VictorJuiz/thesis huggingface dataset:
Alumina based nanocomposites by precipitation
Keywords: nanocomposites
alumina
precipitation
mechanical properties
diffusion

This project addressed two main problems pertaining to Al2O3-FeAl2O4 nanocomposites developed via solid state precipitation: the mechanisms for precipitation in ceramic solid solution via reduction reaction, and the mechanisms for the improved mechanical properties and wear resistance of the developed Al2O3-FeAl2O4 nanocomposites.
A model was proposed for precipitation in ceramic solid solutions via reduction reactions (the PRCS model). The thermodynamics of reduction reactions during aging treatments under various atmospheres were calculated and discussed relative to the second phase precipitate formation. Attempts were made to measure the corresponding diffusion kinetics using a new theory developed here based on volume fraction profiles of second phase particles in the aged samples. It was found that the measured apparent oxygen vacancy diffusivities conform well to the oxygen vacancy grain boundary diffusion coefficients reported in the literature, and the measured apparent matrix diffusivity conforms well to the Fe3+ ion matrix diffusion coefficients reported in literature. Based on the thermodynamics calculations, diffusion kinetics and some essential mechanisms that were discussed, the PRCS model was proposed. This has two aspects: macroscopic and microscopic. The macroscopic aspect of PRCS model was mainly used to explain the general aspects of microstructure and the distribution of intergranualar second phase particles. The microscopic aspect of the PRCS model was mainly used to explain the precipitation of intragranualar nanoparticles.
The mechanical properties, thermal residual stress and wear resistance of selected Al2O3-FeAl2O4 nanocomposites were measured. The results revealed that the Al2O3-FeAl2O4 possessed improved fracture toughness (by around 46%), flexural strength (by around 30%) and abrasive wear resistance (by a factor of around 5) with respect to monolithic alumina. Several mechanisms were proposed to explain the improvements in both mechanical properties and wear resistance. Compressive residual stress was found in the surface layer of Al2O3-FeAl2O4 nanocomposites due to the thermal expansion coefficient mismatch between surface layer and bulk parts. Such residual stress was also interpreted as the main reason for the improvements in both mechanical properties and wear resistance.
A Framework for the semantic representation of energy policies related to electricity generation
Keywords: Energy Models
Knowledge Representation
Ontology

Energy models are optimisation tools which aid in the formulation of energy policies. Built on mathematics, the strength of these models lie in their ability to process numerical data which in turn allows for the generation of an electricity generation mix that incorporates economic and the environmental aspects.
Nevertheless, a comprehensive formulation of an electricity generation mix should include aspects associated with politics and society, an evaluation of which requires the consideration of non-numerical qualitative information. Unfortunately, the use of energy models for optimisation coupled with the evaluation of information other than numerical data is a complicated task.
Two prerequisites must be fulfilled for energy models to consider political and societal aspects. First, the information associated with politics and society in the context of energy policies must be identified and defined. Second, a software tool which automatically converts both quantitative and qualitative data into mathematical expressions for optimisation is required.
We propose a software framework which uses a semantic representation based on ontologies. Our semantic representation contains both qualitative and quantitative data. The semantic representation is integrated into an Optimisation Modelling System which outputs a model consisting of a set of mathematical expressions. The system uses ontologies, engineering models, logic inference and linear programming.
To demonstrate our framework, a Prototype Energy Modelling System which accepts energy policy goals and targets as inputs and outputs an optimised electricity generation mix has been developed. To validate the capabilities of our prototype, a case study has been conducted. This thesis discusses the framework, prototype and case study.
Computational modelling of vascular interventions: endovascular device deployment
Keywords: Virtual stenting
FEA
Stent deployment
Modelling
Genetic algorithm

