郑州激光打近视多少钱(郑州近视治疗手术) (今日更新中)

SAN FRANCISCO, Aug. 15 (Xinhua) -- Facebook and Yahoo on Monday started to test "six degrees of separation," an iconic social experiment in the 1960s that showed everyone is on average approximately six steps away from any other person on earth.The current Facebook-Yahoo "small world" experiment, based on more than 750 million active Facebook users, is expected to determine the social path length between two strangers.Anyone with a Facebook account can participate by going to smallworld.sandbox.yahoo.com and will be assigned a "target person. " The participant will be asked to select one of his or her Facebook friends, whom will be forwarded a message and then pass the message from friend to friend so that the participant will get a message to the "target person" in as few steps as possible.The study is intended as academic social research and will be published in peer-reviews scientific journal, Duncan Watts, Yahoo' s principal research scientist who is leading the experiment, told San Jose Mercury News.In the 1960s, American social psychologist Stanley Milgram and other researchers conducted several experiments to examine the average path length for social networks of people in the United States, suggesting that human society is a small world type network by around 5.5 people steps or about six people on average.It is now currently accepted that there were potential flaws in the so-called "small world experiment" because the conclusions were based on relatively small number of research samples.

New York, Sept. 23 (Xinhua) -- A Chinese scientist was presented a prestigious U.S. award on Friday for the discovery of artemisinin, a drug therapy for malaria that has saved millions of lives across the globe, especially in the developing world.Pharmacologist Tu Youyou, 81, became the first scientist on the Chinese mainland to win Lasker Award, known as "America's Nobels" for their knack of gaining future recognition by the Nobel committee.Tu, a scientist at the China Academy of Chinese Medical Sciences in Beijing, pioneered a new approach to malaria treatment that has benefited hundreds of millions of people and promises to benefit many times more. By applying modern techniques and rigor to a heritage provided by 5000 years of Chinese traditional practitioners, she has delivered its riches into the 21st century."Not often in the history of clinical medicine can we celebrate a discovery that has eased the pain and distress of hundreds of millions of people and saved the lives of countless numbers of people, particularly children, in over 100 countries," Lucy Shapiro, a member of the award jury and professor of Stanford University, said while describing Tu' s discovery.Shapiro said the discovery, chemical identification, and validation of artemisinin, a highly effective anti-malarial drug, is largely due to the "scientific insight, vision and dogged determination" of Professor Tu and her team. She thought Professor Tu's work has provided the world with arguably the most important pharmaceutical intervention in the last half century."The discovery of artemisinin is a gift to mankind from traditional Chinese medicine," Tu said while receiving the award. "Continuous exploration and development of traditional medicine will, without doubt, bring more medicines to the world."

WASHINGTON, July 5 (Xinhua) -- Adhering to a healthy lifestyle, including not smoking, exercising regularly, having a low body weight and eating a healthy diet, appears to lower the risk of sudden cardiac death (SCD) in women, according to a study to be published Wednesday in the Journal of the American Medical Association."Sudden cardiac death (defined as death occurring within one hour after symptom onset without evidence of circulatory collapse) accounts for more than half of all cardiac deaths, with an incidence of approximately 250,000 to 310,000 cases annually in the United States," the authors write as background information in the study.Using data collected as part of the Nurses' Health Study, Stephanie Chiuve, of Brigham and Women's Hospital and Harvard Medical School, and colleagues examined the association between a healthy lifestyle and risk of SCD.A total of 81,722 women who participated in the Nurses' Health Study from June 1984 to June 2010 were included in the new study, and lifestyle factors were assessed via questionnaires every two to four years. A low-risk lifestyle was defined as not smoking, having a body mass index (BMI) of less than 25, exercise duration of 30 minutes/day or longer, and consuming a diet closely related to a Mediterranean-style diet (emphasizes high intake of vegetables, fruits, nuts, legumes, whole grains and fish, with moderate alcohol intake).During the 26 years of follow-up, there were 321 cases of SCD among women (average age 72 years at the time of the SCD event) in the study. All four low-risk factors were significantly and independently associated with a lower risk of SCD. Not smoking, exercising and eating a healthy diet each were inversely associated with risk of SCD. BMI also was associated with the risk of SCD, with women having a BMI between 21 and 24.9 at lowest risk.Women at low risk for all four lifestyle factors had a 92 percent lower risk of SCD when compared with women at low risk for none of the four lifestyle factors."In this cohort of female nurses, adherence to an overall healthy lifestyle was associated with a lower risk of SCD and may be an effective strategy for the prevention of SCD," the authors write.

CANBERRA, Aug. 17 (Xinhua) -- Australian scientist on Wednesday said his international research team has discovered the trick on how butterfly learn to change its wing pattern to avoid being eaten by birds.The Amazonian butterfly, Heliconius numata, has learnt to carry out a single genetic switch to alter its wing pattern so it appears to be another bad-tasting butterfly that birds will avoid.Dr. Siu Fai (Ronald) Lee from the Department of Genetics and Bio21 Institute at Australia's University of Melbourne was part of the international research team, which was led by scientists at Centre National de la Recherche Scientifique (CNRS) and the University of Exeter in United Kingdom.Dr. Lee said the historical mystery had puzzled researchers for decades."Charles Darwin was puzzled by how butterflies evolved such similar patterns of warning coloration," Dr. Siu Fai (Ronald) Lee from the Department of Genetics and Bio21 Institute at the University of Melbourne told Western Australia Today."We have now solved this mystery, identifying the region of chromosome responsible for changing wing pattern."He said the research team identified a genetic switch known as a supergene, which allowed the butterfly to morph into several different forms, allowing one species to mimic another."It is amazing that by changing just one small region of the chromosomes, the butterfly is able to fool its predators by mimicking a range of different butterflies that taste bad," he said."The butterflies rearrange this supergene DNA like a small pack of cards, and the result is new wing patterns. It means that butterflies look completely different but have the same DNA."There are other butterflies doing similar tricks, but this is the most elegant one."I was just fascinated by how elegant they were."He said the discovery proves that small chromosomal changes can preserve successful gene combinations, and thus help a species to adapt.The findings of the study are published on August 14 in the international journal Nature.

WASHINGTON, Aug. 4 (Xinhua) -- Researchers have found a way to turn mouse embryonic stem cells into sperm and this finding opens up new avenues for infertility research and treatment, according to a study published Thursday in the online edition of journal Cell,A Kyoto University team coaxed mouse embryonic stem cells into sperm precursors, called primordial germ cells (PGCs), and shown that these cells can give rise to healthy sperm. The researchers say that such in vitro reconstitution of germ cell development represents one of the most fundamental challenges in biology.When transplanted into mice that were unable to produce sperm normally, the stem cell derived PGCs produced normal-looking sperm, which were then used to successfully fertilize eggs. These fertilized eggs, when transplanted into a recipient mother, produced healthy offspring that grew into fertile male and female adult mice. The same procedure could produce fertile offspring from induced pluripotent stem cells that are often derived from adult skin cells."Continued investigations aimed at in vitro reconstitution of germ cell development, including the induction of female primordial germ cell-like cells and their descendants, will be crucial for a more comprehensive understanding of germ cell biology in general, as well as for the advancement of reproductive technology and medicine," the researchers wrote.

来源：资阳报