TY - THES A1 - Grieme, Ulrich T1 - Pseudo-differential operators with operator-valued symbols on non-compact manifolds Y1 - 1999 ER - TY - THES A1 - Wu, Yuling T1 - Syntheses of defined carbohydrate surfactants and determination of their wetting behaviour under equilibrium and dynamic conditions Y1 - 1998 ER - TY - THES A1 - Kärsten, Fatma T1 - A duality for a compact group and a second cohomology of its dual Y1 - 1998 ER - TY - THES A1 - Stömmer, Ralph T1 - X-ray scattering from silicon surfaces and thin oxides on silicon substrates Y1 - 1998 ER - TY - THES A1 - Abdel-Hamid, Hamed Ahmed T1 - Stellar populations, dust and gas in NGC 3077 Y1 - 1998 SN - 3-932089-08-1 PB - Wiss. Verl. Berlin CY - Berlin ER - TY - THES A1 - Back, Stefan T1 - Tectonics, Climate, and Sedimentation in the Northern Baikal Rift, Russia Y1 - 1998 CY - Potsdam ER - TY - THES A1 - Schäfer, Carsten T1 - Analysis of synchronization in complex systems: application to physiological data Y1 - 1998 CY - Potsdam ER - TY - THES A1 - Orellana, Juan B. Gil T1 - Heat trace asymptotics for cone differential operators Y1 - 1998 ER - TY - THES A1 - Jin, Wen T1 - Redox reaction of proteins at functionalized electrode Y1 - 1998 ER - TY - THES A1 - Abel, Markus T1 - Localization in driven nonlinear lattices Y1 - 1998 CY - Potsdam ER - TY - THES A1 - Lledó, Fernando T1 - Algebraic properties of massless free nets Y1 - 1998 CY - Potsdam ER - TY - THES A1 - Wambsganß, Joachim T1 - Gravitational lensing as a universal astrophysical tool Y1 - 1998 ER - TY - THES A1 - Klein, Andreas T1 - On the syntheses of phosphatidic acids from diglycerides Y1 - 1997 CY - Potsdam ER - TY - THES A1 - Wildner, Uwe T1 - CASC : compiler assisted self-checking of structural integrity Y1 - 1997 ER - TY - THES A1 - Rettinger, Rolf T1 - Thermometamorphic characterisation of the transition zone between the Archean Sao Francisco Craton and the Proterozoic mobile belt, Minas Gerais, Brazil Y1 - 1997 ER - TY - THES A1 - Loll, Renate T1 - Wilson loop and discrete lattice methods in quantum gauge and gravitational theories Y1 - 1997 ER - TY - THES A1 - Maurer, Stefanie T1 - Creating a model for the investigation of the function of the selenoenzyme phospolipid hydroperoxide glutathione peroxidas (PHGPx) in intracellular signalling Y1 - 1997 CY - Potsdam ER - TY - THES A1 - Allam, Sahar Said T1 - IRAS Study of Interacting Galaxies Y1 - 1997 CY - Potsdam ER - TY - THES A1 - Lässig, Michael T1 - On Growth, Disorder, and field Theory Y1 - 1997 CY - Potsdam ER - TY - THES A1 - Dicken, Volker T1 - Simultaneous Activity and Attenuation Reconstruction in Single Photon Emission Computed Tomography, a Nonlinear Ill-Posed Problem Y1 - 1997 CY - Potsdam ER - TY - THES A1 - MacCann, Tommy T1 - Pre-Zechstein tectono-stratigraphy of NE Germany - sediment composition and provenance Y1 - 1997 ER - TY - THES A1 - Seiler, Jörg T1 - Pseudodifferential Calculus on Manifolds with Non-Compact Edges Y1 - 1997 CY - Potsdam ER - TY - THES A1 - Boike, Julia T1 - Thermal, hydrological and geochemical dynamics of the active layer at a continuous permafrost site, Taymyr Peninsula, Siberia Y1 - 1997 ER - TY - THES A1 - Meinunger, André T1 - Discourse dependent DP (de-)placement T2 - Groninger Arbeiten zur germanistischen Linguistik Y1 - 1996 VL - 39 PB - Rijksuniv. CY - Groningen ER - TY - THES A1 - Brügmann, Bernd T1 - Quantum gravity in four dimensions : canonical quantization and dynamical triangulations Y1 - 1996 ER - TY - THES A1 - Popov, K. V. A1 - Liperovsky, Viktor A. A1 - Meister, Claudia-Veronika A1 - Liperovskaya, E. V. T1 - Anthropogenic effects with weekly periodicity in the F-region ionosphere Y1 - 1996 ER - TY - THES A1 - Krabi, Astrid T1 - Electrophoretic and hydrodynamik characterization of neutral polymer depletion layers Y1 - 1996 ER - TY - THES A1 - Raab, Volker T1 - Geregeltes Schalten bistabiler Systeme Y1 - 1996 ER - TY - THES A1 - Kunz, Wolfgang T1 - Testing techniques in logic synthesis Y1 - 1996 ER - TY - THES A1 - Feudel, Ulrike T1 - Dynamics in between regularity and chaos Y1 - 1996 ER - TY - THES A1 - Gerber, Stefan T1 - Using software for fault detection in arithmetical circuits Y1 - 1995 ER - TY - THES A1 - Dorschfeldt, Christoph T1 - An algebra of mellin pseudo-differential operators near corner singularities Y1 - 1995 CY - Potsdam ER - TY - THES A1 - Behm, Sebastian T1 - Pseudo-differential operators with parameters on manifolds with edges Y1 - 1995 PB - Univ. CY - Potsdam ER - TY - THES A1 - Tarnick, Steffen T1 - Data compression techniques for concurrent error detection and built-in self test Y1 - 1995 ER - TY - THES A1 - Rainer, Martin T1 - The topology of the space of real LIE algebras up to dimension 4 with applications to homogeneous cosmological models Y1 - 1994 PB - Univ. ER - TY - THES A1 - Alexiadou, Artemis T1 - Issues in the syntax of adverbs Y1 - 1994 ER - TY - THES A1 - Pikovskij, Arkadij T1 - Dynamics of perturbations in chaotic dynamical systems Y1 - 1994 ER - TY - THES A1 - Kuhrts, Lucas T1 - The effect of Polycations on the Formation of Magnetite Nanoparticles N2 - Nanoparticles of magnetite (Fe3O4) are envisioned to find used in diverse applications, ranging from magnetic data storage, inks, ferrofluids as well as in magnetic resonance imaging, drug delivery, and hyperthermia cancer treatment. Their magnetic properties strongly depend on their size and morphology, two properties that can be synthetically controlled. Achieving appropriate control under soft chemical conditions has so far remained a challenging endeavor. One proven way of exerting this desired control has been using a biomimetic approach that emulates the proteome of magnetotactic bacteria by adding poly-L-arginine in the co- precipitation of ferrous and ferric chloride. The objective of the work presented here is to understand the impact of this polycation on the formation mechanism of magnetite and, through rational design, to enhance the control we can exert on magnetite nanoparticle size and morphology. We developed a SAXS setup to temporally and structurally resolve the formation of magnetite in the presence of poly-L-arginine in situ. Using analytical scattering models, we were able to separate the scattering contribution of a low-density 5 nm iron structure from the contribution of the growing nanoparticles. We identified that the low-density iron structure is a metastable precursor to the magnetite particles and that it is electrostatically stabilized by poly-L-arginine. In a process analogous to biomineralization, the presence of the charged macromolecule thus shifts the reaction mechanism from a thermodynamically controlled one to a kinetically controlled one. We identify this shift in reactions mechanism as the cornerstone of the proposed mechanism and as the crucial step in the paradigm of this extraordinary nanoparticle morphology and size control. Based on SAXS data, theoretical considerations suggest that an observed morphological transition between spherical, solid, and sub-structured mesocrystalline magnetite nanoparticles is induced through a pH-driven change in the wettability of the nanoparticle surface. With these results, we further demonstrate that SAXS can be an invaluable tool for investigating nanoparticle formation. We were able to change particle morphology from spherically solid particles to sub-structured mesocrystals merely by changing the precipitation pH. Improving the synthesis sustainability by substituting poly-L-arginine with renewable, polysaccharide-based polycations produced at the metric ton scale, we demonstrated that the ability to alter the reaction mechanism of magnetite can be generically attributed to the presence of polycations. Through meticulous analysis and the understanding of the formation mechanism, we were able to exert precise control over particle size and morphology, by adapting crucial synthesis parameters. We were thus able to grow mesocrystals up to 200 nm and solid nanocrystals of 100 nm by adding virtually any strong polycation. We further found a way to produce stable single domain magnetite at only slightly increased alkalinity, as magnetotactic bacteria do it. Thus through the understanding of the biological system, the consecutive biomimetic synthesis of magnetite and the following understanding of the mechanism involved in the in vitro synthesis, we managed to improve the synthetic control over the co-precipitation of magnetite, coming close biomineralization of magnetite in magnetotactic bacteria. Polyanions, in both natural as well as in synthetic systems, have been in the spotlight of recent research, yet our work shows the pivotal influence polycations have on the nucleation of magnetite. This work will contribute significantly to our ability to tailor magnetite nanoparticle size and morphology; in addition, we presume it will provide us with a model system for studying biomineralization of magnetite in vitro, putting the spotlight on the important influence of polycations, which have not had the scientific attention they deserve. T2 - Der Effekt von Polykationen auf die Bildung von Magnetitnanopartikeln KW - Mechanism KW - Nanoparticle KW - SAXS KW - Biomimetic KW - Magnetite Y1 - CY - Potsdam ER - TY - THES A1 - Seibert, Tanja Stefanie T1 - The T6P pathway in Solanum tuberosum BT - investigating the link between sugar signaling and developmental transitions Y1 - 2018 ER - TY - THES A1 - Matic, Aleksandar T1 - Myrcene to materials BT - Synthesis of bio-based materials for different applications Y1 - ER - TY - THES