VictorJuiz/thesis huggingface dataset:
Development of Al alloy composites by powder metallurgy routes

Particulate reinforced Al alloy composites (AlMCs) are recognized as important structural materials due to their lightweight, high modulus and strength and high wear resistance. In order to understand the effect of matrix, reinforcement and secondary processing techniques on the microstructure development and mechanical properties of AlMCs produced by powder metallurgy routes, Al alloy composites reinforced with three types of reinforcements by different secondary processing techniques have been produced and examined.
Fabrication of Al or 6061Al alloy based composites reinforced with nano-sized SiC particles (~500nm), micro-sized (<25µm) quasicrystalline alloy particles (hereinafter referred to as “NQX”) and micro-sized Nb particles (~130µm) has been carried out by powder metallurgy routes followed by extrusion or cold rolling. After extrusion, a homogeneous distribution of secondary particles has been obtained with rare interfacial reaction products. The 6061Al/SiC composites exhibit superior mechanical properties than either monolithic alloys or composites reinforced with micro-sized particles with retained ductility while the 6061Al/NQX and 6061Al/Nb composites show limited improvement in tensile strength mainly due to their reinforcement size and poor interfacial bonding.
After cold rolling, the evolution in microstructure, texture and strength has been analysed. A typical near β fibre texture with highest intensities near Copper and Brass orientations has been developed for 6061Al/NQX and 6061Al/Nb composites. For 6061Al/SiC composites, a randomized texture with very small grains has achieved due to the presence of the non-deformable SiC particles. Mechanical property tests including microhardness, three-point bending tests and tensile tests have been carried out on cold rolled samples and the results exhibit some level of improvement when compared with as-extruded samples due to work hardening.
Finally, the work moves on to the general discussion based on the previous result chapters. The microstructural development related to reinforcement, matrix and interfacial areas during extrusion and cold rolling has been summarised and the correlation between microstructure and mechanical properties has been discussed.
The thesis provides a thorough understanding of AlMCs produced by powder metallurgy routes in terms of matrix, reinforcement and processing techniques. It can provide reference to the future development of AlMCs for high strength applications.

Keywords: aluminium; metal matrix composites; extrusion; cold rolling
Advisor: Galano, M
Audebert, F
Function, phenotype and development of human CD161+CD8 T cells

Tc17 cells and the semi-invariant human mucosal associated invariant T (MAIT) cells are important CD8+ tissue-homing cell populations. Both are characterized by high expression of CD161 (++) and type-17 differentiation, yet their origins and relationships remain poorly defined. By transcriptional and functional analyses it is demonstrated that a pool of polyclonal, pre-committed type-17 CD161++CD8αβ+ T cells exists in cord blood, from which a prominent MAIT cell (TCR Vα7.2+/Vβ2 or 13.2) population emerges post-natally. During this expansion, CD8αα T-cells appear exclusively within CD161++CD8+/MAIT subset, sharing cytokine production (IL17, IL-22 and IFN-γ), chemokine-receptor expression (CCR2, CCR6 and CXCR6), TCR-usage and transcriptional profiles with their CD161++CD8αβ+ counterparts. These data demonstrate the origin and differentiation pathway of MAIT cells from a naïve type-17 pre-committed CD161++CD8+ T cell pool and the distinct phenotype and function of CD8αα cells in man. The CD161++CD8αβ and CD8αα T cell subsets are reduced in the peripheral circulation in chronic hepatitis B and C and are enriched in the liver in chronic hepatitis C. Their potential role in immunity to chronic viral hepatitis B and C is demonstrated by their expression of activation/exhaustion markers CD69, CD25, HLA-DR and PD-1. In addition a substantial distinct CD161-CD8βlow population is demonstrated in chronic hepatitis B, co-characterised by a CD28low, HLA-DRhigh phenotype and high expression of IFN-γ, with important implications for the development of immunotherapy and vaccination.

