Shallow lakes in Muskoka-Haliburton have been largely ignored in previous limnological and paleolimnological studies, as many are considered to be less desirable for cottage development and other cultural activities. Nonetheless, shallow lakes offer important habitat for many animals. 30 oligo- and mesotrophic, shallow lakes were chosen for a paleolimnological study to assess the impacts of multiple stressors on cladoceran invertebrates. Fossil cladoceran remains preserved in the sediment samples of the study lakes were used to evaluate the nature and magnitude of any changes in assemblages from both modern and pre-industrial times. Relationships between present-day assemblages and key environmental variables were investigated using redundancy analysis, which identified that lake area (p<0.01) and Secchi depth (p<0.05) were significant predictors of assemblage composition in the shallow lakes. Secchi depth was not correlated to water clarity measures, as it usually is, but rather to macrophyte abundance. The modern-day assemblages were compared to the pre-industrial assemblages using the snapshot “top-bottom” paleolimnological approach. The top and bottom assemblages were compared using an ANOSIM which was not significant (p=0.2), confirming that modern assemblages were similar to pre-industrial assemblages in shallow lakes. Full core analysis from three shallow lakes also showed only subtle changes in littoral assemblage composition through time, further supporting results from the top/bottom study. The changes recorded were mainly in the pelagic taxa, with the littoral taxa relatively very stable through time. These small, shallow lakes were then compared and combined with a deep lake set from the same region. The results show some striking differences between shallow and deep lakes. For example, pelagic taxa appear to be driving changes within assemblages across a depth gradient, with most of the changes in the deeper lakes. Water chemistry has an increasingly important role in structuring cladoceran assemblage as lakes become deeper, although lake morphometry does play an important role in defining cladoceran assemblages in all the study lakes. Cladoceran assemblages in shallow lakes appear to be more stable than deeper lakes, despite being exposed to the same regional stressors, such as acidification, calcium decline, and climate change. / Thesis (Master, Biology) -- Queen's University, 2012-12-31 13:41:52.662

Made available in DSpace on 2014-06-11T19:24:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2002-02-19Bitstream added on 2014-06-13T20:12:03Z : No. of bitstreams: 1 alencarjunior_ea_me_arafo_prot.pdf: 747787 bytes, checksum: fd32e276778e87934566a313af1035b5 (MD5) / O objetivo desta pesquisa foi avaliar a influência da distância de uma fonte de luz halógena na microdureza superficial da resina composta, considerando as superfícies de topo e base dos corpos-de-prova. Foram utilizadas duas marcas comerciais de resina composta, Z250 de partículas pequenas e uma resina de micropartícula, A110, ambas da 3M do Brasil Ltda. O aparelho de ativação da resina composta foi K&M 220- R, cuja intensidade de luz possui um pulso que variava após os 5 primeiros segundos assim alcançando sua intensidade máxima que foi medida em 720 mW/cm2. Para a determinação da intensidade de luz emitida pelo aparelho fotoativador, utilizou-se um radiômetro (Medidor de irradiância 150- CMC , São Carlos - SP). Corpos-de-prova foram confeccionados utilizado-se matrizes metálicas que possuíam um orifício central de 4mm de diâmetro por 2mm de espessura. As resinas foram inseridas no orifício da matriz metálica, em um único incremento, por meio de uma espátula metálica e sobre elas foi sobreposta uma tira matriz transparente de poliéster e, após isto, um peso de 1 Kg foi posto em cima da tira para que houvesse uma melhor condensação da resina composta evitando a presença de bolhas de ar, no interior do corpo-de-prova. A fonte de luz halógena foi fixada em uma mesa de maneira que a saída da ponta de luz ficasse paralela à superfície do corpo-de-prova. Para provocar o distanciamento da fonte de luz, anéis metálicos confeccionados em latão, com espessuras que variavam de 2mm, 4mm e 8mm foram utilizados, os quais, após posicionados, eram removidos para não interferiem no dispersamento da luz. As distâncias imprimidas a fonte de luz na superfície da resina foram de 0mm(tocando a superfície), 2mm, 4mm e 8mm. Para cada uma destas distâncias, a intensidade de luz foi medida. Esta variou de intensidade de... . / The aim of this research was to evaluate the influence of the light tip distance in the superficial microhardness of the composite resin, considering the surfaces of top and base of the samples. Two commercial composite resin marks had been used, Z250 of small particles e a microparticle resin, A110, both of 3m of Brazil Ltda. The device of activation of the composite resin was K&M 220- R, whose intensity of light possess a pulse that varied the 5 first seconds after thus reaching its maximum intensity that was measured in 720 mW/cm2. For the determination of the intensity of light emitted for the fotoativador device, a radiometer (Measuring of irradiance 150- CMC was used, Is Carlos. SP). The samples had been confectioned used first metallic that had a central orifice of 4mm of diameter for 2mm of thickness. The resins had been inserted in the orifice of the metallic array, in an only increment, by means of a metallic spatula and on them a transparent first polyester strap was overlapped and, after this, one weight of 1 kg was rank in top of the strap so that it had one better condensation of the composite resin preventing the presence of air bubbles, in the inward of the body-of-test. The source of light was fixed in a table thus the output of the light tip was parallel to the surface of the body-of-test. To provoke distance from the light source, confectioned metallic rings in brass, with thickness that varied of 2mm, 4mm and 8mm had been used, which, after located, was removed to avoid concentration of light. The printed pitches the source of light in the surface of the resin had been of 0mm(on the surface), 2mm, 4mm and 8mm. For each one of these pitches, the light intensity was measured. This varied of intensity of 720 mW/cm2 for the tip touching the surface of the body-of-test, 650 mW/cm2 for in the distance of 2mm, 600 mW/cm2... (Complete abstract, click electronic address below).

