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Microbial populations in Antarctic permafrost: biodiversity, state, age, and implication for astrobiology 总被引:1,自引:0,他引:1
Gilichinsky DA Wilson GS Friedmann EI McKay CP Sletten RS Rivkina EM Vishnivetskaya TA Erokhina LG Ivanushkina NE Kochkina GA Shcherbakova VA Soina VS Spirina EV Vorobyova EA Fyodorov-Davydov DG Hallet B Ozerskaya SM Sorokovikov VA Laurinavichyus KS Shatilovich AV Chanton JP Ostroumov VE Tiedje JM 《Astrobiology》2007,7(2):275-311
Antarctic permafrost soils have not received as much geocryological and biological study as has been devoted to the ice sheet, though the permafrost is more stable and older and inhabited by more microbes. This makes these soils potentially more informative and a more significant microbial repository than ice sheets. Due to the stability of the subsurface physicochemical regime, Antarctic permafrost is not an extreme environment but a balanced natural one. Up to 10(4) viable cells/g, whose age presumably corresponds to the longevity of the permanently frozen state of the sediments, have been isolated from Antarctic permafrost. Along with the microbes, metabolic by-products are preserved. This presumed natural cryopreservation makes it possible to observe what may be the oldest microbial communities on Earth. Here, we describe the Antarctic permafrost habitat and biodiversity and provide a model for martian ecosystems. 相似文献
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高热安定性喷气燃料JP—8+100的研制 总被引:3,自引:0,他引:3
喷气燃料的技术指标,经过多年已逐渐成为了先进飞机性能(技术需要),燃料成本(经济因素)和燃料利用率(战略因素)三者需求的平衡。在现代收音机中,燃料不仅要为飞机飞行提供推进能量,而且要发飞机和发动机附件系统的主要冷却剂。为了满足这一要求,美国空军、工业部门和科研机构决定联合研制具有高吸热量和热安定性的新型优化燃料。这些先进燃料将会改善2收音机设计,并能减少由于燃料结结/结焦所致燃料的维护费用。这本文 相似文献
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The purpose of this study was to compare cardiorespiratory responses of men and women to submaximal and maximal workloads before and after bed rest (BR). Fifteen male college students (19-23 yr) and 8 female nurses (23-34 yr) underwent 14 d and 17 d, respectively of bed rest. The maximal work capacity test was performed in the supine position on a bicycle ergometer just before and immediately after bed rest. The women's maximal O2 uptake (maximal VO2) was 41% lower (P<0.05) than the men's before bed rest and 42% lower (P<0.05) after bed rest. During bed rest the women's maximal VO2 decreased from 2.06 to 1.86 liter/min (-9.7%, P<0.05), and that of the men decreased from 3.52 to 3.20 liter/min (-9.1%, P<0.05). Compared with pre-BR values, after bed rest the maximal ventilatory volume was essentially unchanged in the men (+1.8%) and women (+ 2.3%), but maximal heart rate was elevated from 185 to 193 b/min (+ 4.3%, P<0.05) in the men and from 181 to 187 b/min (3.3%, P<0.05) in the women. Submaximal VO2 was unchanged after bed rest in the men but was significantly reduced in the women; the women's Hct and RBC levels were lower (P<0.05) than comparable male data. Mean corpuscular volume was unchanged in both groups pre- and post-bed rest. It is concluded that the proportional deterioration in maximal VO2 following prolonged bed rest was essentially the same in young men and women. 相似文献