Identidad cultural o aculturación: el dilema de una escuela indígena en un contexto urbano

El estudio se orienta al tema de la interculturalidad, vista desde las percepciones y acciones de los actores de una escuela primaria indígena ubicada en un contexto urbano marginal de una ciudad del Norte de México. La investigación se ubica en el paradigma cualitativo y se sustenta en la teoría emergente, ya que busca mediante un proceso inductivo generar o descubrir la teoría instalada en la escuela objeto de análisis. Se muestra la noción de interculturalidad que aprecian y viven los diferentes actores de una institución que se identifica como indígena y los dilemas que enfrentan para conservar y fomentar su cultura en un medio donde la fuerza de la cultura y contexto mestizo se impone

Compensation effects in GaN:Mg probed by Raman spectroscopy and photoluminescence measurements

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in J. Appl. Phys. 113, 103504 (2013) and may be found at https://doi.org/10.1063/1.4794094.Compensation effects in metal organic chemical vapour deposition grown GaN doped with magnesium are investigated with Raman spectroscopy and photoluminescence measurements. Examining the strain sensitive E2(high) mode, an increasing compressive strain is revealed for samples with Mg-concentrations lower than 7 × 1018 cm−3. For higher Mg-concentrations, this strain is monotonically reduced. This relaxation is accompanied by a sudden decrease in crystal quality. Luminescence measurements reveal a well defined near band edge luminescence with free, donor bound, and acceptor bound excitons as well as a characteristic donor acceptor pair (DAP) luminescence. Following recent results, three acceptor bound excitons and donor acceptor pairs are identified. Along with the change of the strain, a strong modification in the luminescence of the dominating acceptor bound exciton and DAP luminescence is observed. The results from Raman spectroscopy and luminescence measurements are interpreted as fingerprints of compensation effects in GaN:Mg leading to the conclusion that compensation due to defect incorporation triggered by Mg-doping already affects the crystal properties at doping levels of around 7 × 1018 cm−3. Thereby, the generation of nitrogen vacancies is introduced as the driving force for the change of the strain state and the near band edge luminescence.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelement

Prácticas educativas de escuelas ubicadas en contextos vulnerables: el caso de Chihuahua en México

El estado de Chihuahua en México se caracteriza por contar con localidades específicas en las que la pobreza, la exclusión y la vulnerabilidad están presentes en la población. La ubicación geográfica de nuestro estado, en la frontera con los Estados Unidos, presenta algunos aspectos que pueden explicar los procesos de vulnerabilidad que caracterizan a esta entidad. El fenómeno de la vulnerabilidad social es un proceso multidimensional en el que convergen riesgos y situaciones adversas que colocan a un individuo o un grupo de personas ante un escenario de crisis, contingencia o peligro de ser herido, lesionado o dañado (Busso, 2001 y Golovanevsky, 2007). En este contexto, las escuelas presentan diversas condiciones y problemáticas, mismas que las convierten en espacios educativos vulnerables: deserción, reprobación, violencia escolar, bajo capital cultural de las familias, inefectiva gestión escolar y de aula, ubicadas en comunidades cada vez más vulnerables y riesgosas, además de la escasa comunicación entre la comunidad escolar y su contexto cercano. Ante este escenario, es necesario profundizar en el estudio de lo que acontece en este tipo de escuelas y en las formas que establecen para convivir con el medio social en el que se encuentran. Por ello, como investigadores nos planteamos las siguientes preguntas: ¿Cómo la escuela está afrontando estos procesos de vulnerabilidad? Particularmente: ¿Cómo enseñan los maestros? ¿Cómo se dan los procesos de convivencia?Facultad de Humanidades y Ciencias de la Educació

Temperature dependent photoluminescence of lateral polarity junctions of metal organic chemical vapor deposition grown GaN

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Journal of Applied Physics 110, 093503 (2011) and may be found at https://doi.org/10.1063/1.3656987.We report on fundamental structural and optical properties of lateral polarity junctions in GaN. GaN with Ga- to N-polar junctions was grown on sapphire using an AlN buffer layer. Results from scanning electron microscopy and Raman spectroscopy measurements indicate a superior quality of the Ga-polar GaN. An extremely strong luminescence signal is observed at the inversion domain boundary (IDB). Temperature dependent micro photoluminescence measurements are used to reveal the recombination processes underlying this strong emission. At 5 K the emission mainly arises from a stripe along the inversion domain boundary with a thickness of 4-5 μm. An increase of the temperature initially leads to a narrowing to below 2 μm emission area width followed by a broadening at temperatures above 70 K. The relatively broad emission area at low temperatures is explained by a diagonal IDB. It is shown that all further changes in the emission area width are related to thermalization effects of carriers and defects attracted to the IDB. The results are successfully used to confirm a theoretical model for GaN based lateral polarity junctions. Due to the strong and pronounced emission of IDBs even at elevated temperatures, it is demonstrated that lateral polarity junctions exhibit a strong potential for future high efficiency devices.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelement

