Sub-nanometre metal clusters for catalytic carbon-carbon and carbon-heteroatom cross-coupling reactions

[EN] Catalytic cross-coupling reactions are fundamental transformations in modern organic synthesis. Traditionally based on single-atom transition metal complex catalysts, the use of sub-nanometre metal clusters with enhanced redox and coordinating properties may lead to more efficient catalysts. Recent developments and potential new directions of catalytic sub-nanometre metal clusters for cross-coupling reactions are briefly discussed hereFinancial support by the "Severo Ochoa" program, the RETOS program (CTQ2014-55178-R) and the Ramon y Cajal Program by MINECO (Spain), and also by "Convocatoria 2014 de Ayudas Fundacion BBVA a Investigadores y Creadores Culturales" is acknowledged.Leyva Perez, A. (2017). Sub-nanometre metal clusters for catalytic carbon-carbon and carbon-heteroatom cross-coupling reactions. Dalton Transactions. 46(46):15987-15990. https://doi.org/10.1039/c7dt03203jS15987159904646Phan, N. T. S., Van Der Sluys, M., & Jones, C. W. (2006). On the Nature of the Active Species in Palladium Catalyzed Mizoroki–Heck and Suzuki–Miyaura Couplings – Homogeneous or Heterogeneous Catalysis, A Critical Review. Advanced Synthesis & Catalysis, 348(6), 609-679. doi:10.1002/adsc.200505473Martin, R., & Buchwald, S. L. (2008). Palladium-Catalyzed Suzuki−Miyaura Cross-Coupling Reactions Employing Dialkylbiaryl Phosphine Ligands. Accounts of Chemical Research, 41(11), 1461-1473. doi:10.1021/ar800036sWu, X.-F., Anbarasan, P., Neumann, H., & Beller, M. (2010). From Noble Metal to Nobel Prize: Palladium-Catalyzed Coupling Reactions as Key Methods in Organic Synthesis. Angewandte Chemie International Edition, 49(48), 9047-9050. doi:10.1002/anie.201006374Li, G., & Jin, R. (2013). Catalysis by gold nanoparticles: carbon-carbon coupling reactions. Nanotechnology Reviews, 2(5), 529-545. doi:10.1515/ntrev-2013-0020Corma, A., Juárez, R., Boronat, M., Sánchez, F., Iglesias, M., & García, H. (2011). Gold catalyzes the Sonogashira coupling reaction without the requirement of palladium impurities. Chem. Commun., 47(5), 1446-1448. doi:10.1039/c0cc04564kOliver-Meseguer, J., Dominguez, I., Gavara, R., Leyva-Pérez, A., & Corma, A. (2017). Disassembling Metal Nanocrystallites into Sub-nanometric Clusters and Low-faceted Nanoparticles for Multisite Catalytic Reactions. ChemCatChem, 9(8), 1429-1435. doi:10.1002/cctc.201700037Leyva-Pérez, A., Oliver-Meseguer, J., Rubio-Marqués, P., & Corma, A. (2013). Water-Stabilized Three- and Four-Atom Palladium Clusters as Highly Active Catalytic Species in Ligand-Free CC Cross-Coupling Reactions. Angewandte Chemie International Edition, 52(44), 11554-11559. doi:10.1002/anie.201303188Oliver-Messeguer, J., Liu, L., García-García, S., Canós-Giménez, C., Domínguez, I., Gavara, R., … Corma, A. (2015). Stabilized Naked Sub-nanometric Cu Clusters within a Polymeric Film Catalyze C–N, C–C, C–O, C–S, and C–P Bond-Forming Reactions. Journal of the American Chemical Society, 137(11), 3894-3900. doi:10.1021/jacs.5b00222Surry, D. S., & Buchwald, S. L. (2011). Dialkylbiaryl phosphines in Pd-catalyzed amination: a user’s guide. Chem. Sci., 2(1), 27-50. doi:10.1039/c0sc00331jTkatchouk, E., Mankad, N. P., Benitez, D., Goddard, W. A., & Toste, F. D. (2011). Two Metals Are Better Than One in the Gold Catalyzed Oxidative Heteroarylation of Alkenes. Journal of the American Chemical Society, 133(36), 14293-14300. doi:10.1021/ja2012627Wolf, W. J., Winston, M. S., & Toste, F. D. (2013). Exceptionally fast carbon–carbon bond reductive elimination from gold(III). Nature Chemistry, 6(2), 159-164. doi:10.1038/nchem.1822Leyva-Pérez, A., Doménech-Carbó, A., & Corma, A. (2015). Unique distal size selectivity with a digold catalyst during alkyne homocoupling. Nature Communications, 