Today, I had the good fortune to join the students from East Silver Spring Elementary School in Maryland as they walked and biked to school in celebration of International Walk to School Day. I want to thank Principal Morrow and the entire ESS community for welcoming me so enthusiastically.

    Walk to School Day is a great opportunity for me to spend time with parents, kids, and teachers and to present our Safe Routes to School program and the First Lady Michelle Obama's Let's Move initiative（倡议）.

    As a father, grandfather and former schoolteacher, I know how important it is that we provide students with safe choice to get to school while promoting exercise and healthy lifestyles. That's why I've embraced the Safe Routes to School program so wholeheartedly since I became Secretary of Transportation.

    You know, we're looking at an increasingly sedentary（久坐的）generation of children. One out of every three kids in America is now overweight. And I admire the First Lady's effort to end this within a generation. Safe Routes to School is a natural partner for Let's Move. For more than 10 years, Safe Routes to School has been making it easier for students to walk and bike from home to school. And ESS, where I walked today, is one of the earliest schools to participate.

    We know this program has been enormously effective because of the steady increase in the number of kids walking or biking to school. And as we made our way down the street this morning I was reminded yet again of this program's extraordinary work.

    Look, walking and biking to school is good for students' health. It's good for the environment. And it's good for the entire community's quality of life.

Everybody wins when kids take Safe Routes to School.

    Mandara seemed to know something big was about to happen. So she let out a yell, caught hold of her 2-year-old daughter Kibibi and climbed up into a tree. She lives at the National Zoo in Washington D.C.

    And on Tuesday, August 23rd, witnesses said she seemed to sense the big earthquake that shook much of the East Coast before any humans knew what was going on. And she's not the only one. In the moments before the quake, an orangutan (猩猩) let out a loud call and then climbed to the top of her shelter.

    “It's very different from their normal call,” said Brandie Smith, the zookeeper. “The lemurs (monkey like animals of Madagascar) will sound an alarm if they see or hear something highly unusual.”

    But you can't see or hear an earthquake 15 minutes before it happens, can you? Maybe you can——if you're an animal.

    “Animals can hear above and below our range of hearing,” said Brandie Smith. “That's part of their special abilities. They're more sensitive to the environment, which is how they survive.”

    Primates weren't the only animals that seemed to sense the quake before it happened. One of the elephants made a warning sound and a huge lizard (蜥蜴) ran quickly for cover. The flamingoes (a kind of birds) gathered before the quake and stayed together until the shaking stopped.

    So what kind of vibrations (震动) were the animals picking up in the moments before the quake? Scientist Susan Hough said earthquakes produce two types of waves——a weak “P” wave and then a much stronger “S” wave. The “P” stands for “primary”. And the “S” stands for “secondary”. She thinks the “P” wave might be what sets the animals off.

    Not all the animals behaved unusually before the quake. For example, Smith said the zoo's giant pandas didn't jump up until the shaking actually began. But many of the other animals seemed to know something was coming before it happened. “I'm not surprised at all,” Smith said.

    Have you ever pressed the pedestrian button at a crosswalk and wondered if it really worked? They're called “placebo(安慰剂）buttons” 一buttons that mechanically sound and can be pushed，but provide no functionality.

In New York City, only about 100 of the 1, 000 crosswalk buttons actually function. Crosswalk signals were generally installed before traffic jam had reached today's levels.

    But while their function was taken over by more advanced systems—such as automated lights or traffic sensors — the physical buttons were often kept, rather than being replaced at further expense. Other cities，such as Boston， Dallas and Seattle， have gone through a similar process, leaving them with their own placebo pedestrian buttons. In London, which has 6, 000 traffic signals， pressing the pedestrian button results in a reliable “Wait” light. But that doesn't necessarily mean that the “green man”— or “pedestrian stage” in traffic signal design profession — will appear any sooner.

    “We do have some crossings where the green light comes on automatically, but we still ask people to press the button because that enables accessible features,'' said Glynn Barton, director of network management at Transport for London.

    These features, such as blind tracks and hearable traffic signals, help people with visual disorder cross the road and only function when the button is pressed. As for the lights, a growing number of them are now combined and become a part of an electronic system that detects traffic and adjusts time frequency accordingly (giving priority to buses if they're running late, for example), which means that pressing the button has no effect.

