中山市华都医院胃肠科(中山正常人会出现便血吗) (今日更新中)

WASHINGTON, Aug. 10 (Xinhua) -- After a journey of almost three years, NASA's Mars rover Opportunity has reached the Red Planet's Endeavour crater to study rocks never seen before, the U.S. National Aeronautics and Space Administration (NASA) announced on Wednesday.Scientists hope it will find rocks and terrain much older than any other that the itinerant robot has examined during its seven years on the red planet.The U.S. space agency said that Opportunity arrived at the rim of Endeavour on Tuesday. The golf cart-size rover is expected to remain at the 22-kilometer-wide crater for the next few years.A portion of the west rim of Endeavour crater sweeps southward in this color view from NASA's Mars Exploration Rover Opportunity."NASA is continuing to write remarkable chapters in our nation' s story of exploration with discoveries on Mars and trips to an array of challenging new destinations," NASA Administrator Charles Bolden said in a statement. "Opportunity's findings and data ... will play a key role in making possible future human missions to Mars and other places where humans have not yet been."NASA's Mars Reconnaissance Orbiter, which has been circling the planet since late 2005, detected clay minerals that form in wet conditions in the crater. Scientists want to find out if the minerals date back to Mars' distant past, when the planet is believed to have been wetter and warmer than the dry frozen desert it is today."We're soon going to get the opportunity to sample a rock type the rovers haven't seen yet," said Matthew Golombek, Mars Exploration Rover science team member, at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Clay minerals form in wet conditions so we may learn about a potentially habitable environment that appears to have been very different from those responsible for the rocks comprising the plains."NASA is searching for signs that Mars had a habitable environment billions of years ago. Knowledge of the Martian climate will be important to future manned missions there, and can shed light on the forces that shaped Earth's climate.NASA launched the Mars rovers Opportunity and Spirit in 2003 for what were planned to be three-month missions. But both continued operating well beyond that. Spirit stopped communicating in March 2010.

LOS ANGELES, June 7 (Xinhua) -- Salmonella, not E. coli, poses the greatest health threat to Americans, the U.S. Centers for Disease Control and Prevention (CDC) announced on Tuesday.Salmonella infections have risen 10 percent over the past 15 years, while several types of foodborne illness have been falling, the agency said in a report.Infections from Shiga toxin-producing E. coli O157 (the strain of most concern in the United States) have dropped almost in half and the rates of six other foodborne infections have been cut 23 percent, the CDC said.The agency issued the report as a deadly new strain of E.coli is spreading in several European countries."There are about 50 million people each year who become sick from food in the U.S.. That's about one in six Americans," CDC director Dr. Thomas R. Frieden said.The CDC attributed the reduction in infections from E. coli O157 to better detection and investigation of outbreaks, cleaner slaughterhouse methods, better testing of ground beef for E. coli, improved inspections of ground beef processing plants, regulations prohibiting E. coli O157 in ground beef and increased awareness of the importance of properly cooking beef.Other foodborne illnesses that fell in incidence over the same time period include those caused by the campylobacter, listeria, vibrio and yersinia pathogens.To reduce their risk of foodborne illness, people should assume that raw chicken and other meat have bacteria that can make you sick, the CDC said.In the kitchen, raw meats should not allow to contaminate counter tops or cutting boards and should be kept away from other foods, such as fruits and vegetables, the CDC advised.The agency also called on people to thoroughly cook meat, poultry, eggs and shellfish, while refraining from consuming unpasteurized milk, juice or soft cheese.

