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Die interventionelle Behandlung des Vorhofflimmerns verursacht häufiger als in der Vergangenheit wahrgenommen eine Beeinträchtigung benachbarter Gewebe und Organe. Im Vordergrund der Betrachtungen dieser Arbeit stehen Schäden des Oesophagus, die aufgrund der schlechten Vorhersagbarkeit, des zeitlich verzögerten Auftretens und der fatalen Prognose bei Ausbildung einer atrio-oesophagealen Fistel besondere Relevanz haben.
Das Vorhofflimmern selbst ist nicht mit einer unmittelbaren vitalen Bedrohung verbunden, aber durch seine Komplikationen (z.B. Herzinsuffizienz, Schlaganfall) dennoch prognostisch relevant. Durch Antiarrhythmika gelingt keine Verbesserung der Rhythmuskontrolle (Arrhythmie-Freiheit), eine katheterinterventionelle Behandlung ist der medikamentösen Therapie überlegen. Durch eine frühzeitige und erfolgreiche Behandlung des Vorhofflimmerns konnte eine Verbesserung klinischer Endpunkte und der Prognose erreicht werden. Das Risiko einer invasiven Behandlung (insbesondere hinsichtlich des Auftretens prognoserelevanter Komplikationen) muss jedoch bei der Indikationsstellung und der Prozedur-Durchführung bedacht und gegenüber den günstigen Effekten der Behandlung abgewogen werden.
Untersuchungen zur Vermeidung der sehr seltenen atrio-oesophagealen Fisteln bedienen sich Surrogat-Parametern, hier bisher ausschließlich den ablationsinduzierten Schleimhaut-Läsionen des Oesophagus. Die Untersuchungen dieser Arbeit zeigen ein komplexeres Bild der (peri)-oesophagealen Schädigungen nach Vorhofflimmern-Ablation mit thermischen Energiequellen.
(1) Neue Definition der Oesophagus-Schäden: Oesophageale und perioesophageale Beeinträchtigungen treten sehr häufig auf (nach der hier verwendeten erweiterten Definition bei zwei Drittel der Patienten) und sind unabhängig von der verwendeten Ablationsenergie. Unterschiede finden sich in den Manifestationen der Oesophagus-Schäden für die verschiedenen Energie-Protokolle, ohne dass der Mechanismus hierfür aufgeklärt ist. Diese Arbeit beschreibt die unterschiedlichen Ausprägungen thermischer Oesophagus-Schäden, deren Determinanten und pathophysiologische Relevanz.
(2) Die Detektion (zum Teil subtiler) Oesophagus-Schäden ist maßgeblich von der Intensität der Nachsorge abhängig. Eine Beschränkung auf subjektive Schilderungen (z.B. Schmerzen beim Schluckakt, Sodbrennen) ist irreführend, die Mehrzahl der Veränderungen bleibt asymptomatisch, die Symptome der ausgebildeten atrio-oesophagealen Fistel (meist nach mehreren Wochen) bereits mit einer sehr schlechten Prognose belastet. Eine Endoskopie der Speiseröhre findet in den meisten elektrophysiologischen Zentren nicht oder nur bei anhaltenden Symptomen statt und kann ausschließlich Mukosa-Läsionen nachweisen. Damit wird das Ausmaß des oesophagealen und perioesophagealen Schadens bei Weitem unterschätzt. Veränderungen des perioesophagealen Raums, deren klinische Relevanz (noch) unklar ist, werden nicht erfasst, und damit ein Wandödem und Schäden im Gewebe zwischen linkem Vorhof und Speiseröhre (einschl. Nerven und Gefäßen) ignoriert.
Die Studien tragen auch zur Neubewertung etablierter Messgrößen und Risikofaktoren der Oesophagus-Schäden bei.
(3) Das Temperaturmonitoring im Oesophagus anhand der Maximalabweichungen ist erst für Extremwerte aussagekräftig und dadurch nicht hilfreich, Oesophagus-Läsionen zu vermeiden. Die komplexe Analyse der Temperatur-Rohdaten (bisher nur offline möglich) liefert in der AUC für RF-Ablationen einen prädiktiven Parameter für Oesophagus-Schäden, der eine Strukturierung der weiteren endoskopischen Diagnostik erlaubt. Ein vergleich¬barer Wert für die Cryoablationen konnte in den Analysen nicht gefunden werden.
