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In fact, there was hardly any activity or social event that could not be set to Music. Weddings, births, christening, funerals, picnics, parades-- 21 had their musical accompaniment.After the American Civil War (1860-1865), the Negroes had gained their freedom and were ready 22 a new type of music, 23 that would preserve their musical traditions but be fast and happy 24 their 25 freedom. They wanted something they could play as professional musicians for both black and white audiences. Jazz was the answer. It combined themes from Negro work songs, spirituals and blues, set to a fast beat, 26 the musicians improvising (即兴而作) as they went along, like the funeral marching bands. To be good, a musician had not only to remember his part but also 27 able to invent new variations on the spur (激励) of the moment.Jazz 28 the people, but popular 29 is changed many times in form, style, and tempo. Each change added something 30 . 29()
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教师职业的最大特点是职业角色的多样化。( )
Part B Directions: You are going to read a text about the topic of nuclear fusion, followed by a list of examples. Choose the best example from the list A-F for each numbered subheading (41-45). There is one extra example which you do not need to use. Mark your answers on ANSWER SHEET 1. (10 points) Scientists say they have achieved small-scale nuclear fusion in a tabletop experiment, using tried and true techniques that are expected to generate far less controversy than past such claims. This latest experiment relied on a tiny crystal to generate a strong electric field. While the energy created was too small to harness cheap fusion power, the technique could have potential uses in medicine, spacecraft propulsion, the oil drilling industry and homeland security, said Seth Putterman, a physicist at the University of California at Los Angeles. Putterman and his colleagues at UCLA, Brian Naranjo and Jim Gimzewski, report their results in Thursday’s issue of the journal Nature. 41. Held up to ridicule Previous claims of tabletop fusion have been met with skepticism and even derision by physicists. 42. Sound theoretical basis Fusion experts said the UCLA experiment will face far less skepticism because it conforms to well-known principles of physics. 43. Energy in waiting Fusion power has been touted as the ultimate energy source and a cleaner alternative to fossil fuels like coal and oil. Fossil fuels are expected to run short in about 50 years. 44. Process of fusion In the UCLA experiment, scientists placed a tiny crystal that can generate a strong electric field into a vacuum chamber filled with deuterium gas, a form of hydrogen capable of fusion. Then the researchers activated the crystal by heating it. 45. Commercial uses UCLA’s Putterman said future experiments will focus on refining the technique for potential commercial uses, including designing portable neutron generators that could be used for oil well drilling or scanning luggage and cargo at airports. In the Nature report, Putterman and his colleagues said the crystal-based method could be used in "microthrusters for miniature spacecraft." In such an application, the method would not rely on nuclear fusion for power generation, but rather on ion propulsion, Putterman said. "As wild as it is, that s a conservative application, "he said.[A] In fusion, light atoms are joined in a high-temperature process that frees large amounts of energy. It is considered environmentally friendly because it produces virtually no air pollution and does not pose the safety and long-term radioactive waste concerns associated with modern nuclear power plants, where heavy uranium atoms are split to create energy in a process known as fission.[B] The resulting electric field created a beam of charged deuterium atoms that struck a nearby target, which was embedded with yet more deuterium. When some of the deuterium atoms in the beam collided with their counterparts in the target, they fused. The reaction gave off an isotope of helium along with subatomic particles knoun as neutrons, a characteristic of fusion. The experiment did not, however, produce more energy than the amount put in--an achievement that would be a huge breakthrough.[C] Another technique, known as sonoluminescence, generates heat through the collapse of tiny bubbles in a liquid. Some scientists claim that nuclear fusion occurs during the reaction, but those claims have sparked sharp debate.[D] In a Nature commentary, Michael Saltmarsh of the Oak Ridge National Laboratory said the process was in some ways "remarkably low-tech," drawing upon principles that were first recorded by the Greek philosopher Theophrastus in 314 B. C.. "This doesn’t have any controversy in it because they’re using a tried and true method," David Ruzic, professor of nuclear and plasma engineering at the University of Illinois at Urbana-Champaign, told The Associated Press. "There’s no mystery in terms of the physics."[E] In one of the most notable cases, Dr. B. Stanley Pons of the University of Utah and Martin Fleischmann of Southampton University in England shocked the world in 1989 when they announced that they had achieved so-called cold fusion at room temperature. Their work was discredited after repeated attempts to reproduce it failed.[F] The technology also could conceivably give rise to implantable radiation sources, which could target cancer cells while minimizing damage to healthy tissue. "You could bring a tiny crystal into the body, place it next to a tumor, turn on the radiation and blast the tumor," Putterman told MSNBC. com. 41
"A rolling stone gathers no moss(苔藓) ," but there is one living animal that does gather moss, the three-toed sloth (树獭) of South America. This slowest-moving member of the animal kingdom is so inactive that moss actually gathers on its body and turns it green——strange as it seems!Most of the sloth’s life is spent motionless, hanging upside down from a limb. And that is the way its hair grows. Long and coarse, the strands (串) from receptacles (花托) for the damp jungle algae (水藻) that turn the brown fur a mossy green. Actually this moss helps the animal survive because it serves as a perfect camouflage against the leaf trees and hides the sloth from the jungle’s swift - moving hunters. The sloth would have little chance of survival on the ground. With long, curved claws hooked over the limb of a leafy tree, it spends the long hot hours during the day drowsing and eating. Inch by inch, it strips the leafy limbs bare and crawls slowly down the trunk to find a new dining spot, but only at night.In addition to looking rather like a vegetable, the sloth is a strict vegetarian. Running out of its favorite leaf is about the only thing that will make a sloth move. Then its appetite may even force the animal into swimming a stream to reach a juicy succulent(多汁的植物). It will also force it into fighting to keep the tree all to itself. The sloth is lazy and prefers to be alone, but it will tolerate its own relatives! The author’s purpose in writing the passage is ()
A.trueB.tuneC.fluteD.June
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