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Search Results: 1 - 10 of 5398 matches for " Guadalupe Valverde-Aguilar "
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Evaluación de la degradación de un colorante textil usando el fotocatalizadores Fe/TiO2/SiO2 (0.0, 0.5, 0.7, 1.0 % en masa Fe) y en presencia de H2O2
José Manuel Barrera-Andrade,Sayra Lissette Orozco-Cerros,Guadalupe Valverde-Aguilar,Jorge A. García-Macedo
Tecnología, Ciencia, Educación , 2011,
Abstract: En este trabajo se evalúa la degradación de un colorante textil antraquinónico empleando fototalizadores de TiO2 dopados con iones de Fe soportado sobre SiO2, Fe/TiO2/SiO2. Los foto-catalizadores fueron sintetizados para diferentes contenidos de Fe (0, 0.5, 0.7, 1.0% en masa), empleando la técnica de sol-gel. Como fuente de sílice fue empleada sílice pirogénica (tama o de partícula 0.007 um y área superficial de 390±40 m2 g-1) y los precursores de titanio y hierro fueron TiCl4 y Fe(NO3)3, respectivamente. Los soles de TiO2 fueron preparados vía peptización ácida del precipitado de la solución de TiCl4 con NH3H2O. La proporción de TiO2, en los foto-catalizadores Fe/TiO2/SiO2, fue de 10% en masa. Los materiales sintetizados fueron sometidos a un tratamiento térmico de 550°C por 3 horas. Los foto-catalizadores Fe/TiO2/SiO2 se caracterizaron por espectroscopía óptica, en modo de reflectancia difusa UV-Vis-NIR y difracción de rayos X. La degradación del colorante textil se efectuó en solución acuosa en presencia de H2O2 a pH de 3.0. El proceso de degradación fue llevado a cabo en un reactor intermitente (tipo batch) y bajo radiación UV-A. Los resultados demuestran que la actividad catalítica de los fotocatalizadores se incrementó con la introducción de 0.7% de Fe en la matriz TiO2/SiO2.
Effect of lamellar nanostructures on the second harmonic generation of polymethylmethacrylate films doped with 4-(4-nitrophenylazo)aniline chromophores
Alfredo Franco,Laura Romero-Miranda,Guadalupe Valverde-Aguilar,Jorge García-Macedo,Giovanna Brusatin,Massimo Guglielmi
Physics , 2011,
Abstract: The kinetics of the orientation of Disperse Orange 3 molecules embedded in amorphous and nanostructured Polymethylmethacrylate films was studied under the effect of an intense electrostatic poling field. Non-centrosymmetric chromophore distributions were obtained in Polymethylmethacrylate films by Corona poling technique. These distributions depends on the Corona poling time. The changes in the orientation of the Disperse Orange 3 molecules were followed by in-situ transmitted Second Harmonic Generation measurements. The Second Harmonic Generation signal was recorded as function of time at several temperatures; it was fitted as function of the Corona poling time, considering matrix-chromophore interactions. The Polymethylmethacrylate films were nanostructured by the incorporation of an anionic surfactant, the Sodium Dodecyl Sulfate. The lamellar nanostructures in the films were identified by X-ray diffraction measurements.
