When I was a child, I often dreamed of the time when I could leave home and escape to the city. We lived on a farm, in the winter especially, we wear quite out off from the outside world. As soon as I left school, I packed my bags and moved to the capital.

    However, I soon discovered that one big disadvantage is money. It costs so much to go out, not to mention basics like food and housing. Another disadvantage is pollution. I suffer from asthma(哮喘), and the air is so bad that I am afraid to go outside. Then there is the problem of traveling round. Although I have a car, I seldom use it because of the traffic jams. One choice is to go by bicycle, but that can be quite dangerous.

    Of course there are advantages. First, there is so much to do in the city, whatever you tastes in culture or entertainment(娱乐活动). Besides, there are wonderful jobs and greater chances of moving to a more important job or position. Finally, if you like shopping, the variety of goods is very surprising — and, what is more, shops are often only a short walk away.

    Is life better then, in the city? Perhaps it is, when you are in your teens(十几岁) or twenties. However, as you get older, and especially if you have small children, the peace of the countryside may seem preferable. I certainly hope to move back there soon.

    Like many thickly populated urban neighborhoods, Lincoln Park also has rats. A lot of rats. “Every night when I walk down the sidewalk, I see rats, ” says 36-year-oId Kelly McGee, who has come to accept this aspect of city living. “It's an urban area; I don't know what else we can expect.”

McGee lives just down the block from the old Children's Memorial Hospital, which is about to be torn down as part of a massive redevelopment project. “Construction all over the city often disturbs rats that are living underground,” says Lincoln Park's City Council representative, Alderman Michele Smith. “Every developer has to do active rat reduction on site, ”Smith says. Already, there are poisonous and inviting food boxes all around the old hospital complex. But the developer of the hospital site still warned residents in a recent community meeting that when digging begins later this month, the rat problem could be awful.

Victoria Thomas, who lives a few miles north of Lincoln Park in Chicago's Lake View neighborhood, says she tried everything from underground fencing to poison traps to wipe out rats, but nothing worked until she got some cats. From the first day she got the cats, Thomas says the rats started to disappear.

“The cats will kill off a great deal of the initial population of the rats, ”says Paul Nickerson, who manages the Cats at Work program for Tree House Humane Society. “And through spreading their pheromones, a chemical produced by an animal, the cats will keep other rats from filling their absence.” Nickerson says that is what makes the cat program so successful in keeping rats away for the long term. ” The rats are far from stupid. They smell the cats' pheromones so they'll stay out of the cats' territory(领域).”

    After Smith highlighted the program in a recent newsletter, Nickerson and Tree House Humane Society have been getting lots of calls from people seeking their own cat colonies. That means a lot more wild cats that might otherwise be killed out of pity will be cared for while doing something that they love: hunting rats.

    If you have spent any time living in or visiting a big city in China, you have most likely used the service that Didi provides. The convenient ride-sharing company, now known as Didi Chuxing, was praised last month by Fortune magazine. According to the magazine, it is changing the world with its environmentally friendly solution to getting around in major cities. As the magazine reported: “Didi concluded that last year its car-pooling services helped reduce total car trips in the country by 1 million a day, which saved 500 million liters of gas, cutting 13.5 million tons of carbon emissions (排放) per day.” The transport service was the only Chinese company to make the important magazine's list, and its influence can be felt in many parts of Chinese society.

    Didi is just one example of what is being called the “sharing economy”. The sharing economy is one in which regular people exchange goods and services, usually using an online marketplace. Other similar companies include companies that allow people to rent out their homes to strangers like Airbnb and Couchsurfing, and similar ride sharing services like Uber and Lyft.

    All of these services are possible partly because many people are realizing that they have underused assets in their lives. Millions of people around the world have started renting them out online to earn extra money. They rent their apartments while they are away for the weekend, lend people their cars for money and even sell their spare time.

    The sharing economy is the latest example of the Internet's value to customers. This model is now big enough for regulators and companies to have woken up to it. That is a sign of its great potential. It is time to start caring about sharing.

    Plastic is easy, convenient, cheap and long-lasting, but it does great harm to the environment.

