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Optimisation of the synthesis of CuCrO₂ using molecular beam epitaxy
No full textSince the first discovery of delafossite oxides, numerous combinations of elements have been investigated for the unique properties found within these oxides. In particular, the Cu-based delafossites, of which CuCrO₂ is one, has shown the potential as a p-type transparent conducting oxide. Currently, only a few p-type transparent conducting oxides are commercially used due to the requirement of having a bandgap energy outside the range of visible light. Optical transparency can also be increased by reducing the overall thickness to the nanometre range limiting the amount of light attenuation. Through a combination of these two factors, thin film CuCrO₂, along with its doped varieties, is an ideal candidate for commercial applications. In this thesis, a method was developed for thin film synthesis using molecular beam epitaxy. Single phase, c-axis orientated thin films were synthesised on aluminium oxide (Al₂O₃) substrates. Through the exploration of growth parameters such as substrate temperature, oxidation source, flux ratios and growth modes, the optimal conditions required for epitaxial CuCrO₂ thin film growth were determined. In-situ measurements using reflective, high-energy electron diffraction (RHEED) allowed for visualisation of sample changes throughout the growth. Ex-situ measurements, using X-ray diffraction and atomic force microscopy (AFM), were used to determine sample composition and surface morphology, in an effort to determine the overall quality of samples produced. The changes in oxidation source, flux ratio, temperature and stoichiometric ratio parameters were investigated. In this work, growth conditions were identified for the creation of c-axis orientated thin films of CuCrO₂, without the requirements of additional steps, on aluminium oxide substrates
Infrastructuring mobility via state-led school franchising : leveraging public educational resources to facilitate middle-class residential (im) mobility
Get PDFFunding: This research is supported by the Research Grants Council of the Hong Kong SAR, China (Project No. 17614720).Drawing on the literature of geographies of education, mobilities, and critical infrastructure studies, this study introduces a novel analytical lens of infrastructuring mobility to examine the prevalent phenomenon of school franchising in China. From the vantage point of mobility with an infrastructure focus, we examine how strategic school infrastructural substrates are selectively mobilized to facilitate desired (im)mobilities of the middle class for promoting urban (re)development. Drawing on rich empirical evidence, including policy documents and thirty-nine in-depth interviews with various stakeholders, we found that school franchising mainly revolves around exporting the subinfrastructure (i.e., the brand of key schools) from the city center to strategic locales in the suburbs, and to a lesser extent in the city center. Other infrastructural substrates essential for high-quality schooling experience like good teachers are lagging behind. These franchised schools are nonetheless highly sought after by middle-class parents anxious about social reproduction as infrastructures of promise, who subsequently enact residential mobilities to these urban (re)development areas to access these schools. These mobilities and their infrastructuring processes are underpinned by a nexus of the entrepreneurial local states, profiteering developers, and expansionist schools. Particularly, the state strategically orchestrates and meticulously calibrates school franchising and its geography to enable desired mobilities and facilitate urban (re)development. This study hence unpacks the multiple mobilities (of infrastructural substrates and middle-class households) and the infrastructuring process enabling it. It foregrounds the importance of education as an apparatus of urban governance and an integral part of reshaping the wider sociospatial restructuring processes.Peer reviewe
Towards the new generation of quantum sensors – ultracold atoms and NV centres
Get PDFWe simulate two different sensing platforms – the nitrogen-vacancy (NV) centre in diamond and Bose-Einstein condensates (BECs) in holographic ring traps – and consider how aspects such as sensitivity and speed can be characterised and optimised.
For the case of NV centres, this thesis focuses on their application as high-resolution sensors of magnetic field and investigates optimising the speed of the sensing process as we track a changing magnetic field. Current methods for optimising tracking speed rely on machine learning calculations to reduce the number of measurements required. Our work adds to this speed improvement by reducing the computation time of these calculations via Gaussian approximation. This led to a reduction in computation time by factor 10 in all but the lowest coherence time case, where the more modest improvement in computation time is made up for by an increase in tracking accuracy compared to the original non-approximate method.
