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771.
Microbial life in a liquid asphalt desert 总被引:1,自引:0,他引:1
Schulze-Makuch D Haque S de Sousa Antonio MR Ali D Hosein R Song YC Yang J Zaikova E Beckles DM Guinan E Lehto HJ Hallam SJ 《Astrobiology》2011,11(3):241-258
Pitch Lake in Trinidad and Tobago is a natural asphalt reservoir nourished by pitch seepage, a form of petroleum that consists of mostly asphaltines, from the surrounding oil-rich region. During upward seepage, pitch mixes with mud and gases under high pressure, and the lighter portion evaporates or is volatilized, which produces a liquid asphalt residue characterized by low water activity, recalcitrant carbon substrates, and noxious chemical compounds. An active microbial community of archaea and bacteria, many of them novel strains (particularly from the new Tar ARC groups), totaling a biomass of up to 10(7) cells per gram, was found to inhabit the liquid hydrocarbon matrix of Pitch Lake. Geochemical and molecular taxonomic approaches revealed diverse, novel, and deeply branching microbial lineages with the potential to mediate anaerobic hydrocarbon degradation processes in different parts of the asphalt column. In addition, we found markers for archaeal methane metabolism and specific gene sequences affiliated with facultative and obligate anaerobic sulfur- and nitrite-oxidizing bacteria. The microbial diversity at Pitch Lake was found to be unique when compared to microbial communities analyzed at other hydrocarbon-rich environments, which included Rancho Le Brea, a natural asphalt environment in California, USA, and an oil well and a mud volcano in Trinidad and Tobago, among other sites. These results open a window into the microbial ecology and biogeochemistry of recalcitrant hydrocarbon matrices and establish the site as a terrestrial analogue for modeling the biotic potential of hydrocarbon lakes such as those found on Saturn's largest moon Titan. 相似文献
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用量子化学中的SCF-MO MINDO/3,MNDO,AM1和PM3方法计算研究了亚甲二醇二硝酸酯的几何构型和电子结构2,求得了MGDN的平衡几何构型。不同方法的计算结果均表明,标题物分子中两个ONO2均为平面基团,且O-NO2键的Wiberg键级最淖分子中最弱的键,在分解时可能首先断裂; 相似文献
776.
使用Flash软件制作机构动态演示计算机辅助教学课件 ,并能够通过按钮指令控制机构运动。说明了如何将其插入到软件FrontPage中在网上发布 ,利用此方法 ,可以制作多种网上发布的课件。 相似文献
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民航空管部门是直接保障飞行的,而空管设备则是空管部门有效开展工作、保障飞行安全重要的物质基础,这就需要确保设备的完好率与正常运行。然而,任何设备在单机运行条件下是不会达到100%的设备正常率的,况且这几年空管系统引进的很多设备存在型号杂、不兼容的问题,缺乏可靠性;部分地区的设备老化现象严重,故障率较高。在这种情况下,本文作者提出“从31.5秒所想到的——论现阶段民航空管设备运行风险及防范”的命题,并从五个方面提出了解决的办法,是很有针对性的,应当引起空管全系统、特别是空管设备保障部门的深思与重视。 相似文献
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水平轴风轮空气动力性能的分析计算 总被引:3,自引:0,他引:3
本文用半刚性尾流模型近似表示给出水平轴风轮空气动力性能的分析计算方法。在高尖速比范围内,本方法给出的结果比动量理论给出的更加接加接近实验数据。 相似文献
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G-H Wang G-B Li C-X Hu Y-D Liu L-R Song G-H Tong X-M Liu E-T Cheng 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,34(6):1455-1460
A simple Closed Aquatic Ecosystem (CAES) consisting of single-celled green algae (Chlorella pyrenoidosa, producer), a spiral snail (Bulinus australianus, consumer) and a data acquisition and control unit was flown on the Chinese Spacecraft SHENZHOU-II in January 2001 for 7 days. In order to study the effect of microgravity on the operation of CAES, a 1 g centrifuge reference group in space, a ground 1 g reference group and a ground 1 g centrifuge reference group (1.4 g group) were run concurrently. Real-time data about algae biomass (calculated from transmission light intensity), temperature, light and centrifugation of the CAES were logged at minute intervals. It was found that algae biomass of both the microgravity group and the ground 1 g-centrifuge reference group (1.4 g) fluctuated during the experiment, but the algae biomass of the 1 g centrifuge reference group in space and the ground 1 g reference group increased during the experiment. The results may be attributable to influences of microgravity and 1.4 g gravity on the algae and snails metabolisms. Microgravity is the main factor to affect the operation of CAES in space and the contribution of microgravity to the effect was also estimated. These data may be valuable for the establishment of a complex CELSS in the future. 相似文献