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Search Results: 1 - 10 of 181267 matches for " Juan F. Moreno "
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Optimal intervention in the foreign exchange market when interventions affect market dynamics
Alec N. Kercheval,Juan F. Moreno
Quantitative Finance , 2009,
Abstract: We address the problem of optimal Central Bank intervention in the exchange rate market when interventions create feedback in the rate dynamics. In particular, we extend the work done on optimal impulse control by Cadenillas and Zapatero to incorporate temporary market reactions, of random duration and level, to Bank interventions, and to establish results for more general rate processes. We obtain new explicit optimal impulse control strategies that account for these market reactions, and show that they cannot be obtained simply by adjusting the intervention cost in a model without market reactions.
Una implementación computacional de un modelo de atención visual Bottom-up aplicado a escenas naturales/A Computational Implementation of a Bottom-up Visual Attention Model Applied to Natural Scenes
David F. Ramirez Moreno,Juan F. Ramírez Villegas
Revista de Ingeniería , 2011,
Abstract: El modelo de atención visual bottom-up propuesto por Itti et al., 2000 [1], ha sido un modelo popular en tanto exhibe cierta evidencia neurobiológica de la visión en primates. Este trabajo complementa el modelo computacional de este fenómeno desde la dinámica realista de una red neuronal. Asimismo, esta aproximación se basa en la existencia de mapas topográficos que representan la prominencia de los objetos del campo visual para la formación de una representación general (mapa de prominencia), esta representación es la entrada de una red neuronal dinámica con interacciones locales y globales de colaboración y competencia que convergen sobre las principales particularidades (objetos) de la escena.The bottom-up visual attention model proposed by Itti et al. 2000 [1], has been a popular model since it exhibits certain neurobiological evidence of primates’ vision. This work complements the computational model of this phenomenon using a neural network with realistic dynamics. This approximation is based on several topographical maps representing the objects saliency that construct a general representation (saliency map), which is the input for a dynamic neural network, whose local and global collaborative and competitive interactions converge to the main particularities (objects) presented by the visual scene as well.
Una revisión de modelos de atención visual Bottom-up neurobiológicamente inspirados
Juan F. Ramírez-Villegas,David F. Ramírez-Moreno
El Hombre y la Máquina , 2010,
Abstract: La atención visual es un proceso desarrollado sobre gran parte del área de procesamiento visual primario. El procesamiento cerebral provoca la focalización selectiva de los objetos del campo visual que compiten por procesamiento, esta competencia se encuentra mediada por características primarias de los objetos como el contraste de color, el contraste de intensidad y el contraste de orientación. En esta revisión se procura establecer la conexión de los odelos de atención visual bottom-up disponibles en la literatura, sus arquitecturas y bases matemáticas, con la evidencia neurobiológica sobre el fenómeno de atención visual establecida hasta la actualidad. Adicionalmente, se ilustra una implementación propia de un modelo de atención visual bottom-up y se discuten algunos pormenores sobre el proceso de atención o mecanismo top-down cuya dinámica complementa la función del proceso de pre-atención o bottom-up.
Desarrollo de la atención visual en escenas naturales: un modelo bottom-up basado en mapa de prominencia con dinámica realista
JUAN F. RAMíREZ-VILLEGAS,DAVID F. RAMíREZ-MORENO
El Hombre y la Máquina , 2011,
Abstract: Este trabajo propone un modelo de atención visual para el análisis de escenas dinámicas que complementa el modelo de Itti & Koch (2000) [Itti, L., & Koch, C. (2000). A saliency-based search mechanism for overt and covert shifts of visual attention. Vision Research, 40, 1484-1506] modificado por de Brecht & Saiki (2006). A neural network implementation of a saliency map model. Neural Networks, 19, 1467-1474]. Este modelo incluye dos novedades principales, primero, el cómputo de la prominencia de movimiento por una red neuronal con dinámica realista y su respuesta en el tiempo, y segundo, para la etapa de extracción de características visuales primarias, el cálculo del mapa de color a partir del modelo de Itti & Koch (2000) con la inclusión de modelos de células rojo-cian y verde-magenta en el sistema estándar de color doble-oponente. Las respuestas transitorias de la red a objetos en movimiento así como el tiempo que le toma al sistema alcanzar el estado estable, se encuentra en un intervalo biológicamente plausible. Los mapas de color modificados produjeron mejores respuestas que los mapas de color reportados anteriormente en la literatura a una significancia estadística alta, en adicción, la exactitud del modelo en la predicción de las fijaciones del ojo humano se incrementó.
