Materials Literature
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Neutron spin echo measurements have been performed on the mixed ionic system Ca 0.4 K 0.6 (NO 3 ) 1.4 around the glass transition temperature T g in order to determine the time dependence of the density-density correlation function ϕ q ( t ). This quantity plays a central role in recent mode-coupling theories of the g…
Summary Sulphate-hydrocarbon redox-reactions occur at two specific diagenetic temperature/thermal maturity levels: less than about 75–85°C (0.2–0.3% R 0 ), and more than 100–140°C (> 1.5% R 0 ), respectively. In low-temperature/maturity environments these redox reactions take place only with the mediation of bacter…
(1987). The Biochemistry of Degradation of Polyethers. Critical Reviews in Biotechnology: Vol. 6, No. 3, pp. 273-307.
Four emission bands have been studied at low temperatures with differently doped ZnO crystals. In the ${\mathrm{Co}}^{2+}$(${\mathrm{d}}^{7}$) ion, two transitions to the $^{4}\mathrm{A}_{2}$(F) ground state give rise to new luminescence bands, viz., starting from the $^{4}\mathrm{T}_{2}$(F) term (around 3600 ${\mathr…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStereoselective addition reaction of diethylzinc to aldehydes, catalyzed by cinchona alkaloidsA. A. Smaardijk and Hans WynbergCite this: J. Org. Chem. 1987, 52, 1, 135–137Publication Date (Print):January 1, 1987Publication History Published online1 May 2002Published inissue…
All articles of this category 2,5,7,9-Tetrathiabicyclo[4.3.0)]non-1(6)-en-8-thione ( 3 ) is prepared in increased yield by isolating the intermediate 4,5-dimercapto-1,3-dithiole-2-thione disodium salt ( 2 ) which undergoes efficient ring-closure with 1,2-dibromoethane. Quantitative oxidation of 3 with mercuric acetate…
Mn(III), Fe(III), and Gd(III) complexes of tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and several other porphyrins were evaluated as potential MRI contrast agents. Based on consideration of relaxivity and stability properties in solution, MnTPPS was found to be the compound of choice. At pH 7 the Gd and Mn complexes…
We consider periodic organizations of two fluid media separated by interfaces in which interactions between the two media, normal to the interfaces, maintain constant distances between interfaces and constraints within each medium, parallel to the interfaces, control interfacial curvatures. The structures must therefo…
The calculated hyperpolarisabilities of the symmetrical polyphenyls, containing an electron-donating dimethylamino group and an electron-attracting nitro group positioned at opposite ends of the conjugated system, slowly increase with an increasing number of phenyl units, but the effect per unit volume is a maximum fo…
Y‐TZP ceramics with various amounts of glassy intergranular phase were fabricated in order to investigate the effect of this amorphous phase on the properties of TZP. The presence of a liquid silicate phase not only enhanced sintering but also controlled the evolution of distinctly different grain morphologies, depend…
A method for the preparation of mammalian oocytes and embryos for transmission electron microscopy employing agar embedding of oocytes and re-embedding of semithin sections is described. This method offers rapid and safe handling of small specimens, and it allows analyses of even very small structures in the oocytes.
1. Methods of Investigation in Electron Microscopy. Conventional electron microscopy: fundamentals of electron optics and instrumentation (H. Bethge, J. Heydenreich). Conventional electron microscopy: image formation (J. Heydenreich, W. Neumann). Electron diffraction: fundamentals and application (W. Neumann, K. Schee…
On etudie les effets dopants de SrO, CaO, MgO, Nb 2 O 5 et MnO 2 sur la resistivite de ceramiques de BaTiO 3 frittees sous faible pression partielle d'oxygene. On etudie aussi l'effet de ce frittage sur les proprietes dielectriques. On etudie les possibilites d'emploi des dielectriques developpes dans les condensateur…
Mullite (3Al 2 O 3 ·2SiO 2 ) of stoichiometric composition was prepared by mixing boehmite sol and silica dispersion and gelling at a pH of 3. Complete mullitization takes place at or above 1300°C. Ultrafine mullite powder prepared by calcining gel at 1400°C and attrition milling could be sintered to >98% (theoreti…
Abstract
Electroactive poly(aniline) films, which are electronic conductors in their oxidized form, can be electrochemically formed on metal electrode surfaces. Above in acid solutions, oxidized films undergo a partially reversible transition to an insulating state. Impedance measurements have been used to characterize the ele…
The aim of this review is to present aperiodic crystals from a unifying point of view, showing why it is justified to call them crystals, despite the lack of a three-dimensional lattice periodicity, and to discuss in what sense they differ from periodic crystals in structure, symmetry and other physical properties. Th…
It is shown that the difficulties which appear in the interpretation of optical properties of liquid interfaces disappear when we develop a coupled mode theory of thermal interfacial fluctuations. First, we are able to calculate the optical properties of critical interfaces with only macroscopic non adjustable paramet…
Liquid crystals are usually not thought of as ‘simple’ liquids. Nevertheless, a surprising number of features of liquid crystals can be reproduced in computer simulations of very simple model systems, viz. hard ellipsoids of revolution and parallel spherocylinders. In particular, depending on the density and the shape…
A broad superconducting transition with an onset near 30 K is observed for La-Ba-Cu oxides in the measurement of magnetic susceptibility. The superconductivity is of bulk nature and reproducible after several heat cycles.