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Search Results: 1 - 10 of 212848 matches for " Raúl Aristizábal "
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Real options as an alternative methodology to assess investment projects Las opciones reales como metodología alternativa en la evaluación de proyectos de inversión
Armando Lenin Támara Ayús,Raúl Enrique Aristizábal Velásquez
Ecos de Economía , 2012,
Abstract: This paper aims to broaden the applicability of the assessment methodology of investment projects through real options as a key element for investment decision making. Traditional project valuation methodologies are described and their gaps, which special characteristic is uncertainty, are presented. A parallel between financial and real options that could be used for valuation is made, using the binomial tree method. Finally, a case study in the construction sector shows a project valuation using expand and waiting options. Este trabajo busca ampliar la aplicabilidad de la metodología de valoración de proyectos de inversión por medio de opciones reales como un elemento fundamental al momento de tomar una decisión de si se debe invertir o no. Se hace un recorrido por las técnicas tradicionales para valorar un proyecto de inversión y se plantean los vacíos que estos dejan, con respecto a proyectos en los que su principal característica es la incertidumbre. Se realiza un paralelo entre las opciones financieras y las opciones reales que per- mita valorar, utilizando la metodología de los árboles binomiales. Por último, se elabora un caso del que se plantea valorar una opción de espera y una opción de expandir de manera conjunta en el sector de la construcción.
MATRICES DE TRANSICIóN EN EL ANáLISIS DEL RIESGO CREDITICIO COMO ELEMENTO FUNDAMENTAL EN EL CáLCULO DE LA PéRDIDA ESPERADA EN UNA INSTITUCIóN FINANCIERA COLOMBIANA TRANSITION MATRICES IN CREDIT RISK ANALYSIS AS A FUNDAMENTAL ELEMENT IN THE CALCULATION OF EXPECTED LOSS IN A COLOMBIAN FINANCIAL INSTITUTION
Armando Támara-Ayús,Raúl Aristizábal,Ermilson Velásquez
Revista Ingenierías Universidad de Medellín , 2012,
Abstract: En este artículo se busca ampliar aún más el análisis referente al riesgo crediticio y cómo a través del esquema de matrices de transición se puede calcular la probabilidad de incumplimiento de un deudor frente a un acreedor para una institución financiera en Colombia. Se logra así hacer una comparación del cálculo de la pérdida esperada entre el modelo empleado por la institución financiera, el modelo de referencia de calificación comercial planteado por la Superintendencia Financiera de Colombia y el modelo encontrado bajo el esquema de matrices de transición. This article seeks to further extend the analysis under Credit Risk as through the Transition Matrices scheme can calculate the probability of default of a debtor to a creditor for a financial institution in Colombia. This achieving a comparison by calculating the expected loss between the model used by the financial institution, the reference model of commercial rating raised by the Financial Superintendence of Colombia and the model found under the scheme of Transition Matrices.
Integración viral y cáncer de cuello uterino
López,Jacqueline; Aristizábal,Fabio Ancízar;
Revista Colombiana de Ciencias Químico - Farmacéuticas , 2006,
Abstract: cervical cancer is the second most prevalent cancer worldwide and is the second leading cause of cancer deaths in women. persistent infection with high-risk human papillomaviruses (hpvs) types are the causative agents of cervical cancer, since 99% of tumors are positive for hpv dna, hpv is a necessary cause of invasive cervical cancer worldwide. one of the key events of hpv-induced carcinogenesis is the integration of the hpv genome into a host chromosome, related with precancerous lesions progression. integration follows a more specific pattern with respect to the hpv genome, expression of the viral e6 and e7 genes is consistently maintained, whereas other positions of the viral dna are deleted or their expression is disturbed, like e2 gene. loss of expression of the hpv e2 transcriptional repressor is significant and may be critical for malignant progression, as it may result in increased hpv e6 and e7 expression. the hpv e6 and e7 oncoproteins inactivate the p53 and prb tumor suppressors; expression of high-risk hpv e6/e7 oncogenes provides a subset of the minimally required carcinogenic hits for full transformation of human epithelial cells. there is also evidence for deregulated hpv-16 e6-e7 mrna stability after integration and specific alterations of host cellular gene expression have been detected upon hpv genome integration. currently, integration of hpv is considered to be an important genetic alteration for the progression of intraepithelial lesions to invasive disease with potential clinical applications like mark tumour progression and diagnostic tool.
Caracterización de cepas nativas de Clostridium spp por secuenciación parcial del gen ribosomal 16s rARN
Montoya D.,Perdomo L.,Arévalo C.,Aristizábal F.
