Chemical mapping of proterozoic organic matter at submicron spatial resolution

A NanoSIMS ion microprobe was used to map the submicron-scale distributions of carbon, nitrogen, sulfur, silicon, and oxygen in organic microfossils and laminae in a thin section of the approximately 0.85 billion year old Bitter Springs Formation of Australia. The data provide clues about the original chemistry of the microfossils, the silicification process, and the biosignatures of specific microorganisms and microbial communities. Chemical maps of fossil unicells and filaments revealed distinct wall- and sheath-like structures enriched in C, N, and S, consistent with their accepted biological origin. Surprisingly, organic laminae, previously considered to be amorphous, also exhibited filamentous and apparently compressed spheroidal structures defined by strong enrichments in C, N, and S. By analogy to NanoSIMS data from the well-preserved microfossils, these structures were interpreted as being of biological origin, most likely representing densely packed remnants of microbial mats. Given that the preponderance of organic matter in Precambrian sediments is similarly "amorphous," our findings indicate that a re-evaluation of ancient specimens via in situ structural, chemical, and isotopic study is warranted. Our analyses have led us to propose new criteria for assessing the biogenicity of problematic kerogenous materials, and, thus, these criteria can be applied to assessments of poorly preserved or fragmentary organic residues in early Archean sediments and any that might occur in meteorites or other extraterrestrial samples.     

火星等离子体环境探测

萤火一号(YH-1)探测器将对火星空间环境进行独立而深入的探测研究,探测各空间区域的等离子体特性及其对太阳风扰动的响应,以及火星离子逃逸过程,研究太阳风对火星水体损失的影响。为了实现这一目标,萤火一号搭载了等离子体探测包,包括2个离子分析器和1个电子分析器,具有较高的时间分辨率、能量分辨率,可以探测0.02～10 keV的离子、电子,同时能够对粒子的入射方向及1～44 au(1 au=9.1095×10~(-31)kg)质量范围内的离子成分进行分辨。本文阐述了萤火一号等离子体探测的科学意义,并对等离子体包的工作原理,仪器设计进行了介绍。     

供测量高阻率材料电压、电流和电阻用的前置放大器

本文介绍一种供测量高阻率材料直流电压、电流和电阻用的前置放大器,其测量范围分别为:电压:30μv～10v;电流:10~(-2)～10~(-13)A;电阻:10~3～10~(13)Ω。若在反馈回路中接入适当的电容器还可测量电荷。本前置放大器采用市场上供应的运算放大器制成,其体积较小,并可与市场上大量供应的电压表或记录器联合使用,适用于无定形的(非晶体的)半导体薄膜电气性能的就地测量。     

边界层转捩过程三维扰动的发展和演化

引入展向调制的二维人工扰动激发平板边界层转捩,利用水槽氢气泡流动显示技术观察到转捩边界层中典型三维扰动的产生和发展,包括Λ结构、发卡涡以及发卡涡演化生成环状涡的过程.实验结果显示出环状涡和尖峰结构的关系,直接证实了尖峰结构的产生机理.在流动紊乱化初始阶段发现常出现在湍流边界层中的暗斑结构,结果表明与暗斑相伴随的局部高剪切层不稳定可能是流动紊乱化的重要原因.     

Mission to Mars using integrated propulsion concepts: considerations, opportunities, and strategies

The aim of this paper is to evaluate the feasibility of a mission to Mars using the Integrated Propulsion Systems (IPS) which means to couple Nuclear-MPD-ISPU propulsion systems. In particular both mission analysis and propulsion aspects are analyzed together with technological aspects. Identifying possible mission scenarios will lead to the study of possible strategies for Mars Exploration and also of methods for reducing cost. As regard to IPS, the coupling between Nuclear Propulsion (Rubbia's engine) and Superconductive MPD propulsion is considered for the Earth-Mars trajectories: major emphasis is given to the advantages of such a system. The In Situ Resource Utilization (ISRU) concerns on-Mars operations; In Situ Propellant Utilization (ISPU) is foreseen particularly for LOX-CH4 engines for Mars Ascent Vehicles and this possibility is analyzed from a technological point of view. Tether Systems are also considered during interplanetary trajectories and as space elevators on Mars orbit. Finally strategic considerations associated to this mission are considered also.     