Decoloración fotocatalítica homogénea y heterogénea de un colorante azoico, empleando como catalizador dióxido de titanio dopado con hierro soportado sobre sílice (Fe/TiO2/SiO2)
S. L. Orozco-Cerros,J. M. Barrera-Andrade,G. Valverde-Aguilar,J. A. García-Macedo
Tecnología, Ciencia, Educación , 2010,
Abstract: En esta investigación se presentan los resultados de la decoloración fotocatalítica homogénea y heterogénea de un colorante azoico, anaranjado de metilo, empleando catalizadores de TiO2 dopados con iones de hierro soportados sobre una matriz de sílice, Fe/TiO2/SiO2. El fotocatalizador Fe/TiO2/SiO2 fue preparado por la técnica sol-gel, en una relación molar de 0.01:0.02:1.0, respecto a la sílice. Adicionalmente, se prepararon los materiales Fe/SiO2 (a una relación molar de 0.01:1) y TiO2/SiO2 (a una relación molar de 0.02:1) por impregnación, como fotocatalizadores de control. Los materiales Fe/SiO2, TiO2/SiO2 y Fe/TiO2/ SiO2 fueron sometidos a un tratamiento térmico a 550°C por 24 horas. La caracterización física y óptica de los fotocatalizadores fue realizada empleando espectroscopía vibracional IR y óptica y difracción de rayos X. Los resultados de la caracterización demuestran que el fotocatalizador Fe/TiO2/SiO2 presenta una banda de absorción en la región visible desde 400 a 600 nm, lo que permitirá un uso más eficiente de la energía solar. Los resultados del proceso de decoloración de anaranjado de metilo demuestran que proceso se lleva a cabo principalmente por fotocatálisis heterogénea. La contribución de la fotocatálisis homogénea es mínima, debido a que la concentración de los iones de hierro en solución de muy baja, del orden de 0.5 mg L-1.
Micropropagación de Pilón (Hieronyma Alchorneoides)
Abdelnour,Ana; Aguilar,Ma Elena; Valverde,Lissette;
Agronomía Costarricense , 2011,
Abstract: pilon (hieronyma alchorneoides) (euphorbiaceae) is one of the native timberspecies of costa rica best adapted to conditions of open plantation. due to its growth characteristics and variety of uses, the demand for planting material has increased. this species presents serious problems with seed reproduction; it is adioecious, the fruit production varies overtime and between trees, trees produce largequantities of fruit but are heavily predated by different birds. in recent years, the percentage of damaged fruit has increased due to wasps and the seeds lose their ability to germinate within days of harvest (recalcitrant). thes factorsmake micropropagation an attractive option for masspropagation of the species. in the present study various stages of in vitro cultivation were evaluated. the aseptic establishment of theembryos was achieved by scarifying the seeds with concentrated sulfuric acid for 10 min, followed by incubation in 5.5% sodium hypochloride (naclo) for 30 min, then embryos were inoculated on the culture medium described by murashige and skoog (ms) without growth regulators. when vegetative material was used as initial explant, the use of 0.095% mercuric chloride (hgcl2) during 5 min, allowed 50% of cuttings to develop shoots under aseptic conditions on a simple ms medium. it was observed that pilon does not require the addition of growth regulators during bud induction nor in the multiplication stages. during rooting, the addition of indole butyric acid (iba) at concentrations of 0.1 mg.l-1 promoted the highest percentage of rooted shoots (80%), the largest number of roots per stem (5.0) and the best quality of the roots formed. survival of in vitro plants after acclimation under greenhouse condition reached 70%
MICROPROPAGACIóN DE PILóN (HIERONYMA ALCHORNEOIDES)
Ana Abdelnour,Ma Elena Aguilar,Lissette Valverde
Agronomía Costarricense , 2011,
Abstract: El pilón (Hieronyma alchorneoides, Euphorbiaceae) es una de las especies nativas maderables de Costa Rica mejor adaptadas a condiciones abiertas de plantación; por sus características de crecimiento y variedad de usos, la demanda por material de siembra se ha incrementado. Esta especie presenta serios problemas en su reproducción sexual: es dioica, la producción de frutos muy variable en el tiempo y entre árboles, que producen gran cantidad de frutos, pero son fuertemente depredados por diferentes aves. En los últimos a os el porcentaje de frutos da ados se ha incrementado a niveles considerables debido a avispas y las semillas pierden su capacidad de germinación pocos días después de la cosecha (recalcitrante). Estos factores hacen que la micropropagación sea una opción atractiva para su multiplicación. En el presente estudio se evaluaron las diferentes etapas del cultivo in vitro. El establecimiento aséptico de los embriones se logró mediante incubación de las semillas con ácido sulfúrico concentrado por 10 min, seguido de la inmersión en hipoclorito de sodio (NaOCl) al 5,5% durante 30 min; los embriones fueron inoculados en el medio de cultivo de Murashige y Skoog (MS) sin reguladores del crecimiento. La asepsia de material vegetativo se logró con cloruro de mercurio (HgCl2) al 0,095% por 5 min, el 50% de las microestacas que brotaron en el medio MS simple. Además, se observó que el pilón no requiere de la adición de reguladores del crecimiento en las etapas de brotación y multiplicación. El uso de 0,1 mg.l-1 de ácido indolbutírico (AIB) promovió el enraizamiento del 80% de los tallos y el número mayor de raíces por tallo (5,0) de buena calidad. Se logró un 70% de sobrevivencia en la aclimatación de las plantas en condiciones de invernadero.