Minimally invasive vascular interventions with stent deployment have become a popular alternative to conventional open surgery in the treatment of many vascular disorders. However, the high initial success rates of endovascular repairs have been overshadowed by reported complications that cause re-interventions and, in the worst case, morbidity and mortality. The dangerous complications could be mitigated by better choice of device design and by the appropriate positioning of the implant inside the vessel. However, there is currently no possibility for the interventionist to predict the resulting position and the expanded shape of the device for a given patient, before the actual procedure, within the clinical setting.
Motivated by this unmet clinical need and the lack of suitable methods, this thesis develops a methodology for modelling virtual deployment of implantable devices inside patient vessels, that features fast computational execution times and can be used in clinical practice. This novel deployment method was developed based on a spring-mass model and was tested in different deployment scenarios, expanding stents inside vessels in the order of seconds. Further, the performance of the novel method was optimised by calibrating a set of parameters with the help of a genetic algorithm, which utilises the outcomes of a finite element analysis as a learning reference. After the calibration, the developed stenting method demonstrated acceptable accuracy as compared to the "gold standard" of the finite element simulation. Finally, on a real patient case, 4 alternative stenting scenarios were investigated by comparing the subsequent blood flow conditions, via computational haemodynamics. The obtained results suggested that device design, dimensions, stiffness and positioning have important implications on the post-procedural haemodynamics of the vessel. Ultimately, the presented results can play a transformative role in aiding clinical decision-making and also give rise to overall improvements in implant design and deployment procedure.
Cosmological consequences of supersymmetric flat directions
Keywords: Early Universe
Supersymmetry

In this work we analyze various implications of the presence of large field vacum expectation values (VEVs) along supersymmetric flat directions during the early universe. First, we discuss supersymmetric leptogenesis and the gravitino bound. Supersym- metric thermal leptogenesis with a hierarchical right-handed neutrino mass spectrum normally requires the mass of the lightest right-handed neutrino to be heavier than about 109 GeV. This is in conflict with the upper bound on the reheating temperature which is found by imposing that the gravitinos generated during the reheating stage after inflation do not jeopardize successful nucleosynthesis. We show that a solution to this tension is actually already incorporated in the framework, because of the presence of flat directions in the supersymmetric scalar potential. Massive right- handed neutrinos are efficiently produced non-thermally and the observed baryon asymmetry can be explained even for a reheating temperature respecting the gravitino bound if two conditions are satisfied: the initial value of the flat direction must be close to Planckian values and the phase-dependent terms in the flat direction potential are either vanishing or sufficiently small. We then show that flat directions also contribute to the total curvature perturbation. Such perturbation is generated at the first oscillation of the flat direction condensate when the latter relaxes to the minimum of its potential after the end of inflation. If the contribution to the total curvature perturbation from supersymmetric flat direction is the dominant one, then a significant level of non-Gaussianity in the cosmological perturbation is also naturally expected. Finally, we argue that supersymmetric flat direction VEVs can decay non perturbatively via preheating even in the case where they undergo elliptic motion in the complex plane instead of radial motion through the origin. It has been generally argued that in this case adiabaticity is never violated and preheating is inefficient. Considering a toy U(1) gauge theory, we explicitly calculate the scalar potential, in the unitary gauge, for excitations around several flat directions. We show that the mass matrix for the excitations has non-diagonal entries which vary with the phase of the flat direction vacuum expectation value. Furthermore, this mass matrix has zero eigenvalues whose eigenstates change with time. We show that these light degrees of freedom are produced copiously in the non-perturbative decay of the flat direction VEV.
Large-N correlator systems for low frequency radio astronomy
Keywords: Digital Signal Processing
Metrewave
Correlators and Interferometers
Radio Astronomy

