University of Birmingham
University of Birmingham Research Archive, E-theses RepositoryNot a member yet
11811 research outputs found
Sort by
Development of novel bioactive restorative materials
No full textSubgingival defects/root lesions are becoming increasingly prevalent as life expectancy is increasing globally (WHO) and teeth are retained for longer. These lesions result from attrition/abrasion or caries following the root surface exposure due to gingival recession. Restoring such defects is challenging because of the difficult isolation and the proximity to gingival tissues which could trigger periodontal inflammation due to biofilm formation and/or material toxicity. The current understanding of the interaction between resin-based restorative materials and the soft tissue is still limited. Therefore, the present work aimed to provide a deeper understanding of cellular and bacterial interaction with commonly used resin-based materials and a novel restorative material by performing a wide range of long and short-term bulk/surface characterisation, before correlating these properties -together with the material leaching profile- with epithelial and bacterial attachment to the material surfaces. Thereafter, bioactive surface coats to be applied on commercial materials were proposed and investigated for their ability to improve cellular interaction with the material and exerting an anti-bacterial effect. Viable H400 cell attachment on fresh/aged specimens was determined quantitatively (using the trypan-blue dye exclusion assay) and qualitatively using SEM. The indirect effect of the test materials leachate concentrations on cell attachment to tissue culture wells were also investigated. Attachment of Streptococcus oralis (S. oralis) and Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) was investigated quantitatively using a direct contact test and morphologically using SEM.
Significantly more viable cells were found attached to the Sr-prototype compared with other materials for both fresh and aged samples. SEM revealed higher number of attached cells on the Sr-prototype which showed more spread and cellular processes extending to neighbouring cells. Spearman’s correlation revealed positive association between the number of viable cells attached
to the material surfaces and pH of the media, surface roughness values, surface Si wt.% and Si4- and Sr2+ ion release. For all materials leachate concentrations, cells exposed to the Sr-prototype leachates showed significantly higher attachment to the cell culture wells compared with other materials. Two-way ANOVA revealed that the interaction between material type and leachate concentration significantly affected viable cell attachment (F(10,144)=38.99, P<0.0001). Spearman’s correlation revealed a strong negative relationship between viable cells attached to the well plates and the Al3+ released from the material (100% leachates) as well as the leachate concentration.
Sr-substituted bioglass coatings (SrC) significantly increased surface roughness and changed the surface of the RMGI as SEM-EDS demonstrated decreased Al wt.%, a higher C-O wt.% ratio and the absence of fluoride on the modified surfaces. Poorly crystalline strontianite was formed on SrC after 48 h immersion in culture media. SrC surfaces did not cause the acidity induced by non-modified surfaces (NC) in the culture media. Significantly more cells were attached to Sr-modified surfaces than to NC. Spearman’s correlation revealed positive correlation between viable cells attached to material surfaces and the media pH, surface roughness and Si4-\Sr2+ ion release while negative correlations were found with the Al3+ released and F surface wt.%. In regard to antibacterial properties, the Sr-prototype caused a significant reduction in both S. oralis and A. actinomycetemcomitans colonies compared with control. Likewise, SrC surfaces caused a statistical reduction in both bacterial species counts compared with NC.
