9,500 research outputs found

    Meso-scale FDM material layout design strategies under manufacturability constraints and fracture conditions

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    In the manufacturability-driven design (MDD) perspective, manufacturability of the product or system is the most important of the design requirements. In addition to being able to ensure that complex designs (e.g., topology optimization) are manufacturable with a given process or process family, MDD also helps mechanical designers to take advantage of unique process-material effects generated during manufacturing. One of the most recognizable examples of this comes from the scanning-type family of additive manufacturing (AM) processes; the most notable and familiar member of this family is the fused deposition modeling (FDM) or fused filament fabrication (FFF) process. This process works by selectively depositing uniform, approximately isotropic beads or elements of molten thermoplastic material (typically structural engineering plastics) in a series of pre-specified traces to build each layer of the part. There are many interesting 2-D and 3-D mechanical design problems that can be explored by designing the layout of these elements. The resulting structured, hierarchical material (which is both manufacturable and customized layer-by-layer within the limits of the process and material) can be defined as a manufacturing process-driven structured material (MPDSM). This dissertation explores several practical methods for designing these element layouts for 2-D and 3-D meso-scale mechanical problems, focusing ultimately on design-for-fracture. Three different fracture conditions are explored: (1) cases where a crack must be prevented or stopped, (2) cases where the crack must be encouraged or accelerated, and (3) cases where cracks must grow in a simple pre-determined pattern. Several new design tools, including a mapping method for the FDM manufacturability constraints, three major literature reviews, the collection, organization, and analysis of several large (qualitative and quantitative) multi-scale datasets on the fracture behavior of FDM-processed materials, some new experimental equipment, and the refinement of a fast and simple g-code generator based on commercially-available software, were developed and refined to support the design of MPDSMs under fracture conditions. The refined design method and rules were experimentally validated using a series of case studies (involving both design and physical testing of the designs) at the end of the dissertation. Finally, a simple design guide for practicing engineers who are not experts in advanced solid mechanics nor process-tailored materials was developed from the results of this project.U of I OnlyAuthor's request

    Impact of plant growth promoting rhizobacteria (PGPR) on stress resistance of winter wheat (Triticum aestivum L.)

