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.

    Last summer, as part of my high school graduation project, I volunteered at Saunders House nursing home .I choose this experience because it was something that I had never done before and I wanted to lend a helping hand．At first it was challenging because I was extremely shy. My goal in volunteering was to bring a smile to the residents（住客） by doing different activities from word games to playing chess. I feel as if I had accomplished that goal.

    At the nursing home, I did a lot of different activities with the residents ranging from Jeopardy to Wheel of Fortune. One of my favorites was a word game where I would write a ten -letter word on the board and the residents would try to come up with as many smaller words as possible. I could tell that it was one of their favorite games because they always seemed to be so enthusiastic when they played．I also transported residents to and from their rooms when they needed help; and whenever it was a nice day out, I would take them outside to get some fresh air and relax. On Saturday mornings, I would deliver the newspaper to the residents and on Sundays, I assisted with morning church services.

    The most unforgettable part of this experience was when I had one-on-one conversations with the residents. It was incredible how many great stories they had to tell. Their stories were so interesting and the experience was unforgettable for me .

    More companies and recyclers are taking steps to ensure that old electronic devices such as TVs and computers aren't sent to poor countries.

    The Basel Action Network, a Seattle-based non-profit that largely exposed the overseas discarding (丢弃) of US electronic waste, on Thursday launched a programme to use third-party employees to certify (证实) recyclers who don't export dangerous electronic waste.

    The so-called e-Steward recyclers will also agree not to discard the waste in US landfills and agree to meet other criteria. The certification is intended to provide companies and consumers with some assurance that the waste, which can include toxins (毒素) such as lead and mercury, is disposed of safely.

    The Government Accountability Office, in a 2008 report, declared that US electronic waste was often disposed of unsafely in such countries as India. There, workers recycle gold, silver and copper from the waste, often in open-air acid baths.

    The Basel Network also says it won assurances from 13 organizations, including Samsung, Bank of America, Wells Far-go, that they'll use e-Steward recyclers whenever possible. Wells Fargo had already been using recyclers who declared not to export. So far, Basel has certified three recyclers and seven sites.

    Before e-stewards, even, companies that wanted to avoid export of electronic waste had to “hope for the best”, when, they handed their waste to recyclers, says Robert Houghton, president of Ohio-based recycler Redemtech. It is an e-Steward that counts major companies among its customers. “Now, they can get some proof,” Houghton says.

    Basel's standards compete with another set launched in January. It was made by industry and backed by the Environmental Protection Agency.

    That standard, called R-2, doesn't ban the export of dangerous electronic waste but requires that it be handled safely. Instead of a ban, the Institute of Scrap Recycling Industries says, efforts should be made to help poor countries develop safe recycling.

    Teenagers around the world can be happy with the news that the brain will ignore parents' order when they use their smart phones. A new scientific study from the University College London has shown that humans may temporarily go deaf when they're focusing on something visual (视觉的) at the same time.

    The researchers played the normal-volume sounds in the background. And 13 volunteers experienced inattentional deafness as their visual tasks became increasingly difficult. "We found that when volunteers were performing the difficult visual task, they were unable to hear sounds that they would normally hear," Maria Chait said in a statement. "The brain scans showed that people didn't filter out the sounds on purpose. They were not actually hearing them in the first place."

    The findings, published in the Journal of Neuroscience, suggest that the centre of sights and the center of sounds share limited resources. Inattentional deafness is a common everyday experience and the study explains why, according to UCL Institute of Cognitive Neuroscience Professor Nili Lavie.

    If you try to talk to someone focusing on a book, game, or television program and don't receive a response, they aren't necessarily ignoring you. They simply might not hear you at all. This could also explain why you might not hear your bus or train stop being announced if you're lost in your phone, book or newspaper. However, some loud sounds will still be able to break through.

    Some situations could become possibly dangerous when the quieter ones go unheard. As you can imagine, in the operating room, when a doctor concentrates on his work, he might not hear the equipment beeping. It also applies to drivers who center on complex directions. Fortunately, experts have given us some useful tips on preventing such situations.

    One evening I was going back from a supermarket. As I was approaching my car, I noticed that some person came and stood beside me. He was the one that could be considered as a bum. It seemed that he had no car, no home and no job. I thought that he would ask me for money, but he did not do that, he only said: "Your car is very nice".

    After several moments of silence, I replied: "Thanks", and then the inner voice told me, "Ask him if he needs help". After a short hesitation I asked him if he needed any help. His response was astonishing. I will never forget those simple three words that I heard from him: —"Don't we all?"

    It was a true discovery to me. I needed help. Although I had money and a place to sleep, I recognized that I needed help too. Then I opened my wallet and gave him enough money to get a meal and some shelter for a day.

    Suddenly I understood that no matter how much money we have, we all need help. On the other hand, no matter how poor you are and how many material problems you have, you still might offer your help to others and you still might be giving. Even it's just a nice word, you can give that and it can be priceless to other persons.

    Maybe that man was just a homeless stranger, but to me he was more than that. Maybe he was sent by the Highest Loving Power personally to me to open my eyes and to show me that there is one thing, among all other values, which is very important and irreplaceable for each and every person. Actually, it is a true gift and it is called Giving.

    Cao Zhawa has been planting trees for most of his life. He lives and works in the heart of Mu Us Sandyland, an area in the southwest part of Inner Mongolia.

    In 1958, when he was just 16 years old, Cao started planting trees. Cao's trees now cover an area of more than 1.3 million square meters. Cao's forest is worth an estimated 10 million yuan and can produce 100,000 kilograms oxygen, enough to sustain a full-grown adult for nearly a year.

    Mu Us Sandyland is one of the places in China most affected by erosion(侵蚀) and desertification. The amount of annual rainfall ranges from 150 to 300 millimeters, while evaporation(蒸发) between 2,000 and 3,000 millimeters. Cao recalls that his growing-up was troubled by sandstorms. This was one of the factors that motivated Cao to join and stay on the tree-planting program.

    Popularly known as the "Green Great Wall", the project, which is set for completion in 2050, would be a 4, 800-kilometer greenbelt of trees and shrubs(灌木) protecting the area from strong winds and preventing soil erosion. Since the start of the Three-North Shelter Forest Program, millions of people have joined in and become a vital part of the plan.

    However, the tree-planters face a host of challenges, with watering the most difficult among them. "When I was young, the level of groundwater was high," said Cao, "But with less rain, the trees are hard to plant and keep alive."

    Planting trees has also become harder for Cao as he ages. However, he doesn't want to leave the forest in the care of his children, and he insists the land belongs to the government. "When I die, I just want to be buried under the trees," Cao said. "Then I will be with them forever."