Exercise may help to safeguard the mind against depression 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 lessen 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 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. 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.

    Pat O'Burke was a poor Irishman with a large family, and one morning, waking up very early from cold and hunger, he decided to go shooting in a wood near his cottage. The wood belonged to Lord Northwood, a rich gentleman. Pat had no right to go there, but in it there were swarms of rabbits and flocks of birds that were good to eat, and Pat determined to take the risk. Suddenly he saw the owner, with a group of friends, coming towards him in the wood. There was a look of anger on Lord Northwood's face as he caught sight of the gun in Pat's hands.

    Pat's heart sank with fear, but he saw there was no hope of escape, so he walked boldly(大胆) up to the group and said to Lord Northwood, “Good morning, sir, and what has brought you out so early this morning?”

    Lord Northwood, rather surprised, said he and his friends were taking a little exercise to get an appetite(食欲) for their breakfast. Then, looking at Pat with suspicion(怀疑), he said, “but why are you out so early in the morning?”

    “Well, sir” said Pat, “I just came out to see if I could get a breakfast for my appetite.”

    The whole crowd burst into laughter at Pat's ready wit, and with a smile Lord Northwood walked on, leaving Pat to try his luck with the rabbits.

    Even if trees cannot walk, they are still on the move.

    In parts of the Arctic, entire forests are moving northward. Across the Arctic, temperatures are rising faster than anywhere else in the world. As that happens, the tree line that marks where forests stop and the treeless tundra (冻原) starts has been shifting northward. Trees growing along the tree line must protect themselves from the cold wind. To dothis, plants tend to grow horizontal (水平的) branches low to the ground. The energy it takes for trees to grow this way means they don't have enough energy to make seeds.

    But as Earth's climate has been warming, trees no longer have to just grow horizontally. Many can instead grow up toward the sky. This takes less energy. And with all that leftover energy, these trees have started producing more seeds. This happens especially in places where white spruce (白云杉) grows.

    White spruce, which is a North American tree, is quite able to produce a lot of seeds, which can move long distances in the wind. When wind­blown seeds end up on the tundra beyond the tree line, they eventually can sprout(发芽) new trees. This explains how a forest can move. Of course, the process would work only if the tundra were warm enough. But in recent years, the whole planet has been warming.

    New trees will provide shelters for some snow. Keeping the sun's rays from making the white surface disappear. Instead, the trees absorb the sun's heat. This warms the surrounding air. The extra warmth encourages even more trees to produce seeds. That further boosts a forest's ability to expand. In addition, more trees will trap more snow, preventing much of it from being blown away. Snow can trap heat in the soil below, which encourages trees to grow. The recent rise of temperatures has helped more trees grow past the tree line. People worry about impacts on the animals that depend on frozen conditions for food and shelter.

    Songs that make our hearts happy can make them stronger too, US researchers reported on Tuesday.

    They found that when people listened to their favorite music, their blood vessels (血管) dilated in much the same way as when they are laughing, or taking blood medications.

    “We have a pretty impressive effect,” said Dr Michael Miller, director of preventive cardiology (心脏病学) at the University of Maryland Medical Center in Baltimore.

    “Blood vessel diameter improved,” he said.“The vessel opened up pretty significantly. You can see the vessels opening up with other activities such as exercise.” A similar effect is seen with drugs such as statins.

    When blood vessels open up more, blood flows more smoothly and is less likely to form the clots (凝块) that cause heart attacks and strokes. “We are not saying to stop your statins or not to exercise but rather to add this to an overall program of heart health,” said Miller, who presented his findings to a meeting of the American Heart Association in New Orleans.

    Miller's team tested 10 healthy, non-smoking men and women, who were told to bring their favorite music.They spent half an hour listening to the recordings and half an hour listening to music they said made them feel anxious while the researchers did ultrasound tests designed to show blood vessel function.

    Compared to their normal baseline measurements, blood vessel diameter increased 26 percent on average when the volunteers heard their joyful music.Listening to music they disliked — in most cases in this group — blood vessels narrowed by six percent, Miller said.

    Miller said he came up with the idea after discovering that laughter caused blood to literally flow more smoothly. “I asked myself what other things make us feel really good, besides calories from dark chocolate of course.Music came to mind. It makes me feel really good,” he said.

    Most of the volunteers chose country music but Miller said the style is not so important rather than what pleases each individual.

    The news of Harper Lee's second novel broke the internet. Go Set a Watchman would be published in July. Lee became a recluse (隐士)after the publication of her first book, To Kill a Mockingbird, in 1960. Although the author has been out of the public eye for more than 50 years, the wave that followed the announcement showed her novel's beloved place in the American literary works.

    In 1991, The Book of the Month Club and the library of Congress conducted a survey that made readers identify books that had made a difference in their lives. Lee's book followed only The Bible. Alongside the works of Shakespeare and Twain, To Kill a Mockingbird remains one of the most widely taught books nationwide, reaching an estimated 70% of American public schools. What makes it such a perfect read for young people?

    English class is a place where young Americans come to know themselves. In the folds of dusty books, students can make contact with humanity beyond the superficial(肤浅的) conversations of the school hallways. Literature promises relief, a place to figure out one's problems and get to know oneself better.

    To Kill a Mockingbird particularly distinguishes itself in this regard. It speaks in child's voice without treating its readership as children. People have called it an 'impossible' achievement, a children's book penned in the prose(散文) of a well-educated adult—it's unlikely that a child like Scout could exist in the real world. But that's exactly what makes it such a charming read for young people. It alludes to (转弯抹角地说到)the consciousness of a well-educated adult going through difficult realities, but shows it through the light and playful voice of a curious little girl.

    University Room Regulations

    Approved and Prohibited Items

    The following items are approved for use in residential (提供住宿的) rooms: electric blankets, hairdryers, personal computers, radios, televisions and DVD players. Items that are not allowed in student rooms include: candles, ceiling fans, fireworks, waterbeds, sunlamps and wireless routers (路由器).Please note that any prohibited items will be taken away by the Office of Residence Life.

Access to Residential Rooms

    Students are provided with a combination (组合密码) for their room door locks upon check-in. Do not share your room door lock combination with anyone. The Office of Residence Life may change the door lock combination at any time at the expense of the resident if it is found that the student has shared the combination with others. The fee is $25 to change a room combination.

Cooking Policy

    Students living in buildings that have kitchens are only permitted to cook in the kitchen. Students must clean up after cooking. This is not the responsibility of housekeeping staff. Kitchens that are not kept clean may be closed for use. With the exception of using a small microwave oven to heat food, students are not permitted to cook in their rooms.

    Pet Policy

    No pets except fish are permitted in student rooms .Students who are found with pets, whether visiting or owned by the student, are subject to an initial fine of $100 and a continuing fine of $50 a day per pet. Students receive a written notice when the fine goes into effect. If, one week from the date of the written notice, the pet is not removed, the student is referred to the Student Court.