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Organizations continue to assemble and rely upon teams of remote workers as an essential element of their business strategy; however, knowledge processing is particular difficult in such isolated, largely digitally mediated settings. The great challenge for a knowledge-based organization lies not in how individuals should interact using technology but in how to achieve effective cooperation and knowledge exchange. Currently more attention has been paid to technology and the difficulties machines have processing natural language and less to studies of the human aspect—the influence of our own individual cognitive abilities and preferences on the processing of information when interacting online. This thesis draws on four scientific domains involved in the process of interpreting and processing massive, unstructured data—knowledge management, linguistics, cognitive science, and artificial intelligence—to build a model that offers a reliable way to address the ambiguous nature of language and improve workers’ digitally mediated interactions. Human communication can be discouragingly imprecise and is characterized by a strong linguistic ambiguity; this represents an enormous challenge for the computer analysis of natural language. In this thesis, I propose and develop a new data interpretation layer for the processing of natural language based on the human cognitive preferences of the conversants themselves. Such a semantic analysis merges information derived both from the content and from the associated social and individual contexts, as well as the social dynamics that emerge online. At the same time, assessment taxonomies are used to analyze online comportment at the individual and community level in order to successfully identify characteristics leading to greater effectiveness of communication. Measurement patterns for identifying effective methods of individual interaction with regard to individual cognitive and learning preferences are also evaluated; a novel Cyber-Cognitive Identity (CCI)—a perceptual profile of an individual’s cognitive and learning styles—is proposed. Accommodation of such cognitive preferences can greatly facilitate knowledge management in the geographically dispersed and collaborative digital environment. Use of the CCI is proposed for cognitively labeled Latent Dirichlet Allocation (CLLDA), a novel method for automatically labeling and clustering knowledge that does not rely solely on probabilistic methods, but rather on a fusion of machine learning algorithms and the cognitive identities of the associated individuals interacting in a digitally mediated environment. Advantages include: a greater perspicuity of dynamic and meaningful cognitive rules leading to greater tagging accuracy and a higher content portability at the sentence, document, and corpus level with respect to digital communication.
Glycosylphosphatidylinositols (GPIs) are highly complex glycolipids that serve as membrane anchors to a large variety of eukaryotic proteins. These are covalently attached to a group of peripheral proteins called GPI-anchored proteins (GPI-APs) through a post-translational modification in the endoplasmic reticulum. The GPI anchor is a unique structure composed of a glycan, with phospholipid tail at one end and a phosphoethanolamine linker at the other where the protein attaches. The glycan part of the GPI comprises a conserved pseudopentasaccharide core that could branch out to carry additional glycosyl or phosphoethanolamine units. GPI-APs are involved in a diverse range of cellular processes, few of which are signal transduction, protein trafficking, pathogenesis by protozoan parasites like the malaria- causing parasite Plasmodium falciparum. GPIs can also exist freely on the membrane surface without an attached protein such as those found in parasites like Toxoplasma gondii, the causative agent of Toxoplasmosis. These molecules are both structurally and functionally diverse, however, their structure-function relationship is still poorly understood. This is mainly because no clear picture exists regarding how the protein and the glycan arrange with respect to the lipid layer. Direct experimental evidence is rather scarce, due to which inconclusive pictures have emerged, especially regarding the orientation of GPIs and GPI-APs on membrane surfaces and the role of GPIs in membrane organization. It appears that computational modelling through molecular dynamics simulations would be a useful method to make progress. In this thesis, we attempt to explore characteristics of GPI anchors and GPI-APs embedded in lipid bilayers by constructing molecular models at two different resolutions – all-atom and coarse-grained.
First, we show how to construct a modular molecular model of GPIs and GPI-anchored proteins that can be readily extended to a broad variety of systems, addressing the micro-heterogeneity of GPIs. We do so by creating a hybrid link to which GPIs of diverse branching and lipid tails of varying saturation with their optimized force fields, GLYCAM06 and Lipid14 respectively, can be attached. Using microsecond simulations, we demonstrate that GPI prefers to “flop-down” on the membrane, thereby, strongly interacting with the lipid heads, over standing upright like a “lollipop”. Secondly, we extend the model of the GPI core to carry out a systematic study of the structural aspects of GPIs carrying different side chains (parasitic and human GPI variants) inserted in lipid bilayers. Our results demonstrate the importance of the side branch residues as these are the most accessible, and thereby, recognizable epitopes. This finding qualitatively agrees with experimental observations that highlight the role of the side branches in immunogenicity of GPIs and the specificity thereof. The overall flop-down orientation of the GPIs with respect to the bilayer surface presents the side chain residues to face the solvent. Upon attaching the green fluorescent protein (GFP) to the GPI, it is seen to lie in close proximity to the bilayer, interacting both with the lipid heads and glycan part of the GPI. However the orientation of GFP is sensitive to the type of GPI it is attached to. Finally, we construct a coarse-grained model of the GPI and GPI-anchored GFP using a modified version of the MARTINI force-field, using which the timescale is enhanced by at least an order of magnitude compared to the atomistic system.
This study provides a theoretical perspective on the conformational behavior of the GPI core and some of its branched variations in presence of lipid bilayers, as well as draws comparisons with experimental observations. Our modular atomistic model of GPI can be further employed to study GPIs of variable branching, and thereby, aid in designing future experiments especially in the area of vaccines and drug therapies. Our coarse-grained model can be used to study dynamic aspects of GPIs and GPI-APs w.r.t plasma membrane organization. Furthermore, the backmapping technique of converting coarse-grained trajectory back to the atomistic model would enable in-depth structural analysis with ample conformational sampling.
Due to continuously intensifying human usage of the marine environment worldwide ranging cetaceans face an increasing number of threats. Besides whaling, overfishing and by-catch, new technical developments increase the water and noise pollution, which can negatively affect marine species. Cetaceans are especially prone to these influences, being at the top of the food chain and therefore accumulating toxins and contaminants. Furthermore, they are extremely noise sensitive due to their highly developed hearing sense and echolocation ability. As a result, several cetacean species were brought to extinction during the last century or are now classified as critically endangered. This work focuses on two odontocetes. It applies and compares different molecular methods for inference of population status and adaptation, with implications for conservation. The worldwide distributed sperm whale (Physeter macrocephalus) shows a matrilineal population structure with predominant male dispersal. A recently stranded group of male sperm whales provided a unique opportunity to investigate male grouping for the first time. Based on the mitochondrial control region, I was able to infer that male bachelor groups comprise multiple matrilines, hence derive from different social groups, and that they represent the genetic variability of the entire North Atlantic. The harbor porpoise (Phocoena phocoena) occurs only in the northern hemisphere. By being small and occurring mostly in coastal habitats it is especially prone to human disturbance. Since some subspecies and subpopulations are critically endangered, it is important to generate and provide genetic markers with high resolution to facilitate population assignment and subsequent protection measurements. Here, I provide the first harbour porpoise whole genome, in high quality and including a draft annotation. Using it for mapping ddRAD seq data, I identify genome wide SNPs and, together with a fragment of the mitochondrial control region, inferred the population structure of its North Atlantic distribution range. The Belt Sea harbors a distinct subpopulation oppose to the North Atlantic, with a transition zone in the Kattegat. Within the North Atlantic I could detect subtle genetic differentiation between western (Canada-Iceland) and eastern (North Sea) regions, with support for a German North Sea breading ground around the Isle of Sylt. Further, I was able to detect six outlier loci which show isolation by distance across the investigated sampling areas. In employing different markers, I could show that single maker systems as well as genome wide data can unravel new information about population affinities of odontocetes. Genome wide data can facilitate investigation of adaptations and evolutionary history of the species and its populations. Moreover, they facilitate population genetic investigations, providing a high resolution, and hence allowing for detection of subtle population structuring especially important for highly mobile cetaceans.
