Universität Stuttgart
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Item Open Access Mechanistic studies on the DNA methyltransferases DNMT3A and DNMT3B(2021) Dukatz, Michael; Jeltsch, Albert (Prof. Dr.)In this work, both regulatory and catalytic mechanisms of de novo methyltransferases were investigated, which include interactions with other proteins and the specific recognition of the substrate sequence. Another part of this work strived to elucidate how enzymatic generation of 3-methylcytosine by DNMT3A can occur.Item Open Access Eignung von metallorganischen Gerüstverbindungen als stationäre Phase in der Hochleistungsflüssigchromatographie (HPLC)(2017) Lieder, Christian; Klemm, Elias (Prof. Dr.-Ing.)Anwendung von metallorganischen Gerüstverbindungen als stationäre Phase in der HPLC, Vergleich mit klassischen Silika-Materialien. Synthese der metallorganischen Gerüstverbindungen, Modifizierung. Befüllung chromatographischer Säulen und Gegenüberstellung der Füllmethoden. Methodenentwicklung, Einflüsse auf chromatographische Ergebnisse. Chirale Erkennung, Untersuchung der Wechselwirkungen. Theoretisch chemische Berechnungen der Wechselwirkungen.Item Open Access Optical and magneto-optical investigations on 3D Dirac- and Weyl-semimetals(2017) Neubauer, David; Dressel, Martin (Prof. Dr.)This work concentrates on optical investigations on 3D Dirac- and Weyl-semimetals with and without applied magnetic fields. Four compounds are extensively discussed, namely the 3D Dirac semimetal Cd3As2, the Weyl semimetals TaAs and NbP, and finally evidence is found for 2D Dirac states in the iron based superconductor FeSe. For the measurements in magnetic fields a novel magneto-optical installation is designed and implemented in the lab. The design principle and characterization of this setup is presented.Item Open Access Temperaturbestimmung von Lithium Ionen Zellen mittels künstlicher neuronaler Netze basierend auf Daten der elektrochemischen Impedanzspektroskopie(2025) Ströbel, Marco; Birke, Kai Peter (Prof. Dr.-Ing.)Item Open Access Defined polymer architectures enabled by yttrium-mediated ring-opening polymerization of renewable lactones(2025) Hornberger, Lea-Sophie; Buchmeiser, Michael R. (Prof. Dr.)Although global plastic production exceeds 410 million tons annually, less than 0.7 % currently originates from bio-based sources. Given the finite fossil resources and the low biodegradability of conventional plastics, the development of polymers from renewable feedstocks offers considerable potential. This highlights the largely unexploited opportunities offered by renewable monomers. Ring-opening polymerization (ROP) enables the synthesis of polyesters with precise control over molar mass, polydispersity, and architecture, while reversible-deactivation radical polymerization (RDRP) techniques such as atom transfer radical polymerization (ATRP) provide complementary strategies for post-polymerization modification of functional polyesters. This dissertation employs aminoalkoxy bis(phenolate) yttrium complexes for the controlled ROP of lactones from renewable resources, systematically expanding the accessible monomer scope from small, strained four-membered rings to unstrained macrolactones and functional seven-membered terpene-derived lactones. In the first part, the entropy-driven ROP of the 16-membered macrolactone ω pentadecalactone (PDL) was achieved under controlled conditions, affording high-molar-mass poly(ω-pentadecalactone) (PPDL) with moderate polydispersities. Its aliphatic backbone makes PPDL a promising sustainable analogue to polyolefins. Sequential block copolymerization with the four-membered racemic β-butyrolactone (BBL) yielded semi-crystalline materials that integrate the crystalline domains of both homopolymers, enabling tunable material properties. The second part investigated the effect of substitution pattern and stereochemistry on the polymerization kinetics and mechanism of the seven-membered terpene-based (-)-menthide and (+)-carvomenthide, which differ only in the relative positions of their substituents. Kinetic analysis combined with density functional theory (DFT) calculations revealed that subtle stereoelectronic differences strongly impact activation parameters, propagation rates, and susceptibility to side reactions. In (-)-menthide, the isopropyl group adjacent to the reactive ester moiety introduces steric hindrance and increases the activation, whereas the reduced steric demand near the ester in (+)-carvomenthide enables faster propagation but also promotes side reactions. These findings provide valuable guidelines for the rational design of terpene-based lactones. The third part focused on trans (+)-dihydrocarvide (DHC), a seven-membered lactone bearing a pendant isopropenyl group. ROP of DHC produced amorphous poly(dihydrocarvide) (PDHC) with full retention of the double bond. Block