162 resultados para Hydrous niobium phosphate

em Repositório Institucional UNESP - Universidade Estadual Paulista "Julio de Mesquita Filho"


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A composite of cellulose extracted from bagasse with Nb2O5 center dot nH(2)O in three different proportions (16.67, 37.5 and 50.0 wt%) was prepared using the co-precipitation method. The materials were characterized by X-ray diffractometry (XRD), Fourier transform infra-red spectroscopy (FTIR), thermogravimetric analysis (TG/DTG), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). TG data obtained show that the presence of inorganic material influenced slightly the stability of the hybrid material. The precipitation of 16.67 wt.% of oxide was sufficient to inhibit the combustion peaks present in the DSC curve of cellulose. This work will help find new applications for these materials. Published by Elsevier Ltd.

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In recent years studies concerning the applications of lignocellulosic/ inorganic couples have resulted in the development of an interesting class of functional materials. In this work a cellulose/NbOPO 4.nH 2O hybrid using cellulose from surgacane bagasse was prepared and characterized in order to test for adsorption applications. The preparation process was conducted by carrying out metallic niobium dilution in hydrofluoric acid in the presence of nitric acid, then adding boric acid to form the complex and, finally, the cellulose sugar cane bagasse was added. Concentrated phosphoric acid was also inserted to precipitate hydrous niobium phosphate particles in the cellulose fiber. This material was characterized by X-ray diffractometry (XRD), thermogravimetry (TG/DTG), and scanning electronic microscopy (SEM) connected to an energy dispersive spectrophotometer (EDS). Results by SEM/EDS show that NbOPO 4.nH 2O was present in structure of the cellulose. During the preparation of the material, using boric acid it was observed that the formation of precipitate occurred in a shorter time than the material prepared without boric acid.

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The purpose of this study was to characterize and to evaluate the bioactivity potential of experimental root canal sealers (ES) based on Portland cement, epoxy resin with nano- and micro-particles of niobium or zirconium oxide used as radiopacifiers in comparison to AH Plus and MTA Fillapex. Methods Specimens of the sealers (10 mm in diameter × 1 mm thick) were prepared and the radiopacity was evaluated according to ISO 6876 (2012) specifications. Characterization of the sealers was performed under the scanning electron microscope (SEM) immediately after setting and after immersion for 28 days in Hank's balanced salt solution (HBSS). In addition X-ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy were also performed. The pH and calcium ion release were measured after 1, 7, 14, 21 and 28 days after completion of seating using a digital pH meter and an atomic absorption spectrophotometer, respectively. Results The experimental sealers exhibited an average radiopacity of 2.5 mm thickness of aluminum, which was similar to MTA Fillapex (P > 0.05) and inferior to AH Plus (P < 0.05). AH Plus did not show bioactivity. Although the experimental sealers did not exhibit the formation of hydration product, they encouraged the deposition of crystalline spherical structures of calcium deficient phosphate. The highest pH and calcium release values were observed with the experimental sealers (P < 0.01). ES-Nb-micro was the only sealer to present hexagonal shaped crystal deposition. Significance Novel root canal sealers based on a mixture of Portland cement, epoxy resin and radiopacifier exhibited a degree of bioactivity although no evidence of cement hydration was demonstrated on material characterization. The radiopacifier particle size had limited effect on the sealer microstructure and chemical properties.

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Brazilian soils predominantly consist of iron and aluminum oxides and have a low phosphorus content. The present study was carried out in order to assess the status of phosphate fractions in pasture, forest and agricultural soils and the ability of soil fungi to solubilize iron and aluminum phosphates. The abundance of P fractions in the soils studied occurred in the following order: Fe-P > reductant-soluble Fe-P > occluded Fe-P > occluded Al-P > Al-P > Ca-P. of the 481 fungi isolated, 33 showed the ability to solubilize the inorganic phosphates in culture. of these, 14 were considered to be high or very high solubilizers based on a solubilization capacity > 1000 mu g PO43- ml(-1). Isolate F-111 was the only one that dissolved all the insoluble phosphates used. Nine isolates solubilized both Al-P and Ca-P, and four other isolates only solubilized Ca-P. The highest number of isolates with high solubilization capacity were detected in pasture soil, followed by tropical rain forest and forest patch soils. Pasture soil presented both the largest contents of insoluble phosphates and the largest number of fungal isolates with phosphate-solubilizing ability. The range and size of P fractions influenced the number of fungi and their ability to solubilize hardly soluble phosphates. (c) 2004 Elsevier B.V. All rights reserved.

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O alto custo atual do KCl e a grande dependência de sua importação para suprir a demanda nacional sugerem a necessidade de estudos que procurem avaliar a eficiência de outras fontes de K, principalmente aquelas baseadas em matéria-prima nacional. Nesse sentido, foi conduzido um experimento em casa de vegetação com amostras de um Latossolo Vermelho distrófico textura média, adotando-se o delineamento inteiramente casualizado em esquema fatorial 4 x 3 x 2, sendo quatro doses de K (0, 60, 120 e 180 mg kg-1 de K), três fontes [(cloreto de potássio (KCl)], termofosfato magnesiano potássico (FMPP) e a mistura de 70 % FMPP + 30 % KCl) e duas granulometrias (100 e 60 mesh), com três repetições. Verificou-se que a adubação potássica promoveu incrementos significativos na produção de matéria seca (parte aérea) e nos teores de K no solo e na planta, não havendo diferenças entre as fontes e suas granulometrias. Os níveis críticos de K no solo e na parte aérea das plantas foram de 1,53 mmol c dm-3 e 19,1 g kg-1, respectivamente.

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The objective of this work was to assess the functionality of the glycolytic pathways in the bacterium Xylella fastidiosa. To this effect, the enzymes phosphoglucose isomerase, aldolase, glyceraldehyde-3-phosphate dehydrogenase and pyruvate kinase of the glycolytic pathway, and glucose 6-phosphate dehydrogenase of the Entner-Doudoroff pathway were studied, followed by cloning and expression studies of the enolase gene and determination of its activity. These studies showed that X. fastidiosa does not use the glycolytic pathway to metabolize carbohydrates, which explains the increased duplication time of this phytopatogen. Recombinant enolase was expressed as inclusion bodies and solubilized with urea (most efficient extractor), Triton X-100, and TCA. Enolase extracted from X. fastidiosa and from chicken muscle and liver is irreversibly inactivated by urea. The purification of enolase was partial and resulted in a low yield. No enzymatic activity was detected for either recombinant and native enolases, aldolase, and glyceraldehyde-3-phosphate dehydrogenase, suggesting that X. fastidiosa uses the Entner-Doudoroff pathway to produce pyruvate. Evidence is presented supporting the idea that the regulation of genes and the presence of isoforms with regulation patterns might make it difficult to understand the metabolism of carbohydrates in X. fastidiosa.

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