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Search Results: 1 - 10 of 598798 matches for " J. M.;Aguilar-Reyes "
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Magnetic characteristics and archeointensity determination on Mesoamerican Pre-Columbian Pottery from Quiahuiztlan, Veracruz, Mexico
López-Téllez, J. M.;Aguilar-Reyes, B;Morales, J;Goguitchaichvili, A;Calvo-Rathert, M;Urrutia-Fucugauchi, J;
Geofísica internacional , 2008,
Abstract: we report a detailed archeomagnetic investigation on pre-columbian potteries from quiahuiztlan, veracruz, from ~900 ad to 1521 ad. archeological samples analyzed by modern magnetic techniques carry a stable univectorial thermoremanent magnetization under alternating field treatment. continuous low-field susceptibility vs. temperature curves performed in air indicates ti-poor titanomagnetites as magnetization carriers. few samples, however, show two ferrimagnetic phases with curie temperatures compatible with both ti-poor and ti-rich titanomagnetites. hysteresis parameter ratios fall essentially in the pseudo-single-domain region, which may indicate a mixture of multi-domain and a significant amount of single domain grains. early geomagnetic field intensity determinations using the coe variant of thellier method were performed on 90 selected samples. cooling rate corrected intensity values range from 34.0 ± 1.2 to 62.2 ± 0.2 μt. corresponding virtual axial dipole moments (vadm) range from 5.7 to 10.7 x1022 am2. absolute intensity curves for mesoamerica present limited spatial/temporal resolution. for tentative dating purposes, we used global archeointensity curves reduced to central and eastern mexico that permit preliminary dating of quiahuiztlan potteries. comparison of our data against those reported in archeoint database allow to identify two periods 900- 1000 and 1400-1600 ad as the most probable manufacturing ranges for the potteries studied.
Magnetic characteristics and archeointensity determination on Mesoamerican Pre-Columbian Pottery from Quiahuiztlan, Veracruz, Mexico
J. M. López-Téllez,B. Aguilar Reyes,J. Morales,A. Goguitchaichvili
Geofísica internacional , 2008,
Abstract: We report a detailed archeomagnetic investigation on pre-Columbian potteries from Quiahuiztlan, Veracruz, from ~900 AD to 1521 AD. Archeological samples analyzed by modern magnetic techniques carry a stable univectorial thermoremanent magnetization under alternating field treatment. Continuous low-field susceptibility vs. temperature curves performed in air indicates Ti-poor titanomagnetites as magnetization carriers. Few samples, however, show two ferrimagnetic phases with Curie temperatures compatible with both Ti-poor and Ti-rich titanomagnetites. Hysteresis parameter ratios fall essentially in the pseudo-single-domain region, which may indicate a mixture of multi-domain and a significant amount of single domain grains. Early geomagnetic field intensity determinations using the Coe variant of Thellier method were performed on 90 selected samples. Cooling rate corrected intensity values range from 34.0 ± 1.2 to 62.2 ± 0.2 μT. Corresponding virtual axial dipole moments (VADM) range from 5.7 to 10.7 x1022 Am2. Absolute intensity curves for Mesoamerica present limited spatial/temporal resolution. For tentative dating purposes, we used global archeointensity curves reduced to central and eastern Mexico that permit preliminary dating of Quiahuiztlan potteries. Comparison of our data against those reported in ArcheoInt database allow to identify two periods 900- 1000 and 1400-1600 AD as the most probable manufacturing ranges for the potteries studied.
Análisis de pautas horarias en incendios forestales para el decenio 2001-2010
Rodrigo Roldán Martínez,Esteban Martínez Mesa,Eva M. Aguilar Martínez,J. Reyes Ruiz-Gallardo
Flamma , 2012,
Abstract: El comportamiento de los incendios forestales a lo largo del tiempo, no tiene por qué ser estable. De los múltiples parámetros que pueden ser considerados, el presente trabajo muestra cómo la pauta horaria de ocurrencia de fuego ha variado en el último decenio frente a otro pasado. De esta manera, analizando la base de datos de incendios del área de Defensa Contra Incendios Forestales (Ministerio de Agricultura, Alimentación y Medio Ambiente y comunidades autónomas), se ha observado cómo los incendios que mayor superficie queman actualmente se producen a diferente hora que hace 25 a os y que el número de incendios es siempre superior en el decenio 2001-2010 que en el pasado 1975-1984. No obstante, los máximos y mínimos de este número de incendios coinciden en ambos periodos, aunque la magnitud de los máximos es muy distinta, no así, la de mínimos que se mantiene muy similar. También se ha analizado la relación superficie quemada/número de incendios observando que esta proporción es bastante homogénea en 2001-2010, mientras que aparecen importantes variaciones horarias en el periodo 1975-1984. Finalmente, se deja abierto el futuro a la investigación sus posibles implicaciones en la evaluación del riesgo de incendios forestales.
