On a Saturday morning earlier this September, the world got its first look at the Strati. This electric vehicle is unlike any other currently on the road. It rolls on four wheels, but its body and chassis(底盘) weren't built in a factory. Instead, Strati's designers used a technology called 3-D printing. It created those parts of the car in one piece, from the ground up.

    “Compared to a typical vehicle on the road, the Strati definitely looks different,” says Greg Schroeder, a senior research engineer at the Center for Automotive Research in Ann Arbor, Mich. He did not work on the new car. His organization studies trends and changes in th e auto industry.

    It took 44 hours to print the new car at the International Manufacturing Technology Show in Chicago. Over the next few days, the car's designers installed additional parts. These included the car's engine, brakes and tires. Then, early on September 13, Jay Rogers climbed into the car, started its engine and drove the vehicle onto the street. Rogers helped found Local Motors. It's the Arizona-based company behind the Strati. Two weeks later, his team printed a second Strati, and just as fast, at a fair in New York City.

    Justin Fishkin, a local Motors official, sees the Strati as a window into the future. Today, car buyers are limited in their choice of a vehicle. They can order only what car companies have already designed. But in the future, he says, you may be able to design your own car online and then get it printed to order.

    Manufacturing experts say 3-D printing has begun to revolutionize how they make things. The technology has been around for decades. But these machines used to be so expensive that only large companies could afford them. In the last few years, though, that has changed. Many of the machines are now inexpensive enough for small companies—or even individuals —to own. Some local libraries make them available to the public. High Schools are beginning to use them in classrooms. Wide access to these printers means people can now design and print a wide variety of new things.

    The car's printer is a one-of-a-kind device.

    The technology behind the 3-D printer used in Chicago is an example of additive manufacturing. This proce ss builds solid objects, slice by slice, from the bottom up. (“Strati” means layers, in Italian.) A mechanical arm moves a nozzle from one side to another, back and forth. As it moves, the nozzle deposits a liquid—often melted plastic or metal (but it could be food, concrete or even cells) —that quickly hardens or bonds to become solid or semi-solid. This creates a single, thin layer. Once a layer is complete, the printer starts depositing the next one.

    “There's a lot of interest in 3-D printing in the auto industry,” says Schroeder. Right now, the technology is particularly useful for building models of cars or car parts.

    To compete with current auto manufacturers, the 3-D printer would have to increase in a hurry, Schroeder says. By contrast, he notes, a Ford F-150 pickup truck rolls off an assembly line at a rate of roughly one per minute. To print as many Stratis would require many more printers. Schroeder says he doesn't see 3-D printing soon taking over for such high-volume manufacturing. But, he adds, “Who knows what will h appen in the long term?”

    Scientists at Oak Ridge National Laboratory in Tennessee designed the 3-D printer used in Chicago. Lonnie Love, a research scientist at the lab, led the effort.

    Additive manufacturing often is slow and expensive. It also may produce materials that are unreliable, Love says. So for two years, his team searched for ways to make 3-D printing better. They built new machines and tested them over and over.

    All of that work paid off: their new machine is fast and uses less expensive material than earlier printers. In addition, it prints a plastic embedded with fibers of carbon to produce a stronger material. This helps ensure the material won't crack or break under pressure.

The idea of being able to walk on water has long interested humans greatly. Sadly, biological facts prevent us ever accomplishing such a thing without artificial aid—we simply weigh too much, and all our mass pushes down through our relatively small feet, resulting in a lot of pressure that makes us sink.

    However, several types of animals can walk on water. One of the most interesting is the common basilisk Basilicus basilicus, a lizard (蜥蜴)native to Central and South America. It can run across water for a distance of several meters, avoiding getting wet by rapidly hitting the water's surface with its feet. The lizard will take as many as 20 steps per second to keep moving forward. For humans to do this, we，d need huge feet that we could bring up to our ears in order to create adequate w hitting. ''

    But fortunately there is an alternative : cornflour. By adding enough of this common thickening agent to water (and it does take a lot), you can create a “non-Newtonian” liquid that doesn't behave like normal water. Now, if the surface of the water is hit hard enough, particles(粒子）in the water group together for a moment to make the surface hard. Move quickly enough and put enough force into each step, and you really can walk across the surface of an adequately thick Liquid of cornflour.

    Fun though all this may sound, it's still rather messy and better read about in theory than carried out in practice. If you must do it, then keep the water wings handy in case you start to sink--and take a shower afterward!

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    At exactly eleven Sir Percival knocked and entered, with anxiety and worry in every line of his face. This meeting would decide his future life，and he obviously knew it.

    "You may wonder, Sir Percival,”said Laura calmly, “if I am going to ask to be released (免除）from my promise to many you. I am not going to ask this. I respect my father's wishes too much.”

    His face relaxed a little, but one of his feet kept beating the carpet.

    "No, if we are going to withdraw. (退出）from our planned marriage, it will be because of your wish, not mine.

     “Mine?” he said in great surprise. “What reason could I have for withdrawing?^'

    "A reason that is very hard to tell you," she answered. "There is a change in me.”

    His face went so pale that even his lips lost their color. He turned his head to one side.

    "What change?" he asked, trying to appear calm.

     “When the promise was made two years ago,” she said, ⁴⁴ my love did not belong to anyone. Will you forgive me, Sir Percival, if I tell you that it now belongs to another person?”