Keywords: CD161
CD8 T cells
Hepatitis C
Hepatitis B
MAIT cells
Advisor: Klenerman, P
Barnes, E
Life after life imprisonment

In England and Wales, life imprisonment is the ultimate sanction for the most serious crimes. The introduction of Discretionary Lifer Panels (DLPs) in 1992 was a major development in the way that lifers are managed within the penal system. This thesis explores 'life after life imprisonment' for the first cohort of discretionary lifers who were released into the community through the DLP process. The study is set in the context of a renewed interest in empirical research on the resettlement of ex-prisoners, yet little of this work has focused on life-sentenced offenders. By investigating the resettlement process of 138 discretionary lifers released on life licence between 1992 and 1997, this research contributes to empirical and theoretical understanding of rehabilitation and desistance from crime after long-term imprisonment. Part One considers the various factors that have shaped the discretionary life sentence, and sets out the research methods used. Part Two examines the role of the Probation Service in the process of resettlement. Based on empirical work across probation areas, it sheds light on the claim that contemporary probation practice is indicative of a more general authoritarian and exclusionary approach to resettlement. Part Three explores the 'disistance and persistance' process for lifers. It provides a detailed analysis of the narrative accounts of resettled lifers, and explores the reasons why they had given up crime. It also highlights the growing numbers of recalled lifers, and seeks to identify factors associated with failure on life licence. This thesis concludes by arguing that rehabilitation continues to have a prominent place within the discourse of resettlement. Overall, this thesis lends support to theories of disistance from crime that emphasise the importance of shifts in offenders' narrative identities to explain cessation from criminal behaviour, and highlights the role of a professional relationship as a powerful vehicle for change.

Keywords: identity change
resettlement
desistance from crime
probation service
life imprisonment
Advisor: Ashworth, A
Burnett, R
The Round Table, 1910-66

This thesis traces the history of the London Round Table group and of the Round Table magazine from their origins in 1909-10 until the decision to launch a "new" Round Table in 1966. It takes as its focus the ideas put forward by members of the group, in the Round Table and elsewhere, on a range of Imperial and international problems. It utilises knowledge on the authorship of Round Table articles in order to clarify the processes by which Round Table policy was made, and the role of different individuals within the group. It examines the rôle of the Round Table as a pressure group for Imperial reform and in particular its relationship to Empire federalism, seeking to elucidate the extent to which it was able to act coherently, and attempting to describe its aims, methods and influence. On the question of federalism, the thesis finds an inability to agree on details, but also a continuing belief in the necessity for constitutional unit until the late 1940s. It suggests that this belief was not entirely unrealistic. The thesis argues that, despite differences of emphasis, the Round Table was able to develop a distinctive ideology of Imperialism which was strongly supportive of the Imperial rôle yet also responsive to the need for change. It finds that the group was only briefly influential on government policy, under Lloyd Georfge's administration, but it argues that the group saw its main purpose as that of influencing long-term opinion rather than short-term policy. It suggests that the group was able to play an important mediating rôle, between conservatism and radicalism, and between policy-making and opinion.

Keywords: London Round Table
The social environment of asthma management in early adolescence

For adolescents with asthma, adhering to asthma regimes implies not only taking medications to relieve asthma attacks, but also adjusting their life styles in order to prevent asthma attacks. These life style modifications, such as avoiding allergens or having to limit physical activity, sometimes force adolescents to compromise their social life. On the other hand, the impact of such life style modifications on their social life may in turn force adolescents to give up adhering to asthma regimes. Indeed, adolescents are learning to be more independent while they enjoy a more complicated social life at home and at school than previously, and this rapid social development may thus be a great life challenge to adolescents with asthma. This thesis reports four studies which investigated the relationship between multi-dimensional asthma management (in medication and life style regimes) and the social life of young people with asthma at the transitional age from childhood to adolescence (or early adolescence, age 9-14), which also marks the transition from primary school to secondary school.
In line with the literature on other adolescent chronic illnesses, study 1 demonstrated a downward trend of multi-dimensional asthma management in early adolescence. This developmental change was further investigated in study 2, 3 and 4, in which theories in behavioural psychology were followed to emphasise human behaviour influenced by the social activities and social relationships in the living environment, or the social environment. This was supplemented by theories in developmental psychology to identify relevant aspects of the social environment in early adolescence, especially the social relationships with parents, school staff and peers. Using quantitative and qualitative approaches, the studies not only supported the direct influence of asthma-specific social support, but also explored some mechanisms with which social relationships influenced asthma management in a more subtle and context-dependent way. By approaching asthma management behaviour with theories from behavioural and developmental psychology, it is also hoped that this thesis could be an example that shows the importance of recognising and to understanding the social life of young adolescents when adolescent behaviour is concerned.

