Colombian consensus recommendations for diagnosis, management and treatment of the infection by SARS-COV-2/ COVID-19 in health care facilities - Recommendations from expert´s group based and informed on evidence

La Asociación Colombiana de Infectología (ACIN) y el Instituto de Evaluación de Nuevas Tecnologías de la Salud (IETS) conformó un grupo de trabajo para desarrollar recomendaciones informadas y basadas en evidencia, por consenso de expertos para la atención, diagnóstico y manejo de casos de Covid 19. Estas guías son dirigidas al personal de salud y buscar dar recomendaciones en los ámbitos de la atención en salud de los casos de Covid-19, en el contexto nacional de Colombia

Effective thermal properties of a magnetite-polyester composite conformed in the presence of a constant magnetic field

In this study, we report the thermophysical properties (at room temperature) and the morphology of a composite with a polyester resin matrix and magnetite filler powders (Fe3O4), conformed in three configurations: randomly dispersed particles, particles oriented parallel to a constant 300 mT magnetic field, and particles oriented perpendicular to a constant 300 mT magnetic field. Samples were formed by hand lay-up with weight percentages of 10, 20 and 30%, where the highest concentration corresponds to the resin. The thermophysical properties were determined using the KD2 Pro® system, which uses the physical principle of linear transient heat flow, for which the dual sensor SH-1 was used. The morphology and microanalysis were studied using a scanning electron microscope (SEM, FEI Quanta 650 FEG). It was observed from the morphology that the magnetite particles are oriented in the direction of the magnetic field lines during the process of resin curing. It was also perceived that the values of the thermophysical properties found experimentally are within the limits (upper and lower) of Hashin and Shtrikman and that those values increase when the magnetite concentration increases in the sample. No significant difference was observed in the thermal properties because of the magnetic field applied

Aplicación de FeO, ZnO y CuO como pigmentos en compuestos cerámicos

Entre los problemas más relevantes de la industria alfarera de Boyacá, Colombia, se encuentra la ausencia de una gama de tonalidades uniformes de sus productos finales. El color, por tratarse de una propiedad física fácilmente observable, se convierte en un criterio distintivo para clientes potenciales que buscan un producto diferenciador y a la vanguardia dentro de un medio en constante cambio. Por tal razón, el presente trabajo propuso un compuesto cerámico elaborado a partir de arcillas montmorillonitas y óxidos metálicos tales como FeO, CuO y ZnO. Las arcillas se caracterizaron por Fluorescencia de Rayos X (FRX) y de acuerdo a la composición química de cada arcilla, se determinaron las concentraciones de los óxidos metálicos como agentes colorantes, los cuales variaron de 1 a 8 % (en peso). Los prototipos cerámicos se conformaron por el método de prensado uniaxial a una presión de compactación constante de 15 MPa, posteriormente se sinterizaron a 950 °C durante 2 h. Mediante histogramas RGB se realizaron los análisis de color de los especímenes, los resultados mostraron cambios significativos en la pigmentación del compuesto cerámico reportando tono rojo, café y blanco. Lo anterior, hace viable la utilización de estos óxidos como pigmentos termoestables en la elaboración de productos cerámicos tales como: tejas, tabletas y baldosas, entre otros diseños cerámicos que hoy en día solo se pueden encontrar en tiendas de cerámica avanzada.Among the most relevant problems of the pottery industry in Boyacá, Colombia, is the absence of a range of uniform shades in their final products. The color, being an easily observable physical property, becomes a distinctive criterion for potential customers seeking a differentiating and cutting-edge product within a constantly changing environment. For that reason, the present work proposed a ceramic compound elaborated from montmorillonite clays and metal oxides such as FeO, CuO and ZnO. The clays were characterized by X-Ray Fluorescence (XRF) and according to the chemical composition of each clay, the concentrations of metal oxides were determined as coloring agents, which varied from 1 to 8 % (by weight). The ceramic prototypes were shaped by uniaxial pressing method at a constant compaction pressure of 15 MPa, and then sintered at 950 °C for 2 h. RGB histograms were used to analyze the color of the specimens, the results showed significant changes in the pigmentation of the ceramic compound reporting red, brown and white tone. This makes viable the use of these oxides as thermosetting pigments in the production of ceramic products such as roof tiles, tablets and tiles among other ceramic designs, which today can only be found in advanced ceramic shops

