A Branch and Cut solver for the maximum stable set problem

This paper deals with the cutting-plane approach to the maximum stable set problem. We provide theoretical results regarding the facet-defining property of inequalities obtained by a known project-and-lift-style separation method called edge-projection, and its variants. An implementation of a Branch and Cut algorithm is described, which uses edge-projection and two other separation tools which have been discussed for other problems: local cuts (pioneered by Applegate, Bixby, Chvátal and Cook) and mod-k cuts. We compare the performance of this approach to another one by Rossi and Smiriglio (Oper. Res. Lett. 28:63–74, 2001) and discuss the value of the tools we have tested.     

Progrès économiques et avancées sociales au sein des chaînes d'approvisionnement mondiales: plusieurs exemples dans les pays du cône Sud

Les auteurs s'interrogent sur la nature et la diffusion des progrès induits par les chaînes d'approvisionnement mondiales (CAM), en s'appuyant sur les conclusions de neuf études de cas portant sur des filières implantées dans des pays du sud de l'Amérique latine. Des progrès économiques, associés à certaines avancées en matière sociale, sont observés parmi les entreprises têtes de file, mais les fournisseurs en amont n'en tirent pas toujours profit. Après avoir isolé trois types d'évolutions possibles au sein des CAM (développements «antagoniste», «tronqué» et «intégré»), les auteurs formulent des recommandations en ce qui concerne l'action des pouvoirs publics, des entreprises et des acteurs sociaux.     

Reputation and influence in charitable giving: an experiment

Previous experimental and observational work suggests that people act more generously when they are observed and observe others in social settings. However, the explanation for this is unclear. An individual may want to send a signal of her generosity to improve her own reputation. Alternately (or additionally) she may value the public good or charity itself and, believing that contribution levels are strategic complements, give more to influence others to give more. We perform the first series of laboratory experiments that can separately estimate the impact of these two social effects, and test whether realized influence is consistent with the desire to influence, and whether either of these are consistent with anticipated influence. Our experimental subjects were given the opportunity to contribute from their endowment to Bread for the World, a development NGO. Depending on treatment, “leader” subjects’ donations were reported to other subjects either anonymously or with their identities, and these were reported either before these “follower” subjects made their donation decisions. We find that “leaders” are influential only when their identities are revealed along with their donations, and female leaders are more influential than males. Identified leaders’ predictions suggest that are aware of their influence. They respond to this by giving more than either the control group or the unidentified leaders. We find mixed evidence for “reputation-seeking.”     

Zum Zusammenhang von Führungsqualität und Burnout- bzw. Mobbingprävention

The author discusses how workplace-related phenomena with a high socio-emotional pressure like burn out or workplace bullying relate to the leadership quality or leadership culture of an organisation. Workplace bullying and burn out are thus not understood as mere individual problems but rather are analyzed in an organisational context. The hypothesis developed in this article is that leadership quality can make a considerable contribution to preventing workplace bullying and burn out. The author develops a frame of action at which intervention levels and with what intervention forms one can pro-actively and preventively counteract workplace bullying and burn out.     

Schließung von Schulen — Chancen für schulische Innovationsprozesse

Closing down schools — chances of scholar innovative processes. Coaching as support of merging processesThe author discusses chances and risks of processes of school merging processes as an internal coach of a school board. Conditions for success are named for various levels of hierarchy in the school system. This includes an support by means of coaching and supervision.     

An adolescent services plan to incorporate status offenders into the child welfare system

A model plan is presented for adolescent services that would facilitate the current trend to shift troubled but nondelinquent youngsters from the juvenile justice system into the child welfare system.     

Wo sind die Bachelorabsolventen heute und wie sehen sie ihr Studium?

The paper is based on a survey of graduates of the BA course Social Sciences at the Heinrich-Heine-University Düsseldorf. The course, which is a combination of Sociology, Political Science and Communication and Media Studies, was set up in 1999. In 2002 the first students completed the course. Therefore, the BA course Social Sciences is one of the BA courses with the longest experience in Germany. Four graduate years were interviewed for the survey. The aim of the survey was to find out where the graduates now stand and how they judge the course in retrospect. The results show that half of the graduates currently have an occupation, slightly over a third is doing a Master’s degree and about 10 % are in a temporary situation or performing other activities. Overall, the graduates are satisfied with the course. The evaluation of the individual course elements shows the strengths and weaknesses of the course.     

Opting out of publicly provided services: A majority voting result

Our objective in this paper is to examine majority voting in an environment where both public and private alternatives coexist. We construct a model in which households are differentiated by income and have the option of choosing between publicly provided services and private services. Publicly provided services are financed through income tax revenues and made available to all citizens at zero price. Majority voting determines the tax rate. Even though preferences over tax rates are not single peaked, we provide conditions under which a majority voting equilibrium exists. We illustrate our existence result with CES preferences and a Dagum income distribution. Received: 21 December 1993 / Accepted: 2 September 1996