The world consumes hundreds of billions of single-use plastic bags each year. They are difficult to recycle, wasteful and damage the nature. Environmental activists want to ban plastic bags or—as many communities have done —charge a fee for them. But the plastic bag industry defends their use, saying people reuse plastic bags, and industry officials argue recycling is a matter of personal responsibility and should not be forced.

    City officials say New Yorkers use 5.2 billion plastic bags each year. They are offered free with nearly every supermarket, or convenience store purchase. Many people like them, even if they sometimes feel guilty about using them. But what happens to those bags after they've been used in a huge environmental problem. They are found on beaches. They are caught in trees. They are swallowed by marine life.

    Plastic bags are made of petroleum products and natural gas, and do not biodegrade (分解). And they are difficult to recycle. So New York City spends nearly $ 10 million dollars a year to send 100—thousand tons of plastic bags to landfills out of state.

    In Washington, D.C., a five percent charge on all single-use bags led to about a 60 percent reduction and in Los Angeles County in California , a 10 cent charge on single-use bags led to a 95 percent reduction. With a 10 cent charge on bags, customers are much more likely to stop and think about whether they need a bag or not. And that's really all that these laws are doing.

    She almost did not run. Christine Williams admits that now. She could barely put one foot after another following the wake(守灵) for her sister, who had died in an automobile accident. But she did run. With the cheers of friends and strangers reaching her heart, Williams set a C.W. Post record in Boston. Now she will run again, in the national Division II cross-country championships in Evansville, Ind. She wanted to be sure she was doing the right thing by running. She was the middle of three sisters, between Kerry, who is 25, and Jennifer, who was 18.

    Just going through any motions was hard enough, but Christine Williams wanted to know if she should put on her uniform and her shoes and run through the woods on an autumn afternoon, in the awful gaping time between her sister's wake and her funeral. “I kind of got upset beforehand.”Williams admitted. Not a chatterbox under normal conditions, she now holds herself the best way she can, the fewer words the better. She almost walked away from the start line. But her friend Angela Toscano, who had flown up to Boston with her, directly from the wake, was standing near the line and talked her through it. “She said my sister would have wanted me to run.” Christine said. And that was enough to get her started.

    The accident happened just after midnight on Nov, 4. Four young women were driving in an unfamiliar area of Long Island in Eastport, N.Y., when one of them apparently ran a yield sign, and the car was hit by another vehicle. Heather Brownrigg and Jennifer Williams died, and their friends April Brown and Kaci Moran were treated at a hospital and released.

    The crash made the papers. April Brown was charged with drunken driving and driving without a license.

    The wake began on Nov. 6. The next day Christine was to run with the Post cross-country team at the regional meet. Rich Degnan, the Post coach, and Post officials offered a car service and tickets on the last flight to Boston for Christine and Toscano. When they arrived at the hotel, the entire team was waiting up for her.

    Everybody knew about it at the regional meet. Degnan had to arrange for the flexibility of an alternate, just in case Christine could not go. Several times during the race, Christine felt she could not continue. But then she heard her friends and all those other people, those strangers from other colleges, calling her name. She thought about Jennifer. And she ran. She finished fourth in 22 minutes 58 seconds, breaking the Post record for the 6-kilometer distance by 15 seconds. And although the Post team didn't qualify for the nationals, Christine did.

    When a child is told he is "uncool", it can be very painful. He may say he doesn't care, and even act in ways that are different from cool on purpose(故意地）. But these are simple ways to deal with sadness by pretending it's not there.

    Helping a child feel better in school had to be careful. If you say, "Why are you worried about what other children think about you? It doesn't matter!" Children know that it does matter. Instead, an active way may be best. You could say, "I'm going to do a couple of things for you to help you feel better in school."

    If a boy is having trouble making friends, the teacher can help him. The teacher can arrange things so that he has chances to use his abilities to contribute to class things. This is how the other children learn how to value his good qualities and to like him. A teacher can also raise a child's popularity in the group by showing that he values that child. It even helps to put him in a seat next to a very popular child, or let him be a partner with that child in activities, etc.

    There are things that parents can do at home, too. Be friendly when your child brings others home to play. Encourage him to invite friends to meals and then serve the dishes they consider "super" .When you plan trips, picnics, movies, and other shows, invite another child with whom your child wants to be friends.

    What you can do is to give him a chance to join a group that may be shutting him out. Then, if he has good qualities, he can start to build real friendship of his own.

    A day in the life of 18-year-old David Lanster is full of teenage activities: school, baseball practice, homework. And then he starts cooking. "Some nights I'm up until 1 a.m. making pies, or even later if we're cooking beef," said the student at Ransom Everglades High School in Florida, US.

