After years of heated debate, gray wolves were reintroduced to Yellowstone National Park. Fourteen wolves were caught in Canada and transported to the park. By last year, the Yellowstone wolf population had grown to more than 170 wolves.

Gray wolves once were seen here and there in the Yellowstone area and much of the continental United States, but they were gradually displaced by human development. By the 1920s, wolves had practically disappeared from the Yellowstone area. They went farther north into the deep forests of Canada, where there were fewer humans around.

The disappearance of the wolves had many unexpected results. Deer and elk populations — major food sources (来源) for the wolf — grew rapidly. These animals consumed large amounts of vegetation (植被), which reduced plant diversity in the park. In the absence of wolves, coyote populations also grew quickly. The coyotes killed a large percentage of the park’s red foxes, and completely drove away the park’s beavers.

As early as 1966, biologists asked the government to consider reintroducing wolves to Yellowstone Park. They hoped that wolves would be able to control the elk and coyote problems. Many farmers opposed the plan because they feared that wolves would kill their farm animals or pets.

The government spent nearly 30 years coming up with a plan to reintroduce the wolves. The U.S. Fish and Wildlife Service carefully monitors and manages the wolf packs in Yellowstone. Today, the debate continues over how well the gray wolf is fitting in at Yellowstone. Elk, deer, and coyote populations are down, while beavers and red foxes have made a comeback. The Yellowstone wolf project has been a valuable experiment to help biologists decide whether to reintroduce wolves to other parts of the country as well.

  Every now and then，a product comes along that proves itself a complete game－changer; as is the case with new British brand and invention，Eyejusters － the reading glasses that you can focus yourself － for less than ￡70！

      With 6 in 10 people wearing glasses in the UK，those with perfect vision are increasingly in the minority. And of those who do require glasses，many find themselves requiring two or three pairs of glasses in order to complete different tasks throughout the day. As well as being an added expense on top of everything else，this also means carrying around （and trying not to lose） those extra pairs！

      Evejusters allow you to instantly change the lens（镜片） strength of your glasses with hidden dials，tucked just inside the frames themselves. Eyejusters work by the wearer simply turning the concealed eyeDials to change the focus to fit your needs. The lenses adjust from ＋0.00 to ＋3.00 D，they also have anti－scratch technology and are lightweight in design so you aren't paying the price of comfort for convenience.

      The creator of Eyejusters，Owen Reading － who came up with the idea for Eyejusters with friend David Crosby，who studied physics at Oxford with him，explained: "Lots of people need reading glasses but they need glasses with lots of different strengths. They might have a pair with ＋l prescription－strength lenses for the computer，＋2s for reading and ＋3s for really close－up stuff. Eyejusters replace the need for multiple pairs of reading glasses，by covering the whole range from zero to ＋3，which is the strongest you will find in over－the－counter products."

      He added: "If you wear reading glasses，these are a much more flexible alternative. You can put them on and just turn the dial until what you want to see comes into focus. They are much like using binoculars（望远镜）."

Gray wolves once were seen here and there in the Yellowstone area and much of the continental United States, but they were gradually displaced by human development. By the 1920s, wolves had practically disappeared from the Yellowstone area. They went farther north into the deep forests of Canada, where there were fewer humans around.

The disappearance of the wolves had many unexpected results. Deer and elk populations—major food sources(来源) for the wolf—grew rapidly. These animals consumed large amounts of vegetation(植被), which reduced plant diversity in the park. In the absence of wolves, coyote populations also grew quickly. The coyotes killed a large percentage of the park’s red foxes, and completely drove away the park’s beavers.

As early as 1966, biologists asked the government to consider reintroducing wolves to Yellowstone Park. They hoped that wolves would be able to control the elk and coyote problems. Many farmers opposed the plan because they feared that wolves would kill their farm animals or pets.

The government spent nearly 30 years coming up with a plan to reintroduce the wolves. The U．S. Fish and Wildlife Service carefully monitors and manages the wolf packs in Yellowstone. Today, the debate continues over how well the gray wolf is fitting in at Yellowstone. Elk, deer, and coyote populations are down, while beavers and red foxes have made a comeback. The Yellowstone wolf project has been a valuable experiment to help biologists decide whether to reintroduce wolves to other parts of the country as well.

Scientists recently found three animal species living two miles below the surface of the Mediterranean Sea. They’re multicellular (多细胞的) and look like tiny umbrellas with legs. But they are animals. The most exciting thing about these creatures, say the scientists，is that they don’t need oxygen to live. What biologists know about life so far is that only single-celled organisms (有机体)can live in places that have no oxygen，and that multicellular organisms can visit these places, but not live there. These newly found creatures could change that idea.

They live in a part of the world called LˈAtalante Basin.The basin is a super-salty lake that is at the bottom of the Mediterranean Sea and about 120 miles west of the island of Crete. It may seem strange to think of a lake under a sea，but the water in the lake is so salty that it canˈt mix with the seawater above it.

