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The literature and journalism of nineteenth-century poverty: Charles Dickens and Henry Mayhew
No full textThe representation of the urban poor in Victorian literature and journalism was shaped by the rise of realism as a literary form. Charles Dickens and Henry Mayhew, though working in different genres — novels and nonfiction — both employed realist techniques to depict the struggles of the underclass in nineteenth-century London. Oliver Twist (1837–39) and London Labour and the London Poor (1851) are key examples of how realism functioned as both a formal strategy and a vehicle for social critique. The works of both authors influenced contemporary and historical perceptions of poverty in England.
Dickens’s stylistic realism in Oliver Twist combines vivid social detail, sharply drawn characters, and the techniques of melodrama to make poverty visceral and morally urgent for his readers. His depiction of workhouses, child labour, and the criminal underworld draws on real conditions, but includes his own narrative interventions for emotional effect. Scholars such as Susan Zlotnick (2006) highlight how Oliver Twist documents the social consequences of the 1834 Poor Law, exposing its dehumanising impact on orphans. More pointedly, Michal Peled Ginsburg (1987) argues that Dickens’s realism is not neutral. Rather, Dickens presents details and characters in ways that invite and mould readerly sympathy. Dickens’s novels thus construct a moralised realism that reinforces Victorian ideas of poverty as both a systemic failure and an individual test of character.
In contrast, Mayhew’s documentary realism in London Labour is grounded in journalistic reportage and ethnographic observation. His firsthand interviews, statistical data, and direct testimonies provide one of the earliest systematic studies of the urban underclass. Here, Mayhew documents the lives of costermongers, street-sellers, beggars, and prostitutes with whom he directly interacts. Scholars such as Richard Maxwell (1978) and Barbara Leckie (2020) argue that Mayhew’s realism is immersive, capturing not just material struggles but also the occupational structures and survival strategies of the poor. Unlike Dickens, who fictionalised characters for dramatic effect, Mayhew sought to preserve the authenticity of individual voices, an approach Bryan S. Green (2002) describes as an early attempt at ethnographic neutrality. However, Mayhew does not merely document poverty through statistics; rather, he humanises data by embedding numerical findings within detailed personal testimonies. By combining empirical research with rich narrative storytelling, he presents social data in terms of lived experiences, making the plight of the poor immediate, emotionally resonant, and deeply individualised for his readers.
Despite their differing ways of deploying the hallmarks of literary realism, Dickens and Mayhew together redefined Victorian perceptions of poverty by bringing the urban underclass into mainstream discourse. This study challenges the assumption that fiction and journalism exist in separate spheres, showing instead that their works are mutually reinforcing. Mayhew’s investigative findings informed Dickens’s fictional depictions of street life, while Mayhew’s documentary style borrowed narrative structuring and literary characterisation to heighten emotional impact.
This research contributes to Victorian studies by illustrating the interplay and mutual influence of literature and reportage. Oliver Twist and London Labour did not merely reflect urban realities, but consciously leveraged literary realism to stir emotions, support specific social ideologies, and advocate for change. Dickens’s melodramatic realism shaped middle-class perceptions of workhouses and juvenile criminality, while Mayhew’s ethnographic realism provided unprecedented documentary insights into the daily ordeals of the London poor. Both authors show that realism is neither purely descriptive nor politically neutral; it is intertwined with broader ideological and narrative goals.
