@phdthesis{Riedel2011,
  author    = {Riedel, Katja},
  title     = {Elucidation of the epithelial sodium channel as a salt taste receptor candidate and search for novel salt taste receptor candidates},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-58764},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Salty taste has evolved to maintain electrolyte homeostasis, serving as a detector for salt containing food. In rodents, salty taste involves at least two transduction mechanisms. One is sensitive to the drug amiloride and specific for Na+, involving epithelial sodium channel (ENaC). A second rodent transduction pathway, which is triggered by various cations, is amiloride insensitive and not almost understood to date. Studies in primates showed amiloride-sensitive as well as amiloride-insensitive gustatory responses to NaCl, implying a role of both salt taste transduction pathways in humans. However, sensory studies in humans point to largely amiloride-insensitive sodium taste perception. An involvement of ENaC in human sodium taste perception was not shown, so far. In this study, ENaC subunit protein and mRNA could be localized to human taste bud cells (TBC). Thus, basolateral αβγ-ENaC ion channels are likely in TBC of circumvallate papillae, possibly mediating basolateral sodium entry. Similarly, basolateral βγ-ENaC might play a role in fungiform TBC. Strikingly, δ-ENaC subunit was confined to taste bud pores of both papillae, likely mediating gustatory sodium entry in TBC, either apical or paracellular via tight junctions. However, regional separation of δ-ENaC and βγ-ENaC in fungiform and circumvallate TBC indicate the presence of unknown interaction partner necessary to assemble into functional ion channels. However, screening of a macaque taste tissue cDNA library did neither reveal polypeptides assembling into a functional cation channel by interaction with δ-ENaC or βγ-ENaC nor ENaC independent salt taste receptor candidates. Thus, ENaC subunits are likely involved in human taste transduction, while exact composition and identity of an amiloride (in)sensitive salt taste receptors remain unclear. Localization of δ-ENaC in human taste pores strongly suggests a role in human taste transduction. In contrast, δ-ENaC is classified as pseudogene Scnn1d in mouse. However, no experimental detected sequences are annotated, while evidences for parts of Scnn1d derived mRNAs exist. In order to elucidate if Scnn1d is possibly involved in rodent salt taste perception, Scnn1d was evaluated in this study to clarify if Scnn1d is a gene or a transcribed pseudogene in mice. Comparative mapping of human SCNN1D to mouse chromosome 4 revealed complete Scnn1d sequence as well as its pseudogenization by Mus specific endogenous retroviruses. Moreover, tissue specific transcription of unitary Scnn1d pseudogene was found in mouse vallate papillae, kidney and testis and led to identification of nine Scnn1d transcripts. In vitro translation experiments showed that Scnn1d transcripts are coding competent for short polypeptides, possibly present in vivo. However, no sodium channel like function or sodium channel modulating activity was evident for Scnn1d transcripts and/or derived polypeptides. Thus, an involvement of mouse δ-ENaC in sodium taste transduction is unlikely and points to species specific differences in salt taste transduction mechanisms.},
  language  = {en}
}
@phdthesis{Lauterbach2011,
  author    = {Lauterbach, Stefan},
  title     = {Lateglacial to Holocene climatic and environmental changes in Europe : multi-proxy studies on lake sediments along a transect from northern Italy to northeastern Poland},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-58157},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Sediment records of three European lakes were investigated in order to reconstruct the regional climate development during the Lateglacial and Holocene, to investigate the response of local ecosystems to climatic fluctuations and human impact and to relate regional peculiarities of past climate development to climatic changes on a larger spatial scale. The Lake Hańcza (NE Poland) sediment record was studied with a focus on reconstructing the early Holocene climate development and identifying possible differences to Western Europe. Following the initial Holocene climatic improvement, a further climatic improvement occurred between 10 000 and 9000 cal. a BP. Apparently, relatively cold and dry climate conditions persisted in NE Poland during the first ca. 1500 years of the Holocene, most likely due to a specific regional atmospheric circulation pattern. Prevailing anticyclonic circulation linked to a high-pressure cell above the remaining Scandinavian Ice Sheet (SIS) might have blocked the eastward propagation of warm and moist Westerlies and thus attenuated the early Holocene climatic amelioration in this region until the final decay of the SIS, a pattern different from climate development in Western Europe. The Lateglacial sediment record of Lake Mondsee (Upper Austria) was investigated in order to study the regional climate development and the environmental response to rapid climatic fluctuations. While the temperature rise and environmental response at the onset of the Holocene took place quasi-synchronously, major leads and lags in proxy responses characterize the onset of the Lateglacial Interstadial. In particular, the spread of coniferous woodlands and the reduction of detrital flux lagged the initial Lateglacial warming by ca. 500-750 years. Major cooling at the onset of the Younger Dryas took place synchronously with a change in vegetation, while the increase of detrital matter flux was delayed by about 150-300 years. Complex proxy responses are also detected for short-term Lateglacial climatic fluctuations. In summary, periods of abrupt climatic changes are characterized by complex and temporally variable proxy responses, mainly controlled by ecosystem inertia and the environmental preconditions. A second study on the Lake Mondsee sediment record focused on two small-scale climate deteriorations around 8200 and 9100 cal. a BP, which have been triggered by freshwater discharges to the North Atlantic, causing a shutdown of the Atlantic meridional overturning circulation (MOC). Combining microscopic varve counting and AMS 14C dating yielded a precise duration estimate (ca. 150 years) and absolute dating of the 8.2 ka cold event, both being in good agreement with results from other palaeoclimate records. Moreover, a sudden temperature overshoot after the 8.2 ka cold event was identified, also seen in other proxy records around the North Atlantic. This was most likely caused by enhanced resumption of the MOC, which also initiated substantial shifts of oceanic and atmospheric front systems. Although there is also evidence from other proxy records for pronounced recovery of the MOC and atmospheric circulation changes after the 9.1 ka cold event, no temperature overshoot is seen in the Lake Mondsee record, indicating the complex behaviour of the global climate system. The Holocene sediment record of Lake Iseo (northern Italy) was studied to shed light on regional earthquake activity and the influence of climate variability and anthropogenic impact on catchment erosion and detrital flux into the lake. Frequent small-scale detrital layers within the sediments reflect allochthonous sediment supply by extreme surface runoff events. During the early to mid-Holocene, increased detrital flux coincides with periods of cold and wet climate conditions, thus apparently being mainly controlled by climate variability. In contrast, intervals of high detrital flux during the late Holocene partly also correlate with phases of increased human impact, reflecting the complex influences on catchment erosion processes. Five large-scale event layers within the sediments, which are composed of mass-wasting deposits and turbidites, are supposed to have been triggered by strong local earthquakes. While the uppermost of these event layers is assigned to a documented adjacent earthquake in AD 1222, the four other layers are supposed to be related to previously undocumented prehistorical earthquakes.},
  language  = {en}
}
@phdthesis{Hoehne2011,
  author    = {H{\"o}hne, Janet},
  title     = {Aktivit{\"a}ts- und Herzfrequenz-Monitoring zur Erfassung der Bewegungszeit und der Bewegungsintensit{\"a}t im schulischen und außerschulischen Kontext von Grundsch{\"u}lern im Land Brandenburg},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-57937},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {"Kinderwelt ist Bewegungswelt" (Schmidt, 1997, S. 156, zitiert nach Schmidt, Hartmann-Tews \& Brettschneider, 2003, S. 31). Das kindliche Bewegungsverhalten hat sich bereits im Grundschulalter ver{\"a}ndert, so dass sich Bewegungsaktivit{\"a}ten von Kindern erheblich unterscheiden und keineswegs mehr verallgemeinert werden k{\"o}nnen. Richtet man den Fokus auf die Frage „Wie bewegt sind unsere Kinder?" so scheint diese von den Medien bereits beantwortet zu sein, da dort von ansteigendem Bewegungsmangel der heutigen Kinder gegen{\"u}ber fr{\"u}heren Generationen berichtet wird. Wenn es in den Diskussionen um den Gesundheitszustand unserer Kinder geht, nimmt die k{\"o}rperlich-sportliche Aktivit{\"a}t eine entscheidende Rolle ein. Bewegungsmangel ist hierbei ein zentraler Begriff der in der {\"O}ffentlichkeit diskutiert wird. Bei der Betrachtung der einzelnen Studien f{\"a}llt auf, dass deutliche Defizite in der Messung der k{\"o}rperlich-sportlichen Aktivit{\"a}t bestehen. Zentraler Kritikpunkt in den meisten Studien ist die subjektive Erfassung der k{\"o}rperlich-sportlichen Aktivit{\"a}t. Ein Großteil bisheriger Untersuchungen zum Bewegungsverhalten basiert auf