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In 1960, Fidel Castro’s newly founded revolutionary government created the Federation of Cuban Women (FMC) in an attempt to bring women into the revolutionary process. Vilma Espín, herself a former revolutionary, was asked to lead the FMC in the changes that it brought to women living all over Cuba. This thesis will examine the personal influence that Espín had on the FMC, analyzing her significance in the running of the mass organization, and assessing how during these early years of the revolution women’s roles evolved under the guidance of the FMC.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2015-11-27T13:08:55Z No. of bitstreams: 1 AseneteFrutuosoDaCosta_TESE.pdf: 4115238 bytes, checksum: 72a04780a21fa7344d83533cdbdd3d36 (MD5) / Approved for entry into archive by Elisangela Moura (lilaalves@gmail.com) on 2015-11-27T14:44:06Z (GMT) No. of bitstreams: 1 AseneteFrutuosoDaCosta_TESE.pdf: 4115238 bytes, checksum: 72a04780a21fa7344d83533cdbdd3d36 (MD5) / Made available in DSpace on 2015-11-27T14:44:06Z (GMT). No. of bitstreams: 1 AseneteFrutuosoDaCosta_TESE.pdf: 4115238 bytes, checksum: 72a04780a21fa7344d83533cdbdd3d36 (MD5) Previous issue date: 2014-08-18 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Dentre os principais pigmentos, os materiais cer?micos que possuem a estrutura espin?lio AB2O4 v?m se tornando objeto de grande interesse cient?fico e tecnol?gico devido ? capacidade em acomodar diferentes c?tions em sua estrutura, permitindo diferentes tipos dopagens e, consequentemente, a obten??o de diferentes cores. Estudos sobre pigmentos cer?micos, atualmente, v?m sendo direcionados para o desenvolvimento de pigmentos est?veis e obtidos a baixas temperaturas e com maior reprodutibilidade. O objetivo do seguinte estudo ? a utiliza??o de pigmentos inorg?nicos para aplica??es em revestimentos cer?micos, tentando compreender quais par?metros influenciam na colora??o do pigmento nos esmaltes cer?micos. Pigmentos a base de CoCr2O4, CoAl2O4, Co0,8Zn0,2Cr2O4 e Co0,8Zn0,2Al2O4Co/Cr, foram sintetizados por uma rota qu?mica usando gelatina como precursor org?nico. Tais pigmentos foram caracterizados por An?lise termogravim?trica, Difra??o de raios X (DRX), Espectroscopia na regi?o do Infravermelho, Microscopia eletr?nica de varredura (MEV) Espectroscopia na regi?o do UV-Vis?vel e Colorimetria. Os resultados confirmaram a viabilidade da rota de s?ntese utilizada; com rela??o aos p?s sintetizados, Os pigmentos mostraram-se cristalinos e as fases desejadas foram obtidas a partir de 500oC, com um aumento da cristalinidade, assim como o tamanho m?dio de cristalito. Os pigmentos possuem tonalidades que v?o do verde ao violeta de acordo com as dopagens e suas temperaturas de calcina??o. / Ceramic pigments that own mainly the spinel structure AB2O4 are becoming a matter of great scientific and technological interest due to the ability of accommodate different cations in its structure, allowing different dopings and thus obtaining different colors. Studies on ceramic pigments currently are being directed to the development of stable and pigments obtained at low temperatures and with greater reproducibility. This work aims at the use of inorganic pigments for applications in ceramic tiles, investigating the influence of doping and calcination temperature on the coloring pigments and ceramic glazes. the based pigments of CoCr2O4, CoAl2O4, Co0,8Zn0,2Cr2O4 and Co0,8Zn0,2Al2O4 were synthesized by a chemical route using commercial gelatin as organic precursor. The materials were characterized by thermogravimetric analysis (TG), X-ray diffraction (XRD), infrared spectroscopy (FTIR) spectroscopy scanning electron microscopy (SEM) in the UVVisible region and colorimetry. The results confirmed the feasibility of synthesis used, the route presented pigments crystal structures and the desired phases were obtained from 500 ?C with increased crystallinity and the crystallite size. The pigments have hues ranging from green to violet according to their doping and calcination temperatures.