In terms of the work with BECs, we perform both rotation and magnetic field sensing. To closer predict performance of experimental implementation, we consider the effect of shot noise in the presence of image pixelisation, as a camera would be in a physical set-up. After evaluating sensitivity, we found these to be competitive with state of the art quantum sensing alternatives. Additionally, we explore an innovative approach to engineer the wavefunction of the condensate to create a superposition state
Spatial distribution of the intertidal limpet Patella depressa Pennant, 1777 : patterns across wave exposure and season
No full textFunding: JTM is grateful for the financial support provided by an Erasmus+ traineeship grant, which greatly contributed to the realization of this study. This study also had the support of “Fundação para a Ciência e a Tecnologia (FCT)” through the project UIDP/04292/2020 awarded to MARE and through project LA/P/0069/2020 granted to the Associate Laboratory ARNET. AS is grateful for the Foundation for Science and Technology's support through funding UIDB/04625/2020 from the research unit CERIS. TAM thanks partial support by CEAUL (funded by FCT - Fundação para a Ciência e a Tecnologia, Portugal.Spatial patterns of intertidal rocky shore gastropods depend on various environmental stresses and biological interactions. Understanding how and why these patterns arise can provide important insights into the ecology and behavior of ecologically key organisms. Here, we addressed the unexplored limpet aggregative behavior and the influence of wave action and season. We assessed intraspecific patterns of the spatial distribution of Patella depressa on rocky shores of contrasting wave exposure in seasons with different levels of storminess in central Portugal. We predicted that intraspecific spatial structure estimated through individual-to-individual nearest neighbor distances (NNDs) would be more aggregated on exposed sites than on sheltered sites and, if season-dependent, such aggregation would be greater during the stormier winter months. Two sheltered sites and two exposed sites were sampled three times in winter and in summer. On each sampling occasion, the mean NNDs were measured digitally in 20 replicated random quadrats (0.25 × 0.25 m). We showed that season and exposure significantly affect the spatial distribution of limpets, with an aggregated spatial structure on exposed sites during the stormy winter months. On sheltered sites, limpets were randomly distributed regardless of season. In contrast, on exposed sites, limpets which were randomly distributed during summer changed to an aggregated structure in the winter. This is the first report of seasonally modulated patterns of spatial distribution associated with wave exposure for P. depressa. Such behavior can influence resource availability and outcomes of competitive interactions, with implications for ecosystem functioning.Peer reviewe
Circulation and cloud responses to patterned SST warming
Get PDFFunding: AM and MB acknowledge funding from the UK Natural Environment Research Council (Grant NE/T006269/1). EV acknowledges funding from the UK Natural Environment Research Council, Doctoral Training Partnership in Environmental Research (Grant NE/S007474/1). AW acknowledges funding from the CIMES Postdoctoral Fellowship under award NA18OAR4320123 from the National Oceanic and Atmospheric Administration, U.S. Department of Commerce.The climatological atmospheric circulation is key to establishing the tropical “pattern effect”, whereby cloud feedbacks induced by sea surface temperature (SST) warming depend on the spatial structure of that warming. But how patterned warming-induced circulation changes affect cloud responses is less clear. Here we use idealized simulations with prescribed SST perturbations to understand the contributions to changes in tropical-mean cloud radiative effects (CRE) from different circulation regimes. We develop a novel framework based on moist static energy to understand the circulation response, targeting in particular the bulk circulation metric of ascent fraction. Warming concentrated in regions of ascent leads to a strong “upped-ante” effect and spatial contraction of the ascending region. Our framework reveals substantial contributions to tropical-mean CRE changes not only from traditional “pattern effect” regimes, but also from the intensification of convection in ascent regions as well as a smaller contribution from cloud changes in convective margins.Peer reviewe
A decade of urban fires : Portuguese events between 2013 and 2022
