12456 research outputs found
Sort by
Lead ferrite activated carbon magnetic composite for efcient removal of phenol from aqueous solutions: synthesis, characterization, and adsorption studies
No full textA novel lead ferrite-magnetic activated carbon (lead ferrite-MAC) composite was developed using the chemical co-precipitation method. Instrumental analyses such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) analysis were performed to characterize adsorbent. The uptake of phenol from aqueous solutions using the developed adsorbent was compared to that of pristine activated carbon. The maximum adsorption capacity of lead ferrite-MAC composite (145.708 mg/g) was more than that of pristine activated carbon (116.606 mg/g) due to the metal hydroxides coated on activated carbon since they improve the retention of phenol on the available active sites of adsorbent and create an additional electrostatic interaction with the phenol adsorbate. Regarding the high value of the coefficient of determination (R2) and adjusted determination coefficient (R2adj), coupled with the lower values of average relative error (ARE) and minimum squared error (MSE), it can be found that the isothermal data for the lead ferrite-MAC adsorbent were in agreement with the isotherm models of Redlich-Peterson and Langmuir. From the kinetic viewpoint, pseudo-second-order and linear driving force models explained the phenol adsorption data for both adsorbents. The reusability tests for lead ferrite-MAC composite revealed that after six cycles, 85% of the initial adsorption capacity was maintained. The developed adsorbent can be successfully applied to uptake phenol from aqueous solutio
Follow-up model to evaluate failure factors of single-phase distribution transformers in high environmental pollution zones
No full textSingle-phase distribution transformers are commonly installed in outdoor distribution networks to supply electricity to final users. Utilities are used to receive abnormal operating reports related to typical failures that negatively affect the reliability and security indicators. Therefore, a follow-up model is proposed in this paper to evaluate the failure factors of distribution transformers installed in high environmental pollution zones. The results show that the main factors that cause failures are overload, overvoltage, overcurrent, moisture, hot spots, manufacturing process, and lack of technical knowledge. Furthermore, all those factors are presented in a typical case using time-lines diagrams to characterize the main failures. Finally, hot spots, overloads, and unauthorized connections are the most critical failure factors identified in the research. According to the statistical analysis, those failures could occur 16 days after installing the transformer. The follow-up model presented in this research can characterize the main failures presented in outdoor distribution transformers
Budgetary impact analysis of preexposure prophylaxis (prep) strategy for the prevention of hiv in Colombia, 2019-2021
Get PDFWe aimed to estimate the budgetary impact of a PrEP strategy for the prevention and control of HIV in men who have sex with men (MSM) and transgender women (TGW) in Colombia. We adapted a budgetary impact model developed by Fundación Oswaldo Fiocruz, Brazil. Modelling was performed from the third-payer perspective over a 3-year period. Epidemiological and cost inputs were extracted from literature reviews and Colombian data. Two scenarios were simulated: 1. No PrEP scenario; and, 2. New scenario: MSM and TGW would have access to a PrEP program, which potentially reduce the HIV cases. Costs include the sum of PrEP program costs for MSM and TGW, and the treatment costs of cases that will occur in the 3-years of implementation. The new scenario was modelled at different risk and PrEP program coverage levels. Budget impact analysis (BIA) was calculated as the difference between the two scenarios. Cost were reported in Colombian pesos (COP). At a PrEP coverage of 80% and an incidence of 4.5 per 100 person-year would be avoid 4,057, 4,315 and 4,383 HIV cases in MSM for years 1, 2 and 3, respectively. The BIA was COP20 billion for the second, and for the third year the PrEP program would save COP3.3 billion, COP-8.1 billion, respectively. PrEP strategy should focus on small fractions of the population at high risk, such as those addressed in our study. Our results suggest that PrEP program would avoid cases and save costs for the Colombian health system.ALVIS-ZAKZUK, NELSON J.-will be generated-orcid-0000-0001-9382-214X-600Tolosa Perez, NBuitrago, Giancarlo-will be generated-orcid-0000-0002-7466-8244-600Alvarez Moreno, CarlosCARRASQUILLA SOTOMAYOR, MARIA-will be generated-orcid-0000-0001-5802-1769-600De La Hoz, Fernando Pi
Direct medical costs related to COVID-19 in Colombia
Get PDFWe studied 113 patients hospitalized by COVID-19, 51.3% men. On average, the hospital length of stay for COVID-19 hospitalized patient was 7,3 (± 6,2) days with a median cost of 1,328 (IQR 2,098), while in men was 1.4 times greater. Being 60 years of age or older triggers hospitalization costs almost twice as high as those under this age (2,994), and when the cost is compared by type of hospitalization, this difference is more than three times (ICU: 4,118; general ward: $1,312).ALVIS ZAKZUK, NELSON RAFAEL-will be generated-orcid-0000-0001-9136-9775-600Florez Tanus, ADiaz Jimenez, Diana FChaparro Narvaez, Pablo EnriqueCastaneda Orjuela, Carlos AndresDe La Hoz, Fernando PioCastell C, DuenasAlvis Guzman,
Out-of-pocket health expenditures in Colombia: a systematic review
Get PDFObjectives
To review the evidence of out-of-pocket (OOPE) and catastrophic expenditures (CHE) in health in Colombia.
