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BEIJING, July 26 (Xinhuanet) -- Hong Kong scientists announced that they had determined the idea of time travel is impossible by proving nothing can travel faster than the speed of light.The finding is contained in a study done by a research team from Hong Kong University of Science and Technology. The study was published Monday in a scientific journal "Physical Review Letters" in the United States."The study, which showed that single photons also obey the speed limit c, confirms Einstein's causality, that is, an effect cannot occur before its cause," the university said on its website."By showing that single photons cannot travel faster than the speed of light, our results bring a closure to the debate on the true speed of information carried by a single photon." said Professor Du Shengwang, who led the study.The possibility of time travel was raised 10 years ago when scientists discovered the optical pulses in some specific medium might propagate information in a faster-than-light speed."Our findings will also likely have potential applications by giving scientists a better picture on the transmission of quantum information." Du said.

BEIJING, Sept. 25 (Xinhua) -- As China's economy has soared to the second place in the world, the country's scientific strength has also surged -- if only measured by the numbers.Chinese researchers published more than 1.2 million papers from 2006 to 2010 -- second only to the United States but well ahead of Britain, Germany and Japan, according to data recently published by Elsevier, a leading international scientific publisher and data provider. This figure represents a 14 percent increase over the period from 2005 to 2009.The number of published academic papers in science and technology is often seen as a gauge of national scientific prowess.But these impressive numbers mask an uncomfortable fact: most of these papers are of low quality or have little impact. Citation per article (CPA) measures the quality and impact of papers. China's CPA is 1.47, the lowest figure among the top 20 publishing countries, according to Elsevier's Scopus citation database.China's CPA dropped from 1.72 for the period from 2005 to 2009, and is now below emerging countries such as India and Brazil. Among papers lead-authored by Chinese researchers, most citations were by domestic peers and, in many cases, were self-citations."While quantity is an important indicator because it gives a sense of scientific capacity and the overall level of scientific activity in any particular field, citations are the primary indicator of overall scientific impact," said Daniel Calto, Director of SciVal Solutions at Elsevier North America.Calto attributed China's low CPA to a "dilution effect.""When the rise in the number of publications is so rapid, as it has been in China -- increasing quantity does not necessarily imply an overall increase in quality," said Calto.He noted the same pattern in a variety of rapidly emerging research countries such as India, Brazil, and earlier in places like the Republic of Korea."Chinese researchers are too obsessed with SCI (Science Citation Index), churning out too many articles of low quality," said Mu Rongping, Director-General of the Institute of Policy and Management at the Chinese Academy of Sciences, China's major think tank.SCI is one of the databases used by Chinese researchers to look-up their citation performance. The alternative, Scopus, provides a wider coverage worldwide."Chinese researchers from a wide range of areas and institutions are vying for publication, as it is a key criterion for academic appraisal in China, if not the only one. As a result, the growth of quality pales in comparison to that of quantity," said Mu, an expert on China's national science policy and competitiveness.On the other hand, China also falls behind the United States in multidisciplinary research, which is a core engine for scientific advance and research excellence.From 2006 to 2010, China published 1,229,706 papers while the United States churned out 2,082,733. According to a new metric introduced by Elsevier's Spotlight research assessment solution, China generated 885 competencies while the United States had 1,817.In other words, China's total research output is more than half that of the United States, while the number of competencies showing China's strength in multidisciplinary research is less than half that of the United States.Cong Cao, an expert on China's science and technology, put it more bluntly in an article he wrote: "When the paper bubble bursts, which will happen sooner or later, one may find that the real situation of scientific research in China probably is not that rosy."China has been investing heavily in scientific research and technological development in recent years to strengthen its innovative capacity, The proportion of GDP spent on R&D grew from 0.9 percent in 2000 to 1.4 percent in 2007, according to the World Bank.An IMF forecast in 2010 says China now ranks second globally in R&D spending. The IMF calculates China's R&D expenditure at 150 billion U.S. dollars when based on Purchasing Power Parity, a widely used economic concept that attempts to equalize differences in standard of living among countries.By this measure, China surpassed Japan in R&D spending in 2010.Many see China's huge investment in R&D as the momentum behind the country's explosive increase in research papers."Getting published is, in some ways, an improvement over being unable to get published," Mu said. "But the problem is, if the papers continue to be of low quality for a long time, it will be a waste of resources."In China, academic papers play a central role in the academic appraisal system, which is closely related to degrees and job promotions.While acknowledging the importance of academic papers in research, Mu believes a more balanced appraisal system should be adopted. "This is a problem with science management. If we put too much focus on the quantity of research papers, we leave the job of appraisal to journal editors."In China, the avid pursuit of publishing sometimes gives rise to scientific fraud. In the most high-profile case in recent years, two lecturers from central China's Jinggangshan University were sacked in 2010 after a journal that published their work admitted 70 papers they wrote over two years had been falsified."This is one of the worst cases. These unethical people not only deceived people to further their academic reputations, they also led academic research on the wrong path, which is a waste of resources," Mu said.A study done by researchers at Wuhan University in 2010 says more than 100 million U.S. dollars changes hands in China every year for ghost-written academic papers. The market in buying and selling scientific papers has grown five-fold in the past three years.The study says Chinese academics and students often buy and sell scientific papers to swell publication lists and many of the purported authors never write the papers they sign. Some master's or doctoral students are making a living by churning out papers for others. Others mass-produce scientific papers in order to get monetary rewards from their institutions.A 2009 survey by the China Association for Science and Technology (CAST) of 30,078 people doing science-related work shows that nearly one-third of respondents attributed fraud to the current system that evaluates researchers' academic performance largely on the basis of how many papers they write and publish.Despite rampant fraud, China will continue to inject huge money into science. According to the latest national science guideline, which was issued in 2006 by the State Council, the investment in R&D will account for 2.5 percent of GDP in 2020."If China achieves its stated goal of investing 2.5 percent of its GDP in R&D in 2020, and sustains its very fast economic growth over the next decade, it would quite likely pass the U.S. in terms of total R&D investment sometime in the late 2010s," said Calto, adding that it is also quite likely that at some point China will churn out more papers than the United States.According to Calto, China does mostly applied research, which helps drive manufacturing and economic growth, while basic research only accounts for 6 percent, compared with about 35 percent in Germany, Britain, and the United States, and 16 percent in Japan."In the long term, in order to really achieve dominance in any scientific area, I think it will be necessary to put significant financial resources into fundamental basic research -- these are the theoretical areas that can drive the highest level of innovation," Calto said.

