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郑州激光全飞秒手术价格
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发布时间: 2025-05-25 08:36:55北京青年报社官方账号
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  郑州激光全飞秒手术价格   

After almost two years circling an ancient asteroid hundreds of millions of miles away, a NASA spacecraft this week will attempt to descend to the treacherous, boulder-packed surface and snatch a handful of rubble.The drama unfolds Tuesday as the U.S. takes its first crack at collecting asteroid samples for return to Earth, a feat accomplished so far only by Japan.Brimming with names inspired by Egyptian mythology, the Osiris-Rex mission is looking to bring back at least 2 ounces (60 grams) worth of asteroid Bennu, the biggest otherworldly haul from beyond the moon.The van-sized spacecraft is aiming for the relatively flat middle of a tennis court-sized crater named Nightingale — a spot comparable to a few parking places here on Earth. Boulders as big as buildings loom over the targeted touchdown zone.“So for some perspective, the next time you park your car in front of your house or in front of a coffee shop and walk inside, think about the challenge of navigating Osiris-Rex into one of these spots from 200 million miles away,” said NASA’s deputy project manager Mike Moreau.Once it drops out of its half-mile-high (0.75 kilometer-high) orbit around Bennu, the spacecraft will take a deliberate four hours to make it all the way down, to just above the surface.Then the action cranks up when Osiris-Rex’s 11-foot (3.4-meter) arm reaches out and touches Bennu. Contact should last five to 10 seconds, just long enough to shoot out pressurized nitrogen gas and suck up the churned dirt and gravel. Programmed in advance, the spacecraft will operate autonomously during the unprecedented touch-and-go maneuver. With an 18-minute lag in radio communication each way, ground controllers for spacecraft builder Lockheed Martin near Denver can’t intervene.If the first attempt doesn’t work, Osiris-Rex can try again. Any collected samples won’t reach Earth until 2023.While NASA has brought back comet dust and solar wind particles, it’s never attempted to sample one of the nearly 1 million known asteroids lurking in our solar system until now. Japan, meanwhile, expects to get samples from asteroid Ryugu in December — in the milligrams at most — 10 years after bringing back specks from asteroid Itokawa.Bennu is an asteroid picker’s paradise.The big, black, roundish, carbon-rich space rock — taller than New York’s Empire State Building — was around when our solar system was forming 4.5 billion years ago. Scientists consider it a time capsule full of pristine building blocks that could help explain how life formed on Earth and possibly elsewhere.“This is all about understanding our origins,” said the mission’s principal scientist, Dante Lauretta of the University of Arizona.There also are selfish reasons for getting to know Bennu better.The solar-orbiting asteroid, which swings by Earth every six years, could take aim at us late in the next century. NASA puts the odds of an impact at 1-in-2,700. The more scientists know about potentially menacing asteroids like Bennu, the safer Earth will be.When Osiris-Rex blasted off in 2016 on the more than 0 million mission, scientists envisioned sandy stretches at Bennu. So the spacecraft was designed to ingest small pebbles less than an inch (2 centimeters) across.Scientists were stunned to find massive rocks and chunky gravel all over the place when the spacecraft arrived in 2018. And pebbles were occasionally seen shooting off the asteroid, falling back and sometimes ricocheting off again in a cosmic game of ping-pong.With so much rough terrain, engineers scrambled to aim for a tighter spot than originally anticipated. Nightingale Crater, the prime target, appears to have the biggest abundance of fine grains, but boulders still abound, including one dubbed Mount Doom.Then COVID-19 struck.The team fell behind and bumped the second and final touch-and-go dress rehearsal for the spacecraft to August. That pushed the sample grab to October.“Returning a sample is hard,” said NASA’s science mission chief, Thomas Zurbuchen. “The COVID made it even harder.”Osiris-Rex has three bottles of nitrogen gas, which means it can touch down three times — no more.The spacecraft automatically will back away if it encounters unexpected hazards like big rocks that could cause it to tip over. And there’s a chance it will touch down safely, but fail to collect enough rubble.In either case, the spacecraft would return to orbit around Bennu and try again in January at another location.With the first try finally here, Lauretta is worried, nervous, excited “and confident we have done everything possible to ensure a safe sampling.”___The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content. 4807