The Sr-substituted bioglass could provide a promising potential as a filler for dental composite/surface coat for root restorations as it promoted epithelial attachment (in both direct and indirect contact tests) which can offer a mechanism to prevent gingival recession and at the same time exert an antimicrobial effect
Towards a hybrid framework for rainwater harvesting site selection in arid and semi-arid regions
Full text linkThe lack of precipitation and erratic rainfall patterns in arid and semi-arid regions of the world raise concerns about water scarcity. Rainwater harvesting (RWH) is a traditional technique employed to gather and store rainwater for diverse uses such as drinking water and agricultural applications. A number of frameworks, each with its unique set of criteria, have been developed in recent decades to help detect and prioritise locations for rainwater harvesting (RWH), an essential technique not only for the preservation and enhancement of water resources but also as a key component of sustainable integrated watershed management. To rank possible sites, these frameworks were created using what are known as structural criteria (biophysical and socio-economic). While these frameworks are effective in identifying potential sites for RWH, they often do not account for the broader ecological criteria that are essential for the sustainability of the watershed system as a whole. The sustainability of the system, regulatory compliance, climate resilience, biodiversity preservation, water quality improvement, and environmental protection are all dependent on ecological criteria. In this study, this deficiency is addressed by the development of a hybrid framework which combines structural criteria with important ecological criteria. Planning to identify rainwater harvesting sites in arid and semi-arid regions based on various criteria—namely biophysical, socioeconomic, and ecological—is a complex issue especially when including ecological criteria. The first part of this thesis involved a systematic review to identify the gaps in knowledge and the criteria used in existing frameworks. The conducted systematic review is based on the two major databases of Scopus and Engineering Village. Sixty-eight relevant studies were found and critically analysed to identify patterns and unique features in the adopted frameworks. The results of this review reveal that 41% of the frameworks consider both biophysical and socioeconomic criteria, whereas the remaining 59% of the frameworks depend solely on biophysical criteria. The importance of each criterion is encapsulated through a suitability score. The term "scale" is used here to refer to the system or range used to rate or measure how well a site aligns with specific criteria for suitability, whether through a binary indicator (match or no match) or through graded scales of varying levels of detail. The first scale which accounts for 21% of the frameworks uses a binary (0 or 1) indicator of whether the site matches a criterion or not. While the other frameworks use graded scales of differing granularities, with 52% using a low-resolution scale of 1 to 3, 4, or 5. This is followed by a 7% that uses a medium-resolution scale of 1 to 10, and a further 7% using a high-resolution scale of 1 to 100. The remaining 13% of the frameworks did not specify the scale used. Importantly, this part of the thesis concludes that all existing frameworks for selecting RWH sites are solely based on biophysical and/or socioeconomic criteria; ecological impacts, the consideration of which is vital for building RWH systems sustainably, are currently ignored. The latter part of the thesis is to identify the important ecological criteria and their corresponding weights as well as to use a case study to apply the framework. The important ecological criteria have been identified based on additional literature review. The inter-relationships of ecological criteria are complex, with “independent” criteria affecting the “mediator” criteria (e.g. dissolved oxygen, phosphorous concentration) which directly impact ecological standards, i.e. the “dependent” criteria such as the number of aquatic organisms. This study focuses on the key independent criteria of temperature and light, which are prioritised based on findings from the analysis of the literature. These findings have shown temperature and light to be the most influential factors affecting water quality criteria. However, the hybrid framework could easily be expanded to include additional ecological criteria, depending on the region to which it is applied. The framework encompasses independent, mediator and dependent ecological criteria identified from the literature, and the importance of each (represented as weightings in the framework) has been quantified through a robust combination of data analysis and expert opinion. The importance of the ecological criteria inclusion is demonstrated through a case study of Erbil Province in Iraq, where both climate change and human actions have seriously reduced water supplies in the past 20 years. A number of proposed rainwater harvesting sites are assessed via a structural and the new hybrid framework. The results demonstrate that the inclusion of these ecological criteria changes the ranking of the sites. Four different sites for rainwater harvesting (RWH) were chosen within Erbil city, each identified by its specific geographic coordinates. The hybrid framework implemented on these sites encompasses two distinct scenarios. The first scenario incorporates three key components: biophysical, socio-economic, and ecological criteria. In contrast, the second scenario integrates two components: biophysical and socio-economic criteria. For the first scenario, the suitability scores for the sites, listed in sequence from site numbers 1 to 4, are as follows: 1 (2.71), 2 (2.52), 3 (2.13), and 4 (3.31). For the second scenario, the suitability scores for the sites, listed in sequence from site numbers 1 to 4, are as follows: 1 (2.53), 2 (2.62), 3 (2.26), and 4 (3.03)
Sexual consent amongst young men who have sex with women: how it can be conceptualised, practised and influenced
Full text linkThis research explores how young men who have sex with women, aged 18-25, conceptualise consent, narrate their experiences of practising consent and the personal and contextual factors which influence these two things. Explicit, affirmative consent is widely considered to be ideal; however, it is a theoretical conceptualisation of consent involving a simplistic communicative exchange. Previous research has shown that most adults will define consent as following the affirmative model, but their consent communication in practice does not often follow this model and is more complex, nuanced and fluidly influenced by context. Thus, there is a need to consider how consent is practised in a real-world context when individuals are seeking positive, consensual sexual experiences. This study foregrounds young men’s real-world consent communication experiences, how that communication functions, their feelings about consent and the influence of different contexts.
