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- ItemSomente MetadadadosCharacterization of the Biocompatible Magnetic Colloid on the Basis of Fe(3)O(4) Nanoparticles Coated with Dextran, Used as Contrast Agent in Magnetic Resonance Imaging(Amer Scientific Publishers, 2010-07-01) Gamarra, L. F.; Amaro, E.; Alves, S. [UNIFESP]; Soga, D.; Pontuschka, W. M.; Mamani, J. B.; Carneiro, S. M.; Brito, G. E. S.; Figueiredo Neto, A. M.; IIEPAE; Universidade de São Paulo (USP); Universidade Federal de São Paulo (UNIFESP); Inst ButantanThe magnetic resonance imaging contrast agent, the so-called Endorem (TM) colloidal suspension on the basis of superparamagnetic iron oxide nanoparticles (mean diameter of 5.5 nm) coated with dextran, were characterized on the basis of several measurement techniques to determine the parameters of their most important physical and chemical properties. It is assumed that each nanoparticle is consisted of Fe(3)O(4) monodomain and it was observed that its oxidation to gamma-Fe(2)O(3) occurs at 253.1 degrees C. the Mossbauer spectroscopy have shown a superparamagnetic behavior of the magnetic nanoparticles. the Magnetic Resonance results show an increase of the relaxation times T(1), T(2), and T(2)* with decreasing concentration of iron oxide nanoparticles. the relaxation effects of SPIONs contrast agents are influenced by their local concentration as well as the applied field strength and the environment in which these agents interact with surrounding protons. the proton relaxation rates presented a linear behavior with concentration. the measured values of thermooptic coefficient partial derivative n/partial derivative T, thermal conductivity K, optical birefringence Delta n(0), nonlinear refractive index n(2), nonlinear absorption beta' and third-order nonlinear susceptibility vertical bar chi((3))vertical bar are also reported.
- ItemAcesso aberto (Open Access)Estudo do comportamento térmico, físico-químico e analítico do fruto de Hymenaea courbaril L. (Jatobá)(Universidade Federal de São Paulo, 2013-06-12) Segismundo, Natalia Raiz [UNIFESP]; Mercuri, Lucildes Pita [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Hymenaea courbaril L. ou jatobá é uma árvore que produz frutos em forma de vagem apresentando casca, polpa, fibra e sementes. Os estudos de produtos naturais são importantes para conhecer a sua composição química e determinar as propriedades terapêuticas. Esse trabalho tem como objetivo principal estudar o comportamento térmico com base na caracterização química e físico-química do fruto de jatobá nas safras de 2010 e 2012. Para isso foram utilizada as seguintes técnicas analíticas, físico-química e física: análise elementar (AE), termogravimetria/termogravimetria derivada (TG/DTG), calorimetria exploratória diferencial (DSC), espectroscopia de absorção na região do infravermelho com transformada de Fourier (FTIR) e difratometria de raios X (DRX). Os resultados de AE indicaram que as amostras CASNL10 e CASNL12 apresentaram maiores teores de carbono, mostrando que há resíduos de polpa e fibra nas amostras CASL10 e CASL12, retirados pela lavagem. Os espectros de FTIR evidenciaram a presença de vários compostos, como: carboidratos, lipídeos, óleos vegetais, celulose, carbonatos e outros para ambas as safras. As curvas TG/DTG das amostras de 2010 indicaram que a decomposição térmica, com exceção da polpa, ocorre em três eventos, e a amostra POL10 em cinco eventos consecutivos. Para a safra de 2012, as amostras CASNL12, CASL12 e SEM12, apresentaram decomposição térmica em três eventos consecutivos, enquanto as amostras POL12 e FIB12 tiveram quatro eventos. O estudo dos intermediários de decomposição térmica é necessário para a compreensão da composição química desse material. Os resultados de AE e FTIR dos intermediários corroboram com os dados obtidos das curvas TG/DTG. Os difratogramas desses intermediários obtidos a 900 °C apresentam cristalinidade, devido à presença de compostos inorgânicos, como verificado pelo FTIR. Com base nos resultados de TG/DTG, DSC e FTIR, pode-se avaliar que o comportamento térmico do fruto mudou entre as safras devido às diferenças nas condições climáticas dos anos precedentes às safras escolhidas. Outra observação importante foi quanto aos resultados de DRX, para a safra de 2010, e TG/DTG e DSC, para a safra de 2012, que caracteriza o processo de lavagem como uma etapa que interfere na composição química da casca de jatobá.
