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Dynamics of Surface Catalytic Reactions on TiO2
No full textThis thesis addresses the findings of two projects in the field of photocatalysis on TiO2 single crystal-based model catalysts under ultra-high vacuum (UHV) conditions.
The first concerned the dynamics of the CO photo-oxidation to CO2 on rutile TiO2(110) measured by time-resolved photoelectron spectroscopy at the free-electron laser (FEL) FLASH in Hamburg. For this pump-probe experiment, a laser of 770 nm served as an optical pump to initiate the reaction, and the third harmonic of the FEL with a photon energy of 643 eV probed the O 1s, Ti 2p, and C 1s core levels. The formation of CO2 by CO oxidation was observed within the first 800 ± 250 fs after the reaction was initiated. Calculations using density functional theory propose that the oxygen activation pathway for CO oxidation via an O2-TiO2 charge transfer complex can be directly excited by a 770 nm pump laser. During the reaction, residual traces of water in the UHV environment occupy CO adsorption sites, hindering further CO2 formation. Compared to the anatase-TiO2(101) surface, oxygen is activated via the same mechanism. Interestingly, CO2 is formed more quickly on rutile (110) and remains on the surface for a shorter time, which indicates a shorter lifetime of the charge carriers that initiate the reaction. These findings are important for the design of photocatalysts.
The second project addresses the influence of the localized surface plasmon resonance of TiO2(110) supported Au nanoparticles (NPs) on the oxidation of CO. Gold NPs with diameters between 2 to 12 nm were grown via molecular beam epitaxy under UHV conditions on stoichiometric rutile TiO2(110) single crystal substrates. The samples were characterized via scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and X-ray reflectivity (XRR). The oxidation of (preadsorbed) CO at 95 K under O2 atmosphere was monitored by X-ray photoelectron spectroscopy (XPS). The oxidation was found to be fast and efficient on small 3 nm Au nanoparticles grown at room temperature, as 90 % of the CO molecules were converted into CO2 within 40 minutes.
On larger nanoparticles grown at 500 °C with median diameters between 4.5 to 6 nm, the amount of pre-adsorbed CO was significantly lower due to the decrease in surface area in large particles. Further experiments under UV and 530 nm light illumination were carried out to excite the local surface plasmon resonance (LSPR), resulting in higher and faster CO to CO2 conversion rates compared to dark conditions. To increase the amount of preadsorbed CO, the TiO2 supported Au nanoparticles were overgrown with Pt. Nominal coverages above one monolayer Pt were found to enable room temperature CO adsorption. Room temperature CO oxidation on Pt-Au/TiO2 was then measured in a 1·10−6 mbar O2 atmosphere with 0.5 and 1 L preadsorbed CO. Under 530 nm and in dark conditions, CO oxidation was observed for 0.5 L, but not for 1 L CO. Coverages resulting from 1 L CO exposure block all adsorption sites, leading to the self-poisoning of the catalyst. When the Pt-Au/TiO2 sample is heated, Pt segregates into the subsurface due to its higher surface free energy compared to Au.
The findings provide insight into the influence of preparation parameters on the (photo-) catalytic CO oxidation on Au/TiO2 and Pt-Au/TiO2 as preparation temperature and size. This project is followed up by a time-resolved CO oxidation experiment at the FEL FLASH, for which the insight into the influence of preparation parameters on the light-induced catalysis is of importance.Für diese Dissertation wurden zwei Projekte im Bereich der Photokatalyse an TiO2-Einkristall-Modellkatalysatoren durchgeführt.
