Mexico sites on an island plateau (高原) surrounded by volcanic peaks, which makes air quality a constant concern for people who live there.

    In April, the country took a decisive step toward improving air quality by enacting a temporary ban on private and Federal vehicles in the city. The rule forbids people from driving in the city one day each week and one Saturday each month. Electric vehicles, government service vehicles, public transport options and school buses are not included in the ban.

    Mexico City isn't the first urban center to be involved in car-free living. But the ban is more than an awareness-raiser. It was enacted with the direct aim of solving air pollution. In March, the city sank into a deep brown haze of smog when the pollution levels passed the 200 mark. The city ordered some 1.1m of the area's 4.7m cars off the streets and also offered free bus and subway rides.

    Mexico City's temporary vehicle ban raises questions about the best ways to improve urban air quality. India, whose citizens breathe some of the world's dirtiest air, has tried a variety of solutions. Earlier this year, the Indian government started a 4% sales tax on new-car purchases.

    Beijing also has experience with cleaning the air. The city introduced alternate-day rules in advance of the 2008 Olympic Games, which produced good results. And then there is the London congestion (拥挤) charge, introduced in 2003. The charge has had a measurable effect on air quality.

For now, Mexico City — named by the United Nations as the most polluted city on the planet in 1992 — can look forward to the start of the region's rainy season, when daily showers will help lo clean the air.

    People with bigger brains tend to score higher on standardized tests of intelligence, according to new study findings.

    However, the study author Dr. Michael A.McDaniel of the Virginia Commonwealth University in Richmond emphasized that these findings represent a general trend, and people with small heads should not automatically believe they are less intelligent. For instance, Albert Einstein's brain was "not particularly large", McDaniel noted." There's some relationship between brain size and intelligence on the average, but there's plenty of room for exceptions," he said.

    Interest in the relationship between brain size and intelligence grew in the1830s, when German anatomist(解剖学家) Frederich Tiedmann wrote that he believed there was "an unquestionable connection between the size of the brain and the mental energy displayed by the individual man". Since that statement, scientists have conducted numerous studies to determine if Tiedmann's assertion was correct. Most studies have looked into the link between head size and intelligence. More recently, however, researchers have published additional studies on brain size and intelligence, measured using MRI scan(核磁共振成像扫描).

    For his study, McDaniel analyzed more than 20 studies that looked into the relationship between brain size and intelligence in a total of 1,530 people. The studies showed that on the average, people with larger brain volume tended to be more intelligent. The relationship between brain volume and intelligence was stronger in women than men, and in adults than in children. McDaniel notes in the journal Intelligence.

    McDaniel is not sure why the relationship was stronger for adults and women. "Other research has shown that women, on the average, tend to have smaller brains than men, but score just as well—if not higher—in tests of intelligence," he said.

    McDaniel insisted that the relationship between brain size and intelligence is not a "perfect" one. "One can certainly find lots of examples of smaller-sized people who are highly intelligent," he said, "But, on the average, the relationship holds."

    They already guide blind and disabled people; now dogs are to be trained to help people with dementia(痴呆) or Alzheimer's. Alzheimer's can make people confuse night and day or forget basic things such as washing and drinking enough water.

    The dogs will be trained to respond to sound triggers(触发器) in the home that make them perform tasks. The duties will include reminding their owners to take medicine, as well as encouraging them to eat, drink and sleep regularly.

    The idea was developed by design students at the Glasgow School of Art and will now be put into practice by Alzheimer's Scotland and Dogs for the Disabled. The first dogs will be distributed to four Scottish couples, where one of the partners is in the early stages of dementia. 670,000 people in Britain have dementia and one in three over 65 will develop the condition. By 2021 this is expected rise to one million.

    John Gray of Alzheimer's Scotland said, "People in the early stages of dementia are still able to live a relatively normal life, and dogs help to maintain routine. " Another advantage of using the pets as companions is that dogs can give them a sense of silent support and companionship. Ms Gray said: "The evidence is that people may forget familiar faces but not pets. It's such a strong bond that people often remember them longest. People don't need to communicate verbally(口头上) but they can still interact. You can have a speechless bond."

    Helen McCain, director of Dogs for the Disabled, said, "People with dementia often forget to take medicine. If a dog presents them with a bag with pills in it, there is a greater chance of them taking it. The dogs would also encourage the owners to take them out for walks, ensuring they keep exercising and interacting with other people."

