Delay Dependent Local Stabilization Conditions for Time-delay Nonlinear Discrete-time Systems Using Takagi-Sugeno Models

International Journal of Control, Automation and Systems - We propose convex conditions for stabilization of nonlinear discrete-time systems with time-varying delay in states through a fuzzy...     

Extraction of Polyphenols from Red Grape Pomace Assisted by Pulsed Ohmic Heating

The present work is devoted to the investigation of the effect of pulsed ohmic heating (POH) on cells membrane damage and intensification of polyphenols extraction from red grape pomace. Untreated, POH-treated and freeze-thawed samples were compared. The effects of electric field strength (E?=?100–800 V/cm) and the percentage of ethanol in water (E/W?=?0–50 %) on polyphenols extraction were discussed. Measurements of electrical conductivity and electric energy consumption were performed for POH pretreatment optimization. Results show that POH treatment results in cells membrane denaturation. This permeabilization increases with the elevation of electric field strength and temperature. POH pretreatment accelerates the extraction kinetics of total polyphenols from grape pomace. Freeze-thawed samples are always accompanied with a high degree of cell damage and high concentration of polyphenols in the extract. The highest extraction yields were obtained with a POH pretreatment at 400 V/cm followed by a diffusion step for 60 min at 50 °C and with a solvent composed of 30 % of ethanol in water. In these conditions, the polyphenol content was 36 % more than untreated samples. The proposed technique (POH pretreatment) appears to be promising for future industrial applications of polyphenols extraction from pomace.     

Compatibility Studies Between Ibuprofen or Ketoprofen with Cellulose Ether Polymer Mixtures Using Thermal Analysis

ABSTRACT

Differential scanning calorimetry (DSC) was used to investigate and detect incompatibilities between drugs such as: ibuprofen (IBU) or ketoprofen (KETO) with cellulose ether derivatives, which are frequently applied on controlled release dosage forms. Binary mixtures concerning methylcellulose (MC25) or hydroxypropylcellulose (HPC) with hydroxypropylmethylcellulose (HPMC) K15M or K100M in different ratios were prepared and evaluated by the appearance, shift, or disappearance of peaks and/or variations in the corresponding ΔH values. According to the DSC results, binary mixtures between those polymers were found to be compatible, but their mixture with IBU or KETO, promotes a solid–solid interaction mainly with 1:1:1 (w/w) ratio (drug-excipient). However, when the drug:excipient interactions were detected, they were not found to affect the drug bioavailability. DSC was successfully employed to evaluate the compatibility of the drugs with the selected polymers.     

Electrodeposition and characterization of nickel–copper metallic foams for application as electrodes for supercapacitors

Nickel–copper metallic foams were electrodeposited from an acidic electrolyte, using hydrogen bubble evolution as a dynamic template. Their morphology and chemical composition was studied by scanning electron microscopy and related to the deposition parameters (applied current density and deposition time). For high currents densities (above 1 A cm^?2) the nickel–copper deposits have a three-dimensional foam-like morphology with randomly distributed nearly-circular pores whose walls present an open dendritic structure. The nickel–copper foams are crystalline and composed of pure nickel and a copper-rich phase containing nickel in solid solution. The electrochemical behaviour of the material was studied by cyclic voltammetry and chronopotentiometry (charge–discharge curves) aiming at its application as a positive electrode for supercapacitors. Cyclic voltammograms showed that the Ni–Cu foams have a pseudocapacitive behaviour. The specific capacitance was calculated from charge–discharge data and the best value (105 F g^?1 at 1 mA cm^?2) was obtained for nickel–copper foams deposited at 1.8 A cm^?2 for 180 s. Cycling stability of these foams was also assessed and they present a 90 % capacitance retention after 10,000 cycles at 10 mA cm^?2.     

Optimisation of reactive textile dyes degradation by laccase–mediator system

BACKGROUND: In the textile industry, large quantities of intensely coloured and toxic effluents are released, causing serious environmental pollution. Several biotechnological approaches have been suggested to eliminate this pollution source in an eco‐efficient manner. Laccase can be used to decolourise dyes and its substrate range can be extended by inclusion of a mediator. RESULTS: A screening using several laccase mediators (2,2‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonate) (ABTS), 1‐hydroxybenzotriazole (HBT), N‐hydroxyacetanilide (NHA), polioxometalates, violuric acid (VA) and (2,2,6,6‐tetramethylpiperidin‐1‐yloxy) (TEMPO)) was performed on the degradation of six reactive textile dyes. ABTS was the most effective mediator leading to higher decolourisation. The efficiency of ABTS depends on the type of dye, pH, temperature and dye concentration. The optimum temperature and pH values were 35 °C and 5.0, respectively, for maximum decolourisation (above 70%) of reactive black 5, reactive blue 114 and reactive yellow 15. For reactive red 239 the optimum conditions were found to be a temperature of 40 °C and pH of 4.5 (above 56% decolourisation). ABTS has no effect at low concentrations, except for reactive blue 114, where it resulted in the best decolourisation (93%). A comparison of decolourisation based on the percentage absorbance reduction at the maximum absorbance wavelength of each dye and throughout the visible spectrum was made. CONCLUSIONS: These results suggest that the laccase mediator system could be used to treat textile dying wastewaters. Copyright © 2008 Society of Chemical Industry     

