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We present XMM-Newton and Chandra observations of the born-again planetary nebula A 30. These X-ray observations reveal a bright unresolved source at the position of the central star whose X-ray luminosity exceeds by far the model expectations for photospheric emission and for shocks within the stellar wind. We suggest that a “born-again hot bubble” may be responsible for this X-ray emission. Diffuse X-ray emission associated with the petal-like features and one of the H-poor knots seen in the optical is also found. The weakened emission of carbon lines in the spectrum of the diffuse emission can be interpreted as the dilution of stellar wind by mass-loading or as the detection of material ejected during a very late thermal pulse.
Zwischen Heterogenität und Hierarchie in der Bildung - Studien zur Unvollendbarkeit der Demokratie
(2011)
We introduce an approach to detecting inconsistencies in large biological networks by using answer set programming. To this end, we build upon a recently proposed notion of consistency between biochemical/genetic reactions and high-throughput profiles of cell activity. We then present an approach based on answer set programming to check the consistency of large-scale data sets. Moreover, we extend this methodology to provide explanations for inconsistencies by determining minimal representations of conflicts. In practice, this can be used to identify unreliable data or to indicate missing reactions.
Building biological models by inferring functional dependencies from experimental data is an important issue in Molecular Biology. To relieve the biologist from this traditionally manual process, various approaches have been proposed to increase the degree of automation. However, available approaches often yield a single model only, rely on specific assumptions, and/or use dedicated, heuristic algorithms that are intolerant to changing circumstances or requirements in the view of the rapid progress made in Biotechnology. Our aim is to provide a declarative solution to the problem by appeal to Answer Set Programming (ASP) overcoming these difficulties. We build upon an existing approach to Automatic Network Reconstruction proposed by part of the authors. This approach has firm mathematical foundations and is well suited for ASP due to its combinatorial flavor providing a characterization of all models explaining a set of experiments. The usage of ASP has several benefits over the existing heuristic algorithms. First, it is declarative and thus transparent for biological experts. Second, it is elaboration tolerant and thus allows for an easy exploration and incorporation of biological constraints. Third, it allows for exploring the entire space of possible models. Finally, our approach offers an excellent performance, matching existing, special-purpose systems.
Preference handling and optimization are indispensable means for addressing nontrivial applications in Answer Set Programming (ASP). However, their implementation becomes difficult whenever they bring about a significant increase in computational complexity. As a consequence, existing ASP systems do not offer complex optimization capacities, supporting, for instance, inclusion-based minimization or Pareto efficiency. Rather, such complex criteria are typically addressed by resorting to dedicated modeling techniques, like saturation. Unlike the ease of common ASP modeling, however, these techniques are rather involved and hardly usable by ASP laymen. We address this problem by developing a general implementation technique by means of meta-prpogramming, thus reusing existing ASP systems to capture various forms of qualitative preferences among answer sets. In this way, complex preferences and optimization capacities become readily available for ASP applications.
The armed conflict in Afghanistan since 2001 has raised manifold questions pertaining to the humanitarian rules relative to the conduct of hostilities. In Afghanistan, as is often the case in so-called asymmetric conflicts, the geographical and temporal boundaries of the battlefield, and the distinction between civilians and fighters, are increasingly blurred. As a result, the risks for both civilians and soldiers operating in Afghanistan are high. The objective of this article is to assess whether - and if so how much - the armed conflict in Afghanistan has affected the application and interpretation of the principles of distinction, proportionality, and precaution - principles that form the core of legal rules pertaining to the conduct of hostilities.
Urbanity and literature
(2011)
Transarea studies focus upon spaces as created by the movements that criss-cross them. From this point of view, from its very beginnings, literature is closely interrelated with a vectorial (and much less with a purely spatial) conception of history - and with urbanity, which plays a decisive role in Gilgamesh's travels through a (narrative) cosmos centered upon the city of Uruk. This article explores the city as a transareal space of movement in three examples of literature, with no fixed abode, around the turn of the millennium, i.e. Assia Djebar's Les Nuits de Strasbourg, Emine Sevgi Oezdamar's Istanbul-Berlin Trilogy, and Cecile Wajsbrot's L'ile aux musees. These three writers project, in a very specific way, cities in motion as anagrammatic and fractal structures.
