3,843 research outputs found

    Effects of upland stream nutrient restoration on Atlantic salmon populations

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    Aquatic biodiversity has experienced severe declines over past decades, with many species requiring conservation interventions in order to preserve and protect threatened populations. However, assessing whether conservation measures work effectively with the intended outcome is important when considering their implementation. One conservation target is the Atlantic salmon (Salmo salar), populations of which have declined dramatically since the 1960s. Given that many salmon die during the spawning migration, the reduction in the number of spawning adults has also led to fewer marine-derived nutrients being deposited in upland streams in the form of salmon carcasses. These carcasses fertilise the nursery streams of the salmon, to the potential benefit of the young fish, and so the decline in the number of adult salmon carcasses may have adverse effects on the next generation. In this thesis, I explore in successive chapters the potential for restoring the nutrients that are normally supplied by returning spawning salmon to upland streams, by using carcass analogue pellets. I examine the impacts of different methods of the application of these pellets, and differing doses and timing of applications, on the growth and performance of juvenile salmon populations. I also assess the effect of the application method on aquatic macroinvertebrate communities. I develop a mathematical model to predict the impact of manipulating the early freshwater growth rate of individual salmon on their life history trajectory, following a cohort of fish through to spawning and egg production; this allows exploration of the effect of nutrient additions on the viability of salmon populations. Finally, I detail an incidental study on the effects of high summer temperatures on the performance of juvenile salmon populations. Chapter 1 introduces the main issues and the study species and presents the ecological and conservation context for the study. Juvenile Atlantic salmon often reside in upland streams, and these streams may differ to the degree of nutrient limitation that they experience as a result of cultural practices leading to the oligotrophication of these streams. In Chapter 2, I review the sources, retention and fate of nutrients in upland streams, alongside reviewing the impacts of experimental nutrient additions on salmon populations. In the first experimental chapter (Chapter 3), I present the results of a twoyear experiment that compared two methods of nutrient additions using carcass analogue pellets, one via bagged pellets and the second through hand-scattered pellets. I show the differing impacts of these methods on macroinvertebrates and two cohorts of Atlantic salmon populations. The results varied between treatments and between years, but mainly demonstrated increased body size of individual invertebrates in the scattered treatment. Salmon fry (fish in their first summer of growth) in the scattered treatment showed reduced growth but greater densities, whilst fry in the bagged treatment saw no change in density and a positive effect on growth in one year of the study. There was no impact of either treatment on the body size of salmon parr (fish at least one year old). The impacts of nutrient additions are likely to vary depending on seasonal changes to environmental variables, and the amount of nutrients added is also likely to result in different impacts based on these seasonal changes. These changes are assessed in Chapter 4, where I present the results of an experiment that tested the impact of a single dose applied in early spring against a double dose applied in early spring and early summer. The single dose resulted in increased fry density but reduced growth, whilst the double dose increased both growth and density of Atlantic salmon fry. No study has assessed the impact of nutrient additions over a single generation of Atlantic salmon, and nutrient additions may have unforeseen and adverse consequences. In Chapter 5, I detail an individual-based model that aims to understand the population impact of manipulating early freshwater growth of Atlantic salmon. I demonstrate that increasing early growth results in increased numbers of fish smolting, even though more precociously mature males are produced. The salmon that smolt tend to do so at a younger age but also larger size; these trends are predicted to translate into increases in offspring produced per cohort and hence increases in the population size of Atlantic salmon. In Chapter 6, I present an incidental study on the impacts of high summer temperatures on the density and biomass of juvenile Atlantic salmon. High temperatures can result in heat stress in Atlantic salmon, affecting their growth and behaviour. I demonstrate a negative relationship with degree hours exceeding 23ºC and the log biomass and log density of juvenile salmon. In the final chapter, I put into context the results of the previous chapters, and address the utility of carcass analogue application as a potential conservation tool. Though the impacts of nutrient additions may vary temporally and may be complex, the data I present in this thesis suggests that nutrient additions may be used as a conservation tool with positive impacts on the freshwater growth of salmon, which is positively related to increases in their marine survival and thus increases at the population level

    ‘A little bit patronising if I’m being honest’: working-class mothering and expert discourses.