Role of Oxidative Stress in Transformation Induced by Metal Mixture
Silva-Aguilar Martín,Rojas Emilio,Valverde Mahara
Oxidative Medicine and Cellular Longevity , 2011, DOI: 10.1155/2011/935160
Abstract: Metals are ubiquitous pollutants present as mixtures. In particular, mixture of arsenic-cadmium-lead is among the leading toxic agents detected in the environment. These metals have carcinogenic and cell-transforming potential. In this study, we used a two step cell transformation model, to determine the role of oxidative stress in transformation induced by a mixture of arsenic-cadmium-lead. Oxidative damage and antioxidant response were determined. Metal mixture treatment induces the increase of damage markers and the antioxidant response. Loss of cell viability and increased transforming potential were observed during the promotion phase. This finding correlated significantly with generation of reactive oxygen species. Cotreatment with N-acetyl-cysteine induces effect on the transforming capacity; while a diminution was found in initiation, in promotion phase a total block of the transforming capacity was observed. Our results suggest that oxidative stress generated by metal mixture plays an important role only in promotion phase promoting transforming capacity.
Role of Oxidative Stress in Transformation Induced by Metal Mixture
Silva-Aguilar Martín,Rojas Emilio,Valverde Mahara
Oxidative Medicine and Cellular Longevity , 2011, DOI: 10.1155/2011/935160
Abstract: Metals are ubiquitous pollutants present as mixtures. In particular, mixture of arsenic-cadmium-lead is among the leading toxic agents detected in the environment. These metals have carcinogenic and cell-transforming potential. In this study, we used a two step cell transformation model, to determine the role of oxidative stress in transformation induced by a mixture of arsenic-cadmium-lead. Oxidative damage and antioxidant response were determined. Metal mixture treatment induces the increase of damage markers and the antioxidant response. Loss of cell viability and increased transforming potential were observed during the promotion phase. This finding correlated significantly with generation of reactive oxygen species. Cotreatment with N-acetyl-cysteine induces effect on the transforming capacity; while a diminution was found in initiation, in promotion phase a total block of the transforming capacity was observed. Our results suggest that oxidative stress generated by metal mixture plays an important role only in promotion phase promoting transforming capacity. 1. Introduction Arsenic (As), cadmium (Cd), and lead (Pb) are commonly used in numerous industries to the extent that they have now generated a pollution problem. Numerous studies have reported high levels of these metals near smelter areas [1]. Acute exposure to As, Cd, and Pb produces a variety of toxic effects in several target organ systems; however, most individuals are chronically exposed to low levels of a mixture of these metals [2, 3]. These three metals/metalloids share several common mechanisms underlying their toxicities, including production of oxidative stress, reaction with sulfhydryl groups, and interference with essential metals. In addition, stress proteins and antioxidant enzymes have been proposed to provide common cellular protective mechanisms against the element-induced toxicities when they occur on an individual basis [4]. Furthermore, these metals have been listed in the top ten hazardous substances and proposed as one of the mixtures for interaction profile studies by the Agency for Toxic Substances and Disease Registry (ATSDR). As and Cd have been classified as carcinogens and Pb as a possible carcinogen by the International Agency in Research of Cancer (IARC) [5–9]. As, Cd, and Pb induce the generation of reactive oxygen species (ROS), which can damage DNA, lipids, and proteins. As generates ROS in the form of superoxide ( ), singlet oxygen ( ), peroxyl radical ( ), nitric oxide ( ), hydrogen peroxide (H2O2), dimethylarsinic peroxyl radicals ([ ]), and the
Nitrogen Source Affects Glycolipid Production and Lipid Accumulation in the Phytopathogen Fungus Ustilago maydis  [PDF]
