When a leafy plant is under attack ，it doesn't sit quietly. Back in 1983, two scientists, Jack Schultz and Ian Baldwin,reported that young maple trees getting bitten by insects send out a particular smell that neighboring plants can get. These chemicals come from the injured parts of the plant and seem to be an alarm.What the plants pump through the air is a mixture of chemicals known as volatile organic compounds,VOCs for short.

Scientists have found that all kinds of plants give out VOCs when being attacked .It's a plant's way of crying out.But is anyone listening?Apparently.Because we can watch the neighbours react.

    Some plants pump out smelly chemicals to keep insects away.But others do double duty .They pump out perfumes designed to attract different insects who are natural enemies to the attackers. Once they arrive, the tables are turned. The attacker who was lunching now becomes lunch.

    In study after study,it appears that these chemical conversations help the neighbors .The damage is usually more serious on the first plant,but the neighbors ,relatively speaking ,stay safer because they heard the alarm and knew what to do.

Does this mean that plants talk to each other? Scientists don't know. Maybe the first plant just made a cry of pain or was sending a message to its own branches, and so, in effect, was talking to itself. Perhaps the neighbors just happened to “overhear” the cry. So information was exchanged, but it wasn't a true, intentional back and forth.

    Charles Darwin, over 150 years ago, imagined a world far busier, noisier and more intimate(亲密的) than the world we can see and hear. Our senses are weak. There's a whole lot going on.

    Having friends may well keep you healthier and help you deal with stress better. Some studies show that people with close friends have a greater ability to fight disease than people who are alone.

    Place friendship in the first place. Find the time to be with friends even if it means letting the lawn go unmoved or the dishes unwashed for a while. When you can't get together, use the phone to keep in touch.

    Open up to close friends. Keeping a deep friendship requires a level of “heartfelt” intimacy (亲密). Don't be afraid to express your inner fears and disappointments. Listen to your friends when they have problems, but offer advice only when it's wanted. Help raise friends' self-esteem when they are sad about a job loss, or other such events.

    Have different friends for different activities, such as going to the movies, singing in a choir, and joining in a bowling league.

    Don't wait for a friend to ask for helps. When a friend has the flu, offer to go to the store or drive his or her children to their after-school activities.

    Never take a friendship for granted. Like a good marriage, friendship needs care and patience. Become a joiner. Find a group that matches your interests.

    Talk to strangers. Conversations started in museums, laundry rooms, or bookstores can lead to firm friendship.

    Enroll in an adult-education course. A classroom is an ideal place to meet others with similar interests.

    Ever wonder how much a cloud weighs? What about a hurricane? A meteorologist（气象学家） has done some estimates and the results might surprise you.

    Let's start with a very simple white puffy cloud—a cumulus cloud(积云). How much does the water in a cumulus cloud weigh? Peggy LeMone, senior scientist at the National Center for Atmospheric Research in Boulder, Colorado, did the numbers. “The water in the little cloud weighs about 550 tons,” she calculates. “Or if you want to convert it to something that might be a little more meaningful...think of elephants.” Assume（假设） an elephant weighs about six tons, she says, that would mean the water inside a typical cumulus cloud would weigh about one hundred elephants.

    The thought of a hundred elephants' worth of water floating in the sky begs another question—what keeps it up there?

    “First of all, the water isn't in elephant-sized particles(微粒); it's in tiny tiny tiny particles,” explains LeMone. And those particles float on the warmer air that's rising below. But still, the concept of so much water floating in the sky was surprising even to a meteorologist like LeMone. “I had no idea how much a cloud would weigh, actually, when I started the calculations（计算）,” she says.

    So how many elephant units of water are inside a big storm cloud—10 times bigger all the way around than the “puffy” cumulus cloud? Again, LeMone did the numbers: About 200,000 elephants.

    Now, come to the calculations for a hurricane about the size of Missouri and the figures get really massive. “What we're doing is weighing the water in one cubic meter theoretically pulled from a cloud and then multiplying by the number of meters in a whole hurricane,” she explains.

    The result? Forty million elephants. That means the water in one hurricane weighs more than all the elephants on the planet. Perhaps even more than all the elephants that have ever lived on the planet.

