WorldWideScience

Sample records for network link failure

  1. Impact of Dual-Link Failures on Impairment-Aware Routed Networks

    DEFF Research Database (Denmark)

    Georgakilas, Konstantinos N; Katrinis, Kostas; Tzanakaki, Anna

    2010-01-01

    This paper evaluates the impact of dual-link failures on single-link failure resilient networks, while physical layer constraints are taken into consideration during demand routing, as dual link failures and equivalent situations appear to be quite probable in core optical networks. In particular...

  2. Robustness of complex networks with both unidirectional and bidirectional links against cascading failures

    Science.gov (United States)

    Ding, Lin; Leung, Victor C. M.; Tan, Min-Sheng

    2017-09-01

    The robustness of complex networks against cascading failures has been of great interest, while most of the researchers have considered undirected networks. However, to be more realistic, a part of links of many real systems should be described as unidirectional. In this paper, by applying three link direction-determining (DD) strategies, the tolerance of cascading failures is investigated in various networks with both unidirectional and bidirectional links. By extending the utilization of a classical global betweenness method, we propose a new cascading model, taking into account the weights of nodes and the directions of links. Then, the effects of unidirectional links on the network robustness against cascaded attacks are examined under the global load-based distribution mechanism. The simulation results show that the link-directed methods could not always lead to the decrease of the network robustness as indicated in the previous studies. For small-world networks, these methods certainly make the network weaker. However, for scale-free networks, the network robustness can be significantly improved by the link-directed method, especially for the method with non-random DD strategies. These results are independent of the weight parameter of the nodes. Due to the strongly improved robustness and easy realization with low cost on networks, the method for enforcing proper links to the unidirectional ones may be useful for leading to insights into the control of cascading failures in real-world networks, like communication and transportation networks.

  3. Restorability on 3-connected WDM Networks Under Single and Dual Physical Link Failures

    DEFF Research Database (Denmark)

    Gutierrez Lopez, Jose Manuel; Jensen, Michael; Riaz, Tahir

    2013-01-01

    This work studies the influence the network interconnection has over restoration techniques. The way physical links are distributed to interconnect network nodes has a great impact on parameters such as path distances when failures occur and restoration is applied. The work focuses on single...... and dual physical link failures restorability on WDM transport networks. This failure scenarios are tested over several 3-connected topologies, and studied in graph theory and network planning terms. In connection with the graphs, the resulting hop path distances and lengths are evaluated. In relation...... to network planning, the trade-off network length vs. performance of the different topological options is studied. The results show how 3-connected graphs could provide a reasonable trade-off between costs, link failure rates, and restored path parameters....

  4. Single and Dual Physical Link Failures Stability Effect on Degree Three WDM Networks

    DEFF Research Database (Denmark)

    Gutierrez Lopez, Jose Manuel; Georgakilas, Konstantinos; Riaz, M. Tahir

    2010-01-01

    This paper studies the effects of Single and Dual physical link failures to the stability of WDM networks when deployed as regular 3-degree structures. The failure impact on the source-destination pair connections is evaluated for the different topology scenarios. In this way it is possible...... to provide an overview of the failure effects and their relation to network metrics such as availability or cost. The results quantify how much the different network interconnection designs are affected by Single and Dual Physical link failures. The case study treats a realistic scenario, the interconnection...... of the NSFNET topology nodes. The main conclusions show that, when networks are designed under the same conditions, there is a linear relation between average downtime and ratio of connections affected by failures. Moreover, the most expensive optimized topologies to deploy provide higher availability....

  5. Enhancing network performance under single link failure with AS-disjoint BGP extension

    DEFF Research Database (Denmark)

    Manolova, Anna Vasileva; Romeral, S.; Ruepp, Sarah Renée

    2009-01-01

    In this paper we propose an enhancement of the BGP protocol for obtaining AS-disjoint paths in GMPLS multi-domain networks. We evaluate the benefits of having AS-disjoint paths under single inter-domain link failure for two main applications: routing of future connection requests during routing...... protocol re-convergence and applying multi-domain restoration as survivability mechanism in case of a single link failure. The proposed BGP modification is a simple and effective solution for disjoint path selection in connection-oriented multi-domain networks. Our results show that applying the proper...... failure notification method combined with our proposal reduces the blocking of new connection requests under protocol re-convergence. Furthermore. we show that our proposal is a valuable complementary process for increasing the network resilience....

  6. A Novel Dedicated Route Protection Scheme for Survivability of Link Failure in Elastic Optical Networks

    Directory of Open Access Journals (Sweden)

    Sridhar Iyer

    2017-11-01

    Full Text Available The spectrally efficient transportation of the high bit rate(s data is achievable by the Elastic optical networks (EONs. However, in the EONs, owing to the failure occurrence even in an individual simple element, different service(s maybe interrupted. Hence, it is imperative that the schemes for survivability be developed so that the issues due to the possible failure(s can be overcome. In the current work, in view of survivability of the link failure(s in the EONs, we propose the Spectrum Continuity and Contiguity Established DRP (SCC-E-DRP algorithm which is a novel dedicated route protection (DRP scheme that attempts to avoid the problem of trap topology during its exploration for a pair of link disjoint path. Further, to evaluate the link disjoint paths, we resort to the use of the SCC Established Shortest Route (SCC-E-SR algorithm which is a modified Dijkstra’s algorithm based scheme that selects the path(s pair(s based on the end-toend SCC. We conduct extensive simulations considering realistic network topologies, and compare the performance of the SCCE-DRP scheme with the existing techniques. The obtained results show that, compared to the existing schemes, the SCC-E-DRP scheme achieves better results in terms of blocking probability.

  7. Cascaded failures in weighted networks

    Science.gov (United States)

    Mirzasoleiman, Baharan; Babaei, Mahmoudreza; Jalili, Mahdi; Safari, Mohammadali

    2011-10-01

    Many technological networks can experience random and/or systematic failures in their components. More destructive situations can happen if the components have limited capacity, where the failure in one of them might lead to a cascade of failures in other components, and consequently break down the structure of the network. In this paper, the tolerance of cascaded failures was investigated in weighted networks. Three weighting strategies were considered including the betweenness centrality of the edges, the product of the degrees of the end nodes, and the product of their betweenness centralities. Then, the effect of the cascaded attack was investigated by considering the local weighted flow redistribution rule. The capacity of the edges was considered to be proportional to their initial weight distribution. The size of the survived part of the attacked network was determined in model networks as well as in a number of real-world networks including the power grid, the internet in the level of autonomous system, the railway network of Europe, and the United States airports network. We found that the networks in which the weight of each edge is the multiplication of the betweenness centrality of the end nodes had the best robustness against cascaded failures. In other words, the case where the load of the links is considered to be the product of the betweenness centrality of the end nodes is favored for the robustness of the network against cascaded failures.

  8. Modeling Epidemic Network Failures

    DEFF Research Database (Denmark)

    Ruepp, Sarah Renée; Fagertun, Anna Manolova

    2013-01-01

    This paper presents the implementation of a failure propagation model for transport networks when multiple failures occur resulting in an epidemic. We model the Susceptible Infected Disabled (SID) epidemic model and validate it by comparing it to analytical solutions. Furthermore, we evaluate...

  9. Link failure detection in a parallel computer

    Science.gov (United States)

    Archer, Charles J.; Blocksome, Michael A.; Megerian, Mark G.; Smith, Brian E.

    2010-11-09

    Methods, apparatus, and products are disclosed for link failure detection in a parallel computer including compute nodes connected in a rectangular mesh network, each pair of adjacent compute nodes in the rectangular mesh network connected together using a pair of links, that includes: assigning each compute node to either a first group or a second group such that adjacent compute nodes in the rectangular mesh network are assigned to different groups; sending, by each of the compute nodes assigned to the first group, a first test message to each adjacent compute node assigned to the second group; determining, by each of the compute nodes assigned to the second group, whether the first test message was received from each adjacent compute node assigned to the first group; and notifying a user, by each of the compute nodes assigned to the second group, whether the first test message was received.

  10. Epidemic Network Failures in Optical Transport Networks

    DEFF Research Database (Denmark)

    Ruepp, Sarah Renée; Katsikas, Dimitrios; Fagertun, Anna Manolova

    2013-01-01

    This paper presents a failure propagation model for transport networks which are affected by epidemic failures. The network is controlled using the GMPLS protocol suite. The Susceptible Infected Disabled (SID) epidemic model is investigated and new signaling functionality of GMPLS to support epid...... epidemic failure resolution is proposed. The results provide important input to service recovery mechanisms under epidemic failures.......This paper presents a failure propagation model for transport networks which are affected by epidemic failures. The network is controlled using the GMPLS protocol suite. The Susceptible Infected Disabled (SID) epidemic model is investigated and new signaling functionality of GMPLS to support...

  11. Reliable Broadcast under Cascading Failures in Interdependent Networks

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Sisi [ORNL; Lee, Sangkeun (Matt) [ORNL; Chinthavali, Supriya [ORNL; Shankar, Mallikarjun (Arjun) [ORNL

    2017-01-01

    Reliable broadcast is an essential tool to disseminate information among a set of nodes in the presence of failures. We present a novel study of reliable broadcast in interdependent networks, in which the failures in one network may cascade to another network. In particular, we focus on the interdependency between the communication network and power grid network, where the power grid depends on the signals from the communication network for control and the communication network depends on the grid for power. In this paper, we build a resilient solution to handle crash failures in the communication network that may cause cascading failures and may even partition the network. In order to guarantee that all the correct nodes deliver the messages, we use soft links, which are inactive backup links to non-neighboring nodes that are only active when failures occur. At the core of our work is a fully distributed algorithm for the nodes to predict and collect the information of cascading failures so that soft links can be maintained to correct nodes prior to the failures. In the presence of failures, soft links are activated to guarantee message delivery and new soft links are built accordingly for long term robustness. Our evaluation results show that the algorithm achieves low packet drop rate and handles cascading failures with little overhead.

  12. Cascade of links in complex networks

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Yeqian; Sun, Bihui [Department of Management Science, School of Government, Beijing Normal University, 100875 Beijing (China); Zeng, An, E-mail: anzeng@bnu.edu.cn [School of Systems Science, Beijing Normal University, 100875 Beijing (China)

    2017-01-30

    Cascading failure is an important process which has been widely used to model catastrophic events such as blackouts and financial crisis in real systems. However, so far most of the studies in the literature focus on the cascading process on nodes, leaving the possibility of link cascade overlooked. In many real cases, the catastrophic events are actually formed by the successive disappearance of links. Examples exist in the financial systems where the firms and banks (i.e. nodes) still exist but many financial trades (i.e. links) are gone during the crisis, and the air transportation systems where the airports (i.e. nodes) are still functional but many airlines (i.e. links) stop operating during bad weather. In this letter, we develop a link cascade model in complex networks. With this model, we find that both artificial and real networks tend to collapse even if a few links are initially attacked. However, the link cascading process can be effectively terminated by setting a few strong nodes in the network which do not respond to any link reduction. Finally, a simulated annealing algorithm is used to optimize the location of these strong nodes, which significantly improves the robustness of the networks against the link cascade. - Highlights: • We propose a link cascade model in complex networks. • Both artificial and real networks tend to collapse even if a few links are initially attacked. • The link cascading process can be effectively terminated by setting a few strong nodes. • A simulated annealing algorithm is used to optimize the location of these strong nodes.

  13. Information networks and links

    Science.gov (United States)

    Davydov, G. B.

    The basic operating principles of a telecommunications network are described. The technical characteristics of three types of telecommunications network are discussed, including voice-based (telephone) systems; television networks; and data (digital) communications. Among the specific transmission and channeling systems described are: satellite relays; microwae relays; ground based microwave relays; and pulse code modulation; (PCM). The integration of world wide systems for coordinating voice data, and video communications is also discussed.

  14. Critical links and nonlocal rerouting in complex supply networks

    CERN Document Server

    Witthaut, Dirk; Zhang, Xiaozhu; Hallerberg, Sarah; Timme, Marc

    2015-01-01

    Link failures repeatedly induce large-scale outages in power grids and other supply networks. Yet, it is still not well understood, which links are particularly prone to inducing such outages. Here we analyze how the nature and location of each link impact the network's capability to maintain stable supply. We propose two criteria to identify critical links on the basis of the topology and the load distribution of the network prior to link failure. They are determined via a link's redundant capacity and a renormalized linear response theory we derive. These criteria outperform critical link prediction based on local measures such as loads. The results not only further our understanding of the physics of supply networks in general. As both criteria are available before any outage from the state of normal operation, they may also help real-time monitoring of grid operation, employing counter-measures and support network planning and design.

  15. Dynamic Evolution in Social Cooperation Networks with Node Failure

    OpenAIRE

    Yaofeng Zhang; Renbin Xiao

    2013-01-01

    Social cooperation networks are a kind of social networks in which individuals are linked through cooperation. Interference of economic crises, natural disasters and other emergencies may cause the node fails in social cooperation networks. To further study the influences of node failure on the total fitness degree and the cooperative ratio in social cooperation networks, the update rules of individual strategy and networks self-repair are constructed on the basis of the social cooperation ne...

  16. Cascading failures in spatially-embedded random networks.

    Science.gov (United States)

    Asztalos, Andrea; Sreenivasan, Sameet; Szymanski, Boleslaw K; Korniss, Gyorgy

    2014-01-01

    Cascading failures constitute an important vulnerability of interconnected systems. Here we focus on the study of such failures on networks in which the connectivity of nodes is constrained by geographical distance. Specifically, we use random geometric graphs as representative examples of such spatial networks, and study the properties of cascading failures on them in the presence of distributed flow. The key finding of this study is that the process of cascading failures is non-self-averaging on spatial networks, and thus, aggregate inferences made from analyzing an ensemble of such networks lead to incorrect conclusions when applied to a single network, no matter how large the network is. We demonstrate that this lack of self-averaging disappears with the introduction of a small fraction of long-range links into the network. We simulate the well studied preemptive node removal strategy for cascade mitigation and show that it is largely ineffective in the case of spatial networks. We introduce an altruistic strategy designed to limit the loss of network nodes in the event of a cascade triggering failure and show that it performs better than the preemptive strategy. Finally, we consider a real-world spatial network viz. a European power transmission network and validate that our findings from the study of random geometric graphs are also borne out by simulations of cascading failures on the empirical network.

  17. Signed Link Analysis in Social Media Networks

    OpenAIRE

    Beigi, Ghazaleh; Tang, Jiliang; Liu, Huan

    2016-01-01

    Numerous real-world relations can be represented by signed networks with positive links (e.g., trust) and negative links (e.g., distrust). Link analysis plays a crucial role in understanding the link formation and can advance various tasks in social network analysis such as link prediction. The majority of existing works on link analysis have focused on unsigned social networks. The existence of negative links determines that properties and principles of signed networks are substantially dist...

  18. Enhanced Multiple Routing Configurations For Fast IP Network Recovery From Multiple Failures

    OpenAIRE

    T Anji Kumar & Dr MHM Krishna Prasad

    2011-01-01

    Now a days, Internet plays a major role in our day to day activities e.g., for online transactions,online shopping, and other network related applications. Internet suffers from slow convergenceof routing protocols after a network failure which becomes a growing problem. Multiple RoutingConfigurations [MRC] recovers network from single node/link failures, but does not supportnetwork from multiple node/link failures. In this paper, we propose Enhanced MRC [EMRC], tosupport multiple node/link f...

  19. Enhanced Multiple Routing Configurations for Fast IP Network Recovery from Multiple Failures

    OpenAIRE

    T. Anji Kumar; Dr MHM Krishna Prasad

    2011-01-01

    Now a days, Internet plays a major role in our day to day activities e.g., for online transactions, online shopping, and other network related applications. Internet suffers from slow convergence of routing protocols after a network failure which becomes a growing problem. Multiple Routing Configurations [MRC] recovers network from single node/link failures, but does not support network from multiple node/link failures. In this paper, we propose Enhanced MRC [EMRC], to support multiple node/l...

  20. Robustness of networks against cascading failures

    Science.gov (United States)

    Dou, Bing-Lin; Wang, Xue-Guang; Zhang, Shi-Yong

    2010-06-01

    Inspired by other related works, this paper proposes a non-linear load-capacity model against cascading failures, which is more suitable for real networks. The simulation was executed on the B-A scale-free network, E-R random network, Internet AS level network, and the power grid of the western United States. The results show that the model is feasible and effective. By studying the relationship between network cost and robustness, we find that the model can defend against cascading failures better and requires a lower investment cost when higher robustness is required.

  1. Robustness of network controllability in cascading failure

    Science.gov (United States)

    Chen, Shi-Ming; Xu, Yun-Fei; Nie, Sen

    2017-04-01

    It is demonstrated that controlling complex networks in practice needs more inputs than that predicted by the structural controllability framework. Besides, considering the networks usually faces to the external or internal failure, we define parameters to evaluate the control cost and the variation of controllability after cascades, exploring the effect of number of control inputs on the controllability for random networks and scale-free networks in the process of cascading failure. For different topological networks, the results show that the robustness of controllability will be stronger through allocating different control inputs and edge capacity.

  2. Network Performance Improvement under Epidemic Failures in Optical Transport Networks

    DEFF Research Database (Denmark)

    Fagertun, Anna Manolova; Ruepp, Sarah Renée

    2013-01-01

    In this paper we investigate epidemic failure spreading in large- scale GMPLS-controlled transport networks. By evaluating the effect of the epidemic failure spreading on the network, we design several strategies for cost-effective network performance improvement via differentiated repair times....... First we identify the most vulnerable and the most strategic nodes in the network. Then, via extensive simulations we show that strategic placement of resources for improved failure recovery has better performance than randomly assigning lower repair times among the network nodes. Our OPNET simulation...

  3. Achieving fast and stable failure detection in WDM Networks

    Science.gov (United States)

    Gao, Donghui; Zhou, Zhiyu; Zhang, Hanyi

    2005-02-01

    In dynamic networks, the failure detection time takes a major part of the convergence time, which is an important network performance index. To detect a node or link failure in the network, traditional protocols, like Hello protocol in OSPF or RSVP, exchanges keep-alive messages between neighboring nodes to keep track of the link/node state. But by default settings, it can get a minimum detection time in the measure of dozens of seconds, which can not meet the demands of fast network convergence and failure recovery. When configuring the related parameters to reduce the detection time, there will be notable instability problems. In this paper, we analyzed the problem and designed a new failure detection algorithm to reduce the network overhead of detection signaling. Through our experiment we found it is effective to enhance the stability by implicitly acknowledge other signaling messages as keep-alive messages. We conducted our proposal and the previous approaches on the ASON test-bed. The experimental results show that our algorithm gives better performances than previous schemes in about an order magnitude reduction of both false failure alarms and queuing delay to other messages, especially under light traffic load.

  4. PIPELINES AS COMMUNICATION NETWORK LINKS

    Energy Technology Data Exchange (ETDEWEB)

    Kelvin T. Erickson; Ann Miller; E. Keith Stanek; C.H. Wu; Shari Dunn-Norman

    2005-03-14

    This report presents the results of an investigation into two methods of using the natural gas pipeline as a communication medium. The work addressed the need to develop secure system monitoring and control techniques between the field and control centers and to robotic devices in the pipeline. In the first method, the pipeline was treated as a microwave waveguide. In the second method, the pipe was treated as a leaky feeder or a multi-ground neutral and the signal was directly injected onto the metal pipe. These methods were tested on existing pipeline loops at UMR and Batelle. The results reported in this report indicate the feasibility of both methods. In addition, a few suitable communication link protocols for this network were analyzed.

  5. LinkMind: Link Optimization in Swarming Mobile Sensor Networks

    Directory of Open Access Journals (Sweden)

    Trung Dung Ngo

    2011-08-01

    Full Text Available A swarming mobile sensor network is comprised of a swarm of wirelessly connected mobile robots equipped with various sensors. Such a network can be applied in an uncertain environment for services such as cooperative navigation and exploration, object identification and information gathering. One of the most advantageous properties of the swarming wireless sensor network is that mobile nodes can work cooperatively to organize an ad-hoc network and optimize the network link capacity to maximize the transmission of gathered data from a source to a target. This paper describes a new method of link optimization of swarming mobile sensor networks. The new method is based on combination of the artificial potential force guaranteeing connectivities of the mobile sensor nodes and the max-flow min-cut theorem of graph theory ensuring optimization of the network link capacity. The developed algorithm is demonstrated and evaluated in simulation.

  6. LinkMind: Link Optimization in Swarming Mobile Sensor Networks

    DEFF Research Database (Denmark)

    Ngo, Trung Dung

    2012-01-01

    optimization of swarming mobile sensor networks. The new method is based on combination of the artificial potential force guaranteeing connectivities of the mobile sensor nodes and the max-flow min-cut theorem of graph theory ensuring optimization of the network link capacity. The developed algorithm......A swarming mobile sensor network is comprised of a swarm of wirelessly connected mobile robots equipped with various sensors. Such a network can be applied in an uncertain environment for services such as cooperative navigation and exploration, object identification and information gathering. One...... of the most advantageous properties of the swarming wireless sensor network is that mobile nodes can work cooperatively to organize an ad-hoc network and optimize the network link capacity to maximize the transmission of gathered data from a source to a target. This paper describes a new method of link...

  7. [Competence Network Heart Failure (CNHF). Together against heart failure].

    Science.gov (United States)

    Ertl, Georg; Störk, Stefan; Börste, Rita

    2016-04-01

    Heart failure is one of the most urgent medical and socio-economic challenges of the 21(st) century. Up to three million people are affected in Germany; this means one in ten people over the age of 65  live with heart failure. The current demographic changes will accentuate the importance of this grave health problem. The care of patients with heart failure, as well as the associated research mandates a comprehensive, multidisciplinary approach. The Competence Network Heart Failure (CNHF) pursues this objective. CNHF is a research alliance with 11 sites in Germany and was funded by the Federal Ministry of Research (BMBF) from 2003 through 2014. Since January 2015, the network has been an associate cooperating partner of the German Centre for Cardiovascular Research (DZHK). During the 12-year funding period by the BMBF, scientists in the field of heart failure from 30 university hospitals, 5 research institutes, 7 heart centers, 17 cardiovascular clinics, over 200 general practitioners, 4 rehabilitation clinics, as well as numerous organizations and associations were involved in cooperative CNHF research. In the context of 22 projects, the CNHF covered basic, clinical, and health care research, and generated numerous groundbreaking insights into disease mechanisms, as well as diagnosis and treatment of heart failure, which are documented in more than 350 publications. With its central study database and bank of biomaterials, the network has set up a Europe-wide unique research resource, which can be used in the future for national and international cooperations with the DZHK and other partners. Furthermore, the CNHF strongly promotes nation- and Europe-wide public relations and heart failure awareness activities.

  8. Relationship-Oriented Software Defined AS-Level Fast Rerouting for Multiple Link Failures

    Directory of Open Access Journals (Sweden)

    Chunxiu Li

    2015-01-01

    Full Text Available Large-scale deployments of mission-critical services have led to stringent demands on Internet routing, but frequently occurring network failures can dramatically degrade the network performance. However, Border Gateway Protocol (BGP can not react quickly to recover from them. Although extensive research has been conducted to deal with the problem, the multiple failure scenarios have never been properly addressed due to the limit of distributed control plane. In this paper, we propose a local fast reroute approach to effectively recover from multiple link failures in one administrative domain. The principle of Software Defined Networking (SDN is used to achieve the software defined AS-level fast rerouting. Considering AS relationships, efficient algorithms are proposed to automatically and dynamically find protection paths for multiple link failures; then OpenFlow forwarding rules are installed on routers to provide data forwarding continuity. Our approach is able to ensure applicability to ASes with flexibility and adaptability to multiple link failures, contributing toward improving the network performance. Through experimental results, we show that our proposal provides effective failure recovery and does not introduce significant control overhead to the network.

  9. Synchronous consensus under hybrid process and link failures.

    Science.gov (United States)

    Biely, Martin; Schmid, Ulrich; Weiss, Bettina

    2011-09-16

    WE INTRODUCE A COMPREHENSIVE HYBRID FAILURE MODEL FOR SYNCHRONOUS DISTRIBUTED SYSTEMS, WHICH EXTENDS A CONVENTIONAL HYBRID PROCESS FAILURE MODEL BY ADDING COMMUNICATION FAILURES: Every process in the system is allowed to commit up to fℓs send link failures and experience up to fℓr receive link failures per round here, without being considered faulty; up to some fℓsa≤fℓs and fℓra≤fℓr among those may even cause erroneous messages rather than just omissions. In a companion paper (Schmid et al. (2009) [14]), devoted to a complete suite of related impossibility results and lower bounds, we proved that this model surpasses all existing link failure modeling approaches in terms of the assumption coverage in a simple probabilistic setting.In this paper, we show that several well-known synchronous consensus algorithms can be adapted to work under our failure model, provided that the number of processes required for tolerating process failures is increased by small integer multiples of fℓs, fℓr, fℓsa, fℓra. This is somewhat surprising, given that consensus in the presence of unrestricted link failures and mobile (moving) process omission failures is impossible. We provide detailed formulas for the required number of processes and rounds, which reveal that the lower bounds established in our companion paper are tight. We also explore the power and limitations of authentication in our setting, and consider uniform consensus algorithms, which guarantee their properties also for benign faulty processes.

  10. Strategies for optical transport network recovery under epidemic network failures

    DEFF Research Database (Denmark)

    Ruepp, Sarah Renée; Fagertun, Anna Manolova; Kosteas, Vasileios

    2015-01-01

    manner under different failure scenarios. This work evaluates two rerouting strategies and proposes four policies for failure handling in a connection-oriented optical transport network, under generalized multiprotocol label switching control plane. The performance of the strategies and the policies...... are evaluated under multiple correlated large-scale failures. We employ the Susceptible–Infected– Disabled epidemic failure spreading model and look into possible trade-offs between resiliency and resource effi- ciency. Via extensive simulations, we show that source rerouting outperforms on-site rerouting......, and that there exist a clear trade-off between policy performance and network resource consumption, which must be addressed by network operators for improved robustness of their transport infrastructures. Applying proactive methods for avoiding areas where epidemic failures spread results in 50% less connections...

  11. Analysis of cascading failure in gene networks

    Directory of Open Access Journals (Sweden)

    Shudong eWang

    2012-12-01

    Full Text Available It is an important subject to research the functional mechanism of cancer-related genes make in formation and development of cancers. The modern methodology of data analysis plays a very important role for deducing the relationship between cancers and cancer-related genes and analyzing functional mechanism of genome. In this research, we construct mutual information networks using gene expression profiles of glioblast and renal in normal condition and cancer conditions. We investigate the relationship between structure and robustness in gene networks of the two tissues using a cascading failure model based on betweenness centrality. Define some important parameters such as the percentage of failure nodes of the network, the average size-ratio of cascading failure and the cumulative probability of size-ratio of cascading failure to measure the robustness of the networks. By comparing control group and experiment groups, we find that the networks of experiment groups are more robust than that of control group. The gene that can cause large scale failure is called structural key gene (SKG. Some of them have been confirmed to be closely related to the formation and development of glioma and renal cancer respectively. Most of them are predicted to play important roles during the formation of glioma and renal cancer, maybe the oncogenes, suppressor genes, and other cancer candidate genes in the glioma and renal cancer cells. However, these studies provide little information about the detailed roles of identified cancer genes.

  12. The impact of a network split on cascading failure processes

    OpenAIRE

    Sloothaak, Fiona; Borst, Sem C.; Zwart, Bert

    2017-01-01

    Cascading failure models are typically used to capture the phenomenon where failures possibly trigger further failures in succession, causing knock-on effects. In many networks this ultimately leads to a disintegrated network where the failure propagation continues independently across the various components. In order to gain insight in the impact of network splitting on cascading failure processes, we extend a well-established cascading failure model for which the number of failures obeys a ...

  13. Complex interdependent supply chain networks: Cascading failure and robustness

    Science.gov (United States)

    Tang, Liang; Jing, Ke; He, Jie; Stanley, H. Eugene

    2016-02-01

    A supply chain network is a typical interdependent network composed of an undirected cyber-layer network and a directed physical-layer network. To analyze the robustness of this complex interdependent supply chain network when it suffers from disruption events that can cause nodes to fail, we use a cascading failure process that focuses on load propagation. We consider load propagation via connectivity links as node failure spreads through one layer of an interdependent network, and we develop a priority redistribution strategy for failed loads subject to flow constraint. Using a giant component function and a one-to-one directed interdependence relation between nodes in a cyber-layer network and physical-layer network, we construct time-varied functional equations to quantify the dynamic process of failed loads propagation in an interdependent network. Finally, we conduct a numerical simulation for two cases, i.e., single node removal and multiple node removal at the initial disruption. The simulation results show that when we increase the number of removed nodes in an interdependent supply chain network its robustness undergoes a first-order discontinuous phase transition, and that even removing a small number of nodes will cause it to crash.

  14. Optimisation of the link volume for weakest link failure prediction in NBG-18 nuclear graphite

    Energy Technology Data Exchange (ETDEWEB)

    Hindley, Michael P., E-mail: makke@mweb.co.za [Pebble Bed Modular Reactor (Pty) Ltd., PO Box 12271, Centurion 0046 (South Africa); Groenwold, Albert A.; Blaine, Deborah C.; Becker, Thorsten H. [Department of Mechanical and Mechatronic Engineering, Stellenbosch University, Private Bag X1, Matieland 7602 (South Africa)

    2014-07-01

    This paper describes the process for approximating the optimal size of a link volume required for weakest link failure calculation in nuclear graphite, with NBG-18 used as an example. As part of the failure methodology, the link volume is defined in terms of two grouping criteria. The first criterion is a factor of the maximum grain size and the second criterion is a function of an equivalent stress limit. A methodology for approximating these grouping criteria is presented. The failure methodology employs finite element analysis (FEA) in order to predict the failure load, at 50% probability of failure. The average experimental failure load, as determined for 26 test geometries, is used to evaluate the accuracy of the weakest link failure calculations. The influence of the two grouping criteria on the failure load prediction is evaluated by defining an error in prediction across all test cases. Mathematical optimisation is used to find the minimum error across a range of test case failure predictions. This minimum error is shown to deliver the most accurate failure prediction across a whole range of components, although some test cases in the range predict conservative failure load. The mathematical optimisation objective function is penalised to account for non-conservative prediction of the failure load for any test case. The optimisation is repeated and a link volume found for conservative failure prediction. The failure prediction for each test case is evaluated, in detail, for the proposed link volumes. Based on the analysis, link design volumes for NBG-18 are recommended for either accurate or conservative failure prediction.

  15. Robustness of Interrelated Traffic Networks to Cascading Failures

    Science.gov (United States)

    Su, Zhen; Li, Lixiang; Peng, Haipeng; Kurths, Jürgen; Xiao, Jinghua; Yang, Yixian

    2014-06-01

    The vulnerability to real-life networks against small initial attacks has been one of outstanding challenges in the study of interrelated networks. We study cascading failures in two interrelated networks S and B composed from dependency chains and connectivity links respectively. This work proposes a realistic model for cascading failures based on the redistribution of traffic flow. We study the Barabási-Albert networks (BA) and Erdős-Rényi graphs (ER) with such structure, and found that the efficiency sharply decreases with increasing percentages of the dependency nodes for removing a node randomly. Furthermore, we study the robustness of interrelated traffic networks, especially the subway and bus network in Beijing. By analyzing different attacking strategies, we uncover that the efficiency of the city traffic system has a non-equilibrium phase transition at low capacity of the networks. This explains why the pressure of the traffic overload is relaxed by singly increasing the number of small buses during rush hours. We also found that the increment of some buses may release traffic jam caused by removing a node of the bus network randomly if the damage is limited. However, the efficiencies to transfer people flow will sharper increase when the capacity of the subway network αS > α0.

  16. Cascading Edge Failures: A Dynamic Network Process

    CERN Document Server

    Zhang, June

    2016-01-01

    This paper considers the dynamics of edges in a network. The Dynamic Bond Percolation (DBP) process models, through stochastic local rules, the dependence of an edge $(a,b)$ in a network on the states of its neighboring edges. Unlike previous models, DBP does not assume statistical independence between different edges. In applications, this means for example that failures of transmission lines in a power grid are not statistically independent, or alternatively, relationships between individuals (dyads) can lead to changes in other dyads in a social network. We consider the time evolution of the probability distribution of the network state, the collective states of all the edges (bonds), and show that it converges to a stationary distribution. We use this distribution to study the emergence of global behaviors like consensus (i.e., catastrophic failure or full recovery of the entire grid) or coexistence (i.e., some failed and some operating substructures in the grid). In particular, we show that, depending on...

  17. Link prediction in weighted networks

    DEFF Research Database (Denmark)

    Wind, David Kofoed; Mørup, Morten

    2012-01-01

    Many complex networks feature relations with weight information. Some models utilize this information while other ignore the weight information when inferring the structure. In this paper we investigate if edge-weights when modeling real networks, carry important information about the network...

  18. OPTIMIZATION OF DISJOINTS FOR MINIMIZATION OF FAILURE IN WDM OPTICAL NETWORK

    Directory of Open Access Journals (Sweden)

    A. Renugadevi

    2015-06-01

    Full Text Available In an optical network, the fiber optic cable is used for communication between the nodes in a network by passing lights. The main problem in optical network is finding the link disjoints as well as optimal solution for the disjoints. To tolerate a single link failure in the network, the enhanced active path first algorithm is used which computes the re-routed back-up path. The multiple link failure in a network called fibre span disjoint path problem is solved using integer linear programming algorithm. The loop back recovery is used to provide pre-planned recovery of link or node failures in a network which allows dynamic choice of routes over pre-planned directions. Considering reliability in a mesh networks, the reliability algorithm helps to achieve the maximum reliability in two-path protection. It addresses the multiple disjoint failures that arise in a network and discusses the best solution between paths shared nodes or links. The unified algorithm is used to generate the optimal results with minimum cost for multiple link failures. The heuristic algorithm namely maximum arbitrary double-link protection algorithm helps to pre-compute the back-up path for double-link failures. In all the above approaches the shortest optimized path must be improved. To find the best shortest path, link-disjoint lightpath algorithm is designed to compute the disjoint occurred in a network and it also satisfies the wavelength continuity constraint in wavelength division multiplexing. A polynomial time algorithm Wavelength Division Multiplexing – Passive Optical Networking is used to compute the disjoint happen in the network. The overall time efficiency is analyzed and performance is evaluated through simulations.

  19. Demand on Temporary Parallel Route Recovery for Frequent Link Failure in VANET

    Science.gov (United States)

    Sakthi Ganesh, M.; Venkata krishna, P.

    2015-03-01

    Vehicular Ad-hoc Network (VANET) is an upcoming technology for communication between vehicles during the trip, which provides Internet connectivity resulting in safer roads giving access important alerts and comfort during the slip. VANET technology integrates wireless cellular and ad hoc for seamless connectivity between vehicles. VANETs are organizations that allow vehicles to communicate with each other. Wireless-vice can send data to nearby vehicles, and messages can be transported from one vehicle to another, so that the information can be broadcast throughout the metropolis. In the network, link failure is very common due to the high mobility of clients. Frequent link failure occurs as packets do not arrive at the respective goals. The mechanism proposed here establishes a form of route discovery packet parallel to the real time application to be extradited to the destination, while minimizing losses. The primary aim is to establish parallel paths during link failure scenarios for real-time applications to provide information to their destination safely. During link failures, the recovery road is parallel to the fixed temporary parallel path between the nodes. The node before the link failure packet buffers, after setting the new parallel paths before the packets stored in the buffer via the destination newly created path.

