PECVD deposition of device-quality intrinsic amorphous silicon at high growth rate

The combined influence of RF-power density (RFP) and silane flow-rate (Φ) on the deposition rate of plasma-enhanced chemical vapour deposition (PECVD) intrinsic amorphous silicon has been investigated. The correlation of the results obtained from the characterisation of the material with the silane deposition efficiency, as deduced from mass spectrometry, has led to an interpretation allowing to deposit intrinsic amorphous-silicon films having an optical gap of 1.87 eV and a photoconductive ratio (ratio of ambient-temperature conductivities under 1 sun AM1 and in dark) of 6 orders of magnitude at growth rates up to 10 Å/s, without any structural modification of the PECVD system used. Such results are considered of high relevance regarding industrial competitiveness.     

Fuel-cell energy generation system based on the series-capacitor boost converter

This work introduces the development of a power-electronics customizable energy system for their application on renewable energy generation based on proton-exchange membrane fuel cells. The customizable energy system aims to regulate the output voltage from a fuel cell, which has a relatively low amplitude and wide range of variation, to a fixed voltage to feed a grid-tie inverter. The customizable energy system proposed is based on a dc-dc converter for which different configurations (topologies) are available, such as the traditional single-phase boost or the (interleaved) multi-phase boost. The dc-dc converter of the energy system is based on the series-capacitor boost converter, a recently proposed converter that has a similar configuration to the interleaved boost converter. This article shows that the series-capacitor boost topology offers benefits in the proposed application. An experimental prototype was developed and tested in order to demonstrate the advantages of the system proposed.     

Modified paramagnetic beads in a microfluidic system for the determination of zearalenone in feedstuffs samples

In this work, we have developed and characterised a novel microfluidic immunoassay methodology for rapid and sensitive quantification of ZEA in feedstuffs samples. The detection of ZEA was carried out using a competitive direct immunoassay method based on the use of anti-ZEA monoclonal antibodies immobilized on magnetic microspheres 3-aminopropyl-modified manipulated for an external remobilize magnets. The ZEA in feedstuffs sample is allowed to compete with ZEA-horseradish peroxidase (HPR) conjugated for the immobilized anti-ZEA antibody. The HPR, in the presence of hydrogen peroxide (H₂O₂) catalyses the oxidation of 4-tert-butylcatechol (4-TBC) whose back electrochemical reduction was detected on gold electrode at 0.0 V. The calculated detection limits for electrochemical detection and ELISA procedure were 0.41 and 2.56 μg kg⁻¹ respectively, the intra and inter-assay coefficients of variation were below 6.5% and the total assay time was 30 min. The microfluidic immunosensor showed higher sensitivity and lower detection limits than the standard ELISA method, which shows potential for detecting ZEA in foods and feeds diagnosis.     

Performance model to assist solar thermal power plant siting in northern Chile based on backup fuel consumption

In response to environmental awareness, Chile introduced sustainability goals in its electricity law. Power producers must deliver 5% from renewable sources by 2010 and 10% by 2024. The Chilean desert has a large available surface with one of the highest radiation levels and clearest skies in the World. These factors imply that solar power is an option for this task. However, a commercial plant requires a fossil fuel system to backup the sunlight intermittency. The authors developed a thermodynamical model to estimate the backup fraction needed in a 100 MW hybrid -solar-fossil- parabolic trough power plant. This paper presents the model aiming to predicting the performance and exploring its usefulness in assisting site selection among four locations. Since solar radiation data are only available in a monthly average, we introduced two approaches to feed the model. One data set provided an average month with identical days throughout and the other one considered an artificial month of different daylight profiles on an hourly basis for the same monthly average. We recommend a best plant location based on minimum fossil fuel backup, contributing to optimal siting from the energy perspective. Utilities will refine their policy goals more closely when a precise solar energy data set becomes available.     

Optimisation of Dosidicus gigas mantle proteolysis at industrial scale

The use of enzymatic preparations in food processing is very old and has a number of advantages such as the high specificity of the enzymes, which avoids unwanted products, and their use at moderate temperatures, hence reducing alterations in the most labile components of food. The aim of this work is to supply information that would allow the use of Dosidicus gigas, as a source of raw material, in the preparation of diverse frozen products. With this purpose, we studied the effect of seven proteases: collagenase F, collagenase H, collagenase/dispase, papain, pronase, subtilisin and trypsin, and centered on the rheological and sensory evaluation of the changes which occurred in the texture of D. gigas, in order to establish the optimal conditions for the use of each enzyme.     

