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The three biodegradable polymers polylactic acid (PLA), polyhydroxybutyrate (PHB) and polybutylene adipate terephthalate (PBAT) were coated with hydrogenated amorphous carbon layers (a-C:H) in the context of this thesis. A direct alignment of the sample surface to the source was chosen, resulting in the deposition of a robust, r-type a-C:H. At the same time, a partly covered silicon wafer was placed together with the polymers in the coating chamber and was coated. Silicon is a hard material and serves as a reference for the applied layers. Due to the hardness of the material, no mixed phase occurs between the substrate and the applied layer (no interlayer formation). In addition, the thickness of the applied layer can be estimated with the help of the silicon sample.
The deposition of the layer was realized by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD). For the coating the samples were pre-treated with an oxygen plasma. Acetylene was used as precursor gas for the plasma coating. Coatings with increasing thickness in 50 nm steps from 0-500 nm were realised.
The surface analysis was performed using several techniques: The morphology and layer stability were analyzed with scanning electron microscopy (SEM) measurements. The wettability was determined by contact angle technique. In addition, the contact angles provide macroscopic information about the bond types of the carbon atoms present on the surface. For microscopic analysis of the chemical composition of the sample and layer surfaces, diffuse reflectance Fourier transform infrared spectroscopy (DRIFT) as well as synchrotron based X-ray photon spectroscopy (XPS) and near edge X-ray absorption fine structure spectroscopy (NEXAFS) were used.
All coated polymers showed several cases of layer failure due to internal stress in the layers. However, these were at different layer thicknesses, so there was a substrate effect. In addition, it is visible in the SEM images that the coatings of PLA and PHB can cause the applied layer to wave, the so-called cord buckling. This does not occur with polymer PBAT, which indicates a possible better bonding of the layer to the polymer. The chemical analyses of the layer surfaces show for each material a layer thickness dependent ratio of sp² to sp³ bonds of carbon, which alternately dominate the layer. In all polymers, the sp³ bond initially dominates, but the sp² to sp³ ratio changes at different intervals. Although the polymers were coated in the same plasma, i.e. the respective layer thicknesses (50 nm, 100 nm, ...) were applied in the same plasma process, the respective systems differed considerably from each other. A substrate effect is therefore demonstrably present. In addition, it was found that a change in the dominant bond from sp³ to sp² is an indication ofan upcoming layer failure of the a-C:H layer deposited on the polymer. In the case of PLA, this occurs immediately with change to sp² as the dominant bond; in the case of PHB and PBAT, this occurs with different delay to increased layer thicknesses (at PHB 100 nm, at PBAT approx. 200 nm.
Overall, this thesis shows that there is a substrate effect in the coating of the biodegradable polymers PLA, PHB and PBAT, since despite the same coating there is a different chemical composition of the surface at the respective layer thicknesses. In addition, a layer failure can be predicted by analyzing the existing bond.
Amphibian populations are declining worldwide for multiple reasons such as habitat destruction and climate change. An example for an endangered European amphibian is the yellow-bellied toad Bombina variegata. Populations have been declining for decades, particularly at the northern and western range margin. One of the extant northern range centres is the Westerwald region in Rhineland-Palatinate, Germany. To implement informed conservation activities on this threatened species, knowledge of its life-history strategy is crucial. This study therefore focused on different developmental stages to test predictions of life-history theory. It addressed (1) developmental, (2) demographic and (3) genetic issues of Bombina variegata as a model organism: (1) Carry-over effects from larval environment to terrestrial stages and associated vulnerability to predators were investigated using mesocosm approaches, fitness tests and predation trials. (2) The dynamics and demography of B. variegata populations were studied applying a capture-mark-recapture analysis and skeletochronology. The study was complemented through (3) an analysis of genetic diversity and structuring of B. variegata populations using 10 microsatellite loci. In order to reveal general patterns and characteristics among B. variegata populations, the study focused on three geographical scales: local (i.e. a former military training area), regional (i.e. the Westerwald region) and continental scale (i.e. the geographical range of B. variegata). The study revealed carry-over effects of larval environment on metamorph phenotype and behaviour causing variation in fitness in the early terrestrial stage of B. variegata. Metamorph size and condition are crucial factors for survival, as small-sized individuals were particularly prone to predator attacks. Yellow-bellied toads show a remarkable fast-slow continuum of the life-history trait longevity. A populations’ position within this continuum may be determined by local environmental stochasticity, i.e. an extrinsic source of variation, and the efficiency of chemical antipredator protection, i.e. an intrinsic source of variation. Extreme longevity seems to be an exception in B. variegata. Senescence was absent in this study. Weather variability affected reproductive success and thus population dynamics. The dispersal potential was low and short-term fragmentation of populations caused significant genetic differentiation at the local scale. Long-term isolation resulted in increased genetic distance at the regional scale. At the continental scale, populations inhabiting the marginal regions were deeply structured with reduced allelic richness. As consequence of environmental changes, short-lived and isolated B. variegata populations at the range margin may face an increased risk of extinction. Conservation measures should thus improve the connectivity among local populations and reinforce annual reproductive success. Further research on the intraspecific variation in B. variegata skin toxins is required to reveal potential effects on palatability and thus longevity.
