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Search Results: 1 - 10 of 226963 matches for " RIVERA R. "
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Abonos verdes e inoculación micorrízica de posturas de cafeto sobre suelos Fersialíticos Rojos Lixiviados
Rivera,R;
Cultivos Tropicales , 2010,
Abstract: sorghum vulgare, crotalaria juncea and canavalia ensiformis were seeded and characterized, with the aim of evaluating green manure management in the mycorhized coffee seedling production on chromic luvisols; after 70 days, they were added to the soil for obtaining different substrates, in order to study seedling response to g. fasciculatum inoculation, on a randomized complete design with (5x2) factorial arrangement, besides including the treatments of single soil and soil/earthworm humus (3/1). inoculation of the same effective strain was further studied on the substrates, made up of complementary earthworm humus added to the incorporated sorghum, at the rates of 9/1, 7/1, 5/1, besides including both treatments through a (6x2) factorial arrangement. the greatest dry weight production as well as the highest p and k extractions by sorghum, and n extractions by crotalaria were recorded. green manures increased coffee growth and native mycorhization; however, there was always a significant coffee response to inoculation, with the biggest effects in the substrate made up by crotalaria. nevertheless, even in presence of such a substrate, inoculated seedlings did not show an effective mycorhization and they were inferior to those obtained by the reference treatment of soil/humus (3/1). therefore, to obtain healthy seedlings and an effective mycorhization, it was necessary, besides inoculating, to add complementary earthworm humus at the rate of 9/1 on the incorporated crotalaria substrate.
Estado del arte en la ubicación óptima de capacitores y estudio de optimización de la solución mediante búsqueda exhaustiva
Sergio R. Rivera R.
Visión Electrónica , 2008,
Abstract: En el presente artículo se presenta una revisión del estado del arte de la ubicación óptima de capacitores en sistemas de distribución, para dar una guía sobre los aspectos que deben tener en cuenta los planificadores en la optimización del perfil de tensión y el control de reactivos en la redes de distribución. Aquí se hace un estudio de la optimización de la solución mediante una busqueda exhaustiva, en la que se determina la dimensión del problema, se evalúan las diferentes posbilidades de solución, y se visualizan los tiempos y requerimientos computacionales que el algoritmo de solución utilizaría. Se utilizó un sistema ejemplo (IEEE de 9 nodos) para hacer el estudio de la búsqueda exhaustiva, en la que se encontró que los métodos utilizados en la literatura de este tema no siempre llegan a la solución óptima.
Una aproximación al desarrollo rural de Costa Rica. La extensión agrícola: breve síntesis de su evolución y tendencias hacia su democratización
Fernando Rivera R.
Revista Electrónica Educare , 2002,
Abstract: Resumen. En Costa Rica, la extensión agrícola ha sido un importante instrumento de desarrollo rural. El documento nos presenta una valiosa serie de características de la extensión agrícola a partir del siglo XIX, se alando hitos ligados a los modelos de desarrollo imperantes en diferentes momentos de la historia institucional del país. Desde esta perspectiva de la extensión agrícola, y sobre todo de las características que este revistió desde los a os 90-el autor propone seis líneas de acción con miras al desarrollo rural, que pasan por la democratización de la extensión y el replanteamiento de la investigación y la extensión agrícola dirigida a peque os y medianos agricultores. Abstract. In Costa Rica, agrarian outreach programs have been an important instrument for rural development. This study presents a valuable set of characteristics of the programs carried out since the 19 th century, and points out achievements related to the development models existing at different times in the institutional history of this country. From this perspective of agrarian outreach, and in particular, of the characteristics that it has since the 1990s, the author has proposed six lines of action for rural development. They include the democratization of outreach programs and a new approach toward research and agrarian outreach, oriented toward small and medium farmers.
Identification of Alternaria spp. as Pathogenic on the Native Species Terminalia australis and Salvia guaranitica  [PDF]
Mariana Kameniecki, Eduardo R. Wright, Marta C. Rivera
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.46A006
Abstract:

This work is the result of activities included in the cooperative project between Asociación Ribera Norte (ARN) and the Department of Plant Pathology, School of Agronomy, University of Buenos Aires. ARN is a non-governmental organization created in 1993 mainly for the management of the Reserva Ecológica Municipal Ribera Norte, a preservation area located in San Isidro (North of Buenos Aires), within the Provincia Paranaense region. The aims were to identify diseases in native plant species growing there. Light brown leaf spots with thin brown margins and narrow yellow halos were observed on Terminalia australis (mean disease severity: 25%). The pathogen was isolated, inoculated on healthy plants, reisolated from infected leaves and identified as Alternaria tenuissima. Similarly, another leaf-spot disease was observed on Salvia guaranitica, characterized by reddish brown large spots developed from the apexes and margins towards the centre of the leaves, reaching the veins in some cases (mean severity: 20%). Pathogen isolation, inoculation and reisolation led to the identification of A. alternata as the causal agent of the disease. Unusual heavy rain is analyzed as disease conductive.

