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Mining for cosmological information: Simulation-based methods for Redshift Space Distortions and Galaxy Clustering
Get PDFThe standard model of cosmology describes the complex large scale structure of the Universe through less than 10 free parameters. However, concordance with observations requires that about 95\% of the energy content of the universe is invisible to us. Most of this energy is postulated to be in the form of a cosmological constant, , which drives the observed accelerated expansion of the Universe. Its nature is, however, unknown. This mystery forces cosmologists to look for inconsistencies between theory and data, searching for clues. But finding statistically significant contradictions requires extremely accurate measurements of the composition of the Universe, which are at present limited by our inability to extract all the information contained in the data, rather than being limited by the data itself. In this Thesis, we study how we can overcome these limitations by i) modelling how galaxies cluster on small scales with simulation-based methods, where perturbation theory fails to provide accurate predictions, and ii) developing summary statistics of the density field that are capable of extracting more information than the commonly used two-point functions. In the first half, we show how the real to redshift space mapping can be modelled accurately by going beyond the Gaussian approximation for the pairwise velocity distribution. We then show that simulation-based models can accurately predict the full shape of galaxy clustering in real space, increasing the constraining power on some of the cosmological parameters by a factor of 2 compared to perturbation theory methods. In the second half, we measure the information content of density dependent clustering. We show that it can improve the constraints on all cosmological parameters by factors between 3 and 8 over the two-point function. In particular, exploiting the environment dependence can constrain the mass of neutrinos by a factor of 8$ better than the two-point correlation function alone. We hope that the techniques described in this thesis will contribute to extracting all the cosmological information contained in ongoing and upcoming galaxy surveys, and provide insight into the nature of the accelerated expansion of the universe
Making Shrimp Economies and Hydro-Social Lives: The Hatchery, the Shrimp Farm, and the Laboratory in the Mekong Delta
Get PDFThis thesis explores the formation and operation of shrimp economies that bring together multiple species and their ecological conditions of production through capitalist and more-than-capitalist relations in contexts of agrarian, technical, and environmental changes. It focuses on the Mekong Delta in Vietnam, where due to climate change and salinity intrusion, farmers and companies are shifting from growing rice to breeding shrimp in an effort to adapt to climate change and help alleviate poverty. These strategies of adaptation and livelihood, however, also have effects on delta ecologies and economies. The research draws these dynamics together at the intersection of water and society, or hydro-social life, to examine different sites amid the history of water management in the Mekong Delta. Multi-species and multi-sited ethnography were conducted, following shrimp through the hatchery, the shrimp farm, and the laboratory within and beyond the Mekong Delta.
This research argues that shrimp economies, as a form of bioeconomy, are formed and constructed by organising hydro-social lives across three sites: (1) shrimp reproduction in the hatchery, (2) shrimp growth on the farm, and (3) scientific research in the laboratory. Hydro-social lives assemble and reassemble water-shrimp-human-environment relations to create the material basis of shrimp production. Meanwhile, hydro-social lives involve both capitalist and more-than-capitalist relations, which drive significant agrarian, technical, and environmental changes to farmers and capitalists within and beyond the Mekong Delta.
This study makes three original contributions. First, it extends work in political economy and political ecology on the socio-natural organisation of commodity production by analysing the materiality of shrimp production, and capitalist and more-than-capitalist relations in bioeconomies. Second, it contributes to water research by examining how water-shrimp-human-environment relations are integral to the production of aquatic animals. Third, it unfolds hydro-social life in the hatchery, the delta, and the laboratory to examine these complex and dynamic relations in different environments, contributing to delta studies and STS
'Till we meet again’: Memory, Grief and Popular Religion in England in the Aftermath of the Great War
Get PDFIt became fashionable in the 1970s to associate the Great War with the death of religion. The notion that ‘Tommy’ – the ordinary soldier – despised the war, his senior officers and God was promoted in film (Oh, What a Lovely War!), critical works (Fussell’s The Great War and Modern Memory) and the general revival of interest in the war poets. Historians soon showed that Tommy’s religion did not die in the mud of Passchendaele. From the late 1970s, McLeod showed very nuanced patterns of working-class religiosity. In the 1980s, Parsons revealed that the religion of ordinary people was different from the theology of the churches. Later, Snape described the complex response by Tommy to religion and the churches. All these studies however relied heavily either on statistics, or the writings of the educated middle classes – not the testimony of ordinary people themselves.
