Mechanisms of the oxidation of defect-free surfaces of carbon nanostructures: the influence of surface curvature

This work is concerned with reaction paths in the interaction of carbon defect-free nanostructures with different surface curvatures (graphene, tubulenes, and fullerene C₆₀) with atomic and molecular oxygen. The interaction energies of atoms were calculated by the density functional theory method using the basis set of plane waves and the VASP package. The potential surface of reactions with molecular oxygen was studied by the nudged elastic band method. The energy parameters of the reaction (released energy and barrier) strongly depended on the curvature of carbon structure surfaces. The interaction of atomic oxygen in the ground state with the surface of carbon nanostructures is an exothermic reaction. The barrier to the reaction with molecular oxygen (0.5–2.5 eV) decreases as the curvature of nanostructure surfaces increases. The calculation results are in agreement with the experimental data and other ab initio calculations.     

金属丝的杨氏模量测定实验的改进

对金属丝杨氏模量测定仪重新设计.将金属丝水平放置,在中点处悬挂重物,通过测量金属丝伸长后的转角,进而测量金属丝的杨氏模量.     

The Characterisation of the Products of Reduction of Chinkombe Ilmenite

The characterisation of iron-containing species in Chinkombe ilmenite and its reduction products was undertaken using Mössbauer Spectroscopic techniques. The ore was reduced by graphite in an inert atmosphere. The effects of such variables as quantity of reductant, temperature and preoxidation were investigated. The ore was completely reduced to alpha-iron and titanium dioxide with 20% carbon for a period of one hour at 1373 K. Chemical mechanisms are proposed for the reduction and oxidation of Chinkombe ilmenite. In the processing of ilmenite to obtain synthetic rutile, the ultimate desire is to separate the Fe phase from the TiO₂. Mössbauer Spectroscopy has unambiguously confirmed the desired transformation of the iron phase according to thermodynamic predictions. The information gained would be used to choose the conditions of the reduction process. The alpha-iron could be separated physically or chemically from the completely reduced product mass to obtain synthetic titanium dioxide suitable for the paint industry.     

电爆金属丝质量密度分布的演变过程

基于X-pinch软X射线辐射点源对直径10μm钨丝单丝以及8μm钨丝双丝电爆发展过程进行了背光成像研究,实验平台为清华大学电机系研制的脉冲功率装置PPG-1(500kV/400kA/100ns)。成像光路安排为:作为X射线源的X-pinch和作为目标物的钨丝分别安装在装置的输出主电极阴阳极之间和回流导电杆处,成像胶片采用高分辨率、高灵敏度的X光胶片。利用自行设计的电流传感器和罗氏线圈对目标物实际流过的电流进行监测,从而计算得8μm钨丝丝爆过程中电导随时间变化的曲线。为了观测电爆金属丝质量密度分布的演变过程,设计了μm级厚度的阶梯光楔。通过大量成像实验,获取了丝芯膨胀、晕层等离子体形成及其向外扩张等过程的相关物理图像以及基于原始胶片绘制的质量密度分布图。     

混合菁染料J-聚集体的光谱性能研究

对2种混合菁染料吸附在溴化银颗粒表面形成的J-聚集体的反射光谱及感光性能与对应菁染料单独吸附在溴化银颗粒表面进行了对比研究。用紫外-可见分光光计测定了菁染料吸附在溴化银颗粒表面形成J-聚集体的反射光谱。结果表明:2种混合菁染料吸附在溴化银颗粒表面形成的J-聚集体的反射光谱分别具有2个最大峰值波长,并且与对应菁染料单独使用时的峰值波长相一致。2种混和菁染料的感光性能比对应菁染料单独使用时有较大提高。     

Analysis of diffraction of a plane wave on a grating consisting of impedance bodies of revolution

The problem of wave scattering by a grating consisting of coaxial impedance bodies of revolution is solved. The efficient numerical algorithm based on the modified null field method is offered. The method is applied both to scalar and vector formulations of the problem. The numerical results are obtained for various geometries of the grating elements.     

