The more hours that young children spend in child care, the more likely they are to turn out aggressive and disobedient by the time they are in kindergarten, according to the largest study of child care and development ever conducted. Researchers said this correlation (相关性) held true regardless of whether the children came from rich or poor homes, were looked after by a relative or at a center, and whether they were girls or boys.

    What is uncertain, however, is whether the child care actually causes the problem or whether children likely to turn out aggressive happen to be those who spend more hours in child care. It also remains unclear whether reducing the amount of time in child care will reduce the risk that a child will turn into a mean person. What's more, quality child care is associated with increased skills in intellectual ability such as language and memory, leading some academics to suggest that child care turns out children who are “smart and naughty”.

    The government-sponsored research, which has tracked more than 1,300 children at 10 sites across the country since 1991, is bound to cause the debate over child care again: How should people balance work and family? And how should parents, especially mothers. Resolve the demands that are placed on them to be both breadwinners and supermoms?

    That debate was already on display at a news briefing yesterday, where researchers themselves had different opinions about the data and its implications (含义). “There is a constant relationship between time in care and problem behavior, especially those involving aggression and behavior,” said Jay Belsky of Birkbeck College in London, one of the lead investigators of the study who has previously annoyed women's groups because of his criticisms of child care. “On behalf of fathers or mothers?” interrupted Sarah Friedman, a developmental psychologist at the National Institute of Child Health and Human Development (NICHD) and one of the other lead scientists on the study. “On behalf of parents and families,” responded Belsky.

    “NICHD is not willing to get into policy recommendations.” said Friedman, contradicting her colleague. “There are other possibilities that can be entertained. Yes it is a quick solution—more hours in child care is associated with more problems. The easy solution is to cut the number of hours but that may have implications for the family that may not be beneficial for the development of the children in terms of economics.” In an interview after the briefing, Friedman said that asking parents to work fewer hours and spend more time with their children usually meant a loss of family income, which adversely(不利地) affects children.

    Scientists said that the study was highly reliable. But the researchers said they had no idea whether the behavioral difficulties persisted as the children moved to higher grades.

    Travelling around the world with children is difficult enough, while attempting it without using motorized transport is even more of challenge．Even so, Dario Schworer a 42-year-old climatologist and mountain guide, and his 33-year-old wife Sabine are on a journey to do just that．

    The Swiss couple want to travel across the world's oceans and climb the highest mountain on every continent to promote Earth-friendly ways of life．

    "We are collecting good examples of dealing with climate change and living in harmony with nature and we want to spread such ideas．" Schworer said．"We want to help people affected by global warming and to inspire children for the future．"

    Recently after having spent three months teaching children in the Everest region, the couple want to show it is possible to travel through the world's climate zones using just human-power and forces of nature．

    In the 47 countries they have visited they have collected 22 tons of trash, taught people in Ecuador how the sun's rays can be used to clean water and inspired a person in Chile to build a house on water with recycled plastic bottles as a foundation．They have also collected trash in the mountains of Nepal with school children．

    So far they have communicated with 45,000 children from South America, Australia and Asia, giving presentations about the importance of recycling and using alternative energy like solar and wind power．

    When they began their adventure in 2003 they had no children of their own．But since then two has become five: daughter Sabine is now five years old, Andri was born in Chile and baby Neo was born in Australia．

    Initially the couple thought they would complete their travels in four years, but now, they believe it could take seven more．

    "Since our belief is the need to respect nature, we travel only when conditions are good," Schworer said．

    Vacation is a time for refreshment. In work, we are often called to think. Sometimes, it's good to give our brains a rest. Without a break, we may not be able to perform up to our potential. This can be a problem, not only for the employee, but for the employer as well.

    “The main benefit of vacation is for the worker to come back energized,” says Weaver. “If they haven't had a break, then they're not coming back with new energy. They haven't had a chance to step back and get perspective (远景), and come back with renewed enthusiasm.”

    Long working hours without a break, insecurity (不安) about one's job, and other work-related worries can lead to burnout and stress. Humans can usually adapt to pressure, but not for a limitless amount of time.

    “It is a problem of relating good workers and having them loyal to the firm while they're there,” says David Maume, PhD, professor of sociology at the University of Cincinnati. He says burnout can also affect employees' productivity, creativity, and effectiveness.

    In addition, high levels of stress are likely to be precursors (前兆) to depression, which can hit both the employer and employee's pocketbook. Even people who manage to remain productive at work can have problems. If they're always at work, then they're not with their family and friends. If they're working while on vacation, for the time that they're on the job, they're not really present.