Comparing Dickens’s literary realism to Mayhew’s documentary realism further complicates the line between imaginative storytelling and empirical observation. Each employs a hybrid of methods – Dickens weaving social facts into emotive fiction, Mayhew interspersing data collection with narrative flair. Ultimately, no single genre fully captures the complexity of Victorian poverty; rather, a synthesis of their approaches reveals how sentimentality and statistics, pathos and reportage, intersect to create a fuller picture of how the poor were imagined, recorded, and remembered, in the Victorian era and beyond. This analysis reinforces the idea that realism operated as both a literary device and a cultural force, shaping our contemporary views on social inequality, historical narrative, and the shared ground of literary and journalistic authority
Part A: Cheesemaker Cf77 potato starch interactions with Faba Bean legumin and pea protein isolates Part B: Characterisation of CF77 potato starch and pea protein, and an analysis of how interactions between the two molecules could be affected by heat
Get PDFPart A: This literature review is on the topic of currently available papers and studies
conducted on potato starch interactions with faba bean and pea protein legumins. Including a
detailed summary of individual molecules, of the said interactions, complexes formed, and how
they can be useful. The main focus is on how these complexes could then be utilised in the
formation of vegan cheese, and how then the probable product would taste. As such, this review
will include a detailed summary of gelatinization and retrogradation processes as they are pivotal
processes used in the gel formation. Lastly, gaps in the current literature will be identified with
the focus on how the starch-protein complexes could be further utilized, and then next steps
will be given on how to proceed with the information found.
Part B: Animal-based food products are the biggest contributors to the emission of greenhouse gases in the
food sector. Looking into healthier alternatives which do not contribute to the global climate crisis is very
important. One such product which is recently been on the rise is vegan cheese, and as such, this study will focus on
analysing the characteristics of cheesemaker Cf77 potato starch and pea protein for their viability and usage in
vegan cheesemaking, and the effect excessive heat could have on the interactions between them. To do so,
Analytical ultracentrifugation and dynamic light scattering were used to look at the polydispersity of the said
molecules, and how the interactions between them will differ under different ratios of each component
Influence of aggregate topology and mineralogy on the long-term skid resistance performance of asphalt surface course material
Get PDFSkid resistance is a critical safety property of road pavements, directly affecting wet braking performance and accident risk. Traditional prediction methods—including the Polished Stone Value (PSV) test—focus solely on a small fraction of the coarse aggregate performance and have demonstrated limited reliability in forecasting in situ skid resistance over the service life of an asphalt surface course. This thesis investigates whether a more holistic laboratory measurement—the Friction After Polishing (FAP) test—combined with quantitative characterisation of aggregate topography and mineralogy, can improve prediction of long term in-situ skid resistance as measured by the Sideways Force Coefficient Routine Investigation Machine (SCRIM).
A structured experimental programme was devised to (1) characterise polished aggregate micro texture via Mineral Liberation Analysis (MLA), Mohs hardness grouping, and Alicona infinite focus microscopy; (2) quantify friction evolution during controlled polishing of aggregate mosaics and full asphalt cores using FAP; (3) assess changes in three dimensional surface texture across incremental polishing cycles; and (4) correlate laboratory friction outcomes with extensive SCRIM survey data collected between 2014–2024 on matching asphalt designs under varied traffic volumes.
Results reveal that aggregate mineralogical composition—and specifically the proportion of hard versus soft mineral phases—influences both micro texture retention and friction coefficient trajectories under polishing. FAP measurements reached equilibrium beyond the standard 90 000 polishing cycles, suggesting that current European test protocols underestimate long term wear effects. Alicona G5 Infinite Focus-derived surface and volumetric texture parameters demonstrated statistically significant relationships with FAP friction values. Critically, asphalt cores exhibited stronger FAP–SCRIM correlations than aggregate mosaics alone, validating the importance of binder aggregate interactions and macro texture contributions.
This thesis establishes that combined mineralogical and topographical characterisation integrated with FAP provides a robust predictor of in situ skid resistance performance. These findings support a shift toward performance based surfacing specifications designed to maximise road safety and lifecycle efficiency
BIM-based building circularity assessment for sustainable construction
No full textThe construction industry consumes 50% of raw materials and is responsible for 35% of the waste generated in the European Union. Traditional building design strategies are based on an unsustainable linear model. Therefore, to tackle these issues, there is an urgent need in the construction industry to transition from a linear to a circular economy.
