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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.
161

Investigating the great crested newt landscape in a pond rich environment : developing a landscape scale management perspective

Hollinshead, James Michael January 2011 (has links)
This thesis investigated graph theoretic analysis of connectivity and habitat availability for landscape scale management of Triturus cristatus, the Great Crested Newt. The ecological foundations of wider landscape management concepts and knowledge base on T. cristatus' habitat requirements, dispersal and migration were explored. Species presence, and aquatic and terrestrial habitat on the Cholmondeley Estate, Malpas, Cheshire, UK was mapped and land cover characterized for suitability and traversibility by T. cristatus. Habitat area available and accessible from ponds were identified. Analysis and modelling of pondscape connectivity using Probability of Connectivity (PC) and related indices, was carried out using Euclidean and Cost Weighted Distance and pond clustering at ecologically relevant scales was examined. Association or correlation of presence with proximity to breeding ponds, pond cluster size, proximity and available quantity of terrestrial habitat, proximity to roads and moving water, and connectivity of breeding ponds were examined at Cost Weighted and Euclidean distances. Connectivity, (PC index), pond count in clusters at 250 and 500m thresholds of connectivity, and proximity to core habitat (broad leaved woodland and rough grassland) using Cost Weighted distances were positively associated with breeding presence. Road proximity and density, proximity of core habitat at Euclidean distances and mean inter-pond distance were not significantly associated with breeding presence. Proximity to moving water was negatively associated with breeding presence. Resistance to movement of various land cover types has important implications for habitat availability and connectivity, , / and important questions are raised in terms of "rule of thumb" guidelines for estimation of connectivity between pond populations and habitat availability around breeding ponds. Graph analysis was used to identify priority areas for maintenance of landscape level connectivity, and enhancement of habitat connectivity and availability on the local population scale, with prioritization of pond creation/protection sites against their contribution to connectivity and habitat I availability, examining various scenarios.
162

The use of tree-ring analyses in the absolute dating of historic sites and their use in the interpretation of past climatic trends

Leggett, P. A. January 1980 (has links)
No description available.
163

The environmental physiology of Bufo bufo L. and Bufo calamita Laur. tadpoles

Nicolle, Philip David January 1989 (has links)
Using spawn collected from the north Merseyside sand dune system, the effects of temperature on growth, development, metabolism and metamorphosis in B. bufo and B. calamita tadpoles were investigated, together with a limited study on the effects of L-thyroxine. The effects of density on growth, developteI1t and metamorphosis were examined. Physiological and behavioural effects of B. bufo tadpoles on B. calamita tadpoles were also studied. B. calamita spawn and tadpoles survive at higher temperatures than B. bufo. Below20°CB. bufo spawn, and below 15°Ctheir t.adpcl.es, develop at a greater rate than B. calamita. B. calamita spawn and tadpoles' growth and development is faster at higher temperatures. B. calamita tadpoles have higher metabolic rates than B. bufo across the temperature range 15-30°C. Faster rates of metabolism and development in B. calamita result in smaller tadpoles and toadlets than B. bufo. B. calamita may compensate for this with increased metamorphic efficiency in terms of energy. It is speculated that differences in tadpole thyroid physiology could account for observed differences. metamorphic efficiency was greatest, and rates of development and growth maximised/at the tadpoles' preferred body temperature. Increased density reduced growth-and developteI1t of tadpoles, but influenced different stages in the two species. metamorphosis in all B. bufo tadpoles was delayed, whereas in B. calamita a proportion of the population metamorphosed apparently unaffected by increased density. The responses of tadpoles to temperature and density were related to the species' preferred spawning environments. In the presence of B. bufo tadpoles, B. calamita growth, development and metabolism was suppressed. The pattern of development and timing of metamorphosis in B. calamita became similar to that of B. bufo. Inhibition was not relieved by L-thyroxine, and did not effect tadpole behaviour. Mass specific food consumption was increased. It is speculated that the inhibitor is a parasite or a substance which affects assimilation.
164

The population dynamics of the Natterjack Toad (Bufo calamita Laur.) in the north Merseyside sand-dune system

Davis, C. A. January 1985 (has links)
No description available.
165

Conservation value, biodiversity value and methods of assessment in regenerating and human disturbed tropical forest

Whitworth, Andrew William January 2016 (has links)
Although the value of primary forests for biodiversity conservation is well known, the potential biodiversity and conservation value of regenerating forests remains controversial. Many factors likely contribute to this, including: 1. the variable ages of regenerating forests being studied (often dominated by relatively young regenerating forests); 2. the potential for confounding on-going human disturbance (such as logging and hunting); 3. the relatively low number of multi-taxa studies; 4. the lack of studies that directly compare different historic disturbances within the same location; 5. contrasting patterns from different survey methodologies and the paucity of knowledge on the impacts across different vertical levels of rainforest biodiversity (often due to a lack of suitable methodologies available to assess them). We also know relatively little as to how biodiversity is affected by major current impacts, such as unmarked rainforest roads, which contribute to this degradation of habitat and fragmentation. This thesis explores the potential biodiversity value of regenerating rainforests under the best of scenarios and seeks to understand more about the impact of current human disturbance to biodiversity; data comes from case studies from the Manu and Sumaco Biosphere Reserves in the Western Amazon. Specifically, I compare overall biodiversity and conservation value of a best case regenerating rainforest site with a selection of well-studied primary forest sites and with predicted species lists for the region; including a focus on species of key conservation concern. I then investigate the biodiversity of the same study site in reference to different types of historic anthropogenic disturbance. Following this I investigate the impacts to biodiversity from an unmarked rainforest road. In order to understand more about the differential effects of habitat disturbance on arboreal diversity I directly assess how patterns of butterfly biodiversity vary between three vertical strata. Although assessments within the canopy have been made for birds, invertebrates and bats, very few studies have successfully targeted arboreal mammals. I therefore investigate the potential of camera traps for inventorying arboreal mammal species in comparison with traditional methodologies. Finally, in order to investigate the possibility that different survey methodologies might identify different biodiversity patterns in habitat disturbance assessments, I investigate whether two different but commonly used survey methodologies used to assess amphibians, indicate the same or different responses of amphibian biodiversity to historic habitat change by people. The regenerating rainforest study site contained high levels of species richness; both in terms of alpha diversity found in nearby primary forest areas (87% ±3.5) and in terms of predicted primary forest diversity from the region (83% ±6.7). This included 89% (39 out of 44) of the species of high conservation concern predicted for the Manu region. Faunal species richness in once completely cleared regenerating forest was on average 13% (±9.8) lower than historically selectively logged forest. The presence of the small unmarked road significantly altered levels of faunal biodiversity for three taxa, up to and potentially beyond 350m into the forest interior. Most notably, the impact on biodiversity extended to at least 32% of the whole reserve area. The assessment of butterflies across strata showed that different vertical zones within the same rainforest responded differently in areas with different historic human disturbance. A comparison between forest regenerating after selective logging and forest regenerating after complete clearance, showed that there was a 17% greater reduction in canopy species richness in the historically cleared forest compared with the terrestrial community. Comparing arboreal camera traps with traditional ground-based techniques suggests that camera traps are an effective tool for inventorying secretive arboreal rainforest mammal communities and detect a higher number of cryptic species. Finally, the two survey methodologies used to assess amphibian communities identified contrasting biodiversity patterns in a human modified rainforest; one indicated biodiversity differences between forests with different human disturbance histories, whereas the other suggested no differences between forest disturbance types. Overall, in this thesis I find that the conservation and biodiversity value of regenerating and human disturbed tropical forest can potentially contribute to rainforest biodiversity conservation, particularly in the best of circumstances. I also highlight the importance of utilising appropriate study methodologies that to investigate these three-dimensional habitats, and contribute to the development of methodologies to do so. However, care should be taken when using different survey methodologies, which can provide contrasting biodiversity patterns in response to human disturbance.
166

Effects of water availability on growth and physiology of Ricinus communis L

Dodoo, Gladys January 1978 (has links)
No description available.
167

Predation effects upon the behaviour and ecology of Scottish Gasterosteus aculeatus L. populations

