VictorJuiz/thesis huggingface dataset:
Orbital angular momentum in high-intensity laser interactions
Keywords: high-intensity laser interactions
photon-photon scattering
orbital angular momentum of light

The orbital angular momentum (OAM) of light is one of the most intriguing properties of electromagnetic radiation. Although OAM is more commonly associated with the mechanical movement of massive particles, researchers have shown that, under certain conditions, laser beams can carry it. This is not merely a theoretical proposition, this idea was almost immediately experimentally proven by showing that OAM can be transferred between light and matter. This has, in turn, spurred an ever-increasing interest in leveraging the interesting proprieties of the OAM of light for various technological applications. This work focuses on the effect that OAM has on high-intensity laser interactions.
High-intensity lasers have been a boon to scientific investigations in their own right. They have allowed us to experimentally research astrophysical phenomena inside of laboratories, opened the possibility to tabletop particle accelerators and gotten us closer to useful fusion energy sources. More recently, we have been able to reach extreme intensities that allow us to probe the most fundamental interactions in the universe. Predictions that had been theorized decades ago by the pioneers of the quantum theory of matter are now close to being experimentally verifiable.
In the coming chapters, I look at the fundamental nature of the OAM of light and the many discussions it has spurred. I then show that it modifies an interaction known as vacuum photon-photon scattering where beams of light can interact with each other in the absence of any mediating matter violating the constraints established by the classical theory of electromagnetism. OAM provides an extra signal that makes this light-light interaction more identifiable in an experiment. On a more practical note, I continue to look specifically at high-intensity lasers and how they can be manipulated to produce high-intensity OAM-carrying beams and how said beams can be characterized.
Reputation and self-regulation in securities markets: A study of the London Stock Exchange's Alternative Investment Market (AIM)
Keywords: London Stock Exchange
judicial review
self-regulation
reputation
AIM
securities
stock exchange
Alternative Investment Market

The continual debate over the appropriateness of self-regulation in securities markets has largely focused on North American self-regulatory organizations (SROs). Proponents and detractors typically advocate for more or less ‘regulation’, which is taken to mean legislation or administrative agency rule-making backed by public enforcement. This thesis adds to the debate by conducting a case study of an often-overlooked securities market, AIM, which began in 1995 as the Alternative Investment Market of the London Stock Exchange. This thesis conducts a holistic analysis of AIM. It begins with an analysis of black-letter law and legally enforceable regulation, but it does not end there. It continues by gathering evidence of market practice, regulation ‘off the books’, and how private rule-making on AIM has evolved over time, bringing to light how AIM has significantly changed since its 2007 heyday.
The main contribution of this thesis is to provide empirical evidence and analysis of 25 years of self-regulation on AIM, which is operated and regulated by the London Stock Exchange plc (Exchange). AIM, despite boasts as ‘the world’s largest growth market’, has received little serious legal scholarly treatment in the past decade. A second contribution is to demonstrate how reputational incentives and informal regulation, such as norms and unwritten rules that are imposed by both local market participants and the Exchange as private regulator, constitute an integral part of securities regulation and profoundly influence market conduct. Taken as a whole, this thesis seeks to shift the focus from calls for more or less regulation, and instead emphasizes the need for contextual inquiry of how reputation and informal regulatory mechanisms contribute to self-regulation in any securities market, given its public regulatory environment and private rule-making incentives.
Improving transport and storage of mesenchymal stem cells through investigations into their energy metabolism
Keywords: preservation
metabolism
mesenchymal stem cells

