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Cry the Beloved Media: New Media and Student Perceptions in a World Literature ClassroomGreenwood, Timbre Janiece Newby 08 June 2011 (has links) (PDF)
This qualitative action research project addressed the infusion of media literacy and new media into a standard secondary English language arts curriculum. In examining students' perceptions of South Africa as they interacted with new media texts in conjunction with the traditional literary text Cry, the Beloved Country, this study also explored the manner in which students' media interactions informed their reading of the novel. As a result of the research data, the author asserts that media literacy education can, in fact, play an effective role in teaching literature within the world literature classroom.
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Estrategias para la utilización de la bacteria entomopatógena Bacillus thuringiensis (Berliner) en el control de Ceratitis capitata (Wiedemann)Vidal Quist, José Cristian 24 May 2010 (has links)
La mosca mediterránea de la fruta, Ceratitis capitata, es la principal plaga de la fruticultura en el mundo. El desarrollo de métodos ambientalmente seguros de control de plagas, como Bacillus thuringiensis (Bt), adquiere cada vez mayor importancia. Esta tesis doctoral evalúa la validez de Bt y sus delta-endotoxinas como agentes de control de C. capitata. El análisis de la biodiversidad de Bt ha reflejado la gran riqueza presente en el agroecosistema de los cítricos. Sin embargo, ninguna de las cepas ensayadas (905) muestra alta toxicidad sobre C. capitata cuando esporas/cristales o sobrenadantes de su cultivo son ensayados. En cambio, la solubilización de los cristales de una selección de 42 cepas de Bacillus sp. ha demostrado que, para las cepas de la subespecie israelensis (Bti), este tratamiento produce una ganancia de función biológica. Adicionalmente, la predigestión de dichas protoxinas con proteasas de otro díptero, Culex pipiens, aumenta su actividad larvicida (CL50 31.26 µg/cm2). Por otro lado, se ha demostrado que, entre las delta-endotoxinas producidas por Bti, la protoxina Cyt1Aa es el factor determinante, con una CL50 sobre larvas de 4.93 µg/cm2. Sobre adultos, Cyt1Aa produce efectos subletales. Complementariamente, esta tesis propone un nuevo método de control basado en el desarrollo de toxinas recombinantes de fusión Cry-anticuerpo. Se ha puesto en práctica un sistema modelo para evaluar esta estrategia: se han desarrollado 4 variantes proteicas por la fusión entre partes de la protoxina Cry1Ab y un anticuerpo específico contra GFP (VHH anti-GFP) y éstas se han ensayado sobre larvas transgénicas de Drosophila melanogaster que expresan GFP en su intestino. Deficiencias en la unión de las toxinas de fusión a GFP, han impedido demostrar, por el momento, la estrategia propuesta. Por último, se han detectado al menos 160 proteínas distintas en las membranas intestinales de C. capitata y se han identificado las siguientes: V-ATPasa subunidades A y B, y alfa-tubulina. / Vidal Quist, JC. (2010). Estrategias para la utilización de la bacteria entomopatógena Bacillus thuringiensis (Berliner) en el control de Ceratitis capitata (Wiedemann) [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8336
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Potencial inseticida das proteínas Cry1Ca e Cry2Ac de Bacillus thuringiensis Berliner para populações de Plutella xylostella (L.) (Lepidoptera : Plutellidae) em laboratório. /Cardoso, Camila Pires January 2019 (has links)