Orientador : Crodowaldo Pavan / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-07-14T02:59:22Z (GMT). No. of bitstreams: 1 Azeredo-Espin_AnaMariaLimade_M.pdf: 5964499 bytes, checksum: 3196fcec08b44ca3813fb9e570f77eda (MD5) Previous issue date: 1982 / Resumo: Nesta dissertação foram realizados estudos bio-lógicos e cariotípicos de cinco espécies de Calliphoridae. Três de introdução recente no Brasil: Chrysomya chloropyga_ C. megacephala e C. albiceps albiceps e duas nativas Cochliomyia hominivoraz e C. macellaria. Verificou-se que ao lado da total uniformidade no número de cromossomos das cinco espécies (2n = 12 cromossomos), encontram-se grandes variações quanto à morfologia e comprimento dos cromossomos. Essa variabilidade que se manifesta tanto inter como intraespecificamente, coloca os Calliphoridae entre as espécies de insetos que apresentam maior variabilidade cariotípica em populações naturais. Essas variações ocorrem tanto nos autossomos quanto nos cro-mossomos sexuais sendo que nestes últimos as variações encontradas foram maiores e mais evidentes que a dos autossomos. Além do método usual de coloração com orceína lacto-acética foi utilizado o método da banda C cujos resultados mostra-ram-se muito variáveis. resultados obtidos nas diferentes espécies analisadas, C.chloropyga e C. macellaria mostraram ser as espécies em que as regiões hete-rocromáticas foram mais evidentes. Nas outras três espécies, utilizando-se a mesma metodologia e mesmo introduzindo algumas modificações, os resultados não foram tão satis-fatórios, embora algumas metáfases apresentassem cromosso-mos com banda C. Foram estudados por outros autores os ca-riótipos de duas linhagens de C. chloropyga (África do Sul e Etiópia). Esses dois cariótipos diferem entre si e daque-le encontrado na linhagem de Campinas. O cariótipo de Campinas é mais próximo do apresentado pela linhagem da África do Sul descrito por ULLERICH (1976). De C. megacephala foram analisados os cariótipos da África do Sul(BOYES ,& SHEWELL, 1975) e do Japão (ULLERICH, 1963), sendo estes também diferentes entre si e diferem daquele da linhagem de Campinas por nós estudados. Neste caso o cariótipo da linhagem de Campinas se aproxima mais ao da linhagem do Japão do que o descrito para o da África do Sul. De C. A albiceps existem estudos sobre duas linhagens da África do Sul que diferem entre si e são diferentes do cariótipo que encontramos para a linhagem de Caraguatatuba. Nesta espécie não conseguimos identificar os cromossomos sexuais. Os cariótipos de C. macellaria de Granada., Porto Rico e México, descritos por BOYES (196l) e BOYES & SHEWELL (1975), também diferem entre si e são diferentes ao cariótipo da linhagem de Caraguatatuba por nós analisadas.C. hominivorax a espécie mais estudada por autores estran-geiros e também a mais investigada por nós, foi a que apre-sentou maior variabilidade. Foram descritos na literatura 13 cariótipos diferentes e três por nós para o Estado são Paulo. Temos boas evidências de que C. hominivorax é uma única espécie de Cochliomyia, mas deve representar um complexo taxonômico onde se encontram algumas espécies críticas e muito provavelmente subespécies e formas cariotípicas polimórficas dentro de algumas das espécies bem definidas. A análise cariotípica forneceu excelentes dados complementares aos já existentes sobre biologia e taxonomia dessas cinco espécies e, além disso, abriu novas áreas de estudos desse importante grupo de insetos / Abstract: This dissertation concerns the biological karyotypical studies carried out in five species and of Calliphoridae. Three of these are of recent introduction in Brazil: Chrysomya chloropyga, C. megacephala C. albiceps albiceps while Cochliomyia hominivopax and C. macellaria are native species. It was possible able to verify that, beside the total uniformity in the number of chromosome of these five species (2 n=12 chromosomes), considerable variation related to both morphology and lenght of the chromosomes has been observed. This variability, which manifests itself both inter and intraspecifically, places the Calliphoridae among the species of insects presenting the largest karyotypical variability found in wild populations. Occur-ring in the autosomes as well as in the sexual chromosomes, the variations in the latter have been, however, far more diversified and more evident than in the former. Besides the usual method of staining the slides with lactic-acetic orcein, the C-band method was used which turned out to produce variable results. If one compares the results obtained with this last method in the different species analysed, one will be able to see. that C.chloropyga and C. macellaria are the species in which the heterocromatic regions proved to be most evident. On the other hand, in the remaining three species, using the same methodology, and even introducing some changes, the results have not been so satisfactory, although some metaphase did chromosomes with C-bands. The karyotypes of two strains of C. chloropyga (from South Africa and Ethiopia) have been studied by other authors. These two karyotypes differ from each other and from the one found in the strain collected in Campinas. The karyotype of the