Quito, Provincia de Pichincha, Ecuador

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    ABSTRACT: Stingless bee honey samples from west Amazonian Ecuador were studied for their physiochemical, chemical and functional properties. Reducing sugars (44.9 ± 5.72 g/100 g), water (34.1 ± 4.34 g/100 g), free acidity (31.8 ± 4.05 meq/100 g), diastase activity (1.60 ± 0.20 u.d./g), hydroxymethylfurfural (15.0 ± 1.91 mg/kg), electrical conductivity (0.48 ± 0.06 mS/cm), ash (0.28 ± 0.04 g/100 g), colour (150 mm Pfund) were determined as physicochemical parameters. Melissopalynological analyses were processed evidencing pollen belonging to 14 plant families. Glucose (25.5 ± 3.41 g/100 g), fructose (25.2 ± 3.37 g/100 g) and sucrose (3.72 ± 0.49 g/100 g) contents were determined by HPLC, evidencing equal concentrations between fructose and glucose. Coumarins and flavonoids were determined by densitometric HPTLC: fraxin and bergamotin (0.065 ± 0.009; 0.035 ± 0.005 μg/g) among coumarins; luteolin (0.045 ± 0.006 μg/g), quercitrin (0.020 ± 0.003 μg/g), isoramnetin (0.015 ± 0.002 μg/g) among flavonoids. Among the vitamin E isomers, evaluated by HPLC, the occurrence of the only β-tocopherol (1.12 ± 0.15 μg/g) was noted. All these results were compared with those acquired for two multifloral Apis mellifera honeys. DPPH and β-carotene bleaching tests were performed, showing interesting values for Ecuadorian honey samples, higher than those shown by multifloral A. mellifera honeys (88.1 ± 11.1 DPPH inhibition%; 70.8 ± 8.90 β-carotene inhibition%). Antibacterial activity, against both Gram positive and Gram negative bacteria, revealed MIC values (10–50 μg/ml) always lower than those of A. mellifera honeys. Ecuadorian Meliponinae honey samples also showed anti-mutagenic activity assayed with Saccharomyces cerevisiae D7 strain, inhibiting back mutation over the entire range of concentrations.
    Food Chemistry 06/2009; 114(4):1413-1420. DOI:10.1016/j.foodchem.2008.11.023
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    ABSTRACT: Structural and electronic properties of technologically important lead–zirconate–titanate (PZT) crystals produced by Nb-doping are reported. The results are obtained using semi-empirical quantum–chemical simulations applied to a tetragonal PbZr0.53Ti0.47O3 monocrystal, i.e. the morphotropic phase boundary of the PZT. The proposed concentration of Nb impurity is 1.5%, which, according to some experimental data, gives better piezoelectric properties of the material at this concentration. Analysis of the displacements of atoms surrounding the defect, changes in atomic charges and electronic properties explaining the augmentation of electric conductivity are given in light of the available experimental data. The results suggest the occurrence of free electrons in the conduction band of the material. The former observation might explain the formation of conducting Jahn–Teller (JT) electron polarons previously found in the other titanates.
    Philosophical Magazine A 08/2007; 87(24-24):3545-3554. DOI:10.1080/14786430701344566
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    ABSTRACT: Investigation of an oxygen vacancy and F center in the cubic and tetragonal lattices of PbTiO3 crystals is done by means of quantum-chemical simulations. Displacements of defect-surrounding atoms, electronic and optical properties, lattice relaxation energies and some new effects due to the defects presence are reported and analyzed. A comparison with similar studies is made and conclusions are drawn on the basis of the obtained results.
    Physica B Condensed Matter 05/2006; 381(1-2):82-89. DOI:10.1016/j.physb.2005.12.257


  • Address
    Av. 12 de Octubre N24-22 y Wilson, Quito, Provincia de Pichincha, Ecuador
  • Head of Institution
    P. Javier Herrán
  • Website
  • Phone
    593 72862213
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