136,970 research outputs found
Estudos cenéticos da reação de heck intramolecular catalisada por nanopartículas bimetálicas estabilizadas por polietilenoimina linear funcionalizada
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-graduação em Química, Florianópolis, 2013Reações de acoplamento C-C tem grande destaque na síntese de novos compostos orgânicos, em especial a reação de Heck. Porém, o desenvolvimento de novos sistemas catalíticos, com metodologias livres de ligantes fosfina, ausência de atmosfera inerte e realizadas em meio aquoso, tem sido um grande desafio nos últimos anos. Ainda, dos poucos trabalhos relatados nesta área, raros são os que se dedicam ao estudo sistemático dos mecanismos de reação. Neste sentido, este trabalho pretende contribuir no desenvolvimento de novos catalisadores para reações de acoplamento C-C, nas condições anteriormente citadas, baseando-se no preparo e caracterização de nanopartículas bimetálicas de prata e paládio, estabilizadas por polietilenoimina linear, e sua aplicação em uma reação do tipo Heck intramolecular. Análise Cinética do Progresso da Reação foi utilizada para a determinação da ordem da reação em relação aos reagentes e obtenção de evidências mecanísticas. Também foi verificada a influência da base utilizada (trietilamina) na reação e sobre a morfologia do catalisador. Por fim, experimentos de inibição do catalisador e análise por microscopia eletrônica de transmissão das nanopartículas, após a reação, sugerem a participação da superfície das nanopartículas na catálise de Heck sob as condições estudadas. Abstract: Carbon-carbon coupling is a prominent reaction in the synthesis of new organic compounds, specially the Heck reaction. However, the development of new catalytic systems, with methods free of phosphine ligands, without inert atmosphere and held in an aqueous medium, has been of great challenge in the last years. Moreover, from the few studies reported in this area, very little are dedicated to the systematic study of reaction mechanisms. Thus, this work aims to contribute in the development of new catalysts for C-C coupling reactions, under the conditions previously mentioned, based on the preparation and characterization of bimetallic nanoparticles of silver and palladium, stabilized by linear polyethyleneimine, and its application in an intramolecular Heck type reaction. Reaction Progress Kinetic Analysis was used to determine the reaction order with respect to reactants and obtention of mechanistic evidences. It was also verified the influence of the base (triethylamine) on the reaction and on the catalyst morphology. Finally, catalyst inhibi-tion experiments and analysis by transmission electron microscopy of the nanoparticles, after the reaction, suggest the involvement of the nanoparticles surface on catalysis under the studied conditions
Estudos cinéticos de uma reação de Heck intramolecular em meio aquoso catalisadas por nanopartículas de paládio suportadas em polietilenoimina ramificada
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Química, Florianópolis, 2013Reações de acoplamento Carbono-Carbono do tipo Heck, em meio aquoso, tem se destacado como uma nova forma de realizar síntese orgânica, com uma metodologia mais barata, segura e confiável para a construção de diferentes moléculas. Até o momento poucos trabalhos foram dedicados ao estudo mecanístico destas reações. Neste sentido, este trabalho envolve a preparação, caracterização e o emprego de colóides de paládio, estabilizados pelo polímero comercial polietilenoimina, como catalisador em uma Reação de Heck Intramolecular, na presença de base, usando água como solvente e sem controle da atmosfera. O estudo dos diversos aspectos que influenciaram a velocidade da reação, assim como também a conversão ao produto, foi realizado por uma nova metodologia cinética. Análise Cinética do Progresso da Reação foi aplicada e pelos resultados obtidos foi observado que a reação é de primeira-ordem em relação ao catalisador e ordens em relação aos outros reagentes. Além disso, identificou-se uma forte relação, tanto na velocidade da reação quanto na conversão ao produto, com as concentrações iniciais da base. A análise destes resultados, aliados à estudos morfológicos das nanopartículas de paládio por microscopia eletrônica de transmissão, indicam a participação da superfície da nanopartícula e a alteração de seu tamanho durante o progresso da reação. Ainda, nas condições reacionais estudadas foi possível obter até 90% de conversão a produto após 24 horas, sem uso de atmosfera inerte e em condições brandas de temperatura.Abstract : Carbon-Carbon Heck coupling reactions, in aqueous media, have become a new way to make organic synthesis, as a cheaper, safer and more reliable methodology to build different molecules. So far only a few works have been dedicated to the mechanistic studies of these reactions. Through this way, the present work involves the preparation, characterization and the use of palladium colloids, stabilized by the commercial polymer polyethyleneimine, in an Intramolecular Heck Reaction, in the presence of a base, using water as the reaction solvent and without control of the atmosphere. The study of the different aspects that influenced the reaction rate, as well as the product conversion, was performed by a new kinetic methodology. Reaction Progress Kinetic Analysis was applied and from the results it was observed that the reaction is first-order in respect to the catalyst and have complex orders in respect to other reactants. Besides, it has been identified a strong relationship of the reaction rate, and product conversion, with the initial concentrations of the base. Analysis of these results, allied to the palladium nanoparticles morphological studies by transmission electron microscopy, indicated a participation of the nanoparticle#s surface and its size shifting during the reaction progress. Moreover, in the reaction conditions studied it was possible to obtain up to 90% of conversion to product in 24 hours without inert atmosphere and under mild conditions of temperature
