Reactivity Stability
Mostrando 25-36 de 98 artigos, teses e dissertações.
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25. ZEOLITE AND WOLASTONITE SYNTHESIS FROM RICE HULL ASH / "Síntese de Zeólitas e Wolastonita à partir da cinza da casca do arroz"
Rice hull ash (RHA) is a industry scrap rich in amorphous silica. A simple and low-energy cost method for the extraction of this silica was researched. A low level of impurity and high reactivity material was produced, which is appropriate for the synthesis of zeolites and wolastonite (CaSiO3). The synthetic zeolites, has not similar structures in nature, an
Publicado em: 2006
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26. Síntese e Análise Estrutural de Complexos de Urânio(VI) com Hidrazonas, Semicarbazonas e Ligantes Relacionados. / Synthesis and Structural Analysis of Uranium(VI) Complexes with Hydrazones, Semicabazones and Related Ligands.
Uranyl complexes with ligands with oxygen and nitrogen donors have been extensively reviewed and they have aroused interest on account of their high stability, usefulness in selective chemical separations and their formation in higher coordination numbers, but quite a few complexes of hydrazone and semicarbazone ligands have been reported. This fact was the
Publicado em: 2006
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27. Composition of carotenoids and anthocyanins from acerola : stability and antioxidant activity of anthocyaninc extracts from acerola and açai in model-systems. / Composição de carotenoides e antocianinas em acerola : estabilidade e atividade antioxidante em sistemas-modelo de extratos antocianicos de acerola e de açai.
Natural pigments, such as anthocyanins and carotenoids, are responsible for the colors found in foods, influencing its visual aspect, which is considered the main attribute for the acceptance and preference of a food product. At the same time, these pigments show important biological functions and actions, being considered human health promoters. The associa
Publicado em: 2006
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28. Preparation and characterization of mixed modified electrodes used in electrocatalytic hydrogenation of organic substrates / Preparação e caracterização de eletrodos modificados mistos e seu uso em hidrogenação eletrocatalítica de substratos orgânicos
This thesis describes the preparation of new modified electrodes (MEs) using the method of noble metal particles deposition like nickel, palladium and platinum in the surface of commum metals particles as cooper and iron. This new electrodes were denominated mixed MEs, and can show different caractheristics and present higher efficiency than others already s
Publicado em: 2006
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29. Synthesis, characterization and study of catalytical properties of mixed layered hydroxides containing Cu(II)/Mg(II)/Al(III) / Síntese, caracterização e estudo de propriedades catalíticas de hidróxidos mistos lamelares contendo Cu(II)/Mg(II)/AI(III)
In this work it was investigated the preparation and spectroscopic characterization of layered hydroxides of composition [Mg3-xCuxAl(OH)8](CO3)0.5.yH2O (x = 0.3; 0.6; 0.9; 1.2; 1.5; 1.8; 2.1; 2.4; 2.7 and 3.0), as well the reactivity of these materials towards phenol hydroxylation, using hydrogen peroxide as oxidizing agent. The solids had been prepared thro
Publicado em: 2005
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30. Cross-sectional study defines difference in malaria morbidity in two Yanomami communities on Amazonian boundary between Brazil and Venezuela
It is well established that immunity to malaria is short-lived and is maintained by the continuous contact with the parasite. We now show that the stable transmission of malaria in Yanomami Amerindian communities maintains a degree of immunity in the exposed population capable to reduce prevalence and morbidity of malaria. We examined 508 Yanomami Amerindian
Memórias do Instituto Oswaldo Cruz. Publicado em: 2004-06
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31. The conservative physiology of the immune system
Current immunological opinion disdains the necessity to define global interconnections between lymphocytes and regards natural autoantibodies and autoreactive T cells as intrinsically pathogenic. Immunological theories address the recognition of foreignness by independent clones of lymphocytes, not the relations among lymphocytes or between lymphocytes and t
Brazilian Journal of Medical and Biological Research. Publicado em: 2003-01
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32. Multivariable robust control of an integrated nuclear power reactor
The design of the main control system of the CAREM nuclear power plant is presented. This plant is an inherently safe low-power nuclear reactor with natural convection on the primary coolant circuit and is self-pressurized with a steam dome on the top of the pressure vessel (PV). It is an integrated reactor as the whole primary coolant circuit is within the
Brazilian Journal of Chemical Engineering. Publicado em: 2002-12
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33. Derivados organometálicos de estanho(II) - Parte 1. Compostos ciclopentadienílicos
This paper provides a brief review of the chemistry of cyclopentadienyl Sn(II) derivatives which includes the preparation, the molecular structure and reactivity associated with such bis-sandwich tin(II) species. It is compared structural and spectroscopic results and it is also discussed how the nature of the cyclopentadienyl ring bonded to the Sn centre pl
Química Nova. Publicado em: 2001-08
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34. Blendas de polipirrol e poli(cloreto de vinila) : propriedades termicas, mecanicas e eletroquimicas
Blends including an intrinsically conductive polymer, polypyrrole or polythiophene, and an insulating polymer, PVC, were prepared. The method used was the oxidative chemical polymerization of the heterocyclic monomers, in the vapor phase, in PVC films impregnated with an oxidant agent (FeCl3). This procedure was efficient for the preparation of blends compos
Publicado em: 1995
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35. Oxido de niobio (v) enxertado sobre silica gel : estabilidade termica, acidez e reatividade de especies absorvidas
Silica gel was chemically modified with niobium(V) oxide was obtained reacting silanol groups of the silica gel surface with niobium pentachlorite, in organic solvent. The amount of niobium(V) oxide grafted on silica gel surface was 0.89 x 10mol.g. Only Nb(v) ion in the SiNb material were observed by XPS analysis. The binding energy values found for Nb were
Publicado em: 1994
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36. Estrutura e reatividade de sulfóxidos de rutênio com bases heterocíclicas nitrogenadas / Structure and reactivity of ruthenium sulfoxides containing nitrogen heterocyclic bases
Ruthenium(II) sulfoxides are compounds of great interest in oxidative catalysis and in chemotherapy. In order to contribute for the understanding of the chemistry and electronic structure of this class of compounds, it has been studied a series of [RuCl2(S-dmso)2Lx] complexes, where x = 1 (polymeric compounds) or 2 (monomers) and L = N-heterocyclic ligands (
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 30/11/1990