It is a tall tale（夸张的故事）that terrifies most young children. Swallow a piece of chewing gum and it will remain in your body for seven years before it is digested. An even worse tale is that swallowed（吞） gum can wrap itself around your heart.

    But what does happen if you should accidentally eat a stick of gum? Chewing gum is made out of gum base, sweeteners, coloring and flavoring. The gum base is pretty indigestible(难消化的)—it is a mixture of different ingredients (成分) that our body can't absorb.

    Most of the time, your stomach really cannot break down the gum the way it would break down other foods. However, your digestive system has another way to deal with things you swallow. After all, we eat lots of things that we are unable to fully digest. They keep moving along until they make it all the way through the gut (肠子) and come out at the other end one or two days later.

    The saliva (唾液) in our mouths will make an attempt at digesting chewing gum as soon as we put it in our mouths. It might get through the shell（壳） but many of gum's base ingredients are indigestible. It's then down to our stomach muscles—which contract(收缩) and relax, much like the way an earthworm moves—to slowly force the things that we swallow through our systems.

    Swallowing a huge piece of gum or swallowing many small pieces of gum in a short time can cause a blockage within the digestive system, most often in children, who have a thinner digestive tube than adults—but this is extremely rare.

    The world's most human-like robot has begun work as a university receptionist. And scientists positively predict the new technology will 1 provide childcare and offer 2 to lonely elderly people.

    With her soft skin and flowing dark-brown hair, Nadine does not only meet and greet3, smile, make eye contact and 4 hands, but she can even5 past guests and get into conversation based on 6 chats.

    Unlike 7 robots, Nadine has her own personality and 8 . She can be happy or sad, 9 on the topic.

    Powered by intelligent 10 similar to Apple's Siri or Microsoft's Cortana, she is the creation of scientists at the Nanyang Technological University in Singapore and is based on her creator Prof Nadia Thalmann.

    Prof Thalmann, the director of the Institute for Media Innovation who led the development said robots such as Nadine are bound to become more visible in offices and 11 in future.

    “Robotics technologies have 12 significantly over the past few decades and are already being used in manufacturing and logistics,” she said.

    “As countries worldwide face 13 of an aging population, 14 robots can be one solution to 15 the shrinking(缩小的) workforce, become personal 16 for children and the elderly at home, and 17 serve as a platform for healthcare services in future.”

    “Over the past four years, our team at NTU have been 18 cross-disciplinary(跨学科的) research in social robotics technologies— involving engineering, computer science, linguistics, psychology and other19 — to transform a virtual human(虚拟的人), from within a computer, into a 20 being that is able to observe and interact with other humans.”

    You can use your smartphone to get pretty much anything delivered directly to your door almost immediately. The hardest part is the process of trying to work out if you should tip and if so, doing the quick math before you get to the door. And, you know well that you should tip about 15-20% at restaurants, but do the same rules apply to delivery drivers?

    The co-founder of Grubhub, Matt Maloney, pretty much set the standard for tipping delivery people in a Facebook post. He's a strong supporter of tipping, and Grubhub's website suggests a $5 or a 20% tip. Maloney also said this number should go up if you order during, say, a snowstorm.

    However, most other delivery services say on their websites that tipping is not required. Some services, like Door Dash, do suggest no tip on their checkout window. Many, like Amazon Prime Now, allow customers to change their tip amount after their delivery has been received to reflect the quality of service. These companies help customers save money but delivery drivers are upset. They deal with bad weather, heavy traffic, extreme tiredness, and more, all for a $1 tip. Many feel that if you'd tip your pizza boy or girl, you should tip your delivery driver.

    The Emily Post Institute (EPI)'s official suggestion falls in line with Maloney's: “10-15% of the bill, or $2-5 for pizza delivery depending on the size of the order and difficulty of delivery.”

    Just like servers in a restaurant, delivery drivers almost always rely on your tips for their income. Tipping is a long-standing cultural tradition in America. So, until drones (无人机) can deliver hot dogs straight to your door, it's best to tip the people riding through the city at all hours to bring you hot fresh food.

