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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.
191

Oviposition site preference of lacewings in maize ecosystems and the effect of Bt maize on Chrysoperla pudica (Neuroptera: Chrysopidae) / Rozelle Keulder

Keulder, Rozelle January 2010 (has links)
Resistance development and possible non–target effects have been of concern since the first deployment of genetically modified crops with insecticidal properties. It is especially at the third trophic level and with important predators such as lacewings (Chrysoperla spp.) (Neuroptera: Chrysopidae) where negative effects of Cry 1Ab protein could have adverse effects in agro–ecosystems. Monitoring of the effect of genetically modified Bt maize on non–target organisms is required by law in South–Africa. Neuroptera are excellent indicators of environmental and habitat transformation, and also include key species for signifying areas and faunas that require priority protection. Monitoring techniques, especially for insect eggs, are often labour intensive and time consuming. A study was conducted to determine the preferred oviposition site of Chrysoperla spp. on maize plants to facilitate time–effective searching for eggs of these beneficial insects. Furthermore we determined if the presence of aphids on plants influenced Chrysoperla spp. oviposition preference. Another study was conducted to evaluate the effect of indirect exposure of C. pudica to Cry 1Ab protein, through healthy Bt–maize feeding prey, on its biology. Daily flight activity patterns and the height at which chrysopid adults fly above the crop canopy were also determined, as well as the movement of adult Chrysoperla spp. between maize fields and adjacent headlands. A clear spatial oviposition pattern was observed on maize plants and oviposition was not random as reported in earlier studies. This data facilitates rapid monitoring of the presence of eggs in maize cropping systems and is also of use in general pest management. Choicetest data showed that females responded positively to host plants that were infested with aphids. Feeding studies in which C. pudica larvae were indirectly exposed to Bt–toxin at the 3rd trophic level, showed a limited effect of Bt–toxin on only a few of the parameters that were evaluated. The pupal period and percentage adult emergence of larvae exposed to an unusually high amount of Bt–toxin was significantly shorter and lower respectively than that of the control group. The overall result of this study, in which the possible effect of food quality (prey) was excluded, showed that Cry 1Ab protein had an adverse affect only on certain fitness components during the life cycle of C. pudica. However, since this study represented a worst–case scenario where diverse prey was not available to C. pudica, negligible effects is expected under field conditions where prey is more diverse. It was determined that chrysopids was most active between 16:00 – 23:00 and that they fly largely between 0.5 m – 2.5 m above ground level. An attempt was also made to quantify migration between different vegetations types. This part was terminated because of bad weather conditions at several occasions when the experiment was attempted. Chrysopids were never present in grassland vegetation, but an adjacent lucerne field maintained a large population. As the maize crop developed chrysopid population numbers increased inside the field, presumably originating from the lucerne field. / Thesis (M.Sc (Environmental Science))--North-West University, Potchefstroom Campus, 2011.
192

Oviposition site preference of lacewings in maize ecosystems and the effect of Bt maize on Chrysoperla pudica (Neuroptera: Chrysopidae) / Rozelle Keulder

