@phdthesis{Zoeller2005, author = {Z{\"o}ller, Gert}, title = {Critical states of seismicity : modeling and data analysis}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-7427}, school = {Universit{\"a}t Potsdam}, year = {2005}, abstract = {The occurrence of earthquakes is characterized by a high degree of spatiotemporal complexity. Although numerous patterns, e.g. fore- and aftershock sequences, are well-known, the underlying mechanisms are not observable and thus not understood. Because the recurrence times of large earthquakes are usually decades or centuries, the number of such events in corresponding data sets is too small to draw conclusions with reasonable statistical significance. Therefore, the present study combines both, numerical modeling and analysis of real data in order to unveil the relationships between physical mechanisms and observational quantities. The key hypothesis is the validity of the so-called "critical point concept" for earthquakes, which assumes large earthquakes to occur as phase transitions in a spatially extended many-particle system, similar to percolation models. New concepts are developed to detect critical states in simulated and in natural data sets. The results indicate that important features of seismicity like the frequency-size distribution and the temporal clustering of earthquakes depend on frictional and structural fault parameters. In particular, the degree of quenched spatial disorder (the "roughness") of a fault zone determines whether large earthquakes occur quasiperiodically or more clustered. This illustrates the power of numerical models in order to identify regions in parameter space, which are relevant for natural seismicity. The critical point concept is verified for both, synthetic and natural seismicity, in terms of a critical state which precedes a large earthquake: a gradual roughening of the (unobservable) stress field leads to a scale-free (observable) frequency-size distribution. Furthermore, the growth of the spatial correlation length and the acceleration of the seismic energy release prior to large events is found. The predictive power of these precursors is, however, limited. Instead of forecasting time, location, and magnitude of individual events, a contribution to a broad multiparameter approach is encouraging.}, subject = {Seismizit{\"a}t}, language = {en} } @phdthesis{Zaks2001, author = {Zaks, Michael A.}, title = {Fractal Fourier spectra in dynamical systems}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0000500}, school = {Universit{\"a}t Potsdam}, year = {2001}, abstract = {Eine klassische Art, die Dynamik nichtlinearer Systeme zu beschreiben, besteht in der Analyse ihrer Fourierspektren. F{\"u}r periodische und quasiperiodische Prozesse besteht das Fourierspektrum nur aus diskreten Deltafunktionen. Das Spektrum einer chaotischen Bewegung ist hingegen durch das Vorhandensein einer stetigen Komponente gekennzeichnet. In der Arbeit geht es um einen eigenartigen, weder regul{\"a}ren noch vollst{\"a}ndig chaotischen Zustand mit sogenanntem singul{\"a}rstetigen Leistungsspektrum. Unsere Analyse ergab verschiedene F{\"a}lle aus weit auseinanderliegenden Gebieten, in denen singul{\"a}r stetige (fraktale) Spektren auftreten. Die Beispiele betreffen sowohl physikalische Prozesse, die auf iterierte diskrete Abbildungen oder gar symbolische Sequenzen reduzierbar sind, wie auch Prozesse, deren Beschreibung auf den gew{\"o}hnlichen oder partiellen Differentialgleichungen basiert.}, subject = {Nichtlineares dynamisches System / Harmonische Analyse / Fraktal}, language = {en} } @phdthesis{Zaikin2002, author = {Zaikin, Alexei}, title = {Noise-induced transitions and resonant effects in nonlinear systems}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0000761}, school = {Universit{\"a}t Potsdam}, year = {2002}, abstract = {Unsere allt{\"a}gliche Erfahrung ist mit verschiedenen akustischen Einfluessen wie L{\"a}rm, aber auch Musik verbunden. Jeder weiss, wie L{\"a}rm st{\"o}ren kann und Kommunikation behindert oder gar unterbindet. {\"A}hnliche optische Effekte sind bekannt: starkes Schneetreiben oder Regeng{\"u}sse verschlechtern die Sicht und lassen uns Umrisse nur noch schemenhaft erkennen. Jedoch koennen {\"a}hnliche Stimuli auch sehr positive Auswirkungen haben: Autofahrer fahren bei leiser Musik konzentrierter -- die Behauptung von Schulkindern, nur bei dr{\"o}hnenden B{\"a}ssen die Mathehausaufgaben richtig rechnen zu k{\"o}nnen, ist allerdings nicht wissenschaftlich erwiesen. Außerordentlich interessant aus dieser Sicht sind auch Reizleitungsprozesse: Reize werden nur weitergleitet, wenn die strukturlosen Signale der Neuronen mit ausreichend starker Intensit{\"a}t erfolgen, also ein Schwellwert {\"u}berschritten ist. Der Physiker Dr. Alexei Zaikin von der Universit{\"a}t Potsdam besch{\"a}ftigt sich mit sogenannten rauschinduzierten Ph{\"a}nomenen aus theorischer Sicht. Sein Forschungsgebiet sind Prozesse, bei denen Rauschen mehrfach das Systemverhalten beeinflusst: ist es ausreichend gross, d.h. gr{\"o}ßer als ein kritischer Wert, wird eine regul{\"a}re Struktur gebildet, die durch das immernoch vorhandene Rauschen mit der Struktur des Nachbarsystems synchronisiert. Um ein solches System mit kritischem Wert zu erhalten, bedarf es einer weiteren Rauschquelle. Herr Zaikin analysierte noch weitere Beispiele solcher doppelt stochastischen Effekte. Die Ausarbeitung derartiger theoretischer Grundlagen ist wichtig, da diese Prozesse in der Neurophysik, in technischen Kommunikationssystemen und in den Lebenswissenschaften eine Rolle spielen.