Construction and Properties of Adhesive and Weak Adhesive High-Level Replacement Categories

As presented in Ehrig et al. (Fundamentals of Algebraic Graph Transformation, EATCS Monographs, Springer, 2006), adhesive high-level replacement (HLR) categories and systems are an adequate framework for several kinds of transformation systems based on the double pushout approach. Since (weak) adhesive HLR categories are closed under product, slice, coslice, comma and functor category constructions, it is possible to build new (weak) adhesive HLR categories from existing ones. But for the general results of transformation systems, as additional properties initial pushouts, binary coproducts compatible with a special morphism class and a pair factorization are needed to obtain the full theory. In this paper, we analyze under which conditions these additional properties are preserved by the categorical constructions in order to avoid checking these properties explicitly.      

Schwarz symmetrization and comparison results for nonlinear elliptic equations and eigenvalue problems

We compare the distribution function and the maximum of solutions of nonlinear elliptic equations defined in general domains with solutions of similar problems defined in a ball using Schwarz symmetrization. As an application, we prove the existence and bound of solutions for some nonlinear equation. Moreover, for some nonlinear problems, we show that if the first p-eigenvalue of a domain is big, the supremum of a solution related to this domain is close to zero. For that we obtain L ^∞ estimates for solutions of nonlinear and eigenvalue problems in terms of other L ^p norms.     

Compensation of gradient related effects when using capillary liquid chromatography and inductively coupled plasma mass spectrometry for the absolute quantification of phosphorylated peptides

The application of reversed phase liquid chromatography (RP-LC) hyphenated to inductively coupled plasma mass spectrometry (ICP-MS) for the accurate quantification of bio-molecules via covalently bound hetero atoms such as phosphorus is restricted, due to the known effects of increasing amounts of organic solvents on the ionization behavior of certain elements. An approach for the compensation of variations in the elemental response, due to changes in the solvent composition during the RP gradient separation of phosphorylated peptides is described, which includes the application of a second, matched reversed gradient, that is mixed post-column with the RP column outflow before entering the LC–ICP-MS interface. The experimental design allows the application of gradient separations, while the element-specific detection is carried out under isocratic conditions with a constant organic solvent intake into the plasma. A constant elemental response is a general pre-requisite for the application of ICP-MS for the absolute quantification of peptides via their hetero atom content, especially when no corresponding high purity standards are available or natural mono-isotopic hetero element tags are utilized. As complementary technique LC–electrospray ionization linear ion trap mass spectrometry (ESI-QTRAP-MS) has been used for peptide identification and to elucidate their phosphorus stoichiometry. Highly reproducible separations have been obtained with retention time and peak area RSDs of 0.05% and 7.6% (n = 6), respectively. Detection limits for phosphorus of 6 μg L⁻¹ (6 pg absolute), have been realized, which corresponds to approximately 200 fmol of an average molecular weight, singly phosphorylated peptide. In addition an automatic routine for flow injection analysis (FIA) at the end of each chromatographic separation has been developed, to calibrate each chromatographic separation, which allows absolute quantification of the separated species, whenever their tag stoichiometry is known. Phosphorylated peptides as well as tryptic protein digests have been used as model compounds for method development and to demonstrate the applicability of the proposed setup for phosphopeptide quantification on the basis of simple inorganic phosphorus standards.     

Local canted spin behaviour in Co1.4−x Zn x Ge0.4Fe1.2O4 spinels: A macroscopic, mesoscopic and microscopic study

DC magnetization, neutron depolarization and neutron diffraction (with both polarized and unpolarized neutrons) measurements have been reported for the Co_1.1−x Zn _x Ge_0.1Fe_1.2O₁ spinels with x=0.5, 0.6 and 0.7. Neutron depolarization and neutron diffraction measurements confirm the presence of a long range ferrimagnetic ordering of the local canted spins in these ferrite samples. The observed features of low field magnetization have been explained under the framework of thermally activated domain wall movement of ferrimagnetic arrangement of local canted spins. An important role of magnetic anisotropy (due to the presence of Co²⁺ ions) in establishing the magnetic ordering and domain kinetics in these ferrites has been observed.     

Preparation d'aldehydes deuteries ou trities au carbonyle

The use of silver carbonate on celite in the oxidation of deuteriated or tritiated primary alcohols (RCD₂OH, RCHTOH) gives the corresponding formyl labeled aldehydes in high yields.     

Investigation of S-H bonds in biologically important compounds by sulfur K-edge X-ray absorption spectroscopy

X-ray Absorption Near Edge Structure (XANES) spectroscopy, often provides a direct correlation between observed resonances in the spectrum and molecular bonds in the sample. This can be used as a fingerprint for the presence of a given molecular environment of the absorber atom in a sample. As the white line is found at similar energy positions for S-C and S-H bonds, this approach is impossible when both types of bond are present simultaneously, as often in biological systems. To develop a criterium for the presence of S-H bonds in such samples, reduced glutathione, reduced coenzyme A, cysteine and their corresponding oxidized forms were investigated using sulfur K-edge XANES, revealing a unique feature at 2 475.8 eV in the respective difference spectra. To correlate this structure to S-H bonds, H₂S and H₂S₂ were measured, whose difference spectrum also shows a structure at this energy position, whereas it is not present throughout a variety of C-S-C/C-S-S-C environments. Theoretical investigations suggest its correlation to a Rydberg transition occurring in the case of a S-H bond. Using this criterium, the presence of S-H bonds is in the purple sulfur bacterium Allochromatium vinosum during oxidation of intracellular accumulated sulfur, is proved, as expected from biological considerations. Received 1st February 2002 / Received in final form 10 June 2002 Published online 13 September 2002