The expression “a thirst for knowledge" may soon have a new meaning for millions of people who have no way to get clean water. Researchers have developed a book with specially treated pages that can turn dirty water into clean and drinkable water. They say their invention could improve the lives of many in the developing world.

    About 700 million people around the world are at risk of disease or even death because their drinking water is not clean. The water is polluted by harmful bacteria.

    The book contains 25 pages. Each page is about one millimeter thick. The pages contain very small particles (微粒) of silver. The pages can be used as filters（过滤器）to remove harmful microorganisms (微生物) that can pollute drinking water. The filter kills the organisms that pass throughit.

    Pictures on the pages show the dangers of dirty water and how to use the book for those unable to read. The pages aremade of filter paper. They are designed to be torn from the book. Water can bepoured through the paper to be cleaned.

    Ms. Dankovich, the inventor, says eachpage can treat up to 100 liters of water. She recently presented her invention at the meeting of the American Chemical Society in Boston, Massachusetts. She was asked whether she had considered adding classic literature on the book's pages.

    "The idea of classic texts—that's of interest maybe later. We have discussed a little bit more exciting text. But we really haven't had the time to go through that part," she says.

    Teri Dankovich and another researcher tested the drinkable book in Bangladesh, Ghana and South Africa. The tests proved to be successful.

    Water for Life, a non-government alorganization, has provided financial support for the project.

    For centuries, elephants have played a big role in the world's economies, culture and religion. The African elephant used to be found all over Africa and the Asian elephant moved from Syria to China to Indonesia. Nowadays, elephants are found in small groups in the south of the Sahara Desert and scarcely in Southeast Asia, Sri Lanka and India.

    In the early twentieth century, there were close to ten million elephants, and now the elephant number is as low as 252,000 and expected to drop down to 160,000 by 2025. Between 2007 and 2014, the elephant population fell by at least 30%, or 144,000 elephants. As researchers have traveled over the African plains, they only spotted one herd of 36 elephants in an area like the size of Mexico. It is clear that these gentle mammals are disappearing right before our eyes.

    There are many reasons why the elephant population has been decreasing, one of which is their habitat. Humans are competing with elephants for living space, and as more and more humans clear the land that is being used by elephants, the elephants have less space. Elephant hunting or “poaching” has been a major factor for the disappearance of this species, and they are killed only for their valuable ivory tusks. Although the trade of tusks is illegal, it is still a common practice in many places.

    Often, all the local people living among elephants would be farmers, and found that they could make more money by selling the tusks of one elephant, than doing manual labor for twelve years. That alone makes it really hard to prevent them from killing the elephants.

    Some places such as Botswana, have put in extra effort to protect their wildlife from poachers by founding their Botswana Defense Force, which is made up of around 700 specially-trained soldiers that are stationed in 40 different areas. You may feel worried about the present situations elephants are in, but there are ways to help. To find out how you can help elephant conservation, adopt an elephant, or donate, click here.

    There are lots of insects that farmers hate. But there also are some they like. They protect crops against damage from other insects. A good example is the lady beetle, which is also known as the ladybug(瓢虫)．

    Lady beetles are a natural control for aphids(蚜虫). Lady beetles are red, orange or black. They often have black spots, though some have light colored spots. Different kinds of lady beetles have different numbers of spots. There are lady beetles with four, five, seven and fourteen spots.

    Many of the well-known kinds of lady beetles come from Asia or Europe. They now are common throughout the United States.

    American scientists imported one kind of lady beetle, the multicolored Asian lady beetle, as early as 1916. They released them as an attempt to control some kinds of insects. Over the years, the beetle has become established, possibly helped by some that arrived with imported plants on ships.

    Experts say over 450 kinds of lady beetles are found in North America. Some are native to the area. Others have been brought from other places. Almost all are helpful to farmers.

    The Asian lady beetles now in the United States probably came from Japan. The Asian lady beetle eats aphids that damage crops like soybeans, fruits and berries.

    In the southern United States, Asian lady beetles have reduced the need for farmers to use reskilling poisons on pecan trees. This popular tree nut suffers from aphids and other pests that the lady beetles eat.

