Green coffee seed residue: A sustainable source of antioxidant compounds.

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Long-term aging of fiber-cement corrugated sheets - The effect of carbonation, leaching and acid rain

This paper studies the performance of fiber-cement corrugated sheets exposed to long-term weathering, exploring the effect of different environments on fiber-cement degradation. Fiber-cement corrugated sheets that had been exposed to weathering, and in place for more than 30-years, were collected from two different Brazilian cities (Sao Paulo and Criciuma). Mechanical properties (MOR, MOE and fracture toughness) were tested on samples removed from the corrugated sheets. Microstructure was evaluated by X-ray diffraction, SEM with EDS analysis, MIP and TG. The results show that the 37-year-old asbestos-cement corrugated sheets from Sao Paulo presented similar characteristics to those of the non-aged asbestos-cement readily available on the market place. Conversely, deterioration of the asbestos-cement from the industrial area of Criciuma is related to acidic attack, along with carbonation and leaching as a consequence of continued exposition to acid rain during several decades. This process resulted in higher porosity and lower mechanical strength, revealing that leaching mechanisms can have important effect on the performance of thin fiber-cement sheets. (c) 2007 Elsevier Ltd. All rights reserved

Indirect and direct Chapelle's methods for the determination of lime consumption in pozzolanic materials

In this work, comments are made about indirect methods and direct Chapelle's method applied to the determination of the reactivity of pozzolanic materials. The Chapelle's method is based on the lime-pozzolan reaction and quantifies the pozzolanic reactivity of any material intended to be applied by the cement industry. This lime consumption determination by the pozzolan through this reaction can be made with mass proportions - lime:pozzolan 1:1, as originally proposed by Chapelle or 2:1, as specified in Brazilian and French Standards. Comparative results with both proportions are presented for sugar cane bagasse ash, rice rusk ash, silica fume, fly ash, and metakaolin, commonly studied in our country. Statistical calculations showed that for some materials of similar characteristics to the researched RHA, FA e MK at issue, essays carried out with only 1g of CaO may be underestimating the amounts of CaO consumed per gram of pozzolanic material that can be obtained. Comments were made about the Brazilian and French Standards based on this method and emphasized the expression of lime consumption per mass of the amorphous phase of these materials, as determined by X ray diffraction analysis with the Rietveld refinement method

Simultaneous determination of epinephrine and dopamine by electrochemical reduction on the hybrid material SiO2/graphene oxide decorated with Ag nanoparticles

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQThis paper describes the synthesis, characterization and applications of a new hybrid material composed of mesoporous silica (SiO2) modified with graphene oxide (GO), SiO2/GO, obtained by the sol-gel process using HF as the catalyst. The hybrid material, SiO2/GO, was decorated with silver nanoparticles (AgNPs) with a size of less than 20 nanometres, prepared directly on the surface of the material using N,N-dimethylformamide (DMF) as the reducing agent. The resulting material was designated as AgNP/SiO2/GO. The Ag/SiO2/GO material was characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and high-resolution transmission electron microscopy (HR-TEM). A glassy carbon electrode modified with AgNP/SiO2/GO was used in the development of a sensitive electrochemical sensor for the simultaneous determination of epinephrine and dopamine employing electrocatalytic reduction using squarewave voltammetry. Well-defined and separate reduction peaks were observed in PBS buffer at pH 7. No significant interference was seen for primarily biological interferents such as uric acid and ascorbic acid in the detection of dopamine and epinephrine. Our study demonstrated that the resultant AgNP/SiO2/GO-modified electrode is highly sensitive for the simultaneous determination of dopamine and epinephrine, with the limits of detection being 0.26 and 0.27 mu mol L-1, respectively. The AgNP/SiO2/GO-modified electrode is highly selective and can be used to detect dopamine and epinephrine in a human urine sample.1391846344640FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ2011/23047-72012/18339-1Sem informaçã

Chemical interaction between EVA and Portland cement hydration at early-age

Ethylene/vinyl acetate (EVA) copolymer. as latex or redispersable powder, is added to mortars and concrete to improve the fracture toughness, impermeability and bond strength to various substrates. The physical and chemical interactions were already proved after one day of hydration but during the first hour just the physical interaction was identified and some evidences of a chemical interaction. The aim of this paper was to evaluate the chemical interaction between EVA and Portland cement during the first hours of hydration in the thermogravimetric analysis. The results confirmed that the EVA hydrolyses in pH alkaline and consumes calcium ions from the solution, forming an organic salt (calcium acetate). reducing the calcium hydroxide content. And, its interaction occurred in the first 15 min of hydration. (C) 2009 Elsevier Ltd. All rights reserved.CAPES (Fundacao Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior, Ministerio da Educa do, Brasil