This thesis investigates how the permafrost microbiota responds to global warming. In detail, the constraints behind methane production in thawing permafrost were linked to methanogenic activity, abundance and composition. Furthermore, this thesis offers new insights into microbial adaptions to the changing environmental conditions during global warming. This was assesed by investigating the potential ecological relevant functions encoded by plasmid DNA within the permafrost microbiota. Permafrost of both interglacial and glacial origin spanning the Holocene to the late Pleistocene, including Eemian, were studied during long-term thaw incubations. Furthermore, several permafrost cores of different stratigraphy, soil type and vegetation cover were used to target the main constraints behind methane production during short-term thaw simulations. Short- and long-term incubations simulating thaw with and without the addition of substrate were combined with activity measurements, amplicon and metagenomic sequencing of permanently frozen and seasonally thawed active layer. Combined, it allowed to address the following questions. i) What constraints methane production when permafrost thaws and how is this linked to methanogenic activity, abundance and composition? ii) How does the methanogenic community composition change during long-term thawing conditions? iii) Which potential ecological relevant functions are encoded by plasmid DNA in active layer soils?
The major outcomes of this thesis are as follows. i) Methane production from permafrost after long-term thaw simulation was found to be constrained mainly by the abundance of methanogens and the archaeal community composition. Deposits formed during periods of warmer temperatures and increased precipitation, (here represented by deposits from the Late Pleistocene of both interstadial and interglacial periods) were found to respond strongest to thawing conditions and to contain an archaeal community dominated by methanogenic archaea (40% and 100% of all detected archaea). Methanogenic population size and carbon density were identified as main predictors for potential methane production in thawing permafrost in short-term incubations when substrate was sufficiently available.
ii) Besides determining the methanogenic activity after long-term thaw, the paleoenvironmental conditions were also found to influence the response of the methanogenic community composition. Substantial shifts within methanogenic community structure and a drop in diversity were observed in deposits formed during warmer periods, but not in deposits from stadials, when colder and drier conditions occurred. Overall, a shift towards a dominance of hydrogenotrophic methanogens was observed in all samples, except for the oldest interglacial deposits from the Eemian, which displayed a potential dominance of acetoclastic methanogens. The Eemian, which is discussed to serve as an analogue to current climate conditions, contained highly active methanogenic communities. However, all potential limitation of methane production after permafrost thaw, it means methanogenic community structure, methanogenic population size, and substrate pool might be overcome after permafrost had thawed on the long-term. iii) Enrichments with soil from the seasonally thawed active layer revealed that its plasmid DNA (‘metaplasmidome’) carries stress-response genes. In particular it encoded antibiotic resistance genes, heavy metal resistance genes, cold shock proteins and genes encoding UV-protection. Those are functions that are directly involved in the adaptation of microbial communities to stresses in polar environments. It was further found that metaplasmidomes from the Siberian active layer originate mainly from Gammaproteobacteria. By applying enrichment cultures followed by plasmid DNA extraction it was possible to obtain a higher average contigs length and significantly higher recovery of plasmid sequences than from extracting plasmid sequences from metagenomes. The approach of analyzing ‘metaplasmidomes’ established in this thesis is therefore suitable for studying the ecological role of plasmids in polar environments in general.
This thesis emphasizes that including microbial community dynamics have the potential to improve permafrost-carbon projections. Microbially mediated methane release from permafrost environments may significantly impact future climate change. This thesis identified drivers of methanogenic composition, abundance and activity in thawing permafrost landscapes. Finally, this thesis underlines the importance to study how the current warming Arctic affects microbial communities in order to gain more insight into microbial response and adaptation strategies.
Towards seasonal prediction: stratosphere-troposphere coupling in the atmospheric model ICON-NWP
(2020)
Stratospheric variability is one of the main potential sources for sub-seasonal to seasonal predictability in mid-latitudes in winter. Stratospheric pathways play an important role for long-range teleconnections between tropical phenomena, such as the quasi-biennial oscillation (QBO) and El Niño-Southern Oscillation (ENSO), and the mid-latitudes on the one hand, and linkages between Arctic climate change and the mid-latitudes on the other hand. In order to move forward in the field of extratropical seasonal predictions, it is essential that an atmospheric model is able to realistically simulate the stratospheric circulation and variability. The numerical weather prediction (NWP) configuration of the ICOsahedral Non-hydrostatic atmosphere model ICON is currently being used by the German Meteorological Service for the regular weather forecast, and is intended to produce seasonal predictions in future. This thesis represents the first extensive evaluation of Northern Hemisphere stratospheric winter circulation in ICON-NWP by analysing a large set of seasonal ensemble experiments.
An ICON control climatology simulated with a default setup is able to reproduce the basic behaviour of the stratospheric polar vortex. However, stratospheric westerlies are significantly too weak and major stratospheric warmings too frequent, especially in January. The weak stratospheric polar vortex in ICON is furthermore connected to a mean sea level pressure (MSLP) bias pattern resembling the negative phase of the Arctic Oscillation (AO). Since a good representation of the drag exerted by gravity waves is crucial for a realistic simulation of the stratosphere, three sensitivity experiments with reduced gravity wave drag are performed. Both a reduction of the non-orographic and orographic gravity wave drag respectively, lead to a strengthening of the stratospheric vortex and thus a bias reduction in winter, in particular in January. However, the effect of the non-orographic gravity wave drag on the stratosphere is stronger. A third experiment, combining a reduced orographic and non-orographic drag, exhibits the largest stratospheric bias reductions. The analysis of stratosphere-troposphere coupling based on an index of the Northern Annular Mode demonstrates that ICON realistically represents downward coupling. This coupling is intensified and more realistic in experiments with a reduced gravity wave drag, in particular with reduced non-orographic drag. Tropospheric circulation is also affected by the reduced gravity wave drag, especially in January, when the strongly improved stratospheric circulation reduces biases in the MSLP patterns. Moreover, a retuning of the subgrid-scale orography parameterisations leads to a significant error reduction in the MSLP in all months. In conclusion, the combination of these adjusted parameterisations is recommended as a current optimal setup for seasonal simulations with ICON.