Revista Colombiana de Biotecnología , 1999,
Abstract: Las cepas de Clostridium, productoras de solventes y ácidos, han sido caracterizados empleando una amplia gama de técnicas fisiológicas, bioquímicas y moleculares. Los trabajos más recientes han clasificado estos microorganismos en cuatro grupos y es de esperarse que muchos de los microorganismos anaerobios solventogénicos estén fuera de esta clasificación. El presente trabajo estuvo orientado a caracterizar molecularmente por 16S rARN trece cepas silvestres de Clostridium seleccionadas por su mayor capacidad para producir solventes con respecto a la cepa patrón de Clostridium acetobutylicum ATCC824. Se hizo la secuenciación parcial del gen 16S rARN, sobre su segmento final (aproximadamente 700 pb). Para anali-zar las secuencias, se calculó p y se construyó el dendograma empleando neighborjoining. Se pudo obser-var que las cepas silvestres no pertenecen a ninguno de los cuatro grupos de Clostridium solventogénicos sino que están cercanamente relacionadas con Clostridium butyricum. Solventogenic and acidogenic Clostridium has been characterized by biochemical, physiological and molecular techniques. These microorganisms have been classified into four groups but these may not necessarily be the only four exclusive groups; in fact, many of these microorganisms might not belong to any of these selected groups. The main goal was to classify 13 higher solvent- producing Clostridia strains through molecular biology techniques; strains were isolated by our Group. Sequence analysis was calculated by p and the dendogram was constructed by neighbor-joining. The results obtained strongly suggest the idea of a high similarity between the 13 native strains in the study and the fact that they had no relationship to any of the 4 groups established by Keis et al (1995). It was found that Clostridium butyricum strain is the most related specie to the thirteen Colombian strains.
Primer reporte de susceptibilidad del clon de caucho natural FX-3864 a Microcyclus ulei en la altillanura colombiana
García,Ibonne A.; Castro,Olga M.; Aristizábal,Fabio; Tapiero,Aníbal L.;
Revista Colombiana de Biotecnología , 2011,
Abstract: south american leaf blight (salb), caused by microcyclus ulei (anamorph fusicladium macrosporum), is an endemic major disease of the rubber tree (hevea brasiliensis) in america. as well as in other crop systems, its management on rubber plantations relies on plant genetic resistance availability, among other means. fx 3864 is a rubber tree clone widely planted in colombia due to its production capability and disease resistance. during 2010 salb symptoms developed in commercial crops at the meta region of colombia. crop traps located nearby the plantations showed mean disease severity levels of 5.78%. once the causal organism was microscopically confirmed as responsible for the diseased tissue, their origin was characterized by molecular means using 4 microsatellites specific to the rubber tree. the procedure confirmed that fx 3864 was the clone of origin of the leaf tissue. salb occurring over fx 3864 implies the need to redirect crop disease management measures to be followed on the new development areas of rubber cultivation, warning growers about potential hazards of disease incidence.
Primer reporte de susceptibilidad del clon de caucho natural FX-3864 a Microcyclus ulei en la altillanura colombiana
García Ibonne Aidee,Castro Olga M.,Aristizábal Fabio,Tapiero Aníbal L.
Revista Colombiana de Biotecnología , 2011,
Abstract: First report of susceptibility of natural rubber clone FX-3864 a Microcyclus ulei en la altillanuera colombiana Resumen El mal suramericano de las hojas (SALB), enfermedad endémica del caucho (Hevea brasiliensis), es causado por Microcyclus ulei (forma imperfecta Fusicladium macrosporum) y constituye el principal limitante del cultivo en América, área donde el microorganismo patógeno es endémico. En forma semejante al de otros cultivos agrícolas, el manejo de esta enfermedad está condicionado a la disponibilidad de resistencia genética en el hospedero. En razón de su productividad y condición de resistencia genética, el clon FX 3864 ha sido ampliamente plantado en zonas con diferente potencialidad epidémica a la incidencia del SALB en Colombia, particularmente las denominadas de “no escape” a la enfermedad. Durante el 2010, plantaciones con el clon FX 3864 en fase productiva presentaron síntomas de SALB en zonas de escape ubicadas en la altillanura colombiana (departamento del Meta). En parcelas trampa ubicadas en áreas aleda as a los cultivos se estableció que la severidad promedio de la enfermedad alcanzó niveles de 5,78% en este clon. Verificada la causalidad de la enfermedad mediante observaciones al microscopio se procedió a confirmar el origen del material sobre el cual se desarrollaban las lesiones, utilizando marcadores moleculares (4 microsatélites específicos). Los resultados de la prueba permitieron confirmar la susceptibilidad del hasta hace poco resistente clon FX 3864 al SALB en Colombia. Se sugiere tomar en consideración la nueva condición de este clon y, en concordancia, reorientar los programas de fomento del cultivo advirtiendo a los agricultores sobre los riesgos potenciales de ocurrencia de la enfermedad en las nuevas áreas programadas. Palabras clave: SALB, Hevea brasiliensis, Fusicladium macrosporum, cultivo de caucho. Abstract South American Leaf Blight (SALB), caused by Microcyclus ulei (anamorph Fusicladium macrosporum), is an endemic major disease of the rubber tree (Hevea brasiliensis) in America. As well as in other crop systems, its management on rubber plantations relies on plant genetic resistance availability, among other means. FX 3864 is a rubber tree clone widely planted in Colombia due to its production capability and disease resistance. During 2010 SALB symptoms developed in commercial crops at the Meta region of Colombia. Crop traps located nearby the plantations showed mean disease severity levels of 5.78%. Once the causal organism was microscopically confirmed as responsible for the diseased tissue, their or
Validación por hidrodensitometría de ecuaciones de pliegues cutáneos utilizadas para estimar la composición corporal en mujeres
Aristizábal,Juan Carlos; Restrepo,María Teresa; Amalia,López;
Biomédica , 2008,
Abstract: introduction. skinfold thickness equations are widely used for body composition assessment. however the equations have not been validated in colombia with a reference method. objective. the skinfold thickness equations of durning/womersley, jackson/pollock and ramírez/torun were validated by hydrodensitometry in female from 18 to 40 years old. materials and methods. the percentage of body fat was compared among 52 women, using underwater weighing (chatillon scale) with simultaneous measured of residual lung volume (vmax 22 sensormedics spirometer) and skinfold thickness (harpenden caliper) equations of durning/womersley, jackson/pollock and ramírez/torun. the statistic analysis included paired t test, pearson and intraclass correlation coefficients, and the bland-altman method. results. the mean percentage of body fat by hydrodensitometry (29.6±5.8%) was different (p conclusion. the skinfold thickness equations showed poor validity for body fat assessment. the equations had significant differences and lower correlation coefficients with hydrodensitometry. in addition, the equations indicated agreement with hydrodensitometry over very wide limits. the outcomes suggested that the results obtained by hydrodensitometry were neither comparable nor interchangeable with those from durning/womersley, jackson/pollock y ramírez/torun skinfold thickness equations.