(4) Eine chronische Entzündung des unteren Oesophagus-Drittels behindert nicht nur das Abheilen einer thermischen Oesophagus-Läsion, sondern kann das Auftreten solcher Läsionen durch die Ablation begünstigen. Die große Zahl vorbestehender Oesophagus-Veränderungen, die eine erhöhte Vulnerabilität anzeigen, und die Bedeutung für die Ent¬stehung thermischer Läsionen können der Ansatzpunkt präventiver Maßnahmen sein.
Ergänzend werden Ausprägungen der Oesophagus-Schäden durch umfangreiche Diagnostik erfasst und beschrieben, die aus pathophysiologischen Überlegungen relevant sein können.
(5) Die systematische Erweiterung der bildgebenden Diagnostik auf den perioesophagealen Raum durch Endosonographie zeigte, dass Schleimhaut-Läsionen alleine nur einen geringen Teil der Oesophagus-Schäden darstellen. Schleimhaut-Läsionen infolge einer instrumentellen Verletzung sind nicht mit dem Risiko der Ausbildung einer atrio-oesophagealen Fistel verbunden und unterstreichen die pathophysiologische Relevanz der perioesophagealen Veränderungen.
(6) Eine funktionelle Diagnostik thermischer Schäden des perioesophagealen Vagus-Plexus identifiziert Patienten mit Oesophagus-Schäden, die bildgebend nicht erfasst wurden, jedoch in ihren Auswirkungen (Nahrungsretention und gastro-oesophagealer Reflux) zur Läsionsprogression beitragen können.
Carbon nitride semiconductors: properties and application as photocatalysts in organic synthesis
(2023)
Graphitic carbon nitrides (g-CNs) are represented by melon-type g-CN, poly(heptazine imides) (PHIs), triazine-based g-CN and poly(triazine imide) with intercalated LiCl (PTI/Li+Cl‒). These materials are composed of sp2-hybridized carbon and nitrogen atoms; C:N ratio is close to 3:4; the building unit is 1,3,5-triazine or tri-s-triazine; the building units are interconnected covalently via sp2-hybridized nitrogen atoms or NH-moieties; the layers are assembled into a stack via weak van der Waals forces as in graphite. Due to medium band gap (~2.7 eV) g-CNs, such as melon-type g-CN and PHIs, are excited by photons with wavelength ≤ 460 nm. Since 2009 g-CNs have been actively studied as photocatalysts in evolution of hydrogen and oxygen – two half-reactions of full water splitting, by employing corresponding sacrificial agents. At the same time application of g-CNs as photocatalysts in organic synthesis has been remaining limited to few reactions only. Cumulative Habilitation summarizes research work conducted by the group ‘Innovative Heterogeneous Photocatalysis’ between 2017-2023 in the field of carbon nitride organic photocatalysis, which is led by Dr. Oleksandr Savatieiev.
g-CN photocatalysts activate molecules, i.e. generate their more reactive open-shell intermediates, via three modes: i) Photoinduced electron transfer (PET); ii) Excited state proton-coupled electron transfer (ES-PCET) or direct hydrogen atom transfer (dHAT); iii) Energy transfer (EnT). The scope of reactions that proceed via oxidative PET, i.e. one-electron oxidation of a substrate to the corresponding radical cation, are represented by synthesis of sulfonylchlorides from S-acetylthiophenols. The scope of reactions that proceed via reductive PET, i.e. one-electron reduction of a substrate to the corresponding radical anion, are represented by synthesis of γ,γ-dichloroketones from the enones and chloroform.
Due to abundance of sp2-hybridized nitrogen atoms in the structure of g-CN materials, they are able to cleave X-H bonds in organic molecules and store temporary hydrogen atom. ES-PCET or dHAT mode of organic molecules activation to the corresponding radicals is implemented for substrates featuring relatively acidic X-H bonds and those that are characterized by low bond dissociation energy, such as C-H bond next to the heteroelements. On the other hand, reductively quenched g-CN carrying hydrogen atom reduces a carbonyl compound to the ketyl radical via PCET that is thermodynamically more favorable pathway compared to the electron transfer. The scope of these reactions is represented by cyclodimerization of α,β-unsaturated ketones to cyclopentanoles.
g-CN excited state demonstrates complex dynamics with the initial formation of singlet excited state, which upon intersystem crossing produces triplet excited state that is characterized by the lifetime > 2 μs. Due to long lifetime, g-CN activate organic molecules via EnT. For example, g-CN sensitizes singlet oxygen, which is the key intermediate in the dehydrogenation of aldoximes to nitrileoxides. The transient nitrileoxide undergoes [3+2]-cycloaddition to nitriles and gives oxadiazoles-1,2,4.
