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Developing a calixarene-based dynamic covalent library for steroid sensing
No full textAbstract not currently available
Towards tunable topological insulator surfaces: an EELS study of Bi₂Se₃/organic interfaces
Get PDFTopological insulators (TIs) such as Bi₂Se₃ can host low-loss plasmons with enhanced transport properties at their surfaces that are promising for plasmonic and optoelectronic applications. However, practical use of TIs in plasmonic devices requires tunable control over these plasmonic properties. This thesis explores the use of organic molecular overlayers as surface dopants to modify the plasmonic behaviour of Bi₂Se₃.
Four different different organic overlayers; C₆₀, graphene, H₂Pc and CuPc, were selected to modify the Bi₂Se₃ surface, whilst enclosing the TI as required for potential device integration. Electron transparent lamellae were prepared using focused ion beam techniques from bulk crystals and analysed using transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). Plasmon behaviour across insulator/Bi₂Se₃ and Bi₂Se₃/organic interfaces was probed using EELS and momentum-resolved EELS to investigate changes to plasmon energy, confinement and dispersion. Supporting simulations, calculated from bulk dielectric functions using analytical and finite element methods, were used to interpret EELS spectra and highlight localised plasmon modes.
At a Al₂O3/Bi₂Se₃ interface, a surface plasmon mode at 5.3 eV was identified and shown to be confined to within 2 nm of the interface. Its √q plasmon dispersion is characteristic of a two-dimensional π plasmon, similar to π plasmons in free-standing graphene, likely originating from the the first layer of Se atoms within Bi₂Se₃. At a SiO2/Bi₂Se₃ interface, a surface plasmon at 5.6 eV was observed to coexist with the Bi₂Se₃ π plasmon, illustrating changes to Bi₂Se₃ surface behaviour even at insulating substrate interfaces. In contrast, a highly localised plasmon at 6.3 eV was observed at the Bi₂Se₃/C₆₀ interface, confined to the first layer of C₆₀ molecules. It exhibited very little plasmon dispersion and, with the aid of density functional theory calculations, was proposed arise from the formation of a hybridised plasmon mode. This mode also exhibited enhanced signal in the first molecular layer and a significant charge transfer from Bi₃Se₃ to the first layer of C₆₀ molecules, affirming it to be a hybrid plasmon mode.
These findings were expanded upon by performing similar studies on Bi₂Se₃ graphene, Bi₂Se₃/H₂Pc and Bi₂Se₃/CuPc interfaces. The plasmon energy at each interface was observed at 6.0, 6.4 and 6.4 eV respectively, indicating subtle changes with varied organic overlayers. Plasmon modes at these interfaces were observed to be less confined than at a Bi₂Se₃/C₆₀ interface, indicating that hybrid plasmon confinement could be dependent on a well ordered molecular surface. At lower energies, <200 meV, the plasmonic behaviour at Bi₂Se₃/H₂Pc and Bi₂Se₃/CuPc interfaces was observed to differ more substantially, with variations in plasmon energy throughout the Bi₂Se3 layer and trends towards each interface. Bulk Bi₂Se₃ plasmon modes were observed at different energies in each sample and could be a consequence of different carrier densities from different growth methods. Distinct trends in plasmon energy towards each phthalocyanine interface point towards long interaction depths between Bi₂Se₃ and organic layers at lower energies.
This research demonstrates that organic molecular overlayers can modify the interfacial plasmonic properties in TIs and suggests a route towards tunable plasmonic devices. These results are relevant for potential applications in broadband-TI photodetectors, where organic layers could be tuned electrically or optically to modify a TI interface and enable control of absorption properties
Empagliflozin to prevent worsening of left ventricular volumes and systolic function after myocardial infarction
Get PDFBackground
Heart failure following an acute myocardial infarction (MI) is associated with significant morbidity and mortality, making its prevention a key therapeutic goal. Progressive adverse ventricular remodelling, characterised by ventricular dilation and declining systolic function, is a key precursor to the development of heart failure after MI. Early reperfusion therapy and medications that reduce mortality and heart failure post-MI, such as angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), and beta-blockers, also prevent adverse remodelling. The mineralocorticoid receptor antagonist (MRA) eplerenone improved outcomes post-MI but showed a significant anti-remodelling effect only after adjusting for baseline covariates. Sacubitril/valsartan did not reduce the risk of developing heart failure or cardiovascular mortality in high-risk post-MI patients and had minimal impact on remodelling. Sodium-glucose co-transporter 2 (SGLT2) inhibitors lower the risk of heart failure progression and mortality in patients with chronic heart failure across all ranges of left ventricular ejection fraction (LVEF). One of their key mechanisms of benefit in heart failure with reduced ejection fraction (HFrEF) is a positive effect on ventricular remodelling. Empagliflozin did not significantly reduce the primary outcome of heart failure hospitalisation or all-cause mortality in high-risk post-MI patients, but did lower the incidence of first and total heart failure hospitalisations and other adverse heart failure events. Whether this is related to a remodelling effect remains uncertain. In lower-risk post-MI patients, dapagliflozin improved cardiometabolic outcomes but did not significantly impact the composite outcome of cardiovascular death or heart failure hospitalisation. I conducted the EMpagliflozin to PREvent worSening of left ventricular volumes and Systolic function after Myocardial Infarction (EMPRESS-MI) randomised, placebo-controlled trial, which was designed to test the hypothesis that empagliflozin, when added to standard care, would mitigate adverse left 3 ventricular remodelling in high-risk post-MI patients, as assessed using cardiovascular magnetic resonance (CMR) imaging.
