TY - THES A1 - Wenk, Sebastian T1 - Engineering formatotrophic growth in Escherichia coli N2 - To meet the demands of a growing world population while reducing carbon dioxide (CO2) emissions, it is necessary to capture CO2 and convert it into value-added compounds. In recent years, metabolic engineering of microbes has gained strong momentum as a strategy for the production of valuable chemicals. As common microbial feedstocks like glucose directly compete with human consumption, the one carbon (C1) compound formate was suggested as an alternative feedstock. Formate can be easily produced by various means including electrochemical reduction of CO2 and could serve as a feedstock for microbial production, hence presenting a novel entry point for CO2 to the biosphere and a storage option for excess electricity. Compared to the gaseous molecule CO2, formate is a highly soluble compound that can be easily handled and stored. It can serve as a carbon and energy source for natural formatotrophs, but these microbes are difficult to cultivate and engineer. In this work, I present the results of several projects that aim to establish efficient formatotrophic growth of E. coli – which cannot naturally grow on formate – via synthetic formate assimilation pathways. In the first study, I establish a workflow for growth-coupled metabolic engineering of E. coli. I demonstrate this approach by presenting an engineering scheme for the PFL-threonine cycle, a synthetic pathway for anaerobic formate assimilation in E. coli. The described methods are intended to create a standardized toolbox for engineers that aim to establish novel metabolic routes in E. coli and related organisms. The second chapter presents a study on the catalytic efficiency of C1-oxidizing enzymes in vivo. As formatotrophic growth requires generation of both energy and biomass from formate, the engineered E. coli strains need to be equipped with a highly efficient formate dehydrogenase, which provides reduction equivalents and ATP for formate assimilation. I engineered a strain that cannot generate reducing power and energy for cellular growth, when fed on acetate. Under this condition, the strain depends on the introduction of an enzymatic system for NADH regeneration, which could further produce ATP via oxidative phosphorylation. I show that the strain presents a valuable testing platform for C1-oxidizing enzymes by testing different NAD-dependent formate and methanol dehydrogenases in the energy auxotroph strain. Using this platform, several candidate enzymes with high in vivo activity, were identified and characterized as potential energy-generating systems for synthetic formatotrophic or methylotrophic growth in E. coli.   In the third chapter, I present the establishment of the serine threonine cycle (STC) – a synthetic formate assimilation pathway – in E. coli. In this pathway, formate is assimilated via formate tetrahydrofolate ligase (FtfL) from Methylobacterium extorquens (M. extorquens). The carbon from formate is attached to glycine to produce serine, which is converted into pyruvate entering central metabolism. Via the natural threonine synthesis and cleavage route, glycine is regenerated and acetyl-CoA is produced as the pathway product. I engineered several selection strains that depend on different STC modules for growth and determined key enzymes that enable high flux through threonine synthesis and cleavage. I could show that expression of an auxiliary formate dehydrogenase was required to achieve growth via threonine synthesis and cleavage on pyruvate. By overexpressing most of the pathway enzymes from the genome, and applying adaptive laboratory evolution, growth on glycine and formate was achieved, indicating the activity of the complete cycle. The fourth chapter shows the establishment of the reductive glycine pathway (rGP) – a short, linear formate assimilation route – in E. coli. As in the STC, formate is assimilated via M. extorquens FtfL. The C1 from formate is condensed with CO2 via the reverse reaction of the glycine cleavage system to produce glycine. Another carbon from formate is attached to glycine to form serine, which is assimilated into central metabolism via pyruvate. The engineered E. coli strain, expressing most of the pathway genes from the genome, can grow via the rGP with formate or methanol as a sole carbon and energy source. N2 - Um den steigenden Bedarf einer wachsenden Weltbevölkerung zu decken und gleichzeitig die CO2-Emissionen zu reduzieren, ist es notwendig, CO2 aufzufangen und zu recyceln. Durch gentechnische Veränderungen von Mikroorganismen ist es möglich diese zur Produktion wertvoller organischer Verbindungen zu nutzen. Da mikrobielle Kulturen primär mit Glucose gefüttert werden und somit mit menschlicher Nahrungsversorgung konkurrieren, wurde die C1-Verbindung Formiat als alternativer bakterieller Nährstoff vorgeschlagen.. Formiat kann durch unterschiedliche Verfahren hergestellt werden, unter anderem durch elektrochemische Reduktion von CO2. Dieses Verfahren ermöglicht das Recycling von CO2 und weiterhin eine Speichermöglichkeit für überschüssige Elektrizität. Formiat ist im Vergleich zum gasförmigen CO2 gut wasserlöslich, was den Transport und die Verwendung als mikrobiellen Nährstoff erleichtert. Natürlich vorkommende formatotrophe Mikroorganismen nutzen Formiat als Kohlenstoff- und Energiequelle. Diese lassen sich allerdings meist schwierig kultivieren und genetisch verändern. In dieser Arbeit stelle ich die Ergebnisse verschiedener Projekte vor, die gemeinsam darauf abzielen, effizientes formatotrophes Wachstum von E. coli – welches natürlicherweise nicht auf Formiat wachsen kann – mittels synthetischer Formiat-Assimilierungswege zu ermöglichen. In der ersten Studie stelle ich eine Strategie für wachstumsgekoppeltes Stoffwechsel-Engineering in E. coli vor. Ich erläutere diese Strategie anhand eines Beispiels, der schrittweisen Etablierung eines synthetischen Formiat- Assimilierungswegs, des PFL-Threonin-Zyklus. Die in diesem Kapitel beschriebenen Methoden sollen einen Leitfaden für Ingenieure bereitstellen, die neue Stoffwechselwege in E. coli und verwandten Organismen etablieren wollen. Im zweiten Kapitel stelle ich eine Studie über die katalytische Effizienz von C1-oxidierenden Enzymen vor. Da formatotrophes Wachstum sowohl die Erzeugung von Energie als auch von Biomasse aus Formiat erfordert, müssen synthetisch formatotrophe E. coli Stämme mit einer hocheffizienten Formiat-Dehydrogenase ausgestattet werden, welche Reduktionsäquivalente und ATP für die Assimilierung von Formiat liefert. Um die Effizienz verschiedener Enzyme testen und vergleichen zu können, entwickelte ich einen E. coli Stamm, der aus Acetat weder Reduktionsäquivalente noch Energie für das Zellwachstum erzeugen kann. Dieser „energie-auxotrophe“ Stamm benötigt eines zusätzlichen enzymatischen Systems zur NADH-Regenerierung, um auf Acetat wachsen zu können. Ich testete verschiedene NAD-abhängige Formiat- und Methanol-Dehydrogenasen in diesem Stamm und konnte zeigen, dass Wachstum auf Acetat durch Zugabe von Formiat oder Methanol ermöglicht wurde. Dies zeigt, dass der Stamm eine zuverlässige Testplattform für C1-oxidierende Enzyme darstellt. Unter Verwendung dieser Plattform wurden mehrere Kandidatenenzyme mit hoher in vivo-Aktivität identifiziert und als Kandidatenenzyme für synthetisches formatotrophes oder methylotrophes Wachstum in E. coli charakterisiert.   Im dritten Kapitel stelle ich die Etablierung des Serin-Threonin-Zyklus (STZ) – eines synthetischen Formiat-Assimilationswegs – in E. coli vor. In diesem Stoffwechselweg wird Formiat über die Formiat-Tetrahydrofolat-Ligase (FtfL) aus Methylobacterium extorquens (M. extorquens) assimiliert. Der Kohlenstoff aus Formiat wird an Glycin gebunden, um Serin zu produzieren, welches im nächsten Schritt in Pyruvat umgewandelt wird und so in den zentralen Kohlenstoffmetabolismus gelangt. Über den natürlichen Threonin-Synthese- und Spaltweg wird Glycin regeneriert und Acetyl-CoA als Produkt des Stoffwechselwegs generiert. Ich entwickelte mehrere E. coli Selektionsstämme, deren Wachstum von verschiedenen STZ-Modulen abhängt, und konnte Schlüsselenzyme bestimmen, die einen hohen Reaktionsfluss durch die Threonin-Synthese und -Spaltung ermöglichen. Ich konnte zeigen, dass die Expression einer Formiat-Dehydrogenase erforderlich ist, um Wachstum auf Pyruvat über Threonin zu erreichen. Durch Integration und Überexpression der meisten Enzyme des STZ auf Genomebene und Anwendung adaptiver Laborevolution wurde Wachstum auf Glycin und Formiat erreicht, was bedeutet, dass der gesamte Serin-Threonin-Zyklus in E. coli aktiv ist. Das vierte Kapitel zeigt die Etablierung des reduktiven Glycinwegs (rGW) – eines kurzen, linearen Formiat-Assimilierungswegs – in E. coli. Wie im STZ wird Formiat über M. extorquens FtfL assimiliert. Dabei wird das Kohlenstoffatom aus Formiat mit CO2 über die umgekehrte Reaktion des Glycin-Spaltungssystems zu Glycin kondensiert. Ein weiteres Kohlenstoffatom aus Formiat wird an Glycin gebunden, um Serin zu bilden, welches über Pyruvat in den Zentralstoffwechsel gelangt. Durch Expression der rGW Enzyme auf Genomebene und adaptive Laborevolution wurde ein E. coli Stamm erzeugt welcher über den rGW auf Formiat oder Methanol als einziger Kohlenstoff- und Energiequelle wachsen kann. KW - metabolic engineering KW - E. coli KW - formate assimilation KW - methanol assimilation KW - energy metabolism Y1 - 2020 ER - TY - JOUR A1 - Tofelde, Stefanie A1 - Bufe, Aaron A1 - Turowski, Jens M. T1 - Hillslope Sediment Supply Limits Alluvial Valley Width JF - AGU Advances N2 - River-valley morphology preserves information on tectonic and climatic conditions that shape landscapes. Observations suggest that river discharge and valley-wall lithology are the main controls on valley width. Yet, current models based on these observations fail to explain the full range of cross-sectional valley shapes in nature, suggesting hitherto unquantified controls on valley width. In particular, current models cannot explain the existence of paired terrace sequences that form under cyclic climate forcing. Paired river terraces are staircases of abandoned floodplains on both valley sides, and hence preserve past valley widths. Their formation requires alternating phases of predominantly river incision and predominantly lateral planation, plus progressive valley narrowing. While cyclic Quaternary climate changes can explain shifts between incision and lateral erosion, the driving mechanism of valley narrowing is unknown. Here, we extract valley geometries from climatically formed, alluvial river-terrace sequences and show that across our dataset, the total cumulative terrace height (here: total valley height) explains 90%–99% of the variance in valley width at the terrace sites. This finding suggests that valley height, or a parameter that scales linearly with valley height, controls valley width in addition to river discharge and lithology. To explain this valley-width-height relationship, we reformulate existing valley-width models and suggest that, when adjusting to new boundary conditions, alluvial valleys evolve to a width at which sediment removal from valley walls matches lateral sediment supply from hillslope erosion. Such a hillslope-channel coupling is not captured in current valley-evolution models. Our model can explain the existence of paired terrace sequences under cyclic climate forcing and relates valley width to measurable field parameters. Therefore, it facilitates the reconstruction of past climatic and tectonic conditions from valley topography. Y1 - 2022 U6 - https://doi.org/10.1029/2021AV000641 SN - 2576-604X PB - American Geophysical Union (AGU); Wiley CY - Hoboken, New Jersey, USA ER - TY - JOUR A1 - Miklashevsky, Alex A1 - Fischer, Martin H. A1 - Lindemann, Oliver T1 - Spatial-numerical associations without a motor response? Grip force says ‘Yes’ JF - Acta Psychologica N2 - In numerical processing, the functional role of Spatial-Numerical Associations (SNAs, such as the association of smaller numbers with left space and larger numbers with right space, the Mental Number Line hypothesis) is debated. Most studies demonstrate SNAs with lateralized responses, and there is little evidence that SNAs appear when no response is required. We recorded passive holding grip forces in no-go trials during number processing. In Experiment 1, participants performed a surface numerical decision task (“Is it a number or a letter?”). In Experiment 2, we used a deeper semantic task (“Is this number larger or smaller than five?”). Despite instruction to keep their grip force constant, participants' spontaneous grip force changed in both experiments: Smaller numbers led to larger force increase in the left than in the right hand in the numerical decision task (500–700 ms after stimulus onset). In the semantic task, smaller numbers again led to larger force increase in the left hand, and larger numbers increased the right-hand holding force. This effect appeared earlier (180 ms) and lasted longer (until 580 ms after stimulus onset). This is the first demonstration of SNAs with passive holding force. Our result suggests that (1) explicit motor response is not a prerequisite for SNAs to appear, and (2) the timing and strength of SNAs are task-dependent. (216 words). KW - SNARC KW - Mental number line KW - Number processing KW - Embodied cognition KW - Grip force KW - Motor system Y1 - 2022 U6 - https://doi.org/10.1016/j.actpsy.2022.103791 SN - 1873-6297 VL - 231 SP - 1 EP - 17 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Lindner, Nadja A1 - Moeller, Korbinian A1 - Hildebrandt, Frauke A1 - Hasselhorn, Marcus A1 - Lonnemann, Jan T1 - Children's use of egocentric reference frames in spatial language is related to their numerical magnitude understanding JF - Frontiers in Psychology N2 - Numerical magnitude information is assumed to be spatially represented in the form of a mental number line defined with respect to a body-centred, egocentric frame of reference. In this context, spatial language skills such as mastery of verbal descriptions of spatial position (e.g., in front of, behind, to the right/left) have been proposed to be relevant for grasping spatial relations between numerical magnitudes on the mental number line. We examined 4- to 5-year-old’s spatial language skills in tasks that allow responses in egocentric and allocentric frames of reference, as well as their relative understanding of numerical magnitude (assessed by a number word comparison task). In addition, we evaluated influences of children’s absolute understanding of numerical magnitude assessed by their number word comprehension (montring different numbers using their fingers) and of their knowledge on numerical sequences (determining predecessors and successors as well as identifying missing dice patterns of a series). Results indicated that when considering responses that corresponded to the egocentric perspective, children’s spatial language was associated significantly with their relative numerical magnitude understanding, even after controlling for covariates, such as children’s SES, mental rotation skills, and also absolute magnitude understanding or knowledge on numerical sequences. This suggests that the use of egocentric reference frames in spatial language may facilitate spatial representation of numbers along a mental number line and thus seem important for preschoolers’ relative understanding of numerical magnitude. KW - spatial language KW - frames of reference KW - numerical development KW - mental number line KW - preschool children Y1 - 2022 U6 - https://doi.org/10.3389/fpsyg.2022.943191 SN - 1664-1078 SP - 1 EP - 13 PB - Frontiers CY - Lausanne, Schweiz ER - TY - CHAP A1 - Curzon, Paul A1 - Kalas, Ivan A1 - Schubert, Sigrid A1 - Schaper, Niclas A1 - Barnes, Jan A1 - Kennewell, Steve A1 - Bröker, Kathrin A1 - Kastens, Uwe A1 - Magenheim, Johannes A1 - Dagiene, Valentina A1 - Stupuriene, Gabriele A1 - Ellis, Jason Brent A1 - Abreu-Ellis, Carla Reis A1 - Grillenberger, Andreas A1 - Romeike, Ralf A1 - Haugsbakken, Halvdan A1 - Jones, Anthony A1 - Lewin, Cathy A1 - McNicol, Sarah A1 - Nelles, Wolfgang A1 - Neugebauer, Jonas A1 - Ohrndorf, Laura A1 - Schaper, Niclas A1 - Schubert, Sigrid A1 - Opel, Simone A1 - Kramer, Matthias A1 - Trommen, Michael A1 - Pottbäcker, Florian A1 - Ilaghef, Youssef A1 - Passig, David A1 - Tzuriel, David A1 - Kedmi, Ganit Eshel A1 - Saito, Toshinori A1 - Webb, Mary A1 - Weigend, Michael A1 - Bottino, Rosa A1 - Chioccariello, Augusto A1 - Christensen, Rhonda A1 - Knezek, Gerald A1 - Gioko, Anthony Maina A1 - Angondi, Enos Kiforo A1 - Waga, Rosemary A1 - Ohrndorf, Laura A1 - Or-Bach, Rachel A1 - Preston, Christina A1 - Younie, Sarah A1 - Przybylla, Mareen A1 - Romeike, Ralf A1 - Reynolds, Nicholas A1 - Swainston, Andrew A1 - Bendrups, Faye A1 - Sysło, Maciej M. A1 - Kwiatkowska, Anna Beata A1 - Zieris, Holger A1 - Gerstberger, Herbert A1 - Müller, Wolfgang A1 - Büchner, Steffen A1 - Opel, Simone A1 - Schiller, Thomas A1 - Wegner, Christian A1 - Zender, Raphael A1 - Lucke, Ulrike A1 - Diethelm, Ira A1 - Syrbe, Jörn A1 - Lai, Kwok-Wing A1 - Davis, Niki A1 - Eickelmann, Birgit A1 - Erstad, Ola A1 - Fisser, Petra A1 - Gibson, David A1 - Khaddage, Ferial A1 - Knezek, Gerald A1 - Micheuz, Peter A1 - Kloos, Carlos Delgado ED - Brinda, Torsten ED - Reynolds, Nicholas ED - Romeike, Ralf ED - Schwill, Andreas T1 - KEYCIT 2014 BT - key competencies in informatics and ICT N2 - In our rapidly changing world it is increasingly important not only to be an expert in a chosen field of study but also to be able to respond to developments, master new approaches to solving problems, and fulfil changing requirements in the modern world and in the job market. In response to these needs key competencies in understanding, developing and using new digital technologies are being brought into focus in school and university programmes. The IFIP TC3 conference "KEYCIT – Key Competences in Informatics and ICT (KEYCIT 2014)" was held at the University of Potsdam in Germany from July 1st to 4th, 2014 and addressed the combination of key competencies, Informatics and ICT in detail. The conference was organized into strands focusing on secondary education, university education and teacher education (organized by IFIP WGs 3.1 and 3.3) and provided a forum to present and to discuss research, case studies, positions, and national perspectives in this field. T3 - Commentarii informaticae didacticae (CID) - 7 KW - Schlüsselkompetenzen KW - Informatik KW - Bildung KW - ICT KW - Informatikdidaktik KW - Key Competencies KW - Informatics KW - education KW - ICT KW - Computer Science Education Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-70325 SN - 978-3-86956-292-6 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Ogunkola, Moses Olalekan A1 - Guiraudie-Capraz, Gaelle A1 - Féron, François A1 - Leimkühler, Silke T1 - The Human Mercaptopyruvate Sulfurtransferase TUM1 Is Involved in Moco Biosynthesis, Cytosolic tRNA Thiolation and Cellular Bioenergetics in Human Embryonic Kidney Cells JF - Biomolecules N2 - Sulfur is an important element that is incorporated into many biomolecules in humans. The incorporation and transfer of sulfur into biomolecules is, however, facilitated by a series of different sulfurtransferases. Among these sulfurtransferases is the human mercaptopyruvate sulfurtransferase (MPST) also designated as tRNA thiouridine modification protein (TUM1). The role of the human TUM1 protein has been suggested in a wide range of physiological processes in the cell among which are but not limited to involvement in Molybdenum cofactor (Moco) biosynthesis, cytosolic tRNA thiolation and generation of H2S as signaling molecule both in mitochondria and the cytosol. Previous interaction studies showed that TUM1 interacts with the L-cysteine desulfurase NFS1 and the Molybdenum cofactor biosynthesis protein 3 (MOCS3). Here, we show the roles of TUM1 in human cells using CRISPR/Cas9 genetically modified Human Embryonic Kidney cells. Here, we show that TUM1 is involved in the sulfur transfer for Molybdenum cofactor synthesis and tRNA thiomodification by spectrophotometric measurement of the activity of sulfite oxidase and liquid chromatography quantification of the level of sulfur-modified tRNA. Further, we show that TUM1 has a role in hydrogen sulfide production and cellular bioenergetics. KW - Moco biosynthesis KW - sulfite oxidase KW - cytosolic tRNA thiolation KW - 5-methoxycarbonylmethyl-2-thiouridine KW - H2S biosynthesis KW - cellular bioenergetics Y1 - 2023 U6 - https://doi.org/10.3390/biom13010144 SN - 2218-273X VL - 13 SP - 1 EP - 23 PB - MDPI CY - Basel, Schweiz ET - 1 ER - TY - JOUR A1 - Marggraf, Lara Christin A1 - Lindecke, Oliver A1 - Voigt, Christian C. A1 - Pētersons, Gunārs A1 - Voigt-Heucke, Silke Luise T1 - Nathusius’ bats, Pipistrellus nathusii, bypass mating opportunities of their own species, but respond to foraging heterospecifics on migratory transit flights JF - Frontiers in Ecology and Evolution N2 - In late summer, migratory bats of the temperate zone face the challenge of accomplishing two energy-demanding tasks almost at the same time: migration and mating. Both require information and involve search efforts, such as localizing prey or finding potential mates. In non-migrating bat species, playback studies showed that listening to vocalizations of other bats, both con-and heterospecifics, may help a recipient bat to find foraging patches and mating sites. However, we are still unaware of the degree to which migrating bats depend on con-or heterospecific vocalizations for identifying potential feeding or mating opportunities during nightly transit flights. Here, we investigated the vocal responses of Nathusius’ pipistrelle bats, Pipistrellus nathusii, to simulated feeding and courtship aggregations at a coastal migration corridor. We presented migrating bats either feeding buzzes or courtship calls of their own or a heterospecific migratory species, the common noctule, Nyctalus noctula. We expected that during migratory transit flights, simulated feeding opportunities would be particularly attractive to bats, as well as simulated mating opportunities which may indicate suitable roosts for a stopover. However, we found that when