Modeling and experimental analysis of CO2 methanation reaction using Ni/CeO2 monolithic catalyst.

In this study, the effect of the cell density of monolithic catalysts was investigated and further mathematically modeled on cordierite supports used in CO2 methanation. Commercial cordierite monoliths with 200, 400, and 500 cpsi cell densities were coated by immersion into an ethanolic suspension of Ni/CeO2 active phase. SEM-EDS analysis confirmed that, owing to the low porosity of cordierite (surface area < 1 m2 g-1), the Ni/CeO2 diffusion into the walls was limited, especially in the case of low and intermediate cell density monoliths; thus, active phase was predominantly loaded onto the channels' external surface. Nevertheless, despite the larger exposed surface area in the monolith with high cell density, which would allow for better distribution and accessibility of Ni/CeO2, its higher macro-pore volume resulted in some introduction of the active phase into the walls. As a result, the catalytic evaluation showed that it was more influenced by increments in volumetric flow rates. The low cell density monolith displayed diffusional control at flow rates below 500 mL min-1. In contrast, intermediate and high cell density monoliths presented this behavior up to 300 mL min-1. These findings suggest that the interaction reactants-catalyst is considerably more affected by a forced non-uniform flow when increasing the injection rate. This condition reduced the transport of reactants and products within the catalyst channels and, in turn, increased the minimum temperature required for the reaction. Moreover, a slight diminution of selectivity to CH4 was observed and ascribed to the possible formation of hot spots that activate the reverse water-gas shift reaction. Finally, a mathematical model based on fundamental momentum and mass transfer equations coupled with the kinetics of CO2 methanation was successfully derived and solved to analyze the fluid dynamics of the monolithic support. The results showed a radial profile with maximum fluid velocity located at the center of the channel. A reactive zone close to the inlet was obtained, and maximum methane production (4.5 mol m-3) throughout the monolith was attained at 350 °C. Then, linear streamlines of the chemical species were developed along the channel.

New trends in modelling of breakthrough curves to remove pollutants using adsorption on advanced monoliths geometries.

This work proposes a rigorous mathematical model capable of reproducing the adsorption process in dynamic regime on advanced monoliths geometries. For this, four bed geometries with axisymmetric distribution of channels and similar solid mass were proposed. In each geometry a different distribution of channels was suggested, maintaining constant the bed dimensions of 15 cm high and 5 cm radius. The mathematical modeling includes mass and momentum transfer phenomena, and it was solved with the COMSOL Multiphysics software using mass transfer parameters published in the literature. The overall performance of the column was evaluated in terms of breakthrough (CA/CA0 = 0.1) and saturation times (CA/CA0 = 0.9). The mass and velocity distributions obtained from the proposed model show good physical consistency with what is expected in real systems. In addition, the model proved to be easy to solve given the short convergence times required (2-4 h). Modifications were made to the bed geometry to achieve a better use of the adsorbent material which reached up to 80%. The proposed bed geometries allow obtaining different mixing distributions, in such a way that inside the bed a thinning of the boundary layer is caused, thus reducing diffusive effects at the adsorbent solid-fluid interface, given dissipation rates of about 323 × 10-11 m2/s3. The bed geometry composed of intersecting rings deployed the best performance in terms of usage of the material adsorbent, and acceptable hydrodynamical behavior inside the channels (maximum fluid velocity = 35.4 × 10-5 m/s and drop pressure = 0.19 Pa). Based on these results, it was found that it is possible to reduce diffusional effects and delimit the mass transfer zone inside the monoliths, thus increasing the efficiency of adsorbent fixed beds.

The spreading of Covid-19 in Mexico: A diffusional approach.

In this work, we analyze the spreading of Covid-19 in Mexico using the spatial SEIRD epidemiologic model. We use the information of the 32 regions (States) that conform the country, such as population density, verified infected cases, and deaths in each State. We extend the SEIRD compartmental epidemiologic with diffusion mechanisms in the exposed and susceptible populations. We use the Fickian law with the diffusion coefficient proportional to the population density to encompass the diffusion effects. The numerical results suggest that the epidemiologic model demands time-dependent parameters to incorporate non-monotonous behavior in the actual data in the global dynamic. The diffusional model proposed in this work has great potential in predicting the virus spreading on different scales, i.e., local, national, and between countries, since the complete reduction in people mobility is impossible.

Customizable Heterogeneous Catalysts: Nonchanneled Advanced Monolithic Supports Manufactured by 3D-Printing for Improved Active Phase Coating Performance.