Additionally, this thesis discusses further possible influences on the stratospheric polar vortex, including the influence of tropical phenomena, such as QBO and ENSO, as well as the influence of a rapidly warming Arctic. ICON does not simulate the quasi-oscillatory behaviour of the QBO and favours weak easterlies in the tropical stratosphere. A comparison with a reanalysis composite of the easterly QBO phase reveals, that the shift towards the easterly QBO in ICON further weakens the stratospheric polar vortex. On the other hand, the stratospheric reaction to ENSO events in ICON is realistic. ICON and the reanalysis exhibit a weakened stratospheric vortex in warm ENSO years. Furthermore, in particular in winter, warm ENSO events favour the negative phase of the Arctic Oscillation, whereas cold events favour the positive phase. The ICON simulations also suggest a significant effect of ENSO on the Atlantic-European sector in late winter. To investigate the influence of Arctic climate change on mid-latitude circulation changes, two differing approaches with transient and fixed sea ice conditions are chosen. Neither ICON approach exhibits the mid-latitude tropospheric negative Arctic Oscillation circulation response to amplified Arctic warming, as it is discussed on the basis of observational evidence. Nevertheless, adding a new model to the current and active discussion on Arctic-midlatitude linkages, further contributes to the understanding of divergent conclusions between model and observational studies.
Philosophische Tugenden
(2020)
Worin besteht gutes Philosophieren? Und weshalb ist gerade John Stuart Mill ein außergewöhnlich guter Philosoph? Joachim Toenges-Hinn verbindet in diesem Band die metaphilosophische Suche danach, was gute Philosophie ausmacht, mit einer historischen Betrachtung des Philosophen John Stuart Mill. Dabei fungiert Mill zugleich als Urheber von und Verkörperung des Strebens nach zwei philosophischen Tugenden, die Toenges-Hinn aus Mills philosophischem Werk ableitet und anschließend systematisch verteidigt. Diese als „Bentham-Ideal“ und „Coleridge-Ideal“ bezeichneten Tugenden stehen dabei ebenso im Fokus seiner Untersuchung wie die Bedeutung von Lebensexperimenten für philosophische Biografien.
Sekundäre Pflanzenstoffe und ihre gesundheitsfördernden Eigenschaften sind in den letzten zwei Jahrzehnten vielfach ernährungsphysiologisch untersucht und spezifische positive Effekte im humanen Organismus zum Teil sehr genau beschrieben worden. Zu den Carotinoiden zählend ist der sekundäre Pflanzenstoff Lutein insbesondere in der Prävention von ophthalmologischen Erkrankungen in den Mittelpunkt der Forschung gerückt. Das ausschließlich von Pflanzen und einigen Algen synthetisierte Xanthophyll wird über die pflanzliche Nahrung insbesondere grünes Blattgemüse in den humanen Organismus aufgenommen. Dort akkumuliert es bevorzugt im Makulapigment der Retina des menschlichen Auges und ist bedeutend im Prozess der Aufrechterhaltung der Funktionsfähigkeit der Photorezeptorzellen. Im Laufe des Alterns kann die Abnahme der Dichte des Makulapigments und der Abbau von Lutein beobachtet werden. Die dadurch eintretende Destabilisierung der Photorezeptorzellen im Zusammenhang mit einer veränderten Stoffwechsellage im alternden Organismus kann zur Ausprägung der altersbedingten Makuladegeneration (AMD) führen. Die pathologische Symptomatik der Augenerkrankung reicht vom Verlust der Sehschärfe bis hin zum irreversiblen Erblinden. Da therapeutische Mittel ausschließlich ein Fortschreiten verhindern, bestehen hier Forschungsansätze präventive Maßnahmen zu finden. Die Supplementierung von luteinhaltigen Präparaten bietet dabei einen Ansatzpunkt. Auf dem Markt finden sich bereits Nahrungsergänzungsmittel (NEM) mit Lutein in verschiedenen Applikationen. Limitierend ist dabei die Stabilität und Bioverfügbarkeit von Lutein, welches teilweise kostenintensiv und mit unbekannter Reinheit zu erwerben ist. Aus diesem Grund wäre die Verwendung von Luteinestern als die pflanzliche Speicherform des Luteins im Rahmen eines NEMs vorteilhaft. Neben ihrer natürlichen, höheren Stabilität sind Luteinester nachhaltig und kostengünstig einsetzbar.
In dieser Arbeit wurden physikochemische und ernährungsphysiologisch relevante Aspekte in dem Produktentwicklungsprozess eines NEMs mit Luteinestern in einer kolloidalen Formulierung untersucht. Die bisher einzigartige Anwendung von Luteinestern in einem Mundspray sollte die Aufnahme des Wirkstoffes insbesondere für ältere Menschen erleichtern und verbessern. Unter Beachtung der Ergebnisse und der ernährungsphysiologischen Bewertung sollten u.a. Empfehlungen für die Rezepturzusammensetzungen einer Miniemulsion (Emulsion mit Partikelgrößen <1,0 µm) gegeben werden. Eine Einschätzung der Bioverfügbarkeit der Luteinester aus den entwickelten, kolloidalen Formulierungen konnte anhand von Studien zur Resorption- und Absorptionsverfügbarkeit in vitro ermöglicht werden.
In physikalischen Untersuchungen wurden zunächst Basisbestandteile für die Formulierungen präzisiert. In ersten wirkstofffreien Musteremulsionen konnten ausgewählte Öle als Trägerphase sowie Emulgatoren und Löslichkeitsvermittler (Peptisatoren) hinsichtlich ihrer Eignung zur Bereitstellung einer Miniemulsion physikalisch geprüft werden. Die beste Stabilität und optimale Eigenschaften einer Miniemulsion zeigten sich bei der Verwendung von MCT-Öl (engl. medium chain triglyceride) bzw. Rapsöl in der Trägerphase sowie des Emulgators Tween® 80 (Tween 80) allein oder in Kombination mit dem Molkenproteinhydrolysat Biozate® 1 (Biozate 1).
Aus den physikalischen Untersuchungen der Musteremulsionen gingen die Präemulsionen als Prototypen hervor. Diese enthielten den Wirkstoff Lutein in verschiedenen Formen. So wurden Präemulsionen mit Lutein, mit Luteinestern sowie mit Lutein und Luteinestern konzipiert, welche den Emulgator Tween 80 oder die Kombination mit Biozate 1 enthielten. Bei der Herstellung der Präemulsionen führte die Anwendung der Emulgiertechniken Ultraschall mit anschließender Hochdruckhomogenisation zu den gewünschten Miniemulsionen. Beide eingesetzten Emulgatoren boten optimale Stabilisierungseffekte. Anschließend erfolgte die physikochemische Charakterisierung der Wirkstoffe. Insbesondere Luteinester aus Oleoresin erwiesen sich hier als stabil gegenüber verschiedenen Lagerungsbedingungen. Ebenso konnte bei einer kurzzeitigen Behandlung der Wirkstoffe unter spezifischen mechanischen, thermischen, sauren und basischen Bedingungen eine Stabilität von Lutein und Luteinestern gezeigt werden. Die Zugabe von Biozate 1 bot dabei nur für Lutein einen zusätzlichen Schutz. Bei längerer physikochemischer Behandlung unterlagen die in den Miniemulsionen eingebrachten Wirkstoffe moderaten Abbauvorgängen. Markant war deren Sensitivität gegenüber dem basischen Milieu. Im Rahmen der Rezepturentwicklung des NEMs war hier die Empfehlung, eine Miniemulsion mit einem leicht saurem pH-Milieu zum Schutz des Wirkstoffes durch kontrollierte Zugabe weiterer Inhaltstoffe zu gestalten.
