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Our ability to understand and predict the fate and transport of contaminants in natural systems is vital if we are to be successful in protecting our water resources. One important aspect of understanding chemical fate and transport in natural systems is identifying key kinetic controls on important redox reactions such as sulfate reduction. Anaerobic microbial activities like sulfate reduction are of particular interest because of the important role they play in the degradation of contaminants in the subsurface. However, current rate estimates for sulfate reduction have a wide range in the literature making it difficult to determine representative rates for a given system. These differences in rate data may be explained by varying kinetic controls on reactions. Push-pull tests were used to evaluate sulfate reduction rates at the wetland-aquifer interface. Anaerobic aquifer water containing abundant sulfate was injected into sulfate-depleted wetland porewater. The injected water was subsequently withdrawn and analyzed for geochemical indicators of sulfate reduction. Complexities in rate data, such as presence of a lag phase, changing rate order and spatial variability, were observed and are hypothesized to be linked to activities of the native microbial population. Subsequent experiments explored the response of native microorganisms to geochemical perturbations using a novel approach to measure directly the effects of a geochemical perturbation on an in situ microbial population and measure rates of resulting reactions. In situ experiments involved colonization of a substrate by microorganisms native to the wetland sediments followed by introductions of native water amended with sulfate and tracer. Experimental results showed that higher sulfate concentrations and warmer seasonal temperatures result in faster sulfate reduction rates and corresponding increases in sulfate reducing bacteria. Findings from this research provide quantitative evidence of how geochemical and microbiological processes are linked in a system not at equilibrium.

It is important to optimize glass compositions for their specific purpose but also for the efficiency of the production process, the manufacturing of glass. This will be beneficial economically and environmentally. Today many processes and glass compositions are already optimized, but due to more strict legislation on toxic elements and substances there must be changes in many glass compositions. One of these elements is antimony; the oxide is used as fining agent to obtain a bubble free glass within a reasonable process time. One aim with this thesis is to obtain a deeper understanding of the fining mechanism in 20R2O-10MO-70SiO2 (R=Na and/or K, M = Ca and/or Ba, Mg, Sr) glasses in order to minimise the amount of Sb2O3. Another intention is to study the structure of 20R2O-10CaO-70SiO2 (R = Na, K) with Cu2+ as probe ion and thus get a deeper knowledge of the surrounding glass matrix.  The optical basicity scale is used to determine the acid/base character of the different glass compositions.   Fining efficiency results showed a remarkable increase of the number of remaining bubbles when the glass contains either approximately equal amounts of Na and K or Ca and Ba, Mg or Sr. The much higher number of bubbles in the potassium containing glasses compared to the sodium containing is explained by the increase in viscosity, the increase in optical basicity and thus lower oxygen activity. The differences in the fining efficiency when altering alkaline earth ions cannot be explained by the optical basicity values, it seems to be a more complicated situation.   This thesis also reports maximum in Vickers hardness and packing density as well as minimum in glass transition temperature for the mixed alkali glasses. The mixed alkaline earth glasses do not exhibit any clear nonlinear behaviour. Raman spectroscopy measurements showed a variation in the network connectivity which has a clear relation to the optical basicity of the different glass compositions. The combination of UV-Vis-NIR and X-ray absorption spectroscopy measurements showed that the coordination sphere for Cu(II) is a tetragonal distorted octahedron with two elongated Cu-O bonds along the z axis. There were no trends in the degree of tetragonal distortion, thus it was about the same for all the investigated glass compositions. Cu(I) is found to be coordinated by two oxygen ligands in mainly linear coordination sphere, evidenced from X-ray absorption spectroscopy.

