Adaptive control design for a boost inverter

In this paper, a novel control strategy for a nonlinear boost inverter is proposed. The idea is based on generating an autonomous oscillator that does not need an external reference signal. This aim is achieved by using energy-shaping methodology with a suitable Hamiltonian function which defines the desired system behavior. A phase controller is added to the control law in order to achieve 180°-synchronization between both parts of the circuit as well as synchronize the voltage output with a pre-specified signal, e.g. synchronization with the electrical grid. An adaptive control is designed for dealing with the common problem of unknown load. In order to analyze the stability of the full system, singular perturbation approach is used. The resulting control is tested by means of simulations.     

Impact of Starch Gelatinization on the Kinetics of Maillard Reaction in Freeze-Dried Potato Systems

The objective of the present work was to contribute to the understanding of the changes in water-distribution and water–solids interactions that take place after starch gelatinization and to elucidate their influence on the kinetics of Maillard reaction in low-moisture potato starch systems. Maillard reaction was studied in freeze-dried native (NS) and gelatinized (GS) potato starch systems at 70°C. Water sorption isotherms were studied in a wide range of relative humidities (RH) and Guggenheim-Anderson-de Boer (GAB) model was applied. Thermal transitions were studied by differential scanning calorimetry; molecular mobility was estimated through time-resolved ¹H NMR, and Maillard reaction was followed photocolorimetrically. In NS systems, the Maillard reaction rate was inversely dependent with the increase of RH. These results are due to a heterogeneous distribution of water and reactants within the starch matrix. In GS systems, the rate coefficient of the Maillard reaction increased up to RHs between 75% and 84% and then decreased at higher RH values. In this case, Maillard reaction rate could be related to the physical properties of the matrix: T _g, water sorption, and water mobility can be relevant tools to predict the Maillard reaction rate-dependence on water content.     

Inhomogeneous distribution of fat enhances the perception of fat-related sensory attributes in gelled foods

This study investigated the effect of the spatial distribution of fat on the perception of fat-related sensory attributes using a model system that consisted of layered agar/gelatin gels containing oil-in-water (O/W) emulsion droplets dispersed in the gel matrix. Four layers of gel varying in the amount of emulsion droplets were combined to prepare samples with homogeneous and inhomogeneous distributions of fat (emulsion droplets). The composition of the gels was optimized to obtain samples with comparable mechanical properties.     

Transformation of waterborne hybrid polymer particles into films: Morphology development and modeling

Films cast from multiphase polymer particles have the potential to combine the properties of their components synergistically. The properties of the film depend on the hybrid polymer architecture and the film morphology. However, how the polymer microstructure and particle morphology are transformed during film formation to determine the film morphology is not well understood. Here, using waterborne alkyd-acrylic nanocomposite particles in a case study, it was found that phase migration leading to the formation of aggregates occurred during film formation. A coarse-grained Monte Carlo model was developed to account for the effects of polymer microstructure and particle morphology on the morphology of the film. The model was validated by comparing its predictions with the observed effects, and then used to explore combinations of polymer microstructure and particle morphology not attainable with the system used as a case study. Significantly, the compatibility of the phases was found to have a greater influence than the morphology of the particles in determining the film structure.     

Whole blood, serum, and saliva lead concentrations in 6- to 8-year-old children

With increasing evidence of adverse health effects of lower lead levels (below 10 µg/dL in whole blood), studies on novel internal dose biomarkers are needed. This study aimed at: (1) assessing the lead exposure by measuring this element in whole blood (Pb-blood), serum (Pb-serum), and 3 different types of saliva: whole (Pb-whole-saliva), submandibular/sublingual (Pb-sub-saliva) and parotid saliva (Pb-parotid-saliva); (2) correlating Pb-blood with Pb-serum; and (3) relating Pb-blood and Pb-serum with the lead found in the different salivas. The study population included 444 children aged 6 to 8 years attending 4 government schools in the district of Campos Eliseos, in Ribeirao Preto, Sao Paulo State, Brazil. Whole blood, serum, parotid, submandibular/sublingual (“sub-saliva”), and whole saliva were collected in trace element-free tubes. Lead concentrations were determined by inductively coupled plasma-mass spectrometry (ICP-MS). Median Pb-blood and Pb-serum were 2.1 µg/dL and 0.4 µg/L, respectively. Ten percent of the children had Pb-blood between 4.0 and 9.4 µg/dL. Boys showed higher Pb-blood than girls (2.3 vs. 2.0 µg/dL, p < 0.0003). Lead concentrations in whole, sub, and parotid saliva were 1.7, 1.4, and 1.3 µg/L, respectively. No significant correlations were found between Pb-blood and Pb-serum, between Pb-blood and lead in the 3 different salivas, or between Pb-serum and Pb-whole-saliva or Pb-sub-saliva. However, there was a weak statistically significant correlation between Pb-serum and Pb-parotid-saliva. In conclusion, the mean Pb-blood concentration was 2.4 µg/dL, with 10% of the children exhibiting Pb-blood between 4.0 and 9.4 µg/dL. Boys presented higher Pb-blood. Results suggest that Pb-blood has no correlation with Pb-serum or lead in the 3 different salivas collected here. A weak but statistically significant correlation between Pb-serum and Pb-parotid-saliva was found. Our results also point to the need for carrying out more studies on sources of exposure and lead levels in children in Brazil.     

