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Passage Four Even plants can run a fever, especially when they’re under attack by insects or disease. But unlike humans, plants can have their temperature taken from 3,000 feet away——straight up. A decade ago, adapting the infrared (红外线) scanning technology developed for military purposes and other satellites, physicist Stephen Paley came up with a quick way to take the temperature of crops to determine which ones are under stress. The goal was to let farmers pre-cisely target pesticide (杀虫剂) spraying rather than rain poison on a whole field, which in- variably includes plants that don’t have pest (害虫) problems. Even better, Paley’s Remote Scanning Services Company could detect crop problems be- fore they became visible to the eye. Mounted on a plane flown at 3,000 feet at night, an infra- red scanner measured the heat emitted by crops. The data were transformed into a color-code map showing where plants were running" fevers". Farmers could then spot-spray, using 50 to 70 percent less pesticide than they otherwise would. The bad news is that Paley’s company closed down in 1984, after only three years. Farmers resisted the new technology and long-term backers were hard to find. But with the renewed concern about pesticides on produce, and refinements in infrared scanning, Paley hopes to get back into operation. Agriculture experts have no doubt the technology works. "This technique can be used on 75 percent of agricultural land in the United States", says George Oerther of Texas A&M. Ray Jackson, who recently retired from the Department of Agricultrue, thinks re- mote infrared crop scanning could be adopted by the end of the decade. But only if Paley finds the financial backing which he failed to obtain 10 years ago. In order to apply pesticide spraying precisely, we can use infrared scanning to （）
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Passage Two Your mind like your body is a thing where the powers are developed by effort. This is a principal use, as I see it, of hard work in studies. Unless you train your body you can’t be a good sportsman, and unless you train your mind you can’t be much of a scholar. The four mi- les a boatman covers at top speed is in itself nothing to the good, but the physical capacity to hold out over the distance is thought to be of some value. So a good part of what you learn by hard study may not be retained forever, and may not seem to be of much final value, but your mind is a better and more powerful instrument because you have learned it. "Knowledge is power," but still more the ability of acquiring and using knowledge is power. If you have a trained and powerful mind, you are bound to have stored it with something, its value is more in what it can do, what it can grasp and use, than in what it contains; and if it were possible, as it is not, to come out of college with a trained mind and nothing useful in it, you would still be ahead, and still, in a manner, educated. The man leaving college with a trained mind （）
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