In order to escape from bats’ hunt through sound, some of the moths have therefore evolved a “stealth coat” — made of tiny hairs and a layer of scales(磷片) — that reduces their detectability through echolocation(回声定位).

Mare Holderied, a biologist at the University of Bristol, wanted to know how good the moths were at hiding from bats. So he shaved off their hairs and then sent sound waves towards them, imitating how bats might echolocate to find their prey.

It turned out the moths’ one and-a-half-millimeter layer of fur reduced their detectability by just over 40％. In addition to the fur, moths also have a thin layer of scales, tens to hundreds of thousands of them, on each wing. The scales each respond to specific frequencies of sound waves and when a bat’s echolocation signals hit the moth’s wings, the scales start to shake. The acoustic energy (声能) from the echolocation is thus absorbed.

Dr. Holderied and his colleagues tested how well the scales worked and found that they were as good at absorbing sound as the fur. They absorbed as much as 87% of the incoming sound energy, but at only one tenth of the fur’s thickness. In terms of their ability to absorb sounds, the moth’s scales outperform and are much thinner than any human-designed soundproofing(隔音) used in homes and offices.

Recognizing the significant impact of noise on human health, especially in urban environments, Dr. Holderied’s team has been taking inspiration from the sound-absorbing proper tics of moths to design wallpaper that can reduce the noise of road traffic. Dr. Holderied concluded, “One day it will be possible to adorn the walls of your house with super-thin sound absorbing wallpaper, using a design that copies the mechanisms from moths. Moths are going to inspire the next generation of sound absorbing materials.”

Many films and TV shows will tell you that sharks are scary and often eat beach–goers. 【小题1】 Sharks play an important ecological role in the ocean.

Many of these fish are top predators (捕食者). They can help control populations of other animals. However, other sharks serve as clean- up crews, chowing down on migrating (迁徙的) birds when they fall out of the sky. 【小题2】 Migrating land-based birds that fall from the sky as they cross the Gulf of Mexico can end up in the belly of a young tiger shark. But not all sharks are meat-eaters. 【小题3】

As a group, sharks are much, much older than we are. The first shark— like fish appeared more than 400 million years ago. 【小题4】 Some have saw— toothed noses, and some may have big hooks on their heads.

【小题5】 They have super-sensitive noses and use snouts (鼻子) to find weak electrical signals from their food. Scientists are even trying to design materials to imitate shark’s bacteria-battling skin.

We’ve all done it. For many of us, it’s something that happens so naturally every day. After working on an important project or a task for a little while, you decide to take a break-only to pick up your smartphone and start looking through social media, reading emails, checking out the news and maybe getting in a quick round of “Candy Crush Saga”. A break is supposed to be a time to relax so that you can go back to your work feeling fresh. However, a new study finds that cellphone use during a mental break doesn’t really allow the brain to relax and can actually result in a poorer performance.

For the study, a group of 422 undergraduate students at Rutgers were assigned a set of 20 word puzzles to complete. Halfway through the task, the students were separated into three groups: one group took a break and were told to use their cellphones to go shopping online, another group took a break and were instructed to shop either via their computers or using a paper circular (印刷品广告), and the third group didn’t take a break at all.

Interestingly, the group that took a break with their cellphones displayed the highest levels of mental fatigue (疲劳), and had the hardest time solving the word puzzles following their breaks. In all, the cellphone group took 19% longer to finish the puzzle task, and solved 22% fewer problems than participants in the other two groups combined.

“The act of reaching for your phone between tasks, or the mid-task, is becoming more common. We assume it’s no different from any other break-but the phone may carry increasing levels of distraction (使人分心的事) that make it difficult to return focused attention to work tasks,” explains Terri Kurtzberg.