Microstructural Characterization and Corrosion Behavior of Similar and Dissimilar Welded Advanced High-Strength Steels (AHSS) by Rotary Friction Welding

Advanced high-strength steels (AHSSs) are designed for meeting strict requirements, especially in the automotive industry, as a means to directly influence the reduction in the carbon footprint. As rotary friction welding (RFW) has many important advantages over other welding technologies, it plays an important role in the automotive sector. On the above basis, in this work, combinations of the first (complex phase (CP)), second (TWIP (TW)), and third (quenched and partitioned (Q&P)) generations of similar and dissimilar high-alloyed advanced steels have been joined by the RFW process. Having a specific microstructure, rods of CP/CP, Q&P/Q&P, CP/TW, and Q&P/TW steels were welded by employing a homemade adaptation machine under fixed parameters. Microstructural characterization has allowed us to corroborate the metallic bonding of all the tested advanced steels and to identify the different zones formed after welding. Results indicate that the welding zone widens in the center of the workpiece, and under the current friction action, the intermixing region shows the redistribution of solute elements, mostly in the dissimilarly welded steels. Furthermore, because of their complex chemistry and the different mechanical properties of the used steels, dissimilarly welded steels present the most noticeable differences in hardness. The TWIP steel has the lower hardness values, whilst the CP and Q&P steels have the higher ones. As a direct effect of the viscoplastic behavior of the steels established by the thermomechanical processing, interlayers and oxidation products were identified, as well as some typical RFW defects. The electrochemical response of the welded steels has shown that the compositional and microstructural condition mostly affect the corrosion trend. This means that the dissimilarly welded steels are more susceptible to corrosion, especially at the TWIP–steel interface, which is attributed to the energy that is stored in the distorted microstructure of each steel plate as a consequence of the thermomechanical processing during RFW

Design and characterization of a magneto-dielectric composite in high frequency with aligned magnetite powders

A magneto-dielectric material composed of a polyester resin-based microstrip (P115A), copper sheets and magnetite powders was designed in concentrations of 10, 20 and 30% Wt and with filters of 200, 325 and 500. The particles were aligned vertically and horizontally during the curing process using 300 mT magnetic fields. From a complete factorial design of 33, 27 microstrip-type circuits of 4 mm width, 70 mm length and 0.93 mm thickness were manufactured, characterized by scanning electron microscopy and vector network analysis. The cross-matrix analysis determined an optimal circuit response from the magneto-dielectric material with a concentration of 20% magnetite and an average particle size of 21.48 μm in horizontal alignment to the applied magnetic field and to the transmission line, obtaining a relative dielectric constant of Er 3.88 with a low dielectric loss of 0.054, within an operating range of 150 KHz to 4 GHz

Shape memory behavior of Ni-Fe-Ga and Ni-Mn-Sn ribbons

"Magnetic Shape Memory Alloys exhibit multifunctional properties due the martensitic transformation (MT) and accompanying changes in the magnetic subsystem. In this work, melt spun ribbons of nominal composition Ni55Fe16Ga29 (R1) and Ni50Mn40Sn10 (R2) have been produced and characterized by the calorimetric, thermomechanical, mechanical, microscopic and X-ray measurements. The effect of short annealing on MT and thermo-mechanical properties is rather modest and in the case of R2 enhances its brittleness. R1 and R2 as-spun ribbons show MT at TM ~ 340 K and ~ 420 K, respectively. The strain-stress curves for Ni-Fe-Ga in austenitic phase indicate good visco-elastic properties, although the superelastic effect was not well pronounced. Ni-Fe-Ga as-cast and annealed samples, as well as the as-cast Ni-Mn-Sn ribbons, present a shape memory effect with an anomalous contraction and elongation at low external stresses in the course of the forward and reverse MT, consequence of the compressive internal stresses.