@inproceedings{TodtHamannGraefener2007, author = {Todt, Helge Tobias and Hamann, Wolf-Rainer and Gr{\"a}fener, G.}, title = {Clumping in [WC]-type Central Stars from electron-scattering line wings}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17711}, year = {2007}, abstract = {While there is strong evidence for clumping in the winds of massive hot stars, very little is known about clumping in the winds from Central Stars. We have checked [WC]-type CSPN winds for clumping by inspecting the electron-scattering line wings. At least for three stars we found indications for wind inhomogeneities.}, language = {en} } @inproceedings{StLouisMoffat2007, author = {St-Louis, N. and Moffat, Anthony F. J.}, title = {Do clumping corrections increase with decreasing mass-loss rates?}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17696}, year = {2007}, abstract = {We report on new mass-loss rate estimates for O stars in six massive binaries using the amplitude of orbital-phase dependent, linear-polarimetric variability caused by electron scattering off free electrons in the winds. Our estimated mass-loss rates for luminous O stars are independent of clumping. They suggest similar clumping corrections as for WR stars and do not support the recently proposed reduction in mass-loss rates of O stars by one or two orders of magnitude.}, language = {en} } @inproceedings{VotrubaFeldmeierKubatetal.2007, author = {Votruba, V. and Feldmeier, Achim and Kub{\´a}t, Jiř{\´i} and R{\"a}tzel, D.}, title = {Multicomponent stellar wind of hot stars}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17677}, year = {2007}, abstract = {We developed a time-dependent multicomponent hydrodynamical code for simulation of the stellar wind from hot stars and applied it to stars with high and low density winds.}, language = {en} } @inproceedings{PulsMarkovaNajarroetal.2007, author = {Puls, Joachim and Markova, N. and Najarro, F. and Hanson, M. M.}, title = {Clumping in O-star winds}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17683}, year = {2007}, abstract = {We review various diagnostics of clumping in O-star winds, with special emphasis on its radial stratification. Implications and problems are discussed, and promising NIR methods are presented.}, language = {en} } @inproceedings{BouretLanzHillieretal.2007, author = {Bouret, J.-C. and Lanz, T. and Hillier, D. J. and Foellmi, C.}, title = {Clumping in O-type Supergiants}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17662}, year = {2007}, abstract = {We have analyzed the spectra of seven Galactic O4 supergiants, with the NLTE wind code CMFGEN. For all stars, we have found that clumped wind models match well lines from different species spanning a wavelength range from FUV to optical, and remain consistent with Hα data. We have achieved an excellent match of the P V λλ1118, 1128 resonance doublet and N IV λ1718, as well as He II λ4686 suggesting that our physical description of clumping is adequate. We find very small volume filling factors and that clumping starts deep in the wind, near the sonic point. The most crucial consequence of our analysis is that the mass loss rates of O stars need to be revised downward significantly, by a factor of 3 and more compared to those obtained from smooth-wind models.}, language = {en} } @inproceedings{Smith2007, author = {Smith, Nathan}, title = {Independent signs of lower mass-loss rates for O-type stars}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17659}, year = {2007}, abstract = {I discuss observational evidence - independent of the direct spectral diagnostics of stellar winds themselves - suggesting that mass-loss rates for O stars need to be revised downward by roughly a factor of three or more, in line with recent observed mass-loss rates for clumped winds. These independent constraints include the large observed mass-loss rates in LBV eruptions, the large masses of evolved massive stars like LBVs and WNH stars, WR stars in lower metallicity environments, observed rotation rates of massive stars at different metallicity, supernovae that seem to defy expectations of high mass-loss rates in stellar evolution, and other clues. I pay particular attention to the role of feedback that would result from higher mass-loss rates, driving the star to the Eddington limit too soon, and therefore making higher rates appear highly implausible. Some of these arguments by themselves may have more than one interpretation, but together they paint a consistent picture that steady line-driven winds of O-type stars have lower mass-loss rates and are significantly clumped.}, language = {en} } @inproceedings{FullertonMassaPrinja2007, author = {Fullerton, A. W. and Massa, D. L. and Prinja, R. K.}, title = {Revised mass-loss rates for O stars from the Pv resonance line}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17647}, year = {2007}, abstract = {The P v λλ1118, 1128 resonance doublet is an extraordinarily useful diagnostic of O-star winds, because it bypasses the traditional problems associated with determining mass-loss rates from UV resonance lines. We discuss critically the assumptions and uncertainties involved with using P v to diagnose mass-loss rates, and conclude that the large discrepancies between massloss rates determined from P v and the rates determined from "density squared" emission processes pose a significant challenge to the "standard model" of hot-star winds. The disparate measurements can be reconciled if the winds of O-type stars are strongly clumped on small spatial scales, which in turn implies that mass-loss rates based on Hα or radio emission are too large by up to an order of magnitude.