A culture-independent survey of the bacterial community in a radon hot spring

Paralana is an active, radon-containing hot spring situated in a region of South Australia's Flinders Ranges with a long history of hydrothermal activity. Our aim was to determine the bacterial composition of Paralana using a culture-independent, 16S rRNA-based technique. The presence of a diverse bacterial community was strongly suggested by the large number (approximately 180) of different ribotypes obtained upon analysis of nine hot spring samples. DNA sequencing of Paralana 16S rRNA genes corroborated this observation, identifying representatives of seven confirmed and two candidate divisions of the domain Bacteria. These included Cyanobacteria, Proteobacteria (both beta and delta subdivisions), the Cytophaga-Flexibacter-Bacteroides group, Low G + C Gram-positives, Nitrospira, green non-sulfur bacteria, green sulfur bacteria, OP8, and OP12. No known ionizing radiation-resistant Bacteria were identified. Only one Paralana 16S rRNA sequence type (recombinant B5D) was homologous to a sequence previously identified from a radioactive environment.     

Sulfuric acid Speleogenesis associated with a glacially driven groundwater system-paleo-spring "pipes" at Borup Fiord Pass, Nunavut

Gypsum filled "pipe" features were discovered in the proglacial area of the Borup Fiord Pass supraglacial sulfur spring. Stable isotope data suggest that gypsum is formed through oxidation of sulfides and are consistent with models of sulfuric acid speleogenesis. These results suggest that gypsum pipes are paleo-spring discharge channels analogous to those that feed the modern sulfur spring at Borup Fiord. A conceptual model is proposed whereby retreat of the glacial front and associated growth of permafrost in ground exposed now to low arctic temperatures leads to "freezing-in" of the spring system and abandonment of old channels in favor of more open flow systems in the subglacial region. Results provide a model for glacially driven groundwater systems that may form in association with Mars' polar icecaps and potential geological signatures for paleo-groundwater discharge.     

Sulfur-oxidizing chemolithotrophic proteobacteria dominate the microbiota in high arctic thermal springs on Svalbard

The thermal springs Trollosen and Fisosen, located on the High Arctic archipelago Svalbard, discharge saline groundwaters rich in hydrogen sulfide and ammonium through a thick layer of permafrost. Large amounts of biomass that consist of filamentous microorganisms containing sulfur granules, as analyzed with energy dispersive X-ray analysis, were found in the outflow. Prokaryotic 16S rRNA gene libraries and quantitative polymerase chain reaction (qPCR) analyses reported bacteria of the γ- and ?-proteobacterial classes as the dominant organisms in the filaments and the planktonic fractions, closely related to known chemolithoautotrophic sulfur oxidizers (Thiotrix and Sulfurovum). Archaea comprised ～1% of the microbial community, with the majority of sequences affiliated with the Thaumarchaeota. Archaeal and bacterial genes coding for a subunit of the enzyme ammonia monooxygenase (amoA) were detected, as well as 16S?rRNA genes of Nitrospira, all of which is indicative of potential complete nitrification in both springs. 16S rRNA sequences related to methanogens and methanotrophs were detected as well. This study provides evidence that the microbial communities in Trollosen and Fisosen are sustained by chemolithotrophy, mainly through the oxidation of reduced sulfur compounds, and that ammonium and methane might be minor, additional sources of energy and carbon.     

Mass-independent fractionation of sulfur isotopes in Archean sediments: strong evidence for an anoxic Archean atmosphere

Mass-independent fractionation (MIF) of sulfur isotopes has been reported in sediments of Archean and Early Proterozoic Age (> 2.3 Ga) but not in younger rocks. The only fractionation mechanism that is consistent with the data on all four sulfur isotopes involves atmospheric photochemical reactions such as SO2 photolysis. We have used a one-dimensional photochemical model to investigate how the isotopic fractionation produced during SO2 photolysis would have been transferred to other gaseous and particulate sulfur-bearing species in both low-O2 and high-O2 atmospheres. We show that in atmospheres with O2 concentrations < 10(-5) times the present atmospheric level (PAL), sulfur would have been removed from the atmosphere in a variety of different oxidation states, each of which would have had its own distinct isotopic signature. By contrast, in atmospheres with O2 concentrations > or = 10(-5) PAL, all sulfur-bearing species would have passed through the oceanic sulfate reservoir before being incorporated into sediments, so any signature of MIF would have been lost. We conclude that the atmospheric O2 concentration must have been < 10(-5) PAL prior to 2.3 Ga.     

