拉萨高级电脑儿童心肺复苏模拟人(带考核功能)济南宫腔镜手术训练模型,兰州立体狗牙,平顶山小儿腹腔穿刺模型,甘肃5部件纵隔模型,广东高级胰岛素注射练习模型,杭州产前宫颈变化与产道关系模型,福州烤瓷牙专用体制备

BEIJING, August 1 (Xinhuanet) -- U.S. researchers have discovered a genetic mutation unique to African Americans that links to heighten their asthma risk, according to reports published on Sunday in the journal Nature Genetics.Researchers of University of Chicago found a gene, PYHIN1, and its variations may account for asthma risk in people of African descent. In their study, they examined data from nine previous genome-wide association studies, totaling more than 2 million single nucleotide polymorphisms in 3,246 asthma patients and 3,385 control patient, 1,702 patient-parent groupings, 355 family-based cases, and 468 family-based controls.In the study, the researchers found that between 26 percent and 29 percent of people of African-descent carried at least one copy of the gene.  In particular, one polymorphism of the gene was 34 percent more likely found in African-American and Afro-Caribbean people with asthma.  More interestingly, this variant of the gene is rarely found in Caucasian people and in Latino population, it was found in less than 5 percent.This new variant is part of a family of genes linked with the body's response to viral infections. It is thought to be involved in interferon signaling, which could influence the occurrence of asthma.The team stressed that each gene variant on its own plays only a small role in increasing asthma risk, but that risk could be multiplied when combined with other risk genes and with environmental factors.

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.

BEIJING, July 17 (Xinhua) -- Iraqi Prime Minister Nouri al-Maliki arrived in Beijing Sunday night for his first official visit to China as a guest of his Chinese counterpart Wen Jiabao.During al-Maliki's stay in China from Sunday to Thursday, President Hu Jintao will meet with him, and Premier Wen will hold talks with the Iraqi prime minister, Chinese Foreign Ministry spokesman Hong Lei said earlier.China and Iraq share a traditional friendship, Hong said, adding that the two countries have witnessed smooth development of bilateral relations, steadily growing economic cooperation and increasing cultural exchanges."China is ready to work with the international community and to continue to provide assistance for the Iraqi people to improve their livelihoods," said the spokesman.

BEIJING, Aug. 22 (Xinhuanet) -- Researchers have discovered how a human egg captures an incoming sperm for fertilization, paving the way to help couples suffering from infertility, according to media reports on Monday.An international team of researchers found that a sugar chain known as the sialyl-lewis-x sequence (SLeX) makes the outer coat of the egg “sticky,” which has proven to be helpful in binding the egg and the sperm.As a result, this observation has filled in a huge gap in the understanding of fertility and provides hope for ultimately helping couples who currently cannot conceive.Scientists and doctors know that a sperm identifies an egg when proteins on the head of the sperm match and bind to a series of specific sugars in the egg’s outer coating. With a successful match of proteins, the outside surfaces of the sperm and egg then bind together before merging, which is then followed by delivery of sperm’s DNA into egg.To identify this molecules, the researchers used ultra-sensitive mass-spectrometric imaging technology to observe and identify which molecules are most likely to be key in the binding process.They experimented with a range of synthesised sugars in the laboratory and found that it is SLeX that specifically binds sperm to an egg.According to the World Health Organisation, infertility affects about 15 percent of reproductive-aged couples around the world and almost one in every seven couples in Britain has problems conceiving a child for various reasons.

LOS ANGELES, Sept. 10 (Xinhua) -- Scientists at the University of California Los Angeles campus have announced that they have successfully used new prediction algorithms to forecast climate up to 16 months in advance.Professor Michael Ghil said in a UCLA news release Friday his team used new prediction algorithms based on matching ocean temperature records with new theories on how long-term climate trends are influenced by short-term weather extremes.That's twice as far into the future as previously accomplished.Ghil, a distinguished professor of climate dynamics in the UCLA Department of Atmospheric and Oceanic Sciences and senior author of the research, said the new prediction formulas will give climate experts and governments clues about long-term swings in the El Nino/La Nina oscillation in the Pacific Ocean, which drastically affects weather in the Americas, Asia and Australia.The new forecasting tool uses sea temperatures and has been tested on decades of historical data. The forecasts were then cross-checked against actual climate trends.The UCLA team also said that their 16-month forecasts were more accurate than previous forecasts that went only 8 months forward.Ghil emphasized that the forecasting tools are for climate, which is long-range, global patterns, but not for meteorology, which is short-term weather forecasting."Certain climate features might be predictable, although not in such detail as the temperature and whether it will rain in Los Angeles on such a day two years from now," said Ghil, who is also a member of UCLA's Institute of Geophysics and Planetary Physics. "These are averages over larger areas and longer time spans."The study is currently available online in the journal Proceedings of the National Academy of Sciences (PNAS) and will be published in an upcoming print edition of the journal.