No abstract

An oil spill model, which accounts for the sinking effect, was developed. The main processes that affect the fate of oil processes that affect the fate of oil released into the environment, for the first days of the spill, are included. These are evaporation, spreading, dispersion, emulsification and sinking. Special consideration is given to the process of sinking of oil, and the conditions at which this to occurs are described. Also, the basic equations for determining the breaking of the spill in fragments, the size of this fragments, the overwash depth, the maximum sinking depth and the distribution of oil in the water column are given. The model is applied to two hypothetical spills of 1000 m3 in stratified waters. The two spills differ in the density of the oil, 900 and 990 Kg/m3. In the first case the oil disappears from the surface after seven days at sea, mostly from evaporation and dispersion, while in the second case, because the high density of the oil, the spill sinks completely after 18 hours at sea. Introduction There is a considerable interest in the development of mathematical models for the prediction of the behavior of oil spills in prediction of the behavior of oil spills in water bodies. Such models, apart from the scientific interest, are important tools for contingency planning in oil spills, environmental impact statements and spill response decision making methods. An important aspect to be considered in these models is the sinking effect, specially for heavy and high emulsified oils. Several authors have indicated the sinking of oil slicks in different situations. In Venezuela, specifically in Lake Maracaibo, oil spills have been reported to sink, the resurface after several days in some other location. These situations have produced ecological problems and hence the need to determine problems and hence the need to determine whether a specific oil spill will sink in the water column. This paper is organized in the following major sections. First, the background for the development of the model is outlined. Secondly, the main processes that control oil spills in water and the equations used in the model are described. Then, the factors that control the sinking of oil are presented, as well as the equations used in the model. Following, the computer model and two applications to simulate oil spills are described. Finally, based on the model results, conclusions are drawn regarding the fate of the oil spills and recommendations are given for future studies. Background In 1986, INTEVEP, S.A., the R and D wing of the Venezuelan Oil Industry developed an oil spill trajectory and fate model for the National Contingency Plan (NCP), which take into consideration winds and currents for the trajectory simulation, and spreading, dispersion and evaporation for the fate of the oil spill. P. 445

Functional mitral regurgitation (FMR) is thought to be linked with ventricular afterload. However, the relation between aortic stiffness, which is a main determinant of ventricular afterload, and quantitatively assessed mitral regurgitation is unknown. A total of 175 patients (age 61 ± 13; 85 % male) with left ventricular (LV) systolic dysfunction were studied consecutively. Left ventricular volumes, ejection fraction, and LV outflow tract stroke volume were measured. Aortic pulse wave velocity (PWV), a known marker of aortic stiffness, was determined using Doppler flow recordings as the distance (d) traveled by the pulse wave, measured over the body surface as the distance between the two recording sites, divided by the time (t) taken by the pulse wave to travel from the descending aorta to the abdominal aorta. Mitral effective regurgitant orifice (ERO), regurgitant volume (RV), and fraction (RF) were measured using the proximal isovelocity surface area method. The mean PWV was 6.0 ± 3.5 m/s (range 2.6-25). PWV was significantly associated with ERO (r = 0.35; p < 0.0001), RV (r = 0.36; p < 0.0001) RF (p = 0.41; p < 0.0001). The association of PWV with each variable of mitral regurgitation was independent of LV volume, cardiac output, and systemic vascular resistance. Aortic stiffness is an important determinant of the severity of FMR. Aortic stiffness should be considered an important therapeutic target in patients with LV dysfunction in order to ameliorate both LV systolic and diastolic function and mitral regurgitation.

No abstract