To understand the evolution and morphology of planetary nebulae, a detailed knowledge of their central stars is required. Central stars that exhibit emission lines in their spectra, indicating stellar mass-loss allow to study the evolution of planetary nebulae in action. Emission line central stars constitute about 10 % of all central stars. Half of them are practically hydrogen-free Wolf-Rayet type central stars of the carbon sequence, [WC], that show strong emission lines of carbon and oxygen in their spectra. In this contribution we address the weak emission-lines central stars (wels). These stars are poorly analyzed and their hydrogen content is mostly unknown. We obtained optical spectra, that include the important Balmer lines of hydrogen, for four weak emission line central stars. We present the results of our analysis, provide spectral classification and discuss possible explanations for their formation and evolution.
Der Bürger entscheidet mit
(2011)
»Warum erregt der geplante Abriss eines Bahnhofs die Nation, während gegen das hundertfache Sterben von Bibliotheken immer nur ein paar Stimmen laut werden? Wo sind die Wutbürger, wenn man sie braucht?«, überlegte sich hierzulande Tilman Spreckelsen.1 Die Kernfrage lautet also: Stehen die Bürger eigentlich hinter der Bibliothek? Ob und wie die Bürgerschaft für ihre Öffentliche Bibliothek entscheidet, wenn sie entscheiden darf, wird im vorliegenden Aufsatz thematisiert. Ergebnisse von Bürgerbegehren und Bürgerentscheiden stehen dabei im Fokus, da bürgerschaftliches Engagement bei diesen Mitwirkungsinstrumenten besonders gefragt ist und es gleichzeitig kommunalpolitische Folgen haben kann. Am Beispiel von Stuttgart 21 wird darüber hinaus der Fragestellung nachgegangen, wie sich eine Öffentliche Bibliothek zu Sachverhalten positioniert, die (nicht nur) kommunalpolitisch brisant sind.
Mehr Chancen als Risiken
(2011)
Anne Christensen spricht von partizipativer Entwicklung, wenn sie sich zum Komplex Bibliothek 2.0 äußert, und meint damit primär die stärkere Einbeziehung der Benutzer, wenn es um die Zukunft der kollaborativen Erschließung von Medien in Bibliothekskatalogen geht.1 Diese Art der Partizipation tangiert Kernaufgaben sowohl an Öffentlichen als auch an wissenschaftlichen Bibliotheken. Über die Beteiligung der Benutzer am Katalog 2.0 hinaus könnte auch durch eine weitere Form der Partizipation Einfl uss auf die Zukunft Öffentlicher Bibliotheken genommen werden: durch den Bürgerhaushalt.
Basiswissen BWL – prägnant und verständlich vermittelt. Das Lehrbuch vermittelt Wirtschaftswissenschaftlern, angehenden Wirtschaftsingenieuren und -informatikern sowie Nebenfachstudierenden aus dem technischen Bereich die wichtigsten Grundlagen der BWL. Die 6. Auflage wurde umfassend überarbeitet, an die aktuelle Gesetzeslage angepasst und inhaltlich erweitert. Lernziele, Beispiele, Kontrollfragen und Aufgaben inklusive Lösungen erleichtern das selbstständige Lernen. Das optimierte Layout sorgt für mehr Übersichtlichkeit.
Mindfulness and acceptance describe the skills necessary to experience emotions and thoughts (e.g., performance-interfering cognitions) consciously and without judging them. This article introduces the mindfulness and acceptance approach and its potential in the context of competitive sports. Definitions as well as research results related to mechanisms of action and differential psychological aspects are given and the efficacy of the approach in the field of clinical psychology is reviewed. The rationale and implementation of the mindfulness-acceptance-commitment approach, an approach adapted for performance enhancement, is illustrated. Finally, evidence from psychotherapy research is presented, and a recommendation for the use of mindfulness and acceptance in the context of competitive sports is given.
Spielberger's (1972) Trait-State-Anxiety theory distinguishes between anxiety as a trait (A-trait) - involving a stable characteristic of a person to react with anxiety in response to varying situations and anxiety as a state (A-state), a situation-dependent reaction to a stimulus perceived as threatening. Using a general instead of a sport-specific measure, a previous study provided only mixed support for core predictions of the theory as related to sports (Schwenkmezger, 1985). With the aid of enhanced instruments and statistical methods, we tested these predictions again. The multidimensional and competition-specific assessment of anxiety results in support for the assumption of a stable A-trait and a fluctuating A-state, whereby the A-trait not only predicts the intensity of A-states but also the A-state variability. The repeated assessment of A-states prior to two competitions reveals a rather low relative consistency (i.e., interindividual differences across measurements were only moderately stable). Especially this latter finding suggests that, in order to gain a full understanding of the experience of competitive anxiety in athletes, sport psychologists should not only assess competitive A-traits, but also repeatedly measure competitive A-states.