Low frequency radio astronomy has entered a second golden age driven by the development of a new class of large-N interferometric arrays. The low frequency array (LOFAR) and a number of redshifted HI Epoch of Reionization (EoR) arrays are currently undergoing commission and regularly observing. Future arrays of unprecedented sensitivity and resolutions at low frequencies, such as the square kilometer array (SKA) and the hydrogen epoch of reionization array (HERA), are in development. The combination of advancements in specialized field programmable gate array (FPGA) hardware for signal processing, computing and graphics processing unit (GPU) resources, and new imaging and calibration algorithms has opened up the oft underused radio band below 300 MHz. These interferometric arrays require efficient implementation of digital signal processing (DSP) hardware to compute the baseline correlations. FPGA technology provides an optimal platform to develop new correlators. The significant growth in data rates from these systems requires automated software to reduce the correlations in real time before storing the data products to disk. Low frequency, widefield observations introduce a number of unique calibration and imaging challenges. The efficient implementation of FX correlators using FPGA hardware is presented. Two correlators have been developed, one for the 32 element BEST-2 array at Medicina Observatory and the other for the 96 element LOFAR station at Chilbolton Observatory. In addition, calibration and imaging software has been developed for each system which makes use of the radio interferometry measurement equation (RIME) to derive calibrations. A process for generating sky maps from widefield LOFAR station observations is presented. Shapelets, a method of modelling extended structures such as resolved sources and beam patterns has been adapted for radio astronomy use to further improve system calibration. Scaling of computing technology allows for the development of larger correlator systems, which in turn allows for improvements in sensitivity and resolution. This requires new calibration techniques which account for a broad range of systematic effects. And, a deep integration between DSP hardware and software data reduction into a single backend.
Systematic overviews of the randomised evidence for the effects of traditional non-steroidal anti-inflammatory drugs and selective inhibitors of cyclo-oxygenase-2 on vascular and upper gastrointestinal outcomes
Keywords: Randomised Trials
Epidemiology
Coxibs
Clinical medicine
Meta-analyses
Vascular
Non-steroidal anti-inflammatory drugs
Gastrointestinal Ulcers

Background: Comparative assessments of the vascular and upper gastrointestinal risks of different regimens of non-steroidal anti-inflammatory drugs (NSAIDs) are required.
Methods: Meta-analyses were conducted, using individual participant data where possible, of placebo-controlled trials of a selective cyclo-oxygenase [COX]-2 inhibitor ('coxib') or traditional NSAID, or randomised trials of a coxib versus traditional NSAIDs. A prespecified subdivision of traditional NSAID regimens of those with antiplatelet activity (mainly naproxen) and those without (mainly diclofenac) was made. Primary outcomes were major vascular events (MVEs; nonfatal myocardial infarction, nonfatal stroke or vascular death) and upper gastrointestinal complications (UGICs; perforation, obstruction or bleed).
Findings: Searches identified 788 trials: 200 comparisons of a coxib vs placebo (88,604 participants, mean follow-up 0.60 years), 206 comparisons of a traditional NSAID vs placebo (43,482 participants, 0.46 years) and 149 comparisons of a coxib vs traditional NSAID (137,466 participants, mean follow-up 0.95 years).
Compared to placebo, allocation to a coxib increased the risk of MVEs (rate ratio 1.38, 95% CI 1.14-1.66), vascular mortality (1.58, 1.11-2.24) and UGICs (1.81, 1.17-2.81). Overall, in the population studied, coxibs were associated with three additional major vascular events (one fatal) and two (rarely fatal) upper gastrointestinal complications per 1000 person-years exposure. There was no evidence of heterogeneity by duration of follow-up, coxib type, dose (other than for celecoxib), or patient characteristics, for the primary outcomes.
The risk of MVEs for traditional NSAIDs without antiplatelet activity (mostly diclofenac 75mg bd or ibuprofen 800mg tds) were comparable to coxibs (1.40, 1.15-1.72); but the risk of UGICs (1.98, 1.39-2.84) was significantly greater. For traditional NSAIDs with antiplatelet activity (mostly naproxen 500mg bd) there were no significant excess of MVEs (0.84, 0.66-1.08), but UGICs were substantially increased (4.06, 2.85-5.78). Both coxibs and traditional NSAIDs increased risk of hospitalisation for heart failure by about two-fold.
Interpretation: The vascular and upper gastrointestinal risks of coxibs and high-dose tNSAID regimens can be predicted, allowing the choice of analgesia to be tailored for particular patients.
Carbon Nanotube Growth on Perovskite Substrates
Keywords: Strontium Titanate
Barium Strontium Titanate
catalyst
Carbon nanotubes
Carbon Nanocoil
chemical vapour deposition

