Materials Literature
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The complexes formed by ethylene glycol, HOCH 2 .CH 2 OH, and by glycerol, HOCH 2 .CHOH.CH 2 OH, with smectites (montmorillonite-saponite group), and vermiculites have received more attention than any other group of organo-silicate complexes. This interest arose in the first place from their use for identification pur…
The boundaries of regions of glass‐forming compositions were determined in binary tellurite systems with alkali, alkaline‐earth, and heavy‐metal oxides, and in the ternary systems TeO 2 ‐WO 3 ‐Ta 2 O 5 , TeO 2 ‐WO 3 ‐BaO, TeO 2 ‐WO 3 ‐Bi 2 O 3 , and TeO 2 ‐WO 3 ‐Tl 2 O. On the basis of a structural interpretation of l…
We consider an M×N periodic system of hard squares each of which prohibits the occupation of its nearest-neighbor sites by the other squares. An appropriate unitary transformation factors the matrix required in evaluating the grand canonical partition function into a direct sum of submatrices. Each submatrix belongs t…
Abstract Thin films of phthalocyanine compounds formed on cleaved surfaces of muscovite by the vacuum-condensation method showed well-defined single-directional orientation when their substrates were preheated at 300°C for one hour and then kept at 150°C. Their electron diffraction patterns were fiber diagrams, the fi…
Abstract Polymerization of methyl methacrylate with Grignard reagents in mixed solvent of toluene and dimethyl sulfoxide (DMSO) under ultrasonic irradiation was carried out, and the effects of ultrasonic irradiation in connection with the mixed solvent on the stereoregularity and the properties of the polymers obtaine…
Abstract Decomposition of organic matter within shell fragments appears to result in the formation of localized reducing environments. This has led to the development of pyrite within the shell. This pyrite may indicate relic shell structure and thus show that the aragonite of the shell changed to calcite without a di…
Abstract The glass transitions of an ionic polymer in bulk have been studied as a function of the counterion for various homo‐ and copolymers. It is shown that the glass transition temperature can vary by as much as 530°C., from −10°C. for the nonionic material to +520 for Ca 2+ or Zn 2+ substituted polymer. From simp…
A magnetometric demagnetization tensor is defined for uniformly-magnetized samples of arbitrary geometry. It is shown that this is a real symmetric tensor with non-negative diagonal elements and unit trace. Diagonalization of the magnetometric demagnetization tensor yields the Brown-Morrish equivalent ellipsoid and th…
The decomposition of brucite was studied directly in electron and optical microscopes. A small amount of decomposition caused marked changes in the physical state of the brucite crystal. The decomposition was interpreted as a normal nucleation and growth process in which magnesium oxide nuclei formed coherently with t…
The solid solution limit of titanium dioxide in Al 2 O 3 was investigated using diffuse reflectance and cathodoluminescence measurements on polycrystalline Al 2 O 3 doped with 1.0 mole % or less TiO 2 . The samples had been fired in air at 1300°C. The diffuse reflectance spectra indicated that the solid solubility lim…
The dielectric properties of ice have been studied up to 107 kbar using opposed circular anvils. Ice VII undergoes orientational polarization, and consequently its molecules are orientationally disordered. The volume of activation for the relaxation of the orientational polarization is ∼3 cm3 mole−1, which suggests th…
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…