Tree Species Composition in Tropical Forest Remnants of Highly Deforested Regions: The Case of the Huasteca Potosina Region, Mexico  [PDF]
Humberto Reyes, Blanca M. Vázquez, Carmen Jasso, Miguel Aguilar
Natural Resources (NR) , 2014, DOI: 10.4236/nr.2014.516086
Abstract: Deforestation and fragmentation of tropical forest are the most serious threats to biodiversity. In the lowlands of the Huasteca Potosina region, Mexico, more than 95,000 ha of tropical forest have disappeared. This paper analyses tree species composition in tropical forest patches of this highly deforested region, located in northeast of Mexico. At present, only 57 remnants of arboreal vegetation larger than ten hectares still remain standing, which cover 6117 ha. These decreasing fragments host 140 floristic species, representing 42 families and 85 genera. Compared with previous inventories, these data show a sharp drop in species composition. Most of the forest remnants contain less than 50% of the floristic diversity recorded by previous surveys, particularly in the medium subperennial tropical forest.
Quintessence interacting dark energy from induced matter theory of gravity
L. M. Reyes,Jose Edgar Madriz Aguilar
Physics , 2009,
Abstract: In the context of the induced matter theory of gravity, we investigate the possibility of deriving a 4D quintessential scenario where an interaction between dark energy and dark matter is allowed, and the dark energy component is modeled by a minimally coupled scalar field. Regarding the Ponce de Leon metric, we found that it is possible to obtain such scenario on which the energy densities of dark matter and dark energy, are both depending of the fifth extra coordinate. We obtain that the 4D induced scalar potential for the quintessence scalar field, has the same algebraic form to the one found by Zimdahl and Pavon in the context of usual 4D cosmology.
Embedding General Relativity with varying cosmological constant term in five-dimensional Brans-Dicke theory of gravity in vacuum
L. M. Reyes,Jose Edgar Madriz Aguilar
Physics , 2009,
Abstract: We investigate the possibility to recover a four-dimensional (4D) general theory of relativity, as embedded in a 5D spacetime where gravity is governed by a five-dimensional (5D) Brans-Dicke (BD) theory of gravity. Employing the Gauss-Codazzi-Ricci equations and some ideas of the induced matter theory, we obtain that when the 5D BD scalar field is only depending of the extra coordinate, it is possible to recover on every generic 4D hypersurface the usual Einstein field equations plus a cosmological constant term, with matter sources described by the energy-momentum tensor of induced matter and where the cosmological constant under certain conditions can vary with time. Finally to illustrate the formalism, we give an example in which we induced a cosmological constant from warped product spaces.
Desarrollo y calidad de inflorescencias de Antirrhinum majus L. cultivados en intemperie
Reyes-Montero, J. A.;Gutiérrez-Espinosa, J. A.;García-Villanueva, E.;Carrillo-Salazar, J. A.;Aguilar-Luna, J. M. E.;Gaytán-Acu?a, E. A.;
Revista Chapingo. Serie horticultura , 2009,
Abstract: the flower production of antirrhinum majus l. ("snapdragon") is commonly carried out in greenhouse conditions using traditional cultivars. in the present paper we shown that it is possible the production of a. majus l. in the field conditions of the east of the state of mexico municipality of texcoco with commercial quality. in order to know that, it was designed an experiment in which: the 1) epoch or date of cultivation: autumn-winter 2006 and spring-summer 2007 and 2) four cultivars of a. majus l.: 'plumblossom' and 'orange' potomac series and 'bronze' and 'red' rocket series; were the two factors of an experimental design of randomized blocks. the population density was 80 plants·m-2. the cultivars of the potomac series in the cycle autumn-winter need less accumulation of development day degrees (1,254 °c·día-1) to reach the commercial maturity than the series rocket (1,727 °c·día-1). therefore, they were more efficient in the use of the radiation than the series rocket (0.61g biomasa·mj-1 and 0.36 g biomasa·mj-1 respectively). the cultivars of the potomac series obtained greater fresh biomass (137 g), length of stem (100 cm) and quality index (1.35 g·cm-1). in addition, 70% of the stems of its cultivars 'plumblossom' and 'orange' were of "special" quality, the highest one for this species. the behavior of the cultivars of both series was similar in the cycle spring-summer. although in autumn-winter the dry biomass accumulated, the leaf number and the days to crop were smaller. it is concluded that the cultivars of the series potomac reached better development in both cycles of cultivation, and produced inflorescences with greater commercial quality that the cultivars of the series rocket. therefore, they would be cultivated in similar field conditions to present study.
