8,2'-O-环化-9β-D-腺嘌呤阿拉伯糖苷的NMR及结构研究

8,2'-O-环化-9β-D-腺呤阿拉伯糖苷是阿糖腺苷合成过程中的一个关键性中间体,该化合物的NMR数据只有¹H-NMR谱的糖环1'位质子化学位移和偶合常数的报道,¹³C-NMR谱未曾报道。本文用2D-NMR、NOE-DIF等技术,对它的¹H、¹³C-NMR谱进行归属,进一步明确了它的结构。     

提高综合滤波器鉴别率的一种有效方法

提出一种提高综合滤波器鉴别率的有效方法，其做法是：对样本集在等相关峰条件下求解综合滤波器的同时，使样本集的互补样本满足零件相关峰条件，此方法把训练模式类同所有其它模式类在映射空间的距离拉大，有效地提高了综合滤波器的鉴别率，以取自同一手指纹为样本集，求解综合鉴别函数后，建立了指纹的实时模式识别系统，实验结果表明本文提出的改进方法对提高综合滤波器的鉴别率是非常有效的。     

质子交换光波导生长动力学研究

分析了质子交换光波导的生长动力学并给出了波导层厚度与生长时间的计算公式。     

北京自由电子激光Wiggler中电子轨迹偏离的改进

提出了一种从实验上确定用于北京自由电子激光（ＢＦＥＬ）装置的Ｗｉｇｇｌｅｒ中ＮｄＦｅＢ矩形磁块的轨迹敏感系数β的方法．用β值来表征磁单块在Ｗｉｇｇｌｅｒ中对电子轨迹的贡献，并用此β值对磁块进行挑选，优化组合，可达到改进Ｗｉｇｇｌｅｒ对电子轨迹偏离的目的．     

关于整系数多项式有理根求法的注记

现行高等代数教材给出了求整系数多项式有理根的经典方法 ,周仲旺近日撰文又给出了一个新方法 ,称其“要比经典的方法有趣简捷”,但没有给出两个方法运算量的定量分析与比较 .本文先对经典方法从数学原理和算法设计两个方面作较详细明确的描述 ;再给出经典算法与周方法运算量的定量分析 ,比较的结果是周方法运算量比经典算法运算量多得多 .     

具有不可缩小Beltrami系数的拟共形映射

本文讨论了不可缩小Beltrami系数与无限小不可缩小Beltrami系数的局部 性与整体性的关系;并通过烟囱形区域上仿射拉伸的实例,指出构造一类极值的具有 非常数模的不可缩小Beltrami系数与无限小不可缩小Beltrami系数的方法.     

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。     

Structure and polarity of 8CB films evaporated onto solid substrates

Brewster-angle reflection ellipsometry and surface optical second harmonic generation were used to study the growth of 4'-n-octyl-4-cyanobiphenyl (8CB) films evaporated in air onto polymeric and quartz glass substrates. The layer-by-layer growth of the films terminates after formation of two distinctive interfacial layers. Both of these two layers are polar and tilted. In the first layer the molecules lie nearly flat on the surface, while in the second layer they point on average about 50° toward the surface normal. The dipole moment of the second layer has a lower magnitude and an opposite direction with respect to the dipole moment of the first layer.     

Polymer-assisted complexing controlled orientation growth of ZnO nanorods

The growth of the oriented zinc oxide (ZnO) nanorods on silicon substrates based on a simple novel chemical transformation and thermal hydrolysis by using polyvinyl alcohol (PVA) as self-assembling complex polymer was introduced in this paper. All the polymers were removed after chemical oxidation and only the carbonized grid backbones remained that confines the ZnO nanorod’s diameter and enhance the absorption and diffusion of ZnO at the tips of the nanorods during growth. The ZnO nanorods are investigated by FTIR, XRD and FE-SEM. The results indicated that these nanorods have fine hexagonal wurtzite crystal structure and their diameter varies from 20 to 90 nm and the length up to about 1 μm. A polymer-localized ZnO growth model is proposed, which well explains the growth behavior of ZnO nanorods.This revised version was published online in August 2005 with a corrected issue number.     

Polarisation characteristics of a 12 fibre coupler under femtosecond pulsed and continuous wave illumination

We report on the experimental investigation carried out in the polarisation characteristics of femtosecond pulsed and continuous wave beams propagating through a 1×2 fibre coupler. It is demonstrated that the polarisation states of pulsed and continuous wave illumination over the broad wavelength range can be preserved in a conventional fused fibre coupler. Furthermore, the fibre coupler acts as a low-pass spectral filter in the visible wavelength range with a splitting ratio between 99.6/0.4 and 99.7/0.3. The result is of importance for fibre-optic second harmonic generation microscopy which requires the polarisation preservation to extract molecular organization of a sample.