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Zlatanov N.,University of British Columbia | Ikhlef A.,Toshiba Corporation | Islam T.,University of British Columbia | Schober R.,Friedrich Alexander University Erlangen Nurnberg
IEEE Communications Magazine | Year: 2014

Cooperative communication can increase the throughput and/or extend the coverage of wireless networks. However, in conventional cooperative networks, half-duplex relays transmit and receive under a prefixed schedule, which does not allow them to exploit the best receiving and transmitting channels, thus limiting performance. Recently, new protocols have been proposed that circumvent this problem by making use of the additional flexibility offered by relays with buffers. Compared to conventional relaying protocols, these buffer-aided protocols provide significant gains in terms of throughput, diversity, and signal-to-noise ratio. This article outlines several buffer-aided relaying protocols for different network topologies, including one-way single- and multi-relay networks as well as two-way single-relay networks. Moreover, some practical challenges inherent to buffer-aided relaying, such as increased delay and complexity, and topics for future research are discussed. Copyright © 2014 IEEE. Source

Pattinson D.,Australian National University | Schroder L.,Friedrich Alexander University Erlangen Nurnberg
Electronic Notes in Theoretical Computer Science | Year: 2015

Comodels of Lawvere theories, i.e. models in Setop, model state spaces with algebraic access operations. Standard equational reasoning is known to be sound but incomplete for comodels. We give two sound and complete calculi for equational reasoning over comodels: an inductive calculus for equality-on-the-nose, and a coinductive/inductive calculus for equality modulo bisimulation which captures bisimulations syntactically through non-wellfounded proofs. © 2015 Published by Elsevier B.V. Source

Trammell B.,ETH Zurich | Casas P.,FTW | Rossi D.,University Pierre and Marie Curie | Bar A.,Friedrich Alexander University Erlangen Nurnberg | And 4 more authors.
IEEE Communications Magazine | Year: 2014

The Internet¿s universality is based on its decentralization and diversity. However, its distributed nature leads to operational brittleness and difficulty in identifying the root causes of performance and availability issues, especially when the involved systems span multiple administrative domains. The first step to address this fragmentation is coordinated measurement: we propose to complement the current Internet¿s data and control planes with a measurement plane, or mPlane for short. mPlane¿s distributed measurement infrastructure collects and analyzes traffic measurements at a wide variety of scales to monitor the network status. Its architecture is centered on a flexible control interface, allowing the incorporation of existing measurement tools through lightweight mPlane proxy components, and offering dynamic support for new capabilities. A focus on automated, iterative measurement makes the platform well-suited to troubleshooting support. This is supported by a reasoning system, which applies machine learning algorithms to learn from success and failure in drilling down to the root cause of a problem. This article describes the mPlane architecture and shows its applicability to several distributed measurement problems involving content delivery networks and Internet service roviders. A first case study presents the tracking and iterative analysis of cache selection policies in Akamai, while a second example focuses on the cooperation between Internet service providers and content delivery networks to better orchestrate their traffic engineering decisions and jointly improve their performance. © 2014 IEEE. Source

Yazbeck R.,Flinders University | Yazbeck R.,Center for Paediatric and Adolescent Gastroenterology | Sulda M.L.,Flinders University | Howarth G.S.,Flinders University | And 7 more authors.
Inflammatory Bowel Diseases | Year: 2010

Background: We have previously demonstrated that inhibition of dipeptidyl peptidase (DP) activity partially attenuates dextran sulfate sodium (DSS) colitis in mice. The aim of this study was to further investigate the mechanisms of this protection. Materials and Methods: Wildtype (WT) and DPIV-/- mice consumed 2% DSS in drinking water for 6 days to induce colitis. Mice were treated with saline or the DP inhibitors Ile-Pyrr-(2-CN)*TFA or Ile-Thia. DP mRNA and enzyme levels were measured in the colon. Glucagon-like peptide (GLP)-2 and GLP-1 concentrations were determined by radioimmunoassay, regulatory T-cells (Tregs) by fluorescence activated cell sorting (FACS) on FOXp3+T cells in blood, and neutrophil infiltration assessed by myeloperoxidase (MPO) assay. Results: DP8 and DP2 mRNA levels were increased (P < 0.05) in WT+saline mice compared to untreated WT mice with colitis. Cytoplasmic DP enzyme activity was increased (P < 0.05) in DPIV-/- mice at day 6 of DSS, while DP2 activity was increased (P < 0.05) in WT mice with colitis. GLP-1 (63%) and GLP-2 (50%) concentrations increased in WT+Ile-Pyrr-(2-CN)*TFA mice compared to day-0 controls. MPO activity was lower in WT+Ile-Thia and WT+Ile-Pyrr-(2-CN)*TFA treated mice compared to WT+saline (P < 0.001) at day 6 colitis. Conclusions: DP expression and activity are differentially regulated during DSS colitis, suggesting a pathophysiological role for these enzymes in human inflammatory bowel disease (IBD). DP inhibitors impaired neutrophil recruitment and maintenance of the Treg population during DSS-colitis, providing further preclinical evidence for the potential therapeutic use of these inhibitors in IBD. Finally, DPIV appears to play a critical role in mediating the protective effect of DP inhibitors. Copyright © 2010 Crohn's & Colitis Foundation of America, Inc. Source

Alberti M.,Friedrich Alexander University Erlangen Nurnberg | Fursich F.T.,Friedrich Alexander University Erlangen Nurnberg | Pandey D.K.,University of Rajasthan
Sedimentology | Year: 2013

In large parts of the Kachchh Basin, a Mesozoic rift basin situated in western India, the Oxfordian succession is characterized by strong condensation and several depositional gaps. The top layer of the Early to Middle Oxfordian Dhosa Oolite member, for which the term 'Dhosa Conglomerate Bed' is proposed, is an excellent marker horizon. Despite being mostly less than 1m thick, this unit can be followed for more than 100km throughout the Kachchh Mainland. A detailed sedimentological analysis has led to a complex model for its formation. Signs of subaerial weathering, including palaeokarst features, suggest at least two phases of emersion of the area. Metre-sized concretionary slabs floating in a fine-grained matrix, together with signs of synsedimentary tectonics, point to a highly active fault system causing recurrent earthquakes in the basin. The model takes into account information from outcrops outside the Kachchh Mainland and thereby considerably refines the current understanding of the basin history during the Late Jurassic. Large fault systems and possibly the so-called Median High uplift separated the basin into several sub-basins. The main reason for condensation in the Oxfordian succession is an inversion that affected large parts of the basin by cutting them off from the sediment supply. The Dhosa Conglomerate Bed is an excellent example, demonstrating the potential of condensed units in reconstructing depositional environments and events that took place during phases of non-deposition. Although condensed sequences occur frequently throughout the sedimentary record, they are particularly common around the Callovian to Oxfordian transition. A series of models has been proposed to explain these almost worldwide occurrences, ranging from eustatic sea-level highstands to glacial phases connected with regressions. The succession of the Kachchh Basin shows almost stable conditions across this boundary with only a slight fall in relative sea-level, reaching its minimum not before the late Early Oxfordian. © 2012 The Authors. Journal compilation © 2012 International Association of Sedimentologists. Source

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