龋病人牙釉质表面硬度及抗磨损性能测试

采用人工方法制成人牙釉质浅龋及使用抗龋措施的龋损釉质样本，分别测量各组釉质表面显微硬度，并以微动摩擦磨损试验机测试其抗磨性能，试验结果表明：各组实验组釉质较对照组表面硬度都有不同程度下降，氟化钠前处理会使釉质表达硬度显著下降，人工浅龋牙釉质的抗磨损性能不如正常釉质，使用两种抗龋措施对其抗磨性能没有明显改善。     

Scattering spectra and colour of disperse systems of low-absorptive particles

In this article, the results of calculations of scattering spectra of low-absorptive spherical particles are presented. It was obtained using different approximate and numerical methods. The comparative evaluations of application of single scattering approximation, the average field approximation and of the methods of computer modeling on the basis of Monte-Carlo method on various scattering multiplicity were performed. The comparison demonstrates the good agreement of calculated results with experimental scattering spectra of eye lens. By using the obtained spectral data the colour coordinates are calculated. The regularities of changes in colour characteristics in dependence of disperse system parameters are analyzed.     

光解碎片平动谱中二级过程的运动学及化学动力学

本文发展了一套分析处理分子束光解反应实验中二级分解产物飞行谱的方法, 它改进了Kroger和Riley的最初讨论。本文表明许多重要的信息都可以从高度平均的实验数据中得出。这包括二级分解产物的平均平动能分布、空间各向异性参数、平行竞争通道间的反应比。模拟的结果可以表现二级分解反应的一些主要特征。     

Stochastic simulation of reactive separations in capillary electrophoresis

A stochastic (Monte Carlo) simulation is used to investigate thermodynamic and kinetic contributions from the reversible A <--> B reaction in capillary electrophoresis (CE). The effects of equilibrium constant, rate constant, and electrophoretic mobility on the molecular zone profiles and the corresponding statistical moments are evaluated. As the reaction approaches steady state, the velocity of the zone is governed by the equilibrium constant and the electrophoretic mobilities of the reacting molecules. When the equilibrium constant is less than unity, the mean zone velocity is more similar to that of the reactant A. Conversely, when the equilibrium constant is greater than unity, the velocity is more similar to that of the product B. The extent of zone-broadening and asymmetry at steady state is dependent upon the equilibrium constant, the characteristic reaction lifetime, and the electrophoretic mobility difference between reacting molecules. If all other parameters are held constant, the plate height is greatest and skew is least when the equilibrium constant is unity. The plate height increases linearly with the characteristic reaction lifetime and electrophoretic mobility difference, whereas the skew is independent of these parameters. These conclusions have important implications for the elucidation of thermodynamic and kinetic information from experimental data.     

稀土变质热锻模具铸钢高温磨损性能的研究

研究了稀土（RE）变质热锻模具铸钢的高温磨损性能，并与热锻模具钢H13钢和3Cr2W8V钢进行对比，探讨了稀土元素的作用和热锻模具铸钢的高温磨损机理。结果表明：随着RE加入量的增加，热锻模具铸钢的磨损率先减后增，RE加入量在质量分数为0．05％时热锻模具铸钢具有最佳的高温磨损性能。RE变质热锻模其铸钢的高温耐磨性明最高于H13钢和3Cr2W8V钢。高温磨损机理为氧化磨损和氧化物的疲劳剥落，磨屑为块状的Fe2O3和Fe3O4。     

Monte Carlo simulation of polarizable systems: Early rejection scheme for improving the performance of adiabatic nuclear and electronic sampling Monte Carlo simulations

An early rejection scheme for trial moves in adiabatic nuclear and electronic sampling Monte Carlo simulation (ANES-MC) of polarizable intermolecular potential models is presented. The proposed algorithm is based on Swendsen–Wang filter functions for prediction of success or failure of trial moves in Monte Carlo simulations. The goal was to reduce the amount of calculations involved in ANES-MC electronic moves, by foreseeing the success of an attempt before making those moves. The new method was employed in Gibbs ensemble Monte Carlo (GEMC) simulations of the polarizable simple point charge-fluctuating charge (SPC-FQ) model of water. The overall improvement in GEMC depends on the number of swap attempts (transfer molecules between phases) in one Monte Carlo cycle. The proposed method allows this number to increase, enhancing the chemical potential equalization. For a system with 300 SPC-FQ water molecules, for example, the fractions of early rejected transfers were about 0.9998 and 0.9994 at 373 and 423 K, respectively. This means that the transfer moves consume only a very small part of the overall computing effort, making GEMC almost equivalent to a simulation in the canonical ensemble.     

Structure formation and dynamics of water in strong external electric fields

We have performed molecular dynamics computer simulations of water in homogeneous external electric fields which were varied in a wide range of field strengths. The dielectric response is found to be linear up to fields E₀≈0.01 V/Å from where dielectric saturation effects become important. At fields of E₀≈3 V/Å a phase transition into an ordered, ice-like structure is observed, which is stabilized through hydrogen-bonds. With an increasing external electric field, the frequency spectrum of the water dynamics shows a remarkable red shift of the intramolecular modes and a blue shift of the librational motions, where the frequency varies quadratically with the field strength. A simple analytical model is discussed which reproduces the observed behavior.     

小角X射线散射表征AOT/水层状溶致液晶的有序性

用小角X射线散射研究了AOT/水层状溶致液晶的有序性. 通过对散射曲线的解析, 讨论了表面活性剂浓度、温度和助表面活性剂等三个方面对溶致液晶层状相结构有序性的影响. 在一定的范围内, 提高温度, 改变表面活性剂浓度和加入少量助表面活性剂可使碳氢链排列由稀疏转变为密实, 层状相也相应地由“柔性双层”过渡到更加有序化的“平面双层”. 基于形状因子和体系内分子间作用力, 提出了层状相形成与有序化的机理, 同时采用分子模拟的方法展现了不同浓度下的液晶结构.     

固液相变的分子动力学研究Ⅰ─—(KI)_(108)离子簇的熔化和凝固(英)

通过分子动力学模拟，考查并分析了（KI）108离子簇的结构、能量和相变的动力学行为．在加热和冷却过程中，离子簇再现了熔化和凝固现象，而且熔化起始于立方体的其一顶点，熔化的离子簇不是球形的，说明了离子簇的非湿特征．根据结晶的成核速率，讨论了电子衍射实验中观察KI凝固的可能性