Our body clock, or natural body rhythm, influences our energy and alertness. Paying attention to it can help us choose the suitable time of the day when we best perform specific tasks.

    The reality, however, is that most of us organize the time around work demands, school deadlines, commuting or social events. Doing whatever the body feels like doing is a luxury in today's fast-paced modern society.

    But that doesn't mean it isn't worth trying. Obeying our body clock has significant health benefits. Disrupting our natural body rhythm, on the other hand, has been linked to problems such as depression, obesity, or headache, says Steve Key, a biology professor.

    When the body clock can synchronize (使…同步) the rhythms of its natural processes, it “gives us an advantage in daily life”, says Key.

    According to him, when it comes to cognitive (认知的) work, most adults perform best in the late morning. As our body temperature starts to rise just before awakening in the morning and continues to increase until midday, our memory, alertness and concentration gradually improve.

    However, he adds, our ability to concentrate typically starts to decrease soon thereafter. Most of us are more easily distracted (分心) between noon and 4 pm.

    Alertness also tends to fall after eating a meal and sleepiness tends to peak around 2 pm, making that a good time for a nap.

    Surprisingly, tiredness may increase our creative powers. For most adults, problems that require open-ended thinking are often best dealt with in the evening when they are tired, according to a study in the journal Thinking & Reasoning.

    When choosing a time of the day to exercise, paying attention to your body clock can improve results. Physical performance is usually best from about 3 to 6 pm, says Michael Smolensky, a professor of biomedical engineering.

    Of course, not everyone's body clock is the same, making it even harder to synchronize natural rhythms with daily plans.

    At one time, computers were expected largely to remove the need for paper copies of documents(文件) because they could be stored electronically. But for all the texts that are written, stored and sent electronically, a lot of them are still ending up on paper.

    It is difficult to measure the quantity of paper used as a result of use of Internet-connected computers, although just about anyone who works in an office can tell you that when e-mail is introduced, the printers start working overtime. “I feel in my bones this revolution is causing more trees to be cut down ,” says Ted Smith of the Earth Village Organization.

    Perhaps the best sign of how computer and Internet use pushes up demand for paper comes from the high-tech industry itself, which sees printing as one of its most promising new markets. Several Internet companies have been set up to help small businesses print quality documents from a computer. Earlier this week Hewlett-Packard Co. announced a plan to develop new technologies that will enable people to print even more so they can get a hard copy of a business document, a medical record or just a one-line e-mail, even if they are nowhere near a computer. As the company sees it, the more use of the Internet the greater demand for printers.

    Does all this mean environmental concerns have been forgotten? Some activists suggest people have been led to believe that a lot of dangers to the environment have gone away.

    “I guess people believe that the problem is taken care of, because of recycling,” said Kelly Quirke, director of the Rainforest Action Network in San Francisco. Yet Quirke is hopeful that high-tech may also prove helpful. He says printers that print on both sides are growing in popularity.

    The action group has also found acceptable paper made from materials other than wood, such as agricultural waste.

    Australian scientists are trying to give kangaroo-style stomachs to cattle and sheep in order to cut the greenhouse gases they send out, which is thought to be responsible for global warming.

    Thanks to special bacteria in their stomachs, kangaroo flatulence (肠胃气胀) contains no methane and scientists want to transfer that bacteria to cattle and sheep who produce large quantities of the harmful gas.

    While the usual image of greenhouse gas pollution is a billowing smokestack, pushing out carbon dioxide, farm animals' passing wind contribute a surprisingly high percentage of total emissions in some countries.

    “Fourteen percent of emissions from all sources in Australia are from enteric methane from cattle and sheep,” said Athol Klieve, a senior research scientist with the greensland state government. “And if you look at another country such as New Zealand, which has got a much higher agricultural base, they are actually up around 50 percent,” he said.

    Researchers say the bacteria also make the digestive process much more efficient and could potentially save millions of dollars in feed costs for farmers. But it will take researchers at least three years to isolate the bacteria before they can even start to develop a way of transferring it to cattle and sheep.

    Another group of scientists, meanwhile, have suggested Australians should farm fewer cattle and sheep and just eat more kangaroos. And about 20 percent of health-conscious Australians are believed to eat the national symbol already.

    It's low in fat, it's got high protein levels and it is very clean in the sense that basically it is free-range(放养的) animal,” said Peter Ampt of the University of New South Wales' institute of environmental studies.