INVERSIóN E INVENCIóN DE IMáGENES Y ESPEJOS: EL “POETICISMO” ROMáNTICO DE JULIO CORTáZAR EN SU NARRATIVA BREVE A LA LUZ DE IMAGEN DE JOHN KEATS
Báez Rivera,Emilio R;
Alpha (Osorno) , 2004, DOI: 10.4067/S0718-22012004000200003
Abstract: john keats’ poetic concept of oneness helps to forge a literary framework, which enables julio cortázar to re-make several characters and unusual circumstances in his narrative works. the argentinean writer traces the main theoretical concepts in the works and letters of this english poet in order to give an innovative turn to his incipient way of conceiving short stories from the very beginning, those posthumously published in the collection called la otra orilla. then, cortázar’s dense and lengthy imagen de john keats is the unanswerable proof of his outstanding acquisition of this romantic poetics, essentially as an instrument to reach his literary ambitious goal: the rise among the new ones in latin american prestigious writer listings.
Ensayos de Tolerancia al Aluminio de Bromus stamineus y Bromus lithobius Recolectados en el Sur de Chile
Toneatti,Marcelo; Rivera,Nelson R;
Información tecnológica , 2006, DOI: 10.4067/S0718-07642006000100003
Abstract: a study was made on the effects of several soil treatments on different ecotypes of plants of the genus bromus to determine the tolerance to aluminum under different soil condition. for the first step, out of 20 ecotypes of bromus lithobius and bromus stamineus, the ecotypes pro 95-18, pro 94-25, pro 94-24, pro 94-49 and pro 94-4 were selected, as they represented a declining order of tolerance to aluminum. root growth of all the ecotypes was evaluated over four day exposures in aluminum solutions at 0, 20, 40, 80 and 160 mm. a second stage of testing was carried out in soil containing 42.6% saturation of aluminum, modified by three doses of calcium carbonate. evaluation was made of dry root material produced, as well as concentrations of aluminum in the roots and leaves. it was concluded that behavior of the plants was different between the solution tests and the soil tests due to different mechanisms of tolerance, of which ecotype pro 94-49 was outstanding in its tolerance to aluminum under soil test conditions.
México: del sobreproteccionismo a la apertura comercial
Miguel A. Rivera Ríos
Política y cultura , 1993,
Abstract:
Ensayos de Tolerancia al Aluminio de Bromus stamineus y Bromus lithobius Recolectados en el Sur de Chile Aluminum Tolerance Assays of Bromus stamineus and Bromus lithobius from Southern Chile
Marcelo Toneatti,Nelson R Rivera
Información Tecnológica , 2006,
Abstract: Se han estudiado los efectos de los diferentes tratamientos sobre el desarrollo de distintos ecotipos de plantas del género Bromus para determinar la tolerancia al aluminio en diferentes condiciones de suelo. En una primera etapa se seleccionaron los ecotipos PRO 95-18, PRO 94-25, PRO 94-24, PRO 94-49 y PRO 94-4 por orden decreciente en cuanto a la tolerancia al aluminio, entre 20 pertenecientes a las especies Bromus lithobius y Bromus stamineus. Se evaluó el crecimiento radicular durante cuatro días en soluciones de 0, 20, 40, 80 y 160 mM de aluminio. En la segunda etapa se sometió al material seleccionado a cultivo en maceta con un suelo de 42,6% de saturación de aluminio, modificado con tres dosis de carbonato cálcico. Se evaluó la producción de materia seca radicular así como también se determinaron concentraciones de aluminio radicular y foliar (ppm). Se concluye que el comportamiento en suelo no es similar al obtenido en solución debido a que operan mecanismos diferentes de tolerancia, y se destaca el comportamiento del ecotipo PRO 94-49, por tolerancia al aluminio en condiciones de suelo. A study was made on the effects of several soil treatments on different ecotypes of plants of the genus Bromus to determine the tolerance to aluminum under different soil condition. For the first step, out of 20 ecotypes of Bromus lithobius and Bromus stamineus, the ecotypes PRO 95-18, PRO 94-25, PRO 94-24, PRO 94-49 and PRO 94-4 were selected, as they represented a declining order of tolerance to aluminum. Root growth of all the ecotypes was evaluated over four day exposures in aluminum solutions at 0, 20, 40, 80 and 160 mM. A second stage of testing was carried out in soil containing 42.6% saturation of aluminum, modified by three doses of calcium carbonate. Evaluation was made of dry root material produced, as well as concentrations of aluminum in the roots and leaves. It was concluded that behavior of the plants was different between the solution tests and the soil tests due to different mechanisms of tolerance, of which ecotype PRO 94-49 was outstanding in its tolerance to aluminum under soil test conditions.
