864 resultados para eletrodos modificados


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Los Factores de Riesgo Cardiovascular son aquellos que aumentan las probabilidades de sufrir un evento cardiovascular a largo plazo, los cuales pueden ser modificados o eliminados cambiando el estilo de vida. El objetivo de la investigación fue identificar factores de riesgo cardiovascular en personas mayores de 45 años de edad que consultan en la Unidad Comunitaria de Salud Familiar El Divisadero, Departamento de Morazán. La Metodología fue de tipo prospectivo, transversal, descriptivo, de campo y de laboratorio. La población estaba constituida por 85 personas que consultaron en el período de ejecución y que cumplieron con los criterios de inclusión a quienes se les realizaron las siguientes pruebas de laboratorio: Glucosa, Colesterol total, Triglicéridos, Colesterol HDL, Colesterol LDL y se les aplicó una cédula de entrevista que permitió recolectar información importante sobre los factores de riesgo cardiovascular, la cual constaba de 8 preguntas. Se utilizó la escala de Framingham para calcular riesgo cardiovascular y la categoría en que se presentó. Los Resultados obtenidos en las pruebas de laboratorio las más alteradas para toda la población fueron Colesterol HDL bajo con un 58.8% y Triglicéridos con un 29.4% y otros factores de riesgo predisponentes fueron Sobrepeso y obesidad con un 72.9%, Presión arterial alta con 43.5% y Tabaquismo con 23.5%. Conclusión: El 56.5% del total de la población presentó 3 o más factores de riesgo, para el sexo masculino un 19.2% presentó riesgo alto en personas mayores de 66 años, un 15.4% riesgo moderado en la edad de 45- 55 y 56- 66 años respectivamente, en cuanto al sexo femenino el 18.6% presentó riesgo moderado en la edad de 45- 55 años y el 16.9% en mayores de 66 años respectivamente.

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The direct use of natural gas makes the Solid Oxide Fuel Cell (SOFC) potentially more competitive with the current energy conversions technologies. The Intermediate Temperature SOFC (IT-SOFC) offer several advantages over the High Temperature SOFC (HT-SOFC), which includes better thermal compatibility among components, fast start with lower energy consumption, manufacture and operation cost reduction. The CeO2 based materials are alternatives to the Yttria Stabilized Zirconia (YSZ) to application in SOFC, as they have higher ionic conductivity and less ohmic losses comparing to YSZ, and they can operate at lower temperatures (500-800°C). Ceria has been doped with a variety of cations, although, the Gd3+ has the ionic radius closest to the ideal one to form solid solution. These electrolytes based in ceria require special electrodes with a higher performance and chemical and termomechanical compatibility. In this work compounds of gadolinia-doped ceria, Ce1-xGdxO2-δ (x = 0,1; 0,2 and 0,3), used as electrolytes, were synthesized by polymeric precursors method, Pechini, as well as the composite material NiO - Ce0,9Gd0,1O1,95, used as anode, also attained by oxide mixture method, mixturing the powders of the both phases calcinated already. The materials were characterized by X ray diffraction, dilatometry and scanning electronic microscopy. The refinement of the diffraction data indicated that all the Ce1-xGdxO2-δ powders were crystallized in a unique cubic phase with fluorite structure, and the composite synthesized by Pechini method produced smaller crystallite size in comparison with the same material attained by oxide mixture method. All the produced powders had nanometric characteristics. The composite produced by Pechini method has microstructural characteristics that can increase the triple phase boundaries (TPB) in the anode, improving the cell efficiency, as well as reducing the mass transport mechanism effect that provokes anode degradation

