The influence of microgravity on invasive growth in Saccharomyces cerevisiae

This study investigates the effects of microgravity on colony growth and the morphological transition from single cells to short invasive filaments in the model eukaryotic organism Saccharomyces cerevisiae. Two-dimensional spreading of the yeast colonies grown on semi-solid agar medium was reduced under microgravity in the Σ1278b laboratory strain but not in the CMBSESA1 industrial strain. This was supported by the Σ1278b proteome map under microgravity conditions, which revealed upregulation of proteins linked to anaerobic conditions. The Σ1278b strain showed a reduced invasive growth in the center of the yeast colony. Bud scar distribution was slightly affected, with a switch toward more random budding. Together, microgravity conditions disturb spatially programmed budding patterns and generate strain-dependent growth differences in yeast colonies on semi-solid medium.     

SOLID3: a multiplex antibody microarray-based optical sensor instrument for in situ life detection in planetary exploration

The search for unequivocal signs of life on other planetary bodies is one of the major challenges for astrobiology. The failure to detect organic molecules on the surface of Mars by measuring volatile compounds after sample heating, together with the new knowledge of martian soil chemistry, has prompted the astrobiological community to develop new methods and technologies. Based on protein microarray technology, we have designed and built a series of instruments called SOLID (for "Signs Of LIfe Detector") for automatic in situ detection and identification of substances or analytes from liquid and solid samples (soil, sediments, or powder). Here, we present the SOLID3 instrument, which is able to perform both sandwich and competitive immunoassays and consists of two separate functional units: a Sample Preparation Unit (SPU) for 10 different extractions by ultrasonication and a Sample Analysis Unit (SAU) for fluorescent immunoassays. The SAU consists of five different flow cells, with an antibody microarray in each one (2000 spots). It is also equipped with an exclusive optical package and a charge-coupled device (CCD) for fluorescent detection. We demonstrated the performance of SOLID3 in the detection of a broad range of molecular-sized compounds, which range from peptides and proteins to whole cells and spores, with sensitivities at 1-2?ppb (ng?mL?1) for biomolecules and 10? to 103 spores per milliliter. We report its application in the detection of acidophilic microorganisms in the Río Tinto Mars analogue and report the absence of substantial negative effects on the immunoassay in the presence of 50?mM perchlorate (20 times higher than that found at the Phoenix landing site). Our SOLID instrument concept is an excellent option with which to detect biomolecules because it avoids the high-temperature treatments that may destroy organic matter in the presence of martian oxidants.     

Lava cave microbial communities within mats and secondary mineral deposits: implications for life detection on other planets

Lava caves contain a wealth of yellow, white, pink, tan, and gold-colored microbial mats; but in addition to these clearly biological mats, there are many secondary mineral deposits that are nonbiological in appearance. Secondary mineral deposits examined include an amorphous copper-silicate deposit (Hawai'i) that is blue-green in color and contains reticulated and fuzzy filament morphologies. In the Azores, lava tubes contain iron-oxide formations, a soft ooze-like coating, and pink hexagons on basaltic glass, while gold-colored deposits are found in lava caves in New Mexico and Hawai'i. A combination of scanning electron microscopy (SEM) and molecular techniques was used to analyze these communities. Molecular analyses of the microbial mats and secondary mineral deposits revealed a community that contains 14 phyla of bacteria across three locations: the Azores, New Mexico, and Hawai'i. Similarities exist between bacterial phyla found in microbial mats and secondary minerals, but marked differences also occur, such as the lack of Actinobacteria in two-thirds of the secondary mineral deposits. The discovery that such deposits contain abundant life can help guide our detection of life on extraterrestrial bodies.     