Social-Media Plattformen wie Twitter oder Reddit bieten Nutzern nahezu ohne Beschränkungen die Möglichkeit, ihre Meinungen über aktuelle Ereignisse zu veröffentlichen, diese mit anderen zu teilen und darüber zu diskutieren. Während die Mehrheit der Nutzer diese Plattformen nur als reines Diskussionsportal verwenden, gibt es jedoch Nutzergruppen, welche aktiv und gezielt versuchen, diese veröffentlichten Meinungen in ihrem Sinne zu beeinflussen bzw. zu manipulieren. Durch wiederholtes Verbreiten von bearbeiteten Fake-News oder stark polarisierenden Meinungen im gesamten politischen Spektrum können andere Nutzer beeinflusst, manipuliert und unter Umständen zum Träger von Hassreden und extremen politischen Positionen werden. Viele dieser Nutzergruppen sind vor allem in englischsprachigen Portalen anzutreffen, in denen sie sich überwiegend als Muttersprachler ausgeben. In dieser Arbeit stellen wir eine Methode vor, englische Muttersprachler und Nicht-Muttersprachler, die Englisch als Fremdsprache verwenden, anhand von ausgewählten englischen Social Media Texten zu unterscheiden. Dazu implementieren wir textmerkmalbasierte Modelle, welche für traditionelle Machine-Learning Prozesse und neuartigen AutoML-Pipelines zur Klassifizierung von Texten verwendet werden. Wir klassifizieren dabei Sprachfamilie, Muttersprache und Ursprung eines beliebigen englischen Textes. Die Modelle werden an einem bestehenden Datensatz von Reddit, welcher hauptsächlich aus englischen Texten von europäischen Nutzern besteht, und einem neu erstellten Twitter Datensatz, der Tweets von aktuellen Themen in verschiedenen Ländern enthält, angewandt. Wir evaluieren dabei vergleichsweise die erhaltenen Resultate unserer Pipeline zu traditionellen Maschinenlernprozessen zur Texterkennung anhand von Präzision, Genauigkeit und F1-Maßen der Vorhersagen. Wir vergleichen zudem die Ergebnisse auf Unterschiede der Sprachnutzung auf den unterschiedlichen Plattformen sowie den ausgewählten Themenbereichen. Dabei erzielen wir eine hohe Vorhersagewahrscheinlichkeit für alle gewählten Kategorien des erstellten Twitter Datensatzes und stellen unter anderem eine hohe Abweichung in Bezug auf die durchschnittliche Textlänge insbesondere bei Nutzern aus dem baltoslawischen Sprachraum fest.
Der Industriestandard Decision Model and Notation (DMN) ermöglicht seit 2015 eine neue Art der Formalisierung von Geschäftsregeln. Hier werden Regeln in sogenannten Entscheidungstabellen modelliert, die durch Eingabespalten und Ausgabespalten definiert sind. Zudem sind Entscheidungen in graphartigen Strukturen angeordnet (DRD Ebene), die Abhängigkeiten unter diesen erzeugen. Nun können, mit gegebenen Input, Entscheidungen von geeigneten Systemen angefragt werden. Aktivierte Regeln produzieren dabei einen Output für die zukünftige Verwendung. Jedoch erzeugen Fehler während der Modellierung fehlerhafte Modelle, die sowohl in den Entscheidungstabellen als auch auf der DRD Ebene auftreten können. Nach der Design Science Research Methodology fokus\-siert diese Arbeit eine Implementierung eines Verifikationsprototyps für die Erkennung und Lösung dieser Fehler während der Modellierungsphase. Die vorgestellten Grundlagen liefern die notwendigen theoretischen Grundlagen für die Entwicklung des Tools. Diese Arbeit stellt außerdem die Architektur des Werkzeugs und die implementierten Verifikationsfähigkeiten vor. Abschließend wird der erstellte Prototyp evaluiert.
