• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 352
  • 131
  • 86
  • 72
  • 25
  • 16
  • 12
  • 10
  • 9
  • 8
  • 5
  • 4
  • 3
  • 3
  • 3
  • Tagged with
  • 923
  • 527
  • 116
  • 99
  • 96
  • 89
  • 84
  • 68
  • 63
  • 62
  • 60
  • 49
  • 49
  • 46
  • 46
  • 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.
691

Avaliação da linhagem transgênica, OX3864A de Ceratitis capitata (Wied.,1824) (Diptera: Tephritidae), comparada à linhagem tsl Vienna 8, para aplicação na Técnica do Inseto Estéril / Evaluation of the RIDL transgenic lineage, OX3864A of Ceratitis capitata (Wied.,1824) (Diptera:Tephritidae), compared to tsl-Vienna 8 strain, for sterile insect technique purposes

Jair Fernandes Virginio 29 October 2015 (has links)
As moscas-das-frutas se constituem no maior obstáculo para a produção, processamento e comércio de frutas frescas em todo o mundo. O Brasil não é exceção e, embora as condições brasileiras sejam bastante adequadas à produção de frutas tropicais e temperadas, a fruticultura enfrenta, continuamente, o problema das moscas-das-frutas. Dentre as espécies de maior importância econômica e quarentenária, destaca-se a mosca-do-mediterrâneo Ceratitis capitata (Wied., 1824) que tem, como centro de origem, a África Equatorial, e é uma das pragas mais destrutivas, causando elevados prejuízos à fruticultura mundial. No Brasil, onde sua presença foi registrada no início do século passado, esta praga se encontra amplamente distribuída em todo o território nacional. Os processos integrados de controle de pragas e doenças, com emprego de controle biológico, monitoramento populacional da praga, sistema de informação geográfica e aplicação de técnicas de controle das populações têm se desenvolvido significativamente nos últimos anos, permitindo a obtenção de frutas de alta qualidade. Com o sucesso da aplicação da Técnica do Inseto Estéril (TIE) na erradicação da Cochliomyia hominivorax (Coquerel, 1858) da Ilha de Curaçao e da região Sudeste dos Estados Unidos, houve um estímulo para o uso de programa contra várias espécies de moscas-das-frutas. A necessidade de se buscar respostas para o uso de fontes alternativas na esterilização de insetos, notadamente o uso de raios X, em escala industrial e a busca de novos modelos que possam inovar desde o ponto de vista tecnológico a TIE, com métodos que dispensem, por completo, o uso de radiação ionizante é o desafio do presente estudo, que teve como objetivo avaliar, através de testes em laboratório e em gaiola de campo, a linhagem transgênica de Ceratitis capitata (Wied.), OX3864A, comparada à linhagem tsl Vienna 8 da mesma espécie, esterilizada por raios X, visando a sua possível aplicação em programas de controle de moscas-dasfrutas, com foco na TIE. Os resultados obtidos mostram que a criação massal da linhagem transgênica esta dominada e que a dieta adotada pela BIOFÁBRICA MOSCAMED BRASIL (BMB), para a linhagem tsl Vienna 8, pode ser usada para a criação da linhagem transgênica OX3864A sem afetar o rendimento e os padrões de qualidade requeridos para o uso da linhagem na TIE. No que diz respeito aos bioensaios em gaiola de campo, os machos de ambas linhagens apresentaram uma boa performance sexual sendo capazes de competir com machos coespécificos selvagens pela cópula com fêmeas selvagens virgens. O desempenho dos machos transgênicos OX3864A não deferiu do desempenho dos machos irradiados de tsl Vienna 8. A fim de aprofundar os estudos, necessário se faz a realização de novas pesquisas para avaliar o desempenho de linhagens transgênicas em campo aberto / Fruit flies are within the main barriers to fresh fruit production, processing and trade throughout the world. In that sense, Brazil is not an exception, and although Brazilian conditions are favorable to the production of tropical and temperate fruits, this industry continually faces problems related to the fruit fly. From an economical and quarantine point of view, Ceratitis capitata (Wied., 1824) can be considered the most important fruit fly specie, which has the Equatorial Africa as center of origin, is also one of the most destructive pests, causing high losses to the world fruit industry. In Brazil, where its presence has been first noticed in the beginning of the past century, nowadays this pest is widespread throughout the whole national territory. With the latest developments on biological control, pest monitoring, geographical information systems and application of population control techniques it is seen that the integrated pest management systems are allowing the production of high quality fruits. Since the successful application of the sterile insect technique on the eradication of Cochliomyia hominivorax (Coquerel, 1858) in Curaçao and in the US Southeast region, there has been an incentive to the use of this technique in programs against various fruit fly species. On the search for alternative sources for insect sterilization especially the use of X-ray in high scale and the search for new models able to innovate the sterile insect technique from a technological point of view with methods that exempt the use of ionizing irradiation is the challenge of the present study, whose aim was to evaluate through lab and field cage tests the transgenic OX3864A RIDL of Ceratitis capitata (Wied.) strain, compared to X-ray sterilized tsl Vienna 8 strain, looking for a possible application on fruit fly control programs focused on the Sterile Insect Technique (SIT). Results obtained show that the mass rearing of the transgenic strain is dominated and the diet adopted by MOSCAMED BRAZIL rearing facility, for tsl Vienna 8 can also be used for the OX3864A transgenic strain without affecting its yield and quality standards required for its use in SIT. Regarding the field cage bioassays, males from both strains presented a good sexual performance, being able to compete with wild co-specific to mate with virgin wild females. Transgenic males did not differ from irradiated tsl Vienna 8 males. Further studies on sexual performance evaluation on open field of transgenic strain is recommended in order to provide more knowledge
692