Nesta pesquisa são apresentados os resultados de uma investigação que teve como objetivo acessar o conhecimento docente de futuros professores de química, no contexto do Programa Institucional de Bolsa de Iniciação à Docência (Pibid). Esta pesquisa figura como um estudo de caso. Os dados se baseiam nas narrativas registradas por meio de gravações audiovisuais de três participantes da pesquisa durante as reuniões do subprojeto Pibid-química, regências e entrevistas semiestruturadas. Além destes, foram analisados relatórios, planos de aula, questionários dos pibidianos e um instrumento de percepção dos alunos da escola conveniada sobre o conhecimento docente dos licenciandos. Investigaram-se ainda os possíveis impactos do Pibid na formação da coordenadora e supervisora que orientaram os pibidianos. Buscou-se, por meio dos diversos documentos, indícios do conhecimento docente dos licenciandos bolsistas Pibid. A análise dos dados qualitativos teve como fundamentação teórica a análise de conteúdo, sendo as categorias provenientes do modelo do conhecimento base em conjunto com o modelo pentagonal. A análise do instrumento de percepção permeou métodos estatísticos. Para analisar as marcas deixadas pelo Pibid na formação da coordenadora e supervisora, adotaram-se as categorias do modelo conhecimento docente e outras emergentes. O pibidiano Antônio apresentou um bom conhecimento de conteúdo, de seus alunos e de suas limitações em relação ao conteúdo redox. Por outro lado, em algumas passagens das aulas, teve dificuldades em organizar a classe e o tempo de sua aula ao conteúdo. Antônio fez uso, em suas sequências didáticas, de diferentes instrumentos avaliativos. As suas estratégias de ensino se baseavam principalmente em práticas experimentais, na leitura, entre outros. A pibidiana Melissa demonstrou não dominar o conteúdo de reações redox, não ter conhecimento de currículo e de estratégias para desenvolver o conceito que ensinava. Grande parte dos conhecimentos docentes que emergiram dos documentos analisados da pibidiana foi reflexo das orientações que recebia das tutoras e também da experiência oportunizada pelo Pibid de como acessar as dificuldades dos alunos com o conteúdo específico, experimentar a gestão de classe e a organização de aulas. As avaliações adotadas pela pibidiana tinham por objetivo coletar dados para o subprojeto. Durante a sua regência não demonstrou uma preocupação com a aprendizagem dos alunos, mas em executar o currículo pretendido e aplicar as avaliações. O pibidiano Mateus demonstrou também limitações com o conteúdo e em selecionar os conceitos necessários para a aprendizagem dos discentes. Apresentou ainda dificuldades com a gestão do tempo e da classe. Por outro lado, passou a conhecer as barreiras conceituais dos discentes com o conteúdo redox, a partir de sua vivência no Pibid. Diversas das decisões sobre o fazer no ensino de ciências eleitas por Mateus foram orientações da supervisora. Pelo mapeamento infere-se que os conhecimentos para a docência acessados pelos pibidianos foram reflexo do Pibid personificado na figura das tutoras e pela experiência em sala. Evidenciou-se ainda que o Pibid vem contribuindo para a formação continuada da coordenadora, por possibilitar que a professora universitária conheça, por exemplo, a realidade da escola da educação básica; e da supervisora, por conceber-se como co-formadora dos licenciandos. Conclui-se que o conhecimento docente acessado por Mateus e Melissa foi influenciado pelas orientações da coordenadora. Acredita-se que o contato com o futuro ambiente profissional e a tutoria pelas docentes experientes oportunizaram aos pibidianos acessar os conhecimentos inerentes ao desenvolvimento do conhecimento base e do PCK. / This study presents the results of a research that aimed to access the teacher knowledge of future chemistry teachers, in the context of the Institutional Program for Scholarships for Initiation in Teaching (Pibid). This is a case study. Data were collected from audiovisual recordings of narratives from three participants during the Pibid-chemistry meetings, from regencies and from semi-structured interviews. In addition, Pibid-participants\' reports, lesson plans and questionnaires were analyzed, and an instrument that assessed the students\' perception about the teacher knowledge of the undergraduate students regarding teaching practices. The possible impacts of Pibid on the training of the coordinator and supervisor who guided the Pibid participants were also analyzed. Several documents were analyzed for evidence of the teacher knowledge of the Pibid students. The theoretical background for the analysis of qualitative data was based on content analysis, with categories from the base knowledge and the pentagonal model. The analysis of the students\' perception instrument was based on statistical methods. In order to analyze the marks left by Pibid in the training of the coordinator and supervisor, the study adopted the categories of teaching knowledge´model and other emerging ones. Pibid participant Antônio presented consistent content knowledge, students knowledge and students difficulties