991 resultados para Ce^3
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La station 3-avant de Pointe-du-Buisson (Beauharnois, Haut-Saint-Laurent, Qubec) reprsente la plus importante collection de rcipients de terre cuite datant du Sylvicole moyen ancien (-400 500 de notre re) dans le Nord-Est amricain. De plus, on trouve sur ce site une srie continue doccupations couvrant lensemble de la priode Sylvicole. En dpit de complications dordre stratigraphique (terreau homogne et pdoturbations), des concepts et des mthodes volutionnaires tirs de la thorie de lhrdit duelle sont appliqus ltude de cet assemblage. Dun point de vue anthropologique, que nous apprend ltude de lvolution et de la transmission des savoir-faire dune technologie que nous assumons exclusivement fminine au cours de la priode Sylvicole? Lauteur dfend que larchologie volutionnaire permet de dtecter le contexte de la transmission, cest--dire lorganisation socioconomique des populations du pass. Lexamen des traits stylistiques suggre que la sdentarisation estivale des bandes amrindiennes partir du Sylvicole moyen tardif favorise une homognisation des productions cramiques dans un contexte virilocal qui est la consquence dune transmission de type conformiste oprant sur un axe horizontal (entre pairs). Cependant, le passage probable des tribus iroquoiennes luxorilocalit et la matrilinarit la fin du Sylvicole se traduit par une saisissante htrognisation des pots, qui sexplique possiblement par une slection de marqueurs identitaire dordre clanique (transmission verticale entre parents et descendants). Ltude des traits techno-fonctionnels indique une diversification de la vaisselle de terre cuite mesure que les populations intensifient leurs expriences sur les cultignes. Dans lensemble, cette volution trahit une attention accrue confre la performance des pots en tant que rcipients culinaires. Par ailleurs, le concours de la sriation et de datations AMS permet la reconnaisance dun taxon Sylvicole moyen moyen caractris par une modification morphologique et dcorative des vases. Une enqute comparative portant sur un chantillon de 27 sites archologiques de lhorizon Pseudo-scallop-shell dmontre que la variation populationnelle est structure en fonction de la localisation des communauts dans un bassin hydrographique spcifique. Par consquent, lauteur soumet des pistes en vue de llaboration dune taxonomie robuste et propre au Sylvicole moyen ancien et au Sylvicole moyen moyen. Enfin, des indices de natures diverses (archologiques, paloethnobotaniques, ethnolinguistiques, paloanthropologiques, et dautres issus de la gntique des populations) suggrent une identit proto-algonquienne des bandes des deux sous-priodes susmentionnes.
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Objectif : Cette thse a pour but de prciser les mcanismes neuropsychologiques de la douleur, de la rgulation endogne de la douleur et de l'hypoalgsie induite psychologiquement (HIP) par la synthse de prs de trente ans de recherche imagerie crbrale fonctionnelle. Mthodologie : tant donn l'abondance des tudes sur le sujet et le manque d'intgration de leurs rsultats, la technique de mtaanalyse quantitative base sur les coordonnes d'activation crbrale fut privilgie dans cette thse, telle quimplmente dans l'algorithme ALE (Activation Likelyhood Estimate). Une force supplmentaire de cette thse repose sur la rigueur du processus de slection des articles. En effet, les tudes incluses dans les mtaanalyses devaient satisfaire des critres stricts d'inclusion, ceci dans le but de favoriser la prcision et la validit des conclusions subsquentes. tude 1 : Le premier article visait identifier les aires crbrales impliques dans la rduction de la douleur par des mthodes psychologiques d'interventions. Les articles retenus portent sur une varit de mthodes d'intervention, telles que le placebo, l'hypnose, la mditation, la perception de contrle sur la stimulation douloureuse et l'induction d'motions. Les rsultats indiquent que l'HIP implique un vaste rseau d'activation qui comprend le cortex cingulaire antrieur, l'insula antrieure, les zones orbitofrontale et prfrontale latrale, ainsi que les rgions paritale, temporale et souscorticales. Ces activations reflteraient l'implication des mcanismes neuropsychologiques cognitifs et motionnels sous-tendent les interventions psychologiques cibles par ces tudes, incluant la conscience de soi et la motivation. De plus, les divergences de patron d'activation entre les approches ont t explores, notamment pour le placebo et la distraction. tude 2 : Le deuxime article a identifi des patrons d'activations prfrentiellement associs la perception de la douleur, l'HIP, ainsi que des activations communment associes la douleur et l'HIP. Les rsultats indiquent que 1) la perception de la douleur est associe l'activation d'aires somatosensorielles et motrices, ce qui pourrait tre le reflet de la prparation d'une action adaptative, 2) l'HIP est lie l'engagement de rgions prfrontales antromdianes et orbitales, possiblement en lien avec des processus motivationnels et motionnels, et 3) la douleur et l'HIP sont associs l'activation d'aires prfrontales dorsolatrales, de l'insula antrieure et du cortex cingulaire moyen, ce qui pourrait reflter l'engagement spontan pendant la douleur de mcanismes endognes de rgulation descendante. Conclusion : Par ces tudes, cette thse fait le point sur les mcanismes crbraux impliqus diffrentiellement dans la perception de la douleur, dans sa rgulation endogne et dans l'hypoalgsie induite psychologiquement.