A two-tiered approach to assessing the habitability of exoplanets

In the next few years, the number of catalogued exoplanets will be counted in the thousands. This will vastly expand the number of potentially habitable worlds and lead to a systematic assessment of their astrobiological potential. Here, we suggest a two-tiered classification scheme of exoplanet habitability. The first tier consists of an Earth Similarity Index (ESI), which allows worlds to be screened with regard to their similarity to Earth, the only known inhabited planet at this time. The ESI is based on data available or potentially available for most exoplanets such as mass, radius, and temperature. For the second tier of the classification scheme we propose a Planetary Habitability Index (PHI) based on the presence of a stable substrate, available energy, appropriate chemistry, and the potential for holding a liquid solvent. The PHI has been designed to minimize the biased search for life as we know it and to take into account life that might exist under more exotic conditions. As such, the PHI requires more detailed knowledge than is available for any exoplanet at this time. However, future missions such as the Terrestrial Planet Finder will collect this information and advance the PHI. Both indices are formulated in a way that enables their values to be updated as technology and our knowledge about habitable planets, moons, and life advances. Applying the proposed metrics to bodies within our Solar System for comparison reveals two planets in the Gliese 581 system, GJ 581 c and d, with an ESI comparable to that of Mars and a PHI between that of Europa and Enceladus.     

ESA再入探测器的某些空气热动力问题

给出了两种不同的再入飞行器:充气的再入和下滑演示器(IRDT)和Huygens.两者的任务都涉及在靠近轨道的条件下再入并均已于2005年完成.概述了IRDT的使命和具体设计问题,综述了IRDT最近飞行的初步结果和ESTEC估计Huygens受到的辐射通量采用的方法.     

NASA和波音联合实施X-37试验机计划

图１　Ｘ－３７将是Ｘ系列试验机中第一种在轨进行试验的试验机美国航宇局和波音公司最近签署了一项为期４年的协议，将建造一架Ｘ－３７可重复使用运载器，并在轨道上进行试飞，以验证范围广泛的多项技术。这些新技术最终有可能把每磅（１磅约合０．４５４公斤）有效载荷的发射费用从１万美元降低到１千美元。Ｘ－３７是美国航宇局未来Ｘ探路者试验机中的一种。未来Ｘ计划的目的就是要通过对先进技术进行飞行验证而降低航天发射成本。如果一切顺利的话，Ｘ－３７将在２００２年底装在航天飞机的货舱内进入轨道。按计划该试验机共将进行两次…     

在SA条件下利用GPS的轨道确定和点定位

GPS精度控制(SA)措施降低了GPS标准定位业务(SPS)非差分用户的定位精度。常说的SPS可达精度在正常条件下为100米(2DRMS)。在缺乏更多具体条件下,许多未来的SPS用户在他们的规划中采用了100米这一精度值,但多数情况下,是夸大了实际定位误差。在本文中,我们针对轨道用户星的点定位和动力学轨道确定来研究SA带来的误差。要使SA带来的误差减至最小,非差分用户有几种选择:扩大接收视场;观测尽可能多的GPS卫星;在时间上平滑误差;选用独立计算的GPS精密轨道星历(如NASA和美国测绘局计算的),而不采用广播星历。仿真计算表明,3维点位误差可保持在30米,并且在几小时内能平滑到3米。     

美新型号运载火箭发动机研制进展

美新型号运载火箭发动机研制进展晓雨图１捷径火箭发动机喷注器进行点火试车美国航宇局和空军几家研究试验机构正在着手进行几项关键性的火箭发动机试验。这将加快美国航宇局的Ｘ－３３和Ｘ－３４带翼技术试验火箭及波音公司的德尔它４渐进一次性运载器（ＥＥＬＶ）将要使...     

孔、轮廓和表面(十一)

第七章座标镗床的运行操作(二) 尺寸测量——工件对机床运动方向的方位一经找正,下一步则要求建立工件相对于机床测量系统及主轴轴线的尺寸关系。调整刻度盘或者工作台时,应该总是沿着刻度盘上箭头所示方向运动,以免产生间隙。如需再次回到调整位置,必须首先退离该处千分之几英寸(约百分之几毫米),然后再按照