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De Oliveira C.C.,Federal University of Viçosa | Coimbra J.S.D.R.,Federal University of Viçosa | Zuniga A.D.G.,Federal University of Tocantins | Martins J.P.,Federal Institute of South of Minas Gerais | Siqueira A.M.D.O.,Federal University of Viçosa
Journal of Chemical and Engineering Data | Year: 2012

The effect of poly(ethylene glycol) (PEG) molar mass, pH, and temperature on interfacial tension was investigated for aqueous two-phase systems composed of PEG with molar masses of (1500, 4000, 6000, and 8000) g·mol -1 and potassium phosphate. The temperatures tested were (293 and 313) K at the pH values of 6, 7, and 9. Interfacial tension was determined by using a spinning drop tensiometer and the Vonnegut equation. An increase in both the PEG molar mass and the temperature resulted in an increase of interfacial tension values. The interfacial tension varied from (0.05 to 3.11) mN·m -1 for systems composed by PEG 4000 (mass fraction; w = 0.12) + potassium phosphate (w = 0.11) + water (w = 0.77) at pH 6.0 and 293 K and PEG 4000 (w = 0.19) + potassium phosphate (w = 0.16) + water (w = 0.65) at pH 7.0 and 313 K, respectively. © 2012 American Chemical Society.

MacHado F.L.C.,Federal University of Viçosa | Dos Reis Coimbra J.S.,Federal University of Viçosa | Zuniga A.D.G.,Federal University of Tocantins | Da Costa A.R.,State University of Southwest Bahia | Martins J.P.,Federal Institute of South of Minas Gerais
Journal of Chemical and Engineering Data | Year: 2012

Equilibrium data were determined for aqueous two-phase systems composed of poly(ethylene glycol) (PEG), maltodextrin (MD), and water. The systems were prepared by varying the PEG molar mass (4000 g·mol -1, 6000 g·mol -1, and 8000 g·mol -1) and the dextrose equivalent (DE) of the MD (10.5 and 15). The temperatures tested were 298.2 K, 308.2 K, and 318.2 K. For the systems studied it was observed that the molar mass of the PEG did not sensitively affect the equilibrium curve position, and as the DE of MD increased, the concentration of polymers used to form the phases decreased. In some systems temperature minimally influenced the displacement of the equilibrium curve. © 2012 American Chemical Society.

De Carvalho E.A.,Federal Institute of South of Minas Gerais | Junqueira M.A.F.C.,Federal University of Itajubá | Moreira E.M.,Federal University of Itajubá | Carpinteiro O.A.S.,Federal University of Itajubá
Simulation Series | Year: 2015

This work presents an assessment about the metrics used by the well known load balancing algorithms for optimistic distributed simulations running over the Time Warp protocol. It also introduces a new metric for calculating the simulation load and implements a generic load balancing algorithm that is metric independent, allowing the metrics evaluation under the same execution environment, with the same simulation models, the same load imbalance factors and the same processes migration mechanism. The new metric proposed is based on the straggler messages factor, and the load balancing algorithm was designed to not benefiting anyone of the metrics. With the models evaluated, the proposal metric achieved a good performance, but the most efficient metric was that based on the variance among the processes Local Virtual Time. © 2015 Society for Modeling & Simulation International (SCS).

Vieira R.P.,Federal Institute of South of Minas Gerais | Ossig A.,Federal University of Rio Grande do Sul | Perez J.M.,Federal University of Rio Grande do Sul | Grassi V.G.,Federal University of Rio Grande do Sul | And 4 more authors.
Polymer Engineering and Science | Year: 2015

Atom transfer radical polymerization (ATRP) is a powerful technique for the controlled synthesis of polymers, and one of the most important ATRP characteristics is the possibility to produce functionalized polymers. 2,2,2-Tribromoethanol appears as a promising initiator for the ATRP process, because it allows the production of polymers with end hydroxyl groups, making it easy for copolymerization with biomonomers. This article explores, in experimental and computational level, the styrene ATRP using 2,2,2-tribromoethanol to understand how this new initiator behaves, and presents a powerful tool to predict the polymer properties for different operating conditions. Simulations and experimental results showed that polymers with high molecular weight and low PDI can be simultaneously obtained using 2,2,2-tribromoethanol as initiator. For all operational conditions, the reaction was fast and polydispersity values kept lower than 1.4, confirming the "living"/controlled characteristic. The polymers produced contain hydroxyl as functional group and in some operating conditions, PDI values of 1.1 was obtained, even at high monomer conversion. © 2015 Society of Plastics Engineers.

Alvarenga L.M.,Federal University of Minas Gerais | Alvarenga L.M.,Federal Institute of Minas Gerais | Dutra M.B.L.,Federal Institute of South of Minas Gerais | Alvarenga R.M.,Federal University of Minas Gerais | And 3 more authors.
CYTA - Journal of Food | Year: 2015

The purpose of this paper was to analyze the utilization of pulp and residues from pineapple processing as substrates for alcoholic fermentation. The fruits were cleaned, ground, and hydrolyzed with pectinase, cellulase, hemicellulase, and amylase. Pineapple pulp and whole fruit were analyzed to determine the amounts of amide, hemicellulose, total reducing sugars, °Brix, pectin, cellulose, and lignin present. Fermentation experiments were conducted with 0, 100, 200, and 300 g/kg of peel. Wines were analyzed for total or volatile acidity, total reducing sugars, and ethanol. The assays with the highest fermentation kinetic parameters were analyzed to determine the secondary compounds in the wine. The results showed that the enzymatic hydrolysis decreased the polysaccharide amount and increased reducing sugars and soluble solids, thereby improving the fermentation process, mainly in integral samples. In pineapple fermentation, 100 g/kg of peel addition did not influence the kinetic parameters and secondary compounds analyzed from the pineapple wines were within the legal limits. © 2014 Taylor & Francis.

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