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Rethinking international co-operation on plastic pollution: financial flows and conceptual frameworks
No full textPlastic pollution is a critical global challenge that impacts ecosystems, human health, society and the economy. Tackling it requires urgent action across the plastic life cycle, including measures to reduce production and consumption, and efforts to radically improve solid waste management (SWM), particularly for the 2.7 billion people globally who do not have access to services. Against this backdrop, this thesis provides a detailed analysis of the role of international co-operation efforts in reducing plastic pollution, focusing on the activities of bilateral donors and multi-lateral development banks.
A novel methodology for analysing official development finance (ODF) was developed and used to analyse 19 years of financial flows. It revealed that just USD 1.8 billion - less than 0.5% of all ODF - was focused on SWM in 2021, despite an increase since 2003. This is well below the USD 30 billion needed each year to improve SWM services. Upper middle-income countries receive the most support rather than lower-middle and low-income countries, where needs are greater.
A new conceptual framework was created - combining life cycle and project phase perspectives - to better analyse international co-operation focused on plastic pollution. Its application to four case studies in Southeast Asia, revealed a strong focus on capacity building and a limited emphasis on implementation and upstream solutions.
The broader implications are that efforts to tackle plastic pollution and improve SWM are insufficient. International co-operation has the potential to enable new approaches, de-risk projects and scale up solutions, but a new, ambitious approach is needed that combines system-wide enabling activities with substantial investment across the full life cycle. This could address plastic pollution and SWM challenges in the short term and lay the foundations for a longer-term transition to a circular economy
Nutrient and Weathering Controls on Cretaceous Oceanic Anoxic Events
No full textCretaceous OAE2 (~94 million years ago) functions as a unique event in Earth’s past to decipher biogeochemical dynamics of the ocean-atmosphere system under greenhouse climate conditions. The emission of vast amounts of CO2, linked to the emplacement of Large Igneous Provinces, initiated a cascade of biogeochemical processes, in which increasing global temperatures led to continental weathering enhancement, resulting in a higher nutrient supply to the ocean. A long-term sea-level rise and the subsequent increase in epi-continental shelf areas, as well as strong orbital forcing may have further contributed to an increase in the marine nutrient reservoir. Higher rates of production, export and burial of organic matter eventually led to the deposition of organic-rich successions under anoxic conditions. These successions are typically characterized by a positive carbon isotope excursion, indicative of a perturbed carbon cycle. The initiation of OAE2 has been the focus of various studies utilizing a variety of geochemical proxies, biogeochemical modelling, (cyclo-) stratigraphy and different palaeontological techniques. The termination of the event, however, has received little attention, and the factors leading to the recovery from anoxia on a global scale remain unknown.
In this thesis, I present a multidisciplinary approach using multiple geochemical proxies combined with biogeochemical box modelling and a coupled atmosphere-ocean climate model, focussing on the termination of OAE2. Geochemical analyses (iron-sulfur systematics, redox-sensitive trace metal enrichments and phosphorus phase partitioning) were conducted on sedimentary successions from the Tarfaya Basin, a shallow marine shelf setting located in the proto-North Atlantic. Here, the termination of the event is characterized by a gradual recovery from severe water column anoxia coinciding with lower rates of sedimentary phosphorus recycling and a decrease in chemical weathering input. The resulting lower nutrient availability on the shelf may therefore have been a decisive driver during the recovery of the Earth system.
The decrease in chemical weathering, however, does not seem related to a nascent cooling trend, as global temperatures remained high even after the event. Instead, weak orbital forcing caused by an insolation node at the end of OAE2 may have impacted global chemical weathering trends, as observed in conducted climate simulations. The onset of OAE2, on the other hand, shows a clear link between strong orbital forcing, enhanced chemical weathering input and nutrient availability, following the general theory of the biochemical cascade as the initial trigger for OAE2. However, in the applied box modelling, the CO2-driven weathering enhancement alone does not provide a sufficient amount of nutrients to initiate oceanic anoxia. The release of phosphorus (and iron) from the marine deposition of volcanic ash, as well as from alteration processes of volcanic glass during (submarine) volcanism on a large scale is therefore proposed as an additional direct nutrient source to the marine reservoir. As observed in the models, this additional source is required to boost organic matter production and burial, resulting in the expansion of shelf anoxia and a positive carbon isotope excursion.
Overall, this project highlights the importance of nutrient availability during a prominent deoxygenation event under past greenhouse climates, with implications for potential future greenhouse scenarios
Oceanic redox and nutrient cycling in the mid-Silurian
No full textThis thesis investigates the complex interplay of redox dynamics, nutrient
cycling, and biotic responses during the mid-Silurian, focusing on the Ireviken
Biogeochemical Event (IBE) within the Welsh Basin and Lakesman Basin.