Campinas. strain is closer to the one found in the strain of South Africa (BOYES & SHEWELL_ 1975) and Japan (ULLERICH, 1963) were found to differ one from the other and from the other and from the one in the strain collected in Campinas as well. The Karyotype from the Campinas strain is chromosomally closer to the strains from Japan than it is to the karyotype described for the South Africa strains. The C. a. albiceps strain collected in Caraguatatuba has kariotypical differences when compared to the two South African strains described by BOYES and by ULLERICH, which in turn, represent two different kariotypical groups. The sexual chromosomes of this species have not been identified in this study. The karyotypes of C. macellaria from Grenada, Puerto Rico and Mexico described by BOYES (1961) and BOYES & SHEWELL (1975), are also different one from the other and differ from the karyotype of the strain from Caraguatatuba analyzed in this work. C. Hominivorax the species to which foreign authors have dedicated most of their efforts, and which we also have investigated the most, was the one presenting the largest karyotypical variation. Thirteen different karyotypes have been described in the literature, to which this study has, added three more, for populations collected in the state of São Paulo. There is good evidence showing that C. hominivorax is not only a species of Cochliomyia but it may well represent a taxonomic complex including sibling species, subspecies and polimorfic karyotypical forms within some well-defined species. The karyotypical analysis has furnished excellent data complementary to those already existing on the biosystematic of these five species of Calliphoridae and besides that, it has opened new areas of studies of this important group of insects / Mestrado / Mestre em Biologia Vegetal

La détection des stimuli sensoriels est assurée par des cellules réceptrices spécialisées souvent grâce à des protrusions membranaires apicales telles que les microvillosités. La forme finale des extensions apicales microvilliées conditionne de nombreuses propriétés de la transduction sensorielle mais leur formation reste méconnue. Quels sont les facteurs moléculaires responsables de l’initiation et de l’élongation des filaments d’actine chez les cellules sensorielles microvilliées (CSMs) ? Peut-on décrire des éléments clés de la morphogenèse en commun ? Quel est le rôle structurel des microvillosités dans la fonction sensorielle ?J’ai étudié deux types sensoriels microvilliés : les neurones contactant le liquide cérébrospinal (NcLCS) et les cellules sensorielles des neuromastes (CSn). Mon projet visait à investiguer les mécanismes moléculaires sous-jacents à la morphogenèse des CSMs par l’étude des NcLCS. J’ai décrit les étapes critiques menant à la formation de l’extension apicale des NcLCS auxquelles j’ai pu associer des candidats potentiels grâce l’analyse transcriptomique des NcLCS. J’ai démontré le rôle critique de l’interaction entre Espin et Myo3b dans l’élongation de l’extension apicale des NcLCS et j’ai établi un lien direct entre structure et fonction en montrant que le raccourcissement de l’extension apicale aboutissait à la réduction de la réponse sensorielle.Mon travail a permis d’apporter des éléments de réponse quant à la formation de l’organe sensoriel des NcLCS. L’analyse transcriptomique des CSn a par ailleurs révélé des facteurs de morphogenèse communs avec les NcLCS, suggérant que toutes les CSMs partagent des propriétés de différenciation conservées. / Sensory systems use specialized receptor cells, many of which detect sensory cues through specialized apical membrane protrusions, such as microvilli. The final shape of the microvilliated apical extension requires specific molecular machinery and determines many of the properties of sensory transduction. The establishment of this structure remains however elusive. What molecular factors orchestrate the initiation and elongation of actin filaments in microvilliated sensory cells (MSCs)? Can we find key elements of morphogenesis common to MSCs? What is the precise role of microvilli structure in sensory function? I investigated two sensory cell types harboring microvilli: spinal cerebrospinal fluid-contacting neurons (CSF-cNs) and neuromast hair cells (nHCs). The primary goal was to unravel the molecular mechanisms underlying morphogenesis of MSCs by focusing on CSF-cNs. I was able to describe critical steps leading to the development of CSF-cN apical extension. My participation to the transcriptome analysis of CSF-cNs revealed candidate molecular factors associated with each of these steps. I demonstrated the importance of the interaction between Espin and Myo3b to ensure the proper lengthening of CSF-cN apical extension. In this system, I established a direct link between morphology and function by showing that shorter apical extensions lead to reduced sensory response. Altogether, my work shed light on the formation of CSF-cN sensory organelle and its functional role. In parallel, the establishment of the nHC transcriptome dataset revealed similar morphogenetic factors with CSF-cNs, supporting the idea that all MSCs share conserved features for their differentiation.

