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.

Word of the Day Writing Competition

    Days are getting colder, and everyone is slowly backing to the warm comfort of their homes. It's the best opportunity to make good use of the quietness and peace of the season by taking pen and paper(or a computer) out to write.

OxfordWords of Oxford University Press(OUP) is calling all aspiring(有抱负的) authors out there to take part in our writing competition. What we're looking for are imaginative(富有想象力的) short stories—not more than 500 words—that include every Word of the Day (WOTD) from November.

    Each entry will be carefully considered by the OxfordWords team before deciding on a winner. The best storyteller will be given a year's fee to OxfordDictionaries.com, as well as ￡50 worth of OUP books, and have his or her piece published on that website.

    Before you get started, please make sure you're read our terms and conditions. Entries can be submitted(递交) through the entry form, or posted into the comment section. Closing date for the competition is 5th January 2015.

    And finally, for inspiration, have a look at the charming short story that gives us the idea for this competition, written by a fellow Oxford Dictionaries team member, and including all thirty one Words of the Day from October.

    Find out more about our Word of the Day service and sign up to receive the words via email, or on Facebook, Google, and Twitter.

根据短文内容，选择最佳答案，并将选定答案的字母标号填在题前括号内。

    On the morning of May 20, 1927, Charles A. Lindbergh Jr. took off from a muddy airfield in New York and headed for Paris. During the first fourteen hours of flying, he had had some anxious moments. Sleet had gathered on the wings of the plane and the fog was so thick that he could hardly see the tips of the wings. However, he had come across equally dangerous flying conditions before. Of course, now that he was over the ocean, his parachute（降落伞）was useless. He had only one choice: he had to go on.

    Although he had waited a long time to make this trip, he did not feel strange or nervous. He was accustomed to flying alone, and he had flown this route in his imagination many times. The idea of flying across the Atlantic had occurred to him one night when he had been carrying the mail between St. Louis and Chicago. That night, he told himself that a solo non-stop flight between New York and Paris was possible. He knew that airplanes capable of making the long flight over the ocean could be built. A man of skill and endurance could make his dream come true.

    As he was recalling that night, he reduced the altitude of the plane. Close to the surface of the ocean, he found that the ice on the wings began to melt and the fog disappeared. For the time being, at least, he was safe. The steady sound of the motor seemed like music in his ears. He had perfect confidence in his plane because he knew that there was not a more dependable plane than his. The Ryan Aircraft Company had constructed the plane to meet his special needs. He had worked with the chief engineer of the company, Donald Hall, to produce the airplane as rapidly as possible. Although Hall had worked with the basic design of the Ryan airplane, he had had to make many modifications. As a result, it was a very special airplane. He had named it “The Spirit of St. Louis,” in honour of the St. Louis businessmen whose financial backing had made the trip possible. Besides their money, he had invested all of his own savings, which came to two thousand dollars, in the venture.

    At 12:10 on the afternoon of May 21, Lindbergh caught sight of the coast of Ireland. Now that the flight was almost over, he began to relax a little. Finally, after thirty-four hours in the air without sleep, he arrived at Le Bourget Field, in Paris.

    If your dog looks pleased to see you—it is probably because it loves the particular way you smell.

    The scent (气味)of a familiar human apparently lingers like perfumein the animal's brain—where it causes an instinctive emotional response, research reveals.

    Our scent acts on a part of the canine (犬科的) brain associated with reward and the strongest reactions are produced by humans that pets know best, say scientists in America.

    Gregory Bern, of Emory University in Atlanta, said, “While we might expect that dogs should be highly tuned to the smell of other dogs, it seems that the 'reward response' is reserved for their humans. When humans smell the perfume of someone they love, they may have an immediate, emotional reaction that's not necessarily cognitive (认识的). So is it in dogs. But since dogs have a more sensitive smell than humans, their responses would likely be even more powerful than the ones we might have. In our experiment, however, the owners of the dog were not physically present. The canine brain responses were being caused by something distant in space and time. It shows that dogs' brains have these mental representations of us that persist when we're not there.”