The research is an Interpretative Phenomenological Analysis (IPA) study which centres experience. The qualitative methods involved two in-depth interviews and six weeks of diary entries. During the six weeks, participants were given a sample set of pornography which showcased explicit consent to aid their reflections. When discussions about consent can be highly theoretical, an audio-visual vignette can be a useful resource to ground conversations in a sexual context and aid reflection; and this was the case for the participants.
The key finding was that the participants used mostly physical communication strategies in the moment to navigate consent throughout evolving sexual experiences. However, the participants also engaged in verbal communication with their partners outside of the moment in the form of ongoing conversations about boundaries and desires, which aided their physical communication during sex. The major contribution to the field is the production of a new model for understanding consent communication during sexual experiences: Coordinated Management of Consent (CMC). CMC should not be interpreted as an ideal way to communicate consent but is instead a descriptive model which outlines the participants' processes of communication; how this sample of people approached and enacted consent. In other words, it is a means of describing how the participants practiced consent and what guided their practice
Developing an intervention to reduce sedentary behaviour in non-ambulant young people with long-term disabilities (domore)
No full textThere is strong evidence that sedentary behaviour (> six - eight hours / day) increases risk of all-cause mortality, risk and incidence of cardiovascular disease mortality and incidence of type 2 diabetes in adults. Reducing children and young people’s sedentary behaviour is also likely to positively impact health outcomes. Guidelines therefore advise children and adults to limit their sedentary time.
Children and young people with disabilities experience barriers to reducing sedentary behaviour. Non-ambulant young people (NAYP) with physical disabilities spend more time sedentary than able-bodied and ambulant young people with disabilities. No evidence-based interventions for NAYP specifically target sedentary behaviour.
The aim of this thesis was to co-design a digital behaviour change intervention (mobile application), which supports NAYP to reduce and break up sedentary behaviour by promoting light physical activity. The app was co-designed in partnership with stakeholders, using the Six Steps in Quality Intervention Development (6SQuID) model. Stakeholders included NAYP aged 12-25 years, family members of NAYP, health and educational professionals and experts in sedentary behaviour, disability and behaviour change / intervention development.
Step one of the 6SQuID, defining and understanding the problem and its causes, is reported in Chapters 2, 3 and 4. Undertaking a systematic search and review of the literature relating to sedentary behaviour and NAYP contributed to a defining of the problem and informed intervention development (Chapter 2). To understand the problem and its causes, a thematic analysis of data generated by stakeholders was undertaken to identify barriers and facilitators of sedentary behaviour of NAYP. Two data collection methods were used: an innovative digital methodology (crowdsourcing) (Chapter 3) and virtual co-design workshops and interviews (Chapter 4). This was the first time crowdsourcing had been used to collect data as part of the 6SQuID. The Systems of Sedentary Behaviours (SOS) Framework describes six determinants of sedentary behaviour. The barriers and facilitators of sedentary time in NAYP identified by stakeholders were categorised into the six SOS Framework determinants of sedentary behaviour, prior to step two.
In step two (Chapter 5), stakeholders ranked the SOS Framework determinants of sedentary behaviour according to their potential for change. Three SOS Framework determinants which were amenable to change were selected. Fifteen barriers / facilitators to address within the intervention were chosen from these three determinants. The 15 barriers / facilitators were combined to formulate five intervention goals.