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    Recent early years policy interventions have focussed on the Home Learning Environment. The ‘Home Learning Environment’ relates to the parenting children receive at home, rather than the physical environment in which they live, enabling a focus on individual behaviour. Family and parenting relations have been a target of state intervention for the last century, positioning working-class mothers as deficient and requiring correction. Little is known about how these discourses impact and shape working-class mothering. I explore how intensive parenting and attendant policy and dominant discourses impact on the day-to-day lives of working-class mothers. To do this, I draw on a critical discourse analysis of the BBC’s Tiny Happy People website to discern current ‘good’ mothering discourses being promoted and narrative analysis of twenty biographical interviews with working-class mothers. The interviews revealed a huge gulf between Tiny Happy People’s ‘good’ mother and the women’s lived realities. Absent and ignored were the significant material constraints faced by many of the women and the time burden created by the intensive mothering model being promoted. Working-class mothering values based on relationships and protecting their children from the effects of growing up working-class mean that Tiny Happy People’s good mothering ideals were mainly rejected as unnecessary or unrealistic by the women interviewed. Policy and other initiatives aimed at working-class people must acknowledge the reality of their lives and target improvements to inadequate housing provision and a labour market which creates low-paid, precarious employment; these initiatives would dramatically transform family life. This research provides the first academic analysis of the BBC’s Tiny Happy People. It highlights the gulf between those in positions of power (whether within government or the media) and the working-class women interviewed

    Increasing Sustainable Bivalve Aquaculture Productivity Using Remote Non-Invasive Sensing and Upweller Technologies

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    The work and findings described by this thesis aim to develop technologies and approaches relevant to bivalve aquaculture, focusing on non invasive sensing to monitor bivalve shellfish, primarily the Pacific oyster (Magallana gigas). Following the introduction, Chapter 2 presents an overview of the Non Invasive Oyster Sensor (NOSy), a sensor developed at the University of Essex that records bivalve openness (gape). NOSy was conceived to automatically detect spawning as an aid to oyster growers and has proved useful in field and laboratory, work which underpins three chapters in this thesis. NOSy remains under development, and has potential for use in aquaculture, monitoring and research. Chapter 3 assesses the role of salinity in driving estuarine oyster behaviour. We replicated an estuarine tidal salinity cycle and recorded the gape of oysters exposed to it. Behaviours during the experiment did not resemble those in the estuary, suggesting that salinity alone does not drive estuarine oyster behaviour. We also discuss the challenges of controlling salinity in a laboratory, and suggest it is an under-studied area. Chapter 4 discusses land based systems for young oyster growing. Land-based systems have the potential to improve growth, condition and survival while reducing labour and maintenance costs. We trialled a system over three summers, with promising results. Reduction of localised densities improved growth rate and uniformity. Cost forecasts suggest that adoption of land based growing systems could result in substantial savings. Chapter 5 presents gaping records from an area where Blue mussels (Mytilus edulis) have become non harvestable in recent years due to contamination. We used NOSy to assess gaping patterns of the mussel population to evaluate how their behaviours affect their vulnerability to contamination. Mussels in the bay closed over low tide as a response to extremely low salinity, inferring protection from contamination by limiting the mussel’s exposure

    Understanding Hackers' Work: An Empirical Study of Offensive Security Practitioners

