Is neglected heterogeneity really an issue in binary and fractional regression models? A simulation exercise for logit, probit and loglog models

Theoretical and simulation analysis is performed to examine whether unobserved heterogeneity independent of the included regressors is really an issue in logit, probit and loglog models with both binary and fractional data. It is found that unobserved heterogeneity has the following effects. First, it produces an attenuation bias in the estimation of regression coefficients. Second, although it is innocuous for logit estimation of average sample partial effects, it may generate biased estimation of those effects in the probit and loglog models. Third, it has much more deleterious effects on the estimation of population partial effects. Fourth, it is only for logit models that it does not substantially affect the prediction of outcomes. Fifth, it is innocuous for the size of Wald tests for the significance of observed regressors but, in small samples, it substantially reduces their power.     

Molten salts synthesis and electrical properties of Sr- and/or Mg-doped perovskite-type LaAlO3 powders

Lanthanum-based LaBO₃ oxides adopting the very stable perovskite structure are currently considered attractive materials for a growing number of applications in the field of solid-state ionics. In particular, LaAlO₃-based perovskites are promising electrolyte materials for solid oxide fuel cells because they show almost pure oxygen ion conductivity at low oxygen partial pressures and high temperatures as well as excellent thermal and chemical stability under the standard operating conditions. This article describes a low-temperature synthesis of pure and acceptor-doped perovskite-type LaAlO₃ nanopowders via a facile and environmental-friendly molten salts method. Using hydrated metal nitrates and sodium hydroxide as raw materials, the proposed methodology consists of two steps: a mechanically induced metathesis reaction and short firing above NaNO₃'s melting point. The purpose of the first is twofold: i.e., to generate in situ the NaNO₃ flux and to obtain a suitable precursor for the synthesis of the target materials in molten nitrates. Accordingly, pure and Mg- and/or Sr-doped LaAlO₃ powders were obtained directly without using any purification step at temperatures ≤500 °C. When preparing the Mg-containing samples, NaNO₂ was also added to the reaction mixture to increase melt reactivity. The formation of the target series in the molten salt is thought to proceed through a “dissolution–precipitation” mechanism with LaAlO₃ particles precipitating during cooling from a solution oversaturated with reactants. Electrical properties of the as-prepared materials were measured as a function of temperature and frequency by means of impedance spectroscopy and found comparable to those shown by similar materials prepared using more complicated routes.     

The use of activated charcoal in combination with other fining agents and its influence on the organoleptic properties of sherry wine

Fining experiments have been conducted on fino sherry wine from the Jerez-Xérès-Sherry region (southern Spain), in which the combined use of activated charcoal with proteinaceous fining agents (casein, potassium caseinate, albumin, and gelatin) has been studied. The effect of these fining agents on the polyphenolic content, the aromatic profile, and the resistance to browning of the treated wine has been determined. The polyphenolic content suffers significant decreases following the use of activated charcoal; these decreases are only increased slightly by the subsequent use of the other fining agents. The aromatic profile was not found to be altered by the clarification agents used. Despite the reduction in the polyphenolic content, the treated wines show a tendency to suffer browning similar to that observed in non-clarified wine.     

Morphological, optical and photocatalytic properties of TiO2–Fe2O3 multilayers

Morphological, optical and photocatalytic properties of TiO₂, Fe₂O₃ and TiO₂–Fe₂O₃ samples (formed by 1, 3 and 5 coatings) were studied. The layers were deposited on glass substrate by the sol–gel method. The catalytic activity of the samples was studied by the photodecomposition of methylene blue (MB) under visible light illumination. The FTIR results indicate that all samples present surface OH radicals that are bound either to the Ti or Fe atoms. This effect is better visualized at larger number of coatings in the TiO₂–Fe₂O₃/glass systems. Also, two mechanisms are observed during the photodecomposition of the MB.     

