Carbon nanotubes as materials in nanotechnology

Carbon nanotubes (CNTs) are hollow tubes of sp2-hybridised carbon with diameters of the order of nanometres. Due to their unique physical properties, which include ballistic transport and high mechanical strength, they are of significant interest for technological applications. The electronic properties of CNTs are of particular interest for use as gas sensors, interconnect materials in the semi-conductor industry and as the channel material in CNT based field effect transistors. The primary difficulty associated with the use of CNTs in electronic applications is the inability to control electronic properties at the growth stage; as grown CNTs consist of a mixture of metallic and semi-conducting CNTs. Doping has the potential to solve this problem and is a focus of this thesis. Nitrogen-doped CNTs typically have defective structures; the usual hollow CNT structure is replaced by a series of compartments. Through density functional theory (DFT) calculations and experimental results, we propose an explanation for the defective structures obtained, based on the stronger binding of N to the growth catalyst in comparison to C. In real electronic devices, CNTs need to be contacted to metal, we generate the current-voltage (IV) characteristics of metal-contacted CNTs considering both the effect of dopants and the structure of the interface region on electronic properties. We find that substitutionally doped CNTs produce Ohmic contacts and that scattering at the interface is strongly influenced by structure. In addition, we consider the effect of the common vacancy defects on the electronic properties of large diameter CNTs. Defects increase scattering in the CNT, with the greatest scattering occurring for the largest defect (555777). We validate the independent scattering approximation for small diameter CNTs, which enables mean free paths in large diameter CNTs to be calculated, with a smaller mean free paths found for larger defects.

Analysis of institutional arrangements and common pool resources governance: the case of Lake Tana sub-basin, Ethiopia

Although Common Pool Resources (CPRs) make up a significant share of total income for rural households in Ethiopia and elsewhere in developing world, limited access to these resources and environmental degradation threaten local livelihoods. As a result, the issues of management, governance of CPRs and how to prevent their over-exploitation are of great importance for development policy. This study examines the current state and dynamics of CPRs and overall resource governance system of the Lake Tana sub-basin. This research employed the modified form of Institutional Analysis and Development (IAD) framework. The framework integrates the concept of Socio-Ecological Systems (SES) and Interactive Governance (IG) perspectives where social actors, institutions, the politico-economic context, discourses and ecological features across governance and government levels were considered. It has been observed that overexploitation, degradation and encroachment of CPRs have increased dramatically and this threatens the sustainability of Lake Tana ecosystem. The stakeholder analysis result reveals that there are multiple stakeholders with diverse interest in and power over CPRs. The analysis of institutional arrangements reveals that the existing formal rules and regulations governing access to and control over CPRs could not be implemented and were not effective to legally bind and govern CPR user’s behavior at the operational level. The study also shows that a top-down and non-participatory policy formulation, law and decision making process overlooks the local contexts (local knowledge and informal institutions). The outcomes of examining the participation of local resource users, as an alternative to a centralized, command-and-control, and hierarchical approach to resource management and governance, have called for a fundamental shift in CPR use, management and governance to facilitate the participation of stakeholders in decision making. Therefore, establishing a multi-level stakeholder governance system as an institutional structure and process is necessary to sustain stakeholder participation in decision-making regarding CPR use, management and governance.

The evolution of the medical professions in eighteenth-century Ireland: An institutional perspective