Adsorção de corantes aniônicos de solução aquosa em cinza leve de carvão e zeólita de cinza leve de carvão / Adsorption of anionic dyes from aqueous solutions onto coal fly ash and zeolite synthesized from coal fly ash

Terezinha Elizabeth Mendes de Carvalho 01 June 2010 (has links)
Cinza leve de carvão, resíduo gerado em usina termelétrica, foi usada para sintetizar zeólita por meio de tratamento hidrotérmico com solução de NaOH. A cinza leve (CL-2) e a zeólita sintética (ZM-2) que foi predominantemente identificada como hidroxi-sodalita foram utilizadas como adsorventes dos corantes aniônicos índigo carmina (IC) e reativo laranja 16 (RL16) de soluções aquosas. Nos processos de adsorção, os efeitos de tempo de contato, concentração inicial de corantes, pH, massa de adsorventes e temperatura foram avaliados. O estudo cinético de adsorção demonstrou que os resultados apresentaram melhor ajuste ao modelo de pseudo-segunda ordem e que adsorção de superfície e difusão intrapartícula participaram no mecanismo de adsorção. Os parâmetros termodinâmicos demonstraram que a adsorção foi espontânea em todos os processos de adsorção. Os processos de adsorção foram de natureza endotérmica para todos os sistemas, com exceção do sistema IC/ZM-2, em que foi exotérmico. Os dados de entropia mostraram a ocorrência do aumento da desordem na interface sólido/solução durante a adsorção em todos os sistemas, exceto novamente no IC/ZM-2, no qual se verificou a diminuição da desordem na interface. As isotermas de adsorção ajustaram-se à equação linear de Langmuir. As capacidades máximas de adsorção foram 1,48 mg/g para o sistema IC/CL-2; 1,13 mg/g para IC/ZM-2; 0,96 mg/g para RL16/CL-2 e 1,14 mg/g para RL16/ZM-2 à temperatura ambiente. O estudo de dessorção realizado com água, com soluções aquosas ácidas e com solução aquosa básica demonstrou ser ineficiente tanto para a recuperação dos corantes quanto para a regeneração dos adsorventes. / Coal fly ash, a waste generated in coal-fired electric power plant, was used to synthesize zeolite by hydrothermal treatment with NaOH solution. The fly ash (CL-2) and this synthesized zeolite (ZM-2) that was characterized as hydroxy-sodalite were used as adsorbents for anionic dyes indigo carmine (IC), and reactive orange 16 (RO16) from aqueous solutions. Effects of contact time, initial dye concentration, pH, adsorbent mass, and temperature were evaluated in the adsorption processes. The kinetics studies indicated that the adsorption followed the pseudo-second order kinetics and that surface adsorption and intraparticle diffusion were involved in the adsorption mechanism. The thermodynamics parameters demonstrated that the adsorption was spontaneous for all adsorption processes. The enthalpy data confirmed the endothermic nature for all adsorption processes except for IC/ZM-2 system which was exothermic. The entropy data showed an increased disorder at the solid/solution interface during the adsorption for all systems except for IC/ZM-2 whose negative entropy value indicated a decreased disorder at the interface. The adsorption isotherms were closely fitted to the Langmuir linear equation. The maximum adsorption capacities were 1.48 mg/g for the IC/CL-2 system; 1.13 mg/g for IC/ZM-2; 0.96 mg/g for RO16/CL-2, and 1.14 mg/g for RO16/ZM-2 at room temperature. The desorption study carried out with water, with acid aqueous solutions, and with an alkali aqueous solution showed to be inefficient both for recovering the dyes and regenerating the adsorbents.
693

