If doctors want to test you for something, they'll usually take a blood or urine sample. But wouldn't it be much more convenient if they just asked you to breathe through a special instrument?

    In fact, your breath can say a lot about you. In traditional Chinese medicine, doctors draw a conclusion about the health state of a patient based on the smell of his or her breath; trained dogs and rats can identify the smells of the breaths of people suffering from certain cancers; traffic police also monitor drivers' alcohol consumption by testing their breaths.

    Just like blood and urine, your breath contains lots of “metabolites” —the waste chemicals that the body produces, which vary from person to person. They are like personal health fingerprints, which is why scientists sometimes call them “breathprints”, according to Science Daily.

    Compared to blood or urine testing, breath testing takes only seconds instead of hours, and it requires neither a needle nor a container to hold the body fluids(液). This means the test can be taken frequently to better detect early signs of diseases and monitor the progress of a medical treatment.

    On the other hand, as an identifier, you might think that breaths are not as reliable as fingerprints since they might change based on what you eat. However, researchers in Zurich, Switzerland mapped 11 healthy volunteers' chemical patterns by having them breathe through a special instrument, and they found that each pattern was unique and the patterns didn't change much throughout the day, reported BBC.

    “Our goal is to develop breath analysis to the point where it becomes competitive with the established analysis of blood and urine,” said Malcolm Kohler, professor at the University Hospital Zurich.

    Children start out as natural scientists, eager to look into the world around them. Helping them enjoy science can be easy; there's no need for a lot of scientific terms or expensive lab equipment. You only have to share your children's curiosity. Firstly, listen to their questions. I once visited a classroom of seven-year-olds to talk about science as a job. The children asked me “textbook questions” about schooling, salary and whether I liked my job. When I finished answering, we sat facing one another in silence. Finally I said, “Now that we're finished with your lists, do you have questions of your own about science?”

    After a long pause, a boy raised his hand, “Have you ever seen a grasshopper （蚱蜢）eat? When I try eating leaves like that, I get a stomachache. Why?”

    This began a set of questions that lasted nearly two hours.

    Secondly, give them time to think. Studies over the past 30 years have shown that, after asking a question, adults typically wait only one second or less for an answer, no time for a child to think. When adults increase their “wait time” to three seconds or more, children give more logical, complete and creative answers.

    Thirdly, watch your language. Once you have a child involved in a science discussion, don't jump in with “That's right” or “Very good”. These words work well when it comes to encouraging good behavior. But in talking about science, quick praise can signal that discussion is over. Instead, keep things going by saying “That's interesting” or “I'd never thought of it that way before”, or coming up with more questions or ideas.

    Never push a child to “Think”. It doesn't make sense, children are always thinking, without your telling them to. What's more, this can turn a conversation into a performance. The child will try to find the answer you want, in as few words as possible, so that he will be a smaller target for your disagreement.

    Lastly, show; don't tell. Real-life impressions of nature are far more impressive than any lesson children can learn from a book or a television program. Let children look at their fingertips through a magnifying glass（放大镜）, and they'll understand why you want them to wash before dinner. Rather than saying that water evaporates（蒸发）, set a pot of water to boil and let them watch the water level drop.

    I visited Copenhagen for the first time last Easter. As a student，I'm always strapped for cash，so I assumed I could only afford to breathe the air — but luckily everything about Copenhagen is breathtaking.

I was staying in an Airbnb, and rented a bike so I could cover more ground. One of the first places I visited was the Rundetaarn, or "round tower" built in the 17th century as an astronomical observatory. It has an equestrian staircase (a wide set of stairs big enough for horses to use) that went on and on. As I was going up, I stopped to visit the tower's library hall. At the top, there's a glass platform that gives a view 80-foot straight down, as well as a bell loft. Luckily, the views over Copenhagen from the top were well worth the climb.

    After coming down, I hiked up to the Kastellet Fortress to see the famous Little Mermaid statue. Taking a photo with her was almost impossible with all the tourists crowding around—but sitting there and hearing the lapping waves of the deep blue Baltic Sea, waiting for the sun to set, was an unforgettable and calming experience.

    The next day, I visited the Glyptotek art museum, exploring the grand exhibits. I looked into the marble eyes of many Roman gods，and walked down dimly lit staircases to see mummies from Egypt.

    Before I unwillingly boarded the train back to the airport, I told myself that I must visit again—to experience the thrills of Tivoli Gardens, try more of the street food and everything else from this amazing city.

