@phdthesis{Aich2015,
  author    = {Aich, Valentin},
  title     = {Floods in the Niger River Basin in the face of global change},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-91577},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xxi, 275},
  year      = {2015},
  abstract  = {In the last decade, the number and dimensions of catastrophic flooding events in the Niger River Basin (NRB) have markedly increased. Despite the devastating impact of the floods on the population and the mainly agriculturally based economy of the riverine nations, awareness of the hazards in policy and science is still low. The urgency of this topic and the existing research deficits are the motivation for the present dissertation. The thesis is an initial detailed assessment of the increasing flood risk in the NRB. The research strategy is based on four questions regarding (1) features of the change in flood risk, (2) reasons for the change in the flood regime, (3) expected changes of the flood regime given climate and land use changes, and (4) recommendations from previous analysis for reducing the flood risk in the NRB. The question examining the features of change in the flood regime is answered by means of statistical analysis. Trend, correlation, changepoint, and variance analyses show that, in addition to the factors exposure and vulnerability, the hazard itself has also increased significantly in the NRB, in accordance with the decadal climate pattern of West Africa. The northern arid and semi-arid parts of the NRB are those most affected by the changes. As potential reasons for the increase in flood magnitudes, climate and land use changes are attributed by means of a hypothesis-testing framework. Two different approaches, based on either data analysis or simulation, lead to similar results, showing that the influence of climatic changes is generally larger compared to that of land use changes. Only in the dry areas of the NRB is the influence of land use changes comparable to that of climatic alterations. Future changes of the flood regime are evaluated using modelling results. First ensembles of statistically and dynamically downscaled climate models based on different emission scenarios are analyzed. The models agree with a distinct increase in temperature. The precipitation signal, however, is not coherent. The climate scenarios are used to drive an eco-hydrological model. The influence of climatic changes on the flood regime is uncertain due to the unclear precipitation signal. Still, in general, higher flood peaks are expected. In a next step, effects of land use changes are integrated into the model. Different scenarios show that regreening might help to reduce flood peaks. In contrast, an expansion of agriculture might enhance the flood peaks in the NRB. Similarly to the analysis of observed changes in the flood regime, the impacts of climate- and land use changes for the future scenarios are also most severe in the dry areas of the NRB. In order to answer the final research question, the results of the above analysis are integrated into a range of recommendations for science and policy on how to reduce flood risk in the NRB. The main recommendations include a stronger consideration of the enormous natural climate variability in the NRB and a focus on so called "no-regret" adaptation strategies which account for high uncertainty, as well as a stronger consideration of regional differences. Regarding the prevention and mitigation of catastrophic flooding, the most vulnerable and sensitive areas in the basin, the arid and semi-arid Sahelian and Sudano-Sahelian regions, should be prioritized. Eventually, an active, science-based and science-guided flood policy is recommended. The enormous population growth in the NRB in connection with the expected deterioration of environmental and climatic conditions is likely to enhance the region´s vulnerability to flooding. A smart and sustainable flood policy can help mitigate these negative impacts of flooding on the development of riverine societies in West Africa.},
  language  = {en}
}
@phdthesis{Liebrich2015,
  author    = {Liebrich, Marietta},
  title     = {Einfluss von Prozessoptimierungen auf die mikrobielle Diversit{\"a}t und die Effizienz der Gasbildung in Co-Verg{\"a}rungsanlagen der Abfallwirtschaft},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-91066},
  school      = {Universit{\"a}t Potsdam},
  pages     = {VII, 102},
  year      = {2015},
