中山哪家治疗肛肠好(中山屁股上长痔疮怎么办) (今日更新中)

WASHINGTON, July 7 (Xinhua) -- Space shuttle Atlantis will soar into the sky Friday on NASA's 135th and final flight. Its scheduled return to Earth later this month will mark the end of NASA's 30-year space program.Since its onset with the launch of space shuttle Columbia, the program has been seen as a cheap, safe and reliable way for space exploration.Despite its great contributions to U.S. manned space flight, it has also left some grave and tragic lessons, making its termination inevitable.HIKING COSTSLaunched in 1972 by then President Richard Nixon, the shuttle program aimed to provide a new system of affordable space travel and proved to be NASA's most enduring project in its 50 years of existence.In 1981, shuttle Columbia made its first shuttle flight for two days. It was the ultimate hybrid and the first reusable spacecraft.Launched like a rocket and gliding back to Earth like an airplane, space shuttles not only can act as a space taxi to carry astronauts, but have the muscle of a long-distance trucker to haul heavy machinery.The spaceship boasts more than 3,500 subsystems and 2.5 million parts and is nine times faster than a speeding bullet as it climbs heavenward. That versatility, however, has translated into higher costs.NASA originally estimated the program would cost about 90 billion U.S. dollars. However, its actual cost stands at about 200 billion dollars, compared with the 151 billion dollars spent on Apollo which took Americans to the moon in 1969.In an article in Technology Review, John Logsdon, former head of the Space Policy Institute at George Washington University, drew a direct connection between the ravenous shuttle budget and the lack of other large advances in manned space flight."By operating the system for 30 years, with its high costs and high risk, rather than replacing it with a less expensive, less risky second-generation system, NASA compounded the original mistake of developing the most ambitious version of the vehicle," he wrote."The shuttle's cost has been an obstacle to NASA starting other major projects," he added.HIGH RISKIn terms of safety, the shuttles have never been as reliable as their designers had envisioned.On average, one out of every 67 flights ended up with fatal accidents. Based on the rate of deaths per million miles traveled, the space shuttle is 138 times riskier than a passenger jet.Seven astronauts onboard died when Challenger exploded about a minute after launch in 1986. Nearly two decades after the tragic blast, a new catastrophe descended when the shuttle Columbia disintegrated moments before landing in 2003, killing another seven spacemen.Again, the shuttle program was shelved for more than two years as NASA stepped up efforts to make it safer. But experts say the fundamental problem related to shuttles' safety cannot be solved due to their "birth defects.""It is in the nation's interest to replace the Shuttle as soon as possible," concluded the panel that investigated the 2003 Columbia accident.

CHENGDU, Sept. 3 (Xinhua) -- A list of this year's top 500 Chinese enterprises was unveiled in the city of Chengdu in southwest China's Sichuan Province on Saturday.The Sinopec Group was ranked first, with last year's revenues reaching 1.97 trillion yuan (307.81 billion U.S. dollars), followed by the China National Petroleum Corp. and State Grid Corp., whose revenues hit 1.72 trillion yuan and 1.53 trillion yuan last year, respectively.The rest of the top 10 was rounded out by the Industrial and Commercial Bank of China, China Mobile, China Railway Group, China Railway Construction Corp., China Construction Bank, China Life Insurance Co. and Agricultural Bank of China.The list is the 10th of its kind to be jointly released by the China Enterprise Confederation and the China Enterprise Directors Association. The threshold for entering the list was raised to 14.2 billion yuan in revenues, an increase over the 11.08-billion-yuan threshold used during the previous year.Revenues for China's top 500 companies rose 31.6 percent year-on-year to 36.31 trillion yuan in 2010, while their total assets increased by 18.4 percent to 108.1 trillion yuan, the two organizations said.The companies reported profits of 2.08 trillion yuan for last year, a rise of 38.67 percent from one year earlier.They paid 2.73 trillion yuan in taxes in 2010, accounting for 37.3 percent of the country's total tax revenues.

