VictorJuiz/thesis huggingface dataset:
Short-pulse laser-plasma interactions

This thesis deals with several theoretical aspects of the interaction of an intense femtosecond laser pulse with a plasma. A mechanism for the enhancement of the collisional absorption of light at high intensities is described, involving the direct excitation of collective modes of the plasma, and the importance of this mechanism for a solid-density laser-produced plasma is studied under a range of conditions. An intensity-dependent collision rate is used in a numerical calculation of the reflectivity of a steep-gradient plasma, such as might be produced by an intense femtosecond laser pulse, and the conditions required to maximize absorption at high intensities are determined. The relative contributions of field-induced ionization and collisional ionization in laser-produced plasmas are studied, and it is shown that the behaviour of a gaseous plasma is almost solely governed by the field-induced process. A model is developed to simulate the propagation of an intense femtosecond laser pulse through an initially neutral gas, and this model is used to make predictions about spectral modifications to the laser pulse. Under certain conditions the spectrum is significantly broadened and suffers an overall blue shift. Quantitative fitting of theoretical spectra to experimental results in the literature is attempted, but is complicated by associated defocusing effects in the plasma. Field-induced ionization can produce a gaseous plasma which is significantly colder, for the same degree of ionization, than a plasma produced by collisional ionization. One possible application for a cold highly-ionized plasma is in a recombination x-ray laser, and the propagation model allows the calculation of the plasma temperature, which is a crucial parameter in assessing the feasibility of such schemes.

Advisor: Burnett, K
Flexible labour markets

This thesis investigates the quality of atypical employment to reveal whether support for the generation of temporary and part-time jobs is an effective policy for labour market renewal or whether it leads to labour market segmentation. This issue is investigated through analyses of the quality of atypical employment, with the following components of atypical work investigated: working-conditions, wages, poverty risk, exposure to unemployment and/or labour market drop out, as well as the extent to which atypical employment leads to the standard employment contract, termed its 'bridging function'. Strong and consistent variation in the quality of atypical work (relative to standard contract employment) combined with evidence of a weak bridging function is taken as an indicator of labour market marginalisation for these workers. Evidence of labour market marginalisation would suggest that non-standard contracts foster market segmentation.
A key component of the analyses asserts that institutional context will structure atypical worker outcome with comparative analysis run on three countries to test this hypothesis. The countries chosen for the analysis varied in their combination of institutions thought to structure labour market outcome. The institutions thought to structure labour market outcome were classified into two groups, or axes, thought to structure labour markets in a different manner. The first group of institutions were thought to influence the relative openness or flexibility of markets, while the second was thought to influence the integration of labour market outsiders. Denmark is presented as a flexibly integrative labour market, the French market is presented as rigidly integrative and the United Kingdom is labelled flexibly non-integrative.
The empirical analyses revealed strong and consistent variation in the quality of atypical work (relative to standard contract employment) and while the evidence suggests that temporary employment does provide a bridging function, the same was not true of part- time employment. This led us to conclude that policies which have sought to flexibilise the labour market through the generation of temporary and/or part-time employment are likely to contribute to market segmentation. Nonetheless we established important differences between countries which provided insights into the labour market conditions which were the most supportive of atypical worker inclusion.

Advisor: Gallie, D
Optimisation of light collection in inorganic scintillators for rare event searches

