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Acta Alimentaria
Authors: M. Reiter, H. Volkmann, U. Imianovsky, M. Lopez, L. Medina, and R. Jordano

The incidence of Listeria monocytogenes in refrigerated and frozen chicken parts was investigated, using the Mini-Vidas™ system (bioMérieux). Two hundred and eigthy chicken parts were tested: 40 skin samples from the breast and leg, 120 samples from refrigerated wings, breasts and legs and 120 samples from frozen wings, breasts and legs (40 of each). The 219 samples tested positive (78.21%). The parts with the highest incidence were frozen breasts (100%) and wings (95%). In frozen legs, the values were lower (60%). In refrigerated parts, the incidence was higher in breasts (85%) and in wings (80%). In legs samples, similarly to the frozen ones, the incidence was lower (50%). In the skin of the breasts and legs, the incidence was 77.50%. Statistical evaluation demonstrated that there are no differences between frozen breasts and wings but there are differences between similar refrigerated parts. The refrigerated and frozen legs are the only parts that are statistically equal. The percentages that were detected show the importance of requiring the absence of Listeria spp. in chickens.

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Calorimetric measurements of the heat of adsorption of CO2 on zeolites with variable content of mono- and divalent cations lead to common conclusions. High initial heats (up to 120 kJ·mol−1 for NaA), generally associated with a slow and activated rate of adsorption, are found for high contents of Na+, Li+ or Ca2+. They are attributed to a limited number of chemisorption sites (0.3 per α cage in NaA).

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The evolution in counts of yeasts from six lots of different dry-sausages produced in three European Union (EU) countries (France, Italy and Spain) is tested. Each lot was analyzed in three phases of their production: fresh product, first staged drying and final product. Three samples were analyzed in each test. Counts of yeasts during the ripening process showed an irregular evolution. Regarding the species isolated, the most frequent ones belonged to genera Candida (C. albicans, C. famata, C. guillermondii, C. krusei, C. parapsilosis, C. stellatoidea, C. zeylanoides.), Trichosporon (T. capitatum, T. beigelli), Rhodotorula and Geotrichum (G. candidum).

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Abstract  

The kinetics of a poly(methyl methacrylate) (PMMA)-modified epoxy resin cured with different functionalities amine mixtures was analyzed using differential scanning calorimetry (DSC) in both isothermal and dynamic conditions. A delay in the reaction rate was observed which increased with PMMA content. An approach of kinetic features involved in curing was carried out. A linear dependence of preexponential factors of neat systems with modifier content was considered. The approach shows the contribution of other factors including the dilution effect of the functional groups to the observed delay. Fourier transform infrared spectroscopy (FTIR) indicated a noticeable change in the interactions present in neat systems due to the presence of PMMA. On the other hand, a significant influence of the ratio between each amine in the epoxy/amine mixtures on the final physical appearance was observed. At constant curing conditions, materials from completely opaque (phase separated) to transparent (miscible) were obtained with the increase in monoamine content.

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Journal of Thermal Analysis and Calorimetry
Authors: J. Pascual, F. Corpas, J. López-Beceiro, M. Benítez-Guerrero, and R. Artiaga

Abstract  

A Spanish red mud was thermally characterized. Chemical and mineralogical composition were determined by XRF and XRD.The thermal events observed in the range from room temperature to 1300°C were related to the sample composition. The first mass loss step was related to free water content, while many of the other processes were related to dehydration processes. It was found that most of the decomposition reactions of hydrohematite, ferrihydrite, aluminogoethite, boehmite, silicates and carbonates were strongly overlapping. It was also explained the formation of silicates and calcium titanate, which presence was confirmed at 1000°C by XRD.

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Abstract  

The catalytic behaviour of ceria, zirconia and ceria–zirconia mixed oxides in the temperature-programmed degradation of toluene and n-hexane was analysed by means of evolved gas analysis (mass spectrometry). Pure cerium oxide resulted the most active catalyst in the oxidation of both compounds. This fact revealed the crucial role of the surface oxygen species in the decomposition of this type of hydrocarbons. The low affinity of CeO2 for H2O and CO2, the major oxidation products, may be also responsible for the observed highly active catalytic behaviour.

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Journal of Thermal Analysis and Calorimetry
Authors: C. Gracia-Fernández, J. Tarrío-Saavedra, J. López-Beceiro, S. Gómez-Barreiro, S. Naya, and R. Artiaga

Abstract

The use of pressure cell attached to a temperature modulated differential scanning calorimeter (TMDSC) is investigated to perform modulated DSC experiments at high pressures (TMPDSC). No previous reports were found on the use of TMPDSC. In this study, the proposed method is applied to the study of the pressure effect on the curing reaction of an epoxy system. Curing quasi-isothermal modulated experiments were performed at different pressures to evaluate the vitrification time. Linear heating modulated tests were also successfully performed at different pressures to separate the reversing glass transition effect from the residual exothermic cure reaction. The curing enthalpy, conversion versus temperature, and glass transition of the fully cured thermoset were also evaluated. All the studied parameters resulted to be affected by the pressure in the range from atmospheric pressure to 35 bar. It was observed that the curing enthalpy, the reaction rate and the conversion at any given time increase with any pressure increment. The usefulness of TMDSC to characterize the curing of thermosets is extended by PTMDSC to situations, i.e., aeronautics industry, where pressure curing is needed.

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Abstract  

The objective of this study is to determine the influence of partial substitutions of Ti4+ by isovalent Hf4+ in the perovskite-type crystalline structure of PbTiO3. Different samples over the whole composition range (0 ≤ x≤1) in the PbTi1-xHfxO3 family have been prepared. Phase transitions have been determined by thermal analysis (differential scanning calorimeter: DSC) and complex impedance spectroscopy (IS) over a wide temperature range. As a consequence of the cation replacement the changes that take place in the different phase transition temperature are reported. By both techniques, thermal analysis and electrical characterization, it is shown that for all compositions prepared there is only one phase transition in a temperature range between 230 and 460 °C. With these results and the previously known crystalline structure of pure PbTiO3 and PbHfO3 perovskites, the phase diagram of the PbTi1-xHfxO3 family is presented including a morphotropic phase transition at x ~ 0.5.

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Abstract  

Obsidian samples from 13 Mexican quarries (Sierra de Pachuca and Zacualtipan, Hidalgo, Zaragoza and Oyameles, Puebla, Altotonga Veracruz and eight sites of the Zinaparo — Varal — Churintzio Hills region) have been analyzed by NAA. The concentration of 19 elements, major and trace, are reported. Excepting Altotonga Veracruz, the chemical composition of other obsidian flows was found homogenous. The region of the Varal obsidian was delimited. An excellent correlation between ytterbium and lutetium contents in obsidians was found.

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