Eating too much fatty food, exercising too little and smoking can raise your future risk of heart disease．But there is another factor that can cause your heart problems more immediately: the air you breathe.

    Previous studies have linked high exposure (暴露）to environmental pollution to an increased risk of heart problem, but two analyses(分析) now show that poor air quality can lead to heart attack or stroke (中风）within as little as a few hours after exposure．In one review of the research, scientists found that people exposed to high levels of pollutants (污染物）were up to 5% more likely（可能的） to suffer a heart attack within days of exposure than those with lower exposure．A separate study of stroke patients showed that even air that the U．S．Environmental Protection Agency (EPA) considers to be of “moderate” (良好）quality and relatively safe for our health can raise the risk of stroke as much as 34% within 12 to 14 hours of exposure.

    The authors of both studies stress（强调）that these risks are relatively（相对的）small for healthy people and certainly modest compared with other risk factors such as smoking and high blood pressure．However, it is important to be aware of these dangers because everyone is exposed to air pollution regardless of lifestyle choices．So stricter regulation（规章制度）by the EPA of pollutants may not only improve environmental air quality but could also become necessary to protect public health.

    One Sunday, my son asked me if he could ride up to his elementary school on his bike and meet his friend. He wanted both of them to ride back to our house so they could play video games and jump on the trampoline (蹦床). I have to admit, part of me wanted to say no. We could go to pick him up or his parents could bring him over here. I thought. But my son is eleven years old now. And after all, I do let him ride his bike to school. But I also drive my daughter to school and I can see him on the way, making sure he is getting there safely.

    My husband thinks I am overprotective. I don't dare to let my children walk anywhere without one of us going along. As you go out of our neighborhood, there is a shopping center across the street. My son always asks if he can ride his bike or walk over to the drugstore by himself. But crossing that street is just too dangerous. The cars fly around the comer like they're driving in a car race. What if he gets hurt? What if some teenager bullies are hanging out in the parking lot? I want so much to give my children the freedom that I enjoyed having when I was growing up but I hesitate to do so, because there are dangers around every comer. Too many kidnap, too many robberies and so on.

    I honestly don't think my mom worried about such things when her children were young. Growing lip in the 1970s was indeed very different. I never wore a helmet (头盔) when I rode a bike. We were all over the neighborhood, on our bikes and on foot, coming home for dinner and then-back out again until dark. We rode in the back of the truck and didn't wear seat belts. I walked to and from school every day.

    A few years ago, my wife, Sue had some serious health problems. She had suffered surgery after surgery and had also put on weight. Diets had not helped her and she suffered constantly from undiagnosed pain. One day the whole family sat down and drew up a “wish list”. To our surprise, one of Sue's items was to run in a marathon. Given her history and physical limitations, I thought her goal was completely unrealistic, but Sue became committed to it.

    She began by running very slowly and every day she ran just a little farther than she did the day before. Soon she could run three miles. Then five. Sue kept practicing and longed to run in the St. George Marathon in southern Utah.

    On the big day, I parked our van near the finish line, waiting for Sue. The rain was steady and the wind was cold. The marathon had started over five hours ago. The fast and strong competitors had finished already. Several cold and injured runners had been transported past me, and I began to panic. The image of Sue, alone and cold, off the road somewhere, made me sick with worry.

    Another hour passed and I spotted a small group running up. As they approached, I could see Sue, in the company of three others, and a woman in her twenties was near Sue. It was obvious that they had become friends during the race. I could see her begin to struggle. But when the finish line came into sight, she confidently even happily picked up her pace the last hundred yards to the finish line. Few people were left to congratulate my wife. They openly praised and embraced her, “She made us believe we could do it,” her new friend stated.

    From then on, she was carrying herself differently. Her head was more upright. Her shoulders were squared. Her walk had a new confidence. Her voice held a new, quiet dignity. It was not as if she had become someone new; it was more as if she had discovered a real self she had not known before. It was perseverance that made her realize she was an undiscovered masterpiece with a million things left to learn about herself. She truly liked her newly discovered self. So did I.