  abstract  = {Im Hinblick auf die Problematik der Umweltverschmutzung durch die Nutzung fossiler Brennstoffe ist es n{\"o}tig, eine langfristig stabile und umweltfreundliche Energieversorgung zu gew{\"a}hrleisten. Eine M{\"o}glichkeit, den Energiebedarf CO2-neutral zu decken, ist die Nutzung von Biogas. Hierbei spielt der Einsatz von biogenen Reststoffen, die durch einen hohen Anteil an Kohlenhydraten, Fetten und Proteinen gekennzeichnet sind und daher ein hohes Biogaspotential besitzen, eine wichtige Rolle. Voraussetzung f{\"u}r die Effizienz und Rentabilit{\"a}t solcher Anlagen ist u. a. ein stabiler Gasbildungsprozess. Da bisher noch nicht alle Aspekte der Biogasbildung vollst{\"a}ndig verstanden sind, werden die Anlagen oft nicht optimal ausgelastet, um Prozessst{\"o}rungen wie z. B. {\"U}bers{\"a}uerung zu vermeiden. Um dennoch auftretende Prozessst{\"o}rungen zu beheben, k{\"o}nnen unterschiedliche Maßnahmen durchgef{\"u}hrt werden. Neben der Senkung der Raumbelastung, ist es m{\"o}glich, den pH-Wert durch die Zugabe von Natronlauge oder Calciumoxid anzuheben. In der vorliegenden Arbeit wurden sowohl Prozessst{\"o}rungen als auch Prozessregenerierungen an einer großtechnischen Biogasanlage und in Laborversuchen untersucht. Dabei galt es, neben den physikalischen und chemischen Parametern, die mikrobielle Bioz{\"o}nose mit Hilfe des genetischen Fingerprintings zu charakterisieren und {\"A}nderungen zu detektieren. W{\"a}hrend der Prozessregenerierungen wurden nach der Zugabe von CaO Ver{\"a}nderungen des G{\"a}rrestes beobachtet. Es bildeten sich Pellets, die im Hinblick auf ihre Funktion f{\"u}r die Prozessregenerierung und die Prozessstabilit{\"a}t molekularbiologisch und mikroskopisch untersucht wurden. Es wurde weiterhin der Frage nachgegangen, welche Rolle die Mikroorganismen bei der Entstehung der Pellets spielen. Die vor allem aus Calcium und Fetts{\"a}uren bestehenden Pellets dienten als Aufwuchsfl{\"a}chen f{\"u}r verschiedene Mikroorganismen. Die Bildung von Biofilmen, wie sie auf und in den Pellets nachgewiesen wurde, bot f{\"u}r Mikroorganismen einen Schutz vor negativen Umwelteinfl{\"u}ssen wie z. B. hohe Propions{\"a}urekonzentrationen. Unter diesen g{\"u}nstigen Bedingungen war die Bildung von Biogas auch unter hohen Wasserstoffpartialdr{\"u}cken, die den Abbau von Propions{\"a}ure hemmten, m{\"o}glich. Als Indikator f{\"u}r bessere Lebensbedingungen wurde im Laborversuch ein Methanoculleus receptaculi-verwandter Organismus identifiziert. Dieses methanogene Archaeon wurde im Pellet nachgewiesen, w{\"a}hrend es im G{\"a}rrest erst nach der Prozessregenerierung detektiert wurde. Der Nachweis eines im Vergleich zum umgebenden G{\"a}rrest h{\"o}heren Anteils an Archaeen im Kern der Pellets sowie von Biofilmen/EPS, verschiedenen Phosphatsalzen und schwerl{\"o}slichen Calciumsalzen zeigte, dass sowohl Pr{\"a}zipitation und Adsorption als auch Degradation von LCFA dazu f{\"u}hren, dass deren Konzentration im fl{\"u}ssigen G{\"a}rrest gesenkt wird. Dadurch nimmt die Hemmung auf die Bioz{\"o}nose ab und die Biogasbildungsrate steigt. Daher ist der Abbau der Fetts{\"a}uren auch bei einem niedrigen pH-Wert und unter hohen Wasserstoffpartialdr{\"u}cken m{\"o}glich und der Biogasbildungsprozess ist langfristig stabil. Die Bildung von Pellets unterst{\"u}tzt die Prozessstabilit{\"a}t, sofern diese nicht zu groß werden und dann u. a. die Durchmischung behindern und den Ablauf verstopfen. Nach erfolgreicher Prozessstabilisierung wurden keine Pellets im G{\"a}rrest beobachtet. Der Abbau des organischen Materials wurde sowohl durch die steigende Calciumkonzentration als auch die steigende Gasproduktion angezeigt.},
  language  = {de}
}
@phdthesis{Schroeder2015,
  author    = {Schr{\"o}der, Sarah},
  title     = {Modelling surface evolution coupled with tectonics},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-90385},
  school      = {Universit{\"a}t Potsdam},
  pages     = {viii, 129},
  year      = {2015},
  abstract  = {This study presents the development of 1D and 2D Surface Evolution Codes (SECs) and their coupling to any lithospheric-scale (thermo-)mechanical code with a quadrilateral structured surface mesh. Both SECs involve diffusion as approach for hillslope processes and the stream power law to reflect riverbed incision. The 1D SEC settles sediment that was produced by fluvial incision in the appropriate minimum, while the supply-limited 2D SEC DANSER uses a fast filling algorithm to model sedimantation. It is based on a cellular automaton. A slope-dependent factor in the sediment flux extends the diffusion equation to nonlinear diffusion. The discharge accumulation is achieved with the D8-algorithm and an improved drainage accumulation routine. Lateral incision enhances the incision's modelling. Following empirical laws, it incises channels of several cells width. The coupling method enables different temporal and spatial resolutions of the SEC and the thermo-mechanical code. It transfers vertical as well as horizontal displacements to the surface model. A weighted smoothing of the 3D surface displacements is implemented. The smoothed displacement vectors transmit the deformation by bilinear interpolation to the surface model. These interpolation methods ensure mass conservation in both directions and prevent the two surfaces from drifting apart. The presented applications refer to the evolution of the Pamir orogen. A calibration of DANSER's parameters with geomorphological data and a DEM as initial topography highlights the advantage of lateral incision. Preserving the channel width and reflecting incision peaks in narrow channels, this closes the huge gap between current orogen-scale incision models and observed topographies. River capturing models