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Wolf-Rayet Stars
(2015)
Nearly 150 years ago, the French astronomers Charles Wolf and Georges Rayet described stars with very conspicuous spectra that are dominated by bright and broad emission lines. Meanwhile termed Wolf-Rayet Stars after their discoverers, those objects turned out to represent important stages in the life of massive stars.
As the first conference in a long time that was specifically dedicated to Wolf-Rayet stars, an international workshop was held in Potsdam, Germany, from 1.-5. June 2015. About 100 participants, comprising most of the leading experts in the field as well as as many young scientists, gathered for one week of extensive scientific exchange and discussions. Considerable progress has been reported throughout, e.g. on finding such stars, modeling and analyzing their spectra, understanding their evolutionary context, and studying their circumstellar nebulae. While some major questions regarding Wolf-Rayet stars still remain open 150 years after their discovery, it is clear today that these objects are not just interesting stars as such, but also keystones in the evolution of galaxies.
These proceedings summarize the talks and posters presented at the Potsdam Wolf-Rayet workshop. Moreover, they also include the questions, comments, and discussions emerging after each talk, thereby giving a rare overview not only about the research, but also about the current debates and unknowns in the field. The Scientific Organizing Committee (SOC) included Alceste Bonanos (Athens), Paul Crowther (Sheffield), John Eldridge (Auckland), Wolf-Rainer Hamann (Potsdam, Chair), John Hillier (Pittsburgh), Claus Leitherer (Baltimore), Philip Massey (Flagstaff), George Meynet (Geneva), Tony Moffat (Montreal), Nicole St-Louis (Montreal), and Dany Vanbeveren (Brussels).
Luminous Blue Variables show strong changes in their stellar wind on time scales of typically years to decades when they expand and contract radially at approximately constant luminosity. Micro-variability on shorter time scales and amplitudes can be observed superimposed to the larger scale radial changes. I will show long-term time series of high resolution spectra which we have collected in the past 20 years for many of the well known LBVs together with a few time series of weekly sampling (HR Car, R40, R71, R110, R127, S Dor) covering a time windows of up to a few months. Wind variability is seen on short and intermediate time scales with the line profiles changing from P Cygni to inverse P Cygni and double peeked profiles sometimes for the same star and spectral line. On longer time scales the ionisation levels for all chemical elements change drastically due to the strong change of the temperature on the stellar surface. While on the long term the characteristic radial changes may have impact on the over all mass loss rates, the variabilities and asymmetries on short and intermediate time scales may cause false estimates of the mass loss rates when confronting models with the observed line profiles
The most massive stars are those with the shortest but most active life. One group of massive stars, the Luminous Blue Variables (LBVs), of which only a few objects are known, are in particular of interest concerning the stability of stars. They have a high mass loss rate and are close to being instable. This is even more likely as rotation becomes an important factor in stellar evolution of these stars. Through massive stellar winds and sometimes giant eruptions, LBV nebulae are formed. Various aspects in the evolution in the LBV phase lead, beside the large scale morphological and kinematical differences, to a diversity of small structures like clumps, rims, and outflows in these nebulae.
We discuss the results of time-resolved spectroscopy of three presumably single Population I Wolf-Rayet stars in the Small Magellanic Cloud, where the ambient metallicity is $\sim 1/5 Z_\odot$. We were able to detect and follow numerous small-scale wind-embedded inhomogeneities in all observed stars. The general properties of the moving features, such as their velocity dispersions, emissivities and average accelerations, closely match the corresponding characteristics of small-scale inhomogeneities in the winds of Galactic Wolf-Rayet stars.
The influence of the wind to the total continuum of OB supergiants is discussed. For wind velocity distributions with β > 1.0, the wind can have strong influence to the total continuum emission, even at optical wavelengths. Comparing the continuum emission of clumped and unclumped winds, especially for stars with high β values, delivers flux differences of up to 30% with maximum in the near-IR. Continuum observations at these wavelengths are therefore an ideal tool to discriminate between clumped and unclumped winds of OB supergiants.
One of the informal properties often used to describe a new virtual world is its degree of openness. Yet what is an “open” virtual world? Does the phrase mean generally the same thing to different people? What distinguishes an open world from a less open world? Why does openness matter anyway? The answers to these questions cast light on an important, but shadowy, and uneasy, topic for virtual worlds: the relationship between those who construct the virtual, and those who use these constructions.
