Iterative Beam Search for Simple Assembly Line Balancing with a Fixed Number of Work Stations

The simple assembly line balancing problem (SALBP) concerns the assignment of tasks with pre-defined processing times to work stations that are arranged in a line. Hereby, precedence constraints between the tasks must be respected. The optimization goal of the SALBP-2 version of the problem concerns the minimization of the so-called cycle time, that is, the time in which the tasks of each work station must be completed. In this work we propose to tackle this problem with an iterative search method based on beam search. The proposed algorithm is able to obtain optimal, respectively best-known, solutions in 283 out of 302 test cases. Moreover, for 9 further test cases the algorithm is able to produce new best-known solutions. These numbers indicate that the proposed iterative beam search algorithm is currently a state-of-the-art method for the SALBP-2

Computational Performance Evaluation of Two Integer Linear Programming Models for the Minimum Common String Partition Problem

In the minimum common string partition (MCSP) problem two related input strings are given. "Related" refers to the property that both strings consist of the same set of letters appearing the same number of times in each of the two strings. The MCSP seeks a minimum cardinality partitioning of one string into non-overlapping substrings that is also a valid partitioning for the second string. This problem has applications in bioinformatics e.g. in analyzing related DNA or protein sequences. For strings with lengths less than about 1000 letters, a previously published integer linear programming (ILP) formulation yields, when solved with a state-of-the-art solver such as CPLEX, satisfactory results. In this work, we propose a new, alternative ILP model that is compared to the former one. While a polyhedral study shows the linear programming relaxations of the two models to be equally strong, a comprehensive experimental comparison using real-world as well as artificially created benchmark instances indicates substantial computational advantages of the new formulation.Comment: arXiv admin note: text overlap with arXiv:1405.5646 This paper version replaces the one submitted on January 10, 2015, due to detected error in the calculation of the variables involved in the ILP model

In-vitro-Untersuchung einzelner fluoreszierender Proteine mit spektral und zeitlich aufgelöster Fluoreszenzspektroskopie

Im Rahmen der hier vorgelegten Arbeit wurden die Varianten EYFP und EGFP des grün fluoreszierenden Proteins (GFP) aus der Qualle Aequorea victoria, sowie das aus der Steinkoralle Discosoma stammende rot fluoreszierende Protein DsRed und weitere vier DsRed Varianten mit spektroskopischen Methoden untersucht. Neben einigen ensemblespektroskopischen Untersuchungen wurde die Fluoreszenz einer großen Anzahl einzelner fluoreszierender Proteine und Proteinoligomere, zeitlich und spektral aufgelöst, auf Einzelmolekülebene bei Raumtemperatur in-vitro untersucht. Bei Beobachtung auf Einzelmolekülebene zeigen die Proteine eine erstaunliche intrinsische Vielgestaltigkeit und Dynamik der Fluoreszenz. Es wurde gezeigt, dass die Breite der Verteilung der Lage des Emissionsmaximums eine für jede Variante spezifische Größe ist, die sich direkt aus der Einbettung des Chromophors in die charakteristische Proteinumgebung ergibt. Außerdem konnten zum Teil bisher unbekannte, sich in ihrer Fluoreszenz unterscheidende Formen der Proteine identifiziert und Übergänge zwischen verschiedenen Formen spektral verfolgt werden. Für DsRed und alle DsRed Varianten wurde unter den typischen Bedingungen der Einzelmolekülspektroskopie bei Beobachtung des gereiften Chromophors fast ausschließlich die sog. super rote Form des Chromophors detektiert, die sich durch die hohen Anregungsleistungen schnell bildet. Außerdem wurden bei allen DsRed Varianten gemischte Oligomere aus Proteinen mit ungereiftem und gereiftem Chromophor beobachtet, und es konnte gezeigt werden, dass die unterschiedlichen Chromophore innerhalb eines Oligomers kein hocheffizientes FRET System bilden.This work presents spectroscopic analyses of the EGFP and EYFP variants of the Aequorea green fluorescent protein (GFP) and of the red fluorescing protein DsRed and four of its variants from the coral Discosoma. In addition to ensemble spectroscopy, the fluorescence of a large number of single fluorescing proteins and protein oligomers was temporally- and spectrally- resolved at the single molecule level in vitro at room temperature. These analyses reveal that at the single molecule level these proteins exhibit a striking intrinsic versatility and dynamics of the emission. It was shown that the spread of the distribution of the emission maximum positions is characteristic for each variant and directly reflects the specific nature of the embedding of the chromophore into its neighbouring protein environment. It was further possible to identify different emitting forms of the proteins, some not observed until now, and to follow transitions between the forms by spectrally resolving the single molecule emission. The typical conditions for single molecule detection employed in these experiments, especially the high excitation power, caused an extremely rapid transition of the matured chromophore of DsRed and all of the tested variants into a ‘super-red’ emitting form. Mixed fluorescence of the immature and the mature chromophore was detected for all DsRed variants, yielding evidence of the existence of mixed oligomers of proteins with mature and immature chromophores. Finally it was possible to show that the different chromophores within an oligomer do not form a efficient FRET system

Large neighborhood search for the most strings with few bad columns problem

In this work, we consider the following NP-hard combinatorial optimization problem from computational biology. Given a set of input strings of equal length, the goal is to identify a maximum cardinality subset of strings that differ maximally in a pre-defined number of positions. First of all, we introduce an integer linear programming model for this problem. Second, two variants of a rather simple greedy strategy are proposed. Finally, a large neighborhood search algorithm is presented. A comprehensive experimental comparison among the proposed techniques shows, first, that larger neighborhood search generally outperforms both greedy strategies. Second, while large neighborhood search shows to be competitive with the stand-alone application of CPLEX for small- and medium-sized problem instances, it outperforms CPLEX in the context of larger instances.Peer ReviewedPostprint (author's final draft

Power and its Logic: Mastering Politics

Power is the essence of politics. Whoever seeks to understand and master it must understand its logic. Drawing on two decades of international experience in political consulting, Dominik Meier and Christian Blum give profound and honest insights into the inner workings of power. Introducing their Power Leadership Approach, the authors provide a conceptual analysis of power and present the tools to successfully exercise it in the political domain. "Power and its Logic" is a guidebook for politicians, business leaders, civil society pioneers, public affairs consultants and for every citizen who wants to understand the unwritten rules of politics