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Search Results: 1 - 10 of 325780 matches for " AN;Farías-Sánchez "
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Desempe?o biológico del callo de hacha Atrina maura y el mejillón Mytella strigata en diferentes regímenes de flujo de agua
Arrieche, D;Maeda-Martínez, AN;Farías-Sánchez, JA;Saucedo, PE;
Ciencias marinas , 2010,
Abstract: three water flow rates (3.1, 7.3, and 12.1 cm s-1) were used during a 26-day period to determine their effects on shell dimensions, tissue mass, condition index, biochemical composition of tissues, and mortality of the penshell atrina maura and mussel mytella strigata kept in an open-flow flume. these parameters were measured at the beginning and end of the trial and significant differences were determined using non-parametric comparisons of multiple independent samples. both species were able to withstand high seston loads and daily oscillations of temperature, which yielded negligible mortalities. both species were affected differently by water flow. atrina maura grew significantly larger above a flow of 7.3 cm s-1, which appears typical of species inhabiting tidal channels. at this flow, there was a significant increase in lipids and acylglycerols within the digestive gland, adductor muscle, and mantle tissue, accompanied by a significant decline in proteins and carbohydrates within the same organs. in contrast, the flow did not have a significant effect on m. strigata, except for increased lipid and acylglycerol reserves within body tissues at 3.1 and 7.3 cm s-1, and increased lipid and acylglycerol levels within the gonad at 7.3 and 12.1 cm s-1. digestive gland proteins, carbohydrates, and glycogen increased at the highest flow. data suggest that the penshell is a flow-conforming mollusk that prefers flows exceeding 7.3 cm s-1, and that the strigate mussel is a flow-regulating species in the range of flows that were studied.
Transiciones de fase topológicas en cristales líquidos
Paredes, R;Fari?as-Sánchez, A.I;Berche, B;
Revista mexicana de física , 2006,
Abstract: by means of monte carlo simulations, using finite size scaling and conformal transformations, evidences of a topological phase transition in liquid crystals in two dimensions are reported. a paramagnetic phase appears at high temperature whereas a quasi-long-range-order (qlro) phase is founded at low temperatures. it is determined that the correlation function exponent, at very low temperatures, is linear with the temperature, a typical behavior of spin waves. this contradicts predictions that for systems with non-abelian group of global symmetry the spin waves are not relevant. aditionally, the implications that would have the presence of impurities in this type of transitions is discussed.
Transiciones de fase topológicas en cristales líquidos
R. Paredes,A.I. Fari?as-Sánchez,B. Berche
Revista mexicana de física , 2006,
Abstract: Mediante simulaciones de Monte Carlo, utilizando escalamiento de tama o finito y transformaciones conformes se reportan evidencias de una transición de fase topológica en cristales líquidos en dos dimensiones. A altas temperaturas se presenta una fase paramagnética, mientras que a bajas temperaturas se encuentra un fase de cuasi-largo-orden (QLRO). Se encuentra que a muy bajas temperaturas el exponente de la función de correlación de la fase QLRO es lineal con la temperatura, teniéndose de esta manera un comportamiento típico de ondas de espín. Esto último contradice predicciones de que para sistemas con grupo de simetría global no abeliano las ondas de espín no son relevantes. Adicionalmente se discute que implicaciones tendría la presencia de impurezas en este tipo de transiciones.
Transiciones de fase topológicas en cristales líquidos
R. Paredes,A.I. Fari?as-Sánchez,B. Berche
Revista mexicana de física , 2006,
Abstract: By means of Monte Carlo simulations, using finite size scaling and conformal transformations, evidences of a topological phase transition in liquid crystals in two dimensions are reported. A paramagnetic phase appears at high temperature whereas a quasi-long-range-order (QLRO) phase is founded at low temperatures. It is determined that the correlation function exponent, at very low temperatures, is linear with the temperature, a typical behavior of spin waves. This contradicts predictions that for systems with non-abelian group of global symmetry the spin waves are not relevant. Aditionally, the implications that would have the presence of impurities in this type of transitions is discussed.
