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WASHINGTON, June 6 (Xinhua) -- A new University of Missouri study shows that the exposure to the controversial chemical Bisphenol A (BPA) through diet has been underestimated by previous lab tests.The findings were published on Monday in Environmental Health Perspectives.In the study, researchers compared BPA concentrations in mice that were given a steady diet supplemented with BPA throughout the day, compared to the more common lab method of single exposure, and found an increased absorption and accumulation of BPA in the blood of the mice.The authors continuously exposed the mice to BPA through their feed, which is considered the primary route of exposure to this chemical in animals and humans. In previous studies examining the effects of BPA, mice were exposed to BPA only through a one-time administration.Following the exposure through the diet, a significantly greater increase in the active form of BPA, which is the greatest threat as it is the form that can bind to sex steroid receptors and exert adverse effects, was absorbed and accumulated in the animals."People are primarily and unknowingly exposed to BPA through the diet because of the various plastic and paper containers used to store our food are formulated with BPA," said Cheryl Rosenfeld, associate professor in biomedical sciences and corresponding lead author. "We know that the active form of BPA binds to our steroid receptors, meaning it can affect estrogen, thyroid and testosterone function. It might also cause genetic mutations. Thus, this chemical can hinder our ability to reproduce and possibly cause behavioral abnormalities that we are just beginning to understand."The study notes that more than eight billion pounds of BPA are produced every year, and more than 90 percent of people in the United States have measurable amounts of BPA in their bodies."When BPA is taken through the food, the active form may remain in the body for a longer period of time than when it is provided through a single treatment, which does not reflect the continuous exposure that occurs in animal and human populations," said Rosenfeld. "We need to study this further to determine where the ingested BPA becomes concentrated and subsequently released back into the bloodstream to be distributed throughout the body."

SAN FRANCISCO, July 15 (Xinhua) -- U.S. microblogging platform Twitter on Friday marked its fifth anniversary since public debut."Twitter, then called Twttr, opened to the public five years ago today," the company said in a Tweet, a short message within 140 characters users are allowed to communicate on the website."Twttr is a new mobile service that helps groups of friends bounce random thoughts around with SMS," co-founder Biz Stone described the service in a blog post on July 13, 2006, two days before its public debut."There were 224 Tweets sent on July 15, 2006. Today, users send that many Tweets in less than a tenth of a second," said the San Francisco-based company.Twitter said more than 600,000 new users signed up on Thursday while it took it more than 16 months to reach the first 600,000 Twitter accounts.The tipping point for the service's popularity was the 2007 South by Southwest festival, a set of film, interactive and music festivals and conferences that take place every March in Austin, Texas. During the event, the Tweets sent per day grew from 20,000 to 60,000.With an estimated user base of 200 million worldwide, some 200 million Tweets are generated and 1.6 billion search queries are handled every day, the company said.According to research firm EMarketer, advertising sales on Twitter is expected to reach 150 million U.S. dollars this year. SharesPost, a secondary market for privately held companies, has assessed Twitter's current worth at 6.8 billion dollars.

CANBERRA, Aug. 17 (Xinhua) -- Australian scientist on Wednesday said his international research team has discovered the trick on how butterfly learn to change its wing pattern to avoid being eaten by birds.The Amazonian butterfly, Heliconius numata, has learnt to carry out a single genetic switch to alter its wing pattern so it appears to be another bad-tasting butterfly that birds will avoid.Dr. Siu Fai (Ronald) Lee from the Department of Genetics and Bio21 Institute at Australia's University of Melbourne was part of the international research team, which was led by scientists at Centre National de la Recherche Scientifique (CNRS) and the University of Exeter in United Kingdom.Dr. Lee said the historical mystery had puzzled researchers for decades."Charles Darwin was puzzled by how butterflies evolved such similar patterns of warning coloration," Dr. Siu Fai (Ronald) Lee from the Department of Genetics and Bio21 Institute at the University of Melbourne told Western Australia Today."We have now solved this mystery, identifying the region of chromosome responsible for changing wing pattern."He said the research team identified a genetic switch known as a supergene, which allowed the butterfly to morph into several different forms, allowing one species to mimic another."It is amazing that by changing just one small region of the chromosomes, the butterfly is able to fool its predators by mimicking a range of different butterflies that taste bad," he said."The butterflies rearrange this supergene DNA like a small pack of cards, and the result is new wing patterns. It means that butterflies look completely different but have the same DNA."There are other butterflies doing similar tricks, but this is the most elegant one."I was just fascinated by how elegant they were."He said the discovery proves that small chromosomal changes can preserve successful gene combinations, and thus help a species to adapt.The findings of the study are published on August 14 in the international journal Nature.

