摘要:

The electron microscope was conceived and built in the Technical University of Berlin some 50 years ago. Much of its further development took place in university laboratories. Not entirely fortuitously, some significant contributions came to be made in the Cavendish, in respect of high voltage operation and the improvement of resolution, and in microanalytical instrumentation. The story of this involvement, and the vicissitudes it underwent, throws light on the way conceptions become dised in practice and on the interrelations of academic research and industrial innovation.

ISSN:0010-7514    

DOI:10.1080/00107518108231513

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The conduction of electricity through a gas manifests itself in various forms. The current in visible. self-sustaining electrical discharges may be as small as micro-amperes for coronas or as large as mega-amperes for arcs. The transformation of a gas from being a good insulator to being a good conductor of electricity occurs when electrons are liberated from neutral gas molecules and liquid or solid surfaces. The article describes the mechanisms of such electron production and the fundamental properties of the resultant discharge. Electrical discharges can be of great use to mankind or may cause serious problems; examples of both are given, as seen mainly from the viewpoint of an electricity supply industry.

ISSN:0010-7514    

DOI:10.1080/00107518108231514

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

When the output of a typical Q-switched laser is focused onto a solid target, a short-lived, localized plasma, characterized by very high ion and electron densities and by very high temperatures, is formed. The present article begins with an outline of the essential features of the laser systems used to generate such plasmas followed by a summary of some concepts in plasma physics necessary for their proper interpretation. The theory of the evolution of the plasma is presented in terms of a hydrodynamic model and the relationship between laser irradiance and plasma temperature is discussed. Several of the more important methods used for studying plasma properties, including inter-ferometry, mass-spectrometry and optical and X-ray spectroscopy, are described and the results for some typical plasmas are presented.

ISSN:0010-7514    

DOI:10.1080/00107518108231515

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Radioactive isotopes have been increasingly used for medical diagnosis since the late 1940s. The number in common use is surprisingly limited with a few, like99rnTc1being used to label several different pharmaceuticals that concentrate in specific organs. Imaging of such organs is probably now the main diagnostic clinical use of radioisotopes but other tests such as bone mass measurement, immunoassay, blood volume determination, neutron activation analysis and whole body radioactivity measurement also require them. Most tests can be satisfactorily performed with a radiation dose to the patient of only about 10 mGy. Transmission computerized tomography and ultrasonic imaging made an initial impact on the diagnostic use of radioisotopes, but since the latter measure and make a visual display of organ function rather than anatomical structure, their use is likely to continue growing.

ISSN:0010-7514    

DOI:10.1080/00107518108231516

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

This brief review of the tunnelling-state model explains the observed low-temperature thermal properties of amorphous materials. Below 1.0 K, the amorphous materials have, over and above contribution by phonons, a specific heat capacitycthat varies almost linearly with temperature; and the thermal conductivitykis approximately proportional toT2, becoming almost independent ofTabove 1.0 K. This behaviour is very different from that of crystalline materials, for whichcαT3andkαT3in this range. A broad band of localized excitations is apparently an intrinsic characteristic of the amorphous state. The tunnelling-state model for these localized excitations can explain qualitatively the various unusual low-temperature properties found in amorphous materials, even though no physical description of the tunnelling entity for any material is available.

ISSN:0010-7514    

DOI:10.1080/00107518108231517

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107518108231518

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Pioneers of Science. By Robert L. Weber. (Institute of Physics, 1980.) [Pp. xviii + 272.] £9.95.

ISSN:0010-7514    

DOI:10.1080/00107518108231519

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107518108231520

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor