As soon as the Thanksgiving holiday is over, Santa Clauses start appearing everywhere. It takes more than red clothing and a white beard to be a professional Santa In fact many successful Santas attend special classes.

    The CW Howard Santa School, one of the oldest Santa Claus school in the world, is in Midland, Michigan. It celebrated its 80th anniversary last year. Over 250 Santas gathered at the school to prepare for their seasonal work. Charlie Howard was the Santa Claus in the Macy*s Thanksgiving Day Parade for 17 years. He started the school in 1937.

    “At that time, there was a great need for good Santas. Santas didn't portray the character that we want. Santa Claus stands for all good things hut some of the gentlemen's images (形象) weren't up to the expectation,” said Charlie.

    The three-day Santa workshop teaches people “Santa sign language”, facts about deer and clothing and make-up style. The future Santas also become familiar with the newest wish list toys, gain (获得) interview experience for radio and television and even get advice on how to do their business taxes.

    It's said that about 15,000 students have graduated from the Santa school. They come from all over North America, Europe，Africa and Australia to study. Last year the school welcomed Santas from all 50 states as well as many other countries.

    The Santas never claim (声称) to be the one and only “real” Santa. Instead, they describe themselves as “the spirit of Christmas”. At the school's opening-night activity, they tell visiting children they are the “cousins of Santa”.

    Robert Davis says they also never promise children anything. Instead, they say they will try their best.

    After all, as Charlie Howard liked to say, “He is wrong who thinks Santa enters through the chimney (烟囱). Santa enters through the heart.''

    Around this time a few years ago, it was common to see videos of friends on social media having a bucket of icy water thrown on them. Known as the “ice bucket challenge”, it was created as a way to raise money for the medical condition ALS. But now, there's a new challenge and this time, no water is involved.

    What is it? Well, think of a fruit that you'd never normally sink your teeth into. Perhaps you've got it: a lemon. While we enjoy using lemons to add flavor to dishes, very few of us would actually eat one as we'd eat an apple or an orange.

    But the horrible taste is the precise reason why the “lemon face challenge” is taking off. Participants bite into a lemon, taking a selfie as they do it before posting the photo online. The fun is all about expression people make as all that citric acid (柠檬酸) hits their taste buds (味蕾). Every expression seems to say, “This is worse than freezing water.”

    The serious side to this trend is the good cause it's all in aid of. The challenge aims to raise awareness of a rare brain cancer that affects young children. It was started by Aubregh Nicholas, an 11-year-old US kid. She was diagnosed with this rare brain cancer herself in September 2017, but has since raised almost $50000 to cover her medical expenses thanks to the challenge.

    If a challenge is going to raise publicity and contributions from people, it has to be something interesting and original. That way the ice bucket challenge took off in 2014 and it explains why so many people are now sharing their lemon faces. There are a lot of stories about the downside of social media these days. The charity challenges, however, show how online culture can unite the world and bring help to the people who most need it.

    Every day, we are moving closer to some kind of artificial intelligence(人工智能). Progress in big data, machine learning and robotics are going to give us a world where computers are effectively intelligent in terms of how we deal with them. Should you be scared by this? Absolutely, but not in the usual “robot overlords” (机器人帝国) kind of way. Instead, the real fear should be about getting human beings wrong, not getting AI right.

    The key to the technology is the ability of computers to recognize human emotions based on the ''activation” of muscles in the face. A computer can identify the positions of facial muscles and use them to infer the emotional state of its user. Then the machine responds in ways that take that emotional state into account.

    One potential application of it is to provide “emotional robots” for the elderly. Having a machine that could speak in a kind way would comfort a lonely older person. That is a good thing, right? But that won't also relieve us from questioning how we ended up in a society that takes care of the elderly because we don't know what else to do with them? Can't we have more humane solutions than robots?

    “Emotion data” aren't the same thing as the real and vivid emotional experiences we human beings have. Our emotions are more than our faces or voices. How can they be pulled out like a thread, one by one, from the fabric(组织) of our being?

    Research programs can come with much philosophical(哲学的) concern, too. From the computers' point of view, what the computing technology captures are emotions, but at its root is a reduction of human experience whose outward expressions can be captured algorithmically (计算上). As the technology is used in the world, it can reframe the world in ways that can be hard to escape from.

    The technology will clearly have useful applications, but once it treats emotions as data, we may find that it is the only aspect of emotion we come to recognize or value. Once billions of dollars floods into this field, we will find ourselves trapped in a technology that is reducing our lives. Even worse, our “emotion data” will be used against us to make money for someone else. And that is what scares me about AI.

