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A conceptual framework for scaling up emergent predictions from mechanistic individual-based models
No full textEnvironmental decision-makers need robust, landscape-level predictions of population responses to inform management decisions before implementation. Mechanistic individual-based models (IBMs) can capture how individual behaviour and interactions in heterogeneous environments generate emergent population dynamics, but high computational costs typically restrict applications to small spatial extents. To address this limitation, we synthesise spatial modelling strategies across subfields of ecology and introduce the Spatial Threshold of Emergent Behaviour Stabilisation (STEBS) framework. STEBS capitalises on the biological realism of mechanistic IBMs through an in silico modelling experiment to quantify the Critical Emergence Threshold (CET) — the smallest spatial extent at which emergent system behaviour stabilises. The CET provides a biologically meaningful and computationally efficient scale for developing meta-models that relate environmental variables to emergent population patterns, which can then be extrapolated across unsimulated regions to predict landscape-level dynamics. This approach enables tractable scaling up of mechanistic IBMs, while retaining their biological realism. STEBS therefore offers a systematic pathway for applying IBMs to real-world environmental challenges, enhancing the evidence base for policy and management under accelerating global change. Future development of STEBS into an operational and transferable tool will require empirical validation across diverse species, landscapes and IBM structures, alongside evaluation of whether the upfront investment required to estimate CETs improves predictive efficiency compared to brute-force scaling approaches.This work is supported by UKRI NERC (grant no. NE/W003031/1) and UKRI BBSRC FoodBioSystems Doctoral Training Partnership (grant no. BB/T008776/1).Individual-based Ecolog
How international physical presence and infrastructure differences moderate the link between digital internationalization and MNE performance
No full textWhile prior work has predominantly studied the performance implications of multinational enterprise (MNE) physical internationalization, research on how MNEs perform when simultaneously coordinating international digital channels and physical presence remains scarce. This challenge is particularly acute in retail, where the strategic convergence of born-digital retailers expanding physically and traditional retailers going digital creates new cross-domain challenges. Nonetheless, the impact of international physical presence and differences in home country physical infrastructure relative to host countries on MNE performance remains unexplored. Drawing on the integration-responsiveness (IR) framework, we suggest that a non-linear, U-shaped pattern governs the relationship between digital internationalization and performance for these retail MNEs, because the costs of integration and responsiveness are dominant at lower levels of internationalization while their advantages become more pronounced with increased internationalization. Further, we argue that the digital internationalization and MNE performance relationship steepens (a) with a higher international physical presence and (b) for firms originating from home countries with superior physical infrastructure relative to their host countries. Utilizing an 11-year panel of some of the largest retail MNEs, our research contributes to international strategy literature by extending the IR framework to a multidomain digital and physical context, stressing the strategic importance of firm- and country-level physical resources and infrastructure in digital internationalization.Long Range Plannin
Scalable and generalizable path planning for robotic navigation using transformer-based heuristic learning
No full textEfficient and scalable path planning is a critical challenge for autonomous robotic systems, particularly in complex real-world scenarios. Traditional heuristic search algorithms like A* often struggle with scalability and adaptability in such environments. To address these limitations, we improve a search framework that integrates learned, instance-specific heuristics with conventional pathfinding techniques. Leveraging autoencoder transformer networks, we predict two key heuristic functions—Correction Factor (CF) and Path Probability Map (PPM)—trained on diverse datasets—the Motion Planning (MP) and Tiled-MP datasets—to cover a wide range of path planning scenarios. When integrated with Weighted A* (WA*) algorithm, this approach optimally solves 88% of MP instances, with paths averaging less than 0.7% longer than optimal, and requiring nearly five times fewer node expansions. The framework demonstrates the advantages of heuristic learning in handling larger path planning problems, with inference time accounting for just 10% of the total search duration. It solves nearly half of the most complex instances optimally, showcasing strong scalability for real-time robotics applications. The framework performs well in unseen environments, solving over 25% of new problems perfectly, finding near-optimal solutions with paths less than 7% longer than optimal, and requiring fewer than two-thirds of the typical expansions. Our framework outperforms learnable planners in both scalability and generalization.Information Science
Evaluation of the impact of coagulant choice on phosphorus removal from municipal wastewater
No full textJefferson, Bruce - Associate SupervisorPhosphorus removal is a critical objective in municipal wastewater treatment due to its role in eutrophication and the tightening of regulatory discharge limits. Chemical coagulation remains the most widely adopted method for phosphorus control; however, its effectiveness is influenced by coagulant type, pH conditions, dosing location, and wastewater matrix composition. This thesis aimed to advance the understanding of how these operational and chemical variables govern the mechanisms of phosphorus removal, with the goal of optimising coagulant selection and application strategies under real-world conditions.
