Phylogenetic identification and microbial diversity in snow of the summit （8201 m） of Cho Oyu Mountain,Tibet

The bacterial diversity and abundance in snow of the summit （8201 m） of Cho Oyu mountain, Tibet, were analyzed by 16S rRNA gene sequencing followed by scanning electronic microscopy analysis. Most of bacteria were found to be of spherical or oval shape （〉95%）. Bacterial 16S rDNA sequences were classified into 5 genera （Caulobacter, Ralstonia, Cupriavidus, Pelomonas and Pseudomonas）. Gammaproteobacteria were the most abundant （91.25%） among the library that consists of 594 clones. The sequences found in this study are highly similar to those previously retrieved from other cold environments, such as ice core, sea ice, permafrost and snow. The results showed that the cold and barren environments strongly influence the survival of bacteria. The high similarity among sequences retrieved from snow sample and other places, such as ocean, soil and water, suggested that the bacteria in snow, soil and water environments have the same origin.     

一次春季暴雨不稳定条件和对流触发机制的数值模拟研究

2003 年 4 月中旬发生在山东一带的中尺度对流系统引发了一次罕见的春季大暴雨。在不稳定的大尺度环境中,触发条件决定了对流系统在何时、何地发生。触发条件通常位于近地面层中,水平尺度也很小,常规资料无法揭示出来。为此,采用数值模拟和数值模拟敏感性试验并结合客观分析对它的发生机理进行了诊断。结果表明,此次暴雨是由 MCS（中尺度对流系统）的两次发展造成的。第 1 次是比较典型的华北 MCC（中尺度对流复合体）过程,它是由地形强迫抬升触发了初始对流。第 2 次初始对流是由午后的边界层辐合线触发的,从华北平原南下的浅薄冷空气也起了重要作用。另外,最大对流有效位能（MCAPE）对初始对流的发生位置有很好的指示意义。     

Robust and regulatory expression of defensin A gene driven by vitellogenin promoter in transgenic Anopheles stephensi

The use of genetically modified mosquitoes to reduce or replace field populations is a new strategy to control mosquito-borne diseases. The precondition of the implementation of this strategy is the ability to manipulate the genome of mosquitoes and to induce specific expression of the effector molecules driven by a suitable promoter. The objective of this study is to evaluate the expression of defensin A gene of Anopheles sinensis under the control of a vitellogenin promoter in transgenic Anopheles ste- phensi. The regulatory region of Anopheles gambiae vitellogenin was cloned and subcloned into transfer vector pSLFa consisting of an expression cassette with defensin A coding sequence. Then, the expression cassette was transferred into transformation vector pBac[3xP3-DsRedafm] using Asc I di- gestion. The recombinant plasmid DNA of pBac[3xP3DsRed-AgVgT2-DefA] and helper plasmid DNA of phsp-pBac were micro-injected into embryos of An. stephensi. The positive transgenic mosquitoes were screened by observing specific red fluorescence in the eyes of G1 larvae. Southern blot analysis showed that a single-copy transgene integrated into the genome of An. stephensi. RT-PCR analysis showed that the defensin A gene expressed specifically in fat bodies of female mosquitoes after a blood meal. Interestingly, the mRNA of defensin A is more stable compared with that of the endogenous vitellogenin gene. After multiple blood meals, the expression of defensin A appeared as a reducible and non-cycling type, a crucial feature for its anti-pathogen effect. From data above, we concluded that the regulatory function of the Vg promoter and the expression of defensin A gene were relatively con- served in different species of anopheles mosquitoes. These molecules could be used as candidates in the development of genetically modified mosquitoes.     

复配缓蚀剂在油水混合液中的缓蚀性能

以2-巯基苯并咪唑（MBI）为缓蚀剂,MBI与十六烷基三甲基溴化铵(CTAB)为复配缓蚀剂,考察其在模拟油田情况下对20#钢的缓蚀性能的影响。采用SEM和AES考察缓蚀剂使用前后碳钢的表面形貌和各元素含量,利用腐蚀速率快速评定仪对20#钢材料的腐蚀速率进行测定,由电化学工作站测试20#钢的极化曲线和交流阻抗曲线。实验结果表明,当测试温度为30℃时,单独使用MBI对20#钢有一定缓蚀效果, MBI质量浓度为1.98g/L时缓蚀效率最高,为86.04%;当采用MBI+CTAB复配缓蚀剂时,缓蚀效果优于单独使用MBI时的缓蚀效果, CTAB质量浓度为0.3g/L时缓蚀效率达到95.87%。     

Analysis of period doubling bifurcation and chaos mirror of biped passive dynamic robot gait