Beobachtungen, Befragungen oder Bewegungstageb{\"u}chern. Diese liefern ausschließlich zum Teil subjektive Einsch{\"a}tzungen der Kinder oder Eltern {\"u}ber die tats{\"a}chliche Bewegungszeit und -intensit{\"a}t. Das objektive Erfassen der Aktivit{\"a}t bzw. Inaktivit{\"a}t ist zwar seit einigen Jahren zentraler Gegenstand vieler Studien, dennoch gilt es, dieses noch sachkundiger zu l{\"o}sen, um subjektive und objektive Daten zu vergleichen. Um dem Bewegungsmangel der heutigen Kinder entgegenzuwirken, sind empirisch abgesicherte Erkenntnisse {\"u}ber die Bedingungsfaktoren und die Folgen des ver{\"a}nderten Bewegungsverhaltens dringend n{\"o}tig. Die Quer- und L{\"a}ngsschnittuntersuchung umfasst die Bereiche Anthropometrie, die Erfassung der k{\"o}rperlich-sportlichen Aktivit{\"a}t und die Herzfrequenzmessung {\"u}ber 24h. F{\"u}r die Studie konnten 106 Jungen und M{\"a}dchen im Zeitraum von Januar 2007 bis April 2009 rekrutiert und {\"u}berpr{\"u}ft werden. Die physiologischen Parameter wurden mit Hilfe des ACTIHEART-Messsytems aufgezeichnet und berechnet. Die Ergebnisse zur k{\"o}rperlich-sportlichen Aktivit{\"a}t wurden in die Untersuchungsabschnitte Schulzeit gesamt, Pause, Sportunterricht, Nachmittag und 24h unterteilt. Durch das Messsystem werden die Bewegungsaktivit{\"a}t und die Herzfrequenz synchron aufgezeichnet. Das System nimmt die Beschleunigungswerte des K{\"o}rpers auf und speichert sie im frei w{\"a}hlbaren Zeitintervall, Short oder Long Term, in Form von „activity counts" ab. Das Messsytem berechnet weiterhin die Intensit{\"a}t k{\"o}rperlicher Aktivit{\"a}t.},
  language  = {de}
}
@phdthesis{Sietz2011,
  author    = {Sietz, Diana},
  title     = {Dryland vulnerability : typical patterns and dynamics in support of vulnerability reduction efforts},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-58097},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {The pronounced constraints on ecosystem functioning and human livelihoods in drylands are frequently exacerbated by natural and socio-economic stresses, including weather extremes and inequitable trade conditions. Therefore, a better understanding of the relation between these stresses and the socio-ecological systems is important for advancing dryland development. The concept of vulnerability as applied in this dissertation describes this relation as encompassing the exposure to climate, market and other stresses as well as the sensitivity of the systems to these stresses and their capacity to adapt. With regard to the interest in improving environmental and living conditions in drylands, this dissertation aims at a meaningful generalisation of heterogeneous vulnerability situations. A pattern recognition approach based on clustering revealed typical vulnerability-creating mechanisms at global and local scales. One study presents the first analysis of dryland vulnerability with global coverage at a sub-national resolution. The cluster analysis resulted in seven typical patterns of vulnerability according to quantitative indication of poverty, water stress, soil degradation, natural agro-constraints and isolation. Independent case studies served to validate the identified patterns and to prove the transferability of vulnerability-reducing approaches. Due to their worldwide coverage, the global results allow the evaluation of a specific system's vulnerability in its wider context, even in poorly-documented areas. Moreover, climate vulnerability of smallholders was investigated with regard to their food security in the Peruvian Altiplano. Four typical groups of households were identified in this local dryland context using indicators for harvest failure risk, agricultural resources, education and non-agricultural income. An elaborate validation relying on independently acquired information demonstrated the clear correlation between weather-related damages and the identified clusters. It also showed that household-specific causes of vulnerability were consistent with the mechanisms implied by the corresponding patterns. The synthesis of the local study provides valuable insights into the tailoring of interventions that reflect the heterogeneity within the social group of smallholders. The conditions necessary to identify typical vulnerability patterns were summarised in five methodological steps. They aim to motivate and to facilitate the application of the selected pattern recognition approach in future vulnerability analyses. The five steps outline the elicitation of relevant cause-effect hypotheses and the quantitative indication of mechanisms as well as an evaluation of robustness, a validation and a ranking of the identified patterns. The precise definition of the hypotheses is essential to appropriately quantify the basic processes as well as to consistently interpret, validate and rank the clusters. In particular, the five steps reflect scale-dependent opportunities, such as the outcome-oriented aspect of validation in the local study. Furthermore, the clusters identified in Northeast Brazil were assessed in the light of important endogenous processes in the smallholder systems which dominate this region. In order to capture these processes, a qualitative dynamic model was developed using generalised rules of labour allocation, yield extraction, budget constitution and the dynamics of natural and technological resources. The model resulted in a cyclic trajectory encompassing four states with differing degree of criticality. The joint assessment revealed aggravating conditions in major parts of the study region due to the overuse of natural resources and the potential for impoverishment. The changes in vulnerability-creating mechanisms identified in Northeast Brazil are well-suited to informing local adjustments to large-scale intervention programmes, such as "Avan{\c{c}}a Brasil". Overall, the categorisation of a limited number of typical patterns and dynamics presents an efficient approach to improving our understanding of dryland vulnerability. Appropriate decision-making for sustainable dryland development through vulnerability reduction can be significantly enhanced by pattern-specific entry points combined with insights into changing hotspots of vulnerability and the transferability of successful adaptation strategies.},
  language  = {en}
}
@phdthesis{Massie2011,
  author    = {Massie, Thomas Michael},
  title     = {Dynamic behavior of phytoplankton populations far from steady state : chemostat experiments and mathematical modeling},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-58102},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Nature changes continuously and is only seemingly at equilibrium. Environmental parameters like temperature, humidity or insolation may strongly fluctuate on scales ranging from seconds to millions of years. Being part of an ecosystem, species have to cope with these environmental changes. For ecologists, it is of special interest how individual responses to environmental changes affect the dynamics of an entire population - and, if this behavior is predictable. In this context, the demographic structure of a population plays a decisive role since it originates from processes of growth and mortality. These processes are fundamentally influenced by the environment. But, how exactly does the environment influence the behavior of populations? And what does the transient behavior look like? As a result from environmental influences on demography, so called cohorts form. They are age or size classes that are disproportionally represented in the demographic distribution of a population. For instance, if most old and young individuals die due to a cold spell, the population finally consists of mainly middle-aged individuals. Hence, the population got synchronized. Such a population tends to show regular fluctuations in numbers (denoted as oscillations) since the alternating phases of individual growth and population growth (due to reproduction) are now performed synchronously by the majority of the population.That is, one time the population growths, and the other time it declines due to mortality. Synchronous behavior is one of the most pervasive phenomena in nature. Gravitational synchrony in the solar system; fireflies flashing in unison; coordinate firing of pacemaker cells in the heart; electrons in a superconductor marching in lockstep. Whatever scale one looks at, in animate as well as inanimate systems, one is likely to encounter synchrony. In experiments with phytoplankton populations, I could show that this principle of synchrony (as used by physicists) could well-explain the oscillations observed in the experiments, too. The size of the fluctuations depended on the strength by which environmental parameters changed as well as on the demographic state of a population prior to this change. That is, two population living in different habitats can be equally influenced by an environmental change, however, the resulting population dynamics may be significantly different when both populations differed in their demographic state before. Moreover, specific mechanisms relevant for the dynamic behavior of populations, appear only when the environmental conditions change. In my experiments, the population density declined by 50\% after ressource supply was doubled. This counter-intuitive behavior can be explained by increasing ressource consumption. The phytoplankton cells grew larger and enhanced their individual constitution. But at the same time, reproduction was delayed and the population density declined due to the losses by mortality. Environmental influences can also synchronize two or more populations over large distances, which is denoted as Moran effect. Assume two populations living on two distant islands. Although there is no exchange of individuals between them, both populations show a high similarity when comparing their time series. This is because the globally acting climate synchronizes the regionally acting weather on both island. Since the weather fluctuations influence the population dynamics, the Moran effect states that the synchrony between the environment equals the one between the populations. My experiments support this theory and also explain deviations arising when accounting for differences in the populations and the habitats they are living in. Moreover, model simulations and experiments astonishingly show that the synchrony between the populations can be higher than between the environment, when accounting for differences in the environmental fluctuations ("noise color").},
