Die chirurgische Resektion von Leber- und Lungentumoren ist das einzige Therapieverfahren mit gesicherter kurativer Zielsetzung. Allerdings kann nur eine Minderheit der Patienten einer chirurgischen Therapie zugeführt werden. Bei In-situ-Ablationsverfahren wie der Laserinduzierte Thermotherapie (LITT) und der Radiofrequenzablation (RFA) werden Tumoren mit einem nadelförmigen Applikator punktiert und mittels thermischer Energie in-situ zerstört. Limitiert wird der sichere klinische Einsatz der Ablationsverfahren bislang durch die fehlende Kenntnis der Lichtausbreitung im Gewebe, um eine Vorhersage über das Ausmaß der entstehenden Thermoläsionen zu treffen und die geeigneten Applikationsparameter für eine vollständige Tumorzerstörung im Vorfeld der Behandlung festlegen zu können. Ferner ist aus onkologischen Gründen die Induktion ausreichend großer Läsionen mit vollständiger Tumordestruktion erforderlich. Ziel dieser Habilitationsarbeit war es daher, den genannten Limitationen der LITT und RFA durch die experimentelle und klinische Evaluation neuer Applikationsmodi und Planungsmöglichkeiten an der Leber, Lunge und Schilddrüse entgegen zu wirken und damit das Spektrum der Therapiemöglichkeiten auszuweiten. Der erste Schritt bestand in der Evaluation der optischen Gewebeparameter kolorektaler Lebermetastasen und deren Primärtumoren im nativen und koagulierten Zustand von Patienten mit einem synchron hepatisch metastasierten Kolonkarzinom. Trotz gleicher Histologie zeigten sich keine Übereinstimmungen der optischen Parameter von Primärtumor und Lebermetastase, was auf eine Modifikation durch die Metastasierung hindeutet. Ferner kam es infolge der thermischen Gewebekoagulation zu einer Veränderung der optischen Parameter von Kolonkarzinom- und Lebermetastasengewebe. Mit diesem Projektteil konnten erstmalig die optischen Gewebeparameter kolorektaler Lebermetastasen und deren Primätumoren vorgelegt werden. Die Daten machen deutlich, dass für eine effektive Anwendung der LITT eine Anpassung der Bestrahlungsparameter mit zunehmender Applikationsdauer erforderlich ist. Zur Behandlung auch größerer Lebermetastasen wurde im zweiten Arbeitsschritt eine Optimierung der LITT angestrebt. Hierbei wurde die LITT in Kombination mit einer Unterbrechung der Leberperfusion hinsichtlich ihrer Effektivität im Vergleich zur normalen Perfusion bei Patienten mit irresektablen, hepatischen Metastasen untersucht. Es konnte gezeigt werden, dass die LITT in Kombination mit einer Perfusionsunterbrechung zu einer Erhöhung der Läsionsvolumina führt. Bei gleicher Komplikationsrate im Vergleich zur LITT ohne Perfusionsunterbrechung können auf diesem Wege bedeutend größere Thermoläsionen erzielt werden. Die geringe Invasivität machen die In-situ-Ablationsverfahren auch für die Therapie von Tumoren anderer parenchymatöser Organe, wie der Lunge und der Schilddrüse, interessant. In einem weiteren Arbeitsschritt wurde die LITT zunächst an der Lunge evaluiert. Hierbei wurde die an Schweinelungen ex-vivo mittels eines perkutanen als auch offenen Punktionssystems induzierten Thermoläsionen in Abhängigkeit der verwendeten Applikationsdauer und -leistung untersucht, um so den Leistungsbereich für die Induktion möglichst großer Läsionen zu bestimmen. Es konnten erstmals Daten für eine Dosis-Wirkungs-Beziehung für die LITT an Lungengewebe gewonnen werden. Sowohl das perkutane als auch das offene Applikationssystem der LITT induziert reproduzierbare, klinisch relevante Läsionen in der Lunge. In den letzten hier dargestellten Arbeiten galt es, die LITT sowie die RFA in Hinblick auf die Größe induzierbarer Läsionen in Relation zur Applikationsdauer und –leistung an der Schilddrüse zu evaluieren. Die vorliegenden Arbeiten beschreiben erstmalig die Grundlagen der LITT sowie der RFA an der Schilddrüse. Es gelang mit beiden Ablationsverfahren reproduzierbare Thermoläsionen von relevanter Größe in der Schilddrüse zu induzieren. Zudem wurden beide Ablationsverfahren erstmalig hinsichtlich ihrer Effektivität miteinander verglichen. Ein Vergleich beider Verfahren ist hierbei prinzipiell schwierig, da die LITT und RFA auf unterschiedlichen Technologien mit verschiedenen Energiequellen und –absorptionsraten beruhen. Es konnte jedoch gezeigt werden, dass in unserem experimentellen Ansatz mit der LITT größere Läsionsvolumina zu erzielen sind. Wesentlicher Vorteil der LITT gegenüber der RFA ist hierbei das Fehlen von Impedanzproblemen, zum Nachteil einer manuell aufwendigeren Punktion. Im Ergebnis konnten wir mit der in dieser Arbeit erfolgten experimentellen und klinischen Evaluation neuer Applikationsmodi und Planungsmöglichkeiten Lösungswege aufzeigen, die geeignet sind, den bisherigen Limitationen im Einsatz der LITT und RFA entgegen zu wirken. Durch die im Rahmen dieser Arbeit erfolgte Bestimmung der optischen Gewebeparameter von Lebermetastasen und deren kolorektalen Primärtumoren wurden die Grundlagen für die Entwicklung und erste Evaluation eines Dosimetrie-Modells für die LITT an der Leber geschaffen, wodurch es möglich ist, die Applikationsparameter für eine sichere und vollständige Tumorzellzerstörung prätherapeutisch zu ermitteln. Die Kombination der LITT mit einer Unterbrechung der Leberperfusion bietet darüber hinaus die Möglichkeit, den effektivitätshemmenden Kühleffekten der Leberdurchblutung zu reduzieren und somit die onkologische Effektivität zu verbessern. Durch die Untersuchungen zur Dosimetrie der LITT und RFA an der Lunge sowie der Schilddrüse wurden zudem wesentliche Grundlagen für eine klinische Ausweitung der In-situ-Ablationsverfahren auf weitere parenchymatöse Organe neben der Leber geschaffen. Es bedarf jedoch weiterer Untersuchungen, in denen insbesondere der Einfluss von Perfusion und Ventilation auf die In-situ- Ablationsverfahren während einer in-vivo-Anwendung evaluiert werden sollten.
View lessThis thesis is based on the examination of more than 18,000 photographs taken by participants of German expeditions to the Hindukush and Karakoram in the years between 1954 and 1963. I posit that a thorough analysis of these photographs facilitates a deeper understanding of the crucial role played by visual materials in the production of knowledge about geographical space. Furthermore, I argue that the 20th-century expeditions to the Hindukush-Karakoram can be characterised as ‘visualisation projects’. By using photography, German expedition travellers significantly shaped the contemporary perception and geographical imagination of the region as a high mountain space. Photo collections of three major German expeditions are examined as case studies: the 1954 German-Austrian Himalaya-Karakoram expedition, the 1959 German Karakoram expedition, and the 1962/63 Stuttgart Badakhshan expedition. I have reviewed and evaluated these photographs within the context of contemporary concepts and perspectives in geography and anthropology. Thus, two often overlooked issues have been addressed: firstly, the history of scientific exploration during the latter half of the 20th century, and secondly, the major role played by expedition photography in creating and disseminating knowledge about high mountain spaces. This work contributes to the scientific and historical reappraisal of analogue photographic practices in high mountain research. It also assesses the historical and present value of expedition photographs in the contexts of research, archives, and museums.