    A pretty face is never forgotten. Do you believe so? But maybe it is untrue! Psychologists believe beautiful people are less likely to be recognized. A new study suggests that attractiveness can actually prevent the recognition of faces, unless a pretty face has particularly distinctive features, such as Angelina Jolie's.

    German psychologists think the recognition of pretty faces is distorted (扭曲) by emotions. Researchers Holger Wiese, Carolin Altmann and Stefan Schweinberger at the University of Jena, Germany, discovered in a study that photos of unattractive people were more easily remembered than pretty ones when they showed them to a group of people.

    For the study, which was published in science magazine Neuropsychologia, the psychologists showed photos of faces to test subjects. Half of the faces were considered to be more attractive and the other half as less attractive, but all of them were being thought of as similarly distinctive looking. The test subjects were shown the faces for just a few seconds to memorize them and were shown them again during the test so that they could decide if they recognized them or not.

    The researchers were surprised by the result. “Until now we assumed that it was generally easier to memorize faces which are being considered as attractive, just because we prefer looking at beautiful faces,” Dr. Wiese said. But the study showed that such a connection cannot be easily proven. He assumes that remembering pretty faces is distorted by emotional influences, which enhance the sense of recognition at a later time. The researchers' idea is backed up by evidence from EEG-recordings (脑电图记录) they used during their experiment which show the brains' electric activity.

    The study also revealed that in the case of attractive faces, considerably more false positive results were detected. In other words, people thought they recognized a face without having seen it before. “We obviously tend to believe that we recognize a face just because we find it attractive.” Dr. Wiese said.

    Most people feel lonely sometimes, but it usually lasts only between a few minutes and a few hours. This kind of loneliness is not serious. In fact, it is quite normal. For some people, though, loneliness can last for years. Now researchers say there are three different types of loneliness.

    The first kind of loneliness is temporary. This is the most common type. It usually disappears quickly and does not require any special attention. The second kind, situational loneliness, is a natural result of a particular situation－for example, the death of a loved one, or moving to a new place. Although this kind of loneliness can cause physical problems, such as headaches and sleeplessness, it usually does not last for more than a year.

    The third kind of loneliness is the most severe. Unlike the second type, chronic(长期的) loneliness usually lasts more than two years and has no specific cause. People who experience habitual loneliness have problem socializing and becoming close to others unfortunately, many chronically lonely people think there is little or nothing they can do to improve their condition.

    Many researchers agree that the loneliest people are between the ages 18 and 25, so a group of psychologists decided to study a group of college students. They found that more than 50% of the students were situationally lonely at the beginning of the term as a result of their new circumstances, but had adjusted after a few months, 13% were still lonely after seven months due to shyness and fear. They felt very uncomfortable meeting strangers, even though they understood that their fear was not reasonable. The situationally lonely students overcame their loneliness by making new friends, but the chronically lonely remained unhappy because they were afraid to do so.

    Psychologists are trying to find ways to help habitually lonely people for two reasons: they are unhappy and unable to socialize and there is a connection between chronic loneliness and serious illness such as heart disease. While temporary and situational loneliness can be a normal, healthy part of life, chronic loneliness can be a very sad, and sometimes dangerous condition.

    The Great Depression that followed the stock market crash of 1929 saw hundreds of thousands of Americans out of work. In the years of great fear and depression, a lot of American citizens looked desperately to the federal government for assistance. Of all the programs designed by President Roosevelt when he took office in 1932, few were more criticized - or had more lasting impact - than the Work Projects Administration, better known as the WPA.

    The intention of the WPA, which functioned from 1935 to 1943, was to design and administer public works projects to help relieve unemployment. The majority of these projects involved historic or artistic attempts. The WPA's Writers Project, for example, was responsible not only for such practical works as state guidebooks but also for the collection of historically valuable oral histories. Over 2,900 of these records were collected in 24 states. They provide an irreplaceable firsthand account of people's diets, customs, celebrations, and political and religious beliefs at the time.

    The artworks created through the Federal Arts Project are one of the WPA's most lasting achievements. Out - of - work painters, both famous and unknown, created paintings that beautified schools, libraries, and government buildings, WPA photographers traveled across the country recording the hardships of life on small rural farms. When the United States entered World War Ⅱ in 1941, WPA artists were enlisted to produce posters supporting the war effort. Many WPA artworks, including hundreds of small drawings picturing scenes of everyday life, still exist today.