  language  = {de}
}
@phdthesis{Lossow2011,
  author    = {Loßow, Kristina},
  title     = {Erzeugung und Charakterisierung von Mausmodellen mit lichtsensitivem Geschmackssystem zur Aufkl{\"a}rung der neuronalen Geschmackskodierung},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-58059},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Die Wahrnehmung von Geschmacksempfindungen beruht auf dem Zusammenspiel verschiedener Sinneseindr{\"u}cke wie Schmecken, Riechen und Tasten. Diese Komplexit{\"a}t der gustatorischen Wahrnehmung erschwert die Beantwortung der Frage wie Geschmacksinformationen vom Mund ins Gehirn weitergeleitet, prozessiert und kodiert werden. Die Analysen zur neuronalen Prozessierung von Geschmacksinformationen erfolgten zumeist mit Bitterstimuli am Mausmodell. Zwar ist bekannt, dass das Genom der Maus f{\"u}r 35 funktionelle Bitterrezeptoren kodiert, jedoch war nur f{\"u}r zwei unter ihnen ein Ligand ermittelt worden. Um eine bessere Grundlage f{\"u}r tierexperimentelle Arbeiten zu schaffen, wurden 16 der 35 Bitterrezeptoren der Maus heterolog in HEK293T-Zellen exprimiert und in Calcium-Imaging-Experimenten funktionell charakterisiert. Die Daten belegen, dass das Funktionsspektrum der Bitterrezeptoren der Maus im Vergleich zum Menschen enger ist und widerlegen damit die Aussage, dass humane und murine orthologe Rezeptoren durch das gleiche Ligandenspektrum angesprochen werden. Die Interpretation von tierexperimentellen Daten und die {\"U}bertragbarkeit auf den Menschen werden folglich nicht nur durch die Komplexit{\"a}t des Geschmacks, sondern auch durch Speziesunterschiede verkompliziert. Die Komplexit{\"a}t des Geschmacks beruht u. a. auf der Tatsache, dass Geschmacksstoffe selten isoliert auftreten und daher eine Vielzahl an Informationen kodiert werden muss. Um solche geschmacksstoffassoziierten Stimuli in der Analyse der gustatorischen Kommunikationsbahnen auszuschließen, sollten Opsine, die durch Licht spezifischer Wellenl{\"a}nge angeregt werden k{\"o}nnen, f{\"u}r die selektive Ersetzung von Geschmacksrezeptoren genutzt werden. Um die Funktionalit{\"a}t dieser angestrebten Knockout-Knockin-Modelle zu evaluieren, die eine Kopplung von Opsinen mit dem geschmacksspezifischen G-Protein Gustducin voraussetzte, wurden Oozyten vom Krallenfrosch Xenopus laevis mit dem Zwei-Elektroden-Spannungsklemm-Verfahren hinsichtlich dieser Interaktion analysiert. Der positiven Bewertung dieser Kopplung folgte die Erzeugung von drei Mauslinien, die in der kodierenden Region eines spezifischen Geschmacksrezeptors (Tas1r1, Tas1r2, Tas2r114) Photorezeptoren exprimierten. Durch RT-PCR-, In-situ-Hybridisierungs- und immunhistochemische Experimente konnte der erfolgreiche Knockout der Rezeptorgene und der Knockin der Opsine belegt werden. Der Nachweis der Funktionalit{\"a}t der Opsine im gustatorischen System wird Gegenstand zuk{\"u}nftiger Analysen sein. Bei erfolgreichem Beleg der Lichtempfindlichkeit von Geschmacksrezeptorzellen dieser Mausmodelle w{\"a}re ein System geschaffen, dass es erm{\"o}glichen w{\"u}rde, gustatorische neuronale Netzwerke und Hirnareale zu identifizieren, die auf einen reinen geschmacks- und qualit{\"a}tsspezifischen Stimulus zur{\"u}ckzuf{\"u}hren w{\"a}ren.},
  language  = {de}
}
@phdthesis{Wolff2011,
  author    = {Wolff, Christian Michael},
  title     = {East African monsoon variability since the last glacial},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-58079},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {The impact of global warming on human water resources is attracting increasing attention. No other region in this world is so strongly affected by changes in water supply than the tropics. Especially in Africa, the availability and access to water is more crucial to existence (basic livelihoods and economic growth) than anywhere else on Earth. In East Africa, rainfall is mainly influenced by the migration of the Inter-Tropical Convergence Zone (ITCZ) and by the El Ni{\~n}o Southern Oscillation (ENSO) with more rain and floods during El Ni{\~n}o and severe droughts during La Ni{\~n}a. The forecasting of East African rainfall in a warming world requires a better understanding of the response of ENSO-driven variability to mean climate. Unfortunately, existing meteorological data sets are too short or incomplete to establish a precise evaluation of future climate. From Lake Challa near Mount Kilimanjaro, we report records from a laminated lake sediment core spanning the last 25,000 years. Analyzing a monthly cleared sediment trap confirms the annual origin of the laminations and demonstrates that the varve-thicknesses are strongly linked to the duration and strength of the windy season. Given the modern control of seasonal ITCZ location on wind and rain in this region and the inverse relation between the two, thicker varves represent windier and thus drier years. El Ni{\~n}o (La Ni{\~n}a) events are associated with wetter (drier) conditions in east Africa and decreased (increased) surface wind speeds. Based on this fact, the thickness of the varves can be used as a tool to reconstruct a) annual rainfall b) wind season strength, and c) ENSO variability. Within this thesis, I found evidence for centennialscale changes in ENSO-related rainfall variability during the last three millennia, abrupt changes in variability during the Medieval Climate Anomaly and the Little Ice Age, and an overall reduction in East African rainfall and its variability during the Last Glacial period. Climate model simulations support forward extrapolation from these lake-sediment data, indicating that a future Indian Ocean warming will enhance East Africa's hydrological cycle and its interannual variability in rainfall. Furthermore, I compared geochemical analyses from the sediment trap samples with a broad range of limnological, meteorological, and geological parameters to characterize the impact of sedimentation processes from the in-situ rocks to the deposited sediments. As a result an excellent calibration for existing μXRF data from Lake Challa over the entire 25,000 year long profile was provided. The climate development during the last 25,000 years as reconstructed from the Lake Challa sediments is in good agreement with other studies and highlights the complex interactions between long-term orbital forcing, atmosphere, ocean and land surface conditions. My findings help to understand how abrupt climate changes occur and how these changes correlate with climate changes elsewhere on Earth.},
  language  = {en}
}
@phdthesis{Felber2011,
  author    = {Felber, Juliane},
  title     = {Der Berufseinstieg von {\"A}rztInnen als normatives kritisches Lebensereignis : eine L{\"a}ngsschnittuntersuchung},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-58028},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Im Rahmen einer prospektiven L{\"a}ngsschnittuntersuchung wurde der Berufseinstieg von {\"A}rztInnen (N = 185) als normatives kritisches Lebensereignis untersucht. Dazu wurden sie insgesamt drei Mal im Abstand von jeweils sechs Monaten im ersten Jahr nach ihrem Studiumsabschluss befragt (T1: in den ersten zwei Wochen nach dem Staatsexamen, T2: kurzzeitig nach dem Berufseinstieg, T3: im Schnitt 9.5 Monate nach dem Berufseinstieg). Die Ergebnisse zeigten zun{\"a}chst, dass unl{\"a}ngst examinierte Jung-{\"A}rztInnen, die sich vergleichsweise schlechter auf den Beruf durch das Studium vorbereitet f{\"u}hlten, ihren bevorstehenden Berufseinstieg negativer bewerteten und schon vor diesem beanspruchter waren. Die Bewertung des Berufseinstiegs vermittelte dabei den Zusammenhang zwischen einer schlechten Vorbereitung und der Beanspruchung. Arbeitsspezifische Copingfunktionalit{\"a}t wiederum pufferte den Zusammenhang zwischen einer schlechten Vorbereitung und der Bewertung des Berufseinstiegs. Das Problem einer als schlecht empfundenen Vorbereitung verdeutlichte sich in der L{\"a}ngsschnittanalyse - sie sagte eine h{\"o}here Beanspruchung zum zweiten Messzeitpunkt, d.h. nach dem Berufseinstieg, vorher. In der Untersuchung der Beanspruchungsentwicklung {\"u}ber die drei Messzeitpunkte hinweg fanden sich nur wenige Ver{\"a}nderungen. Es ließ sich zwar eine deutliche Zunahme der mittleren Depressivit{\"a}ts-Auspr{\"a}gungen {\"u}ber den Berufseinstieg hinweg herausstellen (T1-T2); auf anderen Beanspruchungsindikatoren zeigte sich jedoch kein direkter Effekt des Arbeitsbeginns bzw. fand sich auch keine Adaptation der Jung-{\"A}rztInnen an ihre neue Situation im Sinne einer sich verringernden Beanspruchung im weiteren Verlauf (T2-T3). In der Erkl{\"a}rung interindividueller Unterschiede in der Beanspruchung im Untersuchungszeitraum zeigte sich, dass die sich mit dem Berufseinstieg einstellende Arbeitsbelastung zum zweiten und dritten Messzeitpunkt erwartungsgem{\"a}ß positiv mit Beanspruchung assoziiert war. Die Arbeitsbelastungs-Beanspruchungs-Beziehung bestand jedoch nur im Querschnitt; in der L{\"a}ngsschnittanalyse fand sich kein Effekt der T2-Arbeitsbelastung auf die T3-Beanspruchung. Ausgangsunterschiede in psychischen Ressourcen wirkten einerseits direkt auf die Beanspruchung zu T2, zum Teil moderierten sie aber auch den Zusammenhang zwischen der Arbeitsbelastung und Beanspruchung: Eine h{\"o}here Resilienz und die Wahrnehmung sozialer Unterst{\"u}tzung sagten eine geringere Beanspruchung nach dem Berufseinstieg vorher. Jung-{\"A}rztInnen, die sich durch eine st{\"a}rkere Arbeitsbelastung auszeichneten, aber {\"u}ber ein funktionaleres Bew{\"a}ltigungsverhalten im Arbeitskontext verf{\"u}gten, waren kurzzeitig nach dem Berufseinstieg weniger beansprucht als stark arbeitsbelastete Jung-{\"A}rztInnen mit weniger funktionalem Coping. Verringerungen in den psychischen Ressourcen {\"u}ber den Berufseinstieg hinweg wirkten sich direkt, d.h. per se ung{\"u}nstig auf die Beanspruchung zum dritten Messzeitpunkt aus. Zudem interagierten sie mit der zu diesem Zeitpunkt bestehenden Arbeitsbelastung in Vorhersage der Beanspruchung. St{\"a}rker arbeitsbelastete Jung-{\"A}rztInnen, deren Copingfunktionalit{\"a}t und Wahrnehmung sozialer Unterst{\"u}tzung vom ersten zum dritten Messzeitpunkt abgenommen hatte, waren am Ende des Untersuchungszeitraums am st{\"a}rksten beansprucht. Hinsichtlich der Auswirkungen des Berufseinstiegs auf die Pers{\"o}nlichkeit der Jung-{\"A}rztInnen fanden sich ung{\"u}nstige Ver{\"a}nderungen: Sowohl die Auspr{\"a}gungen psychischer Ressourcen (Widerstandsf{\"a}higkeit, Wahrnehmung sozialer Unterst{\"u}tzung hinsichtlich der Arbeitst{\"a}tigkeit) als auch die der Big Five-Faktoren nahmen im Mittel ab. Interindividuelle Unterschiede in den Ver{\"a}nderungen ließen sich auf die Beanspruchung kurzzeitig nach dem Berufseinstieg (T2) bzw. auf deren Entwicklung in den Folgemonaten (T2-T3) zur{\"u}ckf{\"u}hren: Jene Jung-{\"A}rztInnen, die vergleichsweise stark beansprucht auf den Berufseinstieg reagiert hatten bzw. deren Beanspruchung im weiteren Verlauf zunahm, zeigten entsprechend ung{\"u}nstige Ver{\"a}nderungen. Die Ergebnisse zusammengefasst verdeutlicht sich folgende Problematik: Jung-{\"A}rztInnen, die weniger gut, d.h. pers{\"o}nlichkeitsbasiert gesch{\"u}tzt den Berufseinstieg absolvieren, reagieren st{\"a}rker beansprucht und sind dann auch diejenigen, deren Pers{\"o}nlichkeit sich in den ersten Arbeitsmonaten ung{\"u}nstig ver{\"a}ndert. Jung-{\"A}rztInnen mit geringen psychischen Ressourcen sind folglich nicht nur besonders vulnerabel f{\"u}r die Entwicklung von Beanspruchung angesichts belastender Arbeitsbedingungen, sondern ihre vergleichsweise hohe Beanspruchung bedingt eine weitere Verringerung des Schutz- und Pufferpotenzials ihrer Pers{\"o}nlichkeit. Es kommt zu einer ung{\"u}nstigen Akzentuierung der ohnehin schon vergleichsweise ressourcenschwachen Pers{\"o}nlichkeit, welche die Vulnerabilit{\"a}t f{\"u}r zuk{\"u}nftige Beanspruchung erh{\"o}ht. Aus den Ergebnissen l{\"a}sst sich ein Unterst{\"u}tzungsbedarf junger {\"A}rztInnen in der sensiblen und wegweisenden Berufseinstiegsphase ableiten. Neben einer Verbesserung ihrer Arbeitsbedingungen stellen eine rechtzeitige Sensibilisierung junger {\"A}rztInnen f{\"u}r den Arbeitsbelastungs-Beanspruchungs-Zusammenhang, ihre regelm{\"a}ßige Supervision sowie vor allem aber auch kompetenzorientiertes und ressourcenst{\"a}rkendes Feedback von den Mentoren und Vorgesetzten die Grundlage daf{\"u}r dar, dass die Jung-MedizinerInnen selbst gesund bleiben und sie die {\"a}rztliche T{\"a}tigkeit trotz ihres wohl stets hohen Belastungspotenzials als erf{\"u}llend und zufriedenstellend erleben.},
  language  = {de}
}
@phdthesis{Mallien2011,
  author    = {Mallien, Grit},
  title     = {Explorative multizentrische Querschnittsstudie zur Diagnostik der Dysarthrie bei Progressiver Supranukle{\"a}rer Blickparese - PSP},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-58045},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Die Progressive Supranukle{\"a}re Blickparese (PSP) ist eine sporadisch auftretende neurodegenerative Erkrankung im Rahmen der atypischen Parkinson-Syndrome (APS), die im fr{\"u}hen Verlauf h{\"a}ufig mit dem Idiopathischen Parkinson-Syndrom (IPS) verwechselt wird. Dabei ist die Dysarthrie als eine erworbene, zentral bedingte sprechmotorische St{\"o}rung ein h{\"a}ufiges und fr{\"u}h auftretendes Symptom bei PSP. Bislang spricht man von einer eher unspezifischen „gemischten" Dysarthrie aus hypokinetischen, spastischen und auch ataktischen Komponenten. Im Rahmen einer explorativen Querschnittsstudie am „Fachkrankenhaus f{\"u}r Bewegungsst{\"o}rungen und Parkinson" Beelitz-Heilst{\"a}tten in Kooperation mit der „Entwicklungsgruppe Klinische Neuropsychologie" M{\"u}nchen (EKN) sowie der „Interdisziplin{\"a}ren Ambulanz f{\"u}r Bewegungsst{\"o}rungen" am Klinikum M{\"u}nchen-Großhadern wurden 50 Patienten dahingehend untersucht, ob sich f{\"u}r die Progressive Supranukle{\"a}re Blickparese (PSP) eine spezielle, fr{\"u}hzeitig zu diagnostizierende und differentialdiagnostisch relevante Dysarthrie beschreiben ließe. In diesem Zusammenhang soll gekl{\"a}rt werden, ob es sich um ph{\"a}notypische Auspr{\"a}gungen im Rahmen eines St{\"o}rungsspektrums handelt oder ob sich differenzierbare Subtypen der Krankheit, insbesondere ein „klassischer" PSP-Typ (PSP-RS) und ein „atypischer" PSP-Typ (PSP-P), auch im Bereich der Dysarthrie zeigen. Im Rahmen der Untersuchungen wurde der Schweregrad der Erkrankung mittels der „PSP-sensitiven Ratingskala (PSPRS)" gemessen. Die Dysarthriediagnostik erfolgte anhand der „Bogenhausener Dysarthrieskalen (BoDyS)" zur Beschreibung der Art und Auspr{\"a}gung der Dysarthrie bei PSP. Die Verst{\"a}ndlichkeit wurde mithilfe des „M{\"u}nchner Verst{\"a}ndlichkeits-Profils (MVP)" sowie eines weiteren Transkriptionsverfahrens ermittelt, wobei Ausschnitte aus den Tests zum Lesen und Nachsprechen der BoDyS zugrunde lagen. Weiterhin erfolgte eine Einsch{\"a}tzung der Nat{\"u}rlichkeit des Sprechens. Die Ergebnisse hinsichtlich des Einflusses von Nat{\"u}rlichkeit und Verst{\"a}ndlichkeit des Sprechens auf den Schweregrad der Dysarthrie zeigten, dass dieser modalit{\"a}ten{\"u}bergreifend mit beiden Schweregradaspekten korreliert, wenngleich es offenbar die Nat{\"u}rlichkeit des Sprechens ist, die bei PSP bereits fr{\"u}hzeitig beeintr{\"a}chtigt ist und somit als das entscheidende differentialdiagnostische Kriterium zur Differenzierung zwischen beiden PSP-Subtypen zu beurteilen ist, m{\"o}glicherweise auch gegen{\"u}ber anderen Parkinson-Syndromen. Anhand statistisch valider Ergebnisse konnten spezifische St{\"o}rungsmerkmale der Dysarthrie extrahiert werden, die eine signifikante Trennung von PSP-RS und PSP-P erm{\"o}glichen: eine leise und behaucht-heisere Stimme sowie ein verlangsamtes Sprechtempo und Hypernasalit{\"a}t. Damit k{\"o}nnen f{\"u}r die hier fokussierten Subtypen der PSP zwei unterschiedliche Dysarthrietypen postuliert werden. Danach wird dem Subtyp PSP-RS eine spastisch betonte Dysarthrie mit ausgepr{\"a}gter Verlangsamung des Sprechtempos zugeordnet, dem Subtyp PSP-P hingegen eine hypokinetische Dysarthrie mit behaucht-heiserer Hypophonie. Desweiteren konnte ein „Dysarthrie-Schwellenwert" als Zusatzkriterium f{\"u}r eine zeitliche Differenzierung beider PSP-Subtypen ermittelt werden. Anhand der Daten zeigte sich die Dysarthrie bei dem Subtyp PSP-RS gleich zu Beginn der Erkrankung, jedoch sp{\"a}testens 24 Monate danach. Hingegen konnte die Dysarthrie beim Subtyp PSP-P fr{\"u}hestens 24 Monate nach Erkrankungsbeginn festgestellt werden. Die Daten dieser Studie verdeutlichen, dass der Frage nach einer subtypenspezifischen Auspr{\"a}gung der Dysarthrie bei PSP eine L{\"a}ngsschnittsstudie folgen sollte, um die ermittelten Ergebnisse zu konsolidieren.},
  language  = {de}
}
@phdthesis{Malik2011,
  author    = {Malik, Nishant},
  title     = {Extremes in events and dynamics : a nonlinear data analysis perspective on the past and present dynamics of the Indian summer monsoon},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-58016},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {To identify extreme changes in the dynamics of the Indian Summer Monsoon (ISM) in the past, I propose a new approach based on the quantification of fluctuations of a nonlinear similarity measure, to identify regimes of distinct dynamical complexity in short time series. I provide an analytical derivation for the relationship of the new measure with the dynamical invariants such as dimension and Lyapunov exponents of the underlying system. A statistical test is also developed to estimate the significance of the identified transitions. Our method is justified by uncovering bifurcation structures in several paradigmatic models, providing more complex transitions compared with traditional Lyapunov exponents. In a real world situation, we apply the method to identify millennial-scale dynamical transitions in Pleistocene proxy records of the south Asian summer monsoon system. We infer that many of these transitions are induced by the external forcing of solar insolation and are also affected by internal forcing on Monsoonal dynamics, i.e., the glaciation cycles of the Northern Hemisphere and the onset of the tropical Walker circulation. Although this new method has general applicability, it is particularly useful in analysing short palaeo-climate records. Rainfall during the ISM over the Indian subcontinent occurs in form of enormously complex spatiotemporal patterns due to the underlying dynamics of atmospheric circulation and varying topography. I present a detailed analysis of summer monsoon rainfall over the Indian peninsular using Event Synchronization (ES), a measure of nonlinear correlation for point processes such as rainfall. First, using hierarchical clustering I identify principle regions where the dynamics of monsoonal rainfall is more coherent or homogenous. I also provide a method to reconstruct the time delay patterns of rain events. Moreover, further analysis is carried out employing the tools of complex network theory. This study provides valuable insights into the spatial organization, scales, and structure of the 90th and 94th percentile rainfall events during the ISM (June to September). I furthermore analyse the influence of different critical synoptic atmospheric systems and the impact of the steep Himalayan topography on rainfall patterns. The presented method not only helps in visualising the structure of the extremeevent rainfall fields, but also identifies the water vapor pathways and decadal-scale moisture sinks over the region. Furthermore a simple scheme based on complex networks is presented to decipher the spatial intricacies and temporal evolution of monsoonal rainfall patterns over the last six decades. Some supplementary results on the evolution of monsoonal rainfall extremes over the last sixty years are also presented.},
