Special trees that grow faster, fight pollution, produce better wood, and even sense chemical attacks are being planted by scientists in the US.

When 40 percent of Hawaii's US$14 million-a-year papaya (木瓜)industry was destroyed by a virus（病毒）five years ago, work began on creating genetically engineered(转基因的) trees.

Researchers successfully introduced seeds that were designed to resist the virus. Since then, more and more people have been testing genetically engineered trees.Some researchers put special bacteria into trees to help them grow faster and produce better wood. Others are trying to create trees that can clean polluted soil.Meanwhile fruit farmers are looking for trees that are strong enough to resist worms, and paper companies want trees that produce more wood and therefore more paper.

The Pentagon (五角大楼) even gave the researchers US$500,000 this year after they developed a pine tree that changes its colours if it senses a chemical attack..So far,the poplar, eucalyptus (杨树与桉树), apple and coffee trees are among those being engineered. All this can be done today because we have a better understanding of tree genomes(基因组).

However, some people fear that the genetically engineered trees will cause dangerous results. They are worried that the new trees will breed() with natural species and change the balance of the forest environment.

"It could be destructive," said Jim Diamond, an environmentalist. "Trees are what is left of our natural environment and home to many endangered species."

But researchers insist that science could give nature a fighting chance against both natural and man-made dangers.They hope to answer the critics by stopping the new trees from breeding, so their effect on the environment can be controlled.

Starting the day on an egg could keep your blood pressure under control, research suggests. Scientists have shown that eggs produce proteins with a function similar to that of powerful blood pressure-lowering drugs.

    The research, from the University of Alberta in Canada, showed that when eggs come in contact with stomach enzymes (酶) they produce a protein that acts in the same way as Ace inhibitors, but more work is needed to show the effects outside a lab and in the human body.

Earlier this month, British researchers declared that, contrary to popular beliefs, it is healthy to go to work on an egg. They concluded that the type of cholesterol (胆固醇) found in eggs has little effect on increasing heart disease risks.

    Researcher Professor Bruce Griffin, from the University of Surrey, said, "The wrong beliefs linking egg eating to high blood cholesterol and heart disease must be corrected. The amount of fat in our diet has an effect on blood cholesterol that is several times greater than the relatively small amounts of cholesterol found in eggs. The UK public do not need to be limiting the number of eggs they eat. They can be encouraged to include them in a healthy diet as they are one of natureˈs most nutritious foods."

    The British Heart Foundation dropped its three-egg-a-week limit in 2005. However, almost half of Britons believe the limit still applies.

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Whether in the home or the workplace,social robots are going to become a lot more common in the next few years.Social robots are about to bring technology to the everyday world in a more humanized way,said Cynthia Breazeal,chief scientist at the robot company Jibo.

While household robots today do the normal housework,social robots will be much more like companions than mere tools.For example,these robots will be able to distinguish when someone is happy or sad.This allows them to respond more appropriately to the user.

The Jibo robot,arranged to ship later this year,is designed to be a personalized assistant.You can talk to the robot,ask it questions,and make requests for it to perform different tasks.The robot doesn’t just deliver general answers to questions;it responds based on what it learns about each individual in the household.It can do things such as reminding an elderly family member to take medicine or taking family photos.

Social robots are not just finding their way into the home.They have potential applications in everything from education to health care and are already finding their way into some of these spaces.

Fellow Robots is one company bringing social robots to the market.The company’s“Oshbot”robot is built to assist customers in a store,which can help the customers find items and help guide them to the product’s location in the store.It can also speak different languages and make recommendations for different items based on what the customer is shopping for.

The more interaction the robot has with humans,the more it learns.But Oshbot,like other social robots,is not intended to replace workers,but to work alongside other employees.“We have technologies to train social robots to do things not for us,but with us,”said Breazeal.

Most of the suggestions about exercise are pretty clear— do something—anything—to get moving. Any activity is better than no activity, so simply letting the body move is what's important. And there's a good reason for the simplicity of that message—with one third of Americans not exercising at all, the easier the advice, the better

   But for those who follow those suggestions and get regular exercise, things could be a little more difficult to deal with. How far is too far when it comes to pushing your body? Overdoing exercise can lead to injuries, and may end up removing all the benefits physical activity can have.

