Model of a synthetic wind speed time series generator

Wind energy has assumed a great relevance in the operation and planning of today's power systems due to the exponential increase of installations in the last 10 years. For this reason, many performed studies have looked at suitable representations of wind generation for power system analysis. One of the main elements to consider for this purpose is the model of the wind speed that is usually required as input. Wind speed measurements may represent a solution for this problem, but, for techniques such as sequential Monte Carlo simulation, they have to be long enough in order to describe a wide range of possible wind conditions. If these information are not available, synthetic wind speed time series may be a useful tool as well, but their generator must preserve statistical and stochastic features of the phenomenon. This paper deals with this issue: a generator for synthetic wind speed time series is described and some statistical issues (seasonal characteristics, autocorrelation functions, average values and distribution functions) are used for verification. The output of the model has been designed as input for sequential Monte Carlo simulation; however, it is expected that it can be used for other similar studies on wind generation. Copyright © 2007 John Wiley & Sons, Ltd.     

Fabrication and electrical performance of high-density arrays of nanometric silicon tips

We propose and demonstrate a simple and low cost process for the fabrication of large area arrays of nanometric silicon tips, for use as Field Emission Devices (FEDs). The process combines Interference Lithography (IL) with isotropic Reactive Ion Etching (RIE). Si tips with typical curvature radius of 20 nm and height of 900 nm were recorded with a periodicity of 1 μm (density of 10⁶ tips/mm²) covering a Silicon wafer of 2 in. The measurement of the electrical performance of the arrays demonstrates the feasibility of the association of these two techniques for recording Field Emission Tips.     

Evaluation of nutritional characteristics and bioactive compounds of soursop-yoghurt and soursop-frozen dessert

Food Science and Biotechnology - The nutritional quality, sensory attributes, polyphenols and acetogenins content in yoghurt and frozen dessert formulated with soursop pulp were investigated. The...     

Assessment of soil and groundwater impacts by treated urban wastewater reuse. A case study: application in a golf course (Girona, Spain)

Starting in July 2000, treated wastewater of urban origin has been used for the "Serres de Pals" golf course irrigation (Girona, Spain). To evaluate if the soil and the aquifer underneath are affected by the utilization of this type of water, samples have been taken along a period of several months from the wastewater treatment plant, the stabilization lagoon, groundwater and soil profiles. Analyses have been performed for total coliforms and aerobic bacteria, soil water pressure and soil water content as well as chemical analyses of the irrigation water, aquifer and water of the vadose zone. Soil profiles taken at several times during the study indicate the absence of coliforms except for a short period during summer. In the vadose zone an increase of more than 1000 mg kg(-1) of NaO(2) in the top 60 cm of soil was observed while Cl(-) concentration in the aquifer reached up to 1200 mg l(-1) ten months after starting the irrigation.     

Simultaneous Determination of Multiclass Pesticides and Antibiotics in Honey Samples Based on Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry

A simple, fast, and efficient method was developed for simultaneous determination of 79 pesticides and 13 antibiotics compounds of different chemical classes of pesticides and antibiotics in honey samples by ultra-high performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS). The sample preparation procedure includes homogenization with McIlvaine buffer 0.1 mol L^?1 (pH 4), followed by extraction with acetonitrile and cleanup with florisil, using dispersive solid phase extraction (d-SPE). The proposed method was validated with good results, such as linearity (r ²?>?0.9901), normality, and independence of the evaluated data, as well as recoveries between 70 and 120 % with relative standard deviation (RSD) <20 % for most of the compounds spiked from 0.1 to 200 μg kg^?1. The experimental method limits of detection and quantification were from 0.03 to 1.51 μg kg^?1 and from 0.1 to 5 μg kg^?1, respectively, for the pesticides. For the antibiotics, the decision limits (0.1 to 2 μg g^?1) and the detection capacity (0.12 to 2.81 μg g^?1) were below the maximum residue limits (MRLs) established for honey by the Brazilian and European legislation. The method was successfully applied to real samples from different botanical and geographic origins. From them, 44 % presented residues from 0.12 to 10 μg kg^?1 of one or more analytes. The proposed method combines the advantages of a quick sample preparation step with the selectivity and sensitivity of the UHPLC-MS/MS and proved to be suitable for routine analyses.     

Sintering of waste of superalloy casting investment shells as a fine aggregate for refractory tiles

Powders obtained by milling ceramics shells, already used as investment material in casting processes, were sintered to investigate their possible re-use in the production of ceramic refractories. The sintering behaviour of these powders, consisting essentially of silica and mullite, were analysed both in a heating run by conventional contact dilatometry and in an isothermal process via optical dilatometry. The mechanical properties of sintered composites formed with a matrix of fine powders and an inert coarse phase of the same material are evaluated and discussed in view of possible use in the production of refractory tiles.     

Autism and digital learning environments: Processes of interaction and mediation

Using a socio-historical perspective to explain social interaction and taking advantage of information and communication technologies (ICTs) currently available for creating digital learning environments (DLEs), this paper seeks to redress the absence of empirical data concerning technology-aided social interaction between autistic individuals. In terms of social interaction, autism can be likened to the negative of a photograph and it is currently one of the most disturbing and challenging syndromes. This study puts forward another viewpoint on the processes of interaction and mediation established in digital environments. Based on a 3-year multi-case study, which observed groups of autistic individuals in DLE-aided interaction activities, it identifies relevant technological categories that have an important contribution to make in the areas involved (Psychology, Education and Computer Science) in the development of a digital learning environment that takes the results achieved into account.     

Calretinin. A selective marker of normal and neoplastic mesothelial cells in serous effusions

OBJECTIVE: To document that a polyclonal antiserum to calretinin, a 29-kd calcium-binding protein, consistently decorates normal and tumor mesothelial cells in cytologic preparations. STUDY DESIGN: Thirty-three archival cytologic specimens from eight patients with histologically confirmed malignant mesothelioma and 13 from patients with metastatic serous effusions were destained and then immunostained with anticalretinin antiserum. For investigation of cell suspensions, four pleural fluids were incubated with anticalretinin antiserum. After cytocentrifugation the specimens were stained in accordance with the alkaline phosphatase anti-alkaline phosphatase (APAAP) method. For electron microscopic examination the cell suspensions were then incubated with gold-labeled antirabbit antibody. RESULTS: The diagnostic sensitivity of this new immunocytochemical approach reached 100% for the eight malignant mesotheliomas investigated. Only 3 of the 13 adenocarcinomas metastatic to the serous membranes included in this study were weakly reactive, accounting for 81% specificity. Binding of anticalretinin antiserum to living mesothelial cells was consistently documented in all four cases investigated. CONCLUSION: Calretinin is a very useful marker for positive identification of normal and tumor mesothelial cells in serous effusions.