copolymerization with semi-crystalline PPDL or syndiotactic poly(3-hydroxybutyrate) (PHB) introduced crystallinity and phase separation. The pendant double bonds in PDHC were further functionalized via thiol-ene chemistry to generate ATRP macroinitiators, enabling orthogonal grafting-from polymerizations of ethyl acrylate that afforded high-density polyester-based brush architectures. Overall, the combination of yttrium-mediated ROP with orthogonal post-polymerization techniques enables the construction of renewable polyester architectures such as block and graft copolymers that integrate amorphous, semi-crystalline, and functional segments. This modular approach offers a versatile platform to tailor thermal, mechanical, and functional properties, providing new opportunities for advanced biomedical and high-performance materials.Item Open Access Dynamic water masks from optical satellite imagery(München : Verlag der Bayerischen Akademie der Wissenschaften, 2019) Elmi, Omid; Sneeuw, Nico (Prof. Dr.-Ing.)Investigation of the global freshwater system has a vital role in critical issues e.g. sustainable development of water resources, acceleration of the hydrological cycle, variability of global sea level. Measurement of river streamflow is vital for such investigations as it gives a reliable estimate of freshwater fluxes over the continents. Despite such importance, the number of river discharge gauging station has been decreasing. At the same time, information on the global freshwater system has been increasing because of various types of ground observations, water-use information and spaceborne geodetic observations. Nevertheless, we cannot answer properly crucial questions about the amount of freshwater available on a certain river basin, or the spatial and temporal dynamics of freshwater variations and discharge, or the distribution of world’s freshwater resources in the future. The lack of comprehensive measurements of surface water storage and river discharge is a major impediment for a realistic understanding of the hydrological water cycle, which is a must for answering the aforementioned questions. This thesis aims to improve the methods for monitoring the surface extent of inland water bodies using satellite images. Satellite imaging systems capture the Earth surface in a wide variety of spectral and spatial resolution repeatedly. Therefore satellite imagery provides the opportunity to monitor the spatial change in shorelines, which can serve as a way to determine the water extent. Each band of a multispectral image reveals a unique characteristic of the Earth surface features like surface water extent. However selecting the spectral bands which provide the relevant information is a challenging task. In this thesis, we analyse the potential of multispectral transformations like Principal Component Analysis (PCA) and Canonical Correlation Analysis (CCA) to tackle this issue by condensing the information available in all spectral bands in just a few uncorrelated variables. Moreover, we investigate how the change between multispectral images at different epochs can be highlighted by using the transformations. This study proposes an automatic algorithm for extracting the lake water extent from MODIS images and generating dynamics lake masks. For improving the accuracy of the lake masks and computational efficiency of the algorithm, two masks are defined for limiting the search area. The restricting masks are developed according to DEM of the surrounding area together with a map of the long-term variation of pixel values. Subsequently, an unsupervised pixel-based classification algorithm is applied for defining the lake coastline. The algorithm particularly deals with the challenges of generating long time series of lake masks. We apply the algorithm on five lakes in Africa and Asia, each of which demonstrates a challenge for lake area monitoring. However in the validation section, we demonstrate that the algorithm can generate accurate dynamic lake masks. Rivers show diverse behaviour along their path due to the contribution of different parameters like gradient of the elevation, river slope, tributaries and river bed morphology. Therefore for generating accurate river reach mask, we need to consider additional sources of information apart from pixel intensity. The region-based classification algorithm that we propose in this study takes advantages of all types of available information including pixel intensity and spatial and temporal interactions. Markov Random Fields provide a flexible frame for interaction between different sources of data and constraint. To find the most probable configuration of the field, the Maximum A Posteriori solution for the MRF must be found. To this end, the problem is reshaped as an energy minimization. The energy function is minimized applying graph cuts as a powerful optimization