Thickness dependence of temperature coefficient of resistance of MnBi films

In-situ measurements of the temperature coefficient of resistance of electron-beam evaporated MnBi films are reported for the thickness range 30–180 nm. The thickness dependence of the temperature coefficient of resistance curves are plotted for different weight ratios, annealing times and substrate temperatures. The temperature coefficient of resistance shows marked size effect, and is negative for lower thicknesses (<100nm) and positive for higher thicknesses. The experimental data is in good agreement with the Mayadas-Shatzkes theory. The thickness dependence of the Curie temperature also indicates marked size effect.     

Distribution of zeros of the partition function of the lattice gases of fisher and of temperley

The distributions of zeros of the partition function of lattice gas models of Fisher (at some temperature) and of Temperley are obtained. The former is a closed loop crossing the real axis and the latter is a part of the negative real axis.     

BSA-SDS-Ag聚合物纳米微粒的制备及其水凝胶性质的研究（Ⅰ）

报道了BSA－SDS－Ag聚合物纳米微粒的制备及水凝胶的性质,用X射线衍射（XRD）、透射电镜（TEM）、傅里叶变换红外（FT－IR）光谱考察了这种聚合物微粒的结构,微粒粒径32nm左右,用UV／Vis光谱及SEM考察了冰凝胶的性,表明Ag^ 离子先与BSA产生化学键合,再学原了Ag粒,进行聚合成网状结构的聚合物。     

Equation of state of metallic helium

The effective ion-ion interaction, free energy, pressure, and electric resistance of metallic liquid helium have been calculated in wide density and temperature ranges using perturbation theory in the electron-ion interaction potential. In the case of conduction electrons, the exchange interaction has been taken into account in the random-phase approximation and correlations have been taken into account in the local-field approximation. The solid-sphere model has been used for the nuclear subsystem. The diameter of these spheres is the only parameter of this theory. The diameter and density of the system at which the transition of helium from the singly ionized to doubly ionized state occurs have been estimated by analyzing the pair effective interaction between helium atoms. The case of doubly ionized helium atoms has been considered. Terms up to the third order of perturbation theory have been taken into account in the numerical calculations. The contribution of the third-order term is significant in all cases. The electric resistance and its temperature dependence for metallic helium are characteristic of simple divalent metals in the liquid state. The thermodynamic parameters—temperature and pressure densities-are within the ranges characteristic of the central regions of giant planets. This makes it possible to assume the existence of helium in the metallic state within the solar system.     

The effect of the crystalline perfection of quartz on the rotation of the plane of polarization of light

The wavelength dependence of the specific rotation of the plane of polarization of light by quartz crystals is experimentally studied. The chirality coefficients determined from the plots δ(1/λ²) are found to be different for different crystals. The differences between these plots are associated with the perfection of the crystal structure of quartz. The rotation of the plane of polarization is more sensitive to imperfection of the medium and makes it possible to reveal this imperfection without additional irradiation of crystalline quartz by γ quanta.     

单个鼻咽癌细胞的拉曼光谱分析的研究

利用激光镊子拉曼光谱系统研究了鼻咽癌细胞株和正常人鼻咽部气道上皮细胞株的单个细胞的拉曼光谱,对于每个细胞在不同部位测3个点。结果显示：正常细胞和癌细胞的平均拉曼光谱有显著差异：正常的细胞光谱强度比癌细胞的明显要高;正常细胞的1304和1336 cm-1处峰的强度比值为1.05,癌细胞的为1.22。用PCA主成分分析和DFA判别分析分别对单个细胞的平均光谱和不同位置所取得的单独光谱进行分析,结果发现：PCA和DFA均可以把癌细胞和正常细胞正确区分,对于单独光谱,DFA的效果更好一些。同时还发现同一个细胞中不同的光谱位置对PCA和DFA的区分度影响不是很大;PCA和DFA的图中还表明癌细胞的均匀度要比正常细胞的差。以上的研究均表明：激光镊子拉曼光谱可以成为区别正常鼻咽细胞和鼻咽癌细胞的有效手段。     

Determination of the of rate cross slip of screw dislocations

The rate for cross slip of screw dislocations during annihilation of screw dipoles in copper is determined by molecular dynamics simulations. The temperature dependence of the rate is seen to obey an Arrhenius behavior in the investigated temperature range: 225-375 K. The activation energy and the effective attempt frequency can therefore be extracted from the simulations. The transition state energy for the annihilation process is calculated by identifying the transition state using the nudged elastic band path technique. The two activation energies agree very well, indicating that transition state theory is applicable for this type of process.     