Keulder, Rozelle January 2010 (has links)
Resistance development and possible non–target effects have been of concern since the first deployment of genetically modified crops with insecticidal properties. It is especially at the third trophic level and with important predators such as lacewings (Chrysoperla spp.) (Neuroptera: Chrysopidae) where negative effects of Cry 1Ab protein could have adverse effects in agro–ecosystems. Monitoring of the effect of genetically modified Bt maize on non–target organisms is required by law in South–Africa. Neuroptera are excellent indicators of environmental and habitat transformation, and also include key species for signifying areas and faunas that require priority protection. Monitoring techniques, especially for insect eggs, are often labour intensive and time consuming. A study was conducted to determine the preferred oviposition site of Chrysoperla spp. on maize plants to facilitate time–effective searching for eggs of these beneficial insects. Furthermore we determined if the presence of aphids on plants influenced Chrysoperla spp. oviposition preference. Another study was conducted to evaluate the effect of indirect exposure of C. pudica to Cry 1Ab protein, through healthy Bt–maize feeding prey, on its biology. Daily flight activity patterns and the height at which chrysopid adults fly above the crop canopy were also determined, as well as the movement of adult Chrysoperla spp. between maize fields and adjacent headlands. A clear spatial oviposition pattern was observed on maize plants and oviposition was not random as reported in earlier studies. This data facilitates rapid monitoring of the presence of eggs in maize cropping systems and is also of use in general pest management. Choicetest data showed that females responded positively to host plants that were infested with aphids. Feeding studies in which C. pudica larvae were indirectly exposed to Bt–toxin at the 3rd trophic level, showed a limited effect of Bt–toxin on only a few of the parameters that were evaluated. The pupal period and percentage adult emergence of larvae exposed to an unusually high amount of Bt–toxin was significantly shorter and lower respectively than that of the control group. The overall result of this study, in which the possible effect of food quality (prey) was excluded, showed that Cry 1Ab protein had an adverse affect only on certain fitness components during the life cycle of C. pudica. However, since this study represented a worst–case scenario where diverse prey was not available to C. pudica, negligible effects is expected under field conditions where prey is more diverse. It was determined that chrysopids was most active between 16:00 – 23:00 and that they fly largely between 0.5 m – 2.5 m above ground level. An attempt was also made to quantify migration between different vegetations types. This part was terminated because of bad weather conditions at several occasions when the experiment was attempted. Chrysopids were never present in grassland vegetation, but an adjacent lucerne field maintained a large population. As the maize crop developed chrysopid population numbers increased inside the field, presumably originating from the lucerne field. / Thesis (M.Sc (Environmental Science))--North-West University, Potchefstroom Campus, 2011.
193

Traps and Transformations of Grenadian Water Management

Neff, Brian Phillip January 2013 (has links)
The adaptive cycle metaphor provides insight into how and why social-ecological systems change. Literature on 'resilience thinking' has built upon this foundation and further developed the concepts of resilience, adaptation, and transformation to describe social-ecological system behavior. The resilience-thinking literature also describes systems that do not change, even when such change is desirable, as being in a trapped state. However, relatively little research has explored why such systems are trapped and how to free them. This thesis is the product of doctoral research which resolves how to identify, evaluate, and free a system caught in a maladaptive system trap. The study setting is water management in Grenada, a small island developing state in the southeastern Caribbean. Four research questions guide this study: (1) To what extent is Grenadian water management in a trap?, (2) To what extent is Grenadian water management transformable?, (3) Do current and recent interventions effectively foster or utilize transformability?, and (4) Which interventions should be pursued to facilitate transformation of water management in Grenada?. The study is informed by literature on social-ecological systems and integrated water resources management. Methodologically, the study is an explanatory single-case study of water management in Grenada, conducted from 2012 to 2013. The study utilizes data from semi-structured interviews (n=19), a questionnaire (n=180), a document review (n>200), and observation. The general strategy was to evaluate attempts to transform Grenadian water management within the 3-phase transformation framework described in the resilience-thinking literature. 'Points of failure' in transformation are defined as the cause(s) of a trap, and interventions to relieve the points of failure are proposed. Results indicate Grenadian water management is in a rigidity trap, although it exhibits some capacity to transform. A key point of failure of attempts to transform the Grenadian water sector into an integrated and holistic management system has been an inability to seize windows of opportunity to pass key legislation. I conclude the primary cause for this failure is poor fit among the problem, as perceived by various stakeholders, the proposed solution prescribed by water sector reform proponents, and political reality. In addition, reform proponents focus on advocating for reform to water sector professionals and do little to broker passage of legislation politically. Finally, reform proponents also assume legislation will be effectively implemented, which is not certain. Contributions specific to the Grenadian setting include a post-mortem on why efforts to reform the water sector have failed, described above. Five recommendations are made for future interventions to foster transformation of Grenadian water management: (1) engage residents as part of a vision to create political pressure for proposed solutions, (2) frame the problem with substantial resident input and focus, (3) craft solutions which take advantage of political realities such as funding restrictions, (4) anticipate and prepare for crises, and (5) enlist one or more people or organizations to serve as brokers. Empirical contributions include support for the three-streams framework of seizing windows of opportunity as fundamental to explain transformation of social-ecological systems. The primary conceptual contribution is the development of resilience thinking to illuminate ways to free trapped systems. I begin by providing a nomenclature to quantify and describe traps, which includes the type of trap, the degree of persistence and undesirability of the trap, and recent changes in these properties. Then, I develop a framework to assess transformability of a given system based on the existing 3-phase framework of transformation. When applied empirically, this framework illuminates points of failure of transformation, which I define as the cause of a given trap. Once identified, specific strategies can be devised to foster transformation and to break free of a trap.
194