Evaluating reactivity and sorptivity of fly ash for use in concrete construction

Islam, G. January 2012 (has links)
This thesis describes research carried out to investigate techniques for (i) rapidly assessing the reactivity of fly ash; and (ii) evaluating its interaction with air-entraining admixtures (AEAs), both with regard to use in concrete. The materials considered for the project included, 54 fly ashes from 8 UK sources, and an additional three materials from Bangladesh, covering a range of fineness, loss-on-ignition (LOI) and production conditions (run-of-station, carbon removed, air-classified, co-combustion, oxy-fuel technology); Portland Cements (PCs) from five UK sources with various properties (strength classes 32.5 R, 42.5 N and 52.5 N); laboratory grade hydrated and quick limes; and three commercial AEAs and a standard laboratory grade reagent (surfactant). The research examining fly ash reactivity considered activity index tests to BS EN 450 (BSI, 2005c) as the reference and investigated tests covering fly ash properties/providing measures of fly ash behaviour to rapidly assess this. These included (i) fly ash fineness (45 µm sieve residue, or LASER particle size distribution (PSD) parameters), LOI and flow properties; (ii) accelerated curing of PC and lime-based mortars (iii) lime consumption by fly ash when combined with PC in paste or suspension (Frattini) or from a saturated lime solution; (iv) various measures of fly ash chemical composition (based on oxide/mineralogical analysis); and (v) a quicklime slaking test. The test results were validated by strength tests with 100 mm concrete cube. Results of the above indicated good correlations between fly ash fineness, mortar flow/water requirement and (pozzolanic) activity index (standard or accelerated curing). However, fly ash reactivity and fresh properties appeared to be influenced by the properties of the test PC (e.g. chemical composition and fineness) and there is a need to take this into account during assessment. Generally, finer fly ashes gave better flow; however, there is an optimum fineness (d90 ~40 µm) for best performance, and which is similar to the fineness of the test PC. Strong correlations between the accelerated and standard cured PC-based mortar indicate the latter can be used to estimate the former taking account of the fly ash properties. In view of eliminating the effect of PC properties on reactivity, mortar tests with laboratory grade hydrated lime suggested potential for this. However, for better assessment, this approach requires further work to address issues relating to slower rates of strength gain and increased time requirements, although high temperature conditions were used for curing. Measuring Ca(OH)2 consumption from fly ash/PC paste or suspension agreed with the behaviour in mortar, but needs special instruments (e.g. TGA or XRF). A similar approach with saturated lime did not work well, despite several measures being taken to try and improve this. The oxide and mineralogical analysis results of fly ash did not give good correlations with activity index, but improved when a factor combining them with fineness was considered. The test results were validated in concrete and with air-classified fly ashes from single sources which gave clear trend/behaviour. The lime slaking test was found to be ineffective for identifying fly ash reactivity. The reactivity assessment results were validated by carrying out concrete strength tests. In general, more consistent trends were obtained for fly ash from single source as noted with mortar earlier. Methods adopted/developed to assess the interaction of fly ash with AEA included (i) the foam index test; (ii) acid blue 80 (AB80) dye adsorption test (spectroscopic method); and (iii) methylene blue test. High variability in foam index test results between different operators were noted, which reflected differences in the degree of shaking applied and difficulties in identification of the test end point. Adoption of an automatic shaker and determination of suitable test conditions reduced this by more than 50%. Reliable test procedures were also established for the AB80 dye adsorption method. The results obtained from these tests gave very good correlations with fly ash specific surface area and the AEA dose required (both with commercial AEAs and standard reagent) for achieving target air contents in mortar and concrete. The methylene blue dye test also gave good correlations with these parameters, but was less effective for low LOI fly ashes. Between laboratory tests were carried out at three UKQAA members and considered, LOI, fineness (45 µm sieve and LASER PSD), and activity index. The results gave good agreement with those obtained at the Concrete Technology Unit for this work and again emphasized the role of fly ash fineness on its reactivity. Overall, fly ash fineness was found to be the best means of rapidly assessing its reactivity. Some of the other methods considered gave promising behaviour but require further refinements. Therefore, it is suggested that in addition to 45 µm sieve residue, other types of fineness measurement (e.g. sub 10 µm quantities, d50 and d90) can be considered suitable alternatives to activity index. Similarly, foam index tests with the automatic shaker or the AB80 test method could both be used as fly ash physical requirement tests, or in production control for air-entrained concrete.
694

Análises morfométricas e moleculares de espécies de Doryctobracon Enderlein e Opius Wesmael (Hymenoptera: Braconidae), parasitóides de moscas-das-frutas (Diptera: Tephritidae) / Morphometric and molecular analysis of species of Doryctobracon Enderlein and Opius Wesmael (Hymenoptera: Braconidae), parasitoids of fruit flies (Diptera: Tephritidae)

