https://ediss.sub.uni-hamburg.de:443/handle/ediss/2 2026-06-07T00:23:18Z 2026-06-07T00:23:18Z Wirling, Stefan https://ediss.sub.uni-hamburg.de:443/handle/ediss/12402 2026-06-02T23:35:57Z 2026-06-02T15:09:56Z

Title: Functional and Structural Characterization of the Peroxisomal siRNA Binding Protein P15 from the Peanut Clump Virus and the Detection of Functional Orthologs Authors: Wirling, Stefan

2026-06-02T15:09:56Z Ziegler, Julia Anabell https://ediss.sub.uni-hamburg.de:443/handle/ediss/12395 2026-06-02T23:36:01Z 2026-06-02T14:53:26Z

Title: Cosmological Aspects of Minimal and Extended Higgs Sectors Authors: Ziegler, Julia Anabell Abstract: Despite the huge success of the Standard Model (SM) of particle physics, many open problems indicate the need for New Physics. One particular extension of the SM is the Two Higgs doublet model with an additional complex scalar singlet (2HDMS). This model provides an enlarged scalar sector resulting in seven physical Higgs particles, of which one is a suitable candidate to explain dark matter (DM). In this work the DM and collider phenomenology of the 2HDMS is investigated. Representative benchmark points with light, intermediate-range and heavy masses for the DM candidate are chosen. The benchmark points are consistent with all theoretical and experimental constraints and, in some cases, also accommodate the excess around 95 GeV, observed in the b ̄b channel at the Large Electron-Positron Collider (LEP) and in the γγ channel at the Large Hadron Collider (LHC). In terms of DM phenomenology, the focus is on matching the required DM relic density, as well as direct and indirect detection bounds of DM. In terms of collider phenomenology, the focus is on relevant signatures at the LHC and at proposed future lepton colliders, such as electron-positron colliders and a proposed muon collider. The 2HDMS model, as well as other beyond-the-Standard Model (BSM) theories, can provide a first-order electroweak phase transition (EWPT), which proceeds via the formation of bubbles. A second focus of this work is the investigation of the wall velocity of expanding bubbles from first-order phase transitions (FOPTs) with symmetry breaking and with symmetry restoration. In standard symmetry-breaking FOPTs, the frictional pressure on the expanding bubble walls can be dominated by transition radiation, the process of one particle from the surrounding plasma passing into the bubble and radiating off an additional particle. This process is enhanced in the soft-momentum limit of the radiated particle, and is known to produce significant frictional effects that are proportional to the Lorentz factor γ of the bubble wall. This dependence of the frictional pressure on the Lorentz factor prohibits runaway behaviour of the bubble walls. The focus of this work is on the analogous pressure for phase transitions with symmetry restoration. It is shown that, in such transitions the pressure due to transition radiation can be negative for small and intermediate Lorentz factors, leading to a further acceleration of the bubble wall. However, for very large Lorentz factors the pressure approaches the same positive scaling as the standard symmetry-breaking scenarios. Therefore, the terminal Lorentz factor of the bubble wall can be significantly larger (by more than an order of magnitude) than in the corresponding symmetry-breaking scenario. This can carry important implications for various phenomenological applications, from gravitational waves (GWs) up to BSM physics.

2026-06-02T14:53:26Z Bazhanov, Ilia https://ediss.sub.uni-hamburg.de:443/handle/ediss/12419 2026-06-02T23:36:06Z 2026-06-02T14:36:24Z

Title: Long-term outcomes of concomitant left-sided cryoablation during totally endoscopic mitral valve surgery Authors: Bazhanov, Ilia Abstract: Die vorliegende Studie zeigt die langfristige Effektivität und Sicherheit der begleitenden linksseitigen Kryoablation im Rahmen der vollendoskopischen Mitralklappenoperation. Die beobachtete Rezidivrate von Vorhofflimmern entspricht den Ergebnissen früherer Studien bei Patientinnen und Patienten mit konventionellem operativem Zugang. Die niedrige Inzidenz von Schrittmacherimplantationen, verbunden mit einer hohen Rate an Freiheit von Vorhofflimmern, unterstreicht die Vorteile der linksseitigen Kryoablation als eine wertvolle Behandlungsmethode bei diesen Patienten. Allerdings ist es auch wichtig, die Limitationen dieser Studie zu erkennen und den Bedarf an weiterführender Forschung zur Bestätigung der Ergebnisse zu betonen. Darüber hinaus sind prospektive, randomisierte Studien erforderlich, um das optimale Management der Antikoagulationstherapie nach chirurgischer Ablation und Verschluss des linken Vorhofohres zu untersuchen.