6(1). doi:10.1038/ncomms7703Boronat, M., Laursen, S., Leyva-Pérez, A., Oliver-Meseguer, J., Combita, D., & Corma, A. (2014). Partially oxidized gold nanoparticles: A catalytic base-free system for the aerobic homocoupling of alkynes. Journal of Catalysis, 315, 6-14. doi:10.1016/j.jcat.2014.04.003Izawa, Y., & Stahl, S. S. (2010). Aerobic Oxidative Coupling of o-Xylene: Discovery of 2-Fluoropyridine as a Ligand to Support Selective Pd-Catalyzed CH Functionalization. Advanced Synthesis & Catalysis, 352(18), 3223-3229. doi:10.1002/adsc.201000771Wang, D., Izawa, Y., & Stahl, S. S. (2014). Pd-Catalyzed Aerobic Oxidative Coupling of Arenes: Evidence for Transmetalation between Two Pd(II)-Aryl Intermediates. Journal of the American Chemical Society, 136(28), 9914-9917. doi:10.1021/ja505405uSerna, P., & Corma, A. (2014). Towards a Zero-Waste Oxidative Coupling of Nonactivated Aromatics by Supported Gold Nanoparticles. ChemSusChem, 7(8), 2136-2139. doi:10.1002/cssc.201402061Kashin, A. S., & Ananikov, V. P. (2013). Catalytic C–C and C–Heteroatom Bond Formation Reactions: In Situ Generated or Preformed Catalysts? Complicated Mechanistic Picture Behind Well-Known Experimental Procedures. The Journal of Organic Chemistry, 78(22), 11117-11125. doi:10.1021/jo402038pEremin, D. B., & Ananikov, V. P. (2017). Understanding active species in catalytic transformations: From molecular catalysis to nanoparticles, leaching, «Cocktails» of catalysts and dynamic systems. Coordination Chemistry Reviews, 346, 2-19. doi:10.1016/j.ccr.2016.12.021Lu, Y., & Chen, W. (2012). Sub-nanometre sized metal clusters: from synthetic challenges to the unique property discoveries. Chemical Society Reviews, 41(9), 3594. doi:10.1039/c2cs15325dFortea-Pérez, F. R., Mon, M., Ferrando-Soria, J., Boronat, M., Leyva-Pérez, A., Corma, A., … Pardo, E. (2017). The MOF-driven synthesis of supported palladium clusters with catalytic activity for carbene-mediated chemistry. Nature Materials, 16(7), 760-766. doi:10.1038/nmat4910Herzing, A. A., Kiely, C. J., Carley, A. F., Landon, P., & Hutchings, G. J. (2008). Identification of Active Gold Nanoclusters on Iron Oxide Supports for CO Oxidation. Science, 321(5894), 1331-1335. doi:10.1126/science.1159639Huang, J., Akita, T., Faye, J., Fujitani, T., Takei, T., & Haruta, M. (2009). Propene Epoxidation with Dioxygen Catalyzed by Gold Clusters. Angewandte Chemie International Edition, 48(42), 7862-7866. doi:10.1002/anie.200903011Liu, Y., Jia, C.-J., Yamasaki, J., Terasaki, O., & Schüth, F. (2010). Highly Active Iron Oxide Supported Gold Catalysts for CO Oxidation: How Small Must the Gold Nanoparticles Be? Angewandte Chemie International Edition, 49(33), 5771-5775. doi:10.1002/anie.201000452Serna, P., & Gates, B. C. (2014). Molecular Metal Catalysts on Supports: Organometallic Chemistry Meets Surface Science. Accounts of Chemical Research, 47(8), 2612-2620. doi:10.1021/ar500170kCorma, A., Concepción, P., Boronat, M., Sabater, M. J., Navas, J., Yacaman, M. J., … Mayoral, A. (2013). Exceptional oxidation activity with size-controlled supported gold clusters of low atomicity. Nature Chemistry, 5(9), 775-781. doi:10.1038/nchem.1721Liu, L., Díaz, U., Arenal, R., Agostini, G., Concepción, P., & Corma, A. (2016). Generation of subnanometric platinum with high stability during transformation of a 2D zeolite into 3D. Nature Materials, 16(1), 132-138. doi:10.1038/nmat4757Oliver-Meseguer, J., Dominguez, I., Gavara, R., Doménech-Carbó, A., González-Calbet, J. M., Leyva-Pérez, A., & Corma, A. (2017). The wet synthesis and quantification of ligand-free sub-nanometric Au clusters in solid matrices. Chemical Communications, 53(6), 1116-1119. doi:10.1039/c6cc09119aTyo, E. C., & Vajda, S. (2015). Catalysis by clusters with precise numbers of atoms. Nature Nanotechnology, 10(7), 577-588. doi:10.1038/nnano.2015.14