Marinho, Cláudia Fidelis 06 April 2009 (has links)
Este trabalho teve por objetivo esclarecer a identidade de duas espécies próximas a Doryctobracon areolatus (Szépligeti) e de uma relacionada a Opius bellus Gahan, mencionada na literatura nacional como Opius sp. aff. bellus, por meio da morfometria geométrica e da análise das regiões do ITS2 do rDNA e 28S rDNA D2. As medidas das asas de D. areolatus, Doryctobracon sp. 1 e Doryctobracon sp. 2, O. bellus e Opius sp. aff. bellus, provenientes de diversas localidades brasileiras, foram estudadas por meio da morfometria geométrica. A avaliação de 20 pontos anatômicos nas asas, por meio de análise multivariada revelou a existência de variabilidade interpopulacional em 11 populações de D. areolatus, provenientes de localidades das cinco regiões brasileiras. O estudo morfométrico ainda revelou que Doryctobracon sp. 1 (estigma claro) e Doryctobracon sp. 2 (estigma escuro) diferem entre si e também de D. areolatus (Szépligeti). No entanto, entre os espécimes de O. bellus Gahan e Opius sp. aff. bellus, os resultados apontaram a coespecificidade desses indivíduos. Com base no tamanho do centróide, os resultados apontam a existência de dimorfismo sexual em relação ao tamanho das asas, ou seja, as fêmeas possuem asas relativamente maiores que as dos machos. Nas análises moleculares, os resultados indicaram a ocorrência de variabilidade intraespecífica, com relação ao tamanho do fragmento entre as populações de D. areolatus provenientes dos estados do AP, SP, GO e TO com a utilização dos dois marcadores moleculares (ITS2 e 28S rDNA D2). Porém, entre os espécimes de Doryctobracon sp. 1 (estigma claro) e de Doryctobracon sp. 2 (estigma escuro), essas regiões não variaram quanto ao tamanho, mas diferiram na composição das sequências, revelando que correspondem realmente a duas espécies. Portanto, houve congruência entre os resultados morfométricos e moleculares para essas espécies de Doryctobracon. Entre os espécimes identificados como Opius bellus e Opius sp. aff. bellus, a região do ITS2 indicou a ocorrência de variabilidade intrapopulacional, semelhante à interpopulacional, com elevada similaridade entre as morfoespécies analisadas. No entanto, a região do 28S rDNA D2 apresentou elevada similaridade entre as sequências obtidas, fortalecendo as indicações de que os espécimes considerados como O. bellus Gahan e Opius sp. aff. bellus, na realidade, pertencem à uma única espécie, conclusão também sustentada pelas análises morfométricas. / This study aimed to elucidate the identity of two-closely related species of Doryctobracon areolatus (Szépligeti) and a closely related species of Opius bellus Gahan, commonly referred to as Opius sp. aff. bellus, by using geometric morphometry and molecular analysis (ITS2 rDNA and 28S rDNA D2 regions). The analysis based on 20 landmarks through the multivariate analysis (CVA) revealed the existence of interpopulation variability in the wing morphology of 11 populations of D. areolatus, from five Brazilian regions. The morphometric study also showed that specimens of Doryctobracon sp. 1 (clear stigma) and Doryctobracon sp. 2 (dark stigma) were distinct between themselves and also from D. areolatus (Szépligeti). However, specimens of O. bellus Gahan and Opius sp. aff. bellus were found to be cospecifics. Analysis based on the centroid size indicated the existence of sexual dimorphism in relation to the size of the wings, ie, females had relatively larger wings than males. The molecular analysis indicated intraspecific variability in the size of the fragment between populations of D. areolatus from Amapá, São Paulo, Goiás and Tocantins states for both of the molecular markers used (ITS2 and 28S D2 rDNA). But these markers had similar sizes for Doryctobracon sp. 1 (stigma clearly) and Doryctobracon sp. 2 (dark stigma), with a very different base composition, indicating the existence of two distinctive species. Both molecular and morphometric analysis gave similar results. Among the specimens identified as Opius bellus and Opius sp. aff. bellus, analysis of the ITS2 region indicated the intrapopulation variability was similar to the interpopulation, with high similarity between the morphospecies analyzed. However, the region of the 28S D2 rDNA showed high similarity between the sequences obtained, reinforcing the indication that the specimens taken as O. bellus Gahan and Opius sp. aff. bellus in fact, belong to the same species, which was also supported by morphometric analysis.
695

Avaliação da linhagem transgênica, OX3864A de Ceratitis capitata (Wied.,1824) (Diptera: Tephritidae), comparada à linhagem tsl Vienna 8, para aplicação na Técnica do Inseto Estéril / Evaluation of the RIDL transgenic lineage, OX3864A of Ceratitis capitata (Wied.,1824) (Diptera:Tephritidae), compared to tsl-Vienna 8 strain, for sterile insect technique purposes