The emergence of building information modelling (BIM) has supported decision-making processes and can be used to overcome barriers to a circular economy, such as building circularity assessment (BCA), material passport (MP), and material bank. BIM can manage the information embedded in a building, from its early design stage to end-of-life. However, current approaches either focus on geometric data extraction or address only circularity without sustainability considerations. To the author's knowledge, current BIM tools do not provide a comprehensive assessment for effectively supporting decision-making, and no approach simultaneously considers circularity and sustainability trade-offs in early-stage decision-making, informing design decisions at various levels. This thesis investigates how BIM can be leveraged to simultaneously assess building circularity and sustainability at the early design stage for informed decision-making.
This thesis proposes a novel framework that integrates technical circularity (CE indicators) and sustainability by life cycle sustainability assessment (LCSA), combining Life Cycle Assessment (LCA) and Life Cycle Costing (LCC), Multi-Criteria Decision Analysis (MCDA), and Building Information Modelling (BIM) for a comprehensive assessment of design choices to select the ideal solution. The originality of the framework lies in its calculation of circularity and sustainability simultaneously from a lifecycle perspective at various levels of building composition. The thesis contributes to research and knowledge by advancing circularity assessment through the proposal of a novel circularity assessment model, the Predictive Whole Building Circularity Indicator (PWBCI). This model incorporates reusability assessment of building components and combines mathematical modelling, rule-based, and probabilistic approaches to predict end-of-life scenarios. The thesis identifies the required information for the assessment to be included in the BIM model, and it also extends BIM semantics by developing a “Circularity” data dictionary published within the buildingSMART Data Dictionary (bSDD) service.
The implementation of the proposed framework is presented in a prototype tool (BIMCircular) in the form of a plugin that was developed within Autodesk Revit using C#, API, and databases. The presented tool functions as a decision support system (DSS) for comparing and making trade-offs between different aspects (technical circularity, environmental, and economic sustainability indicators) of different design options during the early design stages of buildings. The tool aims to support the selection of the ideal solution among design options for a more circular and sustainable alternative. The developed prototype enriches the BIM model with circularity information, automates the assessment, visualises results through 3D colour-coded models and dashboards, and provides decision-making support via multi-criteria decision analysis -Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). It also supports traceability through digital circular material passports (CPM) aligned with the EU Level(s) framework and QR codes. Additionally, it is connected to a material bank, serving not only for documentation to facilitate the reuse of components but also for the design with reusable materials.
Evaluation is conducted using a simulated case study, demonstrating the framework’s ability to inform early-stage design decisions, provide trade-off analysis, and visualise results within the BIM environment. The evaluation confirmed the tool’s functionality and applicability.
The research concludes that BIM can be leveraged as a data repository by incorporating circularity and sustainability information, facilitating the automation of assessments and generating a material passport and data traceability. The study emphasises the significance of comprehensive assessment and MCDA in informing design decision-making and identifying ideal design options at the early design stage.
The results of implementing the framework demonstrate that BIM-based circularity and sustainability assessments facilitate informed decision-making by identifying the most circular and sustainable materials for buildings. It is hoped that this will be useful for designers to gain more informed insights into the circularity and sustainability performance of their alternative design solutions, thereby raising awareness about circularity and sustainability among designers. Moreover, it will contribute positively to optimising material use and resources efficiently, building stock decarbonisation, and a step toward a twin transition of a sustainable circular economy and digitalisation
Mapping the Breaker Element of the Cuckoo Chromosome 4SshL of Wheat Wild Relative Aegilops sharonensis
No full textWheat (Triticum aestivum), a global food staple, is threatened by climate change and the challenges that it brings. Additionally, its genome has become bottlenecked through millennia of selective breeding making it difficult to exploit new genes to contend with these challenges. Wild relatives of wheat are often utilised as a novel source of genetic diversity for wheat improvement. However, some wild relatives, including Aegilops sharonensis, contain gametocidal genes. These selfish genes ensure preferential transmission to offspring through inducing chromosomal breakages in gametes that lack them, resulting in agronomically unstable lines with shrivelled seeds and significant yield reductions. Due to their selfish nature, these genes are extremely difficult to remove, preventing useful germplasm from being used in breeding programmes.