}, language = {en} } @phdthesis{Yuan2015, author = {Yuan, Jiayin}, title = {Poly(Ionic Liquid)s}, school = {Universit{\"a}t Potsdam}, pages = {300}, year = {2015}, language = {en} } @phdthesis{Yang2019, author = {Yang, Haojin}, title = {Deep representation learning for multimedia data analysis}, school = {Universit{\"a}t Potsdam}, pages = {278}, year = {2019}, language = {en} } @phdthesis{Weikl2007, author = {Weikl, Thomas R.}, title = {Transition states and loop-closure principles in protein folding}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-26975}, school = {Universit{\"a}t Potsdam}, year = {2007}, abstract = {Proteins are chain molecules built from amino acids. The precise sequence of the 20 different types of amino acids in a protein chain defines into which structure a protein folds, and the three-dimensional structure in turn specifies the biological function of the protein. The reliable folding of proteins is a prerequisite for their robust function. Misfolding can lead to protein aggregates that cause severe diseases, such as Alzheimer's, Parkinson's, or the variant Creutzfeldt-Jakob disease. Small single-domain proteins often fold without experimentally detectable metastable intermediate states. The folding dynamics of these proteins is thought to be governed by a single transition-state barrier between the unfolded and the folded state. The transition state is highly instable and cannot be observed directly. However, mutations in which a single amino acid of the protein is substituted by another one can provide indirect access. The mutations slightly change the transition-state barrier and, thus, the folding and unfolding times of the protein. The central question is how to reconstruct the transition state from the observed changes in folding times. In this habilitation thesis, a novel method to extract structural information on transition states from mutational data is presented. The method is based on (i) the cooperativity of structural elements such as alpha-helices and beta-hairpins, and (ii) on splitting up mutation-induced free-energy changes into components for these elements. By fitting few parameters, the method reveals the degree of structure formation of alpha-helices and beta-hairpins in the transition state. In addition, it is shown in this thesis that the folding routes of small single-domain proteins are dominated by loop-closure dependencies between the structural elements.}, language = {en} } @phdthesis{Weckmann2015, author = {Weckmann, Ute}, title = {Die elektrische Leitf{\"a}higkeit von fossilen St{\"o}rungszonen und Mobile Belts}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-88820}, school = {Universit{\"a}t Potsdam}, pages = {vi, VIII, 74}, year = {2015}, abstract = {In der vorliegenden Arbeit werden verschiedene Experimente zur Untersuchung der elektrischen Leitf{\"a}higkeit von Sutur- und Kollisionszonen im Zusammenhang diskutiert, um die M{\"o}glichkeiten, die die moderne Magnetotellurik (MT) f{\"u}r das Abbilden fossiler tektonischer Systeme bietet, aufzuzeigen. Aus den neuen hochaufl{\"o}senden Abbildern der elektrischen Leitf{\"a}higkeit k{\"o}nnen potentielle Gemeinsamkeiten verschiedener tektonischer Einheiten abgeleitet werden. Innerhalb der letzten Dekade haben sich durch die Weiterentwicklung der Messger{\"a}te und der Auswerte- und Interpretationsmethoden v{\"o}llig neue Perspektiven f{\"u}r die geodynamische Tiefensondierung ergeben. Dies wird an meinen Forschungsarbeiten deutlich, die ich im Rahmen von Projekten selbst eingeworben und am Deutschen GeoForschungsZentrum Potsdam durchgef{\"u}hrt habe. In Tabelle A habe ich die in dieser Arbeit ber{\"u}cksichtigten Experimente aufgef{\"u}hrt, die in den letzten Jahren entweder als Array- oder als Profilmessungen durchgef{\"u}hrt wurden. F{\"u}r derart große Feldexperimente ben{\"o}tigt man ein Team von WissenschaftlerInnen, StudentInnen und technischem Personal. Das bedeutet aber auch, dass von mir betreute StudentInnen und DoktorandInnen Teilaspekte dieser Experimente in Form von Diplom-, Bachelor- und Mastersarbeiten oder Promotionsschriften verarbeitet haben. Bei anschließender Ver{\"o}ffentlichung der Arbeiten habe ich als Co-Autor mitgewirkt. Die beiliegenden Ver{\"o}ffentlichungen enthalten eine Einf{\"u}hrung in die Methode der Magnetotellurik und gegebenenfalls die Beschreibung neu entwickelter Methoden. Eine allgemeine Darstellung der theoretischen Grundlagen der Magnetotellurik findet man zum Beispiel in Chave \& Jones (2012); Simpson \& Bahr (2005); Kaufman \& Keller (1981); Nabighian (1987); Weaver (1994). Die Arbeit beinhaltet zudem ein Glossar, in dem einige Begriffe und Abk{\"u}rzungen erkl{\"a}rt werden. Ich habe mich entschieden, Begriffe, f{\"u}r die es keine ad{\"a}quate deutsche {\"U}bersetzung gibt oder die im Deutschen eine andere oder missverst{\"a}ndliche Bedeutung bekommen, auf Englisch in der Arbeit zu belassen. Sie sind durch eine kursive Schreibweise gekennzeichnet.}, language = {de} } @phdthesis{Wagner2007, author = {Wagner, Dirk}, title = {Microbial perspectives of the methane cycle in permafrost ecosystems in the Eastern Siberian Arctic : implications for the global methane budget}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-15434}, school = {Universit{\"a}t Potsdam}, year = {2007}, abstract = {The Arctic plays a key role in Earth's climate system as global warming is predicted to be most pronounced at high latitudes and because one third of the global carbon pool is stored in ecosystems of the northern latitudes. In order to improve our understanding of the present and future carbon dynamics in climate sensitive permafrost ecosystems, the present study concentrates on investigations of microbial controls of methane fluxes, on the activity and structure of the involved microbial communities, and on their response to changing environmental conditions. For this purpose an integrated