@inproceedings{GoltzPieth2010, author = {Goltz, Hans-Joachim and Pieth, Norbert}, title = {A tool for generating partition schedules of multiprocessor systems}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41556}, year = {2010}, abstract = {A deterministic cycle scheduling of partitions at the operating system level is supposed for a multiprocessor system. In this paper, we propose a tool for generating such schedules. We use constraint based programming and develop methods and concepts for a combined interactive and automatic partition scheduling system. This paper is also devoted to basic methods and techniques for modeling and solving this partition scheduling problem. Initial application of our partition scheduling tool has proved successful and demonstrated the suitability of the methods used.}, language = {en} } @inproceedings{BetzRaiserFruehwirth2010, author = {Betz, Hariolf and Raiser, Frank and Fr{\"u}hwirth, Thom}, title = {Persistent constraints in constraint handling rules}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41547}, year = {2010}, abstract = {In the most abstract definition of its operational semantics, the declarative and concurrent programming language CHR is trivially non-terminating for a significant class of programs. Common refinements of this definition, in closing the gap to real-world implementations, compromise on declarativity and/or concurrency. Building on recent work and the notion of persistent constraints, we introduce an operational semantics avoiding trivial non-termination without compromising on its essential features.}, language = {en} } @inproceedings{AbdennadherIsmailKhoury2010, author = {Abdennadher, Slim and Ismail, Haythem and Khoury, Frederick}, title = {Transforming imperative algorithms to constraint handling rules}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41533}, year = {2010}, abstract = {Different properties of programs, implemented in Constraint Handling Rules (CHR), have already been investigated. Proving these properties in CHR is fairly simpler than proving them in any type of imperative programming language, which triggered the proposal of a methodology to map imperative programs into equivalent CHR. The equivalence of both programs implies that if a property is satisfied for one, then it is satisfied for the other. The mapping methodology could be put to other beneficial uses. One such use is the automatic generation of global constraints, at an attempt to demonstrate the benefits of having a rule-based implementation for constraint solvers.}, language = {en} } @inproceedings{Brass2010, author = {Brass, Stefan}, title = {Range restriction for general formulas}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41521}, year = {2010}, abstract = {Deductive databases need general formulas in rule bodies, not only conjuctions of literals. This is well known since the work of Lloyd and Topor about extended logic programming. Of course, formulas must be restricted in such a way that they can be effectively evaluated in finite time, and produce only a finite number of new tuples (in each iteration of the TP-operator: the fixpoint can still be infinite). It is also necessary to respect binding restrictions of built-in predicates: many of these predicates can be executed only when certain arguments are ground. Whereas for standard logic programming rules, questions of safety, allowedness, and range-restriction are relatively easy and well understood, the situation for general formulas is a bit more complicated. We give a syntactic analysis of formulas that guarantees the necessary properties.}, language = {en} } @inproceedings{BandaGallagher2010, author = {Banda, Gourinath and Gallagher, John P.}, title = {Constraint-based abstraction of a model checker for infinite state systems}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41516}, year = {2010}, abstract = {Abstract interpretation-based model checking provides an approach to verifying properties of infinite-state systems. In practice, most previous work on abstract model checking is either restricted to verifying universal properties, or develops special techniques for temporal logics such as modal transition systems or other dual transition systems. By contrast we apply completely standard techniques for constructing abstract interpretations to the abstraction of a CTL semantic function, without restricting the kind of properties that can be verified. Furthermore we show that this leads directly to implementation of abstract model checking algorithms for abstract domains based on constraints, making use of an SMT solver.}, language = {en} } @inproceedings{HerreHummel2010, author = {Herre, Heinrich and Hummel, Axel}, title = {Stationary generated models of generalized logic programs}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41501}, year = {2010}, abstract = {The interest in extensions of the logic programming paradigm beyond the class of normal logic programs is motivated by the need of an adequate representation and processing of knowledge. One of the most difficult problems in this area is to find an adequate declarative semantics for logic programs. In the present paper a general preference criterion is proposed that selects the 'intended' partial models of generalized logic programs which is a conservative extension of the stationary semantics for normal logic programs of [Prz91]. The presented preference criterion defines a partial model of a generalized logic program as intended if it is generated by a stationary chain. It turns out that the stationary generated models coincide with the stationary models on the class of normal logic programs. The general wellfounded semantics of such a program is defined as the set-theoretical intersection of its stationary generated models. For normal logic programs the general wellfounded semantics equals the wellfounded semantics.}, language = {en} } @inproceedings{HerreHummel2010, author = {Herre, Heinrich and Hummel, Axel}, title = {A paraconsistent semantics for generalized logic programs}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41496}, year = {2010}, abstract = {We propose a paraconsistent declarative semantics of possibly inconsistent generalized logic programs which allows for arbitrary formulas in the body and in the head of a rule (i.e. does not depend on the presence of any specific connective, such as negation(-as-failure), nor on any specific syntax of rules). For consistent generalized logic programs this semantics coincides with the stable generated models introduced in [HW97], and for normal logic programs it yields the stable models in the sense of [GL88].}, language = {en} } @inproceedings{OetschSchwengererTompits2010, author = {Oetsch, Johannes and Schwengerer, Martin and Tompits, Hans}, title = {Kato: a plagiarism-detection tool for answer-set programs}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41485}, year = {2010}, abstract = {We present the tool Kato which is, to the best of our knowledge, the first tool for plagiarism detection that is directly tailored for answer-set programming (ASP). Kato aims at finding similarities between (segments of) logic programs to help detecting cases of plagiarism. Currently, the tool is realised for DLV programs but it is designed to handle various logic-programming syntax versions. We review basic features and the underlying methodology of the tool.}, language = {en} } @inproceedings{Cabalar2010, author = {Cabalar, Pedro}, title = {Existential quantifiers in the rule body}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41476}, year = {2010}, abstract = {In this paper we consider a simple syntactic extension of Answer Set Programming (ASP) for dealing with (nested) existential quantifiers and double negation in the rule bodies, in a close way to the recent proposal RASPL-1. The semantics for this extension just resorts to Equilibrium Logic (or, equivalently, to the General Theory of Stable Models), which provides a logic-programming interpretation for any arbitrary theory in the syntax of Predicate Calculus. We present a translation of this syntactic class into standard logic programs with variables (either disjunctive or normal, depending on the input rule heads), as those allowed by current ASP solvers. The translation relies on the introduction of auxiliary predicates and the main result shows that it preserves strong equivalence modulo the original signature.}, language = {en} } @inproceedings{GebserHinrichsSchaubetal.2010, author = {Gebser, Martin and Hinrichs, Henrik and Schaub, Torsten H. and Thiele, Sven}, title = {xpanda: a (simple) preprocessor for adding multi-valued propositions to ASP}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41466}, year = {2010}, abstract = {We introduce a simple approach extending the input language of Answer Set Programming (ASP) systems by multi-valued propositions. Our approach is implemented as a (prototypical) preprocessor translating logic programs with multi-valued propositions into logic programs with Boolean propositions only. Our translation is modular and heavily benefits from the expressive input language of ASP. The resulting approach, along with its implementation, allows for solving interesting constraint satisfaction problems in ASP, showing a good performance.}, language = {en} } @inproceedings{Seipel2010, author = {Seipel, Dietmar}, title = {Practical Applications of Extended Deductive Databases in DATALOG*}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41457}, year = {2010}, abstract = {A wide range of additional forward chaining applications could be realized with deductive databases, if their rule formalism, their immediate consequence operator, and their fixpoint iteration process would be more flexible. Deductive databases normally represent knowledge using stratified Datalog programs with default negation. But many practical applications of forward chaining require an extensible set of user-defined built-in predicates. Moreover, they often need function symbols for building complex data structures, and the stratified fixpoint iteration has to be extended by aggregation operations. We present an new language Datalog*, which extends Datalog by stratified meta-predicates (including default negation), function symbols, and user-defined built-in predicates, which are implemented and evaluated top-down in Prolog. All predicates are subject to the same backtracking mechanism. The bottom-up fixpoint iteration can aggregate the derived facts after each iteration based on user-defined Prolog predicates.}, language = {en} } @inproceedings{HanusKoschnicke2010, author = {Hanus, Michael and Koschnicke, Sven}, title = {An ER-based framework for declarative web programming}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41447}, year = {2010}, abstract = {We describe a framework to support the implementation of web-based systems to manipulate data stored in relational databases. Since the conceptual model of a relational database is often specified as an entity-relationship (ER) model, we propose to use the ER model to generate a complete implementation in the declarative programming language Curry. This implementation contains operations to create and manipulate entities of the data model, supports authentication, authorization, session handling, and the composition of individual operations to user processes. Furthermore and most important, the implementation ensures the consistency of the database w.r.t. the data dependencies specified in the ER model, i.e., updates initiated by the user cannot lead to an inconsistent state of the database. In order to generate a high-level declarative implementation that can be easily adapted to individual customer requirements, the framework exploits previous works on declarative database programming and web user interface construction in Curry.}, language = {en} } @inproceedings{Zhou2010, author = {Zhou, Neng-Fa}, title = {What I have learned from all these solver competitions}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41431}, year = {2010}, abstract = {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.}, language = {en} } @inproceedings{Schrijvers2010, author = {Schrijvers, Tom}, title = {Overview of the monadic constraint programming framework}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41411}, year = {2010}, abstract = {A constraint programming system combines two essential components: a constraint solver and a search engine. The constraint solver reasons about satisfiability of conjunctions of constraints, and the search engine controls the search for solutions by iteratively exploring a disjunctive search tree defined by the constraint program. The Monadic Constraint Programming framework gives a monadic definition of constraint programming where the solver is defined as a monad threaded through the monadic search tree. Search and search strategies can then be defined as firstclass objects that can themselves be built or extended by composable search transformers. Search transformers give a powerful and unifying approach to viewing search in constraint programming, and the resulting constraint programming system is first class and extremely flexible.