Virginio, Jair Fernandes 29 October 2015 (has links)
As moscas-das-frutas se constituem no maior obstáculo para a produção, processamento e comércio de frutas frescas em todo o mundo. O Brasil não é exceção e, embora as condições brasileiras sejam bastante adequadas à produção de frutas tropicais e temperadas, a fruticultura enfrenta, continuamente, o problema das moscas-das-frutas. Dentre as espécies de maior importância econômica e quarentenária, destaca-se a mosca-do-mediterrâneo Ceratitis capitata (Wied., 1824) que tem, como centro de origem, a África Equatorial, e é uma das pragas mais destrutivas, causando elevados prejuízos à fruticultura mundial. No Brasil, onde sua presença foi registrada no início do século passado, esta praga se encontra amplamente distribuída em todo o território nacional. Os processos integrados de controle de pragas e doenças, com emprego de controle biológico, monitoramento populacional da praga, sistema de informação geográfica e aplicação de técnicas de controle das populações têm se desenvolvido significativamente nos últimos anos, permitindo a obtenção de frutas de alta qualidade. Com o sucesso da aplicação da Técnica do Inseto Estéril (TIE) na erradicação da Cochliomyia hominivorax (Coquerel, 1858) da Ilha de Curaçao e da região Sudeste dos Estados Unidos, houve um estímulo para o uso de programa contra várias espécies de moscas-das-frutas. A necessidade de se buscar respostas para o uso de fontes alternativas na esterilização de insetos, notadamente o uso de raios X, em escala industrial e a busca de novos modelos que possam inovar desde o ponto de vista tecnológico a TIE, com métodos que dispensem, por completo, o uso de radiação ionizante é o desafio do presente estudo, que teve como objetivo avaliar, através de testes em laboratório e em gaiola de campo, a linhagem transgênica de Ceratitis capitata (Wied.), OX3864A, comparada à linhagem tsl Vienna 8 da mesma espécie, esterilizada por raios X, visando a sua possível aplicação em programas de controle de moscas-dasfrutas, com foco na TIE. Os resultados obtidos mostram que a criação massal da linhagem transgênica esta dominada e que a dieta adotada pela BIOFÁBRICA MOSCAMED BRASIL (BMB), para a linhagem tsl Vienna 8, pode ser usada para a criação da linhagem transgênica OX3864A sem afetar o rendimento e os padrões de qualidade requeridos para o uso da linhagem na TIE. No que diz respeito aos bioensaios em gaiola de campo, os machos de ambas linhagens apresentaram uma boa performance sexual sendo capazes de competir com machos coespécificos selvagens pela cópula com fêmeas selvagens virgens. O desempenho dos machos transgênicos OX3864A não deferiu do desempenho dos machos irradiados de tsl Vienna 8. A fim de aprofundar os estudos, necessário se faz a realização de novas pesquisas para avaliar o desempenho de linhagens transgênicas em campo aberto / Fruit flies are within the main barriers to fresh fruit production, processing and trade throughout the world. In that sense, Brazil is not an exception, and although Brazilian conditions are favorable to the production of tropical and temperate fruits, this industry continually faces problems related to the fruit fly. From an economical and quarantine point of view, Ceratitis capitata (Wied., 1824) can be considered the most important fruit fly specie, which has the Equatorial Africa as center of origin, is also one of the most destructive pests, causing high losses to the world fruit industry. In Brazil, where its presence has been first noticed in the beginning of the past century, nowadays this pest is widespread throughout the whole national territory. With the latest developments on biological control, pest monitoring, geographical information systems and application of population control techniques it is seen that the integrated pest management systems are allowing the production of high quality fruits. Since the successful application of the sterile insect technique on the eradication of Cochliomyia hominivorax (Coquerel, 1858) in Curaçao and in the US Southeast region, there has been an incentive to the use of this technique in programs against various fruit fly species. On the search for alternative sources for insect sterilization especially the use of X-ray in high scale and the search for new models able to innovate the sterile insect technique from a technological point of view with methods that exempt the use of ionizing irradiation is the challenge of the present study, whose aim was to evaluate through lab and field cage tests the transgenic OX3864A RIDL of Ceratitis capitata (Wied.) strain, compared to X-ray sterilized tsl Vienna 8 strain, looking for a possible application on fruit fly control programs focused on the Sterile Insect Technique (SIT). Results obtained show that the mass rearing of the transgenic strain is dominated and the diet adopted by MOSCAMED BRAZIL rearing facility, for tsl Vienna 8 can also be used for the OX3864A transgenic strain without affecting its yield and quality standards required for its use in SIT. Regarding the field cage bioassays, males from both strains presented a good sexual performance, being able to compete with wild co-specific to mate with virgin wild females. Transgenic males did not differ from irradiated tsl Vienna 8 males. Further studies on sexual performance evaluation on open field of transgenic strain is recommended in order to provide more knowledge
696

Adaptation à la volée de situations d'apprentissage modélisées conformément à un langage de modélisation pédagogique / Adapt on the fly learning situations modeled according to a pedagocical modeling language

