Kaolinitic calcined clays: Factors affecting its performance as pozzolans

Five natural kaolinitic clays from different regions of Argentine, with different kaolinite content, different impurities and different degree of crystallinity were calcined in a fixed-bed electrical furnace at 700 °C. Clays were characterized by X-ray diffraction (XRD) and Fourier transformed infra-red spectrometry (FTIR) that provides an index about the order/disorder of the structure. After heat treatment, the structural changes were characterized by XRD and FTIR, and pore size distribution and specific surface were determined. Their pozzolanic activity was evaluated with the Frattini test, electrical conductivity in saturated Ca(OH)₂ solution and compressive strength on mortars at 7, 28 and 90 days. Among tested clays, four of them can be classified as pozzolan by the Frattini test. The pozzolanic activity of the natural clays showed good correlation with the content of kaolinite, the inversed of structure order determined by FTIR, and the specific surface of calcined clays. This study confirms that natural clays other than pure kaolinite can be interesting pozzolanic materials when thermally activated.     

Correlating indoor and outdoor temperature and humidity in a sample of buildings in tropical climates

The incidence of several respiratory viral infections has been shown to be related to climate. Because humans spend most of their time indoors, measures of indoor climate, rather than outdoor climate, may be better predictors of disease incidence and transmission. Therefore, understanding the relationship between indoor and outdoor climate will help illuminate their influence on the seasonality of diseases caused by respiratory viruses. Indoor-outdoor relationships between temperature and humidity have been documented in temperate regions, but little information is available for tropical regions, where seasonal patterns of respiratory viral diseases differ. We have examined indoor-outdoor correlations of temperature, relative humidity (RH), and absolute humidity (AH) over a 1-year period in each of seven tropical cities. Across all cities, the average monthly indoor temperature was 25 ± 3°C (mean ± standard deviation) with a range of 20–30°C. The average monthly indoor RH was 66 ± 9% with a range of 50–78%, and the average monthly indoor AH was 15 ± 3 g/m³ with a range of 10–23 g/m³. Indoor AH and RH were linearly correlated with outdoor AH when the air conditioning (AC) was off, suggesting that outdoor AH may be a good proxy of indoor humidity in the absence of AC. All indoor measurements were more strongly correlated with outdoor measurements as distance from the equator increased. Such correlations were weaker during the wet season, especially when AC was in operation. These correlations will provide insight for assessing the seasonality of respiratory viral infections using outdoor climate data, which is more widely available than indoor data, even though transmission of these diseases mainly occurs indoors.     

Ascorbic Acid Retention, Microbial Growth, and Sensory Acceptability of Lettuce Leaves Subjected to Mild Heat Shocks

Heat shocks not only produced a reduction in the initial content of ascorbic acid but also affected the rate of degradation of ascorbic acid during refrigerated storage. Samples treated at higher temperatures presented faster rates of degradation. The heat shocks produced an initial reduction in the counts of mesophilic aerobic microorganisms, with greater reductions associated with the higher shock temperatures. However, high shock temperatures promoted faster microbial growths during storage, probably due to the liberation of nutrients by the disruption of membrane barriers. The sensory attributes of lettuce leaves subjected to heat shocks presented mixed results. Thermal treatments affected the enzymatic activity, reducing browning phenomena, but also caused deleterious effects on surface color and texture of lettuce leaves. Heat shocks of 50°C could be useful for short‐term preservation of minimally processed lettuce, where the high rate of metabolic processes cause great deterioration of fresh products.     

Outdoor Measurements of Leaf Water Content Using THz Quasi Time-Domain Spectroscopy

We report the first outdoor measurements for continuous in vivo leaf-water monitoring using THz spectroscopy. For this, we have developed a compact and portable THz quasi time-domain spectrometer which can be powered by a battery. We monitor the water status of a corn plant (Zea mays) and discuss the influence of the day-night variations of the outdoor temperature.     

An empirical analysis of ontology-based query expansion for learning resource searches using MERLOT and the Gene ontology

This paper proposes an expansion of queries based on formal domain ontologies in the context of the search for learning resources in repositories. The expansion process uses the relation types that are represented in these models; common ontological relations, and ontological relations specific to domain and traditional terminology relations, typical of thesauri. The tests were conducted using Gene ontology as the knowledge base and MERLOT is used as the test repository. The results of this study case indicate that, at similar levels of precision, expanded queries improve levels of novelty and coverage compared to the original query (without expansion), i.e. expanded queries allow the user to retrieve relevant objects, which might not be obtained without expansion.     

