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.

    Renaissance is a French word. It means “rebirth”. It's a strange name for a period of history. What was exactly “ reborn” during the Renaissance?

    To answer this question, we need to look back at the time of the Roman Empire. At this time Roman artists, scientists and writers influenced by Greek ideas were the world's most advanced. They had become skilled observers of the natural world around them, and had become experts in studying animals, plants, the human body or the stars and planets. They wrote down their ideas about what they saw, and based their theories about the world on their observations.

    During the fourth and fifth centuries the Roman Empire slowly broke down. Many of the Romans' art and sculptures were destroyed and some manuscripts（原稿）were lost as well. But most importantly, some of the ancient attitudes were lost. A questioning approach to the world was replaced by an unquestioning one.

    Why did this happen? One reason was to do with the influence of the Christian Church. Through the thousand years following the fall of the Roman Empire, the Church controlled many aspects of life including education and learning. The Church ran all the universities and thought that the aim of a university should be to teach old ideas more clearly, not to introduce new ones. The scholars in the universities were expected to study God and heaven from the Bible and ancient books, rather than the world around them.

Take medicine for example. The main textbook for doctors had been written by a Greek doctor called Galen more than a thousand years earlier. But when Roger Bacon, a thirteenth-century priest（牧师）, said that a new approach to medicine was needed — doctors should do their own original research instead of reading writers from the past such as Galen-the Church put him in prison.

    By the time of the fourteenth century, however, some parts of the Christian Church were becoming less strict about their ideas and there was a new state of mind among artists, doctors and scientist. People wanted to find out more about the world by studying it. This attitude of investigation had been common in classical scholars, and it was ‘reborn' during the Renaissance.

    Arriving in Sydney on his own from India, my husband, Rashid, stayed in a hotel for a short time while looking for a house for me and our children.

    During the first week of his stay, he went out one day to do some shopping. He came back in the late afternoon to discover that his suitcase was gone. He was extremely worried as the suitcase had all his important papers, including his passport.

    He reported the case to the police and then sat there，lost and lonely in strange city, thinking of the terrible troubles of getting all the paperwork organized again from a distant country while trying to settle down in a new one.

    Late in the evening, the phone rang. It was a stranger. He was trying to pronounce my husband's name and was asking him a lot of questions. Then he said they had found a pile of papers in their trash can（垃圾桶）that had been left out on the footpath.

    My husband rushed to their home to find a kind family holding all his papers and documents. Their young daughter had gone to the trash can and found a pile of unfamiliar papers. Her parents had carefully sorted them out, although they had found mainly foreign addresses on most of the documents. At last they had seen a half-written letter in the pile in which my husband had given his new telephone number to a friend.

    That family not only restored the important documents to us that day but also restored our faith and trust in people. We still remember their kindness and often send a warm wish their way.

    A build-it-yourself solar still（蒸馏器） is one of the best ways to obtain drinking water in areas where the liquid is not readily available. Developed by two doctors in the U. S. Department of Agriculture, it's an excellent water collector. Unfortunately, you must carry the necessary equipment with you, since it's all but impossible to find natural substitutes. The only components required, though, are a 5＇  5＇ sheet of clear or slightly milky plastic, six feet of plastic tube, and a container — perhaps just a drinking cup — to catch the water. These pieces can be folded into a neat little pack and fastened on your belt.

    To construct a working still, use a sharp stick or rock to dig a hole four feet across and three feet deep. Try to make the hole in a damp area to increase the water catcher's productivity. Place your cup in the deepest part of the hole. Then lay the tube in place so that one end rests all the way in the cup and the rest of the line runs up — and out — the side of the hole.

    Next, cover the hole with the plastic sheet, securing the edges of the plastic with dirt and weighting the sheet's center down with a rock. The plastic should now form a cone(圆锥体) with 45-degree-angled sides. The low point of the sheet must be centered directly over, and no more than three inches above, the cup.

    The solar still works by creating a greenhouse under the plastic. Ground water evaporates (蒸发) and collects on the sheet until small drops of water form, run down the material and fall off into the cup. When the container is full, you can suck the refreshment out through the tube, and won't have to break down the still every time you need a drink.

    Sitting has been called the new smoking for its supposed Public health risks, especially for people with sitting down office jobs. Over the past 15 years or so sitting has been connected with heart disease and diabetes (糖尿病). But is sitting really that risky?

    In our latest study we examined if not only the total amount of sitting, but different types of sitting, were connected with developing type 2 diabetes. We wanted to see if there was any difference among sitting watching TV, sitting at work, or sitting at home but not watching TV.

    We studied sitting habits of 4. 811 middle-aged people, who didn't have diabetes or heart problems at the start of the study. Over the next 13 years, 402 people developed diabetes. Once we considered obesity (AE RF), Physical activity, and other things that may develop type 2 diabetes, neither total sitting time, sitting at work nor sitting at home but not watching TV were connected with developing diabetes. We found only a weak connection with the time spent sitting watching TV and an increased risk of developing diabetes.

    This is different from the results of five older TV studies that showed a stronger connection. But hardly any of the included studies mentioned obesity, a major cause of diabetes.

    For people who are physically inactive, though, the story's different. Two recent studies show the total time spent sitting a day is connected with developing diabetes, but only in people who are physically inactive or both physically inactive and obese.

    That's not the whole story. At least two things determine if sitting is a risk factor in its own right: the type and situation of sitting.

    For example, sitting down at work isn't strongly connected with long-term health risks, Perhaps that's because higher position jobs needs more sitting, and higher socioeconomic (社会经济) position is connected with a lower risk of disease. It's a different case for sitting watching TV, the type of sitting most possibly connected with long-term health risks. People who watch a lot of TV tend to (a) be of lower socioeconomic positions, unemployed, have poorer mental (精神上的) health, eat unhealthy foods and face more unhealthy food advertising.

    My sister Alice and I have been trying to get people to stop dropping cigarette (香烟)butts(烟头)for seven years. One day, we were walking in our hometown and saw hundreds of cigarette butts on the ground. They made the town look so ugly that we decided to start a group to make people dropping butts. We called it "No Butts About It".

    At first, we drew pictures with "The Earth is not your ashtray(烟灰缸)"written on them. We put the pictures around our hometown—in parks, by beaches, and along roads. We wanted to make people understand that dropping butts hurts the environment. Most smokers don't think that dropping butts hurts the Earth. But it does, and all rubbish does!

    Later, we wrote to companies and asked them for money to help us. We used the money to buy ashtrays to give to smokers. We wanted smokers to carry the ashtrays with them so they didn't have to drop butts.

    At the moment, we are trying to get cigarette companies to put an ashtray in each pack of cigarettes. Some companies want to do it. Many people have started to join our group since it began. Today there are 45 other "No Butts About It" groups in America.

    Now there even groups in England, Australia, and India! Many newspapers have written about my sister and me over the last seven years. And we have won many prizes for what we do. But we are not interested in prizes. We just want to make the Earth a better and cleaner place for animals, plants and people.

    One day, it will be.