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Search Results: 1 - 10 of 472470 matches for " Adrián;Villar Sánchez "
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Erosión del suelo, escurrimiento y pérdida de nitrógeno y fósforo en laderas bajo diferentes sistemas de manejo en Chiapas, México
Camas Gómez, Robertony;Turrent Fernández, Antonio;Cortes Flores, José Isabel;Livera Mu?óz, Manuel;González Estrada, Adrián;Villar Sánchez, Bernardo;López Martínez, Jaime;Espinoza Paz, Néstor;Cadena I?iguez, Pedro;
Revista mexicana de ciencias agrícolas , 2012,
Abstract: in chiapas, mexico, soil erosion is the main problem affecting the sustainability of hillside lands. as a result, yields and incomes are low, and soil quality continues to decrease. with the aim of finding sustainable technological alternatives, an evaluation was performed on the following systems: maize in conservation tillage (mlc); maize in plant barriers (mbmv) and maize alternated with fruit trees (miaf), in terms of surface runoff, production of sediments and loss of nitrogen and phosphorous from june to november, 2009. the systems were set up in adjacent microbasins, belonging to the basin of river catarina, jiquipilas, chiapas. the soil is a typic haplustepts, with a slope that varies between 3 0 and 40%. out of the total rainfalls, 54% caused soil erosion, 15 % of these with rains of over 40 mm 62% of the total erosion. the runoff coefficient and the specific soil degradation were similar and lower in the micro basins; miaf (12, 5.8 t ha-1) and mbmv (13, 6.3 t ha-1 ) than in the microbasin with mlc (19, 16.8 t ha-1), respectively. in miaf, the runoff filter and total cover provided by maize and bean plants during most of the growth season played an important part in obtaining these results, despite this microbasin presenting a greater slope steepness and length. in regards to the nutrients, there was a greater loss of nitrates in the microbasin with the system mbmv, possibly due to the nitrogen contribution by the leftovers of the pruning ofgliricidia sepium. in regard to phosphorous, the system miaf displayed a greater loss, caused by the yearly phosphoric fertilization performed on the guava trees for three years.
Presión de caza de la comunidad nativa mushuckllacta de chipaota, zona de amortiguamiento del parque nacional cordillera azul, Perú
Adrián Sánchez,Pedro Vásquez
Ecología Aplicada , 2007,
Abstract: Se determinó la presión de caza para el a o 2005 en la comunidad nativa Mushuckllacta de Chipaota, ubicada en la zona de amortiguamiento del Parque Nacional Cordillera Azul Perú. La metodología empleada se basó en el registro de los animales cazados y censos en tres regiones distintas, empleándose las pruebas estadísticas nMDS y ANOSIM para su diferenciación. Como resultado se encontraron diferencias significativas entre las regiones; indicando alteraciones en la estructura de la comunidad de fauna silvestre de acuerdo a su cercanía a los principales centros poblados. Adicionalmente se estimó la densidad global para 13 especies de animales. A partir de las densidades obtenidas en la Región Sur (identificada como de ligera intervención humana) y considerando los valores de la literatura (Robinson & Redford, 1991), se generó un Modelo de Sostenibilidad, en base al cual se infiere que la caza de Mazama americana, Agouti paca, Eira barbara y Leopardus pardalis no es sostenible. Se muestra que 15 especies se encuentran bajo procesos de extinción local; y que probablemente Ateles sp., Psophia leucoptera, Pipile cumanenses y Aburria aburri han sido extirpadas del área de uso comunal
Los Acuerdos de Bolonia; desafíos y respuestas por parte de los sistemas de educación superior e instituciones en Latinoamérica
Adrián de Garay Sánchez
Universidades , 2008,
Abstract:
Las áreas de Investigación y los Cuerpos Académicos: las tensiones y efectos entre dos espacios de organización de la investigación en la UAM
adrián de garay sánchez
Reencuentro , 2009,
Abstract: El presente trabajo versa sobre las distintas tensiones y efectos, positivos y negativos, que ha tenido la aparición de una nueva forma de organización de la investigación en la uam,los llamados Cuerpos Académicos, producto de las políticas públicas impulsadas por el gobierno federal desde el sexenio pasado para todas las instituciones públicas de educación superior del país. Se trata de problematizar la manera en que las organizaciones educativas, y en particular la uam, atienden la complejidad de las formas de organización de la investigación que conviven en su interior.
Imidoyl Radicals for the Synthesis of Chromenoquinolines and Naphthyridines  [PDF]
Karen C. Vizcaíno-Escobedo, J. Adrián Sánchez-Carrillo, Martha Albores-Velasco
International Journal of Organic Chemistry (IJOC) , 2018, DOI: 10.4236/ijoc.2018.83024
Abstract: The stability of imidoyl radicals prepared from 2-(2-alkenyloxy)-phenyl selenoimidates and 2-(2-allylamino)-phenyl selenoimidates and their intramolecular free radical cyclization through the slow addition of tri-N-butyltin hydride and AIBN to obtain 4-chromanones and 4-quinolones were studied. The extension of the methodology to N-phenyl substituted imidoyl selenoates produced tandem cyclizations of the imidoyl radical with the allyl substituent, followed for a second cyclization of the intermediate radical with the aromatic substituent to produce dihydro-chromenoquinolines or tetrahy-dro-dibenzonaphtyridines. Further oxidation with DDQ produced: 6H-chromeno [4,3,b] quinoline and 7-methyl-6H-chromenoquinoline from 2-alkenylamino-phenylbenzamide and 5,6-dihydro-dibenzo [b,h][1,6] naphthyridine and 5,6-dihydro-7-methyl-dibenzo [b,h][1,6] naphthyridine from 2-2-(alkylamino)-N-phenylbenzamides. The cyclization of 2-(N,N-di-prop-2.enylamino)-N-phenylnicotinamide selenoate obtained from 2-aminonicotinic acid, produced 5,6-dihidro-benzo[b]pyrido2,3-h] [1,6] naphthyridine.
