Materials Literature
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Relatively low-molecular-weight copolyesters of glycolic acid (GA) with lactones such as gamma-butyrolactone (BL), delta-valerolactone (VL), and epsilon-caprolactone (CL) were synthesized by copolycondensation without catalysts. The resulting copolyesters are intended as carriers for drug delivery systems. Copolyester…
Abstract A test methodology was developed for exposing degradable polymer test specimens to a simulated chemical and mechanical body environment and then testing them periodically to detect changes in stress–strain behavior. Poly(ortho ester) specimens were exposed to cyclic loading in aerated tris‐buffered saline (pH…
Abstract Interactions between decyl-, dodecyl-, and tetradecyltrimethylammonium bromide (DeTAB, DTAB, and TTAB) and an anionic porphyrin, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphine (H2TPPS4−), have been studied in water at 298.2 K. Precipitate formation constants between the surfactant cations and the H2TPPS4− ani…
The deposition and dissolution of aluminum in NaAlCl 4 melts saturated with NaCl have been investigated by voltammetry and potentiometry for different electrode materials at 175°C. The tungsten and glassy carbon electrodes are shown to be electrochemically inert in the melts, whereas copper is electrochemically active…
Abstract A quantitative oxygenation of styrene to 1-phenylethanol is realized in a reaction catalyzed by an iron complex of 5,10,15,20-tetrakis(1-methyl-4- pyridinio)porphine tetrachloride (FeTMPyP) in water at pH 12 containing NaBH4. A plausible mechanism involving a styrene carbanion stabilized by Fe(III)TMPyP as an…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTModeling the conformations and mobilities of aliphatic polyamides and polyesters confined to channelsA. E. TonelliCite this: Macromolecules 1991, 24, 6, 1275–1278Publication Date (Print):March 1, 1991Publication History Published online1 May 2002Published inissue 1 March 199…
Abstract The mineralogical and geochemical characteristics of the Tirschenreuth and Kohdachi kaolin deposits, which both occur in granite, are compared and the genesis of the deposits discussed. The Tirschenreuth deposit (Rappauf pit) is considered to have formed by weathering because: (i) the kaolinite has formed by…
For Escherichia coli, growth on acetate requires the induction of the enzymes of the glyoxylate bypass, isocitrate lyase and malate synthase. The branch point between the glyoxylate bypass and the Krebs cycle is controlled by phosphorylation of isocitrate dehydrogenase (IDH), inhibiting that enzyme's activity and thus…
The basic performance requirements for heat-shrinkable components and the compounding and processing techniques that are used to meet these requirements are covered. The emphasis is on the electrical, mechanical, and environmental protection features of components for low-voltage (up to 1 kV) applications. The aim is…
Porous electrodes of Sr‐doped lanthanum manganite in a planar solid oxide fuel cell were made by the plasma spray technique. Spherical carbon particles were utilized as an effective pore former. Spraying a mixture of annealed oxide powders sized between 50 to 200 μm and 15 wt% solid Carbospheres resulted in a uniform…
A treatment based on Badger’s rule is used to estimate symmetric stretching frequencies νs of the nonbridging fluorides of various ZrFn groups in the presence of divalent and monovalent countercations. New vibrational spectra of MgZrF6, Ba2ZrF8, and β-BaZr2F10 are presented and incorporated into the method. The factor…
Previous studies have shown that rat incisor dentin contains a considerable amount of magnesium that is distributed heterogeneously. The cementum-related dentin, especially its incisal portion, is richest in magnesium. It was the purpose of the present study to investigate the changes that occur in the magnesium conte…
The thermodynamic solubility-product of kutnahorite, CaMn(CO)2, was measured following its dissolution in CO2-saturated deionized water and dilute NaCl solutions at 5 , 25o and 40oC. The logarithm of the equilibrium ion activity products derived from solution parameters and model estimates of the ion activity coeffici…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRadiation chemistry of cyanine dyes: oxidation and reduction of merocyanine 540Anthony Harriman, Lian C. T. Shoute, and P. NetaCite this: J. Phys. Chem. 1991, 95, 6, 2415–2420Publication Date (Print):March 1, 1991Publication History Published online1 May 2002Published inissu…
The mechanical properties of alumina have been successfully improved by adding isolated boron carbide particles of two different shapes. A K Ic of 7.26 ± 0.20 MPa · m 1/2 for alumina—boron carbide whiskerlike composites and of 5.27 ± 0.12 MPa · m 1/2 alumina—boron carbide shardlike particle composites has been achieve…
Abstract A temperature-programmed desorption of adsorbed dimethylpyridine clarified the characteristic changes in acid type, acid strength, and acid amount of silica–alumina prepared by depositing silica on an alumina support. Lewis acid sites of the alumina changed into Brønsted acid sites together with a change in t…
Influencing the Aggregation of Manganese Complexes by Different Bases: Formation of [Mn(O 2 CCF 3 ) 2 (py) 4 ] and [Mn 3 (O 2 CCF 3 ) 6 (benz) 6 ] Manganese powder reacts quantitatively with trifluoroacetic acid to yield Mn(O 2 CCF 3 ) 2 ( 1 ). The aggregation of 1 is directed by different N‐containing bases. Pyridine…
The solubility dependence of canavalin on both pH and temperature was determined. The results are presented both as a function of a single parameter (pH or temperature) and as a function of both. The final pH was studied as a function of initial pH and temperature. An estimate of the heat of crystallization of canaval…
The migration of electron density of a substrate (folate) on binding to an enzyme (dihydrofolate reductase) is studied by a quantum-mechanical method originally developed in solid state physics. A significant polarization of the substrate is induced by the enzyme, toward the transition state of the enzymatic reaction,…
In recent years the interest in hybrid bistable devices has increased rapidly because of the possibility of using these properties for optical computing systems. Therefore we investigate optoelectronic features of various CdS layers, pointing out especially the bistability in photoconduction presented by thermo-optica…