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SAN FRANCISCO, July 6 (Xinhua) -- Facebook on Wednesday introduced a new video calling feature powered by Skype and some improvements to the chat designs on the social networking site.According to Facebook, users can reach video calling from a new "Call" button on a friend's profile or from the chat panel after downloading a Skype application. A recipient will receive an alert that they are being called and can then accept or decline.At the press event held at Facebook headquarters in Palo Alto, California, CEO Mark Zuckerberg said the feature will begin with one-on-one video chat. Skype CEO Tony Bates, whose company has been acquired by Microsoft, said Skype is considering having its paid product within the Facebook product.The social networking company also introduced "Ad Hoc Group Chat", which enables users to start a group chat instantly without creating a group with those multiple friends at first. The new group chat feature is also available for Facebook's mobile interfaces.Facebook also introduces a sidebar that lists the people a user messages most, enabling users to chat with close friends, professional contacts or co-workers without being interrupted. The sidebar can adjust with the size of users' browser window and automatically appears when the window is wide enough.In the opening remarks at the press event, Zuckerberg confirmed that Facebook had surpassed 750 million monthly active users. He said the company had declined to announce the number earlier because it has become focused on other metrics, like how actively users are sharing information.The CEO said users are now sharing 4 billion "things" on Facebook every day, which grew at an exponential rate compared to the amount users share a year ago."Social networking is at an inflection point," said Zuckerberg, adding that he believes social networking now is more about the strength of connecting people rather than the quantity of users or ubiquity of the technology.Zuckerberg presented a graph to show how Facebook product launches have helped drive the growth of sharing. He said the social network expects more innovations from other companies involved in everything from music to communication to help drive the growth.

WASHINGTON, Sept. 12 (Xinhua) -- An enzyme that appears to play a role in controlling the brain's response to nicotine and alcohol in mice might be a promising target for a drug that simultaneously would treat nicotine addiction and alcohol abuse in people, U.S. researchers find.Over the course of four weeks, mice genetically engineered to lack the gene for protein kinase C (PKC) epsilon consumed less of a nicotine-containing water solution than normal mice, and were less likely to return to a chamber in which they had been given nicotine. In contrast, normal mice steadily increased their consumption of nicotine solution while the mice lacking PKC epsilon did not.The study conducted by researchers at the Ernest Gallo Clinic and Research Center, affiliated with the University of California, San Francisco, appeared Monday in the online edition of the Proceedings of the National Academy of Sciences.In normal mice, as in humans, nicotine binds to a certain class of nicotinic receptors located on dopamine neurons, which causes dopamine to be released in the brain. Dopamine creates a feeling of enjoyment, and thus prompts a sense of reward. Researchers found that mice lacking PKC epsilon are deficient in these nicotinic receptors.The finding complements earlier research in which researchers found that mice genetically engineered to lack the PKC epsilon enzyme drank less alcohol than normal mice and were disinclined to return to a chamber in which they had been given alcohol."This could mean that these mice might not get the same sense of reward from nicotine or alcohol," said Gallo senior associate director and investigator Robert Messing. "The enzyme looks like it regulates the part of the reward system that involves these nicotinic receptors."The reward system is a complex of areas in the brain that affect craving for nicotine, alcohol and other addictive substances.The next step in the research, said Messing, would be to develop compounds that inhibit PKC epsilon. The ultimate goal, he added, would be medications that could be used "to take the edge off of addiction by helping people get over some of their reward craving."

CANBERRA, June 6 (Xinhua) -- Australian beef is not to blame for a recent outbreak of E.coli in Japan, Meat and Livestock Australia confirmed on Monday.Twenty people have fallen ill in Japan's Toyama prefecture, with 15 of them infected with the O157 strain of E.coli after eating at a popular Korean-style barbecue restaurant chain, Gyukaka, on May 6.The operators of the restaurant chain, REINS International, said they suspected the bacterium might have been carried by beef imported from Australia.After conducting an investigation into the Japanese outbreak, regional manager for Meat and Livestock Australia, Melanie Brock, said testing shows Australian beef was not the source of the outbreak."The Toyama prefecture health authorities have confirmed following a thorough inspection that imported Australian beef was not the source of an incident of E.coli," Brock said in a statement on Monday."The authorities continue to investigate other food consumed by the affected customers."Brock said Australian beef has long been recognized by the Japanese trade and consumers for its strong safety record.Brock added that Australian beef for export to Japan is processed under the veterinary supervision of the Australian Quarantine and Inspection Service, and is recognized internationally as bearing a high hygienic standard.

RIO DE JANEIRO, Sept. 26 (Xinhua) -- Rio de Janeiro has the highest level of air pollution in Brazil, and is more polluted than many other world metropolis like New York, London and Paris, a World Health Organization (WHO) study said Monday.According to the study, which was carried out in 91 countries and regions, the air in Rio's metropolitan area contains 64 micrograms of fine particulate matter per cubic meter, over three times the upper limit set by the WHO, which is 20 micrograms per cubic meter.Despite being larger, having a bigger population and more vehicles, Sao Paulo's metropolitan area has less air pollution, with 38 micrograms of fine particulate matter per cubic meter.According to the WHO, "the largest 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." The organization said that residential wood and coal burning for heating also help increase air pollution, especially in rural areas in the cold months.The WHO expressed concern over air pollution levels in several cities, as some two million people worldwide die annually from conditions resulting from air pollution."Air pollution is a major environmental health issue, and it is vital that we increase efforts to reduce the health burden it creates," said Dr. Maria Neira, WHO's director for Public Health and Environment.According to the study, Ahwaz, Iran, has the most polluted air in the world, with 372 micrograms of fine particulate matter per cubic meter.

WASHINGTON, June 6 (Xinhua) -- Forests in many regions are becoming larger carbon sinks thanks to higher density, U.S. and European researchers say in a new report.In Europe and North America, increased density significantly raised carbon storage despite little or no expansion of forest area, according to the study, led by Aapo Rautiainen of the University of Helsinki, Finland, and published Monday in the on- line, open-access journal PLoS One.Even in the South American nations studied, more density helped maintain regional carbon levels in the face of deforestation.The researchers analyzed information from 68 nations, which together account for 72 percent of the world's forested land and 68 percent of reported carbon mass. They conclude that managing forests for timber growth and density offers a way to increase stored carbon, even with little or no expansion of forest area."In 2004 emissions and removals of carbon dioxide from land use, land-use change and forestry comprised about one fifth of total emissions. Tempering the fifth by slowing or reversing the loss of carbon in forests would be a worthwhile mitigation. The great role of density means that not only conservation of forest area but also managing denser, healthier forests can mitigate carbon emission," says Rautiainen.