  20. Link prediction in multiplex online social networks.

    Science.gov (United States)

    Jalili, Mahdi; Orouskhani, Yasin; Asgari, Milad; Alipourfard, Nazanin; Perc, Matjaž

    2017-02-01

    Online social networks play a major role in modern societies, and they have shaped the way social relationships evolve. Link prediction in social networks has many potential applications such as recommending new items to users, friendship suggestion and discovering spurious connections. Many real social networks evolve the connections in multiple layers (e.g. multiple social networking platforms). In this article, we study the link prediction problem in multiplex networks. As an example, we consider a multiplex network of Twitter (as a microblogging service) and Foursquare (as a location-based social network). We consider social networks of the same users in these two platforms and develop a meta-path-based algorithm for predicting the links. The connectivity information of the two layers is used to predict the links in Foursquare network. Three classical classifiers (naive Bayes, support vector machines (SVM) and K-nearest neighbour) are used for the classification task. Although the networks are not highly correlated in the layers, our experiments show that including the cross-layer information significantly improves the prediction performance. The SVM classifier results in the best performance with an average accuracy of 89%.

  1. Link prediction in multiplex online social networks

    Science.gov (United States)

    Jalili, Mahdi; Orouskhani, Yasin; Asgari, Milad; Alipourfard, Nazanin; Perc, Matjaž

    2017-02-01

    Online social networks play a major role in modern societies, and they have shaped the way social relationships evolve. Link prediction in social networks has many potential applications such as recommending new items to users, friendship suggestion and discovering spurious connections. Many real social networks evolve the connections in multiple layers (e.g. multiple social networking platforms). In this article, we study the link prediction problem in multiplex networks. As an example, we consider a multiplex network of Twitter (as a microblogging service) and Foursquare (as a location-based social network). We consider social networks of the same users in these two platforms and develop a meta-path-based algorithm for predicting the links. The connectivity information of the two layers is used to predict the links in Foursquare network. Three classical classifiers (naive Bayes, support vector machines (SVM) and K-nearest neighbour) are used for the classification task. Although the networks are not highly correlated in the layers, our experiments show that including the cross-layer information significantly improves the prediction performance. The SVM classifier results in the best performance with an average accuracy of 89%.

  2. An algorithm for link restoration of wavelength routing optical networks

    DEFF Research Database (Denmark)

    Limal, Emmanuel; Stubkjær, Kristian

    1999-01-01

    We present an algorithm for restoration of single link failure in wavelength routing multihop optical networks. The algorithm is based on an innovative study of networks using graph theory. It has the following original features: it (i) assigns working and spare channels simultaneously, (ii) prev...... low complexity is studied in detail and compared to the complexity of a classical path assignment algorithm. Finally, we explain how to use the algorithm to control the restoration path lengths.......We present an algorithm for restoration of single link failure in wavelength routing multihop optical networks. The algorithm is based on an innovative study of networks using graph theory. It has the following original features: it (i) assigns working and spare channels simultaneously, (ii......) prevents the search for unacceptable routing paths by pointing out channels required for restoration, (iii) offers a high utilization of the capacity resources and (iv) allows a trivial search for the restoration paths. The algorithm is for link restoration of networks without wavelength translation. Its...

  3. Porous Cross-Linked Polyimide Networks

    Science.gov (United States)

    Meador, Mary Ann B. (Inventor); Guo, Haiquan (Inventor)

    2015-01-01

    Porous cross-linked polyimide networks are provided. The networks comprise an anhydride end-capped polyamic acid oligomer. The oligomer (i) comprises a repeating unit of a dianhydride and a diamine and terminal anhydride groups, (ii) has an average degree of polymerization of 10 to 50, (iii) has been cross-linked via a cross-linking agent, comprising three or more amine groups, at a balanced stoichiometry of the amine groups to the terminal anhydride groups, and (iv) has been chemically imidized to yield the porous cross-linked polyimide network. Also provided are porous cross-linked polyimide aerogels comprising a cross-linked and imidized anhydride end-capped polyamic acid oligomer, wherein the oligomer comprises a repeating unit of a dianhydride and a diamine, and the aerogel has a density of 0.10 to 0.333 g/cm.sup.3 and a Young's modulus of 1.7 to 102 MPa. Also provided are thin films comprising aerogels, and methods of making porous cross-linked polyimide networks.

  4. Missing and forbidden links in mutualistic networks.

    Science.gov (United States)

    Olesen, Jens M; Bascompte, Jordi; Dupont, Yoko L; Elberling, Heidi; Rasmussen, Claus; Jordano, Pedro

    2011-03-07

    Ecological networks are complexes of interacting species, but not all potential links among species are realized. Unobserved links are either missing or forbidden. Missing links exist, but require more sampling or alternative ways of detection to be verified. Forbidden links remain unobservable, irrespective of sampling effort. They are caused by linkage constraints. We studied one Arctic pollination network and two Mediterranean seed-dispersal networks. In the first, for example, we recorded flower-visit links for one full season, arranged data in an interaction matrix and got a connectance C of 15 per cent. Interaction accumulation curves documented our sampling of interactions through observation of visits to be robust. Then, we included data on pollen from the body surface of flower visitors as an additional link 'currency'. This resulted in 98 new links, missing from the visitation data. Thus, the combined visit-pollen matrix got an increased C of 20 per cent. For the three networks, C ranged from 20 to 52 per cent, and thus the percentage of unobserved links (100 - C) was 48 to 80 per cent; these were assumed forbidden because of linkage constraints and not missing because of under-sampling. Phenological uncoupling (i.e. non-overlapping phenophases between interacting mutualists) is one kind of constraint, and it explained 22 to 28 per cent of all possible, but unobserved links. Increasing phenophase overlap between species increased link probability, but extensive overlaps were required to achieve a high probability. Other kinds of constraint, such as size mismatch and accessibility limitations, are briefly addressed.

  5. IP Network Failure Identification Based on the Detailed Analysis of OSPF LSA Flooding

    Science.gov (United States)

    Hei, Yuichiro; Ogishi, Tomohiko; Ano, Shigehiro; Hasegawa, Toru

    It is important to monitor routing protocols to ensure IP networks and their operations can maintain sufficient level of stability and reliability because IP routing is an essential part of such networks. In this paper, we focus on Open Shortest Path First (OSPF), a widely deployed intra-domain routing protocol. Routers running OSPF advertise their link states on Link State Advertisements (LSAs) as soon as they detect changes in their link states. In IP network operations, it is important for operators to ascertain the location and type of a failure in order to deal with failures adequately. We therefore studied IP network failure identification based on the monitoring of OSPF LSAs. There are three issues to consider in regard to identifying network failures by monitoring LSAs. The first is that multiple LSAs are flooded by a single failure. The second is the LSA delay, and the third is that multiple failures may occur simultaneously. In this paper, we propose a method of network failure identification based on a detailed analysis of OSPF LSA flooding that takes into account the above three issues.

  6. M-Burst: A Framework of SRLG Failure Localization in All-Optical Networks

    KAUST Repository

    Ali, Mohammed L.

    2012-07-27

    Fast and unambiguous failure localization for shared risk link groups (SRLGs) with multiple links is essential for building a fully survivable and functional transparent all-optical mesh network. Monitoring trails (m-trails) have been proposed as an effective approach to achieve this goal. However, each m-trail traverses through each link by constantly taking a wavelength channel, causing a significant amount of resource consumption. In this paper, a novel framework of all-optical monitoring for SRLG failure localization is proposed. We investigate the feasibility of periodically launching optical bursts along each m-trail instead of assigning it a dedicated supervisory lightpath to probe the set of fiber segments along the m-trail, aiming to achieve a graceful compromise between resource consumption and failure localization latency. This paper defines the proposed framework and highlights the relevant issues regarding its feasibility. We provide theoretical justifications of the scheme. As a proof of concept, we formulate the optimal burst scheduling problem via an integer linear program (ILP) and implement the method in networks of all possible SRLGs with up to d=3 links. A heuristic method is also proposed and implemented for multiple-link SRLG failure localization, keeping all the assumptions the same as in the ILP method. Numerical results for small networks show that the scheme is able to localize single-link and multiple-link SRLG failures unambiguously with a very small amount of failure localization latency.

  7. Failure dynamics of the global risk network

    Science.gov (United States)

    Szymanski, Boleslaw K.; Lin, Xin; Asztalos, Andrea; Sreenivasan, Sameet

    2015-06-01

    Risks threatening modern societies form an intricately interconnected network that often underlies crisis situations. Yet, little is known about how risk materializations in distinct domains influence each other. Here we present an approach in which expert assessments of likelihoods and influence of risks underlie a quantitative model of the global risk network dynamics. The modeled risks range from environmental to economic and technological, and include difficult to quantify risks, such as geo-political and social. Using the maximum likelihood estimation, we find the optimal model parameters and demonstrate that the model including network effects significantly outperforms the others, uncovering full value of the expert collected data. We analyze the model dynamics and study its resilience and stability. Our findings include such risk properties as contagion potential, persistence, roles in cascades of failures and the identity of risks most detrimental to system stability. The model provides quantitative means for measuring the adverse effects of risk interdependencies and the materialization of risks in the network.

  8. Visualizing Transmedia Networks: Links, Paths and Peripheries

    Science.gov (United States)

    Ruppel, Marc Nathaniel

    2012-01-01

    'Visualizing Transmedia Networks: Links, Paths and Peripheries' examines the increasingly complex rhetorical intersections between narrative and media ("old" and "new") in the creation of transmedia fictions, loosely defined as multisensory and multimodal stories told extensively across a diverse media set. In order…

  9. Robustness Analysis of Real Network Topologies Under Multiple Failure Scenarios

    DEFF Research Database (Denmark)

    Manzano, M.; Marzo, J. L.; Calle, E.

    2012-01-01

    on topological characteristics. Recently approaches also consider the services supported by such networks. In this paper we carry out a robustness analysis of five real backbone telecommunication networks under defined multiple failure scenarios, taking into account the consequences of the loss of established......Nowadays the ubiquity of telecommunication networks, which underpin and fulfill key aspects of modern day living, is taken for granted. Significant large-scale failures have occurred in the last years affecting telecommunication networks. Traditionally, network robustness analysis has been focused...... connections. Results show which networks are more robust in response to a specific type of failure....

  10. Performance of wireless sensor networks under random node failures

    Energy Technology Data Exchange (ETDEWEB)

    Bradonjic, Milan [Los Alamos National Laboratory; Hagberg, Aric [Los Alamos National Laboratory; Feng, Pan [Los Alamos National Laboratory

    2011-01-28

    Networks are essential to the function of a modern society and the consequence of damages to a network can be large. Assessing network performance of a damaged network is an important step in network recovery and network design. Connectivity, distance between nodes, and alternative routes are some of the key indicators to network performance. In this paper, random geometric graph (RGG) is used with two types of node failure, uniform failure and localized failure. Since the network performance are multi-facet and assessment can be time constrained, we introduce four measures, which can be computed in polynomial time, to estimate performance of damaged RGG. Simulation experiments are conducted to investigate the deterioration of networks through a period of time. With the empirical results, the performance measures are analyzed and compared to provide understanding of different failure scenarios in a RGG.

  11. Link Label Prediction in Signed Citation Network

    KAUST Repository

    Akujuobi, Uchenna

    2016-04-12

    Link label prediction is the problem of predicting the missing labels or signs of all the unlabeled edges in a network. For signed networks, these labels can either be positive or negative. In recent years, different algorithms have been proposed such as using regression, trust propagation and matrix factorization. These approaches have tried to solve the problem of link label prediction by using ideas from social theories, where most of them predict a single missing label given that labels of other edges are known. However, in most real-world social graphs, the number of labeled edges is usually less than that of unlabeled edges. Therefore, predicting a single edge label at a time would require multiple runs and is more computationally demanding. In this thesis, we look at link label prediction problem on a signed citation network with missing edge labels. Our citation network consists of papers from three major machine learning and data mining conferences together with their references, and edges showing the relationship between them. An edge in our network is labeled either positive (dataset relevant) if the reference is based on the dataset used in the paper or negative otherwise. We present three approaches to predict the missing labels. The first approach converts the label prediction problem into a standard classification problem. We then, generate a set of features for each edge and then adopt Support Vector Machines in solving the classification problem. For the second approach, we formalize the graph such that the edges are represented as nodes with links showing similarities between them. We then adopt a label propagation method to propagate the labels on known nodes to those with unknown labels. In the third approach, we adopt a PageRank approach where we rank the nodes according to the number of incoming positive and negative edges, after which we set a threshold. Based on the ranks, we can infer an edge would be positive if it goes a node above the

  12. Mitigating TCP Degradation over Intermittent Link Failures using Intermediate Buffers

    Science.gov (United States)

    2006-06-01

    encryption . This encryp- tion occurs at the data link layer, the network layer, and at the application layer. The 802.11 encryption such as WEP and WPA...protocols. For example the requirement that the message not be compromised requires encryption software. As more demands are placed onto the... Encryption protects confidentiality. Asymmetric encryption techniques provide a mechanism for protect- ing integrity. For example, signing an email

  13. Resolving epidemic network failures through differentiated repair times

    DEFF Research Database (Denmark)

    Fagertun, Anna Manolova; Ruepp, Sarah Renée; Manzano, Marc

    2015-01-01

    In this study, the authors investigate epidemic failure spreading in large-scale transport networks under generalisedmulti-protocol label switching control plane. By evaluating the effect of the epidemic failure spreading on the network,they design several strategies for cost-effective network...... performance improvement via differentiated repair times. First, theyidentify the most vulnerable and the most strategic nodes in the network. Then, via extensive event-driven simulations theyshow that strategic placement of resources for improved failure recovery has better performance than randomly...

  14. Mitigate Cascading Failures on Networks using a Memetic Algorithm.

    Science.gov (United States)

    Tang, Xianglong; Liu, Jing; Hao, Xingxing

    2016-12-09

    Research concerning cascading failures in complex networks has become a hot topic. However, most of the existing studies have focused on modelling the cascading phenomenon on networks and analysing network robustness from a theoretical point of view, which considers only the damage incurred by the failure of one or several nodes. However, such a theoretical approach may not be useful in practical situation. Thus, we first design a much more practical measure to evaluate the robustness of networks against cascading failures, termed Rcf. Then, adopting Rcf as the objective function, we propose a new memetic algorithm (MA) named MA-Rcf to enhance network the robustness against cascading failures. Moreover, we design a new local search operator that considers the characteristics of cascading failures and operates by connecting nodes with a high probability of having similar loads. In experiments, both synthetic scale-free networks and real-world networks are used to test the efficiency and effectiveness of the MA-Rcf. We systematically investigate the effects of parameters on the performance of the MA-Rcf and validate the performance of the newly designed local search operator. The results show that the local search operator is effective, that MA-Rcf can enhance network robustness against cascading failures efficiently, and that it outperforms existing algorithms.

  15. Identification of hybrid node and link communities in complex networks.

    Science.gov (United States)

    He, Dongxiao; Jin, Di; Chen, Zheng; Zhang, Weixiong

    2015-03-02

    Identifying communities in complex networks is an effective means for analyzing complex systems, with applications in diverse areas such as social science, engineering, biology and medicine. Finding communities of nodes and finding communities of links are two popular schemes for network analysis. These schemes, however, have inherent drawbacks and are inadequate to capture complex organizational structures in real networks. We introduce a new scheme and an effective approach for identifying complex mixture structures of node and link communities, called hybrid node-link communities. A central piece of our approach is a probabilistic model that accommodates node, link and hybrid node-link communities. Our extensive experiments on various real-world networks, including a large protein-protein interaction network and a large network of semantically associated words, illustrated that the scheme for hybrid communities is superior in revealing network characteristics. Moreover, the new approach outperformed the existing methods for finding node or link communities separately.

  16. Identification of hybrid node and link communities in complex networks

    Science.gov (United States)

    He, Dongxiao; Jin, Di; Chen, Zheng; Zhang, Weixiong

    2015-03-01

    Identifying communities in complex networks is an effective means for analyzing complex systems, with applications in diverse areas such as social science, engineering, biology and medicine. Finding communities of nodes and finding communities of links are two popular schemes for network analysis. These schemes, however, have inherent drawbacks and are inadequate to capture complex organizational structures in real networks. We introduce a new scheme and an effective approach for identifying complex mixture structures of node and link communities, called hybrid node-link communities. A central piece of our approach is a probabilistic model that accommodates node, link and hybrid node-link communities. Our extensive experiments on various real-world networks, including a large protein-protein interaction network and a large network of semantically associated words, illustrated that the scheme for hybrid communities is superior in revealing network characteristics. Moreover, the new approach outperformed the existing methods for finding node or link communities separately.

  17. Adaptive Connectivity Restoration from Node Failure(s in Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Huaiyuan Wang

    2016-09-01

    Full Text Available Recently, there is a growing interest in the applications of wireless sensor networks (WSNs. A set of sensor nodes is deployed in order to collectively survey an area of interest and/or perform specific surveillance tasks in some of the applications, such as battlefield reconnaissance. Due to the harsh deployment environments and limited energy supply, nodes may fail, which impacts the connectivity of the whole network. Since a single node failure (cut-vertex will destroy the connectivity and divide the network into disjoint blocks, most of the existing studies focus on the problem of single node failure. However, the failure of multiple nodes would be a disaster to the whole network and must be repaired effectively. Only few studies are proposed to handle the problem of multiple cut-vertex failures, which is a special case of multiple node failures. Therefore, this paper proposes a comprehensive solution to address the problems of node failure (single and multiple. Collaborative Single Node Failure Restoration algorithm (CSFR is presented to solve the problem of single node failure only with cooperative communication, but CSFR-M, which is the extension of CSFR, handles the single node failure problem more effectively with node motion. Moreover, Collaborative Connectivity Restoration Algorithm (CCRA is proposed on the basis of cooperative communication and node maneuverability to restore network connectivity after multiple nodes fail. CSFR-M and CCRA are reactive methods that initiate the connectivity restoration after detecting the node failure(s. In order to further minimize the energy dissipation, CCRA opts to simplify the recovery process by gridding. Moreover, the distance that an individual node needs to travel during recovery is reduced by choosing the nearest suitable candidates. Finally, extensive simulations validate the performance of CSFR, CSFR-M and CCRA.

  18. A preferential attachment strategy for connectivity link addition strategy in improving the robustness of interdependent networks

    Science.gov (United States)

    Wang, Xingyuan; Cao, Jianye; Li, Rui; Zhao, Tianfang

    2017-10-01

    Given the same two networks and only one-to-one interlinks are allowed, apparently interdependent networks coupled by these two networks has the optimal robustness when we connect every pair of the same nodes in these two networks. According to the structure of this interdependent network with the optimal robustness, we propose a preferential attachment strategy. And by applying this preferential attachment strategy to three existing connectivity link addition strategies RA (random addition strategy), LD (low degree addition strategy) and LIDD (low inter degree-degree difference addition strategy), we find that each improved strategy is obviously better than before in improving the robustness of interdependent networks. Our findings can provide guidance on connectivity link addition strategy to improve robustness of interdependent networks against cascading failures.

  19. Proactive restoration of slow-failures in optical networks

    DEFF Research Database (Denmark)

    Siracusa, Domenico; Pederzolli, Federico; Salvadori, Elio

    2014-01-01

    Current optical networks, while offering outstanding reliability, still suffer from occasional failures. A resource-efficient procedure to handle these failures in un-protected scenarios is to perform restoration, i.e., to dynamically setup a backup lightpath after the primary one stops working......, which leads to traffic losses while such operation completes. In this paper we propose a technique, applicable to optical networks with centralized control, to better handle failures with slow transients. The idea is to proactively perform the backup lightpath's setup, triggered by either a fixed...

  20. Correlations between community structure and link formation in complex networks.

    Directory of Open Access Journals (Sweden)

    Zhen Liu

    Full Text Available BACKGROUND: Links in complex networks commonly represent specific ties between pairs of nodes, such as protein-protein interactions in biological networks or friendships in social networks. However, understanding the mechanism of link formation in complex networks is a long standing challenge for network analysis and data mining. METHODOLOGY/PRINCIPAL FINDINGS: Links in complex networks have a tendency to cluster locally and form so-called communities. This widely existed phenomenon reflects some underlying mechanism of link formation. To study the correlations between community structure and link formation, we present a general computational framework including a theory for network partitioning and link probability estimation. Our approach enables us to accurately identify missing links in partially observed networks in an efficient way. The links having high connection likelihoods in the communities reveal that links are formed preferentially to create cliques and accordingly promote the clustering level of the communities. The experimental results verify that such a mechanism can be well captured by our approach. CONCLUSIONS/SIGNIFICANCE: Our findings provide a new insight into understanding how links are created in the communities. The computational framework opens a wide range of possibilities to develop new approaches and applications, such as community detection and missing link prediction.

  1. Correlations between community structure and link formation in complex networks.

    Science.gov (United States)

    Liu, Zhen; He, Jia-Lin; Kapoor, Komal; Srivastava, Jaideep

    2013-01-01

    Links in complex networks commonly represent specific ties between pairs of nodes, such as protein-protein interactions in biological networks or friendships in social networks. However, understanding the mechanism of link formation in complex networks is a long standing challenge for network analysis and data mining. Links in complex networks have a tendency to cluster locally and form so-called communities. This widely existed phenomenon reflects some underlying mechanism of link formation. To study the correlations between community structure and link formation, we present a general computational framework including a theory for network partitioning and link probability estimation. Our approach enables us to accurately identify missing links in partially observed networks in an efficient way. The links having high connection likelihoods in the communities reveal that links are formed preferentially to create cliques and accordingly promote the clustering level of the communities. The experimental results verify that such a mechanism can be well captured by our approach. Our findings provide a new insight into understanding how links are created in the communities. The computational framework opens a wide range of possibilities to develop new approaches and applications, such as community detection and missing link prediction.

  2. Network protection against worms and cascading failures using modularity partitioning

    NARCIS (Netherlands)

    Omic, J.; Hernandez, J.M.; Van Mieghem, P.

    2010-01-01

    Communication networks are prone to virus and worms spreading and cascading failures. Recently, a number of social networking worms have spread over public Web sites. Another example is error propagation in routing tables, such as in BGP tables. The immunization and error curing applied to these

  3. AUTOCLAVABLE HIGHLY CROSS-LINKED POLYURETHANE NETWORKS IN OPHTHALMOLOGY

    NARCIS (Netherlands)

    BRUIN, P; MEEUWSEN, EAJ; VANANDEL, MV; WORST, JGF; PENNINGS, AJ

    1993-01-01

    Highly cross-linked aliphatic polyurethane networks have been prepared by the bulk step reaction of low molecular weight polyols and hexamethylenediisocyanate (HDI). These polyurethane networks are optically transparent, colourless and autoclavable amorphous glassy thermosets, which are suited for

  4. Survivability Strategies for Epidemic Failures in Heterogeneous Networks

    DEFF Research Database (Denmark)

    Katsikas, Dimitrios; Fagertun, Anna Manolova; Ruepp, Sarah Renée

    2013-01-01

    Nowadays, transport networks, carry extremely large amounts of network traffic, and are widely spread across multiple geographical locations. As a result, any possible connectivity failure could directly impact the service delivery of a vast amount of users. Therefore, the network should be able...... to recover fast from a failure in order to provide service continuity to the user. Several recovery techniques have been employed by the Internet Service Providers (ISPs) such as adding redundancy to network equipment (e.g. routers, optical cross-connects, etc.), or by provisioning alternate paths (path...... (OTN) in order to ensure the service delivery. The remainder of the paper is organized as follows: Section 2 describes the GMPLS framework. Section 3 deals with epidemic failures. The simulation study and its results are presented in section 4. Section 5 concludes the paper....

  5. Research on complex networks' repairing characteristics due to cascading failure

    Science.gov (United States)

    Chaoqi, Fu; Ying, Wang; Xiaoyang, Wang

    2017-09-01

    In reality, most of the topological structures of complex networks are not ideal. Considering the restrictions from all aspects, we cannot timely adjust and improve network defects. Once complex networks collapse under cascading failure, an appropriate repair strategy must be implemented. This repair process is divided into 3 kinds of situations. Based on different types of opening times, we presented 2 repair modes, and researched 4 kinds of repair strategies. Results showed that network efficiency recovered faster when the repair strategies were arranged in descending order by parameters under the immediate opening condition. However, the risk of secondary failure and additional expansion capacity were large. On the contrary, when repair strategies were in ascending order, the demand for additional capacity caused by secondary failure was greatly saved, but the recovery of network efficiency was relatively slow. Compared to immediate opening, delayed opening alleviated the contradiction between network efficiency and additional expansion capacity, particularly to reduce the risk of secondary failure. Therefore, different repair methods have different repair characteristics. This paper investigates the impact of cascading effects on the network repair process, and by presenting a detailed description of the status of each repaired node, helps us understand the advantages and disadvantages of different repair strategies.

  6. Predicting cryptic links in host-parasite networks.

    Directory of Open Access Journals (Sweden)

    Tad Dallas

    2017-05-01

    Full Text Available Networks are a way to represent interactions among one (e.g., social networks or more (e.g., plant-pollinator networks classes of nodes. The ability to predict likely, but unobserved, interactions has generated a great deal of interest, and is sometimes referred to as the link prediction problem. However, most studies of link prediction have focused on social networks, and have assumed a completely censused network. In biological networks, it is unlikely that all interactions are censused, and ignoring incomplete detection of interactions may lead to biased or incorrect conclusions. Previous attempts to predict network interactions have relied on known properties of network structure, making the approach sensitive to observation errors. This is an obvious shortcoming, as networks are dynamic, and sometimes not well sampled, leading to incomplete detection of links. Here, we develop an algorithm to predict missing links based on conditional probability estimation and associated, node-level features. We validate this algorithm on simulated data, and then apply it to a desert small mammal host-parasite network. Our approach achieves high accuracy on simulated and observed data, providing a simple method to accurately predict missing links in networks without relying on prior knowledge about network structure.

  7. Cascading Failures in Networks: Inference, Intervention and Robustness to WMDs

    Science.gov (United States)

    2016-08-01

    8725 John J. Kingman Road, MS 6201 Fort Belvoir, VA 22060-6201 T E C H N IC A L R E P O R T DTRA-TR-16-83 Cascading Failures in Networks...Austin   Project  Title:  Cascading   Failures  in  Networks:  Inference,  Intervention  and  Robustness  to   WMDs   What  are  the  major  goals  of...networks  are  prone  to  creating  cascading   failures :  events  where  the   initial  destruction/compromising  of  a  few  nodes  results  in  the

  8. Energy Efficient Link Aware Routing with Power Control in Wireless Ad Hoc Networks.

    Science.gov (United States)

    Katiravan, Jeevaa; Sylvia, D; Rao, D Srinivasa

    2015-01-01

    In wireless ad hoc networks, the traditional routing protocols make the route selection based on minimum distance between the nodes and the minimum number of hop counts. Most of the routing decisions do not consider the condition of the network such as link quality and residual energy of the nodes. Also, when a link failure occurs, a route discovery mechanism is initiated which incurs high routing overhead. If the broadcast nature and the spatial diversity of the wireless communication are utilized efficiently it becomes possible to achieve improvement in the performance of the wireless networks. In contrast to the traditional routing scheme which makes use of a predetermined route for packet transmission, such an opportunistic routing scheme defines a predefined forwarding candidate list formed by using single network metrics. In this paper, a protocol is proposed which uses multiple metrics such as residual energy and link quality for route selection and also includes a monitoring mechanism which initiates a route discovery for a poor link, thereby reducing the overhead involved and improving the throughput of the network while maintaining network connectivity. Power control is also implemented not only to save energy but also to improve the network performance. Using simulations, we show the performance improvement attained in the network in terms of packet delivery ratio, routing overhead, and residual energy of the network.

  9. Identifying failure in a tree network of a parallel computer

    Science.gov (United States)

    Archer, Charles J.; Pinnow, Kurt W.; Wallenfelt, Brian P.

    2010-08-24

    Methods, parallel computers, and products are provided for identifying failure in a tree network of a parallel computer. The parallel computer includes one or more processing sets including an I/O node and a plurality of compute nodes. For each processing set embodiments include selecting a set of test compute nodes, the test compute nodes being a subset of the compute nodes of the processing set; measuring the performance of the I/O node of the processing set; measuring the performance of the selected set of test compute nodes; calculating a current test value in dependence upon the measured performance of the I/O node of the processing set, the measured performance of the set of test compute nodes, and a predetermined value for I/O node performance; and comparing the current test value with a predetermined tree performance threshold. If the current test value is below the predetermined tree performance threshold, embodiments include selecting another set of test compute nodes. If the current test value is not below the predetermined tree performance threshold, embodiments include selecting from the test compute nodes one or more potential problem nodes and testing individually potential problem nodes and links to potential problem nodes.

  10. Measurement-Based Network Link Dimensioning

    NARCIS (Netherlands)

    de Oliveira Schmidt, R.; van den Berg, Hans Leo; Pras, Aiko

    The ever increasing traffic demands and the current trend of network and services virtualization calls for effective approaches for optimal use of network resources. In the future Internet multiple virtual networks will coexist on top of the same physical infrastructure, and these will compete for

  11. Measurement-based network link dimensioning

    NARCIS (Netherlands)

    Schmidt, R. de O.; Den Berg, J.L. van den; Pras, A.

    2015-01-01

    The ever increasing traffic demands and the current trend of network and services virtualization calls for effective approaches for optimal use of network resources. In the future Internet multiple virtual networks will coexist on top of the same physical infrastructure, and these will compete for

  12. CONSEQUENCES OF FAILURE OF GAS NETWORK INFRASTRUCTURE

    Directory of Open Access Journals (Sweden)

    Marek URBANIK

    2016-06-01

    Full Text Available Ecology today is becoming increasingly important. Increasing air pollution and greenhouse gas emissions make the search for such fuels which will not have such a negative effect on the environment as the fuel use currently - mainly coal. At present it seems that the substitute fuel can be gaseous fuels (propane-butane, methane. Their combustion is less harmful to the environment and their transport is relatively not very complicated. As it turns out, the use of gas is increasing in industry, automotive, heating systems (power plants that operate in the so-called cogeneration. The increase in demand carries continuous development of gas infrastructure, which in turn may increase probability of failure. As a conclusion of this article, taking into account all the construction disasters induced by the gas, the number of such failures is relatively small. It should be remembered, that the disaster caused by gas explosion may cause very large material and human losses. Not without significance is the impact of gas leakage, eg. of the pipeline on the environment. An example is the methane which is a greenhouse gas, less persistent in the air, but much more active than CO2. The article presents selected disasters associated with natural gas or propane-butane and the impact of these gases on the environment because these fuels are most commonly used in most sectors of the economy.

  13. Evaluation of Network Failure induced IPTV degradation in Metro Networks

    DEFF Research Database (Denmark)

    Wessing, Henrik; Berger, Michael Stübert; Yu, Hao

    2009-01-01

    In this paper, we evaluate future network services and classify them according to their network requirements. IPTV is used as candidate service to evaluate the performance of Carrier Ethernet OAM update mechanisms and requirements. The latter is done through quality measurements using MDI...... and subjective evaluations. It is concluded that OAM interval close to 10 ms is a suitable choice for service providers....

  14. Formation of Bargaining Networks Via Link Sharing

    OpenAIRE

    Priazhkina, Sofia; Page, Frank

    2014-01-01

    This paper presents a model of collusive bargaining networks. Given a status quo network, game is played in two stages: in the first stage, pairs of sellers form the network by signing two-sided contracts that allow sellers to use connections of other sellers; in the second stage, sellers and buyers bargain for the product. We extend the notion of a pairwise Nash stability with transfers to pairwise Nash stability with contracts and characterize the subgame perfect equilibria. The equilibrium...

  15. Failure mitigation in software defined networking employing load type prediction

    KAUST Repository

    Bouacida, Nader

    2017-07-31

    The controller is a critical piece of the SDN architecture, where it is considered as the mastermind of SDN networks. Thus, its failure will cause a significant portion of the network to fail. Overload is one of the common causes of failure since the controller is frequently invoked by new flows. Even through SDN controllers are often replicated, the significant recovery time can be an overkill for the availability of the entire network. In order to overcome the problem of the overloaded controller failure in SDN, this paper proposes a novel controller offload solution for failure mitigation based on a prediction module that anticipates the presence of a harmful long-term load. In fact, the long-standing load would eventually overwhelm the controller leading to a possible failure. To predict whether the load in the controller is short-term or long-term load, we used three different classification algorithms: Support Vector Machine, k-Nearest Neighbors, and Naive Bayes. Our evaluation results demonstrate that Support Vector Machine algorithm is applicable for detecting the type of load with an accuracy of 97.93% in a real-time scenario. Besides, our scheme succeeded to offload the controller by switching between the reactive and proactive mode in response to the prediction module output.

  16. Cold-start link prediction in multi-relational networks

    Science.gov (United States)

    Wu, Shun-yao; Zhang, Qi; Wu, Mei

    2017-10-01

    During the last decade, interaction data have accumulated exponentially in many fields and provide a new opportunity for cold start link prediction. It seems necessarily to take full advantages of diversified information. However, correlation between different interactions has to be pre-tested. Therefore, this paper abstracts complex systems as multi-relational networks, and employs latent space network model to extract low-dimensional factors of sub-networks and adopts likelihood ratio test to examine correlation between factors. Then, regression between target sub-networks and correlated auxiliary sub-networks could be established for cold start link prediction. Experiments on 8 bioinformatic data sets validate the effectiveness and potential of our strategy for network correlation analysis and cold-start link prediction.

  17. Linking Environmental Orientation to Start-ups’ Networking Activities

    DEFF Research Database (Denmark)

    Dickel, Petra; Ritter, Thomas

    generation as their primary focus. Addressing this research gap, we develop hypotheses on the different networking activities of environmentally oriented start-ups arguing that their societal focus has a positive impact on the frequency of their networking and the size of their network. For empirically...... investigating such networking differences, we use data from 179 technology-based start-ups and show that start-ups with a strong external environmental orientation have significantly higher networking frequency and build larger networks. On the contrary, strong internal environmental orientation is linked...

  18. An autonomous recovery mechanism against optical distribution network failures in EPON

    Science.gov (United States)

    Liem, Andrew Tanny; Hwang, I.-Shyan; Nikoukar, AliAkbar

    2014-10-01

    Ethernet Passive Optical Network (EPON) is chosen for servicing diverse applications with higher bandwidth and Quality-of-Service (QoS), starting from Fiber-To-The-Home (FTTH), FTTB (business/building) and FTTO (office). Typically, a single OLT can provide services to both residential and business customers on the same Optical Line Terminal (OLT) port; thus, any failures in the system will cause a great loss for both network operators and customers. Network operators are looking for low-cost and high service availability mechanisms that focus on the failures that occur within the drop fiber section because the majority of faults are in this particular section. Therefore, in this paper, we propose an autonomous recovery mechanism that provides protection and recovery against Drop Distribution Fiber (DDF) link faults or transceiver failure at the ONU(s) in EPON systems. In the proposed mechanism, the ONU can automatically detect any signal anomalies in the physical layer or transceiver failure, switching the working line to the protection line and sending the critical event alarm to OLT via its neighbor. Each ONU has a protection line, which is connected to the nearest neighbor ONU, and therefore, when failure occurs, the ONU can still transmit and receive data via the neighbor ONU. Lastly, the Fault Dynamic Bandwidth Allocation for recovery mechanism is presented. Simulation results show that our proposed autonomous recovery mechanism is able to maintain the overall QoS performance in terms of mean packet delay, system throughput, packet loss and EF jitter.