Ariana Zavala-Moreno, Roberto Arreguin-Espinosa, Juan Pablo Pardo, Lucero Romero-Aguilar, Guadalupe Guerra-Sánchez
Advances in Microbiology (AiM) , 2014, DOI: 10.4236/aim.2014.413104
Abstract: When cultured in medium limited of nitrogen sources, the phytopathogen Ustilago maydis produces two amphipathic glycolipids: Ustilagic acid (UA) and Mannosylerythritol lipid (MEL), which in addition to the hydrophilic moiety, contain dior tri-hydroxylated C16 fatty acids (UA), or C8 and C16 saturated fatty acids (MEL). We compared the growth and morphology of cells in YPD and in minimum media containing glucose and nitrogen sources such as nitrate or urea and those deprived of nitrogen. Nitrogen-starved cells showed a dramatic accumulation of internal lipids identified as lipid droplets when stained with the hydrophobic probe BODIPY; these lipid droplets were enriched in unsaturated fatty acids. Fatty acids in YPD or medium containing nitrate as nitrogen source showed a combination of saturated/unsaturated lipids, but when urea was the nitrogen source, cells only contained saturated fatty acids. The glycolipid profiles produced in the presence or absence of nitrogen showed preferences towards the production of one kind of glycolipid: cells in media containing nitrate or urea produced different proportions of UA/MEL, but under nitrogen starvation cells contained only UA. The emulsification capacity of the glycolipids produced in media with or without nitrogen was similar (72% - 76%). HPLC of the glycolipids allowed the separation of fractions with different emulsifying characteristics. Our results indicate that U. maydis accumulates lipid droplets when deprived of nitrogen source and confirm that UA is not under nitrogen control, but rather that MEL and lipid droplets are produced and oppositely regulated by nitrogen.
Alfabetización científica, epistemología y docencia
Martha Guadalupe Aguilar Pérez,José Ramiro Ortega Pérez
Ense?anza e Investigación en Psicología , 2008,
Abstract: En el presente trabajo se discute la importancia de considerar la formación de los docentes universitarios desde una perspectiva crítica y con carácter constructivo. En evaluaciones internacionales y nacionales se ha demostrado la dificultad en una gran parte de docentes para aplicar conocimientos científicos en situaciones concretas. Sin embargo, las labores de alfabetización científica y el trabajo epistemológico basado en la comprensión de la naturaleza de la ciencia han demostrado ser herramientas de gran utilidad para favorecer los procesos constructivos en los educadores. En este sentido, los autores consideran necesario reabrir la discusión sobre los procesos de construcción del conocimiento y favorecer los procesos de aprendizaje reflexivo de las ciencias.
Effect of Glucose Concentrations on the Growth and Metabolism of Brettanomyces bruxellensis under Aerobic Conditions  [PDF]
Ortiz-Mu?iz Benigno, Corro-Herrera Victor, Gomez-Rodriguez Javier, Domínguez-González José Manuel, Aguilar-Uscanga María Guadalupe
Advances in Microbiology (AiM) , 2013, DOI: 10.4236/aim.2013.33034
Abstract:

Acetic acid can be directly produced from glucose in one-step fermentation by using yeasts of the genus Brettanomyces bruxellensis, hence increasing the industrial application to manufacture products with simplified bioprocesses. Thereby, this work evaluates the influence of initial glucose concentration on the growth and acetic acid production by B. bruxellensis. The results obtained confirmed the presence of Crabtree effect on B. bruxellensis under low glucose concentrations. The maximum acetic acid concentration reached was 15.4 g·L-1 starting with 100 g·L-1 leading to a product yield of 0.154 g·g-1 and a specific acetic acid production rate of 0.05 g·g-1·h-1. The results also indicate that after reaching the acetic acid critic threshold of 4 g·L-1 the metabolism can induce the growth second phase even residual glucose was present on the culture media at high starting glucose concentrations. Additionally, it was observed a lineal relationship between cell viability and acetic acid production.

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