Effect of Sample Solubilized Aliquot Volume and Concentration on Hydroperoxide Detection in PUFA-Rich Fish Oil

The objective of this work was to study the effect of sample oil concentration and volume on hydroperoxide determination in n-3 PUFA-rich sardine-anchovy oil. Oil samples were stored at??20°C, 6 d, air-free (T1); and 20°C, 2 d in air (T2). Significant differences between storage conditions were observed on hydroperoxide concentration. High reproducibility was obtained even in sample concentrations as low as 5 mg oil/mL of propan-1-ol. A high correlation was observed between the modified ferrous oxidation-xylenol orange method (FOX2) and AOAC peroxide value analysis methods, although FOX2 was faster, more sensitive, and precise when analyzing small hydroperoxide concentrations.     

Numerical analysis of the influence of the channel cross-section aspect ratio on the performance of a PEM fuel cell with serpentine flow field design

This work numerically investigates the influence of the channel cross-section aspect ratio (defined as the ratio height/width) on the performance of a PEM fuel cell with serpentine flow field (SFF) design. The local current densities, velocity distributions, liquid water concentration in the membrane, hydrogen and oxygen concentrations and temperature were analyzed in the PEM fuel cell for 10 different aspect ratios, varying between 0.07 and 15, to understand the channel cross-section aspect ratio effect. The area of the channel cross section (1.06 mm²) and the total effective reactive area of the PEM fuel cell (256 mm²) were maintained constant in all cases. The obtained results show that at low operating voltages the cell performance is independent of the channel cross-section aspect ratio. At high operating voltages, where the influence of mass transporting velocity is predominant, as the channel cross-section aspect ratio increases the cell performance is improved. The models with high aspect ratio show, in general, more uniform current distributions, with the higher maximum and minimum intensity values, temperature distributions with smaller gradients and a superior contain of water in the membrane, which allows to obtain a higher performance. From these models the 10/06 and 12/05 aspect ratio present the best combination of variables, as shown by their polarization curves.     

Synthesis and characterization of polyurethane cationomer/MMT hybrid composite

BACKGROUND: The development of polymeric nanocomposites incorporating intercalated or exfoliated layered silicate clays into the organic matrix has been substantially motivated by the significant improvements induced by the presence of the inorganic component. Moreover, understanding and controlling the dispersion of inorganic layers into segmented polyurethane matrices by means of ionic interactions, and exploiting these interactions to enhance physicomechanical behaviour, could be of great interest in the field of polymer nanocomposites. RESULTS: New cationic polyurethane elastomers were prepared starting from poly(butylene adipate)diol (M_n = 1000 g mol^?1), 4,4′‐diphenylmethane diisocyanate, 1,4‐butanediol and N‐methyldiethanolamine or N,N′‐β‐hydroxyethylpiperazine, used as potential quaternizable moieties. The characterization of the polymers was achieved using specific analyses employed for the macromolecular samples (Fourier transform infrared and ¹H NMR spectroscopy, thermogravimetric analysis (TGA), gel permeation chromatography). An extension of our research on polymers reinforced with organically modified montmorillonite (OM‐MMT) in order to prepare hybrid composites with improved properties was performed and the resulting materials were characterized using TGA, X‐ray diffraction, atomic force microscopy and scanning electron microscopy. Also, the mechanical properties of the cationic polyurethane/OM‐MMT composites were investigated in comparison with the pristine ionic/non‐ionic polymers and their composites containing non‐ionic polymer blended with OM‐MMT or ionic polymer and unmodified MMT. CONCLUSION: The insertion of the organically modified clay into the polymeric matrix gave an improvement of the mechanical properties of the polyurethane composites, especially the tensile strength and stiffness of the hybrid materials. Copyright © 2009 Society of Chemical Industry     

Adsorption of Zn(II) by crosslinked acrylic copolymers with amine functional groups

Adsorption of Zn(II) ions from diluted aqueous solutions by the acrylic copolymer based on ethylacrylate : acrylonitrile : divinylbenzene matrix with different crosslinking degrees and ethylenediamine and triethylenetetramine functional groups was investigated. Adsorption experiments were carried out by batch method. The effects of the pH, initial concentration of zinc, time of contact, and the crosslinking degree of the copolymers were studied. On the basis of Langmuir and Freundlich isotherms, the parameters that characterize the adsorption were determined. The maximum Zn(II) retention capacity value (500 mg g^?1) was obtained for the acrylic copolymer with 2% crosslinking degree and ethylenediamine, as functional groups. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 803–808, 2004     

An active star topology for improving fault confinement in CAN networks

The controller area network (CAN) is a field bus that is nowadays widespread in distributed embedded systems due to its electrical robustness, low price, and deterministic access delay. However, its use in safety-critical applications has been controversial due to dependability limitations, such as those arising from its bus topology. In particular, in a CAN bus, there are multiple components such that if any of them is faulty, a general failure of the communication system may happen. In this paper, we propose a design for an active star topology called CANcentrate. Our design solves the limitations indicated above by means of an active hub, which prevents error propagation from any of its ports to the others. Due to the specific characteristics of this hub, CANcentrate is fully compatible with existing CAN controllers. This paper compares bus and star topologies, analyzes related work, describes the CANcentrate basics, paying special attention to the mechanisms used for detecting faulty ports, and finally describes the implementation and test of a CANcentrate prototype.     

Enhancing the electrochemical Cr(VI) reduction in aqueous solution

In this study we present the cathodic Cr(VI) reduction using electrodissolution of iron anode. In batch experiments we tested four different cathodic materials; the best conditions were found when copper was used. It is observed that when more current is applied into the electrochemical cell faster reduction rates are achieved. Continuous experiments also reveal that Cr(VI) reduction could be done in a very efficient way. To confirm the experimental data, cyclic voltammetry was used and it was found that the cathodic Cr(VI) reduction is taking place.