单项选择题How sleep helps us consolidate memories is still largely a mystery. A recent study from the University of Lǔbeck, in Germany, offers one clue. Subjects were given a list of 46 word pairs to memorize, just before sleep. Then when they reached the deepest stages of sleep, electrical currents were sent through electrodes on their heads to induce very slow brain waves. Such slow waves were induced at random in the brains of one group of subjects, but not another.
The next morning, the slow-wave group had better recall of the words. Other types of memory were not improved, and inducing the slow waves later in the night did not have the same effect. Why and how the slow waves improved memory is not yet understood, but they are thought to alter the strengths of chemical connections, or synapses, between specific pairs of nerve cells in the brain. Memories are "stored" in these synapses: changing the strength of the synapses increases the strength of the memories they store.
Slow waves functioned in the subjects’ brains in the experiment when
The next morning, the slow-wave group had better recall of the words. Other types of memory were not improved, and inducing the slow waves later in the night did not have the same effect. Why and how the slow waves improved memory is not yet understood, but they are thought to alter the strengths of chemical connections, or synapses, between specific pairs of nerve cells in the brain. Memories are "stored" in these synapses: changing the strength of the synapses increases the strength of the memories they store.
Slow waves functioned in the subjects’ brains in the experiment when
A. they were given a list of words before sleep.
B. they reached the deepest stages of sleep.
C. they were connected to electrical currents.
D. they were asked to recall the words the next mornin
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2.单项选择题The first generation of dot-corns burned through cash rapidly because they had to spend a lot of money building and running their businesses—marketing and advertising to get the word out, not to mention software, consultants, and programmers to run online systems and" analyze theresults. Thanks to Web 2.0, many of these costs have plummeted. Many of the basics are nowessentially free, which means a business built on the infrastructure laid down by the first two generations of Web companies can gain scale on a shoestring budget, all while giving away its products and services for free. Call it Web 2.5.
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3.单项选择题With regular exercise, the body builds up its levels of BDNF (brain-derived neurotrophic factor), and the brain’s nerve cells start to branch out, join together and communicate with each other in new ways. This is. the process that underlies learning: every change in the junctions between brain cells signifies a new fact or skill that’s been picked up and stowed away for future use. BDNF makes that process possible. Brains with more of it have a greater capacity for knowledge. On the other hand, says UCLA neuroscientist Fernando Gámez-Pinilla, a brain that’s low on BDNF shuts itself off to new information,
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4.单项选择题The people who are to be happy fix their attention on the conveniences of things, the pleasant pans of conversation, the well-prepared dishes, the goodness of the wines, the fine weather. They enjoy all the cheerful things. Those who are to be unhappy think and speak only of the contrary things. Therefore, they are continually discontented. By their remarks, they sour the pleasure of the society, offend many people, and make themselves disagreeable everywhere. If this turn of mind were founded in nature, such unhappy persons would be the more to be pities. The tendency to criticize and be disgusted is perhaps taken up originally by imitation. It grows into a habit, unknown to its possessors. The habit may be strong, but it may be cured when those who have it are convinced of its bad effects on their interests and tastes. I hope this little warning may be of service to them, and help them change this habit.
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6.单项选择题Unfortunately, the new swine flu virus can be transmitted between humans. It is not clear yet how easily it is transmitted, nor how it is transmitted. Almost surely it is transmitted by sneezing and coughing, and by skin-to-skin contact with an infected person.
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Newton’s publishing ofhis work on gravity resulted in that
A. Newton became the best known scientist.
B. his corpuscular theory of light was accepted.
C. scientists would believe in Newton only.
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