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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    You may know the Eiffel Tower as one of the most famous man-made monuments in the world, and you'd be absolutely right! Read on to learn about the history of the great Eiffel Tower.

    Travelers from around the world flock(蜂拥)to Paris, France, to visit the Eiffel Tower, making it the most visited paid monument in the entire world! In fact, in 2010, the Eiffel Tower welcomed its 250 millionth visitor!

The history of the Eiffel Tower

    The Eiffel Tower was named after the engineer Gustave Eiffel, whose company designed and built the famous monument. Construction began in January of 1887 and was completed in only two years. Their plan was to finish the tower in time to be the entrance arch for the World's Fair in 1889. This fair celebrated the 100^th anniversary of the French Revolution, which took place from 1789 to 1799.

The height competition

    Located on the Champs de Mars, the tower is the tallest structure in Paris. It was the tallest man-made structure in the world for 41 years until the Chrysler Building in New York surpassed(超过) it. Then the spire(塔尖) on the top of the tower was added, raising its height to 17 feet taller than the Chrysler Building. It is now 1,063 feet tall! There are two replicas(复制品) of the Eiffel Tower in the world: a half scale model at the Paris Hotel in Las Vegas and a full-sized monument of a similar (but not exact) design in Tokyo, Japan.

Three shades of wonder

    Some pictures make the Eiffel Tower look like a dark iron color. But it is, in fact, bronze. Not only that, but the tower is actually painted three different shades to make it appear even taller: darkest on the bottom and lightest on the top.

Advice for High School Students

    As a person who is graduating from high school very soon, I have some suggestions for students in high school or students who are soon going to be high school students.{#blank#}1{#/blank#} I am sure others can benefit from reading them and will not make similar mistakes like me.

    {#blank#}2{#/blank#} Do not value first impression highly. Don't dismiss a person or an idea too early just because you immediately get a bad impression. You will miss many opportunities because of that.

    Although something seems bad at the first impression, it does not mean it is bad all the time. Try to give everything a fair chance.

    Don't try to please everybody. There is no way you can please everybody or get everybody to agree with you.{#blank#}3{#/blank#} It is a huge waste of time.

    Have respect for authority. No matter how much you may dislike them, just remember that teachers and parents care about you and they are only doing their jobs.{#blank#}4{#/blank#} Don't argue with them and just obey them.

    Realize a high school is not the real world. The real world isn't a closed environment. {#blank#}5{#/blank#} What is rewarded in high school such as popularity and agreement is different from what is rewarded in the real world. If high school isn't working out for you, you may find yourself better at handling the real world.

A. Do not be too quick to judge.

B. So just learn to say the word “No” a lot.

C. Listen to their advice and consider it carefully.

D. Many of these are based on regrets that I have.

E. Bad habits are hard to break and remain with you for a long time.

F. Don't spend any effort trying to please others who will never like you.

G. It is a free society where people accept responsibility for their actions.

    Babysitter Wanted

    I am seeking a babysitter for my 6-month-old son. A few hours on Saturdays and Sundays to help me and then other times as needed. He or she should be over 18, responsible, loving, warm, and have some experience in caring for babies. This position also suits a college student with experience looking for a part-time job. The pay is $10 an hour.

    If this sounds like a good job to you, please reply to rebecharv@aol.com or call 800-4964.

    Office Manager Wanted

    Our company is looking for a full-time experienced manager to run the business. Strong skills in organisation and business management are required for this position. The office manager will be responsible for keeping financial（金融的）records, so he or she should be familiar with computers.

    Please reply to jim@californiaaquatics.com or call 800-6978 to apply.

    Waiter/ Waitress Wanted

    A restaurant is looking for an experienced waiter/ waitress. Knowledge of wines and experience in dining are necessary. Must work well under pressure and understand the basics of fine dining and customer service.

    If you're interested, please contact us at job-tkupe-1329358152@craigslist.org to apply.

    This is a part-time job.

    Office Cleaner Wanted

    Looking for a Part-time job? A position in the Mississauga area needs an office cleaner! Part-time 4 hours a day from 10:00 am – 2:00 pm.

    Duties include:

    Cleaning the washrooms

    Cleaning the furniture

    Sweeping the floors

    Other general cleaning

    Some experience is necessary. Pay: $15 per hour

    Reply to: job-p3b7u-1365632206@craigslist.org or call 800-8197.

    Crown shyness(树冠羞避) is a mysterious natural phenomenon in which the crowns of some tree species do not touch each other, but get separated by a gap clearly visible from ground level. The effect usually occurs between trees of the same species, but has also been observed between trees of different species.

    There are many theories going around, most of which make sense, but no one has been able to prove without the shadow of a doubt why some trees avoid touching each other.

    In his 1955 book Growth Habits of the Eucalypts, Australian forester M.R. Jacobs writes that the growing tips of the trees are sensitive to abrasion(擦伤), which results in crown shyness phenomenon. This theory was also supported by Dr. Miguel Franco. Some experiments have shown that if trees displaying crown shyness are artificially prevented from swinging in the wind and touching each other, they gradually fill up the gaps between them.

    But while the above theory is arguably the most widespread, it's certainly not the only one. Some scientists have suggested that crown shyness is a mechanism to stop the spreading of leaf-eating insects. These pests have been known to work together and create structures that extend up to 10 cm off of tree branches in order to reach other plants, so the gaps are the trees' natural defense method.

    One Malaysian scholar studied many trees, but found no traces of abrasions, despite their clear crown shyness. Instead, he suggests that the growing tips of the trees were sensitive to light levels and stopped growing when they got too close to other trees. Plants are able to sense how close they are to other plants and in order to get more light, they give off some chemical element to stop other trees from growing too close.

    Whatever the reason, one thing is for sure: plants are more intelligent than people used to think.

Writing out the same word again and again may bring back bad memories for some, but handwriting can boost connectivity across brain regions, some of which are involved in learning and memory, a new study shows. 

In the study, psychologists Audrey and Ruud, both at the Norwegian University of Science and Technology, stuck electrodes（电极）on the participants' heads. They asked the participants to type out or handwrite with a digital pen words that appeared on a computer screen. Sensors in a cap recorded electrical brain activity. Then the psychologists looked for when two brain areas are active with the same frequency of electrical waves at the same time. This result can reveal the connectivity among different regions across the brain. 

With handwriting, the researchers saw increased activity, specifically in low frequency bands, not only in the expected motor areas but also in others associated with learning. These low frequency bands have previously been shown to support memory processes. When the team compared the two tasks, they realized that handwriting—but not typing—increased the connectivity across parietal（顶叶）brain regions, which are involved in sensory and motor processing, and central regions, many of which are involved in memory. "Even when the movements are very similar, the activation seems much, much higher in handwriting," Audrey says. "It shows that there's more involvement of these brain regions when you're handwriting, which might give you some specific advantages."

These findings suggest that there are distinct processes of brain activation happening while a person types or writes. This boost of stimulation of handwriting facilitates learning because these particular waves between these areas are involved in memory formation and encoding（编码）. 

And although handwriting may help with learning processes, typing is often easier, faster and more practical. "Students and teachers alike should therefore consider the task at hand to decide to handwrite or type, "Audrey says. Despite the need for more studies to determine the best learning strategy, experts say that handwriting shouldn't be left behind in the digital age. "Schools need to bring in more writing into curriculum design," Ruud says.