A Delay-Tolerant Network Routing Algorithm Based on Column Generation

International audienceDelay-Tolerant Networks (DTN) model systems that are characterized by intermittent connectivity and frequent partitioning. Routing in DTNs has drawn much research effort recently. Since very different kinds of networks fall in the DTN category, many routing approaches have been proposed. In particular, the routing layer in some DTNs have information about the schedules of contacts between nodes and about data traffic demand. Such systems can benefit from a previously proposed routing algorithm based on linear programming that minimizes the average message delay. This algorithm, however, is known to have performance issues that limit its applicability to very simple scenarios. In this work, we propose an alternative linear programming approach for routing in Delay-Tolerant Networks. We show that our formulation is equivalent to that presented in a seminal work in this area, but it contains fewer LP constraints and has a structure suitable to the application of Column Generation (CG). Simulation shows that our CG implementation arrives at an optimal solution up to three orders of magnitude faster than the original linear program in the considered DTN examples

Transforming growth factor beta1 (TGF-ß1) levels in a rat model of induced pleural empyema

Purpose: To evaluate the concentration of transforming growth factor beta 1 (TGFB1) levels in a rat pleural effusion obtained by inoculation of intrapleural bacteria or turpentine through thoracentesis. Methods: Thirty-Nine Wistar rats were divided into three groups: Staphylococcus aureus (SA, n = 17); Streptococcus pneumoniae (SP, n = 12); and turpentine (control, n = 10). Pleural fluid was collected through ultrasound-guided thoracentesis 12 h, 24 h, and 36 h after instillation of bacteria or turpentine. Levels of TGFB1 were measured in pleural fluid. Results: At 12 h, mean TGFB1concentrations were 5.3450 pg/mL in the SA group, 5.3449 pg/mL in the SP group, and 5.3450 pg/mL in controls. At 24 h, they were 4.6700 pg/mL in the SA group, 4.6700 pg/mL in the SP group, and 4.6700 pg/mL in controls. At 36 h, they were 4.6699 pg/mL in the SA group and in control. No difference was observed among the groups in mean TGFB1concentration (p = 0.12); however, a significant intragroup reduction in mean TGFB1 was observed between 12 and 24 h (p < 0.01). Conclusion: The transforming growth factor beta 1 concentrations were not useful as a diagnostic tool or an early marker of infected pleural effusion