We consider open networks of queues with Processor-Sharing discipline and signals. The signals deletes all the customers present in the queues and vanish instantaneously. The customers may be usual customers or inert customers. Inert customers do not receive service but the servers still try to share the service capacity between all the customers (inert or usual). Thus a part of the service capacity is wasted. We prove that such a model has a product-form steady-state distribution when the signal arrival rates are positive.

Although historians have shown that there has been a complex and multi-layered relationship between the body, medicine and the force of electricity, many avenues remain to be explored. One of the most prominent of these is the way in which electrotherapy technologies were marketed to a wide variety of different end users and intermediaries. This paper offers the first historical analysis of one such device – the Overbeck Rejuvenator – a 1920s electrotherapy machine designed for use by the general public. Its inventor, Otto Overbeck, was not a medical man and this enabled him to use aggressive strategies of newspaper advertising, using testimonials to market his product alongside appeals to his own scientific authority. He commissioned the prestigious Ediswan Company to manufacture the Rejuvenator on a large scale, and took out patents in eleven countries to persuade users of the efficacy of the device. In response to Overbeck’s activities, the British Medical Association enlisted an electrical engineer to examine the Rejuvenator, contacted practitioners whose endorsements were being used in publicity material, and denied Overbeck permission to advertise in the British Medical Journal. Despite this, the Rejuvenator brought its inventor wealth and notoriety, and helped redefine the concept of ‘rejuvenation’, even if the professional reception of such a device was almost universally hostile. This paper shows how the marketing, patenting and publishing of Overbeck combined to persuade members of the laity to try the Rejuvenator as an alternative form of therapy, bypassing the medical profession in the process.

Long running software systems are known to experience an aging phenomenon called software aging, one in which the accumulation of errors during the execution of software leads to performance degradation and eventually results in failure. To counteract thisphenomenon a proactive fault management approach, called software rejuvenation, is particularly useful. It essentially involves gracefully terminating an application or a system and restarting it in a clean internal state. In this paper, we reconsider the non-homogeneousMarkovian models for a single-server type of software system with rejuvenation in Garg et al. (1998), and revisit them from the theoretical view point. More precisely, it is assumed in these models that software failures can occur with positive probability during idle periods in transaction systems, but we exclude this unreasonable situation in our refined models.