单选题There are______differences between theory and practice.(2010年北京航空航天大学考博试题)

单选题{{B}}Passage 4{{/B}} For years pediatricians didn't worry much about treating hypertension in their patients. After all, kids grow so fast, it's hard keeping up with their shoe size, let alone their blood pressure. Sure, hypertension in adults places them at greater risk of heart, attack and stroke. But nobody likes the idea of starting youngsters on blood-pressure medicine they could wind up taking the rest of their lives. Who knows what previously unheard-of side effects could crop up after five or six decades of daily use? The rationale has been: kids grow out of so many things, maybe they'll grow out of this too. Now, though, comes word that high blood pressure can be destructive even in childhood. According to a recent report in the journal Circulation, 19of 130children with high blood pressure developed a dangerous thickening of the heart muscle that, in adults at least, has been linked to heart failure. "No one knows if this pattern holds true for younger patients as well," says Dr. Stephen Daniels, a pediatric cardiologist who led the study at Children's Hospital Medical Center in Cincinnati, Ohio. "But it's worrisome." Who's most at risk? Boys more man girls, expecially boys who are overweight. Their heart works so hard to force blood through extra layers of fat that its walls grow more dense. Then, after decades of straining, it grows too big to pump blood very well. Fortunately the abnormal, thickering can be spotted by ultrasound. And in most case, getting that blood pressure under control--through weight loss and exercise or, as a last resort, drug treatment--allows the overworked muscle to shrink to normal size. How can you tell if yours are like the 670, 000 American children ages 10 to 18 with high blood pressure? {{B}}It's not the sort of thing you can catch by putting your child's arm in a cuff at the free monitoring station in your local grocery.{{/B}} You should have a test done by a doctor, who will consult special tables that indicate me normal range of blood pressure for a particular child's age, height and sex. If the doctor finds an abnormal result he will repeat the test over a period of months to make sure the reading isn't a fake. He'll also check, whether other conditions, like kidney disease, could be the source of the trouble. Because hypertension can be hard to detect the National Heart. Lung and Blood Institute recommends annual blood-pressure checks for every child over age 3. About half the eases of hypertension stem directly from kids being overweight. And the problem is likely to grow. Over the past 30 years the proportion of children in the U. S. who are overweight has doubled, from 5% to 11% or4.7 million kids. You can keep your children from joining their ranks by clearing the junk food from your pantry and honking your kids--the earlier the better--on healthy, attractive snacks like fruits (try freezing some grapes/or carrot sticks with salsa. Not only will they lower your children's blood pressure: these foods will also boost their immune system and unclog their plumbing. Meanwhile, make sure your kids spend more time on the playground than with their PlayStation. Even if they don't shed a pound, vigorous exercise will help keep their blood vessels nice and wide, lowering their blood pressure. And of course, they'll be more likely to eat light and exercise if you set a good example.

单选题As one works with color in a practical or experimental way, one is impressed by two apparently unrelated facts. Color as seen is a mobile changeable thing depending to a large extent on the relationship of the color to other colors seen simultaneously. It is not fixed in its relation to the direct stimulus which creates it. On the other hand, the properties of surfaces that give rise to color do not seem to change greatly under a wide variety of illumination colors, usually (but not always) looking much the same in artificial light as in daylight. Both of these effects seem to be due in large part to the mechanism of color adaptation mentioned earlier. When the eye is fixed on a colored area, there is an immediate readjustment of the sensitivity of the eye to color in and around the area viewed. This readjustment does not immediately affect the color seen but usually does affect the next area to which the gaze is shifted. The longer the time of viewing, the higher the intensity, and the larger the area, the greater the effect will be in terms of its persistence in the succeeding viewing situation. As indicated by the work of Wright and Shouted, it appears that, at least for a first approximation, full adaptation takes place over a very brief time if the adapting source is moderately bright and the eye has been in relative darkness just previously. As the stimulus is allowed to act, however, the effect becomes more persistent in the sense that it takes the eye longer to regain its sensitivity to lower intensities. The net result is that, if the eye is so exposed and then the gaze is transferred to an area of lower intensity, the loss of sensitivity produced by the first area will still be present and appear as an "afterimage" superimposed on the second. The effect not only is present over the actual area causing the "local adaptation" but also spreads with decreasing strength to adjoining areas of the eye to produce "lateral adaptation." Also, because of the persistence of the effect if the eye is shifted around from one object to another, all of which are at similar brightness or have similar colors, the adaptation will tend to become uniform over the whole eye.

