Crosslinking of poly(vinyl acetate) nanolatices by gamma and UV radiation

Poly(vinyl acetate) PVAc, in nanolatices with 10% polymer content, prepared by microemulsion polymerization was crosslinked by gamma and UV radiation. PVAc colloidal nanoparticles (average diameter, Dp = 58 nm) had M_w = 562,000 g/mol and about 95% conversions. PVAc nanolatices irradiated by gamma rays (1–13 kGy) at room temperature without crosslinking agent and by UV light (30–300 s exposure times) in the presence of divinylbenzene and allyl methacrylate showed crosslinking of up to 96% (high gel content), Dp < 100 nm and did not degrade as shown by FTIR spectroscopy. DSC and TGA characterization of irradiated PVAc samples indicated that T_g temperatures increased from 28°C for PVAc to 42°C and 39°C for UV and gamma rays crosslinked PVAc, respectively, whereas 10% weight losses occurred at 261°C for uncrosslinked PVAc and at 320 and 313°C for UV and gamma rays crosslinked PVAc. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Systematic review: an analysis model for measuring the coopetitive performance in horizontal cooperation networks mapping the critical success factors and their variables

Several strategies have been developed for micro-enterprises and small enterprises in relation to their competitiveness enhancement. In recent years, one of the most widespread strategies has been the formation of horizontal cooperation networks (HCNs), based on the evolutionary development of coopetition. This study aimed to support and validates an analysis model developed by Petter (Modelo para análise da competitividade de redes de cooperação horizontais de empresas, Universidade Tecnológica Federal do Paraná, UTFPR, Ponta Grossa, 2012), in order to point out which are critical success factors (CSF), and their variables which influence the coopetition performance of a HCN under aspects of cooperation and competitiveness. A systematic review supported by Sampaio and Mancini (Revista Brasileira de Fisioterapia 11(1):83–89, 2007) was used to measure the status quo of published journals related to the subject, among several databases. A large informational gap was found concerning the development of methods and tools, as well as subsidies. Regarding the raise of publications found inside the scope, 18 CSF, 52 variables were mapped correlating them with 144 indicators, therefore, supporting and validating the proposed model of analysis.     

Transformation of Mytella falcata residual shell into CaAl/LDH adsorbent: Removal of methyl orange and methylene blue dyes

This study analyzed the viability of using malacoculture residue (Mytella falcata) to produce layered double hydroxides (LDHs) and for its subsequent use as an adsorbent. The CaAl/LDH-RE material was produced with calcium oxide from the residue and the CaAl/LDH-AP was produced with a commercial reagent. Both were used to remove methyl orange (MO) and methylene blue (MB) dyes. The CaAl/LDH-RE presented a surface area of 28.54 m² g⁻¹, being 65.62% larger than the CaAl/LDH-AP material (17.23 m² g⁻¹). The adsorbents showed mesopores distributed on a surface formed by plates in the form of hexagonal sheets arranged in an overlapping manner. The dosage of 0.05 g L⁻¹ obtained the removal of 95% and 97% for MO, while for MB it was 94% and 93% using the adsorbents LDH/CaAl-AP and LDH/CaAl-RE, respectively. The system reached equilibrium at 90 min for MO and 120 min for MB. The pseudo-second order model well represented the kinetic data reaching 11.36 mg g⁻¹ (CaAl/LDH-RE) and 8.42 mg g⁻¹ (CaAl/LDH-AP) for MO, and 4.47 mg g⁻¹ (CaAl/LDH-RE) and 4.14 mg g⁻¹ (CaAl/LDH-AP) for MB. The Freundlich model better represented the isothermal data, where the temperature exerted little influence. Adsorbents showed similar removal percentages in real and synthetic matrices. The LDH/CaAl-RE can be applied in up to 3 cycles, maintaining its adsorption capacity. These results corroborate the use of MFW to produce CaAl/LDH-RE, which can be used for the efficient removal of organic pollutants in an aqueous solution.     

Effect of drying kinetics on main bioactive compounds and antioxidant activity of acerola (Malpighia emarginata D.C.) residue

This study investigates the drying kinetics of residue of acerola, in a fixed‐bed dryer, analysing the effect of the process variables on the antioxidant properties of the residue. A complete factorial design 3² has been performed, where the independent variables studied were as follows: air velocity (0.5, 1.0 and 1.5 m s^?1) and air‐drying temperature (40, 50 and 60 °C). The bioactive compounds studied were L‐ascorbic acid, total phenolic, total flavonoids and antioxidant activity (expressed as IC₅₀) was determined using free radical DPPH^?. Both independent variables studied have shown to be statistically significant. The content of ascorbic acid was the highest at 60 °C and 1.0 m s^?1 (126.2 ± 0.004 mg 100 g^?1) while for the fresh residue 16.12 ± 0.003 mg 100 g^?1, whereas the total phenolic showed the highest content at 50 °C and 1.5 m s^?1 (46.2 ± 0.003 mg gallic acid.100 g^?1) while for the fresh residue 12.59 ± 0.001 mg gallic acid.100 g^?1. The drying conditions play an important role in determining the final quality of the product mainly in terms of antioxidant activity.     