PET, ES-PCET and EnT are fundamental phenomena that are applied beyond organic photocatalysis. Hybrid composite is formed by combining conductive polymers, such as poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) with potassium poly(heptazine imide) (K-PHI). Upon PET, K-PHI modulated population of polarons and therefore conductivity of PEDOT:PSS. The initial state of PEDOT:PSS is recovered upon material exposure to O2. K-PHI:PEDOT:PSS may be applied in O2 sensing.
In the presence of electron donors, such as tertiary amines and alcohols, and irradiation with light, K-PHI undergoes photocharging – the g-CN material accumulates electrons and charge-compensating cations. Such photocharged state is stable under anaerobic conditions for weeks, but at the same time it is a strong reductant. This feature allows decoupling in time light harvesting and energy storage in the form of electron-proton couples from utilization in organic synthesis. The photocharged state of K-PHI reduces nitrobenzene to aniline, and enables dimerization of α,β-unsaturated ketones to hexadienones in dark.
The direct conversion of light from the sun into usable forms of energy marks one of the central cornerstones of the change of our living from the use of fossil, non-renewable energy resources towards a more sustainable economy. Besides the necessary societal changes necessary, it is the understanding of the solids employed that is of particular importance for the success of this target. In this work, the principles and approaches of systematic-crystallographic characterisation and systematisation of solids is used and employed to allow a directed tuning of the materials properties. The thorough understanding of the solid-state forms hereby the basis, on which more applied approaches are founded.
Two material systems, which are considered as promising solar absorber materials, are at the core of this work: halide perovskites and II-IV-N2 nitride materials. While the first is renowned for its high efficiencies and rapid development in the last years, the latter is putting an emphasis on true sustainability in that toxic and scarce elements are avoided.
Alfred Wegeners ideas on continental drift were doubted for several decades until the discovery of polarization changes at the Atlantic seafloor and the seismic catalogs imaging oceanic subduction underneath the continental crust (Wadati-Benioff Zone). It took another 20 years until plate motion could be directly observed and quantified by using space geodesy. Since then, it is unthinkable to do neotectonic research without the use of satellite-based methods.
Thanks to a tremendeous increase of instrumental observations in space and time over the last decades we significantly increased our knowledge on the complexity of the seismic cycle, that is, the interplay of tectonic stress build up and release. Our classical assumption, earthquakes were the only significant phenomena of strain release previously accumulated in a linear fashion, is outdated. We now know that this concept is actually decorated with a wide range of slow and fast processes such as triggered slip, afterslip, post-seismic and visco-elastic relaxation of the lower crust, dynamic pore-pressure changes in the elastic crust, aseismic creep, slow slip events and seismic swarms. On the basis of eleven peer-reviewed papers studies I here present the diversity of crustal deformation processes. Based on time-series analyses of radar imagery and satellited-based positioning data I quantify tectonic surface deformation and use numerical and analytical models and independent geologic and seismologic data to better understand the underlying crustal processes.
The main part of my work focuses on the deformation observed in the Pamir, the Hindu Kush and the Tian Shan that together build the highly active continental collision zone between Northwest-India and Eurasia. Centered around the Sarez earthquake that ruptured the center of the Pamir in 2015 I present diverse examples of crustal deformation phenomena. Driver of the deformation is the Indian indenter, bulldozing into the Pamir, compressing the orogen that then collapses westward into the Tajik depression. A second natural observatory of mine to study tectonic deformation is the oceanic subduction zone in Chile that repeatedly hosts large earthquakes of magnitude 8 and more. These are best to study post-seismic relaxation processes and coupling of large earthquake.
My findings nicely illustrate how complex fashion and how much the different deformation phenomena are coupled in space and time. My publications contribute to the awareness that the classical concept of the seismic cycle needs to be revised, which, in turn, has a large influence in the classical, probabilistic seismic hazard assessment that primarily relies on statistically solid recurrence times.