Im weiteren Entwicklungsprozess des NEMs wurden Fertigrezepturen mit dem Wirkstoff Luteinester aufgestellt. Die alleinige Anwendung des Emulgators Biozate 1 zeigte sich dabei als ungeeignet. Die weiterhin zur Verfügung stehenden Fertigrezepturen enthielten in der Öl-phase neben dem Wirkstoff das MCT-ÖL oder Rapsöl sowie a-Tocopherol zur Stabilisierung. Die Wasserphase bestand aus dem Emulgator Tween 80 oder einer Kombination aus Tween 80 und Biozate 1. Zusatzstoffe waren zudem als mikrobiologischer Schutz Ascorbinsäure und Kaliumsorbat sowie für sensorische Effekte Xylitol und Orangenaroma. Die Anordnung der Basisrezeptur und das angewendete Emulgierverfahren lieferten stabile Miniemulsionen. Weiterhin zeigten langfristige Lagerungsversuche mit den Fertigrezepturen bei 4°C, dass eine Aufrechterhaltung der geforderten Luteinestermenge im Produkt gewährleistet war. Analoge Untersuchungen an einem luteinhaltigen, marktgängigen Präparat bestätigten dagegen eine bereits bei kurzfristiger Lagerung auftretende Instabilität von Lutein.
Abschließend wurde durch Resorptions- und Absorptionsstudien in vitro mit den Präemulsionen und Fertigrezepturen die Bioverfügbarkeit von Luteinestern geprüft. Nach Behandlung in einem etablierten in vitro Verdaumodell konnte eine geringfügige Resorptionsverfügbarkeit der Luteinester definiert werden. Limitiert war eine Micellarisierung des Wirkstoffes aus den konzipierten Formulierungen zu beobachten. Eine enzymatische Spaltung der Luteinester zu freiem Lutein wurde nur begrenzt festgestellt. Spezifität und Aktivität von entsprechenden hydrolytischen Lipasen sind als äußerst gering gegenüber Luteinestern zu bewerten. In sich anschließenden Zellkulturversuchen mit der Zelllinie Caco-2 wurden keine zytotoxischen Effekte durch die relevanten Inhaltsstoffe in den Präemulsionen gezeigt. Dagegen konnten eine Sensibilität gegenüber den Fertigrezepturen beobachtet werden. Diese sollte im Zusammenhang mit Irritationen der Schleimhäute des Magen-Darm-Traktes bedacht werden. Eine weniger komplexe Rezeptur könnte die beobachteten Einschränkungen möglicherweise minimieren. Abschließende Absorptionsstudien zeigten, dass grundsätzlich eine geringfügige Aufnahme von vorrangig Lutein, aber auch Luteinmonoestern in den Enterocyten aus Miniemulsionen erfolgen kann. Dabei hatte weder Tween 80 noch Biozate 1 einen förderlichen Einfluss auf die Absorptionsrate von Lutein oder Luteinestern. Die Metabolisierung der Wirkstoffe durch vorherigen in vitro-Verdau steigerte die zelluläre Aufnahme von Wirkstoffen aus Formulierungen mit Lutein und Luteinestern gleichermaßen. Die beobachtete Aufnahme von Lutein und Luteinmonoestern in den Enterocyten scheint über passive Diffusion zu erfolgen, wobei auch der aktive Transport nicht ausgeschlossen werden kann. Dagegen können Luteindiester aufgrund ihrer Molekülgröße nicht über den Weg der Micellarisierung und einfachen Diffusion in die Enterocyten gelangen. Ihre Aufnahme in die Dünndarmepithelzellen bedarf einer vorherigen hydrolytischen Spaltung durch spezifische Lipasen. Dieser Schritt limitiert wiederum die effektive Aufnahme der Luteinester in die Zellen bzw. stellt eine Einschränkung in ihrer Bioverfügbarkeit im Vergleich zu freiem Lutein dar.
Zusammenfassend konnte für die physikochemisch stabilen Luteinester eine geringe Bioverfügbarkeit aus kolloidalen Formulierungen gezeigt werden. Dennoch ist die Verwendung als Wirkstoffquelle für den sekundären Pflanzenstoff Lutein in einem NEM zu empfehlen. Im Zusammenhang mit der Aufnahme von luteinreichen, pflanzlichen Lebensmitteln kann trotz der zu erwartenden geringen Bioverfügbarkeit der Luteinester aus dem NEM ein Beitrag zur Verbesserung des Luteinstatus erreicht werden. Entsprechende Publikationen zeigten eindeutige Korrelationen zwischen der Aufnahme von luteinesterhaltigen Präparaten und einem Anstieg der Luteinkonzentration im Serum bzw. der Makulapigmentdichte in vivo. Die geringfügig bessere Bioverfügbarkeit von freiem Lutein steht im kritischen Zusammenhang mit seiner Instabilität und Kostenintensität. Bilanzierend wurde im Rahmen dieser Arbeit das marktgängige Produkt Vita Culus® konzipiert. Im Ausblick sollten humane Interventionsstudien mit dem NEM die abschließende Bewertung der Bioverfügbarkeit von Luteinestern aus dem Präparat möglich machen.
The East Asian monsoons characterize the modern-day Asian climate, yet their geological history and driving mechanisms remain controversial. The southeasterly summer monsoon provides moisture, whereas the northwesterly winter monsoon sweeps up dust from the arid Asian interior to form the Chinese Loess Plateau. The onset of this loess accumulation, and therefore of the monsoons, was thought to be 8 million years ago (Ma). However, in recent years these loess records have been extended further back in time to the Eocene (56-34 Ma), a period characterized by significant changes in both the regional geography and global climate. Yet the extent to which these reconfigurations drive atmospheric circulation and whether the loess-like deposits are monsoonal remains debated. In this thesis, I study the terrestrial deposits of the Xining Basin previously identified as Eocene loess, to derive the paleoenvironmental evolution of the region and identify the geological processes that have shaped the Asian climate.
I review dust deposits in the geological record and conclude that these are commonly represented by a mix of both windblown and water-laid sediments, in contrast to the pure windblown material known as loess. Yet by using a combination of quartz surface morphologies, provenance characteristics and distinguishing grain-size distributions, windblown dust can be identified and quantified in a variety of settings. This has important implications for tracking aridification and dust-fluxes throughout the geological record.