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Nickel-based catalysts supported on alumina have been widely used in various reactions to obtain synthesis gas or hydrogen. Usually, higher conversion levels are obtained by these catalysts, however, the deactivation by coke formation and sintering of metal particles are still problems to be solved. Several approaches have been employed in order to minimize these problems, among which stands out in recent years the use of additives such as oxides of alkali metals and rare earths. Similarly, the use of methodologies for the synthesis faster, easier, applicable on an industrial scale and to allow control of the microstructural characteristics of these catalysts, can together provide the solution to this problem. In this work, oxides with spinel type structure AB2O4, where A represents divalent cation and B represents trivalent cations are an important class of ceramic materials investigated worldwide in different fields of applications. The nickel cobaltite (NiCo2O4) was oxides of spinel type which has attracted considerable interest due to its applicability in several areas, such as chemical sensors, flat panel displays, optical limiters, electrode materials, pigments, electrocatalysis, electronic ceramics, among others. The catalyst precursor NiCo2O4 was prepared by a new chemical synthesis route using gelatine as directing agent. The polymer resin obtained was calcined at 350°C. The samples were calcined at different temperatures (550, 750 and 950°C) and characterized by X ray diffraction, measurements of specific surface area, temperature programmed reduction and scanning electron microscopy. The materials heat treated at 550 and 750°C were tested in the partial oxidation of methane. The set of techniques revealed, for solid preparations, the presence of the phase of spinel-type structure with the NiCo2O4 NixCo1-xO solid solution. This solid solution was identified by Rietveld refinement at all temperatures of heat treatment. The catalyst precursors calcined at 550 and 750°C showed conversion levels around 25 and 75%, respectively. The reason H2/CO was around 2 to the precursor treated at 750°C, proposed reason for the reaction of partial oxidation of methane, one can conclude that this material can be shown to produce synthesis gas suitable for use in the synthesis Fischer-Tropsch process

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El carcinoma escamocelular (CEC) representa la entidad patológica maligna de mayor prevalencia en la cavidad bucal. Aunque múltiples estudios respaldan que la aparición de esta enfermedad es de carácter idiopático, factores de riesgo como el alcohol y la exposición al tabaco son elementos directamente desencadenantes de la aparición de esta entidad oncológica, sin dejar a un lado la predisposición a padecer cáncer oral (CO) por parte de la codificación genética entre otros aspectos hereditarios. En la actualidad, se ha evidenciado que la infección por virus del papiloma humano (VPH) y las lesiones que lo relacionan, están profundamente asociados como etiología potencial del CO y suelen tener relación con hábitos sexuales modificados. La profundización de conceptos, efectos y medios de diagnóstico eficaces para establecer relaciones existentes del VPH con el CO, biología del virus y comportamiento cancerígeno, fueron los objetivos de la presente publicación así mismo determinar factores de riesgo predisponentes a la malignización de las lesiones propias del VPH, su incidencia y prevalencia en la comunidad. La identificación clínica oportuna de las lesiones originadas por el VPH, permiten establecer de manera certera el comportamiento, evolución de la lesión y a su vez determinar la presencia de actividad displásica y/o anaplásica propiamente dicha. Cabe resaltar la importancia del empleo de exámenes auxiliares a la clínica, como lo es la citología exfoliativa, la biopsia, los análisis moleculares y genéticos, para establecer mancomunadamente y de manera certera el comportamiento, evolución y pronóstico de una afección por VPH.

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In this work, was studied the formation of a composite of the refractory metal niobium with copper, through the process of high-energy milling and liquid phase sintering. The HEM can be used to synthesize composite powders with high homogeneity and fine size particle distribution. It may also produce the solid solubility in immiscible systems such as Nb-Cu, or extend the solubility of systems with limited solubility. Therefore, in the immiscible system Cu-Nb, the high-energy milling was successfully used to obtain the composite powder particles. Initially, the formation of composite particles during the HEM and the effect of preparation technique on the microstructure of the material was evaluated. Four loads of Nb and Cu powders containing 20%wt Cu were synthesized by MAE in a planetary type ball mill under different periods of grinding. The influence of grinding time on the metal particles is evaluated during the process by the withdrawal of samples at intermediate times of milling. After compaction under different forces, the samples were sintered in a vacuum furnace. The liquid phase sintering of these samples prepared by HEM produced a homogeneous and fine grained. The composite particles forming the sintered samples are the addition of a hard phase (Nb) with a high melting point, and a ductile phase (Cu) with low melting point and high thermal and electrical conductivities. Based on these properties, the Nb-Cu system is a potential material for many applications, such as electrical contacts, welding electrodes, coils for generating high magnetic fields, heat sinks and microwave absorbers, which are coupled to electronic devices. The characterization techniques used in this study, were laser granulometry, used to evaluate the homogeneity and particle size, and the X-ray diffraction, in the phase identification and to analyze the crystalline structure of the powders during milling. The morphology and dispersion of the phases in the composite powder particles, as well the microstructures of the sintered samples, were observed by scanning electron microscopy (SEM). Subsequently, the sintered samples are evaluated for density and densification. And finally, they were characterized by techniques of measuring the electrical conductivity and microhardness, whose properties are analyzed as a function of the parameters for obtaining the composite