Topological biosignatures: large-scale structure of chemical networks from biology and astrochemistry

The chemical basis of life involves more than simply the presence of biological molecules; biochemical systems embody a complex network of reactions with characteristic topological features. At the same time, chemical complexity is also present in nonbiological contexts, inviting us to clarify the relationship between chemistry and life through comparative studies. This study examines chemical networks from biology (the metabolism of E. coli) and astronomy (gas-phase reactions in dark molecular clouds) to establish common topological features that may be generic for any complex chemical system, as well as clear differences that may be topological signatures of life. The biological and astrochemical networks exhibit different scaling behaviors, and the network motifs found in the two systems show similarities as well as significant differences. The PageRank algorithm was used to quantify the degree to which individual species act primarily as products or reactants; in the metabolic network, these two roles are nearly identical for most species, whereas the astrochemical network shows a clearer partitioning into reactants and products.     

汽车钢板弹簧参数化建模研究

研究了汽车钢板弹簧参数化建模的设计方法,确定了钢板弹簧的输入参数,利用共同曲率法设计弹簧各参数,通过VB设计与开发汽车钢板弹簧参数化建模系统的输入界面,并通过编程在CATIA中进行参数化设计,建立了具有可视化界面的汽车钢板弹簧参数化设计系统。通过应用表明,汽车钢板弹簧参数化建模系统提高了设计者的设计效率,避免了重复设计,极大提高了劳动生产率。     

基于接触理论的一类带锁定机构的间隙铰链分析模型研究

重点研究一类在我国航天器上得到广泛应用的带有锁定机构的间隙铰链，基于接触理论建立了该类型间隙铰链的分析模型。首先，将铰链零件间的接触力假设为单向的非线性弹簧，并将铰链简化为由非线性弹簧组约束的摆；然后。将展开扭簧假设为线性力矩弹簧，得到包含间隙影响的铰链的力矩-转角关系曲线。通过仿真分析和试验验证，认为铰链的力矩转角关系曲线是分段光滑的。是铰链结构尺寸、零件间隙以及材料特性的函数。呈现出明显的非线性特征。     

Biogeochemistry of hypersaline springs supporting a mid-continent marine ecosystem: an analogue for martian springs?

Hypersaline springs that host unique mid-continent marine ecosystems were examined in central Manitoba, Canada. The springs originate from a reflux of glacial meltwater that intrudes into underlying bedrock and dissolved buried salt beds. Two spring types were distinguished based both on flow rate and geochemistry. High flow springs (greater than 10 L/s) hosted extensive marine microbial mats, which were dominated by algae but also included diverse microbes. These varied somewhat between springs as indicated by changes in profiles of fatty acid methyl esters. Culture studies confirmed the presence of sulfate-reducing bacteria in sediments at the high flow sites. In contrast, low flow springs were affected by solar evaporation, increasing salinity, and temperature. These low flow springs behaved more like closed nutrient-limited systems and did not support microbial mats. Direct comparison of the high and low flow springs revealed interesting implications for the potential to record biosignatures in the rock record. High flow springs have abundant, well-developed microbial mats, which desiccate and are cemented along the edges of the spring pools; however, the high mass flux overwhelms any geochemical signature of microbial activity. In contrast, the nutrient-limited low flow sites develop strong geochemical signatures of sulfate reduction, even in the absence of microbial mats, due to less dilution with the lower flows. Geochemical and physical evidence for life did not correlate with the abundance of microbial life but, rather, with the extent to which the biological system formed a closed ecosystem.     

Formate as an energy source for microbial metabolism in chemosynthetic zones of hydrothermal ecosystems

Formate, a simple organic acid known to support chemotrophic hyperthermophiles, is found in hot springs of varying temperature and pH. However, it is not yet known how metabolic strategies that use formate could contribute to primary productivity in hydrothermal ecosystems. In an effort to provide a quantitative framework for assessing the role of formate metabolism, concentration data for dissolved formate and many other solutes in samples from Yellowstone hot springs were used, together with data for coexisting gas compositions, to evaluate the overall Gibbs energy for many reactions involving formate oxidation or reduction. The result is the first rigorous thermodynamic assessment of reactions involving formate oxidation to bicarbonate and reduction to methane coupled with various forms of iron, nitrogen, sulfur, hydrogen, and oxygen for hydrothermal ecosystems. We conclude that there are a limited number of reactions that can yield energy through formate reduction, in contrast to numerous formate oxidation reactions that can yield abundant energy for chemosynthetic microorganisms. Because the energy yields are so high, these results challenge the notion that hydrogen is the primary energy source of chemosynthetic microbes in hydrothermal ecosystems.     

