Materials Literature
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The soft-potential model (an extension of the well-known tunneling model for two-level states in glasses) has been formulated in terms of soft-mode eigenvectors in order to characterize the localization of these modes. The interaction with high-frequency modes explains the absence of very small restoring-force constan…
We have applied the theory of McCumber to the (4)4I(13/2) ? (4)I(15/2) transition of Er(3+) -doped glasses and confirmed its ability to provide both spectra and accurate values of cross sections. For an Al/P-silica fiber, the exact McCumber treatment is within 3% of the measured emission cross section, whereas an Eins…
The relationships between the molecular packing and the morphology of rubredoxin crystals, a metalloprotein, have been studied in detail through the periodic bond chains (PBC) method of Hartman and Perdok (1955). To carry out the PBC analysis the authors considered that the crystallizing particle consisted of the prot…
There have been many previous studies of the IV-III phase transition in ammonium nitrate and water is known to play a mechanistic role. This work examines the effect of other solvents and additives on the transition kinetics of single crystals and combines these data with structural information to examine the overall…
An account is given of the origins, in the molecular electronic properties and crystal structure, of the large quadratic optical nonlinearities found in some organic crystals. Particular cases, in which powerful second-harmonic generation or large Pockels effects have been found, chosen to illustrate the influence of…
The structural and stereochemical factors involved in the oriented nucleation of CaCO 3 under compressed Langmuir monolayers have been studied by optical and electron microscopy, and X-ray and electron diffraction. The effect of headgroup charge, stereochemistry and changes in supersaturation have been investigated. A…
Experiments were carried out to study the precipitation of calcium carbonate resulting from the mixing of aqueous solutions of calcium nitrate and sodium carbonate in a continuous-flow crystallizer at 25 degrees C in the pH range 8.5 to 10.5, reagent concentration 0.025 to 0.2 mol/l and solution residence times of 5 t…
The development of structural models for predicting the external morphology of crystalline materials is presented and discussed in terms of their applications to molecular crystals. The predicted crystal morphologies of a number of molecular materials including alpha -sulphur, naphthalene, benzoic acid and hexamine ar…
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” opt…
For pt.I see ibid. vol.1, p.179 (1989). An in situ 54 Mn nuclear orientation (NO) study of a quasi-1D antiferromagnet CsMnCl 3 .4H 2 O is presented and discussed. From a comparison between CsMnCl 3 .2H 2 O, and the 3D antiferromagnet MnCl 2 .2H 2 O, it is shown that there are significant differences in the NO behaviou…
We present the first atomic-resolution images of interfacial ordering occurring in ultrathin (${\mathrm{Si}}_{\mathit{m}}$${\mathrm{Ge}}_{\mathit{n}}$${)}_{\mathit{p}}$ superlattices. The observed asymmetric interfacial abruptness is associated with several distinct ordered configurations, which differ from phases con…
The quantitative determination of atomic hydrogen concentrations cH in the vicinity of hot filaments is performed with two-photon laser-induced fluorescence. The measurements yield atomic hydrogen concentration profiles up to 28 mm from the filament surface with a spatial resolution of about 0.5 mm. The nonequilibrium…
Using small-angle neutron-scattering techniques, the scaling laws between the thickness of a grafted polymer layer h, its graft density \ensuremath{\sigma}, and the molecular weight of the grafted chains M have been determined for polydimethylsiloxane chains end grafted on porous silica. The observed laws h\ensuremath…
Carbon bonding environments (measured by nuclear magnetic resonance spectroscopy) and compressive stress in plasma-deposited hydrogenated diamond-like carbon (DLC) films have been examined systematically as a function of substrate bias voltage. These results are related in terms of random network theory to show that h…
The Monte Carlo method is used to study three systems of fused hard spheres with length-to-width ratios ranging from 3·5 to 5·2. Spontaneous nematic alignment is observed only for the most elongated molecules. The isotropic data are compared with a theoretical expression due to Boublik and are fitted by a y expansion…
Analytical transmission electron microscopy, electron microprobe analyses, and singlecrystal x-ray diffraction data support the conclusion that high potassium contents, up to 1.5 weight percent K(2)O, of some diopside and omphacite inclusions from diamonds represent valid clinopyroxene compositions with K in solid sol…
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” opt…
Abstract Various amines were added to carbanilation reactions of cellulose samples with phenylisocyanate in an effort to aid the preparation of cellulose tricabanilates (CTCs) for determining molecular weight distributions (MWDs). However, the amines catalyzed the conversion of phenylisocyanate to its trimer phenyliso…
Abstract Nascent high‐molecular‐weight (UHMW) polyethylene (PE) samples of different origins show a rather high crystallinity of about 70–75% and contain both a major portion of orthorhombic extended chain crystallites and a minor portion of triclinic crystallites. The triclinic content is greater the higher the molec…
Abstract A viscometric approach to the formation of interpolymer complexes between a polyelectrolyte, polyacrylic acid, and a non‐ionic polymer, polyacrylamide, is investigated. The following method compares the reduced viscosity of the polymer mixture with an “ideal” value which results from the additivity of the red…