Mesenchymal stem cells (MSCs) are plastic adherent spindle shaped cells that express stem cell markers CD73, CD90 and CD105, while lacking leukocyte, endothelial and haematopoietic markers such as CD34 and CD45. They can differentiate into a range of different cell types. Compared to embryonic stem cells, they are easier to purify and can be used for allogenic therapy. As of 2021, over 900 trials have taken place, primarily involving tissue repair, treatment of immune disorders and more recently, COVID-19. Cryopreservation damages cells, while current non-freezing methods require cold temperatures, expensive special materials or serum, and have not been tested beyond 7 days. The project aims to improve on current work by using a simple and chemically defined medium to maintain cell survival, consisting of a DMEM base to provide the necessary substrates, vitamins, salts and amino acids, insulin supplement (ITSE) to keep cells viable in the absence of serum and a low bicarbonate buffer to maintain physiological pH at atmospheric CO2.
The medium was developed at 37°C using hTERT MSC monolayers. When hTERT human MSCs were cultured in the insulin based preservation medium, cells proliferated between day 6 and 12, while in DMEM basal medium cell death occurred. Cell monolayers in ITSE based medium displayed higher levels of oxidative stress, but no significant difference in autophagy compared to cells in expansion media (DMEM/FBS). hTERT MSCs in ITSE based media displayed lower levels of glucose consumption, lactate production and proliferation, and displayed a wire like morphology. When seeded in DMEM/FBS after 12 days in ITSE based media, metabolic and morphological changes were reversed, and cells retained proliferation and differentiation potential.
The ITSE based medium was then adapted to work at room temperature by lowering the bicarbonate concentration from 44 mM to 0.9 mM. The majority of hTERT human and primary bovine MSCs remained viable as monolayers by day 12. hTERT MSCs retained proliferation potential, but primary bovine MSCs remained permanently anchored to the flask. When preserved as 3D structures in alginate beads, at 12k cells/bead and 360k cells/mL of ITSE based media, both hTERT and primary MSCs remained viable and functional for 8 days. At this point the limiting factor was lack of serum and pH acidity. In alginate beads at atmospheric conditions, hTERT MSCs still underwent low levels of glycolysis over 6 days. For primary MSCs, metabolite changes over 6 days were too low to measure.
‘The most companionable composer’: sociability, Robert Schumann, and his chamber music
Keywords: Sociability
Narrative
Chamber Music
Schumann

This thesis explores the notion of sociability as a framework by which to interpret Robert Schumann’s ‘chamber music year’ of 1842. Schumann’s own sociability is examined both biographically and through music analysis. The first part of the thesis is a case study, tracing Schumann’s friendships during his youth in Zwickau and his first year in Leipzig, and analysing his first completed chamber work, the Piano Quartet in C minor, which can be understood as a tribute to his friends. The second part examines Schumann’s subsequent years in Leipzig, establishing that he was a sociable and active contributor to a circle of friends around his wife Clara Schumann, the Gewandhaus director Felix Mendelssohn, and the violinist Ferdinand David. This part of the thesis concludes that, especially in the context of chamber music making within this circle, the spheres of social and musical interaction merged. These findings are contextualised through discussions of musical salon culture in Germany and the distinctions made between public and private spheres. In the third part of the thesis, musical sociability is discerned as a musical motivic web in connection with narrative strategies of evoking a past tense, which is complemented by a discussion of narrative theories in nineteenth-century music. Through the analysis of Schumann’s three String Quartets, op. 41, and the Piano Quintet, op. 44, I suggest that, ultimately, Schumann exemplified the Romantic ideal of chamber music making by portraying his circle of friends in these chamber works. This interpretation of Schumann’s chamber music through a biographic lens exemplifies the importance of and serves as a model for the notion of sociability when writing about nineteenth-century music in general and chamber music in particular.
Objects and agents: women, materiality, and the making of contemporary theatre
Keywords: scenography
agency
gender
performance
women
new materialism
theatre
costume
props
materiality