Here, molecular markers and skim-sequencing were used to characterise a gametocidal gene (Gc2)-containing translocation line, T4B-4Ssh. This line was shown to carry a 9 Mbp Chr. 4Ssh segment from Ae. sharonensis introgressed into wheat Chr. 4B. We developed and treated an F1 population of 4,800 seeds with 0.35% and 0.4% ethyl methane sulfonate (EMS), resulting in 67 M1 plants with potential loss of function in the Gc2 locus. Ten progeny from each M1 plant were genotyped to verify the normal segregation of the Chr. 4Ssh segment. Mendelian segregation was observed in two families, confirming mutations in the gametocidal locus. Two additional mutants demonstrated abnormal segregation patterns. Test crosses were also used to characterise the mutants. One mutant behaved as anticipated, while the others deviated from at least one expected outcome, indicating a more complex dynamic at play.
Chromosome flow-sorting isolated the recombinant Chr. 4B-4Ssh from the wild-type T4B-4Ssh and mutant lines, prior to its sequencing. Single Nucleotide Variations (SNVs) were identified between the wild-type and the mutant lines, in the introgressed 4Ssh segment, using the MutChromSeq bioinformatics pipeline. The analysis identified two contigs within the Chr. 4Ssh segment that had mutations in two and three mutant lines, respectively. One contig aligned highly to an Ae. sharonensis basic helix-loop-helix gene (AE.SHARON.r1.4SG0366250), which may be considered a candidate for Gc2. However, collective consideration of the data generated in this study may indicate the existence of multiple genes responsible for gametocidal action.
This research has taken great steps towards identification of the long sought after gametocidal gene, Gc2. Additionally, these mutant lines can be used to remove Gc2 from wheat-Ae. sharonensis introgression lines. This would allow valuable germplasm with potentially beneficial traits to be released to breeders, helping to improve food security in a more extreme and populated world
Formulaic theme and wisdom in Eddic poetry
Get PDFThis thesis explores how wisdom was delivered in Eddic poetry via the mechanism of formulaic theme. It demonstrates how the delivery of wisdom was a vital part of Eddic poetry, and that even poems not typically counted amongst the wisdom canon contain the same elements found in texts such as Hávamál. Additionally, this thesis explores how the formulaic delivery of wisdom developed from the earliest poems to the latest. This can further inform us on the fundamental creation of Eddic poetry.
After establishing the methodology of this study in the introductory chapter, Chapter 2 provides an in-depth analysis of David Crowne’s 1960 theory of the ‘hero on the beach’ and how such a study may not just be translated from the Old English tradition to the Old Norse, but also across genres from the Heroic to Wisdom, using episodes from Hávamál to illustrate this.
Following this study, the thesis progresses through the Codex Regius considering the following poems: Vafþrúðnismál, Grímnismál, Reginsmál, Fáfnismál, and Sigrdrífumál. Vafþrúðnismál and Grímnismál are found in Chapter 3, along with an analysis of the various forms of staging wisdom and the types of wisdom delivered. Chapter 4 features the three Sigurðr poems, and shows how the wisdom formulaic theme crosses over from the wisdom mythological poem in the heroic poetry, and the impact that this crossing over has on the delivery of wisdom.
Chapters 5 and 6 are each dedicated to a single poem, Grípisspá and Sólarljóð respectively, as these poems serve to illustrate the different ways in which the theme developed and stagnated.
Chapter 7 is the final summation chapter and shapes all the previous analysis into a cohesive theory of what precisely was needed in the theme, and what could change as its users needed.
