Most people know precious gemstones (宝石) by their appearances. An emerald flashes deep green, a ruby seems to hold a red fire inside, and a diamond shines like a star. It's more difficult to tell where the gem was mined, since a diamond from Australia or Arkansas may appear the same to one from the Democratic Republic of the Congo. However, recently, a team of scientists has found a way to identify a gemstone's origin.

    Beneath the surface of a gemstone, on the tiny level of atoms and molecules（分子）, lie clues (线索) to its origin. At this year's meeting of the Geological Society of America in Minneapolis, Catherine McManus reported on a technique that uses lasers (激光) to clarify these clues and identify a stone's homeland. McManus directs scientific research at Materialytics, in Killeen, Texas. The company is developing the technique. “With enough data, we could identify which country, which mining place, even the individual mine a gemstone comes from,” McManus told Science News.

    Some gemstones, including many diamonds, come from war-torn countries. Sales of those “blood minerals” may encourage violent civil wars where innocent people are injured or killed. In an effort to reduce the trade in blood minerals, the U.S. government passed law in July 2010 that requires companies that sell gemstones to determine the origins of their stones.

    To figure out where gemstones come from, McManus and her team focus a powerful laser on a small sample of the gemstone. The technique is called laser-induced breakdown spectroscopy. Just as heat can turn ice into water or water into steam, energy from the laser changes the state of matter of the stone. The laser changes a miniscule part of the gemstone into plasma, a gas state of matter in which tiny particles（微粒）called electrons separate from atoms.

    The plasma, which is superhot, produces a light pattern. (The science of analyzing this kind of light pattern is called spectroscopy.) Different elements produce different patterns, but McManus and her team say that gemstones from the same area produce similar patterns. Materialytics has already collected patterns from thousands of gemstones, including more than 200 from diamonds. They can compare the light pattern from an unknown gemstone to patterns they do know and look for a match. The light pattern acts like a signature, telling the researchers the origin of the gemstone.

    In a small test, the laser technique correctly identified the origins of 95 out of every 100 diamonds. For gemstones like emeralds and rubies, the technique proved successful for 98 out of every 100 stones. The scientists need to collect and analyze more samples, including those from war-torn countries, before the tool is ready for commercial use.

    Scientists like Barbara Dutrow, a mineralogist from Louisiana State University in Baton Rouge, find the technique exciting. “This is a basic new tool that could provide a better fingerprint of a material from a particular locality,” she told Science News.

注意：每个空格只填一个单词。

    Traveling to all corners of the world gets easier and easier. We live in a global village, but this doesn't mean that we all behave in the same way.

    How should we behave when you meet someone for the first time? An American shakes your hand firmly while looking you straight in the eye. In many part of Asia, there is no physical contact (接触)at all. In Japan, you should bow, and the more respect you want to show, the deeper you should bow. In Thailand, people greet each other by pressing both hands together at the chest. In both countries, eye contact is avoided as a sign of respect.

    Many countries have rules about what you should and shouldn't wear. In Muslim countries, you shouldn't reveal (显露)the body, especially women, who Should wear long blouses and skirts .In Korea, you should take off your shoes when entering a house. Remember to place them neatly together where you came in.

    In Spain, lunch is often the biggest meal of the day, and can last two or three hours. For this reason many people eat a light breakfast and a late dinner. In Mexico, lunch is the time to relax, and many people prefer not to discuss business as they eat .In Britain, it's not unusual to have a business meeting over breakfast.

    In most countries, an exchange of business cards is necessary for all introductions. You should include your company name and your position. If you are going to a country where your language is not widely spoken, you can get the back side of your card printed in the local language. In China, you may present your card with the writing facing the person you are giving it to.

Participating (参与) in Class

    Class participation is a valuable part of learning. Many students are unwilling to participate in class{#blank#}1{#/blank#}  Other students participate in class, but do so not correctly. Here is some advice that can help you become an effective class participant.

    {#blank#}2{#/blank#} Do all tasks and readings and go over your notes from previous class periods. This will help to prevent you from making uninformed ( 无知的) comments or asking unsuitable questions. As you get ready for class, think about important questions and concerns that may appear in class. Be sure that you are prepared to deal with these.

