University of Birmingham
University of Birmingham Research Archive, E-theses RepositoryNot a member yet
11811 research outputs found
Sort by
Assessing sustainable livelihood diversification in Goderich, Freetown, Sierra Leone
Full text linkThis thesis provides a thorough examination of the application of the Sustainable Livelihood Framework (SLF) in Goderich, Sierra Leone, highlighting its importance in addressing the livelihood challenges faced by peri-urban communities in the Global South. The study employed a mixed-methods approach, integrating both qualitative and quantitative data to explore the complexities of livelihood diversification and resilience within the framework of socio-economic and environmental constraints. This study enhances our understanding of how local populations manage risks, disturbances, and resource constraints to sustain their livelihoods. It incorporates livelihood solutions into the broad theoretical frameworks of urban political ecology, sustainable development, and rural-urban dynamics.
The results emphasise the potential of personalised interventions to enhance existing community programs, address urgent needs, and foster long-term sustainability. Significant findings reveal that strategies for diversifying livelihoods, informed by the Sustainable Livelihood Framework and diversification theory, effectively mitigate risks and enhance resilience, particularly in response to global challenges such as the COVID-19 pandemic. The study emphasises the significance of governance frameworks, social capital, and natural resources in influencing livelihood results, promoting policies that amalgamate local viewpoints with global sustainability initiatives.
This thesis contributes to the academic discourse by contextualising the SLF within the intricate interactions of environmental, economic, and social factors. It offers evidence-based recommendations for enhancing livelihood resilience and sustainability in marginalised situations, significantly contributing to academic knowledge and practical policies. The findings are intended to inform development policies that are designed to improve the socio-economic well-being of at-risk regions, including Goderich, by reducing vulnerability and promoting equity
Images of divine nursing in the ancient Egyptian New Kingdom: kingship, kinship, and the role of the goddess
Full text linkThis thesis explores the use of divine nursing imagery – depictions of the king being nursed by a goddess – during the ancient Egyptian New Kingdom (ca 1539–1292 BCE) by considering the layers of context that shaped their creation and usage, including their physical, decorative, geographical, and social contexts. Research into this imagery has tended to examine it as a standardized and homogeneous motif across period and location. This thesis challenges this idea by analyzing the adaptations and variations across appearances of the motif as well as shifts in audience and medium to determine how it functioned within the specific decorative programs and narratives in which it was located.
Chapter 2 considers the social context in which images of divine nursing were created and viewed, using archaeological, art historical, and textual evidence to explore ancient Egyptian practices and ideas regarding breastfeeding and wet-nursing during the New Kingdom. Chapters 3–5 presents a series of case studies which seek to reconstruct the layers of context around specific divine nursing scenes and address some seemingly “unusual” depictions that emerge during the New Kingdom. Chapter 3 analyzes the scene of Thutmose IV nursed by Hathor and Werethekau at the temple of Amada in Nubia, the first divine nursing scene to appear in Nubia and a unique adaptation of the double nursing pattern. By considering its context, the scene’s role in efforts to assert Egyptian control in Nubia become more evident. The geographical implications of divine nursing continue to be apparent as Chapter 4 examines the nursing cow-goddess subtype of divine nursing imagery. This case study examines a group of divine nursing scenes tied geographically and iconographically largely to the region of Deir el-Bahari and which were combined with or inserted into existing Hathoric imagery, adding to the layered meaning and functionality of the images, statues, and votive offerings on which it appears. Considering the shift from temple wall reliefs to more public-facing and portable objects, Chapter 5 examines the appearance of divine nursing on stelae. This group of seven stelae represents the range of forms the divine nursing motif took during the New Kingdom and its expanded audience. The imagery takes on elements and implications of self-presentation, communication, relationships, and ritual. Finally, Chapter 6 considers the themes and patterns that appear across these case studies, how they compare with prior research on divine nursing imagery, and how they might influence future approaches to the scenes. I propose that to better understand divine nursing scenes it is more effective to consider divine nursing as an action that could be incorporated or adapted into existing imagery, rather than a static image with largely the same implications across period and location. It was a means of creating relationships and informing the social identity of king, goddess, and image commissioner
In situ characterization of additive manufactured 316L stainless steel and copper
No full textAdditive manufacturing, particularly laser powder bed fusion (L-PBF), has revolutionized the metal manufacturing industry by offering enhanced design flexibility, reduced material waste, and accelerated production capabilities. L-PBF metals exhibit enhanced strength, hardness, and corrosion resistance, but their durability is still limited by porosity and residual stress. This study aims to determine the underlying deformation mechanisms, deepen understanding of the relationship between microstructure and properties, and improve the reliability of L-PBF metals with heat treatment, specifically focusing on 316L stainless steel and copper. Advanced in situ synchrotron techniques provide a real-time insight of the relationships between microstructural evolution and material properties. The superior strength, ductility, and strain hardening ability of L-PBF 316L stainless steel, is shown to be attributed to its specific microstructural features such as high dislocation densities and crystallographic orientations. Furthermore, the impact of varying heat treatment temperatures on the mechanical behavior and fracture toughness of L-PBF metals is systematically examined. Extending the analysis to L-PBF copper, the study investigates microstructural changes and physical properties post heat treatment. It identifies grain coarsening, twinning phenomena, and improvements in ductility, with high electrical and thermal conductivity achieved after heat treatment. Finally, the nucleation and propagation mechanisms of cracks are revealed
Selective extraction and upcycling of LiMn2O4 cathode material from first-generation lithium-ion batteries
Full text linkThe lithium-ion battery scrap pool is set to grow extensively in volume as first-generation electric vehicles reach their end-of-life in upcoming years. There are many key environmental and socioeconomic drivers for the recycling of lithium-ion batteries (Li-ion batteries, or LIBs) and methods to extract and process solid-state electrode materials are an essential part of the recycling process.
