Exercise may help to safeguard the mind against depression(沮丧) through previously unknown effects on working muscles, according to a new study involving mice.

    Mental health experts have long been aware that even mild, repeated stress can contribute to the development of depression and other mood disorders in animals and people. Scientists have also known that exercise seems to cushion against depression. But precisely how exercise, a physical activity can reduce someone's risk for depression, a mood state, has been mysterious. So for the new study, researchers at the Karolinska Institute in Stockholm studied the brains and behavior of mice in a complicated and novel fashion.

    We can't ask mice if they are feeling cheerful or in low spirits. Instead, researchers have pictured certain behaviors that indicate depression in mice. If animals lose weight, stop seeking out a sugar solution when it's available — because, probably, they no longer experience normal pleasures — or give up trying to escape from the cold-water zone just freeze in place, they are categorized as depressed. And in the new experiment, after five weeks of frequent but low-level stress, such as being lightly shocked, mice displayed exactly those behaviors. They became depressed.

    The scientists could then have tested whether exercise blunts (延缓) the risk of developing depression after stress by having mice run first. But, frankly, from earlier research, they wanted to know how, so they bred pre-exercised mice. A wealth of earlier research by these scientists and others had shown that aerobic exercise, in both mice and people, increases the production within muscles of an enzyme (酶) called PGC-1alpha. The Karolinska scientists suspected（怀疑） that this enzyme somehow creates conditions within the body that protect the brain against depression. Then, the scientists exposed the animals, which without exercising, were in high levels of PGC-1alpha to five weeks of mild stress. The mice responded with slight symptoms of worry. But they did not develop depression. They continued to seek out sugar and fought to get out of the cold-water zone. Their high levels of PGC-1alpha appeared to make them depression-resistant（抵抗的）. Finally, to ensure that these findings are relevant to people, the researchers had a group of adult volunteers complete three weeks of frequent endurance training, consisting of 40 to 50 minutes of moderate cycling or jogging. The scientists conducted muscle biopsies (活体检查) before and after the program and found that by the end of the three weeks, the volunteers' muscle cells contained substantially more PGC-1alpha than at the study's start.

    The finding of these results, in the simplest terms, is that “you reduce the risk of getting depression when you exercise,” said Maria Lindskog, a researcher at the Karolinska Institute.

    You've just come home, after living abroad for a few years. Since you've been away, has this country changed for the better—or for the worse?

    If you've just arrived back in the UK after a fortnight's holiday, small changes have probably surprised you—anything from a local greengrocer suddenly being replaced by a mobile-phone shop to someone in your street moving house.

    So how have things changed to people coming back to Britain after seven, ten or even 15 years living abroad? What changes in society can they see that the rest of us have hardly noticed—or now take for granted? To find out, we asked some people who recently returned.

    Debi: When we left, Cheltenham, my home town, was a town of white, middle-class families—all very conservative (保守的). The town is now home to many eastern Europeans and lots of Australians, who come here mainly to work in hotels and tourism. There are even several shops only for foreigners.

    Having been an immigrant (移民) myself, I admire people who go overseas to find a job. Maybe if I lived in an inner city where unemployment was high, I'd think differently, but I believe foreign settlers have improved this country because they're more open-minded and often work harder than the natives.

    Christine: As we flew home over Britain, both of us remarked how green everything looked. But the differences between the place we'd left behind and the one we returned to were brought sharply into focus as soon as we landed.

    To see policemen with guns in the airport for the first time was frightening—in Cyprus, they're very relaxed—and I got pulled over by customs officers just for taking a woolen sweater with some metal-made buttons out of my case in the arrivals hall. Everyone seemed to be on guard. Even the airport car-hire firm wanted a credit card rather than cash because they said their vehicles had been used by bank robbers.

    But anyway, this is still a green, beautiful country. I just wish more people would appreciate what they've got.

Two good friends, Simon and Jason, met with a car accident on their way home one snowy night. The next morning, Simon woke up blind. His legs were broken. The doctor, Mr. Smith, was standing by his bed, looking at him worriedly. When he saw Simon awake, he asked, " How are you feeling, Simon?” Simon smiled and said, “Not bad, doctor. Thank you very much for doing the special operation. Mr. Smith was moved by Simon. When he was leaving, Simon said, "Please don't tell Jason about it. “Well…Well…OK,” Mr. Smith replied.

Months later when Jason's wounds healed, Simon was still very sick. He couldn't see or walk. He could do nothing but stay in his wheelchair all day long. At first, Jason stayed with him for a few days. But days later, Jason thought it boring to spend time with a disabled man like Simon. So he went to see Simon less and less. He made new friends. From then on, he didn't go to visit Simon any more. Simon didn't have any family or friends except Jason. He felt very sad.

    Things went from bad to worse. Simon died a year later. When Jason came, Mr. Smith gave him a letter from Simon. In the letter Simon said, “Dear Jason, I am disabled. But I want you to be a healthy man. So I gave my eyes to you so that you can enjoy life as a healthy man. Now you have new friends.

