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Robots perform a dance in a competition in Mudanjiang, northeast China's Heilongjiang Province, July 24, 2011. A nationwide robot competition was kicked off in the city on Sunday, with participants from 50 colleges and universities

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.

LOS ANGELES, May 30 (Xinhua) -- The American Academy of Pediatrics (AAP) warned on Monday that children should keep away from energy drinks which may be dangerous for minors.The AAP urged young children and teens to avoid energy drinks entirely, saying routine consumption of sports drinks should be limited or eliminated.Energy drinks include such popular brands as Red Bull, AMP and Rockstar, the AAP said in a report.These drinks, the report said, tend to be heavily caffeinated, potentially having several times the level of caffeine found in a cup of coffee.In addition, manufacturers often add sugar and herbal stimulants such as guarana and taurine to the drinks, which are popular among kids, according to the report."There's no place for energy drinks for kids," said report co-author Dr. Marcie Beth Schneider, an adolescent physician in Greenwich, Connecticut. "There's a place for sports drinks, but that place is very specific."The caffeine in energy drinks can lead to high blood pressure, high heart rate and insomnia, she said.The other ingredients can boost the power of the caffeine, she said, adding that the drinks will have a greater effect on children because they're smaller than adults."Kids don't need to have this," she said. "This is not something they should be drinking."Schneider declined to identify any energy drinks that may be better than others for kids who insist on drinking them. If kids use energy drinks because they're tired, she said, they should get more rest instead of chugging caffeine.Half of the nation's 5,448 reported caffeine overdoses in 2007 were in people under age 19, although it's not known how many of the cases were the result of energy drink consumption, according to statistics provided by the AAP.

SAN FRANCISCO, June 14 (Xinhua) -- Apple updated its online store on Tuesday to begin offering unlocked models of iPhone 4 in the United States for the first time."The unlocked iPhone 4 requires an active micro-SIM card that you obtain from a supported GSM wireless carrier," said Apple in the product description. The iPhone requires a smaller version of the standard SIM (Subscriber Identity Module) card.Started at 649 U.S. dollars for the 16 GB version, the unlocked model is a GSM phone, which means, in the United States, the phone runs on networks of T-Mobile or AT&T, although it can only send data over T-Mobile's old EDGE network, not its 3G network and the faster HSPA+ network.Verizon and Sprint, the other two major U.S. wireless carriers, both use CDMA networks that do not use SIM cards.The iPhone 4 has been sold unlocked in other countries. For frequent international travelers, an unlocked iPhone means they just need to pop in a micro-SIM card for whichever country they are going, avoiding provider's high international fees.According to Apple, iPhone sales grew 113 percent year over year in the second quarter of its fiscal 2011, reaching a record high of 18.65 million units.

BEIJING, Sept. 6 (Xinhuanet) -- A short-term memory loss may suggest the Alzheimer's disease, according to a new study made by Spanish researchers.The finding was published on Monday, in Archives of General Psychiatry, an American Medical Association journal.The researchers gathered data of 116 people with mild cognitive impairment (MCI) who developed Alzheimer's disease within two years, 204 patients with the condition who didn't develop Alzheimer's and 197 people with no cognitive problems.Mild cognitive impairment is usually marked by difficulties with short-term memory, such as losing your train of thought repeatedly or having trouble remembering what you did yesterday, according to the study.After assessing them by biomarker tests and cognitive measures, the researcher found the cognitive markers can forecast the variance."Remarkably, they accounted for nearly 50% of the predictive variance," said Dr. Gomar of Centro de Investigation Biomedica en Red de Salud Mental, Barcelona, who led the research.Mild cognitive impairment at the start of the study was a stronger predictor of Alzheimer's than most biomarkers, the researchers concluded.