Examinando por Materia "mathematical model"
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Ítem Numerical-analytical solutions of predator-prey models(World Scientific and Engineering Academy and Society, 2013-01-01) González-Parra Gilberto, G.; Arenas, A.J.; Cogollo, M.R.; Universidad EAFIT. Escuela de Ciencias; Modelado MatemáticoThis paper deals with the construction of piecewise analytic approximate solutions for nonlinear initial value problems modeled by a system of nonlinear ordinary differential equations. In real world several biological and environmental parameters in the predator-prey model vary in time. Thus, non-autonomous systems are important to be studied. We show the effectiveness of the method for autonomous and non-autonomous predator-prey systems. The method we have used is called the differential transformation method which has some suitable properties such as accuracy, low computational cost, easiness of implementation and simulation as well as preserving properties of the exact theoretical solution of the problem. The accuracy of the method is checked by numerical comparison with fourth-order Runge-Kutta results applied to several predator-prey examples.Ítem A possible restriction of ferro- and ferricyanide oxidoreductase activities of rat liver mitochondria by the outer membrane.(ELSEVIER SCIENCE INC, 2005-11-15) Ramirez, LAG; Lemeshko, VV; Universidad EAFIT. Departamento de Ciencias; Ciencias Biológicas y Bioprocesos (CIBIOP)In this work, various ferro-ferricyanide oxidoreductase activities of rat liver mitochondria were studied to find conditions under which the outer membrane might restrict the flux of these highly charged non-biological anions. When the isotonic low ionic strength medium was supplemented with 25mM KCl, a several-fold increase in the succinate-ferricyanide reductase activity of mitochondria and in the rate of external NADH oxidation in the presence of ferrocyanide was observed. Mitochondrial respiration with 5mM ferrocyanide was almost completely inhibited after consumption of 3.8-18.5% of the dissolved oxygen, depending on the medium and the presence of 2,4-dinitrophenol. These and other experimental data together with mathematical modeling of the redox-state equilibrium suggest that the measured activities might be restricted by two factors: first, the permeability of the outer mitochondrial membrane and second, a strong influence of the ionic strength of incubation media on the intermembrane space redox reactions.Ítem Sensitivity, uncertainty and identifiability analyses to define a dengue transmission model with real data of an endemic municipality of Colombia(Public Library of Science, 2020-01-01) Lizarralde-Bejarano, D.P.; Rojas-Díaz, D.; Arboleda-Sánchez, S.; Puerta-Yepes, M.E.; Lizarralde-Bejarano, D.P.; Rojas-Díaz, D.; Arboleda-Sánchez, S.; Puerta-Yepes, M.E.; Universidad EAFIT. Departamento de Ciencias; Matemáticas y AplicacionesDengue disease is a major problem for public health surveillance entities in tropical and subtropical regions having a significant impact not only epidemiological but social and economical. There are many factors involved in the dengue transmission process. We can evaluate the importance of these factors through the formulation of mathematical models. However, the majority of the models presented in the literature tend to be overparameterized, with considerable uncertainty levels and excessively complex formulations. We aim to evaluate the structure, complexity, trustworthiness, and suitability of three models, for the transmission of dengue disease, through different strategies. To achieve this goal, we perform structural and practical identifiability, sensitivity and uncertainty analyses to these models. The results showed that the simplest model was the most appropriate and reliable when the only available information to fit them is the cumulative number of reported dengue cases in an endemic municipality of Colombia. © 2020 Lizarralde-Bejarano et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Ítem Two-dimensional transport analysis of transdermal drug absorption with a non-perfect sink boundary condition at the skin-capillary interface(ELSEVIER SCIENCE INC, 2013-07-01) Simon, Laurent; Ospina, Juan; Simon, Laurent; Ospina, Juan; Universidad EAFIT. Departamento de Ciencias; Lógica y ComputaciónA transient percutaneous drug absorption model was solved in two dimensions. Clearance of the topically-applied pharmaceutical occured at the skin-capillary boundary. Timolol penetration profiles in the dermal tissue were produced revealing concentration gradients in the directions normal and parallel to the skin surface. Ninety-eight percent of the steady-state flux was reached after 85. h or four time constants. The analytical solution procedure agreed with published results. As the clearance rate increased relative to diffusion, the delivery rate and amount of drug absorbed into the bloodstream increased while the time to reach the equilibrium flux decreased. Researchers can apply the closed-form expressions to simulate the process, estimate key parameters and design devices that meet specific performance requirements. © 2013 Elsevier Inc.Ítem Using Phenomenological Models to Characterize Transmissibility and Forecast Patterns and Final Burden of Zika Epidemics.(Public Library of Science,, 2016-05-31) Chowell G; Hincapie-Palacio D; Ospina J; Pell B; Tariq A; Dahal S; Moghadas S; Smirnova A; Simonsen L; Viboud C; Chowell G; Hincapie-Palacio D; Ospina J; Pell B; Tariq A; Dahal S; Moghadas S; Smirnova A; Simonsen L; Viboud C; Universidad EAFIT. Departamento de Ciencias; Lógica y ComputaciónBACKGROUND: The World Health Organization declared the ongoing Zika virus (ZIKV) epidemic in the Americas a Public Health Emergency of International Concern on February 1, 2016. ZIKV disease in humans is characterized by a "dengue-like" syndrome including febrile illness and rash. However, ZIKV infection in early pregnancy has been associated with severe birth defects, including microcephaly and other developmental issues. Mechanistic models of disease transmission can be used to forecast trajectories and likely disease burden but are currently hampered by substantial uncertainty on the epidemiology of the disease (e.g., the role of asymptomatic transmission, generation interval, incubation period, and key drivers). When insight is limited, phenomenological models provide a starting point for estimation of key transmission parameters, such as the reproduction number, and forecasts of epidemic impact. METHODS: We obtained daily counts of suspected Zika cases by date of symptoms onset from the Secretary of Health of Antioquia, Colombia during January-April 2016. We calibrated the generalized Richards model, a phenomenological model that accommodates a variety of early exponential and sub-exponential growth kinetics, against the early epidemic trajectory and generated predictions of epidemic size. The reproduction number was estimated by applying the renewal equation to incident cases simulated from the fitted generalized-growth model and assuming gamma or exponentially-distributed generation intervals derived from the literature. We estimated the reproduction number for an increasing duration of the epidemic growth phase. RESULTS: The reproduction number rapidly declined from 10.3 (95% CI: 8.3, 12.4) in the first disease generation to 2.2 (95% CI: 1.9, 2.8) in the second disease generation, assuming a gamma-distributed generation interval with the mean of 14 days and standard deviation of 2 days. The generalized-Richards model outperformed the logistic growth model and provided forecasts within 22% of the actual epidemic size based on an assessment 30 days into the epidemic, with the epidemic peaking on day 36. CONCLUSION: Phenomenological models represent promising tools to generate early forecasts of epidemic impact particularly in the context of substantial uncertainty in epidemiological parameters. Our findings underscore the need to treat the reproduction number as a dynamic quantity even during the early growth phase, and emphasize the sensitivity of reproduction number estimates to assumptions on the generation interval distribution.Ítem What Emotions Does a Song Evoke? On an Emotional-Musical Probabilistic Model(Universidad EAFIT, 2023) Lugos Abarca, Josué Alexis