It’s a sure sign that summer is over and winter is on the way — leaves that were once deep green turn red, yellow and bright orange. It happens every autumn. But did you ever wonder why?

The leaves start changing color when the nights start getting longer and the temperature starts getting cooler. Some scientists think that as the number of daylight hoursshrinks,the leaves stop making chlorophyll which makes plants green. The reason is that the process of making chlorophyll requires sunlight. But according to horticulture (园艺) educator Susan Rose from Colorado State University, it turns out leaves don’t really change color at all.“The fall colors are actually there all along,” she said.“But they are covered by the green chlorophyll. As the chlorophyll stops being produced, the other colors can shine through.”

The kind of color that the leaves are going to change to is determined by the plant’s genetic (基因的) background. In some places, the leaves start changing color in September— before autumn even officially begins. In other places, they don’t change until late October or even November. Some scientists say the leaves have been changing color later than usual in recent years. And they think global warming has something to do with that.

In one study, researchers found that the growing season in the Northern Hemisphere was nearly a week longer, on average, in 2008 than it was in 1982. And a professor from Harvard University found that the leaves, west of Boston, Massachusetts, are changing color about three days later than they used to. However, other scientists disagree with the global warming theory. Susan Rose said the leaves in her part of Colorado are changing “right on schedule.” But the leaves in other parts of that state are running a little late. “The lateness in the mountains may have something to do with the really warm late summer and early fall,” she said. “But I’m afraid that’s just a guess.”

Jaguars（美洲虎）are the largest cat in North and South America．Their range extends from south of Mexico to Argentina．But in the past hundred years’ logging（伐木），the growth of cities have disturbed more than half of the cats’ main habitat，forcing them into living in small groups in different places．

   Conservationists used to focus on protecting these habitats．But biologists realize now that young jaguars move from one place to another in their hunt for mates and new land．They may trek（长途跋涉）up to 500 miles through the edges of civilization．It is a dangerous journey that takes them far from the shelter of the jungle．

   Scientist Alan Rabinowitz is president of an organization devoted to saving wild cats．One day，while studying a map of all the known areas jaguars live in，Rabinowitz decided to play a game of connecting the dots (小圆点）．He drew a line between one area and another area．Suddenly he was struck by an idea that could help save this threatened species．

   Rabinowitz realized that protecting the pathways is just as important as protecting the habitats themselves．He began an international project called“Path of the Jaguar”to check these pathways and make sure they won’t become dead ends．“A jaguar，unlike a human，is not stopped by many things，”Rabinowitz says．“It’s not stopped by a river or even a mountain covered in snow．”But things such as factories，highways and dams will halt a jaguar in its tracks，forcing it off course．

   Rabinowitz’s project works to persuade countries to limit industrial development that would block Jaguars’ pathways．These protected areas are not always connected．But these cats are smart — they run across open land in the dark．If they find a jungle with something to eat，they’ll stop to rest，just as you might pull over at a restaurant during a family road trip．

Your house may have an effect on your figure . Experts say the way you design your home could play a role in whether you pack on the pounds or keep them off . You can make your environment work for you instead of against you . Here are some ways to turn your home into part of diet plan.

Open the curtains and turn up the lights . Dark environments are more likely to encourage overeating , for people are often less self-conscious（难为情）when they’re in poorly lit places-and so more likely to eat lots of food . If your home doesn’t have enough window light , get more lamps and flood the place with brightness.

Mind the colors . Research suggests warm colors fuel our appetites . In one study , people who ate meals in a blue room consumed 33 percent less than those in a yellow or red room . Warm colors like yellow make tood appear more appetizing , while cold colors make us feel less hungry . So when it’s time to repaint , go blue.

Don’t forget the clock-or the radio. People who eat slowly tend to consume about 70 fewer calories（卡路里） per meal than those who rush through their meals. Begin keeping track of the time, and try to make dinner last at least 30 minutes, And while you’re at it, actually sit down to eat. If you need some help slowing down , turn on relaxing music. It makes you less likely to rush through a meal.

Downsize the dishs, Big serving bowls and plates can easily make us fat. We eat about 22 percent more when using a 12-inch plate instead of a 10-inch plate. When we choose a large spoon over a smaller one ,total intake（摄入） jumps by 14 percent. And we’ll pour about 30 percent more liquid into a short, wide glass than a tall, skinny glass.

The behaviour of a building's users may be at least as important as its design when it comes to energy use, according to new research from the UK Energy Research Centre (UKERC). The UK promises to reduce its carbon emissions(排放) by 80 per cent by 2050, part of which will be achieved by all new homes being zero­carbon by 2016. But this report shows that sustainable(可持续的) building design on its own—though extremely important—is not enough to achieve such reductions: the behaviour of the people using the building has to change too.