View lessMental health care represents a major global health challenge in contemporary societies. The higher frequency of mental health issues in urban, compared to rural areas, gains particular significance in light of the world’s rapidly accelerating urbanisation. Therefore, it is essential to understand how urban and natural environments impact our mental and brain health. Research shows that exposure to nature, in comparison to exposure to urban environments, improves mood, reduces stress, as well as physiological indicators of stress. Yet, the neural mechanisms behind the effects of natural and urban environments are not well understood. First studies have indicated that living environments are associated with mental health, as well as with brain function and structure. However, due to the inherent limitations of cross-sectional studies, the causal relationship between physical environments and brain health remains unestablished. This dissertation consists of four publications investigating the short-term causal effects of exposure to natural and urban environments on stress, stress-related brain function and hippocampal structure. In Paper I (Sudimac et al., 2022) we examined effects of a one-hour walk in a natural versus urban environment on stress-related brain function. The results indicated that activity in the amygdala, a brain region associated with stress, decreased after the nature walk, whereas no significant change was noted after the urban walk. The findings suggest that exposure to nature may have beneficial effects on stress-related brain regions, potentially acting as a preventive measure against stress-related mental health issues. In Paper II (Sudimac & Kühn, 2022) we explored sex differences in the impact of a one-hour walk in a natural versus urban environment on amygdala activity. Our results revealed a decrease in amygdala activity following the nature walk exclusively in women, with no significant change observed in men. This outcome indicates that women may benefit more from exposure to natural environments and underscores the necessity of considering individual differences, like sex, in the neural responses to exposure to natural and urban environments. In Paper III (Sudimac & Kühn, 2024) we investigated the impact of a one-hour walk in a natural versus urban environment on the structure of the hippocampus. We observed an increase in the volume of the hippocampal subfield, subiculum, following the nature walk, while no significant change was observed after the urban walk (though the interaction did not withstand the Bonferroni correction). Since the subiculum plays a role in dampening the stress response via the hypothalamic-pituitary-adrenal axis, our findings suggest that exposure to nature might positively influence a brain region associated with inhibition of stress response. In Paper IV (Sudimac et al., 2024) we assessed the effects of a walk in residential natural versus urban environments on subjective and physiological indicators of stress in mothers and their infants. We found no significant differences between exposure to natural and urban environments in mothers’ self-reported stress or in the stress-related cortisol levels, in both mothers and infants. However, a reduction in cortisol in mothers and infants was observed after walks in both natural and urban environments, indicating that the act of walking in residential areas might have a calming effect, regardless of the environment. In summary, this dissertation reveals a seminal evidence for the potential benefits of short-term exposure to natural relative to urban environments on stress-related brain function and brain structure. Furthermore, it emphasizes the need to consider individual differences, like sex and age, in exploration of natural and urban environments on mental and brain health. In conclusion, this work contributes to the growing body of research on environmental neuroscience and has potential implications for urban planning and public health strategies aimed at mitigating stress and enhancing mental health in urban populations.
View lessPrevious research has identified a common expectancy system, termed the “inconsistency compensation approach”, which governs the activation of cognitive mechanisms in response to socially aversive events, such as exclusion and loss of control. However, the functional properties of the expectancy system, in particular, whether threats to subjective expectations are processed independently or interactively, remain underexplored. To address this gap, this dissertation utilizes a modified Cyberball paradigm to simultaneously induce and monitor two distinct social threats – loss of control and exclusion. This approach incorporates real-time assessment of expectancy states using event-related potentials (ERPs). The main aims of this dissertation are threefold: First, to determine the extent to which the social expectancy system predicts upcoming social interactions. Second, to examine how the temporal overlap between initial and subsequent threats affects expectancy. Third, to assess whether the prediction of the social expectancy system covers a spectrum from negative to positive social interactions. To achieve these aims, three studies have been designed. Studies 1 and 2 explore how the experience of one social threat predict the expectation of another. Specifically, Study 1 investigates whether the experience of loss of control affects the subsequent processing of exclusion within the Cyberball game. Study 2 reverses the order of social threats to examine how prior exclusion experiences affect the subsequent processing of loss of control. Results from these studies indicate that preexposure to one type of social threat reduces expectancy violations for another type of threat, as evidenced by attenuated P3 effects. This preexposure effect is consistent regardless of the order of the threats and is not influenced by the temporal overlap of the preexposure. In addition, self-report data from the first two studies show that cessation of preexposure reduces negative mood and perceived threat to needs at the transition to another threat. Study 3 examines the impact of loss of control on the processing of overinclusion in Cyberball to assess whether the prediction of the social expectancy model extends to sociometer theory as a whole. While ERP results indicate that an expectancy bias induced by preexposure to loss of control does not alter expectations in overinclusion scenarios, self-reports suggest that regaining control positively affects affective states and enhances the satisfaction of the basic need for belonging. These findings indicate that the processing of a social threat can reduce expectancy violations for subsequent threats, regardless of their sequence. Interestingly, the preexposure effect remains stable regardless of the temporal overlap of preexposure and does not span a spectrum from negative to positive social interactions. Furthermore, the observed effects on self-reports appear to be primarily associated with affective states induced by the cessation of preexposure, highlighting a significant emotional factor. Overall, this dissertation provides neural evidence for the prediction of expectancy violations in the domain of negative social interactions. Conversely, self-reports appear to be more influenced by affective states, highlighting the nuanced interaction between cognitive mechanisms and emotional responses in social interactions.
View lessThe main problem studied in this thesis is the Multiobjective Shortest Path (MOSP) problem. We focus on the problem variant with three or more objectives. It is a generalization of the classical Shortest Path problem in which arcs in the input graph are weighted with vectors instead of scalars. The main contribution is the Multiobjective Dijkstra Algorithm (MDA), a label- setting algorithm that achieves state of the art performance in theory and in practice. Motivated by this result, the thesis goes on with the design of variants of the MDA for different variants of the MOSP problem. For the One-to-One MOSP problem the Targeted MDA (T-MDA) has the same asymptotic running time than the MDA but trades in memory for speed in practice. The additional paths stored during the T-MDA are managed in a pseudo-lazy way. This is a novel way to organize explored paths that ensures that the algorithm’s priority queue stores at most one path per node in the input graph simultaneously. The paths that are held back from the queue are organized in lists that are kept sorted by just prepending or appending paths to them, i.e., using constant time insertions. The resulting implementation of the T-MDA solves bigger instances than the MDA and is also faster. We study the generalization of the Time-Dependent Shortest Path problem to the multiobjective case. We provide a detailed analysis of the generalization’s limitations and discuss when the MDA is applicable. For MOSP instances with large sets of optimal paths, good approximation algorithms are important. We combine the MDA with an outcome space partition technique from the literature to obtain a new FPTAS for the MOSP problem. The resulting MD-FPTAS works also for multiobjective instances of the Time-Dependent Shortest Path problem, which is a novelty. Finally, we use the MDA and its biobjective version, the BDA, to solve the Multiobjective Minimum Spanning Tree (MO-MST) problem and the k-Shortest Simple Path (k-SSP) problem, respectively. For the solution of instances of these two problems, the MDA and the BDA are used as subroutines. An MO-MST instance is solved applying the MDA on a so called transition graph. In this graph paths have equivalent costs to trees in the original graph and thus, the optimal solutions computed by the MDA in the transition graph correspond to optimal trees in the original graph. Since the transition graph has an exponential size w.r.t. the size of the original graph, we discuss new pruning techniques to reduce its number of arcs effectively. The solution of the k-SSP, which is a scalar optimization problem, using a biobjective subroutine is surprising but our new algorithm is state of the art in theory and in practice.
View lessGentherapien stellen vielversprechende neue Therapieoptionen für eine Vielzahl von Indikationen dar. Trotz mehrerer zugelassener Medikamente, die auf viralen Gentransfer-Vektoren basieren, bleibt das volle Potenzial gentherapeutischer Ansätze bislang ungenutzt. Dies liegt zum einen an der hohen Immunogenität und aufwändigen Herstellung viraler Vektoren, zum anderen an der geringen Effizienz nicht-viraler Gentransfersysteme, die vor allem auf den Einschluss der verwendeten Nanopartikel in Endosomen und den damit verbundenen Abbau zurückzuführen ist. SO1861, ein aus Saponaria officinalis L. isoliertes Triterpensaponin, kann die Freisetzung aus den Endosomen fördern und wird daher als Transfektionsverstärker eingesetzt. Die Saponin-unterstützte Transfektion wird als Sapofektion bezeichnet und beinhaltet die parallele Verabreichung des Saponins und der Nanopartikel. In vitro funktioniert dies problemlos, in vivo erweist sich die Synchronisation der beiden Komponenten jedoch als schwierig. Ziel der vorliegenden Arbeit war daher die Entwicklung und Optimierung eines nicht-viralen Gentransfersystems, das die zu transfizierende DNA und das transfektionsverstärkende Saponin in einem Partikel enthält und intravenös verabreicht werden kann. Durch die Integration eines zielgerichteten Liganden in den zu entwickelnden Nanopartikel sollte zusätzlich die zielgerichtete Wirkung des Gentransfersystems sichergestellt werden. Um dieses Forschungsziel zu erreichen, wurde SO1861 mit Hilfe eines pH-sensitiven Hydrazon-Linkers kovalent an ein Poly-L-Lysin-basiertes Peptidgerüst konjugiert. Die hergestellten SO1861-funktionalisierten Peptide wurden zur Komplexierung von DNA durch elektrostatische Wechselwirkung verwendet. Die resultierenden Nanoplexe wurden in vitro auf ihre Transfektionseffizienz und Verträglichkeit hin untersucht. In allen untersuchten Zelllinien transfizierten die Nanoplexe mit konjugiertem SO1861 deutlich effektiver als nicht-funktionalisierte Nanoplexe unter Zugabe von freiem SO1861 zum Transfektionsmedium. Die Transfektion mit den SO1861 enthaltenden Nanoplexen beeinflusste die Zellviabilität nicht. Zielgerichtete, konjugiertes SO1861 enthaltende Nanoplexe wurden durch Integration eines zielgerichteten Peptids hergestellt und in vivo in einem Allograft-Tumormodell in Mäusen getestet. Unter Verwendung eines Selbstmordgen-Vektors, der für das zytotoxische Protein Saporin kodiert, wurde bei der Behandlung mit zielgerichteten, SO1861 enthaltenden Nanoplexen im Vergleich zur Vehikelkontrolle ein verlangsamtes Tumorwachstum und eine verbesserte Überlebensrate beobachtet. Die intravenöse Injektion der SO1861 enthaltenden Nanoplexe war dabei gut verträglich.
View lessIn den Originalarbeiten dieser Habilitationsschrift wurde untersucht inwieweit quantitativ messbare Veränderungen verschiedener Aspekte der menschlichen Wahrnehmung Aufschluss über die Pathophysiologie von Schmerzsyndromen und Bewegungsstörungen geben oder gar als diagnostischer Marker für spezifische Erkrankungen herangezogen werden können. Hierzu wurden Verfahren zur Erfassung der somatosensorischen Funktion und von internen prämotorischen Signalen genutzt. Wir konnten für das CRPS zeigen, dass die Druckschmerzschwellen nicht nur über der Muskulatur der betroffenen Extremität, sondern auch über den distalen Gelenken erniedrigt waren. Darüber hinaus korrelierte die erniedrigte Druckschmerzschwelle mit dem erhöhten periartikulären Knochenmetabolismus in der Spätphase der Drei-Phasen-Szintigraphie, was die Validität dieser psychophysikalischen Messung unterstreicht. Die Druckhyperalgesie über den Gelenken war hochspezifisch und sensitiv für das CPRS, so dass diese Untersuchung in Zukunft als diagnostische Ergänzung zu den rein klinischen Diagnosekriterien des CRPS genutzt werden könnte. Weiterhin phänotypisierten wir Patient:innen mit molekulargenetisch gesicherter hereditärer Erythromelalgie bei Mutationen im SCN9A Gen. Bemerkenswerterweise zeichneten die Betroffenen neben den für die Erkrankung klassischen paroxysmalen Schmerzattacken in den Extremitäten auch einen Dauerschmerz auf. Dieser könnte mit der Funktionsstörung der kleinkalibrigen Nervenfasern zusammenhängen, die wir in diesem Kollektiv mittels quantitativ sensorischer Testung detektierten. Bei isolierten fokalen Dystonien fanden wir wider Erwarten keinerlei Veränderung in behavioralen Markern als Korrelate für die kortikale Somatotopie in dystonen und nicht-betroffenen Arealen. Hier könnte eine zu geringe Sensitivität der Methode zur Detektion von Veränderungen in Bezug auf die untersuchte Körperregion eine Rolle gespielt haben. Ergänzend stellten wir fest, dass eine physikalische Dehnung der Haut, wie sie bei abnormen Körperhaltungen bei der Dystonie vorkommt, zu einer veränderten Wahrnehmung der Distanz zwischen zwei taktilen Reizen führt. Dies deutet darauf hin, dass keine korrigierenden top-down-Mechanismen existieren, welche zu einer Größenkonstanz taktiler Reize trotz Dehnung der Haut führen würden. Schließlich demonstrierten wir bei Patient:innen mit Tourette-Syndrom eine durch die Erkrankung beeinträchtigte Entwicklung der Fähigkeit zur Diskrimination interner prämotorischer Signale. Die gestörte Signaldetektion könnte zur Aufrechterhaltung der Erkrankung beitragen, aber auch einen möglichen Ansatzpunkt für behaviorale Therapien darstellen.
View lessIschemic heart disease ranks among the leading causes of death worldwide. Following myocardial infarction, cardiomyocyte loss through necrosis leads to inflammation, fibrosis, and permanent scarring, impairing heart function and leaving it susceptible to failure. Clinical efforts employing progenitor or stem cell-derived cardiomyocyte transplantation or utilizing biomaterials to induce cardiomyocyte proliferation, have proven ineffective in renewing the myocardium due to the human heart’s almost non-existent inherent self-renewal capacity. Unlike most adult mammals, neonatal mice and several non-mammalian vertebrates demonstrate the ability to regenerate cardiac tissue following myocardial infarction. Cardiac regeneration is a complex process, demanding a delicate orchestration of multiple cellular and molecular events. One fundamental aspect of regeneration is the resolution of scarring following injury and its replacement with new cardiomyocytes, partially attributed to fibroblast inactivation. However, a comprehensive understanding of the entire regeneration process is lacking, impeding the development of effective therapeutic strategies. The immune response is a significant event following ischemic injury, with macrophages as primary effectors. These cells are implicated in various processes, from dead cell clearance to tissue remodeling. Their initial pro-inflammatory phenotype is critical for cell influx into the injury area, and their subsequent anti-inflammatory phenotype contributes to the activation of fibroblasts, facilitating collagen deposition for extracellular matrix organization. Consequently, exploring the mechanisms that govern macrophage functional diversification is vital for elucidating the regeneration process. Additionally, the nervous system plays a pivotal role in immune modulation, with sensory neurons capable of relaying the immune state of peripheral locations to the central nervous system to regulate the immune response. Both sympathetic and parasympathetic signaling was shown to be critical for proper regenerative response. Transcriptomic studies in zebrafish have revealed that blocking cholinergic signaling post-cardiac injury impairs the immune response, and sympathetic signaling influences macrophage phenotype. The immunomodulatory capabilities of the nervous system, in conjunction with the multifaceted roles of macrophages, underscore the importance of neuro-immune interactions in cardiac regeneration. This dissertation revealed previously unidentified neural modulation of myocardial regenerative response and delineated the distinct roles of a macrophage subset. Utilizing zebrafish, known for its robust regenerative capacity, genetic tractability, and larval translucency allowing real-time injury event tracing, to model human myocardial infarction, this study identifies adrenergic receptor alpha-1 (Adra1) as a potent modulator of regenerative response and macrophage diversification. Utilizing a macrophage-specific loss-of-function model for Adra1 signaling and single-cell transcriptomics, this study uncovered the activation of an ‘extracellular matrix remodeling’ macrophage population that regulates the extracellular matrix composition and turnover. In vivo and ex vivo validation of the in-silico analyses elucidated the Adra1-activated macrophages’ roles in activating a pro-regenerative collagen XII-expressing fibroblast subset through Mdka-Lrp1aa crosstalk, regulating the cardiac regenerative niche, promoting vessel formation and cardiomyocyte proliferation. In short, this project emphasizes the potential of Adra1-mediated neural input as a key regulator of macrophage function, unveiling a novel mechanism of neuro-immune interactions that modulate fibrosis and myocardial renewal during the regeneration process. The insights into nervous modulation of immune response to regulate cardiac fibrosis and facilitate myocardial self-renewal provide a substantial foundation for development of a much-needed therapeutic strategy for cardiac regenerative medicine.
View lessArtificial light has significantly impacted the value and perception of the night in individuals who apply it, those who develop technologies to supply it, those who assess its environmental impact, and those who use and benefit from it. The unnatural illumination of nightscapes has become seamlessly integrated into society's fabric, making night-time bright and over-illuminated across landscapes where the natural light (e.g. emitted by the moon and stars) is masked by Artificial Light At Night (ALAN). In this way, ALAN has become a pollutant, known as light pollution (LP), that has emerged with the exponential increase of unnatural brightness and the change in spectral composition induced by improperly managed lighting technologies. ALAN has been shown to alter light environments of nocturnal terrestrial and aquatic habitats, which can impact many organisms' physiological processes, body functions and behaviour, affecting multiple intra- and interspecific interactions and even ecosystem processes. Current technological advances in outdoor lighting have the potential to develop light pollution reduction strategies that balance conflicting societal needs and environmental concerns. However, this potential remains largely untapped due to insufficient communication between ALAN researchers and lighting practitioners. The problem of reducing LP remains complex as it involves the active collaboration between ALAN researchers and lighting practitioners and a lingua franca between experts involved to transfer and translate research into practice. This thesis addresses the environmental impact of artificial lighting in urban settings, including existing communication and knowledge gaps, challenges posed by artificial light in aquatic realms and future perspectives towards sustainable lighting design. To mitigate the communication gaps between ALAN researchers and lighting practitioners, I propose a transdisciplinary framework between the experts in the practice, research, production, policy-making and planning of light and lighting. In collaboration with experts from ALAN research and the lighting practice, I suggest a four-step process to aid in establishing collaboration between the domains involved. Moreover, to set a shared understanding between ALAN research and the lighting practice, I propose a collaborative systematic review to aid in the transfer of diverse responses of plants, arthropods, insects, spiders, fish, amphibians, reptiles, birds, and non-human mammals (including bats, rodents, primates, and ungulates) when exposed to ALAN. As well as a mutual agreement on key terms set by representatives from both domains. The systematic review is based on finally 216 studies reporting behavioural and physiological responses across six relevant organism groups. To transfer the results between the research and the lighting practice, collaborative discussions between the experts of each domain resulted in establishing an ALAN lingua franca on key terminologies and definitions related to natural and artificial light as knowledge both domains should acquaint. The collaborative discussions also included a common language on relevant radiometric and photometric parameters that ALAN researchers must consider in their research and lighting practitioners in their day-to-day lighting practice. Also, the discussions led to the proposal of two communication strategies: a communication framework and a knowledge infrastructure scheme to set an ecological ceiling of awareness (responses to avoid) and a lighting foundation (essential knowledge to gain) for a better flow of information between the domains involved. The findings of this study also indicated that aquatic organisms and their realms remain understudied and that further studies on the impact of ALAN on aquatic habitats and their inhabiting biodiversity are needed. Furthermore, I explored the potential implications of bridge illumination on a river transect to confront the existing knowledge gap on the potential impact of ALAN on riverine systems with illuminated bridges. The light field of a river was quantified from a research vessel considering seven illuminated bridges. The results indicated that LP was induced by surrounding illumination and bridge illumination. Via a conceptual model, the unnatural light scenarios at illuminated bridges and their potential impact on the life history of two migrating fish species, Atlantic salmon and European silver eels, were addressed. Additionally, at the same river transect and illuminated bridges, patterns of polarised light pollution (PLP) reflecting at the water's surface were quantified near the illuminated bridges and their potential effects on aquatic insects were discussed. The findings of the four studies highlight the need for (i) better communication frameworks between experts of ALAN research and the lighting practice, (ii) transdisciplinary interfaces and collaborations to efficiently translate ecological research into the lighting practice, as well as the need for (iii) quantified ALAN and PLP across inland waters to develop sustainable lighting solutions to preserve riverine nightscapes. This thesis provides communication frameworks to bridge communication gaps, a knowledge infrastructure scheme to mitigate the transfer of knowledge between the domains, evidence on LP and PLP induced by surrounding and bridge illumination on a river transect, together with a conceptual model on ALAN as a potential barrier for migrating fish. Additionally, this thesis discusses transdisciplinary approaches, perspectives inclusive of natural environments, and a vision towards lighting approaches that require an urgent change and concludes with recommendations for the future of ALAN research and the lighting practice.
View lessSuper-resolution microscopy enables the observation of structures below the diffraction limit of light. A relatively new method, Expansion Microscopy (ExM) involves physically expanding a hydrogel-embedded facsimile of a biological structure by tearing it apart. The resultant larger replica permits sub-diffraction imaging with a typical fluorescent microscope. However, there are challenges, such as retaining the fluorescent signal after expansion and the isotropic nature of the expansion procedure, which this study will address. The signal loss is due to the loss of labels, which is mainly caused by gel formation and digestion. To address this issue, an agent was developed in this study that combines targeting, fluorescent labeling, and gel linkage into a single small molecule. The findings presented here suggest that label loss is due to inadequate surface grafting of fluorophores into the hydrogel. In order to gain a mechanistic understanding of dye retention, it is crucial to understand the function of surface grafting in ExM. By delivering monomers directly to the target of interest via nanobodies, the amount of polymerizable units bound to the surface was increased, resulting in retention of the signal. Consequently, the density of local monomers is crucial for retaining signals. In addition to signal retention, it is essential to verify that the expansion was uniform in all directions, i.e. isotropic, since only a facsimile of the original biological structure is detected after expansion. This is necessary to draw accurate conclusions from the results. Therefore, my goal was to develop a ruler that measures the isotropy of the expansion. For this experiment, tobacco mosaic virus (TMV) particles were fluorescently labeled and introduced as an internal standard into cells by coupling them with microtubules. However, the distribution of particle lengths and the loss of signal after expansion proved to be problematic. These obstacles can be resolved in future research. A uniform virus length could be achieved through size exclusion chromatography. Secondly, signal retention could be improved by fluorescently labeling additional amino acids of TMV coat proteins (CPs) and providing particles with polymerizable groups.
View lessMit dem Ziel der Theoriebildung gehe ich der Fragestellung nach, welchen Einfluss politische Steuerung auf die Versorgungssicherheit mit Strom hat, um die Auswirkungen der Privatisierung und Liberalisierung der Elektrizitätswirtschaft abzuschätzen. Mittels multipler Regression kontrolliere ich auf die Bedeutung technischer Merkmale der physischen Elektrizitätsinfrastruktur, sozioökonomischer Rahmenbedingungen, struktureller und prozeduraler Merkmale des politischen Systems, um den Effekt der Energiewirtschafts- und Infrastrukturpolitik zu isolieren.
Die Versorgungssicherheit mit Strom steigt allgemein an. Die Widerstandsfähigkeit der Elektrizitätsinfrastruktur gegen Störereignisse ist langfristig konstant. Veränderungen der durchschnittlichen Unterbrechungsdauer SAIDI gehen meist auf die Zeit bis zur Wiederversorgung nach einem Stromausfall CAIDI zurück. Dies deutet auf einen Einmaleffekt des Alters der langlebigen Basiskomponenten und einen hohen Einfluss von Investitionsentscheidungen in kurzlebige Komponenten wie die Mess-, Steuerungs- und Regelungstechnik hin.
Weder die durch natürliche Widrigkeiten bedingten Versorgungskosten, die langfristige Stabilität der wirtschaftlichen oder politischen Rahmenbedingungen, die Kapitalverfügbarkeit noch die instrumentelle Energiewirtschafts- oder Infrastrukturpolitik erklären die internationalen Unterschiede bei der Versorgungssicherheit mit Strom. Vielmehr erklärt die Korruptionswahrnehmung knapp die Hälfte der international zu beobachtenden Varianz.
Mit der Theorie der Determinanten der Versorgungssicherheit mit Strom interpretiere ich anschließend an die Capture-Theorie zur Regulierungsgenese in konzentrierten Wirtschaftssektoren das Energiesystem als ein von konkurrierenden Interessen geprägtes, selbstregelndes soziotechnisches System. Die Verbreitung von Korruption bestimmt, ob die Stromversorgung als öffentliches Gut im Bereich des gesellschaftlichen Optimums zwischen Preisgünstigkeit und Zuverlässigkeit oder als privates Gut erbracht wird. Vereinnahmen Interessengruppen die Energiewirtschaftspolitik illegal als privates Gut, sinkt die Versorgungssicherheit mit Strom durch das soziale Dilemma der Korruption und die Erosion des Staatswesens, selbst wenn diese Gruppen sich für eine höhere Versorgungssicherheit mit Strom einsetzen. Aufgrund der Bedeutung der prozessualen Dimension von Politik bewerte ich den Einfluss politischer Steuerung trotz der fehlenden Effekte der instrumentellen Energiewirtschafts- und Infrastrukturpolitik auf die Versorgungssicherheit mit Strom als sehr hoch.
Ich prognostiziere, dass die Privatisierung und Liberalisierung der Energiewirtschaft keinen feststellbaren Effekt auf die Versorgungssicherheit mit Strom haben werden. Erstens können angesichts der schlechten Qualität der Daten zur Quantifizierung der Versorgungssicherheit mit Strom nur große Effekte identifiziert werden. Auf einen substantiellen Effekt dieser Reformen gibt der im internationalen Vergleich fehlende Effekt der instrumentellen Energiewirtschaftspolitik aber keinen Hinweis. Zweitens erwarte ich aus der prozeduralen Konzeption des Energiesystems als selbstregelndes soziotechnisches System, dass mögliche substanzielle Effekte auf die Versorgungssicherheit mit Strom anderweitig über das System der Interessenvermittlung kompensiert würden. Drittens sehe ich keine wesentliche Veränderung der Interessengruppenstruktur durch die Privatisierung und Liberalisierung vormals staatlicher EVU unter dem Gesichtspunkt der Versorgungssicherheit mit Strom. Energieversorgungsunternehmen haben durch ihr natürliches Monopol im Bereich der Stromnetze geringe Anreize, der gesellschaftlichen Nachfrage nach einer preisgünstigen und zuverlässigen Stromversorgung zu entsprechen. Auch bei einer Entflechtung der Bereiche Stromerzeugung, ‑vertrieb und Netzbetrieb sind Strategien der Koexistenz die kosteneffizienteste Art der Interessenwahrnehmung, die auf einen Regulierungsrahmen hinwirken, der zuverlässigkeitssteigernde Investitionen des Netzbetreibers anregt und damit verbundene Kosten auf unorganisierte gesellschaftliche Gruppen abwälzt. Deshalb bedarf es unabhängig vom eigentumsrechtlichen Status der Elektrizitätswirtschaft einer staatlichen Korrektur der Anreizstrukturen.
