For a long time, the traditional method of identifying liars was to watch their body language, including facial expressions.

    What if the person appears to be nervous? Is the person unable to look me in the eye? Is he or she look around the room? What about other nervous movements, such as fidgeting（坐立不安）or shifting from side to side? Many people—from parents to police officers and airport security personnel—depend on this method. But does a person's body and face reveal the truth? Not according to a new study.

    Talking, it seems, is the best way to smoke out a liar. That is what researchers in the United Kingdom found out recently. Their investigation took place at one place where lying can get you into big trouble—an airport.

    The researchers asked volunteers to pretend they were real passengers and then lie to airport security agents. Some of the agents used spoke conversation-based methods to question these make-believe passengers. Others depended instead on the person's body language, like lack of eye contact and showing signs of nervousness. The agents talking with the passengers were 20 times more likely to catch the liars. The study found that these conversation-based techniques can help you recognize when a person is lying to you. Like many methods, this conversation method has a name. It is called Controlled Cognitive Engagement or CCE, for short.

    The British government partly financed this study. The American Psychological (APA) published the findings. Body language cannot be trusted. Using body language and facial expressions to catch someone in a lie is really hard. And it only works, seemingly, by chance.

    Thomas Ormerod is the head of the School of Psychology at the University of Sussex in England. On the APA website, he reported that the “suspicious-signs method”—or using body language—“almost completely fails” in finding lies.

    It happened to me recently. I was telling someone how much I had enjoyed reading Barack Obama's Dreams From My Father and how it had changed my views of our President. A friend I was talking to agree with me that it was, in his words ,“a brilliantly written book” However, he then went on to talk about Mr. Obama in a way which suggested he had no idea of his background at all. I sensed that I was talking to a book liar.

    And it seems that my friend is not the only one. Approximately two thirds of people have lied about reading a book which they haven't. In the World Book Day's “Report on Guilty Secrets”, Dreams From My Father is at number 9. The report lists ten books, and various authors, which people have lied about reading, and as I'm not one to lie too often (I'd hate to be caught out), I will admit here and now that I haven't read the entire top ten. But I'm pleased to say that, unlike 42 percent of people, I have read the book at number one, Gorge Orwell's 1984. I think it's really brilliant.

    The World Book Day report also has some other interesting information in it. It says that many people lie about having read Jane Austin Austen, Charles Dickens, Fyodor Dostoevsky (I haven't read him, but haven't lied about it either) and Herman Melville.

    Asked why they lied, the most common reason was to “impress” someone they are speaking to. This could be tricky if the conversation became more in-depth!

    But when asked which authors they actually enjoy, people named J.K. Rowling, John Grisham, Sophie Kinsella (ah, the big sellers, in other words). Forty-two percent of people asked admitted they turned to the back of the book to read the end before finishing this story (I will come clean: I do this and am astonished that 58 percent said they had never done so.).

    Although his 1-year-old smart-phone still works perfectly, Li Jijia already feels the need to replace it.

    "There are many better ones available now. It's time to upgrade(更新）my phone."

    Li's impatience is shared by many. Shortly after the season when new products are released（发布，发售）, many consumers feel the urge to upgrade their electronic equipment, even though the ones they have still work just fine.

    As consumers' minds are occupied by Apple's newly released products and debate whether the Google tablet is better than the new Amazon Kindle, it might be time to take a step back and ask: "Do we really need the latest upgrades?"

    According to Donald Norman, an American author, "planned obsolescence (淘汰）" is the trick behind the upgrading culture of today's consumer electronics industry.

    Electronics producers strategically release new upgrades periodically, both for hardware and software, so that customers on every level feel the need to buy the newest version.

"This is an old-time trick—they're not inventing anything new," Norman said. "This is a wasteful system through which companies--many of them producing personal electronics—— release poor-quality products simply because they know that, in six months or a year, they'll put out a new one."

    But the new psychology of consumers is part of this system, as Norman admitted, "We now want something new, something pretty, the next shiny thing." In its most recent year, Apple's profit margin(利润) was more than 21 percent. At Hewlett-Packard, the world's biggest PC maker, it was only 7 percent.

    Apple's annual upgrades of its products create sales of millions of units as owners of one year's MacBook or iPhone line up to buy the newest version, even when the changes are slight.