Past reversals of Earth’s magnetic field are recorded in the deposits of the Xining Basin and I use these together with a dated volcanic ash layer to accurately constrain the age to the Eocene period. A combination of pollen assemblages, low dust abundances and other geochemical data indicates that the early Eocene was relatively humid suggesting an intensified summer monsoon due to the warmer greenhouse climate at this time. A subsequent shift from predominantly freshwater to salt lakes reflects a long-term aridification trend possibly driven by global cooling and the continuous uplift of the Tibetan Plateau. Superimposed on this aridification are wetter intervals reflected in more abundant lake deposits which correlate with highstands of the inland proto-Paratethys Sea. This sea covered the Eurasian continent and thereby provided additional moisture to the winter-time westerlies during the middle to late Eocene.
The long-term aridification culminated in an abrupt shift at 40 Ma reflected by the onset of windblown dust, an increase in steppe-desert pollen, the occurrence of high-latitude orbital cycles and northwesterly winds identified in deflated salt deposits. Together, these indicate the onset of a Siberian high atmospheric pressure system driving the East Asian winter monsoon as well as dust storms and was triggered by a major sea retreat from the Asian interior. These results therefore show that the proto-Paratethys Sea, though less well recognized than the Tibetan Plateau and global climate, has been a major driver in setting up the modern-day climate in Asia.
Organizations incorporate the institutional demands from their environment in order to be deemed legitimate and survive. Yet, complexifying societies promulgate multiple and sometimes inconsistent institutional prescriptions. When these prescriptions collide, organizations are said to face “institutional complexity”. How does an organization then incorporate incompatible demands? What are the consequences of institutional complexity for an organization? The literature provides contradictory conceptual and empirical insights on the matter. A central assumption, however, remains that internal incompatibilities generate tensions that, under certain conditions, can escalate into intractable conflicts, resulting in dysfunctionality and loss of legitimacy. The present research is an inquiry into what happens inside an organization when it incorporates complex institutional demands.
To answer this question, I focus on how individuals inside an organization interpret a complex institutional prescription. I examine how members of the French Development Agency interpret ‘results-based management’, a central but complex concept of organizing in the field of development aid. I use an inductive mixed methods design to systematically explore how different interpretations of results-based management relate to one another and to the organizational context in which they are embedded.
The results reveal that results-based management is a contested concept in the French Development Agency. I find multiple interpretations of the concept, which are attached to partly incompatible rationales about “who we are” and “what we do as an organization”. These rationales nevertheless coexist as balanced forces, without escalating into open conflict. The analysis points to four reasons for this peaceful coexistence of diverging rationales inside one and the same organization: 1) individuals’ capacity to manipulate different interpretations of a complex institutional demand, 2) the nature of interpretations, which makes them more or less prone to conflict, 3) the balanced distribution of rationales across the organizational sub-contexts and 4) the shared rules of interpretation provided by the larger socio-cultural context.
This research shows that an organization that incorporates institutional complexity comes to represent different, partly incompatible things to its members without being at war with itself. In doing so, it contributes to our knowledge of institutional complexity and organizational hybridity. It also advances our understanding of internal organizational legitimacy and of the translation of managerial concepts in organizations.
Comment sections of online news platforms are an essential space to express opinions and discuss political topics. However, the misuse by spammers, haters, and trolls raises doubts about whether the benefits justify the costs of the time-consuming content moderation. As a consequence, many platforms limited or even shut down comment sections completely. In this thesis, we present deep learning approaches for comment classification, recommendation, and prediction to foster respectful and engaging online discussions. The main focus is on two kinds of comments: toxic comments, which make readers leave a discussion, and engaging comments, which make readers join a discussion. First, we discourage and remove toxic comments, e.g., insults or threats. To this end, we present a semi-automatic comment moderation process, which is based on fine-grained text classification models and supports moderators. Our experiments demonstrate that data augmentation, transfer learning, and ensemble learning allow training robust classifiers even on small datasets. To establish trust in the machine-learned models, we reveal which input features are decisive for their output with attribution-based explanation methods. Second, we encourage and highlight engaging comments, e.g., serious questions or factual statements. We automatically identify the most engaging comments, so that readers need not scroll through thousands of comments to find them. The model training process builds on upvotes and replies as a measure of reader engagement. We also identify comments that address the article authors or are otherwise relevant to them to support interactions between journalists and their readership. Taking into account the readers' interests, we further provide personalized recommendations of discussions that align with their favored topics or involve frequent co-commenters. Our models outperform multiple baselines and recent related work in experiments on comment datasets from different platforms.
Successfully completing any data science project demands careful consideration across its whole process. Although the focus is often put on later phases of the process, in practice, experts spend more time in earlier phases, preparing data, to make them consistent with the systems' requirements or to improve their models' accuracies. Duplicate detection is typically applied during the data cleaning phase, which is dedicated to removing data inconsistencies and improving the overall quality and usability of data. While data cleaning involves a plethora of approaches to perform specific operations, such as schema alignment and data normalization, the task of detecting and removing duplicate records is particularly challenging. Duplicates arise when multiple records representing the same entities exist in a database. Due to numerous reasons, spanning from simple typographical errors to different schemas and formats of integrated databases. Keeping a database free of duplicates is crucial for most use-cases, as their existence causes false negatives and false positives when matching queries against it. These two data quality issues have negative implications for tasks, such as hotel booking, where users may erroneously select a wrong hotel, or parcel delivery, where a parcel can get delivered to the wrong address. Identifying the variety of possible data issues to eliminate duplicates demands sophisticated approaches.
While research in duplicate detection is well-established and covers different aspects of both efficiency and effectiveness, our work in this thesis focuses on the latter. We propose novel approaches to improve data quality before duplicate detection takes place and apply the latter in datasets even when prior labeling is not available. Our experiments show that improving data quality upfront can increase duplicate classification results by up to 19%. To this end, we propose two novel pipelines that select and apply generic as well as address-specific data preparation steps with the purpose of maximizing the success of duplicate detection. Generic data preparation, such as the removal of special characters, can be applied to any relation with alphanumeric attributes. When applied, data preparation steps are selected only for attributes where there are positive effects on pair similarities, which indirectly affect classification, or on classification directly. Our work on addresses is twofold; first, we consider more domain-specific approaches to improve the quality of values, and, second, we experiment with known and modified versions of similarity measures to select the most appropriate per address attribute, e.g., city or country.
To facilitate duplicate detection in applications where gold standard annotations are not available and obtaining them is not possible or too expensive, we propose MDedup. MDedup is a novel, rule-based, and fully automatic duplicate detection approach that is based on matching dependencies. These dependencies can be used to detect duplicates and can be discovered using state-of-the-art algorithms efficiently and without any prior labeling. MDedup uses two pipelines to first train on datasets with known labels, learning to identify useful matching dependencies, and then be applied on unseen datasets, regardless of any existing gold standard. Finally, our work is accompanied by open source code to enable repeatability of our research results and application of our approaches to other datasets.