Kinetics of Macrolocalization Patterns of Plastic Flow of Metals

The features of the macroscopic inhomogeneity of plastic deformation in the form of autowaves with a pulsating amplitude are analyzed, and data on the localization of sources of acoustic emission at different stages of plastic flow in the stretching of fcc mono- and polycrystals are presented. The relationship between the local components of the plastic distortion tensor in the strain localization zone is traced. The role of acoustic phenomena accompanying the localization of plastic strain in the development of the process of plastic deformation is considered.     

Structural mechanisms of fracture of nanocrystalline materials

Structural mechanisms and features of brittle and quasi-brittle fracture of nanocrystalline materials are theoretically analyzed. The role of size effects and internal stresses caused by a nonequilibrium structure during brittle trans-and intercrystallite fracture is studied. The dependence of the nanocrystalline material durability on the working stress and grain size is calculated. The conditions for certain mechanisms of plastic deformation to be operative in nanocrystalline materials are analyzed. The influence of the grain-boundary and dislocation mechanisms of plastic deformation on the conditions of nanocrack formation is studied. The dependence of the fracture toughness of nanomaterials on structure parameters is calculated.     

液晶磁致旋光的研究

利用矩阵方法分析了液晶的旋光效应，导出了液晶旋光的矩阵表示. 利用JG-3型连续可调谐磁场仪搭建实验装置，红外1350 nm激光器做光源，测量了偏振光通过磁场作用下BL-009型向列相液晶的旋光角，详细分析了磁场对液晶旋光性能的影响. 通过实验测试，对液晶的阈值磁场强度进行了讨论，同时对实验结果进行了理论上的分析，得出了液晶旋光角随磁场与液晶盒表面夹角而变化的结论，验证了液晶分子轴的旋转方向与磁场的方向无关，这为更好的研究液晶的特性以及液晶器件的设计具有重要的参考价值. 关键词： 液晶 矩阵 磁致旋光     

应用振动光谱技术检测鉴定微生物的研究进展

振动光谱（红外光谱和拉曼光谱）技术与化学计量学相结合的方法对微生物进行分类、鉴定和无损检测,该方法快速简便、准确度高、仅需微量样品和少量化学试剂、对样品本身没有损害。介绍了振动光谱技术在微生物鉴定检测中的工作原理、关键技术和应用,并对该方法存在的问题和研究前景进行了分析和展望。     

Calculation of photoelectron spectra of the trihalides of group v elements

The SCF-Xα-SW method is applied to calculate the ionization energies of the trihalides of all of the Group V elements. The calculated orbital energies agree very well with reported experimental ionization energies. The molecular-orbital orderings obtained coincide with recent experimental orbital assignments. The results are also compared with previous ab initio, semiempirical and Xα calculations for NF₃, PF₃, PCl₃ and PBr₃. The comparison indicates that the present results show improved agreement with experiment and clarify certain ambiguities in the earlier molecular-orbital assignments.     

闪光照相系统成像重复性的测量

为了更直观利用照像图像信息考察照相系统的重复性,提出了利用等光程条件下的黑密度分布曲线对成像重复性进行测量的方法,通过两次成像的黑密度分布曲线的线性拟合参数来评估成像系统的成像重复性。实验测量了有无后锥条件下的闪光照相系统的重复性以及底片接收系统的成像重复性,实验结果表明:后锥的存在对成像重复性没有明显影响,底片接收时闪光照相系统的成像重复性约为5%,底片本身引入的成像重复误差约为1.6%。