Ph.D. Theses

Positron annihilation lifetime spectroscopy (PALS) is a powerful tool for defect characterisation in a wide range of materials. To investigate inhomogeneous defect distributions, for example, near fatigue cracks or in dispersive alloys, with PALS, a monochromatic pulsed positron beam of variable energy with a diameter in the range of 1 µm and a pulse width of 200 ps FWHM is required. [...]

This thesis presents a comprehensive investigation of the structural and magnetic properties of biocompatible iron oxide nanoparticles coated with three different ligand materials: sodium citrate, (3-aminopropyl)triethoxysilane (APTES), and dextran. The influence of the coating agents on the agglomeration of iron oxide nanoparticles and their oxidation stability over time was studied. [...]

This work is dedicated to the detailed investigation of the atomic and magnetic structurein a selection of germanium-based melilite-type compounds, namely Ba2TGe2O7(T = Cu, Co and Mn) and the Ba2Cu1-xMnxGe2O7 solid solution series. These materialsgained high interest in the current condensed matter research as they revealed astrong magnetoelectric coupling that could not be explained by the conventional modelsof spin-driven multiferroicity. [...]

Neutron depth profile analysis is a method for the high-precision determination of concentration profiles of certain nuclides in near-surface layers. For an extension to 3D profiling, a detector system based on double-sided silicon strip detectors with a thin and homogeneous dead layer was developed and characterised. [...]

The Standard Model of Particle Physics encompasses our current understanding of particlephysics. However, due to its limitations, one of the goals of modern experimental physics is to probe the model further and look for physics beyond the Standard Model.One approach is to conduct precision physics experiments in free neutron beta decay.Precise measurements of the decay parameters from the decay provide a complementary approach to high energy searches. [...]

Curvature in lipid-based biomembranes provides compartmentalization in cells and can act as regulator of biological activity in living systems. The study of these biomembranes require novel model systems and new methods. [...]

RNA is a single-stranded biopolymer that plays a myriad of roles in physiological and pathological processes and is the carrier of genetic information in many human pathogens. Hepatitis C virus (HCV) is one of the most impactful representatives of RNA viruses. [...]

Nuclear fuel development for the conversion of FRM II towards the use of low-enriched uranium (LEU). Parameter studies for the production of diffusion barriers, which suppress intermixing of U-Mo nuclear fuel and the Al cladding and prevent the formation of detrimental compounds. [...]