Made available in DSpace on 2015-03-03T15:15:27Z (GMT). No. of bitstreams: 1 MateusBB_DISSERT.pdf: 4491805 bytes, checksum: 6567583b83544d78b05fe6787b44a3ce (MD5) Previous issue date: 2012-03-27 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / In this experimental study sintetic samples of Jacobsites (MnFe2O4) were synthesized by the Pechini method and calcined within ambient atmosphere and afterwards in the vacuum from 400 to 700?C, the range of calcination temperatures. The X-Ray Diffraction (XRD) and the Scanning Electronic Microscopy (SEM) analysis have shown that the samples treated at 400?C temperature are composed by a simple type of spinel phase, with a crystallite size of 8:8nm for the sample calcined in ambient atmosphere and 20; 1nm for the sample treated in the vacuum, showing that the cristallite average size can be manipulated by the atmosphere control. The hysteresis loops for the sample calcined at 400?C in ambient atmosphere reveal features of superparamagnetic behavior with magnetization 29:3emu=g at the maximum field of 1:2T. The sample calcined in 400oC under vacuum show magnetization = 67emu=g at the maximum field of 1:5T. The sample treated at 500oC, under ambient atmosphere, has shown besides the spinel phase, secondary phases of hematite (Fe2O3) and bixbyite (FeMnO3). The hysteresis loops demonstrate a sharp drop of the magnetization compared to the previous sample. The analysis has revealed that for the samples treated in higher temperatures (600?C and 700?C) its observed the absence of the spinel phase and the maintenance of the bixbyite and hematite. The hysteresis loops for those samples in accordance to the external magnetic field are straight lines crossing the origin, consistent with the antiferromagnetic behavior of the phases.The M?ssbauer espectroscopy show to the sample calcined at 400?C within ambiente atmosphere two sextet and one doublet. The two sextets are assigned to the hyperfine fields related to the magnetic deployment in the nuclei of Fe3+ ions, at the tetraedric and octaedric sites. The doublet is assigned to superparamagnetic behavior of the particles with smaller diameter than dc . Now the sample calcined at 400?C under vacuum only show two sextet / ?Neste estudo experimental, amostras sint?ticas de Jacobsitas (MnF e2O4) foram sintetizadas pelo m?todo Pechini e calcinadas em atmosfera ambiente e em v?cuo de 400 at? 700?C. An?lises de difra??o de raio-x (DRX) e microscopia eletr?nica de varredura (MEV) revelaram que a amostra calcinada em 400?C ? composta por uma fase simples tipo espin?lio, com tamanho m?dio do cristalito de 8,8nm para amostra calcinada em atmosfera ambiente, e 20,1nm para amostra calcinada em v?cuo, indicando que o tamanho m?dio do cristalito pode ser manipulado pelo controle da atmosfera. A curva de magnetiza??o para amostra calcinada a 400?C em atmosfera ambiente revela caracter?sticas de comportamento superparamagn?tico, com magnetiza??o de 29:3emu=g num campo m?ximo de 1.2T . J? a amostra calcinada em 400?C sob v?cuo apresentou magnetiza??o = 67emu/g no campo m?ximo de 1.5T . A amostra tratada em 500 ]C, em atmosfera ambiente, acusa al?m da fase espin?lio, fases secund?rias de hematita (Fe2O3) e bixbyita (FeMnO3). A curva de magnetiza??o mostra uma queda abrupta na magnetiza??o comparada com as amostras anteriores. A an?lise mostra que, para mais altas temperaturas (600?C and 700?C), observou-se apenas a continua??o das fases hematita e bixbyita. A curva de magnetiza??o dessas amostras s?o linhas retas cortando a origem, consistente com o comportamento antiferromagn?tico dessas fases. A espectroscopia M?ssbauer revelou que para a amostra calcinada em 400?C em atmosfera ambiente h? dois sextetos e um dubleto. Os dois sextetos s?o atribu?dos aos campos hiperfinos referentes ao desdobramento magn?tico no n?cleo dos ?ons Fe3+, nos s?tios tetra?dricos e octa?dricos. O dubleto ? atribu?do ao comportamento superparamagn?tico das part?culas com di?metro menor que dc. J? a amostra calcinada em 400?C sob v?cuo apresenta apenas dois sextetos.