}, language = {en} } @inproceedings{GeskeWolf2010, author = {Geske, Ulrich and Wolf, Armin}, title = {Preface}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41401}, year = {2010}, abstract = {The workshops on (constraint) logic programming (WLP) are the annual meeting of the Society of Logic Programming (GLP e.V.) and bring together researchers interested in logic programming, constraint programming, and related areas like databases, artificial intelligence and operations research. In this decade, previous workshops took place in Dresden (2008), W{\"u}rzburg (2007), Vienna (2006), Ulm (2005), Potsdam (2004), Dresden (2002), Kiel (2001), and W{\"u}rzburg (2000). Contributions to workshops deal with all theoretical, experimental, and application aspects of constraint programming (CP) and logic programming (LP), including foundations of constraint/ logic programming. Some of the special topics are constraint solving and optimization, extensions of functional logic programming, deductive databases, data mining, nonmonotonic reasoning, , interaction of CP/LP with other formalisms like agents, XML, JAVA, program analysis, program transformation, program verification, meta programming, parallelism and concurrency, answer set programming, implementation and software techniques (e.g., types, modularity, design patterns), applications (e.g., in production, environment, education, internet), constraint/logic programming for semantic web systems and applications, reasoning on the semantic web, data modelling for the web, semistructured data, and web query languages.}, language = {en} } @phdthesis{Bojdys2009, author = {Bojdys, Michael Janus}, title = {On new allotropes and nanostructures of carbon nitrides}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41236}, school = {Universit{\"a}t Potsdam}, year = {2009}, abstract = {In the first section of the thesis graphitic carbon nitride was for the first time synthesised using the high-temperature condensation of dicyandiamide (DCDA) - a simple molecular precursor - in a eutectic salt melt of lithium chloride and potassium chloride. The extent of condensation, namely next to complete conversion of all reactive end groups, was verified by elemental microanalysis and vibrational spectroscopy. TEM- and SEM-measurements gave detailed insight into the well-defined morphology of these organic crystals, which are not based on 0D or 1D constituents like known molecular or short-chain polymeric crystals but on the packing motif of extended 2D frameworks. The proposed crystal structure of this g-C3N4 species was derived in analogy to graphite by means of extensive powder XRD studies, indexing and refinement. It is based on sheets of hexagonally arranged s-heptazine (C6N7) units that are held together by covalent bonds between C and N atoms. These sheets stack in a graphitic, staggered fashion adopting an AB-motif, as corroborated by powder X-ray diffractometry and high-resolution transmission electron microscopy. This study was contrasted with one of many popular - yet unsuccessful - approaches in the last 30 years of scientific literature to perform the condensation of an extended carbon nitride species through synthesis in the bulk. The second section expands the repertoire of available salt melts introducing the lithium bromide and potassium bromide eutectic as an excellent medium to obtain a new phase of graphitic carbon nitride. The combination of SEM, TEM, PXRD and electron diffraction reveals that the new graphitic carbon nitride phase stacks in an ABA' motif forming unprecedentedly large crystals. This section seizes the notion of the preceding chapter, that condensation in a eutectic salt melt is the key to obtain a high degree of conversion mainly through a solvatory effect. At the close of this chapter ionothermal synthesis is seen established as a powerful tool to overcome the inherent kinetic problems of solid state reactions such as incomplete polymerisation and condensation in the bulk especially when the temperature requirement of the reaction in question falls into the proverbial "no man's land" of classical solvents, i.e. above 250 to 300 °C. The following section puts the claim to the test, that the crystalline carbon nitrides obtained from a salt melt are indeed graphitic. A typical property of graphite - namely the accessibility of its interplanar space for guest molecules - is transferred to the graphitic carbon nitride system. Metallic potassium and graphitic carbon nitride are converted to give the potassium intercalation compound, K(C6N8)3 designated according to its stoichiometry and proposed crystal structure. Reaction of the intercalate with aqueous solvents triggers the exfoliation of the graphitic carbon nitride material and - for the first time - enables the access of singular (or multiple) carbon nitride sheets analogous to graphene as seen in the formation of sheets, bundles and scrolls of carbon nitride in TEM imaging. The thus exfoliated sheets form a stable, strongly fluorescent solution in aqueous media, which shows no sign in UV/Vis spectroscopy that the aromaticity of individual sheets was subject to degradation. The final section expands on the mechanism underlying the formation of graphitic carbon nitride by literally expanding the distance between the covalently linked heptazine units which constitute these materials. A close examination of all proposed reaction mechanisms to-date in the light of exhaustive DSC/MS experiments highlights the possibility that the heptazine unit can be formed from smaller molecules, even if some of the designated leaving groups (such as ammonia) are substituted by an element, R, which later on remains linked to the nascent heptazine. Furthermore, it is suggested that the key functional groups in the process are the triazine- (Tz) and the carbonitrile- (CN) group. On the basis of these assumptions, molecular precursors are tailored which encompass all necessary functional groups to form a central heptazine unit of threefold, planar symmetry and then still retain outward functionalities for self-propagated condensation in all three directions. Two model systems based on a para-aryl (ArCNTz) and para-biphenyl (BiPhCNTz) precursors are devised via a facile synthetic procedure and then condensed in an ionothermal process to yield the heptazine based frameworks, HBF-1 and HBF-2. Due to the structural motifs of their molecular precursors, individual sheets of HBF-1 and HBF-2 span cavities of 14.2 {\AA} and 23.0 {\AA} respectively which makes both materials attractive as potential organic zeolites. Crystallographic analysis confirms the formation of ABA' layered, graphitic systems, and the extent of condensation is confirmed as next-to-perfect by elemental analysis and vibrational spectroscopy.}, language = {en} } @book{WistSchaeferVogleretal.2010, author = {Wist, Dominic and Schaefer, Mark and Vogler, Walter and Wollowski, Ralf}, title = {STG decomposition : internal communication for SI implementability}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-037-3}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-40786}, publisher = {Universit{\"a}t Potsdam}, pages = {36}, year = {2010}, abstract = {STG decomposition is a promising approach to tackle the complexity problems arising in logic synthesis of speed independent circuits, a robust asynchronous (i.e. clockless) circuit type. Unfortunately, STG decomposition can result in components that in isolation have irreducible CSC conflicts. Generalising earlier work, it is shown how to resolve such conflicts by introducing internal communication between the components via structural techniques only.}, language = {en} } @phdthesis{Breitenbach2009, author = {Breitenbach, Sebastian Franz Martin}, title = {Changes in monsoonal precipitation and atmospheric circulation during the Holocene reconstructed from stalagmites from Northeastern India}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-37807}, school = {Universit{\"a}t Potsdam}, year = {2009}, abstract = {Recent years witnessed a vast advent of stalagmites as palaeoclimate archives. The multitude of geochemical and physical proxies and a promise of a precise and accurate age model greatly appeal to palaeoclimatologists. Although substantial progress was made in speleothem-based palaeoclimate research and despite high-resolution records from low-latitudinal regions, proving that palaeo-environmental changes can be archived on sub-annual to millennial time scales our comprehension of climate dynamics is still fragmentary. This is in particular true for the summer monsoon system on the Indian subcontinent. The Indian summer monsoon (ISM) is an integral part of the intertropical convergence zone (ITCZ). As this rainfall belt migrates northward during boreal summer, it brings monsoonal rainfall. ISM strength depends however on a variety of factors, including snow cover in Central Asia and oceanic conditions in the Indic and Pacific. Presently, many of the factors influencing the ISM are known, though their exact forcing mechanism and mutual relations remain ambiguous. Attempts to make an accurate prediction of rainfall intensity and frequency and drought recurrence, which is extremely important for South Asian countries, resemble a puzzle game; all interaction need to fall into the right place to obtain a complete picture. My thesis aims to create a faithful picture of climate change in India, covering the last 11,000 ka. NE India represents a key region for the Bay of Bengal (BoB) branch of the ISM, as it is here where the monsoon splits into a northwestward and a northeastward directed arm. The Meghalaya Plateau is the first barrier for northward moving air masses and receives excessive summer rainfall, while the winter season is very dry. The proximity of Meghalaya to the Tibetan Plateau on the one hand and the BoB on the other hand make the study area a key location for investigating the interaction between different forcings that governs the ISM. A basis for the interpretation of palaeoclimate records, and a first important outcome of my thesis is a conceptual model which explains the observed pattern of seasonal changes in stable isotopes (d18O and d2H) in rainfall. I show that although in tropical and subtropical regions the amount effect is commonly called to explain strongly depleted isotope values during enhanced rainfall, alone it cannot account for observed rainwater isotope variability in Meghalaya. Monitoring of rainwater isotopes shows no expected negative correlation between precipitation amount and d18O of rainfall. In turn I find evidence that the runoff from high elevations carries an inherited isotopic signature into the BoB, where during the ISM season the freshwater builds a strongly depleted plume on top of the marine water. The vapor originating from this plume is likely to memorize' and transmit further very negative d18O values. The lack of data does not allow for quantication of this plume effect' on isotopes in rainfall over Meghalaya but I suggest that it varies on seasonal to millennial timescales, depending on the runoff amount and source characteristics. The focal point of my thesis is the extraction of climatic signals archived in stalagmites from NE India. High uranium concentration in the stalagmites ensured excellent age control required for successful high-resolution climate reconstructions. Stable isotope (d18O and d13C) and grey-scale data allow unprecedented insights into millennial to seasonal dynamics of the summer and winter monsoon in NE India. ISM strength (i. e. rainfall amount) is recorded in changes in d18Ostalagmites. The d13C signal, reflecting drip rate changes, renders a powerful proxy for dry season conditions, and shows similarities to temperature-related changes on the Tibetan Plateau. A sub-annual grey-scale profile supports a concept of lower drip rate and slower stalagmite growth during dry conditions. During the Holocene, ISM followed a millennial-scale decrease of insolation, with decadal to centennial failures resulting from atmospheric changes. The period of maximum rainfall and enhanced seasonality corresponds to the Holocene Thermal Optimum observed in Europe. After a phase of rather stable conditions, 4.5 kyr ago, the strengthening ENSO system dominated the ISM. Strong El Nino events weakened the ISM, especially when in concert with positive Indian Ocean dipole events. The strongest droughts of the last 11 kyr are recorded during the past 2 kyr. Using the advantage of a well-dated stalagmite record at hand I tested the application of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to detect sub-annual to sub-decadal changes in element concentrations in stalagmites. The development of a large ablation cell allows for ablating sample slabs of up to 22 cm total length. Each analyzed element is a potential proxy for different climatic parameters. Combining my previous results with the LAICP- MS-generated data shows that element concentration depends not only on rainfall amount and associated leaching from the soil. Additional factors, like biological activity and hydrogeochemical conditions in the soil and vadose zone can eventually affect the element content in drip water and in stalagmites. I present a theoretical conceptual model for my study site to explain how climatic signals can be transmitted and archived in stalagmite carbonate. Further, I establish a first 1500 year long element record, reconstructing rainfall variability. Additionally, I hypothesize that volcanic eruptions, producing large amounts of sulfuric acid, can influence soil acidity and hence element mobilization.