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May 10, 2011

The Sherpa phenomenon and human evolution

The "Sherpa Phenomenon": Human Evolution at Work
Scientists have long wondered why the sherpas of the Tibetan Highlands can negotiate with ease elevations that cause some humans to become life-threateningly ill. Tibetans live at altitudes of 13,000 feet, breathing air that has 40 percent less oxygen than is available at sea level, yet suffer very little mountain sickness. The reason, according to a team of biologists in China, is human evolution, in what may be the most recent and fastest instance detected so far. Comparing the genomes of Tibetans and Han Chinese, the majority ethnic group in China, the biologists found that at least 30 genes had undergone evolutionary change in the Tibetans as they adapted to life on the high plateau. Tibetans and Han Chinese split apart as recently as 3,000 years ago, say the biologists, a group at the Beijing Genomics Institute led by Xin Yi and Jian Wang, according to recent reports in Science and the New York Times. Elsewhere, researchers from the University of Utah School of Medicine and Qinghai University Medical School in the People's Republic of China found that thousands of years ago, Tibetan highlanders began to genetically adapt to prevent polycythemia (a process in which the body produces too many red blood cells in response to oxygen deprivation), as well as other health abnormalities such as swelling of the lungs and brain (edema) and hypertension of the lung vessels leading to eventual respiratory failure. Even at elevations of 14,000 feet above sea level or higher, where the atmosphere contains much less oxygen than at sea level, most Tibetans do not overproduce red blood cells and do not develop lung or brain complications. . . .

May 05, 2011

Charlie Stross on the Fukushima disaster

Two months on - Charlie's Diary
The main highlights seem to be: * The accident wasn't the result of a single disaster, but of two, and arguably three: earthquake, tsunami, and subsequent hydrogen explosions. * The plant survived the earthquake (which exceeded its design requirements) quite well, and the reactors scrammed correctly. However, scrammed reactors continue to need power to run their cooling systems. The earthquake tore down the cables connecting the plant to the rest of the grid, forcing them onto backup power. * The tsunami struck 15 minutes later, and was roughly five times higher than the plant had been designed for. A review of disaster preparedness in 2002 recommended raising "the average wave height they needed to be designed to cope with to about double the height of the biggest waves in the historical record" — 5.7 metres, for the FD plant. In the event, the tsunami that struck had 15 metre waves. It washed right over the plant and wrecked the seawater intakes, electrical switchgear, backup generators, and on-site diesel storage. * The 2002 severe accident review that increased the tsunami wave height estimates recommended installing hardened hydrogen release vents, to prevent a build-up of hydrogen in event of a similar accident. These are standard on American and other reactors, but had not been retrofitted to the FD BWRs. Were such vents fitted, the explosions would not have occurred. (The explosions compounded the difficulty of bringing the plant under control.) * Despite all this there appears to have been no public health impact due to radiation (stress and fear are another matter), and no plant workers were exposed to more than 250 millisieverts — the raised limit for emergency nuclear responders, equal to five years' regular working exposure, but insufficient to cause a serious health risk.

Powdered wood pulp is in almost every processed food

The secret ingredient is . . . sawdust! Packaged-Food Producers Increasingly Turn to Cellulose - WSJ.com
What is often in shredded cheese besides cheese? Powdered cellulose: minuscule pieces of wood pulp or other plant fibers that coat the cheese and keep it from clumping by blocking out moisture. One of an array of factory-made additives, cellulose is increasingly used by the processed-food industry, producers say. Food-product makers use it to thicken or stabilize foods, replace fat and boost fiber content, and cut the need for ingredients like oil or flour, which are getting more expensive. Cellulose products, gums and fibers allow food manufactures to offer white bread with high dietary fiber content, low-fat ice cream that still feels creamy on the tongue, and allow cooks to sprinkle cheese over their dinner without taking time to shred. . . . Organic Valley uses powdered cellulose made from wood pulp in its shredded-cheese products. The company would prefer not to use a synthetic ingredient, but cellulose is bland, white and repels moisture, making it the favored choice over products such as potato starch, says Tripp Hughes, director of product marketing for Organic Valley. Only powdered cellulose in its least manipulated form can be used in foods labeled "organic" or "made with organic" ingredients by the U.S. Department of Agriculture. . . . Although the notion of eating fine grains of wood pulp might make some consumers blanch, nutritionists say cellulose—which gives plants their structure—is a harmless fiber that can often cut calories in food. Insoluble dietary fibers like cellulose aren't digestible by humans so add bulk to food without making it more fattening. . . .