Lamarck needs Darwin: the search for purpose in the study of evolution and of history
Moreno, Juan
Asclepio : Revista de Historia de la Medicina y de la Ciencia , 2009,
Abstract: Lamarck′s theory of the inheritance of acquired characteristics and immediate responses to environmental challenges has offered a promise of protagonism of human beings and their fellow trvellers, the other organisms, in the evolutionary process. Darwin’s theory about evolution by natural selection does not offer this consolation and does not presuppose anything else other than gradual cahnges in the composition of natural populations. The study of ecology, ethology, neurobiology, animal culture, psichology and human history reveals that the lamarckian interpretations of change and character transmission processes always assume what they intend to explain, that is previous processes of darwinian evolution that guarantee the adaptive nature of the observed responses. The permanent search of direction and intentionality in evolutionary processes by many scientists suggests the limited acceptance of materilaistic explanations as those offered by Darwin’s theory. a teoría de Lamarck sobre herencia de caracteres adquiridos y sobre respuestas inmediatas a retos ambientales ha ofrecido una promesa de intencionalidad y protagonismo en el proceso evolutivo al ser humano y a los restantes organismos. La teoría de Darwin sobre evolución por selección natural no ofrece este consuelo y no presupone nada más que procesos de recambio gradual en poblaciones naturales. El estudio de la ecología, la etología, la neurobiología, la cultura animal, la psicología y la historia humana revela que las interpretaciones lamarckianas de los cambios y procesos de transmisión de caracteres presuponen siempre lo que pretenden explicar, es decir procesos previos de evolución darwiniana que garantizan la naturaleza adaptativa de las respuestas observadas. La búsqueda continua de dirección y de intención en los procesos evolutivos por muchos científicos sugiere la escasa aceptación de explicaciones materialistas como las que ofrece la teoría de Darwin.
Indicadores bioquímicos en suelos de un transecto altitudinal en el eje neovolcánico mexicano
Pajares-Moreno, Silvia;Gallardo-Lancho, Juan F.;Etchevers-Barra, Jorge D.;
Agrociencia , 2010,
Abstract: the biochemical aspects of the tepetates (hardened volcanic layers) and soils coming from volcanic materials have been little studied. the flow of co2 (fc) and the biochemical properties of volcanic soils representative of méxico were evaluated in this work. five soils were chosen in a transect of the tláloc volcano with different uses: cuminal grassland (pc), pine-oak (pe), reforested pine (pr), bare tepetate (td), and halophytic formations of the former lake of texcoco (lt), located at 2950, 3010, 2700, 2650, and 2220 m altitude. the soils of the transect correspond to the sequence: phaeozems (pc), luvisols (pe and pr), tepetates (td) and solonchacks (lt). in each zone soil samples were taken (0-15 cm deep) and fc and soil moisture (hs) were periodically measured in situ from august 2005 to july 2006. the variables determined were: soil organic c (soc), total n (nt), microbial biomass c and n, basal respiration (rs), ammonification of arginine, and enzyme activities (dehydrogenase, β-glucosidase, phosphatase, urease and protease). the most degraded areas (td and lt) recorded lower values in all variables, whereas the best preserved (pe and pc) showed higher values (especially in soc, nt, microbial biomass and enzyme activities). the rs and fc were low in td (8.1 ug c-co2 g-1 d-1 and 0.05-0.07 g m-2ha-1 ), since this is a hardened substrate without a plant cover and low content of soc and nt (0.8 mg c g-1 and 0.13 mg n g-1). the higher content of soc in pe and pc (55.2 and 32.7 mg c g-1) and hs during the rainfall period promote soil microbial activity and thus fc (1.22 and 1.05 g m-2 ha-1 in august). the biochemical variables selected, of easy measurement and interpretation, are suitable indicators to assess the quality of mexican volcanic soils under different environmental conditions.
Indicadores bioquímicos de calidad en tepetates cultivados del eje neovolcánico mexicano
Pajares-Moreno, Silvia;Gallardo-Lancho, Juan F.;Marinari, Sara;Etchevers-Barra, Jorge D.;
Agrociencia , 2010,
Abstract: tepetates (hardened volcanic tuff located in the mexican transvolcanic belt) conditioned for agricultural use are highly degraded due to poor management practices. the objective of this study was to define biochemical characteristics that can be used as early indicators of the state of tepetate recovery. during the period 2002-2005, experimental plots cultivated since 1986 were subjected to three agronomic management practices: traditional (tt), improved (tm) and organic (to). another two plots plowed in 2002 were treated with traditional (rt) and organic (ro) management. as a reference, two plots of tepetates without cultivation were selected (tv and td). soil samples were collected, and the following variables were determined: soil organic carbon (soc), total n (nt), microbial biomass c and n (bm), soil respiration (rs), n mineralization, dehydrogenase, β-glucosidase, phosphatase, urease and protease activity, ammonification of arginine, and different metabolic indexes. the tepetates without cultivation, containing little soc and nt, had the lowest values of all of the biochemical variables, which increased with years of cultivation, especially with to and tm management. the highestvalues of bm, rs and enzyme activity were associated with the increase in soc in to and tm plots, suggesting improved quality and fertility of these substrates. therefore, appropriate management of tepetates, with supplements of organic matter or fertilizers with harvest residue cover, promoted better biochemical properties. these variables correlated significantly, indicating the existence of close relationships among the biochemical processes in the tepetates. the biochemical variables studied were useful indicators for assessing changes in quality of the tepetates cultivated under different management systems.