}, language = {en} } @book{SmirnovWeidlichMendlingetal.2009, author = {Smirnov, Sergey and Weidlich, Matthias and Mendling, Jan and Weske, Mathias}, title = {Action patterns in business process models}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-009-0}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-33586}, publisher = {Universit{\"a}t Potsdam}, pages = {19}, year = {2009}, abstract = {Business process management experiences a large uptake by the industry, and process models play an important role in the analysis and improvement of processes. While an increasing number of staff becomes involved in actual modeling practice, it is crucial to assure model quality and homogeneity along with providing suitable aids for creating models. In this paper we consider the problem of offering recommendations to the user during the act of modeling. Our key contribution is a concept for defining and identifying so-called action patterns - chunks of actions often appearing together in business processes. In particular, we specify action patterns and demonstrate how they can be identified from existing process model repositories using association rule mining techniques. Action patterns can then be used to suggest additional actions for a process model. Our approach is challenged by applying it to the collection of process models from the SAP Reference Model.}, language = {en} } @phdthesis{Regel2008, author = {Regel, Stefanie}, title = {The comprehension of figurative language : electrophysiological evidence on the processing of irony}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-33376}, school = {Universit{\"a}t Potsdam}, year = {2008}, abstract = {Diese Dissertation untersucht das Verstehen figurativer Sprache, im Besonderen die zeitliche Verarbeitung von verbaler Ironie. In sechs Experimenten wurde mittels ereignis-korrelierter Potentiale (EKP) die Gehirnaktivit{\"a}t beim Verstehen ironischer {\"A}ußerungen im Vergleich zu entsprechenden nicht-ironischen {\"A}ußerungen gemessen und analysiert. Dar{\"u}berhinaus wurde der Einfluss verschiedener sprachbegleitender Hinweisreize, z.B. von Prosodie oder der Verwendung von Satzzeichen, sowie außersprachlicher Hinweisreize, wie bspw. pragmatischen Wissens, auf das Ironieverstehen untersucht. Auf Grundlage dieser Ergebnisse werden verschiedene psycholinguistische Modelle figurativer Sprachverarbeitung, d.h. 'standard pragmatic model', 'graded salience hypothesis', sowie 'direct access view', diskutiert.}, language = {en} } @phdthesis{Boerner2009, author = {B{\"o}rner, Hans Gerhard}, title = {Exploiting self-organization and functionality of peptides for polymer science}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-29066}, school = {Universit{\"a}t Potsdam}, year = {2009}, abstract = {Controlling interactions in synthetic polymers as precisely as in proteins would have a strong impact on polymer science. Advanced structural and functional control can lead to rational design of, integrated nano- and microstructures. To achieve this, properties of monomer sequence defined oligopeptides were exploited. Through their incorporation as monodisperse segments into synthetic polymers we learned in recent four years how to program the structure formation of polymers, to adjust and exploit interactions in such polymers, to control inorganic-organic interfaces in fiber composites and induce structure in Biomacromolecules like DNA for biomedical applications.}, language = {en} } @phdthesis{Gressel2008, author = {Gressel, Oliver}, title = {Supernova-driven turbulence and magnetic field amplification in disk galaxies}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-29094}, school = {Universit{\"a}t Potsdam}, year = {2008}, abstract = {Supernovae are known to be the dominant energy source for driving turbulence in the interstellar medium. Yet, their effect on magnetic field amplification in spiral galaxies is still poorly understood. Analytical models based on the uncorrelated-ensemble approach predicted that any created field will be expelled from the disk before a significant amplification can occur. By means of direct simulations of supernova-driven turbulence, we demonstrate that this is not the case. Accounting for vertical stratification and galactic differential rotation, we find an exponential amplification of the mean field on timescales of 100Myr. The self-consistent numerical verification of such a "fast dynamo" is highly beneficial in explaining the observed strong magnetic fields in young galaxies. We, furthermore, highlight the importance of rotation in the generation of helicity by showing that a similar mechanism based on Cartesian shear does not lead to a sustained amplification of the mean magnetic field. This finding impressively confirms the classical picture of a dynamo based on cyclonic turbulence.}, language = {en} } @phdthesis{Oey2008, author = {Oey, Melanie}, title = {Chloroplasts as bioreactors : high-yield production of active bacteriolytic protein antibiotics}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-28950}, school = {Universit{\"a}t Potsdam}, year = {2008}, abstract = {Plants, more precisely their chloroplasts with their bacterial-like expression machinery inherited from their cyanobacterial ancestors, can potentially offer a cheap expression system for proteinaceous pharmaceuticals. This system would be easily scalable and provides appropriate safety due to chloroplasts maternal inheritance. In this work, it was shown that three phage lytic enzymes (Pal, Cpl-1 and PlyGBS) could be successfully expressed at very high levels and with high stability in tobacco chloroplasts. PlyGBS expression reached an amount of foreign protein accumulation (> 70\% TSP) that has never been obtained before. Although the high expression levels of PlyGBS caused a pale green phenotype with retarded growth, presumably due to exhaustion of plastid protein synthesis capacity, development and seed production were not impaired under greenhouse conditions. Since Pal and Cpl-1 showed toxic effects when expressed in E. coli, a special plastid transformation vector (pTox) was constructed to allow DNA amplification in bacteria. The construction of the pTox transformation vector allowing a recombinase-mediated deletion of an E. coli transcription block in the chloroplast, leading to an increase of foreign protein accumulation to up to 40\% of TSP for Pal and 20\% of TSP for Cpl-1. High dose-dependent bactericidal efficiency was shown for all three plant-derived lytic enzymes using their pathogenic target bacteria S. pyogenes and S. pneumoniae. Confirmation of specificity was obtained for the endotoxic proteins Pal and Cpl-1 by application to E. coli cultures. These results establish tobacco chloroplasts as a new cost-efficient and convenient production platform for phage lytic enzymes and address the greatest obstacle for clinical application. The present study is the first report of lysin production in a non-bacterial system. The properties of chloroplast-produced lysins described in this work, their stability, high accumulation rate and biological activity make them highly attractive candidates for future antibiotics.}, language = {en} } @inproceedings{ZarriessSeeker2008, author = {Zarrieß, Sina and Seeker, Wolfgang}, title = {Finite-state rule deduction for parsing non-constituent coordination}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27254}, year = {2008}, abstract = {In this paper, we present a finite-state approach to constituency and therewith an analysis of coordination phenomena involving so-called non-constituents. We show that non-constituents can be seen as parts of fully-fledged constituents and therefore be coordinated in the same way. We have implemented an algorithm based on finite state automata that generates an LFG grammar assigning valid analyses to non-constituent coordination structures in the German language.}, language = {en} } @inproceedings{YliJyrae2008, author = {Yli-Jyr{\"a}, Anssi}, title = {Transducers from parallel replace rules and modes with generalized lenient composition}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27246}, year = {2008}, abstract = {Generalized Two-Level Grammar (GTWOL) provides a new method for compilation of parallel replacement rules into transducers. The current paper identifies the role of generalized lenient composition (GLC) in this method. Thanks to the GLC operation, the compilation method becomes bipartite and easily extendible to capture various application modes. In the light of three notions of obligatoriness, a modification to the compilation method is proposed. We argue that the bipartite design makes implementation of parallel obligatoriness, directionality, length and rank based application modes extremely easy, which is the main result of the paper.}, language = {en} } @inproceedings{Saleschus2008, author = {Sal{\´e}schus, Dirk}, title = {On resolving long distance dependencies in Russian verbs}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27235}, year = {2008}, abstract = {Morphological analyses based on word syntax approaches can encounter difficulties with long distance dependencies. The reason is that in some cases an affix has to have access to the inner structure of the form with which it combines. One solution is the percolation of features from ther inner morphemes to the outer morphemes with some process of feature unification. However, the obstacle of percolation constraints or stipulated features has lead some linguists to argue in favour of other frameworks such as, e.g., realizational morphology or parallel approaches like optimality theory. This paper proposes a linguistic analysis of two long distance dependencies in the morphology of Russian verbs, namely secondary imperfectivization and deverbal nominalization.We show how these processes can be reanalysed as local dependencies. Although finitestate frameworks are not bound by such linguistically motivated considerations, we present an implementation of our analysis as proposed in [1] that does not complicate the grammar or enlarge the network unproportionally.}, language = {en} } @inproceedings{Piskorski2008, author = {Piskorski, Jakub}, title = {ExPRESS : extraction pattern recognition engine and specification suite}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27227}, year = {2008}, abstract = {The emergence of information extraction (IE) oriented pattern engines has been observed during the last decade. Most of them exploit heavily finite-state devices. This paper introduces ExPRESS - a new extraction pattern engine, whose rules are regular expressions over flat feature structures. The underlying pattern language is a blend of two previously introduced IE oriented pattern formalisms, namely, JAPE, used in the widely known GATE system, and the unificationbased XTDL formalism used in SProUT. A brief and technical overview of ExPRESS, its pattern language and the pool of its native linguistic components is given. Furthermore, the implementation of the grammar interpreter is addressed too.}, language = {en} } @inproceedings{PadroPadro2008, author = {Padr{\´o}, Muntsa and Padr{\´o}, Llu{\´i}s}, title = {ME-CSSR : an extension of CSSR using maximum entropy models}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27210}, year = {2008}, abstract = {In this work an extension of CSSR algorithm using Maximum Entropy Models is introduced. Preliminary experiments to perform Named Entity Recognition with this new system are presented.}, language = {en} } @inproceedings{GonzalezCasacuberta2008, author = {Gonz{\´a}lez, Jorge and Casacuberta, Francisco}, title = {Phrase-based finite state models}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27209}, year = {2008}, abstract = {In the last years, statistical machine translation has already demonstrated its usefulness within a wide variety of translation applications. In this line, phrase-based alignment models have become the reference to follow in order to build competitive systems. Finite state models are always an interesting framework because there are well-known efficient algorithms for their representation and manipulation. This document is a contribution to the evolution of finite state models towards a phrase-based approach. The inference of stochastic transducers that are based on bilingual phrases is carefully analysed from a finite state point of view. Indeed, the algorithmic phenomena that have to be taken into account in order to deal with such phrase-based finite state models when in decoding time are also in-depth detailed.}, language = {en} } @inproceedings{Fernando2008, author = {Fernando, Tim}, title = {Temporal propositions as regular languages}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27194}, year = {2008}, abstract = {Temporal propositions are mapped to sets of strings that witness (in a precise sense) the propositions over discrete linear Kripke frames. The strings are collected into regular languages to ensure the decidability of entailments given by inclusions between languages. (Various notions of bounded entailment are shown to be expressible as language inclusions.) The languages unwind computations implicit in the logical (and temporal) connectives via a system of finite-state constraints adapted from finite-state morphology. Applications to Hybrid Logic and non-monotonic inertial reasoning are briefly considered.}, language = {en} } @inproceedings{IlarrazaGojenolaOronozetal.2008, author = {Ilarraza, Arantza D{\´i}az de and Gojenola, Koldo and Oronoz, Maite and Otaegi, Maialen and Alegria, I{\~n}aki}, title = {Syntactic error detection and correction in date expressions using finite-state transducers}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27180}, year = {2008}, abstract = {This paper presents a system for the detection and correction of syntactic errors. It combines a robust morphosyntactic analyser and two groups of finite-state transducers specified using the Xerox Finite State Tool (xfst). One of the groups is used for the description of syntactic error patterns while the second one is used for the correction of the detected errors. The system has been tested on a corpus of real texts, containing both correct and incorrect sentences, with good results.