Three-dimensional (3D)-printed catalysts are being increasingly studied; however, most of these studies focus on the obtention of catalytically active monoliths, and thus traditional channeled monolithic catalysts are usually obtained and tested, losing sight of the advantages that 3D-printing could entail. This work goes one step further, and an advanced monolith with specifically designed geometry has been obtained, taking advantage of the versatility provided by 3D-printing. As a proof of concept, nonchanneled advanced monolithic (NCM) support, composed of several transversal discs containing deposits for active phase deposition and slits through which the gas circulates, was obtained and tested in the CO-PrOx reaction. The results evidenced that the NCM support showed superior catalytic performance compared to conventional channeled monoliths (CMs). The region of temperature in which the active phase can work under chemical control, and thus in a more efficient way, is increased by 31% in NCM compared to the powdered or the CM sample. Turbulence occurs inside the fluid path through the NCM, which enhances the mass transfer of reagents and products toward and from the active sites to the fluid bulk favoring the chemical reaction rate. The nonchanneled monolith also improved heat dispersion by the tortuous paths, reducing the local temperature at the active site. Thus, the way in which reactants and products are transported inside the monoliths plays a crucial role, and this is affected by the inner geometry of the monoliths.

Gestión de los residuos sólidos en hospitales locales del norte del Valle del Cauca, Colombia / Solid wasted management in local hospitals of the north of Valle del Cauca, Colombia

Las instituciones de salud deben brindar las condiciones necesarias para que tanto de usuarios como empleados mantengan, mejoren o recuperen su estado de salud; el manejo inadecuado de los residuos sólidos hospitalarios (RSH) constituye uno de los factores que pueden limitar el logro de este propósito. Objetivo: estimar la cantidad y composición de los residuos hospitalarios en diez hospitales locales de carácter público, ubicados en igual número de municipios del norte del departamento del Valle del Cauca, Colombia. Metodología: se estimó la cantidad y composición de los RSH a través de dos jornadas de muestreo de 24 horas cada una. Resultados: las proporciones de residuos sólidos hospitalarios de tipo peligroso (RSHP) fueron mayores o iguales a 25% y superaron los valores medios reportados por entidades como la Organización Mundial de la Salud; los residuos biosanitarios fueron la categoría con mayor aporte a la fracción de RSHP. Discusión: los valores obtenidos al determinar los indicadores kg/paciente-día estuvieron en menor o igual rango que los reportados por distintas fuentes, se considera que por el tipo de servicio prestado en las instituciones estudiadas, es más representativo para estudios de RSH el indicador kg/paciente-día.

Health-care institutions must offer adequate conditions for both employers and users in order to maintain, improve or recover their health status; inadequate health-care solid waste (HSW) management is an obstacle to achieve this global. Objective: to estimate the quantity and composition of HSW in the health-care public institutions located in ten municipalities in northern Valle del Cauca region (Colombia). Methodology: quantity and composition of HSW was estimated through two 24 hours sampling rounds. Results: the proportion of hazardous health-care solid wasted (HHSW) was usually equal to or higher than 25% and it also surpassed the mean average values reported by organization like World Health Organization, bio-sanitary waste was the category with major proportion in the HHSW fraction. Discussion: the values obtained in order to determine indicators as kg/patient-day were in a lower or equal range of those values reported by different institutional or scientific sources. Considering the health-care services offered in the evaluated institutions, the kg/patient-day indicator is considered more representative than the kg/bed day.

Estudio clínico-epidemiológico de la criptococosis en Venezuela: años 1994-2003 / Clinical-epidemological study of cryptococcosis in Venezuela: 1994-2003

La criptococosis es una enfermedad oportunista de distribución mundial. Frecuentemente es una infección definitoria de SIDA. El tratamiento antirretroviral ha disminuido su frecuencia. El impacto de esta entidad en Venezuela es desconocido. El objetivo de este trabajo es describir las características más relevantes de la criptococosis en nuestro país. Se revisaron 110 historias clínicas de pacientes hospitalizados con el diagnostico de criptococosis, entre 1994 y 2003, en 6 hospitales. Los datos recolectados incluyeron: características demográficas, clínicas, diagnósticas, terapéuticas y la evolución de los pacientes. Para el análisis se utilizaron los programas SPSS 10.0 y EpiInfo 6.04 (2001). Dentro de los 110 pacientes evaluados se incluyeron 17 protocolos de autopsia. Uno solo de los pacientes tenia 8 años de edad, el resto era mayor de 15 años. 91 eran del sexo masculino y 19 femenino. 91 (82,73 por ciento) tenían SIDA y 19 (17,27 por ciento) eran VIH negativo. En los pacientes con SIDA el valor promedio de CD4+ fue < 200 cel/mm³ y la carga viral era > 30000 copias/mL; 52 (57,14 por ciento) de los casos no tenían otra infección oportunista y 39 (42,86 por ciento) tenían otras condiciones asociadas, tales como tuberculosis (30,97 por ciento), neumocistosis (28,21 por ciento), y toxoplasmosis (20,51 por ciento). En los pacientes VIH negativo, el uso de esteroides (25 por ciento) fue el factor de riesgo predominante. Dos pacientes eran embarazadas. En 107 (57,27 por ciento) se encontró infección del SNC. 12 (13,19 por ciento) de los pacientes con SIDA tenían alteración de pares craneales. Se encontró afectación pulmonar en 4 (3,77 por ciento) pacientes, 1 de ellos con SIDA. La criptococosis fue la enfermedad definitoria de SIDA en el 61,54 por ciento de los casos. 33 (30 por ciento) de los pacientes fallecieron. En la mayoría de los pacientes la criptococosis se asoció a SIDA. A pesar de la eficacia del tratamiento antirretrovial, esta micosis es todavia ...