  19. A new mutually reinforcing network node and link ranking algorithm.

    Science.gov (United States)

    Wang, Zhenghua; Dueñas-Osorio, Leonardo; Padgett, Jamie E

    2015-10-23

    This study proposes a novel Normalized Wide network Ranking algorithm (NWRank) that has the advantage of ranking nodes and links of a network simultaneously. This algorithm combines the mutual reinforcement feature of Hypertext Induced Topic Selection (HITS) and the weight normalization feature of PageRank. Relative weights are assigned to links based on the degree of the adjacent neighbors and the Betweenness Centrality instead of assigning the same weight to every link as assumed in PageRank. Numerical experiment results show that NWRank performs consistently better than HITS, PageRank, eigenvector centrality, and edge betweenness from the perspective of network connectivity and approximate network flow, which is also supported by comparisons with the expensive N-1 benchmark removal criteria based on network efficiency. Furthermore, it can avoid some problems, such as the Tightly Knit Community effect, which exists in HITS. NWRank provides a new inexpensive way to rank nodes and links of a network, which has practical applications, particularly to prioritize resource allocation for upgrade of hierarchical and distributed networks, as well as to support decision making in the design of networks, where node and link importance depend on a balance of local and global integrity.

  20. A new mutually reinforcing network node and link ranking algorithm

    Science.gov (United States)

    Wang, Zhenghua; Dueñas-Osorio, Leonardo; Padgett, Jamie E.

    2015-10-01

    This study proposes a novel Normalized Wide network Ranking algorithm (NWRank) that has the advantage of ranking nodes and links of a network simultaneously. This algorithm combines the mutual reinforcement feature of Hypertext Induced Topic Selection (HITS) and the weight normalization feature of PageRank. Relative weights are assigned to links based on the degree of the adjacent neighbors and the Betweenness Centrality instead of assigning the same weight to every link as assumed in PageRank. Numerical experiment results show that NWRank performs consistently better than HITS, PageRank, eigenvector centrality, and edge betweenness from the perspective of network connectivity and approximate network flow, which is also supported by comparisons with the expensive N-1 benchmark removal criteria based on network efficiency. Furthermore, it can avoid some problems, such as the Tightly Knit Community effect, which exists in HITS. NWRank provides a new inexpensive way to rank nodes and links of a network, which has practical applications, particularly to prioritize resource allocation for upgrade of hierarchical and distributed networks, as well as to support decision making in the design of networks, where node and link importance depend on a balance of local and global integrity.

  1. Network Communication by Optical Directional Link

    Directory of Open Access Journals (Sweden)

    V. Biolkova

    1999-04-01

    Full Text Available In this article, infrared point-to-point technologies (optical directional links are discussed which are designed for digital transmissions. Optical directional links (ODLs are transparent for the SDH/ATM, FDDI-II, Ethernet, and Token Ring protocols. Depending on type, ODL ranges are 300 m, 500 m, 1000 m and 2000 m. Steady and statistical models of ODL are presented as well as the measuring ODL arrangement and the graphs concerning the fluctuations of the received signal.

  2. Congested Link Inference Algorithms in Dynamic Routing IP Network

    Directory of Open Access Journals (Sweden)

    Yu Chen

    2017-01-01

    Full Text Available The performance descending of current congested link inference algorithms is obviously in dynamic routing IP network, such as the most classical algorithm CLINK. To overcome this problem, based on the assumptions of Markov property and time homogeneity, we build a kind of Variable Structure Discrete Dynamic Bayesian (VSDDB network simplified model of dynamic routing IP network. Under the simplified VSDDB model, based on the Bayesian Maximum A Posteriori (BMAP and Rest Bayesian Network Model (RBNM, we proposed an Improved CLINK (ICLINK algorithm. Considering the concurrent phenomenon of multiple link congestion usually happens, we also proposed algorithm CLILRS (Congested Link Inference algorithm based on Lagrangian Relaxation Subgradient to infer the set of congested links. We validated our results by the experiments of analogy, simulation, and actual Internet.

  3. Monitoring burst (M-burst) — A novel framework of failure localization in all-optical mesh networks

    KAUST Repository

    Ali, Mohammed L.

    2011-10-10

    Achieving instantaneous and precise failure localization in all-optical wavelength division multiplexing (WDM) networks has been an attractive feature of network fault management systems, and is particularly important when failure-dependent protection is employed. The paper introduces a novel framework of real-time failure localization in all-optical WDM mesh networks, called monitoring-burst (m-burst), which aims to initiate a graceful compromise between consumed monitoring resources and monitoring delay. Different from any previously reported solution, the proposed m-burst framework has a single monitoring node (MN) which launches optical bursts along a set of pre-defined close-loop routes, called monitoring cycles (m-cycles), to probe the links along the m-cycles. Bursts along different m-cycles are kept non-overlapping through any link of the network. By identifying the lost bursts due to single link failure events only, the MN can unambiguously localize the failed link in at least 3-connected networks. We will justify the feasibility and applicability of the proposed m-burst framework in the scenario of interest. To avoid possible collision among optical bursts launched by the MN, we define the problem of collision-free scheduling and formulate it into an integer linear program (ILP) in order to minimize the monitoring delay. Numerical results demonstrate the effectiveness of the proposed framework and the proposed solution.

  4. Introductions of Invasive Species: Failure of the Weaker Link

    OpenAIRE

    Burnett, Kimberly M.

    2006-01-01

    The prevention of invasive species is modeled as a "weaker link" public good. Under the weaker link aggregation technology, individual contributions beyond the lowest level will provide benefits, but these benefits progressively decline as contributions exceed the minimum. A two-region model is constructed, assuming incomplete information concerning costs of provision. This framework allows us to explain why we observe underinvestment in prevention, how information facilitates efficiency, and...

  5. An algorithm for link restoration in wavwlength translating networks

    DEFF Research Database (Denmark)

    Limal, Emmanuel; Gliese, Ulrik Bo

    1999-01-01

    We propose the BONRA, a new and innovative algorithm for dynamic allocation of working and spare channel capacity for single link restoration in wavelength translating optical networks. The BONRA has very low calculation complexity yet gives high capacity utilisation.......We propose the BONRA, a new and innovative algorithm for dynamic allocation of working and spare channel capacity for single link restoration in wavelength translating optical networks. The BONRA has very low calculation complexity yet gives high capacity utilisation....

  6. Yield and Failure Behavior Investigated for Cross-Linked Phenolic Resins Using Molecular Dynamics

    Science.gov (United States)

    Monk, Joshua D.; Lawson, John W.

    2016-01-01

    Molecular dynamics simulations were conducted to fundamentally evaluate the yield and failure behavior of cross-linked phenolic resins at temperatures below the glass transition. Yield stress was investigated at various temperatures, strain rates, and degrees of cross-linking. The onset of non-linear behavior in the cross-linked phenolic structures was caused by localized irreversible molecular rearrangements through the rotation of methylene linkers followed by the formation or annihilation of neighboring hydrogen bonds. The yield stress results, with respect to temperature and strain rate, could be fit by existing models used to describe yield behavior of amorphous glasses. The degree of cross-linking only indirectly influences the maximum yield stress through its influence on glass transition temperature (Tg), however there is a strong relationship between the degree of cross-linking and the failure mechanism. Low cross-linked samples were able to separate through void formation, whereas the highly cross-linked structures exhibited bond scission.

  7. Link prediction in the network of global virtual water trade

    Science.gov (United States)

    Tuninetti, Marta; Tamea, Stefania; Laio, Francesco; Ridolfi, Luca

    2016-04-01

    Through the international food-trade, water resources are 'virtually' transferred from the country of production to the country of consumption. The international food-trade, thus, implies a network of virtual water flows from exporting to importing countries (i.e., nodes). Given the dynamical behavior of the network, where food-trade relations (i.e., links) are created and dismissed every year, link prediction becomes a challenge. In this study, we propose a novel methodology for link prediction in the virtual water network. The model aims at identifying the main factors (among 17 different variables) driving the creation of a food-trade relation between any two countries, along the period between 1986 and 2011. Furthermore, the model can be exploited to investigate the network configuration in the future, under different possible (climatic and demographic) scenarios. The model grounds the existence of a link between any two nodes on the link weight (i.e., the virtual water flow): a link exists when the nodes exchange a minimum (fixed) volume of virtual water. Starting from a set of potential links between any two nodes, we fit the associated virtual water flows (both the real and the null ones) by means of multivariate linear regressions. Then, links with estimated flows higher than a minimum value (i.e., threshold) are considered active-links, while the others are non-active ones. The discrimination between active and non-active links through the threshold introduces an error (called link-prediction error) because some real links are lost (i.e., missed links) and some non-existing links (i.e., spurious links) are inevitably introduced in the network. The major drivers are those significantly minimizing the link-prediction error. Once the structure of the unweighted virtual water network is known, we apply, again, linear regressions to assess the major factors driving the fluxes traded along (modelled) active-links. Results indicate that, on the one hand

  8. Unavailability of critical SCADA communication links interconnecting a power grid and a Telco network

    Energy Technology Data Exchange (ETDEWEB)

    Bobbio, A. [Dipartimento di Informatica, Universita del Piemonte Orientale, Viale Michel 11, 15121 Alessandria (Italy); Bonanni, G.; Ciancamerla, E. [ENEA - CRE Casaccia, Via Anguillarese 301, 00060 Roma (Italy); Clemente, R. [Telecom Italia Mobile, Via Isonzo112, 10141 Torino (Italy); Iacomini, A. [ACEA, Pl. Ostiense 2, 00154 Roma (Italy); Minichino, M., E-mail: minichino@casaccia.enea.i [ENEA - CRE Casaccia, Via Anguillarese 301, 00060 Roma (Italy); Scarlatti, A. [ACEA, Pl. Ostiense 2, 00154 Roma (Italy); Terruggia, R. [Dipartimento di Informatica, Universita del Piemonte Orientale, Viale Michel 11, 15121 Alessandria (Italy); Zendri, E. [ACEA, Pl. Ostiense 2, 00154 Roma (Italy)

    2010-12-15

    The availability of power supply to power grid customers depends upon the availability of services of supervision, control and data acquisition (SCADA) system, which constitutes the nervous system of a power grid. In turn, SCADA services depend on the availability of the interconnected networks supporting such services. We propose a service oriented stochastic modelling methodology to investigate the availability of large interconnected networks, based on the hierarchical application of different modelling formalisms to different parts of the networks. Interconnected networks are decomposed according to the specific services delivered until the failure and repair mechanisms of the decomposed elementary blocks can be identified. We represent each network by a convenient stochastic modelling formalism, able to capture the main technological issues and to cope with realistic assumptions about failure and recovery mechanisms. This procedure confines the application of the more intensive computational techniques to those subsystems that actually require it. The paper concentrates on an actual failure scenario, occurred in Rome in January 2004 that involved the outage of critical SCADA communication links, interconnecting a power grid and a Telco network.

  9. Reducing Cascading Failure Risk by Increasing Infrastructure Network Interdependence

    Science.gov (United States)

    Korkali, Mert; Veneman, Jason G.; Tivnan, Brian F.; Bagrow, James P.; Hines, Paul D. H.

    2017-01-01

    Increased interconnection between critical infrastructure networks, such as electric power and communications systems, has important implications for infrastructure reliability and security. Others have shown that increased coupling between networks that are vulnerable to internetwork cascading failures can increase vulnerability. However, the mechanisms of cascading in these models differ from those in real systems and such models disregard new functions enabled by coupling, such as intelligent control during a cascade. This paper compares the robustness of simple topological network models to models that more accurately reflect the dynamics of cascading in a particular case of coupled infrastructures. First, we compare a topological contagion model to a power grid model. Second, we compare a percolation model of internetwork cascading to three models of interdependent power-communication systems. In both comparisons, the more detailed models suggest substantially different conclusions, relative to the simpler topological models. In all but the most extreme case, our model of a “smart” power network coupled to a communication system suggests that increased power-communication coupling decreases vulnerability, in contrast to the percolation model. Together, these results suggest that robustness can be enhanced by interconnecting networks with complementary capabilities if modes of internetwork failure propagation are constrained. PMID:28317835

  10. Homophily and missing links in citation networks

    CERN Document Server

    Ciotti, Valerio; Nicosia, Vincenzo; Panzarasa, Pietro; Latora, Vito

    2015-01-01

    Citation networks have been widely used to study the evolution of science through the lenses of the underlying patterns of knowledge flows among academic papers, authors, research sub-fields, and scientific journals. Here we focus on citation networks to cast light on the salience of homophily, namely the principle that similarity breeds connection, for knowledge transfer between papers. To this end, we assess the degree to which citations tend to occur between papers that are concerned with seemingly related topics or research problems. Drawing on a large data set of articles published in the journals of the American Physical Society between 1893 and 2009, we propose a novel method for measuring the similarity between articles through the statistical validation of the overlap between their bibliographies. Results suggest that the probability of a citation made by one article to another is indeed an increasing function of the similarity between the two articles. Our study also enables us to uncover missing ci...

  11. Meta-path based heterogeneous combat network link prediction

    Science.gov (United States)

    Li, Jichao; Ge, Bingfeng; Yang, Kewei; Chen, Yingwu; Tan, Yuejin

    2017-09-01

    The combat system-of-systems in high-tech informative warfare, composed of many interconnected combat systems of different types, can be regarded as a type of complex heterogeneous network. Link prediction for heterogeneous combat networks (HCNs) is of significant military value, as it facilitates reconfiguring combat networks to represent the complex real-world network topology as appropriate with observed information. This paper proposes a novel integrated methodology framework called HCNMP (HCN link prediction based on meta-path) to predict multiple types of links simultaneously for an HCN. More specifically, the concept of HCN meta-paths is introduced, through which the HCNMP can accumulate information by extracting different features of HCN links for all the six defined types. Next, an HCN link prediction model, based on meta-path features, is built to predict all types of links of the HCN simultaneously. Then, the solution algorithm for the HCN link prediction model is proposed, in which the prediction results are obtained by iteratively updating with the newly predicted results until the results in the HCN converge or reach a certain maximum iteration number. Finally, numerical experiments on the dataset of a real HCN are conducted to demonstrate the feasibility and effectiveness of the proposed HCNMP, in comparison with 30 baseline methods. The results show that the performance of the HCNMP is superior to those of the baseline methods.

  12. A novel multilayer model for missing link prediction and future link forecasting in dynamic complex networks

    Science.gov (United States)

    Yasami, Yasser; Safaei, Farshad

    2018-02-01

    The traditional complex network theory is particularly focused on network models in which all network constituents are dealt with equivalently, while fail to consider the supplementary information related to the dynamic properties of the network interactions. This is a main constraint leading to incorrect descriptions of some real-world phenomena or incomplete capturing the details of certain real-life problems. To cope with the problem, this paper addresses the multilayer aspects of dynamic complex networks by analyzing the properties of intrinsically multilayered co-authorship networks, DBLP and Astro Physics, and presenting a novel multilayer model of dynamic complex networks. The model examines the layers evolution (layers birth/death process and lifetime) throughout the network evolution. Particularly, this paper models the evolution of each node's membership in different layers by an Infinite Factorial Hidden Markov Model considering feature cascade, and thereby formulates the link generation process for intra-layer and inter-layer links. Although adjacency matrixes are useful to describe the traditional single-layer networks, such a representation is not sufficient to describe and analyze the multilayer dynamic networks. This paper also extends a generalized mathematical infrastructure to address the problems issued by multilayer complex networks. The model inference is performed using some Markov Chain Monte Carlo sampling strategies, given synthetic and real complex networks data. Experimental results indicate a tremendous improvement in the performance of the proposed multilayer model in terms of sensitivity, specificity, positive and negative predictive values, positive and negative likelihood ratios, F1-score, Matthews correlation coefficient, and accuracy for two important applications of missing link prediction and future link forecasting. The experimental results also indicate the strong predictivepower of the proposed model for the application of

  13. An adaptive actuator failure compensation scheme for two linked 2WD mobile robots

    Science.gov (United States)

    Ma, Yajie; Al-Dujaili, Ayad; Cocquempot, Vincent; El Badaoui El Najjar, Maan

    2017-01-01

    This paper develops a new adaptive compensation control scheme for two linked mobile robots with actuator failurs. A configuration with two linked two-wheel drive (2WD) mobile robots is proposed, and the modelling of its kinematics and dynamics are given. An adaptive failure compensation scheme is developed to compensate actuator failures, consisting of a kinematic controller and a multi-design integration based dynamic controller. The kinematic controller is a virtual one, and based on which, multiple adaptive dynamic control signals are designed which covers all possible failure cases. By combing these dynamic control signals, the dynamic controller is designed, which ensures system stability and asymptotic tracking properties. Simulation results verify the effectiveness of the proposed adaptive failure compensation scheme.

  14. An Integrated Approach for Reliable Facility Location/Network Design Problem with Link Disruption

    Directory of Open Access Journals (Sweden)

    Davood Shishebori

    2015-05-01

    Full Text Available Proposing a robust designed facility location is one of the most effective ways to hedge against unexpected disruptions and failures in a transportation network system. This paper considers the combined facility location/network design problem with regard to transportation link disruptions and develops a mixed integer linear programming formulation to model it. With respect to the probability of link disruptions, the objective function of the model minimizes the total costs, including location costs, link construction costs and also the expected transportation costs. An efficient hybrid algorithm based on LP relaxation and variable neighbourhood search metaheuristic is developed in order to solve the mathematical model. Numerical results demonstrate that the proposed hybrid algorithm has suitable efficiency in terms of duration of solution time and determining excellent solution quality.

  15. Effect of link oriented self-healing on resilience of networks

    Science.gov (United States)

    Shang, Yilun

    2016-08-01

    Many real, complex systems, such as the human brain and skin with their biological networks or intelligent material systems consisting of composite functional liquids, exhibit a noticeable capability of self-healing. Here, we study a network model with arbitrary degree distributions possessing natural link oriented recovery mechanisms, whereby a failed link can be recovered if its two end nodes maintain a sufficient proportion of functional links. These mechanisms are pertinent for many spontaneous healing and manual repair phenomena, interpolating smoothly between complete healing and no healing scenarios. We show that the self-healing strategies have profound impact on resilience of homogeneous and heterogeneous networks employing a percolation threshold, fraction of giant cluster, and link robustness index. The self-healing effect induces distinct resilience characteristics for scale-free networks under random failures and intentional attacks, and a resilience crossover has been observed at certain level of self-healing. Our work highlights the significance of understanding the competition between healing and collapsing in the resilience of complex networks.

  16. Direct link paths detection for observed teleconnections in climate networks

    Science.gov (United States)

    Zhou, Dong; Gozolchiani, Avi; Ashkenazy, Yosef; Havlin, Shlomo

    2015-04-01

    Climate networks have been used to describe certain kind of relations between the climate time series of each pair of nodes. However, all these observed relations should include both the direct relation between these nodes and the indirect effects through other nodes, and the direct link patterns of climate networks are still unclear. In this work, we use the normalized cross-correlation to define both positive and negative link strengths, and for this definition we develop a method based on partial correlation to remove the indirect effect from the observed global air temperature network and obtain the direct positive and negative links. The strong direct links can illustrate how a certain climatic mechanism is propagating step by step in both time and space. Particularly, for the observed teleconnections, we can find the dominant paths of direct links between two nodes by finding the directed shortest paths in the direct link network. The spatial and temporal properties of these paths can help us better understand the origin of such teleconnections.

  17. Influence of Personal Preferences on Link Dynamics in Social Networks

    Directory of Open Access Journals (Sweden)

    Ashwin Bahulkar

    2017-01-01

    Full Text Available We study a unique network dataset including periodic surveys and electronic logs of dyadic contacts via smartphones. The participants were a sample of freshmen entering university in the Fall 2011. Their opinions on a variety of political and social issues and lists of activities on campus were regularly recorded at the beginning and end of each semester for the first three years of study. We identify a behavioral network defined by call and text data, and a cognitive network based on friendship nominations in ego-network surveys. Both networks are limited to study participants. Since a wide range of attributes on each node were collected in self-reports, we refer to these networks as attribute-rich networks. We study whether student preferences for certain attributes of friends can predict formation and dissolution of edges in both networks. We introduce a method for computing student preferences for different attributes which we use to predict link formation and dissolution. We then rank these attributes according to their importance for making predictions. We find that personal preferences, in particular political views, and preferences for common activities help predict link formation and dissolution in both the behavioral and cognitive networks.

  18. Improving Link Reliability through Network Coding in Cooperative Cellular Networks

    Directory of Open Access Journals (Sweden)

    Zs. A. Polgar

    2012-06-01

    Full Text Available The paper proposes a XOR-based network coded cooperation protocol for the uplink transmission of relay assisted cellular networks and an algorithm for selection and assignment of the relay nodes. The performances of the cooperation protocol are expressed in terms of network decoder outage probability and Block Error Rate of the cooperating users. These performance indicators are analyzed theoretically and by computer simulations. The relay nodes assignment is based on the optimization, according to several criteria, of the graph that describes the cooperation cluster formed after an initial selection of the relay nodes. The graph optimization is performed using Genetic Algorithms adapted to the topology of the cooperation cluster and the optimization criteria considered.

  19. Computer simulation of randomly cross-linked polymer networks

    CERN Document Server

    Williams, T P

    2002-01-01

    In this work, Monte Carlo and Stochastic Dynamics computer simulations of mesoscale model randomly cross-linked networks were undertaken. Task parallel implementations of the lattice Monte Carlo Bond Fluctuation model and Kremer-Grest Stochastic Dynamics bead-spring continuum model were designed and used for this purpose. Lattice and continuum precursor melt systems were prepared and then cross-linked to varying degrees. The resultant networks were used to study structural changes during deformation and relaxation dynamics. The effects of a random network topology featuring a polydisperse distribution of strand lengths and an abundance of pendant chain ends, were qualitatively compared to recent published work. A preliminary investigation into the effects of temperature on the structural and dynamical properties was also undertaken. Structural changes during isotropic swelling and uniaxial deformation, revealed a pronounced non-affine deformation dependant on the degree of cross-linking. Fractal heterogeneiti...

  20. The Combined Effect of Connectivity and Dependency Links on Percolation of Networks

    Science.gov (United States)

    Bashan, Amir; Havlin, Shlomo

    2011-11-01

    Percolation theory is extensively studied in statistical physics and mathematics with applications in diverse fields. However, the research is focused on systems with only one type of links, connectivity links. We review a recently developed mathematical framework for analyzing percolation properties of realistic scenarios of networks having links of two types, connectivity and dependency links. This formalism was applied to study Erdős-Rényi (ER) networks that include also dependency links. For an ER network with average degree bar{k} that is composed of dependency clusters of size s, the fraction of nodes that belong to the giant component, P ∞, is given by P_{infty}=p^{s-1}[1-exp{(-bar{k}pP_{infty})} ]s where 1- p is the initial fraction of randomly removed nodes. Here, we apply the formalism to the study of random-regular (RR) networks and find a formula for the size of the giant component in the percolation process: P ∞= p s-1(1- r k ) s where r is the solution of r= p s ( r k-1-1)(1- r k )+1, and k is the degree of the nodes. These general results coincide, for s=1, with the known equations for percolation in ER and RR networks respectively without dependency links. In contrast to s=1, where the percolation transition is second order, for s>1 it is of first order. Comparing the percolation behavior of ER and RR networks we find a remarkable difference regarding their resilience. We show, analytically and numerically, that in ER networks with low connectivity degree or large dependency clusters, removal of even a finite number (zero fraction) of the infinite network nodes will trigger a cascade of failures that fragments the whole network. Specifically, for any given s there exists a critical degree value, bar{k}_{min}, such that an ER network with bar{k}≤ bar{k}_{min} is unstable and collapse when removing even a single node. This result is in contrast to RR networks where such cascades and full fragmentation can be triggered only by removal of a

  1. Connect the dot: Computing feed-links for network extension

    Directory of Open Access Journals (Sweden)

    Boris Aronov

    2011-12-01

    Full Text Available Road network analysis can require distance from points that are not on the network themselves. We study the algorithmic problem of connecting a point inside a face (region of the road network to its boundary while minimizing the detour factor of that point to any point on the boundary of the face. We show that the optimal single connection (feed-link can be computed in O(lambda_7(n log n time, where n is the number of vertices that bounds the face and lambda_7(n is the slightly superlinear maximum length of a Davenport-Schinzel sequence of order 7 on n symbols. We also present approximation results for placing more feed-links, deal with the case that there are obstacles in the face of the road network that contains the point to be connected, and present various related results.

  2. Porous Cross-Linked Polyimide-Urea Networks

    Science.gov (United States)

    Meador, Mary Ann B. (Inventor); Nguyen, Baochau N. (Inventor)

    2015-01-01

    Porous cross-linked polyimide-urea networks are provided. The networks comprise a subunit comprising two anhydride end-capped polyamic acid oligomers in direct connection via a urea linkage. The oligomers (a) each comprise a repeating unit of a dianhydride and a diamine and a terminal anhydride group and (b) are formulated with 2 to 15 of the repeating units. The subunit was formed by reaction of the diamine and a diisocyanate to form a diamine-urea linkage-diamine group, followed by reaction of the diamine-urea linkage-diamine group with the dianhydride and the diamine to form the subunit. The subunit has been cross-linked via a cross-linking agent, comprising three or more amine groups, at a balanced stoichiometry of the amine groups to the terminal anhydride groups. The subunit has been chemically imidized to yield the porous cross-linked polyimide-urea network. Also provided are wet gels, aerogels, and thin films comprising the networks, and methods of making the networks.

  3. Networked Airbourne Communications Using Adaptive Multi Beam Directional Links

    Science.gov (United States)

    2016-03-05

    January 8, 2009. works introduce more sophisticated channel models, and route selection by a method called percolation [7], [8]. For these examples ...Networked Airborne Communications Using Adaptive Multi-Beam Directional Links R. Bruce MacLeod Member, IEEE, and Adam Margetts Member, IEEE MIT...provide new techniques for increasing throughput in airborne adaptive directional net- works. By adaptive directional linking, we mean systems that can

  4. Deflating link buffers in a wireless mesh network

    KAUST Repository

    Jamshaid, Kamran

    2014-05-01

    We analyze the problem of buffer sizing for backlogged TCP flows in 802.11-based wireless mesh networks. Our objective is to maintain high network utilization while providing low queueing delays. Unlike wired networks where a single link buffer feeds a bottleneck link, the radio spectral resource in a mesh network is shared among a set of contending mesh routers. We account for this by formulating the buffer size problem as sizing a collective buffer distributed over a set of interfering nodes. In this paper we propose mechanisms for sizing and distributing this collective buffer among the mesh nodes constituting the network bottleneck. Our mechanism factors in the network topology and wireless link rates, improving on pre-set buffer allocations that cannot optimally work across the range of configurations achievable with 802.11 radios. We evaluate our mechanisms using simulations as well as experiments on a testbed. Our results show that we can reduce the RTT of a flow by 6× or more, at the cost of less than 10% drop in end-to-end flow throughput.

  5. Rainfall monitoring with microwave link networks -state of the art

    Science.gov (United States)

    de Vos, Lotte; Overeem, Aart; Ríos Gaona, Manuel; van Leth, Tommy; Uijlenhoet, Remko

    2017-04-01

    For the purpose of hydrological applications, meteorology, climate monitoring and agriculture, accurate high resolution rainfall monitoring is highly desirable. Often used techniques to measure rainfall include rain gauge networks and radar. However, accurate rainfall information is lacking in large areas in the world, and the number of rain gauges is even severely declining in Europe, South-America and Africa. The investments required for the installation and maintenance of dense sensor networks can form a large obstacle. Over the past decade, various investigations have shown that microwave links from cellular communication networks may be used for rainfall monitoring. These commercial networks are installed for the purpose of cellular communication. These consist of antennas that transmit microwave link signals through the atmosphere over a path of typically several kilometers. Microwave signals are sensitive to rainfall at the frequencies that are typically used. The loss of signal (attenuation) over the link-path, which is logged in real-time by cellular communication companies for quality monitoring, can therefore be interpreted as a rainfall measurement. In recent years, various techniques have been developed to quantitatively determine rainfall from these microwave link attenuations. An overview of error sources in this process, quantitative rainfall determination techniques, as well as the results of various validation studies are provided. These studies show that there is considerable potential in using commercial microwave link networks for rainfall monitoring. This is a promising development, as these networks cover 20% of the land surface of the earth and have high density, especially in urban areas where there is generally a lack of in situ ground measurements.

  6. Optimizing cooperation on complex networks in the presence of failure.

    Science.gov (United States)

    Chen, Yu-Zhong; Lai, Ying-Cheng

    2012-10-01

    Cooperation has been recognized as a fundamental driving force in many natural, social, and economic systems. We investigate whether, given a complex-networked system in which agents (nodes) interact with one another according to the rules of evolutionary games and are subject to failure or death, cooperation can prevail and be optimized. We articulate a control scheme to maximize cooperation by introducing a time tolerance, a time duration that sustains an agent even if its payoff falls below a threshold. Strikingly, we find that a significant cooperation cluster can emerge when the time tolerance is approximately uniformly distributed over the network. A heuristic theory is derived to understand the optimization mechanism, which emphasizes the role played by medium-degree nodes. Implications for policy making to prevent or mitigate large-scale cascading breakdown are pointed out.

  7. Epidemics in Adaptive Social Networks with Temporary Link Deactivation

    Science.gov (United States)

    Tunc, Ilker; Shkarayev, Maxim S.; Shaw, Leah B.

    2013-04-01

    Disease spread in a society depends on the topology of the network of social contacts. Moreover, individuals may respond to the epidemic by adapting their contacts to reduce the risk of infection, thus changing the network structure and affecting future disease spread. We propose an adaptation mechanism where healthy individuals may choose to temporarily deactivate their contacts with sick individuals, allowing reactivation once both individuals are healthy. We develop a mean-field description of this system and find two distinct regimes: slow network dynamics, where the adaptation mechanism simply reduces the effective number of contacts per individual, and fast network dynamics, where more efficient adaptation reduces the spread of disease by targeting dangerous connections. Analysis of the bifurcation structure is supported by numerical simulations of disease spread on an adaptive network. The system displays a single parameter-dependent stable steady state and non-monotonic dependence of connectivity on link deactivation rate.

  8. A robustness metric for cascading failures by targeted attacks in power networks

    NARCIS (Netherlands)

    Koc, Y.; Warnier, M.; Kooij, R.E.; Brazier, F.M.T.

    2013-01-01

    Cascading failures are the main reason blackouts occur in power networks. The economic cost of such failures is in the order of tens of billion dollars annually. In a power network, the cascading failure phenomenon is related to both topological properties (number and types of buses, density of

  9. QoS-aware bandwidth provisioning for IP network links

    NARCIS (Netherlands)

    van den Berg, H; Mandjes, M.R.H.; van de Meent, R.; Pras, A.; Roijers, F.; Venemans, P.H.A.

    2006-01-01

    Current bandwidth provisioning procedures for IP network links are mostly based on simple rules of thumb, using coarse traffic measurements made on a time scale of e.g., 5 or 15 minutes. A crucial question, however, is whether such coarse measurements give any useful insight into the capacity

  10. QoS-aware bandwidth provisioning for IP network links

    NARCIS (Netherlands)

    Berg, J.L. van den; Mandjes, M.; Meent, R. van de; Pras, A.; Roijers, F.; Venemans, P.

    2006-01-01

    Current bandwidth provisioning procedures for IP network links are mostly based on simple rules of thumb, using coarse traffic measurements made on a time scale of e.g., 5 or 15 min. A crucial question, however, is whether such coarse measurements give any useful insight into the capacity actually

  11. Connection Management and Recovery Strategies under Epidemic Network Failures in Optical Transport Networks

    DEFF Research Database (Denmark)

    Fagertun, Anna Manolova; Ruepp, Sarah Renée

    2014-01-01

    The current trend in deploying automatic control plane solutions for increased flexibility in the optical transport layer leads to numerous advantages for both the operators and the customers, but also pose challenges related to the stability of the network and its ability to operate in a robust ...... of their transport infrastructures. Applying proactive methods for avoiding areas where epidemic failures spread results in 50% less connections requiring recovery, which translates in improved quality of service to customers....... manner under attacks. This work proposes four policies for failure handling in a connection-oriented optical transport network, under Generalized MultiProtocol Label Switching control plane, and evaluates their performance under multiple correlated large-scale failures. We employ the Susceptible......-Infected-Disabled epidemic failure spreading model and look into possible tradeoffs between resiliency and resource efficiency. Via extensive simulations we show that there exist a clear tradeoff between policy performance and network resource consumption, which must be addressed by network operators for improved robustness...

  12. Network worlds : from link analysis to virtual places.

    Energy Technology Data Exchange (ETDEWEB)

    Joslyn, C. (Cliff)

    2002-01-01

    Significant progress is being made in knowledge systems through recent advances in the science of very large networks. Attention is now turning in many quarters to the potential impact on counter-terrorism methods. After reviewing some of these advances, we will discuss the difference between such 'network analytic' approaches, which focus on large, homogeneous graph strucures, and what we are calling 'link analytic' approaches, which focus on somewhat smaller graphs with heterogeneous link types. We use this venue to begin the process of rigorously defining link analysis methods, especially the concept of chaining of views of multidimensional databases. We conclude with some speculation on potential connections to virtual world architectures.

  13. Multiservice Switching Networks with Overflow Links and Resource Reservation

    Directory of Open Access Journals (Sweden)

    Mariusz Głąbowski

    2016-01-01

    Full Text Available This paper proposes a new analytical model of a multiservice switching network with overflow links in the first stage and resource reservation for selected call classes in output directions. The proposed model assumes that both the overflow mechanism and the resource reservation mechanism can be used in a number of selected, or all, classes of calls. A particular attention is given to the way the effective availability parameter for networks with overflow links in the point-to-point selection mode is determined. The proposed model makes it possible to determine dependencies between the internal blocking probability, capacity of overflow links, and the number of reserved resources for call classes to be analysed. Simulation experiments confirm high accuracy of the proposed method and potential applications of the model in engineering issues.

  14. TCP flow control using link layer information in mobile networks

    Science.gov (United States)

    Koga, Hiroyuki; Kawahara, Kenji; Oie, Yuji

    2002-07-01

    Mobile Networks have been expanding and IMT-2000 further increases their available bandwidth over wireless links. However, TCP, which is a reliable end-to-end transport protocol, is tuned to perform well in wired networks where bit error rates are very low and packet loss occurs mostly because of congestion. Although a TCP sender can execute flow control to utilize as much available bandwidth as possible in wired networks, it cannot work well in wireless networks characterized by high bit error rates. In the next generation mobile systems, sophisticated error recovery technologies of FEC and ARQ are indeed employed over wireless links, i.e., over Layer 2, to avoid performance degradation of upper layers. However, multiple retransmissions by Layer 2 ARQ can adversely increase transmission delay of TCP segments, which will further make TCP unnecessarily increase RTO (Retransmission TimeOut). Furthermore, a link bandwidth assigned to TCP flows can change in response to changing air conditions to use wireless links efficiently. TCP thus has to adapt its transmission rate according to the changing available bandwidth. The major goal of this study is to develop a receiver-based effective TCP flow control without any modification on TCP senders, which are probably connected with wired networks. For this end, we propose a TCP flow control employing some Layer 2 information on a wireless link at the mobile station. Our performance evaluation of the proposed TCP shows that the receiver-based TCP flow control can moderate the performance degradation very well even if FER on Layer 2 is high.

