VictorJuiz/thesis huggingface dataset:
Inter-theory relations in physics: case studies from quantum mechanics and quantum field theory
Keywords: emergence
reduction
quantum field theory
measurement problem
classical mechanics
inter-theory relations
Everett
de Broglie-Bohm
correspondence principle
Bohm
quantum mechanics
decoherence

I defend three general claims concerning inter-theoretic reduction in physics. First, the popular notion that a superseded theory in physics is generally a simple limit of the theory that supersedes it paints an oversimplified picture of reductive relations in physics. Second, where reduction specifically between two dynamical systems models of a single system is concerned, reduction requires the existence of a particular sort of function from the state space of the low-level (purportedly more accurate and encompassing) model to that of the high-level (purportedly less accurate and encompassing) model that approximately commutes, in a specific sense, with the rules of dynamical evolution prescribed by the models. The third point addresses a tension between, on the one hand, the frequent need to take into account system-specific details in providing a full derivation of the high-level theory’s success in a particular context, and, on the other hand, a desire to understand the general mechanisms and results that under- write reduction between two theories across a wide and disparate range of different systems; I suggest a reconciliation based on the use of partial proofs of reduction, designed to reveal these general mechanisms of reduction at work across a range of systems, while leaving certain gaps to be filled in on the basis of system-specific details.
After discussing these points of general methodology, I go on to demonstrate their application to a number of particular inter-theory reductions in physics involving quantum theory. I consider three reductions: first, connecting classical mechanics and non-relativistic quantum mechanics; second,connecting classical electrodynamics and quantum electrodynamics; and third, connecting non-relativistic quantum mechanics and quantum electrodynamics. I approach these reductions from a realist perspective, and for this reason consider two realist interpretations of quantum theory - the Everett and Bohm theories - as potential bases for these reductions. Nevertheless, many of the technical results concerning these reductions pertain also more generally to the bare, uninterpreted formalism of quantum theory. Throughout my analysis, I make the application of the general methodological claims of the thesis explicit, so as to provide concrete illustration of their validity.
The acoustic properties of gassy soil
Keywords: clay
gas

Compression wave sound speed and attenuation measurements are made in the laboratory over frequencies in the range from 10 kHz to 1 MHz on samples of estuarine silty clay that have been provided with varying amounts of uniformly distributed gas bubbles. The soil can be idealised as a two phase material of spherical gas pockets within a matrix of saturated soil, where the pocket sizes are in the range from 100 to 2000 μm diameter. It is shown that the acoustic response of this soil is dominated by the gas fraction and bubble size of the gas phase, and by the elastic moduli of the matrix phase, within the frequency range that causes bubbles to pulsate radially (resonate). Below this range, it is shown that the sound speed response is not significantly affected by bubble size, except close to the saturated soil condition. The gas fraction and bubble size distribution of each sample is measured and used, with values of the appropriate elastic moduli from the literature, to provide curves from current theory. The theory is evaluated in comparison to the experiment results, and proposals are made, which may provide the basis for the prediction of the gas fraction and bubble sizes of sea-bed sediments that are suspected of containing gas. Such a process would involve the use of an acoustic probe to obtain in situ sound speed and attenuation measurements using the signal analysis techniques developed in this study.
The effect of individual agricultural insurance on transfers by smallholder farmers in informal  risk-sharing networks: empirical evidence from Tigray, Ethiopia
Keywords: agricultural insurance
indemnity insurance
basis risk
index insurance
risk-sharing
informal risk-sharing
group insurance

