Investigation of low-energy proton effects on aptamer performance for astrobiological applications

Biochips are promising instruments for the search for organic molecules in planetary environments. Nucleic acid aptamers are powerful affinity receptors known for their high affinity and specificity, and therefore are of great interest for space biochip development. A wide variety of aptamers have already been selected toward targets of astrobiological interest (from amino acids to microorganisms). We present a first study to test the resistance of these receptors to the constraints of the space environment. The emphasis is on the effect of cosmic rays on the molecular recognition properties of DNA aptamers. Experiments on beam-line facilities have been conducted with 2 MeV protons and fluences much higher than expected for a typical mission to Mars. Our results show that this irradiation process did not affect the performances of DNA aptamers as molecular recognition tools.     

关于普通高校体育教学的思考

通过对高校体育教学中的教学模式、内容设制、考核形式几方面的分析、探讨，提出了高校体育教学应以未来社会人才的需要为出发点，使体育教学从根本上摆脱传统教学观念的束缚，从单纯培养“知识型”、“技能型”人才向培养“创造性”、“综合性”、“应用性”人才转变。     

Stochastic Acceleration by Turbulence

The subject of this paper is stochastic acceleration by plasma turbulence, a process akin to the original model proposed by Fermi. We review the relative merits of different acceleration models, in particular the so called first order Fermi acceleration by shocks and second order Fermi by stochastic processes, and point out that plasma waves or turbulence play an important role in all mechanisms of acceleration. Thus, stochastic acceleration by turbulence is active in most situations. We also show that it is the most efficient mechanism of acceleration of relatively cool non relativistic thermal background magnetized plasma particles. In addition, it can preferentially accelerate electrons relative to protons as is needed in many astrophysical radiating sources, where usually there are no indications of presence of shocks. We also point out that a hybrid acceleration mechanism consisting of initial acceleration by turbulence of background particles followed by a second stage acceleration by a shock has many attractive features. It is demonstrated that the above scenarios can account for many signatures of the accelerated electrons, protons and other ions, in particular ³He and ⁴He, seen directly as Solar Energetic Particles and through the radiation they produce in solar flares.     

A microbial oasis in the hypersaline Atacama subsurface discovered by a life detector chip: implications for the search for life on Mars

The Atacama Desert has long been considered a good Mars analogue for testing instrumentation for planetary exploration, but very few data (if any) have been reported about the geomicrobiology of its salt-rich subsurface. We performed a Mars analogue drilling campaign next to the Salar Grande (Atacama, Chile) in July 2009, and several cores and powder samples from up to 5?m deep were analyzed in situ with LDChip300 (a Life Detector Chip containing 300 antibodies). Here, we show the discovery of a hypersaline subsurface microbial habitat associated with halite-, nitrate-, and perchlorate-containing salts at 2?m deep. LDChip300 detected bacteria, archaea, and other biological material (DNA, exopolysaccharides, some peptides) from the analysis of less than 0.5?g of ground core sample. The results were supported by oligonucleotide microarray hybridization in the field and finally confirmed by molecular phylogenetic analysis and direct visualization of microbial cells bound to halite crystals in the laboratory. Geochemical analyses revealed a habitat with abundant hygroscopic salts like halite (up to 260?g kg(-1)) and perchlorate (41.13?μg g(-1) maximum), which allow deliquescence events at low relative humidity. Thin liquid water films would permit microbes to proliferate by using detected organic acids like acetate (19.14?μg g(-1)) or formate (76.06?μg g(-1)) as electron donors, and sulfate (15875?μg g(-1)), nitrate (13490?μg g(-1)), or perchlorate as acceptors. Our results correlate with the discovery of similar hygroscopic salts and possible deliquescence processes on Mars, and open new search strategies for subsurface martian biota. The performance demonstrated by our LDChip300 validates this technology for planetary exploration, particularly for the search for life on Mars.     

TARANIS—A Satellite Project Dedicated to the Physics of TLEs and TGFs

TARANIS “Tool for the Analysis of RAdiations from lightNIngs and Sprites” is a CNES satellite project dedicated to the study of impulsive transfers of energy between the Earth atmosphere and the space environment. Such impulsive transfers of energy, identified by the observation at ground and in space (rocket, balloons, FORMOSAT 2 satellite) of Transient Luminous Events (TLEs) and the detection on satellites (CGRO, RHESSI) of Terrestrial Gamma ray Flashes (TGFs), are likely to occur in other astrophysical environments as well. The TARANIS mission and instrumentation is presented. The way the TARANIS programme (associated ground-based and balloon-based measurements included) may answer questions about the physics of TLEs and TGFs is examined. The questions addressed include: TLEs and TGFs source regions, associated phenomena, transfers of energy between the radiation belts and the atmosphere, TLEs and TGFs generation mechanisms, input parameters to the modelling of the variation of the atmosphere and the electric circuit.     

Distributed Sources in Comets

The distribution of some molecules and radicals (H₂CO, CO, HNC, CN,?…) in the atmosphere of several comets cannot be explained only by a direct sublimation from the nucleus, or by gas phase processes in the coma. Such molecules are in part the result of a distributed source in the coma, which could be the photo and thermal degradation of dust. We present a review of the degradation processes and discuss possible interpretations of the observations in which the degradation of solid complex organic material in dust particles seems to play a major role. The knowledge of such gas production mechanisms provides important clues on the chemical nature of the refractory organic material contained in comet nuclei.     

Ad hoc wireless sensor networks for exploration of Solar-system bodies

In this work, we evaluate the exploration of the Solar system by ad hoc wireless sensor networks (WSN), i.e., networks where all nodes (either moving or stationary) can both provide and relay data. The two aspects of self-organization and localization are the major challenges to achieve a reliable network for a variety of missions. We point out the diversity of environmental and operational constrains that WSN used for space exploration would face.We evaluate two groups of scenarios consisting in static or moving sensing nodes that can be either located on the ground or in the atmosphere of a Solar-system object. These scenarios enable collecting data simultaneously over a large surface or volume.We consider physical and chemical sensing of the atmosphere, surface and soil using such networks. Emerging technologies such as nodes localization techniques are reviewed. Finally, we compare the specific requirements of WSN for space exploration with those of WSN designed for terrestrial applications.