research strategy was applied, which connects trace gas flux measurements to soil ecological characterisation of permafrost habitats and molecular ecological analyses of microbial populations. Furthermore, methanogenic archaea isolated from Siberian permafrost have been used as potential keystone organisms for studying and assessing life under extreme living conditions. Long-term studies on methane fluxes were carried out since 1998. These studies revealed considerable seasonal and spatial variations of methane emissions for the different landscape units ranging from 0 to 362 mg m-2 d-1. For the overall balance of methane emissions from the entire delta, the first land cover classification based on Landsat images was performed and applied for an upscaling of the methane flux data sets. The regionally weighted mean daily methane emissions of the Lena Delta (10 mg m-2 d-1) are only one fifth of the values calculated for other Arctic tundra environments. The calculated annual methane emission of the Lena Delta amounts to about 0.03 Tg. The low methane emission rates obtained in this study are the result of the used remotely sensed high-resolution data basis, which provides a more realistic estimation of the real methane emissions on a regional scale. Soil temperature and near soil surface atmospheric turbulence were identified as the driving parameters of methane emissions. A flux model based on these variables explained variations of the methane budget corresponding to continuous processes of microbial methane production and oxidation, and gas diffusion through soil and plants reasonably well. The results show that the Lena Delta contributes significantly to the global methane balance because of its extensive wetland areas. The microbiological investigations showed that permafrost soils are colonized by high numbers of microorganisms. The total biomass is comparable to temperate soil ecosystems. Activities of methanogens and methanotrophs differed significantly in their rates and distribution patterns along both the vertical profiles and the different investigated soils. The methane production rates varied between 0.3 and 38.9 nmol h-1 g-1, while the methane oxidation ranged from 0.2 to 7.0 nmol h-1 g-1. Phylogenetic analyses of methanogenic communities revealed a distinct diversity of methanogens affiliated to Methanomicrobiaceae, Methanosarcinaceae and Methanosaetaceae, which partly form four specific permafrost clusters. The results demonstrate the close relationship between methane fluxes and the fundamental microbiological processes in permafrost soils. The microorganisms do not only survive in their extreme habitat but also can be metabolic active under in situ conditions. It was shown that a slight increase of the temperature can lead to a substantial increase in methanogenic activity within perennially frozen deposits. In case of degradation, this would lead to an extensive expansion of the methane deposits with their subsequent impacts on total methane budget. Further studies on the stress response of methanogenic archaea, especially Methanosarcina SMA-21, isolated from Siberian permafrost, revealed an unexpected resistance of the microorganisms against unfavourable living conditions. A better adaptation to environmental stress was observed at 4 °C compared to 28 °C. For the first time it could be demonstrated that methanogenic archaea from terrestrial permafrost even survived simulated Martian conditions. The results show that permafrost methanogens are more resistant than methanogens from non-permafrost environments under Mars-like climate conditions. Microorganisms comparable to methanogens from terrestrial permafrost can be seen as one of the most likely candidates for life on Mars due to their physiological potential and metabolic specificity.}, language = {en} } @phdthesis{Vogel2021, author = {Vogel, Heike}, title = {Genetics of obesity and type 2 diabetes}, address = {Potsdam}, school = {Universit{\"a}t Potsdam}, pages = {183}, year = {2021}, abstract = {By using mouse outcross populations in combination with bioinformatic approaches, it was possible to identify and characterize novel genes regulating body weight, fat mass and β-cell function, which all contribute to the pathogenesis of obesity and T2D. In detail, the presented studies identified 1. Ifi202b/IFI16 as adipogenic gene involved in adipocyte commitment, maintenance of white adipocyte identity, fat cell size and the inflammatory state of adipose tissue. 2. Pla2g4a/PLA2G4A as gene linked to increased body weight and fat mass with a higher expression in adipose tissue of obese mice and pigs as well as in obese human subjects. 3. Ifgga2/IRGM as novel regulator of lipophagy protecting from excess hepatic lipid accumulation. 4. Nidd/DBA as a diabetogenic locus containing Kti12, Osbpl9, Ttc39a and Calr4 with differential expression in pancreatic islets and/or genetic variants. 5. miR-31 to be higher expressed in adipose tissue of obese and diabetic mice and humans targeting PPARy and GLUT4 and thereby involved in adipogenesis and insulin signaling. 