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    Wheat is one of the worldwide most cultivated crop and highly contribute to secure food production in different world regions. Although, it grows almost ubiquitous, its production is severely vulnerable to drought. Soil and rhizosphere microbial communities associated to plants come more and more into the focus of modern agrobiology research, as a solution to maintain productivity under drought, and reinforce sustainable production. Whereas numerous studies on wheat production and the beneficial influence of the soil microbiome under drought have been performed in arid and semiarid regions of the world, comparable studies in Central Europe are rare. This might change due to the ongoing climate crisis and expected less frequent precipitations during the vegetation season. So far, most studies that focus on acclimatization of the wheat rhizobiome to water deficit mostly consider, at best, two interacting factors, and lack to consider other biotic or abiotic drivers of rhizosphere microbial communities structure and function. Therefore, the aim of this thesis was to combine complementary analytical approaches to investigate drought-induced structural and functional changes in wheat rhizosphere bacterial communities and individual species in dependency of soil type, farming system, wheat cultivar and plant development stage, and to determine how these changes affect wheat performance as a consequence of possible climate change scenarios in Central Germany. The presented thesis starts with a general introduction and presentation of the project, followed by three consecutive chapters containing the main findings published in peer-reviewed articles. Starting with an experiment performed in the greenhouse (Chapter 1) and then moving to a realistic climate scenario under field conditions (Chapter 2 and 3), the three chapters demonstrate the sole and interacting effects of drought and farming system (Chapter 1-3), soil type and wheat cultivar (Chapter 1), as well as plant growth stages (Chapter 2 and 3) on bacterial communities and individual taxa of the wheat rhizobiome. The methods used reach from traditional cultivation and in-vitro bioassays (Chapter 3), over extracellular enzyme activity potentials (Chapter 1 and 2) to more advanced technologies such as metabarcoding (Chapter 1 and 2) and computational tools (Chapter 1 and 2), addressing single bacterial taxa as well as community level. Finalizing the thesis, a concluding synopsis compiles and critically reviews the gained results and formulates future study perspectives. In Chapter 1, we evaluated the impact of soil type (loamy vs. sandy), farming management (conventional vs. organic), wheat cultivar (non-demanding vs. demanding), and the interacting effects of these factors on wheat rhizobacterial community composition and function under extreme drought conditions. Water deficit exerted a strong pressure on rhizobacterial communities, and interacted with soil type and farming management, but not with the wheat cultivar types. In the sandy soil, we observed a strong drought-induced shift in community composition, with a decrease in species diversity and extracellulare enzyme production, while changes by drought were less prominent in the fertile loamy soil. A particular exception from this pattern was found for enzyme activities involved in carbon cycling in the sandy soil suggesting a positive plant-soil-feedback on enzyme activities by drought conditioning. In Chapter 2, two individual, but interrelated aims were pursued. First, we used the platform of the Global Change Experimental Facility (GCEF) to explore the impact of two farming practices (conventional vs. organic) and two climate treatments (ambient vs. future) on bacterial community composition and activity profiles of extracellulare enzymes involved in C,N and P cycles in the wheat rhizosphere at two different plant growth stages. The climate treatment in the GCEF had no effect on the rhizobacterial communities. Rhizobacterial community composition and functions significantly differed between vegetative and mature growth stages of the plants, in both conventional and organic farming. In a second step, we reused the data to explore further the accuracy of computational approaches, like Tax4Fun and PanFP, to predict functional profiles of bacterial communities based on 16S rDNA abundance data. To this end, we compared the measured enzyme activities with respective gene abundances in the community under different climate and farming treatments, and at the two plant development stages. This analysis revealed qualitative, but not necessarily quantitative concordances, i.e. we found effects of the different treatments on the measured enzyme activities reflected in the gene abundances. Chapter 3 is a complementary approach to Chapter 2 with a focus on individual bacterial species level. Culture-dependent methods were used to specifically isolate strong P-solubilizing bacteria from the rhizosphere of wheat, which were tested for their in-vitro drought tolerance. Among the more than 800 isolated species, Phyllobacterium, Pseudomonas and Streptomyces species dominated. While farming management and climate treatment had only minor effects on composition and functions of the isolates, the wheat growth stages had an impact, whereby a dominance of Pseudomonas species at the vegetative growth phase was replaced by dominance of Phyllobacterium species at the mature growth phase. Since P-solubilizing potential was paralleled by a high in vitro drought tolerance, Phyllobacterium species were characterized as promising plant growth promoting rhizobacteria (PGPR) of wheat under future drought conditions. In the synopsis part, we evaluated the multifactorial and multidisciplinary approaches and investigated to what extent the adaptations of bacterial communities in field and pot experiments coincided or differed. Overall, we found common