Eutectic phases in ice facilitate nonenzymatic nucleic acid synthesis

Polymeric compounds similar to oligonucleotides are relevant to the origin of life and particularly to the concept of an RNA world. Although short oligomers of RNA can be synthesized nonenzymatically under laboratory conditions by second-order reactions in concentrated solutions, there is no consensus on how these polymers could have been synthesized de novo on the early Earth from dilute solutions of monomers. To address this question in the context of an RNA world, we have explored ice eutectic phases as a reaction medium. When an aqueous solution freezes, the solutes become concentrated in the spaces between the ice crystals. The increased concentration offsets the effect of the lower temperature and accelerates the reaction. Here we show that in the presence of metal ions in dilute solutions, frozen samples of phosphoimidazolide-activated uridine react within days at -18 degrees C to form oligouridylates up to 11 bases long. Product yields typically exceed 90%, and approximately 30% of the oligomers include one or more 3'-5' linkages. These conditions facilitate not only the notoriously difficult oligouridylate synthesis, but also the oligomerization of activated cytidylate, adenylate, and guanylate. To our knowledge, this represents the first report to indicate that ice matrices on the early Earth may have accelerated certain prebiotic polymerization reactions.     

Challenges of assuring crew safety in space shuttle missions with international cargoes

The top priority in America's manned space flight program is the assurance of crew and vehicle safety. This priority gained greater focus during and after the Space Shuttle return-to-flight mission (STS-26). One of the interesting challenges has been to assure crew safety and adequate protection of the Space Shuttle, as a national resource, from increasingly diverse cargoes and operations. The control of hazards associated with the deployment of complex payloads and cargoes has involved many international participants. These challenges are examined in some detail along with examples of how crew safety has evolved in the manned space program and how the international partners have addressed various scenarios involving control and mitigation of potential hazards to crew and vehicle safety.     

Force and power characteristics of a resistive exercise device for use in space

We have developed a non-gravity dependent mechanical device, which provides resistance during coupled concentric and eccentric muscle actions, through the inertia of a spinning fly-wheel (Fly-Wheel Ergometry; FWE). Our research shows that lower-limb FWE exercise can produce forces and thus muscular stress comparable to what is typical of advanced resistance training using free weights. FWE also offers greater training stimuli during eccentric relative to concentric muscle actions, as evidenced by force and electromyographic (EMG) measurements. Muscle use of specific muscle groups, as assessed by the exercise-induced contrast shift of magnetic resonance images, is similar during lower-limb FWE and the barbell squat. Unlike free-weight exercise, FWE allows for maximal voluntary effort in each repetition of an exercise bout. Likewise, FWE exercise, not unassisted free-weight exercise, produces eccentric "overload". Collectively, the inherent features of this resistive exercise device and the results of the physiological evaluations we have performed, suggest that resistance exercise using FWE could be used as an effective exercise counter-measure in space. The flywheel principle can be employed to any exercise configuration and designed into a compact device allowing for exercises stressing those muscles and bone structures, which are thought to be most affected by long-duration spaceflight.     

Psychological health maintenance on Space Station Freedom

The scheduling of crew rotations for up to 180 days on Space Station Freedom presents a special challenge for behavioral scientists who are tasked with providing psychological support for the crews, their families, and mission flight controllers. Preflight psychological support planning may minimize the negative impact of psychological and social issues on mission success, as well as assist NASA management in making real-time mission planning decisions in the event of a significant social event (for example, the death of a family member). During flight, the combined psychological, emotional, and social stressors on the astronauts must be monitored, along with other aspects of their health. The Health Maintenance Facility (HMF) will have the capability of providing preventive, diagnostic, and therapeutic assistance for significant psychiatric and interpersonal problems which may develop. Psychological support will not end with the termination of the mission. Mental health professionals must be part of the team of medical personnel whose job will be to facilitate the transition--physical and mental--from the space environment back to planet Earth. This paper reviews each phase of mission planning for Space Station Freedom and specifies those factors that may be critical for psychological health maintenance on extended-duration space missions.     

Biophysics in space

Biophysics is an interdisciplinary field of study where various disciplines work together, with results of much interest to many scientists and students of the life sciences. Since physics is not always accessible to and understandable to biologists and life sometimes too simplified, this presentation focusses on models to help understand the biological effects of space factors, with emphasis on free radicals.     

多片压电双晶片并联驱动器的设计

针对微型无人机在受到外界干扰时通过自适应控制来实现飞行的稳定性设计了一种多片压电双晶片并联驱动的新型驱动器.用功率放大器和频谱分析仪分别对驱动器的在空载和带栽情况下的静态特性和动态特性进 行了测试,分析比较了在不同负载下单片压电双晶片和双片压电双晶片组成的驱动器的驱动能力,测得了双片 压电双晶片并联驱动器的输出位移和驱动电压之问的传递函数.实验结果表明:该驱动器不仅可以实现位移放 大,而且可以通过多片压电双晶片并联补偿驱动器的输出力,为设计新型压电双晶片驱动器提供了新的思路,同 时为压电双晶片驱动器的自适应控制提供了参考.     

基于蜜罐技术的分布式容侵防御模型

在分析国内外研究现状的基础上,针对目前蜜罐技术应用中存在的问题,提出了一种基于蜜罐的分布式容侵防御模型,并在模型中设计权限状态监控和基于匹配度的检测算法。测试实验证明,该模型能够弥补当前蜜罐技术应用的不足,辅助IDS提高威胁检测的准确度,有效地增强网络的容侵能力和生存能力。     

移动登机桥举升机构设计

移动登机桥举升叉架受力分析计算，突破叉架结构的传统手工计算。借助于现代设计方法，在初步确定该结构的参数基础上，采用SolidWorks软件三维建模，通过COSMOSMotion插件对其工作机构进行运动学仿真；在COSMOSworks模块中，按照实际工况对模型进行约束及加栽、划分网格等操作，进行机构的结构有限元分析，校核该机构的结构参数，提高了举升叉架的设计效率和安全可靠性。通过实地试验，验证该机构参数的合理性及该方法的可信度。     

Exobiology, SETI, von Neumann and geometric phase control

The central difficulties confronting us at present in exobiology are the problems of the physical forces which sustain three-dimensional organisms, i.e., how one dimensional systems with only nearest interaction and two dimensional ones with its regular vibrations results in an integrated three-dimensional functionality. For example, a human lung has a dimensionality of 2.9 and thus should be measured in m2.9. According to thermodynamics, the first life-like system should have a small number of degrees of freedom, so how can evolution, via cycles of matter, lead to intelligence and theoretical knowledge? Or, more generally, what mechanisms constrain and drive this evolution? We are now on the brink of reaching an understanding below the photon level, into the domain where quantum events implode to the geometric phase which maintains the history of a quantum object. Even if this would exclude point to point communication, it could make it possible to manipulate the molecular level from below, in the physical scale, and result in a new era of geometricised engineering. As such, it would have a significant impact on space exploration and exobiology.