    World Book Day falls on April 23 every year．It was set up by the United Nations Educational,Scientific, and Cultural Organization(UNESCO) in 1995 to encourage people, especially teenagers, to discover the pleasure of reading．It is also the day to honor great writers，for example，William Shakespeare，born or dead on that day．

    Many countries celebrate World Book Day．Take UK as an example．On that day，millions of school children can buy books of special price，a much lower price than usual，in any bookstore．It has been done every year since 1998．World Book Day is also celebrated in China. Our Former Premier Wen Jiabao, a bookworm, who does lots of reading every day, has called on people to do more reading. He suggested that young people should spend more time reading．"Books cannot change the world, but people can change the world by changing themselves through reading,” he said．

    Why do people like reading? One big advantage is that reading helps us become more knowledgeable and more intelligent. Also, reading helps us to follow the latest developments of science and technology. Besides, reading gives us information about other cultures and places of the world. When we read, we may find many things that are unfamiliar to us. We would have to use our brain to think about them or do more reading to find out the answers. The more we read, the more we know. What's more, reading is also one of the most important ways to learn a foreign language like English．

    "Reading makes a full man" (Bacon，1597). Books，magazines，newspapers and other kinds of materials can help us to know more about the outside world and perfect us. So it is necessary for us to spend time on reading every day．

    The possibility of self-driving robot cars has often seemed like a futurist's dream, years away from coming into reality in the real world. Well, the future is apparently now. The California Department of Motor Vehicles began giving permits in April for companies to test truly self-driving cars on public roads. The state also cleared the way for companies to sell or rent out self-driving cars, and for companies to operate driverless taxi services. California, it should be noted, isn't leading the way here. Companies have been testing their cars in cities across the country. It's hard to predict when driverless cars will be everywhere on our roads. But however long it takes, the technology may change our transportation systems and our cities, for better or for worse, depending on how the transformation is managed.

    While much of the debate so far has been focused on the safety of driverless cars, policymakers should be talking more about how self-driving cars can help reduce traffic jams, cut emissions(排放)and offer more convenient and affordable choices to move around. The arrival of driverless cars is a chance to make sure that those cars are environmentally friendly and more shared.

    Do we want to copy or even worsen the traffic of today with driverless cars? Imagine a future where most adults own their self-driving cars. They accept long, slow journeys to and from work on crowded highways because they can work, entertain themselves or sleep on the ride. They take their driverless car to a date and set the empty car to circle the building to avoid paying for parking. Instead of walking a few blocks to pick up a child or the dry cleaning, they send the self-driving minibus. The convenience even leads fewer people to take public transport — an unwelcome side effect researchers have already found in ride-hailing(网约车)services. Policymakers should start thinking now about how to make sure the appearance of driverless cars doesn't worsen the transportation system we have today. The coming technological development presents a chance for cities and states to develop transportation systems designed to move more people, and more affordably. The car of the future is coming. We just have to plan for it.

    Wolves travel shorter distances and move slower during snowfall events, according to new research by University of Alberta biologists. The effects were most pronounced at night, when wolves hunt, and behaviour returned to normal within a day. Wolf tracks across snow in northeastern Alberta.

    "Our findings suggest that there is something about actively falling snow that causes wolves to slow down," said Amanda Droghini, a former MSc student in the Department of Biological Science and lead author on the study. "We don't know the exact mechanism behind that. It's unlikely that they were staying still because they were feasting on a recent kill. Instead, active precipitation(降雪量)might affect wolves' hunting abilities. Like rain, snow clears the air column of scent molecules. So, maybe falling snow makes it harder for wolves to detect the smell of prey."

    Over the course of two winters, the researchers used remote cameras to disclose snowfall events and estimate snow depth. To study wolf movement, they collected telemetry(测距仪) data from 17 wolves to calculate travel speed and duration, as well as resting periods. It is the first study to examine how large flesh-eating animals respond to snowfall events.

    With the effects of climate change on precipitation in the north forest region uncertain, it is difficult to predict the implications for wolf populations. Studies such as these increase our understanding of how large mammals react to normal snowfall events, but the type and amount of winter precipitation will likely have an impact on animal behavior and the energetic cost of movement.

    "Winter is already challenging for many wildlife species because moving through snow requires more energy. Snow can also make it harder for animals to access food resources," said Droghini, who conducted the research under the supervision of Professor Stan Boutin, Alberta Biodiversity Conservation Chair.

    "Anything that increases those costs, such as increased rain-on-snow events, could lead to lacking in nutrition, poor body condition, and even starvation as animals are unable to make up for those additional costs. That is one of the worst-case scenarios(设想)but, in truth, we know very little about potential changes to precipitation patterns and how wildlife will respond to those changes."