Densification and electrical conductivity of fast fired manganese-doped ceria ceramics

Reactive pure and manganese-doped (5% and 10 at.%) ceria nanosized powders were prepared by the polymeric precursor technique. Physical properties of powder materials were studied by X-ray diffraction, nitrogen adsorption, and diffuse reflectance infrared Fourier transform spectroscopy. Characterization of powder compacts after fast firing at 1200 degrees C for 5 min was carried out by scanning electron microscopy and impedance spectroscopy measurements. The bulk apparent density of sintered pellets was determined for pellets of different compositions sintered at 1200 degrees C. A gradual decrease of the particle size occurs with increasing doping content. Relatively high values of apparent density were obtained after fast firing doped specimens at 1200 degrees C. DRIFT spectra evidence that a fraction of Mn ions was segregated onto particles surface. The electrical resistivity of sintered pellets reveals different mechanisms of conduction depending on the Mn content. (C) 2005 Elsevier B.V All rights reserved.

Synthesis, characterization and thermal behaviour of solid-state compounds of light trivalent lanthanide succinates

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Improved activity and stability of Ce-promoted Ni/γ-A1 2O3 catalysts for carbon dioxide reforming of methane

The CO2 reforming of CH4 was carried out over Ni catalysts supported on γ-Al2O3 and CeO 2-promoted γ-Al2O3. The catalysts were characterized by means of surface area measurements, TPR, CO2 and H2 chemisorption, XRD, SEM, and TEM. The CeO2 addition promoted an increase of catalytic activity and stability. The improvement in the resistance to carbon deposition is attributed to the highest CO2 adsorption presented by the CeO2 addition. The catalytic behavior presented by the samples, with a different CH4/CO2 ratio used, points to the CH4 decomposition reaction as the main source of carbon deposition.

La technique de l’arc segmenté. Contrôle de l’ancrage et modification significative du profil facial : une étude de cas

This article evaluates space closure mechanics efficiency in an extraction case where maximum anchorage was a requirement. The Segmented Arch Technique (SAT) was utilized as an anchorage control strategy to obtain maximum anterior retraction and, in consequence, significant facial profile change. A 20-year-10-month old woman needed severe labial and profile changes. The patient had four premolars extracted and SAT with type A mechanics [1] (Marcotte [2] activation protocol) was applied. The results showed significant reduction in labial protrusion and incisal angulation with effective anchorage control. The results were compared to others available in the literature derived from different techniques, where anterior retraction was also accomplished with maximum anchorage [3-7]. In conclusion, the SAT with type A mechanics has been shown to be another treatment option when significant changes in the soft-tissue profile are needed in extraction cases. © 2008. CEO. Published by Elsevier Masson SAS. All rights reserved.

Influence of the preparation method and the support on H2O 2electrogeneration using cerium oxide nanoparticles

This work describes the influence of the preparation method and the carbon support using a low contentof cerium oxide nanoparticles (CeO2/C 4%) on H2O2electrogeneration via the oxygen reduction reac-tion (ORR). For this purpose, the polymeric precursor (PPM) and sol-gel (SGM) methods with Vulcan XC72R (V) and Printex L6 (P) supports were employed. The materials were characterized by X-ray diffrac-tion (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). TheXRD analysis identified two phases comprising CeO2and CeO 2-x. The smallest mean crystallite size wasexhibited for the 4% CeO2/C PPM P material, which was estimated using the Debye-Scherrer equation tobe 6 nm and 4 nm for the CeO2and the CeO 2-xphases, respectively, and was determined by TEM to be5.9 nm. XPS analysis was utilized to compare the oxygen content of the 4% CeO2/C PPM P to Printex L6.The electrochemical analysis was accomplished using a rotating ring-disk electrode. The results showedthat the 4% CeO2/C specimen, prepared by PPM and supported on Printex L6, was the best electrocatalystfor H2O2production in 1 mol L -1NaOH. This material showed the highest ring current, producing 88%H2O2and transferring 2.2 electrons per O 2molecule via the ORR at the lowest onset potential. Addition-ally, the ring-current of the 4% CeO2/C PPM P material was higher than that of Vulcan XC 72R and PrintexL6, the reference materials for H2O 2production, indicating the highest electrocatalytic activity for the 4%CeO2/C PPM P material. © 2013 Elsevier Ltd. All rights reserved.

Avaliação do risco de cárie e microbiota fúngica em pacientes pediátricos com anemia falciforme

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Hipomineralização molar-incisivo: prevalência, severidade e etiologia em escolares de Araraquara

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Identificação de marcadores moleculares de resposta à quimioterapia neoadjuvante e associação de radioterapia e quimioterapia em pacientes com carcinoma epidermóide de orofaringe

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Avaliação de quimiocinas séricas em mulheres com câncer epitelial de ovário

Pós-graduação em Ginecologia, Obstetrícia e Mastologia - FMB

Avaliação da presença de lesões de cárie dentária, biofilme bacteriano visível e análise microbiológica de Streptococcus grupo mutans em crianças de 12 a 48 meses de idade, portadoras e não portadoras da Síndrome de Down

Pós-graduação em Odontologia - FOAR

Condições bucais de pacientes com paralisia cerebral: aspectos clínicos e microbiológicos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Detecção da transmissão vertical do S. mutans e S. sobrinus e relação com o micro-ambiente bacteriano, índice de cárie e cuidados maternos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Prevalência de cárie dental em uma população de escolares da região amazônica

Considerando-se a ausência de dados sobre a prevalência de cárie dental em uma população tipicamente amazônida, foi feito um levantamento epidemiológico em 103 escolares na região da Ilha de Sirituba, no Município de Abaetetuba, Estado do Pará, Brasil. O CPOD médio encontrado foi de 6,5 e o ceo de 5,4. Apesar da primitividade do local, o alto índice de cárie pode estar relacionado a diversos fatores, dentre os quais deve ser incluída a influência urbana na alimentação, principalmente pelo açúcar, criando novos hábitos alimentares que alteraram fundamentalmente a dieta da região.

Effect of cerium loading on structure and morphology of modified Ce-USY zeolites

Este trabalho descreve detalhadamente o efeito da quantidade de cério na estrutura e morfologia da zeólita NH4USY. Ce-USY (2-25% m/m de CeO₂) foi obtido por impregnação úmida de CeCl₃ seguida de calcinação a 550ºC por 8 h. Em quantidades baixas (2-10%), foi observado que as espécies de cério encontram-se nas posições de troca iônica na rede, enquanto em maiores teores (15-25%) pequenos agregados formaram-se na superfície da HUSY. Difratometria de raios X (XRD) mostrou apenas reflexões relacionadas à HUSY, confirmando a alta dispersão das espécies de cério, porém as análises por espectroscopia Raman com transformada de Fourier (FT-Raman) detectaram CeO_x para os materiais acima de 10%. A reação do CeCl₃ com NH₄USY produziu NH₄Cl, o qual se decompõe em HCl, ocasionando a desaluminização da rede. Os materiais apresentaram um aumento da razão Lewis/Brønsted com o aumento da quantidade de cério, devido a interação do excesso de cério com os grupos OH da USY e consequente formação de espécies CeO_x.

Aspectos epidemiológicos e estudo dos fatores associados às condições de saúde bucal em residentes no município de Verê-PR

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)