Keywords: peer
family
social environment
asthma management
teacher
adolescence
Advisor: Sylva, K
Lunt, I
Location and distance in economics

In this collection of essays, I explore three topics where space and distance plays a fundamental role in international economics. Not only do spatial considerations affect the pattern of trade, the frictions that arise from distance also determine where and how goods are produced and where people live.
In Chapter 1, I show that human made locational characteristics can determine the spatial allocation of economic activity. I take the standard core-periphery model and add endogenous housing to its forward-looking dynamic adjustment process. By introducing a model of adjustment with an extra state variable, which I interpret as housing, I show that the distribution of housing allows the model to converge to a unique spatial equilibrium. This explains the observed persistence and robustness of economic agglomerations in the data.
Chapter 2 is a theory of task assignment in the production of final goods and across countries. By allowing for tasks to differ in their suitability of being used in the production of multiple goods, my model endogenizes the allocation of tasks in the production of goods that use them. The resulting equilibrium task allocation defines the pattern of off-shoring. Tasks that are used in only one good concentrate in the country with a specialization in production of that good. Tasks used in many goods are allocated across countries, with the more substitutable tasks located in the country with the larger overall output. Gains from off-shoring are derived from a better mix of allocation of tasks into goods as well as larger scale of production.
Finally in Chapter 3, I study how real exchange rate fluctuations determine the size and composition of the export sector. Using the methodology set out in Dixit and Pindyck (1994) in a heterogeneous firms model, I determine the set of trigger real exchange rates for entry and exit into exporting. My primary result of this chapter is that exchange rate uncertainty coupled with sunk cost of entry causes hysteresis in the number and productivity of exporting firms. I then extend the model to allow free entry of firms. This explains the stylized fact of the existence of non-exporting firms with higher productivity than some exporting firms.

Keywords: economic geography
International trade
economics
Advisor: Venables, A
Reconstructing past flow rates of southern component water masses using sedimentary 231Pa/230Th

This thesis uses the paleoceancirculation proxy 231Pa/230Th, coupled with water mass tracers δ13C and εNd, to reconstruct circulation histories for southern source waters masses in the South Atlantic, in addition to North Atlantic Deep Water (NADW) far from its source, for the last ~25 kyrs.
Downcore 231Pa/230Th records from a suite of cores along a depth transect in the Argentine Basin show distinct differences with depth, suggesting that 231Pa/230Th ratios in sediments are reflective of conditions in only the bottom most waters. This indicates the importance of consideration of changes in water mass distribution when interpreting 231Pa/230Th records. Opal and particle flux data from these cores show little correlation with 231Pa/230Th values meaning that changes in 231Pa/230Th cannot be explained by a local composition or particle flux effect and are instead likely to be reflecting changes in circulation.
A core bathed by Antarctic Intermediate Water (AAIW) throughout the last 25 kyrs (GeoB 2107, 1045 m), has relatively high 231Pa/230Th values (0.075) during the Holocene and distincly lower values (0.055) at the LGM suggesting faster AAIW transport during the last glacial. At greater depths, 231Pa/230Th, δ13C and εNd data in core GeoB 2109 (2504 m) indicate a change in both circulation and water mass distribution on glacial-interglacial timescales, with moderate flow of Antarctic Bottom Water (AABW) at the LGM being replaced by more vigorous flow of NADW during the Holocene.
On millenial timescales, 231Pa/230Th values in deep cores GeoB 2109 and GeoB 2112 (4010 m) indicate enhanced production of AABW during northern hemisphere stadials, when variations in 231Pa/230Th records are of opposite sign between hemispheres, supporting a possible bipolar seesaw relationship in deep water formation between hemispheres. These data indicate that the 231Pa/230Th proxy can be used to reconstruct past flow rates of multiple water masses in the Argentine Basin and provide evidence that southern source water masses play a dynamic counterpart to NADW formation on abrupt as well as glacial-interglacial timescales.

