VictorJuiz/thesis huggingface dataset:
Lead oxides for photovoltaics

This thesis investigates lead oxides as photovoltaic materials. Vacuum deposition methods and ex-situ annealing are used to produce different stoichiometries of lead oxide. The relationship between structure and the optoelectronic properties is then investigated. Following this, a number of photovoltaic devices are prototyped and a Kelvin probe used to determine and understand the band structure of devices.
Thin films of PbO produced via air annealing of thermally evaporated lead consist of a mixture of two phases, orthorhombic and tetragonal, that determine the materials properties and effectiveness as absorber layer in a Schottky device. Films of higher tetragonal content are more photoactive, showing lower series resistance. Kelvin probe reveals that with an increasing work function of the PbO with increasing duration of the annealing, the Schottky barrier between PbO and Al increases, which results in a higher VOC. This trend is inverted when the Fermi level of PbO drops below that of ITO, creating an opposing junction.
Reactively sputtered PbO2 films are highly conductive degenerate semiconductors. Increasing oxygen flow rate during deposition leads to increased resistivity and decreased mobility, resulting from a decrease in grain size. Alongside this an increase in carrier concentration is observed as the material gets less ordered at higher oxygen flow rates, which results in an increase in Fermi level. Due to its high conductivity the material is not photoactive, and the high work function between -5.6 and -5.8 eV does not allow the formation of a Schottky junction or a p-n junction with the evaporated p- type PbO.
Post deposition annealing of the sputtered films leads to the formation of the more resistive Pb3O4 phase. This material shows lower carrier concentration and mobility, however, work functions are similarly high. The changes induced by the heat treatment are not substantial enough to be able to create a junction between the as-deposited and the annealed material, as is revealed by Kelvin probe and Hall Effect measurements.
Heterojunctions between P3HT and Pb3O4 were made to test predictions made by KP measurements. A heat treatment on P3HT improved its electronic properties and raised the Fermi level, resulting in the transformation of a diode in to a photovoltaic device and a decrease in dark current.

Keywords: photovoltaics thin film metal oxide thermal evaporation sputtering
Advisor: Watt, AAR
Assender, HE
Constructive mathematics - its set theory and practice

The thesis falls naturally into two parts, in the first of which (comprising Chapter 1) there is laid down a set-theoretic foundation for constructive mathematics as understood by Errett Bishop and his followers. The work of this part closely follows the lines of the corresponding classical development of set theory by Anthony Morse, highlights several classical definitions and results which are inadequate for a proper description of constructive mathematics, and develops constructive replacements for these where possible; of particular importance is the constructive proof of a general recursion theorem, from which the familiar theorems of simple and primitive recursion readily follow.
The second part of the thesis (Chapters 2–5) is concerned with various problems of constructive analysis, the link between these problems being their involvement with compactness or local compactness at some stage. Chapter 2 serves as an introduction to this analysis, and includes the definition of metric injectiveness and the proof of a constructive substitute for the classical result that a continuous injection of a compact Hausdorff space onto a Hausdorff space has continuous inverse.
In Chapter 3 we give an improved definition of one-point compactification of a locally compact space, and then develop the theory of existence and essential uniqueness of such compactifications of a given space. In turn, this is applied in Chapter 4, which deals in full with the space of continuous, complex-valued functions which vanish at infinity on a locally compact space, and with star homomorphisms between such spaces; interpolated within the main body of this chapter is the vital Backward Uniform Continuity Theorem, which leads to a discussion of possible constructive substitutes for the classical Uniform Continuity Theorem.
The final chapter deals with constructive substitutes for various topologies associated with spaces of bounded linear mappings between normed linear spaces. The main results of this chapter concern the weak operator topology on the space Hom(H,H) of bounded linear operators on a Hilbert space H, and include a constructive proof of the weak operator precompactness of the unit ball of Hom(H,H), and a proof that the compactness of this ball is an essentially non-constructive proposition. The chapter ends with a discussion of linear functionals and the weak operator topology on Hom(H,H), and a partial substitute for the classical characterisa- of ultraweakly continuous linear functionals on a linear subset of Hom(H,H).
In addition, there are five appendices, three of which develop material arising from that in the main body of the thesis. In the first of these three, we describe an axiomatic theory of proofs within the formal system of Chapter 1, and derive (amongst other results) a very satisfactory characterisation of proofs of 'p → q'; the second deals with connectedness, and builds up to a constructive proof that a closed ball in finite dimensional Banach space is connected; finally, the last makes a remark on metric injectiveness in the light of a conjecture in Chapter 2.
The politics of social protection in rural India