    As to Li Jijia, the need for upgrading his smart-phone comes mainly from friends and classmates. When they are switching to the latest equipment, he worries about feeling left out.

    "Some games require better hardware to run," said Li. "If you don't join in, you lose part of the connection to your friends."

    Simpson is 53, "not sporty" and has suffered from asthma all her life. Two years ago her son Jay, now 10, took up BMX (自行车越野赛). "I enjoyed watching him and thought I'd like to try it," Simpson recalls. "But I didn't want to embarrass myself. I hadn't ridden for over 40 years."

    Then she noticed a session for women and girls at Burgess Park BMX Track in Peckham, south-east London, where Jay trained. This season Simpson raced at the London BMX series and finished third in her category.

    "It was the most worrying experience of my life. But it was also exhilarating," she says cheerfully. "My son is proud of me. We now share a real love for the sport. It has brought us closer together."

    Since becoming part of the Olympic Games in 2008, the popularity of BMX has risen. A program introduced in London in 2011 by the sports development charity Access Sport has seen tracks built in several London regions, backed up with investment in coaching, and the program is being rolled out to Bristol.

    Wright's children Skye, 11 and Xander, 10 are sponsored riders who have represented Great Britain in every world championship since 2014. Wright says she was motivated to start BMX herself out of an interest aroused by watching so much of it. "It's an eye-opener to share your children's interests," she explains. "You comprehend what they go through in a much more direct way. It adds another dimension to your relationship."

    It is also a high-impact sport and the risks are fairly obvious. "I totally get the fear," says Emma, 51, a BMX exercise coach and cycling instructor. "It's the fear of doing something new, of getting hurt. But I say 'Come and give it a try.' The chance of having an accident is slim, and you can spend time on the flat to improve your confidence."

    Batteries can power anything from small sensors to large systems. While scientists are finding ways to make them smaller but even more powerful, problems can arise when these batteries are much larger and heavier than the devices themselves. University of Missouri (MU) researchers are developing a nuclear energy source that is smaller, lighter and more efficient.

    "To provide enough power, we need certain methods with high energy density (密度)", said Jae Kwon, assistant professor of electrical and computer engineering at MU. ''The radioisotope (放射性同位素) battery can provide power density that is much higher than chemical batteries."

    Kwon and his research team have been working on building a small nuclear battery, presently the size and thickness of a penny, intended to power various micro systems (MNEMS). Although nuclear batteries can cause concerns, Kwon said they are safe.

    "People hear the word 'nuclear' and think of something very dangerous." he said. "However, nuclear power sources have already been safely powering a variety of devices, such as pace-makers, space satellites and underwater systems."

    His new idea is not only in the battery's size, but also in its semiconductor (半导体). Kwon's battery uses a liquid semi conduct or rather than a solid semiconductor.

    "The key part of using a radioactive battery is that when you harvest the energy, part of the radiation energy can damage the lattice structure (晶体结构) of the solid semiconductor." Kwon said, "By using a liquid semiconductor, we believe we can minimize that problem."

    Together with J. David Robertson, chemistry professor and associate director of the MU Research Reactor, Kwon is working to build and test the battery. In the future, they hope to increase the battery's power, shrink its size and try with various other materials. Kwon said that battery could be thinner than the thickness of human hair.

Most of Bangladesh is at or below sea level. Rising seawater linked to climate change has severely affected the country. High water from storms in coastal areas also adds salt to soil. The land is becoming salty. Crops are less productive and many areas of cropland in the country are becoming unfit for farming. These are big problems for the small country. More than 155 million people live in Bangladesh. Growing crops is the most common way Bangladeshis support themselves.

To find a way out，farmers in the country are learning to grow vegetables in so-called "vertical gardens". The soil in these gardens is better because heavy rains have removed much of the salt.

A vertical garden is easy to make. Villagers fill containers with good soil and natural fertilizers. They put the containers on bricks so they are off the ground. They add pieces of the bricks to the soil to help water flow and drain (排水).

The farmers cut small holes into the sides of the containers. This permits vegetables with short roots a place to grow. Vegetables with long roots grow on top of the container. One bag of soil can produce up to eight kilograms of vegetables in one season.

The farmers also grow vegetables in containers made from large, thin pieces of plastic supported by bamboo. This "vertical tower" measures more than a meter wide. Each of these towers can produce more than 100 kilograms of vegetables. It costs about $12—$13 to build.