A1 - Karimi, Marzieh T1 - Mechanical properties of vesicle membranes in asymmetric buffer conditions Y1 - ER - TY - THES A1 - Kar, Manaswita T1 - Energy band gap tuning of halide perovskite materials from first principles N2 - Solar cells based on hybrid perovskites materials have become significantly important among the third generation photovoltaics over the last few years. The first solid state solar cell was reported in 2012. Over the years, the power conversion efficiencies of these devices have increased at a tremendous pace and this has made the perovskite solar cell devices a serious competitor in the well-established market of thin-film and wafer technologies. Over time, a large number of articles on this topic has been published in peer-reviewed journals. The presence of lead in the most efficient hybrid perovskite materials have raised questions about the possible toxicity of these devices and the extent of their environmental impact. Therefore, a lot of research has been devoted to finding alternative perovskite materials with similar or even better opto-electronic properties. An alternative strategy to improve the efficiency of thin film solar cells is to build efficient tandem cells by combining two or more perovskite materials with specifically tailored band gaps. The first step towards the development of perovskite-only tandem solar cells is to identify complementary hybrid perovskite materials with specific band gaps that maximize the efficiency of tandem solar cells. The optimal set of optical gaps for a tandem structure made of two materials is 1.9 eV and 1.0 eV. Since the electronic properties of hybrid perovskites are known to be strongly dependent on the composition and distortion of the crystal lattice, strong focus has been made towards the structure optimisation as well as the calculation of the energy band gaps of the materials using density functional theory (DFT). In an attempt to study the structure-property relationship of these perovskite materials and to find novel perovskite materials for future applications, researchers have employed computational screening procedures to study a large range of these materials by systematic replacement of the cations and anions from the prototypical perovskite. Density functional theory in particular is used as a theoretical tool, because of it’s precision to determine the properties of materials and also it’s computational viability in dealing with complex systems. In this thesis, the main focus is to do a systematic screening of the perovskite materials, of the composition ABX3 again by replacing the A-site, B-site and the X-site elements to find novel materials with band gaps suitable for application in tandem solar cells. As a first step towards contributing to this vibrant field of research, a high-throughput computational screening has been performed by replacing the metal and the halogen in the conventional CH3NH3PbI3 perovskites with homovalent metals and halogens to find materials in the desired range of band gaps that has already been mentioned earlier. This is achieved by performing a geometry optimisation on all the simulated structures followed by calculating their energy band gaps at the semilocal and the hybrid levels of theory. However, it is well known that the rotation of the organic cation CH3NH3 hinders the stability of these devices by the formation of hydrogen bonds between the hydrogen atoms of the cation and the halogens. This causes the materials to degrade under normal temperature and pressure conditions. As an attempt to prevent these devices from being unstable, a next step has been taken where the CH3NH3 cation has been replaced by inorganic cations of similar ionic radius. This is followed by another thorough screening, similar to the previous step. The stability of the materials has been determined by using the empirical Goldschmidt tolerance factor. As a last part of the thesis, a small proportion of the inorganic cation is mixed with CH3NH3 in order to form mixed-halide perovskites. These structures are optimised and their band gaps are calculated using density functional theory in order to predict materials suitable for single junction as well as tandem solar cell devices. It is expected that the contribution made through this thesis will be helpful for the progress of perovskite solar cells in terms of efficiencies and will also allow the community to explore the different properties these materials for further progress and development. KW - Solar cells KW - Perovskites KW - Density functional theory KW - hybrid KW - inorganic Y1 - ER - TY - THES A1 - Goa, Yang T1 - Chloroplast translational regulation during acclimation to low temperature and impact of knockouts of non-essential chloroplast