About the nanoporosity elimination above 800 degrees C in xerogels prepared from TEOS sono-hydrolysis

Small angle X-ray scattering measurements, bulk and skeleton density data and an in-situ study by dilatometric thermal analysis about the nanoporosity elimination above 800 degreesC in TEOS sonogels are presented. Apparently, two processes act during the nanoporosity elimination, which precedes the foaming phenomenon often observed in such systems. The first, with an activation energy of (3.9 +/- 0.4) x 10(2) kJ/mol and high frequency factor, is the controlling process of the most nanoporosity elimination at higher temperature. The value of this activation energy is compatible to that for viscous flux throughout densification process in typical silica-based materials. The second, with an activation energy of (49 +/- 5) kJ/mol and low frequency factor, seems to be the controlling process of the first and extremely slow nanoporosity elimination at low temperature.

Thermal and structural investigation of SnO2/Sb2O3 obtained by the polymeric precursor method

SnO2-based materials are used as sensors, catalysts and in electro-optical devices. This work aims to synthesize and characterize the SnO2/Sb2O3-based inorganic pigments, obtained by the polymeric precursor method, also known as Pechini method (based on the metallic citrate polymerization by means of ethylene glycol). The precursors were characterized by thermogravimetry (TG) and differential thermal analysis (DTA). After characterization, the precursors were heat-treated at different temperatures and characterized by X-ray diffraction. According to the TG/DTA curves basically two-step mass loss process was observed: the first one is related to the dehydration of the system; and the second one is representative to the combustion of the organic matter. Increase of the heat treatment temperature from 500 to 600 degrees C and 700 degrees C resulted higher crystallinity of the formed product.

Estudo da penetração de agentes ácidos para o condicionamento do esmalte dental em cimentos à base de hidróxido de cálcio.

It was verified the penetration of phosphoric acid into 3 commercial calcium hydroxide-based cements (Life, Renew and Prisma VLC Dycal). The colorimetric method employed permitted the identidication of phosphorus amount in representative samples of 6 successive layers 0.1 mm thick of each material. The acid etching used were the commercial products Scotchbond Etching Gel--3M at 36.114% by weight and Solução Condicionadora--Johnson & Johnson at 36.054% by weight. The contact time was 60 seconds. The result showed that layers 0.1 mm tick for Life and Prisma VLC Dycal and 0.2 mm thick for Renew were able to block the penetration of phosphoric acid solution whereas layers 0.1 mm thick for the 3 cements were able to block the penetration of phosphoric acid gel.

Delayed tooth replantation after root surface treatment with sodium hypochlorite and sodium fluoride: Histomorphometric analysis in rats

In cases of delayed tooth replantation, non-vital periodontal ligament remnants have been removed with sodium hypochlorite in an attempt to control root resorption. Nevertheless, reports of its irritating potential in contact with the alveolar connective tissue have been described. Therefore, this study evaluated the healing process on delayed replantation of rat teeth, after periodontal ligament removal by different treatment modalities. Twenty-four rats, assigned to 3 groups (n=8), had their upper right incisor extracted and left on the workbench for desiccation during 60 min. Afterwards, the teeth in group I were immersed in saline for 2 min. In group II, root surfaces were scrubbed with gauze soaked in saline for 2 min; and in group III, scrubbing was done with gauze soaked in 1% sodium hypochlorite solution. Thereafter, root surfaces were etched with 37% phosphoric acid and immersed in 2% acidulate-phosphate sodium fluoride solution, at pH 5.5. Root canals were filled with a calcium hydroxide-based paste and the teeth were replanted. The animals were sacrificed 60 days postoperatively and the pieces containing the replanted teeth were processed and paraffin- embedded. Semi-serial transversally sections were obtained from the middle third of the root and stained with hematoxylin and eosin for histomorphometric analysis. Data were analyzed statistically using Kruskal-Wallis and Dunn's tests. The results showed that root structure and cementum extension were more affected by resorption in group III (p<0.05). All groups were affected by root resorption but the treatment performed in group III was the least effective for its control. The treatment accomplished in groups I and II yielded similar results to each other.

Resposta do manjericão (Ocimum basilicum L.) cultivado em solos corrigidos com calcário e escória silicatada: Caracterí sticas agronômicas e produção de matéria seca

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Deposição de sílica e teor de nitrogênio e silício em arroz

The nitrogen fertilization is an important practice to reach high productivity, however, nitrogen high level can cause lodging and make the plants more sensitive to disease. Numerous studies has demonstrate that a lot of grasses accumulate silicon at its tissues, and the biggest part of this element is deposited on the leaf, that would work like a mechanical barrier to diseases come in. However, high levels of nitrogen can reduce the silica deposition at the plants. The objective of this study was to evaluate silicon and nitrogen content in shoot and silica deposition in upland rice leaf as a result of Si and N levels. The experimental design used was completely randomized in factorial schema 3 x 2 with five replications. The treatments consisted from levels of N (5, 75 and 150 mg dm-3 of soil) in urea form and two levels of SiO2 (0 e 400 mg dm-3) in calcium silicate form (Wollastonita). The increased of urea fertilization reduced the silicon content of rice plants and the silica deposition at the external cells wall the epidermal rice leafs.

Aplicação de calcário, silicato e gesso em soqueira de cana-de-açúcar sem despalha a fogo

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Aplicação de escória de aciaria e calcário no solo e desenvolvimento do primeiro ciclo da grama bermuda

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Persistência de palhada de plantas de cobertura em função de doses de silício e resposta do feijoeiro em sucessão

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Produção de plantas de arroz sob a ação de silício e nitrogênio

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

Efeito da escória de siderurgia como fonte de silício e sua interação com a adubação nitrogenada em Brachiaria brizantha

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Reimplante dentário tardio após o tratamento da superfície radicular com hipoclorito de sódio e fluoreto de sódio: análise histomorfométrica em ratos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise do processo de reparo do reimplante de incisivos de ratos diabéticos após a manutenção dos dentes em leite

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeito de soluções irrigadoras e do hidróxido de cálcio como curativo de demora sobre o LPS-endotoxina. Estudo histopatológico em dentes de cães

Pós-graduação em Odontologia - FOAR

Síntese de templates para aplicação em piezocerâmicas livre de chumbo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)