This thesis uses embedded research to inform understanding of the complex nature of agency in contemporary British theatre-making. The close observation of activities in the rehearsal rooms, workshops, and auditoria of two British theatres – The Theatre Chipping Norton in Oxfordshire and the Royal & Derngate in Northampton – highlights a collaborative creative agency that challenges the tendency to privilege the singular intention of director or playwright in theatre and performance studies. Drawing upon new materialist thinking, agency is conceived as a process enacted across a diverse assemblage of participants that includes the production team, backstage professionals, and performers, as well as the material resources of theatrical production such as costumes and props. Tracing expressions of material agency, I seek to uncover hidden narratives that have been marginalised within accounts of the theatre-making process. I argue, particularly, for methodological resonances between a new materialist turn to matter and feminist strategies for recovering women’s experiences. The materiality of the stage is taken up as a critical lens to unpack material processes engaged in the gendering of labour, performing bodies, and theatrical space.
Five productions staged at The Theatre Chipping Norton and the Royal & Derngate between 2017 and 2019 serve as case studies for my exploration of gendered material agency. Four chapters are divided into two parts. The first, Gendering Bodies: Theatre-Makers and Objects, encompasses Chapter One: Costume and Chapter Two: Props and Puppets which both examine embodied encounters that take place between practitioners and objects in the staging of gendered bodily experience. The second part, Staging Gendered Experience: Theatre Apparatus and Character, sustains the inquiry of the first two chapters but considers how gendered experience is staged through the transformation of the staged environment, rather than through individual entanglements of bodies and stage objects: Chapter Three addresses the gendering of the material apparatus of form in contemporary realist theatre, and Chapter Four examines the how the gendered spatial dynamics of the staged home are reconfigured by contemporary theatre-makers. The local focus of this study, rooted in the observation of live practice, argues for the value of the specific in generating pertinent insights that introduce new perspectives to wider critical discussions; here, the complex question of collaborative agency and the gendering of practice that underpins contemporary theatre-making.
The changing nature of monastic historical writing in late medieval England
Keywords: monasticism
libraries and archives
historiography

The idea for this thesis began by questioning the perceived decline in late-medieval monastic historical writing. It quickly expanded, however, into an exploration of how historical writing was used within the administrative, commemorative, and performative culture of late medieval English monasteries. It is therefore divided into two parts, the first addressing questions of potential decline and identifying trends of change, the second exploring how these changes were manifested in the use of historical texts within a monastic context.
The historiography of historical writing and monasticism provides a contextual grounding for both parts of the study and a number of theoretical literatures inform the discussion including those on social memory and its specific application in monastic commemorative practice, and on the intersections between literary style, material form and monastic function. This theoretical groundwork is elaborated in Chapter One.
Chapter Two undertakes a quantitative assessment of over 340 historical works produced in England between 400 and 1540. The analysis of this dataset provides an indication of the trends in the religious order affiliation and topic focus between 400-1349 and 1350-1539. These trends are then examined through a closer reading of relevant works.
Chapter Three examines the presentation of historical texts in church tablets and as libri vitae, two forms through which historical texts impacted the visual setting of monastic communities and reflected commemorative practice. Chapter Four explores the interconnections between historical writing, the liturgies of late medieval saints, and monastic sermons. Brought together, the influence of historical writing on monastic culture is seen as a central element not only in the creation of monastic identity but a major tool in the monastic response to late medieval criticism of the monastic way of life.
Group 4 permethylpentalene complexes as polymerisation catalysts
Keywords: lactide
catalysis
permethylpentalene
olefin
polymerisation
coordination-insertion

