For the Travel section, writers and editors selected special items to profile from a dozen cities.

Brussels:Chocolate

    Nearly half the chocolate consumed in the world is eaten in Europe, and Belgium—with average consumption of 14.99 pounds per person a year—certainly covers its fair share. While Brussels, the country's capital, is home to hundreds of chocolate makers, what makes a visit necessary is the rich heritage of traditional chocolate makers.

Budapest: Paprika (红辣椒)

    The job of preparing Hungarian paprika was once considered too dangerous for mothers to do. A woman who touched her children upon returning from work risked burning them, so only the elderly and unmarried were allowed the delicate task of separating the skin from the flesh. But by the early 20^th century, sweeter varieties and a machine turned paprika into a common feature of all Hungarian cuisine.

Lisbon: Tiles (瓷砖)

    Is there a bluer Country than Portugal? The blue sky and Atlantic Ocean embrace the land. The blue moods of Fado, the dark folk music, form the national soundtrack. And all across Portugal, the typically blue designs of azulejos—ceramic tiles—are spread across churches, castles, palaces, university halls, parks... The result is a beautiful land of Christian saints, Portuguese kings, historical glories, aristocrats at leisure, seascapes and so on.

Madrid: Guitars

    Walking into one of Madrid's storied guitar makers' workshops can feel like stepping into the past. Curly wood shavings, from the palest pine to ebony, fall onto the floor as artisans turn some humble wood into works of art. It's painstaking work—all done by hand—with classical guitar models and the methods of making them changing little over the last century.

    Think about the different ways that people use the wind. You can use it to fly a kite or to sail a boat. Wind is one of our cleanest and richest power sources, as well as one of the oldest. Evidence shows that windmills(风车) began to be used in ancient Iran back in the 7th century BC. They were first introduced to Europe during the 1100s, when armies returned from the Middle East with knowledge of using wind power.

    For many centuries, people used windmills to grind(磨碎) wheat into flour or pump water from deep underground. When electricity was discovered in the late 1800s, people living in remote(偏远的) areas began to use them to produce electricity. This allowed them to have electric lights and radio. However, by the 1940s when electricity was available(可利用的) to people in almost all areas of the United States, windmills were seldom used.

    During the 1970s, people started becoming concerned about the pollution that is created when coal and gas are burned to produce electricity. People also realized that the supply of coal and gas would not last forever. Then, wind was rediscovered, though it means higher costs. Today, there is a global movement to supply more and more of our electricity through the use of wind.

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Cycling or even walking in city areas can be a little dangerous, thanks to the fact that one is sharing the road with vehicles that are increasingly getting larger and heavier. A recent study proves that of the 1.27million people that die in road traffic crashes each year, about half are walkers, motorcyclists and cyclists. Now there may be a solution that could provide at least some help to protect this helpless group—an airbag!

    If you are worried that this safety measure will involve you taking around a heavy package or worse still, wrapping yourself inside an ugly plastic bag, the bag is fitted not on the human, but on the outside of the vehicle. And, while there are several versions of the idea in the works, the one most recently unveiled by Dutch car company TNO, seems to be the most advanced and ready to go into production.

    In the works since 2011, the airbag covers only the lower part of the windshield. This will provide the much needed buffer(缓冲)between the person's head and the pane of glass he/she would otherwise meet.

The chain of events leading to an airbag cause are quite simple—A camera fitted beneath the rear-view mirror monitors the vehicle's closeness to a walker or cyclist. Any contact with either one of them sets off the sensors in the car's bumper and quickly blows up the airbag. In addition to that the sensors also set off the car's automatic brake, reducing the chances if an even worse injury.

    In tests conducted using a model, the success of not getting injured after being hit by a car travelling at about 40km/h was about 50-50! While not perfect, it will still result in reducing the number of deaths by a huge amount.

    With TNO ready to license its technology to car makers and many more companies trying to develop similar concepts, we would not be surprised if outer airbags become a standard feature in every car pretty soon.

    Frigatebirds seagoing fliers with a 6-foot wingspan, can stay aloft(up in the air) for weeks at a time, a new study has found.

Since the frigatebird spends most of its life at sea, its habits outside of when it reproduces on land aren't well-known-until researchers started tracking them around the Indian Ocean. What the researchers discovered is that the bird's flying ability is unbelievable.

