Neuroscientists have explained the risky, aggressive or just plain baffling behavior of teenagers as the product of a brain that is somehow compromised. Groundbreaking research in the past 10 years, however, shows that this view is wrong. The teen brain is not defective. It is not a half-baked adult brain, either. It has been forged by evolution to function differently from that of a child or an adult.

    The most important of the teen brain's features is its ability to change in response to the environment by modifying the communication networks that connect brain regions. It allows teenagers to make enormous progress in thinking and socialization. But the change also makes them sensitive to dangerous behavior and serious mental disorders.

    The most recent studies indicate that the riskiest behaviors arise from a mismatch between the maturation of networks in the limbic system(边缘系统), which drives emotions at adolescence, and the maturation of networks in the prefrontal cortex（前额皮质）, which occurs later and promotes sound judgment and the control of impulses. Indeed, we now know that one's prefrontal cortex continues to change noticeably until his 20s. And yet adolescence seems to be starting earlier, extending the “mismatch years.”

    The plasticity of networks linking brain regions—and not the growth of those regions, as previously thought—is key to eventually behaving like an adult. Understanding that, and knowing that a widening gap between the development of emotional and judgment networks is happening in young people today, can help parents, teachers, counselors and teenagers themselves. People will better see that behavior such as risk-taking and turning away from parents and toward peers are not signs of cognitive or emotional problems. They are a natural result of brain development, a normal part of adolescents learning how to negotiate with a complex world.

    The same understanding can also help adults decide when to intervene. A 15-year-old girl's departure from her parents' tastes in clothing, music or politics may be a source of anxiety for Mom and Dad but does not indicate mental illness. A 16-year-old boy's tendency to skateboard without a helmet or to accept risky dares from friends is not unimportant but is more likely a sign of short-range thinking and peer pressure than a desire to hurt himself. Knowing more about the unique teen brain will help all of us learn how to separate unusual behavior that is age-appropriate from that which might indicate illness. Such awareness could help society reduce the rates of teen addiction, motor vehicle accidents and depression.

    Computers have beaten human world champions at chess and, earlier this year, the board game Go(围棋). So far, though, they have struggled at the card table. So we challenged one AI(artificial intelligence) to a game.

Why is poker so difficult? Chess and Go are “information complete” games where all players can see all the relevant information. In poker, other players' cards are hidden, making it an “information incomplete” game. Players have to guess opponents' hands from their actions—-tricky for computers. Solving poker could lead to many breakthroughs, from cyber security to driverless cars.

    Scientists believe it is only a matter of time before AI once again vanquishes humans, so our human-machine match comes up in a game of Texas Hold's Em Limit Poker. The AI was developed by Johannes Heinrich, a researcher studying machine learning at UCL. It combines two techniques: neural(神经的)networks and reinforcement learning(强化学习).

    Neural networks, to some degree, copy the structure of human brains: their processors are highly interconnected and work at the same time to solve problems. They are good at spotting patterns in huge amounts of data. Reinforcement learning is when a machine, given a task, carries it out, learning from mistakes it makes. In this case, it means playing poker against itself billions of times to get better.

    Mr Heinrich told Sky News: “Today we are presenting a new procedure that has learned in a different way, more similar to how humans learn. In particular, it is able to learn abstract patterns, represented by its neural network, which allow it to deal with new and unseen situations.”

    After two hours of quite defensive play, from the computer at least, we called it a draw.

    It was hard to accept, but the sad day had finally arrived. I still remember the tears welling up in my six-year-old sister's eyes as she looked around the empty closet in wonder. The space once filled with her clothes now held only loneliness and sorrow. This little child had come to the realization that her father was gone. He had left us, and there was simply no way to change it.

    Being the oldest of four girls has never been easy, but with the departure of our father, our world and dreams were broken beyond repair. My mother, the most amazingly warm-hearted person in the world, has worked harder than anyone should simply to mend our broken household. However, long hours at work often prevented her from physically being there in our times of need. This is where I have stepped up as the temporary caretaker of my three small sisters.

    Many students write college essays about their leadership positions in school and the community but I feel that my greatest accomplishment is the role I have played within my own family.

    Senior year in high school is not simple for anyone, especially when it feels like the entire world is resting on your shoulders, but this is how I have felt for the past two years, I have continually tried to fulfill the dream my mother holds for my future. My mother was not able to complete her college education, and so this success is her top significance for her children.