in a system of fault-bounded block rotations reaffirm the importance of the lateral incision routine for capturing events with channel initiation. The models show a low probability of river capturings with large deflection angles. While the probability of river capturing is directly depending on the uplift rate, the erodibility inside of a dip-slip fault speeds up headward erosion along the fault: The model's capturing speed increases within a fault. Coupling DANSER with the thermo-mechanical code SLIM 3D emphasizes the versatility of the SEC. While DANSER has minor influence on the lithospheric evolution of an indenter model, the brittle surface deformation is strongly affected by its sedimentation, widening a basin in between two forming orogens and also the southern part of the southern orogen to south, east and west.},
  language  = {en}
}
@phdthesis{Kniepert2015,
  author    = {Kniepert, Juliane},
  title     = {Correlation between dynamic parameters and device performance of organic solar cells},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-90087},
  school      = {Universit{\"a}t Potsdam},
  pages     = {129},
  year      = {2015},
  abstract  = {Organic bulk heterojunction (BHJ) solar cells based on polymer:fullerene blends are a promising alternative for a low-cost solar energy conversion. Despite significant improvements of the power conversion efficiency in recent years, the fundamental working principles of these devices are yet not fully understood. In general, the current output of organic solar cells is determined by the generation of free charge carriers upon light absorption and their transport to the electrodes in competition to the loss of charge carriers due to recombination. The object of this thesis is to provide a comprehensive understanding of the dynamic processes and physical parameters determining the performance. A new approach for analyzing the characteristic current-voltage output was developed comprising the experimental determination of the efficiencies of charge carrier generation, recombination and transport, combined with numerical device simulations. Central issues at the beginning of this work were the influence of an electric field on the free carrier generation process and the contribution of generation, recombination and transport to the current-voltage characteristics. An elegant way to directly measure the field dependence of the free carrier generation is the Time Delayed Collection Field (TDCF) method. In TDCF charge carriers are generated by a short laser pulse and subsequently extracted by a defined rectangular voltage pulse. A new setup was established with an improved time resolution compared to former reports in literature. It was found that charge generation is in general independent of the electric field, in contrast to the current view in literature and opposed to the expectations of the Braun-Onsager model that was commonly used to describe the charge generation process. Even in cases where the charge generation was found to be field-dependend, numerical modelling showed that this field-dependence is in general not capable to account for the voltage dependence of the photocurrent. This highlights the importance of efficient charge extraction in competition to non-geminate recombination, which is the second objective of the thesis. Therefore, two different techniques were combined to characterize the dynamics and efficiency of non-geminate recombination under device-relevant conditions. One new approach is to perform TDCF measurements with increasing delay between generation and extraction of charges. Thus, TDCF was used for the first time to measure charge carrier generation, recombination and transport with the same experimental setup. This excludes experimental errors due to different measurement and preparation conditions and demonstrates the strength of this technique. An analytic model for the description of TDCF transients was developed and revealed the experimental conditions for which reliable results can be obtained. In particular, it turned out that the \$RC\$ time of the setup which is mainly given by the sample geometry has a significant influence on the shape of the transients which has to be considered for correct data analysis. Secondly, a complementary method was applied to characterize charge carrier recombination under steady state bias and illumination, i.e. under realistic operating conditions. This approach relies on the precise determination of the steady state carrier densities established in the active layer. It turned out that current techniques were not sufficient to measure carrier densities with the necessary accuracy. Therefore, a new technique {Bias Assisted Charge Extraction} (BACE) was developed. Here, the charge carriers photogenerated under steady state illumination are extracted by applying a high reverse bias. The accelerated extraction compared to conventional charge extraction minimizes losses through non-geminate recombination and trapping during extraction. By performing numerical device simulations under steady state, conditions were