Some electrode materials from first-generation cells, such as lithium manganese oxide spinel, or LiMn2O4 (LMO), are no longer extensively used in current-generation vehicle cells. Therefore, in this thesis, experiments investigating the “upcycling” of LMO from lithium-ion battery cathode material are outlined, from quality control-rejected and end-of-life cathodes, in an array of experiments.
In the first results chapter LMO is selectively extracted from quality control-rejected (QCR) and end-of-life (EOL) cathode material followed by interconversion into an array of upcycling products. The experiments outlined highlighted the effectiveness of a selective leaching process for the extraction of LMO from spent cathode material and the success of the interconversion explored. The LMO, Mn oxalate dihydrate, Mn2O3 and Mn3O4 products formed with structures Fd3 ̅m, C12/c1, Pcab and I41/amd respectively, across the pristine and leached QCR and EOL samples in all cases, with minimal contamination that did not jeopardise the material structure, indicating this success.
In the second results chapter, upcycling experiments are conducted with QCR and EOL-derived Mn oxalate to generate MnO─C nanocomposite conversion anodes. In the first section synthetic conditions are investigated to manufacture nanosized MnO suspended in a carbon matrix to ensure that intrinsic issues seen for conversion electrodes, that lead to poor capacity retention, are minimised for optimal electrochemical performance. The conditions chosen for this synthesis involved a mechanochemical route followed by an inert atmosphere heat treatment step, whereby the mechanochemical product was heated to 600 °C and held at this temperature for 4 hours under nitrogen. These conditions gave rise to the desired nanoMnO─C composite for subsequent electrochemical analysis, which was then applied to generated nanosized carbon composite Mn (II) oxide electrodes from lithium-ion battery-derived Mn-based precursors. The electrochemical performance of these leached nanocomposites highlights the upcycling opportunity for redundant LMO leached from QCR and EOL cathodes, with capacities of 777 (±12), and 916 (±37) mAhg-1 reached after 15 cycles, respectively. These capacities exceed the theoretical capacity for MnO, at 755 mAhg-1, significantly in the EOL case, highlighting the potential for upcycled products from leached cathode materials.
