VictorJuiz/thesis huggingface dataset:
Towards robust steganalysis: binary classifiers and large, heterogeneous data
Keywords: big data
domain adaptation
steganography
information hiding
machine learning
heterogeneous data
steganalysis

The security of a steganography system is defined by our ability to detect it. It is of no surprise then that steganography and steganalysis both depend heavily on the accuracy and robustness of our detectors. This is especially true when real-world data is considered, due to its heterogeneity. The difficulty of such data manifests itself in a penalty that has periodically been reported to affect the performance of detectors built on binary classifiers; this is known as cover source mismatch.
It remains unclear how the performance drop that is associated with cover source mismatch is mitigated or even measured. In this thesis we aim to show a robust methodology to empirically measure its effects on the detection accuracy of steganalysis classifiers. Some basic machine-learning based methods, which take their origin in domain adaptation, are proposed to counter it.
Specifically, we test two hypotheses through an empirical investigation. First, that linear classifiers are more robust than non-linear classifiers to cover source mismatch in real-world data and, second, that linear classifiers are so robust that given sufficiently large mismatched training data they can equal the performance of any classifier trained on small matched data.
With the help of theory we draw several nontrivial conclusions based on our results. The penalty from cover source mismatch may, in fact, be a combination of two types of error; estimation error and adaptation error. We show that relatedness between training and test data, as well as the choice of classifier, both have an impact on adaptation error, which, as we argue, ultimately defines a detector's robustness. This provides a novel framework for reasoning about what is required to improve the robustness of steganalysis detectors. Whilst our empirical results may be viewed as the first step towards this goal, we show that our approach provides clear advantages over earlier methods.
To our knowledge this is the first study of this scale and structure.
Signals in two-sided search
Keywords: signals
Diamond paradox
sorting
matching function
matching
search

We introduce signals to search models of two-sided matching markets and explore the implications for efficiency. In a labour market model in which firms can advertise wages and workers can choose effort, we find that advertisements can help overcome the Diamond paradox. Advertisements fix workers' beliefs, so that workers will react if firms renege on advertisements. Firms then prefer to advertise truthfully. Next, we consider a market with two-sided heterogeneity in which types are only privately observable. We identify a simple condition on the match output function for agents to signal their types truthfully and for the matching to exhibit positive assortative matching despite search frictions. While our theoretical work implies that the efficiency of matching increases as information technology spreads, empirical matching functions typically suggest that it declines. By estimating more general matching functions, we show that the result of declining efficiency can partly be attributed to omitted variable bias.
Dancing diaspora, performing nation: Indian classical dance in multicultural London
Keywords: diaspora
postcolonial
Indian classical dance
multiculturalism
performance
nationalism

This thesis examines the performance of Indian classical dance in the contemporary 'diaspora space' (Brah 1996) represented by the city of London. My aim is to analyse whether and how performances of "national" art, assumed to represent an equally "national" culture, change when performed in transnational contexts. Drawing upon theories of postcolonialism, multiculturalism and diaspora, I begin my study with an historical analysis of the reconstructed origins of the dance in the intertwined discourses of British colonialism and Indian nationalism. Using this analysis to ground my ethnography of the present-day practice of the dance, I unearth its relation to discourses of contemporary multiculturalism and South Asian diasporic identity. I then demonstrate specific ways in which the relationship between colonial and postcolonial artistic production on the one hand and contemporary performances of national and multicultural identity on the other are visible in the current practices and approaches of diasporic and multicultural Indian classical dancers.
My thesis advances the scholarship that has demonstrated the link between the construction of Indian classical dance and the Indian nationalist movement by highlighting particular ways in which historical narrative, national and religious identities, gendered ideals and racialised categories are constituted through, and help produce in turn, contemporary Indian classical dance practices in the diaspora. Locating my study in the UK while still accounting for the Indian nationalist aspects of the dance, my contribution to the scholarly literature is to analyse its performance in relation to both Indian and British national identity. My research demonstrates that Indian classical dance is co-produced by both British and Indian national discourses and their respective cultural and political imperatives, even as the dance contributes to the formation of British, Indian and South Asian diasporic politico-cultural identities.
The role of DLL4-NOTCH signalling in endothelial cell metabolism
Keywords: Cancer
Tumour angiogenesis
NOTCH signalling
metabolism