6. Gjb4 as novel gene triggering the development of T2D by reducing insulin secretion, inducing apoptosis and inhibiting proliferation. The performed studies confirmed the complexity and strong genetic heritability character of obesity and T2D. A high number of genetic variations, each with a small effect, are collectively influencing the degree and severity of the disease. The use of mouse outcross populations is a valid tool for disease gene identification; however, to facilitate and accelerate the process of gene identification the combination of mouse cross data with advanced sequencing resources and the publicly available data sets are essential. The main goal for future studies should be the translation of these novel molecular discoveries to useful treatment therapies. More recently, several classes of novel unimolecular combination therapeutics have emerged with superior efficacy than currently prescribed options and pose the potential to reverse obesity and T2D (Finan et al., 2015). The glucagon-like peptide-1 (GLP-1)- estrogen conjugate, which targets estrogen into cells expressing GLP-1 receptors, was shown to improve energy, glucose and lipid metabolism as well as to reduce food reward (Finan et al., 2012; Schwenk et al., 2014; Vogel et al., 2016). Another possibility is the development of miRNA-based therapeutics to prevent obesity and T2D, such as miRNA mimetics, anti-miRNA oligonucleotides and exosomes loaded with miRNAs (Ji and Guo, 2019; Gottmann et al., 2020). As already described, genome-wide association studies for polygenic obesity and T2D traits in humans have also led to the identification of numerous gene variants with modest effect, most of them having an unknown function (Yazdi et al., 2015). These discoveries resulted in novel animal models and have illuminated new biologic pathways. Therefore, the integration of mouse-human genetic approaches and the utilization of the synergistic effects have the potential to lead to the identification of more genes responsible for common Mendelian forms of obesity and T2D, as well as gene × gene and gene × environment interactions (Yazdi et al., 2015; Ingelsson and McCarthy, 2018). This combination may help to unravel the missing heritability of obesity and T2D, to identify novel drug targets and to design more efficient and personalized obesity prevention and management programs.}, language = {en} } @phdthesis{Vocks2012, author = {Vocks, Christian}, title = {Electron kinetic processes in the solar corona and wind}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-65259}, school = {Universit{\"a}t Potsdam}, year = {2012}, abstract = {The Sun is surrounded by a 10^6 K hot atmosphere, the corona. The corona and the solar wind are fully ionized, and therefore in the plasma state. Magnetic fields play an important role in a plasma, since they bind electrically charged particles to their field lines. EUV spectroscopes, like the SUMER instrument on-board the SOHO spacecraft, reveal a preferred heating of coronal ions and strong temperature anisotropies. Velocity distributions of electrons can be measured directly in the solar wind, e.g. with the 3DPlasma instrument on-board the WIND satellite. They show a thermal core, an anisotropic suprathermal halo, and an anti-solar, magnetic-field-aligned, beam or "strahl". For an understanding of the physical processes in the corona, an adequate description of the plasma is needed. Magnetohydrodynamics (MHD) treats the plasma simply as an electrically conductive fluid. Multi-fluid models consider e.g. protons and electrons as separate fluids. They enable a description of many macroscopic plasma processes. However, fluid models are based on the assumption of a plasma near thermodynamic equilibrium. But the solar corona is far away from this. Furthermore, fluid models cannot describe processes like the interaction with electromagnetic waves on a microscopic scale. Kinetic models, which are based on particle velocity distributions, do not show these limitations, and are therefore well-suited for an explanation of the observations listed above. For the simplest kinetic models, the mirror force in the interplanetary magnetic field focuses solar wind electrons into an extremely narrow beam, which is contradicted by observations. Therefore, a scattering mechanism must exist that counteracts the mirror force. In this thesis, a kinetic model for electrons in the solar corona and wind is presented that provides electron scattering by resonant interaction with whistler waves. The kinetic model reproduces the observed components of solar wind electron distributions, i.e. core, halo, and a "strahl" with finite width. But the model is not only applicable on the quiet Sun. The propagation of energetic electrons from a solar flare is studied, and it is found that scattering in the direction of propagation and energy diffusion influence the arrival times of flare electrons at Earth approximately to the same degree. In the corona, the interaction of electrons with whistler waves does not only lead to scattering, but also to the formation of a suprathermal halo, as it is observed in interplanetary space. This effect is studied both for the solar wind as well as the closed volume of a coronal magnetic loop. The result is of fundamental importance for solar-stellar relations. The quiet solar corona always produces suprathermal electrons. This process is closely related to coronal heating, and can therefore be expected in any hot stellar corona. In the second part of this thesis it is detailed how to calculate growth or damping rates of plasma waves from electron velocity distributions. The emission and propagation of electron cyclotron waves in the quiet solar corona, and that of whistler waves during solar flares, is studied. The latter can be observed as so-called fiber bursts in dynamic radio spectra, and the results are in good agreement with observed bursts.