Retired nurse Sue Collins was just beginning the second length of her local pool when her morning swim suddenly became anything but a pleasure.

    Two months ago Sue, 69, who has never suffered from asthma or any other breathing problem in the past, suddenly found herself hard for breath.

    “I felt as if my throat and oesophagus (食道) were closing up,” says Sue.

    Sue is convinced the problem is related to the indoor swimming baths. “I spend half the year in Turkey and swim every day outside in a pool or the sea there and never have this problem,” she says.

    She may be right, because although a trip to the pool is the perfect exercise for many, the chlorine (氯气) used to keep the water free from germs can lead to problems.

    But in most cases it's not the chlorine that causes problems, but the by-products formed when chlorine interacts with other substances — and this is mostly due to people not showering before they enter the pool.

    “This then poisons the water for them and for others,” says Dr. Hull. “The chlorine interacts with sweat and urine(尿素) on the skin and forms by-products called chloramines that float above the surface as a gaseous solution that can be inhaled in.”

    Chloramines are heavier than air so hang over the water where they are easily breathed in. Some believe they may cause lung disorders. A Swedish study in 2013 examining the health of 146 workers at 46 indoor pools found that 17 per cent had airway trouble at work — but no problems at home.

    As Dr. Hull says: ‘People need to remember that showering isn't just for them. It is for the greater good.'

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    Alibaba started taking the lead in China by connecting big Chinese manufacturers（制造商）with big buyers across the world. Its business-to-business site, Alibaba.com allowed business to buy almost everything. Alibaba's advantage wasn't hard to judge: size. Alibaba is just big, even by Chinese standards. Its market attracts 231 million active buyers, 8 million sellers, 11.3 billion orders a year—and Alibaba is just the middleman. It encourages people to use its markets—not charging small sellers a percentage of the sale.

    If you want a quick look into the influence of Alibaba on daily Chinese life, take my experience. I moved to Beijing a year ago and quickly got tired of visiting small stores across the crowded, polluted city of 20 million people in search of new electronics, bathroom furnishings, and anything else my wife wanted. “You're looking for what exactly? Why not try it?” My Chinese teacher asked me one day. With that, my wonderful new relationship with Alibaba began.

    Alibaba's original business-to-business model now is second to consumer buying. Chinese retail（零售）buying makes up 80% of Alibaba's profit, and leading that group is Taobao, with 800 million items for sale and the most unbelievable selection of things you'll ever find. TMall.com is Alibaba's other big site, where you can find brand name goods from Nike and Unilever near the lowest prices.

    What I have a hard time explaining to friends and family back in the U.S.is how China has gone beyond traditional shopping—big-box retailers especially—in favor of online purchases on Taobao and a few other sites. In smaller towns than Beijing, where big retailers have not yet traveled, shopping online is shopping, and shopping is Taobao.

    I have a list of some of my recent purchases on Taobao for a sense of how wide the marketplace is. Almost everything arrived a day or two after ordering with free shipping. I'm not even a big buyer, because I need friends to help me search the Chinese-language site. When I was searching my purchase history on my Chinese teacher's iPad, which helps me buy goods, I looked through with great difficulty about 10 of her purchases for every one of mine.

    Three men have had a big influence on modern sound and communication technologies. We started with the beginnings of computer-generated music.

Max Vernon Mathews

    Max Vernon Mathews has been called the father of computer music. He created electronic tools so that people could use computers, as musical instruments. He had a huge influence on the development of electronic music and how it is written, recorded and played. In 1957, Max wrote the first: computer program, Music, to enable a computer to create sound and play it back. The computer was so slow that it would have taken an hour to play the piece of music in seventeen seconds. For that reason, Mathews moved the work to a tape player, which could be sped up to play the music at a normal speed.

    Mathews continued creating other versions of the Music program. He became interested in how computers could help musicians outside recording studios. The Groove program he developed was the first computer program made for live performances.

Norio Ohga

    Sony Corporation official Norio Ohga helped to develop, the compact disc in the late 1970s.

    He pushed for CDs to be larger, and with a longer playing time. He wanted them to hold seventy-five minutes so that they could store all of Bcethoven's Ninth Symphony on one disc. This way, listeners could enjoy the musical work without any break. The compact disc changed the electronics industry and the way people listened to music.

Hubert Joseph Schlafly

    Hubert Joseph Schlafly was an electrical engineer who helped change the way actors, politicians and other people speak on television. In 1950, he and two other men developed the teleprompter. One co-worker, Fred Barton, was an actor. He had an idea for a tool that would help television actors read their lines without having to memorize them. The first teleprompter involved a person who turned a long piece of paper printed with tall letters. As the actor read the lines, another person would, move the paper ahead on the device. Later versions used television screens to show the words that were to be read.

    A few weeks ago, I sat with a California farmer named Dave Ribeiro. I asked him what he wished to know about farmers. He smiled and said, "That we walk among you. We look like you and talk like you. We have advanced degrees and hobbies, just like you."

    Take Dave for example: He's a young man with a music degree. And if you walked past him on the street, you'd never think, "There goes a farmer."

    Is someone like Dave who you picture when you think of a farmer? Probably not. I think that most people would picture a man in his overalls(工作服). I can tell you, that does not represent Dave or any of the many other farmers I have gotten to know.

    Not only do we have to throw out our previous impression of farmers, but farming as a whole doesn't look much like it used to either. We recently sent a team out to see what modern farming looks like, and they found farmers to be completely different from our usual ideas about them and also came across them in some unexpected places.

    In a parking lot in a neighborhood of Brooklyn, they met a new crop of young farmers who were trying to bring fresh greens closer to eaters in the city by growing them in high-tech indoor vertical(垂直的) farms. In a Florida field under the fight path of an airport, they discovered farmers with university degrees growing plants that might someday fuel our cars. And in a modern farm in California, they observed how farmers were using technology to take the best possible care of their animals.

    These farmers all spend their days in very different ways—none of them looks like the previous farmer we have in our mind—but they're all working on new ways to feed our planet. Not only do we need to change our idea of what farming looks like, but we also need to change our view of where solutions can come from. Feeding all of us is going to take all of us working together.

Yosemite is a national park in California. It is very beautiful and big. The park includes more than 760,000 acres in the California Mountains. Most of the park is wilderness.

The part of Yosemite that everyone likes is Yosemite Valley. It is a tiny valley that is 7 miles long and less than 1 mile wide. It has tall rock walls and streams that splash down in waterfalls. More than two million visitors come to the valley each year.

One ranger (守护人) says the number of visitors is more than the land can handle. The valley has 4,500 camping spots. It has a hotel that can hold 4, 000 families. This is still not enough to handle all of the visitors. The valley has grown so big that it has a lot of traffic and crime.

A worker says the park is trying to keep the beauty of the park and let everyone visit. Some areas have been fenced off from people and planted with seeds to try to keep them beautiful.

A former worker thinks Yosemite should get more money to take better care of the park. He would also like to teach people what the park service is trying to do.

Some people are trying to save Yosemite Valley. A plan has been made to get rid of some buildings. There will be fewer cars allowed inside the park. More buses will help get people around.

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