}, language = {en} } @inproceedings{Moffat2007, author = {Moffat, Anthony F. J.}, title = {Observational overview of clumping in hot stellar winds}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17633}, year = {2007}, abstract = {In the old days (pre ∼1990) hot stellar winds were assumed to be smooth, which made life fairly easy and bothered no one. Then after suspicious behaviour had been revealed, e.g. stochastic temporal variability in broadband polarimetry of single hot stars, it took the emerging CCD technology developed in the preceding decades (∼1970-80's) to reveal that these winds were far from smooth. It was mainly high-S/N, time-dependent spectroscopy of strong optical recombination emission lines in WR, and also a few OB and other stars with strong hot winds, that indicated all hot stellar winds likely to be pervaded by thousands of multiscale (compressible supersonic turbulent?) structures, whose driver is probably some kind of radiative instability. Quantitative estimates of clumping-independent mass-loss rates came from various fronts, mainly dependent directly on density (e.g. electron-scattering wings of emission lines, UV spectroscopy of weak resonance lines, and binary-star properties including orbital-period changes, electron-scattering, and X-ray fluxes from colliding winds) rather than the more common, easier-to-obtain but clumping-dependent density-squared diagnostics (e.g. free-free emission in the IR/radio and recombination lines, of which the favourite has always been Hα). Many big questions still remain, such as: What do the clumps really look like? Do clumping properties change as one recedes from the mother star? Is clumping universal? Does the relative clumping correction depend on \$\dot{M}\$ itself?}, language = {en} } @inproceedings{Hirschi2007, author = {Hirschi, Raphael}, title = {The impact of reduced mass loss rates on the evolution of massive stars}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17616}, year = {2007}, abstract = {Mass loss is a very important aspect of the life of massive stars. After briefly reviewing its importance, we discuss the impact of the recently proposed downward revision of mass loss rates due to clumping (difficulty to form Wolf-Rayet stars and production of critically rotating stars). Although a small reduction might be allowed, large reduction factors around ten are disfavoured. We then discuss the possibility of significant mass loss at very low metallicity due to stars reaching break-up velocities and especially due to the metal enrichment of the surface of the star via rotational and convective mixing. This significant mass loss may help the first very massive stars avoid the fate of pair-creation supernova, the chemical signature of which is not observed in extremely metal poor stars. The chemical composition of the very low metallicity winds is very similar to that of the most metal poor star known to date, HE1327-2326 and offer an interesting explanation for the origin of the metals in this star. We also discuss the importance of mass loss in the context of long and soft gamma-ray bursts and pair-creation supernovae. Finally, we would like to stress that mass loss in cooler parts of the HR-diagram (luminous blue variable and yellow and red supergiant stages) are much more uncertain than in the hot part. More work needs to be done in these areas to better constrain the evolution of the most massive stars.}, language = {en} } @inproceedings{OPUS4-1574, title = {Clumping in hot-star winds : proceedings of an international workshop held in Potsdam, Germany, 18. - 22. June 2007}, editor = {Hamann, Wolf-Rainer and Feldmeier, Achim and Oskinova, Lida}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-940793-33-1}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13981}, pages = {254}, year = {2007}, abstract = {Stellar winds play an important role for the evolution of massive stars and their cosmic environment. Multiple lines of evidence, coming from spectroscopy, polarimetry, variability, stellar ejecta, and hydrodynamic modeling, suggest that stellar winds are non-stationary and inhomogeneous. This is referred to as 'wind clumping'. The urgent need to understand this phenomenon is boosted by its far-reaching implications. Most importantly, all techniques to derive empirical mass-loss rates are more or less corrupted by wind clumping. Consequently, mass-loss rates are extremely uncertain. Within their range of uncertainty, completely different scenarios for the evolution of massive stars are obtained. Settling these questions for Galactic OB, LBV and Wolf-Rayet stars is prerequisite to understanding stellar clusters and galaxies, or predicting the properties of first-generation stars. In order to develop a consistent picture and understanding of clumped stellar winds, an international workshop on 'Clumping in Hot Star Winds' was held in Potsdam, Germany, from 18. - 22. June 2007. About 60 participants, comprising almost all leading experts in the field, gathered for one week of extensive exchange and discussion. The Scientific Organizing Committee (SOC) included John Brown (Glasgow), Joseph Cassinelli (Madison), Paul Crowther (Sheffield), Alex Fullerton (Baltimore), Wolf-Rainer Hamann (Potsdam, chair), Anthony Moffat (Montreal), Stan Owocki (Newark), and Joachim Puls (Munich). These proceedings contain the invited and contributed talks presented at the workshop, and document the extensive discussions.