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.

    Dreams can be familiar and strange, fantastical or boring, but some dreams might be connected to the mental processes that help us learn. No one knows for certain why people dream, but some dreams might be connected to the mental processes that help us learn. In a recent study, scientists found a connection between nap-time dreams and better memory in people who were learning a new skill.

    In the study, 99 college students between the ages of 18 and 30 each spent an hour on a computer, trying to get through a virtual maze(迷宫). The maze was difficult, and the study participants had to start in a different place each time they tried — making it even more difficult. They were also told to find a particular picture of a tree and remember where it was.

    For the first 90 minutes of a five-hour break, half of the participants stayed awake and half were told to take a short nap. Participants who stayed awake were asked to describe their thoughts. Participants who took a nap were asked about their dream after sleep — and they were awakened within a minute of sleep to describe their dreams.

    Stickgold, a neuroscientist (神经科学家), to know what people were dreaming about when their eyes weren't moving, during sleep.

    Four of the 50 people who slept said their dreams were connected to the maze. Some dreamed about the music that had been playing when they were working; others said they dreamed about seeing people in the maze. When these four people tried the computer maze again, they were able to find the tree faster than before their naps.

    Stickgold suggests the dream itself doesn't help a person learn — it's the other way around. He suspects that the dream was caused by the brain processes associated with learning.

    All four of the people who dreamed about the task had done poorly the first time, which makes Stickgold wonder if the dreams show up when a person finds a new task particularly difficult. People who had other dreams, or people who didn't take a nap, didn't show the same improvement.

    Modem zoos are different from those built fifty years ago.At that time zoos were places where people could go to see animals from many parts of the world.The animals lived in cages with iron bars（栅栏）.Although the zoo keepers took good care of them,many of the animals did not feel comfortable,and they often fell ill.

    In modern zoos,people can see animals in more natural conditions.The animals are given more freedom in larger places so that they can live as they would in nature.Even the appearance of zoos has changed.Trees and grass grow in cages,and water flows through the places the animals live in.There are few bars;instead,there is often a deep ditch（沟）,filled with water,which surrounds a space where several sorts of animals live together as they would naturally.In an American zoo,the visitors can walk through a special huge cage that is filled with trees,some small animals and many birds,and large enough for the birds to live naturally.In a zoo in New York,with the use of special nights,people can observe certain animals that are active only at night,when most zoos are dosed.Some zoos have special places for visitors to watch animals that live in the desert or under water.

    Modern zoos not only show animals to visitors,but also keep and save rare animals.For this reason,fifty years from now,the grandchildren of today's visitors will still be able to enjoy watching these animals.

    Do you know that there's a new frontier in 3D printing that's beginning to come into focus: food. Recent development has made possible machines that print, cook, and serve foods on a mass scale. {#blank#}1{#/blank#}

    Food production

    With a 3D printer, a cook can print complicated chocolate sculptures and beautiful pieces for decoration on a wedding cake. {#blank#}2{#/blank#} —it takes years of experience, but a printer makes it easy. A restaurant in Spain uses a Foodini to "re-create forms and pieces" of food that are "exactly the same," freeing cooks to complete other tasks. In another restaurant, all of the dishes and desserts it serves are 3D-printed, rather than farm to table.

    Sustainability

    According to a new study, the global population is expected to grow to 9.6 billion by 2050, and some analysts estimate that food production will need to be raised by 50 percent to maintain current levels. {#blank#}3{#/blank#} 3D food printing could probably contribute to the solution. 3D printing can reduce fuel use and emissions. Grocery stores of the future might stock "food" that lasts years on end, freeing up shelf space and reducing transportation and storage requirements.

Nutrition

    {#blank#}4{#/blank#} Hod Lipson, a professor at Columbia University, said, "Food printing could allow consumers to print food with customized nutritional content, like vitamins. So instead of eating a piece of yesterday's bread from the supermarket, you'd eat something baked just for you on demand."

    {#blank#}5{#/blank#}

    Despite recent advancements in 3D food printing, the industry has many difficulties to overcome. Currently, most ingredients must be changed to a paste(糊状物) before a printer can use them, and the printing process is quite time-consuming, because ingredients interact with each other in very complex ways. On top of that, most of the 3D food printers now are restricted to dry ingredients, because meat and milk products may easily go bad.

A. Challenges

B. Opportunities

C. And the industry isn't stopping there.

D. Sustainability is becoming a necessity.

E. Future 3D food printers could make processed food healthier.

F. Here are some new ways to produce 3D printing.

G. Not everybody can do that.

No one can believe that the over 6, 300-kilometre Great Wall might disappear some day. Believe it or not, the Great Wall is being destroyed by people. Less than 20 percent of the Great Wall built in the Ming Dynasty is still perfect, and about 80 percent is in danger. 

The Great Wall can be called "great" mostly because of its amazing length. If we do nothing to save the Great Wall, it will become wasteland rather than a historic site. The Great Wall is actually a series of walls built and rebuilt by different dynasties over the past 2, 000 years. It began in the Qin Dynasty, and lasted into the Ming Dynasty. The parts built before the Ming Dynasty have nearly disappeared. People are familiar with sections such as Badaling in Beijing and Jiayuguan Pass in Gansu, because they have been open to tourists for many years. But those sections far away from the public eyes have been almost forgotten. 

Few local people knew the 3-metre-high walls made of earth and stones beside them are part of the Great Wall. The lack of knowledge is considered as one of the main reasons behind humans. 

The bricks on the Great Wall are carried off by countryside people to build their houses. Rubbish is spread over the battlements. Those who destroyed and are destroying the Great Wall know its name, but don't know its cultural meaning. The local farmers not only carried off the body of the Great Wall but dug out the entire base. 

It is necessary to protect the Great Wall. First of all, the officials should be aware of the importance of the Great Wall. Young Chinese should know more about the nation's great civilisation and learn to love it. 

Researchers in Australia recently announced a new device（设备） that absorbs water from air to produce drinkable water. They said it can produce up to 1,000 liters of drinkable water a day, adding that it could be "lifesaving during drought or emergencies". What's more, unlike other water generators（造水机）, their invention works by heating air instead of cooling it.

Researchers at the University of Newcastle call the device the Hydro Harvester. The device absorbs water from the air. Solar energy or heat from other industrial processes can be used to produce hot and wet air. After heating, the air cools, producing water for drinking or watering crops.

The researchers say the device can produce enough drinking water each day for a small rural town of up to 400 people. It could also help farmers keep their crops alive during droughts. Researchers thought their device would be especially useful in Australia because its climate is dry.

More than 2 billion people around the world will benefit from the device. They are in a situation where they do not have access to high-quality water. The device is meant to help alleviatewater shortage and safety.

Studies of the technology will be done in several Australian communities this year. The World Economic Forum （WEF）, a nonprofit group based in Switzerland, says water shortage continues to be a problem worldwide. The WEF said getting water from the atmosphere is a "promising solution that can immediately generate drinkable water using moisture（水汽） in the air". However, the group warns that the technology is costly. It estimates that one mid-sized device could cost between $ 30,000 and $ 50,000. So the group is concerned whether it will be accepted by the public.