Phase formation and characterization of BaBi2Ta2O9 obtained by mixed oxide procedure

Ferroelectric layefed-perovskite BaBi2Ta2O9 (BBT) has been prepared successfully by solid-state reaction. The influence of pressure and temperature/time annealing regime on the BBT phase formation was analyzed. The powders were characterized by thermal analysis and Xray diffraction and the sintered pellets by scanning electron microscopy. The crystalline BBT phase, free of secondary phases was obtained at 950 degreesC for 2 h. For an applied field strength of 380 kV/cm, a remnant polarization of 7.6 muC/cm(2) and an electric coercive field of 45.7 kV/cm were obtained. (C) 2004 Elsevier B.V. All rights reserved.

Niobium doped Bi4Ti3O12 ceramics obtained by the polymeric precursor method

Pure and niobium doped bismuth titanate ceramics (Bi4Ti3-xNbxO12 (BTN)), with x ranging from 0 to 0.4 were prepared by the polymeric precursor method. X-ray diffraction showed no secondary phases. Increasing niobium content leads to more resistive ceramics. The shape and size of the grains are strongly influenced by the niobiurn added to the system. The dielectric constant is not influenced by the niobium addition while hysteresis loops are significantly narrowed. (c) 2006 Elsevier B.V All rights reserved.

Raman scattering, differential scanning calorimetry and Nd3+ spectroscopy in alkali niobium tellurite glasses

Alkali niobium tellurite glasses have been prepared and some of their properties measured by differential scanning calorimetry and Raman scattering. The vitreous domain was established in the pseudo ternary phases diagram for the system TeO2-Nb2O5-(0.5K(2)O-0.5Li(2)O). Raman scattering shows that for samples in the TeO2 rich part of the phase diagram the vitreous structure is composed essentially of (TeO4) units connected by the vertices, as in the alpha-TeO2 crystal. The addition of alkali and niobium oxides causes depolymerization to occur with structures composed essentially of (TeO3) and (NbO6) units. Samples with the composition (mol%) 80TeO(2)-10Nb(2)O(5)-5K(2)O-5Li(2)O, stable against crystallization, were prepared containing up to 10% mol Nd3+. The addition of this oxide increases the rigidity of the vitreous network shifting characteristic temperatures to higher temperatures. For the 10% Nd3+ sample amorphous phase separation is assumed to exist from the observation of two glass transition temperatures. Spectroscopic properties such as Judd-Ofelt Omega(lambda) intensity parameters, radiative emission probabilities, and induced emission cross sections were calculated. From these results and also from the emission quenching observed as a function of Nd3+ concentration, we suggest that these glasses could be utilized in optical amplifying devices. (C) 1999 Elsevier B.V. B.V. All rights reserved.

In situ and simultaneous nanostructural and spectroscopic studies of ZnO nanoparticle and Zn-HDS formations from hydrolysis of ethanolic zinc acetate solutions induced by water

The simultaneous formation of nanometer sized zinc oxide (ZnO), and acetate zinc hydroxide double salt (Zn-HDS) is described. These phases, obtained using the sol-gel synthesis route based on zinc acetate salt in alcoholic media, were identified by direct characterization of the reaction products in solution using complementary techniques: nephelometry, in situ Small-Angle X-ray Scattering (SAXS), UV-Vis spectroscopy and Extended X-ray Absorption Fine Structures (EXAFS). In particular, the hydrolytic pathway of ethanolic zinc acetate precursor solutions promoted by addition of water with the molar ratio N = [H2O]/[Zn2+] = 0.05 was investigated in this paper. The aim was to understand the formation mechanism of ZnO colloidal suspension and to reveal the factors responsible for the formation of Zn-HDS in the final precipitates. The growth mechanism of ZnO nanoparticles is based on primary particle (radius approximate to 1.5 nm) rotation inside the primary aggregate (radius < 3.5 nm) giving rise to an epitaxial attachment of particles and then subsequent coalescence. The growth of second ZnO aggregates is not associated with the Otswald ripening, and could be associated with changes in equilibrium between solute species induced by the superficial etching of Zn-HDS particles at the advanced stage of kinetic.