The “output-orientation” is omnipresent in teacher education. In order to evaluate teachers' and students' performances, a wide range of different quantitative questionnaires exist worldwide. One important goal of teaching evaluation is to increase the quality of teaching and learning. The author argues, that standard evaluations which are typically made at the end of the semester are problematic due to two reasons. The first one is that some of the questions are too general and don`t offer concrete ideas as to what kind of actions can be taken to make the courses better. The second problem is that the evaluation is mostly made when the course is already over. Because of this criticism, Apelojg invented the Felix-App which offers the possibility to give feedback in real-time by asking for the emotions and needs that occur during different learning situations. The idea is very simple: positive emotions and satisfied needs are helpful for the learning process. Negative emotions and unsatisfied needs have negative effects on the learning process. First descriptive results show, that “managing emotions” during classes can have positive effects on both motivation and emotions.
In this talk, I would like to share my experiences gained from participating in four CSP solver competitions and the second ASP solver competition. In particular, I’ll talk about how various programming techniques can make huge differences in solving some of the benchmark problems used in the competitions. These techniques include global constraints, table constraints, and problem-specific propagators and labeling strategies for selecting variables and values. I’ll present these techniques with experimental results from B-Prolog and other CLP(FD) systems.
Web Tracking
(2018)
Web tracking seems to become ubiquitous in online business and leads to increased privacy concerns of users. This paper provides an overview over the current state of the art of web-tracking research, aiming to reveal the relevance and methodologies of this research area and creates a foundation for future work. In particular, this study addresses the following research questions: What methods are followed? What results have been achieved so far? What are potential future research areas? For these goals, a structured literature review based upon an established methodological framework is conducted. The identified articles are investigated with respect to the applied research methodologies and the aspects of web tracking they emphasize.
Visual Social Networking Sites (SNSs) enable users to present themselves favorably to gain likes and the attention of others. Especially, Instagram is known for its focus on beauty, fitness, fashion, and dietary topics. Although a large body of research reports negative weight-related outcomes of SNS usage (e.g., body dissatisfaction, body image concerns), studies examining how SNS usage relates to these outcomes are scarce. Based on the visual normalization theory, we argue that SNS content facilitates normalization of so-called thin- and fit-ideals, thereby leading to biased perceptions of the average body weight in society. Therefore, this study tests whether Instagram use is associated with perceiving that the average person weighs less. Responses of 181 survey participants confirm that Instagram use is negatively related to average weight perception of both women and men. These findings contribute to the growing body of research on how SNS use relates to negative weight-related outcomes.
Component based software development (CBSD) and aspectoriented software development (AOSD) are two complementary approaches. However, existing proposals for integrating aspects into component models are direct transposition of object-oriented AOSD techniques to components. In this article, we propose a new approach based on views. Our proposal introduces crosscutting components quite naturally and can be integrated into different component models.
Das vorliegende Werk ist das Ergebnis der 4. Woche des Russischen Rechts an der Juristischen Fakultät der Universität Potsdam. Namhafte Wissenschaftlerinnen und Wissenschaftler der Moskauer Staatlichen Juristischen Universität O. E. Kutafin hielten Vorträge zum Völkerrecht, Verfassungs- und Staatsangehörigkeitsrecht, Bürgerlichen Recht, Unternehmens- und Gesellschaftsrecht, Finanzrecht und Bankrecht. Das russische Recht befindet sich nach dem Ende der Sowjetunion im Wandel. Die Beiträge zeugen vom hohen Stand der Jurisprudenz an der Moskauer Staatlichen Juristischen Universität O. E. Kutafin. Die Wochen des Russischen Rechts tragen dazu bei, das Recht der Russischen Föderation bei uns in Deutschland bekannt zu machen und rechtsvergleichend zur Diskussion zu stellen.
