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Search Results: 1 - 10 of 12500 matches for " Leonardo Tijerina Chávez "
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Dinamic of Bacteria Desnitrificants and Nitrificants in the Rizospheric of Wheat with Slow Release of Fertilizer, Irrigated with Waste or Well Water  [PDF]
Sandra Grisell Mora-Ravelo, Francisco Gavi Reyes, Jesús Pérez Moreno, Juan José Pe?a Cabriales, Leonardo Tijerina Chávez, Ma. de Lourdes de la Isla de Bauer
Advances in Microbiology (AiM) , 2013, DOI: 10.4236/aim.2013.34048

The study of the paper about the rhizosphere in the transformation of nitrogen compounds can generate knowledge of the microbial and biochemical atmosphere of the rhizosphere of wheat, for the understanding of the dynamics of the N in agricultural zones, with the purpose of optimizing the fertilizer use and increasing the productivity of the cultures. Therefore, the objective of the present work was to know the effect the rhizosphere in the dynamics of the bacterial populations that take part in the cycle of the N in wheat nourished with slow release fertilizer and one commercial, irrigated with waste water or well. Analyses in the soil took place vertisol used in the experiment with the rhizospheric and non rhizospheric fraction. The slow release fertilizer used has a matrix enriched with N and P and is in the process of being patented (it explains in materials and methods). Each fertilizer was evaluated and the combination of the slow release fertilizer with organic fertilizer. The technique of the number most probable was used (MNP) to carry out the quantification of the nitrificants and denitrificants bacteria to the 55, 67 and 97 days after sowing (Dds). The results obtained for the MNP of denitrificants bacteria and Nitrosomonas indicate that the effect average of the types of water, soil and fertilizers, as well as their interaction to each other was not significant (p > 0.05). The effect of the fertilizing type and soil (rhizospheric and non rhizospheric) in the MNP of Nitrobacter was significant (p < 0.05). The tendencies show that the non rhizospheric soil is more favorable for the development of denitrificants bacteria and Nitrobacter, whereas the MNP of Nitrosomonas was greater in rhizospheric soil.

Determinación de zonas agroclimáticas para la producción de mango (Mangifera indica L. "Manila") en Veracruz, México
Jorge Luis Martínez Fonseca,Leonardo Tijerina Chávez,Ramón Arteaga Ramírez,Mario Alberto Vázquez Pe?a
Investigaciones geográficas , 2007,
Abstract: El mango (Mangifera indica L.) es un frutal de importancia económica en México, en el 2004 se reportaron 166 000 ha plantadas en más de once estados del país, en el estado de Veracruz 25 550 ha, donde el 85% es de la variedad Manila . El objetivo de este trabajo fue determinar las regiones agroclimáticas para el cultivo de mango Manila en el estado de Veracruz, México, por medio del Análisis de Componentes Principales (ACP) con variables climatológicas (temperatura, precipitación, evaporación y radiación solar), además se elaboraron gráficas hidro-termales (relacionando: precipitación total y temperatura mínima mensual). Del ACP se derivaron dos vectores asociados con la temperatura mínima anual y precipitación total anual, que juntos explican el 83% de la variación climática total entre las localidades productoras de mango Manila ; se definieron dos grupos de localidades con agroclimas diferentes, mismos que se confirmaron con las gráficas hidro-termales; con apoyo de información bibliográfica y de productividad, se definieron tres zonas de aptitud agroclimáticas para el cultivo de mango Manila , con los siguientes intervalos de variación de la temperatura mínima anual: zona 1 (No Apta) menor de 13.5° C; zona 2 (Apta) de 13.5 a 17.5° C; zona 3 (Moderadamente Apta) de 17.5 a 23.0° C. Con un modelo empírico de temperatura mínima y un modelo de elevación digital, por medio de un sistema de información geográfica (SIG), se realizó la cartografía de las zonas geográficas con diferente grado de aptitud Agroclimática.