View lessAll video coding standards of practical importance, such as Advanced Video Coding (AVC), its successor High Efficiency Video Coding (HEVC), and the state-of-the-art Versatile Video Coding (VVC), follow the basic principle of block-based hybrid video coding. In such an architecture, the video pictures are partitioned into blocks. Each block is first predicted by either intra-picture or motion-compensated prediction, and the resulting prediction errors, referred to as residuals, are compressed using transform coding. This thesis deals with the entropy coding of quantization indices for transform coefficients, also referred to as transform coefficient levels, as well as the entropy coding of directly quantized residual samples. The entropy coding of quantization indices is referred to as level coding in this thesis. The presented developments focus on both improving the coding efficiency and reducing the complexity of the level coding for HEVC and VVC. These goals were achieved by modifying the context modeling and the binarization of the level coding.
The first development presented in this thesis is a transform coefficient level coding for variable transform block sizes, which was introduced in HEVC. It exploits the fact that non-zero levels are typically concentrated in certain parts of the transform block by partitioning blocks larger than \square{4} samples into \square{4} sub-blocks. Each \square{4} sub-block is then coded similarly to the level coding specified in AVC for \square{4} transform blocks. This sub-block processing improves coding efficiency and has the advantage that the number of required context models is independent of the set of supported transform block sizes.
The maximum number of context-coded bins for a transform coefficient level is one indicator for the complexity of the entropy coding. An adaptive binarization of absolute transform coefficient levels using Rice codes is presented that reduces the maximum number of context-coded bins from 15 (as used in AVC) to three for HEVC. Based on the developed selection of an appropriate Rice code for each scanning position, this adaptive binarization achieves virtually the same coding efficiency as the binarization specified in AVC for bit-rate operation points typically used in consumer applications. The coding efficiency is improved for high bit-rate operation points, which are used in more advanced and professional applications.
In order to further improve the coding efficiency for HEVC and VVC, the statistical dependencies among the transform coefficient levels of a transform block are exploited by a template-based context modeling developed in this thesis. Instead of selecting the context model for a current scanning position primarily based on its location inside a transform block, already coded neighboring locations inside a local template are utilized. To further increase the coding efficiency achieved by the template-based context modeling, the different coding phases of the initially developed level coding are merged into a single coding phase. As a consequence, the template-based context modeling can utilize the absolute levels of the neighboring frequency locations, which provides better conditional probability estimates and further improves coding efficiency.
This template-based context modeling with a single coding phase is also suitable for trellis-coded quantization (TCQ), since TCQ is state-driven and derives the next state from the current state and the parity of the current level. TCQ introduces different context model sets for coding the significance flag depending on the current state. Based on statistical analyses, an extension of the state-dependent context modeling of TCQ is presented, which further improves the coding efficiency in VVC. After that, a method to reduce the complexity of the level coding at the decoder is presented. This method separates the level coding into a coding phase exclusively consisting of context-coded bins and another one consisting of bypass-coded bins only. For retaining the state-dependent context selection, which significantly contributes to the coding efficiency of TCQ, a dedicated parity flag is introduced and coded with context models in the first coding phase. An adaptive approach is then presented that further reduces the worst-case complexity, effectively lowering the maximum number of context-coded bins per transform coefficient to 1.75 without negatively affecting the coding efficiency.
In the last development presented in this thesis, a dedicated level coding for transform skip blocks, which often occur in screen content applications, is introduced for VVC. This dedicated level coding better exploits the statistical properties of directly quantized residual samples for screen content. Various modifications to the level coding improve the coding efficiency for this type of content. Examples for these modifications are a binarization with additional context-coded flags and the coding of the sign information with adaptive context models.
View lessProlongation of the light period causes photoperiod stress in plants. During the night following the prolonged light treatment, stress marker gene expression is induced, and stress hormones and ROS accumulate. The next day, the experienced strong photoperiod stress leads to the formation of water-soaked lesions in leaves and eventually programmed cell death ensues. In this study, the impact of light intensity and light quality on the photoperiod stress response has been investigated. A threshold light intensity of about 50 μmol m-2 s-1 was found to be necessary for the induction of photoperiod stress, hinting at the involvement of chloroplasts. Lower photoperiod stress symptoms in gun4, gun5, rcd1, and glk1 glk2 mutants revealed a possible role of retrograde signaling in photoperiod stress and corroborated the involvement of chloroplasts. Furthermore, starch and sugar content were higher in photoperiod stressed plants and starch biosynthesis mutants developed less photoperiod stress symptoms. This indicated that the starch and sugar metabolism might be affecting a plants’ response to photoperiod stress, strengthening the argument for the importance of chloroplast in photoperiod stress. Both monochromatic red and blue light caused a photoperiod stress response, but the response provoked by red light was stronger. Mutant analysis revealed the photoreceptors phyB and CRY2 as probable sensors of photoperiod stress. Among the downstream light signaling components, HY5 and PIF1 have demonstrated potential for involvement in sensing photoperiod stress. Although cry2 mutation did not rescue the strong photoperiod stress phenotype of cca1 lhy, some clock genes were differentially regulated in cry2. This indicates a possible involvement of CRY2 in photoperiod stress through its role in regulating the circadian rhythm. Overall, these results support that both plastid-dependent and photoreceptor-dependent signaling pathways are involved in sensing light conditions causing photoperiod stress and governing the response to it. Since co and ft tsf mutants demonstrated less photoperiod stress symptoms, participation of the photoperiodic flowering pathway in sensing and responding to photoperiod stress has been considered a possibility. Most ecotypes other than Columbia showed low sensitivity to photoperiod stress, suggesting that photoperiod stress sensitivity might be a rare trait in nature. The low photoperiod stress sensitivity of the F1 generation of crosses between Col-0 and some of the ecotypes that show low photoperiod stress sensitivity is evidence of the recessive nature of the photoperiod stress sensitivity trait.
View lessThe necessity to decrease greenhouse gas (GHG) emissions, mainly methane (CH4), is underscored in diverse national and international regulations and conventions. Agriculture, particularly livestock enteric fermentation and manure management, is a significant source of these emissions. In pig and dairy cattle farming, liquid-manure systems are the most prevalent and responsible for an upsurge in CH4 emissions. This study further investigates the potential of CH4 production from manure as a renewable energy source and an effective strategy to decrease GHG emissions, emphasizing the importance of better understanding the factors that regulate CH4 potential loss from manure storage. This study scrutinized the effect of storage conditions and changes in chemical composition on CH4 formation and emissions from dairy and fattening pig manure. Two different experimental techniques were designed to verify the influence of storage temperature on CH4 production and the effects of manure storage on biochemical methane production (BMP). In the first method, samples were stored without inoculum at varying temperatures, and CH4 production was measured. In pig manure stored at 25°C and 20°C, CH4 production amounted to 69.3% and 50.3% of the BMP, respectively. The highest CH4 production for dairy slurry were observed at 25°C but remained low. The production of CH4 in dairy manure was found to be inhibited during storage. The study suggested several potential reasons for this inhibition, though further research is recommended to confirm these hypotheses. The second set of experiments, evaluate the BMP of manure samples collected year-round from different stages on the manure storage in dairy cow and fattening pig farms. The findings indicated a 20.5% reduction in the BMP of dairy manure due to alterations in chemical composition during the transfer from the barn to outdoor storage. Similarly, there was a 39.5% drop in the BMP for samples of fattening pig manure in the transition from intermediate to outdoor storage. When examining BMP relative to the age of the manure, it was observed that pig manure decomposes quicker than dairy manure. Mathematical models were developed to predict BMP from the chemical composition, and the most effective predictors for each livestock category were identified. Improvements to predict BMP for less aged samples with reduced variability in their chemical compositions would be necessary. Overall, this study highlights the necessity of promptly transporting manure to either a biogas plant or outdoor storage facilities. Such measures can help prevent significant CH4 emissions and avoid a decrease in energy production capacity.