Cold single atoms for cavity QED experiments

Kim, Soo Y. 17 November 2008 (has links)
A neutral atom interacting with a single mode of a high finesse cavity provides an opportunity to study uncharted quantum mechanical systems and to explore the field of quantum computing and networking. Ranging from being a deterministic single photon source to a coherent storage unit for quantum information, a strong coupling cavity QED system has proven to be a powerful tool. In this thesis, single atoms are deterministically delivered over long distances and probed in an optical cavity. Once in the cavity, a single atom is stored and continuously observed for over 15 seconds. Progress towards using atoms in the cavity to produce entangled photon pairs is presented. Dual 1D optical lattices are implemented to create a foundation for advancements in two qubit quantum operations and entanglements.
195

Olfactory communication in the codling moth, Cydia pomonella L. /

Bäckman, Anna-Carin, January 1900 (has links) (PDF)
Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniv. / Härtill 6 uppsatser.
196

Trivial movements and redistribution of polyphagous insect herbivores in heterogeneous vegetation /

Hannunen, Salla, January 2003 (has links) (PDF)
Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.
197

Pesquisa participativa na avaliação de armadilhas e contole populacional de cosmopolites sordidus / Participatory research on evaluation of traps and Population control Cosmopolites sordidus

Santos, Saint Clair Lira 06 December 2010 (has links)
Made available in DSpace on 2016-08-12T19:18:38Z (GMT). No. of bitstreams: 1 SaintCLS_TESE.pdf: 4694097 bytes, checksum: 80ab61feec693a67ab89d69cc107d325 (MD5) Previous issue date: 2010-12-06 / The banana (Musa spp) is one of the most consumed fruits in the world. It constitutes an important food, because of their chemical composition and content in vitamins and minerals, especially potassium. It is notable for being versatile, by their taste, low price and their easily of being consumed in natura, favoring the poor population. There are several challenges to banana production in the world, including the aspect of food security, as regards not only the quantity produced, but also the quality of fruits, mainly under the aspect of demand for products free of pesticides. Focused in the perspective of agroecology theme, this study considered the involvement of local farmers, like experimenter farmers offering in their own work, not just a research environment, but also a demonstration unit for students and banana producers of these region. This research had as main objective of studying the population dynamic of C. sordidus traps and evaluate their control in terms of the Vale do Açu-RN. We will also collaborate with the technical support to local producers, since research has allowed him to these, during and after the experiments, as a way to achieve a participatory ownership of the results. It was observed population dynamic of adult C. sordidus, so that the population peak was in June 2010. As the larvae, it was found that two population peaks occurred in the month of December 2009 and in July 2010. The climatic variables did not influence the population dynamics of adults and produced negative effects in the young population of these insects, especially rainfall and relative