Matching a system behavior with a known set of models: A quadratic optimization‐based adaptive solution

The matching process between a time‐domain external behavior of a lumped single‐input single‐output dynamical system and a known set of linear continuous time‐invariant models is tackled in this paper. The proposed online solution is based on an adaptive structure detector, which in finite time locates in the known set of models the one corresponding to the observed external behavior; the detector results from the solution of a constrained quadratic optimization problem. The problem is expressed in terms of the time‐domain activity of a family of discriminating filters and is solved via a normalized gradient algorithm, which avoids mismatching due to the presence of structural zeros in the filters and can take into account band‐limited high‐frequency measurement noise. A failure detection problem concerning a simulated servomechanism is included in order to illustrate the proposed solution. Copyright © 2008 John Wiley & Sons, Ltd.     

Lipase-catalyzed acidolysis of sunflower oil: Kinetic behavior

In the present study, sunflower oil was modified with a palmitic–stearic acids blend by means of an immobilized sn-1,3 specific lipase (Lipozyme RM IM) to produce structured lipids. Products were analyzed to determine fatty acid incorporation (F_M) into triacylglycerol structure and to quantify by-products as monoglycerides (MG) and diglycerides (DG). The effects of the reaction conditions (temperature, time, incorporated water) on enzymatic acidolysis were studied. Nonlinear regression methods were employed to fit experimental data with kinetic models proposed in the literature. The disappearance of reactant fatty acids (RF) over time was successfully modeled by a Ping-Pong Bi-Bi mechanism. F_M was also represented with a lumped parameter model of the enzymatic mechanism. Maximum RF disappearance and F_M onto sunflower oil glycerides increased with increasing reaction temperature. MG and DG concentrations in water-free systems were stabilized in low levels, while the incorporation of water to the reaction mixture produced a considerable increase in DG formation principally. Kinetic and equilibrium parameters showed temperature dependencies.     

Corrosion behavior of thermoelectric clathrates α- and β-Eu8Ga16−xGe30+x in air

The corrosion of thermoelectric clathrates α- and β-Eu₈Ga_16−xGe_30+x is studied under static air (DSC/TG) up to 650 °C. Oxidation product layers with thicknesses of 10.5 μm (α-Eu₈Ga_16−xGe_30+x) and 4.5 μm (β-Eu₈Ga_16−xGe_30+x) are formed. The oxidation begins at 360 and 380 °C, respectively. XRD pattern of the β-Eu₈Ga_16−xGe_30+x oxidized layer shows Ge and four Eu₂O₃ reflections; while α-Eu₈Ga_16−xGe_30+x data (sample crushed and grinded) shows α-Eu₈Ga_16−xGe_30+x reflections (majority phase), two EuGa_2±xGe_4?x strongest reflections and Ge (minority phases). These results indicate the amount of oxides is very small or they are amorphous. High temperature powder XRD measurements on α-Eu₈Ga_16−xGe_30+x under air confirm the oxidation onset temperature determined in DSC studies.     

Removal of Inorganic Mercury from Polluted Water Using Structured Nanoparticles

This paper presents a process for the removal of inorganic mercury from aqueous solutions using alumina nanoparticles, which were prepared by the sol-gel method. Different amounts of mercury were added to the particles until a critical concentration was achieved, thus inducing the alumina sol flocculation. Particle growth was monitored during the process using dynamic light scattering. The amount of metal ion adsorbed on the surface of the alumina sols was determined by atomic absorption spectroscopy. Initial mercury concentrations ranging between 50 and 100 ppm decreased to below 1 ppb in a short time.     