View lessEquines Asthma ist eine häufig vorkommende chronische Erkrankung der Atemwege und kann Pferde jeden Alters betreffen. Neben einer speziellen klinischen Untersuchung des Atemtrakts spielt die zytologische Untersuchung von Tracheobronchialsekret (TBS) und Bronchoalveolärer Lavage (BAL) eine wichtige Rolle bei der Diagnosestellung von equinem Asthma. Ziel dieser Arbeit war der Vergleich zytologischer Ergebnisse und Verdachtsdiagnosen zwischen und innerhalb verschiedener Labore, um die Zuverlässigkeit der zytologischen Untersuchung von TBS und BAL als diagnostisches Mittel zur Diagnosestellung von equinem Asthma zu überprüfen. Die Hypothesen dieser Arbeit waren die Annahmen, dass bei einem intra- und interindividuellen Vergleich zytologischer Ergebnisse von TBS und BAL innerhalb und zwischen mehreren Laboren nur eine geringe oder gar keine Varianz der Ergebnisse und Verdachtsdiagnosen besteht und die Zytologie als zuverlässiges Kriterium zur Atemwegsdiagnostik herangezogen werden kann. Als Studienpopulation standen 15 Pferde zur Verfügung, die zur Abklärung respiratorischer Symptome vorgestellt wurden. Zunächst wurden an allen Pferden Atemwegsuntersuchungen durchgeführt und schließlich die Befunde der klinischen, endoskopischen und zytologischen Untersuchung zur endgültigen Diagnosestellung in der Klinik herangezogen. Auf diese Weise erfolgte die Einteilung der Studienpferde in fünf gesunde, fünf Pferde mit mildem bis moderatem und fünf Pferde mit schwerem equinem Asthma. Im Anschluss erfolgte der Versand von luftgetrockneten Ausstrichen von TBS und BAL der Studienpferde an vier Fremdlabore. Zusätzlich wurden die Ausstriche durch zwei klinikinterne Untersucher beurteilt. Durch einen doppelt verblinden Versand der Proben untersuchte jedes Labor und jeder Untersucher zwei Mal die Proben des gleichen Pferdes. Bei den Ergebnissen der Fremdlabore fiel auf, dass die Angaben zur Differentialzellzählung der zytologischen Auswertung im TBS und in der BAL z.T. erhebliche Unterschiede aufwiesen. Zum einen wurden semiquantitative Angaben, zum anderen Prozentzahlen bei der Differenzialzellzählung angegeben. Um die interindividuelle Varianz der Ergebnisse verschiedener Labore zu ermöglichen, wurde ein vereinheitlichtes Scoring System zur zytologischen Befundung von TBS und BAL erarbeitet. Beim Vergleich der intraindividuellen Übereinstimmung der Ergebnisse innerhalb der Fremdlabore und der Untersucher der Klinik für Pferde konnte bestätigt werden, dass eine gute Übereinstimmung der Ergebnisse der neutrophilen Granulozyten bei fast allen Laboren in der BAL und im TBS erreicht wurde (ICC > 0,75, gewichtetes Kappa >0,6). Darüber hinaus erreichten die Labore, die Prozentangaben zur Differentialzellzählung machten bei Makrophagen, Lymphozyten, eosinophilen Granulozyten und Mastzellen ebenfalls einige gute Ergebnisse der Übereinstimmung. Die semiquantitativen Angaben resultieren in einer geringeren Reproduzierbarkeit der Ergebnisse zu den Zellarten der Differentialzellzählung innerhalb anderer Labore. Somit hatte die Art und Weise der zytologischen Auswertung Einfluss auf die Reproduzierbarkeit der Ergebnisse. Für die BAL variierten die Ergebnisse insgesamt weniger, sodass diese Probenart für validere zytologische Ergebnisse empfohlen wird. Beim interindividuellen Vergleich der Ergebnisse zwischen allen Laboren konnte ebenfalls eine gute Reproduzierbarkeit der Ergebnisse bei den neutrophilen Granulozyten in der BAL und im TBS erreicht werden (Krippendorff’s alpha >0,7). Diese Zellart hat den größten Einfluss auf die zytologische Diagnosestellung. Die Ergebnisse zu allen weiteren Zellarten der Differentialzellzählung variierten deutlicher zwischen den Laboren. Bei den lungengesunden Pferden wurde durch die Fremdlabore häufig mildes-moderates equines Asthma diagnostiziert. Bei den erkrankten Pferden wurde meistens equines Asthma diagnostiziert, allerdings variierte der Schweregrad der Erkrankung zwischen und innerhalb der Labore. Ein Labor stellte darüber hinaus bei einigen Pferden die Diagnose einer bakteriellen Bronchitis. Die Hypothese, dass die TBS- und BAL-Zytologie als zuverlässiges Kriterium zur Atemwegsdiagnostik herangezogen werden kann und einen wichtigen Teil der Diagnosestellung ausmacht, muss aufgrund von einigen intra- und interindividuellen Unterschieden der zytologischen Ergebnisse und bei den Verdachtsdiagnosen zwischen und innerhalb der Labore eingeschränkt werden. Die Unterschiede können z.T. auf die variable Auswertung der Proben zurückgeführt werden. Demnach kann geschlussfolgert werden, dass die zytologische Untersuchung nur zu einem kleinen Teil zur endgültigen Diagnosestellung herangezogen werden sollte und die klinischen Symptome den größten Einfluss auf die Diagnose und damit die weitere Therapie haben sollten. Ohne genaue Angaben der klinischen Symptome und des Vorberichts sind valide zytologische Diagnosen nur eingeschränkt möglich. Das Zusammenspiel aller Befunde sollte als Goldstandard für die Diagnosestellung gelten. Als Empfehlung sollte für valide zytologische Ergebnisse besonders bei Verlaufsuntersuchungen immer das gleiche Labor für die zytologische Auswertung herangezogen werden. Darüber hinaus besteht die Notwendigkeit einer einheitlichen zytologischen Beurteilung von TBS und BAL, um Ergebnisse zwischen verschiedenen Laboren vergleichen zu können. Als Vorschlag für eine vereinheitlichte Befundung soll das in dieser Studie erstellte Scoring System dienen, das in weiteren Studien seine Validität zeigen könnte.