Cryptococcosis is an opportunistic disease of worldwide distribution. It is frequently an AIDS-defining infection. Antiretroviral treatment has reduced its occurrence. In Venezuela, the impact of this disease is unknown. The aim of this study is to describe the most relevant features of cryptococcosis in our country. 110 clinical records with a diagnosis of cryptococcosis hospitalized between 1994 and 2003 in 6 Venezuelan hospitals were analyzed. Data collected included demographic, clinical, diagnostic, therapeutic and outcome information. SPSS 10.0 software and EpiInfo 6, version 6.04 (2001) were used. 110 patients with cryptococcosis were enrolled, including 17 autopsy protocols. One was 8 years old, the rest were over 15. Nineteen were female and 91 male; 91 (82.73 percent) had AIDS, 19 (17.27 percent) were HIV negative. Among the AIDS patients, average CD4+ count was < 200 cel/mm3 and viral load was > 30000 copies/ml; 52 (57.14 percent) did not have other opportunistic infections or AIDS-related disease, and 39 (42.86 percent) had other associated conditions, such as tuberculosis (30.97 percent), PCP (28.21 percent) and toxoplasmosis (20.51 percent). In HIV negative patients, use of steroids (25 percent) was the predominant risk factor. Two patients were pregnant. 107 (57.27 percent) presented CNS infection; 12 (13.19 percent) with AIDS had cranial nerve alterations. Pulmonary disease was found in 4 (3.77 percent), of which one had AIDS. Cryptococcosis was an AIDS-defining infection in 61.54 percent of cases; 33 (30 percent) of the patients died. In most of the patients, cryptococcosis was associated with AIDS. In spite of the efficacy of antiretroviral treatment, this mycosis is still significant in Venezuela, perhaps due to late HIV infection diagnosis

Estudio de la fasciolosis hepática humana y parasitosis intestinales en el caserío Mesa Arriba del municipio Carache, estado Trujillo,Venezuela / Study of human hepatic fasciolosis and intestinal parasitosis in the Mesa Arriba Village, Carache Municipality, Trujillo State, Venezuela

Se realizó un estudio clínico epidemiológico para determinar la ocurrencia de fasciolosis hepática humana y parasitosis intestinales en el caserío Mesa Arriba, municipio Carache. estado Trujillo, Venezuela, zona descrita como endémica para fasciolosis bovina, donde dos casos aislados, se han reportado en humanos. Se estudiaron 98 personas previo consentimiento informado, a quienes se les realizó una encuesta epidemiológica, examen físico, hematología, aminotransferasas, estudio coproparasitológico y serológico: ELISA con antígeno de excreción-secreción de adultos de Fasciola hepatica (AFhES) y “Western blot”(WB). Con base en los datos obtenidos, se conoció que el 88,8% de los participantes había consumido berro silvestre (Rorippa nasturtium aquaticum) y 59,2% tuvo contacto con ganado vacuno. En el estudio coproparasitológico se encontró que el 47,9% presentó algún tipo de parásito intestinal, 20,4% correspondió a helmintos, 15,3% a protozoarios y 12,2% a infecciones mixtas. No se encontraron huevos de Fasciola hepatica. El 18,4% de las personas mostró eosinofilia. Se obtuvo un suero positivo por el método de ELISA, con bandas inespecíficas al WB-AFhES. Se administró tratamiento específico para parásitos intestinales. No se demostró fasciolosis humana en este trabajo, a pesar de encontrar factores favorables a la infección, pero el mismo representó una aproximación a su estudio epidemiológico en el estado Trujillo.

