A simple and cost-effective synthesis of sulfated β-cyclodextrin and its application as chiral mobile phase additive in the separation of cloperastine enantiomers

Journal of Inclusion Phenomena and Macrocyclic Chemistry - A simple and cost-effective method for the synthesis of sulfated β-cyclodextrin, one of the most widely used chiral mobile phase...     

Reduction of flow- and eddy-currents-induced image artifacts in coronary magnetic resonance angiography using a linear centric-encoding SSFP sequence

Coronary magnetic resonance angiography (MRA) acquired using steady-state free precession (SSFP) sequences tends to suffer from image artifacts caused by local magnetic field inhomogeneities. Flow- and gradient-switching-induced eddy currents are important sources of such phase errors, especially under off-resonant conditions. In this study, we propose to reduce these image artifacts by using a linear centric-encoding (LCE) scheme in the phase-encoding (PE) direction. Abrupt change in gradients, including magnitude and polarity between consecutive radiofrequency cycles, is minimized using the LCE scheme. Results from numeric simulations and phantom studies demonstrated that signal oscillation can be markedly reduced using LCE as compared to conventional alternating centric-encoding (ACE) scheme. The image quality of coronary arteries was improved at both 1.5 and 3.0 T using LCE compared to those acquired using ACE PE scheme (1.5 T: ACE/LCE=2.2+/-0.8/3.0+/-0.6, P=.02; 3.0 T: ACE/LCE=2.1+/-1.1/3.0+/-0.8, P=.01). In conclusion, flow- and eddy-currents-induced imaging artifacts in coronary MRA using SSFP sequence can be markedly reduced with LCE acquisition of PE lines.     

The credit risk+ model with general sector correlations

We consider an enhancement of the credit risk⁺ model to incorporate correlations between sectors. We model the sector default rates as linear combinations of a common set of independent variables that represent macro-economic variables or risk factors. We also derive the formula for exact VaR contributions at the obligor level.     

High-performance thin-layer chromatographic method for the determination of chlorpyrifos and its metabolite in visceral samples

JPC – Journal of Planar Chromatography – Modern TLC - In an attempt to determine chlorpyrifos insecticide and its metabolite 3,5,6-trichloropyridinol in visceral samples, a rapid...     

Reaction of hexachloropropene with hydroxy-coumarins and chromones

The reaction of hexachloropropene with hydroxy-coumarins and chromones has been utilized to synthesise dichloro-benzodipyrandiones. The structures of the latter have been deduced from their spectral-analytical data. The reaction with 4-hydroxy-coumarin derivatives affords dichloropyrano-benzpyrandiones.     

Synthesis and spectral studies of mixed copper(II) dipeptide complexes of imidazole and related nitrogen donors

Eight mixed copper(II) complexes of the type [Cu(II)(D)(HL)], where D = anion of glycylglycine, glycyl-L-tyrosine or glycyl-L-phenylalanine, and HL = imidazole, 1-methylimidazole, 2-methylimidazole or benzimidazole have been prepared and characterised. The visible and EPR spectral studies of these complexes indicate that they are monomeric having five coordinate square pyramidal geometry (possibly distorted) about Cu(II). The dipeptide behaves as terdentate ligand in these complexes with amino, ionised amide nitrogen and carboxylate oxygen donor atoms approximately tetragonally disposed about Cu(II). The magnetic and bonding parameters obtained by detailed EPR spectral analysis coupled with electronic absorption spectral data suggest that imidazole, 1-methylimidazole, 2-methylimidazole or benzimidazole occupies the fourth position in the tetragonal plane and water molecule occupies an axial position about Cu(II) in solid state and in solution.     

Efficient asymmetric synthesis of the vasopeptidase inhibitor BMS-189921

[reaction: see text] An efficient asymmetric synthesis of the vasopeptidase inhibitor BMS-189921 was accomplished. Two short enantioselective syntheses of the common key intermediate (S)-alpha-aminoazepinone 6b were developed. Olefin 3 was converted to 6b via asymmetric hydrogenation. Alternatively, enyne 12 was converted to racemic alpha-aminoazepinone 15b, which was transformed to 6b by a practical dynamic resolution.     

Anomalous electrical transport properties of Ag/Al bilayers grown on Si by molecular beam epitaxy

We have investigated the temperature dependent electrical resistivity, ρ(T), of Ag(100 nm)/Al(10 nm) bilayers grown on Si(111) and quartz substrates using molecular beam epitaxy (MBE). Bilayers grown on Si exhibited an anomalous negative temperature coefficient of resistivity (TCR) in the temperature range of 140-165 K of the ρ(T) plot. However, at temperatures below and above this negative TCR region, ρ(T) exhibited a characteristic positive TCR of metallic alloys. No such resistive anomaly was observed for the bilayers grown on quartz substrates. The observed resistive anomaly could be qualitatively explained by assuming two parallel conduction channels, that is, one at the interface having high Si content and obeying the polaronic behavior at <165 K and another far away from the interface having almost no Si impurity and thus exhibiting pure metallic behavior down to 4 K. In addition, bilayers exhibited a sharp resistive transition at ∼6.5 K, indicating a possibility of a new Ag-Al alloy being a superconducting material.     

Laminar jet impingement on an indented wall

Summary The Navier-Stokes equations are solved numerically to study the problems of laminar, axisymmetric jet impinging normally on an indented wall. The results obtained for three different wall geometries and Reynolds number range upto 25 are compared with those for the impingement on a plane wall to study the influence of indentation. The overall flow picture remains similar to the plane wall case qualitatively but the wall shear stress and pressure distribution get altered in the indented region.

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Zusammenfassung Es wird der Strömungsverlauf eines laminaren achsensymmetrischen Strahles nach dem Aufprall auf eine Wand mit Einbuchtung analysiert. Hierzu wird die numerische Lösung der Navier-Stokeschen Gleichungen benutzt. Die Ergebnisse für drei verschiedene Wandgeometrien, als auch für verschiedene Reynolds-Zahlen bis auf 25, sind mit dem Fall der ebenen Wand verglichen, um hieraus den Einfluß der Einbuchtung festzustellen. Das globale Strömungsbild bleibt in allen Fällen qualitativ ähnlich. Es wurde jedoch festgestellt, daß im Bereich der Einbuchtung die Wandschubspannung sowie die Druckverteilung gewisse Änderungen aufweisen.