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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.
1

The biology and dynamics of the oystershell scale, Lepidosaphes Ulmi (L.) (Homoptera: Coccidae), on apple in Quebec.

Samarasinghe, Srimathie. January 1965 (has links)
The quantification of population and mortality data for insect pests of apple is necessary if we are to gain fundamental insight in the dynamics of insect populations of the orchard ecosystem. The need to quantify has recently been emphasized (LeRoux, 1964a; 1964b) and the greater application, practical and scientific, or the quantitative results obtained for agricultural and forest insect pests has been demonstrated (LeRoux et al., 1963). [...]
2

The biology and dynamics of the oystershell scale, Lepidosaphes Ulmi (L.) (Homoptera: Coccidae), on apple in Quebec.

Samarasinghe, Srimathie. January 1965 (has links)
No description available.
3

Investigation of molecular mechanisms regulating biomineralization of pearl oyster Pinctada maxima

Gardner, Luke David January 2008 (has links)
Biomineralization is a process encompassing all mineral containing tissues produced within an organism. The most dynamic example of this process is the formation of the mollusk shell, comprising a variety of crystal phases and microstructures. The organic component incorporated within the shell is said to dictate this remarkable architecture. Subsequently, for the past decade considerable research have been undertaken to identify and characterize the protein components involved in biomineralization. Despite these efforts the general understanding of the process remains ambiguous. This study employs a novel molecular approach to further the elucidation of the shell biomineralization. A microarray platform has been custom generated (PmaxArray 1.0) from the pearl oyster Pinctada maxima. PmaxArray 1.0 consists of 4992 expressed sequence tags (ESTs) originating from the mantle, an organ involved in shell formation. This microarray has been used as the primary tool for three separate investigations in an effort to associate transcriptional gene expression from P. maxima to the process of shell biomineralization. The first investigation analyzes the spatial expression of ESTs throughout the mantle organ. The mantle was dissected into five discrete regions and each analyzed for gene expression with PmaxArray 1.0. Over 2000 ESTs were differentially expressed among the tissue sections, identifying five major expression regions. Three of these regions have been proposed to have shell formation functions belonging to nacre, prismatic calcite and periostracum. The spatial gene expression map was confirmed by in situ hybridization, localizing a subset of ESTs from each expression region to the same mantle area. Comparative sequence analysis of ESTs expressed in the proposed shell formation regions with the BLAST tool, revealed a number of the transcripts were novel while others showed significant sequence similarities to previously characterized shell formation genes. The second investigation correlates temporal EST expression during P. maxima larval ontogeny with transitions in shell mineralization during the same period. A timeline documenting the morphologicat microstructural and mineralogical shell characteristics of P. maxima throughout larval ontogeny has been established. Three different shell types were noted based on the physical characters and termed, prodissoconch I, prodissoconch 11 and dissoconch. PmaxArray 1.0 analyzed ESTs expression of animals throughout the larval development of P. maxima, noting up-regulation of 359 ESTs in association with the shell transitions from prodissoconch 1 to prodissoconch 11 to dissoconch. Comparative sequence analysis of these ESTs indicates a number of the transcripts are novel as well as showing significant sequence similarities between ESTs and known shell matrix associated genes and proteins. These ESTs are discussed in relation to the shell characters associated with their temporal expression. The third investigation uses PmaxArray 1.0 to analyze gene expression in the mantle tissue of P. maxima specimens exposed to sub-lethal concentrations of a shell-deforming toxin, tributyltin (TBT). The shell specific effects of TBT are used in this investigation to interpret differential expression of ESTs with respect to shell formation functions. A lethal and sublethal TBT concentration range was established for P. maxima, noting a concentration of 50 ng L- 1 TBT as sub-lethal over a 21 day period. Mantle tissue from P. maxima animals treated with 50 ng L- 1 TBT was assessed for differential EST expression with untreated control animals. A total of 102 ESTs were identified as differentially expressed in association with TBT exposure, comparative sequence identities included an up-regulation of immunity and detoxification related genes and down-regulation of several shell matrix genes. A number of transcripts encoding novel peptides were additionally identified. The potential actions of these genes are discussed with reference to TBT toxicity and shell biomineralization. This thesis has used a microarray platform to analyze gene expression in spatial, temporal and toxicity investigations, revealing the involvement of numerous gene transcripts in specific shell formation functions. Investigation of thousands of transcripts simultaneously has provided a holistic interpretation of the organic components regulating shell biomineralization.
4