A comprehensive screening of 17 coagulants, including ferric, aluminium, rare earth, zinc, and calcium-based formulations, was conducted under both uncontrolled and pH-adjusted conditions. Ferric sulphate, polyaluminium chloride (PACL), and aluminium sulphate emerged as the most effective agents, achieving residual total phosphorus concentrations as low as 0.35 mg/L, 0.15 mg/L and 0.6 mg/L, respectively, under controlled pH conditions, particularly under neutral pH, where stable hydroxide flocs are favoured. Rare earth coagulants demonstrated high phosphate affinity but formed fragile flocs, limiting their practical application. Floc characterisation revealed that compact, shear-resistant aggregates correlated strongly with higher removal efficiency.
To investigate the role of pH, a detailed comparative analysis of ferric sulphate (FS), aluminium sulphate (ALS), and PACL was performed across a pH range of 4-8. The results confirmed that coagulant solubility, hydrolysis potential, and metal speciation significantly impact phosphorus removal efficiency. FS and ALS were better than PACL under acidic conditions due to more complete hydrolysis and formation of stable flocs. Phosphorus fractionation and turbidity data supported these trends, identifying pH 6-7 as the optimal window for coagulant performance and floc settleability.
The final phase of the study examined how dosing location in the crude influent, after primary settling tanks (PST), and in the final effluent (FE) influences coagulant performance. FS showed enhanced phosphorus removal even in high-strength crude wastewater, though required careful pH control to avoid over-acidification. ALS and PACL were more effective at PST and FE, where organic loading and particulate interference were lower. A two-point dosing strategy applied to crude wastewater was found to enhance phosphorus removal while reducing total coagulant demand, offering a practical route for chemical cost optimisation.
Collectively, this thesis delivers critical insights into the physicochemical and operational factors driving chemical phosphorus removal. The findings inform coagulant selection and deployment in diverse wastewater environments, support compliance with future phosphorus discharge standards, and contribute to the development of cost-effective and environmentally sustainable treatment strategies.PhD in Wate
Examining the relationship between job characteristics and work engagement in mission-oriented and non-mission-oriented roles within the public sector
No full textKelliher, Clare - Associate SupervisorIn recent years, there has been growing academic interest in understanding how contextual features shape employee work engagement, particularly within the public sector where job roles and motivations are highly heterogeneous. While substantial literature has explored engagement through the Job Demands-Resources (JDR) theory, the influence of contextual variation across occupational roles remains under-theorised. This thesis focuses on the heterogeneity of public sector work and examines how differences between mission-oriented and non-mission-oriented roles influence the relationship between job characteristics and employee engagement.
Building on longstanding criticisms that engagement research has often neglected context or reduced it to a statistical control, this study draws on Johns’ (2006) framework to conceptualise context as an integral theoretical element. The research empirically investigates how contextual variation interacts with job demands and resources to shape engagement and exhaustion. Using data from the 2021 European Working Conditions Telephone Survey (EWCTS), this study applies Multigroup Structural Equation Modelling (MG-SEM) and Moderated Structural Equation Modelling (MSEM) to a stratified sample of public sector employees across Europe. The analysis tests the differential salience of job characteristics and the buffering role of resources in mitigating the negative effects of job demands.