Finally, the conclusion offers some final commentary, before exploring how the theory could be studied further beyond the scope of this thesis
Understanding high redshift Active Galactic Nuclei activity through infrared variability
Get PDFIn this thesis, we report on the properties of a new selection of active galaxies found using long-term NIR variability. Data from the UKIRT Infrared Deep Sky Survey Ultra Deep Survey (UKIDSS UDS) is used, which is the deepest near-infrared (NIR) survey over ∼1deg2 and has an 8 year baseline for IR imaging. Here we select 601 AGN based on their (long-term) NIR variability in the J (1.2um) and K (2.2um)photometric bands. We also make use of X-ray imaging from the X-UDS survey, a Chandra space telescope based X-ray survey of a sub-region of the wider UDS field, to detect 710 X- ray bright AGN. We first begin by investigating how the properties of active galaxies change depending on the detection method used to select them. A comparison of the AGN identified by near-infrared variability to those selected by X-ray detection find only modest overlap in the galaxies detected. Only 37 per cent of galaxies are found to be both X-ray bright and IR variable for the same imaging area. We find that NIR variability is able to detect AGN activity in galaxies with a range of stellar masses, which is in contrast to X-ray detection, which preferentially selects AGN in massive galaxies (M∗ ≳ 1010M⊙). From these findings, we conclude that a range of selection methods is required for a complete census of active galaxies to be obtained.
Having established that NIR variability as a relatively new way of finding AGN, we explore how the properties of these variable galaxies differ depending on the band in which the AGN is found to be significantly variable. To inspect their rest-frame properties, we group the variability detected AGN based on their detection band and plot the ratio of their variability amplitude vs redshift. K-band variable AGN are preferentially observed at rest-frame infrared wavelengths whereas J-band variable AGN show no obvious preference for the rest-frame of detection. Inspecting the SED of the galaxies, AGN variable in the K-band have significantly redder UV colours compared to AGN variable in the K-band, with similar results being found between X-ray hard and X-ray soft active galaxies respectively, where the hardness ratio is used as an alternative measure of obscuration. AGN variable in the J-band also show lower variability amplitudes and variability that skews towards longer timescales compared to their J-band variable counterparts. The properties of AGN variable in different bands suggests that the IR spectrum of K-band variable AGN is dominated by thermal emission from hot dust, whereas J-band variable AGN show features consistent with thermal emission from accretion disk processes. These differences identify the rest-frame J to rest-frame J-band as a possible turnover in dominant IR emission processes in AGN and we suggest K-band variability detecting AGN emission in dusty galaxies as a possible explanation for the properties found in these galaxies.
Finally, we examine the environment, observed colours and host galaxies to explore possible reasons for the differences seen in X-ray and variability detected active galaxies and their subgroups. X-ray and variability detected AGN are found in different environments compared to each other as well as when comparing to corresponding sets of control galaxies matched in stellar mass, redshift and effective radius. X-ray bright active galaxies are preferentially found in overdense environments whereas variability detected active galaxies do not show any obvious trends with environment. Optical (V - I) and infrared (J - H) colour comparisons over time find X-ray bright active galaxies to appear redder than variability detected samples at the 4000Å break, a feature that is typical of high mass galaxies with larger passive fractions. In preliminary work, X-ray to IR luminosity comparisons provide evidence that two component Sérsic + point source models are able to effectively decompose AGN from host galaxy emission. Inspecting the host galaxies of X-ray bright AGN finds significantly redder optical colours than control galaxies, but infrared colours are generally indistinguishable over time. Colour evolutions change when grouping galaxies by morphological type, with disk-type X-ray AGN hosts appearing redder both in the optical and infrared colours, but spheroidal hosts showing no clear trend in the optical colour but appearing much bluer than controls in the infrared colour. This preliminary work illustrates the need for AGN-host galaxy decomposition in determining intrinsic host properties in future wide-field studies
Design and evaluation of icephobic coatings for efficient thermal de-icing
Get PDFIce accretion on engineering structures is a significant safety concern, and the current in-use mitigation strategy of electro-thermal de-icing systems is energy-intensive. Icephobic coatings have been identified as a potential zero-energy solution, passively de-icing the surface or altering the accretion formation. Numerous approaches are being studied, and progress is being made towards this goal. However, coating durability remains a significant hurdle.
