Materials Literature
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Abstract Complete conversion of the crystal form in cotton fibers to cellulose IV (cell IV cotton) was obtained by heat treatment of ethylamine‐treated cotton cellulose in either saturated steam or formamide. Degradation of the fibers was not extensive during the conversion process; oxidative damage appeared to have b…
Abstract Triphenylchloromethane and p ‐toluenesulfonyl chloride were reacted with chopped or powdered cellulose, with and without premercerization, to form trityl–cellulose ethers or tosyl–cellulose esters. Powdered and premercerized cellulose samples were more readily derivatized. Differential scanning calorimetric (…
Abstract The effect of the physical aging of ethylene ionomers was studied for the samples with the acid content of 5.4 mol%, and the degree of neutralization, 0%, 60% Na, 60% Zn, and 90% Zn. The information about the crystal and the cluster part of the physically aged ionomers was obtained by differential scanning ca…
Abstract A comprehensive examination of the die‐drawing behavior of polypropylene has been carried out, examining the effects of draw temperature, haul‐off speed, and initial billet size. A range of oriented products was obtained and characterized, primarily by the determination of Young's modulus at room temperature,…
Abstract The reaction of EPR with dicumyl peroxide at 180°C or t ‐butyl perbenzoate at 140°C resulted in the formation of a fraction insoluble in cyclohexane at 22°C. The presence of maleic anhydride (MAH) in the EPR‐peroxide reaction mixture increased the amount of insoluble polymer, whose concentration decreased as…
Abstract The influence of macroscopic dimensions, heat treatment, and polymer morphology on the chemical degradation of poly(glycolic acid) (PGA) fibers and pellets was examined in media of different pH values by monitoring the sample mass, dimensions, crystallinity, mechanical strength, and surface character. The deg…
The role of the secondary structure in the folding mechanism of dihydrofolate reductase from Escherichia coli was probed by studying the effects of amino acid replacements in two alpha helices and two strands of the central beta sheet on the folding and stability. The effects on stability could be qualitatively unders…
Polyacrylonitrile films have been spin cast and pyrolyzed to produce thin (500–1500 Å) carbon films. These films have higher electrical conductivities than films produced by other methods at similar temperatures. The conductivity can be varied by at least four orders of magnitude by changing the pyrolysis temperature.…
The kinetic parameters and emission spectra of TL induced by X-irradiation at RT are studied in two feldspars: albite (Naalsi3O8) and microcline (KAlsi3O8). Peaks with activation energies of ≈ 0.70, 0.82, ≈ 1.05, 1.17, and 1.24 eV are found for both crystals while in albite there are three additional peaks (of 0.60, 0…
The chemical potential of oxygen in nonstoichiometric ceria, CeO2−x, was measured versus composition x (10−4 ≤x ≤10−2) and temperature (823≤T≤1073 K) using a novel solid electrochemical cell, utilizing yttrium stabilized zirconia. The composition of CeO2−x was varied by coulometric titration. The O2 chemical potential…
The properties of thin gelatin films sensitized with a dye (methylene blue) when used as a holographic material are discussed. On illumination the excited dye molecule changes its structure giving a colorless molecule. The higher rate of bleaching and therefore the higher diffraction efficiency of the developed phase…
Numerical experiments have been performed with use of a fairly realistic model for polyethylene which has enabled the effects of anharmonicity, temperature, and positional disorder on the thermal conductivity to be investigated. It has been shown that the classical conductivity may be substantially increased by both i…
The electronic and structural properties of graphite have been determined in the local-density approximation with our precise total-energy full-potential linearized augmented-plane-wave method. We confirm the presence of a low-lying unoccupied ${\ensuremath{\Gamma}}_{1}^{+}$ interlayer state, which is of importance fo…
The bonding at the interface between calcium fluoride and the silicon (111) surface has been studied with surface-sensitive core-level photoemission spectroscopy. The interface is found to consist of predominately Si---Ca bonds, with a dissociation of the ${\mathrm{CaF}}_{2}$ molecule at the interface resulting in dep…
Specific heat capacities of “superionic conductor”, Ag chalcogenides have been measured for Ag 2 S, Ag 2 Se and Ag 2 Te in the temperature range, 120–520 K. In every case, the heat capacity at constant pressure, C p decreases with increasing temperature over the fairly wide range above transition temperature. The beha…
Triplet decay of Mg and Zn phthalocyanins have been studied by laser flash photolysis as a function of concentration. The triplet decay mechanism changes from a near first order in dilute solution to an almost second order in concentrated solutions. This is interpreted in terms of triplet–triplet recombinaison. With t…
The Raman spectrum of the uncoupled O–H and O–D stretching vibrations of HDO dissolved in H2O high-density amorphous ice, that was made from ice Ih, has been measured at 12 K for the sample as recovered at 77 K and after heating it at 5 K min−1 from 12 K to, successively, 80, 90, 100, ..., 170 K and annealing there fo…
Variations in the structural energy of solid carbon along a transformation path from a graphitic structure with . . .[AA] . . . stacking to hexagonal diamond are calculated using the first-principles pseudopotential local-orbital total-energy method. The transformation path is that defined in an earlier study of the t…
An ab initio pseudopotential method is used to study the structural properties of SiC at low and high pressures. For cubic SiC, the calculated ground-state properties, such as the equilibrium lattice constant, bulk modulus, and cohesive energy, are in good agreement with experiment. The indirect band gap of cubic SiC…
The oxygen vacancy in \ensuremath{\alpha}-quartz has been studied in various charge states using the molecular-orbital techniques modified intermediate neglect of differential overlap (MINDO/3) and its open-shell version (MOPN). The solid containing the defect is simulated by a cluster of 30 to 40 atoms, including hyd…