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郑州三十多岁的人可以做眼睛激光手术吗
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发布时间: 2025-05-30 13:02:14北京青年报社官方账号
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  郑州三十多岁的人可以做眼睛激光手术吗   

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

  郑州三十多岁的人可以做眼睛激光手术吗   

About 1 million people in the U.S. are confirmed to have contracted COVID-19 in the last five days, according to a database kept by Johns Hopkins University.As of Tuesday afternoon, 15 million Americans have contracted COVID-19 since the disease arrived in the country in January. The U.S. surpassed the 14 million case threshold on Thursday.According to USA Today, one out of every 22 Americans has contracted the virus.Even with the virus spreading to about 200,000 new Americans every day, top health officials expect the spread to only increase further in the coming days. Even with the current spike in cases, infectious disease expert Dr. Anthony Fauci says the country still is not yet seeing the full brunt of what is expected to be an exponential spread of the virus that was prompted by Thanksgiving travel.More people traveled by airplane during the week of Thanksgiving than at any other time during the pandemic, and officials believe the increase in travel and indoor gatherings will cause a "spike superimposed upon a spike" of virus cases.The spread also comes amid a concerning crowding of hospitals across the country. According to the COVID Tracking Project, a record 102,000 people in the U.S. are currently hospitalized with the virus, putting many hospitals and health care facilities at capacity. Some hospitals have been forced to treat patients in temporary facilities in parking garages because they have run out of beds. The frightening spike and concerning lack of space comes amid the deadliest week of the pandemic yet. The U.S. has reported an average of 2,200 COVID-19 deaths each day for the last week — a number that officials suspect will only increase as the virus continues to spread. Officials are holding Americans heed public health measures for the next few weeks, as two COVID-19 vaccines appear poised for imminent approval. On Tuesday, the UK began distributing its first initial doses of a two-shot Pfizer COVID-19 vaccine — the first Western country to begin distributing vaccinations. 2045

  郑州三十多岁的人可以做眼睛激光手术吗   

After fighting off insurgents in Iraq and Afghanistan, Mike Cutone returned back to the streets of Springfield, Massachusetts, only to discover that the situation wasn’t much better at home.During the late 2000s, it wasn’t out of the normal to see gang members openly riding up and down the community’s streets, openly brandishing assault rifles. The crime problem had gotten so bad that heroin was being sold in broad daylight, just blocks away from the state police barracks, where Cutone was stationed as an officer.“The citizens didn’t feel safe, people felt like prisoners in their own homes,” Cutone recalled of those years.Having recently returned from a counter insurgency tour overseas, Cutone could see that the way the crime ridden neighborhoods were being policed wasn’t working. So, he came up with a plan, drawn directly from his experience as a Green Beret. The idea was called Counter Criminal Continuum Policing or C3. Cutone partnered with Springfield police to create the new concept that focused on gaining the trust of the community instead of just arresting criminals.For the past 12 years, community leaders, city police, state police, residents and business owners have met once a week as part of the C3 program. From getting to know local business owners, to knocking on doors, the program’s foundation is rooted in winning over the trust of the community in an effort to address crime.And it’s working.“You aren’t going to arrest your way out of crime. We weren’t looking at crime through the lens of the people that live there. It starts with law enforcement understanding what these communities are going through,” Cutone said.As the nation currently struggles with police reform, Cutone sees this as a model other city could emulate.“Because of the trust factor, we built legitimacy with the community and meeting with them on a weekly basis, we want to hear what they have to say and solve these problems in their communities. Right now, we’re not hearing about partnership we’re hearing about division, division never wins there has to be a partnership,” he added.Although parts of the city are still dealing with crime, the areas infiltrated by the C3 program are almost unrecognizable. On streets where gang members once dealt drugs in broad daylight, neighbors’ biggest complaints are now typically about illegal dumping.And community leaders can see the long-term impacts the program is having.“We can see businesses are coming back and young people can get a job. Now we look at the city as being one neighborhood because we’re all working together for the same cause,” said Neil Boyd, a local Bishop in the area. 2657

  

After running a year-long competition that drew interest from hundreds of cities and a number of states, Amazon has reportedly chosen New York City and Northern Virginia to split duty as its second headquarters.The Wall Street Journal reported late Monday that Amazon (AMZN) has picked New York's Long Island City and Arlington County's Crystal City neighborhoods, citing people familiar with the matter.Amazon declined to comment to CNN.The development projects, which could be announced as soon as Tuesday, promise to bring the cities a giant infusion of jobs and tax revenue, but are almost certain to draw fire from critics concerned about their impact on infrastructure and property values. 703

  

After 2 weeks of multiple health screens and asking everyone to quarantine, I surprised my closest inner circle with a trip to a private island where we could pretend things were normal just for a brief moment in time. pic.twitter.com/cIFP7Nv5bV— Kim Kardashian West (@KimKardashian) October 27, 2020 308

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