中山为什么大便次数很多有时候出血(痔疮往中山肛泰肛肠医院) (今日更新中)

LOS ANGELES, July 22 (Xinhua) -- Two teams of astronomers have discovered the largest and farthest reservoir of water ever detected in the universe, NASA's Jet Propulsion Laboratory (JPL) said on Friday.The water, equivalent to 140 trillion times all the water in the world's ocean, surrounds a huge, feeding black hole, called a quasar, more than 12 billion light-years away, according to JPL in Pasadena, California."The environment around this quasar is very unique in that it's producing this huge mass of water," said Matt Bradford, a scientist at JPL. "It's another demonstration that water is pervasive throughout the universe, even at the very earliest times. "This artist's concept illustrates a quasar, or feeding black hole, similar to APM 08279+5255, where astronomers discovered huge amounts of water vapor. Gas and dust likely form a torus around the central black hole, with clouds of charged gas above and below. X-rays emerge from the very central region, while thermal infrared radiation is emitted by dust throughout most of the torus. While this figure shows the quasar's torus approximately edge-on, the torus around APM 08279+5255 is likely positioned face-on from our point of view.A quasar is powered by an enormous black hole that steadily consumes a surrounding disk of gas and dust. As it eats, the quasar spews out huge amounts of energy. Both groups of astronomers studied a particular quasar called APM 08279+5255, which harbors a black hole 20 billion times more massive than the sun and produces as much energy as a thousand trillion suns.Astronomers expected water vapor to be present even in the early, distant universe, but had not detected it this far away before. There's water vapor in the Milky Way, although the total amount is 4,000 times less than in the quasar, because most of the Milky Way's water is frozen in ice. Water vapor is an important trace gas that reveals the nature of the quasar. In this particular quasar, the water vapor is distributed around the black hole in a gaseous region spanning hundreds of light-years in size (a light-year is about six trillion miles).Its presence indicates that the quasar is bathing the gas in X- rays and infrared radiation, and that the gas is unusually warm and dense by astronomical standards, JPL said.Although the gas is at a chilly minus 63 degrees Fahrenheit ( minus 53 degrees Celsius) and is 300 trillion times less dense than Earth's atmosphere, it's still five times hotter and 10 to 100 times denser than what's typical in galaxies like the Milky Way, said JPL.Measurements of the water vapor and of other molecules, such as carbon monoxide, suggest there is enough gas to feed the black hole until it grows to about six times its size, JPL said.Whether this will happen is not clear, the astronomers say, since some of the gas may end up condensing into stars or might be ejected from the quasar.Bradford's team made their observations starting in 2008, using an instrument called "Z-Spec" at the California Institute of Technology's (Caltech's) Submillimeter Observatory, a 33-foot (10- meter) telescope near the summit of Mauna Kea in Hawaii. Follow-up observations were made with the Combined Array for Research in Millimeter-Wave Astronomy (CARMA), an array of radio dishes in the Inyo Mountains of Southern California.The second group, led by Dariusz Lis, senior research associate in physics at Caltech and deputy director of the Caltech Submillimeter Observatory, used the Plateau de Bure Interferometer in the French Alps to find water. In 2010, Lis's team serendipitously detected water in APM 8279+5255, observing one spectral signature.Bradford's team was able to get more information about the water, including its enormous mass, because they detected several spectral signatures of the water, according to JPL.

BEIJING, Sept. 6 (Xinhuanet) -- Scientists from Tufts University of the U.S. have created the world's smallest electrical motor in a single molecule.The finding was published in the journal Nature Nanotechnology on Monday.In the research, scientist successfully made a single molecule accept an electrical charge and rotate as fast as 120 revolutions per second."This is the first time that electrically-driven molecular motors have been demonstrated, despite a few theoretical proposals," said Charles H. Sykes, professor of chemistry at Tufts who led the team.The single molecule electric motor could lead to new types of electrical circuitry, giving hope for scientists to apply it in medicine and engineering, he said."The next thing to do is to couple it to other molecules, lining them up next to one another so they're like miniature cog-wheels, and then watch the rotation propagation down the chain," said Sykes.

