液体多脉冲及2D NMR实验的计算机模拟

现代多脉冲及2D NMR技术是过去十年中发展起来的崭新的NMR实验方法。计算机模拟做为NMR实验的强有力分析手段已日益受到重视。国内这方面工作开展得尚很少；国外发表的工作主要采用的是数字模拟，存在分析结果不够直观、物理意义不够清晰等缺陷。本论文工作采用乘积算符方法研制出对分析多脉冲及2D NMR实验普适的模拟程序PROPER；在乘积算符基础上，针对磁等性自旋体系，提出了实用的对称化乘积算符及多量子积算符方法。一、多脉冲及2D NMR实验的计算机模拟 1. 采用乘积算符方法在本所PDP－11／23微机上研制了多脉冲及2D NMR实验的模拟程序PROPER。该程序对不超过4核（I ＝ 1／2）的同核及异核弱耦合自旋体系非选择性脉冲序列的分析是普遍适用的。受计算机内存的限制，PROPER程序所能处理的脉冲序列脉冲间隔数目一般不超过10。2. 应用PROPER模拟程序对INEP和DEPT脉冲序列进行了分析比较；特别对BIRD脉冲序列的各种相位变型进行了模拟分析，给出了分析结果，分析过程中考虑了影响BIRD作用效果的同核耦合因素。应用结果表明，PROPER程序计算正确、迅速、给出的模拟结果较通常的数字模拟方法简单、直观、物理意义清楚，便于分析。由于采用算符模拟，结果的输出打印比较费时。目前，PROPER程序正在改进和完善之中。二、多脉冲及2D NMR实验的密度算符描述 1. 针对磁等性自旋（I ＝ 1／2）体系，首次提出了对称化乘积算符描述方法。在通常的乘积算符基础上，引入了对称化乘积算符，并对其数理基础进行了详细论证。推导了算符循环对易关系决定的Liourill-Von Neumann方程的解，给出了算符间普遍存在的循环对易关系及其相应的演化公式。据此，以InS(I = 1/2, S = 1/2; n = 2,3)自旋体系为例，对DEPT脉冲序列进行了分析；结果表明，该方法较通常的乘积算符方法对磁等性自旋体系的分析要简单、实用，且物理意义更加明确。由于该方法涉及较多的算符对易关系，因此不易计算机编程。2. 在对称化乘积算符基础上引入了多量子积算符的概念。以In(I = 1/2; n = 2,3)体系为例，给出了两者的互换关系。推导出了具有标量耦合作用的两组合粒子体系普适的多量子积算符环对易关系及相应的演化解析式。多量子积算符方法可望将1／2－自旋磁等性组合粒子表象与自旋大于1／2的单粒子表象统一起来，并为计算机模拟提供新的数学方法。该方法尚有待于进一步研究。

三维双楔面定常激波相互作用

本文通过理论分析,将三维对称双楔面上定常激波相互作用简化到二维截面进行分析,利用二维非定常激波楔面反射理论求解该三维激波相互作用结构。同时,通过采用二阶精度的NND格式求解三维Euler方程,对该理论分析结果做出数值模拟验证。理论分析和数值模拟结果显示,对于三维双楔面超声速定常流动在取定的二维截面上激波结构兼有二维非定常及定常激波反射的性质,即形成了类似于二维非定常激波楔面反射的规则反射、单马赫反射、过渡马赫反射及双马赫反射等结构,同时其规则—马赫反射转变却遵循适用于二维定常激波反射的von Neumann准则。理论分析得出的各种反射结构的存在范围与数值模拟结果吻合良好。同时,探讨了两楔面间夹角以及楔面前缘后掠角对该激波结构的影响。

压缩真空场与原子非线性作用过程中的纠缠与消纠缠

用VonNeumann熵研究了附加克尔介质的压缩真空场与二能级原子依赖强度耦合相互作用量子体系的量子纠缠特性 .讨论了初始压缩真空场的压缩度以及克尔非线性作用的强度对该量子体系纠缠特性的影响 .结果表明 ,克尔介质的非线性作用的强弱可以改变体系量子纠缠的周期性 ;在初始压缩度较大 (r =5 )时 ,克尔介质的非线性作用可导致原子与场持续地处于最大纠缠态 ,无消纠缠态或持续地处于消纠缠态 .

