Have you ever considered why you begin yawning too when you see someone yawn? Or how hard it is to be among people laughing and not laugh yourself? Well, apparently it's because we have mirror neurons (神经元）in our brains.

    Put simply, the existence of mirror neurons suggests that every time we see someone else do something, our brains imitate it whether or not we actually perform the same action. This explains a great deal about how, we learn to smile, talk, walk, dance or play sports. But the idea goes further: mirror neurons not only appear to explain physical actions, they also tell us that there is a biological basis for the way we understand other people.

    Mirror neurons can undoubtedly be found all over our brains, but especially in the areas which relate to our ability to use languages, and to understand how other people feel. Researchers have found that mirror neurons relate strongly to language. A group of researchers discovered that if they gave people sentences to listen to ( for example: “The hand took hold of the ball” ) , the same mirror neurons were triggered as when the action was actually performed (in this example, actually taking hold of a ball).

    Any problems with mirror neurons may well result in problems with behavior. Much research suggests that people with social and behavioral problems have mirror neurons which are not fully functioning. However, it is not yet known exactly how these discoveries might help find treatments for social disorders.

    Research into mirror neurons seems to provide us with even more information regarding how humans behave and interact. Indeed, it may turn out to be the equivalent (相等物）for neuroscience of what Einstein's theory of relativity was for physics. And the next time you feel the urge to cough in the cinema when someone else does — well, perhaps you'll understand why.

    Did you know that sixty percent of your body weight is water? However, a loss of only two percent of this water through dehydration (脱水) during exercise can significantly affect your performance. The more you sweat, the more your exercise performance declines, unless you drink enough to replace your loss of fluids (液体).

    When you lose too much water, you can overheat quite easily, especially in a warm environment. But this is not the only problem you may face. Dehydration leads to your heart pumping much faster, which means exercise becomes more difficult and requires more effort. Despite these problems, however, many of us simply do not take enough fluids in when we head for the gym or set out on a run.

    So why is this? How do we manage to lose so much water without simply drinking more to replace it? Well, it's easier than you think. When we are at rest, we quickly become aware that we are thirsty and will put that right by having a drink. When we exercise, on the other hand, our thirst mechanism (结构) does not work as effectively, so we don't notice early enough that we are actually thirsty. In fact, we only start to fed thirsty when we have already lost around two percent of our body weight.

    Another problem is that, the more dehydration we become during exercise, the more difficult it is to prevent further dehydration-because our stomachs become intolerant (不能容忍的) to fluids and we do not absorb water properly, just when we need it most.

    The key thing about fluids and exercise is to manage your intake properly-regular small amounts are preferable, and some should be drunk before the period of exercise begins. You also need to match your intake to the sort of exercise you are doing. For example, for one hour of exercise, such as taking part in a 10 km run, you need to drink about two extra litres of water. For longer periods of exercise, sports drinks are recommended.

    A British friend told me he couldn't understand why Chinese people love eating sunflower seeds as a snack so much. “I've met a lot of older Chinese and many have a crack in their front teeth; I believe that's from cracking the seeds, ” he said.

    I had never noticed the habit, but once he mentioned it, I suddenly became more aware. I realized that whenever I'm watching TV or typing a report, I always start mindlessly cracking sunflower seeds. My friend doesn't like sunflower seeds, and, to him, it seems unnecessary to work so much just to get one small seed.

    When we were young, the whole family would usually get together for Chinese New Year. Then, we all lived close to one another, usually in a small city, and sometimes even neighbors would go door-to-door on Chinese New Year's Eve to check out what every household was making.

    I remember my parents would be in the kitchen cooking. Out in the living room , a large table would already be laid out, complete with fancy tablecloth, ready-made dumpling fillings, and dishes full of candy, fruits and sunflower seeds. Some of the dishes were to be offered to our ancestors later, while others were for neighbors and children to eat before the evening feast. I must have learned how to crack sunflower seeds back then.

    I don't think it's right to criticize one's choice in food or eating habits, no matter how strange they may seem.

    It's not only in China. When I went abroad, I found people had all sorts of strange habits when it came to food. In Denmark, they put salted red fish on bread and eat it for dinner, no matter how much it ruins your breath. They think it's a delicacy, and it's connected to their culture. I think it's a wonderful tradition.

    Josh Hill, a biology teacher at Mar Vista High School in California, US, often gets sick after swimming in the ocean at Imperial Beach in California.