Extraction and characterization of soluble protein fractions from Phaseolus lunatus L seeds

Legume proteins as a potential source of valuable nutrients, are the object of several studies in order to obtain the best use. A basic knowledge becomes more important for those proteins from species not wholly utilized, before using them as food ingredients. The objective of this work was to determine several structural and nutritional characteristics of the protein fractions from Phaseolus lunatus, separated in different solvents. The relative amount of extraction for the albumins (ALB), globulins (GLB), prolamines (PRL), and glutelins (GLT) was 62.3, 34.8, 1.4 and 1.5%, respectively. The SDS-PAGE electrophoretic profile of both ALB and GLB, showed seven common bands in intervals from 10 to 95 kDa, and 14 to 99 kDa, respectively; the amino acids profile showed that PRL was the rich fraction in sulfurated amino acids (11.5 g/100 g protein); the content of lysine in the fraction of ALB was smaller than expected but the requirement of the FAO in the fractions of GLB and GLT was covered. In general, the fraction of GLB had the best balance of amino acids and digestibility (80%); however, it had a relationship of calculated protein efficiency ratio (C-PER) of 0.11, smaller than the ratio in ALB (0.97). The calorimetric analysis showed denatured temperatures around 90 degrees C for the ALB, GLB, and GLU fractions. The PRL fraction probably did not present a thermal transition because the proteins were denaturalized by the extraction conditions.     

Modeling the compressive strength of geopolymeric binders by gene expression programming-GEP

GEP has been employed in this work to model the compressive strength of different types of geopolymers through six different schemes. The differences between the models were in their linking functions, number of genes, chromosomes and head sizes. The curing time, Ca(OH)₂ content, the amount of superplasticizer, NaOH concentration, mold type, aluminosilicate source and H₂O/Na₂O molar ratio were the seven input parameters considered in the construction of the models to evaluate the compressive strength of geopolymers. A total number of 399 input-target pairs were collected from the literature, randomly divided into 299 and 100 sets and were trained and tested, respectively. The best performance model had 6 genes, 14 head size, 40 chromosomes and multiplication as linking function. This was shown by the absolute fraction of variance, the absolute percentage error and the root mean square error. These were of 0.9556, 2.4601 and 3.4716 for training phase, respectively and 0.9483, 2.8456 and 3.7959 for testing phase, respectively. However, another model with 7 genes, 12 head size, 30 chromosomes and addition as linking function showed suitable results with the absolute fraction of variance, the absolute percentage error and the root mean square of 0.9547, 2.5665 and 3.4360 for training phase, respectively and 0.9466, 2.8020 and 3.8047 for testing phase, respectively. These models showed that gene expression programming has a strong potential for predicting the compressive strength of different types of geopolymers in the considered range.     

Enrichment of precooked white corn flour (Zea mays) with amaranth seed flour (Amaranthus sp.)

Three mixtures of precooked white corn flour with 10, 20 and 30% amaranth flour were prepared. The sedimentation and consistency of the mixtures differed from those of the white corn flour, but without altering the capacity of dough formation to prepare arepas. The protein, fiber, and ash contents were higher than those of the precooked white corn flour. The functional properties of water and oil absorption increased in 20 and 10%, respectively. During the three-month storage, the protein and fat contents were not altered. Acceptability tests of the arepas were carried out and results indicated that those mixtures prepared with 10% and 20% substitution levels were acceptable from the sensory point of view. The protein quality was analyzed in terms of protein efficiency ratio (PER), which proved to be higher than that of the commercial white corn flour (PER 1.93), and the apparent digestibility was 92%. As far as lysine is concerned, results showed that arepas prepared with the mixture containing 10% amaranth (1.6 g lysine/100 g protein) and 20% (2.0 g lysine/100 g protein) also proved to be higher than the commercial white corn flour arepas (0.7 g lysine/100 g protein). Based on the above findings, enrichment of commercial white corn flour with grain amaranth flour, prior to the preparation of arepas, a product of high consumption in Venezuela as part of the habitual diet, is recommended.     

Increasing antigenicity of B16 melanoma cell fraction with microwave hyperthermia

An injection of a fraction of a fraction (C30 mw) obtained by centrifugation at 30 kg of homogenate of B16 melanoma cells, treated with microwave hyperthermia (2450 MHz, CW, 44 degrees C, for 20 minutes), increases the survival time (p less than 0.01) of C57-BL/6J male mice inoculated 26 days later with 10(7) cells (viability greater than 95%) of B16 melanoma. This delay of 26 days between these two injections corresponds to the moment where the synthesis of immunoglobulins is increased in protected mice. The earliest death (p less than 0.001) of animals injected with untreated tumoral cell fraction (C30), and that received a suspension of viable B16 melanoma cells (10(7)) can be explained by an inhibition of humoral immunity system.