Survival of rock-colonizing organisms after 1.5 years in outer space

Cryptoendolithic microbial communities and epilithic lichens have been considered as appropriate candidates for the scenario of lithopanspermia, which proposes a natural interplanetary exchange of organisms by means of rocks that have been impact ejected from their planet of origin. So far, the hardiness of these terrestrial organisms in the severe and hostile conditions of space has not been tested over extended periods of time. A first long-term (1.5 years) exposure experiment in space was performed with a variety of rock-colonizing eukaryotic organisms at the International Space Station on board the European EXPOSE-E facility. Organisms were selected that are especially adapted to cope with the environmental extremes of their natural habitats. It was found that some-but not all-of those most robust microbial communities from extremely hostile regions on Earth are also partially resistant to the even more hostile environment of outer space, including high vacuum, temperature fluctuation, the full spectrum of extraterrestrial solar electromagnetic radiation, and cosmic ionizing radiation. Although the reported experimental period of 1.5 years in space is not comparable with the time spans of thousands or millions of years believed to be required for lithopanspermia, our data provide first evidence of the differential hardiness of cryptoendolithic communities in space.     

雷达信号的比较分析

引 言 前几章已经叙述了分析和比较信号的方法,而对具体的应用讲得很少。但因为所得结果的解释,甚至所用方法都将随着不同的应用有所改变,所以前面的分析都是脱离具体应用的理论性研究。现在,我们将着重研究如何选择合适的波形用作雷达系统的发射信号。我们特别关心的是,为使雷达在测量精度和分辨能力达到最佳程度而比较一些信号波形。雷达发射信号的波形对于目标参数、距离、相对径向速度的测量精度至关重要。对于分辨两个或更多个目标的难易程度,波形设计也是很重要的。无模糊的分辨或估计也是分辨问题中的一部分内容。 详细比较所有可能的信号是不现实的。因此,我们将设法找出对雷达测量精度和分辨起重要作用的波形关键参数,按此比较几种候选信号。     

可用于先进复合材料的一种中温固化环氧树脂

本文评价了一种可用于纤维缠绕先进复合材料的,以聚醚三胺进行固化的双酚F 环氧树脂。该树脂系统具有低粘度,长使用期,并能在中温下进行固化。使用这种树脂制造的复合材料,未发现明显的纤维微皱摺或分层现象,这意味着介于纤维和基体之间不同的热膨胀系数已不成为一个问题。该树脂系统浇注体典型力学性能(拉伸、压缩和剪切)已测得。拉伸:最大应力75.8兆帕(Mpa),最大应力下的应变为4.2%,模量为3171兆帕,断裂应力为71兆帕,断裂应变为5.8%。压缩:最大应力为87兆帕,最大应力下的应变为4.7%,模量为3150兆帕。剪切:断裂应力为52.2兆帕,冲击强度为32.6牛顿米/米。     

Characterization of Bacilli isolated from the confined environments of the Antarctic Concordia station and the International Space Station

Bacillus and related genera comprise opportunist and pathogen species that can threaten the health of a crew in confined stations required for long-term missions. In this study, 43 Bacilli from confined environments, that is, the Antarctic Concordia station and the International Space Station, were characterized in terms of virulence and plasmid exchange potentials. No specific virulence feature, such as the production of toxins or unusual antibiotic resistance, was detected. Most of the strains exhibited small or large plasmids, or both, some of which were related to the replicons of the Bacillus anthracis pXO1 and pXO2 virulence elements. One conjugative element, the capacity to mobilize and retromobilize small plasmids, was detected in a Bacillus cereus sensu lato isolate. Six out of 25 tested strains acquired foreign DNA by conjugation. Extremophilic bacteria were identified and exhibited the ability to grow at high pH and salt concentrations or at low temperatures. Finally, the clonal dispersion of an opportunist isolate was demonstrated in the Concordia station. Taken together, these results suggest that the virulence potential of the Bacillus isolates in confined environments tends to be low but genetic transfers could contribute to its capacity to spread.     

用于石英谐振器研究的频域反射计

本文介绍一种用于精确测量石英晶体谐振频率特性的调相频域反射计系统的概念和工作原理。反射计法容许被测晶体谐振器远置于一环境试验箱中;这系统还能同时而又单独地对任一给定晶体中发生的不同谐振模(例如,SC切晶体中的b模和c模谐振)进行频率测量。这一反射计技木主要适用于对谐振器进行以下基本研究:频率一温度特性的研究;滞后现象和热冲击效应的研究;幅度一频率因数和多模激励特性的研究以及核幅射效应的研究,等等。本仪器也可应用于晶体生产过程,包括自动化生产、测试以及质量控制等。     

HIGH TEMPERATURE MOIRE INTERFEROMETRY TECHNOLOGY

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The face inversion effect in microgravity: is gravity used as a spatial reference for complex object recognition?

Complex objects are better recognized under a specific orientation. When presented upside down, a face, even very familiar, is recognized with greater difficulty than when presented upright ("Inversion effect"). Up to now it was not possible to decide whether the direction provided by gravity or the one provided by the retina and the body constitutes the spatial reference involved in this "Inversion effect". Three cosmonautes learned photographed faces on the ground and had to recognize them both on ground and on flight. Other photographed faces were learned in flight and where presented for recognition on flight. Results show that the Inversion effect is still present on flight for faces that have been learned on ground as well as for those learned on flight. Persistence of the inversion effect in 0-G shows that gravity is not involved as a spatial reference in recognition of faces. Learning and recognition performances of faces learned in flight were significantly lower than performances for faces learned on ground. A possible role of gravity in configural processing, but not in the Inversion effect, is suggested.     

IEC六年来的全数字化GPS接收机

本文介绍了州际电子公司(IEC)六年来在GPS信号全数字化基带相关处理方面取得的进展。最初,这种技术随着离散型数字式中规模集成电路而发展起来的。此后,在半定制门阵技术和最近的专用集成电路(ASIC)方面取得了进展,小型、低功耗全数字式GPS接收机得到高度发展。本文介绍了几代全数字化GPS接收机的设计方案。回顾了全数字GPS接收机技术,包括该技术出现以来所取得的进展。本文还介绍了12抽头并行数字式相关器的实施方案,最新研制的接收机中就用这种相关器完成快速捕获和跟踪。还介绍了数控振荡器和伪码产生器门阵。还设计了一种能在1ms以内快速初始化的P码产生器门阵,这样不需要旋动编码装置即可方便快速地多路复用。     

用新的雷达校准和性能监视方法改善飞行试验的数据

性能更高的现代武器系统的飞行试验,要求靶场提供更加精确而一致的测量数据。外测系统测量导弹的位置和速度,是一种独立的外部数据源,用以鉴定武器系统符合设计指标的程度。虽然新的测量系统(例如GPS全球定位系统)提供弹道数据的作用在日益增加,但在最近一段时间,跟踪雷达和光测系统仍将是主要的数据源。按目前西部导弹卫星试验中心(以下简称西试验中心)所用的方法,测定雷达系统的误差并予以修正,是可以改善雷达的数据的。在测定雷达系统的误差和监视C波段雷达总性能方面,GEOS-3和安排在1984年发射的GEOSAT这类卫星起着重要的作用。利用GEOS卫星已经发现了许多问题,如果不予解决,将会大大降低保障导弹和飞机试验用的雷达数据的质量。