完形填空. More about Alzheimer's Disease Scientists have developed skin tests that may be used in the future to identify people with Alzheimer's disease and may ultimately allow physicians to predict 1 is at risk of getting this neurological disorder. The only current means of 2 the disease in a living patient is a long and expensive series of tests that eliminate every other cause of dementia (痴呆). "Since Alois Alzheimer described the 3 nearly a century ago, people have been trying to find a way to 4 diagnose it in its early stages," said Patricia Grady, acting director of the National Institute of Neurological Disorders and Stroke in Bethesda, Maryland. "This discovery, if 5 , could prove a big step forward in our efforts to deal with and understand the disease." Alzheimer's is the single greatest 6 of mental deterioration (退化) in older people, affecting between 2.5 million and 4 million people in the United States 7 . The devastating disorder gradually destroys memory and the ability to function, and eventually causes death. There is currently no known 8 for the disease. Researches 9 that the skin cells of Alzheimer's patients have defects that interfere with their ability to regulate the flow of potassium (钾) in and out of the cells. The fact that the cell defects are present in the skin suggests that Alzheimer's 10 from physiological changes throughout the body, and that dementia may be the first noticeable effect of these changes as the defects 11 the cells in the brain, scientists said. The flow of potassium is especially 12 in cells responsible for memory formation. The scientists also found two other defects that affect the cells' supply of calcium (钙), another critical element. One test developed by researches calls 13 growing skin cells in a laboratory culture and then testing them with an electrical detector to determine if the microscopic tunnels that 14 the flow of potassium are open. Open potassium channels create a unique electrical signature. A spokesman for the Alzheimer's Association said that if the validity of the diagnostic test can be proven it would be an important 15 , but cautioned that other promising tests for Alzheimer's have been disappointing.1.

完形填空. The Greatest Mystery of Whales The whale is a warm-blooded, air-breathing animal, giving birth to its young alive, sucking them—and, like all mammals, originated on land. There are many 1 of this. Its front flippers (鳍状肢), used for steering and stability, are traces of feet. Immense strength is 2 into the great body of the big whales, and in fact most of a whale's body is one gigantic muscle. The blue whale's pulling strength has been estimated 3 400 horsepower. One specimen was reported to have towed (拖) a whaling vessel for seven hours at the 4 of eight knot (节). An angry whale will 5 . A famous example of this was the fate of Whaler Essex, 6 was sunk off the coast of South America early in the last century. More recently, steel ships have 7 their plates buckled (使弯曲) in the same way. Sperm whales (抹香鲸) were known to seize the old-time whaleboats in their jaws and crush them. The greatest 8 of whales is their diving ability. The sperm whale dives to the bottom for his 9 food, the octopus (章鱼). In that search he is known to go as far down as 3,200 feet, where the 10 is 1,400 pounds to a square inch. Doing so he will 11 underwater as long as one hour. Two special skills are involved in this storing up enough 12 (all whales are air-breathed)and tolerating the great change in pressure. Just how he does it scientists have not 13 . It is believed that some of the oxygen is stored in a special 14 of blood vessels, rather than just held in the lungs. And it is believed that a special kind of oil in his head is some sort of a compensating mechanism that 15 adjusts the internal pressure of his body. But since you can't bring a live whale into the laboratory for study, no one knows just how these things work.1.

完形填空. Cell Phone Lets Your Secret out Your cell phone holds secrets about you. Besides the names and 1 that you've programmed into it, traces of your DNA linger on the device, according to a new study. DNA is genetic material that 2 in every cell. Like your fingerprint, your DNA is unique to you— 3 you have an identical twin. Scientists today routinely analyze DNA in blood, saliva, or hair left 4 at the scene of a crime. The results often help detectives identify 5 and their victims. Your cell phone can reveal more about you 6 you might think. Meghan J. McFadden, a scientist at McMaster University in Hamilton, Ontario, heard about a crime in which the suspect bled onto a cell phone and later dropped the 7 . This made her wonder whether traces of DNA lingered on cell phones—even when no blood was involved. 8 she and her colleague Margaret Wallace of the City University of New York analyzed the flip-open phones of 10 volunteers. They used swabs to collect 9 traces of the users from two parts of the phone: the outside, where the user holds it, and the 10 , which is placed at the user's ear. The scientists scrubbed the phones using a solution made mostly 11 alcohol. The aim of washing was to remove all detectable traces of DNA. The owners got their phones 12 for another week. Then the researchers collected the phones and repeated the swabbing of each phone once more. The scientists discovered DNA that 13 to the phone's speaker on each of the phones. Better samples were collected from the outside of each phone, but those swabs also picked up DNA that belonged to other people who had apparently also handled the phone. 14 , DNA showed up even in swabs that were taken immediately after the phones were scrubbed. That suggests that washing won't remove all traces of evidence from a criminal's device. So cell phones can now be added to the 15 of clues that can clinch a crime-scene investigation.1.

