In-situ observations of dissolution process of GaSb into InSb melt by X-ray penetration method

Dissolution process of GaSb into InSb melt was observed by an X-ray penetration method. The intensity of X-rays penetrated through the rectangular shaped GaSb (seed)/InSb/GaSb (feed) sandwich sample was recorded by the CdTe line sensor detector. The penetrated X-ray intensities and images of the sample were obtained as a function of time and temperature. The gallium (Ga) composition profile of the sample was calculated as a function of time by making the calibration line with the penetrated X-ray intensities of GaSb and InSb standard samples. The calculated Ga composition profile of the grown sample agreed well with the data measured by energy dispersive X-ray spectroscopy analysis. The result suggested that lower GaSb seed dissolved faster than upper GaSb feed despite of the low temperature at the lower GaSb seed. It clearly indicates that the solutal transport induced by gravity strongly affects the dissolution process.     

Development and validation of a hydrophilic interaction chromatography–tandem mass spectrometry for quantification of nicotine and its metabolites in human maternal and cord sera

A selective and sensitive HILIC‐MS/MS method for the simultaneous quantification of nicotine and its metabolites in human maternal and cord sera was developed and validated. After solid‐phase extraction, LC separation was achieved on a hydrophilic interaction chromatography. The validated method is capable of selective identification as well as accurate and sensitive quantification. Analyte recovery ranged from 86.2 to 107.7% and intra‐ and inter‐day assay precision were less than 15% relative standard deviation. This sensitive HILIC‐MS/MS method can be used to determine nicotine and its metabolic profile in smokers. This validated method is useful for the determination of nicotine and its metabolites in human serum in future studies of the effects of nicotine exposure on neonatal outcome. Copyright © 2010 John Wiley & Sons, Ltd.     

Charge and radial correlations in helium and helium-like atoms

Summary For two-electron atoms, the method of a variable exponent, which treats the orbital exponent (or effective nuclear charge) of an electron as an explicit function of the radial coordinate of the other electron, is studied. The method is shown to improve the energy and other electronic properties remarkably. An incorporation of the variable exponent into the Kellner approximation for He, for example, gives the energy –2.872 606 1 a.u., which is lower than the original Kellner energy by 0.024 949 8 a.u. and exceeds the Hartree-Fock limit energy by 0.010 926 1 a.u. The improvement due to the variable exponent originates from the inclusion of the charge and radial correlations. Applications of the method to the Eckart and Hylleraas approximations are also presented.     

Formation of a liquid organic ion associate in aqueous solution and its application to the GF-AAS determination of trace cadmium in environmental water as a complex with 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol

The formation of a liquid organic ion associate in an aqueous sample was applied to the concentration and determination of cadmium in environmental water samples. Cadmium was converted into a complex with 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol (5-Br-PAPS) in a 40-mL sample solution, and was extracted into a liquid ion associate of phenolsulfonate and benzethonium during phase formation. More than 400-fold enrichment was easily attained by this technique, because the volume of the liquid organic phase formed was very small, ca. 2 microL. After dilution of the organic phase with a small volume of 2-methoxyethanol, the cadmium in the solution was determined by GF-AAS. The detection limit was 0.09 ng/L (3sigma(b)). This method was applied to the determination of cadmium in river water and seawater.     

Ion-channel sensors based on ETH 1001 ionophore embedded in charged-alkanethiol self-assembled monolayers on gold electrode surfaces.

An ion-channel sensor was demonstrated by immobilizing ETH 1001, an ionophore for ion-selective electrodes, on a gold electrode surface. The approach for preparing the sensor was to incorporate the ionophore into a mixed self-assembled monolayer of 10-mercaptodecanesulfonate and 11-hydroxy-1-undecanethiol formed on the surface. The voltammetric responses for the thus prepared sensor to the primary cation Ca(2+) were observed by using [Fe(CN)(6)](3-/4-) as an electroactive marker. The ionophore was stably immobilized on the electrode surface with the hydrophobic interaction between its alkyl chains and those of the alkanethiol. The introduction of a proper charge density to the electrode surface improved the sensor sensitivity with retaining the selective response to Ca(2+) against Mg(2+) with concentrations above 10(-4) M.     

Thermodynamics and morphology of the amorphization reaction during the rod-milling of Al-50 at.% Ta alloy powder

A report is presented on the crystalline to amorphous phase transition induced by the rod-milling of a mixture of Al and Ta powders using the mechanical alloying method. Based on the thermal and morphological analyses, it is shown that the mechanical alloying process is classified into three stages, i.e., the agglomeration, amorphization and homogenization stages. During the agglomeration and amorphization stages, a thermal-assisted amorphization leads to the formation of an amorphous phase by a solid-state amorphization reaction. At the homogenization stage, however, an amorphous phase with fine nanostructure is formed due to the mechanical driving force generated by the shear force of the rods.