}, language = {en} } @inproceedings{OPUS4-1412, title = {The 3rd international IEEE scientific conference on physics and control (PhysCon 2007) : September 3rd-7th 2007 at the University of Potsdam}, editor = {Kurths, J{\"u}rgen and Fradkov, Alexander and Chen, Guanrong}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-15228}, pages = {345}, year = {2007}, abstract = {During the last few years there was a tremendous growth of scientific activities in the fields related to both Physics and Control theory: nonlinear dynamics, micro- and nanotechnologies, self-organization and complexity, etc. New horizons were opened and new exciting applications emerged. Experts with different backgrounds starting to work together need more opportunities for information exchange to improve mutual understanding and cooperation. The Conference "Physics and Control 2007" is the third international conference focusing on the borderland between Physics and Control with emphasis on both theory and applications. With its 2007 address at Potsdam, Germany, the conference is located for the first time outside of Russia. The major goal of the Conference is to bring together researchers from different scientific communities and to gain some general and unified perspectives in the studies of controlled systems in physics, engineering, chemistry, biology and other natural sciences. We hope that the Conference helps experts in control theory to get acquainted with new interesting problems, and helps experts in physics and related fields to know more about ideas and tools from the modern control theory.}, language = {en} } @inproceedings{OPUS4-964, title = {brandial'06 : Proceedings of the 10th Workshop on the semantics and pragmatics of dialogue (SemDial-10)}, editor = {Schlangen, David and Fern{\´a}ndez, Raquel}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-939469-29-2}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-10484}, pages = {vii ; 201}, year = {2006}, abstract = {brandial06 was the tenth in a series of workshops that aims to bring together researchers working on the semantics and pragmatics of dialogues in fields such as artificial intelligence, formal semantics and pragmatics, computational linguistics, philosophy, and psychology. This volume collects all presented papers and posters and gives abstracts of the invited talks.}, language = {en} } @inproceedings{KempsonCann2006, author = {Kempson, Ruth and Cann, Ronnie}, title = {Dialogue pressures and syntactic change}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-10469}, year = {2006}, abstract = {On the basis of the Dynamic Syntax framework, this paper argues that the production pressures in dialogue determining alignment effects and given versus new informational effects also drive the shift from case-rich free word order systems without clitic pronouns into systems with clitic pronouns with rigid relative ordering. The paper introduces assumptions of Dynamic Syntax, in particular the building up of interpretation through structural underspecification and update, sketches the attendant account of production with close coordination of parsing and production strategies, and shows how what was at the Latin stage a purely pragmatic, production-driven decision about linear ordering becomes encoded in the clitics in theMedieval Spanish system which then through successive steps of routinization yield the modern systems with immediately pre-verbal fixed clitic templates.}, language = {en} } @inproceedings{WolskaKruijffKorbayova2006, author = {Wolska, Magdalena and Kruijff-Korbayov{\´a}, Ivana}, title = {Modeling anaphora in informal mathematical dialogue}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-10455}, year = {2006}, abstract = {We analyze anaphoric phenomena in the context of building an input understanding component for a conversational system for tutoring mathematics. In this paper, we report the results of data analysis of two sets of corpora of dialogs on mathematical theorem proving. We exemplify anaphoric phenomena, identify factors relevant to anaphora resolution in our domain and extensions to the input interpretation component to support it.}, language = {en} } @inproceedings{DeVaultStone2006, author = {DeVault, David and Stone, Matthew}, title = {Scorekeeping in an uncertain language game}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-10448}, year = {2006}, abstract = {Received views of utterance context in pragmatic theory characterize the occurrent subjective states of interlocutors using notions like common knowledge or mutual belief. We argue that these views are not compatible with the uncertainty and robustness of context-dependence in human–human dialogue. We present an alternative characterization of utterance context as objective and normative. This view reconciles the need for uncertainty with received intuitions about coordination and meaning in context, and can directly inform computational approaches to dialogue.