Comparative survival analysis of Deinococcus radiodurans and the haloarchaea Natrialba magadii and Haloferax volcanii exposed to vacuum ultraviolet irradiation

The haloarchaea Natrialba magadii and Haloferax volcanii, as well as the radiation-resistant bacterium Deinococcus radiodurans, were exposed to vacuum UV (VUV) radiation at the Brazilian Synchrotron Light Laboratory. Cell monolayers (containing 10(5) to 10(6) cells per sample) were prepared over polycarbonate filters and irradiated under high vacuum (10(-5) Pa) with polychromatic synchrotron radiation. N. magadii was remarkably resistant to high vacuum with a survival fraction of (3.77±0.76)×10(-2), which was larger than that of D. radiodurans (1.13±0.23)×10(-2). The survival fraction of the haloarchaea H. volcanii, of (3.60±1.80)×10(-4), was much smaller. Radiation resistance profiles were similar between the haloarchaea and D. radiodurans for fluences up to 150?J m(-2). For fluences larger than 150?J m(-2), there was a significant decrease in the survival of haloarchaea, and in particular H. volcanii did not survive. Survival for D. radiodurans was 1% after exposure to the higher VUV fluence (1350?J m(-2)), while N. magadii had a survival lower than 0.1%. Such survival fractions are discussed regarding the possibility of interplanetary transfer of viable microorganisms and the possible existence of microbial life in extraterrestrial salty environments such as the planet Mars and Jupiter's moon Europa. This is the first work to report survival of haloarchaea under simulated interplanetary conditions.     

Thyrotropin receptor and membrane interactions in FRTL-5 thyroid cell strain in microgravity

The aim of this work was to analyze the possible alteration of thyrotropin (TSH) receptors in microgravity, which could explain the absence of thyroid cell proliferation in the space environment. Several forms of the TSH receptor are localized on the plasma membrane associated with caveolae and lipid rafts. The TSH regulates the fluidity of the cell membrane and the presence of its receptors in microdomains that are rich in sphingomyelin and cholesterol. TSH also stimulates cyclic adenosine monophosphate (cAMP) accumulation and cell proliferation. Reported here are the results of an experiment in which the FRTL-5 thyroid cell line was exposed to microgravity during the Texus-44 mission (launched February 7, 2008, from Kiruna, Sweden). When the parabolic flight brought the sounding rocket to an altitude of 264?km, the culture media were injected with or without TSH in the different samples, and weightlessness prevailed on board for 6 minutes and 19 seconds. Control experiments were performed, in parallel, in an onboard 1g centrifuge and on the ground in Kiruna laboratory. Cell morphology and function were analyzed. Results show that in microgravity conditions the cells do not respond to TSH treatment and present an irregular shape with condensed chromatin, a modification of the cell membrane with shedding of the TSH receptor in the culture medium, and an increase of sphingomyelin-synthase and Bax proteins. It is possible that real microgravity induces a rearrangement of specific sections of the cell membrane, which act as platforms for molecular receptors, thus influencing thyroid cell function in astronauts during space missions.     

固体推进剂的非线性结构模型

在大多数固体推进剂特性的线性和非线性理论中,一个主要的缺陷在于忽略了内部损伤。对于那些已引出损伤参数的非线性理论,数值常数与推进剂的物理性质无关。而且,这些理论具有如此复杂的性质以至于要完成一个庞大的实验测试程序。已经提出了一个表示固体推进剂性质的简单方法。这个方法以一个基本定律为基础,该定律用一个应力衰减函数修正粘弹表达式。根据单轴试验数据,可用衰减函数表示推进剂的非线性性质。在卸载期损伤的表达式中,这个方法比过去的方法显示出重大的改进。分别定义松弛和再加载为过去最大应力的正态函数。利用这种方法对复杂的过程进行了预测,而且实测应力与预测应力很接近。     

一种大变形多空间域连续体结构拓扑优化方法

针对大变形非线性结构拓扑优化问题,提出了基于混合细胞自动机(HCA, Hybrid Cellular Automata)多空间域连续体结构拓扑优化方法;采用密度法,建立了单元相对密度表示的材料弹-塑性模型;以单元相对密度和应变能作为细胞自动机(CA,Cellular Automata)的状态信息,利用CA局部控制规则,修改相对密度,迭代实现各设计空间域应变能均匀分布;设计了多空间域拓扑优化HCA算法,采取多个对象同时耦合优化迭代,各自收敛策略,解决了多空间域优化迭代算法收敛稳定性问题;最后,以汽车保险杆结构横梁和支撑等两个设计空间为例,施加大变形动态载荷作用,对提出的多空间结构优化算法进行了验证,优化后结构有效地降低了碰撞作用力峰值达54％,提高了结构安全性.     

Can identification of a fourth domain of life be made from sequence data alone, and could it be done on Mars?