}, language = {en} } @phdthesis{Titirici2013, author = {Titirici, Maria-Magdalena}, title = {Hydrothermal carbonisation}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-66885}, school = {Universit{\"a}t Potsdam}, year = {2013}, abstract = {The world's appetite for energy is producing growing quantities of CO2, a pollutant that contributes to the warming of the planet and which currently cannot be removed or stored in any significant way. Other natural reserves are also being devoured at alarming rates and current assessments suggest that we will need to identify alternative sources in the near future. With the aid of materials chemistry it should be possible to create a world in which energy use needs not be limited and where usable energy can be produced and stored wherever it is needed, where we can minimize and remediate emissions as new consumer products are created, whilst healing the planet and preventing further disruptive and harmful depletion of valuable mineral assets. In achieving these aims, the creation of new and very importantly greener industries and new sustainable pathways are crucial. In all of the aforementioned applications, new materials based on carbon, ideally produced via inexpensive, low energy consumption methods, using renewable resources as precursors, with flexible morphologies, pore structures and functionalities, are increasingly viewed as ideal candidates to fulfill these goals. The resulting materials should be a feasible solution for the efficient storage of energy and gases. At the end of life, such materials ideally must act to improve soil quality and to act as potential CO2 storage sinks. This is exactly the subject of this habilitation thesis: an alternative technology to produce carbon materials from biomass in water using low carbonisation temperatures and self-generated pressures. This technology is called hydrothermal carbonisation. It has been developed during the past five years by a group of young and talented researchers working under the supervision of Dr. Titirici at the Max-Planck Institute of Colloids and Interfaces and it is now a well-recognised methodology to produce carbon materials with important application in our daily lives. These applications include electrodes for portable electronic devices, filters for water purification, catalysts for the production of important chemicals as well as drug delivery systems and sensors.}, language = {en} } @phdthesis{Thonicke2019, author = {Thonicke, Kirsten}, title = {The influence of disturbance, climate extremes and land-use change on vegetation dynamics}, school = {Universit{\"a}t Potsdam}, year = {2019}, language = {en} } @phdthesis{Thieken2009, author = {Thieken, Annegret}, title = {Floods, flood losses and flood risk management in Germany}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-29164}, school = {Universit{\"a}t Potsdam}, year = {2009}, abstract = {Die vorliegende Habilitation besch{\"a}ftigt sich mit verschiedenen Aspekten des Hochwasserrisikos in Deutschland. In zw{\"o}lf Artikeln werden neue wissenschaftliche Erkenntnisse {\"u}ber Hochwassergefahren, {\"u}ber Faktoren, die Hochwassersch{\"a}den beeinflussen, sowie {\"u}ber effektive private Vorsorgemaßnahmen pr{\"a}sentiert. So wird die jahreszeitliche Verteilung von Hochwasser in ganz Deutschland gezeigt. Weiterhin werden m{\"o}gliche Auswirkungen des Klimawandels auf Abflussverh{\"a}ltnisse und H{\"a}ufigkeiten von Hochwasserereignissen am Beispiel des Rhein-Einzugsgebietes abgesch{\"a}tzt. Ferner wird am Niederrhein simuliert, welche Auswirkungen Deichbr{\"u}che haben k{\"o}nnen. Hochwassersch{\"a}den stehen im zweiten Teil der Arbeit im Fokus: Nach dem August-Hochwasser 2002 wurden ca. 1700 Privathaushalte telefonisch befragt. Damit konnten die Einfl{\"u}sse verschiedener Faktoren, wie der {\"U}berflutungsdauer oder der Verunreinigung des Hochwassers mit {\"O}l, auf die H{\"o}he von finanziellen Sch{\"a}den quantifiziert werden. Daraus ist zum einen ein neues Modell entstanden, mit dem Hochwassersch{\"a}den großr{\"a}umig berechnet werden k{\"o}nnen. Zum anderen konnten Hinweise f{\"u}r die Verbesserung der privaten Vorsorge abgeleitet werden. Beispielsweise zeigte sich, dass versicherte Haushalte schneller und besser entsch{\"a}digt werden als Nicht-Versicherte. Ebenfalls wurde deutlich, dass verschiedene Bev{\"o}lkerungsgruppen, wie Mieter und Hauseigent{\"u}mer, unterschiedliche M{\"o}glichkeiten haben, Vorsorge zu betreiben. Dies ist zuk{\"u}nftig in der Risikokommunikation zu ber{\"u}cksichtigen. In den Jahren 2005 und 2006 waren Elbe und Donau wiederum von Hochwasser betroffen. Eine erneute Befragung von Privathaushalten und Beh{\"o}rden erm{\"o}glichte, die Verbesserung des Hochwasserrisikomanagement und der Vorsorge am Beispiel der Stadt Dresden zu untersuchen. Viele Methoden und Erkenntnisse dieser Arbeit sind in der wasserwirtschaftlichen Praxis anwendbar und tragen somit zur Verbesserung der Hochwasserrisikoanalyse und des Risikomanagements in Deutschland bei.}, language = {en} } @phdthesis{Theilmann2011, author = {Theilmann, Florian}, title = {Die Kunst der Untersuchung : Essays zu einem erscheinungsorientierten Physikunterricht}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-56145}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {Die vorliegende Arbeit versammelt zwei einleitende Kapitel und zehn Essays, die sich als kritisch-konstruktive Beitr{\"a}ge zu einem "erlebenden Verstehen" (Buck) von Physik lesen lassen. Die traditionelle Anlage von Schulphysik zielt auf eine systematische Darstellung naturwissenschaftlichen Wissens, das dann an ausgew{\"a}hlten Beispielen angewendet wird: Schulexperimente beweisen die Aussagen der Systematik (oder machen sie wenigstens plausibel), ausgew{\"a}hlte Ph{\"a}nomene werden erkl{\"a}rt. In einem solchen Rahmen besteht jedoch leicht die Gefahr, den Bezug zur Lebenswirklichkeit oder den Interessen der Sch{\"u}ler zu verlieren. Diese Problematik ist seit mindestens 90 Jahren bekannt, didaktische Antworten - untersuchendes Lernen, Kontextualisierung, Sch{\"u}lerexperimente etc. - adressieren allerdings eher Symptome als Ursachen. Naturwissenschaft wird dadurch spannend, dass sie ein spezifisch investigatives