tRNAs on ribosome behavior Y1 - ER - TY - THES A1 - Günther, Erika T1 - Intracellular processes in magnetotactic bacteria studied by optical tools Y1 - ER - TY - THES A1 - Trifonov, Stefan T1 - Diving Deeper into the Activities and Goals in the Entrepreneurial Process of Internet-enabled Startups T2 - an activity-based Perspective in the Context of Accelerator Programs Y1 - ER - TY - THES A1 - Coleman Mac Gregor of Inneregny, Verena T1 - Cell-autonomous and cell-non-autonomous adaptation to skeletal muscle mitochondrial stress Y1 - 2018 ER - TY - THES A1 - Gulati, Sneha T1 - Impact of individual and combined abiotic and biotic stress on plant performance and bacterial root microbiota of tomato N2 - Nutzpflanzen sind zunehmend mit sowohl individuellem als auch kombiniertem abiotischem und biotischem Stress konfrontiert, die Wachstum und Ertrag stark beeinträchtigen. Pflanzen sind mit einer großen Anzahl an Mikroorganismen assoziiert, die sowohl nützlich als auch pathogen wirken können. Aufgrund der positiven Wirkung von nützlichen Mikroorganismen auf Wachstum und Gesundheit von Pflanzen ist dieses Potenzial in nachhaltigen Pflanzenproduktionssystemen zu nutzen. Kenntnisse darüber, wie individueller und kombinierter Stress die Leistung der Pflanze einschließlich deren Mikrobiom beeinflussen, sind derzeit begrenzt. Es stellt sich daher die Frage, wie abiotische Bedingungen (Salzstress, Trockenheit) insbesondere in Kombination mit biotischem Stress (Verticillium dahliae, Fusarium oxysporum) die Mikrobiota der Wurzel beeinflussen und dies die Leistung der Pflanze. Ziel dieser Arbeit war es, das Verständnis der Auswirkungen von individuellem und kombiniertem biotischem und abiotischem Stress auf die endophytische Mikrobiota der Wurzel und die Leistung der Pflanze zu verbessern. Die Untersuchungen erfolgen an der wirtschaftlich bedeutenden gartenbaulichen Kultur Tomate. Die Struktur der bakteriellen endophytischen Mikrobiota der Tomatenwurzel in Abhängigkeit von individuellem und kombiniertem abiotischem und biotischem Stress wurde mit kulturunabhängigen und -abhängigen Methoden analysiert. Die Ergebnisse der Analysen mittels beider Methoden zeigen, dass sowohl abiotische als auch biotische Stressbedingungen signifikant die Struktur der endophytischen Mikrobiota der Wurzel verändern und sich dies auf die Produktivität der Pflanze auswirkt. Insgesamt wurden 683 kultivierbare bakterielle Endophyten hinsichtlich ihrer pflanzenwachstumsfördernden (PGP) Eigenschaften in in vitro und in vivo charakterisiert. Im Ergebnis kulturabhängiger Analysen wurden Endophyten mit wiederholt positiver Wirkung auf das Pflanzenwachstum von Tomate unter individuellem und kombiniertem abiotischen und biotischen Stress selektiert. Die Behandlung von Pflanzen mit diesen nützlichen Mikroorganismen reduzierte den negativen Einfluss von Stress auf das Pflanzenwachstum. Im Weiteren können diese nützlichen Mikroorganismen zu Produkten für die Nutzung in nachhaltigen Pflanzensystemen entwickelt werden. Dazu sind jedoch weitere Untersuchungen insbesondere unter Feldbedingungen notwendig. Zukünftige Arbeiten sollten sich zudem auf die Verbesserung des Verständnisses der Funktionen von Endophyten in der Wurzel konzentrieren. Diese Kenntnisse könnten die Entwicklung neuer Strategien für den Pflanzenschutz unterstützen. N2 - Recently crops encounter an increased number of individual and combined abiotic and biotic stress, which severely affect their growth and yield. Plants are associated with a large number of microorganisms including beneficial as well as pathogenic microorganisms. The interaction of plants with beneficial microorganisms can exert a substantial impact on plant growth and health and their potential can be utilized in sustainable plant production systems. Currently, climate change will increase the impact of stress on crops which will more likely be exposed to combined abiotic and biotic stress. At present, knowledge on how abiotic and biotic stress and the combination of both stresses affect the plant performance and the microbiome is limited. Soil-borne pathogens are responsible for relevant economic losses and are difficult to control. The root bacterial endophytes have shown potential in alleviating stress on plants and improving crop yield and quality. This raises the question how individual abiotic stress like salinity (ionic) and drought (osmotic) and the combination with biotic stress (Verticillium dahliae or Fusarium oxysporum) affects the root microbiota and thus the performance of the plant. Therefore, the goal of this thesis was to improve the understanding of the impact of individual and combined biotic and abiotic stress especially the endophytic root microbiota and thus plant performance. The work is focused on