  language  = {de}
}
@phdthesis{Krause2011,
  author    = {Krause, Jette},
  title     = {An expert-based Bayesian investigation of greenhouse gas emission reduction options for German passenger vehicles until 2030},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-57671},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {The present thesis introduces an iterative expert-based Bayesian approach for assessing greenhouse gas (GHG) emissions from the 2030 German new vehicle fleet and quantifying the impacts of their main drivers. A first set of expert interviews has been carried out in order to identify technologies which may help to lower car GHG emissions and to quantify their emission reduction potentials. Moreover, experts were asked for their probability assessments that the different technologies will be widely adopted, as well as for important prerequisites that could foster or hamper their adoption. Drawing on the results of these expert interviews, a Bayesian Belief Network has been built which explicitly models three vehicle types: Internal Combustion Engine Vehicles (which include mild and full Hybrid Electric Vehicles), Plug-In Hybrid Electric Vehicles, and Battery Electric Vehicles. The conditional dependencies of twelve central variables within the BBN - battery energy, fuel and electricity consumption, relative costs, and sales shares of the vehicle types - have been quantified by experts from German car manufacturers in a second series of interviews. For each of the seven second-round interviews, an expert's individually specified BBN results. The BBN have been run for different hypothetical 2030 scenarios which differ, e.g., in regard to battery development, regulation, and fuel and electricity GHG intensities. The present thesis delivers results both in regard to the subject of the investigation and in regard to its method. On the subject level, it has been found that the different experts expect 2030 German new car fleet emission to be at 50 to 65\% of 2008 new fleet emissions under the baseline scenario. They can be further reduced to 40 to 50\% of the emissions of the 2008 fleet though a combination of a higher share of renewables in the electricity mix, a larger share of biofuels in the fuel mix, and a stricter regulation of car CO\$_2\$ emissions in the European Union. Technically, 2030 German new car fleet GHG emissions can be reduced to a minimum of 18 to 44\% of 2008 emissions, a development which can not be triggered by any combination of measures modeled in the BBN alone but needs further commitment. Out of a wealth of existing BBN, few have been specified by individual experts through elicitation, and to my knowledge, none of them has been employed for analyzing perspectives for the future. On the level of methods, this work shows that expert-based BBN are a valuable tool for making experts' expectations for the future explicit and amenable to the analysis of different hypothetical scenarios. BBN can also be employed for quantifying the impacts of main drivers. They have been demonstrated to be a valuable tool for iterative stakeholder-based science approaches.},
  language  = {en}
}
@phdthesis{Schaal2011,
  author    = {Schaal, Janina},
  title     = {Synthese und Photochemie von photoaktivierbaren Biomolek{\"u}len},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-57929},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Mechanistische und kinetische Untersuchungen von komplexen zellul{\"a}ren Prozessen in situ sind in den vergangenen Jahren durch den Einsatz photoaktivierbarer Biomolek{\"u}le, sogenannter caged Verbindungen, m{\"o}glich geworden. Bei den caged Verbindungen handelt es sich um photolabile inaktive Derivate von biologisch aktiven Molek{\"u}len, aus denen durch ultraviolettes Licht mit Hilfe einer photochemischen Reaktion die nat{\"u}rliche, biologisch aktive Substanz schnell freigesetzt werden kann. Im Rahmen der vorliegenden Arbeit wurden caged Verbindungen von den Neurotransmittern Octopamin und Dopamin, dem Octopamin-Antagonist Epinastin, den Proteinsyntheseinhibitoren Emetin und Anisomycin, dem Protonophor CCCP und dem Riechstoff Bourgeonal hergestellt. Zur Synthese dieser caged Verbindungen wurden sowohl bekannte als auch verschiedene im Rahmen dieser Arbeit neu entwickelte photolabile Schutzgruppen mit einem (Cumarin-4-yl)methyl- bzw. einem 2-Nitrobenzyl-Ger{\"u}st eingesetzt. Entsprechende Syntheseverfahren wurden erarbeitet. Anschließend erfolgte eine umfassende physikalisch-chemische sowie photochemische Charakterisierung der erhaltenen caged Verbindungen. Dabei wurde besonders auf gute L{\"o}slichkeit in Wasser bei physiologischer Ionenst{\"a}rke, schnelle und effiziente Photoreaktivit{\"a}t, hohe Extinktion bei Wellenl{\"a}ngen von 350-430 nm und gute solvolytische Stabilit{\"a}t bei geringer Toxizit{\"a}t der freigesetzten Schutzgruppe geachtet. Ein Schwerpunkt bei der photochemischen Charakterisierung bildeten die Untersuchungen zur Quantifizierung der 2-Photonen-Anregung, uncaging action cross-sections, der Cumarinylmethyl-caged Verbindungen, aufgrund ihrer Bedeutung f{\"u}r die Photofreisetzung von Biomolek{\"u}len, da die gleichzeitige Absorption von 2 IR-Photonen eine h{\"o}here dreidimensionale Aufl{\"o}sung und eine wesentlich tiefere Gewebepenetration erlaubt. Mit Hilfe von Kooperationspartnern wurden zeitaufgel{\"o}sten Fluoreszenz- und IR-Messungen an verschiedenen (Cumarin-4-yl)methoxycarbonyl-caged Modellverbindungen durchgef{\"u}hrt, mit denen die Geschwindigkeitskonstanten k1 und kdecarb des Photolysemechanismus ermittelt wurde. Am Ende folgten die Anwendungserprobungen ausgew{\"a}hlter caged Verbindungen in einem Translationsassay bzw. in Zelluntersuchungen.},
  language  = {de}
}
@phdthesis{Wulf2011,
  author    = {Wulf, Hendrik},
  title     = {Seasonal precipitation, river discharge, and sediment flux in the western Himalaya},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-57905},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Rainfall, snow-, and glacial melt throughout the Himalaya control river discharge, which is vital for maintaining agriculture, drinking water and hydropower generation. However, the spatiotemporal contribution of these discharge components to Himalayan rivers is not well understood, mainly because of the scarcity of ground-based observations. Consequently, there is also little known about the triggers and sources of peak sediment flux events, which account for extensive hydropower reservoir filling and turbine abrasion. We therefore lack basic information on the distribution of water resources and controls of erosion processes. In this thesis, I employ various methods to assess and quantify general characteristics of and links between precipitation, river discharge, and sediment flux in the Sutlej Valley. First, I analyze daily precipitation data (1998-2007) from 80 weather stations in the western Himalaya, to decipher the distribution of rain- and snowfall. Rainfall magnitude frequency analyses indicate that 40\% of the summer rainfall budget is attributed to monsoonal rainstorms, which show higher variability in the orogenic interior than in frontal regions. Combined analysis of rainstorms and sediment flux data of a major Sutlej River tributary indicate that monsoonal rainfall has a first order control on erosion processes in the orogenic interior, despite the dominance of snowfall in this region. Second, I examine the contribution of rainfall, snow and glacial melt to river discharge in the Sutlej Valley (s55,000 km2), based on a distributed hydrological model, which covers the period 2000-2008. To achieve high spatial and daily resolution despite limited ground-based observations the hydrological model is forced by daily remote sensing data, which I adjusted and calibrated with ground station data. The calibration shows that the Tropical Rainfall Measuring Mission (TRMM) 3B42 rainfall product systematically overestimates rainfall in semi-arid and arid regions, increasing with aridity. The model results indicate that snowmelt-derived discharge (74\%) is most important during the pre-monsoon season (April to June) whereas rainfall (56\%) and glacial melt (17\%) dominate the monsoon season (July-September). Therefore, climate change most likely causes a reduction in river discharge during the pre-monsoon season, which especially affects the orogenic interior. Third, I investigate the controls on suspended sediment flux in different parts of the Sutlej catchments, based on daily gauging data from the past decade. In conjunction with meteorological data, earthquake records, and rock strength measurements I find that rainstorms are the most frequent trigger of high-discharge events with peaks in suspended sediment concentrations (SSC) that account for the bulk of the suspended sediment flux. The suspended sediment flux increases downstream, mainly due to increases in runoff. Pronounced erosion along the Himalayan Front occurs throughout the monsoon season, whereas efficient erosion of the orogenic interior is confined to single extreme events. The results of this thesis highlight the importance of snow and glacially derived melt waters in the western Himalaya, where extensive regions receive only limited amounts of monsoonal rainfall. These regions are therefore particularly susceptible to global warming with major implications on the hydrological cycle. However, the sediment discharge data show that infrequent monsoonal rainstorms that pass the orographic barrier of the Higher Himalaya are still the primary trigger of the highest-impact erosion events, despite being subordinate to snow and glacially-derived discharge. These findings may help to predict peak sediment flux events and could underpin the strategic development of preventative measures for hydropower infrastructures.},
