Mathematisch-Naturwissenschaftliche Fakultät

VISOR: VIsual Seizure Onset Detection PeRsonalized for Epilepsy Patients

2026-06-30T10:45:34Z

VISOR: VIsual Seizure Onset Detection PeRsonalized for Epilepsy Patients Kumar, Uttam; Yu, Ran; Wenzel, Michael; Demidova, Elena Wu, Xintao; Spiliopoulou, Myra; Wang, Can; Kumar, Vipin; Cao, Longbing; Wu, Yanqiu; Yao, Yu; Wu, Zhangkai The onset detection of epileptic seizures from multivariate Electroencephalogram (EEG) data is a challenging task. The variation in seizure patterns across patients and epilepsy types makes it particularly difficult to create a generic solution. Existing approaches indicate low recall due to their inability to capture complex seizure onset patterns. In this paper, we propose VISOR – a novel approach to detect the onset of epileptic seizures based on novel patient profiles and visual, personalized feature representations. VISOR leverages a vision transformer model to learn the spatio-temporal relationships between features, capture individual seizure propagation patterns, and perform seizure onset detection in a heterogeneous multi-patient dataset. Evaluation on a real-world dataset demonstrates that VISOR outperforms state-of-the-art baselines by at least 5% points for seizure onset detection in terms of the F1 score and indicates higher effectiveness for more complex patterns of propagating seizures.

Darstellung von Mehrfachbindungen zwischen Kobalt und den schweren Elementen der Tetrele

2026-06-29T14:46:36Z

Darstellung von Mehrfachbindungen zwischen Kobalt und den schweren Elementen der Tetrele Deckstein, Tobias Die Carbin-Komplexe stellen eine zentrale Klasse organometallischer Verbindungen dar und besitzen, wie ihre schweren Homologe, die Tetrelylidin-Komplexe, eine nahezu lineare M–E–R-Struktur mit sehr kurzen M–E-Bindungslängen (E = Si–Pb, M = Übergangsmetall, R = Substituent). Der metathetische Austausch von M≡C-Bindungen in Carbin‑Komplexen mit Alkine ist ein grundlegendes Prinzip der Alkinmetathese und verläuft über metallacyclobutadienartige Zwischenstufen. Die Dreifachbindungsspaltung von Ditetrelinen RE≡ER (E = Si–Pb, R = Substituent) an Metallzentren ist jedoch deutlich weniger erforscht. Bedingt durch das umgekehrte Verhältnis der Bindungsdissoziationsenergien bei schwereren Tetrel-Elementen |ΔH°(M≡E)| > |ΔH°(E≡E)|) im Vergleich zu Kohlenstoff (|ΔH°(C≡C)| > |ΔH°(M≡C)|), eröffnen sich neue Synthesewege für Tetrelylidin-Komplexe und bietet einen alternativen Zugang zur Synthese von Tetrelylidin-Komplexen jenseits klassischer Synthesemöglichkeiten. Ein bedeutender Fortschritt war die metathetische Austausch von [Mo(⁵-C₅H₅)₂(CO)₂]₂ mit Ditetrelinen RE≡ER (E = Ge–Pb, R = ArDipp; ArDipp = C₆H₃-2,6-(C₆H₃-2,6-ⁱPr₂)) zur Darstellung des Komplexes [Cp(CO)₂Mo≡ER]. In dieser Arbeit wird ein systematischer Ansatz zur effizienten Synthese des kationischen Bis-Germylidin-Komplexes [Co(GeMind)₂(PMe₃)₂][B(ArF)₄] durch die gezielte Spaltung der Ge≡Ge-Bindung mit dem Komplex [Co(PMe₃)₄][B(ArF)₄] vorgestellt. Die Vervollständigung der homologen Reihe von Kobalt-Tetrelylidin-Komplexen gelang zum einem durch eine Kobalt-zentrierte Spaltung der E≡E-Bindung der Ditetreline Ge₂Tbb₂ bzw. Sn₂ArDipp₂ mit [Co(PMe₃)₄]. Zusätzlich wird die Darstellung von Tetrelylidin-Komplexen mittels der klassischen Salz-Eliminierungsmethode durch Reaktionen von Tetrel(II)-Halogeniden mit K[Co(PMe₃)₄] beschrieben. Besonders erwähnenswert ist die Synthese des Silylidyne-Komplexes [Co(SiTbb)(PMe₃)₃], der durch eine bisher einzigartige metathetische Austauschreaktion zwischen Co≡Sn/Co≡Si- oder Co≡Pb/Co≡Si-Bindungen dargestellt wurde. Diese Ergebnisse demonstrieren erstmals einen neuartigen, nicht-Katz-basierten Mechanismus zur gezielten Umwandlung von M≡E-Bindungen. Die vorgestellte Methodik erweitert die Synthesemöglichkeiten für Tetrelylidin-Komplexe des Übergangsmetalls Kobalt mit den schweren Tetrel-Elementen und liefert zudem neue Einblicke in das Reaktionsverhalten und die Bindungseigenschaften von schweren Tetrelylidin-Komplexen des Übergangmetalls Kobalt.

