A One-Equation Turbulence Model for Geophysical Applications: Comparison with Data and the k−ε Model

A one-equation turbulence model is presented, in which the turbulent kinetic energy k is calculated with a transport equation whereas the turbulent length scale l is calculated with an algebraic expression. The value of l depends on the local stratification and reduces to the classical |z| scaling for unstratified flows near a wall, where |z| is the distance to the wall. The length scale decreases during stable stratification, and increases for unstable stratification compared to the neutral case. In the limit of strong stable stratification, the so-called buoyancy length scale proportional to k^1/2N^–1 is obtained, where N is the buoyancy frequency. The length scale formulation introduces a single model parameter which is calibrated against experimental data. The model is verified extensively against laboratory measurements and oceanic data, and comparisons are made with the two-equation k- model. It is shown that the performance of the proposed k model is almost identical to that of the k- model. In addition, the stability functions of Launder are revisited and adjusted to obtain better agreement with recent data.     

Uranium in vegetable foodstuffs: should residents near the Cunha Baixa uranium mine site (Central Northern Portugal) be concerned?

Large uranium accumulations in vegetable foodstuffs may present risks of human health if they are consumed. The objective of this study was to evaluate the uranium concentrations in different vegetable foodstuffs and grown in agricultural soils, which are then consumed by the residents of the village of Cunha Baixa (Portugal),—located in an former uranium mining area. This study was conducted to address concerns expressed by the local farmers as well as to provide data for uranium-related health risk assessments for the area. Soils, irrigation water and edible tissues of lettuce, potato, green bean, carrot, cabbage, apple and maize (Latuca sativa L., Solanum tuberosum L., Phaseolus vulgaris L., Daucus carota L., Brassica oleracea L., Malus domestica Borkh, Zea mays L., respectively) were sampled and uranium determined. High uranium concentrations were found in some soils (U_total > 50 mg/kg), in irrigation waters (218 to 1,035 μg/l) and in some vegetable foodstuffs (up to 234, 110, 30, 26, 22, 16 and 1.6 μg/kg fresh weight for lettuce, potato with peel, green bean pods, cabbage, corn, carrot and apple, respectively). However, the results of the toxicity hazard analysis were reassuring the estimated level of uranium exposure through the ingestion of these vegetable foodstuffs was low, suggesting no chemical health risk (hazard quotient <1) to this uranium exposure pathway for a local residents during their lifetime, even for the most sensitive part of the population (child).     

Effects of coconut product–caffeine interactions on liver cells in Wistar albino rats

The effects of interactions between coconut products and caffeine on the induction of drug-metabolizing enzyme in Wistar albino rats were studied. Twenty rats were randomly divided into four groups: (Group 1) control received via oral route a placebo (4 mL distilled water). Groups 2–4 were treated for a 14-day period, respectively, with 50 mg caffeine/kg body weight (BW), 50 mg caffeine/kg plus 50 mg coconut water/kg, or 50 mg caffeine/kg plus 50 mg coconut milk/kg in a 4 mL volume via gastric intubation. One day after the after the final exposure, the animals were euthanized by inhalation of an overdose of chloroform. The blood of each rat was collected by cardiac puncture, and the liver of each was harvested and processed to examine several biochemical parameters, including total protein and RNA levels, protein/RNA ratios, and the activities of alanine and aspartate aminotransferases (ALT and AST, respectively). Results showed that while ingestion of coconut milk and coconut water increased the values of protein and protein/RNA ratios, there was a decrease in ALT and AST activities. These effects were opposite to those produced by caffeine alone and may prevent the adverse effects attributed to caffeine.