完形填空. A Biological Clock Every living thing has what scientists call a biological clock that controls behavior. The biological clock tells 1 when to form flowers and when the flowers should open. It tells 2 when to leave the protective cocoons and fly away, and it tells animals and human beings when to eat, sleep and wake. Events outside the plant and animal 3 the actions of some biological clocks. Scientists recently found, for example, that a tiny animal changes the color of its fur 4 the number of hours of daylight. In the short 5 of winter, its fur becomes white. The fur becomes gray brown in color in the longer hours of daylight in summer. Inner signals control other biological clocks. German scientists found that some kind of internal clock seems to order birds to begin their long migration 6 twice each year. Birds 7 flying become restless when it is time for the trip, 8 they become calm again when the time of the flight has ended. Scientists say they are beginning to learn which 9 of the brain contain biological clocks. An American researcher, Martin Moorhead, said a small group of ceils near the front of the brain 10 to control the timing of some of our actions. These 11 tell a person when to 12 , when to sleep and when to seek food. Scientists say there probably are other biological clock cells that control other body activities. Dr. Moorhead is studying 13 our biological clocks affect the way we do our work. For example, most of us have great difficulty if we must often change to different work hours. 14 can take many days for a human body to accept the major change in work hours. Dr. Moorhead said industrial officials should have a better understanding of biological clocks and how they affect workers. He said 15 understanding could cut sickness and accidents at work and would help increase a factory's production.1.

完形填空. Preferences Vary on Circumstances of Dying Among terminally (晚期) ill people, attitudes differing on what they think constitute a 1 or bad death, the results of a new study suggest. Dr. Elizabeth K. Vig of the University of Washington in Seattle and colleagues interviewed 26 men with 2 heart disease or cancer. The men were asked to describe good and bad deaths, and they also answered 3 about their preferences for dying. In this small study, terminally ill men described good and bad deaths 4 , Vig said. They did not hold the same views about such issues 5 the presence of others at the very end of life or preferred location of death. Many of the men considered 6 in their sleep to be a good death. The reasons were varied and included not 7 that death was imminent (即将发生的), and that death would be painless. For close to half of the men, a prolonged (拖延的) death was 8 a bad death. Some of the men associated a prolonged death with prolonged pain, 9 others thought a prolonged death would be difficult for their families. Most men said that their 10 were very important to them, but this did not mean that they wanted relatives close at the 11 of death. "Valuing family did not also 12 wanting family present at the very end of life," Vig said. "In fact, some expressed concerns 13 burdening loved ones," Vig said. For instance, some men were worried about the emotional or 14 impact on their family members, according to the Washington researcher. Some were worried 15 their need for care would be a burden on their families, she said.1.

完形填空. Avalanche and Its Safety An avalanche is a sudden and rapid flow of snow, often mixed with air and water, down a mountainside. Avalanches are 1 the biggest dangers in the mountains for both life and property. All avalanches are caused by an over-burden of material, typically snowpack, that is too massive and unstable for the slope 2 supports it. Determining the critical load, the amount of over-burden which is 3 to cause an avalanche, 4 a complex task involving the evaluation of a number of factors. Terrain slopes flatter than 25 degrees or steeper than 60 degrees typically have a low 5 of avalanche. Snow does not 6 significantly on steep slopes; also, snow does not 7 easily on flat slopes. Human-triggered avalanches have the greatest incidence when the snow's angle of rest is 8 35 degrees and 45 degrees; the critical angle, the angle at which the human incidence of avalanches is greatest, is 38 degrees. The rule of thumb is: A slope that is 9 enough to hold snow but steep enough to ski has the potential to generate an avalanche, regardless of the angle. Additionally, avalanche risk increases with 10 that is, the more a slope is disturbed by skiers, the more likely it is that an avalanche will occur. Due to the complexity of the subject, winter travelling in the backcountry is never 100% safe. Good avalanche safety is a continuous 11 , including route selection and examination of the snowpack, weather 12 , and human factors. Several well- known good habits can also 13 the risk. If local authorities issue avalanche risk reports, they should be considered and all warnings should be paid 14 to. Never follow in the tracks of others without your own evaluations; snow conditions are almost certain to have changed since they were made. Observe the terrain and note obvious avalanche paths where plants are 15 or damaged. Avoid traveling below others who might trigger an avalanche.1.

