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This paper discusses the structural basis and practice of creating a climate policy framework in Nigeria. The roles of existing and planned institutions and legal frameworks are discussed, as well as how they foster or hinder the design of policies and implementation of climate responses at the domestic and international levels. Data has been collected between autumn 2009 and spring 2010. The paper combines literature review with empirical data from interviews of various actors in the Nigerian climate policy process. Various actors including the federal and state governments, civil society and private sector interest groups as well as the Nigerian oil sector are working conjointly on the elaboration of political frameworks and on the realisation of a multitude of individual projects focused on climate change. The paper examines the role of the institutional framework compassing this multitude of stakeholders for the creation of a sustainable climate policy in Nigeria, thereby discussing and referring to literature on institutional governance in the environment sector and institutional change for sustainability. Currently, there is a lack of cohesion between political initiatives and institutions, and a weak implementation of environmental laws and directives. Although becoming a topic of increasing political interest, a policy framework on climate change is still nonexistent for Nigeria – caused not least by diverging lines of interest between participating institutions. The paper shows that once awareness about climate change has been created, there is a danger of the proliferation of institutions and actors addressing the various dimensions of climate change. This proliferation highlights the lack of coordination between various government entities and their struggle to gain/retain influence over the national climate policy, thereby slowing down the design and implementation of responses to mitigate and adapt to climate change. Suggestions are made on how the barriers to climate policy development and implementation in Nigeria can be overcome.

Janus particles, named after the two faced Roman god Janus, possess unique asymmetry and combine two distinct functions at their opposite sides, allowing them to target complex self-assembled architectures and materials inaccessible for homogeneous building blocks. In this study, three areas regarding the topic of Janus particles were explored: the synthesis of Janus particles, their (self-) assembly, and applications. In the first part of the work, we have drawn our attention to the optimization of the synthetic procedures concerning the preparation of Janus particles and to the extending of the current Janus particle library by adding new geometries to the list. In the case of spherical Janus particles, we have developed an easy approach to tailor the Janus ratio of the resulting particles, thus, extending the possibilities of the Pickering emulsion approach for the creation of a variety of Janus particle architectures. Additionally, a new methodology was employed to measure directly and in situ the position/contact angle of the prepared Janus particles with different Janus ratios at a water-oil interface. It was further concluded that having simply two different functionalities on a particle surface does not necessarily imply amphiphilic behavior: only in the case of large wettability contrasts our particles were in a true Janus regime. In the case of platelet-like Janus particles, we have developed a completely new approach for their large-scale synthesis, which involved a reduced number of steps compared to the spherical Janus particles. In the second part of the work, the assembly behavior of various kinds of functional spherical Janus particles was investigated depending on the nature of the Janus particles and the surrounding media conditions. Oppositely charged, uncharged amphiphilic, and charged amphiphilic Janus particles were fabricated comprising different responsive polymers on their surface, and their assembly was investigated depending on the pH value of the dispersion, the ionic strength, or the solvent. It was found that, under specific conditions, the Janus particles formed hierarchical chain-like structures in solutions, which were not observed in the case of the homogeneous particle mixtures. The obtained results indicate that the fundamental understanding of the Janus particle assembly mechanisms is crucial for the programmed formation of desired structures. In the third part of the work, we have focused on the applications of our developed hybrid hairy Janus particles and proposed two main directions that would benefit from the unique properties or architecture of the Janus particles. The first direction is based on the exploitation of the superior interfacial activity of the Janus particles and their use for interfacial catalysis. The second proposed direction for the application of Janus particles is based on their use as building blocks for functional structured surfaces. The prepared surfaces were thoroughly characterized and tested for their performance toward anti-icing as well as anti-fouling applications. Ultimately, the developed functional surfaces based on Janus particles as building blocks are very promising for their future application in the coating technology.

