Teses / dissertações sobre o tema "Remnants used in"

Angel Jones Artist Statement My mixed media collages address issues concerning the outcast, the overlooked, and the underprivileged. My inspirations come from what I experience and perceive around me. My purpose in life is to use my art to address social issues that involve children. For example, I focus my attention on issues ranging from homelessness to mental illness. I am passionate about how vital these concerns are to our success as human beings. To express my ideas, I layer a variety of materials and textiles. The materials include fragments of photographs, drawings, and objects. The textiles include articles of clothing and fabrics. Recurring symbols and imagery link the individual pieces together. The theme of each work determines the materials and media. While doing research for a piece, new social issues often surface and lead to the next piece.

Agricultural expansion has transformed and fragmented natural forest habitats at an alarming rate, and dramatic increases in agricultural intensification have since taken place in order to keep pace with human population growth and food demands. This simultaneously poses a considerable threat to biodiversity in agricultural landscapes, as production land is now one of the largest terrestrial biomes on the planet. Therefore, its contribution to biodiversity conservation is critical. Links between the intensification of agricultural systems and ‘in situ’ declines of biodiversity on farmland have been well documented. However, despite growing recognition that system inputs such as fertiliser and livestock can move or ‘spillover’ into adjacent natural habitats, there has been no direct quantification of the extent of impacts in recipient ecosystems. These abiotic and biotic pathways can cause dramatic impacts on the diversity, composition, and functioning of remaining natural ecosystems, and on their ability to provide a variety of essential ecosystem services. Due to concerns regarding future food security, balancing trade-offs between agriculture and conservation has subsequently become a hot topic in ecological research. However, without any direct quantification of the off-site ecological impacts of agricultural intensification in mosaic landscapes, it is inherently difficult to fully evaluate strategies aimed at balancing production and conservation. Using New Zealand farming systems as a case study, this thesis aims to address gaps in our current understanding of how increasing agricultural intensification impacts biodiversity in native forest remnants embedded within production landscapes. The first main chapter explores whether the magnitude of ecological impact in forest remnants (for a suite of 26 response measures) and severity of edge effects, scale with the degree of land-use intensity in surrounding agricultural pastures. This chapter also examines whether ecological responses differ in remnants ‘spared’ for conservation purposes (i.e. where livestock are excluded by fencing). The second chapter uses a model food-chain approach native to New Zealand, to test whether nutrient spillover from agricultural pastures influences plant-herbivore and herbivore-parasitoid interactions in forest remnants. This chapter also includes a large-scale common garden fertilisation experiment using the same tri-trophic system, which was established to examine bottom-up multi-trophic responses to the independent and combined effects of Nitrogen (N), Phosphorus (P) and cow dung and urine. The third main chapter uses a novel stable isotope approach for quantifying community-wide incorporation of resources into trophic structure. I test for the first time whether increasing intensity of farming systems drives greater nutrient spillover spatially into adjacent forest remnant soils and examine scaling effects of 15N (as a marker for anthropogenic N) through multiple trophic levels. Beyond finding that agricultural land-use intensity generally has negative off-site effects on biodiversity, the key findings of this thesis were (i) spillover of nitrogen and phosphorus from agricultural systems into adjacent remnant soils is exacerbated by increases in land-use intensity, with (ii) percolating bottom-up effects on plant and insect community dynamics. (iii) The magnitude of ecological impacts in forest remnants scales linearly with increasing land-use intensity, as does (iv) direct anthropogenic N enrichment across multiple trophic levels, which has the potential to severely jeopardise the stability of ecologically important remnant habitats. (v) Although there were stark structural differences in remnants with and without livestock exclusion, impacts of land-use intensity on ecological response metrics were actually comparable across all sites. (vi) Livestock exclusion should be a priority first step towards conserving native forest remnants, however it should be recognised that fencing does not prevent abiotic channels of nutrient spillover (fertiliser drift, overland flow, leaching) in land characteristic of land spared for nature. (vii) Consequently, increasing land-use intensity compromises the effectiveness of the land-sparing trajectory for conserving native biodiversity, which is currently undertaken in New Zealand production systems. Given the overall strength of these findings and the novel, ecosystem-wide and landscape-scale approaches taken to address fundamental questions, the work in this thesis greatly enhances our knowledge of the relationships between agricultural productivity and ecological impacts in spatially-coupled ecosystems. This is highly important, not only in New Zealand but worldwide, as it is anticipated that unstoppable human population growth and food security pressures will cause ecological impacts both on the farm and in adjacent natural ecosystems to become even more severe. Therefore, determining the relationship between land-use intensification and biodiversity loss represents the cornerstone of sustainable agricultural development in the future.