Tumour tissue is characterised by fluctuating oxygen concentrations, decreased nutrient supply, and acidic pH. Angiogenic signalling pathways that drive a certain metabolic 'configuration' may give endothelial cells a selective advantage in the tumour environment. Previously it has been shown that glycolysis drives proliferation, migration and tip cell formation during sprouting of endothelial cells (De Bock, Georgiadou et al. 2013), and is increased by VEGFA. DLL4-NOTCH has been shown to limit angiogenesis and slow down proliferation of endothelial cells, and promote stalk cell formation during angiogenic sprouting, leading to sprout elongation. DLL4-NOTCH is implicated in tumour angiogenesis, and its overexpression is a potential mechanism of resistance to anti-VEGFA therapy (Li, Sainson et al. 2011). This thesis aimed at investigating the effect of the DLL4-NOTCH signalling pathway on endothelial metabolism and its implications in angiogenesis. Firstly, it was found that DLL4-NOTCH decreases the glycolytic rate and mitochondrial respiratory parameters in endothelial cells. When given exogenous fatty acids, DLL4-NOTCH activation caused increased fatty acid uptake, storage and oxidation. This shows that the induction of DLL4-NOTCH signalling results in increased fatty acid utilisation. Secondly, this research identified fatty acid oxidation as a target metabolism pathway for angiogenic therapy. More specifically, inhibition of fatty acid oxidation decreased proliferation of endothelial cells, decreased sprout elongation in the sprouting assay, and decreased sprouting from the axial vein in the zebrafish model. ATP production was not affected. Therefore, it was hypothesised that DLL4-NOTCH activation promotes and maintains the stalk cell phenotype through an increase of fatty acid oxidation, thereby promoting biomass production for endothelial cell proliferation and growth during angiogenic sprout elongation. Thirdly, a key fatty acid metabolism gene, fatty acid binding protein 4 (FABP4), was identified, that is positively regulated by NOTCH at its promoter region. FABP4 is a candidate for mediating increased fatty acid flux in endothelial cells in response to DLL4-NOTCH. This study shows that FABP4 is induced by VEGFA in a manner dependent on DLL4-NOTCH, and the insulin-responsive transcription factor FOXO1 was required for FABP4 expression in response to DLL4-NOTCH. FABP4 is pro-angiogenic and implicated in tumour angiogenesis in ovarian cancer omental metastasis. Taken together, this study shows for the first time that DLL4-NOTCH signalling increases FABP4 induction, contributing to a key pro-angiogenic pathway, and also fatty acid utilisation in endothelial cells, and thereby contributes to the formation of blood vessels.
Investigations on natural silks using dynamic mechanical thermal analysis (DMTA)
Keywords: protein structure
fiber
biopolymer
mechanical properties
structural modeling
dynamic mechanical thermal analysis

This thesis examines the dynamic mechanical properties of natural silk fibres, mainly from silkworm species Bombyx mori (B. mori) and spider species Nephila edulis, using dynamic mechanical thermal analysis, DMTA. The aim is not only to provide novel data on mechanical properties of silk, but also to relate these properties to the structure and morphology of silk. A systematic approach is adopted to evaluate the effect of the three principal factors of stress, temperature and hydration on the properties and structure of silk. The methods developed in this work are then used to examine commercially important aspects of the ‘quality’ of silk.
I show that the dynamic storage modulus of silks increases with loading stress in the deformation through yield to failure, whereas the conventional engineering tensile modulus decreases significantly post-yield.
Analyses of the effects of temperature and thermal history show a number of important effects: (1) the loss peak at -60 °C is found to be associated the protein-water glass transition; (2) the increase in the dynamic storage modulus of native silks between temperature +25 and 100 °C is due simply to water loss; (3) a number of discrete loss peaks from +150 to +220°C are observed and attributed to the glass transition of different states of disordered structure with different intermolecular hydrogen bonding.
Excess environmental humidity results in a lower effective glass transition temperature (Tg) for disordered silk fractions. Also, humidity-dynamic mechanical analysis on Nephila edulis spider dragline silks has shown that the glass transition induces a partial supercontraction, called Tg contraction. This new finding leads to the conclusion of two independent mechanisms for supercontraction in spider dragline silks.
Study of three commercial B. mori cocoon silk grades and a variety of processed silks or artificial silks shows that lower grade and poorly processed silks display lower Tg values, and often have a greater loss tangent at Tg due to increased disorder. This suggests that processing contributes significantly to the differences in the structural order among natural or unnatural silks. More importantly, dynamic mechanical thermal analysis is proposed to be a potential tool for quality evaluation and control in silk production and processing.
In summary, I demonstrate that DMTA is a valuable analytical tool for understanding the structure and properties of silk, and use a systematic approach to understand quantitatively the important mechanical properties of silk in terms of a generic structural framework in silk proteins.
The evolution, ecology and genetics of sex determination in Mercurialis annua
Keywords: Mercurialis annua
sex chromosome evolution
hybridisation
polyploidy
sex determination
environmental sex determination
androdioecy
sex allocation
monoecy
sex ratio
dioecy