To find out the future of nowadays reef ecosystem turnover under the environmental stresses such as global warming and ocean acidification, analogue studies from the geologic past are needed. As a critical time of reef ecosystem innovation, the Permian-Triassic transition witnessed the most severe demise of Phanerozoic reef builders, and the establishment of modern style symbiotic relationships within the reef-building organisms. Being the initial stage of this transition, the Middle Permian (Capitanian) mass extinction coursed a reef eclipse in the early Late Permian, which lead to a gap of understanding in the post-extinction Wuchiapingian reef ecosystem, shortly before the radiation of Changhsingian reefs. Here, this thesis presents detailed biostratigraphic, sedimentological, and palaeoecological studies of the Wuchiapingian reef recovery following the Middle Permian (Capitanian) mass extinction, on the only recorded Wuchiapingian reef setting, outcropping in South China at the Tieqiao section.
Conodont biostratigraphic zonations were revised from the Early Permian Artinskian to the Late Permian Wuchiapingian in the Tieqiao section. Twenty main and seven subordinate conodont zones are determined at Tieqiao section including two conodont zone below and above the Tieqiao reef complex. The age of Tieqiao reef was constrained as early to middle Wuchiapingian.
After constraining the reef age, detailed two-dimensional outcrop mapping combined with lithofacies study were carried out on the Wuchiapingian Tieqiao Section to investigate the reef growth pattern stratigraphically as well as the lateral changes of reef geometry on the outcrop scale. Semi-quantitative studies of the reef-building organisms were used to find out their evolution pattern within the reef recovery. Six reef growth cycles were determined within six transgressive-regressive cycles in the Tieqiao section. The reefs developed within the upper part of each regressive phase and were dominated by different biotas. The timing of initial reef recovery after the Middle Permian (Capitanian) mass extinction was updated to the Clarkina leveni conodont zone, which is earlier than previous understanding. Metazoans such as sponges were not the major components of the Wuchiapingian reefs until the 5th and 6th cycles. So, the recovery of metazoan reef ecosystem after the Middle Permian (Capitanian) mass extinction was obviously delayed. In addition, although the importance of metazoan reef builders such as sponges did increase following the recovery process, encrusting organisms such as Archaeolithoporella and Tubiphytes, combined with microbial carbonate precipitation, still played significant roles to the reef building process and reef recovery after the mass extinction.
Based on the results from outcrop mapping and sedimentological studies, quantitative composition analysis of the Tieqiao reef complex were applied on selected thin sections to further investigate the functioning of reef building components and the reef evolution after the Middle Permian (Capitanian) mass extinction. Data sets of skeletal grains and whole rock components were analyzed. The results show eleven biocommunity clusters/eight rock composition clusters dominated by different skeletal grains/rock components. Sponges, Archaeolithoporella and Tubiphytes were the most ecologically important components within the Wuchiapingian Tieqiao reef, while the clotted micrites and syndepositional cements are the additional important rock components for reef cores. The sponges were important within the whole reef recovery. Tubiphytes were broadly distributed in different environments and played a key-role in the initial reef communities. Archaeolithoporella concentrated in the shallower part of reef cycles (i.e., the upper part of reef core) and was functionally significant for the enlargement of reef volume.
In general, the reef recovery after the Middle Permian (Capitanian) mass extinction has some similarities with the reef recovery following the end-Permian mass extinction. It shows a delayed recovery of metazoan reefs and a stepwise recovery pattern that was controlled by both ecological and environmental factors. The importance of encrusting organisms and microbial carbonates are also similar to most of the other post-extinction reef ecosystems. These findings can be instructive to extend our understanding of the reef ecosystem evolution under environmental perturbation or stresses.
Ein Ergebnis der interkulturellen Beziehungen in Südostasien sind die immer noch existierenden portugiesisch-basierten Kreolsprachen Papia Kristang und Macaísta, die zu Muttersprachen von Generationen von Menschen in Malakka und Macau geworden sind. Welche Faktoren bewirken den Sprachwandel dieser Idiome, und wie ist dieser erkennbar? Dieser Band beschäftigt sich nicht nur mit der Sprachdynamik der portugiesisch-basierten Kreolsprachen Südostasiens, sondern auch mit anderen wesentlichen Fragestellungen der Variationslinguistik. Als Basis dienen die Ergebnisse einer empirischen Datenerhebung, die insbesondere die Veränderungen im Sprachgebrauch dokumentieren. Darüber hinaus stellt der Autor neue Resultate hinsichtlich der Sprachidentifikationen vor, die nicht nur für die Kreolistik von Bedeutung sind, sondern auch fachübergreifend für das Interesse der allgemeinen Sprachwissenschaft.
Cardiac valves are essential for the continuous and unidirectional flow of blood throughout the body. During embryonic development, their formation is strictly connected to the mechanical forces exerted by blood flow. The endocardium that lines the interior of the heart is a specialized endothelial tissue and is highly sensitive to fluid shear stress. Endocardial cells harbor a signal transduction machinery required for the translation of these forces into biochemical signaling, which strongly impacts cardiac morphogenesis and physiology. To date, we lack a solid understanding on the mechanisms by which endocardial cells sense the dynamic mechanical stimuli and how they trigger different cellular responses. In the zebrafish embryo, endocardial cells at the atrioventricular canal respond to blood flow by rearranging from a monolayer to a double-layer, composed of a luminal cell population subjected to blood flow and an abluminal one that is not exposed to it. These early morphological changes lead to the formation of an immature valve leaflet. While previous studies mainly focused on genes that are positively regulated by shear stress, the mechanisms regulating cell behaviors and fates in cells that lack the stimulus of blood flow are largely unknown. One key discovery of my work is that the flow-sensitive Notch receptor and Krüppel-like factor (Klf) 2, one of the best characterized flow-regulated transcriptional factors, are activated by shear stress but that they function in two parallel signal transduction pathways. Each of these two pathways is essential for the rearrangement of atrioventricular cells into an immature double-layered valve leaflets. A second key discovery of my study is the finding that both Notch and Klf2 signaling negatively regulate the expression of the angiogenesis receptor Vegfr3/Flt4, which becomes restricted to abluminal endocardial cells of the valve leaflet. Within these cells, Flt4 downregulates the expressions of the cell adhesion proteins Alcam and VE-cadherin. A loss of Flt4 causes abluminal endocardial cells to ectopically express Notch, which is normally restricted to luminal cells, and impairs valve morphology. My study suggests that abluminal endocardial cells that do not experience mechanical stimuli loose Notch expression and this triggers expression of Flt4. In turn, Flt4 negatively regulates Notch on the abluminal side of the valve leaflet. These antagonistic signaling activities and fine-tuned gene regulatory mechanisms ultimately shape cardiac valve leaflets by inducing unique differences in the fates of endocardial cells.
Potato is the 4th most important food crop in the world. Especially in tropical and sub-tropical potato production, drought is a yield limiting factor. Potato is sensitive to water stress. Potato yield loss under water stress could be reduced by using tolerant varieties and adjusted agronomic practices. Direct selection for yield under water-stressed conditions requires long selection cycles. Thus, identification of markers for marker-assisted selection may speed up breeding. The objective of this thesis is to identify morphological markers for drought tolerance by continuously monitoring plant growth and canopy temperature with an automatic phenotyping system.