Social protection should ideally create a framework of 'welfare rights' for the vulnerable individuals and households. The state, through a set of policies of promotive and protective measures, sets out to achieve this. However, gaining these welfare rights in a decentralised democratic framework could be a function of the bargaining power that each individual, household and social group may possess. Therefore the micro-level interactions involving claimant, bureaucrat and local elites constitute the key policy process. Study of the process itself can reveal why some households gain formal social protection and other fail. This study argues that the local practices and informal rules underlying these public policy processes are purposively guided by the private interests of the local elites.
At the heart of this dissertation is a comparative case-study of two villages in the Indian state of Maharashtra, based on eight months ethnographic fieldwork. Bottomup evaluation of two social protection programmes, public works (promotive) and social assistance (protective) programmes shows that 60 per cent of eligible persons are excluded from welfare rights. The mechanisms of exclusion and inclusion in these programmes are studied. The study reveals that both eligibility and entitlement to 'welfare rights' are contested within the power structure of the local community. The social identity of the claimant, and the ability to build a relationship with the local leaders or labour market managers act as key routes to access welfare rights. The precedence of informal rules at the stage of implementation of social protection programmes reproduced the existing social and economic power structures. As a result, the welfare rights of individuals and households are affected by the competing forces in the non-state sectors. These non-state actors, through their network, were able to weaken the administration and fair allocation of welfare benefits.
Through this analysis the thesis contributes to the understanding of the local state, and decision-making practices over welfare rights in a decentralised context.

Advisor: Smith, G
Planar heterojunction perovskite solar cells via vapour deposition and solution processing

Hybrid organic-inorganic solar photovoltaic (PV) cells capable of directly converting sunlight to electricity have attracted much attention in recent years. Despite evident technological advancements in the PV industry, the widespread commercialisation of solar cells is still being mired by their low conversion efficiencies and high cost per Watt. Perovskites are an emerging class of semiconductors providing a low-cost alternative to silicon-based photovoltaic cells, which currently dominate the market. This thesis develops a series of studies on “all-solid state perovskite solar cells” fabricated via vapour deposition which is an industrially-accessible technique, to achieve planar heterojunction architectures and efficient PV devices.
Chapter 2 presents a general outlook on the operating principles of solar cells, delving deeper into the specific operational mechanism of perovskite solar cells. It also explores the usual methods employed in the fabrication of perovskite thin films. Chapter 3 describes the experimental procedures followed during the fabrication of the individual components constituting the device from the synthesis of the precursors to the construction of the functioning perovskite PV devices. Chapter 4 demonstrates pioneering work involving the dual-source vapour deposition (DSVD) of planar heterojunction perovskite solar cells which generated remarkable power conversion efficiency values surpassing 15%. These significant results pave the way for the mass-production of perovskite PVs. To further expand the range of feasible vapour deposition techniques, a two-layer sequential vapour deposition (SVD) technique is explored in Chapter 5. This chapter focusses on identifying the factors affecting the fundamental properties of the vapour-deposited films. Findings provide an improved understanding of the effects of precursor compositions and annealing conditions on the films. Chapter 5 concludes with a comparison between SVD and DSVD fabricated films, highlighting the benefits of each vapour deposition technique.
Furthermore, hysteretic effects are analysed in Chapter 6 for the perovskite PV devices fabricated based on different structural configurations. An interesting discovery involving the temporary functioning of compact layer-free perovskite PV devices suggests the presence of a built-in-field responsible for the hysteresis of the cells. The observations made in this chapter yield a new understanding of the functionality of individual cell layers. Combining the advantages of the optimum vapour deposition technique established in Chapter 4 and Chapter 5, with the enhanced understanding of perovskite PV cell operational mechanism acquired from Chapter 6, an ongoing study on an “all-perovskite” tandem solar cell is introduced in Chapter 7. This demonstration of the “all-perovskite” tandem devices confirms the versatility of perovskites for a broader range of PV applications.

Keywords: Perovskite
Hybrid inorganic-organic
Solution processing
Solar cells
Vapour deposition
Advisor: Snaith, H
Johnston, M
Mapping of behavioural quantitative trait loci

Anxiety is a common disorder which affects about 25% of the population and whose pathophysiology is still poorly understood. Animal models of disease have been widely used to investigate the molecular basis of human disorders, including psychiatric illnesses. This thesis is about the study of the genetic basis of a mouse model of anxiety.
I have carried out a QTL mapping study of behavioural measures thought to model anxiety. I report results from 1,636 mice, assessed for a large number of phenotypes in five ethological tests. Mice belonged to two F2 intercrosses originated by four lines generated in a replicate selection experiment. By comparing mapping results between the two crosses, I have demonstrated that selection operated on the same relatively small number of loci in the four selected lines.
Analysis of genetic effect of QTL across phenotypes has allowed me to identify loci with specific roles on different dimensions of anxious behaviour, therefore enhancing our understanding of the anxiety phenotype in mice. For some of these QTL I have also accomplished fine mapping experiments: a locus on chromosome 15 is now contained in an interval of only 3 centimorgans.
This work is the basis for further molecular dissection of the genetic loci that underlie anxiety and provides a starting point for the discovery of genes involved in a common psychiatric condition.

