If it really is what's on the inside that counts, then a lot of thin people might be in trouble.

    Some doctors now think that the internal(内部的) fat surrounding important organs like the heart or liver could be as dangerous as the external fat which can be noticed more easily.

    “Being thin doesn't surely mean you are not fat,” said Dr Jimmy Bell at Imperial College. Since 1994, Bell and his team have scanned nearly 800 people with MRI machines to create “fat maps” showing where people store fat.

    According to the result, people who keep their weight through diet rather than exercise are likely to have major deposits of internal fat, even if they are slim.

    Even people with normal Body Mass Index scores can have surprising levels of fat deposits inside. Of the women, as many as 45 percent of those with normal BMI scores (20 to 25) actually had too high levels of internal fat. Among men, the percentage was nearly 60 percent.

    According to Bell, people who are fat on the inside are actually on the edge of being fat. They eat too many fatty and sugary foods, but they are not eating enough to be fat. Scientists believe we naturally store fat around the belly first, but at some point, the body may start storing it elsewhere.

    Doctors are unsure about the exact dangers of internal fat, but some think it has something to do with heart disease and diabetes(糖尿病). They want to prove that internal fat damages the body's communication systems.

    The good news is that internal fat can be easily burned off through exercise or even by improving your diet. “If you want to be healthy, there is no shortcut. Exercise has to be an important part of your lifestyle.” Bell said.

    Before the invention of hair dryer,vacuum cleaners were being used for the purpose of drying and styling hair. The early vacuum cleaners could draw in air as well as blowing air.So,towards the end of the 19^th century,women used to dry their hair by using a vacuum cleaner.

    In 1890,a French salon owner Alexander F.Godefroy invented the first hair dryer.It blew warm air.However,it was not widely used,mainly because of its large size.

    The first convenient hand-held hair dryer used at home came up in 1920.It weighed over 2 lbs.However,it only produced 100 watts of power,which was not enough to dry the hair.After almost ten years came the gas-heated dryers that were widely used in barber shops.However,these dryers produced heat that was harmful to hair and the air from them made people sick,so they were soon gone.

    Around the 1940s and 1950s,the helmet（头盔）style electric dryers came into being.Curly hairstyles were popular during that time.Therefore,women used curlers and sat under the dryers to set their curls.Later,the curly style began to drop,and so did the popularity of the helmet style electric dryer.

    In the late 1950s,the first workable hair dryer was made.It had a hand-held dryer.It used only 300-400 watts. Ever since the 1950s,hand-held dryers have experienced many changes,in order to become quieter,lighter and smaller.However,how it works largely remains the same.The modem technology has made improvements to the hair dryer,reducing the heat damage to a person's hair.For producing shinier,smoother and healthier hair,dryers have been included with negative ion（负离子）technology that dries hair faster and with less heat.

    Bad news sells. If it bleeds, it leads. No news is good news, and good news is no news. Those are the classic rules for the evening broadcasts and the morning papers. But now that information is being spread and monitored（监控）in different ways, researchers are discovering new rules. By tracking people's e-mails and online posts, scientists have found that good news can spread faster and farther than disasters and sob stories.

    “The 'if it bleeds' rule works for mass media,” says Jonah Berger, a scholar at the University of Pennsylvania. “They want your eyeballs and don't care how you're feeling. But when you share a story with your friends, you care a lot more how they react. You don't want them to think of you as a Debbie Downer.”

    Researchers analyzing word-of-mouth communication-e-mails, Web posts and reviews, face-to-face conversations-found that it tended to be more positive than negative, but that didn't necessarily mean people preferred positive news. Was positive news shared more often simply because people experienced more good things than bad things? To test for that possibility, Dr. Berger looked at how people spread a particular set of news stories: thousands of articles on The New York Times' website. He and a Penn colleague analyzed the “most e-mailed” list for six months. One of his first findings was that articles in the science section were much more likely to make the list than non-science articles. He found that science amazed Times' readers and made them want to share this positive feeling with others.

    Readers also tended to share articles that were exciting or funny, or that inspired negative feelings like anger or anxiety, but not articles that left them merely sad. They needed to be aroused（激发）one way or the other, and they preferred good news to bad. The more positive an article, the more likely it was to be shared, as Dr. Berger explains in his new book, “Contagious: Why Things Catch On.”