We investigate the effect of formal individual agricultural insurance on transfers by farmers in informal risk sharing networks using an experiment conducted in rural Tigray in Ethiopia. Both index and indemnity insurance are investigated for a holistic picture. However, we focus on index insurance, particularly when there is basis risk.We employ a multi-stage sampling design in a framed field experiment, simulating three possibilities, namely, insurance availability, insurance take-up and insurance rejection.
Based on empirical considerations, we treat transfers as categorical and use multilevel analysis to fit a Cumulative Link Mixed-effects Model (CLMM). Thus we compare the odds of transfers under the three possibilities; insurance availability, insurance take-up and insurance rejection to transfers in a control in which formal insurance is unavailable. Having explored how transfers change in response to the three possibilities, we tentatively explore the underlying motives.
We find that farmers do not offer compensation for basis risk. When there is basis risk, farmers are 48% less likely to make transfers. This non-compensation for basis risk is worst for farmers in prescribed groups. Assuming socio-economic-dependent factors to be the underlying motives, we posit that the resultant economic incentives motivate farmers to punish their partners for their insurance decisions.
Providers of micro insurance in low-income farming markets will find the empirical findings useful in that they show the need for careful evaluation when designing agricultural insurance interventions aimed at realising a mutually beneficial relationship between index insurance and informal risk sharing. The findings also highlight the need for caution in prescribing farmers into groups as a condition for offering insurance.
Constructing Minnesang musically
Keywords: manuscripts
Minnesang
musicology
medieval song
historiography

While troubadour and trouvère repertoires have recently received fresh attention from music scholars, the study of medieval German vernacular song—Minnesang—continues to be located firmly outside the canon(s) of musicology. The present thesis seeks to re-insert Minnesang into musicological discourse by demonstrating the ways in which the repertoire has been constructed as musical, both by the creators of medieval manuscript sources and by modern scholars.
The modern ontology of music as defined by notation and performance has prevented scholars from understanding manuscripts such as the Codex Manesse (C) as intrinsically musical. While the texts alone may have sufficed to enable their intended audiences to view them as musical entities, C’s 137 author miniatures further contribute to the manuscript’s musicality: the Minnesänger are depicted as authors and experiencing personae, revealing a strong concern for oral communication—which, in the Middle Ages, was inherently musical. The Jenaer Liederhandschrift (J) and other manuscripts equally reveal their musicality when scrutinised beyond the search for musical notation: through ordering and folio design.
The thesis establishes the influence exerted by previous scholarship on today’s lack of interest in the music of Minnesang, and outlines the importance of scholarly discourse and its study in a historiographical context. Before the 1970s, an existing musical discourse on Minnesang encouraged musicologists and philologists to continue to engage in it—despite the fact that the dominant interest in contrafacture and rhythm found few answers in the surviving source material. A concluding case study of Walther von der Vogelweide’s Palästinalied exemplifies the musicality of medieval manuscripts and its complex (mis)construction by modern scholarship. The thesis provides the basis for a fresh assessment of the music of Minnesang: beyond the confines of modern ontologies of music, and as part of the study of medieval song.
Ultrafast spectroscopy of charge separation, transport and recombination processes in functional materials for thin-film photovoltaics
Keywords: CH3NH3PbI(3-x)Clx
solar cells
photoluminescence
perovskites
TiO2
CH3NH3PbI3
dye-sensitized
terahertz
charge carrier dynamics
THz
nanotubes