Formation of higher plant component microbial community in closed ecological system

Closed ecological systems (CES) place at the disposal of a researcher unique possibilities to study the role of microbial communities in individual components and of the entire system. The microbial community of the higher plant component has been found to form depending on specific conditions of the closed ecosystem: length of time the solution is reused, introduction of intrasystem waste water into the nutrient medium, effect of other component of the system, and system closure in terms of gas exchange. The higher plant component formed its own microbial complex different from that formed prior to closure. The microbial complex of vegetable polyculture is more diverse and stable than the monoculture of wheat. The composition of the components' microflora changed, species diversity decreased, individual species of bacteria and fungi whose numbers were not so great before the closure prevailed. Special attention should be paid to phytopathogenic and conditionally pathogenic species of microorganisms potentially hazardous to man or plants and the least controlled in CES. This situation can endanger creation of CES and make conjectural existence of preplanned components, man, specifically, and consequently, of CES as it is.     

FeS/S/FeS(2) redox system and its oxidoreductase-like chemistry in the iron-sulfur world

The iron-sulfur world (ISW) theory is an intriguing prediction regarding the origin of life on early Earth. It hypothesizes that life arose as a geochemical process from inorganic starting materials on the surface of sulfide minerals in the vicinity of deep-sea hot springs. During the last two decades, many experimental studies have been carried out on this topic, and some interesting results have been achieved. Among them, however, the processes of carbon/nitrogen fixation and biomolecular assembly on the mineral surface have received an inordinate amount of attention. To the present, an abiotic model for the oxidation-reduction of intermediates participating in metabolic pathways has been ignored. We examined the oxidation-reduction effect of a prebiotic FeS/S/FeS(2) redox system on the interconversion between several pairs of α-hydroxy acids and α-keto acids (i.e., lactate/pyruvate, malate/oxaloacetate, and glycolate/glyoxylate). We found that, in the absence of FeS, elemental sulfur (S) oxidized α-hydroxy acids to form corresponding keto acids only at a temperature higher than its melting point (113°C); in the presence of FeS, such reactions occurred more efficiently through a coupled reaction mechanism, even at a temperature below the phase transition point of S. On the other hand, FeS was shown to have the capacity to reversibly reduce the keto acids. Such an oxidoreductase-like chemistry of the FeS/S/FeS(2) redox system suggests that it can determine the redox homeostasis of metabolic intermediates in the early evolutionary phase of life. The results provide a possible pathway for the development of primordial redox biochemistry in the iron-sulfur world. Key Words: Iron-sulfur world-FeS/S/FeS(2) redox system-Oxidoreductase-like chemistry. Astrobiology 11, 471-476.     

复合式空气弹簧的开发设计

针对国内汽车空气弹簧市场需求，开发出由胶囊和减振器装配成一体的复合式空气弹簧，该结构产品取代传统的螺旋弹簧减振器，即解决了空气悬挂空间狭小的问题，又实现了空气弹簧的变刚度调节，大大降低悬挂系统的固有频率，提高了乘车的舒适性和稳定性。借助有限元分析软件进行汽车空气弹簧的性能参数计算，确定了半成品的裁断角度等技术参数，通过产品试验，验证了有限元计算及工艺参数选取的正确性。     

皮卫星星箭分离动力学模拟及其灵敏度分析

皮卫星能源有限、姿控能力差等特点决定其对星箭分离初始姿态要求较高。在采用自主研发的皮卫星星箭分离机构的基础上，以多体动力学理论为基础，采用ADAMS软件建立了皮卫星及其星箭分离机构虚拟样机模型，分别就皮卫星质心偏离量、分离弹簧与舱门扭簧弹性系数对入轨初始姿态影响展开了分析。分析结果表明：质心偏心量对分离姿态影响最明显，分离弹簧与舱门扭簧弹性系数对其影响次之，合理配置分离弹簧与舱门扭簧弹性系数有利于卫星保持良好的姿态分离。在轨分离试验显示：分离时刻皮卫星滚动角速度、俯仰角速度、偏航角速度分别为-0.18（°）/s，-1.6（°）/s，0.95（°）/s，与在轨环境下仿真结果基本相符；入轨初始姿态能满足皮卫星的姿控要求，为其后续工作提供了保障。     

An Experimental Study of the Effect of Vibrations on Supercritical Fluid Transfer Processes under Microgravity Conditions

On the basis of the data obtained in experiments onboard the Mirorbital complex (OC) in March and April 1999 with the ALICE-2 instrument, the influence of vibrations on heat propagation from a point-like source in the hexafluoride sulfur (SF₆) under supercritical parameters is analyzed. The appearance of two different heat propagation regimes is found: along and across the direction of vibrations. Upon the occurrence of the second-type regime, the heating region first stretches in the direction perpendicular to the direction of vibrations and then propagates at a rate typical for the undisturbed case. The temperature relaxation process is analyzed, which takes place near the heater after its turn-off. The relaxation rate grows as the intensity of vibrations increases and the initial temperature tends to the critical one. The determining dimensionless parameters of the problem are suggested.     

