Thesis (Ph. D.)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2002. / "Joint Program in Oceanography/Applied Ocean Science and Engineering."--Cover. "June 2002." Funding was provided by NASA through grants NAG5-3264, NAG5-4806, NAG5-11113 and NAG5-9143 and by a National Defense Science and Engineering Graduate Fellowship. Includes bibliographical references (p. 221-243).

Thesis (M.Eng.)--Memorial University of Newfoundland, 2003. / Bibliography: leaves 204-212.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1980. / Supervised by Tanya Atwater. Vita. Includes bibliographical references (leaves 206-213).

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Corn (Zea mays L.) and soybean (Glycine max L.) production in the Midwest US can result in significant nutrient leaching to groundwater and surface waters, which contributes to eutrophication and hypoxia in the Gulf of Mexico. A promising strategy to control nutrient leaching and sediment runoff loss during winter fallow period is the use of cover crops (CCs). In southern Illinois, CCs are not widely adopted by farmers due to economic constraints and the lack of scientific data that supports benefits of incorporating CCs into the corn-soybean rotation. Therefore, this doctoral dissertation addresses the critical question of the feasibility of the use of CCs in southern Illinois and is divided into three overarching research studies with different objectives divided into six research chapters. Research study 1 was a field experiment conducted from 2013 to 2017 to examine the effect of CCs (CC vs noCC) under two tillage systems [(no-tillage (NT) and conventional tillage (CT)] on aboveground plant attributes [dry matter yield, C:N ratio and nitrogen uptake (N uptake)], crop yields, available soil N content and N leaching in the vadose zone. The experimental layout was a randomized design with three rotations including corn-noCC-soybean-noCC [CncSnc], corn-cereal rye (Secale cereale L.) –soybean-hairy vetch (Vicia villosa R.) [CcrShv], and corn-cereal rye-soybean-oats+radish (Avena sativa L. + Raphanus sativus L.) [CcrSor] and two tillage systems. Soil samples collected after corn or soybean harvest and CC termination were analyzed for standard soil fertility parameters. Pan lysimeters installed below the ‘A’ horizon with depth varying from 22 to 30 cm were used for measuring soil solution nutrient concentration on weekly or biweekly basis depending on the precipitation. In NT system, the corn yield was 14% greater with CcrShv compared to CncSnc, whereas no significant difference existed in corn yield due to CC treatments within CT. Both CC treatments under NT reduced soybean yield by 24 to 27% compared to noCC. The rotations CcrShv and CcrSor with hairy vetch and oats+radish as preceding CCs resulted in 89% (37.73 vs 19.96 kg ha-1) and 68% (33.46 vs 19.96 kg ha-1) more nitrate-N (NO3-N) leaching than the CncSnc during cash crop season 2015. During the CC season in spring 2016, cereal rye CC in CcrShv and CcrSor reduced the NO3-N leaching by 84% (0.68 kg ha-1) and 78% (0.63 kg ha-1) compared to the CncSnc, respectively, under the CT system. Overall, our results indicated that the CT system had greater N leaching losses compared to NT system due to higher N availability in the tilled soil profile. The goal of the second research study was to understand the mechanisms of N cycling by CCs. Therefore, we applied 15N labeled urea fertilizer (9.2% atom) to corn that followed hairy vetch and noCC in May 2017 to evaluate the contribution of fertilizer and soil organic matter to N leaching and quantify the 15N content of surface runoff after storm events. During the 2017 corn season, repeated soil samples were collected and analyzed for 15N fertilizer recovery in soil at three depths. 15N recovery was higher in the corn that had hairy vetch as the preceding CC than the corn that had noCC by 13.13 and 3.68 kg ha-1 on soil sampling events of 7 and 21 days after planting of corn, respectively, at the depth 15-30 cm. Overall, the cumulative loss of 15NO3-N during corn season 2017 was <2% of the applied fertilizer. The contribution of NO3-N from soil organic matter to leaching was 61% higher for the corn rotation with hairy vetch CC compared to corn rotation with noCC (1.12 vs 0.69 kg ha-1). Research study 3 evaluated the effects of CCs (cereal rye and hairy vetch) and topography (shoulder, backslope, footslope) on corn-soybean production, soil and water quality, nutrient and sediment export in agricultural headwater streams in a paired-watershed experimental design. The crop rotation followed in the CC-watershed was corn-cereal rye-soybean-hairy vetch whereas the rotation in the noCC watershed was corn-noCC-soybean-noCC. Use of hairy vetch CC increased N uptake at shoulder, backslope and footslope positions by 110.90, 85.02, and 44.89 kg ha-1, respectively, when compared to noCC treatment. The corn yield at the shoulder position was increased by 69% in CC-watershed compared to noCC watershed in 2017 likely by providing large N additions following decomposition. Cereal rye increased soybean yield by 17% and 8% at the shoulder and backslope position, respectively in 2016. Additionally, the effects of topography and CCs on soil N levels and N leaching in the watersheds were also evaluated. The NO3-N concentrations measured using suction cup lysimeters in CC-watershed were reduced by 2.54 mg L-1 (67%) when compared to noCC watershed. During the hairy vetch CC season, the reduction in NO3-N concentrations in soil solution was only seen at the footslope position. The excessive N at footslope positions may have been immobilized or denitrified due to soil waterlogging from higher water availability at the footslope. Forty-two and 18 storm events were collected during a 4-yr calibration period and CC-treatment period, respectively. Predictive regression equations developed from the calibration period were used for calculating TSS, NO3-N, NH4-N, and DRP losses of surface runoff for the CC-treatment watershed. The CCs reduced TSS and discharge by 33% and 34%, respectively in the CC-watershed during the treatment period. However, EMCs for NO3-N, NH4-N, and DRP did not decrease. Overall, CCs are a recommended conservation practice for farmers who want to enhance the long term profitability of their production systems, while building soil health and protecting downstream water quality. The CCs have the potential to reduce nutrient leaching, peak/total discharge, improve soil quality and crop yields. However, reduction in leaching will depend on the type of CC (legume vs non-legume crops) used in rotation, the time of termination of CCs, cover crop establishment and number of years under CCs. Synchronizing N availability from CCs to N uptake by cash crop is important for reducing nitrate leaching and increasing crop yields.

