VictorJuiz/thesis huggingface dataset:
Adults' responses to infant vocalisations: a neurobehavioural investigation
Keywords: deep brain stimulation
depression
vocalisations
local field potential
infant
parent

Infant vocalisations are uniquely salient sounds in the environment. They universally attract attention and compel the listener to respond with speed and care. They provide a wealth of information to parents about their infant’s needs and affective state. There is a scientific consensus that early parenting has a profound impact on child development. In particular, the sensitivity with which parents respond to their infant’s communicative cues has been shown to affect cognitive and socio-emotional outcomes. The mechanisms underlying such sensitivity are not well understood.
In this thesis, adults’ sensitivity to infant cues will be considered in terms of two components, the ‘promptness’ and ‘appropriateness’ of responses, as originally conceptualised by Bell and Ainsworth (1972). Promptness of responses is considered in terms of adults’ ability to move with speed and effort after listening to infant vocalisations. Appropriateness, on the other hand, is considered in terms of adults’ ability to differentiate between functionally significant parameters in infant vocalisations. The effect of modifiable environmental factors on the promptness and appropriateness of responses is also investigated. Finally, a focused investigation of the brain basis of responses to infant vocalisations is presented.
Overall, findings demonstrated that infant vocalisations undergo privileged, specialised processing in the adult brain. After hearing an infant cry, adults with and without depression were found to move with greater coordination and effort. Adults were also found to be attuned to subtle parameters in infant cries. This sensitivity was shown to be affected by two participant-level factors, depression and previous musical training. Furthermore, this sensitivity could be enhanced through intervention, as evidenced by findings from short-term, perceptual discrimination training. The notion of privileged processing of infant vocalisations is further supported by evidence of early discrimination of infant sounds in a survival-related subcortical brain structure.
Future directions for this work include directly relating current experimental measures of adults’ responses to infant cues with parental sensitivity to infant communication during dynamic interactions. Translating current findings into applied settings would require an investigation of the effects of factors such as musical and perceptual training on sensitivity to infant cues in at-risk populations, such as mothers and fathers with depression. Lastly, an increased understanding of the brain basis of adults’ sensitivity to infant cues will provide insight into our greatest challenge: parenting our young.
New detectors for electron microscopy
Keywords: Electron Microscopy
DQE
MTF
Detectors

Detectors for Electron Microscopy have traditionally used a scintillator to generate photons from fast electrons, which are then detected by a sensor. However, in recent years direct detection has become an area of interest due to the potential improvements to detector performance.
In this thesis various aspects of direct detection are presented. I will begin with simulations of direct detectors based on Joy’s model of straight trajectories between Rutherford scattering events, where signal is generated by inelastic scattering events. The effects of microscope operating voltage, detector thickness, a surface electrically dead layer and diode depth on detector performance are presented.
A prototype detector was developed using the DUOS sensor, two thicknesses of the sensor were produced a 50μm thick detector and a 20μm thick detector. EBSD results are presented which show how the use of a reactive ion etch to reduce the dead layer thickness of a mechanically thinned sensor improve the detection efficiency of a sensor allowing EBSD work to be carried out at operating voltages as low as 5keV.
The MTF and DQE of both thicknesses of DUOS sensor are measured at 80kV and 200kV, which show that there is little difference between the two thicknesses at 80kV, but at 200kV the thinner detector shows an improved MTF. The results are then and compared with the equivalent simulated detectors. I show how the high frame rate of a detector and rigid and non-rigid registration can be used to improve image quality, resolving the {331} lattice spacing which is not visible with a simple summation of frames.
Detectors using gallium nitride rather than silicon as the base semiconductor are simulated. The MTF at the Nyquist frequency for a GaN detector is double that of a Si detector at an operating voltages of 80kV due to the smaller interaction volume of an electron in GaN. However, at higher voltages the improvement is much smaller as most electrons pass through the detector.
Degree completion in the UK: individual, institutional and contextual factors that explain students’ chances of educational success in British universities
Keywords: Educational inequalities
Higher Education