Orientador: Sergio Antonio de Bortoli / Resumo: O cultivo intensivo de Brassicaceae favorece o aparecimento de algumas pragas como Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae), a traça-das-crucíferas, cujos danos podem comprometer seriamente a produção. Esse inseto-praga pode ser controlado tanto com inseticidas sintéticos, como com biológicos, sendo, no entanto, usualmente utilizados os sintéticos em seu combate. A traça-das-crucíferas foi a primeira espécie de inseto a ser constatada resistência a inseticidas biológicos, com o uso indiscriminado de inseticidas sintéticos para o seu controle contribuindo também para a seleção de indivíduos tolerantes ou resistentes, além de causar a mortalidade de organismos não alvos. Sendo assim, este trabalho teve por objetivo avaliar a atividade inseticida e os efeitos subletais de duas toxinas lepidóptero-ativas de Bacillus thuringiensis, Cry1Ca e Cry2Ac, em três populações de traças-das-crucíferas, sendo uma delas suscetível (PC) e duas consideradas resistentes (Bt e NO-QA) a toxinas de B. thuringienis, em condições de laboratório. Foram realizados bioensaios de suscetibilidade com as três populações e as toxinas Cry1Ca e Cry2Ac, estimando-se a concentração letal (CL50) e os seus efeitos subletais. A toxina Cry2Ac não causou mortalidade nas lagartas das três populações, então os testes subletais foram realizados apenas com a toxina Cry1Ca que provocou mortalidade. Os parâmetros biológicos avaliados foram: período e peso pupal, sobrevivência larval e pupal, longevi... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Intensive brassics cultivation favors appearing of some pests as Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae), diamondback moth (DBM), whose damage can seriously compromise production. This insect-pest can be controlled either synthetic insecticides as biological insecticides, but synthetics are usually used to combat. Diamondback moth was the first insect species to be verified resistance to biological insecticides, with indiscriminate use of synthetic insecticides for its control, also contributing to selection of tolerant or resistant individuals, as well as causing mortality on non-target organisms. Therefore, the objective of this work was to evaluate insecticide activity and sublethal effects of two lepidopteran-active toxins of Bacillus thuringiensis, Cry1Ca and Cry2Ac, on three DBM populations, one of them susceptible (PC) and two considered as resistant (Bt and NO-QA) to B. thuringiens toxins under laboratory conditions. Susceptibility bioassays were performed on the three populations and toxins Cry1Ca and Cry2Ac, estimating lethal concentration (LC50) and its sublethal effects. Cry2Ac toxin did not cause mortality on the caterpillars from the three populations, so the sublethal tests were performed only with Cry1Ca toxin. The biological parameters evaluated were: pupal period and weight, caterpillar and pupal survival, male and female longevity and fecundity. The populations showed susceptibilities to Cry1Ca toxin, with statistically equal behavio... (Complete abstract click electronic access below) / Mestre
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Productions of ideology : a comparative and contrasting analysis of representations of Black urban experience in Peter Abrahams's Mine boy ; Alan Paton's Cry, the beloved country and Phyllis Altman's The law of the vultures.Mowat, Sharon. January 2000 (has links)
The broad aim of this study is to show, through a comparative and contrasting analysis
of three thematically related texts - namely Peter Abrahams's Mine Boy; Alan Patan's
Cry, the Beloved Country and Phyllis Altman's The Law of the Vultures - the
ideologically mediated nature of the relationship between the 'real' history which
constituted their context, and the representations of it in the historical realist form. An
examination afthe texts' characters and events; political formulations, and formal
devices reveals three very different representations of the same object. This diversity is
significant in so far as it supports a Marxist conceptualisation of the [historical] realist
text as a production of ideology as opposed to a portrayal of reality. The study
considers the nature of the relationship between each text and ideology in terms of
three aspects of this relationship: the 'objectively determinable' relation between
history, ideology and text; the ideology of the text itself, and the mode of a text's
insertion into an 'ideological sub-ensemble.' In relation to the modes of a text's
insertion into an ideological sub-ensemble, my specific aim is to assess the extent to
which each text actually challenges the political dispensation to which it was
addressed. / Thesis (M.A.)-University of Natal, Durban, 2000.
