VictorJuiz/thesis huggingface dataset:
Ultrafast spectroscopy of charge-carrier dynamics and stability in lead-halide perovskites for thin-film photovoltaics

Hybrid metal halide perovskites have emerged as an important new class of materials for photovoltaics. For their integration in tandem solar cells, optimised photocurrent matching between top and bottom cells requires careful control over bandgap energy and charge transport properties, for which tunable mixed bromide-iodide lead perovskites are the most prominent contenders. This thesis investigates photophysical properties of highly tunable mixed-halide and mixed-cation perovskite films with the aim of correlating their optoelectronic parameters with crystal phase changes induced by compositional variations.
Firstly, the compositional variation of mixed-halide FAPb(BrxI(1-x))3 perovskites is explored. Bimolecular and Auger charge-carrier recombination rate constants strongly correlate with the bromide content, x, suggesting a link with electronic structure. With rising x, the constants increase by up to an order of magnitude, yet still remain significantly below the Langevin limit. FAPbBr3 and FAPbI3 exhibit charge-carrier mobilities of 14 and 27 cm2 V-1 s-1 and diffusion lengths exceeding 1 μm, while mobilities across the mixed bromide-iodide system depend on crystalline phase disorder. Particularly, the mid-bandgap and bromide rich regions are found to be disordered and prone to photo-induced halide segregation.
Subsequently, a highly crystalline mid-bandgap mixed-cation lead mixed-halide FA0.83Cs0.17Pb(Br0.4I0.6)3 perovskite is developed and investigated with focus on understanding the impact of adding caesium to the A-cation site in the lattice. Compared to single-cation FAPb(Br0.4I0.6)3, the crystal phase is stable and the chargecarrier mobility measured from THz spectroscopy reaches 21 cm2 V-1 s-1 resulting in a diffusion length of 3 μm. With photoinduced halide segregation being inherently suppressed, another benefit of controlled A-cation mixing could be revealed. In an aging-study, the correlation between the colloids concentration present in the precursor solution of FA0.83Cs0.17Pb(I0.8Br0.2)3 and nucleation stages for the crystallization of perovskite is explored. Having direct impact on morphology and photophysical properties, charge-carrier mobilities are reported to correlate with colloid concentration reaching > 20 cm2 V-1 s-1 for an optimum concentration.
Ultimately, the full parameter space of mixed-cation (0 < y < 1) lead mixedhalide (0 < x < 1) CsyFA(1-y)Pb(BrxI(1-x))3 perovskites is examined, where crucial links between crystal phase stability, photo-stability and optoelectronic properties are highlighted. Finely tuning the caesium cation in the lattice yields excellent structural stability and charge-carrier transport properties for the parameter space between 0.1 < y < 0.3. For an optimized caesium content, the orthogonal halide-variation parameter space for Cs0.17FA0.83Pb(BrxI(1-x))3 achieves charge-carrier mobilities of 11 -40 cm2 V-1 s-1 and diffusion lengths of 0.8-4.4 μm.

Advisor: Herz, L
The formation of International Relations: ideas, practices, institutions, 1914-1940

The study of International Relations (IR) emerged in the context of transnational networks of scholars, politicians, and philanthropists who sought to devise a peaceful world order in the face of international conflict. Prompted by the Great War, the pioneers of IR argued that international politics should be subject to public and academic investigation. In order to generate the required expertise, they established a range of university-based as well as policy-oriented institutions during the 1910s and 20s. Rather than studying political theory or advancing scientific methodology, however, early IR scholars focused on current affairs and became involved in foreign politics themselves. Throughout the formative period of IR, from 1914 to 1940, its protagonists oscillated between understanding and making international politics.
This dissertation examines the formation of IR from about 1914 to the Second World War, with particular emphasis on the range of international actors and institutions that shaped the discipline. Based on multi-archival research in Austria, Britain, France, Germany, Switzerland, and the United States, it explores the key venues for the study of IR. In particular, the dissertation reflects how IR scholars used transnational forms of exchange, such as the organs of intellectual cooperation at the League of Nations. It also incorporates women and feminist approaches to IR.
Contrary to conventional historiography, the dissertation argues that IR was neither founded in 1919, nor dominated by coherent schools of thought during the inter-war period. Instead, it demonstrates how the discipline was formed by an eclectic group of scholars and practitioners, men and women, English-speaking and international. By building on recent revisionist literature and by re- integrating neglected actors, the dissertation reveals the complex and sometimes inconsistent ways in which issues of international politics became the subject of academic study.

