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Search Results: 1 - 10 of 339263 matches for " Marco S. Caicedo "
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Mecanismo de selección de consorcios bacterianos compatibles con A. ferrooxidans y A. thiooxidans en procesos de biodesulfurización de carbón
Caicedo,Gerardo Andrés; Márquez,Marco Antonio;
Revista Facultad de Ingeniería Universidad de Antioquia , 2010,
Abstract: in a flask, biodesulfurization processes of a coal with high sulfur content were evaluated. the particle size of coal ranged between 0.24 cm - 0.06 cm. the processes used consortiums compounds by acidithiobacillus ferrooxidans like bacteria + acidithiobacillus thiooxidans like bacteria. in the biodesulfurization processes, the principal factors like ph, redox potential and sulfate in solution and precipitated, produced from sulfur compounds reduced in the coal and medium were analyzed. according to the results a 71.50% of sulfate produced with respect to the maximum possible was obtained after 16 days of processing. these results are key to select cultures for biodesulfurization process in a larger scale.
Influencia de la concentración de hierro y pH iniciales en un proceso de biodesulfurización de carbón - ensayos a nivel de laboratorio
Caicedo Pineda,Gerardo Andrés; Márquez Godoy,Marco Antonio; Moreno Herrera,Claudia Ximena;
Revista Colombiana de Biotecnología , 2011,
Abstract: biodesulfurization process for colombian coal (2.34% total sulfur: 1.34% as pyritic, 0.90% as organic and 0.10% from sulfates) from municipality of puerto libertador (córdoba, colombia) was carried out. a mixed culture of a. ferrooxidans and a. thiooxidans was used. the study was mainly focused on the influence of ph, and iron concentration in coal leaching pro- cess. two mineral particle sizes were evaluated: less 8 mesh (-malla 8) and less 60 mesh (-malla 60), tyler series. biodesulfurization processes were determined by measuring changes in soluble iron, ph, redox potential and microbial populations approach. the results showed above 50% of pyritic sulphur oxidation after 12 days. coal type and evaluated conditions influence in leaching process. less to 1200 ppm of iron concentration and initial ph between 1.5-1.3, were considered to have critical roles in optimizing pyrite dissolution.
Influencia de la concentración de hierro y pH iniciales en un proceso de biodesulfurización de carbón – ensayos a nivel de laboratorio
Caicedo Pineda Gerardo Andrés,Márquez Godoy Marco Antonio,Moreno Herrera Claudia Ximena
Revista Colombiana de Biotecnología , 2011,
Abstract: Título en ingles: Particle size, iron concentration and pH influence in biodesulfurization process of coal – laboratory tests Resumen A un carbón proveniente del municipio de Puerto Libertador, Córdoba-Colombia (2.34% de azufre total, con 1.34% pirítico, 0.90% orgánico y 0.10% de sulfatos), se le aplicó un cultivo mixto de Acidithiobacillus ferrooxidans y Acidithiobacillus thiooxidans, con el fin de evaluar procesos de biodesulfurización en suspensión, a partir de variables que influyen en el proceso: concentración inicial de hierro y pH de la solución lixiviante, bajo dos configuraciones de tama o de partícula: pasante malla 8 (-malla 8) y pasante malla 60 (-malla 60), acorde con la serie Tyler de tamices. Los procesos de biodesulfurización se evaluaron cada dos días, mediante mediciones de la concentración de hierro, pH, potencial de óxido-reducción y crecimiento celular, en la solución. A partir de los ensayos realizados, se alcanzaron oxidaciones de azufre pirítico por encima del 50%, después de 12 días de proceso. Se pudo constatar que tanto el tipo de carbón tratado, como de las condiciones evaluadas, inciden en el grado de lixiviación alcanzado. La mejor eficiencia del proceso se observó al utilizar concentraciones de hierro iniciales menores a 1200 ppm y un pH inicial entre 1.5 y 1.3. Palabras clave: Acidithiobacillus, biodesulfurización, carbón, hierro removido, pirita. Abstract Biodesulfurization process for Colombian coal (2.34% total sulfur: 1.34% as pyritic, 0.90% as organic and 0.10% from sulfates) from municipality of Puerto Libertador (Córdoba, Colombia) was carried out. A mixed culture of A. ferrooxidans and A. thiooxidans was used. The study was mainly focused on the influence of pH, and iron concentration in coal leaching process. Two mineral particle sizes were evaluated: less 8 mesh (-malla 8) and less 60 mesh (-malla 60), Tyler series. Biodesulfurization processes were determined by measuring changes in soluble iron, pH, redox potential and microbial populations approach. The results showed above 50% of pyritic sulphur oxidation after 12 days. Coal type and evaluated conditions influence in leaching process. Less to 1200 ppm of iron concentration and initial pH between 1.5-1.3, were considered to have critical roles in optimizing pyrite dissolution. Key words: Acidithiobacillus, biodesulfurization, coal, iron removed, pyrite.