The study suggests that the ways that people use and live in their homes have been largely ignored by existing efforts to improve energy efficiency(效率)，whichinstead focus on architectural and technological developments.

“Technology is going to assist but it is not going to do everything，” explains Katy Janda, a UKERC senior researcher，“consumption（消费） patterns of building users can defeat the most careful design.”In other words，old habits die hard, even in the best­designed eco­home.

Another part of the problem is information. Households and bill-payers don't have the knowledge they need to change their energy-use habits. Without specific information，it's hard to estimate the costs and benefits of making different choices. Feedback(反馈) facilities, like smart meters and energy monitors，could help bridge this information gap by helping people see how changing their behaviour directly affects their energy use; some studies have shown that households can achieve up to 15 per cent energy savings using smart meters.

Social science research has added a further dimension(方面)，suggesting that individuals' behaviour in the home can be personal and cannot be predicted—whether people throw open their windows rather than turn down the thermostat(恒温器), for example.

Janda argues that education is the key. She calls for a focused programme to teach people about buildings and their own behaviour in them.

Plants are flowering faster than scientists predicted（预测）in reaction to climate change, which could have long damaging effects on food chains and ecosystems.

    Global warming is having a great effect on hundreds of plant and animal species around the world, changing some living patterns, scientists say.

    Increased carbon dioxide（CO2）in the air from burning coal and oil can have an effect on how plants produce oxygen, while higher temperatures and changeable rainfall patterns can change their patterns of growth.

    “Predicting species’ reaction to climate change is a major challenge in ecology,” said the researches of several U.S. universities. They said plants had been the key object of study because their reaction to climate change could have an effect on food chains and ecosystem services.

    The study, published on the Nature website, uses the findings from plant life cycle studies and experiments across four continents and 1,634 species. It found that some experiments had underestimated（低估）the speed of flowering by 8.5 times and leafing by 4 times.

    “Across all species, the experiments under-predicted the speed of the advance — for both leafing and flowering — that results from temperature increases,” the study said.

    The design of future experiments may need to be improved to better predict how plants will react to climate change, it said.

    Plants are necessary for life on the Earth. They are the base of the food chain, using photosynthesis（光合作用）to produce sugar from carbon dioxide and water. They let out oxygen which is needed by nearly every organism on the planet.

    Scientists believe the world’s average temperature has risen by about 0.8 ℃ since 1900, and nearly 0.2 ℃ every ten years since 1979.

    So far, efforts to cut emissions（排放）of planet-warming greenhouse gases are not seen as enough to prevent the Earth heating up beyond 2 ℃ this century — a point scientists say will bring the danger of a changeable climate in which weather extremes are common, leading to drought, floods, crop failures and rising sea levels.

You can’t always predict a heavy rain or remember your umbrella. But designer Mikhail Belvacv doesn’t think that forgetting to check the weather forecast before heading out should result in you getting wet. That’s why he created lampbrella, a lamp post with its own rain sensing umbrella.

The designer says he come up with the idea after watching people get wet on streets in Russia. “once, I was driving on a central Saint Petersburg street ad saw the street lamps lighting up people trying to hide from the rain. I thought it would be appropriate to have a canopy(伞蓬)built into a street lamp.” he said.

The lampbrella is a standard-looking street lamp fitted with an umbrella canopy. It has a built-in electric motor which can open or close the umbrella on demand. Sensors(传感器)then ensure that the umbrella offers pedestrians shelter whenever it starts raining.

In addition to the rain sensor, there’s also a 360°motion sensor on  the biberglass street lamp which detects whether anyone’s using the lampbrella. After three minutes of not being used the canopy is closed.

According to the designer, the lampbrella would move at a relatively low speed, so as not to cause harm to the pedestrians. Besides, it would be grounded to protect from possible lighting strike. Each lampbrella would offer enough shelter for several people. Being installed at 2 meters off the ground, it would only be a danger for the tallest of pedestrians.

While there are no plans to take lampbrella into production, Belyacv says he recently introduced his creation one Moscow Department, and insists this creation could be installed on my street where a lot of people walk but there are no canopies to provide shelter.

The bed should be reserved as a place for sleep, but people tend to read an iPad a lot in bed before they go to sleep.

Charles Czeisler, a professor at Harvard Medical School, and his colleagues got a small group of people for an experiment. For five days in a row, the people read either a paper book or an iPad for four hours before sleep. Their sleep patterns were monitored all night. Before and after each trial period, the people took hourly blood tests to paint a day-long picture of just how much melatonin (褪黑激素) was in their blood at any given time.