WASHINGTON, June 15 (Xinhua) -- Using the deepest X-ray image ever taken, astronomers found the first direct evidence that massive black holes were common in the early universe, the U.S. National Aeronautics and Space Administration (NASA) said Wednesday in a statement.The discovery from NASA's Chandra X-ray Observatory shows that very young black holes grew more aggressively than previously thought, in tandem with the growth of their host galaxies.By pointing Chandra at a patch of sky for more than six weeks, astronomers obtained what is known as the Chandra Deep Field South (CDFS). When combined with very deep optical and infrared images from NASA's Hubble Space Telescope, the new Chandra data allowed astronomers to search for black holes in 200 distant galaxies, from when the universe was between about 800 million to 950 million years old."Until now, we had no idea what the black holes in these early galaxies were doing, or if they even existed," said Ezequiel Treister of the University of Hawaii, lead author of the study to appear Thursday in journal Nature. "Now we know they are there, and they are growing like gangbusters."The super-sized growth means that the black holes in the CDFS are less extreme versions of quasars -- very luminous, rare objects powered by material falling onto supermassive black holes. However, the sources in the CDFS are about a hundred times fainter and the black holes are about a thousand times less massive than the ones in quasars.The observations found that between 30 and 100 percent of the distant galaxies contain growing supermassive black holes. Extrapolating these results from the small observed field to the full sky, there are at least 30 million supermassive black holes in the early universe. This is a factor of 10,000 larger than the estimated number of quasars in the early universe."It appears we've found a whole new population of baby black holes," said co-author Kevin Schawinski of Yale University. "We think these babies will grow by a factor of about a hundred or a thousand, eventually becoming like the giant black holes we see today almost 13 billion years later."

BEIJING, July 20 (Xinhuanet) -- Some U.S. soldiers returning from the Middle East have acquired constrictive bronchiolitis, a kind of lung damage virtually unknown in young adults, according to U.S. News & World Report."Respiratory disorders are emerging as a major consequence of service in southwest Asia," said study author Dr. Matthew S. King, an assistant professor of pulmonary and critical care at Meharry Medical College in Nashville, Tenn."In addition to our study, there have been studies showing increases in asthma, obstructive lung disease, allergic rhinitis and a general increase in reports of respiratory symptoms," he added. "Most of the patients say they can’t seem to catch their breath when exerting themselves."On the other hand, Anthony Szema, a physician and engineer at Stony Brook University in New York, has examined a soldier and found tiny complexes of titanium and iron in the man’s lungs, where metals can cause severe damage.Mined separately, the two metals could have gotten together only through a manufacturing process, Szema reported. While the metals’ origin is unclear, he presents a new case study, suspecting garbage-burning pits or exploding devices sent them airborne.While the cases in the study represent only a few dozen people of the hundreds of thousands serving in the Middle East, there is no estimate of how many more might have bronchiolitis.it is recommended that soldiers exercise caution in the field until more is known. Soldiers are now told to wear a mask when burning garbage.

LOS ANGELES, July 3 (Xinhua) -- Warming of the ocean's subsurface layers will melt underwater portions of the Greenland and Antarctic ice sheets faster than previously thought, increasing the sea level more than already projected, a new study suggests.The subsurface ocean layers surrounding the polar ice sheets will warm substantially as global warming progresses, according to the study led by researchers from the University of Arizona (UA).In addition to being exposed to warming air, underwater portions of the polar ice sheets and glaciers will be bathed in warming seawater, said the study appearing on the website of the American Association for the Advancement of Science (AAAS) on Sunday.The research, based on 19 state-of-the-art climate models, proposes a new mechanism by which global warming will accelerate the melting of the great ice sheets during this century and the next."To my knowledge, this study is the first to quantify and compare future ocean warming around the Greenland and the Antarctic ice sheets using an ensemble of models," said lead author Jianjun Yin, a UA assistant professor of geosciences.According to the study, the subsurface ocean along the Greenland coast could increase as much as 3.6 F (2 C) by 2100.Most previous research has focused on how increases in atmospheric temperatures would affect the ice sheets, he said."Ocean warming is very important compared to atmospheric warming because water has a much larger heat capacity than air," Yin said. "If you put an ice cube in a warm room, it will melt in several hours. But if you put an ice cube in a cup of warm water, it will disappear in just minutes."Given a mid-level increase in greenhouse gases, the researchers found the ocean layer about 650 to 1,650 feet (200 to 500 meters) below the surface would warm, on average, about 1.8 F (1 C) by 2100. Along the Greenland coast, that layer would warm twice as much, but along Antarctica would warm less, only 0.9 F (0.5 C)."No one has noticed this discrepancy before -- that the subsurface oceans surrounding Greenland and Antarctica warm very differently," Yin said.Part of the warming in the North comes from the Gulf Stream carrying warm subtropical waters north. By contrast, the Antarctic Circumpolar Current blocks some of the subtropical warmth from entering the Antarctic's coastal waters.Even so, the Antarctic ice sheet will be bathed in warming waters, according to the study.This paper adds to the evidence that sea level would rise by the end of this century by around one meter and a good deal more in succeeding centuries, the study noted.The study, "Different Magnitudes of Projected Subsurface Ocean Warming Around Greenland and Antarctica," is scheduled for the upcoming edition of Nature Geoscience later this month.

来源：资阳报