http://www.dspace.cam.ac.uk:80/handle/1810/219477 Fri, 24 May 2013 20:51:09 GMT 2013-05-24T20:51:09Z http://www.dspace.cam.ac.uk:80/handle/1810/244398 Title: Geochemical and sedimentological investigations of Youngest Toba Tuff ashfall deposits Authors: Gatti, Emma Abstract: The ~ 73 ka ‘super-eruption’ of the Toba caldera in Sumatra is the largest known eruption of the Quaternary. The products of this eruption, the Youngest Toba Tuff (YTT), have been implicated in global and regional climate deterioration with widespread ecological effects. In this thesis I study the YTT co-ignimbrite ashfall, in particular the mechanisms of transport, sedimentation and preservation of ash deposits. I use distal marine and terrestrial ash sediments: a) to estimate the volume of YTT ash fallout; b) to quantify variability in the geochemistry of YTT ash; c) to assess the reliability of YTT ash as a chronostratigraphic marker; and d) to determine local influences on the reworking of YTT ash deposits. Following the introductory chapters, I address topics a) and b) through detailed investigations of published physical and chemical evidence. Chapter three shows that particle size and sediment thickness do not decline exponentially with distance from the eruption vent, highlighting the limitations of current methods of volume estimation for co-ignimbrite super-eruptions. Chapter four analyses geochemical variation in 72 YTT samples, and reveals the signatures of magma chamber zonation and post-depositional alteration. I address topics c) and d) through fieldwork in six locations, and detailed analysis of ash samples from a wide variety of local depositional environments. Chapter five uses high-resolution stratigraphic analysis of the YTT layer in the Son Valley, India, to show that variable deposition and sediment reworking may compromise the reliability of the ash layer as an isochronous marker for interpreting archaeological sequences. Chapter six combines a new understanding of the mechanisms of reworking, using new data on microscopic characteristics of reworked ash at four sites in Malaysia to demonstrate the necessity of accounting for reworking in palaeoenvironmental reconstructions. I conclude that accurate analyses of distal ash deposits can reliably determine the chemical properties of the YTT eruption, and that a detailed understanding of deposition and reworking processes is essential to inference of the environmental impacts of super-eruptions. Tue, 12 Mar 2013 00:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/244398 2013-03-12T00:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/238073 Title: A protocol for investigation of the effects of outdoor air pollution on stroke incidence, phenotypes and survival using the South London Stroke Register Authors: Maheswaran, Ravi; Pearson, Tim; Campbell, Michael J; Haining, Robert P; McLeod, Cameron W; Smeeton, Nigel; Wolfe, Charles D A Abstract: Abstract Stroke is a major cause of death and disability. About 5.3 million people die every year from stroke worldwide with over 9 million people surviving at any one time after suffering a stroke. About 1 in 4 men and 1 in 5 women aged 45 years will suffer a stroke if they live to their 85th year. It is estimated that by 2023 there will be an absolute increase in the number of people experiencing a first ever stroke of about 30% compared with 1983. In the UK, stroke is the third commonest cause of death and the most common cause of adult physical disability and consumes 5% of the health and social services budget. Stroke is assuming strategic public health importance because of increased awareness in society, an ageing population and emerging new treatments. It is an NHS health service and research priority, being identified as a target in Our Healthier Nation and the NSF for Older People for prevention and risk factor control and in the NHS Plan as a disease requiring intermediate care planning and reduction in inequalities of care. Whilst a number of risk factors for stroke are well known (e.g. increasing age, ethnicity, socioeconomic deprivation, hypertension), the potential importance of outdoor air pollution as a modifiable risk factor is much less well recognised. This is because studies to date are inconclusive or have methodological limitations. In Sheffield, we estimated that 11% of stroke deaths may be linked to current levels of outdoor air pollution and this high figure is explained by the fact that so many people are exposed to air pollution. We plan to study the effects of outdoor air pollution on stroke using a series of epidemiological (i.e. population based) studies. The purpose of this project is: • to examine if short term increases in pollution can trigger a stroke in susceptible individuals; • to investigate if the occurrence of stroke is higher amongst people living in more polluted areas (which would be explained by a combination of exposure to short term increases and longer term exposure to higher pollution levels); and • to see if people living in more polluted areas have reduced survival following their stroke. We will use geographical information systems, robust statistical methods and powerful grid computing facilities to link and analyse the data. The datasets we will use are the South London Stroke Register database, daily