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    Measles(麻疹), which once killed 450 children each year and disabled even more, was nearly wiped out in the United States 14 years ago by the universal use of the MMR vaccine(疫苗). But the disease is making a comeback, caused by a growing anti-vaccine movement and misinformation that is spreading quickly. Already this year, 115 measles cases have been reported in the USA, compared with 189 for all of last year.

    The numbers might sound small, but they are the leading edge of a dangerous trend. When vaccination rates are very high, as they still are in the nation as a whole, everyone is protected. This is called “herd immunity”, which protects the people who get hurt easily, including those who can't be vaccinated for medical reasons, babies too young to get vaccinated and people on whom the vaccine doesn't work.

    But herd immunity works only when nearly the whole herd joins in. When some refuse vaccination and seek a free ride, immunity breaks down and everyone is in even bigger danger.

    That's exactly what is happening in small neighborhoods around the country from Orange County, California, where 22 measles cases were reported this month, to Brooklyn, N.Y., where a 17-year-old caused an outbreak last year.

    The resistance to vaccine has continued for decades, and it is driven by a real but very small risk. Those who refuse to take that risk selfishly make others suffer.

    Making things worse are state laws that make it too easy to opt out(决定不参加) of what are supposed to be required vaccines for all children entering kindergarten. Seventeen states allow parents to get an exemption（豁免), sometimes just by signing a paper saying they personally object to a vaccine.

    Now, several states are moving to tighten laws by adding new regulations for opting out. But no one does enough to limit exemptions.

    Parents ought to be able to opt out only for limited medical or religious reasons. But personal opinions? Not good enough. Everyone enjoys the life-saving benefits vaccines provide, but they'll exist only as long as everyone shares in the risks.

    “A room without books is like a body without a soul,” observed the Roman philosopher, Cicero. It can also be a sign of financial problems to come. New research has uncovered a strong connection between the earning of adults and whether they grew up surrounded by books as children.

    Three economists at the University of Padua—Giorgio Brunello, Guglielmo Weber and Christoph Weiss—studied 6000 men born in nine European countries and concluded that children with access to books could expect to earn more money than those who grew up with few or no books.

    They studied the period from 1920 to 1956, when school reforms saw the minimum school leaving age raised across Europe. They booked at whether, at the age of 10, a child lived in a house with fewer than 10 books, a shelf of books, a bookcase with up to 100 books, two bookcases, or more than two bookcases.

    Over the period studied, the research, published in The Economic Journal, found that an additional year of education increased a man's average lifetime earnings by 9%. Men brought up in houses with less than a shelf of books earned only 5% more as a result of the extra year's education, compared with 21% more for those who had access to a lot of books. And those who had access to books were more likely to move to the better-earning opportunities in cities than those without books. The men's first job was also much more likely to be a white-collar job.

    The economists offer a number of theories for the results. “Perhaps books matter because they encourage children to read more and reading can have positive effects on school performance,” they said.

    The number of books in children's homes can effectively predict their cognitive(认知的) test scores. This may indicate a home that encourages cognitive skills, which are important for economic success in life.

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    Social media is one of the fastest growing industries in today's world. A study conducted by the US Pew Research Center showed that 92 percent of teenagers go online daily. The wide spread of social media has changed nearly all parts of teenagers' lives.

    Changing relationships

    High school student Elly Cooper from Illinois said social media often reduces face- to-face communication. “It makes in-person relationships harder because of people's attention given to their phones instead of their boyfriends or girlfriends,” Cooper said.

    Yet, some people believe social media has made it easier to start relationships with anyone from anywhere. Beth Kaplan from Illinois met her long-distance friend through social media. He currently lives in Scotland, but they're still able to frequently communicate with each other. “I can feel close to someone that I'm talking to via FaceTime,” Kaplan said.

    Wanting to be “liked”

    The rise of social media has changed the way teenagers see themselves. The 19- year-old Essena O'Neill announced on the social networking service Instagram that she was quitting social media because it made her unable to stop thinking about appearing perfect online. Negative comments also can do great damage to a teenager's self-esteem. Teenagers who get negative comments can't help but feel hurt.

    Opening new doors

    However, Armin Korsos, a student from Illinois, takes advantage of the comments he receives over social media to improve his videos on the social networking site YouTube. “Social media can help people show themselves and their talents to the world in a way that has never been possible before,” Korsos said.

    Here are some recommendations for tourists to choose from.

    Banff, Canada

    Banff, located in the Rockies, has a view of tall mountains, deep valleys and lakes, making it the first town to become part of the country's national parks. Tourists can enjoy its beauty by hiking, horse riding and boat trips. Banff was founded in 1883 while a railroad was in construction. It was the water springs that drew the engineers' attention to the place as a settlement. With such a fantastic view, it's no surprise that Banff hosts a number of cultural festivals.

