27716 research outputs found
Sort by
Application of Johnson's approximation in finite element modeling for electric field-dependent materials for use in multi-layer ceramic capacitor applications.
Full text linkThis thesis investigates the complex relationships between material properties and their response to electric fields, with a particular focus on voltage-dependent capacitance. A key objective was to develop and validate a simulation code based on Johnson’s equation to model the voltage dependency of dielectric materials. The code successfully captures the nonlinear behaviour of relative permittivity under varying electric fields, with simulation results closely aligned with established models and experimental data. This verification process demonstrates the reliability of the code for predicting dielectric behaviour.
The thesis further explores the impact of parameters such as Johnson’s parameter, applied electric field strength, material thickness, and intrinsic permittivity on the dielectric response. Results reveal that effective permittivity is highly sensitive to Johnson’s parameter and field strength, particularly in high-permittivity materials like barium titanate, where a decline in dielectric response is observed at higher values of these parameters. A saturation effect is also noted at higher Johnson’s parameter and field strengths. Additionally, material thickness plays a critical role in the final temperature coefficient of capacitance (TCC), with thickness having a stronger influence than other factors like volume fraction and conductivity ratio.
The thesis also compares analytical and simulated models, demonstrating that the simulations provide accurate results with minimal deviations from analytical solutions (less than 2%). A finite element modeling approach is developed to study multilayer ceramic capacitors (MLCCs), revealing how the core-shell structure of BaTiO3 influences voltage-capacitance characteristics. The findings offer new insights into the design of MLCCs with improved performance, tailored voltage dependence, and enhanced breakdown strength. Overall, this research contributes significantly to understanding dielectric material behaviour
Development of lithium-rich, high-nickel-content cathodes to increase energy density of lithium-ion batteries
No full textNickel-rich cathodes are anticipated to function as essential components for highcapacity
lithium-ion batteries. Though it normally results in more complicated synthesis
conditions, increasing the Ni content can substantially enhance the energy density,
hence restricting its development. This study presents a straightforward one-step solidstate
procedure for synthesising Li-rich and Ni-rich (Li2NiO3) materials. The synthesis
conditions were thoroughly investigated and analysed. The study revealed that the
synthesis circumstances had a significant influence on the electrochemical performance,
especially the calcination temperature.
In addition, the study utilises a straightforward microwave-assisted approach.
The products obtained by synthesis were analysed using X-ray diffraction,
electron microscopy, and galvanostatic electrochemistry. When compared to the
original Li2NiO3, the Li2NiO3 that was exposed to microwaves exhibited a 20%
increase in capacity after undergoing 100 cycles at a rate of C/5
Remembering the Holocaust: A Portfolio of Compositions Exploring Jewish History, Memory and Culture
Full text linkThis PhD submission comprises a portfolio of four original compositions composed between 2020 and 2024, with a total duration of approximately 90-minutes, accompanied by a commentary of approximately 10,000 words. It explores the composer’s perspective as a second-generation Holocaust survivor by blending Jewish musical and symbolic elements within a Western classical idiom. The central work of the portfolio is 'Holocaust - Remembrance', a 60-minute work in six movements for orchestra (incorporating shofarot, castanets, timpani, quad toms and bass drum) and SATB chorus, composed as a musical monument to metaphorically stand alongside the Holocaust Memorial Monument erected at the Neve Shalom Synagogue in Paramaribo, Suriname. Movement IV is a setting of Primo Levi’s poem 'Shema' (1946). The portfolio also includes 'The Wanderer' (10-minutes, for string quartet), 'Resistance' (8-minutes, for percussion ensemble and two violins) and 'A Prayer for Peace' (12-minutes, for solo viola). The accompanying commentary provides context for and explanation of the composer’s use of specific elements, including the shofar, the Sephardic Jewish scale, the Ashkenazi 'Ahavoh-Rabboh' mode, Sephardic rhythms and palindromic structures. The overarching mission of the PhD is to create awareness of and to educate audiences about the Holocaust and anti-Semitism (Jew-hatred). As far as is known, it represents the first body of such work by a composer of Surinamese Jewish descent, and further addresses a gap in the repertoire through the aim to integrate materials from Sephardic and Ashkenazi traditions
Group 8 & 9 catalysts for the dehydropolymerisation of amine-boranes
Full text linkChapter 1: This introductory chapter covers topics that are necessary to understand
the research background upon which this thesis is built. These include fundamental
amine-borane and polyaminoborane chemical properties, the origin of catalytic routes
to polyaminoborane formation, the potential applications of polyaminoboranes, the
mechanisms of amine-borane dehydropolymerisation and the general concept of metal
ligand cooperative catalysis.
