Houses fall down. Trees fall over. Large holes form in the ground. Could Alaska be sinking? That's what some villagers in Alaska have been asking themselves recently and scientists think they know why. Warmer temperatures may be causing Alaska's frozen ground to thaw (解冻).

    About 85 percent of Alaska's land surface has permafrost (永久冻结带). Permafrost supports the ground above it—including trees, houses, and roads. But why is the permafrost thawing?

    Some scientists say that human-caused pollution is leading to global warming. And most scientists agree that Alaska has been getting warmer. They say that the warmer temperature is causing permafrost to thaw in some areas. The thawing permafrost can cause problems for people, plants, and animals.

    The collapsing (倒塌) is a problem in the villages in Alaska which are built on permafrost, and some of them may have to move to safer ground, where there is no permafrost.

    The Alaskan town of Glennallen saw its old post office collapse. And, according to James Walters, a permafrost expert at the University of Northern Iowa, house-moving companies have been very busy.

    “Melting permafrost can also destroy trees and forests,” Walters said. “When holes in the ground form, trees fall into them and die. This could turn a forest into a swamp (沼泽), and animals which need the forests will have to move elsewhere.”

    “The melting could cause severe problems.” Walters says, “This could take hundreds of years, but in the end Alaska will look quite different from what it looks like now.”

    In 1999, twelve percent of public elementary schools in the United States required students to wear uniforms. Just three years later, the amount was almost double that.

    A study of six big-city Ohio public schools showed students who were required to wear uniforms had improved graduation, behavior and attendance rates. Academic performance was unchanged.

    Some high schools in Texas have also joined in the movement. Yet studies find mixed results from requiring uniforms. And some schools have turned away from such policies.

    Supporters believe dressing the same creates a better learning environment and safer schools. The school district in Long Beach, California, was the first in the country to require uniforms in all elementary and middle schools. The example helped build national interest in uniforms as a way to deal with school violence and improve learning.

    Findings in Long Beach suggested that the policy resulted in fewer behavior problems and better attendance. But researcher Viktoria, who has looked at those findings, says they were based only on opinions about the effects of uniforms.

    She says other steps taken at the same time to improve schools in Long Beach and statewide could have influenced the findings. The district (the area marked by government) increased punishments for misbehavior. And California passed a law to reduce class sizes.

    In Florida, for example, researcher Sharon found that uniforms seemed to improve behavior and reduce violence. In Texas, Eloise found fewer discipline problems among students required to wear uniforms, but no effect on attendance.

    Sociologist David has studied school uniform policies since1998.He collected the reports in the book. In his own study, he found that reading and mathematics performance dropped after a school in Pennsylvania（宾夕法尼亚州）required uniforms.

    Political and community pressures may persuade schools to go to uniforms to improve learning. But David and others believe there is not enough evidence of a direct relationship. In fact, he says requiring uniforms may even increase discipline problems.

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    The term “formal learning” refers to all learning which takes place in the classroom regardless of whether such learning is informed by conservative or progressive ideologies(思想意识). “Informal learning”, on the other hand, is used to refer to learning which takes place outside the classroom.

    These definitions(定义) provide the basic difference between the two models of learning. Formal learning is separated from daily life and may actually promote ways of learning and thinking which often run counter to those obtained form practical daily life. A characteristic feature of formal learning is the centrality of activities which can prepare for the changes of adult life outside the classroom, but it cannot, by its nature, consist of these challenges.

    In doing this, language plays an important role as a major channel for information exchange.  The language of the classroom is more similar to the language used by middle-class families than that used by working-class families. Middle class children thus find it easier to gain the language of the classroom than their working-class classmates.

Informal learning, in contrast, occurs in the setting to which it relates, making learning immediately relevant (相关的). In this context, language does not occupy such an important role: the child's experience of learning is more direct, involving sight, touch, taste, and smell senses that are not used in the classroom. Whereas formal learning is transmitted by teachers selected to perform this role, informal learning is gained as a natural part of child's socialization. Adults or older children who are proficient (熟练的) in skill or activity provide—sometimes unintentionally (无意义地)—target models of behavior in the course of everyday activity.

    Informal learning, therefore, can take place at any time and place. The motivation of learner provides another important difference between the two models of learning. The formal learner is generally motivated by some kind of external goal such as parental approval, social status, and possible financial reward. The informal learner, however, tends to be motivated by successful completion of the task itself and the partial knowledge of adult status.

    Given that learning systems develop as a response to the social and economic contexts in which they are firmly, it is understandable that modern, high urbanized (城市化) societies have concentrated almost specially on the establishment of formal education systems. What these societies have failed to recognize are the ways in which formal learning inhibits the child's multi-sensory acquisition of practical skills. The failure to provide a child with a direct education may in part account for many of the social problems which trouble our societies.

