VictorJuiz/thesis huggingface dataset:
Advancing large scale object retrieval
Keywords: image search
visual search
object retrieval

The objective of this work is object retrieval in large scale image datasets, where the object is specified by an image query and retrieval should be immediate at run time. Such a system has a wide variety of applications including object or location recognition, video search, near duplicate detection and 3D reconstruction. The task is very challenging because of large variations in the imaged object appearance due to changes in lighting conditions, scale and viewpoint, as well as partial occlusions.
A starting point of established systems which tackle the same task is detection of viewpoint invariant features, which are then quantized into visual words and efficient retrieval is performed using an inverted index. We make the following three improvements to the standard framework: (i) a new method to compare SIFT descriptors (RootSIFT) which yields superior performance without increasing processing or storage requirements; (ii) a novel discriminative method for query expansion; (iii) a new feature augmentation method.
Scaling up to searching millions of images involves either distributing storage and computation across many computers, or employing very compact image representations on a single computer combined with memory-efficient approximate nearest neighbour search (ANN). We take the latter approach and improve VLAD, a popular compact image descriptor, using: (i) a new normalization method to alleviate the burstiness effect; (ii) vocabulary adaptation to reduce influence of using a bad visual vocabulary; (iii) extraction of multiple VLADs for retrieval and localization of small objects. We also propose a method, SCT, for extremely low bit-rate compression of descriptor sets in order to reduce the memory footprint of ANN.
The problem of finding images of an object in an unannotated image corpus starting from a textual query is also considered. Our approach is to first obtain multiple images of the queried object using textual Google image search, and then use these images to visually query the target database. We show that issuing multiple queries significantly improves recall and enables the system to find quite challenging occurrences of the queried object.
Current retrieval techniques work only for objects which have a light coating of texture, while failing completely for smooth (fairly textureless) objects best described by shape. We present a scalable approach to smooth object retrieval and illustrate it on sculptures. A smooth object is represented by its imaged shape using a set of quantized semi-local boundary descriptors (a bag-of-boundaries); the representation is suited to the standard visual word based object retrieval. Furthermore, we describe a method for automatically determining the title and sculptor of an imaged sculpture using the proposed smooth object retrieval system.
Coherent spin dynamics of radical pairs in weak magnetic fields
Keywords: spin dynamics
magnetoreception
spin chemistry
magnetic field effects
NMR spectroscopy
EPR spectroscopy

The outcome of chemical reactions proceeding via radical pair (RP) intermediates can be influenced by the magnitude and direction of applied magnetic fields, even for interaction strengths far smaller than the thermal energy. Sensitivity to Earth-strength magnetic fields has been suggested as a biophysical mechanism of animal magnetoreception and this thesis is concerned with simulations of the effects of such weak magnetic fields on RP reaction yields.
State-space restriction techniques previously used in the simulation of NMR spectra are here applied to RPs. Methods for improving the efficiency of Liouville-space spin dynamics calculations are presented along with a procedure to form operators directly into a reduced state-space. These are implemented in the spin dynamics software Spinach.
Entanglement is shown to be a crucial ingredient for the observation of a low field effect on RP reaction yields in some cases. It is also observed that many chemically plausible initial states possess an inherent directionality which may be a useful source of anisotropy in RP reactions.
The nature of the radical species involved in magnetoreception is investigated theoretically. It has been shown that European Robins are disorientated by weak radio-frequency (RF) fields at the frequency corresponding to the Zeeman splitting of a free electron. The potential role of superoxide and dioxygen is investigated and the anisotropic reaction yield in the presence of a RF-field, without a static field, is calculated. Magnetic field effect data for Escherichia coli photolyase and Arabidopsis thaliana cryptochrome 1, both expected to be magnetically sensitive, are satisfactorily modelled only when singlet-triplet dephasing is included.
With a view to increasing the reaction yield anisotropy of a RP magnetoreceptor, a brief study of the amplification of the magnetic field experienced by a RP from nearby magnetite particles is presented.
Finally in a digression from RPs, Spinach is used to determine the states expected to be immune from relaxation and therefore long-lived in NMR experiments on multi-spin systems.
Fatal distraction: does the Texas capital sentencing statute discourage the consideration of mitigating evidence?
Keywords: aggravating factors
mitigating factors
capital punishment
juror decision-making
sentencing

