郑州18岁激光治疗近视(郑州眼科咨询医生) (今日更新中)

WASHINGTON, May 11 (Xinhua) -- NASA's Dawn spacecraft has obtained its first image of the giant asteroid Vesta, which will help fine-tune navigation during its approach, the U.S. space agency announced Wednesday.Dawn expects to achieve orbit around Vesta on July 16, when the asteroid is about 117 million miles from Earth.The image from Dawn's framing cameras was taken on May 3 when the spacecraft began its approach and was approximately 752,000 miles (1.21 million km) from Vesta. The asteroid appears as a small, bright pearl against a background of stars. Vesta also is known as a protoplanet, because it is a large body that almost formed into a planet."After plying the seas of space for more than a billion miles, the Dawn team finally spotted its target," said Carol Raymond, Dawn's deputy principal investigator at NASA's Jet Propulsion Laboratory in Pasadena, California. "This first image hints of detailed portraits to come from Dawn's upcoming visit."Vesta is 330 miles (530 km) in diameter and the second most massive object in the asteroid belt. Ground- and space-based telescopes obtained images of the bright orb for about two centuries, but with little surface detail.Mission managers expect Vesta's gravity to capture Dawn in orbit on July 16. To enter orbit, Dawn must match the asteroid's path around the sun, which requires very precise knowledge of the body's location and speed. By analyzing where Vesta appears relative to stars in framing camera images, navigators will pin down its location and enable engineers to refine the spacecraft's trajectory.Dawn will start collecting science data in early August at an altitude of approximately 1,700 miles (2,700 km) above the asteroid's surface. As the spacecraft gets closer, it will snap multi-angle images allowing scientists to produce topographic maps. Dawn will later orbit at approximately 120 miles (200 km) to perform other measurements and obtain closer shots of parts of the surface. Dawn will remain in orbit around Vesta for one year. After another long cruise phase, Dawn will arrive in 2015 at its second destination, Ceres, an even more massive body in the asteroid belt.Gathering information about these two icons of the asteroid belt will help scientists unlock the secrets of our solar system's early history. The mission will compare and contrast the two giant asteroids shaped by different forces. Dawn's science instruments will measure surface composition, topography and texture. Dawn also will measure the tug of gravity from Vesta and Ceres to learn more about their internal structures. The spacecraft's full odyssey will take it on a 3-billion-mile (5-billion-km) journey, which began with its launch in September 2007.

SAN FRANCISCO, March 8 (Xinhua) -- Google on Tuesday released a new stable version of its Chrome web browser, which the company said is speedier, simpler and safer."With today's stable release, even your most complex web apps will run more quickly and responsively in the browser," Tim Steele, a Google software engineer, said in a blog post announcing the release.The new version of Chrome features a simpler settings page that opens in a tab rather than a dialog box, and contains a search box showing users the settings they are looking for while they type.Users can also synchronize passwords in the browser across their computers, and will be able to encrypt those passwords for extra security.Google said that the latest Chrome browser provides additional layer of protection against malicious web pages, with the extended application of sandboxing technology.The browser can be downloaded for free, and current Chrome users will be automatically updated to the new version soon, Google said.

SHANGHAI, March 17 (Xinhua) -- Lenovo Group and a subsidiary of Shanghai Media Group (SMG) signed an agreement on Thursday to create a firm that would provide mobile-Internet video services.BesTV New Media Co., a subsidiary of SMG, owns 51 percent of the venture, named Shanghai Video Cloud Company Limited, while Lenovo owns the remainder. The total investment of both parties in the new firm exceeded 10 million yuan (1.52 million U.S. dollars), according to the agreement.Lenovo is currently the largest personal computer maker in China. BesTV New Media is a provider of Internet Protocol Television (IPTV), mobile television and other forms of new media. 

LOS ANGELES, May 9 (Xinhua) -- Drinking alcohol may raise the likelihood among teenagers to spend more time on computers, a new study suggests.The study, conducted by researchers at Weill Cornell Medical College, was based on a survey of 264 teenagers, aged 13 to 17.Results showed that compared with teens who did not report drinking, those who drank alcohol in the last month used a computer more hours per week for non-school-related activities, including the use of social networking sites.Drinking was also linked to more frequent social networking and listening to and downloading music, according to the study published Monday in the on-line edition of the journal Addictive Behaviors.However, there was no demonstrated link between alcohol use and computer use for school work, neither there was strong link between video games and drinking or on-line shopping and drinking."While the specific factors linking teenage drinking and computer use are not yet established, it seems likely that adolescents are experimenting with drinking and activities on the Internet," said Dr. Epstein, assistant professor of public health at the college."In turn, exposure to on-line material such as alcohol advertising or alcohol-using peers on social networking sites could reinforce teens' drinking."Children are being exposed to computers and the Internet at younger ages. For this reason it's important that parents are actively involved in monitoring their children's computer usage, as well as alcohol use."Teenagers typically first experiment with alcohol at age 12 or 13, according to the study.Family risk factors include lax parental supervision and poor communication, family conflicts, inconsistent or harsh discipline and a family history of alcohol or drug abuse."According to a national study conducted by the Pew Internet and American Life Project, more than half of parents of teenagers had filters installed on the computers their child uses to block content parents find objectionable, yet many parents do not use any form of parental monitoring, particularly for older teens," Epstein said.

BEIJING, Feb. 20 (Xinhua) -- China's railways handled 7.13 million passengers Saturday, setting a new one day record, the Ministry of Railways (MOR) said Sunday.The figure was 16 percent higher year on year, the MOR said.Chinese railways are witnessing a new wave of travel after the Lantern Festival celebration (the 15th day of the first month in the Lunar New Year) Thursday, which is considered a symbolic ending of the festival season.China's Spring Festival fell on Feb. 3 this year.The busy Spring Festival transportation season runs for 40 days and is calculated in two phases: 15 days before the Spring Festival and 25 days after the Spring Festival.

来源：资阳报