The allocation of resources to male or female progeny, or to male or female reproductive function more generally, is one of the most important life history decisions a sexually reproducing individual must ever make. Sex determination is thus a fundamental process, yet the mechanisms which control it are surprisingly diverse. In this thesis, I examine sex determination in the plant species Mercurialis annua L. (Euphorbiaceae). I assess the mechanism of sex determination operating in dioecious and androdioecious populations of M. annua and also investigate the conservation and evolution of sex-determining mechanisms across the annual mercury clade, the lineages of which display exceptional variation in sexual system.
First, using crosses, I establish that sex in dioecious M. annua is controlled by a single-locus genetic mechanism, consistent with recent work that identified a single male-linked DNA marker in the species. My search for new sex-linked genes revealed none, however, suggesting that M. annua possesses at most a small non-recombining region around sex-determining loci. Why many dioecious plants lack heteromorphic sex chromosomes is still poorly understood and I consider explanations for this. I extend my investigation by comparing genetic diversity between loci that differ in their linkage to the sex-determining locus. I find a single male-linked marker to possess significantly lower diversity than autosomal loci, but no difference in the diversity of partially sex-linked and non-sex-linked genes.
I also assess the conservation of a sex-linked marker among annual mercury lineages and conduct crosses between lineages to examine the conservation of sex determination. My findings indicate a conserved mechanism of single-locus genetic sex determination and I consider the role polyploidisation and hybridisation have played in sexual system evolution and the modification of sex-determining mechanisms in the clade. Finally, I assess the presence of environmental sex determination in androdioecious M. annua, concluding that although male frequency is not influenced by growing density, a degree of sexual lability exists in the lineage.
Studies of emotionality in genetic mouse models of altered glutamate or 5-HT function
Keywords: behaviour
glutamate
anxiety
Amperometry
depression
5-HT

The role of 5-HT in depression and its treatment is well established but there is also growing evidence for the role of glutamate in emotionality. Several transgenic mouse lines were used to investigate how alterations in the glutamate or 5-HT systems impact upon emotional behaviour and relevant neuronal systems.
Transgenic mice with direct manipulations of the glutamate system did not provide a selective model with which to further investigate changes in emotionality. GluA1 knockout mice showed only transient effects on antidepressant-sensitive tests which may alternatively be explained by deficits in habituation. GluN1 hypomorph mice displayed altered behaviours in all tests performed, including global cognitive impairments, making further interpretation of the results difficult. Vesicular glutamate transporter 1 heterozygote mice, which have been implicated as a model depression, were found to have only minor alterations in behaviour, none relating to emotionality.
In contrast, the 5-HT transporter overexpressor mice have previously been shown to reliably display reduced anxiety and a fear conditioning deficit in line with results in humans with differing expression levels of the 5-HT transporter. Constant potential amperometry was used to measure local tissue oxygen content as an equivalent to the BOLD response in fMRI, and local field potential recordings of population electrical activity were also recorded in the basolateral amygdala of 5-HT transporter overexpressor and wildtype mice during a differential fear conditioning paradigm. This revealed that 5-HT transporter overexpressor mice have reduced basolateral amygdala oxygen responses to a conditioned stimulus associated with footshock, correlating with fMRI responses to fearful faces, and a reduced theta:delta ratio in this brain area that is most prominent following conditioning, implying a less active amygdala in these mice under these conditions.
In summary, gross manipulations of glutamate function may not be useful in investigating the role of this neurotransmitter system in emotionality. Manipulation of the expression levels of the 5-HT transporter that mimics the variation seen across the human population alters neurochemical responses to conditioned fear stimuli, providing a translational model for future investigations into emotional processing.
Modelling the role of nitric oxide in cerebral autoregulation
Keywords: stroke
blood flow
nitric oxide
NO
myogenic response
sensitivity analysis
vasomotion
dementia
arteriole
endothelium
autoregulation