Inorganic scintillators are playing an ever increasing role in the search for rare events. Progress in the use of cryogenic phonon-scintillation detectors (CPSD) has allowed for a rapid increase in sensitivity and resolution of experiments using this technique. It is likely that CPSD will be used in future dark matter searches with multiple scintillator materials. Further improvements in the performance of CPSD can be expected if the amount of light collected is increased. In this thesis, two approaches are used to look at ways of maximising the amount of light collected in CPSD modules. The first approach is to obtain a detailed understanding of the spectroscopic properties in the crystal to identify ways of increasing their scintillation intensity. The second is to simulate the light collection properties using a Monte-Carlo simulation program. This requires a detailed understanding of the optical properties of inorganic scintillators and obtaining this information is the focus of the current work. Two new methods have been developed to evaluate the scintillation decay time and the intrinsic light yield of scintillators. These methods are tested on CRESST CaWO4 crystals so that all the input parameters necessary for the simulation of CRESST modules is available. These input parameters are used to successfully explain features of the light collection in CRESST CPSD modules and to suggest possible improvements to the design of the modules. In summary, the current work has contributed to the development of a standardised method to maximise the light yield that can be obtained from CPSD for application to rare event searches.

Advisor: Kraus, H
Factors affecting the status of the chough in Britain, with observations on its behaviour

This thesis aims to fill gaps unfilled by the recent upsurge in Chough studies. These are: the classification and functional analysis of aspects of their behaviour, examining feeding preferences in relation to land management, finding how literary attitudes towards them developed and obtaining quantitative insights into their past distribution to apply to possible explanations for their status changes.
Three pairs near Llangranog, Dyfed were observed and findings were complemented with analysis of RSPB film offcuts.
All observed behaviours were defined and classified according to social context and frequency of use. Of 45 behaviours seen, 21 had not previously been recorded. Single-link cluster diagrams were presented to illustrate observed postures and comparable corvid postures.
Three aspects of their social behaviour were further examined: Food-begging by juveniles and females was related to time since fledging and copulation date respectively. Begging success depended on technique repertoire, which increased with time; increased foraging group size decreased the individual's vigilance time spent, with an earlier detection of potential tourist disturbance; wing-flicking did not occur with short flights nor after flights due to disturbance. It was frequent after landing while as frequent before take-off as during foraging excepting tourist disturbed flights. Ritualised forms of wing-flicking and bill-wiping formed the basis of Chough communication. Flow diagrams and canal models describing the functional organisation of these behaviours are presented.
Choughs feed on short, mainly grass swards maintained by grazing, exposure and occasionally, cutting.
When given the Jackdaw's old name, Choughs acquired their thieving reputation and were also regarded as fire-raisers until the 1830's. Distribution and abundance from 1750 to 1982 were estimated at county and national level. Their status was not significantly affected by climate. Grazing artificially boosted their numbers, agricultural changes and persecution from 1750 until 1940 caused their decline.

Advisor: Perrins, C
Towards a computational model of the colonic crypt with a realistic, deformable geometry

Colorectal cancer (CRC) is one of the most prevalent and deadly forms of cancer. Its high mortality rate is associated with difficulties in early detection, which is crucial to survival. The onset of CRC is marked by macroscopic changes in intestinal tissue, originating from a deviation in the healthy cell dynamics of glands known as the crypts of Lieberkuhn. It is believed that accumulated genetic alterations confer on mutated cells the ability to persist in the crypts, which can lead to the formation of a benign tumour through localised proliferation. Stress on the crypt walls can lead to buckling, or crypt fission, and the further spread of mutant cells. Elucidating the initial perturbations in crypt dynamics is not possible experimentally, but such investigations could be made using a predictive, computational model. This thesis proposes a new discrete crypt model, which focuses on the interaction between cell- and tissue-level behaviour, while incorporating key subcellular components. The model contains a novel description of the role of the surrounding tissue and musculature, which allows the shape of the crypt to evolve and deform. A two-dimensional (2D) cross-sectional geometry is considered. Simulation results reveal how the shape of the crypt base may contribute mechanically to the asymmetric division events typically associated with the stem cells in this region. The model predicts that epithelial cell migration may arise due to feedback between cell loss at the crypt collar and density-dependent cell division, an hypothesis which can be investigated in a wet lab. Further, in silico experiments illustrate how this framework can be used to investigate the spread of mutations, and conclude that a reduction in cell migration is key to confer persistence on mutant cell populations. A three-dimensional (3D) model is proposed to remove the spatial restrictions imposed on cell migration in 2D, and preliminary simulation results agree with the hypotheses generated in 2D. Computational limitations that currently restrict extension to a realistic 3D geometry are discussed. These models enable investigation of the role that mechanical forces play in regulating tissue homeostasis, and make a significant contribution to the theoretical study of the onset of crypt deformation under pre-cancerous conditions.