Dye-sensitized solar cells (DSSCs) and perovskite solar cells are emerging as promising potential low-cost alternatives to established crystalline silicon photovoltaics. Of the employed functional materials, however, many fundamental optoelectronic properties governing photovoltaic device operation are not sufficiently well understood. This thesis reports on a series of studies using ultrafast THz and photoluminescence spectroscopy on two classes of such materials, providing insight into the dynamics of charge-transport and recombination processes following photoexcitation.
For TiO2-nanotubes, which have been proposed as easy-to-fabricate electron transporters for DSSCs, fast, shallow electron trapping is identified as a limiting factor for efficient charge collection. Trapping lifetimes are found to be about an order of magnitude shorter than in the prevalently employed sintered nanoparticles under similar excitation conditions and trap saturation effects are not observed, even at very high excitation densities.
In organo-lead halide perovskites - specifically CH3NH3PbI3 and CH3NH3PbI3-xClx, which have only recently emerged as highly efficient absorbers and charge transporters for thin-film solar cells, carrier mobilities and fundamental recombination dynamics are revealed. Extremely low bi-molecular recombination rates at least four orders of magnitude below the prediction of Langevin's model are found as well as relatively high charge-carrier mobilities in comparison to other solution-processable materials. Furthermore a very low influence of trap-mediated recombination channels was observed. Due to a combination of these factors, diffusion lengths reach hundreds of nanometres for CH3NH3PbI3 and several microns for CH3NH3PbI3-xClx. These results are shown to hold for both, solution processed and vapour-deposited CH3NH3PbI3-xClx and underline the superb suitability of the materials as absorbers in solar cells, even in planar heterojunction architectures.
The THz-frequency spectrum of the conductivity of the investigated perovskites is consistent with Drude-like charge transport additionally exhibiting weak signatures of phonon coupling. These coupling effects are also reflected in the luminescence of CH3NH3PbI3-xClx, where they are believed to be the cause of the observed homogeneous spectral broadening. Further photoluminescence measurements were performed at temperatures between 4 K and room temperature to study the nature of recombination pathways in the material.
High magnetic field effects in low-dimensional carbon nanostructures
Keywords: Physics
Nanotechnology
Carbon nanotubes
Graphene

This thesis describes studies of graphene, single walled carbon nanotubes (SWNTs) and InSb. Optical and electronic measurements probe the effects of high magnetic fields on these low-dimensional systems.
Chapter 1 introduces a theoretical description and background behind the materials and physical phenomena studied in this work. The structure and unique properties of carbon nano-materials are described. The experimental methods used in this thesis are described in Chapter 2.
Chapter 3 describes magnetotransport measurements on InSb/AlInSb heterostructures revealing that the large energy gaps, and extremely high mobility, associated with this system leads to exceptionally well defined quantum Hall plateaux for both even (Landau level) and odd (spin-split) filling factors. Even higher cyclotron energy gaps are expected in graphene. Chapter 4 reveals that due to a combination of large cyclotron energy gaps and fast electron-phonon energy loss rates, the quantum Hall effect (QHE) in graphene can be observed to unprecedented current densities (43 A/m) and temperatures (> 45 K). The behaviour of epitaxial graphene grown on silicon carbide in the quantum Hall regime is shown to be characterised by a strongly magnetic field dependent carrier density due to charge transfer from surface donor states in the substrate.
Chapter 5 shows that polymer wrapping of SWNTs can achieve high quality purified samples. Individual SWNTs were probed using micro-photoluminescence measurements in magnetic fields up to 30 T. The combination of high magnetic fields and high spectral and spatial resolution allowed a detailed study of exciton fine structure. High intensity laser irradiation is shown to induce bound excitons in pristine tubes. The optical properties of a number of tubes are dominated by defect sites which may be imaged along the tube using the magnetic brightening of dark excitons associated with such defects.
Generalized compactification in heterotic string theory
Keywords: heterotic string theory
compactification
torsion classes
fluxes

In this thesis, we consider heterotic string vacua based on a warped product of a four-dimensional domain wall and a six-dimensional internal manifold preserving only two supercharges. Thus, they correspond to half-BPS states of heterotic supergravity. The constraints on the internal manifolds with SU(3) structure are derived. They are found to be a generalization of half-flat manifolds with a particular pattern of torsion classes and they include half-flat manifolds and Strominger's complex non-Kahler manifolds as special cases. We also verify that heterotic compactifications on half-flat mirror manifolds are based on this class of solutions.
Furthermore, within this context, we construct specific examples based on six-dimensional nearly-Kahler homogeneous manifolds and non-trivial vector bundles thereon. Our solutions are based on three specific group coset spaces satisfying the half-flat torsion class conditions. It is shown how to construct line bundles over these manifolds, compute their properties and build up vector bundles consistent with supersymmetry and the heterotic anomaly cancellation. It turns out that the most interesting solutions are obtained from SU(3)/U(1)². This space supports a large number of vector bundles leading to consistent heterotic vacua with GUT group and, for some of them, with three chiral families.
Unfolding and refolding of monomeric and heptameric α-hemolysin
Keywords: alpha-hemolysin
protein structure
protein folding