    Ornithologist(鸟类学家) Henri Weimerskirch put satellite tage(标签) on a couple of dozen frigatebirds. When the data started to come in, he could hardly believe how high the birds flew.

    "First, we found, 'Whoa, 1,500 meters. Excellent,' " says Weimerskirch, "And after 2,000, after 3,000, after 4,000 meters-OK, at this altitude they are in freezing conditions, especially surprising for a tropical bird."

"There is no other bird flying so high relative to the sea surface," he says. "It's the only bird that is known to intentionally enter into a cloud," Weimerskirch says. And not just any cloud—a soft, white cumulus cloud(积云). Over the ocean, these clouds tend to form in places where warm air rises from the sea surface. The birds take a ride on the current of rising air, all the way up to the top of the cloud.

    Frigatebirds have to find ways to stay aloft because they can't land on the water. Since their feathers aren't waterproof, the birds would drown in short order. They feed by harassing other birds in flight until they bring whatever fish they've swallowed back into their mouth and the frigatebird takes it.

So in between meals, frigatebirds fly higher... and higher.

    In one case, for two months-continuously aloft.

    One of the tagged birds flew 40 miles without a wing-flap. Several covered more than 300 miles a day on average, and flew continuously for weeks. They are blessed with an unusual body. No bird has a larger wing surface area compared with body weight.

    Think of a seed buried in a pot. It's dark down there in the potting soil. There's no light, no sunshine. So how does it know which way is up and which way is down? It does know. Seeds send shoots up toward the sky, and roots the other way. Darkness doesn't confuse them. Somehow, they get it right.

    More surprisingly, if you turn a seedling (秧苗) or a whole bunch of seedlings upside down, as Thomas Andrew Knight of the Royal Society did around 200 years ago, the tips and roots of the plant will sense, “Hey, I'm upside down. Look! I. will turn my way to the right direction and do a U-turn.”

    How do they know? According to botanist Daniel Chamovitz, Thomas Knight about 200 years ago guessed that plants must sense gravity. Knight proved it with a crazy experiment involving a spinning plate.

    He attached a bunch of plant seedlings onto a disc. The plate was then turned by a water wheel powered by a local stream at a speed of 150 revolutions (旋转) per minute for several days.

    If you have been at an amusement park in a spinning teacup, you know that because of centrifugal force (离心力) you get pushed away from the center of the spinning object toward the outside.

    Knight wondered, would the plants respond to the centrifugal pull of gravity and point their roots to the outside of the spinning plate? When he looked, that's what they'd done. Every plant on the disc had responded to the pull of gravity, and pointed its roots to the outside. The roots pointed out, and the shoots pointed in. So Thomas Knight proved that plants can and do sense the pull.

    A typical child plays many roles, such as friend, neighbor, son or daughter. Simply reminding children of that fact can lead to better problem-solving and more flexible thinking, according to new research from Duke University.

    Better problem-solving was just one positive finding of the study, said lead author Sarah Gaither, an assistant professor of psychology and neuroscience at Duke. After thinking about their own various identities, children also showed more flexible thinking about race and other social groupings—a behavior that could be valuable in an increasingly diverse society.

    In a series of experiments, Gaither and her colleagues looked at 196 children, ages 6 and 7. In an experiment, one group of children was reminded that they had various identities, such as son, daughter, reader or helper. A second group of children was reminded of their multiple physical attributes, such as a mouth, arms and legs. All the children then needed to handle a few tasks

    Children who were reminded of their various identities showed stronger problem-solving and creative thinking skills. When shown pictures of a bear staring at honey-filled beehive(蜂窝)high up in a tree, these children had more creative ideas for how the bear might get the honey, such as turning over a bowl so that it became a stool(凳子). In other words, they saw a new use for the bowl. Children who were reminded of their multiple roles also showed more flexible thinking about social groupings. When asked to categorize different photos of faces, they suggested many ways to Spso. They identified smiling faces such as unsmiling ones, and old and young faces. The other children, meanwhile, primarily grouped people's faces by race and gender(性别).

    The-study suggests ways to promote flexible thinking for the young, which could be especially valuable for teachers." Gaither said.

    "We have this tendency in our society to only think about ourselves in connection with one important group at a time," Gaither said. "When kids think that they have various identities, they show greater abilities."