I'm glad to see that you are as healthy and happy as usual. I'm glad you live a happy life. You are always my best friend". Simon”. When he finished reading the letter, Mr. Smith said, “I have promised that I will keep this a secret until Simon is gone. Now you know it.

    Jason stood there like a stone. Tears ran down his face.

    An autonomous vehicle designed for making local commerce deliveries was uncovered by Nuro. The vehicle is about the height of an SW but far narrower than a typical car. The electric car features four outside compartments（暗格）—two on each side -to hold separate deliveries. Each compartment can be tailored to a specific use, such as cooking a pizza or refrigerating a package.

    “We can use self-driving technology to deliver anything, anytime, anywhere for basically all local goods and services,” Nuro co-founder Dave Ferguson said. “Consumers used to be okay with two-week paid shipping. It became two-week free delivery, followed by one week, two days, and the same day. Now same-day delivery isn't fast enough for some customers.”

    Nuro isn't alone in building robots for local commerce deliveries. Earlier this month, Toyota, a Japanese car company, uncovered a concept vehicle that could be used for package delivery. A handful of startups—including Starship Technologies, Marble and Dispatch—are testing small robots for deliveries on sidewalks.

    Nuro's vehicle will likely face legal hurdles. Fully autonomous vehicles without a test diver aren't legal in California today, and many companies have shifted testing o states where regulators are more welcoming of autonomous vehicles, such as Arizona.

    Nuro expects to face fewer challenges because it doesn't carry passengers. Nuro's narrow size may also be helpful when navigating streets and avoiding pedestrians. The vehicle isn't equipped with any special features to communicate with pedestrians or other road users. Some companies have tested and patented solutions such as digital screens that signal the car's next move. Ferguson said his team conducted studies and found that such techniques could confuse people. Nuro believes it's better to make sure the car performs predictably, so that human drivers know what to expect from it.

    “We feel by creating this new technology that's going to enable this last mile delivery, we're going to be creating new markets and doing things that previously weren't possible,” Ferguson said. “This is not swapping out jobs with robots. It's creating new markets. There will definitely be new employment opportunities.”

    I believe in the power of science fiction, not just for its capacity to transform dreams into reality, but also for its power to bond together those who share a common vision of the future. For me, that's true for my relationship with my dad. Some fathers and sons bond over sports, fishing or hunting, but my dad and I bond over Star Trek. We tried a trip to Disney World, but one of my earliest memories wasn't Mickey, but a Klingon battle cruiser(巡洋) on the screen.

    Over the years, nearly every setting and situation has become far away for my dad and me. When it's warm at night, we're not driving along some dark streets in Indiana, but going at a slow speed with stars dimly shining. Both of us are thinking of them, without needing to say a word. All these visions of other universes have together created a private universe for my dad and me.

    Gene Rodenberry, creator of Star Trek, once said, " Science fiction is a way of thinking, a way of logic that bypasses(绕过)a lot of nonsense. It allows people to look directly at important subjects. "A lifetime of science fiction has influenced more than just my relationship with my dad, but has also helped me shape my own hopes for the future. I'm now a science writer.

    Yes, science fiction has made me into a "nerd"(书呆子), and it also has been a source of joy for my family, making me an optimist while enabling me to think critically about the danger of technology. Thank those authors who have shared their visions; the world and my family are better for it. Thank my dad, who is both the best storyteller and the best man I have ever known because he helped me realize the truth of Tennyson's words," Since I dipped into the future, I saw the vision of the world, and all the wonders that would be."

    With the explosion of consumer choices in recent history, the latest must-haves would surely need to be upgraded more often than every 10 years. In 2002 a computer and basic mobile phone would have been enough for most people, but now? The public need a trendy notebook computer and a smart phone with WiFi connection to feel they are up-to-date. So when will we have enough things? When will we finally be happy? Well, it looks like the things we buy today will barely keep us satisfied for a few months.

    In the eyes of some psychologists, far from making us happy, greater consumer choice creates many serious psychological problems. A fundamental principle of the society is that more freedom is better and more choice in the marketplace means more freedom. Therefore more choice leads to more happiness. This is not the case, however.

    Imagine you go to a café offering chocolate and vanilla ice cream. You choose the chocolate and eat it happily. But what if the café serves 50 kinds of ice cream? You choose chocolate and then start to worry, "maybe blueberry would have been better, perhaps the half-fat ice cream would have been healthier. Stupid me, all these choices and I didn't make the best one! "

    In China's major cities we have now passed the point where more consumer choice is making us happier. We are annoyed by all the options we have, disappointed because our expectations are so high and angered at ourselves when we don't make a perfect choice every time.

    A newspaper reporter tells a story about traveling on a plane with high-speed Internet access. He thought this was amazing—the newest piece of technology he had heard of. Then the service went down. The man next to him was angry and swore. The reporter thought, "How quickly the world owes him something he knew existed only 10 seconds ago!"