Materials Literature
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The polymerization of lactones provides a facile route to polyesters that is unimpeded by the long reaction cycles and elevated temperatures inherent in the condensation of hydroxyl and acid functional groups. Depending on the structure of the lactone monomer, catalyst/initiator systems are known which allow preparati…
The mean-square end-to-end distance and the second virial coefficient are evaluated for stiff chains with excluded volume. The calculation is based on a wire-bead model whose backbone in the unperturbed state obeys wormlike-chain statistics. In order to establish the necessary distribution functions, results derived i…
High‐temperature diffusion kinetics and phase relations between couples of fused SiO 2 or cristobalite and sapphire or mullite were investigated in air and in helium. Subsolidus liquid formation between sapphire and cristobalite indicates the existence of a metastable system without mullite. A liquid phase is consider…
The electrical relaxation associated with alkali diffusion in Na 2 O·3SiO 2 glass was studied from 0.2 Hz to 700 kHz at –1° to 163°C. A formalism for analysis of electrical relaxation in conducting dielectrics which associates the nonexponential decay of the electric field to zero and the dispersions in the dielectric…
A neutron diffraction study was carried out on SrFeO 3 . The results indicate that the magnetic structure is a helical one with the helicoid vector k ; k //<111> and | k |=0.112 a * . The Fe 4+ magnetic moment is 2.7±0.4 µ B at liquid nitrogen temperature.
The X-ray photoelectron spectra of some forty-six copper compounds and complexes have been measured. The chemical shifts obtained from accurate determinations of the binding energies have been qualitatively explained on the basis of the Pauling electronegativity concept using the group electronegatives of Huheey for t…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStable free radicals. X. Nitronyl nitroxide monoradicals and biradicals as possible small molecule spin labelsEdwin F. Ullman, Jeanne H. Osiecki, D. G. B. Boocock, and R. DarcyCite this: J. Am. Chem. Soc. 1972, 94, 20, 7049–7059Publication Date (Print):October 1, 1972Publica…
It is shown that two-step, two-wave mixing makes a substantial contribution to the total three-wave mixing process in a noncentrosymmetric crystal. The efficiency of generating $2{\ensuremath{\omega}}_{1}\ensuremath{-}{\ensuremath{\omega}}_{2}$ was observed as a function of the difference frequency ${\ensuremath{\omeg…
Foam fractionation is a process whereby dissolved (or colloidal) material is selectively adsorbed on the surfaces of rising bubbles and then is partially segregated by the foam. Even in the absence of foam, a bubble fractionation process may occur in the liquid, the process yielding a concentration gradient therein. B…
Serratia marcescens has been used to demonstrate that bacterial concentrations in jet drops from bursting bubbles can be much higher than the concentration in the water in which the bubbles burst. The ratio of the concentrations is the concentration factor C. A rotating tank was used to study the stripping of bacteria…
The tight-binding approximation has been applied for calculation of the band structure of planar hexagonal crystal layers of graphite and boron nitride. The theoretical width of the valence band of 15.9 eV in graphite and the distance between the centers of $\ensuremath{\pi}$ and $\ensuremath{\sigma}$ band of 5.3 eV a…
A piezospectroscopic study of the Lyman spectra of arsenic, antimony, phosphorus, and magnesium donors in silicon has been made using a quantitative-stress cryostat. Within experimental error, all four impurities yield the same value for the shear-deformation-potential constant ${\ensuremath{\Xi}}_{u}$ of the $〈100〉$…
TE0 mode selection was observed in an asymmetric dielectric light guide with a metal-film outer coating. TM0 mode and higher-order modes could not transmit through the guide, whereas the loss of the TE mode, the insertion loss, was small. The experimental data were in good agreement with the theoretical results given…
A hydrodynamic regime in dynamic scattering has been observed in which the relaxation time depends on the voltage at turnoff. This regime manifests itself, above a threshold voltage, with microscopic regions of increased on-axis optical density which grow until the whole cell area is converted. It has been found in al…
The optical spectrum and exchange splittings of the two types of nearest neighbor Cr3+ pairs in orthorhombic YAlO3 have been studied. The emission spectrum from 7200 to 7350 Å yields the ground state exchange −JS.S+j(S.S)2 with Ja=−24.7, ja=−0.66 cm−1 and Jb=−26.2 and jb=−0.91 cm−1. From the shift of the lines under u…
Potassium in graphite shows distinctive reducing properties towards carbonyls. The reaction products can be related to a mechanism similar to electrochemical reduction. The steric orientation of the reduction can be explained by the particular structure of potassium–graphite.Chromic anhydride in graphite offers a new…
The limiting high frequency permittivity ε ∞ of hexagonal ice, measured using a coaxial three terminal dielectric cell designed to minimize errors arising from differential thermal contraction, varies from 3.093 ± 0.003 at 2 K to 3.15 ± 0.02 at 200 K. The result is discussed in relation to the translational lattice vi…
A general semiclassical derivation is given of the efficiency of the scattering of light from a longitudinal-optical (LO) phonon coupled to a single-component plasma in a semiconductor. The efficiency is the sum of two terms. One is due to the modulation of polarizability by atomic displacements and by the macroscopic…
The compressibilities of the monotellurides of Pr, Sm, Eu, Tm, and Yb and the monoselenide and sulfide of Sm have been investigated to \ensuremath{\sim} 300 kbar using high-pressure $x$-ray-diffraction techniques. SmTe, SmSe, TmTe, and YbTe show abnormal volume changes in the 20-50-, 15-40-, 15-30-, and 150-200-kbar r…
Abstract Transition bands are regions of high lattice distortion which result from inhomogeneous deformation in metals. During annealing of cold-worked metals, nucleation of recrystallization is frequently observed to occur within these bands. An analysis has been made of some of the conditions under which transition…