Absolute cross sections for one electron capture into excited projectile states in collisions between He2+ (15–150 keV) and Li atoms

We have studied the He²⁺-Li collision system at laboratory energies between 15 and 150 keV using optical methods. From the measured emission cross sections we derive state-selective capture cross sections for n = 2,3,4 and n ? 5 states of the He⁺ ions. Our data are consistent with theoretical predictions of Bransden and Ermolaev. The total capture cross sections as evaluated from our emission cross section data, agree very well with the results of McCullough et al. obtained from projectile charge detection measurements. Near 15 keV our emission cross sections for 30.4 nm and 25.6 nm are much larger than those measured previously by Barrett and Leventhal at slightly lower energies.     

Determination of trace fluorine in biological materials by photonuclear activation analysis

Summary By using the photonuclear activation technique, fluorine has been determined in biological materials. After alkali fusion, fluorine is adsorbed on an anion exchange resin. The irradiated resin sample is soaked and stirred in 5N hydrochloric acid solution. After filtering, fluorine-18 resulting from the (, n) reaction was extracted with 0.2 % dimethyldichlorosilane in xylene. The fluorine-18 0.51 MeV annihilation peak in an aliquot of the organic phase was measured by gamma-ray spectrometry. The precision of this method calculated from replicate analyses of standard specimen is ±11 % and sensitivity is estimated as 0.01g for this element.

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Zusammenfassung Mit Hilfe der photonuklearen Aktivierung wurde Fluor in biologischem Material bestimmt. Nach der Alkalischmelze wird das Fluor an einem Anionenaustauscher adsorbiert. Das bestrahlte Harz wird in5-n Salzsäure eingerührt und zum Quellen gebracht. Nach dem Abfiltrieren wird das aus der, n-Reaktion stammende¹⁸F mit einer 0,2% igen Lösung von Dimethyl-dichlorsilan in Xylol extrahiert. In einem aliquoten Anteil der organischen Phase wird es gammaspektrometrisch gemessen. Die Genauigkeit des Verfahrens wurde durch wiederholte Analysen von Standardproben ermittelt und beträgt ±11%. Die Empfindlichkeit wurde zu 0,01g geschätzt.

     

Pressure effects on electrical conduction in glasses

Electrical conduction in various inorganic glasses was studied as a function of hydrostatic pressure up to 2000 atm and phenomenologically classified into electronic, ionic and mixed types. In electronically conducting glasses such as AsSe chalcogenide glasses and Fe₂O₃P₂O₅ glass, the conduction is enhanced by application of pressure. On the other hand in ionically conducting glass such as Na₂OB₂O₃ glass, the conduction is suppressed through the concept of an activation volume. The compatibility of electronic and ionic conduction processes in glasses such as Ag-doped AsSe glasses and Bi₂O₃B₂O₃ glass, which have more complex conduction processes, was discussed from these aspects.     

A convergent synthesis of the right-hand fragment of ciguatoxin CTX3C

A convergent synthesis of the right-hand fragment of ciguatoxin CTX3C was investigated. The first and second generation stereocontrolled syntheses of the LM ring fragment were achieved via spiroacetalization as a key step, respectively. The polyether framework of the HIJKLM ring fragment was constructed in a convergent manner by using intramolecular allylation, ring-closing metathesis, and stereoselective hydrogenation to form the 36-methyl substituent as the key transformations.     

Stereoselective synthesis of the C94-C104 fragment of symbiodinolide

Stereoselective synthesis of the C94-C104 fragment of symbiodinolide which is a polyol marine natural product with a molecular weight of 2860 has been accomplished. The synthetic route features Achmatowicz rearrangement and RuO₄-catalyzed dihydroxylation for the construction of the tetrahydropyran moiety and the dithiane addition to the aldehyde for the introduction of the side chain.     

Total synthesis and absolute configuration of (-)-gummiferol

Stereoselective synthesis of two possible diastereomers of (-)-gummiferol was accomplished by the stepwise epoxidation and Cadiot-Chodkiewicz reaction as the key transformations. Detailed comparison of their (1)H and (13)C NMR data and specific rotation with those of the natural product led to the absolute structural elucidation of (-)-gummiferol.     