    For the past year, Lanster and Kelly Moran, his classmate, have been hosting fancy dinner parties at Lanster's parents' home. Their meals have 17 courses and are all made by them. Their guests used to give them gifts to thank them, until the pair decided to do something nice for charity. "We got some really great Miami Heat tickets, a nice watch, and many kitchen machines," Lanster said. "But we wanted to make this something positive for people rather than us."

    Lanster and Moran focused on Common Threads, a charity(慈善机构) that helps to teach kids in poor neighborhood to cook and make healthy eating choices. The young cooks ask their guests to give however much they want as payment for their meals. It all goes to Common Threads because Lanster's parents cover their food costs. After their last 12-person event, Lanster and Moran gave $1,600 to the charity. Now, they're taking their show out of the kitchen and on the road. Lanster and Moran have started to organize private dinner parties in a similar way: the host pays for the ingredients(食材), and the guests make a donation (捐赠) to a charity.

    Outside the kitchen, the two are busy preparing their college applications. Neither is sure what they will do in the future, but they've promised their parents that they'll leave cooking alone until they finish high school.

    ARCHAEOLOGISTS (考古学家) GUIDED BY laser images of a remote region of northern Guatemala have discovered 20-foot-high walls, watchtowers, and other evidence that ancient Maya societies had been annoyed by warfare threat over many years. The finds have upended long-established impressions of a civilization that it tamed the jungle and built thriving cities, then declined and disappeared quietly beneath the dense tropical forest.

    Among the most surprising discoveries was a large stone complex now called La Cuemavilla. Built on a steep ridge, the heavily fortified site included high walls. Moats which serves as the largest defensive system ever discovered in the region.

    This was surprising says an archaeologist, because we had a tendency to romanticize Maya warfare as something that was largely ritualized. But the fortifications were seeing suggest an elevated level of antagonism over centuries. Rulers were so deeply alarmed that they felt the need to invest in all these hilltop fortifications. There is an almost visible sense of fear in this landscape.

    All these findings owe credit to PACUNAM LIDAR Initiative, a laser survey of some 800 square miles of the Maya Biosphere Reserve in northern Guatemala. Using revolutionary Laser technology, the survey revealed the long-hidden ruins of a sprawling pre-Columbian civilization that was far more complex and interconnected than most Maya specialists had supposed.

    Guided by the new Laser treasure maps, the LIDAR team deployed through the jungle over the past year to conduct hands-on investigations of more than a dozen of the most promising sites-most of which would have been imperceptible without LIDAR.

    "You could walk over the top of a major ruin and miss it, "says an archaeologist who's part of the PACUNA project. But LIDAR picks up the patterns and makes the features pop out with surprising clarity.

    Three-dimensional maps generated by the survey yielded surprises even at Tikal, the largest and most extensively explored archaeological site in Guatemala. The ancient city was at least four times bigger than previously thought, and surrounded by a massive ditch and fortified base stretching for miles.

    Archaeologists stress that LIDAR, for all its utility, will never see below the ground or yield direct dates of occupation. "We still need to dig and hack our way through the jungle, but now we have a very accurate map to guide us."

For future humans to survive long periods on Mars, growing food on the planet is a must. It would be too costly and risky to rely upon rocket deliveries to meet the food needs of settlers. With this in mind, scientists are exploring ways to improve space farming.

Researchers work in a controlled greenhouse. They have identified a way that could improve crop production in simulated （模拟的） Martian soil, with different crops grown together. The method is called "intercropping", invented by ancient Maya farmers in what is now Central America.

In their experiments, the researchers grew cherry tomatoes, peas and carrots together in small, round containers. Tomatoes grown in this way produced about double the amount of tomatoes grown alone—or "monocropped"—in the same simulated Martian soil. The tomatoes were also bigger. They flowered and matured earlier, gave more fruit per plant and had thicker stems. The amounts of peas and carrots did not increase with intercropping.

Rebeca Goncalves, an astrobiologist and lead writer of the study, said the research is the first time the intercropping technique was used in space soil, and that it was a big find—one that they could now build further research on. The crops were grown in simulated Martian regolith, a soil with no organic matter —a near-perfect physical and chemical match to real Martian soil.

The researchers added useful bacteria and nutrients. They also controlled the gases, temperature and humidity inside the greenhouse to match conditions expected in a Martian greenhouse. Intercropping involves growing plants with properties that could help each other grow. The method makes the best use of resources including water and nutrients.

The researchers said the tomato plants in intercropping may have benefited from being close to the pea plants. That is because the peas are good at turning nitrogen from the air, with the help of bacteria introduced into the soil, into an important nutrient. Overall, the tomatoes, peas and carrots grew well, though not as well as in Earth soil in the same greenhouse.