Aims and methods
The aim of the EMPRESS-MI trial was to examine the effect of empagliflozin on left ventricular remodelling in patients with left ventricular systolic dysfunction after an acute MI using the gold-standard method, CMR. I performed a randomised, placebo-controlled trial comparing empagliflozin 10mg once daily with placebo, in addition to standard care, in patients within 12 hours and 14 days of an acute type 1 MI and an LVEF<45% by CMR. Key exclusion criteria were a history of HFrEF or contraindications to SGLT2 inhibitors. Patients with an estimated glomerular filtration rate (eGFR) <30 mL/min/1.73m2 (measured using the modification of diet in renal disease formula) were excluded. Patients with permanent or persistent atrial fibrillation or an implanted cardiac device were excluded to avoid potential CMR image degradation. The primary outcome was the change in left ventricular end-systolic volume index (LVESVI) from baseline to 24 weeks as measured by CMR. The secondary outcomes, measured as change from baseline to 24 weeks, were: left ventricular end-diastolic volume index (LVEDVI), LVEF, left atrial volume index (LAVI), left ventricular mass index (LVMI), N-terminal prohormone of B-type natriuretic peptide (NT-proBNP), high-sensitivity cardiac troponin I (hs-TnI), and infarct size measured using CMR. Exploratory outcomes included the change in biomarkers relevant to the actions of empagliflozin (uric acid, glycated haemoglobin, and haematocrit), kidney function, and body weight. I also examined the relationship between intramyocardial haemorrhage (IMH) and left ventricular remodelling and the effect of empagliflozin.
Results
In 104 patients included in the final analysis set, mean±standard deviation age was 63.0±11.2 years and 90 (86.5%) patients were male. The median time from MI to randomisation was 3.0 days (interquartile range 2.0-5.0). 92 (88.5%) patients had an ST-elevation MI (STEMI) and 12 (11.5%) had a non-STEMI (NSTEMI). 83 (79.8%) MIs were in the anterior location. Nearly all patients (103 4 [99.0%]) had percutaneous coronary intervention (PCI) or thrombolysis. At randomisation, 97 (93.2%) patients were taking an ACE inhibitor or an ARB, 89 (85.6%) a beta blocker, 66 (63.5%) an MRA, and 30 (28.8%) were on a loop diuretic. 46 (44.2%) patients received a loop diuretic at any point during the index admission before randomisation. The mean LVEF by echocardiography was 35.0±4.9% and by CMR was 34.8±6.0%. In the placebo group, LVESVI decreased by 7.8±16.3 mL/m2, LVEDVI did not change (-0.3±18.7 mL/m2) and LVEF increased by 8.5±7.4% from baseline to 24 weeks. Empagliflozin had no effect compared with placebo on the change in LVESVI from baseline to 24 weeks; adjusted between-group difference 0.3 mL/m2 (95% confidence interval [CI] -5.2 to 5.8); P=0.92. Empagliflozin had no effect on the change in LVEDVI, LVEF, LAVI, LVMI, NT-proBNP, hs-TnI or infarct size but did increase haematocrit (P=0.006) and reduced uric acid (P=0.006) and body weight (P=0.006). At baseline, of 93 patients with complete data, 45 (48.4%) patients had IMH and 48 (51.6%) did not. In patients with IMH, LVESVI did not change between baseline and 24 weeks whereas in patients without IMH LVESVI decreased (-0.9±11.4 mL/m2 vs. 14.7±14.7 mL/m2; P<0.001). In patients with IMH, LVEDVI increased whereas in patients without IMH LVEDVI decreased (9.1±12.7 mL/m2 vs. - 7.8±16.8 mL/m2; P<0.001). LVEF improved in patients with and without IMH but to a lesser degree in those with IMH (7.4±7.1% vs. 10.7±7.7%; P=0.004). Empagliflozin had no effect on remodelling in patients with and without IMH at baseline.
