Prosser, Wash)

Pacific Northwest National Laboratory

ASPIRIN: YES, NO, MAYBE?

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You’ve probably seen low-dose aspirin in the drugstore, in packages with a red heart on them, as well as ads promoting aspirin for its heart benefits. You may even be taking "baby" aspirin, following your doctor’s advice—or on your own, "just to be safe." So you may be surprised to learn that there’s still controversy about low-dose aspirin as a preventive for heart disease.

The evidence is indeed solid concerning aspirin therapy for secondary prevention—that is, for preventing recurrences in people who’ve already had a heart attack, angina, or ischemic stroke (the most common type of stroke, caused by a blood clot). That’s the only explicit heart-health claim the FDA allows aspirin companies to make. However, for healthy people without symptoms or a history of cardiovascular disease (CVD)—that is, for primary prevention—the benefit is far from clear, and recent research has made it more uncertain.

Aspirin helps prevent heart attacks and ischemic strokes by decreasing the tendency of blood to clot. On average, all it takes is about 81 milligrams (one-quarter of a standard 325-milligram tablet) a day to accomplish this, though some experts advise 162 milligrams a day or 162 to 325 milligrams every other day.

Unfortunately, even at low doses, aspirin can cause stomach or intestinal bleeding and ulcers. It also increases the risk of hemorrhagic ("bleeding") stroke slightly, at least in men. If aspirin were developed today, there’s little chance it would be approved for over-the-counter sale because of these risks. (In fact, all pain relievers have serious risks, which we’ll discuss in an upcoming issue.) Stomach bleeding may not sound that scary, at least compared to a heart attack, but it can lead to potentially deadly complications, especially among older people and heavy drinkers.

So the trick is to figure out for whom the potential CVD benefits of aspirin therapy outweigh the risks. Experts disagree about which "high-risk" people are good candidates. And some believe that no one should be taking aspirin for primary prevention.

In 2009 the U.S. Preventive Services Task Force, a government-appointed panel of experts that evaluates medical research, expanded its recommendations about aspirin for primary prevention. It gave different advice for men and women, since CVD affects them differently, and thus aspirin has different potential benefits in them. Notably, men have a higher risk of heart attack at younger ages; women have a higher lifetime risk of stroke.

The Task Force concluded that doctors should encourage low-dose aspirin in men age 45 to 79 to help prevent heart attacks, and in women age 55 to 79 to help prevent ischemic strokes—but only when the potential benefit outweighs the risk of gastrointestinal bleeding. To weigh your risks and benefits, it advised consulting your doctor, as well as using an online CVD risk assessment tool. Because of insufficient evidence, the Task Force gave no advice for people 80 or older, for whom the potential benefits and risks are greater.

The American Heart Association gives no specifics—it merely recommends aspirin therapy for primary prevention in people at high CVD risk. That means, again, talking to your doctor.

The Task Force based its guidelines for primary prevention on nine studies, including the well-known Women’s Health Study, which helped identify aspirin’s anti-stroke effect in women. Other researchers, however, have looked at some or all of these studies and concluded that the data do not support the use of aspirin in healthy people, even those at higher risk—either because the overall results were not significant, or because the very modest benefit was offset by adverse effects. The doubters include experts at the FDA, who a few years ago decided not to allow the labeling of aspirin for primary prevention of CVD. Both sides make good arguments, which hinge largely on methodological issues of the studies.

Adding to the doubts about aspirin therapy for primary prevention are several recent studies that focused on people with diabetes, published too late to be included in the Task Force’s review. People with diabetes are at least twice as likely to have a heart attack or stroke, so they are obvious "high-risk" candidates for aspirin therapy. That’s why the American Diabetes Association and American Heart Association have for years advised aspirin for primary prevention in most people with diabetes. But the new studies raised questions about this advice. This June, in a revised position statement, the two associations concluded that results have been inconsistent and overall suggest only a modest benefit for people with diabetes, which may be outweighed by the risk of bleeding. Thus they now recommend aspirin primarily for men over 50 and women over 60 with diabetes, if they have at least one other CVD risk factor and are not at high risk for bleeding.

If you do not have diabetes, you may wonder what this has to do with you. But if there are uncertainties about aspirin’s benefit for these people at high risk, that raises questions about primary prevention for everyone.

If you already take low-dose aspirin, make sure your doctor knows, and review this decision periodically. Do not start taking aspirin on your own. A few years ago a survey in the American Journal of Preventive Medicine found that 30% of people over 40 who are at low CVD risk were taking low-dose aspirin, which makes no sense. And 31% of people with a history of CVD, most of whom should be taking aspirin, were not taking it.