Adsorción de Fenol y 3-Cloro Fenol sobre Carbones Activados mediante Calorimetría de Inmersión
Moreno-Piraján,Juan C; Navarrete,Luisa F; Giraldo,Liliana; García,Vanessa;
Información tecnológica , 2007, DOI: 10.4067/S0718-07642007000300009
Abstract: immersion enthalpies of five samples of activated carbon obtained from diverse lignocellulosic materials are determined, each with different activation degree in aqueous solutions of phenol and 3-chlorophenol for characterising the solid-aqueous dissolution interaction. the values obtained were between 6.80 y 13.9 jg-1. also, immersion enthalpies of these activated carbons in naoh and hcl 0.1 m solutions were determined, obtaining higher values for the immersion enthalpy in hcl that ranged between 32.6 and 68.3 jg-1. immersion enthalpies values decrease with the increase of superficial acid group content of the activated carbons, which constitutes the determinant factor for the phenol and 3-chlorophenol adsorption in the solids studied.
Polimorfismos de receptores semejantes a Toll 2 y 4 en pacientes con asma bronquial y enfermedad pulmonar obstructiva crónica (EPOC)
Larocca G,Nancy Elizabeth; De Sanctis,Juan Bautista; Toro,Félix; Moreno,Dolores; Tálamo,Carlos;
Revista de la Facultad de Medicina , 2008,
Abstract: toll like receptors are important in the inflammatory immune response. several mutations of these receptors have been related to the development and chronicity of different inflammatory diseases as bronchial asthma and obstructive pulmonary disease. a case control study was performed, 100 patients with bronchial asthma, 100 obstructive pulmonary disease and 100 controls. restriction based polymorphism pcr analysis was performed for tlr2 (arg677trp and arg753gln) and tlr4 (asp299gly and thr399ile) genes and its association with asthma and obstructive pulmonary disease was assessed. the frequency of tlr4 polymorphism was 9 % in each group studied (asthma, obstructive pulmonary disease and controls). no association was found among tlr4 polymorphism and stage of disease for asthma or obstructive pulmonary disease. tlr4 polymorphism are not associated with the presence or severity of asthma or obstructive pulmonary disease in the venezuelan population.
Comportamiento de dos variedades de sandía Citrullus lanatus (Thunb Matsura y Nakan), injertadas sobre los portainjertos de calabaza, Lagenaria siceraria, zapallo Cucurbita moschata, ahuyama Cucurbita máxima y estropajo Luffa cylindrica The performance of two varieties of water melon Citrullus lanatus (Thub) Matsura and nakai, grafted over pumpkin Lagenaria siceraria, zapallo Cucurbita moschata, ahuyama Cucurbita maxima and estropajo Luffa cylindrica graftholders
Moreno Juan Carlos,Tanaka N. Edgar,Bruzón C. Serapio F.
Acta Agronómica , 1992,
Abstract: En 1987-I, se realizó en predios de la Universidad Nacional de Colombia, Sede Palmira un estudio para evaluar la viabilidad de los injertos, cuantificar la producción e introducir alternativas de manejo de los problemas fitosanitarios. El suelo bien estructurado tiene textura FArL, pH 7.0, materia orgánica 3%, P 48 ppm, K .7 me/100g de suelo y una CIC de 19 me/100g de suelo. Se realizó un injerto de púa o escudete con plántulas de sandía de las variedades Charleston Gray y Sugar baby sobre los patrones de las especies citadas. Al patrón se le eliminó el meristemo apical y se rajó longitudinalmente 1.0 - 1.5 cm y se le introdujo la púa en forma de cu a. La púa consistió en el 50% del tallo, las hojas cotiledonares y el meristemo apical. Las unidades experimentales en el campo se distribuyeron en bloques completos al azar, en donde los tratamientos fueron las plantas injertadas y los tratamientos testigos las variedades de sandía sembradas directamente por semillas. El prendimiento de las púas superó el 90% en todos los casos. Los portainjertos Lagenaria y Cucurbita influyeron en mayor aumento de área foliar, mientras que Luffa disminuyó ostensiblemente. Los portainjertos no desmejoraron las características organolépticas de las frutas de las dos variedades. El número de frutos en las plantas infestadas sobre zapallo y estropajo disminuyeron. In the first semester of 1987 was done this experiment at Universidad Nacional, Palmira. The objectives were to evaluate grafts viability, to quantify production and to give alternatives to phytosanitary problems. It was done a prick or escutcheon graft with water melon small plants from Charleston Gray and Sugar Baby. The summit bud was eliminated and it was longitudinally cut 1.0 - 1.5 cm for inserting the prick cotyledon leaves and the summit bud. Experimental units were distributed in random complete blocks, where experiment treatments were grafted plants and control the varieties sown directly by seeds. The success of the graft system in the described patterns was 90%. The Lagenaria and Cucurbita graftholders produced greater amount of foliate area than Luffa which reduced it greatly. Graftholders did not reduce the organoleptic characteristics of the fruits from the two varieties. - Pests infection in fruits of plants over Cucurbita and Luffa graftholders were reduced.
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