Nuevas vistas y visitas al estridentismo

Los textos que integran este libro tienen en común el interés por instaurar el diálogo en el tiempo y en la diversidad sobre las expresiones literarias y artísticas del México de la primera mitad del siglo xx. Es una realidad que el estridentismo regresa con ímpetu, y en él el lector y el crítico pueden leer a detalle los nuevos significados con los que se nos presenta la vieja vanguardia mexicana a la luz de los estudios literarios. Los autores aquí glosados son un claro ejemplo de cómo la investigación académica ha emprendido la reinterpretación de los signos y de los usos de una generación de artistas que sorprendió por la pluralidad de su discurso, por la naturalidad de su expresión artística.Universidad Autónoma del Estado de Méxic

Использование ассоциативного метода поиска слов в процессе дистанционного обучения

Two high-capacity thiol functionalized adsorbents are prepared, using sol-gel processing, and applied to the removal of lead(II) from aqueous streams. The first adsorbent (SN) is prepared by co-condensing oligomers of tetraethoxysilane (TEOS) and 3-mercaptopropyltrimethoxysilane (MPS); the second adsorbent (MI) is synthesized by a combined co-condensation/molecular imprinting route of TEOS and MPS. The resulting physicochemical properties of adsorbents are investigated by nitrogen sorption measurements, elemental analysis, Fourier transform infrared spectroscopy (FTIR), solid-state 13C and 29Si crosspolarization magic angle spinning nuclear magnetic resonance (13C and 29Si CPMAS NMR, respectively), and X-ray photoelectron spectroscopy (XPS). The adsorbents exhibit high ligand densities (1.19 mmol/g for SN and 1.03 mmol/g for MI), improved Brunauer-Emmett-Teller (BET) surface areas (SBET ) 129 m 2/g for SN and 464 m2/g for MI), and highly developed mesoporosity (Dp ) 15.1 nm for SN and 8.3 nm for MI). 29Si CPMAS NMR measurements indicate that the silicon oxide solid structure of adsorbents is not modified by lead adsorption. XPS results indicate the presence of lead acetate species on the surface of adsorbents. Batch adsorption data are explained by a mechanism in which a hydrated species (Pb(OOCCH 3)(H2O)5 +) forms a monodentate complex with thiol surface groups. Further characterization of the adsorbents shows rapid adsorption kinetics and equilibrium lead(II) adsorption capacities of 1.13 and 0.715 mmol/g for SN and MI. Lead adsorption dynamics in a packed column indicates high lead uptakes (155 and 80 mg Pb/g-adsorbent for SN and MI, respectively). Combined and simple sol-gel synthesis routes for preparation of adsorbents with high ligand densities and mesoporous structures are demonstrated here. © 2009 American Chemical Society

Cationic imprinting of Pb(II) within composite networks based on bovine or fish chondroitin sulfate

9 pages, 4 tables, 5 figuresImprinting chondroitin sulfate (CS)/silica composites with Pb(II) and Cu(II) cations wasexplored with CS of bovine and different fish species origin. The process was based onthe assumption that particular arrangements of the linear CS chains in aqueous solution,induced so as to accommodate cross complexation with the cations, would be embodied intoa tridimensional matrix created through an organoalkoxysilane sol‐gel scheme. The presenceof Cu(II) in the synthesis of the composites did not result in the production of significantlystronger Cu(II)‐oriented binding arrangements, and therefore, the imprinting was not success-ful. Inversely, for Pb(II), the materials obtained exhibited a“memory”effect for the Pb(II) ions,expressed in the observation of stronger (13%‐44%) binding as compared to thenonimprinted counterparts, and increased selectivity (1.5‐2 folds) against Cd(II). The imprint-ing features observed were dependent on the CS source. However, it was not possible toidentify, among a set of their properties (carboxylate and sulfate abundance, percent ofdisulfated units, 4S/6S ratio, and molecular weight), any that correlated directly with theobserved imprinting features. The augmented selectivity provided by the cation‐imprintingprocess may be advantageous in areas such as analytical separation, remediation, purification,sensing, and others, particularly in those cases where a certain cation is of special interestwithin a mixture of them.FEDER/COMPETE and FCT, Grant/Award Number: Pest‐C/QUI/UI0081/2013.Programa de Cooperação Transfronteiriça Espanha‐Portugal, Grant/Award Number: 0687‐Novomar1-P.Peer reviewe