VictorJuiz/thesis huggingface dataset:
Topics in analytic number theory
Keywords: sieve methods
number theory
prime numbers

In this thesis we prove several different results about the number of primes represented by linear functions.
The Brun-Titchmarsh theorem shows that the number of primes which are less than x and congruent to a modulo q is less than (C+o(1))x/(phi(q)log{x}) for some value C depending on log{x}/log{q}. Different authors have provided different estimates for C in different ranges for log{x}/log{q}, all of which give C>2 when log{x}/log{q} is bounded. We show in Chapter 2 that one can take C=2 provided that log{x}/log{q}> 8 and q is sufficiently large. Moreover, we also produce a lower bound of size x/(q^{1/2}phi(q)) when log{x}/log{q}>8 and is bounded. Both of these bounds are essentially best-possible without any improvement on the Siegel zero problem.
Let k>1 and Pi(n) be the product of k linear functions of the form a_in+b_i for some integers a_i, b_i. Suppose that Pi(n) has no fixed prime divisors. Weighted sieves have shown that for infinitely many integers n, the number of prime factors of Pi(n) is at most r_k, for some integer r_k depending only on k. In Chapter 3 and Chapter 4 we introduce two new weighted sieves to improve the possible values of r_k when k>2. In Chapter 5 we demonstrate a limitation of the current weighted sieves which prevents us proving a bound better than r_k=(1+o(1))klog{k} for large k.
Zhang has shown that there are infinitely many intervals of bounded length containing two primes, but the problem of bounded length intervals containing three primes appears out of reach. In Chapter 6 we show that there are infinitely many intervals of bounded length containing two primes and a number with at most 31 prime factors. Moreover, if numbers with up to 4 prime factors have `level of distribution' 0.99, there are infinitely many integers n such that the interval [n,n+90] contains 2 primes and an almost-prime with at most 4 prime factors.
Ultracold quantum gases in time-averaged adiabatic potentials
Keywords: adiabatic
ultracold
time-averaged

This thesis describes the experimental realisation and characterisation of three non-trivial trapping geometries for ultracold atoms. The double-well, ring and to some degree shell trap are examples of a highly versatile class of traps called time-averaged adiabatic potentials (TAAPs). In this experiment the TAAPs arise from the combination of three independent magnetic fields; a static quadrupole field dressed by a uniform radio-frequency field is time-averaged by a bias field oscillating at in the kHz regime. The result is a very smooth potential, within which ultracold atoms can be evaporatively cooled to quantum degeneracy, and subsequently manipulated into new geometries without destroying the quantum coherence.
The vertically offset double-well potential provided the first example of ultracold atoms confined in a TAAP. The same potential is used to demonstrate efficient evaporative cooling across the Bose-Einstein condensate (BEC) phase transition using only the Landau-Zener loss mechanism. Switching off the time-averaging fields loads atoms from the double-well TAAP into the rf-dressed shell trap. A characterisation of this potential measured low heating rates and lifetimes of up to 58s. With efforts ongoing to increase the trap anisotropy, this potential shows promise for research into the static and rapidly rotating 2D systems. In the presence of a single time-averaging field, the shell geometry is transformed into a ring-shaped trap with an adjustable radius. The ring trap can be controllably tilted and progress towards multiply connected condensates is being made. A rotation scheme to spin up atoms in the ring trap has been demonstrated, presenting the opportunity to investigate the dynamics of superflow in degenerate quantum gases.
Micromechanics of stress corrosion cracking in 304 stainless steel and Ni Alloy 600
Keywords: IGSCC
micro mechanical testing

