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Dissertation
Ultraschnelle kohärente Kontrollmethoden für die nichtlineare Mikroskopie und Spektroskopie
(2023-11-28)
Ultrakurze Laserpulse im Nanojoule-Energiebereich auf der Femto- bis Pikosekunden-Zeitskala ermöglichen die Erzeugung immenser Feldstärken bei Fokussierung auf wenige Quadratmikrometer Fläche. In diesem Szenario wirken starke Kräfte auf die Elektronensysteme von Atomen und Molekülen im Fokus ein, so dass sich die linearen optischen Eigenschaften von Stoffen ändern können – nichtlineare Eigenschaften treten zutage. Mit einem Pulsformer kann auf die breiten Spektren ultrakurzer Laserpulse per spektraler Phasenmodulation ...
Dissertation
On the analysis of path-dependent functionals of stochastic PDEs
(2023)
Weak approximation methods for stochastic partial differential equations (SPDEs) are concerned with approximating the probability distribution of the solution process rather than the realizations of the solution process itself. In this thesis, we provide new results and methods concerning the weak error analysis of numerical approximations of path-dependent functionals of solution processes of SPDEs. Two separate approaches to analyzing weak approximation errors are considered: the Itô calculus approach and the ...
Dissertation
Biochemical Characterization of Microtubule-Associated Serine/Threonine Kinases
(2023)
The association of human microtubule-associated serine/threonine (MAST) kinases with different diseases, such as neurodevelopmental disorders and cancer, leads to hight interest in understanding the function of these understudied kinases. This PhD thesis provides the first consolidated biochemical analysis of three different human MAST kinases (MAST1-3) and the Drosophila melanogaster homologue drop out protein (DOP).
Dissertation
A Unifying Theory for Runge-Kutta-like Time Integrators: Convergence and Stability
(2024)
The work deals with two major topics concerning the numerical analysis of Runge-Kutta-like (RK-like) methods, namely their stability and order of convergence. RK-like methods differ from additive RK methods in that their coefficients are allowed to depend on the solution and the step size. As a result of this, we also refer to them as non-standard additive RK (NSARK) methods. We motivate and introduce modified Patankar (MP) schemes as a subclass of NSARK methods and emphasize their importance. The first major part ...
Dissertation
Immobilization of Neodymium Complexes on Semiconductor Surfaces and Processing of GaAs-based Photonic Crystals
(2024)
Lanthanide ion luminescence exhibits characteristic narrow emission bands ranging from VIS to NIR along with relatively long emission lifetimes which makes them attractive for applications in lighting, sensing, and display technologies. The focus of this dissertation lies on the optical characterization of newly synthesized neodymium complexes bearing phosphonate ester ligands and the fabrication of photonic crystal (PhC) cavities. Micro-photoluminescence (PL) spectroscopy is used to investigate the NIR emission bands ...
Dissertation
Functional Analysis of Src42A in embryonic epithelial morphogenesis of Drosophila melanogaster
(2023)
Src42A is one of the Src family kinases (SFKs) present in Drosophila melanogaster. In mammals there are 8 SFKs and so far, a loss of function analysis of SFKs were difficult to conduct due to their functional redundancy. In Drosophila, there are only two SFKs namely Src42A and Src64B, the former is essential for embryonic development and the latter is a non-essential gene. Since Src42A is supplied as a maternal component, the zygotic mutant were showing defects in later developmental stages, because the contribution ...
Dissertation
Functional analyses of Dph1•Dph2 in synthesis of diphthamide, a clinically relevant modification on eEF2
(2024)
Diphthamide is a unique post-translational modification of a conserved histidine on the eukaryotic translation elongation factor 2 (eEF2). During translation elongation, eEF2 induces translocation of codon-anticodon duplexes across the ribosomal decoding center. Diphthamide is involved in fine-tuning of this process by stabilizing the codon-anticodon duplex and maintaining reading frame accuracy. Initially, diphthamide was identified as the target for diphtheria toxin, enabling ADP-ribosylation of eEF2 and resulting ...
Aufsatz
Spatio-temporal resolution studies on a highly compact ultrafast electron diffractometer
(2015)
Time-resolved diffraction with femtosecond electron pulses has become a promising technique to directly provide insights into photo induced primary dynamics at the atomic level in molecules and solids. Ultrashort pulse duration as well as extensive spatial coherence are desired, however, space charge effects complicate the bunching of multiple electrons in a single pulse.Weexperimentally investigate the interplay between spatial and temporal aspects of resolution limits in ultrafast electron diffraction (UED) on our ...
Dissertation
Towards the investigation of ultrafast dynamics in chiral systems using free-electron lasers
(2024)
Chiral molecules are life’s building blocks, making the study of their ultrafast processes a pursuit across various fundamental research fields. The results presented in this dissertation contain methodological, technical and scientific advancements that pave the way for future time-resolved, site-specific investigations into chiral photochemistry of randomly orientated molecules, using photoelectron circular dichroism and free-electron lasers. The high-repetitionrate free-electron lasers EuXFEL and FLASH2 will soon ...
Dissertation
Existence and Asymptotic Behavior of Solutions to the Time-Periodic Navier-Stokes Equations in a Layer Domain with Nonhomogeneous Boundary Data
(2024)
This dissertation is dedicated to the analysis of the Navier-Stokes equations in a timeperiodic framework in the so-called layer domain Π = R2 × (0, 1), described by:
∂tu − νΔu + (u · ∇)u + ∇p = f in [0, T] × Π,
div u = 0 in [0, T] × Π,
u|∂Π = a for all t ∈ [0, T] ,
u|t=0 = u|t=T in Π.
The velocity field u and the pressure p are unknowns, while the external force f is prescribed. Challenges arise due to unboundedness of the layer Π and from introduction of a nonhomogeneous boundary condition a. The investigated ...