This thesis reports on the chemical vapour deposition (CVD) growth of carbon nanostructures (mainly carbon nanotubes (CNTs)) on perovskite oxide surfaces with the aid of various catalysts. Two types of perovskite oxide, single crystal SrTiO3 (001) and polycrystalline BaSrTiO3, have been used as catalyst supports (in metal-catalyst-involved CVD routes) or as catalysts (via metal-catalyst-free CVD routes) for the growth of carbon nanostructures.
In metal-catalyst-involved cases, SrTiO3 (001) single crystal has been proven, for the first time, to serve as a substrate for the growth of CNTs. Fe and Ni catalysts can be tailored in a controllable manner on SrTiO3 (001) surfaces prior to the CNT synthesis, forming truncated pyramid shaped nanocrystals with uniform size distributions. The growth of vertically aligned CNT carpets was realised with the aid of Fe on SrTiO3 (001) surfaces, and it was further found that the CNTs grow via a base growth model. Furthermore, it is possible to grow helical carbon nanostructures on BaSrTiO3 substrates by introducing a Sn catalyst into the system. The synthesised helical carbon nanostructures follow a tip growth mode, where the structural and chemical aspects of catalyst particles gave rise to a wide range of carbon morphologies.
CNTs were also grown on single crystal SrTiO3 (001) and polycrystalline BaSrTiO3 substrates via metal-catalyst-free routes. The surface-roughness-tailored growth of CNTs was surprisingly achieved on a series of engineered SrTiO3 (001) surfaces, where a correlation between the surface roughness/morphology of the substrates and the relevant catalytic activity was revealed. The growth of CNTs arises because the catalyst fabrication methods lead to the formation of SrTiO3 asperities with nanoscale curvatures, over which the CNTs are generated throughout a lift-off process. Facet-selective growth of CNTs was observed on polycrystalline BaSrTiO3 surfaces, where BaSrTiO3 (110) facets lead to the growth of CNTs on them, whereas the (001) facets result in no growth at all. This observation was further analysed in the content of the adsorption and diffusion of carbon species on distinct BaSrTiO3 facets, before reaching the conclusion that the formation of CNTs occurs through a metal-free, stack-up process driven by the assembly of the carbon fragments.
Analysis and synthesis of inductive families
Keywords: inductive families
datatype ornamentation
dependent types

Based on a natural unification of logic and computation, Martin-Löf’s intuitionistic type theory can be regarded simultaneously as a computationally meaningful higher-order logic system and an expressively typed functional programming language, in which proofs and programs are treated as the same entities. Two modes of programming can then be distinguished: in externalism, we construct a program separately from its correctness proof with respect to a given specification, whereas in internalism, we encode the specification in a sophisticated type such that any program inhabiting the type also encodes a correctness proof, and we can use type information as a guidance on program construction. Internalism is particularly effective in the presence of inductive families, whose design can have a strong influence on program structure. Techniques and mechanisms for facilitating internalist programming are still lacking, however.
This dissertation proposes that internalist programming can be facilitated by exploiting an interconnection between internalism and externalism, expressed as isomorphisms between inductive families into which data structure invariants are encoded and their simpler variants paired with predicates expressing those invariants. The interconnection has two directions: one analysing inductive families into simpler variants and predicates, and the other synthesising inductive families from simpler variants and specific predicates. They respectively give rise to two applications, one achieving a modular structure of internalist libraries, and the other bridging internalist programming with relational specifications and program derivation. The datatype-generic mechanisms supporting the applications are based on McBride’s ornaments. Theoretically, the key ornamental constructs — parallel composition of ornaments and relational algebraic ornamentation — are further characterised in terms of lightweight category theory. Most of the results are completely formalised in the Agda programming language.
Discrete quantum walks and quantum image processing
Keywords: image processing
quantum algorithms
quantum walks
quantum computation

