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    Do you and your friends ever talk about your dreams with each other? If you do, you might have noticed something interesting – some of your friends seldom remember their dreams, but some can always describe their dreams so clearly that it seems like they're describing things that really happened to them. What makes those people different?

    The answer is simple. There are two different types of dreamers – low dream recallers（回忆者）and high dream recallers.

    Low dream recallers usually remember their dreams only twice a month. But high dream recallers are able to remember them about five mornings a week. And a new study suggests that activity in a certain part of the brain could have something to do with it, reported The Huffington Post.

    Perrine Ruby, a French researcher at the Lyon Neuroscience Research Center, studied 41 people (21 high dream recallers and 20 low dream recallers) and recorded their brain activity.

    She found that a part of the brain called the temporo-parietal junction (颞顶联合区) was more active in high dream recallers than in low dream recallers – both when they were sleeping and awake.

    This brain area collects and processes（编程）information from the outside world. This means that high dream recallers know more about what's happening around them. For example, when they are awake, they respond (对……有反应) more strongly to hearing their own names, and when they are sleeping, they are woken more easily by sounds and movements.

    By closely studying people's brain activities, Ruby found that high dream recallers have twice as much “wakefulness time” during sleep as low dream recallers do. And it is during these short times of wakefulness that the brain remembers dreams.

    “The sleeping brain is not able to remember new information,” Ruby told The Washington Post. “It needs to wake up to be able to do that.”

    This is not hard to understand. Just try to think of your own sleeping experiences. If you are worried during the night, you are more likely to remember your dreams, but if you sleep well, you will remember little in the morning, and this is because “you never get a chance to remember”, Robert Stickgold, a Harvard Medical School researcher, told The Washington Post.

    Smog(雾霾) is a big problem in many Chinese cities. But it seems that besides wearing a mask, few of us know what has caused the smog and what to do to beat it. Chai Jing, a former news hostess with China Central Television, discussed the questions in her documentary Under the Dome.

    The 103 - minute film was published on major Chinese video - sharing websites on Feb 28. In the film, Chai visits polluted places and talks to officials and scientists. She comes to the conclusion that burning too much coal and oil are the main causes of PM2.5 and smog.

    To make things worse, according to Chai, the coal and oil we are burning is of poor quality and don't meet the standards for environmental protection. Therefore they have produced more harmful gas to pollute the air.

    To solve the problem, Chai suggests that we should clean our coal and oil or replace them with cleaner energy such as natural gas. In her film, Chai also pointed out that ordinary people can do something to help control smog too. For example, we live a greener life by using more public traffic. Or if we see things that could harm the environment, we can try to stop it. In one scene from the film, Chai sees a dirt mound in a building site exposed in the air, and asks the person in charge to cover it. When she sees a restaurant cooking without any suitable filter facilities, she calls the hotline 12369. The restaurant installed the filter a week later.

    Chen Jining, the new minister of environmental protection, praised Chai. "This film encourages ordinary people to care about the environment. This is what we need in the future. "

There are a lot of museums in the world. A museum has many important objects related to (有关联) science, culture, or history.

Did you know that humans aren't the only species (物种) that use language? Bees communicate by dancing. Whales talk to each other by singing. And some apes talk to humans by using American Sign Language. 

A female gorilla(大猩猩), Koko, was born at the San Francisco Zoo on July 4th, 1971. Koko learned sign language from her trainer, Dr. Penny Patterson. Patterson began teaching sign language to Koko in 1972, when Koko was one year old. Koko must have been a good student, because two years later she moved onto the Stanford University campus with Dr. Patterson. Koko continued to learn on the campus until 1976. That's when she began living full﹣time with Patterson's group, the Gorilla Foundation. Patterson and Koko's relationship has been very close ever since. 

Dr. Patterson says that Koko has mastered sign language and known over 1,000 words, and that Koko makes up new words. For example, Koko didn't know the sign for ring, so she signed the words finger and bracelet(手镯). Dr. Patterson thinks that this shows meaningful and constructive use of language. 

