A comparative study of the structure and crystallization of bulk metallic amorphous rod Pr60Ni30Al10 and melt-spun metallic amorphous ribbon Al87Ni10Pr3

Pr-based bulk metallic amorphous （BMA） rods （Pr60Ni30Al10） and Al-based amorphous ribbons （Al87Ni10Pr3） have been prepared by using copper mould casting and single roller melt-spun techniques, respectively. Thermal parameters deduced from differential scanning calorimeter （DSC） indicate that the glass-forming ability （GFA） of Pr60Ni30Al10 BMA rod is far higher than that of Al87Ni10Pr3 ribbon. A comparative study about the differences in structure between the two kinds of glass-forming alloys, superheated viscosity and crystallization are also made. Compared with the amorphous alloy Al87Ni10Pr3, the BMA alloy Pr60Ni30Al10 shows high thermal stability and large viscosity, small diffusivity at the same superheated temperatures. The results of x-Ray diffraction （XRD） and transmission electron microscope （TEM） show the pronounced difference in structure between the two amorphous alloys. Together with crystallization results, the main structure compositions of the amorphous samples are confirmed. It seems that the higher the GFA, the more topological type clusters in the Pr-Ni-Al amorphous alloys, the GFAs of the present glass-forming alloys are closely related to their structures.     

空心阴极灯激发的微波等离子体炬原子/离子荧光光谱研究--钙的原子/离子荧光光谱

用强短脉冲供电技术的空心阴极灯作激发源、微波等离子体炬作原子／离子化器，建立了原子／离子荧光光谱实验装置。详细研究了微波等离子体功率、观察高度、空心阴极灯电流等因素对原子／离子荧光信号强度的影响，测量了系统对Ca的原子／离子荧光光谱的检出限。     

变系数非线性方程的Jacobi椭圆函数展开解

把Jacobi椭圆函数展开法扩展并应用到求解变系数的非线性演化方程,比较方便地得到新的解析解 关键词： Jacobi椭圆函数 变系数非线性方程 类椭圆余弦波解 类孤子解     

溴酸钾-亚甲蓝催化光度法测定硝酸盐和亚硝酸盐

用镉柱将NO-3 还原为NO-2 ,利用在磷酸介质中NO-2 对溴酸钾氧化亚甲蓝这一褪色反应具有强烈的催化作用而建立了同时测定痕量硝酸盐和亚硝酸盐的新方法。本方法简便、快速、灵敏 ,对亚硝酸盐和硝酸盐测定的线性范围分别为 0～ 2 0 0 μg·L-1和 0 0 0 3～ 310 μg·L-1,用于测定各种水样中痕量NO-2 和NO-3 的含量均获得满意结果     

直流磁控溅射一步法原位制备MgB2超导薄膜

用MgB2靶,控制直流磁控溅射工作在异常辉光放电或弧光放电状态,在SrTiO3衬底上原位一次性得到了MgB2超导薄膜,其起始转变温度为32K,零电阻温度为15K. 关键词： 高温超导体 超导薄膜 磁控溅射 二硼化镁     

静态球对称黑洞Dirac场的统计熵

利用改进的brickwall模型,给出了一类静态球对称黑洞Dirac场的熵,结果表明,在取相同的截断因子时,Dirac场的熵均为标量场的熵的72倍 关键词： 黑洞 统计熵 brickwall模型 Dirac场     

FTIR光谱遥测红外药剂的燃烧温度

本文利用遥感FTIR光谱，对红外药剂的燃烧特性进行了研究。在分辨率为4cm^-1时，收集4700－740cm^-1波段的光谱。从HF等燃烧产物发射的分子振转基带精细结构的谱线强度分布，可以对燃烧温度进行遥感测定，并给出了燃烧温度随时间的变化关系，实验结果表明燃烧表面附近温度梯度很大，存在着急剧的变化温度场，同时也说明，在不干扰火焰温度场的情况下，利用遥感FTIR光谱对剧烈的、非稳态快速燃烧的火焰温度进行连续实时的遥感测量，是一种快速、准确、灵敏度高的测温方法，显示了它在燃烧温度测量、产物浓度测试以及燃烧机理研究等方面的应用前景。     

Structures and stability of Al<Subscript><Emphasis Type="Bold">7</Emphasis></Subscript>C and Al<Subscript><Emphasis Type="Bold">7</Emphasis></Subscript>N clusters

We report results of the atomic and electronic structures of Al₇C cluster using ab initio molecular dynamics with ultrasoft pseudopotentials and generalized gradient approximation. The lowest energy structure is found to be the one in which carbon atom occupies an interstitial position in Al₇ cluster. The electronic structure shows that the recent observation [Chem. Phys. Lett. 316, 31 (2000)] of magic behavior of Al₇C^- cluster is due to a large highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gap which makes Al₇C^- chemically inert. These results have further led us to the finding of a new neutral magic cluster Al₇N which has the same number of valence electrons as in Al₇C^- and a large HOMO-LUMO gap of 1.99 eV. Further, calculations have been carried out on (Al₇N)₂ to study interaction between magic clusters. Received 28 July 2001     

Circular dichroism of some bisbenzyltetrahydroisoquinoline alkaloids

The circular dichroism (CD) method has been used to study the stereochemistry of the bisbenzyltetrahydroisoquinoline alkaloids. A relationship has been established between the absolute configurations of the asymmetric centers and the parameters of the Cotton effects in the CD spectra. The changes in the CD spectra on protonation have been correlated with conformational rearrangements of the molecules due to the different attachment of the oxygen bridges.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 818–823, November–December, 1979.     

关于广义分数次积分的合成

Compositions of generalized fractional integral operators involving Gauss hy-pergeometric function with power weights are studied. Composition formulas for such integrals which are the operators of the same type are obtained. In parti-cular, compositions of two identical operators are given.