    A leader is defined as one who has influence on others. I hope that my leadership affects the lives of my sisters and everyone around me. In dedicating myself to my family and school, I have set goals that I will do anything to accomplish. I am an extremely determined individual, and my university will help me take the next step in climbing the ladder of success.

    The flowers are blooming and the birds are singing as Melinda sits in the rose garden of the nursing home. She is recalling old times as she waits for her family's arrival. The nursing home has been Melinda's new settlement ever since Thomas passed away a week ago. Thomas had fought a long and hard battle against lung cancer for three years. Unfortunately, he has broken the promise that he and Melinda had made: to be with each other for every birthday. Melinda knew this was unrealistic (不现实的) but agreed to the promise for Thomas's sake.

    "Thomas, you are completely a dreamer." Melinda shouted to Thomas as he dragged on about living on an island with his beautiful wife. That's what she loved about him most—he had a vivid imagination. They got married at age eighteen and began having children right away. Mary came within the year, followed by Thomas Benjamin II, Lilly-Ann, and Joseph “Little Joey” George. The family lived an exultant life filled with laughter and love.

    "Mom!" Lilly shouted, but it really sounded like a howl. Melinda had lost herself in thinking about the life she had shared with her late husband. Lilly pushed her down the long dark halls of the nursing home until they arrived at the recreational room.

When the doors opened, Melinda put her hand over her mouth and was completely speechless. The room was crowded with the people nearest and dearest to her and the warmth and love was felt instantly. The night went on; stories and cocktails were shared and everything was perfect.

    However, when Melinda caught a moment to herself she looked around at her family. With a smile on her face, she raised her Manhattan and called out for a toast. “This one is for you, Thomas, though you are not here.”

    One day, on a small farm in Maine, a man sat in a barn watching a large grey spider spin a web. The man was E.B. White — or Andy, as he was called — who thought spiders were wonderful creatures. He thought that one day he might like to write a children's book about a spider.

    But writing was hard work for Andy. He had written many articles and essays and poems. He had also written one children's book, Stuart Little. But Andy could never just rush to turn an idea into an article or a book. He told his editor (编辑) that he needed to let his ideas ripen.

    So for years, Andy continued to think about writing a children's book about a spider. He did some of his best thinking while he wandered around his farm.

    Once while he was cleaning his barn, he found a spider's egg sac (卵囊). Andy wanted to see the eggs hatch. But he was scheduled to leave for a trip to New York City. So he found a small box and carefully placed the egg sacinside. When he got to his hotel, he put the box on the dresser. One morning he woke up, and there were hundreds of baby spiders rushing across the dresser!

    Years later, Andy finally began writing Charlotte's Web, the story of a spider named Charlotte and a pig named Wilbur. Andy created most of the book sitting by himself in the tiny boathouse of his farm.

    Sometimes he stopped writing and aimlessly drew pictures of spiders. Andy always said Charlotte's Web was more than just a children's story about animals. It was a timeless story about true friendship.

I believe in the power of science fiction,not just for its capacity to transform dreams into reality, but also for its power to bond together those who share a common vision of the future. For me, that's true for my relationship with my dad. Some fathers and sons bond over sports, fishing or hunting, but my dad and I bond over Star Trek. We tried a trip to Disney World, but one of my earliest memories wasn't Mickey, but a Klingon battle cruiser（巡洋舰）on the screen.
Over the years, nearly every setting and situation has become far away for my dad and me. When it's warm at night, we're not driving along some dark streets in Indiana,but.going at a slow speed with stars dimly shining. Both of us are thinking of them,without needing to say a word. All these visions of other universes have together created a private universe for my dad and me.

Gene Roddenberry, creator of Star Trek,once said, "Science fiction is a way of thinking，a way of logic that bypasses（绕过）a lot of nonsense. It allows people to look directly at important subjects." A lifetime of science fiction has influenced more than just my relationship with my dad, but has also helped me shape my own hopes for the future.I'm now a science writer.

Yes,science fiction has made me into a nerd. And it also has been a source of joy for my family,making me an optimist while enabling me to think critically about the danger of technology.thank those authors who have shared their visions, the world and my family are better for it. Thank my dad, who is both the best storyteller and the best man i have ever known because he helped me realize the truth of Tennyson's words," since i dipped into the future,i saw the vision of the world,and all the wonders that would be.