On the critical behaviour of two-dimensional liquid crystals
A.l. Fari?as-Sánchez,R. Botet,B. Berche,R. Paredes
Condensed Matter Physics , 2010,
Abstract: The Lebwohl-Lasher (LL) model is the traditional model used to describe the nematic-isotropic transition of real liquid crystals. In this paper, we develop a numerical study of the temperature behaviour and of finite-size scaling of the two-dimensional (2D) LL-model. We discuss two possible scenarios. In the first one, the 2D LL-model presents a phase transition similar to the topological transition appearing in the 2D XY-model. In the second one, the 2D LL-model does not exhibit any critical transition, but its low temperature behaviour is rather characterized by a crossover from a disordered phase to an ordered phase at zero temperature. We realize and discuss various comparisons with the 2D XY-model and the 2D Heisenberg model. Having added finite-size scaling behaviour of the order parameter and conformal mapping of order parameter profile to previous studies, we analyze the critical scaling of the probability distribution function, hyperscaling relations and stiffness order parameter and conclude that the second scenario (no critical transition) is the most plausible.
On the critical behavior of two-dimensional liquid crystals
Ana Isabel Fari?as-Sánchez,Robert Botet,Bertrand Berche,Ricardo Paredes
Physics , 2009,
Abstract: The Lebwohl-Lasher (LL) model is the traditional model used to describe the nematic-isotropic transition of real liquid crystals. In this paper, we develop a numerical study of the temperature behaviour and of finite-size scaling of the two-dimensional (2D) LL-model. We discuss two possible scenarios. In the first one, the 2D LL-model presents a phase transition similar to the topological transition appearing in the 2D XY-model. In the second one, the 2D LL-model does not exhibit any critical transition, but its low temperature behaviour is rather characterized by a crossover from a disordered phase to an ordered phase at zero temperature. We realize and discuss various comparisons with the 2D XY-model and the 2D Heisenberg model. Adding to previous studies of finite-size scaling behaviour of the order parameter and conformal mapping of order parameter profile, we analyze the critical scaling of the probability distribution function, hyperscaling relations and stiffness order parameter and conclude that the second scenario (no critical transition) is the most plausible.
No quasi-long-range order in the two-dimensional liquid crystal
Ricardo Paredes,Ana-Isabel Fari?as-Sánchez,Robert Botet
Physics , 2008,
Abstract: Systems with global symmetry group O(2) experience topological transition in the 2-dimensional space. But there is controversy about such a transition for systems with global symmetry group O(3). In this paper, we study the Lebwohl-Lasher model for the two-dimensional liquid crystal, using three different methods independent of the proper values of possible critical exponents. Namely, we analyze the at-equilibrium order parameter distribution function with: 1) the hyperscaling relation; 2) the first scaling collapse for the probability distribution function;and 3) the Binder's cumulant. We give strong evidences for definite lack of a line of critical points at low temperatures in the Lebwohl-Lasher model, contrary to conclusions of a number of previous numerical studies.
Topological phase transitions in liquid crystals -- Transiciones de fase topológicas en cistales l{'?}quidos
V. Ricardo Paredes,Ana I. Fari?as-Sánchez,Bertrand Berche
Physics , 2004,
Abstract: By means of Monte Carlo simulations, using finite size scaling and conformal transformations, evidences of a topological phase transition in liquid crystals in two dimensions are reported. A paramagnetic phase appears at high temperature whereas a quasi-long-range-order (QLRO) phase is founded at low temperatures. It is determined that the correlation function exponent, at very low temperatures, is linear with the temperature, a typical behavior of spin waves. This contradicts predictions that for systems with non-abelian group of global symmetry the spin waves are not relevant. Aditionally, the implications that would have the presence of impurities in this type of transitions is discussed. ----- Mediante simulaciones de Monte Carlo, utilizando escalamiento de tama\~no finito y transformaciones conforme, se reportan evidencias de una transici\'on de fase topol\'ogica en cristales l{\'\i}quidos en dos dimensiones. A altas temperaturas se presenta una fase paramagn\'etica mientras que a bajas temperaturas se encuentra un fase de cuasi-largo-orden (QLRO). Se encuentra que a muy bajas temperaturas el exponente de la funci\'on de correlaci\'on de la fase QLRO es lineal con la temperatura teni\'endose de esta manera un comportamiento t{\'\i}pico de ondas de esp{\'\i}n. Esto \'ultimo contradice predicciones de que para sistemas con grupo de simetr{\'\i}a global no abeliano las ondas de esp{\'\}n no son relevantes. Adicionalmente se discute que implicaciones tendr{\'\i}a la presencia de impurezas en este tipo de transiciones.