Weltverh{\"a}ltnis stiftet: man m{\"u}sste gleichsam nicht Wissen, sondern "Fragen lernen" (und nat{\"u}rlich auch, wie Antworten gefunden werden...). Doch wie kann dergleichen auf dem Niveau von Schulphysik aussehen, was f{\"u}r einen theoretischen Rahmen kann es hier geben? In den gesammelten Arbeiten wird einigen dieser Spuren nachgegangen: Der Absage an das zu modellhafte Denken in der ph{\"a}nomenologischen Optik, der Abgrenzung formal-mathematischen Denkens gegen wirklichkeitsn{\"a}here Formen naturwissenschaftlicher Denkbewegungen und Evidenz, dem Potential alternativer Interpretationen von "Physikunterricht", der Frage nach dem "Verstehen" u.a. Dabei werden nicht nur Bez{\"u}ge zum modernen bildungstheoretischen Paradigma der Kompetenz sichtbar, sondern es wird auch versucht, eine ganze Reihe konkrete (schul-)physikalische Beispiele daf{\"u}r zu geben, was passiert, wenn nicht schon gewusste Antworten Thema werden, sondern Expeditionen, die sich der physischen Welt widmen: Die Schl{\"u}sselbegriffe des Fachs, die Methoden der Datenerhebung und Interpretation, die Such- und Denkbewegungen kommen dabei auf eine Weise zur Sprache, die sich nicht auf die Fachsystematik abst{\"u}tzen m{\"o}chte, sondern diese motivieren, konturieren und verst{\"a}ndlich machen will.}, language = {de} } @phdthesis{Stroncik2019, author = {Stroncik, Nicole A.}, title = {Volatiles as tracers for mantle processes and magma formation and evolution}, pages = {102}, year = {2019}, abstract = {The geochemical composition of oceanic basalts provides us with a window into the distribution of geochemical elements within the Earth's mantle in space and time. In conjunction with a throughout knowledge on how the different elements behave e.g. during melt formation and evolution or on their partition behaviour between e.g. minerals and melts this information has been transformed into various models on how oceanic crust is formed along plume influenced or normal mid-ocean ridge segments, how oceanic crust evolves in response to seawater, on subduction recycling of oceanic crust and so forth. The work presented in this habilitation was aimed at refining existing models, putting further constraints on some of the major open questions in this field of research while at the same time trying to increase our knowledge on the behaviour of noble gases as a tracer for melt formation and evolution processes. In the line of this work the author and her co-workers were able to answer one of the major questions concerning the formation of oceanic crust along plume-influenced ridges - in which physical state does the plume material enter the ridge? Based on submarine volcanic glass He, Ne and Ar data, the author and her co-workers have shown that the interaction of mantle plumes with mid-ocean ridges occurs in the physical form of melts. In addition, the author and her co-workers have also put further constraints on one of the major questions concerning the formation of oceanic crust along normal mid-ocean ridges - namely how is the mid-ocean ridge system effectively cooled to form the lower oceanic crust? Based on Ne and Ar data in combination with Cl/K ratios of basaltic glass from the Mid-Atlantic ridge and estimates of crystallisation pressures they have shown, that seawater penetration reaches lower crustal levels close to the Moho, indicating that hydrothermal circulation might be an effective cooling mechanism even for the deep parts of the oceanic crust. Considering subduction recycling, the heterogeneity of the Earth's mantle and mantle dynamic processes the key question is on which temporal and spatial scales is the Earth's mantle geochemically heterogeneous? In the line of this work the author along with her co-workers have shown based on Cl/K ratios in conjunction with the Sr, Nd, and Pb isotopes of the OIBs representing the type localities for the different mantle endmembers that the quantity of Cl recycled into the mantle via subduction is not uniform and that neither the HIMU nor the EM1 and EM2 mantle components can be considered as distinct mantle endmembers. In addition, we have shown, based on He, Ne and Ar isotope and trace-element data from the Foundation hotspot that the near ridge seamounts of the Foundation seamount chain formed by the Foundation hotspot erupt lavas with a trace-element signature clearly characteristic of oceanic gabbro which indicates the existence of recycled, virtually unchanged lower oceanic crust in the plume source. This is a clear sign of the inefficiency of the stirring mechanism existing at mantle depth. Similar features are seen in other near-axis hotspot magmas around the world. Based on He, Sr, Nd, Pb and O isotopes and trace elements in primitive mafic dykes from the Etendeka flood basalts, NW Namibia the author along with her co-workers have shown that deep, less degassed mantle material carried up by a mantle plume contributed significantly to the flood basalt magmatism. The Etendeka flood basalts are part of the South Atlantic LIP, which is associated with the breakup of Gondwana, the formation of the Paran{\´a}-Etendeka flood basalts and the Walvis Ridge - Tristan da Cunha hotspot track. Thus reinforcing the lately often-challenged concept of mantle plumes and the role of mantle plumes in the formation of large igneous provinces. Studying the behaviour of noble gases during melt formation and evolution the author along with her co-workers has shown that He can be considerable more susceptible to changes during melt formation and evolution resulting not only in a complete decoupling of He isotopes from e.g. Ne or Pb isotopes but also in a complete loss of the primary mantle isotope signal. They have also shown that this decoupling occurs mainly during the melt formation processes requiring He to be more compatible during mantle melting than Ne. In addition, the author along with her co workers were able to show that incorporation of atmospheric noble gases into igneous rocks is in general a two-step process: (1) magma contamination by assimilation of altered oceanic crust results in the entrainment of air-equilibrated seawater noble gases; (2) atmospheric noble gases are adsorbed onto grain surfaces during sample preparation. This implies, considering the ubiquitous presence of the contamination signal, that magma contamination by assimilation of a seawater-sourced component is an integral part of mid-ocean ridge basalt evolution.