WELLINGTON, June 10 (Xinhua) -- Scientists have uncovered an almost complete picture of the remains of a geological formation that was one of the great wonders of the 19th Century world before it was covered in ash and water during a volcanic eruption.Scientists from New Zealand and the United States said Friday they had discovered the White Terraces, half of the famous Pink and White Terraces in the central North Island's Lake Rotomahana.The same group of scientists found the remnants of the pink half of the former world-famous tourist attraction on the lake floor in January.The Pink and White Terraces were buried by the eruption of Mount Tarawera 125 years ago on 10 June 1886. The two sets of cascading silica terraces were separated by several hundred metres.The two formerly glistening terraces were formed on the shores of the lake, where the silica rich waters were warmed by the magma beneath.In the late 19th Century, the cascading terraces attracted people from all over the world. The White Terraces were the larger and stretched to a height of 30 meters, forming a 240-meter face. Visitors could walk up to a crater platform where they could bathe in the clear blue waters in naturally-formed basins up to three meters deep.Project Leader Cornel de Ronde, of New Zealand's GNS Science geosciences research institute, said the sonar images from Lake Rotomahana showed the lake floor was covered overwhelmingly by soft sediment and mud.The side-scan sonar data of the lake floor was collected on the last day of the 10-day project at Lake Rotomahana during the southern summer, but was analyzed using new software, which became available after the data collection had finished.The scientists found the sonar data contained images of hard, crescent-shaped structures on the lake bed in a similar location to where the White Terraces were before the eruption of 1886.The structures were about 60 meters below the surface, a similar depth to the Pink Terraces found in January. The lake is about 122 meters deep at its deepest point."The two places on the lake floor where we encountered hard, up- standing crescent-shaped features correspond to the locations of the Pink and White Terraces before the Tarawera eruption," de Ronde said."The sonar image that appears to show part of the White Terraces came to light after the project had finished. It shows a horizontal segment of terraces over 100 meters long, although we don't know which part of the terraces it is."The rounded terrace edges are standing up from the lake floor by about a meter in some places. The sonar images of both sets of terraces are strikingly similar."Scientists managed to capture several color photographs of part of the Pink Terraces in January, but they did not lower an underwater camera over the White Terraces location during the project as they were unaware of what the sonar data was showing at the time.The fate of the remaining sections of the Pink and White Terraces was unclear, said a statement from GNS. "They might have been destroyed in the eruption. Alternatively, they could be lying under thick sediment, which is impenetrable to sonar signals sent out by the two autonomous underwater vehicles (AUVs) used in the survey."De Ronde said finding remnants of both sets of terraces was a remarkable outcome for the project."The project team was absolutely thrilled in January when we realised our AUVs had detected remnants of the Pink Terraces. Finding part of what we believe is the White Terraces as well has been surprising and very satisfying."The original aim of the project at Lake Rotomahana was to map the lake floor and investigate the extensive geothermal system under the lake and how it evolved from an on-land geothermal system to a submerged one. Anything else was a bonus," de Ronde said."It's gratifying to be part of a science project that can answer a century-old mystery about the fate of the Pink and White Terraces."De Ronde said the announcement of the find was timed to coincide with the 125th anniversary of Tarawera's eruption.The 10-day project was a collaboration involving GNS Science, Woods Hole Oceanographic Institution in Massachusetts, Lamont- Doherty Earth Observatory at Columbia University in New York, the National Oceanic and Atmospheric Administration in Seattle, and New Zealand's University of Waikato.

LOS ANGELES, June 17 (Xinhua) -- The size of low-oxygen zones created by respiring bacteria is extremely sensitive to changes in depth caused by oscillations in climate, thus posing a distant threat to marine life, a new study suggests."The growth of low-oxygen regions is cause for concern because of the detrimental effects on marine populations -- entire ecosystems can die off when marine life cannot escape the low- oxygen water," said lead researcher Curtis Deutsch, assistant professor of atmospheric and oceanic sciences at University of California, Los Angeles."There are widespread areas of the ocean where marine life has had to flee or develop very peculiar adaptations to survive in low- oxygen conditions," Deutsch said in the study to be published in an upcoming print edition of the journal Science.A team led byDeutsch used a specialized computer simulation to demonstrate for the first time that fluctuations in climate can drastically affect the habitability of marine ecosystems.The study also showed that in addition to consuming oxygen, marine bacteria are causing the depletion of nitrogen, an essential nutrient necessary for the survival of most types of algae."We found there is a mechanism that connects climate and its effect on oxygen to the removal of nitrogen from the ocean," Deutsch said. "Our climate acts to change the total amount of nutrients in the ocean over the timescale of decades."Low-oxygen zones are created by bacteria living in the deeper layers of the ocean that consume oxygen by feeding on dead algae that settle from the surface. Just as mountain climbers might feel adverse effects at high altitudes from a lack of air, marine animals that require oxygen to breathe find it difficult or impossible to live in these oxygen-depleted environments, Deutsch said.Sea surface temperatures vary over the course of decades through a climate pattern called the Pacific Decadal Oscillation, during which small changes in depth occur for existing low-oxygen regions, Deutsch said. Low-oxygen regions that rise to warmer, shallower waters expand as bacteria become more active; regions that sink to colder, deeper waters shrink as the bacteria become more sluggish, as if placed in a refrigerator."We have shown for the first time that these low-oxygen regions are intrinsically very sensitive to small changes in climate," Deutsch said in remarks published Friday by the American Association for the Advancement of Science on its website. "That is what makes the growth and shrinkage of these low-oxygen regions so dramatic."Molecular oxygen from the atmosphere dissolves in sea water at the surface and is transported to deeper levels by ocean circulation currents, where it is consumed by bacteria, Deutsch said."The oxygen consumed by bacteria within the deeper layers of the ocean is replaced by water circulating through the ocean," he said. "The water is constantly stirring itself up, allowing the deeper parts to occasionally take a breath from the atmosphere."A lack of oxygen is not the only thing fish and other marine life must contend with, according to Deutsch. When oxygen is very low, the bacteria will begin to consume nitrogen, one of the most important nutrients that sustain marine life."Almost all algae, the very base of the food chain, use nitrogen to stay alive," Deutsch said. "As these low-oxygen regions expand and contract, the amount of nutrients available to keep the algae alive at the surface of the ocean goes up and down. "Understanding the causes of oxygen and nitrogen depletion in the ocean is important for determining the effect on fisheries and fish populations, he said.

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