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LOS ANGELES, July 22 (Xinhua) -- Two teams of astronomers have discovered the largest and farthest reservoir of water ever detected in the universe, NASA's Jet Propulsion Laboratory (JPL) said on Friday.The water, equivalent to 140 trillion times all the water in the world's ocean, surrounds a huge, feeding black hole, called a quasar, more than 12 billion light-years away, according to JPL in Pasadena, California."The environment around this quasar is very unique in that it's producing this huge mass of water," said Matt Bradford, a scientist at JPL. "It's another demonstration that water is pervasive throughout the universe, even at the very earliest times. "This artist's concept illustrates a quasar, or feeding black hole, similar to APM 08279+5255, where astronomers discovered huge amounts of water vapor. Gas and dust likely form a torus around the central black hole, with clouds of charged gas above and below. X-rays emerge from the very central region, while thermal infrared radiation is emitted by dust throughout most of the torus. While this figure shows the quasar's torus approximately edge-on, the torus around APM 08279+5255 is likely positioned face-on from our point of view.A quasar is powered by an enormous black hole that steadily consumes a surrounding disk of gas and dust. As it eats, the quasar spews out huge amounts of energy. Both groups of astronomers studied a particular quasar called APM 08279+5255, which harbors a black hole 20 billion times more massive than the sun and produces as much energy as a thousand trillion suns.Astronomers expected water vapor to be present even in the early, distant universe, but had not detected it this far away before. There's water vapor in the Milky Way, although the total amount is 4,000 times less than in the quasar, because most of the Milky Way's water is frozen in ice. Water vapor is an important trace gas that reveals the nature of the quasar. In this particular quasar, the water vapor is distributed around the black hole in a gaseous region spanning hundreds of light-years in size (a light-year is about six trillion miles).Its presence indicates that the quasar is bathing the gas in X- rays and infrared radiation, and that the gas is unusually warm and dense by astronomical standards, JPL said.Although the gas is at a chilly minus 63 degrees Fahrenheit ( minus 53 degrees Celsius) and is 300 trillion times less dense than Earth's atmosphere, it's still five times hotter and 10 to 100 times denser than what's typical in galaxies like the Milky Way, said JPL.Measurements of the water vapor and of other molecules, such as carbon monoxide, suggest there is enough gas to feed the black hole until it grows to about six times its size, JPL said.Whether this will happen is not clear, the astronomers say, since some of the gas may end up condensing into stars or might be ejected from the quasar.Bradford's team made their observations starting in 2008, using an instrument called "Z-Spec" at the California Institute of Technology's (Caltech's) Submillimeter Observatory, a 33-foot (10- meter) telescope near the summit of Mauna Kea in Hawaii. Follow-up observations were made with the Combined Array for Research in Millimeter-Wave Astronomy (CARMA), an array of radio dishes in the Inyo Mountains of Southern California.The second group, led by Dariusz Lis, senior research associate in physics at Caltech and deputy director of the Caltech Submillimeter Observatory, used the Plateau de Bure Interferometer in the French Alps to find water. In 2010, Lis's team serendipitously detected water in APM 8279+5255, observing one spectral signature.Bradford's team was able to get more information about the water, including its enormous mass, because they detected several spectral signatures of the water, according to JPL.

BEIJING, July 17 (Xinhua) -- China's land prices in 105 cities rose 1.87 percent on average in the second quarter over the first, but the rate of growth slowed, the China Urban Land Price Dynamic Monitor, a land price information provider, announced Sunday. < In the second quarter, land price for business properties averaged 5,506 yuan (about 847 U.S. dollars) per square meter, up 2.77 percent from the previous quarter. The growth rate slowed by 0.56 percentage points.Land price for residential properties averaged 4,443 yuan per square meter, up 2.17 percent. The growth slowed by 0.27 percentage points. The price for industrial uses, meanwhile, was up 1.13 percent to reach 645 yuan per square meter. The growth fell 0.3 percentage points.The country's three most prosperous regions, the Yangtze River Delta Region, Pearl River (Zhujiang) Delta Region, and the Bohai Rim, all reported slower land price growth in the second quarter.

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.

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.

GENEVA, Sept. 26 (Xinhua) -- Two million people worldwide are estimated to die from air pollution each year, the Geneva based World Health Organization (WHO) said in its air quality report published on Monday.According to data collected by the WHO from nearly 1,100 cities across 91 countries, elevated level of fine particle pollution, which could cause heart diseases, lung cancer, asthma and acute lower reparatory infections, are common across many urban areas, with some cities registering fine particle pollution levels 15 times as much as the WHO guidelines.For both developed and developing countries, the biggest 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.Residential wood and coal burning for space heating is said to be an important contributor to air pollution, especially in rural areas during colder months, the WHO report said.