Materials Literature
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A series of novel specifically substituted 6-O-trityl-2,3-O-alkyl cellulose derivatives have been prepared by the reaction of triphenylmethyl (trityl) cellulose in DMSO with powdered sodium hydroxide and an alkyl iodide (iodohexane, iodopentane, and iodobutane). These derivatives form lyotropic chiral nematic mesophas…
Abstract The mutual miscibility of random poly (styrene‐co‐methylmethacrylate)s with different compositions but a constant molecular weight of M w ≅ 150,000 was studied at room temperature and at 180°C. Compatibility was analyzed with films cast from solutions with different solvents. The reliability of the analytical…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhotoinduced conformational ruffling of distorted porphyrin. Optical resolution and photochemical behavior of chiral "single-armed" porphyrin complexesKatsuaki Konishi, Kazuharu Miyazaki, Takuzo Aida, and Shohei InoueCite this: J. Am. Chem. Soc. 1990, 112, 14, 5639–5640Publi…
A protein factor with an estimated molecular mass of 50 kDa has been purified to homogeneity from the silk gland of Bombyx mori. In the presence of a molar excess of this factor and eukaryotic DNA topoisomerase II, relaxed circular DNA is converted to the negatively supercoiled form. Eukaryotic DNA topoisomerase I can…
Abstract Uses are growing for rubbers with varying levels of resistivity. High electrical resistivity is very much essential in wire and cable insulation applications. Low levels of resistivity are needed for electrostatic discharge in phonograph records and many medical, industrial, and military products and for semi…
The codeposition of red phosphorus particles and copper from an electrolytic bath constitutes an attractive method for the production of phosphorized copper, which is the preferred anode material in bright acid copper electroplating. The effects of suspension concentration, current density, temperature, solution addit…
A novel photo-addressed LC-SLM featuring TN-ECB (twisted nematic electrically controlled birefringence) is presented. The LC-SLM consists of an a-Si photoconductor, a dielectric mirror and a TN-ECB liquid crystal layer. TN-ECB is a kind of ECB mode which has been developed by simulating light propagation in a reflecti…
We have observed small changes in the ultraviolet photoemission spectra of NiS across the temperature-induced phase transition between the Pauli-paramagnetic metal and the antiferromagnetic nonmetal. In going from the nonmetallic to the metallic phases, the main band (${\mathit{d}}^{8}$L) within \ensuremath{\sim}3 eV…
All long‐duration spacecraft are susceptible to high‐speed impacts by meteoroids and pieces of orbiting space debris. Damage to critical spacecraft systems caused by such impacts can lead to spacecraft failure and loss of life. In order to develop adequate protection against penetration for crew compartments and other…
High resolution electron microscopy, convergent beam electron diffraction and Raman scattering reveal that Pb2ScTaO6 crystals belong to the Fm3m space group. They can be more or less ordered at the atomic scale in the Sc:Ta arrangement resulting in the existence of microdomains. Disordering is accompanied by a broaden…
The fracture properties of three polycrystalline Y 2 O 3 materials: one fully cubic phase, one containing an Al 2 O 3 grain‐boundary phase, and one containing hexagonal phase, were examined by indentation over a wide range of contact loads. The two former microstructures displayed tendencies at large indentation loads…
ABSTRACT Convective heat transfer between fluids and a particle was investigated as a function of fluid rheological properties and position in the ultrasonic field, expressed as dimensionless parameters. The convective heat transfer coefficient was determined for an irregularly shaped particle immersed in sodium carbo…
Taraxerol, careaborin (taraxeryl trans-p-hydroxycinnamate), and the novel triterpenoid taraxeryl cis-p-hydroxycinnamate were isolated from the leaves of Rhizophora apiculata. © 1990, American Chemical Society. All rights reserved.
We consider two simplified models of the formation of patterns emerging from the growth and coalescence of water droplets on a substrate (breath figures). The study is restricted here to the case of a one-dimensional substrate. In the first model we assume a monodisperse distribution of droplet sizes. In the second mo…
Dense, polycrystalline AlN samples of grain size between 1.8 and 19 μm were fabricated by hot‐pressing. Bar‐shaped samples were subjected to creep in four‐point bending under static loads in nitrogen atmosphere. The outer fiber stress was varied between 20 and 140 MPa and the temperature between 1650 and 1940 K. Stead…
Abstract Wegen der Sprödigkeit Keramischer Bauteile kommt deren oberflächennahen Werkstoffzuständen für das Festigkeitsverhalten eine besondere Bedeutung zu Neben der Oberflächentopographie und den vorliegenden Gefügezuständen sind dabei insbesondere die auftretenden Eigenpannungen wichtig Für die Analyse oberflächenn…
In fatigue both monotonic and cyclic plastic zones are formed ahead of the crack tip, inside which the strain history can be studied on the basis of stable hysteresis loops and structure anticipated in the crack-tip process zone and in the area of the maximum tensile stress (MTS) ahead of the crack tip. With these mat…
A test methodology that uses thermal resistance-time curves deter mined on thin shces of the foam and the scaling technique to relate aging time to the specimen thickness, was applied to evaluate long-term thermal performance of six polyurethane foams manufactured with the same polymer but different blowing agents. Th…
Abstract A set of Ni/SiO 2 catalysts with metal loadings between 1 and 8% by weight has been prepared by several methods. Metal dispersions have been determined by H 2 chemisorption and x‐ray line broadening analysis, giving metal particle sizes from ∼30 to 250 Å. XPS analysis of the samples has been recorded after re…
The Eu3+ and Y3+ complexes of 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane-N, N' - diacetic acid (K22DA), 1,7-diaza-4,10,13-trioxacyclopentadecane-N, N' - diacetic acid (K21DA), and the open-chain analogue ethylene glycol bis (ß-aminoethyl ether) - N,-N,N',N'-tetraacetic acid (EGTA) have been characterized in solution…