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Pyrroles are found in various natural products and in the chemical composition of certain drugs because of their interesting biological properties. Lipitor, Tolmetin and Amtolmetin are examples of drugs with 1,2,5-substituted pyrroles in their composition, in which biological activities have been certified. Moreover, pyrroles are used as precursors of semiconductor polymers, oligomers and dendrimers useful for the synthesis of electroluminescent materials used in devices, such as organic light-emitting diodes, field-effect transistors, solar and organic photovoltaic cells. We are interested in conjugated polymers based on pyrrole due to their optical properties, electrochemical and the conductivity produced by electron delocalization along their carbon chains. The overall objective of the work presented in this thesis is the synthesis of new molecules based on pyrrole for studying their electronic and electrochemical properties as well for the synthesis of conjugated polymers. Initially, we performed the synthesis of 1,3,5-tri-(1-alkyl-5-methylpyrrol-2-yl)benzenes, which may serve as precursors for the synthesis of conjugated dendrimers. Their synthesis was made in three steps starting from trimethyl 1,3,5-benzene-tricarboxylate which was converted to 1,3,5-tri-(pent-4-enoyl)benzene using vinylmagnesium bromide in a Grignard reaction catalyzed by copper cyanide. The olefins of 1,3,5-tri-(pent-4-enoyl)benzene were oxidized to produce 1,3,5-tri-(4-oxopentanoyl)benzene using a modified protocol of the Tsuji-Wacker reaction. Subsequent, Paal-Knorr condensation reactions on 1,3,5-tri-(4-oxopentanoyl)benzene with different amines were used to synthesize 1,3,5-tri-(1-alkyl-5-methylpyrrol-2-yl)benzenes with different N-substituents in yields between 44 and 60%. Incomplete reaction of vinylmagnesium bromide with trimethyl 1,3,5-benzenetricarboxylate gave the methyl-3,5-di(pent-4-enoyl)benzoate, which was converted to methyl-3,5-dipyrrolylbenzoate following the reaction of Tsuji- Wacker and Paal-Knorr with yields between 30 and 60%. The photochemical and electrochemical properties of the 1,3,5-tri-(1-alkyl-5-methylpyrrol-2-yl)benzenes and methyl-3,5-dipyrrolylbenzoates were studied in collaboration with the research group of professor William Skene. The results have shown that both types of pyrrole have potential for the synthesis of conjugated polymers and dendrimers used in the manufacture of electroluminescent materials. Following these encouraging results, we performed the synthesis of 6,12-dimethyl-1,5-dipyrrolediazocane. Methyl N-(Boc)--alaninate was converted to its corresponding homoallylic ketone, which was oxidized to N-(Boc)aminoheptan-3,6-dione. The Paal-Knorr condensation between N-(Boc)aminoheptan-3,6-dione and aminoheptan-3,6-dione hydrochloride gave 6,12-dimethyl-1,5-dipyrrolediazocane in 17% yield. In sum, we have synthesized and characterized seven new molecules, six of them having photochemical and electrochemical properties interesting for the synthesis of conjugated polymers and dendrimers. The latter offering potential as precursor for the conception of compounds of therapeutic interest.