Chapter 2: In the second chapter, the activation and deactivation pathways of group 9
metal ligand cooperative amine-borane dehydropolymerisation catalysts are
investigated, primarily focussing on rhodium metal-ligand cooperative aminophosphine
complexes (such as Rh(iPr-PNHP)H2Cl) that have recently been reported by the Weller
group. The slow spontaneous dissociation of amine-boranes in solution is discussed
and its poisoning effect on amine-borane dehydropolymerisation catalysts, forming
borohydride complexes. This is related to the as-yet unsolved problem that the
substrate scope for previously reported amine-borane dehydropolymerisation catalysts
is limited primarily to the parent ammonia-borane and its N-methyl derivative.
Chapter 3: In this chapter the structure, mechanism and speciation are investigated
for amine-borane dehydropolymerisation catalysts based upon the previously reported
but broadly overlooked ruthenium aminophosphine precatalyst
Ru(iPr2PCH2CH2NH2)2Cl2. The highly unusual and reactive square-planar, d6 and low�spin precatalyst Ru(iPr2CH2CH2NH)2 is characterised and its electronic structure
discussed. Such precatalysts are shown to exhibit the highest-yet reported rate of
amine-borane dehydropolymerisation, and this rapid catalysis is utilised for the
synthesis of high molecular weight N-methyl polyaminoborane. ethyl and propyl
polyaminoboranes. Parts of this chapter are published as a communication in an
Angew. Chem. Int. Ed. article.
Chapter 4: This final discussion chapter covers the first report of selective N-ethyl and
N-propyl amine-borane catalytic dehydropolymerisation, forming the N-ethyl and N�propyl polyaminoboranes utilising the ruthenium catalyst discussed in chapter 3
(Ru(iPr2PCH2CH2NH2)2Cl2). The possible routes of catalyst deactivation when using
these amine-boranes as substrates is also discussed.
Chapter 5: Experimental data, figures, tables and methods
Design and synthesis of novel compounds for the treatment of septic shock
No full textSeptic shock is the most severe form of sepsis and is caused by a dysregulated immune response to infection. Patients experience dangerously low blood pressure, and this is believed to be caused by the vasodilatory peptide hormone, adrenomedullin, which shows significantly elevated levels in the plasma during septic shock. Adrenomedullin causes vasodilation through binding to the adrenomedullin-1 receptor (AM1r), which is a heteromeric complex comprised of the calcitonin receptor-like receptor (CLR) and receptor activity-modifying protein 2 (RAMP2). Two closely related receptors are the calcitonin gene-related peptide receptor (CGRPr) and the adrenomedullin-2 receptor (AM2r), which are formed by the association of CLR with RAMP1 and RAMP3, respectively. This work aims to develop the first small molecule antagonists of AM1r. Such compounds, that can block the binding of adrenomedullin to AM1r, have the potential to arrest the severe drop in blood pressure observed during septic shock
Tales of Addiction in Sports Life Writing
Full text linkMy thesis addresses the lack of critical engagement with sports life writing in the literary field. It fills this gap by analysing the genre’s unique and understudied presentation of addiction, both to various substances and sporting praxis itself. Working through the literature of three sporting contexts – professional football, professional cycling and ultra-distance running – I show how the life of the athlete and their writing are embedded in addiction and recovery. They embody and describe compulsive, addictive attitudes to training, cultures of performance enhancement, recreational substance abuse, alcoholism, substitutive addictions and the failed or successful rehabilitation from these factors. Thus, this thesis establishes a large sub-section of sports life writing as an integral source of