Keywords: mathematical modelling
Colorectal cancer
Advisor: Gavaghan, D
Chapman, S
Byrne, H
Osborne, J
Magneto-optics of complex oxides at terahertz frequencies

This thesis presents experimental results on two complex oxide systems: Cu1-xZnxO and La0.7Sr0.3MnO3:ZnO. The dynamic magnetoelectric response of these materials is obtained using terahertz time-domain spectroscopy, supported by Fourier-transform infrared spectroscopy, Raman spectroscopy and X-ray diffraction.
Evidence for an electromagnon in the multiferroic phase of CuO is presented for the first time. This high temperature (213-230K) electromagnon is linked to intersublattice exchange between two Cu sublattices. The temperature dependence of a magnon in the collinear antiferromagnetic phase is indicative of biquadratic exchange.
Broadening of the multiferroic phase on substitution of copper with zinc is reported along with a 25% depression of the Néel temperature due to spin dilution. Phonons and magnons broaden and shift in energy on alloying. However, the electromagnon is relatively insensitive, increasing in energy without widening. This indicates that electromagnons and dynamic magnetoelectric coupling can be mantained even in disordered spin systems. Strong spin-phonon coupling is present in both magnetically ordered phases as shown by the anomalous behavior of the A3u phonon at TN1 and a Raman-active mode associated with a magnetic modulation of a zone-folded acoustic phonon.
Dynamic 1THz magnetoresistance is found to be significantly larger than static magnetoresistance in La0.7Sr0.3MnO3:ZnO vertically-aligned nanocolumns on LaAlO3 substrates. The metal-insulator transition temperature is determined to be 300 K. Temperature dependent static and dynamic resistivity and magnetoresistance are discussed in terms of strain and grain boundary effects. Negative photoconductivity is observed and the dynamic response analysed.

Keywords: multiferroic
terahertz spectroscopy
magnon
electromagnon
Advisor: Lloyd-Hughes, J
Radaelli, P
Playing with fire: an MNC’s inability to translate its market logic in a culturally complex exchange setting in rural India

This dissertation describes the manner by which a multinational corporation (MNC) enacts a market-based logic with a locally embedded partner in a complex and unfamiliar operating setting to fulfil both business and social objectives. It examines a hybrid partnership between BP, an MNC, and SSP, a rural Indian non-governmental organisation (NGO). Together, the organisations trained rural women, who were affiliated with SSP, as agents to distribute and sell BP’s ‘smokeless’ cookstoves and fuel pellets to households who cook on smoky firewood stoves. The research draws on two theories—neo-institutional organizational theory and real markets theory—to examine the process by which logics are aligned across partners and projected and translated into the rural Indian exchange setting. It constructs a four-actor model (MNC, NGO, agent, customer) to explore the exchange relationships between the actors at the meso- and micro-levels. At the meso-level, it explains how the MNC and NGO’s non-aligned logics, asymmetric power dynamics, and lack of mutual trust contribute to the venture’s failure. In addition, the NGO was so determined to succeed as a professional, market-driven, channel partner that it shed part of its identity as a civil advocacy organisation and adopted mainstream commercial practices that were not sensitive to the needs of its local stakeholders. At the micro-level, the partners did not come to a common understanding with the agents regarding the cultural challenges they faced marketing the stove. Moreover, the marketing strategy glossed over the multi-layered social relationships and culinary, behavioural, and religious practices that needed to be translated for the technology to meet the needs of consumers. Using gritty ethnographic data, the dissertation highlights a challenge that large, foreign companies face when entering ‘Base of the Pyramid’ markets, namely the inconsistency between the MNC’s market logic and the wider associational logics that motivate village agents and customers.

