69 research outputs found
The cosmological Higgstory of the vacuum instability
No full textAbstract: The Standard Model Higgs potential becomes unstable at large field values. After clarifying the issue of gauge dependence of the effective potential, we study the cosmological evolution of the Higgs field in presence of this instability throughout inflation, reheating and the present epoch. We conclude that anti-de Sitter patches in which the Higgs field lies at its true vacuum are lethal for our universe. From this result, we derive upper bounds on the Hubble constant during inflation, which depend on the reheating temperature and on the Higgs coupling to the scalar curvature or to the inflaton. Finally we study how a speculative link between Higgs meta-stability and consistence of quantum gravity leads to a sharp prediction for the Higgs and top masses, which is consistent with measured values. © 2015, The Author(s)
Brand Search.
No full textConsumers frequently buy the products they find most easily. This has forced manufacturers and retailers to invest in package design, shelf layouts, and expensive advertising campaigns to facilitate findability of their products. Surprisingly, there is no research in marketing that investigates how consumers localize products, which we call brand search. This dissertation investigates the brand search process and develops a statistical model that describes the eye movements of consumers while they are searching for a specific product. The proposed model uncovers the search strategies of consumers and suggests which marketing tools manufacturers and retailers may use to influence this process.
Checklist of the mosses of sub-Saharan Africa
No full text2939 moss taxa are listed for sub-Saharan Africa and adjacent islands, with distribution by country. Each distribution record is supported by a literature reference. The following new combinations are made: Calyptrochaeta cristata (Hedw.) O’Shea, Groutiella elimbata (Thér) O’Shea, Meiothecium undulatum (Ren. & Card.) O’Shea, Orthodontium ruwenzorensis (Thér. & Nav.) O’Shea, Pohlia lacouturei (Thér.) O’Shea, Sematophyllum corticolum (Aongstr.) O’Shea, Sematophyllum dixonii (Thér.) O’Shea, Sematophyllum nanopyxis (Geh.) O’Shea, Sematophyllum rigescens (Card.) O’Shea, and Thamnobryum malgachum (Card.) O’Shea
The apocalyptic tradition in Scotland, 1588-1688
No full textThroughout the seventeenth century, numerous Scots became convinced that the major political and religious upheavals of their age signified the fulfillment of, or further unfolding of, the vivid prophecies described in the Book of Revelation which foretell of the final consummation of all things. To date, however, an in-depth analysis of the evolution of Scottish apocalyptic belief during the seventeenth century has never been undertaken. This thesis utilizes a wide variety of source material to demonstrate the existence of a cohesive, persistent, and largely conservative tradition of apocalyptic thought in Scotland that spanned the years 1588 to 1688. Chapter One examines several influential commentaries on the Book of Revelation published by notable Scots during the decades either side of the Union of Crowns. These works reveal many of the principal characteristics that formed the basis of the Scottish apocalyptic tradition. The most important of these traits which became a consistent feature of the tradition was the rejection of millenarianism. In recent years, historians have exaggerated the influence of millenarian ideals in Scotland during the Covenanting movement which began in 1638. Chapter Two argues that Scottish Covenanters consistently denounced millenarianism as a dangerous, subversive doctrine that could lead to the religious radicalism espoused by sixteenth-century German Anabaptists. Chapter Three looks at political and religious factors which led to the general decline of apocalyptic expectancy in Scotland during the Interregnum. It also demonstrates how, despite this decline, Scottish apocalyptic thinkers continued to uphold the primary traits of the apocalyptic tradition which surfaced over the first half of the century. Lastly, Chapter Four explains how state-enforced religious persecution of Scottish Presbyterians during the Restoration period led to the radicalisation of the tradition and inspired the violent actions of Covenanter extremists who believed they had been chosen by God to act as instruments of his divine vengeance in the latter-days
Reduced levels of dopamine and altered metabolism in brains of HPRT knock-out rats: a new rodent model of Lesch-Nyhan Disease
No full textLesch-Nyhan disease (LND) is a severe neurological disorder caused by loss-of-function mutations in the gene encoding hypoxanthine phosphoribosyltransferase (HPRT), an enzyme required for efficient recycling of purine nucleotides. Although this biochemical defect reconfigures purine metabolism and leads to elevated levels of the breakdown product urea, it remains unclear exactly how loss of HPRT activity disrupts brain function. As the rat is the preferred rodent experimental model for studying neurobiology and diseases of the brain, we used genetically-modified embryonic stem cells to generate an HPRT knock-out rat. Male HPRT-deficient rats were viable, fertile and displayed normal caged behaviour. However, metabolomic analysis revealed changes in brain biochemistry consistent with disruption of purine recycling and nucleotide metabolism. Broader changes in brain biochemistry were also indicated by increased levels of the core metabolite citrate and reduced levels of lipids and fatty acids. Targeted MS/MS analysis identified reduced levels of dopamine in the brains of HPRT-deficient animals, consistent with deficits noted previously in human LND patients and HPRT knock-out mice. The HPRT-deficient rat therefore provides a new experimental platform for future investigation of how HPRT activity and disruption of purine metabolism affects neural function and behaviour
Computer algebra and transputers applied to the finite element method