Nanocatalisadores metálicos de paládio e prata estabilizados com novos líquidos iônicos piridínicos para aplicação em reações de Heck e redução
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Química, Florianópolis, 2015.Este trabalho foi dividido em: (i) síntese de novos líquidos iônicos (LIs) piridínicos para utilização na estabilização de nanopartículas de prata (Ag-NPs) para aplicação na reação de redução do p-nitrofenol (NIP) e (ii) a introdução da ciclização do N-(o-iodobenzoil)-3-metilindol (MIAc), como modelo de reação de Heck para avaliação in situ, por espectroscopia UV-visível (UV-vis), da atividade de catalisadores a base de paládio molecular ou coloidal. Nove LIs foram sintetizados variando-se a cadeia alquílica ligada ao nitrogênio piridínico (metil, butil e octil) e contra-íons (haletos, tetrafluoroborato (BF4) e bis(trifluorometilsulfonil)imidato (NTf2)) e utilizados na estabilização de Ag-NPs. Para comparar os nove sistemas Ag-NPs/LI, verificou-se sua atividade catalítica na reação de redução do NIP, cujo progresso é facilmente monitorado por UV-vis. Todos os nanocatalisadores apresentaram atividade na redução do NIP sendo que, em geral, as maiores constantes de velocidade foram obtidas quando LIs metilados foram utilizados como estabilizante. Na reação de ciclização do MIAc, três sistemas catalíticos foram testados: nanopartículas de paládio (Pd-NPs/LI-Me(I)) pré-formadas e estabilizadas pelo LI N-metilpiridínico (LI-Me(I)); Pd(OAc)2 e Pd(OAc)2 com adição de LI-Me(I) (Pd(OAc)2/LI-Me(I)). Diversos experimentos foram realizados como variação da quantidade do catalisador, da concentração e natureza da base, do solvente e do LI, além de análises por microscopia eletrônica de transmissão (TEM) em diferentes tempos de reação e envenenamento com Hg. Após essa série de experimentos, pode-se dizer que a ciclização do MIAc foi introduzida com êxito como modelo de reação de Heck uma vez que seu progresso foi acompanhado in situ por UV-vis facilitando a realização de diversos experimentos para obtenção dos parâmetros cinéticos TON (mol de catalisador/mol de produto) e TOF (TON/tempo), com os quais comparou-se a atividade e aplicabilidade de sistemas catalíticos a base de paládio. Além disso, demonstrou ser uma reação relativamente branda ocorrendo em meio aquoso, na ausência de atmosfera inerte e a 80 ºC. O sistema Pd(OAc)2/LI-Me(I), com 1x10-3 mmol L-1 de LI-Me(I), resultou nos maiores parâmetros TON e TOF e maior conversão ao produto de ciclização.Abstract : The present work is divided in: (i) synthesis of new pyridinium ionic liquids (LIs) to use as stabilizing agents of silver nanoparticles (Ag-NPs), whose application was the reduction reaction of p-nitrophenol (NIP) and (ii) the introdution of (2-iodophenyl)(3-methyl-1H-indol-1-yl)methanone (MIAc) ciclization as a model reaction, for the in situ evaluation by UV-vis Spectroscopy (UV-vis) of Pd catalysts based on molecular or colloidal palladium. Nine LIs were synthesized modifying the alkyl chain bounded to the pyridine nitrogen (methyl, butyl and octyl) and the counteranion (halides, tetrafluoroborate (BF4-) and bis(trifluoromethylsulfonyl)imidate (NTf2-)). To compare the nine Ag-NPs/LI systems, their catalytic activity was evaluated in the NIP reduction reaction, whose progress can be easily monitored by UV-vis. All Ag-NPs/LI catalyst showed a good catalytic activity for the NIP reduction but, in general, the highest rate constants were obtained with methylic LIs. For the MIAc ciclization, three catalytic systems were evaluated: as-formed palladium nanoparticles (Pd-NPs/LI-Me(I)) stabilized by N-methylpyridinic LI, Pd(OAc)2, and Pd(OAc)2 with LI-Me(I) addition (Pd(OAc)2/LI-Me(I)). A series of experiments was carried out including varying the amount of catalyst, the concentration and nature of the base, solvent, and LI, analysis by transmission electronic microscopy (TEM) at different times of the reaction and poisoning tests with Hg. After this series of experiments, it can be said that the cyclization of MIAc was successfully introduced as a model for Heck reaction since its progress was easily monitored in situ by UV-vis, facilitating the implementation of several experiments and obtaining the kinetic parameters TON (mol of product/mol of catalyst) and TOF (TON/time), in which the activity and applicability of the catalytic systems could be compared. Furthermore, the reaction was carried out at relatively mild conditions once it occurs in aqueous medium, in the absence of inert atmosphere, and at 80 ° C. The Pd(OAc)2/LI-Me(I) system with 1x10-3 mmol L-1 of LI-Me(I) resulted in both, highest kinetic parameters TON and TOF and ciclization product conversion
Greek Life By Heck!