established under which quantitative information on the dynamics can be retrieved from BACE measurements. The applied experimental techniques allowed to sensitively analyse and quantify geminate and non-geminate recombination losses along with charge transport in organic solar cells. A full analysis was exemplarily demonstrated for two prominent polymer-fullerene blends. The model system P3HT:PCBM spincast from chloroform (as prepared) exhibits poor power conversion efficiencies (PCE) on the order of 0.5\%, mainly caused by low fill factors (FF) and currents. It could be shown that the performance of these devices is limited by the hole transport and large bimolecular recombination (BMR) losses, while geminate recombination losses are insignificant. The low polymer crystallinity and poor interconnection between the polymer and fullerene domains leads to a hole mobility of the order of 10^-7 cm^2/Vs which is several orders of magnitude lower than the electron mobility in these devices. The concomitant build up of space charge hinders extraction of both electrons and holes and promotes bimolecular recombination losses. Thermal annealing of P3HT:PCBM blends directly after spin coating improves crystallinity and interconnection of the polymer and the fullerene phase and results in comparatively high electron and hole mobilities in the order of 10^-3 cm^2/Vs and 10^-4 cm^2/Vs, respectively. In addition, a coarsening of the domain sizes leads to a reduction of the BMR by one order of magnitude. High charge carrier mobilities and low recombination losses result in comparatively high FF (>65\%) and short circuit current (J_SC ≈ 10 mA/cm^2). The overall device performance (PCE ≈ 4\%) is only limited by a rather low spectral overlap of absorption and solar emission and a small V_OC, given by the energetics of the P3HT. From this point of view the combination of the low bandgap polymer PTB7 with PCBM is a promising approach. In BHJ solar cells, this polymer leads to a higher V_OC due to optimized energetics with PCBM. However, the J_SC in these (unoptimized) devices is similar to the J_SC in the optimized blend with P3HT and the FF is rather low (≈ 50\%). It turned out that the unoptimized PTB7:PCBM blends suffer from high BMR, a low electron mobility of the order of 10^-5 cm^2/Vs and geminate recombination losses due to field dependent charge carrier generation. The use of the solvent additive DIO optimizes the blend morphology, mainly by suppressing the formation of very large fullerene domains and by forming a more uniform structure of well interconnected donor and acceptor domains of the order of a few nanometers. Our analysis shows that this results in an increase of the electron mobility by about one order of magnitude (3 x 10^-4 cm^2/Vs), while BMR and geminate recombination losses are significantly reduced. In total these effects improve the J_SC (≈ 17 mA/cm^2) and the FF (> 70\%). In 2012 this polymer/fullerene combination resulted in a record PCE for a single junction OSC of 9.2\%. Remarkably, the numerical device simulations revealed that the specific shape of the J-V characteristics depends very sensitively to the variation of not only one, but all dynamic parameters. On the one hand this proves that the experimentally determined parameters, if leading to a good match between simulated and measured J-V curves, are realistic and reliable. On the other hand it also emphasizes the importance to consider all involved dynamic quantities, namely charge carrier generation, geminate and non-geminate recombination as well as electron and hole mobilities. The measurement or investigation of only a subset of these parameters as frequently found in literature will lead to an incomplete picture and possibly to misleading conclusions. Importantly, the comparison of the numerical device simulation employing the measured parameters and the experimental \$J-V\$ characteristics allows to identify loss channels and limitations of OSC. For example, it turned out that inefficient extraction of charge carriers is a criticical limitation factor that is often disobeyed. However, efficient and fast transport of charges becomes more and more important with the development of new low bandgap materials with very high internal quantum efficiencies. Likewise, due to moderate charge carrier mobilities, the active layer thicknesses of current high-performance devices are usually limited to around 100 nm. However, larger layer thicknesses would be more favourable with respect to higher current output and robustness of production. Newly designed donor materials should therefore at best show a high tendency to form crystalline structures, as observed in P3HT, combined with the optimized energetics and quantum efficiency of, for example, PTB7.},
  language  = {en}
}
@phdthesis{Wohlfarth2015,
  author    = {Wohlfarth, Kai},
  title     = {PPP: zu Finanzierungsformen, Kapitalmarktrelevanz und {\"o}ffentlicher Verschuldung},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-90216},
  school      = {Universit{\"a}t Potsdam},
  pages     = {X, 184},
  year      = {2015},
