Avaliação dos mecanismos de aderência entre argamassa colante e substrato não poroso

A resistência de aderência de um sistema de revestimento cerâmico é uma das mais importantes propriedades deste tipo de acabamento. O conhecimento das propriedades dos substratos e argamassas, e a capacidade de bem avaliar a interação entre os elementos são preceitos básicos para construírem-se revestimentos duráveis. Nesse sentido, o aperfeiçoamento dos modelos que descrevem os mecanismos de aderência, objetos de estudo deste trabalho, são essenciais, principalmente devido a diferenças nas características dos materiais relativas à porosidade, verificadas tanto em substratos como nas placas. O planejamento experimental consistiu no assentamento de um revestimento cerâmico externo utilizando-se a técnica de piso sobre piso, ensaios de resistência de aderência, aquisição de imagens em MEV dos pisos retirados do campo de testes e caracterização das argamassas colantes de estudo. Os resultados mostraram uma relação entre a resistência de aderência e a extensão de contato entre a argamassa e o substrato, indicando que o mecanismo de aderência para o assentamento de placas sobre substratos não porosos está diretamente relacionado com a extensão do contato entre os materiais, resultando em um modelo de aderência para o caso de revestimento cerâmico em substrato pouco poroso

Field Attractants for Pachnoda interrupta Selected by Means of GC-EAD and Single Sensillum Screening

The sorghum chafer, Pachnoda interrupta Olivier (Coleoptera: Scarabaeidae: Cetoniinae), is a key pest on sorghum, Sorghum bicolor (L.) Moench (Poaceae), in Ethiopia. At present there is a lack of efficient control methods. Trapping shows promise for reduction of the pest population, but would benefit from the development of attractive lures. To find attractants that could be used for control of P. interrupta, either by mass trapping or by monitoring as part of integrated pest management, we screened headspace collections of sorghum and the highly attractive weed Abutilon figarianum Webb (Malvaceae) for antennal activity using gas chromatograph-coupled electroantennographic detection (GC-EAD). Compounds active in GC-EAD were identified by combined gas chromatography and mass spectrometry (GC-MS). Field trapping suggested that attraction is governed by a few influential compounds, rather than specific odor blends. Synthetic sorghum and abutilon odor blends were attractive, but neither blend outperformed the previously tested attractants eugenol and methyl salicylate, of which the latter also was part of the abutilon blend. The strong influence of single compounds led us to search for novel attractive compounds, and to investigate the role of individual olfactory receptor neurons (ORNs) in the perception of kairomones. We screened the response characteristics of ORNs to 82 putative kairomones in single sensillum recordings (SSR), and found a number of key ligand candidates for specific classes of ORNs. Out of these key ligand candidates, six previously untested compounds were selected for field trapping trials: anethole, benzaldehyde, racemic 2,3-butanediol, isoamyl alcohol, methyl benzoate and methyl octanoate. The compounds were selected on the basis that they activated different classes of ORNs, thus allowing us to test potential kairomones that activate large non-overlapping populations of the peripheral olfactory system, while avoiding redundant multiple activations of the same ORN type. Field trapping results revealed that racemic 2,3-butanediol is a powerful novel attractant for P. interrupta

Influencia del transporte de agua en morteros de revestimiento, en la resistencia a la adherencia

En el presente trabajo se determina cómo ocurre el transporte de agua, en el sistema mortero/bloque, con el objetivo de vincular el comportamiento de la resistencia a la adherencia por tracción perpendicular, con el transporte de agua y la porosidad del substrato. Para ello fueron fabricados dos morteros con áridos de diferentes granulometrías, a los cuales se le determinó sus propiedades en estado fresco y en estado endurecido. Se determinó la cantidad de agua transportada, a partir de mediciones de humedad con sensores resistivos, en diferentes camadas de los morteros aplicados sobre sustrato de hormigón y sustrato cerámico. Los bloques de albañilería usados como sustrato, fueron caracterizados atendiendo a sus propiedades físicas, relacionadas con la absorción de agua y la porosidad. Los resultados mostraron que existe una relación directa entre el porciento de agua transportada en las diferentes camadas, con la resistencia a la adherencia del mortero. Comprobándose además, la no existencia de relación entre los ensayos de retención de agua del mortero y el total de agua transportada en el sistema mortero/bloque

Multiresidue determination of pesticides in industrial and fresh orange juice by hollow fiber microporous membrane liquid-liquid extraction and detection by liquid chromatography-electrospray-tandem mass spectrometry

