Mosquitoes have an extraordinary ability to find humans far away and fly straight to their skin. Mosquitoes can do more than cause an itchy (发痒的）wound. Some mosquitoes spread several serious diseases, including Dengue, yellow fever and malaria.

    Over one million people worldwide die from these diseases each year. New research now shows how mosquitoes choose who to bite.

    Mosquitoes need blood to survive. They are attracted to human skin and breath. They smell the carbon dioxide gas, which all mammals breathe out. This gas is the main way for mosquitoes to know that a warm-blooded creature is nearby.

    But mosquitoes also use their eyes and sense of touch. Michael Dickinson is a professor at the California Institute of Technology. His research shows how these small insects, with even smaller brains, use three senses to find a blood meal.

    Michael Dickinson's team used plumes—a material that rises into the air of carbon dioxide gas into a wind tunnel (隧道). They then used cameras to record the mosquitoes. The insects followed the plume.

    Then, the scientists placed dark objects on the lighter colored floor and walls of the tunnel. Mr. Dickinson said, at first, the mosquitoes showed no interest in the objects at all. “What was quite surprising is that the mosquitoes fly back and forth for hours. These are hungry females and they completely ignore the objects on the floor and wall of the tunnel. But the moment they get a hit of CO₂, they change their behavior quite obviously and now would become attracted to these little visual blobs (斑点).”

    This suggested to the researchers that a mosquito's sense of smell is more important in the search for food. Once mosquitoes catch a smell of a human or animal, they also follow visual signals.

    Obama, Lady Gaga and Steve Jobs—what do they have in common? They are, of course, all Americans. And according to a survey by social networking site baidu. com, they all best illustrate(举例说明) the word “cool”.

    But just what does it mean to say someone is “cool”? Most would answer that it is something to do with being independent-minded and not following the crowd.

    Yale University art professor Robert Farris Thompson says that the term “cool” goes back to 15th century West African philosophy. “Cool” relates to ideas of grace under pressure.

    “In Africa,” he writes, “coolness is a positive quality which combines calmness, silence, and life.”

    The modern idea of “cool” developed largely in the US in the period after World War II. “Post-war 'cool' was in part an expression of war-weariness (厌战情绪), . . . it went against the strict social rules of the time,” write sociologists Dick Pountain and David Robins in Cool Rules: Anatomy of an Attitude.

    But it was the American actor James Dean who became the symbol for “cool” in the hugely successful 1955 movie Rebel without a Cause. Dean plays a tough guy who disobeys his parents and the authorities. He always gets the girl, smokes cigarettes, wears a leather jacket and beats up bullies. In the movie, Dean showed what “cool” would mean to American young people for the next 60 years.

    Today the focus of “cool” has changed to athletics (体育运动) stars. Often in movies about schools, students gain popularity on the athletics field more than in the classroom. This can be seen quite clearly in movies like Varsity Blues and John Tucker Must Die.

    But many teenagers also think being smart is cool. Chess and other thinking games have been becoming more popular in schools.

    “Call it the Harry Potterization of America—a time when being smart is the new cool,” writes journalist Joe Sunnen.

    For centuries, medical pioneers have refined a variety of methods and medicines to treat sickness, injury, and disability, enabling people to live longer and healthier lives.

    “A salamander (a small lizard-like animal) can grow back its leg. Why can't a human do the same?” asked Peruvian-born surgeon Dr. Anthony Atala in a recent interview. The question, a reference to work aiming to grow new limbs for wounded soldiers, captures the inventive spirit of regenerative medicine. This innovative field seeks to provide patients with replacement body parts.

These parts are not made of steel; they are the real things — living cells, tissue, and even organs.

    Regenerative medicine is still mostly experimental, with clinical applications limited to procedures such as growing sheets of skin on burns and wounds. One of its most significant advances took place in 1999，when a research group at North Carolina's Wake Forest Institute for Regenerative Medicine conducted a successful organ replacement with a laboratory-grown bladder. Since then, the team, led by Dr. Atala, has continued to generate a variety of other tissues and organs—from kidneys to ears.