In dem ersten Projekt wurde die Dynamik der CO-Photooxidation zu CO2 auf Rutil-TiO2(110) mittels zeitaufgelöster Photoelektronenspektroskopie am Freie-Elektronen-Laser (FEL) FLASH in Hamburg untersucht. In diesem Pump-Probe-Experiment wurde die Reaktion mit einem 770-nm-Laser initiiert, während die dritte Harmonische des Freie-Elektronen-Lasers (FEL) mit einer Photonenenergie von 643 eV zur Anregung der O 1s-, Ti 2p- und C 1s-Kernniveaus diente. Die Bildung von CO2 durch CO-Oxidation wurde innerhalb der ersten 800 ±250 fs nach Reaktionsbeginn beobachtet. Berechnungen auf Basis der Dichtefunktionaltheorie legen nahe, dass der Sauerstoffaktivierungsweg für die CO-Oxidation über einen O2-TiO2-Ladungstransferkomplex direkt durch den 770-nm-Pumplaser angeregt wird. Während der Reaktion blockiert Wasser, das in Spuren in der UHV-Umgebung vorkommt, die CO-Adsorptionsstellen, was die weitere CO2-Bildung behindert. Genau wie bei der Anatas-TiO2(101) Oberfläche wird Sauerstoff durch den gleichen Mechanismus aktiviert. Interessant ist, dass CO2 auf Rutil (110) schneller gebildet wird und kürzer auf der Oberfläche verbleibt, was auf eine geringere Lebensdauer der Ladungsträger, die die Reaktion initiieren, hinweist.
Das zweite Projekt untersucht den Einfluss der lokalisierten Oberflächenplasmonresonanz von TiO2(110)-geträgerten Au-Nanopartikeln auf die lichtinduzierte CO-Oxidation. Goldnanopartikel mit Durchmessern zwischen 2 und 12 nm wurden mittels Molekularstrahlepitaxie unter UHV-Bedingungen auf stöchiometrischen Rutil-TiO2(110) Einkristallsubstraten aufgewachsen. Die Proben wurden mittels Rastertunnelmikroskopie (STM), niederenergetischer Elektronenbeugung (LEED) und Röntgenreflektivität (XRR) charakterisiert.
Die Oxidation von voradsorbiertem CO bei 95 K unter O2-Atmosphäre wurde mittels Röntgenphotoelektronenspektroskopie (XPS) verfolgt. Es zeigte sich, dass die Reaktion auf 3 nm großen Au-Nanopartikeln, die bei Raumtemperatur gewachsen wurden, besonders schnell und effizient verlief. Innerhalb von 40 Minuten wurden 90 % des CO in CO2 umgewandelt. Auf größeren Nanopartikeln mit mittleren Durchmessern von 4.5 bis 6 nm, die bei 500 °C gewachsen wurden, war die Menge des voradsorbierten CO aufgrund zunehmend bulk-ähnlicher Eigenschaften signifikant geringer. Experimente unter 530-nm-Licht zur Anregung der lokalen Oberflächenplasmonresonanz (LSPR) und unter UV-Licht zeigten eine schnellere Umwandlung von CO zu CO2 im Vergleich zu dunklen Bedingungen.
Um die Menge des voradsorbierten CO zu erhöhen, wurden die auf TiO2-geträgerten Au-Nanopartikel mit Pt überwachsen. Eine nominale Bedeckung von mehr als einer Monolage Pt ermöglichte die CO-Adsorption bei Raumtemperatur. Die CO-Oxidation auf Pt-Au-TiO2 wurde bei Raumtemperatur unter O2-Atmosphäre mit 0.5 L und 1 L voradsorbiertem CO untersucht. Unter 530-nm-Bestrahlung sowie unter dunklen Bedingungen wurde eine CO-Oxidation für 0.5 L, jedoch nicht für 1 L CO beobachtet. Eine Bedeckung durch 1 L CO blockiert alle Adsorptionsstellen, was zu einer Inaktivierung des Katalysators führt. Beim Erhitzen der Pt-Au-TiO2-Probe segregieren Pt-Atome aufgrund der höheren freien Oberflächenenergie im Vergleich zu Au in die Nanopartikel und Au-Atome an die Oberfläche. Dieses Projekt wird durch ein zeitaufgelöstes CO-Oxidationsexperiment am Freie-Elektronen-Laser FLASH fortgeführt, bei dem das Verständnis des Einflusses von Präparationsparametern auf die lichtinduzierte Katalyse von entscheidender Bedeutung ist
Rigid Convolution Structures
No full textA monoidal category is called a convolution monoidal category if it arises from linearizing a 2-Segal space. The goal of this thesis is to study for which 2-Segal spaces the induced convolution monoidal category is a multi-fusion category.
