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Search Results: 1 - 10 of 232874 matches for " OCTAVIO R ROJAS-SOTO "
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Activity Response to Climate Seasonality in Species with Fossorial Habits: A Niche Modeling Approach Using the Lowland Burrowing Treefrog (Smilisca fodiens)
Alondra Encarnación-Luévano, Octavio R. Rojas-Soto, J. Jesús Sigala-Rodríguez
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0078290
Abstract: The importance of climatic conditions in shaping the geographic distribution of amphibian species is mainly associated to their high sensitivity to environmental conditions. How they cope with climate gradients through behavioral adaptations throughout their distribution is an important issue due to the ecological and evolutionary implications for population viability. Given their low dispersal abilities, the response to seasonal climate changes may not be migration, but behavioral and physiological adaptations. Here we tested whether shifts in climatic seasonality can predict the temporal variation of surface activity of the fossorial Lowland Burrowing Treefrog (Smilisca fodiens) across its geographical distribution. We employed Ecological Niche Modeling (ENM) to perform a monthly analysis of spatial variation of suitable climatic conditions (defined by the July conditions, the month of greatest activity), and then evaluated the geographical correspondence of monthly projections with the occurrence data per month. We found that the species activity, based on the species' occurrence data, corresponds with the latitudinal variation of suitable climatic conditions. Due to the behavioral response of this fossorial frog to seasonal climate variation, we suggest that precipitation and temperature have played a major role in the definition of geographical and temporal distribution patterns, as well as in shaping behavioral adaptations to local climatic conditions. This highlights the influence of macroclimate on shaping activity patterns and the important role of fossorials habits to meet the environmental requirements necessary for survival.
Dispersión de semillas por aves en un paisaje de bosque mesófilo en el centro de Veracruz, México: Su papel en la restauración pasiva
HERNáNDEZ-LADRóN DE GUEVARA,IVETTE; ROJAS-SOTO,OCTAVIO R; LóPEZ-BARRERA,FABIOLA; PUEBLA-OLIVARES,FERNANDO; DíAZ-CASTELAZO,CECILIA;
Revista chilena de historia natural , 2012, DOI: 10.4067/S0716-078X2012000100007
Abstract: seed dispersal by birds may play a major role in the successful natural forest restoration process as birds can deposit pioneer and primary seeds species, thereby defining the recovery of plant community composition over time. in this study, seed ingestion and dispersion by frugivorous birds were analyzed as processes facilitating the restoration of tropical cloud montane forests in central veracruz, mexico. birds were classified according to their affinity to the forest and their preference to a particular forest stratum, in order to determine whether these factors were related to the richness, abundance and diversity of ingested and dispersed seeds. we analyzed 93 fecal samples from 23 bird species. a total of 2699 seeds from 17 plant species were found in the fecal samples, the most abundant seed was from the shrub conostegia xalapensis. we analyzed the correlation between seed size and beak size for the six most frequently captured bird species. we also evaluated the effect of bird ingestion on seed germination by performing two experiments, the first one using the total number of seeds found in fecal samples, and the second one using c. xalapensis seeds that were administered artificially to the birds and their germination compared with control seeds. we found significant differences among the ingested seed diversity indexes for the most commonly captured birds, which supports a differential seed consumption and dispersion. however, there were no significant differences of the seed abundance and richness between birds with different forest affinity or forest stratum preference. also, there was no significant association between seed size and the height and the width of the beak, but there was a difference found in the length measured from the base and from the nostrils. from the total seed species, 59 % germinated from fecal samples belonging to 78 % of the bird species. as has been suggested for lowland tropical forests, this study also showed that in tropical
Dispersión de semillas por aves en un paisaje de bosque mesófilo en el centro de Veracruz, México: Su papel en la restauración pasiva Seed dispersal by birds in a cloud forest landscape in central Veracruz, Mexico: Its role in passive restoration
IVETTE HERNáNDEZ-LADRóN DE GUEVARA,OCTAVIO R ROJAS-SOTO,FABIOLA LóPEZ-BARRERA,FERNANDO PUEBLA-OLIVARES
Revista chilena de historia natural , 2012,
Abstract: La dispersión de semillas por aves puede jugar un papel determinante en el éxito de la restauración pasiva de los bosques ya que las aves pueden depositar semillas de especies pioneras y primarias, definiendo con ello la recuperación de la composición de la comunidad vegetal en el tiempo. En este trabajo se analizó la ingesta y dispersión de semillas por aves frugívoras como coadyuvantes en la restauración del bosque mesófilo de monta a en el centro de Veracruz, México. Las aves fueron clasificadas de acuerdo a su afinidad por el bosque y al estrato arbóreo en que concentran su actividad, con el fin de determinar si estas características se relacionan con la abundancia, riqueza y diversidad de las semillas que ingieren y dispersan. Se analizaron 93 excretas de 23 especies de aves; en ellas se encontraron 2699 semillas de 17 especies vegetales, siendo las más abundantes