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LOS ANGELES, June 17 (Xinhua) -- The size of low-oxygen zones created by respiring bacteria is extremely sensitive to changes in depth caused by oscillations in climate, thus posing a distant threat to marine life, a new study suggests."The growth of low-oxygen regions is cause for concern because of the detrimental effects on marine populations -- entire ecosystems can die off when marine life cannot escape the low- oxygen water," said lead researcher Curtis Deutsch, assistant professor of atmospheric and oceanic sciences at University of California, Los Angeles."There are widespread areas of the ocean where marine life has had to flee or develop very peculiar adaptations to survive in low- oxygen conditions," Deutsch said in the study to be published in an upcoming print edition of the journal Science.A team led byDeutsch used a specialized computer simulation to demonstrate for the first time that fluctuations in climate can drastically affect the habitability of marine ecosystems.The study also showed that in addition to consuming oxygen, marine bacteria are causing the depletion of nitrogen, an essential nutrient necessary for the survival of most types of algae."We found there is a mechanism that connects climate and its effect on oxygen to the removal of nitrogen from the ocean," Deutsch said. "Our climate acts to change the total amount of nutrients in the ocean over the timescale of decades."Low-oxygen zones are created by bacteria living in the deeper layers of the ocean that consume oxygen by feeding on dead algae that settle from the surface. Just as mountain climbers might feel adverse effects at high altitudes from a lack of air, marine animals that require oxygen to breathe find it difficult or impossible to live in these oxygen-depleted environments, Deutsch said.Sea surface temperatures vary over the course of decades through a climate pattern called the Pacific Decadal Oscillation, during which small changes in depth occur for existing low-oxygen regions, Deutsch said. Low-oxygen regions that rise to warmer, shallower waters expand as bacteria become more active; regions that sink to colder, deeper waters shrink as the bacteria become more sluggish, as if placed in a refrigerator."We have shown for the first time that these low-oxygen regions are intrinsically very sensitive to small changes in climate," Deutsch said in remarks published Friday by the American Association for the Advancement of Science on its website. "That is what makes the growth and shrinkage of these low-oxygen regions so dramatic."Molecular oxygen from the atmosphere dissolves in sea water at the surface and is transported to deeper levels by ocean circulation currents, where it is consumed by bacteria, Deutsch said."The oxygen consumed by bacteria within the deeper layers of the ocean is replaced by water circulating through the ocean," he said. "The water is constantly stirring itself up, allowing the deeper parts to occasionally take a breath from the atmosphere."A lack of oxygen is not the only thing fish and other marine life must contend with, according to Deutsch. When oxygen is very low, the bacteria will begin to consume nitrogen, one of the most important nutrients that sustain marine life."Almost all algae, the very base of the food chain, use nitrogen to stay alive," Deutsch said. "As these low-oxygen regions expand and contract, the amount of nutrients available to keep the algae alive at the surface of the ocean goes up and down. "Understanding the causes of oxygen and nitrogen depletion in the ocean is important for determining the effect on fisheries and fish populations, he said.

CANBERRA, June 10 (Xinhua) -- Going to work when you are feeling sick can make you sicker in the long run, an expert told Australia's media on Friday.New Zealand sociologist Professor Kevin Dew from the Victoria University in Wellington, has assessed more than 40 papers about " presenteeism".He defined presenteeism as: "People that are turning up at work when they feel that they should be at home sick.""People feel compelled to go to work because someone else would have to take up the workload (and they have a) feeling of responsibility for not being able to care properly for patients (if they don't show up)," he told the Australia Associated Press on Friday.He said that evidence suggested people who go to work when they are sick can have long term negative effects on health and productivity.Evidence shows that presenteeism increases illness, including musculoskeletal pain, fatigue, depression, and serious coronary events. It also leads to exhaustion which, in turn, leads to more presenteeism.Prof. Dew said certain medical conditions like depression and migraine are also linked with presenteeism because they are not seen as legitimate reasons for absence.He has written an editorial in the latest issue of the British Medical Journal about his findings.

THE HAGUE, Aug. 16 (Xinhua) -- ESBL-enzymes, which are known for their ability to stop the effects of antibiotics, can directly pass from chicken to people, said a research published on Tuesday.Veterinary researcher Dik Mevius of the Wageningen University released the finding in the magazine Resource.The research group led by Mevius has isolated six ESBL-genes varieties and compared them to bacteria found on hospital patients, on super market poultry and in laying batteries. In 35 percent of all cases, they discovered a match of 100 percent.Bacteria like Klebsiella on E. coli can produce the ESBL-enzymes. A healthy person will not feel any effect, but people with a lower immune system can get very sick. In areas like a hospital, the infection can easily spread."The main concern is that the enzyme resists the most used antibiotics, which makes the treatment of infected persons difficult," said Mevius.According to Mevius, 94 percent of supermarket poultry carries the enzyme, but all enzymes will be killed during the heating process of cooking.

COPENHAGEN, May 29 (Xinhua) -- The number of confirmed E.coli cases has risen to 11 with at least another eight persons suspected of having the intestinal infection in Denmark, according to Denmark's National Serum Institute on Sunday.Five of the confirmed cases show symptoms of kidney failure which marks an advanced stage of the sickness, the institute said.Danish cucumbers are suspected of helping spread the E. coli bacteria believed to be causing a deadly outbreak of intestinal infection in Denmark and Germany, local media reported Sunday.The Danish cucumbers were mixed in Germany with cucumbers originating in the Netherlands, making it difficult to determine if Danish cucumbers are in fact contaminated.Denmark's Veterinary and Food Administration (DVFA) had earlier said the suspicion against Danish cucumber was "vague", but advised Danish consumers not to eat raw tomatoes, lettuces and cucumbers from Germany, and cucumber from Spain.It is now checking Danish cucumbers for traces of E. coli with results expected on Tuesday.Some Danish retailers have now removed these products from their supermarket shelves. And the Danish branch of fast-food chain McDonald's announced Saturday that it was dropping fresh cucumbers from its menu until further notice.The infection, which is food-borne, can be caused by eating raw or uncooked foods such as vegetables contaminated with the E. coli bacteria.Symptoms of infection include mild fever, bloody diarrhea and vomiting, and can last five to seven days. It can prove fatal in the very young, sick, or elderly.

SAN FRANCISCO, Sept. 22 (Xinhua) -- Facebook on Thursday introduced Timeline, a new profile design featuring milestones of one's life on a single page.At Facebook's f8 developer conference, Chief Executive Officer Mark Zuckerberg promoted the new feature, a blog-like presentation that let users scrolls vertically through the big moments of one's life."It's how you can tell the whole story of your life in a single page," said Zuckerberg, showing his Timeline which started from a baby photo.Zuckerberg assured users that they have complete control over their Timeline, saying that they can decide what content will appear and who can see it. The new feature will be available in a few weeks.Half a billion people are using Facebook in the world everyday, according to Zuckerberg.

来源：资阳报