Procedimiento de obtención directa de oxima de ciclohexanona a partir de nitroderivados

La presente patente de invención describe un procedimiento para producir oxima de ciclohexanona directamente a partir de nitroderivados, como por ejemplo nitrobenceno, que se puede llevar a cabo en un mismo “batch” mediante hidrogenación, usando un catalizador con al menos un metal soportado. La invención describe las condiciones de reacción necesarias para conseguir la secuencia reactiva que conduce a oxima de ciclohexanona desde el material de partida.Peer reviewedConsejo Superior de Investigaciones Científicas, Universitat Politecnica de ValenciaR Informe sobre el estado de la técnica publicado separadament

Arsenic Phytoremediation: Finally a Feasible Approach in the Near Future

Arsenic, a class-1 carcinogenic, is a ubiquitous metalloid found in the atmosphere, soils, natural waters, and organisms. The World Health Organization (WHO) estimates that hundred million people worldwide might be chronically exposed to arsenic in drinking water at concentrations above the safety standard. Conventionally applied techniques to remove arsenic species show low removal efficiency, high operational costs, and high-energy requirements. The biological methods, especially phytoremediation, could be cost-effective for protecting human health and the environment from toxic metal contamination. Plants, as sessile organisms, have developed an extraordinary capacity to tolerate arsenic through three main strategies: uptake repression, sequestration into the vacuole, or extrusion. Therefore, arsenic perception and tolerance require a coordinated response that involves arsenic transporters, extrusion pumps, vacuole transporters, and the activation of the phytochelatin biosynthetic pathway. For phytoremediation to become a feasible strategy for arsenic removal from contaminated sites, it is essential to completely understand the molecular mechanisms of arsenic uptake, extrusion, and sequestration, as well as how this response is coordinated. The new genome-wide technologies provide a unique opportunity to understand the molecular mechanisms underlying arsenic perception and accumulation in plants that will open up new possibilities for phytoremediation of arsenic-contaminated waters and soils

A bifunctional palladium-acid solid catalyst performs the direct synthesis of cyclohexylanilines and dicyclohexylamines from nitrobenzenes