No full textFunding: This work is funded by national funds through the FCT - Fundação para a Ciência e a Tecnologia, I.P., under the scope of the project DSAIPA/DS/0088/2019 and research and development units UNIDEMI (project UIDB/00667/2020) and NOVAMath (projects UIDB/00297/2020 and UIDP/00297/2020).This study describes a dataset containing urban fire events that took place in mainland Portugal between 2013 and 2022. The Regulation n.º3317-A/2018, established by the Portuguese National Emergency and Civil Protection Authority (Autoridade Nacional de Emergência e Proteção Civil, ANEPC), defines the Operations Management System (Sistema de Gestão de Operações, SGO). Among other attributions, this system allows to manage the lyfe-cycle of the urban fire events, from ignition to extinction, through the Operations Decision Support System (Sistema de Apoio à Decisão Operacional, SADO). This system supports the systematic collection of a minimum set of data on each event. All instances included in the dataset were retrieved from SADO. To make the data suitable for analytic purposes, several pre-processing actions were taken, including the steps of data transformation and cleaning. The dataset was further validated by a set of technical procedures aiming to verify both data correctness and utility. The final dataset provides the most recent multi-year record of Portuguese urban fires including 27 variables on 72641 events.Peer reviewe
Public-targeted interventions addressing antimicrobial resistance and antibiotic use in Sub-Saharan Africa : a scoping review
Get PDFFunding: This work was supported by the Data Literacy for Social and Environmental Justice, School of Geography and Sustainable Development (Data for Justice PhD research grant 2023/2024) University of St Andrews United Kingdom.Introduction: Antimicrobial resistance (AMR) is a global health threat, with sub-Saharan Africa (SSA) experiencing the heaviest health burden and the highest AMR-related mortality. Most interventions in the region focus on hospital settings and provider behaviour, with few empirical papers discussing how theories inform those interventions specifically, community-centred interventions often lack a theoretical framework. However, using behavioural change theories can help us understand public behaviour around antibiotic usage and how to develop theoretically based interventions to maximise effectiveness. This scoping review critically investigates public-targeted interventions on AMR and antibiotic use within SSA, paying close attention to the theories underpinning those interventions. Given the concerning global rise in the spread of AMR and its severe implications, the situation may likely deteriorate if interventions are not significantly enhanced. Methods: A comprehensive search of peer-reviewed literature published in three databases (PubMed, Web of Science and Google Scholar) between 1997 and 2023 was conducted to determine the extent, range and nature of existing studies in this area. This review used the Arksey and O’Malley five-step scoping review framework. Results: The final review included seven publications, with three of the studies conducted in Ghana and the remaining studies carried out across other SSA nations. Findings revealed that AMR interventions were tailored to various demographics, including school children, parents, patients and online audiences. There is a notable lack of inclusive interventions for vulnerable populations, such as persons living with disabilities. Conclusion: The study findings emphasise the critical need for more community-centred research and AMR interventions that integrate relevant theoretical frameworks while being appropriately tailored to local contexts.Peer reviewe
Indian women, refugees, and decolonisation across India, British Malaya, and China, 1940-1953
Get PDFThis article studies two refugee political communities, the Indian National Army (INA) and Faridabad, during the 1940s. It follows two Indian women who supported the refugees: the captain of the INA’s women’s regiment, Lakshmi Sahgal (née Swaminadhan, 1914–2012), and the socialist freedom fighter Kamaladevi Chattopadhyay (1903–88). Indian and Chinese anti-colonialism and working-class protests in Malaya inspired the INA’s war against British rule in India and Southeast Asia. This article conceptualizes the INA as a refugee polis, comprising Indians displaced by Japanese and British imperialism. Uprooted by the Partition of India, the refugees in Faridabad brought practices of state evasion from the Indo/Pak-Afghan borderlands. Kamaladevi and the Indian Cooperative Union helped organize them into a refugee polis. Thus, the INA and Faridabad, shaped by imperial crises and decolonization, emerged as two refugee poleis. They embodied political alternatives to the nation-state as an outcome of decolonization. The refugees advocated direct democracy, egalitarian redistribution of land, and co-operative economic management. The postcolonial Indian state saw this as a challenge. It transformed refugees into workers, whose labour would generate profits for the state. Although the refugees protested through unionization, strikes, and civil disobedience, ultimately, the Nehruvian state brutally suppressed these refugee poleis.Peer reviewe