    Who's in control of your life? Who's pulling your strings? For the majority of us, it's other people-society, colleagues, friends, family or our community. We learned this way of operating when we were very young, of course. We were brainwashed. We discovered that feeling important and feeling accepted was a nice experience and so we learned to do everything we could to make other people like us. As Oscar Wilde puts it," Most people are other people. Their thoughts are someone else's opinions, their lives a mimicry, their passions a quotation."

    So when people tell us how wonderful we are, it makes us feel good. We long for this good feeling like a drug-we are addicted to it and seek it out wherever we can. Therefore, we are so eager for the approval of others that we live unhappy and limited lives, failing to do the things we really want to. Just as drug addicts and alcoholics live worsened lives to keep getting their fix(成瘾物)we worsen our own existence to get our own constant fix of approval.

    But, just as with any drug, there is a price to pay. The price of the approval drug is freedom-the freedom to be ourselves. The truth is that we cannot control what other people think. People have their own agenda, and they come with their own baggage and, in the end, they're more interested in themselves than in you. Furthermore, if we try to live by the opinions of others, we will build our life on sinking sand. Everyone has a different way of thinking, and people change their opinions all the time. The person who tries to please everyone will only end up getting exhausted (tired) and probably pleasing no one in the process.

    So how can we take back control? I think there's only one way-make a conscious decision to stop caring what other people think. We should guide ourselves by means of a set of values- not values imposed from the outside by others, but innate values which come from within. If we are driven by these values and not by the changing opinions and value systems of others, we will live a more authentic, effective, purposeful and happy life.

    Batteries can power anything from small sensors to large systems. While scientists are finding ways to make them smaller but even more powerful, problems can arise when these batteries are much larger and heavier than the devices themselves. University of Missouri (MU) researchers are developing a nuclear energy source that is smaller, lighter and more efficient.

    "To provide enough power, we need certain methods with high energy density (密度)", said Jae Kwon, assistant professor of electrical and computer engineering at MU. ''The radioisotope (放射性同位素) battery can provide power density that is much higher than chemical batteries."

    Kwon and his research team have been working on building a small nuclear battery, presently the size and thickness of a penny, intended to power various micro systems (MNEMS). Although nuclear batteries can cause concerns, Kwon said they are safe.

    "People hear the word 'nuclear' and think of something very dangerous." he said. "However, nuclear power sources have already been safely powering a variety of devices, such as pace-makers, space satellites and underwater systems."

    His new idea is not only in the battery's size, but also in its semiconductor (半导体). Kwon's battery uses a liquid semi conduct or rather than a solid semiconductor.

    "The key part of using a radioactive battery is that when you harvest the energy, part of the radiation energy can damage the lattice structure (晶体结构) of the solid semiconductor." Kwon said, "By using a liquid semiconductor, we believe we can minimize that problem."

    Together with J. David Robertson, chemistry professor and associate director of the MU Research Reactor, Kwon is working to build and test the battery. In the future, they hope to increase the battery's power, shrink its size and try with various other materials. Kwon said that battery could be thinner than the thickness of human hair.

    America is a mobile society. Friendships between Americans can be close and real, yet disappear soon if situations change. Neither side feels hurt by this. Both may exchange Christmas greetings for a year or two, perhaps a few letters for a while—then no more. If the same two people meet again by chance, even years later, they pick up the friendship. This can be quite difficult for us Chinese to understand, because friendships between us flower more slowly but then may become lifelong feelings, extending (延伸) sometimes deeply into both families.

    Americans are ready to receive us foreigners at their homes, share their holidays, and their home life. They will enjoy welcoming us and be pleased if we accept their hospitality (好客) easily, but truly can't manage the time to do a great deal with a visitor outside their daily routine. They will probably expect us to get ourselves from the airport to our own hotel by bus. And they expect that we will phone them from there. Once we arrive at their homes, the welcome will be full, warm and real. We will find ourselves treated hospitably.

    Another difficult point for us Chinese to understand Americans is that although they include us warmly in their personal everyday lives, they don't show their politeness to us if it requires a great deal of time. This is usually the opposite of the practice in our country where we may be generous with our time. Sometimes, we, as hosts, will appear at airports even in the middle of the night to meet a friend. We may take days off to act as guides to our foreign friends. The Americans, however, express their welcome usually at homes,

    For the Americans, it is often considered more friendly to invite a friend to their homes than to go to restaurants, except for pure business matters. So accept their hospitality at home!