Materials Literature
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An explanation is provided for the phonon conductivity results of trivalent rare-earth-doped gallium and aluminium garnets in the temperature range 2-300 \ifmmode^\circ\else\textdegree\fi{}K. It is found that in GdAlG and GdGaG where the magnetic energy levels are so separated that an electronic transition between the…
A domain model is proposed for nepheline to explain the weak, paired, non-Bragg reflexions. Within the domains the nepheline structure is described in terms of a supercell, consisting of three subcells and stacked in AAA … sequence along c . The domains themselves are in regular sequence corresponding to ABCA … ACBA ……
Integrated intensity measurements of the (100) and (101) x-ray diffraction peaks of hexagonal selenium at pressures up to 52 kbar have permitted a determination of the atomic positions so that the bond distances and chain angle have been obtained at high pressure. The near-neighbor bond distances along the Se chain re…
Abstract Rigid urethane foams were prepared from hydroxymethylated linseed oil and its esters of glycerol, trimethylolpropane and pentaerythritol. These polyols were made by selective hydroformylation with a rhodium‐triphenylphosphine catalyst followed by catalytic hydrogenation with Raney nickel. Although the hydroxy…
Abstract A diffusion equation for the distribution of ionic impurities in a polymer under a dc field has been solved analytically for the conditions that neither injection nor absorption of impurity ions takes place at either electrode and that the ions do not interact. By using the solution of the diffusion equation,…
Infrared absorption spectra of 12 sodium silicate glasses of varying composition (10 to 45 mole% Na2O) are examined at varying pressures to 58.8 kbar. The pressure dependences of all the infrared absorption frequencies studied are found to be positive. Grüneisen γ's are evaluated from the pressure dependence of the in…
A system for designation of various types of mutual orientation of crystals and the processes during which they are formed is proposed. The neutral terms oriented overgrowth, oriented intergrowth and oriented inclusions, and in special cases polycrystal and single-crystal films, are considered to be sufficient for des…
The mechanisms of dezincification of single phase alpha and beta brasses were studied using X-ray diffraction, electron microprobe, metallographic, atomic absorption, and electrochemical techniques. The two mechanisms of dezincification which had been previously reported, (1) dissolution of both alloy constituents fol…
Raman spectra of polycrystalline crystobalite were measured over the frequency interval of the fundamental optical modes from 77°K to 538°C. Spectra recorded above and below the α–β transition temperature were strikingly different. The strong bands measured at 416 and 230 cm−1 with α cristobalite at 25°C were not obse…
The lattice parameters of the α-phase (disordered bcc), the metastable α''-phase (Fe 3 Al type) and the stable β-phase (Cu 3 Au type) in the Fe-Ga system containing 15∼30% Ga were determined and a phase diagram is proposed according to X-ray and magnetic measurements. The magnetic properties of these phases were inves…
When conducting particles are added to a nonconducting matrix, conductivity increases abruptly at a critical concentration. The theory of infinite chains is used to predict the variation of conductivity with particle concentration. Factors which determine the critical concentration are discussed.
Highly dense translucent polycrystalline bodies of stoichiometric aluminum silicate (mullite) were obtained by vacuum‐hot‐pressing of high‐purity submicron mixed oxide powders. The powders were prepared by the hydrolytic decomposition of mixed metal alkoxides. X‐ray diffraction and electron microscopy indicated that t…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSubtilisin. Stereochemical mechanism involving transition-state stabilizationJon D. Robertus, Joseph Kraut, Richard A. Alden, and Jens J. BirktoftCite this: Biochemistry 1972, 11, 23, 4293–4303Publication Date (Print):November 1, 1972Publication History Published online1 May…
A procedure is given which determines the best rigid-body rotation and translation that matches a given set of measured atomic coordinates to a fixed set of guide coordinates and minimizes the weighted sum of squared deviations.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTConformational analysis of the sugar ring in nucleosides and nucleotides. New description using the concept of pseudorotationC. Altona and M. SundaralingamCite this: J. Am. Chem. Soc. 1972, 94, 23, 8205–8212Publication Date (Print):November 1, 1972Publication History Publish…
The energy bands of graphite and boron nitride have been calculated using the tight-binding approximation, with atomic potentials obtained by the SCF CNDO method. On the basis of the calculated bands some optical properties of the above materials are discussed. The optical absorption of the hot-pressed pyrolitic boron…
Band structures of the stoichiometric titanium dichalcogenides TiS 2 , TiSe 2 and TiTe 2 are calculated using a semi-empirical tight binding method. The results are fitted to optical reflectivity and absorption data and are compared with similar calculations on other group IVA dichalcogenides.
The individual ligand contributions to the dominant (quadrupole) component of the Gd 3+ ground state splitting for nine compounds with zircon structure are determined. The results of this analysis show that the theoretical problems previously encountered in explaining the ground state splitting were due to an incorrec…
The temperature dependences of the seven adiabatic elastic stiffness moduli of CaWO4 between 1.5 K and 300 K have been determined by measurements of ultrasound wave velocities using the pulse superposition method.
A new model is presented for the insulator-metal transition in Eu-rich EuO: At low temperatures the electrons are only very weakly bound to oxygen vacancies and conduction is metallic; near and above ${T}_{c}$ the electrons localize and form bound magnetic polarons by ordering the ${\mathrm{Eu}}^{2+}$ spins neighborin…