Biodiesel is a renewable liquid fuel that can be produced by a transesterification reaction between a vegetable oil and an alcohol. This paper evaluates and optimizes the production of ethyl esters (biodiesel) from soybean oil and ethanol. The reaction was carried out by applying ultrasound under atmospheric pressure and ambient temperature. Response surface methodology was used to evaluate the influence of alcohol to oil molar ratio and catalyst concentration on the yield of conversion of soybean oil into ethyl esters. The process resulted in a maximum yield of 91.8% after 30 minutes of reaction. The process variables alcohol to oil ratio and catalyst to oil ratio were statistically significant regarding the yield of ethyl esters. The optimal operating condition was obtained applying an alcohol to oil molar ratio of 10.2 and a catalyst to oil weight ratio of 0.0035.

The present study was carried out at the Army Central Hospital, Rio de Janeiro, Brazil, from September 2000 to December 2001, employing diethylenetriamine penta-acetic acid labeled with technetium-99m (99mTc-DTPA) to evaluate the renal function of nineteen symptomatic patients infected with S. haematobium during a peace mission in Mozambique. Results evidenced that the most frequent clinical manifestations were hematuria (68.4%) and low back pain (68.4%) and 73.7% patients had altered dynamic renal scintigraphy expressed by an increase in the excretory phase independently of the symptoms duration; furthermore, none of them had mechanical obstructive pattern. Schistosoma haematobium glomerulopathy could be considered a pathological finding without correlation with the disease clinical manifestations.