Chapter 1 provides an introduction to the PhD project and a brief overview of
previous progress in the relevant field. Chapter 2 describes in detail the
methodologies applied to address the project objectives. Chapter 3 explores
early Silurian deep-water sedimentary systems, revealing how substrate
consistency and oxygenation influenced bioturbation. Macrofaunal activity in
the Aberystwyth Grits Group (AGG) was restricted to firm substrates exposed
by sediment gravity flows, while meiofaunal burrows dominated the soupy
substrates of the Borth Mudstone Formation (BMF). These findings challenge
traditional interpretations of laminated sediments as dysoxic indicators,
emphasising substrate properties over oxygen availability.
Chapters 4 and 5 highlight the progression of redox instability from oxic-
ferruginous to euxinic conditions, documenting the impact of marine redox
evolution on marine biodiversity and primary productivity during the IBE. The
Banwy River section demonstrates how dynamic redox oscillations and
localized euxinia triggered biotic stress, particularly in benthic fauna and
graptolites. A mass balance model shows that cooling-induced intensification
of ocean circulation drove nutrient recycling, organic carbon burial, and
prolonged deoxygenation. This kind of marine deoxygenation during the mid-
Paleozoic contrasts with the rapid hyperthermal-driven Oceanic Anoxic Events
(OAEs) of the Mesozoic and Cenozoic, offering a unique perspective on mid-
Paleozoic anoxia.
Chapter 6 examines phosphorus and cadmium cycling as proxies for
nutrient dynamics and productivity. Redox-controlled phosphorus release
during euxinic conditions sustained high productivity, reflected in elevated
Corg/P ratios and cadmium isotope trends. The results underscore the role of
nutrient feedbacks in amplifying marine productivity and deoxygenation during
the IBE. Additionally, climatic cooling enhanced terrigenous phosphorus
delivery, linking terrestrial weathering processes to marine redox evolution.
Collectively, this research demonstrates the interconnectedness of redox
shifts, nutrient cycling, and climatic perturbations in shaping mid-Silurian ocean
chemistry and ecosystems. It provides new insight into the drivers of Paleozoic
anoxia and highlights the significance of transient cooling events in the long-
term oxygenation of Earth's oceans
Quinoa Protein and Peptides as a Gateway to Functional Health Benefits: A Down-Top Journey Through In silico and In vitro Exploration
No full textTest Suite Health: Automatically Improving the Reliability and Effectiveness of Test Suites
Get PDFSoftware systems are inherently prone to faults, stemming from human errors and incorrect assumptions made during the development process. Additionally, due to the evolving nature of codebases, even a correct code behaviour can degrade, becoming faulty. To mitigate these issues, unit testing is widely adopted, providing developers with a systematic way to exercise the system and verify individual units. Typically, developers write tests that exercise the production code, with the goal of achieving a certain level of code coverage and fault detection capabilities. However, writing tests that only achieve high code coverage and mutation scores alone is not enough; tests must also be reliable. Advancements in automated test generation techniques have decreased the burden of developers. However, developers remain primarily responsible for writing reliable and effective test suites, as these tools often fall short in areas requiring human expertise. Inadequate developer-written tests—whether due to low fault detection capability, flakiness, brittleness, or lack of realism—not only increase the maintenance overhead of the software systems, but also undermine the reliability of the test suite. This thesis takes a holistic approach to assessing and improving the quality of unit test suites, focusing on its reliability and effectiveness. To address these challenges, I set two primary objectives for this thesis: (1) understanding the factors that limit the reliability and effectiveness of test suites, and (2) developing and empirically evaluating automated techniques to improve and repair existing test suites. Firstly, to ensure that the state-of-the-art automated test generation tool, EvoSuite, could be utilised to enhance existing developer-written tests, I conducted an empirical study to investigate the issue of flakiness in tests generated by such tools. Following this, I evaluated the effectiveness of search-based test generation of EvoSuite capabilities to amplify existing developer-written test suites’ mutation score. To gain insights into software developer’s perspectives on test brittleness, I then conducted a developer survey of 73 professional software developers, evaluated 60 StackOverflow threads, and empirically evaluated 4,801 open-source projects. This is then followed by utilising EvoSuite’s search-based test generation technique to replace tests that make calls directly to implementation details with more reliable alternatives. These efforts contribute to understanding and improving four main indicators of test suite quality: fault detection capabilities, test flakiness, test brittleness, and test “realism”
The epidemiology of colorectal cancer: global implications for measuring incidence, with a focus on trends, risk factors, and screening uptake in Saudi Arabia
