Hummingbirds(蜂鸟) are one of nature's most energetic fliers and the only birds to hover(盘旋) in the air by relying on their strength alone.

    Now scientists have found that it is the ratio(比值) of the bird's wing length to its width that makes them so efficient. The discovery is helping experts compete with 42 million years of natural selection to build helicopters that are increasingly efficient.

    David Lentink, an assistant professor at Stanford University in California, tested wings from 12 different species of hummingbirds, which he sourced from museums. He placed them on a machine used to test the aerodynamics(气力学) of the helicopter blades(桨叶). Professor Lentink's team used the same machine to test the blades from an advanced micro-helicopter used by the UK's army. They found that the micro-helicopter's blades are as efficient at hovering as the average hummingbirds.

    But while the micro-helicopter's blades kept pace with the average hummingbird wings, they could not keep up with the most efficient hummingbird's wing. The wings of Anna's hummingbird were found to be about 27 percent more efficient than the man-made micro- helicopter's blades.

    While Professor Lentink wasn't surprised at nature's superiority, he said that helicopter blades have come a long way. “The technology is at the level of an average hummingbird,” he said. “A helicopter is really the most efficient hovering device that we can build. The best hummingbirds are still better, but I think it's amazing that we're getting closer. It's not easy to match their performance, but if we build better wings with better shapes, we might match hummingbirds.”

    Professor Lentink said that we don't know how hummingbirds maintain their flight in a strong wind, how they navigate(确定方向) through branches, or how they change direction so quickly. He thinks that great steps could be made by studying wing aspect ratios-the ratio of wing length to wing width. Understanding these abilities and characteristics could be a benefit for robotics and will be the focus of future experiments.

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    Instagram is containing so many photos of food—now a pop-up diner in London is taking advantage of this new trend by letting people settle the bill for their meals simply by uploading photos of their dishes to social networks.

    I always thought people's taking pictures of their food was kind of silly, but at this new pop-up restaurant in the UK,I'd probably do it too.“The Picture House” is the world's first pay-by-photo restaurant—you order, click a photo of the food,share on Instagram and eat for free!

    The restaurant belongs to frozen food giant (巨人) Birds Eye,who came up with the idea to cash in on people's addiction with photographing food and sharing the pictures online.They conducted a survey and found out that more than half of the British population regularly took pictures of their meals.So they realized it was a better way to advertise their new dining range.

    The pop-up diner was open in Soho, London for three days in May,and is now moving to other major UK cities. They serve two-course meals that customers don't have to pay for,if they photo and Instagram it.

    The restaurant is a part of Birds Eye's 'Food for Life' campaign,a new marketing project that aims at changing the way people look at frozen food."Taking photos of food enables people to show off and to share their mealtime moments—from the everyday to the special," said marketing director Margaret Jobling .

    The reaction to The Picture House has been great so far.And The pay-by-picture concept has proven to be an effective way.Alternative payment methods are actually gaining popularity among a lot of businesses.Last year,in a cafe in Germany customers pay by how much time they spend there,not by what they eat.

    Dreams can be familiar and strange, fantastical or boring, but some dreams might be connected to the mental processes that help us learn. No one knows for certain why people dream, but some dreams might be connected to the mental processes that help us learn. In a recent study, scientists found a connection between nap-time dreams and better memory in people who were learning a new skill.

    In the study, 99 college students between the ages of 18 and 30 each spent an hour on a computer, trying to get through a virtual maze(迷宫). The maze was difficult, and the study participants had to start in a different place each time they tried — making it even more difficult. They were also told to find a particular picture of a tree and remember where it was.

    For the first 90 minutes of a five-hour break, half of the participants stayed awake and half were told to take a short nap. Participants who stayed awake were asked to describe their thoughts. Participants who took a nap were asked about their dream after sleep — and they were awakened within a minute of sleep to describe their dreams.

    Stickgold, a neuroscientist (神经科学家), to know what people were dreaming about when their eyes weren't moving, during sleep.

    Four of the 50 people who slept said their dreams were connected to the maze. Some dreamed about the music that had been playing when they were working; others said they dreamed about seeing people in the maze. When these four people tried the computer maze again, they were able to find the tree faster than before their naps.

    Stickgold suggests the dream itself doesn't help a person learn — it's the other way around. He suspects that the dream was caused by the brain processes associated with learning.

    All four of the people who dreamed about the task had done poorly the first time, which makes Stickgold wonder if the dreams show up when a person finds a new task particularly difficult. People who had other dreams, or people who didn't take a nap, didn't show the same improvement.

