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Spatial distribution of zonal flow drive: from tokamaks via novel hybrids to stellarators
Get PDFZonal flows are of central importance for the confinement and therefore performance of future fusion reactors that are based on the idea of toroidal magnetic confinement. By taking energy out of turbulent fluctuations and by shearing turbulent eddies apart, these flows reduce the radial turbulent transport which is responsible for the majority of the heat and particle losses in tokamaks and optimised stellarators.
Turbulent transport properties are known to be strongly affected by plasma shaping. Yet not all origins are identified, and one key missing gap in our understanding is the spatial distribution of the nonlinear drive of zonal flows due to Reynolds stress. In this work we show that this spatial distribution is generally non-trivial and generally not correlated with the distribution of turbulent fluctuations, for both axisymmetric and non-axisymmetric shaping of the nested toroidal surfaces. In particular, it is found that the zonal flow drive peaks away from the outboard midplane, where turbulent fluctuations are usually the strongest.
In pursuit of combining the advantages of tokamaks and stellarators and to bridge the gap between them, a new method was developed to optimise three-dimensionally perturbed tokamak equilibria for quasi-axisymmetry, strong enough for key stabilising benefits of stellarators to be expected. We examined the general turbulent properties in this continuous parameter space from tokamaks to stellarators, and showed that the zonal flow drive envelope here also is non-trivial, developing additional local maxima due to the localised three-dimensional shaping. Further, by extending the analysis to more traditional stellarators, the zonal flow drive is also shown to be non-trivial in the most unstable flux tube of the largest stellarator experiment, Wendelstein 7-X.
Finally, we derive and discuss how the Reynolds stress analysis can be generalised to the gyrokinetic nonlinearity, describing the zonal flow drive with kinetic effects
A mixed methods study exploring how multidisciplinary teams support people with motor neuron disease to make decisions about gastrostomy placement
Get PDFDeconstructed Learning in Pre-Clinical Dental Education Using Virtual Reality Simulation
Get PDFAim:
The aim of this project is to assess if Virtual Reality, as an operative dental education tool, results in superior learning (as measured via a transfer task) when it is employed to provide deconstructed part-task exercises instead of facilitating whole-task repetitive practice.
- Literature Review: Explore contemporary uses and applications of VR in operative dental education (Scoping Review).
- Design of a Task Analysis approach through which operative tasks can be deconstructed into their sub-component tasks and reveal their underlying cognitive structure.
- Application of the Task Analysis approach to deconstruct an operative procedure (caries removal and cavity preparation).
- Creation of task-specific VR simulator exercises from the identified sub-components.
- Randomised control trial to assess the interventions: Deconstructed part-task versus whole-task training using VR simulation.
- Evaluation of results using: 1) Quantitative measures of performance, retention and transfer to establish superiority. 2) Qualitative evaluation of participant opinion to explore themes relating to perceptions and acceptability of the experimental approach.
- Presentation of a recommended approach for Task Analysis of operative tasks to support learning using deconstructed VR simulator exercises.
Results:
- Motor skills research and student opinion do not support the premise that VR simulation should replace traditional phantom head simulation.
- The theory of motor skills specificity should be integrated into teaching to optimise transfer to target contexts.
- Task Analysis can be applied to produce a consensus, revealing divergence in operative approaches and promoting discussions leading to an agreed institutional approach.
- Task Analysis is a powerful tool for uncovering the underlying cognitive basis of tasks which can be used to develop deconstructed exercises or other new learning materials.
- Deconstructed exercises manage the complexity of learning operative tasks and facilitate the optimisation of transfer to other contexts. Such exercises can be effective and are welcomed by learners.
- Deconstructed learning may result in superior retention of declarative facts and improved judgement when compared to whole-task teaching approaches
“We can just say it and we say we know what it means, but then do you really know what it means?”. Understanding experiences, constructions and management of toxic gaming communities: A League of Legends case study
Get PDFThis thesis reports a study of the interpretation and management of toxic gaming communities through the case of League of Legends (LoL). The thesis positions games as a form of interactional culture where meanings about belonging, behaviour and language are created, and thereby shape, gaming communities. A critical review of the literature on community, culture and toxicity identifies a knowledge gap in understanding toxicity in online gaming.
As insider research, this study privileges participant voice in using players’ accounts to understand how players interpret toxicity, and second, why players continue to play LoL when their gaming community is described as ‘toxic’. This is explored through a mixed methods research design, beginning with a mixed methods survey with 152 participants from thirty countries. This is followed by seventeen qualitative interviews, with participants located in seven countries. Analysis of descriptive statistics from the quantitative survey is followed by thematic analysis of qualitative survey data and semi-structured interviews.
