Microstructure and mechanical properties at TiCp/Ni-alloy interfaces in laser-synthesized coatings

Titanium carbide particle (TiCp) reinforced Ni alloy composite coatings were synthesized by laser cladding using a cw 3 kW CO2 laser. Two kinds of coatings were present in terms of TiCp origins, i.e. undissolved and in situ reacted TiCp, respectively. The former came from the TiCp pre-coated on the sample, whereas the latter from in situ reaction between titanium and graphite in the molten pool during laser irradiation. Conventional and high-resolution transmission electron microscope observations showed the epitaxial growth of TiC, the precipitation of CrB, and the chemical reaction between Ti and B elements around phase interfaces of undissolved TiCp. The hardness, H, and elastic modulus, E, were measured by nanoindentation of the matrix near the TiCp interface. For undissolved TiCp, the loading curve revealed pop-in phenomena caused by the plastic deformation of the crack formation or debounding of TiCp from the matrix. As for in situ generated TiCp, no pop-in mark appears. On the other hand, in situ reacted TiCp led to much higher hardness and modulus than that in the case of undissolved TiCp. The coating reinforced by in situ generated TiCp displayed the highest impact wear resistance at both low and high impact conditions, as compared with coatings with undissolved TiCp and without TiCp. The impact wear resistance of the coating reinforced by undissolved TiCp increases at a low impact work but decreases at a high impact work, as compared with the single Ni alloy coating. The degree of wear for the composite coating depends primarily on the debonding removal of TiCp.

The Stability of a Vertical Single-Walled Carbon Nanotube Under Its Own Weight

It has been reported recently that single carbon nanotubes were attached to AFM tips to act as nanotweezers. In order to investigate its stability, a vertical single-walled carbon nanotube (SWCNT) under its own weight is studied in this paper. The lower end of the carbon nanotube is clamped. Firstly the governing dimensionless numbers are derived by dimensional analysis. Then the theoretical analysis based on an elastic column model is carried out. Two ratios, I.e., the ratio of half wall thickness to radius (t=R) and the ratio of gravity to elastic resilience ($\rho$gR=E), and their influences on the ratio of critical length to radius are discussed. It is found that the relationship between the critical ratio of altitude to radius and ratio of half thickness to radius is approximately linear. As the dimensionless number $\rho$gR=E increases, the compressive force per unit length (weight) becomes larger, thus critical ratio of altitude to radius must become smaller to maintain stability. At last the critical length of SWCNT is calculated. The results of this paper will be helpful for the stability design of nanotweezers-like nanostructures.

飞秒强激光作用下电子振荡导致的谐波辐射频谱的展宽和红移

采用单电子模型研究了圆偏振飞秒脉冲激光作用下电子振荡导致的谐波辐射频谱的特性。研究发现随着激光强度的增加，电子在激光场中运动的相对论效应可以导致谐波辐射，并且发现谐波辐射频谱随着激光强度的增加发生了展宽和红移。电子与强激光脉冲相互作用，电子除了在激光场的作用下做横向振荡运动之外，激光脉冲的纵向有质动力对电子还有推动作用，这是产生谐波频谱红移的原因，而谐波辐射频谱展宽是由电子纵向速度的变化引起的。分析激光场中电子在不同方向的辐射频谱表明：随着谐波阶数的升高，红移在有规律地变大；在θ=3π／4方向上电子频谱的

Sensitivity improvement by UV-light recording in LiNbO3 : Ce : Cu crystals

Modulated UV light is used to increase the sensitivity of the two-centre holographic recording. Inherent mechanisms of nonvolatile holographic recording in oxidized and reduced crystals are numerically analysed based on solving the two-centre material equations modilied for UV-Iight recording. Experiments verification is performed with an oxidized crystal and a reduced crystal, and the role of UV intensity on the sensitivity is presented.

