A study of the mechanisms underlying the cardiac effects of exercise training in angina pectoris

This thesis investigates the use of exercise training as a therapy in the management of angina pectoris. The hypothesis underlying this work is that in the presence of ischaemia the myocardium will, if possible, respond in such a way as to minimise the effects of ischaemia. Improved collateral function was felt to be the most likely mechanism.A series of non-invasive investigations was developed in such a way as to make them useful for the detection of any possible improvement in myocardial ischaemia. These investigations included treadmill exercise tolerance testing, Thallium scintigraphy, Technetium ventriculography, exercise echocardiography and 24 hour ambulatory ECG monitoring. These techniques were refined for use in this study by the development of computerised analysis where appropriate.Forty male patients under 60 years of age with angina pectoris and no prior myocardial damage were recruited and randomised into exercise and control groups. Both groups were followed up over a one year period, the exercise group carrying out a brief daily home-based exercise programme, using the Canadian Airforce PBX Program for Physical Fitness.The techniques developed proved to be effective follow up tools in this group. Using them significant improvements in treadmill performance were demonstrated in the exercise group. These improvements were found to be partly due to changes in the peripheral control of exercise induced heart rate increases but viii also due to myocardial improvements. The peripheral effects were compared to and contrasted with betablockade. Within the myocardium significant reductions in ischaemic area were demonstrated, particularly in the territory of the left anterior descending coronary artery. These improvements in perfusion were accompanied by improvements in left ventricular function and regional wall motion. The improvements demonstrated in the laboratory were also evident during ambulatory ECG monitoring.The results demonstrated support the hypothesis outlined that controlled myocardial ischaemia can induce improvements in myocardial perfusion, perhaps due to collateral enhancement, and furthermore support the use of these techniques in such follow up studies.Further studies would be justified and indeed necessary to convincingly prove the hypothesis. Such studies may need to be multicentre in order to recruit sufficient numbers and ideally should involve coronary angiography and coronary perfusion assessment

Long-term changes in water quality downstream of three abandoned metal mines

Abandoned metal mines pollute rivers with both acidic and circumneutral metal-rich waters, sometimes from well-mapped mines, but often from long-abandoned adits with limited historical records. Changes in water quality over the monitored timescales were calculated for three mines across Wales (Nantymwyn, Parys Mountain and Frongoch), each abandoned since the early 20th century. Using all available spot sampling data provided by the environmental regulator, it was found that there was a sustained input of metals to the receiving watercourses with no or limited reduction in the concentrations from the mines without remediation, despite the passage of time and impacts of weathering. At Nantymwyn, comparison with five months’ sampling in 2019 showed no significant change (p > 0.05) in metal concentrations compared to the same months in 1985. Parys Mountain showed an increase in filtered zinc concentrations of 2 % between 2004 and 2020. At Frongoch, however, a substantial reduction in its environmental impact was observed after remediation, including a 90 % reduction in total lead concentrations. Realisation that the pollution from these sites does not reduce over the decades since abandonment should galvanize the resolve to understand the highest priority sites, and where possible remediate them

Identification and quantification of diffuse groundwater pollution in a mineralised watershed

A tracer injection and synoptic sampling experiment was carried out in a tributary catchment of the River Tywi (Carmarthenshire, Wales) during a very low streamflow event to locate and quantify sources of groundwater metal pollution from the abandoned Nantymwyn Pb mine. High resolution sampling at 22 stream locations and 12 inflows along a 2 km stretch of the Nant y Bai was deployed. This high spatial resolution sampling technique allowed point and diffuse sources of metal pollution to be identified enabling their contribution to the overall stream load to be quantified. It was found that the highest proportion of filtered Zn load originated from diffuse groundwater sources from the upper mine tailings (43%), and that the highest proportion of filtered Pb load originated from diffuse groundwater sources from the lower mine tailings (40%), with smaller inputs from a field on the River Tywi floodplain. These results demonstrate that tracer dilution and synoptic sampling is a powerful tool to locate and apportion diffuse sources of groundwater metal pollution in small, mineralised watersheds

Solidification microstructure selection in aluminium-based alloys.