[EN] Nitroderivatives are transformed to cyclohexylanilines at room temperature in good yields and selectivity via a hydrogenation-amine coupling cascade reaction using Pd nanoparticles on carbon as a catalyst and a Bronsted acid.Financial support by Consolider-Ingenio MULTICAT 2010, subprograma de Apoyo a Centros y Universidades de Excelencia Severo Ochoa (SEV 2012 0267), and MAT2009-00889 projects from MICINN is acknowledged. P. R.-M. thanks the Ministry of Education for a concession of a FPU contract. A. L. P thanks ITQ for a contract. We thank Dr J.C. Hernandez-Garrido for the microscopic images.Rubio Marqués, P.; Leyva Perez, A.; Corma Canós, A. (2013). A bifunctional palladium-acid solid catalyst performs the direct synthesis of cyclohexylanilines and dicyclohexylamines from nitrobenzenes. Chemical Communications. 49(74):8160-8162. https://doi.org/10.1039/c3cc44064hS816081624974He, J., Kim, J., Yamaguchi, K., & Mizuno, N. (2009). Efficient Catalytic Synthesis of Tertiary and Secondary Amines from Alcohols and Urea. Angewandte Chemie International Edition, 48(52), 9888-9891. doi:10.1002/anie.200905385Hamid, M. H. S. A., Slatford, P. A., & Williams, J. M. J. (2007). Borrowing Hydrogen in the Activation of Alcohols. Advanced Synthesis & Catalysis, 349(10), 1555-1575. doi:10.1002/adsc.200600638Merino, E. (2011). Synthesis of azobenzenes: the coloured pieces of molecular materials. Chemical Society Reviews, 40(7), 3835. doi:10.1039/c0cs00183jBlaser, H.-U., Steiner, H., & Studer, M. (2009). Selective Catalytic Hydrogenation of Functionalized Nitroarenes: An Update. ChemCatChem, 1(2), 210-221. doi:10.1002/cctc.200900129Hayes, K. S. (2001). Industrial processes for manufacturing amines. Applied Catalysis A: General, 221(1-2), 187-195. doi:10.1016/s0926-860x(01)00813-4Guillena, G., Ramón, D. J., & Yus, M. (2009). Hydrogen Autotransfer in theN-Alkylation of Amines and Related Compounds using Alcohols and Amines as Electrophiles. Chemical Reviews, 110(3), 1611-1641. doi:10.1021/cr9002159Hollmann, D., Bähn, S., Tillack, A., & Beller, M. (2008). N-Dealkylation of aliphatic amines and selective synthesis of monoalkylated aryl amines. Chemical Communications, (27), 3199. doi:10.1039/b803114bHollmann, D., Bähn, S., Tillack, A., & Beller, M. (2007). A General Ruthenium-Catalyzed Synthesis of Aromatic Amines. Angewandte Chemie International Edition, 46(43), 8291-8294. doi:10.1002/anie.200703119Deng, G., Chen, W., & Li, C.-J. (2009). An Unusual Peroxide-Mediated Amination of Cycloalkanes with Nitroarenes. Advanced Synthesis & Catalysis, 351(3), 353-356. doi:10.1002/adsc.200800689Han, S., & Movassaghi, M. (2011). Concise Total Synthesis and Stereochemical Revision of all (−)-Trigonoliimines. Journal of the American Chemical Society, 133(28), 10768-10771. doi:10.1021/ja204597kPingen, D., Müller, C., & Vogt, D. (2010). Direct Amination of Secondary Alcohols Using Ammonia. Angewandte Chemie International Edition, 49(44), 8130-8133. doi:10.1002/anie.201002583Corma, A., Ródenas, T., & Sabater, M. (2010). A Bifunctional Pd/MgO Solid Catalyst for the One-Pot Selective N-Monoalkylation of Amines with Alcohols. Chemistry - A European Journal, 16(1), 254-260. doi:10.1002/chem.200901501Dobereiner, G. E., & Crabtree, R. H. (2010). Dehydrogenation as a Substrate-Activating Strategy in Homogeneous Transition-Metal Catalysis. Chemical Reviews, 110(2), 681-703. doi:10.1021/cr900202jPrades, A., Corberán, R., Poyatos, M., & Peris, E. (2008). [IrCl2Cp*(NHC)] Complexes as Highly Versatile Efficient Catalysts for the Cross-Coupling of Alcohols and Amines. Chemistry - A European Journal, 14(36), 11474-11479. doi:10.1002/chem.200801580Corma, A., Concepción, P., & Serna, P. (2007). A Different Reaction Pathway for the Reduction of Aromatic Nitro Compounds on Gold Catalysts. Angewandte Chemie International Edition, 46(38), 7266-7269. doi:10.1002/anie.200700823Corma, A. (2006). Chemoselective Hydrogenation of Nitro Compounds with Supported Gold Catalysts. Science, 313(5785), 332-334. doi:10.1126/science.1128383Grirrane, A., Corma, A., & Garcia, H. (2008). Gold-Catalyzed Synthesis of Aromatic Azo Compounds from Anilines and Nitroaromatics. Science, 322(5908), 1661-1664. doi:10.1126/science.1166401Huang, S.-Y., Chang, S.-M., & Yeh, C. (2006). Characterization of Surface Composition of Platinum and Ruthenium Nanoalloys Dispersed on Active Carbon. The Journal of Physical Chemistry B, 110(1), 234-239. doi:10.1021/jp054870kReetz, M. T., & Maase, M. (1999). Redox-Controlled Size-Selective Fabrication of Nanostructured Transition Metal Colloids. Advanced Materials, 11(9), 773-777. doi:10.1002/(sici)1521-4095(199906)11:93.0.co;2-

