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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.

LOS ANGELES, June 3 (Xinhua) -- Eating earth may protect the stomach against toxins, parasites and pathogens, a new study suggests.To examine the possible benefits from eating earth, researchers at Cornell University analyzed reports from missionaries, plantation doctors, explorers, and anthropologists to put together a database of more than 480 cultural accounts of geophagy -- the eating of earth.The database includes as many details as possible about the circumstances under which earth was consumed, and by whom. The researchers could then use patterns in the data to evaluate each potential explanation.Studies in the database indicate that geophagy is common even when food is plentiful. Moreover, when people eat dirt they tend to eat only small quantities that are unlikely to fill an empty stomach.The database shows that geophagy is documented most commonly in women in the early stages of pregnancy and in pre-adolescent children. Both categories of people are especially sensitive to parasites and pathogens, according to the researchers.In addition, geophagy is most common in tropical climates where foodborne microbes are abundant. Finally, the database shows that people often eat earth during episodes of gastrointestinal stress.It's unlikely the intestinal problems are caused by the dirt itself because the type of clay people usually eat comes from deep in the ground, where pathogens and parasites are unlikely to contaminate it. Plus, people usually boil the clay before eating it.More study would be helpful to confirm the protection hypothesis, the researchers say, but the available data at this point clearly support it over the other explanations for eating earth."We hope this paper stimulates (more) research," said Sera Young, a researcher at Cornell University and the study's lead author. "More importantly, we hope readers agree that it is time to stop regarding geophagy as a bizarre, non-adaptive gustatory mistake.""With these data, it is clear that geophagy is a widespread behavior in humans ...that occurs during both vulnerable life stages and when facing ecological conditions that require protection."The study is appearing in the June issue of The Quarterly Review of Biology.

LOS ANGELES, June 8 (Xinhua) -- NASA's Mars Exploration Rover Opportunity is heading toward "Spirit Point" on the rim of a large crater, a long-term destination that the rover has been trying to reach for nearly three years, the Jet Propulsion Laboratory (JPL) announced on Wednesday.Opportunity has moved toward the crater, Endeavour, since climbing out of Victoria crater in August 2008.Having driven 11 miles (18 kilometers), the rover has about two miles (about three kilometers) to go before reaching the rim of Endeavour, said JPL in Pasadena, Los Angeles.Rover team members last week selected "Spirit Point" as the informal name for the site on the rim where Opportunity will arrive at Endeavour crater. The choice commemorates Opportunity's rover twin, Spirit, which has ended communication and finished its mission."Spirit achieved far more than we ever could have hoped when we designed her," said Steve Squyres of Cornell University, Ithaca, New York, principal investigator for the rovers. "This name will be a reminder that we need to keep pushing as hard as we can to make new discoveries with Opportunity. The exploration of Spirit Point is the next major goal for us to strive for."Endeavour offers the setting for plenty of productive work by Opportunity. The crater is 14 miles (22 kilometers) in diameter -- more than 20 times wider than Victoria crater, which Opportunity examined for two years. Orbital observations indicate that the ridges along its western rim expose rock outcrops older than any Opportunity has seen so far. Spirit Point is at the southern tip of one of those ridges, "Cape York," on the western side of Endeavour.Opportunity and Spirit completed their three-month prime missions on Mars in April 2004. Both rovers continued for years of bonus, extended missions. Both have made important discoveries about wet environments on ancient Mars that may have been favorable for supporting microbial life.NASA's JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover Project for the NASA Science Mission Directorate, Washington.

BEIJING, August 23 (Xinhuanet) -- In the U.S., the rate of injuries related to children and teens falling out of windows declined over a 19-year period, although not nearly as fast as in some cities with comprehensive prevention programs, researchers found.From 1990 to 2008, the overall rate of injuries in children and teens was 7.3 per 100,000 per year, going as high as 11.4 in 1992 and as low as 5.8 in 1999, according to Gary Smith, MD, DrPh, of the Research Institute at Nationwide Children's Hospital in Columbus, Ohio, and colleagues.The annual rate of injuries fell slightly but significantly over the study period, driven entirely by a reduction of 0.426 cases per 100,000 per year in children up to age four, the researchers reported online ahead of the September issue of Pediatrics.That is much less than the reduction seen in previous studies of fall prevention programs in New York City and Boston, which achieved declines of up to 96 percent during a 10-year period through education, increased access to window guards, and a mandate to use window guards in certain homes (only in New York City)."The slower decrease followed by a plateau in injury rates found in this study underscores the fact that prevention efforts of the magnitude undertaken in New York and Boston have not occurred nationwide," Smith and hiscolleagues wrote.The researchers also acknowledged that the study underestimated the number of injuries related to falling out of a window because it included only those children treated in emergency rooms. An additional limitation is that the case narratives often lacked details about the circumstances surrounding the injury, including any suicidal intent.

LOS ANGELES, June 7 (Xinhua) -- Salmonella, not E. coli, poses the greatest health threat to Americans, the U.S. Centers for Disease Control and Prevention (CDC) announced on Tuesday.Salmonella infections have risen 10 percent over the past 15 years, while several types of foodborne illness have been falling, the agency said in a report.Infections from Shiga toxin-producing E. coli O157 (the strain of most concern in the United States) have dropped almost in half and the rates of six other foodborne infections have been cut 23 percent, the CDC said.The agency issued the report as a deadly new strain of E.coli is spreading in several European countries."There are about 50 million people each year who become sick from food in the U.S.. That's about one in six Americans," CDC director Dr. Thomas R. Frieden said.The CDC attributed the reduction in infections from E. coli O157 to better detection and investigation of outbreaks, cleaner slaughterhouse methods, better testing of ground beef for E. coli, improved inspections of ground beef processing plants, regulations prohibiting E. coli O157 in ground beef and increased awareness of the importance of properly cooking beef.Other foodborne illnesses that fell in incidence over the same time period include those caused by the campylobacter, listeria, vibrio and yersinia pathogens.To reduce their risk of foodborne illness, people should assume that raw chicken and other meat have bacteria that can make you sick, the CDC said.In the kitchen, raw meats should not allow to contaminate counter tops or cutting boards and should be kept away from other foods, such as fruits and vegetables, the CDC advised.The agency also called on people to thoroughly cook meat, poultry, eggs and shellfish, while refraining from consuming unpasteurized milk, juice or soft cheese.

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