An early-life survival and reproductive trade-off shapes selection on body size
Get PDFFunding: Field data collection was funded by the UK Natural Environment Research Council, and SNP genotyping was funded by a European Research Council grant (Wild Evolutionary Genomics). M.B.M. was supported by a University Research Fellowship from the Royal Society (London). J.G.P., J.M.P., M.B.M., and M.J.J. were supported by a UK Natural Environment Research Council grant (NE/R011109/1). J.M.H. was funded by the German Federal Ministry of Education and Research (BMBF) and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under project number 456626331.Evolutionary trade-offs—opposing trait effects on total fitness via different fitness components—are likely to be widespread. Some key trade-offs are expected to be the result of chains of causation acting across an organism’s lifetime. For example, a trait imparting reproductive benefits early in life may trade off against reduced survival to attain later-life reproductive opportunities. Tools in evolutionary quantitative genetics have recently been developed to formally characterize selection acting through different causal pathways throughout the life cycle and, therefore, to formally characterize evolutionary trade-offs. We use these methods to investigate a trade-off between early life reproduction and survival and how that trade-off affects selection on body size in the Soay sheep population inhabiting St Kilda (Outer Hebrides, Scotland). We decompose and quantify the total effects of first-year female body mass on lifetime fitness, with particular attention to the effect of body mass on early-life reproduction and the potential survival cost of early-life reproduction. Our results establish that the total effect of body mass on lifetime fitness is positive, despite the strong negative contribution acting via early life reproduction. Moreover, we show that the magnitude of the selection on body mass acting through different causal paths highly depends on population density. At higher densities, the cost of early-life reproduction is higher, and therefore, it contributes a strong negative component to the total selection of body mass—i.e., at higher population density, selection on body mass is weaker than it is when the population density is smaller. By decomposing total selection and quantifying selection acting through different causal paths, we expose the underlying mechanics shaping body mass in Soay sheep female lambs, and we provide a meaningful contribution to the understanding of the evolution of body size in this population.Peer reviewe
A full-factorial test of motivational and volitional intervention strategies for promoting exercise habit formation and exercise maintenance among new users of an online exercise class platform
Get PDFInterventions often fail to achieve long-term behavioral maintenance. Utilizing motivational and volitional strategies to promote behavioral maintenance factors may improve this. Using a full-factorial experiment, we tested the effects of three intervention components (focused on intrinsic motivation and identity, exercise preparation habit, and exercise instigation habit) on exercise participation over a year, among new users (N = 751; 91% identifying as female, 54% identifying as White race) of a global, online exercise class platform, run by Les Mills International Ltd, called LM+. We also tested the intervention components' theoretical mechanisms of action—habit formation, intrinsic motivation, identity, and self-efficacy. Multi-level models found some support for a main effect of the exercise preparation habit intervention component in promoting self-reported and objective exercise participation (behavioral outcomes measured via monthly surveys and the LM+ platform; mechanisms measured via monthly surveys)—in particular online exercise class frequency (fixed effect estimate = 0.84, p < 0.05, and = 0.12, p < 0.05, respectively). The preparation habit component also significantly increased preparation habit strength (0.30, p < 0.05) and instigation habit strength (0.33, p < 0.05). Other expected effects were nonsignificant. Helping individuals form an exercise preparation habit may facilitate initiating and maintaining exercise over time, in particular for attending online exercise classes, potentially through promoting greater preparation and exercise instigation habit strength.Peer reviewe
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