    Ever get that feeling you're being watched? Well, if you're a dog-owner, you may have a point. Dogs are able to watch people's interactions with one another to determine who holds yummier treats, according to a new study. This study joins others that show dogs are good observers of human behaviors and feelings. It offers evidence that dogs use information not only from people's direct interactions with them, but also their interactions with one another.

    In the study, dogs watched a man ask two women for some of their corns. Both women gave the man corns when he asked, but in response to one woman, the man showed his enthusiasm and said the corns were so delicious. In response to the other woman, he gave the corns back and called them gross（in Spanish；the study was conducted in Argentina）. After these interactions, the man left and an assistant holding the dog let the dog go. While many dogs didn't approach either woman, the dogs that did have a preference tended to prefer the woman with the yummier(美味的) food.

    Other studies of dogs' people-watching ability have found dogs are able to tell the difference between happy and sad faces in their owners. They prefer people who give others food when asked over people who don't give others food. And in one study, dogs turned toward crying people more often than toward talking people.

    So how much do dogs really understand about the humans around them? That's not totally settled yet. In a strange twist to the Argentine study above, when the researchers tried an experiment in which they put two plates of corns on a table and had a man react to each plate, dogs didn't preferentially approach the tastier plate afterward. You could say dogs watch for the interaction between two persons, not just how a person reacts. Yet a previous study found dogs will choose boxes that people reacted to happily, but not boxes people reacted to with a disgusted face.

    Well, either way, you can be sure Fluffs is keeping an eye on you, to the best of her ability. The study was published in the journal PLOS One.

    Argentina in the late nineteenth century was an exciting place. Around 1870, it was experiencing an economic boom（繁荣）, and the capital, Buenos Aires, attracted many people. Farmers, as well as a flood of foreigners from Spain and Italy, came to Buenos Aires seeking jobs. These jobs didn't pay well, and the people felt lonely and disappointed with their new life in the city. As the unhappy newcomers mixed together in the poor parts of the city, the dance known as the tango(探戈舞) came into being.

    At the beginning the tango was a dance of the lower classes. It was danced in the bars and streets. At that time there were many fewer women than men, so if a man didn't want to be left out, his only choice was to dance with another man so that he could attract the attention of the few available women. Gradually, the dance spread into the upper classes of Argentinean society and became more respectable.

    In Europe at this time, strong interest in dance from around the world was beginning. This interest in international dance was especially evident in Paris. Every kind of dance from ballet(芭蕾舞) to belly dancing could be found on the stages of the Paris theaters. After tango dancers from Argentina arrived in Europe, they began to draw the interest of the public as they performed their exciting dance in cafes. Though not everyone approved of the new dance, saying it was a little too shocking, the dance did find enough supporters to make it popular.

    The popularity of the tango continued to grow in many other parts of the world. Soldiers who returned to the United States from World War I brought the tango to North America. It reached Japan in 1926, and in 2003 the Argentinean embassy(大使馆) in Seoul hired a local tango dancer to act as a kind of dance ambassador, and promote tango dancing throughout South Korea.

    A European Union program is letting blind people experience famous paintings for the first time. It uses three dimensional (3-D) printing to re-create famous paintings so they can be touched.

    One painting printed with the new technology is Gustav Klimt's “The Kiss.” It is a popular attraction at the Belvedere Museum in Vienna, Austria. The painting shows a man and a woman standing in a field filled with flowers. They are wearing gold robes and have their arms around each other. The man leans down to kiss the woman.

    Klimt finished the painting in 1908. Until now, people who had trouble seeing could not appreciate the artwork. But thanks to the reproduction they can touch the piece and feel the ridges and depressions. Andreas Reichinger started making 3-D versions of artwork in 2010. He said this reproduction was his most difficult project because the couple's robes are so detailed.

    Dominika Raditsch is a blind museum visitor. She touched the reproduction. As she moved her hands around it she said, ”Exactly, can you see these? There are so many details.“ Raditsch said she can imagine what the original painting looks like when she touches the reproduction. “It's somehow round. You can feel it. It comes with it. And in many places it's so smooth. And then I think to myself: it probably shines too!” Raditsch said.

    The Belvedere is not the only museum to have 3-D versions of its artwork. Some of the pieces at the Prado, in Madrid, Spain, have reproductions that can be touched. But the piece in Vienna has one special part: it is made with widely available 3-D printing technology. That means one day, blind art fans anywhere in the world could download the source files and print the reproductions themselves.