Determinación de zonas agroclimáticas para la producción de mango (Mangifera indica L. "Manila") en Veracruz, México
Martínez Fonseca, Jorge Luis;Tijerina Chávez, Leonardo;Arteaga Ramírez, Ramón;Vázquez Pe?a, Mario Alberto;Becerril-Román, A. Enrique;
Investigaciones geográficas , 2007,
Abstract: mango (mangifera indica l.) is a fruit of great economic importance in méxico. in 2004, 166 000 ha of mango were reported in different regions of more than eleven states of the country and the state of veracruz, 25 550haof mango were grown, 85% belonging to the "manila" variety. the objective of the present study was to define agroclimatic regions for the cultivation of "manila" mango in the state of veracruz, méxico. the method used was the components principal analysis (cpa) with climatological variables (temperature, precipitation, evaporation, solar radiation), along, as well as hydro-thermal graphs (relation: mean total monthly precipitation and minimum monthly temperature). two vectors were derived from the analysis associate with the variables, minimum annual temperature and total annual precipitation, which join explain 83% of the total variation. they were defined two groups of towns with different agroclimate. with the hydro-thermal graphs and bibliographical information, and of productivity, they three agroclimatic regions were defined with different degrees of suitability with the following variation intervals of minimum annual temperature: zone 1 (not suitable) below 13.5° c; zone 2 ( suitable) from 13.5 to 17.5° c; zone 3 (moderately suitable) from 17.5 to 23.0° c. with a linear model to estimate minimum temperature, and a digital elevation model, using a geographical information system (gis), maps were made of the geographic regions with different agroclimatic suitability for the cultivation of "manila" mango.
Sistema de riego automatizado en tiempo real con balance hídrico, medición de humedad del suelo y lisímetro
Castro Popoca, Martiniano;águila Marín, Francisco Miguel;Quevedo Nolasco, Abel;Kleisinger, Siegfried;Tijerina Chávez, Leonardo;Mejía Sáenz, Enrique;
Agricultura técnica en México , 2008,
Abstract: the aim of this research was to develop an automated irrigation system in real-time to determine the right moment and quantity of irrigation, monitored through information technologies (it). the study was carried out at the colegio de postgraduados campus montecillo, from june 10 to september 11 of 2006. the system is composed of a microcomputer software and a control device (datalogger cr10x campbell scientific). the system considers three irrigation strategies which were tested. in the first irrigation strategy a weight lysimeter was utilized, in the second the volumetric soil water content was measured with a trime tdr sensor and for the third a climatic water balance method based on the reference evapotranspiration (eto) (penman-monteith) was used. the general operation of the irrigation system was evaluated and monitored through internet and mobile devices through a central computer configured as server (web and wap). the yield of the test crop pumpkin zucchini grey (cucurbita spp.) was calculated, as well as water consumption of each irrigation strategy and water productivity. the results indicated that is possible to automatize and control the water application according to the irrigation strategies considering an irrigation program, a control unit and using information technologies.
Técnica de riego para incrementar la eficiencia del uso de agua en jitomate
López Ordaz, Anselmo;Trejo López, Carlos;Ramírez Ayala, Carlos;Pe?a Valdivia, Cecilia Beatriz;Tijerina Chávez, Leonardo;Carrillo Salazar, José Alfredo;
Revista mexicana de ciencias agrícolas , 2011,
Abstract: the aim of this research was to study in hydroponics and greenhouse conditions the effect of two levels of usable moisture from the substrate in tomato plants (solanum lycopersicum l.), by the irrigation technique of partial root drying (prd). for that, physiological variables were evaluated (dry matter of leaf, stem, root and fruit, water relations, gas exchange, yield), fruit quality (firmness, total soluble solids, ph and electrical conductivity) and the efficiency of water use. the experiment was done in lomas de san esteban, texcoco, mexico state in 2006. plants grew in homogeneous volume containers with tezontle, the root was divided in two parts and two available moisture (am) treatments were applied residual in substrate, control: 80%≤am≤ 100% and 80%≤am≤ 100% and prd: 80%≤ am≤ 100% and 30%≤ am≤ 100%. the treatments started 28 days after transplantation and continued until the end of the experiment. results indicated that prd treatment, showed statistically significant differences (p≤ 0.05) than the control, in relation to co2 fixation rate (prd, 17.67 and control 9.23 μmol m2 s1) at 86 days of initiating the treatment (dait), evapotranspirated volume per plant throughout the experiment (prd 186.7 l and control 229 l), fruit quality increased: firmness 25%, total soluble solids 13% and electrical conductivity 13%, compared with control; efficiency in water use (ewu) based on dry matter increased by 29% and instantly ewu was 57, 61 and almost 100% respect to the control at 65, 80 and 86 dait respectively, without affecting yield (prd 363.2 g and control 345.8 g) and total water potential (prd -0.54 and control -0.57; prd -0.46 and control -0.55 mpa), at 79 and 118 dait respectively.
