透射式负电子亲和势光电阴极基片的无损检测

本文对用作透射式负电子亲和势光电阴极的Ⅲ—V族半导体基片的无损检测进行了研究。建立了一套带微机处理的高信噪比的激光荧光测试系统,测试了基片的发射层GaAs的掺杂浓度、过渡层Gal_(-x)Al_xAs的组分X值及沿表面X值的均匀性、高X值的测量等。实验结果表明,激光荧光检测为Ⅲ—V族半导体材料的研究提供了一种快速的非破坏性的检测方法,对研究透射式负电子亲和势光电阴极具有重要意义。     

各种支承连续梁的振动频率方程

本文利用传递矩阵法,导出各种支承和各种边界条件连续梁振动频率方程的统一公式。公式形式简单,关系清楚,便于电子计算机计算。     

Fullerenes C60 and C70 in flames

The fullerenes C60 and C70 were first identified in carbon vapour produced by laser irradiation of graphite, and have recently been produced in macroscopic quantities by vaporization of graphite with resistive heating. It has also been suggested that fullerenes might be formed in sooting flames, and indeed all-carbon ions with mass/charge ratios suggestive of fullerenes have been detected in flames. These species were assumed to have the cage structures of fullerenes, but the mass spectroscopic evidence could not establish this conclusively. We have now collected samples of condensible compounds and soot from hydrocarbon combustion under a range of conditions, and analysed these using conventional techniques in an effort to detect fullerenes. Spectroscopic studies reveal the presence of C60 and C70 in yields and ratios that depend on temperature, pressure, carbon/oxygen ratio and residence time in the flame. Control of these conditions allows optimal yields of 3 g of fullerenes per kilogram of fuel carbon burned, and variation of the C70/C60 ratio over the range 0.26-5.7.     

Neurotransmitter receptors as glycoproteins

Incubation of calf brain membrane preparations with the plant lectins, concanavalin A and wheat germ agglutinin did not inhibit neurotransmitter receptor binding sites directly. Plant lectins did however protect these sites against subsequent trypsin digestion suggesting that neurotransmitter binding sites may be associated with glycoprotein structures.     

The effect of tilting ultrathin sections on the image of the Z-disc of skeletal muscle

Résumé A l'aide du microscope électronique muni d'un goniomètre, la structure tri-dimensionelle du disque Z de la fibre musculaire striée a été analysée. Les résultats obtenus sont comparés avec un modèle construit en perspex et avec les images conventionnelles du disque Z.

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Acknowledgment. We wish to thank Pye Unicam (Philips) an Jeol (U. K.) Ltd. for kindly allowing us to use their electron microscopes. Technical assistance from Messrs.H. Fisher, J. Manston andR. Birchenough is gratefully acknowledged.