Every animal sleeps,but the reason for this has remained foggy. When lab rats are not allowed to sleep, they die within a month.{#blank#}1{#/blank#} 

    One idea is that sleep helps us strengthen new memories. {#blank#}2{#/blank#} We  know that, while awake,fresh memories are recorded by reinforcing (加强)connections between brain cells, but the  memory processes that take place while we sleep  have been unclear.

    Support is growing for a theory that sleep evolved so that connections between neurons(神经元)in the brain can be weakened overnight, making room for fresh memories to form the next day.  {#blank#}3{#/blank#}

    Now we have the most direct evidence yet that he is right. {#blank#}4{#/blank#} The synapses in the mice taken at the end of a period of sleep were 18 per cent smaller than those taken before sleep,showing that the connections between neurons weaken while sleeping.

If Tononi's theory is right, it would explain why, when we miss a night's, we find it harder the next day to concentrate and learn new information —our brains may have smaller room for new experiences.

    Their research also suggests how we may build lasting memories over time even though the synapscs become thinner. The team discovered that some synapses seem to be protected and stayed the same size. {#blank#}5{#/blank#}  “You keep what matters,” Tononi says.

    When we were kids, if our parents wanted us to stop the screen time, they would turn off the TV. {#blank#}1{#/blank#} They grab the cell phone, the tablet or the laptop. Here we will talk about how to control their screen time.

    First, limit the time they use screens. {#blank#}2{#/blank#} Kids are smart. Once you go back to your daily routine, they will quickly be back on a screen. Because they just don't understand that when you tell them to get off the tablet or computer, you mean for the rest of the day.

    {#blank#}3{#/blank#} It can be going outside to play, reading a fun book or cleaning their room. Presenting them with an alternative helps the under-developed planning part of their little brains get past what they can't do and see what else is possible.

    And third, hide the screen device. That one may not seem very fair. {#blank#}4{#/blank#} If they don't see the device around the house, they can't grab it. This way, works for us adult-types who may be a little too addicted to screens ourselves.

    Ultimately, the best way to help kids recognize how much is too much screen time is to limit our own. Yeah, you may have to stare at one all day for your job, but do you really have to come home and immediately turn on the TV or answer that email on your phone? Don't think your kids aren't taking excuses from your actions. {#blank#}5{#/blank#}

A. Second, give them an alternative.

B. So, it's necessary to set a limited time.

C. It may seem easy, but it can be challenging.

D. Now, kids often have a choice of which screen they want.

E. They watch you just as closely as they watch those screens.

F. Now go to find a screen and turn it off, for you and for your kids.

G. But the phrase “out of sight, out of mind” actually works sometimes.

    Do women make BETTER astronauts? Russia locks an all-female crew in space simulator (太空模拟器) for eight days to find out. Six Russian women have been sent into a spaceship to begin a unique experiment testing how an all- female crew would relate to others on a trip to the Moon and back.

    "It's interesting for us to see what is special about the way a female crew communicates," said Sergei Ponomaryov, the experiment's leader." it will be particularly interesting in terms of psychology," said the institute's director Igor Ushakov. "I'd like to wish you a lack of conflicts, even though they say that in one kitchen, two housewives find it hard to live together," he added.

    The volunteers include scientific researchers, a doctor and a psychologist. The test period simulates (模仿) a flight to the Moon and back, with the women carrying out 10 experiments covering psychology and human biology. Russia sent the first woman into space, Valentina Tereshkova, in 1963 but has fallen behind since. Last year, it sent its fourth female astronaut into space, Yelena Serova. Serava complained of a great deal of media interest in how she would wash her hair aboard the International Space Station, pointing out that male astronauts did not face the same line of questioning.

    The women found themselves fielding questions at a press conference about how they would act without men or makeup for eight days, "We are very beautiful without makeup," said participant Darya Komissarova. Her colleague Anna Kussmaul was more direct: "We are doing work. When you're doing your work, you don't think about men and women." They plan to spend their 11/2 hours per day of free time watching films, reading and playing board games. Team leader Yelena Luchnitskaya said she expected the women to deal with any conflict.

    On Nov. 24, near Yellowstone's northeast entrance, Spitfire, a female grey wolf, was shot and killed by a hunter as she approached a group of cottages.

    "It was a legal harvest," Abby Nelson, a wolf management specialist said. "The facts are obviously a little bit harder for people to bear, but that pack has showed signs of habituation. They just stand there and have no fear. Wolf hunters can easily pick the one they want."

    The carefree relation that some Yellowstone wolves have built with humans is reportedly attractive for hunters who look for an easy kill.

    In the overnight, yet another famous Yellowstone wolf met a violent end outside the park, officials are actively rethinking how to manage wildlife habituation.