and distinct adaptation processes of bacterial communities and individual species in the rhizosphere of wheat to drought, whereby single factors, but also interacting effects exerted a strong impact on these processes. This study underlines the importance of multifactorial approaches to reveal community- or species-specific plant-soil-feedbacks.:Contents 3 Preface 5 Bibliographic description 6 Zusammenfassung 9 Summary 13 Introduction 16 When extreme events become the new normal 17 Feedback to agricultural production and need for management adaptation 20 Difficulties in exploring the soil microbiome and identification of plant beneficial microbial taxa 22 Our approach with wheat 24 Bibliography 27 ֎ Chapter 1 31 Interactions Between Soil Properties, Agricultural Management and Cultivar Type Drive Structural and Functional Adaptations of the Wheat Rhizosphere Microbiome To Drought 31 Supplemental Tables 51 Supplemental Figures 55 ╬ Chapter 2 59 Can We Estimate Functionality of Soil Microbial Communities from Structure-Derived Predictions? A Reality Test in Agricultural Soils 59 Supplementary Tables 79 Supplemental Figures 84 Supplemental Material 1: 87 Variation in edaphic parameters according to experimental factors 87 Supplemental Material 2 88 Effect of abiotic soil parameters on bacterial community structure and function 88 Supplemental Material 3 90 Indicator species analysis 90 ۝ Chapter 3 95 Shifts Between and Among Populations of Wheat Rhizosphere Pseudomonas, Streptomyces and Phyllobacterium Suggest Consistent Phosphate Mobilization at Different Wheat Growth Stages Under Abiotic Stress 95 Supplementary Figures 112 Supplementary Tables 117 Synopsis 152 Multidisciplinary approaches combine advantages of cultivation-based and high throughput community-based methods 155 Multifactorial approaches to gain a more holistic understanding of plant-microbe interactions in pot experiments 157 Transferability of findings gained in the pot experiment to field conditions 159 Towards a wheat core microbiome? 161 Study limitations and outlook 163 Bibliography 164 Acknowledgements 169 Curriculum Vitae 171 Personal details 171 Education 171 Work experience 172 Research and Mentoring experience 172 Extracurricular activities 173 List of publications and Presentations 174 Publications in peer-reviewed journals: 174 Oral Presentations: 175 Poster Presentations: 175 Statutory declaration 176 Eidesstattliche ErklĂ€rung 177 Author contributions 178Weizen ist eine der weltweit am hĂ€ufigsten angebauten Kulturpflanzen und trĂ€gt zur Sicherung der Nahrungsmittelproduktion in verschiedenen Regionen der Welt bei. Obwohl er fast ĂŒberall angebaut werden kann, ist die Produktion durch Trockenheit limitiert. Daher rĂŒcken mehr und mehr die mikrobiellen Gemeinschaften im Boden und in der RhizosphĂ€re in den Mittelpunkt der modernen agrarbiologischen Forschung, um die ProduktivitĂ€t bei Trockenheit aufrechtzuerhalten und eine nachhaltige Produktion zu fördern. WĂ€hrend bereits zahlreiche Studien ĂŒber die Weizenproduktion und den positiven Einfluss des Bodenmikrobioms in ariden und semiariden Regionen der Welt durchgefĂŒhrt wurden, sind vergleichbare Studien in Mitteleuropa selten. Dies könnte sich aufgrund der anhaltenden Klimakrise und der zu erwartenden ausbleibenden SommerniederschlĂ€ge Ă€ndern. Dabei haben die meisten Studien, die sich mit der Akklimatisierung des Weizenrhizobioms an Wasserdefizite befasst haben, bestenfalls den Einfluss von Trockenheit und ein oder zwei weiteren biotischen oder abiotischen Einflussfaktoren, die zudem miteinander interagieren können, auf die Struktur und Funktion der mikrobiellen Gemeinschaften in der RhizosphĂ€re untersucht. Ziel dieser Arbeit war es daher, verschiedene komplementĂ€re Analysemethoden zu kombinieren, um trockenheitsbedingte strukturelle und funktionelle VerĂ€nderungen in den bakteriellen Gemeinschaften und auch einzelner Arten in der WeizenrhizosphĂ€re, in AbhĂ€ngigkeit von Bodentyp, Landnutzungssystem, Weizensorte und Pflanzenentwicklungsstadium zu untersuchen, und zu ermitteln, wie sich diese VerĂ€nderungen auf die ProduktivitĂ€t des Weizens als Folge möglicher Szenarien des Klimawandels in Mitteldeutschland auswirken. Die vorliegende Arbeit leitet mit einer allgemeinen EinfĂŒhrung und Vorstellung des Projekts ein, gefolgt von drei aufeinanderfolgenden Kapiteln, die die wichtigsten Ergebnisse enthalten, die in von Fachleuten begutachteten Artikeln veröffentlicht wurden. Beginnend mit einem Experiment im GewĂ€chshaus (Kapitel 1) und weiterfĂŒhrend zu einem realistischen Klimaszenario unter Feldbedingungen (Kapitel 2 und 3), beschreiben die drei Kapitel die alleinigen und interagierenden Auswirkungen von Trockenheit und Anbausystem (Kapitel 1-3), Bodentyp und Weizensorte (Kapitel 1), sowie Pflanzenwachstumsstadien (Kapitel 2 und 3) auf Bakteriengemeinschaften und einzelne Taxa des Weizenrhizobioms. Die verwendeten Methoden reichen dabei von der traditionellen Kultivierung und In-vitro-Bioassays (Kapitel 3), ĂŒber extrazellulĂ€re EnzymaktivitĂ€tspotenziale (Kapitel 1 und 2), bis hin zu fortschrittlicheren Technologien, wie Metabarcoding (Kapitel 1 und 2) und computergestĂŒtzten Vorhersagen (Kapitel 1 und 2). Zum Abschluss der Arbeit werden in einer abschließenden Synopsis die gewonnenen Ergebnisse zusammengetragen und kritisch betrachtet, sowie Ideen fĂŒr zukĂŒnftige Studien formuliert. In Kapitel 1 untersuchten wir die Auswirkungen des Bodentyps (lehmig vs. sandig), der Bewirtschaftung (konventionell vs. ökologisch), der Weizensorte (anspruchslos vs. anspruchsvoll) und die Wechselwirkungen zwischen diesen Faktoren auf die Zusammensetzung und Funktion der Bakteriengemeinschaft in der RhizosphĂ€re von Weizen unter extremen Trockenheitsbedingungen. Das Wasserdefizit ĂŒbte einen starken Druck auf die RhizosphĂ€renbakteriengemeinschaften aus und stand in Wechselwirkung mit dem Bodentyp und der Bewirtschaftung, nicht aber mit den Weizensorten. In den