}, language = {en} } @inproceedings{Didakowski2008, author = {Didakowski, J{\"o}rg}, title = {SynCoP : combining syntactic tagging with chunking using weighted finite state transducers}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27172}, year = {2008}, abstract = {This paper describes the key aspects of the system SynCoP (Syntactic Constraint Parser) developed at the Berlin-Brandenburgische Akademie der Wissenschaften. The parser allows to combine syntactic tagging and chunking by means of constraint grammar using weighted finite state transducers (WFST). Chunks are interpreted as local dependency structures within syntactic tagging. The linguistic theories are formulated by criteria which are formalized by a semiring; these criteria allow structural preferences and gradual grammaticality. The parser is essentially a cascade of WFSTs. To find the most likely syntactic readings a best-path search is used.}, language = {en} } @inproceedings{Daciuk2008, author = {Daciuk, Jan}, title = {Perfect hashing tree automata}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27163}, year = {2008}, abstract = {We present an algorithm that computes a function that assigns consecutive integers to trees recognized by a deterministic, acyclic, finite-state, bottom-up tree automaton. Such function is called minimal perfect hashing. It can be used to identify trees recognized by the automaton. Its value may be seen as an index in some other data structures. We also present an algorithm for inverted hashing.}, language = {en} } @inproceedings{BoegelButtHautlietal.2008, author = {B{\"o}gel, Tina and Butt, Miriam and Hautli, Annette and Sulger, Sebastian}, title = {Developing a finite-state morphological analyzer for Urdu and Hindi}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27155}, year = {2008}, abstract = {We introduce and discuss a number of issues that arise in the process of building a finite-state morphological analyzer for Urdu, in particular issues with potential ambiguity and non-concatenative morphology. Our approach allows for an underlyingly similar treatment of both Urdu and Hindi via a cascade of finite-state transducers that transliterates the very different scripts into a common ASCII transcription system. As this transliteration system is based on the XFST tools that the Urdu/Hindi common morphological analyzer is also implemented in, no compatibility problems arise.}, language = {en} } @inproceedings{BonfanteLeRoux2008, author = {Bonfante, Guillaume and Le Roux, Joseph}, title = {Intersection optimization is NP-complete}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27146}, year = {2008}, abstract = {Finite state methods for natural language processing often require the construction and the intersection of several automata. In this paper, we investigate the question of determining the best order in which these intersections should be performed. We take as an example lexical disambiguation in polarity grammars. We show that there is no efficient way to minimize the state complexity of these intersections.}, language = {en} } @inproceedings{BlancConstantWatrin2008, author = {Blanc, Olivier and Constant, Matthieu and Watrin, Patrick}, title = {Segmentation in super-chunks with a finite-state approach}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27133}, year = {2008}, abstract = {Since Harris' parser in the late 50s, multiword units have been progressively integrated in parsers. Nevertheless, in the most part, they are still restricted to compound words, that are more stable and less numerous. Actually, language is full of semi-fixed expressions that also form basic semantic units: semi-fixed adverbial expressions (e.g. time), collocations. Like compounds, the identification of these structures limits the combinatorial complexity induced by lexical ambiguity. In this paper, we detail an experiment that largely integrates these notions in a finite-state procedure of segmentation into super-chunks, preliminary to a parser.We show that the chunker, developped for French, reaches 92.9\% precision and 98.7\% recall. Moreover, multiword units realize 36.6\% of the attachments within nominal and prepositional phrases.}, language = {en} } @inproceedings{Barthelemy2008, author = {Barth{\´e}lemy, Fran{\c{c}}ois}, title = {Finite-state compilation of feature structures for two-level morphology}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27120}, year = {2008}, abstract = {This paper describes a two-level formalism where feature structures are used in contextual rules. Whereas usual two-level grammars describe rational sets over symbol pairs, this new formalism uses tree structured regular expressions. They allow an explicit and precise definition of the scope of feature structures. A given surface form may be described using several feature structures. Feature unification is expressed in contextual rules using variables, like in a unification grammar. Grammars are compiled in finite state multi-tape transducers.}, language = {en} } @inproceedings{BarbaianiCanceddaDanceetal.2008, author = {Barbaiani, Mădălina and Cancedda, Nicola and Dance, Chris and Fazekas, Szil{\´a}rd and Ga{\´a}l, Tam{\´a}s and Gaussier, {\´E}ric}, title = {Asymmetric term alignment with selective contiguity constraints by multi-tape automata}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27115}, year = {2008}, abstract = {This article describes a HMM-based word-alignment method that can selectively enforce a contiguity constraint. This method has a direct application in the extraction of a bilingual terminological lexicon from a parallel corpus, but can also be used as a preliminary step for the extraction of phrase pairs in a Phrase-Based Statistical Machine Translation system. Contiguous source words composing terms are aligned to contiguous target language words. The HMM is transformed into a Weighted Finite State Transducer (WFST) and contiguity constraints are enforced by specific multi-tape WFSTs. The proposed method is especially suited when basic linguistic resources (morphological analyzer, part-of-speech taggers and term extractors) are available for the source language only.}, language = {en} } @inproceedings{YliJyrae2008, author = {Yli-Jyr{\"a}, Anssi}, title = {Applications of diamonded double negation}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27109}, year = {2008}, abstract = {Nested complementation plays an important role in expressing counter- i.e. star-free and first-order definable languages and their hierarchies. In addition, methods that compile phonological rules into finite-state networks use double-nested complementation or "double negation". This paper reviews how the double-nested complementation extends to a relatively new operation, generalized restriction (GR), coined by the author (Yli-Jyr{\"a} and Koskenniemi 2004). This operation encapsulates a double-nested complementation and elimination of a concatenation marker, diamond, whose finite occurrences align concatenations in the arguments of the operation. The paper demonstrates that the GR operation has an interesting potential in expressing regular languages, various kinds of grammars, bimorphisms and relations. This motivates a further study of optimized implementation of the operator.}, language = {en} } @inproceedings{Watson2008, author = {Watson, Bruce W.}, title = {Advances in automata implementation techniques (Abstract)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27094}, year = {2008}, language = {en} } @inproceedings{Karttunen2008, author = {Karttunen, Lauri}, title = {New features in PARC finite state toolkits (Abstract)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27085}, year = {2008}, language = {en} } @article{Tomioka2007, author = {Tomioka, Satoshi}, title = {Intervention effects in focus}, series = {Interdisciplinary studies on information structure : ISIS ; working papers of the SFB 632}, volume = {9}, journal = {Interdisciplinary studies on information structure : ISIS ; working papers of the SFB 632}, editor = {Ishihara, Shinichiro and Petrova, Svetlana and Schwarz, Anne}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, issn = {1866-4725}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-24502}, pages = {97 -- 118}, year = {2007}, abstract = {The most recent trend in the studies of LF intervention effects makes crucial reference to focusing effects on the interveners, and this paper critically examines the representative analyses of the focus-based approach. While each analysis has its own merits and shortcomings, I argue that a pragmatic analysis that does not make appeal to syntactic configurations is better equipped to deal with many of the complex and delicate facts surrounding intervention effects.}, language = {en} } @article{Kitagawa2007, author = {Kitagawa, Yoshihisa}, title = {When we fail to question in Japanese}, series = {Interdisciplinary studies on information structure : ISIS ; working papers of the SFB 632}, volume = {9}, journal = {Interdisciplinary studies on information structure : ISIS ; working papers of the SFB 632}, editor = {Ishihara, Shinichiro and Petrova, Svetlana and Schwarz, Anne}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, issn = {1866-4725}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-24481}, pages = {29 -- 64}, year = {2007}, abstract = {When we pay close attention to the prosody of Wh-questions in Japanese, we discover many novel and interesting empirical puzzles that would require us to devise a much finer syntactic component of grammar. This paper addresses the issues that pose some problems to such an elaborated grammar, and offers solutions, making an appeal to the information structure and sentence processing involved in the interpretation of interrogative and focus constructions.}, language = {en} } @article{Kubozono2007, author = {Kubozono, Haruo}, title = {Focus and intonation in Japanese}, series = {Interdisciplinary studies on information structure : ISIS ; working papers of the SFB 632}, volume = {9}, journal = {Interdisciplinary studies on information structure : ISIS ; working papers of the SFB 632}, editor = {Ishihara, Shinichiro and Petrova, Svetlana and Schwarz, Anne}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, issn = {1866-4725}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-24472}, pages = {1 -- 27}, year = {2007}, abstract = {This paper discusses how focus changes prosodic structure in Tokyo Japanese. It is generally believed that focus blocks the intonational process of downstep and causes a pitch reset. This paper presents experimental evidence against this traditional view by looking at the prosodic behavior of Wh words, which receive focus lexically in Japanese as in other languages. It is demonstrated, specifically, that the focused Wh element does not block downstep although it receives a much higher pitch than its preceding element. This suggests that presence of lexical focus does not trigger pitch reset in Japanese.}, language = {en} } @article{Harvey2001, author = {Harvey, David}, title = {Globalization and the "Spatial Fix"}, series = {Geographische Revue : Zeitschrift f{\"u}r Literatur und Diskussion}, volume = {3}, journal = {Geographische Revue : Zeitschrift f{\"u}r Literatur und Diskussion}, number = {2}, issn = {1438-3039}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-24366}, pages = {23 -- 30}, year = {2001}, language = {en} } @article{Smith2001, author = {Smith, Neil}, title = {Marxism and Geography in the Anglophone World}, series = {Geographische Revue : Zeitschrift f{\"u}r Literatur und Diskussion}, volume = {3}, journal = {Geographische Revue : Zeitschrift f{\"u}r Literatur und Diskussion}, number = {2}, issn = {1438-3039}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-24357}, pages = {5 -- 21}, year = {2001}, abstract = {Content: Activism: The Origins of Marxism in English-language Geography After the Revolution: Critique, Institutionalization and Backlash Marxist Geography Today: Scale, Labour Geography, Activism Conclusion}, language = {en} } @article{Mitchell2000, author = {Mitchell, Don}, title = {The end of culture?}, series = {Geographische Revue : Zeitschrift f{\"u}r Literatur und Diskussion}, volume = {2}, journal = {Geographische Revue : Zeitschrift f{\"u}r Literatur und Diskussion}, number = {2}, issn = {1438-3039}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-24016}, pages = {3 -- 17}, year = {2000}, abstract = {Content: -"Post-Culture" -Cultural Studies, Geography, and Culturalism -Taking Culture Seriously in the Post-Cultural World -Conclusion}, language = {en} } @article{Bauman1999, author = {Bauman, Zygmunt}, title = {Local Orders, Global Chaos}, series = {Geographische Revue : Zeitschrift f{\"u}r Literatur und Diskussion}, volume = {1}, journal = {Geographische Revue : Zeitschrift f{\"u}r Literatur und Diskussion}, number = {1}, issn = {1438-3039}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-23782}, pages = {64 -- 72}, year = {1999}, language = {en} } @misc{StieglitzFuchssHillmannetal.2007, author = {Stieglitz, Stefan and Fuchß, Christoph and Hillmann, Oliver and Lattemann, Christoph}, title = {Mobile learning by using ad hoc messaging network}, issn = {1867-5808}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-19960}, year = {2007}, abstract = {The requirements of modern e-learning techniques change. Aspects such as community interaction, flexibility, pervasive learning and increasing mobility in communication habits become more important. To meet these challenges e-learning platforms must provide support on mobile learning. Most approaches try to adopt centralised and static e-learning mechanisms to mobile devices. However, often technically it is not possible for all kinds of devices to be connected to a central server. Therefore we introduce an application of a mobile e-learning network which operates totally decentralised with the help of an underlying ad hoc network architecture. Furthermore the concept of ad hoc messaging network (AMNET) is used as basis system architecture for our approach to implement a platform for pervasive mobile e-learning.