How fit are your teeth? Are you lazy about brushing them? Never fear: An inventor is on the case. An electric toothbrush senses how long and how well you brush, and it lets you track your performance on your phone.

    The Kolibree toothbrush was exhibited at the International Consumer Electronics Show in Las Vegas this week. It senses how it is moved and can send the information to an Android phone or iPhone via a Bluetooth wireless connection.

    The toothbrush will be able to teach you to brush right (don't forget the insides of the teeth!) and make sure you're brushing long enough. “It's kind of like having a dentist actually watch your brushing on a day-to-day basis,” says Thomas Serval, the French inventor.

    The toothbrush will also be able to talk to other applications on your phone, so developers could, for instance, create a game controlled by your toothbrush. You could score points for beating monsters among your teeth. “We try to make it smart but also  fun,” Several says.

    Serval says he was inspired by his experience as a father. He would come home from work and ask his kids if they had brushed their teeth. They said “yes,” but Serval would find their toothbrush heads dry. He decided he needed a brush that really told him how well his children brushed.

    The company says the Kolibree will go on sale this summer, for $99 to $199, developing on features. The U.S. is the first target market.

    Serval says that one day, it'll be possible to replace the brush on the handle with a brushing unit that also has a camera. The camera can even examine holes in your teeth while you brush.

    Why do you go to the library? For books, yes—but you like books because they tell stories You hope to get lost in a story or be transported into someone else's life. At one type of library you can do just that—even though there's not a single book.

    At a Human Library, instead of books, you can "borrow" people. People with unique life stories volunteer to be the "books." For a certain amount of time, you can ask them questions and listen to their stories, which are as fascinating as any you can find in a book. (If you attend, make sure to review the habits that make you a good listener.) Many of the stories have to do with some kind of depressing topic. You can speak with a refugee, a soldier suffering from PTSD (创伤后遗症), a homeless person and a woman living with HIV. The Human Library encourages people to take time to truly get to know and learn from someone they might otherwise make a snap judgement about. According to its website, the Human Library is "a place where difficult questions are expected, appreciated and answered."

    The Human Library Organization came to be in Copenhagen, Denmark in 2000. Romni Abergel and his colleagues hosted a four-day event during a major Northern European festival. After the success of this event, Abergel founded the Human Library Organization, hoping to raise awareness among youth about depression, which has been growing ever since.

    Though there a few permanent human libraries, most aren't place at all, but events. Though many do take place at physical libraries, you don't need a library card—anyone can come and be part of the experience. There have been human library events all over the globe, in universities and in pubs, from Chicago to Tunis to Edinburgh to San Antonio. Check out the organization's Facebook page to see when the Human Library might be arriving near you.

    Anyone can try to lead a group, but not every individual is cut out for leadership. The better leaders possess a few qualities that can mean the difference between the success and failure of the group. These are the qualities the leader of higher rank will look for when choosing a leader for a group, or when evaluating the performance of a leader. They're also the qualities team members want in a group leader, and appreciate when they find them.

    Take Responsibility

    Group leaders might share tasks around a group as necessary, but eventually a group leader needs to be able to accept that responsibility lies on his shoulders. That means that if things go wrong in a group project, he's the one who must accept the consequences and work out what mistakes are made. The group leader won't always have the power to control everything group members do, but he should be ready to admit any mistakes the group has made as a result of his leadership

    Concern for Members

    The group leader has a commitment to the task or project at hand, but perhaps more importantly, he has a real concern for each and every person who is part of his group. This means getting to know the strengths, weaknesses and goals of team members, as well as making time to build the group through collective activities. The group leader should make sure that everyone is included, even if an individual is new to a group.

    Good Listener

    The group leader needs to be able to listen to the suggestions, complaints and ideas of group members. Not only will this allow complaints to be addressed and potentially suitable ideas to be put into practice, but a leader who listens will also encourage group members to share their concerns and thoughts, creating an atmosphere of free speech and productivity.

