Some educators told us that more years of school could help students get higher scores on intelligence tests. That was a finding of a study of teenage males in some countries. Now, another research shows that physical activity may help students do better in their classes.

    The research comes as educators in some countries are reducing time for activities like physical education. They are using the time instead for academic（学术的）subjects like math and reading. The studies appeared between 2008 and 2014. They included more than 55, 000 children, aged 6 to 18.

    Amika Singh:“ According to the results of our study, we can conclude that being physically active is beneficial for academic performance. There are, first, Physiological explanations, like more blood flow, and so more oxygen to the brain. Being physically active means there are more hormones(荷尔蒙)produced like endorphins(内啡肽). And endorphins make your stress level lower and your mood improved, which means you also perform better.”

    Also, students taking part in organized sports learn rules and how to follow them. This could improve their classroom behavior and help them keep their mind on their work.

    The study leaves some questions unanswered, however. Ms. Stash says it is not possible to say whether the amount or kind of activity affected the level of academic improvement. This is because of differences among the studies.

    The researchers said they found only two high-quality studies. They needed more high-quality studies to confirm (证实) their findings. They also pointed out that “results for other parts of the world may be quite different.”

    Still，the general finding was that physically active kids are more likely to do better in school. Ms. Singh says schools should consider that finding before they cut physical education programs. Her paper on “Physical Activity and Performance at School” is published in the Archives of Pediatric and Adolescent Medicine.

    Plastic is easy, convenient, cheap and long-lasting, but it does great harm to the environment.

    Since plastic entered mass production, 8 billion tons have been produced – and we aren't very good at recycling. By 2015, 6,945 tons of plastic waste had formed, with around 9 percent of it getting recycled. About 79 percent of it ends up in landfills or around the environment, including the ocean. We may end up drowning in plastic before long.

    Chemists at Colorado State University have found a polymer（聚酯）that has many of the qualities of plastics – it's light, strong, durable and heat-resistant – but that can be changed back to its original small-molecule（分子）state for complete recycling. Even after being recycled, the polymer can be turned back into its plastic-like state, and this can be done quickly and cheaply.

    This new polymer has all the good qualities of plastics, yet it is relatively easy to make and to recycle. Making it requires room temperature conditions, a short reaction time to bond the monomer（单体）into polymers and only a small amount of the catalyst（催化剂）remains in the end product. It has a high molecular weight, stands up to heat and generally behaves like plastic. Recycling it requires similarly little effort. Mild lab conditions are required and so is a catalyst. Once applied, the polymers are once again monomers in a matter of minutes and can be used to create another product.

    But don't get too excited about this just yet. Scientists stressed that the polymer isn't ready for mass products just yet. There's still plenty of development to do, including making it more economical to produce and recycle.

Senses That Work Together

    When we think about how our senses work, we usually imagine them operating separately: you sniff a flower, and the smell is delivered uninterrupted from nose to brain. However, it's more complex than that. Most evidence for cross modal perception (知觉) comes from studies into sound and vision (视觉). But research that shows other senses crossing over is coming out all the time, and it seems that even sound and smell sometimes form an unlikely pairing.

    When New York researchers, Daniel Wesson and Donald Wilson, tried to find out the truth about a "mysterious” area of the brain called the olfactory tubercle, they had to deal with this fact. Originally, they only intended to measure how olfactory tubercle cells in mice responded to smell. But during testing, Wesson noticed that every time he put his coffee cup down, the mouse cells jumped in activity. In fact, the olfactory tubercle is well-placed to receive both smell and sound information from the outside world. Later they found that among separate cells, most responded to a smell but a significant number were also active when a sound was made. Some cells even behaved differently when smell and sound were presented together, by increasing or decreasing their activity.

    Of course, mice aren't people, so research team has been carrying out further experiments. They pulled together a group of people and gave them various drinks to smell. Participants were asked to sniff the drinks, and then match them to appropriate musical instruments and produce the notes at different levels. The results were interesting: piano was regularly paired with fruity fragrances; strong smells sounded like the instruments that are made of metal.

    Further research found that listening to different sounds can change your perceptions. Studying taste this time, the team ordered some special toffee (太妃糖) and put together “soundscapes” corresponding to bitterness and sweetness. Participants tasted similar pieces of toffee while listening to each soundscape, and found the toffee more bitter or sweeter, depending on which soundrack they were listening to.

