The effect of temperature on the surface tension and adsorption functions of the Fe-S-O melts - an analysis based on interaction parameters

The present investigation analyses the thermodynamic behaviour of the surfaces and adsorption as a function of temperature and composition in the Fe-S-O melts based on the Butler's equations. The calculated-values of the surface tensions exhibit an elevation or depression depending on the type of the added solute at a concentration which coincides with that already present in the system. Generally, the desorption of the solutes as a function of temperature results in an initial increase followed by a decrease in the values of the surface tension. The observations are analyzed based on the surface interaction parameters which are derived in the present research.

Synthesis and cation binding properties of new bile acid-based crown ethers

A series of bile acid-based crown ethers (7a-c,12 and 13) were easily constructed from readily available precursors. Measurement of association constants (K-a) with alkali metal picrates in CHCl3 showed that azacrown ethers 7a-c and Chola-Cuowns 12 and 13 show greater binding towards Rb+ and K+. The presence of the aromatic moieties showed subtle changes in the binding properties. Insight II minimized structures show very different conformations of aromatic units in 7a-b and 13.

Thermodynamics of surfaces and adsorption in the Fe-S, Fe-N, and Fe-S-N systems at 1823 K

The present investigation calculates the surface tension and adsorption functions of the Fe-S, Fe-N, and Fe-S-N melts at 1823 K using the modified form of Butler's equations and the derived values of the surface interaction parameters of the systems. The calculated values are found to be in good agreement with those of the experimental data of the systems. The present analysis indicates similar adsorption behavior of sulfur for the Fe-S and Fe-S-N systems at 1823 K. Although a linear adsorption behavior is observed in the Fe-N system, an inverse relationship in the adsorption behavior exists between sulur and nitrogen in the Fe-S-N system.

Electrocatalytic efficiency of polyaniline by cyclic voltammetry and electrochemical impedance spectroscopy studies

Electrochemical redox reactions of ferrous/ferric (Fe2+/Fe3+) and hydroquinone/quinone (H(2)Q/Q) were studied on Pt and polyaniline (PANI)-deposited Pt electrodes in 0.5 M H2SO4-supporting electrolyte by cyclic voltammetry and ac impedance spectroscopy. A comparison of the experimental data obtained with the Pt and PANI/Pt electrodes suggested that the reactions were catalyzed by the PANI. Based on a relative increase in peak currents of cyclic voltammograms, catalytic efficiency (gamma(cv)) of the PANI was defined. There was an increase in gamma(cv) with an increase of scan rate and a decrease of concentration of Fe2+/Fe3+ or H(2)Q. The complex plane impedance spectrum of the electrode consisted of a semicircle in high frequency range and a linear spike in low frequency range. The exchange current density (i(0)) calculated using the semicircle part of the impedance showed Butler-Volmer kinetics with respect to concentration dependence. From a relative increase of i(0) on the PANI/Pt electrode, catalytic efficiency (gamma(eis)) was evaluated. (C) 2002 Elsevier Science B.V. All rights reserved.

Efficient syntheses of benzothiazepines as antagonists for the mitochondrial sodium-calcium exchanger: Potential therapeutics for type II diabetes

Type II diabetes mellitus is a chronic metabolic disorder that can lead to serious cardiovascular, renal, neurologic, and retinal complications. While several drugs are currently prescribed to treat type II diabetes, their efficacy is limited by mechanism-related side effects (weight gain, hypoglycemia, gastrointestinal distress), inadequate efficacy for use as monotherapy, and the development of tolerance to the agents. Consequently, combination therapies are frequently employed to effectively regulate blood glucose levels. We have focused on the mitochondrial sodium-calcium exchanger (mNCE) as a novel target for diabetes drug discovery. We have proposed that inhibition of the mNCE can be used to regulate calcium flux across the mitochondrial membrane, thereby enhancing mitochondrial oxidative metabolism, which in turn enhances glucose-stimulated insulin secretion (GSIS) in the pancreatic beta-cell. In this paper, we report the facile synthesis of benzothiazepines and derivatives by S-alkylation using 2-aminobenzhydrols. The syntheses of other bicyclic analogues based on benzothiazepine, benzothiazecine, benzodiazecine, and benzodiazepine templates are also described. These compounds have been evaluated for their inhibition of mNCE activity, and the results from the structure-activity relationship (SAR) studies are discussed.