Every time your fingers touch your cell phone, they leave behind trace of amounts of chemicals. And each chemical offers clues to you and your activities. By studying them, scientists might be able to piece together a story about your recent life, a new study finds.

    A molecule (分子) is a group of atoms. It is the smallest amounts of some chemicals. Your skin is covered in molecules picked up by everything you touched. With each new thing your skin contacts, you leave behind some small share of what it'd touched earlier.

    Researchers at the University of California, San Diego (UCSD) recently studied such chemical leftovers on the phones of 39 volunteers. The study was led by biochemist Amina Bouslimani. To explore those residues (剩余物), the UCSD team wiped the surface of each volunteer's phone with a cotton swab (药签). The scientists also swabbed each person's right hand. Then the researchers compared the chemicals found on each cell phone.

    The scientists discovered as many of the molecules as they could. They then compared those to a database of chemicals. Pieter Dorrestein, a UCSD pharmaceutical chemist, had helped set up that database a few years earlier, which contains various substances, including spices, caffeine and medicines.

    Traces of everything from hundreds to thousands of different molecules turned up on each phone. The molecules suggested what had been in the body, and what each person had handled before touching the phone. From all these molecules, Bouslimani says, “We could tell if a person is likely female, uses high-end cosmetics (化妆品), colors her hair, drinks coffee, prefers beer over wine or likes spicy food.”

    Police already use molecular analyses to look for traces of explosives or illegal drugs. To date, Dorrestein says, he's never heard of police using phone residues to narrow down behaviour clues to search for a suspect. But detectives might one day use such data to track down someone who left a phone behind at a crime scene.

    Surely, given the near-universal use of home computers and smart devices(设备 )like smartphones and tablets, most of us would suspect that watching TV-seen as out dated or even old-fashioned by some-is on the decline. We probably would. And we would be wrong. A new study on screen time conducted by researchers from Robert Stempel College of Public Health Social Work have found that TV-watching has actually gone up since the moment when smart devices became widely available in 2014.

    "The findings are surprising as it feels like mobile devices are omnipresent, but the television still commands more eyeballs than its more advanced brothers and sisters" said Dr. Jenny Radskey" And there is a growing concern over the screen time of children, particularly very young children, for whom watching shows in front of screens is still the most common way to consume media."

    According to a study published in JAMA (The Journal of the American Medical Association) Pediatrics the increase in the amount of screen time for inns and toddlers(婴幼儿) is telling. Specifically, in 1997 children under the age of 2 spent 1.3 hours in front of TV per day on average, while children between the ages of3 and 5 did the same for 2.5 hours. By 2014, however, the latter group showed no significant change, while the former group more than doubled their time spent watching TV, clocking in at 3 hours per day.

    The research also shows that too much screen time before age 2 or 3 is associated with language development delays, ADHD, and learning difficulties. A child's brain develops rapidly during the first years, and young children learn best by interacting with people, not screens.

    Based on these findings, parents who worry about the excessive amount of time their children spend glued to their smartphones and tablets might do well to pay more attention to their littlest ones, for whom viewing time in front of the TV should be greatly cut down.

    Scientists think that growing garden grass could be the secret to solving our energy needs, and we may soon be able to replace our gasoline with "grassoline".

    The team, including experts from Cardiff University in Wales, has shown that hydrogen can be taken from grass in useful amounts with the help of sunlight and a cheap catalyst(催化剂) —something that speeds up a chemical reaction without being used up.

    It is the first time that this has been shown and it could lead to a sustainable(可持续的) way of making hydrogen, reported Asian News International. This could be an important kind of renewable energy because it is high in energy and it does not give out harmful gases when it is burned.

    Study co-author Michael Bowker said, "This is really a green source of energy. Hydrogen is seen as an important future energy carrier as the world moves from fossil fuels to renewable energy, and our research has shown that even garden grass could be a good way of getting it."

