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    Measles(麻疹), which once killed 450 children each year and disabled even more, was nearly wiped out in the United States 14 years ago by the universal use of the MMR vaccine(疫苗). But the disease is making a comeback, caused by a growing anti-vaccine movement and misinformation that is spreading quickly. Already this year, 115 measles cases have been reported in the USA, compared with 189 for all of last year.

    The numbers might sound small, but they are the leading edge of a dangerous trend. When vaccination rates are very high, as they still are in the nation as a whole, everyone is protected. This is called “herd immunity”, which protects the people who get hurt easily, including those who can't be vaccinated for medical reasons, babies too young to get vaccinated and people on whom the vaccine doesn't work.

    But herd immunity works only when nearly the whole herd joins in. When some refuse vaccination and seek a free ride, immunity breaks down and everyone is in even bigger danger.

    That's exactly what is happening in small neighborhoods around the country from Orange County, California, where 22 measles cases were reported this month, to Brooklyn, N.Y., where a 17-year-old caused an outbreak last year.

    The resistance to vaccine has continued for decades, and it is driven by a real but very small risk. Those who refuse to take that risk selfishly make others suffer.

    Making things worse are state laws that make it too easy to opt out(决定不参加) of what are supposed to be required vaccines for all children entering kindergarten. Seventeen states allow parents to get an exemption（豁免), sometimes just by signing a paper saying they personally object to a vaccine.

    Now, several states are moving to tighten laws by adding new regulations for opting out. But no one does enough to limit exemptions.

    Parents ought to be able to opt out only for limited medical or religious reasons. But personal opinions? Not good enough. Everyone enjoys the life-saving benefits vaccines provide, but they'll exist only as long as everyone shares in the risks.

    Don't you just love ice skating every winter?I am sure that since winter is approaching,your skates are set to come out,just waiting to be used.Impress your friends with your new trick on how to ice-skate backwards with the help of these tips.

Stand Straight

    The first thing that you need to do is,stand straight.If you feel that you are falling backwards,just put your chin up and slightly bend your knees.

Confidence is What You Need

    The most important step while learning how to skate backwards,is having enough confidence in what you are doing.How can you achieve this?By practice.Just practice rolling backwards down a gentle slope everyday or just by pushing off from a wall or something of that sort.But before you do that,make sure that the place where you are practicing is free from any kind of debris（碎片）because otherwise,you could land up in the hospital due to some accident.While going backwards,just get used to the feeling of moving backwards.One of the important ice skating tips and techniques is that if you feel that you are losing your balance,then scissor（做剪式运动）your skates.Keep practicing this till you are confident about it.

Maintain Speed

    Confident now?Great!Now the next step is to maintain your speed.While rolling in a straight line with one skate, with the other try sculling（划桨）,that is,keep pushing yourself backwards with an outwards stroke（滑动）.Make sure that you put most of your weight on the skate which is moving straight and not the one with which you are sculling.Now,try the same thing using the other foot.Again keep doing this till you are confident enough.

Increase Your Speed Now

    Once you are confident that you can scull with either foot,the next thing that you have to do is increase your speed.Try some of your own tricks now.Scull with either foot or with both at the same time. 

Scull and Be Aware

    While you keep one foot straight,keep sculling with the other.You can do that with both feet at the same time. Concentrate on what you are doing but don't get so absorbed,that you don't see where you are going.If you are not watching your back,you might bang（碰撞）against something or someone.

    After spending three months in and out of the hospital with numerous health issues, Donald Austin had his leg partially cut off. He was relieved to finally be able to go home after just four days recovering from the operation. When he reached his porch, though, the joy drained away.

    Donald thought he'd be able to make it up the steps to the front door on crutches, but his strength and balance weren't as strong as he'd hoped. The wheelchair was too heavy for his wife, Jennifer Austin, to lift up the steps, even when his mom offered a hand to help. Donald ended up on the concrete, the family feeling totally at a loss. They were out of strength and out of options. Just then, a car caught the family's eyes. It had driven past once but was slowly circling back. The stranger, Steven Smith, pulled up and asked if he could help. Relieved, the family watched Smith lift Donald inside and lay him safely on a couch.