BEIJING, Aug. 16 (Xinhuanet) -- Almost one in four Chinese students aged between 12 and 14 have tried smoking, according to the results of a survey released by the Chinese Association on Tobacco Control (CATC).The survey, carried out among 38,839 students and 6,503 teachers from middle and high schools in 11 provinces across the country between May and June, showed that 22.5 percent of students aged between 12 and 14 had tried smoking and that 15.8 percent of middle and high school students smoke regularly."There are definitely quite a number of boy students in my class who smoke regularly as some have been found smoking outside campus during lunch break," said Li Xiaolan, an English teacher from a high school in Shanghai. The survey also found that 39 percent of students took their first cigarette from their classmates."It was quite common to smoke with my classmates at school and we usually smoked in toilets or in corners of the playground after lunch," said Zhou Guangrong, a 22-year-old university student from Guiyang, Guizhou province, who started smoking when he was 12.The majority of student smokers buy cigarettes themselves and about 76 percent of the adolescent smokers said that there is at least one cigarette shop within 200 meters from their school."When I was a student at middle and high schools, they were surrounded by cigarette shops," said Zhou who used to smoke two cigarettes per day in primary school and two packs per week in middle and high school."We're keen to show that more adolescents are starting smoking much younger than before, and that we need to minimize the number of young smokers," said Duan Jiali, secretary-general of the youth tobacco control commission under CATC. Duan added that teachers and parents should set a good example for teenagers by not smoking in front of them at school or at home, which is the most influential way of stopping adolescents from smoking.China banned smoking in 16 types of public indoor venues - including hospitals, schools, bars, restaurants and hotels - on May 1 in an attempt to curb tobacco use in the country with the world's largest number of smokers.Currently, there are more than 300 million smokers in China, and about 1.2 million people die from smoking-related diseases every year, accounting for one-fifth of the world's total, according to statistics from the World Health Organization."Meanwhile, about 540 million people are exposed to secondhand smoke, 48.9 percent of which are adolescents (from 15 to 19 years old)," said Xu Guihua, deputy director of the CATC."It's essential and urgent for us to control the number of adult smokers who potentially tempt adolescents to smoke."

CANBERRA, Sept. 24 (Xinhua) -- Australian scientists on Saturday said a satellite due to re-enter Earth poses a negligible threat to life and property on Earth.U.S. National Aeronautics and Space Administration's Upper Atmosphere Research Satellite (UARS), which weighs more than five tons, is expected to re-enter the Earth's atmosphere at 1058 (AEST) on Saturday. The U.S.-based Center for Orbital and Re-entry Debris Studies estimates that re-entry could occur up to seven hours before or after this time.According to Nonathan Nally, a former editor of two space magazines and currently editor of the Australian Space News website, the satellite poses a negligible threat to life and property on Earth."Most of the satellite will burn up on re-entry, with perhaps as many as 26 stronger or harder small pieces surviving to reach the surface," Nally said in a statement."But with the majority of the Earth comprising oceans or uninhabited (or very sparsely populated) remote regions, the chances are overwhelming that any pieces of UARS that survive re- entry will fall harmlessly and never be seen again."Since the spacecraft is no longer powered, U.S. National Aeronautics and Space Administration has no control over where it comes down, but Nally said there is a small chance that debris from the satellite could land in Australia.Debris from SkyLab, another satellite which plunged to Earth, was scattered over parts of Western Australia in 1979. Skylab weighed about 77 tonnes, many times more than the UARS.?Dr Alice Gorman, a lecturer in the Department of Archaeology, specializing in space archaeology, at Flinders University in South Australia, said the UARS satellite re-entry is very reminiscent of Skylab in 1979."There is the same exaggeration of the hazard through the media, public anxiety as the advance warning allows for speculation, and a lack of understanding of what the risks actually are," he said in a statement."Should it land in Australia, we might expect the same rush for souvenirs as we saw with Skylab, as anything that has been in space has a special meaning on Earth."?UARS was launched on 12 September 1991 and decommissioned on 15 December 2005. Its total dry mass is about 5.5 tonnes. UARS is one of the largest NASA satellites to plunge back to Earth uncontrolled in the last 30 years.Since the beginning of the Space Age in the late-1950s, there have been no confirmed reports of an injury resulting from re- entering space objects.? Nor is there a record of significant property damage resulting from a satellite re-entry.

WASHINGTON, July 12 (Xinhua) -- Two U.S. astronauts stepped out the International Space Station on Tuesday to retrieve a failed ammonia pump, which is the last spacewalk of the shuttle era, NASA announced.Space station astronauts Mike Fossum and Ron Garan completed the six-hour, 31-minute spacewalk at 3:53 p.m. EDT (1953 GMT). The duo retrieved a pump module from an external stowage platform on station and store it in shuttle Atlantis' cargo bay for return to Earth.The pump module failed in 2010, shutting down half of the space station's cooling system. Engineers will evaluate the module to determine the cause of the failure and plan to refurbish it for use as a spare.The astronauts also attached a Robotic Refueling Module experiment to the space station, which aims to test technologies for repairing and refueling satellites in space.It was the 249th spacewalk by U.S. astronauts and the 160th spacewalk in support of space station assembly and maintenance, totaling 1009 hours, nine minutes.Atlantis lifted off on Friday morning from Kennedy Space Center in Florida, on the 135th and final flight in NASA's shuttle program. Its return to the earth later this month will mark the end of the 30-year shuttle program.

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