    Smith, a wolf biologist for Yellowstone, says, "Now we're thinking of pounding them," Park officials might use fireworks, and paintball or beanbag guns when they approach humans in the park. "If you get close to people, you're going to get attacked."

    If you think this sounds cruel, you're not alone. Seeing these creatures from the roads that wind through the park not only allows tourists to witness something amazing, but also to reconnect with nature in a way that is better than any conservation campaign. But there's a growing sense that the present policy of doing nothing isn't working; more wolves will unnecessarily die and the broken record of hunters scoring easy kills will go on.

    As Smith adds, urging people to keep wolves wild when meeting them halfway is a big ask. Still, he's hopeful to preserve the world's best place to observe free­ranging wolves; it's a policy change that tourists can be involved in.

    "... perhaps Spitfire's death will accomplish some good, and we'll all come together to do a better job on managing crowds and roads and wolves in Yellowstone, " Smith said.

    Children exposed to "safe" levels of air pollution in the womb(子宫) develop brain damage that damages their concentration, a study has shown.

    The research is the first too link common pollutants such as nitrogen(氮) dioxide and soot(油烟) to changes in the brains of unborn babies that mean they may struggle to focus at school in later life. The findings suggest that even comparatively clean city air could lead to worse academic performance and an increased risk of mental health problems such as addition or attention deficit hyperactivity disorder(缺陷多动障碍).

    In recent years scientists have found that children who grow up surrounded by air pollution are more likely to have a broad range of "neuro(神经)­developmental" difficulties, including autism and various kinds of cognitive(认知) damage. However, only a handful of studies have looked at the ways in which the poisonous gases and microscopic particles(微粒) that mothers and young children take in affect the brain during critical stages of its growth.

    A group led by Monica Guxens, of the Barcelona Institute for Global Health, found that exposure to air pollution before birth appeared to have slowed the development of several brain regions that play an important role in people's capacity for self­denial and sustained effort. This lack of inhibition could in turn cause "cognitive delays" when the children get older, the scientists argue in Biological Psychiatry.

    "We need this function in our daily life," Dr. Guxens said. "It controls our impulses(冲动) and our selective attention. Children need it to learn and for making decisions in later life. We're interested to see what will happen: is there going to be an impact on their academic work, are there going to be clinical implications? It might be that this will lead to problems later."

    The results were drawn from MRI scans of 873 children between the ages of six and ten in Rotterdam. Even though 99.5 percent of their mothers had lived with nanoparticle pollution levels well below EU legal limits while they were pregnant the pollution still appeared to have taken its toll(伤亡人数).

    Children who had been exposed to more pollution in the womb did worse on a test of their ability to block out irrelevant stimuli(刺激). They also had thinner outer layers in the precuneus(楔前叶) and the rostral middle frontal regions of their brains, both of which are involved in cognitive inhibition, which refers to the mind's ability to tune out stimuli that are irrelevant to the task at hand or to the mind's current state.

    Experiments on animals show that so­called fine particles are able to pass through the placenta and affect the brain of the fetus(胎儿). Dr Guxens said there were probably no such thing as a safe concentration of air pollution.

Customs on either side of the Atlantic

    We all know that Britain and the US are two countries connected by a common language. But in fact, {#blank#}1{#/blank#} as BBC did in a recent story called 8 Situations When Britons Behave Differently From Americans. Below Teens has picked out four for you. Take a look.

    When someone knocks into you.

    If someone bumps into an American, the victim will most likely look the accidental aggressor in the face and expect an apology. If however, {#blank#}2{#/blank#} chances are that the victim will say "sorry" before the other can make his or her own apology.

    {#blank#}3{#/blank#}.

    Britons don't all change into evening dress for supper like what you may have seen in popular TV shows like Downton Abbey. But they do tend to make an effort when going out for dinner somewhere nice. Americans, however, will probably wear a casual shirt to a fancy eatery.

    When you drift finish your food.

    When dining out at a restaurant, {#blank#}4{#/blank#}. They think the food is somehow "tainted" once they've poked at it with a knife and fork. In the US, wrapping it up to take home is a standard practice.

    When you get into a taxi.

    Britons will give the cab driver an address, then assume that's it for the interaction until it's time to pay. Even if they're being taken in a roundabout way, {#blank#}5{#/blank#}. In the US, however, most passengers think nothing of telling the driver what route to take after telling him or her the destination.

A. When you get dressed for dinner

B. When you go out with your friends

C. the differences are more fun to observe

D. they're very unlikely to say anything

E. the victim happens to be British

F. Britons wouldn't think to take the leftovers home

G. they will point it out immediately and politely