Keywords: glocalization
base of the pyramid
market-based poverty alleviation
social structures
neo-institutional theory
last mile distribution
private sector
clean cookstoves
rural India
corporate partnerships
women's empowerment
behaviour change
social entrepreneurship
economic development
Advisor: Harriss-White, B
Nicholls, A
Loveridge, R
The duality between two-index potentials and the non-linear sigma model in field theory

We interpret the generalised gauge symmetry introduced in string theory and M-Theory as a special case of Grothendieck's stability equivalence relation in the definition of the 0th K-group and we calculate the Euler number of the elliptic de Rham complex twisted by a flat connection. Then using Polyakov's classical equivalence of flat bundles with non-linear sigma models we define a new topological invariant for foliations using techniques from noncommutative geometry, in particular the Connes' pairing between K-Theory and cyclic cohomology. This new invariant classifies foliations up to Morita equivalence.

Keywords: K-Theory
Superstring theory
M-Theory
Index Theory
Foliations
Global Analysis
Advisor: Tsou, S
Optical methods for monitoring physiological and biochemical variables

The use of optical methods for performing non-invasive physiological and biochemical monitoring has been investigated, with particular emphasis on the application of near-infrared spectrophotocetry for following changes in the redox state of cytochrome oxidase. Initial studies of the gross optical properties of in vivo tissue were made using an image intensifier. These demonstrated that some light is transmitted through biological tissues and that such material is very highly scattering.
In order to investigate the feasibiity of non-invasively monitoring changes in the redox state of cytochrome oxidase in vivo. spectrophotometric and oxygen measurements were made on solutions containing the pure enzyme and yeast cell suspensions. These demonstrated the high affinity that the enzyme has for oxygen in such preparations, in contrast to the much lower apparent affinities in vivo that have been reported. These results were then modelled mathematically, and a possible-explanation for this anomaly suggested. Potential problems with applying this method are also presented. The interest in cytochrome oxidase is due to its importance in oxidative metabolism. However in performing this role it also assists in the prevention of oxidative damage, whose contribution to various disease states in paediatrics is briefly considered.
Two instruments were also constructed, and used, firstly to measure the spectral characteristics of transmitted and reflected light in vivo. ana secondly to study the cardiac synchronous pulsatile component of this light (commonly referred to as the photoplethysmogram).

Advisor: Rea, P
Spin(7)-manifolds and calibrated geometry

In this thesis we study Spin(7)-manifolds, that is Riemannian 8-manifolds with torsion-free Spin(7)-structures, and Cayley submanifolds of such manifolds. We use a construction of compact Spin(7)-manifolds from Calabi–Yau 4-orbifolds with antiholomorphic involutions, due to Joyce, to find new examples of compact Spin(7)-manifolds. We search the class of well-formed quasismooth hypersurfaces in weighted projective spaces for suitable Calabi–Yau 4-orbifolds. We consider antiholomorphic involutions induced by the restriction of an involution of the ambient weighted projective space and we classify anti-holomorphic involutions of weighted projective spaces.
We consider the moduli problem for Cayley submanifolds of Spin(7)-manifolds and show that there is a fine moduli space of unobstructed Cayley submanifolds. This result improves on the work of McLean in that we consider the global issues of how to patch together the local result of McLean. We also use the work of Kriegl and Michor on ‘convenient manifolds’ to show that this moduli space carries a universal family of Cayley submanifolds.
Using the analysis necessary for the study of the moduli problem of Cayleys we find examples of compact Cayley submanifolds in any compact Spin(7)-manifold arising, using Joyce’s construction, from a suitable Calabi–Yau 4-orbifold with antiholomorphic involution. For the analysis to work, we need to show that a given Cayley submanifold is unobstructed. To show that particular examples of Cayley submanifolds are unobstructed, we relate the obstructions of complex surfaces in Calabi–Yau 4-folds as complex submanifolds to the obstructions as Cayley submanifolds.