humidity. There were differences between the traps studied on the capture efficiency of C. sordidus. Considering the four collections, economically, the best treatment was the "T4" Bait type "tile" (80 baits / ha), which had the lowest ratio of total cost and average of trapped insects. Considering eight samples, economically the best treatment was the "T1", Cosmolure ® Drum, which had the lowest ratio of Total Cost and Average of trapped insects. Treatment with bait type "roof" (T4) is greater sustainability for family farmers, not creating dependency on external inputs and on the other hand, provide occupation of manpower, thus contributing to income generation and environmental preservation . / A banana (Musa spp) é uma das frutas mais consumidas no mundo. Constituise num importante alimento, em razão de sua composição química e conteúdo em vitaminas e minerais, principalmente potássio. Destaca-se por ser versátil, pelo seu sabor, baixo preço e facilidade de consumo in natura, favorecendo a população de menor poder aquisitivo economicamente. São vários os desafios que se colocam à produção de banana no mundo, dentre eles o aspecto da segurança alimentar, no que concerne não só à quantidade produzida, mas também à qualidade dos frutos, principalmente sob o aspecto da exigência de produtos livres de agrotóxicos. Focado sob a ótica da temática agroecológica, este estudo considerou a participação dos agricultores locais, como agricultores experimentadores oportunizando em sua área de trabalho, não só um ambiente de pesquisa, mas também uma unidade de demonstração para estudantes e produtores(as) de banana da região. Esta pesquisa teve como principal objetivo, estudar a dinâmica populacional de C. sordidus e avaliar armadilhas ao seu controle nas condições do Vale do Açu-RN. Objetivou-se também, colaborar com o suporte técnico aos produtores locais, já que a pesquisa proporcionou o envolvimento desses, durante e pós os experimentos, como forma de se lograr uma apropriação participativa dos resultados. Verificou-se dinâmica populacional dos adultos de C. sordidus, de modo que o pico populacional foi no mês de junho de 2010. Quanto às larvas, verificou-se que ocorreram dois picos populacionais, no mês de dezembro de 2009 e no mês de julho de 2010. As variáveis climáticas não influenciaram na dinâmica populacional de adultos e produziram efeitos negativos na população jovem desses insetos, sobretudo a precipitação pluvial e umidade relativa do ar. Houve diferença entre as armadilhas estudadas quanto à eficiência de captura do C. sordidus. Considerando-se 4 coletas, economicamente, o melhor tratamento foi o T4 , Isca tipo telha (80 iscas/ha), que apresentou a menor relação entre custo total e média de insetos capturados. Considerando-se 8 coletas, economicamente o melhor tratamento foi o T1 , Cosmolure® Tambor, que apresentou a menor relação entre Custo Total e Média de insetos capturados. O tratamento com isca tipo telha (T4) representa maior sustentabilidade para a agricultura familiar, por não criar a dependência externa de insumos e por outro lado, propiciar ocupação da mão-de-obra, contribuindo para a geração de renda e preservação ambiental.
198

Neoleucinodes elegantalis (Guenée) (Lep.: Crambidae) em tomateiro estaqueado: dinâmica populacional, nível de controle com feromônio sexual e eficiência de agrotóxicos

