Long-term performance assessment and future proofing of a raingarden for stormwater management

Raingardens are a type of Sustainable Drainage Systems (SUDS) that provides a nature-based solution to stormwater control. Research into the performance of raingardens is relatively scarce in the UK and effort is needed to provide data and improved scientific understanding to deliver a strong evidence-base. The overarching goal of this study is to evaluate the long-term performance of a raingarden, designed over a low-conductivity soil. To this effect, an experimental raingarden with two amended soil types (Sandy loam with 24% fines content; Loamy sand with 13% fines) was installed within the Royal Botanic Garden Edinburgh (RBGE) in Scotland, and monitored between Summer 2019 and Winter 2022-23. This study documents the qualitative and quantitative methods in evaluating a field scale raingarden. Antecedent soil moisture between storm events, saturated hydraulic conductivity, and climate season were found to be key factors that controlled surface ponding in the sandy loam media. The time to drain ponded water in this media in Winter was on average twice longer than that of Summer due to 71% lesser median percolation in the cold season. In comparison, loamy sand media exhibited a lesser influence of temperature on infiltration, with average values in Winter being 40% lower than those in summer. Computer model of the raingarden developed in this study predicts that infiltration in the sandy loam soil must be at a minimum of 64 mm/h to prevent overflow from the raingarden under a reasonable worst- case scenario projected for 2050. The efficiency of evapotranspiration (ET) removal on rainfall was on average of 43% in summer highlighting the significance of the role of vegetation in the hydrological cycle of the raingarden. Species Festuca altissima, Primula posioni and Ligularia fischeri, Rodgersia pinnata and Gunnera manicata were found not suitable in a raingarden setting due to either stringent habitat requirements or prone to wilting during prolonged dry periods. Organic wood mulch is preferred over gravel mulch as the later potentially increases the solar radiation exacerbating heat stress in times of drought. Overall, the results of this work indicate that raingardens installed over low-conductivity soils can still be an effective technology for stormwater management, when designed suitably. The findings of this work provide clear and transferable insights that can be applied to the design, monitoring and maintenance of raingardens in similar climatic and soil conditions, both in the UK and around the world

Computational modelling of ruthenium catalysed C–H alkylation of heteroarenes

A mechanistic study of the C–H alkylation of 2-phenylpyridine (2-ppy) using alkyl halides and catalysed by [Ru(2-ppy)(MeCN)4] + has been carried out using density functional theory (DFT). A general mechanism has been proposed for the reaction of primary alkyl halides, modelled as 1-bromopropane, in the presence of a carboxylate additive (Chapter 3). Following C–H activation and cyclometallation via deprotonation by the additive, an SN2 mechanism was identified for the C–Br activation step, leading to an ortho-alkylated product after reductive coupling and product release. The latter has been identified as the rate-determining step in catalysis. Subsequently, the role of the carboxylate additive has been assessed by studying the above reaction in its absence (Chapter 4). The results have shown that the substrate can perform the deprotonation. It was found that the rate limiting-determining step in catalysis becomes the formation of the C–H activation precursor, but the C–Br activation is not significantly affected. A complete mechanistic study of the C–X activation (with X = Cl, Br, I) of 1- chloro-, 1-iodo-, 2-bromopropane and 2-bromo-2-methylpropane in the presence of a carboxylate has also been performed (Chapter 5). While the nature of the halide does not significantly influence either the mechanism or the selectivity of the reaction, it was found that secondary and tertiary alkyl halides can follow a radical mechanism, affording some or exclusive meta-alkylation. Finally, the key results obtained in this thesis have been subjected to a benchmark study, compared against the available experimental data (Chapter 6), and GGA functionals have been proposed as the most appropriate method for this system

Engaging older adults in cognitive activities through socially assistive robots and sensory feedback

