Materials Literature
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A rigorous coupled-wave approach is used to analyze diffraction by general planar gratings bounded by two different media. The grating fringes may have any orientation (slanted or unslanted) with respect to the grating surfaces. The analysis is based on a state-variables representation and results in a unifying, easil…
Temperature-dependent phonons have been observed in the Raman spectrum of incommensurate psi -Na2CO3. Two modes are identified as q approximately=0 librational modes of the CO32- groups, which soften at the alpha - beta transition at Tc1=763K. At Tc2=633K a modulation of the structure sets in which is believed to be d…
Abstract Der Elektronentransfer von Me 2 COH‐Radikalen (durch γ‐Bestrahlung einer Aceton + Propanol‐(2)‐haltigen Lösung) auf kolloidale Ag‐Teilchen und die Reduktion von H 2 O durch die an den Ag‐Teilchen gespeicherten Elektronen werden mit Hilfe konduktometrischer Methoden untersucht.
We review the theoretical and experimental studies on the helically twisted supemolecular structure of cholesteric liquid crystals (CLCs). We discuss the problem of the nature of the forces responsible for the helical twist, generalize the results of studying the orientational order in CLCs, and treat the features of…
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The chalcogen site in bulk glasses of Ge${\mathrm{Se}}_{2}$ and Ge${\mathrm{S}}_{2}$ has been probed via nuclear quadrupole interactions with use of $^{129}\mathrm{Te}^{m}$ impurity atoms as parent in $^{129}\mathrm{I}$ M\"ossbauer emission spectroscopy. Two distinct types of chalcogen sites are observed and are shown…
The structure of yeast phosphoglycerate mutase determined by X-ray crystallographic and amino acid sequence studies has been interpreted in terms of the chemical, kinetic and mechanistic observations made on this enzyme. There are two histidine residues at the active site, with imidazole groups almost parallel to each…
Abstract We have considered the methods available for distinguishing between the rate-controlling mechanisms for gas bubble migration in metals at temperatures below 0.6Tm. We show that several combinations of mechanism, gas behaviour and rate-controlling process give rise to similar power laws describing the rate of…
Neutron diffraction patterns from methane-d4 on the graphitized carbon black, Vulcan III, have been measured over a range of coverage and temperature. At coverages up to 0·9 monolayers the methane forms a two dimensional layer in registry (√3 × √3) with the basal planes of graphite that make up the surface. At higher…
A calcium-binding soluble protein extracted from oyster shell suppresses calcium carbonate nucleation and decreases the rate of crystal growth in vitro. These findings suggest that soluble matrix may regulate shell growth.
The Mössbauer spectrum of the low temperature phase of Fe3, O4, is studied at 4.2 and 78 K. The spectrum can be resolved in five sextets, one arising from the Fe3+ ions on the A-sites, two from the Fe3+ ions on B-sites, and two from Fe2+ ions on the B-sites. The data of quadrupole splitting and hyperfine fields are us…
Electronic band gaps of various polytypes of SnS2, are estimated from the measurements of the variation of conductivity with temperature. It is found that for hexagonal polytypes, the band gap decreases as the polytype periodicity increases, as for instance the band gap values for the basic polytype 2H and the long pe…
The far-infrared spectra of five mixed ferrites in the range 200 to 640 cm−1 are reported. Four bands are observed. The high frequency band (v1) and low frequency band (v2) are assigned to the tetrahedral and octahedral complexes, respectively. A small band (v3) around v2 is observed and its intensity increases with d…
A three-dimensional analysis is given of the generation, diffusion, and collection of minority carriers injected by an electron beam in a semiconductor containing a p–n junction parallel to the surface. Using a modified Gaussian approximation to the three-dimensional electron beam dissipation function, analytical expr…
Two photoluminescence bands characterized by their excitation energy are observed in orpiment ($c\ensuremath{-}{\mathrm{As}}_{2}{\mathrm{S}}_{3}$). We assign the emission band with the peak energy of 1.53 eV to defect-related bound-exciton recombination. The luminescence band at 1.25 eV is induced by band-to-band exci…
A simple treatment of vibronic coupling in metalloporphyrins is described. Electronic degeneracy in the excited states is treated to arrive at simple expressions for the Raman excitation spectra and the absorption spectrum. The expressions are simple analogs of the usual A and B term expressions for the scattering ten…
In order to extend existing ideas on isotropic spin transfer mechanisms in bipyridine–metal complexes, a series of unsymmetrical methyl-substituted bipyridine ligands, and their nickel(II) and cobalt(II) complexes, have been prepared, and their 1 H nmr isotropic shifts measured experimentally. Simulating different ele…
ESR measurements are reported for Mn2 in kypton and xenon matrices at 4 °K.(AIP)
The oxo process consists of the reaction between an olefin, carbon monoxide, and hydrogen, in the presence of a catalyst (rhodium or cobalt) to form an aldehyde with one more carbon atom than the starting olefin. R-CH=CH 2 + CO + H 2 Catalyst/ R-CH 2 -CH 2 CHO The only exception is with the cobalt catalyst when the st…
We give two general integral expressions for the first and second derivatives of the so-called stick probability functions which are commonly used in analyzing x-ray-scattering results. Then it is shown that by letting the length of the stick go to zero, the limit of the second derivative can be expressed in terms of…