With this aim, we show that multi-fusion categories admit an intrinsic description as rigid algebras in the symmetric monoidal 2-category of C-linear additive categories. We use this observation to define, by analogy, a derived version of a multi-fusion category as a rigid algebra in the symmetric monoidal (infinity,2)-category of stable infinity-categories. We show that examples of these arise as derived categories of multi-fusion categories and as categories of modules over smooth and proper E2-algebras.
Afterward, we show that rigid algebras in the (infinity, 2)-category of spans are precisely given by those 2-Segal objects that are Čech-nerves. Together with our previous result, we use this to provide an answer to our initial question. To prove this result, we provide a description of bimodules in the infinity-category of spans as birelative 2-Segal objects. Furthermore, we introduce a notion of morphism between birelative 2-Segal objects that extends this classification to an equivalence of infinity-categories.
We use this classification to construct examples of convolution monoidal structures that form derived multi-fusion categories and discuss some aspects of the associated fully extended TFTs. We finish by studying Grothendieck–Verdier-structures on convolution monoidal infinity-categories and by comparing them with rigid dualities
Beyond Plastic Degradation: Microbial Sensing and Response of Vibrio sp. to PET Breakdown Products within the Plastisphere
No full textPlastic production and the resulting waste significantly threaten the environment and numerous ecosystems. Due to increasing production rates, global plastic pollution is also rising rapidly.
Plastic particles accumulate in a wide range of habitats, and nowadays are found all around the globe. These particles are rapidly colonized by diverse microorganisms. While microbial colonization offers potential advantages, such as contributing to plastic degradation, it also presents risks, particularly due to the accumulation of potentially pathogenic bacteria on plastic surfaces. Another major consequence of microbial colonization is biofouling, where bacteria adhere to plastic materials, used in various industries, leading to surface damage and reduced material durability.
This thesis encompasses three chapters. In chapter one, this study gives for the first time insights into molecular keys, involved in Vibrio gazogenes polyethylene terephthalate (PET) colonization and subsequent polymer degradation, using deep transcriptomics, advanced imaging analyses and analytic technologies. The first part of the study focuses on the analysis and transcriptional profiling of the PET6 gene expression. PET6 is a recently discovered PETase in the marine bacterium Vibrio gazogenes DSM 21264. Within 24 hours of incubation, degradation products such as bis(2-hydroxyethyl) terephthalate (BHET), mono(2-hydroxyethyl) terephthalate (MHET) and terephthalic acid (TPA) were detected, when DSM 21264 was incubated with PET foil or powder. For a deep understanding of bacterial response in the presence of PET and its degradation products BHET and TPA, focusing on the transcription of the pet6 gene, multiple RNAseq approaches were conducted. Further, a number of natural substrates like chitin and cellulose were used, to study the response of DSM 21264 and its gene expression profile.
Interestingly, the incubation of DSM 21264 in biofilm condition on PET vs PE surface or planktonic samples with PET powder did not increase the transcription of the pet6 gene. Highest transcription, however, was detected in planktonic samples, supplemented with BHET. Notably, the intermediate BHET significantly influenced bacterial gene expression on a global level by disrupting key signaling systems like quorum sensing (QS), c-di-GMP and CRP-cAMP signaling pathway. Using these second messenger bacteria adapt to their environment, regulating numerous metabolic pathways. This resulted in failure to form biofilms, altered colony morphology, and inhibited the biosynthesis of the red pigment prodigiosin. These findings imply that microbial and enzyme driven plastic degradation and the generated metabolites, thereby, may not only serve as carbon sources but also as potential signaling molecules.
