Quadratic and Superlinear Convergence of the Huschens Method for Nonlinear Least Squares Problems

This paper is concerned with quadratic and superlinear convergence of structured quasi-Newton methods for solving nonlinear least squares problems. These methods make use of a special structure of the Hessian matrix of the objective function. Recently, Huschens proposed a new kind of structured quasi-Newton methods and dealt with the convex class of the structured Broyden family, and showed its quadratic and superlinear convergence properties for zero and nonzero residual problems, respectively. In this paper, we extend the results by Huschens to a wider class of the structured Broyden family. We prove local convergence properties of the method in a way different from the proof by Huschens.     

A Mössbauer study on remarkable changes in chemical states of iron in silica-supported Pd-Fe bimetallic catalysts by varying Fe contents

Fe-57 Mössbauer spectra of silica-supported Pd–Fe bimetallic catalysts show remarkable changes with varying Fe/Pd atomic ratios. From the spectra, the main Fe-component is estimated as highly dispersed Fe in the Fe/Pd range of 0.05–0.3 and -Fe ensemble and Fe–Pd intermetallics in the Fe/Pd range above 0.3. It is suggested that the chemical state of iron is associated with the catalytic performance in effective CO–H₂ conversion to methanol.     

Self-diffusion of water-ethanol mixtures in polyacrylic acid-polysulfone composite membranes obtained by pulsed-field gradient nuclear magnetic resonance spectroscopy

The self-diffusion of water, ethanol and water-ethanol mixtures in polyacrylic acid (PAA) and PAA-polysulfone (PSF) composite membranes was measured with pulsed-field gradient (PFG)-nuclear magnetic resonance (NMR) spectroscopy. The partial solubilities and self-diffusion coefficients were obtained. An attempt was made to explain the transport properties of water and ethanol through the PAA layer and PAA-PSF composite membranes. It was concluded that there are two types of channels for diffusate transfer in PAA: an ionogenic hydrophilic channel which is selective for water and a hydrophobic channel which contains a predominance of ethanol molecules. The existence of aluminum nitrate in PAA influences the morphology of the latter channel. There is a good agreement between of the separation factors estimated from PFG-NMR data and those obtained by pervaporation testing.     

X-Ray photoelectron and mössbauer spectroscopy studies on molybdenum-bearing ferrite

The X-ray photoelectron spectra of Mo 3d electrons (232.4–232.9 and 229.4–229.6 eV) for Mo-bearing ferrites have suggested that molybdenum ions are in the 4+ valence state on the lattice points in the spinel structure. The XPS data for Mo 3d and Fe 2p electrons combined with the Mössbauer data at room temperature suggest that Fe₂MoO₄ takes a valence state (Fe²⁺)_tet[Fe²⁺Mo⁴⁺]_octO₄.     

High performance liquid chromatographic determination of bound sulfide and sulfite and thiosulfate at their low levels in human serum by pre-column fluorescence derivatization with monobromobimane.

A sensitive and specific high performance liquid chromatographic method for the determination of sulfide, sulfite, and thiosulfate was established. Inorganic sulfur anions were converted into fluorescent derivatives with monobromobimane. The derivatives were separated on a coupled column chromatography with a reversed-phase octadecyl silica column connected with a weakly basic anion exchanger column by isocratic elution with acetic acid solution (pH 3)-acetonitrile (13:3, v/v) containing 25 mM NaClO4. The method was applied to the determination of bound sulfide and sulfite and thiosulfate in normal human serum. Thiosulfate could be determined directly by use of an ultrafiltered sample. For the determination of bound sulfide and sulfite, the pretreatment step with continuous flow gas dialysis was effective for the sample after releasing sulfide and sulfite by reduction with dithiothreitol. The limits of quantification by the present method were 0.05 microM for thiosulfate, 0.5 microM for bound sulfide, and 0.2 microM for bound sulfite.     

Rhodium-catalyzed asymmetric 1,4-addition of organoboron reagents to 5,6-dihydro-2(1H)-pyridinones. Asymmetric synthesis of 4-aryl-2-piperidinones

Catalytic asymmetric synthesis of 4-aryl-2-piperidinones was realized for the first time by asymmetric 1,4-addition of arylboron reagents to 5,6-dihydro-2(1H)-pyridinones in the presence of a chiral bisphosphine-rhodium catalyst. In the reaction introducing 4-fluorophenyl group, the use of 4-fluorophenylboroxine and 1 equiv (to boron) of water at 40 degrees C gave the highest yield of the arylation product with high enantioselectivity (98% ee). The (R)-4-(4-fluorophenyl)-2-piperidinone obtained here is a key intermediate for the synthesis of (-)-Paroxetine.