Phase mapping of aging process in InN nanostructures: oxygen incorporation and the role of the zincblende phase

Uncapped InN nanostructures undergo a deleterious natural aging process at ambient conditions by oxygen incorporation. The phases involved in this process and their localization is mapped by Transmission Electron Microscopy (TEM) related techniques. The parent wurtzite InN (InN-w) phase disappears from the surface and gradually forms a highly textured cubic layer that completely wraps up a InN-w nucleus which still remains from original single-crystalline quantum dots. The good reticular relationships between the different crystals generate low misfit strains and explain the apparent easiness for phase transformations at room temperature and pressure conditions, but also disable the classical methods to identify phases and grains from TEM images. The application of the geometrical phase algorithm in order to form numerical moire mappings, and RGB multilayered image reconstructions allows to discern among the different phases and grains formed inside these nanostructures. Samples aged for shorter times reveal the presence of metastable InN:O zincblende (zb) volumes, which acts as the intermediate phase between the initial InN-w and the most stable cubic In2O3 end phase. These cubic phases are highly twinned with a proportion of 50:50 between both orientations. We suggest that the existence of the intermediate InN:O-zb phase should be seriously considered to understand the reason of the widely scattered reported fundamental properties of thought to be InN-w, as its bandgap or superconductivity.Comment: 18 pages 7 figure

Diseño y construcción de un dispositivo para la alerta de obstáculos (DAO)

este proyecto se presenta el desarrollo de un sistema electrónico portátil para personas ciegas. Está compuesto por un emisor y un receptor de ultrasonidos, manejados por un microcontrolador. Un bloque emisor genera ondas ultrasónicas, que al chocar con un obstáculo se reflejan y son captadas por un sistema receptor. La señal del eco es posteriormente amplificada, y tras la selección de un umbral en el microcontrolador, este informa la presencia o no de un obstáculo activando el motor de un vibrador ubicado en la cintura del paciente. Se exponen el diagrama de bloques del sistema, la lógica de programación del microcontrolador, el diseño mecánico y los esquemas de los circuitos.This paper presents the development of a portable electronic device for blind people. It is composed of an ultrasonic pair (emitter-receiver), and lead by a microcontroller. First, an emitter block generates ultrasonic waves that are reflected after they had collided with an obstacle. The reflected signal is captured by the receiver. The signal is then amplified, and after a threshold comparison is made by the microcontroller, an output is carried to the motor of a vibrator located in the patient’s waist.The systems block diagram, the programming logic, the mechanical design, and the electrical circuit schematics are presented

M-learning en zonas de recursos limitados

Las zonas rurales de recursos limitados del país se caracterizan, entre otros aspectos, por su baja densidad demográfica, cobertura de red celular muy limitada y carencia de servicio de distribución de energía eléctrica. Los habitantes de estas zonas utilizan energías alternativas, como paneles solares y grupos electrógenos, para cubrir necesidades energéticas elementales. La región Noroeste de Argentina (NOA) posee numerosas zonas de este tipo, donde los pobladores son personas de bajos recursos y tienen pocas posibilidades de educación en su entorno; se garantiza la educación primaria pero son pocas las escuelas secundarias. En este contexto, el aprendizaje mediado por tecnologías es prácticamente nulo debido al elevado consumo de energía que requieren los equipos computacionales. Sin embargo los dispositivos móviles representan una alternativa viable por su bajo consumo energético. En este trabajo se presentan los resultados (tecnológicos y educativos) de la aplicación de estrategias de m-learning en una escuela del Dpto. Pellegrini de la provincia de Santiago del Estero. Se sustenta en el despliegue de MANETs de bajo consumo y en la figura de un profesor itinerante que imparte educación secundaria en el área Matemática en zonas rurales utilizando objetos de aprendizaje almacenados en un servidor de recursos m-learning. Los objetos son accedidos desde teléfonos celulares sencillos que utilizan tecnología bluetooth.Red de Universidades con Carreras en Informática (RedUNCI

Antioxidant activity, photosynthetic rate, and Spectral mass in bean Plants (Phaseolus vulgaris L.) in Response to Stress Defense Activators

An increase in antioxidant activity is a common response in plants as a defense mechanism against biotic and abiotic stress factors, such response is also generated with the exogenous application of "defense activators", which have negative effects on plant metabolism. In this work, bean plants (Phaseolus vulgaris L.) cv. Pinto Nacional were treated with jasmonic acid (0.5 mM), salicylic acid (2 mM), Trichoderma asperellum (105 spores/ml), and Bacillus pumilus (105 CFU / mL), in order to determine the level of structural and metabolic response of the plants. On the seventh day after the application of the treatments, it was measured the enzymatic activity of catalase (CAT), peroxidase (POX), and superoxide dismutase (SOD). In addition, leaf impressions were taken to measure the stomatal opening and conductance, photosynthetic rate, and the mass spectrum (mass/charge, m/z). The antioxidant activity increased in plants treated with jasmonic acid and T. asperellum, which in turn significantly increased the stomatal opening and conductance, and photosynthetic rate. The mass profile showed that the plants treated with T. asperellum have a greater quantity of masses/charge, of which some had statistically highly significant difference according to the means test Tukey (

