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Search Results: 1 - 10 of 376685 matches for " Néstor Noé 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.

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.
Adolescentes en las aulas: la irrupción de la diferencia y el fin de la expansión educativa
López, Néstor;
Educa??o & Sociedade , 2012, DOI: 10.1590/S0101-73302012000300012
Abstract: the article begins by reviewing recent trends in the education of adolescents in latin america. specifically, the analysis is focused on to which extent the expansion of education since the early 1990's resulted in an important reduction of inequalities in the access to education and at the same time how the deceleration of the education process, that has been going on over the last five years, reinstalls the challenge of inequalities in the core of the educational agenda. the second part of the article suggests some hypothesis regarding the causes for this deceleration that may be seen in the universalization process of access to education. a special attention is paid to those hypothesis focusing on inequalities that result from the educational system's difficulties in operating in contexts of increasing cultural and identity diversity that clearly shows the persistence of multiple daily and common discriminatory practices at schools.
La educación en América Latina, entre el cambio social y la inercia institucional
Néstor López
Revista Galega de Economía , 2005,
Abstract: América latina viene de grandes cambios sociales, políticos, económicos y culturales, y una de las consecuencias de estas transformaciones es el asentamiento de situaciones de pobreza extrema y de exclusión. Frente a este nuevo contexto surge la pregunta sobre si no se estarán conformando escenarios sociales en los cuales no están garantizadas las condiciones mínimas para que las prácticas educativas tengan lugar. El trabajo aborda este interrogante, desarrollándolo en tono de ensayo a partir de la observación de situaciones de pobreza y de exclusión social en diversos países de la región. La conclusión es que, frente a la profundidad de los cambios ocurridos, la debilidad institucional de las escuelas y de los sistemas educativos de la región pone en riesgo la posibilidad de garantizar una educación de calidad para todos.
Los moradores de Gorgona: Protagonistas de unparadigma penitenciario en Colombia, 1959-1975
López Néstor
Anuario Colombiano de Historia Social y de la Cultura , 2006,
Abstract: El artículo expone las circunstancias sociales y políticas en que fue aprobada lacreación de un penal insular, la Isla Prisión de Gorgona, con claros fines políticos,entre ellos, segregar a los criminales supuestamente más peligrosos de la violenciabipart
Aterosclerosis en sujetos con periodontitis
López,Néstor J; Chamorro,Adriana; Llancaqueo,Marcelo;
Revista médica de Chile , 2011, DOI: 10.4067/S0034-98872011000600004
Abstract: background: chronic infl ammation and infections are involved in the development and progression of atherosclerotic vascular disease. aim: to evaluate the association between periodontitis and early atherosclerosis. material and methods: fifty-three subjects who received periodontal treatment and regular maintenance for at least 10 years, and 55 subjects with periodontitis but without a history of periodontal treatment were studied. carotid artery intima-media wall thickness (cimt) was measured with high-resolution b-mode ultrasonography. a blood sample was obtained to measure high sensitivity c-reactive protein, fibrinogen, lipoprotein cholesterol, leukocyte count and erythrocyte sedimentation rate. covariates included age, gender, smoking, level of education, body mass index and physical activity. the benzoyl-dl-arginine-naphthylamide (bana) test was used to determine the number of periodontal sites with periodontal pathogens. results: cimt value was significantly higher in subjects with periodontitis than those without it (0.775 ± 0.268 and 0.683 ± 0.131 mm respectively, p = 0.027). c-reactive protein, leukocyte count and percentage of sites with periodontal pathogens were also significantly higher in subjects with periodontitis. regression analysis identified age, periodontitis, and smoking as independent predictors of cimt. conclusions: these results suggest that untreated periodontitis is associated with early atherosclerotic carotid lesions and higher levels of infl ammatory markers.
