VictorJuiz/thesis huggingface dataset:
Location and distance in economics
Keywords: economic geography
International trade
economics

In this collection of essays, I explore three topics where space and distance plays a fundamental role in international economics. Not only do spatial considerations affect the pattern of trade, the frictions that arise from distance also determine where and how goods are produced and where people live.
In Chapter 1, I show that human made locational characteristics can determine the spatial allocation of economic activity. I take the standard core-periphery model and add endogenous housing to its forward-looking dynamic adjustment process. By introducing a model of adjustment with an extra state variable, which I interpret as housing, I show that the distribution of housing allows the model to converge to a unique spatial equilibrium. This explains the observed persistence and robustness of economic agglomerations in the data.
Chapter 2 is a theory of task assignment in the production of final goods and across countries. By allowing for tasks to differ in their suitability of being used in the production of multiple goods, my model endogenizes the allocation of tasks in the production of goods that use them. The resulting equilibrium task allocation defines the pattern of off-shoring. Tasks that are used in only one good concentrate in the country with a specialization in production of that good. Tasks used in many goods are allocated across countries, with the more substitutable tasks located in the country with the larger overall output. Gains from off-shoring are derived from a better mix of allocation of tasks into goods as well as larger scale of production.
Finally in Chapter 3, I study how real exchange rate fluctuations determine the size and composition of the export sector. Using the methodology set out in Dixit and Pindyck (1994) in a heterogeneous firms model, I determine the set of trigger real exchange rates for entry and exit into exporting. My primary result of this chapter is that exchange rate uncertainty coupled with sunk cost of entry causes hysteresis in the number and productivity of exporting firms. I then extend the model to allow free entry of firms. This explains the stylized fact of the existence of non-exporting firms with higher productivity than some exporting firms.
Reconstructing past flow rates of southern component water masses using sedimentary 231Pa/230Th
Keywords: 231Pa/230Th
paleoceanography
Argentine basin

This thesis uses the paleoceancirculation proxy 231Pa/230Th, coupled with water mass tracers δ13C and εNd, to reconstruct circulation histories for southern source waters masses in the South Atlantic, in addition to North Atlantic Deep Water (NADW) far from its source, for the last ~25 kyrs.
Downcore 231Pa/230Th records from a suite of cores along a depth transect in the Argentine Basin show distinct differences with depth, suggesting that 231Pa/230Th ratios in sediments are reflective of conditions in only the bottom most waters. This indicates the importance of consideration of changes in water mass distribution when interpreting 231Pa/230Th records. Opal and particle flux data from these cores show little correlation with 231Pa/230Th values meaning that changes in 231Pa/230Th cannot be explained by a local composition or particle flux effect and are instead likely to be reflecting changes in circulation.
A core bathed by Antarctic Intermediate Water (AAIW) throughout the last 25 kyrs (GeoB 2107, 1045 m), has relatively high 231Pa/230Th values (0.075) during the Holocene and distincly lower values (0.055) at the LGM suggesting faster AAIW transport during the last glacial. At greater depths, 231Pa/230Th, δ13C and εNd data in core GeoB 2109 (2504 m) indicate a change in both circulation and water mass distribution on glacial-interglacial timescales, with moderate flow of Antarctic Bottom Water (AABW) at the LGM being replaced by more vigorous flow of NADW during the Holocene.
On millenial timescales, 231Pa/230Th values in deep cores GeoB 2109 and GeoB 2112 (4010 m) indicate enhanced production of AABW during northern hemisphere stadials, when variations in 231Pa/230Th records are of opposite sign between hemispheres, supporting a possible bipolar seesaw relationship in deep water formation between hemispheres. These data indicate that the 231Pa/230Th proxy can be used to reconstruct past flow rates of multiple water masses in the Argentine Basin and provide evidence that southern source water masses play a dynamic counterpart to NADW formation on abrupt as well as glacial-interglacial timescales.
A stochastic partial differential equation approach to mortgage backed securities
Keywords: stochastic PDEs
mathematics
finance