    Try to sit close to the front of the class{#blank#}3{#/blank#} Besides, you can hear what the teachers say clearly.

    Listen to what the other students say. You can then build on their comments to make your own. Be active when you respond to something another student says. You can disagree, but don't go into an “attack mode”.

    Don't be afraid to be wrong{#blank#}4{#/blank#} You can learn from being wrong. Don't be afraid to ask questions. This is a good learning skill. Also, the chances are that other students in the class have the same questions as you do, and they will appreciate your asking.

    Be sure that your questions and comments are closely connected with the class topic.

    Don't waste the time of the teacher and other students by going off way. Don't take it in person if others disagree with what you say{#blank#}5{#/blank#}

A. Creating a personal connection helps you feel more comfortable about participating in class.

B. Be confident that your opinions will be valued by your teacher and other students.

C. It's hard to stay unconcerned when you are near to the teacher.

D. Be sure that you are well prepared before coming to class.

E. This may be because they are shy or fearful of being judged and criticized (批评).

F. Your class should be a good place for giving opinions and taking advice.

G. Learning is a change in behavior based on experience.

    Getting rid of dirt, in the opinion of most people, is a good thing. However, there is nothing fixed about attitudes to dirt.

    In the early 16th century, people thought that dirt on the skin was a means to block out disease, as medical opinion had it that washing off dirt with hot water could open up the skin and let ills in. A particular danger was thought to lie in public baths. By 1538, the French king had closed the bath houses in his kingdom. So did the king of England in 1546. Thus began a long time when the rich and the poor in Europe lived with dirt in a friendly way. Henry IV, King of France, was famously dirty. Upon learning that a nobleman had taken a bath, the king ordered that, to avoid the attack of disease, the nobleman should not go out.

    Though the belief in the merit of dirt was long-lived, dirt has no longer been regarded as a nice neighbor ever since the 18th century. Scientifically speaking, cleaning away dirt is good to health. Clean water supply and hand washing are practical means of preventing disease. Yet, it seems that standards of cleanliness have moved beyond science since World War II. Advertisements repeatedly sell the idea; clothes need to be whiter than white, cloths ever softer, surfaces to shine. Has the hate for dirt, however, gone too far?

    Attitudes to dirt still differ hugely nowadays. Many first-time parents nervously try to warn their children off touching dirt, which might be responsible for the spread of disease. On the contrary, Mary Ruebush, an American immunologist (免疫学家), encourages children to play in the dirt to build up a strong immune system. And the latter position is gaining some ground.

    Do you know the difference between a food chain anda food web? Food chains show how a living thing such as a plant or an animal gets its energy. A food web consists of multiple food chains and includes many more plants and animals than a food chain includes. This diagram shows a food chain within a food web of the African savanna.

A new study of fifth and sixth graders in Germany examined the relation between classmates' gender stereotypes (性别刻板印象) and individual students' reading outcomes to explain how these stereotypes contribute to the gender gap in reading.

"It's a cycle of sorts," explains Francesca Muntoni, a researcher at the University of Hamburg, who leads the study. "Reading is first thought as a female advantage." It stresses that girls are born to have an advantage in reading, which in turn greatly affects boys by causing them to devalue their actual reading ability. So finally, it damages their reading motivation (积极性)."

The study has proven that boys are less motivated to read and hold weaker reading-related beliefs about their own skills if they hold the strong stereotype mentioned above. And accordingly, they perform poorly in the reading test. The effect of classmates' stereotypes is seen over and above the effect of individual stereotypes. The study found fewer individual positive effects and no effects of classmates, stereotyping on reading-related outcomes for girls.

The researchers say although their study provides evidence of lasting negative effects of stereotypical beliefs in a classroom context, they need more experimental findings on the subject. They also note that students' gender stereotypes were measured by self-reports, which might limit their accuracy. Finally, they point out that their study did not settle how gender stereotypes were formed.

"To solve socially the determined gender inequality in reading and help create classroom contexts that discourage students from acting on their stereotypical beliefs, teacher and parents may consider educating boys and girls in ways that change stereotypical behaviors. And thus students can become aware of their gender stereotypes to counteract their effects on other students' outcomes and to create a gender-fair learning environment," says Jan Retelsdorf, professor of the University of Hamburg, who co-authored the study.