The processes by which urban areas come to be and evolve create outdoor spaces that experience different uses and have different characteristics over a period of time. For example, a space previously used for industrial purposes may presently be used as a community park. In some cases, a significant area of land may become a kind of leftover or remnant space whose uses are unclear, undefined, or unprogrammed, but exhibits natural characteristics. The purpose of this study is to utilize one of these natural remnants, Marott Park, in the cultural arts district of Broad Ripple in Indianapolis, Indiana as the basis for a design effort that provides access to the site while retaining both its site-specific and contextual characteristics. The intent of this effort is to enhance the community/pedestrian recreational, educational, and cultural experience through a detailed design for a portion of Marott Park. A set of recommendations also addresses the potential for connections between the site and other features such as existing open space, schools, and cultural features in the Indianapolis area.
Department of Landscape Architecture

Thesis (M.S. in crop science)--Washington State University, August 2010.
Title from PDF title page (viewed on July 30, 2010). "Department of Crop and Soil Sciences." Includes bibliographical references.

Although semi-natural grasslands in Europe are declining there is often a time delay in the local extinction of grassland species due to development of remnant populations, i.e., populations with an extended persistence despite a negative growth rate. The objectives of this study were to examine the occurrence of remnant populations after abandonment of semi-natural grasslands and to examine functional traits of plants associated with the development of remnant populations. We surveyed six managed semi-natural grasslands and 20 former semi-natural grasslands where management ceased 60-100 years ago, and assessed species response to abandonment, assuming a space-for-time substitution. The response of species was related to nine traits representing life cycle, clonality, leaf traits, seed dispersal and seed mass. Of the 67 species for which data allowed analysis, 44 species declined after grassland abandonment but still occurred at the sites, probably as remnant populations. Five traits were associated with the response to abandonment. The declining but still occurring species were characterized by high plant height, a perennial life form, possession of a perennial bud bank, high clonal ability, and lack of dispersal attributes promoting long-distance dispersal. Traits allowing plants to maintain populations by utilizing only a part of their life cycle, such as clonal propagation, are most important for the capacity to develop remnant populations and delay local extinction. A considerable fraction of the species inhabiting semi-natural grasslands maintain what is most likely remnant populations after more than 60 years of spontaneous succession from managed semi-natural grasslands to forest.

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The world-wide intensification of agriculture has led to a decline in species richness due to land use change, isolation, and fragmentation of natural and semi-natural habitats in agricultural and forestry landscapes. As a consequence, there is a current landscape management focus on the importance of green infrastructure to mitigate biodiversity decline and preserve ecosystem functions e.g. pollination services and pest control. Even though intensification in agriculture has been ongoing for several hundreds of years, remnant habitats from earlier management practices may still be remaining with a surprisingly high plant richness. Preserving these habitats could help conserving plant species richness in agricultural landscapes, as well as other organisms that are dependent on plants for food and shelter. In this thesis I focus on two small remnant habitats; midfield islets and borders between managed forest and crop field in southeastern Sweden. In the past, both habitats were included in the grazing system and therefore often still have remnant population of grassland specialist species left today. I have used these two remnant habitats as model habitats to investigate the effect of landscape factors and local factors on species richness of plants, flower morphologies and plants with fleshy fruits. Additively, I analysed the effect of surrounding landscape and local openness on the functions; pollination success, biological pest control of aphids and seed predation on midfield islets. One of my studies showed that spatial distribution and size of the habitat affected plant species richness. Larger habitat size and higher connectivity between habitats increased species richness of plants in the habitats. Openness of the habitats was shown to be an important factor to increase species richness and richness of flower morphologies, both on midfield islets and in forest borders. Even though midfield islets had the highest species and morphology richness, both habitat types are needed for habitat complementary as forest borders have more plants with fleshy fruits and a higher richness of plant species that flowers in spring/early summer. It was also shown that a more complex forest border, not just with gaps in the canopy, but also with high variation in tree stem sizes increases plant species richness in the field layer. The conclusion is that by managing small remnant habitats to remain or become more semi-open and complex in their structure, would increase species richness of plants, grassland specialist species, and flower morphologies. It would also increase some ecosystem functions as seed predation and biologic pest control of aphids are more effective close to trees. If both midfield islets and forest borders would be managed to be semi-open, the area and connectivity of semi-open habitat would increase in the agricultural landscape, which may also improve pollination success as the connectivity between populations has a possibility to increase. Grassland specialist species are clearly abundant in the small remnant habitats. As the decline of semi-natural grasslands is causing a decline in grassland specialists’ species, not only plants, I recommend that small remnant habitats are included in conservation and management plans and strategies to improve habitat availability and connectivity for grassland species in agricultural landscapes.

Research funder Ekoklim. Project:4339602.

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.

Invasive phragmites (Phragmites australis) has encroached on the central Platte River in recent years potentially out-competing native stands of phragmites. Invasive stands are thought to have an overall negative impact on ecosystems, but do provide ecological benefits to some species as food or shelter. Little research has been conducted on its impacts on small mammals. The goals of this project were to identify potential native and invasive stands along the central Platte River and determine small mammals use of invasive phragmites. I examined 35 phragmites samples along the central Platte River using restriction fragment length polymorphism. I used molecular sequencing and morphological features to identify stands. All samples were determined to be invasive. Four study sites along the Platte River were selected to evaluate phragmites use and potential impacts on small mammals. Each study site was in a wooded grassland area and consisted of three patches of invasive phragmites and three patches of wooded grassland vegetation. Study sites were sampled using Sherman live traps from April to October 2014. I found no significant difference in overall small mammal use between vegetation types and no seasonal difference between use of phragmites and wooded grassland stands. I did, however, catch fewer individuals in both habitat types during August. Deer mice ( Peromyscus maniculatus) selected native vegetation whereas the white-footed mouse (Peromyscus leucopus), meadow vole (Microtus pennsylvanicus) hispid cotton rat (Sigmodon hispidus) and meadow jumping mouse (Zapus hudsonius) selected phragmites. Capture of hispid cotton rat was the first documentation of this species in Dawson County, Nebraska. Differences in selection by these species could be attributed to their different life histories or habitat preferences. The focus of management for invasive phragmites may not need to focus on total eradication. Additional sampling would be required to document the spatial extent of native phragmites stands along the central Platte River.