The market for mortgage backed securities (MBS) was active and fast growing from the issuance of the first MBS in 1981. This enabled financial firms to transform risky individual mortgages into liquid and tradable market instruments. The subprime mortgage crisis of 2007 shows the need for a better understanding and development of mathematical models for these securities. The aim of this thesis is to develop a model for MBS that is flexible enough to capture both regular and subprime MBS.
The thesis considers two models, one for a single mortgage in an intensity based framework and the second for mortgage backed securities using a stochastic partial differential equation approach. In the model for a single mortgage, we capture the prepayment and default incentives of the borrower using intensity processes. Using the minimum of the two intensity processes, we develop a nonlinear equation for the mortgage rate and solve it numerically and present some case studies.
In modelling of an MBS in a structural framework using stochastic PDEs (SPDEs), we consider a large number of individuals in a mortgage pool and assume that the wealth of each individual follows a stochastic process, driven by two Brownian mo- tions, one capturing the idiosyncratic noise of each individual and the second a common market factor. By defining the empirical measure of a large pool of these individuals we study the evolution of the limit empirical measure and derive an SPDE for the evolution of the density of the limit empirical measure.
We numerically solve the SPDE to demonstrate its flexibility in different market environments. The calibration of the model to financial data is the focus of the final part of thesis. We discuss the different parameters and demonstrate how many can be fitted to observed data. Finally, for the key model parameters, we present a strategy to estimate them given observations of the loss function and use this to determine implied model parameters of ABX.HE.
The rational design of photocatalytic semiconductor nanoparticles
Keywords: type II heterojunctions
II-VI nanocrystals
colloidal semiconductor nanocrystals
heterostructures
semiconductor photocatalysis
shape effects on photocatalysis

This thesis reports the successful rational design of three highly active photocatalytic semiconductor nanocrystal (SNC) systems by exploiting morphology effects and the electronic properties of type II semiconductor heterojunctions. Novel architectures of colloidal SNCs are produced with the aim of suppressing exciton recombination and improving charge extraction for the successful initiation of desirable redox chemistry.
Rod-shaped niobium pentoxide Nb2O5 nanocrystals (NCs) are shown to exhibit significantly enhanced activity (10-fold increase in rate constant) relative to spherical-shaped NCs of the same material. The increase is attributed to Nb5+ Lewis acid site rich (001) surfaces, present in higher proportions in the rod morphology, which bind organic substrates from solution resulting in direct interaction with photogenerated charges on the surface of the NC. Building on the insights into morphology-activity dependence, type II semiconductor heterojunctions are exploited for their ability to increase exciton lifetimes and spatially separate charges. Two novel II-VI heterostructured semiconductor nanocrystals (HSNCs) systems are investigated: a series of CdX/ZnO (X = S, Se, Te) HSNCs and ZnS/ZnO HSNCs capped with two different surface ligands. In the first case, substantial photocatalytic activity improvement is observed for HSNCs (relative to pure ZnO analogues) according to the following trend: CdTe/ZnO > CdS/ZnO > CdSe/ZnO. The observed trend is explained in terms of heterojunction structure and fundamental chalcogenide chemistry. In the second case, both ZnS/ZnO HSNCs exhibit activity enhancement over analogous pure ZnO, but the degree of enhancement is found to be a function of surface ligand chemistry.
Photocatalytic activity testing of all the materials investigated in this work is performed via the photodecomposition of methylene blue dye in aerated aqueous conditions under UVA (350 nm) irradiation.
The synthetic techniques employed for the synthesis of colloidal SNCs investigated in this thesis range from chemical precipitation and solvothermal techniques to several different organometallic approaches.
A wide variety of analytical techniques are employed for the chemical, structural and optical characterisation of SNC photocatalysts including: XRD, XPS, TEM, UV-vis absorption, PL spectroscopy and FTIR. Atom Probe Tomography (APT) is employed for the first time in the structural characterisation of II-VI heterojunctions in colloidal HSNCs.
Overall, this thesis provides a useful contribution to the growing body of knowledge pertaining to the enhancement of photocatalytic SNCs for useful applications including: solar energy conversion to chemical fuels, the photodecomposition of pollutants and light-driven synthetic chemistry.
Fabrication of an aptamer-functionalised silica nanoparticle construct  and its separation by magnetic capture-hybridisation
Keywords: magnetic separation
nanoparticles
aptamers
nanotechnology