Step three (chapter 6) involved selection of a mid-range theory (Self-Determination Theory) to inform development of programme theory and production of a logic model for the intervention. Using the Behaviour Change Wheel (COM-B) approach, 11 mechanisms of action and 32 behaviour change techniques were selected from two taxonomies. Further data collection with stakeholders informed this decision making. Potential unintended outcomes of the intervention were discussed.
The thesis concludes at step four of the 6SQuID, delivering the change mechanisms. An implementation plan was formulated with stakeholders. A prototype app was produced and evaluated, using the Person-Based Approach to supplement the 6SQuID model. A table of changes prioritised modifications to be made in a first iteration of optimisation prior to feasibility testing (step five). Strengths and limitations of this work and directions for future research are outlined in Chapter 8
Transfer learning of sentiment analysis between highly dissimilar domains
No full textThe aim of this thesis is to improve upon the current state of transfer learning technology in text based problems, with a specific focus on sentiment analysis. This improvement is in the form of increased distance between training and target domains. It proposes a method for defining inter-domain distance. Then examines the shortcomings of classical transfer learning methods, and proposes two novel approaches. The first `TransferGAN' extends on the use of Adversarial Learning Techniques for transfer learning, and the second demonstrates how Grammatical Evolution can be used to optimize existing sentiment analysis techniques to better suit transfer learning between dissimilar domains. Both of these methods demonstrate improvement over the comparison systems for transfer learning sentiment analysis with a high inter-domain distance. Finally these systems are demonstrated to be effective against the Motivational Interview dataset (A dataset of clinical conversations between diabetes patients and clinicians), which was the primary motivator for this work. This work could be further extended by field-testing of the systems against real world usage of the Motivational Interviews, and by working with clinicians to refine the system for automatic assessment of the Interviews
Recycling of lithium-ion batteries
No full textThe demand for electric vehicles has greatly increased, driven by the public’s awareness of global warming and electric vehicles being part of the solution to reduce greenhouse gas emissions that are the cause of it. Although electric vehicles have been shown to be better for the environment it is important that they are treated correctly at the end of life as they contain many valuable and hard-to-extract materials within them, particularly within the battery pack and the cells therein. Recycling of cells has the potential to further boost the environmental credentials of electric vehicles (and other battery-powered devices). Recycling of cells already takes place and more processes are being developed, however, more work is still needed. The work presented in this thesis focuses on understanding how we can move towards zero-waste recycling processes. To understand how we recycle lithium-ion batteries, we need to understand the current composition and construction of the different cells, and if we are to improve our materials reclamation yield, and if there is any scope for an improved design for disassembly.
Chapter 4 characterises three cell types: cylindrical (end-of-life samples), pouch (production scrap samples) and prismatic (end-of-life samples). Indicative of the cell types in the current market. A complete cell tear-down and cathode materials evaluation is performed with a critique and discussion of how improvements can be made for design for disassembly and recycling. This is the first time that a range of commercial cells have been compared using the same suit of techniques, and their recyclability has been the focus.
In Chapter 5, this work will look at organic acids. Can these be used for the direct recycling of cathode black mass? For this to be the case the recovered black mass must have greater capacity than the End-of-life cell (107.62 mAh/g as found by preliminary testing). Otherwise, can organic acids be used as a pre-treatment step for valorisation and hydro-metallurgical treatments? For this, the leaching of metals must be controlled. Depending on the desired outcome various acids were successful for example, if retaining nickel in the black mass is the goal, succinic acid is the most effective for separation. Conversely, if cobalt retention is preferred, citric acid should be used. If optimizing first-cycle capacity is the objective, acetic acid yields the best performance.