Presentación
Adrián de Garay Sánchez,Roberto Gutiérrez L.
El Cotidiano , 2007,
Abstract:
Los 25 a os de El Cotidiano: un balance del estudio y reflexión sobre la educación superior
Adrián de Garay,Roberto Sánchez Medina
El Cotidiano , 2009,
Abstract: Los temas que se han abordado en los veinticinco a os de existencia de El Cotidiano son, en verdad, extensos y complejos, e intentar hacer una revisión detallada de cada uno de ellos rebasaría los alcances de este artículo. Más bien, nuestro interés es menos ambicioso y buscamos dar cuenta del análisis que se ha hecho sobre la educación superior en estos veinticinco a os de vida de El Cotidiano. La idea consiste así en hacer un recuento de los principales temas que han estado en el centro de la discusión, focalizarlos por décadas identificando de esta manera sus procesos de transformación, resaltar los problemas nacionales que directa o indirectamente la afectan, para desembocar finalmente en los temas que aún siguen pendientes en la agenda de políticas de la educación superior.
La modificación de la política de admisión en la UAM y los cambios en las trayectorias escolares al primer a o de estudios en la Unidad Azcapotzalco
Adrián de Garay Sánchez,Roberto Leonardo Sánchez Medina
Perfiles educativos , 2012,
Abstract: El objetivo del artículo consiste en identificar los cambios ocurridos en las trayectorias escolares de dos generaciones de estudiantes de licenciatura en la Universidad Autónoma Metropolitana durante el primer a o de estudios, específicamente en el caso de la Unidad Azcapotzalco. En el a o 2008 la Universidad modificó su política de admisión al considerar, además del puntaje alcanzado en el examen de selección, una ponderación del 25 por ciento al promedio de calificaciones obtenido en el bachillerato. Para tal efecto, trabajamos comparativamente con la generación que ingresó a la UAM en la primavera de 2003 con el anterior mecanismo de admisión, y la primera generación que ingresó con el nuevo mecanismo en la primavera de 2008. Empleando modelos de regresión logística se exploraron los factores que incidieron en la generación de primavera de 2008 para comprender la diversidad de trayectorias escolares de los estudiantes.
Occurrence Patterns of Afrotropical Ticks (Acari: Ixodidae) in the Climate Space Are Not Correlated with Their Taxonomic Relationships
Agustín Estrada-Pe?a, Adrián Estrada-Sánchez, David Estrada-Sánchez
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0036976
Abstract: Foci of tick species occur at large spatial scales. They are intrinsically difficult to detect because the effect of geographical factors affecting conceptual influence of climate gradients. Here we use a large dataset of occurrences of ticks in the Afrotropical region to outline the main associations of those tick species with the climate space. Using a principal components reduction of monthly temperature and rainfall values over the Afrotropical region, we describe and compare the climate spaces of ticks in a gridded climate space. The dendrogram of distances among taxa according to occurrences in the climate niche is used to draw functional groups, or clusters of species with similar occurrences in the climate space, as different from morphologically derived (taxonomical) groups. We aim to further define the drivers of species richness and endemism at such a grid as well as niche similarities (climate space overlap) among species. Groups of species, as defined from morphological traits alone, are uncorrelated with functional clusters. Taxonomically related species occur separately in the climate gradients. Species belonging to the same functional group share more niche among them than with species in other functional groups. However, niche equivalency is also low for species within the same taxonomic cluster. Thus, taxa evolving from the same lineage tend to maximize the occupancy of the climate space and avoid overlaps with other species of the same taxonomic group. Richness values are drawn across the gradient of seasonal variation of temperature, higher values observed in a portion of the climate space with low thermal seasonality. Richness and endemism values are weakly correlated with mean values of temperature and rainfall. The most parsimonious explanation for the different taxonomic groups that exhibit common patterns of climate space subdivision is that they have a shared biogeographic history acting over a group of ancestrally co-distributed organisms.
Assemblage of a Semi-Arid Annual Plant Community: Abiotic and Biotic Filters Act Hierarchically
Arantzazu L. Luzuriaga, Ana M. Sánchez, Fernando T. Maestre, Adrián Escudero
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0041270
Abstract: The study of species coexistence and community assembly has been a hot topic in ecology for decades. Disentangling the hierarchical role of abiotic and biotic filters is crucial to understand community assembly processes. The most critical environmental factor in semi-arid environments is known to be water availability, and perennials are usually described as nurses that create milder local conditions and expand the niche range of several species. We aimed to broaden this view by jointly evaluating how biological soil crusts (BSCs), water availability, perennial species (presence/absence of Stipa tenacissima) and plant-plant interactions shape a semi-arid annual plant community. The presence and cover of annual species was monitored during three years of contrasting climate. Water stress acted as the primary filter determining the species pool available for plant community assembly. Stipa and BSCs acted as secondary filters by modulating the effects of water availability. At extremely harsh environmental conditions, Stipa exerted a negative effect on the annual plant community, while at more benign conditions it increased annual community richness. Biological soil crusts exerted a contradictory effect depending on climate and on the presence of Stipa, favoring annuals in the most adverse conditions but showing repulsion at higher water availability conditions. Finally, interactions among co-occurring annuals shaped species richness and diversity of the final annual plant assembly. This study sheds light on the processes determining the assembly of annual communities and highlights the importance of Biological Soil Crusts and of interactions among annual plants on the final outcome of the species assembly.
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