Methods
Systematic review of the literature (SLR). Searches were performed in PubMed, Scopus, Scielo and Google Scholar. We used the MESH terms: out-of-pocket, catastrophic health expenditure, health and Colombia. We included cost description or cost analysis studies. Cost-effectiveness analysis of health technologies and qualitative studies were excluded. Data about period of analysis, type of study, costing perspective, OOPE, and CHE were extracted. Studies were classified as macroeconomic, microeconomic, and diseases analysis. All costs were indexed to 2018 and reported in Colombian pesos (COP).Alvis Zakzuk, N. JCastillo Rodriguez, LDiaz Jimenez, DCastaneda Orjuela, COchoa, MCubillos, M.
Theoretical study and analysis of o-nitrophenol adsorption using layered double hydroxides containing ca-al, ni-al and zn-al
Get PDFA theoretical assessment of the o-nitrophenol adsorption on layered double hydroxides containing different metallic species (Ca-Al, Ni-Al and Zn-Al) was performed. Experimental o-nitrophenol adsorption isotherms obtained at different adsorption temperatures with these layered double hydroxides were analyzed using a statistical physics monolayer model. Model calculations showed that the o-nitrophenol aggregation could occur with a high degree. It was estimated that the o-nitrophenol adsorption implied a non-flat orientation on all adsorbent surfaces and this process was multi-molecular. It was also demonstrated that there was no significant difference on the o-nitrophenol adsorption capacities of tested adsorbents, which varied from 77 to 135, 95 to 122 and 74 and 130 mg/g for Ca-Al, Ni-Al and Zn-Al layered double hydroxides, respectively. This finding suggested that the incorporation of Ca-Al, Ni-Al and Zn-Al in the layered double hydroxide structure played a similar role to adsorb o-nitrophenol molecules from aqueous solution. Calculated adsorption energies and thermodynamic functions confirmed an exothermic adsorption with the presence of physical-based interaction forces. This paper highlights the importance of reliable theoretical calculations based on statistical physics theory to contribute in the understanding of the adsorption mechanisms of a relevant water pollutant using layered double hydroxides as promising adsorbents for industrial applications.lotfi, sellaoui-will be generated-orcid-0000-0002-3124-4273-600Yazidi, AmiraAli, Jawad-will be generated-orcid-0000-0002-6015-0663-600Dotto, Guilherme Luiz-will be generated-orcid-0000-0002-4413-8138-600Bonilla-Petriciolet, Adrian-will be generated-orcid-0000-0002-0197-3539-600Silva O., Luis F.Badawi, Michael-will be generated-orcid-0000-0002-3504-4180-600Chen, Zhuq
Statistical modeling of compressive strength of hybrid fiber-reinforced concrete—HFRC
No full textThe incorporation of reinforcements is a necessity to compensate for the deficiency that concrete presents with its fragile behavior and low deformation capacity. One of the solutions to improve tensile performance is the addition of fiber in random distributions throughout the volume. However, this strategy can compromise the compressive strength of concrete; consequently, the purpose of this study was to analyze the compressive strength of conventional concrete with hybrid fiber reinforcement. A behavioral equation of compressive strength as a function of the hybridization of three types of fibers (steel, polypropylene, and carbon) was determined. This equation accounted for the proportions, as well as the binary and tertiary combinations, of fibers. Results showed that the effective participation of metallic fibers and their combination with synthetic fibers contributed positively to the performance of fiber-reinforced concrete. The gain in axial compression strength reached values in the range of 10% to 19% depending on the content of total fibers and their combination, without problems in the production process
DOE-ANOVA to optimize hydrokinetic turbines for low velocity conditions
No full textThe need of reducing the dependence of fossil fuels and CO2 emissions have motivated the diversification of energy matrix. Among the Renewables, the hydropower shows better characteristics compared to solar, wind, biomass and geothermal, because its low CO2 emissions, higher density and others technical factors. Within the Hydropower, the Hydrokinetic turbines (HT) are considered as a promising technology because can provide electricity during low flow velocity conditions (< 2 m/s) and is able to operate in shallow waters < 8 m and in secluded areas without access to the energy network. In this sense, the present study incentivizes the research in Hydropower and proposes and new application of DOE-ANOVA combined with Computational Fluid Dynamics (CFD) modelling for the HT design and optimization. Accordingly, this work evaluated the performance of a HT with 1.9 m of rotor diameter operating in a water flow of 1.5 m/s through a 23 factorial design with 9 modelling cases (MC). The results showed that the increment of outlet diameters increased the downstream velocity and the hydrodynamic pressure over the HT, and the reduction of the blade tip edge distance generated an increment of the response of the HT hydraulic and mechanical properties
Creation scenarios: graphic communication in virtual teaching and learning processes