    Lisbon, Portugal

    Lisbon is the capital of Portugal, with the warmest winters of any major European city.

    Belem Tower and Jeronimos Monastery are listed as UNESCO World Heritage Sites. The former was built in the 16^th century as a symbol of Portugal's Extraordinary Age and the latter is one of the greatest examples of the Portuguese late-Gothic style of architecture. The Lisbon Oceanaium is among Europe's finest aquariums. The Museum Calouste Gulbenkian is among the best museums in Europe containing priceless artworks covering 4000 years from ancient Egyptian times to the late 20^th century.

    Portland, US

    Portland is frequently recognized as one of the world's most environmentally-friendly cities because of its well-built pavements, large community of cyclists and convenient public transportation. Us climate is ideal for growing roses and it's called the “City of Roses”. Besides, the seaport is also known as a city of beer: it has the largest number of beer breweries（啤酒厂）of any city in the world. Today's Portland is better known for its music. It's called “the capital of karaoke” and “one of the most exciting music scenes” in the US.

    Bordeaux, France

    Bordeaux attracts tourists with its rich cultural heritage, especially its wealth of architectural treasures. Besides the Cathedral of Saint Andrew dating back to 12^th century, the Basilica of Saint Michael is another one of the city's UNESCO World Heritage Sites. It took 200 years to build from 14^th to 16^th centuries. Other significant buildings include the Grand Theater built in 1780 in the new Classical style and the Stone Bridge built in 1821.

    The best bikes for the beginners

    When it comes to purchasing your first bike, the choice is endless, making it tough to know what to go for. Here are the best buys on the market right now.

    Boardman CX Comp

    This is a cross-country bike, and it's so versatile(多用途的)that you can handle any terrain(地势)on it, making it a great choice for those wanting to try various cycling subjects. If you leave on the thick tires it comes with, it can ride on various paths and can even handle some less demanding mountain bike routes. Alternatively, put on thin, slick tires and treat it as a road bike. It has basket and comes with Shimano Sora gears(齿轮), which are outstanding for its price.

    $650, Halfords

    Planet X RT-58 v2

    Planet X is based in Yorkshire, which means you'd probably have to buy this bike without seeing it. But it's worth it, because this is an excellent machine at a lower price. Planet X is a highly rated manufacture and this model comes with Shimano Sora gears.

    $439, Planet X

    Specialized Allez ES

    Specialized is one of the biggest and most popular brands in cycling, and this is its hugely popular primary road bike. It comes with solid components from front to back and you'll look great out on the road.

    $575, Evans Cycles

    Boardman Road Team Carbon

    If you can push budget further still, this bike is worth the extra investment. The frame is made entirely from carbon, which is lighter, faster and more comfortable than the composition metal models above and gives you an all-round more enjoyable ride. It also means that if you get really serious about cycling, you don't have to upgrade as quickly as you would with a cheaper bike.

    $800, Halfords

    Lucy, whose skeleton（骨骼） was discovered in Ethiopia in 1974, died shortly after she fell out of a tree, according to a new study published Monday in the British journal Nature.

    For their research, Kappelman and Dr. Richard Ketcham used a CT scanner to create more than 35,000 "slices" of Lucy's skeleton. Scientists named her Lucy from the Beatles song "Lucy in the Sky with Diamonds", which was played at the camp the night of her discovery.

    The following analysis of the slices showed sharp, clean breaks seen at the end of Lucy's right humerus （肱骨） are similar to bone breaks seen in victims of falls.

    The researchers concluded that these and other breaks in her skeleton show that Lucy, who is believed to have stood about 3 feet 6 inches and weighed about 60 pounds, fell feet first and used her arms to support herself﹣but that the injury was too severe to have been survivable.

    The researchers estimate that Lucy was going about 35 miles an hour when she hit the ground after falling from a height of roughly 40 feet, according to the statement.

    That sounds plausible. But other scientists are doubtful. "There are countless explanations for bone breaks," Dr, Donald C, Johanson, director of the Institute of Human Origins and one of the scientists who discovered Lucy, said, "The suggestion that she fell out of a tree is largely a just﹣so story and therefore unprovable." Johanson said it was more likely that Lucy's breaks occurred long after she died, saying that "elephant bones appear to have the same kind of breaks, It's unlikely they fell out of a tree.

    But the new research focused on "a small number of breaks" that are consistent with "high﹣energy bone﹣to﹣bone influences" and which differ from the sorts of breaks commonly seen in other collected bones. Kappelman responded in an email, "These appear to have occurred at or near the time of death."