The current thesis takes a step forward into understanding the intergranular stress corrosion cracking (IGSCC) by applying a relatively new micro-mechanical technique to look at the crack growth rate of individual grain boundaries in 304 stainless steel (SS) and to measure fracture toughness for different grain boundaries in Ni Alloy 600. In addition, a model is tested and proposed that could predict crack initiation in 304 SS. Pentagonal cross-section cantilevers 5 μm wide by 25 μm long were milled at individual grain boundaries in both 304 SS and Ni Alloy 600. The cantilevers milled in 304 SS were tested in-situ in a customised stage, using the nanoindenter. Crack growth rate was measured for two different cantilevers to be approximately 40 μm/s (K = 1.1 MPa(m)^(1/2)) and 120 μm/s (K = 1.7 MPa(m)^(1/2)). Cantilevers were milled in Ni Alloy 600 for three different samples: samples that were exposed to simulated pressurized water reactors (PWR) environment for 4500 h, for 1500 h and un-oxidised samples. The fracture toughness calculated for the fractured cantilevers in samples that were exposed for 4500 h was measured to be between 0.73 and 1.82 MPa(m)^(1/2). No intergranular fracture occurred in the samples that were exposed for 1500 h and in the un-oxidised samples. The grain boundary misorientation was measured for the tested cantilevers but no direct correlation was observed between the misorientation angle and the fracture toughness.
A Schmid-modified grain boundary stress (SMGBS) model previously used to study the intergranular behaviour of irradiated 316L steel in supercritical water was applied to predict crack initiation in 304 stainless steel. The model was successfully applied and accurately predicted crack initiation. To extend the model, sensitisation was also included. In addition, different areas of the specimen, including the initiation site were analysed using High resolution electron backscatter diffraction (HR-EBSD) technique to measure the geometrically necessary dislocations (GNDs) density. It was observed that the boundary average GNDs is lower for the intact boundaries and higher for the cracked grain boundaries.
B cell and antibody responses to influenza a virus in human
Keywords: Influenza A virus
B cell
Monoclonal antibody

Neutralising antibodies and antigen-specific B cells are important for protection against influenza A virus. However, the antigenic evolution of influenza A viruses has made a continuing challenge to the design of vaccine and the public health. The ability to generate cross-reactive response against influenza remains unclear in human. It is important to explore the antibody and B cell repertoire at single cell level.
The pandemic H1N1 and seasonal influenza vaccine induced robust antibody response in adults. However, pre- or co-vaccination with the seasonal vaccine led to a significantly reduced antibody response to pandemic H1N1 virus. Whether this interference has impact on subsequent infection rates remains undetermined. There observed substantial cross-reactive antibody response upon vaccination, as measured by HI, MN and B cell ELISpot assays. The antibody recognizing conserved proteins could be the main component of cross-reactivity against influenza A strains and subtypes. A significant expansion of influenza-specific MBC was observed after infection. Crossreactive response was also noted in the MBC response. Importantly, a robust early-phase ASC response was detected in the peripheral blood upon influenza vaccination or infection. The size of ASC response significantly correlated with serum HI, MN and anti-HA IgG titre three weeks after vaccination. The sequence analysis revealed that early-phase ASC accumulated high level of somatic mutations on Ig variable region and affinity maturation, as well as anti-influenza mAb, which suggested their origin from pre-existing MBC. Eight anti-influenza mAb were made from early-phase ASC, including one high-titre virus-neutralising HA1-specific, two other HA1-specific, one cross-reactive HA2-specific, and four cross-reactive NP-specific antibodies, indicating of the broad diversity of ASC repertoire.
In conclusion, this study demonstrated the properties of antibody and B cell responses to influenza A virus at serological, cellular and sequence level. The virus-neutralising and cross-reactive mAb derived from ASC could have therapeutic potential and their analysis might direct the vaccine design in the near future.
Molecular dynamics simulations of the equilibrium dynamics of non-ideal plasmas
Keywords: strongly coupled plasma
one-component plasma

