Polyaromatic hydrocarbons biodegradation using mix culture of microorganisms from sewage waste sludge: application of artificial neural network modelling.

Purpose: In this study, we aimed to examine the tolerance of mixed culture of microorganisms isolated from sewage waste sludge to degrade high concentrations of polyaromatic hydrocarbons, naphthalene, and phenanthrene. The performance of the artificial neural network (ANN) model to predict and simulate the experimental biodegradation results was investigated. Methods: The mixed culture of microorganisms was isolated from sewage waste sludge and adopted to biodegrade naphthalene and phenanthrene at different concentrations (100-1000mg/L). Sewage waste sludge obtained from wastewater treatment plants. A three-layer feed-forward network with a sigmoid transfer function (logsig) at the hidden layer, a linear transfer function (purelin) at the output layer, and a backpropagation training algorithm was used to set the ANN model. Results: The results of this study show that naphthalene at concentrations of 100, 300, 700, and 1000 mg/L was depleted after incubation with the mixed culture for 6, 8, 14, and 16 days, respectively. For phenanthrene, depletion of 100, 300, 600, and 1000 mg/L was achieved after 8, 11, 16, and 19 days of incubation, respectively. A high correlation coefficient of 99.5% between the predicted and the experimental results were obtained by using the AAN model. Conclusion: The results indicated that the mixed culture of microorganisms from sewage waste sludge could effectively consume naphthalene and phenanthrene as carbon and energy sources. Also, the ANN model could efficiently predict the experimental results for biodegradation treatment.

[Diffusion of hydroxyl ions from calcium hydroxide in the dentinal tubules]. / Etude de la diffusion des ions OH- de l'hydroxyde de calcium dans les tubuli dentinaires.

The aim of this study was to compare hydroxyl ions diffusion from various calcium hydroxide forms: Hycal (1), Roeko points (2) and aqueous suspension placed in the pulpar chamber (3) or in the root canal (4). These experiments were conducted with bovine incisors in order to obtain quantitative evaluation. 540 lateral cavities, deep and superficial, were created in root dentin to measure the hydroxyl ions diffusion with a color indicator, the Blue epsilon With Hycal and aqueous suspension the diffusion of the OH- is obtained in the superficial cavities situated in the coronal part at 14 days (1 = 72%; 3 = 44%; 4 = 100%, (n=18)). In the apical part of the canal this phenomenon is never complete at 21 days (1 = 17%; 3 = 22%; 4 = 17%, (n=18)). No diffusion was observed with the Roeko points (the first generation).