Players’ introductions to LoL are found to be primarily through friends, family or partners, and established players become instrumental in supporting new players through toxicity. The nuances of interpreting and understanding toxicity are identified, noting a discrepancy between players and game developers. Interpretation of toxic behaviours is found to be driven by five factors, including offline characteristics, approaches to play, and knowledge. Players’ agency in mitigating and manging their gameplay experiences was reported to include use of muting and pre-made teams. Players continued engagement with LoL was due to its uniqueness, and its provision of immersive lore, familiarity and social opportunities. An original tool, the Toxicity Interpretation Framework, is derived from the study to further understanding of toxicity. The thesis concludes by considering toxicity as a reflection of aspects of our social world, with recommendations for addressing toxicity via player agency
Pedagogical adaptions of Chinese students on a UK Music Education MA programme: Perceptions of Chinese students, MA teaching staff, and Chinese returnees
Get PDFGlobalisation and internationalisation have interconnected people through
education. While much intercultural research focuses on the culture shocks and
adaptive challenges faced by international students due to academic, cultural, and
educational differences, fewer studies have examined how these experiences impact
their instrumental and vocal teaching approaches, career expectations, and
employability. Haddon (2019) explored how Chinese students viewed their prior
educational experiences in relation to their MA music studies. Further research
(Haddon, 2024) examined how their overseas education could be perceived as both
beneficial and potentially at odds with their home country’s educational values upon
their return.
The thesis extends Haddon’s (2019; 2024) research by investigating enrolled
students’ and returnees’ pedagogical and intercultural perceptions before, during,
and after UK Music Education masters study, also investigating the related
perceptions of programme teaching staff. Qualitative data were gathered through
three sets of interviews (13 instrumental/vocal teaching students, 13 masters
teaching staff, and 13 returnees). The findings reveal that overseas learning and
teaching training is seen as an expansion of students’ understanding of education
and impacts their career decisions. Various factors, such as personality, career
expectations, pre-MA educational experiences, post-MA teaching contexts, changing
societal values, and the influence of the COVID-19 pandemic, impact students’
adaptabilities during UK study and returnees’ employability and challenges in
applying MA knowledge to their teaching in China. This research has implications for
the teaching adjustments and adaption of overseas students, and educators in both
UK and China contexts
Understanding Differences in Mental Health for LGBTQ+ Adolescents
No full textLGBTQ+ adolescents have higher rates of mental health problems and reduced wellbeing compared to non-LGBTQ+ adolescents (where LGBTQ+ is used an an umbrella term for all those with diverse gender identities or sexual orientations). This thesis aimed to understand whether these disparities are increasing over time, and possible differences in causal mechanisms behind them using a representative UK cohort.
A systematic review was carried out to assess whether trends in mental health differ for LGBTQ+ and non-LGBTQ+ adolescents over time. The outcomes of interest were measures of wellbeing, anxiety, depression, self harm or suicidality. Database searches found 2753 studies (1939 after removal of duplicates), 53 of which were potentially relevant after title and abstract screening and were screened using their full text. This resulted in 15 studies which met the criteria for inclusion. The review found that LGBTQ+ groups had poorer rates for all included outcomes across the studies compared to the non-LGBTQ+ groups. Anxiety and depression showed a statistically significant widening of disparities over time for those with diverse sexualities compared to heterosexuals, while there was no consensus for self harm, suicidality or wellbeing. Only 2 studies included analyses for those with diverse gender identities, and though they found elevated rates for all reported outcomes, they did not find any significant differences in trends compared to the cisgender groups which was likely due to the small sample sizes. The lack of findings in those with diverse genders highlights an urgent need for more data from this population to reduce the current blind spots, and aid in policy development.