In the final chapter Mn oxalate, generated from pristine and leached material in the first chapter, is studied as a conversion anode. Though this anode material has been investigated in the literature, this chapter outlines innovative experiments to develop an electrochemical understanding of Mn oxalate anodes and to determine whether upcycled QCR and EOL Mn oxalate exhibit enhanced electrochemical behaviour when compared to the performance of pristine material. Firstly, electrochemical conditions are tailored to probe the anode material’s fascinating capacity behaviour, by cycling the anode to a 2 V and 3 V voltage maximum. By the 100th cycle, the discharge capacity of the 2 V max cells averaged out at 160 (± 7) mAhg-1 and the 3 V max cells averaged out at 723 (±8) mAhg-1 at 14% and 70% of their first discharge capacity, respectively, indicating the effect of the 3 V maximum voltage on capacity retention. Furthermore, redox activity was much more significant out to 100 cycles for the 3 V max than the 2 V max anode, as exhibited in differential capacity analysis, which indicates that the 3 V max cell undergoes additional redox activity through increased oxidation state of Mn, or even through anionic redox of the oxalate group within the polyanion. In-situ pair distribution function (PDF) analysis gave additional insights into the origin of the interesting electrochemical behaviour, indicating that the conversion product at the end of the first cycle does not resemble Mn oxalate. This structure at the end of charge has been hypothesised to match with a zincblende-structured MnO with space group F4 ̅3m, countering the reports of the reversible conversion reaction outlined extensively in the literature for Mn oxalate, but providing more insights into the electrochemical deviation between the 2 V and 3 V max half-cells. Finally, the electrochemical behaviour of Mn oxalate derived from pristine and leached QCR and EOL LiMn2O4 has been explored to determine the success of upcycling LMO into Mn oxalate conversion anodes. After 100 cycles the capacity recovery of the 3 V max cycled half-cells remained as high as 650 mAhg-1 for the QCR and 475 mAhg-1 for the EOL sample, proving to be highly successful in upcycling the interconverted LiMn2O4 into Mn oxalate material. Though the capacity retention after 100 cycles was lower with an increased degree of contamination from the leached samples, the capacity still outperforms the expected capacity based on the theoretical calculation, at 375 mAhg-1
Decarbonising the energy system with an integrated high temperature electrolyser and fuel cell
No full textThis thesis presents an innovative integrated power-to-gas (PTG) energy system, primarily focusing on decarbonising the power generation sector and heating networks. It introduces a system-level simulation model combining Solid Oxide Electrolysers (SOEs), Molten Carbonate Fuel Cells (MCFC), Solid Oxide Fuel Cells (SOFC), and a methanation unit. The study explores the system's ability to produce electrical energy, methane, oxygen, biomethane, and thermal energy, thus contributing to sustainable and clean energy production aligned with the seventh UN Sustainable Development Goal, which emphasises 'Clean Energy'.
The research demonstrates over 85% CO separation using an MCFC for upgrading raw biogas and methane production. A comprehensive techno-economic analysis of the fuel-cell-based PTG integrated energy system is conducted, focusing on thermodynamic efficiency and economic viability. The study also highlights the potential of leveraging in-situ CO for PTG technology through the upgradation of raw biogas.
The proposed system achieves significant efficiencies: an energy efficiency of 79.7% and an exergy efficiency of 55.5%. It is economically viable, with a calculated levelised cost of energy (LCOE) of £72.2 per MWh and a payback period of 2.92 years. The system model is detailed and validated using data from literature, and it integrates various subsystems, each with its flowsheet and auxiliary units, into a novel PTG energy system.
The thesis concludes by identifying challenges in commercialising cost-effective fuel cell technologies and the uncertainties in energy demand. Future research directions include conducting in-depth analyses using real-world energy demand data, exploring the integration with a steam turbine for enhanced power generation, and conducting experimental tests to validate the model and assess the impact of pollutants on cell performance and lifespan. This research opens new avenues for various engineering fields by integrating sustainable practices into project designs and contributes significantly to the power-to-gas field
Application of Nanomaterials in Precision Agriculture to Optimise Nitrogen Use Efficiency and Increase Global Food Security
No full textEngineered nanomaterials (NM) are man-made nanoscale compounds, with at least one dimension between 1-100nm. Their utilisation presents a novel method to reduce the excessive use of synthetic fertiliser prevalent in industrial agriculture. The excess synthetic fertilisers are lost through the gaseous emission of N compounds, including N2O, NH3 and NOY, as well as through surface run-off and groundwater losses, increasing NO3- and NH4+ concentrations in waterways, impacting water quality. For NMs to be effective and sustainably used in agriculture there are several essential considerations that must be optimised: increased crop productivity and quality; positive effects on nutrient biogeochemical cycling, particularly N cycling to reduce emissions and run-off; and limiting impacts on soil biota including microbes and soil fauna, like earthworms.
The effects of NM exposure on seed germination were tested using seed priming experiments. NM effects were both species and NM dependent, although trends within “classes” of NMs were hard to predict, with constituent elements, concentration, agglomerate size, zeta potential and more sophisticated structure, like pore size, all impacting NM-plant interactions. NM application to soils in conjunction with reduced fertiliser application was used to determine NMs effects on plant growth and N cycling, using N2O gas sampling and N compound losses in leachate. Zeolite NMs can have very different effects on terrestrial N cycling, with the sophisticated structure of the NM likely the root cause of these differences. Zeolites of the same type, like BEA-19 and BEA-150, were used in different soils and had very different impacts on N emissions and losses, reflecting the importance of NM characteristics, on NM environmental effects. BEA-150 triggered elevated N2O emissions in the presence of microbes, while ZSM-5-15, another zeolite, decreased emissions in this soil type and increased them in another. This is indicative of the importance of soil abiotic factors, like soil moisture, clay and colloids, and soil microbial community composition on NM effect. Increased N2O emissions may be generated through a process of ion exchange, with ZSM-5-15’s extra-framework ion being exchanged for H+ ions in its pores, leading to an increase in NH4+ accessible for nitrifying microbes to act upon and increasing nitrification derived N2O. Wider effects of NMs on the soil environment were studied using earthworm reproduction assays. ZSM-5-15 also triggered sub-lethal effects on reproduction of the earthworm Eisenia fetida, reducing the number of unhatched cocoons at 25 mg L-1, a relatively low concentration. This may be through lower concentrations producing smaller NM agglomerates that are more able to pass through the worm epithelia and thus result in higher exposure at lower concentrations.