It’s a familiar refrain: talk to your doctor about your risk factors for heart disease and stroke. That survey also found that 28% of people who are at high risk for CVD thought they were at low risk, while 44% at low risk thought they were at high risk. It may help to fill out one of the risk assessments with your doctor. If that suggests you’re a good candidate, and you’re not at elevated risk for bleeding, you might consider aspirin therapy.

Wellness Letter

LAND ON YOUR TOES, SAVE YOUR KNEES

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Anterior cruciate ligament injuries are a common and debilitating problem, especially for female athletes. A new study from UC Davis shows that changes in training can reduce shear forces on knee joints and could help cut the risk of developing ACL tears. The research was published online Aug. 3 in the Journal of Biomechanics.

"We focused on an easy intervention, and we were amazed that we could reduce shear load in 100 percent of the volunteers," said David Hawkins, professor of neurobiology, physiology and behavior at UC Davis. Hawkins conducted the study at the UC Davis Human Performance Laboratory with graduate student Casey Myers.

The anterior cruciate ligament lies in the middle of the knee and provides stability to the joint. Most ACL injuries do not involve a collision between players or a noticeably bad landing, said Sandy Simpson, UC Davis women's basketball coach.

"It almost always happens coming down from a rebound, catching a pass or on a jump-stop lay-up," Simpson said. "It doesn't have to be a big jump."

Hawkins and Myers worked with 14 female basketball players from UC Davis and local high schools. They fitted them with instruments and used digital cameras to measure their movements and muscle activity, and calculated the forces acting on their knee joints as they practiced a jump-stop movement, similar to a basketball drill.

First, they recorded the athletes making their normal movement. Then they instructed them in a modified technique: Jumping higher to land more steeply; landing on their toes; and bending their knees more deeply before taking off again.

After learning the new technique, all 14 volunteers were able to reduce the force passed up to the knee joint through the leg bone (the tibial shear force) by an average of 56 percent. At the same time, the athletes in the study actually jumped an inch higher than before, without losing speed.

Hawkins recommends warm-ups that exercise the knee and focusing on landing on the toes and balls of the feet. The study does not definitively prove that these techniques will reduce ACL injuries, Hawkins said: that would require a full clinical trial and follow-up. But the anecdotal evidence suggests that high tibial shear forces are associated with blown knees.

Hawkins and Myers shared their findings with Simpson and other UC Davis women’s basketball and soccer coaches, as well as with local youth soccer coaches.

Simpson said that the team had tried implementing some changes during last year's preseason, but had found it difficult to continue the focus once the full regular season began. In live play, athletes quickly slip back to learned habits and "muscle memory" takes over, he noted. More intensive off-court training and practice would be needed to change those habits, he said.

"We will be talking about this again this season," Simpson said. Implementing the techniques in youth leagues, while children are still learning how to move, might have the most impact, he said.

(Photo: Wayne Tilcock/Davis Enterprise)

UC Davis

SCIENTISTS SHOW THERE’S NOTHING BORING ABOUT WATCHING PAINT DRY

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It turns out that watching paint dry might not be as boring as the old adage claims. A team led by Yale University researchers has come up with a new technique to study the mechanics of coatings as they dry and peel, and has discovered that the process is far from mundane.

In the August 9-13 edition of the Proceedings of the National Academy of Sciences, the team presents a new way to image and analyze the mechanical stress that causes colloidal coatings—those in which microscopic particles of one substance are dispersed throughout another—to peel off of surfaces.

Understanding how and why coatings fail has broad applications in the physical and biological sciences, said Eric Dufresne, the John J. Lee Associate Professor of Mechanical Engineering at Yale and lead author of the study.

“Coatings protect almost every surface you encounter, from paint on a wall to Teflon on a frying pan to the skin on our own bodies. When coatings peel and crack they put the underlying material at risk,” Dufresne said. “Our research is aimed at pinpointing the failure of coatings. We’ve developed this new technique to zoom in on coatings and watch them fail at the microscopic level.”

To visualize the microscopic motion of paint in 3D, the team mixed in tiny fluorescent particles that glow when illuminated by a laser. By tracing the motion of these particles over time with a microscope, they captured the motion of the paint as it peeled and dried in detail.

In addition, the team was able to track the 3-D forces generated by the paint as it dried, producing a “stress map” of the mechanical deformation of the coating as it failed. “The trick was to apply the paint to a soft surface, made of silicone rubber, that is ever so slightly deformed by the gentle forces exerted by the drying paint,” Dufresne said.

Although the current study focuses on colloidal coatings, the technique could be applied to all kinds of coatings, Dufresne said. Next, the team hopes to improve on current methods for mitigating peeling in a wide range of coatings.