    Since plastic entered mass production, 8 billion tons have been produced – and we aren't very good at recycling. By 2015, 6,945 tons of plastic waste had formed, with around 9 percent of it getting recycled. About 79 percent of it ends up in landfills or around the environment, including the ocean. We may end up drowning in plastic before long.

    Chemists at Colorado State University have found a polymer（聚酯）that has many of the qualities of plastics – it's light, strong, durable and heat-resistant – but that can be changed back to its original small-molecule（分子）state for complete recycling. Even after being recycled, the polymer can be turned back into its plastic-like state, and this can be done quickly and cheaply.

    This new polymer has all the good qualities of plastics, yet it is relatively easy to make and to recycle. Making it requires room temperature conditions, a short reaction time to bond the monomer（单体）into polymers and only a small amount of the catalyst（催化剂）remains in the end product. It has a high molecular weight, stands up to heat and generally behaves like plastic. Recycling it requires similarly little effort. Mild lab conditions are required and so is a catalyst. Once applied, the polymers are once again monomers in a matter of minutes and can be used to create another product.

    But don't get too excited about this just yet. Scientists stressed that the polymer isn't ready for mass products just yet. There's still plenty of development to do, including making it more economical to produce and recycle.

    Weighing too much can damage your health, and obesity is a growing problem for both kids and adults around the world. Sleep might be one answer to the problem. A new study has found that elementary school students who slept too little were more likely to gain pounds.

    Past studies have shown a link between sleeping less and weighing more, but scientists have had a tough time determining "which came first, the chicken or the egg," says Julie C. Lumeng of the university of Michigan in Ann Arbor. In other words, it hasn't been clear whether kids who weigh too much have trouble sleeping, or whether sleeping less leads to weight gain. Both scenarios (可能出现的情况) seemed equally possible.

    To get a better idea of which causes which, Lumeng and her colleagues interviewed the parents of 785 third graders from around the United States. The parents answered questions about how well their kids slept that year. Three years later, the parents answered the same questions. By sixth grade, 18percent of kids involved in the study were obese.

    The scientists found no relationship between weight and the students' race or gender. It also didn't matter how strict their parents were, or whether they were boys or girls. Obesity struck all of these groups equally. Instead, sleep seemed to be the key factor. Over the three years of study, the children averaged a healthy 9. 5 hours of sleep a night. Some kids, however, slept a lot more or less than others.

    For the sixth graders, every hour of sleep above the 9. 5houraverage was linked to a 20 percent lower risk of being obese. Sleep appeared doubly important for the third graders. Every extra hour of sleep they got was linked to a 40 percent drop in obesity.

    I got into the teaching profession purely by choice. I was then in 9th grade when my mathematics teacher asked me to take a class for a few students to whom the subject seemed difficult. And believe me, I enjoyed the entire teaching session. I never knew teaching would be so interesting. I loved my freshmen and was delighted to teach my so-called students who came up with lots of good questions.

    After my post-graduation, I worked as a software developer with a public sector(部门) in Bangalore for a few years. But I realized that no job could provide me with the satisfaction that I experienced while teaching and training. I always wanted to connect with a wider group of people. In fact, I felt it was a timely realization for me to choose the teaching profession. I applied to a few colleges, and finally I was chosen as a lecturer, and I had to lecture graduate and post-graduate students in a college.

On the first day, I was nervous thinking that I had to teach the senior classes. But now I can say that giving lectures was one of the best experiences of my life. I was a Computer Science and Information Technology lecturer, but I tried to help my students with subjects that were not within my domain(范围). It was a new feeling to me every morning before I went to the classes. I used to feel energized and excited thinking that the class would be lit up with bright faces to greet me, "Good morning, Madam."

    To me each day was a new beginning, with new feelings, new experiences and new queries(疑问). I loved to explore their young minds and read their inquisitive faces when a particular topic seemed tough. It was extremely challenging to motivate them to participate, think critically, question and also respect others' points of view. Though few things never seemed easy, it was extremely exciting to assure them that they really can. That is the reason I love to teach.