Corrosion resistance of a water-borne resin doped with graphene derivatives applied on galvanized steel

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGThe present work reports the effect of adding Graphene Oxide (GO) and reduced Graphene Oxide (rGO) in the corrosion protection provided by a water-borne resin applied on a galvanized steel substrate. Three concentrations, 0.05, 0.1 and 0.15 (all wt%) were tested. The results were markedly affected not only by the concentration of particles but also by their nature. Although the zeta potential values suggested good dispersibility of the particles in the resin, certain aggregation was observed, mainly in rGO 0.1 wt% and rGO 0.15 wt% formulations. The electrochemical impedance spectroscopy (EIS) technique characterised the free films' transport properties. The results suggested that the aggregation strongly influenced the film morphology. The rGO 0.1 wt% and rGO 0.15 wt% formulations exhibited percolating pores that facilitated the electrolyte uptake through the films. The EIS technique was also used to study the protective performance of the films when applied to the metallic substrate. The results confirmed the harmful effect of the particle's aggregation. The results were interesting for the rGO 0.05 wt% system, which displayed long-lasting protection properties. This performance was explained considering its good barrier properties and the zinc surface passivation by the generation of zincite, ZnO

Electrochemical characterization of a Fe-based shape memory alloy in an alkaline medium and the behaviour in aggressive conditions

A Fe-17Mn-6Si-19Cr-4Ni-1(V,C) shape memory steel (SMS) was characterised electrochemically in its unstrained and pre-strained conditions. The work focused on analysing the passive films generated in alkaline conditions, and on the behaviour of those passive samples in various Cl /OH ratios. The passive films were developed by cyclic voltammetry and their characterisation was performed by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS); these tests were also carried out in 304 L stainless steel specimens for comparison purposes. The results indicated that the film characteristics (thickness and composition) were similar in all the samples, although higher corrosion resistance was observed in the 304 L due to the higher Cr content. In addition, the behaviour of the passive samples in aggressive conditions was assessed by potentiodynamic measurements. The results stated that the shape memory steels were more sensitive than the stainless steel to the aggressive conditions, especially when the alloy was pre-strained. It was also observed that the SMS exhibited a characteristic corrosion morphology localized at the grain boundariesAgencia Estatal de Investigación | Ref. TED2021-130605B-I00Financiado para publicación en acceso aberto: Universidade de Vigo/CISU

Vinculación del profesor a la producción de laboratorios virtuales. Estudio de su impacto en la integración de las TIC

La presente investigación defiende la idea de que la vinculación del profesor a la producción de materiales educativos digitales puede ser una vía eficaz para propiciar la integración de las TIC en su proceso de enseñanza aprendizaje.Se exponen los resultados de una experiencia donde los profesores se vincularon a un equipo multidisciplinario para desarrollar laboratorios virtuales destinados a la enseñanza de las ciencias técnicas y donde el resultado fundamental redundó en la preparación del profesor para transformar su asignatura

Polarity Control in Group-III Nitrides beyond Pragmatism

Controlling the polarity of polar semiconductors on nonpolar substrates offers a wealth of device concepts in the form of heteropolar junctions. A key to realize such structures is an appropriate buffer-layer design that, in the past, has been developed by empiricism. GaN or ZnO on sapphire are prominent examples for that. Understanding the basic processes that mediate polarity, however, is still an unsolved problem. In this work, we study the structure of buffer layers for group-III nitrides on sapphire by transmission electron microscopy as an example. We show that it is the conversion of the sapphire surface into a rhombohedral aluminum-oxynitride layer that converts the initial N-polar surface to Al polarity. With the various AlxOyNz phases of the pseudobinary Al2O3-AlN system and their tolerance against intrinsic defects, typical for oxides, a smooth transition between the octahedrally coordinated Al in the sapphire and the tetrahedrally coordinated Al in AlN becomes feasible. Based on these results, we discuss the consequences for achieving either polarity and shed light on widely applied concepts in the field of group-III nitrides like nitridation and low-temperature buffer layers