    As soon as a person dies, decomposition(分解) begins. And the first visitors arrive. “Within 5 to 15 minutes of death, flies or other insects begin to colonize the body.” says Rabi Musah, an organic chemist at the University at Albany.

    She says different species turn up at different stages of decomposition. “So because of that, depending upon what entomological(昆虫学的) evidence you find, you can learn something about when the person died in terms of the timing of the death.”

    Flies don't tend to stick around when disturbed by detectives. But they do leave behind eggs. The eggs are hard to tell apart by appearance alone, so specialists raise them until they hatch, a few weeks later—and they get a species ID and, with a little guesswork, a person's time of death.   But Musah has come up with a more time-saving approach: chemical analysis of the eggs. She and her team investigated that method by first harvesting flies with pig-liver traps hidden throughout New York City. They collected the trapped flies and then chemically analyzed their eggs. And it turns out each species of fly egg has a unique chemical fingerprint—enough to tell the eggs apart without raising the eggs to maturity. The study is in the journal Analytical Chemistry.

    Musah and her colleague Jennifer Rosati are now testing the method on a real case. “And once we do that we will be publishing some case studies to illustrate(阐明) that this is a method that can be used, and hopefully eventually it's something that will stand up in court, and something that could speed up detective work—or help deal with a cold case.”

    When pups are between 2 and 3months old, their mothers will abandon them for any number of reasons. With no mother to watch out for them, infant (婴儿) mortality of pups under one year skyrockets (飞涨) to around 90%. So, only about 10% of motherless, homeless pups survive.

    Without mothers, how are these abandoned pups supposed to survive? For the study, researchers Clive Wynne at Arizona State, Nadine Chersini at Utecht University, and Nathan Hal at Texas Tech University brought in 51 college students and asked them to rate the attractiveness of headshots (头部特写) of puppies at different ages.

    The pups peaked at different ages, but they were all ranked likable between six to eight weeks, since newly abandoned pups are competing with each other for human heartstrings (怜悯), evolution says they should be most likable around 6 and 11 weeks. This is around the time they are weaned (断奶) and let go of by their mothers.

    There are a few characteristics that humans find particularly adorable across species: big, forward-facing eyes, floppy and unstable limbs (肢), and a soft, rounded body shape. We're also keen to scream when animals have large heads in comparison to their bodies, and this reaction goes back to evolution.

    Called kinderschema (婴儿萌), these qualities are also apparent in human babies and necessary for their survival. The characteristics activate the decision-making part of the brain to encourage you to protect and nurture the baby. At the same time, the brain's pleasure center releases dopamine (多巴胺). With these two reactions, your brain makes you want to protect the baby and rewards you for doing so. With your protection, the baby can survive.

Urban Transportation in Canada

Public transportation & Transit passes

All cities and most major towns in Canada have a public transportation system with one or more modes of transportation（bus, subway, train, etc.）. The bus is the most common form of urban transportation in Canada. To use public transportation, you must purchase a ticket or a transit pass. Transit passes allow you unlimited use of public transportation for a specific period（one month or more）. They are usually cheaper than buying many tickets if you plan to use public transportation often.

Transportation for people with disabilities

Public transportation often has features to assist people with disabilities. In many cities and towns, there are also transportation services available specifically for people with limited mobility, such as specially equipped buses. You can find out about these services in the same way you would learn more about other public transportation options.

Etiquette（礼节）on public transportation

When taking public transportation such as a bus or train, it is important to understand the unspoken rules of conduct in the shared space. Here are a few things to note:

Be polite and respectful to others around you. For example, maintain an appropriate noise level when talking or making a phone call.

If you are carrying a back pack or a large shoulder bag in a crowded public transit vehicle, keep it close to you, preferably at your feet to avoid hitting people with it as you walk by.

Avoid pushing or touching others in order to make more room for yourself. Sometimes public transit can become very crowded, but it is important to keep calm and give others appropriate personal space.

Have your proof（证明）of payment accessible in case you are asked to show it.