}, language = {en} } @misc{AlbrechtCummingKreuderetal.1986, author = {Albrecht, O. and Cumming, W. and Kreuder, W. and Laschewsky, Andr{\´e} and Ringsdorf, Helmut}, title = {Monolayers of rod-shaped and disc-shaped liquid crystalline compounds at the air-water interface}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17124}, year = {1986}, abstract = {Calamitic (rod-shaped) and discotic (disc-shaped) thermotropic liquid crystalline (LC) compounds were spread at the air-water interface, and their ability to form monolayers was studied. The calamitic LCs investigated were found to form monolayers which behave analogously to conventional amphiphiles such as fatty acids. The spreading of the discotic LCs produced monolayers as well, but with a behaviour different from classical amphiphiles. The areas occupied per molecule are too small to allow the contact of all hydrophilic groups with the water surface and the packing of all hydrophobic chains. Various molecular arrangements of the discotics at the water surface to fit the spreading data are discussed.}, language = {en} } @misc{KochLaschewskyRingsdorfetal.1986, author = {Koch, Horst and Laschewsky, Andr{\´e} and Ringsdorf, Helmut and Teng, Kang}, title = {Photodimerization and photopolymerization of amphiphilic cinnamic acid derivatives in oriented monolayers, vesicles and solution}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17111}, year = {1986}, abstract = {Cinnamic acid moieties were incorporated into amphiphilic compounds containing one and two alkyl chains. These lipid-like compounds with photoreactive units undergo self-organization to form monolayers at the gas-water interface and bilayer structures (vesicles) in aqueous solutions. The photoreaction of the cinnamic acid moiety induced by 254 nm UV light was investigated in the crystalline state, in monolayers, in vesicles and in solution in organic solvents. The single-chain amphiphiles undergo dimerization to yield photoproducts with twice the molecular weight of the corresponding monomers in organized systems. The photoreaction of amphiphiles containing two cinnamic acid groups occurs via two mechanisms: The intramolecular dimerization produces bicycles, with retention of the molecular weight of the corresponding monomer. The intermolecular reaction leads to oligomeric and polymeric photoproducts. In contrast to the single-chain amphiphiles, photodimerization processes of lipoids containing two cinnamic acid moieties also occur in solution in organic solvents.}, language = {en} } @misc{WernerCiceroneKliegletal.1984, author = {Werner, John S. and Cicerone, Carola M. and Kliegl, Reinhold and DellaRosa, Denise}, title = {Spectral efficiency of blackness induction}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16897}, year = {1984}, abstract = {The spectral efficiency of blackness induction was measured in three normal trichromatic observers and in one deuteranomalous observer. The psychophysical task was to adjust the radiance of a monochromatic 60-120′ annulus until a 45′ central broadband field just turned black and its contour became indiscriminable from a dark surrounding gap that separated it from the annulus. The reciprocal of the radiance required to induce blackness with annulus wavelengths between 420 and 680 nm was used to define a spectral-efficiency function for the blackness component of the achromatic process. For each observer, the shape of this blackness-sensitivity function agreed with the spectral-efficiency function based on heterochromatic flicker photometry when measured with the same 60-120′ annulus. Both of these functions matched the Commission Internationale de l'Eclairage Vλ function except at short wavelengths. Ancillary measurements showed that the latter difference in sensitivity can be ascribed to nonuniformities of preretinal absorption, since the annular field excluded the central 60′ of the fovea. Thus our evidence indicates that, at least to a good first approximation, induced blackness is inversely related to the spectral-luminosity function. These findings are consistent with a model that separates the achromatic and the chromatic pathways.}, language = {en} } @misc{OlsonDavidsonKliegletal.1984, author = {Olson, Richard K. and Davidson, Brian J. and Kliegl, Reinhold and Davies, Susan E.}, title = {Development of phonetic memory in disabled and normal readers}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16888}, year = {1984}, abstract = {The development of phonetic codes in memory of 141 pairs of normal and disabled readers from 7.8 to 16.8 years of age was tested with a task adapted from L. S. Mark, D. Shankweiler, I. Y. Liberman, and C. A. Fowler (Memory \& Cognition, 1977, 5, 623-629) that measured false-positive errors in recognition memory for foil words which rhymed with words in the memory list versus foil words that did not rhyme. Our younger subjects replicated Mark et al., showing a larger difference between rhyming and nonrhyming false-positive errors for the normal readers. The older disabled readers' phonetic effect was comparable to that of the younger normal readers, suggesting a developmental lag in their use of phonetic coding in memory. Surprisingly, the normal readers' phonetic effect declined with age in the recognition task, but they maintained a significant advantage across age in the auditory WISC-R digit span recall test, and a test of phonological nonword decoding. The normals' decline with age in rhyming confusion may be due to an increase in the precision of their phonetic codes.}, language = {en} } @misc{MacWhinneyBatesKliegl1984, author = {MacWhinney, Brian and Bates, Elizabeth and Kliegl, Reinhold}, title = {Cue validity and sentence interpretation in English, German, and Italian}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16847}, year = {1984}, abstract = {Linguistic and psycholinguistic accounts based on the study of English may prove unreliable as guides to sentence processing in even closely related languages. The present study illustrates this claim in a test of sentence interpretation by German-, Italian-, and English-speaking adults. Subjects were presented with simple transitive sentences in which contrasts of (1) word order, (2) agreement, (3) animacy, and (4) stress were systematically varied. For each sentence, subjects were asked to state which of the two nouns was the actor. The results indicated that Americans relied overwhelming on word order, using a first-noun strategy in NVN and a second-noun strategy in VNN and NNV sentences. Germans relied on both agreement and animacy. Italians showed extreme reliance on agreement cues. In both German and Italian, stress played a role in terms of complex interactions with word order and agreement. The findings were interpreted in terms of the "competition model" of Bates and MacWhinney (in H. Winitz (Ed.), Annals of the New York Academy of Sciences Conference on Native and Foreign Language Acquisition. New York: New York Academy of Sciences, 1982) in which cue validity is considered to be the primary determinant of cue strength. According to this model, cues are said to be high in validity when they are also high in applicability and reliability.}, language = {en} } @misc{WernerDonnellyKliegl1987, author = {Werner, John S. and Donnelly, Seaneen K. and Kliegl, Reinhold}, title = {Aging and human macular pigment density : appended with translations from the work of Max Schultze and Ewald Hering}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16836}, year = {1987}, abstract = {The optical density of human macular pigment was measured for 50 observers ranging in age from 10 to 90 years. The psychophysical method required adjusting the radiance of a 1°, monochromatic light (400-550 nm) to minimize flicker (15 Hz) when presented in counterphase with a 460 nm standard. This test stimulus was presented superimposed on a broad-band, short-wave background. Macular pigment density was determined by comparing sensitivity under these conditions for the fovea, where macular pigment is maximal, and 5° temporally. This difference spectrum, measured for 12 observers, matched Wyszecki and Stiles's standard density spectrum for macular pigment. To study variation in macular pigment density for a larger group of observers, measurements were made at only selected spectral points (460, 500 and 550 nm). The mean optical density at 460 nm for the complete sample of 50 subjects was 0.39. Substantial individual differences in density were found (ca. 0.10-0.80), but this variation was not systematically related to age.}, language = {en} } @misc{AllefeldFrischSchlesewsky2005, author = {Allefeld, Carsten and Frisch, Stefan and Schlesewsky, Matthias}, title = {Detection of early cognitive processing by event-related phase synchronization analysis}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-20126}, year = {2005}, abstract = {In order to investigate the temporal characteristics of cognitive processing, we apply multivariate phase synchronization analysis to event-related potentials. The experimental design combines a semantic incongruity in a sentence context with a physical mismatch (color change). In the ERP average, these result in an N400 component and a P300-like positivity, respectively. The synchronization analysis shows an effect of global desynchronization in the theta band around 288ms after stimulus presentation for the semantic incongruity, while the physical mismatch elicits an increase of global synchronization in the alpha band around 204ms. Both of these effects clearly precede those in the ERP average. Moreover, the delay between synchronization effect and ERP component correlates with the complexity of the cognitive processes.}, language = {en} } @misc{HowaldElsenbeerLaczkoetal.1995, author = {Howald, Markus and Elsenbeer, Helmut and Laczko, Endre and Schlunegger, Urs Peter}, title = {Capillary electrophoresis as a fast and universal tool in soil analysis}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16913}, year = {1995}, abstract = {Fast analysis of different species of molecules in soils is investigated by capillary electrophoresis (CE). Several CE techniques for the analysis of inorganic ions and carbohydrates have been tested. With regard to the intents of pedologists and the usually large number of soil analyses a bundle of CE systems is proposed, capable of effecting time-saving soil analyses. Adapted electrolyte systems recently published and new separation systems are described. Examples of the application of these methods to two different soil samples are presented.}, language = {en} } @misc{KortPeterKoopmanschap1983, author = {Kort, C. A. D. de and Peter, Martin G. and Koopmanschap, A. B.}, title = {Binding and degradation of juvenile hormone III by haemolymph proteins of the Colorado potato beetle: a re-examination}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16777}, year = {1983}, abstract = {The haemolymph of the adult Colorado potato beetle, Lepinotarsa decemlineata Say, contains a high molecular weight (MW > 200,000) JH-III specific binding protein. The Kd value of the protein for racemic JH-III is 1.3 ± 0.2 × 10-7 M. It has a lower affinity for racemic JH-I and it does not bind JH-III-diol or JH-III-acid. The binding protein does discriminate between the enantiomers of synthetic, racemic JH-III as was determined by stereochemical anaysis of the bound and the free JH-III. Incubation of racemic JH-III with crude haemolymph results in preferential formation of (10S)-JH-III-acid, the unnatural configuration. The JH-esterase present in L. decemlineata haemolymph is not enantioselective. It is concluded that the most important function of the binding protein is that of a specific carrier, protecting the natural hormone against degradation by esterases. The carrier does not protect JH-I as efficiently as the lower homologue.}, language = {en} } @misc{WatanabePueschelGardemannetal.1994, author = {Watanabe, Yuji and P{\"u}schel, Gerhard Paul and Gardemann, Andreas and Jungermann, Kurt}, title = {Presinusoidal and proximal intrasinusoidal confluence of hepatic artery and portal vein in rat liver : functional evidence by orthograde and retrograde bivascular perfusion}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16702}, year = {1994}, abstract = {The site of confluence of the artery and the portal vein in the liver still appears to be controversial. Anatomical studies suggested a presinusoidal or an intrasinusoidal confluence in the first, second or even final third of the sinusoids. The objective of this investigation was to study the problem with functional biochemical techniques. Rat livers were perfused through the hepatic artery and simultaneously either in the orthograde direction from the portal vein to the hepatic vein or in the retrograde direction from the hepatic vein to the portal vein. Arterial how was linearly dependent on arterial pressure between 70 cm H2O and 120 cm H2O at a constant portal or hepatovenous pressure of 18 cm H2O. An arterial pressure of 100 cm H2O was required for the maintenance of a homogeneous orthograde perfusion of the whole parenchyma and of a physiologic ratio of arterial to portal how of about 1:3. Glucagon was infused either through the artery or the portal vein and hepatic vein, respectively, to a submaximally effective ''calculated'' sinusoidal concentration after mixing of 0.1 nmol/L. During orthograde perfusions, arterial and portal glucagon caused the same increases in glucose output. Yet during retrograde perfusions, hepatovenous glucagon elicited metabolic alterations equal to those in orthograde perfusions, whereas arterial glucagon effected changes strongly reduced to between 10\% and 50\%. Arterially infused trypan blue was distributed homogeneously in the parenchyma during orthograde perfusions, whereas it reached clearly smaller areas of parenchyma during retrograde perfusions. Finally, arterially applied acridine orange was taken up by all periportal hepatocytes in the proximal half of the acinus during orthograde perfusions but only by a much smaller portion of periportal cells in the proximal third of the acinus during retrograde perfusions. These findings suggest that in rat liver, the hepatic artery and the portal vein mix before and within the first third of the sinusoids, rather than in the middle or even last third.