Iron is the most common impurity found in aluminium. It has a high solubility in molten aluminium and is therefore readily dissolved at all molten stages in production. The solubility of iron in the solid state is, however, very low (0.04%)1. As a result most of the iron present above this level appears as an intermetallic second phase in combination with aluminium and other elements. Numerous AI-Fe and AI-Fe-Si intermetallics have been identified in as-cast commercial purity aluminium and these have been the subject of extensive research because they can influence the material behaviour during subsequent fabrication steps and may have a critical influence on material quality. It is, therefore, of considerable technological interest to be able to exert control over the formation of these phases especially in dilute aluminium alloy compositions. This can be done most readily by controlling cooling rate during solidification or by modification of alloy chemistry to enhance the stability of a desired phase. Several authors have dealt with the effects of further additions on phase stability in the binary AI-Fe alloy system. In particular the effect on phase stability of other transition metals which are known from studies of their equilibrium behaviour to be at least partially soluble in binary AI-Fe phases have shown that additions of these elements can cause significant changes in phase stability with respect to both the cooling rate during solidification and solidification front velocity. It has also been suggested on a number of occasions that the discrepancies often found when comparing the results of published work on both the binary AI-Fe and ternary AI-Fe-Si systems, are attributable even to trace levels of impurity in the compositions investigated. As a result the relative effects of each component present on phase incidence and stability remains uncertain. This is especially true of ternary compositions with low Si:Fe ratios and AI-rich quaternary AI-Fe-Si-Mg alloys where a clear picture of phase incidence versus solidification cooling rate has yet to emerge. To date no systematic investigation has been conducted into the cumulative effect of common alloying additions and impurities on intermetallic phase stability in AI-base alloys. One objective of this thesis work was to determine the effect on phase stability and incidence of cumulative additions of 0.1 %Si, 0.75%Mg and 0.04%Cr to a base composition of AI-0.5wt.%Fe over the range of solidification front velocity between 0.05 and 2.00mmls during steady state growth at an imposed temperature gradient of 8 to 12 Klmm. The effect of minor changes in Fe, Si and Mg content on intermetallic phase selection in AI-Fe-Si-Mg alloys was also investigated under these imposed solidification conditions. Chapter 2 provides a review of the phases reported to have been formed in dilute AI-Fe, AI-Fe-Si and AI-Fe-Si-Mg alloys and the local solidification conditions reported as being necessary for their formation. In addition, the effects reported in the available literature of low levels of impurities on the stability and morphology of the intermetallics will be surveyed. Chapter 3 describes the experimental procedures used including alloy preparation, directional solidification, and the techniques employed in the identification of the intermetallic phases formed. Chapter 4 presents the Results and Chapter 5 is the Discussion which attempts to interpret these results and to draw conclusions concerning their implications which are detailed in Chapter 6

Hot Spine Loops and the Nature of a Late-Phase Solar Flare

The fan-spine magnetic topology is believed to be responsible for many curious features in solar explosive events. A spine field line links distinct flux domains, but direct observation of such feature has been rare. Here we report a unique event observed by the Solar Dynamic Observatory where a set of hot coronal loops (over 10 MK) connected to a quasi-circular chromospheric ribbon at one end and a remote brightening at the other. Magnetic field extrapolation suggests these loops are partly tracer of the evolving spine field line. Continuous slipping- and null-point-type reconnections were likely at work, energizing the loop plasma and transferring magnetic flux within and across the fan quasi-separatrix layer. We argue that the initial reconnection is of the "breakout" type, which then transitioned to a more violent flare reconnection with an eruption from the fan dome. Significant magnetic field changes are expected and indeed ensued. This event also features an extreme-ultraviolet (EUV) late phase, i.e. a delayed secondary emission peak in warm EUV lines (about 2-7 MK). We show that this peak comes from the cooling of large post-reconnection loops beside and above the compact fan, a direct product of eruption in such topological settings. The long cooling time of the large arcades contributes to the long delay; additional heating may also be required. Our result demonstrates the critical nature of cross-scale magnetic coupling - topological change in a sub-system may lead to explosions on a much larger scale.Comment: Accepted for publication in ApJ. Animations linked from pd

Leaders and laggards in the pursuit of an EU just transition

The just transition from coal, oil, and gas to renewable energy sources involves commitment from all EU states. But who is leading, or lagging? We apply an innovative DeePeR framework to identify these states, using open-access quantitative global data from multiple sources, by evaluating the energy and equity dimensions of Distributive, Procedural and Restorative justice. Using rank percentile scores, we assessed EU nations\u27 level of fossil fuel dependency (including both energy and financial dependency) and distributional inequality, their fossil fuel CO2 emissions, climate finance pledges and a calculated procedural justice score, and their commitment to modern renewable electricity output and rankings on fair and renewable jobs. We find that EU states\u27 performances on just transition are distinct across four broad regions; Scandinavia, eastern Europe, western Europe, and the Mediterranean. We discuss the nuances of fossil fuel embeddedness in the EU. This is followed by reflection on the importance of embedding fairness in the deployment of new renewable jobs. Finally, we consider the implications for a better-targeted financial mechanism for just transition alongside a fossil fuel divestment strategy

Nondestructive testing of high strength conductors for high field pulsed magnets

High field pulsed magnets at the NHMFL use high strength conductor wires up to 90% of their ultimate tensile strength. Therefore it is very important to ensure that the wires are free of flaws. It is known that in the conductors cold drawing process, internal chevron crack could occur due to unsuitable drawing die schedule or inadequate lubrication. These internal cracks occurs infrequently along the wire, so tensile tests of short samples cut from the ends of a long length conductor often miss the problem. In addition, small inclusions on the wire surface can compromise wires fatigue properties. In this paper, we present results of our non-destructive testing (NDT) inspection of Glidcop AL60 wires using eddy current testing (ECT), ultrasonic testing (UT) and x-ray radiography (2D and 3D). Chevron cracks were found in some AL60 conductors by all three NDT techniques. Surface inclusions were found by ECT. We have developed a long length ECT wire inspection capability.Comment: 4 pages, 9 figure