las del arbusto Conostegia xalapensis. Analizamos la correlación entre tama o de las semillas y tama o del pico para las seis especies de aves más capturadas. Complementariamente, evaluamos el efecto de la ingesta de semillas por aves sobre la germinación, realizando dos experimentos, uno con el total de las semillas obtenidas en las excretas, y otro con semillas de C. xalapensis que fueron administradas a las aves artificialmente y su germinación comparada con semillas control. Se encontraron diferencias significativas entre los índices de diversidad de semillas ingeridas para las seis especies de aves con mayor número de registros, lo que sugiere un consumo diferencial. Sin embargo, no se encontraron diferencias significativas en la riqueza y abundancia de semillas consumidas entre aves con diferente afinidad al bosque y preferencia de estrato arbóreo. Tampoco se observó una asociación significativa entre el tama o de semillas con el ancho y lo alto del pico, pero sí con la longitud tomada desde la base y desde los nostrilos del mismo. Del total de las especies de semillas encontradas, el 59 % germinó en las excretas del 78 % de las especies de aves. Este trabajo muestra que en los bosques mesófilos de monta a las aves son agentes dispersores importantes de especies de plantas pertenecientes a bosques secundarios y también dispersores de algunas plantas del bosque primario, por ello son agentes que facilitan el proceso de sucesión forestal. Seed dispersal by birds may play a major role in the successful natural forest restoration process as birds can deposit pioneer and primary seeds species, thereby defining the recovery of plant community composition over time. In this study, seed inge
Avifauna de Campo Morado, Guerrero, México Avifauna of Campo Morado, Guerrero, Mexico
Octavio R. Rojas-Soto,Adán Oliveras de Ita,Roberto Carlos Almazán-Nú?ez,Adolfo G. Navarro-Sigüenza
Revista mexicana de biodiversidad , 2009,
Abstract: Se presenta una lista de 124 especies de aves para la región de Campo Morado, Guerrero, México, con información sobre el estatus estacional, categoría de riesgo y endemismo. Se resaltan 15 registros sobresalientes, ya sea porque son nuevos para el estado, o porque amplían su distribución geográfica y/o modifican su distribución estacional conocida. Además se discute la importancia de la localidad dentro de la cuenca del río Balsas. We report a list of 124 bird species from Campo Morado, Guerrero, Mexico, with information on seasonality, risk categories, and endemism. Fifteen records are noteworthy, as they are new state records, expand significantly their known geographical distribution, and/or modify their seasonal status within the area. We also highlight the importance of the study area within the Balsas River Basin.
Avifauna de Campo Morado, Guerrero, México
Rojas-Soto, Octavio R.;Oliveras de Ita, Adán;Almazán-Nú?ez, Roberto Carlos;Navarro-Sigüenza, Adolfo G.;Sánchez-González, Luis Antonio;
Revista mexicana de biodiversidad , 2009,
Abstract: we report a list of 124 bird species from campo morado, guerrero, mexico, with information on seasonality, risk categories, and endemism. fifteen records are noteworthy, as they are new state records, expand significantly their known geographical distribution, and/or modify their seasonal status within the area. we also highlight the importance of the study area within the balsas river basin.
Novel Data on the Ecology of Cochranella mache (Anura: Centrolenidae) and the Importance of Protected Areas for This Critically Endangered Glassfrog in the Neotropics
H. Mauricio Ortega-Andrade, Octavio Rojas-Soto, Christian Paucar
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0081837
Abstract: We studied a population of the endangered glassfrog, Cochranella mache, at Bilsa Biological Station, northwestern Ecuador, from 2008 and 2009. We present information on annual abundance patterns, behavioral ecology, habitat use and a species distribution model performed with MaxEnt. We evaluate the importance of the National System of Protected Areas (SNAP) in Colombia and Ecuador, under scenarios of climate change and habitat loss. We predicted a restricted environmental suitability area from 48,509 Km2 to 65,147 Km2 along western Ecuador and adjacent Colombia; ~8% of the potential distribution occurs within SNAP. We examined four aspects of C. mache ecology: (1) ecological data suggests a strong correlation between relative abundance and rainfall, with a high probability to observe frogs through rainy months (February–May); (2) habitat use and the species distribution model suggest that this canopy dweller is restricted to small streams and rivulets in primary and old secondary forest in evergreen lowland and piedmont forest of western Ecuador, with predictions of suitability areas in adjacent southern Colombia; (3) the SNAP of Colombia and Ecuador harbor a minimum portion of the predicted model of distribution (<10%); and (4) synergetic effects of habitat loss and climate change reduces in about 95% the suitability areas for this endangered frog along its distributional range in Protected Areas. The resulting model allows the recognition of areas to undertake conservation efforts and plan future field surveys, as well as forecasting regions with high probability of C. mache occurrence in western Ecuador and southern Colombia. Further research is required to assess population tendencies, habitat fragmentation and target survey zones to accelerate the discovery of unknown populations in unexplored areas with high probability of suitability. We recommend that Cochranella mache must be re-categorized as “Critically Endangered” species in national and global status, according with criteria and sub-criteria A4, B1ab(i,ii,iii,iv),E.