Respuesta kairomonal de coleópteros asociados a Dendroctonus frontalis y dos especies de Ips (Coleoptera: Curculionidae) en bosques de Chiapas, México
Domínguez-Sánchez, Bernardo;Macías-Sámano, Jorge E.;Ramírez-Marcial, Neptalí;León-Cortés, Jorge L.;
Revista mexicana de biodiversidad , 2008,
Abstract: we assessed the bark beetle diversity and the response of associated predators to aggregation pheromones in pine forests in chiapas, mexico. from june to october 2006, 40 lindgren funnel traps were established with different baits that included frontalin, ipsenol and ipsdienol pheromones and a control (without pheromone). we registered the attractiveness of frontalin to the bark beetle dendroctonus frontalis (zimmermann), and ipsenol and ipsdienol to ips spp. kairomonal specific response of the predators temnochila chlorodia (mannerheim), enoclerus ablusus (barr) and elacatis sp. was detected. we registered an important increase in abundance of bark beetles and predators during the summer to the beginning of fall. t. chlorodia exhibited differential attraction to the three pheromones evaluated, whereas e. ablusus, elacatis sp. and leptostylus sp. were significantly attracted to ipsenol and ipsdienol. this is the first report of kairomonal response of the phytophagous leptostylus sp. (cerambycidae) for méxico. our results showed that inter-and intra-specific communication between different bark beetles and associated species may occur, which promotes competitive and predator interaction between them.
Respuesta kairomonal de coleópteros asociados a Dendroctonus frontalis y dos especies de Ips (Coleoptera: Curculionidae) en bosques de Chiapas, México Kairomonal response of coleopterans associated with Dendroctonus frontalis and two Ips species (Coleoptera: Curculionidae) in forest of Chiapas, Mexico
Bernardo Domínguez-Sánchez,Jorge E. Macías-Sámano,Neptalí Ramírez-Marcial,Jorge L. León-Cortés
Revista mexicana de biodiversidad , 2008,
Abstract: Se evaluó la diversidad de escarabajos descortezadores y la respuesta diferencial de sus coleópteros asociados a feromonas comerciales de agregación, en bosques de pino del estado de Chiapas, México. Durante los meses de junio a octubre del 2006, se colocaron 40 trampas multiembudo tipo Lindgren cebadas con las feromonas racémicas frontalina, ipsenol e ipsdienol y un testigo (sin feromona). La captura fue más abundante para los escarabajos descortezadores Dendroctonus frontalis (Zimmermann) con frontalina, y de Ips spp. con ipsenol e ipsdienol. Se registró respuesta kairomonal específica de los depredadores Temnochila chlorodia (Mannerheim), Enoclerus ablusus (Barr) y Elacatis sp. hacia las feromonas de agregación. Tanto para descortezadores como para depredadores, las mayores abundancias fueron registradas durante el verano y a comienzos del oto o. Temmnochila chlorodia exhibió una atracción diferencial hacia los semioquímicos evaluados, mientras que E. ablusus, Elacatis sp. y Leptostylus sp. fueron atraídos principalmente por las feromonas ipsenol e ipsdienol. Además, por primera vez para México se determinó la respuesta kairomonal del fitófago Leptostylus sp. (Cerambycidae). Estos resultados indican que hay una comunicación intra e inter específica entre los escarabajos descortezadores y sus especies asociadas que promueven interacciones de competencia y depredación. We assessed the bark beetle diversity and the response of associated predators to aggregation pheromones in pine forests in Chiapas, Mexico. From June to October 2006, 40 Lindgren funnel traps were established with different baits that included frontalin, ipsenol and ipsdienol pheromones and a control (without pheromone). We registered the attractiveness of frontalin to the bark beetle Dendroctonus frontalis (Zimmermann), and ipsenol and ipsdienol to Ips spp. Kairomonal specific response of the predators Temnochila chlorodia (Mannerheim), Enoclerus ablusus (Barr) and Elacatis sp. was detected. We registered an important increase in abundance of bark beetles and predators during the summer to the beginning of fall. T. chlorodia exhibited differential attraction to the three pheromones evaluated, whereas E. ablusus, Elacatis sp. and Leptostylus sp. were significantly attracted to ipsenol and ipsdienol. This is the first report of kairomonal response of the phytophagous Leptostylus sp. (Cerambycidae) for México. Our results showed that inter-and intra-specific communication between different bark beetles and associated species may occur, which promotes competitive and predator interaction b
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