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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.

WASHINGTON, Sept. 15 (Xinhua) -- A team of researchers has discovered a planet that orbits around a pair of stars, the U.S. space agency NASA announced Thursday.This is the first instance of astronomers finding direct evidence of a so-called circumbinary planet. A few other planets have been suspected of orbiting around both members of a dual-star system, but the transits of the circumbinary planet have never been detected previously.The team, led by Laurance Doyle of the SETI Institute in California, used photometric data from the NASA Kepler space telescope, which monitors the brightness of 155,000 stars.NASA's Kepler mission has discovered a world where two suns set over the horizon instead of just one. The planet, called Kepler-16b, is the most "Tatooine-like" planet yet found in our galaxy. Tatooine is the name of Luke Skywalker's home world in the science fiction movie Star Wars. In this case, the planet it not thought to be habitable. It is a cold world, with a gaseous surface, but like Tatooine, it circles two stars.They found the binary star system by detecting a system where the stars eclipsed each other from the perspective of the Kepler spacecraft. These stars have two eclipses: A primary eclipse when the larger star is partially blocked by the smaller star and a secondary eclipse where the smaller star is fully blocked by the larger star.But the researchers also noticed other times when the brightness of the two stars dropped, even when they were not in an eclipse position. This pattern suggested that there was likely a third object involved. The fact that these so-called tertiary and quaternary eclipses recurred after varying intervals of time, and were of different depths, indicated that the stars were in different positions in their orbit at each instance. This result showed that the tertiary and quaternary eclipses were being caused by something circling both stars, and not an object circling one or the other star.Measurements of the variations in the timing of all four types of eclipses, resulting from the mutual gravitational interactions of the two stars and the third body, demonstrated that the third object was, indeed, a planet. Their work indicates that the planet is less massive than Jupiter, possibly comparable in mass to Saturn, and that the larger of the two binary stars is smaller than our Sun.Their findings will be published Friday in Science."This discovery confirms a new class of planetary systems that could harbor life," Kepler principal investigator William Borucki said in a statement. "Given that most stars in our galaxy are part of a binary system, this means the opportunities for life are much broader than if planets form only around single stars. This milestone discovery confirms a theory that scientists have had for decades but could not prove until now."

YUEYANG, Hunan, June 2 (Xinhua) -- The population of finless porpoises, an endangered species of freshwater dolphin that lives in China's Yangtze River, may decrease by over 80 percent over the next 30 years, experts said on Thursday after conducting a field survey along the river.The rare species will edge closer to extinction if no action is taken, said Wang Ding, a dolphin expert from the Hydrobiology Institute of the Chinese Academy of Sciences.Wang's team conducted a survey on Poyang Lake, Dongting Lake and other locations along the Yangtze from Sunday to Wednesday this week.The dolphin population currently stands at 1,000, even lower than that of the giant panda, Wang said.The dolphin population is decreasing by a rate of 6.4 percent annually, Wang said."The next ten years will be a critical period for the conservation of this species," Wang said.A long-lasting drought in central China has lowered water levels in many of the region's lakes and rivers, doing great harm to the dolphins' habitat and leading to a decrease in population, Wang said.Mei Zhigang, a member of Wang's survey team, said that human activity has also contributed to the dropping population.Mei said that large numbers of shipping vessels on the Yangtze have impeded the dolphins' migration path, causing them to reproduce less frequently.

SAN FRANCISCO, Aug. 10 (Xinhua) -- Amazon on Wednesday launched Kindle Cloud Reader, a web-based app that may help the on-line retailer to sidestep Apple's App Store restrictions.In its announcement, Amazon said Kindle Could Reader uses the HTML5 web standard to let users read e-books from their Kindle library from the Safari browser or Google's Chrome browser on their desktops or tablet, including the iPad.Support for Internet Explorer, Firefox and the Blackberry Playbook will be launched later this year.The app has a button linked to the Kindle Store, which was removed recently from the Kindle apps for iPad and iPhone.The move is taken as an answer to Apple's latest App Store restrictions, which banned developers to have any external links for purchasing digital books or subscriptions in the app, unless they give Apple a 30 percent cut from the in-app sales.Besides Amazon, Barnes & Noble, Google Books and Canadian e- book seller Kobo have also altered their iPad and iPhone apps to comply with the rules.Meanwhile, publishers and retailers have been developing web- based HTML5 apps to sidestep Apple for more control, which is an approved-of technology for iOS devices.The Financial Times, Kobo and video-on-demand service Vudu have recently launched their HTML5 app to avoid paying Apple a 30 percent cut.Industry watchers said it is unknown how Apple will deal with such apps. It would be easy for Apple to disable Web apps in the iPad's Safari browser, but the company would certainly face some backlash, said tech media website CNET.

SAN FRANCISCO, Sept. 13 (Xinhua) -- Microsoft released on Tuesday a test version of Windows 8 to developers, posing to regain ground of the tablet market dominated by Apple and Google.At its developer-focused BUILD conference held in Anaheim, California, the software giant handed out new Samsung tablet computers with a test version of the code-named "Windows 8," the first detailed preview of the system for developers and people outside Microsoft.Generally expected to be launched in fall 2012, Microsoft did not say when the system will ship or its price.Microsoft Windows President Steven Sinofsky introduces the new tablet running a test version of its touch-enabled Windows 8 at the Build conference in Anaheim, California September 13, 2011Featuring a home page filled with colorful application tiles, the new system boots up in seconds. Microsoft said the system will run on low-power ARM-based chips that power smartphones and tablets. Windows 8 also introduces a new "Metro style" interface, which run full-screen and users can multitask in two at a time."We reimagined Windows," said Steven Sinofsky, president of the Windows and Windows Live Division at Microsoft, in his keynote address to the thousands of developers in attendance. "From the chipset to the user experience, Windows 8 brings a new range of capabilities without compromise."Analysts said the new system is consumer-oriented and intuitive but it will take time to see whether it is an "iPad killer."As professionals and consumers began to spend more time on smartphones and tablets, Microsoft has not got a significant bite of the market, losing ground to Apple's iPad and devices running Google's Android system.