Mathematical model for the bulk polymerization of styrene using the symmetrical cyclic trifunctional initiator diethyl ketone triperoxide. I. Chemical initiation by sequential decomposition

In this study, we experimentally and theoretically investigated the use of the symmetrical cyclic trifunctional initiator diethyl ketone triperoxide (DEKTP) in the bulk polymerization of styrene. The experimental study consisted of a series of isothermal batch polymerizations at different temperatures (120 and 130°C) with different initiator concentrations (0.005, 0.01, and 0.02 mol/L). A mathematical model was developed to predict the evolution of the reacting chemical species and the produced molecular weight distributions. The kinetic model included chemical and thermal initiation, propagation, transfer to the monomer, termination by combination, and reinitiation reactions. The simulation results predict the concentration of diradicals, monoradicals, and polymeric chains, characterized by the number of undecomposed peroxide groups. The experimental results showed that at reaction temperatures of 120–130°C, initiation by DEKTP produced an increase in the polymerization rates (R_p's) and average molecular weights, depending on the initiator concentration, due to sequential decomposition. The mathematical model was adjusted and validated with the experimental data. The theoretical predictions were in very good agreement with the experimental results. Also, an optimum initiator concentration was observed that achieved high R_p's and high molecular weights simultaneously. For polymerization temperatures of 120–130°C, the optimum concentration was 0.01 mol/L. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A Lamarckian Approach for Neural Network Training

In Nature, living beings improve their adaptation to surrounding environments by means of two main orthogonal processes: evolution and lifetime learning. Within the Artificial Intelligence arena, both mechanisms inspired the development of non-orthodox problem solving tools, namely: Genetic and Evolutionary Algorithms (GEAs) and Artificial Neural Networks (ANNs). In the past, several gradient-based methods have been developed for ANN training, with considerable success. However, in some situations, these may lead to local minima in the error surface. Under this scenario, the combination of evolution and learning techniques may induce better results, desirably reaching global optima. Comparative tests that were carried out with classification and regression tasks, attest this claim. This revised version was published online in June 2006 with corrections to the Cover Date.     

Multiscale carbon fibre–reinforced polymer (CFRP) composites containing carbon nanotubes with tailored interfaces

Pristine and functionalized multiwalled carbon nanotubes (MWCNTs) with tailored interfaces were efficiently dispersed in an epoxy matrix using a three‐roll mill and further reinforced with carbon fibres. 1.3‐Dipolar cycloaddition of azomethine ylides was used for the chemical modification of MWCNTs by a solvent‐free approach. The influence of different loadings and types of MWCNTs on the final properties of the epoxy matrix was studied. Moreover, the most promising formulations were selected for manufacturing of prepreg sheets. The transversal tensile properties and the interlaminar fracture toughness under mode I loading (G_IC) of multiscale carbon fibre–reinforced polymer (CFRP) composites were characterized. The results point out that it is not straightforward to transfer the remarkable intrinsic properties of MWCNTs to the composite level, although an overall positive trend was found. Double cantilever beam experiments showed that G_IC of CFRP composites was improved 44% at ultralow content of functionalized MWCNTs (0.043 wt%).     

The satisfaction of healthcare consumers: analysis and comparison of different methodologies

Patient satisfaction and the factors influencing it are becoming a significant concern for health organizations and patients around the world. This study evaluates patients' satisfaction regarding the inpatient service while tackling the existent literature gap on which method best suits the patient satisfaction analysis. We perform a methodological comparison (using factor analysis, structural equation modeling, ordinal logistic regression (OLR), and multicriteria satisfaction analysis (MUSA)) to contrast the different results from different methodologies. After implementing the methods, we concluded that, out of the eleven analyzed factors, seven influence satisfaction: accommodations, auxiliary staff, exams and treatments, medical staff, food quality, volunteering staff, and obtained information. Three were consistent for structural equation modeling and OLR: accommodations, exams and treatments, and health services. The outputs of MUSA were not compatible with the other methods. However, we concluded that the MUSA method is a good option when dealing with patient satisfaction studies since it provides insightful outputs that facilitate managers' decision making and improve the provider's performance efficiency.