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BEIJING, Sept. 23 (Xinhua) -- A defunct U.S. satellite is expected to crash down to Earth Friday, with nobody knowing where or when exactly it will hit. This was avoidable, a Chinese expert said Thursday.Pang Zhihao, a researcher from the Chinese Research Institute of Space Technology, told Xinhua that the crash could have been avoided had the satellite been put into a higher orbit, or manipulated to drop in the South Pacific when it had abundant fuel. It would pose no threat to Earth if these measures had been taken.NASA's tumbling, 5,900 kg Upper Atmosphere Research Satellite, or UARS, is the first of such man-made space vehicles that have been launched into outer space according to the agency's Mission to Planet Earth. The mission was launched in the 1990s.The mission is designed to provide data for better understanding Earth's upper atmosphere and the effects of natural and human interactions on the atmosphere.The satellite was deactivated in 2005 as it ran out of fuel and was left orbiting Earth like a big piece of space junk.There are other cases of defunct satellites. The European Space Agency said earlier its observation satellite ERS-2 has run out of fuel and is deorbiting. It would therefore also crash sooner or later.Pang said all countries which are operating space vehicles should take care of their own spacecrafts so that they won't pose any danger.The expert also said that the public need not worry too much.Pang said most spacecrafts will be incinerated upon re-entering Earth's atmosphere, and the debris will mostly likely fall into the ocean or hit an uninhabited area. In addition, a debris tracker is able to give a comparatively accurate prediction where the craft will fall about two hours before it hits Earth, giving residents, if there are any, time to evacuate.He added that there are several ways to minimize the threat of decommissioned spacecrafts, like putting them into higher orbits and crashing them into designated waters.Scientific progress would possibly bring about more ways of dealing with tumbling satellites. Scientists have already been trying to build spacecrafts with degradable materials so that they can self-destruct when re-entering Earth's atmosphere.

GENEVA, Sept. 26 (Xinhua) -- Two million people worldwide are estimated to die from air pollution each year, the Geneva based World Health Organization (WHO) said in its air quality report published on Monday.According to data collected by the WHO from nearly 1,100 cities across 91 countries, elevated level of fine particle pollution, which could cause heart diseases, lung cancer, asthma and acute lower reparatory infections, are common across many urban areas, with some cities registering fine particle pollution levels 15 times as much as the WHO guidelines.For both developed and developing countries, the biggest contributors to urban outdoor air pollution include motor transport, small-scale manufacturers and other industries, burning of biomass and coal for cooking and heating, as well as coal-fired power plants.Residential wood and coal burning for space heating is said to be an important contributor to air pollution, especially in rural areas during colder months, the WHO report said.

WASHINGTON, Aug. 18 (Xinhua) -- Using integrated radar observations from a consortium of international satellites, NASA-funded researchers have created the first complete map of the speed and direction of ice flow in Antarctica, the U.S. National Aeronautics and Space Administration (NASA) announced Thursday.The map, which shows glaciers flowing thousands of miles from the continent's deep interior to its coast, will be critical for tracking future sea-level increases from climate change."This is like seeing a map of all the oceans' currents for the first time. It's a game changer for glaciology," said Eric Rignot of NASA's Jet Propulsion Laboratory and the University of California (UC), Irvine. Rignot is lead author of a paper about the ice flow published online Thursday in Science Express. "We are seeing amazing flows from the heart of the continent that had never been described before."Rignot and UC Irvine scientists used billions of data points captured by European, Japanese and Canadian satellites to weed out cloud cover, solar glare and land features masking the glaciers. With the aid of NASA technology, the team painstakingly pieced together the shape and velocity of glacial formations, including the previously uncharted East Antarctica, which comprises 77 percent of the continent.Like viewing a completed jigsaw puzzle, the scientists were surprised when they stood back and took in the full picture. They discovered a new ridge splitting the 5.4-million-square-mile landmass from east to west.The team also found unnamed formations moving up to 800 feet annually across immense plains sloping toward the Antarctic Ocean and in a different manner than past models of ice migration."The map points out something fundamentally new: that ice moves by slipping along the ground it rests on," said Thomas Wagner, NASA's cryospheric program scientist in Washington. "That's critical knowledge for predicting future sea level rise. It means that if we lose ice at the coasts from the warming ocean, we open the tap to massive amounts of ice in the interior."

