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发布时间: 2025-06-02 12:28:45北京青年报社官方账号
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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.

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WASHINGTON, July 8 (Xinhua) -- U.S. space shuttle Atlantis lifted off on Friday morning from Kennedy Space Center in Florida, on the 135th and final flight in NASA's shuttle program.The shuttle blasted off at about 11:29 a.m. EDT (1529 GMT) on a tower of flame, NASA TV showed.Before taking flight, shuttle Commander Christopher Ferguson saluted all those who contributed over the years to the shuttle program."The shuttle is always going to be a reflection of what a great nation can do when it dares to be bold and commits to follow through,'' he said. "We're not ending the journey today ... we're completing a chapter of a journey that will never end.''In this photo released by NASA, space shuttle Atlantis lifts off from NASA's Kennedy Space Center in Florida, the United States, July 8, 2011. U.S. space shuttle Atlantis lifted off at about 11:29 a.m. EDT (1529 GMT) on Friday from Kennedy Space Center in Florida, on the 135th and final flight in NASA's shuttle program.Atlantis's primary payload is an Italian-built cargo hauler named Raffaello which is loaded with 8,640 pounds (3,919 kgs) of food, clothing, supplies and science equipment to sustain space station operations after the shuttles are retired.Only four astronauts take to the skies because there is no shuttle available for a rescue flight should anything go wrong. Normally NASA sends six or seven astronauts on space shuttle flights -- with the last four-person shuttle crew launched 28 years ago.But Atlantis' status as the final flight means there is no other space shuttle on standby and the U.S. would have to call on Russia for any rescue operation. The Russian Soyuz capsules hold just three astronauts and at least one must be Russian, so two crew members would have to fly up and bring home the Americans from the International Space Station one at a time.The crew will also return an ammonia pump that recently failed on the station. Engineers want to understand why the pump failed and improve designs for future spacecraft. One spacewalk is planned during Atlantis' mission, though it will be conducted by NASA's two resident space station astronauts, rather than the shuttle crew.It is the 33rd voyage for Atlantis. Its return to the earth later this month will mark the end of the 30-year shuttle program.Atlantis will be the last shuttle to be retired. Discovery was first in March, followed by Endeavour at the beginning of June. Each shuttle will head to a museum.When the U.S. space shuttle program officially ends later this year, the Russian space program's Soyuz capsule will be the only method for transporting astronauts to and from the station.Space shuttles have made great contributions to U.S. space exploration. They allowed astronauts to not only launch satellites, but to grab and repair them and put them back into service. Most remarkably, they allowed NASA to regularly rejuvenate the Hubble Space Telescope, which for 21 years has produced images that are transforming astronomers' understanding of the universe. With their enormous cargo bays, the shuttles also enabled the United States and its partners to build the International Space Station.However, high costs, risks, policy shift force the U.S. to quit the space shuttle program.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.Seven astronauts perished when Challenger exploded about a minute after launch in 1986. Nearly two decades after the Challenger explosion, a new catastrophe shocked NASA when the shuttle Columbia disintegrated moments before landing in 2003.One out of every 67 flights ended in death. Based on deaths per million miles traveled, the space shuttle is 138 times riskier than a passenger jet.The panel that investigated the 2003 Columbia accident concluded: "It is in the nation's interest to replace the Shuttle as soon as possible.''The Obama administration wants to spur private companies to get into the space taxi business, freeing NASA to focus on deep space exploration and new technology development.During his first-ever Twitter town hall meeting on Wednesday, Obama said NASA needs new technology breakthroughs to revitalize its mission to explore the universe."The shuttle did some extraordinary work in low-orbit experiments, the International Space Station, moving cargo. It was an extraordinary accomplishment. And we're very proud of the work that it did," Obama said. "But now what we need is that next technological breakthrough."

  

JIANGYIN, Jiangsu, July 1 (Xinhua) -- China's manned deep-diving submersible, the Jiaolong, embarked on a journey on Friday during which it will make a 5,000-meter dive in the Pacific Ocean.During the dive, the submersible will undergo several operational tests in which it will take photos, shoot video, survey seabeds and take samples from the ocean floor, according to Jin Jiancai, deputy director of the submersible's diving test program team.The tests will be conducted in the Pacific Ocean in accordance with a contract signed between the China Ocean Mineral Resources Research & Development Association and the International Seabed Authority (ISA).The submersible is scheduled to spend 47 days at sea, according to a statement from the Ministry of Science and Technology.A submersible differs from a submarine, as it typically depends on another vessel or facility for support.The Jiaolong, designed to reach a depth of 7,000 meters, completed 17 dives in the South China Sea between May 31 and July 18 last year, reaching 3,759 meters during its deepest dive.In the year since the submersible's last dive, program team members have made several technical improvements to the submersible and its support vessel, Jin said.Jin said the program team members are "very confident" about the test.He also stressed that the test will be carried out in accordance with the provisions of the United Nations Convention on the Law of the Sea as well as the ISA's rules and regulations.The Jiaolong is the world's first manned submersible designed to reach depths of 7,000 meters below sea level, according to Xu Qinan, the submersible's chief designer.

  

CANBERRA, Sept. 9 (Xinhua) -- Australia on Friday launched the first national study to find out whether low to moderate levels of alcohol drank by pregnant women are harmful or not to an unborn child, hoping to provide a clear indication about the safe amount of alcohol for pregnant women.The Murdoch Children's Research Institute in Melbourne, which commissioned the study, is recruiting 2000 pregnant women who will be quizzed throughout their pregnancy about their drinking habits, general health and diets.Their babies will then undergo medical checks, when they turn one and again at two to see if their brains, development and behavior was affected by alcohol consumed by their mums.According to lead researcher associate professor, Jane Halliday, while there was solid evidence about the dangers of heavy drinking for an unborn baby, it was not known if there was a safe amount of alcohol pregnant women could drink.She said the study hoped to shed light on the best approach to alcohol use during pregnancy."The problem is that for about half of women that get pregnant it is unplanned, and a lot of women are drinking around the time they get pregnant and may drink for the first month or so and that creates a lot of anxiety," Assoc Prof Halliday said in a statement."From the few international and Australian studies there's conflicting evidence as to whether there's an adverse effect."We firmly believe that no drinking is the safest option, but our main aim is to provide an evidence base to the policy and answer questions about individual risks."The study came after research by the University of Newcastle published in 2010 revealed 80 percent of Australian women drank during pregnancy.

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