Effect of yttrium doping in barium zirconium titanate ceramics: A structural, impedance, modulus spectroscopy study

In the current article, we studied the effect of yttrium [Y3+] ions' substitution on the structure and electric behavior of barium zirconate titanate (BZT) ceramics with a general formula [Ba1-x Y 2x/3](Zr0.25Ti0.75)O3 (BYZT) with [x = 0, 0.025, 0.05] which were prepared by the solid-state reaction method. X-ray diffraction patterns indicate that these ceramics have a single phase with a perovskite-type cubic structure. Rietveld refinement data confirmed [BaO 12], [ZrO6], [TiO6], [YO6] clusters in the cubic lattice. The Y3+ ions' effects on the electric conductivity behavior of BZT ceramics as a function of temperature and frequency are described, which are based on impedance spectroscopy analyses. The complex impedance plots display a double semicircle which highlights the influences of grain and grain boundary on the ceramics. Impedance analyses showed that the resistance decreased with the increasing temperature and resulted in a negative temperature coefficient of the resistance property in all compositions. Modulus plots represent a non-Debye-type dielectric relaxation which is related to the grain and grain boundary as well as temperature-dependent electric relaxation phenomenon and an enhancement in the mobility barrier by Y3+ ions. Moreover, the electric conductivity increases with the replacement of Ba 2+ by Y3+ ions may be due to the rise in oxygen vacancies. © 2013 The Minerals, Metals & Materials Society and ASM International

Commercial babassu mesocarp: microbiological evaluation and analysis of label information

<p>The babassu mesocarp is easily found in supermarkets and other commercial establishments in Brazil. Despite its widespread use in both pharmaceutical and food industries, the literature has neither scientific studies about microbial contamination for these products nor about legal information expressed on label. The aim of this study was to evaluate the level of microbiological contamination in babassu mesocarp sold in commercial establishments in Teresina-PI/Brazil besides the conformity of label information according to the rules of Brazilian Sanitary Surveillance Agency (ANVISA). Ten samples of babassu mesocarp powder sold in the region were selected for study. Determination of heterotrophic microorganisms was carried out using the seeding technique of Plate Count Agar (CFU g-1). It was used Sabouraud Dextrose Agar medium for cultivation of fungi. For the analysis of label information, the resolutions (RDC), 259 of September 20, 2002, and 360 of December 23, 2003, beyond the law 10,674 of May 16, 2003 were used. The results of levels of contamination for heterotrophic bacteria and fungi showed high contamination for all samples. Most of the label samples were according to the rules. Therefore, the results suggest a more comprehensive monitoring of these microorganisms besides the development of more effective methods for decontamination of these products sold in Brazil.</p><p>Keywords: Babassu. Label. Contamination. Food. Pharmacy.</p><p> </p><p>RESUMO</p><p> </p><p>O mesocarpo de babaçu é encontrado facilmente em supermercados e em outros estabelecimentos comercias e apesar de sua ampla utilização, tanto na indústria farmacêutica e de alimentos, na literatura não há trabalhos científicos que avaliem sua contaminação microbiológica ou informações legais necessárias para rótulos. O objetivo do estudo foi avaliar o nível de contaminação microbiológica do mesocarpo de babaçu, vendidos no comércio de Teresina-PI, bem como verificar a conformidade das informações dos rótulos com as normas da Agencia de Vigilância Sanitária (ANVISA). Foram selecionadas dez amostras do pó comercializadas no mercado regional. Para a determinação de microrganismos heterotróficos foi realizada a técnica de semeadura utilizando o meio Plate Count Agar, para fungos, utilizou-se o meio Sabouraud Dextrose Ágar e para a avaliação dos rótulos tomaram-se como base as resoluções, RDC 259, de 20/09/2002, RDC 360, de 23/12/2003, e a Lei nº10.674, de 16/05/2003. Os resultados dos índices de contaminação para bactérias heterotróficas e fungos mostraram-se bastante elevados. Quanto à rotulagem, a maioria das amostras estava de acordo com as regras. Com os resultados obtidos sugere-se um monitoramento mais abrangente desses microrganismos além do desenvolvimento de métodos de descontaminação mais efetivos para esses produtos comercializados no Brasil.</p><p>Palavras-chave: Babaçu. Rótulos. Contaminação. Alimentos. Farmácia.</p

Synthesis of poly(ethyl methacrylate-co-methyl methacrylate) obtained via ATRP using ruthenium benzylidene complexes

<div><p>Abstract Atom-Transfer Radical Copolymerization (ATRP) of methyl methacrylate (MMA) and ethyl methacrylate (EMA) under different reaction conditions was conducted using Grubbs 1st ( 1) and 2nd (2) generation catalysts. Initially, the study focused on the reactivity of the catalysts in ATRP of EMA individually, then the syntheses of poly(MMA-co-EMA) were also conducted in different mixtures of monomers ([MMA]/[EMA] = 100/200 and [MMA]/[EMA] = 200/100). Conversion and semilogarithmic kinetic plots as a function of time were related to the different catalysts and reaction conditions. The values of Mn and PDI also changed when different catalysts were used in the presence of Al(OiPr)3, and more controlled polymerizations were achieved using 1. In the syntheses of poly(MMA)-co -(EMA), conversion of 60% was reached for both catalysts at different [MMA]/[EMA] ratios for 16 h; however, for shorter time, 4 h, better conversion values were obtained using 1 as catalyst for both [MMA]/[EMA] = 100/200 or 200/100.</p></div

Synthesis of poly(ethyl methacrylate-co-methyl methacrylate) obtained via ATRP using ruthenium benzylidene complexes

<div><p>Abstract Atom-Transfer Radical Copolymerization (ATRP) of methyl methacrylate (MMA) and ethyl methacrylate (EMA) under different reaction conditions was conducted using Grubbs 1st ( 1) and 2nd (2) generation catalysts. Initially, the study focused on the reactivity of the catalysts in ATRP of EMA individually, then the syntheses of poly(MMA-co-EMA) were also conducted in different mixtures of monomers ([MMA]/[EMA] = 100/200 and [MMA]/[EMA] = 200/100). Conversion and semilogarithmic kinetic plots as a function of time were related to the different catalysts and reaction conditions. The values of Mn and PDI also changed when different catalysts were used in the presence of Al(OiPr)3, and more controlled polymerizations were achieved using 1. In the syntheses of poly(MMA)-co -(EMA), conversion of 60% was reached for both catalysts at different [MMA]/[EMA] ratios for 16 h; however, for shorter time, 4 h, better conversion values were obtained using 1 as catalyst for both [MMA]/[EMA] = 100/200 or 200/100.</p></div