    The field of regenerative medicine builds on work conducted in the early twentieth century with the first successful transplants of donated human soft tissue and bone. However, donor organs are not always the best option. First of all, they are in short supply, and many people die while waiting for an available organ; in the United States alone, more than 100,000 people are waiting for organ transplants. Secondly, a patient's body may ultimately reject the transplanted donor organ. An advantage of regenerative medicine is that the tissues are grown from a patient's own cells and will not be rejected by the body's immune system.

    Today, several labs are working to create bioartificial body parts. Scientists at Columbia and Yale Universities have grown a jawbone and a lung. At the University of Minnesota, Doris Taylor has created a beating bioartificial rat heart. Dr. Atala's medical team has reported long-term success with bioengineered bladders implanted into young patients with spina bifida (a birth defect that involves the incomplete development of the spinal cord). And at the University of Michigan, H. David Humes has created an artificial kidney.

    So far, the kidney procedure has only been used successfully with sheep, but there is hope that one day similar kidney will be implantable in a human patient. The continuing research of scientists such as these may eventually make donor organs unnecessary and, as a result, significantly increase individuals' chances of survival.

    Recently some American scientists have given a useful sincere piece of advice to people in industrialized nations that they would be much healthier if they ate more of the same kind of food eaten by humans living more than 10,000 years ago.

    The scientists say that the human body has changed very little since humans first appeared on the earth, but the way we live has changed greatly. Our body has not been able to deal with (处理,对付)these changes in life style and this has led to new kinds of sicknesses. These new sicknesses were not known in ancient times, so they are called "diseases of civilization". Many cancers and diseases of the blood system, including heart attacks and strokes (中风) are examples of such diseases.

    Scientists noted that people in both the Old Stone Age and the New Stone Age enjoyed very little alcohol (酒精) or tobacco (烟草), probably none. Ancient people also got a great deal of physical exercise, but a change in food is one of the main differences between life in ancient times and that of today.

    Stone-age people hunted wild animals for their meat, which had much less fat than domestic or tame ones (家畜). They also ate a lot of fresh wild vegetables and fruits. They didn't have milk or any other dairy products, and they made very little use of grains. But today, we eat a large amount of these. We eat six times more salt than our remote ancestors (祖先). We eat more sugar. We eat twice as much fat but only one third as much protein (蛋白质) and much less vitamin C.

    People today probably do not want to live the way people thousands of years ago did, but scientists say that we would be much healthier if we ate much the same way as remote ancestors did, cutting the amount of fatty, salty and sweet food.

    Do you ever pull your phone out of your pocket, thinking it is vibrating(振动), only to find that it isn't? This phenomenon, which scientists call "phantom(幻觉的)phone vibration", is very common. Around 80% of people surveyed say they have imagined their phones vibrating when they were actually still.

    So, what leads to this universal behavior? According to the BBC, the explanation lies in your brainˈs ability to discover signals from the outside world. When your phone is in your pocket, there are two possible states: it is either vibrating or not. Meanwhile, you also have two possible states of mind: the judgment that the phone is vibrating, or that it isn't. Ideally, you match the four states correctly.

However, sometimes your brain decides that the results of missing a call are more serious than a "false alarm". Therefore, you become more sensitive(敏感的) to vibrations so that you don't miss anything. This is just like the fire alarm in your home—it can be annoying when it goes off in response to just a tiny bit of smoke. But that's a small price to pay compared to a fire really breaking out because the alarm fails to alert you. Now, you might still ask: why can't our brains just make every judgment correctly without being too sensitive to false signals? The answer is that your brain bears a heavy burden every day. "You get a large amount of sensory(感觉的) information that's coming from your eyes, ears and skin, and you can't deal with all that information all the time, "Michael Rothberg, a researcher at Baystate Medical Center in Springfield, US, told Live Science.

    For example, the rustling(沙沙声)of clothing or the growling(咕咕声)of your stomach may both lead your brain to believe that they come from the vibration of your phone-it is like trying to hear your name being called in a noisy room.

    So, perhaps you should just check your phone whenever you think it's vibrating. It's not too much trouble to do that, is it?