Materials Literature
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The dipole-dipole network model of the porphyrin macrocyclic ring current is used to investigate the ring currents in reduced (hydro)porphyrins derived from phylloerythrin methyl ester. Reduction of ring D to afford the corresponding chlorin results in a decrease of the inner loop and pyrrole subunit ring currents by…
Pre-breakdown currents in polyimide (PI) films were measured under the application of dc ramp voltage (30 V/s) and the breakdown mechanism is discussed on the basis of the results. A steep current increase was observed from about 10-3 before the breakdown and was ascribed to a thermal runway which results in a filamen…
Fission product release from fully irradiated light water reactor fuel under accident conditions and the chemical forms and behavior of the released material have been studied at high temperatures. This work has emphasized release from commercial fuels, but tracer-level tests using specific fission product species hav…
I. THE SOFT MODE CONCEPT: In the late fifties ferroelectric research underwent a serious transition. Until that time the theory of ferroelectricity has been either phenomenological or consisted of attempts to develop microscopic theories for specific atomic structures. In 1959 Cochran1 pointed out that at second order…
Fine‐grained polycrystalline zirconia fibers have been formed from an acetate precursor. The fibers contained a Y 2 O 3 additive, which inhibited grain growth (grain size ≤0.5 μm) and allowed the tetragonal phase to be retained at room temperature. Fibers with diameters in the range 2 to 5 μm had strengths in the rang…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPolymerization of monomers containing functional silyl groups. 4. Anionic polymerization of 2-(trimethoxysilyl)-1,3-butadieneKatsuhiko Takenaka, Akira Hirao, Takashi Hattori, and Seiichi NakahamaCite this: Macromolecules 1987, 20, 8, 2034–2035Publication Date (Print):August…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBenzothiet-2-ones: synthesis, reactions, and comparison with benzoxet-2-ones and benzazetin-2-onesCurt Wentrup, Harald Bender, and Gerhard GrossCite this: J. Org. Chem. 1987, 52, 17, 3838–3847Publication Date (Print):August 1, 1987Publication History Published online1 May 20…
This paper describes a research programme at the Austrian School of Mines (Montanuniversität) at Leoben, carried out since 1981 in cooperation with the Max-Planck-Institute for metals research in Stuttgart, on the fundamentals of alloy design for high speed tool steels. Among the results, the development of niobium-al…
▪ Abstract The phase-field method has recently emerged as a powerful computational approach to modeling and predicting mesoscale morphological and microstructure evolution in materials. It describes a microstructure using a set of conserved and ...Read More
Abstract The thermal decomposition of pyruvic acid into carbon dioxide and acetaldehyde is a unimolecular first‐order reaction and takes place according to the rate equation, log k = 13.53–41,250/4.575 K. These parameters contrast markedly with those recently reported, viz. log k = 7.19–27,700/4.575 K and confirm that…
Abstract The effect of aliphatic diols on the structure and some mechanical properties of polyurethane elastomers containing hydroxyl‐terminated polybutadiene and three different diisocyanates was studied. Differential scanning calorimetric studies revealed the existence of several thermal transitions, characteristic…
Microalloyed medium-carbon steels with ferrite-pearlite microstructure were developed in the FRG in early 1972, with the primary aim of saving the cost of heat treatment. A steel with roughly 0.47% C, 0.75% Mn, 0.060% S and 0.1 % V was first used for crankshafts in cars manufactured by one of the largest European auto…
Determination de la structure modulee incommensurablement de TaTe 4 par diffraction RX sur la base d'une surmaille 2a×2a×3c. Le groupe d'espace de la sousmaille est P4/mcc, celui de la surmaille P4/ncc. Affinement de la structure jusqu'a 0,064. La structure se caracterise par des chaines TaTe 4 le long de l'axe c. Ces…
Abstract Previous work by a number of researchers has noted the presence of anhydride during the imidization step of polyimide polymer processing from diester‐diacids and diamines. This has been often, and incorrectly, dismissed as being due to the reversion of the intermediate amide‐acid. Comparison of the relative r…
Abstract Aqueous solutions of the salt sodium polytungstate can be prepared with varying densities up to 3.1 g/cm 3 . The salt is nontoxic and it is recommended as a substitute for the hazardous halogenated hydrocarbons, tetrabromoethane and bromoform, customarily used in geological laboratories to perform light/heavy…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA copper(II) dope as a detector for the high-spin .tautm. low-spin transition in the two-dimensional compound [trans-bis(thiocyanato)bis(4,4'-bi-1,2,4-triazole)iron] hydrateWim Vreugdenhil, Jaap G. Haasnoot, Olivier Kahn, Pierre Thuery, and Jan ReedijkCite this: J. Am. Chem.…
Abstract Core cuttings from numerous wells traversing Oligocene through Recent sediments of the Texas Gulf Coast were examined with a scanning electron microscope using the back-scattered electron imaging mode (BSE) to ascertain diagenetic changes in clays and associated minerals of mudrocks and of adjacent sandstones…
V 2 O 3 was incorporated into polymer matrices to produce composite materials with low room‐temperature resistivities and sizable positive temperature coefficient (PTC) resistance effects. In addition, a negative temperature coefficient effect, associated with the semiconductor‐to‐metal phase transition in V 2 O 3 , w…
La phase haute temperature (T>83,5 K) du benzile cristallise dans le systeme rhomboedrique avec le groupe d'espace P3 1 21. Affinement de la structure jusqu'a 0,043 (T=294 K) et 0,041 (T=100 K). La phase basse temperature cristallise dans le systeme monoclinique avec le groupe d'espace P2 1 . Affinement jusqu'a 0,066…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectrochemical reactivity of manganese(II) porphyrins. Effects of dioxygen, benzoic anhydride, and axial ligandsS. E. Creager and Royce W. MurrayCite this: Inorg. Chem. 1987, 26, 16, 2612–2618Publication Date (Print):August 1, 1987Publication History Published online1 May 2…