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The partial fixed prosthodontics restoration is used to rehabilitate form and function of partial or total compromised teeth, having to remain permanently joined to remainder tooth. The most useful material on prosthodontics is the feldspar porcelain, commercialized as aluminosilicate powders. Dental porcelains are presented with limited mechanical properties to rehabilitate extensive spaces. The association with Ni-Cr metallic systems (metal-ceramic system) allows that the metallic substructure compensates the fragile porcelain nature, preserving the thermal insulation and aesthetics desirable, as well as reducing the possibility of cracking during matication efforts. Cohesive flaws by low mechanical strength connect the metallic substructure to the oral environment, characterized by a electrolytic solution (saliva), by aggressive temperature, pH cyclic changes and mechanical requests. This process results on ionic liberation that could promote allergic or inflammatory responses, and/or clinical degradation of ceramometal system. The aim of this study was to evaluate the presence of an intermediate titanium layer on the microscopic fracture behavior of porcelains on ceramometal systems. Plasma deposition of titanium films result in regular passivating oxide layers which act as barriers to protect the metallic substrate against the hazardous effects of corrosive saliva. Tribocorrosion tests were performed to simulate the oral environment and mechanical stress, making it possible the early detection of crack formation and growth on metal-ceramic systems, which estimate the adherence between the compounds of this system. Plain samples consisting of dental feldspar porcelain deposited either onto metallic substrates or titanium films were fired and characterized by scanning electron microscopy. The result showed that the titanium film improved the adherence of the system compared to conventional metal-ceramic interfaces, thus holding crack propagation

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Objetivo: Validar los criterios de CENTOR modificados (CENTOR-m) y los tests rápidos de detección del antígeno de Estreptococo del Grupo A (SGA) en la faringitis aguda. Diseño: Estudio de validación de pruebas diagnósticas. Emplazamiento y participantes: Ciento un pacientes elegibles, que consultaron al departamento de urgencias de un hospital de tercer nivel con cuadro clínico compatible con faringitis aguda. Mediciones Principales: Se obtuvieron muestras de hisopados faríngeos para la realización del test rápido antigénico para SGA (FAMR) y para cultivo, respectivamente. Se calculó en cada caso los criterios de CENTOR-m. Resultados: La edad media de los pacientes incluidos en el estudio fue de 22,6 años (DE:13,8). El 48,5 % eran varones. El SGA fue el patógeno aislado en el 20,79 % de los casos. El CENTOR-m presentó una sensibilidad del 83,3 % (50,9 %-97,1 %), especificidad del 45,5 % (30,7 %-61,0 %) valor predictivo positivo (VPP) del 29,4 % (15,7 %-47,7 %) y valor predictivo negativo (VPN) del 90,9 % (69,4 %-98,4 %). El FAMR presento una sensibilidad del 81,5 % (61,3 %-93,0 %) especificidad del 98,6 % (91,4 %-99,9 %), VPP del 95,7 % (76,0 %-99,8 %) y VPN del 93,3 % (84,5 %-97,5 %). El 49,5 % de los pacientes recibieron antibióticos basándose en el juicio médico, lo que resultó en una proporción de sobreindicación de antimicrobianos del 62 %. Conclusiones: Los criterios de CENTOR-m demostraron adecuado valor pronóstico negativo y el FAMR buena sensibilidad, especificidad y valor pronóstico positivo para faringitis por SGA. La utilización de ambos métodos en la atención urgente podría optimizar el manejo de la patología y la adecuación antibiótica.