Life in the Clear

    Transparent animals let light pass through their bodies the same way light passes through a window. These animals typically live between the surface of the ocean and a depth of about 3,300 feet — as far as most light can reach. Most of them are extremely delicate and can be damaged by a simple touch. Sonke Johnsen, a scientist in biology, says, "These animals live through their life alone. They never touch anything unless they're eating it, or unless something is eating them."

    And they are as clear as glass. How does an animal become see­through? It's trickier than you might think.

    The objects around you are visible because they interact with light.  Light typically travels in a straight line. But some materials slow and scatter (散射) light, bouncing it away from its original path. Others absorb light, stopping it dead in its tracks.  Both scattering and absorption make an object look different from other objects around it, so you can see it easily.

    But a transparent object doesn't absorb or scatter light, at least not very much. Light can pass through it without bending or stopping. That means a transparent object doesn't look very different from the surrounding air or water. You don't see it — you see the things behind it.

    To become transparent, an animal needs to keep its body from absorbing or scattering light. Living materials can stop light because they contain pigments (色素) that absorb specific colors of light. But a transparent animal doesn't have pigments, so its tissues won't absorb light. According to Johnsen, avoiding absorption is actually easy. The real challenge is preventing light from scattering.

    Animals are built of many different materials — skin, fat, and more — and light moves through each at a different speed. Every time light moves into a material with a new speed, it bends and scatters. Transparent animals use different tricks to fight scattering. Some animals are simply very small or extremely flat.  Without much tissue to scatter light, it is easier to be see­through. Others build a large, clear mass of non­living jelly­lie (果冻状的) material and spread themselves over it.

    Larger transparent animals have the biggest challenge, because they have to make all the different tissues in their bodies slow down light exactly as much as water does. They need to look uniform. But how they're doing it is still unknown. One thing is clear for these larger animals, staying transparent is an active process.  When they die, they turn a non­transparent milky white.

    We often ask these questions: Are African wild dogs really dogs? What's the difference between African wild dogs and the dogs we know as pets? For one thing, African wild dogs, which live in Africa, only have four toes, while domestic(驯养的）dogs and wolves have five. But you won't want to count for yourself, because they are truly wild animals.

    “Wild dogs are not somebody's domestic dogs that ran away and didn't come back, although some people used to think that,” explains Dr. MeNutt, who studies these animals at Wild Dog Research Camp in the African country of Botswana. “They are actually Africa's wolves, and just like wolves, and they do not make good pets. They need to be out in the wild doing what they are supposed to do — find the food they need to survive and feed their babies.” In fact, they travel so far that researchers have to use radio collars (颈圈) to keep track of them. The collars send out radio signals that tell people where the dogs are. No two wild dogs have the same pattern of coats, so it is easy to tell them apart.

    African wild dogs are smart and sociable, like pet dogs. Adult wild dogs, male and female, are willing to take good care of young ones.

    Millions of domestic dogs live on the planet, but there are probably fewer than 6000 African wild dogs left. Humans hunt them and farmers who don，t want them to go after cows and sheep poison them. Humans are also destroying the wild, natural habitat (栖息地) they need to survive in. Fortunately, today more farmers are finding other ways to protect their cows and sheep from African wild dogs instead of killing the animals.

    With the explosion of consumer choices in recent history, the latest must-haves would surely need to be upgraded more often than every 10 years. In 2002 a computer and basic mobile phone would have been enough for most people, but now? The public need a trendy notebook computer and a smart phone with WiFi connection to feel they are up-to-date. So when will we have enough things? When will we finally be happy? Well, it looks like the things we buy today will barely keep us satisfied for a few months.

    In the eyes of some psychologists, far from making us happy, greater consumer choice creates many serious psychological problems. A fundamental principle of the society is that more freedom is better and more choice in the marketplace means more freedom. Therefore more choice leads to more happiness. This is not the case, however.

    Imagine you go to a café offering chocolate and vanilla ice cream. You choose the chocolate and eat it happily. But what if the café serves 50 kinds of ice cream? You choose chocolate and then start to worry, "maybe blueberry would have been better, perhaps the half-fat ice cream would have been healthier. Stupid me, all these choices and I didn't make the best one! "

    In China's major cities we have now passed the point where more consumer choice is making us happier. We are annoyed by all the options we have, disappointed because our expectations are so high and angered at ourselves when we don't make a perfect choice every time.

    A newspaper reporter tells a story about traveling on a plane with high-speed Internet access. He thought this was amazing—the newest piece of technology he had heard of. Then the service went down. The man next to him was angry and swore. The reporter thought, "How quickly the world owes him something he knew existed only 10 seconds ago!"