Keywords: special holonomy
spin(7)-manifolds
Cayley submanifolds
Advisor: Joyce, D
Making home safe? The role of criminal law and punishment in British immigration controls

This thesis is an enquiry into the regulation of immigration through criminal law and its institutions. It looks at the range of immigration offences in British legislation, and whether and how they are being used in practice. The criminalisation of immigration status has historically served functions of exclusion and control against those who defy the state’s powers over its territory and population. In the last two decades, the prerogatives to exclude and punish have been enhanced by the expansion of the catalogue of immigration offences and the more systematic enforcement of these powers. The great reliance on the criminal law to regulate immigration is distinctive of a period in which crime and immigration have been increasingly politicised. As a consequence, more offences have been created and more individuals have been subject to the hybrid immigration and criminal justice system. While immigration offences largely remain under-enforced, some of them –particularly those penalising document fraud and identity stripping- are used against foreign nationals who cannot be removed from the country.
In this thesis I explain what I consider to be the most pernicious consequences of this expansion of formal and substantive criminalisation of immigration breaches. The existence of a parallel system of sanctions allows enforcement agencies wide margins of discretion. Therefore, similar cases may be dealt with in very different ways. When the criminal route is chosen, the use of criminal law in the vast majority of cases reaching the criminal courts is unnecessary, disproportionate and extremely harmful. Both the decision to prosecute and the sanction eventually imposed are justified by preventive and regulatory purposes. The actual practice of criminalisation reveals that the criminal procedural safeguards are weakened and those accused of immigration crimes are likely to be convicted and imprisoned for these offences.
I conclude that the formal and substantive criminalisation of immigration represents a departure from liberal criminal law principles and the purposes of criminal punishment. These conclusions cast doubts about the pragmatic, non-principled use of criminal law to regulate immigration flows, and call for the need to look at other, more humane alternatives in the treatment of ‘unwelcome’ migrants.

Keywords: regulation
immigration
criminalisation
control of immigration
Advisor: Bosworth, M
The history of the Society of Jesus in Colombia, 1844-1861

This thesis examines the activity of the Jesuits in Colombia during the nineteenth century; it demonstrates how their return to the country in 1844 became a highly controversial political issue until 1884, when the national government authorized their permanent residence. The Jesuits were established in the country from 1844 to 1850, and then from 1858 to 1861. These two short sojourns generated significant debate between the Conservative and Liberal parties. The first return of the Jesuits coincided with the formation of these two parties and the debate over the separation of Church and State. It was after the Guerra de los Supremos, with the defeat of the Liberal Party and victory for the Conservative Party, that the latter passed a law on mission schools that allowed the return of the Society after its exile during colonial times.
The Liberals considered the law of April 1842 to be a tactic used by the Conservatives to empower their political project, and when the Jesuits arrived in the country, the Liberal Party started a campaign against them in Congress and through the press. As the invitation for their return to New Granada had been issued by the Conservative government, Liberals considered them to be allies of the Conservatives and deserving of their political antipathy.
The decrees issued regarding the return of the Jesuits clearly stated that they were to be assigned to Colegios de Misiones and Casas de Escala (Rest Residences) in mission territories. The Superior General of the order in Rome and the ecclesiastical authorities in Colombia interpreted the law as justifying the work of the Jesuits in establishing missions among the indigenous people and also in education in general.
Eladio Urisarri, the official in Rome in charge of arranging the return of the Jesuits, supported this interpretation, but the latent ambiguity was a continual issue.
The thesis analyses these episodes within the context of the republic’s politics and the state of the Colombian Church at the time, and examines the Jesuits’s experiences in Bogotá and the other dioceses where they were present.

Keywords: Jesuits in Colombia
Catholic Church in Colombia
The Society of Jesus
Advisor: Deas, M