The convection velocities of ejections, sweeps, and shear layers have been studied in a turbulent boundary layer at Reθ=1409 by means of two-point correlations. Except in the buffer layer, where the convection velocities are reasonably constant, considerable variations in Uc are observed, both with respect to the distance from the wall and the scale of the event. The largest-scale motions (of the order of the boundary layer thickness) are convected at velocities close to the local mean. However, the velocities drop significantly as the scales are reduced for all types of events studied. Hence, the concept of a unique structure convection velocity does not appear to be very useful, since it must depend on the state of evolution of the structure. The propagation velocity also appears to be different for different parts of the event. It is found that for all scales and positions, the convection velocity for ejections is distinctly lower than that for sweeps, suggesting that the mechanisms responsible for the two types of events are quite different.

Background and Purpose-Cerebral artery aneurysms rupture when wall tension exceeds the strength of the wall tissue.At present, risk-assessment of unruptured aneurysms does not include evaluation of the lesions shape, yet clinical experience suggests that this is of importance. We aimed to develop a computational model for simulation of fluid-structure interaction in cerebral aneurysms based on patient specific lesion geometry, with special emphasis on wall tension. Methods-An advanced isogeometric fluid-structure analysis model incorporating flexible aneurysm wall based on patient specific computed tomography angiogram images was developed. Variables used in the simulation model were retrieved from a literature review. Results-The simulation results exposed areas of high wall tension and wall displacement located where aneurysms usually rupture. Conclusion-We suggest that analyzing wall tension and wall displacement in cerebral aneurysms by numeric simulation could be developed into a novel method for individualized prediction of rupture risk. (Stroke. 2008;39:3172-3178.)

We believe that image fusion between intraoperative 3D ultrasound and preoperative MRI might improve the quality of the surgical procedure and hence also improve the patient outcome.

In the reported cases, the LNP was a useful tool for image guidance in laparoscopic surgery, both for planning the surgical approach in detail and for guidance. The authors believe that adominal 3D image guidance using an LNP has a large potential for improving laparoscopic surgery, especially when vessels and anatomic relations may be difficult to identify using only a laparoscope. Accordingly, they believe this new technology could increase safety and make it easier for the surgeon to perform successful laparoscopic surgery.