Alpha-hemolysin (αHL) is a membrane protein derived from Staphylococcus aureus. The structural stability of the monomeric and heptameric protein was investigated under high pH conditions (8.0−13.0) and in various concentrations of urea (0−8.0 M). The dimensions of the αHL heptameric pore are ideal for the translocation of single-stranded polynucleotides such as DNA or RNA. Therefore, it could potentially be used as a DNA sequencing device. Exploring the pore’s ability to withstand harsh conditions would help determine whether it could be used in the translocation of double stranded DNA (dsDNA), which dissociates into single-stranded DNA (ssDNA) at high pH or ssDNA that loses its secondary structure in the presence of urea. Studying the behavior of monomeric αHL under various denaturing and renaturing conditions will aid in improving the conditions used to purify and refold mutated forms of αHL.
The pH and urea studies revealed that the heptamer is more resistant to structural change than the monomer. The heptamer remained stable up to pH 12.0, which is ideal since dsDNA dissociates into ssDNA at pH 11.7. The majority of the heptamer’s structure was lost at pH conditions above 12.5. Structural studies on the heptamer at various urea concentrations revealed that a fraction of the heptamer was still intact even at 8.0 M urea whereas the monomer seems to unfold completely at high urea concentrations. However, upon refolding via dilution, the monomer seems to regain its structure and function. Urea was determined as an ideal denaturant even after incubating the monomer in guanidinium chloride (GdnCl) or organic acids.
The structural stability of the αHL monomer and heptamer was elucidated using techniques such as circular dichroism, intrinsic tryptophan emission spectroscopy, SDS-PAGE, light scattering hemolytic assays and single-channel recording experiments.
T cell phenotype and function in Spondyloarthritis
Keywords: immunomodulatory receptors
Spondyloarthritis
HLA-B27
Th17

Th17 cells are implicated in a variety of inflammatory disorders including Spondyloarthritis (SpA). Ankylosing spondylitis (AS), the most common SpA, is genetically associated with HLA-B27 and IL-23R polymorphisms, although the link remains unexplained. In addition to classically folded heterotrimers, HLA-B27 can form β2m-free homodimers (B272). B272, as well as free heavy chains, are able to interact with KIR3DL2.
I have shown an expansion of KIR3DL2+ CD4+ T cells in peripheral blood of AS patients and HLA-B27+ healthy controls. Although KIR3DL2+ CD4+ T cells comprise a minority of CD4+ T cells in peripheral blood, KIR3DL2+ CD4+ T cells account for the majority of peripheral blood CD4+ T cell IL-23R expression. KIR3DL2+ CD4+ T cells from synovial fluid are also enriched for IL-23R expression compared to matched peripheral blood samples. Moreover, treatment exposure to rIL-1/23 significantly increases IL-17 production by KIR3DL2+ CD4+ T cells in AS patients but not RA patients and healthy controls.
KIR3DL2+ CD4+ T cells from AS patients produce more IL-17 than KIR3DL2+ CD4+ T cells from HLA-B27- healthy controls. KIR3DL2+ CD4+ T cells from AS patients and healthy controls are also enriched for dual production of IL-17 and IFNγ, consistent with the theory that AS is a Th17 or a Th17/1 driven disease.
I have shown that naïve CD4+ T cells express KIR3DL2 de novo after activation. Interaction with B272-expressing cells acts to maintain and/or further increase KIR3DL2 expression. Interaction with B272-expressing cells also increases expression of Bcl-2. I propose that interaction of KIR3DL2+ CD4+ T cells with B272 preferentially promotes the survival of these pro-inflammatory cytokine-producing KIR3DL2+ CD4+ T cells in SpA. HD6, a B272-specific monoclonal antibody, decreases IL-17 production by PBMCs from AS patients, making it an attractive candidate therapeutic reagent in the treatment of AS and other HLA-B27-associated SpA.
Reformulating corporate residence: a coherent response to international tax avoidance
Keywords: tax planning
resident
companies
corporations
tax avoidance
residence
multinational enterprises

