Here is an astonishing and significant fact: Mental work alone can't make us tire. It sounds absurd. But a years ago, scientists tried to find out how long the human brain could labor without reaching a stage of fatigue (疲劳). To the amazement of these scientists, they discovered that blood passing through the brain, when it is active, shows no fatigue at all! If we took a drop of blood from a day laborer, we would find it full of fatigue toxins(毒素) and fatigue products. But if we took blood from the brain of an Albert Einstein, it would show no fatigue toxins at the end of the day.

    So far as the brain is concerned, it can work as well and swiftly at the end of eight or even twelve hours of effort as at the beginning. The brain is totally tireless. So what makes us tired?

    Some scientists declare that most of our fatigue comes from our mental and emotional(情绪的) attitudes. One of England's most outstanding scientists, J.A. Hadfield, says, “The greater part of the fatigue from which we suffer is of mental origin. In fact, fatigue of purely physical origin is rare.” Dr. Brill, a famous American scientist, goes even further. He declares, “One hundred percent of the fatigue of sitting worker in good health is due to emotional problems.”

What kinds of emotions make sitting workers tired? Joy? Satisfaction? No! A feeling of being bored, anger, anxiety, tenseness, worry, a feeling of not being appreciated—those are the emotions that tire sitting workers. Hard work by itself seldom causes fatigue. We get tired because our emotions produce nervousness in the body.

    When asked about happiness, we usually think of something extraordinary, an absolute delight, which seems to get rarer as we get older.

    For kids, happiness has a magical quality: Their delight at winning a race or getting a new bike is unreserved (毫不掩饰的).

    In the teenage years, the concept of happiness changes. Suddenly it's conditional on such things as excitement, love and popularity. I can still recall the excitement of being invited to dance with the most attractive boy at the school party.

    In adulthood the things that bring deep joy－love, marriage, birth－also bring responsibility and the risk of loss. For adults, happiness is complicated (复杂的).

    My definition of happiness is “the capacity for enjoyment”. The more we can enjoy what we have, the happier we are. It's easy to overlook(忽视) the pleasure we get from the company of friends, the freedom to live where we please, and even good health.

    I experienced my little moments of pleasure yesterday. First I was overjoyed when I shut the last lunchbox and had the house to myself. Then I spent an uninterrupted morning writing, which I love. When the kids and my husband came home, I enjoyed their noise after the quiet of the day.

    Psychologists tell us that to be happy we need a mix of enjoyable leisure time and satisfying work. I don't think that my grandmother, who raised 14 children，had much of either. She did have a network of close friends and family, and maybe this is what satisfied her most.

    We, however, with so many choices and such pressure to succeed in every area, have turned happiness into one more thing we've got to have. We're so self-conscious about our “right” to it that it's making us miserable. So we chase it and equal it with wealth and success, without noticing that the people who have those things aren't necessarily happier.

    Happiness isn't about what happens to us－it's about how we see what happens to us. It's the skillful way of finding a positive for every negative. It's not wishing for what we don't have, but enjoying what we do possess.

    I believe in the power of holding on. What do I mean by holding on? Hugging, or holding on, is the power we possess when we put our arms around someone. It can change relationships, makes a patient a person, an acquaintance a friend.

    My grandmother taught me about holding on, whenever she gathered me in her strong, loving Irish arms. She always hugged even when her back became curved .My mother hugs my children the same way—heart open and arms wide, breathing them into her soul.

    Once I became aware of its power, I started experimenting: I held my mother-in-law a moment too long then moved onto my sisters-in-law, aunts, nieces, nephews, and cousins. I tried it with a friend who had made my life rich with laughter, but I was too embarrassed to tell her, and acquaintances that I wanted to be friends with. Some were bothered, others accepting, but all had one thing in common—the next time I hugged them, they hugged me back.

    For me, holding on has become more than a physical interaction; it has become a way of thinking. My answer to life's dilemmas and tough choices, it's a mixture of acceptance, forgiveness, and patience—not always easy or understood but it guides me to be quiet and listen, look for the good, have a sense of humor and laugh, stop worrying and be patient because if I let it, something will change.

    I've often wondered how different my life would have been if I hadn't learned the power of holding on. If during that time in my life, when I was crumbling into myself, my mother had stopped holding on to me, I might have missed something so vital to my existence. I believe that a hug is like a battery charger—a good one can keep me going for a long time.