    The experiment involved 12 dogs of various kinds by brain scans while five different scents were placed in front of them. The scent samples (样本)came from the subject (接受试险者) itself, a dog the subject had never met, a dog living in the subject's household. The familiar human scent samples were taken from someone else from the house other than the handlers during the experiment, so that none of the scent donors were physically present.

    The results showed all five scents gained a similar response in parts of the dogs brains involved in detecting smells. Responses were significantly stronger for the scent of familiar humans, followed by that of familiar dogs. The findings showed dogs reacted strongest to the scent of familiar humans even when they were not there. Pets trained as help or therapy dogs showed greater brain activity than the other dogs in the test.

    Researchers say the findings could improve the way to select animals helping wounded old soldiers or disabled people.

    That the US stock market dropped sharply immediately after the US government put forward the proposal on Tuesday to tighten the control on exports of various artificial intelligence technologies indicates what the market thinks of the move.

    Multi-national corporations have led the way in the profound compressing(压缩) of time and space that has flattened and changed the world over the last couple of decades, and the overwhelming majority of international technological transfers have been conducted among multi-national companies in pursuit of profits.

    Thus the proposal the US government put forward on Tuesday to tighten the control to "avoid negatively impacting US leadership in the science, technology, engineering and manufacturing sector" is being viewed not only as a brake on the US economy but also as a barrier to maintaining that leadership since it will reduce cooperation with the rest of the world and shrink the market for US companies preventing them from investing research and development.

    The bigger its market, the more profits a technology company can earn, and the more money it then has to invest in developing even more advanced technologies. This is as true for US companies as it is for others.

    Behind the proposal is the narrow-mindedness of policymakers in the US administration, who choose to ignore the fact that the United States would not have become the world leader in science and technology if it had kept its doors closed.

    If such controls are intended to contain China's development, they will certainly fail.

    It is true that China has a lot to do to catch up with the US and other developed countries. Yet it has made great steps forward by opening its doors and cooperating with other economies.

    As it opens its door wider, it will have even more opportunities to cooperate with other countries in science and technology.

The de-materialization of economic activities — with economic output and income generation increasingly reliant on information rather than inputs of raw materials — only increases the need for cooperative agreements and a cross-disciplinary approach to increase the capabilities of AI and advance its application.

    By trying to enforce and exploit an invented-here ideal that is untenable, the US will undoubtedly lose the leadership in science and technology gradually to which it has become accustomed, and prevent the progress of both humans and machines.

    People love cellphones, which is why nine in ten Americans own one. But does heavy use of cellphones pose a risk of cancer? This question has caused controversy for many years. A new study in rats now augments those concerns. Its data linked long-term, intense exposure to radiation from cellphones with an increased risk of cancer in the heart or brain. The results have yet to be confirmed, the authors note.

    Indeed, although the rat study found a link between cellphone radiation and cancer, it offers no clues to why such a link might exist, notes Jonathan Samet. He teaches preventative medicine and directs the Institute for Global Health at the University of Southern California in Los Angeles. Still, he calls the new study's findings “significant”.They could lead to studies researching how cellphone radiation might cause cancer, he says.

    Phone signals are relayed between cell towers and cellphones via radio waves. This radio frequency—or RF—radiation is a type known as non-ionizing (非电离的).Unlike X-rays, non-ionizing radiation does not deposit enough energy into cells to release electrons from atoms or molecules, producing ions. So it tends to be far less harmful than ionizing radiation, such as X-rays. But that does not mean radio waves might not cause harm.

    In very large doses (量) this radiation will heat the body and cause tissue damage. But it's not yet known what much lower RF levels might do, such as those from cellphone use. Five years ago, the World Health Organization's International Agency for Research on Cancer, or IARC, concluded that cellphone use “is possibly carcinogenic (致癌的)”.

    Its conclusion was based on what little research data was available at that time. But notice that IARC was not certain. It said only that phone use might “possibly” cause cancer. So scientists at the National Toxicology Program, or NTP, investigated further.