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Search Results: 1 - 10 of 276969 matches for " Juan C; Hernández-Livera "
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Rendimiento y calidad de la semilla de cebada y trigo en campo e invernadero
Casta?eda-Saucedo,María Claudia; López-Casta?eda,Cándido; Colinas-De León,María Teresa B; Molina Moreno,Juan C; Hernández-Livera,Adrián;
Interciencia , 2009,
Abstract: two experiments were carried out under field conditions; one was conducted in winter-spring (fews) growing season under irrigation and another experiment was conducted under rainfall conditions in the summer (fes), while a third experiment was carried out in green house conditions in the summer (ges), in order to study the environmental effects in grain yield (gy) and seed quality between barley and bread wheat. in the combined analysis of the experiments carried out under field conditions, the results showed that the barley had 21, 31, 28 y 22% higher grain yield (gy), above-ground dry matter (agdm), number of spikes/m2, number of grains/m2 (ngpsm), respectively, with respect to wheat. barley plantlets were 6cm higher and reached its larger yield 18 days before those of wheat, although wheat showed an 11% larger harvest index (hi) than barley. gy, hi, agdm, ngpsm and plant height all decrease in fes for barley in 30, 29, 2, 12% and 25cm, respectively, and for wheat in 38, 10, 32, 27% and 32cm, respectively, compare with fews. the number of days to anthesis was 28 days and 46 days before in fes than in fews, respectively, in barley and wheat. also, in ges barley was better than the wheat on gy and agdm in 17 and 33%, respectively. barley showed a better seed quality than wheat in plantlet vigor, whereas wheat plantlets showed 10 and 23% larger germination and volumetric weight, respectively.
Variación morfológica de semillas de Taxus globosa Schltdl. provenientes de dos regiones geográficas de México
Ramírez-Sánchez, Susana E.;López-Upton, Javier;García de los Santos, Gabino;Vargas-Hernández, J. Jesús;Hernández-Livera, Adrián;Ayala-Garay, óscar J.;
Revista fitotecnia mexicana , 2011,
Abstract: taxus globosa schltdl. is the only species of the genus taxus that grows in mexico and is protected by the mexican government. its bark and leaves contain taxol, a high value compound used as a cancer drug. natural regeneration of taxus globosa is by seeds which germinate scarcely and present dormancy. the present study was done in order to determine the morphological variation of taxus globosa seeds and to learn if seed dormancy is caused by physical factors. collected seeds from northern (nuevo león) and central (hidalgo and queretaro) méxico were used to measure seed dimensions (length, width, area, perimeter and embryo/megagametophyte ratio) by image analysis, in addition to volumetric weight, and weight of 1000 seeds. to evaluate the physical characteristics of the seed coat, a scarification test with sulfuric acid for 5, 10, 15, 20, 25 and 30 min was done followed a tetrazolium viability test. seed coat hardness and imbibition rate were also measured. there were differences in seed size betwee geographical origins (28 % bigger in the northern region). the embryo/megagametophyte ratio of was only 4% in seeds from the northern region and 3% in the central region. seeds of both regions only supported 5 min immersed in h2so4, and seeds from the northern region were harder (1.29 vs. 0.86 kg cm-2). seeds from the northern absorbed more water than those from the central region. taxus globosa seeds do not need scarification to soften the seed coat, and the possible cause of seed dormancy appears to be their undeveloped embryos.
Calidad fisiológica en semillas de maíz con diferencias estructurales
Pérez de la Cerda, Felipe de Jesús;Carballo Carballo, Aquiles;Santacruz Varela, Amalio;Hernández Livera, Adrián;Molina Moreno, Juan Celestino;
Agricultura técnica en México , 2007,
Abstract: fifty-six single crosses of maize (zea mays l.) with different type of endosperm, from floury to horny types were evaluated with the aim of establishing the relationship between the structural seed characteristics and physiological seed quality. the study was carried out during 2001 in the colegio de posgraduados at montecillo, state of mexico. tests were carried out on industrial quality: texture as determined by dissection to determine percentages of pedicel, pericarp, germ, floury starch and horny starch; and physiological quality tests: standard germination test, cold and a vigor te st in a microtunnel using seeds with and without accelerated aging. results showed differential response among genotypes, increasing vigor and physiological quality as the proportion of horny endosperm increased. a high and positive correlation between germ and horny endosperm was reflected in a higher dry weight of both shoot and root in the cold and the standard germination tests, which indicates higher vigor. from the test conducted in the microtunnel a high correlation was found between horny endosperm and dry weight of both shoot and root and rate of emergency. a canonical correlation analysis, with data from standard germination and cold tests confirmed the main conclusion of this study in the sense that a large expression of vigor corresponds to genotypes with horny endosperm.
Rendimiento y calidad de semilla del frijol ayocote en el Valle de México
Ayala Garay, Oscar Javier;Pichardo González, Juan Manuel;Estrada Gómez, Julio Arturo;Carrillo Salazar, José Alfredo;Hernández Livera, Adrián;
Agricultura técnica en México , 2006,
Abstract: in the conservation and propagation of runner bean (phaseolus coccineus l.), the seed is a basic element. in this study, the seed yield and seed quality of nine runner bean cultivars were evaluated in two planting dates 1) may 2nd and 2) june 17th, 2003) at montecillo, state of mexico, mexico. seed physiological quality was evaluated by the accelerated aging test at 42 °c and high relative humidity for 120 h. seed vigor was determined by the velocity of seed emergence in sand, the percentage of emergence and the dry weight of 10 seedlings. seed yield from the first planting date (529 g plant-1) was significantly higher than the yield from the second date (334 g plant-1), this was also true for the seed physical quality with a hectoliter weight of 75 and 73 kg hl-1 and 100-seed weight with 123 and 110 g, respectively. on the contrary, the parameters related to seed physiological quality were higher in the second planting date in relation to the first, whose percent of emergency were 84 and 62%, and 2.81 and 2.15 for the number of seedlings emerged d-1 and 3.7 and 3.1 g for the average dry weight of 10 seedlings, respectively. higher yields and seed physical quality were obtained in the first planting date, while high seed physiological quality was observed in the second. this last result was due to the fact that the seed produced in the second date had less exposure to the environmental conditions after maturation. early sowing dates and harvesting as soon as maturity is reached is necesary to obtain seeds of high quality and vigor.