  language  = {en}
}
@phdthesis{BarbosaPfannes2011,
  author    = {Barbosa Pfannes, Eva Katharina},
  title     = {Probing the regulatory mechanisms of the actomyosin system in motile cells},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-57812},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Actin-based directional motility is important for embryonic development, wound healing, immune responses, and development of tissues. Actin and myosin are essential players in this process that can be subdivided into protrusion, adhesion, and traction. Protrusion is the forward movement of the membrane at the leading edge of the cell. Adhesion is required to enable movement along a substrate, and traction finally leads to the forward movement of the entire cell body, including its organelles. While actin polymerization is the main driving force in cell protrusions, myosin motors lead to the contraction of the cell body. The goal of this work was to study the regulatory mechanisms of the motile machinery by selecting a representative key player for each stage of the signaling process: the regulation of Arp2/3 activity by WASP (actin system), the role of cGMP in myosin II assembly (myosin system), and the influence of phosphoinositide signaling (upstream receptor pathway). The model organism chosen for this work was the social ameba Dictyostelium discoideum, due to the well-established knowledge of its cytoskeletal machinery, the easy handling, and the high motility of its vegetative and starvation developed cells. First, I focused on the dynamics of the actin cytoskeleton by modulating the activity of one of its key players, the Arp2/3 complex. This was achieved using the carbazole derivative Wiskostatin, an inhibitor of the Arp2/3 activator WASP. Cells treated with Wiskostatin adopted a round shape, with no of few pseudopodia. With the help of a microfluidic cell squeezer device, I could show that Wiskostatin treated cells display a reduced mechanical stability, comparable to cells treated with the actin disrupting agent Latrunculin A. Furthermore, the WASP inhibited cells adhere stronger to a surface and show a reduced motility and chemotactic performance. However, the overall F-actin content in the cells was not changed. Confocal microscopy and TIRF microscopy imaging showed that the cells maintained an intact actin cortex. Localized dynamic patches of increased actin polymerization were observed that, however, did not lead to membrane deformation. This indicated that the mechanisms of actin-driven force generation were impaired in Wiskostatin treated cells. It is concluded that in these cells, an altered architecture of the cortical network leads to a reduced overall stiffness of the cell, which is insufficient to support the force generation required for membrane deformation and pseudopod formation. Second, the role of cGMP in myosin II dynamics was investigated. Cyclic GMP is known to regulate the association of myosin II with the cytoskeleton. In Dictyostelium, intracellular cGMP levels increase when cells are exposed to chemoattractants, but also in response to osmotic stress. To study the influence of cyclic GMP on actin and myosin II dynamics, I used the laser-induced photoactivation of a DMACM-caged-Br-cGMP to locally release cGMP inside the cell. My results show that cGMP directly activates the myosin II machinery, but is also able to induce an actin response independently of cAMP receptor activation and signaling. The actin response was observed in both vegetative and developed cells. Possible explanations include cGMP-induced actin polymerization through VASP (vasodilator-stimulated phosphoprotein) or through binding of cGMP to cyclic nucleotide-dependent kinases. Finally, I investigated the role of phosphoinositide signaling using the Polyphosphoinositide-Binding Peptide (PBP10) that binds preferentially to PIP2. Phosphoinositides can recruit actin-binding proteins to defined subcellular sites and alter their activity. Neutrophils, as well as developed Dictyostelium cells produce PIP3 in the plasma membrane at their leading edge in response to an external chemotactic gradient. Although not essential for chemotaxis, phosphoinositides are proposed to act as an internal compass in the cell. When treated with the peptide PBP10, cells became round, with fewer or no pseudopods. PH-CRAC translocation to the membrane still occurs, even at low cAMP stimuli, but cell motility (random and directional) was reduced. My data revealed that the decrease in the pool of available PIP2 in the cell is sufficient to impair cell motility, but enough PIP2 remains so that PIP3 is formed in response to chemoattractant stimuli. My data thus highlights how sensitive cell motility and morphology are to changes in the phosphoinositide signaling. In summary, I have analyzed representative regulatory mechanisms that govern key parts of the motile machinery and characterized their impact on cellular properties including mechanical stability, adhesion and chemotaxis.},
  language  = {en}
}
@phdthesis{Fellinger2011,
  author    = {Fellinger, Tim-Patrick},
  title     = {Hydrothermal and ionothermal carbon structures},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-57825},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {The needs for sustainable energy generation, but also a sustainable chemistry display the basic motivation of the current thesis. By different single investigated cases, which are all related to the element carbon, the work can be devided into two major topics. At first, the sustainable synthesis of "useful" carbon materials employing the process of hydrothermal carbonisation (HC) is described. In the second part, the synthesis of heteroatom - containing carbon materials for electrochemical and fuel cell applications employing ionic liquid precursors is presented. On base of a thorough review of the literature on hydrothermolysis and hydrothermal carbonisation of sugars in addition to the chemistry of hydroxymethylfurfural, mechanistic considerations of the formation of hydrothermal carbon are proposed. On the base of these reaction schemes, the mineral borax, is introduced as an additive for the hydrothermal carbonisation of glucose. It was found to be a highly active catalyst, resulting in decreased reaction times and increased carbon yields. The chemical impact of borax, in the following is exploited for the modification of the micro- and nanostructure of hydrothermal carbon. From the borax - mediated aggregation of those primary species, widely applicable, low density, pure hydrothermal carbon aerogels with high porosities and specific surface areas are produced. To conclude the first section of the thesis, a short series of experiments is carried out, for the purpose of demonstrating the applicability of the HC model to "real" biowaste i.e. watermelon waste as feedstock for the production of useful materials. In part two cyano - containing ionic liquids are employed as precursors for the synthesis of high - performance, heteroatom - containing carbon materials. By varying the ionic liquid precursor and the carbonisation conditions, it was possible to design highly active non - metal electrocatalyst for the reduction of oxygen. In the direct reduction of oxygen to water (like used in polymer electrolyte fuel cells), compared to commercial platinum catalysts, astonishing activities are observed. In another example the selective and very cost efficient electrochemical synthesis of hydrogen peroxide is presented. In a last example the synthesis of graphitic boron carbon nitrides from the ionic liquid 1 - Ethyl - 3 - methylimidazolium - tetracyanoborate is investigated in detail. Due to the employment of unreactive salts as a new tool to generate high surface area these materials were first time shown to be another class of non - precious metal oxygen reduction electrocatalyst.},
  language  = {en}
}
@phdthesis{Pourteau2011,
  author    = {Pourteau, Amaury},