The phenotyping was performed in drought-stress experiments that were conducted in population A with 64 genotypes and population B with 21 genotypes in the screenhouse in 2015 and 2016 (population A) and in 2017 and 2018 (population B). Drought tolerance was quantified as deviation of the relative tuber starch yield from the experimental median (DRYM) and parent median (DRYMp). Relative tuber starch yield is starch yield under drought stress relative to the average starch yield of the respective cultivar under control conditions in the same experiment. The specific DRYM value was calculated based on the yield data of the same experiment or the global DRYM that was calculated from yield data derived from data combined over yeas of respective population or across multiple experiments including VALDIS and TROST experiments (2011-2016).
Analysis of variance found a significant effect of genotype on DRYM indicating that the tolerance variation required for marker identification was given in both populations.
Canopy growth was monitored continuously six times a day over five to ten weeks by a laser scanner system and yielded information on leaf area, plant height and leaf angle for population A and additionally on leaf inclination and light penetration depth for population B. Canopy temperature was measured 48 times a day over six to seven weeks by infrared thermometry in population B. From the continuous IRT surface temperature data set, the canopy temperature for each plant was selected by matching the time stamp of the IRT data with laser scanner data.
Mean, maximum, range and growth rate values were calculated from continuous laser scanner measurements of respective canopy parameters. Among the canopy parameters, the maximum and mean values in long-term stress conditions showed better correlation with DRYM values calculated in the same experiment than growth rate and diurnal range values. Therefore, drought tolerance index prediction was done from maximum and mean values of canopy parameters.
The tolerance index in specific experiment condition was linearly predicted by simple regression model from different single canopy parameters under long-term stress condition in population A (2016) and population B (2017 and 2018). Among the canopy parameters maximum light penetration depth (2017), mean leaf angle (2017, 2018, and 2016), mean leaf inclination or mean canopy temperature depression (2017 and 2018), maximum plant height (2017) were selected as tolerance predictors. However, no single parameters were sufficient to predict DRYM. Therefore, several independent parameters were integrated in a multiple regression model.
In multiple regression model, specific experiment DRYM values in population A was predicted from mean leaf angle (2016). In population B, specific tolerance could be predicted from maximum light penetration depth and mean leaf inclination (2017) and mean leaf inclination (2018) or mean canopy temperature depression and mean leaf angle (2018).
In data combined over season of population A, the multiple linear regression model selected maximum plant height and mean leaf angle as tolerance predictor. In Population B, mean leaf inclination was selected as tolerance predictor. However, in population A, the variation explained by the final model was too low.
Furthermore, the average tolerances respective to parent median (2011-2018) across FGH plants or all plants (FGH and field) were predicted from maximum plant height (population A) and maximum plant height and mean leaf inclination (population B). Altogether, canopy parameters could be used as markers for drought tolerance. Therefore, water stress breeding in potato could be speed up through using leaf inclination, light penetration depth, plant height and canopy temperature depression as markers for drought tolerance, especially in long-term stress conditions.
The current thesis is focused on the properties of graphene supported by metallic substrates and specifically on the behaviour of electrons in such systems. Methods of scanning tunneling microscopy, electron diffraction and photoemission spectroscopy were applied to study the structural and electronic properties of graphene. The purpose of the first part of this work is to introduce the most relevant aspects of graphene physics and the methodical background of experimental techniques used in the current thesis.
The scientific part of this work starts with the extensive study by means of scanning tunneling microscopy of the nanostructures that appear in Au intercalated graphene on Ni(111). This study was aimed to explore the possible structural explanations of the Rashba-type spin splitting of ~100 meV experimentally observed in this system — much larger than predicted by theory. It was demonstrated that gold can be intercalated under graphene not only as a dense monolayer, but also in the form of well-periodic arrays of nanoclusters, a structure previously not reported. Such nanocluster arrays are able to decouple graphene from the strongly interacting Ni substrate and render it quasi-free-standing, as demonstrated by our DFT study. At the same time calculations confirm strong enhancement of the proximity-induced SOI in graphene supported by such nanoclusters in comparison to monolayer gold. This effect, attributed to the reduced graphene-Au distance in the case of clusters, provides a large Rashba-type spin splitting of ~60 meV.
The obtained results not only provide a possible mechanism of SOI enhancement in this particular system, but they can be also generalized for graphene on other strongly interacting substrates intercalated by nanostructures of heavy noble d metals.
Even more intriguing is the proximity of graphene to heavy sp-metals that were predicted to induce an intrinsic SOI and realize a spin Hall effect in graphene. Bismuth is the heaviest stable sp-metal and its compounds demonstrate a plethora of exciting physical phenomena. This was the motivation behind the next part of the current thesis, where structural and electronic properties of a previously unreported phase of Bi-intercalated graphene on Ir(111) were studied by means of scanning tunneling microscopy, spin- and angle-resolved photoemission spectroscopy and electron diffraction. Photoemission experiments revealed a remarkable, nearly ideal graphene band structure with strongly suppressed signatures of interaction between graphene and the Ir(111) substrate, moreover, the characteristic moiré pattern observed in graphene on Ir(111) by electron diffraction and scanning tunneling microscopy was strongly suppressed after intercalation. The whole set of experimental data evidences that Bi forms a dense intercalated layer that efficiently decouples graphene from the substrate. The interaction manifests itself only in the n-type charge doping (~0.4 eV) and a relatively small band gap at the Dirac point (~190 meV). The origin of this minor band gap is quite intriguing and in this work it was possible to exclude a wide range of mechanisms that could be responsible for it, such as induced intrinsic spin-orbit interaction, hybridization with the substrate states and corrugation of the graphene lattice. The main origin of the band gap was attributed to the A-B symmetry breaking and this conclusion found support in the careful analysis of the interference effects in photoemission that provided the band gap estimate of ~140 meV.
While the previous chapters were focused on adjusting the properties of graphene by proximity to heavy metals, graphene on its own is a great object to study various physical effects at crystal surfaces. The final part of this work is devoted to a study of surface scattering resonances by means of photoemission spectroscopy, where this effect manifests itself as a distinct modulation of photoemission intensity. Though scattering resonances were widely studied in the past by means of electron diffraction, studies about their observation in photoemission experiments started to appear only recently and they are very scarce.
For a comprehensive study of scattering resonances graphene was selected as a versatile model system with adjustable properties. After the theoretical and historical introduction to the topic of scattering resonances follows a detailed description of the unusual features observed in the photoemission spectra obtained in this work and finally the equivalence between these features and scattering resonances is proven. The obtained photoemission results are in a good qualitative agreement with the existing theory, as verified by our calculations in the framework of the interference model. This simple model gives a suitable explanation for the general experimental observations.
The possibilities of engineering the scattering resonances were also explored. A systematic study of graphene on a wide range of substrates revealed that the energy position of the resonances is in a direct relation to the magnitude of charge transfer between graphene and the substrate. Moreover, it was demonstrated that the scattering resonances in graphene on Ir(111) can be suppressed by nanopatterning either by a superlattice of Ir nanoclusters or by atomic hydrogen. These effects were attributed to strong local variations of tork function and/or destruction of long-range order of thephene lattice. The tunability of scattering resonances can be applied for optoelectronic devices based on graphene. Moreover, the results of this study expand the general understanding of the phenomenon of scattering resonances and are applicable to many other materials besides graphene.