Molecular dynamics (MD) simulations are used to compute the equilibrium dynamics of a single component fluid with Yukawa interaction potential v(r) = (Ze)^2 exp(−r/λs )/4π eps_0 r. This system, which is known as the Yukawa one-component plasma (YOCP), represents a simplified description of a non-ideal plasma consisting of ions, charge Ze, and electrons.
For finite screening lengths λs, the MD results are used to investigate the domain of validity of the hydrodynamic description, i.e., the description given by the Navier-Stokes equations. The way in which this domain depends on the thermodynamic conditions of the YOCP, as well as the strength and range of the interactions, is determined. Remarkably, it is found that the domain of validity is completely determined by the range of the interactions (i.e., λs); this alone determines the maximum wave number k_max at which the hydrodynamic description is applicable.
The dynamics of the YOCP at wavevectors beyond k_max are then investigated; these are shown to be in striking agreement with a simple and well known generalisation of the Navier-Stokes equations.
In the extreme case of the Coulomb interaction potential (λs = ∞), the very existence of a hydrodynamic description is a known but unsolved problem [Baus & Hansen, 1980]. For this important special case, known as the one-component plasma (OCP), it is shown that the ordinary hydrodynamic description is never valid.
Since the OCP is the prototypical system representing a non-ideal plasma, a number of different approaches for modelling its dynamics have been formulated previously. By computing the relevant quantities with MD, the applicability of a number of models proposed in the literature is examined for the first time.
Decision-making in the context of pain
Keywords: Anxiety
Pain
Functional MRI
Neuroimaging
Decision-making

Clinical and behavioural evidence has shown that the threat value of pain biases decisions about whether a stimulus is perceived as painful or not, and if yes, how intense is the sensation. This thesis aims to investigate the neural mechanisms underlying the effect of perceived threat on perceptual decisions about pain. The first study investigates the neural mechanisms underlying the effect of threat on the decision about the quality of the sensation, i.e., whether it is perceived as painful or not. The perception of pain (relative to no pain) was associated with activation in the anterior insula as well as an increased connectivity between this region and the mid-cingulate cortex (MCC). Activity in the MCC was correlated with the threat-related bias to perceived pain. In the second study, probabilistic tractography was performed with diffusion tensor imaging to investigate the structural connectivity between subdivisions of the insula and other pain-related regions. Additional analyses revealed that the structural connectivity between the anterior insula and the MCC, and between the posterior insula and somatosensory cortices, is positively correlated with the threat-related bias toward pain. In the third study, a multivariate pattern analysis (MVPA) was performed to investigate whether pain can be decoded from functional neuroimaging data acquired during the anticipation and during the receipt of pain. The results show that pain can be predicted by the pattern of neural activity in the right anterior insula during anticipation and stimulation. The fourth study investigated the effect of uncertainty about the stimulation intensity as a form of threat on the perceived intensity of pain. Uncertainty was found to be associated with an increased activation in the anterior insula. Overall, these findings suggest that a neural network consisting of the anterior insula and the MCC plays a key role in decisions about the quality and the quantity of nociceptive sensation. Results from the MVPA analysis support the notion that perceptual decisions are encoded by a distributed network of brain regions. The variability in anatomical connections between these regions may account for the individual differences in the susceptibility to a threat-mediated bias toward pain.
Observations of the Sunyaev-Zel'dovich effect using the Cosmic Background Imager 2
Keywords: radio interferometry
Sunyaev-Zel'dovich effect
clusters of galaxies
cosmic microwave background
cosmology
radio astronomy

This thesis describes the analysis of pointed thermal Sunyaev-Zel'dovich (SZ) effect data from observations using the Cosmic Background Imager 2 (CBI2). CBI2 is an upgrade to the original Cosmic Background Imager, with antennas that have twice the effective collecting area, and hence provide greater sensitivity on longer baselines. Observations of the thermal SZ effect constrain the line-of-sight integrated gas pressure within clusters of galaxies and, when combined with X-ray data, provide an excellent tool for deriving the physical properties of these large structures. The CBI2 SZ data combine relatively low-resolution with a large field-of-view, and can therefore be used to constrain the gas properties of medium-redshift clusters out to the virial radius. By jointly fitting a suitable analytical model to SZ data and X-ray surface brightness data, it is possible to obtain constraints on the temperature and total mass of the cluster. For the analysis work presented in this thesis I choose to parametrise the gas based upon the known behaviour of the entropy, and the total mass by the Navarro, Frenk and White (NFW) prescription. This model is tested against Hydrodynamic/N-body simulations and is found to reproduce the radial behaviour of key cluster properties. The CBI2 observations presented in this work focus on the REFLEX-DXL clusters, an X-ray luminous sub-sample of the REFLEX survey at z ~ 0.3, which have previously published X-ray surface brightness data. The Bullet Cluster, a significant merger system, is a member of this sample and is presented here as a case study for use of the entropy-based model. The derived total mass and gas mass fraction of this cluster are found to be consistent with results from previous X-ray observations. The derived properties from the REFLEX-DXL sample are used to construct a preliminary set of SZ scaling relations out to the virial radius, and are found to be consistent with the self-similar model for massive clusters.
Land acquisition in British India c. 1894-1927
Keywords: India
History
Eminent domain

