https://ediss.sub.uni-hamburg.de:443/handle/ediss/2 2026-10-02T00:04:20Z https://ediss.sub.uni-hamburg.de:443/handle/ediss/12634 Title: Enhancing Elastic Scattering via Transient Resonances Authors: Ronchetti, Daniele Abstract: In recent years, X-ray Free Electron Lasers (XFELs) sources have seen a tremendous increase in their performance. X-ray pulses with duration breaching the femtosecond frontier – entering the attosecond domain – and intensities reaching the 10^20 W cm−2 regime have become available and, most importantly, a reliable tool for scientific exploration. Growing on the backbone of these capabilities, the field of nonlinear and ultrafast X-ray science has expanded, with a plethora of novel phenomena being observed and investigated. Upon irradiation with ultrashort and intense pulses, a defining feature of non-linear X-ray science emerges: the ability to transiently excite atoms into non-equilibrium core-excited configurations opens otherwise forbidden transitions. Under particular circumstances, these transient resonances can provide additional scattering channels and substantially increase the atomic scattering factor. In this thesis, we demonstrate that the Lα (2p3/2 − 3d) transition at 929.7 eV transiently enhances the elastic scattering factor of copper atoms. The process is initiated by 2p photo-ionization, followed by Auger decay that triggers a cascade of inter-atomic electron-impact ionizations, ultimately populating metastable states with multiple 3d holes. Using 15 fs pulses reflected from a Cu-containing [SiC/Cu/B4C] multilayer, we observe an intensity-dependent peak around the Lα energy whose amplitude and width evolve non-linearly with excitation intensity. Theoretically, a self-consistent model linking the transient electronic population to the scattering response reproduces the observed behavior. A minimal two-level description quantifies a 12-fold enhancement of the imaginary scattering factor f2. Our findings confirm the role of transient resonances in elastic scattering and establish a route towards innovative methods for improved contrast and resolution in ultrafast X-ray imaging. 2026-10-01T15:53:42Z https://ediss.sub.uni-hamburg.de:443/handle/ediss/12636 Title: Mehrwert der iktalen Hirnperfusions-SPECT nach sicherer Lateralisation der Anfallsursprungszone in der interiktalen SPECT Authors: Baradaran-Salimi, Kian Abstract: Ziel dieser Studie war es, die Häufigkeit sicherer Kandidaten für die Anfallsursprungszone in interiktaler und iktaler Hirnperfusions-SPECT und deren Zuverlässigkeit in der präoperativen Diagnostik von Patienten mit medikamentenresistenter Epilepsie zu ermitteln. 177 Patienten wurden eingeschlossen. Die visuelle Beurteilung der SPECT-Bilder erfolgte durch drei unabhängige Befunder in drei Settings: „nur interiktal“, nur „iktal“ und „vollständig“, d.h. Zusammenschau von interiktaler und iktaler SPECT mit Subtraktions-Analyse (Referenzstandard). Die Sicherheit der Lateralisierung der Anfallsursprungszone in eine Hirnhemisphäre wurde mit 1 (sehr gering) bis 5 (sehr hoch) bewertet. Ein Fall galt als mit hoher Sicherheit lateralisiert, falls alle Befunder mit hoher Sicherheit (≥ 4 Punkte) in dieselbe Hemisphäre lateralisierten. Die Lateralisationsrate mit hoher Sicherheit betrug 4,5 % im „nur interiktal“ Setting, 31,6 % im „nur iktal“ Setting und 38,4 % im „vollständig“ Setting. Im „nur interiktal“ Setting lateralisierte einer (12,5 %) der acht sicheren Fälle in die falsche Hemisphäre. Im „nur iktal“ Setting lateralisierten alle sicheren Fälle in die korrekte Hemisphäre. Es ist daher nicht empfehlenswert, die präoperative Hirnperfusions-SPECT mit einer interiktalen Untersuchung zu beginnen. Stattdessen sollte zuerst eine iktale Untersuchung erfolgen. Falls diese einen sicheren Kandidaten für die Anfallsursprungszone liefert, kann auf eine interiktale SPECT verzichtet werden.; The aim of this study was to determine the frequency of high-confidence candidates for the seizure onset zone in interictal and ictal brain perfusion SPECT, and their reliability in the preoperative workup of patients with drug-resistant epilepsy. 177 patients were included. The visual assessment of the SPECT images was performed by three independent readers in three settings: 'interictal only', 'ictal only' and 'full', i.e. side-by-side interpretation of interictal and ictal SPECT with subtraction analysis (reference standard). The confidence of the readers regarding their lateralizations of the seizure onset zone to one hemisphere was scored on a scale from 1 (very low) to 5 (very high). A case was considered to be lateralizing with high confidence if all readers lateralized it with high confidence (≥4 points) to the same hemisphere. The lateralization rate with high confidence was 4.5% in the 'interictal only' setting, 31.6% in the 'ictal only' setting and 38.4% in the 'full' setting. In the 'interictal only' setting, one (12.5%) of the eight certain cases lateralized to the wrong hemisphere. In the 'ictal only' setting, all cases with a high level of confidence were lateralized to the correct hemisphere. Therefore, it is not advisable to begin the preoperative brain perfusion SPECT with an interictal scan. Instead, an ictal scan should be performed first. If this provides a candidate for the seizure onset zone with high confidence, an interictal SPECT can be avoided. 2026-10-01T15:26:53Z https://ediss.sub.uni-hamburg.de:443/handle/ediss/12637 Title: Computational characterization of macromolecular interfaces in AI-predicted complex structures Authors: Genz, Luca Ragna 2026-10-01T15:13:17Z https://ediss.sub.uni-hamburg.de:443/handle/ediss/12568 Title: Mandatory Sustainability Due Diligence: Normative foundations, operating principles and economic perspectives on legal design Authors: Ciacchi, Silvia 2026-10-01T13:52:55Z