Neste trabalho foram soldadas 4 amostras de rodas para veículos comerciais pelo processo de soldagem Tandem-MIG. Para cada amostra foram utilizados parâmetros de soldagem diferentes de modo a se obter formatos de cordão de solda distintos. O objetivo do trabalho foi avaliar a influência desses formatos de cordão de solda no desempenho em fadiga. Para os materiais utilizados, SAE1010AA e SAE1015A, foram realizados os seguintes ensaios: análise de composição química, análise micrográfica, levantamento das curvas tensão x deformação, medidas de microdureza Vickers e levantamento das curvas SN pelo método de flexão alternada (R=-1). Através da composição química constatou-se que ambos os aços são de baixo carbono e atendem o especificado pela norma SAEJ403. Através da análise micrográfica foi verificado que as fases presentes foram ferrita e perlita, e o tamanho médio de grão foi de 11,2 ?m para os dois materiais. O aço SAE1010AA apresentou limite de escoamento médio de 265,2 MPa, limite de resistência de 384,8 MPa e alongamento médio de 43,9%. Já o aço SAE1015AA apresentou limite de escoamento médio de 260,1 MPa, limite de resistência de 407,3 MPa e alongamento de 41,9%. Para os dois materiais, o limite de resistência à fadiga (2.10-6 ciclos) foi de 225 MPa. Foi realizada a caracterização das 4 amostras soldadas. Através das curvas SN observou-se que o limite de resistência à fadiga para as amostras soldadas apresentou redução para valores entre 180 e 160 MPa. Com os mapas de microdureza Vickers levantados foi possível perceber as diferenças de microdureza obtidas de acordo com os parâmetros de soldagem utilizados e consequentemente com as microestruturas formadas. Com as imagens obtidas na análise micrográfica observou-se a formação de microestruturas com formatos e tamanhos diversos tanto nas regiões da zona termicamente afetada das amostras como na região de solidificação do cordão de solda. Finalmente, com a realização da análise via MEV, constatou-se que todas as trincas por fadiga iniciaram na superfície dos corpos de prova. Foram observadas estrias de fadiga, com maior e menor intensidade de acordo com cada amostra, ao longo da região de fratura. Além disso, foi observada a geração de múltiplas trincas por fadiga em duas amostras. / In this study four samples of commercial vehicle wheels were welded using the Tandem-MIG process. For each sample different welding parameters were used to get different kinds of weld bead shape. The aim of this study was to evaluate the influence of these weld bead shapes in fatigue performance. For the SAE1010AA and SAE1015AA materials the following tests were performed: chemical composition analysis, microstructure characterization, SN curves by alternating bending method (R=-1). Through analyzing chemical composition, it was found that both materials are low carbon steel and they meet the SAE J403 standard. In microstructure characterization, ferrite and perlite microstructure were found, with an average grain size of 11,2 ?m for both steels. The SAE1010AA showed an average yield strength of 265,2 MPa, an average tensile strength of 384,8 MPa, and alongation of 43,9%. The SAE1015AA showed an average yield strength of 260,1 MPa, an average tensile strength of 407,3 MPa, and alongation of 41,9%. For both materials, the fatigue limit (2.10-6 ciclos) was 225 MPa. The characterization of the four samples was done. In SN curves the fatigue limit for welded samples showed a reduction to values of between 180 and 160 MPa. In the Vickers microhardness test, it was possible to notice the differences between the microhardness obtained in accordance with welding parameters used and, consequently, the microstructure formed. In microstructure analysis, different kinds and sizes of microstructure were observed to have formed in both the heat-affected zone and the welded zone. Finally, through MEV analysis, all fatigue cracks were seen to have begun on the surface of the samples. Fatigue estriaton, with major and minor intensity depending on the sample, was observed along the fracture region. Furthermore, the beginning of multiple fatigue cracks were seen in two samples.

O relevante conceito de sustentabilidade dos dias atuais leva a população a pensar no tratamento dos recursos naturais e principalmente na qualidade e escassez da água. A grave problemática quanto à gestão dos resíduos urbanos no país, desde sua produção, coleta e disposição final são os desafios colocado aos municípios e a sociedade em geral. O uso cada vez mais abundante dos medicamentos farmacêuticos gera uma demanda de resíduos que acabam atingindo os leitos dos rios. Com avanço das tecnologias é possível monitorar e conhecer os resíduos que afetam indiretamente e diretamente as águas das bacias hidrográficas. O objetivo deste trabalho foi desenvolver e validar uma metodologia analítica para a determinação dos resíduos de fármacos (ácido acetil salicílico, diclorofenaco de sódio, paracetamol, ibuprofeno e fenoprofeno) em águas utilizando a cromatografia líquida de ultra performance acoplada à espectrometria de massas tipo tandem (UPLC-MS/MS). Foram utilizadas duas fases moveis distintas. Para os fármacos paracetamol e diclofenaco foi utilizado como fase móvel água: metanol (1:1; V/V) com adição de ácido fórmico e a ionização de eletrospray em modo positivo; para os fármacos acetil salicílico, ibuprofeno e fenoprofeno foi utilizado água: metanol (1:1; v/v) com adição de acetato de amônio e a ionização de eletrospray em modo negativo. O desempenho do método foi avaliado quanto aos seguintes parâmetros: especificidade e seletividade, faixa de trabalho, linearidade; limite de detecção e limite de quantificação, exatidão, robustez e incerteza de medição. Os resultados obtidos comprovaram a adequabilidade do método ao propósito supracitado. Os valores obtidos para o limite de decisão (ccα) e capabilidade de detecção (ccβ) foram: paracetamol 0,21 e 0,34 μg L -1; diclofenaco 2,42 e 3,24 μg L -1 ; AAS 1,56 e 2,45 μg L -1; ibuprofeno 2,34 e 3,21 μg L -1 e fenoprofeno 1,89 e 2,33 μg L-1, respectivamente. A metodologia foi aplicada na caracterização de amostras de água superficial (bruta) e tratada proveniente de áreas de captação e de tratamento de água da bacia hidrográfica do Paraíba do Sul. Foram realizadas duas coletas distintas, setembro/ 2010 e novembro/ 2010, nos municípios de Guararema, São José dos Campos, Taubaté e Pindamonhangaba. Em 31,2 % das amostras, Cinco amostras de água bruta das 16 amostras analisadas, foram encontrados resíduos de paracetamol. Os resultados obtidos apresentaram-se em uma faixa de concentração de 0,10 a 0,50 μg L -1. / The relevant concept of sustainability of the present day leads people to think about the treatment of natural resources and particularly in the quanlity and scarcity of water. The serious problems regarding the management of municipal waste in the country, from production, collection and disposal are the challenges facing municipalities and society in general. The increasing use of pharmaceutical drugs most abundant generates a demand for waste that eventually reach the river beds. With advancement of technologies and know you can monitor the waste that directly and indirectly affect the waters of river basins. The objective of this study was to develop and validade analytical methods for residues of drugs (aspirin, sodium diclofenac, paracetamol, ibuprofen and fenoprofen) in water using ultra performance liquida chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). We used two different mobile phases. For the drugs paracetamol and diclofenac was used as mobile phase water:methanol (1:1, v/v) with addition of formic acid in positive electrospray ionization mode. For drugs acetyl salicylic acid, ibuprofen and fenoprofen was used mobile phase water:methanol (1:1, v/v) with addition of ammonium acetate and negative electrospray ionization mode. The performance of the method was evaluated on the following parameters: specificity and selectivity, working range, lineariry, limit of detection and limit of quantification, accuracy, ruggedness and uncertainty measurement. The result obtained proved the suitability of the method for fit purpose. The values obtained for the decision limit (ccα) and detection capability (ccβ) were 0.21 and 0.34 μg L-1, diclofenac 2.42 and 3.24 μgL-1, ASA 1.56 and 2.45 μgL-1, respectively. The methodology was applied in the characterization of samples of surface water (raw) and treated from catchment areas and water treatment basin of Paraíba do sul were two distinct collections, September/2011 and November 2010 in the municipalities of Guararema, São José dos Campos, Taubaté and Pindamonhangaba. In 32,2% of all samples, five samples of 16 raw water samples, residues were found for paracetamol. The results were presented in a concentration range from 0.10 to 0.50 μg L-1.