Ordinary people (apart from the religiously committed) did not normally write about their religious feelings. However, thanks to the Imperial War Graves Commission, tens of thousands of families were able to record epitaphs for their dead servicemen. Further, the expansion of cheap local newspapers and the growth of literacy promoted the use of In Memoriam notices. These sources provide a rich mix of religious and secular messages that families used to record their deepest feelings of loss, regret and hope. Through them, we are able to see the texts, sentiments and articles of faith that infused the religious responses of ordinary people in the period between 1914 and 1925. The religion of ordinary people emerges as a strong but subtle faith, subject to the stresses of social class, but inextricably interwoven with ideas of love, family and life after death
Mitigation of Single Event Burnout for Future Aerospace Applications
No full textWith the global challenge to achieve Net Zero, the balance between greenhouse gasses produced and removed from the atmosphere, by 2050, aviation, a major contributor to the generation of greenhouse gas emissions, producing over 900 million tonnes of CO2 emissions annually, is committed to a step change in propulsion technology. The most realistic strategy to achieve these drastic CO2 reductions is through the electrification of aircraft, which will utilise the all-electric and hybrid power systems. The realisation of these MW scale power systems will inevitably rely on the incorporation of wide bandgap semiconductors, such as SiC - a semiconductor with excellent material properties, including critical electric field strength, high thermal conductivity and high electron saturation drift velocity. To make this goal a reality, the superior properties of SiC are required - through offering the ability to operate at power levels significantly beyond those of traditional Si.However, at the current time, knowledge of the interaction of radiation from cosmic rays with SiC power electronic devices is unknown, limiting their adoption in flight critical aerospace applications.
The increasing supply voltages required to make the future of flight a reality will generate extremely high electric fields within devices. Coupled with the elevated concentration of cosmic rays at flight altitudes, these conditions create the perfect storm for the Single Event Effect (SEE) - the instantaneous alteration of device response to radiation interaction. The destructive form of the SEE is the Single Event Burnout (SEB), which results in the catastrophic failure of a device, with often explosive consequences. SiC is rapidly becoming the semiconductor of choice to enable circuits to operate with high supply voltages. However, the response of SiC power devices during operation to radiation is unknown. In this research it is shown that SiC, in comparison to Si, offers a 60% reduction in cosmic ray sensitivity when equivalent voltage ratings are considered. It has been found that Si fails when a
deposited charge equivalent to 0.2% that of a silver ion commonly used in SEB testing. In contrast the radiation response of SiC is superior, with no failures occurring for
any deposited charge up to three times greater than those used in testing for any bias derating up to 99% of the breakdown voltage. Here the data show that SiC is robust
against aerospace specific operating conditions and has the potential to replace Si as the material of choice for high reliability aerospace applications. The suitability of 2D SiC structures for aerospace, however, remains unclear.
For future aerospace applications the SiC JFET is the device of choice for use in power systems and flight control surfaces. With strong electrical performance and minimal response to total dose effects it seems to be the ideal candidate, however, questions still exist with regards to its single event response. For the first time the SEB sensitivity of a JFET designed for real world aerospace specific scenarios has been examined. The 2D nature of the device results in increased SEB sensitivity with elevated electric fields at the gate and source - leading to catastrophic failure and device melting at drain - source bias deratings as low as 40%. To mitigate this the separation between the gate and source has been increased - leading to radiation hardened designs which reduce the SEB sensitivity. By increasing the gate - source separation of the original JFET by 4.0 µm a peak electric field reduction of 64% is observed which had resulted in a 99% reduction in peak drain - source current density of the radiation hardened structure in comparison to that of the original. Despite these modifications, high peak temperatures existed for the SiC JFETs studied, with even the modified device reaching over 1500 K after heavy ion impact. A bespoke SiC
JFET with an additional channel was investigated as a potential device to mitigate the SEB induced currents.