    Studies like this are helping scientists correctly describe our understanding of the senses, and how the brain combines them with its advantage. The consequences are worth considering. Could we see musicians work together with chefs to produce sound-improved food and drink? Will you be ordering a coffee with a soundrack to bring out your favorite smell? Come to think of it, that could be one thing you hope coffee shop chains don't get round to.

    Captain America and Blackpanther were about to defend Earth from the criminal Thanos when Kevin Foley first noticed something was wrong. Foley, a 46-year old information-technology worker from Kyle, Texas, was heading into the theater to see Avengers: Infinity War when he realized he was having trouble breathing normally. The same symptom struck again during another movie the following night, but more severe this time. Once the cast on the second film rolled, Foley took action: he looked at his wristwatch. It was a bigger step than you might imagine, because Foley was wearing an Apple Watch equipped with medical sensors and experimental software to track basic functions of his heart. And the watch was worried. It had, according to the display, detected signs of an irregular heartbeat.

    Before long, Foley was in an emergency room, where doctors hooked him up to an ECG(心电图), which showed that he was in atrial fibrillation(心房颤动), an irregular heartbeat that can lead to blood clots(血栓), stroke and other potentially disastrous diseases. Foley spent the next few days in the hospital while doctors worked to return him to a normal heart rhythm eventually turning to a procedure called electrical cardioversion to shock his heart back to normal. Foley is doing fine now. But he believes that, if not for the warning on his watch, he might not have sought help in time. “I would have never known,” he says.

    Foley and his watch were part of an experiment run by Apple and Stanford's medical school. But beginning Dec. 6, anyone can get an on-the-fly heart checkup, assuming they've paid $399 or more for an Apple Watch. That's when Apple will launch a software update that turns its latest model, called the Series 4, into a personal ECG, thanks to an innovative new sensor. Though less complicated than hospital ECG machines, the watch version can still provide basic information and warnings of potential risks worthy of a closer look by a medical professional.

    For Apple, this new ECG-on-your-wrist is its biggest bet yet that personal technology will inevitably include personal health. Along with competitors, Apple has already offered fitness functions, such as apps to track the steps you've walked. But with the new ECG scan, Apple is moving straight into medical aspects of heath, a distinction underlined by the fact it sought and received Food and Drug Administration clearance for the clearance for the heart monitor.

    During an earthquake, you should know what to do. If the earthquake strikes while you're inside a house, you should lie on the floor under a strong table or other furniture. If there is no furniture, you can cover your head with your arms and keep still in the corner of the room. You should keep away from windows, glass walls, or anything that can fall.

    If you are in bed, hold firmly onto your bed and make use of a pillow to safeguard your head. You may use a doorway but only when it is close to you. It should also be considered whether it is strong enough to deal with the load.

    If you are running out, do not use lifts, even if they work. Electricity may go out at any time. Many injuries happen when people try to rush out. This means you ought to stay in your house or perhaps wherever you are.

    When you stay outdoors, you should stay far from buildings, power wires or lights. You should be in the open until the quake stops. Remember that many earthquake deaths outside the house come from falling-apart walls, flying glass and other falling things.

    If an earthquake strikes and you are driving, you should pull up to the side of the highway and stop as quickly as possible. You ought not to stop under trees, buildings or energy wires. Don't stop in the middle of the street as it could trouble others.

    When trapped, you shouldn't move. Your mouth should be covered with a piece of clothing or a handkerchief. This is because it is possible for you to breathe in some dust. Do not shout whenever possible. You should only shout in the end to get help from rescuers.

    Do you think the United Kingdom and the United States are alike? Winston Churchill once joked that the people of Britain and the people of America are separated only by their language. Do you think that is true? The British and the Americans both speak English as the official language. However, each uses some different words. We Americans are similar to the British. After all, our country was once owned by the UK,so we have a lot in common. But there are many differences between us.

    The UK has a king or queen, and the leader of the government is the Prime Minister. The US has no kings or queens. Our leader is the President.

    Both the British and Americans use pounds and ounces, pints, quarts, and gallons. Both use miles, yards, and feet. Our money is different, though. The British use pounds and pence. Americans use dollars and cents.

    Driving in a car is very different in the UK. They drive on the left side of the road. We drive on the right. What we call the hood of the car, the British call the "bonnet". British cars run on "petrol", which we call gasoline.

    In our everyday life, we do many of the same things as the British. But we describe them differently.

    A young mother here might push a baby in a baby carriage. A British mum pushes a "pram". The British watch "telly", while we watch TV. We like to eat French fries, but the British call them "chips". Millions of Americans drink coffee, but most British prefer tea.

    So we are different in many ways. But we stay friendly anyway.