Muon spin relaxation in different samples of DyAl2

Two samples of DyAl₂ were studied by longitudial μSR in the paramagnetic and ferromagnetic regime. In a region T_c±40 K the samples give different signals although X-ray analysis can not detect any impurity phase in either of them.     

Zur intramolekularen nucleophilen Addition von 2,3-Dihydrodipyrrin-1(10H)-onen

Model compound5 was prepared by acid catalyzedintramolecular nucleophilic addition of the alcohol (Z)-4. In comparison to theintermolecular addition productl-2, differences in structure and reactivity could be determined by X-ray crystal structure analysis and¹H-NMR-spectroscopic investigations. The interpretation of these differences are based on the assumption of stereoelectronic advantages in the intermolecular adductl-2. Its methoxy group was found to beperiplanar with respect to the -(NCO)-plane of the lactam unit enabeling efficient delocalization of the amide lone pair to the *-orbital of the C-OMe-bond. The orientation of the corresponding C-O-bond in5 is fixed by the rigid structure of the bicyclic ring system and can be classified assynclinal. Consequentlyl-2 eliminates methanol very easily under acidic or high temperature conditions, whereas5 is a stable compound.In the stereoelectronically favoured adductl-2 n *-delocalization increases elimination reactivity on the one hand and thermodynamic stability on the other hand. Therefore adducts of this kind may be good candidates for biological regulators—a matter of interest with regard to the protein-chromophore interaction in biliproteins.

     

Hyperbolicity of the complement of plane curves

In this paper it is proved that the complement in ₂ of a holomorphic curve D of genus g2 is a hermitian hyperbolic complex manifold provided that certain conditions on the singularities of the dual D* of D are satisfied and that every tangent at D* intersects D* in at least two distinct points.Dedicated to Karl Stein     

Synthesis and evaluation of antitrypanosomal activity of some thiosemicarbazide derivatives of 1-butyl-6-fluoro-7-morpholino-4-oxo-1,4-dihydroquinoline-3-carboxylic acid

The synthesis of thiosemicarbazide of 1-butyl-6-fluoro-7-morpholino-4-oxo-1,4-dihydroquinoline-3-carboxylic acid as well as its heterocyclic derivatives – 1,3,4-thiadiazole and 1,2,4-triazole are described; the modification of proper 1,2,4-triazole derivative by maleimides is also presented. Spectral properties of the prepared compounds and X-ray analysis for the selected compounds were studied. For the compounds antitrypanosomal potential and the toxicity were determined.     

Atomic-Scale Studies of Fe3O4(001) and TiO2(110) Surfaces Following Immersion in CO2-Acidified Water

Difficulties associated with the integration of liquids into a UHV environment make surface-science style studies of mineral dissolution particularly challenging. Recently, we developed a novel experimental setup for the UHV-compatible dosing of ultrapure liquid water and studied its interaction with TiO₂ and Fe₃O₄ surfaces. Herein, we describe a simple approach to vary the pH through the partial pressure of CO₂ ( ) in the surrounding vacuum chamber and use this to study how these surfaces react to an acidic solution. The TiO₂(110) surface is unaffected by the acidic solution, except for a small amount of carbonaceous contamination. The Fe₃O₄(001)-( × )R45° surface begins to dissolve at a pH 4.0–3.9 ( =0.8–1 bar) and, although it is significantly roughened, the atomic-scale structure of the Fe₃O₄(001) surface layer remains visible in scanning tunneling microscopy (STM) images. X-ray photoelectron spectroscopy (XPS) reveals that the surface is chemically reduced and contains a significant accumulation of bicarbonate (HCO₃⁻) species. These observations are consistent with Fe(II) being extracted by bicarbonate ions, leading to dissolved iron bicarbonate complexes (Fe(HCO₃)₂), which precipitate onto the surface when the water evaporates.     

Development of Passive and Active Barrier Coatings on the Basis of Inorganic–Organic Polymers

Summary. With a new kind of barrier coating material, namely inorganic–organic polymers, it is possible to obtain excellent barrier properties against oxygen, water vapor, and flavor permeation. These hybrid polymers can be synthesized by the sol–gel technique. If extremely low permeation values are needed, the combination of hybrid polymer coatings with thin inorganic oxidic layers (SiO_x, AlO_x) is very effective and leads to permeation values for oxygen and water vapor below 10⁻³ cm³/m² · d · bar or g/m² · d. These passive barrier layers can be further improved by the combination with active oxygen barrier layers which have been developed for the food packaging industry. This approach makes these multilayer laminates promising candidates for special applications in the food packaging industry as well as for sophisticated applications in technical areas: the encapsulation of sensitive organic devices like solar cells, organic light emitting diodes, or polymer electronic systems.     

Quantitation of talinolol and other beta-blockers by capillary electrophoresis for in vitro drug absorption studies

A capillary zone electrophoresis method is described for the enantioseparation of talinolol using heptakis(2,3-diacetyl-6-sulfo)-beta-cyclodextrin (HDAS-beta-CD) as a chiral selector. After liquid-liquid extraction of talinolol from physiological solution, electrokinetic injection was employed to improve the sensitivity. The use of a coated capillary was necessary to achieve stable and reproducible enantioseparations. A baseline separation of the talinolol enantiomers was achieved in less than 10 min using 100 mM phosphate solution as background electrolyte and pH 3.5, at the presence of 3.0 mM HDAS-beta-CD and at 20 degrees C. In addition, this analytical condition proved to be useful for the enantioseparation of a number of other beta-blocking agents such as alprenolol, atenolol, bisoprolol, celiprolol, metipranolol, oxprenolol, and sotalol. For determining talinolol, the method could be validated in terms of precision, accuracy and linearity, and was found to be suitable in determination of talinolol enantiomers in highly diluted samples obtained from in vitro experiments.