Performance of Balanced Two-Stage Empirical Predictors of Realized Cluster Latent Values from Finite Populations: A Simulation Study

Predictors of random effects are usually based on the popular mixed effects (ME) model developed under the assumption that the sample is obtained from a conceptual infinite population; such predictors are employed even when the actual population is finite. Two alternatives that incorporate the finite nature of the population are obtained from the superpopulation model proposed by Scott and Smith (1969. Estimation in multi-stage surveys. J. Amer. Statist. Assoc. 64, 830-840) or from the finite population mixed model recently proposed by Stanek and Singer (2004. Predicting random effects from finite population clustered samples with response error. J. Amer. Statist. Assoc. 99, 1119-1130). Predictors derived under the latter model with the additional assumptions that all variance components are known and that within-cluster variances are equal have smaller mean squared error (MSE) than the competitors based on either the ME or Scott and Smith's models. As population variances are rarely known, we propose method of moment estimators to obtain empirical predictors and conduct a simulation study to evaluate their performance. The results suggest that the finite population mixed model empirical predictor is more stable than its competitors since, in terms of MSE, it is either the best or the second best and when second best, its performance lies within acceptable limits. When both cluster and unit intra-class correlation coefficients are very high (e.g., 0.95 or more), the performance of the empirical predictors derived under the three models is similar.     

Thinking about the future moves attention to the right.

Previous studies have shown that past and future temporal concepts are spatially represented (past being located to the left and future to the right in a mental time line). This study aims at further investigating the nature of this space–time conceptual metaphor, by testing whether the temporal reference of words orient spatial attention or rather prime a congruent left/right response. A modified version of the spatial cuing paradigm was used in which a word’s temporal reference must be kept in working memory whilst participants carry out a spatial localization (Experiment 1) or a direction discrimination, spatial Stroop task (Experiment 2). The results showed that the mere activation of the past or future concepts both oriented attention and primed motor responses to left or right space, respectively, and these effects were independent. Moreover, in spite of the fact that such time-reference cues were nonpredictive, the use of a short and a long stimulus onset asynchrony in Experiment 3 showed that these cues modulated spatial attention as typical central cues like arrows do, suggesting a common mechanism for these two types of cuing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mesenchymal Stem Cells Preserve Working Memory in the 3xTg-AD Mouse Model of Alzheimer’s Disease

The transplantation of stem cells may have a therapeutic effect on the pathogenesis and progression of neurodegenerative disorders. In the present study, we transplanted human mesenchymal stem cells (MSCs) into the lateral ventricle of a triple transgenic mouse model of Alzheimer´s disease (3xTg-AD) at the age of eight months. We evaluated spatial reference and working memory after MSC treatment and the possible underlying mechanisms, such as the influence of transplanted MSCs on neurogenesis in the subventricular zone (SVZ) and the expression levels of a 56 kDa oligomer of amyloid β (Aβ*56), glutamine synthetase (GS) and glutamate transporters (Glutamate aspartate transporter (GLAST) and Glutamate transporter-1 (GLT-1)) in the entorhinal and prefrontal cortices and the hippocampus. At 14 months of age we observed the preservation of working memory in MSC-treated 3xTg-AD mice, suggesting that such preservation might be due to the protective effect of MSCs on GS levels and the considerable downregulation of Aβ*56 levels in the entorhinal cortex. These changes were observed six months after transplantation, accompanied by clusters of proliferating cells in the SVZ. Since the grafted cells did not survive for the whole experimental period, it is likely that the observed effects could have been transiently more pronounced at earlier time points than at six months after cell application.     

Thermal stability of some commercial synthetic antioxidants

Synthetic antioxidants are widely applied substances in human food and in animal feed industries. These products, which are mainly derived from phenolic structures, were developed to avoid or retard the oxidative rancidity of fats and oils when added either to raw material or to end-products. Synthetic antioxidants such as butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), tertiary butylhydroxyquinone (TBHQ), and ethoxyquin (EQ) are frequently applied during the cooking of the by-products (viscera, blood, and feathers) in the poultry feed industry. However, results in terms of oxidative prevention are unequal and usually modest. Because information about the thermal stability of synthetic antioxidants is scarce, we developed a laboratory model that simulates the cooking of poultry by-products to study the effectiveness of BHT, BHA, TBHQ, and EQ. The antioxidants were thermally treated at 100–200°C, over 1 or 2 h. The effectiveness of each antioxidant after the thermal treatment was assessed with the Rancimat test by measuring the modification of the induction period for the oxidation of sardine oil and comparing it to the oxidation kinetics of the oil without added antioxidants. Within our experimental conditions, all antioxidants assayed showed different degrees of thermal instability. BHT and TBHQ were effective as antioxidants at temperatures up to 175°C, exhibiting only 25 to 30% inactivation. However, BHA and EQ were inactivated by 70 and 60%, respectively, at 150°C. Heating time (1 and 2 h) at a given temperature did not significantly modify the behavior of the antioxidants assayed. EQ is the most frequently applied antioxidant to prevent oxidative rancidity in the cooking of poultry by-products. However, according to our results, EQ and BHA, which is another antioxidant frequently used by the poultry industry, are less suitable