  15. Analysis of Road Traffic Network Cascade Failures with Coupled Map Lattice Method

    Directory of Open Access Journals (Sweden)

    Yanan Zhang

    2015-01-01

    Full Text Available In recent years, there is growing literature concerning the cascading failure of network characteristics. The object of this paper is to investigate the cascade failures on road traffic network, considering the aeolotropism of road traffic network topology and road congestion dissipation in traffic flow. An improved coupled map lattice (CML model is proposed. Furthermore, in order to match the congestion dissipation, a recovery mechanism is put forward in this paper. With a real urban road traffic network in Beijing, the cascading failures are tested using different attack strategies, coupling strengths, external perturbations, and attacked road segment numbers. The impacts of different aspects on road traffic network are evaluated based on the simulation results. The findings confirmed the important roles that these characteristics played in the cascading failure propagation and dissipation on road traffic network. We hope these findings are helpful to find out the optimal road network topology and avoid cascading failure on road network.

  16. Strength of weak layers in cascading failures on multiplex networks: case of the international trade network

    Science.gov (United States)

    Lee, Kyu-Min; Goh, K.-I.

    2016-05-01

    Many real-world complex systems across natural, social, and economical domains consist of manifold layers to form multiplex networks. The multiple network layers give rise to nonlinear effect for the emergent dynamics of systems. Especially, weak layers that can potentially play significant role in amplifying the vulnerability of multiplex networks might be shadowed in the aggregated single-layer network framework which indiscriminately accumulates all layers. Here we present a simple model of cascading failure on multiplex networks of weight-heterogeneous layers. By simulating the model on the multiplex network of international trades, we found that the multiplex model produces more catastrophic cascading failures which are the result of emergent collective effect of coupling layers, rather than the simple sum thereof. Therefore risks can be systematically underestimated in single-layer network analyses because the impact of weak layers can be overlooked. We anticipate that our simple theoretical study can contribute to further investigation and design of optimal risk-averse real-world complex systems.

  17. Improving Sample Estimate Reliability and Validity with Linked Ego Networks

    CERN Document Server

    Lu, Xin

    2012-01-01

    Respondent-driven sampling (RDS) is currently widely used in public health, especially for the study of hard-to-access populations such as injecting drug users and men who have sex with men. The method works like a snowball sample but can, given that some assumptions are met, generate unbiased population estimates. However, recent studies have shown that traditional RDS estimators are likely to generate large variance and estimate error. To improve the performance of traditional estimators, we propose a method to generate estimates with ego network data collected by RDS. By simulating RDS processes on an empirical human social network with known population characteristics, we have shown that the precision of estimates on the composition of network link types is greatly improved with ego network data. The proposed estimator for population characteristics shows superior advantage over traditional RDS estimators, and most importantly, the new method exhibits strong robustness to the recruitment preference of res...

  18. A Survey of Link Prediction in Social Networks

    Science.gov (United States)

    Hasan, Mohammad Al; Zaki, Mohammed J.

    Link prediction is an important task for analying social networks which also has applications in other domains like, information retrieval, bioinformatics and e-commerce. There exist a variety of techniques for link prediction, ranging from feature-based classification and kernel-based method to matrix factorization and probabilistic graphical models. These methods differ from each other with respect to model complexity, prediction performance, scalability, and generalization ability. In this article, we survey some representative link prediction methods by categorizing them by the type of the models. We largely consider three types of models: first, the traditional (non-Bayesian) models which extract a set of features to train a binary classification model. Second, the probabilistic approaches which model the joint-probability among the entities in a network by Bayesian graphical models. And, finally the linear algebraic approach which computes the similarity between the nodes in a network by rank-reduced similarity matrices. We discuss various existing link prediction models that fall in these broad categories and analyze their strength and weakness. We conclude the survey with a discussion on recent developments and future research direction.

  19. Orthogonal least squares based complex-valued functional link network.

    Science.gov (United States)

    Amin, Md Faijul; Savitha, Ramasamy; Amin, Muhammad Ilias; Murase, Kazuyuki

    2012-08-01

    Functional link networks are single-layered neural networks that impose nonlinearity in the input layer using nonlinear functions of the original input variables. In this paper, we present a fully complex-valued functional link network (CFLN) with multivariate polynomials as the nonlinear functions. Unlike multilayer neural networks, the CFLN is free from local minima problem, and it offers very fast learning of parameters because of its linear structure. Polynomial based CFLN does not require an activation function which is a major concern in the complex-valued neural networks. However, it is important to select a smaller subset of polynomial terms (monomials) for faster and better performance since the number of all possible monomials may be quite large. Here, we use the orthogonal least squares (OLS) method in a constructive fashion (starting from lower degree to higher) for the selection of a parsimonious subset of monomials. It is argued here that computing CFLN in purely complex domain is advantageous than in double-dimensional real domain, in terms of number of connection parameters, faster design, and possibly generalization performance. Simulation results on a function approximation, wind prediction with real-world data, and a nonlinear channel equalization problem exhibit that the OLS based CFLN yields very simple structure having favorable performance. Copyright © 2012 Elsevier Ltd. All rights reserved.

  20. Link-quality measurement and reporting in wireless sensor networks.

    Science.gov (United States)

    Chehri, Abdellah; Jeon, Gwanggil; Choi, Byoungjo

    2013-03-04

    Wireless Sensor networks (WSNs) are created by small hardware devices that possess the necessary functionalities to measure and exchange a variety of environmental data in their deployment setting. In this paper, we discuss the experiments in deploying a testbed as a first step towards creating a fully functional heterogeneous wireless network-based underground monitoring system. The system is mainly composed of mobile and static ZigBee nodes, which are deployed on the underground mine galleries for measuring ambient temperature. In addition, we describe the measured results of link characteristics such as received signal strength, latency and throughput for different scenarios.

  1. Link-Quality Measurement and Reporting in Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Byoungjo Choi

    2013-03-01

    Full Text Available Wireless Sensor networks (WSNs are created by small hardware devices that possess the necessary functionalities to measure and exchange a variety of environmental data in their deployment setting. In this paper, we discuss the experiments in deploying a testbed as a first step towards creating a fully functional heterogeneous wireless network-based underground monitoring system. The system is mainly composed of mobile and static ZigBee nodes, which are deployed on the underground mine galleries for measuring ambient temperature. In addition, we describe the measured results of link characteristics such as received signal strength, latency and throughput for different scenarios.

  2. A Novel Learning Scheme for Chebyshev Functional Link Neural Networks

    Directory of Open Access Journals (Sweden)

    Satchidananda Dehuri

    2011-01-01

    dimensional-space where linear separability is possible. Moreover, the proposed HCFLNN combines the best attribute of particle swarm optimization (PSO, back propagation learning (BP learning, and functional link neural networks (FLNNs. The proposed method eliminates the need of hidden layer by expanding the input patterns using Chebyshev orthogonal polynomials. We have shown its effectiveness of classifying the unknown pattern using the publicly available datasets obtained from UCI repository. The computational results are then compared with functional link neural network (FLNN with a generic basis functions, PSO-based FLNN, and EFLN. From the comparative study, we observed that the performance of the HCFLNN outperforms FLNN, PSO-based FLNN, and EFLN in terms of classification accuracy.

  3. Improving link prediction in complex networks by adaptively exploiting multiple structural features of networks

    Science.gov (United States)

    Ma, Chuang; Bao, Zhong-Kui; Zhang, Hai-Feng

    2017-10-01

    So far, many network-structure-based link prediction methods have been proposed. However, these methods only highlight one or two structural features of networks, and then use the methods to predict missing links in different networks. The performances of these existing methods are not always satisfied in all cases since each network has its unique underlying structural features. In this paper, by analyzing different real networks, we find that the structural features of different networks are remarkably different. In particular, even in the same network, their inner structural features are utterly different. Therefore, more structural features should be considered. However, owing to the remarkably different structural features, the contributions of different features are hard to be given in advance. Inspired by these facts, an adaptive fusion model regarding link prediction is proposed to incorporate multiple structural features. In the model, a logistic function combing multiple structural features is defined, then the weight of each feature in the logistic function is adaptively determined by exploiting the known structure information. Last, we use the "learnt" logistic function to predict the connection probabilities of missing links. According to our experimental results, we find that the performance of our adaptive fusion model is better than many similarity indices.

  4. Network modeling links breast cancer susceptibility and centrosome dysfunction.

    Science.gov (United States)

    Pujana, Miguel Angel; Han, Jing-Dong J; Starita, Lea M; Stevens, Kristen N; Tewari, Muneesh; Ahn, Jin Sook; Rennert, Gad; Moreno, Víctor; Kirchhoff, Tomas; Gold, Bert; Assmann, Volker; Elshamy, Wael M; Rual, Jean-François; Levine, Douglas; Rozek, Laura S; Gelman, Rebecca S; Gunsalus, Kristin C; Greenberg, Roger A; Sobhian, Bijan; Bertin, Nicolas; Venkatesan, Kavitha; Ayivi-Guedehoussou, Nono; Solé, Xavier; Hernández, Pilar; Lázaro, Conxi; Nathanson, Katherine L; Weber, Barbara L; Cusick, Michael E; Hill, David E; Offit, Kenneth; Livingston, David M; Gruber, Stephen B; Parvin, Jeffrey D; Vidal, Marc

    2007-11-01

    Many cancer-associated genes remain to be identified to clarify the underlying molecular mechanisms of cancer susceptibility and progression. Better understanding is also required of how mutations in cancer genes affect their products in the context of complex cellular networks. Here we have used a network modeling strategy to identify genes potentially associated with higher risk of breast cancer. Starting with four known genes encoding tumor suppressors of breast cancer, we combined gene expression profiling with functional genomic and proteomic (or 'omic') data from various species to generate a network containing 118 genes linked by 866 potential functional associations. This network shows higher connectivity than expected by chance, suggesting that its components function in biologically related pathways. One of the components of the network is HMMR, encoding a centrosome subunit, for which we demonstrate previously unknown functional associations with the breast cancer-associated gene BRCA1. Two case-control studies of incident breast cancer indicate that the HMMR locus is associated with higher risk of breast cancer in humans. Our network modeling strategy should be useful for the discovery of additional cancer-associated genes.

  5. Failure-recovery model with competition between failures in complex networks: a dynamical approach

    CERN Document Server

    Valdez, L D; Braunstein, L A

    2016-01-01

    Real systems are usually composed by units or nodes whose activity can be interrupted and restored intermittently due to complex interactions not only with the environment, but also with the same system. Majdand\\v{z}i\\'c $et\\;al.$ [Nature Physics 10, 34 (2014)] proposed a model to study systems in which active nodes fail and recover spontaneously in a complex network and found that in the steady state the density of active nodes can exhibit an abrupt transition and hysteresis depending on the values of the parameters. Here we investigate a model of recovery-failure from a dynamical point of view. Using an effective degree approach we find that the systems can exhibit a temporal sharp decrease in the fraction of active nodes. Moreover we show that, depending on the values of the parameters, the fraction of active nodes has an oscillatory regime which we explain as a competition between different failure processes. We also find that in the non-oscillatory regime, the critical fraction of active nodes presents a...

  6. Visual Tracking With Convolutional Random Vector Functional Link Network.

    Science.gov (United States)

    Zhang, Le; Suganthan, Ponnuthurai Nagaratnam

    2017-10-01

    Deep neural network-based methods have recently achieved excellent performance in visual tracking task. As very few training samples are available in visual tracking task, those approaches rely heavily on extremely large auxiliary dataset such as ImageNet to pretrain the model. In order to address the discrepancy between the source domain (the auxiliary data) and the target domain (the object being tracked), they need to be finetuned during the tracking process. However, those methods suffer from sensitivity to the hyper-parameters such as learning rate, maximum number of epochs, size of mini-batch, and so on. Thus, it is worthy to investigate whether pretraining and fine tuning through conventional back-prop is essential for visual tracking. In this paper, we shed light on this line of research by proposing convolutional random vector functional link (CRVFL) neural network, which can be regarded as a marriage of the convolutional neural network and random vector functional link network, to simplify the visual tracking system. The parameters in the convolutional layer are randomly initialized and kept fixed. Only the parameters in the fully connected layer need to be learned. We further propose an elegant approach to update the tracker. In the widely used visual tracking benchmark, without any auxiliary data, a single CRVFL model achieves 79.0% with a threshold of 20 pixels for the precision plot. Moreover, an ensemble of CRVFL yields comparatively the best result of 86.3%.

  7. Design and Analysis of Underwater Acoustic Networks with Reflected Links

    Science.gov (United States)

    Emokpae, Lloyd

    Underwater acoustic networks (UWANs) have applications in environmental state monitoring, oceanic profile measurements, leak detection in oil fields, distributed surveillance, and navigation. For these applications, sets of nodes are employed to collaboratively monitor an area of interest and track certain events or phenomena. In addition, it is common to find autonomous underwater vehicles (AUVs) acting as mobile sensor nodes that perform search-and-rescue missions, reconnaissance in combat zones, and coastal patrol. These AUVs are to work cooperatively to achieve a desired goal and thus need to be able to, in an ad-hoc manner, establish and sustain communication links in order to ensure some desired level of quality of service. Therefore, each node is required to adapt to environmental changes and be able to overcome broken communication links caused by external noise affecting the communication channel due to node mobility. In addition, since radio waves are quickly absorbed in the water medium, it is common for most underwater applications to rely on acoustic (or sound) rather than radio channels for mid-to-long range communications. However, acoustic channels pose multiple challenging issues, most notably the high transmission delay due to slow signal propagation and the limited channel bandwidth due to high frequency attenuation. Moreover, the inhomogeneous property of the water medium affects the sound speed profile while the signal surface and bottom reflections leads to multipath effects. In this dissertation, we address these networking challenges by developing protocols that take into consideration the underwater physical layer dynamics. We begin by introducing a novel surface-based reflection scheme (SBR), which takes advantage of the multipath effects of the acoustic channel. SBR works by using reflections from the water surface, and bottom, to establish non-line-of-sight (NLOS) communication links. SBR makes it possible to incorporate both line

  8. Directed networks' different link formation mechanisms causing degree distribution distinction

    Science.gov (United States)

    Behfar, Stefan Kambiz; Turkina, Ekaterina; Cohendet, Patrick; Burger-Helmchen, Thierry

    2016-11-01

    Within undirected networks, scientists have shown much interest in presenting power-law features. For instance, Barabási and Albert (1999) claimed that a common property of many large networks is that vertex connectivity follows scale-free power-law distribution, and in another study Barabási et al. (2002) showed power law evolution in the social network of scientific collaboration. At the same time, Jiang et al. (2011) discussed deviation from power-law distribution; others indicated that size effect (Bagrow et al., 2008), information filtering mechanism (Mossa et al., 2002), and birth and death process (Shi et al., 2005) could account for this deviation. Within directed networks, many authors have considered that outlinks follow a similar mechanism of creation as inlinks' (Faloutsos et al., 1999; Krapivsky et al., 2001; Tanimoto, 2009) with link creation rate being the linear function of node degree, resulting in a power-law shape for both indegree and outdegree distribution. Some other authors have made an assumption that directed networks, such as scientific collaboration or citation, behave as undirected, resulting in a power-law degree distribution accordingly (Barabási et al., 2002). At the same time, we claim (1) Outlinks feature different degree distributions than inlinks; where different link formation mechanisms cause the distribution distinctions, (2) in/outdegree distribution distinction holds for different levels of system decomposition; therefore this distribution distinction is a property of directed networks. First, we emphasize in/outlink formation mechanisms as causal factors for distinction between indegree and outdegree distributions (where this distinction has already been noticed in Barker et al. (2010) and Baxter et al. (2006)) within a sample network of OSS projects as well as Java software corpus as a network. Second, we analyze whether this distribution distinction holds for different levels of system decomposition: open

  9. Impact of treatment on myocardial lysyl oxidase expression and collagen cross-linking in patients with heart failure

    OpenAIRE

    Lopez, B. (Begoña); Querejeta, R. (Ramón); Gonzalez, A. (Arantxa); Beaumont, J. (Javier); Larman, M. (Mariano); Diez, J. (Javier)

    2009-01-01

    The aim of this study was to investigate whether torasemide modifies collagen cross-linking in the failing human heart. We analyzed the degree of cross-linking and the expression of the enzyme lysyl oxidase, which regulates cross-linking, in the myocardium of patients with chronic heart failure at baseline and after 8 months of treatment with either torasemide or furosemide in addition to their standard heart failure therapy. Whereas lysyl oxidase protein expression was very scarce in normal ...

  10. Community detection, link prediction, and layer interdependence in multilayer networks

    Science.gov (United States)

    De Bacco, Caterina; Power, Eleanor A.; Larremore, Daniel B.; Moore, Cristopher

    2017-04-01

    Complex systems are often characterized by distinct types of interactions between the same entities. These can be described as a multilayer network where each layer represents one type of interaction. These layers may be interdependent in complicated ways, revealing different kinds of structure in the network. In this work we present a generative model, and an efficient expectation-maximization algorithm, which allows us to perform inference tasks such as community detection and link prediction in this setting. Our model assumes overlapping communities that are common between the layers, while allowing these communities to affect each layer in a different way, including arbitrary mixtures of assortative, disassortative, or directed structure. It also gives us a mathematically principled way to define the interdependence between layers, by measuring how much information about one layer helps us predict links in another layer. In particular, this allows us to bundle layers together to compress redundant information and identify small groups of layers which suffice to predict the remaining layers accurately. We illustrate these findings by analyzing synthetic data and two real multilayer networks, one representing social support relationships among villagers in South India and the other representing shared genetic substring material between genes of the malaria parasite.

  11. Optimal Configuration of Virtual Links for Avionics Network Systems

    Directory of Open Access Journals (Sweden)

    Dongha An

    2015-01-01

    Full Text Available As the bandwidth and scalability constraints become important design concerns in airborne networks, a new technology, called Avionics Full Duplex Switched Ethernet (AFDX, has been introduced and standardized as a part 7 in ARNIC 664. However, since previous research interests for AFDX are mainly bounded for analyzing the response time where flows information is given, configuration problem for both Maximum Transmission Unit (MTU and Bandwidth Allocation Gap (BAG over virtual links in AFDX networks has not been addressed yet even though it has great impact on required bandwidth. Thus, in this paper, we present two configuration approaches to set MTU and BAG values on virtual links efficiently while meeting the requirement of AFDX. The first is to search available feasible configuration (MTU, BAG pairs to satisfy application requirements as well as AFDX switch constraints, and the second is to get an optimal pair to minimize required bandwidth through well-known branch-and-bound algorithm. We analyze the complexity of the proposed algorithm and then evaluate the proposed algorithm by simulation. Finally, we prove that the proposed schemes are superior to general approach in the aspects of speed and required bandwidth in AFDX networks.

  12. The vulnerability of the global container shipping network to targeted link disruption

    CSIR Research Space (South Africa)

    Viljoen, NM

    2016-11-01

    Full Text Available transport, complex network theory has had limited application in studying the vulnerability of maritime networks. This study uses targeted link disruption to investigate the strategy specific vulnerability of the network. Although nodal infrastructure...

  13. Shuttle Planning for Link Closures in Urban Public Transport Networks

    DEFF Research Database (Denmark)

    van der Hurk, Evelien; Koutsopoulos, Haris N.; Wilson, Nigel

    2016-01-01

    cost, which includes transfers and frequency-dependent waiting time costs. This model is applied to a shuttle design problem based on a real-world case study of the Massachusetts Bay Transportation Authority network of Boston, Massachusetts. The results show that additional shuttle routes can reduce......Urban public transport systems must periodically close certain links for maintenance, which can have significant effects on the service provided to passengers. In practice, the effects of closures are mitigated by replacing the closed links with a simple shuttle service. However, alternative...... passenger delay compared to the standard industry practice, while also distributing delay more equally over passengers, at the same operating budget. The results are robust under different assumptions about passenger route choice behavior. Computational experiments show that the proposed formulation...

  14. Linking structure and activity in nonlinear spiking networks.

    Directory of Open Access Journals (Sweden)

    Gabriel Koch Ocker

    2017-06-01

    Full Text Available Recent experimental advances are producing an avalanche of data on both neural connectivity and neural activity. To take full advantage of these two emerging datasets we need a framework that links them, revealing how collective neural activity arises from the structure of neural connectivity and intrinsic neural dynamics. This problem of structure-driven activity has drawn major interest in computational neuroscience. Existing methods for relating activity and architecture in spiking networks rely on linearizing activity around a central operating point and thus fail to capture the nonlinear responses of individual neurons that are the hallmark of neural information processing. Here, we overcome this limitation and present a new relationship between connectivity and activity in networks of nonlinear spiking neurons by developing a diagrammatic fluctuation expansion based on statistical field theory. We explicitly show how recurrent network structure produces pairwise and higher-order correlated activity, and how nonlinearities impact the networks' spiking activity. Our findings open new avenues to investigating how single-neuron nonlinearities-including those of different cell types-combine with connectivity to shape population activity and function.

  15. MicroRNA-19b is a potential biomarker of increased myocardial collagen cross-linking in patients with aortic stenosis and heart failure.

    Science.gov (United States)

    Beaumont, Javier; López, Begoña; Ravassa, Susana; Hermida, Nerea; José, Gorka San; Gallego, Idoia; Valencia, Félix; Gómez-Doblas, Juan José; de Teresa, Eduardo; Díez, Javier; González, Arantxa

    2017-01-16

    This study analyzed the potential associations of 7 myocardial fibrosis-related microRNAs with the quality of the collagen network (e.g., the degree of collagen fibril cross-linking or CCL) and the enzyme lysyl oxidase (LOX) responsible for CCL in 28 patients with severe aortic stenosis (AS) of whom 46% had a diagnosis of chronic heart failure (HF). MicroRNA expression was analyzed in myocardial and blood samples. From the studied microRNAs only miR-19b presented a direct correlation (p collagen network in AS patients, particularly in patients with HF.

  16. An ant colony based resilience approach to cascading failures in cluster supply network

    Science.gov (United States)

    Wang, Yingcong; Xiao, Renbin

    2016-11-01

    Cluster supply chain network is a typical complex network and easily suffers cascading failures under disruption events, which is caused by the under-load of enterprises. Improving network resilience can increase the ability of recovery from cascading failures. Social resilience is found in ant colony and comes from ant's spatial fidelity zones (SFZ). Starting from the under-load failures, this paper proposes a resilience method to cascading failures in cluster supply chain network by leveraging on social resilience of ant colony. First, the mapping between ant colony SFZ and cluster supply chain network SFZ is presented. Second, a new cascading model for cluster supply chain network is constructed based on under-load failures. Then, the SFZ-based resilience method and index to cascading failures are developed according to ant colony's social resilience. Finally, a numerical simulation and a case study are used to verify the validity of the cascading model and the resilience method. Experimental results show that, the cluster supply chain network becomes resilient to cascading failures under the SFZ-based resilience method, and the cluster supply chain network resilience can be enhanced by improving the ability of enterprises to recover and adjust.

  17. Limits of Predictability of Cascading Overload Failures in Spatially-Embedded Networks with Distributed Flows.

    Science.gov (United States)

    Moussawi, A; Derzsy, N; Lin, X; Szymanski, B K; Korniss, G

    2017-09-15

    Cascading failures are a critical vulnerability of complex information or infrastructure networks. Here we investigate the properties of load-based cascading failures in real and synthetic spatially-embedded network structures, and propose mitigation strategies to reduce the severity of damages caused by such failures. We introduce a stochastic method for optimal heterogeneous distribution of resources (node capacities) subject to a fixed total cost. Additionally, we design and compare the performance of networks with N-stable and (N-1)-stable network-capacity allocations by triggering cascades using various real-world node-attack and node-failure scenarios. We show that failure mitigation through increased node protection can be effectively achieved against single-node failures. However, mitigating against multiple node failures is much more difficult due to the combinatorial increase in possible sets of initially failing nodes. We analyze the robustness of the system with increasing protection, and find that a critical tolerance exists at which the system undergoes a phase transition, and above which the network almost completely survives an attack. Moreover, we show that cascade-size distributions measured in this region exhibit a power-law decay. Finally, we find a strong correlation between cascade sizes induced by individual nodes and sets of nodes. We also show that network topology alone is a weak predictor in determining the progression of cascading failures.

  18. Cascading failures in interdependent modular networks with partial random coupling preference

    Science.gov (United States)

    Tian, Meng; Wang, Xianpei; Dong, Zhengcheng; Zhu, Guowei; Long, Jiachuang; Dai, Dangdang; Zhang, Qilin

    2017-10-01

    Cascading failures have been widely analyzed in interdependent networks with different coupling preferences from microscopic and macroscopic perspectives in recent years. Plenty of real-world interdependent infrastructures, representing as interdependent networks, exhibit community structure, one of the most important mesoscopic structures, and partial coupling preferences, which can affect cascading failures in interdependent networks. In this paper, we propose the partial random coupling in communities, investigating cascading failures in interdependent modular scale-free networks under inner attacks and hub attacks. We mainly analyze the effects of the discoupling probability and the intermodular connection probability on cascading failures in interdependent networks. We find that increasing either the dicoupling probability or the intermodular connection probability can enhance the network robustness under both hub attacks and inner attacks. We also note that the community structure can prevent cascading failures spreading globally in entire interdependent networks. Finally, we obtain the result that if we want to efficiently improve the robustness of interdependent networks and reduce the protection cost, the intermodular connection probability should be protected preferentially, implying that improving the robustness of a single network is the fundamental method to enhance the robustness of the entire interdependent networks.

  19. Using Semantic Linking to Understand Persons’ Networks Extracted from Text

    Directory of Open Access Journals (Sweden)

    Alessio Palmero Aprosio

    2017-11-01

    Full Text Available In this work, we describe a methodology to interpret large persons’ networks extracted from text by classifying cliques using the DBpedia ontology. The approach relies on a combination of NLP, Semantic web technologies, and network analysis. The classification methodology that first starts from single nodes and then generalizes to cliques is effective in terms of performance and is able to deal also with nodes that are not linked to Wikipedia. The gold standard manually developed for evaluation shows that groups of co-occurring entities share in most of the cases a category that can be automatically assigned. This holds for both languages considered in this study. The outcome of this work may be of interest to enhance the readability of large networks and to provide an additional semantic layer on top of cliques. This would greatly help humanities scholars when dealing with large amounts of textual data that need to be interpreted or categorized. Furthermore, it represents an unsupervised approach to automatically extend DBpedia starting from a corpus.

  20. A Model to Convert Airport Geographic and Geometric Information into a Node-Link Network

    OpenAIRE

    Zhang, Yang

    2015-01-01

    An airport node-link network model is an important input for most airport simulation models. Developing, maintaining and updating detailed airport surface node-link models require significant work. A model to convert airport geographic and geometric information into a node-link network is thus needed. In this thesis, an efficient model to automate the procedure of converting airport geographic and geometric information into a node-link network is proposed. The geographic and geometric info...

  1. Capacity Limit, Link Scheduling and Power Control in Wireless Networks

    Science.gov (United States)

    Zhou, Shan

    2013-01-01

    The rapid advancement of wireless technology has instigated the broad deployment of wireless networks. Different types of networks have been developed, including wireless sensor networks, mobile ad hoc networks, wireless local area networks, and cellular networks. These networks have different structures and applications, and require different…

  2. Identifying the Critical Links in Road Transportation Networks: Centrality-based approach utilizing structural properties

    Energy Technology Data Exchange (ETDEWEB)

    Chinthavali, Supriya [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-04-01

    Surface transportation road networks share structural properties similar to other complex networks (e.g., social networks, information networks, biological networks, and so on). This research investigates the structural properties of road networks for any possible correlation with the traffic characteristics such as link flows those determined independently. Additionally, we define a criticality index for the links of the road network that identifies the relative importance in the network. We tested our hypotheses with two sample road networks. Results show that, correlation exists between the link flows and centrality measures of a link of the road (dual graph approach is followed) and the criticality index is found to be effective for one test network to identify the vulnerable nodes.

  3. Time Score: A New Feature for Link Prediction in Social Networks

    Science.gov (United States)

    Munasinghe, Lankeshwara; Ichise, Ryutaro

    Link prediction in social networks, such as friendship networks and coauthorship networks, has recently attracted a great deal of attention. There have been numerous attempts to address the problem of link prediction through diverse approaches. In the present paper, we focus on the temporal behavior of the link strength, particularly the relationship between the time stamps of interactions or links and the temporal behavior of link strength and how link strength affects future link evolution. Most previous studies have not sufficiently discussed either the impact of time stamps of the interactions or time stamps of the links on link evolution. The gap between the current time and the time stamps of the interactions or links is also important to link evolution. In the present paper, we introduce a new time-aware feature, referred to as time score, that captures the important aspects of time stamps of interactions and the temporality of the link strengths. We also analyze the effectiveness of time score with different parameter settings for different network data sets. The results of the analysis revealed that the time score was sensitive to different networks and different time measures. We applied time score to two social network data sets, namely, Facebook friendship network data set and a coauthorship network data set. The results revealed a significant improvement in predicting future links.

  4. End-stage renal failure in a child with X-linked ichthyosis.

    Science.gov (United States)

    Matsukura, Hiro; Fuchizawa, Tatsuya; Ohtsuki, Akio; Higashiyama, Hiroyuki; Higuchi, Osamu; Higuchi, Akira; Miyawaki, Toshio

    2003-03-01

    We describe an 8-year-old boy who presented with steroid-resistant nephrotic syndrome (SRNS) associated with X-linked ichthyosis (XLI). At birth, the patient exhibited scaly skin, cryptorchidism, and steroid sulfatase (STS) deficiency. DNA analysis showed deletion of exons 1-10 of the STS gene. Proteinuria developed at 6 years and was resistant to steroid therapy. Kidney biopsy findings prior to steroid therapy were compatible with minimal change nephrotic syndrome. By immunofluorescence, glomerular basement membranes exhibited diffuse linear staining for the alpha5 chain of collagen IV, making X-linked Alport syndrome an unlikely explanation for the association of SRNS and ichthyosis. Despite immunosuppressive therapy together with oral prednisolone, no clinical response was achieved. He rapidly reached end-stage renal failure and finally underwent renal transplantation. We propose that SRNS should be considered as one of the highly variable phenotypes associated with XLI.

  5. Failure prediction using machine learning and time series in optical network.

    Science.gov (United States)

    Wang, Zhilong; Zhang, Min; Wang, Danshi; Song, Chuang; Liu, Min; Li, Jin; Lou, Liqi; Liu, Zhuo

    2017-08-07

    In this paper, we propose a performance monitoring and failure prediction method in optical networks based on machine learning. The primary algorithms of this method are the support vector machine (SVM) and double exponential smoothing (DES). With a focus on risk-aware models in optical networks, the proposed protection plan primarily investigates how to predict the risk of an equipment failure. To the best of our knowledge, this important problem has not yet been fully considered. Experimental results showed that the average prediction accuracy of our method was 95% when predicting the optical equipment failure state. This finding means that our method can forecast an equipment failure risk with high accuracy. Therefore, our proposed DES-SVM method can effectively improve traditional risk-aware models to protect services from possible failures and enhance the optical network stability.

  6. Legal Effects of Link Sharing in Social Networks

    Directory of Open Access Journals (Sweden)

    Eugenio Gil

    2015-12-01

    Full Text Available Knowledge sharing among individuals has changed deeply with the advent of social networks in the environment of Web 2.0. Every user has the possibility of publishing what he or she deems of interest for their audience, regardless of the origin or authorship of the piece of knowledge. It is generally accepted that as the user is sharing a link to a document or video, for example, without getting paid for it, there is no point in worrying about the rights of the original author. It seems that the concepts of authorship and originality is about to disappear as promised the structuralists fifty years ago. Nevertheless the legal system has not changed, nor have the economic interests concerned. This paper explores the last developments of the legal system concerning these issues.

  7. PREDICTION OF FINANCIAL FAILURE OF BANKS BY ARTIFICAL NEURAL NETWORK MODEL

    National Research Council Canada - National Science Library

    Utku ALTUNÖZ

    2013-01-01

    In this article financial failure prediction models based on artificial neural network model, which is among the multivariable statistical techniques has been tested in a parallel with literature surveys...

  8. PREDICTION OF FINANCIAL FAILURE OF BANKS BY ARTIFICAL NEURAL NETWORK MODEL

    Directory of Open Access Journals (Sweden)

    Utku ALTUNÖZ

    2013-12-01

    Full Text Available In this article financial failure prediction models based on artificial neural networkmodel, which is among the multivariable statistical techniques has been tested in a parallelwith literature surveys. As a result of the study, it has been observed that the power ofartificial neural network model in terms of predicting financial failure give a highprobability for both 1 and 2 years before the financial failure.

  9. A method for identifying hierarchical sub-networks / modules and weighting network links based on their similarity in sub-network / module affiliation

    Directory of Open Access Journals (Sweden)

    WenJun Zhang

    2016-06-01

    Full Text Available Some networks, including biological networks, consist of hierarchical sub-networks / modules. Based on my previous study, in present study a method for both identifying hierarchical sub-networks / modules and weighting network links is proposed. It is based on the cluster analysis in which between-node similarity in sets of adjacency nodes is used. Two matrices, linkWeightMat and linkClusterIDs, are achieved by using the algorithm. Two links with both the same weight in linkWeightMat and the same cluster ID in linkClusterIDs belong to the same sub-network / module. Two links with the same weight in linkWeightMat but different cluster IDs in linkClusterIDs belong to two sub-networks / modules at the same hirarchical level. However, a link with an unique cluster ID in linkClusterIDs does not belong to any sub-networks / modules. A sub-network / module of the greater weight is the more connected sub-network / modules. Matlab codes of the algorithm are presented.

  10. Speedy routing recovery protocol for large failure tolerance in wireless sensor networks.

    Science.gov (United States)

    Lee, Joa-Hyoung; Jung, In-Bum

    2010-01-01

    Wireless sensor networks are expected to play an increasingly important role in data collection in hazardous areas. However, the physical fragility of a sensor node makes reliable routing in hazardous areas a challenging problem. Because several sensor nodes in a hazardous area could be damaged simultaneously, the network should be able to recover routing after node failures over large areas. Many routing protocols take single-node failure recovery into account, but it is difficult for these protocols to recover the routing after large-scale failures. In this paper, we propose a routing protocol, referred to as ARF (Adaptive routing protocol for fast Recovery from large-scale Failure), to recover a network quickly after failures over large areas. ARF detects failures by counting the packet losses from parent nodes, and upon failure detection, it decreases the routing interval to notify the neighbor nodes of the failure. Our experimental results indicate that ARF could provide recovery from large-area failures quickly with less packets and energy consumption than previous protocols.

