Materials Literature
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A new method was developed for determining the dynamic stress-strain relationships of materials subjected to high rate of torsional loading. In addition, an investigation of propagation of torsional plastic waves in a long tube was conducted. Commercially pure copper was used throughout both investigations. In the mat…
Abstract Dye molecules containing two or more polymethine structural units, or at least one polymethine and one polyene structural unit, generally exhibit coupling effects that determine the spectroscopic behavior and other physicochemical properties of the substance. The coupling concept can be used inter alia to fit…
Following a suggestion by Kingery and Francois, the theory of grain growth in porous compacts controlled by the migration of pores with the boundaries is developed for all possible transport processes. Contrary to the assumption of these authors, it is shown that the cubic rate law reported for both UO2 and Al2O3 comp…
The optical absorption edge (indirect energy gap) for PbTe was determined in the temperature range of 80°–520°K. It was found that dEg/dT had a value of 4.1×10−4 eV/°K in the temperature range from 80°–350°K, while above 400°K, dEg/dT was approximately zero. The low-temperature linear portion extrapolated to 0.19 eV a…
A simple, closed-form expression is obtained for the ballistic demagnetizing factor of a uniformly magnetized cylinder. Detailed comparison is made between the present results and both the previously derived series expansion (in which the radial variation of magnetization is neglected), valid for p(=length/diameter) ≥…
The kinetics of wetting of both high-energy (aluminum, mica) and low-energy (FEP Teflon) surfaces by thermostated polyethylene and ethylene-vinyl acetate copolymer melts in air were followed by the rate of approach of the apparent contact angle θ to its final value θ∞ and the change of the radius of the base of the po…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhotochromism of Synthetic and Naturally Occurring 2H-Chromenes and 2H-PyransRalph S. Becker and J. MichlCite this: J. Am. Chem. Soc. 1966, 88, 24, 5931–5933Publication Date (Print):December 1, 1966Publication History Published online1 May 2002Published inissue 1 December 19…
Abstract The bell-shaped pH rate profile for the reaction of tetrahydrofolic acid with formaldehyde to form 5,10-methylene tetrahydrofolic acid has been shown to result from a change in rate-determining step with changing acidity. In alkaline solution, the rate-determining step is the acid-catalyzed dehydration of hyd…
Abstract A process for preparing metiallic cobalt particles of uniform size in the 10–1000 A. range is described. Dicobalt octacarbonyl is thermally decomposed in solutions of dispersant polymers to form stable colloids of discrete particles which are separated by polymer coatings. Variatin of polymer composition, mol…
120 substances with one or more liquid crystalline phases have been studied in 180 binary systems by the combined examination of the relations of miscibility and the observation of the textures by means of a micro heating stage. The examinations enable us to give two systems of liquid crystalline phases. The system ba…
In enriched sea-water cultures inoculated with a mixture of algae and other organisms, concentrations of GeO2 above 1.5 mg/l specifically suppressed the growth of diatoms. In experiments with 14 pure cultures of diatoms (10 species), 1 mg GeO2/l sufficed to reduce the growth rates significantly; 10 mg GeO2/l was even…
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Proceedings of the National Academy of Sciences (PNAS), a peer reviewed journal of the National Academy of Sciences (NAS) - an authoritative source of high-impact, original research that broadly spans the biological, physical, and social sciences.
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Abstract A review with 79 references.
A variational approximation is obtained for the resistance (or total entropy production) of a circular orifice in a plane diaphragm at which the scattering is specular. It is found that the Ohm's law prediction must be multiplied by a correction factor of the order of unity and added to the `small orifice' Knudsen con…
Abstract The viscoelastic properties of some polyester‐urethanes are compared with the properties of other polymers. The behavior observed is anomalous in that these polyurethanes exhibit an unusually high value of modulus well above their T g , unaccounted for by either crosslinking or crystallinity. Various experime…