The effect of the counter anion on the transport of thiourea in a PVC-based polymer inclusion membrane using Capriquat as carrier

This paper describes the effect of four counter anions (CH₃COO⁻, Cl⁻, NO₃⁻, ClO₄⁻) of the trioctylmethylammonium (TOMA) cation on the rate of solvent extraction of thiourea and its transport across poly(vinyl chloride) (PVC)-based polymer inclusion membranes (PIMs). The membranes also contained 2-nitrophenyl octyl ether (NPOE) as the plasticizer while chloroform was used as diluent in the solvent extraction studies. It is demonstrated that the counter anion affects substantially the rate of membrane transport and the degree of extraction follows the order: CH₃COO⁻ > Cl⁻ > NO₃⁻ ? ClO₄⁻. The transport rate is negligible for the perchlorate anion. This order is consistent with thiourea interacting with the counter anion through hydrogen bonding to form a heteroconjugate anion.     

Aggregation modeling of calcium carbonate particles by Monte Carlo simulation

The mechanism on aggregation of spindle granular particles of calcite was investigated for the carbonation of calcium hydroxide in aqueous suspension for the purpose of controlling morphology of CaCO₃. The experimental carbonation process was carried out in a semi-batch bubble column reactor under different conditions. Although, fine rhombic nano-particles diameter ranged from 100 to 200 nm were obtained at 291 K, a higher temperature of 300 K provided spindle granular particles with a length of 1.0–1.5 μm and a width of 0.3–0.5 μm. The average crystallite size was 28 nm for the fine rhombic nano-particles and 43 nm for the spindle granules. Zeta potential measurement for the spindle granules indicated that the suspension tended to be aggregated during the carbonation process. The effect of the degree of particle aggregation on the shape of the obtained calcite particles was studied by Monte Carlo simulations. Our simulation results elucidated the dependence of aggregation on unit particles, i.e., primary particles, on the experiment carbonation condition where the spindle granules were formed out of the unit particles under the same condition as the experiments. In addition, the formation mechanism of the granules was investigated by applying classical nucleation theory to the present simulations.     

Development of a simultaneous liquid chromatography/tandem mass spectrometric method for the determination of type B trichothecenes, their derivatives, and precursors in wheat

A method coupling liquid chromatography with tandem mass spectrometry (LC/MS/MS) was developed for the simultaneous quantitative determination of trichothecenes, nivalenol, deoxynivalenol, deoxynivalenol‐3‐glucoside, fusarenon‐X, 3‐acetyldeoxynivalenol, 15‐acetyldeoxynivalenol, isotrichodermin, calonectrin, 3‐deacetylcalonectrin, 15‐deacetylcalonectrin, 3,15‐diacetylnivalenol, 4,15‐diacetylnivalenol, 3,15‐diacetyldeoxynivalenol, and 3,4,15‐triacetylnivalenol. The analytical parameters of trichothecenes and their derivatives were optimized to enable their highly sensitive detection. Evaluation of clean‐up procedures using Multisep #226 and #227 indicated that Multisep #227 was more suitable for their simultaneous detection in wheat. In performance validation studies using the LC/MS/MS method with Multisep #227 cleanup, good recoveries ranging from 84% to 115% with relative standard deviations from 0.4% to 7.2% were measured. The limits of detection and quantification ranged from 0.03 to 1.4 ng·g^?1 and from 0.1 to 4.7 ng·g^?1, respectively. The effect of matrices using matrix‐matched calibration was estimated to range from 80% to 117% after Multisep #227 cleanup. Multisep #227 clean‐up procedure with matrix‐free standard calibration achieved accurate quantification without having a considerable effect on matrix compounds. Using the developed method, several trichothecene derivatives and precursors were detected in fungally inoculated wheat samples. The developed LC/MS/MS method is a practical technique that can be used for the quantification of trichothecenes in wheat. This study is the first report of an analytical method used for the simultaneous quantification of major trichothecenes, their derivatives and precursors. Copyright © 2011 John Wiley & Sons, Ltd.