Effects of Environmental Oxygen Content and Dissolved Oxygen on the Surface Tension and Viscosity of Liquid Nickel

The NASA Marshall Space Flight Center’s electrostatic levitation (ESL) laboratory has recently added an oxygen partial pressure controller. This system allows the oxygen partial pressure within the vacuum chamber to be measured and controlled in the range from approximately \(10^{-28}\,{\mathrm {to}}\,10^{-9}\) bar, while in a vacuum atmosphere. The oxygen control system installed in the ESL laboratory’s main chamber consists of an oxygen sensor, oxygen pump, and a control unit. The sensor is a potentiometric device that determines the difference in oxygen activity in two gas compartments (inside the chamber and the air outside of the chamber) separated by an electrolyte. The pump utilizes coulometric titration to either add or remove oxygen. The system is controlled by a desktop control unit, which can also be accessed via a computer. The controller performs temperature control for the sensor and pump, has a PID-based current loop and a control algorithm. Oxygen partial pressure has been shown to play a significant role in the surface tension of liquid metals. Oxide films or dissolved oxygen may lead to significant changes in surface tension. The effects on surface tension and viscosity by oxygen partial pressure in the surrounding environment and the melt dissolved oxygen content will be evaluated, and the results will be presented. The surface tension and viscosity will be measured at several different oxygen partial pressures while the sample is undercooled. Surface tension and viscosity will be measured using the oscillating droplet method.     

CD57+/CD28- T cells in untreated hemato-oncological patients are expanded and display a Th1-type cytokine secretion profile, ex vivo cytolytic activity and enhanced tendency to apoptosis

Protopolystoma (Monogenea, Polystomatidae) is strictly specific to the anuran amphibian genus Xenopus. The host group is characterised by a polyploid series in which chromosome numbers reflect diploid, tetraploid, octoploid and dodecaploid constitutions; the series is considered to have evolved through interspecies hybridisation and genome duplication. This study correlates information on host evolutionary relationships with patterns of parasite speciation and host specificity. Protopolystoma is restricted to one subgenus (Xenopus) with multiples of 36 chromosomes, and is absent from the subgenus Silurana (with multiples of 20 chromosomes). Molecular, biochemical and karyotype evidence distinguishes three subgroups within Xenopus. Representative species from each subgroup, Xenopus muelleri, Xenopus fraseri and Xenopus laevis, have been examined for polystomatid infection. Two species of Protopolystoma occur in each of these host species. In X. muelleri, the two Protopolystoma species reflect parasite co-speciation corresponding with the divergence of two sibling host species. Xenopus fraseri and X. laevis (both with 2n = 36 chromosomes) are implicated in the hybrid origin of two octoploid species, Xenopus wittei and Xenopus vestitus (both 2n = 72). The relationships of the Protopolystoma species in these Xenopus taxa reflect this presumed ancestry. Xenopus wittei carries two species of Protopolystoma, one shared with X. fraseri and the other shared with X. laevis. Xenopus vestitus carries a single species of Protopolystoma which is shared with X. laevis but there is no "heirloom" which reflects its hybrid origin involving X. fraseri. In addition to these shared parasite species which may reflect shared host genes, X. fraseri and X. laevis each carry separate species-specific Protopolystoma which do not occur in other Xenopus species even where there is evidence of common genetic information (as in the allopolyploid wittei and vestitus). This case study may be interpreted as indicating a powerful influence of host genetic factors on susceptibility to infection, host-specificity, and parasite speciation.     

氡及其子体运移仿真系统开发

基于.net开发平台,借助C讨论了仿真系统的软件实现过程,简述了系统的功能模块及关键技术实现.实现了氡及其子体运移机制研究的计算机化.     

面向自治系统间IP前缀劫持的一种无证书安全防范机制

自治系统间的IP前缀劫持是互联网安全的重大威胁.目前基于非对称密码学的前缀劫持防范机制都无可避免地面临复杂的公钥证书存储管理问题或者密钥托管问题,并且在前缀源自治系统在线验证时计算量太大,难以在实际中布署实施.本文提出的这种防范机制,采用公钥自证明签名方案进行前缀源自治系统的验证,无需公钥证书和密钥托管,可从多方面提高防范机制的性能,有望促进IP前缀劫持防范机制的实际布署实施.     

ITS中基于模糊关系数据模型的知识表示及推理研究

使用模糊关系模型讨论建立学科知识库的方法,并用隶属度函数及模糊中心数等方法描述知识点属性,以知识点的模糊关系建立知识库,并且,就实现基于模糊关系数据模型推理过程,给出了两个关键性的算法。     

Crystallographic and morphological characteristics of oxidation growth pits in wustite grown at 1200 °C

In situ oxidation of polycrystalline iron at 1200 °C and atm has revealed symmetrical square growth pits in the wustite scale. The pit walls are nominally oriented with the {110} planes of the wustite lattice but are dissociated into macro- and microledges consisting of {100}-type planes. Such growth pits intrude into the wustite scale at the gas/oxide interface, and at the oxide/metal interface small oxide nodules intrude into the metal. After sufficiently long oxidation times at 1200 °C, rate control should shift from oxidant arrival to cation volume diffusion, and pits are then destabilized and a planar morphology is achieved.     

Increased messenger RNA from protein synthesis inhibited human fibroblasts

Numerous reports have demonstrated that specific protein synthesis in response to specific inducers is markedly stimulated by a simultaneous brief exposure to protein synthesis inhibitors such as cycloheximide. This phenomenon is known as "superinduction" and is most often attributed to the accumulation of cytoplasmic messenger RNA during the inhibition period. Messenger RNA, as defined by rapid labeling, oligo (dt)-cellulose binding, and cell free protein synthesis stimulation was measured in cycloheximide treated human fibroblasts. In spite of a consistent 40% decrease in total polysomal 3H-uridine labeled RNA, a 1.5- to 2-fold increase in extractable mRNA was observed. These data provide direct evidence that protein synthesis inhibition stimulates the appearance of cytoplasmic mRNA and/or completely blocks its degradation and, are consistent with the hypothesis that mRNA accumulation partly underlies the superinduction phenomena.     

承包商素质与项目成功关系的实证研究

承包商素质是项目成功的重要影响因素,其主要包括经验、管理能力、财务能力和技术能力。项目成功主要界定在项目成本、进度和质量3个方面。假定承包商的各项素质对项目成功具有正向作用,经检验该假定得到了实证结果的支持。     

基于ABAQUS的群锚加固岩质边坡 效果评价方法研究

针对在岩质边坡内存在多组锚索群且缺乏预应力锚索周围注浆体参数的情况,提出了一种岩 质边坡加固效果的评价方法,即:在用摩尔一库伦本构模型模拟岩质边坡的基础上,利用ABAQUS 有限元软件中的TRUSS单元模拟预应力锚索,并结合强度折减法,通过数值计算对岩质边坡的群锚 加固效果进行评价。研究结果表明,与未进行群锚加固相比,群锚加固可显著提高岩质边坡稳定安全 系数,并且减缓边坡塑性区的发展和破坏过程。为此,该评价方法可用于实际工程中对各类群锚加固 方案进行比较优选。     

营造军队院校和谐学术环境途径分析

营造军队院校和谐学术环境是高等军事教育的发展要求．针对当前军队院校中由于体制、观念等方面的原因存在着诸多不和谐学术现象,提出了可从牢固树立科学发展理念、务实军队院校的价值基础、淡化学术权利中的行政色彩、建立相应的学术道德运行机制四个方面营造和谐学术环境的建议,为军队院校学术环境的构建提供了一些借鉴．