The history of human kind is characterized by social conflict. Every conflict can be the starting point of social change or the escalation into more destructive forms. The social conflict in regard to rising numbers of refugees and their acceptance that arose in most host countries in 2015 already took on destructive forms – in Germany, right-wing extremists attacked refugee shelters and even killed multiple people, including political leaders who openly supported refugees. Thus, incompatible expectancies and values of different parts of the society led to violent action tendencies, which tremendously threaten intergroup relations. Psychological research has developed several interventions in past decades to improve intergroup relations, but they fall short, for example, when it comes to the inclusion of people with extreme attitudes and to precisely differentiate potential prosocial outcomes of the interventions. Thus, this dissertation aimed to a) develop psychological interventions, that could also be applied to people with more extreme attitudes, thereby putting a special emphasis on collecting a diverse sample; b) gain knowledge about target- and outcome specific effects: Who benefits from which intervention and how can specific prosocial actions be predicted in order to develop interventions that guide needs-based actions; and c) shed light on potential underlying mechanisms of the interventions.
The dissertation will be introduced by the socio-political background that motivated the line of research pursued, before providing an overview of the conceptualization of social conflicts and potential psychological inhibitors and catalyzers for conflict transformation. Based on past research on socio-psychological interventions and their limitations, the aims of the dissertation will be presented in more detail, followed by a short summary of each manuscript. Overall, the present thesis comprises four manuscripts that were summarized in the general discussion into a road map for social-psychological interventions to put them into a broader perspective. The road map aspires to provide recommendations for increasing – either approach-oriented or support-oriented actions – by the socio-psychological interventions for a variety of host society groups depending on their pre-existing attitude towards refugees.
A Paradoxical Intervention targeting central beliefs of people with negative attitudes towards refugees influenced inhibitory and catalyzing factors for conflict transformation over the course of three experiments – thereby providing an effective tool to establish approach-oriented action tendencies, such as the willingness to get in contact with refugees. Further, the dissertation presents a novel mechanism – namely Cognitive Flexibility – which could explain the Paradoxical Interventions’ effect of past research. By positively affecting a context-free mindset, the Paradoxical Intervention could impact more flexible thought processes in general, irrespective of the topic tackled in the Paradoxical Intervention itself. For people with rather positive attitudes addressing emotions may increase specific support-oriented action tendencies. The dissertation provides evidence of a positive relation between moral outrage and hierarchy-challenging actions, such as solidarity-based collective action, and sympathy with prosocial hierarchy-maintaining support-oriented actions, such as dependency-oriented helping. These exclusive relations between specific emotions and action intentions provide important implications for the theorizing of emotion-behavior relations, as well as for practical considerations. In addition, a diversity workshop conducted with future diplomats showed indirect effects on solidarity-based collective action via diversity perception and superordinate group identification, thereby extending past research by including action intentions and going beyond the focus on grassroot-initiatives by presenting an implementable intervention for future leaders in a real world context.
Taken together, this dissertation provides important insights for the development of socio-psychological interventions. By integrating a diverse sample, including members of institutions on meso- and macro-levels (non-governmental organizations and future politicians) of our society, this dissertation presents a unique multi-perspective of host society members on the social conflict of refugee acceptance and support. Thereby, this work contributes to theoretical and practical advancement of how social psychology can contribute not only to negative peace – by for example (indirectly) reducing support of violence against refugees – but also to positive peace – by for example investigating precursors of hierarchy-challenging actions that enable equal rights.