Biomarker and stable isotope characterization of coastal pond-derived organic matter, McMurdo Dry Valleys, Antarctica

Small coastal ponds that contain photosynthetic microbial mat communities represent an extreme environment where a potentially significant source of labile organic carbon can be found within the McMurdo Dry Valleys, Antarctica. To distinguish coastal pond-derived organic matter from other sources of organic matter in the Dry Valleys, bulk organic carbon, nitrogen, and sulfur isotope signatures and phospholipid fatty acid (PLFA) profiles of benthic microbial mats located at two sites--Hjorth Hill coast and Garwood Valley--were investigated. The average isotope values at Hjorth Hill coast and Garwood Valley are, respectively, -10.9 per thousand and -10.2 per thousand for delta(13) C, 3.7 per thousand and -1.3 per thousand for delta(15)N, and 8.1 per thousand and 16.7 per thousand for delta(34)S. Microbial mats from all ponds are dominated by monounsaturated PLFAs (indicative of Gram-negative bacteria) and polyunsaturated PLFAs (indicative of microeukaryotes). Biomarkers specific to aerobic prokaryotes, eukaryotes, and photoautotrophic microeukaryotes, as well as sulfur-reducing bacteria, are present in all samples. Benthic mats at Garwood Valley are thicker and more laminated, have a higher biomass, and have a greater carbon and nitrogen content, which suggests greater productivity than mats at Hjorth Hill coast. Greater productivity is supported, as well, by higher dissolved oxygen contents likely derived from heightened photosynthetic productivity. More productivity at Garwood Valley likely results from a larger influx of terrestrial surface waters together with a concomitant nutrient loading.     

一种浮动锁销式柔性气浮组件的承载特性测试及分析

为在空间机构产品集成与测试中合理使用气浮组件,采用刚度试验台模拟加载的方案对一种浮动锁销式柔性气浮组件的承载特性进行测试。试验结果表明:浮动锁销式柔性气浮组件在未预压缩状态下,承载特性近似为线性弹簧压缩模型;在预压缩状态下,初始承载特性近似为刚体,承载力超过气浮组件的保持力后承载特性近似为线性弹簧压缩模型。因此,为避免气浮组件在承载过程中表现出的作用力与位移变化等特性对空间机构产品的运动特性、系统性能造成显著的附加影响,气浮组件在使用前应根据产品重力调节弹簧预压缩量,并严格控制4组可调弹簧支撑组件的制造误差;同时,在产品重力完全被卸载之前需要借助压紧释放机构或刚性支撑工装对产品进行约束。     

Iron meteorites can support the growth of acidophilic chemolithoautotrophic microorganisms

Chemolithoautotrophy based on reduced inorganic minerals is considered a primitive energy transduction system. Evidence that a high number of meteorites crashed into the planet during the early period of Earth history led us to test the ability of iron-oxidizing bacteria to grow using iron meteorites as their source of energy. Here we report the growth of two acidophilic iron-oxidizing bacteria, Leptospirillum ferrooxidans and Acidithiobacillus ferrooxidans, on a piece of the Toluca meteorite as the only source of energy. The alteration of the surface of the exposed piece of meteorite, the solubilization of its oxidized metal constituents, mainly ferric iron, and the formation of goethite precipitates all clearly indicate that iron-meteorite-based chemolithotrophic metabolism is viable.     

电子设备结构“解耦设计”理论及方法

文章运用结构动力修改的方法对电子设备的动力响应进行控制,即通过修改电子设备中机壳与电路板组件两部分的基频（指同一方向的基频,尤其是垂直于电路板方向）,使两者的基频相互错开来降低电路板组件的动力响应。采用两自由度基础强迫振动系统来模拟电子设备的振动响应,经分析给出了“非解耦系统”与“解耦系统”的概念,指出应将电子设备设计为“解耦系统”。最后对两自由度系统进行“分解”分析,给出了电子设备的“解耦设计”方法。     

悬空衔铁式电磁阀中S形簧片的研制

介绍了一种悬空衔铁式电磁阀用S形簧片的研制,该簧片用于航天器推进系统150 N发动机电磁阀。簧片研制的目标是高寿命、高可靠性和稳定性。根据要求设计生产了工程样机,在研制过程中对簧片的设计,仿真,工艺制造和试验方法进行了探索,并得到了较好的结果,通过了鉴定试验,即将进入工程应用阶段研制。     

一种涡卷弹簧分离螺母装置设计及仿真分析

航天器的连接与分离技术是航天运输系统中的关键技术，连接分离装置作为该技术领域的关键装置，一直是航天领域的重要研究内容。针对航天器连接与分离的要求，提出一种涡卷弹簧非火工分离螺母装置，并对装置进行结构设计。涡卷弹簧是装置的关键部分，直接影响涡卷弹簧分离螺母装置的承载和工作特性。对涡卷弹簧的张力和扭矩特性进行分析，并通过仿真分析研究涡卷弹簧分离螺母装置的工作特性。