Use of different morphological techniques to analyze the cellular composition of the adult zebrafish optic tectum

Cellular composition of the adult zebrafish (Danio rerio) optic tectal cortex was examined in this study. Morphological techniques such as 1 μm thick serial plastic sections stained with osmium tetroxide and toluidine blue, modified rapid Golgi silver impregnation, GFAP immunohistochemistry, confocal microscopy, as well as scanning and transmission electron microscopy were used. Neuronal and glial components are described and the layers of the cortex are revisited. Specific neuronal arrangements as well as unique glial/ependymal cells are described. A three dimensional rendering of the astrocytic fiber arrangement in the marginal zone is presented and a composite drawing summarizes the cellular composition of the optic tectum.     

Presence of Escherichia coli O157:H7, Listeria monocytogenes and Salmonella spp. in food from animal origin in Costa Rica

The presence of Escherichia coli O157:H7, Listeria monocytogenes and Salmonella spp was analyzed in two kinds of food from animal origin in Costa Rica. 100 samples of non pasteurized milk, from the principal producing zones of the country, and 100 samples of chicken giblets, purchased in retail markets, were analyzed according to the methodology described by Food and Drug Administration, 1995. Escherichia coli O157:H7 was analyzed in both kinds of food, while L. monocytogenes was evaluated in raw milk and Salmonella spp. in chicken giblets. Five strains of E. coli O157:H7 were isolated, three of them coming from chicken giblets and the other two from raw milk. 15% positivity for Salmonella spp. was found in chicken giblet samples and 3% positivity for L. monocytogenes in raw milk samples. The results obtained show the importance of the adequate processing of food from animal origin in order to decrease the potential transmission of pathogenic agents. The introduction of Hazard Analysis Critical Control Points system (HACCP) and Good Manufacturing practices in food industry keep on being the principal control measures and inocuity warranty.     

New backing layer for transdermal drug delivery systems: coatings based on fatty acid and beeswax on chitosan films

Fatty acids and beeswax are known to improve barrier properties of biodegradable materials. Thanks to their hydrophobic character, they can act as a barrier against water giving to the material more occlusive properties. This work was aimed at preparing fatty acid and beeswax coatings for a transdermal drug delivery system. In order to study occlusive properties of these coatings, water vapor permeability and contact angle measurements were carried out. The most homogeneous coatings were obtained from the beeswax mixture. Coatings made from emulsified beeswax exhibit high hydrophobic properties and relatively good mechanical properties compared to chitosan film without coatings.     

Obesity in Mexican school age children is associated with out of-home food consumption: in the journey from home to school

The objective of our study was to evaluate the association between consumption of food during the journey from home to school and back, with overweight and obesity, in a nationwide representative sample of school children. We assessed consumption outside the home in 9537 children, with information on availability and consumption of selected groups of food and beverages. Height, weight, total energy consumption, and sociodemographic variables were also obtained. We developed logistic regression models, and tested interactions with sociodemographic variables. The results of our study show that the prevalence of overweight and obesity was positively associated with dairy consumption in girls (OR:1.70; p = 0.01), as well as fried snacks consumption in school children living in Mexico City (OR: 1.68; p = 0.06). Consumption of fruits and vegetables in medium and high socioeconomic levels was negatively associated with the prevalence of overweight and obesity (OR: 0.54; p = 0.01 and 0.59; p = 0.07, respectively). We concluded that children during their stay away from home have a high availability of energy dense foods, which can influence their consumption and contribute to the development of overweight and obesity, so it is important to investigate this association in prospective studies.     

Structure and physical properties of nickel manganite NiMn2O4 obtained from nickel permanganate precursor

In this paper we present the structural, magnetic and dielectric properties of ceramic nickel manganite NiMn₂O_4+δ produced by using nickel permanganate Ni(MnO₄)₂xH₂O as a precursor. We have characterized the NiMn₂O_4+δ stoichiometry using quantitative energy-dispersive analysis of X-rays and thermal gravimetry under reducing conditions. Increased oxygen and Mn⁴⁺ contents were detected. X-ray diffraction and Rietveld refinement of X-ray data were carried out. Temperature dependent magnetization measurements were performed and the ferri-magnetic transition was identified at ≈100 K. The ferri-magnetic moment was found to be ≈1μ_B and hysteretic magnetization vs applied field curves were obtained. Dielectric properties were measured using impedance spectroscopy. Two dielectric relaxation processes were detected, which were associated with grain boundary and bulk contributions. The Arrhenius plots of resistivity and the temperature dependent dielectric permittivity were obtained for the two relaxations by means of an equivalent circuit model based on a series of two parallel RC elements.