Degree completion is as important as participation in higher education. To date, most of the research on this subject has investigated the association between socio-economic background and academic preparation to explain lower rates or non-completion. This thesis explores the role that individual, institutional and contextual factors have on degree completion chances.
The first empirical chapter uses an individual-level longitudinal dataset to study the role that attainment on entry and socio-economic background have on students’ chances of completion. The chapter finds that attainment on entry significantly affects students’ chances of degree completion. It also reveals, however, that attainment on entry does not completely explain the socio-economic differences in degree completion chances in the system.
The second empirical chapter examines the role that institutions have on students’ chances of degree completion. Like the first chapter, this one draws on the individual-level longitudinal dataset. Although the analyses discover institutional effects, they show them to have a small effect on the system.
The third empirical chapter examines the role that teaching has on the probability that students complete their degrees in higher education. The findings show that teaching has a small but significant effect on students’ chances of degree completion. Teaching effects take place only at the most selective institutions of the system.
The final empirical chapter examines the role that unemployment has on students’ decisions to complete a university degree. Using data from the Labour Force Survey, the research finds that higher unemployment rates have a positive effect on students’ chances of degree completion. This thesis contributes to the field by showing that stratification of higher education also translates to degree completion. The results confirm that selectivity and institutional effects are strongly associated. In addition, they show that where the institutional framework is concerned, there is a gradient for class effect in educational outcomes.
Comparing stochastic discrete and deterministic continuum models of cell migration
Keywords: continuum
discrete
equivalence framework
cell migration
stochastic
position-jump
non-uniform domain
deterministic

Multiscale mathematical modelling is one of the major driving forces behind the systems biology revolution. The inherently interdisciplinary nature of its study and the multiple spatial and temporal scales which characterise its dynamics make cell migration an ideal candidate for a systems biology approach. Due to its ease of analysis and its compatibility with the type of data available, phenomenological continuum modelling has long been the default framework adopted by the cell migration modelling community. However, in recent years, with increased computational power, complex, discrete, cell-level models, able to capture the detailed dynamics of experimental systems, have become more prevalent. These two modelling paradigms have complementary advantages and disadvantages. The challenge now is to combine these two seemingly disparate modelling regimes in order to exploit the benefits offered by each in a comprehensive, multiscale equivalence framework for modelling cell migration.
The main aim of this thesis is to begin with an on-lattice, individual-based model and derive a continuum, population-based model which is equivalent to it in certain limits. For simple models this is relatively easy to achieve: beginning with a one-dimensional, discrete model of cell migration on a regular lattice we derive a partial differential equation for the evolution of cell density on the same domain. We are also able to simply incorporate various signal sensing dynamics into our fledgling equivalence framework. However, as we begin to incorporate more complex model attributes such as cell proliferation/death, signalling dynamics and domain growth we find that deriving an equivalent continuum model requires some innovative mathematics. The same is true when considering a non-uniform domain discretisation in the one-dimensional model and when determining appropriate domain discretisations in higher dimensions. Higher-dimensional simulations of individual-based models bring with them their own computational challenges. Increased lattice sites in order to maintain spatial resolution and increased cell numbers in order to maintain consistent densities lead to dramatic reductions in simulation speeds. We consider a variety of methods to increase the efficiency of our simulations and derive novel acceleration techniques which can be applied to general reaction systems but are especially useful for our spatially extended cell migration algorithms.
The incorporation of domain growth in higher dimensions is the final hurdle we clear on our way to constructing a complex discrete-continuum modelling framework capable of representing signal-mediated cell migration on growing (possibly non-standard) domains in multiple dimensions.
Sunset clauses: a historical, positive and normative analysis
Keywords: rule of law
separation of powers
sunset clauses

Sunset clauses are a commonly used statutory provision related to the temporary duration of various laws. Such clauses are scattered throughout the statute books. This thesis aims to shed light on the constitutional value of such clauses, in order to value them from the perspective of the separation of powers and the rule of law.
We have an extant amount of literature on sunset clauses, especially regarding their utility in the United States. In the United Kingdom, we have a limited analysis with respect to specific fields, including emergency legislation. However, we lack a comprehensive analysis with regard to their constitutional value.
This thesis’s analysis is conducted in three parts, separated into the historical, the positive, and the normative. All three parts of this thesis are interdependent, and the analysis of each subsequent part builds on the conclusion of its antecedent. The first part investigates the historical development of sunset clauses since the first Parliament in England. The positive analysis examines the contemporary utility of sunset clauses. Finally, the normative evaluation examines their interaction with several models of separation of powers as it values their impact on the rule of law.
Depending on the separation of power model, such clauses play a role in the system of checks and balances. On the one hand, they impact the institutional relationship between the executive and legislative branches. On the other hand, they influence the interaction between the legislature and the courts. Although I acknowledge that their legislative use in limiting human rights diminishes the rule of law, they might have the exact opposite effect: on several occasions in the past, they were used to advance the rule of law, including the adoption of innovative legislation and the annulment of the death penalty. Indeed, this thesis attests to the constitutional value of sunset clauses.
Negotiating a living: working children in Kolkata
Keywords: South Asia
India
Kolkata
childhoods
geography
labour