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Introducción: las enfermedades crónicas no transmisibles, fundamentalmente la enfermedad cardiovascular, la diabetes, el cáncer y las enfermedades respiratorias, son la primera causa de muerte en los países desarrollados y el Uruguay no escapa a esta realidad. El 30% de esas muertes se produce antes de los 60 años. Las discapacidades generadas por estas enfermedades tienen un alto impacto social y también económico. Los principales factores de riesgo conductuales para el desarrollo de estas enfermedades se relacionan con los estilos de vida: alimentación inadecuada, sedentarismo y consumo de alcohol y tabaco. Estas conductas llevan a desarrollar factores de riesgo metabólicos: obesidad, dislipemias, hipertensión arterial y prediabetes. Estos factores de riesgo pueden ser modificados, pudiéndose así prevenir las propias enfermedades no transmisibles. El lugar de trabajo está reconocido mundialmente como un marco adecuado para la promoción de salud. Objetivo: conocer la prevalencia de factores de riesgo conductuales y metabólicos en funcionarios de una institución bancaria estatal del Uruguay. Metodología: estudio descriptivo, de corte transversal, sobre una muestra probabilística de los funcionarios de una institución bancaria. Se aplicó cuestionario y se realizó antropometría. Para estudiar la asociación de los factores de riesgo se usaron tablas de contingencia y modelos de regresión logística. Resultados: se encuestaron 136 funcionarios. La distribución por sexo fue pareja, la edad promedio fue de 48 años. El 16% refirió fumar actualmente; 58% beber alcohol en forma semanal; 85% consumir fruta y verdura por debajo de las recomendaciones, y 46% no realizar actividad física. El 63% presentó sobrepeso u obesidad; 30% declaró ser hipertenso; 33% tener una dislipemia, y 12% presentar prediabetes. La obesidad abdominal se asoció con mayor riesgo de desarrollar hipertensión arterial y prediabetes. El tabaquismo y la inactividad física son menos frecuentes en esta población que en poblaciones similares en otros países de la región, sin embargo los factores de riesgo metabólicos tienen casi la misma prevalencia. Conclusiones: si bien no se trata de una población representativa del país, se hizo una comparación con la situación nacional y en relación con la población adulta uruguaya se encontró una mayor prevalencia de obesidad, hipertensión arterial, hipercolesterolemia, prediabetes, sedentarismo, consumo inadecuado de frutas y verduras y consumo de alcohol en forma semanal. A su vez, esta población presentó una prevalencia menor de tabaquismo, sobreagregado de sodio, consumo de alimentos que son una fuente de grasas trans e ingesta de bebidas azucaradas. Estos resultados representan un aporte para futuras intervenciones.

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Biodiesel is a fuel obtained from vegetable oils, such as soy, castorbean, among others. The monoester of fatty acid of these oils have chains with mono, di and tri double connections. The presence of these insaturations are susceptible to oxidization. Antioxidants are substances able to prevent oxidization from oils, fats, fat foods, as well as esters of Alquila( biodiesel). The objective of this work is to summarize a new antioxidant from the Cashew Nut Shell Liquid (CNSL) using the electrolysis technique. A current of 2 amperes was used in a single cell of only one group and two eletrodos of stainless steel 304 in a solution of methanol, together with the eletrolits: acetic acid, sodium chloride and sodium hydroxide, for two hours of agitation. The electrolysis products are characterized by the techniques of cromatography in a thin layer, spectroscopy of infrared and gravimetric analysis. The material was submitted to tests of oxidative stability made by the techniques of spectropy of impendancy and Rancimat (EN 14112). The analyses of characterization suggest that the polimerization of the electrolytic material ocurred. The application results of these materials as antioxidants of soy biodiesel showed that the order of the oxidative stability was obtained by both techniques used

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Esta publicação tem a finalidade de esclarecer dúvidas que porventura ainda persistam quanto a aplicabilidade de plantas transgêncas para o beneficio da qualidade alimentar e nutricional. Traz em seu bojo, a converg~encia entre biodiversidade, biotecnologia e fundamentos técnico-científicos para a geração de organismos geneticamente modificados (OGMs).