View lessAls Enzephalitis bezeichnet man die Entzündung des Hirngewebes. Jedes Jahr werden etwa 1,5-20/100.000 Einwohner mit Verdacht auf Enzephalitis hospitalisiert. In den meisten Fällen kann keine Ursache identifiziert werden. Mehr als 100 verschiedene Viren können eine Enzephalitis verursachen. Die große Anzahl und Vielfalt der möglichen Erreger erschweren die Diagnostik. Die Routinediagnostik konzentriert sich daher in der Regel auf die häufigsten Erreger und wird gegebenenfalls iterativ erweitert, wenn die initialen Tests keinen Erreger nachweisen. Das (Wieder-)Auftauchen neuer und seltener Viren wird wahrscheinlich durch Faktoren wie Klimawandel, Entwaldung, Globalisierung und Urbanisierung weiter zunehmen und ist in den letzten Jahren durch die Zika-Virus-Ausbrüche in Lateinamerika, das Auftreten autochthoner West-Nil-Virus (WNV) Infektionen in Deutschland und die COVID-19-Pandemie eindrücklich belegt worden. Daher ist es wichtig, eine breite Diagnostik zur schnellen und zuverlässigen Identifizierung von Viren zu entwickeln. Diese muss in der Lage sein, bekannte Krankheitserreger, aber auch unbekannte oder ungewöhnliche, zum Beispiel reiseassoziierte Erreger, nachzuweisen. Das initiale Ziel dieser Arbeit war daher die Entwicklung einer Hochdurchsatz-Sequenziermethode mit möglichst kurzer Zeitspanne von der Probenentnahme bis zur Erreger-Identifikation. Dies ist von entscheidender Bedeutung für eine schnelle Diagnose, Behandlung und somit für das Überleben der Patienten. Mit dem etablierten Arbeitsablauf können die Ergebnisse innerhalb von drei Tagen nach dem Probeneingang bereitgestellt werden. Kritisch ist dabei die Erkennung klinisch relevanter Nachweise, die Abgrenzung von möglichen Virusnachweisen ohne ursächliche Bedeutung für die Enzephalitis sowie das Erfassen von Kontaminationen. Die hier etablierte Methode wurde bei der retrospektiven Untersuchung von 1676 Liquorproben von Enzephalitis-/Meningitis-Patienten ungeklärter Ursache angewendet und in der Routinediagnostik angewendet. Bei den untersuchten Personen wurden bereits bekannte Infektionen festgestellt, aber auch zahlreiche seltene, zuvor nicht diagnostizierte Erreger. Dazu gehören ein humanes Cosavirus bei einem Kind mit akuter schlaffer Lähmung und ein Dobrava-Belgrad-Hantavirus im Liquor eines Patienten mit Enzephalitis. Besonders erwähnenswert sind der mehrfache Nachweis des Hepatitis-E-Virus (HEV), die Identifikation zuvor unbekannter WNV-Infektionen und der Nachweis von humanen Pegiviren (HPgV) im zentralen Nervensystem (ZNS) bei Patienten mit Enzephalitis. Die Etablierung von Methoden zur Vollgenomsequenzierung und der mehrfache Nachweis von HEV und HPgV in ZNS-Proben ermöglichten eine vertiefende Untersuchung dieser Erreger. So wurde die Virus-Diversität in einer chronischen HEV-Infektion mit neurologischen Symptomen untersucht. Dabei konnten distinkte virale Populationen in verschiedenen Kompartimenten festgestellt werden. Diese zeigten eine unterschiedliche Komposition von Mutationen, die zuvor im Zusammenhang mit einer Ribavirin-Resistenz beschrieben wurden. Ausgelöst durch WNV-Nachweise in der retrospektiven Kohorte wurde ein weiteres Ziel dieser Dissertation definiert: Die Untersuchung der Rolle des WNV bei Berliner Enzephalitis-Fällen. Nach dem Auftreten erster WNV-Fälle bei Vögeln in Deutschland war es wichtig zu verstehen, ob es sich bei humanen Fällen um reiseassoziierte oder lokal erworbene Infektionen handelt. Zu diesem Zweck wurden verschiedene Strategien für die Vollgenomsequenzierung entwickelt. In dieser Dissertation wurden insgesamt 13 menschliche WNV-Fälle untersucht. Eine phylogenetische Studie zeigte eine enge Verwandtschaft zwischen den WNV-Sequenzen von Menschen, Vögeln sowie Stechmücken. Dies deutet darauf hin, dass sich in Berlin eine isolierte und stabile WNV-Population etabliert hat. Die serologische Untersuchung von 105 Freiwilligen aus einer Kleingartenkolonie führte zur Entdeckung einer weiteren möglichen WNV-Infektion. Da WNV nur in etwa 1% der Fälle neurologische Symptome hervorruft, ist auf Grundlage unserer Nachweise im Liquor davon auszugehen, dass es eine hohe Zahl nicht diagnostizierter Infektionen in Berlin gibt. Ausgelöst durch den häufigen Nachweis von HPgV im Liquor stellte sich die Frage nach deren Bedeutung als Auslöser einer Enzephalitis. Humane Pegiviren wurden bisher nicht mit einer Erkrankung in Verbindung gebracht. Sie wurden aber in den letzten Jahren vereinzelt in Liquorproben von Enzephalitis-Patienten nachgewiesen. Analysen der Virusdiversität zeigten das Vorhandensein von Viruspopulationen in verschiedenen Kompartimenten und somit eine unabhängige Replikation im ZNS. Intensive Untersuchungen zeigten einen anhaltenden Nachweis von HPgV-RNA im Serum und Liquor über teilweise mehr als einem Jahr und führten zur Klassifizierung des Bildes einer HPgV-Enzephalitis. Die Sensitivität der etablierten Hochdurchsatz-Sequenziermethode ist fast mit der einer quantitativen Polymerase-Kettenreaktion vergleichbar. Aufgrund der zeitnahen Ergebnisse des nicht-zielgerichteten Arbeitsablaufs könnte der Einsatz dieser Methodik die Diagnostik in Zukunft erheblich erleichtern und weitere Daten zum Tropismus verschiedener Erreger bereitstellen. Eine verbleibende Herausforderung bleibt aber die Frage der Qualitätssicherung einer solchen breiten Diagnostik. Es stellt sich besonders die Frage nach der klinischen Signifikanz bei der Detektion einzelner Viren.
View lessWith its significant contribution to sociology, political science, and critical race theory, this doctoral research addresses two sets of questions by unfolding two contrasting discourses about race and racism, as it took place in the USA. What defines the dominant interpretation of race-related injustice in the USA? What are the shortcomings of the hegemonic view of social justice in the 1954-1968 Civil Rights Era to remedy injustice entangled with racial discrimination? Drawing on those two questions, the dissertation seeks to grasp two understandings of injustice in the color line and its historical and critical repercussions in public spheres. The first view, the so-called race liberalism, consolidates as the hegemonic standpoint along segments of the Civil Rights movement and subsequent legislation in the 1954-1968 civil rights era. It furnishes numerous channels and actors, such as government institutions, educational systems, and media platforms, with the ideological contours of the interpretation of the causes of the problem of the color line and the institutional problem-solving to injustices and inequalities. In short, race liberal view shapes the blueprint for laws and social engineering responsive to the demands of the Civil Rights Movement segments in the United States. Race Liberalism mesmerizes policy-making with political implications on the normative compass and policy-making strategies put into practice in the 1954-1968 Civil Rights Era to remedy race-related injustice. Contrasting to that belief, a philosophical trait present in radical black visions spells out racism interwoven with capitalist exploitation whose economic injustices insistently harm racial and ethical groups. The opposing discourse of black radical visions from social movements and political activism carried out by the Black Panthers up to organic intellectuals of the Critical Race Theory views racism as a far more complicated matter amalgamated with other inequalities in the existing social stratification. The radical view challenges disentailing racism from complex structures at the bottom of a web of existing institutions, the economy, and social and cultural practices. The radical vision of revolutionary sectors in social movements and academia sets up to critically reevaluate consolidated patterns in the US American understanding of the legitimate democratic organization and fair economic structures and prompt emancipatory thinking and social changes for racial and ethnic minorities. This doctoral research seeks to develop a 'descriptive overview' that provides a comprehensive and detailed account of two discursive matrixes about racism and a 'normative conceptualization' that offers a theoretical framework for understanding and critiquing these discourses. These critical theories of race and racism prompt social critique and paradigmatically point towards a blueprint to tackle racism and interrelated injustices. Initially, it outlines a social and historical analysis of how pervasive injustices and inequalities harm Blacks and Browns. Furthermore, this dissertation aims to underline the normative force of counter-discourse critical race theories, pinpointing a few elements in the making of countervailing public spheres. In this spirit, it stresses how the powerful spirit of critique of racial hierarchy has endured the hegemonic ideology of race liberalism in distinct channels within civil society and political activism and electrifyingly reanimates political debate today. This doctoral study draws on the unfolding of these two contrasting discourses and their implications for understanding and envisioning problem-solving for the problem of the color line: Race liberalism and radical black visions or critique of racial hierarchy. The dissertation proceeds in three parts. Each, in its turn, draws on how these two discursive matrixes – race liberalism and critique of racial hierarchy –, despite their 'heterogenous inflections' which refer to the various interpretations and applications of these discourses, have shaped distinct views of the permanence of inequality allocated in racial and ethical groups and the perceptions of foundational institutions in coping with the crucial matter of injustices tied with race in the US. The first part (Chapters 1-2) concentrates on the conceptual presuppositions and political implications underlying the hegemonic view and the critique of how racial differentiation has been crucial in configuring the existing social stratification and hierarchy in the racial line. The conceptual distinctions are essential for the discursive landscape in civil-rights policy-making and radical visions of the quest for equal citizenship and black liberation. The second part (Chapters 3-4) outlines race-sensitive affirmative programs as a problem-solving ideal and equity-enhancing policy in higher education. It revises the normative presuppositions and the moral and legal disputes underlying race-based college admissions to shed light on how the hegemonic view illustrated in the Bakke landmark decision (1978) and reiterated by many liberals (Chap. 4) has favored market-led interests to the detriment of members of racialized and ethnic minorities. Finally, the third part (chapters 5-7) spells out critical race theories in challenging the dominant race liberal view and pinpointing the normative force of countervailing public spheres in two directions: (i) by raising awareness of the intricacies of racism in institutional, structural and systemic levels and by urging public spheres to rethink the problem of the color line today; (ii) concurrently, as elaborated by radical visions in organic practices of intellectual activities and social movements, by reassessing resources far beyond legal entitlements to reach feasible social mobility and empowerment in redesigning alternatives to cope with the pervasive problem of inequality in the color line. These findings hold the potential to inspire transformative change in our understanding and approach to racial inequality. Critical Race scholarship elaborates a rich conceptual framework to examine the range of intersecting forces and dynamics reproducing race-related disadvantages that operate through entrenched values and political economy within the liberal system. More significantly, for this doctorate's normative purpose and appreciation of the political effects of the unfolding of counteracting discourse, the last chapters stress how the social critique of critical race theories gives vigor to diverse public spheres in ongoing attempts to contest the current status quo in matters about race and beyond. With its rigorous and comprehensive approach, this research calls attention to how critical race theories have been organically tied with political engagement to encourage discursive practices about the hegemonic explanation of racial matters and race-based policies in the US and abroad.