}, language = {en} } @phdthesis{Imranulhaq2008, author = {Imran ul-haq, Muhammad}, title = {Synthesis of fluorinated polymers in supercritical carbon dioxide (scCO₂)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-19868}, school = {Universit{\"a}t Potsdam}, year = {2008}, abstract = {For the first time stabilizer-free vinylidene fluoride (VDF) polymerizations were carried out in homogeneous phase with supercritical CO₂. Polymerizations were carried out at 140°C, 1500 bar and were initiated with di-tert-butyl peroxide (DTBP). In-line FT-NIR (Fourier Transform- Near Infrared) spectroscopy showed that complete monomer conversion may be obtained. Molecular weights were determined via size-exclusion chromatography (SEC) and polymer end group analysis by 1H-NMR spectroscopy. The number average molecular weights were below 104 g∙mol-1 and polydispersities ranged from 3.1 to 5.7 depending on DTBP and VDF concentration. To allow for isothermal reactions high CO₂ contents ranging from 61 to 83 wt.\% were used. The high-temperature, high-pressure conditions were required for homogeneous phase polymerization. These conditions did not alter the amount of defects in VDF chaining. Scanning electron microscopy (SEM) indicated that regular stack-type particles were obtained upon expansion of the homogeneous polymerization mixture. To reduce the required amount of initiator, further VDF polymerizations using chain transfer agents (CTAs) to control molecular weights were carried out in homogeneous phase with supercritical carbon dioxide (scCO₂) at 120 °C and 1500 bar. Using perfluorinated hexyl iodide as CTA, polymers of low polydispersity ranging from 1.5 to 1.2 at the highest iodide concentration of 0.25 mol·L-1 were obtained. Electrospray ionization- mass spectroscopy (ESI-MS) indicates the absence of initiator derived end groups, supporting livingness of the system. The "livingness" is based on the labile C-I bond. However, due to the weakness of the C-I bond perfluorinated hexyl iodide also contributes to initiation. To allow for kinetic analyses of VDF polymerizations the CTA should not contribute to initiation. Therefore, additional CTAs were applied: BrCCl3, C6F13Br and C6F13H. It was found that C6F13H does not contribute to initiation. At 120°C and 1500 bar kp/kt0.5~ 0.64 (L·mol-1·s-1)0.5 was derived. The chain transfer constant (CT) at 120°C has been determined to be 8·10-1, 9·10-2 and 2·10-4 for C6F13I, C6F13Br and C6F13H, respectively. These CT values are associated with the bond energy of the C-X bond. Moreover, the labile C-I bond allows for functionalization of the polymer to triazole end groups applying click reactions. After substitution of the iodide end group by an azide group 1,3 dipolar cycloadditions with alkynes yield polymers with 1,2,3 triazole end groups. Using symmetrical alkynes the reactions may be carried out in the absence of any catalyst. This end-functionalized poly (vinylidene fluoride) (PVDF) has higher thermal stability as compared to the normal PVDF. PVDF samples from homogeneous phase polymerizations in supercritical CO₂ and subsequent expansion to ambient conditions were analyzed with respect to polymer end groups, crystallinity, type of polymorphs and morphology. Upon expansion the polymer was obtained as white powder. Scanning electron microscopy (SEM) showed that DTBP derived polymer end groups led to stack-type particles whereas sponge- or rose-type particles were obtained in case of CTA fragments as end groups. Fourier-Transform Infrared spectroscopy and wide angle X-ray diffraction indicated that the type of polymorph, α or β crystal phase was significantly affected by the type of end group. The content of β-phase material, which is responsible for piezoelectricity of PVDF, is the highest for polymer with DTBP-derived end groups. In addition, the crystallinity of the material, as determined via differential scanning calorimetry is affected by the end groups and polymer molecular weights. For example, crystallinity ranges from around 26 \% for DTBP-derived end groups to a maximum of 62 \% for end groups originating from perfluorinated hexyl iodide for polymers with Mn ~2200 g·mol-1. Expansion of the homogeneous polymerization mixture results in particle formation by a non-optimized RESS (Rapid Expansion from Supercritical Solution) process. Thus, it was tested how polymer end groups affect the particles size distribution obtained from RESS process under controlled conditions (T = 50°C and P = 200 bar). In all RESS experiments, small primary PVDF with diameters less than 100 nm without the use of liquid solvents, surfactants, or other additives were produced. A strong correlation between particle size and particle size distribution with polymer end groups and molecular weight of the original material was observed. The smallest particles were found for RESS of PVDF with Mn~ 4000 g·mol-1 and PFHI (C6F13I) - derived end groups.}, language = {en} } @phdthesis{Mueller2008, author = {M{\"u}ller, Melanie J. I.}, title = {Bidirectional transport by molecular motors}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18715}, school = {Universit{\"a}t Potsdam}, year = {2008}, abstract = {In biological cells, the long-range intracellular traffic is powered by molecular motors which transport various cargos along microtubule filaments. The microtubules possess an intrinsic direction, having a 'plus' and a 'minus' end. Some molecular motors such as cytoplasmic dynein walk to the minus end, while others such as conventional kinesin walk to the plus end. Cells typically have an isopolar microtubule network. This is most pronounced in neuronal axons or fungal hyphae. In these long and thin tubular protrusions, the microtubules are arranged parallel to the tube axis with the minus ends pointing to the cell body and the plus ends pointing to the tip. In such a tubular compartment, transport by only one motor type leads to 'motor traffic jams'. Kinesin-driven cargos accumulate at the tip, while dynein-driven cargos accumulate near the cell body. We identify the relevant length scales and characterize the jamming behaviour in these tube geometries by using both Monte Carlo simulations and analytical calculations. A possible solution to this jamming problem is to transport cargos with a team of plus and a team of minus motors simultaneously, so that they can travel bidirectionally, as observed in cells. The presumably simplest mechanism for such bidirectional transport is provided by a 'tug-of-war' between the two motor teams which is governed by mechanical motor interactions only. We develop a stochastic tug-of-war model and study it with numerical and analytical calculations. We find a surprisingly complex cooperative motility behaviour. We compare our results to the available experimental data, which we reproduce qualitatively and quantitatively.}, language = {en} } @misc{KoechyMathajJeltschetal.2008, author = {K{\"o}chy, Martin and Mathaj, Martin and Jeltsch, Florian and Malkinson, Dan}, title = {Resilience of stocking capacity to changing climate in arid to Mediterranean landscapes}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18720}, year = {2008}, abstract = {Small livestock is an important resource for rural human populations in dry climates. How strongly will climate change affect the capacity of the rangeland? We used hierarchical modelling to scale quantitatively the growth of shrubs and annual plants, the main food of sheep and goats, to the landscape extent in the eastern Mediterranean region. Without grazing, productivity increased in a sigmoid way with mean annual precipitation. Grazing reduced productivity more strongly the drier the landscape. At a point just under the stocking capacity of the vegetation, productivity declined precipitously with more intense grazing due to a lack of seed production of annuals. We repeated simulations with precipitation patterns projected by two contrasting IPCC scenarios. Compared to results based on historic patterns, productivity and stocking capacity did not differ in most cases. Thus, grazing intensity remains the stronger impact on landscape productivity in this dry region even in the future.}, language = {en} } @misc{ChampagnatRoelly2008, author = {Champagnat, Nicolas and Roelly, Sylvie}, title = {Limit theorems for conditioned multitype Dawson-Watanabe processes and Feller diffusions}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18610}, year = {2008}, abstract = {A multitype Dawson-Watanabe process is conditioned, in subcritical and critical cases, on non-extinction in the remote future. On every finite time interval, its distribution is absolutely continuous with respect to the law of the unconditioned process. A martingale problem characterization is also given. Several results on the long time behavior of the conditioned mass process - the conditioned multitype Feller branching diffusion - are then proved. The general case is first considered, where the mutation matrix which models the interaction between the types, is irreducible. Several two-type models with decomposable mutation matrices are analyzed too .}, language = {en} } @phdthesis{Schroeder2007, author = {Schr{\"o}der, Birgit Eva}, title = {Spatial and temporal dynamics of the terrestrial carbon cycle : assimilation of two decades of optical satellite data into a process-based global vegetation model}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17596}, school = {Universit{\"a}t Potsdam}, year = {2007}, abstract = {This PhD thesis presents the spatio-temporal distribution of terrestrial carbon fluxes for the time period of 1982 to 2002 simulated by a combination of the process-based dynamic global vegetation model LPJ and a 21-year time series of global AVHRR-fPAR data (fPAR - fraction of photosynthetically active radiation). Assimilation of the satellite data into the model allows improved simulations of carbon fluxes on global as well as on regional scales. As it is based on observed data and includes agricultural regions, the model combined with satellite data produces more realistic carbon fluxes of net primary production (NPP), soil respiration, carbon released by fire and the net land-atmosphere flux than the potential vegetation model. It also produces a good fit to the interannual variability of the CO2 growth rate. Compared to the original model, the model with satellite data constraint produces generally smaller carbon fluxes than the purely climate-based stand-alone simulation of potential natural vegetation, now comparing better to literature estimates. The lower net fluxes are a result of a combination of several effects: reduction in vegetation cover, consideration of human influence and agricultural areas, an improved seasonality, changes in vegetation distribution and species composition. This study presents a way to assess terrestrial carbon fluxes and elucidates the processes contributing to interannual variability of the terrestrial carbon exchange. Process-based terrestrial modelling and satellite-observed vegetation data are successfully combined to improve estimates of vegetation carbon fluxes and stocks. As net ecosystem exchange is the most interesting and most sensitive factor in carbon cycle modelling and highly uncertain, the presented results complementary contribute to the current knowledge, supporting the understanding of the terrestrial carbon budget.}, language = {en} } @misc{FayGuillaume2007, author = {Fay, Doris and Guillaume, Yves R. F.}, title = {Team diversity}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18295}, year = {2007}, abstract = {Team diversity refers to the differences between team members on any attribute that may lead each single member of the group to perceive any other member of the group as being different from the self of this particular member. These attributes and perceptions refer to all dimensions people can differ on, such as age, gender, ethnicity, religious and functional background, personality, skills, abilities, beliefs, and attitudes.}, language = {en} } @misc{FreseGarstFay2007, author = {Frese, Michael and Garst, Harry and Fay, Doris}, title = {Making things happen : reciprocal relationships between work characteristics and personal initiative in a four-wave longitudinal structural equation model}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18278}, year = {2007}, abstract = {The authors used the frameworks of reciprocal determinism and occupational socialization to study the effects of work characteristics (consisting of control and complexity of work) on personal initiative (PI)--mediated by control orientation (a 2nd-order factor consisting of control aspiration, perceived opportunity for control, and self-efficacy) and the reciprocal effects of PI on changes in work characteristics. They applied structural equation modeling to a longitudinal study with 4 measurement waves (N = 268) in a transitional economy: East Germany. Results confirm the model plus 1 additional, nonhypothesized effect. Work characteristics had a synchronous effect on PI via control orientation (full mediation). There were also effects of control orientation and of PI on later changes in work characteristics: As predicted, PI functioned as partial mediator, changing work characteristics in the long term (reciprocal effect); unexpectedly, there was a 2nd reciprocal effect of an additional lagged partial mediation of control orientation on later work characteristics.