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Propósito y Método del Estudio: El semiconductor más utilizado para su uso en fotocatálisis es el TiO2 debido a sus características como bajo costo, inocuidad y eficiencia fotocatalítica; alguno de los inconvenientes del uso de este material es su capacidad de activarse con radiación UV. En el presente trabajo se modificó al catalizador TiO2 con N a través del método de síntesis coloidal con el propósito de hacerlo fotoactivo bajo radiación visible; se sintetizaron catalizadores modificados a diferentes cantidades teóricas de nitrógeno, los cuales se caracterizaron morfológica y estructuralmente; posteriormente se evaluó la actividad fotocatalítica, bajo radiación visible con una solución de Bisfenol A realizando el seguimiento de la degradación fotocatalítica mediante espectroscopia UV-Vis y cromatografía de líquidos de alta resolución acoplado a espectrometría de masas (HPLC-MS). Contribuciones y Conclusiones: los resultados confirmaron que la incorporación de Nitrógeno al TiO2 provoca cambios en la cristalinidad, morfología y área superficial, así como en su actividad con radiación visible. La evolución fotocatalitica demostró que el catalizador modificado con 5% fue el que presento mayor eficiencia en la degradación de Bisfenol A.

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Fuel cells are electrochemical devices that convert chemical energy in electrical energy by a reaction directly. The solid oxide fuel cell (SOFC) works in temperature between 900ºC up to 1000ºC, Nowadays the most material for ceramic electrolytes is yttria stabilized zirconium. However, the high operation temperature can produce problems as instability and incompatibility of materials, thermal degradation and high cost of the surround materials. These problems can be reduced with the development of intermediate temperature solid oxide fuel cell (IT-SOFC) that works at temperature range of 600ºC to 800ºC. Ceria doped gadolinium is one of the most promising materials for electrolytes IT-SOFC due high ionic conductivity and good compatibility with electrodes. The inhibition of grain growth has been investigated during the sintering to improve properties of electrolytes. Two-step sintering (TSS) is an interesting technical to inhibit this grain growth and consist at submit the sample at two stages of temperature. The first one stage aims to achieve the critical density in the initiating the sintering process, then the sample is submitted at the second stage where the temperature sufficient to continue the sintering without accelerate grain growth until to reach total densification. The goal of this work is to produce electrolytes of ceria doped gadolinium by two-step sintering. In this context were produced samples from micrometric and nanometric powders by two routes of two-step sintering. The samples were obtained with elevate relative density, higher than 90% using low energy that some works at the same area. The average grain size are at the range 0,37 μm up to 0,51 μm. The overall ionic conductivity is 1,8x10-2 S.cm and the activation energy is 0,76 eV. Results shown that is possible to obtain ceria-doped gadolinium samples by two-step sintering technique using modified routes with characteristics and properties necessary to apply as electrolytes of solid oxide fuel cell

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Concern with the environment has lead to an increase in the research for new adsorption techniques, low cost adsorvent materials and with high availability. Many works search the development of higher selectivity modified adsorvents. The Brazil has the second world reserve of oiled shale, because of it, the use of that reject is of great interest. This study has the goal of characterize and analyze the retorted shale, reject of the pirobetuminous shale pyrolysis, and the retorted shale modified through the humid impregnation method, wich the precursors were the metals nitrates ( Cobalt, Nickel and Copper), to the usage has adsorvent materials. The samples were characterized chemically, textually and structurally by the X ray fluorescence (XRF), BET, X ray diffraction (XRD) and scanning electronic microscopy (SEM) techniques. The impregnated samples showed a reduction in the superficial area and in the pore volume when compared with the retorted shale. Besides that, diffractions referred to the impregnated metals where observed in the XRD analysis, wich were the same metals detected in the XRF and SEM analysis. The materials showed homogeneity in it s composition. The results shows that the materials presents adequate adsorption characteristics

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Dissertação de Mestrado, Ciências Biomédicas, Departamento de Ciências Biomédicas e Medicina, Universidade do Algarve, 2016