China Train Guide

    Quick Guide on China Train Travel

    If you're looking for an affordable and comfortable way to get around China, train travel is the way to go. Getting train information and cheap train tickets has never been easier. Online train ticket booking makes it easy for travelers to look through China's train timetable, compare train fares, and look for ticket availability. Once you've found a suitable train, you can book online and pick your tickets up at the train station or get them delivered to your home or hotel. Train tickets can be booked online a minimum of 35 minutes and a maximum of 60 days before departure.

    How to choose train types

    When you're buying China train tickets online, you'll notice that the journey duration differs depending on which type of train you choose. China train types can be recognized by their letter codes G, D and C trains are high-speed trains, while Z, T and K are slower or overnight trains. China's high-speed trains run between Chinese provincial capitals and first-tier Chinese cities. G trains (high-speed trains, standing for gāotiě) are China's bullet trains—the fastest trains with a maximum speed of 400 km／h. Tickets for these trains are the most expensive.

    How to buy train tickets

    Unless you can read Chinese, there are only two ways to make train reservations in China:

    —Online train ticket booking with a travel agency (up to 60 days before departure).

    —At the train station／local ticket agency with your passport (up to 58 days before departure).

    How to read train tickets

    When reading your train ticket, please take note of the Chinese characters and Pinyin printed next to your departure / arrival city. Directions (North, South, East, and West) appear in Pinyin (Bei, Nan, Dong, and Xi), not English. Please make sure you are going to the correct train station.

    The Broadcom MASTERS competition aims to find a balance between celebrating individual accomplishments and acknowledging that science seldom happens alone. The competition takes off when students from around the country are teamed up and have to solve a series of hands—on challenges in the spotlight.

    Nowadays, kids are fed with “the myth of the lone scientist”, so placing such challenges in the middle school period has a huge potential for impact. The focus on teambuilding skills gets students excited before more fears and stereotypes(成见)set in.

    The initial pool of qualified students comes from the participants in nation-wide science fairs. Those who score in the top 10％(about 10, 000 kids)have the qualification to apply. The judges select the top 300 young scientists, and that group is finally narrowed to 30 finalists.

    Selection at this stage is clearly an honor in itself, but it counts as step one for the finalists. They are then flown to Washington, D. C. and placed into teams of five for the hands-on part of the competition. Each team is made up of students with different talents and skills, including academic focus and experience.

    Unlike the science fairs, where most of the work takes place behind the scenes and students share a polished outcome, the hands-on challenges create a space where the work is the competition itself. The students take up a range of challenges in science, technology, engineering, math and so on. Each of the challenges will need the insight and skills of multiple team members.

    Judges observing the challenges aren't just looking for outcomes but also for leadership, teamwork and problem solving.

    The Broadcom MASTERS attracts increasing numbers of passionate and talented young people who are eager to take part in a program that helps them grow as scientists, engineers and inventors. It lets the students experience a sense of coming together with true peers. More importantly, it provides them with new skills to tackle future challenges.

    On a rainy winter day, several decades ago, a British artist named Christopher got on a train in Oxford to go to London. When he began his journey, he never knew that it was the beginning of almost 40 years of accidents and near death experiences.

    During the journey, the train fell into an icy river, killing 12 passengers. Christopher managed to swim back to the river bank. He only had a broken leg.

    Two years later, Christopher was on a plane from London to Manchester when a door suddenly opened and he fell out. A few minutes later, the plane crashed; 27 people were killed. Christopher was so lucky that he landed in a haystack (干草堆).

    A few years later, he was hit by a bus, but again had no serious injuries. Then a year after that, he was driving on a mountain road when he saw a truck coming straight at him. He drove the car off the road, jumped out, landed in a tree — and watched his car fall 100 meters down the mountain.

    "There are two ways you can look at it," Christopher said. "I'm either the worlds unluckiest man, or the world's luckiest." When a reporter asked Christopher what he thought, he chose the "luckiest" one.

    Two years ago, aged 71, Christopher bought his first lottery ticket (彩票) in 50 years and won more than 2 million. After this, a TV company in America said they wanted him to make an advertisement. At first he accepted, but then he changed his mind. Christopher said he would not fly to Los Angeles for the filming, because he did not want to push his luck. Who knows? If he had accepted the invitation, maybe he would have had another accident. But Mr. Christopher is a lucky man. If he had had another accident, he probably would have survived that too!