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Problematika a prevence syndromu třeseného dítěte z retrospektivního pohledu sestry / Shaken baby syndrome problems and prevention from the nurse retrospective viewDRAXLEROVÁ, Milena January 2010 (has links)
Abstract {--} Shaken baby syndrome problems and prevention from retrospective nurse point of view The dissertation objective on the theme {\clqq}Shaken baby syndrome problems and prevention from retrospective nurse point of view`` is to process an entire literature and outline the shaken baby syndrome problem. Further to find out the shaken baby syndrome knowledge at nurses and parents by way of analysis and questionnaires evaluation. The third aim of this thesis was to develop the simple educational material for the parents within this work. To meet these objectives the dissertation is divided into theoretical and practical parts. The theoretical one devotes to entire available literature processing related to shaken baby syndrome. The practical part focuses on the quantitative knowledge extent finding out at nurses and parents referring to shaken baby syndrome above all and concentrates on the parents education from nurse side, especially in the field of the baby cry as the main shaken baby syndrome initiator. The data of the quantitative research part have been learned by means of questionnaire disquisition. There were used two kinds of questionnaires, the first for nurses and the second one for parents and home nurses. Both of them were anonymous. The simple developed information material for parents concentrating mainly on correct ways of cry soothing related to shaken baby syndrome is the part of results. Three hypothesises have been set for work needs. Hypothesis 1 {\clqq}There are many sources of the professional literature concerning shaken baby syndrome in the Czech Republic`` hasn´t come true. Hypothesis 2 {\clqq}The parents and health workers knowledge about shaken baby syndrome is wanting`` has come true. Hypothesis 3 {\clqq}Shaken baby syndrome primary prevention doesn´t exist in the Czech Republic`` has also come true. The nurses and parents poor knowledge about the shaken baby syndrome was the important fact found out within research disquisition. With respect to serious consequences of shaken baby syndrome which can be sometime fatal for children there is a need to meet nurses this syndrome and enable them to be familiar with recognition and determination of the shaken baby syndrome risk factors both from the parents and children side. Thus this work could also serve as a source of more information about mentioned problems. The developed information material for parents could have another utilization during their care of child.
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”Ibland känns det som om att det finns en dragkedja i mig” : En undersökning av porträtteringen av transmän i filmernaPojkarna och Boys Don’t CryThorslund, Linnéa, Bergman, Sofia January 2018 (has links)
Denna uppsats behandlar porträtteringen av transmän i filmerna Pojkarna (2015) och Boys Don’t Cry (1999). Syftet är att undersöka hur karaktärernas könsidentiteter är porträtterade och även att kunna bidra med kunskap till filmskapare om hur man kan utveckla porträtteringar av transmän i film. Analysen skrivs ur ett queerteoretiskt och normkritiskt perspektiv och genomförs med hjälp av Jens Eders analysmetod Karaktärsklockan. Maskulinitetsteori används för att undersöka karaktärernas maskulina uttryckssätt. Resultatet av denna undersökning visar att karaktärerna är nyanserade men att filmskaparna berövar karaktärerna rätten till sina könsidentiteter genom att de ständigt behöver rättfärdiga sig själva och sedan avslutar de filmerna med en tragisk eftersmak. Att karaktärerna berövas ett lyckligt slut kan skapa reflektioner om att det är ouppnåeligt att leva ett bra liv som transperson. / This thesis will examine the portrayal of trans men in the films Girls Lost (2015) and Boys Don’t Cry (1999). The purpose is to analyse how the characters’ gender identities are portrayed, and be able to contribute with knowledge of how to further advance the portrayal of trans men in film. The analysis is written from a queer theoretical and norm-critical perspective, with support from Jens Eder’s method of analysis Clock of Character. Masculine theory is used in order to examine how the characters express their masculine traits. The result of this study shows that the characters are nuanced, though, the filmmakers deprive them of their right to their gender identities as they constantly need to justify themselves, as well as ending both films with a tragic aftertaste. As the characters are deprived of a happy ending, this might create reflections that a good life as a trans person is unachievable.