  11. System Reliability Evaluation in Water Distribution Networks with the Impact of Valves Experiencing Cascading Failures

    Directory of Open Access Journals (Sweden)

    Qing Shuang

    2017-06-01

    Full Text Available Water distribution networks (WDNs represent a class of critical infrastructure networks. When a disaster occurs, component failures in a WDN may trigger system failures that result in larger-scale reactions. The aim of the paper is to evaluate the evolution of system reliability and failure propagation time for a WDN experiencing cascading failures, and find the critical pipes which may reduce system reliability dramatically. Multiple factors are considered in the method such as network topology, the balance of water supply and demand, demand multiplier, and pipe break isolation. The pipe-based attack with multiple failure scenarios is simulated in the paper. A case WDN is used to illustrate the method. The results show that the lowest capacity gets stronger when a WDN is short of supply, becoming the dominant factor that decides the evolution of system reliability and failure propagation time. The valve ratio (VR and system reliability present a flattened S curve relationship, and there are two turning points in VR. The critical pipes can be identified. With the fixed 5% valves, a WDN can improve system reliability and resist cascading failures effectively. The findings provide insights into the system reliability and failure propagation time for WDNs experiencing cascading failures. It is proven to be useful in future studies focused on the operation and management of water services.

  12. Impact of treatment on myocardial lysyl oxidase expression and collagen cross-linking in patients with heart failure.

    Science.gov (United States)

    López, Begoña; Querejeta, Ramón; González, Arantxa; Beaumont, Javier; Larman, Mariano; Díez, Javier

    2009-02-01

    The aim of this study was to investigate whether torasemide modifies collagen cross-linking in the failing human heart. We analyzed the degree of cross-linking and the expression of the enzyme lysyl oxidase, which regulates cross-linking, in the myocardium of patients with chronic heart failure at baseline and after 8 months of treatment with either torasemide or furosemide in addition to their standard heart failure therapy. Whereas lysyl oxidase protein expression was very scarce in normal hearts, it was highly expressed in failing hearts. Cross-linking was increased (Pcross-linking (r=0.661; Pcross-linking correlated with left ventricular chamber stiffness (r=0.452; P=0.002) in all patients. These findings show for the first time that lysyl oxidase overexpression is associated with enhanced collagen cross-linking in the failing human heart. In addition, we report that the ability of torasemide to correct both lysyl oxidase overexpression and enhanced collagen cross-linking results in normalization of left ventricular chamber stiffness in patients with heart failure. Lysyl oxidase may thus represent a target for reduction of stiff collagen and improvement of left ventricular mechanical properties in heart failure patients.

  13. Epidemic Survivability: Characterizing Networks Under Epidemic-like Failure Propagation Scenarios

    DEFF Research Database (Denmark)

    Manzano, Marc; Calle, Eusebi; Ripoll, Jordi

    2013-01-01

    in telecommunication networks has not been extensively considered, nowadays, with the increasing computation capacity and complexity of operating systems of modern network devices (routers, switches, etc.), the study of possible epidemic-like failure scenarios must be taken into account. When epidemics occur......, such as in other multiple failure scenarios, identifying the level of vulnerability offered by a network is one of the main challenges. In this paper, we present epidemic survivability, a new network measure that describes the vulnerability of each node of a network under a specific epidemic intensity. Moreover......, this metric is able to identify the set of nodes which are more vulnerable under an epidemic attack. In addition, two applications of epidemic survivability are provided. First, we introduce epidemic criticality, a novel robustness metric for epidemic failure scenarios. A case study shows the utility...

  14. Molecular Dynamics Simulations of Polymer Networks Undergoing Sequential Cross-Linking and Scission Reactions

    DEFF Research Database (Denmark)

    Rottach, Dana R.; Curro, John G.; Budzien, Joanne

    2007-01-01

    The effects of sequential cross-linking and scission of polymer networks formed in two states of strain are investigated using molecular dynamics simulations. Two-stage networks are studied in which a network formed in the unstrained state (stage 1) undergoes additional cross-linking in a uniaxia......The effects of sequential cross-linking and scission of polymer networks formed in two states of strain are investigated using molecular dynamics simulations. Two-stage networks are studied in which a network formed in the unstrained state (stage 1) undergoes additional cross......, a fraction (quantified by the stress transfer function ) of the second-stage cross-links contribute to the effective first-stage cross-link density. The stress transfer functions extracted from the MD simulations of the reacting networks are found to be in very...

  15. Design and application of link: A DSL for network frame manipulation

    CSIR Research Space (South Africa)

    Pennefather, S

    2017-08-01

    Full Text Available This paper describes the design and application of Link, a Domain Specific Language (DSL) targeting the development of network applications focused on traffic manipulation at the frame level. The development of Link is described through...

  16. Link prediction in social network based on local information and attributes of nodes

    Science.gov (United States)

    Liang, Yingying; Huang, Lan; Wang, Zhe

    2017-08-01

    Link prediction is essential to both research areas and practical applications. In order to make full use of information of the network, we proposed a new method to predict links in the social network. Firstly, we extracted topological information and attributes of nodes in the social network. Secondly, we integrated them into feature vectors. Finally, we used XGB classifier to predict links using feature vectors. Through expanding information source, experiments on a co-authorship network suggest that our method can improve the accuracy of link prediction significantly.

  17. Network Adaptability from WMD Disruption and Cascading Failures

    Science.gov (United States)

    2016-04-01

    and this will cause a traffic flood which may cause blocking or congestion of services required for rescue operations. After the post-attack period...Transparent Optical Networks (ICTON), Stockholm, Sweden ; June 27, 2011. 4. B. Mukherjee, "Panorama of Optical Network Survivability," Keynote Talk...Design and Modeling Conference, Kista, Sweden , May 22, 2014. 8. B. Mukherjee, “Disaster preparedness for network and information infrastructures

  18. Comparing risk of failure models in water supply networks using ROC curves

    Energy Technology Data Exchange (ETDEWEB)

    Debon, A., E-mail: andeau@eio.upv.e [Centro de Gestion de la Calidad y del Cambio, Dpt. Estadistica e Investigacion Operativa Aplicadas y Calidad, Universidad Politecnica de Valencia, E-46022 Valencia (Spain); Carrion, A. [Centro de Gestion de la Calidad y del Cambio, Dpt. Estadistica e Investigacion Operativa Aplicadas y Calidad, Universidad Politecnica de Valencia, E-46022 Valencia (Spain); Cabrera, E. [Dpto. De Ingenieria Hidraulica Y Medio Ambiente, Instituto Tecnologico del Agua, Universidad Politecnica de Valencia, E-46022 Valencia (Spain); Solano, H. [Universidad Diego Portales, Santiago (Chile)

    2010-01-15

    The problem of predicting the failure of water mains has been considered from different perspectives and using several methodologies in engineering literature. Nowadays, it is important to be able to accurately calculate the failure probabilities of pipes over time, since water company profits and service quality for citizens depend on pipe survival; forecasting pipe failures could have important economic and social implications. Quantitative tools (such as managerial or statistical indicators and reliable databases) are required in order to assess the current and future state of networks. Companies managing these networks are trying to establish models for evaluating the risk of failure in order to develop a proactive approach to the renewal process, instead of using traditional reactive pipe substitution schemes. The main objective of this paper is to compare models for evaluating the risk of failure in water supply networks. Using real data from a water supply company, this study has identified which network characteristics affect the risk of failure and which models better fit data to predict service breakdown. The comparison using the receiver operating characteristics (ROC) graph leads us to the conclusion that the best model is a generalized linear model. Also, we propose a procedure that can be applied to a pipe failure database, allowing the most appropriate decision rule to be chosen.

  19. Permanent Set of Cross-Linking Networks: Comparison of Theory with Molecular Dynamics Simulations

    DEFF Research Database (Denmark)

    Rottach, Dana R.; Curro, John G.; Budzien, Joanne

    2006-01-01

    The permanent set of cross-linking networks is studied by molecular dynamics. The uniaxial stress for a bead-spring polymer network is investigated as a function of strain and cross-link density history, where cross-links are introduced in unstrained and strained networks. The permanent set...... is found from the strain of the network after it returns to the state-of-ease where the stress is zero. The permanent set simulations are compared with theory using the independent network hypothesis, together with the various theoretical rubber elasticity theories: affine, phantom, constrained junction...

  20. Failure load prediction of single lap adhesive joints using artificial neural networks

    Directory of Open Access Journals (Sweden)

    Erdi Tosun

    2016-06-01

    Full Text Available The objective of this paper was to predict the failure load in single lap adhesive joints subjected to tensile loading by using artificial neural networks. Experimental data obtained from the literature cover the single lap adhesive joints with various geometric models under the tensile loading. The data are arranged in a format such that two input parameters cover the length and width of bond area in single lap adhesive joints and the corresponding output is the ultimate failure load. An artificial neural network model was developed to estimate relationship between failure loads by using geometric dimensions of bond area as input data. A three-layer feedforward artificial neural network that utilized Levenberg–Marquardt learning algorithm model was used in order to train network. It was observed that artificial neural network model can estimate failure load of single lap adhesive joints with acceptable error. Mean absolute percentage error and Nash–Sutcliffe coefficient of efficiency values of both training and testing data were 3.523 and 3.524 and 0.997 and 0.992, respectively. The results showed that the artificial neural network is an efficient alternative method to predict the failure load of single lap adhesive joints. Also estimated results are in very good agreement with the experimental data.

  1. Epidemic Propagation of Control Plane Failures in GMPLS Controlled Optical Transport Networks

    DEFF Research Database (Denmark)

    Ruepp, Sarah Renée; Fagertun, Anna Manolova

    2013-01-01

    In this paper, we investigate the behaviour of a dataplane-decoupled GMPLS control plane, when it is affected by failures that spread in the network in an epidemic manner. In particular, we consider network nodes to be either fully functional, or having a failed control plane, or having both...... a failed control and data plane. Through large-scale network simulation, we evaluate the effect of epidemically spreading control plane failures in terms of blocked connections requests and the amount of stranded capacity due to a dysfunctional control plane. Furthermore, we investigate the effect...

  2. Dipeptidyl peptidase-4 independent cardiac dysfunction links saxagliptin to heart failure.

    Science.gov (United States)

    Koyani, Chintan N; Kolesnik, Ewald; Wölkart, Gerald; Shrestha, Niroj; Scheruebel, Susanne; Trummer, Christopher; Zorn-Pauly, Klaus; Hammer, Astrid; Lang, Petra; Reicher, Helga; Maechler, Heinrich; Groschner, Klaus; Mayer, Bernd; Rainer, Peter P; Sourij, Harald; Sattler, Wolfgang; Malle, Ernst; Pelzmann, Brigitte; von Lewinski, Dirk

    2017-12-01

    Saxagliptin treatment has been associated with increased rate of hospitalization for heart failure in type 2 diabetic patients, though the underlying mechanism(s) remain elusive. To address this, we assessed the effects of saxagliptin on human atrial trabeculae, guinea pig hearts and cardiomyocytes. We found that the primary target of saxagliptin, dipeptidyl peptidase-4, is absent in cardiomyocytes, yet saxagliptin internalized into cardiomyocytes and impaired cardiac contractility via inhibition of the Ca2+/calmodulin-dependent protein kinase II-phospholamban-sarcoplasmic reticulum Ca2+-ATPase 2a axis and Na+-Ca2+ exchanger function in Ca2+ extrusion. This resulted in reduced sarcoplasmic reticulum Ca2+ content, diastolic Ca2+ overload, systolic dysfunction and impaired contractile force. Furthermore, saxagliptin reduced protein kinase C-mediated delayed rectifier K+ current that prolonged action potential duration and consequently QTc interval. Importantly, saxagliptin aggravated pre-existing cardiac dysfunction induced by ischemia/reperfusion injury. In conclusion, our novel results provide mechanisms for the off-target deleterious effects of saxagliptin on cardiac function and support the outcome of SAVOR-TIMI 53 trial that linked saxagliptin with the risk of heart failure. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  3. Robustness of scale-free networks to cascading failures induced by fluctuating loads.

    Science.gov (United States)

    Mizutaka, Shogo; Yakubo, Kousuke

    2015-07-01

    Taking into account the fact that overload failures in real-world functional networks are usually caused by extreme values of temporally fluctuating loads that exceed the allowable range, we study the robustness of scale-free networks against cascading overload failures induced by fluctuating loads. In our model, loads are described by random walkers moving on a network and a node fails when the number of walkers on the node is beyond the node capacity. Our results obtained by using the generating function method show that scale-free networks are more robust against cascading overload failures than Erdős-Rényi random graphs with homogeneous degree distributions. This conclusion is contrary to that predicted by previous works, which neglect the effect of fluctuations of loads.

  4. The rise and fall of global network alliances : success or failure?

    OpenAIRE

    Ulset, Svein

    2002-01-01

    The purpose of this article is to examine and explain the changing use of different modes of organizing global telecom networks that provide global telecom services to multinational business customers. In this market, service contracting and integrated network firms eventually replaced global network alliances. Whereas efficient adaptation of governance modes to changing conditions may explain a significant part, strategy mistakes and governance failures definitely also play an important expl...

  5. Constrained Active Learning for Anchor Link Prediction Across Multiple Heterogeneous Social Networks.

    Science.gov (United States)

    Zhu, Junxing; Zhang, Jiawei; Wu, Quanyuan; Jia, Yan; Zhou, Bin; Wei, Xiaokai; Yu, Philip S

    2017-08-03

    Nowadays, people are usually involved in multiple heterogeneous social networks simultaneously. Discovering the anchor links between the accounts owned by the same users across different social networks is crucial for many important inter-network applications, e.g., cross-network link transfer and cross-network recommendation. Many different supervised models have been proposed to predict anchor links so far, but they are effective only when the labeled anchor links are abundant. However, in real scenarios, such a requirement can hardly be met and most anchor links are unlabeled, since manually labeling the inter-network anchor links is quite costly and tedious. To overcome such a problem and utilize the numerous unlabeled anchor links in model building, in this paper, we introduce the active learning based anchor link prediction problem. Different from the traditional active learning problems, due to the one-to-one constraint on anchor links, if an unlabeled anchor link a = ( u , v ) is identified as positive (i.e., existing), all the other unlabeled anchor links incident to account u or account v will be negative (i.e., non-existing) automatically. Viewed in such a perspective, asking for the labels of potential positive anchor links in the unlabeled set will be rewarding in the active anchor link prediction problem. Various novel anchor link information gain measures are defined in this paper, based on which several constraint active anchor link prediction methods are introduced. Extensive experiments have been done on real-world social network datasets to compare the performance of these methods with state-of-art anchor link prediction methods. The experimental results show that the proposed Mean-entropy-based Constrained Active Learning (MC) method can outperform other methods with significant advantages.

  6. Linking Behavior in the Physics Education Research Coauthorship Network

    Science.gov (United States)

    Anderson, Katharine A.; Crespi, Matthew; Sayre, Eleanor C.

    2017-01-01

    There is considerable long-term interest in understanding the dynamics of collaboration networks, and how these networks form and evolve over time. Most of the work done on the dynamics of social networks focuses on well-established communities. Work examining emerging social networks is rarer, simply because data are difficult to obtain in real…

  7. A network approach for power grid robustness against cascading failures

    NARCIS (Netherlands)

    Wang, X.; Koç, Y.; Kooij, R.E.; Mieghem, P. van

    2015-01-01

    Cascading failures are one of the main reasons for blackouts in electrical power grids. Stable power supply requires a robust design of the power grid topology. Currently, the impact of the grid structure on the grid robustness is mainly assessed by purely topological metrics, that fail to capture

  8. Study of Robustness in Functionally Identical Coupled Networks against Cascading Failures.

    Directory of Open Access Journals (Sweden)

    Xingyuan Wang

    Full Text Available Based on coupled networks, taking node load, capacity and load redistribution between two networks into consideration, we propose functionally identical coupled networks, which consist of two networks connected by interlinks. Functionally identical coupled networks are derived from the power grid of the United States, which consists of many independent grids. Many power transmission lines are planned to interconnect those grids and, therefore, the study of the robustness of functionally identical coupled networks becomes important. In this paper, we find that functionally identical coupled networks are more robust than single networks under random attack. By studying the effect of the broadness and average degree of the degree distribution on the robustness of the network, we find that a broader degree distribution and a higher average degree increase the robustness of functionally identical coupled networks under random failure. And SF-SF (two coupled scale-free networks is more robust than ER-ER (two coupled random networks or SF-ER (coupled random network and scale-free network. This research is useful to construct robust functionally identical coupled networks such as two cooperative power grids.

  9. Study of Robustness in Functionally Identical Coupled Networks against Cascading Failures

    Science.gov (United States)

    Wang, Xingyuan; Cao, Jianye; Qin, Xiaomeng

    2016-01-01

    Based on coupled networks, taking node load, capacity and load redistribution between two networks into consideration, we propose functionally identical coupled networks, which consist of two networks connected by interlinks. Functionally identical coupled networks are derived from the power grid of the United States, which consists of many independent grids. Many power transmission lines are planned to interconnect those grids and, therefore, the study of the robustness of functionally identical coupled networks becomes important. In this paper, we find that functionally identical coupled networks are more robust than single networks under random attack. By studying the effect of the broadness and average degree of the degree distribution on the robustness of the network, we find that a broader degree distribution and a higher average degree increase the robustness of functionally identical coupled networks under random failure. And SF-SF (two coupled scale-free networks) is more robust than ER-ER (two coupled random networks) or SF-ER (coupled random network and scale-free network). This research is useful to construct robust functionally identical coupled networks such as two cooperative power grids. PMID:27494715

  10. Timing and Causes of Readmission After Acute Heart Failure Hospitalization-Insights From the Heart Failure Network Trials.

    Science.gov (United States)

    Vader, Justin M; LaRue, Shane J; Stevens, Susanna R; Mentz, Robert J; DeVore, Adam D; Lala, Anuradha; Groarke, John D; AbouEzzeddine, Omar F; Dunlay, Shannon M; Grodin, Justin L; Dávila-Román, Victor G; de Las Fuentes, Lisa

    2016-11-01

    Readmission or death after heart failure (HF) hospitalization is a consequential and closely scrutinized outcome, but risk factors may vary by population. We characterized the risk factors for post-discharge readmission/death in subjects treated for acute heart failure (AHF). A post hoc analysis was performed on data from 744 subjects enrolled in 3 AHF trials conducted within the Heart Failure Network (HFN): Diuretic Optimization Strategies Evaluation in Acute Heart Failure (DOSE-AHF), Cardiorenal Rescue Study in Acute Decompensated Heart Failure (CARRESS-HF), and Renal Optimization Strategies Evaluation in Acute Heart Failure (ROSE-AHF). All-cause readmission/death occurred in 26% and 38% of subjects within 30 and 60 days of discharge, respectively. Non-HF cardiovascular causes of readmission were more common in the ≤30-day timeframe than in the 31-60-day timeframe (23% vs 10%, P = .016). In a Cox proportional hazards model adjusting a priori for left ventricular ejection fraction <50% and trial, the risk factors for all-cause readmission/death included: elevated baseline blood urea nitrogen, angiotensin-converting enzyme inhibitor (ACEI)/angiotensin receptor blocker (ARB) non-use, lower baseline sodium, non-white race, elevated baseline bicarbonate, lower systolic blood pressure at discharge or day 7, depression, increased length of stay, and male sex. In an AHF population with prominent congestion and prevalent renal dysfunction, early readmissions were more likely to be due to non-HF cardiovascular causes compared with later readmissions. The association between use of ACEI/ARB and lower all-cause readmission/death in Cox proportional hazards model suggests a role for these drugs to improve post-discharge outcomes in AHF. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Teaming Up: Linking Collaboration Networks, Collective Efficacy, and Student Achievement

    Science.gov (United States)

    Moolenaar, Nienke M.; Sleegers, Peter J. C.; Daly, Alan J.

    2012-01-01

    Improving student achievement through teacher collaboration networks is a current focus of schools in many countries. Yet, empirical evidence on the relationship between teacher networks and student achievement and mechanisms that may explain this relationship is limited. This study examined the relationship between teacher networks and student…

  12. Cascading Failures in Flow-Driven Networks Induced by Multiple Initiators

    Science.gov (United States)

    Moussawi, Alaa; Derzsy, Noemi; Lin, Xin; Szymanski, Boleslaw; Korniss, Gyorgy

    Flow-driven networks are particularly prone to cascading failures. These failures are non self-averaging and this makes them very difficult to predict or subdue. Previous work has suggested that uniformly increasing edge or node capacities may lead to larger failures. This suggests that some nodes/edges may act as fuses and mitigate cascading failures. We investigate this idea, and analyze how properties of the initiators of the cascade influence its outcome. We also discuss how stochastic node capacity allocation can be utilized to mitigate cascades induced by multiple initiators. We demonstrate the efficacy of these strategies on random geometric graphs (RGG) and the UCTE European electrical power transmission network, with capacities allocated in a fashion similar to the industry standard. Supported in part by DTRA and NSF.

  13. Centrality Robustness and Link Prediction in Complex Social Networks

    DEFF Research Database (Denmark)

    Davidsen, Søren Atmakuri; Ortiz-Arroyo, Daniel

    2012-01-01

    This chapter addresses two important issues in social network analysis that involve uncertainty. Firstly, we present am analysis on the robustness of centrality measures that extend the work presented in Borgati et al. using three types of complex network structures and one real social network....... Secondly, we present a method to predict edges in dynamic social networks. Our experimental results indicate that the robustness of the centrality measures applied to more realistic social networks follows a predictable pattern and that the use of temporal statistics could improve the accuracy achieved...

  14. The interplay of network structure and dispatch solutions in power grid cascading failures

    Science.gov (United States)

    Reynolds-Barredo, Jose M.; Newman, David E.; Carreras, Benjamin A.; Dobson, Ian

    2016-11-01

    For a given minimum cost of the electricity dispatch, multiple equivalent dispatch solutions may exist. We explore the sensitivity of networks to these dispatch solutions and their impact on the vulnerability of the network to cascading failure blackouts. It is shown that, depending on the heterogeneity of the network structure, the blackout statistics can be sensitive to the dispatch solution chosen, with the clustering coefficient of the network being a key ingredient. We also investigate mechanisms or configurations that decrease discrepancies that can occur between the different dispatch solutions.

  15. Explainable and Efficient Link Prediction in Real-World Network Data

    NARCIS (Netherlands)

    van Engelen, J.E.; Boekhout, H.D.; Takes, F.W.; Boström, H.; Knobbe, A.; Soares, C.; Papapetrou, P.

    2016-01-01

    Data that involves some sort of relationship or interaction can be represented, modelled and analyzed using the notion of a network. To understand the dynamics of networks, the link prediction problem is concerned with predicting the evolution of the topology of a network over time. Previous work in

  16. Reducing the Spectral Radius of a Torus Network by Link Removal.

    Directory of Open Access Journals (Sweden)

    Xiaofan Yang

    Full Text Available The optimal link removal (OLR problem aims at removing a given number of links of a network so that the spectral radius of the residue network obtained by removing the links from the network attains the minimum. Torus networks are a class of regular networks that have witnessed widespread applications. This paper addresses three subproblems of the OLR problem for torus networks, where two or three or four edges are removed. For either of the three subproblems, a link-removing scheme is described. Exhaustive searches show that, for small-sized tori, each of the proposed schemes produces an optimal solution to the corresponding subproblem. Monte-Carlo simulations demonstrate that, for medium-sized tori, each of the three schemes produces a solution to the corresponding subproblem, which is optimal when compared to a large set of randomly produced link-removing schemes. Consequently, it is speculated that each of the three schemes produces an optimal solution to the corresponding subproblem for all torus networks. The set of links produced by each of our schemes is evenly distributed over a network, which may be a common feature of an optimal solution to the OLR problem for regular networks.

  17. Modeling cascading failures with the crisis of trust in social networks

    Science.gov (United States)

    Yi, Chengqi; Bao, Yuanyuan; Jiang, Jingchi; Xue, Yibo

    2015-10-01

    In social networks, some friends often post or disseminate malicious information, such as advertising messages, informal overseas purchasing messages, illegal messages, or rumors. Too much malicious information may cause a feeling of intense annoyance. When the feeling exceeds a certain threshold, it will lead social network users to distrust these friends, which we call the crisis of trust. The crisis of trust in social networks has already become a universal concern and an urgent unsolved problem. As a result of the crisis of trust, users will cut off their relationships with some of their untrustworthy friends. Once a few of these relationships are made unavailable, it is likely that other friends will decline trust, and a large portion of the social network will be influenced. The phenomenon in which the unavailability of a few relationships will trigger the failure of successive relationships is known as cascading failure dynamics. To our best knowledge, no one has formally proposed cascading failures dynamics with the crisis of trust in social networks. In this paper, we address this potential issue, quantify the trust between two users based on user similarity, and model the minimum tolerance with a nonlinear equation. Furthermore, we construct the processes of cascading failures dynamics by considering the unique features of social networks. Based on real social network datasets (Sina Weibo, Facebook and Twitter), we adopt two attack strategies (the highest trust attack (HT) and the lowest trust attack (LT)) to evaluate the proposed dynamics and to further analyze the changes of the topology, connectivity, cascading time and cascade effect under the above attacks. We numerically find that the sparse and inhomogeneous network structure in our cascading model can better improve the robustness of social networks than the dense and homogeneous structure. However, the network structure that seems like ripples is more vulnerable than the other two network

  18. Serviceability Assessment for Cascading Failures in Water Distribution Network under Seismic Scenario

    Directory of Open Access Journals (Sweden)

    Qing Shuang

    2016-01-01

    Full Text Available The stability of water service is a hot point in industrial production, public safety, and academic research. The paper establishes a service evaluation model for the water distribution network (WDN. The serviceability is measured in three aspects: (1 the functionality of structural components under disaster environment; (2 the recognition of cascading failure process; and (3 the calculation of system reliability. The node and edge failures in WDN are interrelated under seismic excitations. The cascading failure process is provided with the balance of water supply and demand. The matrix-based system reliability (MSR method is used to represent the system events and calculate the nonfailure probability. An example is used to illustrate the proposed method. The cascading failure processes with different node failures are simulated. The serviceability is analyzed. The critical node can be identified. The result shows that the aged network has a greater influence on the system service under seismic scenario. The maintenance could improve the antidisaster ability of WDN. Priority should be given to controlling the time between the initial failure and the first secondary failure, for taking postdisaster emergency measures within this time period can largely cut down the spread of cascade effect in the whole WDN.

  19. An adaptive failure detector based on quality of service in peer-to-peer networks.

    Science.gov (United States)

    Dong, Jian; Ren, Xiao; Zuo, Decheng; Liu, Hongwei

    2014-09-05

    The failure detector is one of the fundamental components that maintain high availability of Peer-to-Peer (P2P) networks. Under different network conditions, the adaptive failure detector based on quality of service (QoS) can achieve the detection time and accuracy required by upper applications with lower detection overhead. In P2P systems, complexity of network and high churn lead to high message loss rate. To reduce the impact on detection accuracy, baseline detection strategy based on retransmission mechanism has been employed widely in many P2P applications; however, Chen's classic adaptive model cannot describe this kind of detection strategy. In order to provide an efficient service of failure detection in P2P systems, this paper establishes a novel QoS evaluation model for the baseline detection strategy. The relationship between the detection period and the QoS is discussed and on this basis, an adaptive failure detector (B-AFD) is proposed, which can meet the quantitative QoS metrics under changing network environment. Meanwhile, it is observed from the experimental analysis that B-AFD achieves better detection accuracy and time with lower detection overhead compared to the traditional baseline strategy and the adaptive detectors based on Chen's model. Moreover, B-AFD has better adaptability to P2P network.

  20. An Adaptive Failure Detector Based on Quality of Service in Peer-to-Peer Networks

    Directory of Open Access Journals (Sweden)

    Jian Dong

    2014-09-01

    Full Text Available The failure detector is one of the fundamental components that maintain high availability of Peer-to-Peer (P2P networks. Under different network conditions, the adaptive failure detector based on quality of service (QoS can achieve the detection time and accuracy required by upper applications with lower detection overhead. In P2P systems, complexity of network and high churn lead to high message loss rate. To reduce the impact on detection accuracy, baseline detection strategy based on retransmission mechanism has been employed widely in many P2P applications; however, Chen’s classic adaptive model cannot describe this kind of detection strategy. In order to provide an efficient service of failure detection in P2P systems, this paper establishes a novel QoS evaluation model for the baseline detection strategy. The relationship between the detection period and the QoS is discussed and on this basis, an adaptive failure detector (B-AFD is proposed, which can meet the quantitative QoS metrics under changing network environment. Meanwhile, it is observed from the experimental analysis that B-AFD achieves better detection accuracy and time with lower detection overhead compared to the traditional baseline strategy and the adaptive detectors based on Chen’s model. Moreover, B-AFD has better adaptability to P2P network.

  1. An improved approximate network blocking probability model for all-optical WDM Networks with heterogeneous link capacities

    Science.gov (United States)

    Khan, Akhtar Nawaz

    2017-11-01

    Currently, analytical models are used to compute approximate blocking probabilities in opaque and all-optical WDM networks with the homogeneous link capacities. Existing analytical models can also be extended to opaque WDM networking with heterogeneous link capacities due to the wavelength conversion at each switch node. However, existing analytical models cannot be utilized for all-optical WDM networking with heterogeneous structure of link capacities due to the wavelength continuity constraint and unequal numbers of wavelength channels on different links. In this work, a mathematical model is extended for computing approximate network blocking probabilities in heterogeneous all-optical WDM networks in which the path blocking is dominated by the link along the path with fewer number of wavelength channels. A wavelength assignment scheme is also proposed for dynamic traffic, termed as last-fit-first wavelength assignment, in which a wavelength channel with maximum index is assigned first to a lightpath request. Due to heterogeneous structure of link capacities and the wavelength continuity constraint, the wavelength channels with maximum indexes are utilized for minimum hop routes. Similarly, the wavelength channels with minimum indexes are utilized for multi-hop routes between source and destination pairs. The proposed scheme has lower blocking probability values compared to the existing heuristic for wavelength assignments. Finally, numerical results are computed in different network scenarios which are approximately equal to values obtained from simulations. Since January 2016, he is serving as Head of Department and an Assistant Professor in the Department of Electrical Engineering at UET, Peshawar-Jalozai Campus, Pakistan. From May 2013 to June 2015, he served Department of Telecommunication Engineering as an Assistant Professor at UET, Peshawar-Mardan Campus, Pakistan. He also worked as an International Internship scholar in the Fukuda Laboratory, National

  2. X-linked adrenoleukodystrophy: are signs of hypogonadism always due to testicular failure?

    Science.gov (United States)

    Karapanou, Olga; Vlassopoulou, Barbara; Tzanela, Marinella; Papadopoulos, Dimitrios; Angelidakis, Panagiotis; Michelakakis, Helen; Ioannidis, George; Mihalatos, Markos; Kamakari, Smaragda; Tsagarakis, Stylianos

    2014-01-01

    We present the clinical and hormonal findings of a young male with X-linked adrenoleukodystrophy (X-ALD), with special emphasis on the biochemical and clinical pattern of hypogonadism. A patient, with primary adrenal insufficiency since the age of 5 years, developed progressive neurological symptoms at the age of 29. Diagnosis of X-ALD was established by elevated serum very long chain fatty acids (VLCFAs) and genetic testing. His sexual body hair was sparse. Hormonal investigations revealed normal testosterone and inappropriately elevated LH levels. Androgen receptor gene analysis was negative for mutations or polymorphic variants associated with decreased receptor activity. Signs of hypogonadism in patients with confirmed X-ALD are not exclusively due to primary testicular failure. Tissue specific androgen resistance represents an alternative possibility. Since no loss-of-function mutations were detected in the androgen receptor, it is speculated that the patient's androgen resistance could be part of a functional defect mediated through VLCFA accumulation at the testosterone receptor and/or post-receptor levels.

  3. Limitation of collagen cross-linking with hypoosmolar riboflavin solution: failure in an extremely thin cornea.

    Science.gov (United States)

    Hafezi, Farhad

    2011-08-01

    We report a case of failure of corneal collagen cross-linking (CXL) for progressive keratoconus after preoperative stromal swelling with hypoosmolar riboflavin solution in an extremely thin cornea. CXL was performed using the protocol established for the treatment of thin corneas. Preoperative minimal thickness after abrasion was 268 μm and increased to 406 μm after swelling with hypoosmolar riboflavin solution. Despite CXL, a distinct progression of up to 1.9 diopters was observed at 3 months after the procedure on the anterior corneal surface. At 6 months after CXL, progression had increased to 2.3 diopters. Although swelling with hypoosmolar riboflavin solution was effective and led to a preoperative thickness of more than 400 μm, the increase in biomechanical resistance was not sufficient to arrest the progression of the disease. Little is known about the minimal stromal thickness required for effective CXL to occur. Although swelling with hypoosmolar riboflavin solution over 400 μm and safety of the procedure can be achieved in even thinner corneas, the outcome of this case suggests that a minimal preoperative stromal thickness of 330 μm needs to be respected for a successful CXL procedure.

  4. The vulnerability of the global container shipping network to targeted link disruption

    Science.gov (United States)

    Viljoen, Nadia M.; Joubert, Johan W.

    2016-11-01

    Using complex network theory to describe the relational geography of maritime networks has provided great insights regarding their hierarchy and evolution over the past two decades. Unlike applications in other transport fields, notably air transport, complex network theory has had limited application in studying the vulnerability of maritime networks. This study uses targeted link disruption to investigate the strategy specific vulnerability of the network. Although nodal infrastructure such as ports can render a network vulnerable as a result of labour strikes, trade embargoes or natural disasters, it is the shipping lines connecting the ports that are more probably disrupted, either from within the industry, or outside. In this paper, we apply and evaluate two link-based disruption strategies on the global container shipping network, one based on link betweenness, and the other on link salience, to emulate the impact of large-scale service reconfiguration affecting priority links. The results show that the network is by and large robust to such reconfiguration. Meanwhile the flexibility of the network is reduced by both strategies, but to a greater degree by betweenness, resulting in a reduction of transshipment and dynamic rerouting potential amongst the busiest port regions. The results further show that the salience strategy is highly effective in reducing the commonality of shortest path sets, thereby diminishing opportunities for freight consolidation and scale economies.

  5. Rainfall measurement using radio links from cellular communication networks

    NARCIS (Netherlands)

    Leijnse, H.; Uijlenhoet, R.; Stricker, J.N.M.

    2007-01-01

    We investigate the potential of radio links such as employed by commercial cellular communication companies to monitor path-averaged rainfall. We present an analysis of data collected using two 38-GHz links during eight rainfall events over a 2-month period (October¿November 2003) during mostly

  6. Teaming up: Linking collaboration networks, collective efficacy, and student achievement

    NARCIS (Netherlands)

    Moolenaar, Nienke; Sleegers, P.J.C.; Daly, A.J.; Daly, Alan J.

    2012-01-01

    Improving student achievement through teacher collaboration networks is a current focus of schools in many countries. Yet, empirical evidence on the relationship between teacher networks and student achievement and mechanisms that may explain this relationship is limited. This study examined the

  7. Ultra-Reliable Communications in Failure-Prone Realistic Networks

    DEFF Research Database (Denmark)

    Gerardino, Guillermo Andrés Pocovi; Lauridsen, Mads; Alvarez, Beatriz Soret

    2016-01-01

    We investigate the potential of different diversity and interference management techniques to achieve the required downlink SINR outage probability for ultra-reliable communications. The evaluation is performed in a realistic network deployment based on site-specific data from a European capital....... Micro and macroscopic diversity techniques are proved to be important enablers of ultra-reliable communications. Particularly, it is shown how a 4x4 MIMO scheme with three orders of macroscopic diversity can achieve the required SINR outage performance. Smaller gains are obtained from interference...

  8. Traffic Management in ATM Networks Over Satellite Links

    Science.gov (United States)

    Goyal, Rohit; Jain, Raj; Goyal, Mukul; Fahmy, Sonia; Vandalore, Bobby; vonDeak, Thomas

    1999-01-01

    This report presents a survey of the traffic management Issues in the design and implementation of satellite Asynchronous Transfer Mode (ATM) networks. The report focuses on the efficient transport of Transmission Control Protocol (TCP) traffic over satellite ATM. First, a reference satellite ATM network architecture is presented along with an overview of the service categories available in ATM networks. A delay model for satellite networks and the major components of delay and delay variation are described. A survey of design options for TCP over Unspecified Bit Rate (UBR), Guaranteed Frame Rate (GFR) and Available Bit Rate (ABR) services in ATM is presented. The main focus is on traffic management issues. Several recommendations on the design options for efficiently carrying data services over satellite ATM networks are presented. Most of the results are based on experiments performed on Geosynchronous (GEO) latencies. Some results for Low Earth Orbits (LEO) and Medium Earth Orbit (MEO) latencies are also provided.

  9. Identifying Vulnerable Nodes of Complex Networks in Cascading Failures Induced by Node-Based Attacks

    Directory of Open Access Journals (Sweden)

    Shudong Li

    2013-01-01

    Full Text Available In the research on network security, distinguishing the vulnerable components of networks is very important for protecting infrastructures systems. Here, we probe how to identify the vulnerable nodes of complex networks in cascading failures, which was ignored before. Concerned with random attack (RA and highest load attack (HL on nodes, we model cascading dynamics of complex networks. Then, we introduce four kinds of weighting methods to characterize the nodes of networks including Barabási-Albert scale-free networks (SF, Watts-Strogatz small-world networks (WS, Erdos-Renyi random networks (ER, and two real-world networks. The simulations show that, for SF networks under HL attack, the nodes with small value of the fourth kind of weight are the most vulnerable and the ones with small value of the third weight are also vulnerable. Also, the real-world autonomous system with power-law distribution verifies these findings. Moreover, for WS and ER networks under both RA and HL attack, when the nodes have low tolerant ability, the ones with small value of the fourth kind of weight are more vulnerable and also the ones with high degree are easier to break down. The results give us important theoretical basis for digging the potential safety loophole and making protection strategy.

  10. A neutral grounding metallic resistor failure in a 35 kV network

    Directory of Open Access Journals (Sweden)

    Simić Ninoslav

    2011-01-01

    Full Text Available This paper presents the results of observations and measurements of the impedance of the metal resistor for grounding neutral of the 35 kV network, before and after damaging event. The proposed measures are to be taken in order to eliminate a failure in this particular case, as well as the prevention of similar events.

  11. Beyond a complete failure : The impact of partial capacity reductions on public transport network vulnerability

    NARCIS (Netherlands)

    Cats, O.; Jenelius, E.

    2015-01-01

    Disruptions often result with partial capacity reduction without resulting with a complete breakdown. This study aims to move beyond the analysis of complete failure by investigating the impacts of partial capacity reduction on public transport network performance. We analyse the relation between

  12. Linking behavior in the physics education research coauthorship network

    Directory of Open Access Journals (Sweden)

    Katharine A. Anderson

    2017-05-01

    Full Text Available There is considerable long-term interest in understanding the dynamics of collaboration networks, and how these networks form and evolve over time. Most of the work done on the dynamics of social networks focuses on well-established communities. Work examining emerging social networks is rarer, simply because data are difficult to obtain in real time. In this paper, we use thirty years of data from an emerging scientific community to look at that crucial early stage in the development of a social network. We show that when the field was very young, islands of individual researchers labored in relative isolation, and the coauthorship network was disconnected. Thirty years later, rather than a cluster of individuals, we find a true collaborative community, bound together by a robust collaboration network. However, this change did not take place gradually—the network remained a loose assortment of isolated individuals until the mid 2000s, when those smaller parts suddenly knit themselves together into a single whole. In the rest of this paper, we consider the role of three factors in these observed structural changes: growth, changes in social norms, and the introduction of institutions such as field-specific conferences and journals. We have data from the very earliest years of the field, a period which includes the introduction of two different institutions: the first field-specific conference, and the first field-specific journals. We also identify two relevant behavioral shifts: a discrete increase in coauthorship coincident with the first conference, and a shift among established authors away from collaborating with outsiders, towards collaborating with each other. The interaction of these factors gives us insight into the formation of collaboration networks more broadly.

  13. Linking behavior in the physics education research coauthorship network

    Science.gov (United States)

    Anderson, Katharine A.; Crespi, Matthew; Sayre, Eleanor C.

    2017-06-01

    There is considerable long-term interest in understanding the dynamics of collaboration networks, and how these networks form and evolve over time. Most of the work done on the dynamics of social networks focuses on well-established communities. Work examining emerging social networks is rarer, simply because data are difficult to obtain in real time. In this paper, we use thirty years of data from an emerging scientific community to look at that crucial early stage in the development of a social network. We show that when the field was very young, islands of individual researchers labored in relative isolation, and the coauthorship network was disconnected. Thirty years later, rather than a cluster of individuals, we find a true collaborative community, bound together by a robust collaboration network. However, this change did not take place gradually—the network remained a loose assortment of isolated individuals until the mid 2000s, when those smaller parts suddenly knit themselves together into a single whole. In the rest of this paper, we consider the role of three factors in these observed structural changes: growth, changes in social norms, and the introduction of institutions such as field-specific conferences and journals. We have data from the very earliest years of the field, a period which includes the introduction of two different institutions: the first field-specific conference, and the first field-specific journals. We also identify two relevant behavioral shifts: a discrete increase in coauthorship coincident with the first conference, and a shift among established authors away from collaborating with outsiders, towards collaborating with each other. The interaction of these factors gives us insight into the formation of collaboration networks more broadly.

  14. Topological traps control flow on real networks: the case of coordination failures.

    Science.gov (United States)

    Roca, Carlos P; Lozano, Sergi; Arenas, Alex; Sánchez, Angel

    2010-12-09

    We study evolutionary games in real social networks, with a focus on coordination games. We find that populations fail to coordinate in the same behavior for a wide range of parameters, a novel phenomenon not observed in most artificial model networks. We show that this result arises from the relevance of correlations beyond the first neighborhood, in particular from topological traps formed by links between nodes of different degrees in regions with few or no redundant paths. This specificity of real networks has not been modeled so far with synthetic networks. We thus conclude that model networks must be improved to include these mesoscopic structures, in order to successfully address issues such as the emergence of cooperation in real societies. We finally show that topological traps are a very generic phenomenon that may arise in very many different networks and fields, such as opinion models, spread of diseases or ecological networks.

  15. Common neighbours and the local-community-paradigm for topological link prediction in bipartite networks

    Science.gov (United States)

    Daminelli, Simone; Thomas, Josephine Maria; Durán, Claudio; Vittorio Cannistraci, Carlo

    2015-11-01

    Bipartite networks are powerful descriptions of complex systems characterized by two different classes of nodes and connections allowed only across but not within the two classes. Unveiling physical principles, building theories and suggesting physical models to predict bipartite links such as product-consumer connections in recommendation systems or drug-target interactions in molecular networks can provide priceless information to improve e-commerce or to accelerate pharmaceutical research. The prediction of nonobserved connections starting from those already present in the topology of a network is known as the link-prediction problem. It represents an important subject both in many-body interaction theory in physics and in new algorithms for applied tools in computer science. The rationale is that the existing connectivity structure of a network can suggest where new connections can appear with higher likelihood in an evolving network, or where nonobserved connections are missing in a partially known network. Surprisingly, current complex network theory presents a theoretical bottle-neck: a general framework for local-based link prediction directly in the bipartite domain is missing. Here, we overcome this theoretical obstacle and present a formal definition of common neighbour index and local-community-paradigm (LCP) for bipartite networks. As a consequence, we are able to introduce the first node-neighbourhood-based and LCP-based models for topological link prediction that utilize the bipartite domain. We performed link prediction evaluations in several networks of different size and of disparate origin, including technological, social and biological systems. Our models significantly improve topological prediction in many bipartite networks because they exploit local physical driving-forces that participate in the formation and organization of many real-world bipartite networks. Furthermore, we present a local-based formalism that allows to intuitively

  16. Mechanisms linking electrical alternans and clinical ventricular arrhythmia in human heart failure.

    Science.gov (United States)

    Bayer, J D; Lalani, G G; Vigmond, E J; Narayan, S M; Trayanova, N A

    2016-09-01

    Mechanisms of ventricular tachycardia (VT) and ventricular fibrillation (VF) in patients with heart failure (HF) are undefined. The purpose of this study was to elucidate VT/VF mechanisms in HF by using a computational-clinical approach. In 53 patients with HF and 18 control patients, we established the relationship between low-amplitude action potential voltage alternans (APV-ALT) during ventricular pacing at near-resting heart rates and VT/VF on long-term follow-up. Mechanisms underlying the transition of APV-ALT to VT/VF, which cannot be ascertained in patients, were dissected with multiscale human ventricular models based on human electrophysiological and magnetic resonance imaging data (control and HF). For patients with APV-ALT k-score >1.7, complex action potential duration (APD) oscillations (≥2.3% of mean APD), rather than APD alternans, most accurately predicted VT/VF during long-term follow-up (+82%; -90% predictive values). In the failing human ventricular models, abnormal sarcoplasmic reticulum (SR) calcium handling caused APV-ALT (>1 mV) during pacing with a cycle length of 550 ms, which transitioned into large magnitude (>100 ms) discordant repolarization time alternans (RT-ALT) at faster rates. This initiated VT/VF (cycle length <400 ms) by steepening apicobasal repolarization (189 ms/mm) until unidirectional conduction block and reentry. Complex APD oscillations resulted from nonstationary discordant RT-ALT. Restoring SR calcium to control levels was antiarrhythmic by terminating electrical alternans. APV-ALT and complex APD oscillations at near-resting heart rates in patients with HF are linked to arrhythmogenic discordant RT-ALT. This may enable novel physiologically tailored, bioengineered indices to improve VT/VF risk stratification, where SR calcium handling and spatial apicobasal repolarization are potential therapeutic targets. Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

  17. Modeling of Failure Prediction Bayesian Network with Divide-and-Conquer Principle

    Directory of Open Access Journals (Sweden)

    Zhiqiang Cai

    2014-01-01

    Full Text Available For system failure prediction, automatically modeling from historical failure dataset is one of the challenges in practical engineering fields. In this paper, an effective algorithm is proposed to build the failure prediction Bayesian network (FPBN model with data mining technology. First, the conception of FPBN is introduced to describe the state of components and system and the cause-effect relationships among them. The types of network nodes, the directions of network edges, and the conditional probability distributions (CPDs of nodes in FPBN are discussed in detail. According to the characteristics of nodes and edges in FPBN, a divide-and-conquer principle based algorithm (FPBN-DC is introduced to build the best FPBN network structures of different types of nodes separately. Then, the CPDs of nodes in FPBN are calculated by the maximum likelihood estimation method based on the built network. Finally, a simulation study of a helicopter convertor model is carried out to demonstrate the application of FPBN-DC. According to the simulations results, the FPBN-DC algorithm can get better fitness value with the lower number of iterations, which verified its effectiveness and efficiency compared with traditional algorithm.

  18. Network Delays and Link Capacities in Application-Specific Wormhole NoCs

    Directory of Open Access Journals (Sweden)

    Zvika Guz

    2007-01-01

    Full Text Available Network-on-chip- (NoC- based application-specific systems on chip, where information traffic is heterogeneous and delay requirements may largely vary, require individual capacity assignment for each link in the NoC. This is in contrast to the standard approach of on- and off-chip interconnection networks which employ uniform-capacity links. Therefore, the allocation of link capacities is an essential step in the automated design process of NoC-based systems. The algorithm should minimize the communication resource costs under Quality-of-Service timing constraints. This paper presents a novel analytical delay model for virtual channeled wormhole networks with nonuniform links and applies the analysis in devising an efficient capacity allocation algorithm which assigns link capacities such that packet delay requirements for each flow are satisfied.

  19. Application of Functional Link Artificial Neural Network for Prediction of Machinery Noise in Opencast Mines

    Directory of Open Access Journals (Sweden)

    Santosh Kumar Nanda

    2011-01-01

    Full Text Available Functional link-based neural network models were applied to predict opencast mining machineries noise. The paper analyzes the prediction capabilities of functional link neural network based noise prediction models vis-à-vis existing statistical models. In order to find the actual noise status in opencast mines, some of the popular noise prediction models, for example, ISO-9613-2, CONCAWE, VDI, and ENM, have been applied in mining and allied industries to predict the machineries noise by considering various attenuation factors. Functional link artificial neural network (FLANN, polynomial perceptron network (PPN, and Legendre neural network (LeNN were used to predict the machinery noise in opencast mines. The case study is based on data collected from an opencast coal mine of Orissa, India. From the present investigations, it could be concluded that the FLANN model give better noise prediction than the PPN and LeNN model.

  20. Link Prediction in Criminal Networks: A Tool for Criminal Intelligence Analysis

    OpenAIRE

    Giulia Berlusconi; Francesco Calderoni; Nicola Parolini; Marco Verani; Carlo Piccardi

    2017-01-01

    The problem of link prediction has recently received increasing attention from scholars in network science. In social network analysis, one of its aims is to recover missing links, namely connections among actors which are likely to exist but have not been reported because data are incomplete or subject to various types of uncertainty. In the field of criminal investigations, problems of incomplete information are encountered almost by definition, given the obvious anti-detection strategies s...

  1. Mapping Systemic Risk: Critical Degree and Failures Distribution in Financial Networks.

    Science.gov (United States)

    Smerlak, Matteo; Stoll, Brady; Gupta, Agam; Magdanz, James S

    2015-01-01

    The financial crisis illustrated the need for a functional understanding of systemic risk in strongly interconnected financial structures. Dynamic processes on complex networks being intrinsically difficult to model analytically, most recent studies of this problem have relied on numerical simulations. Here we report analytical results in a network model of interbank lending based on directly relevant financial parameters, such as interest rates and leverage ratios. We obtain a closed-form formula for the "critical degree" (the number of creditors per bank below which an individual shock can propagate throughout the network), and relate failures distributions to network topologies, in particular scalefree ones. Our criterion for the onset of contagion turns out to be isomorphic to the condition for cooperation to evolve on graphs and social networks, as recently formulated in evolutionary game theory. This remarkable connection supports recent calls for a methodological rapprochement between finance and ecology.

  2. Mapping Systemic Risk: Critical Degree and Failures Distribution in Financial Networks

    Science.gov (United States)

    Smerlak, Matteo; Stoll, Brady; Gupta, Agam; Magdanz, James S.

    2015-01-01

    The financial crisis illustrated the need for a functional understanding of systemic risk in strongly interconnected financial structures. Dynamic processes on complex networks being intrinsically difficult to model analytically, most recent studies of this problem have relied on numerical simulations. Here we report analytical results in a network model of interbank lending based on directly relevant financial parameters, such as interest rates and leverage ratios. We obtain a closed-form formula for the “critical degree” (the number of creditors per bank below which an individual shock can propagate throughout the network), and relate failures distributions to network topologies, in particular scalefree ones. Our criterion for the onset of contagion turns out to be isomorphic to the condition for cooperation to evolve on graphs and social networks, as recently formulated in evolutionary game theory. This remarkable connection supports recent calls for a methodological rapprochement between finance and ecology. PMID:26207631

  3. A method for joint routing, wavelength dimensioning and fault tolerance for any set of simultaneous failures on dynamic WDM optical networks

    Science.gov (United States)

    Jara, Nicolás; Vallejos, Reinaldo; Rubino, Gerardo

    2017-11-01

    The design of optical networks decomposes into different tasks, where the engineers must basically organize the way the main system's resources are used, minimizing the design and operation costs and respecting critical performance constraints. More specifically, network operators face the challenge of solving routing and wavelength dimensioning problems while aiming to simultaneously minimize the network cost and to ensure that the network performance meets the level established in the Service Level Agreement (SLA). We call this the Routing and Wavelength Dimensioning (R&WD) problem. Another important problem to be solved is how to deal with failures of links when the network is operating. When at least one link fails, a high rate of data loss may occur. To avoid it, the network must be designed in such a manner that upon one or multiple failures, the affected connections can still communicate using alternative routes, a mechanism known as Fault Tolerance (FT). When the mechanism allows to deal with an arbitrary number of faults, we speak about Multiple Fault Tolerance (MFT). The different tasks before mentioned are usually solved separately, or in some cases by pairs, leading to solutions that are not necessarily close to optimal ones. This paper proposes a novel method to simultaneously solve all of them, that is, the Routing, the Wavelength Dimensioning, and the Multiple Fault Tolerance problems. The method allows to obtain: a) all the primary routes by which each connection normally transmits its information, b) the additional routes, called secondary routes, used to keep each user connected in cases where one or more simultaneous failures occur, and c) the number of wavelengths available at each link of the network, calculated such that the blocking probability of each connection is lower than a pre-determined threshold (which is a network design parameter), despite the occurrence of simultaneous link failures. The solution obtained by the new algorithm is

  4. Prognostic impact of diastolic dysfunction in systolic heart failure-A cross-project analysis from the German Competence Network Heart Failure.

    Science.gov (United States)

    Lüers, Claus; Edelmann, Frank; Wachter, Rolf; Pieske, Burkert; Mende, Meinhard; Angermann, Christiane; Ertl, Georg; Düngen, Hans-Dirk; Störk, Stefan

    2017-09-01

    We investigated the modifying role and prognostic importance of diastolic dysfunction (DD) in patients with heart failure and systolic dysfunction (SD). The echocardiographic evaluation of diastolic function in patients with SD provides further prognostic information. From the German Competence Network Heart Failure, 1046 heart failure patients with reduced left ventricular ejection fraction (LVEF; failure patients with reduced LVEF, the evaluation of diastolic function provides additional prognostic information. Although severe SD generally increased the risk for all endpoints, the degree of DD and its impact as a prognostic marker for overall and cardiovascular mortality appeared of particular relevance in subjects with nonsevere SD. © 2017 Wiley Periodicals, Inc.

  5. Leveraging Social Links for Trust and Privacy in Networks

    Science.gov (United States)

    Cutillo, Leucio Antonio; Molva, Refik; Strufe, Thorsten

    Existing on-line social networks (OSN) such as Facebook suffer from several weaknesses regarding privacy and security due to their inherent handling of personal data. As pointed out in [4], a preliminary analysis of existing OSNs shows that they are subject to a number of vulnerabilities, ranging from cloning legitimate users to sybil attacks through privacy violations. Starting from these OSN vulnerabilities as the first step of a broader research activity, we came up with a new approach that is very promising in re-visiting security and privacy problems in distributed systems and networks. We suggest a solution that both aims at avoiding any centralized control and leverages on the real life trust between users, that is part of the social network application itself. An anonymization technique based on multi-hop routing among trusted nodes guarantees privacy in data access and, generally speaking, in all the OSN operations.

  6. Effects of active links on epidemic transmission over social networks

    Science.gov (United States)

    Zhu, Guanghu; Chen, Guanrong; Fu, Xinchu

    2017-02-01

    A new epidemic model with two infection periods is developed to account for the human behavior in social network, where newly infected individuals gradually restrict most of future contacts or are quarantined, causing infectivity change from a degree-dependent form to a constant. The corresponding dynamics are formulated by a set of ordinary differential equations (ODEs) via mean-field approximation. The effects of diverse infectivity on the epidemic dynamics ​are examined, with a behavioral interpretation of the basic reproduction number. Results show that such simple adaptive reactions largely determine the impact of network structure on epidemics. Particularly, a theorem proposed by Lajmanovich and Yorke in 1976 is generalized, so that it can be applied for the analysis of the epidemic models with multi-compartments especially network-coupled ODE systems.

  7. Measuring urban rainfall using microwave links from commercial cellular communication networks

    NARCIS (Netherlands)

    Overeem, A.; Leijnse, H.; Uijlenhoet, R.

    2011-01-01

    The estimation of rainfall using commercial microwave links is a new and promising measurement technique. Commercial link networks cover large parts of the land surface of the earth and have a high density, particularly in urban areas. Rainfall attenuates the electromagnetic signals transmitted

  8. Modeling the video distribution link in the Next Generation Optical Access Networks

    DEFF Research Database (Denmark)

    Amaya, F.; Cárdenas, A.; Tafur Monroy, Idelfonso

    2011-01-01

    In this work we present a model for the design and optimization of the video distribution link in the next generation optical access network. We analyze the video distribution performance in a SCM-WDM link, including the noise, the distortion and the fiber optic nonlinearities. Additionally, we c...

  9. Building Student Networks with LinkedIn: The Potential for Connections, Internships, and Jobs

    Science.gov (United States)

    Peterson, Robert M.; Dover, Howard F.

    2014-01-01

    Networking is a chance to interact with people, build friendships or business partners, identify opportunities, and create value. Technology has made this process easier, since individuals can readily contact others who were previously unknown. In the professional world, LinkedIn has become the standard way to build virtual and personal networks.…

  10. Networking for Innovation in South Wales. Experiences in Developing Productive Links between University and Industry.

    Science.gov (United States)

    Jones, Haydn; Jenkins, Sarah

    1999-01-01

    To develop productive links between industry and university, the style and ethos of networks focused on innovation are crucial. Cardiff University (Wales) has an innovation network that stimulates collaborative work and technology transfer through its informal open nature that encourages partnership. (SK)

  11. A Resilience Approach to Symbiosis Networks of Ecoindustrial Parks Based on Cascading Failure Model

    Directory of Open Access Journals (Sweden)

    Yu Zeng

    2013-01-01

    Full Text Available Evaluation and improvement of resilience in ecoindustrial parks have been the pressing issues to be addressed in the study of safety. In this paper, eco-industrial systems are extracted as symbiosis networks by using social network analysis first. We then construct a novel cascading failure model and propose an evaluation method of node importance according to the features of symbiosis networks of eco-industrial parks. Based on the cascading model, an effective new method, that is, the critical threshold, is put forward to quantitatively assess the resilience of symbiosis networks of eco-industrial parks. Some theoretical analysis is furthermore provided to the critical threshold. Finally, we take Jinjie eco-industrial system in Shanxi Province of China as a case to investigate its resilience. The key potential nodes are identified by using our model. We also find the respective relation among the resilience of symbiosis networks and the parameters in our cascading model. Theoretical analysis results and numerical simulations both show the optimal value of the tunable load parameter with which the strongest resilience level against cascading failures can be attained in symbiosis networks of eco-industrial parks.

  12. Young China Scholars Poverty Research Network: A bridge linking ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    2011-07-08

    Jul 8, 2011 ... ... more about this successful Canada-China collaboration: "A strong competition" · Two-way learning · Declining poverty, rising inequality · Fresh insights · Mapping the network · One scholar's story · On the world stage · The CHIP surveys · "We chose the mentors carefully" · "The good work is collaborative" ...

  13. LINKEDIN TRILOGY: Part 1. Top 10 Reasons You Should NOT Join LinkedIn Professional Network!

    Science.gov (United States)

    Berk, Ronald A.

    2013-01-01

    Disclaimer: I have been an active "free" user of LinkedIn for 5.463 years with more than 3000 (1st degree) connections from all over the world. I have no vested interest in LinkedIn other than as a user of the services it provides. Despite the fact that LinkedIn was originally designed as a network for business professionals, not…

  14. Covalent Cross-Linking of Porous Poly(ionic liquid) Membrane via a Triazine Network

    OpenAIRE

    Täuber, K.; Dani, A.; Yuan, J.

    2017-01-01

    Porous poly(ionic liquid) membranes that were prepared via electrostatic cross-linking were subsequently covalently cross-linked via formation of a 1,3,5-triazine network. The additional covalent cross-links do not affect the pore size and pore size distribution of the membranes and stabilize them towards salt solutions of high ionic strength, enabling the membranes to work in a broader environmental window.

  15. Feasibility of using adaptive logic networks to predict compressor unit failure

    Energy Technology Data Exchange (ETDEWEB)

    Armstrong, W.W.; Chungying Chu; Thomas, M.M. [Dendronic Decisions Limited, Edmonton (Canada)] [and others

    1995-12-31

    In this feasibility study, an adaptive logic network (ALN) was trained to predict failures of turbine-driven compressor units using a large database of measurements. No expert knowledge about compressor systems was involved. The predictions used only the statistical properties of the measurements and the indications of failure types. A fuzzy set was used to model measurements typical of normal operation. It was constrained by a requirement imposed during ALN training, that it should have a shape similar to a Gaussian density, more precisely, that its logarithm should be convex-up. Initial results obtained using this approach to knowledge discovery in the database were encouraging.

  16. A robust biomarker of large-scale network failure in Alzheimer's disease.

    Science.gov (United States)

    Wiepert, Daniela A; Lowe, Val J; Knopman, David S; Boeve, Bradley F; Graff-Radford, Jonathan; Petersen, Ronald C; Jack, Clifford R; Jones, David T

    2017-01-01

    Biomarkers for Alzheimer's disease (AD) pathophysiology have been developed that focus on various levels of brain organization. However, no robust biomarker of large-scale network failure has been developed. Using the recently introduced cascading network failure model of AD, we developed the network failure quotient (NFQ) as a biomarker of this process. We developed and optimized the NFQ using our recently published analyses of task-free functional magnetic resonance imaging data in clinically normal (n = 43) and AD dementia participants (n = 28) from the Alzheimer's Disease Neuroimaging Initiative. The optimized NFQ (oNFQ) was then validated in a cohort spanning the AD spectrum from the Mayo Clinic (n = 218). The oNFQ (d = 1.25, 95% confidence interval [1.25, 1.26]) had the highest effect size for differentiating persons with AD dementia from clinically normal participants. The oNFQ measure performed similarly well on the validation Mayo Clinic sample (d = 1.44, 95% confidence interval [1.43, 1.44]). The oNFQ was also associated with other available key biomarkers in the Mayo cohort. This study demonstrates a measure of functional connectivity, based on a cascading network failure model of AD, and was highly successful in identifying AD dementia. A robust biomarker of the large-scale effects of AD pathophysiology will allow for richer descriptions of the disease process and its modifiers, but is not currently suitable for discriminating clinical diagnostic categories. The large-scale network level may be one of the earliest manifestations of AD, making this an attractive target for continued biomarker development to be used in prevention trials.

  17. Link Investigation of IEEE 802.15.4 Wireless Sensor Networks in Forests

    Science.gov (United States)

    Ding, Xingjian; Sun, Guodong; Yang, Gaoxiang; Shang, Xinna

    2016-01-01

    Wireless sensor networks are expected to automatically monitor the ecological evolution and wildlife habits in forests. Low-power links (transceivers) are often adopted in wireless sensor network applications, in order to save the precious sensor energy and then achieve long-term, unattended monitoring. Recent research has presented some performance characteristics of such low-power wireless links under laboratory or outdoor scenarios with less obstacles, and they have found that low-power wireless links are unreliable and prone to be affected by the target environment. However, there is still less understanding about how well the low-power wireless link performs in real-world forests and to what extent the complex in-forest surrounding environments affect the link performances. In this paper, we empirically evaluate the low-power links of wireless sensors in three typical different forest environments. Our experiment investigates the performance of the link layer compatible with the IEEE 802.15.4 standard and analyzes the variation patterns of the packet reception ratio (PRR), the received signal strength indicator (RSSI) and the link quality indicator (LQI) under diverse experimental settings. Some observations of this study are inconsistent with or even contradict prior results that are achieved in open fields or relatively clean environments and thus, provide new insights both into effectively evaluating the low-power wireless links and into efficiently deploying wireless sensor network systems in forest environments. PMID:27355957

  18. Link Investigation of IEEE 802.15.4 Wireless Sensor Networks in Forests.

    Science.gov (United States)

    Ding, Xingjian; Sun, Guodong; Yang, Gaoxiang; Shang, Xinna

    2016-06-27

    Wireless sensor networks are expected to automatically monitor the ecological evolution and wildlife habits in forests. Low-power links (transceivers) are often adopted in wireless sensor network applications, in order to save the precious sensor energy and then achieve long-term, unattended monitoring. Recent research has presented some performance characteristics of such low-power wireless links under laboratory or outdoor scenarios with less obstacles, and they have found that low-power wireless links are unreliable and prone to be affected by the target environment. However, there is still less understanding about how well the low-power wireless link performs in real-world forests and to what extent the complex in-forest surrounding environments affect the link performances. In this paper, we empirically evaluate the low-power links of wireless sensors in three typical different forest environments. Our experiment investigates the performance of the link layer compatible with the IEEE 802.15.4 standard and analyzes the variation patterns of the packet reception ratio (PRR), the received signal strength indicator (RSSI) and the link quality indicator (LQI) under diverse experimental settings. Some observations of this study are inconsistent with or even contradict prior results that are achieved in open fields or relatively clean environments and thus, provide new insights both into effectively evaluating the low-power wireless links and into efficiently deploying wireless sensor network systems in forest environments.

  19. Effectiveness evaluation of double-layered satellite network with laser and microwave hybrid links based on fuzzy analytic hierarchy process

    Science.gov (United States)

    Zhang, Wei; Rao, Qiaomeng

    2018-01-01

    In order to solve the problem of high speed, large capacity and limited spectrum resources of satellite communication network, a double-layered satellite network with global seamless coverage based on laser and microwave hybrid links is proposed in this paper. By analyzing the characteristics of the double-layered satellite network with laser and microwave hybrid links, an effectiveness evaluation index system for the network is established. And then, the fuzzy analytic hierarchy process, which combines the analytic hierarchy process and the fuzzy comprehensive evaluation theory, is used to evaluate the effectiveness of the double-layered satellite network with laser and microwave hybrid links. Furthermore, the evaluation result of the proposed hybrid link network is obtained by simulation. The effectiveness evaluation process of the proposed double-layered satellite network with laser and microwave hybrid links can help to optimize the design of hybrid link double-layered satellite network and improve the operating efficiency of the satellite system.

  20. Distributed and Cooperative Link Scheduling for Large-Scale Multihop Wireless Networks

    Directory of Open Access Journals (Sweden)

    Swami Ananthram

    2007-01-01

    Full Text Available A distributed and cooperative link-scheduling (DCLS algorithm is introduced for large-scale multihop wireless networks. With this algorithm, each and every active link in the network cooperatively calibrates its environment and converges to a desired link schedule for data transmissions within a time frame of multiple slots. This schedule is such that the entire network is partitioned into a set of interleaved subnetworks, where each subnetwork consists of concurrent cochannel links that are properly separated from each other. The desired spacing in each subnetwork can be controlled by a tuning parameter and the number of time slots specified for each frame. Following the DCLS algorithm, a distributed and cooperative power control (DCPC algorithm can be applied to each subnetwork to ensure a desired data rate for each link with minimum network transmission power. As shown consistently by simulations, the DCLS algorithm along with a DCPC algorithm yields significant power savings. The power savings also imply an increased feasible region of averaged link data rates for the entire network.

  1. Real time data acquisition of a countrywide commercial microwave link network

    Science.gov (United States)

    Chwala, Christian; Keis, Felix; Kunstmann, Harald

    2015-04-01

    Research in recent years has shown that data from commercial microwave link networks can provide very valuable precipitation information. Since these networks comprise the backbone of the cell phone network, they provide countrywide coverage. However acquiring the necessary data from the network operators is still difficult. Data is usually made available for researchers with a large time delay and often at irregular basis. This of course hinders the exploitation of commercial microwave link data in operational applications like QPE forecasts running at national meteorological services. To overcome this, we have developed a custom software in joint cooperation with our industry partner Ericsson. The software is installed on a dedicated server at Ericsson and is capable of acquiring data from the countrywide microwave link network in Germany. In its current first operational testing phase, data from several hundred microwave links in southern Germany is recorded. All data is instantaneously sent to our server where it is stored and organized in an emerging database. Time resolution for the Ericsson data is one minute. The custom acquisition software, however, is capable of processing higher sampling rates. Additionally we acquire and manage 1 Hz data from four microwave links operated by the skiing resort in Garmisch-Partenkirchen. We will present the concept of the data acquisition and show details of the custom-built software. Additionally we will showcase the accessibility and basic processing of real time microwave link data via our database web frontend.

  2. Distributed and Cooperative Link Scheduling for Large-Scale Multihop Wireless Networks

    Directory of Open Access Journals (Sweden)

    Ananthram Swami

    2007-12-01

    Full Text Available A distributed and cooperative link-scheduling (DCLS algorithm is introduced for large-scale multihop wireless networks. With this algorithm, each and every active link in the network cooperatively calibrates its environment and converges to a desired link schedule for data transmissions within a time frame of multiple slots. This schedule is such that the entire network is partitioned into a set of interleaved subnetworks, where each subnetwork consists of concurrent cochannel links that are properly separated from each other. The desired spacing in each subnetwork can be controlled by a tuning parameter and the number of time slots specified for each frame. Following the DCLS algorithm, a distributed and cooperative power control (DCPC algorithm can be applied to each subnetwork to ensure a desired data rate for each link with minimum network transmission power. As shown consistently by simulations, the DCLS algorithm along with a DCPC algorithm yields significant power savings. The power savings also imply an increased feasible region of averaged link data rates for the entire network.

  3. High speed serial link for UA1 microprocessor network

    CERN Document Server

    Cittolin, S; Zurfluh, E

    1981-01-01

    The UA1 data acquisition system consists of a set of distributed microprocessor units. An interprocessor link, independent of the CAMAC data readout, has been developed in order to have continuous remote control and run-time data handling, e.g. transmission of calibration programs/parameters, equipment test/status and histogram accumulation. The data transmission system is designed to be used in a loop configuration equipped with transceivers for twisted pair cables (RS-422). As an economical system, it is running as an ancillary serial loop-link between microprocessors, like Data Acquisition Crate Controllers and systems with distributed intelligence. The software driver consists of a loop-controller package, which may run in a BAMBI Computer Language environment and a fully interrupt controlled program for all other secondary stations. A special single-character mode provides a handy link for remote debugging in a pseudo-full-duplex mode. The format is based on the HDLC protocol without sequence numbering. ...

  4. High speed serial link for UA1 microprocessor network

    CERN Document Server

    Cittolin, Sergio; Zurfluh, E

    1981-01-01

    The UA1 data acquisition system consists of a set of distributed microprocessor units. An interprocessor link, independent of the CAMAC data readout, has been developed in order to have continuous remote control and run-time data handling, e.g. transmission of calibration programs/parameters, equipment test/status and histogram accumulation. The data transmission system is designed to be used in a loop configuration equipped with transceivers for twisted pair cables (RS-422). As an economical system, it is running as an ancillary serial loop-link between microprocessors, like data acquisition crate controllers and systems with distributed intelligence. The software driver consists of a loop-controller package, which may run in a BAMBI computer language environment and a fully interrupt controlled program for all other secondary stations. A special single-character mode provides a handy link for remote debugging in a pseudo-full-duplex mode. The format is based on the HDLC protocol without sequence numbering. ...