O município de São Luiz do Paraitinga, SP, originalmente coberto pela Floresta Atlântica estabelecida sobre os mares de morros do Planalto Atlântico, testemunhou o uso intensivo da terra que resultou em uma paisagem onde predominam pequenos fragmentos de floresta secundária. Considerando práticas agrícolas orientadas pela topografia nesta paisagem, avaliei o efeito da orientação e inclinação das vertentes na cobertura florestal e na estrutura da vegetação. Orientadas por aspectos produtivos, as preferências de utilização tiveram efeitos expressivos na configuração da paisagem. Enquanto as pastagens ocorreram preferencialmente nas vertentes mais produtivas (norte/leste), a cobertura florestal concentrou-se nas vertentes opostas e nas áreas mais declivosas, de mais difícil cultivo e acesso. A regeneração florestal ocorreu preferencialmente nas vertentes sul e nas maiores declividades, enquanto o desmatamento relativo foi maior nas vertentes norte/leste. Podemos apontar na configuração da paisagem uma origem híbrida, determinada pelas preferências (atributos culturais) e topografia (atributo natural), associados, que não poderia ser explicada por domínios separados de natureza e cultura. A estrutura da vegetação dos fragmentos desta paisagem está correlacionada apenas parcialmente com intervenções humanas que dependem da topografia, podendo sofrer influência, também, de intervenções associadas a outros elementos da paisagem, como a propriedade rural. As ações humanas, suas origens variadas e seus efeitos sobre a vegetação podem ser mais bem compreendidos de forma contextualizada, associados aos processos sociais em curso na paisagem. Ao incluirmos a ação humana nos modelos de paisagem, podemos compreender melhor os processos envolvidos na produção (e degradação) destas paisagens e ficar mais aptos a elaborar propostas de conservação adequadas às paisagens fragmentadas
This study was carried out in São Luiz do Paraitinga a county located in a hilly area in Southeastern Brazil that was originally covered by Atlantic Rainforest. The region has a history of intensive land use which resulted in a severely fragmented landscape. Under the hypothesis that agricultural practices and topography are closely linked in this landscape, I evaluated the effect of slopes orientation and inclination in forest cover and vegetation structure. Land use preferences had significant effects in shaping the landscape. While land use occurred mainly in most productive slopes (north/east), forest covered preferentially south and west facing slopes and steeper slopes. Forest regeneration occurred mainly on south facing slopes and steeper slopes, while deforestation was higher on north/east facing slopes. We propose that the landscape configuration has a hybrid origin, a product of the interplay between human choices (cultural attributes) and topography (a natural attribute), and which could not be explained by separate domains of nature and culture. Vegetation structure was only partly correlated with human interventions that are related to topography, and could also be influenced by actions related to other landscape elements, such as rural properties. Human actions, their varied origins and their effects on vegetation can be better understood if linked to social processes. Hence, if we want to improve our understanding on landscapes production and degradation, as well as propose conservation strategies appropriate to fragmented landscapes we need to explicitly include human activity in our landscape models.