Quantitative measurement of domain inversion in RuO2 : LiNbO3 crystal by digital holographic interferometry

We quantitatively study the domain inversion in a RuO2:LiNbO3 crystal wafer by the digital holographic interferometry. The crystal wafer is placed into one arm of a Mach-Zehnder-type interferometer to record a series of holograms. Making use of the angular spectrum backward propagation algorithm, we reconstruct the optical wave field in the crystal plane. The extracted phase difference from the reconstructed optical wave field is a well linear function of the applied external voltage. We deduce that the linear electro-optic coefficient of the detected RuO2:LiNbO3 crystal sample is 9.1x10(-12) m/V. An unexpected phase contrast at the antiparallel domain wall is observed and the influence of the applied external voltage on it is studied in detail. Also the built-in internal field is quantitatively measured as 0.72 kV/mm. (c) 2006 American Institute of Physics.

Design and analysis of a kind of large flattened mode optical fibre

In this paper, a refractive index pro. le design enabling us to obtain a. at modal field around the fibre centre is investigated. The theoretical approach for designing such multilayer large flattened mode (LFM) optical fibres is presented. A comparison is made between the properties of a three-layer LFM structure and a standard step-index pro. le with the same core size. The obtained results indicate that the effective area of the LFM fibre is about twice as large as that of the standard step-index fibre, but the LFM fibre has less effective ability to filter out the higher order modes than the standard step-index fibre with the same bending radius.

Photoinduced effects in amorphous Ge-Se films

With light illumination from an Ar ion laser, the photoinduced changes in vacuum evaporated amorphous GeSe2 films; were investigated with the X-ray diffraction (XRD), infrared absorption (IR), scanning electron microscope (SEM), transmitting electron microscope (TEM) and transmittance spectra analysis. It was observed that the optical transmittance edges of films shifted to shorter wavelength according to annealing and light illumination and the shift in well-annealed films could be recovered by annealing at 200 degrees C for 1 h in Ar air. The magnitude of shift increased with the increase of the intensity of illumination light and the illumination time. By sides, photoinduced crystallization was also observed in the exposed regions of GeSe2 films and more of it was observed with stronger intensity of illumination light.

光聚物材料中布喇格偏移的动态分析

对光致聚合全息存储材料光化学反应过程和引起布喇格偏移的因素进行了分析，通过理论推导，得到了曝光时间与布喇格偏移量的关系．实验曲线表明，材料的布喇格偏移先是随着曝光量的增加而增加，最后达到饱和值．实验的结果与理论分析进行比较，两者符合较好，说明对于布喇格偏移随时间变化动态过程的分析比较合理．