View lessThis thesis introduces the novel hybrid algorithm DisCOptER for globally optimal flight planning. DisCOptER (Discrete-Continuous Optimization for Enhanced Resolution) com- bines discrete and continuous optimization in a two-stage approach to find optimal trajectories up to arbitrary precision in finite time. In the discrete phase, a directed auxiliary graph is created in order to define a set of candidate paths that densely covers the relevant part of the trajectory space. Then, Yen’s algorithm is employed to identify a set of promising candidate paths. These are used as starting points for the subsequent stage in which they are refined with a locally convergent optimal control method. The correctness, accuracy, and complexity of DisCOptER are intricately linked to the choice of the switch-over point, defined by the discretization coarseness. Only a sufficiently dense graph enables the algorithm to find a path within the convex domain surrounding the global minimizer. Initialized with such a path, the second stage rapidly converges to the optimum. Conversely, an excessively dense graph poses the risk of overly costly and redundant computations. The determination of the optimal switch-over point necessitates a profound understanding of the local behavior of the problem, the approximation properties of the graph, and the convergence characteristics of the employed optimal control method. These topics are explored extensively in this thesis. Crucially, the density of the auxiliary graph is solely dependent on the en- vironmental conditions, yet independent of the desired solution accuracy. As a consequence, the algorithm inherits the superior asymptotic convergence properties of the optimal control stage. The practical implications of this computational efficiency are demonstrated in realistic environments, where the DisCOptER algorithm consistently delivers highly accurate globally optimal trajectories with exceptional computational efficiency. This notable improvement upon existing approaches underscores the algorithm’s significance. Beyond its technical prowess, the DisCOptER algorithm stands as a valuable tool contributing to the reduction of costs and the overall enhancement of flight operations efficiency.
View lessPolymeric Core-Multishell-Nanocarriers (CMS) are a family of molecules designed to function as universal drug carriers. Their architecture resembles unimolecular micelles/liposomes, with shell-like, hydrophobic, and hydrophilic domains. Studies using ex vivo/in vitro conditions have shown that they can be used to topically deliver drugs to the skin, including strongly hydrophobic drugs in water-based formulations. Interestingly, these studies reported that CMS not only successfully delivered cargo substances, but in fact increased their concentrations in the target area, the viable skin. Along with the relatively good biocompatibility reported, these properties make them interesting as tools for the treatment of inflammatory skin conditions and other topical applications. The work described here is part of a project that aimed to reproduce and further investigate these findings under conditions of inflammatory skin diseases in vivo. The project was part of a Collaborative Research Center of the German Research Foundation that aimed to develop and investigate a range of nanocarriers for topical delivery to the skin. The specific CMS architectures investigated here were hPG-C18-mPEG CMS (C18CMS) as well as hPG-PCL-mPEG CMS (bCMS). Both architectures have been developed at the Institute of Chemistry and Biochemistry, Freie Universität Berlin. C18CMS represent the prototypical CMS architecture, best characterized for topical delivery. bCMS are easily cleaved by esterases to improve long-term biocompatibility. As a model for a prototypical inflammatory skin condition, an oxazolone-induced mouse model with characteristics of atopic dermatitis (AD) was used. The cargo investigated was tacrolimus (TAC). TAC is a potent anti-inflammatory drug and one of the two main pharmacological treatment options for AD. With a relatively large molecular mass of 822 Da, it is considered at the threshold of substances that can penetrate into the skin in relevant amounts for topical treatment. In the first part of the project, the penetration of C18CMS into the skin, their potential systemic distribution, and the effect of oxazolone-induced inflammation on the penetration were investigated by fluorescence microscopy. Furthermore, the potential effects of the carriers on clinical and histological parameters were evaluated. In the second part of the project, the delivery of TAC by bCMS into inflamed skin, resulting systemic drug concentrations, as well as the clinical and histologic anti-inflammatory efficacy, were investigated. Under the conditions used, bCMS did not seem to increase the skin concentrations of the cargo drug in the viable skin compared to the standard ointment formulation. What is more, concentrations measured in the systemic circulation were significantly lower. This in fact suggests that bCMS decreased overall skin penetration. This differs from previous reports obtained using ex vivo/in vitro conditions, which consistently found penetration enhancement for TAC in bCMS and for various other cargo substances in multiple CMS architectures. Nevertheless, drug delivery to the skin and the anti-inflammatory efficacy of the formulation could be demonstrated. Although C18CMS penetrated into the stratum corneum, no penetration was observed into the viable layers of healthy skin. This penetration behavior of the carrier was not affected by oxazolone-induced dermatitis. The same was observed for bCMS in inflamed skin. These results seem to be partially in line with previous ex vivo/in vitro results under certain conditions, such as relatively short incubation times and relatively mild barrier alterations but differ from results under other conditions, such as longer incubation times and models of more severe barrier alterations. When modeling complete penetration of C18CMS through the viable skin, the fluorescently labeled carriers were found in the main sites of the mononuclear phagocyte system and particle clearance, i.e., the local lymph nodes, spleen, lung, liver, and kidney. No adverse effects were observed histologically. Overall, the results seem to confirm that CMS can be used for topical delivery and treatment of inflammatory skin conditions with TAC. However, CMS may not necessarily enhance penetration or efficacy. Moreover, the results suggest a potential systematic difference between ex vivo/in vitro and in vivo conditions. On the one hand, this cautions that murine models may be unsuitable to investigate the penetration enhancement effect of CMS. On the other hand, it suggests parameters that could potentially be optimized in ex vivo/in vitro models to increase predictability. Of these, particularly relevant parameters seem to be incubation times, exposure periods with subsequent removal of formulations, occlusion/hydration status, effects of repeated applications, steady-state conditions and drug depots, effects that depend on tissue layers other than the stratum corneum, and time-resolved kinetics. This may be particularly important when comparing water-based, volatile formulations with less volatile ointment formulations, and for drugs with comparatively high steady-state concentrations in the skin. With respect to the 3R principles, the results strongly suggest that no further in vivo studies should be performed to investigate the penetration enhancement effects of CMS or similar delivery solutions before 1.) a systematic analysis has shown what caused these discrepancies, 2.) all relevant aspects discussed have been modeled in vitro for the specific nanocarrier-drug combination in question, and 3.) an evidence-based estimate is available on whether the expected penetration enhancement would lead to a relevant benefit for the specific use case.
View lessLithium-sulfur (Li-S) batteries have the potential to become one of the energy storage systems of the future due to their ability to store significantly more energy than current battery types today. Furthermore, sulfur is an abundant element that is cheap and environmentally friendly in its processing, making it an optimal material for sustainable energy systems. However, this type of battery also has some disadvantages, mainly related to the sulfur-containing cathode. This dissertation comprises the results of three research projects that investigated the structural and electronic properties of a polymer-based cathode material. The individual studies employ a combination of different theoretical multiscale ap- proaches, which are further compared and discussed with experimental measurements. In the first project, the novel fabrication route for the polymer cathode, which combines the processes of electro-polymerization and vulcanization, is presented. The structural evolution of the material during the synthesis is theoretically rationalized, and experiments show that using this material helps to overcome the typical problems associated with Li-S batteries. The second project focuses on the structure of the vulcanized polymer representing the initial stage of a charged cathode. A combination of electronic structure theory and statistical mechanics is used to bridge between the microscopic description of the vulcanization of polymer and sulfur and the derivation of the macroscopic properties of the cathode. This study reveals that the electronic stability on a microscopic level most likely leads to a sulfur cross-linking of neighboring polymer chains, which is experimentally supported. Furthermore, we find that the extent of cross-linking on a macroscopic scale can be controlled by the amount of sulfur and the temperature during vulcanization. The third project covers the interplay between the polymer’s structural morphology and its electronic properties. Here, we focus on the influence of regiochemistry on the polymer’s aggregation behavior and charge transport. A multiscale approach comprising classical molecular dynamic simulation, electronic band structure calculations, and statistical charge transport theory demonstrates the polymers’ ability to form well-ordered crystalline phases, allowing fast charge transport. The comparison of experimental and simulated X-ray diffractograms confirms the presence of crystalline phases in the electro-polymerized polymer. Overall, this thesis’s findings help advance the understanding of a polymer material in the context of its application as a Li-S battery cathode. Furthermore, this work demonstrates the benefit of using multiscale approaches to investigate such a system’s structural and electronic properties.
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