Garcia M.A.,University of Habana |
Perez L.,University of Habana |
De La Paz N.,Drugs Research and Development Center |
Gonzalez J.,Food Industry Research Institute |
And 2 more authors.
Materials Science and Engineering C
The present work aimed the influence of molecular weight (MW) reduction by irradiation with 60Co and polymer concentration on some physical properties of chitosan films. Irradiation of chitosan with a MW of 275.221 kDa and 74.74% of deacetylation degree was performed using a 60Co source to provide doses of 5, 10, 20 and 50 kGy to obtain chitosans with molecular weights of 247.847, 221.563, 126.469 and 77.063 kDa, respectively. Films were prepared via the solution casting method. Film-forming solutions (FFS) of chitosan irradiated or not, were prepared at 1.5 and 2% (w/v) in a solution of lactic acid at 1% (v/v) and 0.1% (v/v) of Tween 80. The FFS were poured into glass plates of 400 cm2 and dried at 60 °C during 10 h without airflow. The decrease of MW and increase of chitosan concentration increased the tensil strength and water vapor permeability while decreased the elongation at break of the films. The chitosan MW did not significantly influence (p > 0.05) the water solubility of films within a same polymer concentration. There was a decrease in the films' brightness with the increase of concentration and a decrease of the MW of irradiated chitosan, while the b∗values of films increased and there was an increasing tendency of their apparent opacity. © 2015 Elsevier B.V. All rights reserved. Source
Forster R.,Geneva Lab |
Margoto Rodriguez O.,Geneva Lab |
Margoto Rodriguez O.,University of Pinar del Rio |
Park W.,Geneva Lab |
And 9 more authors.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
We report the results of three MRPC detectors built with soda lime glass and tested in the T10 beam line at CERN. The detectors consist of a stack of 280 μm thick glass sheets with 6 gaps of 220μm. We built two identical MRPCs, except one had the edges of glass treated with resistive paint. A third detector was built with one HV electrode painted as strips. The detectors' efficiency and time resolution were studied at different particle flux in a pulsed beam environment. The results do not show any improvement with the painted edge technique at higher particle flux. We heated the MRPCs up to 40 °C to evaluate the influence of temperature in the rate capability. Results from this warming has indicated an improvement on the rate capability. The dark count rates show a significant dependence with the temperature. © 2016 Elsevier B.V. Source
Paredes M.,Sao Paulo State University |
Paredes M.,Center for Technological Applications and Nuclear Development |
Pulcinelli S.H.,Sao Paulo State University |
Peniche C.,University of Habana |
And 2 more authors.
Journal of Sol-Gel Science and Technology
The effect of chitosan addition on the structure and drug release properties of ureasil–polyethylene oxide (U–PEO) hybrid materials was examined. The hybrids and the blends were prepared by the sol–gel route and their structural features were characterized by infrared spectroscopy, differential scanning calorimetry, X-ray powder diffraction, and small angle X-ray scattering. The different characterization techniques revealed the formation of transparent, rubbery, flexible, water-insoluble, and low crystalline chitosan/(U–PEO hybrid) blends, which could easily dissolve pramoxine (used as a model drug). The results showed that the combined addition of chitosan and pramoxine improved the compatibility of the organic and inorganic components of the U–PEO matrix, and provided a means of tailoring the amount of drug released at steady state equilibrium. © 2014, Springer Science+Business Media New York. Source
Application of Cold Vapor-Atomic Absorption (CVAAS) Spectrophotometry and Inductively Coupled Plasma-Atomic Emission Spectrometry methods for cadmium, mercury and lead analyses of fish samples. Validation of the method of CVAAS
Fernandez Z.H.,Center for Technological Applications and Nuclear Development |
Valcarcel Rojas L.A.,Center for Technological Applications and Nuclear Development |
Alvarez A.M.,Center for Technological Applications and Nuclear Development |
Estevez Alvarez J.R.,Center for Technological Applications and Nuclear Development |
And 6 more authors.
This paper presents the results of the implementation and application of methods for cadmium (Cd), mercury (Hg) and lead (Pb) analyses in fish samples. The determination of elements by Inductively Coupled Plasma-Atomic Emission Spectrometry and Cold Vapor-Atomic Absorption Spectrophotometry (CVAAS) was carried out using calibration curves, prepared from certified stock standard solutions of the elements. A Certified Reference Material (DOLT-2) has been successfully analyzed with CVAAS method. Sample preparation was performed by microwave-assisted acid digestion using a mixture of HNO3, H2O2 concentrated for the determination of Hg and HNO3 with HClO4 for Pb and Cd analyses using platinum vessel for the digestion. Limits of detection and quantitation were at least a factor of ten and five below the Residual Maximum Limit, respectively, showing that the CVAAS technique is well suited for quantitation of elemental impurities of mercury. It was obtained a good linearity with a linear regression coefficients higher than 0.99. An acceptable reproducibility, repeatability and trueness were found, in agreement with "Harmonized guide of method validation and estimation of uncertainty calculation applied to determination of inorganic pollutants" that it was studied in the theoretical course of validation organized by the project RLA 5060, for the validation of CVAAS method in Hg analyses of fish samples. Mercury showed the higher values in fish samples analyzed, finding content below the permissible maximum limits established by the World Health Organization (less than 0.5μg/g fresh wet weight). © 2014 Elsevier Ltd. Source