}, language = {en} } @phdthesis{Strauss2023, author = {Strauß, Volker}, title = {Laser-induced carbonization - from fundamentals to applications}, doi = {10.25932/publishup-59199}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-591995}, school = {Universit{\"a}t Potsdam}, pages = {VIII, 78, A245}, year = {2023}, abstract = {Fabricating electronic devices from natural, renewable resources has been a common goal in engineering and materials science for many years. In this regard, carbon is of special significance due to its biological compatibility. In the laboratory, carbonized materials and their composites have been proven as promising solutions for a range of future applications in electronics, optoelectronics, or catalytic systems. On the industrial scale, however, their application is inhibited by tedious and expensive preparation processes and a lack of control over the processing and material parameters. Therefore, we are exploring new concepts for the direct utilization of functional carbonized materials in electronic applications. In particular, laser-induced carbonization (carbon laser-patterning (CLaP)) is emerging as a new tool for the precise and selective synthesis of functional carbon-based materials for flexible on-chip applications. We developed an integrated approach for on-the-spot laser-induced synthesis of flexible, carbonized films with specific functionalities. To this end, we design versatile precursor inks made from naturally abundant starting compounds and reactants to cast films which are carbonized with an infrared laser to obtain functional patterns of conductive porous carbon networks. In our studies we obtained deep mechanistic insights into the formation process and the microstructure of laser-patterned carbons (LP-C). We shed light on the kinetic reaction mechanism based on the interplay between the precursor properties and the reaction conditions. Furthermore, we investigated the use of porogens, additives, and reactants to provide a toolbox for the chemical and physical fine-tuning of the electronic and surface properties and the targeted integration of functional sites into the carbon network. Based on this knowledge, we developed prototype resistive chemical and mechanical sensors. In further studies, we show the applicability of LP-C as electrode materials in electrocatalytic and charge-storage applications. To put our findings into a common perspective, our results are embedded into the context of general carbonization strategies, fundamentals of laser-induced materials processing, and a broad literature review on state-of-the-art laser-carbonization, in the general part.}, language = {en} } @phdthesis{Schwarz2004, author = {Schwarz, Ulrich Sebastian}, title = {Forces and elasticity in cell adhesion}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0001343}, school = {Universit{\"a}t Potsdam}, year = {2004}, abstract = {Das Verhalten adh{\"a}renter Zellen h{\"a}ngt stark von den chemischen, topographischen und mechanischen Eigenschaften ihrer Umgebung ab. Experimentelle Untersuchungen der letzten Jahre haben gezeigt, dass adh{\"a}rente Zellen aktiv die elastischen Eigenschaften ihrer Umgebung erkunden, indem sie an dieser ziehen. Der resultierende Kraftaufbau h{\"a}ngt von den elastischen Eigenschaften der Umgebung ab und wird an den Adh{\"a}sionskontakten in entsprechende biochemische Signale umgewandelt, die zellul{\"a}re Programme wie Wachstum, Differenzierung, programmierten Zelltod und Zellbewegung mitbestimmen. Im Allgemeinen sind Kr{\"a}fte wichtige Einflussgr{\"o}ßen in biologischen Systemen. Weitere Beispiele daf{\"u}r sind H{\"o}r- und Tastsinn, Wundheilung sowie die rollende Adh{\"a}sion von weißen Blutk{\"o}rperchen auf den W{\"a}nden der Blutgef{\"a}ße. In der Habilitationsschrift von Ulrich Schwarz werden mehrere theoretische Projekte vorgestellt, die die Rolle von Kr{\"a}ften und Elastizit{\"a}t in der Zelladh{\"a}sion untersuchen. (1) Es wurde eine neue Methode entwickelt, um die Kr{\"a}fte auszurechnen, die Zellen an den Kontaktpunkten auf mikro-strukturierte elastische Substrate aus{\"u}ben. Das Hauptergebnis ist, dass Zell-Matrix-Kontakte als Mechanosensoren funktionieren, an denen interne Kr{\"a}fte in Proteinaggregation umgewandelt werden. (2) Eine Ein-Schritt-Master-Gleichung, die die stochastische Dynamik von Adh{\"a}sionsclustern als Funktion von Clustergr{\"o}ße, R{\"u}ckbindungsrate und Kraft beschreibt, wurde sowohl analytisch als auch numerisch gel{\"o}st. Zudem wurde dieses Modell auf Zell-Matrix-Kontakte, dynamische Kraftspektroskopie sowie die rollende Adh{\"a}sion angewandt. (3) Im Rahmen der linearen Elastizit{\"a}tstheorie und mit Hilfe des Konzepts der Kraftdipole wurde ein Modell formuliert und gel{\"o}st, das die Positionierung und Orientierung von Zellen in weicher Umgebung vorhersagt. Diese Vorhersagen sind in guter {\"U}bereinstimmung mit zahlreichen experimentellen Beobachtungen f{\"u}r Fibroblasten auf elastischen Substraten und in Kollagen-Gelen.