Optimization of Solid-Phase Microextraction Procedure Coupled to GC-ECD for Triazole Fungicides Determination in Juice Samples

A solid-phase microextraction (SPME) procedure followed by gas chromatography electron capture detection (GC/ECD) for the determination of triazole residues was developed. An experimental design with two steps was done. Firstly, a 2⁶⁻² fractional factorial design for screening several experimental variables (fiber-coating type, extraction temperature, extraction time, stirring rate, desorption temperature, and desorption time) was done. After, a two-factor central composite design for optimizing, the experimental conditions were carried out. The chosen experimental conditions were: fiber, PDMS/DVB; extraction time, 45 min; extraction temperature, 60 °C; desorption time, 3 min; desorption temperature, 260 °C, and stirring speed, 500 rpm. Using those conditions the limits of detection obtained for tetraconazole, myclobutanil, and diniconazole were in the order of few μg L⁻¹ in grape and apple liquid extracts. Recoveries were from 93.6% to 112.1%. Relative standard deviation ranged from 1.2% to 11.6% (apple) and 6.7 to 18.0% (grape). The method was applied to five grape samples and 13 apple samples collected in Navarra, Rioja, and Basque Country. Quantification was performed by the standard addition method. Three standard additions by duplicate covering adequate range concentration were used. Myclobutanil was found in three apple samples (110–122 μg L⁻¹) and diniconazole in one grape sample (9.4 μg L⁻¹).     

Oxidative capacity and hemolytic activity of settled dust from moisture‐damaged schools

Exposure to moisture‐damaged indoor environments is associated with adverse respiratory health effects, but responsible factors remain unidentified. In order to explore possible mechanisms behind these effects, the oxidative capacity and hemolytic activity of settled dust samples (n = 25) collected from moisture‐damaged and non‐damaged schools in Spain, the Netherlands, and Finland were evaluated and matched against the microbial content of the sample. Oxidative capacity was determined with plasmid scission assay and hemolytic activity by assessing the damage to isolated human red blood cells. The microbial content of the samples was measured with quantitative PCR assays for selected microbial groups and by analyzing the cell wall markers ergosterol, muramic acid, endotoxins, and glucans. The moisture observations in the schools were associated with some of the microbial components in the dust, and microbial determinants grouped together increased the oxidative capacity. Oxidative capacity was also affected by particle concentration and country of origin. Two out of 14 studied dust samples from moisture‐damaged schools demonstrated some hemolytic activity. The results indicate that the microbial component connected with moisture damage is associated with increased oxidative stress and that hemolysis should be studied further as one possible mechanism contributing to the adverse health effects of moisture‐damaged buildings.     

Partial replacement of fat and salt in liver pâté by addition of Agaricus bisporus and Pleurotus ostreatus flour

The effect of incorporation of 7.5% (hydrated 50/50 w/w) and 10% (hydrated 70/30 w/w) of Agaricus bisporus (Ab) and Pleurotus ostreatus (Po) flours as partial replacers of fat and salts (sodium chloride and phosphates) on physicochemical properties, microbiological and sensory properties of pâté was studied during cold storage. Mushroom flours increased moisture, dietary fibre and protein contents improving the nutritional value of pâtés. Mushroom flour influenced the colour parameters, especially Ab, and gave harder pâtés in 10% mushroom flour addition. Sensorially, the odour and taste of 7.5% of mushroom flour were considered acceptable, and its addition hydrated in a ratio 50/50 w/w should be the most suitable to improve the nutritional value of this product without significantly affecting the sensory properties. The addition of Ab and Po flours was a feasible strategy to replace fat and salts in pâté.     

Characterisation,storage viabilit,and application of microspheres with Lactobacillus paracasei obtained by the extrusion technique

The objective of this study was to evaluate the influence of pH, bile salts and different storage conditions at two different temperatures (30 and 4 °C) on the viability of free and microencapsulated Lactobacillus paracasei. Microspheres encapsulating L. paracasei were obtained using an extrusion method. The efficiency was 87.6%, the diameter 70 µm and the zeta potential 7.22 ± 0.05 mV. Encapsulated L. paracasei showed higher resistance to stomach pH and bile salts compared to free cells. Microspheres were evaluated under four different storage conditions: fresh, suspended in a solution with a pH of 4, suspended in saline solution and lyophilised. The lyophilised microspheres presented the highest stability with 89.2% survival rate after six weeks of storage; however, free bacteria in saline solution (0.145 N) presented a 65.3% survival rate. Finally, a new product (a strawberry ice popsicle) with possible functional characteristics was obtained using microencapsulated L. paracasei.