This thesis explores how the relationships between factors related to mental health differ for LGBTQ+ and non-LGBTQ+ adolescents using data from the Millennium Cohort Study (MCS), a nationally representative UK cohort study following children born in 2000-2002 in England, Scotland, Wales and Northern Ireland. We analysed data from this study split into LGBTQ+ and non-LGBTQ+ groups to see if and how the relationship between determinants of mental health outcomes differ for the two groups. Outcome variables were self-harm and suicide attempts from responses provided at age 17. The determinants included demographics, and variables describing experiences, behaviours, and social environments provided both at ages 14 and 17, to explore the interaction of variables between time points. The analysis utilised a Bayesian Network (BN) approach with Directed Acyclic Graphs (DAGs) to estimate the likely direction of conditional dependencies between the variables and assess possible causal mechanisms. Hypothesis testing was performed to determine if the DAGs for the two groups were statistically significantly different. The intention to estimate causal relationships required several assumptions, including no unobserved confounding variables, and faithfulness. While these assumptions limit the certainty of causal claims and require caution in interpretation of results, steps were taken to mitigate these limitations, such as integrating domain knowledge and sampling from likely structures.
At age 17, 9612 of 10757 cohort members provided responses about their sexuality and gender identity. 2645 of 9612 were identified as LGBTQ+ and 6967 of 9612 were identified as non-LGBTQ+. Compared to the non-LGBTQ+ group, the LGBTQ+ group had higher rates for the outcome variables (42.50% vs 17.31% for self-harm, 16.07% vs 4.37% for suicide attempts), and higher rates of victimisation (68.50% vs 52.64% at age 17) and lower rates of high self-esteem (52.27 % vs 75.07% at age 17), both identified as key variables for both groups. The structures for the two groups were found to be significantly different (p¡0.001), and inspection of the DAGs showed some key differences. In particular, peer problems and substance use were more important for the LGBTQ+ group, and emotional symptoms and conduct problems were more important to the non-LGBTQ+ group.
The relationships found for the two groups were also used to explore downstream causal effects of interventions on the factors included in the structures. This analysis found that factors such as victimisation and self esteem had significant effects on self harm and suicide attempts for both the LGBTQ+ group and the non-LGBTQ+ group, while conduct problems and emotional symptoms were only significant for the non-LGBTQ+ group and substance use and peer problems were only significant for the LGBTQ+ group. These findings underscore the importance of tailoring interventions using insights on group specific mechanisms and designing policies that address the unique experiences of LGBTQ+ adolescents.
This thesis provides robust evidence of the persistence of mental health disparities experienced by LGBTQ+ adolescents, identifying key drivers and demonstrating the potential unintended consequences of well meaning interventions. Therefore, policy makers should implement targeted interventions, such as anti-bullying programmes, and ensure that policies consider the effects on LGBTQ+ adolescents specifically to avoid inadvertently widening inequalities. Consistent and inclusive data collection is also vital to validate the results in this thesis and to inform future policy decisions. Future research should aim to evaluate the long term effect of policies to guide evidence based strategies to effectively address the mental health inequities faced by LGBTQ+ adolescents
Decay Spectroscopy of Isomerically Pure Beams of 178Au and its Daughters
Get PDFIn many regions of the nuclear landscape, competition between spherical and deformed configurations leads to the phenomenon of shape coexistence due to the delicate balance between shell and collective effects. The region around the Z = 82 proton-shell closure and the N = 104 neutron midshell contains some of the clearest examples of this phenomenon and has thus been the focus of intense theoretical and experimental study in recent decades.
The results presented in this thesis form a contribution to this long-term programme through an in-depth decay spectroscopy study of 178Au (Z =79, N =99) and its daughters. In-source laser spectroscopy by Cubiss et al. [1] at the ISOLDE facility confirmed the existence of a previously predicted, strongly deformed isomer, 178Aum, coexisting with the more weakly deformed ground state, 178Aug. As part of Cubiss’ study, highly selective resonant laser ionisation allowed separate α-decay studies of 178Aug,m to be performed. In the present work, the same technique was used to produce isomerically pure beams of each of these two states for a detailed decay spectroscopy study of the α- and EC/β+-decay branches of 178Aug,m, and their daughters, at the ISOLDE Decay Station (IDS).