Desnitrificación de un fertilizante de lenta liberación y urea+fosfato monoamónico aplicados a trigo irrigado con agua residual o de pozo
Revista internacional de contaminación ambiental , 2007,
Abstract: the study of n2o emission originated by the combination of different types of fertilizers and water on rizospheric soil, and non- rizospheric soil along the crop cycle, can contribute to useful knowledge in order to increase fertilizer and manure n recovery efficiency and to reduce the n loss by denitrification. the efficient use of nitrogen fertilizers and non- treated urban waste water for crops is an agronomic, economic and environmental need. the denitrification is an important factor that diminishes the n efficiency in crops. the objective of this investigation was to evaluate the denitrification of a slow release fertilizer using as reference urea plus monoamonium phosphate and an organic fertilizer, applied to wheat irrigated with urban waste water or well water. analyses were made in the vertisol type soil used in the experiment with both, rizospheric and non-rizospheric soil. the slow release fertilizer used has a matrix enriched with n and p and its patent is currently in progress. each fertilizer was evaluated alone, as well as the slow release fertilizer plus organic fertilizer. the samples of rhizospheric and non-rhizospheric soils for each treatment were collected at 55, 67 and 97 days after sowing and incubated during 18 days at 25 °c, controlling the soil humidity daily. the results (p < 0.05) showed that the interactions between samplings and types of water, samplings and fertilizers, and types of water and fertilizers affected (p < 0.06) the emission of n2o, which was increased when urea plus monoamonium phosphate and waste water were applied. on average, there was less n2o when emissions slow release fertilizer or organic fertilizer were applied and irrigated with well water as compared to irrigation with waste water. as well, use of waste water was, on average, associated with a bigger loss of n. the highest average emission in n2o was observed 67 days after sowing. the average denitrification was similar in the rhizospheric and non-rhizospheric
Efecto del tama?o de partícula sobre algunas propiedades físicas del tezontle de Guanajauto, México
Vargas-Tapia, Patricia;Castellanos-Ramos, Javier Zaragoza;Mu?oz-Ramos, José de Jesús;Sánchez-García, Prometeo;Tijerina-Chávez, Leonardo;López-Romero, Rosa María;Martínez-Sánchez, Cinthia;Ojodeagua-Arredondo, José Luis;
Agricultura técnica en México , 2008,
Abstract: the particle size in the substrate has an important effect on its physical characteristics, mainly on the proportion moisture:air. the objective of the present study was to determine the effect of particle size on the physical proprieties of 'tezontle' (volcanic rock). in june 2005, samples were collected from six mines of tezontle in guanajuato, mexico. material of each source was separated in fractions of 0 to 0.125, 0.125-0.25, 0.25-0.50, 0.50-0.71, 0.71-1.0, 1.0-2.0, 2.0-4.0, 4.0-6.5, 6.5-8.5 and 8.5-12.6 mm in diameter. bulk density, particle density, total porous space, occluded porosity, air capacity and moisture-retention capacity were determined to each fraction at the laboratory of substrates of the unit of protected horticulture of the national research institute for agriculture, forest and livestock (inifap), located at celaya, guanajuato, mexico. bulk density and particle density increased as the particle diameter decreased. the air capacity decreased significantly as particle size diminished from fraction 0.50-0.25 mm; moisture-retention capacity increased from the fraction 0.50-0.71 mm to a maximum in 0.25-0.50 mm. total porous space and occluded porosity increased as particle size increased. a highly significant (p<0.01) inverse relationship was observed between moisture retention capacity and air capacity.
