Examinando por Materia "Kinetics"

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    Acetyl-L-carnitine supplementation reverses the age-related decline in carnitine palmitoyltransferase 1 (CPT1) activity in interfibrillar mitochondria without changing the L-carnitine content in the rat heart
    (Elsevier BV, 2012-02-01) Gómez, Luis A.; Du Heath, Shi-Hua; Hagen, Tory M.; Universidad EAFIT. Departamento de Ciencias; Ciencias Biológicas y Bioprocesos (CIBIOP)
    The aging heart displays a loss of bioenergetic reserve capacity partially mediated through lower fatty acid utilization. We investigated whether the age-related impairment of cardiac fatty acid catabolism occurs, at least partially, through diminished le
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    Extraction kinetics and physicochemical characteristics of Colombian propolis
    (Universidad EAFIT, 2023) Barrientos Lezcano, Juan Camilo; Barrientos, Juan Camilo; Builes Toro, Santiago
    Propolis, a resinous matter collected by Apis mellifera bees from exudates of plants, exhibits different biological properties, such as antimicrobial, antifungal, antiviral, and antioxidant activities. Standardization of the extraction of their bioactive compounds is a complex issue in particular for rural regions in developing countries due to the need for specialized equipment and personnel. Herein, kinetic extractions by maceration over 7 days were compared with ultrasound and supercritical fluids extractions in terms of the polyphenolic content obtained. Ultrasound showed the fastest kinetic extraction for each propolis without affecting the antioxidant activity. Supercritical fluids showed the lowest polyphenolic content recovery and no selectivity for antioxidant activity, in agreement with the solubility predictions. The main difference among the extraction methods was the extraction time required to reach the equilibrium concentration. No significant differences in selectivity were observed for the different methods. The antioxidant activity remained almost constant with the extraction method and extraction time, indicating similar extraction kinetics for the extracted polyphenols. We found that the physicochemical characteristics and UVvis spectra could be used as predictors of the polyphenolic contents for the studied samples.
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    A FIRST-ORDER TIME CONSTANT ESTIMATION FOR NONLINEAR DIFFUSION PROBLEMS
    (TAYLOR & FRANCIS INC, 2014-06-03) Simon, Laurent; Ospina, Juan; Simon, Laurent; Ospina, Juan; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
    A Laplace transform-based procedure was proposed to calculate the effective time constant for a class of nonlinear diffusion problems. The governing mathematical representation was first estimated with a linear model by omitting the nonlinear term. The solution to this problem was later introduced into the original equation, which was solved with Laplace transforms, resulting in a first-order approximation of the real system's behavior. A time constant was calculated using frequency-domain expressions. Two case studies were considered to illustrate the methodology. As the rate of heat supplied to a rod is raised, the speed at which the temperature reached an equilibrium value decreased. Increasing the maximum velocity in reaction-diffusion transport by a factor of three lowered the time constant by only 1.7%. The applications of this method range from biosensor dynamics to process control. © 2014 Copyright Taylor and Francis Group, LLC.
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    Mejoramiento de medio de cultivo para la producción de biomasa y polisacáridos a partir de Amauroderma omphalodes
    (Universidad EAFIT, 2022) Almánzar Agudelo, María Mercedes; Moreno Valencia, Kevin; Marín Palacio, Luz Deisy
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    Mineralization of cyanide originating from gold leaching effluent using electro-oxidation: multi-objective optimization and kinetic study
    (SPRINGER, 2020-01-01) Dobrosz-Gómez I.; Gómez García M.Á.; Gaviria G.H.; GilPavas E.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Desarrollo y Diseño de Procesos
    Abstract: This study examines the electro-oxidation (EO) of cyanide originating from an industrial plant´s gold leaching effluent. Experiments were carried out in a laboratory-scale batch cell reactor. Monopolar configuration of electrodes consisting of graphite (anode) and aluminum (cathode) was employed, operating in galvanostatic mode. Response Surface Methodology (RSM), based on a Box–Behnken experimental Design (BBD), was used to optimize the EO operational conditions. Three independent process variables were considered: initial cyanide concentration ([CN-]0 = 1000–2000 mg L-1), current density (J =7–107 mA cm-2), and stirring velocity (? = 250–750 rpm). The cyanide conversion (XCN-), Chemical Oxygen Demand (COD) removal percentage (%RCOD), and specific Energy Consumption per unit mass of removed cyanide (EC) were analyzed as response variables. Multi-objective optimization let to establish the most effective EO conditions ([CN-]0 = 1000 mg L-1, J = 100 mA cm-2 and ? = 750 rpm). The experimental data (XCN-, %RCOD, and EC) were fitted to second-order polynomial models with adjusted correlation coefficients (Radj2) of ca. 98, 99 and 87%, respectively. The kinetic analysis, performed at optimal EO operational conditions, allowed determination of time required to meet Colombian permissible discharge limits. The predictive capacity of kinetic expressions was verified against experimental data obtained for gold leaching effluent. Total cyanide removal and 96% of COD reduction were obtained, requiring EC of 71.33 kWh kg-1 and 180 min. The BOD5 (biological oxygen demand)/COD ratio increased from 4.52 × 10-4 to 0.5573, confirming effluent biodegradability after EO treatment. Graphic Abstract: [Figure not available: see fulltext.]The variation of cyanide (CN-), cyanate (CNO-) and ammonium (NH4 +) ions concentrations vs. time at alkaline conditions. EO operational conditions: [CN-]0 = 1000 mg/L, J = 100 mA/cm2 , ? = 750 rpm, [NaCl] = 0.15 M and pH 11.1. © 2020, Springer Nature B.V.