Separate fine-structure α-decay schemes for 178g,mAu →174g,mIr and 174g,mIr →170Re were produced, expanding substantially on those from earlier works. The first ever isomerically selective electron-capture (EC)/β+ decay studies of 178Aug,m →178Pt and 174Irg,m →174Os were also performed for this thesis. All together, these decay schemes include 70 new states, 11 new α decays and 119 new γ-ray transitions. The half lives of 178Aug,m were measured which gave values consistent with those determined by Cubiss but have smaller uncertainties. The multipolarities of γ-ray transitions observed following the α decay of 178Aug,m to 174Ir were determined, as were reduced α-decay widths and hindrance factors, HFα. The proportion of EC/β+ decay feeding to each state in 178Pt and 174Os was calculated, allowing log f t values for these decays to be experimentally determined for the first time. These were used in conjunction with HFα to propose spin-parity and configuration assignments for 178Aug,m and 174Irg,m and infer information on the shape of 178Pt. The E0-transition strengths for decays between the states in two strongly mixed rotational bands in 178Pt were determined and used to calculate a lower limit for the difference in the mean-square charge radii of the bandheads. Using mass measurements reported by Cubiss and α-decay Q values deduced in this work, the excitation energy of the states fed by the α decay of 178Aug,m and 174Irg,m were determined. While all α decays from 178Aug were assigned as feeding directly or indirectly to 174Irg (and 178Aum to 174Irm), it was found that 174Irg feeds to a long-lived, low-spin state 47(17) keV more energetic than the high-spin state fed by 174Irm. This indicates a possible inversion of state ordering in 170Os relative to 174Ir and 178Au
Field Marshal Lord Nicholson (1845-1918) a great brain: the making and impact of a Whitehall warrior
Get PDFThe subject of this thesis, Sir William Gustavus Nicholson (1845-1918), later Baron Nicholson of Roundhay, was a significant and often controversial figure in the British army during the later Victorian and Edwardian periods. He rose to become Chief of the General Staff in 1908 and was described as the most powerful personality in the army. This thesis will aim to understand Nicholson’s influence on the development of the War Office and the establishment of a General Staff. The period 1901-1914, which coincides almost exactly with Nicholson’s time at the War Office, was one of the most critical in the history of the development of the British army, and this thesis will examine Nicholson’s influence within the army at this crucial period.
This work is important because of the absence of any previous study of Nicholson’s career, and of any critical appraisal of his influence upon the War Office and the army. It will also explore reasons why historians have largely ignored Nicholson, who never distinguished himself in the field but proved himself to be an outstanding army administrator. Being regarded as the most powerful personality in the army, he earned the reputation of being a difficult man with whom to work, and yet he was a significant figure within the War Office. It will analyse how he helped to move the army towards being a more professional entity, and his contribution to what John Dunlop described as ‘incomparably the best trained, best organised, and best equipped British Army which ever went forth to war’. This thesis will analyse and challenge generally accepted views about Nicholson’s work and character. Haldane described him as ‘an acute big brain’ and, ‘not an easy man’, however, he also said that he was someone that he needed in the War Office during the period of the implementation of his reforms. It will examine how Nicholson’s reputation was acquired, and his influence in the War Office and within Whitehall. The thesis will show that even during his retirement Nicholson remained active and continued to be both influential and controversial
Assessing the impacts of natural flood management on downstream flood risk: a case study of the River Aire
No full textNatural flood management (NFM) offers a potentially sustainable solution to mitigating flood risks, yet its effectiveness at larger catchment scales and under varying rainfall intensities remains uncertain. This thesis combined a quantitative meta-analysis of 454 NFM studies with hydrological (SD-TOPMODEL) and coupled hydrological-hydrodynamic (SD-TOPMODEL to Flood Modeller 2D) modelling in the River Aire Catchment (81.4 km2), to address research gaps. The meta-analysis revealed a shift in focus over time from localized flood mitigation to catchment-wide strategies, accompanied by increasing emphasis on ecosystem services. Contrary to previous findings, the effectiveness of NFM interventions were not found to diminish with increased catchment size nor rainfall intensity. Using SD-TOPMODEL, this research simulated diverse NFM interventions and their combinations at a high resolution (5m), including woodland planting, soil aeration, and hedgerow planting, achieving 4.2-16.0% flood peak reductions. NFM interventions were found to be most effective during single-peaked storm events and dry antecedent conditions. Combined interventions demonstrated greater resilience and effectiveness than single interventions in the catchment, emphasising the importance of integrated flood management strategies. A coupling of SD-TOPMODEL with Flood Modeller 2D was used to investigate downstream impacts of NFM scenarios (combining leaky dams, riparian buffer strips and other interventions mentioned above) and the maximum catchment woodland scenario, revealing changes in inundation extent and depth. An unintended inundation increases for a large village occurred under a widespread woodland creation scenario highlighting the importance of integrated and targeted NFM planning at the catchment scale. This thesis concludes that storm characteristics and pre-event conditions play a more significant role in determining NFM efficacy than catchment size or rainfall intensity. The findings emphasise the need for strategically designed, catchment-scale intervention networks and advocates for modelling approaches as essential tools for optimizing NFM planning and ensuring its effectiveness in wider flood risk management
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