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Microwave dielectric ceramics based on RETiTaO6 (RE = La, Cc, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Yb, Al, and In) were prepared using a conventional solid-state ceramic route. The structure and microstructure of the samples were analyzed using x-ray diffraction and scanning electron microscopy techniques. The sintered samples were characterized in the microwave frequency region. The ceramics based on Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy, which crystallize in orthorhombic aeschynite structure, had a relatively high dielectric constant and positive T f while those based on Ho, Er, and Yb, with orthorhombic euxenite structure, had a low dielectric constant and negative Tf. The RETiTaO6 ceramics had a high-quality factor. The dielectric constant and unit cell volume of the ceramics increased with an increase in ionic radius of the rare-earth ions, but density decreased with it. The value of Tf increased with an increase in RE ionic radii, and a change in the sign of Tf occurred when the ionic radius was between 0.90 and 0.92 A. The results indicated that the boundary of the aeschynite to euxenite morphotropic phase change lay between DyTiTaO6 and HoTiTaO6. Low-loss ceramics like ErTiTaO6 (Er = 20.6, Qxf = 85,500), EuTiTaO6 (Er = 41.3, Qxf = 59,500), and YTiTaO6 (Er = 22.1, Qxf = 51,400) are potential candidates for dielectric resonator applications
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Distribution of toxic metal in the sediment core is an important area of research for environmental impact studies. Sediment cores were collected from two prominent region(C1 and C2) of CE and subjected to geochemical analysis to determine distribution of toxic metals (Cd, Co, Cr, Cu and Pb ), texture characteristics, total organic carbon (TOC) and CHNS. Statistical analysis was done to understand the interrelationship between the components. In the studied cores, metal contamination level was identified for Pb, Cu; Cr, in C1 and C2 respectively. The metal distribution depends on the granulometric factor, geogenic mineral components and anthropogenic input. Correlation analysis (CA) and Principal component(PCA) analysis also support these results
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En una clase en la cuarta serie de la Escuela de Educacin Bsica Joo Alencar de Figueiredo, en Juazeiro do Norte CE/Brasil, mi plan de actividad fue la lectura de las imgenes que formaban parte de nuestra vida diaria y he pedido que los estudiantes traigan a la clase imgenes de publicidad, revistas, etiquetas de los productos, fotografas y cualquier informacin visual que pudieran de su entorno. As, se puso en marcha una exposicin de estas imgenes y la construccin de un gran panel con informaciones que forman parte del universo cultural/visual de los alumnos. En ese sentido, se organizaron textos escritos por los alumnos con diferentes temas sobre la razn de la presencia de esas imgenes en nuestra vida cotidiana. Durante las presentaciones de los textos producidos, he percibido en la exposicin de ellos, algunas cuestiones latentes que merecen respuestas, entre los cuales, una con nfasis: "Somos nosotros los que necesitamos estos productos y la informacin contenida en las imgenes, o hay ms inters para que las personas posean y consuman estos productos?. Ante la pregunta yo sent la necesidad de una investigacin sobre la enseanza del arte en las escuelas de nuestra regin, el tiempo dedicado a esta actividad, las propuestas pedaggicas y los objetivos de las mismas, las preguntas acerca de la alfabetizacin visual, el conocimiento/reconocimiento de las culturas presentes no slo en la escuela, sino en el espacio social. Ntese que tal percepcin no siempre consegua superar la evidente falta de trabajo sobre cuestiones multiculturales en las propuestas de los currculos de las escuelas
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Analizar la problemtica de la Reforma escolar en Barcelona y su difcil implantacin en los barrios populares. Analizar la oferta de la Pedagoga modernista activa y los recursos que tienen las familias para utilizar este tipo de oferta. 3 grupos de familias: 5 de posicin social inferior, 3 de posicin social media y 1 de posicin social alta, de una escuela que reune las siguientes caractersticas: pblico popular, se adapta a la Reforma escolar, utiliza nuevos mtodos y tcnicas. Realiza una introduccin general al problema. Escoge la muestra y analiza los tres tipos de familias. Compara los tres grupos y elabora las conclusiones. Plantea la siguiente hiptesis: la incidencia diferencial de una misma Pedagoga depende de los medios de los que se dispone para poderla utilizar. Encuesta, observacin, entrevista. Anlisis comparativo, anlisis cuantitativo, anlisis estadstico. Una escuela pedaggica activa puede tener dos efectos diferenciales en la familia: segn la clase social de los padres, segn las competencias y disposiciones que la definicin de infancia implique en los padres del nio.