Made available in DSpace on 2014-06-11T19:31:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-09-28Bitstream added on 2014-06-13T19:41:59Z : No. of bitstreams: 1 rodrigues_rj_dr_botfca.pdf: 3227583 bytes, checksum: 14b236f9426135b6b2ad6a3d22097d4f (MD5) / Com a adoção da lei 10.267 para o uso do georreferenciamento em aplicações topográficas que visa estabelecer os preceitos técnicos aplicáveis aos serviços de agrimensura objetivando a caracterização e o georreferenciamento de imóveis rurais por meio de levantamento topográfico e posterior certificação junto ao INCRA, a nova lei do georreferenciamento tem como seu objetivo principal padronizar os trabalhos de agrimensura. Segundo a nova lei, as coordenadas a serem utilizadas para essa finalidade estão expressas apenas na forma planimétrica considerando como objeto de valor apenas as coordenadas plano-retangulares X e Y, ou seja, sua longitude e latitude descartando a coordenada Z, altitude. O presente trabalho constatou a possibilidade de utilização dessa coordenada Z, a altitiude adquirida sem esforços extras em levantamentos georreferenciados para utilização em um possível novo modelo digital e conseqüente edição de novas cartas planialtimétricas, em especial para regiões em que tais cartas somente são disponíveis em pequenas escalas... / With the adoption of the law 10 267 for the use of Georreferencing in topographical applications that aims to establish the technical applicable precepts to the services of surveying aiming to characterization and the Georreferencing of rural property by survey and subsequent certification with INCRA, the new law of georreferenced has as its main objective to standardize the work of surveying. According to new law, the coordinates to be used for this purpose are expressed only in the boundary form considering like valuable only the plane-rectangular coordinates X and Y, its longitude and latitude, discarding the Z coordinate altitude. This study verified the feasibility of this Z coordinate, i.e, the altitiude gained without extra efforts in georreferenced surveys for use in a possible new digital model and the consequent edition of new topographic maps, especially for regions where such maps are only available in small scales