    Mya Le Thai is a scientist studying at the University of California, Irvine. She recently discovered a process that may result in batteries that last forever. Thai said she had been discouraged that the batteries for her wireless devices degrade. Over time, they fail to charge fully.

    Thai did not like to have keep her wireless laptop connected to an electrical outlet. She decided to do something about that problem.

    At first, she and her team thought about inventing a new battery. But as they experimented, Thai discovered something that might permit lithium-ion(锂离子) batteries to last forever. Lithium-ion batteries power most wireless devices. Over time, the batteries lose the ability to hold a charge. Most of these batteries have a life span of about 7,000 charging cycles before they die.

    One of the reasons lithium-ion batteries degrade is their use of nanowires(纳米线) to carry electricity. Nanowires are extremely thin. A human hair is thousands of times thicker, for example. Nanowires are extremely efficient carriers of electricity, which makes them useful in batteries. But Thai said their thinness also makes them weak. "Nanowires break over time," she said. "That's why they lose capacity."

    But, Thai had a theory: The nanowires might last longer if covered with a material. She and the team tested her theory. The team tried many coverings for the wires. PMMA was one of them. The nanowires were coated with PMMA and cycled through charges 200,000 times. The PMMA coated nanowires showed no evidence of damage. The results suggest that batteries could last forever, without losing charging ability.

    Thai hopes to continue her research to understand why this material works so well and to see if any other material could create better results.

"It's kind of cool," she said. "I'm really glad people are showing interest in my work and not just in the work itself, but also in technology and energy."

    Sports can help you keep fit and get in touch with nature. However, whether you are on the mountains, in the waves, or on the grassland, you should be aware that your sport of choice might have great influence on the environment.

    Some sports are resource-hungry. Golf, as you may know, eats up not only large areas of countryside, but also tons of water. Besides, all sorts of chemicals and huge amounts of energy are used to keep its courses (球场) in good condition. This causes major environmental effects. For example, in the dry regions of Portugal and Spain, golf is often held responsible for serious water shortage in some local areas.

    There are many environment-friendly sports. Power walking is one of them that you could take up today. You don't need any special equipment except a good pair of shoes; and you don't have to worry about resources and your purse. Simple and free, power walking can also keep you fit. If you walk regularly, it will be good for your heart and bones. Experts say that 20 minutes of power walking daily can make you feel less anxious, .sleep well and have better weight control.

    Whatever sport you take up, you can make it greener by using environment-friendly equipment and buying products made from recycled materials. But the final goal should be "green gyms". They are better replacements for traditional health clubs and modem sports centers. Members of green gyms play sports outdoors, in the countryside or other open spaces. There is no special requirement for you to start your membership. And best of all, it's free.

    Do you like to show off your expensive items? You could find yourself without friends! Scientists prove that expensive status symbols make you look less socially attractive.

    Items such as a fancy car and a Rolex watch are often thought to increase our social standing(地位) and often come with a high price tag(标签).According to the latest research, however, it has the opposite effect and people would prefer to be friends with someone who places less value on material objects.

    "Often we think that status symbols will make us look more socially attractive to others," says Stephen Garcia, the study's leading author from the University of Michigan. He adds, "However, our research suggests that these status signals actually make us look less socially attractive.

    The researchers conducted six studies which assessed how people presented themselves and how people viewed strangers. People who chose to wear higher status items tended to get a negative response, but people wanted to be friends with people who preferred lower status symbols.

    The study took the role of the luxury(奢侈) item to see if it was possible that the expensive item itself played a part in people's reactions. The definition of a status symbol changed based on a person's socioeconomic status, but the same effect of keeping off potential friends was seen regardless of social position.

    "At a social level, we may be wasting billions of dollars on expensive status symbols that finally keep others from wanting to associate with us, "says Kimberlee Weaver Livnat at the University of Haifa. She says, "And to the extent that close friendships are important to well-being, and we may be unintentionally hurting ourselves."

    However, Patricia Chen of the National University of Singapore said this does not necessarily mean status symbols are a bad thing. She says, "Our findings right now only apply to the formation of new friendships. Status symbols may be beneficial at other times and in other settings, such as when trying to establish new business contacts."