The Use of Ecological Niche Modeling to Infer Potential Risk Areas of Snakebite in the Mexican State of Veracruz
Carlos Ya?ez-Arenas, A. Townsend Peterson, Pierre Mokondoko, Octavio Rojas-Soto, Enrique Martínez-Meyer
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0100957
Abstract: Background Many authors have claimed that snakebite risk is associated with human population density, human activities, and snake behavior. Here we analyzed whether environmental suitability of vipers can be used as an indicator of snakebite risk. We tested several hypotheses to explain snakebite incidence, through the construction of models incorporating both environmental suitability and socioeconomic variables in Veracruz, Mexico. Methodology/Principal Findings Ecological niche modeling (ENM) was used to estimate potential geographic and ecological distributions of nine viper species' in Veracruz. We calculated the distance to the species' niche centroid (DNC); this distance may be associated with a prediction of abundance. We found significant inverse relationships between snakebites and DNCs of common vipers (Crotalus simus and Bothrops asper), explaining respectively 15% and almost 35% of variation in snakebite incidence. Additionally, DNCs for these two vipers, in combination with marginalization of human populations, accounted for 76% of variation in incidence. Conclusions/Significance Our results suggest that niche modeling and niche-centroid distance approaches can be used to mapping distributions of environmental suitability for venomous snakes; combining this ecological information with socioeconomic factors may help with inferring potential risk areas for snakebites, since hospital data are often biased (especially when incidences are low).
Efectos de la capacitación pedagógica en la práctica docente universitaria en salud
Sáenz-Lozada,María L; Cárdenas-Mu?oz,María L; Rojas-Soto,Edgar;
Revista de Salud Pública , 2010, DOI: 10.1590/S0124-00642010000300008
Abstract: objective evaluating changes in teaching adopted by teachers after participating in the pedagogical health science formation extension course taught by the national university of colombia's pedagogical support and teaching formation group from the medicine faculty. this was a part-time course; it dealt with topics such as didactics, curriculum, evaluation and the teacher's role. methods a qualitative, exploratory study was carried out, involving a personal interview formulated by the investigators; this was held in each participant's place of work. fifty teachers who had taken the course between 2003 and 2004 were interviewed. the questionnaire consisted of ten semi-structured questions. results after taking the course, 82 % of the participants considered that the quality of their communication with students was one of their most valued qualities, having understood that learning is a process which must be shared by both teachers and students. 64 % of the participants stated that they had acquired new concepts about evaluation and had increased their use of more participative pedagogical strategies. conclusion teaching training courses had a positive effect on teaching, reflected in the quality of communication, teacher-student relationships and the pedagogic strategies used, all being very important elements in constructivist-orientated pedagogical models. the study's results agreed with other investigators' prior experience. the university must encourage this kind of intervention which will promote its own academic development by improving its teachers' performance.
Rodless Weissenberg effect
Enrique Soto,Oscar R. Enríquez,Roberto Zenit,Octavio Manero
Physics , 2008,
Abstract: The climbing effect of a viscoelastic fluid when stirred by a spinning rod is well documented and known as Weissenberg effect(Wei et al, 2006). This phenomenon is related to the elasticity of the fluid. We have observed that this effect can appear when the fluid is stirred without a rod. In this work, a comparison of the flow around a spinning disk for a Newtonian and a non-Newtonian liquids is presented. The flow is visualized with ink and small bubbles as fluid path tracers. For a Newtonian fluid, at the center of the spinning disk, the fluid velocity is directed towards the disk (sink flow); on the other hand, for a viscoelatic liquid, a source flow is observed since the fluid emerges from the disk. The toroidal vortices that appear on top of the disk rotate in opposite directions for the Newtonian and non-Newtonian cases. Similar observations have been reported for the classical rod climbing flow (Siginer, 1984 and Escudier, 1984). Some authors have suggested that this flow configuration can be used to determine the elastic properties of the liquid (Escuider, 1984 and Joshep, 1973).
Active temperature and velocity correlations produced by a swimmer suspension
C. Parra-Rojas,R. Soto
Physics , 2013, DOI: 10.1103/PhysRevE.87.053022
Abstract: The agitation produced in a fluid by a suspension of micro-swimmers in the low Reynolds number limit is studied. In this limit, swimmers are modeled as force dipoles all with equal strength. The agitation is characterized by the active temperature defined, as in kinetic theory, as the mean square velocity, and by the equal-time spatial correlations. Considering the phase in which the swimmers are homogeneously and isotropically distributed in the fluid, it is shown that the active temperature and velocity correlations depend on a single scalar correlation function of the dipole-dipole correlation function. By making a simple medium range oder model, in which the dipole-dipole correlation function is characterized by a single correlation length $k_0^{-1}$ it is possible to make quantitative predictions. It is found that the active temperature depends on the system size, scaling as $L^{4-d}$ at large correlation lengths $L\ll k_0^{-1}$, while in the opposite limit it saturates in three dimensions and diverges logarithmically with the system size in two dimensions. In three dimensions he velocity correlations decay as $1/r$ for small correlation lengths, while at large correlation lengths the transverse correlation function becomes negative at maximum separation $r\sim L/2$, effect that disappears as the system increases in size.
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