Model-based classification with dissimilarities: a maximum likelihood approach

Most of classification problems concern applications with objects lying in an Euclidean space, but, in some situations, only dissimilarities between objects are known. We are concerned with supervised classification analysis from an observed dissimilarity table, which task is classifying new unobserved or implicit objects (only known through their dissimilarity measures with previously classified ones forming the training data set) into predefined classes. This work concentrates on developing model-based classifiers for dissimilarities which take into account the measurement error w.r.t. Euclidean distance. Basically, it is assumed that the unobserved objects are unknown parameters to estimate in an Euclidean space, and the observed dissimilarity table is a random perturbation of their Euclidean distances of gaussian type. Allowing the distribution of these perturbations to vary across pairs of classes in the population leads to more flexible classification methods than usual algorithms. Model parameters are estimated from the training data set via the maximum likelihood (ML) method, and allocation is done by assigning a new implicit object to the group in the population and positioning in the Euclidean space maximizing the conditional group likelihood with the estimated parameters. This point of view can be expected to be useful in classifying dissimilarity tables that are no longer Euclidean due to measurement error or instabilities of various types. Two possible structures are postulated for the error, resulting in two different model-based classifiers. First results on real or simulated data sets show interesting behavior of the two proposed algorithms, ant the respective effects of the dissimilarity type and of the data intrinsic dimension are investigated. For these latter two aspects, one of the constructed classifiers appears to be very promising. Interestingly, the data intrinsic dimension seems to have a much less adverse effect on our classifiers than initially feared, at least for small to moderate dimensions.     

Sequential decolourization of reactive textile dyes by laccase mediator system

BACKGROUND: The use of enzymes has attracted much interest for the decolourization of dyes from wastewater as an alternative to conventional treatments, which have limitations. Laccase can be used to decolourize dyes and its substrate range can be extended by inclusion of mediators. RESULTS: Sequential decolourization of reactive dyes was carried out by a laccase mediator system using as mediators violuric acid and 1‐hydroxybenzotriazole. Violuric acid resulted in a high level of decolourization on the first and second cycles for reactive blue 114 (≥95%), reactive yellow 15 and reactive red 239 (≥80%), while for reactive black 5 a slightly lower value was observed (70%) on the second cycle. The degree of reactive blue decolourization remained at 90% after the third cycle, and at about 60% after seven cycles. With the other dyes decolourization decreased to 50–70% on the third cycle and further up to the final cycle (lower than 20%). When using 1‐hydroxybenzotriazole as mediator a slight decrease in decolourization efficiency was obtained. Correlation between dye oxidation peak potential and dye degradation after 10 min reaction was obtained for both mediators. CONCLUSIONS: These results show that sequencing batch decolourization by laccase mediator system is a useful methodology for treating textile dying wastewaters with a high potential for application at industrial level. Copyright © 2008 Society of Chemical Industry     

Ochratoxin A in coffee beans (Coffea arabica L.) processed by dry and wet methods

The incidence of ochratoxin A was studied in different coffee (Coffea arabica L.) samples. A higher incidence of filamentous fungi was observed in the coffee swept from ground and floating coffee samples. The species Aspergillus ochraceus, Aspergillus sulphureus and Aspergillus sclerotiorum were ochratoxin A producing. In 128 (44%) samples ochratoxin A was not detected; however, in 89 samples (31%), ochratoxin A was detected at 0.1–5.0 μg/Kg levels. Other 25% samples presented contamination above 5.0 μg/Kg. This study showed that the fractions coffee swept from ground and floating coffee represents a serious risk of ochratoxin A contamination.     

Route-Specific Urinary Biomarkers in the Risk Assessment of PAH Exposure

The route of exposure (oral or inhalatory) of the general population to polycyclic aromatic hydrocarbons (PAH) is toxicologically very important. From a literature survey on the toxicity of benzo[a]pyrene (BP) in relation to the route of exposure, it is concluded that although exposure by food is quantitatively the major route of exposure of B[a]P (94%), inhalation exposure is by far more adverse from a toxicological point of view.

Because of the different composition of the PAH mixture in food and air it is possible to distinguish between the route of exposure by monitoring specific metabolites in human urine. Exposure by food and air can be monitored independently by the determination of 1-hydroxypyrene and 1-hydroxynaphthalene in urine, respectively. A very sensitive GCMS method has been developed for urinary 1- and 2- hydroxynaphthalene, which has been applied to urines of non-occupationally exposed smokers and non-smokers. A large difference in urinary concentrations of hydroxynaphthalenes between both groups was observed being a factor 5.9 and 14 for 1- and 2-hydroxynaphthalene, respectively.