Nanoparticles produced with surfaces functionalised by highly specific molecular tags are able to target aberrant cells and detect or eliminate them without causing damage to surrounding healthy tissues. Single-stranded DNA (ssDNA) and RNA which fold to form secondary or tertiary structures, termed aptamers, represent a new class of such molecular tags. The nanoparticles, in turn, may carry therapeutic payload or luminescent entities which enable elimination or visualisation of targeted cells respectively.
This project presents fabrication and isolation of a surface-functionalised nanoparticle construct, namely aptamer-tagged silica nanoparticles. DNA aptamers were chosen with the intention to make them useful for clinical or diagnostic applications of targeting neoplastic cells. Indeed, the ssDNA applied here is known to bind mucin-1 which in turn is a biomarker found on the surface of metastatic breast cancer cells. The separation of the construct was made possible by the inclusion of oligonucleotide-bound superparamagnetic particles in the construct; these enabled separation by magnetic capture.
This project investigates two approaches to fabrication of the construct. In the first approach, aptamers, oligonucleotides and magnetic particles are mixed in solution. In the second, silica nanoparticles are functionalised with aptamers, oligonucleotides are bound to magnetic particles and the resulting two parts are hybridised together. The first approach gives higher yields. This may suggest that binding of silica nanoparticles to aptamers may hinder aptamer hybridisation to oligonucleotide fragments, thus resulting in lower construct synthesis yields. However, it is not known yet how the yield changes upon addition of silica nanoparticles into the solution. Therefore, the second experimental approach provides a starting point for fabrication and purification of an anti-cancer drug targeting platform in a simple bench-top setting.
In addition, this thesis discusses the fabrication of silica nanoparticles which were intended to constitute an element of the construct. The work on nanoparticle fabrication aimed to develop a quick and repeatable synthesis method which would result in monodisperse entities. Despite trying various experimental approaches, suitable particles could not be reproducibly obtained. Agglomeration was identified as a major obstacle in the silica nanoparticle production process.
Finally, this project assesses whether the chosen aptamers bind to the metastatic breast cancer cells, which would be necessary if they were to be used for diagnosis or therapy. FACS analysis indeed indicate that ssDNA aptamers attach to the MCF7 cell line, but the optimum conditions for that attachment remain to be determined.
Controlling controversial science: biotechnology policy in Britain and the United States (1984-2004)
Keywords: genetic engineering
human embryonic stem cell research
genetically engineered food
genetically modified food
genetically modified organisms
GMOs
biotechnology
stem cell research

This thesis addresses the puzzle of variation in first-generation regulatory policies for controversial science and technology, as demonstrated in the cases of agricultural genetically modified organisms (GMOs) and human embryonic stem cell research in the United Kingdom and the United States. Why did policy outcomes vary in each technology case? This study answers this question by placing greater emphasis on institutional factors.
Although works within institutional analysis, bureaucracy and regulation literatures make significant progress in revealing how existing institutions can shape outcomes, how far one can characterize bureaucratic behavior and whether interest groups capture regulation, they nevertheless create an opening for research that: describes a mechanism for path dependence to explain variation in policies; shows the degree to which bureaucratic behaviors can influence outcomes; and, highlights instances in which regulatory officials hold power. This thesis makes an original contribution by providing new historical details relating to these cases, and by providing an extensive elaboration of Pierson’s criteria for increasing returns and a so-called secondary test of path dependence to explain outcomes.
The study recounts the biography of key policy documents in each case by tracing the process of decision-making through government and archival sources, secondary literature and more than 40 elite interviews. In doing so, it details the activities of key governmental bodies within the European Union, UK and US. Moreover, it shows how the Coordinated Framework (1986) and Human Fertilisation and Embryology Act 1990 framework represented decision-making structures which triggered changes in actors and interests and shaped permissive outcomes for GMOs and stem cell research in the US and UK, respectively. Furthermore, lack of comparable structures may help account for restrictive policies for GMOs in Europe and the UK, and for stem cell research in the US.
State and ritual in a Marxist-Leninist society: East Berlin, 1951
Keywords: Marxism-Leninism
communism
Marx
socialism
German Democratic Republic
ideology
ritual
East Germany
Germany
Lennin

This dissertation examines the relationship between state, ritual, and Stalinism in the context of the Soviet occupation of Germany after 1945, the establishment of the German Democratic Republic, and finally the World Festival of Youth and Students (Weltfestspiele) held in East Berlin in 1951. On the connection between these three phenomena, I take an anti-Durkheimian stance, asserting that ritual, far from being merely epiphenomenal to 'society' or 'the state', is in fact constitutive of them. It is the contention of this thesis that the entity known as 'the state', despite the capacity of some of its organs to project massive physical force, is in ontological term an amorphous, fragile thing. It is a further contention of this thesis that mass public ritual is one of the cornerstones of the ideological work of the state. I argue that the emphasis that the East German state placed on mass ritual was a function of its political and social insecurity. I propose that the German Democratic Republic's fixation on mass displays of unity during the first years of its existence were a function of its insecurity. In 1951, the year in which the Weltfestspiele took place, the German Democratic Republic was barely two years old and was uncertain of its future, wary of both the decidedly limited enthusiasm Germans had displayed for Soviet-backed Marxism-Leninism and the plans its allies in Moscow had for the future of a divided Germany. The East German authorities accordingly set a great deal of store by mass displays of the unity and enthusiasm of 'the people'-yet at the same time, these mass rituals ultimately became carnivals of the regime's insecurity, and demonstrations of its failure to secure authentic political legitimacy amongst its population.
Selfless love and human flourishing: a theological and a secular perspective in dialogue
Keywords: self
love
eros
agape
existentialism
Iris Murdoch
Paul Tillich
human flourishing