Railway safety is a topic which gains the public attention only if major railway accidents happen. This is because railway is considered as a safe mode of travel by the public. However, to ensure the safety of the railway system railway companies as well as universities conduct a broad spectrum of research. An overview of this research has not yet been provided in the scholarly literature. Therefore, this thesis follows two objectives. First an overview and ranking of railway safety research universities should be provided. Second, based on these universities, it should be identified which are the most relevant and influential research topics. The ranking is based on the research method “literature review” which forms the methodical basis for this thesis. To evaluate the universities based on a measurable and objective criterion, the number of citations of the researchers from each university is gathered. As a result, the University of Leuven for the civil engineering, Milan Politechnico for mechanical enginering and the University of Loughborough for electrical engineering are identified as the leading university in their field of railway safety research. The top universities for each discipline are distributed all over Europe, North America and Asia. However, a clear focus on the US and British universities is observed. For identification of the most relevant and influential topics the keywords from the publications which are considered in the ranking procedure are analyzed. Focus areas among these keywords are revealed by calculating the count of each keyword. High-speed trains as well as maintenance are recognized as the highly relevant topics in both civil and mechanical engineering. Furthermore, the topic of railway dynamics for mechanical engineering and noise and vibration for civil engineering are identified as the leading topics in the respective discipline. Achieving both research goals required exploratory approaches. Therefore, this thesis leaves open space for future research to deepen the individual topics which are approached in each section. A validation of the results through experts interviews as well as a deepening of the analysis through increasing the number of analyzed universities as well as applying statistical methods is recommended.
Da die Belastung von Gewässern mit Mikroorganismen ein Gesundheitsrisiko für den Menschen unter anderem bei dessenFreizeitnutzung birgt, wurde die mikrobielle Belastung der Flüsse Rhein, Mosel und Lahn anhand von Indikatoren für fäkalbürtige bakterielle (Escherichia coli, intestinale Enterkokken) und virale Belastungen (somatische Coliphagen) untersucht. Des Weiteren wurden blaCTX-MGene als Marker für die Verbreitung von Antibiotikaresistenzen in der Lahn quantifiziert. Durch vergleichende Analysen von Monitoringdaten gegensätzlicher Abflussgeschehen in Rhein und Mosel wurde ein Einfluss von Veränderungen klimarelevanter Parameter auf die Verbreitung der fäkalen Indikatororganismen (FIO) geprüft. Die Analysen an Rhein, Mosel und Lahn zeigen deutlich, dass hohe Abflüsse und Niederschläge den Eintrag von FIO und Antibiotikaresistenzgenen (ARG) und damit potentiell antibiotikaresistenter Bakterien in Gewässer begünstigten, während unter dem Einfluss hoher Globalstrahlung und steigenden Wassertemperaturen ein Rückgang zu beobachtenwar. Basierend auf als relevant identifizierten Einflussparametern wurden multiple lineare Regressionsmodelle (MLR Modelle) entwickelt, die eine zeitnahe Vorhersage von FIO Konzentrationen an fünf Stellen eines Lahnabschnitts ermöglichen. Wechselwirkungenzwischen abiotischen und biotischen (Fraßdruck) Faktoren tragen zur Entstehung saisonaler Muster in den FIO Konzentrationenbei. Diese sind unter Niedrigwasserverhältnissen und besonders in Flüssen mit ausgeprägten trophischen Interaktionen besonders deutlich ausgeprägt und beeinflussen eine Übertragbarkeit von Modellansätzen zwischen Flüssen unterschiedlicher biologischer und hydrologischer Charakteristika. Daraus, dass Bakterien davon stärker betroffen sind als Coliphagen, lässt sich schließen, dass bakterielle Indikatoren virale Belastungen nicht ausreichend abbilden. BlaCTX-MGene waren in der Lahn parallel zu den FIO ubiquitär nachzuweisen, was auf einen fäkalen Ursprung hinweist. Landwirtschaft und kommunale Kläranlageneinleiter trugen zur Belastung mit FIO bei. Es zeigte sich, dass auch nicht badende Wassersportler mit eingeschränktem Wasserkontakt nachweislich dem Risiko ausgesetzt waren, antibiotikaresistente Bakterien (ARB) samt ihren Genen zu verschlucken, was das Risiko einer Infektion oder Kolonisierung mit den entsprechenden Bakterien birgt. Da ARG zu großen Teilen durch E. colierklärt werden konnten, könnenARG gegebenenfalls in MLR Modellemit E. colispezifischen Vorhersagevariablenintegriert werden. Kurzeitige und kurzfristig auftretende Verschmutzungsereignisse werden in Zukunft als eine Folge des Klimawandels in ihrer Häufigkeit weiter zunehmen. Identifizierte Herausforderungen hinsichtlich der Implementierung von Frühwarnsystemen zur Bewertung der mikrobiellen Wasserqualität in Flüssen liegen in den Anforderungen der Badegewässerrichtlinie (Richtlinie 2006/7/EC) und in einer unzureichenden Harmonisierung des Rechtsrahmens der Europäischen Union (EU) begründet, um Gesundheitsrisiken aufgrund mikrobieller Belastung in multifunktional genutzten Gewässern angemessen zu begegnen.