Neste trabalho foram soldadas 4 amostras de rodas para veículos comerciais pelo processo de soldagem Tandem-MIG. Para cada amostra foram utilizados parâmetros de soldagem diferentes de modo a se obter formatos de cordão de solda distintos. O objetivo do trabalho foi avaliar a influência desses formatos de cordão de solda no desempenho em fadiga. Para os materiais utilizados, SAE1010AA e SAE1015A, foram realizados os seguintes ensaios: análise de composição química, análise micrográfica, levantamento das curvas tensão x deformação, medidas de microdureza Vickers e levantamento das curvas SN pelo método de flexão alternada (R=-1). Através da composição química constatou-se que ambos os aços são de baixo carbono e atendem o especificado pela norma SAEJ403. Através da análise micrográfica foi verificado que as fases presentes foram ferrita e perlita, e o tamanho médio de grão foi de 11,2 ?m para os dois materiais. O aço SAE1010AA apresentou limite de escoamento médio de 265,2 MPa, limite de resistência de 384,8 MPa e alongamento médio de 43,9%. Já o aço SAE1015AA apresentou limite de escoamento médio de 260,1 MPa, limite de resistência de 407,3 MPa e alongamento de 41,9%. Para os dois materiais, o limite de resistência à fadiga (2.10-6 ciclos) foi de 225 MPa. Foi realizada a caracterização das 4 amostras soldadas. Através das curvas SN observou-se que o limite de resistência à fadiga para as amostras soldadas apresentou redução para valores entre 180 e 160 MPa. Com os mapas de microdureza Vickers levantados foi possível perceber as diferenças de microdureza obtidas de acordo com os parâmetros de soldagem utilizados e consequentemente com as microestruturas formadas. Com as imagens obtidas na análise micrográfica observou-se a formação de microestruturas com formatos e tamanhos diversos tanto nas regiões da zona termicamente afetada das amostras como na região de solidificação do cordão de solda. Finalmente, com a realização da análise via MEV, constatou-se que todas as trincas por fadiga iniciaram na superfície dos corpos de prova. Foram observadas estrias de fadiga, com maior e menor intensidade de acordo com cada amostra, ao longo da região de fratura. Além disso, foi observada a geração de múltiplas trincas por fadiga em duas amostras. / In this study four samples of commercial vehicle wheels were welded using the Tandem-MIG process. For each sample different welding parameters were used to get different kinds of weld bead shape. The aim of this study was to evaluate the influence of these weld bead shapes in fatigue performance. For the SAE1010AA and SAE1015AA materials the following tests were performed: chemical composition analysis, microstructure characterization, SN curves by alternating bending method (R=-1). Through analyzing chemical composition, it was found that both materials are low carbon steel and they meet the SAE J403 standard. In microstructure characterization, ferrite and perlite microstructure were found, with an average grain size of 11,2 ?m for both steels. The SAE1010AA showed an average yield strength of 265,2 MPa, an average tensile strength of 384,8 MPa, and alongation of 43,9%. The SAE1015AA showed an average yield strength of 260,1 MPa, an average tensile strength of 407,3 MPa, and alongation of 41,9%. For both materials, the fatigue limit (2.10-6 ciclos) was 225 MPa. The characterization of the four samples was done. In SN curves the fatigue limit for welded samples showed a reduction to values of between 180 and 160 MPa. In the Vickers microhardness test, it was possible to notice the differences between the microhardness obtained in accordance with welding parameters used and, consequently, the microstructure formed. In microstructure analysis, different kinds and sizes of microstructure were observed to have formed in both the heat-affected zone and the welded zone. Finally, through MEV analysis, all fatigue cracks were seen to have begun on the surface of the samples. Fatigue estriaton, with major and minor intensity depending on the sample, was observed along the fracture region. Furthermore, the beginning of multiple fatigue cracks were seen in two samples.

Aujourd'hui, la majorité des plastiques de commodité est issue de ressources fossiles. Ces ressources sont limitées et un certain nombre d'études prédisent l'épuisement des gisements dans quelques siècles avec un pic de consommation dans les dix prochaines années. Dans ce contexte, la biomasse représente une ressource abondante pour la synthèse de bio-matériaux. Nous reportons ici une nouvelle stratégie de synthèse de polyesters alternés à partir de ressources renouvelables, basée sur la synthèse tandem. Des complexes organométalliques disponibles commercialement ont montré leur activité catalytique dans la cyclisation de diacides carboxyliques en anhydrides cycliques puis dans la copolymérisation de ces anhydrides avec des époxydes. Cette méthode facile à mettre en oeuvre est une stratégie innovante pour la production de nouveaux polyesters biodégradables.