Advisor: Flint, J
Incremental sheet forming: modelling and path optimisation

Incremental sheet forming (ISF) is a novel metal shaping technology that is economically viable for low-volume manufacturing, customisation and rapid-prototyping. It uses a small tool that is controlled by a computer-numerically controlled sequence and the path taken by this tool over the sheet defines the product geometry. Little is currently known about how to design the tool-path to minimise geometric errors in the formed part. The work here addresses this problem by developing a model based tool-path optimisation scheme for ISF. The key issue is how to generate an efficient model for ISF to use within a path optimisation routine, since current simulation methods are too slow. A proportion of this thesis is dedicated to evaluating the applicability of the rigid plastic assumption for this purpose. Three numerical models have been produced: one based on small strain deformation, one based on limit analysis theory and another that approximates the sheet to a network of rods. All three models are formulated and solved as second-order cone programs (SOCP) and the limit analysis based model is the first demonstration of an upper-bound shell finite element (FE) problem solved as an SOCP. The models are significantly faster than commercially available FE software and simulations are compared with experimental and numerical data, from which it is shown the rigid plastic assumption is suitable for modelling deformation in ISF. The numerical models are still too slow for the path optimisation scheme, so a novel linearised model based on the concept of spatial impulse responses is also formulated and used in an optimal control based tool-path optimisation scheme for producing axisymmetric products with ISF. Off-line and on-line versions of the scheme are implemented on an ISF machine and it is shown that geometric errors are significantly reduced when using the proposed method. This work provides a new structured framework for tool-path design in ISF and it is also a novel use of feedback to compensate for geometrical errors in ISF.

Keywords: metal forming
path optimisation
incremental forming
limit analysis
rigid plastic
Advisor: Duncan, S
The politics of asylum in Africa

There is a crisis of asylum in Africa. In response to large and protracted refugee populations, declining donor assistance and a range of related security concerns, a significant number of African states have limited the asylum they offer to refugees. Some states have closed their borders to new arrivals and pursued early repatriations. Many other states have contained refugees in isolated and insecure camps. Given the scale of this crisis, the global pressures on asylum, and the disproportionate share of the global refugee burden borne by Africa, understanding the responses of African states poses an important challenge.
A critical examination of the factors influencing the refugee policies of African states is, however, strikingly absent from the scholarly literature. The objective of this thesis is to address this gap by examining the responses of Kenya, Tanzania and Guinea to the arrival and prolonged presence of significant refugee populations. Drawing on field research, this thesis argues that the asylum policies of the three cases are the result of factors both related to the presence of refugees, such as burden sharing and security concerns, and unrelated to the presence of refugees, such as foreign policy priorities, democratization, economic liberalization and the sense of vulnerability experienced by many regimes in Africa.
Drawing on a political history of the post-colonial African state, this thesis argues for an approach that recognizes the politics of asylum in Africa. Such an approach highlights the importance of incorporating the host state into any examination of asylum in Africa and the predominant role that broader political factors play in the formulation of asylum policies. This is not to suggest that factors such as the protracted nature of refugee populations, levels of burden sharing and security concerns are irrelevant to the study of asylum in Africa. Instead, the thesis argues that such factors are very relevant, but need to be understood in a more critical way, mindful of the political context within which asylum policies are formulated. This approach leads to important lessons not only for the study of asylum in Africa, but also for the future of the refugee protection regime in Africa.