Keywords: History of Social Sciences
Diplomacy
International Relations
Intellectual Cooperation
League of Nations
Advisor: Clavin, PM
Structural studies of defects in two-dimensional materials with atomic resolution

Defective structures in two-dimensional (2D) materials have been proved to have significant influences on the materials’ properties. Understanding structural defects in 2D materials at atomic scale is therefore required. With the use of advanced imaging techniques, one of the main approaches applied in this project was aberration-corrected transmission electron microscopy (AC-TEM), the structures are able to be resolved with single-atom sensitivity with the reduction of both spherical aberration and the influence of chromatic aberration. This laid the foundation for the first two experiments, which involve the bond length measurement of each C-C bond within three types of divacancies and Si-C bonds at graphene edges. The former explains the tendency of bond rotations within the divacancies from the perspective of strain inside the defective areas and surrounding lattice; the latter revels the interactions between isolated Si atoms and zigzag/armchair graphene edges.
The use of in-situ heating holder in the AC-TEM makes the direct visualization of structures and their dynamics at elevated temperatures possible. The Si-graphene edge interactions, as well as the following two experiments are all designed to study the high-temperature performances for different systems. Gold nanoclusters are introduced to monolayer graphene by thermal evaporation to study the interaction between gold and graphene at elevated temperature. Due to the strong interaction between gold and graphene, gold crystals are able to adapt to planar configurations with two different crystalline forms, and an epitaxial relationship was found for planar gold crystals and graphene. Atomically flat and long line defects and zigzag edges in monolayer molybdenum disulfide (MoS2) are successfully created by in-situ thermal annealing. The relationship between S vacancy mobility and defect forms are revealed based on the experiment. High-temperature atomic configurations of line defects and edge terminations are resolved in the first time. Their electronic properties are also explored with the support of density functional theory calculations.

Keywords: HRTEM
Graphene
Structural defects
2D materials
Advisor: Warner, J
In search of effectful dependent types

Real world programming languages crucially depend on the availability of computational effects to achieve programming convenience and expressive power as well as program efficiency. Logical frameworks rely on predicates, or dependent types, to express detailed logical properties about entities. According to the Curry-Howard correspondence, programming languages and logical frameworks should be very closely related. However, a language that has both good support for real programming and serious proving is still missing from the programming languages zoo. We believe this is due to a fundamental lack of understanding of how dependent types should interact with computational effects. In this thesis, we make a contribution towards such an understanding, with a focus on semantic methods.
Our first line of work concerns a dependently typed version of linear logic (which can be seen as a calculus for commutative effects). We develop a dependently typed dual intuitionistic linear logic as well as a sound and complete categorical semantics using certain indexed monoidal categories satisfying a comprehension axiom. We present a range of models, based on monoidal families, commutative effects, a double gluing construction, domains and strict functions and coherence spaces.
Our second line of work develops a game semantics for dependent type theory, which had so far been missing altogether. We show that, if we work with deterministic well-bracketed history-free winning strategies, the semantics satisfies a full and faithful completeness result with respect to call-by-name dependent type theory for a hierarchy of types built from certain finite inductive families. We show that by relaxing the notion of strategy, we can further model various effects rather than the pure type theory.
Our final line of work explores a generalisation of Levy’s call-by-push-value (CBPV) to encompass dependent types. We show that the syntax of CBPV naturally extends to a calculus we call dCBPV- in which types are allowed to depend on values but not computations. We show it has an elegant categorical semantics and a well-behaved operational semantics and that it admits a wide range of models arising from indexed monads on models of pure dependent type theory and from models of linear dependent type theory. By contrast with the simply typed situation, however, it does not suffice to encode call-by-value and call-by-name versions of dependent type theories with unrestricted effects. To obtain those, we need a richer calculus dCBPV+ with a Kleisli extension principle for dependent functions, which turns out to be less well-behaved from a semantic point of view.

Advisor: Abramsky, S
The old and the new: mouse models for evaluating the therapeutic margin of radiation in lung cancer