No full textA coloring book of cartoons from the 1929 Sibyl, drawn by J. Parker Heck (class of 1930).These coloring pages are cartoon illustrations that were published in the “Social Groups” section of the 1929 Sibyl, with additional facts about the fraternities and sororities taken from the Otterbein University Archives.18 pages, 8 ½” x 11”.https://digitalcommons.otterbein.edu/coloring/1003/thumbnail.jp
Bilder-Atlas zum Conversations-Lexicon, Johann Georg Heck, 1849
No full textBilder-Atlas zum Conversations-Lexikon : Ikonographiche Encyklopadie der Wissenschaften und Kunste / entworfen und nach den vorzuglichsten Quellen bearbeitet von Johann Georg Heck. Images consist of a selection of sixteen illustrations from the 1849 edition of Bilder-Atlas zum Conversations-Lexicon by Johann Georg Heck. Two of the illustrations show mid-19th century surgical procedures and instruments. The remaining illustrations are human anatomical drawings, including one contrasting facial features and skulls of different human races. The introduction to the encyclopedia is also included
Furthering research and practice in school-university partnerships in the context of preservice teacher education
No full textBeyond boundaries in teacher education: Promoting collaboration and partnership
Together with my colleagues, Associate Professor Debbie Heck from the University of the Sunshine Coast and Dr Helen Grimmett from Monash University, I have an interest in engaging in furthering research and practice in school-university partnerships in the context of preservice teacher education. Since 2014, when I was appointed the Director of the Master of Teaching (Primary) program at The University of Queensland, Debbie, Helen and I have been using innovative strategies such as cogenerative dialogues and metalogues to investigate how effective school-university partnerships may be developed and sustained. Simultanesously, we have explored these and other dialogic pedagogies together with the concept of cogenerativity to probe the notion of teacher professionalism – both for preservice teachers and our own as teacher educators. Debbie, Helen, and I have continued to collaborate over the past five years, having benefited from earlier TERI ventures and translation of our participation in these activities into international publications (peer-reviewed journal articles and chapters) and national conference presentations. A list of relevant outputs follows:
Forgasz, R., Heck, D., Williams, J., Ambrosetti, A., & Willis, L.-D. (2018). Theorising the third space of Professional Experience partnerships. In J. Kriewaldt, A. Ambrosetti, D. Rorrison, & R. Capeness (Eds.), Educating future teachers: Innovative perspectives in professional experience, (pp. 33–47). Springer: Singapore.
Grimmett, H., Heck, D., & Willis, L.-D. (2018). Becoming dialogical practitioners in initial teacher education classrooms. In Australian Association for Research in Education (AARE) Conference, Education Research Matters: Impact and Engagement, 2-6 December 2018, Sydney University, Sydney, New South Wales.
Heck, D., Forgasz, R., White, S, Williams, J., Tobin, K, Ambrosetti, A., & Willis, L.-D. (2016). Theorising the third space of professional experience partnerships. Australian Teacher Education Association (ATEA) Conference, 3-6 July 2016, Ballarat, VIC.
Heck, D., Grimmett, H., & Willis, L.-D. (2017). Using metalogue to develop an understanding of cogenerativity and school-university partnerships in initial teacher education. In Australian Association for Research in Education (AARE) Conference, Education: What’s politics got to do with it?, 26-30 December 2017, Hotel Realm Canberra, Canberra.