Soil Management for Improved Rice Production in Casamance, Senegal

Fall, Thioro 06 July 2016 (has links)
Rice is a staple crop for many countries around the world, and is one of the top three food sources globally. Many environments where rice is grown contain stressors likely to limit its growth and yield. In southern Senegal (Casamance region), rice is mainly cultivated in lowlands near estuaries where drought, salinity, acidity, poor soil fertility, and iron toxicity are the main limiting factors. In Casamance, average rice yield for local farmers is 1 to 2 tons per hectare (809 to 1618 pounds per acre), compared to worldwide average yield of more than 4 tons per hectare. The soil where our 2-year experiment (2014 and 2015) was conducted is highly saline-sodic and acidic, and the salt tolerant cultivar we grew yielded 3.4 tons per hectare in 2013. Our main objective was to increase rice yield. The water table height, salinity, and pH were measured weekly during the rice growing season, and the soil was described, sampled, and analyzed to better understand the water and soil resources. Two planting methods were tested: flat planting and planting on beds. Two soil amendments were compared with each planting method: biochar and crushed oyster shells, alone and in combination. An untreated control was included in the experiment. All plots were fertilized. Treatment effects on soil properties and yield were compared in a split-plot design. Plant tissue was sampled for elemental content. The water table was above the surface and was saline during half of the growing season in 2014, and decreased after rice grain head emerged. Planting methods and amendments did not have an effect on yield in 2014, but biochar amendment increased yield in 2015. In 2014, soil salinity and sodium decreased to below toxic levels late in the growing season in the flat plots but not in the bedded plots. Therefore, flat planting is more appropriate in these lowland rice production systems. Soil pH increased from 4.4 to 7.7 in flat planting where biochar+shell was applied. Soil available nutrients such as P, Mn, and Zn were significantly higher in flat planting compared to beds. Toxic levels of Na (> 2000 milligrams per kilogram) were measured in leaves sampled just before flowering. We recommend flat planting and amending soil with biochar in saline-sodic acid-sulfate paddy soils in Casamance to improve rice yield. / Master of Science
5

Improved Management of Acid Sulfate Soils for Rice Production in Casamance, Senegal

Diallo, Ndeye Helene 19 July 2016 (has links)
Casamance is a region in southern Senegal that traditionally produces rainfed rice, but Senegal produces only 1/3 of its rice consumption. Lowland areas, where rice is primarily produced, have acid sulfate soils with low pH and potential aluminum and iron toxicity. The goal of this work was to determine if soil amendments can alleviate soil acidity, counteract the negative biogeochemical effects that occur in flooded conditions, and increase rice yield. A two-year experiment was conducted to test the following soil treatments – agricultural lime, pulverized oyster shell, biochar, and control (no amendment) – in flat and raised beds. Plots amended with lime and shell materials had increased soil pH, base saturation, Ca, and cation exchange capacity. Meanwhile, biochar elevated particulate organic matter and C:N ratios. Exchangeable Fe and Al were negatively correlated with soil pH, while Geobacteraceae populations (Fe reducing bacteria) increased with pH. A greater proportion of the total Fe was strongly bound in fractions that were less bioavailable in plots amended with shell or lime, and overall rice yields were significantly higher following amendment with shell or lime. During the second growing year these effects diminished, suggesting that liming effects did not persist as expected. These results demonstrate the benefits of soil amendments that raise soil pH and suggest that this effect operates by influencing overall soil nutrient availability to rice plants, but further research is needed regarding the timing and sustainability of the beneficial liming effect. / Master of Science
6

Desempenho produtivo e qualidade de ovos de poedeiras alimentadas com diferentes fontes de cálcio / Productive performance and eggs quality of laying hens fed with different calcium sources