    But some people say the Asian lady beetle has itself become a pest. They worry that the lady beetles may eat their late autumn fruit crops.

    Experts say Asian lady beetles may appear in large numbers in some years. But they say the insects are too helpful to be considered as pests.

    If you're showering every day, you're probably over doing it. In fact, showering too often can actually hurt your body in the long run.

    As Time's public health column explains, daily showers are common due to social norms more than any proper health need. We connect being freshly showered with being attractive and pleasing, so we tend to showering often to feel better.

    But what's the ideal shower frequency? In terms of your health — not how you look or smell — probably once or twice a week, assistant professor of dermatology at George Washington University, Dr. C. Brandon Mitchell says. “Your body is naturally a well-oiled machine,” he says. “A daily shower isn't necessary.”

    Of course, your situation may vary. If you have a job like car maintenance or construction, you'll obviously have a visible layer of dirt you'll need to wash off every single day. Similarly, if you work out every day, you may not have any health risks by washing every day, but you'll still be smelly. If you feel like you need to take daily showers for aesthetic（审美的）reasons, at least make most of them light showers. “I tell patients who shower daily not to soap their whole bodies,” Mitchell says. Hit your pits, butt and groin, which are the areas that produce strong smells. The rest of your body doesn't need much soaping, he says.

    Too much time spent under the hot water can dry out your skin, cause cracks（裂纹）that can lead to infections or germs getting into your skin, and take away the natural oils on your skin that help keep it healthy. So, even if you're aiming to be your most presentable, be sure to keep it moderate to avoid hurting your skin in the long run.

    Many automobile makers present their newest designs at car shows around the world. Many designers seek to create the car of the future. One device that is popular among car manufacturers(生产商) is an autopilot. Autopilot permits a car to drive itself without human control.

    A recent car show in Geneva, Switzerland also presented other possible designs, including cars manufactured in 3-D printers.

    Rinspeed is a Swiss design company. It showed a vehicle based on the US electric car Tesla Model S, but the Rinspeed car includes a large television and an espresso coffee maker.

    Frank Rinderknecht is the CEO of Rinspeed. He says he does not want to just sit and watch the steering wheel(方向盘) turn as he rides in a car with autopilot.

    "I want to ride; I want to sleep, relax, watch movies, news, anything else. So that's the vision which we have. One day on the boring motorway traffic, you just do anything which makes your life better," said Rinderknecht.

    One of the most interesting ideas presented at the show is a car built on a 3-D printer. The German engineering firm EDAG designed the car. The body of the vehicle called "Genesis" is printed in one piece from a material called thermoplastic(热塑性塑料).

    Christoph Horvath is spokesman for EDAG.

    "To create a car without the use of any tool. This would be a real revolution for the industry," said Horvath.

    EDAG says it based its design on a turtle shell. The company says the design provides the right amount of strength and firmness.

    Other automakers did not look so far into the future. Czech automaker Skoda presented its "Vision C" model vehicle. The car has an environmentally friendly natural gas engine.

    Jo Davidson is a company spokeswoman. She says the car releases very low levels of the pollutant gas CO₂. Ms Davidson says the "Vision C" plans to be launched in two years.

    All the housewives who went to the new supermarket had one great ambition: to be the lucky customer who did not have to pay for her shopping. For this was what the notice just inside the entrance promised. It said: "Remember, once a week, one of our customers gets free goods. This May Be Your Lucky Day!"

    For several weeks, Mrs Edwards hoped, like many of her friends, to be the lucky customer. Unlike her friends, she never gave up hoping. The cupboards in kitchen were full of things which she did not need. Her husband tried to advise her against buying things but failed. She dreamed of the day when the manager of the supermarket would approach her and say:" Madam, this is Your Lucky Day. Everything in your basket is free."

    One Friday morning, after she had finished her shopping and had taken it to her car, she found that she had forgotten to buy any tea. She dashed back to the supermarket, got the tea and went towards the cash-desk. As she did so, she saw the manager of the supermarket approach her. "Madam," he said, holding out his hand, "I want to congratulate you! You're our lucky customer and everything you have in your basket is free!"