Fast extraction methodologies for the determination of toxic arsenic in meat

A nonchromatographic analytical procedure has been developed for the determination of arsenic in meat samples including the major toxic arsenic species arsenite, arsenate, monomethylarsonic acid (MMA) and dimetylarsinic acid (DMA). The method is based on the extraction of arsenic species in mild conditions, selective trivalent hydride formation and final determination by hydride generation atomic fluorescence spectroscopy (HG‐AFS). Different extractant agents and two different procedures, microwave‐assisted extraction (MAE) and ultrasound assisted extraction at room temperature, were evaluated for As species extraction. The method provided a limit of detection of 0.013 ng mL^?1 and a mean relative standard deviation in actual samples of 0.3%. Data found for toxic As in meat samples varied from 0.42 ng g^?1 in chicken muscle to 68 ng g^?1 in pork liver. Percentage of toxic As respect to total As varied in the 9–46% range depending on the meat product.     

Influence of storage period and packaging method on sliced dry cured beef "Cecina de Leon": Effects on microbiological, physicochemical and sensory quality

Quality aspects of sliced dry-cured beef “Cecina de León” preserved in vacuum and gas mixtures (20%/80% CO₂/N₂ and 80%/20% CO₂/N₂) were studied. The evolution of microbiological, physicochemical and sensory parameters were analysed during storage (210 days) at 6 °C. Although microbial counts at 60 days of the gas-packaged samples were lower than the vacuum-packed ones, they were never higher than the spoilage limit (7 log ufc/g). A slight increase (p < 0.05) in pH was observed throughout storage of “Cecina de León” packaged under vacuum and in gas mixtures. However, a decrease (p < 0.05) in a_w was observed during storage of “Cecina de León” packaged under vacuum but a_w did not vary (p > 0.05) during storage in the gas-packaged samples. No changes were observed (p > 0.05) in lightness (L^*), redness (a^*) and yellowness (b^*) in vacuum and gas packaged samples during storage. However, sensorially evaluated colour showed lower values in gas packaged samples during 30 days storage. This difference was decisive in establishing the shelf-life of “Cecina de León” slices preserved in gas mixtures (20%/80% CO₂/N₂ and 80%/20% CO₂/N₂). Therefore, from a microbiological point of view, gas mixtures are more effective in extending the shelf-life of “Cecina de León” slices. It is concluded that vacuum packaging allows longer storage than gas-packaging as it maintains a good visual appearance of “Cecina de León”, the main parameter in consumers’ perception of meat quality.     

Influence of sepiolite on spherulite growth rate in polyvinylidene fluoride-based polyblends

This work reports on the effects exerted by polymethylmethacrylate, polystyrene and sepiolite on several factors which affect spherulite growth of polyvinylidene fluoride, such as growth rate, nucleation factor and nucleation density. Interpretation of the data obtained will support the discussion on miscibility of binary polyvinylidene fluoride/polymethylmethacrylate and poly-vinylidene fluoride/polystyrene, as well as the miscibilizing effect of sepiolite on both systems.     

Jasmonate in Lepidopteran Larvae

Jasmonic acid (JA) is a key molecule initiating plant defensive responses to herbivory. Our previous work has shown that this phytohormone is often present at high concentrations in eggs and neonates of lepidopteran species. In this work, we document the concentrations of JA found in various tissues of larval H. virescens fed on artificial diets with varying JA concentrations and on transgenic tobacco lines with different capabilities of producing JA. At high JA concentrations, excess jasmonate appeared to be voided in frass, but significant amounts were found in most larval tissues we analyzed as well as in regurgitant. At lower concentrations, caterpillars excreted less JA and appeared to accumulate relatively greater amounts of JA in their tissues. In both experiments, substantial amounts of JA were found in labial salivary glands, a notable result since JA is an important signaling molecule involved in the induction of plant defenses.     