Malfunction of the system which regulates the bloodflow in the brain is a major cause of stroke and dementia, costing many lives and many billions of pounds each year in the UK alone. This regulatory system, known as cerebral autoregulation, has been the subject of much experimental and mathematical investigation yet our understanding of it is still quite limited. One area in which our understanding is particularly lacking is that of the role of nitric oxide, understood to be a potent vasodilator. The interactions of nitric oxide with the better understood myogenic response remain un-modelled and poorly understood. In this thesis we present a novel model of the arteriolar control mechanism, comprising a mixture of well-established and new models of individual processes, brought together for the first time. We show that this model is capable of reproducing experimentally observed behaviour very closely and go on to investigate its stability in the context of the vasculature of the whole brain. In conclusion we find that nitric oxide, although it plays a central role in determining equilibrium vessel radius, is unimportant to the dynamics of the system and its responses to variation in arterial blood pressure. We also find that the stability of the system is very sensitive to the dynamics of Ca2+ within the muscle cell, and that self-sustaining Ca2+ waves are not necessary to cause whole-vessel radius oscillations consistent with vasomotion.
ASEAN, social conflict and intervention in Southeast Asia
Keywords: intervention
Cambodia
Myanmar
ASEAN
Timor Leste
Burma
social conflict
East Timor
non-intervention

This thesis challenges the prevailing academic and journalistic consensus that ASEAN states, bound by a cast-iron norm of non-interference, do not intervene in other states’ internal affairs. It argues that ASEAN states have frequently engaged in acts of intervention, often with very serious, negative consequences. Using methods of critical historical sociology, the thesis reconstructs the history of ASEAN’s non-interference principle and interventions from ASEAN’s inception onwards, drawing on sources including ASEAN and UN documents, US and UK archives, and policymaker interviews. It focuses especially on three case studies: East Timor, Cambodia, and Myanmar. The thesis argues that both the emergence of ideologies of non-intervention and their violation can be explained by the social conflicts animating state policies. Non-interference was developed by embattled, authoritarian, capitalist elites in an attempt to bolster their defence of capitalist social order from radical challenges. Where adherence to non-intervention failed to serve this purpose, it was discarded or manipulated to permit cross-border ‘containment’ operations. After communism was defeated in the ASEAN states, foreign policy continued to promote the interests of dominant, state-linked business groups and oligarchic factions. Non-interference shifted to defend domestic power structures from the West’s liberalising agenda. However, ASEAN elites continued meddling in neighbouring states even as containment operations were discarded. This contributed to the collapse of Cambodia’s ruling coalition in 1997, and ASEAN subsequently intervened to restore it. The 1997 Asian financial crisis dealt a crippling blow to ASEAN. To contain domestic unrest in Indonesia, core ASEAN states joined a humanitarian intervention in East Timor in 1999. In the decade since, non-interference has been progressively weakened as the core members struggle to regain domestic legitimacy and lost international political and economic space. This is expressed most clearly in ASEAN’s attempts to insert itself into Myanmar’s democratisation process after decades of failed ‘constructive engagement’.
Clinical and imaging characteristics of early Parkinson's disease
Keywords: pakrinson disease
MRI
imaging
biomarker

Background
. Pathological processes in Parkinson’s disease (PD) start long before the first symptoms appear and by the time the disease is clinically established the results of neurodegeneration may be irreversible. Efforts to prevent or stem disease progression need to start in early disease and good characterization and new markers of early PD are urgently needed.
Objectives
. This thesis aims to characterize early disease stages in three projects. Firstly, clinical features of PD within 3 years of diagnosis will be explored in an incident cohort of patients and controls, using a range of tools to cover the whole breadth of clinical presentation of PD. Secondly, functional imaging studies in PD published so far will be examined through a meta-analysis to identify the most robust functional imaging markers. Thirdly, a functional MRI resting-state study in early PD will be performed to identify reproducible differences between patients and matched control subjects.
Results
. The cohort analysis found that age was a strong predictor of disease severity, independent of disease duration, while gender was seen to affect disease severity depending on the body region. A meta-analysis of all published functional imaging studies across all disease stages showed abnormal activations in the Basal Ganglia but also in a wide range of motor and non-motor brain areas. Dopamine supplementation normalized activations in the Basal Ganglia and some other areas, while other circuits remained resistant to medication suggesting non-dopaminergic abnormality. In the resting-state study, the Basal Ganglia Network showed greatly reduced connectivity in early PD compared to controls, which normalized on administration of dopaminergic medication. Reduced BGN connectivity was also validated on a separate group of PD subjects achieving very good separation of patients from controls.
Conclusions
. The effect of gender and age on early presentation of PD has potential significance for early diagnosis and choice of outcome measures for clinical trials. Within the realm of imaging, traditional task-based fMRI studies fail to show a clear and reproducible pattern of activations making this method unfeasible for early diagnostic testing. In contrast, resting-state fMRI connectivity in the Basal Ganglia Network appears to be a promising and reliable method even in the early stages of PD. Clinical profiling and resting imaging changes offer avenues for developing future biomarkers in early PD.