Materials Literature
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The treatment of the deterioration of insulation as a chemical rate phenomenon has been extended to cover complex multiple reactions. The relationships between the parameters goveming the thermal stability of a polymer in a given environment are calculated first for isothermal thermal endurance test conditions and sec…
The difficulties involved in the accurate measurement of the flow stress of materials at high rates of deformation are reviewed, and methods of overcoming these difficulties are discussed. It is concluded that the best experimental method is that in which a split Hopkinson bar is adapted for torsion testing, and the l…
Abstract Small‐angle multiple scattering of low‐energy heavy particles (Born parameter α > 1) in solid layers is calculated, using a scattering cross section derived from classical mechanics. The angular distribution of the scattered particles is given as a sum of two functions, which are tabulated. The calculated…
Two-electron oxidation of cobaltous octaethylporphyrin [Co(II)(Et)(8)P] yields a stable pi-cation radical [Co(III)(Et)(8)P](2+.), the optical spectrum of which exhibits spectral changes dependent upon the nature of the counterion. Comparison of these spectra with those of Compounds I of horseradish peroxidase and cata…
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Summary Examination of the clay fraction of the Gezira and Kenana soils of the Sudan revealed montmorillonite as the dominant clay mineral, accompanied by kaolinite. The presence of illite and vermiculite is questionable. Quartz was found as an accessory mineral. Most of the kaolinite is concentrated in the ‘coarse cl…
In any false-twist-crimping process, a heat treatment followed by a cooling treatment is given to the threadline in the twist zone in order to ‘set’ the inserted twist. The majority of commercial machines use metal contact heaters to heat the threadline, and cooling is achieved by exposure to ambient air. The data in…
The principal soft ferromagnetic materials in use today are still iron and silicon-iron alloys. Factors affecting magnetic properties of importance in practical use are evaluated and related to properties attainable in iron and electrical steels. Developments in metallurgy and technology leading up to the present stat…
With the recent growth in interest in the ir and Raman spectra of crystals, it has become very important to know which vibrational modes are optically active. Hornig, Winston and Halford, and Bhagavantam and Venkatarayudu pioneered in developing methods for this. However, heretofore the determination has been a labori…
The literature on experiments on a.c. conductivity in various disordered semiconductors is briefly summarized. A theory of the a.c. conductivity, suitable for hopping conduction in the pseudogap of amorphous semiconductors, is developed, and expressions applicable under various conditions are derived. Comparing some o…
Recent progress in understanding the origin of the lanthanide crystal field is summarized. The basic assumption of the crystal field parametrization is shown to be that the crystalline environment can be represented as a one-electron potential, and the consequences of removing this assumption are traced. It is further…
Table of Contents I. Introduction 180 II. The Structure of Diamond 180 III. Formation of the Energy Bands 181 IV. The Brillouin Zone 182 V. Quantitative Calculations of the Energy Bands 183 VI. Investigation of the Band Structure by Optical Methods 187 VII. Fundamental Physical Properties 188 VIII. Semiconducting Diam…