Aterosclerosis en sujetos con periodontitis Association between atherosclerosis and periodontitis
Néstor J López,Adriana Chamorro,Marcelo Llancaqueo
Revista médica de Chile , 2011,
Abstract: Background: Chronic infl ammation and infections are involved in the development and progression of atherosclerotic vascular disease. Aim: To evaluate the association between periodontitis and early atherosclerosis. Material and Methods: Fifty-three subjects who received periodontal treatment and regular maintenance for at least 10 years, and 55 subjects with periodontitis but without a history of periodontal treatment were studied. Carotid artery intima-media wall thickness (CIMT) was measured with high-resolution B-mode ultrasonography. A blood sample was obtained to measure high sensitivity C-reactive protein, fibrinogen, lipoprotein cholesterol, leukocyte count and erythrocyte sedimentation rate. Covariates included age, gender, smoking, level of education, body mass index and physical activity. The benzoyl-DL-arginine-naphthylamide (BANA) test was used to determine the number of periodontal sites with periodontal pathogens. Results: CIMT value was significantly higher in subjects with periodontitis than those without it (0.775 ± 0.268 and 0.683 ± 0.131 mm respectively, p = 0.027). C-reactive protein, leukocyte count and percentage of sites with periodontal pathogens were also significantly higher in subjects with periodontitis. Regression analysis identified age, periodontitis, and smoking as independent predictors of CIMT. Conclusions: These results suggest that untreated periodontitis is associated with early atherosclerotic carotid lesions and higher levels of infl ammatory markers.
Resincronización ventricular: nueva técnica y dispositivo para el implante endocavitario de un catéter en el ventrículo izquierdo
Elencwajg,Benjamín; López Cabanillas,Néstor; Cardinali,Eduardo L; Trainini,Jorge C;
Revista argentina de cardiolog?-a , 2010,
Abstract: the difficulties regarding the implantation of devices for cardiac resynchronization therapy have generated the necessity to look for alternative pacing techniques, such as endocardial left ventricular lead placement via the transseptal approach from the right atrium. in this sense, several studies have been published in the last years. al-though all these studies have reported satisfactory outcomes, they all use "special" techniques with their own limitations, as the procedures should be performed by experienced op-erators who have overcome the learning curve. this might be the reason why these techniques have not become "popular" yet despite the favorable outcomes reported. the procedure here described intends to establish a methodology based on routine techniques used worldwide in the electrophysiology labs to allow a simple, effective, fast and safe lead placement with a minimum learning curve. the procedure consists in introducing an endocardial lead in the left ventricle through a conventional transfemorally performed transseptal puncture; the lead is then tunneled to the right or left subclavian vein and the implant is com-pleted in the conventional fashion.
Resincronización ventricular: nueva técnica y dispositivo para el implante endocavitario de un catéter en el ventrículo izquierdo
Benjamín Elencwajg,Néstor López Cabanillas,Eduardo L. Cardinali,Jorge C. Trainini
Revista Argentina de Cardiología , 2010,
Abstract: RESUMENLas dificultades inherentes a la técnica de implante de resincronizadores han generado lanecesidad de buscar nuevas opciones, como el implante endocavitario en el ventrículo izquierdopor vía transeptal auricular desde la aurícula derecha. En tal sentido, en los últimosa os ya se realizaron varias publicaciones. Si bien los resultados son satisfactorios, entodos los casos se utilizan técnicas “especiales”, que tienen sus dificultades propias y requierengran experiencia y una curva de aprendizaje por parte del operador. Es probableque ésta sea la razón por la cual estas técnicas no se “popularizaron”, pese a sus buenosresultados. El procedimiento que se describe en esta presentación pretende establecer unmétodo basado en técnicas de rutina en los laboratorios de electrofisiología de todo el mundoque permita un implante sencillo, efectivo, rápido y pasible de ser utilizado en formasegura con una curva de aprendizaje mínima.Básicamente, el procedimiento consiste en la introducción de un catéter endocavitario en elventrículo izquierdo a través de una punción transeptal convencional por la vena femoral ysu exteriorización por la vena subclavia (derecha o izquierda) para completar el implante enforma convencional.REV ARGENT CARDIOL 2010;78:143-146.
Gerencia de empresas recuperadas por los trabajadores en Argentina
Bialakowsky,Alberto L; Grima,José M; Costa,María Ignacia; López,Néstor;
Revista Venezolana de Gerencia , 2005,
Abstract: in this paper we discuss the traditional sense of the term management in order to construct a more appropriate concept in relation to recent experience in the emerging social movements to recover businesses on the part of their workers in argentina after the crisis of the 1970s. in these movements a new type of management is emerging on the part of their work force within the context of a movement to recover businesses based on a sampling of the same. this is ethnographic, sociological and co-productive research that is articulated along three tangents: power, knowledge and cooperation. the conclusion is that the recovered businesses discovered hidden dimensions in traditional management, which makes it more plastic and creative based on the collective aspect, when it assumes its identity as an anti-taylorist collective
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