This habilitation thesis summarises the research work performed by the author during the last quindecennial period. The dissertation reflects his main research interests, which revolve around quantum dynamics of small-sized molecular systems, including their interactions with electromagnetic radiation or dissipative environments. This covers various dynamical processes that involve bound-bound, bound-free, and free-free molecular transitions. The latter encompass light-triggered rovibrational or rovibronic dynamics in bound molecules, molecular photodissociation induced by weak or strong laser fields, state-to-state reactive and/or inelastic molecular collisions, and phonon-driven vibrational relaxation of adsorbates at solid surfaces. Although the dissertation covers different topics of molecular reaction dynamics, most of these studies focus on nuclear quantum effects and their manifestations in experimental measures. The latter are assessed through comparison between quantum and classical predictions, and/or direct confrontation of theory and experiment. Most well known quantum concepts and effects will be encountered in this work. Yet, almost all these quantum notions find their roots in the central pillar of quantum theory, namely, the quantum superposition principle. Indeed, quantum coherence is the main source of most quantum effects, including interference, entanglement, and even tunneling. Thus, the common and predominant theme of all the investigations of this thesis is quantum coherence, and the survival or quenching of subsequent interference effects in various molecular processes. The lion's share of the dissertation is devoted to two associated quantum concepts, which are usually overlooked in computational molecular dynamics, viz. the Berry phase and identical nuclei symmetry. The importance of the latter in dynamical molecular processes and their direct fingerprints in experimental observables also rely very much on quantum coherence and entanglement. All these quantum phenomena are thoroughly discussed within the four main topics that form the core of this thesis. Each topic is described in a separate chapter, where it is briefly summarised and then illustrated with three peer-reviewed publications. The first topic deals with the relevance of quantum coherence/interference in molecular collisions, with a focus on the hydrogen-exchange reaction, H+H2 --> H2+H, and its isotopologues. For these collision processes, the significance of interference of probability amplitudes arises because of the existence of two main scattering pathways. The latter could be inelastic and reactive scattering, direct and time-delayed scattering, or two encircling reaction paths that loop in opposite senses around a conical intersection (CI) of the H3 molecular system. Our joint theoretical-experimental investigations of these processes reveal strong interference and geometric phase (GP) effects in state-to-state reaction probabilities and differential cross sections. However, these coherent effects completely cancel in integral cross sections and reaction rate constants, due to efficient dephasing of interference between the different scattering amplitudes. As byproducts of these studies, we highlight the discovery of two novel scattering mechanisms, which contradict conventional textbook pictures of molecular reaction dynamics. The second topic concerns the effect of the Berry phase on molecular photodynamics at conical intersections. To understand this effect, we developed a topological approach that separates the total molecular wavefunction of an unbound molecular system into two components, which wind in opposite senses around the conical intersection. This separation reveals that the only effect of the geometric phase is to change the sign of the relative phase of these two components. This in turn leads to a shift in the interference pattern of the molecular system---a phase shift that is reminiscient of the celebrated Aharonov-Bohm effect. This procedure is numerically illustrated with photodynamics at model standard CIs, as well as strong-field dissociation of diatomics at light-induced conical intersections (LICIs). Besides the fundamental aspect of these studies, their findings allow to interpret and predict the effect of the GP on the state-resolved or angle-resolved spectra of pump-probe experimental schemes, particularly the distributions of photofragments in molecular photodissociation experiments. The third topic pertains to the role of the indistinguishability of identical nuclei in molecular reaction dynamics, with an emphasis on dynamical localization in highly symmetric molecules. The main object of these studies is whether nuclear-spin statistics allow dynamical localization of the electronic, vibrational, or even rotational density on a specific molecular substructure or configuration rather than on another one which is identical (indistinguishable). Group-theoretic analysis of the symmetrized molecular wavefunctions of these systems shows that nuclear permutation symmetry engenders quantum entanglement between the eigenstates of the different molecular degrees of freedom. This subsequently leads to complete quenching of dynamical localization over indistinguishable molecular substructures---an observation that is in sharp contradiction with well known textbook views of iconic molecular processes. This is illustrated with various examples of quantum dynamics in symmetric double-well achiral molecules, such as the prototypical umbrella inversion motion of ammonia, electronic Kekulé dynamics in the benzene molecule, and coupled electron-nuclear dynamics in laser-induced indirect photodissociation of the dihydrogen molecular cation. The last part of the thesis is devoted to the development of approximate wavefunction approaches for phonon-induced vibrational relaxation of adsorbates (system) at surfaces (bath). Due to the so-called 'curse of dimensionality', these system-bath complexes cannot be handled with standard wavefunction methods. To alleviate the exponential scaling of the latter, we developed approximate yet quite accurate numerical schemes that have a polynomial scaling with respect to the bath dimensionality. The corresponding algorithms combine symmetry-based reductions of the full vibrational Hilbert space and iterative Krylov techniques. These approximate wavefunction approaches resemble the 'Bixon-Jortner model' and the more general 'quantum tier model'. This is illustrated with the decay of H-Si (D-Si) vibrations on a fully H(D)-covered silicon surface, which is modelled with a phonon-bath of more than two thousand oscillators. These approximate methods allow reliable estimation of the adsorbate vibrational lifetimes, and provide some insight into vibration-phonon couplings at solid surfaces. Although this topic is mainly computational, the developed wavefunction approaches permit to describe quantum entanglement between the system and bath states, and to embody some coherent effects in the time-evolution of the (sub-)system, which cannot be accounted for with the widely used 'reduced density matrix formalism'.