When subjects read on the iPad as compared to the paper books, they reported feeling less sleepy at night and less active the following morning. People also took longer to fall asleep on the iPad nights, and the blood tests showed that their melatonin secretion (分泌) was delayed by an hour and a half.

The researchers conclude in today’s journal article that given the rise of e-readers and the increasingly widespread use of e-things among children and adolescents, more research into the long-term consequences of these devices on health and safety is urgently needed. Czeisler and colleagues go on, in the research paper, to note: “Reading an iPad in bed may increase cancer risk.”

However, software has been developed that can reduce some of the blue light from the screens of phones and computers according to time of day, and there are also glasses that are made to filter (过滤) short wavelengths. While they seem like a logical solution for the nighttime tech users, it needs more research.

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Automation refers to the introduction of electronic control and automatic operation of productive machinery. It reduces the human factors, mental and physical, in production, and is designed to make possible the manufacture of more goods with fewer workers. The development of automation in American industry has been called the “Second Industrial Revolution”.
   Labour’s concern over automation arises from uncertainty about the effects on employment, and fears of major changes in jobs. In the main, labour has taken the view that resistance to technical change is unfruitful. Eventually, the result of automation may well be an increase in employment, since it is expected that vast industries will grow up around manufacturing, maintaining, and repairing automation equipment. The interest of labour lies in bringing about the transition with a minimum of inconvenience and distress to the workers involved. Also, union spokesmen emphasize that the benefit of the increased production and lower costs made possible by automation should be shared by workers in the form of higher wages, more leisure, and improved living standards.
   To protect the interests of their members in the era of automation, unions have adopted a number of new policies. One of these is the promotion of supplementary unemployment benefit plans. It is emphasized that since the employer involved in such a plan has a direct financial interest in preventing unemployment, he will have a strong drive for planning new installations so as to cause the least possible problems in jobs and job assignment. Some unions are working for dismissal pay agreements, requiring that permanently dismissed workers be paid a sum of money based on length of service. Another approach is the idea of the “improvement factor”, which calls for wage increases based on increases in productivity. It is possible, however, that labour will rely mainly on reduction in working time.

  Water goes around and around Earth in a never ending journey called the water cycle(循环). The sun heats up lakes, oceans, and other wet places on Earth. When the water gets warm enough, it changes into vapour. Plants also give off lots of water vapour. Some of this water vapour cools off high in the sky and becomes clouds. Then it falls back to Earth in a new place as rain or snow. This cycle happens over and over again.

　　The ground can absorb water like a sponge (海绵). If you could see this groundwater, it wouldn’t look like a lake or river. The groundwater is mixed in with the rocks and sand that lie in layers(层) below Earth’s surface.

　　Groundwater moves along slowly. How slowly? Maybe 1.5 kilometres in one century. Some of this water has been underground for thousands of years. And once groundwater is pumped out of the ground from a deep well(井) by people, it may take hundreds of years for another water to take its place.

The movies just wouldnˈt be the same without the warm buttery taste of popcorn. Amazingly，this delicious treat started its life as a corn kernel(玉米粒)—and not from just any corn. Popcorn is a type of sweet corn that was originally grown in Mexico and spread to China，India and elsewhere. It is the only kind of corn that will pop. Today，most of the worldˈs popcorn is grown in the United States.

Every popcorn kernel contains a tiny drop of water，surrounded by soft starch(淀粉)．When the popcorn is heated，the water turns into steam.This puts pressure on the surrounding hard kernel，forcing it to explode.The soft starch increases about 40 times in size as the corn kernel turns itself inside out.

In the 1500s popcorn was an important food source for the Aztec Indians of central and southern Mexico.But it wasnˈt only food.It was also used in ceremonies or in headdresses and necklaces.By the time the Europeans arrived in America，popcorn had spread through most of the American Indians.

Some early American settlers ate popcorn with cream and sugar for breakfast.But it wasnˈt until the late 1800s that popcorn became popular.The demand for popcorn increased and farmers began farming popcorn.The first mobile popping machine was invented in 1885，and popcorn was sold by street sellers much like hot dogs are sold today.

During the Great Depression of the 1930s，the popcorn business still thrived as people could still afford it.Then in the 1950s television arrived and popcorn consumption decreased.People stayed home and stopped going to the theatre.But the link between movies and popcorn had already existed.Soon people began making popcorn at home on the stove.Later，microwave popcorn was introduced.

Today the movies have regained popularity and popcorn has once again become the favorite.