   Our bodies are trained to adapt, so even if you run or bike every day, at a certain point, your body starts to coast. Your muscles don't work as hard, your heart doesn't beat as quickly, and you don't breathe as heavily to pump oxygen to your cells. "When you hit a plateau (稳定状态), it is your body getting used to an activity. You have achieved your body's potential for that activity." says Scott Danberg, Director of Fitness. "If you keep working at the same activity, it's impossible sometimes to keep moving up. It means you are still in great shape, but you have to start changing things to move forward."

   So how do you make sure that your exercise continues to work for you? Some fitness trainers recommend changing workouts every four to six weeks to strengthen the body. Others say that the best test is whether your workout challenges you—if you're breathing hard and feel tired after exercising, then you're harvesting the benefits of that workout, whatever it might be.

   And how do you know if you're pushing too hard? While putting some stress on the body is required to improve fitness, Barbara Bushman, a professor at Missouri State University, says exercise overload can cause injury. "Typically for beginners, gradual increases in duration (期间) are recommended until the person is comfortable with longer exercise duration. Then the duration might be cut back a bit but the stress increased. The idea is not to increase all areas at once," she says.

   Figuring out when to push and when to pull back isn't an exact science. Genes, for example, influence metabolic rates(代谢速率)and body types, both of which contribute to fitness. One of the best ways to find the most effective exercise plan for you—suited to your body type and your fitness goals—is to regularly step back. A doctor or trainer can help, or you can try the assessments (评估)from the American College of Sports Medicine (ACSM). A good check-in should include your heart rate and body composition. Tracking these measures while you exercise will not only tell you how far you have progressed, but let you know if you've either hit a plateau or are overdoing the workouts.

A new study shows that fat people in the United States suffer direct economic(经济的) and social effects because of their size. The findings are from an 8-year study of about 100 000 people. The people studied were between the ages of 16 and 24 when the research began.

The researchers who carried out the study say they consider the people fat if they are in the top of 5% of the measurement in which weight is connected with height. For example, fat women in the study were about 160 centimeters tall and weighed about 90  kilograms. Fat men in the study were about 175 centimeters tall and weighed 100  kilograms. The researchers say that more than 1, 000, 000 Americans are that big. The researchers found that fat young women were more likely to lose social and economic power even if they were form wealthy families. The fat women also were 20% less likely to get married and they earned an average of about $6 700 a year less than other women. The study showed less severe effect on fat men. They earned an average of about $3 000 a year less than other men. Fat men also were 11% less likely to get married.

We find different kinds of animals in the world. Some animals, such as   (1)    and lions, live in big forest and they are called   (2)    animals. Some others like sheep and dogs are kept by men and they are called domestic animals. These animals are very different from one another, but we can   (3)   them into big groups: those that eat other animals and those that eat grass and leaves. Animals like the tiger   (4)    to the first group   (5)    eat other animals.

Animals are   (6)    great use to human beings. Men hunt wild animals for their fur and meat. Domestic animals are   (7)    more important to men. Without them, life will be difficult. People make use of animals in many   (8)   .

Cows and pigs are useful to men’s food. They give 80% of the   (9)    men eat every year. Skin of some animals can be   (10)    into expensive overcoats and shoes, which are warm and comfortable and   (11)   a long time. They are very popular in   (12)    countries. Wool, which is now one of the most important materials for textile（纺织）   (13)   , comes from some certain   (14)   . From cows, we get   (15)   . And we shouldn’t   (16)    that some domestic animals are kept for   (17)   , for example, many people   (18)    ride horses. Arabs ride on camels that travel in deserts for days without   (19)   . In some places animals are still used to plough field.   (20)    is clear that men just can’t live without these animals.

Our risk of cancer rises sharply as we age. So it makes sense that the elderly should be routinely screened for new tumors(肿瘤)—or doesn’t it?