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-12-29T16:19:40Z No. of bitstreams: 1 AntonioCarlosSilvaDaCosta_TESE.pdf: 7680931 bytes, checksum: 91f08aea889978538206d110a2645e63 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-01-02T16:50:12Z (GMT) No. of bitstreams: 1 AntonioCarlosSilvaDaCosta_TESE.pdf: 7680931 bytes, checksum: 91f08aea889978538206d110a2645e63 (MD5) / Made available in DSpace on 2017-01-02T16:50:12Z (GMT). No. of bitstreams: 1 AntonioCarlosSilvaDaCosta_TESE.pdf: 7680931 bytes, checksum: 91f08aea889978538206d110a2645e63 (MD5) Previous issue date: 2015-02-27 / Ferritas de estrutura espin?lio (MFe2O4; M= metal alcalino terroso ou metal de transi??o) desempenham um papel importante na ci?ncia fundamental e na tecnologia moderna. A ferrita de magn?sio (MgFe2O4) e seus compostos dopados tem recebido especial aten??o devido a sua vasta ?rea de atua??o, que inclui aplica??es em m?dia de alta grava??o, cat?lise heterog?nea, adsor??o, sensores e tecnologias magn?ticas, de um modo geral. Suas propriedades estruturais, el?tricas e magn?ticas dependem da composi??o qu?mica, estrutura, tamanho de part?culas, al?m da substitui??o de c?tions nos s?tios A e/ou B que s?o diretamente influenciados pelo m?todo de s?ntese, as condi??es empregadas no processamento desses materiais (temperatura, taxa de aquecimento e tempo). Neste trabalho, ferritas do tipo Mg1-xBxFe2O4 (B= Ni; Cu; x= 0; 0,25; 0,50; 0,75 e 1) foram preparadas pelo m?todo de combust?o assistido por micro-ondas com a finalidade de avaliar tanto o efeito da substitui??o parcial do magn?sio por n?quel e cobre quanto o tratamento t?rmico sobre as propriedades magn?ticas. Os p?s precursores foram tratados termicamente a 600?C, 800?C e 1000?C/2h e caracterizados por An?lise Termogravim?trica (ATG), Difra??o de Raios X (DRX) em conjunto com o Refinamento pelo m?todo Rietveld, Microscopia eletr?nica de varredura (MEV) e Medidas de histerese magn?ticas realizadas ? temperatura ambiente. De acordo com as curvas termogravim?tricas dos p?s precursores, um comportamento semelhante foi observado para ambos os sistemas de amostras, onde o processo de perda total de massa aconteceu basicamente em duas etapas e na faixa de temperatura entre 30 e 500?C para o sistema Mg1-xNixFe2O4 e entre 30 e 400?C para o sistema Mg1-xCuxFe2O4. Os difratogramas de raios X revelaram a forma??o da fase espin?lio MgFe2O4 (ICSD 76176) de estrutura c?bica, e de fases secund?rias como Fe2O3 (ICSD 88418), NiO (ICSD 9866) e CuO (ICSD 87125) para os sistemas estudados. Em rela??o ?s curvas de histerese, verificou-se uma depend?ncia da magnetiza??o em fun??o do teor de dopante e da temperatura de tratamento t?rmico adotada. / The magnesium ferrite (MgFe2O4) and their doped compounds has received special attention due to its wide area of use, including applications in high recording media, heterogeneous catalysis, adsorption, sensors and magnetic technologies. Its structural, electrical and magnetic properties depend on the chemical composition, structure, particle size, and the replacement of cations in the sites A and/or B, which are directly influenced by the synthesis method, the conditions employed in processing these materials. In this work, ferrites of the type Mg1-xBxFe2O4 (B = Ni, Cu; x = 0, 0.25, 0.50, 0.75 and 1) were prepared by combustion method assisted by microwave in order to evaluate both the effect of partial substitution of Mg2+ for Ni2+ and/or Cu2+ as thermal treatment on the magnetic properties. Precursor powders were treated at the temperatures of 600 ?C, 800 ?C and 1000 ?C with 2h level and characterized by Thermogravimetric Analysis (TGA), X-Ray Diffraction (XRD) and refinement by the Rietveld method, Scanning Electron Microscopy (SEM) and magnetic hysteresis measurements at room temperature. According to the TG curves of the precursor powders, a similar behavior was observed for both systems where the total mass loss process occurred in two stages and in the temperature range between 30 and 500 ?C for Mg1-xNixFe2O4 system (x = 0, 0.25, 0.50 and 0.75) and between 30 and 450 ?C for Mg1-xCuxFe2O4 system (x = 0, 0.25, 0.50 and 0.75). The X-ray diffraction revealed the formation of the spinel phase MgFe2O4 (ICSD 76176) of cubic symmetry, and secondary phases such as ?-Fe2O3 (ICSD 88418), NiO (ICSD 9866) and CuO (ICSD 87125), for the studied systems. Regarding the hysteresis curves, there was a dependence of the magnetization as a function of the dopant content and the heat treatment temperature adopted. For Mg0,25Ni0,75Fe2O4 Mg0,75Cu0,25Fe2O4 and samples treated at 1000 ?C showed the highest saturation magnetization values of 41.9 emu/g and 35.76 emu/g, respectively.