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Pginas de anexos: p. 159-160
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Ofrecer informacin acerca de como se enfrentan algunos pases de la Comunidad Europea a los problemas que plantea el ingreso en centros de Educacin Superior. Los sistemas educativos y los modelos de acceso a la Educacin Superior en: Blgica, Espaa, Francia, Italia, Reino Unido y la Repblica Federal Alemana. Esbozo del sistema espaol de acceso a la Educacin Superior. El estudio est dividido en tres partes. 1) Se describen los sistemas educativos de seis pases europeos y como cada uno de ellos aborda el tema de acceso a la Educacin Superior. 2) Se realiza un estudio comparado de los sistemas de acceso y de las pruebas que se exigen superar con el fin de constatar aspectos comunes y diferentes entre ellos. 3) Se establecen las tendencias generales mayoritariamente observadas en los seis pases analizados. Posteriormente se analiza el sistema de acceso espaol en concreto, as como las pruebas que utiliza. Recopilacin de los sistemas educativos de los seis pases escogidos de la CEE. Tendencias generales en cuanto al sistema de acceso: todos los pases, excepto Blgica, establecen pruebas acadmicas, que deben ser superadas, acreditando con un certificado o diploma de validez nacional y convalidables entre los pases estudiados. La edad de obtencin oscila entre los 18 y 19 aos. Existe limitacin de plazas en algunas carreras universitarias. En cuanto a la prueba: son organizadas externamente. La presidencia de los tribunales calificadores est encomendada a un profesor universitario, participando profesores de Secundaria en el proceso. El expediente acadmico es valorado. Los materiales objeto de examen son los cursados en el ltimo ao de estudios de Secundaria, oscilando entre 4 y 7. El idioma oficial es materia objeto de examen. Todos los pases, excepto Espaa, establecen una convocatoria por curso acadmico para realizar las pruebas de acceso. Distintos sectores sociales espaoles coinciden en la necesidad de modificar el sistema espaol de acceso a la Universidad. Para obtener plaza en los estudios elegidos se debera dar mayor valoracin al expediente acadmico y considerar el tiempo de espera transcurrido tras la superacin de las PAAV incluir en las pruebas cuestiones ms interdisciplinares. Introducir la modalidad de prueba oral para la Lengua espaola. Posibilidad de aprobar independientemente los dos ejercicios que existen ahora. Ampliar el nmero de convocatorias. Mayor coordinacin entre los profesores universitarios y de Enseanzas Medias.
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Le rapport entre la recherche en didactique des disciplines scolaires et la notion dinnovation mrite dtre interrog. Quelles sont en effet les finalits de ladite recherche? Visent-elles en priorit une mise en perspective analytique des programmes et des ressources scolaires? Une meilleure connaissance des pratiques effectives au sein de la classe? Ou bien une meilleure perception des processus qui aboutissent aux apprentissages des lves? Cherchent-elles produire des tats des lieux substantiels ou encourager linnovation et lvolution des pratiques? Et si ctait le cas, dans quelles perspectives et selon quels critres? En effet, comment dfinir et identifier une pratique innovante dans la classe? Rpondre ces diffrentes questions conduit le chercheur, et le praticienchercheur qui intervient dans la formation des enseignants, orienter ses travaux dans une direction donne, mais aussi les situer par rapport des questions vives qui touchent sa discipline et qui impliquent lexercice dune responsabilit sociale au coeur de son expertise, loin de toute vellit de senfermer dans une tour divoire
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Presentaci sobre l'experincia dels autors relacionada amb la creaci del Projecte gvSIG CE: naixement del projecte, estructura de la nova comunitat i avantatges i inconvenients
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Umas das grandes causas de problemas nutricionais a falta de Educao Alimentar e Nutricional, que, na maioria das vezes, consiste em simples orientaes e tcnicas educativas inadequadas e tradicionais. Portanto, a pesquisa analisou a Educao Alimentar e Nutricional, mais especificamente as prticas pedaggicas utilizadas pelos professores das escolas pblicas do municpio de Ubajara-Ce, realizando entrevistas com os docentes que ministram Cincias Naturais no 8 ano de trs escolas municipais e aplicando-se tambm um questionrio para os alunos. Todos os docentes possuem graduao em Pedagogia e Ps-Graduao em reas no afins com a temtica. No houve formao continuada sobre o assunto, mas de acordo com o questionrio, os alunos possuem os conhecimentos sobre o tema, onde estatisticamente no houve diferenas significativas ao nvel de 5% para a maioria das questes. Ao analisar o discurso dos docentes, a metodologia de ensino utilizada tem tendncia ao ensino scio e individualizado com a exposio oral, debates, dinmicas e entre os recursos didticos esto a lousa, livros e recursos audiovisuais. Somente as prticas pedaggicas dos Professores 1 e 3 tomam um carter de prticas reflexivas, nos levando a concluir que independente das diferenas entre as prticas pedaggicas, todas levaram ao aprendizado do aluno.