Chapter 6, the use of DMSO, (which is considered a green solvent, but still carries some challenges such as its ability to permeate the skin barrier and carry through transition metals) is investigated to further improve valorisation of the cathodic black mass using solvent delamination to enable better valorisation by avoiding leaching if possible. Stirring and ultrasonication were used to agitate the solution at a range of temperatures to find the optimum processing conditions for the release of black mass from the current collector. This is the first time DMSO has been used in the recovery and recycling of black mass, and the first time that optimisation has been carried out on this system
Unfolding shared semantic representations in vision and language
No full textWhen we interact with language, the brain effortlessly draws vivid mental images that resemble representations of directly perceived visual scenes. Similarly, research shows that the visual system encodes representations of visual scenes in a manner akin to how embeddings from large language models encode the meaning of a sentence. This implies that vision and language draw on a shared representational system for semantic encoding, but the precise nature of this visuo-linguistic overlap in the brain, as well as its implications for behaviour, remain unknown. The present thesis leveraged similarity judgements of natural scene images and their corresponding sentence captions to explore how vision and language converge in their ability to recognise semantic regularities of the visual world. We found that the visual and linguistic similarity judgements not only converge in the behavioural context but both also predict a remarkably similar network of visually evoked patterns along the mid- and high-level visual regions. Furthermore, we established the behavioural relevance by showing that the perceived dissimilarities in both vision and language effectively predict response times to a visual target primed by a sentence. Upon the observation that linguistic similarity judgements exhibit a higher interindividual variability, we used the participants’ own perceived dissimilarities to make predictions about their priming effect. This revealed that idiosyncratic linguistic dissimilarity is the strongest predictor of participants’ response times. The findings of the present thesis demonstrate that vision and language project their representations onto a shared similarity space, most likely embedded in the representational structure of the visual brain. Along with the observation that language plays a distinct role in eliciting individually relevant representations, these findings may profoundly impact our understanding of the visual system by placing greater emphasis on semantic idiosyncrasies
The moral complexity of the border: A critical examination of the normative foundations of admission and exclusion
No full textIt is common in popular and policy discussions to assume that states possess the near-unilateral right to set and enforce their own immigration policies without examining or articulating the underlying normative justifications. In recent years, various liberal theorists have examined the normative foundations of border admission and exclusion. While these approaches are unified in criticising particular border policies, they are highly polarised between those who view nearly all immigration restrictions as unjust and those who broadly support state discretionary control of immigration. This thesis examines the constraints that justice claims place on Western liberal democratic states’ immigration policies and argues that we cannot take for granted the claim that states possess a ‘right to exclude. It then argues that this broader debate in normative political theory suffers from two problems: (1) it uses a partial and idealised conception of the border, and (2) it offers an overly narrow response to the questions of whose freedom and what constitutes freedom. Finally, I argue that immigration policy must be constituted with reference to the freedom of both citizens and non-citizens based on their situationally defined claims
Resilience of river-based livelihoods on flood-prone area covering the lower Niger river in Nigeria
No full textClimate change exerts direct and indirect impacts on the livelihoods of local communities, fundamentally altering the behaviour of farmers and fishers reliant on natural resources. Shifts in climatic factors, notably temperature variations, significantly affect crop yields, thereby influencing the behaviour of communities relying on these resources. Adverse climate events, including floods and droughts, disrupt the economic stability of farmers and fishers, causing varying repercussions across global regions. The escalating frequency and severity of floods pose substantial challenges, impeding agricultural activities, damaging infrastructure, and displacing communities. This leads to income loss, food insecurity, and heightened vulnerability, necessitating resilient measures for river-based livelihoods to withstand and recover from severe flood events. This research employs a comprehensive methodology that integrates physical and human geography to explore the impact of changing climatic factors on floodplain communities' livelihoods. Adopting a mixed-methods approach, the study combines a household survey, key stakeholder interviews, and the analysis of climatic data covering a 30-year period (1991-2021) to provide a nuanced understanding of the vulnerabilities faced by communities along the Lower Niger River.
The primary data collection involved surveying 198 households, selected through a stratified sampling method, capturing diverse perspectives from small, medium, and large farmers, as well as fishers. Additionally, 24 key stakeholder interviews were conducted, identified in collaboration with the All-Farmers Association of Nigeria, ensuring a comprehensive representation of community voices. The use of both quantitative and qualitative methods enhances the robustness of the research, allowing for a multifaceted exploration of the challenges and adaptive strategies employed by these communities.