Vegetation's red edge: a possible spectroscopic biosignature of extraterrestrial plants

Earth's deciduous plants have a sharp order-of-magnitude increase in leaf reflectance between approximately 700 and 750 nm wavelength. This strong reflectance of Earth's vegetation suggests that surface biosignatures with sharp spectral features might be detectable in the spectrum of scattered light from a spatially unresolved extrasolar terrestrial planet. We assess the potential of Earth's step-function-like spectroscopic feature, referred to as the "red edge," as a tool for astrobiology. We review the basic characteristics and physical origin of the red edge and summarize its use in astronomy: early spectroscopic efforts to search for vegetation on Mars and recent reports of detection of the red edge in the spectrum of Earthshine (i.e., the spatially integrated scattered light spectrum of Earth). We present Earthshine observations from Apache Point Observatory (New Mexico) to emphasize that time variability is key to detecting weak surface biosignatures such as the vegetation red edge. We briefly discuss the evolutionary advantages of vegetation's red edge reflectance, and speculate that while extraterrestrial "light-harvesting organisms" have no compelling reason to display the exact same red edge feature as terrestrial vegetation, they might have similar spectroscopic features at different wavelengths than terrestrial vegetation. This implies that future terrestrial-planet-characterizing space missions should obtain data that allow time-varying, sharp spectral features at unknown wavelengths to be identified. We caution that some mineral reflectance edges are similar in slope and strength to vegetation's red edge (albeit at different wavelengths); if an extrasolar planet reflectance edge is detected care must be taken with its interpretation.     

轴流风扇“尖峰型”失速起始特征及其物理机制的实验及数值研究

为了探索风扇失速起始特征及诱因,采用动态流场测量试验与三维粘性流场数值模拟技术,对单级轴流风扇NPU-fan的"尖峰型"旋转失速流场和基本特征进行了研究。实验研究结果表明,轴流风扇NPU-fan在设计转速和非设计转速下均出现了典型的"尖峰型"全叶展失速的旋转失速现象,动态探针测量捕捉到了"尖峰型"失速先兆波及其特征,并且测量得到扰动波的初始转速均约为70%转速;三维流场计算表明,静子叶根角区失速会严重影响风扇的效率,但并未触发压气机的失稳。NPUfan风扇的失速情形符合Vo等提出的尖峰波失速先兆出现准则,是典型的叶尖区流动诱发的风扇/压气机失稳。     

Laser Hardening of Metals

The first experiments on hardening metals by laserpeening induced residual compressive stress in the sur-face of metals for improving their resistance to cracking,stress corrosion and fatigue took place more than 30years ago. However, only today, with the development ofhigh-intensity pulse repetitive rate lasers, this methodstarts to compete to traditional peening, which use influ-ence of small metal balls.Laser peening uses pulses with high intensity 109￣1010 W/cm2 [1]. The laser energy abso…     

The Main Results and the Perspectives in the Researches at SSRT

In this report briefly presented the contemporary state of the experimental base of Radio Astrophysical Observatory (RAO) of the Institute of Solar-Terrestrial Physics (ISTP), the methodology of radioheliographic monitoring of the solar corona, the SSRT database, the RAO Web-pages, factors limiting the effective use of SSRT. Here are formulated the original results of the basic directions of the solar activity researches and the problems solutions on SSRT: (1) active regions at various development stages, morphology, modeling,signs of energy accumulation and flares buildup, forecast of powerful flares; (2) scenario, topology and the fine temporal picture of flares development, signs of primary energy release, radio emission mechanisms, scatter effects of radio emission in turbulent corona, energetic particles fluxes; (3) filaments; (4) CME with the localization of their initiation at the solar disk background, development scenario of filament activation + CME +flare; (5) coronal holes, and (6) bright coronal points.      

Science Missions Using CubeSats

As the role of missions and experiments carried out in outer space becomes more and more essential in our understanding of many earthly problems, such as resource management, environmental problems, and disaster management, as well as space science questions, thanks to their lower cost and faster development process CubeSats can benefit humanity and therefore, young scientists and engineers have been motivated to research and develop new CubeSat missions. Not very long after their inception, CubeSats have evolved to become accepted platforms for scientific and commercial applications. The last couple of years showed that they are a feasible tool for conducting scientific experiments, not only in the Earth orbit but also in the interplanetary space. For many countries, a CubeSat mission could prompt the community and young teams around the world to build the national capacity to launch and operate national space missions. This paper presents an overview of the key scientific and engineering gateways opened up to the younger scientific community by the advent and adaptation of new technology into CubeSat missions. The role of cooperation and the opportunities for capacity-building and education are also explored. Thus, the present article also aims to provide useful recommendations to scientists, early-career researchers, engineers, students, and anyone who intends to explore the potential and opportunities offered by CubeSats and CubeSats-based missions.