Not everyone agrees with Dr. Patterson. Some argue that apes(类人猿) like Koko do not understand the meaning of what they are doing. Some people who don't believe that say that these apes are just performing complex tricks (戏法). For example, if Koko points to an apple and signs red or apple, Dr. Patterson will give her an apple. They argue that Koko does not really know what the sign apple means. She only knows that that if she makes the right movement, one which Dr. Patterson has shown her, then she gets an apple. The argument is not solved, but one thing is for certain: Koko is an extraordinary ape. 

It seems like Patterson and Koko have a good relationship, but not everyone agrees with it. Some people believe that Patterson is humanizing the ape. They think that apes should be left in the most natural state possible. Even Dr. Patterson struggles with these feelings. When she was asked if her findings could be duplicated by another group of scientists, she said, "We don't think that it would be ethical (道德的) to do again. " She went on to argue that animals should not be kept in such unnatural environment. 

As for the future, Dr. Patterson and the Gorilla Foundation would love to get Koko to an ape preserve (保护区) in Maui, but they are having trouble getting the land. So unless you have a few million dollars to give, Koko's going to be spending her time in Woodland, California with Dr. Patterson. Koko probably doesn't mind that. If she moved to Hawaii, she'd have to give up her Facebook page and Twitter feed, and she's got like 50 thousand "likes". Some may deny (否认) that she knows sign language, but nobody says that she doesn't know social networking.

Tourism has become a huge industry. Tourists make millions of foreign trips a year, twice as m {#blank#}1{#/blank#}as 20 years ago. It's now the largest employer on Earth. Clearly, it can do great good, but it can also do great damage.

It's true that tourism has brought benefits to many areas of the world that were very poor. However, mass tourism also has some bad e {#blank#}2{#/blank#}. Local culture and customs change as more tourists arrive. Too much tourism damages the environment. And more and more tourists are behaving badly.

Complaints from local people are growing. In cities such as Barcelona or Venice residents say that too many tourists arrive on cruise ships(游轮). As a result, town centres are overcrowded. They tell stories about n {#blank#}3{#/blank#} parties that keep people awake all night. In famous beauty spots, where tourist money was welcomed, people are now worried about the damage tourists do to the environment.

Of course, many tourists enjoy the benefits of tourism in a responsible way. They choose holidays that support the local economy and they respect the local culture and the environment. Environmentally friendly tourism, or eco-tourism, is becoming more p {#blank#}4{#/blank#}.

Responsible tourist behaviour is necessary, but it isn't enough to solve the problem. Many people now believe that governments should control how many visitors enter their country. They believe they should limit the n {#blank#}5{#/blank#}of cruise ships that use their ports and should not allow too many hotel developments.

U {#blank#}6{#/blank#}, governments are in a difficult situation. Tourism brings in a lot of money and this helps them i {#blank#}7{#/blank#} life for the local people. However, some governments are beginning to understand that too much tourism can be bad for the local population and the environment. They've taken some measures to promote environmentally friendly tourism. There may still be hope.

 When you look into the mirror, you may wonder whether it is possible for us to have a twin self who can do lots of challenging things for us, like the difficult project to be finished ahead. Now with the invention of digital twins, it seems possible.

A digital twin is a copy of things like the products or persons in the online forms. Like humans,    a digital twin can also develop itself as long as they are fed with enough data(数据).

 In 1970, when Apollo 13 was carrying out its task in space, something went wrong with the spaceship, leaving astronauts stranded(困住)200,000 miles from Earth, NASA engineers used spacecraft data to recreate the conditions of the broken part of the spacecraft. This method allowed them to develop solutions that finally brought the astronauts safely home. This event is widely thought as the birth of digital twins. Since then, this technology has been used in many fields, including business, medicine, and more recently, human modelling.

 One of the most fantastic uses of digital twins is in health care. Professor Declan O' Regan, an    AI expert, shows the new method can help doctors treat certain illness easily and quickly, and it can even help doctors to find ways to stop some kind of illness before it is too late.

 Another successful example is to use the digital twin to change the sports science to some degree. Compared with the past when the coaches needed to set up a program to help train the sportspersons, they now use the data to build the digital twin to help the athletes to improve their skills and avoid accidents in sports.

 Not everything about the digital twin is good. It is clear that the new technology will influence us a lot, but what direction it will take in the future remains to be seen. There are some doubts over it, as it will result in problems related to ethical(道德的) consideration.