Made available in DSpace on 2014-12-17T15:41:43Z (GMT). No. of bitstreams: 1 JoseEMS.pdf: 2230919 bytes, checksum: f0f4e57c89f3eae4282c6daae0fe0aba (MD5) Previous issue date: 2008-04-18 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / It was synthesized different Ni1-xMgxFe2O4 (0,2 ≤ x ≤ 0,7) compositions by use of citrate precursor method. Initially, the precursory citrates of iron, nickel and magnesium were mixed and homogenized. The stoichiometric compositions were calcined from 350?C to 1200?C at ambient atmosphere or in argon atmosphere. The calcined powders were characterized by XRD, TGA/DTG, FTIR, magnetic measures and reflectivity using the wave guide method. I was observed pure magnetic phase formation between 350?C and 500?C, with formation of ferrite and hematite after 600?C at ambient atmosphere. The calcined powder at argon atmosphere formed pure ferromagnetic phase at 1100?C and 1200?C. The Rietveld analyses calculated the cations level occupation and the crystallite size. The analyses obtained nanometric crystals (11-66 nm), that at 900?C/3h presents micrometric sizes (0,45 - 0,70 Om). The better magnetization results were 54 Am2/Kg for x= 0,2 composition, calcined at 350?C/3h and 30 min, and 55,6 Am2/Kg for x= 0,2 1200?C, calcined in argon. The hysteresis shows characteristics of soft magnetic material. Two magnetization processes were considered, superparamagnetism at low temperature and the magnetic domains formation at high temperatures. The materials presented absorption less or equal the 50 % in ranges specific frequency. As for the 2,0 and 3,0 thickness (in 11,0 - 11,8 GHz), the reflectivity of the x= 0,3, 0,5 and 0,4 compositions, all calcined at 900?C/3h showed agreement with MS and O. Various factors contribute for the final radiation absortion effect, such as, the particle size, the magnetization and the polymer characteristics in the MARE composition. The samples that presented better magnetization does not obtaining high radiation absorption. It is not clear the interrelaction between the magnetization and the radiation absorption in the strip of frequencies studied (8,2 - 12,4 GHz) / Foram sintetizadas diferentes composi??es da ferrita Ni1-xMgxFe2O4 com (0,2 ≤ x ≤ 0,7) pelo uso do m?todo dos citratos precursores. Para se obter a fase estequiom?trica Ni1-xMgxFe2O4, inicialmente foram misturados e homogeneizados os citratos precursores de ferro, n?quel e magn?sio. As composi??es estequiom?tricas foram calcinadas entre as temperaturas de 350?C e 1200?C, em atmosfera ambiente ou de arg?nio. Os p?s calcinados foram caracterizados por DRX, TGA/DTG, FTIR, medidas magn?ticas e refletividade pelo m?todo de guia de ondas. Foi observada a forma??o de fase pura ferrimagn?tica entre 350?C e 500?C, formando ferrita e hematita ap?s 600?C, em atmosfera ambiente. O p? calcinado em atmosfera de arg?nio formou fase ferrimagn?tica pura em 1100?C e 1200?C. A an?lise pelo m?todo de Rietveld calculou o n?vel de ocupa??o dos c?tions e o tamanho de cristalito. A an?lise obteve tamanhos de cristais nanom?tricos, (11 - 66 nm), que a 900?C/3h apresentam tamanhos microm?tricos (0,45 0,70 Om). Os melhores resultados de magnetiza??o foram 54 Am2/Kg para a composi??o x= 0,2, calcinada a 350?C/3h e 30 min, e 55,6 Am2/Kg para x= 0,2 a 1200?C, calcinada em arg?nio. As histereses mostraram um perfil de materiais magn?ticos moles. Dois processos de magnetiza??o foram considerados, o superparamagnetismo a baixa temperatura e a forma??o de dom?nios magn?ticos em altas temperaturas. Os materiais apresentaram absor??o igual ou inferior a 50 % em faixas de freq??ncias espec?ficas. Para as espessuras 3,0 e 2,0 mm (em 11-11,8 GHz), as refletividades das composi??es x= 0,3, x= 0,5 e x= 0,4, todas a 900?C/3h demonstraram concord?ncia com MS e O. V?rios fatores contribuem para o efeito final de absor??o de radia??o, tais como, o tamanho de part?culas, a magnetiza??o, e as caracter?sticas do pol?mero na composi??o do MARE. As amostras que apresentaram maiores magnetiza??es n?o atingiram alta absor??o de radia??o. N?o ficou esclarecido a interrela??o entre a magnetiza??o e a absor??o de radia??o na faixa de freq??ncia estudada (8,2 12,4 GHz)

