Supercritical extraction of sunflower seed oil: Experimental data and model validation

In this work experimental results of sunflower seed oil extraction using supercritical CO₂ are presented, together with the outcome obtained by applying to the same data a theoretical model recently developed and further improved here.We performed extraction tests utilizing a supercritical extraction equipment having a volumetric capability of 100 ml; the seeds were milled to obtain different particle sizes (mean diameter between 0.19 and 1.2 mm); the range of pressure investigated was 280–550 bar, the temperature and solvent flow rate were maintained constant at about 40 °C and 10 g/min, respectively.The model accounts for the distinction between broken and intact oil-bearing cells and describes the extraction kinetics similar to the shrinking core models: it allowed satisfactory fitting of the experimental data and permitted to calculate the effective diffusivity of the oil in the seed, which resulted equal to 3 × 10⁻¹¹ m²/s. The reliability of the model is demonstrated by the fact that the value of the effective diffusivity, resulting from model optimization procedures, is similar for the various experimental tests.     

Fast fixed-point neural blind-deconvolution algorithm

The aim of this letter is to introduce a new blind-deconvolution algorithm based on fixed-point optimization of a "Bussgang"-type cost function. The cost function relies on approximate Bayesian estimation achieved by an adaptive neuron. The main feature of the presented algorithm is fast convergence that guarantees good deconvolution performances with limited computational demand as compared with algorithms of the same class.     

A new nonlinear model of EMI-induced distortion phenomena in feedback CMOS operational amplifiers

This paper deals with distortion phenomena induced by radio-frequency interference (RFI) in analog integrated circuits and it concentrates on the effects induced by RFI on the operation of feedback CMOS operational amplifiers (opamps). In particular, the paper describes a new nonlinear model, which makes possible the prediction of upset in the opamp output nominal signal when RFI is superimposed on the input nominal signals. Such a model can be employed when the transistors of the input differential pair are driven by RFI either in strong or weak nonlinear operation. Results of experimental tests performed on a Miller CMOS opamp connected in the voltage follower configuration are presented and compared with model predictions.     

Neural minor component analysis approach to robust constrained beamforming

Since the pioneering work of S.-I. Amari (1977) and E. Oja (1982; 1989; 1992), principal component neural networks and their extensions have become an active adaptive signal processing research field. One of such extensions is minor component analysis (MCA), that proves to be effective in tasks such as robust curve/surface fitting and noise reduction. The aims of the paper are to give a detailed and homogeneous review of one-unit first minor/principal component analysis and to propose an application to robust constrained beamforming. In particular, after a careful presentation of first/minor component analysis algorithms based on a single adaptive neuron, along with relevant convergence/steady-state theorems, it is shown how the adaptive robust constrained beamforming theory by H. Cox et al. (see IEEE Trans. Acoust. Speech. Sig. Process., vol.34, no.3, p.393-8, 1986; vol.35, no.10, p.1365-76, 1987) may be advantageously recast into an MCA setting. Experimental results obtained with a triangular array of microphones introduced in a teleconference context help to assess the usefulness of the proposed theory.     

Finite common-mode rejection in fully differential operational amplifiers

A nonlinear mechanism which affects common-mode rejection (CMR) of fully differential integrated operational amplifiers (opamps) is highlighted and analysed by computer simulations. In particular, it is shown how the finite CMR of fully differential opamp circuits under practical operating conditions is mainly related to such a mechanism rather than to transistor mismatch.     

Three-dimensional simulation of realistic single electron transistors

We present an approach, and its implementation in a computer program, for the three-dimensional (3-D) simulation of realistic single electron transistor (SET) structures, in which subregions with different degrees of quantum confinement are simultaneously considered. The proposed approach is based on the self-consistent solution of the many body Schrodinger equation with density functional theory and on the computation of the conductance of tunnel constrictions through the solution of the 3-D Schrodinger equation with open boundary conditions. We have developed an efficient code (ViDES) based on such an approach. As examples of addressable SET structures, we present the simulation of a SET, one defined by metal gates on an AlGaAs/GaAs heterostructures, and of a SET defined by etching and oxidation on the silicon-on-insulator material system. Since SETs represent prototypical nanoscale devices, the code may be a valuable tool for the investigation and optimization of a broad range of nanoelectronic solid-state devices.     