Ordinary seawater has oxygen in it which allows animals like fish to live, but the super-salty waters of LˈAtalante Basin donˈt have oxygen. Finding animals down there was so surprising that the scientists couldnˈt believe it. At first, “we thought they were dead，”Roberto Danovaro said. Roberto worked on the recent study and is a scientist at the Polytechnic University of Marche in Italy.

To find out whether the animals could actually live in the basin, and to be sure the animals werenˈt dead, Roherto and his colleagues brought up more samples from the ocean floor. They placed the samples in small containers filled with nitrogen，which kept out oxygen. Studying the animals in the containers showed that the animals appeared to be alive.

The researchers did more tests, and found that some of the animals had eggs, which suggests they were reproducing. These clues suggest the animals donˈt need oxygen, but scientists still have not observed how the animals live without oxygen. This means more studies are needed, but the scientists think theyˈre on the right track.

Most people are aware that outdoor air pollution can damage their health, but many do not know that indoor air pollution can also have significant health effects. Environmental Protection Agency studies indicate that indoor levels of pollutants(污染物) may be 2～5 times, and occasionally more than 100 times, higher than outdoor levels. These levels of indoor air pollutants may be of particular concern because most people spend about 90％ of their time indoors.

There are many sources of indoor air pollution in any home. These include combustion（燃烧）sources such as oil, gas, coal, wood, and tobacco products; building materials and furnishings such as wet or damp carpet, furniture made of certain pressed wood products; products for household cleaning and maintenance, personal care or hobbies; central heating and cooling systems and humidification devices(加湿器); and outdoor sources such as pesticides（农药）, and outdoor air pollution.

Immediate effects may show up after a single exposure or repeated exposures. These include irritation of the eyes, nose, and throat, headaches, dizziness(晕眩), and fatigue(乏力). Such immediate effects are usually short-term and treatable. Sometimes the treatment is simply eliminating(清除) the person’s exposure to the source of the pollution, if it can be identified. Symptoms(症状) of some diseases, including asthma, hypersensitivity, pneumonitis, and fever, may also show up soon after exposure to some indoor air pollutants.

The likelihood of immediate reactions to indoor air pollutants depends on several factors. Age and pre-existing medical conditions are two important influences. In other cases, whether a person reacts to a pollutant depends on individual sensitivity, which varies tremendously from person to person. Some people can become sensitized to biological pollutants after repeated exposures, and it appears that some people can become sensitized to chemical pollutants as well.

Certain immediate effects are similar to those from colds or other viral diseases, so it is often difficult to determine if the symptoms are a result of exposure to indoor air pollution. For this reason, it is important to pay attention to the time and place the symptoms occur. If the symptoms fade or go away when a person is away from the home and return when the person returns, an effort should be made to identify indoor air sources that may be possible causes. Some effects may be made worse by an inadequate supply of outdoor air or from the heating, cooling, or humidity conditions prevalent in the home.

“He looks red.” “I’m feeling blue.” “She was green.” How often have you heard these expressions? They are actually fairly common. And they show how color relates to our emotions.

  Actually, color does have physical effect on the human body. It can influence the pituitary gland (脑下垂体), which helps control hormone production. Hormones can affect our moods, so it makes sense that color would, too. But it can also be used to change our moods.

  How do colors relate to moods and emotions?

  Red is all about energy, but it can also indicate anger.

  Orange is simulating, good for times when we just can’t seem to get started with something. It may be useful for reducing stress.

  Yellow is good for mental activities like reasoning and analysis. It can promote self—confidence and is helpful in situations when you need to be more optimistic.

  Green tends to make most people think of nature, since so much of the natural world is green. It’s about connections—with nature, or with our fellow humans. It’s also good for general stress, since it can help balance emotions.

  Blue is relaxing. It can stimulate creativity. Light blue can mean quiet, and dark blue can be depressing.

  White is definitely about peace. But it’s also associate with purity.

  How can you use colors to change your mood? Well, clothing is the most obvious choice. What you wear not only helps you feel a certain way, but also can give a strong impression about you to others—especially people you have never met.

  But you don’t have to change everything about your appearance. Sometimes a cap, a tie or a scarf, in a particular color will have the desired effect—without being too noticeable to others.

There are an extremely large number of ants worldwide.Each individual(个体的)ant hardly weighs anything,but put together they weigh roughly the same as all of mankind.They also live nearly everywhere,except on frozen mountain tops and around the poles.For animals their size,ants have been astonishingly successful,largely due to their wonderful social behavior.

In colonies(群体)that range in size from a few hundred to tens of millions,they organize their lives with a clear division of labor.Even more amazing is how they achieve this level of organization.Where we use sound and sight to communicate,ants depend primarily on pheromones(外激素),chemicals sent out by individuals and smelled or tasted by fellow members of their colony.When an ant finds food,it produces a pheromone that will lead others straight to where the food is.When an individual ant comes under attack or is dying,it sends out an alarm pheromone to warn the colony to prepare for a conflict as a defense unit.

