Life and light: exotic photosynthesis in binary and multiple-star systems

The potential for Earth-like planets within binary/multiple-star systems to host photosynthetic life was evaluated by modeling the levels of photosynthetically active radiation (PAR) such planets receive. Combinations of M and G stars in (i) close-binary systems; (ii) wide-binary systems, and (iii) three-star systems were investigated, and a range of stable radiation environments were found to be possible. These environmental conditions allow for the possibility of familiar, but also more exotic, forms of photosynthetic life, such as IR photosynthesizers and organisms that are specialized for specific spectral niches.     

Classification of modern and old Río Tinto sedimentary deposits through the biomolecular record using a life marker biochip: implications for detecting life on Mars

The particular mineralogy formed in the acidic conditions of the Río Tinto has proven to be a first-order analogue for the acid-sulfate aqueous environments of Mars. Therefore, studies about the formation and preservation of biosignatures in the Río Tinto will provide insights into equivalent processes on Mars. We characterized the biomolecular patterns recorded in samples of modern and old fluvial sediments along a segment of the river by means of an antibody microarray containing more than 200 antibodies (LDCHIP200, for Life Detector Chip) against whole microorganisms, universal biomolecules, or environmental extracts. Samples containing 0.3-0.5?g of solid material were automatically analyzed in situ by the Signs Of LIfe Detector instrument (SOLID2), and the results were corroborated by extensive analysis in the laboratory. Positive antigen-antibody reactions indicated the presence of microbial strains or high-molecular-weight biopolymers that originated from them. The LDCHIP200 results were quantified and subjected to a multivariate analysis for immunoprofiling. We associated similar immunopatterns, and biomolecular markers, to samples with similar sedimentary age. Phyllosilicate-rich samples from modern fluvial sediments gave strong positive reactions with antibodies against bacteria of the genus Acidithiobacillus and against biochemical extracts from Río Tinto sediments and biofilms. These samples contained high amounts of sugars (mostly polysaccharides) with monosaccharides like glucose, rhamnose, fucose, and so on. By contrast, the older deposits, which are a mix of clastic sands and evaporites, showed only a few positives with LDCHIP200, consistent with lower protein and sugar content. We conclude that LDCHIP200 results can establish a correlation between microenvironments, diagenetic stages, and age with the biomarker profile associated with a sample. Our results would help in the search for putative martian biomarkers in acidic deposits with similar diagenetic maturity. Our LDCHIP200 and SOLID-like instruments may be excellent tools for the search for molecular biomarkers on Mars or other planets.     

一种接近最优JPDA算法

多目标跟踪的关键问题是点迹－航迹数据关联。点迹是从能够提供位置信息的目标或背景杂波中接收到的信号。如果一条航迹关联上不正确的点迹，那么该航迹会偏离目标且过早终止。甚至会引起其它航迹也偏离目标，大多数点迹－航迹数据关联方法分为两类：多假设跟踪（ＭＨＴ）和联合概率数据关联（ＪＰＤＡ）。ＭＨＴ方法用所有或部分适宜的点迹修正航迹，并延迟判断那一个点迹是正确的。ＪＰＤＡ用合理点迹的加权和修正航迹，这些权值是     

双燃料地球入轨运载工具的火箭喷管膨胀比分析

可完全重复使用的地球入轨运载工具终将扩大现有运载工具如航天飞机的运载能力,甚至取而代之.我们已对两种运载工具进行了讨论.一种是单级运载工具,另一种是两级平行燃烧运载工具,它们在起飞时都同时采用烃和氢发动机,到达轨道前,烃发动机熄火,由氢发动机推进来爬升到轨道.在以前的研究中,航天飞机主发动机(SSME)是采用氢发动机和双位喷管,喷管膨胀比为40和150.     

On the survivability and detectability of terrestrial meteorites on the moon

Materials blasted into space from the surface of early Earth may preserve a unique record of our planet's early surface environment. Armstrong et al. (2002) pointed out that such materials, in the form of terrestrial meteorites, may exist on the Moon and be of considerable astrobiological interest if biomarkers from early Earth are preserved within them. Here, we report results obtained via the AUTODYN hydrocode to calculate the peak pressures within terrestrial meteorites on the lunar surface to assess their likelihood of surviving the impact. Our results confirm the order-of-magnitude estimates of Armstrong et al. (2002) that substantial survivability is to be expected, especially in the case of relatively low velocity (ca. 2.5 km/s) or oblique (相似文献   

空军航空高超声速系统:需求,方案及技术要求之间的关系

为了协助美国空军高超声速技术发展战略的制订，本文评估了作战部队对高超声速武器系统的潜在需求和研制各种高超声速武器系统方案所需要的技术，这项评估包括选取一些可能解决已查明的作呀部队短缺问题的高超声速系统方案和评估实施这些方案所必需的各项技术，然后根据每一种技术在满足用户需求和方案中记分次数的多少加以排队，以确定该项技术的普遍适用程度。研究结果表明，高超声速系统能够满足大量的用户需求，高超声速系统固有