PARIS, Aug. 7 (Xinhua) -- European heavy-lift launcher Ariane 5 lifted off two communication satellites on Saturday.The Ariane 5, carrying Astra 1N and BSAT-3c/JCSAT-110R, was launched at 2252 GMT on Saturday from Kourou launch centre in French Guiana, according to live broadcast of the launching process.This was the fourth mission of Ariane 5 in 2011 and its 203th flight that sent off the two satellites Saturday night to their respective geostationary transfer orbits.Astra 1N, to be separated first, is built by EADS Astrium in Toulouse, France, for the Luxembourg-based operator SES Astra. With a designed lifespan of 15 years, it has an estimated liftoff mass of 5,350 kg and is fitted with 52 active Ku-band transponders.It is initially to deliver interim capacity from an orbital position of 28.2 degree East, and will subsequently move to SES Astra's prime location at 19.2 degree East for primary and backup services.BSAT-3c/JCSAT-110R is manufactured by Lockheed Martin Commercial Space Systems in Newtown, Pennsylvania, for Japanese operators B-SAT Corporation and SKY Perfect JSAT Corporation. This satellite weighs approximately 2,910 kg at launch time. It is to be positioned at 110 degree East longitude in geostationary orbit with a lifetime exceeding 16 years.This Ariane 5 flight has been postponed twice, firstly due to some technical problem in early July and then delayed by bad weather.Arianespace plans to achieve six Ariane 5 missions through this year.

BEIJING, July 19 (Xinhuanet) -- Lifestyle changes such as exercise, eating healthily and not smoking could reduce the chances of having Alzheimer’s disease by half, researchers said in a study quoted by news reports Tuesday.Hundreds of thousands of patients could potentially avoid the devastating illness by simply changing bad habits, according to the study published in the journal Lancet NeurologyFor the first time, scientists have calculated the extent to which certain lifestyle traits -- including lack of exercise, smoking and obesity -- all contributed to the disease.Researchers found that in the Western world, an inactive “couch potato” lifestyle was the most important possible cause.Smoking, obesity in middle-age, high blood pressure and diabetes all increased the risk as they cause damage to blood vessels in the brain, leading to death of brain cells. Together, the modifiable risk factors contributed to 50 percent of Alzheimer’s cases worldwide.The researchers want to carry out more work to find out how many people can prevent the disease by making small changes to their lifestyle.