}, language = {en} } @phdthesis{Schwanghart2022, author = {Schwanghart, Wolfgang}, title = {Digital elevation model analysis in geomorphology and natural hazards research}, year = {2022}, language = {en} } @phdthesis{Schroeter2020, author = {Schr{\"o}ter, Kai}, title = {Improved flood risk assessment}, doi = {10.25932/publishup-48024}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-480240}, school = {Universit{\"a}t Potsdam}, pages = {408}, year = {2020}, abstract = {Rivers have always flooded their floodplains. Over 2.5 billion people worldwide have been affected by flooding in recent decades. The economic damage is also considerable, averaging 100 billion US dollars per year. There is no doubt that damage and other negative effects of floods can be avoided. However, this has a price: financially and politically. Costs and benefits can be estimated through risk assessments. Questions about the location and frequency of floods, about the objects that could be affected and their vulnerability are of importance for flood risk managers, insurance companies and politicians. Thus, both variables and factors from the fields of hydrology and sociol-economics play a role with multi-layered connections. One example are dikes along a river, which on the one hand contain floods, but on the other hand, by narrowing the natural floodplains, accelerate the flood discharge and increase the danger of flooding for the residents downstream. Such larger connections must be included in the assessment of flood risk. However, in current procedures this is accompanied by simplifying assumptions. Risk assessments are therefore fuzzy and associated with uncertainties. This thesis investigates the benefits and possibilities of new data sources for improving flood risk assessment. New methods and models are developed, which take the mentioned interrelations better into account and also quantify the existing uncertainties of the model results, and thus enable statements about the reliability of risk estimates. For this purpose, data on flood events from various sources are collected and evaluated. This includes precipitation and flow records at measuring stations as well as for instance images from social media, which can help to delineate the flooded areas and estimate flood damage with location information. Machine learning methods have been successfully used to recognize and understand correlations between floods and impacts from a wide range of data and to develop improved models. Risk models help to develop and evaluate strategies to reduce flood risk. These tools also provide advanced insights into the interplay of various factors and on the expected consequences of flooding. This work shows progress in terms of an improved assessment of flood risks by using diverse data from different sources with innovative methods as well as by the further development of models. Flood risk is variable due to economic and climatic changes, and other drivers of risk. In order to keep the knowledge about flood risks up-to-date, robust, efficient and adaptable methods as proposed in this thesis are of increasing importance.}, language = {en} } @phdthesis{Schmidt2020, author = {Schmidt, Bernhard V. K. J.}, title = {Polymers, self-assembly and materials}, doi = {10.25932/publishup-48481}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-484819}, school = {Universit{\"a}t Potsdam}, pages = {VI, 350}, year = {2020}, abstract = {In der vorliegenden Arbeit wurden die Selbstorganisation von hydrophilen Polymeren, verst{\"a}rkte Hydrogele, sowie anorganische/Polymer Hybridmaterialien untersucht. Dabei beschreibt die Arbeit den Weg von Polymersynthese mittels verschiedener Methoden {\"u}ber Polymerselbstanordnung bis zur Herstellung von Polymermaterialien mit vielversprechenden Eigenschaften f{\"u}r zuk{\"u}nftige Anwendungen. Hydrophile Polymere wurden verwendet, um Mehrphasensysteme herzustellen, Wasser-in-Wasser Emulsionen zu bilden und selbstangeordneten Strukturen zu erzeugen, z. B. Partikel/Aggregate oder hohle Strukturen aus komplett wasserl{\"o}slichen Bausteinen. Die Strukturbildung in w{\"a}ssriger Umgebung wurde ferner f{\"u}r supramolekulare Hydrogele mit definierter Unterstruktur und reversiblem Gelierungsverhalten eingesetzt. Auf dem Gebiet der Hydrogele wurde das anorganische Material graphitisches Kohlenstoffnitrid (g-CN) als Photoinitiator f{\"u}r die Hydrogelsynthese und als Verst{\"a}rker der Gelstruktur beschrieben. Hierbei konnten Hydrogele mit herausragenden Eigenschaften generiert werden, z. B. hohe Kompressibilit{\"a}t, hohe Speichermodule oder Gleitf{\"a}higkeit. Die Kombinationen von g-CN mit verschiedenen Polymeren erlaubte es zudem neue Materialien f{\"u}r die Photokatalyse bereitzustellen. Als weiteres anorganisches Material wurden Metall-organische Ger{\"u}ste (MOFs) mit Polymeren kombiniert. Es konnte gezeigt werden, dass die Verwendung von MOFs in der Polymersynthese einen starken Einfluss auf die erzeugte Polymerstruktur hat und MOFs als Katalysator f{\"u}r Polymerisationen verwendet werden k{\"o}nnen. Zuletzt wurde die MOF Synthese an sich untersucht, wobei Polymeradditive oder L{\"o}sungsmittel eingesetzt wurden um die kristalline Struktur der MOFs zu modulieren. Insgesamt wurden hier verschiedene Errungenschaften f{\"u}r die Polymerchemie beschrieben, z.B. neuartige hydrophile Polymere und Hydrogele, die zur Zeit wichtige Materialien im Polymerbereich durch ihre vielversprechenden Anwendungen im biomedizinischen Sektor darstellen. Außerdem ergab die Kombination von Polymeren mit Materialien aus anderen Bereichen der Chemie, z. B. g-CN und MOFs, neue Materialien mit bemerkenswerten Eigenschaften, die ebenfalls von Interesse f{\"u}r zuk{\"u}nftige Anwendungen sind, z. B. Beschichtungen, Partikeltechnologie und Katalyse.}, language = {en} }