This thesis investigates how the novel combination of socially assistive robots and sensory feedback can foster engagement in cognitive activities for the older adult population. Cognitive decline is a natural part of ageing, and whether it arises from pathological or non-pathological origins, nonpharmaceutical methods can retain cognitive function and delay cognitive decline. Namely, cognitive training and leisure-based cognitive activities can positively impact older adults’ cognition. While consistent long-term engagement is required to attain the cognitive benefits, adherence has been identified as a common challenge for older adults. Therefore, tools which can promote engagement in cognitive activities can benefit the ageing population. This doctoral work employed validated user-centred methodologies to investigate whether the unique combination of socially assistive robots and sensory feedback could promote older adults’ engagement in cognitive activities. This research began with a feasibility study with young adults and a usability study with older adults, which both confirmed the potential for combining socially assistive robots and sensory feedback to foster engagement in cognitive activities. This was followed by a Participatory Design workshop with older adults and therapists that identified concrete interaction designs and themes for encouraging cognitive activity engagement. These results were integrated into a prototype, and its evaluation with older adults confirmed its effectiveness in promoting engagement with cognitive activities. The subsequent study identified enhanced performance and usability of engaging with a cognitive activity through a socially assistive robot over a laptop, in addition to a preference for kinesthetic feedback over non-contact cutaneous feedback. This thesis further contributed a long-term experiment with eleven older adults to determine whether the promising results from the prior user-centred evaluations would promote sustained engagement. Contrary to other robotic experiments, this study led to a consistent level of engagement with the robot, and it was also preferred over typical interactions with cognitive activities. Haptic feedback also enhanced engagement for visual-based activities over the long term. The principal finding from this work is that the novel combination of a SAR and sensory feedback can promote short- and long-term engagement in cognitive activities for older adults, which has the potential to lead to benefits in cognition. The thesis concludes with a set of guidelines for designing socially assistive robots and sensory feedback to foster cognitive engagement for older adults. This work, along with these guidelines, can assist future researchers in human-robot interaction and human-computer interaction to develop mechanisms for enhancing cognitive engagement for the ageing population moving forward.Engineering and Physical Sciences Research Council (EPSRC) funding Grant ID: EP/S023208/

Modelling the impact of shared pathogens in wildlife communities

The thesis uses mathematical modelling to answer important eco-epidemiologial questions in scenarios where interacting species share an infectious disease. These questions are important as shared disease is often linked to successful species invasion and so the disease increases the threat for native species. Shared disease is also linked to spillover and zoonotic infection and so can pose a threat to human health. We develop a model to assess the threat of the shared disease, squirrelpox, carried by the invasive grey squirrel to the conservation of red squirrels in the UK. We show that the grey squirrel epidemiological dynamics include reinfection and partial immunity and that squirrelpox infection levels can be high. This can lead to spillover to red squirrels when the species are sympatric, leading to epidemic outbreaks in red squirrel populations. We analyse general models that examine the role of shared infectious disease on the spatial spread of invasive species and the replacement of native species. We show that shared infectious disease can increase the rate of replacement of a native species even when the disease is not supported in the native species system. We develop a model for a prey, specialist predator, and generalist predator system in which the predators can become infected through consumption of infected prey and can transmit infection back to the prey species. The analysis shows that predators can increase the persistence of infectious disease and may act as epidemic bridges that support the infection during low density phases in the prey species.UK Engineering and Physical Sciences Research Council grant EP/S023291/

Retrofit ready : redefining energy and carbon life cycle methods

Retrofits are a necessity for reducing the UK’s energy demand and carbon emissions. However, with 26 million homes to treat and massive implications for material consumption, life cycle energy and carbon impacts demand close attention; this refers to the operating impacts, as well as the embodied impacts, i.e. those expended in products for resource extraction, manufacture, and end-of-life waste treatment and disposal. Sparse data on retrofits and inconsistency in life cycle methods confounds the relationship between operating and embodied impacts at a population-level, meaning that identification of the dominant factor, and hence retrofit’s overall benefit, remains ambiguous. Variability of embodied impact data, and underrepresentation of prominent retrofit materials were found to present further barriers to robust analysis. A redefined approach for a “retrofit life cycle analysis” (RLCA) is proposed, alleviating inconsistencies present in previous studies, and pinpointing the focus on the life cycle performance of thermal measures. This enables the derivation of an operating savings and embodied expenditure balance (O:E), which facilitates better evaluation of the life cycle performance than simply describing the resulting operating or embodied impacts. Through RLCA and the O:E balance, quantifiable parameters for proceeding, redesigning, or discontinuing the retrofit may be established, described as the “Retrofit Tipping Point”. The approach is tested with two archetypal UK case study houses and proposed retrofits, plus variants. Operating impact savings were found to dominate the O:E balance in all variants, demonstrating that the retrofits achieved operating savings in excess of the embodied expenditure, indicative of a favourable energy and carbon life cycle impact. Insulation materials made the largest embodied contribution in most cases. Case study data was comparable in magnitude to other literature studies; linear regressions relating operating and embodied impacts revealed line gradients close to zero, indicating very minimal change in embodied impacts as operating energies reduce. This suggests that even extensive retrofits can be beneficial over their life cycle.EPSRC Doctoral Training Partnership fundin