Although most plastic pollution originates on land, current research largely remains focused on aquatic ecosystems. Studies pioneering terrestrial microplastic research have adapted analytical methods from aquatic research without acknowledging the complex nature of soil. Meanwhile, novel methods have been developed and further refined. However, methodical inconsistencies still challenge a comprehensive understanding of microplastic occurrence and fate in and on soil. This review aims to disentangle the variety of state-of-the-art sample preparation techniques for heterogeneous solid matrices to identify and discuss best-practice methods for soil-focused microplastic analyses. We show that soil sampling, homogenization, and aggregate dispersion are often neglected or incompletely documented. Microplastic preconcentration is typically performed by separating inorganic soil constituents with high-density salt solutions. Not yet standardized but currently most used separation setups involve overflowing beakers to retrieve supernatant plastics, although closed-design separation funnels probably reduce the risk of contamination. Fenton reagent may be particularly useful to digest soil organic matter if suspected to interfere with subsequent microplastic quantification. A promising new approach is extraction of target polymers with organic solvents. However, insufficiently characterized soils still impede an informed decision on optimal sample preparation. Further research and method development thus requires thorough validation and quality control with well-characterized matrices to enable robust routine analyses for terrestrial microplastics.
The distributed setting of RDF stores in the cloud poses many challenges. One such challenge is how the data placement on the compute nodes can be optimized to improve the query performance. To address this challenge, several evaluations in the literature have investigated the effects of existing data placement strategies on the query performance. A common drawback in theses evaluations is that it is unclear whether the observed behaviors were caused by the data placement strategies (if different RDF stores were evaluated as a whole) or reflect the behavior in distributed RDF stores (if cloud processing frameworks like Hadoop MapReduce are used for the evaluation). To overcome these limitations, this thesis develops a novel benchmarking methodology for data placement strategies that uses a data-placement-strategy-independent distributed RDF store to analyze the effect of the data placement strategies on query performance.
With this evaluation methodology the frequently used data placement strategies have been evaluated. This evaluation challenged the commonly held belief that data placement strategies that emphasize local computation, such as minimal edge-cut cover, lead to faster query executions. The results indicate that queries with a high workload may be executed faster on hash-based data placement strategies than on, e.g., minimal edge-cut covers. The analysis of the additional measurements indicates that vertical parallelization (i.e., a well-distributed workload) may be more important than horizontal containment (i.e., minimal data transport) for efficient query processing.
Moreover, to find a data placement strategy with a high vertical parallelization, the thesis tests the hypothesis that collocating small connected triple sets on the same compute node while balancing the amount of triples stored on the different compute nodes leads to a high vertical parallelization. Specifically, the thesis proposes two such data placement strategies. The first strategy called overpartitioned minimal edge-cut cover was found in the literature and the second strategy is the newly developed molecule hash cover. The evaluation revealed a balanced query workload and a high horizontal containment, which lead to a high vertical parallelization. As a result these strategies showed a better query performance than the frequently used data placement strategies.
Despite widespread plans of big companies like Amazon and Google to develop unmanned delivery drones, scholarly research in this field is scarce, especially in the information systems field. From technical and legal perspectives, drone delivery in last-mile scenarios is in a quite mature state. However, estimates of user acceptance are varying between high skepticism and exaggerated optimism. This research follows a mixed method approach consisting both qualitative and quantitative research, to identify and test determinants of consumer delivery drone service adoption. The qualitative part rests on ten interviews among average consumers, who use delivery services on a regular basis. Insights gained from the qualitative part were used to develop an online survey and to assess the influence of associated risks on adoption intentions. The quantitative results show that especially financial and physical risks impede drone delivery service adoption. Delivery companies who are currently thinking about providing a delivery drone service may find these results useful when evaluating usage behaviors in the future market for delivery drones.