2026-06-02T14:36:24Z Logemann, Ella Lu https://ediss.sub.uni-hamburg.de:443/handle/ediss/12408 2026-06-02T23:37:21Z 2026-06-02T13:38:54Z

Title: The Role of Plant-Soil Interactions for Carbon Cycling in Baltic and North Sea Coastal Wetlands Authors: Logemann, Ella Lu Abstract: Plants in coastal wetlands act as ecosystem engineers, as they shape ecosystem development through bio geomorphic feedbacks and exert strong control over carbon cycling in these dynamic systems and globally important carbon sinks. High primary productivity supplies large amounts of organic matter to the soil, while water saturation slows soil organic matter (SOM) decomposition. The fate of the sequestered carbon further depends on plant-soil interactions, as plants modify soil conditions such as redox potential and pH - key drivers of microbial activity. In addition, plants influence microbial decomposition by supplying substrates of differing quality. Compared to upland ecosystems, plant-mediated control over microbial activity is particularly pronounced in wetlands, where roots not only provide organic inputs but also release oxygen, altering redox conditions through radial oxygen loss. These interactions are particularly important for methane dynamics - a greenhouse gas with greater radiative forcing potential than carbon dioxide - which can be high in wetlands due to the waterlogged soils. Despite their disproportionate role as carbon sinks, the effects of global warming on ecosystem carbon responses in wetlands remain poorly understood. The net climate-carbon feedback of wetlands is strongly dependent on plant-soil interactions and their warming-induced alterations, as both plant carbon assimilation (inputs) and SOM decomposition (outputs) are temperature-sensitive. Warming-driven increases in SOM decomposition are likely to enhance plant-available nitrogen, potentially alleviating nitrogen limitation and promoting greater biomass production and carbon retention. However, if decomposition outpaces plant carbon inputs, this will result in substantial SOM loss, creating a positive climate-carbon feedback accelerating climate change. This thesis investigates carbon cycling and storage under current and warmer climate conditions in coastal wetlands of the North Sea and Baltic Sea, with a particular focus on plant-soil interactions. Four complementary studies were conducted. First, carbon stocks (chapter 2) and methane emissions (chapter 3) were quantified across German coastal wetlands, addressing both large-scale differences (between coasts) and small-scale variation (within sites and plant communities). Second, two studies (chapter 4 and 5) were conducted in a mesocosm warming experiment and investigated warming effects on transplanted vegetated soil-sods originating coastal wetlands from Denmark, Sweden, and Finland spanning distinct soil morphologies and plant communities. Here we assessed warming effects on aboveground biomass, soil organic matter (SOM), and microbial communities. Across these studies, several key findings emerged. Low-energy Baltic Sea salt marshes contained higher soil organic carbon (SOC) stocks than high-energy North Sea marshes. Livestock grazing increased SOC stocks in the North Sea by enhancing soil compaction but showed mixed effects in the Baltic, driven by changes in plant biomass. Contrary to expectations, grazing effects on soil compaction and plant communities did not increase methane emission but varied strongly among sites. Grazing-induced shifts in plant community composition and subsequent alterations in belowground biomass and hence redox potentials explained methane emission. Grazing often excluded high-emission species such as Phragmites australis, highlighting complex underlying plant-soil interactions that vary between species and connected functional traits. The studies conducted in the mesocosm warming experiment revealed that elevated temperatures increased plant-available nitrogen and enhanced aboveground biomass especially in SOM-rich systems, though systems with nitrogen-fixing plants and lower SOM content showed weaker responses. SOM losses occurred in soils initially rich in SOM, suggesting that ecosystem carbon responses to warming depend strongly on initial resource status. Warming also induced significant restructuring of soil microbial communities in SOM richer tall-grass communities but not in the SOM-poorer tall-grass community, likely reflecting differences in successional stage and microbial specialization. Taxa that increased under warming were linked to nutrient cycling and organic matter breakdown, whereas those that decreased under warming were associated with cold and low-oxygen adaptation. Together, these studies demonstrate the pivotal role of plant-soil-microbe interactions in regulating carbon dynamics in coastal wetlands under both current and future climate conditions. Future research should prioritize two key pathways: (1) developing a mechanistic understanding of plant-soil interactions and how they are altered under warming, understanding particularly the influence of plant traits such as radial oxygen loss and root exudation on microbial activity and SOM decomposition; and (2) assessing SOM as a central variable in ecosystem carbon responses to warming, supported by further experimental studies to test the generality of this pattern.

2026-06-02T13:38:54Z