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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Organisation, landowner and farmer management in the conservation of blanket mires

O'Brien, Elizabeth January 2000 (has links)
Despite being Britain's most extensive semi-natural habitat, less research has been carried out on blanket mires than on many other habitats. This is possibly a result of their relative inaccessibility, since they are mainly confined to upland areas in England and Wales and remoter parts of Scotland; also to their apparent abundance, given that they cover significant portions of the landscape. Blanket mires in Britain cover approximately 1.5-2 million hectares; studies have documented substantial losses and up to ninety percent of blanket mires in Britain have been adversely affected. Literature on blanket mires suggests that poor management is one of the key issues for this habitat together with a lack of financial resources and commitment by the Government to protect and conserve sites adequately. The range of land uses of blanket mires is complex and includes agriculture, conservation, recreation, water catchment, grouse and deer management and forestry. These various uses have led to conflict among certain groups and a number of uses have had a detrimental effect on this habitat. Often the value of blanket mires has been overlooked even though this habitat, as part of natural ecosystem process, can provide functions and services such as wildlife interest and hydrological supply systems. A gap has been identified in the current literature on blanket mires, which suggests that research into the broader issues of strategy and management of this habitat, by organisations, landowners and farmers, has not been undertaken. Interview data have been obtained from organisations, landowners and farmers involved with blanket mire management and assessed by interpretational analysis. The research has been carried out both at a national level in Britain and at a local level with a case study of the Forest of Bowland in Lancashire. The local case study has been related to the wider context of blanket mire management and conservation. A total of fifty four in-depth interviews were undertaken in order to gain information on the views, perspectives and experiences of those involved with blanket mire management. How blanket mires are valued has a significant impact on how peatlands are conserved and for what reason. This research reveals that, in order to be effective, organisations will have to have a clear vision of what end point they are working towards and devise practical sategies that are flexible enough to incorporate the distinctiveness of different blanket mire areas.
12

The mesophase structure of surfactants

Burgoyne, John January 1994 (has links)
The binary surfactant system nona (ethylene glycol) mono-( 11 -oxa- 14,18.22,26-tetramethylheptacosylether) in heavy water has been investigated using deuterium nuclear magnetic resonance, optical polarising microscopy and small angle scattering techniques. The phase diagram has been established and the phases encountered exist for the most part from 24 to 60% surfactant by weight. Above and below these concentrations exist isotropic and lamellar phases respectively. The phase diagram features three main phases, a hexagonal phase of circular rods, a lamellar phase and an intermediate phase. The length of the alkyl chain is shown to be the most important factor in stabilising intermediate phases in preference to the bicontinuous cubic phases usually encountered between hexagonal and lamellar phases in shorter chain homologues. A nematic phase has also been observed in the water penetration scan. The intermediate phase is extensive, ranging from 32 to 60% surfactant by weight and is about 5°C wide. It has a body centred tetragonal mesh structure, comprised of layers of surfactant with regularly spaced holes which are also correlated between the layers, the hole of one layer overlapping the intersection of the layer below. As the concentration is decreased, from 60% to 30% (surfactant by weight) this correlation relaxes. The actual form of the aggregate appears to be elliptical rods (ellipticity - 1.7) joined four by four to form the basis of the mesh structure. A simplified version of the model based on circular rods joined by cube junction regions has been used to quantitatively investigate this phase. The results from this crude model produce results very close to those anticipated and produces results to within 2% of those generated using a more sophisticated model. This system is unusual in that the nature of the interaction between aggregates appears to be dominated by a single interaction - 'headgroup overlap force. This arises from the repulsive pressure experienced by the headgroups penetrating from the aggregate interface and also between headgroups on the same aggregate.

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