Ueber die Darstellung von Traubenzucker

Ohne Zusammenfassung     

Some Decidability and Undecidability Results on Green's Relations for Automatic Monoids

We consider the problem of deciding Green's relations for various types of finitely presented automatic monoids. We establish some decidability as well as some undecidability results.     

A new group of fluorescent pH-indicators for an extended pH-range

Summary The pH versus fluorescence intensity profiles of a series of new pH-indicators are reported. They are characterized by two pK_a-values in the 3.7–4.9 and 6.9–7.9 range, respectively. The strong change in fluorescence intensity with pH allows the determination of pH's over a much wider range (typically 2–9) than with one-step indicators. They are therefore considered to be of potential utility for measurement of pH over the neutral and slightly acidity range which occurs, for instance, in bioliquids such as urine.

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Eine neue Gruppe fluorescierender pH-Indicatoren für einen erweiterten pH-Bereich

Zusammenfassung Die Fluorescenzintensitätsprofile als Funktion des pH-Wertes einer Reihe von neuen pH-Indicatoren werden untersucht. Sie sind charakterisiert durch zwei pK_a-Werte im Bereich 3,7–4,9 bzw. 6,9–7,9. Die gefundene starke Änderung der Fluorescenzintensität mit dem pH-Wert erlaubt eine pH-Bestimmung über einen viel weiteren Bereich (typischerweise 2 – 9) als mit einstufigen Indicatoren. Aus diesem Grund werden sie als potentiell nützlich angesehen zur Messung von pH-Werten im neutralen und schwach sauren Bereich, wie er z.B. in biologischen Flüssigkeiten, etwa im Urin, gegeben ist.

     

Ueber geodätische Bogenstücke von algebraischer Längen-differenz auf dem Ellipsoid

Ohne Zusammenfassung     

Critical Fields in Ferromagnetic Thin Films: Identification of Four Regimes

We are interested in critical fields for ferromagnetic elements: At which strength of the external field does a branch of stationary magnetizations become unstable, and what is the unstable mode? We consider samples which are infinite in the direction of the external field and have a rectangular cross-section, of much smaller thickness than width, as an idealization of a thin film element. For this geometry Aharoni [Phys. Stat. Sol. 16, 3-42 (1966)] claims that there are only three different regimes: The unstable mode is either of coherent rotation type, of buckling type, or of curling type. We discover a large fourth parameter regime with an unstable mode displaying an oscillation in the infinite direction. We prove the existence of exactly four regimes by rigorously analyzing the scaling of the Rayleigh quotient of the Hessian of the energy functional. The parameters are the film width, the film thickness, and the exchange length.     

Structural changes by sulfoxidation of phenothiazine drugs

Summary The side-chain conformations of psychoactive phenothiazine drugs in crystals are different from those of biologically inactive ring sulfoxide metabolites. This study examines the potential energies, molecular conformations and electrostatic potentials in chlorpromazine, levomepromazine (methotrimeprazine), their sulfoxide metabolites and methoxypromazine. The purpose of the study was to examine the significance of the different crystal conformations of active and inactive phenothiazine derivatives, and to determine why phenothiazine drugs lose most of their biological activity by sulfoxidation. Quantum mechanics and molecular mechanics calculations demonstrated that conformations with the side chain folded over the ring structure had lowest potential energy in vacuo, both in the drugs and in the sulfoxide metabolites. In the sulfoxides, side chain conformations corresponding to the crystal structure of chlorpromazine sulfoxide were characterized by stronger negative electrostatic potentials around the ring system than in the parent drugs. This may weaken the electrostatic interaction of sulfoxide metabolites with negatively charged domains in dopamine receptors, and cause the sulfoxides to be virtually inactive in dopamine receptor binding and related pharmacological tests.