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Pue., Mexico

Escobedo-Martinez C.,National Autonomous University of Mexico | Concepcion Lozada M.,Metropolitan Autonomous University | Hernandez-Ortega S.,National Autonomous University of Mexico | Villarreal M.L.,Autonomous University of the State of Morelos | And 3 more authors.
Magnetic Resonance in Chemistry | Year: 2012

From the stem bark of Mangifera indica, seven cycloartane-type secondary metabolites were isolated. Compound 1 has been isolated for the first time from M. indica, whereas compounds 2 (2a and 2b, as an epimeric mixture), 3, and 4 are new triterpenoid-type cycloartanes. Unambiguous 13C and 1H NMR assignments for these compounds and the known compounds mangiferonic acid (compound 5), isomangiferolic acid (compound 6), ambolic acid (compound 7), and friedelin (compound 8) are reported; the latter because full NMR data for these compounds are not available in the literature. © 2012 John Wiley & Sons, Ltd. Source

Serkin V.N.,Institute Ciencias | Belyaeva T.L.,National Autonomous University of Mexico
Journal of Modern Optics | Year: 2010

The fundamental concept of colored nonautonomous solitons in nonlinear and dispersive nonautonomous physical systems is introduced. Novel soliton solutions for the nonautonomous nonlinear Schrodinger equation models with linear and harmonic oscillator potentials substantially extend the concept of classical solitons and generalize it to the plethora of nonautonomous solitons that interact elastically and generally move with varying amplitudes, speeds and spectra adapted both to the external potentials and to the dispersion and nonlinearity variations. The parallels between nonlinear guided wave phenomena in optics and nonlinear guided wave phenomena in Bose condensates are clearly demonstrated by considering optical and matter wave soliton dynamics in the framework of nonautonomous evolution equations. The exact analytical solutions and numerical experiments reveal many specific features of nonautonomous solitons. Fundamental laws of the soliton adaptation to the external potentials are derived. Bound states of colored nonautonomous solitons are studied in detail and a comparison of the canonical Satsuma-Yajima breather dynamics with a nonautonomous 'agitated' breather is presented. The nonautonomous soliton concept can be applied to different physical systems, from hydrodynamics and plasma physics to nonlinear optics and matter waves, and offer many opportunities for further scientific studies © 2010 Taylor & Francis. Source

Prutskij T.,Institute Ciencias | Pelosi C.,CNR Institute of Materials for Electronics and Magnetism
Crystal Research and Technology | Year: 2010

The temperature behavior of the integrated intensity of photoluminescence (PL) emission from ordered GaInP2 epitaxial layer was measured at temperatures of 10 - 300 K. Within this temperature range the PL emission is dominated by band-to-band radiative recombination. The PL intensity temperature dependence has two regions: at low temperatures it quenches rapidly as the temperature increases, and above 100 K it reduces slowly. This temperature behavior is compared with that of disordered GaInP2 layer. The specter of the PL emission of the disordered layer has two peaks, which are identified as due to donor-accepter (D-A) and band-to-band recombination. The PL intensity quenching of these spectral bands is very different: With increasing temperature, the D-A peak intensity remains almost unchanged at low temperatures and then decreases at a higher rate. The intensity of the band-to-band recombination peak decays gradually, having a higher rate at low temperatures than at higher temperatures. Comparing these temperature dependencies of these PL peaks of ordered and disordered alloys and the temperature behavior of their full width at half maximum (FWHM), we conclude that the different morphology of these alloys causes their different temperature behavior. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA. Source

Mendoza C.,Institute Ciencias | Bernes S.,National Autonomous University of Mexico | Torrens H.,Dep | Arroyo M.,Institute Ciencias
Organometallics | Year: 2010

Thermolysis reactions of [Os(SC6F5) 4(P(C6H4X-4)3)] (X = CF3 1, Cl 2, F 3, H 4, CH3 5, and OCH3 6) in refluxing toluene yield compounds [OsF(SC6F5)2(SC 6F4(SC6F5)-2)(P(C6H 4X-4)3)] (1a-6a) and [Os(SC6F5) 2(SC6F4(SC6F5)-2)(C 6H4X-4)] (1b-6b). In addition, [Os(SC6F 5)3(SC6F4(SC6F 5)-2)] (c) is yielded from 1-4 and 6, compounds [OsF(SC 6F5)3(P(C6H4X-4) 3)] [X = CF3 (1e), X = Cl (2e)] are also identified as products of the thermolysis reactions of 1 and 2, while [Os(SC6F 5)2(S2C6F4)(P(C 6H4CH3-4)3)] (5d) is obtained from 5. Compounds c, e, and d are produced in low yields (ca. 2-4%). Formation of all products involves the rupture of ortho C-F bonds. The first complexes systematically detected in these thermolysis reactions are compounds a, which are isomers of the starting complexes. Thus, the C-F activation involves the metal-mediated generation of the covalent Os-F bond. Single-crystal X-ray diffraction studies of the new compounds 4a, 5a, 2b-6b, 2e, and 5d indicate that these compounds consist of five-coordinated metal ions in essentially trigonal-bipyramidal geometries. In addition, thermolysis of the isolated compound [OsF(SC6F5)2(SC6F 4(SC6F5)-2)(P(C6H4CH 3-4)3)] (5a) in refluxing toluene gives rise to [Os(SC6F5)2(SC6F4(SC 6F5)-2)(C6H4CH3-4)] (5b) and [Os(SC6F5)2(S2C 6F4)(P(C6H4CH3-4) 3)] (5d), confirming that compounds a can generate compounds b when the thermolysis is prolonged. Compounds 1a-6a, 2b-6b, 1e, and 2e are investigated in solution by NMR studies, including variable-temperature 19F NMR experiments. These molecules are fluxional. Some of the activation parameters for the dynamic processes are determined. © 2010 American Chemical Society. Source

Romano-Trujillo R.,Institute Ciencias | Rosendo E.,Institute Ciencias | Ortega M.,National Polytechnic Institute of Mexico | Morales-Sanchez A.,CIMAV | And 6 more authors.
Nanotechnology | Year: 2012

Lead selenide nanoparticles (PbSe NPs) have been obtained through an easy and low cost route using colloidal synthesis in aqueous solution. The synthesis was carried out at room temperature using Extran (Na 5P 3O 10, NaOH and H 2O) as surfactant. Hydrochloric acid (HCl) was used to eliminate the generated by-products. The size of PbSe NPs was varied by changing the Pb:Se molar concentration. The PbSe NPs were characterized by powder x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDAX), high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. The XRD measurements showed that the PbSe NPs have the face-centered cubic phase structure. The crystal size was found to be between 14 and 20nm as calculated from the XRD patterns and these values were corroborated with SEM and TEM. Additionally, HRTEM micrographs showed crystalline planes at (200), (220) and (111) of the PbSe NPs, in agreement with the XRD results. © 2012 IOP Publishing Ltd. Source

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