Materials Literature
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Abstract 1,2-Dimethylindolylfulgides with 5-methylthio, 5-methoxy, or 5-dimethylamino group on the indole ring were synthesized and their photochromic properties were examined. Electron donating substituents lengthened the absorption maximum of the colored form and decreased the quantum yields of the photoreactions. T…
The digestive gland of Pecten maximus consists, as in other lamellibranchs, of numerous blindending tubules which communicate with the stomach by partially ciliated main ducts and non ciliated secondary ducts. The non-ciliated cells of the main ducts are characterized by a well developed brush border constituted by hi…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThermal process for orientation of polyaniline filmsK. R. Cromack, M. E. Jozefowicz, J. M. Ginder, A. J. Epstein, R. P. McCall, G. Du, J. M. Leng, K. Kim, C. Li, and Cite this: Macromolecules 1991, 24, 14, 4157–4161Publication Date (Print):July 1, 1991Publication History Pub…
The interactions of a lyotropic liquid crystal with boundary amorphous glass surfaces are investigated using optical techniques. An unusual phenomenon is observed: the gliding of the director at the surface. A qualitative model is proposed to explain the experimental results.
We consider the problem of wave guiding by optical fibers with nematic liquid crystal cores. The dielectric properties of the core which govern wave guiding in the fiber are determined by the nematic director field. We focus on the problem of determining the configuration of the liquid crystal in a cylindrical cavity…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAlkyl iodide decomposition on copper surfaces: .alpha.-elimination and .beta.-hydride elimination from adsorbed alkylsCynthia J. Jenks, Chao Ming Chiang, and Brian E. BentCite this: J. Am. Chem. Soc. 1991, 113, 16, 6308–6309Publication Date (Print):July 1, 1991Publication Hi…
Sundström (1986) erected the genus Proboscia for solenoid diatoms whose valves tapered to a proboscis, but only assigned one species to it, the boreal Rhizosolenia alata Brightwell. We have found three species in the modem Antarctic phytoplankton that are affiliated to Proboscia. One is apparently identical to Sundstr…
Abstract Styrene‐butadiene‐styrene linear block copolymer (SBS) can be epoxidized with hydrogen peroxide in the presence of methyltrioctylammonium tetrakis (diperoxotungsto) phosphate(3‐) as the catalyst in a biphasic system. The effects of reaction time, temperature, solvent, the ratio of the organic phase to the aqu…
This paper will focus on the influence exerted by a nonuniform flow distribution at the inlet of oxidizers to catalytic converters on conversion efficiency evaluated channel by channel. To this aim the flow inside the whole domain, constituted by the exhaust manifold and an elliptic-cross-sectional pipe connecting it…
Abstract Polyolefinic thermoplastic elastomer (TPE) is a two‐phase material in which cured EPDM (ethylene‐propylene‐diene rubber) particles are densely dispersed in a PP (polypropylene) matrix. It can be melt‐processed at high temperatures and behaves like a vulcanized rubber at ambient temperature. The question is on…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEvaluation of domain spacing scaling laws for semicrystalline diblock copolymersKonstadinos C. Douzinas, Robert E. Cohen, and Adel F. HalasaCite this: Macromolecules 1991, 24, 15, 4457–4459Publication Date (Print):July 1, 1991Publication History Published online1 May 2002Pub…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTransition-metal complexes with sulfur ligands. 62. Hydrogen evolution upon reaction of protons with sulfur-coordinated iron(II) complexes. Investigation of the proton, hydrogen and hydride interactions with iron 1,2-benzenedithiolate complexesDieter Sellmann, Michael Geck,…
A formula is presented for the mechanics of a fiber mass under extensive compres sion. The mass is treated as the assembly of the fiber elements whose individual bending behaviors are combined into the overall response of the mass. The stress-strain relation and Poisson's ratio are expressed in terms of the strain-dep…
Polycarbosilane was modified by reaction with an aluminum alkoxide to get a precursor for Si‐Al‐C‐O ceramics. The precursor was essentially characterized by magic‐angle spinning nuclear magnetic resonance ( 29 Si, 27 Al, and 13 C) and appeared as a dispersion of Al(OH) 3 ‐based particles in a polycarbosilane chain mat…
A proposed model which takes into account an elastic interaction between a polydomain grain and a surrounding ceramic matrix under weak external mechanical stresses has been used for evaluating a contribution from 90° domain wall displacements to piezoelectric and elastic constants of the perovskite ferroelectric cera…
The dynamic properties of hot-pressed aluminum nitride ceramics were determined in a series of plate impact experiments using longitudinal and transverse in-material manganin gauges. The Hugoniot curve for hot pressed specimens was determined in the range of 0–190 kbar with a value of 94±2 kbar for the Hugoniot elasti…
The nuclear-magnetic-resonance (NMR) technique is employed to liquid-crystal-dispersed-polymer (LCDP) systems. Deuterium NMR is used to determine director distributions in LCDP cells in the presence of a magnetic field. The samples consist of a nematic liquid crystal mixed with small percentages of a monomer that is p…
Abstract Differential scanning calorimetry, dynamic mechanical measurements, and thermal gravimetric analysis techniques have been used to thermally characterize blends of poly(etherether ketone)‐thermotropic liquid crystalline polymer (LCP) based on hydroxybenzoic and hydroxynaphthoic acid (HBA/HNA). Based upon diffe…
Abstract Imogolite and allophane have been found in various soil environments, but most commonly occur in Spodosols and Andisols. Controversy exists regarding the origin of these short‐range‐order aluminosilicates, especially in Spodosols. The proto‐imogolite theory suggests that imogolite forms in the surficial miner…
Silicon dioxide exists in a number of structures. The lowest-energy structure is that of \ensuremath{\alpha}-quartz. We predict the structural properties of \ensuremath{\alpha}-quartz as a function of pressure via total-energy calculations. The calculations are based on recently developed pseudopotentials constructed…