1000 resultados para Química seca


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Combinatorial chemistry has emerged as a tool to circumvent a major problem of pharmaceutical industries to discover new lead compounds. A rapid and massive evaluation of a myriad of newly synthesised compounds can be carried out. Combinatorial synthesis leads to high throughput screening en masse towards another myriad of biological targets. The design of a set of compounds based upon combinatorial chemistry may be envisaged by using of QSPR-SIMCA and QSAR-SIMCA as tools for classification purposes. This work deals with the definition and establishment of a spanned substituent space (SSS) that reduces the analogue numbers with no exclusion of global content. The chemical diversity may be set properly within a specified pharmacological field. This allows a better use of its potentiality without loosing information.

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This article presents the basic ideas that oriented the elaboration of the new Chemistry Curriculum for the High Schools in the State of Minas Gerais, Brazil. The main features of traditional Brazilian Chemistry Curriculum are critically discussed, namely, the excessive number of concepts, the overemphasis in procedures and rituals instead of chemical principles and the lack of relationship between the concepts and the social, technological and environmental contexts. Trying to overcome these features, the proposed curriculum deals with a fewer number of concepts, clearly related in a conceptual structure, opening space to a balanced emphasis on phenomena, theory and representation, and on conceptual and contextual aspects of chemical knowledge.

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The chemical reactivity of safrole, eugenol, piperonal, vanillin and derivates toward ozone, aluminium chloride, brominating agents and butyl lithium was investigated. The synthesis of naturally occuring anthraquinones, furonaphthoquinones, naphthoquinones, lignans and pterocarpans from these easily available staring materials is also discussed.

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This work intends to identify the reasons why people either like or dislike chemistry classes, based on a written questionnaire answered by 157 students of private and public schools. It has a main question - "Do you like to study chemistry? Why?" - and along with others that complement it, we attempt to explore both pupils' school and personal experiences which help them to increase their learning capacities. The answers have given us a very rich piece of discussing material about the like-and-dislike on the study of chemistry mainly about the social interactions in teaching not only this but all other subjects.

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An overview of the last thirty years of the General Chemistry Course applied to the freshmen in our Institute is presented. All the changes introduced in the course since the first time it was offered up to our days are described and a discussion of the program now developed is given.

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The topics developed in the first discipline applied to the freshmen at the Chemistry Institute of UNICAMP are described, along with a discussion of how the program is developed in our days.

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Chemical Technology and Fine Chemicals, in the sense we understand them, go back not to Leblanc's soda production process, as many historians of Science and chemists suggest, but to the XVIIth Century, with the "technological" activities of Glauber and others; the Paracelsian Thurneisser can be seen as the first to produce "fine chemicals".

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In this paper we discuss an approach for two initial topics in Chemistry: atomic structure and periodic table. The focus of this approach is the use of educational software resources in the perspective of teacher's formation.

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Some general features about the role of Science and Technology in the modern western civilizations are discussed, emphasizing those related to Chemistry. The discussion is centered on the social regulation of technological and scientific institutions and on the way this regulation takes place in response to social demands. Finally, some new trends are presented about the Brazilian chemistry courses and how the local educational authorities intend to modernize them.

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The chemical and physical characterization of coastal peat has been studied. It was examined the pH, organic matter content and elementary and XRD analyses, among other characteristics. The peat was then applied to the retention and competition of metal micronutrients (Cu and Zn) from metal nitrate solutions. The retention was affected by both the pH and time of adsorption, while the competitive character of these metals for the substrate was relevant to each pH examined.

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This review deals with the general use of the surfactants in Analytical Chemistry. Principal characteristic of the micelle is the improvement in selectivity and/or sensitivity of the analytical determination with emphasis on the catalytic reaction and "cloud point" extraction.

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There is no question that students majoring in chemistry graduate with underdeveloped writing skills. Many educators have expressed concern about the obvious deficiencies in student writing. This article is designed to aid professors interested in teaching writing skills in their classrooms and laboratories.

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Chemically modified electrodes based on hexacyanometalate films are presented as a tool in analytical chemistry. Use of amperometric sensors and/or biosensors based on the metal-hexacyanoferrate films is a tendency. This article reviews some applications of these films for analytical determination of both inorganic (e.g. As3+, S2O3(2-)) and organic (e.g. cysteine, hydrazine, ascorbic acid, gluthatione, glucose, etc.) compounds.

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Combinatorial Chemistry has become a very efficient methodology in drug research. Recent progress in combinatorial synthesis performed both in solid and solution phase have led to a change in the paradigm for the identification and optimization of lead compounds. This article gives an overview of the principal characteristics of combinatorial libraries and some examples of the application of this methodology in the identification of test compounds and lead compound optimization, either from synthetic or natural sources.