This study finds that employees in mission-oriented public sector roles experience both higher work engagement and higher exhaustion than their non-mission-oriented counterparts, showing the importance of context in shaping psychological experiences at work. Emotional demands function as challenge demand but primarily as hindrance demands in mission roles, being strongly associated with exhaustion but not significantly with engagement. Contrary to expectations, work intensity and work-life interference showed similar effects across both role types. Among job resources, social support had greater significance for engagement in mission-oriented roles, while autonomy and voice were beneficial across roles. Only autonomy demonstrated a significant buffering effect, mitigating the impact of work intensity on exhaustion, but only in mission-oriented roles.
Theoretically, the study advances JDR theory by integrating role context as a central explanatory mechanism, using Johns’ (2006) contextual framework. It challenges assumptions of motivational homogeneity in public sector work and illustrates that the effect of job demands and resources is contingent on role type. Methodologically, it employs Multigroup Structural Equation Modelling (MG-SEM) to test the moderating role of context, positioning it as a central variable rather than a control variable. Practically, the study provides a foundation for more tailored, role-sensitive engagement strategies in public sector human resource management.PhD in Leadership and Managemen
Data supporting Molecular and metabolic response of ‘Piccolo’ cherry tomato to Graduated Controlled Atmosphere
No full textControlled atmosphere (CA) can trigger metabolic and hormonal disruptions that negatively impact fruit quality. This study aimed to understand the mechanisms underlying ethylene sensitivity under low oxygen conditions through the application of a novel approach to CA, called Graduated Controlled Atmosphere (GCA), in ‘Piccolo’ cherry tomato. Compared to standard CA, GCA treatment resulted in greater suppression of respiration and improved firmness retention, indicating reduced physiological stress and slower cell wall degradation. Gene expression analysis revealed downregulation of NCED1, ACS, and ACO genes under GCA, indicating delayed ethylene-associated transcriptional activity. These hormonal adjustments were also reflected in lower abscisic acid (ABA) concentrations, implying a more stable ripening trajectory. Besides hormonal modulation, GCA-treated fruit exhibited alterations in primary metabolism. Sucrose accumulation and changes in malate levels under GCA conditions suggest a shift in energy metabolism, consistent with improved hypoxia tolerance. However, a notable trade-off was observed in reduced lycopene accumulation, potentially due to lower oxidative signalling and shared precursors between carotenoid and ABA biosynthesis. GCA promotes a more controlled physiological and molecular response to hypoxic storage by reducing stress-associated metabolic and hormonal activity.Biotechnology and Biological Sciences Research Council (BBSRC
Aerodynamics of short intake at high incidence
No full textThis work assesses the aerodynamics of a short aero-engine intake for a new rig that is planned to be tested at the Large Low-Speed Facility of the German Dutch Wind Tunnels (LLF-DNW) in 2025. A range of computations were performed to assess whether the expected aerodynamics in this arrangement encompass the envisaged range of flow field characteristics of the equivalent isolated configuration. The effect of massflow capture ratio and angle of attack are investigated. In addition, an intake flow separation taxonomy is proposed to characterise the associated flows. The wind tunnel analysis is based on two different modelling approaches: an aspirated isolated intake and a coupled fan–intake configuration. The coupled configuration uses a full-annulus model with a harmonic mixing plane method. Across the range of operating conditions with changes in the massflow capture ratio and angle of attack, there are attached and separated flows. The main separation mechanisms are diffusion-driven and shock-induced, which shows the different aerodynamics that may be encountered in a short intake. Overall, this work provides an initial evaluation of the aerodynamics of the new fan/intake test rig configuration, provides guidance for wind tunnel testing, and lays a foundation for subsequent unsteady coupled fan–intake studies.This research was funded in scope of the 6th Federal Aeronautical Research Program (LuFo VI-1) by the German Federal Ministery of Economic Affairs and Climate Action (BMWK, formerly BMWi) and is part of the project ModeGo (FKZ: 20T1914A).International Journal of Turbomachinery, Propulsion and Powe