A sample preparation for quantitative determination of magnesium in individual lymphocytes by electron probe X-ray microanalysis

We present a sample preparation method for measuring magnesium in individual whole lymphocytes by electron probe X-ray microanalysis. We use Burkitt's lymphoma cells in culture as the test sample and compare X-ray microanalysis of individual cells with atomic absorption analysis of pooled cell populations. We determine the magnesium peak-to-local continuum X-ray intensity ratio by electron probe X-ray microanalysis and calculate a mean cell magnesium concentration of 39± 19 mmol/kg dry weight from analysis of 100 cells. We determine a mean cell magnesium concentration of 34 ±4 mmol/kg dry weight by atomic absorption analysis of pooled cells in three cell cultures. The mean cell magnesium concentrations determined by the two methods are not significantly different. We find a 10% coefficient of variation for both methods of analysis and a 30% coefficient of variation in magnesium concentration among individual cells by electron probe X-ray microanalysis. We wash cells in ammonium nitrate for microanalysis or in buffered saline glucose for atomic absorption analysis. We find cells washed in either solution have the same cell viability (85%), recovery (75%), cell volume (555 μm³) and cytology. We air dry cells on thin film supports and show by magnesium X-ray mapping that magnesium is within the cells. We conclude that: (a) our microanalysis cell preparation method preserves whole intact lymphocytes; (b) there is no systematic difference in results from the two methods of analysis; (c) electron probe X-ray microanalysis can determine the variation in magnesium concentration among individual cells.     

Cloning and molecular characterization of a cDNA clone coding for Trichomonas vaginalis alpha-actinin and intracellular localization of the protein

We have identified and sequenced a cDNA clone coding for Trichomonas vaginalis alpha-actinin. Analysis of the obtained sequence revealed that the 2,857-nucleotide-long cDNA contained an open reading frame encoding 849 amino acids which showed consistent homology with alpha-actinins of different species. Such homology was particularly significant in regions which have been reported to represent the actin-binding and Ca2+-binding domains in other alpha-actinins. The deduced protein was also characterized by the presence of a divergent central region thought to play a role in its high immunogenicity. A study of protein localization performed by immunofluorescence revealed that the protein is diffusely distributed throughout the T. vaginalis cytoplasm when the cell is pear shaped. When parasites adhere and transform into the amoeboid morphology, the protein is located only in areas close to the cytoplasmic membrane and colocalizes with actin. Concomitantly with transformation into the amoeboid morphology, alpha-actinin mRNA expression is upregulated.     

Effects of olive paste fast preheating on the quality of extra virgin olive oil during storage

The olive paste obtained after crushing was fast preheated under different time/temperature conditions and then malaxed in an industrial oil mill (600 kg Frantoio/Leccino olive blend). Legal parameters (peroxides, free acidity and sensory panel), oil yield, total phenolic content, oxidative stability and phenolic profile were monitored during 12 months of storage of the virgin olive oil (VOO) kept in closed bottles in the dark. A fast preheating not longer than 72 s at 38 °C without malaxation lead to an extra VOO with a shelf-life of at least 12-months, similarly to the traditional EVOO obtained with malaxation. A fast preheating not longer than 72 s at 38 °C followed by 10 min malaxation lead to an EVOO with a ‘mild’ sensory profile and a shelf life of at least 12-months. Thus, the use of a specific designed fast preheater instead or before (a shortened) malaxation allows to obtain an EVOO with a low bitter/pungent attribute from olives which are rich of (sometimes unpleasant) phenolic compounds with the aim to meet the preference of targeted groups of consumers. Time and temperature of fast preheating are the critical parameters of the process.