Cobalt-Alloy Implant Debris Induce HIF-1α Hypoxia Associated Responses: A Mechanism for Metal-Specific Orthopedic Implant Failure
Lauryn Samelko, Marco S. Caicedo, Seung-Jae Lim, Craig Della-Valle, Joshua Jacobs, Nadim J. Hallab
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0067127
Abstract: The historical success of orthopedic implants has been recently tempered by unexpected pathologies and early failures of some types of Cobalt-Chromium-Molybdenum alloy containing artificial hip implants. Hypoxia-associated responses to Cobalt-alloy metal debris were suspected as mediating this untoward reactivity at least in part. Hypoxia Inducible Factor-1α is a major transcription factor involved in hypoxia, and is a potent coping mechanism for cells to rapidly respond to changing metabolic demands. We measured signature hypoxia associated responses (i.e. HIF-1α, VEGF and TNF-α) to Cobalt-alloy implant debris both in vitro (using a human THP-1 macrophage cell line and primary human monocytes/macrophages) and in vivo. HIF-1α in peri-implant tissues of failed metal-on-metal implants were compared to similar tissues from people with metal-on-polymer hip arthroplasties, immunohistochemically. Increasing concentrations of cobalt ions significantly up-regulated HIF-1α with a maximal response at 0.3 mM. Cobalt-alloy particles (1 um-diameter, 10 particles/cell) induced significantly elevated HIF-1α, VEGF, TNF-α and ROS expression in human primary macrophages whereas Titanium-alloy particles did not. Elevated expression of HIF-1α was found in peri-implant tissues and synovial fluid of people with failing Metal-on-Metal hips (n = 5) compared to failed Metal-on-Polymer articulating hip arthroplasties (n = 10). This evidence suggests that Cobalt-alloy, more than other metal implant debris (e.g. Titanium alloy), can elicit hypoxia-like responses that if unchecked can lead to unusual peri-implant pathologies, such as lymphocyte infiltration, necrosis and excessive fibrous tissue growths.
Goodstein's function
CAICEDO,ANDRéS EDUARDO;
Revista Colombiana de Matemáticas , 2007,
Abstract: goodsteins function ?:n → n is an example of a fast growing recursive function. introduced in 1944 by r. l. goodstein [9], kirby and paris [12] showed in 1982, using model theoretic techniques, that goodsteins result that ? is total, i.e., that ?(n) is defined for all n ? n, is not a theorem of first order peano arithmetic. we compute goodsteins function in terms of the l?b-wainer fast growing hierarchy of functions; from this and standard proof theoretic results about this hierarchy, the kirby-paris result follows immediately. we also compute the functions of the hardy hierarchy in terms of the l?b-wainer functions, which allows us to provide a new proof of a similar result, due to cichon [2].
Goodstein's function Función de Goodstein
ANDRéS EDUARDO CAICEDO
Revista Colombiana de Matemáticas , 2007,
Abstract: Goodsteins function :N → N is an example of a fast growing recursive function. Introduced in 1944 by R. L. Goodstein [9], Kirby and Paris [12] showed in 1982, using model theoretic techniques, that Goodsteins result that is total, i.e., that (n) is defined for all n N, is not a theorem of first order Peano Arithmetic. We compute Goodsteins function in terms of the L b-Wainer fast growing hierarchy of functions; from this and standard proof theoretic results about this hierarchy, the Kirby-Paris result follows immediately. We also compute the functions of the Hardy hierarchy in terms of the L b-Wainer functions, which allows us to provide a new proof of a similar result, due to Cichon [2]. La función de Goodstein :N → N es un ejemplo de una función recursiva de crecimiento rápido. Introducida en 1944 por R. L. Goodstein [9], Kirby y Paris [12] demostraron en 1982, usando técnicas de teoría de modelos, que el resultado de Goodstein de que es total, es decir, que (n) está definida para todo n N, no es un teorema de la Aritmética de Peano de primer orden. Calculamos la función de Goodstein en términos de la jerarquía de funciones de crecimiento rápido de L b y Wainer; usando esto y resultados clásicos de teoría de la demostración acerca de esta jerarquía, el teorema de Kirby y Paris se sigue de inmediato. También calculamos las funciones de la jerarquía de Hardy en términos de las funciones de L b y Wainer, con lo que obtenemos una nueva demostración de un resultado similar, debido a Cichon [2].