- ItemAcesso aberto (Open Access)Formation of Composite Polyaniline and Graphene Oxide by Physical Mixture Method(Inst Aeronautica & Espaco-Iae, 2017) Vargas, Ludmila Resende; Poli, Anne Karoline; Lazzarini Dutra, Rita de Cassia; Souza, Camila Brito de [UNIFESP]; Baldan, Mauricio Ribeiro; Goncalves, Emerson SarmentoThe development of polyaniline and graphene oxide composites aims to join the unique properties of each material for aerospace applications. The present paper demonstrates an easy and quick method, compared to the ones found in the literature, to obtain a composite made with polyaniline doped with dodecylbenzenesulfonic acid, a combination commonly called polyaniline, and graphene oxide. Nowadays, the most common studied methods are electrochemistry and in situ chemical polymerization. Differently from these methods, the films were obtained by a physical mixture of equimolar suspension of graphene oxide (4 mg/mL) with 3 concentrations of polyaniline powder: 25
- ItemAcesso aberto (Open Access)Lipid bilayer pre-transition as the beginning of the melting process(Elsevier B.V., 2009-05-01) Riske, Karin Amaral [UNIFESP]; Barroso, Rafael P.; Vequi-Suplicy, Cíntia Cristina; Germano, Renato; Henriques, Vera B.; Lamy, Maria Teresa; Universidade de São Paulo (USP); Universidade Federal de São Paulo (UNIFESP)We investigate the bilayer pre-transition exhibited by some lipids at temperatures below their main phase transition, and which is generally associated to the formation of periodic ripples in the membrane. Experimentally we focus on the anionic lipid dipalmytoylphosphatidylglycerol (DPPG) at different ionic strengths, and on the neutral lipid dipalmytoylphosphatidylcholine (DPPC). From the analysis of differential scanning calorimetry traces of the two lipids we find that both pre- and main transitions are part of the same melting process. Electron spin resonance of spin labels and excitation generalized polarization of Laurdan reveal the coexistence of gel and fluid domains at temperatures between the pre- and main transitions of both lipids, reinforcing the first finding. Also, the melting process of DPPG at low ionic strength is found to be less cooperative than that of DPPC. From the theoretical side, we introduce a statistical model in which a next-nearest-neighbor competing interaction is added to the usual two-state model. for the first time, modulated phases (ordered and disordered lipids periodically aligned) emerge between the gel and fluid phases as a natural consequence of the competition between lipid-lipid interactions. (C) 2009 Elsevier B.V. All rights reserved.
- ItemSomente MetadadadosSíntese e estudo das transições de fases estruturais no sistema (1−x)Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3 (BCZT) utilizando a associação de diferentes técnicas de caracterização(Universidade Federal de São Paulo (UNIFESP), 2019-07-31) Aredes, Rangel Graudiston [UNIFESP]; Antonelli, Eduardo [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Lead-free piezoelectric ceramics can demonstrate excellent properties when their compositions are projected with sequences of specific phase transitions and / or the coexistence of phases. It has been reported that some compositions of (1−x)Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3 (xBCZT) may present phases coexistence (rhombohedral “R” and orthorhombic “O”) at room temperature. Besides, recent studies have observed the O phase as an intermediate phase before the tetragonal “T”-cubic “C” phase transitions. Herein, we study the xBCZT to verify if the experimental characterizations can detect R-O, O-T and T-C phase transitions and identify the physical anomalies that confirm the phases coexistence. The phase transitions were studied during a heating program for xBCZT and compared with pure BaTiO3 by dielectric spectroscopy, pyroelectric coefficient analyses, thermal analyses, linear expansion and powder X-ray diffraction. The interpretation of different responses allows us to conclude that the substitutions of Ca2+ for Ba2+ or Zr4+ for Ti4+ in the formulation xBCZT can result in two or more different solid solutions, belonging to the perovskite family, which coexist in the ceramic. The transitions of each one of the phases happen in a cooperative effect and, in some specific interval of temperatures, the break of the cooperative effect happens and make clear the phase coexistence.
- ItemSomente MetadadadosThermoanalytical study of inner and outer residue of coffee harvest(Springer, 2011-12-01) Orsini, Rosely dos Reis; Moscardini Filho, Elder [UNIFESP]; Mercuri, Lucildes Pita [UNIFESP]; Matos, Jivaldo do Rosario; Sequeira de Carvalho, Fatima Maria; IPEN CNEN SP; Universidade Federal de São Paulo (UNIFESP); Universidade de São Paulo (USP)The better use of agricultural residues is expected, when they are mostly disposed of improperly and it is often burned in the natural environment. This study of the thermal decomposition of residues was performed from the coffee crop for energy purposes and in this case was used thermal analysis techniques for such assessment. the TG/DTG and DSC curves showed that the thermal decomposition occurs in four consecutive events and it is predominantly exothermic. the first mass loss evidenced in TG/DTG curves has an endothermic peak in DSC curve, which it can be associated with the water liberation of the material. This first thermal event also can be related to the liberation of volatile compounds present in the sample, which is also corroborated by the endothermic peak. the other events of mass loss are related with the thermal decomposition of the material. This decomposition has an exothermic behavior, which is positively applied to the main aim of this scientific research: the coffee straw use like biomass energy font. the thermoanalytical techniques were satisfactory in the characterization of this material.