  abstract  = {Die vorliegende Arbeit thematisiert die Finanzierungsmodelle von Public-Private-Partnership-Projekten (PPP) und deren Refinanzierung durch die Kapitalgeber. Dabei wurden zwei zentrale Fragestellungen thematisiert. Erstens: F{\"u}hren PPP­Projekte zu einer Verschuldung der {\"o}ffentlichen Hand und sind sie entsprechend bei den Berechnungen der Konvergenzkriterien bzw. der Schulden- und Neuverschuldungsquoten zu ber{\"u}cksichtigen? Die zu pr{\"u}fende Arbeitshypothese geht von einer Verschuldung der {\"o}ffentlichen Hand in Folge von PPP-Projekten aus. Zweitens: Unterstellt wird eine bedeutsame Funktion von PPP f{\"u}r die Infrastrukturfinanzierung, wobei im Sinne einer Effizienzsteigerung die Passgenauigkeit beziehungsweise Konsistenz der haushaltsrechtlichen Regelungen mit den regulatorischen Vorgaben f{\"u}r die Kapitalgeber von PPP-Projekten analysiert wird. Diese Schnittstelle und die zur Generierung g{\"u}nstiger („kommunal{\"a}hnlicher") Finanzierungskonditionen notwendigen staatlichen Garantien bei PPP dr{\"a}ngt geradezu zu einem ordnungspolitischen Vergleich von Ans{\"a}tzen bzw. Projekten im Bereich PPP und in Cash-Flow-Kalk{\"u}len. Die Arbeit f{\"u}hrt mit einem gewissen gesamtwirtschaftlichen Fokus der PPP tief in die Analyse des Kapitalmarktes und der Bankenregulierung. Es erfolgt ein Vergleich der gedeckten Refinanzierungsinstrumente f{\"u}r PPP, die durch Forderungen besichert sind (Asset Backed Securities) und solche, die beispielsweise durch Forderungen gegen die {\"o}ffentliche Hand besichert sind (Covered Bonds). Letztere k{\"o}nnen auch grundpfandrechtlich gesichert sein. Hier setzt der Verfasser sp{\"a}ter seine Skizze eines „Infrastructure Covered Bonds" f{\"u}r die Finanzierung notwendiger Infrastrukturmaßnahmen nicht nur in Deutschland an, wobei das Wertpapier hier ausschließlich zur Finanzierung der Infrastruktur bei einem entsprechend neu zuschaffenden (Deckungs-) Registers begeben werden wird.},
  language  = {de}
}
@phdthesis{Helpa2015,
  author    = {Helpa, Vanessa},
  title     = {Interplay between mineral reaction and deformation via structural defects},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-90332},
  school      = {Universit{\"a}t Potsdam},
  pages     = {x, 104},
  year      = {2015},
  abstract  = {This thesis contains three experimental studies addressing the interplay between deformation and the mineral reaction between natural calcite and magnesite. The solid-solid mineral reaction between the two carbonates causes the formation of a magnesio-calcite precursor layer and a dolomite reaction rim in every experiment at isostatic annealing and deformation conditions. CHAPTER 1 briefly introduces general aspects concerning mineral reactions in nature and diffusion pathways for mass transport. Moreover, results of previous laboratory studies on the influence of deformation on mineral reactions are summarized. In addition, the main goals of this study are pointed out. In CHAPTER 2, the reaction between calcite and magnesite single crystals is examined at isostatic annealing conditions. Time series performed at a fixed temperature revealed a diffusion-controlled dolomite rim growth. Two microstructural domains could be identified characterized by palisade-shaped dolomite grains growing into the magnesite and granular dolomite growing towards calcite. A model was provided for the dolomite rim growth based on the counter-diffusion of CaO and MgO. All reaction products exhibited a characteristic crystallographic relationship with respect to the calcite reactant. Moreover, kinetic parameters of the mineral reaction were determined out of a temperature series at a fixed time. The main goal of the isostatic test series was to gain information about the microstructure evolution, kinetic parameters, chemical composition and texture development of the reaction products. The results were used as a reference to quantify the influence of deformation on the mineral reaction. CHAPTER 3 deals with the influence of non-isostatic deformation on dolomite and magnesio-calcite layer production between calcite and magnesite single crystals. Deformation was achieved by triaxial compression and by torsion. Triaxial compression up to 38 MPa axial stress at a fixed time showed no significant influence of stress and strain on dolomite formation. Time series conducted at a fixed stress yield no change in growth rates for dolomite and magnesio-calcite at low strains. Slightly larger magnesio-calcite growth rates were observed at strains above >0.1. High strains at similar stresses were caused by the activation of additional glide systems in the calcite single crystal and more mobile dislocations in the magnesio-calcite grains, providing fast diffusion pathways. In torsion experiments a gradual decrease in dolomite and magnesio-calcite layer thickness was observed at a critical shear strain. During deformation, crystallographic orientations of reaction products rearranged with respect to the external framework. A direct effect of the mineral reaction on deformation could not be recognized due to the