  5. Hypergraph Modeling and Approximation Algorithms for the Minimum Length Link Scheduling in Multiuser MIMO Networks

    Directory of Open Access Journals (Sweden)

    Hu Shen

    2013-01-01

    Full Text Available This paper investigates the problem of the minimum length link scheduling (MLLS in multiuser MIMO (MU-MIMO networks. Generally, in the networks with MU-MIMO capability, the number of concurrent transmissions can be as large as that of antenna elements at the receiver. As a result, link interference is no longer binary but demonstrates a strong correlation among multiple links, which cannot be captured by the conventional conflict graph interference model. Hence, we propose a novel hypergraph interference model, which can accurately and efficiently characterize the relationship of multiple interferences induced by concurrent transmissions, and provide a tractable formalization of the minimum length link scheduling in MU-MIMO networks (MU-MIMO MLLS. Afterwards, we prove that the MU-MIMO MLLS problem is NP-hard and introduce two approximation algorithms to find the near-optimal feasible schedule. Finally, extensive simulation experiments are presented.

  6. Bounds on Worst-Case Deadline Failure Probabilities in Controller Area Networks

    Directory of Open Access Journals (Sweden)

    Michael Short

    2016-01-01

    Full Text Available Industrial communication networks like the Controller Area Network (CAN are often required to operate reliably in harsh environments which expose the communication network to random errors. Probabilistic schedulability analysis can employ rich stochastic error models to capture random error behaviors, but this is most often at the expense of increased analysis complexity. In this paper, an efficient method (of time complexity O(n log n to bound the message deadline failure probabilities for an industrial CAN network consisting of n periodic/sporadic message transmissions is proposed. The paper develops bounds for Deadline Minus Jitter Monotonic (DMJM and Earliest Deadline First (EDF message scheduling techniques. Both random errors and random bursts of errors can be included in the model. Stochastic simulations and a case study considering DMJM and EDF scheduling of an automotive benchmark message set provide validation of the technique and highlight its application.

  7. Mesoscopic simulations of hydrophilic cross-linked polycarbonate polyurethane networks: structure and morphology.

    Science.gov (United States)

    Iype, E; Esteves, A C C; de With, G

    2016-06-14

    Polyurethane (PU) cross-linked networks are frequently used in biomedical and marine applications, e.g., as hydrophilic polymer coatings with antifouling or low-friction properties and have been reported to exhibit characteristic phase separation between soft and hard segments. Understanding this phase-separation behavior is critical to design novel hydrophilic polymer coatings. However, most of the studies on the structure and morphology of cross-linked coatings are experimental, which only assess the phase separation via indirect methods. Herein we present a mesoscopic simulation study of the network characteristics of model hydrophilic polymer networks, consisting of PU with and without methyl-polyethylene glycol (mPEG) dangling chains. The systems are analyzed using a number of tools, such as the radial distribution function, the cross-link point density distribution and the Voronoi volume distribution (of the cross-linking points). The combined results show that the cross-linked networks without dangling chains are rather homogeneous but contain a small amount of clustering of cross-linker molecules. A clear phase separation is observed when introducing the dangling chains. In spite of that, the amount of cross-linker molecules connected to dangling chains only, i.e., not connected to the main network, is relatively small, leading to about 3 wt% extractables. Thus, these cross-linked polymers consist of a phase-separated, yet highly connected network. This study provides valuable guidelines towards new self-healing hydrophilic coatings based on the molecular design of cross-linked networks in direct contact with water or aqueous fluids, e.g., as anti-fouling self-repairing coatings for marine applications.

  8. Social networks and links to isolation and loneliness among elderly HCBS clients.

    Science.gov (United States)

    Medvene, Louis J; Nilsen, Kari M; Smith, Rachel; Ofei-Dodoo, Samuel; DiLollo, Anthony; Webster, Noah; Graham, Annette; Nance, Anita

    2016-01-01

    The purpose of this study was to explore the network types of HCBS clients based on the structural characteristics of their social networks. We also examined how the network types were associated with social isolation, relationship quality and loneliness. Forty personal interviews were carried out with HCBS clients to assess the structure of their social networks as indicated by frequency of contact with children, friends, family and participation in religious and community organizations. Hierarchical cluster analysis was conducted to identify network types. Four network types were found including: family (n = 16), diverse (n = 8), restricted (n = 8) and religious (n = 7). Family members comprised almost half of participants' social networks, and friends comprised less than one-third. Clients embedded in family, diverse and religious networks had significantly more positive relationships than clients embedded in restricted networks. Clients embedded in restricted networks had significantly higher social isolation scores and were lonelier than clients in diverse and family networks. The findings suggest that HCBS clients' isolation and loneliness are linked to the types of social networks in which they are embedded. The findings also suggest that clients embedded in restricted networks are at high risk for negative outcomes.

  9. [Loss of anesthesia records during network failure of anesthesia management information system: a case of malfunction of backup system].

    Science.gov (United States)

    Fujii, Seishi; Moriwaki, Katsuyuki; Sanuki, Mikako; Tajima, Minoru; Kurita, Shigeaki; Shiroyama, Kazuhisa; Hashimoto, Ken

    2014-05-01

    We report a case of an accidental loss of anesthesia records through network failure of an anesthesia information management system (AIMS). The backup data were not kept in the anesthesia workstations or the server during the failure. Accordingly, anesthesia records of five patients were lost for one hour. Our AIMS has a network redundancy where the server keeps anesthesia monitoring data via two pathways: one via the monitoring server to the AIMS server and the other via anesthesia workstation to the server. Despite the redundant pathways, transient power failures of network switches caused interruptions in both pathways. Our case indicates that, to improve the robustness of the AIMS as electronic medical records, every network apparatus of AIMS, should be supplied with an uninterrupted power supply. Furthermore, each anesthesia workstation should function independently as an anesthesia record keeping client when network failure occurs.

  10. Failure Diagnosis and Prognosis of Rolling - Element Bearings using Artificial Neural Networks: A Critical Overview

    Science.gov (United States)

    Rao, B. K. N.; Srinivasa Pai, P.; Nagabhushana, T. N.

    2012-05-01

    Rolling - Element Bearings are extensively used in almost all global industries. Any critical failures in these vitally important components would not only affect the overall systems performance but also its reliability, safety, availability and cost-effectiveness. Proactive strategies do exist to minimise impending failures in real time and at a minimum cost. Continuous innovative developments are taking place in the field of Artificial Neural Networks (ANNs) technology. Significant research and development are taking place in many universities, private and public organizations and a wealth of published literature is available highlighting the potential benefits of employing ANNs in intelligently monitoring, diagnosing, prognosing and managing rolling-element bearing failures. This paper attempts to critically review the recent trends in this topical area of interest.

  11. Enhanced Mechanical Properties of Nanoparticle Networks Cross-Linked by Biomimetic Catch Bonds

    Science.gov (United States)

    Mbanga, Badel L.; Iyer, Balaji V. S.; Yashin, Victor V.; Balazs, Anna C.

    2015-03-01

    The tunable behavior of cross-linked networks of Polymer-Grafted Nanoparticles (PGNs) makes them excellent candidates for designing novel materials with enhanced mechanical properties. The building block of a PGN network is a nanoparticle with grafted polymer chains whose free ends' reactive groups can form bonds with the end chains on the nearby particles. We use computer modeling to study the tensile behavior of 3D samples, in which some fraction of cross-links is formed through the biomimetic ``catch'' bonds. In contrast to conventional ``slip'' bonds, the catch bonds might become stronger under an applied force due to transitions between two conformational states. The mechanical properties of the PGN networks are shown to exhibit a drastic improvement upon introduction of the catch bonds into the network. We discuss how ductility, toughness, and rate of strain recovery of the network depend on the catch bond content.

  12. A Glider-Assisted Link Disruption Restoration Mechanism in Underwater Acoustic Sensor Networks.

    Science.gov (United States)

    Jin, Zhigang; Wang, Ning; Su, Yishan; Yang, Qiuling

    2018-02-07

    Underwater acoustic sensor networks (UASNs) have become a hot research topic. In UASNs, nodes can be affected by ocean currents and external forces, which could result in sudden link disruption. Therefore, designing a flexible and efficient link disruption restoration mechanism to ensure the network connectivity is a challenge. In the paper, we propose a glider-assisted restoration mechanism which includes link disruption recognition and related link restoring mechanism. In the link disruption recognition mechanism, the cluster heads collect the link disruption information and then schedule gliders acting as relay nodes to restore the disrupted link. Considering the glider's sawtooth motion, we design a relay location optimization algorithm with a consideration of both the glider's trajectory and acoustic channel attenuation model. The utility function is established by minimizing the channel attenuation and the optimal location of glider is solved by a multiplier method. The glider-assisted restoration mechanism can greatly improve the packet delivery rate and reduce the communication energy consumption and it is more general for the restoration of different link disruption scenarios. The simulation results show that glider-assisted restoration mechanism can improve the delivery rate of data packets by 15-33% compared with cooperative opportunistic routing (OVAR), the hop-by-hop vector-based forwarding (HH-VBF) and the vector based forward (VBF) methods, and reduce communication energy consumption by 20-58% for a typical network's setting.

  13. Dynamic link load balancing based integrated routing algorithm in IP-over-WDM networks

    Science.gov (United States)

    Zhang, Zhizhong; Zhang, Yunlin; Zeng, Qingji; Wang, Jianxin; Ye, Tong; Zhou, Yuli

    2004-04-01

    Integrated routing is a routing approach to support the peer interconnection model in IP over WDM networks. To have a better network link load distribution and network usage in IP over WDM networks, in which network nodes may have the ability to handle traffic in fine granularities, it is important to take into account the combined routing at the IP and WDM layers. Based upon this, this paper develops an algorithm for integrated dynamic routing of bandwidth guaranteed paths in IP over WDM networks. For newly dynamic arriving requests, as the developed algorithm takes into account the combined topology and resource usage information at the IP and WDM layers, and the routing procedure makes full use of the statistic information of the users" bandwidth requirement and considers carefully both the routing cost and the corresponding length of the routing path, thus a better link load balancing and network usage can be achieved. Simulation results show that the developed scheme performs well in terms of performance metrics such as the number of rejected demands and the network link load balancing.

  14. Value Co-creation and Co-innovation: Linking Networked Organisations and Customer Communities

    Science.gov (United States)

    Romero, David; Molina, Arturo

    Strategic networks such as Collaborative Networked Organisations (CNOs) and Virtual Customer Communities (VCCs) show a high potential as drivers of value co-creation and collaborative innovation in today’s Networking Era. Both look at the network structures as a source of jointly value creation and open innovation through access to new skills, knowledge, markets and technologies by sharing risk and integrating complementary competencies. This collaborative endeavour has proven to be able to enhance the adaptability and flexibility of CNOs and VCCs value creating systems in order to react in response to external drivers such as collaborative (business) opportunities. This paper presents a reference framework for creating interface networks, also known as ‘experience-centric networks’, as enablers for linking networked organisations and customer communities in order to support the establishment of user-driven and collaborative innovation networks.

  15. Link removal for the control of stochastically evolving epidemics over networks: A comparison of approaches

    Science.gov (United States)

    Brandeau, Margaret L.

    2015-01-01

    For many communicable diseases, knowledge of the underlying contact network through which the disease spreads is essential to determining appropriate control measures. When behavior change is the primary intervention for disease prevention, it is important to understand how to best modify network connectivity using the limited resources available to control disease spread. We describe and compare four algorithms for selecting a limited number of links to remove from a network: two “preventive” approaches (edge centrality, R0 minimization), where the decision of which links to remove is made prior to any disease outbreak and depends only on the network structure; and two “reactive” approaches (S-I edge centrality, optimal quarantining), where information about the initial disease states of the nodes is incorporated into the decision of which links to remove. We evaluate the performance of these algorithms in minimizing the total number of infections that occur over the course of an acute outbreak of disease. We consider different network structures, including both static and dynamic Erdős-Rényi random networks with varying levels of connectivity, a real-world network of residential hotels connected through injection drug use, and a network exhibiting community structure. We show that reactive approaches outperform preventive approaches in averting infections. Among reactive approaches, removing links in order of S-I edge centrality is favored when the link removal budget is small, while optimal quarantining performs best when the link removal budget is sufficiently large. The budget threshold above which optimal quarantining outperforms the S-I edge centrality algorithm is a function of both network structure (higher for unstructured Erdős-Rényi random networks compared to networks with community structure or the real-world network) and disease infectiousness (lower for highly infectious diseases). We conduct a value-of-information analysis of knowing

  16. A Continuous Object Boundary Detection and Tracking Scheme for Failure-Prone Sensor Networks.

    Science.gov (United States)

    Imran, Sajida; Ko, Young-Bae

    2017-02-13

    In wireless sensor networks, detection and tracking of continuous natured objects is more challenging owing to their unique characteristics such as uneven expansion and contraction. A continuous object is usually spread over a large area, and, therefore, a substantial number of sensor nodes are needed to detect the object. Nodes communicate with each other as well as with the sink to exchange control messages and report their detection status. The sink performs computations on the received data to estimate the object boundary. For accurate boundary estimation, nodes at the phenomenon boundary need to be carefully selected. Failure of one or multiple boundary nodes (BNs) can significantly affect the object detection and boundary estimation accuracy at the sink. We develop an efficient failure-prone object detection approach that not only detects and recovers from BN failures but also reduces the number and size of transmissions without compromising the boundary estimation accuracy. The proposed approach utilizes the spatial and temporal features of sensor nodes to detect object BNs. A Voronoi diagram-based network clustering, and failure detection and recovery scheme is used to increase boundary estimation accuracy. Simulation results show the significance of our approach in terms of energy efficiency, communication overhead, and boundary accuracy.

  17. Time development in the early history of social networks: link stabilization, group dynamics, and segregation.

    Science.gov (United States)

    Bruun, Jesper; Bearden, Ian G

    2014-01-01

    Studies of the time development of empirical networks usually investigate late stages where lasting connections have already stabilized. Empirical data on early network history are rare but needed for a better understanding of how social network topology develops in real life. Studying students who are beginning their studies at a university with no or few prior connections to each other offers a unique opportunity to investigate the formation and early development of link patterns and community structure in social networks. During a nine week introductory physics course, first year physics students were asked to identify those with whom they communicated about problem solving in physics during the preceding week. We use these students' self reports to produce time dependent student interaction networks. We investigate these networks to elucidate possible effects of different student attributes in early network formation. Changes in the weekly number of links show that while roughly half of all links change from week to week, students also reestablish a growing number of links as they progress through their first weeks of study. Using the Infomap community detection algorithm, we show that the networks exhibit community structure, and we use non-network student attributes, such as gender and end-of-course grade to characterize communities during their formation. Specifically, we develop a segregation measure and show that students structure themselves according to gender and pre-organized sections (in which students engage in problem solving and laboratory work), but not according to end-of-coure grade. Alluvial diagrams of consecutive weeks' communities show that while student movement between groups are erratic in the beginning of their studies, they stabilize somewhat towards the end of the course. Taken together, the analyses imply that student interaction networks stabilize quickly and that students establish collaborations based on who is immediately

  18. The catastrophic failures of plants hydraulic network examined trough an model system

    Science.gov (United States)

    Bienaimé, Diane; Marmottant, Philippe; Brodribb, Tim

    2015-11-01

    Plants live a dangerous game: they have to facilitate water transport in their xylem conduits while minimizing the consequence of hydraulic failure. Indeed, as water flows under negative pressure inside these conduits, cavitation bubbles can spontaneously occur. The failure dynamics of this hydraulic network is poorly studied, while it has important ecological and bioengineering implications. Here, by using dark-field transmission microscopy, we were able to directly visualize the spreading of cavitation bubbles within leaves, where the xylem conduits form a 2D and transparent network. We observe the surprising fact that the probability of cavitation increases in larger veins, where the majority of water flows. Next, in order to understand the physical mechanism of nucleation and propagation, we built artificial networks of channels made in hydrogel, where evaporation generates negative pressures. We find the hydraulic failure follows two stages: first a sudden bubble nucleation relaxing to the elastic stored of the system, and then a slow expansion driven by the flow of water in the surrounding medium. Channel constrictions slow the propagation of the bubble, similarly to the small valves that connect plants conduits. P.M. acknowledges support from the University of Tasmania for a visiting scholar grant.

  19. Link prediction measures considering different neighbors’ effects and application in social networks

    Science.gov (United States)

    Luo, Peng; Wu, Chong; Li, Yongli

    Link prediction measures have been attracted particular attention in the field of mathematical physics. In this paper, we consider the different effects of neighbors in link prediction and focus on four different situations: only consider the individual’s own effects; consider the effects of individual, neighbors and neighbors’ neighbors; consider the effects of individual, neighbors, neighbors’ neighbors, neighbors’ neighbors’ neighbors and neighbors’ neighbors’ neighbors’ neighbors; consider the whole network participants’ effects. Then, according to the four situations, we present our link prediction models which also take the effects of social characteristics into consideration. An artificial network is adopted to illustrate the parameter estimation based on logistic regression. Furthermore, we compare our methods with the some other link prediction methods (LPMs) to examine the validity of our proposed model in online social networks. The results show the superior of our proposed link prediction methods compared with others. In the application part, our models are applied to study the social network evolution and used to recommend friends and cooperators in social networks.

  20. The Weakest Link: The Risks Associated with Social Networking Website

    Directory of Open Access Journals (Sweden)

    Yosef Lehrman

    2010-01-01

    Full Text Available The relatively rapid rise in popularity of social networking services is now well known. MySpace, Twitter, and Facebook have become well known sites and terms. According to the Web traffic tracking site Alexa.com, as of December 2009, Facebook had 350 million registered users, MySpace just under 475 million, and Twitter 44.5 million. Many people think very little of posting prodigious amounts of personal information on social networking sites, not realizing that this information puts them at risk. Specifically, those in the law enforcement and military communities may not realize that information posted on these sites can compromise operational security and potentially endanger lives. In July 2009, the Associated Press ran a story which was picked up by most major news outlets in the USA, in which it was reported that the wife of the incoming head of Britain's MI6 intelligence agency had posted pictures and family details on her Facebook page. Astonishingly, there were those that argued that this was not a security breach! Although it is true that, in general, photos of a vacationing family would not be considered sensitive, when you consider that the family taking the vacation includes the head of the British foreign intelligence service, it is easy to see how this kind of exposure could open the door to potential blackmail.We are all too aware of the possibility of terrorist "sleeper cells" living among typical American families under false identities. It is vital to understand how these individuals melt into the crowd, hiding their true identities while they hatch their nefarious plots. Recent events in Denver and New York City only serve to underscore the urgency of this need. This article will examine social networking in the context of social engineering. There are no easy or fast solutions to this problem, and this paper does not pretend to propose any. Rather, it is the purpose of this paper to enhance understanding of this very critical

  1. β2-Microglobulin and TIMP1 Are Linked Together in Cardiorenal Remodeling and Failure.

    Science.gov (United States)

    Vianello, Annamaria; Caponi, Laura; Galetta, Fabio; Franzoni, Ferdinando; Taddei, Marco; Rossi, Marco; Pietrini, Pietro; Santoro, Gino

    2015-02-01

    The cardiorenal syndrome is a complication in patients hospitalized with chronic heart failure (CHF). The β2-microglobulin (b2M) level is an index of decreased glomerular filtration rate (GFR), tissue turnover and inflammation. It is an emerging new predictive marker of cardiovascular events and mortality, but its role as a biomarker of cardiorenal remodeling and failure is still unknown. TIMP1, an endogenous tissue inhibitor of activated matrix metalloproteinases, is a biomarker of heart remodeling and failure. We aimed to evaluate the circulating profile of b2M and TIMP1 in CHF patients, in sedentary controls with no tissue remodeling and in veteran athletes with physiological cardiorenal remodeling and athlete's heart (AH). We investigated the plasma levels of b2M and TIMP1 in 24 subjects with CHF without primitive renal disease, in 25 sedentary controls and in 30 veteran marathoners with AH over 50 years. The b2M and TIMP1 levels were higher in CHF patients, and there was a correlation between them (r = 0.5287, p cardiorenal impairment: with proBNP (r = 0.66, p > 0.0007), percent ejection fraction (r = -0.56, p = 0.0162) and GFR (r = 0.83, p cardiorenal failure. Moreover, a strong correlation between b2M and TIMP1 characterized cardiovascular remodeling not only in CHF patients but also in AH subjects. These findings suggest that clinicians should use b2M and TIMP1 as associated biomarkers of cardiorenal remodeling and failure.

  2. Error Control for Network-on-Chip Links

    CERN Document Server

    Fu, Bo

    2012-01-01

    As technology scales into nanoscale regime, it is impossible to guarantee the perfect hardware design. Moreover, if the requirement of 100% correctness in hardware can be relaxed, the cost of manufacturing, verification, and testing will be significantly reduced. Many approaches have been proposed to address the reliability problem of on-chip communications. This book focuses on the use of error control codes (ECCs) to improve on-chip interconnect reliability. Coverage includes detailed description of key issues in NOC error control faced by circuit and system designers, as well as practical error control techniques to minimize the impact of these errors on system performance. Provides a detailed background on the state of error control methods for on-chip interconnects; Describes the use of more complex concatenated codes such as Hamming Product Codes with Type-II HARQ, while emphasizing integration techniques for on-chip interconnect links; Examines energy-efficient techniques for integrating multiple error...

  3. Intelligent On/Off Dynamic Link Management for On-Chip Networks

    Directory of Open Access Journals (Sweden)

    Andreas G. Savva

    2012-01-01

    Full Text Available Networks-on-chips (NoCs provide scalable on-chip communication and are expected to be the dominant interconnection architectures in multicore and manycore systems. Power consumption, however, is a major limitation in NoCs today, and researchers have been constantly working on reducing both dynamic and static power. Among the NoC components, links that connect the NoC routers are the most power-hungry components. Several attempts have been made to reduce the link power consumption at both the circuit level and the system level. Most past research efforts have proposed selective on/off link state switching based on system-level information based on link utilization levels. Most of these proposed algorithms focus on a pessimistic and simple static threshold mechanism which determines whether or not a link should be turned on/off. This paper presents an intelligent dynamic power management policy for NoCs with improved predictive abilities based on supervised online learning of the system status (i.e., expected future utilization link levels, where links are turned off and on via the use of a small and scalable neural network. Simulation results with various synthetic traffic models over various network topologies show that the proposed work can reach up to 13% power savings when compared to a trivial threshold computation, at very low (<4% hardware overheads.

  4. Multi-link faults localization and restoration based on fuzzy fault set for dynamic optical networks.

    Science.gov (United States)

    Zhao, Yongli; Li, Xin; Li, Huadong; Wang, Xinbo; Zhang, Jie; Huang, Shanguo

    2013-01-28

    Based on a distributed method of bit-error-rate (BER) monitoring, a novel multi-link faults restoration algorithm is proposed for dynamic optical networks. The concept of fuzzy fault set (FFS) is first introduced for multi-link faults localization, which includes all possible optical equipment or fiber links with a membership describing the possibility of faults. Such a set is characterized by a membership function which assigns each object a grade of membership ranging from zero to one. OSPF protocol extension is designed for the BER information flooding in the network. The BER information can be correlated to link faults through FFS. Based on the BER information and FFS, multi-link faults localization mechanism and restoration algorithm are implemented and experimentally demonstrated on a GMPLS enabled optical network testbed with 40 wavelengths in each fiber link. Experimental results show that the novel localization mechanism has better performance compared with the extended limited perimeter vector matching (LVM) protocol and the restoration algorithm can improve the restoration success rate under multi-link faults scenario.

  5. The optical antenna system design research on earth integrative network laser link in the future

    Science.gov (United States)

    Liu, Xianzhu; Fu, Qiang; He, Jingyi

    2014-11-01

    Earth integrated information network can be real-time acquisition, transmission and processing the spatial information with the carrier based on space platforms, such as geostationary satellites or in low-orbit satellites, stratospheric balloons or unmanned and manned aircraft, etc. It is an essential infrastructure for China to constructed earth integrated information network. Earth integrated information network can not only support the highly dynamic and the real-time transmission of broadband down to earth observation, but the reliable transmission of the ultra remote and the large delay up to the deep space exploration, as well as provide services for the significant application of the ocean voyage, emergency rescue, navigation and positioning, air transportation, aerospace measurement or control and other fields.Thus the earth integrated information network can expand the human science, culture and productive activities to the space, ocean and even deep space, so it is the global research focus. The network of the laser communication link is an important component and the mean of communication in the earth integrated information network. Optimize the structure and design the system of the optical antenna is considered one of the difficulty key technologies for the space laser communication link network. Therefore, this paper presents an optical antenna system that it can be used in space laser communication link network.The antenna system was consisted by the plurality mirrors stitched with the rotational paraboloid as a substrate. The optical system structure of the multi-mirror stitched was simulated and emulated by the light tools software. Cassegrain form to be used in a relay optical system. The structural parameters of the relay optical system was optimized and designed by the optical design software of zemax. The results of the optimal design and simulation or emulation indicated that the antenna system had a good optical performance and a certain

  6. Application of a neural network as a potential aid in predicting NTF pump failure

    Science.gov (United States)

    Rogers, James L.; Hill, Jeffrey S.; Lamarsh, William J., II; Bradley, David E.

    1993-01-01

    The National Transonic Facility has three centrifugal multi-stage pumps to supply liquid nitrogen to the wind tunnel. Pump reliability is critical to facility operation and test capability. A highly desirable goal is to be able to detect a pump rotating component problem as early as possible during normal operation and avoid serious damage to other pump components. If a problem is detected before serious damage occurs, the repair cost and downtime could be reduced significantly. A neural network-based tool was developed for monitoring pump performance and aiding in predicting pump failure. Once trained, neural networks can rapidly process many combinations of input values other than those used for training to approximate previously unknown output values. This neural network was applied to establish relationships among the critical frequencies and aid in predicting failures. Training pairs were developed from frequency scans from typical tunnel operations. After training, various combinations of critical pump frequencies were propagated through the neural network. The approximated output was used to create a contour plot depicting the relationships of the input frequencies to the output pump frequency.

  7. Detection of the dominant direction of information flow and feedback links in densely interconnected regulatory networks

    Directory of Open Access Journals (Sweden)

    Ispolatov Iaroslav

    2008-10-01

    Full Text Available Abstract Background Finding the dominant direction of flow of information in densely interconnected regulatory or signaling networks is required in many applications in computational biology and neuroscience. This is achieved by first identifying and removing links which close up feedback loops in the original network and hierarchically arranging nodes in the remaining network. In mathematical language this corresponds to a problem of making a graph acyclic by removing as few links as possible and thus altering the original graph in the least possible way. The exact solution of this problem requires enumeration of all cycles and combinations of removed links, which, as an NP-hard problem, is computationally prohibitive even for modest-size networks. Results We introduce and compare two approximate numerical algorithms for solving this problem: the probabilistic one based on a simulated annealing of the hierarchical layout of the network which minimizes the number of "backward" links going from lower to higher hierarchical levels, and the deterministic, "greedy" algorithm that sequentially cuts the links that participate in the largest number of feedback cycles. We find that the annealing algorithm outperforms the deterministic one in terms of speed, memory requirement, and the actual number of removed links. To further improve a visual perception of the layout produced by the annealing algorithm, we perform an additional minimization of the length of hierarchical links while keeping the number of anti-hierarchical links at their minimum. The annealing algorithm is then tested on several examples of regulatory and signaling networks/pathways operating in human cells. Conclusion The proposed annealing algorithm is powerful enough to performs often optimal layouts of protein networks in whole organisms, consisting of around ~104 nodes and ~105 links, while the applicability of the greedy algorithm is limited to individual pathways with ~100

  8. Linking social and pathogen transmission networks using microbial genetics in giraffe (Giraffa camelopardalis).

    Science.gov (United States)

    VanderWaal, Kimberly L; Atwill, Edward R; Isbell, Lynne A; McCowan, Brenda

    2014-03-01

    Although network analysis has drawn considerable attention as a promising tool for disease ecology, empirical research has been hindered by limitations in detecting the occurrence of pathogen transmission (who transmitted to whom) within social networks. Using a novel approach, we utilize the genetics of a diverse microbe, Escherichia coli, to infer where direct or indirect transmission has occurred and use these data to construct transmission networks for a wild giraffe population (Giraffe camelopardalis). Individuals were considered to be a part of the same transmission chain and were interlinked in the transmission network if they shared genetic subtypes of E. coli. By using microbial genetics to quantify who transmits to whom independently from the behavioural data on who is in contact with whom, we were able to directly investigate how the structure of contact networks influences the structure of the transmission network. To distinguish between the effects of social and environmental contact on transmission dynamics, the transmission network was compared with two separate contact networks defined from the behavioural data: a social network based on association patterns, and a spatial network based on patterns of home-range overlap among individuals. We found that links in the transmission network were more likely to occur between individuals that were strongly linked in the social network. Furthermore, individuals that had more numerous connections or that occupied 'bottleneck' positions in the social network tended to occupy similar positions in the transmission network. No similar correlations were observed between the spatial and transmission networks. This indicates that an individual's social network position is predictive of transmission network position, which has implications for identifying individuals that function as super-spreaders or transmission bottlenecks in the population. These results emphasize the importance of association patterns in

  9. Proposing an Integrative Approach for Efficiency Evaluation of Network Structures Including Tour and Allocation Link

    Directory of Open Access Journals (Sweden)

    reza hejazi

    2012-02-01

    Full Text Available Data envelopment analysis (DEA is known as one of the most common approaches for efficiency evaluation. Network models are new subjects in which, a DMU with all its subunits and links is considered as a network structure. One of the most widely used DEA methods for network data is the suggested approach of Lewis and Sexton. In this approach, performance of each DMU is measured compared to a similar DMU by moving on the effective paths and then computing the final outputs and classic primary inputs . In reality, many cases can be found that an original input or an intermediate product allocates to several subunits or forms a tour in a network. In such networks, the approach of Lewis and Sexton is not able to calculate efficiency. Therefore, in this paper, an approach has been proposed for solving such problems and computing the efficiency of such networks.

  10. Energy-Aware Topology Evolution Model with Link and Node Deletion in Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Xiaojuan Luo

    2012-01-01

    Full Text Available Based on the complex network theory, a new topological evolving model is proposed. In the evolution of the topology of sensor networks, the energy-aware mechanism is taken into account, and the phenomenon of change of the link and node in the network is discussed. Theoretical analysis and numerical simulation are conducted to explore the topology characteristics and network performance with different node energy distribution. We find that node energy distribution has the weak effect on the degree distribution P(k that evolves into the scale-free state, nodes with more energy carry more connections, and degree correlation is nontrivial disassortative. Moreover, the results show that, when nodes energy is more heterogeneous, the network is better clustered and enjoys higher performance in terms of the network efficiency and the average path length for transmitting data.

  11. Galectin-3: A Link between Myocardial and Arterial Stiffening in Patients with Acute Decompensated Heart Failure?

    Directory of Open Access Journals (Sweden)

    Radu Ioan Lala

    2016-01-01

    Full Text Available Abstract Background: Heart failure is accompanied by abnormalities in ventricular-vascular interaction due to increased myocardial and arterial stiffness. Galectin-3 is a recently discovered biomarker that plays an important role in myocardial and vascular fibrosis and heart failure progression. Objectives: The aim of this study was to determine whether galectin-3 is correlated with arterial stiffening markers and impaired ventricular-arterial coupling in decompensated heart failure patients. Methods: A total of 79 inpatients with acute decompensated heart failure were evaluated. Serum galectin-3 was determined at baseline, and during admission, transthoracic echocardiography and measurements of vascular indices by Doppler ultrasonography were performed. Results: Elevated pulse wave velocity and low arterial carotid distensibility are associated with heart failure in patients with preserved ejection fraction (p = 0.04, p = 0.009. Pulse wave velocity, carotid distensibility and Young’s modulus did not correlate with serum galectin-3 levels. Conversely, raised galectin-3 levels correlated with an increased ventricular-arterial coupling ratio (Ea/Elv p = 0.047, OR = 1.9, 95% CI (1.0‑3.6. Increased galectin-3 levels were associated with lower rates of left ventricular pressure rise in early systole (dp/dt (p=0.018 and raised pulmonary artery pressure (p = 0.046. High galectin-3 levels (p = 0.038, HR = 3.07 and arterial pulmonary pressure (p = 0.007, HR = 1.06 were found to be independent risk factors for all-cause mortality and readmissions. Conclusions: This study showed no significant correlation between serum galectin-3 levels and arterial stiffening markers. Instead, high galectin-3 levels predicted impaired ventricular-arterial coupling. Galectin-3 may be predictive of raised pulmonary artery pressures. Elevated galectin-3 levels correlate with severe systolic dysfunction and together with pulmonary hypertension are independent markers of

  12. Galectin-3: A Link between Myocardial and Arterial Stiffening in Patients with Acute Decompensated Heart Failure?

    Science.gov (United States)

    Lala, Radu Ioan; Darabantiu, Dan; Pilat, Luminita; Puschita, Maria

    2016-02-01

    Heart failure is accompanied by abnormalities in ventricular-vascular interaction due to increased myocardial and arterial stiffness. Galectin-3 is a recently discovered biomarker that plays an important role in myocardial and vascular fibrosis and heart failure progression. The aim of this study was to determine whether galectin-3 is correlated with arterial stiffening markers and impaired ventricular-arterial coupling in decompensated heart failure patients. A total of 79 inpatients with acute decompensated heart failure were evaluated. Serum galectin-3 was determined at baseline, and during admission, transthoracic echocardiography and measurements of vascular indices by Doppler ultrasonography were performed. Elevated pulse wave velocity and low arterial carotid distensibility are associated with heart failure in patients with preserved ejection fraction (p = 0.04, p = 0.009). Pulse wave velocity, carotid distensibility and Young's modulus did not correlate with serum galectin-3 levels. Conversely, raised galectin-3 levels correlated with an increased ventricular-arterial coupling ratio (Ea/Elv) p = 0.047, OR = 1.9, 95% CI (1.0‑3.6). Increased galectin-3 levels were associated with lower rates of left ventricular pressure rise in early systole (dp/dt) (p=0.018) and raised pulmonary artery pressure (p = 0.046). High galectin-3 levels (p = 0.038, HR = 3.07) and arterial pulmonary pressure (p = 0.007, HR = 1.06) were found to be independent risk factors for all-cause mortality and readmissions. This study showed no significant correlation between serum galectin-3 levels and arterial stiffening markers. Instead, high galectin-3 levels predicted impaired ventricular-arterial coupling. Galectin-3 may be predictive of raised pulmonary artery pressures. Elevated galectin-3 levels correlate with severe systolic dysfunction and together with pulmonary hypertension are independent markers of outcome.

  13. A Review Paper On Exploring Text Link And Spacial-Temporal Information In Social Media Networks

    Directory of Open Access Journals (Sweden)

    Dr. Mamta Madan

    2015-03-01

    Full Text Available ABSTRACT The objective of this paper is to have a literature review on the various methods to mine the knowledge from the social media by taking advantage of embedded heterogeneous information. Specifically we are trying to review different types of mining framework which provides us useful information from these networks that have heterogeneous data types including text spacial-temporal and data association LINK information. Firstly we will discuss the link mining to study the link structure with respect to Social Media SM. Secondly we summarize the various text mining models thirdly we shall review spacial as well the temporal models to extract or detect the frequent related topics from SM. Fourthly we will try to figure out few improvised models that take advantage of the link textual temporal and spacial information which motivates to discover progressive principles and fresh methodologies for DM Data Mining in social media networks SMNs.