The primary aims of this thesis were to: (1) prepare new permethylpentalene complexes and to investigate their performance as homogeneous and heterogeneous α-olefins polymerisation catalysts, (2) investigate the polymerisation of polar monomers and (3) discover new (hydro)permethylpentalene catalysts for the Ring Opening Polymerisation (ROP) of lactide monomers.
The thesis begins by offering an introduction to the chemistry of pentalene and its metal derivatives including ligand synthesis, organometallic chemistry and catalytic performances. The application of Cp*TiCl3 (Cp* = -C5Me5) and Pn*(H)TiCl3 (Pn*H = 5-C8Me6H) as olefin polymerisation catalysts, in both solution phase and immobilised on an insoluble methylaluminoxane (sMAO) support is described. Very high activities are observed for the styrene polymerisation using the supported Pn*(H)TiCl3. The systems were able to produce atactic polystyrene as well as high density polyethylene (HDPE). The ethylene/styrene copolymerisation ability of the catalysts is then demonstrated. A negative comonomer effect is described as well a low styrene incorporation. A variety of polymerisation conditions were studied, including the effects of temperature, styrene volume and solvent. Polymerisation of para-functionalised styrenes was studied using Cp*TiCl3 and Pn*(H)TiCl3. Para-functionalised styrenes containing electron donating groups NR2 (R = H, Me) and OMe lead to very high activities whereas the catalysts perform poorly in the presence of the electron-withdrawing substituent, Br. It was found that Cp*TiCl3 and Pn*(H)TiCl3 exhibited some of the highest activities for para-aminostyrene polymerisation reported in literature. Copolymerisations of 4-NR2-styrene with ethylene were attempted but no reaction occurred after poisoning of the catalyst by the comonomer.
The (hydro)permethylpentalene titanium alkoxide and aryloxide complexes, Pn*(H)TiCl2(OR) were tested as ethylene and styrene polymerisation catalysts in solution and slurry phases. Pn*(H)TiCl2(O-Si(Me)2tBu) exhibited high styrene homopolymerisation activities in both phases. The three pre-catalysts tested produced high molecular weight polyethylene (Mw > 106 g/mol) but were unable to copolymerise other olefins. These complexes were also found to be initiators for the ROP of lactide. The kinetics of polymerisation, rates, effect of temperature, initiator concentration are discussed. The polymers were characterised by a range of physical methods to determine the tacticity, molecular weights and chain end groups.
Finally, eight amidinate permethylpentalene complexes (Pn*ZrCl1–x[(NR’)2CR”]x) were prepared and investigated as slurry phase olefin polymerisation catalysts. Electronic and steric effects were studied by varying the amidinate substituents. Overall, low homopolymerisation activities were observed and these catalysts were unable to copolymerise ethylene with styrene and 4-NH2-styrene.
The thesis concludes with experimental details and all characterisations performed as appendices.
Mathematical modelling of cereal extrusion
Keywords: Fluid mechanics
Asymptotics
Cereal
Extrusion
Industrial mathematics

In this thesis we analyse a mathematical model for an industrial process known as extrusion, and develop techniques for finding solutions to this model. The model for extrusion describes the evolution of a viscous liq- uid containing small vapour bubbles. The lengthscales corresponding to different features in this model can differ by orders of magnitude; so, we first distinguish a macroscale and a microscale. The parameters govern- ing the dynamics of the system also vary over orders of magnitude. We exploit the asymptotic structure of the model to develop reduced systems of equations that are easier to solve, and give physical insight more readily.
In Chapter 1 we describe extrusion, and existing models for extrusion. In Chapter 2 we describe the model for extrusion used throughout this thesis. This model is decomposed into a macroscale model, describing the flow of a viscous, compressible fluid on lengthscales comparable to the extruder; and a microscale model, describing the evolution of vapour bubbles in the mixture. In Chapter 3 we consider the microscale model. We develop reduced models in different parameter regimes and estimate a macroscopic lengthscale for bubble growth, from which we predict param- eter regimes for which the extruded product is long and thin. In Chapter 4 we exploit the slenderness of the product to construct reduced macroscale models, similar to the Trouton model for incompressible flows. In Chapter 5 we develop a numerical scheme capable of solving the full system de- scribed in Chapter 2, and compare these solutions to those of the reduced models developed in Chapters 3 and 4. Finally, in Chapter 6 we provide some concluding remarks on the model for extrusion we have considered, and on the key findings of Chapters 3, 4, and 5.
Design of mixed ionic-electronic polymeric conductors for organic electrochemical transistors
Keywords: Organic Bioelectronics
Conjugated Polymers
Organic Electrochemical Transistors
Organic Semiconductors
Mixed Ionic-Electronic Conductors