relatively small reaction product widths. In CHAPTER 4, the influence of starting material microfabrics and the presence of water on the reaction kinetics was evaluated. In these experimental series polycrystalline material was in contact with single crystals or two polycrystalline materials were used as reactants. Isostatic annealing resulted in different dolomite and magnesio-calcite layer thicknesses, depending on starting material microfabrics. The reaction progress at the magnesite interface was faster with smaller magnesite grain size, because grain boundaries provided fast pathways for diffusion and multiple nucleation sites for dolomite formation. Deformation by triaxial compression and torsion yield lower dolomite rim thicknesses compared to annealed samples for the same time. This was caused by grain coarsening of polycrystalline magnesite during deformation. In contrast, magnesio-calcite layers tended to be larger during deformation, which triggered enhanced diffusion along grain boundaries. The presence of excess water had no significant influence on the reaction kinetics, at least if the reactants were single crystals. In CHAPTER 5 general conclusions about the interplay between deformation and the mineral reaction in the carbonate system are presented. Finally, CHAPTER 6 highlights possible future work in the carbonate system based on the results of this study.},
  language  = {en}
}
@phdthesis{Olszewska2015,
  author    = {Olszewska, Agata},
  title     = {Forming magnetic chain with the help of biological organisms},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-89767},
  school      = {Universit{\"a}t Potsdam},
  pages     = {101},
  year      = {2015},
  abstract  = {Magnetite nanoparticles and their assembly comprise a new area of development for new technologies. The magnetic particles can interact and assemble in chains or networks. Magnetotactic bacteria are one of the most interesting microorganisms, in which the assembly of nanoparticles occurs. These microorganisms are a heterogeneous group of gram negative prokaryotes, which all show the production of special magnetic organelles called magnetosomes, consisting of a magnetic nanoparticle, either magnetite (Fe3O4) or greigite (Fe3S4), embedded in a membrane. The chain is assembled along an actin-like scaffold made of MamK protein, which makes the magnetosomes to arrange in mechanically stable chains. The chains work as a compass needle in order to allow cells to orient and swim along the magnetic field of the Earth. The formation of magnetosomes is known to be controlled at the molecular level. The physico-chemical conditions of the surrounding environment also influence biomineralization. The work presented in this manuscript aims to understand how such external conditions, in particular the extracellular oxidation reduction potential (ORP) influence magnetite formation in the strain Magnetospirillum magneticum AMB-1. A controlled cultivation of the microorganism was developed in a bioreactor and the formation of magnetosomes was characterized. Different techniques have been applied in order to characterize the amount of iron taken up by the bacteria and in consequence the size of magnetosomes produced at different ORP conditions. By comparison of iron uptake, morphology of bacteria, size and amount of magnetosomes per cell at different ORP, the formation of magnetosomes was inhibited at ORP 0 mV, whereas reduced conditions, ORP - 500 mV facilitate biomineralization process. Self-assembly of magnetosomes occurring in magnetotactic bacteria became an inspiration to learn from nature and to construct nanoparticles assemblies by using the bacteriophage M13 as a template. The M13 bacteriophage is an 800 nm long filament with encapsulated single-stranded DNA that has been recently used as a scaffold for nanoparticle assembly. I constructed two types of assemblies based on bacteriophages and magnetic nanoparticles. A chain - like assembly was first formed where magnetite nanoparticles are attached along the phage filament. A sperm - like construct was also built with a magnetic head and a tail formed by phage filament. The controlled assembly of magnetite nanoparticles on the phage template was possible due to two different mechanism of nanoparticle assembly. The first one was based on the electrostatic interactions between positively charged polyethylenimine coated magnetite nanoparticles and negatively charged phages. The second phage -nanoparticle assembly was achieved by bioengineered recognition sites. A mCherry protein is displayed on the phage and is was used as a linker to a red binding nanobody (RBP) that is fused to the one of the proteins surrounding the magnetite crystal of a magnetosome. Both assemblies were actuated in water by an external magnetic field showing their swimming behavior and potentially enabling further usage of such structures for medical applications. The speed of the phage - nanoparticles assemblies are relatively slow when compared to those of microswimmers previously published. However, only the largest phage-magnetite assemblies could be imaged and it is therefore still unclear how fast these structures can be in their smaller version.},
