Professional athletes in most sports start to slow down after the age of 35. Some retire (退役). Jamaican Olympic runner Usain Bolt has talked about retiring, for example. He is only 30 years old. But on Thursday, Serena Williams earned a spot in the Australian Open finals. She will face her older sister, Venus, who won her semifinal (半决赛) match a day earlier. It is the first time that the Williams sisters will play in a Grand Slam final since 2009. Venus is 36. Serena is 35. One of them will win the championship (冠军) at last.

    One older champion will play in the men's final, too. Roger Federer qualified for the final by defeating Stan Wawrinka. Federer, like Serena Williams, is 35 years old It will be one of the sport's oldest finals in a long time.

    Ken Rosewall of Australia is the oldest winner of a Grand Slam. He was 37 when he won the Australian Open in 1972.

    Serena Williams is already the oldest winner of a women's Grand Slam match. She won Wimbledon last year at the age of 34.

    Many people are impressed that three of the finalists are 35 or older. All of the players have recently had injuries (受伤). Federer missed six months due to back and knee injuries.

    He told the crowd that he did not think he would be able to make it back to a Grand Slam final.

    The Williams sisters have had difficulties, too. Earlier this month, Venus won a match in New Zealand but withdrew (退出) from the final after hurting her arm. She also learned in 2011 she had the immune system disorder. The disorder kept her from practicing and staying in good physical condition for a number of years.

    Serena took time off to recover from knee and shoulder injuries after losing in the semifinals of the U. S. Open last September. It is the ninth time that the sisters will face each other in a major final. Serena has defeated her sister six of those times. If she wins, Serena will beat Steffi Graff's record for the most Grand Slam titles ever in women's tennis.

    An autonomous vehicle designed for making local commerce deliveries was unveiled by Nuro. The vehicle is about the height of an SW but far narrower than a typical car. The electric car features four exterior compartments (暗格) — two on each side — to hold separate deliveries. Each compartment can be tailored to a specific use, such as cooking a pizza or refrigerating a package.

    “We can use self-driving technology to deliver anything, anytime, anywhere for basically all local goods and services,” Nuro co-founder Dave Ferguson said. “Consumers used to be okay with two-week paid shipping. It became two-week free delivery, followed by one week, two days, and the same day. Now same-day delivery isn't fast enough for some customers.”

    Nuro isn't alone in building robots for local commerce deliveries. Earlier this month, Toyota, a Japanese car company, unveiled a concept vehicle that could be used for package delivery. A handful of startups — including Starship Technologies, Marble and Dispatch — are testing small robots for deliveries on sidewalks.

    Nuro's vehicle will likely face legal hurdles. Fully autonomous vehicles without a test driver aren't legal in California today, and many companies have shifted testing to states where regulators are more welcoming of autonomous vehicles, such as Arizona.

    Nuro expects to face fewer challenges because it doesn't carry passengers. Nuro's narrow size may also be helpful when navigating streets and avoiding pedestrians. The vehicle isn't equipped with any special features to communicate with pedestrians or other road users. Some companies have tested and patented solutions such as digital screens that signal the car's next move. Ferguson said his team conducted studies and found that such techniques could confuse people. Nuro believes it's better to make sure the car performs predictably, so that human drivers know what to expect from it.

    “We feel by creating this new technology that's going to enable this last mile delivery, we're going to be creating new markets and doing things that previously weren't possible,” Ferguson said. “This is not swapping out Jobs with robots. It's creating new markets. There will definitely be new employment opportunities.”

    “Heaven (天堂) is where the police are English, the cooks are French, the mechanics are German, the lovers are Italian and everything is organized by the Swiss. Hell (地狱) is where the police are German, the cooks are English, the mechanics are French, the lovers are Swiss, and everything is organized by the Italians.”

    Obviously the national stereotypes (模式化的思想) in this old joke are generalizations (普遍化), but such stereotypes are often said to “exist for a reason”. Is there actually a sliver (裂片) of truth in them? Not likely, an international research team now says.

    “National and cultural stereotypes do play an important role in how people see themselves and others, and being aware that these are not dependable is a useful thing,” said study author Robert McCrae of the National Institute on Aging. “These are in fact unfounded stereotypes. They don't come from looking around you,” McCrae said.

