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Search Results: 1 - 10 of 376685 matches for " Néstor N. López-Castillo "
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Process for the Obtention of Coumaric Acid from Coumarin: Analysis of the Reaction Conditions  [PDF]
Néstor N. López-Castillo, Alma D. Rojas-Rodríguez, Brenda M. Porta, M. Javier Cruz-Gómez
Advances in Chemical Engineering and Science (ACES) , 2013, DOI: 10.4236/aces.2013.33025
Abstract:

Coumaric acid can be obtained from basic hydrolysis of coumarin, through a reaction process consisting on opening the lactone ring and cis-trans isomerization. Parameters such as reaction time, temperature, NaOH concentration, solvent and reaction atmosphere, have been thoroughly studied and analyzed, in order to determine the appropriate conditions for the maximum conversion efficiency of coumarin into coumaric acid. Experimental results show that the best conditions are a 1 hour reaction time, at 160, with a 20% sodium hydroxide aqueous solution, and in an inert reaction atmosphere.

Factores de riesgo en mujeres embarazadas, infectadas por Toxoplasma gondii en Armenia-Colombia
López-Castillo,Christian A.; Díaz-Ramírez,Julieth; Gómez-Marín,Jorge E.;
Revista de Salud Pública , 2005, DOI: 10.1590/S0124-00642005000200006
Abstract: objectives: to determine the risk factors associated with acute toxoplasmosis during pregnancy in armenia. methods: case-control study; 14 cases and 34 controls (mean ages 23±5.5 and 23±5.1 respectively; p = 0.93). cases were pregnant women with serological criteria for acute toxoplasmosis and controls were seronegative pregnant women for toxoplasma igg. results: the risk factors more strongly predictive of acute toxoplasmosis in pregnant women were: eating undercooked meat (or: 13.2; 95% ci: 1.3-132; p = 0.01), drinking beverages prepared with un-boiled water (or: 4.5; 95% ci: 1.1-17; p = 0.01), and contact with cats aged less than 6 months (or: undefined, p = 0.01). drinking of bottled water was a protective factor (or: 0.24; 95% ci: 0.06-0.95; p = 0.02). conclusions: 42% of toxoplasma gondii infections in pregnant women armenia were associated to contact with young cats and to consumption of undercooked meat. drinking of bottled water to prevent toxoplasma infection during pregnancy is also recommended.
Investigación Médica Estudiantil: Perspectiva desde Colombia
Francisco Javier Bonilla-Escobar,Juliana Bonilla-Vélez,Christian Adrián López-Castillo
CIMEL. Ciencia e Investigación Médica Estudiantil Latinoamericana , 2010,
Abstract:
Postoperative Alcaligenes xylosoxidans endophthalmitis: report of two cases
de-la-Torre, Alejandra;López-Castillo, Christian Adrián;Bernal-Urrego, Javier Andrés;Sinisterra-Pava, Juan Pablo;Gómez-Marín, Jorge Enrique;
Arquivos Brasileiros de Oftalmologia , 2008, DOI: 10.1590/S0004-27492008000100025
Abstract: we report two cases of postoperative alcaligenes xylosoxidans endophthalmitis. a 78-year-old woman in good general health developed a. xylosoxidans endophthalmitis one month after an uncomplicated phacoemulsification procedure with posterior chamber intraocular lens. it was performed on her left eye, at another institution. removal of the intraocular lens and capsule was performed because of recurrent inflammation after vitrectomy and intravitreal antibiotic injections. her son, a 55-year-old man, developed a. xylosoxidans endophthalmitis in his left eye, two months after an uncomplicated phacoemulsification procedure with posterior chamber intraocular lens (it also was performed by the same surgeon). he also required vitrectomy with removal of the intraocular lens and capsule because of persistent disease. a. xyloso - xidans can cause chronic low-grade and progressive endophthalmitis after cataract extraction that is often resistant to corrective antibiotic therapy. this kind of case is rare. there have been only previously reported seven cases worldwide to the best of our knowledge.
Simula??o do equilíbrio: o método de Monte Carlo
López-Castillo, Alejandro;Souza Filho, José Candido de;
Química Nova , 2007, DOI: 10.1590/S0100-40422007000700045
Abstract: we make several simulations using the monte carlo method in order to obtain the chemical equilibrium for several first-order reactions and one second-order reaction. we study several direct, reverse and consecutive reactions. these simulations show the fluctuations and relaxation time and help to understand the solution of the corresponding differential equations of chemical kinetics. this work was done in an undergraduate physical chemistry course at unifieo.