    Cellulose(纤维素), which is a key part of plants and the biopolymer(生物聚合物) found in the largest numbers on the earth, could be a great source of hydrogen.

In its study, the team looked at the possibility of getting hydrogen from cellulose using sunlight and a simple catalyst.

    This is called photocatalysis(光催化作用) and in it, the sunlight starts the catalyst, which then makes cellulose and water into hydrogen. The researchers studied the effectiveness of three metal-based catalysts, of which nickel(镍) especially interested the researchers, as it is a much more common metal than gold and palladium(钯) and it saves more money.

    According to Bowker, producing hydrogen from cellulose using photocatalysis has not been studied in detail. The team's research shows that large amounts of hydrogen can be produced using this method with the help of a bit of sunlight and a cheap catalyst.

    The study shows that it is effective to use real grass taken from a garden. "This is important as it avoids the need to separate and clean up cellulose, which can be both difficult and costly," said Bowker.

    Happy, angry, amazed—these are some of the emotions we like to express these days when we're sending a message on our smart phones! That's why many of us now add little pictures to our texts to brighten up someone's mobile screen but we're also using them as a quick way of telling someone how we're feeling. Yes, emojis (表情符号) have become a popular tool for communication.

    The emoji was first invented in Japan in the late 1990s and the word "emoji" comes from the Japanese words for "picture" and "character". The number of different images has greatly increased since then and now we have a picture for nearly every mood or situation.

    Why are emojis widely used today? Professor Vyv Evans says, "Increasingly, what we're finding is that digital communication is replacing face-to-face talk in some ways. One of the reasons why emojis are so interesting is that they really do enable us to express our emotional selves much more effectively."

    Another advantage of emojis is that they are an international language—they don't use words but tell a message with pictures so they can be easily understood whatever your native language is.

    But as linguist (语言学家) Neil Cohn says, "To many, emojis are an exciting evolution (进化) of the way we communicate; but to others, they are linguistic Armageddon." It does show by using emojis, there is a lot more to our communication than words alone, but does this also mean that the traditional writing will die out one day?

    The U. S. Thanksgiving holiday is symbolized (象征) by its traditional food-roast turkey. But turkey is certainly not from Turkey. In fact, its English name is based on one big mistake. We could say it is a case of mistaken identity. The word "Turkey" has meant "the land of the Turks" since ancient times. In the mid-1500s, the word "turkey" was first used to refer to the bird in the English language.

    The misunderstanding over the word happened because of two similar-looking kinds of birds.

    There is an African bird called the guinea fowl(珍珠鸡). It has dark feathers with white spots and a patch of brown on the back of its neck. Traders brought the guinea fowl to Europe through North Africa. This foreign bird came to Europe through Turkish lands. So, the English thought the bird as a "Turkish chicken".

    When Europeans came to North America, they saw a bird that looked like the guinea fowl. This bird was native to the North American continent. But they thought that it was the guinea fowl, which at that time, was called the "turkey cock", so they gave it the same name.

    Hundreds of years later, we continue to call this North American bird "turkey", even though it has no connection at all with the country Turkey, or even with Europe.

    But English is not the only language with interesting names for this North American bird.

    The Turkish call turkey "hindi", the Turkish name for India. The reference(涉及)to India probably conies from the old wrong idea that the New World was in Eastern Asia.

    The French call it "dinde", a name that also connects the bird to India. "Dinde" means "from India" in the French language. "Turkey" has similar names in several other languages.

    Taking your pulse during physical activity allows you to measure how hard you are exercising. You should exercise to stay within your target heart range.

    Increasing your heart rate is a key part of exercise but it is important that your heart rate is not too high or too low. If you are a beginner, you should also be able to breathe comfortably while exercising. This will ensure that you are exercising at a level that is safe and effective for your body.

    The chart below illustrates target heart rate ranges for exercise based on the maximal heart rate for selected ages. Here are the steps for using the chart: