Examinando por Materia "Chromium"
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Ítem Electronic and Topological Analysis for New Phases of Chromium Nitride(WILEY-V C H VERLAG GMBH, 2018-01-01) Marin-Suarez, Marco; Alzate-Vargas, Leidy L.; David, Jorge; Arroyave-Franco, Mauricio; Velez, Mario E.; Universidad EAFIT. Departamento de Ciencias Básicas; Electromagnetismo Aplicado (Gema)Chromium nitride (CrN) in its NaCl-type phase has been widely studied through density functional theory (DFT) in order to analyze its electronic properties. By the means of DFT with the Becke's three parameter Lee-Yang-Parr (B3LYP) hybrid functional, the same stoichiometry is studied in two unreported hypothetical phases in addition to the nonsynthesized and previously reported zinc-blende-type phase. The cohesive energy of every structure is calculated, and the analysis of this quantity indicated that all crystals are stable and that there is an unreported phase more stable than the synthesized one. The calculated electronic dispersion relation and density of electronic states allowed for the determination that these three phases have a conducting behavior. The symmetry of some bands is determined as a result of the crystal field splitting for chromium d states. The topology of the electron density was studied in order to determine its properties at bond critical points (BCPs). The form of the Laplacian of the density and its gradient trajectories allowed to locate ring critical points in these structures. From these calculations, it is concluded that all three phases are ionic crystals. The synthesized NaCl-type phase is studied in order to compare and confirm the results. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimÍtem Pollutant Remotion and Growth of Scenedesmus sp. on Wastewater from Tannery. A Comparison Between Free and Immobilized Cells(Universidad EAFIT, 2018-11-23) Rosales, A G; Rodríguez, C D; Ballen Segura, M; Universidad Sergio ArboledaÍtem The removal of the trivalent chromium from the leather tannery wastewater: the optimisation of the electro-coagulation process parameters.(IWA PUBLISHING, 2011-02-01) GilPavas, E.; Dobrosz-Gomez, I.; Gomez-Garcia, M. A.; GilPavas, E.; Dobrosz-Gomez, I.; Gomez-Garcia, M. A.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Procesos Ambientales (GIPAB)The capacity of the electro-coagulation (EC) process for the treatment of the wastewater containing Cr3+, resulting from a leather tannery industry placed in Medellin (Colombia), was evaluated. In order to assess the effect of some parameters, such as: the electrode type (Al and/or Fe), the distance between electrodes, the current density, the stirring velocity, and the initial Cr3+ concentration on its efficiency of removal (%RCr+3), a multifactorial experimental design was used. The %RCr3+ was defined as the response variable for the statistical analysis. In order to optimise the operational values for the chosen parameters, the response surface method (RSM) was applied. Additionally, the Biological Oxygen Demand (BOD5), the Chemical Oxygen Demand (COD), and the Total Organic Carbon (TOC) were monitored during the EC process. The electrodes made of aluminium appeared to be the most effective in the chromium removal from the wastewater under study. At pH equal to 4.52 and at 28 degrees C, the optimal conditions of Cr3+ removal using the EC process were found, as follows: the initial Cr3+ concentration=3,596 mg/L, the electrode gap=0.5 cm, the stirring velocity=382.3 rpm, and the current density=57.87 mA/cm2. At those conditions, it was possible to reach 99.76% of Cr3+ removal, and 64% and 61% of mineralisation (TOC) and COD removal, respectively. A kinetic analysis was performed in order to verify the response capacity of the EC process at optimised parameter values.Ítem Stratifying the potential local transmission of Zika in municipalities of Antioquia, Colombia(Blackwell Publishing Ltd, 2017-10-01) Ospina J.; Hincapie-Palacio D.; Ochoa J.; Molina A.; Rúa G.; Pájaro D.; Arrubla M.; Almanza R.; Paredes M.; Mubayi A.; Ospina J.; Hincapie-Palacio D.; Ochoa J.; Molina A.; Rúa G.; Pájaro D.; Arrubla M.; Almanza R.; Paredes M.; Mubayi A.; Universidad EAFIT. Departamento de Ciencias; Lógica y ComputaciónOBJECTIVE To stratify and understand the potential transmission processes of Zika virus in Colombia, in order to effectively address the efforts on surveillance and disease control. METHODS We compare R-0 of Zika for municipalities based on data from the regional surveillance system of Antioquia, Colombia. The basic reproduction number (R-0) and its 95% confidence intervals were estimated from an SIR model with implicit vector dynamics, in terms of recovered individuals in each time unit, using an approximate solution. These parameters were estimated fitting the solution of the model to the daily cumulative frequency of each Zika case according to symptoms onset date relative to the index case reported to the local surveillance system. RESULTS R-0 was estimated for 20 municipalities with a median of 30 000 inhabitants, all located less than 2200 m above sea level. The reported cases ranged from 17 to 347 between these municipalities within 4 months (January to April of 2016). The results suggest that 15 municipalities had a high transmission potential (R-0 > 1), whereas in five municipality transmissions were potentially not sustaining (R-0 < 1), although the upper bound of the confidence interval of the R-0 for 3 of these 5 was greater than one, indicating the possibility of an outbreak later on. CONCLUSION The study identified high-risk municipalities (R-0 > 1) and provide a technique to optimise surveillance and control of Zika. Health authorities should promote the collection, analysis, modelling and sharing of anonymous data onto individual cases to estimate R-0.