    An unbalanced emphasis on work can strain family and social life. When you come up for air, you may see that you're alone, or that your relationships have gone on without you.

    We brush our teeth daily, but do you know everything you need to know about dental care and hygiene? Believe it or not, there is a lot more than most people realize. Luckily, here are several apps that can help you.

●Brush DJ

    You should brush your teeth for full two minutes as recommended by dentists, but that time can be difficult to judge. Many recommend you listen to music, because many songs are just around two minutes in length. Brush DJ has loads of great tunes that will get you into the two­minute habit. There are both songs to listen to, and videos to watch, and you'll find a variety of awesome tunes.

●Orasphere

    It's recommended that Orasphere videos be used by dentists for their patients, so they can learn about procedures. Those who do use these videos say that the software can greatly decrease the amount of time it takes to explain procedures to patients.

●American Dental Association(ADA)

    Everything you ever wanted to know about your teeth, and then some, can be found on the American Dental Association(ADA) website. You'll find loads of great articles that have the latest news about dentistry（牙科）. Those interested in dental careers will find plenty of information to head them in the right direction, and there's even a section devoted to public dental programs, including Give Kids a Smile and Fluoride in Water.

●DDS GP

    Here is more presentation software that explains all types of dental procedures. This is helpful for dentists to have, because they can better explain procedures to their patients.

●Dentistry IQ

    You can find information for dentists, hygienists, assistants, office managers, and more at Dentistry IQ. You can also get information about new products, clinical practices, and much more. In addition, you can learn about career opportunities, the most recent practices, and a whole lot more.

    When Jenny Benson was eight, her mother took her to soccer practice for the first time.

    "She's never played soccer before," Mrs. Benson told the coach." I'm not sure how she'll do."

    Jenny ran onto the field and joined the other players. Over the next hour, Mrs. Benson and the coach watched as Jenny out­ran many of the more experienced players.

    "I knew then that soccer would be Jenny's sport." Mrs. Benson recalls. And she was right.

    It may have helped that Jenny had spent much of her time trying to keep up with her three brothers." I wanted to be just like them," Jenny says." My family has inspired me for my entire life."

    Jenny has retired from the United States women's national soccer team. She started out on her professional career in the Philadelphia Charge, a team in the Women's United Soccer Association (WUSA)．Later on, she joined FC Energy Voronezh, and then New Jersey Wildcats.

    When the WUSA was being formed, league officials watched many college soccer games, looking for players good enough to join the league. They were very interested in Jenny, who played for the University of Nebraska.

    "Throughout that college season, I knew I was being watched," Jenny says, "I knew I couldn't be perfect, so I just tried to be very consistent and have fun."

    As a professional, Jenny relied on her focused but fun­loving attitude. "In a game, I try never to put too much pressure on myself. The more I concentrate on having fun, the better I play." She says. "I have good and bad days, just like everyone else, but I know the sun will always come up after a bad day. So all I have to do is to adjust myself, either to the change of my inner feelings or to the change of circumstances. That helps me get through anything."

    As the temperature rises, sweaty humans are making a response that is further worsening the problem of climate change. At present, the world just has 1.6 billion air conditioning units, but these units use a surprising total of ten percent of all global electricity supply. While less than a third of families globally are so equipped, the most AC-addicted countries are Japan (in 91 percent of families), the US (90 percent) and South Korea(86 percent).

    New research by the International Energy Agency (IEA) guesses that the total number of AC units is likely to increase to over 5.6 billion by 2050－equal to ten new units being sold every second for more than 30 years－with sales driven particularly by India, China and Indonesia. This will make the use of air conditioning one of the world's largest demands for energy.

    "Growing electricity demand for air conditioning is one of the most critical blind spots in today's energy debate," argues Faith Birol, executive director of the IEA. "With rising incomes, air conditioner ownership will skyrocket, especially in the developing world. While this will improve daily lives, it is quite necessary that efficiency performance be prioritized."

    Birol and the IEA stress the need for new efficiency standards to ensure that consumers are at least buying units that require significantly less power to function, therefore decreasing the total energy demand. Variations on the traditional "vapor compression" technology, which has formed the basis for AC units for more than a century, may appear really important. A water-based system was recently developed by researchers at the National University of Singapore (NUS), which uses 40 percent less electricity and produces only one by-product: drinkable water.

    "Our cooling system can be tailored for all types of weather conditions, from wet climate in the tropics to dry climate in the deserts," says associate professor Ernest Chua at NUS. "While it can be used for indoor living and commercial spaces, it can also be easily used to provide air conditioning for blocks of buildings in an energy-efficient manner."