    When the telephone rings late at night, most women guess it must be one of only four or five people calling. A sister? Maybe. An emergency? Possibly. A mother? Probably not at that time of night. Much more probably it is a close female friend calling to tell you that she has split up with her boyfriend again or perhaps simply that a good movie has just started on TV.

    At a time when families are spread far and wide and marriages often end in divorce, friendships are becoming more and more important. Erika, a 32-year-old lawyer, is strengthened by her ten-year friendship with her married friend Jane. “I was very sick one night, so I called Jane at about 3:00 a.m. to talk about it,” she says. “She was very supportive and even came over to take me to the doctor's the next morning.”

    As American TV shows like Friends, which follows the lives of a very close group of young friends, have become more popular, many of us are beginning to see the value of such friendships. TV shows like this tell us that our romantic relationships may not last, but we need to keep in touch with our close friends if we want to survive.

A TV show called Real Women is about the lives and relationships of five former school friends. In this show, family, husbands, and work are all less important than friendships. One of its actresses says the show reflects her own experience. “Friendship is about commitment. I don't see some of my friends for ages but when we get together, it is as if time hasn't passed.”

    This is true of Erika and Jane's friendship. With Erika's family 200 miles away, it is Jane who keeps a spare set of keys to Erika's apartment and waters her plants whenever she is away. “Having Jane around gives me a certain amount of freedom. It is not the kind of thing that you could ask anyone to do, but she knows I would do the same for her.” Erika feels that because she no longer sees her family every day, she now enjoys a closer relationship with her best friend. Jane, who may move to a different city soon, is worried about leaving such a support system of friends. “My friends have more to do with my life than my parents and, therefore, I don't have to spend a lot of time explaining things to them. Friends are more up to date with what is happening.”

My wife and I were at a crowded grocery store not long ago. It was a weekday evening, cold and wet—and tense. People were carelessly blocking aisles, cutting one another off with their carts.

    Things got worse at the checkout line. The cashier scanned a man's discount card, but he misread the savings on her screen as an additional charge. He decided she was acting deliberately and began to argue.

    "She is being spiteful (恶意的)!" he yelled. "This is unbelievable."

    Other customers looked away as the cashier tried to reason with him. She called a manager, who accompanied him to customer service. Shaken, she moved to the next customer in line.

We've all witnessed uncomfortable scenes like this in public places. The grocery scene was another example of how our trust in others has eroded. But it was also a teachable moment on how we can rebuild our faith—starting with just one person.

    Back at the grocery store, my wife and I reached our uneasy cashier. I grabbed a bottle of water from a nearby cooler and handed it to her. "We felt bad about how that man treated you and wanted to buy this for you." I said. Her face lit up, and we talked as she scanned our items. She told us she had been working that evening through severe foot pain and would be having surgery later that week. We wished her well in her recovery, and she thanked us as we left.

    Those are the balancing acts, the moments of responding social and emotional pain with healing, which will add up to restore trust among people. You can start that pattern in someone else's life, even in a place as ordinary as the neighborhood grocery store.

    Every year in May, art galleries and museums prepare shows to honor Leonardo Da Vinci, who died in France on May 2, 1519. He is remembered as one of the greatest artists and creative thinkers of all time. His most famous paintings are The Mona Lisa and The Last Supper.

    Recently, researchers have been studying a painting-Landscape 8P which, they think, is Da Vinci's earliest-known artwork. They used special lighting to study the artwork and discovered there were two images(图像), not one. One drawing is on the back of the piece, which dates back to August 5, 1473.

    The drawing on the front was painted when Leonardo was 21 years old. It shows a river valley and a castle outside the city of Florence. There is little left of the drawing on the back, perhaps because it was wiped off. Only a bridge over a river can be seen. But there is writing on both sides.

    The writing on the front gives the date and goes from right to left. Some people would call this "mirror-writing". It's a way Leonardo often wrote in his notebooks. The writing on the back goes from left to right and tells about an agreement, probably to produce a work of art.

    Cecilia Frosinini is an art historian. She said, "Leonardo was born left-handed, but was taught to write with his right hand from a very young age. By looking at his writings, including from this drawing, we can see his right-handed handwriting is educated and well done. "

    Experts compared the two handwriting samples(样本)and said they were both made by Leonardo. They show he could write well using his left hand or his right hand.

    The drawing is known as Landscape 8P from its number in an art list. It will be part of an exhibit at Italy's Uffizi Gallery. The gallery director, Eike Schmidt, said by studying the drawing researchers gave us a new way of looking at Leonardo's drawing technique and his abilities in writing.