Ce0.75Zr0.25O2 NMs didn’t increase N2O emissions in the loam soil studied but did in the sandy loam, also increasing NO3- leachate concentration. Ce0.75Zr0.25O2 leaches Zr4+ ions into soil, transforming the NM into Ce0.9Zr0.1O2 and CeO2, as determined using X-ray near-edge absorption spectroscopy (XANES). Ce0.75Zr0.25O2 is able to translocate from lettuce roots to shoots, with the NM found in aboveground lettuce tissue after soil-based NM application. Zr metal and ZrCl4 were also found to be present in lettuce leaves, but whether these transformations occur in the soil before uptake and translocation or in lettuce shoots and leaves after uptake is uncertain. Other nano metal oxides used were TiO2 PVP and Co2.25Fe0.75O4 which were both applied in hydroponic medium. NM impact on N2O emissions from hydroponics was minimal, however K15NO3 stable isotope application showed that the majority of the N2O emissions were nitrification derived. This reflects the aeration of the rockwool substrate that the lettuce roots were grown in. TiO2 PVP and Co2.25Fe0.75O4 NMs may act on denitrifying microbes hence the minimal impact they have on total N2O emissions.
NM co-application with synthetic fertiliser was found to increase the risk of N losses to the environment, while NMs with nutrients as part of their physical structure may be able to limit these losses. Urea-doped amorphous calcium phosphate (U-ACP), a hydroxyapatite NM with both N and P within its structure, was able to reduce NOY emissions from soil. The lack of N2O and NH3 gas data however means that there are several N cycling endpoints that are missed, so whether U-ACP application reduces net N losses or shifts the balance of the soil N cycle is unknown. U-ACP increased lettuce production as compared to urea, with this mostly being derived from urea application triggering soil acidification and limiting lettuce growth. U-ACP application also increased the community of nitric oxide reductase (qNorB in particular) expressing soil bacteria, indicative of an increase in the soil microbial community active in denitrification.
Understanding NM impacts on N cycling is essential for a holistic view of fertilisation and for nano-enabled agriculture to truly increase sustainability while minimising the risk of regrettable substitutions. This thesis presents a first step towards achieving this holistic view
Optimising recombinant protein production in E. coli
No full textRecombinant protein production (RPP), the heterologous overexpression of high-value proteins in more amenable host organisms, is essential for synthesising proteins used in research and with commercial or clinical applications. The use of Escherichia coli, exploited as a host in RPP for over 40 years, is not without caveats; this work has addressed several. Firstly, green fluorescent protein (GFP) was overexpressed from the urea inducible Proteus mirabilis urease promoter Puti101 as a cost-effective alternative to established systems. Optimisation from flask to bioreactor scale indicated that basal GFP expression from Puti101 was low, typically around 2.5-fold higher than that of untransformed cells. Adding urea resulted in an up to 75-fold increase in GFP expression; even concentrations up to 500 mM were shown to have little effect on biomass accumulation. Secondly, many valuable proteins require disulphide bonding for bioactivity, necessitating periplasmic expression in E. coli. Oxidation-resistant GFP derivatives sfGFP and cfSGFP2 were evaluated under RPP-centric conditions to understand their application in improving screening throughput. While the export of GFP to the periplasm was detrimental to host physiology, super-resolution microscopy supported prior indications that periplasmic sfGFP fluoresces. Finally, as periplasmic expression was problematic, our focus shifted to detecting host stress via GFP fusion to the Pspy promoter from the periplasmic chaperone spheroplast protein Y (Spy). Pspy responded to both overexpression of periplasmic recombinant proteins and direct inhibition of translocation machinery. Then, combined with novel repressors, Pspy was exploited as a trigger for negative feedback to greatly improve host physiology during overexpression of poorly tolerated periplasmic recombinant proteins
Investigating how post translational modifications of p97 affect its function and regulation during DNA synthesis