Chemical Treatment to Recover Molybdenum and Vanadium from Spent Heavy Gasoil Hydrodesulfurization Catalyst  [PDF]
Alma Delia Rojas-Rodríguez, Orlando Flores-Fajardo, Fabiola Selene Alcántar González, Néstor Noé López Castillo, Modesto Javier Cruz Gómez
Advances in Chemical Engineering and Science (ACES) , 2012, DOI: 10.4236/aces.2012.23050
Abstract: Large quantities of spent hydrodesulfurization (HDS) catalysts are available from petrochemical industry. Disposal of spent catalyst is a problem as it falls under the category of hazardous industrial waste due to its vanadium concentration. Most of these catalysts are usually supported on alumina containing a variable percentage of elements such as nickel or molybdenum. Hence these catalysts contain environmentally critical, and economically valuable metals such as molyb denum, vanadium, and, nickel. In this paper, a spent HDS catalyst was treated with caustic soda solution. Parameters such as temperature, time, and NaOH solution concentration have been studied thoroughly, in order to settle the appropriate conditions for the maximum recovery of molybdenum and vanadium. Under the best leaching conditions (20 %w NaOH, room temperature, 2 h) about 95% recovery of Mo and V was achieved, and the recovery of nickel obtained was of 99% in the form of NiAlO4.
Quantum Charge Transfer Study of Triply Charged Ions in the Adiabatic Representation: the (BHe)3+ System
López-Castillo, A.;Belchior, J.C.;Braga, J.P.;
Journal of the Brazilian Chemical Society , 1998, DOI: 10.1590/S0103-50531998000500007
Abstract: full quantum charge transfer study of the process b3+ + he ? b2+ + he+ has been investigated in the collision energy range 1-102 ev using an ab-initio interaction potential. a new method to solve the schr?dinger equation in an adiabatic basis was used, where the radial and rotational coupling were taken into account, and the importance of the coupling between states of different symmetry was discussed. moreover, by using the well known landau-zener model, it was concluded that the two state model cannot be applied for the present system, and this might indicate that such a model should be applied carefully for other systems when a charge transfer process is considered. finally, the quantum total cross sections were compared with the previous published work of gargaud and co-workers and a fair agreement was achieved.
Definición de la adquisición de la infección toxoplásmica: cuándo es congénita o adquirida? Definition of acquired toxoplasmosis infection: when is it congenital or acquired?
C.A. López-Castillo,A. de-la-Torre
Archivos de la Sociedad Espa?ola de Oftalmología , 2011,
Abstract:
Quantum Charge Transfer Study of Triply Charged Ions in the Adiabatic Representation: the (BHe)3+ System
López-Castillo A.,Belchior J.C.,Braga J.P.
Journal of the Brazilian Chemical Society , 1998,
Abstract: Full quantum charge transfer study of the process B3+ + He -> B2+ + He+ has been investigated in the collision energy range 1-102 eV using an ab-initio interaction potential. A new method to solve the Schr dinger equation in an adiabatic basis was used, where the radial and rotational coupling were taken into account, and the importance of the coupling between states of different symmetry was discussed. Moreover, by using the well known Landau-Zener model, it was concluded that the two state model cannot be applied for the present system, and this might indicate that such a model should be applied carefully for other systems when a charge transfer process is considered. Finally, the quantum total cross sections were compared with the previous published work of Gargaud and co-workers and a fair agreement was achieved.
Complementarity and efficiency of bat capture methods in a lowland tropical dry forest of Yucatán, Mexico Complementariedad y eficiencia de métodos de captura de murciélagos en una selva baja caducifolia de Yucatán, México
Juan M. Pech-Canche,Erendira Estrella,Diana L. López-Castillo,Silvia F. Hernández-Betancourt
Revista mexicana de biodiversidad , 2011,
Abstract: The combined use of different methods for surveying bat assemblages has increased over the last few decades. The objective of this study was to assess the efficiency of bat inventories by comparing assemblages parameters (species richness, abundance and composition) using the 3 most conventional capture methods (ground-level and sub-canopy mist nets and harp traps), in a lowland tropical dry forest in Yucatán, Mexico. In ground mist nets, only phyllostomid species were recorded, principally frugivorous and nectarivorous species, while in harp traps the majority were insectivorous species from other families. Our results indicate that for the order Chiroptera the most efficient combination of capture methods is the simultaneous use of ground mist nets and harp traps. However, an inventory of Phyllostomidae is reliably achieved with only ground mist nets. Also, a combination of ground and sub-canopy mist nets does not provide an efficient sampling strategy. El uso combinado de diferentes métodos de muestreo de ensambles de murciélagos se ha incrementado en las últimas décadas. El objetivo de este estudio fue evaluar la eficiencia de los inventarios de murciélagos comparando los parámetros del ensamble (riqueza de especies, abundancia y composición) usando los 3 métodos de captura convencionales (redes de niebla a nivel de sotobosque y sub-dosel, y trampas arpa), en una selva baja caducifolia de Yucatán, México. En las redes de sotobosque se registraron solamente especies de filostómidos, principalmente especies frugívoras y nectarívoras; mientras que en las trampas arpa, la mayoría fueron especies insectívoras de otras familias. Nuestros resultados indican que para el orden Chiroptera la combinación más eficiente de métodos de captura es el uso simultáneo de redes de sotobosque y trampas arpa. Sin embargo, se alcanza un inventario confiable de filostómidos sólo con las redes de sotobosque. Además, una combinación de redes de sotobosque y sub-dosel no provee una eficiente estrategia de muestreo.
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