Get PDFColorectal cancer (CRC) is a global public health concern, imposing considerable health and economic burdens. While population-based studies worldwide closely monitor CRC incidence, variations in incidence methods hinder reliable interpretation and comparisons of rates. A description of variations in incidence calculation and the quality of reporting incidence methods is lacking. In Saudi Arabia, CRC is the second most common cancer; about one-third of cases present with a late-stage disease, resulting in poor prognosis. A comprehensive analysis of CRC rates, trends, and factors associated with late-stage diagnosis is currently lacking. The Ministry of Health recently launched a national CRC screening program, yet the public’s perceptions and acceptance of screening remain limited. This thesis aims to address the identified gaps by conducting five studies. Study One is a systematic review describing variations in the methods used in CRC incidence and the quality of their reporting. Variations in incidence calculation were identified, and recommendations were provided to enhance the reliability and reporting of incidence estimations. Study Two describes methods for estimating CRC incidence trends, highlighting the most common methods and the need for clarity and transparency in their reporting. Insights from studies One and Two informed methodological and reporting decisions in subsequent quantitative studies. Study Three is a retrospective analysis examining CRC incidence rates and trends in Saudi Arabia. Over time, CRC incidence rates increased across all age groups and stages at diagnosis, highlighting the critical need for cancer control policies and strategies. Study Four examines risk factors associated with late-stage CRC diagnosis in Saudi patients. Women under 50 had an increased risk, emphasizing the need for targeted preventive efforts. Study Five is a qualitative exploration of Saudi women’s perceptions and attitudes towards CRC screening. The interviews revealed multifaceted factors influencing screening uptake, underscoring the need for tailored health promotion interventions
Crystallisation Modelling and Measurement for Control of Crystal Size and Morphology in Chiral Systems
No full textInvestigation of ageing associated inflammation and genomic instability in zebrafish
No full textThe global population is living longer thanks to advancements in treatments for diseases that previously significantly shortened lifespans. However, these extra years are often accompanied by ill health and frailty, placing a considerable burden on both individuals and society, prompting the requirement into further research. One of the primary hallmarks of ageing is genomic instability, suggesting that increased DNA damage is partly responsible for why we age. One of the most common forms of DNA damage is the incorporation of single ribonucleotides into the DNA. A ribonucleotide is more reactive than a deoxyribonucleotide and if not removed, it can cause replication and transcription stalling as well as DNA breaks.
Here I use zebrafish (Danio rerio) as a model to study whether a reduced ribonucleotide removal activity from the genome is related to why someone becomes frail. I have made a frailty index for zebrafish, and I see that the frail fish have a reduced ability to cleave single ribonucleotides in the brain. This suggests that removal of ribonucleotides is important in robust ageing, and a loss of this function might be linked to frailty.
Further, I investigate FASTKD2 as a potential alternative enzyme that can remove single ribonucleotides from the mitochondrial DNA by creating a fastkd2 homozygous knockout zebrafish mutant. I show that whilst the mutant is viable, it is not efficient in producing energy, and it has no defects in single ribonucleotide removal. I also create a mutant for APRATAXIN, which resolves alternative ligation products, but is hindered by ribonucleotides. I show that the aprataxin mutant has reduced movement abilities. Lastly, I attempt to rescue a lethal zebrafish phenotype caused by loss of NuMA in zebrafish larvae by injecting parts of human cDNA NuMA into the genome of the mutant. However, I was unsuccessful in causing a rescue
Experimental and Finite Element Investigation on the Flexural Behaviour of LCA studied Steel-Concrete Composite Prefabricated Ultra-Shallow Slabs (PUSS)
Get PDFThis thesis investigates the environmental and flexural performance of the recently developed ultra-shallow flooring system known as Prefabricated Ultra-Shallow Slab (PUSS®). The prefabricated units consists of T-ribbed concrete slabs partially embedded within and connected to two side PFC channel steel beams via a novel horizontally-oriented shear connection system. This connection system incorporates either horizontally-oriented web-welded shear studs (WWSS), horizontal steel dowels welded to the webs, or a combination of both (WWSS with dowels). The unique configuration of the flooring system minimises its structural depth, yielding ultra-shallow floors with a high span-to-depth ratio, surpassing other shallow flooring systems in efficiency. Additionally, it reduces the material usage, and when combined with lightweight concrete, the flooring overall weight (load on beneath structure) and the associated environmental impacts are significantly reduced.