O uso abusivo e indiscriminado de medicamentos tornou-se um dos grandes problemas mundiais de saúde pública, sobretudo para os velhos, por ser a população etária mais medicalizada. O objetivo deste trabalho foi identificar as dimensões que influenciam o uso racional de medicamentos em uma população de velhos Remanescentes Quilombolas por meio de uma abordagem educativa á luz Freiriana, da comunidade de Malhadinha situada na cidade de Brejinho de Nazaré – Tocantins. Um estudo descritivo, de natureza quali-quantitativa, essa verificação ocorreu por meio da realização de entrevistas semiestruturadas, e uma sensibilização conforme as necessidades, denominada por intervenção educativa. Participaram do estudo Remanescentes Quilombolas acima de 60 anos, acadêmicos da Universidade da Maturidade da Universidade Federal do Tocantins do polo de Malhadinha no município de Brejinho de Nazaré -TO. Os resultados identificaram alto indicie de velhos no grupo de analfabetos (46,2%) e 1-4 anos de escolaridade (34,6%). Evidencia-se que o exercício da automedicação é saliente entre os participantes, bem como o descuido com o tratamento, o uso de medicamentos sem prescrição médica e o descarte inadequado dos fármacos. Ocorre, ainda, casos de abandono de prescrição e o uso de medicamentos com indicação de familiares e amigos. Confirma que o armazenamento e descarte dos medicamentos ocorre de maneira inadequada. Destaca-se a busca de informações por meio da TV e dificuldade de acesso ao sistema de saúde. Quanto aos medicamentos relatados 34,61% dos participantes utilizam medicamento inapropriados conforme os Critérios de Beers-Fick, correspondendo a 21,21% de todos os medicamentos citados. Conclui-se que a cartilha proposta nesta pesquisa contribuirá para a construção de uma sociedade mais preparada para enfrentar criticamente as informações vinculadas sobre cuidados medicamentos e com a saúde. Estimulando quanto ao desenvolvimento de hábitos saudáveis e o uso racional de medicamentos, sem submergir a essência da cultura Quilombola, não apenas respeitando as diferenças, mas adotando os conceitos de Paulo Freire, compreendendo como riquezas culturais com as quais todos podem aprender e desenvolver.
The Indiscriminate use of drugs has become a world leading public health problems , especially for the old , for being the most medicalized age population. The goal of this study was to identify the dimensions that influence the rational use of drugs in an elder Quilombolas remnants population through an educative approach based on Freire’s thoughts, in the community of Malhadinha located in the city of Brejinho de Nazaré – Tocantins. A Descriptive Study, of quantitative and qualitative nature, this verification occured through semi-structured interviews and a sensibilization as required, nominated by educative intervention. Participated in the study Quilombolas remnants over 60 years, academics from the Malhadinha pole of Universidade da Maturidade of the Universidade Federal do Tocantins in the city of Brejinho de Nazaré – TO. The results showed high elderly rate in the illiterate group (46.2%) and 1-4 years of education (34.6%). It is evident that the act of self-medication is relevant among the participants as well as the careless treatment, the use of non-prescription drugs and the improper drug disposal. It may also happen prescription leavers and the drug use indicated by family and friends. Supports that the storage and drugs disposal occurs inappropriately. Noteworthy is the search of information through the TV and difficult acces to health care. As for the drugs reported by the participants, 21.21% are included in the Beers-Fick Criteria. We conclude that the booklet proposed in this research will contribute to build a more prepared society to critically face the linked information on health care and medicines. Corroborating to the development of healthy habits, encouraging the rational drug use, without submerging the essence of Quilombola culture, not only respecting differences, but adopting the Paulo Freire’s concepts, comprising as a cultural enrichment in which everyone can learn and develop.

Land has been extensively modified in response to human needs for thousands of years. In recent times, the change in land use from agricultural areas to tree plantations has been expanding worldwide to satisfy the increasing demands for wood/paper products. In Australia, some areas of cleared agricultural land have been transformed into exotic pine plantations, particularly in New South Wales (NSW). Species occurring in fragments of remnant native vegetation, including birds, may be influenced by the effects of new forms of surrounding land use dominated by exotic Radiata Pine (Pinus radiata) plantations. In this thesis, I sought to quantify how the transformation of landscapes from grazing land to exotic pine plantations influenced the breeding success of small-bodied birds in woodland remnants. I also sought to determine if the results from artificial nests were broadly consistent with those obtained from natural nests. To achieve these aims, I conducted a series of studies of natural and artificial nests in the Nanangroe State Forest and in the surrounding private farmlands in south-eastern NSW, Australia. My study sites were Eucalyptus woodland remnants surrounded by one of two types of matrix; grazing land or maturing stands of Radiata pine plantation. In the natural nest study (Chapter 2), I found significantly fewer nests in woodland remnants surrounded by the plantation than in woodland remnants located in farmland. The proportion of nests of generalist avian nest predators was significantly higher in woodland remnants surrounded by the plantation, compared to woodland remnants surrounded by farmland. In general, I found that breeding success of birds with a larger mean body mass was higher than small-bodied birds, and small-bodied birds reproduced more successfully at a lower nest height. Notably, nesting activity of some forest taxa, including species of conservation concern, was observed both in woodland remnants surrounded by the plantation and in the plantation matrix. In experiments using two types of artificial nests (Chapter 3), I found the following patterns. (1) The majority of nest predators were birds. (2) There were higher levels of nest predation in woodland remnants surrounded by the plantation than in woodland remnants located within farmland, with cup nests being inferior to domed nests against nest predation in the both landscape contexts, and (3) Both natural and artificial nests were more susceptible to nest predation in woodland remnants surrounded by the plantation than in woodland remnants located within grazing paddocks. Overall, my research has shown that land use change from grazing areas to exotic pine plantations may provide more habitats for small-bodied forest species including the Flame Robin (Petroica phoenicea), a vulnerable species in NSW. Conversely, landscape transformation may reduce the amount of habitat for ground-foraging small-bodied woodland birds, such as the Brown Treecreeper (Climacteris picumnus victoriae) and Dusky Woodswallow (Artamus cyanopterus), which are also vulnerable in NSW. Conservation of small-bodied forest versus woodland taxa may require different kinds of management within plantations. However, retaining woodland remnants within the boundaries of plantations benefits a range of kinds of native birds, including forest and woodland taxa.