    According to Langer, a Harvard psychologist, placebo buttons give us the illusion (错觉)of control — and something to do in situations where the alternative would be doing nothing. In the case of pedestrian crossings, they may even make us safer by forcing us to pay attention to our surroundings. “They serve a psychological purpose at the very least,” she added.

    You may have heard adults say they are uncomfortable in the morning without a cup of coffee. One reason they may feel that way is that coffee contains caffeine(咖啡因). Caffeine appears naturally in coffee, tea, and cocoa beans, which are used to make chocolate. But now food makers are adding it to many products, from potato chips to water.

    The US government is especially worried about the problem. That's why the Food and Drug Administration (FDA) is studying the health effects of caffeine on young people. Studies show that too much caffeine can make people nervous and unable to sleep. What's more, caffeine is habit- forming. Those who consume it regularly and stop suddenly may experience headaches and feel tired.

    One of the biggest concerns is the large amount of caffeine added to so-called energy drinks, like Red Bull. A 12-ounce can of cola has about 35 milligrams of caffeine. A similar serving of Red Bull contains more than three times that amount.

    The Institute of Medicine is also working on caffeine-safety measures. "Teenagers should not drink beverages that contain caffeine. They should be aware of caffeine's effects on health and on how the brain works. Take, for example, teenagers who consume caffeine to stay awake and study for a test. They will remember less of what they just studied," said Stallings, a member of the institute.

    Companies that make products with added caffeine claim they do not advertise them to kids. However, there is no law to stop children from buying them. So the FDA needs to set limits on caffeine, especially in energy drinks. As for added caffeine in foods, the government should just say no. If not, the amount of caffeine should be printed on food labels to remind consumers. The government must do that.

    Doctors say kids should avoid caffeine. If you need extra energy, try these natural boosters: eat right, exercise, and get plenty of sleep.

    The meaning of the word "volunteer" may be a little different in different countries, but it usually means "one who offers his or her services". There are many different ways in which people can volunteer, such as taking care of sick people, working in homes for homeless children, and picking up garbage from beaches and parks. Volunteers may work within their own countries or in other countries. They are often people with a strong wish to help those who are less fortunate than themselves. Volunteer don't expect any kind of pay.

    At the root of volunteering is the idea that one person may have the ability to offer services that can help other people. Tracy, a good friend of mine, however, recently came back from India with a new idea of what being a volunteer means. She worked for two and a half weeks in one of Mother Teresa's homes in Calcutta. The following is her story.

    "I first heard about Mother Teresa in my high school. We watched a video about her work in India and all over the world. I was so moved by her spirit to help others and her endless love for every human being that after I graduated from high school, I also wanted to try her kind of work. So with two friends, I flew to Caltutta for a few weeks."

    "I was asked to work in a home for sick people. I helped wash clothes and sheets and passed out lunch. I also fed the people who were too weak to feed themselves and tried to cheer them up. I felt it was better to share with them than to think that I have helped them. To be honest, I don't think I was helping very much. It was then that I realized that I had not really come to help, but to learn about and experience another culture that helped improve my own understanding of life and the world."

Ken was my best friend for 30 years. I told him I would leave Chicago for Philadelphia to receive a new job there. "What do you mean you're leaving?" Ken asked angrily. "When did you interview for a job in another city? You had never told me before." I explained that was the new company's rule. "Like you couldn't tell me?" he asked. "I thought our friendship meant more to you than that." "I'm sorry," I said. But I would never give up the job because of friends.

Ken and I had met in a church. Then Ken was a college student studying mental health and I was working in a company. I found we both grew up in small towns and struggled for school life. He often volunteered in Thailand during school holidays. And I once worked there for five years. Talking with Keri gave me great pleasure. Gradually, our conversations even involved in deeper subjects, like our dreams.

I was older than Ken. When he married Lee, I gave him advice about marriage. By that time, I was running a television production business, and was under a lot of stress. It was Ken who encouraged me and helped me get through the hard time. He was a great guy. Even so, I didn't change my mind.

Anyway, when leaving Chicago, Ken and Lee had a warm farewell (告别) party. But we didn't talk much later. After September 2012, everything changed. It started with a letter from Ken: Lee had cancer. Unfortunately, I got divorced (离婚) later and everything was a mess.

In February 2013,I flew to Chicago to see Ken and Lee. We talked. I found there was no one I had ever been able to talk to quite like Ken. I needed to be there for Ken in any way I could. This friendship mattered more than work. When going back to Philadelphia, I left my job and bought a plane ticket that would mean a lot to the rest of my life.