No full textRecent developments in computing technology have opened new prospects for computationally intensive numerical methods such as the finite element method. More complex and refined problems can be solved, for example increased number and order of the elements improving accuracy. The power of Computer Algebra systems and parallel processing techniques is expected to bring significant improvement in such methods. The main objective of this work has been to assess the use of these techniques in the finite element method. The generation of interpolation functions and element matrices has been investigated using Computer Algebra. Symbolic expressions were obtained automatically and efficiently converted into FORTRAN routines. Shape functions based on Lagrange polynomials and mapping functions for infinite elements were considered. One and two dimensional element matrices for bending problems based on Hermite polynomials were also derived. Parallel solvers for systems of linear equations have been developed since such systems often arise in numerical methods. Both symmetric and asymmetric solvers have been considered. The implementation was on Transputer-based machines. The speed-ups obtained are good. An analysis by finite element method of a free surface flow over a spillway has been carried out. Computer Algebra was used to derive the integrand of the element matrices and their numerical evaluation was done in parallel on a Transputer-based machine. A graphical interface was developed to enable the visualisation of the free surface and the influence of the parameters. The speed- ups obtained were good. Convergence of the iterative solution method used was good for gated spillways. Some problems experienced with the non-gated spillways have lead to a discussion and tests of the potential factors of instability
John Tillotson: a reappraisal
No full textJohn Tillotson (1630-94) was fellow of Clare, lecturer at St Lawrence Jewry, preacher at Lincoln's Inn, dean first of Canterbury and briefly of St Paul's, and archbishop of Canterbury (1691-4).This thesis seeks to review the career of a much-neglected and misrepresented clergyman, who lived and held office during the most turbulent phase of English history. The last attempt at a full-length biography was published in the eighteenth century. The judgements of Tillotson's enemies have often been uncritically repeated, and he has often been depicted as an enemy of the true Church of England and condemned as a Socinian and a rationalist, who preached nothing but morality. Reworking of old material and introducing new enables a more just appraisal to be made. The thesis describes and explains his rise from a humble background in Yorkshire to the see of Canterbury. The nature and content of his pamphleteering against atheism and Roman Catholicism is summarised. His part in the comprehension schemes of the period is discussed. The professionalism with which he approached his duties is revealed. Tillotson's involvement in political life is explained. Aspects of his pastoral work and personal life are described. From the large corpus of his printed sermons, the theological content of his preaching is examined. Tillotson emerges as a sincere, generous and tolerant Christian. He was a conscientious and hardworking clergyman. He was a convinced and campaigning, but never bigoted or a strident, protestant. His preaching reveals a concern for Christian commitment to, and growth of maturity in, the faith, which can be justified through reason. He was orthodox in theology and preached on all the main doctrines of the creed as well as stressing the ethical implications of faith
Phenotypic dissection of the mouse Ren-1(d) knockout by complementation with human renin
No full textNormal renin synthesis and secretion is important for the maintenance of juxtaglomerular apparatus architecture. Mice lacking a functional Ren-1(d) gene are devoid of renal juxtaglomerular cell granules and exhibit an altered macula densa morphology. Due to the species-specificity of renin activity, transgenic mice are ideal models for experimentally investigating and manipulating expression patterns of the human renin gene in a native cellular environment without confounding Renin-angiotensin-system interactions. A 55 kb transgene encompassing the human renin locus was crossed onto the mouse Ren-1(d)-null background, restoring granulation in juxtaglomerular cells. Correct processing of human renin in dense core granules was confirmed by immunogold labelling. After stimulation of the renin-angiotensin system, juxtaglomerular cells contained rhomboid protogranules with paracrystalline contents, dilated rough endoplasmic reticulum and electron-lucent granular structures. However, complementation of Ren-1(d-/-) mice with human renin was unable to rescue the abnormality seen in macula densa structure. The juxtaglomerular apparatus was still able to respond to tubuloglomerular feedback in isolated perfused juxtaglomerular apparatus preparations, although minor differences in glomerular tuft contractility and macula densa cell calcium handling were observed. This study reveals that the human renin protein is able to complement the mouse Ren-1(d-/-) non-granulated defect and suggests that granulopoiesis requires a structural motif that is conserved between the mouse Ren-1(d) and human renin proteins. It also suggests that the altered macula densa phenotype is related to the activity of the renin-1d enzyme in a local juxtaglomerular renin-angiotensin system.</p
Peat slides : morphology, mechanisms and recovery
No full textEThOS - Electronic Theses Online ServiceGBUnited Kingdo
Tetraria triangularis (Boeck.) C.B. Clarke and the Cape fold archipelago : an analysis of genetic and morphological variation in a high-altitude species native to the moutains of the Cape floristic region
No full textIncludes bibliographical references (leaves 102-127).The Cape Floristic Region (CPR) is renowned for its high plant species richness and high floristic endemism (Marloth 1929, Takahatjan, 1986, Goldblatt and Manning 2000, Linder 2003). A small number of clades (33) account for 50% of the species diversity, indicating that much of the diversification has occurred in situ, rendering it reminiscent of island archipelago radiations (Marloth 1929, Linder 2003). At a higher taxonomic level, 16.2 % of genera and four families are endemic to the area (Goldblatt et al. 2005
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