安康在线咨询孕产科医生安康怀孕多久做b超可以看出来,安康孕早期吃什么有利于胎心胎芽发育,安康外阴肿大的原因,安康孕周到底以什么为准,安康早孕试纸弱阳性,安康排卵期痛同房几个月为啥没怀孕,安康怀孕试纸一深一浅

CANBERRA, Sept. 24 (Xinhua) -- Australian scientists on Saturday said a satellite due to re-enter Earth poses a negligible threat to life and property on Earth.U.S. National Aeronautics and Space Administration's Upper Atmosphere Research Satellite (UARS), which weighs more than five tons, is expected to re-enter the Earth's atmosphere at 1058 (AEST) on Saturday. The U.S.-based Center for Orbital and Re-entry Debris Studies estimates that re-entry could occur up to seven hours before or after this time.According to Nonathan Nally, a former editor of two space magazines and currently editor of the Australian Space News website, the satellite poses a negligible threat to life and property on Earth."Most of the satellite will burn up on re-entry, with perhaps as many as 26 stronger or harder small pieces surviving to reach the surface," Nally said in a statement."But with the majority of the Earth comprising oceans or uninhabited (or very sparsely populated) remote regions, the chances are overwhelming that any pieces of UARS that survive re- entry will fall harmlessly and never be seen again."Since the spacecraft is no longer powered, U.S. National Aeronautics and Space Administration has no control over where it comes down, but Nally said there is a small chance that debris from the satellite could land in Australia.Debris from SkyLab, another satellite which plunged to Earth, was scattered over parts of Western Australia in 1979. Skylab weighed about 77 tonnes, many times more than the UARS.?Dr Alice Gorman, a lecturer in the Department of Archaeology, specializing in space archaeology, at Flinders University in South Australia, said the UARS satellite re-entry is very reminiscent of Skylab in 1979."There is the same exaggeration of the hazard through the media, public anxiety as the advance warning allows for speculation, and a lack of understanding of what the risks actually are," he said in a statement."Should it land in Australia, we might expect the same rush for souvenirs as we saw with Skylab, as anything that has been in space has a special meaning on Earth."?UARS was launched on 12 September 1991 and decommissioned on 15 December 2005. Its total dry mass is about 5.5 tonnes. UARS is one of the largest NASA satellites to plunge back to Earth uncontrolled in the last 30 years.Since the beginning of the Space Age in the late-1950s, there have been no confirmed reports of an injury resulting from re- entering space objects.? Nor is there a record of significant property damage resulting from a satellite re-entry.

PARIS, Sept. 21 (Xinhua) -- European heavy-lift launcher Ariane 5 lifted off two communication satellites Wednesday from the Kourou launch centre in French Guiana, live broadcast of the launching process showed.The rocket, carrying the two communication satellites Arabsat 5C and SES-2, was launched at GMT 2138.This was the fifth heavy-lift mission of Ariane 5 in 2011. Arianespace had planned six Ariane 5 missions through 2011.The satellite Arabsat-5C was developed for the Arab Satellite Communications Organization (Arabsat) to provide satellite capacity in both C-band and Ka-band frequencies for a wide range of communications services.Jointly produced by Europe's EADS Astrium and Thales Alenia Space, it will be positioned at 20 degree East orbital location to cover the Middle East and Africa.Manufactured by Orbital Sciences Corporation of the United States, SES-2 will join the fleet of European satellite telecommunications operator SES, and is to be positioned at 87 degree West for coverage over North America and the Caribbean.Both Arabsat-5C and SES-2 have life-spans as long as 15 years.This Ariane 5 dual-passenger mission was postponed from Tuesday due to local strikes of French Guiana workers.Founded in 1980 as the world's first launch service and solutions company, Arianespace planned to achieve six Ariane 5 missions through 2011. Through 2010, heavy-lift workhorse Ariane 5 finished six missions, sending a dozen spacecraft into expected orbits.The next mission from Arianespace centre in Kourou was scheduled for Oct. 20 by medium-lift vehicle Soyuz. It will be Soyuz' first mission from French Guiana with a pair of satellites for Europe's Galileo satellite navigation system.