The majority of children, involved in both waged and unwaged work exist beyond the control and comprehension of national and international regulation, within the informal economy. Research has shown that the informal economy, contrary to general perception, is not a sphere of unregulated activity, but rather, operates through alternative structures and techniques of power. Children's work within the informal economy, and therefore outside the regulative reach of the state, is subject to extra-legal modes of regulation that are pursued through elaborate systems of discipline and power exercised by non-state actors, groups, and social institutions and networks.
Through a case study on children in Kolkata, India, who are engaged in specific forms of informal work in three distinct urban spaces – domestic servitude in the private realm of the home, small-scale manufacturing and service work in factories and shops, and ragpicking, scavenging and begging on the streets – this thesis aims to explore the way children's lives are constructed through work and space, to uncover the social processes and relations of power that working children navigate in order to build and sustain their livelihoods. I examine the way that children's spaces of work are imbued with social relations of gender, caste, religion, ethnicity and power that are enacted through the construction of hierarchies, divisions of labour, and work regimes. I also explore the politics of these spaces, revealing the primary economic partnerships and obstacles that children contend with in constructing their working lives. Overall, I aim to uncover the ways in which children engage with and negotiate the extra-legal systems of regulation by categorically analysing children's work in the home, shop and factory, and street.
The AdS/CFT correspondence and generalized geometry
Keywords: AdS/CFT correspondence
generalized complex geometry
string theory

The most general AdS5imesY solutions of type IIB string theory that are AdS/CFT dual to superconformal field theories in four dimensions can be fruitfully described in the language of generalized geometry, a powerful hybrid of complex and symplectic geometry. We show that the cone over the compact five-manifold Y is generalized Calabi-Yau and carries a generalized holomorphic Killing vector field xi, dual to the R-symmetry. Remarkably, this cone always admits a symplectic structure, which descends to a contact structure on Y, with xi as Reeb vector field. Moreover, the contact volumes of Y, which can be computed by localization, encode essential properties of the dual CFT, such as the central charge and the conformal dimensions of BPS operators corresponding to wrapped D3-branes. We then define a notion of generalized Sasakian geometry'', which can be characterized by a simple differential system of three symplectic forms on a four-dimensional transverse space. The correct Reeb vector field for an AdS5 solution within a given family of generalized Sasakian manifolds can be determined---without the need of the explicit metric---by a variational procedure. The relevant functional to minimize is the type IIB supergravity action restricted to the space of generalized Sasakian manifolds, which turns out to be just the contact volume. We conjecture that this contact volume is equal to the inverse of the trial central charge whose maximization determines the R-symmetry of the dual superconformal field theory. The power of this volume minimization is illustrated by the calculation of the contact volumes for a new infinite family of solutions, in perfect agreement with the results of a-maximization in the dual mass-deformed generalized conifold theories.
The electrochemistry of hydrogen sulfide in room temperature ionic liquids
Keywords: room temperature ionic liquids
gas detection
voltammetry
electrochemistry

The work presented in this thesis involves the use of room temperature ionic liquids (RTILs) as solvents in electrochemical experiments for the detection of hydrogen sulfide. The fundamentals of electrochemistry are presented, followed by an overview of RTILs in terms of their properties, applications and their behaviour as electrochemical solvents compared to conventional solvents. This is followed by an outline of electrochemical detection of various gases in aqueous, organic and ionic solvents. The results of 8 original studies are then presented as follows:
The study of the electrochemical window of twelve different room temperature ionic liquids using cyclic voltammetry vs. an internal redox couple for two defined current densities, and observation of water uptake of different ionic liquids under different conditions using a Karl Fischer titrator.
The reduction of hydrogen sulfide in various room temperature ionic liquids at a platinum electrode, measured using cyclic voltammetry. Also, solubilities and diffusion coefficients of hydrogen sulfide determined by potential step chronoamperometry.
The oxidation of hydrogen sulfide in various room temperature ionic liquids at a platinum electrode measured using cyclic voltammetry and the simulation of the electrochemical signal using experimentally defined parameters.
The disproportionation of N,N-dimethyl-p-phenylenediamine (DMPD) in room temperature ionic liquids using cyclic voltammetry, and computational simulation of the voltammetry of DMPD using experimentally defined parameters to elucidate kinetic and thermodynamic data. DMPD was examined as a mediating species for hydrogen sulfide detection.
The oxidation of catechol and dopamine in ionic liquids using cyclic voltammetry and observing adsorption effects when varying solvent anion. Catechol was examined as a mediating species for hydrogen sulfide detection.
The electrochemical oxidation of NADH in ionic liquids using cyclic voltammetry and observing the ”switching on or off” of the electrochemical signal when varying the solvent anion. NADH was examined as a mediating species for hydrogen sulfide detection.
The mediated detection of hydrogen sulfide utilizing various mediating species in several ionic liquids using cyclic voltammetry, and the elucidation of the mediating mechanism of hydrogen sulfide in 3,5-tert-butyl-o-benzoquinone.
The observation of the diffusion of ferrocene in an ionic liquid at ring-recessed disc microelectrode arrays in generator-collector mode using potential step chronoamperometry.
The results presented show that room temperature ionic liquids perform well as solvents in gas sensors, and could be viable alternatives to traditional organic solvents. Ionic liquids have also been observed to be tuneable in their reactions with analytes depending on the constituent cations and, in particular, anions. This tuneability is advantageous as specific combinations of cations and anions can be chosen to suit particular experiments.
Model-based ultrasonic temperature estimation for monitoring HIFU therapy
Keywords: Temperature estimation
HIFU
Temperature model
Kalman filtering
Ultrasound
Echo strain

