Real-time and conventional polymerase chain reaction systems based on the metallo-carboxypeptidase inhibitor gene for specific detection and quantification of potato and tomato in processed food

In this paper, a method for the specific detection and quantification of potato and tomato DNA in food samples with the use of conventional and real-time polymerase chain reaction (PCR) is described. This method is adequate for use in food quality routine assays involving highly processed samples for which very tiny amounts of DNA are expected. Detection was achieved by amplifying a region of the metallo-carboxypeptidase inhibitor gene from either the potato (PCI) or the tomato (MCPI) and by using specific primers complementary to the propeptide regions of these inhibitors, which were found to differ for the potato and tomato proproteins. Conventional and real-time PCR systems were based on the same potato- or tomato-specific primer pairs, and quantification was carried out with a TaqMan chemistry-based probe. The methods developed proved to be very specific and sensitive and highly reliable for the identification and quantification of DNA from both plant species. In addition, the construction of plasmids pPAT and pTOM, suitable for use as external calibration standards for the elaboration of comparative amplification profiles, is reported. Limits of detection and quantification with the use of these plasmid standards are given. Specificity and copy number conservation among different cultivars were analyzed, and the reliability of these systems was tested through their application to the analysis of commercial food samples including potato and/or tomato as components.     

Electrochemical performance of low temperature PEMFC with surface tailored carbon nanofibers as catalyst support

The present work is focused on the synthesis of new catalysts of platinum supported on carbon nanofibers and their use in PEMFC electrodes. Carbon nanofibers (CNF) and functionalized carbon nanofibers (CNF-f), synthesized via the thermocatalytic decomposition of CH₄, were characterized, in the presence and the absence of deposited Pt, by porosimetric, SEM, TPD, and HRTEM analyses, and compared to commercial Vulcan^® XC72R carbon black (CB). CNF and CNF-f show similar BET surface areas, but smaller than that of CB, which have a large quantity of micropores. On the contrary, the microporosity in CNF and CNF-f was negligible, and the mesopores were the dominant pore structure.A single cell characterization of three catalysts Pt/CNF, Pt/CNF-f and Pt/CB was carried out, measuring the relevant kinetic parameters. The power density given by the Pt/CNF catalyst in the cathode catalyst layer was 1.5 times higher than that given by the Pt/CB catalyst at 0.600 V. It is shown when using functionalized carbon nanofibers in the anode catalyst layer, that functionalization by chemically modifying the surface of the nanofibers significantly affects the PEMFC performance.     

Chemoenzymatic synthesis and antimicrobial and haemolytic activities of amphiphilic bis(phenylacetylarginine) derivatives

Novel bis(N(alpha)-phenylacetyl-L-arginine)-alpha,omega-alkanediamide dihydrochloride (bis(PhAcArg)) derivatives with antimicrobial activity were designed and synthesised by a chemoenzymatic strategy. The new structures consist of two N(alpha)-phenylacetyl-L-arginine moieties connected by an alkanediamine spacer chain of 6, 8, 10, 12, and 14 methylene units through amide bonds. The key step in the chemoenzymatic strategy is the double aminolysis of the N(alpha)-phenylacetyl-L-arginine methyl ester by the corresponding alpha,omega-alkanediamine catalyzed by papain in ethanolic media. The compounds synthesised were tested as antimicrobials against 15 bacterial and 8 fungal species. The antimicrobial activity and selectivity depend strongly on the spacer chain length. The bis(PhAcArg) derivative with the spacer chain of 12 methylene groups gave the lowest MIC values against Gram-positive bacteria, whereas that with 14 methylene units was the best against Gram-negative bacteria. Interestingly, these novel compounds showed enhanced antibacterial activity relative to the lead compound, bis(N(alpha)-caproyl-L-arginine)-1,3-propanediamide dihydrochloride (C(3)(CA)(2)), and moderate antifungal activity. Moreover, tests of haemolytic activity toward human erythrocytes revealed that haemolysis increases with spacer chain length. Importantly, the compounds were classified as not irritating to eyes, with the exception of the compound with the spacer chain of 14 methylene groups, which was a slight eye irritant.     

