Materials Literature
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Abstract Like some other oxides of the actinide elements, uranium dioxide has a fluorite structure and a propensity towards deviation from simple stoichiometry. Because oxygen can be transferred with ease between the UO2 lattice and the ambient gas phase, gross departures from stoichiometry occur readily. Diffraction…
Abstract The gamma‐ray‐induced crosslinking of polyacrylamide was carried out under various conditions. The molecular weight of the polymer before inrradiation was found to be the most important factor for crosslinking. When polymers have low molecular weights such as 80,000, the intensity of radiation, the external p…
Abstract The recent considerable interest in the transport and solubility properties of low‐molecular weight penetrants in elastomers arises largely because a number of important practical applications depend wholly or in part on such phenomena. These applications include various protective coatings, packaging materia…
Abstract A series of cyanoethylated celluloses with various degrees of substitution was prepared by homogeneous reaction of cellulose in PF/DMSO system. Their thermal deformation properties changed regularly with the degree of cyanoethylation. By comparing highly cyanoethylated cellulose in the series with that prepar…
Abstract The effect of precipitation on the molecular weight distributions of cellulose tricarbanilate (CTC) samples prepared from α‐pulp, hydrolyzed α‐pulp, and Avicel was determined using size exclusion chromatography (SEC). Precipitation of the CTC samples in methanol resulted in the loss of a low molecular weight…
Abstract The effects of particle concentration on the shear‐rate‐dependent viscosity, stress relaxation, and stress growth function were investigated for various molecular weight polydimethylsiloxane (PDMS) fluids filled with colloidal fumed silica. Shear‐rate‐dependent stress relaxation was observed for all dispersio…
Abstract Fluorocarbon elastomers exhibit high volume swell in methanol, but not in ethanol or other alcohols. Proton nuclear magnetic resonance (NMR) data indicate that neat methanol exists as a hydrogen‐bonded tetramer with a solubility parameter close to that of the fluorocarbon elastomer, thus causing the high swel…
Abstract The effect of 2,2′‐oxydiethanol (diethylene glycol, DEG) content (ranging from 2 to 15 mol %) and of the annealing temperature (in the range from 100 to 260°C) on the density, calorimetric, dynamic‐ and static‐mechanical and small angle X‐ray scattering (SAXS) behavior of undrawn and drawn samples (granules,…
Abstract A series of high‐molecular weight condensation polyimides was evaluated to determine the effect of polymer molecular structure on the transmission rate of oxygen, carbon dioxide, and water vapor. The polyimide films were prepared from either 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA) or pyromel…
Epitaxial growth of metastable phases is discussed. A linearized theory predicts new ordered compounds stabilized by the interaction of atomic size differences with epitaxial strain during growth.Received 17 March 1986DOI:https://doi.org/10.1103/PhysRevLett.57.599©1986 American Physical Society
We report the observation of second harmonic generation in a new class of organic polymeric materials, namely, electric field poled polymer glasses. Both the observed second harmonic coefficient (d33=6.0±1.3×10−9 esu, at 1.58 μm wavelength) and the poling process are described by a thermodynamic model that we have dev…
Nematic liquid crystal mixtures with a low ratio of k 33/k 11 and reasonably low k 11 are particularly important for improving the performance of complex, highly multiplexed twisted nematic displays. Measurements of the splay and bend elastic constants of a series of hybrid mixtures containing terminally cyano substit…
Abstract Analysis is made of the asymmetry of the carbonyl stretching vibration of poly(ethylene terephthalate) and poly(propylene terephthalate) as a function of annealing frrom amorphous to crystalline polymer. An apparently anomalous behavior of carbonyl band half‐width as a function of density for PPT is shown to…
Abstract Bispyridylnorbornadienes were synthesized using the Diels–Alder reaction of HBF4 salts of bispyridylacetylenes with cyclopentadiene. They underwent the photocyclization to give quadricyclanes which reverted to norbornadienes by heating or a catalyst. Bis(N-methylpyridyl)norbornadienes were also synthesized an…
Not only the size of the anions but also their “Pearson softness” is decisive for determining which structures (ET) 2 X radical‐cation salts form. Exchange of the anion in superconducting, two‐dimensional β‐(ET) 2 AuI 2 for Au(CN) or AuBr leads to quasi one‐dimensional twist structures with ET double bonds and two‐dim…
The temperature variation of the lattice parameters of orthorhombic sulfur was determined in the range 100 to 300 K using X-ray powder diffractometry. The following equations represent the results: aT = 10.3506−2.962 × 10−4T + 2.346 × 10−6T2 Å bT = 12.8518 − 1.198 × 10−3T + 4.038 × 10−6T2 Å cT = 24.1986 + 7.952 × 10−4…
Melting experiments were performed encompassing both pure and impure substances. The pure substances included n-octadecane paraffin and n-eicosane paraffin, while the impure substances were mixtures synthesized from the pure paraffins. The experiments were carried out in a closed vertical tube whose wall was subjected…
The paper discusses the application of signal processing techniques in the interpretation of partial discharge (PD) pulses as detected at the terminals of power transformers. Special consideration is given to the concept of PD energy and to the effect of waveshapes. Examples are included of FFT analyses of PD waves as…
A new species Stephanodiscus vestibulis is described from an eutrophic, hardwater habitat in western North America. Under the light microscope it resembles, and has perhaps been confused with, certain other small species of the genus. Structural features of the valve resolved by SEM, however, show that it is unique. T…
Pure 2-keto-4-hydroxyglutarate aldolase of Escherichia coli, a "lysine-type" trimeric enzyme which has the unique properties of forming an "abortive" Schiff-base intermediate with glyoxylate (the aldehydic product/substrate) and of showing strong beta-decarboxylase activity toward oxalacetate, binds any one of its sub…