单选题Nanotechnology, according to its fans, will jump-start a new industrial revolution with molecular-sized structures as complex as the human cell and 100 times stronger than steel. The new technology transforms everyday products and the way they are made by manipulating atoms so that materials can be shrunk, strengthened and lightened all at once. To date only modest nanotech-based products—such as stain-resistant fabrics and fresh food packaging—have entered the market, but some scientists predict nanotechnology will eventually be the only game in town. "It will be a ubiquitous technology," said George Stephanopoulos, professor of chemical engineering at the Massachusetts Institute of Technology. He echoes other nanotech supporters who say industrial countries are already sliding toward its use in every aspect of manufacturing. Aided by recent advances in microscopes, scientists can now place single atoms where they want for the first time. The potential applications are numerous, with microscopic computers, cancer-killing antennae and nonpolluting car engines on the distant horizon. When it's all going to happen, though, is another matter. According to most scientific accounts, the nanotech future may be 10 to 20 years off. Major hurdles need to be jumped. First, there is a lack of economic mass production. Some of the more complicated devices would require exact placement of billions of atoms. "It may take the lifetime of the universe to complete the construction of (such a) device," said George Barbastathis, assistant professor at MIT. Another challenge is bridging the nanoscale and macroscopic, he said. In other words, the smallness of a nano device is useless when it must be attached to large wires. It's unclear how scientists will overcome these problems. And fears derived from science fiction threaten to derail nanotechnology even as it emerges, in much the same way popular anxiety over "super-weeds" and "frankenfoods" have hobbled biotechnology in agriculture and fear of "designer babies" has set back stem-cell research. Lured by a market with billions of dollars in potential profits, giants like GE, Intel, Motorola and IBM are already heavily involved in research. Worldwide, the two industries with the potential to win big with nanotechnology are electronics and biotechnology, according to MIT researchers. On the biotech front, scientists are promoting the notion of nanoparticles made from gold that could be triggered remotely to heat and kill individual cancer cells. Nanotechnology holds equal promise for wealth creation, hut there isn't a consensus among venture capitalists on how to realize it. "Which direction is it going to work out in? That's the question on everyone's mind," Gang Chen, an associate professor at the MIT, told scientists at a Boston nano gathering.

单选题The company used so much coal that it has a train to______the delivery process. (2004年上海理工大学考博试题)

单选题Building this road will ______ the construction of ten bridges, and then the total cost reaches 1 million US dollars. A. evolve B. involve C. revolve D. devolve

单选题As online computer systems become more popular, televisions and computers are increasingly______. Such technologies combine the capabilities of computers, television etc, and greatly expand the services that can be provided.

单选题A young man sees a sunset and, unable to understand or express the emotion that it ______ in him, concludes that it must be the gateway to a world that lies beyond.

单选题We do deal with paintings here, but this is ______ a furniture shop.

单选题There is a hotel in the______ neighborhood.

单选题Our bodies are wonderfully skilful at maintaining balance. When the temperature jumps, we sweat to cool down. When our blood pressure falls, our hearts pound to compensate. As it turned out, though, our natural state is not a steady one. Researchers are finding that everything from blood pressure to brain function varies rhythmically with the cycles of sun, moon and seasons. And their insights are yielding new strategies for keeping sway such common killers as heart disease and cancer. Only one doctor in 20 has a good knowledge of the growing field of "chronotherapeutics (历时治疗术)", the strategic use of time (chronos) in medicine. But according to a new American Medical Association poll, three out of four are eager to change that. "The field is exploding," says Michael Smolensky. "Doctors used to look at us like "What spaceship did you guys get off?" Now they"re thirsty to know more." In medical school, most doctors learn that people with chronic conditions should take their medicine at steady rates. "It"s a terrible way to treat disease," says Dr. Richard Martin. For example, asthmatics (气喘患者) are most likely to suffer during the night. Yet most patients strive to keep a constant level of medicine in their blood day and night, whether by breathing in on an inhaler (吸器) four times a day or taking a pill each morning and evening. In recent studies, researchers have found that a large mid-afternoon dose of a bronchodilator (支所管张剂) can be as safe as several small doses, and better for preventing nighttime attacks. If the night belongs to asthma, the dawn belongs to high blood pressure and heart disease. Heart attacks are twice as common at 9 a.m. as at 11 p.m. Part of the reason is that our blood pressure falls predictably at night, then peaks as we start to work for the day. "Doctors know that," says Dr. Henry Black of Chicago Medical Center, "but until now, we haven"t been able to do anything about it." Most blood pressure drugs provide 18 to 20 hours of relief. But because they"re taken in the morning, they"re least effective when most needed. "You take your pill at 7 and it"s working by 9," says Dr. William White of the University of Connecticut Health Center, "but by that time you"ve gone through the worst four hours of the day with no protection." Bedtime dosing would prevent that lapse, but it would also push blood pressure to dangerously low levels during the night.

单选题Superficial differences between the special problems and techniques of the physical sciences and those of the biological sciences are sometimes cited as evidence for the ______ of biology and for the claim that the methods of physics are therefore not adequate to biological inquiry.(2014年北京航空航天大学考博试题)

单选题Borders these days have little meaning for Singapore-based regional ______ of electronics firms like Sanyo and Philips.

单选题Probably there is a good reason for her absence, as she doesn"t usually stay away from work.

单选题Which of the following is NOT the reason that the woman thinks Yoshida is qualified for the position?

单选题English ______ in idioms, and so does Chinese.(2008年北京航空航天大学考博试题)

单选题Despite their intense pain and suffering, the Black men found a small measure of comfort in ______.