Materials Literature
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Ferroelectric phenomena in chiral smectic liquid crystals appearing as a result of the piezo- and flexoelectric effects in these substances are considered theoretically. The dependence of the amplitude and the pitch of ferroelectric helix on the material parameters is calculated in the framework of the phenomenologica…
This paper deals experimentally with the mechanism of an impulsive pressure generated by a collapsing bubble. In a water filled shock tube, an expansion wave and a subsequent compression wave are applied to single, twin and triadic bubbles. The growth, collapse and rebound of bubbles situated at various distances from…
Molybdenum peroxo complexes stabilized by picolinato and pyridine 2,6-dicarboxylato ligands catalyse oxidation of cyclic ketones by H2O2 to lactones and their derivatives; this represents a catalytic analogue of the Baeyer–Villiger reaction.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetics of endothermic decomposition reactions. 2. Effects of the solid and gaseous productsAlan W. Searcy and Dario BerutoCite this: J. Phys. Chem. 1978, 82, 2, 163–167Publication Date (Print):January 1, 1978Publication History Published online1 May 2002Published inissue 1…
Previous work on the oxidation of chromium is briefly reviewed and the theoretical aspects relating to the determination of surface concentrations of metal oxide films by X-ray photoelectron spectroscopy is discussed. An ultra-high vaccum, high resolution X-ray photoelectron/Auger electron spectrometer was used to obs…
Abstract Because of the generally immiscible nature of polymers, multicomponent polymers or polymeric alloys often exhibit microphase separation. The morphologies of these heterogeneous materials are determined not only by the composition of the system, but also by the processing conditions. The resulting microstructu…
Observations are reported of the behaviour of a smectic-A liquid crystal, 4-n-octyl-4’-cyanobiphenyl (8CB), as it is sheared in two geometries. In the first an initially-homeo-tropic sample is sheared in a planar shear flow cell, and it is observed that the shear creates textures which resemble those caused by dilatin…
A high-resolution structural study of strain-free SrTiO3 in its cubic phase at room temperature shows that the oxygen thermal motion is not very significantly anharmonic.
The first liquid crystal was discovered about a century ago by Reinitzer (1888), who observed that the organic crystal cholesteryl benzoate melted at a temperature of 145°C yielding a turbid fluid which, upon the further addition of heat, became clear at a temperature of 179°C. The turbid fluid was found to exhibit op…
The theory of intermolecular nuclear spin relaxation by translational self-diffusion in liquid crystals is developed. Torrey's treatment of simple liquids is extended and modified for the liquid-crystalline phases by taking into account the anisotropy of the molecular motion, the elongated molecular shape, and the spi…
A geometrical model is developed for monomeric TMS and PDS phases that are chemically bonded to silica. Using experimental data for maximum surface coverage and considering amorphous silica as a collection of distorted crystals, we calculate that each nm2 of the silica surface contains 2.3 modified hydroxyl groups, 1.…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMolecular structure of diaquo-.alpha.,.beta.,.gamma.,.delta.-tetraphenylporphinatoiron(III) perchlorate and perchlorato-.alpha.,.beta.,.gamma.,.delta.-tetraphenylporphinatoiron(III). Two new structural types for iron(III) porphyrinsM. E. Kastner, W. Robert Scheidt, Toshio Ma…
Abstract As is most clearly seen in the results of A. J. Kovacs on the volumetric relaxation following changes in temperature, the initial relaxation in polymers is surprisingly rapid, considering how slowly relaxation becomes later. We suggest that this rapid initial relaxation is due to relaxing molecular rearrangem…
The behavior of borate-boron in a calcium bicarbonate parent solution during the precipitation of calcium carbonate has been studied experimentally. The amount of borate-boron coprecipitated with calcium carbonate is proportional to the concentration of borate-boron dissolved in a parent solution, and this relationshi…
Abstract X‐ray diffraction has been used to further investigate the quenched form of polypropylene. The diffractometer traces were analyzed by a mathematical peak separation procedure which assumed a combined Cauchy and Gaussian shape for the peaks. The results confirmed that the quenched form contains about 60% of am…
Abstract The relation between the chemical structure of a protein and the physical properties of a heat‐set gel of that protein has been investigated. The physical properties of the gel are determined by means of mechanical experiments in which the viscoelastic properties of the gel are determined in terms of the stor…
It is shown that phase transitions in three dimensions breaking up an ordered state by polar defect lines can be modelled on the xy model, at least if the interaction of the lines is only steric. The analogy is established for a lattice model by means of a xy high-temperature expansion for spin 1/2. The defect model i…
A review of the foundation, developments and latest results of the so-called vibronic theory of ferroelectricity—a new approach to the microtheory of spontaneous polarization and ferroelectric phase transitions in crystals incorporating the interactions of electrons with nuclear displacements (vibronic interactions),…
The anisotropy of the magnetic susceptibility and the density of the series of nematic p,p′-di-n-alkyl and p,p′-di-n-alkoxy azoxybenzenes are reported as a function of temperature. Assuming that the molecules are effectively axially symmetric the anisotropy of the susceptibility is a direct measure of the nematic orde…
The fate of the energy release in highly exoergic surface-catalysed chemical reactions is of considerable fundamental interest and influences catalyst volatilization/sintering, the aerodynamic heating of hypersonic glide vehicles subject to bombardment by atomic nitrogen and atomic oxygen, etc. To provide the first av…