Continuous enzymatic synthesis of Z-kyotorphin amide in an enzyme-immobilized fixed-bed reactor

α-Chymotrypsin immobilized on natural and inexpensive supports such as diatomaceous earth was used as catalyst for Z-Tyr-Arg-NH₂ (Z-kyotorphin amide) synthesis. In order to obtain the optimal reaction conditions, a 2² factorial experimental design was used. The factors considered were cosolvent (dimethylformamide) concentration and temperature; optimal product yield was achieved at 40% (v/v) dimethylformamide and 25°C. A sequential kinetic model was considered which generally gave good agreement between experimental and theoretical data for continuous synthesis of Z-kyotorphin amide in a packed-bed immobilized reactor system. The activation energy for the synthesis was determined to be 48.0 ± 2.3 kJ mol^?1.     

Influence of electrode thickness on the performance of composite electrodes for SOFC

Measurements on half-cells consisting of yttria-stabilized zirconia (YSZ) electrolyte pellets and slurry-coated cathodes of different thickness were performed in order to determine the active area for oxygen reduction in composite cathodes of lanthanum strontium manganite (LSM) and YSZ. Electrochemical impedance spectroscopy was used to evaluate the main electrochemical parameters of the cathodic process. The temperature range was between 500 and 900 °C. The experimental results show a remarkable effect of the electrode thickness on the overall reaction rate in all the temperature range. At 750 °C a change in the controlling regime of the oxygen reduction is detectable and has been ascribed to the transition of the rate-determining step from a charge transfer to a mass transfer of the ionic species. A simplified theoretical model of the cathode that accounts for charge transfer and ionic conduction was developed to give insight into the experimental results. The model simulations compared satisfactorily with the experimental data confirming that the behaviour experimentally observed could be approached with the proposed model.     

A Methodology to Model Water Demand based on the Identification of Homogenous Client Segments. Application to the City of Barcelona

Water management has become a vital concern for both water supply companies and public administrations due to the importance of water for life and current scarcity in many areas. Studies exist that attempt to explain which factors influence water demand. In general, these studies are based on a small sample of consumers and they predict domestic water consumption using ordinary least squares regression models with a small number of socioeconomic variables as predictors, usually: price, population, population density, age, and nationality. We have followed a different approach in two ways; one, in the scope of the study: we have included in the study all consumers of the Barcelona area and as many socioeconomic variables as possible (all the available data from official statistics institutions); and also in the methodology: first, we have segmented clients into homogeneous socioeconomic groups that, as we show later in the Barcelona case, also have homogeneous water consumption habits. This allows for a better understanding of water consumption behaviours and also for better predictions through modeling water consumption in each segment. This is so because the segments’ inner variability is smaller than the general one; thus, the models have a smaller residual variance and allow for more accurate forecasts of water consumption. The methodology was applied to the Barcelona metropolitan area, where it was possible to construct a database including both water consumption and socioeconomic information with more than one million observations. Data quality was a primary concern, and thus a careful exploratory data analysis procedure led to a careful treatment of missing observations and to the detection and correction or removal of anomalies. This has resulted in a stable division of the one million water consumers into 6 homogeneous groups and models for each of the groups. Although the methodology has been developed and applied to the Barcelona area, it is general and thus can be applied to any other region or metropolitan area.     

Structural properties of microcrystalline Si films prepared by hot-wire/catalytic chemical vapor deposition under conditions close to the transition from amorphous to microcrystalline growth

The structural properties of microcrystalline Si films prepared by hot-wire/catalytic chemical vapor deposition, with various dilution ratios of silane in hydrogen, were investigated as regards to the role of hydrogen. A large surface roughness correlated with a low crystalline nuclei density was observed for microcrystalline Si films deposited near the transition from amorphous to microcrystalline growth. Investigations of hydrogen-related properties suggest the presence of molecular hydrogen in these films. We tentatively propose that the diffusion of atomic hydrogen into the subsurface layer of growing films, which leads to the relaxation of amorphous Si network and to the generation of molecular hydrogen, plays an important role for determining the film properties, besides top surface reactions.