This work is primarily motivated by the extreme use case of ice accretion on a helicopter blade. The leading edge, where ice typically forms, experiences abrasive wear through sea spray and particulate erosion so severe that damage to the titanium erosion shield can be a life-limiting issue. Icephobic coatings may never have a sufficient lifespan to be applied as a stand-alone passive solution to solve this particular problem.
We consider a hybrid approach, with the coating considered a sacrificial barrier, extending the life of the erosion shield with the additional benefit of icephobic properties, leading to a reduction in the electro-thermal energy required to de-ice the leading edge. The goal of this coating would be to minimise cumulative energy costs by reducing the frequency and severity of icing incidents, the energy cost per de-icing cycle, or both.
While the need for a hybrid solution may only be suitable for niche or low-volume applications, many others where a passive solution would be appropriate will have that passive solution retroactively applied. Testing such coatings alongside an electro-thermal de-icing system would not be necessary to improve function. Still, it would provide confidence in early candidates. If the coating failed to passively de-ice due to unexpected performance outcomes or incurred damage inhibiting its capabilities, the active system would remain effective as a secondary safety system. In comparison, a hybrid coating system would be an electro-thermal de-icing system that is enhanced by an icephobic coating and not replaced by one.
This thesis addresses the new considerations required of a hybrid icephobic coating deployed alongside an electro-thermal de-icing system. We show that altering a coating's properties to optimise the performance of an electro-thermal de-icing system produces detrimental changes to its performance in passive icephobic metrics. An example of such a modification would be the addition of fillers to increase the thermal conductivity for use as part of an active system, but which also increases the frequency and growth rate of ice accretions and also increases the Young's modulus of the elastomer matrix material, increasing the ice adhesion strength. Every factor that can be manipulated to improve one performance metric is often a detriment to another, meaning any potential success would be application-specific, with carefully delineated optimisation requirements.
Polydimethylsiloxane (PDMS) was chosen as a matrix material following accepted best practices from icephobic literature. It was tested through a range of thicknesses and with the addition of filler material. A static electro-thermal de-icing experiment was produced that was capable of characterising the energy cost associated with a coating's surface properties and bulk materials properties. The energy required to de-ice the surface increases linearly with coating thickness. PDMS containing 8.3 wt% of SiC submicron fibres reduced the per-thickness energy cost by 59% compared to PDMS alone. Dynamic electro-thermal de-icing was tested by attaching an iced sample atop an electro-thermal de-icing system at the end of a rotating arm. Spinning the arm at a fixed speed applied shear stress to the surface-ice interface subject to electro-thermal de-icing.
When the rotational speed was sufficiently high, airflow over the rotor increased the heat lost to the environment, significantly increasing the energy cost to de-ice. The linear relationship between coating thickness and energy cost was lost, with some samples failing to de-ice with sufficiently thick coatings. This highlights a key safety concern if an early passive coating fails.
Adding thermally conductive fillers to a coating will also change the accretion process as the transfer of latent heat of freezing will be higher for a more thermally conductive coating. Altering the coating could therefore alter the accretion formation process for a given environment. If a coating changes the accretion structure to one that has not been optimised to de-ice, then an iterative design would be necessary.
A cloud was simulated with a nebuliser in a freezing environment to form ice on the leading edge of spinning turbine blades. Properties of the cloud, flow conditions relative to the blades' motion and environmental temperature were successfully used to analyse a wide range of ice accretion structures and to understand how they form. This experiment has shown that it could provide a basis for modelling techniques to predict ice accretions and show how implementing a coating could alter the accretion. A second icing experiment forming accretions on a spinning disc shows promise as a preliminary icing test for candidate coatings. The results can inform how the coating will alter the accretions formed in the blade icing experiment
Topographical and chemical characterisation of temperature controlled on-surface reactions
Get PDFOn-surface synthesis, the process of producing covalently bonded structures from molecular building blocks confined on a surface, is a research theme worthy of investigation as it offers a route towards the fabrication of nanoscale two-dimensional devices. Alongside the potential applications within the burgeoning field of nanoelectronics, confining materials to surfaces allows the use of a variety of surface analysis techniques. Scanning probe microscopy, for example, can reveal with unrivalled detail mechanistic information about the progress of reactions in general. Developing our understanding of these processes can allow for the formation of more precise and complex structures ‘on-surface’ and may pave the way for developing new methodologies within solution phase synthesis.
