Microbial diversity of Indian Ocean hydrothermal vent plumes: microbes tolerant of desiccation, peroxide exposure, and ultraviolet and gamma-irradiation

The microbial diversity of Kali chimney plumes, part of a hydrothermal vent field in the Rodriguez Triple Junction, Indian Ocean (depth approximately 2,240 m), was examined in an attempt to discover "extremotolerant" microorganisms that have evolved unique resistance capabilities to this harsh environment. Water and sediment samples were collected from the vent and from sediments located at various distances (2-20 m) away from and surrounding the chimney. Samples were screened for hypertolerant microbes that are able to withstand multiple stresses. A total of 46 isolates were selected for exposure to a number of perturbations, such as heat shock, desiccation, H(2)O(2), and ultraviolet (UV) and gamma-irradiation. The survival of Psychrobacter sp. L0S3S-03b following exposure to >1,000 J/m(2) UV(254) radiation was particularly intriguing amid a background of varying levels of resistance. Vegetative cells of this non-spore-forming microbe not only survived all of the treatments, but also exhibited a 90% lethal dose of 30 s when exposed to simulated martian UV radiation and a 100% lethal dose of 2 min when exposed to full spectrum UV, which is comparable to findings for bacterial endospores.     

Coronal mass ejection (CME) activity of low mass M stars as an important factor for the habitability of terrestrial exoplanets. II. CME-induced ion pick up of Earth-like exoplanets in close-in habitable zones

Atmospheric erosion of CO2-rich Earth-size exoplanets due to coronal mass ejection (CME)-induced ion pick up within close-in habitable zones of active M-type dwarf stars is investigated. Since M stars are active at the X-ray and extreme ultraviolet radiation (XUV) wave-lengths over long periods of time, we have applied a thermal balance model at various XUV flux input values for simulating the thermospheric heating by photodissociation and ionization processes due to exothermic chemical reactions and cooling by the CO2 infrared radiation in the 15 microm band. Our study shows that intense XUV radiation of active M stars results in atmospheric expansion and extended exospheres. Using thermospheric neutral and ion densities calculated for various XUV fluxes, we applied a numerical test particle model for simulation of atmospheric ion pick up loss from an extended exosphere arising from its interaction with expected minimum and maximum CME plasma flows. Our results indicate that the Earth-like exoplanets that have no, or weak, magnetic moments may lose tens to hundreds of bars of atmospheric pressure, or even their whole atmospheres due to the CME-induced O ion pick up at orbital distances 相似文献   

A thermodynamic analysis of microbial growth experiments

The common thread of energy release suggests that diverse microbial metabolic processes can be compared through thermodynamic analyses. The resulting energy and power requirements can provide quantitative constraints on habitability. Because previous thermodynamic analyses have focused on the minimum amount of energy needed for the growth of a microorganism or community, the focus of this study is to gain a fuller understanding of the microbial response to highly habitable conditions. This communication summarizes the results of a thermodynamic analysis of the energy and power consumed by microorganisms in experiments that were designed to optimize growth. Reports of microbial growth experiments taken from the literature were combined with speciation and standard state calculations to assess the overall Gibbs energy change during the experiments. Results show that similar numbers of cells (10(9) to 10(10) ) were produced in these experiments regardless of the duration of log phase growth (from <2 to >200 hours) or the total Gibbs energy change [from 1.3-29.6 kJ (mol electrons transferred)(1)]. As a result, optimal growth conditions appear to produce between 10(10) and 10(14) cells per watt of power consumed.     