With a reasonable parameter configuration,the passive dynamic walking model has a stable,efficient,natural periodic gait,which depends only on gravity and inertia when walking down a slight slope.In fact,there is a delicate balance in the energy conversion in the stable periodic gait,making the gait adjustable by changing the model parameters.Poincaré mapping is combined with Newton-Raphson iteration to obtain the numerical solution of the final state of the passive dynamic walking model.In addition,a simulation on the walking gait of the model is performed by increasing the slope step by step,thereby fixing the model’s parameters synchronously.Then,the gait features obtained in the different slope stages are analyzed and discussed,the intrinsic laws are revealed in depth.The results indicate that the gait can present features of a single period,doubling period,the entrance of chaos,merging of sub-bands,and so on,because of the high sensitivity of the passive dynamic walking to the slope.From a global viewpoint,the gait becomes chaotic by way of period doubling bifurcation,with a self-similar Feigenbaum fractal structure in the process.At the entrance of chaos,the gait sequence comprises a Cantor set,and during the chaotic stage,sub-bands in the final-state diagram of the robot system present as a mirror of the period doubling bifurcation.     

过渡金属氧化物自旋和电荷相关信息存储

信息技术的快速发展在某种程度上要求有高速度和大容量的非易失存储器.然而,随着晶体管尺度达到其量子极限,传统硅半导体器件的继续集成化发展遇到了瓶颈.因此,人们提出了一系列有潜力成为下一代更具功能性的存储器原型器件,并引起了广泛而持续的研究热潮.本文介绍3种基于新材料和新结构的新型存储原型器件：阻变开关器件、有机自旋阀和多铁隧道结.我们发现通过改变界面态,可将阻变式开关器件的反应速度提高数个量级,达到5ns;在实验上确认了超精细相互作用对自旋阀效应的影响;利用多铁隧道结实现了室温下的四重阻态存储.基于自旋、电荷相关信息存储的原理和实验结果,我们对这3种过渡金属氧化物器件目前还存在的问题及未来的应用前景进行了分析和讨论.     

稳定核^91Zr高自旋态实验研究

利用能量为44MeV的13C束流,通过重离子熔合蒸发反应82Se（13C,4n）91Zr布居了稳定核91Zr的高自旋态.基于γ-γ符合关系扩展了91Zr21/2＋同核异能态上的能级纲图,根据实验提取的γ跃迁的角分布系数对部分能级的自旋进行了指认.前人对21/2＋同核异能态下正负宇称能级已指认为质子在π（p1/2,g9/2）轨道的激发耦合价中子vd5/2;在π（f5/2,p3/2,p1/2,g9/2）和v（d5/2,s1/2,d3/2,g7/2,h11/2）空间内,经过系统性的分析和比较91Zr邻近核高自旋态能级结构,指出同核异能态上正宇称态激发机制依次为质子跨越38子壳π（f5/2,p3/2）→πp1/2激发和中子跨越50闭壳vg9/2→vd5/2激发,同核异能态上负宇称态可能涉及质子跨越38子壳π（f5/2,p3/2）→πg9/2激发与价中子vd5/2→vh11/2激发的竞争.     

Hardness estimation for covalent crystals using empirical electron theory

Covalent electrons substantially determine the intrinsic hardness of inorganic crystals. A hardness model is presented on the basis of the Empirical Electron Theory generated from Pauling’s covalent bond length equation and the bond length difference method. The calculated hardness values of inorganic crystals are in good agreement with experimental and other theoretical values. Covalent bond energy with polarity correction can be used as an intrinsic indicator linking microscopic electronic structure to macroscopic hardness. A simple mathematical processing of bond energy is performed to extend the model to multi-bonding or multi-component systems. It is also found that spatial distribution of covalent bonds has a great influence on the hardness of inorganic crystals.     

Static coarsening of titanium alloys in single field by cellular automaton model considering solute drag and anisotropic mobility of grain boundaries

Static coarsening is an important physical phenomenon that influences microstructural evolution and mechanical properties. How to simulate this process effectively has become an important topic which needs to be dealt with. In this paper, a new cellular automaton (CA) model, which considers the effect of solute drag and anisotropic mobility of grain boundaries, was developed to simulate static grain coarsening of titanium alloys in the beta-phase field. To describe the effect of the drag caused by different solute atoms on coarsening, their diffusion velocities in beta titanium were estimated relative to that of titanium atoms (Ti). A formula was proposed to quantitatively describe the relationship of the diffusion velocity of Ti to that of solute atoms; factors influencing the diffusion velocity such as solute atom radius, mass, and lattice type were considered. The anisotropic mobility of grain boundaries was represented by the parameter c0, which was set to 1 for a fully anisotropic effect. These equations were then implemented into the CA scheme to model the static coarsening of titanium alloys Ti-6Al-4V, Ti17 (Ti-5Al-4Mo-4Cr-2Sn-2Zr, wt%), TG6 (Ti-5.8Al-4.0Sn-4.0Zr-0.7Nb-1.5Ta-0.4Si-0.06C, wt%) and TA15 (Ti-6Al-2Zr-1Mo-1V, wt%) in the beta field. The predicted results, including coarsening kinetics and microstructural evolution, were in good agreement with experimental results. Finally, the effects of time, temperature, and chemical composition on grain coarsening and the limitations of the model were discussed.