Ouari, Salim 25 November 2011 (has links)
Le travail présenté dans ce mémoire s'inscrit dans le domaine des Environnements Informatiques pour l'Apprentissage Humain (EIAH), plus précisément celui de l'ingénierie des EIAH dans le cadre d'une approche de type « Learning Design ». Cette approche propose de construire des EIAH à partir de la description formelle d'une activité d'apprentissage. Elle suppose l'existence d'un langage de modélisation communément appelé EML (Educational Modelling Language) et d'un moteur capable d'interpréter ce langage. LDL est le langage sur lequel nous avons travaillé, en relation avec l'infrastructure LDI intégrant un moteur d'interprétation de LDL. L'EML est utilisé pour produire un scénario, modèle formel d'une activité d'apprentissage. L'EIAH servant de support au déroulement de l'activité décrite dans le scénario est alors construit de manière semi-automatique au sein de l'infrastructure associée au langage selon le processus suivant : le scénario est créé lors d'une phase de conception ; il est instancié et déployé sur une plate-forme de services lors d'une phase d'opérationnalisation (choix des participants à l'activité, affectation des rôles, choix des ressources et services) ; le scénario instancié et déployé est pris en charge par le moteur qui va l'interpréter pour en assurer l'exécution. Dans ce cadre, l'activité se déroule conformément à ce qui a été spécifié dans le scénario. Or il est impossible de prévoir par avance tout ce qui peut se produire dans une activité, les activités étant par nature imprévisibles. Des situations non prévues peuvent survenir et conduire à des perturbations dans l'activité, voire à des blocages. Il devient alors primordial de fournir les moyens de débloquer la situation. L'enseignant peut par ailleurs vouloir exploiter une situation ou une opportunité en modifiant l'activité en cours d'exécution. C'est le problème qui est traité dans cette thèse : il s'agit de fournir les moyens d'adapter une activité « à la volée », c'est-à-dire pendant son exécution, de manière à pouvoir gérer une situation non prévue et poursuivre l'activité. La proposition que nous formulons s'appuie sur la différentiation entre les données convoquées dans chacune des trois phases du processus de construction de l'EIAH : la conception, l'opérationnalisation et l'exécution. Nous exhibons un modèle pour chacune de ces phases, qui organise ces données et les positionne les unes par rapport aux autres. Adapter une activité « à la volée » revient alors à modifier ces modèles en fonction des situations à traiter. Certaines nécessitent la modification d'un seul de ses modèles, d'autres conduisent à propager les modifications d'un modèle vers un autre. Nous considérons l'adaptation « à la volée » comme une activité à part entière menée, en parallèle de l'activité d'apprentissage, par un superviseur humain qui dispose d'un environnement adéquat pour observer l'activité, détecter les éventuels problèmes et y remédier par intervention dans l'activité d'apprentissage en modifiant les modèles qui la spécifient. Pour développer les outils support à la modification et les intégrer dans l'infrastructure LDI, nous avons eu recours à des techniques de l'Ingénierie Dirigée par les Modèles. Les modèles manipulés dans ces outils en sont ainsi des données à part entière : les outils réalisés n'en offrent ainsi que plus de flexibilité et d'abstraction. Les modèles sont alors exploités comme des leviers pour atteindre et modifier les données ciblées par l'adaptation. / The work presented in this paper is in the field of Technology for Human Learning (TEL), specifically that of engineering in the context of TEL-type approach "Learning Design". This approach proposes to build ILE from the formal description of a learning activity. It assumes the existence of a common modeling language called EML (Educational Modelling Language) and an engine capable of interpreting this language. LDL is the language on which we worked in conjunction with the LDI infrastructure including a motor interpretation of LDL. The EML is used to produce a scenario, a formal model of learning activity. The ILE serving to support the conduct of the activity described in the scenario is then constructed semi-automatically in the infrastructure associated with the language using the following process: the script is created during a design phase; it is instantiated and deployed on a platform of services in an operational phase (selection of participants in the activity, role assignment, choice of resources and services); instantiated and deployed scenario is supported by the engine will interpret it to ensure its implementation. In this context, the activity takes place in accordance with what was specified in the script. It is impossible to predict in advance all that can occur in an activity, the activities are by nature unpredictable. Unforeseen situations can occur and lead to disturbances in the activity, or even blocks. It then becomes important to provide the means to break the deadlock. The teacher may also want to exploit a situation or opportunity by altering the activity in progress. This is the problem that is addressed in this thesis: to provide the means to adapt an activity "on the fly", that is to say while running, so you can not handle a situation provided and continue the activity. The proposal we make is based on the differentiation between data convened in each of the three phases of construction of the ILE: design, operationalization and implementation. We exhibit a model for each phase, which organizes the data and positions to each other. Adapt an activity "on the fly" then returns to modify these models in different situations to deal with. Some require the modification of one of its models, while others lead to propagate changes from one model to another. We consider adaptation "on the fly" as a separate activity conducted in parallel with the learning activity by a human supervisor has an adequate environment to observe the activity, identify potential problems and be remedied by intervention in the learning activity by modifying the templates that specify. To develop tools to support the change and integrate them into the LDI infrastructure, we have used the techniques of Model Driven Engineering. Handled in these models are tools and data in its own right tools and made no offer more flexibility and abstraction. The models are then used as levers to achieve and change the data targeted by the adaptation.
697

RNAi-mediated knockdown of chromatin modifier proteins and their effect on long-term memory in Drosophila : a thesis presented to Massey University in partial fulfillment of the requirements for the degree of Master of Science in Genetics