The SiC Lateral JFET (LJFET), consisting of both a vertical and a lateral channel provides enhanced current control over the standard JFET studied. Through simulation of an array of real world aerospace specific scenarios this bespoke device showed no regions of heightened SEB sensitivity with no failures at a 40% drain - source bias derating with a deposited charge equivalent to 300% that of a silver ion commonly used in SEB testing. Like the standard JFET SEB did occur, however, at elevated biases. At an industry standard drain - source bias derating of 70% the LJFET failed with device melting after impact. Through using the same technique employed to radiation harden the standard JFET a reduction in the SEB sensitivity of the LJFET was observed. Through including an additional 4.2 µm of regrowth between the gate and source of the device it could withstand harsher radiation conditions, due to the creation of a low electric field region below a magnitude of 0.5 MV/cm, 30% that of
the original. The modified LJFET at an industry standard drain - source derating is robust against all heavy ion deposited charge conditions studied, up to and including
300% that of a silver ion commonly used in SEB testing. As future aerospace applications will require the use of high voltages in the presence of real world cosmic ray environments, the use of the LJFET and modifications are key towards the mitigation of Single Event Burnout
Using the fucosylation mutant sensitive-to-freezing8 (sfr8) to explore the influence of plant cell wall on transpiration
Get PDFCell walls have a specialised structure and function in guard cells that surround and control the openness of the stomata, microscopic pores allowing CO2 uptake and water loss. The Arabidopsis thaliana senstive-to-freezing8 (sfr8) mutant loses water more quickly than wildtype and has severely reduced levels of cellular fucose, affecting multiple aspects of cell wall, including xyloglucan, pectin, proteins and mechanical strength. The defective cell wall components of sfr8 may result in a higher transpiration rate. This study aims to discover how the sfr8 cell wall mutation influences transpiration.
Arabidopsis mutants affected in different aspects of cell wall were measured for their transpiration rate and stomatal conductance, the rate of stomatal gas exchange. Mutants in fucosylation, pectin abundance, xyloglucan and mechanical stress all had transpiration or stomatal conductance during dehydration stress similar to wildtype. Only one mutant other than sfr8 had transpiration and stomatal conductance significantly higher than wildtype during drought stress and changing CO2 concentration; the pectin modification mutant, reduced wall acetylation2 (rwa2). Further measures of stomatal structure and function were taken. sfr8 had significantly different stomatal development to wildtype and limited stomatal dynamics, whereas, rwa2 had stomatal size, density and aperture equivalent to wildtype. Mutants were tested for drought tolerance and surprisingly, sfr8 had a better survival rate than wildtype, which may be attributed to the altered stomatal development.
The results of this study and supporting literature indicate that pectin crosslinking, but not all pectin modification, affects transpiration, stomatal behaviour and drought tolerance. The higher transpiration rate of rwa2 is probably due to cuticle damage. Moreover, sfr8 had the highest transpiration of all tested mutants suggesting that other factors may influence sfr8 transpiration, which are explored. Understanding the mechanistic basis of genes, like SFR8, that affect stomatal characteristics and drought tolerance will become increasingly important as drought becomes more prevalent
A consideration of the current view and history of the people of Canvey Island, Essex, in the context of modern England with regard to the place of the church in community particularly in the face of bereavement and the conduct of funeral rites.
Get PDFThis study is the result of six years of part-time research by a practising Church of England minister. It focusses on the people of Canvey Island in Essex from the early 20th century when the church held sway over every aspect of their lives, to the present day when engagement with the church is one option of many. The study seeks to show how and why many who belong to no church congregation still call on the church at a time of bereavement and how the church might better recognise and sanctify the language and practice of those who would not call themselves religious.
The thesis explores the many-faceted and often contradictory contextual issues of contemporary ministry with particular focus on the whole gamut of funeral ministry from miscarriage and neo-natal death to a death occurring naturally in old age. It examines the relationship between the intrinsic and the vernacular on the one hand and the language of the established church on the other. It recognises the so-called folk religion as the basic longing of humanity for meaning and order in a chaotic and seemingly random life: a longing which the church has largely adopted, organised, formalised, institutionalised and often fossilized. It considers how such desire is met by Civil celebrants and others if church ministers are slow to respond to the need.
In this third decade of the twenty-first century, society is at a crucial crossroad with regard to the way in which we handle death, grief and an understanding of on-going life which survives the physical. A society increasingly at home with the connectedness of everything through the internet requires a church that understands and recognises its language and its longing. This thesis repeatedly addresses the ways that the church and its ministers need to embrace its changing role, particularly at the time of death.