Keywords: 231Pa/230Th
paleoceanography
Argentine basin
Advisor: Henderson, G
Thomas, A
Studies in sonoelectrochemistry

The work described in this thesis employs 'dual activation' methodologies and in particular sonovoltammetry to study a variety of electrochemical systems. First, the effect of 20 kHz power ultrasound on the electrochemistry of simple redox systems in both water and acetonitrile is explored and characterised for different cell geometries. A simple Nernst diffusion layer model is validated.
Second, the use of insonation for efficient pre-concentration of target species in anodic stripping voltammetry (ASV) is reported. 'Sonotrodes', where the electrodes are incorporated into the ultrasonic horn tips are shown to offer particularly high rates of mass transport and additionally cause ablation of mercury from plated platinum electrodes. The key benefits of sonication are shown to be electrode depassivation and extraction plus rapidity and ease of determination, coupled with the lack of any sample pre-treatment for the detection of lead in both wine and petrol by ASV. Lead levels determined by this method and calibrated by use of standard microaddition are in excellent agreement with those obtained 'blind' by atomic absorption spectroscopy performed at independent laboratories.
Third, the novel use of ultrasonically formed emulsions is examined for both analytical and synthetic purposes. The possibility of extracting species both out of an organic phase for analysis and into an organic phase for the synthesis of water-insoluble redox products is realised.
Fourth, the sonovoltammetric determination of ascorbic acid in both aqueous solution and the fruit drink Ribena®, is compared with results obtained by laser activated electroanalysis, where low level laser illumination of an electrode is employed to maintain a fresh electrode surface. Small amounts of laser-induced thermal convection at the electrode result in steady-state voltammetry. The level of agreement is excellent between the two methods and also agrees very well with independent chemical analysis.
Fifth, laser activated voltammetry (LAV) is further explored and a simple mass transport model verified. Damage caused by high power laser ablation is evidenced by atomic force microscopy (AFM). Applications of the technique for depassivation are illustrated by the reduction of toluidine blue dye and oxidation of ferrocyanide in the presence of blood proteins. The technique is further employed under channel flow conditions to elucidate an unambiguous mechanism for aqueous iodide oxidation at platinum electrodes in the absence of the usual build up of bulk iodine (as evidenced by AFM).
Finally, the reduction of methylene green dye at platinum electrodes is used to compare and contrast sonovoltammetry and LAV with thermal and microwave dual activation techniques. The build-up of the passivating reduced form of the dye on the electrode surface, again seen by AFM, is removed by sono-emulsion and laser activation but not by microwave heating. However, greater conductivity is observed at higher temperatures and an electron-hopping mechanism is postulated.
A stochastic partial differential equation approach to mortgage backed securities

