When people reunite with their loved ones, it's usually all extremely happy moment. But what is their most common response to seeing them again? It may seem strange，but most of the time they break down in tears.

    Now a group of psychologists from Yale University say they have found the reason why, and that crying tears of joy may well be the body's way of keeping emotional balance. “They seem to take place when people are overtaken by strong positive emotions, and people who do this seem to recover better from those strong emotions,” Oriana Aragon, the lead researcher said.

    Aragon and her fellow psychologists looked at hundreds of participants' emotional responses to different things, including happy reunions and cute babies. Many participants said they would react in a negative or aggressive way to the positive things —— to cry at happy moments and want to pinch(捏)a cute baby's face or even tell them “I want to eat you up!” But then researchers found that these people were able to calm down from strong emotions more quickly.

    There are many other examples of times when people respond to a positive experience with a negative emotional reaction. At an exciting concert, fans scream at their idols(偶像). People who have just had a big lottery win are often in floods of tears. “These findings advance our understanding of how people express and control their emotions, which is importantly related to mental and physical health, the quality of relationships with others, and even how well people work together.” said Aragon．

    When my sister Gina was born, she had a problem with her heart. Her heart was pretty bad in the beginning and she stayed in the hospital for a month. The first few years were very difficult because she was very sick. She had five operations before she was three years old. She had trouble walking, playing with other children, and going to school.

    Although Gina couldn't laugh and talk, we all knew that she just needed love and care. Our parents wanted to take Gina to a special place in Florida where she could swim with dolphins. Gina was afraid of swimming with them because she had never been around dolphins before. We had also never traveled that far as a family.

    When we got to Florida, we saw where the dolphins lived. It was a place where kids with special needs like Gina could come and spend time. I thought it was going to be a vacation, but it wasn't. Gina had to work hard every day for a week.

    The trip was amazing .Gina laughed and clapped(拍手) when she saw the dolphin, and the dolphin splashed (溅起水花) when it saw Gina. They swam together all day. Gina was able to move her body more than she normally did at home. Mom and dad were proud of Gina. I was, too.

    Most people know something about the greenhouse effect. Factories send gasses such as carbon dioxide, or CO₂, into the atmosphere, the air around the earth. In the past, this wasn't a problem because trees absorbed the CO₂. But now people in many countries are cutting down billions of trees all around the world. At the same time, factories are sending more CO₂ into the atmosphere. It's difficult to believe, but factories put billions of tons of CO₂ into the atmosphere every year. One ton is over 2000 pounds, so it is a lot of pollution. There is too much CO₂ and there aren't enough trees, so the world is getting warmer. In other words, we have a greenhouse effect. This is terrible for the environment.

    What can we do about this? Firsts we can stop using so much coal and oil. We can learn to use different kinds of energy: the sun, wind, steam from volcanoes，and heat from inside the earth. Second, instead of cutting down trees, we should plant more trees. One tree can absorb ten pounds of carbon dioxide every year.

    The trees are good for the earth's atmosphere and for Guatemala (拉丁美洲国家危地马拉).In small towns and villages in Guatemala, most women are poor and have hard lives. Trees help them in three ways. First, the Connecticut factories pay them to plant the trees. Their pay is com, not money. The com is good for their children. Second, these women know a lot about their environment. They know where to plant when to plant, and what kinds of trees to plant. For example，they plant many fruit trees. The fruit gives them vitamins for their families^, diets. Other trees are good for firewood. In a few years, the women won't spend so much time looking for firewood. Third, all these trees are good for the soil. Now rain can't wash the soil down from the mountains so easily.

    This plan isn't enough to stop the greenhouse effect. However, it's a start. The woman of Guatemala are helping themselves and helping their environment.

    A new study suggests that people who drank a certain amount of alcohol（酒）had a lower risk of cancer and death than those who drank more or none during a nine-year period. And with each additional drink a week, the risk of cancer and death from any cause increased, the scientists reported.

    However, the study found only an association between alcohol and cancer and death, and did not prove cause and effect, the researches said. What sets the new study apart, said lead study author Andrew Kunzmann, is that previous studies looked at cancer and death separately. “What our study does is combine the two outcomes together and we find that lighter drinking is associated with the lowest risk of cancer or death,” Kunzmann said.

    But Kunzmann noted that the participants（参与者）were all older adults. That means that “we're not really showing what happens in younger people if they drink,” he said. Also, it's difficult to account for other lifestyles that could have affected the results. “These could also influence health. But the results did take into consideration differences in diet, smoking and education among participants,” Kunzmann noted.

    The researchers said that they hope their study sparks conversation about reducing the suggested alcohol intake in countries' guidelines. “We're not telling people what they can or can't do or what they can or can't drink,” Kunzmann said. “We're just trying to give them reliable evidence so that they can make their own informed, healthy decisions.”

Cattle manure(粪肥) has become one of the world's greatest environmental killers, but one Dutch artist is using chemistry to turn it into something that is both eco-friendly and valuable.

In recent years, scientists around the world have made great progress in their attempts to recycle cattle manure, including turning it into natural fertilizer, but Eindhoven designer Jalila Essaidi didn't think they were efficient enough to solve the global manure problem. So she started on her very own solution, one that approached animal waste as a valuable material that could be processed into useful products.

She started by separating the waste, with the dry manure used to get pure cellulose(纤维素) from the grass that cows eat. From the wet manure, she got acids used to create a natural liquid plastic which was used to make fiber that are later turned into fabric(material used for making clothes).

This new material was named Mestic, from mest, the Dutch word for manure. Essaidi claim that it has the same function as plastic from fossil fuels, but is bio-degradable(可生物降解的). Better yet, the degradability can be dealt with in the lab, making it possible to create materials that last for different periods of time depending on their purpose. "This is not the first time that scientists have been looking for ways to solve the manure problem, but it is the first time that manure is being considered as a valuable resource." the Dutch designer said.

Last year, Jalila Essaldi partnered with the city of Eindhoven to produce a fashion show using Mestic-based fabrics. Her Mestic collection was so impressive that clothing giant H&M awarded her the Global Change Award and a $1million prize. And cow manure is just the beginning of Jalila Essaldi's experiments with animal waste. "After cows, we'll deal with pigs and other animals," she said.