完形填空 Can Loud Music Cause Hearing Impairment (损伤)

完形填空. Robots May Allow Surgery in Space Small robots designed by University of Nebraska researchers may allow doctors on Earth to help perform surgery on patients in space. The tiny, wheeled robots, 1 are about 3 inches tall and as wide as a lipstick case, can be slipped into small incisions (切口) and computer-controlled by surgeons in different locations. Some robots are equipped 2 cameras and lights and can send images back to surgeons and others, to which surgical tools are attached, can be 3 remotely. "We think this is going to 4 open surgery," Dr. Dmitry Oleynikov said at a news conference. Oleynikov is a 5 in computer-assisted surgery at the University of Nebraska Medical Center in Omaha. Officials hope that NASA will teach 6 to use the robots soon enough so that surgeries could one day be performed in space. On earth, the surgeons could control the robots themselves 7 other locations. For example, the robots could enable surgeons in other places to 8 on injured soldiers on the front line. Researchers plan to seek federal regulatory 9 early next year. Tests on animals have been successful, and tests on humans in England will begin very soon. The camera-carrying robots can provide 10 of affected areas and the ones with surgical tools will be able to maneuver (操控) inside the body in ways surgeons' hands can't. The views from the camera-carrying robots are 11 than the naked eye, because they 12 back color images that are magnified (放大). Because several robots can be inserted through one incision, they could reduce the amount and 13 of cuts needed for surgery, which would decrease recovery time. This is particularly 14 to those patients who have been debilitated (使虚弱) by long illness. Eventually, Oleynikov said that the tiny robots may enable surgeons to work without ever 15 their hands in patients' bodies. "That's the goal," Oleynikov said. "It's getting easier and easier. We can do even more with these devices."1.

完形填空. Robots May Allow Surgery in Space Small robots designed by University of Nebraska researchers may allow doctors on Earth to help perform surgery on patients in space. The tiny, wheeled robots, 1 are about 3 inches tall and as wide as a lipstick case, can be slipped into small incisions (切口) and computer-controlled by surgeons in different locations. Some robots are 2 with cameras and lights and can send images back to surgeons and others have surgical 3 attached that can be controlled remotely. "We think this is going to 4 open surgery," Dr. Dmitry Oleynikov said at a news conference. Oleynikov is a specialist 5 computer-assisted surgery at the University of Nebraska Medical Center in Omaha. Officials hope that NASA will teach 6 to use the robots soon enough so that surgeries could one day be performed in space. On earth, the surgeons could 7 the robots themselves from other locations. For example, the robots could 8 surgeons in other places to work on injured soldiers on the front line. Researchers plan to seek federal regulatory (联邦管理局的) 9 early next year. Tests on animals have been successful, and tests on humans in England will begin very soon. The camera-carrying robots can provide 10 of affected areas and the ones with surgical tools will be able to maneuver (操控) inside the body in ways surgeons' hands can't. The views from the camera-carrying robots are better than the naked eye, because they send back color images that are magnified (放大). Because several robots can be 11 through one incision, they could reduce the 12 and size of cuts needed for surgery, which would 13 recovery time. This is particularly helpful to those patients who have been debilitated (使虚弱) by long illness. Eventually, Oleynikov said, the tiny robots may enable surgeons to 14 without ever placing their hands in patients' bodies. "That's the goal;" Oleynikov said. "It's getting easier and easier. We can do even more with these 15 "1.

完形填空. Earth's Inner Core Scientists have long struggled to understand what lies at the planet's center. Direct observation of its center is impossible, so researchers must 1 to other evidence. In 1889, a German scientist detected a severe earthquake in Japan. Geophysicists concluded that shock waves 2 jolts (晃动) from one side of Earth through the center to the other side. Then in 1936, Danish geophysicist Inge Lehmann studied the waves 3 to determine that within Earth's core of molten (熔化了的) iron lies a solid inner core-but 4 that core was made of eluded (难倒) her. Other geophysicists quickly determined that Lehmann's inner core was composed mostly 5 iron. Since then, Lehmann's discovery has 6 conventional Earth science. But now scientists are challenging traditional theory with new and radical 7 . For example, Earth's center could actually contain an "inner core within the inner core, claim Ishii and colleague Adam Dziewonski. Analyzing hundreds of thousands of earthquake wave 8 , they maintain that the inner core has at its heart a tiny, even more solid sphere (球体). This sphere "may be the oldest fossil 9 from the formation of Earth," says Dziewonski. Dziewonski and Ishii speculate that shortly 10 earth formed around 4.8 billion years ago, a giant asteroid (小行星) smashed into the young planet and nearly melted it. But Earth's center didn't quite melt; it 11 mass as the planet cooled. The core within a core may be the kernel (核心) that endured. "Its presence could change our basic ideas about the 12 of the planet," Dziewonski says idea is tame (温和的) compared to the 13 theories of independent geophysicist J. Marvin Herndon. Earth's inner core is made not of iron, he claims, but a 14 of nickel and silicon. Herndon has a truly revolutionary notion: Within the nickel silicide (硅化物) inner core is also an "inner" inner core—an 8 km—wide ball of the element uranium. Uranium is radioactive. Herndon thinks the uranium releases heat energy as its atoms 15 fission-split and crash into another in a chain reaction. In other words, we may live on top of a gigantic, "natural" nuclear power plant.1.

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