Acceptance of yoghurt with different functional ingredients among consumers in supermarkets in southern Chile

In view of the interest in the role of foodstuffs in improving wellbeing and health, the object of this study is to distinguish consumer typologies in Temuco, La Araucanía Region, Chile, according to their preferences for different functional ingredients, flavouring, colouring and price in yoghurt. A semi-structured survey was applied to 400 supermarket customers. The respondents ordered eight alternative yoghurts according to their preferences, with different functional ingredients (fibre, antioxidants), flavourings (sugar, sweetener), colouring (natural, artificial) and three price options, for a conjoint analysis with fractional factorial design. Variables affecting knowledge of "functional food" were evaluated using a binomial logit model. It was determined by conjoint analysis that in general a preference existed for yoghurt containing fibre, sweetener, natural colouring, and at the lowest price. Three typologies were distinguished by analysis of hierarchical conglomerates: the majority segment (48.8%) displayed a greater preference for fibre; the second (41.7%) also preferred fibre, but gave first priority to artificial colouring and preferred a higher price. The minority (9.5%) was the only segment to prefer antioxidants. The typologies differed significantly in satisfaction with their food-related life, knowledge of the function of fibre and presence of cancer and obesity in some member of the respondent's family. The binomial logit model was significant (P < 0.01), indicating that if the consumer has a job or has had access to information on functional foods, the probability increased of knowledge of what these mean. There was thus majority acceptance of yoghurt enriched with fibre and with added sweetener.     

Influence of hydrogen bonding upon the TiO2 photooxidation of isopropanol and acetone in aqueous solution

This study investigates the aqueous photocatalytic degradation of small polar organic compounds (SPOCs) that bear hydrogen-bonding capabilities but do not readily adsorb to the TiO₂ catalyst. The effect of pH on the TiO₂ surface hydroxyl speciation and surface acid/base equilibria was used to elucidate the possible role of hydrogen-bonding interactions in the degradation of acetone and isopropanol in aqueous TiO₂ photocatalytic systems. The kinetic parameters describing the decomposition of these two model compounds were obtained by gas chromatographic analysis of their photoreaction systems and interpreted on the grounds of the Brönsted acid/base properties of the TiO₂ surface speciation and solute hydrogen-bonding numerical scales. The results showed that the fastest initial degradation rates of acetone and isopropanol occurred in a pH range where the optimal conditions for adsorption through hydrogen bonding to the TiO₂ surface and optimum concentration of hydroxyl radicals (OH) coincide. The fastest degradation constants were observed at pH 6.04 and 8.61 for acetone and isopropanol, respectively. The hypothesis of hydrogen bonding to surface hydroxyl groups presented in this study challenges the common assumption that these model compounds do not adsorb to surface sites, and that their oxidative pathways of degradation only occur via homogeneous-phase reaction with free OH radicals.     

Osmoregulation of the resident estuarine fish Atherinella brasiliensis was still affected by an oil spill (Vicuña tanker, Paranaguá Bay, Brazil), 7 months after the accident

An oil tanker loaded with methanol and bunker oil has exploded in November 2004 in Paranaguá Bay, in front of Paranaguá Harbor, southern Brazil. In order to investigate the chronic effects of an oil spill on a resident estuarine fish, the Brazilian silverside Atherinella brasiliensis was sampled 1, 4, and 7 months after the spill, from 2 sites inside Paranaguá Bay, and also from a reference site inside nearby Guaratuba Bay, non-affected by the spill. Increases in plasma osmolality (reaching ~ 525 mOsm/kg H₂O, or ~ 70% above values in reference fish) and chloride (reaching 214 mM in site C, or ~ 51% above values in reference fish) were detected 4 months after the spill, in parallel with branchial carbonic anhydrase inhibition (to 56% of the activity measured in reference fish) in silversides obtained from the contaminated sites. Plasma cortisol concentration increased progressively in samples from fish obtained 4 (462 ng/mL) and 7 (564-650 ng/mL) months after the spill, when compared to values in reference fish (192 ng/mL). Osmoregulation of a resident estuarine fish is still affected by an oil spill, months after the accident. It is, thus, a sensitive tool for the evaluation of the chronic effects of oil spills inside tropical estuarine systems, and A. brasiliensis is proposed as an adequate sentinel species for monitoring protocols.