}, language = {en} } @inproceedings{SagetGuyomard2006, author = {Saget, Sylvie and Guyomard, Marc}, title = {Goal-oriented dialog as a collaborative subordinated activity involving collective acceptance}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-10420}, year = {2006}, abstract = {Modeling dialog as a collaborative activity consists notably in specifying the contain of the Conversational Common Ground and the kind of social mental state involved. In previous work (Saget, 2006), we claim that Collective Acceptance is the proper social attitude for modeling Conversational Common Ground in the particular case of goal-oriented dialog. We provide a formalization of Collective Acceptance, besides elements in order to integrate this attitude in a rational model of dialog are provided; and finally, a model of referential acts as being part of a collaborative activity is provided. The particular case of reference has been chosen in order to exemplify our claims.}, language = {en} } @inproceedings{MillsHealey2006, author = {Mills, Gregory J. and Healey, Patrick G. T.}, title = {Clarifying spatial descriptions : local and global effects on semantic co-ordination}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-10414}, year = {2006}, abstract = {A key problem for models of dialogue is to explain the mechanisms involved in generating and responding to clarification requests. We report a 'Maze task' experiment that investigates the effect of 'spoof' clarification requests on the development of semantic co-ordination. The results provide evidence of both local and global semantic co-ordination phenomena that are not captured by existing dialogue co-ordination models.}, language = {en} } @inproceedings{MacuraGinzburg2006, author = {Macura, Zoran and Ginzburg, Jonathan}, title = {Acquiring words across generations : introspectively or interactively?}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-10408}, year = {2006}, abstract = {How does a shared lexicon arise in population of agents with differing lexicons, and how can this shared lexicon be maintained over multiple generations? In order to get some insight into these questions we present an ALife model in which the lexicon dynamics of populations that possess and lack metacommunicative interaction (MCI) capabilities are compared. We ran a series of experiments on multi-generational populations whose initial state involved agents possessing distinct lexicons. These experiments reveal some clear differences in the lexicon dynamics of populations that acquire words solely by introspection contrasted with populations that learn using MCI or using a mixed strategy of introspection and MCI. The lexicon diverges at a faster rate for an introspective population, eventually collapsing to one single form which is associated with all meanings. This contrasts sharply with MCI capable populations in which a lexicon is maintained, where every meaning is associated with a unique word. We also investigated the effect of increasing the meaning space and showed that it speeds up the lexicon divergence for all populations irrespective of their acquisition method.}, language = {en} } @inproceedings{LueckingRieserStaudacher2006, author = {L{\"u}cking, Andy and Rieser, Hannes and Staudacher, Marc}, title = {Multi-modal integration for gesture and speech}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-10393}, year = {2006}, abstract = {Demonstratives, in particular gestures that "only" accompany speech, are not a big issue in current theories of grammar. If we deal with gestures, fixing their function is one big problem, the other one is how to integrate the representations originating from different channels and, ultimately, how to determine their composite meanings. The growing interest in multi-modal settings, computer simulations, human-machine interfaces and VRapplications increases the need for theories ofmultimodal structures and events. In our workshopcontribution we focus on the integration of multimodal contents and investigate different approaches dealing with this problem such as Johnston et al. (1997) and Johnston (1998), Johnston and Bangalore (2000), Chierchia (1995), Asher (2005), and Rieser (2005).}, language = {en} } @inproceedings{Diderichsen2006, author = {Diderichsen, Philip}, title = {Cross recurrence quantification analysis of indefinite anaphora in Swedish dialog : an eye-tracking pilot experiment}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-10388}, year = {2006}, abstract = {A new method is used in an eye-tracking pilot experiment which shows that it is possible to detect differences in common ground associated with the use of minimally different types of indefinite anaphora. Following Richardson and Dale (2005), cross recurrence quantification analysis (CRQA) was used to show that the tandem eye movements of two Swedish-speaking interlocutors are slightly more coupled when they are using fully anaphoric indefinite expressions than when they are using less anaphoric indefinites. This shows the potential of CRQA to detect even subtle processing differences in ongoing discourse.}, language = {en} }