No abstract

Solid waste disposal is one of the major environmental issues facing Morocco. More than 5 million tons of solid waste is generated across the country, with annual waste generation growth rate reaching 3%. From this waste, there is production of fresh leachate with a high level of chemical oxygen demand (COD). The authors studied the removal of pollution from municipal solid waste fresh leachate using a technique of continuous and discontinuous aeration in order to predict the efficiency of a low-cost biological treatment for this type of effluent. The physico-chemical characteristics of the leachate showed that the pollution load has high levels of COD, biological oxygen demand (BOD5), phenol and surfactant. A removal of 90 and 60% of surfactant was obtained during discontinuous and continuous aeration, respectively. The phenol concentration decreased from 600 to 220 mg/l corresponding to 63% of phenol removal by aeration. This was also accompanied by a change in pH and sludge biodegradation. Discontinuous aeration for a period of 9 d achieved a removal efficiency of COD and BOD5 of 44 and 39% that corresponds to the removal of 19·92 g/l of COD and 7·05 g/l of BOD5, respectively.

A series of N-carbonyl-functionalized ureas, carbamates and thiocarbamates derivatives (or N-Chloro sulfonyl isocyanate "N-CSI") were involved in linear and nonlinear physicochemical quantitative structure-activity relationship "QSAR" analysis to find out the structural keys to control the inhibition against Sterol O-Acyl-Transferase-1 "SOAT-1". The results indicate the important effects of geometrical and chemical descriptors on the inhibitory activity of SOAT-1. The molecules were also screened for three-dimensional molecular docking on the crystal structure of ACAT-1 (1WL5 for ACAT-1, PDB). A comparison between 2D-QSAR and 3D molecular docking studies shows that the latter confirm the first results and represent a good prediction of the chemical and physical nature of interactions between our drug molecules and enzyme SOAT-1.

Artificial neural networks (ANNs) can be utilized to generate predictive models of quantitative structure-activity relationships (QSAR) between a set of molecular descriptors and activity. In the present work, QSAR analysis for a set of 95 1-[(2-hydroxyethoxy)-methyl]-6-(phenylthio)thymine (HEPT) derivatives has been investigated by means of a three-layered neural network (NN). It has been shown that NN can be a potential tool in the investigation of QSAR analysis compared with the models given in the literature. The results obtained by using the NN adopted for QSAR models showing not only good statistical significance in fitting, but also high predictive ability. (0.916< r <0.968 and q 2 = 0.8779). The relevant factors controlling the anti-HIV-1 activity of HEPT derivatives have been identified. The results are along the same lines as those of our previous studies on HEPT derivatives and indicate the importance of the hydrophobic parameter in modelling the QSAR for HEPT derivatives

The effect of environmental factors on different bacterial populations and cultivable heterotrophic bacteria community dynamics in an experimental high-rate oxidation pond (HROP) was studied. After 24 months of weekly and bimonthly sampling, the relationships between bacteriological and environmental variables at the outflow of the HROP were modeled. Path analysis applied to the in-situ data provided evidence of very different behavioral models according to bacteriological variables and the scale of sampling. The fecal coliform and fecal streptococci distributions showed seasonal cycles, with low summer and high winter abundances. Solar radiation, water temperature, pH and chlorophyll a concentration were the main environmental variables affecting the temporal dynamics of these bacterial populations, the effects of which were different on each bacterial group. No cyclic behavior was found for Aeromonas spp. whose abundances were irregular and closely related to water temperature and chemical oxygen demand. The temporal dynamic of the cultivable heterotrophic bacteria community was found to be independent of the majority of the model's predictive variables, indicating its maturation as an endogenous community in the high-rate pond ecosystem. These results suggest that fecalindicator bacteria are controlled by different processes occurring in the high-rate pond than are the Aeromonas spp. and aerobic heterotrophic bacteria. Water Environ. Res., 70, 1186Res., 70, (1998.