Broadband laser pulse pre-amplification and characterisation for petawatt-scale facilities

The amplification and characterisation of broadband near-infrared pulses in Petawatt-scale laser facilities presents unique challenges not encountered at lower pulse energies. This thesis research contributes to the development of two petawatt-scale laser projects at the UK’s Central Laser Facility, with a focus on a front-end noncollinear optical parametric amplifier (OPA) architecture and novel short pulse temporal characterisation techniques. An OPA system of four stages was demonstrated in the picosecond regime to amplify nanojoule seed pulses with a 160-nm bandwidth about 880 nm to energies of 1 mJ at 100 Hz. Compression of the picosecond front end was implemented using a transmissive grating compressor with 50% efficiency and optimised using a Fastlite DAZZLER acousto-optic programmable dispersive filter to produce 16–17 fs pulses. A complete design for a nsOPA pre-amplifier was developed for use at the Extreme Photonics Applications Centre, a 10 Hz short pulse petawatt facility, in which a nanosecond OPA amplifier was constructed, showing a large initial gain (×104 ) over 750–850 nm, with a final performance intended to amplify from 10 µJ to 1.5 J using barium borate and lithium triborate nonlinear crystals. A novel diagnostic was developed that visualises, calculates, and compensates for beam angular dispersion and was shown to have a precision of 1.4 nrad/nm. This result demonstrated simple laser pulse manipulation of angular dispersion, and thereby pulse-front tilt, for optimal pulse duration when focused, without adjustments of the large compressor gratings, which are required in high-power laser facilities. The diagnostic was applied to an existing, operational petawatt facility, VEGA, to record the angular dispersion in 13 different locations throughout the beamline to highlight areas of improvement within the laser alignment—specifically the compressor(s) and stretcher(s). This project substantially contributed to the development of the EPAC system, which, once operational, will be a world-leading user facility

Accurate estimation of macroscopic flow properties in porous media : from REV to upscaling

Representative Elementary Volume (REV) is the smallest volume of a porous media above which further size increases do not yield any changes in the measurements of a specific property. It is well established that the REV can vary across geological scales for different static (e.g., porosity) and flow-based properties (e.g., permeability). Most REV studies available in the literature are focused on static properties at the pore scale. However, in this study, we have focused on determining REV for single-phase flow parameters at the core scale to investigate whether SCAL experiments are performed on a representative volume. Also, the feasibility of using tracer tests for determining core scale REV was investigated since the shape of the effluent tracer tests can be a good qualitative indication of the heterogeneity, and the Peclet number can be a quantitative measure. For this purpose, several heterogeneous reservoir sections were generated, and tracer flood simulations were conducted on sub-samples of various sizes. It was demonstrated that, in general, permeability-based REV based on the common approach in the literature closely match the corresponding REV figures showing the accuracy of the novel tracer-based technique. As part of this study, the numerical dispersion associated with various techniques available for the simulation of tracer flow were also investigated and quantified. After identifying REV and performing SCAL experiments on a representative volume, an upscaling method is needed to use the results in reservoir-scale simulations. In this study, a complete set of two-phase numerical coreflood tests, along with a Gaussian Process Regression algorithm (GPR), was used to obtain a data-driven model. This model relates the measured oil production and pressure drop to the basic fluid and rock properties through dimensionless groups. Using dimensionless groups eliminate the impact of sample size on the results. Therefore, a new oil production and pressure drop curve can be calculated using the data-driven model for any larger or smaller sample. The obtained curves can be history matched to find the relative permeability at a larger scale. Next, the proposed upscaling method is extended to three-phase flow by introducing relevant dimensionless groups. The three-phase upscaling methodology is validated against large-scale numerical tests representing different reservoir heterogeneity patterns and fluid properties. The proposed approach demonstrates excellent performance in predicting oil recovery, water production, and pressure drop in three-phase flow systems and also upscaling three-phase relative permeability functions in heterogeneous porous media. In summary, this study contributes to the advancement of REV characterisation and relative permeability upscaling techniques for multi-phase flow in porous media. The developed tracer technique and dimensional analysis approach, coupled with the GPR algorithm, provide an accurate and reliable framework for capturing reservoir heterogeneity and predicting flow behaviour at larger scales. Also, the proposed approach demonstrates superior performance compared to the existing methods. The findings of this study have implications for optimising sampling strategies and enhancing the predictive capabilities of reservoir upscaling models