    If national stereotypes aren't rooted in real experiences, then where do they come from? One possibility is that they reflect national values, which may become known from historical events. For example, many historians have argued that the spirit of American individualism (个人主义) has its origins in the experiences of the pioneers on the Old West.

    Social scientists such as psychologist Richard Robins have given several other possible explanations for stereotypes and why they may be incorrect. Robins notes that some stereotypes may have been correct at one point in history and then remained unchanged while the culture changed.

    We may be “hard-wired”, to some degree, to keep incorrect stereotypes, since we are less likely to notice and remember information that is different from our stereotypes. Generally, according to Robins, when we meet people who are different from our stereotypes, we see them as unique individuals rather than typical national or cultural groups.

    One of the most striking findings of a newly research in the UK is that of the people interviewed, one in two believes that it is becoming more difficult to meet someone to start a family with.

    Why are many finding it increasingly difficult to start close relationships? Does modem life really make it harder to fall in love? Or are we making it harder for ourselves? It is certainly the case today that contemporary couples benefit in different ways from relationships. Women no longer rely upon partners for money or status. A man doesn't expect his wife to be in (唯一的) charge of running his household and raising his children.

    But perhaps the knowledge that we can live perfectly well without a partnership means that it takes much more to persuade people to abandon their independence.

    In theory, finding a partner should be much simpler these days. Only a few generations ago, your choice of soul mate was limited by geography, social convention and family tradition. Although it was never clear，many marriages were essentially arranged. Now those barriers have been broken down. You can approach a builder or a brain surgeon in any bar in any city on any given evening. When the world is your oyster ( 牡蛎), you surely have a better chance of finding a pearl.

    But it seems that the old conventions have been replaced by the limitations of choice. The expectations of partners are raised to an unmanageable degree: good looks, impressive salary, kind to grandmother, and right socks. There is no room for error in the first impression.

    We think that a relationship can be perfect. If it isn't, it should be ended. We work to protect ourselves against future heartache and don't put in the hard emotional labor needed to build a strong relationship. Twelve-hour work at the office makes relaxed after-hours dating difficult. The cost of housing and child-raising creates pressure to have a stable income and Career before a life partnership.

    They were a happy family: four daughters all in the same school in different grades. The youngest, Janice, who was in my class, seemed to be glued (粘) to her mother's skirts. The three older girls took the bus to school every morning, but Janice was always driven to school by her mother.

    One Friday, Janice's mother asked for a talk with me. She said in a soft voice, "My husband is going to Europe on business for two weeks, and he insists that I go with him. I have tried to explain over and over that Janice needs me here. But he thinks that she will be fine without me so I have no choice; I have to go. I have told the babysitter to drive her every morning. Will you please give Janice special attention and help her? I want to be sure everything goes well for her."

    I told her that we would make every effort to support Janice. I even volunteered to meet Janice at her car so she would see a familiar face. As a mother myself, I'd like to help. Janice's mother thanked me for our understanding.

    On Monday morning, expecting a tearful, anxious child, I planned a special program of fun and games. I waited outside to greet Janice, but just then the bus arrived and not three, but four girls got off. Janice skipped along joyfully, saying "goodbye" to her sisters as she ran with two friends into the classroom. I walked slowly into the classroom and called Janice over to ask how the bus ride went. Impatiently she said, "Oh, I always want to take the bus with the other kids, but Mother needs to be with me. You see there won't be any more babies, so I have to be a baby a little longer. While she is away, I'll just ride the bus every day. I am five, you know."

    The fiddler crab (蟹) is a living clock. It indicates the time of day by the colour of its skin, which is dark by day and pale by night. The crabs changing colour follows a regular twenty-four hour plan that exactly matches the daily rhythm (节奏) of the sun.

    Does the crab actually keep time, or does its skin simply answer to the sun's rays, changing colour according to the amount of light strikes it? To find out, biologists kept crabs in a dark room for two months. Even without daylight, the crab's skin colour continued to change exactly on time.

    This characteristic(特性) probably developed gradually in answer to the daily rising and setting of the sun, to help protect the crab from sunlight and enemies. After millions of years it has become completely regulated (受控制) inside the living body of the crab.

    The biologists noticed that once each day the colour of the fiddler crab is especially dark, and that each day this happens fifty minutes later than on the day before. From this they discovered that each crab follows not only the rhythm of the sun but also that of the tides (潮水). The crabs period of greatest darkening is exactly the time of low tide on the beach where it was cought!