Lima, Hiagos Felipe Firmino de 23 February 2016 (has links)
Made available in DSpace on 2016-08-15T20:31:28Z (GMT). No. of bitstreams: 1 HiagosFFL_DISSERT.pdf: 794630 bytes, checksum: b9112529e3742dd0a6d9fbab5a1a63fa (MD5) Previous issue date: 2016-02-23 / In animal production, where food represents about 70% of the cost of production, the supply of calcium to participate in large numbers in feed formulations, become the use of mineral origin organic important to maximize animal performance and minimize costs. Taking up the importance of integrity and eggshell strength in the conservation of its nutritional and microbiological property that mean the product quality and food safety, these features become essential for the approval of the egg by the consumer market. The objective was to evaluate different sources of calcium in diets on growth performance and eggs quality of laying hens light. The cages are equipped with linear feeder in galvanized sheet and drinker type nipple. The birds were housed in shed screen, in masonry, with clay tile roof equipped with 120 metal cages (0,20m x 0,40m x 0,40m) galvanized wire provided sideboard eggs arranged in four rows with corridor central. We used 120 birds of Bankiva line in the initial laying phase, starting the experiment when animals were in egg production and body weight even, the experimental period was 22-34 weeks old and the birds distributed in a completely randomized design with four treatments. Each treatment had 10 repetitions with 3 birds each unit experimental and consisted of four experimental diets with different sources of calcium: limestone, búzio shell flour (Anomalocardia brasiliana), oyster shell flour (Crassostrea brasiliana) and egg shell flour. Were evaluated: egg production rate, feed intake, feed conversion, absolute and relative weight of yolk, albumen and shell, height and width of the egg, specific gravity, yolk color, eggshell thickness, Haugh unit, albumen and yolk index. Had no significant effect (P> 0.05) between the treatments, for performance variables, egg production rate had a significant effect (P <0.05), its worst result egg shell flour. The egg shell flour was the only treatment showed significantly (P <0.05) for the weight, height and width of the egg, specific gravity, height and width albumen yolk, yolk absolute weight, albumen and shell, relative weight of the albumen and shell thickness, with worse results compared to the other treatments. Therefore, limestone, búzio shell flour and oyster shell flour, can be used as a source of calcium for laying rations / Na produção animal, onde a alimentação representa cerca de 70% do custo de produção, o suprimento de cálcio por participar em grande quantidade nas formulações de rações, torna a utilização de minerais de origem orgânica importante para se maximizar o desempenho animal e minimizar os custos. Levando-se a importância da integridade e resistência da casca do ovo na conservação de sua propriedade nutricional e microbiológica que significam a qualidade do produto e segurança alimentar, estas características tornam-se essenciais para a aprovação do ovo por parte do mercado consumidor. Diante disso, objetivou-se avaliar diferentes fontes de cálcio em rações, no desempenho produtivo e qualidade de ovos de poedeiras de linhagem leves. As aves foram alojadas em galpão telado, em alvenaria, com cobertura de telha de barro equipado com 120 gaiolas metálicas (0,20m x 0,40m x 0,40m) de arame galvanizado providas de aparador de ovos, dispostas em quatro fileiras com corredor central. As gaiolas são equipadas com comedouro linear em chapa galvanizada e bebedouro do tipo nipple. Foram utilizadas 120 aves da linhagem Bankiva em fase inicial de postura, iniciando o experimento quando os animais estavam com produção de ovos e peso corporal uniforme, o período experimental compreendeu de 22 a 34 semanas de idade sendo as aves distribuídas em delineamento inteiramente ao acaso com quatro tratamentos. Cada tratamento composto por 10 repetições com 3 aves por unidade experimental e sendo constituídos por quatro rações experimentais, com diferentes fontes de cálcio: calcário calcítico, farinha de concha búzio (Anomalocardia brasiliana), farinha de concha de ostra (Crassostrea brasiliana) e farinha de casca de ovo. Foram avaliados: taxa de postura, consumo de ração, conversão alimentar, peso absoluto e relativo de gema, albúmen e casca, peso, altura e largura do ovo, gravidade específica, espessura de casca, unidade Haugh, índice de albúmen e de gema. Não foram significativas (P>0,05) entre os tratamentos estudados, as variáveis de desempenho, exceto taxa de postura, a qual obteve efeito significativo (P<0,05), tendo resultado inferior para o tratamento com a farinha de casca de ovo. A farinha de casca de ovo foi o único tratamento que apresentou efeito significativo (P<0,05), para as variáveis de peso, altura e largura do ovo, gravidade específica, altura da gema e largura do albúmen, peso absoluto de gema, albúmen e casca, peso relativo do albúmen e espessura de casca, apresentando resultados inferiores em comparação aos demais tratamentos. Portanto, o calcário calcítico, farinha de concha de búzio e farinha de concha de ostra, por apresentarem uma maior granulometria demonstrou melhores resultados, podendo ser utilizadas como fonte de cálcio em rações de poedeiras de linhagem leves

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