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SAN FRANCISCO, July 15 (Xinhua) -- U.S. microblogging platform Twitter on Friday marked its fifth anniversary since public debut."Twitter, then called Twttr, opened to the public five years ago today," the company said in a Tweet, a short message within 140 characters users are allowed to communicate on the website."Twttr is a new mobile service that helps groups of friends bounce random thoughts around with SMS," co-founder Biz Stone described the service in a blog post on July 13, 2006, two days before its public debut."There were 224 Tweets sent on July 15, 2006. Today, users send that many Tweets in less than a tenth of a second," said the San Francisco-based company.Twitter said more than 600,000 new users signed up on Thursday while it took it more than 16 months to reach the first 600,000 Twitter accounts.The tipping point for the service's popularity was the 2007 South by Southwest festival, a set of film, interactive and music festivals and conferences that take place every March in Austin, Texas. During the event, the Tweets sent per day grew from 20,000 to 60,000.With an estimated user base of 200 million worldwide, some 200 million Tweets are generated and 1.6 billion search queries are handled every day, the company said.According to research firm EMarketer, advertising sales on Twitter is expected to reach 150 million U.S. dollars this year. SharesPost, a secondary market for privately held companies, has assessed Twitter's current worth at 6.8 billion dollars.

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, Aug. 5 (Xinhuanet) -- A study conducted by Israeli researchers at the Albert Einstein College of Medicine in New York shows that genes, rather than good eating and lifestyle habits, determine longevity, according to media reports Friday. "This study suggests that centenarians may possess additional longevity genes that help to buffer them against the harmful effects of an unhealthy lifestyle," said senior author Nir Barzilai, director of the Institute for Aging Research at Yeshiva University's Albert Einstein College of Medicine.The study involves 477 Ashkenazi Jews between the ages of 95 and 122, of whom 75 percent are women. According to the study, Ashkenazi Jews are chosen as subjects because they are more "genetically uniform than other populations, making it easier to spot gene differences that are present."The study also found that the long-lived Ashkenazi Jews drank slightly more and exercised less than their average counterparts. But Barzilai also warned: “Although this study demonstrates that centenarians can be obese, smoke and avoid exercise, those lifestyle habits are not good choices for most of us who do not have a family history of longevity.""We should watch our weight, avoid smoking and be sure to exercise, since these activities have been shown to have great health benefits for the general population, including a longer lifespan," He added.

WASHINGTON, May 30 (Xinhua) -- After nearly 12 days together in orbit, U.S. space shuttle Endeavour undocked from the International Space Station on Sunday night, NASA announced on Monday.According to NASA, the undocking took place at 11:55 p.m. EDT ( 0355 GMT Monday) as the spacecraft sailed 215 miles (346 km) above Bolivia.Pilot Greg Johnson, at the aft flight deck controls, flew Endeavour in a circle around the station at distances of about 450 to 650 feet. Crew members took still and video images of the station.The Space Shuttle Endeavour is seen as it departs the International Space Station after undocking in this image from NASA TV May 29, 2011.As Johnson was about to begin the flyaround, Commander Mark Kelly radioed mission control that he could see the two-billion-U. S.-dollar Alpha Magnetic Spectrometer (AMS) particle physics detector Endeavour had brought to orbit. "It's a new day for science on the space station," he said to mission control.The AMS will be left at the space station to scour the universe for clues about dark matter and antimatter. Endeavour is scheduled to land at the Kennedy Space Center at 2:35 a.m. (0635 GMT) on Wednesday.During their stay at the space station, the Endeavour crew conducted four spacewalks to complete construction of the U.S. side of the 100-billion-dollar outpost, a project of 16 nations that has been being assembled in orbit since 1998.They also brought up a logistics carrier with spare parts and performed some maintenance and installation work during the four spacewalks, the last to be carried out by an American shuttle crew.NASA plans to decommission Endeavour, its youngest shuttle with 25 voyages, and send it to a museum in Los Angeles for display.NASA's 30-year-old shuttle program is ending due to high operating costs. 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.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 space station.

CHICAGO, Aug. 25 (Xinhua) -- Gold futures on the COMEX Division of the New York Mercantile Exchange on Thursday bounced off the biggest drop since March 2008, as the weakness in stock market enhanced appeal of gold as a safe-have investment.The most active gold contract for Dec. delivery gained 5.9 U.S. dollars, or 0.3 percent, to 1,763.2 dollars per ounce. The metal suffered on Wednesday the biggest one-day drop since March 19, 2008.Market analysts said that gold extended losses in earlier trading, hit by a margin-requirement increase, but the drop in global stock market gave a push to the metal. Both Dow Jones industrial average and S&P 500 declined on Thursday after a 3-day rise as a government report showed U.S. jobless claims rose last week.Besides, market hearsay went that Germany might be next to get a sovereign-debt downgrade, adding to the positive tone on gold market. German equity market also suffered sharp drop in the day.Many market watchers remained long-term bullish attitude toward gold although they said the precious metal could correct further in the short term. A trader noted that the fundamental factors driving uncertainty and fears are all still there.Expectations are growing that the Federal Reserve Chairman Ben Bernanke would not provide any form of stimulus in a speech scheduled for Friday at a yearly gathering of central bankers in Jackson Hole.Silver for Sept. delivery also rose 1.583 dollars, or four percent, to 40.745 dollars per ounce. Platinum for Oct. delivery lost 3.9 dollars, or 0.2 percent, to 1822.4 dollars per ounce.