三种兰科植物的保护遗传学研究

本研究在野外调查的基础上，采用随机扩增多态DNA (RAPD)分析和形态学方法，研究了我国三种珍稀濒危兰科植物硬叶兜兰（Paphiopedilummicranthum）、麻栗坡兜兰（P. malipoense）和独花兰（Changnienia amoena）的遗传多样性与群体遗传结构，主要结果如下： 1．采用1 2个引物对分布于我国云贵地区的4个硬叶兜兰群体共161个体进行RAPD扩增和分析，得出物种水平的多态条带百分率（PPB）为71.6%，Nci的基因多样度(h)为0.217，Shannon多样性指数（1)为0.3301;4个群体的平均多样性水平为PPB=45.2%，h=0.1457，1= 0.2204：低于远交兰花的平均水平。分子方差分析(AMOVA)表明，在总遗传变异中，群体间遗传变异占20.31%．群体内占79.69%;POPGENE给出的基因分化系数 （Gst）为0.2958;遗传分化略高于远交物种的平均水平。空间自相关分析表明，所检测的两个群体中存在明显的空间结构，基因型在群体中以不同的小斑块存在。遗传距离和空间距离不存在相关关系。 2．用于麻栗坡兜兰的RAPD引物同上，但取样范围只有贵州的2个群体共10个个体。就所研究的个体柬看，麻栗坡兜兰的遗传多样性明显低于远交兰花物种的平均水平。物种水平上，多态条带百分率(PPB)为49.5%。Nei的基因多样度（h）为0. 1174， Shannon多样性指数(I)为0.1764：在群体水平上，上述三个指标的平均值则分别为12. 75%、0.0486和0.0712，均大大低于硬叶兜兰。然而，尽管作了种种努力，麻栗坡兜兰的取样个体数量仍很少，因此所得结果可能会有误差。 3．用16个引物对分布于河南、湖北、湖南、江西4个省11个独花兰群体共216个体进行了RA PD扩增和分析，独花兰在物种水平PPB=80. 7%，h=0.197．1=0. 3116;在群体水平，上述三个指标的平均值则分别为40. 9%、0.1247和0. 1902，均低于远交兰花的平均水平。AMOVA分析表明，11个独花兰群体间的遗传变异占43.48%，群体内的占56.52%：在神农架和新宁地区内部，群体间的遗传变异分别占13.68%和49.3g%(AMOVA)。POPGENE给出的11个群体的基因分化系数(Gst)为0.3580．神农架和新宁地区内的Gst，值分别为0.1194和0.2597。可见，群体间的遗传分化明显高于远交物种的平均水平。空间自相关分析表明，独花兰的遗传变异在群体内不存在明显的空间结构。群体之间的遗传距离和空间距离不存在相关关系。 4．对独花兰7个群体形态性状的分析发现，12个形态性状在群体内均有较高的变异性，cv值变动于0.022-0.30O。庐山群体(LS)在所有性状上的平均值均为最高。营养性状和花部性状的变异性基本一致。除花葶长和花距直径与某些花部性状之间没有显著的相关关系外，各性状之间均有显著的相关性。对XN4群体的统计没有发现假磷茎数目与其他性状之间存在显著相关性。 根据以上对硬叶兜兰、麻粟坡兜兰和独花兰遗传多样性和群体遗传结构韵研究，结合其他方面的资料;对三种兰花的濒危机制进行了初步的分析。首先，人为采挖和破坏是导致这些兰花物种濒危的直接原因，尤其是麻栗坡兜兰。其次， 适宜兰花生存的生境正在只益萎缩、退化和片段化。这两方面因素的共同作用导致上述兰花群体的数目和规模日益下降，由此引发的遗传多样性降低和遗传结构的改变进一步加剧其濒危状况。对于独花兰而言，较低的繁殖能力又使其生存状态雪上加霜。针对三个物种不同的繁殖特性和遗传学状况，提出如下保护措施。(1)硬叶兜兰由于繁殖能力较强、现存个体尚多，遗传多样性损失不甚严重，因此以保护其所在的生境为基础、实施原位保护，是比较合适的保护策略。(2)麻粟坡兜兰目前受破坏程度非常严重;所剩个体很少，遗传多样性较低，已经很难进行有效的原位保护。因此;应利用迁地保护手段抢救目前尚存的个体。(3)独花兰的繁殖能力较弱，因此在保护生境和严禁采摘的基础上，可采用人工授粉等方式，提高结实率、增加繁殖效率，促使其复壮：在进行迁地保护时，则应注意不同群体间存在较大遗传变异而群体内多样性较低这一现实。

炭球菌素及其制备方法和应用

本发明涉及新颖的化学结构式(I)的炭球菌素。本发明还涉及该化合物的制备方法，以该化合物为活性成分的药物组合物，以及本发明化合物和药用组合物在制备治疗和预防艾滋病的药物中的应用。

中国鲤科鱼类新记录--小口猪嘴ba

鲤科鱼类区系中猪嘴ba属Systomus和小口猪嘴Systomus orphoides(Valenciennes 1842)的首次记录。标本保存于中国科学院昆明动物研究所鱼类标本室。

抗抑郁药物及其应用

提供一种抗抑郁药物，含有2，5-二羟基苯甲醇衍生物2，6-二甲氧基苯甲酸-2，5-二羟基(2-葡萄糖基)苯甲酯(仙茅苷，curculigoside) 及其衍生物及可药用载体和/赋形剂，以及它在制备抗抑郁药物中的应用和在制备功能食品中的应用。