    “I wish you to understand, “Laura continued, “that I will never see this person again, and that if you leave me, you only allow mc to remain a single woman for the rest of my life. All I ask is that you forgive mc and keep my secret."

    ‘I will do both those things, “he said. Then he looked at Laura, as if he was waiting to hear more.

    "I think I have said enough to give you reason to withdraw from our marriage, “she added quietly.

    “No. You have said enough to make it the dearest wish of my life to marry you, ” he said.

    Stephen Hawking has said he believes brains could exist independently of the body after people die, but that the idea of a conventional afterlife（传统意义上的死后重生）is a fairy tale. Speaking at the premiere（首映）of a documentary film about his life, Stephen Hawking said: “I think the brain is like a program in the mind, which is like a computer, so it's theoretically possible to copy the brain onto a computer and so provide a form of life after death.”

    “However, this is way beyond our present scientific and technological level. I think the conventional afterlife is a fairy tale for people afraid of the dark.” The author of “A Brief History of Time”, who earlier approved of the right for the deadly ill to end their lives as long as safeguards were in place, suffered from motor neurone(运动神经元) disease at the age of 21 and was given two to three years to live.

    “All my life I have lived with the menace of an early death, so I hate wasting time,” Hawking said on Thursday night, using the computer-created voice he controls with a facial muscle and a blink(贬眼) from one eye. The documentary explores a brilliant schoolboy with unclear handwriting who enjoyed the life of Oxford University before illness led to a lifelong desire of discovery about the origins of the universe, which began as a graduate at Cambridge University and has shocked the world.

    Hawking's sister Mary says in the film that her brother was highly competitive and curious about everything in a household which friends described as very academic, and explains how she received a toy house as a present when they were children, to which Stephen immediately added electricity.

    She said that life with her brother was attractive and exciting. “It's a waste of time arguing with Stephen because he always manages to turn the argument round,” she said. The film goes back to his childhood and his student days and shows the scientist, who uses a wheelchair, at home with break. It also explores his family life with his first wife, Jane, and their three children, the breakdown of their marriage and his marriage to one of his carers.

    Jane appears on camera to explain how the pressures of caring for the children and the increasingly disabled Hawking became even worse once full-time nurses were brought into the home, destroying any privacy（隐私）. His second wife and former nurse, Elaine Mason, does not appear in the film, and Hawking introduces their 1995-2007 marriage with a few pictures and a brief description.

    For many, music is as important to the human experience as eating and breathing. We hear music everywhere—at home, the gym, parties and stores. But what kind of music do we prefer to listen to, and when and why do our musical preferences change?

    The relationship between the change of seasons and musical preferences was the focus of a study led by psychologist Terry Pettijohn. He and his team based their research on a previous study that examined the relationship between popular music preferences and the Environmental Security Hypothesis(假设). The results showed that over time, when social and financial conditions were more risky, the songs of the year that were slower, longer, more comforting and serious were most popular. And during periods in which social and financial conditions were generally stable, the result was opposite.

    Building on these findings, Pettijohn and his team wondered if the Hypothesis could also be applied to the change of seasons. For college students, the participants in this study, autumn begins at the start of the school year. Gone are the carefree days of summer, when school is out. Winter means colder temperatures, shorter days, and, in many places in the country, snow. Spring, however, is a different story. It represents a fresh start and when clocks spring forward, we gain an extra hour of daylight. As students walk into summer, they're absorbed in the sunshine and social activities—and enjoy a break from school.

    But do changing seasonal conditions influence musical preferences? To answer this question, the researchers designed two studies. What did they find? Both groups of college students favored more serious music during the seasons of fall and winter, and more active and energetic music during the spring and summer seasons. And these findings, Pettijohn argues, have practical significances.

    I was very excited on the first day of high school! I had P.E for the first period. We hurriedly gathered in the locker room (衣帽间) when the headmaster began to speak, “Good morning, boys and girls! Welcome to the first day of the great new school year. We will begin with the pledge (誓言) of loyalty.”

    I pulled my shirt over my head and my right hand immediately rested over my heart. A few tears came to my eyes as every time I pledged. I thought of my grandpa. He had died almost a year before, but I still missed him every day. Grandpa served in World War II and the flag had a very special meaning for him.

    The next morning in the locker room, I noticed something strange. Some girls talked through the pledge. After that, even fewer did the pledge, including the teachers. By the second week of school, I was the only girl in the whole locker room that did the pledge.

    The next morning, I hid in the bathroom to change clothes and pledge. There I couldn't see the flag and I had a sense of sorrow to be hiding like that. I kept hiding for the next week and felt worse.

    I spent a weekend gathering up my nerve. On Monday, I changed into my gym clothes right away and was standing by my locker when the headmaster began morning announcements. The pledge started and I put my hand over my heart. A girl nearby locked her locker and asked, “Why are you doing that? ” She looked confused.

    “My grandpa fought in World War II and he died last year,” I said. “I'm doing it for him.”

    She felt embarrassed and looked away. “Oh.” She said.

    Over the next few weeks, more girls questioned me about the pledge. I gave them all that same answer. I never inspired other girls to do the pledge along with me. They made their choice; I made mine. I was doing it for my Grandpa, but more than that, I was doing it for myself. Grandpa raised me to be proud of my country and that pride didn't stop.