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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 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 ...
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
The anatomy of velvet worms (Onychophora) as revealed by a multimethodological approach and three-dimensional reconstructions
(2024)
Onychophorans, or velvet worms, comprise a small group of worm-like, multi-legged terrestrial invertebrates. Since their discovery in 1826, these organisms have been investigated from different perspectives, particularly in the field of morphology—a discipline that provides the basis for functional and evolutionary inferences. Onychophorans are currently classified within Ecdysozoa (moulting animals) and form together with Tardigrada (water bears) and Arthropoda a clade named Panarthropoda. Therefore, onychophorans ...
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 ...
Dissertation
Die Synthese planar-chiraler 1,1´–Diaminoferrocenderivate
(2024)
Dieses Forschungsprojekt beschäftigt sich mit 1,1´-Diaminoferrocenderivaten, die aufgrund ei-nes weiteren Substituenten X in Nachbarstellung (ortho-Position) zu einer der Stickstoffgrup-pen planare Chiralität aufweisen. Obgleich 1,1´-Diaminoferrocen eine bewährte Schlüsselver-bindung innerhalb der Ferrocenchemie ist, insbesondere zur Darstellung von N,N-Chelatligan-den und N-heterozyklischen Tetrylenen, jeweils mit 1,1´-Ferrocenylenrückgrat, war der syn-thetische Zugang zu den hier behandelten planar-chiralen ...
Dissertation
Pentamethylcyclopentadienyl-Halbsandwich-Eisenkomplexe mit ungewöhnlichen Carbenliganden
(2024)
This dissertation project deals with the electronic properties of the pentamethylcyclopentadienyl halfsandwich iron complex with bis(trimethylsilyl)amido ligand ([Fe(Cp*)(HMDS)], HMDS = N(SiMe₃)₂) and its reactivity towards carbenes or their direct precursor compounds. The compound was published in 1998 by the Siemeling group and described at the time as diamagnetic. Structurally very similar representatives with penta-isopropylcyclopentadienyl- (⁵Cp) and 1,2,4-tri-tert-butylcyclopentadienyl ligands (Cp‘) have been ...