knowledge in relation to the redox content. On the other hand, in some occasions during classes, he had difficulties organizing the class and the content into the class time. Antônio used, in his didactic sequences, different evaluation instruments. His teaching strategies were based mainly on experimental practices, reading, among others. Pibid-participant Melissa demonstrated not master the redox reactions content, she did not have any knowledge about curricula and so could not develop strategies to work with the subject she taught. Much of the teaching knowledge that emerged from the documents analyzed from Melissa reflects the guidelines that she received from the coordinator and supervisor and from the experience offered by Pibid: how to access students\' difficulties with a specific content, how to deal with class management and organizing the classrooms. The assessment instruments adopted by Melissa were aimed at collecting data for the subproject. During her regency, she did not show concern for student learning, but in executing the intended curriculum and applying the assessments. Another Pibid participant, Mateus also seemed to have limited content knowledge and about selecting the necessary concepts for students learning. He also presented difficulties with time and class management. On the other hand, he came to understand the students\' conceptual difficulties with the redox content from his experience in Pibid. Several of the decisions that must be made in science education chosen by Mateus were guidelines given by his supervisor. From the mapping, it is inferred that the teaching knowledge accessed by the participants was a reflection of Pibid participation, personified in the figure of the tutor and by the experience in the classroom. It was also evidenced that Pibid contributes to the continued professional developing of the coordinator, by enabling university professors to know, for instance, the reality of basic education schools; and of supervisors, for conceiving themselves as co-teachers of the teaching students. The conclusion drawn is that the teaching knowledge accessed by Mateus and Melissa were influenced mainly by the coordinator\'s guidelines. It is believed that contact with their future work environment and tutoring by experienced teachers were fundamental for Pibid participants to access the knowledge inherent to the development of basic knowledge and the PCK.

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Made available in DSpace on 2014-10-09T12:46:08Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:59Z (GMT). No. of bitstreams: 1 07531.pdf: 3726046 bytes, checksum: b6529bbc772b1dbd5d07980b9fc50ca0 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Nesta pesquisa são apresentados os resultados de uma investigação que teve como objetivo acessar o conhecimento docente de futuros professores de química, no contexto do Programa Institucional de Bolsa de Iniciação à Docência (Pibid). Esta pesquisa figura como um estudo de caso. Os dados se baseiam nas narrativas registradas por meio de gravações audiovisuais de três participantes da pesquisa durante as reuniões do subprojeto Pibid-química, regências e entrevistas semiestruturadas. Além destes, foram analisados relatórios, planos de aula, questionários dos pibidianos e um instrumento de percepção dos alunos da escola conveniada sobre o conhecimento docente dos licenciandos. Investigaram-se ainda os possíveis impactos do Pibid na formação da coordenadora e supervisora que orientaram os pibidianos. Buscou-se, por meio dos diversos documentos, indícios do conhecimento docente dos licenciandos bolsistas Pibid. A análise dos dados qualitativos teve como fundamentação teórica a análise de conteúdo, sendo as categorias provenientes do modelo do conhecimento base em conjunto com o modelo pentagonal. A análise do instrumento de percepção permeou métodos estatísticos. Para analisar as marcas deixadas pelo Pibid na formação da coordenadora e supervisora, adotaram-se as categorias do modelo conhecimento docente e outras emergentes. O pibidiano Antônio apresentou um bom conhecimento de conteúdo, de seus alunos e de suas limitações em relação ao conteúdo redox. Por outro lado, em algumas passagens das aulas, teve dificuldades em organizar a classe e o tempo de sua aula ao conteúdo. Antônio fez uso, em suas sequências didáticas, de diferentes instrumentos avaliativos. As suas estratégias de ensino se baseavam principalmente em práticas experimentais, na leitura, entre outros. A pibidiana Melissa demonstrou não dominar o conteúdo de reações redox, não ter conhecimento de currículo e de estratégias para desenvolver o conceito que ensinava. Grande parte dos conhecimentos docentes que emergiram dos documentos analisados da pibidiana foi reflexo das orientações que recebia das tutoras e também da experiência oportunizada pelo Pibid de como acessar as dificuldades dos alunos com o conteúdo específico, experimentar a gestão de classe e a organização de aulas. As avaliações adotadas pela pibidiana tinham por objetivo coletar dados para o subprojeto. Durante a sua regência não demonstrou uma preocupação com a