}, language = {en} } @inproceedings{Reimer2007, author = {Reimer, A.}, title = {Clumping effects on non-thermal particle spectra in massive star systems}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18246}, year = {2007}, abstract = {Observational evidence exists that winds of massive stars are clumped. Many massive star systems are known as non-thermal particle production sites, as indicated by their synchrotron emission in the radio band. As a consequence they are also considered as candidate sites for non-thermal high-energy photon production up to gamma-ray energies. The present work considers the effects of wind clumpiness expected on the emitting relativistic particle spectrum in colliding wind systems, built up from the pool of thermal wind particles through diffusive particle acceleration, and taking into account inverse Compton and synchrotron losses. In comparison to a homogeneous wind, a clumpy wind causes flux variations of the emitting particle spectrum when the clump enters the wind collision region. It is found that the spectral features associated with this variability moves temporally from low to high energy bands with the time shift between any two spectral bands being dependent on clump size, filling factor, and the energy-dependence of particle energy gains and losses.}, language = {en} } @inproceedings{Weis2007, author = {Weis, K.}, title = {Wind relics : clumps, inhomogeneities and outflows in LBV nebulae}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18235}, year = {2007}, abstract = {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.}, language = {en} } @inproceedings{RomeroOwockiAraudoetal.2007, author = {Romero, G. E. and Owocki, S. P. and Araudo, A. T. and Townsend, R. H. D. and Benaglia, P.}, title = {Using gamma-rays to probe the clumped structure of stellar winds}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18210}, year = {2007}, abstract = {Gamma-rays can be produced by the interaction of a relativistic jet and the matter of the stellar wind in the subclass of massive X-ray binaries known as "microquasars". The relativistic jet is ejected from the surroundings of the compact object and interacts with cold protons from the stellar wind, producing pions that then quickly decay into gamma-rays. Since the resulting gamma-ray emissivity depends on the target density, the detection of rapid variability in microquasars with GLAST and the new generation of Cherenkov imaging arrays could be used to probe the clumped structure of the stellar wind. In particular, we show here that the relative fluctuation in gamma rays may scale with the square root of the ratio of porosity length to binary separation, \$\sqrt{h/a}\$, implying for example a ca. 10\% variation in gamma ray emission for a quite moderate porosity, h/a ∼ 0.01.}, language = {en} } @inproceedings{Nielsen2007, author = {Nielsen, K. E.}, title = {On irregular line profiles in the optical spectrum of Eta Carinae}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18227}, year = {2007}, abstract = {The optical spectrum of Eta Carinae (η Car) is prominent in H I, He i and Fe ii wind lines, all of which vary both in absorption and emission with phase. The phase dependance is a consequence of the interaction between the two objects in the η Car binary (η Car A \& B). The binary system is enshrouded by ejecta from previous mass ejection events and consequently, η Car B is not directly observable. We have traced the He i lines over η Car's spectroscopic period, using HST/STIS data obtained with medium spectral, but high angular, resolving power, and created a radial velocity curve for the system. The He I lines are formed in the core of the system, and appear to be a composite of multiple features formed in spatially separated regions. The sources of their irregular line profiles are still not fully understood, but can be attributed to emission/absorption near the wind-wind interface and/or a direct consequence of the η Car A's, massive, clumpy wind. This paper will discuss the spectral variability, the narrow emission structure of the He i lines and how clumpiness of the winds may impede the construction of the reliable radial velocity curve, necessary for characterizations of especially η Car B.}, language = {en} } @inproceedings{Gull2007, author = {Gull, T. R.}, title = {Eta Carinae viewed from different vantages}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18200}, year = {2007}, abstract = {The spatially-resolved winds of the massive binary, Eta Carinae, extend an arcsecond on the sky, well beyond the 10 to 20 milliarcsecond binary orbital dimension. Stellar wind line profiles, observed at very different angular resolutions of VLTI/AMBER, HST/STIS and VLT/UVES, provide spatial information on the extended wind interaction structure as it changes with orbital phase. These same wind lines, observable in the starlight scattered off the foreground lobe of the dusty Homunculus, provide time-variant line profiles viewed from significantly different angles. Comparisons of direct and scattered wind profiles observed in the same epoch and at different orbital phases provide insight on the extended wind structure and promise the potential for three-dimensional imaging of the outer wind structures. Massive, long-lasting clumps, including the nebularWeigelt blobs, originated during the two historical ejection events. Wind interactions with these clumps are quite noticeable in spatially-resolved spectroscopy. As the 2009.0 minimum approaches, analysis of existing spectra and 3-D modeling are providing bases for key observations to gain further understanding of this complex massive binary.}, language = {en} } @inproceedings{Cassinelli2007, author = {Cassinelli, Joseph P.}, title = {Discussion: Magnetic fields, variability}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18195}, year = {2007}, language = {en} } @inproceedings{ReimerAharonianHintonetal.2007, author = {Reimer, O. and Aharonian, Felix A. and Hinton, J. and Hofmann, W. and Hoppe, S. and Raue, M. and Reimer, A.}, title = {VHE gamma-rays from Westerlund 2 and implications for the inferred energetics}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18172}, year = {2007}, abstract = {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.}, language = {en} } @inproceedings{Kholtygin2007, author = {Kholtygin, A. F.}, title = {Modelling the induced clumping stochastic line profile variability}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18180}, year = {2007}, abstract = {We model the line profile variability (lpv) in spectra of clumped stellar atmospheres using the Stochastic Clump Model (SCM) of the winds of early-type stars. In this model the formation of dense inhomogeneities (clumps) in the line driven winds is considered as being a stochastic process. It is supposed that the emission due to clumps mainly contributes to the intensities of emission lines in the stellar spectra. It is shown that in the framework of the SCM it is possible to reproduce both the mean line profiles and a common pattern of the lpv.}, language = {en} } @inproceedings{CheneMoffatCrowther2007, author = {Chen{\´e}, A.-N. and Moffat, Anthony F. J. and Crowther, P. A.}, title = {Rapidly accelerating clumps in the winds of the very hot WNE Stars}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18163}, year = {2007}, abstract = {We study the time variability of emission lines in three WNE stars : WR 2 (WN2), WR 3 (WN3ha) and WR152 (WN3). While WR 2 shows no variability above the noise level, the other stars do show variation, which are like other WR stars in WR 152 but very fast in WR 3. From these motions, we deduce a value of β ∼1 for WR 3 that is like that seen in O stars and β ∼2-3 for WR 152, that is intermediate between other WR stars and WR 3.}, language = {en} } @inproceedings{StLouis2007, author = {St-Louis, N.}, title = {Discussion: Binaries, colliding winds, LBVs and high energy radiation}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18155}, year = {2007}, abstract = {Clumping in hot-star winds : proceedings of an international workshop held in Potsdam, Germany, 18. - 22. June 2007}, language = {en} } @inproceedings{Szeifert2007, author = {Szeifert, T.}, title = {Wind variabilities and asymmetries in Luminous Blue Variables}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18146}, year = {2007}, abstract = {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}, language = {en} } @inproceedings{MorrisonRotherKurschat2007, author = {Morrison, N. D. and Rother, R. and Kurschat, N.}, title = {Hα line profile variability in the B8Ia-type supergiant Rigel (β Ori)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18120}, year = {2007}, abstract = {Hα observations of Rigel obtained on 184 nights during the past ten years with the 1-m telescope and ´echelle spectrograph of Ritter Observatory are surveyed. The line profiles were classified in terms of morphology. About 1/4 of them are of P Cygni type, about 15\% inverse P Cygni, about 25\% double-peaked, about 1/3 pure absorption, and a few are single emission lines. Transformation of the profile from one type to another typically takes a few days. Although the line stays in absorption for extended intervals, only one high-velocity absorption event of the intensity reported by Kaufer et al. (1996a) was observed, in late 2006. Late in this event, Hα absorption occurred farther to the red than the red wing of a plausible photospheric absorption component, an indication of infalling material. In general, as the absorption events come to an end, the emission typically returns with an inverse P Cygni profile. The Hα profile class shows no obvious correlation with the radial velocity of C II λ6578, a photospheric absorption line.}, language = {en} } @inproceedings{CohenLeuteneggerTownsend2007, author = {Cohen, David H. and Leutenegger, M. A. and Townsend, R. H. D.}, title = {Quantitative analysis of resolved X-ray emission line profiles of O stars}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18115}, year = {2007}, abstract = {By quantitatively fitting simple emission line profile models that include both atomic opacity and porosity to the Chandra X-ray spectrum of ζ Pup, we are able to explore the trade-offs between reduced mass-loss rates and wind porosity. We find that reducing the mass-loss rate of ζ Pup by roughly a factor of four, to 1.5 × 10-6 M⊙ yr-1, enables simple non-porous wind models to provide good fits to the data. If, on the other hand, we take the literature mass-loss rate of 6×10-6 M⊙ yr-1, then to produce X-ray line profiles that fit the data, extreme porosity lengths - of h∞ ≈ 3 R∗ - are required. Moreover, these porous models do not provide better fits to the data than the non-porous, low optical depth models. Additionally, such huge porosity lengths do not seem realistic in light of 2-D numerical simulations of the wind instability.}, language = {en} } @inproceedings{Blomme2007, author = {Blomme, R.}, title = {Corotating Interaction Regions and clumping}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18100}, year = {2007}, abstract = {We present hydrodynamical models for Corotating Interaction Regions, which were used by Lobel (2007) to model the Discrete Absorption Components in HD 64760. We also discuss our failure to model the rotational modulations seen in the same star.}, language = {en} } @inproceedings{MassaPrinjaFullerton2007, author = {Massa, D. L. and Prinja, R. K. and Fullerton, A. W.}, title = {The effects of clumping on wind line variability}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18095}, year = {2007}, abstract = {We review the effects of clumping on the profiles of resonance doublets. By allowing the ratio of the doublet oscillator strenghts to be a free parameter, we demonstrate that doublet profiles contain more information than is normally utilized. In clumped (or porous) winds, this ratio can lies between unity and the ratio of the f-values, and can change as a function of velocity and time, depending on the fraction of the stellar disk that is covered by material moving at a particular velocity at a given moment. Using these insights, we present the results of SEI modeling of a sample of B supergiants, ζ Pup and a time series for a star whose terminal velocity is low enough to make the components of its Si VIλλ1400 independent. These results are interpreted within the framewrok of the Oskinova et al. (2007) model, and demonstrate how the doublet profiles can be used to extract infromation about wind structure.}, language = {en} } @inproceedings{LeuteneggerCohenKahnetal.2007, author = {Leutenegger, M. A. and Cohen, David H. and Kahn, S. M. and Owocki, S. P. and Paerels, F. B. S.}, title = {Resonance scattering in the X-ray emission lines profiles of ζ Puppis}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18085}, year = {2007}, abstract = {We present XMM-Newton Reflection Grating Spectrometer observations of pairs of X-ray emission line profiles from the O star ζ Pup that originate from the same He-like ion. The two profiles in each pair have different shapes and cannot both be consistently fit by models assuming the same wind parameters. We show that the differences in profile shape can be accounted for in a model including the effects of resonance scattering, which affects the resonance line in the pair but not the intercombination line. This implies that resonance scattering is also important in single resonance lines, where its effect is difficult to distinguish from a low effective continuum optical depth in the wind. Thus, resonance scattering may help reconcile X-ray line profile shapes with literature mass-loss rates.