Ireland, in the eighteenth century, followed the classic tripartite division of regular medical practitioners into physicians, surgeons and apothecaries. At the beginning of the century surgeons and apothecaries were regarded as mere tradesmen, but by the end of the century both were regarded as professionals and had the right to regulate their respective professions. Practitioners in different regions of Europe developed in a different manner, and eighteenth-century practitioners in Ireland developed independently from their English counterparts. In common with Britain and Europe in the eighteenth century, the total number of practitioners increased in Ireland, and by the end of the century, apothecaries were the largest group in Dublin, closely followed by the surgeons. Surgeons and apothecaries at the start of the eighteenth century belonged to the same guild. However in mid-century, St Luke's guild of apothecaries was established and this provided the apothecaries with a new identity that allowed them to pursue auto regulation, rather than hitherto, when they had been regulated by the physicians. This was vital to the apothecaries as they were in direct commercial competition with both the physicians and the surgeons and faced increasing pressure from both druggists and the disparate group of practitioners known as the irregulars. The 1765 County Infirmaries Act established a hospital in virtually every county in Ireland, and cast the surgeon as the primary medical officer in the countrywide network of hospitals. This legislation, which was unique in Europe, had the unintended consequence of elevating the status of the surgeons, as prior to this physicians were always in the ascendancy in the voluntary hospitals in Ireland and Britain, in contrast to France. The status of the surgeons was further enhanced by the establishment of the College of Surgeons in Ireland in 1784, which provided them with a new corporate identity, the authority to regulate the profession countrywide, and, also, the ability to educate surgeons in Ireland. The establishment of the College of Surgeons placed further pressure on the apothecaries to demonstrate that they also had a recognisable identity, and the authority to regulate their own profession. This was achieved with the 1791 Apothecaries Act which established the Apothecaries Hall and give the apothecaries the right to regulate themselves. This innovative legislation deemed the apothecaries a profession, and was enacted twenty-four years prior to similar legislation in Britain. Commercial pressure from druggists and, probably, irregulars expedited the requirement of the apothecaries to establish a new corporate identity, in order to distance themselves from these groups. The changing status of both apothecaries and surgeons had little effect on the physicians as a group, and, despite being the beneficiaries of a generous bequest from Sir Patrick Dun in 1711 to provide medical chairs in Dublin, the physicians displayed an inertia during the eighteenth century that was not in keeping with the developments that occurred in the contemporary Dublin medical world. The fact that it took ninety-five years, and that five acts of parliament, two House of Commons enquiries and a House of Lords enquiry were required to ensure that Dun's wishes were brought to fruition demonstrates that the physicians did not develop at the same pace as the other medical groups in the city. Had Dun’s bequest been implemented as he desired, Dublin, with a number of voluntary hospitals, would have been well placed to provide comprehensive tuition for medical students in the eighteenth century. It was not until the nineteenth century that the city, and the populace, benefited from this legacy. This thesis will trace these developments in the context of changes that occurred in contemporary medical education and diagnosis in Ireland, Britain and France. It will demonstrate that Irish practitioners developed independently, influenced mainly by local issues, but also by those who had travelled abroad and returned to Ireland with new concepts and ideas, ensuring that Irish medical practitioners had the institutional structure that could encompass the diagnostic and regulatory changes that would become accepted in the nineteenth century.

The study of molecular variation in Atlantic salmon (Salmo salar L.) and brown trout (Salmo trutta L.)

Polymorphic microsatellite DNA loci were used here in three studies, one on Salmo salar and two on S. trutta. In the case of S. salar, the survival of native fish and non-natives from a nearby catchment, and their hybrids, were compared in a freshwater common garden experiment and subsequently in ocean ranching, with parental assignment utilising microsatellites. Overall survival of non-natives was 35% of natives. This differential survival was mainly in the oceanic phase. These results imply a genetic basis and suggest local adaptation can occur in salmonids across relatively small geographic distances which may have important implications for the management of salmon populations. In the first case study with S trutta, the species was investigated throughout its spread as an invasive in Newfoundland, eastern Canada. Genetic investigation confirmed historical records that the majority of introductions were from a Scottish hatchery and provided a clear example of the structure of two expanding waves of spread along coasts, probably by natural straying of anadromous individuals, to the north and south of the point of human introduction. This study showed a clearer example of the genetic anatomy of an invasion than in previous studies with brown trout, and may have implications for the management of invasive species in general. Finally, the genetics of anadromous S. trutta from the Waterville catchment in south western Ireland were studied. Two significantly different population groupings, from tributaries in geographically distinct locations entering the largest lake in the catchment, were identified. These results were then used to assign very large rod caught sea trout individuals (so called “specimen” sea trout) back to region of origin, in a Genetic Stock Identification exercise. This suggested that the majority of these large sea trout originated from one of the two tributary groups. These results are relevant for the understanding of sea trout population dynamics and for the future management of this and other sea trout producing catchments. This thesis has demonstrated new insights into the population structuring of salmonids both between and within catchments. While these chapters look at the existence and scale of genetic variation from different angles, it might be concluded that the overarching message from this thesis should be to highlight the importance of maintaining genetic diversity in salmonid populations as vital for their long-term productivity and resilience.