With the purpose of increasing the embryogenesis regeneration process in vitroplants obtained from somatic embryos of the indica rice variety CR-5272 (Oryza sativa L.), two independent experiments were performed. The first experiment consisted in the effect of combination of three concentrations of the gelling agent Phytagel (1.8, 2.4, and 3 gL-1) and four 2,4-D concentrations (2.26, 4.52, 6.78, and 9.05 M) on the induction and subsequent regeneration of embryogenic calli. On the second experiment, the pre-regeneration phase was modified; calli were subjected to darkness or diffuse light conditions for one, two, and three weeks. In embryogenesis induction, 35% calligenesis was obtained using the MS culture medium supplemented with 6.78 M of 2,4-D and 2.4 gL-1 Phytagel , whereas on the control treatment (MS medium supplemented with 9.05 M of 2,4-D and 3 gL-1 Phytagel) 24% calligenesis was obtained. In addition, regeneration percentages were improved (22% and 16% for calli induced with the above treatments, respectively). Furthermore, in light exposure experiments, the best result was obtained by exposing the embryogenic calli to darkness for one week in pre-regeneration, followed by direct light exposure during the regeneration phase.
Se propone una taxonomía de las universidades chilenas mediante análisis factorial, que resulta distinta a las tipologías de Brunner (2005, 2009), Parada (2010), Torres y Zenteno (2011) y Rosso y Reyes (2012), y supera las objeciones de Bernasconi (2006). Evita, además, distinciones binarias del tipo tradicional/privada, investigación/docencia, metropolitana/regional, católica/laica, etc. Tampoco establece rankings ni utiliza condiciones históricas, legales u otras alejadas de los modos de operación efectivos de las universidades. La siguiente taxonomía las agrupa según un pool de variables relevantes (investigación, tamaño, composición, acreditación, etc.) que da pie a cinco tipos de universidades: investigación, masivas, de acreditación, elitistas y no elitistas. Se espera aportar en la comprensión de las universidades y contribuir a las políticas públicas con herramientas conceptuales para abordar la diversidad universitaria.
A geometric approach to Sundman transformation defined by basic functions for systems of second-order differential equations is developed and the necessity of a change of the tangent structure by means of the function defining the Sundman transformation is shown. Among other applications of such theory we study the linearisability of a system of second-order differential equations and in particular the simplest case of a second-order differential equation. The theory is illustrated with several examples.
RESUMEN Se propone una taxonomía de las universidades chilenas mediante análisis factorial, que resulta distinta a las tipologías de Brunner (2005, 2009), Parada (2010), Torres y Zenteno (2011) y Rosso y Reyes (2012), y supera las objeciones de Bernasconi (2006). Evita, además, distinciones binarias del tipo tradicional/privada, investigación/docencia, metropolitana/regional, católica/laica, etc. Tampoco establece rankings ni utiliza condiciones históricas, legales u otras alejadas de los modos de operación efectivos de las universidades. La siguiente taxonomía las agrupa según un pool de variables relevantes (investigación, tamaño, composición, acreditación, etc.) que da pie a cinco tipos de universidades: investigación, masivas, de acreditación, elitistas y no elitistas. Se espera aportar en la comprensión de las universidades y contribuir a las políticas públicas con herramientas conceptuales para abordar la diversidad universitaria.
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