the economically important horticultural crop tomato. The bacterial rootendophytes of tomato plants exposed to individual and combined abiotic and biotic stress was studied with culture-independent and culture-dependent methods. Bacterial root endophytes obtained from tomato roots exposed to individual and combined stress were characterized for their traits that are beneficial to plant growth and health in in vitro and in vivo assays. Finally, the efficacy of selected endophytes in alleviating individual and combined abiotic and biotic stress in tomato plants was assessed. Furthermore, stress conditions can alter the composition of root exudates and volatiles, which may in turn affect the root microbiota assembly. Therefore, the volatile profiles of healthy and pathogen (F. oxysporum) infected tomato roots grown in soil was investigated. A soil olfactometer was established to study the impact of root volatiles of healthy and infected tomato on migration of applied beneficial bacteria. The results of tomato characteristics (plant growth, photosynthesis rate) confirmed the negative effect of individual abiotic and biotic stress reported in other studies. However, the response of combined abiotic stress with biotic stress on plant growth varied depending on the type of combined stress.. For instance, a significant higher negative impact on plant growth was observed when tomato plants were cultivated under ionic stress and infected with F. oxysporum. No additional negative effect on plant growth was observed when tomato was infected with V. dahliae. Both culture-dependent and cultureindependent analyses of the root microbiota revealed that individual and combined abiotic and biotic stress alter the root microbiota structure and diversity of tomato. A significantly lower number of cultivable root endophytes was obtained from roots exposed to ionic stress. 16S rRNA amplicon analysis revealed a stronger impact on the diversity of root-associated bacteria in comparison to biotic stress. The endophytes were characterized as member of the phyla Proteobacteria, Actinobacteria and Firmicutes, and members of Bacteriodetes were only detected by culture-independent approach. A total of 683 cultivable bacterial endophytes were characterized using various in vitro and in vivo plant growth-promoting (PGP) assays. As expected, the highest number of root endophytes with tolerance to ionic stress were obtained from tomato roots exposed to ionic stress. Comparably, a high percentage of root endophytes isolated from roots exposed to osmotic were tolerant to osmotic stress showing that the environment affects the selection of microorganisms by the plant. Interestingly, endopyhtes obtained from roots exposed to abiotic stress showed no traits related to plant growth promotion. Based on in vivo and in vitro traits, five selected endophytes were able to alleviate abiotic and biotic stress on plants. These endophytes were obtained from tomato roots infected with V. dahliae. The blend of root emitted volatiles also differed between healthy and F. oxysporum infected tomato plants. The olfactometer setup results highlighted that root volatiles were involved in attraction of bacteria to the plant roots and beneficial bacteria were observed to migrate towards both, diseased and healthy plants in comparable density. It is proposed that root volatiles from healthy and pathogen infected plants not only work as signals but are also used as an energy source for the rhizosphere bacteria. Concluding, the results of this study indicate that abiotic and biotic stress altered the bacterial rootendophytes and thus affects plant performance. The treatment of plants with beneficial microorganisms reduced the negative impact of stress conditions on plant performance. However, more studies using the selected isolates must be performed in the field for drawing inferences on the efficacy of the selected bacterial isolates in ameliorating the effect of abiotic and biotic stress in plants. The extensive isolate collection will serve as a basis for conducting investigations of root-associated bacteria on plant performance. This is important for the development of new plant protection strategies. KW - F. oxysporum KW - V. dahliae KW - root volatiles KW - root microbiota KW - plant-microbe interaction KW - tomato(Solanum lycopersicum) Y1 - 2020 CY - Potsdam ER - TY - THES A1 - Mumm, Rebekka T1 - Eat and you should grow BT - nutritional and social influence on height in children and adolescents Y1 - ER - TY - THES A1 - Colangeli, Pierluigi T1 - From pond metacommunities to life in a droplet BT - causes and consequences of movement in zooplankton Y1 - ER - TY - THES A1 - Hüttel, Alexandra T1 - The role of human values in sustainable consumption Y1 - ER -