Background: Radiotherapy is widely used in the treatment of lung cancer, with both curative and palliative intent according to the stage of the disease. The tumour control potential of radiotherapy is limited by the induction of side effects; in the case of thoracic radiotherapy (tRTX), common side effects are oesophagitis, pneumonitis and pulmonary fibrosis. The main challenges in the field are, therefore, to find ways to increase tumour killing and/or decrease normal tissue toxicity, to improve the therapeutic margin of radiation. Aims: Firstly, to characterise selected early and late tissue responses in a mouse model of tRTX. Secondly, to investigate approaches to improve the therapeutic margin of tRTX by modulating the inflammatory response or the DNA damage response (DDR). Methods: To evaluate normal tissue responses, we used tRTX of C57BL6 mice, a well-established preclinical model of radiation-induced pulmonary fibrosis. In parallel, human lung cancer cells were grown as subcutaneous xenografts in immune compromised nude mice, and used to evaluate anti-tumour responses. A/J mice bearing urethane-induced lung tumours were used to evaluate normal and tumour lung tissue responses simultaneously. Immunohistochemistry, western blotting and non-invasive imaging were used to assess treatment responses. Results: Acute and transient local (neutrophil lung infiltration) and systemic (plasma levels of pro-inflammatory cytokines) inflammatory/immune responses were induced by tRTX. Thoracic radiation induced DNA double-strand breaks in lung tissue, a proportion of which were persistent. Fractionation schedules of tRTX led to pneumonitis and pulmonary fibrosis. Knock-out of myeloperoxidase activity was associated with decreased early and late normal tissue responses to tRTX. In separate mouse models, we observed that DDR inhibitors effectively radiosensitised xenograft tumours, but differentially affected thoracic normal tissues. PARP inhibition in combination with tRTX lead to oesophagitis whereas ATM inhibition increased radiation-induced lung damage. Using the A/J strain, we simultaneously evaluated normal and tumour lung tissues responses to tRTX, establishing a novel mouse model for the study of therapeutic index. In the A/J model, ATM inhibition in combination with tRTX showed significant anti-tumour activity, but was also associated with increased late normal tissue effects. Conclusions: Myeloperoxidase contributes to early inflammatory responses and late effects induced by tRTX. DDR inhibitors have similar tumour responses but differential normal tissue responses when combined to tRTX. A newly established A/J mouse model has the potential to have a significant impact on studies evaluating the therapeutic index of novel therapies in combination with thoracic radiation by allowing for the simultaneous assessment of normal and tumour lung tissues in the context of a fully functional immune system.

Advisor: Ryan, A
All that glitters is not gold: the re-use of securities collateral as a source of systemic risk

Since the 1980s, regulators in the U.S. and the U.K. have protected the collateral taker’s right to re-use securities collateral in securities financing and OTC derivatives markets on the understanding that it would promote liquidity and credit growth, and reduce systemic risk. However, this rationale was incomplete: it failed to acknowledge the full implications of collateral re-use for systemic risk. In this dissertation, I aim to complete that understanding by illustrating how the re-use of securities collateral in those markets can aggravate systemic risk. In particular, I describe two effects. First, re-using securities collateral multiplies the number of market participants that will be exposed to changes in the price of the collateral asset and can thus amplify the role of asset prices as channels of contagion. Second, by conferring a right to re-use, the collateral provider will effectively waive its proprietary interests in the collateral assets and retain a mere contractual claim against the collateral taker for the return of equivalent securities. This transformation will accentuate the incentive of the collateral provider to run from an over-collateralised collateral taker if the latter were to experience financial difficulty. Information asymmetries and a lack of coordination among collateral providers could push the collateral taker over the brink of insolvency. These risks pose an obvious question for regulators: what should we do about collateral re-use? At a time when international bodies are drawing their attention to this widespread market practice, the question is an invitation to a very timely reflection. The final chapter of the dissertation offers an answer to this question and assesses the potential efficacy of the most recent regulatory initiatives in relation to collateral re-use.

Keywords: Financial Collateral
Contagion
Re-use
Securities financing
Systemic risk
Repos
Re-hypothecation
Derivatives
Advisor: Awrey, D
The power of business and the power of people: understanding remedy and business accountability for human rights violations - Colombia 1970-2014

The questions of business involvement in human rights violations in countries facing civil conflict, as well as access to remedy and accountability for these violations have generated a considerable amount of attention from academia and practitioners. While most theoretical efforts on access to remedy and accountability have focused on identifying the obstacles to access to justice, these do not explain the unlikely case of Colombia, where despite all structural obstacles being present (e.g. armed conflict, corruption), the country has positioned itself as a leader in the region in terms of judicialisation and convictions of economic actors for their complicity with grave human rights violations committed in the course of the 50 year internal armed conflict. This thesis is a theory building and theory-testing project that looks for alternative explanations to the outcomes registered in Colombia, focusing on the agents involved in these cases and how the variation in the power of the people (claimants) and the power of businesses (defendants) explains access to justice.
This thesis uses the most comprehensive datasets in existence of business involvement in human rights violations (the Corporations and Human Rights Database and the Corporate Accountability and Transitional Justice Database) to present a novel and much needed systematic analysis to identify the factors explaining why and when remedy and accountability is possible. The results of the study suggest that the variations in the power of people and the power of business do offer a plausible alternative explanation to the unlikely case of Colombia. The Colombia data analyzed in this thesis suggests that while an increase in the power of the people (through the support of global actors and political opportunities) is necessary to secure judicialisation and remedy, these results are only possible when they face an economic actor with reduced veto power.