  title     = {Closure of the Neotethys Ocean in Anatolia : structural, petrologic and geochronologic insights from low-grade high-pressure metasediments, Afyon Zone},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-57803},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {The complete consumption of the oceanic domain of a tectonic plate by subduction into the upper mantle results in continent subduction, although continental crust is typically of lower density than the upper mantle. Thus, the sites of former oceanic domains (named suture zones) are generally decorated with stratigraphic sequences deposited along continental passive margins that were metamorphosed under low-grade, high-pressure conditions, i.e., low temperature/depth ratios (< 15°C/km) with respect to geothermal gradients in tectonically stable regions. Throughout the Mesozoic and Cenozoic (i.e., since ca. 250 Ma), the Mediterranean realm was shaped by the closure of the Tethyan Ocean, which likely consisted in numerous oceanic domains and microcontinents. However, the exact number and position of Tethyan oceans and continents (i.e., the Tethyan palaeogeography) remains debated. This is particularly the case of Western and Central Anatolia, where a continental fragment was accreted to the southern composite margin of the Eurasia sometime between the Late Cretaceous and the early Cenozoic. The most frontal part of this microcontinent experienced subduction-related metamorphism around 85-80 Ma, and collision-related metamorphism affected more external parts around 35 Ma. This unsually-long period between subduction- and collision-related metamorphisms (ca. 50 Ma) in units ascribed to the same continental edge constitutes a crucial issue to address in order to unravel how Anatolia was assembled. The Afyon Zone is a tectono-sedimentary unit exposed south and structurally below the front high-pressure belt. It is composed of a Mesozoic sedimentary sequence deposited on top of a Precambrian to Palaeozoic continental substratum, which can be traced from Northwestern to southern Central Anatolia, along a possible Tethyan suture. Whereas the Afyon Zone was defined as a low-pressure metamorphic unit, high-pressure minerals (mainly Fe-Mg-carpholite in metasediments) were recently reported from its central part. These findings shattered previous conceptions on the tectono-metamorphic evolution of the Afyon Zone in particular, and of the entire region in general, and shed light on the necessity to revise the regional extent of subduction-related metamorphism by re-inspecting the petrology of poorly-studied metasediments. In this purpose, I re-evaluated the metamorphic evolution of the entire Afyon Zone starting from field observations. Low-grade, high-pressure mineral assemblages (Fe-Mg-carpholite and glaucophane) are reported throughout the unit. Well-preserved carpholite-chloritoid assemblages are useful to improve our understanding of mineral relations and transitions in the FeO-MgO-Al2O3-SiO2-H2O system during rocks' travel down to depth (prograde metamorphism). Inspection of petrographic textures, minute variations in mineral composition and Mg-Fe distribution among carpholite-chloritoid assemblages documents multistage mineral growth, accompanied by a progressive enrichment in Mg, and strong element partitioning. Using an updated database of mineral thermodynamic properties, I modelled the pressure and temperature conditions that are consistent with textural and chemical observations. Carpholite-bearing assemblages in the Afyon Zone account for a temperature increase from 280 to 380°C between 0.9 and 1.1 GPa (equivalent to a depth of 30-35 km). In order to further constrain regional geodynamics, first radiometric ages were determined in close association with pressure-temperature estimates for the Afyon Zone, as well as two other tectono-sedimentary units from the same continental passive margin (the {\"O}ren and Kurudere-Nebiler Units from SW Anatolia). For age determination, I employed 40Ar-39Ar geochronology on white mica in carpholite-bearing rocks. For thermobarometry, a multi-equilibrium approach was used based on quartz-chlorite-mica and quartz-chlorite-chloritoid associations formed at the expense of carpholite-bearing assemblages, i.e., during the exhumation from the subduction zone. This combination allows deciphering the significance of the calculated radiometric ages in terms of metamorphic conditions. Results show that the Afyon Zone and the {\"O}ren Unit represent a latest Cretaceous high-pressure metamorphic belt, and the Kurudere-Nebiler Unit was affected by subduction-related metamorphism around 45 Ma and cooled down after collision-related metamorphism around 26 Ma. The results provided in the present thesis and from the literature allow better understanding continental amalgamation in Western Anatolia. It is shown that at least two distinct oceanic branches, whereas only one was previously considered, have closed during continuous north-dipping subduction between 92 and 45 Ma. Between 85-80 and 70-65 Ma, a narrow continental domain (including the Afyon Zone) was buried into a subduction zone within the northern oceanic strand. Parts of the subducted continent crust were exhumed while the upper oceanic plate was transported southwards. Subduction of underlying lithosphere persisted, leading to the closure of the southern oceanic branch and to subduct the front of a second continental domain (including the Kurudere-Nebiler Unit). This followed by a continental collisional stage characterized by the cease of subduction, crustal thicknening and the detachment of the subducting oceanic slab from the accreted continent lithosphere. The present study supports that in the late Mesozoic the East Mediterranean realm had a complex tectonic configuration similar to present Southeast Asia or the Caribbean, with multiple, coexisting oceanic basins, microcontinents and subduction zones.},
  language  = {en}
}
@phdthesis{Spreyer2011,
  author    = {Spreyer, Kathrin},
  title     = {Does it have to be trees? : Data-driven dependency parsing with incomplete and noisy training data},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-57498},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {We present a novel approach to training data-driven dependency parsers on incomplete annotations. Our parsers are simple modifications of two well-known dependency parsers, the transition-based Malt parser and the graph-based MST parser. While previous work on parsing with incomplete data has typically couched the task in frameworks of unsupervised or semi-supervised machine learning, we essentially treat it as a supervised problem. In particular, we propose what we call agnostic parsers which hide all fragmentation in the training data from their supervised components. We present experimental results with training data that was obtained by means of annotation projection. Annotation projection is a resource-lean technique which allows us to transfer annotations from one language to another within a parallel corpus. However, the output tends to be noisy and incomplete due to cross-lingual non-parallelism and error-prone word alignments. This makes the projected annotations a suitable test bed for our fragment parsers. Our results show that (i) dependency parsers trained on large amounts of projected annotations achieve higher accuracy than the direct projections, and that (ii) our agnostic fragment parsers perform roughly on a par with the original parsers which are trained only on strictly filtered, complete trees. Finally, (iii) when our fragment parsers are trained on artificially fragmented but otherwise gold standard dependencies, the performance loss is moderate even with up to 50\% of all edges removed.},
  language  = {en}
}
@phdthesis{Schuette2011,
  author    = {Sch{\"u}tte, Moritz},
  title     = {Evolutionary fingerprints in genome-scale networks},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-57483},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Mathematical modeling of biological phenomena has experienced increasing interest since new high-throughput technologies give access to growing amounts of molecular data. These modeling approaches are especially able to test hypotheses which are not yet experimentally accessible or guide an experimental setup. One particular attempt investigates the evolutionary dynamics responsible for today's composition of organisms. Computer simulations either propose an evolutionary mechanism and thus reproduce a recent finding or rebuild an evolutionary process in order to learn about its mechanism. The quest for evolutionary fingerprints in metabolic and gene-coexpression networks is the central topic of this cumulative thesis based on four published articles. An understanding of the actual origin of life will probably remain an insoluble problem. However, one can argue that after a first simple metabolism has evolved, the further evolution of metabolism occurred in parallel with the evolution of the sequences of the catalyzing enzymes. Indications of such a coevolution can be found when correlating the change in sequence between two enzymes with their distance on the metabolic network which is obtained from the KEGG database. We observe that there exists a small but significant correlation primarily on nearest neighbors. This indicates that enzymes catalyzing subsequent reactions tend to be descended from the same precursor. Since this correlation is relatively small one can at least assume that, if new enzymes are no "genetic children" of the previous enzymes, they certainly be descended from any of the already existing ones. Following this hypothesis, we introduce a model of enzyme-pathway coevolution. By iteratively adding enzymes, this model explores the metabolic network in a manner similar to diffusion. With implementation of an Gillespie-like algorithm we are able to introduce a tunable parameter that controls the weight of sequence similarity when choosing a new enzyme. Furthermore, this method also defines a time difference between successive evolutionary innovations in terms of a new enzyme. Overall, these simulations generate putative time-courses of the evolutionary walk on the metabolic network. By a time-series analysis, we find that the acquisition of new enzymes appears in bursts which are pronounced when the influence of the sequence similarity is higher. This behavior strongly resembles punctuated equilibrium