Lokalisierung von Substituenten bei Porphyrinen: Das Massenspektroskopische Fragmentierungsverhalten von Porphyrinogenen

The possibilities and limitations for localization of substituents in porphyrins from the fragmentation patterns of porphyrinogens are discussed.     

Landfill Gas: From Rubbish to Resource

The prospects of using landfill gas (LFG) as a high-grade fuel in the immediate future, in view of environmental regulations, the Kyoto Protocols, and energy prices, are discussed. Adsorption cycles suggested in the late 1980s by Sircar and co-workers for treating LFG are reviewed: one produced CO₂-free methane and the other produced both CO₂-free methane and methane-free CO₂. Neither of those could be used to produce pipeline quality gas from LFG, due to contaminants such as nitrogen. Two new three-stage flowsheets are discussed as a means to separate pipeline-grade methane from LFG. One is a hybrid membrane—PSA system. The other is a TSA—PSA system. The third stage of both of these systems is crucial to obtaining pipeline quality gas, i.e., a PSA unit to extract the nitrogen and other light gases from methane. A novel PSA cycle is suggested and explained in terms of: a model by which the recovery, power requirements, and adsorbent bed size can be estimated.     

Oligosaccharide Structural Studies by On-Line HPLC-MS using Fast Atom Bombardment Ionization

Abstract

A moving polyimide belt was used as an HPLC-MS interface for the purification and structural studies of oligosaccharides. The samples, desorbed by FAB in the absence of added liquid matrix, exhibited the following characteristics: a) good signal to noise ratio at low mass; b) a variation in the degree of fragmentation and relative sensitivity with changes in belt speed; c) a diminished sensitivity to signal suppression by contaminants when contrasted to FAB matrix; and d) fragment ions which can provide useful structural information. The moving belt HPLC-MS interface was tested with a series of known standards and a sample of high mannose oligosaccharides isolated from animal urines.     

Zum 100. Jahrestag der Entdeckung der Brown'schen Bewegung

Ohne Zusammenfassung     

Characterizing the Phragmén‐Lindelöf condition for evolution on algebraic curves

For an algebraic curve V in ${\mathbb C}^k \times {\mathbb C}^n$ it is investigated when it satisfies the Phragmén‐Lindelöf condition PL(ω) of evolution in certain classes of ultradifferentiable functions. Necessary as well as sufficient conditions are obtained which lead to a complete characterization for curves in ${\mathbb C}\times {\mathbb C}^n$. Some examples illustrate how these results can be applied. © 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Hydrophobically modified polyelectrolytes I. Dilute solution properties of fluorocarbon-containing poly (acrylic acid)

Dilute solution viscosity of fluorocarbon‐containing hydrophobically modified poly (acrylic add) was measured in aqueous solutions of various NaCl concentrations. The intrinsic viscosity ([η]) and Huggins coefficient (k_H) were evaluated using Huggins equations. It is found that, at low Nacl concentration, the modified polymers exhibit values of intrinsic viscosity ([η]) and Huggins coefficient (k_H) similar to those of unmodified polymers. For both of the modified and unmodified polymers, the intrinsic viscosity decreases with increase of NaCl concentration, while the Huggins coefficient increases upon addition of NaCl. But the variation of [η] and k_H is more significant for the modified polymers, which reflects the enhanced intra‐ and intermolecular hydrophobic association at higher Nacl concentration.     

Neutral Pentacoordinate Halogeno‐ and Pseudohalogenosilicon(IV) Complexes with an SiSONCX Skeleton (X=F,Cl, Br,I, N,C): Synthesis and Structural Characterization in the Solid State and in Solution

A series of neutral pentacoordinate silicon(IV) complexes with an SiSONCX skeleton (X=F, Cl, Br, I, N, or C) was synthesized and structurally characterized by multinuclear solution‐state and solid‐state NMR spectroscopy and single‐crystal X‐ray diffraction. These compounds contain an identical tridentate dianionic S,N,O ligand, a monodentate (pseudo)halogeno ligand (F, Cl, Br, I, NCS, N₃, or CN), and a monodentate organyl ligand (methyl, phenyl, 4‐(trifluoromethyl)phenyl, or pentafluorophenyl). For most of these compounds, a dynamic equilibrium between the pentacoordinate silicon(IV) complex and two isomeric tetracoordinate silicon species in solution was observed. Most surprisingly, comparison of two series of analogous compounds containing fluoro, chloro, bromo, or iodo ligands demonstrated that pentacoordination in these series of silicon(IV) complexes is favored in the rank order I≈Br>Cl>F; i.e., increasing the softness of the halogeno ligand favors pentacoordination.