Made available in DSpace on 2014-12-17T15:42:27Z (GMT). No. of bitstreams: 1 MariaJOSB.pdf: 5434037 bytes, checksum: 1a000204d534c8f41a3acbfce7dfaef5 (MD5) Previous issue date: 2007-09-17 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / It was synthesized MnZn ferrite with general formulae Mn1-xZnxFe2O4 (mol%), 0,3 &#8804; x &#8804; 0,7 by using the citrate precursor method. The precursors decomposition was studied by thermogravimetric analysis (TGA), differential thermogravimetric analysis (DTG), differential thermal analysis (DTA) and Fourier transform infrared (FTIR) of powder calcined at 350?C/3,5h. X-ray diffraction pattern (XRD) of samples was done from 350 to 1200?C/2h using various atmospheres. The power calcined at 350?C/3,5h formed spinel phase. It is necessary atmosphere control to avoid secondary phase such as hematite. From 900 to 1200?C was obtained 90,66 and 100% of MnZn spinel ferrite phase, respectively. Analysis by dispersive energy scanning (EDS) at 350?C shows high Mn and Zn dispersion, indicating that the diffusion process was homogeneous. Semi-quantitative analysis by EDS verified that despite the atmosphere control during calcinations at high temperatures (< 800?C) occurred ZnO evaporation causing stoichiometric deviation. Vibrating sample magnetometer (VSM) measures show soft ferrite material characteristics with Hc from 6,5 x 10-3 to 11,1 x 10-2 T. Saturation magnetization (Ms) and initial permeability (?i) of MnZn spinel phase obtained, respectively, from 14,3 to 83,8 Am2/kg and 14,1 to 62,7 (Am2/kg)T / Foi sintetizada ferrita de MnZn com f?rmula geral Mn1-xZnxFe2O4 (mol%) para 0,3 &#8804; x &#8804; 0,6 com uso do m?todo dos citratos precursores. A decomposi??o dos precursores foi estudada por an?lise termogravim?trica (TGA), termogravim?trica diferencial (DTG), an?lise t?rmica derivada (DTA) e espectroscopia na regi?o do infravermelho (FTIR) dos p?s calcinados em 350?C/3,5h. Foram feitas difra??es de raios X (DRX) entre 350 e 1200?C/2h usando v?rias atmosferas. O p? calcinado a 350?C/3,5h formou fase espin?lio. ? necess?rio o controle da atmosfera para evitar fases secund?rias como a hematita. Em 900 e 1200?C foram obtidos respectivamente, 90,7 e 100% de fase ferrita espin?lio. An?lises por espectroscopia de energia dispersiva (EDS) em 350?C mostrou alta dispers?o de Mn e Zn, indicando que o processo de difus?o foi homog?neo. A an?lise semi-quantitativa por EDS verificou que apesar do controle da atmosfera durante a calcina??o em altas temperaturas (> 800?C), ocorreu vaporiza??o de ZnO causando desvio estequiom?trico. Medidas por magnet?metro de amostra vibrante (MAV) mostraram caracter?sticas de materiais magneticamente macios com Hc de 6,5 x 10-3 at? 11,1 x 10-2 T. A magnetiza??o de satura??o e a permeabilidade inicial da fase espin?lio de MnZn foi obtida entre 14,3 a 83,8 Am2/kg e 14,1 a 62,7 (Am2/kg)T, respectivamente

Submitted by Celso Magalhaes (celsomagalhaes@ufrrj.br) on 2017-05-15T11:16:01Z No. of bitstreams: 1 2016 - Maria Clara Adum de paiva.pdf: 2279180 bytes, checksum: d1de128b3d5f5984c844a68538cd255e (MD5) / Made available in DSpace on 2017-05-15T11:16:01Z (GMT). No. of bitstreams: 1 2016 - Maria Clara Adum de paiva.pdf: 2279180 bytes, checksum: d1de128b3d5f5984c844a68538cd255e (MD5) Previous issue date: 2016-08-04 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / The demand for electricity production, and the need for thermoelectric use as power generating units, makes it necessary to search for less polluting matrices. In this search the catalytic combustion of methane, both from natural gas and other sources (residue disposal, for example) have shown promising. It is known the use of cobalt oxides is an alternative to the use of catalysts based on noble metals which has shown high performance. In order to potentiate the activity of the cobalt based catalyst, thus reducing both the ignition temperature and the temperature of total burning of methane, this work proposes the production of cobalt-based precursors using