In this thesis, a variety of molecular species, confined to two-dimensions by supporting substrates, are investigated, and the self-assembled structures formed following deposition, and subsequent temperature-induced reaction steps, are characterised. Particular emphasis is placed on Ullmann-type coupling reactions, a versatile and oft-utilised route to covalent bonding on surfaces. The work described within this thesis takes place predominantly under ultra-high vacuum (UHV) conditions, utilising a variety of surface-sensitive techniques: primarily scanning tunnelling microscopy (STM), but also X-ray spectroscopy techniques such as X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption spectroscopy (NEXAFS) and X-ray standing wave (XSW) analysis. Each of the chapters describing the experimental results aims to develop our understanding of the mechanisms underlying the behaviours of molecules in surfaces and particularly on the kinetic properties of reactions, in order to better facilitate more efficient and selective synthetic pathways.
The species covered in this thesis span a broad range, and demonstrate the breadth of utility for this type of ‘surface science’ based approach. Firstly, the formation of a polymer based upon a diketopyrrolopyrrole (DPP) is studied. This monomer unit possesses aryl-halide groups to facilitate on- surface covalent coupling and is functionalised with alkyl chains which drive the self-assembly of both the monomer material prior to reaction and the domains of polymeric material following on-surface synthesis. The self-assembled structure of closepacked domains of the monomer units, and the ordered polymers, are investigated and characterised using STM and XPS.
Secondly, two groups of larger molecular species are investigated: a series of porphyrin-based nanorings, and porphyrin-doped polymer chains, which serve as a precursor to a target porphyrin-graphene nanoribbon. Both are formed via novel in-solution synthesis, and require vital on- surface characterisation to accompany the in-solution chemistry and to confirm the successful synthesis of these materials. Both are investigated via STM, with morphological characterisation of the nanorings via this technique crucial to understanding the cyclic structure and flexibility of the molecules. For the graphitic nanoribbon species, our focus is the inclusion of porphyrin species within graphene nanoribbons to create porphyrinfused graphene nanoribbons (PGNRs). A combination of scanning tunnelling microscopy (STM) and photoelectron spectroscopy (PES) techniques are used to characterise the novel porphyrin-fused graphene nanoribbon. This nanoribbon is formed on-surface from a linear polymer consisting of regularly spaced Ni-porphyrin units linked by sections of aryl rings which fuse together during the reaction to form graphitic regions between neighbouring Ni-porphyrin units.
Lastly, a temperature-programmed PES study of brominated tetraphenyl porphyrin is conducted, with a novel Arrhenius analysis opening a pathway to empirical measurement of kinetic properties of reactions. This is enabled via temperature-controlled continuous XPS measurement, and the reaction is also characterised by stepwise STM, NEXAFS and XPS. A comparison is made between the properties of the Ullmann-type coupling reaction on both Au(111) and Cu(111) surfaces.
The work described in this thesis develops atop the existing literature for the stepwise analysis of surface-confined covalent reactions, and demonstrates the flexibility of surface-confined techniques such as STM for their unrivalled molecular resolution. The combination of STM with X-ray spectroscopic techniques underpins much of the work and displays the strength of combined topographic and chemical characterisation when analysing the evolution of a system, and demonstrates novel ways in which these techniques can be used to further our understanding of on-surface synthesis
Transmissive solar sailing
Get PDFUniquely, solar sails are a means of accelerating a spacecraft via ambient space radiation rather than onboard propellant. In principle, this allows for continuous acceleration, and for the attaining of higher velocities than a reaction engine may achieve. These sails are also amongst the most sustainable orbit control systems, being associated with reduced satellite weight, mission cost and space debris footprint. However, they also have weaknesses that constrain how and where they can be used --- most notably, their poor performance in low Earth orbit (LEO), where the majority of satellite missions occur. {\textit{Transmissive}} solar sails may mitigate these weaknesses and thereby promote the broader adoption of solar sails. Advocating for this future, this thesis seeks to collate and expand the existing literature pertaining to these sails across three core domains: orbital dynamics, optical design, and manufacturing processes.