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    Offensive security-tests are a common way to pro-actively discover potential vulnerabilities. They are performed by specialists, often called penetration-testers or white-hat hackers. The chronic lack of available white-hat hackers prevents sufficient security test coverage of software. Research into automation tries to alleviate this problem by improving the efficiency of security testing. To achieve this, researchers and tool builders need a solid understanding of how hackers work, their assumptions, and pain points. In this paper, we present a first data-driven exploratory qualitative study of twelve security professionals, their work and problems occurring therein. We perform a thematic analysis to gain insights into the execution of security assignments, hackers' thought processes and encountered challenges. This analysis allows us to conclude with recommendations for researchers and tool builders to increase the efficiency of their automation and identify novel areas for research.Comment: 11 pages, we have chosen the category "Software Engineering" and not "Cryptography and Security" as while this is a paper about security practices, we target software engineering researcher

    Under construction: infrastructure and modern fiction

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    In this dissertation, I argue that infrastructural development, with its technological promises but widening geographic disparities and social and environmental consequences, informs both the narrative content and aesthetic forms of modernist and contemporary Anglophone fiction. Despite its prevalent material forms—roads, rails, pipes, and wires—infrastructure poses particular formal and narrative problems, often receding into the background as mere setting. To address how literary fiction theorizes the experience of infrastructure requires reading “infrastructurally”: that is, paying attention to the seemingly mundane interactions between characters and their built environments. The writers central to this project—James Joyce, William Faulkner, Karen Tei Yamashita, and Mohsin Hamid—take up the representational challenges posed by infrastructure by bringing transit networks, sanitation systems, and electrical grids and the histories of their development and use into the foreground. These writers call attention to the political dimensions of built environments, revealing the ways infrastructures produce, reinforce, and perpetuate racial and socioeconomic fault lines. They also attempt to formalize the material relations of power inscribed by and within infrastructure; the novel itself becomes an imaginary counterpart to the technologies of infrastructure, a form that shapes and constrains what types of social action and affiliation are possible

    Advances and Applications of DSmT for Information Fusion. Collected Works, Volume 5

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    This fifth volume on Advances and Applications of DSmT for Information Fusion collects theoretical and applied contributions of researchers working in different fields of applications and in mathematics, and is available in open-access. The collected contributions of this volume have either been published or presented after disseminating the fourth volume in 2015 in international conferences, seminars, workshops and journals, or they are new. The contributions of each part of this volume are chronologically ordered. First Part of this book presents some theoretical advances on DSmT, dealing mainly with modified Proportional Conflict Redistribution Rules (PCR) of combination with degree of intersection, coarsening techniques, interval calculus for PCR thanks to set inversion via interval analysis (SIVIA), rough set classifiers, canonical decomposition of dichotomous belief functions, fast PCR fusion, fast inter-criteria analysis with PCR, and improved PCR5 and PCR6 rules preserving the (quasi-)neutrality of (quasi-)vacuous belief assignment in the fusion of sources of evidence with their Matlab codes. Because more applications of DSmT have emerged in the past years since the apparition of the fourth book of DSmT in 2015, the second part of this volume is about selected applications of DSmT mainly in building change detection, object recognition, quality of data association in tracking, perception in robotics, risk assessment for torrent protection and multi-criteria decision-making, multi-modal image fusion, coarsening techniques, recommender system, levee characterization and assessment, human heading perception, trust assessment, robotics, biometrics, failure detection, GPS systems, inter-criteria analysis, group decision, human activity recognition, storm prediction, data association for autonomous vehicles, identification of maritime vessels, fusion of support vector machines (SVM), Silx-Furtif RUST code library for information fusion including PCR rules, and network for ship classification. Finally, the third part presents interesting contributions related to belief functions in general published or presented along the years since 2015. These contributions are related with decision-making under uncertainty, belief approximations, probability transformations, new distances between belief functions, non-classical multi-criteria decision-making problems with belief functions, generalization of Bayes theorem, image processing, data association, entropy and cross-entropy measures, fuzzy evidence numbers, negator of belief mass, human activity recognition, information fusion for breast cancer therapy, imbalanced data classification, and hybrid techniques mixing deep learning with belief functions as well
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