Orientador: Ronaldo Aloise Pilli / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-08T04:04:52Z (GMT). No. of bitstreams: 1 Robello_LuisGustavo_D.pdf: 7203530 bytes, checksum: a92a57231d7587b04ebb16da51b52419 (MD5) Previous issue date: 2006 / Doutorado / Quimica Organica / Doutor em Ciências

Submitted by JÚLIO HEBER SILVA (julioheber@yahoo.com.br) on 2017-12-20T11:51:07Z No. of bitstreams: 2 Dissertação - Quintino Martins de Oliveira - 2017.pdf: 2368197 bytes, checksum: 82997942dc17c82770e72ce9d7a1209d (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-12-21T12:34:26Z (GMT) No. of bitstreams: 2 Dissertação - Quintino Martins de Oliveira - 2017.pdf: 2368197 bytes, checksum: 82997942dc17c82770e72ce9d7a1209d (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-12-21T12:34:26Z (GMT). No. of bitstreams: 2 Dissertação - Quintino Martins de Oliveira - 2017.pdf: 2368197 bytes, checksum: 82997942dc17c82770e72ce9d7a1209d (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-12-15 / This study focuses on the collaborative learning between two deaf and two hearing students who take Libras as a major at Universidade Federal de Goiás. They had to teach their language to each other in a tandem collaborative learning processes. The study took place on the first term of 2017. Tandem learning is a process of cultural and linguistic exchanges among individuals who have different languages and are willing to teach each other their language in a collaborative way. Thus, the deaf participant taught Libras to the hearing peer and learned written Portuguese from him/her. This study also aims to investigate if collaboration in tandem context can favor the learning of Libras and Portuguese, since they are languages that have different linguistic modalities. It also investigates which strategies were taken by the participants to teach each other´s language and the perceptions they had about the collaborative learning process in tandem context. It is a qualitative case study whose data were collected through the video recording of the interactions and the interviews. Data analysis shows that the students used some strategies that mediated the learning process, such as the use of realia, the use of images, etc. The results also show that the interactions favored not only linguistic knowledge, but also cultural exchanges and that the deaf students ought to be taught by the use of sign language. This study aims to bring some reflections on the learning process in tandem context when the languages involved have different linguistic modalities, as well as bring some guidance to future language teachers who might teach those languages in similar contexts. / Esta pesquisa tem como foco a aprendizagem colaborativa realizada por quatro alunos, sendo dois surdos e dois ouvintes, do curso de Letras: Libras da Universidade Federal de Goiás, que ensinaram suas línguas ao seu parceiro em um contexto de aprendizagem de tandem, durante um semestre letivo de 2017. A aprendizagem em tandem é um processo de trocas linguísticas e culturais entre indivíduos que possuem línguas diferentes e que se propõem a ensinar, de forma livre, sua língua a outra pessoa de modo colaborativo. Dessa forma, o participante surdo ensinou libras ao ouvinte, e o ouvinte ensinou ao surdo português escrito. Este estudo busca também investigar se a colaboração pode viabilizar a aprendizagem das línguas mencionadas, visto que são línguas de modalidades linguísticas diferentes. Busca também investigar quais são as estratégias utilizadas pelos pares para esse fim. Trata-se de um estudo de caso qualitativo em que os dados foram coletados por meio de gravação em vídeo das sessões de tandem e entrevistas, analisados sob a luz dos pressupostos da teoria sociocultural e da aprendizagem colaborativa. Os resultados mostram que os alunos usaram algumas estratégias que mediaram o processo de aprendizagem, tais como o uso de objetos e o uso de imagens. Os resultados também mostram que as oportunidades de interação dos alunos surdos com os alunos ouvintes, no contexto estudado, viabilizaram trocas culturais, e que o ensino eficaz para os alunos surdos se faz necessário ocorrer na língua de sinais. Com este estudo, pretendemos suscitar reflexões sobre a aprendizagem colaborativa no contexto de tandem quando temos línguas de modalidades linguísticas diferentes: português – uma língua oral; e libras – uma língua vísuo-espacial, bem como trazer algumas orientações para futuros professores de libras para ouvintes, ou de português para surdos, que venham a ensinar essas línguas em contextos semelhantes.

