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 see-through? 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 see--through. Others build a large, clear mass of

 non-living jelly-lie(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 non-transparent milky white.

    Young sunflowers turn and swing every day. New findings add to evidence that the plants are animal-like.

    Harmer, a professor in the University of California at Davis, Department of Plant Biology, carried out a series of experiments on sunflowers in the field, in pots outdoors and in indoor growth chambers.

    By staking plants so that they could not move, Harmer showed that he could destroy their ability to track the sun. He also noticed that sunflowers prevented from moving were not as tough and leafy as those that were free to move. When plants were moved indoor with a settled overhead light, they continued to swing back and forth for a few days.

    The indoor plants did start tracking the “sun” again when the apparent source of lighting was moved across the room. The plants could reliably track the movement and return at night when the artificial day was close to a 24-hour cycle, but not when it was closer to 30 hours.

    When sunflowers track the sun, the east sides of their stems grew more rapidly than the west sides. At night, the west sides grew faster as the stem swung the other way. The team identified a number of genes that were expressed at higher levels on the sunward side of the plant during the day or on the other side at night. A plant growth-regulating hormone (激素), called auxin, appears to be a key driver.

    The “dance” to the sun cycle obviously slows when the sunflower matures (成熟) and its flowers open up. At that point, the plants stop moving during the day and settle down facing the sun in the east.

    “Bees like warm flowers.” Harmer said, adding that the bees are cold-blooded, so landing on a warm flower saves them energy and perhaps feels really good.

    “The morning warmth changes the flowers in a way to make them more appealing to insects, perhaps causing them to release more attractive scents earlier in the day.” he said “We're currently testing this idea.”

    Chocolate is good for your heart, skin and brain. Usually, people think that chocolate is bad for their health. They describe chocolate as “something to die for” or say “death by chocolate”. Now they should bite their tongues! Evidence is showing that some kinds of chocolate are actually good for you in the following ways:

    A happier heart

    Scientists at Harvard University recently examined 136 studies on cocoa—the main ingredient in chocolate and found that it does seem to strengthen the heart．Studies have shown heart benefits from increased blood flow. These benefits are the result of coca's chemicals, which seem to prevent both cell damage and inflammation (炎症)．

    Better blood pressure

    If yours is high, chocolate may help. Jeffrey Blumberg from Tufts University recently found that people with high blood pressure who ate 3.5 ounces of dark chocolate per day for two weeks saw their blood pressure drop quickly.

    Muscle magic

    Chocolate milk may help you recover after a hard workout (锻炼). In a small study at Indiana University, people who drank chocolate milk between workouts did better on a tiredness test than those who had some sports drinks.

    Better for your skin

    German researchers gave 24 women a half-cup of special cocoa every day. After three months, the women's skin was moister (滑润的) and smoother. The research shows that chocolate helps protect and increase blood flow to the skin, improving its appearance．

Brain gains

    It sounds almost too good to be true, but research suggests that chocolate may improve your memory, attention span, reaction time, and problem-solving by increasing blood flow to the brain．

    Bullying(霸凌) can take a variety of forms, from the verbal to the physical as well as indirect forms, such as being excluded from social groups. Bullying is clearly unpleasant, and can make the child experiencing it feel unworthy and depressed. In extreme cases it can even lead to suicide, though this is thankfully rare.

    Until recently, not much was known about the topic, and little help was available to teachers to deal with bullying. Perhaps as a consequence, schools would often deny the problem. There is no bullying at this school' has been a common answer if asked, almost certainly untrue. Fortunately more schools are now saying: “There is not much bullying here, but when it occurs we have a clear policy for dealing with it.” Three factors are involved in this change. First is an awareness of the severity of the problem. Second, a number of resources to help tackle bullying have become available in Britain. For example, the Scottish Council for Research in Education produced a package of materials, Action Against Bullying, circulated to all schools in England and Wales as well as in Scotland. In Ireland, Guidelines on Countering Bullying Behaviour in Post-Primary Schools was published, too. Third, there is evidence that these materials work, and that schools can achieve something.

