The simultaneous separation and quantification of two casein peptides (IPP, VPP) presenting potent inhibitory activity of angiotensin-converting-enzyme (ACE) and casein in fermented milks was developed. Gradient elution was carried out at a flow-rate of 1 mL/min, using a mixture of two solvents. Solvent A was 0.1% TFA in water and solvent B was acetonitrile-water-trifluoracetic acid 95:5:0.1. The effluent was monitored by UV detector at 214 nm. Calibration curves were constructed in the interval of 0.01-1.0 mg/mL for VPP, 0.005-1.0 mg/mL for IPP, and 0.05-3.0 mg/mL for casein. R 2 invariably exceeded 0.999. The detection limits were 0.004 for VPP, 0.002 mg/mL for IPP, and 0.02 mg/mL for casein. Repeatability of the method was evaluated by six consecutive injections of two standard solutions containing VPP, IPP, and casein. The RSD values for concentration were all below 5.08%. Recovery studies were carried out to determine the accuracy of the method. Recoveries ranged between 88 and 98.2%. The methodology was applied, not only, for the monitorization of VPP, IPP, and casein in commercial fermented milks labeled as presenting anti hypertensive properties, but also, in milk with different degrees of fermentation by L Helveticus, and in other commercial functional fermented milks, such as, those presenting cholesterol lowering properties.

A homogeneous black coloured glass was obtained by melting the bottom ashes produced by a municipal solid waste incinerator at 1300°C for 2 h without any chemical additives. Based on thermal analysis data glass-ceramics were produced by heat treating the glass, doped with additional TiO2 as a nucleating agent, at temperatures between 870 and 1000°C. The crystalline phases precipitated during the heat treatments were identified by powder XRD and the microstructures were examined using SEM. After a heat treatment at 900°C for 2 h, the glass was converted into a fine grained glass-ceramic with uniform microstructure. The major crystalline phases precipitated in the glass-ceramics were augite (Ca(Mg,Fe)Si2O6), gehlenite (Ca2Al2SiO7) and clinopyroxene (Ca(Ti,Mg,Al)(Si,Al)2O6). Preliminary evaluation of the mechanical and chemical properties of the bottom ash glasses and glass-ceramics suggest that they have potential to compete with existing natural and commercial outdoor cladding materials.

The devices analyzed in this work present an S-shape J-V characteristic when illuminated. By changing the light flux a non linear dependence of the photocurrent with illumination is observed. Thus a low intensity light beam can be used to probe the local illumination conditions, since a relationship exists between the probe beam photocurrent and the steady state illumination. Numerical simulation studies showed that the origin of this S-shape lies in a reduced electric field across the intrinsic region, which causes an increase in the recombination losses. Based on this, we present a model for the device consisting of a modulated barrier recombination junction in addition to the p-i-n junction. The simulated results are in good agreement with the experimental data. Using the presented model a good estimative of the LSP signal under different illumination conditions can be obtained, thus simplifying the development of applications using the LSP as an image sensor, with advantages over the existing imaging systems in the large area sensor fields with the low cost associated to the amorphous silicon technology. © 2007 Materials Research Society.

The isoconversional methods (Friedman (FR), Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS)) were applied for evaluating the dependencies of the activation energy (E) on the mass loss (Δm) corresponding to the non-isothermal decomposition of two Zn acetate-based gel precursors for ZnO thin films whose preparation differs by the drying temperature of the liquid sol-precursor (125°C for sample A, and 150°C for sample B). Although both investigated samples exhibit similar decomposition steps, strong differences between E vs. Δm curves as well as among the characteristic parameters of the decomposition steps, directly evaluated from TG, DTG and DTA curves, were put in evidence. © 2007 Springer Science+Business Media LLC.

This study describes the characterisation of whey protein hydrolysates obtained from tryptic hydrolysis to assess their application as ingredients with angiotensin-converting-enzyme (ACE) inhibitory action. The levels of a-lactalbumin (alpha-la) and P-lactoglobulin (beta-lg) remaining after hydrolysis were quantified. Peptides were separated by RP-HPLC, and Ala-Leu-Pro-Met-His-Ile-Arg (ALPMHIR), the most potent beta-lg-derived ACE-inhibitory peptide was monitored. A correlation curve was established for the production of this peptide as a function of hydrolysis time. Heat-induced gelation of hydrolysates was studied by small-deformation rheology. The gelation times and the strength of the final gels were highly dependent on the degree of hydrolysis. Smaller peptides liberated by hydrolysis contributed to the inability of whey protein hydrolysates to gel. (c) 2006 Elsevier Ltd. All rights reserved.

Cross-linked polyethylene (XLPE) is currently widely used as an insulating material for power cables due to its good physical properties, however when in use it undergoes an electrical ageing process. Its ability to trap electric charge can give rise to space charge accumulation in the bulk of the polymer and produce localised electric stresses that can lead to cable failure, since the electric field will be increased above the design stress in some regions favouring the initiation of degradation there. In this work the PEA (pulsed electro-acoustic) method was used to compare the charge dynamics in three samples (XLPE cable peelings) aged in different ways (electrothermally in the laboratory, field aged in service and thermally aged in the laboratory). Very different transient behavior was found depending upon the ageing history. This is related to differences in the migration of chemical species in the insulation layer, which are known to act as charge traps. All materials showed heterocharge peaks when the space charge reached stability, the magnitude of which seems to be related to the severity of the ageing. (c) 2007 Elsevier B.V. All rights reserved.

Reactive oxygen species (ROS), when in excess, are among the most deleterious species an organism can deal with. The physiological effects of ROS include amino acid chain cleavage, DNA degradation and lipid oxidation, among others. They can be formed in the cytoplasm in a variety of ways, including autooxidation reactions (FMN- and FAD-containing enzymes) and Fenton reactions as a result of the cytoplasmatic pool of iron ions. The superoxide anion (021, despite its short half-life in solution, is particularly pernicious as it can form other reactive ROS (such as the strong oxidant peroxynitrite) or oxidize and/or reduce cellular components. For strict anaerobic or microaerophilic bacteria it is of particular importance to be able to dispose of ROS in a controlled manner, especially if these organisms are temporarily exposed to air. This review aims to describe the structural characteristics of superoxide reductases (SORs) and mechanistic aspects of biological superoxide anion reduction. SORs can be considered the main class of enzymes behind the oxygen detoxification pathway of anaerobic and microaerophilic bacteria. The geometry of the active site (three classes have been described), the possible electron donors in vivo and the current hypothesis for the catalytic mechanism will be discussed. Some phylogenetic considerations are presented, regarding the primary structure of SORs currently available in genome databases. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).