Instanton partition functions in eight-dimensional cohomological gauge theory

We elaborate on the analysis of noncommutative instantons on C4 with SU(4)- holonomy and their generalized ADHM construction. They are realized in a dimensional reduction of supersymmetric Yang–Mills theory from ten dimensions and also in string theory. The instanton partition function can be evaluated using torus equivariant localization, and we extend it to Calabi-Yau orbifolds C4/Γab with Γab a finite abelian subgroup of SU(4). For some classes of Γab, we exhibit the dimensional reduction to orbifold partition functions of Donaldson–Thomas theory on the toric Kähler three-orbifold C3/Γab. Through such reduction we conjecture closed formulas for the instanton partition function on the orbifolds C2/Zn × C2 and C3/(Z2 × Z2) × C. Solutions of the noncommutative instanton equations localized on collections of hyperplanes C3 in C4 are called tetrahedron instantons. They can be similarly studied as noncommutative six-dimensional instantons. We investigate their partition functions on orbifolds, generalising the discussion on Calabi-Yau orbifolds C4/τ (Γ), where τ is a homomorphism from a finite group Γ inside SU(4). When Γ is a finite abelian subgroup of SL(2, C), we show the reduction of of the 8d instanton partition functions on C2/Γ × C2 to tetrahedron instanton partition functions on C2/Γ × C2 . For Γ = Zn we expand our conjecturesEngineering and Physical Sciences Research Council (EPSRC) Doctoral Training Partnership grant

Functionalisation of polymeric materials with palladium nanostructures for applications in bioorthogonal prodrug activation

The use of bioorthogonal organometallic chemistry to facilitate the localised conversion of a chemotherapy prodrug into an active drug has been explored in a novel approach to targeted drug delivery. Chemotherapeutic prodrugs containing a palladium (Pd)-labile propargyl protecting group have been established, necessitating a suitable method to deliver the Pd trigger to its desired location. To this end, implants that can be inserted into the tumour site and contain catalytic Pd nanoparticles are being developed. This work demonstrates the functionalisation of non-degradable polymeric materials, poly(ethylene glycol) (PEG) microbeads or poly(2-hydroxyethyl methacrylate) (pHEMA)-based hydrogels, with Pd nanostructures. New methods for the in situ preparation of Pd nanoparticles, nanocubes and nanosheets inside these novel polymeric materials are presented. The ability of these materials to facilitate the key depropargylation reaction using a model compound, propargylated-Resorufin, is presented, with Pd-nanosheets displaying superior catalytic activity, entrapment, and reusability. The distinctive nanostructures synthesised within these PEG or pHEMA materials were examined using electron microscopy techniques, also showing the complexity of the polymer networks arising from inclusion of sheared gellan gum as a unique suspending additive. The results presented herein contribute to the development of implantable Pd-containing polymeric materials, capable of the required prodrug activating depropargylation reaction, and preliminary in vitro cytotoxicity tests show promise for the biocompatibility of some of these materials

Acoustic emission propagation through bone tissue with focus on a jaw bone surrogate model

Implants are used to improve quality of life, for example, dental implants can resolve negative effects of tooth loss, however current techniques for monitoring dental implants have limitations. An Acoustic Emission Finite Element framework could reduce limitations, whilst adding more capabilities. To realise this, simulations of AE propagation through an implant-less system are needed. Therefore the aim of this study was to simulate AE propagation through bone tissue. To that end, a material model for bone was developed and implemented into FE, in-conjunction with µCT-image-based 3D rib models created from fifteen rib samples used in the AE experiments. These experiments were then sim ulated in FE – ten of the samples were used to identify viscoelastic parameter β for the material model. The remaining five were used to validate the simulations of AE propa gation through bone. The material model was verified against theory, and the viscoelastic parameter, β, was identified to range from 0.0648 to 0.22 for the ten samples, with no clear correlation with bone sample properties. The material model was validated with three out of the five samples used for validation. Simulation of AE propagation through bone can be accomplished, thus there is potential for development of an AE FE implant monitoring framework