Sandböden beobachteten wir eine starke trockenheitsbedingte VerĂ€nderung der Zusammensetzung der Gemeinschaft mit einem RĂŒckgang der Artenvielfalt und der extrazellulĂ€ren Enzymproduktion, wĂ€hrend die VerĂ€nderungen durch die Trockenheit in den fruchtbaren Lehmböden weniger stark ausgeprĂ€gt waren. Eine besondere Ausnahme von diesem Muster wurde fĂŒr EnzymaktivitĂ€ten gefunden, die am Kohlenstoffkreislauf im Sandboden beteiligt sind, was auf eine positive RĂŒckkopplung zwischen Pflanze und Bodengemeinschaften unter Trockenheit hindeutet. In Kapitel 2 wurden zwei einzelne, jedoch miteinander verknĂŒpfte Ziele verfolgt. Erstens nutzten wir die Plattform der Global Change Experimental Facility (GCEF), um die Auswirkungen von zwei Anbaupraktiken (konventionell vs. ökologisch) und zwei Klimabehandlungen (ambient vs. zukĂŒnftig) auf die Zusammensetzung der Bakteriengemeinschaft und die AktivitĂ€tsprofile extrazellulĂ€rer Enzyme, die an den C-, N- und P-Zyklen in der RhizosphĂ€re von Weizen beteiligt sind, in zwei verschiedenen Pflanzenwachstumsstadien zu untersuchen. Die Klimabehandlung in der GCEF hatte keinen Einfluss auf die RhizosphĂ€renbakteriengemeinschaften. Die Zusammensetzung und die Funktionen der RhizosphĂ€renbakteriengemeinschaften unterschieden sich signifikant zwischen dem vegetativen und dem generativen Wachstumsstadium der Pflanzen, sowohl im konventionellen als auch im ökologischen Landbau. In einem zweiten Schritt nutzten wir die gewonnenen Daten, um die Genauigkeit rechnerischer AnsĂ€tze wie Tax4Fun und PanFP zur Vorhersage funktioneller Profile von Bakteriengemeinschaften auf der Grundlage von 16S rDNA-Daten zu ĂŒberprĂŒfen. Zu diesem Zweck verglichen wir die gemessenen EnzymaktivitĂ€ten mit den jeweiligen GenhĂ€ufigkeiten in der Gemeinschaft unter verschiedenen Klima- und Anbaubedingungen und in den beiden Entwicklungsstadien der Pflanzen. Diese Analyse ergab qualitative, aber nicht unbedingt quantitative Übereinstimmungen, d. h. wir fanden Auswirkungen der verschiedenen Behandlungen auf die gemessenen EnzymaktivitĂ€ten, die sich auch in den GenhĂ€ufigkeiten widerspiegeln. Kapitel 3 stellt einen ergĂ€nzenden Ansatz zu Kapitel 2 dar, wobei der Schwerpunkt auf einzelnen Bakterienarten liegt. Mit kulturabhĂ€ngigen Methoden wurden gezielt stark Phosphat-solubilisierende Bakterien aus der RhizosphĂ€re von Weizen isoliert und auf ihre In-vitro-Trockenheitstoleranz getestet. Unter den mehr als 800 isolierten Arten dominierten Phyllobacterium-, Pseudomonas- und Streptomyces-Arten. WĂ€hrend Anbaumanagement und Klimabehandlung nur geringe Auswirkungen hatten, wirkten sich die Wachstumsstadien des Weizens signifikant auf die Zusammensetzung und Funktionen der Isolate aus, wobei eine Dominanz von Pseudomonas-Arten in der vegetativen Wachstumsphase durch eine Dominanz von Phyllobacterium-Arten in der generativen Wachstumsphase ersetzt wurde. Da das Potenzial zur P-Solubilisierung mit einer hohen in vitro-Trockenheitstoleranz einherging, wurden Phyllobacterium-Arten als vielversprechende pflanzenwachstumsfördernde Rhizobakterien (PGPR) fĂŒr Weizen unter zukĂŒnftigen Trockenheitsbedingungen charakterisiert. In der Synopsis dieser Arbeit bewerteten wir die multifaktoriellen und multidisziplinĂ€ren AnsĂ€tze, und untersuchten, inwieweit die Anpassungen der Bakteriengemeinschaften in Feld- und Topfversuchen ĂŒbereinstimmen oder sich unterscheiden. Insgesamt fanden wir allgemeine, aber auch differenzielle Anpassungsprozesse von Bakteriengemeinschaften und einzelnen Arten in der RhizosphĂ€re von Weizen an die Trockenheit, wobei einzelne Faktoren, aber auch interagierende Effekte einen starken Einfluss auf diese Prozesse ausĂŒbten. Diese Studie unterstreicht damit die Bedeutung multifaktorieller AnsĂ€tze, um gemeinschafts- oder artspezifische RĂŒckkopplungen zwischen Pflanze und Boden zu untersuchen.:Contents 3 Preface 5 Bibliographic description 6 Zusammenfassung 9 Summary 13 Introduction 16 When extreme events become the new normal 17 Feedback to agricultural production and need for management adaptation 20 Difficulties in exploring the soil microbiome and identification of plant beneficial microbial taxa 22 Our approach with wheat 24 Bibliography 27 ֎ Chapter 1 31 Interactions Between Soil Properties, Agricultural Management and Cultivar Type Drive Structural and Functional Adaptations of the Wheat Rhizosphere Microbiome To Drought 31 Supplemental Tables 51 Supplemental Figures 55 ╬ Chapter 2 59 Can We Estimate Functionality of Soil Microbial Communities from Structure-Derived Predictions? A Reality Test in Agricultural Soils 59 Supplementary Tables 79 Supplemental Figures 84 Supplemental Material 1: 87 Variation in edaphic parameters according to experimental factors 87 Supplemental Material 2 88 Effect of abiotic soil parameters on bacterial community structure and function 88 Supplemental Material 3 90 Indicator species analysis 90 ۝ Chapter 3 95 Shifts Between and Among Populations of Wheat Rhizosphere Pseudomonas, Streptomyces and Phyllobacterium Suggest Consistent Phosphate Mobilization at Different Wheat Growth Stages Under Abiotic Stress 95 Supplementary Figures 112 Supplementary Tables 117 Synopsis 152 Multidisciplinary approaches combine advantages of cultivation-based and high throughput community-based methods 155 Multifactorial approaches to gain a more holistic understanding of plant-microbe interactions in pot experiments 157 Transferability of findings gained in the pot experiment to field conditions 159 Towards a wheat core microbiome? 161 Study limitations and outlook 163 Bibliography 164 Acknowledgements 169 Curriculum Vitae 171 Personal details 171 Education 171 Work experience 172 Research and Mentoring experience 172 Extracurricular activities 173 List of publications and Presentations 174 Publications in peer-reviewed journals: 174 Oral Presentations: 175 Poster Presentations: 175 Statutory declaration 176 Eidesstattliche ErklĂ€rung 177 Author contributions 17