To analyse climatic trends, open-source terra climate data from the Climate Research Unit (CRU) dataset covering precipitation, runoff, and temperature trends from 1991 to 2021 were utilized. The examination of these climatic variables aims to unravel the intricate relationship between changing environmental conditions and the vulnerability of floodplain communities. Concurrently, a land use land cover change analysis spanning the same period was conducted, providing insights into alterations in the physical landscape.
The participatory approach in this research extends beyond traditional data collection methods, delving into the behavioural dynamics of farmers and fishers during extreme weather events. By assessing the risks posed by flooding and revealing coping strategies employed by these communities, the study goes beyond statistical analysis, providing a deeper understanding of the lived experiences of those directly impacted. The synthesis of quantitative and qualitative data allows for a holistic exploration of the interconnected factors shaping vulnerability. This research not only identifies the climatic stressors affecting floodplain communities but also examines the social, economic, and cultural dimensions that mediate their adaptive capacity. The research reveals multifaceted findings that intricately dissect the vulnerability of floodplain communities along the Lower Niger River. The climatic analysis spanning 1991 to 2021 uncovers alarming trends in precipitation, runoff, and temperature, underscoring the intensification of climatic stressors. Concurrently, the land use land cover change analysis exposes significant alterations in the physical landscape, pointing to the dynamic environmental shifts in the region. The findings highlight disparities in vulnerability, with small farmers facing heightened risks due to individual land ownership constraints and limited resources. Medium farmers, primarily family landowners, exhibit a slightly lower vulnerability, while large farmers demonstrate comparatively lower vulnerability, leveraging diversified land ownership.
The participatory approach delves into the behavioural dynamics of communities during extreme weather events. The study identifies significant risks posed by flooding, affecting agricultural operations, damaging infrastructure, and uprooting communities. Coping strategies employed by these communities range from traditional practices to innovative adaptations.
The study recommends the implement community-based climate education programs to enhance awareness and understanding of climate risks which can empower farmers and fishers to make informed decisions and adopt adaptive strategies. Furthermore, the study prioritizes infrastructure investments that bolster flood resilience, particularly for small farmers. This includes the development of flood-resistant agricultural practices, early warning systems, and improved transportation infrastructure
Powder bed fusion – laser beam of ti-6al-4v lattice structures for biomedical applications
No full textPowder bed fusion – laser beam (PBF-LB) as a technology of additive manufacturing, has provided great potential for the fabrication of porous lattice structures applied in orthopaedic devices to achieve anatomic and customised functions. However, the mechanical properties and surface characterisation involved in the osseointegration process remain challenges, causing patients risk in revision surgeries. The physiochemical properties of implants are governed by various behaviour of lattice structures and is subject to the nature of PBF-LB. To address this, the PBF-LB process need to be optimised to ensure the fabrication quality and stability of lattice structures. Fundamental understanding of lattice structures is required to satisfy wider designable possibility and improvement of mechanical and biological behaviours of skeletal devices.
First, the processing window and scanning strategy of manufacturing lattice structures with ultrafine struts thickness below 350 μm was investigated. Compared to the contour plus hatching scanning strategy, a single contour strategy was developed and optimized to ensure a more homogenous energy input for improving the geometric accuracy and internal defects reduction in lattice structures.
Secondly, performances of lattice struts with varying built angles and process parameters were studied. Both the mechanical and in-vitro biological response demonstrated the distinct impact of lattice struts angle. Results showed that under the optimised processing parameters, internal porosity can be reduced to 99.8% regardless of the geometric differences.
Considering wider feasibility of contour strategy for lattice manufacturing, multi-contour was explored to accommodate the PBF-LB fabrication of lattice structures composed with various geometries and dimensions design. Surface roughness, compressive test, and microstructures were conducted, illustrating that the ductility, surface condition and geometric accuracy and can be improved via multi-contour strategy.
At last, to further verify the potential of PBF-LB lattice structures via tailoring the struts angle, rotation strategy study was conducted and evaluated through compressive, high- cycle fatigue, and mammalian cell test. The specimen with both struts angle and unit cell orientated presents an improved fatigue strength and biological response. Overall, this thesis contributes to the development of PBF-LB lattice structures applied for biomedical implants
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! 👇