Dataset: The performance of low-coherence and confocal refractometry with reduced index contrast
No full textThis paper looks to evaluate the performance of combined low-coherence and confocal refractometry under conditions of reduced refractive index contrast. The instrument measures the refractive index and thickness of transparent objects using a fibre-based low-coherence interferometer with a line-scan spectrometer. A sample was designed that roughly mimics the structure of the eye, consisting of a lens tube holding window pairs surrounded on either side by fluid chambers and sealed at the far end by diffuse black metallic plugs. Sucrose solutions of increasing concentrations were injected into the fluid chambers providing a linear variation in refractive index from 1.3330 to 1.4416. The instrument was used to measure both the phase and group refractive indices, np and ng, as well as the physical thickness t of the windows and the fluid in the chambers. Measurements show that the accuracy and uncertainty decrease with reduced refractive index contrast but remain better than 0.6% for sucrose concentrations of up to 60.3%, which is close to the saturation limit.Engineering and Physical Sciences Research Council (EPSRC
Case study of air transport in Barbados: a decade of evolution
No full textThe Caribbean island-nation of Barbados represents an intriguing and valuable case study in air transport, with very little scholarly attention to date. This paper aims to investigate the state of air transport in the country over a decade-long period using three full years as reference points starting in 2014, then 2019 before onset of the COVID-19 global pandemic; and finally, 2023. The overall air market is assessed, then major markets by region are detailed; and lastly, the CARICOM air market’s direct links to Barbados are covered. By employing data from these three 12-month time periods over a decade (2014, 2019 & 2023), a clearer sense of the key insights into the country’s air transport industry’s size, scope and prospects can be achieved, while the composition of the air transport industry can also be better ascertained. Added to this, the likely future trajectory of the industry can be more accurately gauged and forecast. The core lessons and major implications from this study, not just for Caribbean nations and territories, but for other similarly sized and situated islands in places like the South Pacific and Indian Ocean, are many and varied. Chiefly, air transport development plays a pivotal role in not only connecting these communities with their neighboring regions and wider world, but in ensuring that island economies can diversify beyond a traditional focus on agriculture and tourism and expand into a wider array of sectors. In this context, the internal/national socio-economic benefits of air transport represent more than just the external links that air transport creates; but rather, national economic development and diversification with air transport acting as a key enabler.Transportation Research Procedi
Near-source wastewater surveillance as a non-invasive tool for disease detection in prisons
No full textNear-source wastewater-based epidemiology (WBE) offers a non-intrusive alternative to clinical testing of whole prison populations. Prisons sit at the centre of high transmission risk but experience limited health-care access and barriers to testing individual prisoners. However, the use of WBE for health protection in prison settings has been limited. To assess its merit during the COVID-19 pandemic, SARS-CoV-2 RNA concentrations were quantified in 680 composite wastewater samples collected from 14 prisons across England and Wales between January and June 2021. Viral RNA was detected in 48% of samples, and wastewater viral loads were found to closely mirror clinical case numbers Lead–lag analysis with adjacent municipal wastewater samples indicated a bidirectional flow between the prisons and their local community: seven prisons exhibited wastewater peaks ahead of their communities, while six lagged, highlighting heterogeneous epidemiological coupling. Marked differences between prisons were apparent in both physicochemical wastewater traits and clinical testing uptake, indicating each institution constitutes a distinct surveillance unit. Collectively, findings here indicate near-source WBE as a rapid, unbiased and scalable tool for disease outbreak detection and for mapping disease flow between prisons and their surrounding communities, advocating its integration into routine health-security frameworks for custodial and other high-density settings.Funding was provided by a UK EPSRC Impact Acceleration Award (EP/R511584/1) and a UK NERC award (NE/V004883/1) in the COVID-19 Urgency Programme. Funds were also provided by the UK Department of Health & Social Care (Grant Reference 2020_086)Scientific Report