长安区冲刺排名(高陵区高一补习价格) (今日更新中)

WASHINGTON, Jan. 16 (Xinhua) -- A new study examining weather patterns around the worldwide pandemics of influenza, which caused widespread death and illness in 1918, 1957, 1968 and 2009, finds that each of them was preceded by La Nina conditions in the equatorial Pacific. The study findings are published online Monday in the Proceedings of the National Academy of Science.The study's authors -- Jeffrey Shaman of Columbia University's Mailman School of Public Health and Marc Lipsitch of the Harvard School of Public Health -- note that the La Nina pattern is known to alter the migratory patterns of birds, which are thought to be a primary reservoir of human influenza. The scientists theorize that altered migration patterns promote the development of dangerous new strains of influenza.To examine the relationship between weather patterns and influenza pandemics, the researchers studied records of ocean temperatures in the equatorial Pacific in the fall and winter before the four most recent flu pandemics emerged. They found that all four pandemics were preceded by below-normal sea surface temperatures -- consistent with the La Nina phase of the El Nino- Southern Oscillation.The authors cite other research showing that the La Nina pattern alters the migration, stopover time, fitness and interspecies mixing of migratory birds. These conditions could favor the kind of gene swapping or genetic reassortment that creates novel and therefore potentially more variations of the influenza virus."We know that pandemics arise from dramatic changes in the influenza genome. Our hypothesis is that La Nina sets the stage for these changes by reshuffling the mixing patterns of migratory birds, which are a major reservoir for influenza," says Shaman.Changes in migration not only alter the pattern of contact among bird species, they could also change the ways that birds come into contact with domestic animals like pigs. Gene-swapping between avian and pig influenza viruses was a factor in the 2009 swine flu pandemic.

WASHINGTON, Nov. 8 (Xinhua) -- Children with autism have more brain cells and heavier brains compared to typically developing children, according to a study to be published on Wednesday in the Journal of the American Medical Association.The small, preliminary study provides direct evidence for possible prenatal causes of autism.The prefrontal cortex is involved in various higher order functions such as language and communication, social behavior, mood, and attention. Children who have autism tend to show deficits in such functions.Eric Courchesne, of the University of San Diego School of Medicine Autism Center of Excellence, and colleagues conducted direct counts of brain cells in specific regions of the prefrontal cortex in postmortem brains of seven boys who had autism and six typically developing males, ranging in age from 2-16 years. Most participants had died in accidents, but the researchers did not base their selection on causes of death.The researchers found that children with autism had 67 percent more neurons in the prefrontal cortex and heavier brains for their age compared to typically developing children. Since these neurons are produced before birth, the study's findings suggest that faulty prenatal cell birth or maintenance may be involved in the development of autism. Another possible factor that may contribute to the neuronal excess is a reduction in apoptosis, or programmed cell death, which normally occurs during the third trimester and early postnatal life.Though small, this preliminary study examined all relevant postmortem tissue available at the time. The relative scarcity of tissue from very young children may limit future research as well, but efforts to include a larger number of samples are needed to confirm these findings and to identify patterns of age-related changes in autism, the researchers say."Earlier studies of head circumference and early brain overgrowth have pointed us in this direction, but there have been few quantitative neuroanatomical studies due to the lack of postmortem tissue from children with autism," said Thomas Insel, director of the National Institute of Mental Health, in a statement. "These new results, along with an earlier study reporting altered wiring of the prefrontal cortex, focus our attention on this critical area of the brain in autism."

OTTAWA, Oct. 26 (Xinhua) -- Canadians are working about three years longer before retirement than they were in the 1990s, and have a longer life in retirement, an official study said Wednesday.Statistics Canada, the federal statistics agency, reports that Canada' s men and women, who don't face compulsory retirement, are increasingly choosing to delay retirement, as part of a long-term trend that has begun before the recent recession.The trend of later retirement dates back to the mid-1990s, when a 50-year-old employee could expect to work another 12.5 years before retiring from the daily grind.Today, that same 50-year-old worker could expect another 16 years of employment.The study says that 34 percent of Canadians aged 55 and older were employed in 2010, compared to just 22 percent in 1996.A longer working life would unnecessarily imply a shorter life in retirement due to increased life expectancy, the study says.The study notes that men and women leaving the work force today are spending as much time in their post-career life as many of their predecessors did.For example, between 1977 and 1994, the typical retirement length for a man in Canada rose from 11.2 to 15.4 years; as of 2008, it was 15 years.For women, the average retirement length similarly rose from 16.4 to 20.6 years between 1977 and 1996; as of 2008, it was 19 years.From another point of observation, 50-year-old men can expect to spend 48 percent of their remaining years of life in retirement in 2008,compared with 45 percent in 1977.In 2008, 50-year-old women could expect to spend 55 percent of their remaining years of life in retirement, nearly identical to the proportion in 1977.