A clinical-epidemiological study to determine the occurrence of human hepatic fasciolosis and intestinal parasitosis was done at the Mesa Arriba Village, Carache Municipality, Trujillo State, Venezuela, area which has been described as endemic for bovine fasciolosis and where two isolated cases have been reported in humans. The study included 98 persons who, after previously signing an informed consent form, answered an epidemiological survey and were physically examined and submitted to the following laboratory tests: complete hematology, aminotransferase, and coproparasitology and serology; ELISA using Fasciola hepatica adult excretion-secretion antigen (AFhES) and “Western Blot” (WB). Based on the results obtained, it was found that 88.8% of participants had consumed wild watercress (Rorippa nasturtium aquaticum) and 59.2% had contact with bovine cattle. The coproparasitological study showed that 47.9% had some type of intestinal parasite: 20.4% corresponded to helmints, 15.3% to protozoa, and 12.2% mixed infections. There were no Fasciola hepatica eggs; 18.4% of the individuals showed eosinophilia. The ELISA test gave one positive serum with non-specific WB-AFhES bands. Specific anti-intestinal parasite treatment was indicated. Human fasciolosis was not demonstrated in this study, in spite of finding favorable factors for this infection, but is represents and approximation to its epidemiological study at Trujillo State.

Transmisión de protozoarios patógenos a través del agua para consumo humano: [revisión] / Parasitic protozoa transmission by drinking water: [review]

Los protozoarios patógenos Cryptosporidium parvum y Giardia sp. han demostrado su infectividad e impacto negativo en la salud de miles de personas tanto en naciones industrializadas como en los países en desarrollo. La mayoría de los protozoarios por presentar una forma resistente a las condiciones ambientales, les permite la supervivencia a los tratamientos físico-químicos del agua para consumo humano. De igual forma, la aparición de nuevos patógenos demuestra la necesidad de desarrollar nuevos indicadores de calidad microbiológica que permitan ofrecer productos verdaderamente seguros en el agua para uso humano. El presente artículo es una revisión de literatura que señala el impacto de este riesgo microbiológico, asociado fundamentalmente con el consumo de aguas cuyos indicadores clásicos de contaminación microbiológica (coliformes fecales y Escherichia coli) en casi todos los casos cumplen con las normas vigentes.

The pathogenic protozoa Cryptosporidium sp. and Giardia sp. showed their infectivity and negative effects on the health of thousands of people in both developed and developing countries. Protozoa have ambient resistant stages that permit survived to physical and chemical treatment of drinking water. This risk is mainly related to the consumption of water whose microbiological quality indicators typically fulfill with current standards (fecal coliforms and Escherichia coli). Likewise, the discovery of new pathogens is calling for the development of new microbiological quality indicators that allow the production of really safe goods and services such as water for human consumption. Herein the authors present a literature review showing the impact of this microbiological risk in different populations.

Eosinofilia: estudio de ocurrencia en población infantil / Eosinophilia: study of ocurrence in infantile population

La eosinofilia es un hallazgo de laboratorio que puede estar relacionado con diversidad de enfermedades, transformandose en un dilema clínico. En nuestro país los datos son escasos, pues no hay estudios de prevalencia y menos en población infantil, es por ésto que se efectúa un estudio de prevalencia en la consulta de Hematología del Instituto de Medicina Tropical "Félix Pifano", por ser lugar de referencia para esclarecer este problema. Se realizó el estudio entre enero de 1997 y diciembre de 2000 entre pacientes que asistieron a la consulta. Se seleccionaron 135 niños menores de 12 años con eosinofilia absoluta igual o mayor de 500 eosinófilos/mm³, se llenó una planilla de datos, realizandose estudios coprológicos, serológicos para identificar enfermedades parasitarias y criterios clínicos para no parasitarias. Los datos se resumieron en tablas y gráficos en frecuencia y porcentaje. Se clasificaron las enfermedades de acuerdo a los niveles de eosinofilia. El sexo masculino predominó con 57,8 por ciento; la edad promedio fue 4,9 SD ± 2,91; el grupo etario más afectado correspondió al de pre-escolares con 39,3 por ciento. El Distrito Metropolitano aportó la mayoría de los casos. Las enfermedades parasitarias fueron las más frecuentes representadas por toxocariasis visceral humana y ascariasis. Las alergias como causa no parasitaria correspondió al 10,4 por ciento. El nivel de eosinofilia marcada representó 52,6 por ciento asociada a helmintiasis. Los resultados obtenidos inducen a recomendar estudiar sistemáticamente este problema donde se deben tomar en cuenta las enfermedades parasitarias en primer lugar. El hecho de basarse en los niveles de eosinofilia mejorará la conducta clínica y diagnóstica