Getting less sleep has become a bad habit for most American kids. According to a new survey(调查) by the National Sleep Foundation, 51% of kids aged 10 to 18 go to bed at 10 pm or later on school nights, even though they have to get up early. Last year the Foundation reported that nearly 60% of 7- to 12-year-olds said they felt tired during the day, and 15% said they had fallen asleep at school.

    How much sleep you need depends a lot on your age. Babies need a lot of rest: most of them sleep about 18 hours a day! Adults need about eight hours. For most school-age children, ten hours is ideal(理想的). But the new National Sleep Foundation survey found that 35% of 10- to 12-year-olds get only seven or eight hours. And guess what almost half of the surveyed kids said they do before bedtime? Watch TV.

“More children are going to bed with TVs on, and there are more opportunities(机会) to stay awake, with more homework, the Internet and the phone,” says Dr. Mary Carskadon, a sleep researcher at Brown University Medical School. She says these activities at bedtime can get kids all excited and make it hard for them to calm down and sleep. Other experts say part of the problem is chemical. Changing levels of body chemicals called hormones not only make teenagers' bodies develop adult characteristics, but also make it hard for teenagers to fall asleep before 11 pm.

Because sleepiness is such a problem for teenagers, some school districts have decided to start high school classes later than they used to. Three years ago, schools in Edina, Minnesota, changed the start time from 7:25 am to 8:30 am. Students, parents and teachers are pleased with the results.

    French writer Frantz Fanon once said: “To speak a language is to take on a world, a culture.” Since the world changes every day, so does our language.

     More than 300 new words and phrases have recently made it into the online Oxford Dictionary, and in one way or another they are all reflections of today's changing world.

    After a year that was politically unstable, it's not hard to understand the fact that people's political views are one of the main drives of our expanding vocabulary. One example is “clicktivism”, a compound of “click” and “activism”. It refers to “armchair activists” — people who support a political or social cause, but only show their support from behind a computer or smartphone. And “otherize” is a verb for “other” that means to alienate (使疏远) people who are different from ourselves — whether that be different skin color, religious belief or sexuality.

    Lifestyle is also changing our language. For example, “fitspiration” — a compound of fit and inspiration — refers to a person or thing that encourages one to exercise and stay fit and healthy.

    The phrase “climate refugee” — someone who is forced to leave their home due to climate change — reflects people's concern for the environment.

    According to Stevenson, social media was the main source for the new expressions. “People feel much freer to coin their own words these days,” he said.

    But still, not all newly-invented words get the chance to make their way into a mainstream (主流的) dictionary. If you want to create your own hit words, Angus Stevenson, Oxford Dictionaries head of content development, suggests that you should not only make sure that they are expressive (有表现力的) and meaningful, but also have an attractive sound so that people will enjoy saying them out loud.

    The setting was a packed gymnasium just before the start of a game against another school. There were five girls who were members of the Danville High School basketball team-all of them starters. They were not in uniform to play that night and would not be on the team for the rest of this season. They were there to admit their breaking of team rules. They were there to support their coach's decision to take them off the team. They were there to let the town know there was a problem in their little community that needed to be addressed. And they did it with sincere regret rather than defensiveness.

    While the school had been out for the New Year's holiday, the five girls had gone to the party with several of their friends. There was alcohol there. And they all drank some.

    Coach Rainville has a zero tolerance rule on drugs and alcohol for her members though it was a hard decision to make. When classes resumed and accounts of holiday parties were shared, rumors about the five girls began closing in on them. The coach said she couldn't back down on her rules. And the players-two junior students and senior students-agreed. That night in the gym was part of their public support of the coach's decision.

    “We hope you will understand that we are not bad kids. What we did was definitely not worth it. We hope this event will make everyone realize that there is a big drug and alcohol problem in our community,” one of the senior students said, “And if you work with us to try to solve this problem, you will help us feel that we have not been thrown off our basketball team for nothing.” The five left the floor to deafening applause.

    The team may not win another game this year. But they've learnt something about personal responsibility, the effect of one's action on others, and honesty that will serve them well throughout life.

    Here are some of the strangest aviation(航空)ideas in recent history.

    Double-Decker Seating

    In 2015, Airbus filed a patent for a design for a double-decker cabin seating arrangement. Passengers would sit on top of the other, with upper-tier passengers climbing steps or a small ladder to reach their seats. While the design does have some advantages, the idea of climbing a ladder during flight seems unreliable.

