Backbone has been used extensively in various aspects (e.g., routing, route maintenance, broadcast, scheduling) for wireless networks. Previous methods are mostly designed to minimize the backbone size. However, in many applications, it is desirable to construct a backbone with small cost when each wireless node has a cost of being in the backbone. In this paper, we first show that previous methods specifically designed to minimize the backbone size may produce a backbone with a large cost. We then propose an efficient distributed method to construct a weighted sparse backbone with low cost. We prove that the total cost of the constructed backbone is within a small constant factor of the optimum for homogeneous networks when either the nodes' costs are smooth or the network maximum node degree is bounded. We also show that with a small modification the constructed backbone is efficient for unicast: the total cost (or hop) of the least cost (or hop) path connecting any two nodes using backbone is no more than 3 (or 4) times of the least cost (or hop) path in the original communication graph. As a side product, we give an efficient overlay based multicast structure whose total cost is no more than 10 times of the minimum when the network is modeled by UDG. Our theoretical results are corroborated by our simulation studies.
Software Defined Networks has seen tremendous growth and deployment in different types of networks. Compared to traditional networks it decouples the control logic from network layer devices, and centralizes it for efficient traffic forwarding and flow management across the domain. This multilayered architecture has data forwarding devices at the bottom in data plane, which are programmed by controllers in the control plane. The high level application or management plane interacts with control layer to program the whole network and enforce different policies. The interaction among these layers is done through interfaces which work as communication/programming protocols. In this survey, we present a comprehensive study of such interfaces available for southbound, northbound, and east/westbound communication. We have classified each type into different categories based on their properties and capabilities. Virtualization of networks devices is a common practice in Software Defined Networks. This paper also analyzes interface solution which work with different virtualization schemes. In addition, the paper highlights a number of short term and long term research challenges and open issues related to SDN interfaces.
The funding sources had no role in the design, execution, analyses and data interpretation of this study, and the decision to submit results for publication.Abstract (247 / 250 word limit) BACKGROUND. Matrix metalloproteinases (MMPs) are implicated as key regulators of tissue destruction in tuberculosis (TB) and may be a target for host-directed therapy. Here, we conducted a Phase randomized, double-blind, placebo-controlled trial investigating doxycycline, a licensed broad spectrum MMP inhibitor, in pulmonary TB patients.
METHODS.Thirty pulmonary TB patients were enrolled within 7 days of initiating anti-TB treatment and randomly assigned to receive either doxycycline 100 mg or placebo twice a day for 14 days in addition to standard care.
RESULTS.There were significant changes in the host transcriptome, and suppression of systemic and respiratory markers of tissue destruction with the doxycycline intervention. Whole blood RNA-sequencing demonstrated that doxycycline accelerated restoration of dysregulated gene expression patterns in TB towards normality, with more rapid down-regulation of type I and II interferon and innate immune response genes and concurrent up-regulation of B-cell modules relative to placebo. The effects persisted for 6 weeks after doxycycline was discontinued, concurrent with suppression of plasma MMP-1. In respiratory samples, doxycycline reduced MMP-1, -8, -9, -12 and -13 concentrations, suppressed type I collagen and elastin destruction, and reduced pulmonary cavity volume despite unchanged sputum Mycobacterium tuberculosis loads between the study arms. Two weeks of adjunctive doxycycline with standard anti-TB treatment was well-tolerated, with no serious adverse events related to doxycycline.CONCLUSION. These data demonstrate that adjunctive doxycycline with standard anti-TB treatment suppresses pathological MMPs in pulmonary tuberculosis patients, and suggest that larger studies on adjunctive doxycycline to limit immunopathology in TB are merited. 4
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