This study offers the first instalment of a general history of land acquisition in British India, c. 1894–1927. It advances eight principal theses: (i) that the first law of land acquisition was enacted in 1668, as part of a political settlement by the East India Company with the Portuguese landlords of Bombay island; (ii) that, to a remarkable degree, land acquisition law was shaped in the interest of the sterling railway companies; (iii) that the state habitually used land acquisition not so much to effect non- consensual transfers but to ‘launder’ titles free of encumbrances and other claims; (iv) that the primary beneficiaries of land acquisition were public bodies, the sterling railway companies, and elite private interests; (v) that the executive was hostile to legislative and judicial oversight of land acquisition, and successfully resisted or co-opted attempts to impose such oversight; (vi) that the courts were in any event content with the role they were assigned under the 1894 Act, and generally deferred to the executive in land acquisition cases; (vii) that the land-acquiring executive, although hostile to and unencumbered by meaningful legislative and judicial oversight, as a general rule displayed a legal fastidiousness; (viii) that, despite an appearance of impartiality, land acquisition bore the stain of imperialism. These theses are advanced in the course of explaining the failure of the forgotten Kelkar Bill (1927), an attempt by the Maharashtrian nationalist N. C. Kelkar (1872–1947) to enact far-reaching amendments to the Land Acquisition Act 1894. Kelkar’s fellow nationalists withheld their open support from the measure and thereby guaranteed its failure: a counterintuitive choice that, it is argued, exemplifies the tactical compromises of nationalism.
Miniature buildings in the Liao (907-1125) and the Northern Song (960-1127) periods
Keywords: models
Song
architecture
Liao
China
miniature

This thesis is concerned with the construction and uses of miniature buildings in the Liao (907-1125) and the Northern Song (960-1127) periods in China. These miniature buildings exploited the components of Chinese traditional architecture on a small or greatly reduced scale. To date no work has taken the position of this thesis to examine this corpus of miniature buildings that were used widely in tombs and temples as containers to provide coverings for coffins, and to hold images of deities, Buddhist relics and sutras, as seen in both archaeological discoveries and textual resources. The purpose of the thesis is to define this corpus and to consider its significance in the light of the functions that these tiny buildings fulfilled.
This thesis proposes that these miniature buildings contributed a unique and indispensable part in presenting the positions of their owners in society. Made as containers, miniature buildings particularly emphasize decoration, which enabled viewers to make a connection with life-size buildings, in the ways of which they were fitted into an existing architectural hierarchied system in the deeply rooted tradition of the Liao and the Northern Song. The thesis makes considerable use of the concepts of reception, for the reaction of viewers to these miniature buildings defined also their reactions to the contents. Several types of analogies were achieved between full-scale buildings and miniature representations, as well as between their contents, which allowed specific types of interpretation of the miniature buildings as taking the roles of actual buildings and fictional structures.
The thesis considers the use of miniature buildings as one of the ways in which complex ideas can be reinforced by material forms. A wider discussion on miniature models presents that the significance of miniaturization lies in the power of control that can be achieved by creating and using the miniature.
Substance use, situational characteristics and sexual outcomes in men who have sex with men
Keywords: Systematic review
substance use
gay men
social research methods
epidemiology
HIV/AIDS

