Laser-induced fluorescence study of the hydrogen atom formation dynamics in the 248 nm gas-phase photodissociation of vibrational state selected water (H<Subscript>2</Subscript>O (|04<Superscript>−</Superscript>〉))

The vibrationally-mediated H₂O gas-phase photodissociation was studied at a photolysis wavelength of 248 nm. Single rotational states of the |03⁻〉|2〉 and |04⁻〉 H₂O overtone vibrations were prepared by laser photoexcitation around 720 nm. H atoms formed in the photodissociation of the H₂O (|04⁻〉 = 3₁₃) were detected by Lyman-α laser-induced fluorescence spectroscopy with sub-Doppler resolution to determine their translational energy. The present result confirms that in the dissociation process the major part (ca. 93%) of the available energy is released as relative translational energy of the nascent H + OH photofragments, in agreement with earlier complementary measurements (R. L. Vander Wal, J. L. Scott and F. F. Crim, J. Chem. Phys. 94, 1859 (1991)), where the internal excitation of the OH product radical was investigated at different photolysis wavelengths.     

Eine Neue Einfache Synthese von L-Vinelose

Reduction of methyl 6-deoxy-2,3-0-isopropylidene-3-C-methyl-α-L-lyxo-hexopyranosid-4-ulose (2) with sodium tetrahydroborate or L-selectride produces exclusively the L-talo-configurated 4-hydroxy compound (3), which is transformed to methyl 6-deoxy-3,4-O-isopropylidene-3-C-methyl-α-L-talopyranoside (4). Methylation of the 2-hydroxy group and hydrolysis yields L-vinelose (6) .     

Recognition of profiles of alcohols and ketones in urine of patients with diabetes mellitus by gas chromatography and mass fragmentography

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Recognition of profiles of alcohols and ketones in urine of patients with diabetes mellitus by gas chromatography and mass fragmentography

     

Application of chemometric methods in Auger electron microanalysis of composites

Principal component analysis and cluster analysis have been used in AES investigations of fibre-matrix interactions in alumina fibre reinforced MgLi-alloys prepared by high-pressure infiltration. The samples have been fractured in ultra high vacuum to expose surfaces and interfaces without contamination. All main components exhibit Auger valence band transitions which change their shape with the chemical state. Chemometric methods have been utilized to identify characteristic peak shapes and to classify the investigated areas by composition. Fibre fracture surfaces are characterized by Al, magnesia and Li oxide formed by a redox reaction of alumina with Mg and Li penetrating along grain boundaries. For samples with high silica content a thin interfacial oxide layer on matrix grain boundaries and matrix-fibre interfaces has been found.     

Simplified, rapid and inexpensive extraction procedure for a high-performance liquid chromatographic method for determination of disopyramide and its main metabolite mono-N-dealkylated disopyramide in serum.

A simplified, rapid and inexpensive extraction procedure for the determination of the antiarrhythmic drug disopyramide and its main metabolite mono-N-desalkylated disopyramide in serum by high-performance liquid chromatography has been developed. The analysis uses ultraviolet detection at 254 nm, and a 5 micron reversed-phase column with a mobile phase of water-triethylamine-acetonitrile-PIC-B8 reagent. Serum extraction is performed with dichloromethane and 1 M sodium hydroxide. p-Chlorodisopyramide is used as internal standard. Recovery rates were 94.5% (S.D. 5.7%) for disopyramide, 96.8% (S.D. 2.2%) for mono-N-desalkylated disopyramide and 97.9% (S.D. 2.8%) for the internal standard.