Perhaps it is time to turn down your smart phones to stop your hearing being harmed without being noticed. The UN sounded a warning Tuesday 【小题1】 more than one billion young people are in danger of damaging their hearing through overuse of smart phones and other audio devices , 【小题2】 (suggest) new safety standards (标准) for safe volume (音量) levels.

Young people tend to fall into risky listening habits easily. Around half of those 【小题3】 the ages of 12 and 35, or 1.1 billion people, are at risk as a result of long hours of enjoying loud sounds, including music they listen to through 【小题4】 (person) audio devices, the UN health agency said.

At present, about five percent of the global population, or some 466 million people, 34 million children included, suffer from disabling hearing loss. WHO considers a volume above 85 decibels (分贝) for eight hours or 100 decibels for 15 minutes 【小题5】 (high) unsafe levels.

The organization is calling for parental as well as automatic volume controls on audio devices 【小题6】 (prevent) dangerous use.

While some smart phones and other audio devices already offer some of these features, the UN would like to see 【小题7】 uniform standard used to help protect against disabling hearing loss.

“Think of it like driving on a highway, but without a speedometer in your car or a speed limit,” Shelly Chadha of the WHO told 【小题8】 (report) in Geneva. “【小题9】 we've advised is that your smart phones 【小题10】 ( fit) with a speedometer, with a measurement system which tells you how much sound you're getting and tells you if you are going over the limit.”

Challenging work that requires lots of analytical thinking, planning and other managerial skills might help your brain stay sharp 【小题1】 you age, a study published Wednesday in the journal Neurology suggests.

Researchers from the University of Leipzig in Germany gathered more than 1, 000 retired workers who were over age 75 and had the volunteers’ memory and thinking skills 【小题2】(assess)through a battery of tests. Then, for eight years, the scientists asked the same group to come back to the lab every 18 months 【小题3】(take) the same sorts of tests.               

Those who 【小题4】(hold) mentally stimulating, demanding jobs before retirement tended to do the best on the tests. And they tended to lose cognitive(认知) function 【小题5】 a much slower rate than those with the least mentally challenging jobs. The results held true even after the scientists accounted for the participants’ overall health status.

“This works just like physical exercise,” says Francisca Then, who led the study. “After a long run, you may feel like you’re in pain, you may feel tired. But it makes you fit. After a long day at work — sure, you will feel tired, 【小题6】it can help your brain stay healthy. ” It’s not just corporate jobs, or even paid work【小题7】can help keep your brain fit, Then points out. A waiter’ s job, for example, 【小题8】( require) multitasking, teamwork and decision-making could be just as stimulating as any high-level office work. And “running a family household requires high-level planning and coordinating（协调）,” she says. “You   【小题9】 organize the activities of the children and take care of the bills and groceries.”

Of course, our brains can decline as we grow older for lots of reasons — including other environmental influences or genetic factors. Still, continuing to challenge 【小题10】mentally and keeping your mind busy can only help.

Being nearsighted is more common 【小题1】 it once was. It occurs when eyeballs are longer than normal, 【小题2】 (change) the angle (角度) at which light enters the eye and therefore the ability to focus on distant objects.

More and more researchers indicate that 【小题3】 lack of direct sunlight may reshape the human eye and damage vision. Those 【小题4】 were exposed to the sun frequently, particularly between the ages 14 and 19, were about 25 percent 【小题5】 (little) likely to have developed nearsightedness by middle age.

So, how much sunlight should you get?

Scientist Kathryn Rose recommends at least 10 to 14 hours per week in addition to any time 【小题6】 (spend) outdoors while at school. This is the level at which her 【小题7】 (study) have found a preventative effect. Lower amounts of sunlight, like 3 to 6 hours, 【小题8】 (show) no effect on vision.

Ten to 14 hours a week may seem like a lot to you, but you need the sun for more than just your vision. Sunlight has a direct 【小题9】 (connect) to vitamin D levels, mood, and even weight.

And these benefits aren't limited to children. Exposure 【小题10】 sunlight up to the age of 30 also confers (授予) a protective benefit.