    But the Good Samaritan knew there was more to do. Smith figured this wasn't the only time Donald would need to climb those steps. So the next day, Smith, who's an ordinary worker, came back and asked if he could build a ramp(斜坡) in front of the house. With his dad and a couple more helping hands, Smith set up a ramp over the steps to make the home wheelchair accessible. The act of kindness brought the family to tears.

    “This stranger has saved the day for us twice within 24 hours. He also brightened our spirits that had become increasingly dimmed over the difficult months,” Jennifer wrote on Facebook. “There is a sense of optimism back in our home because of his kindness.”

    Computers have beaten human world champions at chess and, earlier this year, the board game Go(围棋). So far, though, they have struggled at the card table. So we challenged one AI(artificial intelligence) to a game.

Why is poker so difficult? Chess and Go are “information complete” games where all players can see all the relevant information. In poker, other players' cards are hidden, making it an “information incomplete” game. Players have to guess opponents' hands from their actions—-tricky for computers. Solving poker could lead to many breakthroughs, from cyber security to driverless cars.

    Scientists believe it is only a matter of time before AI once again vanquishes humans, so our human-machine match comes up in a game of Texas Hold's Em Limit Poker. The AI was developed by Johannes Heinrich, a researcher studying machine learning at UCL. It combines two techniques: neural(神经的)networks and reinforcement learning(强化学习).

    Neural networks, to some degree, copy the structure of human brains: their processors are highly interconnected and work at the same time to solve problems. They are good at spotting patterns in huge amounts of data. Reinforcement learning is when a machine, given a task, carries it out, learning from mistakes it makes. In this case, it means playing poker against itself billions of times to get better.

    Mr Heinrich told Sky News: “Today we are presenting a new procedure that has learned in a different way, more similar to how humans learn. In particular, it is able to learn abstract patterns, represented by its neural network, which allow it to deal with new and unseen situations.”

    After two hours of quite defensive play, from the computer at least, we called it a draw.

    Many people believe that you lose the ability to learn new languages as you get older. Language experts, however, will tell you that you're never too old to learn a new language. As you get older, it can be more difficult to learn a new language, though.

    Children and adults learn new languages in different ways. For children, language is their life. They study for thousands of hours every year, because they need to learn languages to become part of their communities. Adults, on the other hand, are already part of a language community. Learning a new language means becoming part of another language community, and adults rarely get the chance to practice as much as young children do.

    Moreover, children learning a new language are expected to make mistakes. This gives them freedom when learning to be daring and confident. Adults, however, often feel pressured to be perfect when learning a new language. This can discourage many people and make it even harder to learn a new language.

    When young children learn a new language, they come to see various languages as a “normal” part of society. This mindset(思维模式) helps them embrace learning a new language without feeling like they're doing something unusual or “too hard”.

    So if you want to learn a new language, go for it! It's never too late to learn a new language. If you're older, it may take more work, but it can be done. If you're a young child, though, now is the time to step out and learn a new language!

    Why not consider spending the holiday at Harvard if you are a high school student who will have a holiday in this coming summer?

    About the program

    This is a five-week program^ from July 16 to August 17, 2018, which is designed to help high school students to pave the way for a successful college experience. We have 200-plus courses, such as film, philosophy, creative writing, and computer science. Besides, we offer you two types of credit courses—4-credil course and 8-credit course. You can earn college credit here. Whether you choose to sign up for one or two courses, you will still have some flexibility (灵活性) to schedule your days'.

    Tuition and Fees

    Application fee (the application period opens in December): $50

    Tuition: $3,300 for 4-credit course;

    $6,600 for 8-credit course

    Housing (room and board) fee: $5, 700

    Health insurance fee: $200

    Financial Aid(援助)

    Financial aid is a scholarship award. It is available to Secondary School Program students with excellent academic records who give evidence of financial need. It does not have to be paid back. Awards cover only a part of the program cost. Families should expect to contribute to the remaining part. Award amounts are determined by many sides, including family finances, availability of fund (基金), and whether students are resident. ... Local students may be eligible (有资格的) for additional funding towards room and board.