Viscous forces on nematic point defects

The effect of backflow in defect dynamics is assessed by computing the viscous force on point and line defects that move due to reorientation. It is found that defects with a positive winding number are accelerated while defects with a negative winding number are slowed down by the backflow. The results are in agreement with experimental and numerical results for defect annihilation

Production of extracellular lipase by the phytopathogenic fungus Fusarium solani FS1 Produção de lipase extracelular pelo fungo fitopatogênico Fusarium solani FS1

A Brazilian strain of Fusarium solani was tested for extracellular lipase production in peptone-olive oil medium. The fungus produced 10,500 U.l-1 of lipase after 72 hours of cultivation at 25oC in shake-flask at 120 rpm in a medium containing 3% (w/v) peptone plus 0.5% (v/v) olive oil. Glucose (1% w/v) was found to inhibit the inductive effect of olive oil. Peptone concentrations below 3% (w/v) resulted in a reduced lipase production while increased olive oil concentration (above 0.5%) did not further stimulate lipase production. The optimum lipase activity was achieved at pH 8.6 and 30oC and a good enzyme stability (80% activity retention) was observed at pH ranging from 7.6 to 8.6, and the activity rapidly dropped at temperatures above 50oC. Lipase activity was stimulated by the addition of n-hexane to the culture medium supernatants, in contrast to incubation with water-soluble solvents