On the recurrence of edge-reinforced random walk on ℤ×G

Let G be a finite tree. It is shown that edge-reinforced random walk on ℤ×G with large initial weights is recurrent. This includes recurrence on multi-level ladders of arbitrary width. For edge-reinforced random walk on {0,1, . . . ,n}×G, it is proved that asymptotically, with high probability, the normalized edge local times decay exponentially in the distance from the starting level. The estimates are uniform in n. They are used in the recurrence proof.     

Nichtassoziative Ringe

Ohne Zusammenfassung     

Zweiseitige Ideale in Algebren endlichen Ranges

Ohne Zusammenfassung     

Kristall- und molekülstruktur des bis(6,6-dimethylpentafulven)pentacarbonyl-dieisens und des 6,6-diphenylpentafulven-pentacarbonyl-dieisens

X-Ray diffraction analysis of bis(6,6-dimethylpentafulvene)pentacarbonyldiiron and 6,6-diphenylpentafulvenepentacarbonyldiiron has provided the first detailed information about the bonding in 6,6-disubstituted pentafulvenecarbonyliron complexes.     

Function of the antigen transport complex TAP in cellular immunity

The immune system consists of several kinds of cells and molecules whose complex interactions form an efficient system for the protection of an individual from outside invaders and its own transformed cells. Innate immunity refers to the immediate antimicrobial response that occurs regardless of the nature of the invader. The adaptive immune system, on the other hand, mounts specialized immune responses to protect the individual against foreign cells from specific invaders or even tumorigenic cells, and provides long-term protection from subsequent exposure to these foreign cells. Antibody production and cell-mediated responses are the two interconnected branches of the adaptive immune system. Antigenic peptides displayed on the cell surface usually activate the cellular immune response. The transporter associated with antigen processing (TAP) plays a key role in the peptide-processing and -presentation pathway. This Review discusses the latest progress in the structure and mechanism as well as the diseases arising from dysfunction of the TAP complex.     

Importance of interorbital charge transfers for the metal-to-insulator transition of BaVS3

The underlying mechanism of the metal-to-insulator transition (MIT) in BaVS3 is investigated, using dynamical mean-field theory in combination with density functional theory. It is shown that correlation effects are responsible for a strong charge redistribution, which lowers the occupancy of the broader A(1g) band in favor of the narrower E(g) bands and thereby substantially modifies the Fermi surface. This resolves several discrepancies between band theory and the experimental findings, such as the observed value of the charge-density-wave ordering vector associated with the MIT, and the presence of local moments in the metallic phase.     

Protein film voltammetry of Rhodobacter capsulatus xanthine dehydrogenase

Xanthine dehydrogenase (XDH) from the bacterium Rhodobacter capsulatus catalyzes the hydroxylation of xanthine to uric acid with NAD(+) as the electron acceptor. R. capsulatus XDH forms an (alphabeta)(2) heterotetramer and is highly homologous to homodimeric eukaryotic XDHs. The crystal structures of bovine XDH and R. capsulatus XDH showed that the two proteins have highly similar folds; however, R.capsulatus XDH is at least 5 times more active than bovine XDH and, unlike mammalian XDH, does not undergo the conversion to the oxidase form. Here we demonstrate electrocatalytic activity of the recombinant enzyme, expressed in Escherichia coli, while immobilized on an edge plane pyrolytic graphite working electrode. Furthermore, we have determined all redox potentials of the four cofactors (Mo(VI/V), Mo(V/IV), FAD/FADH, FADH/FADH(2) and two distinct [2Fe-2S](2+/+) clusters) using a combination of potentiometric and voltammetric methods. A novel feature identified in catalytic voltammetry of XDH concerns the potential for the onset of catalysis (ca. 400 mV), which is at least 600 mV more positive than that of the highest potential cofactor. This unusual observation is explained on the basis of a pterin-associated oxidative switch during voltammetry that precedes catalysis.     

Identification of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) pyrolysis products by simultaneous thermogravimetric modulated beam mass spectrometry and time-of-flight velocity-spectra measurements

The pyrolysis products formed during the isothermal decomposition of HMX at 211°C are H₂O, HCN, CO, CH₂O, NO, N₂O, methylformamide, C₂H₆N₂O, octahydro-1-nitroso-3,5,7-trinitro-1,3,5,7-tetrazocine, and a nonvolatile residue. The temporal behaviors of these products during the decomposition are presented. The method for using time-of-flight (TOF) velocity spectra to assist mass-spectrometry measurements in identifying the different gaseous products formed from the pyrolysis of a material by determining the approximate molecular weights of the different gaseous products contributing to the different m/z values in the mass spectrum of the mixture is described. The ion fragmentation of HMX as a function of electron energy shows complete fragmentation of the HMX molecular ion for electron energies ≥ 12.4 eV. No fragments from the pyrolysis of HMX other than those mentioned above are observed.