Advisor: Gibney, M
MacFarlane, S
MacFarlane, N
In the shadow of politicisation

This thesis researches the variation in levels of liberalisation within the European services market, focusing in detail on four selected service sectors (i.e. postal services, electricity services, healthcare services and the services covered by the Services Directive) from 2001 until 2011. In this thesis, I propose a model of European integration capable of explaining the exact levels of liberalisation in each service sector. I argue that the level of liberalisation can be explained by looking at the drivers of integration (i.e. expected economic benefits from further integration and the level of supranational activity), which determine the societal demand for further integration and the shape legislators’ preferences and constraints, and the intervening influence of adhoc politicisation (i.e. the influence of public opinion through mass mobilisation). To illustrate this, this thesis applies a two-tiered approach of analysis. First, it explains the context in which the legislation is made to understand the economic implications of the proposed legislation, the level of supranational activity preceding the tabling of the legislation and the preferences of all actors involved. Second, taking preferences as exogenously given, this thesis applies a method of process tracing to study in detail the negotiations between legislators – the amending stage of the legislation. The case studies show that the drivers are crucial to explain the general demand for integration and at the same time show how politicisation, taking various guises, influences the level of liberalisation – primarily by altering legislators’ relative power. Particularly interesting is that politicisation can affect the negotiations even in absence of politicisation actually materialising causing some legislation to be made in the ‘shadow of politicisation’. These findings confirm existing explanations of European integration and add new insights as to how we can understand the process of European integration more generally.

Keywords: liberalisation
services market
European policy-making
Advisor: Nicolaidis, K
Mattli, W
Novel adenoviral vectored vaccines and the implications of viral diversity in therapeutic strategies against Hepatitis C Virus infection

Hepatitis C virus (HCV) is a major global pathogen estimated to infect over 170 million people worldwide. A recent study has shown that vaccination with adenoviral vectors, based on rare human and simian serotypes encoding the non-structural (NS) proteins of HCV, induces highly potent, multi-specific and durable T cell responses in healthy human volunteers. In this thesis I assess the safety and immunogenicity of these vaccines (ChAd3–NSmut and Ad6-NSmut), for the first time in HCV infected patients. This work also explores whether vaccine-induced T cell responses target in vivo circulating HCV antigens and common naturally occurring epitope variants.
Patients with treatment naive chronic genotype 1 HCV infection were vaccinated (i.m.) with ChAd3-NSmut and Ad6-NSmut in a heterologous prime boost schedule, either with or without current IFN and ribavirin (IFN/RBV). Epitope-specific T cell responses were defined by fine mapping using HCV peptides. Circulating viral genomic sequence was determined in vaccinated patients at baseline and at any point of viral relapse. Cross-reactivity of vaccine-induced T cell responses was determined in T cell assays, using peptides corresponding to both circulating host virus and common population HCV epitope variants. An in vitro dendritic cell /T cell priming model was used to identify possible candidates for a cross-reactive vaccine immunogen at the most immunodominant epitope, NS31406.
33 patients were vaccinated. Vaccination was well tolerated. At the highest vaccine dose (2.5 x 1010vp) vaccine-induced T cell responses were detectable in 11/20 patients receiving concurrent IFN/RBV and 2/4 patients receiving vaccination alone. In total 14 antigenic targets were identified, 2 of which have not previously been described. However, T cell responses were of lower magnitude and more narrowly focused than those observed in healthy volunteers vaccinated with the same regimen.
Analysis of viral sequence showed that in many cases vaccine-induced T cells did not target the circulating virus. At the most immunodominant epitope (NS31406), T cells induced by vaccination failed to target common circulating genotype 1 HCV variants. An in vitro model suggested that in order to target all genotype 1 sequences at this epitope, it would be necessary to insert both a genotype 1a and 1b version of this epitope into a vaccine immunogen.
Vaccination with adenoviral vectors induces T cell responses in patients with chronic HCV infection, however immune responses are attenuated compared with healthy volunteers. Ultimately a successful therapeutic or prophylactic vaccine strategy will rely on inducing responses that target conserved or cross-reactive epitopes.

Keywords: adenoviral vectors
vaccines
viral sequence
T cells
Hepatitis C Virus
Advisor: Barnes, E
Klenerman, P
Extensions of the case-control design in genome-wide association studies

The case-control design is one of the most commonly used designs in genome- wide asociation studies. When we increase the sample size of either the controls or, more importantly, the cases, the power of whatever test we use will certainly increase. However increasing the sample size, means that addi- tional individuals need to be genotyped and this implies extra financial costs. However, nowadays with the emergence of genetic studies, a large number of genetic data are available at low or no extra cost. Even though those data may not be completely relevant to the current study, they can still be used to increase the probability to identify true associations. Furthermore, additional information, non-necessarily genetic, can also be used to improve the power of a method.
In this thesis we extend the case-control design in order to take ad- vantage of such types of additional data and/or information. We discuss three designs; the case-cohort-control, the kin-cohort and the super-case– case–control–super-control designs. For each of these, we present methods that are adjusted or modified versions of standard case-control methods but we also propose novel ones developed with those extended designs in mind. Ultimately, we describe how those methods can be used in order to increase the power of association tests, especially compared to similar methods of the case-control design.

Keywords: gwas
association tests
genome-wide association studies
Advisor: Holmes, C