Analysis of a polling system modeling QoS differentiation in WLANs

This paper investigates a polling system with a random polling scheme, a 1-limited service discipline and deterministic service requirement modeling WLANs with QoS differentation capability. The system contains high and low priority queues that are distinguished via the probability of being served next. We propose a new iteration algorithm to approximate the waiting time of customers in the high and low priority queues. As shown by simulation results, our approximation is accurate for light to moderately loaded networks

Architectural aspects of QoS-aware personal networks

Personal Networks (PN) are future communication systems that combine wireless and infracuture based networks to provide users a variety of services anywhere and anytime. PNs introduce new design challenges due to the heterogeneity of the involved technologies, the need for self-organization, the dynamics of the system composition, the application-driven nature, the co-operation with infrastructure-based networks, and the security hazards. This paper discusses the challenges of security and QoS provisioning in designing self-organized personal networks and combines them all into an integrated architectural framework

Math saves the forest

Wireless sensor networks are decentralised networks consisting of sensors that can detect events and transmit data to neighbouring sensors. Ideally, this data is eventually gathered in a central base station. Wireless sensor networks have many possible applications. For example, they can be used to detect gas leaks in houses or fires in a forest.\ud In this report, we study data gathering in wireless sensor networks with the objective of minimising the time to send event data to the base station. We focus on sensors with a limited cache and take into account both node and transmission failures. We present two cache strategies and analyse the performance of these strategies for specific networks. For the case without node failures we give the expected arrival time of event data at the base station for both a line and a 2D grid network. For the case with node failures we study the expected arrival time on two-dimensional networks through simulation, as well as the influence of the broadcast range

A breakthrough in cryosurgery.

Item does not contain fulltextLiver cryosurgery is one of the treatment options for unresectable liver metastases. Indications for the use of this treatment instead of classic surgery are bilobar disease, location of the tumor at an irresectable anatomic site, and comorbid conditions of the patient. Possible complications of cryosurgery are hemorrhage, coagulopathy, pneumonia, pleural effusion, abdominal abscess, and bile fistula. We describe a patient in whom a hepatobronchial fistula developed after cryosurgery. The patient had cryosurgery because of an unresectable liver metastasis in a Dukes' C rectal carcinoma. More details are given in the case report. To our knowledge, a hepatobronchial fistula as a complication of cryosurgery has never been reported. It therefore should be added to the list of possible cryosurgery complications

Bottlenecks and stability in networks with contending nodes

This paper considers a class of queueing network models where nodes have to contend with each other to serve their customers. In each time slot, a node with a non-empty queue either serves a customer or is blocked by a node in its vicinity. The focus of our study is on analyzing the throughput and identifying\ud bottleneck nodes in such networks. Our modeling and analysis approach consists of two steps. First, considering the slotted model on a longer timescale, the behavior is described by a continuous time Markov chain with state dependent service rates. In the second step, the state dependent service rates are replaced by their long run averages resulting in an approximate product form network. This enables us to determine the bottleneck nodes and the stability condition of the system. Numerical results show that our approximation approach provides very accurate results with respect to the maximum throughput a network can support. It also reveals a surprising effect regarding the location of bottlenecks in the network when the offered load is further increased

Grace And The Development Of An Education And Training Curriculum

Clin Microbiol Infect 2012; 18: E308E313 Abstract Antimicrobial resistance is a serious threat and compromises the management of infectious disease. This has particular significance in relation to infections of the respiratory tract, which are the lead cause of antibiotic prescribing. Education is fundamental to the correct use of antibiotics. A novel open access curriculum has been developed in the context of a European Union funded research project Genomics to combat Resistance against Antibiotics in Community-acquired lower respiratory tract infections in Europe (GRACE http://www.grace-lrti.org). The curriculum was developed in modular format and populated with clinical and scientific topics relevant to community-acquired lower respiratory tract infections. This curriculum informed the content of a series of postgraduate courses and workshops and permitted the creation of an open access e-Learning portal. A total of 153 presentations matching the topics within the curriculum together with slide material and handouts and 104 webcasts are available through the GRACE e-Learning portal, which is fully searchable using a mindmap to navigate the contents. Metrics of access provided a means for assessing usage. The GRACE project has permitted the development of a unique on-line open access curriculum that comprehensively addresses the issues relevant to community-acquired lower respiratory tract infections and has provided a resource not only for personal learning, but also to support independent teaching activities such as lectures, workshops, seminars and course work.WoSScopu