Waiting times in queueing networks with a single shared server

We study a queueing network with a single shared server that serves the queues in a cyclic order. External customers arrive at the queues according to independent Poisson processes. After completing service, a customer either leaves the system or is routed to another queue. This model is very generic and finds many applications in computer systems, communication networks, manufacturing systems, and robotics. Special cases of the introduced network include well-known polling models, tandem queues, systems with a waiting room, multi-stage models with parallel queues, and many others. A complicating factor of this model is that the internally rerouted customers do not arrive at the various queues according to a Poisson process, causing standard techniques to find waiting-time distributions to fail. In this paper we develop a new method to obtain exact expressions for the Laplace-Stieltjes transforms of the steady-state waiting-time distributions. This method can be applied to a wide variety of models which lacked an analysis of the waiting-time distribution until now

Transcatheter Aortic Valve Implantation: Insights into Clinical Complications

__Abstract__ Transcatheter Aortic Valve Implantation (TAVI) has emerged as a viable and safe treatment for patients with severe aortic stenosis (AS) who are considered ineligible or at prohibitive risk for Surgical Aortic Valve Replacement (SAVR)1–4. The aim of the present thesis was to evaluate the in-hospital complications and the determinants or factors associated with outcome after TAVI, thereby, offering insight into the pathophysiology of complications that in turn may help to propose recommendations to improve the planning, execution and follow-up of TAVI