    Evidence suggests that a key step is to develop a policy on bullying, saying clearly what bullying means, and giving explicit guidelines on what will be done if it occurs, what records will be kept, who will be informed and what punishments will be employed. The policy should be developed through consultation over a period of time. Pupils, parents and staff should feel they have been involved in the policy. Other actions can be taken to back up the policy. There are ways of dealing with the topic through the curriculum, using video, drama and literature. But curriculum work alone may only have short-term effects; it should be an addition to policy work. There are also ways of working with individual pupils, or in small groups. Work in the playground is important, too. One helpful step is to train lunchtime supervisors to distinguish bullying from playful fighting, and help them break up conflicts. Another possibility is to improve the playground environment, so that pupils are less likely to be led into bullying from boredom or frustration.

    With these developments, schools can expect that at least the most serious kinds of bullying can largely be prevented. The more effort is put in and the wider the whole school is involved, the more substantial the results are likely to be. The reduction in bullying and the consequent improvement in pupil happiness is surely a worthwhile objective.

    NEW HAVEN, Connecticut—A surprise awaited students in Yale who showed up for Professor Laurie Santos's class. They got slips of paper that said, "No class today." There was only one rule for the students' unexpected free time—They were not allowed to study, but to relax. Since exams and papers were coming up, everyone was tired and stressed. At this moment they were touched. With around applause, nine students hugged Santos, and two burst into tears.

    Yet, cancelling class was not just a break. It was also a challenge, as she was asking them to stop worrying about their grades, even if it was just an hour. One student went to the Yale University Art Gallery for the first time in her four years at Yale. A group of students went to a recording studio and played a new song. More people were outside, and more were smiling. That's why about 1, 200 students were taking Santos's class, called "Psychology and the Good Life," the largest class in Yale's 317-year history. Even non-Yale students had the chance to take Santos's class. It was offered as an online course and she immediately became an Internet hit.

    Skyler Robinson, one of her students, was at a loss for a while about what to do during his break, and then decided to take a nap. "It was a great nap," he commented. Santos designed the class after she realized that her students kept busy through long days that seemed far more depressing and joyless than her own college years. "They feel they're in this crazy rat race. They're working so hard that they can't take a single hour off. That's awful."

    The ideas behind the class are simple. Santos said, "It is the hope that science can help students find peace among all the stresses and difficulties they face at college." The lessons include showing more gratitude, performing acts of kindness and increasing social connections. The students really wanted to learn to lead a happy life in a science -driven way. Santos also noted the psychological happening of "mis-wanting", which led people to work towards the wrong goals in life.

    One week, Santo asked students to exercise. Another week, she wanted them to get more sleep. They worked hard to keep some new habits. Social science research led to many new understandings of how people find happiness. She thinks her class can change Yale, or rather, not just Yale.

    Portland, Oregon, just got another reason to call itself "Bike City USA".

UPS has started a trial program to deliver packages there using an electric-powered bicycle. The environmentally friendly Cargo Cruiser is a tricycle with a large brown box on the back. Like any electronic bike, the Cargo Cruiser can be powered by foot, motor, or a combination of both.

    UPS began testing e-Bikes in Hamburg, Germany, in 2012, but this is the first time the technology has been used for package deliveries in the United States.

The e-Bikes support UPS's efforts to reduce its carbon emissions, ease urban noise levels, and improve air quality. The amount of energy to be saved by using e-Bikes hasn't been quantified, but the test vehicle in Portland "will probably displace about two gallons of fuel every day", said Scott Phillippi, UPS's engineering manager.

    Phillippi says that one e-Bike alone won't create a huge difference in UPS's carbon emissions, but he describes it as “a piece of our overall strategy” as far as environmental impacts and efficiencies.

    It also ties into the company's broader strategy to settle a problem that troubles Portland and other cities around the world: traffic jam. According to UPS, traffic jam costs it hundreds of millions of dollars a year in additional operating costs. The time when the average UPS delivery truck is stuck in traffic is about 16 minutes a day, slowing its deliveries and increasing the company's carbon emissions.

    The pilot program is in its early stages and already has hit its first stage: ice storms pulled trees and branches down all over the city, blocking bike lanes and making travel dangerous. How do e-Bikes deal with it?

    If the trial proves successful, you may be able to see UPS delivery people wearing bike shorts in other places around the country, "Other cities have expressed some interest," Phillippi said.