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大全里面的一补充题passage71(8/22)
Behavior is one of two general responses available to endothermic (endothermic: adj.吸热(性)的,[动]温血的) (warm-blooded) species for the regulation of body temperature, the other being innate (reflexive) mechanisms of heat production and heat loss. Human beings rely primarily on the first to provide a hospitable thermal microclimate (microclimate: n.[气]小气候(指森林、城市、洞穴等局部地区的气候)) for themselves, in which the transfer of heat between the body and the environment is accomplished with minimal involvement of innate mechanisms of heat production and loss. Thermoregulatory (thermoregulatory: adj.体温调节的,保持(一定)体温的) behavior anticipates hypothermia, and the organism adjusts its behavior to avoid becoming hypothermic: it removes layers of clothing; it goes for a cool swim, etc. The organism can also respond to changes in the temperature of the body core, as is the case during exercise; but such responses result from the direct stimulation of thermo receptors distributed widely within the central nervous system (central nervous system: n. 中枢神经系统), and the ability of these mechanisms to help the organism adjust to gross changes in its environment is limited.
Until recently it was assumed that organisms respond to microwave radiation in the same way that they respond to temperature changes caused by other forms of radiation. After all, the argument runs, microwaves are radiation and heat body tissues. This theory ignores the fact that the stimulus to a behavioral response is normally a temperature change that occurs at the surface of the organism. The thermo receptors that prompt behavioral changes are located within the first millimeter of the skin’s surface, but the energy of a microwave field (microwave field: 超高频场, 微波场) may be selectively deposited in deep tissues, effectively bypassing these thermoreceptors, particularly if the field is at near-resonant frequencies. The resulting temperature profile (temperature profile: 温度曲线图, 温度轮廓) may well be a kind of reverse thermal gradient in which the deep tissues are warmed more than those of the surface. Since the heat is not conducted outward to the surface to stimulate the appropriate receptors, the organism does not “appreciate” this stimulation in the same way that it “appreciates” heating and cooling of the skin. In theory (in theory: 理论上), the internal organs of a human being or an animal could be quite literally cooked well-done (well-done: adj.做得好的, 完全煮熟的) before the animal even realizes that the balance of its thermomicroclimate has been disturbed.
Until a few years ago, microwave irradiations at equivalent plane-wave power densities of about 100 mW/cm2 were considered unequivocally to produce “thermal” effects; irradiations within the range of 10 to 100 mW/cm2 might or might not produce “thermal” effects; while effects observed at power densities below 10 mW/cm2 were assumed to be “nonthermal” in nature. Experiments have shown this to be an oversimplification, and a recent report suggests that fields as weak as 1 mW/cm2 can be thermogenic. When the heat generated in the tissues by an imposed radio frequency (radio frequency: n.无线电频率) (plus the heat generated by metabolism) exceeds the heat-loss capabilities of the organism, the thermoregulatory system has been compromised. Yet surprisingly, not long ago (not long ago: adv.不久前), an increase in the internal body temperature was regarded merely as “evidence” of a thermal effect.
实 在不明白第一段是在讲什么，它与后面的段是什么关系， 请哪位高手帮我分析一下
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发表于 2005-10-14 22:49:00
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