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    Mineralization of cyanide originating from gold leaching effluent using electro-oxidation: multi-objective optimization and kinetic study
    (SPRINGER, 2020-01-01) Dobrosz-Gómez I.; Gómez García M.Á.; Gaviria G.H.; GilPavas E.; Dobrosz-Gómez I.; Gómez García M.Á.; Gaviria G.H.; GilPavas E.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Procesos Ambientales (GIPAB)
    Abstract: This study examines the electro-oxidation (EO) of cyanide originating from an industrial plant´s gold leaching effluent. Experiments were carried out in a laboratory-scale batch cell reactor. Monopolar configuration of electrodes consisting of graphite (anode) and aluminum (cathode) was employed, operating in galvanostatic mode. Response Surface Methodology (RSM), based on a Box–Behnken experimental Design (BBD), was used to optimize the EO operational conditions. Three independent process variables were considered: initial cyanide concentration ([CN-]0 = 1000–2000 mg L-1), current density (J =7–107 mA cm-2), and stirring velocity (? = 250–750 rpm). The cyanide conversion (XCN-), Chemical Oxygen Demand (COD) removal percentage (%RCOD), and specific Energy Consumption per unit mass of removed cyanide (EC) were analyzed as response variables. Multi-objective optimization let to establish the most effective EO conditions ([CN-]0 = 1000 mg L-1, J = 100 mA cm-2 and ? = 750 rpm). The experimental data (XCN-, %RCOD, and EC) were fitted to second-order polynomial models with adjusted correlation coefficients (Radj2) of ca. 98, 99 and 87%, respectively. The kinetic analysis, performed at optimal EO operational conditions, allowed determination of time required to meet Colombian permissible discharge limits. The predictive capacity of kinetic expressions was verified against experimental data obtained for gold leaching effluent. Total cyanide removal and 96% of COD reduction were obtained, requiring EC of 71.33 kWh kg-1 and 180 min. The BOD5 (biological oxygen demand)/COD ratio increased from 4.52 × 10-4 to 0.5573, confirming effluent biodegradability after EO treatment. Graphic Abstract: [Figure not available: see fulltext.]The variation of cyanide (CN-), cyanate (CNO-) and ammonium (NH4 +) ions concentrations vs. time at alkaline conditions. EO operational conditions: [CN-]0 = 1000 mg/L, J = 100 mA/cm2 , ? = 750 rpm, [NaCl] = 0.15 M and pH 11.1. © 2020, Springer Nature B.V.
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    Multifactorial optimization of the decolorisation parameters of wastewaters resulting from dyeing flowers.
    (IWA PUBLISHING, 2009-01-01) Gil Pavas, Edison; Angel Gomez-Garcia, Miguel; Gil Pavas, Edison; Angel Gomez-Garcia, Miguel; Universidad EAFIT. Departamento de Ingeniería de Procesos; Procesos Ambientales (GIPAB)
    This work deals with the treatment of the wastewaters resulting from the process of dyeing flowers. In some local cases for growing flowers near to Medellin (Colombia), wastewater color was found to be one of the main problems in meeting local effluent standards. Wastewaters were treated by photodegradation process (which includes photocatalysis) to achieve the degradation of dyes mixture and organic matter in the wastewater. A multifactorial experimental design was proposed, including as experimental factors the following variables: pH, and the concentration of both catalyst (TiO(2)) and hydrogen peroxide (H(2)O(2)). According to the obtained results, at the optimized variables values, it is possible to reach a 99% reduction of dyes, a 76.9% of mineralization (TOC) and a final biodegradability of 0.834. Kinetic analysis allows proposing a pseudo first order reaction for the reduction, the mineralization, and the biodegradation processes.