A flight model was developed to characterise the behaviour of differently designed and differently steered solar sails in LEO, with consideration given to atmospheric drag, eclipse and orbital precession during orbit-raising manoeuvres. These designs included transmissive sail proposals of both {\it{refractive}} and {\it{diffractive}} varieties and a contemporary {\it{reflective}} solar sail for comparison. Simplified `zero-' steering was found to constrain the flight envelope of transmissive sails. When optimally steered, these sails unanimously demonstrated lower performance sensitivity to altitude but greater sensitivity to orbital inclination than contemporaries. Greater synergy with certain Sun-synchronous orbits (SSO) was found, but also greater sensitivity to the orbital plane changes that arise in non-SSOs. Sails were sorted according to performance: some refractive and diffractive {\it{metasails}} surpassed reflectors in every flight regime ({\textit{Type A}} transmissive sails); simpler refractive and diffractive sails surpassed reflectors only in low altitude, high inclination orbits, particularly SSO ({\textit{Type B}}); other diffractive sails surpassed reflectors in low altitude orbits more generally, and were otherwise comparable to reflectors ({\textit{Type C}}). A case study with a Type A sail demonstrated transit times from LEO that were comparable to mid-range electric thrusters.
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The optical design of refractive sail patterns using single-index materials was explored in-depth via numerical optimisation: a ray tracing simulation was developed to calculate the solar radiation pressure (SRP) and torque per unit area generated by refractive objects illuminated in vacuum. A model-free reinforcement learning optimiser was developed to iterate upon geometries according to a user-defined fitness function. These tools were integrated to generate numerically optimised patterns ranging from high acceleration micro-prisms to passively stable freeform {\it{lightfoils}}. The optimiser was shown to substantially improve the performance of optical elements, usually by harnessing total internal reflection. In one notable example, a simple pattern of cylinders evolved into a pattern of freeform elements that achieved of the theoretical maximum tangential SRP --- compared to the efficiency reported for single-index refractive designs in prior literature. In another case, a single lightfoil was optimised for stability, and had its maximum corrective torque increased by over that of the initial proposal. However, the optimisation process was shown to be highly sensitive to the configuration of both the simulation and the optimiser AI. For example, identical fitness functions applied to different initial geometries often resulted in very different solutions. Furthermore, geometries were seen to lose resolution during optimisation as a result of the optimiser removing `low reward' vertices from convex hull calculation. These findings demonstrate the validity --- but also the complexity --- of using model-free reinforcement learning for the design of non-imaging optical devices.
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The manufacturing of transmissive solar sails was investigated with a focus on feasibility, cost, and accessibility from the perspective of a small satellite developer. The viability and cost of executing processes in-house was compared with the cost of commercial outsourcing, and several in-house trials were conducted. For fabricating the unpatterned sail sections, thin film fabrication trials were carried out using doctor blading and a water-float method. For fabricating patterned moulds, greyscale lithography and dry plasma etching comprised the conventional manufacturing methods trialled, while digital light processing and two-photon polymerisation comprised the additive methods trialled. Finally, pattern transfer trials included silicone moulding, linear thermal nanoimprint lithography, and roll-to-plate UV nanoimprint lithography. The evaluation favoured a commercial solution for the thin film fabrication stage. For mould manufacture, several viable conventional and additive methods were discussed, but a clear winner was not identified. For the pattern transfer stage, procuring a rolling nanoimprinter for in-house use was favoured above a certain volume or size of sail. A prototype solar sail payload was also designed for the University of Nottingham CubeSat {\it{JamSail}} in preparation for a future in-orbit demonstration mission
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