    A Decision Support System for Economic Viability and Environmental Impact Assessment of Vertical Farms

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    Vertical farming (VF) is the practice of growing crops or animals using the vertical dimension via multi-tier racks or vertically inclined surfaces. In this thesis, I focus on the emerging industry of plant-specific VF. Vertical plant farming (VPF) is a promising and relatively novel practice that can be conducted in buildings with environmental control and artificial lighting. However, the nascent sector has experienced challenges in economic viability, standardisation, and environmental sustainability. Practitioners and academics call for a comprehensive financial analysis of VPF, but efforts are stifled by a lack of valid and available data. A review of economic estimation and horticultural software identifies a need for a decision support system (DSS) that facilitates risk-empowered business planning for vertical farmers. This thesis proposes an open-source DSS framework to evaluate business sustainability through financial risk and environmental impact assessments. Data from the literature, alongside lessons learned from industry practitioners, would be centralised in the proposed DSS using imprecise data techniques. These techniques have been applied in engineering but are seldom used in financial forecasting. This could benefit complex sectors which only have scarce data to predict business viability. To begin the execution of the DSS framework, VPF practitioners were interviewed using a mixed-methods approach. Learnings from over 19 shuttered and operational VPF projects provide insights into the barriers inhibiting scalability and identifying risks to form a risk taxonomy. Labour was the most commonly reported top challenge. Therefore, research was conducted to explore lean principles to improve productivity. A probabilistic model representing a spectrum of variables and their associated uncertainty was built according to the DSS framework to evaluate the financial risk for VF projects. This enabled flexible computation without precise production or financial data to improve economic estimation accuracy. The model assessed two VPF cases (one in the UK and another in Japan), demonstrating the first risk and uncertainty quantification of VPF business models in the literature. The results highlighted measures to improve economic viability and the viability of the UK and Japan case. The environmental impact assessment model was developed, allowing VPF operators to evaluate their carbon footprint compared to traditional agriculture using life-cycle assessment. I explore strategies for net-zero carbon production through sensitivity analysis. Renewable energies, especially solar, geothermal, and tidal power, show promise for reducing the carbon emissions of indoor VPF. Results show that renewably-powered VPF can reduce carbon emissions compared to field-based agriculture when considering the land-use change. The drivers for DSS adoption have been researched, showing a pathway of compliance and design thinking to overcome the ‘problem of implementation’ and enable commercialisation. Further work is suggested to standardise VF equipment, collect benchmarking data, and characterise risks. This work will reduce risk and uncertainty and accelerate the sector’s emergence

