Experimentelle Untersuchung der radialen Verformbarkeit von Stents

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Infolge der mechanischen Unterstützung der Gefäßwand nach Stentimplantation kann eine akute Durchmesservergrößerung gegenüber konventioneller Ballonangioplastie (PTCA) erreicht und die Restenoserate gesenkt werden. Eine ausreichende Widerstandsfähigkeit gegenüber äußeren Kräften ist eine Grundvoraussetzung für optimale Ergebnisse in der Stentapplikation. Aufgrund der Vielzahl der verwendeten Materialien und Gestaltungsprinzipien bestehen große Unterschiede in dem mechanischen Verhalten der kommerziell verfügbaren Stents. Die Kenntnis dieser Verhaltensweisen stellt eine essentielle Grundlage einer an die Läsion angepaßten Stentauswahl dar. Obwohl bisher verschiedene Studien das Stentverhalten analysierten, fehlt es aufgrund unterschiedlicher Prüfverfahren an einer Vergleichbarkeit der Ergebnisse. Ziel dieses Beitrages ist die parallele Untersuchung von acht aktuellen Stenttypen. Zu diesem Zweck wurde eine Ultraschall-Meßvorrichtung zur standardisierten, quantitativen Evaluation der kompressiv-mechanischen Eigenschaften von Koronarstents entwickelt. Mit Hilfe dieser Vorrichtung konnte darüberhinaus der Einfluß der Stentimplantation auf das radiale Dehnungsverhalten der Arterienwand untersucht werden

Stability of wall-bounded flows using one-way spatial integration of Navier-Stokes equations

A method for constructing well-posed one-way equations for calculating disturbances of slowly-varying flows was recently introduced (Towne & Colonius, JCP, Vol. 300, 2015). The linearized Navier-Stokes equations are modified such that all upstream propagating modes are removed from the operator. The resulting equations, termed one-way Navier-Stokes equations, are stable and can be solved efficiently in the frequency domain as a spatial initial value problem in which initial perturbations are specified at the domain inlet and propagated downstream by spatial integration. To date, the method has been used to predict large-scale wavepacket structures and their acoustic radiation in turbulent jets. In this paper, the method is extended and applied to wall-bounded flows. Specifically, we examine the spatial stability of two- and three-dimensional boundary layers, corresponding to the Blasius and the Falkner-Skan-Cooke flows, and predict the evolution of unstable Tollmien-Schlichting waves and crossflow vortices, respectively. The method is validated against well-known results from the literature

Turbine Powered Simulator Calibration and Testing for Hybrid Wing Body Powered Airframe Integration

Propulsion airframe integration testing on a 5.75% scale hybrid wing body model us- ing turbine powered simulators was completed at the National Full-Scale Aerodynamics Complex 40- by 80-foot test section. Four rear control surface con gurations including a no control surface de ection con guration were tested with the turbine powered simulator units to investigate how the jet exhaust in uenced the control surface performance as re- lated to the resultant forces and moments on the model. Compared to ow-through nacelle testing on the same hybrid wing body model, the control surface e ectiveness was found to increase with the turbine powered simulator units operating. This was true for pitching moment, lift, and drag although pitching moment was the parameter of greatest interest for this project. With the turbine powered simulator units operating, the model pitching moment was seen to increase when compared to the ow-through nacelle con guration indicating that the center elevon and vertical tail control authority increased with the jet exhaust from the turbine powered simulator units

Design, development and evaluation of a compact telerobotic catheter navigation system.

BACKGROUND: Remote catheter navigation systems protect interventionalists from scattered ionizing radiation. However, these systems typically require specialized catheters and extensive operator training. METHODS: A new compact and sterilizable telerobotic system is described, which allows remote navigation of conventional tip-steerable catheters, with three degrees of freedom, using an interface that takes advantage of the interventionalist\u27s existing dexterity skills. The performance of the system is evaluated ex vivo and in vivo for remote catheter navigation and ablation delivery. RESULTS: The system has absolute errors of 0.1 ± 0.1 mm and 7 ± 6° over 100 mm of axial motion and 360° of catheter rotation, respectively. In vivo experiments proved the safety of the proposed telerobotic system and demonstrated the feasibility of remote navigation and delivery of ablation. CONCLUSION: The proposed telerobotic system allows the interventionalist to use conventional steerable catheters; while maintaining a safe distance from the radiation source, he/she can remotely navigate the catheter and deliver ablation lesions. Copyright © 2015 John Wiley & Sons, Ltd