Preparation and characterization of nanosized SrBi2Nb2O9 powder by the combustion synthesis

This work presents the preparation of SrBi2Nb2O9 (SBN) directly by the combustion synthesis. Strontium nitrate, niobium ammonium oxalate (NH4H2[NbO-(C2O4)(3)].3H(2)O) and bismuth oxide were used as oxidant reactants and urea as fuel. The influence of the fuel was evaluated by the addition of different fuel amounts (50%, 100%, 200% and 300%), 100% being the stoichiometric proportion. The XRD patterns showed that the SBN perovskite crystallized as the majority phase. The as-synthesized stoichiometric powder presented a specific surface area of around 13 m(2)/g and a mean grain size of around 16 nm. Dilatometric measurements showed that the maximum sintering rate occurs at 1275degreesC. The determination of the ferroparaelectric transition showed a Curie temperature (T-c) of 429degreesC. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Enhanced luminescence of Tb3+/Eu3+ doped tellurium oxide glass containing silver nanostructures

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

pH changes at the surface of root dentin when using root canal sealers containing calcium hydroxide

The purpose of this study was to investigate long-term pH changes in cavities prepared in root surface dentin of extracted teeth after obturation of the root canal with gutta-percha and a variety of sealers containing calcium hydroxide. After cleaning and shaping, root canals in 50 recently extracted, human single-rooted teeth were divided into five groups. Each of four groups was obturated with gutta-percha and either Sealapex, Sealer 26, Apexit, or CRCS, all of which contain calcium hydroxide. The remaining group served as the control and was not obturated with gutta-percha or sealer. Cavities were prepared in the facial surface of the roots in the cervical and middle regions. The pH was measured in these dentinal cavities at the initiation of the experiment, and 3, 7, 14, 21, 28, 45, 60, 90, and 120 days after obturation. Results indicate that the pH at the surface of the root does not become alkaline when calcium hydroxide cements are used as root canal sealers. Regardless of the sealer used, the observed pattern of pH change was not different from that seen in the control group of roots that were not treated with sealer. It is concluded that calcium hydroxide-containing cements, although suitable for use as root canal sealants, do not produce an alkaline pH at the root surface. If such a pH change is related to treatment of root resorption, these sealants do not contribute to this treatment. Copyright © 1996 by The American Association of Endodontists.

Calcium hydroxide root canal sealers: Evaluation of pH, calcium ion concentration and conductivity

The calcium hydroxide ionization of four root canal sealers (Sealapex, CRCS, Sealer 26, and Apexit) was studied by measuring conductivity and pH and by conducting atomic absorption spectrophotometry. Samples 6 mm in diameter and 15 mm long were prepared from these sealers. After setting and 48 h storage in a desiccator, five samples of each material were placed in 50 mL distilled water and analysed after 0,1,2,4, 6 and 24 h and 5, 15 and 30 days. The results showed that Sealapex was the root canal sealer showing the highest pH, ionic calcium and total calcium values (P<0.05) throughout the experimental period, followed by CRCS, Apexit and Sealer 26.

Magneto-optical rotation of heavy-metal oxide glasses

Magneto-optical rotation was measured at room temperature for glasses containing Bi2O3-CdO-GeO2 (BCG), and Bi2O3-PbO-GeO2-B2O3 (BPGP). A pulsed magnetic field between 50 and 80 KG was used to measure Faraday rotation at 632.8 nm as a function of the concentration of Bi and Cd for BCG and Bi and Pb for BPGB. Verdet constant as high as 0.162 min G-1 cm-1 at 632.8 nm for the BPGB sample with the highest concentrations of Bi and Cd was found. Verdet constant increases linearly with the heavy-metal concentration for the BPGB whereas it reaches some saturation for the BCG system. Measurements of the magneto-optical rotation at other wavelengths in the visible and the refractive index at 632.8 nm are also reported. © 1998 Elsevier Science B.V. All rights reserved.

