Studies on Non-natural Deoxyammonium Cellulose

Summary: Ammonium group containing cellulose derivatives are prepared from homogeneously synthesized cellulose p-toluenesulfonic acid esters (tosyl cellulose) by conversion with sodium azide and subsequent reduction of the azido moiety applying NaBH₄/CoBr₂/2,2′-bipyridine as reagent. Regarding the tosylation, cellulose samples of different degree of polymerization and hemicellulose content possess a different reactivity. The deoxyamino cellulose is water soluble in the protonated state. Elemental analysis, FTIR- and NMR spectroscopy were carried out to analyze the degree of substitution and functionalization pattern. It was also studied to synthesize deoxyazido celluloses without isolation of the tosyl cellulose. However, a predominant formation of deoxychloro moieties occurs.     

On the Induction of Kazhdan-Lusztig Cells

Barbasch and Vogan showed that the Kazhdan–Lusztig cellsof a finite Weyl group are compatible with parabolic subgroups.Their proof uses the known bridge between the theory of cellsand the theory of primitive ideals. In this paper, an elementary,self-contained proof of this result is provided, which worksfor arbitrary Coxeter groups and Lusztig's general definitionof cells (involving Iwahori–Hecke algebras with unequalparameters). The argument is based on a recent paper by Howlettand Yin. 2000 Mathematics Subject Classification 20C08.     

Crew Assignment via Constraint Programming: Integrating Column Generation and Heuristic Tree Search

The Airline Crew Assignment Problem (ACA) consists of assigning lines of work to a set of crew members such that a set of activities is partitioned and the costs for that assignment are minimized. Especially for European airline companies, complex constraints defining the feasibility of a line of work have to be respected. We developed two different algorithms to tackle the large scale optimization problem of Airline Crew Assignment. The first is an application of the Constraint Programming (CP) based Column Generation Framework. The second approach performs a CP based heuristic tree search. We present how both algorithms can be coupled to overcome their inherent weaknesses by integrating methods from Constraint Programming and Operations Research. Numerical results show the superiority of the hybrid algorithm in comparison to CP based tree search and column generation alone.     

Basic sets of Brauer characters of finite groups of Lie type,III

LetG(F ^q ) be a finite classical group whereq is odd and the centre ofG is connected. We show that there exists a set of irreducible characters ofG(F ^q ) such that the corresponding matrix of scalar products with the characters of Kawanaka’s generalized Gelfand-Graev representations is square unitriangular. This uses in an essential way Lusztig’s theory of character sheaves. As an application we prove that there exists an ordinary basic set of 2-modular Brauer characters and that the decomposition matrix of the principal 2-block ofG(F ^q ) has a lower unitriangular shape.     

Polyfluorinated arylnitrosamines

N-Methyl-, N-n-butyl-, N-t-butylperfluoroarylamines undergo nitrosation with nitrous acid to give the corresponding N-nitroso derivatives. Perfluoroaryl groups were selected from the benzene, indane, biphenyl, naphthalene and pyridine series. According to ¹H and ¹⁹F NMR spectra, N-nitroso-N-methyl derivatives of polyfluoroarenes consist of E and Z isomers with the former prevailing. The more bulky n-butyl group promotes an increase in the formation of Z isomers. Only Z isomers have been obtained from N-t-butyl derivatives of perfluorinated 4-toluidine and 4-aminopyridine. The structure of the Z isomer of N-nitroso-N-methylperfluoro-4-toluidine is confirmed by X-ray data.     

Mo2O3Cl4(Pyridin)4 · CH2Cl2 Synthese,IR-Spektrum und Kristallstruktur

Mo₂O₃Cl₄(Pyridine)₄ · CH₂Cl₂. Synthesis, IR Spectrum, and Crystal Structure Reduction of MoO₂Cl₂(pyridine)₂ with triphenylphosphane in toluene and recrystallisation from CH₂Cl₂ yields brown crystal needles of the complex Mo₂O₃Cl₄(pyridine)₄ · CH₂Cl₂. The compound crystallizes monoclinic in the space group P2₁/c with four formula units per unit cell of the dimensions a = 1 234.6 pm; b = 1 593 pm, c = 1 522.3 pm and β = 105.66° A structural investigation by X-ray methods (3 276 independent observed reflexions, R = 0.033) reveals the molecule with two molybdenum atoms in a distorted octahedral coordination linked by an almost linear Mo? O? Mo bridge with bond distances of 167 and 168 pm, respectively. The chlorine atoms are located in trans-position to the oxygen atoms which have different trans effects: The Mo? Cl bond opposite the bridge (length 242 pm) is 8 pm shorter than the bond in trans position to the terminal oxo ligands. The pyridine nitrogen atoms are in trans position to each other and complete the coordination of the molybdenum atoms. The i.r. spectrum of the compound is reported.     

Substrate binding modulates the reduction potential of DNA photolyase

The reduction potential of the (FADH-/FADH*) couple in DNA photolyase was measured, and the value was found to be significantly higher than the values estimated in the literature. In the absence of substrate, the enzyme has a reduction potential of 16 +/- 6 mV vs NHE. In the presence of excess substrate the reduction potential increases to 81 +/- 8 mV vs NHE. The increase in reduction potential has physiological relevance since it gives the catalytic state greater resistance to oxidation. This is the first measurement of a reduction potential for this class of DNA-repair enzymes and the larger family of blue-light photoreceptors.     

Kopplung von HPLC und chemischem Reaktionsdetektor zur Trennung und Bestimmung von bleiorganischen Verbindungen

Zusammenfassung Blei(II), Di- und Triorganobleiverbindungen sowie Bleitetraalkyle werden mit reversed-phase-HPLC getrennt und mit einem chemischen Reaktionsdetektor über 4-(2-Pyridylazo)-resorcin (PAR) als Nachweisreagenz im Konzentrationsbereich von 0,1–1,6 g/ml bestimmt. Die Anwendbarkeit des chemischen Reaktionsdetektors für die Bestimmung von Organozinnverbindungen und anderen Metallionen wird ebenfalls gezeigt.

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Coupling of HPLC and chemical reaction detector for the separation and determination of organolead compounds

Summary Lead(II), di- and triorganolead salts as well as tetraalkyllead compounds are separated by reversed phase HPLC and determined in the concentration range of 0.1–1.6 g/ml by a chemical reaction detector based on the use of 4-(2-pyridylazo)-resorcinol (PAR) as analytical reagent. The applicability of the chemical reaction detector for the determination of organotin species and different metal-ions is also shown.

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Prof. Dr. W. Fresenius zum 70. Geburtstag gewidmet

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Der Deutschen Forschungsgemeinschaft sind wir für die freundliche Unterstützung der Untersuchungen zu Dank verpflichtet.