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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, Aug. 30 (Xinhua) -- China's second moon orbiter, the Chang'e-2, has arrived in outer space about 1.5 million km away from Earth and is now orbiting the second Lagrange Point (L2), where gravity from the sun and Earth balances the orbital motion of a satellite, Chinese scientists said Tuesday.Chang'e-2 entered L2's orbit at 11:27 p.m. last Thursday after spending 77 days traveling away from its previous orbital path around the moon, according to the State Administration of Science, Technology and Industry for National Defence (SASTIND).The SASTIND said that China is now the world's third country or organization to successfully put a spacecraft into orbit around L2, after the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA) of the United States.The Chang'e-2 orbiter will carry out exploration activities around L2 in the coming year, SASTIND said.There are five so-called "Lagrange Points" about 1.5 million km way from the Earth in the exact opposite direction from the sun. Putting a spacecraft at any of these points allows it to stay in a fixed position relative to the Earth and sun with a minimal amount of energy needed for course correction.The orbiter completed all of its assigned tasks after blasting off on Oct. 1, 2010, according to the SASTIND. Although the orbiter was only supposed to remain in space for six months, the SASTIND decided to assign additional tasks to it, as it still had fuel in its reserve tanks.Traveling into outer space from the moon's orbit was one of the orbiter's most important missions, according to the SASTIND.Before arriving at its current position in outer space, the Chang'e-2 took photos of the northern and southern poles of the moon. It then descended to a lower orbit, approximately 15 km away from the moon's surface, where it captured high-resolution images of the Sinus Iridum, or "Bay of Rainbows," an area where future moon probes may land.The SASTIND is reportedly planning to launch measure and control stations into outer space by the end of the second half of next year. The Chang'e-2 will be used to test the two stations' functionality at that time.China's ambitious three-stage moon mission will include a moon landing, as well as the launch of a moon rover during the second stage, which is scheduled to take place in 2012. During the third phase, another rover will land on the moon and return to Earth with lunar soil and stone samples for scientific research around 2017.China does not currently have a timetable in place for a manned moon landing. It launched its first lunar probe, the Chang'e-1, in October 2007.In 2003, China became the third country after Russia and the United States to send a human into space. Two more manned space missions followed, the most recent of which took place in 2008.0 The Chang'e probes are named after the Chinese legendary goddess of the moon.

SYDNEY, Sept. 5 (Xinhua) -- Australian scientists believe " brown fat," a wondrous tissue that burns energy to generate heat, could help people fight obesity, local media reported on Monday.A research team from Sydney's Garvan Institute of Medical Research (GIMR) has worked out how to grow brown fat from stem cells biopsied from adults, raising hopes that one day brown fat could be transplanted in obese people to speed up calories they burn, the Australian Associated Press (AAP) reported.Garvan endocrinologist Paul Lee, who led the research, is optimistic about targeting brown fat as an obesity intervention, commenting "it's a highly metabolically active form of fat, and very exciting that we may be able to stimulate its growth in people."People are born with supplies of brown fat around their neckline to keep them warm as infants, according to scientists at GIMR.Scientists now know that brown fat is present in most, if not all, adults mainly just behind the collarbone.Studies have found that adults with brown fat are slimmer than those without."Although this is early work, it is a proof of concept study showing that the growth of brown fat cells is possible, using precursor cells taken from adult humans, under appropriate stimulation," Lee said."Regardless of whether or not someone has lots of or little brown fat, the precursor cells are universally present. Under the appropriate growth factor and hormonal stimulation, the cells all grow and differentiate into mature brown fat cells."However, Lee warned more work was needed.Lee said even if brown fat was transplanted into obese people or drugs developed to stimulate the growth of brown fat, exercise and a healthy diet would still be crucial to aiding weight loss."So I don't think this is a solution to obesity because there are so many other factors (involved in obesity)," he said."Despite how efficient brown fat is at burning energy, we would only need a few doughnuts to diminish or negate its benefits."Lee said it would be years before tests could be carried out on brown fat transplants.In the meantime, he is expanding his study to test different ways to grow brown fat.His study, to be printed in the October issue of Endocrinology, has been published in the online edition of the journal.

LOS ANGELES, June 5 (Xinhua) -- U.S. researchers have developed two new drugs that can prolong the lives of patients with advanced melanoma, it was announced on Sunday.Research on both drugs was presented at the on-going annual meeting of the American Society of Clinical Oncology in Chicago, according to HealthDay News.This is the first big news in years for treatment of melanoma, one of the deadliest forms of skin cancer and one that is notoriously difficult to treat, let alone cure, the report said.The first treatment, vemurafenib, inhibits a gene mutation harbored in half of all melanoma patients, but is not yet approved by the U.S. Food and Drug Administration.The other drug, Yervoy (ipilumumab), is an immune system therapy that won approval in March."The March FDA approval of ipilumumab (Yervoy) was the first new drug approval for melanoma in 13 years," said Tim Turnham, executive director of the Melanoma Research Foundation.The two drugs were developed by researchers at Memorial Sloan- Kettering Cancer Center in New York City, the report said."This is really a huge step toward personalized care in melanoma," Dr. Paul Chapman, lead author of the first study and the attending physician in the melanoma/sarcoma service at Memorial Sloan-Kettering, said in a statement. "This (vemurafenib) is the first successful melanoma treatment tailored to patients who carry a specific gene mutation in their tumor, and could eventually become one of only two drugs available that improves overall survival in advanced cancers.""Having two trials that show a benefit in survival in patients with melanoma, both of these in first-line settings -- we weren't here just a few years ago," said Dr. Stephen Hodi, director of the Melanoma Center at Dana Farber Cancer Institute in Boston. "These are huge, paradigm-shifting results for the field."In the vemurafenib trial, sponsored by the drug's makers, researchers randomly assigned 675 patients with advanced, inoperable melanoma to receive either the chemotherapy drug dacarbazine or vemurafenib. Vemurafenib targets the V600E mutation in the BRAF gene.At the three-month mark, patients taking vemurafenib were 63 percent less likely to die and 74 percent less likely to die or see their cancer return, compared to patients taking dacarbazine alone.Few patients had side effects in the vemurafenib group, although some did develop squamous cell carcinoma, a less dangerous form of skin cancer.This is the first drug that has been proven superior to chemotherapy in this group of hard-to-treat patients, the researchers said."There was such a substantial benefit that we recommended that patients cross over," Chapman said at a Sunday news briefing. "It' s unprecedented to report a trial this early. The median follow-up time was three months." Yet the differences between the two groups became evident almost immediately.Dr. Lynn Schuchter, co-moderator of the briefing and division chief of hematology-oncology at Abramson Cancer Center of the University of Pennsylvania in Philadelphia, said symptoms subsided in some patients almost immediately, enabling them to cut back on pain medication in just 72 hours."The median time to progression with dacarbazine was 1.6 months versus three months with vemurafenib, which is a huge difference," said Chapman.In the second study, about 500 patients were randomly picked to receive Yervoy plus dacarbazine or dacarbazine alone.Those taking both drugs lived a median of 11.2 months compared to 9.1 months for those taking dacarbazine alone. Time to recurrence of disease was about the same for both groups: 2.8 months and 2.6 months, respectively.Almost half of those taking the combination therapy were alive after one year, compared to 36.3 percent in the other group. After two years, the rates were 28.5 percent and 17.9 percent, respectively.By three years out, 20.8 percent of those in the combination group were alive compared with 12.2 percent of those taking chemotherapy alone.This is the first study to combine chemotherapy and immunotherapy both safely and effectively.A study to test vemurafenib in combination with Yervoy has already begun, according to HealthDay News.