Conclusion
In patients with left ventricular systolic dysfunction after an acute MI treated with contemporary reperfusion and medical therapy, the addition of empagliflozin to standard care did not have any effect on improving left ventricular volumes or function compared with placebo, and did not reduce biomarkers of left ventricular wall stress (NT-proBNP) or myocardial injury (hs- TnI). Progressive adverse cardiac remodelling did not occur in the majority of patients
The role of paradoxical leadership in influencing followers to deal with multiple contradictory demands
Get PDFParadoxes have become increasingly prominent and unavoidable in contemporary organisational life. Paradox refers to the simultaneous existence of contradictory yet interdependent elements that persist over time. Rather than problems to be solved, paradoxes represent tensions that need to be managed. Therefore, practising paradoxical leadership is necessary for leaders, especially future leaders, as it may unlock benefits for their followers. Paradoxical leadership refers to a leadership approach that embraces and effectively manages tensions, contradictions, and uncertainties within the workplace.
There is extensive research on paradox and paradoxical leadership. However, how organisational leaders navigate and manage paradoxes by employing paradoxical leadership and influencing followers to deal with them has been overlooked. This research addresses this gap by analysing the role of paradoxical leadership in influencing followers to navigate paradoxes. Accordingly, the main research question guiding this thesis is: What are the global applications of paradox theory through paradoxical leadership? To analyse this question, this research addressed two sub-research questions: How do leaders and followers make sense of and navigate paradoxes in their work? This is qualitative research. To analyse paradoxical leadership, I drew on paradox theory and conducted 35 in-depth, semi-structured interviews with managers and team members from four multinational clothing companies in Bangladesh.
The findings of this research reveal several perceived sources of paradoxes within organisational settings. Additionally, this research identifies that Bangladeshi organisational culture plays a role in creating paradoxes. In exploring how leaders and followers navigate paradoxes, the research identifies several ways to manage these paradoxes. Furthermore, the research analyses the impact of paradoxical leadership on leaders themselves, revealing both enabling and constraining effects. This research offers both theoretical and practical contributions. Theoretically, it advances paradox theory by clarifying the lexicon through which paradoxes are addressed and uncovering the dynamic, cyclical processes by which paradoxes are navigated. It extends the literature by incorporating perspectives from the Global South, highlighting the influence of culture and paradoxes—an area often overlooked in existing studies. Practically, this research provides actionable insights for leaders, followers, and organisations. It underscores the importance of practising paradoxical leadership and fostering a culture of open communication to support leaders and followers in navigating paradoxes. By viewing paradoxes as opportunities rather than obstacles, organisations can enhance innovation, adaptability, and resilience
Non-traditional entry routes to higher education: a cross-national study of inclusion in access for adults in New York State and Scotland
Get PDFThe lifelong learning topics of 'widening access' and 'widening participation', particularly for 'mature learners', have been of discerning interest to academics, educators, and policymakers for decades (Gallacher, 2010). In both the UK and U.S., initiatives have aimed to recruit and retain students from more intersectionally diverse and historically excluded backgrounds, particularly those above the traditional school transition age (e.g. Espinosa et al., 2019; Gallacher, 2010; Riddell, 2015). Such 'widening recruitment' initiatives have seen significant growth in each country (e.g. Calahan et al., 2022; Espinosa et al., 2019; Boliver, Gorard, Siddiqui, 2021). Scotland and New York State, in particular, both have a longstanding history of lifelong learning programmes and initiatives to address urgent skill shortages, enhance social and economic mobility, and support workforce development (Boeren, 2016; Reder, 2007; Roumell, Salajan, &Todoran, 2020; White & Lee, 2020). Despite this, most recent widening access policy still primarily benefit young, full-time, first-degree undergraduates, (e.g. Commission on Widening Access [CoWA] in Scotland; Excelsior Scholarship, 2017 & José Peralta New York State Dream Act, 2019). In the aftermath of the COVID-19 pandemic, mature student enrolment in higher education (HE) continues to decline in both regions (HESA, 2023; Kamssu & Kouam, 2021), highlighting the urgent need for the present multilevel, exploratory and experiential research in adult learning inclusive policy and practice. Using an ecological lens, it examines how individual, institutional, and policy factors interact to impact participation in higher education, guided by Boeren’s (2016) Integrative Model of Lifelong Learning Participation as the core conceptual framework for this analysis.
