Optimization of chemical solution concentration and exposure time in the alkaline pretreatment applied to sugarcane bagasse for methane production.

ABSTRACTSugarcane is the most traded crop in the world, with Brazil being the world's largest producer. Sugarcane processing generates up to 28% of sugarcane bagasse (SB) from the entire plant, with only 50% of it used for energy generation. SB is a lignocellulosic biomass that can be converted into biogas. However, the optimization of pretreatment process parameters is essential for its successful scaling up. This study evaluated the effect of mild alkaline pretreatment of SB using NaOH and KOH at concentrations of 1-10% and exposure time of 1-12 hours) on the biochemical methane potential (BMP) under mesophilic temperature. The central composite rotatable design (CCRD) was applied as statistical tool to generate optimal operating pretreatment conditions. The tests were performed in triplicates totalizing 84 batch bottles. The BMP of the untreated SB varied between 297-306 LN CH4 kg VS-1 while the BMP of the pretreated samples with NaOH and KOH were 19% and 20% higher. The optimized conditions were NaOH at 7.7% and KOH at 8.3% KOH for 12 hours. However, the range indicated by the statistical design with CCRD revealed that there was no statistical difference in terms of methane yield when concentrations between 4-10% NaOH and 6-10% KOH during 12 hours were applied, when compared to the specific optimized points. The optimization of the pretreatment parameters demonstrated to be a key-factor to improve the anaerobic digestion of lignocellulosic substrates, leading to a less chemically dependent and more sustainable approach, while allowing a more profitable process.

Estudo epidemiologico de orovalvulopatias submetidas a cateterismo cardíaco: análise do últimos 10 anos da casuística da 6 enfermaria da Santa Casa da Misericórdia do Rio de Janeiro / Epidemiologic study of heart valve diseases submitted at cardiac catheterization

The authors studied 6,627 patients submitted to cardiac catheterization. These, about 825 had orovalvular disease. Orovalvular disease was more frequent in women in reason of three to two for man. The mitral valve lesion was the most frequent, with 53.78 per cent of cases. In men, the most frequent lesion was aortic. In women, the mitral. In most cases, there was only one valve with lesion, with predominance of mitral stenosis and, after, aortic insuficiency. In cases where there was association of lesions, the predominance was of mitro-aortica lesion. About half of patients who have had isolated lesion had too left ventricular disfunction. In these cases, the aortic insufficiency predominated.