Heck, D., Grimmett, H., & Willis, L.-D. (2019 in press). Teacher educators using cogenerative dialogue to reclaim professionalism. In A. Gutierrez, J. Fox, & C. Alexander, Professionalism and teacher education: Voices from policy and practice, (Chapter 7). Springer: Singapore.
Willis, L.-D. (2016). Exploring cogenerativity for developing a coteaching community of practice in a parent-teacher engagement project. International Journal of Educational Research, 80,124–133. doi: http://dx.doi.org/10.1016/j.ijer.2016.08.009
Willis, L.-D., Grimmett, H., & Heck, D. (2018). Exploring cogenerativity in initial teacher education school-university partnerships using the methodology of metalogue. In J. Kriewaldt, A. Ambrosetti, D. Rorrison, & R. Capeness (Eds.), Educating future teachers: Innovative perspectives in professional experience, (pp. 49–69). Springer: Singapore.
Willis, L.-D., Heck, D., & Grimmett, H. (2019 submitted). Can LEGO® Serious Play® help teacher educators better understand the notion of professional identity? Australian Teacher Education Association (ATEA) Conference, 3-5 July 2019, Sunshine Coast, QLD.No Full Tex
Aurochs and heck cattle
No full textLes bovins de Heck, descendants de la re-création expérimentale de l\u27aurochs par les frères allemans Heinz et Lutz Heck, ont été introduits dans deux Projets hollandais de Dévelopement de la Nature. Les dynamiques des populations et la structure sociale des troupeaux, de même que leur impact sur la végétation font l\u27objet d\u27un suivi à long terme. Les données ostéométriques d\u27un individu mâle mort en 1987 sont comparées avec les données d\u27aurochs danois rassemblées par Degerbol et Fredskild (1970). À l\u27exception des largeurs proximale et distale de l\u27humérus, aucune des mesures prise sur les bovins de Heck n\u27atteint la taille des plus petits aurochs danois. Des écarts nets ont été trouvés dans les estimations des hauteurs au garrot en fonction de l\u27élément squelettique utilisé.So-called Heck cattle, descendants of the experimental rebreeding of the aurochs by the German brothers Heinz and Lutz Heck, have been introduced in two Dutch Nature Development Projects. The population dynamics and social structure of the herds as well as its impact on the vegetation are subject to long-term monitoring. The osteometric data of a male individual that died in 1987 are compared to the data of Danish aurochs assembled by Degerbol and Fredskild (1970). With the exception of the proximal and distal width of the humerus none of the heck measurements were found to reach the size of the smallest Danish aurochs. Large discrepancies were found in the estimated shoulder height according to the skeletal element that is used.</p
Review of The Inklings and Culture: A Harvest of Scholarship from the Inklings Institute of Canada
No full textJoel D. Heck: Review of Monika B. Hilder, Sara L. Pearson, and Laura N. Van Dyke, eds., The Inklings and Culture: A Harvest of Scholarship from the Inklings Institute of Canada (Newcastle upon Tyne, England: Cambridge Scholars Publishing, 2020). 397 pages. ISBN 9781527560147
Electrochemically Assisted Heck Reactions
No full textDuring efforts to develop chip-based Heck reaction chemistry, it was discovered that normal solution-phase Heck reactions can be dramatically
accelerated using electrochemistry. The acceleration makes room temperature Heck reactions proceed at synthetically useful rates in the
absence of added ligand. Presumably, the current passed through the reaction maintains a high level of active catalyst
Sequential stimulation of rat and guinea pig cerebellar granular cells in vitro leads to increasing population activity in parallel fibers
No full textSequential stimulation of the granular layer of the cerebellar cortex in vitro using II linearly aligned stimulating electrodes leads to massive population activity in the parallel fiber system and to spike activity in Purkinje cells (Heck, D., Neurosci. Lett., 157 (1993) 95-98; Heck, D., Naturwissenschaften, 82 (1995) 201-2030). The induced parallel fiber activity, however, might have been a result of direct stimulation of parallel fibers themselves and not of stimulation of granular cells or their ascending axons. We report here that using sequential 'moving' stimuli and varying the distance covered by the 'movement', parallel fiber population spike amplitude increases with distance and saturates for distances longer than 1.0 mm. This effect cannot be explained if parallel fibers are directly stimulated, but requires stimulation of the granular cells or their ascending axons. We conclude that the population spike activity and Purkinje cell responses induced by sequential stimulation of the granular layer of the cerebellar cortex slices in this and earlier experiments consists of orthodromic parallel fiber spikes. (C) 1999 Published by Elsevier Science Ireland Ltd. All rights reserved
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