The Preliminary Evaluation of Liquid Lubricants for Space Applications by Vacuum Tribometry

Four different vacuum tribometers for the evaluation of liquid lubricants for space applications are described. These range from simple ball-on-flat sliders with maximum in-situ control and surface characterization to an instrument bearing apparatus having no in-situ characterization. Thus, the former provides an abundance of surface chemical information but is not particularly simulative of most triboelements. On the other hand, the instrument bearing apparatus is completely simulative, but only allows post-mortem surface chemical information. Two other devices, a four-ball apparatus and a ball-on-plate tribometer, provide varying degrees of surface chemical information and tribo-simulation. Examples of data from each device are presented

Massive stars exploding in a He-rich circumstellar medium. VI. Observations of two distant Type Ibn supernova candidates discovered by La Silla-QUEST

We present optical observations of the peculiar stripped-envelope supernovae (SNe) LSQ12btw and LSQ13ccw discovered by the La Silla-QUEST survey. LSQ12btw reaches an absolute peak magnitude of M(g) = -19.3 +- 0.2, and shows an asymmetric light curve. Stringent prediscovery limits constrain its rise time to maximum light to less than 4 days, with a slower post-peak luminosity decline, similar to that experienced by the prototypical SN~Ibn 2006jc. LSQ13ccw is somewhat different: while it also exhibits a very fast rise to maximum, it reaches a fainter absolute peak magnitude (M(g) = -18.4 +- 0.2), and experiences an extremely rapid post-peak decline similar to that observed in the peculiar SN~Ib 2002bj. A stringent prediscovery limit and an early marginal detection of LSQ13ccw allow us to determine the explosion time with an uncertainty of 1 day. The spectra of LSQ12btw show the typical narrow He~I emission lines characterising Type Ibn SNe, suggesting that the SN ejecta are interacting with He-rich circumstellar material. The He I lines in the spectra of LSQ13ccw exhibit weak narrow emissions superposed on broad components. An unresolved Halpha line is also detected, suggesting a tentative Type Ibn/IIn classification. As for other SNe~Ibn, we argue that LSQ12btw and LSQ13ccw likely result from the explosions of Wolf-Rayet stars that experienced instability phases prior to core collapse. We inspect the host galaxies of SNe Ibn, and we show that all of them but one are hosted in spiral galaxies, likely in environments spanning a wide metallicity range.Comment: 15 pages, 9 figures, 4 tables. Accepted by MNRA

Perinatal asphyxia: CNS development and deficits with delayed onset

Perinatal asphyxia constitutes a prototype of obstetric complications occurring when pulmonary oxygenation is delayed or interrupted. The primary insult relates to the duration of the period lacking oxygenation, leading to death if not re-established. Re-oxygenation leads to a secondary insult, related to a cascade of biochemical events required for restoring proper function. Perinatal asphyxia interferes with neonatal development, resulting in long-term deficits associated to mental and neurological diseases with delayed clinical onset, by mechanisms not yet clarified. In the experimental scenario, the effects observed long after perinatal asphyxia have been explained by over expression of sentinel proteins, such as poly(ADP-ribose) polymerase-1 (PARP-1), competing for NAD+ during re-oxygenation, leading to the idea that sentinel protein inhibition constitutes a suitable therapeutic strategy. Asphyxia induces transcriptional activation of proinflammatory factors, in tandem with PARP-1 overactivation, and pharmacologically induced PARP-1 inhibition also down-regulates the expression of proinflammatory cytokines. Nicotinamide has been proposed as a suitable PARP-1 inhibitor. Its effect has been studied in an experimental model of global hypoxia in rats. In that model, the insult is induced by immersing rat foetuses into a water bath for various periods of time. Following asphyxia, the pups are delivered, treated, and nursed by surrogate dams, pending further experiments. Nicotinamide rapidly distributes into the brain following systemic administration, reaching steady state concentrations sufficient to inhibit PARP-1 activity for several hours, preventing several of the long-term consequences of perinatal asphyxia, supporting the idea that it constitutes a lead for exploring compounds with similar or better pharmacological profiles

Inhibición de Porphyromonas gingivalis por Cinnamomum verum eE Illicium verum.

Las plantas medicinales han sido empleadas por el humano como alternativa o complemento a los tratamientos contra diversas afecciones, entre ellas la periodontitis, se ha reportado que alimentos como Cinnamomum verum e Illicium verum tienen compuestos con actividad antimicrobiana. Por otra parte, la periodontitis es una enfermedad de origen bacteriano, que afecta de un 5%-20% de los adultos entre 30 y 60 años a nivel mundial. Una de las bacterias implicadas en la periodontitis crónica y agresiva además de ser considerada como su principal agente etiológico es Porphyromonas gingivalis. El objetivo de éste trabajo fue determinar la actividad biológica del extracto metanólicos de I. verum y extracto acuoso de Cinnamomum verum sobre P. gingivalis. Los resultados indican que los extracto evaluados de C. verum e I. verum inhiben el crecimiento in vitro de P. gingivalis. Estos resultados brindan perspectivas de estudio encaminadas a la búsqueda de nuevas alternativas de terapia antimicrobiana relacionadas con enfermedades periodontales