CCD互相关粒子图像测速及其在对抗流流场测量中的应用

在常规自相关粒子图像测速（ＰＩＶ）系统的基础上,发展了一个采用ＣＣＤ像机的互相关粒子图像测速系统。用这一新系统测量了对抗流流场的结果表明,这一技术克服了自相关粒子图像测速技术在测量具有滞止点的流场中的困难。实验说明,与自相关粒子图像测速技术相比,这一技术更快捷有效。     

Microorganisms metabolizing on clay grains in 3-km-deep Greenland basal ice

We have discovered > 10(8) microbial cells/cm3 attached to clay grains in the bottom 13 m of the GISP2 (Greenland Ice Sheet Project) ice core. Their concentration correlates with huge excesses of CO2 and CH4. We show that Fe-reducing bacteria produce most of the excess CO2 and methanogenic archaea produce the excess CH4. The number of attached cells per clay grain is proportional to grain perimeter rather than to area, which implies that nutrients are accessed at grain edges. We conclude that Fe-reducing microbes immobilized on clay surfaces metabolize via "shuttle" molecules that transport electrons to grain edges, where they reduce Fe(III) ions at edges to Fe(II) while organic acid ions are oxidized to CO2. Driven by the concentration gradient, electrons on Fe(II) ions at grain edges "hop" to Fe(III) ions inward in the same edges and oxidize them. The original Fe(III) ions can then attach new electrons from shuttle molecules at the edges. Our mechanism explains how Fe-reducers can reduce essentially all Fe(III) in clay minerals. We estimate that the Fe(III) in clay grains in the GISP2 silty ice can sustain Fe-reducing bacteria at the ambient temperature of -9 degrees C for approximately 10(6) years. F420 autofluorescence imaging shows that > 2.4% of the cells are methanogens, which account for the excess methane.     

Multiobjective Design of Line-of-Sight Stabilization System for Airborne Electro-Optical Device

A technique of multiobjective parametric design of line-of-sight stabilization system for an airborne electro-optical device is developed. The multiobjective design of the PI controller for the stabilization system being considered is performed.     

Coupled CFD/CSD simulation of the helicopter main rotor in high-speed forward flight

The helicopter main rotor in forward flight is considered in this paper. The results for rigid blades and elastic blades are compared by the method of coupled simulation. The influence of the structural damping coefficient on the blade in-flight deformation is also considered.     

Optimization of measurements of the Earth’s radiation belt particle fluxes

The Earth’s radiation belts discovered at the end of the 1950s have great scientific and practical interest. Their main characteristics in magnetically quiet periods are well known. However, the dynamics of the Earth’s radiation belts during magnetic storms and substorms, particularly the dynamics of relativistic electrons of the outer belt, when Earth’s radiation belt particle fluxes undergo significant time variations, is studied insufficiently. At present, principally new experiments have been performed and planned with the intention to better study the dynamics of the Earth’s radiation belts and to operationally control the space-energy distributions of the Earth’s radiation belt particle fluxes. In this paper, for spacecraft designed to measure the fluxes of electrons and protons of the Earth’s radiation belts at altitudes of 0.5–10000 km, the optimal versions for detector orientation and orbital parameters have been considered and selected.     

Radiation environment at the end of active functioning of <Emphasis Type="Italic">Vernov</Emphasis> satellite

Factors of radiation environment in near-Earth space in a period from December 1 to 10, 2014 have been analyzed, which could affect serviceability of the onboard systems of Vernov spacecraft.     

Estimation of potential abilities of middle atmosphere density measurements from a near-Earth orbit within the UV wavelength range

Analysis of errors in atmospheric density measurements by lidar on board the ISS is performed. It is shown that using as the lidar transmitter a Nd:YAG laser with moderate parameters of emission at a wavelength of 353 nm and a receiving mirror diameter of 0.4 m, it is possible to cover with a 10% measurement error a height range, on average, from 40–60 km and 30–40 km in the nighttime and daytime, respectively, down to the troposphere. Working with emission at 266 nm with a 10% error, it is possible to move to the heights of the mesosphere (70 km) and penetrate the atmosphere down to a height of 40 km. Thus, the use of two harmonics makes it possible to assimilate the height range of atmospheric density measurements from on board the ISS beginning from 70 km and down to the troposphere.