Furthermore, with this work I provided evidence that UlaG, which has been described as a highly promiscuous esterase, involved in ascorbate metabolism under anaerobic conditions, plays a significant role in BHET degradation. The transcription was 7.9-fold upregulated in the presence of BHET, and biochemical tests using recombinant UlaG verified that the Vibrio gazogenes UlaG is involved in BHET metabolism. Further work will have to evaluate its role in the plastisphere.
In the second chapter, the colonization behavior of the Gram-negative bacterium Kaistella jeonii, native host of PET 30, was observed on PET surface, using Laser scanning microscopy (LSM). Kaistella jeonii is a member of the phylum Bacteroidetes and wide spread in nature. It plays an important role in the plastisphere. Thereby, my imaging analyses contributed to the characterization of the first PET-degrading enzymes from the phylum Bacteroidetes.
In chapter three, Vibrio campbelli, a pathogenic member of the plastisphere, was analyzed on treated and untreated polyethylene (PE) foils with the aim to prevent biofouling. A novel surface treatment with poly-N-oxides grafted onto PE surface revealed significantly less bacterial colonization.
Altogether, this study investigated for the first the influence of PET degradation products on the microbial community of the plastisphere, and offers solutions towards biodegradation and biofouling
Broadening Views on Adolescents’ Personalities: Investigating Construct Clarity, Intertwined Developments, and (Mal)adjustment
No full textAdolescence is characterized by profound biological, psychological, and social changes that come with increased opportunities for personal growth but also potential vulnerabilities. Against this backdrop, different personality characteristics and their developments may provide valuable insights into how adolescents differ in their adjustment to these changes. People’s personalities—the entirety of characteristics that make up someone’s style of thinking, feeling, and behaving—have long been recognized as a key factor in understanding human development and functioning. Over the years, most researchers have adopted a dynamic perspective, viewing personality as a complex, evolving system that is not only influenced by genetic and environmental influences but is also inherently shaped by interactions among its components. This perspective raises important questions about how personality is organized, how different personality characteristics develop compared to and in relation to one another, and how they might complement each other in contributing to people’s psychosocial (mal)adjustment. Given that adolescence is a central period of personality (re-)organization, it provides a unique developmental context to investigate these questions. Building on theoretical considerations from the fields of developmental, personality, and clinical psychology and integrating them under three overarching principles from lifespan psychology, this dissertation aimed to explore how the simultaneous consideration of different personality characteristics informs three global research aims: First, to increase our understanding of less established personality characteristics by localizing them in the nomological network of other, more widely studied characteristics (multidimensionality). Second, to investigate the developments of different personality characteristics on their own and in relation to each other (multidirectionality). And third, to assess how personality characteristics might complement each other in their predictive effects on psychosocial (mal)adjustment across different life domains (multifunctionality). To address these aims, this cumulative dissertation comprises three preregistered studies, drawing on data from four adolescent samples (individuals aged between 14 and the early twenties) that provide insights into the development of three groups of personality characteristics and different indicators of psychosocial (mal)adjustment. All studies focused on one of the following personality characteristics or a combination of them: The Big Five personality traits, general self-esteem, or multidimensional perfectionism.
Aiming for construct clarity of a newly proposed conceptualization of perfectionistic strivings, Study I focused on the nomological networks of striving toward perfection vs. excellence in adolescence. Using structural equation modeling, this study investigated differential cross-sectional associations of striving toward perfection vs. excellence with the Big Five traits and self-esteem. Study II focused on the intertwined developments among personality characteristics, specifically between each Big Five trait and self-esteem, while also examining their respective interindividual stabilities. I used continuous time modeling to investigate rank-order stabilities and the developmental interplay between each Big Five trait with self-esteem in a time-sensitive manner. Further, this study extended rater-perspectives and compared results from adolescents’ personality self-reports to results derived from other-reports. Finally, Study III adopted a longitudinal perspective on striving toward perfection vs. excellence, using latent-growth curve modeling and cross-lagged panel modeling, to examine stability and change of the different strivings and investigate their longitudinal interplays with indicators of psychosocial maladjustment across three central life domains (i.e., school, social relationships, and mental health). Moreover, this study aimed to investigate potential mediating processes within these interplays by considering the role of perfectionistic concerns.