  language  = {en}
}
@phdthesis{Buss2015,
  author    = {Buß, Claudia},
  title     = {Instrumente der B{\"u}rgerbeteiligung in St{\"a}dten},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-88888},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xi, 468},
  year      = {2015},
  abstract  = {Die vergleichende Arbeit besch{\"a}ftigt sich mit der B{\"u}rgerbeteiligung in St{\"a}dten in Deutschland und Frankreich. In den letzten 20 Jahren haben sich die Formen lokaler Demokratie immer wieder ver{\"a}ndert und sich den {\"o}rtlichen Gegebenheiten angepasst. Das Interesse der B{\"u}rger, Verwaltung und politisch gew{\"a}hlten Vertreter an Partizipation w{\"a}chst stetig . Das heißt aber auch, dass sich diese 3 Akteure den neuen Strukturen anpassen und eigene Strategien entwickeln m{\"u}ssen. Die demokratischen Formen der kooperativen bzw. partizipativen Demokratie werden immer h{\"a}ufiger angewandt. Diese Arbeit evaluiert die verschiedenen B{\"u}rgerbeteiligungsinstrumente in Frankreich und Deutschland in dem zwischen Input, Output und Outcome unterschieden wird. Insbesondere die B{\"u}rgerhaushalte, Beir{\"a}te und Quartiersr{\"a}te werden genauer betrachtet. Die Ergebnisse zeigen erste Hinweise in welche demokratische Richtung sich die deutschen St{\"a}dte k{\"u}nftig entwickeln.},
  language  = {de}
}
@phdthesis{Schernthanner2015,
  author    = {Schernthanner, Harald},
  title     = {Untersuchungen zur r{\"a}umlichen Analyse und Visualisierung von Mietpreisdaten f{\"u}r Immobilienportale},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-89492},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xiii, 136},
  year      = {2015},
  abstract  = {Die vorliegende Arbeit verfolgt das Ziel, aus geoinformatischer Sicht eine konzeptionelle Grundlage zur r{\"a}umlichen Optimierung von Immobilienportalen zu schaffen. Die Arbeit geht dabei von zwei Hypothesen aus: 1. Verfahren der r{\"a}umlichen Statistik und des Maschinellen Lernens zur Mietpreissch{\"a}tzung sind den bisher eingesetzten Verfahren der hedonischen Regression {\"u}berlegen und eignen sich zur r{\"a}umlichen Optimierung von Immobilienportalen. 2. Die von Immobilienportalen publizierten webbasierten Mietpreiskarten geben nicht die tats{\"a}chlichen r{\"a}umlichen Verh{\"a}ltnisse auf Immobilienm{\"a}rkten wieder. Alternative webbasierte Darstellungsformen, wie z.B. Gridmaps, sind dem Status Quo der Immobilienpreiskarten von Immobilienportalen {\"u}berlegen und visualisieren die tats{\"a}chlichen r{\"a}umlichen Verh{\"a}ltnisse von Immobilienpreisen zweckm{\"a}ßiger. Beide Thesen k{\"o}nnen bewiesen werden. Es erfolgt zun{\"a}chst eine umfangreiche Erhebung des Forschungsbedarfs mittels Literaturstudien und technologischer Recherche. Zur Beantwortung der Forschungsfragen wird als quantitative Datenbasis ein 74.098 Mietangebote umfassender Datensatz (von Januar 2007 bis September 2013) eines Immobilienportals akquiriert. Dieser reicht jedoch nicht in vollem Umfang zur Beantwortung der Fragestellungen aus. Deshalb f{\"u}hrt der Autor Experteninterviews zur Erhebung einer qualitativen Datenbasis. Deren Analyse ergibt in Kombination mit der Literaturstudie und der technologischen Recherche ein umfassendes, bisher so nicht verf{\"u}gbares Bild. Es stellt den Status Quo der r{\"a}umlichen Sicht sowie der raumanalytischen und geovisuellen Defizite von Immobilienportalen dar. Zur Optimierung der raumanalytischen und geovisuellen Defizite werden forschungsbasierte L{\"o}sungsans{\"a}tze herausgearbeitet und teilimplementiert. Methoden des Maschinellen Lernens und r{\"a}umliche Sch{\"a}tzverfahren werden als Alternativen zu den von Immobilienportalen bisher genutzten „nicht r{\"a}umlichen" Analyseverfahren zur Preismodellierung untersucht. Auf Grundlage eines hierf{\"u}r konzipierten Validierungsrahmens werden diese Methoden f{\"u}r die Nutzung im Kontext von Immobilienportalen adaptiert. Die prototypische Teilimplementierung zeigt die programmiertechnische Umsetzung des Konzeptes auf. Eine umfassende Analyse geeigneter Sekund{\"a}rvariablensets zur Mietpreissch{\"a}tzung liefert als methodisches Resultat, dass Interpolatoren, die Sekund{\"a}rvariablen ben{\"o}tigen (Kriging with external drift, Ordinary Cokriging), kaum zu valideren Mietpreissch{\"a}tzergebnissen gelangen als die Methode des Ordinary Kriging, die keine Sekund{\"a}rvariablen ben{\"o}tigt. Die Methoden Random Forest aus dem Maschinellen Lernen und die Geographisch Gewichtete Regression hingegen bergen großes Potential zur Nutzung der r{\"a}umlichen Mietpreissch{\"a}tzung im Kontext von Immobilien-portalen. Die Forschungsergebnisse der r{\"a}umlichen Preismodellierung werden in die r{\"a}umliche Visualisierung von Mietpreisen transferiert. F{\"u}r die webbasierte Mietpreisdarstellung wird ein Set alternativer Darstellungsmethoden entwickelt, um Mietpreiskarten-Prototypen abzuleiten. Ein methodisches Ergebnis der Entwicklung der Mietpreiskarten-Prototypen ist die Entwicklung eines geeigneten Ansatzes der