The environmental performance of the flooring system is evaluated through a comparative Life Cycle Assessment (LCA) study, focusing on the global warming potential (GWP) and embodied energy (EE) impacts of PUSS compared with the widely used hollow core precast slabs. The study examines 16 live load/ floor span scenarios and evaluates the benefits and drawbacks of utilising different concrete types in PUSS flooring, namely normal weight concrete (NWC), lightweight aggregates concrete (LWC) and geopolymer concrete (GPC). Results indicate that PUSS outperforms hollow core slabs in all scenarios, regardless of the concrete type used. PUSS with GPC offers the greatest GWP savings, achieving up to 50% reductions compared to hollow core slabs. However, PUSS with LWC demonstrates the best overall performance in terms of both GWP and EE, with up to 35% savings in EE and 46% in GWP, and its lighter weight reduces the load on supporting structural elements, further amplifying the overall environmental benefits.
Furthermore, the research explores the effect of a group of parameters on the flexural behaviour of PUSS and the performance of the implemented shear connectors under bending through a series of experimental and computational studies. The investigated parameters include concrete type, concrete strength, degree of shear connection, span and slab depth. Four full-scale specimens, each with a span of 4 m were constructed and tested under four-point bending tests at George Earle laboratory (GEL), University of Leeds. The results indicate that PUSS with LWC achieves similar flexural capacity to PUSS with NWC, though it exhibits lower initial stiffness and develops larger cracks. Additionally, the tests reveals that reducing the degree of shear connection lowers the slabs’ moment capacity and leads to failure of some shear connectors. Despite this, PUSS units demonstrates ductile behaviour in all cases.
A finite element model resembling the experimental tests was then developed, validated against the experimental results, and used in a comprehensive parametric Finite Element Analysis (FEA) study involving 324 models. The study shows that reducing the degree of shear connection leads to decrease in moment capacity, but the reduction is non-linear due to the parabolic relationship between moment capacity and the degree of shear connection. This highlights the complex interaction between shear connectors and overall slab performance. Larger discrepancies are noted between FE-derived moment capacities and hand calculations using existing shear capacity formulas, especially in lightweight concrete (LWC) models, underscoring the need for refinements in the shear resistance equation to achieve more accurate predictions.
The gathered data from both experimental and FEA studies were extensively studied, and analysed through regression analysis, leading to the development of an optimised empirical formula to predict the shear resistance of the shear connectors employed in PUSS and their corresponding degrees of shear connection. This formula provides a more accurate prediction of shear resistance and degree of shear connection compared to existing methods, aligning closely with the results of 328 experiments and FEA models. Additionally, a moment capacity design methodology for PUSS flooring system in accordance with the Eurocode 4 standards is presented. This methodology offers a solid framework for the practical implementation of PUSS in construction, with the potential to inform future revisions of design codes
Nonlinear evolution of vortical disturbances entrained in the entrance region of confined flows
No full textThe nonlinear evolution of free-stream vortical disturbances entrained in the entrance region of confined flows---pipe and channel flows---is investigated using asymptotic and numerical methods. The focus is on low-frequency disturbances that induce streamwise-elongated structures and on Reynolds numbers for which the flow is linearly stable but undergoes intense algebraic growth of disturbances. The disturbance flow along the entrance is generated by free-stream disturbances at the pipe and channel inlets, with their amplitudes being sufficiently intense for nonlinear interactions to occur. The formation and evolution of the disturbance flow are described by the nonlinear unsteady boundary-region equations, derived and solved numerically herein in the pipe and channel flow geometries for the first time. Matched asymptotic expansions are employed to construct appropriate initial conditions, and the initial-boundary value problem is solved numerically by a marching procedure. A parametric study is conducted to examine the effects of the Reynolds number and the characteristics of the inlet disturbances on the nonlinear flow evolution. Numerical results show the stabilising effect of nonlinearity on the intense algebraic growth of the disturbances and an increase of the wall-shear stress due to the nonlinear interactions in both flows. Streamwise elongated pipe- and channel-entrance nonlinear structures (EPENS and ECENS) occupying the whole cross-section are discovered. EPENS possessing a rotational symmetry comprise high-speed streaks near the wall, and low-speed streaks centred around the pipe core. These distinct structures display a striking resemblance to nonlinear travelling waves found numerically and observed experimentally in fully developed pipe flow. ECENS are characterised by low- and high-speed streaks and streamwise vortices whose cores are centred at the channel centreplane. A rotational symmetry with respect to the vortex centres is identified for ECENS. For sufficiently large inlet amplitudes, their dynamics becomes largely independent from the symmetrical properties of the inlet disturbances
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