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)A procedure involving hollow fiber microporous membrane liquid-liquid extraction (HF-MMLLE) and detection by liquid chromatography with tandem mass spectrometry was developed and applied. The extraction is based on liquid-liquid microextraction with a polypropylene porous membrane as a solid support for the solvent. On the membrane walls the solvent forms a renewable liquid membrane which improves the trueness of the method and promotes the sample clean-up. The applicability of this method was evaluated through the simultaneous extraction of 18 pesticides of different classes: polar organophosphates, carbamates, neonicotinoids, amides, pyrimidines, benzimidazoles and triazoles in industrial and fresh orange juice. The parameters affecting the extraction efficiency were optimized by multivariable designs. Under optimized conditions, analytes were concentrated onto 1.5 cm long microporous membranes placed directly into the sample containing 9 mL of juice at pH 7.0, 4g of ammonium sulfate and 400 mu L of toluene:ethyl acetate (85:15, v/v). The best extraction conditions were achieved at 25 degrees C with 35 min of extraction time. The analyte desorption was carried out using 50 mu L of methanol:acetone (50:50, v/v) for 2 min in an ultrasonic bath. Limits of detection ranging between 0.003-0.33 mg L-1, 0.003-0.35 mg L-1 and 0.003-0.15 mg L-1 were obtained for the carton orange juice, carton light orange juice and fresh orange juice samples, respectively. Good repeatability (lower than 7.6%) was obtained for all three sample types. The method was applied to five different juice samples containing soybean extract, orange pulp, nectar, light juice and fresh orange juice. The results suggest that the proposed method represents a very simple and low-cost alternative microextraction procedure rendering adequate limits of quantification for the determination of these pesticides in juice samples. (C) 2011 Elsevier B.V. All rights reserved.88573580Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

A simple hollow fiber renewal liquid membrane extraction method for analysis of sulfonamides in honey samples with determination by liquid chromatography-tandem mass spectrometry

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)A sensitive and precise analysis using hollow fiber renewal liquid membrane (HFRLM) extraction followed by high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) is described for determination of five sulfonamides in honey samples. In this procedure, the organic solvent introduced directly into the sample matrix extracts the sulfonamides and carries them over the polypropylene porous membrane. An organic solvent is immobilized inside the polypropylene porous membrane, leading to a homogeneous phase. The stripping phase at higher pH in the lumen of the membrane promotes the ionization of the target compounds releasing them to this phase. The most important parameters affecting the extraction efficiency were optimized by multivariable designs (pH and sample mass, pH and buffer for stripping phase, extraction temperature and time, type and volume of extractor solvent and use of salt to saturate the sample). Detection limits in the range of 5.1-27.4 mu g kg(-1) and linearity coefficient of correlation higher than 0.987 were obtained for the target analytes. The results obtained for the proposed method show that HFRLM-LC-MS/MS can be used for determination of the five sulfonamides studied in honey samples with excellent precision, accuracy, practicality and short analysis time. (C) 2010 Elsevier B.V. All rights reserved.12174264496454Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

A comparative study of homemade C-18 and commercial C-18 sorbents for preconcentration of lead by minicolumn solid phase extraction

A comparative study of commercial C-18 chemically immobilized on silica and homemade C-18, as sorbents for Pb complexed with O,O-diethyl-dithiophosphate (DDTP) in a flow injection preconcentration system is reported. The homemade C-18 sorbent was obtained by sorption of poly(methyloctadecylsiloxane) (PMODS) on the silica support followed by immobilization using thermal treatment. The method follows the concept of green chemistry, since there are no toxic residues after synthesis. The complexed Pb was formed in 1.0 mol L-1 HCl medium and retained on the minicolumn filled with the sorbents. The elution was carried out using ethanol, and the richest 210 muL fraction was collected and analyzed by flame atomic absorption spectrometry. Chemical and flow variables were optimized for each sorbent. The results demonstrated that the performance of the proposed homemade C-18 sorbent for preconcentration of Pb complexed with DDTP is very similar to commercial C-18 chemically bonded on silica. By processing 25 mL, the enrichment factors were 129 and 125 for commercial C-18 and homemade C-18, respectively. The limit of detection for commercial and homemade C-18 was 0.2 mug L-1 and 0.6 mug L-1, respectively. The relative standard deviation (RSD) was lower than 1.2% for both sorbents for a Pb concentration of 100 mug L-1. The method was also applied successfully to the analysis of water samples, and the accuracy was tested by recovery measurements on spiked samples and biological reference material.14441699172