Together, the three studies offer nuanced insights into the development and functioning of adolescents’ personalities. The findings support the conceptual distinction between striving toward perfection and striving toward excellence and demonstrate their differential associations with the Big Five and self-esteem. Further, personality characteristics exhibit moderate to high rank-order stability during adolescence, yet also change and interact in meaningful, temporally sensitive ways. Specifically, reciprocal associations were found between certain Big Five traits and adolescents’ self-esteem, underscoring the dynamic interplay of different personality characteristics during this time of life. Finally, no longitudinal effects of striving toward perfection or excellence across different indicators of psychosocial maladjustment were observed. Theoretically, the key findings from this dissertation extend the multidimensional, multidirectional, and multifunctional principles of lifespan psychology by specifying how specific personality characteristics develop and function during adolescence. This dissertation further emphasizes the need to incorporate (developmental) timing and the intertwinement of personality characteristics to broaden our understanding of personality in adolescent (mal)adjustment. Methodologically, the use of continuous time modeling and multi-informant data highlights the value of fine-grained, temporally sensitive, and cross-perspective approaches. Future research should integrate multiscale, person-centered designs to explore how short-term personality dynamics accumulate into long-term developmental outcomes
Die Rolle der Typ-II-Immunität im Wachstum und in der Differenzierung intestinaler epithelialer Zellen
No full textRole of the C-type lectin receptor MINCLE in recognition of Strongyloides ratti and initiation of anti-helminth immune responses
No full textStrongyloides ratti is a parasitic nematode with tissue migrating and intestinal life stages. Recognition of pathogens and initiation of immune responses is promoted by interaction between pattern-recognition-receptors (PRRs) on immune cells and pathogen-associated-molecular-patterns (PAMPs) present on the parasite. Screening a crude S. ratti-derived protein lysate against a library of C-type lectin receptors (CLR), an ancient family of PRR, we found that Macrophage-inducible-C-type lectin receptor (MINCLE) binds immobilized S. ratti lysate and activates a MINCLE expressing reporter cell line. As this suggests presence of agonistic MINCLE-ligands in the S. ratti lysate, we analysed a putative function for MINCLE in vivo. Strikingly, MINCLE-deficient (KO) mice displayed reduced intestinal S. ratti parasite burden compared to their wildtype (WT) mice, suggesting an improved and not the expected impaired host defence in the absence of a stimulating PRR. To elucidate, which effector cell expressing MINCLE might be responsible for this protective immunity, we show that eosinophils and neutrophils represent the dominant MINCLE expressing cell population in vivo. Comparing their function in vitro, WT and MINCLE KO granulocytes inhibited motility of S. ratti third stage larvae (L3), indicating potential killing of L3. However, MINCLE-deficient eosinophils showed significantly increased capacity to impair S. ratti motility. These cells also produced more reactive oxygen species (ROS) compared to the WT. Therefore, indicating that, MINCLE-mediated signalling changes the function of eosinophils during S. ratti infection. Thus, expression of MINCLE on eosinophils protect S. ratti from immune response by host and as a result, contributing to high parasite adults in the intestine
Classification and Characterization of the Metabolome of foods with Random Forest Methods
No full textIm Rahmen dieser Arbeit wurden große analytische Datensätze des Metaboloms mit random forest (RF) Verfahren untersucht. Dabei wurden ausgewählte Lebensmittel hinsichtlich verschiedener Eigenschaften klassifiziert, relevante Variablen mit Variablenselektionsmethoden ausgewählt und deren gemeinsamer Einfluss auf das Klassifikationsmodell analysiert. Die auf diese Weise gefundenen Zusammenhänge wurden bezüglich des analytischen und biologischen Hintergrunds interpretiert und damit gezeigt, dass anhand der hier angewendeten Methoden eine detaillierte Analyse der untersuchten Proben, die weit über die bei machine learning-Verfahren häufig angewendete „black box“ Untersuchung hinaus geht, ermöglicht wird.