The impact that catalysis has on global economy and environment is substantial, since 85% of all chemical industrial processes are catalytic. Among those, 80% of the processes are heterogeneously catalyzed, 17% make use of homogeneous catalysts, and 3% are biocatalytic processes. Especially in the pharmaceutical and agrochemical industry, a significant part of these processes involves chiral compounds. Obtaining enantiomerically pure compounds is necessary and it is usually accomplished by asymmetric synthesis and catalysis, as well as chiral separation. The efficiency of these processes may be vastly improved if the chiral selectors are positioned on a porous solid support, thereby increasing the available surface area for chiral recognition. Similarly, the majority of commercial catalysts are also supported, usually comprising of metal nanoparticles (NPs) dispersed on highly porous oxide or nanoporous carbon material.
Materials that have exceptional thermal and chemical stability, and are electrically conductive are porous carbons. Their stability in extreme pH regions and temperatures, the possibility to tailor their pore architecture and chemical functionalization, and their electric conductivity have already established these materials in the fields of separation and catalysis. However, their heterogeneous chemical structure with abundant defects make it challenging to develop reliable models for the investigation of structure-performance relationships. Therefore, there is a necessity for expanding the fundamental understanding of these robust materials under experimental conditions to allow for their further optimization for particular applications. This thesis gives a contribution to our knowledge about carbons, through different aspects, and in different applications.
On the one hand, a rather exotic novel application was investigated by attempts in synthesizing porous carbon materials with an enantioselective surface. Chapter 4.1 described an approach for obtaining mesoporous carbons with an enantioselective surface by direct carbonization of a chiral precursor. Two enantiomers of chiral ionic liquids (CIL) based on amino acid tyrosine were used as carbon precursors and ordered mesoporous silica SBA-15 served as a hard template for obtaining porosity. The chiral recognition of the prepared carbons has been tested in the solution by isothermal titration calorimetry with enantiomers of Phenylalanine as probes, as well as chiral vapor adsorption with 2-butanol enantiomers. Measurements in both solution and the gas phase revealed the differences in the affinity of carbons towards two enantiomers.
The atomic efficiency of the CIL precursors was increased in Chapter 4.2, and the porosity was developed independently from the development of chiral carbons, through the formation of stable composites of pristine carbon and CIL-derived coating. After the same set of experiments for the investigation of chirality, the enantiomeric ratios of the composites reported herein were even higher than in the previous chapter.
On the other hand, the structure‒activity relationship of carbons as supports for gold nanoparticles in a rather traditional catalytic model reaction, on the interface between gas, liquid, and solid, was studied. In Chapter 5.1 it was shown on the series of catalysts with different porosities that the kinetics of ᴅ-glucose oxidation reaction can be enhanced by increasing the local concentration of the reactants around the active phase of the catalyst. A large amount of uniform narrow mesopores connected to the surface of the Au catalyst supported on ordered mesoporous carbon led to the water confinement, which increased the solubility of the oxygen in the proximity of the catalyst and thereby increased the apparent catalytic activity of this catalyst.
After increasing the oxygen concentration in the internal area of the catalyst, in Chapter 5.2 the concentration of oxygen was increased in the external environment of the catalyst, by the introduction of less cohesive liquids that serve as efficient solvent for oxygen, perfluorinated compounds, near the active phase of the catalyst. This was achieved by a formation of catalyst particle-stabilized emulsions of perfluorocarbon in aqueous ᴅ-glucose solution, that further promoted the catalytic activity of gold-on-carbon catalyst.
The findings reported within this thesis are an important step in the understanding of the structure-related properties of carbon materials.
This book endeavours to understand the seemingly direct link between utopianism and the USA, discussing novels that have never been brought together in this combination before, even though they all revolve around intentional communities: Imlay’s The Emigrants (1793), Hawthorne’s The Blithedale Romance (1852), Howland’s Papas Own Girl (1874), Griggs’s Imperium in Imperio (1899), and Du Bois’s The Quest of the Silver Fleece (1911). They relate nation and utopia not by describing perfect societies, but by writing about attempts to immediately live radically different lives. Signposting the respective communal history, the readings provide a literary perspective to communal studies, and add to a deeply necessary historicization for strictly literary approaches to US utopianism, and for studies that focus on Pilgrims/Puritans/Founding Fathers as utopian practitioners. This book therefore highlights how the authors evaluated the USA’s utopian potential and traces the nineteenth-century development of the utopian imagination from various perspectives.
The development of methods such as super-resolution microscopy (Nobel prize in Chemistry, 2014) and multi-scale computer modelling (Nobel prize in Chemistry, 2013) have provided scientists with powerful tools to study microscopic systems. Sub-micron particles or even fluorescently labelled single molecules can now be tracked for long times in a variety of systems such as living cells, biological membranes, colloidal solutions etc. at spatial and temporal resolutions previously inaccessible. Parallel to such single-particle tracking experiments, super-computing techniques enable simulations of large atomistic or coarse-grained systems such as biologically relevant membranes or proteins from picoseconds to seconds, generating large volume of data. These have led to an unprecedented rise in the number of reported cases of anomalous diffusion wherein the characteristic features of Brownian motion—namely linear growth of the mean squared displacement with time and the Gaussian form of the probability density function (PDF) to find a particle at a given position at some fixed time—are routinely violated. This presents a big challenge in identifying the underlying stochastic process and also estimating the corresponding parameters of the process to completely describe the observed behaviour. Finding the correct physical mechanism which leads to the observed dynamics is of paramount importance, for example, to understand the first-arrival time of transcription factors which govern gene regulation, or the survival probability of a pathogen in a biological cell post drug administration. Statistical Physics provides useful methods that can be applied to extract such vital information. This cumulative dissertation, based on five publications, focuses on the development, implementation and application of such tools with special emphasis on Bayesian inference and large deviation theory. Together with the implementation of Bayesian model comparison and parameter estimation methods for models of diffusion, complementary tools are developed based on different observables and large deviation theory to classify stochastic processes and gather pivotal information. Bayesian analysis of the data of micron-sized particles traced in mucin hydrogels at different pH conditions unveiled several interesting features and we gained insights into, for example, how in going from basic to acidic pH, the hydrogel becomes more heterogeneous and phase separation can set in, leading to observed non-ergodicity (non-equivalence of time and ensemble averages) and non-Gaussian PDF. With large deviation theory based analysis we could detect, for instance, non-Gaussianity in seeming Brownian diffusion of beads in aqueous solution, anisotropic motion of the beads in mucin at neutral pH conditions, and short-time correlations in climate data. Thus through the application of the developed methods to biological and meteorological datasets crucial information is garnered about the underlying stochastic processes and significant insights are obtained in understanding the physical nature of these systems.