iversity Magdeburg

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Magdeburg, Germany
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Frey T.,iversity Magdeburg | Gelhausen M.,TU Darmstadt
Proceedings - International Conference on Software Engineering | Year: 2011

Separation of concerns is a central element for program comprehension. This note briefly explains why human categorization can be interesting for program comprehension. © 2011 Authors.


Barden S.,Bielefeld University | Schomburg B.,Bielefeld University | Conradi J.,Bielefeld University | Backert S.,iversity Magdeburg | And 3 more authors.
Acta Crystallographica Section D: Biological Crystallography | Year: 2014

A new crystal form of the Helicobacter pylori type IV secretion system (T4SS) pilus protein CagL is described here. In contrast to two previously reported monomeric structures, CagL forms a three-dimensional domain-swapped dimer. CagL dimers can arise during refolding from inclusion bodies or can form spontaneously from purified monomeric CagL in the crystallization conditions. Monomeric CagL forms a three-helix bundle, with which the N-terminal helix is only loosely associated. In the new crystal form, the N-terminal helix is missing. The domain swap is owing to exchange of the C-terminal helix between the two protomers of a dimer. A loop-to-helix transition results in a long helix of 108 amino acids comprising the penultimate and the last helix of the monomer. The RGD motif of dimeric CagL adopts an -helical conformation. In contrast to the previously reported structures, the conserved and functionally important C-terminal hexapeptide is resolved. It extends beyond the three-helix bundle as an exposed helical appendage. This new crystal form contributes to the molecular understanding of CagL by highlighting rigid and flexible regions in the protein and by providing the first view of the C-terminus. Based on the structural features, a previously unrecognized homology between CagL and CagI is discussed. © 2014 International Union of Crystallography.


Barden S.,Bielefeld University | Lange S.,Bielefeld University | Tegtmeyer N.,iversity Magdeburg | Tegtmeyer N.,Friedrich - Alexander - University, Erlangen - Nuremberg | And 5 more authors.
Structure | Year: 2013

RGD tripeptide motifs frequently mediate ligand binding to integrins. The type IV secretion system (T4SS) protein CagL of the gastric pathogen Helicobacter pylori also contains an RGD motif. CagL decorates the T4SS pilus and may function as an adhesin for host cells. Whether CagL binds integrins via its RGD motif is under debate. Here, we present crystal structures of CagL revealing an elongated four-helix bundle that appears evolutionarily unrelated to the proposed VirB5 orthologs. The RGD motif is surface-exposed but located within a long α helix. This is unprecedented as previously characterized integrin-binding RGD motifs are located within extended or flexible loops. Yet, adhesion of gastric epithelial cells to CagL was strictly RGD-dependent. Comparison of seven crystallographically independent molecules reveals substantial structural flexibility. Intramolecular disulfide bonds engineered to reduce CagL flexibility resulted in more stable protein, but unable to support cell adhesion. CagL may thus partly unfold during receptor binding. © 2013 Elsevier Ltd.


Aliev I.,University of Cardiff | Henk M.,iversity Magdeburg | Linke E.,iversity Magdeburg
Electronic Journal of Combinatorics | Year: 2013

Given a matrix A ∈ ℤm×n satisfying certain regularity assumptions, we consider for a positive integer s the set Fs(A) ⊂ ℤm of all vectors b ∈ ℤm such that the associated knapsack polytope P(A; b) = {x ∈ ℝ n ≥0: Ax = b} contains at least s integer points. We present lower and upper bounds on the so called diagonal s-Frobenius number associated to the set Fs (A). In the case m = 1 we prove an optimal lower bound for the s-Frobenius number, which is the largest integer b such that P(A, b) contains less than s integer points.