different types of layered double hydroxides (LDHs). Cobalt based catalysts partially substituted in layered double hydroxides (LDH Mg, Al and CO32-) were prepared by co-precipitation and impregnation with a nominal content of 9% CoII in LDH, or by impregnating a commercial hydrotalcite (HT). The LDH precursors were characterized by X-ray powder diffraction (XRD) and infrared absorption spectroscopy (FTIR). The XRD patterns indicated a LDH of 3R polytype. XRD showed the presence of Gibbisite in the HT precursor. The infrared spectra of precursor LDHs presented bands related to ?1, ?2 and ?3 vibrations of the carbonate anion, and interlayer water characteristic bands, thus in line with the XRD data. Analysis by XRD of the catalysts after calcination at 800 ?C showed the presence of periclase and spinel phases. Infrared spectra showed bands ascribed to the Mg-O and Co-O stretching in tetrahedral and octahedral sites as well as bands attributed to the Mg-O-Al bond and the cobalt spinel. The catalytic activity of these materials was investigated in the catalytic combustion of methane under kinetic regime, using predetermined reaction conditions to avoid diffusional limitations, resulting in a significant decrease in the combustion temperature, with the higher activity observed for the catalyst prepared by impregnating a commercial HT. Scanning electron microscopy (SEM) and quantitative chemical analysis (EDS) of catalysts with improved performance show both the homogeneous dispersion of the components in the sample surface and the higher aluminum content of the sample supported on HT. / A demanda de produ??o de energia el?trica, e a necessidade do uso de termel?tricas como unidades geradoras de energia, fazem com que seja necess?ria a busca por matrizes menos poluentes. Nessa busca a combust?o catal?tica do metano, tanto proveniente do g?s natural como de outras fontes (res?duo do tratamento de lixo, por exemplo), tem se mostrado promissora. Sabidamente o uso de ?xidos de cobalto ? uma alternativa, que vem mostrando alto desempenho, ao uso de catalisadores a base de metais nobres. Com o intuito de potencializar a atividade do catalisador a base de cobalto, reduzindo assim tanto a temperatura de igni??o quanto a de queima total do metano, esse trabalho prop?e sua produ??o utilizando como precursor diferentes tipos de hidr?xidos duplos lamelares (HDLs). Catalisadores ? base de cobalto parcialmente substitu?dos em hidr?xidos duplos lamelares (HDL de Mg, Al e CO32-) foram preparados por co-precipita??o e impregna??o num teor nominal de 9% de CoII em HDL, ou por impregna??o em hidrotalcita comercial (HT). Os HDLs precursores foram caracterizados por difra??o de raios?X pelo m?todo de p? (DRX) e por espectroscopia de absor??o no infravermelho (FTIR). Os difratogramas indicaram a obten??o de um HDL de politipo 3R. Por meio do DRX foi identificada a presen?a de Gibbisita no suporte de HT. Os espectros de infravermelho dos HDLs precursores presentaram bandas referentes ?s vibra??es ?1, ?2 e ?3 do ?nion carbonato, al?m de bandas caracter?sticas de ?gua interlamelar, estando portanto de acordo com os dados de DRX. A an?lise por difra??o de raios-X dos catalisadores ap?s calcina??o a 800?C mostrou apenas as fases espin?lio e pericl?sio. Os espectros de infravermelho apresentaram bandas atribu?das aos estiramentos Mg?O e Co?O em s?tios tetra?dricos e octa?dricos, assim como bandas caracter?sticas de Mg?O?Al e de Co3O4. A atividade catal?tica desses materiais foi investigada na combust?o catal?tica do metano, em regime cin?tico, empregando-se condi??es reacionais preestabelecidas de forma a evitar limita??es difusionais, obtendo-se uma significativa diminui??o na temperatura de combust?o, sendo que a maior atividade foi observada para o catalisador preparado por impregna??o em HT comercial. Foi realizada microscopia eletr?nica de varredura (MEV) e an?lise qu?mica quantitativa (EDS) para os catalisadores com melhor desempenho, mostrando tanto a dispers?o homog?nea dos componentes na superf?cie das amostras como o maior teor de alum?nio presente na amostra suportada em HT.