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Abstract  

Sol-gel zirconia was characterized using high-resolution thermogravimetry (Hi-Res TG) and differential scanning calorimetry (DSC) and compared with X-ray diffraction, Raman scattering, and UV-Vis spectroscopy. ZrO2-x(OH)2x·yH2O annealed below 400°C show typical behavior of amorphous material. As the annealing temperature is increased, the tetragonal and monoclinic phases crystallize. Typical Hi-Res TG curve shows that the samples are continuously dehydrated in a long temperature range, between room temperature and 600°C. The total mass loss relative to the initial mass is of about 29%. The DSC analysis coupled with TG and structural information, indicate that the exothermic processes about 355 and 447°C can be related to the nucleation process of the formation of tetragonal zirconia, with bulk crystallization at 447°C.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: A. Montero Alvarez, J. R. Estévez Alvarez, H. Iglesias Brito, O. Pérez Arriba, D. López Sánchez, and H. T. Wolterbeek

Summary  

An epiphytic lichen (Physcia alba sp.) grown over Roystonea regia tree was used as biomonitor of air quality in the Havana City west side. During the survey, 81 sampling sites were selected according to traffic and industry conditions. The concentration for 14 elements (Mg, Al, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Cd and Pb) was determined by flame atomic absorption spectrometry (FAAS) and anodic stripping voltammetry (ASV). Contents of Cu, Zn, Cd and Pb obtained by both techniques were compared. Several biological reference materials (RM's) were analyzed in order to assure the quality of analytical results. Some pollution sources were identified using principal component analysis. A total of 5 factors were achieved, of which 4 could be interpreted in terms of anthropogenic pollution sources. However, the expected correlation between traffic influence and lead concentration in lichen could not be demonstrated. The factor values patterns are presented.

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

Abstract

The development of photopolymers was helped by the development of photocalorimetry, which is now a basic technique for the study of these materials. This work shows how to obtain vitrification times in single isothermal curing experiments by monitoring the reversing heat capacity along time in modulated temperature DSC–photocuring systems, overcoming the time-consuming problem of standard DSC. The effects of the light intensity and the isothermal curing temperature on the vitrification time of a photocurable system were evaluated. The results obtained at a given curing temperature with different light intensities indicate that the UV-light affects the molecular mobility hindering the vitrification process. The effects of the curing temperature on the vitrification time, the conversion at the vitrification time and the maximum conversion were also evaluated.

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Journal of Thermal Analysis and Calorimetry
Authors: W. Liu, S. Kim, J. Lopez, B. Hsiao, M. Keating, I.-H. Lee, B. Landes, and R. Stein

Abstract  

In this study, the stepwise isothermal crystallization or thermal fractionation of Ziegler—Natta and metallocene based polyethylenes (ZN-PE and m-PE) with two kinds of branch lengths (ethyl and hexyl) and branch compositions were studied using simultaneous synchrotron small-angle X-ray scattering (SAXS)/wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The crystal long period and the invariant were determined by SAXS, and the variations of crystal unit cell parameters and the degree of crystallinity were determined by WAXD. The arithmetic mean length (Ln), the weightedmean length (Lw) and the broadness index (Lw/Ln) of the studied polyethylenes were previously determined by DSC. Results from these studies were interpreted using the model of branch exclusion, which affects the ability of the chain-reentry into the crystal phase. Multiple SAXS peaks and step-change in crystallinity change (WAXD) were seen during heating, which corresponded well with the crystal thickness distribution induced by stepwise crystallization. The effects of the heterogeneity of the 1-olefin branch length and the distribution on the crystal long period and the invariant as well as the degree of crystallinity were discussed.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: G. Capote Rodriguez, R. Padilla Alvarez, G. Pérez Zayas, A. Hernández Rivero, M. López Reyes, S. Ribeiro Guevara, and J. Molina Insfrán

Abstract  

Thirty elements were determined by INAA in Cuban soil samples collected in 17 zones from western regions of Cuba, which were affected by neuropathy epidemic in 1992. The presence of toxic elements was evaluated to provide data for the analysis of possible paths of intoxication through local agriculture product consumption. The results obtained for As, Th and U are compared with similar data reported on literature.

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Acta Alimentaria
Authors: C. Cano-Molina, A. López-Fernández, N. Díaz-González, R. González-Barrio, N. Baenas, M.J. Periago, and F.J. García-Alonso

Abstract

Tomato is rich in different bioactive compounds, especially the carotenoid lycopene, which intake is associated with various health benefits. Post-harvest use of ultraviolet light (UV) and light-emitting diode (LED) has been shown to increase the concentration of tomato bioactive compounds. The aim of this study was to evaluate the effect of ultraviolet (A and C) and red-blue LED light on the concentration of carotenoids during a 7-days storage trial of mature green tomatoes. Exposure to combined UV and LED light nearly doubled the total carotenoid concentration and had no negative impact on sensory attributes.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: N. Alberro Macias, I. Pupo González, L. Valcárcel Rojas, D. Frías Fonseca, J. R. Estévez Álvarez, D. López Sánchez, A. Montero Álvarez, D. Simón Pérez, M. A. Isaac Tejera, and J. F. Pérez Oliva

Summary  

The quality of the potable and purified for haemodialysis waters used in the National Institute of Nephrology was evaluated since 2002 up to now. A total of 20 chemical components were analyzed. The analytical results were compared with the admissible maximum concentrations according to the Cuban Standard NC 92-02:85 for potable water and with the Spanish Standard UNE 111-301-90, related to the quality of water for use in haemodialysis. The quality of both types of water was found to comply with the Standards regulations. The CEADEN analytical chemistry laboratory operates a quality management system since 1992, that was credited according to ISO/IEC 17025 requirements.

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