This thesis analyzes the concept of corporate residence, with particular reference to the law in the UK and Canada. It explores why corporate residence is relevant in tax policy, how corporate residence is understood in law, and how revenue authorities respond to the use and alleged 'abuse' of residence rules. Part I argues that the residence of taxpayers generally (individual or corporate) remains a relevant factor in international tax design, that taxation of corporations on the basis of residence has some justification, but that there is a disjunction between meaningful residence-based taxation and current definitions of corporate residence in domestic law and tax treaties. The formulations of residence based on incorporation, central management and control, and place of effective management, particularly as applied to multinational enterprises, are considered and are found to be deficient. Part II critically analyzes the major policy responses of the UK and Canadian governments to the exploitation of corporate residence. It argues that key legislative and administrative responses to international tax avoidance activities, for both outbound and inbound investment, are purportedly based on the acceptance of formal corporate residence yet undermine that concept in an effort to impose tax or refuse treaty relief based on where economic interests actually exist. The responses considered are the application of controlled foreign companies legislation to offshore subsidiaries, the invocation of treaty anti-abuse rules with respect to offshore intermediaries, and the use of overarching general anti-avoidance measures to challenge varied structures that rely on offshore entities. These haphazard anti-avoidance rules are overlaid with revenue authorities' indignation at the motivations that underlie many corporate relocations. It is argued that a more coherent approach would be to focus on the objective reality or unreality of corporate establishment, by reformulating corporate residence in domestic law and tax treaties.
First-principles investigation of electron-phonon interactions in novel superconductors
Keywords: Density functional theory
Electron-phonon
Superconductivity

Despite over 100 years of scientific research, a full understanding of superconductivity remains elusive. While it is known that the electron-phonon interaction is responsible for the formation of Cooper pairs in conventional superconductors, many superconductors exhibit behaviour suggestive of more exotic pairing mechanisms.
In this thesis, two novel superconducting materials are considered, monolayer transition metal dichalcogenide, MoS2, and iron-based superconductor, LaFeAsO1−xFx. The former is ideal for the study of the electron-phonon interaction, as it not only has potential applications as an atomically thin transistor, but also displays a dome-shaped superconductive state as a function of electron doping. In the latter, the superconductive state emerges from a magnetic parent compound upon flourine doping. Its high critical temperature is thought to be enhanced by magnetic fluctuation rather than being purely phonon-mediated.
By using novel first-principles techniques, the electron-phonon interaction in electron doped single-layer MoS2 is investigated. The superconducting gap is calculated using the Migdal-Eliashberg theory, and by considering the electronic structure and lattice dynamics in this material, an explanation is provided for the experimentally observed doping-dependent critical temperature in this material.
The origin of the doping-induced transition from a magnetic phase to a nonmagnetic phase in LaFeAsO1−xFx is determined. A new model to capture the effects of the fluorine dopants is developed, which has implications for the electron-phonon interaction in this material.
A cascade approach towards the gephyrotoxins
Keywords: natural product synthesis
organic chemistry

The aim of this project was to develop a cascade approach towards perhydropyrrolo-[1,2-a]-quinolines and to apply this to the asymmetric synthesis of the gephyrotoxin alkoids.
Chapters Two and Three outline the development of a synthetic route towards a range of cascade precursors, whilst Chapter Four outlines investigations into the enamine-Michael cascade. Central to understanding the cascade process was the discovery that the major product of the enamine-Michael cascade was the unusual tricyclic hydroquinium salt. This can subsequently be engaged in a diastereoselective inter- or intramolecular reduction to afford either a trans-perhydro-[1,2-a]-quinoline or a tetracyclic aminal in high overall yield depending on the C1 oxygen substituent.