Influence of moisture on transient oxidation and reduction of alumina-supported platinum

The transient surface behavior on oxidation and reduction of a partially oxidized alumina-supported platinum catalyst containing residual water have been observed by AC electrical conductance (G) measurements.     

The Gravitational Field of an Electrically Charged Mass Point and the Causality Principle in the RTG

We find the effective Riemannian space–time corresponding to the gravitational field generated by a charged mass point in the framework of the relativistic theory of gravity. The causality principle plays an important role in solving this problem. The analytic form and the domain of definition, i.e., the gravitational radius, of the obtained solution differ from the corresponding results in Einstein's general relativity theory.     

Fractal dimensions of lanthanum ferrite samples by adsorption isotherm method

Fractal dimensions of three different samples of lanthanum ferrite were computed using single adsorption method. The fractal Dubinin–Radushkevitch isotherm was used to fit directly the experimental nitrogen adsorption data. Avnir–Jaroniec method for fractal dimension determination was also used. Low and intermediate fractal dimensions were obtained according to BET specific surface areas.     

Higher-order effects studied for K-shell excitation of high-Z projectiles

The study of projectile excitation of high-Z ions in collisions with light target atoms is a powerful tool for the investigation of magnetic and higher-order effects occurring in relativistic collisions. Very first investigations performed for bismuth ions were recently extended at the ESR storage ring by using He-like uranium ions in collisions with gaseous targets. At the ESR jet target, the absence of solid-state effects (e.g., multiple collisions) allows one to study higher order processes, such as excitation and ionization or excitation and capture, occurring in single collisions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of some parasite surface reactions on the variation of electrical conductance in the H2?Pt/Al2O3 system

The charge transfer at the interface H₂-0.5% Pt/Al₂O₃ was studied by using the transient response of the AC electrical conductance. The transient response for water and oxygen contaminated surface was of the overshoot-type.     

Improved enzyme retention from an electropolymerized polypyrrole-alginate matrix in the development of biosensors

A novel pyrrole-alginate was synthesized providing a gel by Ca²⁺ cross-linking. The subsequent in situ electrochemical polymerization of the linked pyrrole groups at 0.93 V led to the formation of a composite polypyrrole–gel matrix exhibiting a greater enzyme retention as well as increased alginate stability towards the destructive effect of phosphate anions unlike the natural alginate gel. The presence of the electropolymerized chains was clearly indicated by the decrease of the permeability when compared to natural alginate gel, namely 2.7 × 10⁻² and 3.65 × 10⁻¹ cm s⁻¹ respectively, using as an electroactive permeate, hydroquinone. Moreover, the analytical performance of glucose oxidase-based composite alginate for the determination of glucose was determined.     

Conditions for the appearance of thermal oscillations during the catalytic oxidation of methanol

The experimental conditions in which thermal oscillations may be detected during methanol oxidation on palladium catalyst were determined for methanol concentration, oxygen flow rate, temperature of the gaseous reaction mixture and weight of the catalyst sample. Catalyst powder disposal may influence the characteristics of oscillations.

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Theoretical study of non-radiative deactivation pathways for some heterocyclic compounds. I. Pyrrolyl-izoxazole derivatives

We perform an experimental and theoretical study on some pyrrolyl-izoxazole derivatives with single bridged donor (D) and acceptor (A) moieties, potentially Twisted Intramolecular Charge Transfer (TICT) state forming compounds. The emission spectra in solvent of different polarities and at different excitation wavelengths were performed. The fluorescence quantum yield is very low and the emission band shifts towards long wavelengths in polar solvents and on increasing the excitation wavelength. Solvent dependent semiempirical calculations were performed. The ground and excited states potential energy surfaces were built in terms of the torsion angle about the single bond joining D and A. The ground states have quasiplanar geometry, but the minimum of the excited states corresponds to the orthogonal conformation, stabilised in methanol due to the large charge separation between the D and A fragments. The possibility of forming TICT excited states for the studied pyrrolyl derivatives is discussed.     

Synthesis and applications of chiral phosphite ligands derived from incompletely condensed silsesquioxane backbones

The synthesis of novel chiral tri- and bidentate phosphites 2, 5, 6 and 8, derived from incompletely condensed silsesquioxane backbones and binaphthol, is described. These compounds can be obtained in good yield and are characterized by multinuclear NMR spectroscopy, mass spectrometry and elemental analyses. The complexation with [Rh(cod)₂]BF₄ has been studied for all bidentate ligands. These nanosized ligands have been applied in the rhodium-catalyzed asymmetric hydroformylation of vinyl acetate and in the rhodium-catalyzed hydrogenation of methyl-(Z)-2-acetamidocinnamate.