Whether the capital sentencing statute in Texas provides a vehicle for jurors to give effect to mitigation evidence has been a critical factor when the United States Supreme Court has sought to determine its constitutionality. Unlike the majority of other American jurisdictions which maintain capital punishment as a penalty, Texas utilizes a particularly unique scheme which places an assessment of the defendant’s dangerousness at the center of the sentencing decision. Using data gathered from personally conducted interviews with forty-six former capital jurors and trial transcripts from each trial in which they served, this thesis demonstrates how the current sentencing scheme in Texas fails to provide jurors with an adequate vehicle for considering mitigation evidence. Beginning with an analysis of the process of jury selection this study examines the various ways in which the sentencing scheme is explained to potential jurors by the judge, prosecution, and defense attorneys. Of crucial importance is how the mitigation instruction is reconstituted by trial judges and prosecutors into an extension of the defendant’s potential future dangerousness. Emerging from this analysis is the central role that the interpretation of the sentencing statute by legal actors play in determining how jurors view the evidence presented throughout the trial, as well as what factors they believe they are legally permitted to consider in sentencing. The findings of this study strongly suggest that the focus of the sentencing scheme on the defendant’s dangerousness inhibits jurors’ ability to view mitigation evidence unrelated to the crime as mitigating. Thus, the Texas capital sentencing statute in its application appears to prevent jurors from giving effect to personal mitigation, an essential element of a constitutionally satisfactory death penalty statute.
The double CUE domain of chromatin remodelling factor SMARCAD1
Keywords: CUE domain
ubiquitin
nuclear magnetic resonance
SMARCAD1
chromatin remodelling
protein structure

ATP-dependent chromatin remodellers represent a class of proteins that restructure chromatin through the action of a conserved helicase-like ATPase domain. Remodellers typically have several accessory binding domains alongside the ATPase. These confer target specificity and most commonly recognise histone post-translational modifications.
SMARCAD1 is a ubiquitous chromatin remodeller involved with DNA replication and re- pair. It binds directly to PCNA at the site of DNA replication and recruits co-repressor KAP1 in order to silence newly produced chromatin. In contrast to most other chromatin remodellers, SMARCAD1 does not contain several different types of accessory domains. Only two CUE do- mains have been identified in addition to the SMARCAD1 core ATPase domain. CUE domains are a type of helical ubiquitin-binding domain.
This thesis presents the findings of an investigation into the structure and function of the SMARCAD1 double CUE domain. The solution NMR structure is presented with results from NMR binding experiments mapped onto the structure. Each CUE domain was found to be an independent helix bundle connected by a dynamic flexible linker. The N-terminal CUE domain, CUE-1, binds ubiquitin and has an adjacent SUMO (a ubiquitin-like protein) binding motif on a protruding extended helix. The C-terminal CUE domain, CUE-2, has a very similar structure to several published CUE domains but does not bind ubiquitin due to a charged substitution at a highly conserved CUE consensus position. The SMARCAD1 double CUE domain binds KAP1 from nuclear extract and is likely to mediate the interaction between SMARCAD1 and KAP1. SMARCAD1 double CUE domain is not involved with PCNA binding.
Popular Humour in Stalin's 1930s: A Study of Popular Opinion and Adaptation
Keywords: Soviet Union
Popular Opinion
Resistance
Trust
Stalinism
Popular Humour

This thesis contributes primarily to answering two broad questions within the current scholarship on ‘everyday life’ in the Soviet Union: (1) How did Soviet citizens perceive, understand, and adapt to the 1930s? And (2) What were the principal associational structures of Soviet society in these years? These issues are not easily separated, with the second constituting a vital element of the first. They are therefore explored simultaneously in the first three chapters, which examine, respectively, the nature and possibilities of joke-telling in the 1930s; the principal targets of that humour; and, thirdly, its implicit assumptions, values and thematic proclivities. The fourth chapter concentrates on the structure and nature of sociability in the 1930s, and the final chapter incorporates those conclusions in order to address the larger question of how Soviet citizens came to understand and adapt to life in these years – for they did so together, rather than alone as old totalitarian theories of ‘atomisation’ proposed.
The thesis makes two principal arguments. Firstly, all unofficial associational ties in this decade were necessarily underlaid by (and hence reliant upon) trust; therefore, the fundamental social unit in the 1930s was the trust group (small groups of citizens bound together by trust). Secondly, citizens adapted to the 1930s via an intricate blend of acceptance and criticism or, rather, of acceptance through the process of criticism. By criticising that which could not be changed, ‘ordinary’ Soviet citizens could retain some agency of their own and shared these interpretive acts with those whom they trusted. Rather than forming a critical ‘resistance’ or ‘dissent’, these processes created a pathway to adaptation without becoming simply crushed or brainwashed by ideology, and simultaneously shaped a complex, mutually affective interaction between popular values and official ideology.
Electrically detected magnetic resonance in semiconductor and carbon nanodevices
Keywords: solar cell
carbon nanotube
semiconductor
electrically detected magnetic resonance
Czochralski silicon
silicon
carbon
magnetic resonance
microwave cavity
quantum information
field-effect transistor