}, language = {en} } @inproceedings{SchnerrHenrichs2007, author = {Schnerr, R. S. and Henrichs, H. F.}, title = {Magnetic fields and wind variability in massive stars}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18075}, year = {2007}, abstract = {This paper describes the thesis work of Schnerr (2007) entitled "Magnetic fields and mass loss in massive stars", which aimed at a better understanding of the impact of magnetic fields on the winds of massive stars.}, language = {en} } @inproceedings{IgnaceGayley2007, author = {Ignace, R. and Gayley, K. G.}, title = {Circumstellar Magnetic Field Diagnostics from Line Polarization}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18066}, year = {2007}, language = {en} } @inproceedings{CassinelliIgnaceWaldronetal.2007, author = {Cassinelli, Joseph P. and Ignace, R. and Waldron, W. and Cho, J. and Murphy, N. and Lazarian, A.}, title = {X-ray line emission produced in clump bow shocks}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18057}, year = {2007}, abstract = {We summarize Chandra observations of the emission line profiles from 17 OB stars. The lines tend to be broad and unshifted. The forbidden/intercombination line ratios arising from Helium-like ions provide radial distance information for the X-ray emission sources, while the H-like to He-like line ratios provide X-ray temperatures, and thus also source temperature versus radius distributions. OB stars usually show power law differential emission measure distributions versus temperature. In models of bow shocks, we find a power law differential emission measure, a wide range of ion stages, and the bow shock flow around the clumps provides transverse velocities comparable to HWHM values. We find that the bow shock results for the line profile properties, consistent with the observations of X-ray line emission for a broad range of OB star properties.}, language = {en} } @inproceedings{Vink2007, author = {Vink, J. S.}, title = {Discussion: Hydrodynamic modeling}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18046}, year = {2007}, language = {en} } @inproceedings{Runacres2007, author = {Runacres, M. C.}, title = {Hydrodynamical models of clumping beyond 50 R∗}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18030}, year = {2007}, abstract = {We present one-dimensional, time-dependent models of the clumps generated by the linedeshadowing instability. In order to follow the clumps out to distances of more than 1000 R∗, we use an efficient moving-box technique. We show that, within the approximations, the wind can remain clumped well into the formation region of the radio continuum.}, language = {en} } @inproceedings{WalterZuritaHerasLeyder2007, author = {Walter, R. and Zurita-Heras, J. and Leyder, J.-C.}, title = {Probing clumpy stellar winds with a neutron star}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18024}, year = {2007}, abstract = {INTEGRAL tripled the number of super-giant high-mass X-ray binaries (sgHMXB) known in the Galaxy by revealing absorbed and fast transient (SFXT) systems. Quantitative constraints on the wind clumping of massive stars can be obtained from the study of the hard X-ray variability of SFXT. A large fraction of the hard X-ray emission is emitted in the form of flares with a typical duration of 3 ksec, frequency of 7 days and luminosity of \$10^{36}\$ erg/s. Such flares are most probably emitted by the interaction of a compact object orbiting at \$\sim10~R_*\$ with wind clumps (\$10^{22 ... 23}\$ g) representing a large fraction of the stellar mass-loss rate. The density ratio between the clumps and the inter-clump medium is \$10^{2 ... 4}\$. The parameters of the clumps and of the inter-clump medium, derived from the SFXT flaring behavior, are in good agreement with macro-clumping scenario and line-driven instability simulations. SFXT are likely to have larger orbital radius than classical sgHMXB.}, language = {en} } @inproceedings{udDoula2007, author = {ud-Doula, A.}, title = {Large-scale wind structure due to magnetic fields}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18010}, year = {2007}, abstract = {Magnetic fields influence the dynamics of hot-star winds and create large scale structure. Based on numerical magnetohydrodynamic (MHD) simulations, we model the wind of θ¹ Ori C, and then use the SEI method to compute synthetic line profiles for a range of viewing angles as function of rotational phase. The resulting dynamic spectrum for a moderately strong line shows a distinct modulation, but with a phase that seems at odds with available observations.}, language = {en} } @inproceedings{Puls2007, author = {Puls, Joachim}, title = {Discussion : X-rays}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18000}, year = {2007}, abstract = {Clumping in hot-star winds : proceedings of an international workshop held in Potsdam, Germany, 18. - 22. June 2007}, language = {en} } @inproceedings{Owocki2007, author = {Owocki, S. P.}, title = {Dynamical simulation of the "velocity-porosity" reduction in observed strength of stellar wind lines}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17992}, year = {2007}, abstract = {I use dynamical simulations of the line-driven instability to examine the potential role of the resulting flow structure in reducing the observed strength of wind absorption lines. Instead of the porosity length formalism used to model effects on continuum absorption, I suggest reductions in line strength can be better characterized in terms of a velocity clumping factor that is insensitive to spatial scales. Examples of dynamic spectra computed directly from instability simulations do exhibit a net reduction in absorption, but only at a modest 10-20\% level that is well short of the ca. factor 10 required by recent analyses of PV lines.}, language = {en} } @inproceedings{Sonneborn2007, author = {Sonneborn, G.}, title = {Imaging and spectroscopy with the James Webb Space Telescope}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17983}, year = {2007}, abstract = {The James Webb Space Telescope (JWST) is a large, infrared-optimized space telescope scheduled for launch in 2013. JWST will find the first stars and galaxies that formed in the early universe, connecting the Big Bang to our own Milky Way galaxy. JWST will peer through dusty clouds to see stars forming planetary systems, connecting the MilkyWay to our own Solar System. JWST's instruments are designed to work primarily in the infrared range of 1 - 28 μm, with some capability in the visible range. JWST will have a large mirror, 6.5 m in diameter, and will be diffraction-limited at 2 μm (0.1 arcsec resolution). JWST will be placed in an L2 orbit about 1.5 million km from the Earth. The instruments will provide imaging, coronography, and multi-object and integral-field spectroscopy across the 1 - 28 μm wavelength range. The breakthrough capabilities of JWST will enable new studies of massive star winds from the Milky Way to the early universe.}, language = {en} } @inproceedings{MoffatHillierHamannetal.2007, author = {Moffat, Anthony F. J. and Hillier, D. J. and Hamann, Wolf-Rainer and Owocki, S. P.}, title = {General Discussion}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17953}, year = {2007}, abstract = {Clumping in hot-star winds : proceedings of an international workshop held in Potsdam, Germany, 18. - 22. June 2007}, language = {en} } @inproceedings{KrtičkaPulsKubat2007, author = {Krtička, Jiri and Puls, Joachim and Kub{\´a}t, Jiř{\´i}}, title = {The influence of clumping on predicted O star wind parameters}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17969}, year = {2007}, abstract = {We study the influence of clumping on the predicted wind structure of O-type stars. For this purpose we artificially include clumping into our stationary wind models. When the clumps are assumed to be optically thin, the radiative line force increases compared to corresponding unclumped models, with a similar effect on either the mass-loss rate or the terminal velocity (depending on the onset of clumping). Optically thick clumps, alternatively, might be able to decrease the radiative force.}, language = {en} } @inproceedings{VinkBenagliaDaviesetal.2007, author = {Vink, J. S. and Benaglia, P. and Davies, B. and de Koter, A. and Oudmaijer, R. D.}, title = {Advances in mass-loss predictions}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17948}, year = {2007}, abstract = {We present the results of Monte Carlo mass-loss predictions for massive stars covering a wide range of stellar parameters. We critically test our predictions against a range of observed massloss rates - in light of the recent discussions on wind clumping. We also present a model to compute the clumping-induced polarimetric variability of hot stars and we compare this with observations of Luminous Blue Variables, for which polarimetric variability is larger than for O and Wolf-Rayet stars. Luminous Blue Variables comprise an ideal testbed for studies of wind clumping and wind geometry, as well as for wind strength calculations, and we propose they may be direct supernova progenitors.}, language = {en} } @inproceedings{DaviesVinkOudmaijer2007, author = {Davies, B. and Vink, J. S. and Oudmaijer, R. D.}, title = {Modelling the polarimetric variability of hot stars}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17939}, year = {2007}, abstract = {Many hot stars exhibit stochastic polarimetric variability, thought to arise from clumping low in the wind. Here we investigate the wind properties required to reproduce this variability using analytic models, with particular emphasis on Luminous Blue Variables. We find that the winds must be highly structured, consisting of a large number of optically-thin clumps; while we find that the overall level of polarization should scale with mass-loss rate - consistent with observations of LBVs. The models also predict variability on very short timescales, which is supported by the results of a recent polarimetric monitoring campaign.}, language = {en} } @inproceedings{Fullerton2007, author = {Fullerton, A. W.}, title = {Discussion: Spectral modeling}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17917}, year = {2007}, language = {en} } @inproceedings{Hillier2007, author = {Hillier, D. J.}, title = {On the influence of clumping on O and Wolf-Rayet spectra}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17903}, year = {2007}, abstract = {Overwhelming observational and theoretical evidence suggests that the winds of massive stars are highly clumped. We briefly discuss the influence of clumping on model diagnostics and the difficulties of allowing for the influence of clumping on model spectra. Because of its simplicity, and because of computational ease, most spectroscopic analyses incorporate clumping using the volume filling factor. The biases introduced by this approach are uncertain. To investigate alternative clumping models, and to help determine the validity of parameters derived using the volume filling factor method, we discuss results derived using an alternative model in which we assume that the wind is composed of optically thick shells.}, language = {en} } @inproceedings{IpingSonnebornMassaetal.2007, author = {Iping, R.C. and Sonneborn, G. and Massa, D.L. and Gies, D. and Williams, Simon E.}, title = {Far-ultraviolet spectroscopy of O+O binaries in the Magellanic Clouds}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17896}, year = {2007}, abstract = {We report FUSE observations in 2005-2006 of three O-type, double-lined spectroscopic binaries in the Magellanic Clouds. The systems have very short periods (1.4-2.25 d), represent rare, young evolutionary stages of massive stars and binaries, and provide a unique glimpse at some of the most massive systems that form in dense clusters of massive stars. Improved orbit parameters, including revised masses, for LH54-425 are derived from new ctio spectroscopy. The systems are: LH54-425 in the LMC (O3V + O5V, P=2.25d, 62+37M⊙), J053441-693139 in the LMC (O2-3If+O6V, P=1.4 d, 41+27M⊙), and Hodge 53-47 in the SMC (O6V + O4-5IIIf, P=2.2 d, 24+14M⊙, where the O4 star appears to be less massive than the O6 star). Their short periods indicates that wind interaction and mass transfer are likely important factors in their evolution. The spectra provide quantitative and systematic studies of phase-dependent stellar wind properties, wind collision effects in O+O binaries at lower metallicities, improved radial velocity curves, and FUV spectro-photometric changes as a function of orbital phase.}, language = {en} } @inproceedings{SchnurrCrowther2007, author = {Schnurr, O. and Crowther, P. A.}, title = {Mid-IR observations of WC stars, and the connection to wind clumping}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17884}, year = {2007}, abstract = {We present preliminary results of a tailored atmosphere analysis of six Galactic WC stars using UV, optical, and mid-infrared Spitzer IRS data. With these data, we are able to sample regions from 10 to 10³ stellar radii, thus to determine wind clumping in different parts of the wind. Ultimately, derived wind parameters will be used to accuratelymeasure neon abundances, and to so test predicted nuclear-reaction rates.}, language = {en} }