Depuis la révolution industrielle, la chimie ne cesse de prospérer en développant des procédés de plus en plus performants souvent aux dépens de l’environnement. Dans le cadre du développement d’une chimie durable, des procédés catalytiques dans le domaine de la chimie d’oxydation sont mis en place en utilisant des métaux physiologiques et des oxydants doux. En combinant les avantages de la catalyse homogène et de la biocatalyse, de nouveaux catalyseurs bio-inspirés ont émergé, les métalloenzymes artificielles. Elles sont constituées d’un complexe inorganique, choisi en fonction de la réaction visée, qui est ancré au sein d’une protéine, qui apporte la sélectivité de la réaction. Au cours des travaux de cette thèse, de nouvelles métalloenzymes artificielles ont été créées par ancrage de divers complexes de Fe ou de Ru au sein de la protéine NikA. Dans un premier temps, l’hybride NikA/Ru-bpza a été synthétisé pour réaliser l’hydroxychloration d’alcènes en présence d’un iode hypervalent. Bien que d’excellentes propriétés catalytiques aient été obtenues, l’amélioration de la stabilité de ce type de catalyseurs, en particulier pour des réactions d’oxydation, reste un challenge important à relever pour leur utilisation au niveau industriel. Une des solutions originale est basée sur le développement de la catalyse hétérogène, en utilisant de cristaux de métalloenzymes artificielles grâce à la technologie CLEC (Cross-Linked Enzyme Crystals). Cette technologie permet, d’une part, d’améliorer la stabilité et la recyclabilité des catalyseurs, et d’autre part, d’élargir les conditions réactionnelles utilisées (solvants, pH, températures). Trois réactivités ont été développées à base de CLEC NikA/FeL : (i) la sulfoxydation de thioéthers, (ii) l’hydroxychloration d’alcènes en présence d’Oxone® et de chlore et (iii) la coupure oxydante d’alcènes par activation d’O2. Ces résultats ont permis d’explorer de nouvelles réactivités en chimie cascade soit en combinant les CLEC mis au point, soit en combinant différents catalyseurs homogènes. / Since the industrial revolution, chemistry has continually thriven by developing new efficient processes at the expense of the environment. As an example, oxidation reactions are performed under harsh conditions with the use of toxic oxidants. With the emergence of green chemistry, catalytic processes using physiological metals and soft oxidants are privileged. Combining the advantages of biocatalysis and homogeneous catalysis, the design of novel bioinspired catalysts, consisting on the synthesis of artificial enzymes has recently emerged. These hybrids are composed of an inorganic complex, driving the reactivity of the enzyme, inserted into a protein, which drives the reaction selectivity. The thesis described new developments in original artificial metalloenzymes, based on the use of the NikA protein and Fe or Ru catalysts. First, a new hybrid has been developed by anchoring the Ru-bpza complex to NikA to catalyze alkene hydroxychloration with hypervalent iodine. Although excellent catalytic efficiencies were obtained, the stability improvement remains a major challenge for the industrial use of these catalytic processes, especially when oxidation chemistry is concerned. One possible strategy is based on the development of heterogeneous catalysis, by using a crystal/solution version of the artificial metalloenzymes thank to the cross-linked enzyme crystals (CLEC) technology. On the one hand, this technology allows to increase the stability and the recyclability of the catalysts. On the other hand, catalysis can be performed under a various reactions conditions (organic solvent, temperature, pH). Three reactivities have been developed with NikA/FeL-CLEC catalysts: (i) thioether sulfoxidation with NaOCl, (ii) alkene hydroxychloration with Oxone® and chloride source and (iii) oxidative cleavage of alkenes by O2 activation. To go further, new reactivities in cascade reactions have been explored combining either NikA-based CLEC developed, or different homogenous catalysts.

Grâce à leurs multiples sites de fonctionnalisation, les cyclopenténones sont des intermédiaires particulièrement utiles dans la synthèse de produits naturels d’intérêt thérapeutique. En particulier, les composés 4-aminocyclopenténones permettent l’accès au motif aminocyclopentitol présent dans des molécules bioactives telles que le peramivir, la pactamycine, ou encore la trehazoline. L’une des méthodes les plus efficaces pour accéder aux 4-aminocyclopenténones est la réaction de cyclisation d’aza-Piancatelli. Cette réaction est basée sur le réarrangement de 2-furylcarbinols en présence d’un nucléophile azoté suivant un mécanisme faisant intervenir une électrocyclisation 4π-conrotatoire. Au sein de notre laboratoire, un système catalytique simple, utilisant un complexe de calcium combiné à un sel d’ammonium, a été mis au point pour avoir accès à ces composés. Cette méthode présente de nombreux avantages : elle est efficace (rendements allant jusqu’à 98%), rapide (15 à 30 minutes), elle nécessite seulement 1 mol% de catalyseur dans des conditions commodes (solvants non distillés et réaction à l’air libre) sur une grande échelle (multi-grammes). Dans ce contexte, nous avons cherché à exploiter tout le potentiel de cette réaction en synthétisant des 2-furylcarbinols plus complexes dans le but de concevoir un accès direct à des squelettes de composés bioactifs. Nous