University of Technology, Sydney. Faculty of Environmental Sciences.
This thesis presents the results of work undertaken to examine daily, seasonal and annual patterns of water use by a native remnant woodland in temperate Australia. The focus of the study was on the two dominant tree species of the woodland, but limited assessments of understorey and soil evapotranspiration were also undertaken. One of dominant species was Eucalyptus crebra, a broad-leaved tree and the other was Callitris glaucophylla a needle-leaved tree. At the start of the study, much of the eastern seaboard of Australia experienced a severe and prolonged drought but towards the end of the field work, rainfall at the site was significantly larger than the long-term average. This provided a fortuitous opportunity to compare the responses of vegetation water use to drought and nondrought periods. The study was conducted on the Liverpool Plains, of western New South Wales, Australia. Principle methods applied were (a) use of heat-pulse technology to measure rates of sap flow through trees; (b) open-top chambers to measure understorey and soil evapotranspiration; (c) application of the Penman-Monteith equation to estimate canopy conductance and transpiration rates; (d) two methods to scale spatially from measurements of individual trees to estimates of stand water use; (e) three methods to scale temporally from measurements conducted over a few weeks each year to provide annual estimates of stand water use; (f) a simple water balance was constructed to approximate the rate of deep drainage of water (rate of recharge). An annual water budget for the site was estimated for the drought and post-drought periods. The relationship between tree water use and diameter at breast height (DBH) was similar for the two species in each season, but the relationship for both species differed between seasons and years. In contrast, the relationships amongst DBH, sapwood area and leaf area differed between species at all times. This suggests that the same rate of water use by the eucalypt and Callitris (at a common size) was achieved through different mechanisms. Daily rates of stand water use showed significant intra- and inter-seasonal variation, with the lowest rates observed in winter and largest rates in summer. A simple model based upon solar radiation and vapour-pressure deficit was able to account for approximately 80 % of variation of stand water use under summer conditions with wet soil. Estimates of stand water use derived from the Penman-Monteith equation generally agreed well with those based upon measurements of sap velocity, with a slope of the regression of the two estimates being 1.03. In the drought-year, stand water use was approximately 59 % of rainfall and recharge was approximately 2% but in the post-drought year, when rainfall doubled compared to the drought year, stand water use was also 59 % whereas recharge was 4 %. This showed that despite the impact of an extensive and pronounced drought, the trees were able to rapidly adjust to more favourable conditions and maintain a low rate of recharge. These results are discussed in relation to the management of water resources for human consumptive use and in relation to the development of dryland salinity across Australian landscapes that have been cleared of trees.