While such vigilant(警觉的) tracking of cancer is a good thing in general, researchers are increasingly questioning whether all of this testing is necessary for the elderly. With the percentage of people over 65 expected to nearly double by 2050, it’s important to consider the health benefits of screening against the risks and costs of routine testing.

In many cases, screening can lead to surgeries to remove cancer, while the cancers themselves may be slow-growing and may not have serious health problems in patients’ remaining years. But he message that everyone must screen for cancer has become so deep-rooted that when health care experts recommended that women under 50 and over 74 stop screening for breast cancer, it caused a fierce reaction among doctors, patients and groups who are in favor of the screening.

It’s hard to remove deeply held beliefs about cancer screening with scientific data. Certainly, there are people over age 75 who have had cancers detected by routine screening, and gained several extra years of life because of treatment. And clearly, people over age 75 who have other risk factors for cancer, such as a family history or formerly personal experience with the disease, should continue to get screened regularly. But for the remainder, the risk of cancer, while increased at the end of life, must be balanced with other factors like remaining life expectancy(预期寿命).

A recent study suggests that doctors start to make more objective decisions about who will truly benefit from screening—especially considering the explosion of the elderly that will soon increase in our population.

It’s not an easy calculation to make, but one that makes sense for all patients. Dr. Otis Brawley said, “Many doctors are ordering screening tests purely to cover themselves. We need to think about the reasonable use of health care.”

That means making some difficult decisions with elderly patients, and going against the misguided belief that when it comes to health care, more is always better.

A warm drink of milk before bed has long been the best choice for those wanting a good night’s sleep. But now a study has found it really does help people nod off—if it is milked from a cow at night.

   Researchers have discovered that “night milk” contains more melatonin (褪黑激素), which has been proven to help people feel sleepy and reduce anxiety.

   The study, by researchers from Seoul, South Korea, involved mice being fed with dried milk powder made from cows milked both during the day and at night.

   Those given night milk, which contained 10 times the amount of melatonin, were less active and less anxious than those fed with the milk collected during daytime, according to the study published in The Journal of Medicinal Food.

   Night milk quickened the start of sleep and caused the mice to sleep longer.

   While the effect of cows’ milk harvested at different time has not been tested on humans up to now, taking melatonin drugs has been suggested to those who are struggling to fall asleep at night.

   Previous studies have also indicated that milk can be excellent for helping sleep because of the calcium content, which helps people to relax.

   Milk is also sugar-free and additive-free with nutritionists recommending skimmed milk as the best choice before bed as it is the least fattening. The more fat you take in before bedtime, the greater burden you will put on your body at night.

Why elephants rarely get cancer is a mystery that has confused scientists for decades. A study was led by researchers at Huntsman Cancer Institute(HCI)at the University of Utah and Arizona State University, including researchers from the Ringling Bros. Center for Elephant Conservation may have found the answer.  According to the results, elephants have 38 additional modified copies of a gene(基因)that encodes p53, a well-defined tumor(肿瘤)suppressor, as compared to humans, who have only two.  Further, elephants may have a more powerful mechanism for killing damaged cells that are at risk for becoming cancerous.  In isolated elephant cells, this activity is doubled compared to healthy human cells, and five times that of cells from patients with Li-Fraumeni Syndrome, who have only one working copy of p53 and more than a 90 percent lifetime cancer risk in children and adults. The results suggest extra p53 could explain elephants’ increased resistance to cancer.

 “Nature has already figured out how to prevent cancer.  It’s up to us to learn how different animals overcome the problem so we can adapt those strategies to prevent cancer in people, ”says co-senior author Joshua Schiffman, M. D. , pediatric oncologist(肿瘤学家)at Huntsman Cancer Institute, University of Utah School of Medicine, and Primary Children’s Hospital.

 According to Schiffman, elephants have long been considered a walking problem.  Because they have 100 times as many cells as people, they should be 100 times more likely to have a cell slip into a cancerous state and cause the disease over their long life span of 50 to 70 years. And yet it’s believed that elephants get cancer less often, a theory confirmed in this study.  Analysis of a large database of elephant deaths estimates a cancer death rate of less than 5 percent compared to 11 to 25 percent in people.