Benvenga, Sérgio Roberto [UNESP] 30 April 2009 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:32:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-04-30Bitstream added on 2014-06-13T20:02:56Z : No. of bitstreams: 1 benvenga_sr_dr_jabo.pdf: 687682 bytes, checksum: 87972d03b6fb3f2cb343c0a702c9b1ba (MD5) / Gravena Manecol Ltda / A relação entre a infestação da broca-pequena-do-fruto, Neoleucinodes elegantalis, e a produtividade foi avaliada na cultura do tomate, Lycopersicon esculentum, em ciclo de verão e inverno, com o objetivo de analisar a influência da infestação na produtividade da cultura e aperfeiçoar a tomada de decisão de controle. Armadilhas com feromônio sexual foram instaladas em parcelas experimentais e na mesma data foi avaliada a densidade de adultos capturados e a infestação de plantas com ovos nos frutos. A pressão populacional foi mais expressiva nos cultivos de verão. O aumento no número de adultos capturados nas armadilhas correspondeu a um incremento na infestação de ovos nos frutos e houve influência positiva da infestação de plantas com a produção descartada. Definiu-se que a tomada de decisão de controle deve ocorrer quando for capturada a média de 0,24 e de 0,23 adultos na armadilha por dia, nos cultivos de verão e de inverno, respectivamente. Numa etapa complementar avaliou-se a eficiência de inseticidas sobre os ovos (ação ovicida), lagartas recém-eclodidas (ação de choque) e em fase de crescimento (ação fisiológica), sob condições de laboratório. Para tanto, frutos com ovos foram imersos na calda inseticida para avaliação da ação ovicida e ação de choque aos 7 dias após a imersão e aos 21 dias, para a ação fisiológica. Foram avaliados 24 inseticidas e uma testemunha em aplicação isolada e com a adição de óleo vegetal (0,25%), respectivamente. Trebon 100 SC (etofenprox; 200 mL de produto comercial/100 L), Lannate BR (methomil; 100 mL), Thiobel 500 (cartap; 250 g) e Vertimec 18 CE (abamectin; 100 mL) apresentaram ação efetiva sobre os ovos e lagartas de N. elegantalis. A adição do adjuvante interfiriu de forma significativa e positiva na eficiência dos inseticidas. / The relationship between the infestation of Neoleucinodes elegantalis and productivity was evaluated in tomato crops, Lycopersicon esculentum, in summer and winter cycles, with the objective of analyzing the infestation influence on the productivity and improving the decision making control. Sex pheromone traps were installed in experimental plots and at the same date was assessed the density of adults caught and infestation of plants with eggs in fruits. The population pressure was more significant in the summer crops. The increase in the number of adults caught in traps corresponded to an increase in infestation of eggs in the fruit and with positive influence of the infestation on plants with the production. Decision-making control should occur when the average catch of 0.24 and 0.23 adults in the trap per day in the summer and winter crops, respectively. An additional step was conducted to evaluate the efficiency of insecticides on the eggs (ovicidal action), newly-hatched larvae (shock action) and in the growth phase (physiological action) under laboratory conditions. Fruit with eggs were emmerged in the insecticide solutions for assessing ovicidal action and the shock action at 7 days after immersion and at 21 days, to physiological action. It was evaluated 24 insecticides and a control application in with and without addition of vegetable oil (0.25%). Trebon 100 SC (etofenprox; 200 mL of commercial product/100 L), Lannate BR (methomil; 100 mL), Thiobel 500 (cartap; 250 g) and Vertimec 18 EC (abamectin; 100 mL) had action on the eggs and larvae of N. elegantalis. The addition of adjuvant showed significantly and positively effects in the insecticides efficiency.
199

Improved Model for Excess Base Current in Irradiated Lateral PNP Bipolar Junction Transistors

January 2017 (has links)
abstract: A modeling platform for predicting total ionizing dose (TID) and dose rate response of commercial commercial-off-the-shelf (COTS) linear bipolar circuits and technologies is introduced. Tasks associated with the modeling platform involve the development of model to predict the excess current response in a bipolar transistor given inputs of interface (NIT) and oxide defects (NOT) which are caused by ionizing radiation exposure. Existing models that attempt to predict this excess base current response are derived and discussed in detail. An improved model is proposed which modifies the existing model and incorporates the impact of charged interface trap defects on radiation-induced excess base current. The improved accuracy of the new model in predicting excess base current response in lateral PNP (LPNP) is then verified with Technology Computer Aided Design (TCAD) simulations. Finally, experimental data and compared with the improved and existing model calculations. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2017
200

Petrology and geochemistry of basaltic rocks of the Falkland Islands and Deccan Traps (India)

Mitchell, Clive J. January 1988 (has links)
No description available.

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