Effect of Agglomerate Size Distribution on Loose Packing Fraction

Discrete element modeling was used to establish the effects of size distribution on loose packing fraction during the fall of 5000 to 10 000 agglomerates. Monosized distributions exhibited slightly lower packing fraction than narrow distributions. However, broad distributions always produced the lowest packing fraction. The application of radius ratio rules had an effect opposite to that intended. Smaller fines had a disproportionately large effect on packing fraction, an effect attributed to gaslike behavior. Gravity-driven random packing in ceramic agglomerates was governed by a combination of bridge formation and kinetic agglomerate–agglomerate interactions, not by geometric constraints.     

Synthesis and characterization of P-modified mesoporous CoMo/HMS–Ti catalysts

A hexagonal mesoporous siliceous material with a wormhole framework structure incorporating Ti (HMS-Ti; Si/Ti atomic ratio of 40) was modified with variable amounts of phosphorous and used as support for CoMo phases. The catalysts were prepared by successive impregnation, with Mo being introduced first. The supports and catalysts were characterized by N₂ adsorption–desorption, High-resolution transmission electron microscopy, X-ray diffraction, FT-IR study of the framework vibrations, DRIFT spectra in the OH region, ¹H NMR, FT-IR spectra of adsorbed NO, micro-Raman spectroscopy and X-ray photoelectron spectroscopy. The catalysts were tested in the reaction of hydrodesulfurization (HDS) of dibenzothiophene (DBT) and their activity compared with that of a commercial P-containing CoMo/γ-Al₂O₃ catalyst. The physical and chemical characterization of the P-modified HMS–Ti substrates shows that the presence of P₂O₅ on the support surface does not change its mesoporous character, but modifies its surface properties. In addition, characterization data of the oxide catalysts show that phosphate favors the dispersion of the active phases and increases the population of octahedral Co²⁺ ions associated to Mo species. As a result, HDS activity was strongly enhanced upon P-loading, which reached a maximum of 0.64 wt%. This catalyst is 3.7 times more active than the commercial one and 2.4 times more active than its P-free counterpart. The highest activity of this catalyst was explained in terms of the specific electronic properties of its active phases and the largest Mo surface exposure on the support.     

Development of the Multidimensional Acculturative Stress Inventory for adults of Mexican origin.

The Multidimensional Acculturative Stress Inventory (MASI), a 36-item stress measure that was developed to assess acculturative stress among persons of Mexican origin living in the United States, was tested on a community sample of 174 adults (117 women, 57 men). Principal-components analyses yielded 4 stable and internally consistent factors: Spanish Competency Pressures (7 items), English Competency Pressures (7 items), Pressure to Acculturate (7 items), and Pressure Against Acculturation (4 items). These 4 factors accounted for 64.4% of the variance and correlated in the expected directions with criterion measures of acculturation and/or psychological adjustment. Further reliability and validity testing of the MASI is discussed as well as the utility of this measure in assessing acculturative stress among adults of Mexican origin. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

A combined measure for quantifying and qualifying the topology preservation of growing self-organizing maps

The Self-Organizing Map (SOM) is a neural network model that performs an ordered projection of a high dimensional input space in a low-dimensional topological structure. The process in which such mapping is formed is defined by the SOM algorithm, which is a competitive, unsupervised and nonparametric method, since it does not make any assumption about the input data distribution. The feature maps provided by this algorithm have been successfully applied for vector quantization, clustering and high dimensional data visualization processes. However, the initialization of the network topology and the selection of the SOM training parameters are two difficult tasks caused by the unknown distribution of the input signals. A misconfiguration of these parameters can generate a feature map of low-quality, so it is necessary to have some measure of the degree of adaptation of the SOM network to the input data model. The topology preservation is the most common concept used to implement this measure. Several qualitative and quantitative methods have been proposed for measuring the degree of SOM topology preservation, particularly using Kohonen's model. In this work, two methods for measuring the topology preservation of the Growing Cell Structures (GCSs) model are proposed: the topographic function and the topology preserving map.