compared to the natural silence of both pre-and post-playback phases, bats called indifferently during the playback of conspecific feeding sounds, whereas P. nathusii echolocation call activity increased during simulated feeding of N. noctula. In contrast, the call activity of P. nathusii decreased during the playback of conspecific courtship calls, while no response could be detected when heterospecific call types were broadcasted. Our results suggest that while on migratory transits, P. nathusii circumnavigate conspecific mating aggregations, possibly to save time or to reduce the risks associated with social interactions where aggression due to territoriality might be expected. This avoidance behavior could be a result of optimization strategies by P. nathusii when performing long-distance migratory flights, and it could also explain the lack of a response to simulated conspecific feeding. However, the observed increase of activity in response to simulated feeding of N. noctula, suggests that P. nathusii individuals may be eavesdropping on other aerial hawking insectivorous species during migration, especially if these occupy a slightly different foraging niche. KW - playback KW - phonotaxis KW - bats KW - acoustic communication KW - animal migration KW - eavesdropping KW - echolocation KW - Pipistrellus nathusii Y1 - 2023 U6 - https://doi.org/10.3389/fevo.2022.908560 SN - 2296-701X SP - 1 EP - 10 PB - Frontiers CY - Lausanne, Schweiz ER - TY - JOUR A1 - Kühne, Franziska A1 - Fauth, Henriette A1 - Destina Sevde, Ay-Bryson A1 - Visser, Leonie N.C. A1 - Weck, Florian T1 - Communicating the diagnosis of cancer or depression: Results of a randomized controlled online study using video vignettes JF - Cancer Medicine N2 - Background Communicating a diagnosis is highly important, yet complex, especially in the context of cancer and mental disorders. The aim was to explore the communication style of an oncologist vs. psychotherapist in an online study. Methods Patients (N = 136: 65 cancer, 71 depression) were randomly assigned to watch a standardized video vignette with one of two communication styles (empathic vs. unempathic). Outcome measures of affectivity, information recall, communication skills, empathy and trust were applied. Results Regardless of diagnosis, empathic communication was associated with the perception of a significantly more empathic (p < 0.001, η2partial = 0.08) and trustworthy practitioner (p = 0.014, η2partial = 0.04) with better communication skills (p = 0.013, η2partial = 0.05). Cancer patients reported a larger decrease in positive affect (p < 0.001, η2partial = 0.15) and a larger increase in negative affect (p < 0.001, η2partial = 0.14) from pre- to post-video than depressive patients. Highly relevant information was recalled better in both groups (p < 0.001, d = 0.61–1.06). Conclusions The results highlight the importance of empathy while communicating both a diagnosis of cancer and a mental disorder. Further research should focus on the communication of a mental disorder in association with cancer. KW - consultation KW - mental health KW - oncology KW - psycho-oncology KW - skills Y1 - 2021 U6 - https://doi.org/10.1002/cam4.4396 SN - 2045-7634 VL - 10 SP - 9012 EP - 9021 PB - Wiley CY - Hoboken, New Jersey, USA ET - 24 ER - TY - JOUR A1 - Reeg, Jette A1 - Strigl, Lea A1 - Jeltsch, Florian T1 - Agricultural buffer zone thresholds to safeguard functional bee diversity BT - Insights from a community modeling approach JF - Ecology and Evolution N2 - Wild bee species are important pollinators in agricultural landscapes. However, population decline was reported over the last decades and is still ongoing. While agricultural intensification is a major driver of the rapid loss of pollinating species, transition zones between arable fields and forest or grassland patches, i.e., agricultural buffer zones, are frequently mentioned as suitable mitigation measures to support wild bee populations and other pollinator species. Despite the reported general positive effect, it remains unclear which amount of buffer zones is needed to ensure a sustainable and permanent impact for enhancing bee diversity and abundance. To address this question at a pollinator community level, we implemented a process-based, spatially explicit simulation model of functional bee diversity dynamics in an agricultural landscape. More specifically, we introduced a variable amount of agricultural buffer zones (ABZs) at the transition of arable to grassland, or arable to forest patches to analyze the impact on bee functional diversity and functional richness. We focused our study on solitary bees in a typical agricultural area in the Northeast of Germany. Our results showed positive effects with at least 25% of virtually implemented agricultural buffer zones. However, higher amounts of ABZs of at least 75% should be considered to ensure a sufficient increase in Shannon diversity and decrease in quasi-extinction risks. These high amounts of ABZs represent effective conservation measures to safeguard the stability of pollination services provided by solitary bee species. As the model structure can be easily adapted to other mobile species in agricultural landscapes, our community approach offers the chance to compare the effectiveness of conservation measures also for other pollinator communities in future. KW - agricultural landscape KW - buffer zones KW - community model KW - functional traits KW - solitary bees KW - spatially explicit Y1 - 2022 U6 - https://doi.org/10.1002/ece3.8748 SN - 2045-7758 VL - 12 SP - 1 EP - 17 PB - Wiley Online Library CY - Hoboken, New Jersey, USA ET - 3 ER - TY - JOUR A1 - Liebe, Thomas A1 - Dordevic, Milos A1 - Kaufmann, Jörn A1 - Avetisyan, Araks A1 - Skalej, Martin A1 - Müller, Notger Germar T1 - Investigation of the functional pathogenesis of mild cognitive impairment by localisation-based locus coeruleus resting-state fMRI JF - Human Brain Mapping N2 - Dementia as one of the most prevalent diseases urges for a better understanding of the central mechanisms responsible for clinical symptoms, and necessitates improvement of actual diagnostic capabilities. The brainstem nucleus locus coeruleus (LC) is a promising target for early diagnosis because of its early structural alterations and its relationship to the functional disturbances in the patients. In this study, we applied our improved method of localisation-based LC resting-state fMRI to investigate the differences in central sensory signal processing when comparing functional connectivity (fc) of a patient group with mild cognitive impairment (MCI, n = 28) and an age-matched healthy control group (n = 29). MCI and control participants could be differentiated in their Mini-Mental-State-Examination (MMSE) scores (p < .001) and LC intensity ratio (p = .010). In the fMRI, LC fc to anterior cingulate cortex (FDR p < .001) and left anterior insula (FDR p = .012) was elevated, and LC fc to right temporoparietal junction (rTPJ, FDR p = .012) and posterior cingulate cortex (PCC, FDR p = .021) was decreased in the patient group. Importantly, LC to rTPJ connectivity was also positively correlated to MMSE scores in MCI patients (p = .017). Furthermore, we found a hyperactivation of the left-insula salience network in the MCI patients. Our results and our proposed disease model shed new light on the functional pathogenesis of MCI by directing to attentional network disturbances, which could aid new therapeutic strategies and provide a marker for diagnosis and prediction of disease progression. KW - attention KW - locus coeruleus KW - mild cognitive impairment KW - resting-state fMRI Y1 - 2022 U6 - https://doi.org/10.1002/hbm.26039 SN - 1097-0193 VL - 43 SP - 5630 EP - 5642 PB - Wiley CY - New York, NY, USA ET - 18 ER - TY - JOUR A1 - Hauffe, Robert A1 - Rath, Michaela A1 - Agyapong, Wilson A1 - Jonas, Wenke A1 - Vogel, Heike A1 - Schulz, Tim Julius A1 - Schwarz, Maria A1 - Kipp, Anna Patricia A1 - Blüher, Matthias A1 - Kleinridders, André T1 - Obesity Hinders the Protective Effect of Selenite Supplementation on Insulin Signaling JF - Antioxidants N2 - The intake of high-fat diets (HFDs) containing large amounts of saturated long-chain fatty acids leads to obesity, oxidative stress, inflammation, and insulin resistance. The trace element selenium, as a crucial part of antioxidative selenoproteins, can protect against the development of diet-induced insulin resistance in white adipose tissue (WAT) by increasing glutathione peroxidase 3 (GPx3) and insulin receptor (IR) expression. Whether selenite (Se) can attenuate insulin resistance in established lipotoxic and obese conditions is unclear. We confirm that GPX3 mRNA expression in adipose tissue correlates with BMI in humans. Cultivating 3T3-L1 pre-adipocytes in palmitate-containing medium followed by Se treatment attenuates insulin resistance with enhanced GPx3 and IR expression and adipocyte differentiation. However, feeding obese mice a selenium-enriched high-fat diet (SRHFD) only resulted in a modest increase in overall selenoprotein gene expression in WAT in mice with unaltered body weight development, glucose tolerance, and insulin resistance. While Se supplementation improved adipocyte morphology, it did not alter WAT insulin sensitivity. However, mice fed a SRHFD exhibited increased insulin content in the pancreas. Overall, while selenite protects against palmitate-induced insulin resistance in vitro, obesity impedes the effect of selenite on insulin action and adipose tissue metabolism in vivo. KW - selenite KW - insulin KW - adipose tissue KW - obesity KW - insulin resistance Y1 - 2022 U6 - https://doi.org/10.3390/antiox11050862 SN - 2076-3921 VL - 11 SP - 1 EP - 16 PB - MDPI CY - Basel, Schweiz ET - 5 ER - TY - JOUR A1 - Kayhan, Ezgi A1 - Matthes, Daniel A1 - Marriott Haresign, Ira A1 - Bánki, Anna A1 - Michel, Christine A1 - Langeloh, Miriam A1 - Wass, Sam A1 - Hoehl, Stefanie T1 - DEEP: A dual EEG pipeline for developmental hyperscanning studies JF - Developmental Cognitive Neuroscience N2 - Cutting-edge hyperscanning methods led to a paradigm shift in social neuroscience. It allowed researchers to measure dynamic mutual alignment of neural processes between two or more individuals in naturalistic contexts. The ever-growing interest in hyperscanning research calls for the development of transparent and validated data analysis methods to further advance the field. We have developed and tested a dual electroencephalography (EEG) analysis pipeline, namely DEEP. Following the preprocessing of the data, DEEP allows users to calculate Phase Locking Values (PLVs) and cross-frequency PLVs as indices of inter-brain phase alignment of dyads as well as time-frequency responses and EEG power for each participant. The pipeline also includes scripts to control for spurious correlations. Our goal is to contribute to open and reproducible science practices by making DEEP publicly available together with an example mother-infant EEG hyperscanning dataset. KW - Developmental hyperscanning KW - Dual EEG analysis KW - Adult-child interaction KW - Phase Locking Value KW - PLV KW - Cross-frequency PLV KW - FieldTrip Y1 - 2022 U6 - https://doi.org/10.1016/j.dcn.2022.101104 SN - 1878-9307 VL - 54 SP - 1 EP - 11 PB - Elsevier CY - Amsterdam, Niederlande ER - TY - JOUR A1 - Tiedemann, Kim A1 - Iobbi-Nivol, Chantal A1 - Leimkühler, Silke T1 - The Role of the Nucleotides in the Insertion of the bis-Molybdopterin Guanine Dinucleotide Cofactor into apo-Molybdoenzymes JF - Molecules N2 - The role of the GMP nucleotides of the bis-molybdopterin guanine dinucleotide (bis-MGD) cofactor of the DMSO reductase family has long been a subject of discussion. The recent characterization of the bis-molybdopterin (bis-Mo-MPT) cofactor present in the E. coli YdhV protein, which differs from bis-MGD solely by the absence of the nucleotides, now enables studying the role of the nucleotides of bis-MGD and bis-MPT cofactors in Moco insertion and the activity of molybdoenzymes in direct comparison. Using the well-known E. coli TMAO reductase TorA as a model enzyme for cofactor insertion, we were able to show that the GMP nucleotides of bis-MGD are crucial for the insertion of the bis-MGD cofactor into apo-TorA. KW - bis-MGD KW - chaperone KW - molybdenum cofactor KW - TMAO reductase Y1 - 2022 U6 - https://doi.org/10.3390/molecules27092993 SN - 1420-3049 VL - 27 SP - 1 EP - 15 PB - MDPI CY - Basel, Schweiz ET - 9 ER - TY - CHAP A1 - Reimer, O. A1 - Aharonian, Felix A. A1 - Hinton, J. A1 - Hofmann, W. A1 - Hoppe, S. A1 - Raue, M. A1 - Reimer, A. T1 - VHE gamma-rays from Westerlund 2 and implications for the inferred energetics N2 - 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. Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-18172 ER - TY - JOUR A1 - Weithoff, Guntram A1 - Bell, Elanor Margaret T1 - Complex Trophic Interactions in an Acidophilic Microbial Community JF - Microorganisms N2 - Extreme habitats often harbor specific communities that differ substantially from non-extreme habitats. In many cases, these communities are characterized by archaea, bacteria and protists, whereas the number of species of metazoa and higher plants is relatively low. In extremely acidic habitats, mostly prokaryotes and protists thrive, and only very few metazoa thrive, for example, rotifers. Since many studies have investigated the physiology and ecology of individual species, there is still a gap in research on direct, trophic interactions among extremophiles. To fill this gap, we experimentally studied the trophic interactions between a predatory protist (Actinophrys sol, Heliozoa) and its prey, the rotifers Elosa woralli and Cephalodella sp., the ciliate Urosomoida sp. and the mixotrophic protist Chlamydomonas acidophila (a green phytoflagellate, Chlorophyta). We found substantial predation pressure on all animal prey. High densities of Chlamydomonas acidophila reduced the predation impact on the rotifers by interfering with the feeding behaviour of A. sol. These trophic relations represent a natural case of intraguild predation, with Chlamydomonas acidophila being the common prey and the rotifers/ciliate and A. sol being the intraguild prey and predator, respectively. We further studied this intraguild predation along a resource gradient using Cephalodella sp. as the intraguild prey. The interactions among the three species led to an increase in relative rotifer abundance with increasing resource (Chlamydomonas) densities. By applying a series of laboratory experiments, we revealed the complexity of trophic interactions within a natural extremophilic community. KW - acid mine drainage KW - extremophiles KW - food web KW - heliozoa KW - intraguild predation KW - mining lakes KW - Rotifera Y1 - 2022 U6 - https://doi.org/10.3390/microorganisms10071340 SN - 2076-2607 VL - 10 SP - 1 EP - 10 PB - MDPI CY - Basel, Schweiz ET - 7 ER - TY - BOOK A1 - Weiß, Norman A1 - Verlaan, Stephanie A1 - Vasquez Carruthers, Juan Francisco A1 - Mair, Theresa A1 - Conner, Sean A1 - Maaser, Lucas A1 - Röthlisberger, Livia ED - Weiß, Norman T1 - Transitional Justice BT - Theoretical and Practical Approaches T3 - Potsdamer Studien zu Staat, Recht und Politik N2 - This publication deals with the topic of transitional justice. In six case studies, the authors link theoretical and practical implications in order to develop some innovative approaches. Their proposals might help to deal more effectively with the transition of societies, legal orders and political systems. Young academics from various backgrounds provide fresh insights and demonstrate the relevance of the topic. The chapters analyse transitions and conflicts in Sierra Leone, Argentina, Nicaragua, Nepal, and South Sudan as well as Germany’s colonial genocide in Namibia. Thus, the book provides the reader with new insights and contributes to the ongoing debate about transitional justice. N2 - Gegenstand dieser Publikation ist das Thema „Transitional Justice“. In sechs Fallstudien verknüpfen die Autoren theoretische und praktische Implikationen, um innovative Ansätze zu entwickeln. Ihre Vorschläge wollen dazu beitragen, den Übergangsprozess von Gesellschaften, Rechtsordnungen und politischen Systemen effektiver zu gestalten. Nachwuchswissenschaftler mit unterschiedlichem fachlichem Hintergrund geben hier neue Einblicke und zeigen die fortdauernde Relevanz des Themas. Die Kapitel analysieren Übergänge und Konflikte in Sierra Leone, Argentinien, Nicaragua, Nepal und Süd-Sudan sowie den kolonialen Völkermord in Namibia. So liefert das Buch dem Leser neue Erkenntnisse und trägt zur laufenden Debatte über das Thema „Transitional Justice“ bei. T3 - Potsdamer Studien zu Staat, Recht und Politik - 7 KW - transitional justice KW - transformation KW - transformative justice KW - reconciliation KW - political opportunism KW - Übergangsjustiz KW - Transformation KW - Versöhnung KW - Demokratisierung Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-431711 SN - 978-3-86956-473-9 SN - 1869-2443 SN - 1867-2663 IS - 7 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Prasse, Paul A1 - Iversen, Pascal A1 - Lienhard, Matthias A1 - Thedinga, Kristina A1 - Herwig, Ralf A1 - Scheffer, Tobias T1 - Pre-Training on In Vitro and Fine-Tuning on Patient-Derived Data Improves Deep Neural Networks for Anti-Cancer Drug-Sensitivity Prediction JF - MDPI N2 - Large-scale databases that report the inhibitory capacities of many combinations of candidate drug compounds and cultivated cancer cell lines have driven the development of preclinical drug-sensitivity models based on machine learning. However, cultivated cell lines have devolved from human cancer cells over years or even decades under selective pressure in culture conditions. Moreover, models that have been trained on in vitro data cannot account for interactions with other types of cells. Drug-response data that are based on patient-derived cell cultures, xenografts, and organoids, on the other hand, are not available in the quantities that are needed to train high-capacity machine-learning models. We found that pre-training deep neural network models of drug sensitivity on in vitro drug-sensitivity databases before fine-tuning the model parameters on patient-derived data improves the models’ accuracy and improves the biological plausibility of the features, compared to training only on patient-derived data. From our experiments, we can conclude that pre-trained models outperform models that have been trained on the target domains in the vast majority of cases. KW - deep neural networks KW - drug-sensitivity prediction KW - anti-cancer drugs Y1 - 2022 U6 - https://doi.org/10.3390/cancers14163950 SN - 2072-6694 VL - 14 SP - 1 EP - 14 PB - MDPI CY - Basel, Schweiz ET - 16 ER - TY - JOUR A1 - Omane, Paul Okyere A1 - Höhle, Barbara T1 - Acquiring syntactic variability BT - The production of Wh-questions in children and adults speaking Akan JF - Frontiers in communication N2 - This paper investigates the predictions of the Derivational Complexity Hypothesis by studying the acquisition of wh-questions in 4- and 5-year-old Akan-speaking children in an experimental approach using an elicited production and an elicited imitation task. Akan has two types of wh-question structures (wh-in-situ and wh-ex-situ questions), which allows an investigation of children’s acquisition of these two question structures and their preferences for one or the other. Our results show that adults prefer to use wh-ex-situ questions over wh-in-situ questions. The results from the children show that both age groups have the two question structures in their linguistic repertoire. However, they differ in their preferences in usage in the elicited production task: while the 5-year-olds preferred the wh-in-situ structure over the wh-ex-situ structure, the 4-year-olds showed a selective preference for the wh-in-situ structure in who-questions. These findings suggest a developmental change in wh-question preferences in Akan-learning children between 4 and 5 years of age with a so far unobserved u-shaped developmental pattern. In the elicited imitation task, all groups showed a strong tendency to maintain the structure of in-situ and ex-situ questions in repeating grammatical questions. When repairing ungrammatical ex-situ questions, structural changes to grammatical in-situ questions were hardly observed but the insertion of missing morphemes while keeping the ex-situ structure. Together, our findings provide only partial support for the Derivational Complexity Hypothesis. KW - Akan KW - wh-questions KW - wh-in-situ KW - wh-ex-situ KW - derivational complexity KW - language acquisition Y1 - 2021 U6 - https://doi.org/10.3389/fcomm.2021.604951 SN - 2297-900X VL - 2021 PB - Frontiers Media CY - Lausanne, Schweiz ER - TY - THES A1 - Müller, Melanie J. I. T1 - Bidirectional transport by molecular motors T1 - Bidirektionaler Transport durch molekulare Motoren N2 - 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. N2 - In biologischen Zellen transportieren molekulare Motoren verschiedenste Frachtteilchen entlang von Mikrotubuli-Filamenten. Die Mikrotubuli-Filamente besitzen eine intrinsische Richtung: sie haben ein "Plus-" und ein "Minus-"Ende. Einige molekulare Motoren wie Dynein laufen zum Minus-Ende, während andere wie Kinesin zum Plus-Ende laufen. Zellen haben typischerweise ein isopolares Mikrotubuli-Netzwerk. Dies ist besonders ausgeprägt in neuronalen Axonen oder Pilz-Hyphen. In diesen langen röhrenförmigen Ausstülpungen liegen die Mikrotubuli parallel zur Achse mit dem Minus-Ende zum Zellkörper und dem Plus-Ende zur Zellspitze gerichtet. In einer solchen Röhre führt Transport durch nur einen Motor-Typ zu "Motor-Staus". Kinesin-getriebene Frachten akkumulieren an der Spitze, während Dynein-getriebene Frachten am Zellkörper akkumulieren. Wir identifizieren die relevanten Längenskalen und charakterisieren das Stauverhalten in diesen Röhrengeometrien mit Hilfe von Monte-Carlo-Simulationen und analytischen Rechnungen. Eine mögliche Lösung für das Stauproblem ist der Transport mit einem Team von Plus- und einem Team von Minus-Motoren gleichzeitig, so dass die Fracht sich in beide Richtungen bewegen kann. Dies wird in Zellen tatsächlich beobachtet. Der einfachste Mechanismus für solchen bidirektionalen Transport ist ein "Tauziehen" zwischen