Electrically detected magnetic resonance (EDMR) is a sensitive spectroscopic technique, which can be used to readout few to single electron spins in semiconductor and carbon nanodevices for applications in solid state quantum information processing (QIP). Since only electrically active defects contribute to the EDMR signal, this technique can be used further to investigate defects and impurities in photovoltaic devices, in which they limit the sunlight-to-energy conversion efficiency significantly. Here, I employ X-band EDMR for semiconductor defect analysis and identify the most important recombination centres in Czochralski silicon with oxide precipitates, which can be intentionally grown to confine detrimental metallic impurities to inactive regions of the wafer in order to serve as a defect-free substrate for modern silicon photovoltaic devices. Those experiments show that oxide precipitation is accompanied by the formation of silicon dangling bonds. Furthermore, I describe a very promising route towards the fabrication and readout of few to single electron spins in carbon nanotube devices, which can be characterised structurally via transmission electron microscopy in order to relate their electrical and spin properties with their structure. Finally, I employ EDMR to read out electron spin states in donor-doped silicon field-effect transistors as a prerequisite for their application in QIP. I report on a novel cryogenic probe head for EDMR experiments in resonant microwave cavities operating at 0.35 T (9.7 GHz, X-band) and 3.34 T (94 GHz, W-band). This approach overcomes the inherent limitations of conventional X-band EDMR and permits the investigation of paramagnetic states with a higher spectroscopic resolution and signal intensity. Both advantages are demonstrated and discussed. I further report on a novel mechanism giving rise to the EDMR effect in donor-doped silicon field-effect transistors, which is capable of explaining why the EDMR signal intensities of the conduction electrons are enhanced by a factor of ∼100, while the donor resonance signals increase by a factor of ∼20 from X- to W-band only. The spin-relaxation and dephasing times are extracted from a series of pulsed-EDMR measurements and confirm this model. The author gratefully acknowledges funding from Trinity College Oxford, Department of Materials, EPSRC DTA, and Konrad-Adenauer-Stiftung e.V. (Begabtenförderung).
A Bayesian approach to financial model calibration, uncertainty measures and optimal hedging
Keywords: finance
model risk
risk measures
calibration
uncertainty
Bayesian
hedging
modelling

In this thesis we address problems associated with financial modelling from a Bayesian point of view. Specifically, we look at the problem of calibrating financial models, measuring the model uncertainty of a claim and choosing an optimal hedging strategy. Throughout the study, the local volatility model is used as a working example to clarify the proposed methods. This thesis assumes a prior probability density for the unknown parameter in a model we try to calibrate. The prior probability density regularises the ill-posedness of the calibration problem. Further observations of market prices are used to update this prior, using Bayes law, and give a posterior probability density for the unknown model parameter. Resulting Bayes estimators are shown to be consistent for finite-dimensional model parameters. The posterior density is then used to compute the Bayesian model average price. In tests on local volatility models it is shown that this price is closer than the prices of comparable calibration methods to the price given by the true model. The second part of the thesis focuses on quantifying model uncertainty. Using the framework for market risk measures we propose axioms for new classes of model uncertainty measures. Similar to the market risk case, we prove representation theorems for coherent and convex model uncertainty measures. Example measures from the latter class are provided using the Bayesian posterior. These are used to value the model uncertainty for a range of financial contracts priced in the local volatility model. In the final part of the thesis we propose a method for selecting the model, from a set of candidate models, that optimises the hedging of a specified financial contract. In particular we choose the model whose corresponding price and hedge optimises some hedging performance indicator. The selection problem is solved using Bayesian loss functions to encapsulate the loss from using one model to price and hedge when the true model is a different model. Linkages are made with convex model uncertainty measures and traditional utility functions. Numerical experiments on a stochastic volatility model and the local volatility model show that the Bayesian strategy can outperform traditional strategies, especially for exotic options.
Automatic simplification of differential equation models by a posteriori analysis
Keywords: computational physiology