The Galaxy Three-Point Correlation Function: From Theory to Forecasts

2026-06-29T14:20:51Z

The Galaxy Three-Point Correlation Function: From Theory to Forecasts Pugno, Anna (noch nicht zugänglich / not yet accessible)

Exploring Phase-Change Materials for Heat-Storage from First Principles

2026-06-29T15:37:34Z

Exploring Phase-Change Materials for Heat-Storage from First Principles Jütten, Stefan The transition towards a carbon-neutral energy landscape necessitates the development of efficient thermal energy storage systems to bridge the temporal gap between renewable energy supply and thermal demand. The polymorphic ceramic trititanium pentoxide (Ti₃O₅) has emerged as a promising candidate for latent heat storage, capable of storing thermal energy in a metastable high-temperature phase indefinitely. Here, a comprehensive first-principles investigation of the Ti₃O₅ heat-storage system is presented, ranging from the electronic structure of the bulk material to the complex thermodynamic and kinetic behavior of doped systems, interfaces, surfaces and nanoparticles.
The initial part of this work establishes a robust theoretical framework for describing the open-shell transition metal oxide. It is demonstrated that the meta-GGA functional r²SCAN, augmented with the D3 dispersion correction, provides an accurate description of the structure of Ti₃O₅ polymorphs, superior to standard hybrid functionals. In the bulk, the thermodynamic ground state of the β-phase is identified as an antiferromagnetic semiconductor, while the metastable λ-phase is shown to be a ferromagnetic semiconductor. The transition state is characterized by a rotation of a central Ti-dimer, and predicted r²SCAN-D3 phase transition enthalpy and phase transition temperature are in good agreement with experiment.
Building on this foundation, the modulation of heat-storage properties via aliovalent cation doping (Sc, Al, Mg) is explored. The results reveal that doping lowers the phase transition temperature and enthalpy, primarily through local lattice distortions rather than direct electronic effects. Substitution turns the semiconducting bulk materials into metals, with significant electron density accumulation at the defect site. At low dopant concentration the β-Ti₃O₅ to λ-Ti₃O₅ barrier remains unchanged while the substitution stabilizes the λ-phases relative to β-Ti₃O₅. This provides a theoretical basis for tuning the operational temperature window of the material for specific waste-heat recovery applications.
A central challenge in the theoretical description of Ti₃O₅ has been the discrepancy between calculated and experimental pressures required to induce the phase transition. This thesis resolves this issue by moving beyond bulk models. First, the close degree of lattice matching between β- and λ-phases results in stable optimized phase interfaces along the (100), (010) and (001) grain boundaries between the phases. A more refined picture of the phase transition pathway is obtained by varying the β/λ ratio in large supercell models, revealing a distinct anisotropy in the phase transition pathway involving the (001) interface, which proceeds with a significantly lower barrier as compared to the other considered interfaces, confirming experimental trends. Hydrostatic pressure simulation on these mixed-phase models reveals pressure to destabilize high λ-phase fraction systems, however, these pressures of several GPa still overestimate experimental values by orders of magnitude. Second, the influence of particle size and morphology is quantified. By calculating surface free energies and applying the Wulff construction, it is shown that surface effects stabilize the λ-phase in particles smaller than 43 nm in diameter, providing a thermodynamic explanation for the experimentally observed thermal hysteresis and the persistence of the metastable phase at room temperature. The phase transition temperature is also shown to be influenced by particle size, with nanoparticles exhibiting diameters in the experimentally synthesized regime displaying phase transition temperatures in excellent agreement with experiment.
Finally, the atomistic mechanism of the pressure-induced phase transition is elucidated using machine-learned potentials driven on-the-fly probability enhanced sampling simulations. Simulated annealing simulations reveal a favorable surface reconstruction of the (001) λ-phase surface, which is then subject to repulsive harmonic potentials to model pressure effects. A comprehensive, universal and transferable framework for the translation of the slab compression to a pressure value is introduced. By modeling the uniaxial compression of nanoparticle surfaces rather than hydrostatic bulk compression, the predicted transition threshold of ≈700 bar is brought into better agreement with experimental values (≈600 bar). The mechanism is shown to involve a sequential, system size independent nucleation and a resulting layer-by-layer transformation, which is resolved in detail from direct molecular dynamics simulations under pressure at ambient temperatures.
Collectively, this work bridges the gap between quantum-chemical predictions and experimental observations in Ti₃O₅. It establishes a validated computational workflow for the discovery and optimization of phase-change materials, highlighting the critical importance of the correct choice of computational method, uncovering the fundamental effects of cation substitution in the modulation of material properties and the use of realistic models accounting for finite-size effects for accurate predictions of thermodynamic material properties.