Full text linkp97 is a AAA+ ATPase with very diverse functions, from DNA replication to proteolysis. However, it is unknown how p97 is regulated throughout the cell cycle to affect the variety of its substrates differently in the right place and at the right time. In DNA replication, it is involved in removing the helicase from the chromatin when replication has ended. A previous member in the lab, discovered that p97 has different post translational modifications in S and M phases of the cell cycle including phosphorylation and ubiquitination. His-tagged mutant p97 proteins were made that were either catalytically dead, phospho-dead, phospho-mimicking or ubiquitin dead. These were then tested in the cell free Xenopus egg extract to see how they affect the protein dynamics of the replication machinery components: Mcm7, PCNA, Psf2 and Cdc45 during DNA replication via chromatin isolations. The interactions of these mutants with some of p97’s cofactors were also studied via His-pulldowns and it was found that in S-phase, phosphorylation could increase interaction of p97 with Npl4 and p47, while in M-phase, it may also increase with p47 and Ufd1. When p97 is catalytically dead, it may increase interaction with Ufd1. Alongside this, RPA and WRN were identified as proteins that may interact with p97 during DNA replication
Unsupervised deep learning for removing structured noise in microscopy and flow cytometry
Full text linkMicroscopy and flow cytometry are pillars of life science research. They use agents such as light or electrons to analyse the structure and composition of biological samples at micrometre and nanometre scales. However, the samples can be damaged by this very process, resulting in observations that do not capture them in their most natural state. Illumination intensity must therefore be minimised, but this reduces the ratio of signal to noise. When signal intensity is limited by practical constraints, and noise cannot be mitigated at the time of observation, denoisers must be employed to estimate the signal underlying a noisy observation post hoc. Currently, the most accurate estimates are made by deep learning-based denoisers. Their strength comes from utilising the information contained in training data, but this is also one of their greatest limitations.
To reliably remove all forms of noise, existing deep learning-based denoisers require paired training data, typically consisting of noisy observations and corresponding clean signals. In the life sciences, paired data and clean signals may be unobtainable. Techniques exist to train denoisers with unpaired noisy observations, i.e., the very data that is to be denoised, but these face another challenge: structured noise. Structured noise is prevalent in both microscopy and flow cytometry, and it is defined as noise that is correlated over pixels or time points. Currently, no deep learning-based denoiser can reliably remove it without either paired training data or by making sacrifices in the quality of the output.
In this thesis, we develop unsupervised deep learning-based denoisers for structured noise as it commonly occurs in microscopy and flow cytometry. These methods are trained without paired observations or clean signals, and have quality approaching and sometimes exceeding that of denoisers trained with paired data. We also identify another limitation of unsupervised deep learning-based denoisers – their slow inference time – and present a method to reduce their inference time by three orders of magnitude. We believe that the methods presented here will remove some of the biggest barriers to applying deep learning denoisers to life science data
Characterisation of low gain avalanche detectors for large area precision timing at particle colliders
Full text linkLow Gain Avalanche Detectors (LGADs) are the chosen technology for the timing layers which are to be placed in the forward region of the inner trackers in the ATLAS and CMS experiments. Teledyne e2v (Te2v) is a silicon foundry known for producing large volume CCDs. This work aims to establish them as a future vendor of LGADs, particularly for High Energy Physics applications. Experimental set-ups and techniques have been successfully developed and refined in order to characterise the IV, CV, gain and timing properties of LGADs. Characterisation has been completed before and after irradiation with 27 MeV protons at the MC40 cyclotron in Birmingham. These results are reported here with key values compared to LGADs from alternative vendors. Te2v’s LGADs achieve sub-40 ps time resolution at a gain of ∼20 or above. The time resolution also behaves similarly as a function of gain compared to other vendors. After irradiation, they can still achieve this time resolution below a fluence of 5.7 × 1014 1 MeV neq/cm2. At this fluence and above, the timing performance is limited to 50 ps at a gain of ∼10. Gain non-uniformity across similar devices was observed in IV and gain measurements. The acceptor removal coefficient was measured to be (9.7 ± 0.5) × 10−16 cm2, 45 % larger than reported for Fondazione Bruno Kessler’s (FBK) UFSD2 production where it is 6.7 × 10−16 cm2. Overall, this work has demonstrated that Te2v is capable of manufacturing LGADs with comparable performance to existing vendors. With further refinement of the gain layer implant energy and dose, Te2v would be a highly competitive supplier with potential for meeting the large orders anticipated for many future particle physics facilities
Data sources:
Access Repository Dashboard
Do you manage Open Research Online? Become a CORE Member to access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard! 👇