WASHINGTON, July 13 (Xinhua) -- Human neural stem cells are capable of helping people regain learning and memory abilities lost due to radiation treatment for brain tumors, a University of California, Irvine (UCI) study suggests.Research with rats found that stem cells transplanted two days after cranial irradiation restored cognitive function, as measured in one- and four-month assessments. In contrast, irradiated rats not treated with stem cells showed no cognitive improvement."Our findings provide solid evidence that such cells can be used to reverse radiation-induced damage of healthy tissue in the brain," said Charles Limoli, a UCI radiation oncology professor.Study results will appear Friday in Cancer Research, a journal of the American Association for Cancer Research.Radiotherapy for brain tumors is limited by how well the surrounding tissue tolerates it. Patients receiving radiation at effective levels suffer varying degrees of learning and memory loss that can adversely affect their quality of life."In almost every instance, people experience severe cognitive impairment that's progressive and debilitating," Limoli said. " Pediatric cancer patients can experience a drop of up to three IQ points per year."For the UCI study, multipotent human neural stem cells were transplanted into the brains of rats that had undergone radiation treatment. They migrated throughout the hippocampus -- a region known for the growth of new neurons -- and developed into brain cells.Researchers assessed the rats one month and four months after transplantation, noting enhanced learning and memory abilities at both intervals.Additionally, they found that transplanting as few as 100,000 human neural stem cells was sufficient to improve cognition after cranial irradiation. Of cells surviving the process, about 15 percent turned into new neurons, while another 45 percent became astrocytes and oligodendrocytes -- cells that support cerebral neurons.Most notably, Limoli said, he and his colleagues discovered that about 11 percent of the engrafted cells expressed a behaviorally induced marker of learning, indicating the functional integration of those cells into memory circuits in the hippocampus."This research suggests that stem cell therapies may one day be implemented in the clinic to provide relief to patients suffering from cognitive impairments incurred as a result of their cancer treatments," Limoli said.

LOS ANGELES, July 5 (Xinhua) -- NASA's Juno spacecraft is 30 days away before its first launch window opens, the Jet Propulsion Laboratory (JPL) announced on Tuesday."One month from today, our first launch window opens at 11:34 a. m. EDT (8:34 a.m. PDT) and lasts 69 minutes," said Jan Chodas, Juno project manager from NASA's JPL in Pasadena, Los Angeles."Our primary launch period is 22 days long, and so if weather or other issues come up on Aug. 5, we have 21 more days to get Juno flying. Once we get Juno into space, it's a five-year cruise to Jupiter.""The launch window is the length of time allotted every day for an attempt to launch the spacecraft," said Chodas. "The launch period is the period of time in days when everything is in the right place to get your mission off to the right start."For a mission like Juno, getting everything in the right place includes considering the size of the rocket and spacecraft, where our home planet -- and in particular Juno's launch pad -- is pointed at any moment, and its location in space relative to other celestial objects like Juno's final target, Jupiter.Juno is scheduled to launch aboard a United Launch Alliance Atlas V rocket from pad 41-C at the Cape Canaveral Air Force Station, Florida.The solar-powered spacecraft will orbit Jupiter's poles 33 times to find out more about the gas giant's origins, structure, atmosphere and magnetosphere and investigate the existence of a solid planetary core.JPL manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio.The Juno mission is part of the New Frontiers Program managed at NASA's Marshall Space Flight Center in Huntsville, Alaska. Lockheed Martin Space Systems, Denver, built the spacecraft.