literature on and about addiction. Then, specifically, it shows how the genre’s presentation of addiction is mediated through the confessional and (non-)confessional modes, a structure which provides a contemporary literary catharsis upon which the sporting recovery narrative is built. Moreover, the thesis emphasises that this recovery narrative presents sport, and the continued, addictive and excessive engagement with it, as a potential rehabilitating solution to addiction issues. Like the very sporting careers described across sports life writing, the thesis frames this active recovery as a form of what I term renewal-in-depletion: an intensely consumptive mode of athletic praxis that mimics unsustainable neoliberal patterns of resource extraction. Lastly, throughout its three chapters, the thesis successfully explicates the strong bind and interrelation between the addictive narratives of professional sportspeople and the neoliberal contexts from which they arise
Pathway-dependent block copolymer self-assembly
No full textPolymer nanoparticles are key for a wide range of applications, such as nano-reactors, encapsulating agents, and biological drug delivery. The synthesis and self-assembly of block copolymers have been studied previously, but a holistic understanding of how the self-assembly pathway affects the size, shape, and morphology of the polymer nanoparticles has yet to be reported. This work takes a functionalisable block copolymer (polydimethyl acrylamide-b-polydiacetone acrylamide) and synthesises it via Polymerisation Induced Self Assembly (PISA) for a range of block copolymer molecular weights. This results in well-defined block copolymers characterised by gel permeation chromatography (GPC), nuclear magnetic resonance spectroscopy (NMR), dynamic light scattering (DLS), and transmission electron microscopy (TEM). The PISA syntheses suggest a hydrophobic block length of 100 self-assembles into a mixed morphology of nano-objects, but increasing this to 200 results in pure vesicular phases. The pH and salt concentration were varied to physiological conditions (pH 7.5, 140 mM NaCl), and polymer vesicles persisted at neutral pHs and with added electrolyte concentration. The next step was to investigate alternative self-assembly pathways, such as Thin Film Rehydration (TFR) and Solvent Exchange (SE), with the same block copolymer used for the PISA syntheses. TFR proved to be unsuccessful with the targeted block copolymers at pH 2.5. Differential Scanning Calorimetry (DSC) was employed to identify any phase changes of the block copolymer in the solid state. SE was studied as a potential self-assembly pathway for the block copolymer. Methanol was chosen as a co-solvent, and low methanol (5-15%) SE experiments yielded spherical micelles. Upon increasing the methanol concentration to 50%, cylindrical micelles were observed. Upon methanol evaporation, the PDAMm50-b-PDAAm300 sample produced a mixed phase of vesicles and kinetically trapped spheres. Increasing the pH led to the production of cylindrical micelles and spherical micelles; however, when salt was added, the charge was screened, leading to distorted vesicles. A key finding was that the volume of the hydrophobic block is affected when changing self-assembly conditions, which in turn changes the interfacial curvature of the block copolymer, leading to different morphologies being formed during SE. When methanol is increased to 50%, the added solvent plasticises the hydrophobic block, increasing its volume and decreasing the block-copolymer curvature, leading to worms. When 140 mM of NaCl was added to the SE mixture, this result suggests that the NaCl screens the charge on the polymer enough for the polymer to decrease the hydrophilic volume and reduce the interfacial curvature to form larger order nano-objects such as membrane-bound vesicles.