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Fulgimides monosubstituted with [M(bpy)(3)](2+) (M = Ru, Os; bpy = 2,2'-bipyridine) chromophore units and with a single bpy group were synthesized and investigated as components of conceivable dinuclear photochromic switches of luminescence. The E-, Z- and closed-ring (C) photoisomer forms of the bpy-bound fulgimide were successfully separated by semi-preparative HPLC. The same procedure failed, however, in the case of the [M(bpy)(3)](2+)-substituted fulgimides. Energy transfer from the excited photochromic unit to the metal-bpy centre competes with the fulgimide cyclization, reducing the photocyclization quantum yields by approximately one order of magnitude compared to the non-complexed fulgimide-bpy ligand (phi(EC) = 0.17, phi(EZ) = 0.071, phi(ZE) = 0.15 at lambda(exc) = 334 nm). The cycloreversion of the fulgimide-bpy ligand is less efficient (phi(CE) = 0.047 at lambda(exc) = 520 nm). The intensity of the (MLCT)-M-3-based luminescence of the metal-bpy chromophore (in MeCN, phi(deaer) = 6.6 x 10(-2) and tau(deaer) = 1.09 mu s for Ru; phi(deaer) = 6.7 x 10(-3) and tau(deaer) = 62 ns for Os) is not affected by the fulgimide photoconversion. These results and supporting spectro-electrochemical data reveal that the lowest triplet excited states of the photochromic fulgimide moiety in all its E-, Z- and closed-ring forms lie above the lowest 3MLCT levels of the attached ruthenium and osmium chromophores. The actual components are therefore unlikely to form a triad acting as functional switch of energy transfer from [Ru(bpy)(3)](2+) to [Os(bpy)(3)](2+) through the photochromic fulgimide bridge.
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The quadridentate N-heterocyclic ligand 6-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin- 3-yl)-2,2 : 6,2-terpyridine (CyMe4-hemi-BTBP) has been synthesized and its interactions with Am(III),U(VI), Ln(III) and some transition metal cations have been evaluated by X-ray crystallographic analysis, Am(III)/Eu(III) solvent extraction experiments, UVabsorption spectrophotometry, NMR studies and ESI-MS. Structures of 1 : 1 complexes with Eu(III), Ce(III) and the linear uranyl (UO2 2+) ion were obtained by X-ray crystallographic analysis, and they showed similar coordination behavior to related BTBP complexes. In methanol, the stability constants of the Ln(III) complexes are slightly lower than those of the analogous quadridentate bis-triazine BTBP ligands, while the stability constant for the Yb(III)complex is higher. 1H NMR titrations and ESI-MS with lanthanide nitrates showed that the ligand forms only 1 : 1 complexes with Eu(III), Ce(III) and Yb(III), while both 1 : 1 and 1 : 2 complexes were formed with La(III) and Y(III) in acetonitrile. A mixture of isomeric chiral 2 : 2 helical complexes was formed with Cu(I), with a slight preference (1.4 : 1) for a single directional isomer. In contrast, a 1 : 1 complex was observed with the larger Ag(I) ion. The ligand was unable to extract Am(III) or Eu(III) from nitric acid solutions into 1-octanol, except in the presence of a synergist at low acidity. The results show that the presence of two outer 1,2,4-triazine rings is required for the efficient extraction and separation of An(III)from Ln(III) by quadridentate N-donor ligands.