    Growing up in one of the poorest communities with most crimes in Los Angeles, US, being raised by a poorly-educated single mother and attending the worst-quality public school, not many people expected much of me, so I chose to expect something of myself.

    On my 12th birthday, I bought a poster of Harvard University to hang in my room. Being at Harvard became my dream: I saw myself attending class in Sanders Theater, studying in Widener Library and eating in Annenberg Hall. Driven by this dream, I kept studying hard. I'd begin my day by asking myself these two questions: “What do I want in my life?” and “Are the things I am doing today going to get me closer to that life?”

    Asking myself the questions gave me the courage to ask over 50 Harvard, students for advice on my application essays; it gave me the energy to study just one more hour on my SATs when others were asleep; and it gave me the determination to apply for just one more scholarship when already refused many times. Moreover, reminding myself of my goal each day made it easy to say no to the same choices my friends made, because they would never get me closer to my goal. I found that even being poor could not take away my power to decide what I choose to do with my life.

    Every day I could feel myself getting closer and closer to my goal as my writing got better, my SAT score increased, and my scholarship offers started coming in. On March 31st, 2011, an email arrived from Harvard. The first word was “Congratulations!”. Tears of joy filled my eyes.

    Who you are today is the result of the decisions you made yesterday, and who you will be tomorrow will be the result of the choices you make today. Who do you want to be tomorrow?

    At 29 years old, Ding Ding, who has cerebral palsy (脑瘫), has been accepted to Harvard University. Ding Ding succeeded in his academic studies and overcoming many of his physical disabilities because of his mother's persistence(坚持不懈) and endless love.

    In 1988, when Ding Ding was found born with cerebral palsy, Doctors suggested to his mother Zou Hongyan that she give up the baby, saying it was worthless trying to rescue him as he would grow up either disabled or with low intelligence. Even the boy's father agreed with the doctors and told Zou that the boy would be a burden for the family for his entire life. But Zou insisted on saving the boy and soon divorced (离婚).

    To support the family and provide treatment for her son, Zou took up several jobs. In her spare time, she regularly took Ding to a recovery hospital. She taught herself how to exercise his muscles, and would also play educational games with him.

    Zou also insisted from the start that her son would learn to overcome his disabilities as far as possible. She insisted on teaching him how to use chopsticks during mealtimes, even though he found this extremely difficult at first, so he would not have to always explain his disability to others when he had meals with them.

    "I didn't want him to feel sorry for his physical problems," she said. "Because he had poor abilities in many areas, I was quite strict on him to work hard to catch up where he had difficulties. "

    Ding graduated with a degree in environmental science from Peking University's school of engineering in 2011. That same year, he took part in a second degree program at the university's international law school. In 2016, after working for two years, Ding was accepted into Harvard Law School.

    "I never dared to dream of applying to Harvard," Ding said. "It was my mother who never stopped encouraging me to give it a try. Whenever I had any doubts, she would guide me forward."

    I've never been the kind of person to say, “it's the thought that counts” when it comes to gifts. That was until a couple of weeks ago, when my kids gave me a present that blew me away.

    For years now, I've been wanting to sell our home, the place where my husband and I raised our kids. But to me, this house is much more than just a building. In the front room, there's a wall that has hundreds of pencil lines, marking the progress of my children's growth. Every growth stage is marked in grey, with each child's name and the date they were measured. Most people I know have been featured on a wall like this, or at least had a wall like it in their home.

    Of all the objects and all the memories, it's this one thing in a home that's the hardest to leave behind. Friends I know have returned home after work only to discover their wall of heights has been freshly painted over. A new paint job wouldn't normally be greeted by tears, but erasing that evidence of motherhood hurts more than it should. Our kids grow in so many ways, but the wall is physical evidence of their progress, right there for everyone to see.

    Over the years, I've talked about how much I would hate leaving that wall behind when I moved, even though the last marks were made 10 years ago when my kids stopped growing. So one day, while I was at work, my children decided to do something about it.

    They hired Jacquie Manning, a professional photographer whose work is about capturing (捕捉) the beautiful things in life, from clear lakes and skies to diamonds and ballgowns. She came to our house while I was at work, and over several hours, took photos of the hundreds of drawings and lines, little grey fingerprints (手印), and old marks. Somehow, she managed to photograph all those years of memories perfectly. Afterwards, she put all the photos together into one image, transforming them into a beautiful history of my family.

    Three weeks later, my children's wonderful gift made its way to me – a life-size photo of the pencil lines and fingerprints that represents entire lifetimes of love and growth.