BIOTRANSFORMACIóN DE LOS SUSTRATOS 2-FENILETANOL Y ACETOFENONA CON EL HONGO FITOPATóGENO Colletotrichum acutatum
Aristizábal,Diego A.; Lezcano,Clara S.; García,Carlos M.; Durango,Diego L.;
Revista Colombiana de Química , 2008,
Abstract: the microbial transformation of 2-phenilethanol 1 and acetophenone 2 was investigated using the plant pathogenic fungus colletotrichum acutatum; the process was carried out in liquid media culture czapeck-dox at an average temperature of 24 oc, a relative humidity between 45% and 60% and with agitation in a shaker at 150 rpm. the biotransformation of the substrate 1 produced the metabolic products 1-phenyl-1,2-ethanediol 3, (2- methoxyethyl)benzen 4 and 2-phenylethyl acetate 5, and from substrate 2 were obtained the compounds 1-phenyl- 1,2-ethanediol 3, 1-phenylethanol 6 and 2-phenylethanol 1. the structures of metabolic products were determined by gas chromatography coupled with mass spectrometry (gc-ms) and nuclear magnetic resonance of proton and of carbon (1h and 13c nmr). the process has a strong tendency of the pathogen to produce hydroxylations on the substituents attached to the aromatic ring. additionally, c. acutatum was effective to reduce the carbonyl group and produce esterification reactions in the hydroxyl groups from primary alcohols. the metabolic pathway of both substrates is discussed.
Virus del papiloma humano, respuesta inmune y cáncer cervical: una relación compleja
Rincón,Olga L; Pareja,Luis René; Jaramillo,Sergio; Aristizábal,Beatriz H;
Revista Colombiana de Obstetricia y Ginecología , 2007,
Abstract: cervical cancer is considered to be a serious public health problem having a high incidence in developing countries. high-risk cervical human papillomavirus (hpv) infection, permanence and replication are closely related to the development of cervical cancer. the immune system is able to control and clear such infection in normal conditions by innate immunity action, activating a cellular response and creating antibodies, mainly directed against virion capsid proteins (l1 and l2). in spite of the host?s entire immune protection machinery, the virus can take evasion strategies, maintaining a reduced number of copies in proliferating base cells and taking advantage of the keratinocyte?s short natural life. this review attempts to show the host?s different immunological mechanisms elicited in response to hpv infection.
Effect of the incubation temperature on the embryonic development and hatching time of eggs of the red porgy Pagrus pagrus (Linne, 1758) (Pisces: Sparidae)
Radonic,Mariela; López,Andrea V; Oka,Masakazu; Aristizábal,Eddie O;
Revista de biología marina y oceanografía , 2005, DOI: 10.4067/S0718-19572005000200001
Abstract: assessment of egg quality at early embryonic stages may be useful predictive criterion to evaluate the potential mass juvenile production in red porgy pagrus pagrus. the objective of the present study is to describe in detail the embryonic developmental stages in the red porgy and the time taken by larvae to hatch at three incubation temperatures. fertilized eggs obtained from natural spawnings were incubated at 15, 20 and 25oc. photomicrographs of all the embryonic stages were taken at the three temperatures. cell divisions after fertilization and organ appearance during the embryonic development were identified. the sequence in cellular divisions and appearance of sensory and motor organs were the same for the three temperatures, although the higher the temperature, the faster the stages of development. hatching time was also determined by the incubation temperature. at 25oc the completely-formed embryo hatched at approximately 25 h 26 min after fertilization whereas at 20oc and 15oc hatching occurred 37 and 60 h post fertilization. knowledge of the normal embryonic stages, the sequence of cleavages, the egg diameter, the number of oil drops, the timing of organ formation and the hatching rate is a basic requirement for assessing the eggs batches quality during seed mass production
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