University of Duisburg-Essen

About: University of Duisburg-Essen is a education organization based out in Essen, Nordrhein-Westfalen, Germany. It is known for research contribution in the topics: Population & Transplantation. The organization has 16072 authors who have published 39972 publications receiving 1109199 citations.

Distributive Lattices, Bipartite Graphs and Alexander Duality

Abstract: A certain squarefree monomial ideal HP arising from a finite partially ordered set P will be studied from viewpoints of both commutative algbera and combinatorics. First, it is proved that the defining ideal of the Rees algebra of HP possesses a quadratic Grobner basis. Thus in particular all powers of HP have linear resolutions. Second, the minimal free graded resolution of HP will be constructed explicitly and a combinatorial formula to compute the Betti numbers of HP will be presented. Third, by using the fact that the Alexander dual of the simplicial complex ? whose Stanley---Reisner ideal coincides with HP is Cohen---Macaulay, all the Cohen---Macaulay bipartite graphs will be classified.

Self-Perceived Job Insecurity and Social Context : A Multi-Level Analysis of 17 European Countries

Abstract: Job insecurity causes far-reaching negative outcomes. The fear of job loss damages the health of employees and reduces the productivity of firms. Thus, job insecurity should result in increasing social costs. Analysing representative data from 17 European countries, this paper investigates self-perceived job insecurity. Our multi-level analysis reveals significant cross-country differences in individuals' perception of job insecurity. This finding is not only driven by social-structural or institutional differences, but the perception of job insecurity is also influenced by nation-specific unobserved characteristics.

Mastering hysteresis in magnetocaloric materials.

Abstract: Hysteresis is more than just an interesting oddity that occurs in materials with a first-order transition. It is a real obstacle on the path from existing laboratory-scale prototypes of magnetic refrigerators towards commercialization of this potentially disruptive cooling technology. Indeed, the reversibility of the magnetocaloric effect, being essential for magnetic heat pumps, strongly depends on the width of the thermal hysteresis and, therefore, it is necessary to understand the mechanisms causing hysteresis and to find solutions to minimize losses associated with thermal hysteresis in order to maximize the efficiency of magnetic cooling devices. In this work, we discuss the fundamental aspects that can contribute to thermal hysteresis and the strategies that we are developing to at least partially overcome the hysteresis problem in some selected classes of magnetocaloric materials with large application potential. In doing so, we refer to the most relevant classes of magnetic refrigerants La–Fe–Si-, Heusler- and Fe 2 P-type compounds. This article is part of the themed issue ‘Taking the temperature of phase transitions in cool materials’.

Mechanical restriction versus human overreaction triggering congested traffic states.

Abstract: A new cellular automaton traffic model is presented. The focus is on mechanical restrictions of vehicles realized by limited acceleration and deceleration capabilities. These features are incorporated into the model in order to construct the condition of collision-free movement. The strict collision-free criterion imposed by the mechanical restrictions is softened in certain traffic situations, reflecting human overreaction. It is shown that the present model reliably reproduces most empirical findings including synchronized flow, the so-called pinch effect, and the time-headway distribution of free flow. The findings suggest that many free flow phenomena can be attributed to the platoon formation of vehicles (platoon effect).