Generating reference evapotranspiration surfaces from the Hargreaves equation at watershed scale
C. Aguilar ,M. J. Polo
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2011,
Abstract: In this study, Hargreaves' formulation is considered to be appropriate for the water and energy balance at a daily scale due to its simplicity of application once the distributed values of temperature are available at cell scale. However, the coefficient of the Hargreaves equation must be previously calibrated. The interplay of different factors at different temporal scales became evident in the calibration process at the local scale of weather stations. The best fits against daily estimates by ASCE-PM were achieved when differentiating between the wet and the dry season. For the spatial distribution of Hargreaves coefficient at watershed scale, a regionalization in the area around each weather station was proposed in terms of areas of influence. The best results at watershed scale were obtained after a spatial correction for alpine areas, when the average of the difference cell by cell between ASCE-PM and Hargreaves's distributed daily estimates were 0.02 and 0.15 mm day 1 for the wet and the dry seasons, respectively. In all the cases, the best interpolation results were obtained using C-I (calculate and interpolate) procedures.
Calculation of reference evapotranspiration surfaces in distributed hydrological modelling at different temporal scales
C. Aguilar,M. J. Polo
Hydrology and Earth System Sciences Discussions , 2011, DOI: 10.5194/hessd-8-4813-2011
Abstract: Each individual process in the soil water balance affected by evaporation processes has a certain representative temporal scale (e.g. canopy evapotranspiration, snowmelt or soil water loss). In this study, the implementation in distributed hydrological modelling at cell scale of the ASCE-Peman-Monteith (ASCE-PM) equation is proposed at hourly time steps whilst the Hargreaves formulation was considered to be appropriate for the water and energy balance at a daily scale due to its simplicity of application once the distributed values of temperature are available at cell scale. However, the coefficient of Hargreaves equation must be previously calibrated. The interplay of different factors at different temporal scales became evident in the calibration process at the local scale of weather stations. However, the best fits against daily estimates by ASCE-PM were achieved when differentiating between the wet and the dry season. For the spatial distribution of Hargreaves coefficient at watershed scale, a regionalization in the area around each weather station was proposed in terms of areas of influence. The best results at watershed scale were obtained after a spatial correction for alpine areas, when the average of the difference cell by cell between ASCE-PM and Hargreaves distributed daily estimates were 0.02 and 0.15 mm day 1 for the wet and the dry seasons respectively. In all the cases, the best interpolation results were obtained using C–I (calculate and interpolate) procedures.
The Social Conditions in the Genesis of Preeclampsia  [PDF]
Jaime Salvador-Moysén, Yolanda Martínez-López, José M. Ramírez-Aranda, Marisela Aguilar-Durán, Miguel A. Reyes-Romero
Open Journal of Epidemiology (OJEpi) , 2014, DOI: 10.4236/ojepi.2014.43016
Abstract:

This article highlights the importance of preeclampsia as a global public health problem and the lack of a satisfactory model to explain its genesis. Scientific advances relevant to the placental pathophysiology, which have resulted in a deeper understanding of the immunological mechanisms associated to preeclampsia and have been translated into better treatment options, are also highlighted, although to date these approaches cannot explain the origin of the disease. From a theoretical approach underpinned by the concepts related to the social determinants of the health, and specifically from current psychosocial epidemiology, an alternative approach that gives account for the genesis of preeclampsia is proposed. The proposal is based in the scientific literature as well as in the work of the authors; it takes as references unfavorable socioeconomic and psychosocial conditions in pregnant women, linking these conditions to a series of failed adaptive biological processes closely related to an ineffective allostatic response by the body, which ultimately determines the occurrence of the disease.

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