Ellen, Charles January 2008 (has links)
Memory formation in Drosophila melanogaster is composed of two pathways that are genetically distinct, and functionally independent of each other. These are short-term and long-term memory. Short-term memory is a transient phenomenon, located in the cytoplasm of the neuronal cells, which requires no alteration of gene expression. The formation of long-term memory requires a change in gene expression, therefore chromatin-modifying complexes may play an integral part. The mushroom-bodies of Drosophila are a distinct bilateral brain structure and are essential for the formation and recollection of long-term memory. Therefore, an alteration in gene expression within the mushroom bodies is essential to the formation of long-term memory. Disruption of a gene within the mushroom-bodies that resulted in an alteration in the formation of long-term memory would indicate that the gene is involved in long-term memory. In order to investigate the role of the two chromatin-modifying proteins, HDACX and pr-Set7, whose role in memory function is unknown, RNA interference was used to knockdown expression of their respective mRNA. Published GAL4 lines were used to drive down expression in the mushroom bodies. The efficacy of the knockdown on levels of mRNA was measured by quantitative RT-PCR. The effect of these knockdowns on the formation of long-term memory was assayed using conditioned courtship. Additionally, the actual spatial and temporal expression of the GAL4 drivers was investigated using fluorescent proteins, and analysed using fluorescent microscopy. Both pr-set7 and HDACX appear to play a role in long-term memory function. The RNAi-induced knockdown of the individual mRNAs caused impairment in long-term memory formation, although the exact mode of action is still to be elucidated. The levels of mRNA from these knockdowns were reduced within the head, although not to the extent expected. The fluorescent microscopy analysis indicated that the expression of mushroom-body specific GAL4 drivers was more widespread than previously reported.
698

The Autecology of Bactrocera cacuminata (Hering) (Diptera:Tephritidae:Dacinae): Functional Significance of Resources

Raghu, Sathyamurthy, n/a January 2003 (has links)
This thesis investigated the autecology of the dacine species, Bactrocera cacuminata (Hering) (Diptera: Tephritidae: Dacinae). I specifically focused on the adult phase of the life cycle and resources believed to be significant to this life stage. The prevailing paradigm in dacine ecology predicts that the larval host plant serves as the centre of dacine activity, a state mediated by mutualistic associations with fruit fly-type bacteria. Contrary to predictions, an explicit test of this hypothesis found that the host plant of B. cacuminata, Solanum mauritianum Scopoli, acted almost exclusively as a site for oviposition and larval development. Other key adult behaviours, most notably feeding and mating, were rare at the host plant. Even in disturbed habitats, the paucity of key adult behaviours such as mating was striking. Adult flies of this species were therefore hypothesized to be utilizing other components of their habitat, i.e. resources vital to their life history requirements. Some of the resources that B. cacuminata are known to respond to include sugar, protein, methyl eugenol and the host plant. The latter three resources are believed to be critical in the reproductive success of dacine flies in general. I assessed the physiological status of flies arriving at these resources to determine if flies of different status foraged for resources differently. In dacines, the internal reproductive structures of the male and female flies have been used as predictors of physiological status. I quantified expansion of the male ejaculatory apodeme in B. cacuminata with age of fly and found that there is a threshold apodeme size that is strongly correlated Abstract with sexual maturity. Maturity of female flies could be accurately predicted by ovarian development. Using these methods to assess the physiological and nutritional status of flies arriving at resources (larval host plant, protein and methyl eugenol) in the field, I discovered that only sexually mature and mated females were responding to the host plant, while the males at the host plant were sexually immature. This confirmed the hypothesis that the host plant primarily served as an oviposition site. Additionally, this study revealed that sexually mature males with high nutritional reserves were most commonly collected at methyl eugenol (a plant-derived chemical that elicits a strong response in males of many dacine species) at dusk, the time of peak sexual activity in this species. This indicated that methyl eugenol was perhaps a significant resource in the context of the reproductive behaviour of this species. Methyl eugenol (ME) is one of group of phenyl propanoids to which males of certain species of Dacinae respond. The current hypothesis of the role of these phenyl propanoids is that they function as pheromone precursor chemicals. Response to these chemicals is hypothesized to be a trait under sexual selection. In Bactrocera dorsalis (Hendel), this effect is so strong that a single feeding on ME results in a strong mating advantage up to a month after males feed on the chemical. Bactrocera cacuminata fed on multiple occasions on ME in a laboratory bioassay. After a single 24-hour exposure to ME, investigations of mating competitiveness did not reveal any obvious advantage for ME-fed males over unfed males. However, ME-fed males did enjoy a higher mating success 16 and 32 days after exposure to the chemical, suggesting that some physiological benefits unrelated to the pheromone synthesis was driving this delayed advantage. Investigation of the physiological consequences of feeding on ME revealed no enhancement of nutritional or energetic reserves, suggesting that the delayed mating advantage observed was more likely a chance event. An alternate hypothesis about the proximate function of ME, proposed by Robert Metcalf, is that it serves as a mate rendezvous site. As mating behaviour was notably absent at the host plant, I tested Metcalf’s hypothesis. A field-cage experiment, spatially separating adult resources (host plant, methyl eugenol, sugar and protein) clearly demonstrated that methyl eugenol was functioning as a mate rendezvous stimulus for B. cacuminata. This is the first direct support for Metcalf’s hypothesis. A synthesis of the literature revealed that significantly greater ecological and evolutionary information was required to understand the basis of dacine response to phenyl propanoids. Different dacine species may be utilizing these chemicals differently, even if their evolutionary origin may have been as a plant based kairomone. My studies show that generalizations on the ecology and behaviour of Dacinae, often extrapolated from research on a few pest species, do not hold up in the case of B. cacuminata. This suggests that a more autecological, species-specific approach is required in dacine research, before any predictive generalizations can be made.
699

