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.

    For most of us Veterans Day just means a chance to enjoy an extra day off from school or work．However this November 11th，be sure to spend a few minutes on its true purpose，by acknowledging（感谢）the men and women who have served in our armed forces．

    And you don't have to stop at just this one day．Join the over 10，000youth members of the Young Marines group that honor these brave men and women all year long with special events and completely spoil them for an entire week，from November 4th to 11th，by visiting hospitalized veterans，performing chores for disabled veterans and even organizing community－wide social event．The program open to kids ranging from the age of eight all the way to high school，is a great way to not only show your appreciation，but also get a chance to do some fun activities with like－minded kids and make a real difference in a veteran's life．

    People often believe that Memorial Day and Veterans Day are celebrated for the same reason．There is however a subtle but important difference between the two．While both honor our military personnel，the former is a day to remember and pay respect to all the men and women that died serving our country in a war，while Veterans Day is to celebrate the soldiers who are still alive and served in the forces at any time，during peace or war． Though several other countries celebrate this day in honor of their own veterans，the meaning is slightly different for each one．Some like the United Kingdom，celebrate it in honor of all soldiers－living or dead，while others like Canada celebrate it to honor all living veterans．They also call it different names．France and New Zealand sill call it Armistice Day．In the United Kingdom，Australia and Canada it is referred to as Remembrance Day，while Malta and South Africa celebrate it as Poppy Day．

    No matter what it is called，the reason for observing the day is the same－to show our appreciation to the brave men and women who sacrifice（牺牲）everything to make this world a safer place for the rest of us．

    If you have spent any time living in or visiting a big city in China, you have most likely used the service that Didi provides. The convenient ride-sharing company, now known as Didi Chuxing, was praised last month by Fortune magazine. According to the magazine, it is changing the world with its environmentally friendly solution to getting around in major cities. As the magazine reported: “Didi concluded that last year its car-pooling services helped reduce total car trips in the country by 1 million a day, which saved 500 million liters of gas, cutting 13.5 million tons of carbon emissions (排放) per day.” The transport service was the only Chinese company to make the important magazine's list, and its influence can be felt in many parts of Chinese society.

    Didi is just one example of what is being called the “sharing economy”. The sharing economy is one in which regular people exchange goods and services, usually using an online marketplace. Other similar companies include companies that allow people to rent out their homes to strangers like Airbnb and Couchsurfing, and similar ride sharing services like Uber and Lyft.

    All of these services are possible partly because many people are realizing that they have underused assets in their lives. Millions of people around the world have started renting them out online to earn extra money. They rent their apartments while they are away for the weekend, lend people their cars for money and even sell their spare time.

    The sharing economy is the latest example of the Internet's value to customers. This model is now big enough for regulators and companies to have woken up to it. That is a sign of its great potential. It is time to start caring about sharing.

    Winslow Homer was a famous American painter. Since Art History class in college, I had always admired his works and I was lucky to see a large exhibition of his works when I was in my early 30s.It was at this event that I bought a print of his painting, “Snap the Whip”. It always hung in my classroom until I retired from teaching.

    I thought it truly captured the freedom and fun of childhood. In the painting, a group of young boys are playing a game arm in arm on grass ground in front of a farm house. They are jumping and laughing wildly with great joy. One of the boys is falling down to the ground. They are not even wearing shoes!

    During my last year of teaching, there was a young woman in her first year of teaching right next door to me and we got to be good friends. She had been an art student before taking up education. Her eyes were drawn immediately to this print when she entered my room. So on my last day of teaching, after the students had left, I took the painting off the wall and walked next door and gave it to her.

    She was really surprised, but very glad to have it. I was delighted that she liked it and all the students she would have would treasure it as much as I had. We found the perfect place for it on one of her walls and hung it together. I was happy that she brought back this wonderful memory for me.

    The American newspaper has been around for about three hundred years. In 1721, the printer James Franklin, Benjamin's older brother, started the New England Courant, and that was what we might recognize today as a real newspaper. He filled his paper with stories of adventure, articles on art, on famous people, and on all sorts of political subjects.

    Three centuries after the appearance of Franklin's Courant, few believe that newspapers in their present printed form will remain alive for long, Newspaper companies are losing advertisers, readers, market value, and in some cases, their sense of purpose at a speed that would not have been imaginable just several years ago. The chief editor of the Times said recently, “At places where they gather, editors ask one another, 'How are you?', as if they have just come out of the hospital or a lost law case.” An article about the newspaper appealed on the website of the Guardian, under the headline “NOT DEAD YET.”

    Perhaps not, but the rise of the Internet, which has made the daily newspaper look slow and out of step with the world, has brought about a real sense of death, Some American newspapers have lost 42% of their market value in the past three years. The New York Times Company has seen its stock（股票）drop by 54% since the end of 2004, with much of the loss coming in the past year. A manager at Deutsche Bank suggested that stock - holders sell off their Times stock. The Washington Post Company has prevented the trouble only by changing part of its business to education; its testing and test — preparation service now brings in at least half the company's income,

    When you get a cut, you cover it with a bandage. How do you know when to change it? Maybe you just wait until it's wet or dirty. But when people have long-term or chronic (慢性的)wounds that take months to get better, changing bandages too early or to late could make healing take even longer. Changing the dressing on a wound too often can provide an opportunity for infections to get in. But if a bandage gets very wet very quickly from the inside, it might be filling with pus (脓)--a sign an infection has begun. Judging just when to change is important.

    Chronic wounds are common in people who are older or who have certain health conditions. Chronic wounds affect around 6.5 million people per year in the United States. When Anushka Naiknaware, 13, learned about chronic wounds, she decided to make a device that could alert a person when it's time to change their bandages.

    After a lot of trials and errors, the teen settled on a design that used an “ink” filled with carbon nanoparticles(纳米粒子). The teen loaded her ink into a printer cartridge (墨盒) to print onto her special paper, which was to be made into bandage. Well, actually, Anushka loaded her ink into many, many printer cartridges. Just changing a printer cartridge isn't easy, and filling one is even harder.

    The small printed papers cost only 5 to 10 cents, Anushka estimates. The Bluetooth sensor is more expensive, but the teen notes that it could be used over and over again. She also knows there is a long way to go before her design can help patients. It hasn't been tested on a real person yet. “You have to make sure everything works perfectly,” she says.