monitored pollution data from national monitoring networks and modelled pollution data for London from the Greater London Authority. The South London Stroke Register records information on all patients who suffer a stroke ("incident" cases) living within a defined area. This stroke incidence dataset offers major advantages over previous studies examining the effects of pollution on hospital admissions and mortality, as not all patients with stroke are admitted or die and there may be a delay between the onset of stroke and admission or death. In addition, it contains other useful information, particularly the type of stroke people have suffered. Air pollution is a potentially modifiable risk factor for stroke. This study will provide robust population level evidence regarding the effects of outdoor air pollution on stroke. If it confirms the link, it will suggest to policy-makers at national and international levels that targeting policy interventions at high pollution areas may be a feasible option for stroke prevention. Fri, 17 Mar 2006 00:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/238073 2006-03-17T00:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/237159 Title: Mohajir subnationalism and the Mohajir Qaumi Movement in Sindh Province, Pakistan Authors: Richards, Julian James Abstract: This dissertation examines the rise of the Mohajir subnationalist movement in Sindh Province, Pakistan. It focusses on the Mohajir Qaumi Movement (Mohajir National Movement; MQM) - the party that has constructed a version of a Mohajir identity for political purposes. The analysis begins with a critical examination of the Muslim movement in British India, which culminated in the formation of Pakistan. The political history of Pakistan up to 1993 is then examined, with particular reference to the development of subnationalist movements. There then follows a detailed appraisal of debates and theories on identity, ethnicity and nationalism. The second section of the dissertation focusses on the Province of Sindh in southern Pakistan. It introduces the research framework and methodologies, and details the range of interviews conducted and archival and other sources consulted. The section proper examines, firstly, the construction of diverse community identities in Sindh Province, and, secondly, the MQM in terms of its political history, patterns of mobilisation, internal structure and aims and rhetoric. The third section of the dissertation is focussed on the city of Karachi; very much the heartland of the MQM- I first examine how and why the MQM came to be the city's dominant agency in the 1980s, and how it ran a "parallel local state" in urban Sindh. I then consider the relationship between Mohajir subnationalism and violent civil disorder in Karachi and Hyderabad. This analysis in turn highlights certain contradictions in the policies and activities of the MQM. These contradictions are explored at length in a concluding chapter which considers the rise and fall of the MQM in the wider context of stateformation in postcolonial developing countries. Tue, 25 Jan 1994 00:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/237159 1994-01-25T00:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/237058 Title: Pans of the southern Kalahari, Botswana Authors: Lancaster, Ian Nicholas Abstract: The main geomorphic features of the southern Kalahari in Botswana are the 1000 pans or small dry lakes which lie along the broad watershed between the Nossop - Molopo and Makgadikgadi drainages. No previous detailed studies exist of the pans, which appear to have developed under climatic conditions unlike those of today, and appear to represent further evidence for Quaternary climatic change in the region. The pans, whioh may have a grassed, partly grassed or bare clay surface, are contained in shallow sub circular to sub elliptical isolated depressions, on the southern side of which is an area of fringing dunes, indicative of a deflation origin for the pan depressions. Analysis of the distribution of the pans shows that they are strongly clustered but do not form aligned groupings. Two dune ridges, both formed by northerly winds, are identified. The composition of the dunes shows that the outer dunes were formed by deflation from the site of the pan depressions and the inner dunes by deflation of sandy pan deposits. The nature of the deposits which underlie the pans and the flanks of the inner dunes is described, and upper sandy and lower clayey phases identified. Their composition indicates that the pan depressions once held extensive permanent lakes, which gradually contracted as the climate became drier. The nature of the pan surfaces today is shown to represent a sequence as the pans are excavated by deflation. The paleoclimatic significance of the three main periods in the origin and development of the southern Kalahari pans is discussed. The pan deposits provide further evidence for a major wet period in the Kalahari some 12000 to 20000 years ago. Deflation to form the outer dunes took place in the arid period that occured 20000 to 25000 years ago, and the inner dunes were formed during dessication of the climate some 10000 to 12000 years ago. Tue, 22 Feb 1977 00:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/237058 1977-02-22T00:00:00Z