摘要:

The first two articles discuss from different viewpoints the presentation of the Boltzmann distribution formula in sixth-form teaching. Dr. Grassie considers R. P. Feynman's approach, in terms of competing kinetic and potential energies. Dr. Spice gives a simple inductive statistical argument, following R. W. Gurney.

ISSN:0010-7514    

DOI:10.1080/00107516508202142

出版商:Taylor & Francis Group    

年代:1965

数据来源: Taylor

摘要:

This second part of the article on nuclear magnetic resonance considers systems which produce narrow resonance lines. The origins of line splitting are first considered, one type due to the chemical environment and a second type due to interaction between the nuclear spins within the molecule itself. The technique of double resonance simplifies complex spectra by applying a second radiofrequency at the same time. After a brief summary of results obtained from metals and ferromagnetics, the more recent Overhauser effects are described since the effective sensitivity of nuclear resonance spectrometers can be increased by several orders of magnitude by applying microwave power at the electron resonance frequency at the same time. The final section of the article considers echo and pulse techniques, and the way in which these can be applied in very low magnetic field strengths.

ISSN:0010-7514    

DOI:10.1080/00107516508202143

出版商:Taylor & Francis Group    

年代:1965

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107516508202144

出版商:Taylor & Francis Group    

年代:1965

数据来源: Taylor

摘要:

It has recently been realized that there is more than one kind of superconductor, and we now recognize superconducting metals and alloys as being either ‘type-1’ or ‘type-2’. The ‘new’ type-2 superconductors can exist in a state which allows them to carry isrestanceless currents even in very strong magnetic fields, and they are used to construct very powerful electromagnets. This article describes the properties of type-2 superconductors, why very strong magnetic fields are required to drive them normal and why under certain circumstances they can carry large lossless currents.

ISSN:0010-7514    

DOI:10.1080/00107516508202145

出版商:Taylor & Francis Group    

年代:1965

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107516508202146

出版商:Taylor & Francis Group    

年代:1965

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107516508202147

出版商:Taylor & Francis Group    

年代:1965

数据来源: Taylor