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计算机病毒是可以造成计算机故障的一种计算机( )。
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在会计电箅化信息系统的开发与应用中，( )是电算化系统的应用阶段。
Trillions of incredibly tiny diamonds, possibly formed by a dying star before the solar system was born 4.5 billion years ago, have been found by researchers (26) four meteorites. The powder-like diamonds could be among the oldest things in the (27) , said Roy Lewis, senior research associate at the University of Chicago. The diamonds may (28) clues about the chemistry of stars, and if scientists can determine how they formed, that could suggest better ways of manufacturing tiny diamonds for (29) purposes, he said. "It’s quite possible that nature is doing it more (30) than we’ve been doing it," he said. "So maybe we’ve got something to learn." The new find is (31) , said John Wood, staff scientist at the Harvard-Smithsonian Centre for Astrophysics. Although diamonds have been found before in meteorites, they were formed relatively recently (32) the shock of impact, he said in a telephone interview. But Wood said the new report made him "quite sure" the newly found diamonds are older than the sun. Lewis said researchers never expected to find diamonds when they started (33) a stone-like meteorite that had plunged into Mexican cornfield in 1969. They were studying an unusual carbon dust in the meteorite, and to purify the sample they went though several steps to dissolve other materials. They expected the sample to remain black through the purification, but to their surprise in the final step it turned (34) . Lewis said they believed the final stage had dissolved the carbon they wanted to study. But tests showed that the white residue was in fact made of carbon. Other tests found that it contained an unusual combination of forms of the gas xenon, (35) that it came from outside the solar system. Still another battery of tests (36) the residue as diamond dust, so fine that a row of 20,000 grains would extend about the (37) of a human hair. The researchers also found diamonds in three other meteorites, Lewis said. Tests showed all four meteorites were as old as the solar system, and that the embedded diamonds did not form within the meteorite (38) of collisions. So the diamonds must have (39) somewhere else before the meteorites formed, making them as old or older than the solar system. The diamonds may have formed in the upper atmosphere of a star in the late "red giant" stage, where the temperature and abundance of hydrogen could (40) diamonds to form as carbon gas condenses.
Trillions of incredibly tiny diamonds, possibly formed by a dying star before the solar system was born 4.5 billion years ago, have been found by researchers (26) four meteorites. The powder-like diamonds could be among the oldest things in the (27) , said Roy Lewis, senior research associate at the University of Chicago. The diamonds may (28) clues about the chemistry of stars, and if scientists can determine how they formed, that could suggest better ways of manufacturing tiny diamonds for (29) purposes, he said. "It’s quite possible that nature is doing it more (30) than we’ve been doing it," he said. "So maybe we’ve got something to learn." The new find is (31) , said John Wood, staff scientist at the Harvard-Smithsonian Centre for Astrophysics. Although diamonds have been found before in meteorites, they were formed relatively recently (32) the shock of impact, he said in a telephone interview. But Wood said the new report made him "quite sure" the newly found diamonds are older than the sun. Lewis said researchers never expected to find diamonds when they started (33) a stone-like meteorite that had plunged into Mexican cornfield in 1969. They were studying an unusual carbon dust in the meteorite, and to purify the sample they went though several steps to dissolve other materials. They expected the sample to remain black through the purification, but to their surprise in the final step it turned (34) . Lewis said they believed the final stage had dissolved the carbon they wanted to study. But tests showed that the white residue was in fact made of carbon. Other tests found that it contained an unusual combination of forms of the gas xenon, (35) that it came from outside the solar system. Still another battery of tests (36) the residue as diamond dust, so fine that a row of 20,000 grains would extend about the (37) of a human hair. The researchers also found diamonds in three other meteorites, Lewis said. Tests showed all four meteorites were as old as the solar system, and that the embedded diamonds did not form within the meteorite (38) of collisions. So the diamonds must have (39) somewhere else before the meteorites formed, making them as old or older than the solar system. The diamonds may have formed in the upper atmosphere of a star in the late "red giant" stage, where the temperature and abundance of hydrogen could (40) diamonds to form as carbon gas condenses.
1 In the second half of the 20th century, the world became, quite literally, a darker place.2 Defying expectation and easy explanation, hundreds of instruments around the world recorded a drop in sunshine reaching the surface of Earth, as much as 10 percent from the late 1950’s to the early 90’s, or 2 percent to 3percent a decade. In some regions like Asia, the United States and Europe, the drop was even steeper. In Hong Kong, sunlight decreased 37 percent.3 No one is predicting that it may soon be night all day, and some scientists theorize that the skies have brightened in the last decade as the suspected cause of global dimming, air pollution, clears up in many parts of the world.4 Yet the dimming trend — noticed by a handful of scientists 20 years ago but dismissed then as unbelievable — is attracting wide attention.5 "There could be a big gorilla sitting on the dining table, and we didn’t know about it," said Dr. Veerabhadran Ramanathan, a professor of climate and atmospheric sciences at the University of California, San Diego. "There are many, many issues that it raises."6 Dr. James E. Hansen, director of the NASA Goddard Institute for Space Studies in Manhattan, said that scientists had long known that pollution particles reflected some sunlight, but that they were now realizing the magnitude of the effect.7 "It’s occurred over a long time period," Dr. Hansen said. "So it’s not something that, perhaps, jumps out at you as a person in the street. But it’s a large effect."8 Satellite measurements show that the sun remains as bright as ever, but that less and less sunlight has been making it through the atmosphere to the ground.9 Pollution dims sunlight in two ways, scientists theorize. Some light bounces off soot particles in the air and goes back into outer space. The pollution also causes more water droplets to condense out of air, leading to thicker, darker clouds, which also block more light. For that reason, the dimming appears to be more pronounced on cloudy days than sunny ones. Some less polluted regions have had little or no dimming.10 The dynamics of global dimming are not completely understood. Antarctica, which would be expected to have clean air, has also dimmed.11 "In general, we don’t really understand this thing that’s going on," said Dr. Shabtai Cohen, a scientist in the Israeli Agriculture Ministry who has studied dimming for a decade. "And we don’t have the whole story.\ The following are suspected causes of global dimming EXCEPT ______.
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