Preservation of microbial lipids in geothermal sinters

Lipid biomarkers are widely used to study the earliest life on Earth and have been invoked as potential astrobiological markers, but few studies have assessed their survival and persistence in geothermal settings. Here, we investigate lipid preservation in active and inactive geothermal silica sinters, with ages of up to 900 years, from Champagne Pool, Waiotapu, New Zealand. Analyses revealed a wide range of bacterial biomarkers, including free and bound fatty acids, 1,2-di-O-alkylglycerols (diethers), and various hopanoids. Dominant archaeal lipids include archaeol and glycerol dialkyl glycerol tetraethers (GDGTs). The predominance of generally similar biomarker groups in all sinters suggests a stable microbial community throughout Champagne Pool's history and indicates that incorporated lipids can be well preserved. Moreover, subtle differences in lipid distributions suggest that past changes in environmental conditions can be elucidated. In this case, higher archaeol abundances relative to the bacterial diethers, a greater proportion of cyclic GDGTs, the high average chain length of the bacterial diethers, and greater concentrations of hopanoic acids in the older sinters all suggest hotter conditions at Champagne Pool in the past.     

先进的砷化镓制造设备

哈里斯微波半导体公司研制了一种先进的GaAs(砷化镓)制造设备,力图成为军用单片微波集成电路(MMIC)的主要生产厂家.哈里斯公司掌握GaAs MMIC从晶体生长(几乎不用铸造工艺)到封装整个电路的每一道生产工序.该公司已对生产厂和设备投资了3000万美元,雇用人员仅70人,年产近 5万个MMIC和多达40万个微波元件(如场效应晶体管).年销售额达1000万美元.哈里斯同通用电气和休斯公司一起参与了DARPA(国防预研项目局)的微波/毫米波MMIC硬件研制计划第一阶段的机载和陆基雷达系统研究工作.这些公司于1988年     

跟踪雷达的复合控制

 本文研究了不变性理论在跟踪雷达中的应用,提出跟踪雷达的一种复合控制体制。以雷达一红外复合控制系统为例,介绍了这种跟踪体制的理论依据、设计方法和试验结果。通过分析和试验,说明这种跟踪体制具有极为显著的优点并可以广泛应用于空-空、地-空导弹等武器系统。     

Silicifying biofilm exopolymers on a hot-spring microstromatolite: templating nanometer-thick laminae

Exopolymeric substances (EPS) are an integral component of microbial biofilms; however, few studies have addressed their silicification and preservation in hot-spring deposits. Through comparative analyses with the use of a range of microscopy techniques, we identified abundant EPS significant to the textural development of spicular, microstromatolitic, siliceous sinter at Champagne Pool, Waiotapu, New Zealand. Examination of biofilms coating sinter surfaces by confocal laser scanning microscopy (CLSM), environmental scanning electron microscopy (ESEM), cryo-scanning electron microscopy (cryo-SEM), and transmission electron microscopy (TEM) revealed contraction of the gelatinous EPS matrix into films (approximately 10 nm thick) or fibrillar structures, which is common in conventional SEM analyses and analogous to products of naturally occurring desiccation. Silicification of fibrillar EPS contributed to the formation of filamentous sinter. Matrix surfaces or dehydrated films templated sinter laminae (nanometers to microns thick) that, in places, preserved fenestral voids beneath. Laminae of similar thickness are, in general, common to spicular geyserites. This is the first report to demonstrate EPS templation of siliceous stromatolite laminae. Considering the ubiquity of biofilms on surfaces in hot-spring environments, EPS silicification studies are likely to be important to a better understanding of the origins of laminae in other modern and ancient stromatolitic sinters, and EPS potentially may serve as biosignatures in extraterrestrial rocks.