Unbiased Diffusion to Escape Complex Geometries: Is Reduction to Effective One-Dimensional Description Adequate to Assess Narrow Escape Times?  [PDF]
Yoshua Chávez, Guillermo Chacón-Acosta, Marco-Vinicio Vázquez, Leonardo Dagdug
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.58113

This study is devoted to unbiased diffusion of point Brownian particles inside a tube of varying cross-section (see Figure 1). An expression for the mean survival time, \"\", of the particles inside the tube is obtained in terms of the bulk diffusion constant, D0 and the system’s geometrical parameters, namely, the tube’s axial semi-length, L, the minor radius, \"\", and the slope of the tube’s wall, \"\". Our expression for \"\" correctly retrieves the limit behavior of the system under several conditions. We ran Monte Carlo numerical simulations to compute the mean survival time by averaging the survival time of 5 × 104 trajectories, with time step \"\"t = 10-6, D0 = 1, and L = 1. The simulations show good agreement with our model. When the geometrical parameters of this system are varied while keeping constant the tube’s enclosed volume, it resembles the problems of Narrow Escape Time (J. Chem. Phys

Caracterización física, química y biológica de sustratos de polvo de coco
Patricia Vargas Tapia,Javier Z. Castellanos Ramos,Prometeo Su00E1nchez Garcu00EDa,Leonardo Tijerina Chu00E1vez
Revista fitotecnia mexicana , 2008,
Abstract: El polvo de coco (Cocos nucifera L.) es un material usado como sustrato, que destaca por su buena capacidad de retención de agua, alto contenido de agua fácilmente disponible, estabilidad como sustrato orgánico y bajo costo de adquisición en comparación con otros sustratos. Sin embargo, la salinidad y variabilidad son dos de los principales problemas de este sustrato, atribuidos al proceso de producción y a su origen. En el presente estudio se caracterizaron siete materiales (cinco mexicanos y dos de Sri Lanka) de empresas con diferente proceso de molienda. Se determinaron las características físicas, químicas y biológicas. Las propiedades físicas y químicas difirieron significativamente entre materiales. Las variaciones respectivas en índice de grosor fueron de 32 a 64%; en densidad aparente y real, de 0.08 a 0.12 y 1.48 a 1.49 g cm-3; en capacidad de aireación, de 11 a 53%; en capacidad de retención de agua, de 50 a 81%; en el agua fácilmente disponible, de reserva y total disponible, de 18 a 35, 3 a 14 y de 21 a 40%. El espacio poroso total fue mayor de 92% en todos los materiales. En cuanto a características químicas el pH de los materiales fue ligeramente ácido (5.1 a 5.6), la conductividad eléctrica del extracto de saturación varió de 1.5 a 4.5 dS m-1, la concentración de N-NO3, Ca, Mg y micronutrimentos en extracto de saturación fue baja, el N-NH4 se encontró en un rango óptimo, mientras que las concentración de K, P, Na y Cl fueron marcadamente altas, con valores de 420 a 1261, 7 a 61, 60 a 226 y 244 a 1700 mg L-1, respectivamente. Los valores de capacidad de intercambio catiónico variaron de 39 a 53 cmolc kg-1, mientras que el índice de germinación fue de 30 a 114%. Las características físicas y químicas fueron afectadas en mayor medida por las variaciones en el tama o de partícula, que por el proceso molienda
Diagnóstico de laboratorio en pacientes ingresados por infección urinaria en un hospital pediátrico
Chávez Isla,Margarita Isabel; Rodríguez Hechavarría,Félix; Chávez Solís,Leonardo F;
MEDISAN , 2012,
Abstract: a descriptive, longitudinal and retrospective study of 64 patients with urinary infection, admitted at the southern children hospital in santiago de cuba was carried out from january to december, 2010, with the objective of determining some clinical and diagnostic aspects. in most of the hospitalized children, anemia, leucocytosis, accelerated erytrosedimentation, as well as mild leucocyturia prevailed; and among the organisms: escherichia coli, proteus mirabilis and enterobacteriaceae. to verify the presence of these changes, additional tests such as complete blood count, erytrosedimentation, cyturia and urine culture should be indicated as their results facilitate to establish a conclusive diagnosis.
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