aprendizagem dos alunos, mas em executar o currículo pretendido e aplicar as avaliações. O pibidiano Mateus demonstrou também limitações com o conteúdo e em selecionar os conceitos necessários para a aprendizagem dos discentes. Apresentou ainda dificuldades com a gestão do tempo e da classe. Por outro lado, passou a conhecer as barreiras conceituais dos discentes com o conteúdo redox, a partir de sua vivência no Pibid. Diversas das decisões sobre o fazer no ensino de ciências eleitas por Mateus foram orientações da supervisora. Pelo mapeamento infere-se que os conhecimentos para a docência acessados pelos pibidianos foram reflexo do Pibid personificado na figura das tutoras e pela experiência em sala. Evidenciou-se ainda que o Pibid vem contribuindo para a formação continuada da coordenadora, por possibilitar que a professora universitária conheça, por exemplo, a realidade da escola da educação básica; e da supervisora, por conceber-se como co-formadora dos licenciandos. Conclui-se que o conhecimento docente acessado por Mateus e Melissa foi influenciado pelas orientações da coordenadora. Acredita-se que o contato com o futuro ambiente profissional e a tutoria pelas docentes experientes oportunizaram aos pibidianos acessar os conhecimentos inerentes ao desenvolvimento do conhecimento base e do PCK. / This study presents the results of a research that aimed to access the teacher knowledge of future chemistry teachers, in the context of the Institutional Program for Scholarships for Initiation in Teaching (Pibid). This is a case study. Data were collected from audiovisual recordings of narratives from three participants during the Pibid-chemistry meetings, from regencies and from semi-structured interviews. In addition, Pibid-participants\' reports, lesson plans and questionnaires were analyzed, and an instrument that assessed the students\' perception about the teacher knowledge of the undergraduate students regarding teaching practices. The possible impacts of Pibid on the training of the coordinator and supervisor who guided the Pibid participants were also analyzed. Several documents were analyzed for evidence of the teacher knowledge of the Pibid students. The theoretical background for the analysis of qualitative data was based on content analysis, with categories from the base knowledge and the pentagonal model. The analysis of the students\' perception instrument was based on statistical methods. In order to analyze the marks left by Pibid in the training of the coordinator and supervisor, the study adopted the categories of teaching knowledge´model and other emerging ones. Pibid participant Antônio presented consistent content knowledge, students knowledge and students difficulties knowledge in relation to the redox content. On the other hand, in some occasions during classes, he had difficulties organizing the class and the content into the class time. Antônio used, in his didactic sequences, different evaluation instruments. His teaching strategies were based mainly on experimental practices, reading, among others. Pibid-participant Melissa demonstrated not master the redox reactions content, she did not have any knowledge about curricula and so could not develop strategies to work with the subject she taught. Much of the teaching knowledge that emerged from the documents analyzed from Melissa reflects the guidelines that she received from the coordinator and supervisor and from the experience offered by Pibid: how to access students\' difficulties with a specific content, how to deal with class management and organizing the classrooms. The assessment instruments adopted by Melissa were aimed at collecting data for the subproject. During her regency, she did not show concern for student learning, but in executing the intended curriculum and applying the assessments. Another Pibid participant, Mateus also seemed to have limited content knowledge and about selecting the necessary concepts for students learning. He also presented difficulties with time and class management. On the other hand, he came to understand the students\' conceptual difficulties with the redox content from his experience in Pibid. Several of the decisions that must be made in science education chosen by Mateus were guidelines given by his supervisor. From the mapping, it is inferred that the teaching knowledge accessed by the participants was a reflection of Pibid participation, personified in the figure of the tutor and by the experience in the classroom. It was also evidenced that Pibid contributes to the continued professional developing of the coordinator, by enabling university professors to know, for instance, the reality of basic education schools; and of supervisors, for conceiving themselves as co-teachers of the teaching students. The conclusion drawn is that the teaching knowledge accessed by Mateus and Melissa were influenced mainly by the coordinator\'s guidelines. It is believed that contact with their future work environment and tutoring by experienced teachers were fundamental for Pibid participants to access the knowledge inherent to the development of basic knowledge and the PCK.