This thesis presents an empirical investigation into substance use, situational characteristics and sexual outcomes in men who have sex with men (MSM) motivated by the high rates of substance use in MSM; the association between substance use and sexual risk behaviours in MSM; the lack of specific theory addressing relationships between substance use, sexual interactions and social interactions between MSM; and the need for clearer understandings of encounter-level associations with sexual risk.
Qualitative metasynthesis. This thesis begins with laying the methodological groundwork for a qualitative metasynthesis that theorises the relationship between substance use and social spaces in MSM, with a particular focus on sexual outcomes. The qualitative metasynthesis derives the key organising perspective of ‘littoral spaces’ in which substance use is associated with a pre-planned, though temporary, escape from the boundaries of everyday life to engage in maximal sensory exploration, including through sexual contact.
Systematic review of multiple-event analyses. The thesis then turns to a systematic review of previous quantitative multiple-event analyses examining associations between situational characteristics and sexual outcomes, which establishes the need for additional multiple-event analyses addressing specific substance use, location of sex, partner serodiscordance and partner type.
Multiple-event analyses. Finally, informed by the qualitative metasynthesis and the systematic review of event-level analyses, this thesis presents multiple-event analyses addressing unprotected anal intercourse (UAI), pleasure and control as sexual outcomes in MSM in England. These analyses found that substance use was associated with greater odds of UAI and pleasure, but not with control, and that non-private locations of sex were associated with decreased odds of UAI and pleasure, but not control. Furthermore, there was sparse evidence of interactions between respondent and partner substance use and between respondent substance use and location of sex in associations with sexual outcomes. These analyses contribute to understandings of associations between substance use, situational characteristics and sexual risk behaviour by presenting the first known analyses on MSM in England and by examining sexual outcomes besides UAI.
Functional characterisation of cardiac progenitors from patients with ischaemic heart disease 
Keywords: ischaemic heart disease
myocardial infarction
ischaemic cardiomyopathy
cardiac stem cell
mesenchymal stromal cell
neovascularisation
extra-cellular matrix

Ischaemic heart disease (IHD) is the leading cause of death worldwide. Currently, even optimal medical therapies do not attenuate deterioration of the left ventricular (LV) function completely. Stem cell therapies, and recently cardiac stem cell therapies, have emerged as potential novel treatments for IHD. However, clinical evidence from randomised controlled studies has shown mixed results. Thus understanding what patient-related factors may affect the therapeutic performance of the cells may help improving treatment outcomes. The studies described in this thesis aim to understand how cardiac progenitor cells (CPCs) can re-vascularise ischaemic myocardium and promote functional repair of the heart. Resident CPCs were isolated and expanded from the right atrial appendage of 68 patients following the ‘cardiosphere’ method (cardiosphere-derived cells or CDCs). They resemble mesenchymal progenitors as they lack the expression of endothelial and haematopoietic cell surface markers but express mesenchymal progenitor cell markers (e.g. CD105, CD90). Cell function was evaluated by support of angiogenesis, mesenchymal lineage differentiation potential in vitro, and improvement in heart function in vivo. Notably in vitro, CDC from different patients differed in their angiogenic supportive and differentiation potentials. In a rodent model of myocardial infarction (MI), transplantation of CDC reduced infarct size significantly (p<0.05). However, only those CDCs with a robust pro-angiogenic ability in vitro improved vessel density and heart systolic function (p<0.05) in vivo. A multiple regression model, which accounted for 51% of the variability observed, identified New York Heart Association (NYHA) class, smoking, hypertension, type of ischaemic disease and diseased vessel as independent predictors of angiogenesis. In addition, gene expression analyses revealed that differential gene expression of several extracellular matrix components (e.g. CUX1, COL1A2, BMP1 genes and microRNA-29b) could explain the differences observed in CDC’s vascular supportive function. In summary, this is the first description of variability in the pro-angiogenic and differentiation potential of CDCs and its correlation with their therapeutic potential. This study indicates that patient stratification may need to be included in the design of future trials to improve the efficacy of cell-based therapies.