which denotes the observation that new species tend to appear in bursts as well rather than in a gradual manner. Thus, our model helps to establish a better understanding of punctuated equilibrium giving a potential description at molecular level. From the time-courses we also extract a tentative order of new enzymes, metabolites, and even organisms. The consistence of this order with previous findings provides evidence for the validity of our approach. While the sequence of a gene is actually subject to mutations, its expression profile might also indirectly change through the evolutionary events in the cellular interplay. Gene coexpression data is simply accessible by microarray experiments and commonly illustrated using coexpression networks where genes are nodes and get linked once they show a significant coexpression. Since the large number of genes makes an illustration of the entire coexpression network difficult, clustering helps to show the network on a metalevel. Various clustering techniques already exist. However, we introduce a novel one which maintains control of the cluster sizes and thus assures proper visual inspection. An application of the method on Arabidopsis thaliana reveals that genes causing a severe phenotype often show a functional uniqueness in their network vicinity. This leads to 20 genes of so far unknown phenotype which are however suggested to be essential for plant growth. Of these, six indeed provoke such a severe phenotype, shown by mutant analysis. By an inspection of the degree distribution of the A.thaliana coexpression network, we identified two characteristics. The distribution deviates from the frequently observed power-law by a sharp truncation which follows after an over-representation of highly connected nodes. For a better understanding, we developed an evolutionary model which mimics the growth of a coexpression network by gene duplication which underlies a strong selection criterion, and slight mutational changes in the expression profile. Despite the simplicity of our assumption, we can reproduce the observed properties in A.thaliana as well as in E.coli and S.cerevisiae. The over-representation of high-degree nodes could be identified with mutually well connected genes of similar functional families: zinc fingers (PF00096), flagella, and ribosomes respectively. In conclusion, these four manuscripts demonstrate the usefulness of mathematical models and statistical tools as a source of new biological insight. While the clustering approach of gene coexpression data leads to the phenotypic characterization of so far unknown genes and thus supports genome annotation, our model approaches offer explanations for observed properties of the coexpression network and furthermore substantiate punctuated equilibrium as an evolutionary process by a deeper understanding of an underlying molecular mechanism.},
  language  = {en}
}
@phdthesis{Jurish2011,
  author    = {Jurish, Bryan},
  title     = {Finite-state canonicalization techniques for historical German},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-55789},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {This work addresses issues in the automatic preprocessing of historical German input text for use by conventional natural language processing techniques. Conventional techniques cannot adequately account for historical input text due to conventional tools' reliance on a fixed application-specific lexicon keyed by contemporary orthographic surface form on the one hand, and the lack of consistent orthographic conventions in historical input text on the other. Historical spelling variation is treated here as an error-correction problem or "canonicalization" task: an attempt to automatically assign each (historical) input word a unique extant canonical cognate, thus allowing direct application-specific processing (tagging, parsing, etc.) of the returned canonical forms without need for any additional application-specific modifications. In the course of the work, various methods for automatic canonicalization are investigated and empirically evaluated, including conflation by phonetic identity, conflation by lemma instantiation heuristics, canonicalization by weighted finite-state rewrite cascade, and token-wise disambiguation by a dynamic Hidden Markov Model.},
  language  = {en}
}
@phdthesis{Off2011,
  author    = {Off, Thomas},
  title     = {Durchg{\"a}ngige Verfolgbarkeit im Vorfeld der Softwareentwicklung von E-Government-Anwendungen : ein ontologiebasierter und modellgetriebener Ansatz am Beispiel von B{\"u}rgerdiensten},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-57478},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Die {\"o}ffentliche Verwaltung setzt seit mehreren Jahren E-Government-Anwendungssysteme ein, um ihre Verwaltungsprozesse intensiver mit moderner Informationstechnik zu unterst{\"u}tzen. Da die {\"o}ffentliche Verwaltung in ihrem Handeln in besonderem Maße an Recht und Gesetz gebunden ist verst{\"a}rkt und verbreitet sich der Zusammenhang zwischen den Gesetzen und Rechtsvorschriften einerseits und der zur Aufgabenunterst{\"u}tzung eingesetzten Informationstechnik andererseits. Aus Sicht der Softwaretechnik handelt es sich bei diesem Zusammenhang um eine spezielle Form der Verfolgbarkeit von Anforderungen (engl. Traceability), die so genannte Verfolgbarkeit im Vorfeld der Anforderungsspezifikation (Pre-Requirements Specification Traceability, kurz Pre-RS Traceability), da sie Aspekte betrifft, die relevant sind, bevor die Anforderungen in eine Spezifikation eingeflossen sind (Urspr{\"u}nge von Anforderungen). Der Ansatz dieser Arbeit leistet einen Beitrag zur Verfolgbarkeit im Vorfeld der Anforderungsspezifikation von E-Government-Anwendungssystemen. Er kombiniert dazu aktuelle Entwicklungen und Standards (insbesondere des World Wide Web Consortium und der Object Management Group) aus den Bereichen Verfolgbarkeit von Anforderungen, Semantic Web, Ontologiesprachen und modellgetriebener Softwareentwicklung. Der L{\"o}sungsansatz umfasst eine spezielle Ontologie des Verwaltungshandeln, die mit den Techniken, Methoden und Werkzeugen des Semantic Web eingesetzt wird, um in Texten von Rechtsvorschriften relevante Urspr{\"u}nge von Anforderungen durch Annotationen mit einer definierten Semantik zu versehen. Darauf aufbauend wird das Ontology Definition Metamodel (ODM) verwendet, um die Annotationen als spezielle Individuen einer Ontologie auf Elemente der Unified Modeling Language (UML) abzubilden. Dadurch entsteht ein neuer Modelltyp Pre-Requirements Model (PRM), der das Vorfeld der Anforderungsspezifikation formalisiert. Modelle diesen Typs k{\"o}nnen auch verwendet werden, um Aspekte zu formalisieren die sich nicht oder nicht vollst{\"a}ndig aus dem Text der Rechtsvorschrift ergeben. Weiterhin bietet das Modell die M{\"o}glichkeit zum Anschluss an die modellgetriebene Softwareentwicklung. In der Arbeit wird deshalb eine Erweiterung der Model Driven Architecture (MDA) vorgeschlagen. Zus{\"a}tzlich zu den etablierten Modelltypen Computation Independent Model (CIM), Platform Independent Model (PIM) und Platform Specific Model (PSM) k{\"o}nnte der Einsatz des PRM Vorteile f{\"u}r die Verfolgbarkeit bringen. Wird die MDA mit dem PRM auf das Vorfeld der Anforderungsspezifikation ausgeweitet, kann eine Transformation des PRM in ein CIM als initiale Anforderungsspezifikation erfolgen, indem der MOF Query View Transformation Standard (QVT) eingesetzt wird. Als Teil des QVT-Standards ist die Aufzeichnung von Verfolgbarkeitsinformationen bei Modelltransformationen verbindlich. Um die semantische L{\"u}cke zwischen PRM und CIM zu {\"u}berbr{\"u}cken, erfolgt analog zum Einsatz des Plattformmodells (PM) in der PIM nach PSM Transformation der Einsatz spezieller Hilfsmodelle. Es kommen daf{\"u}r die im Projekt "E-LoGo" an der Universit{\"a}t Potsdam entwickelten Referenzmodelle zum Einsatz. Durch die Aufzeichnung der Abbildung annotierter Textelemente auf Elemente im PRM und der Transformation der Elemente des PRM in Elemente des CIM kann durchg{\"a}ngige Verfolgbarkeit im Vorfeld der Anforderungsspezifikation erreicht werden. Der Ansatz basiert auf einer so genannten Verfolgbarkeitsdokumentation in Form verlinkter Hypertextdokumente, die mittels XSL-Stylesheet erzeugt wurden und eine Verbindung zur graphischen Darstellung des Diagramms (z. B. Anwendungsfall-, Klassendiagramm der UML) haben. Der Ansatz unterst{\"u}tzt die horizontale Verfolgbarkeit zwischen Elementen unterschiedlicher Modelle vorw{\"a}rts- und r{\"u}ckw{\"a}rtsgerichtet umfassend. Er bietet außerdem vertikale Verfolgbarkeit, die Elemente des gleichen Modells und verschiedener Modellversionen in Beziehung setzt. {\"U}ber den offensichtlichen Nutzen einer durchg{\"a}ngigen Verfolgbarkeit im Vorfeld der Anforderungsspezifikation (z. B. Analyse der Auswirkungen einer Gesetzes{\"a}nderung, Ber{\"u}cksichtigung des vollst{\"a}ndigen Kontextes einer Anforderung bei ihrer Priorisierung) hinausgehend, bietet diese Arbeit eine erste Ansatzm{\"o}glichkeit f{\"u}r eine Feedback-Schleife im Prozess der Gesetzgebung. Stehen beispielsweise mehrere gleichwertige Gestaltungsoptionen eines Gesetzes zur Auswahl, k{\"o}nnen die Auswirkungen jeder Option analysiert und der Aufwand ihrer Umsetzung in E-Government-Anwendungen als Auswahlkriterium ber{\"u}cksichtigt werden. Die am 16. M{\"a}rz 2011 in Kraft getretene {\"A}nderung des NKRG schreibt eine solche Analyse des so genannten „Erf{\"u}llungsaufwands" f{\"u}r Teilbereiche des Verwaltungshandelns bereits heute verbindlich vor. F{\"u}r diese Analyse kann die vorliegende Arbeit einen Ansatz bieten, um zu fundierten Aussagen {\"u}ber den {\"A}nderungsaufwand eingesetzter E-Government-Anwendungssysteme zu kommen.},
  language  = {de}
}