  郑州激光全飞秒手术价格   

AGOURA, Calif. (KGTV) - The movie set ranch featured in the HBO television series “Westworld” and almost 500 other productions was destroyed in the Woolsey Fire, Santa Monica Mountains park rangers tweeted Friday.The piece of Hollywood history, known as “Western Town” at Paramount Ranch, was located in Agoura. With its rolling hills and canyons, it was used to create an Old West look for film and television shoots.Paramount Studios bought the 2,700 acre ranch in the golden era of Hollywood. According to the National Park Service, the permanent Western Town was built in the 1950s and posed as Tombstone, Arizona, and Dodge City, Kansas.In addition to “Westworld”, the set also served as the home of “Dr. Quinn, Medicine Woman” and episodes of Gunsmoke. See a complete list of productions here.WILDFIRES: 10News Complete CoverageThe public was welcome to visit the set’s hiking trails and picnic areas until its destruction.  943

  郑州激光全飞秒手术价格   

ALPINE, Calif. (KGTV) - For some students in Alpine, the first week of school has meant distance learning pods inside a school, hosted by their school district.Like for so many kids, the switch to distance learning in March was tough for 8-year-old Ashlyn, according to her mother Stephanie Green."She thrives more when she's with her peers. One-on-one with me and her just didn't really work as well," said Green.So when distance learning was mandated to begin the school year, there was disappointment, and then came a different reaction."I thought thought it was great. It was really innovative," said Green.Photos sent to ABC 10News reveal what the first week of school looked like for nearly 100 students in the Alpine Union School District. Inside one school gym, there was a distance learning pod with Ashlyn and seven other kids, in the 1st, 3rd and 4th grades. Set up by the district, the pods are being held on school grounds. Students are separated by plexiglass dividers. A substitute teacher is on hand to guide them through the process. Parents in the pods take shifts supervising the kids, making sure they get breaks outside.About half of the learning pods are within their before-and-after-school care programs, expanded into a 10-and-a-half hour days."The learning pods are a good way to have a bit normalcy to begin the school year," said Green.Despite initial concerns, the county officials tells ABC 10News the district-hosted learning pods do fall within the latest state guidelines.District superintendent rich Newman says they launched the program to address challenges their families were facing with distance learning, from internet access and social isolation to distractions and parents' work schedules."The number one feedback is 'Thank you. Thank you for thinking of us, for giving kids a safe place to learn. And thank you for letting us go back to work,'" said Newman.With the county giving schools to open for in-person instruction next week, Newman says they are working on a hybrid option for their K-to-8 classes, before transitioning to an in-person learning model option. 2117

  

About 2.5 million more working-age Americans were uninsured last year, even before the coronavirus pandemic struck, according to a government report issued Wednesday.The study from the Centers for Disease Control and Prevention found that 14.5% of adults ages 18 to 64 were uninsured in 2019, a statistically significant increase from 2018, when 13.3% lacked coverage.The increase in the uninsured rate came even as the economy was chugging along in an extended period of low unemployment. The findings suggest that even during good times, the U.S. was losing ground on coverage gains from the Obama-era health care overhaul.Health insurance coverage has eroded under President Donald Trump, who is still trying to overturn the Affordable Care Act, or “Obamacare.” By contrast, Democratic presidential candidate Joe Biden wants to expand the ACA and add a new public plan in a push to eventually cover all Americans.The new numbers come from the CDC’s National Health Interview Survey, which is considered one of the government’s most authoritative reports. Lack of affordable coverage was the top reason given for being uninsured, cited by nearly 3 out of 4 surveyed.In 2018, 26.3 million adults ages 18 to 64 were uninsured. Last year, that number rose to 28.8 million, CDC said.The situation has only worsened since COVID-19 began to spread in the U.S. early this year, forcing a sudden economic shutdown that left millions out of work. How much worse is not yet known, because government surveys like the CDC’s have a significant lag time.Initial estimates from private experts that suggested more than 25 million people could have become uninsured due to pandemic job losses appear to have been too high.More recent estimates suggest there are 5 million to 10 million newly uninsured. In the midst of a pandemic, that would still represent a sharp increase in the number of people who may face problems getting medical attention. Uninsured people often postpone going to see a doctor until their symptoms become severe.Experts say there could be several reasons why coverage losses due to the pandemic have not been as deep as initial feared, including people switching to a spouse’s plan and more people qualifying for Medicaid or for an ACA “special enrollment period.”The Trump administration has resisted calls to fully open the ACA insurance markets during the ongoing public health emergency.The CDC report found that adults who were uninsured last year because coverage was not affordable were more likely to be in poor health, a group that’s at higher risk of serious complications from COVID-19. Uninsured women were more likely to cite affordability problems than men, and those 50 and older were also more likely than the group under 30 to report a financial hardship. 2792

  

A woman threw a tantrum at a Popeyes restaurant in Staten Island, New York.Then she threw a chair through the establishment's window. Video showed the woman slamming a promotional sign against the restaurant's door before lifting a chair and banging it against the window.  301

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