University of Paderborn

About: University of Paderborn is a education organization based out in Paderborn, Nordrhein-Westfalen, Germany. It is known for research contribution in the topics: Computer science & Context (language use). The organization has 6684 authors who have published 16929 publications receiving 323154 citations.

A Theoretical Analysis of the Proton and Hydride Transfer in Liver Alcohol Dehydrogenase (LADH)

Abstract: The proton and hydride transfers in horse liver alcohol dehydrogenase (LADH) were studied with a potential surface obtained by use of the self-consistent-charge−density-functional-tight-binding (SCC−DFTB) QM/MM method implemented in the CHARMM program; a correction for solvent shielding was introduced by use of a continuum model. The proton transfers were found to proceed in a virtually concerted fashion before the hydride transfer. The calculations also showed that a radical mechanism, suggested as a possibility in the literature for the H transfer between the substrate and NAD+, is very unlikely. The energetics of the reaction and pKa‘s of residues involved in catalysis indicate that the chemical steps of LADH, as characterized by the calculated value of kcat, are slow for a pH below 5.5, and the hydride transfer is hardly affected for pH between 5.5 and 8.1. These results are compared with the experimentally measured pH dependence of kcat for LADH, although a quantitative comparison is difficult becaus...

Competitive exclusion in a two-species chemotaxis model.

Abstract: We consider a mathematical model for the spatio-temporal evolution of two biological species in a competitive situation. Besides diffusing, both species move toward higher concentrations of a chemical substance which is produced by themselves. The resulting system consists of two parabolic equations with Lotka–Volterra-type kinetic terms and chemotactic cross-diffusion, along with an elliptic equation describing the behavior of the chemical. We study the question in how far the phenomenon of competitive exclusion occurs in such a context. We identify parameter regimes for which indeed one of the species dies out asymptotically, whereas the other reaches its carrying capacity in the large time limit.

Averaged modelling of switching power converters: reformulation and theoretical basis

Abstract: Uniform averaged modeling methods for switching power converters (SPCs) are established. Averaging methods for differential equation systems with continuous right-hand sides are discussed and then generalized to discontinuous ones. It is shown that these methods are applicable to most known types of SPC, including PWM, resonant, and quasi-resonant converters. PWM converters under discontinuous conducting mode are taken as examples to further demonstrate the applicability of these methods. It is shown that the currently used state space averaging and its several extensions can be derived from these methods. >