den beiden Motor-Teams, das nur mit mechanischer Interaktion funktioniert. Wir entwickeln ein stochastisches Tauzieh-Modell, das wir mit numerischen und analytischen Rechnungen untersuchen. Es ergibt sich ein erstaunlich komplexes Motilitätsverhalten. Wir vergleichen unsere Resultate mit den vorhandenen experimentellen Daten, die wir qualitativ und quantitativ reproduzieren. KW - molekulare Motoren KW - bidirektionaler intrazellulärer Transport KW - Tauziehen KW - stochastische Prozesse KW - kooperative Phänomene KW - molecular motors KW - bidirectional intracellular transport KW - tug-of-war KW - stochastic processes KW - cooperative phenomena Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-18715 ER - TY - JOUR A1 - Rose, Robert A1 - Groeger, Lars A1 - Hölzle, Katharina T1 - The Emergence of Shared Leadership in Innovation Labs JF - Frontiers in Psychology N2 - Implementing innovation laboratories to leverage intrapreneurship are an increasingly popular organizational practice. A typical feature in these creative environments are semi-autonomous teams in which multiple members collectively exert leadership influence, thereby challenging traditional command-and-control conceptions of leadership. An extensive body of research on the team-centric concept of shared leadership has recognized the potential for pluralized leadership structures in enhancing team effectiveness; however, little empirical work has been conducted in organizational contexts in which creativity is key. This study set out to explore antecedents of shared leadership and its influence on team creativity in an innovation lab. Building on extant shared leadership and innovation research, we propose antecedents customary to creative teamwork, that is, experimental culture, task reflexivity, and voice. Multisource data were collected from 104 team members and 49 evaluations of 29 coaches nested in 21 teams working in a prototypical innovation lab. We identify factors specific to creative teamwork that facilitate the emergence of shared leadership by providing room for experimentation, encouraging team members to speak up in the creative process, and cultivating a reflective application of entrepreneurial thinking. We provide specific exemplary activities for innovation lab teams to increase levels of shared leadership. KW - innovation laboratories KW - intrapreneurship KW - team creativity KW - shared leadership KW - social network analysis Y1 - 2021 U6 - https://doi.org/10.3389/fpsyg.2021.685167 SN - 1664-1078 VL - 12 SP - 1 EP - 13 PB - Frontiers in psychology CY - Lausanne, Schweiz ER - TY - JOUR A1 - Dordevic, Milos A1 - Hölzer, Sonja A1 - Russo, Augusta A1 - García Alanis, José Carlos A1 - Müller, Notger Germar T1 - The Role of the Precuneus in Human Spatial Updating in a Real Environment Setting—A cTBS Study JF - Life N2 - As we move through an environment, we update positions of our body relative to other objects, even when some objects temporarily or permanently leave our field of view—this ability is termed egocentric spatial updating and plays an important role in everyday life. Still, our knowledge about its representation in the brain is still scarce, with previous studies using virtual movements in virtual environments or patients with brain lesions suggesting that the precuneus might play an important role. However, whether this assumption is also true when healthy humans move in real environments where full body-based cues are available in addition to the visual cues typically used in many VR studies is unclear. Therefore, in this study we investigated the role of the precuneus in egocentric spatial updating in a real environment setting in 20 healthy young participants who underwent two conditions in a cross-over design: (a) stimulation, achieved through applying continuous theta-burst stimulation (cTBS) to inhibit the precuneus and (b) sham condition (activated coil turned upside down). In both conditions, participants had to walk back with blindfolded eyes to objects they had previously memorized while walking with open eyes. Simplified trials (without spatial updating) were used as control condition, to make sure the participants were not affected by factors such as walking blindfolded, vestibular or working memory deficits. A significant interaction was found, with participants performing better in the sham condition compared to real stimulation, showing smaller errors both in distance and angle. The results of our study reveal evidence of an important role of the precuneus in a real-environment egocentric spatial updating; studies on larger samples are necessary to confirm and further investigate this finding. KW - precuneus KW - spatial updating KW - TMS KW - cTBS Y1 - 2022 U6 - https://doi.org/10.3390/life12081239 SN - 2075-1729 VL - 12 SP - 1 EP - 13 PB - MDPI CY - Basel, Schweiz ET - 8 ER - TY - JOUR A1 - Westphal, Andrea A1 - Kalinowski, Eva A1 - Hoferichter, Clara Josepha A1 - Vock, Miriam T1 - K−12 teachers' stress and burnout during the COVID-19 pandemic: A systematic review JF - Frontiers in Psychology N2 - We present the first systematic literature review on stress and burnout in K−12 teachers during the COVID-19 pandemic. Based on a systematic literature search, we identified 17 studies that included 9,874 K−12 teachers from around the world. These studies showed some indication that burnout did increase during the COVID-19 pandemic. There were, however, almost no differences in the levels of stress and burnout experienced by K−12 teachers compared to individuals employed in other occupational fields. School principals' leadership styles emerged as an organizational characteristic that is highly relevant for K−12 teachers' levels of stress and burnout. Individual teacher characteristics associated with burnout were K−12 teachers' personality, self-efficacy in online teaching, and perceived vulnerability to COVID-19. In order to reduce stress, there was an indication that stress-management training in combination with training in technology use for teaching may be superior to stress-management training alone. Future research needs to adopt more longitudinal designs and examine the interplay between individual and organizational characteristics in the development of teacher stress and burnout during the COVID-19 pandemic and beyond. KW - burnout KW - stress KW - COVID-19 KW - pandemic KW - K−12 teachers KW - remote teaching Y1 - 2022 U6 - https://doi.org/10.3389/fpsyg.2022.920326 SN - 1664-1078 SP - 1 EP - 29 PB - Frontiers CY - Lausanne, Schweiz ER - TY - JOUR A1 - Spikes, Montrai A1 - Rodríguez-Silva, Rodet A1 - Bennett, Kerri-Ann A1 - Bräger, Stefan A1 - Josaphat, James A1 - Torres-Pineda, Patricia A1 - Ernst, Anja A1 - Havenstein, Katja A1 - Schlupp, Ingo A1 - Tiedemann, Ralph T1 - A phylogeny of the genus Limia (Teleostei: Poeciliidae) suggests a single-lake radiation nested in a Caribbean-wide allopatric speciation scenario JF - BMC Research Notes N2 - Objective The Caribbean is an important global biodiversity hotspot. Adaptive radiations there lead to many speciation events within a limited period and hence are particularly prominent biodiversity generators. A prime example are freshwater fish of the genus Limia, endemic to the Greater Antilles. Within Hispaniola, nine species have been described from a single isolated site, Lake Miragoâne, pointing towards extraordinary sympatric speciation. This study examines the evolutionary history of the Limia species in Lake Miragoâne, relative to their congeners throughout the Caribbean. Results For 12 Limia species, we obtained almost complete sequences of the mitochondrial cytochrome b gene, a well-established marker for lower-level taxonomic relationships. We included sequences of six further Limia species from GenBank (total N  = 18 species). Our phylogenies are in concordance with other published phylogenies of Limia. There is strong support that the species found in Lake Miragoâne in Haiti are monophyletic, confirming a recent local radiation. Within Lake Miragoâne, speciation is likely extremely recent, leading to incomplete lineage sorting in the mtDNA. Future studies using multiple unlinked genetic markers are needed to disentangle the relationships within the Lake Miragoâne clade. KW - Cytochrome b KW - Island biogeography KW - Fresh water fish KW - Phylogeny Y1 - 2021 U6 - https://doi.org/10.1186/s13104-021-05843-x SN - 1756-0500 VL - 14 SP - 1 EP - 8 PB - BMC Research Notes / Biomed Central CY - London ER - TY - JOUR A1 - Krüger, Johanna A1 - Foerster, Verena Elisabeth A1 - Trauth, Martin H. A1 - Hofreiter, Michael A1 - Tiedemann, Ralph T1 - Exploring the Past Biosphere of Chew Bahir/Southern Ethiopia: Cross-Species Hybridization Capture of Ancient Sedimentary DNA from a Deep Drill Core JF - Frontiers in Earth Science N2 - Eastern Africa has been a prime target for scientific drilling because it is rich in key paleoanthropological sites as well as in paleolakes, containing valuable paleoclimatic information on evolutionary time scales. The Hominin Sites and Paleolakes Drilling Project (HSPDP) explores these paleolakes with the aim of reconstructing environmental conditions around critical episodes of hominin evolution. Identification of biological taxa based on their sedimentary ancient DNA (sedaDNA) traces can contribute to understand past ecological and climatological conditions of the living environment of our ancestors. However, sedaDNA recovery from tropical environments is challenging because high temperatures, UV irradiation, and desiccation result in highly degraded DNA. Consequently, most of the DNA fragments in tropical sediments are too short for PCR amplification. We analyzed sedaDNA in the upper 70 m of the composite sediment core of the HSPDP drill site at Chew Bahir for eukaryotic remnants. We first tested shotgun high throughput sequencing which leads to metagenomes dominated by bacterial DNA of the deep biosphere, while only a small fraction was derived from eukaryotic, and thus probably ancient, DNA. Subsequently, we performed cross-species hybridization capture of sedaDNA to enrich ancient DNA (aDNA) from eukaryotic remnants for paleoenvironmental analysis, using established barcoding genes (cox1 and rbcL for animals and plants, respectively) from 199 species that may have had relatives in the past biosphere at Chew Bahir. Metagenomes yielded after hybridization capture are richer in reads with similarity to cox1 and rbcL in comparison to metagenomes without prior hybridization capture. Taxonomic assignments of the reads from these hybridization capture metagenomes also yielded larger fractions of the eukaryotic domain. For reads assigned to cox1, inferred wet periods were associated with high inferred relative abundances of putative limnic organisms (gastropods, green algae), while inferred dry periods showed increased relative abundances for insects. These findings indicate that cross-species hybridization capture can be an effective approach to enhance the information content of sedaDNA in order to explore biosphere changes associated with past environmental conditions, enabling such analyses even under tropical conditions. KW - Chew Bahir KW - hybridization capture KW - ICDP KW - paleoclimate KW - past biosphere KW - sedaDNA KW - sediment core Y1 - 2021 U6 - https://doi.org/10.3389/feart.2021.683010 SN - 2296-6463 SP - 1 EP - 20 PB - Frontiers in Earth Science CY - Lausanne, Schweiz ER - TY - CHAP A1 - Banda, Gourinath A1 - Gallagher, John P. T1 - Constraint-based abstraction of a model checker for infinite state systems N2 - 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. Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-41516 ER - TY - JOUR A1 - Benacka, Jan T1 - BubbleSort, SelectSort and InsertSort in Excel & Delphi BT - learning the Concepts in a Constructionist Way JF - Commentarii informaticae didacticae : (CID) N2 - A method is presented of acquiring the principles of three sorting algorithms through developing interactive applications in Excel. KW - spreadsheets KW - sorting KW - constructionism Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64636 SN - 1868-0844 SN - 2191-1940 IS - 6 SP - 153 EP - 154 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Ragonis, Noa T1 - Problem-solving strategies must be taught implicitly JF - Commentarii informaticae didacticae : (CID) N2 - Problem solving is one of the central activities performed by computer scientists as well as by computer science learners. Whereas the teaching of algorithms and programming languages is usually well structured within a curriculum, the development of learners’ problem-solving skills is largely implicit and less structured. Students at all levels often face difficulties in problem analysis and solution construction. The basic assumption of the workshop is that without some formal instruction on effective strategies, even the most inventive learner may resort to unproductive trial-and-error problemsolving processes. Hence, it is important to teach problem-solving strategies and to guide teachers on how to teach their pupils this cognitive tool. Computer science educators should be aware of the difficulties and acquire appropriate pedagogical tools to help their learners gain and experience problem-solving skills. KW - Problem solving KW - Problem solving strategies KW - Teaching problem solving strategies Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64645 SN - 1868-0844 SN - 2191-1940 IS - 6 SP - 155 EP - 157 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Sentance, Sue A1 - Hodges, Steve T1 - .NET Gadgeteer Workshop JF - Commentarii informaticae didacticae : (CID) Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64654 SN - 1868-0844 SN - 2191-1940 IS - 6 SP - 159 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Berry, Carol A1 - Kusterer, Peter T1 - Using Teachers’ TryScience to support educators and improve teaching JF - Commentarii informaticae didacticae : (CID) N2 - The challenge is providing teachers with the resources they need to strengthen their instructions and better prepare students for the jobs of the 21st Century. Technology can help meet the challenge. Teachers’ Tryscience is a noncommercial offer, developed by the New York Hall of Science, TeachEngineering, the National Board for Professional Teaching Standards and IBM Citizenship to provide teachers with such resources. The workshop provides deeper insight into this tool and discussion of how to support teaching of informatics in schools. KW - science KW - teacher KW - collaboration KW - teaching material KW - instruction KW - lesson KW - social networking Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64665 SN - 1868-0844 SN - 2191-1940 IS - 6 SP - 161 EP - 162 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Gujberová, Monika A1 - Tomcsányi, Peter T1 - Environments for programming in primary education JF - Commentarii informaticae didacticae : (CID) N2 - The aim of our article is to collect and present information about contemporary programming environments that are suitable for primary education. We studied the ways they implement (or do not implement) some programming concepts, the ways programs are represented and built in order to support young and novice programmers, as well as their suitability to allow different forms of sharing the results of pupils’ work. We present not only a short description of each considered environment and the taxonomy in the form of a table, but also our understanding and opinions on how and why the environments implement the same concepts and ideas in different ways and which concepts and ideas seem to be important to the creators of such environments. KW - Primary informatics KW - Programming environments for children KW - Comparing programming environments Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64499 SN - 1868-0844 SN - 2191-1940 IS - 6 SP - 53 EP - 60 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Dagiene, Valentina A1 - Jevsikova, Tatjana A1 - Schule, Carsten A1 - Sentance, Sue A1 - Thota, Neena T1 - A comparison of current trends within computer science teaching in school in Germany and the UK JF - Commentarii informaticae didacticae : (CID) N2 - In the last two years, CS as a school subject has gained a lot of attention worldwide, although different countries have differing approaches to and experiences of introducing CS in schools. This paper reports on a study comparing current trends in CS at school, with a major focus on two countries, Germany and UK. A survey was carried out of a number of teaching professionals and experts from the UK and Germany with regard to the content and delivery of CS in school. An analysis of the quantitative data reveals a difference in foci in the two countries; putting this into the context of curricular developments we are able to offer interpretations of these trends and suggest ways in which curricula in CS at school should be moving forward. KW - CS Ed Research KW - ICT KW - CS at school KW - CS curriculum KW - topics KW - international comparison KW - international study Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64504 SN - 1868-0844 SN - 2191-1940 IS - 6 SP - 63 EP - 75 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Gülbahar, Yasemin A1 - Ilkhan, Mustafa A1 - Kilis, Selcan A1 - Arslan, Okan T1 - Informatics education in Turkey BT - national ICT curriculum and teacher training at elementary level JF - Commentarii informaticae didacticae : (CID) N2 - This article is a summary of the work carried out by the Ministry of Education in Turkey, in terms of the development of a new ICT Curriculum, together with the e-Training of teachers who will play an important role in the forthcoming pilot study. Based on recent literature on the topic, the article starts by introducing the “F@tih Project”, a national project that aims to effectively integrate technology into schools. After assessing teachers’ and students’ ICT competencies, as defined internationally, the review continues with the proposed model for the e-training of teachers. Summarizing the process of development of the new ICT curriculum, researchers underline key points of the curriculum such as dimensions, levels and competencies. Then teachers’ e-training approaches, together with selected tools, are explained in line with the importance and stages of action research that will be used throughout the pilot implementation of the curriculum and e-training process. KW - informatics education KW - ICT curriculum KW - teacher training Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64517 SN - 1868-0844 SN - 2191-1940 IS - 6 SP - 77 EP - 87 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Nakano, Yoshiaki A1 - Izutsu, Katsunobu T1 - The new course of study and a prospect of information studies education in Japan JF - Commentarii informaticae didacticae : (CID) N2 - Japan launched the new Course of Study in April 2012, which has been carried out in elementary schools and junior high schools. It will also be implemented in senior high schools from April 2013. This article presents an overview of the information studies education in the new Course of Study for K-12. Besides, the authors point out what role experts of informatics and information studies education should play in the general education centered around information studies that is meant to help people of the nation to lead an active, powerful, and flexible life until the satisfying end. KW - General subject “Information” KW - Course of Study KW - Scientific understanding of Information KW - Information Ethics Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64522 SN - 1868-0844 SN - 2191-1940 IS - 6 SP - 89 EP - 96 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Lessner, Daniel T1 - The role of algorithm in general secondary education revisited JF - Commentarii informaticae didacticae : (CID) N2 - The traditional purpose of algorithm in education is to prepare students for programming. In our effort to introduce the practically missing computing science into Czech general secondary education, we have revisited this purpose.We propose an approach, which is in better accordance with the goals of general secondary education in Czechia. The importance of programming is diminishing, while recognition of algorithmic procedures and precise (yet concise) communication of algorithms is gaining importance. This includes expressing algorithms in natural language, which is more useful for most of the students than programming. We propose criteria to evaluate such descriptions. Finally, an idea about the limitations is required (inefficient algorithms, unsolvable problems, Turing’s test). We describe these adjusted educational goals and an outline of the resulting course. Our experience with carrying out the proposed intentions is satisfactory, although we did not accomplish all the defined goals. KW - computing science education KW - general secondary education KW - mandatory computer science foundations KW - concept of algorithm Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64534 SN - 1868-0844 SN - 2191-1940 IS - 6 SP - 99 EP - 110 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Reffay, Christophe A1 - Miled, Mahdi A1 - Ortiz, Pascal A1 - Février, Loic T1 - An epistemic hypermedia to learn python as a resource for an introductory course for algorithmic in France JF - Commentarii informaticae didacticae : (CID) N2 - We launched an original large-scale experiment concerning informatics learning in French high schools. We are using the France-IOI platform to federate resources and share observation for research. The first step is the implementation of an adaptive hypermedia based on very fine grain epistemic modules for Python programming learning. We define the necessary traces to be built in order to study the trajectories of navigation the pupils will draw across this hypermedia. It may be browsed by pupils either as a course support, or an extra help to solve the list of exercises (mainly for algorithmics discovery). By leaving the locus of control to the learner, we want to observe the different trajectories they finally draw through our system. These trajectories may be abstracted and interpreted as strategies and then compared for their relative efficiency. Our hypothesis is that learners have different profiles and may use the appropriate strategy accordingly. This paper presents the research questions, the method and the expected results. KW - Adaptive hypermedia KW - Navigation KW - Programming learning KW - Pytho n KW - Trajectories Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64545 SN - 1868-0844 SN - 2191-1940 IS - 6 SP - 111 EP - 118 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Grgurina, Nataša T1 - Computational thinking in Dutch secondary education JF - Commentarii informaticae didacticae : (CID) N2 - We shall examine the Pedagogical Content Knowledge (PCK) of Computer Science (CS) teachers concerning students’ Computational Thinking (CT) problem solving skills within the context of a CS course in Dutch secondary education and thus obtain an operational definition of CT and ascertain appropriate teaching methodology. Next we shall develop an instrument to assess students’ CT and design a curriculum intervention geared toward teaching and improving students’ CT problem solving skills and competences. As a result, this research will yield an operational definition of CT, knowledge about CT PCK, a CT assessment instrument and teaching materials and accompanying teacher instructions. It shall contribute to CS teacher education, development of CT education and to education in other (STEM) subjects where CT plays a supporting role, both nationally and internationally. KW - computational thinking KW - situated learning KW - engaged computing KW - computer science Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64556 SN - 1868-0844 SN - 2191-1940 IS - 6 SP - 119 EP - 123 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Weise, Martin T1 - A model for teaching informatics to German secondary school students in English-language bilingual education JF - Commentarii informaticae didacticae : (CID) N2 - Informatics as a school subject has been virtually absent from bilingual education programs in German secondary schools. Most bilingual programs in German secondary education started out by focusing on subjects from the field of social sciences. Teachers and bilingual curriculum experts alike have been regarding those as the most suitable subjects for bilingual instruction – largely due to the intercultural perspective that a bilingual approach provides. And though one cannot deny the gain that ensues from an intercultural perspective on subjects such as history or geography, this benefit is certainly not limited to social science subjects. In consequence, bilingual curriculum designers have already begun to include other subjects such as physics or chemistry in bilingual school programs. It only seems a small step to extend this to informatics. This paper will start out by addressing potential benefits of adding informatics to the range of subjects taught as part of English-language bilingual programs in German secondary education. In a second step it will sketch out a methodological (= didactical) model for teaching informatics to German learners through English. It will then provide two items of hands-on and tested teaching material in accordance with this model. The discussion will conclude with a brief outlook on the chances and prerequisites of firmly establishing informatics as part of bilingual school curricula in Germany. Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64568 SN - 1868-0844 SN - 2191-1940 IS - 6 SP - 127 EP - 137 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Bellettini, Carlo A1 - Lonati, Violetta A1 - Malchiodi, Dario A1 - Monga, Mattia A1 - Morpurgo, Anna A1 - Torelli, Mauro T1 - What you see is what you have in mind BT - constructing mental models for formatted text processing JF - Commentarii informaticae didacticae : (CID) N2 - In this paper we report on our experiments in teaching computer science concepts with a mix of tangible and abstract object manipulations. The goal we set ourselves was to let pupils discover the challenges one has to meet to automatically manipulate formatted text. We worked with a group of 25 secondary school pupils (9-10th grade), and they were actually able to “invent” the concept of mark-up language. From this experiment we distilled a set of activities which will be replicated in other classes (6th grade) under the guidance of maths teachers. Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64612 SN - 1868-0844 SN - 2191-1940 IS - 6 SP - 139 EP - 147 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Planteu, Lukas A1 - Standl, Bernhard A1 - Grossmann, Wilfried A1 - Neuwirth, Erich T1 - Integrating school practice in Austrian teacher education JF - Commentarii informaticae didacticae : (CID) N2 - We present a concept of better integration of practical teaching in student teacher education in Computer Science. As an introduction to the workshop different possible scenarios are discussed on the basis of examples. Afterwards workshop participants will have the opportunity to discuss the application of the aconcepts in other settings. Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64628 SN - 1868-0844 SN - 2191-1940 IS - 6 SP - 151 EP - 152 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - THES A1 - Lenz, Josefine T1 - Thermokarst dynamics in central-eastern Beringia T1 - Thermokarstdynamik im zentral-östlichen Beringia BT - insights from permafrost and lacustrine sediment cores BT - Einblicke durch Permafrost- und Seesedimentkerne N2 - Widespread landscape changes are presently observed in the Arctic and are most likely to accelerate in the future, in particular in permafrost regions which are sensitive to climate warming. To assess current and future developments, it is crucial to understand past environmental dynamics in these landscapes. Causes and interactions of environmental variability can hardly be resolved by instrumental records covering modern time scales. However, long-term environmental variability is recorded in paleoenvironmental archives. Lake sediments are important archives that allow reconstruction of local limnogeological processes as well as past environmental changes driven directly or indirectly by climate dynamics. This study aims at reconstructing Late Quaternary permafrost and thermokarst dynamics in central-eastern Beringia, the terrestrial land mass connecting Eurasia and North America during glacial sea-level low stands. In order to investigate development, processes and influence of thermokarst dynamics, several sediment cores from extant lakes and drained lake basins were analyzed to answer the following research questions: 1. When did permafrost degradation and thermokarst lake development take place and what were enhancing and inhibiting environmental factors? 2. What are the dominant processes during thermokarst lake development and how are they reflected in proxy records? 3. How did, and still do, thermokarst dynamics contribute to the inventory and properties of organic matter in sediments and the carbon cycle? Methods applied in this study are based upon a multi-proxy approach combining sedimentological, geochemical, geochronological, and micropaleontological analyses, as well as analyses of stable isotopes and hydrochemistry of pore-water and ice. Modern field observations of water quality and basin morphometrics complete the environmental investigations. The investigated sediment cores reveal permafrost degradation and thermokarst dynamics on different time scales. The analysis of a sediment core from GG basin on the northern Seward Peninsula (Alaska) shows prevalent terrestrial accumulation of yedoma throughout the Early to Mid Wisconsin with intermediate wet conditions at around 44.5 to 41.5 ka BP. This first wetland development was terminated by the accumulation of a 1-meter-thick airfall tephra most likely originating from the South Killeak Maar eruption at 42 ka BP. A depositional hiatus between 22.5 and 0.23 ka BP may indicate thermokarst lake formation in the surrounding of the site which forms a yedoma upland till today. The thermokarst lake forming GG basin initiated 230 ± 30 cal a BP and drained in Spring 2005 AD. Four years after drainage the lake talik was still unfrozen below 268 cm depth. A permafrost core from Mama Rhonda basin on the northern Seward Peninsula preserved a full lacustrine record including several lake phases. The first lake generation developed at 11.8 cal ka BP during the Lateglacial-Early Holocene transition; its old basin (Grandma Rhonda) is still partially preserved at the southern margin of the study basin. Around 9.0 cal ka BP a shallow and more dynamic thermokarst lake developed with actively eroding shorelines and potentially intermediate shallow water or wetland phases (Mama Rhonda). Mama Rhonda lake drainage at 1.1 cal ka BP was followed by gradual accumulation of terrestrial peat and top-down refreezing of the lake talik. A significant lower organic carbon content was measured in Grandma Rhonda deposits (mean TOC of 2.5 wt%) than in Mama Rhonda deposits (mean TOC of 7.9 wt%) highlighting the impact of thermokarst dynamics on biogeochemical cycling in different lake generations by thawing and mobilization of organic carbon into the lake system. Proximal and distal sediment cores from Peatball Lake on the Arctic Coastal Plain of Alaska revealed young thermokarst dynamics since about 1,400 years along a depositional gradient based on reconstructions from shoreline expansion rates and absolute dating results. After its initiation as a remnant pond of a previous drained lake basin, a rapidly deepening lake with increasing oxygenation of the water column is evident from laminated sediments, and higher Fe/Ti and Fe/S ratios in the sediment. The sediment record archived characterizing shifts in depositional regimes and sediment sources from upland deposits and re-deposited sediments from drained thaw lake basins depending on the gradually changing shoreline configuration. These changes are evident from alternating organic inputs into the lake system which highlights the potential for thermokarst lakes to recycle old carbon from degrading permafrost deposits of its catchment. The lake sediment record from Herschel Island in the Yukon (Canada) covers the full Holocene period. After its initiation as a thermokarst lake at 11.7 cal ka BP and intense thermokarst activity until 10.0 cal ka BP, the steady sedimentation was interrupted by a depositional hiatus at 1.6 cal ka BP which likely resulted from lake drainage or allochthonous slumping due to collapsing shore lines. The specific setting of the lake on a push moraine composed of marine deposits is reflected in the sedimentary record. Freshening of the maturing lake is indicated by decreasing electrical conductivity in pore-water. Alternation of marine to freshwater ostracods and foraminifera confirms decreasing salinity as well but also reflects episodical re-deposition of allochthonous marine sediments. Based on permafrost and lacustrine sediment records, this thesis shows examples of the Late Quaternary evolution of typical Arctic permafrost landscapes in central-eastern Beringia and the complex interaction of local disturbance processes, regional environmental dynamics and global climate patterns. This study confirms that thermokarst lakes are important agents of organic matter recycling in complex and continuously changing landscapes. N2 - Derzeit werden deutliche Landschaftsveränderungen in der Arktis beobachtet, welche sich höchstwahrscheinlich zukünftig v.a. in den Permafrostregionen verstärken, da diese besonders empfindlich auf Klimaveränderungen reagieren. Um derzeitige und zukünftige Entwicklungen einschätzen zu können, ist es wichtig vergangene Umweltprozesse zu verstehen. Ursachen und Wechselwirkungen von Umweltveränderungen können nur bedingt durch instrumentelle Aufzeichnungen erklärt werden, doch Paleo-Umweltarchive können weit in die Vergangenheit reichende Umweltdynamiken aufzeichnen. Seesedimente sind wichtige Archive, die lokale limnogeologische Prozesse, aber auch direkt oder indirekt klimatisch gesteuerte Umweltveränderungen der Vergangenheit aufzeichnen. Ziel der vorliegenden Arbeit ist es, spätquartäre Permafrost- und Thermokarstdynamik im zentral-östlichen Beringia zu rekonstruieren. Beringia umfasst jene terrestrische Landmasse, welche Eurasien und Nord-Amerika zu Zeiten von Meeresspiegeltiefständen verband. Um die Entwicklung, die Prozesse und den Einfluss von Thermokarstdynamik zu untersuchen, wurden mehrere Sedimentkerne von rezenten Seen und ausgelaufenen Seebecken analysiert, um folgende Forschungsfragen zu beantworten: 1. Zu welcher Zeit degradierte Permafrost und wann entwickelten sich Thermokarstseen? Was waren hemmende oder verstärkende Faktoren? 2. Was sind dominierende Prozesse während der Entwicklung von Thermokarstseen und wie spiegeln sich diese in Proxy-Aufzeichnungen wieder? 3. Wie hat Thermokarstdynamik damals und heute zur Bedeutung von organischer Substanz in Sedimenten und im Kohlenstoffkreislauf beigetragen? Die in dieser Arbeit angewandten Methoden basieren auf einem sogenannten „multi-proxy“ Ansatz, der sedimentologische, geochemische, geochronologische und mikropaläontologische Analysen, sowie die Untersuchung von stabilen Isotopen und die Hydrochemie von Porenwasser und -eis, verbindet. Feldmessungen der modernen Wasserqualität und Beckenmorphometrie komplettieren die Umweltuntersuchungen. Auf Grundlage der untersuchten Sedimentkerne lässt sich die Degradation von Permafrost und die Dynamik von Thermokarst auf zeitlich verschiedenen Skalen rekonstruieren. Die Analyse eines Sedimentkerns vom GG-Becken auf der nördlichen Seward-Halbinsel (Alaska) zeigt eine vorwiegend terrestrische Akkumulation von Yedoma während des Früh- und Mittel-Wisconsin mit zwischenzeitlich feuchteren Verhältnissen zwischen 44,5 und 41,5 ka BP. Diese frühe Feuchtgebietsphase wurde durch die Akkumulation einer 1 m dicken Tephra-Lage beendet, welche sehr wahrscheinlich von der Eruption des heutigen South Killeak Maar vor etwa 42.000 Jahren stammt. Eine Schichtlücke im Sedimentkern von etwa 22,5 und 0,23 ka BP gibt einen Hinweis auf Thermokarstentwicklung in der Umgebung der Kernlokation, welche bis heute ein Yedoma-Rudiment bildet. Der Thermokarstsee, der GG-Becken formte, entstand 230 ± 30 cal a BP und drainierte im Frühling 2005 AD. Vier Jahre nach der Drainage war der Talik des Sees in einer Tiefe von 268 cm noch ungefroren. Ein Permafrostkern vom Mama Rhonda-Becken auf der nördlichen Seward-Halbinsel archivierte eine vollständige limnische Fazies mit mehreren Seephasen. Die erste Seegeneration entstand am Übergang vom Spätglazial zum Frühholozän um etwa 11,8 cal ka BP; das alte Seebecken (Grandma Rhonda) ist bis heute südlich der Kernlokation erhalten. Etwa um 9,0 cal ka BP entwickelte sich ein eher flaches und dynamisches Seesystem mit aktiv erodierenden Ufern und potenziell zwischengeschalteten Flachwasser- oder Feuchtgebietsphasen (Mama Rhonda). Die Drainage vom Mama Rhonda-See etwa 1,1 cal ka BP wurde gefolgt von gradueller Torfakkumulation und einem von oben zurückfrierenden See-Talik Es wurde ein deutlich geringerer organischer Kohlenstoff-Gehalt in Grandma Rhonda-Ablagerungen (TOC im Mittel 2,5 Gew.-%) festgestellt, als in Mama Rhonda Ablagerungen (TOC im Mittel 7,9 Gew.-%). Dies zeigt den bedeutenden Einfluss von Thermokarst auf biogeochemische Kreisläufe, da in verschiedenen Seegenerationen organischen Kohlenstoff durch Permafrost-Tauen im Seesystem mobilisiert wird. Seesedimentkerne aus der Uferzone und dem zentralen Bereich von Peatball Lake auf der Arktischen Küstenebene von Alaska, ergaben eine junge Thermokarstdynamik von 1.400 Jahren, welche auf der Basis von absoluten Datierungen und Uferexpansionsraten rekonstruiert wurde. Nach der Seeinitiierung als Rest-See eines zuvor ausgelaufenen Seebeckens, vertiefte sich Peatball Lake verhältnismäßig schnell mit zunehmender Sauerstoffanreicherung der Wassersäule, wie aus laminierten Sedimenten und hohen Fe/Ti- und Fe/S-Verhältnissen im Sediment ersichtlich ist. Die Sedimente von Peatball Lake archivierten einen Wechsel des Ablagerungsregimes bei Ausdehnung der Seefläche und einen Wechsel der Sedimentquelle von ursprünglichen, rein terrestrischen Ablagerungen und bereits umgelagerten Sedimenten aus drainierten Seebecken. Angezeigt wird dieser Wechsel durch eine Veränderung im Eintrag organischen Materials in das Seesystem, was wiederum das Potential von Thermokarstseen bei der Aufarbeitung alten Kohlenstoffs aus degradierendem Permafrost im Einzugsgebiet verdeutlicht. Der Seesedimentkern von der Herschel Insel im Yukon (Kanada) deckt das gesamte Holozän ab. Nach der Seeentstehung um 11,7 cal ka BP und einer Zeit intensiver Thermokarstaktivität bis 11,0 cal ka BP, wird die Phase einer eher kontinuierlichen Sedimentation von einer Schichtlücke um 1,6 cal ka BP unterbrochen. Diese wurde entweder durch die Drainage des Sees oder einer allochthonen Rutschung instabiler Uferlinien verursacht. Die spezielle Situation des Sees auf einer Stauchendmoräne aus marinem Material spiegelt sich auch in dem Seesedimentarchiv wieder. Das Aussüßen des wachsenden Sees wird durch die abnehmende elektrische Leitfähigkeit im Porenwasser angezeigt. Der Wechsel von marinen und Süßwasserostrakoden- und Foraminiferengemeinschaften bestätigt zum einen die abnehmende Salinität des Sees, aber zeigt zum anderen auch episodische Umlagerung von allochthonem, marinem Sediment. Auf der Grundlange von Permafrost- und Seesedimentkernen zeigt diese Arbeit Beispiele spätquartärer Entwicklungsgeschichte typischer Arktischer Permafrostlandschaften im zentral-östlichen Beringia. Es werden komplexe Zusammenhänge zwischen lokalen Störungsprozessen, regionaler Umweltdynamik und globalen Klimaveränderungen aufgezeigt. Thermokarstseen spielen dabei eine wichtige Rolle im sich kontinuierlich verändernden Landschaftsbild der hohen Breiten und im Stoffkreislauf bei der Aufarbeitung organischer Substanz. KW - paleolimnology KW - permafrost degradation KW - periglacial landscape evolution KW - thermokarst processes KW - carbon cycling KW - central-eastern Beringia KW - Paläolimnologie KW - Permafrostdegradation KW - periglaziale Landschaftsentwicklung KW - Thermokarstprozesse KW - Kohlenstoffkreislauf KW - zentral-östliches Beringia Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-101364 ER - TY - BOOK A1 - Smirnov, Sergey A1 - Reijers, Hajo A. A1 - Nugteren, Thijs A1 - Weske, Mathias T1 - Business process model abstraction : theory and practice N2 - Business process management aims at capturing, understanding, and improving work in organizations. The central artifacts are process models, which serve different purposes. Detailed process models are used to analyze concrete working procedures, while high-level models show, for instance, handovers between departments. To provide different views on process models, business process model abstraction has emerged. While several approaches have been proposed, a number of abstraction use case that are both relevant for industry and scientifically challenging are yet to be addressed. In this paper we systematically develop, classify, and consolidate different use cases for business process model abstraction. The reported work is based on a study with BPM users in the health insurance sector and validated with a BPM consultancy company and a large BPM vendor. The identified fifteen abstraction use cases reflect the industry demand. The related work on business process model abstraction is evaluated against the use cases, which leads to a research agenda. T3 - Technische Berichte des Hasso-Plattner-Instituts für Digital Engineering an der Universität Potsdam - 35 Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-41782 SN - 978-3-86956-054-0 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - THES A1 - Löffler, Frank T1 - Numerical simulations of neutron star - black hole mergers T1 - Computersimulationen von Zusammenstößen eines schwarzen Lochs und eines Neutronensterns N2 - Collisions of black holes and neutron stars, named mixed binaries in the following, are interesting because of at least two reasons. Firstly, it is expected that they emit a large amount of energy as gravitational waves, which could be measured by new detectors. The form of those waves is expected to carry information about the internal structure of such systems. Secondly, collisions of such objects are the prime suspects of short gamma ray bursts. The exact mechanism for the energy emission is unknown so far. In the past, Newtonian theory of gravitation and modifications to it were often used for numerical simulations of collisions of mixed binary systems. However, near to such objects, the gravitational forces are so strong, that the use of General Relativity is necessary for accurate predictions. There are a lot of problems in general relativistic simulations. However, systems of two neutron stars and systems of two black holes have been studies extensively in the past and a lot of those problems have been solved. One of the remaining problems so far has been the use of hydrodynamic on excision boundaries. Inside excision regions, no evolution is carried out. Such regions are often used inside black holes to circumvent instabilities of the numerical methods near the singularity. Methods to handle hydrodynamics at such boundaries have been described and tests are shown in this work. One important test and the first application of those methods has been the simulation of a collapsing neutron star to a black hole. The success of these simulations and in particular the performance of the excision methods was an important step towards simulations of mixed binaries. Initial data are necessary for every numerical simulation. However, the creation of such initial data for general relativistic situations is in general very complicated. In this work it is shown how to obtain initial data for mixed binary systems using an already existing method for initial data of two black holes. These initial data have been used for evolutions of such systems and problems encountered are discussed in this work. One of the problems are instabilities due to different methods, which could be solved by dissipation of appropriate strength. Another problem is the expected drift of the black hole towards the neutron star. It is shown, that this can be solved by using special gauge conditions, which prevent the