The author’s upbringing in the British West Indies is very different from that of the people of Canvey Island. In distilling the fruit of twenty-four years of ministry among them, he has sought to use readily intelligible language to tell the stories of the dying and the bereaved and to bring to bear academic studies from the fields of sociology, anthropology and theology in the context and light of the lived experience of parish life
Design and Application of Probes to Understand Peroxisomal Localisation of BODIPYs
Get PDFBODIPYs (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) constitute an important class of fluorophores. The excellent qualities of BODIPY comprise relatively high fluorescence quantum yields and molar absorption coefficients, narrow emission bandwidths, high elevated stability towards chemicals and light, and the extra feature of excitation/emission wavelengths in the visible region.
Previous work in our group generated a small set of BODIPY fluorophores, including one, nitro-BODIPY, 1,3,5,7‐tetramethyl-8‐(4‐nitrophenyl)‐BODIPY, that is intrinsically non-fluorescent but upon incubation of cells with this compound, fluorescence is observed at the target site. The target site in plant cells was identified as peroxisomes, as verified by co-localization with an SKL-FP construct (peroxisome-specific carboxyl-terminal targeting sequence fluorescent proteins). It is key to future applications to be able to understand how this is occurring at a molecular level.
These objectives are challenged by a lack of knowledge of this protein target and the physicochemical profile of nitro-BODIPY. This leads to the specific aims of this project which are: 1. To develop a ‘toolbox’ of analogues that enable multicolour visualisation. 2. To confirm the nature of the binding process between nitro-BODIPY and the target protein and to determine its reversibility. 3. To identify the target protein of nitro-BODIPY in plant peroxisomes.
Therefore, a family of red-shifted nitro-BODIPY probes were synthesised. Most of them showed selectivity towards plant peroxisomes and their emission wavelength could reach to a maximum of around 700 nm. Water-soluble probes were prepared and proved to exhibit selective labelling towards plant peroxisomes as well. In addition, a group of dual-fluorophore probes (nitro-BODIPY probes with a second fluorophore including Rhodamine B, Cy5, dansyl and NBD) were developed to determine whether nitro-BODIPY only localizes at peroxisome or somewhere else. Although several dual-fluorophore probes showed selective labelling of the peroxisome, the reporter function of the second fluorophore in all probes was challenged by various degrees of FRET. Finally, a photoaffinity labelling probe (nitro-BODIPY core attatched with a benzophenone photoaffinity group) was prepared to determine the target proteins of nitro-BODIPY in plant peroxisomes. Several potential protein targets of nitro-BODIPY in plant peroxisomes were detected by this photoaffinity labelling probe via SDS-PAGE technique
Use of resistivity to measure deterioration of engineered soils
Get PDFClimate change induced seasonal water content variations are likely to influence the soil parameters that determine the stability of engineered slopes. These slopes constitute a large amount of UK transport infrastructure, Repeated fluctuations of water content affect the soil water retention behaviour and hence the suction-dependent shear strength behaviour of engineered soils, resulting in deterioration in both the soil suction and shear strength, which impact the long-term slope stability. Resistivity methods can provide spatial information on the electrical properties of underground soils and therefore has a great potential to be used to monitor subsurface geotechnical property changes by applying geotechnical-geophysical transformation approaches. In order that the resistivity method can be used more effectively in slope monitoring, the interrelationships between soil geotechnical and geophysical properties need to be more fully understood. Therefore, this research focused on establishing an improved understanding of soil deterioration by investigating the effects of repeated drying and wetting cycles on soil property interrelationships and investigating the potential use of resistivity methods to qualitatively and quantitatively describe the property variation of engineered soils subjected to drying and wetting cycles.
In this thesis, three phases of laboratory-based experiment programmes were conducted to investigate the interrelationships between soil electrical and geotechnical properties on samples with different sizes by using different measurement techniques. In the first phase, several point measurement sensors were employed for estimating the soil water content, electrical resistivity, and suction on a cubic glacial till sample during cyclic drying and wetting. In the second phase, soil electrical resistivity, suction and shear strength were determined by a four-electrode resistivity probe, WP4C potential meter and performing Unconsolidated Undrained triaxial test on triaxial specimens with 38mm diameter made of three different types of soils. In the third phase, the 3D time-lapse ERT method was employed to map the in-time resistivity changes in a 1.2m diameter cylindrical lysimeter; point sensors were also used to provide water content and suction measurements on different depths within the lysimeter.