Losl{\"o}sung des Preisbezugs von fachfremd verwendeten Bezugsgeometrien. Hierf{\"u}r wird vom Autor der Begriff der zonenlosen Preiskarte gepr{\"a}gt. Diese werden mit Methoden des Gridmapping erstellt. Es werden optimale Rasteraufl{\"o}sungen zur Darstellung interpolierter Rastergr{\"o}ßen ermittelt. Zonenlose Preiskarten mit Methoden des Gridmapping, gepaart mit einer optionalen geb{\"a}udescharfen Darstellung in gr{\"o}ßeren Maßst{\"a}ben, sind als Resultate der Forschung die bestm{\"o}gliche, sich an realen Verh{\"a}ltnissen orientierende, r{\"a}umliche Mietpreisdarstellung. Die entstandenen Prototypen sind eine Ann{\"a}herung der wahren Verteilung des Mietpreises im Raum und um einiges sch{\"a}rfer, als die auf der hedonischen Regression basierenden Darstellungen. Somit kann die wahre „Topographie" der Mietpreislandschaft abgebildet werden. Ein Einsatz der Karten f{\"u}r Nutzergruppen wie Makler, Investoren oder Kommunen zur Analyse st{\"a}dtischer Mietm{\"a}rkte ist denkbar. Alle entstandenen Prototypen sind unter der Nutzung von Map APIs umgesetzt. Ein Ergebnis dessen ist, dass Map APIs noch an diversen „Kinderkrankheiten" leiden und derart umgesetzte Mietpreiskarten noch einen weiten Weg vor sich haben, bis sie das Niveau thematischer Karten von Immhof oder Arnberger erreichen. Die konzeptionellen {\"U}berlegungen und Teilimplementierungen m{\"u}nden in drei Prozessketten, die Umsetzungsoptionen f{\"u}r eine r{\"a}umliche Optimierung von Immobilienportalen darstellen. Dabei werden zwei Szenarien f{\"u}r eine r{\"a}umlich optimierte Mietpreissch{\"a}tzung und ein Szenario f{\"u}r eine r{\"a}umlich optimierte Mietpreisdarstellung herausgearbeitet.},
  language  = {de}
}
@phdthesis{Boesche2015,
  author    = {B{\"o}sche, Nina Kristine},
  title     = {Detection of rare earth elements and rare earth oxides with hyperspectral spectroscopy},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-85363},
  school      = {Universit{\"a}t Potsdam},
  pages     = {147},
  year      = {2015},
  abstract  = {The continuously increasing demand for rare earth elements in technical components of modern technologies, brings the detection of new deposits closer into the focus of global exploration. One promising method to globally map important deposits might be remote sensing, since it has been used for a wide range of mineral mapping in the past. This doctoral thesis investigates the capacity of hyperspectral remote sensing for the detection of rare earth element deposits. The definition and the realization of a fundamental database on the spectral characteristics of rare earth oxides, rare earth metals and rare earth element bearing materials formed the basis of this thesis. To investigate these characteristics in the field, hyperspectral images of four outcrops in Fen Complex, Norway, were collected in the near-field. A new methodology (named REEMAP) was developed to delineate rare earth element enriched zones. The main steps of REEMAP are: 1) multitemporal weighted averaging of multiple images covering the sample area; 2) sharpening the rare earth related signals using a Gaussian high pass deconvolution technique that is calibrated on the standard deviation of a Gaussian-bell shaped curve that represents by the full width of half maxima of the target absorption band; 3) mathematical modeling of the target absorption band and highlighting of rare earth elements. REEMAP was further adapted to different hyperspectral sensors (EO-1 Hyperion and EnMAP) and a new test site (Lofdal, Namibia). Additionally, the hyperspectral signatures of associated minerals were investigated to serve as proxy for the host rocks. Finally, the capacity and limitations of spectroscopic rare earth element detection approaches in general and of the REEMAP approach specifically were investigated and discussed. One result of this doctoral thesis is that eight rare earth oxides show robust absorption bands and, therefore, can be used for hyperspectral detection methods. Additionally, the spectral signatures of iron oxides, iron-bearing sulfates, calcite and kaolinite can be used to detect metasomatic alteration zones and highlight the ore zone. One of the key results of this doctoral work is the developed REEMAP approach, which can be applied from near-field to space. The REEMAP approach enables rare earth element mapping especially for noisy images. Limiting factors are a low signal to noise ratio, a reduced spectral resolution, overlaying materials, atmospheric absorption residuals and non-optimal illumination conditions. Another key result of this doctoral thesis is the finding that the future hyperspectral EnMAP satellite (with its currently published specifications, June 2015) will be theoretically capable to detect absorption bands of erbium, dysprosium, holmium, neodymium and europium, thulium and samarium. This thesis presents a new methodology REEMAP that enables a spatially wide and rapid hyperspectral detection of rare earth elements in order to meet the demand for fast, extensive and efficient rare earth exploration (from near-field to space).},
  language  = {en}
}