1,721,104 research outputs found
Endoscopic removal of an ectopic tooth in maxillary sinus
No full textEctopic teeth erupted in the maxillary sinus are rarely reported. Although the causes of eruption of a tooth into the maxillary sinus are unclear, some clinical conditions are suspected to be responsible, such as developmental disturbances (cleft palate), displacement of teeth by trauma, interventions or cyst, infection, genetic factors, crowding, and dense bone. Most cases of ectopic teeth in the maxillary sinus are asymptomatic and are occasionally diagnosed thanks to routine radiographic investigations.The aim of this article is to present and discuss the surgical management of an ectopic third molar in the roof of the maxillary sinus
Dispersion processes and residence times in a semi-enclosed basin with recirculating gyres: An application to the Tyrrhenian Sea
No full textIn this paper we investigate the dispersion of a tracer in a semi-enclosed basin characterized by a steady flow with recirculations. In particular, we focus on the macroscopic behavior of the system, characterized by the total concentration of the tracer in the basin, C(t), and by its residence time T. As a case study, the circulation in an idealized basin mirroring some of the major characteristics of the Tyrrhenian Sea is considered, with a northward current connecting the inflow and the outflow regions of the basin, and with a main cyclonic gyre in the northern part of it. Numerical simulations are performed from several release points in the basin and for two different values of the diffusivity coefficient K. Two independent models for dispersion are used, an Eulerian and a Lagrangian one, allowing us to validate both the basic formalism and the numerical results. The experiments show that the macroscopic properties of dispersion are largely influenced by the presence of the main gyre, while they do not depend strongly on K in the considered range. Namely, after a first phase which depends on the initial conditions, the tracer tends to be concentrated in the region of the northern gyre, and this influences the trend of C(t) versus time and the value T. For almost all the simulations, the decrease of C(t) in time can be approximated by an exponential decay, indicating a constant probability of tracer escaping the basin. The e-folding timescale of the decay is the inverse of the principal eigenvalue of the advection-diffusion operator, and it can be computed a priori knowing the flow field; this allows us to compute also an a priori estimate for the residence time T. Only when the initial release is very close to the outflow, is the initial decay of C(t) distinctly different from an exponential, and a more detailed analysis is necessary. The basic results appear generalizable to a number of other similar systems with recirculations
Dispersion Processes and Residence Time in a Semi Enclosed Basin with Recirculating Gyres. The case of the Tyrrhenian Sea
No full textTransport Properties in the Adriatic Sea as deduced from Drifter Data
No full textThe surface transport properties in the Adriatic Sea, a semienclosed subbasin of the Mediterranean Sea, have been studied using a drifter dataset in the period December 1994-March 1996. Three main points have been addressed. First, the exchange between southern and northern regions and between deep and coastal areas have been studied, focusing on the role of topography. A significant cross-topography or cross-shelf exchange has been found, probably due to the direct wind forcing and to the influence of stratification that isolates the surface flow from bottom effects, especially in the open sea. Second, a Lagrangian transport model with parameters derived from the data has been implemented. Simulated particles have been compared with drifter data with positive results. The model is found to be able to reproduce reality with good approximation, except for a specific advective event during the late summer season. Finally, the residence timescale T, that is, the average time spent by a surface particle in the basin, has been estimated. Direct estimates from the data suggest T ~ 70-90 days, but these values are biased due to the finite lifetime of the drifters. Model results have been used to estimate the bias, and they suggest a 'true' value of T ~ 200 day
- …