Many mathematical models in biology and physiology are represented by systems of nonlinear differential equations. In recent years these models have become increasingly large-scale and multiphysics, as increasing amounts of data are available on the properties and behaviour of biological systems. Often an observed behaviour of interest in a model may be written as a linear functional. A key question therefore is to determine which terms in the model have the greatest effect on functionals of interest.
An approach for answering this question has recently been developed, called model reduction using a posteriori analysis. The method was initially developed for systems of nonlinear initial value ordinary differential equations, and automatically identifies regions of the computational domain and components of the model solution where an accurate mathematical representation of the model is required to accurately calculate a linear functional of interest. Initial-value ordinary differential equations can be written as a first-order derivative term plus an algebraic 'reaction' term. In previous work on model reduction using a posteriori analysis the algebraic 'reaction' term is removed from the equations in the reduced model.
The first contribution of this thesis is to extend the method so that the first-order derivative term is removed from the differential equation instead of the algebraic 'reaction' term, resulting in a quasi-steady state approximation in automatically identified regions of the domain and components of the solution. The second contribution of this thesis is to extend the method to boundary value problems and partial differential equations. We consider differential equations with algebraic terms, first order terms and second order terms, any combination of which may be nonlinear. The method is used to automatically simplify several differential equation models including models of chemotaxis and tissue-level cardiac electrophysiology.
Everyday networks, politics, and inequalities in post-tsunami recovery: fisher livelihoods in South Sri Lanka
Keywords: Sri Lanka
intersectionality
informal politics
2004 tsunami
ethnography
disaster recovery
clientelism
corruption
Sustainable Livelihoods Framework
political patronage
non-government organizations
rural livelihoods

The aim of this thesis is to explore how livelihoods are recovering in the aftermath of the 2004 tsunami in Sri Lanka through the lens of the Sustainable Livelihoods Framework and the social networks approach—methods of inquiry that have gained considerable impetus in livelihoods research. The study is conducted with reference to two tsunami-affected fisher villages in the Hambantota District, Southern Province. It employs a qualitative ethnographic methodology that examines narratives emerging from households, local officials of government and non-government organizations, office bearers of community-based organizations, local politicians, village leaders, and key informants. Focus is on evaluating how particular roles, activities, and behaviour are given importance by these groups in specific post-tsunami contexts and how these aspects relate to broader conceptualizations of social networks, informal politics, social inequality, and ethnographic research in South Asia. The findings support four major contributions to the literature. First, social networks are significant as an object of study and a method of inquiry in understanding livelihoods post-disaster. Second, paying heed to varied forms of informal politics is critical in post-disaster analyses. Third, the concept of intersectionality can extend and improve upon prevailing approaches to social inequality in disaster recovery. Fourth, ethnographic research is valuable for understanding everyday networks, informal politics, and change in South Asia. Collectively, these findings present a human geography of post-tsunami livelihoods in Sri Lanka, where networks, politics, and inequalities, which form an essential part of everyday livelihoods, have been reproduced in disaster recovery. The thesis constitutes a means of offering expertise in the sphere of development practice, highlighting internal differentiation in access to aid as a key issue that needs to be identified and systematically addressed by policymakers and practitioners.
Angels in Anglo-Saxon England, 700-1000
Keywords: Anglo-Saxon England
angels
early medieval Christianity

This thesis seeks to understand the changing place of angels in the religious culture of Anglo-Saxon England between AD 700 and 1000. From images carved in stone to reports of prophetic apparitions, angels are a remarkably ubiquitous presence in the art, literature and theology of early medieval England. That very ubiquity has, however, meant that their significance in Anglo-Saxon thought has largely been overlooked, dismissed as a commonplace of fanciful monkish imaginations. But angels were always bound up with constantly evolving ideas about human nature, devotional practice and the workings of the world. By examining the changing ways that Anglo-Saxon Christians thought about the unseen beings which shared their world, it is possible to detect broader changes in religious thought and expression in one part of the early medieval West.
The six chapters of this thesis each investigate a different strand from this complex of ideas. Chapters One and Two begin with Anglo-Saxon beliefs at their most theological and speculative, exploring ideas about the early history of the angels and the nature of their society – ideas which were used to express and promote changing ideals about religious practice in early England. Chapters Three and Four turn to the ways that angels were believed to interact more directly in earthly affairs, as guardians of the living and escorts of the dead, showing how even apparently traditional beliefs reveal changing ideas about intercession, moral achievement and the supernatural. Lastly, Chapters Five and Six investigate the complicated ways that these ideas informed two central aspects of Anglo-Saxon religion: the cult of saints, and devotional prayer. A final Conclusion considers the cumulative trajectory of these otherwise distinct aspects of Anglo-Saxon thought, and asks how we might best explain the changing importance of angels in early medieval England.