The Mawrth Vallis region of Mars: A potential landing site for the Mars Science Laboratory (MSL) mission

The primary objective of NASA's Mars Science Laboratory (MSL) mission, which will launch in 2011, is to characterize the habitability of a site on Mars through detailed analyses of the composition and geological context of surface materials. Within the framework of established mission goals, we have evaluated the value of a possible landing site in the Mawrth Vallis region of Mars that is targeted directly on some of the most geologically and astrobiologically enticing materials in the Solar System. The area around Mawrth Vallis contains a vast (>1?×?10? km2) deposit of phyllosilicate-rich, ancient, layered rocks. A thick (>150?m) stratigraphic section that exhibits spectral evidence for nontronite, montmorillonite, amorphous silica, kaolinite, saponite, other smectite clay minerals, ferrous mica, and sulfate minerals indicates a rich geological history that may have included multiple aqueous environments. Because phyllosilicates are strong indicators of ancient aqueous activity, and the preservation potential of biosignatures within sedimentary clay deposits is high, martian phyllosilicate deposits are desirable astrobiological targets. The proposed MSL landing site at Mawrth Vallis is located directly on the largest and most phyllosilicate-rich deposit on Mars and is therefore an excellent place to explore for evidence of life or habitability.     

缩短飞控装置战备维修保障时间

面向军方战备需求,开展了"缩短飞控装置战备维修保障时间"的QC活动。从现场调查、数据分析和新技术论证等方面深入探究目标可行性,并运用头脑风暴法构建了原因分析关联图;针对分析出的末端因素,运用直方图、散布图、卡方检验、直接排除等方法,从中确定主要因素,并针对要因提出对策和改进方案;按照"5W1H"原则制定对策落实表,开展改进活动,实现活动目标,并形成了一系列标准和规范。最后,使维修保障时间在巩固期内达到稳定,证明实施后效果稳定、措施有效,活动取得圆满成功。     

镍基单晶叶片制造技术及再结晶研究进展

针对航空发动机单晶涡轮叶片的制造技术以及再结晶缺陷进行分析,结合国内外研究现状,从单晶空心涡轮叶片铸造技术、单晶空心涡轮叶片再结晶缺陷及单晶叶片再结晶控制方法等方面,对单晶叶片制造技术及再结晶控制方法取得的研究成果进行总结和分析。重点介绍了叶片制造技术和再结晶控制技术的方法及研究。对我国单晶空心涡轮叶片制造技术及再结晶缺陷的进一步研究重点进行分析。     

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.