Soil water retention and shear strength behaviour under multiple drying-wetting cycles has been investigated in this research. Result showed that the both the SWRCs and the undrained shear strength-water content relationships changes over time with drying-wetting cycling, indicating a hysteresis between drying and wetting paths and a deterioration over cycling. The hysteresis of SWRC and shear strength-water content relationship was found to be more pronounced in the first drying-wetting cycle and decreased over cycling. Deterioration in soil suction (i.e. negative pore water pressure) were found to be most significant between the first and the second cycle. Similar evolutionary trends were found in the cyclic swelling and shrinkage behaviour of the soils which may be a key factor to the hysteresis and deterioration. Furthermore, the spatial geotechnical information (i.e., the water content distributions) within the large lysimeter sample can be extrapolated from the ERT-derived resistivity data by applying the proxy relationships (i.e., the Waxman-Smits model)
Wetting Behaviour of Droplets and Capillary Liquid Bridges Involving Liquid Infused Surfaces
Get PDFLiquid-infused surfaces (LIS), formed of a nano- or micro-structured porous material that is impregnated with a lubricating fluid, are biomimics of the pitcher plant. Their slippery surface makes them ideal candidates for a wide range of applications, from anti-corrosive, anti-fouling and anti-icing coatings to self-healing surfaces and controlled wetting. Here, LIS are studied to determine the fundamental interactions of the lubricant layer with the porous medium, and with droplets and capillary liquid bridges under different environmental conditions. When LIS are exposed to realistic environmental conditions, they rapidly lose their desirable slippery properties and age, which may compromise their original application. This may occur through a process of oil loss, smoothing of the porous layer and porous substrate degradation. Oil loss is attributed to the formation of micro-emulsion in the lubricant layer which displaces oil away from the surface.
LIS interactions with stretching capillary liquid bridges (CLB) are also considered. Measuring capillary forces on LIS is challenging as they present a surface with little friction or pinning. A novel set-up is created to study the comparatively small forces exhibited by LIS, and extract the bridge geometry. CLBs on non-infused surfaces are strongly affected by contact line pinning, and hysteretic behaviours are commonly observed for the measured contact radii, contact angles, and capillary forces. In contrast, CLBs on LIS experience no pinning and hysteretic behaviours are largely absent. Furthermore, cloaking and the formation of oil ridges change the effective CLB surface tension and contact angle, and gravity has a more dominant effect due to small changes in capillary forces on LIS. In all cases, including for asymmetric bridges (with one LIS and one other surface), it is shown that the measured capillary forces can be well-described by a simple theoretical model that uses the CLB contact radius, contact angle and curvature as input parameters
UnQuantum Woolf: The Many Intellectual Contexts of To the Lighthouse's Metaphorical Wave-Particle Binary
Get PDFThis thesis is a sceptical investigation into the notion that the metaphorical wave-particle binary of Virginia Woolf's To the Lighthouse is related to quantum physics. Indeed, the field of literature and science has employed conceptual similarities as the main means of connecting quantum concepts to novels, however, this has led to a host of scholarly difficulties, prompting the need for a re-examination of analogical linkages. Woolf is the model candidate for such a re-examination, given her historical and philosophical proximity with the developments of quantum mechanics. To the Lighthouse, in particular, was written between 1925 and 1927: precisely when quantum physicists were attempting to resolve the wave-particle duality, leading to Niels Bohr's complementarity. This parallel has been noted by researchers as relevant to the novel, as it too displays a general binary that can be read as wave-particle-like, which the author also attempts to resolve along similar philosophical lines. Nevertheless, other than proximity and similarity, there are no reasons to affirm that the science is related to the novel; hence, it is an ideal case study to examine in order to ascertain the value of conceptual similarities in literature and science. To do so, To the Lighthouse's binary and its resolution are interpreted in a thesis-long close reading, in order to compare aspects of it firstly to Woolf's personal thought, and secondly to various non-quantum intellectual contexts that preceded and surrounded her. In doing so, it becomes clear not only that invoking quantum physics serves no clear purpose in better understanding the novel, but also that the notion of resolving wave- particle-like binaries was a widespread philosophical procedure at the turn of the century, decades before Bohr's concept. This negative conclusion interrogates what the scholarly value of interpreting similarities is, though a hypothetical solution can be found in conceptual metaphor theory
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