Evaluation of cell culture cytotoxicity of five root canal sealers

The cytotoxicity of four calcium hydroxide-based root canal sealers (Sealapex, CRCS, Apexit, and Sealer 26) and one zinc oxide-eugenol-based sealer (Fill Canal) was evaluated microscopically for morphological changes in rat peritoneal macrophages. The least cytotoxic sealer was Fill Canal, followed in increasing order of cytotoxicity by CRCS, Sealer 26, Apexit, and Sealapex. Copyright © 2000 by The American Association of Endodontists.

Calcium salts deposition in rat connective tissue after the implantation of calcium hydroxide-containing sealers

This study was conducted to observe the rat subcutaneous connective tissue reaction to implanted dentin tubes that were filled with mineral trioxide aggregate, Sealapex, Calciobiotic Root Canal Sealer (CRCS), Sealer 26, and the experimental material, Sealer Plus. The animals were sacrificed after 7 and 30 days, and the specimens were prepared for histological analysis after serial sections with a hard-tissue microtome. The undecalcified sections were examined with polarized light after staining according to the Von Kossa technique for calcium. At the tube openings, there were Von Kossa-positive granules that were birefringent to polarized light. Next to these granulations, there was irregular tissue, like a bridge, that was Von Kossa-positive. The dentin walls of the tubes exhibited a structure highly birefringent to polarized light, usually like a layer, in the tubules. These results were observed with all the studied materials, except the CRCS, which didn't exhibit any kind of mineralized structure. The results suggest that among the materials studied, the CRCS could have the least possibility of encouraging hard tissue deposition.

Relative bioavailability of zinc in supplemental inorganic and organic sources for Nile tilapia Oreochromis niloticus fingerlings

A 90-day feeding experiment was conducted with sex reversed Nile tilapia (Oreochromis niloticus) fingerlings fed purified or practical diets supplemented with different zinc sources to evaluate fish growth performance and zinc and iron retention in fish bones, fillets, liver, skin and eyes. The relative bioavailability value (RBV) of zinc in the supplemental sources tested was also calculated. Fish were fed with isonitrogenous and isoenergetic purified or practical diets supplemented with 150 mg Zn kg -1, as zinc sulphate monohydrate (ZnSO 4), zinc oxide (ZnO) or zinc amino acid complex (Zn-AA). The feeding trial was conducted in 30, 50 L aquaria where four 0.66 ± 0.01 g (mean ± SD) fingerlings were initially stocked. No significant differences were observed for any growth performance variables (P > 0.05). In practical diets, only ZnSO 4 and ZnO presented bone zinc retention similar to that for the standard zinc source. Zinc concentration in the bone of fish fed practical diet supplemented with Zn-AA (171 ± 3.62 μg g -1) was significantly lower than that verified for the practical diets supplemented with the standard zinc source (200 ± 17.7 μg g -1) or with ZnSO 4 (204 ± 19.9 μg g -1). Assuming the concentration of zinc in bones as the response criterion, the supplemental zinc RBV from ZnSO 4 (105%) was higher than the RBV for Zn-AA (95.1%) or ZnO (94.9%). Iron concentration in the bones of animals fed the non-zinc-supplemented purified diet was significantly higher than that observed for purified diet supplemented with Zn-AA (P < 0,05). The results of the present work allowed us to conclude that ZnSO 4 in relation to ZnO or Zn-AA was the supplemental zinc source with higher zinc bioavailability to Nile tilapia. © 2005 Blackwell Publishing Ltd.

Apparent absorption of zinc from supplemental inorganic and organic sources to Nile tilapia Oreochromis niloticus juveniles

