If a diver surfaces too quickly, he may suffer the bends. Nitrogen (氮) dissolved (溶解) in his blood is suddenly liberated by the reduction of pressure. The consequence, if the bubbles (气泡) accumulate in a joint, is sharp pain and a bent body—thus the name. If the bubbles form in his lungs or his brain, the consequence can be death.

    Other air-breathing animals also suffer this decompression (减压) sickness if they surface too fast: whales, for example. And so, long ago, did ichthyosaurs. That these ancient sea animals got the bends can be seen from their bones. If bubbles of nitrogen form inside the bone they can cut off its blood supply. This kills the cells in the bone, and consequently weakens it, sometimes to the point of collapse. Fossil (化石) bones that have caved in on themselves are thus a sign that the animal once had the bends.

    Bruce Rothschild of the University of Kansas knew all this when he began a study of ichthyosaur bones to find out how widespread the problem was in the past. What he particularly wanted to investigate was how ichthyosaurs adapted to the problem of decompression over the 150 million years. To this end, he and his colleagues traveled the world's natural-history museums, looking at hundreds of ichthyosaurs from the Triassic period and from the later Jurassic and Cretaceous periods.

    When he started, he assumed that signs of the bends would be rarer in younger fossils, reflecting their gradual evolution of measures to deal with decompression. Instead, he was astonished to discover the opposite. More than 15% of Jurassic and Cretaceous ichthyosaurs had suffered the bends before they died, but not a single Triassic specimen (标本) showed evidence of that sort of injury.

    If ichthyosaurs did evolve an anti-decompression means, they clearly did so quickly—and, most strangely, they lost it afterwards. But that is not what Dr Rothschild thinks happened. He suspects it was evolution in other animals that caused the change.

    Whales that suffer the bends often do so because they have surfaced to escape a predator (捕食动物) such as a large shark. One of the features of Jurassic oceans was an abundance of large sharks and crocodiles, both of which were fond of ichthyosaur lunches. Triassic oceans, by contrast, were mercifully shark- and crocodile-free. In the Triassic, then, ichthyosaurs were top of the food chain. In the Jurassic and Cretaceous, they were prey (猎物) as well as predator—and often had to make a speedy exit as a result.

    The Loss of Innocence

    Innocence is such a precious gift. It's explained as freedom from guilt or wrong doing. Just imagine never having to worry about anything and having a guilt free mind. Some people wish to save this kind of innocence from being lost from childhood to adulthood.

    What would the world be like if innocence were never lost? One way it would benefit humanity is the lack of hatred （仇恨）among the world. During youth, there may be an occasional argument, even a little physical fight, but nothing like firing a handgun at a fellow human being. And children are blind towards the racial differences of others. A kid will hang out with any other kid. It is the lack of innocence and the ignorance we learn from adults that influence children otherwise. Another benefit is the constant desire for fun and adventure. With very little if any time at all for fun，the adventurous mind is lost in time with the responsibilities placed upon adults. If innocence were kept alive, these ambitions would never depart from our lives.

    However, other people actually hate the idea of innocence lasting forever. They feel that the lack of organization and mental power of those with innocence would cause extremely destructive consequences to society in general. A large number of individuals would never have the urge to learn, work, and act upon the necessary needs for humanity to survive. Without a proper education which is usually provided by those who no longer live in a world of innocence, people would not have the desire to succeed, get a good job in life, or provide income for their families, which would hurt the lives of children.

    The lack of a good education and career would also harm the economy. As long as innocence is kept alive, no one would be terribly angered at the lack of effort people put out in the workplace, resulting in a strong decline in production and quality of needed goods.

    Maybe it is wrong in wanting to save innocence. It sure is a nice thought, though. Perhaps innocence was meant to be lost. It was God's will to make things the way they are, and there is a good purpose for everything. All that remains to be said about innocence is to enjoy it while it lasts.

    You probably know who Marie Curie was, but you may not have heard of Rachel Carson. Of the outstanding ladies listed below, who do you think was the most important woman of the past 100 years?

    Jane Addams (1860-1935)

    Anyone who has ever been helped by a social worker has Jane Addams to thank. Addams helped the poor and worked for peace. She encouraged a sense of community by creating shelters and promoting education and services for people in need. In 1931, Addams became the first American woman to win the Nobel Peace Prize.

    Rachel Carson (1907-1964)

    If it weren't for Rachel Carson, the environmental movement might not exist today. Her popular 1962 book Silent Spring raised awareness of the dangers of pollution and the harmful effects of chemicals on humans and on the world's lakes and oceans.