Keywords: access to justice
Transitional justice
Corporate complicity
business and human rights
Colombia
Advisor: Payne, L
Relativistic channeling with applications to inertial confinement fusion

The goal of controlled fusion energy has been pursued by the international community for decades. The majority of research into inertial confinement fusion, one branch of fusion research as a whole, has been focused on central hot spot ignition. However, alternative approaches such as fast ignition present the opportunity to achieve higher gains with reduced symmetry requirements, making them ideal for fusion energy production.
One important component of the original fast ignition scheme is the formation of a persistent low-density channel through an inhomogeneous plasma. This thesis revolves around channeling with laser pulses of highly relativistic intensities through plasmas relevant to fast ignition research, an intensity regime which has not received thorough attention in the existing literature. In this thesis, several particle-in-cell simulations are run to analyze various schemes in an effort to gain greater control over the channeling process.
An expanded physical model of the hosing instability that includes relativistic laser intensities and near-critical densities is presented and derives the density dependence of the hosing equation. This is then tested through simulations, and an examination of its consequences on multiple-pulse channeling schemes is conducted. The results show that the hosing instability grows more rapidly in dense plasmas, reducing the benefits of the multiple-pulse scheme when using realistic pulses of relativistic intensity.
Phenomena such as a ponderomotive self-correction mechanism, self-focusing-induced filamentation, and a modulated wavepacket known as the "pathfinder" pulse all become more relevant at higher pulse intensities. These have interesting consequences for future channeling schemes.
Finally, an experiment performed at the OMEGA EP facility at the Laboratory for Laser Energetics in Rochester, NY, USA is presented and analyzed. This experiment explored the effects of pulse timing, intensity, and focal position on channel formation. The findings of this experiment have important consequences for experimental design and have already improved the results of integrated fast ignition experiments.

Advisor: Norreys, P
Interactions between the Nrf2 antioxidant response and mammalian iron homeostasis

Iron is an essential micronutrient as it contributes to the oxygen-carrying capacity of blood and is a cofactor for many enzymes. However, excess iron is toxic as it promotes the formation of reactive oxygen species (ROS), which react with and alter the functions of biomolecules. Moreover, there is no regulated iron excretion mechanism from our body. Hence, iron homeostasis is tightly regulated by the hormone hepcidin that restricts iron absorption and controls iron distribution in the body. Accumulation of iron in the liver increases the expression of bone morphogenetic protein-6 (Bmp6), which induces hepcidin synthesis via Bmp responsive elements in the hepcidin promoter. The mechanism by which excess iron is ‘sensed’, leading to increased Bmp6, is unknown. Since excess iron induces oxidative stress, we hypothesized that Bmp6 expression is upregulated during iron-overload via the Nrf2-driven antioxidant response pathway. Nrf2 is a transcriptional activator that is activated by oxidative stimuli and binds to antioxidant responsive elements (AREs) to induce the expression of a battery of ARE-regulated antioxidant genes. Bach1 is a transcriptional repressor that binds AREs and suppresses gene expression. Haem can induce the degradation of Bach1 and derepress the expression of ARE-regulated genes. In this thesis, we demonstrated the simultaneous induction of Bmp6 and classical Nrf2/ARE-driven genes in mice and cell lines by iron and hemin (haem-chloride). ChIP-sequencing analyses showed binding of Nrf2 to a conserved ARE within intron 1 of Bmp6. The antioxidant mitoTEMPO blunted the activation of Nrf2 and upregulation of Bmp6 by iron. Furthermore, siRNA-mediated knockdown of Nrf2 decreased basal Bmp6 expression and inhibited the upregulation of Bmp6 by iron in vitro, whereas knockdown of Bach1 increased Bmp6 expression. Similarly, the upregulation of Bmp6 and hepcidin expression was blunted or completely abrogated in several models of iron overloading in Nrf2-knockout mice. Nrf2-knockout mice were more prone to iron accumulation and susceptible to oxidative stress-induced liver damage. Deletion of Nrf2 in Hfe-knockout haemochromatosis mice, and a SNP associated with reduced NRF2 expression in HFE-hereditary haemochromatosis patients, worsened the iron accumulation phenotype; conversely, pharmacological activation of Nrf2 upregulated the Bmp6/hepcidin axis and alleviated iron accumulation and oxidative stress in Hfe-knockout mice. In summary, Nrf2 links cellular and systemic iron homeostasis, is required for the upregulation of Bmp6 by iron, and is an important modifier and therapeutic target for iron overload disorders.

Advisor: Drakesmith, A