Abstract Anaerobic digestion of livestock waste has benefits such as reduction of odours and pathogens, production of biogas and biofertilizers. Methane production is influenced, among other factors, by the hydrodynamic performance of the digester. The objective of this research was to construct and validate a numerical model based on Computational Fluid Dynamics (CFD), from a prototype of a covered lagoon anaerobic digester. CFD model simulations were performed from reactor characteristics and working fluid properties. To check the agreement of the model, the numerical results were related to experimental data generated by Particle Imaging Velocimetry (PIV) in a scale model of the original digester. With the validated model, four design alternatives were simulated. The results showed greater efficiency of the flow pattern by including recirculation. The reduction in dead space between proposed configurations with respect to the original, ranged from 12.7-19.2%. The best hydrodynamic performance configuration was with recirculation of 2/3 of the feed at the original inlet and the other third at 12 m and at an angle of 90° to the input line.

Resumen La digestión anaeróbica de residuos de explotaciones pecuarias presenta beneficios tales como, la reducción de olores y agentes patógenos, la producción de biogás y biofertilizantes. La producción de metano está influenciada, entre otros factores, por el desempeño hidrodinámico del digestor. El objetivo de esta investigación fue construir y validar un modelo numérico basado en Dinámica de Fluidos Computacional (CFD), a partir de un prototipo de un digestor anaeróbico de laguna cubierta. Las simulaciones del modelo en CFD fueron realizadas a partir de las características del reactor y las propiedades del fluido de trabajo. Para comprobar la concordancia del modelo, los resultados numéricos se relacionaron con datos experimentales generados mediante Velocimetría de Imágenes de Partículas (PIV) en un modelo a escala del digestor original. Con el modelo validado, se simularon cuatro alternativas de diseño. Los resultados mostraron mayor eficiencia del patrón de flujo al incluir recirculación. La reducción de espacio muerto entre configuraciones propuestas con respecto al original osciló entre 12,7-19,2%. La configuración de mejor desempeño hidrodinámico fue con recirculación de 2/3 de la alimentación en la entrada original y el otro tercio la distancia de 12 m y con un ángulo de 90° respecto a la línea de entrada.

Crystalline cellulose nanofibers are obtained from the bark of Cereus Forbesii, a cactus native to the arid areas of South America. The obtaining of cellulose nanofibers was carried out in several steps: pretreatment of the raw material, elimination of hemicellulose and lignin to obtain cellulose, and an acid hydrolysis of cellulose to obtain crystalline cellulose nanofibers. The cellulose nanofibers obtained have a crystallinity index of 82% and a nanofiber diameter of 18 nm. An average crystallite size of 6 nm was calculated for the crystalline domains that form cellulose nanofibers. The high crystallinity of the obtained cellulose nanofibers makes the sample very homogeneous and decomposes in a relatively narrow temperature range (between 290°C and 375°C). The complete degradation of crystalline cellulose polymer chains takes place between 375°C and 600°C. The morphological and structural studies are carried out by scanning electron microscopy of field emission, infrared spectrometry with Fourier transform, and powder X-ray diffraction. The thermal stability of the samples is determined by thermogravimetric analysis.

La histoplasmosis es una micosis causada por el hongo dimorfo Histoplasma capsulatum. El síndrome hemofagocítico es una enfermedad potencialmente mortal causada por la activación inapropiada de linfocitos y macrófagos, que conduce a daño celular en múltiples órganos y sistemas. Describimos el caso de un paciente masculino de 46 años de edad, con infección VIH/SIDA, con fiebre, disnea, pérdida de peso y pancitopenia, quien presenta un síndrome hemofagocítico secundario a una histoplasmosis diseminada, diagnóstico este realizado por estudios de médula ósea.

Histoplasmosis is a mycosis caused by the dimorphic fungus Histoplasma capsulatum. Hemophagocytic syndrome is a potentially lethal condition caused by inappropriate activation of lymphocytes and macrophages, leading to cellular damage in multiple organs and systems. We describe the case of a male patient 46 years old with HIV Infection/AIDS, with fever, dyspnea, diarrhea, weight loss and pancytopenia, who presents a disseminated histoplasmosis with a secondary HFS, this diagnosis made by bone marrow studies.