black hole from moving on the computational grid. The methods and simulations shown in this work are only the starting step for a much more detailed study of mixed binary system. Better methods, models and simulations with higher resolution and even better gauge conditions will be focus of future work. It is expected that such detailed studies can give information about the emitted gravitational waves, which is important in view of the newly built gravitational wave detectors. In addition, these simulations could give insight into the processes responsible for short gamma ray bursts. N2 - Zusammenstöße eines schwarzen Lochs und eines Neutronensterns, im Folgenden "gemischte Zusammenstöße" genannt, sind aus wenigstens zwei Gründen interessant. Erstens wird erwartet, dass dabei große Mengen Energie als Gravitationswellen freigesetzt werden und diese mit neuen Detektoren gemessen werden können. Die Form dieser Wellen verrät viel über die Beschaffenheit eines solchen Systems und stellt neben elektromagnetischen Wellen eine wichtige Informationsquelle dar. Zweitens sind Zusammenstöße von kompakten Objekten wie Neutronensternen und schwarze Löchern sehr wahrscheinlich die Ursache sogenannter kurzer Gammastrahlungsblitze. Deren genauer Mechanismus für die Umwandlung der gewaltigen Energiemengen, die bei diesen Blitzen ausgesandt werden, ist jedoch bisher unbekannt. Computersimulationen von Zusammenstößen eines gemischten Systems wurden bisher oft unter Benutzung der Newtonschen Gravitationstheorie, bzw. Korrekturen dazu, durchgeführt. In der Nähe so kompakte Objekte wie schwarzer Löcher oder Neutronensterne ist jedoch die Gravitationswirkung so stark, dass Näherungen wie die erwähnten Korrekturen der Newtonschen Gravitationstheorie zu ungenau sind. Eine Benutzung der allgemeinen Relativitätstheorie ist daher für dieses Problem unumgänglich. Die Probleme allgemein-relativistischer Simulationen sind vielfältig. Jedoch wurden Binärsysteme zweier schwarzer Löcher und zweier Neutronensterne schon eingehend untersucht, und so viele Probleme, die auch Simulationen gemischter Systeme betreffen, gelöst. Eins der bisher ausstehenden Probleme war die Behandlung der Hydrodynamik an Ausschneiderändern; Rändern zu Gebieten, die in der Zeitentwicklung der Simulation ignoriert werden. Solche Ränder werden zum Beispiel innerhalb eines schwarzen Lochs benutzt, um Instabilitäten des Programms in der Nähe der Singularität zu vermeiden. Methoden, solche Ränder zu behandeln wurden in der Arbeit entwickelt, getestet und gezeigt, dass sie verlässlich arbeiten. Ein wichtiger Test für diese Methoden, der gleichzeitig der Gewinnung neuer Erkenntnisse diente, war deren Anwendung auf Simulationen von zu schwarzen Löchern kollabierenden, rotierenden Sternen. Der Erfolg, diese Simulationen ohne Probleme mit den erwähnten Methoden durchzuführen, war ein wichtiger Schritt zu Simulationen gemischter Binärsysteme. Für Computersimulationen sind Anfangsdaten notwendig, die das gewünschte Problem beschreiben. Die Erstellung solcher Anfangsdaten ist jedoch unter Benutzung der allgemeinen Relativitätstheorie ausser in Spezialfällen sehr komplex. Wir zeigen, wie man einen schon vorhandenen Algorithmus für Anfangsdaten für zwei schwarze Löcher ändern kann, um Anfangsdaten für ein gemischtes Binärsystem zu erhalten. Diese Anfangsdaten wurden für Simulationen eines gemischten Binärsystems benutzt. Während dieser Simulationen traten mehrere Probleme auf. Zwei dieser Probleme waren numerische Instabilitäten unterschiedlicher Herkunft. Beide konnten jedoch mit angepasst starker Dissipation (der künstliche Entnahme von hochfrequenter Energie aus dem System) unterdrückt werden. Ein weiteres Problem war die erwartete Bewegung des schwarzen Lochs in Richtung des Neutronensterns. Da ein Teil des Simulationsgebietes innerhalb des schwarzen Lochs ausgeschnitten wird und das verwendete Programm bewegte Ausschneidegebiete nicht behandeln kann, darf sich das schwarze Loch jedoch auf dem Gitter kaum bewegen. Wir haben dieses Problem durch eine an das Problem angepasste Eichbedingung gelöst, die auf Bewegungen des scheinbaren Horizons reagiert und die Position des schwarzen Lochs auf diese Weise nahezu konstant hält. Die Methoden und Simulationen dieser Arbeit sind nur der Anfangspunkt einer ausführlichen Studie von Binärsystemen eines schwarzen Lochs und eines Neutronensterns. Bessere Methoden, Modelle und Simulationen mit höherer Auflösung und besser an das System angepassten Koordinaten werden Mittelpunkt zukünftiger Arbeit sein. Es wird erwartet, dass solche detailierten Studien Erkenntnisse über die abgestrahlten Gravitationswellen liefern, die gerade in Hinblick auf die neuen Gravitationswellendetektoren wichtig sind. Weiterhin könnten diese Simulationen dabei helfen, die Prozesse, die kurze Gammastrahlungsblitze hervorrufen, und über die im Moment kaum etwas bekannt ist, aufzuklären. KW - Relativistische Astrophysik KW - Neutronensterne KW - schwarze Löcher KW - neutron stars KW - black holes Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-7743 ER - TY - THES A1 - Prevot, Michelle Elizabeth T1 - Introduction of a thermo-sensitive non-polar species into polyelectrolyte multilayer capsules for drug delivery T1 - Einbettung unpolarer, temperaturempfindlicher Substanzen in Polyelektrolytkapselsysteme zur Wirkstofffreisetzung N2 - The layer-by-layer assembly (LBL) of polyelectrolytes has been extensively studied for the preparation of ultrathin films due to the versatility of the build-up process. The control of the permeability of these layers is particularly important as there are potential drug delivery applications. Multilayered polyelectrolyte microcapsules are also of great interest due to their possible use as microcontainers. This work will present two methods that can be used as employable drug delivery systems, both of which can encapsulate an active molecule and tune the release properties of the active species. Poly-(N-isopropyl acrylamide), (PNIPAM) is known to be a thermo-sensitive polymer that has a Lower Critical Solution Temperature (LCST) around 32oC; above this temperature PNIPAM is insoluble in water and collapses. It is also known that with the addition of salt, the LCST decreases. This work shows Differential Scanning Calorimetry (DSC) and Confocal Laser Scanning Microscopy (CLSM) evidence that the LCST of the PNIPAM can be tuned with salt type and concentration. Microcapsules were used to encapsulate this thermo-sensitive polymer, resulting in a reversible and tunable stimuli- responsive system. The encapsulation of the PNIPAM inside of the capsule was proven with Raman spectroscopy, DSC (bulk LCST measurements), AFM (thickness change), SEM (morphology change) and CLSM (in situ LCST measurement inside of the capsules). The exploitation of the capsules as a microcontainer is advantageous not only because of the protection the capsules give to the active molecules, but also because it facilitates easier transport. The second system investigated demonstrates the ability to reduce the permeability of polyelectrolyte multilayer films by the addition of charged wax particles. The incorporation of this hydrophobic coating leads to a reduced water sensitivity particularly after heating, which melts the wax, forming a barrier layer. This conclusion was proven with Neutron Reflectivity by showing the decreased presence of D2O in planar polyelectrolyte films after annealing creating a barrier layer. The permeability of capsules could also be decreased by the addition of a wax layer. This was proved by the increase in recovery time measured by Florescence Recovery After Photobleaching, (FRAP) measurements. In general two advanced methods, potentially suitable for drug delivery systems, have been proposed. In both cases, if biocompatible elements are used to fabricate the capsule wall, these systems provide a stable method of encapsulating active molecules. Stable encapsulation coupled with the ability to tune the wall thickness gives the ability to control the release profile of the molecule of interest. N2 - Verkapselung ist ein vielseitiges Werkzeug, das zum Schutz und zum Transport von Molekülen ebenso eingesetzt werden kann, wie zur Verbindung von Reaktionspartnern in einem gemeinsamen, von der Umgebung abgeschirmten Raum. Es basiert auf einem einfachen Vorbild der Natur. Pflanzen schützen ihren Samen zum Beispiel durch eine harte, nahezu undurchdringbare Schale (Nüsse) oder durch eine selektiv durchlässige Hülle, wie bei Weizen, der sobald er feucht wird zu keimen beginnt. Die Natur setzt durch den Einsatz des Hülle-Kern Prinzips sehr effizient die Kontrolle über Durchlässigkeit und Anpassung an bestimmte Aufgaben um. Wird das Hülle-Kern-Prinzip zum Schutz oder Transport von Molekülen eingesetzt, so sind die zu verwendenden Kapseln nur wenige Mikrometer groß. Sie werden dann als Mikrokapseln bezeichnet. Zur Erzeugung dieser Mikrokapseln werden verschiedene Methoden verwendet. Der heute übliche Weg geht von einer ca. 5-10 Mikrometer großen Kugel (Kern) aus, die mit einer stabilen und an die gewünschten Eigenschaften angepassten Schicht von wenigen Nanometern versehen wird. Im Anschluss wird der Kern herausgelöst und eine hohle, stabile Kapsel erhalten. Schichten von wenigen Nanometern Dicke können aus Polyelektrolyten durch das Layer-by-Layer-Verfahren (LbL) hergestellt werden. Dieses Verfahren eignet sich auf Grund seiner vielen Anpassungsmöglichkeiten besonders zum Aufbau der Schichten für Mikrokapseln, da sich die Eigenschaften der Beschichtung bereits beim Aufbau der Schicht auf die Bedürfnisse maßschneidern lassen. Diese Arbeit befasst sich mit der Erzeugung von Mikrokapseln, deren Eigenschaften temperaturabhängig sind. Dies wurde auf zwei Wegen erreicht. Zum einen wurden Kapseln aus Polyelektrolyten und Wachs aufgebaut. Bei Temperaturerhöhung schmilzt das Wachs und versiegelt die Kapsel. Zum anderen werden Kapseln mit einem Wärme empfindlichen Polymer gefüllt. Bei Temperaturerhöhung kollabiert das Polymergerüst. Der enthaltene Wirkstoff wird freigesetzt. KW - Mikrokapsel KW - Polyelektrolyt KW - Mehrschichtsysteme KW - Polyelectrolyte KW - Multilayers KW - Capsule Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-7785 ER - TY - THES A1 - Schauer, Nicolas T1 - Quantitative trait loci (QTL) for metabolite accumulation and metabolic regulation : metabolite profiling of interspecific crosses of tomato T1 - Metabolomische Analyse von interspezifischen Tomaten N2 - The advent of large-scale and high-throughput technologies has recently caused a shift in focus in contemporary biology from decades of reductionism towards a more systemic view. Alongside the availability of genome sequences the exploration of organisms utilizing such approach should give rise to a more comprehensive understanding of complex systems. Domestication and intensive breeding of crop plants has led to a parallel narrowing of their genetic basis. The potential to improve crops by conventional breeding using elite cultivars is therefore rather limited and molecular technologies, such as marker assisted selection (MAS) are currently being exploited to re-introduce allelic variance from wild species. Molecular breeding strategies have mostly focused on the introduction of yield or resistance related traits to date. However given that medical research has highlighted the importance of crop compositional quality in the human diet this research field is rapidly becoming more important. Chemical composition of biological tissues can be efficiently assessed by metabolite profiling techniques, which allow the multivariate detection of metabolites of a given biological sample. Here, a GC/MS metabolite profiling approach has been applied to investigate natural variation of tomatoes with respect to the chemical composition of their fruits. The establishment of a mass spectral and retention index (MSRI) library was a prerequisite for this work in order to establish a framework for the identification of metabolites from a complex mixture. As mass spectral and retention index information is highly important for the metabolomics community this library was made publicly available. Metabolite profiling of tomato wild species revealed large differences in the chemical composition, especially of amino and organic acids, as well as on the sugar composition and secondary metabolites. Intriguingly, the analysis of a set of S. pennellii introgression lines (IL) identified 889 quantitative trait loci of compositional quality and 326 yield-associated traits. These traits are characterized by increases/decreases not only of single metabolites but also of entire metabolic pathways, thus highlighting the potential of this approach in uncovering novel aspects of metabolic regulation. Finally the biosynthetic pathway of the phenylalanine-derived fruit volatiles phenylethanol and phenylacetaldehyde was elucidated via a combination of metabolic profiling of natural variation, stable isotope tracer experiments and reverse genetic experimentation. N2 - Die Einführung von Hochdurchsatzmethoden zur Analyse von biologischen Systemen, sowie die umfangreiche Sequenzierung von Genomen haben zu einer Verlagerung der Forschung „im Detail“ zu einer ganzheitlicheren Betrachtungsweise auf Systemebene geführt. Aus einer jahrhundertlangen, intensiven Züchtung und Selektion von Nutzpflanzen resultierte gleichzeitig eine Abnahme der genetischen Varianz. Daraus resultierend sind Nutzpflanzen anfälliger gegenüber Stressfaktoren, wie Pathogenen, hohen Salzkonzentrationen oder Trockenheit, als ihre Wildarten. Das Potential konventioneller Züchtung scheint somit heute an seine Grenzen gekommen zu sein. Daher versucht man mittels moderner Molekulartechnik, wie zum Beispiel Marker-gestützte Selektion, Gene oder ganze Genombereiche von Wildarten mit hoher genetischer Variation in Nutzpflanzen einzukreuzen, vornehmlich mit dem Ziel einer Ertrags- bzw. Resistenzsteigerung. Neueste medizinische Studien belegen, dass die Ernährung eine wesentliche Rolle für die menschliche Gesundheit spielt. Besonders wichtig sind hierbei die gesundheitsfördernden Substanzen in pflanzlichen Nahrungsmitteln. Aus diesem Grund kommt der Erforschung der biochemischen Zusammensetzung von biologischen Proben eine immer größere Bedeutung zu. Diese Untersuchung kann elegant durch Metabolitenprofile, welche die multivariate Analyse komplexer biologischer Proben erlauben, durchgeführt werden. In dieser Arbeit wurde zur Untersuchung der biochemischen Zusammensetzung von Tomatenwildarten und interspezifischen S. pennellii Tomatenintrogressionslinien (IL) eine GC/MS basierte Metabolitenanalyseplattform verwendet. Hierzu war es zunächst notwendig eine Massenspektrenbibliothek, zur Annotierung von Massenspektren und Retentionsindices von, in pflanzlichen Proben vorkommenden, Metaboliten anzulegen. Die Analyse der Tomatenwildarten ergab große Unterschiede gegenüber der Kulturtomate im Hinblick auf den Gehalt an Amino- und organischen Säuren, sowie der Zuckerzusammensetzung und den Gehalt an Sekundärmetaboliten. Die darauf folgende Analyse der ILs, von den jede ein genau definiertes genomisches Segment von S. pennellii beinhaltet, bestätigte diese enorme Variation mit 889 metabolischen und 326 ertragsassozierten-Veränderungen in den ILs. Die metabolischen Veränderungen zeichneten sich durch abnehmende bzw. steigende Gehalte von einzelnen Metaboliten, aber auch durch eine koordinierte Änderung aus. In dieser Arbeit wurde weiterhin der Biosyntheseweg der Volatilenstoffe Phenylethanol und Phenylacetaldehyd mit Hilfe einer IL untersucht. Hierbei konnten durch stabile Isotopenmarkierung und eines „reverse genetics“-Ansatzes Gene bzw. Enzyme identifiziert werden, die für die Dekarboxylierung des Eduktes Phenylalanin verantwortlich sind. Diese Arbeit beschreibt erstmals die umfassende Analyse von biochemischen Komponenten auf Genombasis in Tomatenintrogressionslinien und zeigt damit ein Werkzeug auf zur Identifizierung von qualitativen biochemischen Merkmalen in der modernen molekularen Züchtung. KW - Tomate KW - Metabolit KW - GC-MS KW - Introgression KW - Frucht KW - Metabolome KW - Züchtung KW - metabolic genomics KW - Tomato KW - metabolite profiling KW - metabolome KW - breeding KW - crops KW - fruit KW - metabolite breeding KW - metabolic genomics Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-7643 ER - TY - INPR A1 - Roelly, Sylvie A1 - Fradon, Myriam T1 - Infinite system of Brownian balls : equilibrium measures are canonical Gibbs N2 - We consider a system of infinitely many hard balls in Rd undergoing Brownian motions and submitted to a smooth pair potential. It is modelized by an infinite-dimensional stochastic differential equation with a local time term. We prove that the set of all equilibrium measures, solution of a detailed balance equation, coincides with the set of canonical Gibbs measures associated to the hard core potential added to the smooth interaction potential. KW - Stochastic Differential Equation KW - hard core potential KW - Canonical Gibbs measure KW - detailed balance equation KW - reversible measure Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-6720 ER - TY - BOOK ED - Ishihara, Shinichiro ED - Schmitz, Michaela ED - Schwarz, Anne T1 - Interdisciplinary studies on information structure : ISIS ; working papers of the SFB 632. - Vol. 1 N2 - Contents: A1: Phonology and syntax of focussing and topicalisation: Gisbert Fanselow: Cyclic Phonology–Syntax-Interaction: Movement to First Position in German Caroline Féry and Laura Herbst: German Sentence Accent Revisited Shinichiro Ishihara: Prosody by Phase: Evidence from Focus Intonation–Wh-scope Correspondence in Japanese A2: Quantification and information structure: Cornelia Endriss and Stefan Hinterwimmer: The Influence of Tense in Adverbial Quantification A3: Rhetorical Structure in Spoken Language: Modeling of Global Prosodic Parameters: Ekaterina Jasinskaja, Jörg Mayer and David Schlangen: Discourse Structure and Information Structure: Interfaces and Prosodic Realization B2: Focussing in African Tchadic languages: Katharina Hartmann and Malte Zimmermann: Focus Strategies in Chadic: The Case of Tangale Revisited D1: Linguistic database for information structure: Annotation and retrieval: Stefanie Dipper, Michael Götze, Manfred Stede and Tillmann Wegst: ANNIS: A Linguistic Database for Exploring Information Structure T3 - Interdisciplinary studies on information structure : ISIS ; working papers of the SFB 632 - 1 Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-8237 SN - 1866-4725 ER - TY - BOOK ED - Dipper, Stefanie ED - Götze, Michael ED - Stede, Manfred T1 - Heterogeneity in focus : creating and using linguistic databases N2 - The papers in this volume were presented at the workshop Heterogeneity in Linguistic Databases', which took place on July 9, 2004 at the University of Potsdam. The workshop was organized by project D1: Linguistic Database for Information Structure: Annotation and Retrieval', a member project of the SFB 632, a collaborative research center entitled Information Structure: the Linguistic Means for Structuring Utterances, Sentences and Texts'. The workshop brought together both developers and users of linguistic databases from a number of research projects which work on an empirical basis, all of which have to cope with different sorts of heterogeneity: primary linguistic data and annotated information may be heterogeneous, as well as the data structures representing them. The first four papers (by Wagner, Schmidt, Lüdeling, and Witt) address aspects of heterogeneous data from the point of view of database developers; the remaining three papers (by Meyer, Smith, and Teich/Fankhauser) focus on data exploitation by the users. T3 - Interdisciplinary studies on information structure : ISIS ; working papers of the SFB 632 - 2 Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-8244 SN - 978-3-937786-48-3 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - THES A1 - Andersen, Audrée T1 - Surfactant dynamics at interfaces : a series of second harmonic generation experiments T1 - Surfactant Dynamik an Grenzflächen : eine Studie über SHG-Experimente N2 - Adsorption layers of soluble surfactants enable and govern a variety of phenomena in surface and colloidal sciences, such as foams. The ability of a surfactant solution to form wet foam lamellae is governed by the surface dilatational rheology. Only systems having a non-vanishing imaginary part in their surface dilatational modulus, E, are able to form wet foams. The aim of this thesis is to illuminate the dissipative processes that give rise to the imaginary part of the modulus. There are two controversial models discussed in the literature. The reorientation model assumes that the surfactants adsorb in two distinct states, differing in their orientation. This model is able to describe the frequency dependence of the modulus E. However, it assumes reorientation dynamics in the millisecond time regime. In order to assess this model, we designed a SHG pump-probe experiment that addresses the orientation dynamics. Results obtained reveal that the orientation dynamics occur in the picosecond time regime, being in strong contradiction with the two states model. The second model regards the interface as an interphase. The adsorption layer consists of a topmost monolayer and an adjacent sublayer. The dissipative process is due to the molecular exchange between both layers. The assessment of this model required the design of an experiment that discriminates between the surface compositional term and the sublayer contribution. Such an experiment has been successfully designed and results on elastic and viscoelastic surfactant provided evidence for the correctness of the model. Because of its inherent surface specificity, surface SHG is a powerful analytical tool that can be used to gain information on molecular dynamics and reorganization of soluble surfactants. They are central elements of both experiments. However, they impose several structural elements of the model system. During the course of this thesis, a proper model system has been identified and characterized. The combination of several linear and nonlinear optical techniques, allowed for a detailed picture of the interfacial architecture of these surfactants. N2 - Amphiphile vereinen zwei gegensätzliche Strukturelemente in einem Molekül, eine hydrophile Kopfgruppe und ein hydrophobe, meist aliphatische Kette. Aufgrund der molekularen Asymmetrie erfolgt eine spontane Adsorption an der Wasser-Luft Grenzfläche. Die Adsorptionsschicht verändert die makroskopischen Eigenschaften des Materials, z.B. die Grenzflächenspannung wird erniedrigt. Amphiphile sind zentrale Bauelemente der Kolloid- und Grenzflächenforschung, die Phänomene, wie Schäume ermöglichen. Eine Schaumlamelle besteht aus einem dünnen Wasserfilm, der durch zwei Adsorptionsschichten stabilisiert wird. Die Stabilität der Lamelle wird durch die Grenzflächenrheologie entscheidend geprägt. Die wesentliche makroskopische Größe in diesem Zusammenhang ist das so genannte Grenzflächendilatationsmodul E. Es beschreibt die Fähigkeit des Systems die Gleichgewichtsgrenzflächenspannung nach einer Expansion oder Dilatation der Adsorptionschicht wieder herzustellen. Das Modul E ist eine komplexe Größe, in dem der Imaginärteil direkt mit der Schaumstabilität korreliert. Diese Arbeit widmet sich der Grenzflächenrheologie. In der Literatur werden zwei kontroverse Modelle zur Interpretation dieser Größe diskutiert. Diese Modelle werden experimentell in dieser Arbeit überprüft. Dies erfordert die Entwicklung neuer experimenteller Aufbauten basierend auf nichtlinearen, optischen Techniken. Mit diesen Experimenten konnte eines der Modelle bestätigt werden. KW - Tensid KW - Grenzflächenchemie KW - Nichtlineare Spektroskopie KW - Oscillating Bubble KW - surfactants KW - nonlinear optics KW - surface rheology KW - air-water interface KW - oscillating bubble Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-6553 ER - TY - JOUR A1 - Dipper, Stefanie A1 - Götze, Michael A1 - Stede, Manfred A1 - Wegst, Tillmann T1 - ANNIS BT - a linguistic database for exploring information structure JF - Interdisciplinary studies on information structure : ISIS ; working papers of the SFB 632 N2 - In this paper, we discuss the design and implementation of our first version of the database "ANNIS" ("ANNotation of Information Structure"). For research based on empirical data, ANNIS provides a uniform environment for storing this data together with its linguistic annotations. A central database promotes standardized annotation, which facilitates interpretation and comparison of the data. ANNIS is used through a standard web browser and offers tier-based visualization of data and annotations, as well as search facilities that allow for cross-level and cross-sentential queries. The paper motivates the design of the system, characterizes its user interface, and provides an initial technical evaluation of ANNIS with respect to data size and query processing. Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-8432 SN - 1866-4725 SN - 1614-4708 IS - 1 SP - 245 EP - 279 ER - TY - BOOK A1 - Gabbert, Silke A1 - Weikard, Hans-Peter T1 - Food deficits, food security and food aid : concepts and measurement N2 - The concepts of food deficit, hunger, undernourishment and food security are discussed. Axioms and indices for the assessment of nutrition of individuals and groups are suggested. Furthermore a measure for food aid donor performance is developed and applied to a sample of bilateral and multilateral donors providing food aid for African countries. T3 - Finanzwissenschaftliche Diskussionsbeiträge - Bd. 21 Y1 - 1998 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-8589 ER - TY - JOUR A1 - Wagner, Andreas T1 - Unity in diversity BT - integrating different linguistic data in TUSNELDA JF - Interdisciplinary studies on information structure : ISIS ; working papers of the SFB 632 N2 - This paper describes the creation and preparation of TUSNELDA, a collection of corpus data built for linguistic research. This collection contains a number of linguistically annotated corpora which differ in various aspects such as language, text sorts / data types, encoded annotation levels, and linguistic theories underlying the annotation. The paper focuses on this variation on the one hand and the way how these heterogeneous data are integrated into one resource on the other hand. Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-8625 SN - 1866-4725 SN - 1614-4708 IS - 2 SP - 1 EP - 20 ER - TY - JOUR A1 - Witt, Andreas T1 - Multiple hierarchies BT - new aspects of an old solution JF - Interdisciplinary studies on information structure : ISIS ; working papers of the SFB 632 N2 - In this paper, we present the Multiple Annotation approach, which solves two problems: the problem of annotating overlapping structures, and the problem that occurs when documents should be annotated according to different, possibly heterogeneous tag sets. This approach has many advantages: it is based on XML, the modeling of alternative annotations is possible, each level can be viewed separately, and new levels can be added at any time. The files can be regarded as an interrelated unit, with the text serving as the implicit link. Two representations of the information contained in the multiple files (one in Prolog and one in XML) are described. These representations serve as a base for several applications. Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-8657 SN - 1866-4725 SN - 1614-4708 IS - 2 SP - 55 EP - 85 ER - TY - JOUR A1 - Meyer, Roland T1 - VP-fronting in Czech and Polish BT - a case study in corpus-oriented grammar research JF - Interdisciplinary studies on information structure : ISIS ; working papers of the SFB 632 N2 - Fronting of an infinite VP across a finite main verb-akin to German "VP-topicalization"-can be found also in Czech and Polish. The paper discusses evidence from large corpora for this process and some of its properties, both syntactic and information-structural. Based on this case, criteria for more user-friedly searching and retrieval of corpus data in syntactic research are being developed. Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-8662 SN - 1866-4725 SN - 1614-4708 IS - 2 SP - 87 EP - 115 ER - TY - JOUR A1 - Elbourne, Paul T1 - The Semantics of Ellipsis JF - Interdisciplinary studies on information structure : ISIS ; working papers of the SFB 632 N2 - There are four phenomena that are particularly troublesome for theories of ellipsis: the existence of sloppy readings when the relevant pronouns cannot possibly be bound; an ellipsis being resolved in such a way that an ellipsis site in the antecedent is not understood in the way it was there; an ellipsis site drawing material from two or more separate antecedents; and ellipsis with no linguistic antecedent. These cases are accounted for by means of a new theory that involves copying syntactically incomplete antecedent material and an analysis of silent VPs and NPs that makes them into higher order definite descriptions that can be bound into. KW - VP-ellipsis KW - NP-deletion KW - definite descriptions Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-8722 SN - 1866-4725 SN - 1614-4708 IS - 3 SP - 63 EP - 109 ER - TY - BOOK A1 - Hans, Silke T1 - Migrants in Germany, Sweden and the United Kingdom BT - patterns of assimilation and welfare N2 - Contents: 1. Introduction 2. Migration and Assimilation – Theoretical Approaches 2.1 Meaning and Definition of the Terms Migration and Migrant 2.2 Milton M. Gordon – Sub Processes of Assimilation 2.3 Hartmut Esser - Acculturation, Integration, and Assimilation 2.4 The Concept of Integration and Assimilation 2.5 Straight–line Assimilation and its Implications 2.6 Segmented Assimilation and its Implications 3. Social Inequality and Welfare – Theoretical Approaches 3.1 Dimensions of Inequality 3.2 Welfare Regimes and Social Inequality 3.3 Migration, Assimilation and Inequality 4. Research Design 4.1 Research Question and General Proceeding 4.2 Sample and Data Base 4.3 Operationalisation and Indicators 5. Migration, Welfare and Inequality in Three European Countries 6. Empirical Results 6.1 Performance of Migrants Compared With Natives 6.2 Different Trajectories of Assimilation 6.3 Trajectories of Segmented Assimilation and their Determinants 6.4 Policies, Attitudes and Assimilation – An Aggregate Analysis 6.5 Summary – What Determines the Performance of Migrants? 7. Discussion of Empirical Results in Terms of Theoretical Approaches 7.1 The Situation of Migrants in Three European Countries 7.2 Assessment of the Trajectories of Assimilation 8. Conclusion – Future Prospects of Migration in Europe T3 - Potsdamer Beiträge zur Sozialforschung - 21 Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-11248 ER - TY - CHAP A1 - Doktor, Daniel A1 - Badeck, Franz-Werner A1 - Bondeau, Alberte A1 - Koslowsky, Dirk A1 - Schaber, Jörg A1 - McAllister, Murdock T1 - Using satellite imagery and ground observations to quantify the effect of intra-annually changing temperature patterns on spring time phenology N2 - Interdisziplinäres Zentrum für Musterdynamik und Angewandte Fernerkundung Workshop vom 9. - 10. Februar 2006 Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-7244 N1 - [Poster] ER - TY - CHAP A1 - Märker, Michael A1 - Schröder-Esselbach, Boris A1 - Capolongo, Domenico A1 - Bentivenga, Mario T1 - Geomorphological and pedological processes in badland areas of Southern Italy and their interaction with Mediterranean vegetation N2 - Interdisziplinäres Zentrum für Musterdynamik und Angewandte Fernerkundung Workshop vom 9. - 10. Februar 2006 Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-7288 N1 - [Poster] ER - TY - GEN A1 - Koch, Horst A1 - Laschewsky, André A1 - Ringsdorf, Helmut A1 - Teng, Kang T1 - Photodimerization and photopolymerization of amphiphilic cinnamic acid derivatives in oriented monolayers, vesicles and solution N2 - 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. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 078 Y1 - 1986 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17111 ER - TY - GEN A1 - Albrecht, O. A1 - Cumming, W. A1 - Kreuder, W. A1 - Laschewsky, André A1 - Ringsdorf, Helmut T1 - Monolayers of rod-shaped and disc-shaped liquid crystalline compounds at the air-water interface N2 - 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. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 079 KW - Monolayers KW - liquid crystals KW - discotics Y1 - 1986 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17124 ER - TY - CHAP A1 - Hirschi, Raphael T1 - The impact of reduced mass loss rates on the evolution of massive stars N2 - Mass loss is a very important aspect of the life of massive stars. After briefly reviewing its importance, we discuss the impact of the recently proposed downward revision of mass loss rates due to clumping (difficulty to form Wolf-Rayet stars and production of critically rotating stars). Although a small reduction might be allowed, large reduction factors around ten are disfavoured. We then discuss the possibility of significant mass loss at very low metallicity due to stars reaching break-up velocities and especially due to the metal enrichment of the surface of the star via rotational and convective mixing. This significant mass loss may help the first very massive stars avoid the fate of pair-creation supernova, the chemical signature of which is not observed in extremely metal poor stars. The chemical composition of the very low metallicity winds is very similar to that of the most metal poor star known to date, HE1327-2326 and offer an interesting explanation for the origin of the metals in this star. We also discuss the importance of mass loss in the context of long and soft gamma-ray bursts and pair-creation supernovae. Finally, we would like to stress that mass loss in cooler parts of the HR-diagram (luminous blue variable and yellow and red supergiant stages) are much more uncertain than in the hot part. More work needs to be done in these areas to better constrain the evolution of the most massive stars. Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17616 ER - TY - CHAP A1 - Fullerton, A. W. A1 - Massa, D. L. A1 - Prinja, R. K. T1 - Revised mass-loss rates for O stars from the Pv resonance line N2 - The P v λλ1118, 1128 resonance doublet is an extraordinarily useful diagnostic of O-star winds, because it bypasses the traditional problems associated with determining mass-loss rates from UV resonance lines. We discuss critically the assumptions and uncertainties involved with using P v to diagnose mass-loss rates, and conclude that the large discrepancies between massloss rates determined from P v and the rates determined from “density squared” emission processes pose a significant challenge to the “standard model” of hot-star winds. The disparate measurements can be reconciled if the winds of O-type stars are strongly clumped on small spatial scales, which in turn implies that mass-loss rates based on Hα or radio emission are too large by up to an order of magnitude. Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17647 ER - TY - CHAP A1 - Bouret, J.-C. A1 - Lanz, T. A1 - Hillier, D. J. A1 - Foellmi, C. T1 - Clumping in O-type Supergiants N2 - We have analyzed the spectra of seven Galactic O4 supergiants, with the NLTE wind code CMFGEN. For all stars, we have found that clumped wind models match well lines from different species spanning a wavelength range from FUV to optical, and remain consistent with Hα data. We have achieved an excellent match of the P V λλ1118, 1128 resonance doublet and N IV λ1718, as well as He II λ4686 suggesting that our physical description of clumping is adequate. We find very small volume filling factors and that clumping starts deep in the wind, near the sonic point. The most crucial consequence of our analysis is that the mass loss rates of O stars need to be revised downward significantly, by a factor of 3 and more compared to those obtained from smooth-wind models. Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17662 ER - TY - CHAP A1 - Gull, T. R. T1 - Eta Carinae viewed from different vantages N2 - 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. Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-18200 ER - TY - CHAP A1 - Reimer, A. T1 - Clumping effects on non-thermal particle spectra in massive star systems N2 - 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. Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-18246 ER - TY - CHAP A1 - Schnurr, O. A1 - Crowther, P. A. T1 - Mid-IR observations of WC stars, and the connection to wind clumping N2 - 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. Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17884 ER - TY - CHAP A1 - Vink, J. S. A1 - Benaglia, P. A1 - Davies, B. A1 - de Koter, A. A1 - Oudmaijer, R. D. T1 - Advances in mass-loss predictions N2 - 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. Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17948 ER - TY - CHAP A1 - Moffat, Anthony F. J. A1 - Hillier, D. J. A1 - Hamann, Wolf-Rainer A1 - Owocki, S. P. T1 - General Discussion N2 - Clumping in hot-star winds : proceedings of an international workshop held in Potsdam, Germany, 18. - 22. June 2007 Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17953 ER - TY - CHAP A1 - Sonneborn, G. T1 - Imaging and spectroscopy with the James Webb Space Telescope N2 - 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. Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17983 ER - TY - CHAP A1 - Owocki, S. P. T1 - Dynamical simulation of the “velocity-porosity” reduction in observed strength of stellar wind lines N2 - 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. Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17992 ER - TY - CHAP A1 - Blomme, R. T1 - Corotating Interaction Regions and clumping N2 - 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. Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-18100 ER - TY - CHAP A1 - Kholtygin, A. F. T1 - Wavelets for looking for clumping in the wind of OB stars N2 - Clumping in hot-star winds : proceedings of an international workshop held in Potsdam, Germany, 18. - 22. June 2007 Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17796 ER - TY - CHAP A1 - Urbaneja, M. A. A1 - Kudritzki, R.-P. A1 - Puls, Joachim T1 - Clumping in the winds of O-type CSPNs N2 - Recent studies of massive O-type stars present clear evidences of inhomogeneous and clumped winds. O-type (H-rich) central stars of planetary nebulae (CSPNs) are in some ways the low mass–low luminosity analogous of those massive stars. In this contribution, we present preliminary results of our on-going multi-wavelength (FUV, UV and optical) study of the winds of Galactic CSPNs. Particular emphasis will be given to the clumping factors derived by means of optical lines (Hα and Heii 4686) and “classic” FUV (and UV) lines. Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17801 ER - TY - CHAP A1 - de Koter, A. A1 - Vink, J. S. A1 - Muijres, L. T1 - Constraints on wind clumping from the empirical mass-loss vs. metallicity relation for early-type stars N2 - We present the latest results on the observational dependence of the mass-loss rate in stellar winds of O and early-B stars on the metal content of their atmospheres, and compare these with predictions. Absolute empirical rates for the mass loss of stars brighter than 10$^{5.2} L_{\odot}$, based on H$\alpha$ and ultraviolet (UV) wind lines, are found to be about a factor of two higher than predictions. If this difference is attributed to inhomogeneities in the wind this would imply that luminous O and early-B stars have clumping factors in their H$\alpha$ and UV line forming regime of about a factor of 3--5. The investigated stars cover a metallicity range $Z$ from 0.2 to 1 $Z_{\odot}$. We find a hint towards smaller clumping factors for lower $Z$. The derived clumping factors, however, presuppose that clumping does not impact the predictions of the mass-loss rate. We discuss this assumption and explain how we intend to investigate its validity in more detail. Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17736 ER - TY - CHAP A1 - Reyes-Iturbide, J. A1 - Velázquez, P. A1 - Rosado, M. T1 - 3D numerical model for an asymmetrical superbubble N2 - Massive stars usually form groups such as OB associations. Their fast stellar winds sweep up collectively the surrounding insterstellar medium (ISM) to generate superbubbles. Observations suggest that superbubble evolution on the surrounding ISM can be very irregular. Numerical simulations considering these conditions could help to understand the evolution of these superbubbles and to clarify the dynamics of these objects as well as the difference between observed X-ray luminosities and the predicted ones by the standard model (Weaver et al. 1977). Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17724 ER - TY - CHAP A1 - Groh, J. H. A1 - Hillier, D. J. A1 - Damineli, A. T1 - Mass-loss rate and clumping in LBV stars : the impact of time-dependent effects N2 - This paper outlines a newly-developed method to include the effects of time variability in the radiative transfer code CMFGEN. It is shown that the flow timescale is often large compared to the variability timescale of LBVs. Thus, time-dependent effects significantly change the velocity law and density structure of the wind, affecting the derivation of the mass-loss rate, volume filling factor, wind terminal velocity, and luminosity. The results of this work are directly applicable to all active LBVs in the Galaxy and in the LMC, such as AG Car, HR Car, S Dor and R 127, and could result in a revision of stellar and wind parameters. The massloss rate evolution of AG Car during the last 20 years is presented, highlighting the need for time-dependent models to correctly interpret the evolution of LBVs. Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17773 ER - TY - GEN A1 - Howald, Markus A1 - Elsenbeer, Helmut A1 - Laczko, Endre A1 - Schlunegger, Urs Peter T1 - Capillary electrophoresis as a fast and universal tool in soil analysis N2 - 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. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 070 KW - capillary electrophoresis KW - soil analysis KW - UV-detection KW - inorganic ions KW - monosaccharides Y1 - 1995 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-16913 ER - TY - JOUR A1 - Kitagawa, Yoshihisa ED - Ishihara, Shinichiro ED - Petrova, Svetlana ED - Schwarz, Anne T1 - When we fail to question in Japanese JF - Interdisciplinary studies on information structure : ISIS ; working papers of the SFB 632 N2 - 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. KW - focus KW - (implicit) prosody KW - information structure KW - processing KW - Wh-question Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-24481 SN - 1866-4725 SN - 1614-4708 VL - 9 SP - 29 EP - 64 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - JOUR A1 - Mitchell, Don T1 - The end of culture? BT - culturalism and cultural geography in the Anglo-American “University of Excellence” JF - Geographische Revue : Zeitschrift für Literatur und Diskussion N2 - Content: -”Post-Culture” -Cultural Studies, Geography, and Culturalism -Taking Culture Seriously in the Post-Cultural World -Conclusion Y1 - 2000 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-24016 SN - 1438-3039 VL - 2 IS - 2 SP - 3 EP - 17 ER - TY - JOUR A1 - Smith, Neil T1 - Marxism and Geography in the Anglophone World JF - Geographische Revue : Zeitschrift für Literatur und Diskussion N2 - 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 Y1 - 2001 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-24357 SN - 1438-3039 VL - 3 IS - 2 SP - 5 EP - 21 ER - TY - THES A1 - Hoffmann, Toni T1 - Cloning and characterisation of the HMA3 gene and its promoter from Arabidopsis halleri (L.) O'Kane and Al'Shehbaz and Arabidopsis thaliana (L.) Heynhold T1 - Klonierung und Charakterisierung des HMA3 Genes und seines Promotors aus Arabidopsis halleri (L.) O'Kane und Al'Shehbaz und Arabidopsis thaliana (L.) Heynhold N2 - Being living systems unable to adjust their location to changing environmental conditions, plants display homeostatic networks that have evolved to maintain transition metal levels in a very narrow concentration range in order to avoid either deficiency or toxicity. Hence, plants possess a broad repertoire of mechanisms for the cellular uptake, compartmentation and efflux, as well as for the chelation of transition metal ions. A small number of plants are hypertolerant to one or a few specific transition metals. Some metal tolerant plants are also able to hyperaccumulate metal ions. The Brassicaceae family member Arabidopis halleri ssp. halleri (L.) O´KANE and AL´SHEHBAZ is a hyperaccumulator of zinc (Zn), and it is closely related to the non-hypertolerant and non-hyperaccumulating model plant Arabidopsis thaliana (L.) HEYNHOLD. The close relationship renders A. halleri a promising emerging model plant for the comparative investigation of the molecular mechanisms behind hypertolerance and hyperaccumulation. Among several potential candidate genes that are probably involved in mediating the zinc-hypertolerant and zinc-hyperaccumulating trait is AhHMA3. The AhHMA3 gene is highly similar to AtHMA3 (AGI number: At4g30120) in A. thaliana, and its encoded protein belongs to the P-type IB ATPase family of integral membrane transporter proteins that transport transition metals. In contrast to the low AtHMA3 transcript levels in A. thaliana, the gene was found to be constitutively highly expressed across different Zn treatments in A. halleri, especially in shoots. In this study, the cloning and characterisation of the HMA3 gene and its promoter from Arabidopsis halleri (L.) O´KANE and AL´SHEHBAZ and Arabidopsis thaliana (L.) HEYNHOLD is described. Heterologously expressed AhHMA3 mediated enhanced tolerance to Zn and to a much lesser degree to cadmium (Cd) but not to cobalt (Co) in metal-sensitive mutant strains of budding yeast. It is demonstrated that the genome of A. halleri contains at least four copies of AhHMA3, AhHMA3-1 to AhHMA3-4. A copy-specific real-time RT-PCR indicated that an AhHMA3-1 related gene copy is the source of the constitutively high transcript level in A. halleri and not a gene copy similar to AhHMA3-2 or AhHMA3-4. In accordance with the enhanced AtHMA3mRNA transcript level in A. thaliana roots, an AtHMA3 promoter-GUS gene construct mediated GUS activity predominantly in the vascular tissues of roots and not in shoots. However, the observed AhHMA3-1 and AhHMA3-2 promoter-mediated GUS activity in A. thaliana or A. halleri plants did not reflect the constitutively high expression of AhHMA3 in shoots of A. halleri. It is suggested that other factors e. g. characteristic sequence inserts within the first intron of AhHMA3-1 might enable a constitutively high expression. Moreover, the unknown promoter of the AhHMA3-3 gene copy could be the source of the constitutively high AhHMA3 transcript levels in A. halleri. In that case, the AhHMA3-3 sequence is predicted to be highly homologous to AhHMA3-1. The lack of solid localisation data for the AhHMA3 protein prevents a clear functional assignment. The provided data suggest several possible functions of the AhHMA3 protein: Like AtHMA2 and AtHMA4 it might be localised to the plasma membrane and could contribute to the efficient translocation of Zn from root to shoot and/or to the cell-to-cell distribution of Zn in the shoot. If localised to the vacuolar membrane, then a role in maintaining a low cytoplasmic zinc concentration by vacuolar zinc sequestration is possible. In addition, AhHMA3 might be involved in the delivery of zinc ions to trichomes and mesophyll leaf cells that are major zinc storage sites in A. halleri. N2 - Pflanzen sind lebende Systeme, die nicht in der Lage sind ihren Standort sich ändernden Umweltbedingungen anzupassen. Infolgedessen weisen Pflanzen homöostatischeNetzwerke auf, welche die Mengen an intrazellulären Übergangsmetallen in einem sehr engen Konzentrationsbereich kontrollieren um somit Vergiftungs- oder Mangelerscheinungen zu vermeiden. Eine kleine Anzahl von Pflanzen ist hypertolerant gegenüber einem oder mehreren Übergangsmetallen. Einige wenige dieser metalltoleranten Pflanzen sind fähig Übergangsmetalle in beträchtlichen Mengen zu speichern, sprich zu hyperakkumulieren, ohne Vergiftungserscheinungen zu zeigen. Die Haller’sche Schaumkresse (Arabidopis halleri ssp. halleri (L.) O´KANE und AL´SHEHBAZ) aus der Familie der Kreuzblütler (Brassicaceae) ist ein solcher Hyperakkumulator für Zink (Zn). Sie ist nah verwandt mit der Modellpflanze Ackerschmalwand (Arabidopsis thaliana (L.) HEYNHOLD), die jedoch nicht-hypertolerant und nicht-hyperakkumulierend für Übergangsmetalle ist. Diese nahe Verwandtschaft erlaubt vergleichende Studien der molekularen Mechanismen, die Hypertoleranz und Hyperakkumulation zu Grunde liegen. Zu der Gruppe von Kandidatengenen, die möglicherweise von Bedeutung für die Zink-hypertoleranten und -hyperakkumulierenden Eigenschaften von A. halleri sind, gehört AhHMA3, ein Gen mit großer Ähnlichkeit zu AtHMA3 (AGI Nummer: At4g30120) aus A. thaliana. Es kodiert ein Protein aus der Familie transmembraner Übergangsmetall-Transportproteine, den P-typ IB ATPasen. Im Gegensatz zu den niedrigen AtHMA3 Transkriptmengen in A. thaliana wird das AhHMA3 Gen in A. halleri in Gegenwart verschiedener Zn Konzentrationen konstitutiv hoch exprimiert, insbesondere im Spross der Pflanze. Diese Arbeit beschreibt die Klonierung und Charakterisierung des HMA3 Gens und seines Promoters aus A. halleri und A. thaliana. Es wurde gezeigt, dass heterolog exprimiertes AhHMA3 Protein in metallsensitiven Hefestämmen eine erhöhte Toleranz gegenüber Zink und zu einem geringen Grad gegenüber Kadmium (Cd) jedoch nicht gegenüber Kobalt (Co) vermittelt.Weiterhin wurden im Genom von A. halleri mindestens vier AhHMA3 Genkopien, AhHMA3-1 bis AhHMA3-4, nachgewiesen. Eine Genkopie-spezifische Echtzeit-RT-PCR (real-time RT-PCR) deutete darauf hin, dass eine zu AhHMA3-1 und nicht zu AhHMA3-2 oder AhHMA3-4 ähnliche Genkopie die Quelle der konstitutiv hohen Transkriptmengen in A. halleri ist. In Übereinstimmung mit erhöhten mRNS Transkriptmengen inWurzeln von A. thaliana, vermittelte ein AtHMA3 Promoter-GUS (ß-Glucuronidase) Genkonstrukt GUS-Aktivität hauptsächlich in den Leitgeweben der Wurzeln jedoch nicht des Sprosses. Die vermittelte GUS-Aktivität durch Promoterfragmente von AhHMA3-1 und AhHMA3-2 in A. thaliana oder A. halleri Pflanzen spiegelte jedoch nicht die konstitutiv hohe AhHMA3 Expression im Spross von A. halleri wieder. Es wird vermutet, dass andere Faktoren die konstitutiv hohe Expression ermöglichen wie zum Beispiel die gefundenen kopiespezifischen Sequenzinsertionen innerhalb des ersten AhHMA3-1 Introns. Weiterhin ist es denkbar, dass der unbekannte Promoter der AhHMA3-3 Genkopie die Quelle der konstitutiv hohen AhHMA3 Transkriptmengen ist. In diesem Fall wird eine sehr hohe Ähnlichkeit zwischen den Sequenzen von AhHMA3-3 und der AhHMA3-1 vorhergesagt. Es konnten keine deutlichen Ergebnisse zur intrazellulären Lokalisierung gemacht werden, die eine exakte Einordnung der Funktion des AhHMA3 Proteins erlauben würden. Die bisher ermittelten Ergebnisse schlagen jedoch mehrere mögliche Funktionen für AhHMA3 vor: Ähnlich den AhHMA3 homologen Proteinen, AtHMA2 und AtHMA4, könnte AhHMA3 in der Plasmamembran der Zelle sitzen und dort zur effizienten Translokation von Zink aus der Wurzel in den Spross und/oder zur Zell-zu-Zell Verteilung von Zn im Spross beitragen. Falls AhHMA3 in der Membran der Vakuole sitzt, könnte es eine Rolle bei der Aufrechterhaltung niedriger zytoplasmatischer Zinkkonzentrationen durch vakuoläre Zinksequestrierung spielen. Zusätzlich ist es denkbar, dass AhHMA3 an der Abgabe von Zinkionen an Trichome und Blattmesophyllzellen beteiligt ist, die die Haupteinlagerungsorte für Zink in A. halleri darstellen. KW - P-Typ ATPase KW - Übergangsmetalle KW - Hyperakkumulation KW - Zink KW - HMA KW - p-type ATPase KW - transition metals KW - hyperaccumulation KW - zinc KW - HMA Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-15259 ER - TY - THES A1 - Köchert, Karl T1 - Development of a method to assess EAAT1 transcription levels in Alzheimer's disease N2 - Zur Zeit leiden ca. 24 Millionen Menschen auf der ganzen Welt unter Demenz, Alzheimer macht dabei 50-60% aller Demenzfälle aus. Da der Anteil der Bevölkerung, der an Demenz leidet, proportional zum Alter zunimmt und der Anteil älterer Menschen in der Gesellschaft von Jahr zu Jahr steigt, wird Alzheimer immer mehr zu einem ernstzunehmenden, gesellschaftlichen Problem. Zum Stand der heutigen Forschung ist es etabliert, dass die Aminosäure Glutamat - quantitativ einer der wichtigsten Neurotransmitter im Zentralen Nervensystem (ZNS) - toxische Konzentrationen erreichen kann wenn sie - im Zuge der Übertragung von Aktionspotentialen - nach ihrer Freisetzung nicht aus dem Synaptischen Spalt entfernt wird. Viele Studien haben gezeigt, dass in der Alzheimerschen Krankheit die Glutamataufnahme beeinträchtigt ist, was zu toxischen Konzentrationen von Glutamat und dem daraus folgenden Absterben von Neuronen führt. Der exitatorische Aminosäuretransporter 1 (EAAT1) gehört zu der Familie der Na+-abhängigen Glutamattransporter und stellt nach EAAT2 den quantitativ wichtigsten Glutamattransporter im ZNS dar. In diesem Projekt wurde eine bis dahin für den Menschen nicht bekannte EAAT1 Spleißvariante, in der Exon 3 ausgeschnitten wird, nachgewiesen. Diese Variante wurde EAAT1Δ3 genannt und stellt damit mit EAAT1Δ9 die zweite für EAAT1 nachgewiesene Spleißvariante dar. Eine auf real-time RT-PCR basierende Methode wurde entwickelt, um die Transkripte von EAAT1 wildtyp (EAAT1 wt), EAAT1Δ3 und EAAT1Δ9 zu quantifizieren. Proben aus verschiedenen Hirnarealen wurden aus einem Set von Kontrollen und Alzheimerfällen bei der Quantifizierung verwendet. Die gewählten Areale sind von der Alzheimerschen Krankheit unterschiedlich stark betroffen. Dies diente als interne Kontrolle für die durchgeführten Experimente und ermöglichte so die Differenzierung zwischen beobachteten Effekten: Nur Effekte die alleinig in von Alzheimer betroffenen Gehirnarealen auftreten, können als spezifisch für die Krankheit angesehen werden. Die Resultate diese Projektes zeigen, dass EAAT1Δ3 in sehr geringer Anzahl transkribiert wird, die nur 0.15% der EAAT1 wt Transkription entspricht. Dahingegen entspricht das EAAT1 Δ9 Transkript im Durchschnitt 26.6% des EAAT1 wt Transkripts. Es wurde nachgewiesen, dass die Transkriptionsrate aller EAAT1 Varianten in Alzheimerfällen signifikant reduziert ist (P<0.0001). Dies unterstützt die Theorie, dass bei Alzheimerfällen die EAAT1 Proteinexpression stark reduziert und der Glutamattransport, der normalerweise durch diesen Transporter gewährleistet wird, stark eingeschränkt ist. Dies wiederum resultiert in toxisch hohen Glutamatkonzentrationen und damit dem Absterben von Neuronen. Die gefundene Reduktion der EAAT1Transkription ist nicht spezifisch für Gehirnareale die von Alzheimer betroffen sind, sondern tritt in selbem Maße in nicht von Alzheimer betroffenen Gehirnarealen auf. Daraus lässt sich schließen, dass die Reduktion der EAAT1 Transkription eher ein Resultat eines in der Alzheimerschen Krankheit präsenten, grundlegenden Krankheitsmechanismus ist als deren Ursache. N2 - Today about 24 Million people worldwide suffer from dementia, Alzheimer’s Disease accounts for approximately 50-60% of all dementia cases. As the prevalence of dementia grows with increasing age Alzheimer’s Disease becomes more and more of an issue for society as the proportion of elderly people increases from year to year. It is well established, that the amino acid glutamate - quantitatively being the most important neurotransmitter in the central nervous system (CNS) - may reach toxic concentrations if not cleared from the synaptic cleft into which it is released during transmittance of action potentials. In Alzheimer’s Disease there is strong evidence for a generally impaired glutamate uptake system which in turn is thought to result in toxic levels of the amino acid with the potential to kill off neurons. The excitatory amino acid transporter 1 (EAAT1) belongs to the family of Na+-dependent glutamate transporter and accounts together with EAAT2 for most of the glutamate uptake in the CNS. In this project a new splice variant of EAAT1, skipping exon 3 was detected in human brain samples and subsequently called EAAT1Δ3, this being the second splice variant found after the recent detection of EAAT1Δ9. A method was developed to quantify the transcript of EAAT1 wt, EAAT1Δ3 and EAAT1Δ9 by means of real-time PCR. Samples were taken from different brain areas of a set of control and AD cases. The areas chosen for examination are affected differently in Alzheimer’s Disease, this was used an internal control for the experiments done in this project as to determine whether any effect observed is specific for AD, i.e. AD affected areas or is generally seen in all areas examined. The results of this project show that EAAT1Δ3 is transcribed in very low copy numbers making up a proportion of 0.15% of EAAT1 wt whereas EAAT1Δ9 is transcribed in a considerably large proportion of EAAT1 wt of 26.6%. It was moreover found that all EAAT1 variants are transcribed at significantly lower rates (P<0.0001) in AD cases, supporting the theory that EAAT1 protein expression is reduced to a point where glutamate uptake normally mediated by this transporter is impaired. This in turn is thought to result in toxic levels glutamate accounting for neuronal loss in the disease. No area-dependent effects were found, suggesting that the reduction of EAAT1 transcription is rather a result of an underlying general mechanism present in AD. Further research will have to be done to assess the degree of EAAT1 expression in AD and whether those future findings match with the result of this project. KW - Morbus Alzheimer KW - Glutamat KW - EAAT1 KW - Spleißvariante KW - Alzheimer's Disease KW - Glutamate KW - EAAT1 KW - Splice Variant Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-15965 ER - TY - GEN A1 - Kort, C. A. D. de A1 - Peter, Martin G. A1 - Koopmanschap, A. B. T1 - Binding and degradation of juvenile hormone III by haemolymph proteins of the Colorado potato beetle: a re-examination N2 - 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. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 068 KW - Juvenile hormone KW - Leptinotarsa decemlineata KW - JH-III-specific carrier protein KW - enantioselectivity Y1 - 1983 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-16777 ER - TY - THES A1 - Imran ul-haq, Muhammad T1 - Synthesis of fluorinated polymers in supercritical carbon dioxide (scCO₂) T1 - Synthese von Fluorpolymeren in überkritischem Kohlendioxid (scCO₂) N2 - 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. N2 - Erstmalig gelang es, stabilisatorfreie Vinylidenfluorid (VDF)-Polymerisationen in homogener Phase mit überkritischem CO₂ (scCO₂) bis zu vollständigem Monomerumsatz durchzuführen. Die Homogenität während der Polymerisation wurde durch in-line Fourier-Transform Nahinfrarot Spektroskopie beobachtet. Für Polymerisationen bei 140 °C und 1500 bar wurde Di-tert-butylperoxid (DTBP) als Initiator verwendet. Es wurden Polymere mit einem Zahlenmittel der Molmasse kleiner 104 g·mol–1 und Polydispersitäten zwischen 3.1 und 5.7. erhalten. Um isotherme Reaktionen zu ermöglichen, wurden CO₂-Gehalte zwischen 61 und 83 wt.% verwendet. Die für die homogene Reaktionsführung erforderlichen hohen Drücke und Temperaturen haben keinen Einfluss auf die Mikrostruktur des Polymers. Zur Verringerung der Initiatorkonzentration wurden weitere Polymerisationen unter Verwendung von Kettentransferreagenzien (CTA) bei 120 °C und 1500 bar in homogener Phase mit scCO₂ durchgeführt. Perfluoriertes Hexyliodid als CTA ermöglicht kontrollierte radikalische Polymerisationen, wobei Polymere mit geringer Polydispersität zwischen 1.5 und 1.2 erhalten wurden. Endgruppenanalyse mit Elektronenspray-Ionisations-Massen¬spektro¬metrie (ESI-MS) zeigte, dass keine Initiatorendgruppen im Polymer enthalten sind. Diese Beobachtung unterstützt den lebenden Charakter der Polymerisationen und basiert auf einer labilen C-I-Bindung im Polymer. Aufgrund der schwachen C-I-Bindung trägt das perfluorierte Hexyliodid (C6F13I) auch zur Initiierung bei. Polymerisationen in Gegenwart von BrCCl3, C6F13Br und C6F13H zeigten, dass nur C6F13H keinen Beitrag zur Initiierung leistet. Bei 120 °C und 1500 bar wurde ein kp/kt0.5 von ~ 0.64 (L·mol−1·s−1)0.5 bestimmt, wobei kp der Wachstums- und kt der Terminierungsgeschwindigkeitskoeffizient sind. Die Kettentransfer¬konstanten (CT) bei 120°C betragen 8·10−1, 9·10−2 und 2·10−4 für C6F13I, C6F13Br und C6F13H. Die Änderung der CT-Werte lässt sich mit der zunehmenden Bindungsenergie in der Reihe C-I, C-Br und C-H erklären. Die labile C-I-Bindung ermöglicht eine Funktionalisierung des Polymers durch Click-Reaktionen. Nach Substitution der Iodid-Endgruppe durch eine Azidgruppe erfolgte eine katalysatorfreie 1,3-dipolare Cyclaoaddition mit Alkinen zu Polymeren mit 1,2,3-Triazol-Endgruppen. Dieses endfunktionalisierte PVDF besitzt im Vergleich zu konventionellem PVDF eine höhere thermische Stabilität. Nach der Expansion der Polymerisationsmischung mit scCO₂ auf Umgebungsbedingungen lag das Polymer als weißes Pulver vor, das im Hinblick auf z.B. Polymerendgruppen, Kristallinität, Gestalt und Größe der Partikel untersucht wurde. Rasterelektronenmikroskopie zeigte, dass Polymere mit DTBP-Endgruppen zu stapelförmigen Partikeln führen, während bei CTA-Fragmenten als Endgruppen schwamm- oder rosenartige Partikel erhalten wurden. Ergebnisse der FT-IR Spektroskopie und Weitwinkelröntgenbeugung zeigten, dass der höchste Gehalt an β-phasigem Material, der für die Piezoelektrizität des PVDF verantwortlich ist, für PVDF mit Initiatorendgruppen erhalten wurde. DSC (Differential Scanning Calorimetry) Messungen ergaben zudem, dass der Kristallinitätsgrad durch Endgruppen und Polymermasse beeinflusst wird. Die Expansion der homogenen Polymermischung kann als nicht-optimierter RESS-Prozess (Rapid Expanison from Supercritical Solution,) angesehen werden. Aus RESS Experimenten unter kontrollierten Bedingungen wurden jeweils nanoskalige primäre PVDF-Partikel ohne Verwendung von Lösungsmitteln, Tensiden oder anderen Additiven erhalten. Es besteht ein enger Zusammenhang zwischen einerseits der Partikelgröße und der Partikelgrößenverteilung und andererseits der Polymerkonzentration in scCO₂ vor der Expansion, bestimmt durch Polymerendgruppen und Molmassen der eingesetzten Materialien. KW - Synthese KW - Fluorpolymere KW - überkritisches Kohlendioxid (scCO₂) KW - Synthesis KW - fluorinated polymers KW - supercritical carbon dioxide (scCO₂) Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-19868 ER - TY - GEN A1 - Köchy, Martin A1 - Bråkenhielm, Sven T1 - Separation of effects of moderate N deposition from natural change in ground vegetation of forests and bogs N2 - The effect of moderate rates of nitrogen deposition on ground floor vegetation is poorly predicted by uncontrolled surveys or fertilization experiments using high rates of nitrogen (N) addition. We compared the temporal trends of ground floor vegetation in permanent plots with moderate (7–13 kg ha−1 year−1) and lower bulk N deposition (4–6 kg ha−1 year−1) in southern Sweden during 1982–1998. We examined whether trends differed between growth forms (vascular plants and bryophytes) and vegetation types (three types of coniferous forest, deciduous forest, and bog). Trends of site-standardized cover and richness varied among growth forms, vegetation types, and deposition regions. Cover in spruce forests decreased at the same rate with both moderate and low deposition. In pine forests cover decreased faster with moderate deposition and in bogs cover decreased faster with low deposition. Cover of bryophytes in spruce forests increased at the same rate with both moderate and low deposition. In pine forests cover decreased faster with moderate deposition and in bogs and deciduous forests there was a strong non-linear increase with moderate deposition. The trend of number of vascular plants was constant with moderate and decreased with low deposition. We found no trend in the number of bryophyte species. We propose that the decrease of cover and number with low deposition was related to normal ecosystem development (increased shading), suggesting that N deposition maintained or increased the competitiveness of some species in the moderate-deposition region. Deposition had no consistent negative effect on vegetation suggesting that it is less important than normal successional processes. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 034 KW - Nitrogen deposition KW - Vascular plants KW - Bryophytes KW - Species richness KW - Succession KW - Understorey Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-16621 ER - TY - GEN A1 - Elsenbeer, Helmut A1 - Lack, Andreas A1 - Cassel, Keith T1 - Chemical fingerprints of hydrological compartments and flow paths at La Cuenca, western Amazonia N2 - A forested first-order catchment in western Amazonia was monitored for 2 years to determine the chemical fingerprints of precipitation, throughfall, overland flow, pipe flow, soil water, groundwater, and streamflow. We used five tracers (hydrogen, calcium, magnesium, potassium, and silica) to distinguish “fast” flow paths mainly influenced by the biological subsystem from “slow” flow paths in the geochemical subsystem. The former comprise throughfall, overland flow, and pipe flow and are characterized by a high potassium/silica ratio; the latter are represented by soil water and groundwater, which have a low potassium/silica ratio. Soil water and groundwater differ with respect to calcium and magnesium. The groundwater-controlled streamflow chemistry is strongly modified by contributions from fast flow paths during precipitation events. The high potassium/silica ratio of these flow paths suggests that the storm flow response at La Cuenca is dominated by event water. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 047 KW - Chemistry of fresh water KW - Runoff and streamflow KW - Weathering Y1 - 1995 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-16937 ER - TY - GEN A1 - Elsenbeer, Helmut A1 - Lorieri, Daniel A1 - Bonell, Mike T1 - Mixing model approaches to estimate storm flow sources in an overland flow-dominated tropical rain forest catchment N2 - Previous hydrometric studies demonstrated the prevalence of overland flow as a hydrological pathway in the tropical rain forest catchment of South Creek, northeast Queensland. The purpose of this study was to consider this information in a mixing analysis with the aim of identifying sources of, and of estimating their contribution to, storm flow during two events in February 1993. K and acid-neutralizing capacity (ANC) were used as tracers because they provided the best separation of the potential sources, saturation overland flow, soil water from depths of 0.3, 0.6, and 1.2 m, and hillslope groundwater in a two-dimensional mixing plot. It was necessary to distinguish between saturation overland flow, generated at the soil surface and following unchanneled pathways, and overland flow in incised pathways. This latter type of overland flow was a mixture of saturation overland flow (event water) with high concentrations of K and a low ANC, soil water (preevent water) with low concentrations of K and a low ANC, and groundwater (preevent water) with low concentrations of K and a high ANC. The same sources explained the streamwater chemistry during the two events with strongly differing rainfall and antecedent moisture conditions. The contribution of saturation overland flow dominated the storm flow during the first, high-intensity, 178-mm event, while the contribution of soil water reached 50% during peak flow of the second, low-intensity, 44-mm event 5 days later. This latter result is remarkably similar to soil water contributions to storm flow in mountainous forested catchments of the southeastern United States. In terms of event and preevent water the storm flow hydrograph of the high-intensity event is dominated by event water and that of the low-intensity event by preevent water. This study highlights the problems of applying mixing analyses to overland flow-dominated catchments and soil environments with a poorly developed vertical chemical zonation and emphasizes the need for independent hydrometric information for a complete characterization of watershed hydrology and chemistry. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 048 KW - SOILWATER END-MEMBERS KW - HYDROGRAPH SEPARATION KW - STREAMWATER CHEMISTRY KW - ACIDIFICATION KW - MIXTURE KW - TRACERS KW - EVENTS Y1 - 1995 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-16948 ER - TY - GEN A1 - Höhle, Barbara A1 - Weissenborn, Jürgen A1 - Kiefer, Dorothea A1 - Schulz, Antje A1 - Schmitz, Michaela T1 - Functional elements in infants’ speech processing : the role of determiners in the syntactic categorization of lexical elements N2 - How do children determine the syntactic category of novel words? In this article we present the results of 2 experiments that investigated whether German children between 12 and 16 months of age can use distributional knowledge that determiners precede nouns and subject pronouns precede verbs to syntactically categorize adjacent novel words. Evidence from the head-turn preference paradigm shows that, although 12- to 13-month-olds cannot do this, 14- to 16-month-olds are able to use a determiner to categorize a following novel word as a noun. In contrast, no categorization effect was found for a novel word following a subject pronoun. To understand this difference we analyzed adult child-directed speech. This analysis showed that there are in fact stronger co-occurrence relations between determiners and nouns than between subject pronouns and verbs. Thus, in German determiners may be more reliable cues to the syntactic category of an adjacent novel word than are subject pronouns. We propose that the capacity to syntactically categorize novel words, demonstrated here for the first time in children this young, mediates between the recognition of the specific morphosyntactic frame in which a novel word appears and the word-to-world mapping that is needed to build up a semantic representation for the novel word. T3 - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe - paper 023 Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-16285 ER - TY - GEN A1 - Höhle, Barbara A1 - Schmitz, Michaela A1 - Müller, Anja A1 - Weissenborn, Jürgen T1 - The recognition of discontinuous verbal dependencies by German 19-month-olds : evidence for lexical and structural influences on children’s early processing capacities N2 - Recent work has shown that English-learning 18-month-olds can detect the relationship between discontinuous morphemes such as is and -ing in Grandma is always running (Gomez, 2002; Santelmann & Jusczyk, 1998) but only at a maximum of 3 intervening syllables. In this article we examine the tracking of discontinuous dependencies in children acquiring German. Due to freer word order, German allows for greater distances between dependent elements and a greater syntactic variety of the intervening elements than English does. The aim of this study was to investigate whether factors other than distance may influence the child’s capacity to recognize discontinuous elements. Our findings provide evidence that children’s recognition capacities are affected not only by distance but also by their ability to linguistically analyze the material intervening between the dependent elements. We speculate that this result supports the existence of processing mechanisms that reduce a discontinuous relation to a local one based on subcategorization relations. T3 - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe - paper 024 Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-16297 ER - TY - GEN A1 - Höhle, Barbara A1 - van de Vijver, Ruben A1 - Weissenborn, Jürgen T1 - Word processing at 19 months and its relation to language performance at 30 months : a retrospective analysis of data from German learning children N2 - Recent research has shown that the early lexical representations children establish in their second year of life already seem to be phonologically detailed enough to allow differentiation from very similar forms. In contrast to these findings children with specific language impairment show problems in discriminating phonologically similar word forms up to school age. In our study we investigated the question whether there would be differences in the processing of phonological details in normally developing and in children with low language performance in the second year of life. This was done by a retrospective study in which in the processing of phonological details was tested by a preferential looking experiment when the children were 19 months old. At the age of 30 months children were tested with a standardized German test of language comprehension and production (SETK2). The preferential looking data at 19 months revealed an opposite reaction pattern for the two groups: while the children scoring normally in the SETK2 increase their fixations of a pictured object only when it was named with the correct word, children with later low language performance did so only when presented with a phonologically slightly deviant mispronunciation. We suggest that this pattern does not point to a specific deficit in processing phonological information in these children but might be related to an instability of early phonological representations, and/or a generalized problem of information processing as compared to typically developing children. T3 - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe - paper 025 KW - Word processing KW - late talker KW - early indicators for SLI KW - processing of phonological details Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-16302 ER - TY - CHAP A1 - Piskorski, Jakub T1 - ExPRESS : extraction pattern recognition engine and specification suite N2 - 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. Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-27227 ER - TY - CHAP ED - Kurths, Jürgen ED - Fradkov, Alexander ED - Chen, Guanrong T1 - The 3rd international IEEE scientific conference on physics and control (PhysCon 2007) : September 3rd-7th 2007 at the University of Potsdam N2 - During the last few years there was a tremendous growth of scientific activities in the fields related to both Physics and Control theory: nonlinear dynamics, micro- and nanotechnologies, self-organization and complexity, etc. New horizons were opened and new exciting applications emerged. Experts with different backgrounds starting to work together need more opportunities for information exchange to improve mutual understanding and cooperation. The Conference "Physics and Control 2007" is the third international conference focusing on the borderland between Physics and Control with emphasis on both theory and applications. With its 2007 address at Potsdam, Germany, the conference is located for the first time outside of Russia. The major goal of the Conference is to bring together researchers from different scientific communities and to gain some general and unified perspectives in the studies of controlled systems in physics, engineering, chemistry, biology and other natural sciences. We hope that the Conference helps experts in control theory to get acquainted with new interesting problems, and helps experts in physics and related fields to know more about ideas and tools from the modern control theory. KW - nonlinear dynamics KW - micro- and nanotechnologies KW - self-organization KW - complexity Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-15228 PB - Universitätsverlag Potsdam CY - Potsdam ER - TY - THES A1 - Miteva, Rositsa Stoycheva T1 - Electron acceleration at localized wave structures in the solar corona T1 - Elektronenbeschleunigung an lokalen Wellenstrukturen in der Sonnenkorona N2 - Our dynamic Sun manifests its activity by different phenomena: from the 11-year cyclic sunspot pattern to the unpredictable and violent explosions in the case of solar flares. During flares, a huge amount of the stored magnetic energy is suddenly released and a substantial part of this energy is carried by the energetic electrons, considered to be the source of the nonthermal radio and X-ray radiation. One of the most important and still open question in solar physics is how the electrons are accelerated up to high energies within (the observed in the radio emission) short time scales. Because the acceleration site is extremely small in spatial extent as well (compared to the solar radius), the electron acceleration is regarded as a local process. The search for localized wave structures in the solar corona that are able to accelerate electrons together with the theoretical and numerical description of the conditions and requirements for this process, is the aim of the dissertation. Two models of electron acceleration in the solar corona are proposed in the dissertation: I. Electron acceleration due to the solar jet interaction with the background coronal plasma (the jet--plasma interaction) A jet is formed when the newly reconnected and highly curved magnetic field lines are relaxed by shooting plasma away from the reconnection site. Such jets, as observed in soft X-rays with the Yohkoh satellite, are spatially and temporally associated with beams of nonthermal electrons (in terms of the so-called type III metric radio bursts) propagating through the corona. A model that attempts to give an explanation for such observational facts is developed here. Initially, the interaction of such jets with the background plasma leads to an (ion-acoustic) instability associated with growing of electrostatic fluctuations in time for certain range of the jet initial velocity. During this process, any test electron that happen to feel this electrostatic wave field is drawn to co-move with the wave, gaining energy from it. When the jet speed has a value greater or lower than the one, required by the instability range, such wave excitation cannot be sustained and the process of electron energization (acceleration and/or heating) ceases. Hence, the electrons can propagate further in the corona and be detected as type III radio burst, for example. II. Electron acceleration due to attached whistler waves in the upstream region of coronal shocks (the electron--whistler--shock interaction) Coronal shocks are also able to accelerate electrons, as observed by the so-called type II metric radio bursts (the radio signature of a shock wave in the corona). From in-situ observations in space, e.g., at shocks related to co-rotating interaction regions, it is known that nonthermal electrons are produced preferably at shocks with attached whistler wave packets in their upstream regions. Motivated by these observations and assuming that the physical processes at shocks are the same in the corona as in the interplanetary medium, a new model of electron acceleration at coronal shocks is presented in the dissertation, where the electrons are accelerated by their interaction with such whistlers. The protons inflowing toward the shock are reflected there by nearly conserving their magnetic moment, so that they get a substantial velocity gain in the case of a quasi-perpendicular shock geometry, i.e, the angle between the shock normal and the upstream magnetic field is in the range 50--80 degrees. The so-accelerated protons are able to excite whistler waves in a certain frequency range in the upstream region. When these whistlers (comprising the localized wave structure in this case) are formed, only the incoming electrons are now able to interact resonantly with them. But only a part of these electrons fulfill the the electron--whistler wave resonance condition. Due to such resonant interaction (i.e., of these electrons with the whistlers), the electrons are accelerated in the electric and magnetic wave field within just several whistler periods. While gaining energy from the whistler wave field, the electrons reach the shock front and, subsequently, a major part of them are reflected back into the upstream region, since the shock accompanied with a jump of the magnetic field acts as a magnetic mirror. Co-moving with the whistlers now, the reflected electrons are out of resonance and hence can propagate undisturbed into the far upstream region, where they are detected in terms of type II metric radio bursts. In summary, the kinetic energy of protons is transfered into electrons by the action of localized wave structures in both cases, i.e., at jets outflowing from the magnetic reconnection site and at shock waves in the corona. N2 - Die Sonne ist ein aktiver Stern, was sich nicht nur in den allseits bekannten Sonnenflecken, sondern auch in Flares manifestiert. Während Flares wird eine große Menge gespeicherter, magnetischer Energie in einer kurzen Zeit von einigen Sekunden bis zu wenigen Stunden in der Sonnenkorona freigesetzt. Dabei werden u.a. energiereiche Elektronen erzeugt, die ihrerseits nichtthermische Radio- und Röntgenstrahlung, wie sie z.B. am Observatorium für solare Radioastronomie des Astrophysikalischen Instituts Potsdam (AIP) in Tremsdorf und durch den NASA-Satelliten RHESSI beobachtet werden, erzeugen. Da diese Elektronen einen beträchtlichen Anteil der beim Flare freigesetzten Energie tragen, ist die Frage, wie Elektronen in kurzer Zeit auf hohe Energien in der Sonnenkorona beschleunigt werden, von generellem astrophysikalischen Interesse, da solche Prozesse auch in anderen Sternatmosphären und kosmischen Objekten, wie z.B. Supernova-Überresten, stattfinden. In der vorliegenden Dissertation wird die Elektronenbeschleunigung an lokalen Wellenstrukturen im Plasma der Sonnenkorona untersucht. Solche Wellen treten in der Umgebung der magnetischen Rekonnektion, die als ein wichtiger Auslöser von Flares angesehen wird, und in der Nähe von Stoßwellen, die infolge von Flares erzeugt werden, auf. Generell werden die Elektronen als Testteilchen behandelt. Sie werden durch ihre Wechselwirkung mit den elektrischen und magnetischen Feldern, die mit den Plasmawellen verbunden sind, beschleunigt. Infolge der magnetischen Rekonnektion als Grundlage des Flares werden starke Plasmaströmungen (sogenannte Jets) erzeugt. Solche Jets werden im Licht der weichen Röntgenstrahlung, wie z.B. durch den japanischen Satelliten YOHKOH, beobachtet. Mit solchen Jets sind solare Typ III Radiobursts als Signaturen von energiereichen Elektronenstrahlen in der Sonnenkorona verbunden. Durch die Wechselwirkung eines Jets mit dem umgebenden Plasma werden lokal elektrische Felder erzeugt, die ihrerseits Elektronen beschleunigen können. Dieses hier vorgestellte Szenarium kann sehr gut die Röntgen- und Radiobeobachtungen von Jets und den damit verbundenen Elektronenstrahlen erklären. An koronalen Stoßwellen, die infolge Flares entstehen, werden Elektronen beschleunigt, deren Signatur man in der solaren Radiostrahlung in Form von sogenannten Typ II Bursts beobachten kann. Stoßwellen in kosmischen Plasmen können mit Whistlerwellen (ein spezieller Typ von Plasmawellen) verbunden sein. In der vorliegenden Arbeit wird ein Szenarium vorgestellt, das aufzeigt, wie solche Whistlerwellen an koronalen Stoßwellen erzeugt werden und durch ihre resonante Wechselwirkung mit den Elektronen dieselben beschleunigen. Dieser Prozess ist effizienter als bisher vorgeschlagene Mechanismen und kann deshalb auch auf andere Stoßwellen im Kosmos, wie z.B. an Supernova-Überresten, zur Erklärung der dort erzeugten Radio- und Röntgenstrahlung dienen. KW - Elektronenbeschleunigung KW - Sonnenkorona KW - Jets KW - Stoßwellen KW - Nichtlineare Wellen KW - Electron acceleration KW - Solar corona KW - Jets KW - Shock waves KW - Nonlinear waves Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14775 ER - TY - GEN A1 - Ascher, Uri M. A1 - Chin, Hongsheng A1 - Reich, Sebastian T1 - Stabilization of DAEs and invariant manifolds N2 - Many methods have been proposed for the stabilization of higher index differential-algebraic equations (DAEs). Such methods often involve constraint differentiation and problem stabilization, thus obtaining a stabilized index reduction. A popular method is Baumgarte stabilization, but the choice of parameters to make it robust is unclear in practice. Here we explain why the Baumgarte method may run into trouble. We then show how to improve it. We further develop a unifying theory for stabilization methods which includes many of the various techniques proposed in the literature. Our approach is to (i) consider stabilization of ODEs with invariants, (ii) discretize the stabilizing term in a simple way, generally different from the ODE discretization, and (iii) use orthogonal projections whenever possible. The best methods thus obtained are related to methods of coordinate projection. We discuss them and make concrete algorithmic suggestions. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 030 Y1 - 1994 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-15625 ER - TY - GEN A1 - Leimkuhler, Benedict A1 - Reich, Sebastian T1 - Symplectic integration of constrained Hamiltonian systems N2 - A Hamiltonian system in potential form (formula in the original abstract) subject to smooth constraints on q can be viewed as a Hamiltonian system on a manifold, but numerical computations must be performed in Rn. In this paper methods which reduce "Hamiltonian differential algebraic equations" to ODEs in Euclidean space are examined. The authors study the construction of canonical parameterizations or local charts as well as methods based on the construction of ODE systems in the space in which the constraint manifold is embedded which preserve the constraint manifold as an invariant manifold. In each case, a Hamiltonian system of ordinary differential equations is produced. The stability of the constraint invariants and the behavior of the original Hamiltonian along solutions are investigated both numerically and analytically. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 032 KW - differential-algebraic equations KW - constrained Hamiltonian systems KW - canonical discretization schemes KW - symplectic methods Y1 - 1994 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-15653 ER - TY - GEN A1 - Ascher, Uri M. A1 - Chin, Hongsheng A1 - Petzold, Linda R. A1 - Reich, Sebastian T1 - Stabilization of constrained mechanical systems with DAEs and invariant manifolds N2 - Many methods have been proposed for the simulation of constrained mechanical systems. The most obvious of these have mild instabilities and drift problems. Consequently, stabilization techniques have been proposed A popular stabilization method is Baumgarte's technique, but the choice of parameters to make it robust has been unclear in practice. Some of the simulation methods that have been proposed and used in computations are reviewed here, from a stability point of view. This involves concepts of differential-algebraic equation (DAE) and ordinary differential equation (ODE) invariants. An explanation of the difficulties that may be encountered using Baumgarte's method is given, and a discussion of why a further quest for better parameter values for this method will always remain frustrating is presented. It is then shown how Baumgarte's method can be improved. An efficient stabilization technique is proposed, which may employ explicit ODE solvers in case of nonstiff or highly oscillatory problems and which relates to coordinate projection methods. Examples of a two-link planar robotic arm and a squeezing mechanism illustrate the effectiveness of this new stabilization method. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 033 Y1 - 1994 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-15698 ER - TY - CHAP A1 - Watson, Bruce W. T1 - Advances in automata implementation techniques (Abstract) Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-27094 ER - TY - CHAP A1 - Barthélemy, François T1 - Finite-state compilation of feature structures for two-level morphology N2 - 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. Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-27120 ER - TY - CHAP A1 - Blanc, Olivier A1 - Constant, Matthieu A1 - Watrin, Patrick T1 - Segmentation in super-chunks with a finite-state approach N2 - 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. Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-27133 ER - TY - CHAP A1 - Bonfante, Guillaume A1 - Le Roux, Joseph T1 - Intersection optimization is NP-complete N2 - 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. Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-27146 ER - TY - CHAP A1 - Daciuk, Jan T1 - Perfect hashing tree automata N2 - 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. Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-27163 ER -