Analizador Sintáctico de Lenguaje Natural con Reglas Editables para la Generación de Primitivas UML.
Carlos M. Zapata,Juan C. Hernández
Avances en Sistemas e Informática , 2007,
Abstract: We propose, in this paper, a constituent-based automated syntactic analyzer fr om natural language it has capabilities for grammatical rules modification. The parser uses bottom-up method for syntactic tree generation and right-left, left-right verifying for level tree building. The parser itself was built as a part of an application for automatic obtaining of UML primitives from natural language due to this fact, weneed syntactic rules edition for incorporing new phrases and for easing data processing to other analysis modules.
Alteraciones de la función autonómica cardiovascular en pacientes con anemia drepanocítica Alterations of the autonomic cardiovascular function in patients with sickle-cell anemia
Porfirio Hernández Ramírez,Juan C Romero Mestre,Alicia Hernández Hernández,Olga Agramonte Llano
Revista Cubana de Hematolog?-a, Inmunolog?-a y Hemoterapia , 1999,
La máquina de Atwood y el estudio del movimiento de esferas simétricas en fluidos incomprensibles y viscosos
Maria C. Cifuentes A.,Juan P. Hernández B.
Visión Electrónica , 2011,
Abstract: En este trabajo se presenta un sistema desarrollado para el estudioexperimental del movimiento de una máquina de Atwood, que posibilitala determinación del cambio de posición de las masas en el tiempo,así como la fuerza de fricción en el eje de la polea y el momentode inercia de la misma. Se comparan los resultados calculados a travésdel modelo que caracteriza el comportamiento de una Máquinade Atwood, cuando una de sus masas (esferas simétricas) se muevea través de un fl uido, con los valores determinados a partir de lasmediciones experimentales con el sistema desarrollado. Finalmente,se discuten las ventajas del sistema frente a los prototipos que seencuentran en el mercado y se realiza la refl exión sobre su uso comoruta alternativa para el estudio experimental, en los primeros cursosde física universitaria, del movimiento de cuerpos esféricos a travésde fl uidos incompresibles y viscosos.
Seguridad pública y participación ciudadana en el Distrito Federal
Georgina Isunza Vizuet,Juan C. Hernández Esquivel
El Cotidiano , 2001,
Abstract: El artículo tiene como finalidad presentar un breve análisis del papel que juega la participación ciudadana en la gestión de la seguridad pública en el Distrito Federal. Para ello se sostiene que la participación de la ciudadanía es vital en los procesos de seguridad, pues contribuye a fortalecer una actitud preventiva, de denuncia ciudadana y da mayor cohesión social frente a las redes delictivas y a la impunidad imperante. Sin plantear suplir las funciones que legítimamente le corresponden al Estado, se propone una nueva correlación entre éste y la sociedad civil. Se analizan los antecedentes de la participación en la materia, el periodo de gestión reciente en el Distrito Federal de 1997 a 2000 y el funcionamiento de los Comités de Seguridad Pública, con la finalidad de contribuir al debate sobre la agenda en la materia
Evaluation of the Thickness in Nanolayers Using the Transfer Matrix Method for Modeling the Spectral Reflectivity
Juan E. González-Ramírez,Juan Fuentes,Luis C. Hernández,Luís Hernández
Physics Research International , 2009, DOI: 10.1155/2009/594175
Abstract: The reflectivity spectra have been traditionally used to determine the thicknesses in semiconductor films. However, thicknesses of nanofilms are not easy to evaluate because the interference fringes are not visible in the transparent region. In this paper, we present a computed method based on the transfer matrix (TM) which is used to match the calculated and experimental room temperature reflectivity spectra of the ZnTe/GaAs films and to determine its thickness film values afterwards. The TM method needs only to know refraction indices and absorption coefficients as a function of wavelength for the film and the substrate. The thickness nanofilms evaluated by our method are in agreement with the values measured by ellipsometry, Rutherford backscattering spectroscopy and transmission electron microscopy techniques. The present procedure extends the application of the standard spectral reflectance technique to determine semiconductor nanolayer thicknesses.
The Incubation of 13a,17-Dihydroxystemodane with Cephalosporium aphidicola
Braulio M. Fraga,Ricardo Guillermo,Melchor G. Hernández,María C. Chamy,Juan A. Garbarino
Molecules , 2012, DOI: 10.3390/molecules17021744
Abstract: The biotransformation of 13a,17-dihydroxystemodane (3) with the fungus Cephalosporium aphidicola afforded 13a,17,18-trihydroxystemodane (4), 3b,13a,17-tri-hydroxystemodane (5), 13a,17-dihydroxy-stemodan-18-oic acid (6), 3b,11β,13a,17-tetra-hydroxystemodane (7), 11β,13a,17,18-tetrahydroxystemodane (8) and 3b,13a,17,18-tetra-hydroxystemodane (9). The hydroxylation at C-18 of the substrate points to a biosynthetically-directed transformation, because aphidicolin (2) is hydroxylated at this carbon. However, the C-3(b) and C-11(b) hydroxylations seem to indicate a xenobiotic biotransformation.
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