Resistance of bacterial endospores to outer space for planetary protection purposes--experiment PROTECT of the EXPOSE-E mission

Spore-forming bacteria are of particular concern in the context of planetary protection because their tough endospores may withstand certain sterilization procedures as well as the harsh environments of outer space or planetary surfaces. To test their hardiness on a hypothetical mission to Mars, spores of Bacillus subtilis 168 and Bacillus pumilus SAFR-032 were exposed for 1.5 years to selected parameters of space in the experiment PROTECT during the EXPOSE-E mission on board the International Space Station. Mounted as dry layers on spacecraft-qualified aluminum coupons, the "trip to Mars" spores experienced space vacuum, cosmic and extraterrestrial solar radiation, and temperature fluctuations, whereas the "stay on Mars" spores were subjected to a simulated martian environment that included atmospheric pressure and composition, and UV and cosmic radiation. The survival of spores from both assays was determined after retrieval. It was clearly shown that solar extraterrestrial UV radiation (λ≥110?nm) as well as the martian UV spectrum (λ≥200?nm) was the most deleterious factor applied; in some samples only a few survivors were recovered from spores exposed in monolayers. Spores in multilayers survived better by several orders of magnitude. All other environmental parameters encountered by the "trip to Mars" or "stay on Mars" spores did little harm to the spores, which showed about 50% survival or more. The data demonstrate the high chance of survival of spores on a Mars mission, if protected against solar irradiation. These results will have implications for planetary protection considerations.     

失谐叶片轮盘的减缩建模及动力响应预测方法

为解决高保真失谐叶盘计算量大的问题,提出了一种新的减缩建模及动力响应预测方法。该方法对叶盘单扇区有限元模型进行圆周对称分析,获取谐调叶盘在局部坐标系下的基本模态特性。同时,运用主节点的概念,仅对少量节点进行模态分析,在大大降低矩阵维度的同时获取准确的失谐模态特性。在动力响应预测分析时,利用失谐固有频率点处响应的基本特性,仅选取危险频段内、危险叶片上的危险节点进行响应分析计算,既极大地提高了运算效率,又能够准确地获取叶盘最大受迫响应幅值。实例分析结果表明:相较于传统的有限元方法,该方法中模态分析的求逆过程矩阵维度从150万下降到384,计算所得的前50阶固有频率的精度保持在0.005%以内,最大响应计算过程运算量下降超过99%时,仅存在-0.35%的误差。     

Chicxulub and climate: radiative perturbations of impact-produced S-bearing gases

We use one-dimensional (1D) atmospheric models coupled to a sulfate aerosol model to investigate climate forcing and short-term response to stratospheric sulfate aerosols produced by the reaction of S-bearing gases and water vapor released in the Chicxulub impact event. A 1D radiation model is used to assess the climate forcing due to the impact-related loading of S-bearing gases. The model suggests that a climate forcing 100 times larger than that from the Pinatubo volcanic eruption is associated with the Chicxulub impact event for at least 2 years after the impact. In particular, we find a saturation effect in the forcing, that is, there is no significant difference in the maximum forcing between the highest (approximately 300 Gt) and lowest (approximately 30 Gt) estimated stratospheric S-loading from the Chicxulub impact. However, higher S-loads increase the overall duration of the forcing by several months. We use a single column model for a preliminary investigation of the short-term climate response to the impact-related production of sulfate aerosols (the lack of horizontal feedbacks limits the usefulness of the single column model to the first few days after the impact). Compared with the present steady-state climate, the introduction of large amounts of sulfate aerosols in the stratosphere results in a significant cooling of the Earth's surface. A long-term climate response can only be investigated with the use of a three-dimensional atmospheric model, which allows for the atmospheric circulation to adjust to the perturbation. Overall, although the climate perturbation to the forcing appears to be relatively large, the geologic record shows no sign of a significant long-term climatic shift across the K/T boundary, which is indicative of a fast post-impact climatic recovery.     

压力指数对温度敏感性的影响

本文提出了一种发动机温度敏感系数的新表达式,该温度敏感系数可由燃速、特征速度和燃烧室压力与K_n的关系来确定。     

Pre-cometary ice composition from hot core chemistry

Pre-cometary ice located around star-forming regions contains molecules that are pre-biotic compounds or pre-biotic precursors. Molecular line surveys of hot cores provide information on the composition of the ice since it sublimates near these sites. We have combined a hydrostatic hot core model with a complex network of chemical reactions to calculate the time-dependent abundances of molecules, ions, and radicals. The model considers the interaction between the ice and gas phase. It is applied to the Orion hot core where high-mass star formation occurs, and to the solar-mass binary protostar system IRAS 16293-2422. Our calculations show that at the end of the hot core phase both star-forming sites produce the same prebiotic CN-bearing molecules. However, in the Orion hot core these molecules are formed in larger abundances. A comparison of the calculated values with the abundances derived from the observed line data requires a chemically unprocessed molecular cloud as the initial state of hot core evolution. Thus, it appears that these objects are formed at a much younger cloud stage than previously thought. This implies that the ice phase of the young clouds does not contain CN-bearing molecules in large abundances before the hot core has been formed. The pre-biotic molecules synthesized in hot cores cause a chemical enrichment in the gas phase and in the pre-cometary ice. This enrichment is thought to be an important extraterrestrial aspect of the formation of life on Earth and elsewhere.     

一个由可匹配的互易无损五端口和优良的定向耦合器组成的理想六端口网络

由一个可匹配的互易无损五端口串接一个优良的定向耦合器组成的六端口。根据Engen所发展的理论,证明它具有理想六端口的特性。诸q点以120°间距分布在公共圆上。可匹配的五端口本身具有四路分配网络的功能,并与一个可匹配的非互易的无损三端口(环行器)非常类似。这种类似可用于设计几种可匹配对称微带线式的五端口,以便进行六端口测量。     

高Sc数下湍流喷流混合流的初步实验观测

对低斯密特数(Schmidt数)下的剪切流动已作过不少实验观测。为了解分子扩散作用和Sc数的影响,作者提供了一种低温喷流混合流实验设备,实验观测在高Sc数下喷流混合流动。实验观测表明:在高Sc数下的湍流喷流混合流动的基本流态与在低Sc数下类同;其喷流(火焰)无量纲长度与其质量流量比(Φ)也有类似关系。实验也部分观测了浮力对该喷流混合流动特性的影响。     

利用两颗地球同步卫星的通信与定位系统——系统与试验

我们研制了能在一个系统里提供卫星通信和定位服务的两种类型的混合终端，一种采用单信道单载波技术，另一种采用护谱技术。为了检验这两种终端的性能，我们在日本和太平洋区利用ＥＴＳ－Ｖ和Ｉｎｍａｒｓａｔ两颗地球同步卫星进行了一系列实验。