Yan Liu X.,Hunan University | Specht E.,iversity Magdeburg
Chemical Engineering Science | Year: 2010

The thermal efficiency of a rotary kiln is predominantly influenced by the amount of lateral mixing of the material bed. In this paper, the fraction of the mixing zone in the material bed is predicted for the rolling motion. For a given material, the fraction is found to depend only on three dimensionless variables-the ratio of the particle diameter to the kiln diameter, the Froude number and the filling degree. Experiments were carried out on a rotating cylinder with beans as testing material. The predicted results are in good agreement with the measurements with a maximal error of 12%. The fraction of the mixing zone is then analyzed for industrial rotary kilns. Its value is found to increase approximately linearly with increasing Froude number and the dynamic angle of repose of the material. For all investigated cases, the fraction of the mixing zone lies in the range of 20-45%. Results of this study can provide orientating values of the mixing zone fraction, which are needed to calculate the thermal efficiency of the rotary kiln. © 2010 Elsevier Ltd. All rights reserved.


Leone M.,iversity Magdeburg | Mantzke A.,iversity Magdeburg
IEEE Transactions on Electromagnetic Compatibility | Year: 2014

A passive and inherently stable multiport equivalent circuit for lossy transmission lines is presented. The convergence of the infinite modal representation is accelerated by appropriate inductances, for which an exact closed-form expression is developed. The order number of the truncated modal circuit is estimated by a simple relation, according to the required signal bandwidth. The coupling of arbitrary external electromagnetic fields is incorporated by a limited number of corresponding modal sources. The accuracy and versatility of the suggested SPICE-compatible equivalent circuit is demonstrated by examples in frequency and time-domain, including nonlinear terminations. © 1964-2012 IEEE.


Friedrich M.,iversity Magdeburg | Leone M.,iversity Magdeburg
IEEE Transactions on Electromagnetic Compatibility | Year: 2014

A very efficient boundary-element method for the calculation of the quasi-static port inductances of vertical interconnections within parallel-plate structures is developed. It requires only a one-dimensional discretization along the contour of the plate pair and can be applied to arbitrary geometries. The algorithm is validated by the exact analytical solution for the circular geometry. The low-frequency response of an arbitrary multiport structure can be directly analyzed by the coupled port-inductance network together with the plate capacitance. As examples a circular-shaped and two irregularly shaped plane pairs are considered. The comparison with exact analytical solutions and three-dimensional-full-wave field simulation shows a very good agreement. © 2014 IEEE.


This paper explains the idea to load source code into a Data Warehouse. First, separation of concerns is explained. Following, the motivation to load source code in a Data Warehouse is briefly presented. Afterwards, the multi-dimensionality of software is discussed. Also, a first model for software in a Data Warehouse is shown. Nearby, the challenge that multiple cubes will be needed in order to load software in a Data Warehouse is elucidated. Thereafter, related work is shown and its relation to the revealed idea is explained. Finally, conclusions are done and future work paths are described.


Bednarz C.,iversity Magdeburg | Beyer J.,iversity Magdeburg | Leone M.,iversity Magdeburg
IEEE Transactions on Electromagnetic Compatibility | Year: 2015

A simple and straightforward method to estimate the maximal instantaneous voltage peak during switching operations in resonant structures is presented. It is based on the time-domain analysis of an elementary RLC circuit as a model for such systems. For short pulses, a very simple relation is obtained, independent of the pulse shape. For slow excitations, the noise amplitude is safely estimated solely by the slew rate. Pulses with arbitrary length and shape are approximately treated by a trapezoid with effective width and rise time, for which an accurate solution is derived. The approach is extended to current pulse trains. Several validation examples demonstrate the applicability and versatility of the developed estimation formulas. © 1964-2012 IEEE.


Zometa P.,iversity Magdeburg | Kogel M.,iversity Magdeburg | Faulwasser T.,iversity Magdeburg | Findeisen R.,iversity Magdeburg
Proceedings of the American Control Conference | Year: 2012

We discuss implementation related aspects of model predictive control schemes on embedded platforms. Ex-emplarily, we focus on fast gradient methods and present results from an implementation on a low-cost microcontroller. We show that input quantization in actuators should be exploited in order to determine a suboptimality level of the online optimization that requires a low number of algorithm iterations and might not significantly degrade the performance of the real system. As a case study we consider a Segway-like robot, modeled by a linear time-invariant system with 8 states and 2 inputs subject to box input constraints. The test system runs with a sampling period of 4 ms and uses a horizons up to 20 steps in a hard real-time system with limited CPU time and memory. © 2012 AACC American Automatic Control Council).

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