Environmental levels of thallium : Influence of redox properties and anthropogenic sources

Karlsson, Ulrika January 2006 (has links)
<p>Thallium is a highly toxic element that humans are exposed to mainly by consumption of drinking water and vegetables grown in soil with high thallium content but also through inhalation of particles in the air. Thallium is also present in fossil fuels, alloys, and in electronic utilities. The increasing use of the element and emissions from notably energy production has lead to a higher load on the surface of the Earth. This study aims at increasing the knowledge about the behaviour of thallium in aquatic environments. Focus has been on the redox chemistry of thallium in relation to its mobility, which is of great importance because Tl(I) and Tl(III) have very different properties in this respect.</p><p>The relationship between Tl(I) and Tl(III) in surface waters from contaminated and uncontaminated environments was examined by ion chromatography connected on line to ICP-MS (inductively coupled plasma mass spectrometry). It was found in controlled systems that even though Tl(III) is thermodynamically unstable under fresh water conditions Tl(I) was oxidised in the presence of light and iron(III). This was also confirmed in field studies. When lake water samples were exposed to light, Tl(I) was oxidised and thallium was lost from the solution. The most likely explanation for this was adsorption of thallium to particle surfaces.</p><p>The concentration of thallium in Swedish lakes and soil were measured. In unpolluted lakes the concentration ranges between 4.5-12 ng/l, the sediment concentration was 0.07-1.46 mg/kg. The anthropogenic load was found to have increased since the end of the Second World War although concentrations above background were found since the early industrialisation. In contaminated areas the concentration in soil ranges from 0.64-88 mg/kg, high concentrations were found in systems with alum shale and in soil exposed to runoff from a lead and zinc enrichment plant.</p><p>The mobilisation of thallium from solid phases in contaminated areas was dependent on pH and about 50% of the leachable content was mobilised already at pH 5-6. Once it had been released to water it was highly mobile. These conditions suggest that in a large part of the Swedish environment a high mobility of thallium can be expected.</p>
700

Trace analysis of dioxins and dioxin-like PCBs using comprehensive two-dimensional gas chromatography with electron capture detection

Danielsson, Conny January 2006 (has links)
Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), two groups of struc-turally related chlorinated aromatic hydrocarbons, generally referred to as “dioxins” are of great concern due to their extreme toxicity and presence in all compartments of the environment. Since they occur at very low levels, their analysis is complex and challenging, and there is a need for cost-efficient, reliable and rapid analytical alternatives to the expensive methods in-volving use of gas chromatography high-resolution mass spectrometry (GC-HRMS). It is im-portant to routinely monitor food and feed items to detect contaminations at an early stage. For the regulation of dioxins and dioxin-like PCBs in food and feed according to current legis-lation, large numbers of samples have to be analysed. Furthermore, soils at many industrial sites are also contaminated with dioxins and need remediation. In order to optimize the cost-efficiency of reclamation activities it is important to acquire information about the levels and distribution of dioxins in the contaminated areas. The aim of the studies underlying this thesis was to investigate the potential of comprehen-sive two-dimensional gas chromatography with a micro-electron capture detector (GC × GC-µECD) as a cost-effective method for analysing dioxins and dioxin-like PCBs in food, feed, fly ash and contaminated soils. Quantification studies of dioxins and dioxin-like PCBs were con-ducted and results were compared with GC-HRMS reference data. Generally, there was good agreement between both the congener-specific results and data expressed as total toxic equiva-lents (TEQs). The developed GC × GC-µECD method meets the European Community (EC) requirements for screening methods for control of dioxins and dioxin-like PCBs in food and feed. The presented results also indicate that GC × GC-µECD has potential to be used as a routine method for the congener-specific analysis of 2,3,7,8-PCDD/Fs and dioxin-like PCBs in matrices such as food and feed, fly ash and soil. However, to fully exploit the potential of the GC × GC-µECD technique, it should be combined with a fast and cost-efficient sample preparation procedure. Therefore, a number of certified reference materials (CRMs) were extracted using a new shape-selective pressurized liquid extraction technique with integrated carbon fractionation (PLE-C), and the purified extracts were analysed for PCDD/Fs using GC × GC-µECD. The results compared well with the certified values of a fly ash and a sandy soil CRM, but they were much too high for a com-plex clay soil CRM. It was concluded that this combination of techniques was very promising for screening ash and highly permeable soils. Further assessments and method revisions are still required before GC × GC-µECD can be used on a routine basis, and available software packages need to be refined in order to accelerate the data-handling procedures, which currently restrict the sample throughput.

Page generated in 0.0489 seconds