Liquid crystalline oligomers derived from cholesterol: synthesis and columnar mesomorphism

The novel columnar liquid crystals based on symmetric hairpin-shaped cholesterol tetramers bridged by rigid or hydrogen-bonding Schiff-base spacers were prepared by reacting cholesterol dimer with phenylenediamines or dihydrazides in yields of 70–85%. Structural characterisation of these new compounds had been achieved by infrared, nuclear magnetic resonance and mass spectrometry. Their mesomorphic properties were investigated by polarising optical microscopy, differential scanning calorimetry and X-ray diffraction. They exhibited good hexagonal columnar mesophase with three molecules in a disc of the columnar hexagonal state. This study implied that the symmetric cholesterol tetramers with rigid cores or hydrogen-bonding cores prefer to columnar mesophase.     

GaN薄膜的蓝光和红光发射机理研究

由于生长工艺的不完善，非掺杂GaN薄膜中通常存在未知的杂质和缺陷，产生与这些未知杂质和缺陷能级相关的发光。报道了非掺杂GaN薄膜的692nm红色发光．并研究了非掺杂GaN薄膜的蓝、红色发光的发射机理；利用作者提出的吸收归一化光致发光激发光谱，直接测量出了非掺杂GaN薄膜的蓝、红色发光的初始态能级，确定蓝色发光为施主-价带跃迁复合，而红色发光为施主-受主跃迁复合；给出了黄、蓝、红光的发射模型。所取得的结果对于确定未知杂质和缺陷的种类具有重要的参考价值。     

对相干态与级联三能级原子相互作用过程中原子与场的动力学特性

研究对相干态与级联三能原子相互作用的动力学特性。结果表明，无论场模与原子的中间能级是否失谐，拉比振荡和互关联函数的时间演化都呈现崩溃与回复现象，但崩溃的持续时间随失谐量的增加而迅速延长，且两模之间随时间的演化即出现关联也出现反关联。     

Nd薄膜靶表面氧化过程研究

用Ａｕｇｅｒ电子能谱（ＡＥＳ）对Ｘ光激光实验使用的Ｎｄ薄膜靶的表面氧化进行了分析，结合Ａｒ离子束刻蚀进行元素的深度分布剖析，得到了表面氧化层厚度，所得结果与Ｒｕｔｈｅｒ－ｆｏｒｄ背散射（ＲＢＳ）方法测量的结果相吻合。实验表明，样品暴露在空气中２０至３０ｍｉｎ，氧化即基本达到饱和，相应的氧化层厚度约为２０ｎｍ。     

K1±(892) Production in π−N interactions at 200 GeV/c

K^1±(892) production is studied in the reaction π^?N → K_S⁰K_S⁰ + X where X includes up to five observed charged particles. An excess of K^1? over K¹⁺ is observed for Feynman-x > 0.1. The ratio of K¹⁺ to K^1? decreases with x as predicted by QCD counting rules. K_S⁰ and K¹ production are compared to recent D and D¹ data from other experiments.     

铈对混合型贵金属尾气净化催化剂性能的影响

系统地研究了CeO2对负载型混合贯金属催化剂性能的影响，考察了模拟尾气排放条件下铈对催化剂CO氯化性能的影响，并应用XRD、TPD等手段对CeO2在催化剂中的作用机理进行了研究。结果表明，添加助剂后催化剂活性明显提高．铈的添加改变了催化剂的吸附性能．有利于降低催化反应的活化能。     

Asymptotic approximation of kernel-type estimators with its application

Sufficient conditions are given under which a generalized class of kernel-type estimators allows asymptotic approximation on the modulus of continuity. This generalized class includes sample distribution function, kernel-type estimator of density function, and an estimator that may apply to the censored case. In addition, an application is given to asymptotic normality of recursive density estimators of density function at an unknown point.     

Interface characterization and indium content of indium-rich quantum dots in InGaN/GaN multiple quantum wells

We report on the interface characterization of InGaN/GaN multiple quantum wells with indium aggregation grown by metalorganic chemical vapor deposition. The interface related microstructure was analyzed by high-resolution transmission electron microscopy, high-resolution X-ray diffraction and high angle annular dark field. Luminescence measurements were carried out by micro-photoluminescence measurement. In addition, quantitative determination of the indium concentration inside the ultra-small dots was attempted. We demonstrate that the quantum dots are coherent and the interfaces remain sharp. The In content inside ∼2 nm InGaN dots is about 65% determined by spectrum imaging in energy-filtered transmission electron microscopy combined with multiple linear least squares fitting, which is slighter higher than the value obtained either from HRTEM or theoretical calculations. This discrepancy is briefly discussed but demands further studies for complete understanding.