    A tetrachotomy of ontology-mediated queries with a covering axiom

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    Our concern is the problem of efficiently determining the data complexity of answering queries mediated by descrip- tion logic ontologies and constructing their optimal rewritings to standard database queries. Originated in ontology- based data access and datalog optimisation, this problem is known to be computationally very complex in general, with no explicit syntactic characterisations available. In this article, aiming to understand the fundamental roots of this difficulty, we strip the problem to the bare bones and focus on Boolean conjunctive queries mediated by a simple cov- ering axiom stating that one class is covered by the union of two other classes. We show that, on the one hand, these rudimentary ontology-mediated queries, called disjunctive sirups (or d-sirups), capture many features and difficulties of the general case. For example, answering d-sirups is Π2p-complete for combined complexity and can be in AC0 or L-, NL-, P-, or coNP-complete for data complexity (with the problem of recognising FO-rewritability of d-sirups be- ing 2ExpTime-hard); some d-sirups only have exponential-size resolution proofs, some only double-exponential-size positive existential FO-rewritings and single-exponential-size nonrecursive datalog rewritings. On the other hand, we prove a few partial sufficient and necessary conditions of FO- and (symmetric/linear-) datalog rewritability of d- sirups. Our main technical result is a complete and transparent syntactic AC0 / NL / P / coNP tetrachotomy of d-sirups with disjoint covering classes and a path-shaped Boolean conjunctive query. To obtain this tetrachotomy, we develop new techniques for establishing P- and coNP-hardness of answering non-Horn ontology-mediated queries as well as showing that they can be answered in NL

    Increased lifetime of Organic Photovoltaics (OPVs) and the impact of degradation, efficiency and costs in the LCOE of Emerging PVs