“This is a completely new way of looking at a very old problem.”

(Photo: Wendolyn Hill/Ye Xu/Eric Dufresne)

Yale University

STEREOTYPING HAS A LASTING NEGATIVE IMPACT

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Aggression. Over-eating. Inability to focus. Difficulty making rational decisions. New research out of the University of Toronto Scarborough shows prejudice has a lasting negative impact on those who experience it.

"Past studies have shown that people perform poorly in situations where they feel they are being stereotyped," says Associate Professor of Psychology Michael Inzlicht, who led the study, published in this month's edition of the Journal of Personality and Social Psychology. "What we wanted to do was look at what happens afterwards. Are there lingering effects of prejudice? Does being stereotyped have an impact beyond the moment when stereotyping happens?"

In order to determine whether negative stereotyping in a particular situation had lasting effects, Inzlicht's team performed a series of tests. First, they placed participants in situations where they had to perform a task in the face of negative stereotyping. After the participants were removed from the prejudicial situation, researchers measured their ability to control their aggression, eat appropriate amounts, make rational decisions, and stay focused.

Their results show that prejudice and stereotyping have lingering adverse impacts.

"Even after a person leaves a situation where they faced negative stereotypes, the effects of coping with that situation remain," says Inzlicht. "People are more likely to be aggressive after they've faced prejudice in a given situation. They are more likely to exhibit a lack of self control. They have trouble making good, rational decisions. And they are more likely to over-indulge on unhealthy foods."

In one portion of the study, researchers had a group of women write a math test. They told the women this test would determine whether or not they were capable and smart in math, subtly injecting stereotypes about women and math skills "into the air," says Inzlicht. A separate group of women wrote the same test, except this group was given support and coping strategies to deal with the stress they'd face when writing the test.

After completing the math test, the two groups performed another series of tasks designed to gauge their aggression levels, their ability to focus and to exercise self control.

"In these follow-up tests, the women who felt discriminated against ate more than their peers in the control group. They showed more hostility than the control group. And they performed more poorly on tests that measured their cognitive skills," says Inzlicht.

The pattern remained the same, regardless of the test groups. People who felt they were discriminated against – whether based on gender, age, race or religion – all experienced significant impacts even after they were removed from the situation, says Inzlicht.

"These lingering effects hurt people in a very real way, leaving them at a disadvantage," says Inzlicht. "Even many steps removed from a prejudicial situation, people are carrying around this baggage that negatively impacts their lives."

University of Toronto

HOTTER NIGHTS THREATEN FOOD SECURITY -- RICE AT RISK

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Production of rice—the world's most important crop for ensuring food security and addressing poverty—will be thwarted as temperatures increase in rice-growing areas with continued climate change, according to a new study by an international team of scientists.

The research team found evidence that the net impact of projected temperature increases will be to slow the growth of rice production in Asia. Rising temperatures during the past 25 years have already cut the yield growth rate by 10% in several locations.

As nights get hotter, as predicted with climate change, rice yields will drop.

Published in the Proceedings of the National Academy of Sciences (PNAS)—a peer-reviewed, scientific journal from the United States—the report analyzed 6 years of data from 227 irrigated rice farms in 6 major rice-growing countries in Asia, which produces more than 90% of the world's rice.

"We found that as the daily minimum temperature increases, or as nights get hotter, rice yields drop," said Mr. Jarrod Welch, lead author of the report and graduate student of economics at the University of California, San Diego.

This is the first study to assess the impact of both daily maximum and minimum temperatures on irrigated rice production in farmer-managed rice fields in tropical and subtropical regions of Asia.

"Our study is unique because it uses data collected in farmers' fields, under real-world conditions," said Mr. Welch. "This is an important addition to what we already know from controlled experiments."

"Farmers can be expected to adapt to changing conditions, so real-world circumstances, and therefore outcomes, might differ from those in controlled experimental settings," he added.

Around three billion people eat rice every day, and more than 60% of the world's one billion poorest and undernourished people who live in Asia depend on rice as their staple food. A decline in rice production will mean more people will slip into poverty and hunger, the researchers said.

"Up to a point, higher day-time temperatures can increase rice yield, but future yield losses caused by higher night-time temperatures will likely outweigh any such gains because temperatures are rising faster at night," said Mr. Welch. "And if day-time temperatures get too high, they too start to restrict rice yields, causing an additional loss in production."

If day-time temperatures get too high, they will also restrict rice yields.

"If we cannot change our rice production methods or develop new rice strains that can withstand higher temperatures, there will be a loss in rice production over the next few decades as days and nights get hotter. This will get increasingly worse as temperatures rise further towards the middle of the century," he added.

International Rice Research Institute

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