High Intensity Focused Ultrasound (HIFU) is a new cancer thermal therapy method which has achieved encouraging results in clinics recently. However, the lack of a temperature monitoring makes it hard to apply widely, safely and efficiently. Conventional ultrasonic temperature estimation based on echo strain suffers from artifacts caused by signal distortion over time, leading to poor estimation and visualization of the 2D temperature map. This thesis presents a novel model-based stochastic framework for ultrasonic temperature estimation, which combines the temperature information from the ultrasound images and a theoretical model of the heat diffusion. Consequently the temperature estimation is more consistent over time and its visualisation is improved.
There are 3 main contributions of this thesis related to: improving the conventional echo strain method to estimate temperature, developing and applying approximate heat models to model temperature, and finally combining the estimation and the models. First in the echo strain based temperature estimation, a robust displacement estimator is first introduced to remove displacement outliers caused by the signal distortion over time due to the thermo-acoustic lens effect. To transfer the echo strain to temperature more accurately, an experimental method is designed to model their relationship using polynomials. Experimental results on a gelatine phantom show that the accuracy of the temperature estimation is of the order of 0.1 ◦C. This is better than results reported previously of 0.5 ◦C in a rubber phantom.
Second in the temperature modelling, heat models are derived approximately as Gaussian functions which are mathematically simple. Simulated results demonstrate that the approximate heat models are reasonable. The simulated temperature result is analytical and hence computed in much less than 1 second, while the conventional simulation of using finite element methods requires about 25 minutes under the same conditions.
Finally, combining the estimation and the heat models is the main contribution of this thesis. A 2D spatial adaptive Kalman filter with the predictive step defined by the shape model from the heat models is applied to the temperature map estimated from ultrasound images. It is shown that use of the temperature shape model enables more reliable temperature estimation in the presence of distorted or blurred strain measurements which are typically found in practice. The experimental results on in-vitro bovine liver show that the visualisation on the temperature map over time is more consistent and the iso-temperature contours are clearly visualised.
Sequestering of Kähler moduli in type IIB string theory
Keywords: string theory
strings and branes phenomenology
intersecting branes models
supersymmetry breaking
conformal field models in string theory
compactification and string models
particle physics

In this thesis we employ string perturbation theory in toroidal orbifold models to study aspects of supersymmetry breaking in type IIB string theory.
First, we determine the dependence of physical Yukawa couplings on blow-up moduli in models with D3-branes at orbifold singularities. Blow-up moduli are scalar fields describing the size of small blow-up cycles in the compactification geometry. In models implementing moduli stabilisation these fields can acquire F-terms and break supersymmetry. We examine the moduli-dependence of physical Yukawa couplings at string tree-level by computing disk correlation functions involving a Yukawa interaction of visible sector fields and an arbitrary number of blow-up moduli. We perform the calculation for one blow-up insertion explicitly and find that the correlation function vanishes if the blow-up modulus is associated with a small cycle distant to the visible sector. For more than one blow-up insertion we show that all such correlation functions are exponentially suppressed by the compactification volume. We explain how these results are relevant to suppressing soft terms to scales parametrically below the gravitino mass.
Further, we determine corrections to holomorphic Yukawa couplings on D3-branes at an orbifold singularity due to non-perturbative effects such as gaugino condensation on a stack of D7-branes. This can be done by calculating a one-loop threshold correction to the gauge coupling on the D7-branes. We show that, if present, the new contributions to Yukawa couplings are not aligned with the tree-level couplings. As the new Yukawa couplings contribute to soft A-terms they are sources of flavour-changing neutral currents.
Last we discuss an effect unrelated to supersymmetry breaking. We show that orbifold models with D3-branes at orbifold singularities can exhibit kinetic mixing of different massless Abelian factors. For this to be possible, the relevant U(1) factors have to be associated with more than one orbifold singularity.