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.

    Children like to imagine they are someone else in a game. As a parent you might never guess how it can benefit your child. It helps your child:

Develop Social Skills

    As children play pretend games, they explore relationships between family members, friends and coworkers and learn more about how people interact. Playing doctor, they imagine how physicians care for their patients. Imaginative play helps of a game or to lose a pet, they are better able to help those in need. They become more willing to play fair, to share, and to cooperate.

Build Self-confidence

    Children have very little control over their lives. Imagining oneself as a builder of skyscrapers or a super hero defending the planet is inspiring to children. It helps them develop confidence in their abilities and their potential.

Promote Intellectual Growth

    Using imagination is the beginning of abstract thought. Children who can see a king's castle in a mound of sand or a delicious dinner in a mud pie are learning to think symbolically(象征性地). This skill is important in school where a child will have to learn that numbers symbolize groups of objects, letters symbolize sounds, and so on.

Practice Language Skills

    Kids who pretend with their friends do a lot of talking. This helps increase their vocabulary, improve sentence structure and develop communication skills.

Get Rid of Fears

    Pretending can help children get rid of their fears and worries. When children role-play the big, bad monsters under the bed, they gain a sense of control over him and he doesn't seem quite so big or so bad.

    Most people know that Marie Curie(居里夫人) was the first woman to win the Nobel Prize, and the first person to win it twice. However, few people know that she was also the mother of a Nobel Prize winner.

    Born in September, 1887, Irene Curie was the first of the Curies' two daughters. Along with nine other children whose parents were also famous scholars, Irene studied in their own school, and her mother was one of the teachers. She finished her high school education at the College of Sévigné in Paris. Irene entered the University of Paris in 1914 to prepare for a degree in mathematics and physics. When World War I began, Irene went to help her mother, who was using X-ray facilities（设备） to help save the lives of wounded soldiers. Irene continued the work by developing X-ray facilities in military hospitals in France and Belgium. Her services were recognized in the form of a Military's Medal by the French government.

    In 1918, Irene became her mother's assistant at the Curie Institute. In December 1924, Frederic Joliot joined the Institute, and Irene taught him the techniques required for his work. They soon fell in love and were married in 1926. Their daughter Helene was born in 1927 and their son Pierre five years later.

    Like her mother, Irene combined family and career. Like her mother, Irene was awarded a Nobel Prize, along with her husband, in 1935. Unfortunately, also like her mother, she developed leukemia because of her work with radioactivity（辐射能）. Irene Joliot-Curie died from leukemia on March 17, 1956.

    Cameron is no ordinary dog, and not just because he was born on Valentine's Day. To Maggie, a first grader at Burgundy Farm Country Day School, the dog who spends most days on campus is more like a friend. When Cameron is near, Maggie feels "really, really, happy," she said, "I feel safe around him, she added." "He'll lie down and ask me to scratch his tummy," she explained, because Cameron likes Maggie.

    Cameron is one of a handful of dogs at Burgundy, a K-8 private day school in Alexandria, Virginia. Dogs started showing up there when the head of school, Jeff Sindler, brought his clumsy Labrador, Luke, to the main office building where Sindler works. After Luke died, Sindler adopted Cameron and brought him to campus, too, where the dog Maggie described as really cute" became a school favorite.

    "They don't care if you are good at basketball or a great reader, or popular," Sindler said. "They just want to be loved—equal opportunity," he added. "Cameron and the other dogs on campus—are always fastened with a rope and with their owner—go a long way toward improving students' social and emotional well-being," he said. They reduce tension and ease anxiety, and inspire happy feelings from students.

    "They bring out some important emotions/' he said, "and are especially helpful to children and adults who struggle in social communication, Children often came from challenging backgrounds: many lived in poverty, or had to travel through dangerous neighborhoods to get to school, or shared a too-crowded home. When these emotionally needy children met the dogs, they relaxed and were more prepared to learn.

    Just as important, dogs on school grounds set a positive, welcoming tone. They help preserve the school climate that is accepting, supportive and curious・"Dogs are one way to hold on to Sindler said, adding that "schools should be fun and exciting, and dogs can be a big part of that."

    For Sindler, including Cameron was all part of an effort to create a safe environment where learning could flourish.

    Although the idea of "zero emission net carbon-positive, sustainable (可持续)" development was promoted worldwide, most cities are at a loss what to do or even some have objected to it. But in Liuzhou, a city in southern China, attitudes could not be more different.

    The Liuzhou Municipality Urban Planning Bureau has signed up Italian architect Stefano Boeri, the father of the forest city movement, to build a self-contained community for up to 30, 000 people. He is the go-to man for such projects thanks to the success of his "vertical forests", two residential (住宅的) towers. Completed in 2014, they remove up to 17.5 tons of soot (煤烟) from the air each year, and a year later one of them was named Best Tall Building Worldwide.

    The Liuzhou project is a much more ambitious undertaking, however. Its homes, hospitals, hotels, schools and offices will be built on a 340-acre site in what Boeri calls the first attempt to create an "urban environment that is really trying to find a balance with nature". Its 100 species of plant life are expected to absorb almost 10, 000 tons of carbon dioxide and 57 tons of pollutants per year, while at the same time producing 900 tons of life-giving oxygen.

    Although the architects haven't published the cost of the forest city, the Milan towers cost only five percent more than traditional skyscrapers.

    The construction of his forest city at Liuzhou is set to begin in 2020, and there is still a great deal of planning and research required before a projected completion date can be set. However, Boeri remains optimistic about the project and has confidence in the soundness of his vision: "I really think that bringing forests into the city is a way to deal with global warming."

    If you have never been on a cruise (乘船游览), it can seem like its own world—with its own rules and secret language. So here we are going to lay out the very basics of going on a cruise.

    Do I need a passport to go on a cruise?

    You may need a passport, but you should take one anyway. Besides the fact that you are going to need an ID card to board the ship in the first place, a lot of ports require one.

    How much luggage can I take on board?

    For the most part, cruise ships aren't like planes—there isn't a strictly regulated amount of luggage you can take with you, and you are not going to be charged for bringing too much. Keep in mind that cabin storage space can be tight. Everything, including your empty luggage, is going to have to fit inside and you don't want to be tripping over it for your whole vacation.

    Things like guns and knives are banned, but regulations vary from ship to ship about things like irons (generally a no) and hair dryers (generally a yes). Some ships allow you to bring a bottle of wine, but nearly all ban bringing your own hard alcohol.

    What's the process for boarding a cruise ship?

    Boarding a cruise ship is like boarding a plane—there are regulations or when to arrive, how to check-in, and what security you have to go through. Most cruise lines have transportation available from the airport; otherwise they normally own a paid parking lot where you can leave your car.