Organic electrochemical transistors (OECTs) are electronic devices that have gained significant attention for many biomedical applications, including as electrophysiological recording elements, cell activity monitors, and biomolecule sensors. Compared to conventional transistors, one distinguishing feature of OECTs is the requirement of the employed channel material to conduct both ionic and electronic charge carriers. Currently, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), has established itself as OECT benchmark channel material, predominantly due to its widespread commercial availability. PEDOT:PSS-based OECTs, however, display several disadvantages, such as moderate steady-state performances and PEDOT:PSS’ limited chemical tunability preventing the formulation of structure-property relationships to guide future material design. Based on these limitations, this thesis focuses on the development of ethylene glycol (EG) functionalised conjugated polymers capable of conducting both ionic and electronic charge carriers to advance OECT performance, while concomitantly also establishing molecular design guidelines for the development of future channel materials.
In Chapter 2 a series of four polythiophenes with pendant EG side-chain lengths ranging between two and six EG repeat units is synthesised and characterised. Specifically, p(g3T2- T), the polymer employing triethylene glycol side-chains is shown to incur the highest OECT performance, with both EG side-chain length shortening and lengthening proving to be detrimental towards OECT performance.
Chapter 3 builds on the results of Chapter 2 and explores how variation in the relative distribution of the EG side-chains in polythiophenes impacts their swelling and therefore their OECT performance and stability. While intermediate degrees of polymer swelling boost device performance, minimising the polymers’ swelling improves device stability.
The importance of maximising OECT device performance and stability are highlighted by employing one of the newly developed polymers as the channel material in a SARS-CoV-2 OECT biosensor, incurring better sensing performances compared to the PEDOT:PSS benchmark.
Chapter 4 investigates the use of the diketopyrrolopyrrole (DPP) unit to improve the p-type performance of donor-acceptor copolymers in OECTs, whose performance has lagged far behind their all-donor counterparts. In particular, control over both the overall and relative energy levels in these polymers is demonstrated to be of utmost importance to tune their performance and stability in devices.
Impacts of tree diversity and drought on forest resilience to pathogens
Keywords: forest diversity experiment
forest resilience
tree diversity
forestry
biodiversity ecosystem functioning
forest pathogens
climate change

The area of planted forest around the globe is increasing. Most new plantations are planted as monocultures, but evidence shows that mixed species forests can provide higher levels of multiple ecosystem functions without compromising productivity. In addition, mixed species forests are often purported to be more resilient to natural disturbances such as pest and pathogen outbreaks. In European forests, widespread species such as oak (Quercus robur) are currently under threat from multiple interacting abiotic and biotic threats, including pathogen damage and drought, both of which could increase under conditions of climate change.
In this thesis, I used planted experiments in which tree species and genetic diversity had been varied and studied the impacts on a specific, widespread forest pathogen (oak powdery mildew, Erysiphe spp.), and how it interacted with the insect herbivore community on oak. I found that the effects of tree diversity were strongly dependent on environmental context. In my UK field study, results were variable between years and study sites. I also found no evidence for local adaptation of the insect and pathogen community on oak to local hosts. In my field study from SW France, in which both tree species diversity and drought were experimentally varied, I did find evidence for lower pathogen damage at higher diversity levels, as well as effects of tree neighbour identity. Drought did not alter pathogen damage, but it did alter the strength of the diversity effects on insect herbivory. I also found evidence for tripartite interactions between host, pathogen and insects, showing that interactions between multiple damage agents can play an important role in determining tree health.
Lastly, I synthesised evidence of the effects of mixed species forests on pathogen damage using meta-analysis and systematic review of previous studies. I found a negative effect of tree diversity on pathogens that was only significant in temperate forests. Synthesis of both quantitative and qualitative evidence again showed the importance of tree neighbour identity rather than host abundance in determining diversity effects.
Overall, I show that tree diversity can lower forest pathogen damage, but that consideration of specific interacting abiotic and biotic variables is also crucial to provide evidence-based recommendations to practitioners.