Feral goat (Capra hircus) populations adversely impact native insular biota and physical habitats worldwide. The effectiveness of the Judas goat technique for eradicating remnant feral goats was studied on San Clemente Island (SCI), California from June 1989 through April 1991. By April 1991, 263 feral goats were killed on SCI; only 2 adult females and their offspring were believed to remain. The length of time required by radio-collared (Judas) goats to establish initial contact with remnant goats was 1 to 5 days, and time to subsequent encounters with new goats averaged 3.5 days. Duration of association between Judas goats and remnant herds ranged from 1-60 days. Judas goat home ranges averaged 4.4 km² and maximum distances Judas goats traveled to find conspecifics averaged 4.8 km. Observations of Judas goats that were associated with remnant feral goats allowed individual identification of most goats and prediction of their temporal and spatial activity patterns. This knowledge greatly expedited the eradication process and likely contributed to the preservation of threatened and endangered endemic species on SCI. Natality, survivorship, and condition of SCI goats were inversely related to decreases in population density when compared to goat populations from other islands. higher and mortality lower than in other feral goat populations, presumably because of the unusually low density of goats on SCI. The Judas goat technique allows removal of low density feral goat herds in a timely manner and should be used by resource managers wherever feral goats threaten native flora and fauna.
Graduation date: 1992

Physical volcanological features are presented for a 710-m-thick section, of the Naude’s Nek Pass, within the lower part of the Lesotho remnant of the Karoo Large Igneous Province. The section consists of inflated pāhoehoe lava with thin, impersistent sedimentary interbeds towards the base. There are seven discreet packages of compound and hummocky pāhoehoe lobes containing flow-lobe tumuli, making up approximately 50% of the section. Approximately 45% of the sequence consists of 14 sheet lobes, between 10 and 52-m-thick. The majority of the sheet lobes are in two packages indicating prolonged periods of lava supply capable of producing thick sheet lobes. The other sheet lobes are as individual lobes or pairs, within compound flows, suggesting brief increases in lava supply rate. We suggest, contrary to current belief, that there is no evidence that compound flows are proximal to source and sheet lobes (simple flows) are distal to source and we propose that the presence of flow-lobe tumuli in compound flows could be an indicator that a flow is distal to source. We use detailed, previously published, studies of the Thakurvadi Formation (Deccan Traps) as an example. We show that the length of a lobe and therefore the sections that are ‘medial or distal to source’ are specific to each individual lobe and are dependent on the lava supply of each eruptive event, and as such flow lobe tumuli can be used as an indicator of relative distance from source.

New radio telescopes under development, will significantly enhance the capabilities of radio astronomy in the Southern Hemisphere. South Africa, in particular, is actively involved in the development of a new array (MeerKAT) as well as in the expansion of existing very long baseline interferometer arrays in the south. Participation in these new developments demands a thorough understanding of radio astronomy techniques, and data analysis, and this thesis focusses on two projects with the aim of gaining such experience. The Southern Hemisphere very long baselines array is not well served with calibrator sources and there are significant gaps in the present calibrator distribution on the sky. An adequately dense, well distributed, set of strong, compact calibrator or reference sources is needed. With this in mind, observations using the Southern Hemisphere long baseline array were conducted to investigate a sample of candidate calibrator sources. The compactness of the sources was investigated and new potential calibrators have been identified. Single antenna radio spectroscopy of OH masers has identified sources of 1720 MHz emission associated with supernova remnants at the shock interface between the expanding supernova remnant and a molecular cloud. Models indicate that these masers are shock excited and can only be produced under tight physical constraints. Out ows from newly-formed stars create nebulous regions known as Herbig-Haro objects when they interact with the surrounding medium, and these regions are potentially similar to those seen in supernova remnants. If conditions behind the shock fronts of Herbig-Haro objects are able to support 1720-MHz OH masers they could be a useful diagnostic tool for star formation. A survey toward Herbig-Haro objects using a single-dish radio telescope did detect 1720-MHz OH lines in emission, but neither their spectral signature nor follow-up observations with the Very Large Array showed evidence of maser emission.
Mathematical Sciences
Ph.D. (Astronomy)