LOS ANGELES, June 23 (Xinhua) -- The sun and its inner planets may have formed differently than previously thought, NASA's Jet Propulsion Laboratory (JPL) said on Thursday.Data revealed differences between the sun and planets in oxygen and nitrogen, which are two of the most abundant elements in our solar system, said JPL in Pasadena, Los Angeles.Although the difference is slight, the implications could help determine how our solar system evolved, JPL said.NASA researchers drew the conclusion after analyzing samples returned by NASA's 2004 Genesis mission, according to JPL.The air on Earth contains three different kinds of oxygen atoms which are differentiated by the number of neutrons they contain. Nearly 100 percent of oxygen atoms in the solar system are composed of O-16, but there are also tiny amounts of more exotic oxygen isotopes called O-17 and O-18. Researchers studying the oxygen of Genesis samples found that the percentage of O-16 in the sun is slightly higher than on Earth or on other terrestrial planets. The other isotopes' percentages were slightly lower."We found that Earth, the moon, as well as Martian and other meteorites which are samples of asteroids, have a lower concentration of the O-16 than does the sun," said Kevin McKeegan, a Genesis co-investigator from University of California, Los Angeles (UCLA) and the lead author of one of two papers published this week in Science journal. "The implication is that we did not form out of the same solar nebula materials that created the sun -- just how and why remains to be discovered." Another paper detailed differences between the sun and planets in the element nitrogen. Like oxygen, nitrogen has one isotope, N- 14, that makes up nearly 100 percent of the atoms in the solar system, but there is also a tiny amount of N-15. Researchers studying the same samples saw that when compared to Earth's atmosphere, nitrogen in the sun and Jupiter has slightly more N-14, but 40 percent less N-15. Both the sun and Jupiter appear to have the same nitrogen composition. As is the case for oxygen, Earth and the rest of the inner solar system are very different in nitrogen."These findings show that all solar system objects including the terrestrial planets, meteorites and comets are anomalous compared to the initial composition of the nebula from which the solar system formed," said Bernard Marty, a Genesis co- investigator from Petrographic and Geochemical Research Center in Fracne and the lead author of the other new Science paper. " Understanding the cause of such a heterogeneity will impact our view on the formation of the solar system."Data were obtained from analysis of samples Genesis collected from the solar wind, or material ejected from the outer portion of the sun. This material can be thought of as a fossil of our nebula because the preponderance of scientific evidence suggests that the outer layer of our sun has not changed measurably for billions of years."The sun houses more than 99 percent of the material currently in our solar system, so it's a good idea to get to know it better, " said Genesis Principal Investigator Don Burnett of the California Institute of Technology, Pasadena, California. "While it was more challenging than expected, we have answered some important questions, and like all successful missions, generated plenty more."Genesis was launched in August 2000. The spacecraft traveled to Earth's L1 Lagrange Point about one million miles from Earth, where it remained for 886 days between 2001 and 2004, passively collecting solar-wind samples.JPL managed the Genesis mission for NASA's Science Mission Directorate, Washington. The Genesis mission was part of the Discovery Program managed at NASA's Marshall Space Flight Center in Huntsville, Alasca.

BEIJING, Sept. 2 (Xinhuanet) -- Firefighters who worked in the wreckage of the World Trade Center in 2001 were 19 percent more likely to develop cancer than those who were not there, according to a study.The study, published Thursday in the British medical journal The Lancet, surveyed cancer occurrence in nearly 10,000 male firefighters in the seven years after Sept. 11, 2001. (There were too few women to create a meaningful sample size.)The 9/11 attacks occurred on Tuesday, Sept. 11, 2001. As a result, the World Trade Center collapsed, and nearly 3,000 Americans killed. Among the 2,753 victims killed in the World Trade Center were 343 firefighters.There were 263 cancer cases in the exposed population, showing a cancer rate 19 percent higher than that of the group not exposed.The study indicated that cancers like melanoma, non-Hodgkin’s lymphoma, thyroid and prostate cancer occurred more frequently among exposed firefighters than in the general population. But occurrences of lung cancer did not increase.The findings “provide information that there may be a significant cancer risk for these people”, said Dr. James Melius, the administrator of the New York State Laborers’ Health and Safety Trust Fund and one of the peer reviewers of the study.But the results were far from conclusive. “This is not an epidemic,” said Dr. David J. Prezant, a lead researcher and the chief medical officer for the New York Fire Department.

CANBERRA, Sept. 9 (Xinhua) -- Managing other people at work triggers structural changes in the brain, protecting its memory and learning center well into old age, Australia's study revealed on Friday.Australia's University of New South Wales (UNSW) researchers have, for the first time, identified a clear link between managerial experience throughout a person's working life, and the integrity and larger size of an individual's hippocampus (the area of the brain responsible for learning and memory) at the age of 80. "We found a clear relationship between the number of employees a person may have supervised or been responsible for and the size of the hippocampus," Dr Michael Valenzuela, Leader of Regenerative Neuroscience in UNSW's School of Psychiatry, said in a statement released on Friday."This could be linked to the unique mental demands of managing people, which requires continuous problem solving, short term memory and a lot of emotional intelligence, such as the ability to put yourself in another person's shoes. Over time this could translate into the structural brain changes we observed."The findings confirmed that staying mentally active promotes brain health, potentially warding off neurodegenerative diseases such as Alzheimer's.Using MRI imagery in a cohort of 75-92 year-olds, researchers found larger hippocampal volumes in those with managerial experience compared to those without. The effect was also seen in women who had taken on managerial roles in nursing or teaching, for example.The study was presented at this week's Brain Sciences UNSW symposium Brain Plasticity The Adaptable Brain, held in Australia.