    He and a group of students are raising awareness(意识)about water pollution by taking weekly water samples(样本)of the ocean and publishing their results online.

    Every Thursday, Hill and his students collect water from the ocean. Students then take the samples to their school and test them for levels of bacteria. Usually, samples closer to the border have higher levels of bacteria, Hill said.

    “Water quality is usually the worst at the southern end and it increasingly gets better,” he said.

    Hill collects the samples on Thursdays so that students can publish the results on the Surfrider Foundation's website in time for the weekend. The Surfrider Foundation has give Mar Vista lab equipment and promote the students' results on its site.

    Most of Hill's students grew up in Imperial Beach. Many have gotten sick from the water or know someone who has.

    Cameron Bell, 17, who is currently applying to college, wants to pursue a STEM career. He appreciates the fact the he can get lab experience at school. “Our research really impacts our community because it's keeping people safe,” he said.

    On a recent Thursday morning, Anthony Gass, 15, collected some samples. Before he got into the water, his classmates helped him put on waterproof(防水的)clothes and tie a rope around his waist to protect him from the onrush of water.

    Hill said the protection probably wasn't necessary, but that it was better to be safe than to be sorry. “We just want to make sure we protect the students,” he said.

    At the age of seven, while his friends were spending their allowances on candy and toys, Jose Adolfo Quisocola, Peru, came up with the creative idea of an eco­bank which allows kids of all ages to become economically independent and financially wise while helping the environment.

    Established in 2012, The Bartselana Student Bank is the world's first cooperative bank for kids. Whoever wants to join has to bring in at least 5 kilograms (11 pounds) of solid waste (paper or plastic) and establish a savings goal. Once accepted, all bank "partners" are required to deposit at least one additional kilogram (2* 2 pounds) of recydables on a monthly basis and obey other requirements, such as attending financial education and environmental management workshops. The waste accumulated is sold to local recycling companies, who, thanks to some clever negotiation by Jose, pay a higher­than­market rate for everything brought in by Bartselana Student Bank members. The funds received are placed in the individual's account where they collect until his/her savings goal is reached. The account holder can then withdraw his/her money, or choose to leave it and continue to grow for a bigger target.

    "At the beginning, my teachers thought I was crazy or that a child could not undertake this type of project," Jose recalls. "They did not understand that we are not the future of the country but its present. Luckily, I had the support of the school principal and an assistant in my classroom."

    The youngster's persistence paid off. Today, the eco­bank, which now has the support of several local institutions, has ten educational centers and begins accepting applications from kids all across Peru. On November 20, 2018, the young boy was awarded the famous Children's Climate Prize (CCP). "Jose's eco­bank is a brilliant way of linking economy and climate impact, both in thought and practice. The potential impact is amazing", a judge said.

    Hopefully, Jose's success will inspire more kids and adults to come up with new ideas that create value while helping the environment. As the boy says, "Together we can change the world, we just need an opportunity."

    A butterfly's wings can have many jobs besides keeping the insect in the air. They may be called on to attract mates, to warn potential enemies to stay away, to do other animals or even to provide disguise(伪装).

    All of these roles, though, depend on their colouration-which is unchanging. This plays into the idea that butterfly wings are dead tissue, like a bird's feathers or a mammal's hair. In fact, that is not true. For example, in some species males' wings harbour special cells that release chemicals which attract females.

    Nanfang Yu, a physicist at Columbia University, in New York, has been looking into the matter. One of his interests is the optical (光学的) properties of biological materials. That has led him to study butterfly wings in more detail. And, in cooperation with Naomi Pierce, a butterfly specialist at Harvard University, he has now shown, in a paper published this week in Nature Communications, that butterfly wings are, indeed, very much alive.

    Initially, Dr Yu and Dr Pierce wanted to know how the insects keep their body temperatures up without their wings overheating. Unlike birds and mammals, butterflies do not produce enough internal heat to metabolize(新陈代谢). Instead, they rely on outside heat sources-usually the sun-to bring their bodies up to speed. But their wings, being thin protein membranes (膜), have a limited thermal capacity. Those wings can therefore overheat quickly if the insects are exposed to the sunlight too long, or, oppositely, can cool down too rapidly if they are flying through cold air.

In their experiments, the two researchers used a laser (激光) to heat up spots on the wings of dozens of butterfly species. When the temperature of the area under the laser reached 40℃ or so, the insects responded within seconds by doing things that stopped their wings heating up further. These actions included a butterfly turning around to minimize its exposure to the laser, beating its wings or simply walking away.