A central question in astrobiology is whether life exists elsewhere in the universe. If so, is it related to Earth life? Technologies exist that enable identification of DNA- or RNA-based microbial life directly from environmental samples here on Earth. Such technologies could, in principle, be applied to the search for life elsewhere; indeed, efforts are underway to initiate such a search. However, surveying for nucleic acid-based life on other planets, if attempted, must be carried out with caution, owing to the risk of contamination by Earth-based life. Here we argue that the null hypothesis must be that any DNA discovered and sequenced from samples taken elsewhere in the universe are Earth-based contaminants. Experience from studies of low-biomass ancient DNA demonstrates that some results, by their very nature, will not enable complete rejection of the null hypothesis. In terms of eliminating contamination as an explanation of the data, there may be value in identification of sequences that lie outside the known diversity of the three domains of life. We therefore have examined whether a fourth domain could be readily identified from environmental DNA sequence data alone. We concluded that, even on Earth, this would be far from trivial, and we illustrate this point by way of examples drawn from the literature. Overall, our conclusions do not bode well for planned PCR-based surveys for life on Mars, and we argue that other independent biosignatures will be essential in corroborating any claims for the presence of life based on nucleic acid sequences.     

实时显示生成器

实时显示生成器(RTDB)是一种生成逻辑驱动显示的交互式图形工具样机。这些显示反映了当前系统状态,实时完成故障检测算法,采纳老练飞控人员的操作知识。该RTDB采用面向目标的方法,将基本操作逻辑和显示符号结合起来。要生成显示时,用户利用这种方法可规定屏幕布局和驱动逻辑。RTDB正在UNLX下用C语言开发,利用了MASSCOMP图形环境,作了适当的功能划分,以便于移植到其它图形环境。RTDB是为用户化实时数据驱动的航天飞机系统显示而开发的。使用该工具初始功能度的显示在STS—26发现者号轨道运行阶段投入了实用。目前正在NASA/JSC任务操作部开发的实时数据系统工程准备利用RTDB产生几种显示。本文介绍了这种工具的特点、目前的发展状况及其应用。     

跟踪与数据中继卫星系统的性能

一、引言 自60年代初,NASA就组建和操作一个为近地轨道卫星服务的跟踪和数据获取网。TDRSS是一个新测控网,为目前和直到2000年的预期卫星任务服务。该网利用了已经验证的空间和地面系统有关技术构成一个全新的测控站,只是其前端设备置于地球同步轨道上。尽量采用了自动化技术,使系统设置到数据采集以及整个跟踪期间的通信几乎都不需要人操作。     

陆军机动防空的发展趋势

地面部队的低空防空可分为保护固定发射场和机动设施两种.后者或者安装在机动车辆上限随机动部队进行,或者被牵引着用于保护构筑工事的部队.     

New results for the space radiation environment of MIR space station obtained by Liulin dosimeter-radiometer. Comparison with LET spectrometer NAUSICAA

Since 1988 high sensitivity semiconductor dosimeter-radiometer “Liulin” worked on board of MIR space station. Device measured the absorbed dose rate and the flux of penetrating particles. The analysis of the data hows the following new results:

In October 1989 and after March 24, 1991, two additional stable maximums in flux channel were observed in the southern-eastern part of South Atlantic Anomaly (SAA). These two maximums existed at least several months and seem to be due to trapped high energy electron and proton fluxes. In April 1991 additional maximums were localized in the following geographical coordinates regions: LATITUDE = (−35 °)–(−50 °) LONGITUDE = 332 ° − 16 ° and lat.(−46 °)–(−52 °) long. 360 ° − 60 °. Additional maximums diffusion occurs inside radiation belt. Appearance of these maximums seems to be closely connected with preceding powerful solar proton events and associated geomagnetic dynamics of new belt disturbances. After the series of solar proton events in June 1991 we observed significant enhancement of this new radiation belt formation. To achieve sufficient accuracy of dose rate predictions in low Earth orbits the structure and dynamics of new belt should be carefully analyzed to be included in a new environment model.

From the inter comparison of the data from “Liulin” and French developed tissue equivalent LET spectrometer NAUSICAA in the time period August–November 1992 we come to the following conclusions: Mainly there is good agreement between both data sets for absorbed dose in the region of SAA; Different situation of the instruments on the station can explain the cases when differences up to 2 times are observed; At high latitudes usually the tissue equivalent absorbed dose observations are 2 times larger than “Liulin” doses.     

含摩擦和加热的跨声速流动数值模拟研究

喷管中跨声速流动的反应流体动力学是实验和理论研究的一个重要领域.本文主要由两部分构成,在第一部分中对文献[2]中的Murman格式[1]的一般形式进行了简化,得到了守恒形式的欧拉方程,并对其求解方法进行了讨论,同时针对Chattot等的工作展开了分析,并给出了带激波的流动计算结果;而文章的第二部分则研究了包含摩擦、加热以及耗散的跨声速流动,并重点关注了一步Arrhenius化学反应模型下的爆震现象.本文还探究了摩擦力和带燃烧的跨声速流动之间的相互作用,同时详细给出了新的欧拉方程数值求解算法并同已有文献算例进行了对比验证.