Die Untersuchungen erfolgten an Metabolom-Daten aus 1H Kernspinresonanz-spektroskopie (engl.: nuclear magnetic resonance, NMR-Spektroskopie) und gekoppelter Flüssigchromatographie mit Massenspektrometrie (engl.: liquid chromatography coupled with mass spectrometry, LC-MS) von Apfel-, Spargel- und Trüffelproben. Die Daten wurden dabei zuerst mit der oft eingesetzten Hauptkomponentenanalyse (principal component analysis, PCA) untersucht, um die Hauptunterschiede in den Datensätzen zu analysieren. Dabei zeigte sich, dass diese meistens keine klare Unterscheidung der analysierten Klassen ermöglichte und somit überwachte Verfahren angewendet werden sollten. RF zeigte sich als sehr gut geeignet, um die Datensätze mit teilweise recht geringen Stichprobengrößen einzelner Klassen zu klassifizieren, da durch die interne Validierung in Kombination mit dem Verzicht auf eine Optimierung der Modellparameter ein unabhängiger Validierungsfehler erhalten werden konnte, ohne zusätzliche Daten zu benötigen. Dabei konnten Klassifizierungsgenauigkeiten über 70 %, meist zwischen 80-100 %, erreicht werden.
Die Anwendung von surrogate minimal depth (SMD) zur Selektion relevanter Variablen und deren Beziehungsanalyse, zusammen mit der anschließenden Identifizierung mit Datenbankabgleich und LC-MS-MS Analyse, bzw. der zusätzlichen Analyse mit weiteren Methoden der NMR-Spektroskopie und spike-in-Experimenten erwies sich als ein leistungsfähiger Ansatz zur Untersuchung der Wirkung von Variablen in den RF Modellen und damit deren Beitrag zur erfolgreichen Klassifizierung von Lebensmitteln. Dabei konnten sowohl Signale der gleichen Metabolite als auch biologisch sinnvolle Beziehungen zwischen einzelnen Metaboliten aufgedeckt werden
Sexuelle Funktion nach Holmium Laser Enukleation der Prostata
No full textDie benigne Prostatahyperplasie (BPH) ist der häufigste gutartige Tumor des erwachsenen Mannes. Die Inzidenz steigt mit zunehmendem Lebensalter und somit auch die des damit assoziierten Symptomkomplexes des Lower- Urinary- Tract- Symptoms (LUTS) und der erektilen Dysfunktion. Die transurethrale Resektion der Prostata (TUR-P) war über 50 Jahre Goldstandard in der operativen Therapie der BPH. In den letzten Jahrzehnten wurden zunehmend sichere und effiziente Laserverfahren, einschließlich der Holmium Enukleation der Prostata (HoLEP), entwickelt. Bei der Enukleation bleibt die Prostatakapsel und die darauf verlaufenden, für die erektile Funktion zuständigen Nerven, erhalten. Allerdings kommt es postoperativ in bis zu 80% der Fälle zu Störungen der Ejakulation im Sinne einer Retrograden Ejakulation (RE). Es liegen jedoch bisher keine Erkenntnisse vor, inwieweit sich die RE auf die subjektive Zufriedenheit mit dem Sexualleben auswirkt.
Unsere Hypothese ist, dass der Einfluss der HoLEP auf die Zufriedenheit mit der sexuellen Funktion vernachlässigbar ist. Die zentrale Fragestellung ist, welche Faktoren die sexuelle Funktion kurz- mittel- und langfristig beeinflussen und wie diese die allgemeine Zufriedenheit der Patienten mit ihrem Sexualleben bestimmen