Situated within their respective policy contexts, this cross-national, multilevel qualitative study examines the impact of non-traditional trajectories into HE and the strategies employed by university stakeholders to facilitate access in the face of dwindling government funding in both regions. It explores the experiences of 24 adult learners (Scotland n=14, New York n=10) and the perspectives of 7 university stakeholders (Scotland n=4, New York n=3), to gain triangulated insights into current and future inclusivity of widening access and participation programmes for mature learners in a post-COVID world.
These triangulated findings highlight the significant impact of institutional habitus, learners' identity/belonging, as well as university 'reputation' and perceived elite status, on both learners’ experiences and stakeholders’ approaches to widening access. It further highlights the shared, and differential, institutional and learner experiences of bureaucratic/policyrelated barriers to both mature student access and HEI facilitation of access, into retention, achievement, and ideally satisfaction and shared belonging.
Ultimately, this study contributes to our understanding of how institutional and national policies affect mature learners’ trajectories, as well as how organisational identity and regional policies affect university stakeholders’ facilitation practices. It calls for strengthened, ongoing collaboration among researchers, HEIs/practitioners, and policymakers to develop sustainable strategies for mitigating challenges to mature student access and participation in higher education in a post-COVID world
Thermal processing of agricultural waste-based biorefinery residues and plastics for producing sustainable fuels and end of life value
Get PDFThe depletion of fossil fuel reserves and escalating environmental concerns—such as greenhouse gas emissions and plastic pollution—have intensified the global pursuit of renewable and circular energy solutions. Thermochemical conversion technologies, particularly pyrolysis, offer effective pathways for valorising carbon-rich waste into fuels, chemicals, and functional materials. The co-pyrolysis of lignocellulosic biomass with plastic waste exploits synergistic effects between hydrogen-deficient and hydrogen-rich feedstocks, improving product yield and quality. However, feedstock heterogeneity, complex reaction mechanisms, and variability from environmental aging and industrial processing remain key challenges to optimizing and scaling pyrolysis systems. This dissertation presents a systematic research framework addressing these challenges through the investigation of co-pyrolysis behaviour, catalytic upgrading, and kinetic modelling of integrated bio-based and polymeric residues, with an emphasis on process circularity, feedstock interdependency, and environmental resilience.
The study began with thermogravimetric analysis (TGA) of various corn stalk tissues (stem, husk, ear, cob, and leaf), high-density polyethylene (HDPE), and their blends. Structural differences in the plant tissues strongly influenced decomposition behaviour and product distribution. The corn cob/HDPE blend achieved the highest yields of valuable chemicals (such as furan derivatives and aromatics) and exhibited the lowest activation energy (149.3 kJ/mol). Machine learning models, including random forest (RF) and gradient boost regression tree (GBRT), were applied to predict mass loss, with RF showing superior performance. Building upon these findings, downstream ethanol processing residue (EPR) from a corn cob-based biorefinery was co-pyrolyzed with HDPE. In situ catalysis with bottom ash (BA) from the same biorefinery reduced activation energy and promoted deoxygenation and aromatic hydrocarbon formation. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) confirmed catalytic improvements in product distribution. To further enhance circularity, wood-plastic composites (WPCs) were examined. TGA and TG-FTIR revealed synergistic effects between EPR and plastic, lowering activation energies and facilitating a one-dimensional diffusion pyrolysis mechanism. Additionally, artificial weathering of WPCs altered plastic crystallinity and pyrolysis behaviour, informing post-consumer management strategies.