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Parent-Child Intervention Decreases Stress and Increases Maternal Brain Activity and Connectivity in Response to Own Baby-CrySwain, James E., Ho, S. Shuan, Rosenblum, Katherine, Morelen, Diana M., Dayton, Carolyn Joy, Muzik, Maria 06 April 2017 (has links)
There is a growing understanding of the neural mechanisms of human maternal attachment. Human mothers’ neural responses to infants are associated with their behavioral sensitivity observed during interactions with infants. The current symposium aims to provide understanding of the core neural basis for mother-infant attachment, how prenatal and postnatal risk factors influence the maternal brain, and finally whether the negative changes in the maternal brain may be reversed by an intervention effort. The first paper presents converging evidence on neural, psychological and physiological responses to infants in new mothers across diverse cultural contexts. The paper highlights the common core neural processes of mother-infant attachment, which sets the foundation of understanding maternal brain’s successful and unsuccessful adaptation to parenthood. The second paper presents the role of prenatal risk factors, specifically prenatal maternal anxiety, in maternal brain adaptation to parenthood. This longitudinal study suggests that negative effects of maternal anxiety in mothers’ neural adaptation to parenthood may emerge during pregnancy. The third paper presents evidence that socioeconomic stress may also disrupt mothers’ neural adaptation to parenthood. Low family income is associated with dampened neural sensitivity to positive infant expressions and elevated neural sensitivity to negative infant expressions, which further influence disruptions in maternal behavioral responsiveness to own infants. The last presentation suggests that aberrant neural sensitivity to infants among distressed mothers may be improved via an intervention. Among depressed mothers, interventions to improve mental health reduced parental stress and strengthened neural functional connectivity in response to their infant.
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Dysphonations in Infant Cry: A Potential Marker for Health StatusAbbs, Katlin Jennifer 23 March 2015 (has links)
No description available.
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Impact des plantes Bt sur la biologie de Plodia interpunctella - Evaluation de l'efficacité de la stratégie agricole 'Haute Dose - Refuge' pour la gestion de la résistance des insectes ravageurs aux plantes Bt / Impact of the Bt plants on the biology of Plodia interpunctella - Effectiveness of the 'High Dose – Refuge' strategy for managing pest resistance to Bt plantsGryspeirt, Aiko 17 January 2008 (has links)
Commercialisées depuis 1996, les plantes génétiquement modifiées produisant une toxine insecticide (toxine Cry) dérivée de Bacillus thuringiensis et appelées plantes Bt ciblent certains Lépidoptères ou Coléoptères ravageurs. Au fil des ans, les surfaces cultivées en plantes Bt sont de plus en plus importantes et contrôlent de larges populations d'insectes. Pour limiter le risque de développement de populations résistantes, une stratégie agricole appelée 'Haute Dose / Zone Refuge' est actuellement recommandée aux Etats-Unis par l'Environmental Protection Agency. Cette stratégie préventive nécessite la plantation d'une 'zone refuge' composée de plantes non-Bt utilisables par le ravageur ciblé et plantée à proximité de la 'zone Bt' qui synthétise une haute dose de toxine Cry.
Mon projet de recherche s’inscrit dans le cadre de l’évaluation de l'efficacité de cette stratégie et s’articule en deux phases : une phase expérimentale et une phase théorique. La première se concentre sur la caractérisation en laboratoire de l'impact des toxines Cry sur la biologie d'un ravageur. Cette phase constitue un support au volet théorique : la mise au point d’un modèle mathématique évaluant l'efficacité de la stratégie HD/R. L'originalité de ce projet repose entre autre sur l'interactivité entre ces deux volets.
Volet expérimental. Impact des toxines Cry sur la biologie de Plodia interpunctella. Nous évaluons séparément l'impact d'une gamme de concentrations de deux toxines Cry (CryXX et CryYY) sur une série de paramètres comportementaux et biologiques d'un insecte commun des denrées stockées: Plodia interpunctella (Hübner) (Lepidoptera : Pyralidae). Ces paramètres sont sélectionnés car leur variation pourrait avoir un impact sur l'efficacité de la stratégie HD/R dans le contrôle de la résistance. Il est donc pertinent de les quantifier pour intégrer dans le modèle des ordres de grandeur réalistes et générer des résultats qui ne sont pas uniquement basés sur des spéculations théoriques.
