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WASHINGTON, June 16 (Xinhua) -- Cells in the human body are constantly being exposed to stress from environmental chemicals or errors in routine cellular processes. While stress can cause damage, it can also provide the stimulus for undoing the damage. New research by a team of scientists at the University of Rochester has unveiled an important new mechanism that allows cells to recognize when they are under stress and prime the DNA repair machinery to respond to the threat of damage.Their findings will be published Friday in journal Science. Cells in the human body are constantly being exposed to stress from environmental chemicals or errors in routine cellular processes. While stress can cause damage, it can also provide the stimulus for undoing the damage.The scientists, led by biologists Vera Gorbunova and Andrei Seluanov, focused on the most dangerous type of DNA damage -- double strand breaks. Unrepaired, this type of damage can lead to premature aging and cancer. They studied how oxidative stress affects efficiency of DNA repair. Oxidative stress occurs when the body is unable to neutralize the highly-reactive molecules, which are typically produced during routine cellular activities.The research team found that human cells undergoing oxidative stress synthesized more of a protein called SIRT6. By increasing SIRT6 levels, cells were able to stimulate their ability to repair double strand breaks. When the cells were treated with a drug that inactivated SIRT6, DNA repair came to a halt, thus confirming the role of SIRT6 in DNA repair. Gorbunova notes that the SIRT6 protein is structurally related to another protein, SIR2, which has been shown to extend lifespan in multiple model organisms."SIRT6 also affects DNA repair when there is no oxidative stress," explains Gorbunova. "It's just that the effect is magnified when the cells are challenged with even small amounts of oxidative stress."SIRT6 allows the cells to be economical with their resources, priming the repair enzymes only when there is damage that needs to be repaired. Thus SIRT6 may be a master regulator that coordinates stress and DNA repair activities, according to Gorbunova.

SAN FRANCISCO, June 13 (Xinhua) -- Social networking giant Facebook will likely go public in the first quarter of 2012 with a valuation that could top 100 billion U.S. dollars, U.S. media reported on Monday.In a report, CNBC quoted people familiar with the matter as saying that Facebook could submit filing to register its securities with the U.S. Securities and Exchange Commission (SEC) as early as October or November this year.People who are on Wall Street and track this information told the business news television channel that they think the Facebook initial public offering (IPO), if and when it happens could value the company of more than 100 billion dollars.A factor in the company's IPO timing is the SEC's requirement that companies must disclose financial information if they have more than 500 private investors."The company has until the end of April 2012 to disclose their financials, but they may just want to get ahead of that by doing a formal initial public offering, I'm told. And that could happen in the first quarter of the year," said CNBC Wall Street reporter Kate Kelly.Facebook is also facing internal pressure as employees have not been permitted to sell their private shares on the secondary market since last spring. An IPO would make it easier for employees to monetize their shares, said Kelly, citing sources.Facebook shares have been traded in private markets such as Sharepost.com, which puts the social networking company's valuation at 85 billion dollars.Meanwhile, latest data show that Facebook is losing users last month in the United States, Canada and several European countries, indicating that the company could have hit the limits of expansion in its mature markets.

SAN FRANCISCO, June 14 (Xinhua) -- Google on Tuesday introduced several new features of its search services on desktops and smartphones, which the Internet search giant said could help users get to their search results faster.SEARCH BY VOICE, IMAGESpeaking at Google's Inside Search event in San Francisco, Mike Cohen, head of the company's speech technology efforts, said its voice search is now available in 27 languages and dialects, an estimated coverage of around 5 billion people or two-thirds of world population.Voice search has already been available in Google's mobile search application from 2008. Adding the feature to desktops is part of Google's strategy to bring mobile innovations to its desktop search.The voice search on desktop performs similarly to voice search on smartphones -- users can click the microphone button and speak the query. It is only available via Google's Chrome browser for now.Cohen noted that the volume of Google mobile speech inputs has increased by six times in the last year.Also at the event, Google introduced search-by-image, which enables users to drag-and-drop, copy-and-paste image URL, or upload the image from the desktop into the search box. They can also use a Chrome or FireFox software extension to add images to the search.Google said the search-by-image feature will be available in most countries and regions over the next few days to Chrome users, noting that it will not collect and store any images that users use.

BEIJING, June 28 (Xinhuanet) -- A truck-sized asteroid passed over the Atlantic Ocean within 7,500 miles of the Earth on Monday, according to NASA's Jet Propulsion Laboratory.The space rock, called asteroid 2011 MD, is the second space rock to zip extremely close to the Earth this year.The asteroid, with latest size estimates ranging from 16 to 66 feet (5 to 20 meters) wide, was discovered just last week on June 22, but there was never any risk of it impacting the Earth, NASA scientists said. That means asteroid 2011 MD would likely be too small to survive the fiery plunge through the Earth's atmosphere, let alone reach the surface, NASA scientists said. Asteroids this size can be expected to buzz Earth with close shaves about once every six years, they added.The space rock flew well below geosynchronous satellites, which orbit 22,236 miles (35,786 km) above the Earth, but well above the 220-mile (354-km) altitude of the International Space Station.There was little chance that the asteroid would hit a satellite because of the vastness of space and relatively small number of satellites, experts said.

BEIJING, June 21 (Xinhua) -- China will launch a new icebreaker for use during an upcoming 2013 polar expedition, a senior oceanic official said on Tuesday.Both the new icebreaker and Xuelong ("Snow Dragon"), an icebreaker that operated in Antarctica, will form an Arctic-Antarctic maritime research team."China will have at least two icebreakers concurrently operating at both the north and south poles," Chen Lianzeng, deputy director of the State Oceanic Administration, told a national conference on polar research, which has been the first since 1984 when the country started expeditions in polar regions.The new icebreaker will boast facilities that will allow it to research the oceanic environment, integrate data for real-time oceanic monitoring, deploy and retrieve detectors and conduct aerial studies using helicopters, Chen said.The two icebreakers will conduct expeditions in polar regions for more than 200 days annually, he said.Fixed-wing aircraft will also be added to the expedition team before 2015, allowing researchers to be transported between China's Zhongshan and Kunlun research stations and Antarctica's Grove Mountains.The Kunlun station went into operation in early 2009 as the first Chinese research station on Antarctica's inland. The Zhongshan station, established in 1989, now serves as a supply base for the Kunlun station.A written comment by Vice Premier Li Keqiang sent to the conference said the polar research, a magnificent feat of the mankind, has great significance for China's oceanic work and sustainable development."Over the past two decades, China's polar research made great achievements and became influential globally," Li said.Li encouraged Chinese scientists to actively participate in international exchanges and cooperation, safeguard national interests and contribute to the peaceful use of polar regions.Since the early 1980s, China has sent 27 Antarctic expedition teams and completed four research missions to the Arctic Ocean.Besides the Xuelong icebreaker, China has built three Antarctic stations -- Changcheng (Great Wall), Zhongshan and Kunlun -- and one Arctic station -- Huanghe (Yellow River) Station.