technique. The uncertainty in the graph cuts solution is also measured by calculating the minimum marginal energies. The proposed method is applied to four rivers reaches with different hydrological characteristics. We validate the obtained river area time series by comparing with in situ river discharge and satellite altimetric water level time series. Moreover, in this study, we present river discharge estimation models using the generated river reach masks. Our aim is to find an empirical relationship between the average river reach width and river discharge. The statistics in the validation periods support the idea of using river width-discharge prediction models as a complementary technique to the other spaceborne geodetic river discharge prediction approaches.Item Open Access Beendigung von Kontraktlogistikbeziehungen : Häufigkeiten, Treiber, Gründe und Phasen der Beendigung kontraktlogistischer Beziehungen(2017) Drodofsky, Michael; Large, Rudolf (Prof. Dr.)Item Open Access Improving usability of gaze and voice based text entry systems(2023) Sengupta, Korok; Staab, Steffen (Prof. Dr.)Item Open Access Zur optimalen Standortplatzierung von leistungselektronischen Kompensationsvorrichtungen : ein Beitrag zum Problem der Spannungsstützung in ausgedehnten Verbundsystemen(2025) Lisin, Wladimir; Scheffknecht, Günter (Prof. Dr. techn.)Behandelt wird ein NP-hartes Zuordnungsproblem. Die Lösung dieses Problems versteht sich als Antwort auf die Frage nach der optimalen Platzierung von leistungselektronischen Kompensationsvorrichtungen - den sog. FACTS. Die Güte einer Platzierungswahl bemisst sich dann am dynamischen Antwortverhalten infolge ausgelöster Netzfehler. Eine adäquate Abwägung zwischen Geräteanzahl und den dazu erforderlichen Aufwendungen überführt die Aufgabe in eine Pareto-optimale Mehrzielsuche. Des Weiteren ist die Frage nach einer optimalen Standortwahl zugleich auch ein fallvariables Problem, da die individuellen Netznutzungsfälle auch jeweils individuelle Probleminstanzen definieren. Zu ermitteln sind schließlich Ort, Art, Anzahl und die Auslegung von Parametern der Dynamikmodelle der dabei platzierten Anlagen. Konstruiert wurde hierzu ein modulares Bestimmungsverfahren. Die Gütebewertung ermittelter Konfigurationen erfolgt mithilfe von Lastflussberechnungen im detaillierten Netzmodell des europäischen Stromverbundsystems. Die ermittelte Lösung ist schließlich ein aus optimal-korrespondierenden Ort-Geräte-Paaren erweiterter Netz-Anlagen-Park, der bei optimal bestimmten Installationsorten, der optimal bestimmten Anzahl jeder verwendeten Geräteart sowie der optimalen, ortsgebundenen Parametrierung ihrer jeweiligen Dynamikmodelle das anfängliche Systemverhalten eines ausgewählten Netzgebiets bzgl. Stabilität und Robustheit in optimaler Weise verbessert.Item Open Access User experience with the technology of virtual reality in the context of training and learning in vocational education(2021) Guo, Qi; Zinn, Bernd (Prof. Dr.)The virtual reality (VR) technology, with its features of simulation, interaction, and gamification, as well as the various technical aspects of input and output for movements and feedback, provides learners in the VR training and learning environment with the perception of immersion, spatial presence, and flow experience. Based on the theoretical research findings in terms of the learning processes and the learning motivation, the design and development of a VR training and learning environment should adhere to the principles of the UX design and the didactical design. This presented research focuses on the generation of an explanatory and description knowledge about user experience with virtual reality technology in the context of training and learning in virtual environments. Based on the current development of VR technology, as well as the significant application areas, two empirical studies (VILA and VPSL) on the user experience of learners and (prospective) teachers with different types of virtual reality technologies in the field of vocational education are conducted. To test the user experience in the virtual reality training and learning environment, several aspects related to the user experience will be analyzed, including usability of the application, spatial presence, learning motivation, and flow experience of the students. Based on the literature review, the empirical studies, as well as practical experience in the development of the VR training and learning environments, the recommendations for the design, development, evaluation, and implementation of the VR training and learning environments are discussed. With regards to the further implementation of the applications, the requirements from the technological, administrative, and didactical perspectives are discussed. The limitations in the current research, as well as the directions for further research, are outlined.