You've just come home, after living abroad for a few years. Since you've been away, has this country changed for the better—or for the worse?

    If you've just arrived back in the UK after a fortnight's holiday, small changes have probably surprised you—anything from a local greengrocer suddenly being replaced by a mobile-phone shop to someone in your street moving house.

    So how have things changed to people coming back to Britain after seven, ten or even 15 years living abroad? What changes in society can they see that the rest of us have hardly noticed—or now take for granted? To find out, we asked some people who recently returned.

    Debi: When we left, Cheltenham, my home town, was a town of white, middle-class families—all very conservative (保守的). The town is now home to many eastern Europeans and lots of Australians, who come here mainly to work in hotels and tourism. There are even several shops only for foreigners.

    Having been an immigrant (移民) myself, I admire people who go overseas to find a job. Maybe if I lived in an inner city where unemployment was high, I'd think differently, but I believe foreign settlers have improved this country because they're more open-minded and often work harder than the natives.

    Christine: As we flew home over Britain, both of us remarked how green everything looked. But the differences between the place we'd left behind and the one we returned to were brought sharply into focus as soon as we landed.

    To see policemen with guns in the airport for the first time was frightening—in Cyprus, they're very relaxed—and I got pulled over by customs officers just for taking a woolen sweater with some metal-made buttons out of my case in the arrivals hall. Everyone seemed to be on guard. Even the airport car-hire firm wanted a credit card rather than cash because they said their vehicles had been used by bank robbers.

    But anyway, this is still a green, beautiful country. I just wish more people would appreciate what they've got.

    Now many young people are traveling around the world on their own, not because they have no one to travel with, but because they prefer to go alone．

     Kristina Wegscheider from California first traveled alone when she was at college and believes that it is something everyone should do at least once in their life. “It opens up your mind to new things and pushes you out of your comfort zone.” Wegscheider has visited 46 countries covering all seven continents(洲)．

    In foreign countries, with no one to help you read a map, look after you if you get ill, or lend you money if your wallet is stolen. It is challenging. This is what drives young people to travel alone．It is seen as character building and a chance to prove that they can make it on their own．

    Chris Richardson decided to leave his sales job in Australia to go traveling last year．He set up a website, The Aussie Nomad, to document（记录） his adventures. He said he wished he had traveled alone earlier. “The people you meet, the places you visit, or the things you do, everything is up to you and it forces you to grow as a person,” said the 30-year-old．

    Richardson describes traveling alone like “a shot in the arm”, which “makes you a more confident person that was ready to deal with anything”. He said: “The feeling of having conquered something on my own is a major part of what drives me each day when I'm dealing with a difficult task. I walk around with my head up because I know deep down inside that nothing is impossible if you try.”

    The great 19th century explorer John Muir once said: “Only by going alone in silence can one truly get into the heart of the wilderness.

    Now people are very concerned about the food problem. Steve Wilson prefers organic fruit, delivered right to the doorstep. He is willing to pay for it. If this is not possible, the 30-year-old computer technician will spend the extra money at the supermarket to buy organic food.

    “Organic product is always better,” Wilson said. “The food is free of pesticides(农药), and you are generally supporting family farms instead of large farms. And more often than not that it is locally grown and seasonal, so it is more tasty.” Wilson is one of the growing number of shoppers buying into the organic trend, and supermarkets across Britain are counting on more like him as they grow their organic food business. But how many shoppers really know what they are getting, and why are they willing to pay a higher price for organic product? Market research shows that Wilson and others who buy organic food can generally give clear reasons for their preferences—but their knowledge of organic food is far from complete. For example, small amounts of pesticides can be used on organic products. And about three quarters of organic food in Britain is not local but imported(进口)to meet growing demand. “The demand for organic food is increasing by about one third every year, so it is a very fast-growing market,” said Sue Flock, a specialist in this line of business.

    Two new studies suggest that modem running shoes could increase the risk of injuries to runners.

    One study involved sixty-eight healthy young women and men who ran at least twenty-four kilometers a week. The runners were observed on a treadmill machine (跑步机). Sometimes they wore running shoes. Other times they ran barefoot.

    Researchers from the JKM Technologies Company in Virginia, the University of Virginia and the University of Colorado did the study.

They found that running shoes create more stress that could damage knees, hips and ankle joints than running barefoot. They observed that the effect was even greater than the effect reported earlier for walking in high heels.