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    Emerging photovoltaic (PV) technologies such as organic photovoltaics (OPVs) and perovskites (PVKs) have the potential to disrupt the PV market due to their ease of fabrication (compatible with cheap roll-to-roll processing) and installation, as well as their significant efficiency improvements in recent years. However, rapid degradation is still an issue present in many emerging PVs, which must be addressed to enable their commercialisation. This thesis shows an OPV lifetime enhancing technique by adding the insulating polymer PMMA to the active layer, and a novel model for quantifying the impact of degradation (alongside efficiency and cost) upon levelized cost of energy (LCOE) in real world emerging PV installations. The effect of PMMA morphology on the success of a ternary strategy was investigated, leading to device design guidelines. It was found that either increasing the weight percent (wt%) or molecular weight (MW) of PMMA resulted in an increase in the volume of PMMA-rich islands, which provided the OPV protection against water and oxygen ingress. It was also found that adding PMMA can be effective in enhancing the lifetime of different active material combinations, although not to the same extent, and that processing additives can have a negative impact in the devices lifetime. A novel model was developed taking into account realistic degradation profile sourced from a literature review of state-of-the-art OPV and PVK devices. It was found that optimal strategies to improve LCOE depend on the present characteristics of a device, and that panels with a good balance of efficiency and degradation were better than panels with higher efficiency but higher degradation as well. Further, it was found that low-cost locations were more favoured from reductions in the degradation rate and module cost, whilst high-cost locations were more benefited from improvements in initial efficiency, lower discount rates and reductions in install costs

    Early Neanderthal social and behavioural complexity during the Purfleet Interglacial: handaxes in the latest Lower Palaeolithic.

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    Only a handful of ‘flagship’ sites from the Purfleet Interglacial (Marine Isotope Stage 9, c. 350-290,000 years ago) have been properly examined, but the archaeological succession at the proposed type-site at Purfleet suggests a period of complexity and transition, with three techno-cultural groups represented in Britain. The first was a simple toolkit lacking handaxes (the Clactonian), and the last a more sophisticated technology presaging the coming Middle Palaeolithic (simple prepared core or proto-Levallois technology). Sandwiched between were Acheulean groups, whose handaxes comprise the great majority of the extant archaeological record of the period – these are the focus of this study. It has previously been suggested that some features of the Acheulean in the Purfleet Interglacial were chronologically restricted, particularly the co-occurrence of ficrons and cleavers. These distinctive forms may have exceeded pure functionality and were perhaps imbued with a deeper social and cultural meaning. This study supports both the previously suggested preference for narrow, pointed morphologies, and the chronologically restricted pairing of ficrons and cleavers. By drawing on a wide spatial and temporal range of sites these patterns could be identified beyond the handful of ‘flagship’ sites previously studied. Hypertrophic ‘giants’ have now also been identified as a chronologically restricted form. Greater metrical variability was found than had been anticipated, leading to the creation of two new sub-groups (IA and IB) which are tentatively suggested to represent spatial and perhaps temporal patterning. The picture in the far west of Britain remains unclear, but the possibility of different Acheulean groups operating in the Solent area, and a late survival of the Acheulean, are both suggested. Handaxes with backing and macroscopic asymmetry may represent prehensile or ergonomic considerations not commonly found on handaxes from earlier interglacial periods. It is argued that these forms anticipate similar developments in the Late Middle Palaeolithic in an example of convergent evolution

    Foundations for programming and implementing effect handlers

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    First-class control operators provide programmers with an expressive and efficient means for manipulating control through reification of the current control state as a first-class object, enabling programmers to implement their own computational effects and control idioms as shareable libraries. Effect handlers provide a particularly structured approach to programming with first-class control by naming control reifying operations and separating from their handling. This thesis is composed of three strands of work in which I develop operational foundations for programming and implementing effect handlers as well as exploring the expressive power of effect handlers. The first strand develops a fine-grain call-by-value core calculus of a statically typed programming language with a structural notion of effect types, as opposed to the nominal notion of effect types that dominates the literature. With the structural approach, effects need not be declared before use. The usual safety properties of statically typed programming are retained by making crucial use of row polymorphism to build and track effect signatures. The calculus features three forms of handlers: deep, shallow, and parameterised. They each offer a different approach to manipulate the control state of programs. Traditional deep handlers are defined by folds over computation trees, and are the original con-struct proposed by Plotkin and Pretnar. Shallow handlers are defined by case splits (rather than folds) over computation trees. Parameterised handlers are deep handlers extended with a state value that is threaded through the folds over computation trees. To demonstrate the usefulness of effects and handlers as a practical programming abstraction I implement the essence of a small UNIX-style operating system complete with multi-user environment, time-sharing, and file I/O. The second strand studies continuation passing style (CPS) and abstract machine semantics, which are foundational techniques that admit a unified basis for implementing deep, shallow, and parameterised effect handlers in the same environment. The CPS translation is obtained through a series of refinements of a basic first-order CPS translation for a fine-grain call-by-value language into an untyped language. Each refinement moves toward a more intensional representation of continuations eventually arriving at the notion of generalised continuation, which admit simultaneous support for deep, shallow, and parameterised handlers. The initial refinement adds support for deep handlers by representing stacks of continuations and handlers as a curried sequence of arguments. The image of the resulting translation is not properly tail-recursive, meaning some function application terms do not appear in tail position. To rectify this the CPS translation is refined once more to obtain an uncurried representation of stacks of continuations and handlers. Finally, the translation is made higher-order in order to contract administrative redexes at translation time. The generalised continuation representation is used to construct an abstract machine that provide simultaneous support for deep, shallow, and parameterised effect handlers. kinds of effect handlers. The third strand explores the expressiveness of effect handlers. First, I show that deep, shallow, and parameterised notions of handlers are interdefinable by way of typed macro-expressiveness, which provides a syntactic notion of expressiveness that affirms the existence of encodings between handlers, but it provides no information about the computational content of the encodings. Second, using the semantic notion of expressiveness I show that for a class of programs a programming language with first-class control (e.g. effect handlers) admits asymptotically faster implementations than possible in a language without first-class control