To better understand the morphological changes occurring during methanol evaporation, a three-hour SE evaporation was undertaken at various pHs and ionic strengths, monitoring the methanol content via benchtop NMR. The main morphological changes were from worms to spherical micelles before aggregation occurred. A membrane directing lipid (POPC) was used with the block copolymer during SE experiments to see if this could alter the morphology towards vesicles. This led to a range of spherical micelles being produced at various POPC block copolymer ratios. The self-assembly pathways studied prove that you can get a variety of morphologies from one starting material
Understanding urban trees: form, function and vulnerability
No full textUrban trees provide critical ecosystem services for the sustainability and resilience of cities. Ecosystem service delivery by urban trees is determined by tree species and physiological function, but urban environments can present challenges to this. However, our understanding of the physiological function of many common urban tree species, and the long-term impact of urban pressures, is limited. This thesis examines urban tree form, function and vulnerability at the leaf, tree and city-level to address these knowledge gaps. Chapter 2 demonstrates that tree species was the dominant control of urban tree physiology, with no impact of pollution or soil sealing, and that hyperspectral remote sensing could reliably predict urban tree leaf traits, reducing dependence on field surveying. In Chapter 3, the impact of a widespread pathogen (Phytophthora plurivora) on the water use, growth rate and cooling capacity of a common urban tree species (Tilia x europaea) was quantified using IoT linked sensors. While these parameters were significantly higher in asymptomatic trees, infected trees with less advanced disease still provided ecosystem benefit, highlighting trade-offs between public safety and tree disease management. Chapter 4 used a novel network of IoT linked sensors across the urban environment to explore water use and growth rate of urban trees. There were significant differences between tree species, but street trees were not water limited, with significantly higher water use than woodland trees. Extreme heat and drought events dramatically reduced this. Chapter 5 demonstrates the potential of radiative transfer modelling and high-resolution satellite imagery to map urban tree leaf chlorophyll content, a key indicator of tree vitality, across a city. Collectively, the results show that increasing urban tree species diversity via strategic species selection could improve the benefits and resilience of urban forests. Remote sensing offers a robust way to monitor urban trees, vital under global environmental change
Essays on Cryptocurrency Markets: Price Dynamics, Adoption, and Crash Prediction Using Econometric and Machine Learning Models
No full textResearch priority setting on maternal, perinatal and newborn health in LMICs: Theory and practice in relation to preterm birth
Full text linkBackground: Despite progress in reducing neonatal deaths, preterm birth (PTB) remains the leading cause, with millions of babies affected and significant survival gaps between high- and low-resource settings. Addressing the burden of PTB in resource-limited settings requires targeted research on its causes, mechanisms, and risks, along with cost-effective maternal and newborn health interventions. My PhD aimed to address this evidence gap and inform future recommendations regarding PTB in LMICs within the SDG era by: (i) identifying and prioritising research on PTB and pre-eclampsia and eclampsia (PE/E) (ii) conducting community-level exploration to identify gaps and opportunities for improving care for preterm babies among high-risk adolescents in rural Bangladesh.
Methods: I used an adapted Child Health and Nutrition Research initiative (CHNRI) method to determine research priorities on PTB in LMICs and Bangladesh, and PE/E in LMICs. Using qualitative research, I explored perception and experiences of adolescents and communities in caring for preterm babies in rural Bangladesh. This involved in-depth or key informant interviews with mothers of premature and term babies, family members and healthcare providers and focus groups with community members.
Results: In study 1 on PTB research priority setting, health systems and policy related research were prominent among the top 20 priorities for LMICs. These were related to facility and community-based Kangaroo Mother Care (KMC), breastfeeding, referral and transportation, use of skilled attendants, quality improvement, and antenatal steroid use. There was substantial overlap in research priorities for LMICs and Bangladesh.
In study 2 on PE/E priority setting, experts prioritised health systems and delivery research to enhance detection, transfer, and management of women with PE/E in LMICs. Topics were related to care delays, availability of supplies and quality of care in facilities, provider and facility readiness, guideline implementation, Magnesium Sulphate use, providers’ knowledge gaps, referral systems, early identification and screening.
Study 3 examined two main themes: perception and understanding of preterm birth and care practices for preterm babies. The first theme revealed inconsistent knowledge about preterm birth's definition, appearance, causes, and associated problems. The second theme highlighted inappropriate care, multiple healthcare provider usage and delayed care-seeking due to factors like perceived illness severity, costs, and quality, including inadequate equipment and trained personnel. Adolescents showed significant knowledge gaps and relied on family members for baby’s care.
Conclusions: My PhD systematically identifies and prioritises future research areas for preventing and managing PTB and PE/E in LMICs, particularly Bangladesh. By integrating research prioritisation with insights from high-risk groups, especially adolescents in low-resource settings, this study informs policy and practice to reduce maternal and newborn health disparities
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! 👇