HONOLULU, United States, Nov. 12 (Xinhua) -- Chinese President Hu Jintao said here Saturday that China will deepen economic structural reform, grow a green economy, enhance protection of intellectual property rights and open wider to the outside world.Hu made the remarks at the CEO summit of the Asia-Pacific Economic Cooperation (APEC) ahead of the APEC Economic Leaders' Meeting.Hu noted that while China's economy has grown steadily and the country is opening wider to the outside world, China still faces the major challenge of unbalanced, uncoordinated and unsustainable development.China, he said, will continue to deepen reform and opening-up, improve people's livelihood and promote sustained, steady and fairly fast economic growth and social harmony and stability.Hu then laid out a four-point proposal to achieve the goals, with the first being that China will deepen economic structural reform and improve business and investment environment.Second, China will honor its commitment to growing a green economy and promoting the conservation culture, Hu said.From 2011 to 2015, China's investment in the environmental sector will double that of the previous five years to about 3.1 trillion yuan (about 488.5 billion U.S. dollars), Hu said, adding that China's green industry is a key area for foreign investment.Third, China will step up protection of intellectual property rights and make itself a country driven by innovation, he said.China will vigorously boost scientific and technological innovation and turn enterprises into major players of such innovation, while further improving the legal system for intellectual property rights protection, he said.Fourth, China will open wider to the outside world and take an active part in global economic governance and regional cooperation, Hu said.China, he said, will give equal importance to import and export and focus more on increasing import while maintaining a stable level of export.Noting that China's development constitutes an important force driving regional and global economic growth, Hu said that China will work together with others to create a better future for the Asia-Pacific region.

SAN FRANCISCO, Oct. 4 (Xinhua) -- Apple Inc. on Tuesday unveils iPhone 4S, the much-anticipated latest generation of iPhone.At the event held at Apple headquarters in Cupertino, California, U.S., newly installed Chief Executive Officer Tim Cook took stage to give a general introduction of Apple's products, his first product presentation after taking over the reins from Steve Jobs in August.According to Apple, there are several key features that make the new iPhone 4S different from the current iPhone 4. With a 3.5- inch widescreen multitouch display, the new device features dual- core A5 processor, the chip used in the iPad 2, and a higher- resolution eight megapixel camera which can grab 73 percent more light and take a 1080p high-definition video.The battery can support internet use up to six hours on 3G network and nine hours on Wi-Fi, as well as talk time up to eight hours on 3G and 14 hours on 2G. U.S., newly installed Chief Executive Officer Tim Cook takes stage to give a general introduction of Apple's products, Oct. 4, 2011. Apple Inc. on Tuesday unveils iPhone 4S, the much-anticipated latest generation of iPhone.Based on the dual-antenna design of iPhone 4, Apple said that iPhone 4S can intelligently switch back and forth between them to send and receive, improving the reception and throughput on the device. The iPhone 4S is also a world phone, which means both GSM and CDMA network customers can roam internationally on GSM networks on a single phone. It also supports HSPA+, a 4G mobile technology that allows for data transmission speeds up to 42 Mbps.Another important feature is the new voice control called Siri, an intelligent assistant that helps users get things done just by asking questions, such as call people, reminders, compose and dictate email, weather, stocks, search web and etc..For example, Siri understands users who are looking for a weather forecast when they ask questions like "Do I need an umbrella today," "What's the upcoming forecast," and "Is the weather going to get worse today."The iPhone 4S will run the latest version of Apple's mobile operating system iOS 5, which will be available as free update next Wednesday. The new iOS 5 has more than 200 new features, such as a deep Twitter integration, Notification Center and iMessage, a new messaging service.The latest smartphone also comes with the launch of iCloud, Apple's cloud computing service which automatically and wirelessly store users' content and push it to all Apple devices from mobile devices and music players to desktops and notebooks. Apple will launch iCloud next Wednesday."iPhone 4S plus iOS 5 plus iCloud is a breakthrough combination that makes the iPhone 4S the best iPhone ever," said Philip Schiller, Apple's senior vice president of Worldwide Product Marketing. "While our competitors try to imitate iPhone with a checklist of features, only iPhone can deliver these breakthrough innovations that work seamlessly together," said Schiller, who led the iPhone 4S introduction at the Tuesday's event.The new iPhone 4S will start at 199 U.S. dollars with a storage capacity of 16 GB and 399 dollars for the 64 GB model. The pre- orders begin on Friday and the phone will ship next Friday. Apple said that iPhone will be in 70 countries and regions, on 100 carriers when the roll out is done. In the United States, along with AT&T and Verizon, iPhone 4S will also come to Sprint, the third-largest mobile-phone carrier in the country.

来源：资阳报