    Tracking and Nowcasting Directional Changes in the Forex Market

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    Price changes in financial markets are typically summarized as time series (TS). Directional Change (DC) is an alternative, data-driven way to sample data points. The main objective of this thesis is to find new ways to extract new, useful information from the market. This is broken down into three directions: (1) to summarize price changes with DC, one must first determine the threshold to be used. We ask: could a threshold be too big or too small? If so, how could we determine the range of usable thresholds? (2) Could DC indicators extract volatility information from the market that is not observable under TS? (3) In DC, the start of a new trend is only confirmed in hindsight – to be precise, at the DC Confirmation (DCC) point when the price has reversed by the threshold specified. Could we detect that a new trend has begun before the DCC point? This is known as a nowcasting problem. This thesis has made three contributions. Firstly, we have created a guideline to determine the range of useable thresholds under DC. This supports the research that follows. Secondly, we have demonstrated how DC indicators could complement TS in tracking the market for volatility information. Thirdly, we have introduced new DC indicators; by using these indicators, we have proposed an algorithm and demonstrated how it could help us nowcast whether a new trend has begun in DC

    In her own words: exploring the subjectivity of Freud’s ‘teacher’ Anna von Lieben

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    This project is inspired by Roy Porter (1985), who draws attention to the patient-shaped gap in medical history, and Rita Charon (2006), who emphasises the need to bring the patient’s narrative to the fore in the practice of medicine. The principal aim was to devise a means of accessing the lived experience of a patient who is no longer alive in order to gain an understanding of her narrative. Anna von Lieben was identified as a suitable subject as she wrote a substantial quantity of autopathographical poetry suitable for analysis and her status as Freud’s patient makes her a person of significant interest to the history of medicine. The poems were analysed using Interpretative Phenomenological Analysis (IPA), an idiographic and inductive method of qualitative research, based on Heideggerian hermeneutic phenomenology, which explores the lived experience of individuals and is committed to understanding the first-person perspective from the third-person position. The main findings from the IPA study reveal that Anna experienced a prolonged period of malaise, starting in late adolescence which she believed to result, at least partly, from a traumatic experience which occurred at that time. The analysis also indicates that Anna suffered from deep and lasting feelings of guilt and shame. The discovery of additional family documentation enabled me to contextualise and add substance to the findings of the IPA study. Anna’s husband’s diaries in particular reveal that Anna: ‱ had a severe and longstanding gynaecological disorder ‱ suffered from severe morphinism ‱ did not benefit from Freud’s treatment which seemed neither to ease her symptoms nor identify any cause ‱ was treated in Paris, not by Jean-Martin Charcot as previously supposed, but by a French hydrotherapist, Theodore Keller, who appears to have become a person of considerable significance in her life. The above findings led me to investigate Anna’s comorbidities (gynaecological disease and morphinism) and to show how those could be responsible for much of the symptomatology identified by Freud as ‘hysteria’. I then explore the possibility that her psychotic-like experiences could have been iatrogenically induced by her treatment first by Keller and then by Freud. Finally, I propose a fourfold set of hypotheses as an alternative to Freud’s diagnosis of hysteria
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