Puzzle de Realidad Aumentada para el entrenamiento cognitivo (Original)

Cognitive training allows preserving or maximizing a person's cognitive abilities. The techniques and activities applied in this therapy have been widely supported in recent times by information and communication technologies. Augmented Reality is one of these technologies that allows new forms of tangible interaction to manipulate the virtual information added to a physical environment in real time. The JSRARC Serious Augmented Reality computer game system for cognitive rehabilitation presents therapeutic exercises in game format to increase the motivation of patients in computerized cognitive activities. Despite the availability of their purposeful games for rehabilitation, games focused on cognitive training are required to primarily enhance attention and memory capabilities. The objective of this work is the development of an Augmented Reality puzzle for cognitive training. The puzzle is a serious game that is integrated into the JSRARC computer system and can be parameterized with the authoring tool of this software. The osgART library with the Qt framework, OpenAL for audio management and SQLite for data storage were used for its development. To evaluate the usability of the game, a usability test was designed and executed where a questionnaire was applied. The responses were processed with the one-way ANOVA statistical analysis.El entrenamiento cognitivo posibilita conservar o maximizar las capacidades cognitivas de una persona. Las técnicas y las actividades que se aplican en esta terapia han sido ampliamente apoyadas en los últimos tiempos por tecnologías de la información y las comunicaciones. La Realidad Aumentada es una de estas tecnologías que permite nuevas formas de interacción tangible para manipular la información virtual añadida a un entorno físico en tiempo real. El sistema computacional de juegos serios de Realidad Aumentada para la rehabilitación cognitiva (JSRARC) presenta ejercicios terapéuticos en formato de juegos, para incrementar la motivación de los pacientes en las actividades cognitivas computarizadas. A pesar de la disponibilidad de sus juegos con propósitos para la rehabilitación, se requieren juegos enfocados al entrenamiento cognitivo para potenciar principalmente las capacidades de la atención y la memoria. El objetivo del presente trabajo es el desarrollo de un puzzle de Realidad Aumentada para el entrenamiento cognitivo. El puzzle constituye un juego serio que se integra al sistema computacional JSRARC y puede ser parametrizado con la herramienta de autor de este software. Para su desarrollo se utilizó la librería osgART con el framework Qt, OpenAL para la gestión del audio y SQLite para el almacenamiento de los datos. Para evaluar la usabilidad del juego se diseñó y ejecutó una prueba de usabilidad donde se aplicó un cuestionario. Las respuestas fueron procesadas con el análisis estadístico ANOVA de un factor

Refractive or diffractive interpretation of heavy-ion elastic scattering

A characteristic pattern frequently observed in the angular distribution of heavy-ion elastic scattering at moderate energies above the Coulomb barrier has been attributed either to a Fresnel diffraction or to a rainbow effect. We propose a comparison between the strong absorption radius Rsa and the rainbow radius Rr at different energies, which may have some relevance on deciding whether the absorptive or the refractive interpretation is to be preferred. Despite the difficulties in the exact determination of these two distances, an analytical expression for their energy dependence is found empirically by analyzing data of fifteen pairs of heavy ions. According to this criterion the center-of-mass energy, above which refraction prevails over absorption, is proportional to Z1Z2. NUCLEAR SCATTERING Optical and diffraction models, rainbow refraction of heavy ions

A Ligand-Free Pt3 Cluster Catalyzes the Markovnikov Hydrosilylation of Alkynes with up to 106 Turnover Frequencies

[EN] The Pt-catalyzed hydrosilylation of alkynes is the procedure of choice to obtain vinylsilanes, and is claimed to be the most relevant application of Pt in organic synthesis. More than half a century after its discovery, only b-vinylsilanes (anti-Markovnikov addition) are obtained with simple Pt catalysts, whereas a-vinylsilanes (Markovnikov addition)remain elusive compounds.Here the catalysis of the Markovnikov hydrosilylation of terminal alkynes by Pt3clusters, in parts-per-million amounts, to give a wide variety of a-vinylsi-lanes in reasonable isolated yields and with turnover fre-quencies that can reach up to one million per hour is reported. Moreover, these a-vinylsilanes are reactive in well-stablished C@Cbond-forming cascade reactions, in which thecorresponding b-isomers are unreactive. Besides its efficiency and synthetic usefulness, this catalytic system is an excellent example of how the atom-by-atomaggregation of a catalytic metal leads to a different selectivity for a given reactionFinancial support by MINECO (RETOS program, CTQ201455178-R) and "Severo Ochoa" program is acknowledged. M. A. R.-C. thanks for a FPU scholarship.Rivero-Crespo, MÁ.; Leyva Perez, A.; Corma Canós, A. (2017). A Ligand-Free Pt3 Cluster Catalyzes the Markovnikov Hydrosilylation of Alkynes with up to 106 Turnover Frequencies. Chemistry - A European Journal. 23(7):1702-1708. https://doi.org/10.1002/chem.201605520S1702170823