    Sandra Day O'Connor (1930-present)

    When Sandra Day O'Connor finished third in her class at Stanford Law School, in 1952, she could not find work at a law firm because she was a woman. She became an Arizona state senator (参议员) and, in 1981, the first woman to join the U.S. Supreme Court. O'Connor gave the deciding vote in many important cases during her 24 years on the top court.

    Rosa Parks (1913-2005)

    On December 1,1955, in Montgomery, Alabama, Rosa Parks would not give up her seat on a bus to a white passenger. Her simple act landed Parks in prison. But it also set off the Montgomery bus boycott. It lasted for more than a year, and kicked off the civil-rights movement. “The only tired I was, was tired of giving in,” said Parks.

    The 67th Miss Universe beauty pageant (选美比赛) will take place December 16 in Bangkok, Thailand. The competition will include young women from around the world representing their countries. But one South American country, Chile, will not be represented by a native Chilean. Instead, Andrea Diaz, a native of Venezuela (委内瑞拉) will have that honor.

    Diaz grew up in Valencia, Venezuela. She began training as a model at age 12 at a school there. At 19, she won a pageant organized by her town's baseball team. As Diaz moved along her career path, she also moved away from home. She went first to Panama, and later to Mexico, for modeling jobs. In 2015, she settled in Chile, where most of her family members now live. The 27-year-old woman told the reporter, “I represent the new Chile. This is an inclusive (包容的) country where immigrants come in search of opportunities.”

    Thousands of people leave Venezuela each day to escape a lack of food and medicine in the country. Its economic crisis (危机) has created an almost 1 million percent inflation (通货膨胀) rate. Many beauty pageant hopefuls have left Venezuela and have found work in modeling and media fields. Diaz is one of several Venezuelan beauty pageant competitors representing countries other than their homeland.

    A recent Miss Earth pageant had two Venezuelan models who competed for other countries, including Jessica Russo. Russo represented Peru just one year after moving to the country. She said, “My dream of being a beauty queen is not going to stop just because I arrived in a new country.” The 22-year-old competitor did not make it into the Miss Earth finals. But she is not giving up. She says she hopes to one day win a competition for Peru, the country where her mother was born.

    I was on my way home from work, cutting through the Bryant Park. On that day, the sun seemed to set faster than usual, and suddenly I found myself walking in the dark. I was less than half a mile from my apartment, but the path would lead me over a bridge, across train tracks, and through an unlit underpass.

    Then I heard him – a stranger running alongside me, partly obscured(遮掩) by the bushes. My mouth went dry; my legs felt like water. But I didn't pick up my pace – instead, I stopped, turned, and faced him. He came out of the bushes and said he'd been watching me "for a long time".

    As he walked beside me, I guided us towards the edge of the park. When we reached the bridge, a train rumbled(轰鸣着缓慢行进) past, and he seized the moment, attacking me with a knife around my throat. The self-defense skills I had learned years before kicked in, and I pushed my finger into his eye, hard. And then came the shock: That didn't frighten him away. My mind flashed back to a tip from an old guitar teacher: "Press the strings like you're squeezing a flea(跳蚤)." I put all my strength into that finger, and finally he let go.

    I was shaking with fear, but I looked him straight in the eye and began to back away. I turned to run the hell out of there, but then I remembered another self-defense lesson: Never run, because then you're a target. So I walked away alone – through the dark tunnel as I dialed 911 with trembling fingers. If you ever find yourself in this situation, use these self-defense skills that you already know. They can really make all the difference to you.

Adults check their phones, on average,360 times a day, and spend almost three hours a day on their devices in total. The problem for many of us is that one quick phone-related task leads to a quick check of our emails or social media feeds, and suddenly we've been sucked into endless scrolling.

It's an awful circle. The more useful our phones become, the more we use them. The more we use them, the more we lay neural（神经的） pathways in our brains that lead to pick up our phones for whatever task is at hand-and the more we feel an urge to check our phones even when we don't have to.

What we do know is that the simple distraction of checking a phone or seeing a notification（通知）can have negative consequences. This isn't very surprising; we know that, in general, multitasking does harm to memory and performance. One of the most dangerous examples is phone use while driving. One study found that merely speaking on the phone, not texting, was enough to make drivers slower to react on the road. It's true for everyday tasks that are less high-risk, too. Simply hearing a notification "ding" made participants of another study perform far worse on a task-almost as badly as participants who were speaking or texting on the phone during the task.

It isn't just the use of a phone that has consequences-its me re presence can affect the way we think.

In one recent study, for example, researchers asked participants to either put their phones next to them so they were visible（like on a desk）, nearby and out of sight（like in a bag or pocket）, or in another room. They were found to perform far better when their phones were in another room instead of nearby-whether visible, powered on or not.