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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    Mom and Dad are two of the most important people in your life. You probably see at least one of them every day. If your dad worships(崇拜) the Pittsburgh Stealers, you're likely to grow up being a big fan of that football team. And if your mom loves to read, you just might grow up carrying a book wherever you go, just like she does.

    Here are four ways you can stay close and build a strong relationship with your parents.

( 1 )Spent time together. How much time do you spend just enjoying each other's company?

Instead of playing a computer game or watching TV, maybe you can ask your mom and dad to play with you. Go outside together, try a board game, or read a book out.

( 2 )Share your feelings and ask for help. Your mom or dad might not know that you're having a problem. Tell a parent if you're sad or struggling with something.

( 3 )Show your care. Some families are always kissing, hugging, and saying “I love you”. It's important to show that you care for each other. In addition to kisses and hugs, kids and parents show their love by respecting each other, being caring, polite, and thoughtful.

( 4 )Whatever you do, do your best! You don't have to be perfect, but when you do your best, you make your parents proud. It makes them happy to see how you're turning into such a great kid. Why? Because it lets them know they're doing a good job.

    The word advertising refers to any kind of public announcement that brings products and services to the attention of people. Throughout history, advertising has been an effective way to promote(促进)the trading and selling of goods. In the Middle Ages, merchants employed "town criers" to read public messages aloud to promote their goods. When printing was invented in the fifteenth century, pages of advertisements(ads)could be printed easily and were either hung in public places or put in books.

    By the end of the seventeenth century, when newspapers were beginning to be read by more people, printed materials became an important way to promote products and services. The London Gazette was the first newspaper to set aside a place just for advertising. This was so successful that by the end of the century several companies started businesses for the purpose of making newspaper ads for merchants.

    Advertising spread quickly throughout the eighteenth century. Ad writers were starting to pay more attention to the design of the ad text. Everything, from clothes to drinks, was promoted with clever methods such as repetition of the firm's name or product, words organized in eyecatching patterns, the use of pretty pictures and expressions easy to remember.

    Near the end of the nineteenth century, companies that were devoted to the production of ads came to be known as "advertising agencies(广告商)．"The agencies developed new ways to get people to think of themselves as members of a group. Throughout the twentieth century, advertising agencies promoted consumerism(消费主义)as a way of life, spreading the belief that people could be happy only if they bought the "right" products.

    When most of us look at our hands, we might notice that we need to clean, or stop biting our fingernails, and that's about it. But if you ask a doctor, he can see a whole lot more. Everything from poor diet and stress to serious kidney (肾) problems can be revealed by a glance at your fingernails.

    There are about 30 different nail signs that can be associated with medical issues, though may indicate more than one problem, according to Dr. Amy Derick, a clinical instructor of dermatology at Northwestern University.

    Here are five of the things a doctor can tell about your health based on your fingernails.

    ⒈People who aren't eating well and lack vitamin or dietary may have thinner than normal nails, which are more likely to break.

    ⒉Horizontal lines are associated with serious physical stress. They frequently occur in people who have gone through chemotherapy(化疗).They can also occur after some illnesses, injuries, or with severe malnourishment(营养不良).Interestingly, there may be an altitude connection too. They've also been found in people who dove 1,000 feet and others who participated in an Everest exploration.

    ⒊Vertical lines, however, are generally not such a big deal. Some people are more genetically prone to them than others, but they're commonly associated with aging.

    ⒋When people lack iron, their nails can turn spoon-like. Instead of curving down and covering the finger normally, they'll start to rise up on the sides and front, like the part of a spoon that holds liquid.

    ⒌Kidney and liver problems can create “half-and-half nails”, where one part of the nail is white and the other part dark or pink, according to Derick.

    Doctors note that because disease diagnosis is complex and some symptoms can be associated with different diseases, you should always see a medical professional if you are concerned about something you notice.

    It was at least two months before Christmas when nine-year-old Rose told her father and me that she wanted a new bicycle.

As Christmas drew nearer, her desire for a bicycle seemed to fade—or so we thought, as she didn't mention it again. We bought the latest fashionable Baby Sitter's Club dolls, a holiday dress and some beautiful story books. Then, much to our surprise, on December 23rd, she proudly announced that she "really wanted a bike more than anything else."

    It was just too late, what with all the details of preparing Christmas dinner and buying last-minute gifts. We could only think of the bicycle and the disappointment of our child. "What if I make a little bicycle out of clay and write a note that she could trade the clay model in for a real bike?" Her dad asked. The theory, of course, being that since that is a high-ticket item and she is "such a big girl", it would be much better for her to pick it out. So he spent the next five hours painstakingly working with clay to make a tiny bike.

    Three hours later, on Christmas morning, we were excited for Rose to open the little heart-shaped package with the beautiful red and white clay bike and the note. Finally, she opened it and read the note aloud.

    She looked at me and then at her dad and said, "so does this mean that I trade in this bike that Daddy made me for a real one?"

    Beaming, I said, "Yes."

    Rose had tears in her eyes when she replied, "I could never trade in this beautiful bicycle that Daddy made me. I'd rather keep this than get a real bike."

    At that moment, we would have moved heaven and earth to buy her every bicycle on the planet!

There was an encounter that later sparked scientists' investigations into using jellyfish as a greater source of food, as well as a potential ingredient in medicines and nutraceuticals. In the summer of 2013, while Stefano Piraino was wandering along the rocky shoreline, he noticed a washed-up jellyfish. Then, he tore off a piece and put it in his mouth. It was salty, crunchy and crispy from the sun. "It was very tasty, " remembers Piraino, a zoologist. After a few days of lying on the shore, their stinging cells(刺细胞)are deactivated, Piraino explains. Still, he warns that people should not eat jellyfish straight out of the sea, because raw jellyfish contains bacteria that can cause food poisoning. 

Recently, there have been numerous reports of jellyfish blooms—seasonal events where there is a large and sudden increase in jellyfish numbers. These population explosions break the balance of ocean ecosystems, and have the potential to harm biodiversity and reduce fish stocks. 

Some scientists, such as Piraino, believe one solution is broadening our palates(口味)since the world is in urgent need of sustainable food resources. Jellyfish can be integrated into traditional recipes and local cuisine. Not only are they high in protein, but the microalgae inside the cells of some jellyfish are rich in fatty acids. In fact, jellyfish is already eaten across Asia. In China, jellyfish has been eaten for more than 1, 000 years, with jellyfish salad a popular delicacy. 

Jonathan Houghton, a senior lecturer in marine biology, believes that jellyfish can be a better source of collagen(胶原蛋白). There are a number of companies already using jellyfish as a substitute(替代品) for cow and pig collagen, which is often used in medical treatments for humans. One British company says collagen from jellyfish offers a better choice, because their collagen can work with a wide variety of human cell types.