Determinación del costo real en la ejecución del servicio de mantenimiento periódico Camino Vecinal: Puente Ecash, Auquipampa, Ampu, Quimish, Maya, Puente Lelis - Carhuaz – Ancash 2020

El trabajo de investigación tuvo como finalidad principal determinar el costo real en la ejecución del servicio de mantenimiento periódico del Camino Vecinal Puente Ecash, Auquipampa, Ampu, Quimish, Maya, Puente Lelis (9.898 Km.). La metodología fue de un enfoque cuantitativo, de tipo aplicada, diseño no experimental y tipo descriptivo. Se determinó que el Costo Real ascendente a 803,647.68 soles es superior al presupuesto aprobado en el Plan, representando una variación porcentual entre ambos presupuestos de 19.06%; en el material granular de Cantera E=0.15M tuvo una variación porcentual en la cantidad (m3) de 23.14% entre el costo real y plan, en lo que respecta al costos la variación porcentual total en soles entre ambos presupuestos (real y plan) fue de 22.78%. En cuanto al transporte la variación porcentual total en metros cúbicos por kilómetros entre ambos presupuestos (real y plan) fue de 20.97%. Concluyéndose que el costo real a la fecha de ejecución del mantenimiento periódico del camino vecinal Ecash, Auquipampa, Ampu, Quimish, Maya, Puente Lelis (9.898 Km.) fue superior en comparación al presupuesto aprobado en el Plan de Trabajo

Jazz Chants para promover la producción oral de alumnos de inglés como lengua extranjera

This work is based on a quasi-environmental approach and it was carried out in the second year of the English Language career at the “Escola Superior Pedagógica do Kwanza Norte” (Kwanza Norte Pedagogical Higher School), Angola. It was aimed to promote oral production in terms of fluency, accuracy, pronunciation and intonation, by applying the Jazz Chants method in the teaching-learning process of the subject Practice of the English Language II. In the study, the parametric Student's t test was performed to determine the significant differences between the means from the pre-test and post-test developed before and after applying the Jazz Chants. These evaluations were correlated with the responses of a Likert-type questionnaire, applied to the sample for self-evaluation. The results showed the acceptance of the Jazz Chants by Angolan students in the subject Practice of the English Language II and a positive impact on the fluency, accuracy, pronunciation and intonation of the students. Keywords: oral production; Jazz Chants; learning; language teaching; methodology.  El presente trabajo se basa en un enfoque cuasiexpermiental y se realizó en el segundo año de la carrera de Lengua Inglesa de la “Escola Superior Pedagógica do Kwanza Norte” (Escuela Superior Pedagógica de Kwanza Norte), Angola. El mismo tuvo como objetivo promover la producción oral en términos de fluidez, precisión, pronunciación y entonación, mediante la aplicación del método Jazz Chants en el proceso de enseñanza-aprendizaje de la asignatura Práctica de la Lengua Inglesa II. En el estudio se realizó la prueba paramétrica t de Student para determinar las diferencias significativas entre las medias de la preprueba y la postprueba desarrolladas antes y después del aplicar los Jazz Chants. Estas evaluaciones fueron correlacionadas con las respuestas de un cuestionario con formato tipo Likert, aplicado a la muestra para su autoevaluación. Los resultados evidenciaron la aceptación de los Jazz Chants por los alumnos angoleños en la asignatura Práctica de la Lengua Inglesa II y una incidencia positiva en la fluidez, la precisión, la pronunciación y la entonación de los estudiantes.   Palabras clave: producción oral; Jazz Chants; aprendizaje; enseñanza de lenguas; metodología