Authors:R. Mercader, E. Baran, and A. López-García
The Mössbauer parameters of anhydrous monoclinic tin/II/ phosphate, Sn3/PO4/2, are reported and briefly discussed. The results agree with the interactions expected from the crystalline structure but differ from previously reported data.
Authors:M. López, L. M. Medina, R. Huerta, and R. Jordano
The aim of this work was to study in six different types of European dry-sausages (of the Mediterranean area) the ocurrence of contaminant biota: enterobacteria, coliforms, E. coli, enterococci, sulphite-reducing clostridia, Salmonella-Shigella and Listeria monocytogenes, in the course of the ripening process. A total of 162 samples were analysed at different stages of the elaboration process. These were grouped in eighteen lots, three for each type of dry-sausages. Throughout the ripening process a decrease in some microbe groups (enterobacteria, coliforms, E. coli) occurred in all cases. Yeasts and enterococci remained the same or even increased in number. We have also confirmed the presence of Salmonella, sulphite-reducing clostridia and Listeria in some samples of unripened product. Consequently, an improvement could be desirable in the hygienic quality of the raw material of dry-sausages. Nevertheless, the final products analysed showed an acceptable state of food safety in all cases.
Authors:R. López-Valenzuela, J. López-Palacios, M. Jiménez-Reyes, G. Cataño, and D. Tenorio
Thirteen Teotihuacan-style ornaments of an incense burner were studied. Ceramic pastes, pigments and mica were analyzed by
neutron activation, X-ray diffraction and scanning electron microscopy. Elemental (Sc, Cr, Fe, Co, Rb, Cs, La, Ce, Nd, Sm,
Eu, Tb, Yb, Lu, Hf, Th and U) and statistical analyses of ceramic-body data showed that these pieces were made from the same
raw material, which is chemically different from the fine orange ceramic of Teotihuacan. Montmorillonite and the classical
components of sand were the minerals identified in the ceramic pastes. The white pigment contained calcium, titanium and aluminium,
the yellow pigment was ocher, and the red pigment was a mixture of red ocher and cinnabar, the binder of the pigments being
clay. Exoskeletons of diatoms and locust ootecs were found in the pigments. Mica was identified as biotite, identical with
that coming from Monte Alban Oaxaca. We wish to undertake a historical reconstrution of these ornaments based on archaeometric
and literature data.
Authors:A. Montero, J. Estévez, R. Padilla, and D. López
A study was carried out in Havana City using lichen as monitor of air pollution. The concentration of several trace elements
(Ca, Mn, Fe, Ni, Cu, Zn, Sr, Cd, Pb) in a total of 225 samples was determined by Total Reflection X Ray Fluorescence (TRXRF),
Flame Atomic Absorption Spectroscopy (FAAS) and Anodic Stripping Voltammetry (ASV). In addition several Biological Certified
Reference Materials (CRM’s) were analyzed in order to assess the analytical performance of the results. In general a relatively
good agreement was found among the techniques. No significant differences were found between the obtained results and the
certified reference values.
Authors:J. C. Sari, R. Gilli, C. Lopez, and C. Briand
Direct microcalorimetric measurements allow determination of both the δH and association constant of biological complexes ifKa value does not exceed 106M−1. For higherKa values, δH can obviously be determined; this paper describes an original microcalorimetric method that permits determination of such high association constants. This method is based on the analysis of the competitive effect between two ligands having the same binding site in their receptor. As an example, the affinity constant for thymidylate synthase of a novel antifolate, CB 3717. was found to be 1.4 · 107M−1 using methotrexate polyglutamate MTX-G2 (Ka=2.3·105M−1) as competitor.
Authors:V. González-González, R. O. Valero-Coss, and E. Campos-López
The thermal behaviour of Jojoba (Simmondsia chinensis) liquid wax was studied by differential scanning calorimetry (DSC), varying the annealing conditions. The fusion enthalpy (ΔHf) of the unannealed material was 27.1 cal/g; the relationship between heat capacity (Cp) and temperature could be expressed by the following equation:Cp=9.51×10−4 T+0.129. It was found that Jojoba wax presents four endothermic transitions (α, β, γ andδ) including fusionα, estimable at low heating rates (1 K/min); the activation energies (Ea) for transitionsα andγ were 51.18 and 64.82 Kcal/mole respectively; and it was observed that the transition temperaturesα andγ maintained a lineal relationship with the square root of the heating rate (Hr).
Authors:J. I. Gutiérrez-Ortiz, B. de Rivas, R. López-Fonseca, and J. R. González-Velasco
Summary The catalytic properties of ceria-zirconia mixed oxides have been characterized using temperature-programmed techniques such as temperature-programmed desorption of ammonia and water, and temperature-programmed reduction with hydrogen. The acidity and hydrophobicity of these materials increased with zirconia content while the reducibility was maximum for Ce0.5Zr0.5O2 sample.
Authors:R. López-Fonseca, I. Landa, M. A. Gutiérrez-Ortiz, and J. R. González-Velasco
Summary Non-isothermal thermogravimetric data were used to evaluate the Arrhenius parameters (activation energy and the pre-exponential factor) of the combustion of two carbonaceous materials, selected as diesel soot surrogates. The paper reports on the application of model-free isoconversional methods (Flynn-Wall-Ozawa and Kissinger methods) for evaluating the activation energy of the combustion process. On the other hand, by means of the compensation relation between E and lnA, which was established by the model-dependent Coats-Redfern method, the value of the pre-exponential factor was estimated from the known value of the model-independent activation energy.
Authors:E. Herrera Peraza, O. Rizo, M. Montero Cabrera, A. Hernández, R. Folgar, M. Cabrera, O. Aguilar, M. Guevara, I. Pellon, R. López Duménigo, G. González, and M. López Reyes
This paper explains chronologically the implementation of thek0-standardization and other parametric methods in Cuba. Fundamental and applied results in the determination of the most important
parameters are obtained, using the IBR-2 at Dubna and Triga Mark III at Mexico reactor facilities. Some modifications in the
Stoughton-Halpering convention, and its comparison with the modified Westcott and Høgdahl method are presented. The application
of the described methods at the CS-ISCTN low flux facility, using the big samples techniques, is presented.