nous sommes en particulier concentrés sur la synthèse totale de la jogyamycine. Par ailleurs, nous avons effectué la synthèse totale de la bruceolline D avec un rendement global de 16% sur 5 étapes. Nous avons également développé une nouvelle séquence réactionnelle impliquant une réaction d’aza-Piancatelli suivie d’une réaction d’hydroamination promue par des sels de cuivre qui fournit un large éventail de cyclopenta[b]pyrroles polyfonctionnels à partir de 2-furylcarbinols facilement accessibles incorporant un groupement alcyne. Par cette méthode, 42 cyclopenta[b]pyrroles ont été obtenus avec des rendements atteignant 98%. Une caractéristique originale de notre approche est liée à l'utilisation d'anilines ortho-substituées. En effet, dans ce cas, des atropisomères avec un excès diastéréomérique supérieur à 20:1 ont pu être obtenus, accompagnés par la création d'une chiralité axiale N-C lors de l'étape d'hydroamination. A ce jour, il n'existait aucun autre exemple de synthèse atropodiastéréosélective de cyclopenta[b]pyrroles. Au cours de nos recherches sur le champ d’application de la réaction, nous avons remarqué que les cyclopenta[b]pyrroles pouvaient se réarranger spontanément en cyclopenta[b]pyrrolines suivant une déaromatisation lorsque l’hexafluoroisopropanol était utilisé comme solvant, permettant d’obtenir 13 cyclopenta[b]pyrrolines avec des rendements variant de 44 à 73%. Nous nous sommes également intéressés à la fonctionnalisation du motif cyclopenta[b]pyrrole pour illustrer l'utilité de notre méthodologie, en combinant en particulier cette séquence réactionnelle avec des réactions de type Friedel-Crafts. L’un des objectifs du projet de thèse était le développement de la version énantiosélective de la réaction. Après la publication récente de trois articles utilisant des acides phosphoriques chiraux en tant que catalyseurs, nous avons envisagé une autre approche pour la synthèse asymétrique de 4-aminocyclopenténones, s’appuyant sur l’utilisation d’une copule chirale (sulfoxyde chiral) portée par l’aniline en collaboration, avec le Dr. Wencel-Delord et le Pr. Colobert (Université de Strasbourg). Ainsi nous avons pu générer les 4-aminocyclopenténones correspondantes avec d’excellents rendements et diastéréosélectivités. / Due to their various functionalizable sites, cyclopentenones are very useful intermediates for the synthesis of natural products of therapeutic value. In particular, 4-aminocyclopentenones enable the access to the aminocyclopentitol frameworks, which are present in a variety of bioactive molecules such as peramivir, pactamycin, or trehazolin. One of the most efficient methods to access 4-aminocyclopentenones is the aza-Piancatelli reaction. It is based on the rearrangement of 2-furylcarbinols in the presence of a nitrogen nucleophile following a mechanism involving a 4π-conrotatory electrocyclization. In our laboratory, a simple catalytic system using a calcium complex combined with an ammonium salt was developed to gain access to these compounds. This method has many advantages : it is effective (yields up to 98%), fast (15 to 30 minutes), it requires only 1 mol% of catalyst under pratical conditions (undistilled solvents without an inert atmosphere) on a large scale (multi-gram). In this context, we sought to extend the scope of this reaction by designing more complex 2-furylcarbinols in order to directly access skeletons of bioactive compounds. In particular, we focused on the total synthesis of jogyamycin. In addition, we achieved the total synthesis of bruceollin D with an overall yield of 16% over five steps. We also developed a new reaction sequence involving an aza-Piancatelli reaction followed by a hydroamination reaction promoted by a copper salt. This sequence provides a wide range of highly functionalized cyclopenta[b]pyrroles from readily-available 2-furylcarbinols substituted by an alkyne moiety. Following this method, 42 cyclopenta[b]pyrroles were obtained with yields up to 98%. An original feature of this transformation is related to the use of ortho-substituted anilines. Indeed, in this case, atropisomers with a diastereomeric excess superior to 20:1 could be obtained accompanied by the creation of an chiral N-C axis during the hydroamination step. To date, no other example of atropodiastereoselective synthesis of cyclopenta[b]pyrroles has been reported. During our investigations on the scope of the reaction, we noticed that cyclopenta[b]pyrroles underwent a rearrangement into cyclopenta[b]pyrrolines, following a dearomatization when hexafluoroisopropanol was used as solvent. This transformation led to 13 cyclopenta[b]pyrrolines with yields ranging from 44% to 73%. We also investigated the functionalization of the cyclopenta[b]pyrrole motif to illustrate the synthetic utility of our methodology, notably by combining this reaction sequence with a Friedel-Crafts reaction. One of the objectives of this Ph.D. was the development of an enantioselective version of the reaction. After the recent publication of three papers using chiral phosphoric acids as catalysts, we devised another approach for the asymmetric synthesis of 4-aminocyclopentenones, relying on the use of a chiral auxiliary (chiral sulfoxide) in collaboration with Dr. Wencel-Delord and Pr. Colobert (University of Strasbourg). Thus, we were able to provide the corresponding 4-aminocyclopentenones with excellent yields and diastereoselectivity.