Giles, Nicholas January 1981 (has links)
No description available.
168

Natural History of Asymptomatic Valvar Pulmonary Stenosis Diagnosed in Infancy

Anand, Rajani, Mehta, Ashok V. 01 January 1997 (has links)
Background and hypothesis: Valvar pulmonary stenosis is a common congenital heart defect. Progression of stenosis over time, even when mild initially, has been shown by serial cardiac catheterization studies in children and adults. We studied the natural history of asymptomatic valvar pulmonary stenosis diagnosed in infancy with two-dimensional echocardiography and Doppler method. Methods: Between November 1986 and March 1993, 51 infants in the Northeast Tennessee and Southwest Virginia region were clinically diagnosed to have isolated valvar pulmonary stenosis. In 40 patients, the diagnosis was confirmed by two-dimensional echocardiogram/Doppler and color- flow mapping study at the time of presentation, and only their course is reported. Of 40 infants, six asymptomatic infants (15%) showed rapid progression of pulmonary stenosis over a relatively short period of time. Within the first 6 months of life, three of the six infants showed worsening of the stenosis needing intervention (one had surgical vulvectomy and the others had percutaneous balloon valvuloplasty). The three other infants showed a more gradual increase of pulmonary stenosis over the first 2 years of life. Results: Pulmonary stenosis even when mild can worsen in infancy, and it is not possible to predict which patients will follow this course. In our group of asymptomatic infants with initial mild pulmonary stenosis, 15% developed significant stenosis that needed intervention. Conclusion: We recommend frequent follow-up of asymptomatic infants with mild pulmonary stenosis during the first 2 years of life to detect rapid progression that may need intervention.
169

Progressive Congenital Valvar Aortic Stenosis During Infancy: Five Cases

Anand, R., Mehta, A. V. 01 January 1997 (has links)
We report our experience with asymptomatic valvar aortic stenosis diagnosed during infancy. During the period between November 1, 1986 and October 31, 1992 a total of 13 infants were diagnosed with asymptomatic aortic stenosis, 5 of whom showed rapid progression over the first 2 years of life. Two of these asymptomatic infants had severe aortic stenosis by 2 months of age, requiring intervention. We agree that aortic stenosis is a progressive lesion even in mild cases, but we emphasize the need for close clinical and echocardiographic follow-up of these asymptomatic children during infancy to prevent congestive heart failure and sudden death.
170

The unidentified long bone fragments from the middle stone age Still Bay layers at Blombos Cave, Southern Cape, South Africa

Reynard, Jerome Peter 07 March 2012 (has links)
M.Sc., Faculty of Science, University of the Witwatersrand, 2011 / The aim of this investigation was to explore the relationship between the unidentified and identified fauna from the Still Bay period at Blombos Cave between ca. 77 and 72 ka. The size, breakage patterns and surface modifications of unidentified long bone fragments from the M1 and upper M2 phases were analysed. The results of the analyses were then compared to a sample of faunal remains identified by Klein (Henshilwood et al. 2001b) and Thompson (2008) from the Still Bay layers at Blombos Cave. The length of each fragment was measured to ascertain the degree of fragmentation of the assemblage. Long bone fragments generally become slightly shorter with increasing depth. This may be because smaller fauna are relatively more prevalent in the deeper layers. Cortical thickness of the bone fragments was measured and grouped into small, medium and large categories. These categories were correlated to Brain‟s (1974a) bovid size classes to investigate whether the unidentified faunal remains mimic the identified bone sample in terms of animal size. While small-sized fauna dominate the identified archaeofaunal assemblages at Blombos Cave, the cortical thickness of unidentified long bone fragments suggest that medium-sized fauna was more common. The breakage pattern of each fragment was assessed, indicating that the majority of specimens exhibited spiral fractures. Burning is more common in the unidentified faunal sample than in the identified sample and may have resulted in the relatively low frequencies of cut-marked and percussion-marked fragments. Polished bone fragments may also be a consequence of burning, abrasion or compaction, though its prevalence in the upper M2 with formal bone tools suggests that it was the result of human activities. Higher bone fragment densities in the upper layers at Blombos Cave suggests that changes in human occupation and faunal density patterns during the Still Bay at Blombos Cave may relate to environmental conditions.

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