The H.E.S.S. collaboration recently reported the discovery of VHE γ-ray emission coincident with the young stellar cluster Westerlund 2. This system is known to host a population of hot, massive stars, and, most particularly, the WR binary WR 20a. Particle acceleration to TeV energies in Westerlund 2 can be accomplished in several alternative scenarios, therefore we only discuss energetic constraints based on the total available kinetic energy in the system, the actual mass loss rates of respective cluster members, and implied gamma-ray production from processes such as inverse Compton scattering or neutral pion decay. From the inferred gammaray luminosity of the order of 1035erg/s, implications for the efficiency of converting available kinetic energy into non-thermal radiation associated with stellar winds in the Westerlund 2 cluster are discussed under consideration of either the presence or absence of wind clumping.
Der Tagungsband enthält die Referate und Diskussionsbeiträge des in Moskau an der Staatlichen Juristischen Kutafin-Universität am 9. und 10. Oktober 2012 durchgeführten Rundtischgespräches zur Verfassungsgerichtsbarkeit. Behandelt werden ausgewählte rechtshistorische und -politische Fragen sowie aktuelle rechtliche Probleme der Verfassungsgerichtsbarkeit in der Russischen Föderation und der Bundesrepublik Deutschland sowohl aus der Sicht der Rechtspraxis als auch der Wissenschaft: insbesondere die Entwicklung der Verfassungsgerichtsbarkeit in Geschichte und Gegenwart, Status, Rechtsnatur und Aufgaben des Verfassungsgerichts in den Subjekten der Föderation und in den Ländern sowie Verfassungsgericht und Gesetzgebung. Zudem werden Spezialfragen der Verfassungsgerichtsbarkeit erörtert, z.B. die Institution des Bevollmächtigten Vertreters des Präsidenten im Verfassungsgericht in Russland, der Eilrechtsschutz durch das BVerfG und der Rechtsschutz bei überlangen Verfahren vor dem BVerfG in Deutschland.
Der Band enthält die Tagungsmaterialien des deutsch-russichen Symposiums zum Thema "Verfassungsentwicklung in Russland und Deutschland", welches am 25. und 26. September 2013 in Potsdam stattfand. Die Tagung wurde anlässlich des 20. Jahrestages der russischen Verfassung vom Dezember 2013 durchgeführt. Die inhaltlichen Schwerpunkte bilden die Themen: Verfassungsentstehung, Verfassungsänderung, Verfassungsprinzipien, Landesverfassungen, Fortentwicklung der Verfassung durch die Verfassungsgerichtsbarkeit und Grundrechte, die jeweils aus russischer und deutscher Sicht behandelt werden. Ergänzend befasst sich jeweils ein Betrag mit aktuellen Problemen der Menschenrechtsverwirklichung in Russland und der Ausländerintegration in Deutschland und Russland im Vergleich.
In den zeitgenössischen slavischen Literaturen ist Gewalt allgegenwärtig – als Echo der Revolutionen, Kriege, Diktaturen und Systemumbrüche des 20. Jahrhunderts, als Reaktion auf andauernde und neu ausbrechende Konflikte, als Faszination, Sensation und Kaufanreiz. Gewalt erscheint als narrativ-ästhetischer, tradierter Bestandteil der literarischen Darstellung und als aussagekräftiges, tabubrechendes Motiv. Dieser Band trägt die Ergebnisse einer internationalen Konferenz an der Universität Hamburg zusammen, die sich im Herbst 2012 diesem Thema unter der Trias "Verbrechen – Fiktion - Vermarktung" gewidmet hat. Das breite Spektrum der untersuchten Literaturen (von ost- und west- über südslavische Literaturen, von Prosa über Lyrik und Dramatik) aber auch der Blick über die Literatur hinaus (unter anderem auf Film und Musik), die Vielfalt der Themen, Darstellungsweisen und analytischen Zugänge ergeben ein vielfältiges Bild, das eine Annäherung an die Frage nach den Spezifika literarischer Gewaltdarstellungen ermöglicht.
Verbal or visual? : How information is distributed across speech and gesture in spatial dialog
(2006)
In spatial dialog like in direction giving humans make frequent use of speechaccompanying gestures. Some gestures convey largely the same information as speech while others complement speech. This paper reports a study on how speakers distribute meaning across speech and gesture, and depending on what factors. Utterance meaning and the wider dialog context were tested by statistically analyzing a corpus of direction-giving dialogs. Problems of speech production (as indicated by discourse markers and disfluencies), the communicative goals, and the information status were found to be influential, while feedback signals by the addressee do not have any influence.