Mechanism of the silver-catalysed heterogeneous epoxidation of ethylene
Chemisorbed atomic oxygen is the crucial surface species which selectively oxidises ethylene to ethylene oxide; adsorbed dioxygen plays no direct role in this reaction.
Materials Literature
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Statistical description of multimodal atomic probability densities
A general method for describing multimodal atomic densities is presented. It is based on series expansions of a harmonic Gaussian probability density function. The most suitable expansion is of the Gram-Charlier type; its Fourier transform can be easily inserted in a structure factor equation. This statistical method…
A melt mechanism for the thermal decomposition of ammonium dichromate
Microscopic examination of (NH4)2Cr2O7 crystallites, previously decomposed to measured extents, has given strong evidence that reaction proceeds through the intervention of a melt. This reaction has previously been accepted as occurring in the solid phase and the use of higher magnifications than were applied previous…
Structure and Dynamics of Liquid Crystalline Polymers from Deuteron NMR
Abstract The molecular structures of thermotropic liquid crystalline polymers, which have been synthesized systematically in recent years, are described according to the model of decoupling the molecular motions of the mesogenic groups and the polymer chain by inserting a flexible spacer. The molecular structure is re…
Polymer stabilization by hindered amines
Abstract
Kinetics of metalloporphyrin formation with particular reference to the metal ion assisted mechanism
Article Kinetics of metalloporphyrin formation with particular reference to the metal ion assisted mechanism was published on January 1, 1983 in the journal Pure and Applied Chemistry (volume 55, issue 1).
Heat Capacity and Other Thermodynamic Properties of Linear Macromolecules. IX. Final Group of Aromatic and Inorganic Polymers
In this final review, a series of polymers which include aromatic rings and/or inorganic chain atoms are treated. Heat capacities of poly(4,4′-isopropylidenediphenylene carbonate), polyphenylenediamides, polyheteroarylenes, poly(dimethyl siloxane), poly(diethyl siloxane), poly(trimethylsilyl ethylene), poly(dimethylph…
Effect of grinding on the degree of crystallinity of cephalexin powder.
The effect of grinding on the degree of crystallinity of cephalexin (CEX) powder was investigated. The intensities of the X-ray diffraction peaks of crystalline CEX decreased with increasing grinding time in an agate shaker mill, and after 4 h showed the same halo pattern as the noncrystalline solid (NC) obtained by t…
A Landau-de Gennes theory of nematic polymers
For a semi-flexible, nematic polymer, the Landau-de Gennes expansion for the free energy of the homogeneous melt is derived. The theory contains three parameters : the degree of polymerization, the inherent elasticity of the polymer chain, and the quadrupolar mean field between monomers. The dependence on chain length…
Thin colloidal crystals : a series of structural transitions
We study thin layers of colloidal crystals made of polystyrene balls (1.1 μm diameter) in aqueous suspension. These thin layers are produced by confining colloidal crystals between two glass planes, which act as repulsive and perfectly smooth boundaries at colloidal scales. When the two planes form a wedge, a continuo…
Flow stress of low carbon steel at high temperature and strain rate. I: Propriety of incremental strain method in impact compression test with rapid heating and cooling systems
Description d'un essai de compression par choc dans lequel un echantillon est chauffe rapidement en utilisant une bobine d'induction a haute frequence et refroidi par de l'eau apres chaque choc, le but etant d'obtenir experimentalement les caracteristiques de contrainte d'ecoulement des aciers a faible teneur en carbo…
Photoelectrochromic Behavior of Prussian Blue‐Modified TiO2 Electrodes
Abstract not Available.
IRT versus Conventional Equating Methods: A Comparative Study of Scale Stability
Nancy S. Petersen, Linda L. Cook, Martha L. Stocking, IRT versus Conventional Equating Methods: A Comparative Study of Scale Stability, Journal of Educational Statistics, Vol. 8, No. 2 (Summer, 1983), pp. 137-156
Photoreduction of polymolybdates(VI) in aqueous solutions containing acetic acid
Polymolybdates(VI) have been photochemically reduced to Mov in aqueous solutions containing acetic acid. Carbon dioxide, methane, and succinic acid were isolated as decomposition products of the acetic acid but the quantum yield of their formation was ca. 20 times smaller than that of Mov formation. E.s.r, spin-trappi…
Mechanisms of the Microbial Corrosion of Aluminum Alloys
Pitting potential was used recently to asses the aggressiveness of the biological species in the microbial corrosion of aluminum alloys in fuel-water systems. This parameter is analyzed here in relation to the electrolyte composition of the medium, especially with reference to chloride, nitrate, and phosphate levels.…
New Liquid Crystal Materials; Physical Properties and Performance in Displays for Automobile, High Information Density and Guest-host Applications
Four novel liquid crystal classes are presented, namely bi-, tri-, and tetracyclic ethanes, pyridazines, and tetracyclic chloro-diesters. Each class exhibits distinct physical characteristics, such as low viscosities η − 12 cP, low elastic ratios k33/k11 ∼ 1, large mesomorphic ranges −40°C. 250°C, large negative diele…
Spin Equilibria in Some New cis-Diisothiocyanato Iron(II) Complexes with Tetradentate Ligands of the Tris(2-pyridylmethyl)amine Type.
Les etats de spin de plusieurs complexes de fer(II) ont ete caracterises a partir de la variation de la susceptibilite magnetique entre 4 et 300 K
Additivity of simultaneous masking
Simultaneous masking functions (signal level at threshold versus masker level) were obtained for equally intense maskers presented individually and in pairs. The signal was a 2.0-kHz sinusoid. The pairs of maskers were (1) two sinusoids with frequencies 1.9 and 2.1 kHz, (2) two narrow bands of noise (50 Hz wide) cente…
The influence of thermal properties on the glass transition temperature in styrene/divinylbenzene network–diluent systems
Abstract The depression of glass transition temperature in polystyrene and styrene/divinylbenzene networks, by the addition of ethylbenzene, ethyl acetate, and m ‐diethylbenzene, respectively, has been investigated by differential scanning calorimetry. The predictive quality of the Couchman–Karasz treatment for the co…
The inelastic scattering matrix element and its application to electron energy loss spectroscopy
Using a simple hydrogenic scattering model, the matrix element with full phase information is derived for the ejection of K-shell electrons from atoms by an energetic electron beam. The scattering kinematics are defined and polar diagrams of the angular dependence of the ejected electron intensity are presented. The e…