快重离子在石墨中引起表面及体径迹的STM研究

用多种快重离子辐照高定向石墨 (HOPG) ,借助扫描隧道显微镜 (STM )系统地研究了表面及体内缺陷。结果表明 ,离子在表面及解理面上都形成了小丘状的缺陷 ,且在表面较容易形成 ,可以用非连续损伤径迹结构来对其进行解释

Raman spectroscopy of apatite irradiated with swift heavy ions with and without simultaneous exertion of high pressure

Durango apatite was irradiated with energetic U ions of 2.64 GeV and Kr ions of 2.1 GeV, with and without simultaneous exposure to a pressure of 10.5 GPa. Analysis by confocal Raman spectroscopy gives evidence of vibrational changes being marginal for fluences below 5x10(11) ions/cm(2) but becoming dominant when increasing the fluence to 8x10(12) ions/cm(2). Samples irradiated with U ions experience severe strain resulting in crystal cracking and finally breakage at high fluences. These radiation effects are directly linked to the formation of amorphous tracks and the fraction of amorphized material increasing with fluence. Raman spectroscopy of pressurized irradiated samples shows small shifts of the band positions with decreasing pressure but without a significant change of the Gruneisen parameter. Compared to irradiations at ambient conditions, the Raman spectra of apatite irradiated at 10.5 GPa exhibit fewer modifications, suggesting a higher radiation stability of the lattice by the pressure applied.

Electrochemical fabrication of single-crystalline and polycrystalline Au nanowires: the influence of deposition parameters

We report the electrochemical growth of gold nanowires with controlled dimensions and crystallinity. By systematically varying the deposition conditions, both polycrystalline and single-crystalline wires with diameters between 20 and 100 nm are successfully synthesized in etched ion-track membranes. The nanowires are characterized using scanning electron microscopy, high resolution transmission electron microscopy, scanning tunnelling microscopy and x-ray diffraction. The influence of the deposition parameters, especially those of the electrolyte, on the nanowire structure is investigated. Gold sulfite electrolytes lead to polycrystalline structure at the temperatures and voltages employed. In contrast, gold cyanide solution favours the growth of single crystals at temperatures between 50 and 65 degrees C under both direct current and reverse pulse current deposition conditions. The single-crystalline wires possess a [110] preferred orientation.

Segmented All-Platinum Nanowires with Controlled Morphology through Manipulation of the Local Electrolyte Distribution in Fluidic Nanochannels during Electrodeposition

Synthesis of segmented all-Pt nanowires is achieved by a template-assisted method. The combination of a suitably chosen electrolyte/template system with pulse-reverse electrodeposition allows the formation of well-defined segments linked to nanowires. Manipulation of the morphology is obtained by controlling the electrokinetie effects on the local electrolyte distribution inside the nanochannels during the nanowire growth process, allowing a deviation from the continuously cylindrical geometry given by the nanoporous template. The length of the segments can be adjusted as a function of the cathodic pulse duration. Applying constant pulses leads to segments with homogeneous shape and dimensions along most of the total wire length. X-ray diffraction demonstrates that the preferred crystallite orientation of the polycrystalline wires varies with the average segment length. The results are explained considering transitions in texture formation with increasing thickness of the electrodeposit. A mechanism of segment formation is proposed based on structural characterizations. Nanowires with controlled segmented morphology are of great technological importance, because of the possibility to precisely control their substructure as a means of tuning their electrical, thermal, and optical properties. The concept we present in this work for electrodeposited platinum and track-etched polycarbonate membranes can be applied to other selected materials as well as templates and constitutes a general method to controlled nanostructuring and synthesis of shape controlled nanostructures.

Host sex and ectoparasite infections of plateau pika (Ochotona curzoniae, Hodgson) on the Qinghai-Tibetan Plateau

A total of 449 plateau pika (Ochotona curzoniae Hudgson) individuals were sampled with rattraps from 21 plots (size 1 ha) randomly scattered over the area of the species distribution at the altitude 3275-4807 in a.s.l. in the Qinghai-Tibetan Plateau (West China). Two main ectoparasite species Hypoderma satyrus Brauer and Ixodes crenulatus Neumann of plateau pika were surveyed, and the relations between host sex and parasitism were analyzed. The results were: (i) although not significantly, the infection rate of female young was close to zero and lower than that of male young (6%), while the infection rate of female sub-adults (19%) was contrarily - higher than that of male sub-adults (11%); adult females had significantly higher (41%) infection rate than that of males (18%) (P<0.001); (ii) the parasite infection rates for both males and females increased with increasing age, but female age-groups had obviously steeper slope. We suggested that the differences of body mass, growth rate and home range between males and females had mainly caused the sex-biased parasitism (SBP) of plateau pika at each age stage. Also, due to the higher increases of body mass and maybe as well as of the home range differences between consecutive age-groups, the parasite infections of females became more sensitive to the influences of age than that of males.