Materials Literature
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A volumetric 10:1 ratio of citric acid (50% by weight) and hydrogen peroxide (30%) is shown to be a better selective etchant of GaAs/Al0.30Ga0.70As systems than the more commonly used ammonium-hydroxide/hydrogen peroxide solutions in terms of the selectivity of the etching rate, the smoothness of the etched surface, a…
The current model for hepatic 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase divides the protein into two functional domains: an N-terminal kinase domain and a carboxyl-terminal bisphosphatase domain. Site-directed mutagenesis was used to evaluate the role of two putative bisphosphatase active site histidyl resi…
Several important aspects of the vapor deposition of diamond thin films by hot filament associated chemical vapor deposition (CVD) are described. This deposition technique is economical and scalable to large areas. However, practical difficulties such as deformation of the filament and its relatively short lifetime of…
Threo-Ds-3-isopropylmalate dehydrogenase coded by the leuB gene from an extreme thermophile, Thermus thermophilus strain HB8, was expressed in Escherichia coli carrying a recombinant plasmid. The thermostable enzyme thus produced was extracted from the E. coli cells, purified, and crystallized. The enzyme was shown to…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInfrared study of syngas adsorption on zirconiaEugenio GuglielminottiCite this: Langmuir 1990, 6, 9, 1455–1460Publication Date (Print):September 1, 1990Publication History Published online1 May 2002Published inissue 1 September 1990https://pubs.acs.org/doi/10.1021/la00099a00…
The isotropic phase of nematogenic substances above the nematic–isotropic phase transition temperature Tni is characterized by short range orientational correlation of the molecules and the existence of pseudonematic domains. This microscopic structure has a strong influence on reorientational dynamics in the liquid.…
Abstract The morphology and impact properties of polystyrene‐maleic anhydride/bromobutyl rubber blends have been studied as a function of interfacial modification and melt processing conditions. It is found that dimethylaminoethanol (DMAE) serves as a reactive compatibilizing agent for these blends and that the additi…
ZrO 2 powder was prepared by a sol–emulsion–gel method at temperatures below 140°C from ZrO(NO 3 ) 2 · n H 2 O. The asprepared powder was amorphous, but crystallized into the tetragonal structure by 600°C. The metastable tetragonal powder (600°C) was comprised of ultrafine 4‐ to 6‐nm size particles. On heat treatment,…
SUMMARY The dissolution rates of feldspars in the presence of naturally occurring organic solutes were compared at pH 5.1. Natural silt or ground feldspar minerals were suspended in water, streamwater, soil water, water extracts of peat and mor and a citrate solution for approximately 100 d. The increase of major cati…
The glass quality, physical properties, and thermal stability of fluorozirconate and fluorozirco‐hafnate glasses were investigated as a function of the AIF 3 content. The AlF 3 concentration varied from 2 to 3.25 mol%. The ratio of the other components was constant, except for 50% substitution of ZrF 4 by HfF 4 in the…
Abstract Multiple crevice assemblies (MCAs) have been used for over a dozen years to assess the crevice corrosion resistance of stainless-type alloys in seawater and other chloride-containing environments. This paper provides a review of the technique's development, modification, and present usage and discusses its li…
Abstract Molecular weight distributions of poly(dimethyl diallyl ammonium chloride) were determined from sedimentation velocity measurements. After a presentation of the experimental basis for the evaluation of distribution curves, molecular weight distribution curves for different samples were discussed and compared…
A mushy region (a two-phase zone) between the solid and liquid phases occurs often in the process of solidification of a binary melt. An analysis of the structure of the mushy region, which includes the liquid, solid particles, and dendrites extending from the bulk solid surface, is suggested. The processes of heat an…
Abstract Systematic thermal degradation studies of PVC solutions have been carried out in the presence of different metal carboxylates (Pb‐, Cd‐, Ba‐, Ca‐ and Zn‐ stearates). ZnSt 2 markedly accelerates degradation of the polymer. Significant induction periods ( t i ) for the appearance of free HCI are obtained in the…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and characterization of alkaline-earth indium sulfidesD. O. Kipp, C. K. Lowe-Ma, and T. A. VanderahCite this: Chem. Mater. 1990, 2, 5, 506–511Publication Date (Print):September 1, 1990Publication History Published online1 May 2002Published inissue 1 September 1990h…
The ideas of the electron theory of chemisorption are applied to the behaviour of H, B, C, N, and 0 atoms segregated on and in iron. The general theory can be divided naturally into two branches depending on whether the valence levels of the embedded atoms ‘float’ at the Fermi level, as in the case of B, C, and N; or…
Abstract The angular distributions of elastically reflected electrons from an evaporated gold film surface are measured at primary energies 400, 600, and 800 eV for different angles of incidence between 0° and 75°, and the influence of 2 keV Ar + ion bombardment is investigated. By means of Monte Carlo simulations the…
Abstract A systematic study was conducted to determine the optimum polyvinylchloride (PVC) molecular weight and impact modifier concentration blend for the construction or outdoor application. This application called for a material with superior impact and weathering properties as well as cost efficiency. Three differ…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThree Pentacyclic Triterpenoids from the Leaves of Plumeria obtusaSalimuzzaman Siddiqui, Bina Shaheen Siddiqui, Akhtar Naeed, and Sabira BegumCite this: J. Nat. Prod. 1990, 53, 5, 1332–1336Publication Date (Print):September 1, 1990Publication History Published online1 July 2…
The kinetics of oxidation of potassium iodide by hydrogen peroxide in aqueous perchloric acid has been studied both in the absence and in the presence of sodium molybdate by means of the initial-rates method. The law found for the total initial reaction rate is[Formula: see text]The activation energies associated with…