Mitteilung aus dem chemischen laboratorium fresenius zu wiesbaden

Ohne Zusammenfassung     

Cusps of Lattices in Rank 1 Lie Groups over Local Fields

Let G be the group of rational points of a semisimple algebraic group of rank 1 over a non-Archimedean local field. We improve upon Lubotzky's analysis of graphs of groups describing the action of lattices in G on its Bruhat–Tits tree assuming a condition on unipotents in G. The condition holds for all but a few types of rank 1 groups. A fairly straightforward simplification of Lubotzky's definition of a cusp of a lattice is the key step to our results. We take the opportunity to reprove Lubotzky's part in the analysis from this foundation.     

Krümmungseigenschaften Konvexer Flächen

Ohne Zusammenfassung     

The complexity of machine scheduling for stability with a single disrupted job

A stable schedule is a robust schedule that will change little when uncertain events occur. The purpose of this paper is to investigate the complexity status of a number of machine scheduling problems with stability objective, when the duration of a single job is anticipated to be disrupted.     

Eine neue Methode zur stereochemischen Analyse offenkettiger terpenoider Carbonyl-Verbindungen,

A New Method for the Stereochemical Analysis of Acyclic Terpenoid Carbonyl Compounds A new method for the determination of the enantiomeric and diastereoisomeric composition of terpenoid carbonyl compounds is presented. Separation of the diastereoisomeric (+)-L -diisopropyl-tartrate acetals derived from dihydrocitronellal ( 6 ), hexahydropseudoionone ( 3 ), hexahydrofarnesal ( 7 ), and hexahydro far nesy lace tone ( 4 ), the C₁₀, C₁₃, C₁₅, and C₁₈ intermediates in various syntheses of naturally occurring tocopherols and vitamin K₁, can be achieved by capillary GC on a cyanopropylsilicon-coated glass column under standardized conditions. This technique, presenting a significant improvement over existing methodologies, is considered to be particularly useful for the analysis of highly enriched samples, typically obtained by present-day asymmetric synthesis. With reproducibilities of ± 0.3%, and, therefore, safe for routine analysis, the complete Stereochemical characterization of terpenoids with 15 and 18 C-atoms bearing two stereogenic centres is performed in a single operation for the first time.     

Determination of ephedrine and related compounds in pharmaceutical preparations by ion chromatography with direct conductivity detection

An ion chromatographic method with conductivity detection for the simultaneous determination of ephedrine, pseudoephedrine and norephedrine was developed. A mixture of 2.0 mmol/L HNO3 and 2% (v/v) acetonitrile was used as eluent. The three ephedrine-like compounds were separated and determined within 20 min. The linear ranges were 0.08-50 microg/mL for ephedrine, 0.08-40 microg/mL for pseudoephedrine and 0.06-40 microg/mL for norephedrine. The detection limits were 0.03 microg/mL for ephedrine and pseudoephedrine, and 0.02 microg/mL for norephedrine. The method has been applied successfully to the determination of these sympathomimetics in pharmaceutical preparations and in Ephedra herbs.     

Synthesis of primary-alkyl selenols and selenides from primary-alkyl thiols involving diphenyl sulfonium salts

Hexyl thiol has been transformed to hexyl selenol and related selenides and selenocyanate by substitution of the corresponding hexyldiphenylsulfonium tetrafluoroborate with selenium nucleophiles.     

On the Ordering of Energy Levels in Homogeneous Magnetic Fields

We study the energy levels of a single particle in a homogeneous magnetic field and in an axially symmetric external potential. For potentials that are superharmonic off the central axis, we find a general pseudoconcave ordering of the ground state energies of the Hamiltonian restricted to the sectors with fixed angular momentum. The physical applications include atoms and ions in strong magnetic fields. There the energies are monotone increasing and concave in angular momentum. In the case of a periodic chain of atoms, the pseudoconcavity extends to the entire lowest band of Bloch functions.