Assuntos
Margens de Excisão , Neoplasias Retais , Humanos , Imageamento Tridimensional , Recidiva Local de Neoplasia/diagnóstico por imagem , Recidiva Local de Neoplasia/patologia , Recidiva Local de Neoplasia/cirurgia , Estadiamento de Neoplasias , Neoplasias Retais/diagnóstico por imagem , Neoplasias Retais/patologia , Neoplasias Retais/cirurgia , Reto/patologia , Resultado do TratamentoAssuntos
Neoplasias da Próstata , Neoplasias Retais , Humanos , Imageamento por Ressonância Magnética , Masculino , Estadiamento de Neoplasias , Próstata/patologia , Neoplasias da Próstata/diagnóstico por imagem , Neoplasias Retais/diagnóstico por imagem , Neoplasias Retais/patologia , Reto/patologiaRESUMO
This article describes the bed expansion characteristics of a down-flow anaerobic fluidized bed reactor treating a synthetic wastewater. Experiments were carried out in a 0.08 m diameter and 1 m length PVC column. The carrier used was ground perlite (an expanded volcanic rock). Particles characteristics were 0.968 mm in diameter, specific density of 213 kg x m-3 and Umf (minimal fluidization velocity): 2.3 m x h-1. Experimental data of terminal velocities and bed expansion parameters at several biofilm thicknesses were compared to different models predicting the bed expansion of up-flow and down-flow fluidized beds. Measured bed porosities at different liquid superficial velocities for the different biofilm thicknesses were in agreement with the Richardson-Zaki model, when Ut (particle terminal velocity) and n (expansion coefficient) were calculated by linear regression of the experimental data. Terminal velocities of particles at different biofilm thicknesses calculated from experimental bed expansion data, were found to be much smaller than those obtained when Cd (drag coefficient) is determined from the standard drag curve (Lapple and Sheperd, 1940) or with others' correlations (Karamanev and Nikolov, 1992a,b). This difference could be explained by the fact that free-rising particles do not obey Newton's law for free-settling, as proposed by Karamanev and Nikolov (1992a,b) and Karamanev et al. (1996). In the present study, the same free-rising behavior was observed for all particles (densities between 213 and 490 kg x m-3).