Volet théorique A. Efficacité de la stratégie HD/R pour des plantes Bt synthétisant une ou deux toxines simultanément. La stratégie 'HD/R' a été développée pour prévenir la résistance envers les plantes Bt synthétisant une seule toxine. Or, depuis 2003, de nouvelles variétés de coton Bt synthétisant simultanément deux toxines Cry sont commercialisées (BollgardII® et WidestrikeTM). Nous évaluons, grâce au modèle que nous avons développé, l'efficacité de cette stratégie lors d'une utilisation exclusive de plantes Bt synthétisant une ou deux toxines.
Volet théorique B. Impact du ralentissement du développement des insectes sur les plantes Bt sur l'efficacité de la stratégie HD/R. Le volet expérimental met en évidence un allongement de la durée du développement des larves se nourrissant sur une diète contaminée en toxine Cry. Ce ralentissement induit une séparation temporelle entre l'émergence des adultes de la zone Bt et de la zone refuge et perturbe une hypothèse principale de la stratégie HD/R: le croisement aléatoire entre adultes, indépendamment du génotype et de la zone d'origine. Dans ce troisième chapitre, nous étudions l'impact de la perturbation du croisement aléatoire sur l'efficacité de la stratégie HD/R. Nous testons également deux options pour optimiser la stratégie en cas d'asynchronie: l'utilisation de plantes Bt synthétisant une faible concentration en toxine (atténuant le décalage entre l'émergence des adultes) ou l'augmentation de la taille de la zone refuge (favorisant la survie des individus porteurs d'allèle de sensibilité et donc optimisant la dilution de la résistance à la génération suivante).
Ce travail s'intègre dans une problématique actuelle et utilise des outils de biologie théorique (théories de la dynamique et de la génétique des populations) ainsi que le développement d'un modèle mathématique. Il apporte des éléments de réponse et de réflexion sur l'optimisation de la gestion de la résistance des insectes mais c'est aussi une illustration de la complémentarité entre la biologie expérimentale et théorique.
/
On the market since 1996, genetically modified plants synthesizing an insecticidal toxin (Cry toxin) stemmed from Bacillus thuringiensis, called Bt plants, target several insect pests (Lepidoptera or Coleoptera). Bt crops cover increasingly larger areas and control important pest populations The Insect Resistance Management Strategy (IRM) strategy currently recommended in the U.S.A. to limit the development of resistant populations is the High Dose / Refuge zone (HD/R) strategy. This pre-emptive strategy requires a refuge zone composed by non-Bt plants, usable by the target insect and in close proximity of the Bt zone synthesizing a high toxin concentration.
My research project contributes to the effectiveness assessment of this HD/R strategy. It is structured on two main parts: an experimental, and a theoretical section. The first part characterizes the impact of Cry toxins on the biology of an insect pest. It is the basis of the theoretical part: the implementation of a mathematical model, which evaluates the effectiveness of the HD/R strategy.
The originality of this project is based on the interactivity of these two components.
Experimental section. Impact of the Cry toxins on the biology of Plodia interpunctella. We assess the impact of a range of concentrations of two Cry toxins (CryXX et CryYY) on several behavioural and biological parameters of a common pest of stored products: Plodia interpunctella (Hübner) (Lepidoptera : Pyralidae). These parameters are selected because their variation could influence the effectiveness of a HD/R strategy. So, it is important to quantify these parameters so that realistic values can be integrated in our model. The results of the model are thus not based on theoretical assumptions alone.
Theoretical section A. Effectiveness of a HD/R strategy with Bt plants synthesizing one or two toxins. Initially, the HD/R strategy has been developed to limit the resistance towards Bt plants synthesizing one toxin. However, since 2003, new Bt cotton varieties synthesize two toxins simultaneously (BollgardII® et WidestrikeTM). We assess, with our model, the effectiveness of this strategy for Bt plants synthesizing one or two toxins.
Theoretical section B. Impact of the slowing down of the insect development reared on Bt plants on the effectiveness of the HD/R strategy. The experimental part demonstrates that larvae reared on a Bt diet have a protracted development duration. The consequence of this is a temporal separation between adult emergence in the two zones (Bt zone and refuge zone). This could affect the main assumption of the HD/R strategy, i. e. random mating independently of the genotype and of the native zone. In this third chapter, we study the impact of random mating disruption on the effectiveness of a HD/R strategy. We test two options to optimise the strategy in case of asynchrony: the use of Bt plants synthesizing a lower toxin concentration (limiting emergence asynchrony) or increasing the refuge zone size (favouring the survival of insect carrying one or two susceptible allele and thus optimising the dilution of resistance at the next generation).