Orientador: Marcelo Ferrarezi de Andrade / Banca: José Roberto Cury Saad / Banca: Mânio de Carvalho Tibúrcio / Resumo: O objetivo desta pesquisa foi avaliar a influência da distância de uma fonte de luz halógena na microdureza superficial da resina composta, considerando as superfícies de topo e base dos corpos-de-prova. Foram utilizadas duas marcas comerciais de resina composta, Z250 de partículas pequenas e uma resina de micropartícula, A110, ambas da 3M do Brasil Ltda. O aparelho de ativação da resina composta foi K&M 220- R, cuja intensidade de luz possui um pulso que variava após os 5 primeiros segundos assim alcançando sua intensidade máxima que foi medida em 720 mW/cm2. Para a determinação da intensidade de luz emitida pelo aparelho fotoativador, utilizou-se um radiômetro (Medidor de irradiância 150- CMC , São Carlos - SP). Corpos-de-prova foram confeccionados utilizado-se matrizes metálicas que possuíam um orifício central de 4mm de diâmetro por 2mm de espessura. As resinas foram inseridas no orifício da matriz metálica, em um único incremento, por meio de uma espátula metálica e sobre elas foi sobreposta uma tira matriz transparente de poliéster e, após isto, um peso de 1 Kg foi posto em cima da tira para que houvesse uma melhor condensação da resina composta evitando a presença de bolhas de ar, no interior do corpo-de-prova. A fonte de luz halógena foi fixada em uma mesa de maneira que a saída da ponta de luz ficasse paralela à superfície do corpo-de-prova. Para provocar o distanciamento da fonte de luz, anéis metálicos confeccionados em latão, com espessuras que variavam de 2mm, 4mm e 8mm foram utilizados, os quais, após posicionados, eram removidos para não interferiem no dispersamento da luz. As distâncias imprimidas a fonte de luz na superfície da resina foram de 0mm(tocando a superfície), 2mm, 4mm e 8mm. Para cada uma destas distâncias, a intensidade de luz foi medida. Esta variou de intensidade de... (Resumo completo, clicar acesso eletrônico abaixo). / Abstract: The aim of this research was to evaluate the influence of the light tip distance in the superficial microhardness of the composite resin, considering the surfaces of top and base of the samples. Two commercial composite resin marks had been used, Z250 of small particles e a microparticle resin, A110, both of 3m of Brazil Ltda. The device of activation of the composite resin was K&M 220- R, whose intensity of light possess a pulse that varied the 5 first seconds after thus reaching its maximum intensity that was measured in 720 mW/cm2. For the determination of the intensity of light emitted for the fotoativador device, a radiometer (Measuring of irradiance 150- CMC was used, Is Carlos. SP). The samples had been confectioned used first metallic that had a central orifice of 4mm of diameter for 2mm of thickness. The resins had been inserted in the orifice of the metallic array, in an only increment, by means of a metallic spatula and on them a transparent first polyester strap was overlapped and, after this, one weight of 1 kg was rank in top of the strap so that it had one better condensation of the composite resin preventing the presence of air bubbles, in the inward of the body-of-test. The source of light was fixed in a table thus the output of the light tip was parallel to the surface of the body-of-test. To provoke distance from the light source, confectioned metallic rings in brass, with thickness that varied of 2mm, 4mm and 8mm had been used, which, after located, was removed to avoid concentration of light. The printed pitches the source of light in the surface of the resin had been of 0mm(on the surface), 2mm, 4mm and 8mm. For each one of these pitches, the light intensity was measured. This varied of intensity of 720 mW/cm2 for the tip touching the surface of the body-of-test, 650 mW/cm2 for in the distance of 2mm, 600 mW/cm2... (Complete abstract, click electronic address below). / Mestre