Spatial navigation is essential for everyday function. It is successfully achieved by combining internally generated information – such vestibular and self-motion cues (known as path integration) – with external sources of information such as visual landmarks. These multiple sources and sensory domains are often associated with uncertainty and can provide conflicting information. The key to successful navigation is therefore how to integrate information from these internal and external sources in the best way. Healthy younger adults do this in a statistically optimal fashion by considering the perceived reliability of a cue during integration, consistent with the rules of Bayesian integration. However, the precise impact of ageing on the component senses of path integration and integration of such self-motion with external information is currently unclear. Given that impaired spatial ability is a common problem associated with ageing and is often a primary indicator of Alzheimer’s disease, this thesis asks whether age-related navigational impairments are related to fundamental deficits in the components of path integration and/or inadequate integration of spatial cues. Part 1 focussed on how ageing impacts the vestibular, kinaesthetic and visual components of path integration during linear navigation in the real world. Using path reproduction, distance estimation and depth perception tasks, I found that older adults showed no performance deficits in conditions that replicated those of everyday walking when visual and self-motion cues were present. However, they were impaired when relying on vestibular information alone. My results suggest that older adults are especially vulnerable to sensory deprivation but that weaker sensory domains can be compensated for by other sensory information, potentially by integrating different spatial cues in a Bayesian fashion: where the impact of unreliable/diminished senses can be minimised. Part 2 developed the conclusions of Part 1 by testing younger and older adults’ integration of visual landmarks and self-motion information during a simple homing task. I investigated the hypothesis that the integration of spatial information from multiple sensory domains is driven by Bayesian principles and that old age may affect the efficiency and elasticity of reliability-driven integration. Younger and older participants navigated to a previously visited location using self-motion and/or visual information. In some trials there was a conflict of information, which revealed the relative influence of self-motion and visual landmarks on behaviour. Findings revealed that both younger and older adults integrated visual and self-motion information to improve accuracy and precision, but older adults did not place as much influence on visual information as would have been optimal. This may have been the result of increased noise in the underlying spatial representations of older adults. Furthermore, older adults did not effectively re-weight visual and self-motion cues in line with the changing reliability of visual information, suggesting diminished plasticity in the underlying spatial representations. However, further development of the testing paradigm would strengthen support for these findings. Together, the findings of Part 2 suggest that increased neural noise and the suboptimal weighting of spatial cues might contribute to the common problems with navigation experienced by many older adults. This thesis provides original evidence for age-related changes to multisensory integration of spatial cues. Path integration abilities are relatively preserved when older adults navigate linear paths in the real world, despite loss of vestibular function. However, navigation is affected by old age when the task becomes more complex. Multisensory integration of spatial cues is partially preserved but it is not fully efficient. I offer evidence that the navigational impairments common to old age are related to fundamental deficits in the components of path integration, task complexity, and suboptimal integration of spatial cues. Crucially however, path integration is preserved sufficiently in older adults that they are able to navigate in small scale with relative success.

We are providing the geophysical data used to develop a gravity validated 3D lithospheric configuration of the Caribbean and north South American plates. The sources of these data are described in Section 4 of this README. Republication of subsets of these data are with permission of the authors or allowed by the licences of the input data. This data repository contains the lithospheric layers of the gravity validated 3D structural and density model of the Caribbean and north South American plates. In this model, the integration of different publicly available geophysical datasets was made, after an interpolation to a homogeneous spatial resolution of 25 km was performed. The data repository also contains the average density of the crystalline crust obtained after forward modelling the gravity anomalies. Additionally, the rotation files of the GPlates reconstructions of the Caribbean Large Igneous Plateau (CLIP) back to 90 Ma are included. This kinematic analysis was based on different reconstructions previously published by other authors. Further information and citations are given on the README file associated to this data repository.