O objetivo desse trabalho de tese foi a coleta de novas informações e a avaliação de dados disponíveis, visando a análise das melhores alternativas para a obtenção de um modelo digital de terreno (MDT) para a América do Sul. O modelo compreendeu a parte continental e oceânica, limitada pelas latitudes de 60º S a 25º N e longitudes de 100º W a 25º W. Na área continental foram usadas informações provenientes de cartas topográficas digitalizadas, do recente modelo Shuttle Radar Topography Mission (SRTM) e do modelo disponível DTM2002. Na área oceânica foram utilizadas informações de profundidade do DTM2002, de cartas náuticas em diferentes escalas, folhas de bordo e o projeto LEPLAC, para o Brasil, e de cartas náuticas na Argentina. O trabalho ensejou um processo intensivo e exaustivo de comparação dos modelos existentes (SRTM, DTM2002, GLOBE, GTOPO30, ETOPO2, JGP95E, TERRAINBASE e ETOPO5) e das novas informações disponíveis. No estudo do SRTM analisou-se 2.013 quadrículas de 1ºX1º da região continental, obtendo-se para cada quadrícula os valores máximo e mínimo da altitude com suas respectivas posições, o valor médio e o número de pontos sem informação, além da representação 3D e do histograma das altitudes. Foi também realizada a comparação das altitudes interpoladas do modelo SRTM com os pontos GPS implantados ao longo dos rios Madeira, Solimões e Amazonas e com RNs na grande São Paulo. Com os oito MDTs citados foram construídos perfis longitudinais e latitudinais de toda a área continental passando sobre a altitude máxima de cada quadrícula do SRTM. Os modelos SRTM, DTM2002, GLOBE, GTOPO30, ETOPO2 e ETOPO5 foram comparados entre si nos pontos da grade em comum. Além disso, foram realizadas comparações utilizando uma importante fonte de informação altimétrica representada pela rede de nivelamento geométrico. As análises realizadas resultaram na geração de três modelos alternativos de MDT para a América do Sul. A opção do espaçamento da malha para a construção do modelo foi proveniente da compatibilização entre a capacidade computacional e o resultado esperado nas diferentes aplicações de um MDT. Além disso, foram implementadas duas aplicações específicas importantes na área de exploração mineral e no cálculo das alturas geoidais: a correção de terreno e o efeito indireto. / The objective of this thesis has been to collect new information and to evaluate available data in order to provide arguments in the analysis for the derivation of the best DTM for South America. The continental and oceanic part of a block limited by latitudes 60º S and 25º N and longitudes 100º W and 25º W is the object of the model. In the continental area data derived from topographic maps, the recent Shuttle Radar Topography Mission (SRTM) and the available DTM2002 model were used. In the oceanic area the depth data from DTM2002, nautical maps of different scales, boarding maps and LEPLAC project were used in Brazil and nautical maps in Argentina. The activities involved an intensive process of comparison between the existing models (SRTM, DTM2002, GLOBE, GTOPO30, ETOPO2, JGP95E, TERRAINBASE e ETOPO5) and the new information. With respect to SRTM 2,013 blocks of 1º X 1º in the continental area were analysed, deriving for each block the maximum and minimum values for the height with the respective position, the mean value and the number of points without information. The 3D representation as well as the histogram of the heights for each block is also presented. The GPS points established along the Amazonas, Solimões and Madeira rivers in Amazonas on the BMs in São Paulo area were also compared with SRTM interpolated values. SRTM, DTM2002, GLOBE, GTOPO30, ETOPO2 and ETOPO5 were also compared between themselves in the common points of the grid. Besides, an important comparison were carried out with the first order levelling network. After the analysis were finished three different DTM were generated for South America. The grid spacing were select envisaged a compatibilization between computer capacity and the applications requirements. Finally, two specific applications for mineral exploration and geoid computation were implemented: the terrain correction and the indirect effect.

O objetivo deste trabalho e desenvolver um instrumento computadorizado para análise da superfície anterior da córnea humana, gerando para isto, um mapa topográfico bidimensional em código de cores. Utilizando a córnea como um espelho esférico convexo, projeta-se anéis luminosos sobre sua superfície e aquisiciona-se com uma câmera a imagem por ela refletida. Esta imagem e digitalizada e armazenada em um microcomputador para posterior processamento. Através de técnicas de computação gráfica e processamento de imagens digitais, extrai-se da imagem as informações necessárias para construção da topografia desejada. Por fim, a topografia e apresentada em forma de mapas coloridos, sendo cada cor associada a uma determinada dioptria, transmitindo ao médico oftalmologista uma noção exata da superfície da córnea do paciente em análise. / The main goal of this work is to develop a computerized instrument for the analysis of the anterior portion of the human cornea, which displays its result in topographic color maps. Approximating the cornea to a spherical convex mirror, and by projecting a known pattern over it, the reflected image is captured and stored. By means of computer graphics technology and image processing, the necessary information for mathematical calculations is extracted. The resulting maps are color-coded in accordance to the degree of power of each corneal region, that is, to the diopter value. The ophthalmologist can then make important diagnostics and surgery tactics from the analysis of these topographic maps.

This qualitative research study focuses explicitly on understanding the experiences and perceptions of urban Aboriginal women living with HIV/AIDS. Stigmatizing attitudes and language have serious impacts upon the lives of HIV-positive Aboriginal women. The ways our society presently addresses the women needs to change. With the insights and assistance of four Aboriginal women living with HIV, this project adds to the presently sparse qualitative literature in this research area. Current research indicates that there are many factors associated with urban Aboriginal women being at higher risk for infection and lower physical and mental health, such as race, socio-economic conditions, isolation, oppression and violence, family history, substance abuse, discrimination, and often the responsibilities of childrearing. However, current research analysis and presentation is insufficient, and more in-depth questions arise. Material was collected using semi-structured, open-ended questioning conversations with the participants. Two guiding research questions were asked: 1) What is it like for you, living with HIV right now? and 2) What would you want other people to learn from your experiences? The women’s stories provide an avenue for participants to voice some of their triumphs and challenges about being an Aboriginal woman living with HIV/AIDS. For the community at large, this is also an opportunity to hear first hand, important information such as this. In this work, I have tried to adhere to the tenets of Indigenous methodologies by allowing the life-stories to resonate as holistic representations. Rather than deconstructing the women’s stories through naturalistic analysis (which continues to categorize and to objectify participants), the stories are viewed through a Health Narrative Topography whereby thematic genres such as Restitution, Chaos, and Quest are illuminated, while also being critically aware of some of the limitations to this framework. Three overarching themes are revealed through the women’s stories: 1) the empowerment and resiliency demonstrated by the participants; 2) the need for cultural competency in a society that continues to stigmatize Aboriginal and HIV-positive women; and, 3) the need for a more holistic approach within society when it comes to education, learning, and healing. / Graduate Studies, College of (Okanagan) / Graduate