INVERSIóN E INVENCIóN DE IMáGENES Y ESPEJOS: EL “POETICISMO” ROMáNTICO DE JULIO CORTáZAR EN SU NARRATIVA BREVE A LA LUZ DE IMAGEN DE JOHN KEATS Inversion and Invention of Images and Mirrors: The Romantic “Poeticism” of Julio Cortázar in His Short Stories Through the Light of Imagen de John Keats
Emilio R Báez Rivera
Alpha (Osorno) , 2004,
Abstract: La poética romántico-ontológica de John Keats contribuye a la fijación de un armazón literario que posibilita a Julio Cortázar la re-creación de personajes y de circunstancias insólitas en toda su narrativa. En la obra literaria y epistolar del poeta inglés, el cuentista argentino rastrea los conceptos que vertebran ese ideario estético con el fin de imprimir un nuevo giro a los textos fantásticos que conforman su cuentística desde la etapa inicial de La otra orilla. El denso y extenso estudio de Imagen de John Keats se impone como testimonio irrefutable de la adquisición instrumental de una poética puesta al servicio de un proyecto literario ambicioso y efectivo: reclamar su espacio entre las nuevas voces de la narrativa hispanoamericana. John Keats’ poetic concept of oneness helps to forge a literary framework, which enables Julio Cortázar to re-make several characters and unusual circumstances in his narrative works. The Argentinean writer traces the main theoretical concepts in the works and letters of this English poet in order to give an innovative turn to his incipient way of conceiving short stories from the very beginning, those posthumously published in the collection called La otra orilla. Then, Cortázar’s dense and lengthy Imagen de John Keats is the unanswerable proof of his outstanding acquisition of this Romantic poetics, essentially as an instrument to reach his literary ambitious goal: the rise among the new ones in Latin American prestigious writer listings.
La Europa que nos elude: la Unión Europea como ente político complejo
José R. Rivera González
Revista Umbral , 2010,
Abstract: Resumen La noción de la Unión Europea (UE) como una entidad política ideal y funcional choca constantemente con la dificultad de su práctica cotidiana presentada en rese as mediáticas y en el largo plazo a través de trabajos académicos que estudian el variopinto de aspectos de su andamiaje institucional. El argumento de este artículo sostiene que, si bien la UE contiene elementos funcionales, éstos son productos de intensas negociaciones interestatales a nivel comunitario y de una coordinación de política pública entre los Estados miembros. La ausencia de una o ambas, implicaría un estancamiento crítico prolongado que afectaría considerablemente el proceso de integración. La evidencia apunta parcialmente a que, entre 1997 y 2005 la UE sostuvo varios episodios de crisis, entre los cuales se distinguen dos pertinentes a la integración europea: las negociaciones que produjeron el tratado de Niza en 2000 y las negociaciones a partir de la cumbre de Laeken (2001) para la redacción de una Constitución Europea que en 2005 acabó en fracaso. Una mirada a reportajes periodísticos e investigaciones posteriores presentan el inventario de adversidades sobrellevadas por el binomio Estados Miembros/Instituciones Europeas para superar dificultades y reformular el proceso de integración europea concluyendo favorablemente en el Tratado de Lisboa (2009). Tomando en cuenta lo anterior se precisa en el estudio de la integración europea la consideración de una interacción dinámica ( conflicto?) constante de lo óntico y lo ontológico de la UE. Se concluye con una serie de recomendaciones prácticas que giran en torno a asumir el proceso de integración a múltiples niveles y velocidades (Grasa 2007) y el acercamiento –igualmente multidimensional– a nivel teórico en la comprensión de la Unión Europea como objeto de estudio. Palabras clave: Unión Europea, integración europea, gobernanza, interdependencia compleja In the past the European Union was perceived as a functional and ideal polity despite media coverage pointing to the contrary and academic literature featuring its complexities. This article agrees with the assessment that the EU is not quite the ideal polity of yore and its functionality is the product of intense interstate bargains and policy coordination between member states. The absence of these would comprise a critical juncture, which would usually mean stagnation in the process of integration. These junctures were especially poignant between 1997 and 2005 but were also frequent in the period leading up to the institutional overhaul made possible by the Treaty of Li
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