The market for mortgage backed securities (MBS) was active and fast growing from the issuance of the first MBS in 1981. This enabled financial firms to transform risky individual mortgages into liquid and tradable market instruments. The subprime mortgage crisis of 2007 shows the need for a better understanding and development of mathematical models for these securities. The aim of this thesis is to develop a model for MBS that is flexible enough to capture both regular and subprime MBS.
The thesis considers two models, one for a single mortgage in an intensity based framework and the second for mortgage backed securities using a stochastic partial differential equation approach. In the model for a single mortgage, we capture the prepayment and default incentives of the borrower using intensity processes. Using the minimum of the two intensity processes, we develop a nonlinear equation for the mortgage rate and solve it numerically and present some case studies.
In modelling of an MBS in a structural framework using stochastic PDEs (SPDEs), we consider a large number of individuals in a mortgage pool and assume that the wealth of each individual follows a stochastic process, driven by two Brownian mo- tions, one capturing the idiosyncratic noise of each individual and the second a common market factor. By defining the empirical measure of a large pool of these individuals we study the evolution of the limit empirical measure and derive an SPDE for the evolution of the density of the limit empirical measure.
We numerically solve the SPDE to demonstrate its flexibility in different market environments. The calibration of the model to financial data is the focus of the final part of thesis. We discuss the different parameters and demonstrate how many can be fitted to observed data. Finally, for the key model parameters, we present a strategy to estimate them given observations of the loss function and use this to determine implied model parameters of ABX.HE.

Keywords: stochastic PDEs
mathematics
finance
Advisor: Hambly, B
The rational design of photocatalytic semiconductor nanoparticles

This thesis reports the successful rational design of three highly active photocatalytic semiconductor nanocrystal (SNC) systems by exploiting morphology effects and the electronic properties of type II semiconductor heterojunctions. Novel architectures of colloidal SNCs are produced with the aim of suppressing exciton recombination and improving charge extraction for the successful initiation of desirable redox chemistry.
Rod-shaped niobium pentoxide Nb2O5 nanocrystals (NCs) are shown to exhibit significantly enhanced activity (10-fold increase in rate constant) relative to spherical-shaped NCs of the same material. The increase is attributed to Nb5+ Lewis acid site rich (001) surfaces, present in higher proportions in the rod morphology, which bind organic substrates from solution resulting in direct interaction with photogenerated charges on the surface of the NC. Building on the insights into morphology-activity dependence, type II semiconductor heterojunctions are exploited for their ability to increase exciton lifetimes and spatially separate charges. Two novel II-VI heterostructured semiconductor nanocrystals (HSNCs) systems are investigated: a series of CdX/ZnO (X = S, Se, Te) HSNCs and ZnS/ZnO HSNCs capped with two different surface ligands. In the first case, substantial photocatalytic activity improvement is observed for HSNCs (relative to pure ZnO analogues) according to the following trend: CdTe/ZnO > CdS/ZnO > CdSe/ZnO. The observed trend is explained in terms of heterojunction structure and fundamental chalcogenide chemistry. In the second case, both ZnS/ZnO HSNCs exhibit activity enhancement over analogous pure ZnO, but the degree of enhancement is found to be a function of surface ligand chemistry.
Photocatalytic activity testing of all the materials investigated in this work is performed via the photodecomposition of methylene blue dye in aerated aqueous conditions under UVA (350 nm) irradiation.
The synthetic techniques employed for the synthesis of colloidal SNCs investigated in this thesis range from chemical precipitation and solvothermal techniques to several different organometallic approaches.
A wide variety of analytical techniques are employed for the chemical, structural and optical characterisation of SNC photocatalysts including: XRD, XPS, TEM, UV-vis absorption, PL spectroscopy and FTIR. Atom Probe Tomography (APT) is employed for the first time in the structural characterisation of II-VI heterojunctions in colloidal HSNCs.
Overall, this thesis provides a useful contribution to the growing body of knowledge pertaining to the enhancement of photocatalytic SNCs for useful applications including: solar energy conversion to chemical fuels, the photodecomposition of pollutants and light-driven synthetic chemistry.

Keywords: type II heterojunctions
II-VI nanocrystals
colloidal semiconductor nanocrystals
heterostructures
semiconductor photocatalysis
shape effects on photocatalysis
Advisor: Tsang, S