    Golden Gate Bridge

    Located in San Francisco,the Golden Gate Bridge started in the year 1933 to connect the San Francisco Peninsula with Marin County.It was finally thrown open to public traffic in 1937.It cost $25.7 million in the construction.Till the year 1957,the Golden Gate Bridge,at a length of 2,737 meters,was the longest suspension bridge in the world.

    Brooklyn Bridge

    The Brooklyn Bridge is located in Brooklyn.It is one of the oldest suspension bridges in the United States, having been opened in the year 1883.The length of the bridge is 1,843 meters.The bridge has been featured in several Hollywood movies.

    George Washington Bridge

    Also known as the Hudson River Bridge and the Columbus Bridge,the George Washington Bridge which connects Fort Lee to Manhattan came into use in 1931 after a construction period of almost 4 years.It is a two level suspension bridge that cost about $52 million to build.

    Mackinac Bridge

    This is the third biggest suspension bridge in the world at a length of 8,038 meters.The architect of this bridge was Dr.David B. Steinman who directed the construction of the bridge which started in the year 1054 and opened to the public in 1958.People using this bridge are charged a certain amount of money.

    Navajo Bridge

    Located in Arizona,this bridge crosses the Colorado River and is almost 250 meters long.The construction of this bridge started in the year 1927,ending two years later,costing $390,000.In the 1990s a second bridge was built which was opened to the public in 1994.The first bridge is now used only by pedestrians.

    More than 10 million Chinese cultural relics have been lost overseas, lost of which were stolen and illegally shipped out of China during the times of war before 1949. About 1.67million pieces are housed in more than 200 museums in 47 countries, which accounts for 10 percent of all lost Chinese cultural relics, and the rest are in the hands of private collectors.

    Most of these treasures are owned by museums or private collectors in the United States, Europe, Japan and Southeast Asian countries. There are more than 23, 000 pieces in the British Museum, most of which were stolen or bought for pennies more than 100 years ago.

    The major method to recover these national treasures was to buy them back. In some cases, private collectors donated the relics to the government. Also the government can turn to official channels to demand the return of relics.

    In 2003, a priceless bronze pig's head dating from the Qing Dynasty was returned to its home in Beijing after it was removed by the Anglo-French Allied Army over 140 years ago. Macao entrepreneur (企业家) Stanley Ho donated 6 million yuan to buy it back from a US art collector and then donated it to the Poly Art Museum in Beijing. Although buying-back is the most feasible way to recover the lost treasures, limited funding is always a big headache.

    In recent years, the Chinese government has improved efforts to recover the precious cultural relics lost overseas. It has started a national project on the recovery of the treasures and has set up a database (数据库) collecting relevant information. It has signed several international agreements with many countries on this matter, and is also looking for international cooperation to recover the relics by working closely with several international organizations.

    People have been wondering why elephants do not develop cancer even though they have lifespans (寿命) that are similar to humans, jiving for around 50 to 70 years.

    Now scientists believe they know why. A team at the University of Chicago, US has found that elephants carry a large number of genes that stop tumors (肿瘤) developing. To be precise, they found 20 copies of an anti-tumor gene called TP53 in elephants. Most other species, including humans, only carry one copy.

    According to the research, the extra copies of the gene improved the animal's sensitivity to DNA damage, which lets the cells quickly kill themselves when damaged before they can go on to form deadly tumors.

    "An increased risk of developing cancer has stood in the way of the evolution of large body sizes in many animals," the study author Dr Vincent Lynch told The Guardian. If every living cell has the same chance of becoming cancerous (癌变的), large creatures with a long lifespan like whales and elephants should have a greater risk of developing cancer than humans and mice. But across species, the risk of cancer does not show a connection with body mass.

    This phenomenon was found by Oxford University scientist Richard Peto in the 1970s and later named "Peto's paradox (悖论)”". Biologists believe it results from larger animals using protection that many smaller animals do not. In the elephant's case, the making of TP53 is nature's way of keeping this species alive.

    The study also found that when the same genes were brought to life in mice, they had the same cancer resistance as elephants. This means researchers could use the discovery to develop new treatments that can help stop cancers spreading or even developing in the first place.

    "Nature has already figured out how to prevent cancer," said Joshua Schiffman, a biologist at the School of Medicine, University of Utah, US. "It's up to us to learn how different animals deal with the problem so that we can use those strategies to prevent cancer in people."