Pablo Rodríguez Jiménez y María Emma Mannarelli (coordinadores).Historia de la infancia en América Latina.Bogotá: Universidad Externado de Colombia, 2007. 675 páginas.
Caicedo Gaviria Nicolás
Anuario Colombiano de Historia Social y de la Cultura , 2007,
Abstract:
Th1 type lymphocyte reactivity to metals in patients with total hip arthroplasty
Nadim Hallab, Marco Caicedo, Alison Finnegan, Joshua J Jacobs
Journal of Orthopaedic Surgery and Research , 2008, DOI: 10.1186/1749-799x-3-6
Abstract: Lymphocytes from young healthy individuals without an implant or a history of metal allergy (Group 1: n = 8) were used to assess lymphocyte responses to metal challenge agents. In addition, individuals (Group 2: n = 15) with well functioning total hip arthroplasties (average Harris Hip Score = 91, average time in-situ 158 months) were studied. Age matched controls with no implants were also used for comparison (Group 3, n = 8, 4 male, 4 female average age 70, range 49–80). Group 1 subjects' lymphocyte proliferation response to Aluminum+3, Cobalt+2, Chromium+3, Copper+2, Iron+3, Molybdenum+5, Manganeese+2, Nickel+2, Vanadium+3 and Sodium+2 chloride solutions at a variety of concentrations (0.0, 0.05, 0.1, 0.5, 1.0 and 10.0 mM) was studied to establish toxicity thresholds. Mononuclear cells from Group 2 and 3 subjects were challenged with 0.1 mM CrCl3, 0.1 mM NiCl2, 0.1 mM CoCl2 and approx. 0.001 mM titanium and the reactions measured with proliferation assays and cytokine analysis to determine T-cell subtype prominence.Primary lymphocytes from patients with well functioning total hip replacements demonstrated a higher incidence and greater magnitude of reactivity to chromium than young healthy controls (p < 0.03). Of the 15 metal ion-challenged subjects with well functioning total hip arthroplasties, 7 demonstrated a proliferative response to Chromium, Nickel, Cobalt and/or Titanium (as defined by a statistically significant >2 fold stimulation index response, p < 0.05) and were designated as metal-reactive. Metals such as Cobalt, Copper, Manganese, and Vanadium were toxic at concentrations as low as 0.5 mM while other metals, such as Aluminum, Chromium, Iron, Molybdenum, and Nickel, became toxic at much higher concentrations (>10 mM). The differential secretion of signature T-cell subsets' cytokines (Th1 and Th2 lymphocytes releasing IFN-gamma and IL-4, respectively) between those total hip arthroplasty subjects which demonstrated metal-reactivity and those that did
DEMOCRACIA, NACIóN Y SOCIEDAD: LA CRISIS Y DECADENCIA DEL BIPARTIDISMO EN COLOMBIA
Julián Andrés Caicedo O.
Latinoamérica. Revista de estudios Latinoamericanos , 2008,
Abstract: Este artículo es una reflexión sobre los sistemas de partidos latinoamericanos en el marco de la crisis de Estado a finales del siglo XX. Analizando el caso colombiano, particularmente el abolengo dominante bipartidista, Liberal y Conservador, se explica por qué la promulgación de la Constitución de 1991, el surgimiento del Uribismo y la reforma constitucional de 2003, evidencia su crisis y decadencia, dejándolos excluidos del nuevo orden político, y debate sobre la gobernabilidad democrática incluyente, tolerante y necesaria en el país.
Enfoque sistémico de la organización, la tecnología y los modelos de gestión
Caicedo Escobar Carlos,Cortés Amador Carlos
Ingeniería e Investigación , 1997,
Abstract: Este ensayo presenta los siguientes aspectos: 1. Un enfoque integral. 2. La organización como sistema. 3. La organización comunicante. 4. La organización: gestión y dirección. 5. Articulación de la organización, el trabajo y la tecnología. 6. Los modelos de gestión. 7. Resumen y Conclusiones.
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