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.     

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.     

Probabilistic Projections of the Total Fertility Rate for All Countries

We describe a Bayesian projection model to produce country-specific projections of the total fertility rate (TFR) for all countries. The model decomposes the evolution of TFR into three phases: pre-transition high fertility, the fertility transition, and post-transition low fertility. The model for the fertility decline builds on the United Nations Population Division’s current deterministic projection methodology, which assumes that fertility will eventually fall below replacement level. It models the decline in TFR as the sum of two logistic functions that depend on the current TFR level, and a random term. A Bayesian hierarchical model is used to project future TFR based on both the country’s TFR history and the pattern of all countries. It is estimated from United Nations estimates of past TFR in all countries using a Markov chain Monte Carlo algorithm. The post-transition low fertility phase is modeled using an autoregressive model, in which long-term TFR projections converge toward and oscillate around replacement level. The method is evaluated using out-of-sample projections for the period since 1980 and the period since 1995, and is found to be well calibrated.     

Similarity in friendship networks: Selection or influence? The effect of constraining contexts and non-visible individual attributes

Most research on similarity in friendship networks focuses on clearly visible individual attributes (i.e. attitudes and behaviors) in contexts where choices whom to befriend are relatively unconstrained. These studies often reveal that social selection rather than social influence is the dominant cause of similarity among friends. We argue that in a setting where social collaboration is crucial and friendship choices are more constrained, influence might be the main reason for similarity found among friends. In addition, we examined whether social categorization and peer control amplifies the social influence process among friends. Using a stochastic actor-based model for network dynamics, we analyzed a three-wave dataset of first year Royal Netherlands Naval College officer students on friendship formation and military discipline. The data supports our first hypothesis that students adjust their own military discipline to that of their friends. Contrary to our expectations, we did not find support for the idea that individuals adjust their discipline more to friends who are of the same military specialty, and neither more to friends who exert peer control. We elaborate on these findings in the discussion.