This work is applied to a current issue. It uses some of the tools of theoretical biology (theories of population dynamics and population genetics) and develops a mathematical model. It provides some responses and some elements of thought about insect resistance management. It is also an illustration of the complementarity between experimental and theoretical biology.
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Impact des plantes Bt sur la biologie de Plodia interpunctella: évaluation de l'efficacité de la stratégie agricole "Haute dose - refuge" pour la gestion de la résistance des insectes ravageurs aux plantes Bt / Impact of the Bt plants on the biology of Plodia interpunctella: effectiveness of the "High Dose - Refuge" strategy for managing pest resistance to Bt plantsGryspeirt, Aiko 17 January 2008 (has links)
Commercialisées depuis 1996, les plantes génétiquement modifiées produisant une toxine insecticide (toxine Cry) dérivée de Bacillus thuringiensis et appelées plantes Bt ciblent certains Lépidoptères ou Coléoptères ravageurs. Au fil des ans, les surfaces cultivées en plantes Bt sont de plus en plus importantes et contrôlent de larges populations d'insectes. Pour limiter le risque de développement de populations résistantes, une stratégie agricole appelée 'Haute Dose / Zone Refuge' est actuellement recommandée aux Etats-Unis par l'Environmental Protection Agency. Cette stratégie préventive nécessite la plantation d'une 'zone refuge' composée de plantes non-Bt utilisables par le ravageur ciblé et plantée à proximité de la 'zone Bt' qui synthétise une haute dose de toxine Cry. <p><p>Mon projet de recherche s’inscrit dans le cadre de l’évaluation de l'efficacité de cette stratégie et s’articule en deux phases :une phase expérimentale et une phase théorique. La première se concentre sur la caractérisation en laboratoire de l'impact des toxines Cry sur la biologie d'un ravageur. Cette phase constitue un support au volet théorique :la mise au point d’un modèle mathématique évaluant l'efficacité de la stratégie HD/R. L'originalité de ce projet repose entre autre sur l'interactivité entre ces deux volets.<p><p>Volet expérimental. Impact des toxines Cry sur la biologie de Plodia interpunctella. Nous évaluons séparément l'impact d'une gamme de concentrations de deux toxines Cry (CryXX et CryYY) sur une série de paramètres comportementaux et biologiques d'un insecte commun des denrées stockées: Plodia interpunctella (Hübner) (Lepidoptera :Pyralidae). Ces paramètres sont sélectionnés car leur variation pourrait avoir un impact sur l'efficacité de la stratégie HD/R dans le contrôle de la résistance. Il est donc pertinent de les quantifier pour intégrer dans le modèle des ordres de grandeur réalistes et générer des résultats qui ne sont pas uniquement basés sur des spéculations théoriques.<p><p>Volet théorique A. Efficacité de la stratégie HD/R pour des plantes Bt synthétisant une ou deux toxines simultanément. La stratégie 'HD/R' a été développée pour prévenir la résistance envers les plantes Bt synthétisant une seule toxine. Or, depuis 2003, de nouvelles variétés de coton Bt synthétisant simultanément deux toxines Cry sont commercialisées (BollgardII® et WidestrikeTM). Nous évaluons, grâce au modèle que nous avons développé, l'efficacité de cette stratégie lors d'une utilisation exclusive de plantes Bt synthétisant une ou deux toxines.<p><p>Volet théorique B. Impact du ralentissement du développement des insectes sur les plantes Bt sur l'efficacité de la stratégie HD/R. Le volet expérimental met en évidence un allongement de la durée du développement des larves se nourrissant sur une diète contaminée en toxine Cry. Ce ralentissement induit une séparation temporelle entre l'émergence des adultes de la zone Bt et de la zone refuge et perturbe une hypothèse principale de la stratégie HD/R: le croisement aléatoire entre adultes, indépendamment du génotype et de la zone d'origine. Dans ce troisième chapitre, nous étudions l'impact de la perturbation du croisement aléatoire sur l'efficacité de la stratégie HD/R. Nous testons également deux options pour optimiser la stratégie en cas d'asynchronie: l'utilisation de plantes Bt synthétisant une faible concentration en toxine (atténuant le décalage entre l'émergence des adultes) ou l'augmentation de la taille de la zone refuge (favorisant la survie des individus porteurs d'allèle de sensibilité et donc optimisant la dilution de la résistance à la génération suivante). <p><p>Ce travail s'intègre dans une problématique actuelle et utilise des outils de biologie théorique (théories de la dynamique et de la génétique des populations) ainsi que le développement d'un modèle mathématique. Il apporte des éléments de réponse et de réflexion sur l'optimisation de la gestion de la résistance des insectes mais c'est aussi une illustration de la complémentarité entre la biologie expérimentale et théorique.