    Separated Cabins

    This patent was awarded to Airbus. Rather than waiting for a flight to arrive and be cleaned,passengers could simply board a ready cabin, which would be moved into the plane's body as soon as it was ready. When the plane reached its destination, the cabin would be separated again. Different cabins with different kinds of seating or levels of comfort could be used for flights of different lengths or destinations.

    Windowless Cockpits(驾驶舱)

    For ideal design, airplane noses should be long and pointy. But there's the whole "pilots have to fit in the cockpit" problem. Well, what if the cockpit didn't have to go in the nose of the plane? That's part of the thinking behind this Airbus patent application* which suggests replacing the plane's window with a digital viewing surface. Without a window, there's no reason the cockpit needs to go in the front of the plane —it could go in the middle of the plane, or even in the tail.

    Nap Straps (睡眠吊带)

    Airbus is not the only company in the strange patent contest. Boeing's got its own patent, Nap Straps. With this invention, passengers looking for a nap can find an "upright sleep system^" beneath their seat. In action, the whole thing is somewhat like a traction device for someone who's been in a terrible accident.

    Next month, I'm traveling to a remote area of Central Africa and my aim is to know enough Lingala — one of the local languages — to have a conversation. I wasn't sure how I was going to manage this — until I discovered a way to learn all the vocabulary I'm going to need. Thanks to Memrise, the application I'm using. It feels just like a game.

    "People often stop learning things because they feel they're not making progress or because it all feels like too much hard work," says Ed Cooke, one of the people who created Memrise. "We're trying to create a form of learning experience that is fun and is something you'd want to do instead of watching TV."

    Memrise gives you a few new words to learn and these are "seeds" which you plant in your "greenhouse". When you learn the words, you "water your plants". When the application believes that you've really memorized a word, it moves the word to your "garden". And if you forget to log on, the application sends you emails, reminding you to "water your plants".

    The application uses two principles about learning. The first is that people memorize things better when they link them to a picture in their mind. Memrise translates words into your own language, but it also encourages you to use "mems". For example, I memorized motele, the Lingala word for "engine", using a mem I created — I imagined an old engine in a motel (汽车旅馆) room.

    The second principle is that we need to stop after studying words and then repeat them again later, leaving time between study sessions. Memrise helps you with this, because it's the kind of application you only use for five or ten minutes a day.

    I've learnt hundreds of Lingala words with Memrise. I know this won't make me a fluent speaker, but I hope I'll be able to do more than just smile when I meet people in Congo. Now, I need to go and water my Vocabulary!

    A Latin phrase beloved by every old-fashioned British schoolmaster was mens sana in corpora sano—a healthy mind in a healthy body. Greater physical activity is associated with better mental, as well as physical health. And it might also be linked to greater worker productivity, and thus faster economic growth. That is the conclusion of a new report from a European think tank — RAND.

    The RAND study looks at different measures: absenteeism (when workers take time off for illness) and presenteeism (when they turn up for work but are less productive because of sickness). The latter measure was self-reported by employees, who were asked whether their work was negatively affected by health issues. The survey suggests that between 3 and 4.5 working days each year are lost as a consequence of workers being physically inactive. This is between 1.3% and 2% of annual working time. Most of this was down to presenteeism.

    Another potential gain from improved fitness is reduced health-care costs. In America, where health care is often provided through employment-based systems, firms could benefit. RAND estimates that total American health savings could be $6bn a year by 2025. But the study's authors conclude that if people met certain exercise targets, global GDP could be around 0.17-0.24% higher by 2050. Nothing to laugh at in a world of slowing growth.

    How to encourage workers to become more active? Rewards are useful but only if they have conditions; giving all employees free gym membership does not seem to work. Another RAND Europe study examined an experiment in which workers were each given an Apple watch, payable in instalments (分期付款) at a discounted price—but only to those who agreed to have their physical activity monitored. Monthly repayments depended on how much exercise they took.

    The problem is that many people are too optimistic about their health, ignoring the risks they face. This means that participation in workplace exercise plans tends to be low, around 7% in the sample studied by RAND. Firms are not the only ones that can encourage a healthier lifestyle; friends and families are likely to be more important. But businesses can play a bigger role.

    If RAND is right, this may bring them financial benefits. Company taskmasters may yet grow fond of an adapted saying: mens sana in corporate sano.