A Model for diffusion controlled bioavailability of crude oil components

Crude oil is a complex mixture of several different structural classes of compounds including alkanes, aromatics, heterocyclic polar compounds, and asphaltenes. The rate and extent of microbial degradation of crude oil depends on the interaction between the physical and biochemical properties of the biodegradable compounds and their interactions with the non-biodegradable fraction. In this study we have systematically altered the concentration of non-biodegradable material in the crude oil and analyzed its impact on transport of the biodegradable components of crude oil to the microorganisms. We have also developed a mathematical model that explains and accounts for the dependence of biodegradation of crude oil through a putative bioavailability parameter. Experimental results indicate that as the asphaltene concentration in oil increases, the maximum oxygen uptake in respirometers decreases. The mathematically fitted bioavailability parameter of degradable components of oil also decreases as the asphaltene concentration increases.     

Comparative cradle to grave environmental life cycle assessment of traditional and extensive vegetative roofs: an application for the Lebanese context

The International Journal of Life Cycle Assessment - Vegetative roofs (VRs) are fully planted roof spaces that offer aesthetic view, storm water management, sound insulation, energy savings, and...     

Polycystin-1 activates and stabilizes the polycystin-2 channel

Autosomal dominant polycystic kidney disease (ADPKD) is a prevalent genetic disorder largely caused by mutations in the PKD1 and PKD2 genes that encode the transmembrane proteins polycystin-1 and -2, respectively. Both proteins appear to be involved in the regulation of cell growth and maturation, but the precise mechanisms are not yet well defined. Polycystin-2 has recently been shown to function as a Ca(2+)-permeable, non-selective cation channel. Polycystin-2 interacts through its cytoplasmic carboxyl-terminal region with a coiled-coil motif in the cytoplasmic tail of polycystin-1 (P1CC). The functional consequences of this interaction on its channel activity, however, are unknown. In this report, we show that P1CC enhanced the channel activity of polycystin-2. R742X, a disease-causing polycystin-2 mutant lacking the polycystin-1 interacting region, fails to respond to P1CC. Also, P1CC containing a disease-causing mutation in its coiled-coil motif loses its stimulatory effect on wild-type polycystin-2 channel activity. The modulation of polycystin-2 channel activity by polycystin-1 may be important for the various biological processes mediated by this molecular complex.     

Cubic-spline interpolation to estimate effects of inbreeding on milk yield in first lactation Holstein cows

Milk yield records (305d, 2X, actual milk yield) of 123,639 registered first lactation Holstein cows were used to compare linear regression (y = β(0) + β(1)X + e), quadratic regression, (y = β(0) + β(1)X + β(2)X(2) + e) cubic regression (y = β(0) + β(1)X + β(2)X(2) + β(3)X(3) +e) and fixed factor models, with cubic-spline interpolation models, for estimating the effects of inbreeding on milk yield. Ten animal models, all with herd-year-season of calving as fixed effect, were compared using the Akaike corrected-Information Criterion (AICc). The cubic-spline interpolation model with seven knots had the lowest AICc, whereas for all those labeled as "traditional", AICc was higher than the best model. Results from fitting inbreeding using a cubic-spline with seven knots were compared to results from fitting inbreeding as a linear covariate or as a fixed factor with seven levels. Estimates of inbreeding effects were not significantly different between the cubic-spline model and the fixed factor model, but were significantly different from the linear regression model. Milk yield decreased significantly at inbreeding levels greater than 9%. Variance component estimates were similar for the three models. Ranking of the top 100 sires with daughter records remained unaffected by the model used.     

Bioremediation and Biorestoration of a Crube Oil-Contaminated Freshwater Wetland on the St.Lawrence River

Biostimulation by nutrient enrichment and phytoremediation were studied for the restoration of an acutely stressed freshwater wetland experimentally exposed to crude oil. The research was carried out along the shores of the St. Lawarence River at Ste. Croix, Quebec, Canada. The research determined the effectiveness of fertilizer addition in enhancing the biodegradation rates of residual oil. It further examined the rate at which the stressed ecosystem recovered with and without the addition of inorganic fertilizers and the role of nutrients in enhancing wetland restoration in the absence of healthy wetland plants. Chemical analysis of integrated sediment core samples to the depth of oil penetration within the experimental plots indicated that addition of inorganic nutrients did not enhance the disappearance of alkanes or PAHs. In surface samples, however, hydrocarbon disappearance rates were higher when the metabolic activity of wetland plants was suppressed by the removal of emergent plant growth. These results suggest that oxygen limitation plays a major role in preventing rapid biodegradation of hydrocarbons in anoxic wetland sediment.