104,024 research outputs found
Stapled versus handsewn methods for ileocolic anastomoses
No full textBackground: This is the first systematic review specifically investigating ileocolic anastomosis. Objectives: To compare outcomes of ileocolic anastomoses performed using stapling and handsewn techniques. The hypothesis tested was that the stapling technique is associated with fewer complications. Search strategy: MEDLINE, EMBASE, Cochrane Colorectal Cancer Group specialised register SR-COLOCA, and Cochrane Library were searched for randomised controlled trials comparing the use of a linear cutter stapler with any type of suturing technique for ileocolic anastomoses in adults from 1970 to 2005. Selection criteria were randomised controlled trials comparing the use of linear cutter stapler (isoperistaltic side to side or functional end to end) with any type of suturing technique in adults. Regarding data collection and analysis, eligible studies were selected and their methodological quality assessed. Sub-group analyses for cancer and inflammatory bowel disease as indication for ileocolic anastomoses were performed. Results: Six trials (including one unpublished) with 955 ileocolic participants were included. The three largest trials had adequate allocation concealment. Stapled anastomosis was associated with significantly fewer anastomotic leaks compared with the handsewn technique (S = 5/357, HS = 36/598, OR 0.34 [0.14, 0.82] p = 0.02). For the sub-group of 825 cancer patients in four studies, stapled anastomosis led to significantly fewer anastomotic leaks (S = 4/300, HS = 35/525, OR 0.28 [0.10, 0.75] p = 0.01). There were very less Crohn’s disease patients to perform a sub-group analysis. All other outcomes showed no significant difference. Conclusions: Stapled functional end-to-end ileocolic anastomosis is associated with fewer leaks than handsewn anastomosis
A geostationary satellite system for mobile multimedia applications using portable, aeronautical and mobile terminals
No full textA geostationary satellite system for mobile multimedia services via portable, aeronautical and mobile terminals was developed within the framework of the Advanced Communications Technology Service (ACTS) programs. The architecture of the system developed under the 'satellite extremely high frequency communications for multimedia mobile services (SECOMS)/ACTS broadband aeronautical terminal experiment' (ABATE) project is presented. The system will be composed of a Ka band system component, and an extremely high frequency band component. The major characteristics of the space segment, the ground control station and the portable, aeronautical and mobile user terminals are outlined
Sono teorie politically correct, ma deboli. Recensione di C. Deregibus e G. L. Beccaria al libro: P. Gregory, Teorie di architettura contemporanea. Percorsi del postmodernismo, Carocci editore, Roma 2010 (2° Ristampa, Luglio 2012)
No full textRecensione di C. Deregibus e G. L. Beccaria al libro: P. Gregory, Teorie di architettura contemporanea. Percorsi del postmodernismo, Carocci editore, Roma 2010 (2° Ristampa Luglio 2012
CAC-TCP cross-layer interaction in a HAPS-satellite integrated scenario
No full textThe integration of a satellite system with a HAPS segment appears very suitable to provide communication services, including Internet access, for a large set of applications. In fact, the-satellite capability to provide wide coverage and broadband access can be enhanced by the use of cost-effective, mobile/portable and low-power consuming user terminals, when HAPS acts as an intermediate repeater. Moreover, also TCP-based applications, which suffer from long latency introduced by the satellite link and in general by errors, can get benefits in terms of end-to-end performance. In this frame, this paper deals with the introduction, on board the HAPS, of an efficient CAC scheme in order to guarantee an optimal utilization of the precious radio resources. In particular, we propose an innovative TCP driven CAC algorithm, which shall take into account not only the QoS requirements, but also TCP statistics obtained through a proxy installed on the HAPS. Results show that the overall system performance in terms of both average throughput and blocking probability is significantly improved
The SECOMS broadband satellite network in the multimedia services and multi-environment coverage scenario
No full textProviding multimedia services is one of the major key issues in the world of telecommunications. If mobility and ubiquity is required, the satellite assumes an essential role due to its flexibility and to the possibility of global coverage. The paper briefly describes the SECOMS satellite system aiming at providing multimedia services to ubiquitous and mobile users. This will be fully addressed in a wide range of environments, from the open country to heavily dense cities and built-up areas as well as the indoor environment. The possibility to create a global broadband mobile communication system consisting of multiple system components with different characteristics will be investigated
TCP-Call Admission Control Interaction in Multiplatform Space Architectures
No full textThe implementation of efficient call admission control (CAC) algorithms is useful to prevent congestion and guarantee target quality of service (QoS). When TCP protocol is adopted, some inefficiencies can arise due to the peculiar evolution of the congestion window. The development of cross-layer techniques can greatly help to improve efficiency and flexibility for wireless networks. In this frame, the present paper addresses the introduction of TCP feedback into the CAC procedures in different nonterrestrial wireless architectures. CAC performance improvement is shown for different space-based architectures, including both satellites and high altitude platform (HAP) systems
A TCP Driven CAC scheme: efficient resource utilization in a leaky HAP-satellite integrated scenario
No full textAn integrated high altitude platform (HAP)-satellite communication system appears to be very suitable for a large set of scenarios including emergency situations, exceptional events, etc. In fact, the satellite capability to provide a broadband and ubiquitous access can be enhanced by the deployment of HAP that allows the use of low-power consuming, cost-efficient, and portable terminals. To obtain an optimum utilization of radio resource, without renouncing to QoS satisfaction, a suitable call admission control scheme must be implemented. Nevertheless, transmission control protocol (TCP) behavior, mainly affected by the high latency and shadowing events, can impact call admission control (CAC) performance. Therefore, it would be desirable that the CAC scheme takes into account also the TCP congestion window real evolution. We present an innovative CAC scheme that uses TCP statistics as one of its inputs and is able to manage different classes of users. Results show that CAC performance is significantly improved by introducing TCP statistics about network congestion as an input parameter
Network layer security: Design for a cross layer architecture
No full textTraditional modular layering schemes have served a major part in the development of a variety of protocols. However, as the physical layer impairments become more unpredictable, a cross layer design (CLD) which is dynamic in nature provides better performance. CLD introduces new challenges in protocol design as well as in the area of security. Using numerical analysis, we show that a link layer design employing header compression and cross layer signalling to protect protocol headers can limit packet discarding. This paper also reviews the IPsec protocol and describes how IPsec can be modified for cross layer architecture. © 2007 IEEE
Link design and fade countermeasures for multimedia satellite services in the frame of the SECOMS project
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