Inspection date: 20 July 2021

Eine Absenkung der Betriebstemperatur von Festoxidbrennstoffzellen (SOFCs) in den Bereich um 500 °C wird angestrebt um Anwendungsfelder wie Brennstoffzellengeneratoren für mobile Anwendungen zu erschließen. Jedoch weist yttriumstabilisiertes Zirkonoxid (YSZ), der nach aktuellem Stand der Technik verwendete Elektrolytwerkstoff, eine unzureichende ionische Leitfähigkeit in diesem Niedertemperaturbereich auf. Zwei Lösungsansätze können hier Abhilfe schaffen. Der erste, weitverbreitete Ansatz ist die Verwendung eines alternativen Elektrolytwerkstoffs mit höherer Leitfähigkeit. Ein Vergleich von in der relevanten Fachliteratur angegebenen Daten zeigt allerdings uneinheitliche Leitfähigkeitswerte der einzelnen Werkstoffe und deren Verhältnisse zueinander. Der zweite Ansatz ist eine Verringerung der Elektrolytdicke. Über Schleuderbeschichtung (engl: spin coating) können Schichtdicken von etwa 1 μm realisiert werden. Diese Herstellungsmethode ist sehr arbeitsintensiv, da mehrfache Durchläufe von Beschichtungszyklus, Trocknung und Wärmebehandlung notwendig sind. Zudem stellt eine weitere Reduzierung der Schichtdicke eine große Herausforderung dar. Ziel dieser Arbeit ist ein systematischer Vergleich der ionischen Leitfähigkeit der drei überwiegend verwendeten und kommerziell erhältlichen Elektrolytwerkstoffe. Diese sind YSZ, scandiumstabilisiertes Zirkonoxid (ScSZ) und gadoliniumdotiertes Ceroxid (GDC). Mittels elektrochemischer Impedanzspektroskopie (EIS) konnte gezeigt werden, dass GDC mit 5,8 x 10$^{-3}$ S cm$^{-1}$ eine höhere ionische Leitfähigkeit bei 500 °C aufweist als ScSZ (2,5 x 10$^{-3}$ S cm$^{-1}$) und YSZ (1,1 x 10$^{-3}$ S cm$^{-1}$). Diese Analyse erfolgte unter Berücksichtigung von Ausgangspulver, Herstellungsmethode und resultierender Mikrostruktur nach der Sinterung. In weiterführenden Versuchen wurde ein Prozessablauf für die Herstellung eines 5cm x 5cm GDC Elektrolyten über Siebdruck auf eine herkömmliche anodengestützte Zelle entwickelt. Nach der Sinterung bei 1400 °C für 5 Stunden wurde eine Elektrolytdicke von 3,5 μm erreicht, sowie eine ausreichende Luftdichtigkeit mit einer Leckrate von 3,54 x 10$^{-6}$ hPa dm$^{2}$ s$^{-1}$ cm$^{-2}$ ermittelt. Die elektrochemische Charakterisierung einer solchen Einzelzelle zeigte eine hohe Leistungsfähigkeit von 2A cm$^{-2}$ bei 750 °C und einer Zellspannung von 0,84 V (Kathodengas: Luft, Anodengas: 10% H$_{2}$O in H$_{2}$). Mittels EIS wurde ein ohmscher Widerstand von 125,2m$\Omega$ cm$^{2}$ bei 500 °C ermittelt. Der vorliegende Vergleich der ionischen Leitfähigkeiten kann als Referenz für weiterführende Arbeiten dienen und Hilfestellung bei der Auswahl eines geeigneten Elektrolytwerkstoffs für die jeweils angestrebte SOFC Anwendung leisten. Dies gilt insbesondere, wenn die Herstellung unterschiedlicher Schichtdicken berücksichtigtwerden soll. Diese Arbeit bietet somit eine solide Basis zur Weiterentwicklung, die in der zuvor publizierten Literatur durch teils widersprüchliche Angaben nicht gegeben war. Die erfolgreiche Entwicklung der dünnen und dichten GDC Elektrolytschicht zeigt die Anwendbarkeit von GDC auf üblichen SOFC Substraten und bestätigt die höhere Leistungsfähigkeit im Vergleich zu YSZ, während ein hoher Herstellungsaufwand für sub-μm Schichten vermieden wird.