一种低功率易校准的温度传感器

本文描述一种具有内部参考的改进的线性集成电路温度传感器,其主要的性能是:易校准(只有一个步骤),在宽温度范围内(-4.6mv/℃;-50℃到+125℃)具有高灵敏度,低输出阻抗(40Q),低功耗(200μw)。此器件中的扩散电阻以通用线性集成电路的工艺过程制造。文中还讨论了这种传感器在热电偶冷接点补偿中的应用。     

Travel, Sex, and Food: What's Speciation Got to Do with It?

Abstract We discuss the potential interactions among travel (dispersal and gene flow), bacterial "sex" (mainly as horizontal gene transfer), and food (metabolic plasticity and responses to nutrient availability) in shaping microbial communities. With regard to our work at a unique desert oasis, the Cuatro Ciénegas Basin in Coahuila, Mexico, we propose that diversification and low phosphorus availability, in combination with mechanisms for nutrient recycling and community cohesion, result in enhanced speciation through reproductive as well as geographic isolation. We also discuss these mechanisms in the broader sense of ecology and evolution. Of special relevance to astrobiology and central to evolutionary biology, we ask why there are so many species on Earth and provide a working hypothesis and a conceptual framework within which to consider the question. Key Words: Microbial ecology-Microbial mats-Evolution-Horizontal gene transfer-Metabolism. Astrobiology 12, 634-640.     

Comparative Metagenomics of Two Microbial Mats at Cuatro Ciénegas Basin II: Community Structure and Composition in Oligotrophic Environments

Abstract Microbial mats are self-sustained, functionally complex ecosystems that make good models for the understanding of past and present microbial ecosystems as well as putative extraterrestrial ecosystems. Ecological theory suggests that the composition of these communities might be affected by nutrient availability and disturbance frequency. We characterized two microbial mats from two contrasting environments in the oligotrophic Cuatro Ciénegas Basin: a permanent green pool and a red desiccation pond. We analyzed their taxonomic structure and composition by means of 16S rRNA clone libraries and metagenomics and inferred their metabolic role by the analysis of functional traits in the most abundant organisms. Both mats showed a high diversity with metabolically diverse members and strongly differed in structure and composition. The green mat had a higher species richness and evenness than the red mat, which was dominated by a lineage of Pseudomonas. Autotrophs were abundant in the green mat, and heterotrophs were abundant in the red mat. When comparing with other mats and stromatolites, we found that taxonomic composition was not shared at species level but at order level, which suggests environmental filtering for phylogenetically conserved functional traits with random selection of particular organisms. The highest diversity and composition similarity was observed among systems from stable environments, which suggests that disturbance regimes might affect diversity more strongly than nutrient availability, since oligotrophy does not appear to prevent the establishment of complex and diverse microbial mat communities. These results are discussed in light of the search for extraterrestrial life. Key Words: Cuatro Ciénegas-Metagenomics-Microbial mats-Oligotrophic-Phosphorus limitation-Stromatolites. Astrobiology 12, 659-673.     

Training astronauts using three-dimensional visualisations of the International Space Station

Recent advances in personal computer technology have led to the development of relatively low-cost software to generate high-resolution three-dimensional images. The capability both to rotate and zoom in on these images superposed on appropriate background images enables high-quality movies to be created. These developments have been used to produce realistic simulations of the International Space Station on CD-ROM. This product is described and its potentialities demonstrated. With successive launches, the ISS is gradually built up, and visualised over a rotating Earth against the star background. It is anticipated that this product's capability will be useful when training astronauts to carry out EVAs around the ISS. Simulations inside the ISS are also very realistic. These should prove invaluable when familiarising the ISS crew with their future workplace and home. Operating procedures can be taught and perfected. "What if" scenario models can be explored and this facility should be useful when training the crew to deal with emergency situations which might arise. This CD-ROM product will also be used to make the general public more aware of, and hence enthusiastic about, the International Space Station programme.     

Potential of cathodoluminescence microscopy and spectroscopy for the detection of prokaryotic cells on minerals

Detecting mineral-hosted ecosystems to assess the extent and functioning of the biosphere from the surface to deep Earth requires appropriate techniques that provide, beyond the morphological criteria, indubitable clues of the presence of prokaryotic cells. Here, we evaluate the capability of cathodoluminescence microscopy and spectroscopy, implemented on a scanning electron microscope, to identify prokaryotes on mineral surfaces. For this purpose, we used, as a first step, a simple model of either unstained or stained cultivable cells (Escherichia coli, Deinococcus radiodurans) deposited on minerals that are common in the oceanic crust (basaltic glass, amphibole, pyroxene, and magnetite). Our results demonstrate that the detection of cells is possible at the micrometric level on the investigated minerals through the intrinsic fluorescence of their constituting macromolecules (aromatic amino and nucleic acids, coenzymes). This allows us to distinguish biomorph inorganic phases from cells. This easily implemented technique permits an exploration of colonized rock samples. In addition, the range of spectrometric techniques available on a scanning electron microscope can provide additional information on the nature and chemistry of the associated mineral phases, which would lead to a simultaneous characterization of cells, their microhabitats, and a better understanding of their potential relationships.     

洁齿

在一个世纪以前及更早的时候,要想在自然环境下拍摄到野生动物,简直无法想象的困难。1906年,美国《国家地理》杂志首次刊登了74张夜行动物的照片,之后,就开始不断展现野生动物摄影突破性的成就。这张1966年摄于锡兰     

苏联早期的“警棍”和“凉鞋”“短剑”导弹

赫鲁晓夫唬住了美国人1960年1月14日,赫鲁晓夫在苏联最高苏维埃会议上以《为了永久和平与友谊而裁军》为题发表演说,首次形成了国家核军事理论。该理论认定弹道导弹应在军事战略中占据中心位置,并应成为欧洲战争及有超级大国参加的战斗中的决定因素。赫鲁晓夫认为,新的战争将从使用核武器的大规模突袭开始。