Materials Literature
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Three empirical equations introduced by Jonscher to represent the imaginary part of the small-signal frequency response of dielectric materials and termed ‘‘universal dielectric response’’ by him are generalized in three ways. The equations may be applied in normalized form at the impedance level as well as at the usu…
When the small-signal ac frequency response of a dielectric or conductive system is known, either functionally or as data, it is shown that the corresponding response of an associated conductive or dielectric system may be immediately obtained through the use of new duality relations. A specific model is considered wh…
Abstract Chemically modified electrodes are prepared by deposition of copper hexacyanoferrate (CuHCF) on glassy carbon. These electrodes are characterized by voltammetric and potentiometric measurements. After suitable conditioning they exhibit nearly Nernstian response to changes in activity of potassium or ammonium…
Abstract Previous work has shown that sorption of CO 2 at relatively high pressures by glassy polymers reduces their glass transition temperatures and may convert the glass into a rubber under certain conditions. It is shown here that this plasticization by a gas can induce crystallization just as sorption of vapors o…
Details of the optical-spectroscopic properties of alexandrite (${\mathrm{BeAl}}_{2}$${\mathrm{O}}_{4}$:${\mathrm{Cr}}^{3+}$) crystals were studied by different laser-spectroscopy techniques. The temperature dependences of the fluorescence lifetimes and widths of the zero-phonon lines were found to be quite different…
Ribonuclease A has been used as a model protein for studying the specificity of glycation of amino groups in protein under physiological conditions (phosphate buffer, pH 7.4, 37 degrees C). Incubation of RNase with glucose led to an enhanced rate of inactivation of the enzyme relative to the rate of modification of ly…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCatalytic photochemical dehydrogenation of organic substrates by polyoxometalatesCraig L. Hill and Donald A. BouchardCite this: J. Am. Chem. Soc. 1985, 107, 18, 5148–5157Publication Date (Print):September 1, 1985Publication History Published online1 May 2002Published inissue…
Abstract The microdomain structure of a series of segmented polyurethane block copolymers is characterized by small‐angle x‐ray and neutron scattering analyses. The materials contain hard segments formed from 4,4′‐ diphenylmethane diisocyanate (MDI) and butanediol (BD), and range in hard‐segment content from 20 to 80%…
I describe some results of the first systematic study of above-bandgap optical anisotropies in cubic semiconductors. The anisotropies are large, of the order of 1% of the relative reflectance differences for light polarized along orthogonal principal axes of the dielectric tensor of the anisotropic phase. Extrinsic co…
The various photo-induced phenomena that occur in chalcogenide glasses are classified and described, with particular emphasis on the photo-dissolution effect. The detailed mechanisms responsible for many of these processes are still unknown, although in the case of photo-darkening in annealed a-As2S3 films, Raman expe…
Over-quenched melt-spun ribbons of nominal composition Nd0.14(Fe0.91B0.09)0.86can be compacted to fully dense permanent magnets by hot-pressing at 700-750°C to 100 kPa (-15 kpsi). The resulting material is only slightly magnetically aligned with room temperature magnetics:B_{r}/H_{ci}\simeq 8kG/19 kOe. Die-upsetting t…
A square-lattice model of amphiphile-oil–water systems is developed in which oil and water molecules occupy single sites and amphiphiles occupy chains of sites. Energies and free energies estimated by Monte Carlo sampling of configuration space show that when the head, or water-loving portion, of the amphiphile has no…
The transformation, microstructural development, and densification of an α‐alumina‐seeded boehmite sol‐gel was studied. α‐Alumina particles are shown to act as nuclei for the trans‐ formation of θ‐ to α‐alumina and to result in an increase in the transformation kinetics and lowering of the transformation temperature b…
This work explains with comprehensive terms for non specialists what the Organic Metals are ("coductive plastics"). Those new materials will be in the near future a true revolution on several technology fields.
To sit in judgement values of the technic level reached in a cement plant, it is surprisingly objetive to analyse work, planning and control development about Refractories subject. Considering and recognizing the validity of this pragmatic axiom it will offer unexpected improvement perspectives of the productivity rat…
In this work an account is given of the results obtained when the differential pulse polarography (differential pulse anodic stripping voltametry) is applied to the determination of the contents of the compounds by molybdenum (VI), nickel (II) and vanadium (V) in a common portland cement which are in quantities of the…
TGL 11357 Norm specifies the express use of the cement: — Portland with a content between 0% and 5% of C3A, or — Supersulphathed iron foundry (with conditions), or — Aluminates (with conditions) when the agressiveness of the water and/or of an agressive sulphatic ground (among others) will be touching the concrete wor…
In this article there are explained the necessary steps to make up a quantitative analysis of alpha-quartz applying the technique of rays X diffraction, in artificial mixtures of anhydrous portland cement and synthetic calcite, which contents are known.