The point of departure of this thesis is derived from a modern tendency to create a dichotomy between selfless love and human flourishing. Modern attempts to liberate the human being from heteronomous oppression and the moral norms promoting this have sometimes led to the conclusion that selfless love is harmful to human flourishing. Such a conclusion has gained momentum also through modernist re-conceptualisations of the self as an autonomous but empty consciousness which must guard itself against determination by the other. In effect, significant thinkers have replaced the notion of selfless love with a call for self-assertion over against the other, as key to the individual person’s well-being.
This has been matched by Christian dismissals of the individual’s pursuit of human flourishing. In the face of modern insights into the ‘desirous’ nature of the human being, modern Christian theology has equally struggled to sustain the tension between the traditional Christian notion of selfless or self-giving love and human beings’ desire to affirm themselves and to find personal fulfilment in this world. Strands of Christian theology have, for instance, affirmed a self-surrendering love at the cost of dismissing the individual’s worldly desires entirely.
In this thesis, I outline this situation in modern thought and its problematic consequences. With a view to discerning whether selfless love and human flourishing can be re-connected, I then undertake close studies of the theologian Paul Tillich’s and the moral philosopher and novelist Iris Murdoch’s conceptualisations of the self and of love. As I will argue, Tillich’s and Murdoch’s engagement with modern thought leads them to develop accounts of the self, which correspond with understandings of love as both selfless and conducive to human flourishing. On the basis of their thought I thus argue that selfless love and human flourishing can be understood as interdependent even today.
Organ reform in England: aesthetics and polemics, 1901-1965
Keywords: organ (instrument)
J. S. Bach
early music

This thesis examines organ reform in England between 1901 and 1965, an arena of practical music-making and intellectual and ideological debates in which a number of related practices surrounding the English organ – notably its scholarship, aesthetics of design, liturgical functions, native and foreign repertoires, including J. S. Bach’s organ music – played a central role in transforming the sound, design, and appearance of the instrument. Whilst influential musicians asserted that the English organ of the first half of the twentieth century was a great work of art, and survived in what could be termed ‘splendid isolation’ from Continental models, others contended that it lacked a logical relationship with more than a home-grown repertory. However, supporters of the English organ claimed that technological and tonal improvements made it the most perfect medium for Bach performance. It was a renewed interest in historical organs and repertory that exposed the limitations of cultural centrism, pointing to the English organ’s weakness as a point of departure for understanding its European repertory. This insistence paved the way for an enthusiastic reception of other organs, which, through their construction and new tonal qualities, won the favour of musicians who had found the English organ too limited and focused on a particular culture. The thesis allows historical actors to populate the discourse, revealing the diverse practices out of which a quest for reform emerged. As such the organ provides a fascinating and preliminary rehearsal case for what in the 1970s and 80s would be termed the early music revival.
Novel methods for brainstem FMRI
Keywords: magnetic resonance imaging
neuroscience
physics

The brainstem plays a crucial role in a great number of vital functions such as respiratory regulation, visual reflexes, and the perception of pain. The small size and close proximity of the nuclei requires high-resolution functional magnetic resonance imaging (FMRI). However, brainstem FMRI using conventional gradient-echo echo-planar imaging (GRE-EPI) techniques is challenging due to the increased signal dropout and geometric distortions in the brainstem.
The primary aim of the work presented in this thesis was to investigate alternative methods for brainstem FMRI in order to overcome some of the challenges associated with single-shot GRE-EPI techniques. Towards this goal 3D segmented sequences were explored, which have the advantage that the size of the geometric distortions is not proportional to the resolution at which is scanned. In particular, two sequences were investigated: balanced steady-state free-precession (bSSFP) and spoiled gradient echo (SPGR).
First, a set of experiments was conducted, in which each experiment aimed to isolate a limited range of sequence properties in order to characterize and assess the potential of the candidate sequences. It was found that bSSFP has better noise characteristics compared to GRE-EPI when applied with a 2D acquisition, but when 3D readouts were used the signal instabilities increased dramatically.
Based on these findings, experiments that investigate the influence of multishot acquisitions on signal instabilities caused by physiological noise were performed. The signal instabilities were found to mainly originate from regions of CSF and blood and were highly correlated to the cardiac cycle. Several correction methods were explored and one method was identified to be implemented in vivo.
A novel method that allows real-time cardiac synchronization of the k-space acquisition was developed. The developed methods used a custom parallel imaging reconstruction to allow for acquisition with a fixed volume frame rate, which is desirable for FMRI purposes. The method was found to reduce the signal instabilities in 3D SPGR and bSSFP significantly.
A comprehensive assessment of two currently available retrospective correction techniques was conducted and their practicalities were compared. Recommendations are made to improve the robustness of the investigated correction methods. A novel optimization method was implemented, which was developed to determine the optimal regressor set for retrospective corrections. The method can be applied to image based as well as k-space based methods.