    The study appeared in the official scientific journal of the American Academy of Physical Medicine.

    The other study appeared in the journal Nature. It compared runners in the United States and Kenya. The researchers were from Harvard University in Massachusetts, Moi University in Kenya and the University of Glasgow in Scotland.

    They divided the runners into three groups. One group had always run shoeless. Another group had always run with shoes. And the third group had changed to shoeless running.

    Runners who wear shoes usually come down heel first. That puts great force on the back of the foot. But the study found that barefoot runners generally land on the front or middle of their foot. That way they ease into their landing and avoid striking their heel.

    Harvard's Daniel Lieberman led the study. He says the way most running shoes are designed may explain why those who wear them land on their heels. The heel of the shoe is bigger and heavier than other parts of the shoe, so it would seem more likely to come down first. Also, the heel generally has thick material under it to soften landings.

    But the researchers do not suggest that runners immediately start running barefoot. They say it takes some training. And there can be risks, like running when your feet are too cold to feel if you get injured.

    The study was partly supported by Vibram, which makes a kind of footwear that it says is like running barefoot. The findings have gotten a lot of attention. But the researchers say there are many problems in the way the press has reported in their paper. So they have tried to explain their findings on a Harvard Website.

    Sitting on the peaceful coast of Galapagos Islands. Ecuador, watching the sun move quietly into the sea, you shouldn't forget that Charles Darwin (1809-1882) arrived here in 1835. He stayed on the islands for five weeks, observing various animals. This finally inspired (启发) his famous work, On the Origin of Species. You can certainly follow Darwin's footsteps and enjoy a trip from four to seven days to the islands. The islands are certainly a paradise (天堂) for wildlife, as there are no natural killers on the islands and the number of boats and visitors is under government control. Though you cannot walk freely as Darwin did about 200 years ago, each day is as impressive as it could be. The most well-known animal of the Galapagos is the giant tortoise(巨型海龟), which can be seen moving slowly around the highlands of Sanra Cruz, the second largest island in the archipelago(群岛). Some of these creatures are so old that they might have been seen in their youth by Darwin himself. Despite strict control over activities and timing, your stay on the Galapagos will be remembered as a chain of incomparable pictures: diving with sea lions that swim and play within inches of you; feeling small sharks touch your feet as you swim; and, most magically, seeing a whale and her baby surface with a great breath of air. Travelling between the islands and observing the wildlife that so inspired Darwin, you will feel as though you are getting a special view of an untouched world. At night you will sleep on board the ship, leaving the wildlife in complete occupation of the islands, which are as undisturbed now as they have been since the beginning of time.

Scientists at the Department of Energy's Lawrence Berkeley National Laboratory and the California Institute of Technology have-in just two years-nearly doubled the number of materials known to have potential for use in solar fuels.

They did so by developing a process that promises to speed the discovery of commercially viable (商业可行性) generation of solar fuels that could replace coal, oil, and other fossil fuels.

Solar fuels, a dream of clean-energy research, are created using only sunlight, water, and carbon dioxide. Researchers are exploring a range of possible target fuels, but one possibility is to produce hydrogen by splitting water.

Each water molecule (分子) consists of one oxygen atom and two hydrogen atoms. The hydrogen atoms are extracted, and then can be reunited to create highly flammable hydrogen gas or combined with CO 2 to create hydrocarbon fuels, creating a plentiful and renewable energy source. The problem, however, is that water molecules do not simply break down when sunlight shines on them-if they did, the oceans would not cover most of the planet. They need a little help from a solar-powered catalyst (催化剂).

To create practical solar fuels, scientists have been trying to develop low-cost and efficient materials that perform the necessary chemistry using only visible light as an energy source.

A new method was developed through a partnership between the Joint Center for Artificial Photosynthesis (JCAP) and Berkeley Lab's Materials Project, using resources at the Molecular Foundry and the National Energy Research Scientific Computing Center (NERSCC). JCAP focused on developing a cost-effective method of turning sunlight, water, and carbon dioxide into fuel. It is led by Caltech with Berkeley Lab as a major partner. The Materials Project is a program based at Berkeley Lab that aims to remove the guesswork from materials design in a variety of applications.

"What is particularly significant about this study, which combines experiment and theory, is that in addition to identifying several new compounds for solar fuel applications, we can also learn something new about the basic electronic structure of the materials themselves." says Neaton, the director of the Molecular Foundry.