Les structures protéiques peuvent être divisées en répétitives et apériodiques, les structures apériodiques correspondant pour la plupart à des protéines globulaires. Les protéines répétitives (PRs) contiennent des unités de répétitions adjacentes, appelées séquences répétées en tandem (TRs). Les PRs sont abondantes et ont une importance fonctionnelle fondamentale. De plus de nombreuses études ont démontré l'implication des TRs dans les pathologies humaines. Ainsi, la découverte des PRs et la compréhension de leur relation séquence-structure-fonction, offrent des perspectives de recherche prometteuses.Le développement d’initiatives en génomique structurale, combiné à une meilleure adaptation des techniques de cristallographie et de RMN à l’étude des protéines non globulaires, a permis d’élucider la structure d’un nombre croissant de PRs, d’où la nécessité de mettre en place un système de classification. Les structures répétitives ont été réparties en cinq classes, principalement fondées sur la longueur des TRs: Classe I - agrégats cristallins; Classe II - structures fibreuses; Classe III - structures allongées, dont la stabilité dépend des interactions qui s’établissent entre les motifs répétés. Classe IV - structures répétitives fermées ; Classe V - structures en collier de perles. Les efforts de ces dernières années ont abouti au développement d’outils bioinformatiques utiles à la détection et l'analyse d'éléments répétitifs présents au sein des structures protéiques (3D TRs). En fonction des caractéristiques des répétitions, certaines méthodes fonctionnent mieux que d'autres, mais, jusqu’à présent, aucune ne permettait de couvrir toute la gamme des répétitions. Ce constat nous a incités à développer une nouvelle méthode, appelée détecteur de protéines en tandem (TAPO). TAPO exploite les périodicités des coordonnées atomiques ainsi que d'autres types de représentation structurale, comprenant les chaînes générées par un alphabet conformationnel, les cartes de contact entre résidus, et les arrangements en vecteurs d'éléments de structure secondaire. Actuellement, sept scores, issus des caractéristiques analysées par TAPO, sont combinés à l’aide d’une Machine à Vecteur Support pour produire un score final permettant de différencier les protéines renfermant ou non des 3D TRs. En atteignant 94% de sensibilité et 97% de spécificité pour la référence actuelle, TAPO présente des performances améliorées par rapport aux autres méthodes de pointe. Le développement de TAPO offre de nouvelles opportunités pour l’analyse à grande échelle des protéines renfermant des 3D TRs. Ainsi, notre analyse de la base de données PDB, à l’aide de TAPO, a montré que 19% des protéines contiennent des 3D TRs. L'analyse à grande échelle des structures 3D TRs dans PDB nous a également permis de découvrir plusieurs nouveaux types de structures répétitives, absents de la classification existante et dont certains sont décrits ici.Nous avons entrepris une analyse complète des 3D TRs constitutifs du Rossmann Fold (RF). Notre intérêt pour les RFs a été suscité par le fait que de nombreuses protéines RFs représentent un cas ambigüe vis à vis des structures répétitives et non répétitives. A priori, les unités hélice α - feuillet β des RFs devraient avoir une forte tendance à s’empiler et donc, à former des structures répétitives. Afin de déterminer la fréquence à laquelle les RFs forment de longues unités de répétition empilées, nous avons sélectionné, à l’aide de TAPO, des structures contenant des RFs et les avons classées. Notre analyse montre que les RFs typiques ne peuvent pas être clairement définis comme des structures répétitives mais plutôt comme des unités de structures globulaires, comptant au plus trois répétitions α-β. Des éléments de discussion seront proposés pour tenter d’expliquer cette observation surprenante. / In general, protein structures can be divided into: repetitive and aperiodic structures. Most of the aperiodic structures are globular proteins. The repetitive proteins contain arrays of repeats that are adjacent to each other, called Tandem Repeats (TRs). Proteins containing TRs are abundant and have fundamental functional importance. Numerous studies demonstrated the involvement of such TR-containing proteins in human diseases. Furthermore, genetic instability of these regions can lead to emerging infection threats. Additionally, TR-containing structures have generated significant interest with respect to protein design as they can make excellent scaffolds for specific recognition of target molecules. Therefore, the discovery of these domains, understanding of their sequence–structure–function relationship promises to be a fertile direction for research.The growth of structural genomics initiatives, in combination with improvements in crystallographic