In this thesis we have focused on two topics: Discrete Quantum Walks and Quantum Image Processing. Our work is a contribution within the field of quantum computation from the perspective of a computer scientist. With the purpose of finding new techniques to develop quantum algorithms, there has been an increasing interest in studying Quantum Walks, the quantum counterparts of classical random walks. Our work in quantum walks begins with a critical and comprehensive assessment of those elements of classical random walks and discrete quantum walks on undirected graphs relevant to algorithm development. We propose a model of discrete quantum walks on an infinite line using pairs of quantum coins under different degrees of entanglement, as well as quantum walkers in different initial state configurations, including superpositions of corresponding basis states. We have found that the probability distributions of such quantum walks have particular forms which are different from the probability distributions of classical random walks. Also, our numerical results show that the symmetry properties of quantum walks with entangled coins have a non-trivial relationship with corresponding initial states and evolution operators. In addition, we have studied the properties of the entanglement generated between walkers, in a family of discrete Hadamard quantum walks on an infinite line with one coin and two walkers. We have found that there is indeed a relation between the amount of entanglement available in each step of the quantum walk and the symmetry of the initial coin state. However, as we show with our numerical simulations, such a relation is not straightforward and, in fact, it can be counterintuitive. Quantum Image Processing is a blend of two fields: quantum computation and image processing. Our aim has been to promote cross-fertilisation and to explore how ideas from quantum computation could be used to develop image processing algorithms. Firstly, we propose methods for storing and retrieving images using non-entangled and entangled qubits. Secondly, we study a case in which 4 different values are randomly stored in a single qubit, and show that quantum mechanical properties can, in certain cases, allow better reproduction of original stored values compared with classical methods. Finally, we briefly note that entanglement may be used as a computational resource to perform hardware-based pattern recognition of geometrical shapes that would otherwise require classical hardware and software.
Study of platelet-mediated clumping adhesion phenotypes in Plasmodium falciparum malaria
Keywords: malaria
platelet-mediated clumping
Plasmodium falciparum
var gene
PfEMP1

Platelet-mediated clumping of Plasmodium falciparum-infected erythrocytes (IEs) is a common property of field isolates associated with severe disease (Pain, Ferguson et al. 2001). Platelet receptors CD36 (Pain, Ferguson et al. 2001), P-Selectin (Wassmer, Taylor et al. 2008) and gC1qR (Biswas, Hafiz et al. 2007) mediate clumping. To characterize the molecular specificities of the clumping phenotype, I cloned clumping parasite line IT/C10 by limiting dilution. I characterized var gene expression in the IT/C10 clones using generic primers for the DBL tag region (Bull, Berriman et al. 2005). Clumping assays were conducted in the presence of specific reagents to delineate host factors hypothesized to contribute to development of the clumping phenotype. Finally, I conducted a clinical study with isolates from children with malaria in Kilifi, Kenya.
This study shows that in parasite line IT/C10, platelet-mediated clumping is associated with Itvar30 suggesting a prominent role for the PfEMP-1 encoded by this var gene in development of platelet-mediated clumping. For IT/C10 parasites, platelet activation appears to be involved in platelet-mediated clumping. Platelet P-Selectin appears to mediate clumping using lectin-dependent interactions. To further elucidate the mechanisms that mediate clumping by host platelets, I have used a panel of platelet antagonists to delineate specific platelet activation pathways. Our results show that platelet activation plays an important role in platelet-mediated clumping. Finally, in this study, platelet-mediated clumping was associated with parasitaemia, but not with disease severity.