<p><p><p>/<p><p>On the market since 1996, genetically modified plants synthesizing an insecticidal toxin (Cry toxin) stemmed from Bacillus thuringiensis, called Bt plants, target several insect pests (Lepidoptera or Coleoptera). Bt crops cover increasingly larger areas and control important pest populations The Insect Resistance Management Strategy (IRM) strategy currently recommended in the U.S.A. to limit the development of resistant populations is the High Dose / Refuge zone (HD/R) strategy. This pre-emptive strategy requires a refuge zone composed by non-Bt plants, usable by the target insect and in close proximity of the Bt zone synthesizing a high toxin concentration.<p><p>My research project contributes to the effectiveness assessment of this HD/R strategy. It is structured on two main parts: an experimental, and a theoretical section. The first part characterizes the impact of Cry toxins on the biology of an insect pest. It is the basis of the theoretical part: the implementation of a mathematical model, which evaluates the effectiveness of the HD/R strategy.<p>The originality of this project is based on the interactivity of these two components.<p><p>Experimental section. Impact of the Cry toxins on the biology of Plodia interpunctella. We assess the impact of a range of concentrations of two Cry toxins (CryXX et CryYY) on several behavioural and biological parameters of a common pest of stored products: Plodia interpunctella (Hübner) (Lepidoptera :Pyralidae). These parameters are selected because their variation could influence the effectiveness of a HD/R strategy. So, it is important to quantify these parameters so that realistic values can be integrated in our model. The results of the model are thus not based on theoretical assumptions alone.<p> <p>Theoretical section A. Effectiveness of a HD/R strategy with Bt plants synthesizing one or two toxins. Initially, the HD/R strategy has been developed to limit the resistance towards Bt plants synthesizing one toxin. However, since 2003, new Bt cotton varieties synthesize two toxins simultaneously (BollgardII® et WidestrikeTM). We assess, with our model, the effectiveness of this strategy for Bt plants synthesizing one or two toxins.<p><p>Theoretical section B. Impact of the slowing down of the insect development reared on Bt plants on the effectiveness of the HD/R strategy. The experimental part demonstrates that larvae reared on a Bt diet have a protracted development duration. The consequence of this is a temporal separation between adult emergence in the two zones (Bt zone and refuge zone). This could affect the main assumption of the HD/R strategy, i. e. random mating independently of the genotype and of the native zone. In this third chapter, we study the impact of random mating disruption on the effectiveness of a HD/R strategy. We test two options to optimise the strategy in case of asynchrony: the use of Bt plants synthesizing a lower toxin concentration (limiting emergence asynchrony) or increasing the refuge zone size (favouring the survival of insect carrying one or two susceptible allele and thus optimising the dilution of resistance at the next generation). <p><p>This work is applied to a current issue. It uses some of the tools of theoretical biology (theories of population dynamics and population genetics) and develops a mathematical model. It provides some responses and some elements of thought about insect resistance management. It is also an illustration of the complementarity between experimental and theoretical biology.<p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished
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