No full textIntroducción: En la actualidad, son innegables los cambios ocasionados por las Tecnologías de la Información y la Comunicación-TIC en ámbitos como la educación y la comunicación, por tal razón, es necesario la observación de dichos impactos para reconocer otras formas de enseñar y aprender y posibilitar escenarios de formación acordes a una sociedad en constante transformación. Objetivo: Analizar la incidencia de la comunicación gráfica en los procesos de enseñanza-aprendizaje soportados en las TIC, a partir de la teoría seleccionada y las experiencias de docentes y estudiantes del programa Ude@ Educación Virtual de la Universidad de Antioquia en Medellín (Antioquia, Colombia). Metodología: Incluye una revisión bibliográfica, para conformar un estado del arte, y un trabajo de campo. Como parte de la sistematización se comparan las experiencias de los actores con la información obtenida en un cuestionario. Resultados y discusión: Evidencian la relación entre comunicación y TIC, desde la integración de recursos audiovisuales para mejorar prácticas pedagógicas en el contexto de los procesos de enseñanza. En cuanto a las experiencias, se encontró que para el docente la comunicación gráfica potencia la mediación didactica y para los estudiantes, la relación entre TIC y comunicación gráfica facilita la comprensión e incrementa el grado de conocimiento del objeto. Conclusiones: La tecnología y su relación con lo gráfico es un soporte que posibilita otras interacciones y enriquece los procesos de enseñanza y aprendizaje, tanto para el docente como para el estudiante.Introduction: Currently, the changes caused by Information and Communication Technologies-ICT in areas such as education and communication are undeniable, for this reason, it is necessary to observe these impacts to recognize other ways of teaching and learn and enable training scenarios in accordance with a society in constant transformation. Objective: To analyze the incidence of graphic communication in the teaching-learning processes supported by ICT, based on the selected theory and the experiences of teachers and students of the Ude@ Virtual Education program of the University of Antioquia in Medellín (Antioquia, Colombia). Methodology: Includes a bibliographic review, to form a state of the art, and field work. As part of the systematization, the experiences of the actors are compared with the information obtained in a questionnaire. Results and discussion: They show the relationship between communication and ICT, from the integration of audiovisual resources to improve pedagogical practices in the context of teaching processes. Regarding the experiences, it was found that for the teacher, graphic communication enhances didactic mediation and for students, the relationship between ICT and graphic communication facilitates understanding and increases the degree of knowledge of the object. Conclusions: technology and its relationship with graphics is a support that enables other interactions and enriches the teaching and learning processes, both for the teacher and for the student
Legalization of criminally obtained property committed by organized criminal groups: European and Ukrainian standards
No full textEl fenómeno del blanqueo de capitales como consecuencia de la actuación de grupos criminales constituye un factor negativo que retrasa el desarrollo global de la comunidad internacional. La necesidad de este estudio se debe al aumento de la escala de tales actos delictivos que afectan negativamente al desarrollo de la nación, y amenazan directamente a la seguridad del Estado de Derecho, lo que evidencia falta de base regulativa para combatir este flagelo. Por lo tanto, como propósito del estudio se definió el concepto y alcance del lavado de activos por parte de grupos de crimen organizado, así como el estudio de las medidas y políticas para combatir este fenómeno en lo que respecta a las relaciones europea y ucraniana. Se utilizaron métodos en el estudio, en particular: dialéctico, histórico-legal y el formal-lógico. Se utilizó también el método comparativo, que ayudó a caracterizar las especificidades del derecho penal frente a la protección de las relaciones públicas derivadas del lavado de dinero en Ucrania, los países de Europa Occidental y los Estados Unidos. Los autores concluyen que la política pública de Ucrania contra los delitos cometidos por grupos de crimen organizados se caracteriza por la obsolescencia del marco normativo y jurídico; por tanto, las lagunas en la organización de la lucha contra ese tipo de delitos, la reducción de las unidades especiales de la policía y el insuficiente nivel de cooperación de los órganos estatales constituyen las razones principales del aumento que presenta el blanqueo de capitales. El material empírico original recopilado permitirá a los teóricos de este campo continuar sus investigaciones y contrarrestar eficazmente este fenómeno negativo.The phenomenon of money laundering as a result of the actions of criminal groups is a negative factor in the global development of the international community. The need for this study is due to the increase in the scale of such criminal acts that negatively affect the development of the state, threatening the rule of law and security of the state in general and society in particular; lack of legislative and practical basis for combating this phenomenon. Therefore, the purpose of the study is to define the concept and the essence of money laundering by organized criminal groups and elaborate scientifically sound measures to combat this phenomenon in terms of European and Ukrainian dimensions. Several methods were used in the study, in particular: dialectical, system-structural, historical-legal and formal-logical. Leading research method was comparative method, which helped to characterize the specifics of criminal law protection of public relations arising from money laundering in Ukraine, Western European countries, and the United States. The authors determine the national policy of Ukraine against crimes committed by organized groups is characterized by the obsolescence of the regulatory and legal framework, gaps in the organization of combating such types of crimes, reduction of special units in the police, and insufficient level of cooperation of state bodies. The collected original empirical material will allow theorists in this field to continue their research and effectively counteract this negative phenomenon