Fabricating electronic devices from natural, renewable resources has been a common goal in engineering and materials science for many years. In this regard, carbon is of special significance due to its biological compatibility. In the laboratory, carbonized materials and their composites have been proven as promising solutions for a range of future applications in electronics, optoelectronics, or catalytic systems. On the industrial scale, however, their application is inhibited by tedious and expensive preparation processes and a lack of control over the processing and material parameters. Therefore, we are exploring new concepts for the direct utilization of functional carbonized materials in electronic applications. In particular, laser-induced carbonization (carbon laser-patterning (CLaP)) is emerging as a new tool for the precise and selective synthesis of functional carbon-based materials for flexible on-chip applications.
We developed an integrated approach for on-the-spot laser-induced synthesis of flexible, carbonized films with specific functionalities. To this end, we design versatile precursor inks made from naturally abundant starting compounds and reactants to cast films which are carbonized with an infrared laser to obtain functional patterns of conductive porous carbon networks. In our studies we obtained deep mechanistic insights into the formation process and the microstructure of laser-patterned carbons (LP-C). We shed light on the kinetic reaction mechanism based on the interplay between the precursor properties and the reaction conditions. Furthermore, we investigated the use of porogens, additives, and reactants to provide a toolbox for the chemical and physical fine-tuning of the electronic and surface properties and the targeted integration of functional sites into the carbon network. Based on this knowledge, we developed prototype resistive chemical and mechanical sensors. In further studies, we show the applicability of LP-C as electrode materials in electrocatalytic and charge-storage applications.
To put our findings into a common perspective, our results are embedded into the context of general carbonization strategies, fundamentals of laser-induced materials processing, and a broad literature review on state-of-the-art laser-carbonization, in the general part.
Ecce figura
(2023)
Worüber wir reden, wenn wir von Figuren reden, ist eine komplexe Fragestellung, die unterschiedliche Disziplinen berührt. Mit Erich Auerbachs figura/Mimesis-Projekt wurde die interdiszplinäre Forschung dieses Begriffs initiiert. Ob Literatur-, Bild- oder Wissensgeschichte – die Präsenz und Aktualität von figura in der romanistischen und komparatistischen Forschung bezeugt ein anhaltendes Interesse an der Theoriearbeit zwischen Theologie, Philosophie, Literatur- und Kunstwissenschaft. Allerdings fehlt bislang eine grundlegende methodologische Reflexion, die die interdisziplinären Aspekte gleichrangig berücksichtigt und zu einer gemeinsamen Arbeit am Begriff vereinigt.
Dieses Versäumnis zu beheben, ist Aufgabe der vorliegenden Arbeit. Ausgehend von Erich Auerbach, Walter Benjamin und Hannah Arendt verfolgt die Monographie in vergleichenden Konstellationen von der Antike bis in die Moderne die literatur- und kunsthistorischen, theologischen und philosophischen Spuren von figura, die zu einer Methode der literaturphilosophischen Figuralogie ausgebaut werden.
Ecce figura versteht sich als ein Kompendium interdisziplinärer Begriffsgeschichte zwischen Literatur, Philosophie und Theologie, das dazu einlädt, in neuen Konstellationen gelesen und erweitert zu werden.