有关光电倍加管中的几个问题

本文简要叙述了射线的探测技术对光电倍加管的各种要求,以及管子的基本参数与应用的关系,综合了近年来文献中与此有关的光阴极、二次极和结构方面的工作情况。在阴极方面介绍了锑-铯、锑-钾-钠-铯光阴极和新的反射式锑-铯光阴极。在二次极方面介绍了锑-铯二次极和银-镁、铝-镁合金二次极等。在结构方面介绍了光阴极到第一个二次极区域的电子光学输入部分的结构和二次发射倍增系统的结构。本文还初步讨论了光阴极、二次极及管型结构方面的若干改进意见。     

A Note on the Impact of a Jet on a Porous Wall

The problem of determining the free surface of a jet of idealfluid which is incident on a porous wall is reconsidered. Considerationof the w and dw/dz hodograph planes reveals a curved boundarywhich cannot be conformally transformed onto a simple regionusing standard transformations. The use of a generalized Schwarz-Christoffeltransformation, however, enables this shape to be mapped ontoa half-plane and, when appropriate boundary conditions are applied,results in the free surface being described by an ordinary differentialequation. Numerical and asymptotic solutions to this equationare given and a comparison with previous results is made.     

Effect of substrate temperature on electrical and magnetic properties of epitaxial La1−x Pb x MnO3 films

Epitaxial La_1−x Pb _x MnO₃ (LPMO) thin films, grown on (100) SrTiO₃ substrates by laser ablation technique at different temperatures between 600 and 850°C, have been characterized for electrical and magnetic properties. The temperature dependence of resistivity showed that the metal-insulator transition temperature (T _MI) decreases with increasing substrate temperature, which has been attributed to decrease in Pb content in the filsm. The YBa₂Cu₃O _x /La_1−x MnO₃ heterostructures, exhibiting both superconductivity and ferromagnetism, have been fabricated.     

4-硝基-3-吲(口乃木)乙酸的制备

5-,6-,7-硝基取代的3-吲(口乃木)乙酸已分别由Cavallini^[1],Brown^[2],Hiremath^[3]与他们的合作者合成。本文报告从4-硝基吲(口乃木)通过相应的3-二甲氨代甲基吲(口乃木)(芦竹碱),按标准步骤合成4-硝基-3-吲(口乃木)乙酸。Berti等^[4]曾用3-二甲氨代甲基吲(口乃木)直接硝化的方法制得4-硝基-3-二甲氨代甲基吲(口乃木)(4-硝基芦竹碱),熔点120—122°,产率很低。     

A reaction-diffusion model for autocatalytic polymerization: I. Permanent form travelling waves

As a simple model for radical chain polymerization, the authorsstudy a system of coupled reaction-diffusion equations in whichthe reaction terms are autocatalytic and one of the diffusivities,representative of the evolving polymer structure, vanishes ata finite and nonzero polymer concentration. The existence ofa family of travelling wave solutions to the evolution equationsis proved, and some properties of these waveforms are derived.