In fact,when it comes to the art of war,ants have no equal.They are completely fearless and will readily take on a creature much larger than themselves,attacking in large groups and overcoming their target.Such is their devotion to the common good of the colony that not only soldier ants but also worker ants will sacrifice their lives to help defeat an enemy. 

Behaving in this selfless and devoted manner,these little creatures have survived on Earth for more than 140 million years,far longer than dinosaurs.Because they think as one,they have a collective(集体的)intelligence greater than you would expect from its individual parts.

The dangers of sitting all day are obvious. Researchers have shown that remaining sitting for extended periods of time (like at your 9-to-5 desk job) can do harm to your health. While exercise is a big part of reducing the harmful effects of sitting, it was unclear how many gym periods were needed to help – until now.

A new study, published in The Lancet, shows the ideal formula for reducing the negative effects of a sedentary（久坐的）job. Instead of a fixed number of hours spent exercising, the ratiodepends on how much you sit: people who work a typical eight-hour day should spend at least one hour each day moving. If you sit six hours a day, you should spend half an hour exercising. The research also indicates that the exercise doesn’t have to be all once – or rigorous（严格的）. It can be spread throughout the day and be as simple as walking.

The team behind the study analyzed data from a pool of a million adults over the age of 45 in Western Europe, the United States, and Australia. Using previous data, the researches examined data from 16 published studies and used it to determine how much exercise is required to compensate for sitting. Their recommended daily exercise goal is higher than previous advice but not necessarily less achievable, given it can be completed throughout the day.

Fitting in an hour of exercise a day sounds especially discouraging if you have a desk job, but there are plenty of workouts you can complete before and after work. Even if it means taking a 10-minute walk during lunch, your body will thank you in the long run.

The sun’s ultraviolet(UV) rays can do more a tan(棕褐色) or burn. Indeed, their influence goes more than skin deep, a new study finds. It showed that exposure to ultraviolet light causes mice to make a feel-good chemical, and this chemical may explain why so many people want to get a tan. The study may also help explain why people flock o beaches and coasts for relaxation, Steven Feldman said. He studies public health and skin diseases.

   High-energy, UV rays come from the sun and the special lights used in tanning booths. Even though people know UV radiation can be dangerous, they continue to risk sunburns for a tan. Rates of skin cancer have been going up. David Fisher wanted to know why. He is an oncologist- a doctor who treats people with cancer- at Massachusetts General Hospital in Boston. “We know UV light is dangerous,” Fisher says, but many people choose not to protect themselves.

   Fisher and his colleagues exposed mice to a moderate amount of UV light five days a week, for six weeks. The scientists shaved the mice so the light would reach their skin. The animals received an exposure to UV light that was similar to what a fair-skinned person gets after 20 or 30 minutes in the Florida sun. After just a week of the UV treatment, mice had higher levels of molecule in their blood called beta-endorphin (内啡肽) than mice not exposed to this radiation did. Similar to drugs such as heroin and opium, beta-endorphin activates feel-good processes in the brain. Previous studies had found beta-endorphin in the skin. This new study showed the molecule also ends up in the blood. UV light didn’t boost beta-endorphin for very long, though. Levels returned to normal a week after the UV treatments stopped. And the mice didn’t seem to have wanted those treatments to end. In fact, they showed signs of an addiction to this light.

   Fisher’s group gave a drug, called naloxone(Naa-LOX-ohn), to the UV-treated mice. Doctors prescribe this drug to people who have been abusing heroin. It blocked the places in the brain where heroin triggers the feel-good response. When a heroin addict receives naxolone, the drug can set off withdrawal symptoms within minutes. In the UV-treated mice, the drug seemed to block the feel-good effects of UV exposure. It also caused chattering teeth and shaking in the animals. Those symptoms looked similar to what people go through when they are suffering from withdrawal from heroin.

  The new data is “fascinating”, David Fisher said. Still, she says, the new study falls short of proving the mice had become addicted to UV light. “Addiction” means craving, loss of control and tolerance,” he explains. And the new study “didn’t look at any of those things.”

C

I am Peter Hodes, a volunteer stem cell courier. Since March 2012, I've done 89 trips — of those, 51 have been abroad. I have 42 hours to carry stem cells (干细胞) in my little box because I've got two ice packs and that's how long they last. In all, from the time the stem cells are harvested from a donor (捐献者) to the time they can be implanted in the patient, we've got 72 hours at most. So I am always conscious of time.

I had one trip last year where I was caught by a hurricane in America. I picked up the stem cells in Providence, Rhode Island, and was meant to fly to Washington then back to London. But when I arrived at the check-in desk at Providence, the lady on the desk said: "Well, I'm really sorry, I've got some bad news for you—there are no flights from Washington." So I took my box and put it on the desk and I said: "In this box are some stem cells that are urgently needed for a patient—please, please, you've got to get me back to the United Kingdom." She just dropped everything. She arranged for a flight on a small plane to be held for me, re-routed (改道) me through Newark and got me back to the UK even earlier than originally scheduled.

For this courier job, you're consciously aware that in that box you've got something that is potentially going to save somebody's life.

Which of the following can replace the underlined word "courier" in Paragraph 1?