and NMR techniques aimed at non-globular proteins, has resulted in an increase in structurally elucidated TR proteins. This has necessitated the development of classification schemes. Structural repeats were broadly divided into five classes mainly based on repeat length; Class I – crystalline aggregates; Class II – fibrous structures such as collagen; Class III – elongated structures where the repetitive units require each other for structural stability such as solenoid proteins; Class IV – closed repetitive structures, such as TIM-barrels and Class V – bead on a string structures such as tandems of Ig-fold domains. Despite this progress, the majority of bioinformatics approaches have focused on non-repetitive globular proteins.In recent years, efforts have been made to develop bioinformatics tools for the detection and analysis of repetitive elements in protein structures (3D TRs). Depending on the size and character of the repeats, some methods perform better than others, but currently no best approach exists to cover the whole range of repeats. This served as a motivation for the development of our method called the TAndem PrOtein detector (TAPO). TAPO exploits, periodicities of atomic coordinates and other types of structural representation, including strings generated by conformational alphabets, residue contact maps, and arrangements of vectors of secondary structure elements. Currently, seven feature based scores produced by TAPO are combined using a Support Vector Machine, producing a score to enable the differentiation between proteins with and without 3D TRs. TAPO shows an improved performance over other cutting edge methods, achieving 94% sensitivity and 97% specificity on the current benchmark. The development of TAPO provided new opportunities for large scale analysis of proteins with 3D TRs. In accordance with our analysis of PDB using TAPO, 19% of proteins contain 3D TRs. The large scale analysis of the 3D TR structures in PDB also allows us to discover several new types of TR structures that were absent in the existing classification. Some of them are described in the thesis manuscript. This suggests that TAPO can be used to regularly update the collection and classification of existing repetitive structures. In particular, a comprehensive analysis of 3D TRs related to Rossmann Fold (RF) was undertaken. Our special interest in RFs was based on the observation that many proteins with RFs represent borderline cases between repetitive and non-repetitive structures. In principle, α-helix-β-strand units of RFs should have a strong potential to stack one over the other, forming repetitive structures. To probe the question of how frequently RFs form long arrays of stacked repeats, we selected by using TAPO known RF-containing structures and classified them. Our analysis shows that typical RFs cannot be clearly defined as repetitive, rather they are part of globular structures with up to 3 αβ-repeats. We provide some explanations for this surprising observation.

In the context of education mediated by new technologies, information is available to anyone who may be interested in it, and the roles of student and teacher, especially in the last decade, have taken other contours. My work has an extension project developed in the context of language teaching and learning mediated by new technologies as its background, and it is aimed at analyzing my teacher education process as an active member of this project. I aim to understand, looking back to my own story, what was the impact that this extension project had either over my academic, personal and professional journeys. For that, I base myself on the conceptual framework of Dewey (1953) on Teacher Education and Reflective Practice, on Communities of Practice by Wenger (2000), as well as on the Theory of Engagement by Shneiderman (1994, 1998) and Kearsley (1997). / No contexto de ensino mediado pelas novas tecnologias, a informação está à disposição de quem quer que se interesse por ela, e os papéis de aluno e professor, especialmente na última década, têm tomado outros contornos. Meu trabalho tem como pano de fundo um projeto de extensão desenvolvido nesse contexto de ensino e aprendizagem de línguas mediados por novas tecnologias, e tem por meta analisar meu processo de formação docente. Quero entender, olhando em retrospecto para minha própria história, qual foi o impacto que a graduação, o projeto de extensão e o mestrado tiveram tanto em minha jornada acadêmica, quanto em minha vida pessoal e profissional. Para tanto, me baseio nos pressupostos teóricos de Dewey (1953) sobre Formação de Professores e a Prática Reflexiva, as Comunidades de Prática de Wenger (2000), assim como a Teoria do Engajamento de Shneiderman (1994, 1998) e Kearsley (1997). / Mestre em Estudos Linguísticos