The reversible reduction of hexacyanoferrate(III) to the Fe(II) form is a well-known standard in electrochemistry. It is however reported to be highly dependent on the solvent environment.[i] This electrochemical project has aimed to examine the behaviour of ferricyanide in aprotic environment by changing the solvent to acetonitrile, a medium polar solvent with a high dielectric constant. The method used for research is cyclic voltammetry. Ferricyanide has been examined in aqueous and aprotic solvent and has been studied in comparison to ferrocene, which is a well-known chemical substance. When studying ferricyanide in acetonitrile solvent under inert conditions, a completely new voltammetric picture was drawn where the standard reduction potential in aqueous solvent of 43 mV (SCE) was dramatically lowered and a new redox reaction with a higher reduction potential seemed to be present at -97mV (Ag/Ag+) when ferricyanide went through redox process from 0 V to +1.3 V to -0.5 V and back to 0V again. When examining the redox process an EC reaction was found to be coupled to the new peak. This process was studied within the time limit for the project. Some properties of the possible chemical has been presented and the conclusions are discussed in the report. Suggestions are made for how to move forward with the research. [i] (a) Gutmann V., Gritzner G., and Danksagmuller K., Inorganica Chimica Acta, 17 1976 81; (b) Noftle R.E. and Pletcher D., Journal of Electroanalytical Chemistry, 1990 273, 293.

Redox reactions are crucial to biological processes that protect organisms against oxidative stress. Metalloenzymes, such as cytochrome c peroxidases which reduce excess hydrogen peroxide into water in the periplasm of multiple bacterial organisms, play a key role in detoxification mechanisms. While accurate computational tools can be used to simulate ground state redox potentials in biomolecules, adapting such approaches to properly describe redox reactions in transition metal complexes, particularly in hemes in heterogeneous protein environments, remains a significant challenge. Here we present the results of polarizable hybrid QM/MM studies of the reduction potentials of two heme sites in the cytochrome c peroxidase of Nitrosomonas europaea. The simulated redox potential of the catalytic site Low Potential (LP) is in good agreement with the experiment, while for the High Potential (HP) heme the computational estimate significantly overestimate the experimental value. We have found that environment polarization shifts the computed value of the redox potential of the catalytic LP heme by 1.3 V, while it does not affect that of the non-catalytic High Potential (HP) heme. We demonstrate that it is necessary to account for mutual polarization of heme site and the protein environment when describing redox processes, particularly those that involve more charged heme sites. We have explored the role of various factors such as heme geometries, axial ligands, propionate side chains, and electrostatic field of the protein in tuning the redox potentials of hemes in NeCcP. The fluctuations in computed vertical ionization and electron attachment energies are predominantly affected by fluctuations in the electrostatic field of the environment but not by fluctuations in heme geometries. We attribute the difference in computed LP and HP heme reduction potentials of 0.05 V and 1.15 V, respectively, to different axial ligands and electrostatic interactions of the hemes with the protein environment. / 2023-06-30T00:00:00Z