    German engineers Gottlieb Daimler and Karl Benz built the first successful gasoline engines in 1885.After 1900, however, the United States became a leader in automobile production.

    The first cars were handmade and very expensive. Only people in rich cities could afford them. The first company to make gasoline cars in the U.S. was the Duryea Motor Wagon Company. Then, in 1901, Ransom E. Olds Began mass-producing his car, the Oldsmobile. In 1913Henry Ford made great strides in the mass production of cars by using an assembly line in his factory. Mass production meant that each car was less expensive to make. Now car ownership was affordable for the average person. By 1916there were more than one million cars in the United States.

    The automobile gave people the freedom to travel anywhere there were passable roads. Families that lived great distance apart could travel by automobile to visit each other. People could visit places they had never seen before.

    Before the mass production of cars, people lived close to work. Their means of transportation included walking, riding a bicycle, using a horse and carriage, or taking a train. The automobile gave people the ability to live farther away from work. The result was that gradually people moved out of the cities to the less crowded suburbs.

    The automobile industry created millions of jobs. The jobs were not just in the auto factories, where the cars were assembled. Workers were needed to make auto parts, run gas stations and repair shops, and work at new motels and restaurants that served people who traveled by car. Jobs became available at car rental companies. People were needed to build roads. These jobs and many others still exist because of the automobile.

    Frequently, we speak about people being “color-blind” but very few of us are. Even those who describe themselves as color-blind are normally just color lack. A strongly, color-blind person will still be able to tell 20 different colors, compared to the 100 or so that normal-sighted people see.

    Pingelap, a tiny island in the Pacific, is a beautiful spot but one that has a genetic trouble. It is known as Color-blind Island because so many people who live on this remote island can only see black and white.

    Not being able to see colors is bad enough. But one islander, Herrol, who's a fisherman, also struggles in full sunlight because all he sees is a painful burnt-out image. “I find it difficult to go outside in the sun,” he says, “because when it's sunny I cannot see to do my work.”

    But if being truly color-blind is rare, why is it that around 10% of the population of Pingelap live in a totally black and white world?

    Well, we know that in 1780 the population of Pingelap was all but wiped out by a tsunami (海啸). As few as 20 people survived, one of whom was the king. It's believed he had a genetic fault that causes colour-blindness and he passed this fault on to his many generations.

    There is one advantage. Herrol can see well, really well, in the dark. So when it gets dark, Herrol and his friends get in their boats and hunt flying fish. They hang up flaming torches and the fish are attracted to the flames. “This type of fishing is fun,” Herrol says, “especially if we catch plenty. So even though it's hard work we enjoy it.”

    Most people who own iPhones use them as their alarm clocks―making it very easy to check emails one last time before falling asleep and hard to ever feel away from work and social networks.

    Several years ago, my boss fainted due to exhaustion after staying up late to catch up on work. She banged her head and ended up with five stitches (缝针) and became what she calls a "sleep evangelist (传教士)." Now she leaves her phone charging in another room when she goes to bed and encourages her friends to do the same.

    "I sent all my friends the same Christmas gift―a lovely alarm clock―so they could stop using the excuse that they needed their very attractive iPhones by their beds to wake them up in the morning." she said.

    If your phone wakes you up in the morning, it may also be keeping you up at night. A 2008 study showed that people exposed to mobile radiation took longer to fall asleep and spent less time in deep sleep. "The study indicates that during laboratory exposure to 884 MHz wireless signals, components of sleep believed to be important for recovery from daily wear and tear are severely affected," the study concluded.

    A quarter of young people feel like they must be available by phone around the clock, according to a Swedish study that linked heavy cellphone use to sleeping problems, stress and depression. Unreturned messages carry more guilt when the technology to deal with them lies at our fingertips. Some teens even return text messages at midnight.

    Most of us choose not to set limits on our nighttime availability. Nearly three quarters of people from the age of 18 to 44 sleep with their phones within reach, according to a 2012 Time poll. That number falls off slightly in middle age, but only people aged 65 and older are leaving the phone in another room as common as sleeping right next to it.