Overall, this research advances a comprehensive approach to the circular pyrolytic valorisation of biorefinery residues and plastics. Through integrated thermal analysis, catalytic enhancement, kinetic modelling, and machine learning, the findings contribute to the development of efficient, low-emission thermochemical processes for sustainable waste management and renewable energy production
Learning low-dimensional latent spaces for Hand-pose interaction systems
Get PDFIn recent years, mid-air gesture recognition and control have emerged as touch-free interaction mechanisms with significant potential, but human-centered design challenges persist, particularly due to the complexity of user hand movements, user-learnability of interaction system, and usability across varied contexts. This research addresses limitations in current mid-air gesture systems by introducing strategies that reduce the latency of real-time interaction and enhance hand pose interpretability. We introduce a hand pose recognition approach using only two video frames, optimizing for speed and accuracy while minimizing time dependencies, thereby allowing users to experience a more responsive system. Building on these insights, the Hand-pose Embedding Interactive System (HpEIS) employs a Variational Autoencoder to map gestures to a two-dimensional space, introducing visualized feedback mechanisms that improve user experience. At the same time, interaction stability improved through smoothing and anti-jitter methods. While this approach improves robustness in dynamic movements, further challenges remain in adaptability and flexible user control. To expand flexibility, the HandSolo model introduces a disentangled hand pose embedding space, supporting multi-dimensional control with independent degrees of freedom, thus enabling interactions adaptable across devices and contexts. Coupled with a Visual Interaction Evaluation Strategy (VIEs), HandSolo provides a guidance for system designers to align model capabilities with user preferences. The experimentation underscores the effectiveness of these systems. This integrated research establishes a framework for mid-air hand pose control, advancing usability, flexibility and extensibility in the interaction design of mid-air hand pose with high dimensional input
Differential effects of childhood abuse and neglect on executive and reflective functioning across the lifespan
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To what extent did the existing health and safety legislation protect the health and safety of healthcare workers in the UK during the Covid-19 pandemic?
Get PDFThis thesis aims to examine whether existing health and safety laws were sufficient to protect the health and safety of healthcare workers in the United Kingdom during the Covid-19 pandemic. The Covid-19 pandemic was incredibly challenging to National Health Service (NHS) healthcare workers due to a multitude of reasons. Healthcare workers were required to provide care to patients that contracted the novel virus without knowing its severity. The highly transmissible nature of the virus overwhelmed hospitals with a surge of critically ill patients. This ultimately led towards overworking workers, causing immense physical and mental distress. Having learned the highly infectious nature of the virus, NHS healthcare workers were required to wear personal protective equipment (PPE) to protect themselves and reduce the transmission of infection. However, due to the widespread transmission of the virus, there was a shortage of PPE, significantly increasing the risk to workers’ health and safety. Despite these impacts, workers were hopeful that their employers would protect them from the occupational health and safety hazards. Employers are under a legal duty to ensure that the health and safety of their employees are protected as far as it is reasonably practicable. This is highlighted under the Health and Safety at Work etc. Act 1974. In line with the above, the research aims to explore if the health and safety of healthcare workers was adequately protected during the Covid-19 pandemic.
This study adopted a socio-legal methodology and thematic qualitative analysis to answer the research question. Socio-legal method examines the relationship between law and society. In the context of health and safety, while the Health and Safety at Work etc. Act 1974 was enacted with the intention of protecting workers, the legal rules are interpreted and applied differently in practice within the NHS. In order to understand this further, data was collected through reviewing testimonies published by healthcare workers online. Collecting secondary data was straightforward due to the vast number of testimonies available online. The testimonies were naturally categorised into themes which assisted the data analysis. Five key themes emerged from the data analysis; prejudicial treatment of black minority ethnic workers, the lack of support for migrant workers, supply of PPE, inconsistent advice across the NHS workforce and the intention to leave the healthcare profession.
Having established the methodology and theoretical framework, the analysis explored the effectiveness of the health and safety laws and how it was practised by employers within the workplace. The mental and physical health impact on healthcare workers were significant. The unfair treatment that minority groups faced during the pandemic exposed them to higher risks of infection. The shortage of PPE resulted in a series of unfortunate incidents, it increased the risk of workers contracting the virus and elevated their anxiety when providing care to patients. When PPE was available, workers were subjected to wearing it for prolonged periods of time which caused physical discomfort. Workers also had to provide care whilst navigating the constantly changing government guidelines, which were often more of an encumbrance than a support.
The research concludes that in instances where legislation fails to offer adequate protection for the health and safety of workers, the trade unions are able to play a vital role in advocating for health and safety policies to be implemented and protective equipment to be stipulated. The analysis also highlights that while the health and safety legislation enables employers to implement health and safety policies for the specific needs of their workplace through the self-regulating system, the lack of consistency in implementation across different NHS trusts caused confusion amongst workers. Overall, although legislation exists to protect workers, many health and safety safeguards were not effectively implemented to adequately protect the health and safety of healthcare workers during the Covid-19 pandemic
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