BEIJING, July 26 (Xinhuanet) -- Some forms of medical research involving animals containing human material should be more tightly regulated, a report warned.The warning was issued on Friday by an expert working group from the Academy of Medical Sciences in Britain.The report suggested the ban of the use of animal cells that can produce human sperm or egg cells. "We don't want scientists to cause problems for the future by overstepping the mark of what is publicly acceptable," said Professor Robin Lovell-Badge, a member of the expert working group.The controversy partly originated from a medical research in Britain. Three years ago, the researchers produced human embryos with the nucleus hollowed cow eggs, according to the Associated Press."This is a complex research area and there should be an ongoing dialogue between scientists, regulators and the wider public to address emerging issues." said Martin Bobrow, a professor of medical genetics at the University of Cambridge.

LOS ANGELES, June 14 (Xinhua) -- Rural elders are far more likely to be overweight or obese, physically inactive and food insecure than their suburban counterparts, three risk factors for heart disease, diabetes and repeated falls, a new study suggests."The countryside can have an isolating effect," said lead researcher Steven P. Wallace, deputy director of the Center for Health Policy Research at the University of California, Los Angeles. "When even a trip to the grocery store is a significant drive, seniors can become trapped in their houses."The researchers based their finding on analyzing the lifestyles and living conditions in California countryside.The study found that despite living in the countryside, where open space is plentiful and there is often significant agricultural production, California's more than half a million rural elders have higher rates of developing various health problems than their urban and suburban counterparts.These problems include:-- Older adults in rural areas are more often overweight or obese (61.3 percent) than their urban (57.3 percent) and suburban (54.0 percent) counterparts;-- Rural older adults do not get enough exercise;-- One in five rural elders do not participate in either moderate or vigorous physical activity in their leisure time;-- Rural and urban older adults are more likely to be food insecure; and-- One in five low-income older adults in rural settings report that they cannot consistently afford enough food to last the month, a rate is about twice that of low-income suburban adults.Approximately 710,000 Californians aged 65 and over live in the countryside -- almost one-fifth of all older adults in the state. Yet rural elders experience unique challenges to healthy living, including a lack of sidewalks, street lights, transportation services, access to healthy food outlets, parks, exercise facilities and health care sites. California's rural areas are also challenged by a dearth of physicians and other primary care providers, compelling many seniors to travel long distances to seek care, according to the study.The findings were published Tuesday on the website of the American Association for the Advancement of Science.

SAN FRANCISCO, July 28 (Xinhua) -- Amazon announced Thursday that it had reached an agreement with NBC Universal to allow its members to view certain movies from Universal Pictures on-line through its movie streaming service.According to the on-line retail giant, Oscar-winning movies such as "Eternal Sunshine of the Spotless Mind," "Gosford Park" and "Elizabeth" as well as other favorites like "Notting Hill" and "Billy Elliot" are part of the pact.The movies will be available to Amazon Prime members through its streaming service Prime Instant Video. Amazon Prime is a membership program that gives subscribers discounts on shipping for a 79 U.S. dollar annual fee.In February, Amazon said it would offer Prime customers unlimited access to an on-line video library. Last Wednesday, Amazon announced an accord with CBS that expanded the video library to more than 8,000 movies and TV shows. It said Thursday that the NBC deal will bring the number to more than 9,000.With the CBS, NBC Universal deals, Amazon steps up its rivalry against other movie streaming services, especially Netflix, a popular on-line and mail-order movie rental company which just boosted prices by 60 percent for some subscribers. Analysts said Amazon is trying to make the pitch to those customers who are disappointed with Netflix.In a second-quarter earnings letter to investors distributed on Monday, Netflix CEO Reed Hastings said Netflix had more than 24.6 million subscribers in the U.S. at the end of June and vastly more streaming content than its competitors."We haven't detected an impact on our business from Amazon Prime," he noted.

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