Nile tilapia Oreochromis niloticus fingerlings were fed with purified or practical diets, supplemented with 150 Ing Zn/kg, from different sources. Dry matter (DM), crude protein (CP), ether extract (EE), and gross energy (GE) apparent digestibility coefficients (ADC), as well as zinc, copper, calcium, and phosphorus apparent absorption coefficients (AAC) were determined by the addition of 0.1% chromic oxide to the diets. The supplemental zinc sources utilized were commercial grade zinc sulfate monohydrate (ZnSO 4), zinc oxide (ZnO) and a zinc amino acid complex (Zn-AA). Analytical grade zinc sulfate heptahydrate was also utilized as a standard reference zinc source. There was a significant difference between purified (74.9%) and practical (41.3%) zinc AAC for the ZnO supplemented diets (P < 0.05). The supplemental zinc sources presented similar AAC when purified diets were utilized. However, ZnSO 4 was the best supplemental zinc source when practical type diets were used. There were no significant differences between supplemental zinc AAC from ZnS0 4 (68.9%), and supplemental zinc AAC from Zn-AA (61.3%) in practical diets, but Zn-AA diet showed a statistically lower zinc AAC when compared with the standard zinc source diet (75.6%). The practical diet supplemented with ZnO had the worst supplemental zinc AAC (41.3%). Dietary copper (74.21%), calcium (70.9%), and phosphorus (71.9%) AAC of the practical diets supplemented with ZnO were statistically lower (P < 0.05) than the respective AAC of the practical ZnSO 4 supplemented diets (83.6%, 84.1%, 87.1%).The ADC of the practical ZnO supplemented diet for DM (76.3%), CP (88.6%), EE (82.4%), and GE (81.6%) were statiscally lower than the respective ADC of the ZnSO 4 practical diet (86.0, 92.7, 93.6, 89.6%, respectively) and those ADC of the Zn-AA practical diet (84.7, 92.7, 93.7, 88.2%, respectively) (P < 0.05). Hence, these results indicate that ZnSO 4 and Zn-AA have equivalent intestinal absorption as supplemental zinc sources for Nile tilapia juveniles and both are superior to ZnO. © Copyright by the World Aquaculture Society 2005.

Antimicrobial activity of endodontic sealers based on calcium hydroxide and MTA.

The aim of this study was to evaluate the antimicrobial activity of a new root canal sealer containing calcium hydroxide (Acroseal) and the root canal sealer based on MTA (Endo CPM Sealer), in comparison with traditional sealers (Sealapex, Sealer 26 and Intrafill) and white MTA-Angelus, against five different microorganism strains. The materials and their components were evaluated after manipulation, employing the agar diffusion method. A base layer was made using Müller-Hinton agar (MH) and wells were made by removing agar. The materials were placed into the wells immediately after manipulation. The microorganisms used were: Micrococcus luteus (ATCC9341), Staphylococcus aureus (ATCC6538), Pseudomonas aeruginosa (ATCC27853), Candida albicans (ATCC 10231), and Enterococcus faecalis (ATCC 10541). The plates were kept at room temperature for 2 h for prediffusion and then incubated at 37 degrees C for 24 h. The results showed that Sealapex and its base paste, Sealer 26 and its powder, Endo CPM Sealer and its powder, white MTA and its powder all presented antimicrobial activity against all strains. Intrafill and its liquid presented antimicrobial activity against all strains except P. aeruginosa and Acroseal was effective only against M. luteus and S. aureus.

Supplementation of diets for Santa Ines sheep with organic and inorganic zinc sources

This research was conducted with objective to evaluate the effect of different zinc (Zn) sources and doses in the diet for Santa Ines sheep. Forty lambs at weaning, with 18.4 kg of body weight were supplemented with three different sources of zinc (zinc oxide (ZnO), zinc amino acid and zinc proteinate) and three doses of zinc (200, 400 and 600 mg/kg DM) added to the basal diet. At every 28 days, animals were weighted and blood samples were collected for analyses of zinc (Zn), alkaline phosphatase and immunoglobulin G (IgG) and M (IgM). At the end of experiment, liver samples were collected for determination of the hepatic zinc levels. Zinc was analyzed with atomic absorption spectrophotometer, while phosphatase alkaline and immunoglobulins G and M were analyzed using Laborlab and Bioclin kits, respectively. There was no effect of diets on phosphatase alkaline levels and hepatic zinc, but there was difference in the plasmatic zinc levels and IgG and IgM levels. Based on the accumulation of hepatic zinc, the estimate of the zinc bioavailability, through the regression equation, showed that supplementation with organic and inorganic sources of zinc did not differ in the diet of Santa Ines sheep. © 2012 Sociedade Brasileira de Zootecnia.