  14. A link based network route choice model with unrestricted choice set

    DEFF Research Database (Denmark)

    Fosgerau, Mogens; Frejinger, Emma; Karlstrom, Anders

    2013-01-01

    This paper considers the path choice problem, formulating and discussing an econometric random utility model for the choice of path in a network with no restriction on the choice set. Starting from a dynamic specification of link choices we show that it is equivalent to a static model...... of the multinomial logit form but with infinitely many alternatives. The model can be consistently estimated and used for prediction in a computationally efficient way. Similarly to the path size logit model, we propose an attribute called link size that corrects utilities of overlapping paths but that is link...... additive. The model is applied to data recording path choices in a network with more than 3000 nodes and 7000 links....

  15. Impacts of link addition and removal on synchronization of an elementary power network

    Science.gov (United States)

    Yang, Li-xin; Jiang, Jun

    2017-08-01

    This paper is devoted to the impacts of link addition and removal on synchronization of an elementary oscillatory network. By means of numerical simulations, it is found that the characteristics of edge have important consequences to synchronization in oscillatory networks. To be specific, we find that the heterogeneous (generators to consumer nodes and vice versa) edge additions whether in a separate community or between communities is beneficial for the enhancement of the synchronization. Nevertheless, the influence of homogeneous (generators to generators or consumers to consumers) edge additions is not obvious on the synchronizability of the power network. Furthermore, it is observed that a heterogeneous edge is deleted, the network exhibits weak synchronizability. However, the removal of a homogeneous edge does not affect the synchronizability. Besides, the numerical simulation results indicate that whereas the impact of a link additional and removal in a separate community become more sensitive to synchronizability than different communities.

  16. Investigation of failures in operation of heat networks of large heat supply systems

    Science.gov (United States)

    Rafalskaya, T. A.

    2017-04-01

    The effect of deviations in heat network parameters on operation of heating system and hot-water supply systems in buildings is examined. The consequences of a decrease in the water temperature in a heat network under extreme weather conditions in a range below the design ambient air temperature, the efficiency of disconnection of a hot water supply system (HWSS) heater in this period, and deviations in the normal heat supply in the transition period at relatively high outdoor temperatures are considered. The specific and scope of failures depend on the design-heating load to design hot water supply load ratio for the heat network. A mathematical model was developed, and numerical investigation was performed of modern schemes of heat points which are designed primarily for covering the hot water supply load and recovering the heating system heat output in case of low or no hot water consumption in HWSS. The performed calculations demonstrate that the heating system has no time to restore its heat output, thereby considerably reducing air temperature in the heated premises. The lower the ambient air temperature and the lower the ratio of the design loads for hot water supply and heating, the greater is this decrease. At the same time, in case of a sudden decrease in the outdoor temperature and an accident in the heat supply system, the heating system must be the priority consumer, since a heating failure not only decreases the thermal comfort of consumers but can cause emergency situations in local utility systems, such as a cold water supply system. Correction of failures in a heat supply system requires calculation of operating conditions of heat networks.

  17. A Glider-Assisted Link Disruption Restoration Mechanism in Underwater Acoustic Sensor Networks

    Directory of Open Access Journals (Sweden)

    Zhigang Jin

    2018-02-01

    Full Text Available Underwater acoustic sensor networks (UASNs have become a hot research topic. In UASNs, nodes can be affected by ocean currents and external forces, which could result in sudden link disruption. Therefore, designing a flexible and efficient link disruption restoration mechanism to ensure the network connectivity is a challenge. In the paper, we propose a glider-assisted restoration mechanism which includes link disruption recognition and related link restoring mechanism. In the link disruption recognition mechanism, the cluster heads collect the link disruption information and then schedule gliders acting as relay nodes to restore the disrupted link. Considering the glider’s sawtooth motion, we design a relay location optimization algorithm with a consideration of both the glider’s trajectory and acoustic channel attenuation model. The utility function is established by minimizing the channel attenuation and the optimal location of glider is solved by a multiplier method. The glider-assisted restoration mechanism can greatly improve the packet delivery rate and reduce the communication energy consumption and it is more general for the restoration of different link disruption scenarios. The simulation results show that glider-assisted restoration mechanism can improve the delivery rate of data packets by 15–33% compared with cooperative opportunistic routing (OVAR, the hop-by-hop vector-based forwarding (HH-VBF and the vector based forward (VBF methods, and reduce communication energy consumption by 20–58% for a typical network’s setting.

  18. A Mobility-Aware Link Enhancement Mechanism for Vehicular Ad Hoc Networks

    Directory of Open Access Journals (Sweden)

    Huang Chenn-Jung

    2008-01-01

    Full Text Available Abstract With the growth up of internet in mobile commerce, researchers have reproduced various mobile applications that vary from entertainment and commercial services to diagnostic and safety tools. Mobility management has widely been recognized as one of the most challenging problems for seamless access to wireless networks. In this paper, a novel link enhancement mechanism is proposed to deal with mobility management problem in vehicular ad hoc networks. Two machine learning techniques, namely, particle swarm optimization and fuzzy logic systems, are incorporated into the proposed schemes to enhance the accuracy of prediction of link break and congestion occurrence. The experimental results verify the effectiveness and feasibility of the proposed schemes.

  19. A Mobility-Aware Link Enhancement Mechanism for Vehicular Ad Hoc Networks

    Directory of Open Access Journals (Sweden)

    Kai-Wen Hu

    2008-04-01

    Full Text Available With the growth up of internet in mobile commerce, researchers have reproduced various mobile applications that vary from entertainment and commercial services to diagnostic and safety tools. Mobility management has widely been recognized as one of the most challenging problems for seamless access to wireless networks. In this paper, a novel link enhancement mechanism is proposed to deal with mobility management problem in vehicular ad hoc networks. Two machine learning techniques, namely, particle swarm optimization and fuzzy logic systems, are incorporated into the proposed schemes to enhance the accuracy of prediction of link break and congestion occurrence. The experimental results verify the effectiveness and feasibility of the proposed schemes.

  20. Overcoming TCP Degradation in the Presence of Multiple Intermittent Link Failures Utilizing Intermediate Buffering

    Science.gov (United States)

    2007-03-01

    however to expect link proxy routers to provide infinite buffer capacity . Accordingly, the centralized memory manager built into the model requires...utilized within strategically placed backbone routers under military jurisdiction. 5.3.4 Custodial TCP Flow Control Link proxy buffer capacity enables...Moderate and heavy channel losses however would require considerable buffer capacity , 5−8 especially if multiple high capacity TCP flows

  1. Space Link Extension (SLE) Emulation for High-Throughput Network Communication

    Science.gov (United States)

    Murawski, Robert W.; Tchorowski, Nicole; Golden, Bert

    2014-01-01

    As the data rate requirements for space communications increases, significant stress is placed not only on the wireless satellite communication links, but also on the ground networks which forward data from end-users to remote ground stations. These wide area network (WAN) connections add delay and jitter to the end-to-end satellite communication link, effects which can have significant impacts on the wireless communication link. It is imperative that any ground communication protocol can react to these effects such that the ground network does not become a bottleneck in the communication path to the satellite. In this paper, we present our SCENIC Emulation Lab testbed which was developed to test the CCSDS SLE protocol implementations proposed for use on future NASA communication networks. Our results show that in the presence of realistic levels of network delay, high-throughput SLE communication links can experience significant data rate throttling. Based on our observations, we present some insight into why this data throttling happens, and trace the probable issue back to non-optimal blocking communication which is sup-ported by the CCSDS SLE API recommended practices. These issues were presented as well to the SLE implementation developers which, based on our reports, developed a new release for SLE which we show fixes the SLE blocking issue and greatly improves the protocol throughput. In this paper, we also discuss future developments for our end-to-end emulation lab and how these improvements can be used to develop and test future space communication technologies.

  2. Similarity-based Regularized Latent Feature Model for Link Prediction in Bipartite Networks.

    Science.gov (United States)

    Wang, Wenjun; Chen, Xue; Jiao, Pengfei; Jin, Di

    2017-12-05

    Link prediction is an attractive research topic in the field of data mining and has significant applications in improving performance of recommendation system and exploring evolving mechanisms of the complex networks. A variety of complex systems in real world should be abstractly represented as bipartite networks, in which there are two types of nodes and no links connect nodes of the same type. In this paper, we propose a framework for link prediction in bipartite networks by combining the similarity based structure and the latent feature model from a new perspective. The framework is called Similarity Regularized Nonnegative Matrix Factorization (SRNMF), which explicitly takes the local characteristics into consideration and encodes the geometrical information of the networks by constructing a similarity based matrix. We also develop an iterative scheme to solve the objective function based on gradient descent. Extensive experiments on a variety of real world bipartite networks show that the proposed framework of link prediction has a more competitive, preferable and stable performance in comparison with the state-of-art methods.

  3. Regional Attenuation Correction of Weather Radar Using a Distributed Microwave-Links Network

    OpenAIRE

    Yang Xue; Xi-chuan Liu; Tai-chang Gao; Chang-ye Yang; Kun Song

    2017-01-01

    The complex temporal-spatial variation of raindrop size distribution will affect the precision of precipitation quantitative estimates (QPE) produced from radar data, making it difficult to correct echo attenuation. Given the fact that microwave links can obtain the total path attenuation accurately, we introduce the concept of regional attenuation correction using a multiple-microwave-links network based on the tomographic reconstruction of attenuation coefficients. Derived from the radar-ba...

  4. Linking Social Networking Sites to Scholarly Information Portals by ScholarLib

    OpenAIRE

    Mutschke, Peter; Thamm, Mark

    2012-01-01

    Online Social Networks usually provide no or limited way to access scholarly information provided by Digital Libraries (DLs) in order to share and discuss scholarly content with other online community members. The paper addresses the potentials of Social Networking sites (SNSs) for science and proposes initial use cases as well as a basic bi-directional model called ScholarLib for linking SNSs to scholarly DLs. The major aim of ScholarLib is to make scholarly information provided by DLs acces...

  5. Joint Hybrid Backhaul and Access Links Design in Cloud-Radio Access Networks

    KAUST Repository

    Dhifallah, Oussama Najeeb

    2015-09-06

    The cloud-radio access network (CRAN) is expected to be the core network architecture for next generation mobile radio systems. In this paper, we consider the downlink of a CRAN formed of one central processor (the cloud) and several base station (BS), where each BS is connected to the cloud via either a wireless or capacity-limited wireline backhaul link. The paper addresses the joint design of the hybrid backhaul links (i.e., designing the wireline and wireless backhaul connections from the cloud to the BSs) and the access links (i.e., determining the sparse beamforming solution from the BSs to the users). The paper formulates the hybrid backhaul and access link design problem by minimizing the total network power consumption. The paper solves the problem using a two-stage heuristic algorithm. At one stage, the sparse beamforming solution is found using a weighted mixed 11/12 norm minimization approach; the correlation matrix of the quantization noise of the wireline backhaul links is computed using the classical rate-distortion theory. At the second stage, the transmit powers of the wireless backhaul links are found by solving a power minimization problem subject to quality-of-service constraints, based on the principle of conservation of rate by utilizing the rates found in the first stage. Simulation results suggest that the performance of the proposed algorithm approaches the global optimum solution, especially at high signal-to-interference-plus-noise ratio (SINR).

  6. Link Prediction in Criminal Networks: A Tool for Criminal Intelligence Analysis.

    Directory of Open Access Journals (Sweden)

    Giulia Berlusconi

    Full Text Available The problem of link prediction has recently received increasing attention from scholars in network science. In social network analysis, one of its aims is to recover missing links, namely connections among actors which are likely to exist but have not been reported because data are incomplete or subject to various types of uncertainty. In the field of criminal investigations, problems of incomplete information are encountered almost by definition, given the obvious anti-detection strategies set up by criminals and the limited investigative resources. In this paper, we work on a specific dataset obtained from a real investigation, and we propose a strategy to identify missing links in a criminal network on the basis of the topological analysis of the links classified as marginal, i.e. removed during the investigation procedure. The main assumption is that missing links should have opposite features with respect to marginal ones. Measures of node similarity turn out to provide the best characterization in this sense. The inspection of the judicial source documents confirms that the predicted links, in most instances, do relate actors with large likelihood of co-participation in illicit activities.

  7. Link Prediction in Criminal Networks: A Tool for Criminal Intelligence Analysis.

    Science.gov (United States)

    Berlusconi, Giulia; Calderoni, Francesco; Parolini, Nicola; Verani, Marco; Piccardi, Carlo

    2016-01-01

    The problem of link prediction has recently received increasing attention from scholars in network science. In social network analysis, one of its aims is to recover missing links, namely connections among actors which are likely to exist but have not been reported because data are incomplete or subject to various types of uncertainty. In the field of criminal investigations, problems of incomplete information are encountered almost by definition, given the obvious anti-detection strategies set up by criminals and the limited investigative resources. In this paper, we work on a specific dataset obtained from a real investigation, and we propose a strategy to identify missing links in a criminal network on the basis of the topological analysis of the links classified as marginal, i.e. removed during the investigation procedure. The main assumption is that missing links should have opposite features with respect to marginal ones. Measures of node similarity turn out to provide the best characterization in this sense. The inspection of the judicial source documents confirms that the predicted links, in most instances, do relate actors with large likelihood of co-participation in illicit activities.

  8. Increased cardiac work provides a link between systemic hypertension and heart failure.

    Science.gov (United States)

    Wilson, Alexander J; Wang, Vicky Y; Sands, Gregory B; Young, Alistair A; Nash, Martyn P; LeGrice, Ian J

    2017-01-01

    The spontaneously hypertensive rat (SHR) is an established model of human hypertensive heart disease transitioning into heart failure. The study of the progression to heart failure in these animals has been limited by the lack of longitudinal data. We used MRI to quantify left ventricular mass, volume, and cardiac work in SHRs at age 3 to 21 month and compared these indices to data from Wistar-Kyoto (WKY) controls. SHR had lower ejection fraction compared with WKY at all ages, but there was no difference in cardiac output at any age. At 21 month the SHR had significantly elevated stroke work (51 ± 3 mL.mmHg SHR vs. 24 ± 2 mL.mmHg WKY; n = 8, 4; P failure in this animal model. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

  9. Risk Analysis on Leakage Failure of Natural Gas Pipelines by Fuzzy Bayesian Network with a Bow-Tie Model

    Directory of Open Access Journals (Sweden)

    Xian Shan

    2017-01-01

    Full Text Available Pipeline is the major mode of natural gas transportation. Leakage of natural gas pipelines may cause explosions and fires, resulting in casualties, environmental damage, and material loss. Efficient risk analysis is of great significance for preventing and mitigating such potential accidents. The objective of this study is to present a practical risk assessment method based on Bow-tie model and Bayesian network for risk analysis of natural gas pipeline leakage. Firstly, identify the potential risk factors and consequences of the failure. Then construct the Bow-tie model, use the quantitative analysis of Bayesian network to find the weak links in the system, and make a prediction of the control measures to reduce the rate of the accident. In order to deal with the uncertainty existing in the determination of the probability of basic events, fuzzy logic method is used. Results of a case study show that the most likely causes of natural gas pipeline leakage occurrence are parties ignore signage, implicit signage, overload, and design defect of auxiliaries. Once the leakage occurs, it is most likely to result in fire and explosion. Corresponding measures taken on time will reduce the disaster degree of accidents to the least extent.

  10. On the Impacts and Benefits of Implementing Full-Duplex Communications Links in an Underwater Acoustic Network

    National Research Council Canada - National Science Library

    Gibson, J; Larraza, A; Rice, J; Smith, K; Xie, G

    2002-01-01

    .... These networks may provide command and control for autonomous underwater vehicles, forward reporting by arrays of sensor grids, ad hoc communications links to covert forces, or positive control...

  11. Oxidative stress modulates mitochondrial failure and cyclophilin D function in X-linked adrenoleukodystrophy.

    Science.gov (United States)

    López-Erauskin, Jone; Galino, Jorge; Bianchi, Patrizia; Fourcade, Stéphane; Andreu, Antoni L; Ferrer, Isidre; Muñoz-Pinedo, Cristina; Pujol, Aurora

    2012-12-01

    A common process associated with oxidative stress and severe mitochondrial impairment is the opening of the mitochondrial permeability transition pore, as described in many neurodegenerative diseases. Thus, inhibition of mitochondrial permeability transition pore opening represents a potential target for inhibiting mitochondrial-driven cell death. Among the mitochondrial permeability transition pore components, cyclophilin D is the most studied and has been found increased under pathological conditions. Here, we have used in vitro and in vivo models of X-linked adrenoleukodystrophy to investigate the relationship between the mitochondrial permeability transition pore opening and redox homeostasis. X-linked adrenoleukodystrophy is a neurodegenerative condition caused by loss of function of the peroxisomal ABCD1 transporter, in which oxidative stress plays a pivotal role. In this study, we provide evidence of impaired mitochondrial metabolism in a peroxisomal disease, as fibroblasts in patients with X-linked adrenoleukodystrophy cannot survive when forced to rely on mitochondrial energy production, i.e. on incubation in galactose. Oxidative stress induced under galactose conditions leads to mitochondrial damage in the form of mitochondrial inner membrane potential dissipation, ATP drop and necrotic cell death, together with increased levels of oxidative modifications in cyclophilin D protein. Moreover, we show increased expression levels of cyclophilin D in the affected zones of brains in patients with adrenomyeloneuropathy, in spinal cord of a mouse model of X-linked adrenoleukodystrophy (Abcd1-null mice) and in fibroblasts from patients with X-linked adrenoleukodystrophy. Notably, treatment with antioxidants rescues mitochondrial damage markers in fibroblasts from patients with X-linked adrenoleukodystrophy, including cyclophilin D oxidative modifications, and reverses cyclophilin D induction in vitro and in vivo. These findings provide mechanistic insight into the

  12. A Closed Network Queue Model of Underground Coal Mining Production, Failure, and Repair

    Science.gov (United States)

    Lohman, G. M.

    1978-01-01

    Underground coal mining system production, failures, and repair cycles were mathematically modeled as a closed network of two queues in series. The model was designed to better understand the technological constraints on availability of current underground mining systems, and to develop guidelines for estimating the availability of advanced mining systems and their associated needs for spares as well as production and maintenance personnel. It was found that: mine performance is theoretically limited by the maintainability ratio, significant gains in availability appear possible by means of small improvements in the time between failures the number of crews and sections should be properly balanced for any given maintainability ratio, and main haulage systems closest to the mine mouth require the most attention to reliability.

  13. Selective removal of heavy metal ions by disulfide linked polymer networks

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Dongah [Department of Environmental Engineering, Technical University of Denmark, Miljøvej 113, 2800 Kgs. Lyngby (Denmark); Lee, Joo Sung [Graduate School of EEWS, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141 (Korea, Republic of); Patel, Hasmukh A. [Department of Chemistry, Northwestern University, Evanston, IL 60208 (United States); Jakobsen, Mogens H. [Department of Micro and Nano technology, Technical University of Denmark, Ørsteds Plads, 345B, 2800 Kgs. Lyngby (Denmark); Hwang, Yuhoon [Department of Environmental Engineering, Seoul National University of Science and Technology, 232 Gongreung-ro, Nowon-gu, Seoul 01811 (Korea, Republic of); Yavuz, Cafer T. [Graduate School of EEWS, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141 (Korea, Republic of); Hansen, Hans Chr. Bruun [Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg, Thorvaldsensvej 40, 1871 Frederiksberg C (Denmark); Andersen, Henrik R., E-mail: henrik@ndersen.net [Department of Environmental Engineering, Technical University of Denmark, Miljøvej 113, 2800 Kgs. Lyngby (Denmark)

    2017-06-15

    Highlights: • Disulfide/thiol polymer networks are promising as sorbent for heavy metals. • Rapid sorption and high Langmuir affinity constant (a{sub L}) for stormwater treatment. • Selective sorption for copper, cadmium, and zinc in the presence of calcium. • Reusability likely due to structure stability of disulfide linked polymer networks. - Abstract: Heavy metal contaminated surface water is one of the oldest pollution problems, which is critical to ecosystems and human health. We devised disulfide linked polymer networks and employed as a sorbent for removing heavy metal ions from contaminated water. Although the polymer network material has a moderate surface area, it demonstrated cadmium removal efficiency equivalent to highly porous activated carbon while it showed 16 times faster sorption kinetics compared to activated carbon, owing to the high affinity of cadmium towards disulfide and thiol functionality in the polymer network. The metal sorption mechanism on polymer network was studied by sorption kinetics, effect of pH, and metal complexation. We observed that the metal ions–copper, cadmium, and zinc showed high binding affinity in polymer network, even in the presence of competing cations like calcium in water.

  14. Link-prediction to tackle the boundary specification problem in social network surveys

    Science.gov (United States)

    De Wilde, Philippe; Buarque de Lima-Neto, Fernando

    2017-01-01

    Diffusion processes in social networks often cause the emergence of global phenomena from individual behavior within a society. The study of those global phenomena and the simulation of those diffusion processes frequently require a good model of the global network. However, survey data and data from online sources are often restricted to single social groups or features, such as age groups, single schools, companies, or interest groups. Hence, a modeling approach is required that extrapolates the locally restricted data to a global network model. We tackle this Missing Data Problem using Link-Prediction techniques from social network research, network generation techniques from the area of Social Simulation, as well as a combination of both. We found that techniques employing less information may be more adequate to solve this problem, especially when data granularity is an issue. We validated the network models created with our techniques on a number of real-world networks, investigating degree distributions as well as the likelihood of links given the geographical distance between two nodes. PMID:28426826

  15. xiNET: Cross-link Network Maps With Residue Resolution*

    Science.gov (United States)

    Combe, Colin W.; Fischer, Lutz; Rappsilber, Juri

    2015-01-01

    xiNET is a visualization tool for exploring cross-linking/mass spectrometry results. The interactive maps of the cross-link network that it generates are a type of node-link diagram. In these maps xiNET displays: (1) residue resolution positional information including linkage sites and linked peptides; (2) all types of cross-linking reaction product; (3) ambiguous results; and, (4) additional sequence information such as domains. xiNET runs in a browser and exports vector graphics which can be edited in common drawing packages to create publication quality figures. Availability: xiNET is open source, released under the Apache version 2 license. Results can be viewed by uploading data to http://crosslinkviewer.org/ or by downloading the software from http://github.com/colin-combe/crosslink-viewer and running it locally. PMID:25648531

  16. xiNET: cross-link network maps with residue resolution.

    Science.gov (United States)

    Combe, Colin W; Fischer, Lutz; Rappsilber, Juri

    2015-04-01

    xiNET is a visualization tool for exploring cross-linking/mass spectrometry results. The interactive maps of the cross-link network that it generates are a type of node-link diagram. In these maps xiNET displays: (1) residue resolution positional information including linkage sites and linked peptides; (2) all types of cross-linking reaction product; (3) ambiguous results; and, (4) additional sequence information such as domains. xiNET runs in a browser and exports vector graphics which can be edited in common drawing packages to create publication quality figures. xiNET is open source, released under the Apache version 2 license. Results can be viewed by uploading data to http://crosslinkviewer.org/ or by downloading the software from http://github.com/colin-combe/crosslink-viewer and running it locally. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  17. Network analysis of physics discussion forums and links to course success

    Science.gov (United States)

    Traxler, Adrienne; Gavrin, Andrew; Lindell, Rebecca

    2017-01-01

    Large introductory science courses tend to isolate students, with negative consequences for long-term retention in college. Many active learning courses build collaboration and community among students as an explicit goal, and social network analysis has been used to track the development and beneficial effects of these collaborations. Here we supplement such work by conducting network analysis of online course discussion forums in two semesters of an introductory physics class. Online forums provide a tool for engaging students with each other outside of class, and offer new opportunities to commuter or non-traditional students with limited on-campus time. We look for correlations between position in the forum network (centrality) and final course grades. Preliminary investigation has shown weak correlations in the very dense full-semester network, so we will consider reduced ''backbone'' networks that highlight the most consistent links between students. Future work and implications for instruction will also be discussed.

  18. Retrieval algorithm for rainfall mapping from microwave links in a cellular communication network

    NARCIS (Netherlands)

    Overeem, Aart; Leijnse, Hidde; Uijlenhoet, Remko

    2016-01-01

    Microwave links in commercial cellular communication networks hold a promise for areal rainfall monitoring and could complement rainfall estimates from ground-based weather radars, rain gauges, and satellites. It has been shown that country-wide (≈ 35 500 km2) 15 min rainfall maps can

  19. Efficient Algorithm for Computing Link-based Similarity in Real World Networks

    DEFF Research Database (Denmark)

    Cai, Yuanzhe; Cong, Gao; Xu, Jia

    2009-01-01

    Similarity calculation has many applications, such as information retrieval, and collaborative filtering, among many others. It has been shown that link-based similarity measure, such as SimRank, is very effective in characterizing the object similarities in networks, such as the Web, by exploiti...

  20. Hospital cost effect of a heart failure disease management program: the Specialized Primary and Networked Care in Heart Failure (SPAN-CHF) trial.

    Science.gov (United States)

    Gregory, Douglas; Kimmelstiel, Carey; Perry, Kathleen; Parikh, Amay; Konstam, Varda; Konstam, Marvin A

    2006-05-01

    Determine the effect on hospitalization cost of a heart failure disease management (HFDM) program delivered within a diverse provider network as demonstrated in the SPAN-CHF randomized controlled trial. The SPAN-CHF trial was a prospective randomized assessment of the effectiveness of HFDM delivered for 90 days across a diverse provider network in a heterogeneous population of 200 patients. Baseline clinical and demographic data were obtained on each patient, mortality was monitored, and hospitalizations were tracked for 90 days. Cost estimates for each hospitalization were based on a subsample of patients seen at Tufts-New England Medical Center for whom hospitalization costs were calculated. Heart failure disease management program costs were estimated using a programmatic budget model. Hospital utilization and cost data were combined to estimate medical costs for intervention and control groups. Heart failure disease management had a favorable effect on heart failure hospitalization, which was partially offset by noncardiac hospitalizations. The relative odds of at least one all-cause hospitalization during the intervention period trended less for the intervention group compared with the control group (0.76 [95% CI 0.38-1.51]). The point estimate of the differential hospitalization cost between control and intervention groups was a reduction in cost of $375 per patient. The net effect including the costs of the program was an increase of $488 per patient for the intervention group compared with the control group. The program would have been cost saving if HFDM costs had been 24% lower. The HFDM intervention, administered over 90 days to patients hospitalized for heart failure, succeeded in reducing the rate of heart failure hospitalizations, although this effect was partially offset by an increase in non-heart failure hospitalizations. The resulting modest reduction in all-cause hospitalization costs was exceeded by the cost of the intervention. Thus, although

  1. [ANMCO/SIC Consensus document: The heart failure network: organization of outpatient care].

    Science.gov (United States)

    Aspromonte, Nadia; Gulizia, Michele Massimo; Di Lenarda, Andrea; Mortara, Andrea; Battistoni, Ilaria; De Maria, Renata; Gabriele, Michele; Iacoviello, Massimo; Navazio, Alessandro; Pini, Daniela; Di Tano, Giuseppe; Marini, Marco; Ricci, Renato Pietro; Alunni, Gianfranco; Radini, Donatella; Metra, Marco; Romeo, Francesco

    2016-01-01

    Changing demographics and an increasing burden of multiple chronic comorbidities in western countries dictate refocusing of heart failure (HF) services from acute in-hospital care to better support the long inter-critical out-of-hospital phases of HF. The needs of the HF population are not adequately addressed by current HF outpatient services, as documented by differences in age, gender, comorbidities and recommended therapies between patients discharged for hospitalized HF and those followed up at HF clinics.The Working Group on Heart Failure of the Italian Association of Hospital Cardiologists (ANMCO) has drafted a consensus document for the organization of a national HF care network. The aims of this document are to describe tasks and requirements of the different health system points of contact for HF patients, and to define how diagnosis, management and care processes should be documented and shared among healthcare professionals. In this document, HF clinics are classified into three groups: 1) community HF clinics, devoted to the management of stable patients in strict liaison with primary care, regular re-evaluation of emerging clinical needs and prompt treatment of impending destabilizations, 2) hospital HF clinics, that target both new-onset and chronic HF patients for diagnostic assessment, treatment planning and early post-discharge follow-up. They act as main referral for medicine units and community clinics; 3) advanced HF clinics, directed at patients with severe disease or persistent clinical instability, candidates to advanced treatment options such as heart transplant or mechanical circulatory support. These different types of HF clinics are integrated in a dedicated network for the management of HF patients on a regional basis, according to geographic features. By sharing predefined protocols and communication systems, these HF networks integrate multiprofessional providers to ensure continuity of care. This consensus document is expected to

  2. Failure of irradiated onion to induce sex-linked recessive lethal mutations in Drosophila melanogaster

    Energy Technology Data Exchange (ETDEWEB)

    Mittler, S. (Northern Illinois Univ., De Kalb (USA). Dept. of Biological Sciences); Eiss, M.I. (McCormick and Co., Inc., Hunt Valley, MD (USA). Research and Development Labs.)

    1982-01-01

    The feeding of Drosophila for all of their entire larval life plus 2 days as an adult on onion powder that had been irradiated with 15, 950 or 1500 krad did not significantly increase sex-linked recessive lethal mutations. The Drosophila were fed on a mixture that contained 24.5% of onion powder by dry weight. The onion powder had been exposed to a cobalt-60 source of 1.2 million Curies.

  3. Power-Aware Routing and Network Design with Bundled Links: Solutions and Analysis

    Directory of Open Access Journals (Sweden)

    Rosario G. Garroppo

    2013-01-01

    Full Text Available The paper deeply analyzes a novel network-wide power management problem, called Power-Aware Routing and Network Design with Bundled Links (PARND-BL, which is able to take into account both the relationship between the power consumption and the traffic throughput of the nodes and to power off both the chassis and even the single Physical Interface Card (PIC composing each link. The solutions of the PARND-BL model have been analyzed by taking into account different aspects associated with the actual applicability in real network scenarios: (i the time for obtaining the solution, (ii the deployed network topology and the resulting topology provided by the solution, (iii the power behavior of the network elements, (iv the traffic load, (v the QoS requirement, and (vi the number of paths to route each traffic demand. Among the most interesting and novel results, our analysis shows that the strategy of minimizing the number of powered-on network elements through the traffic consolidation does not always produce power savings, and the solution of this kind of problems, in some cases, can lead to spliting a single traffic demand into a high number of paths.

  4. A density based link clustering algorithm for overlapping community detection in networks

    Science.gov (United States)

    Zhou, Xu; Liu, Yanheng; Wang, Jian; Li, Chun

    2017-11-01

    Overlapping is an interesting and common characteristic of community structure in networks. Link clustering method for overlapping community detection has attracted a lot of attention in the area of social networks applications. However, it may make the clustering result with excessive overlap and cluster bridge edge and border edge mistakenly to adjacent communities. To solve this problem, a density based link clustering algorithm is proposed to improve the accuracy of detecting overlapping communities in networks in this study. It creates a number of clusters containing core edges only based on concept named as core density reachable during the expansion. Then an updating strategy for unclassified edges is designed to assign them to the closest cluster. In addition, a similarity measure for computing the similarity between two edges is presented. Experiments on synthetic networks and real networks have been conducted. The experimental results demonstrate that our method performs better than other algorithms on detecting community structure and overlapping nodes, it can get nearly 15% higher than the NMI value of other algorithms on some synthetic networks.

  5. SDN control of optical nodes in metro networks for high capacity inter-datacentre links

    Science.gov (United States)

    Magalhães, Eduardo; Perry, Philip; Barry, Liam

    2017-11-01

    Worldwide demand for bandwidth has been growing fast for some years and continues to do so. To cover this, mega datacentres need scalable connectivity to provide rich connectivity to handle the heavy traffic across them. Therefore, hardware infrastructures must be able to play different roles according to service and traffic requirements. In this context, software defined networking (SDN) decouples the network control and forwarding functions enabling the network control to become directly programmable and the underlying infrastructure to be abstracted for applications and network services. In addition, elastic optical networking (EON) technologies enable efficient spectrum utilization by allocating variable bandwidth to each user according to their actual needs. In particular, flexible transponders and reconfigurable optical add/drop multiplexers (ROADMs) are key elements since they can offer degrees of freedom to self adapt accordingly. Thus, it is crucial to design control methods in order to optimize the hardware utilization and offer high reconfigurability, flexibility and adaptability. In this paper, we propose and analyze, using a simulation framework, a method of capacity maximization through optical power profile manipulation for inter datacentre links that use existing metropolitan optical networks by exploiting the global network view afforded by SDN. Results show that manipulating the loss profiles of the ROADMs in the metro-network can yield optical signal-to-noise ratio (OSNR) improvements up to 10 dB leading to an increase in 112% in total capacity.

  6. Long-term Failure Prediction based on an ARP Model of Global Risk Network

    Science.gov (United States)

    Lin, Xin; Moussawi, Alaa; Szymanski, Boleslaw; Korniss, Gyorgy

    Risks that threaten modern societies form an intricately interconnected network. Hence, it is important to understand how risk materializations in distinct domains influence each other. In the paper, we study the global risks network defined by World Economic Forum experts in the form of Stochastic Block Model. We model risks as Alternating Renewal Processes with variable intensities driven by hidden values of exogenous and endogenous failure probabilities. Based on the expert assessments and historical status of each risk, we use Maximum Likelihood Evaluation to find the optimal model parameters and demonstrate that the model considering network effects significantly outperforms the others. In the talk, we discuss how the model can be used to provide quantitative means for measuring interdependencies and materialization of risks in the network. We also present recent results of long-term predictions in the form of predicated distributions of materializations over various time periods. Finally we show how the simulation of ARP's enables us to probe limits of the predictability of the system parameters from historical data and ability to recover hidden variable. Supported in part by DTRA, ARL NS-CTA.

  7. Multi-Party Optimal Operation for Distribution Networks Containing DC-Linked Microgrids: Integrated Network Reconfigurations and Energy Sharing

    Directory of Open Access Journals (Sweden)

    Nian Liu

    2017-11-01

    Full Text Available With the development of Microgrids (MG in distribution networks, how to coordinate the reconfiguration of distribution networks with the energy sharing of Direct Current (DC-linked multi-MG is an unsolved problem. In this paper, a multi-party optimization framework is proposed, the involving parties include the Distribution Network Operator (DNO, the Multi-MG Coalition Operator (MCO, and the MG operator. For the DC-linked MGs, the MCO is obligated to coordinate the energy sharing, a stochastic optimal scheduling model for the MG coalition is formulated, considering the uncertainties of Photovoltaic (PV, Wind Turbines (WT, and load power. Moreover, a billing mechanism is designed to distribute the cost of each MG participated in the energy sharing. For the distribution network, an event triggered dynamic reconfiguration model is proposed. Based on the scheduling results of MCO, the decisions of switch operations are finally co-decided by the expected exchanging power of the MGs and the real-time errors caused by uncertainty factors. Finally, a modified IEEE-33 nodes distribution system are used to test and verify the effectiveness of the method.

  8. Nitric oxide and related factors linked to oxidation and inflammation as possible biomarkers of heart failure.

    Science.gov (United States)

    Bonafede, Roberto; Manucha, Walter

    2018-02-21

    As a prevalent cardiovascular disease, heart failure is one of the leading causes of morbidity and premature mortality. Therefore, there is a special interest in the study of efficient markers associated with risk and / or prediction of cardiovascular events. Multiple candidates are proposed, especially those involved in oxidative and inflammatory processes typical of cardiovascular disease, such as superoxide anion, nitric oxide, and peroxynitrite. There is a lack of knowledge on the potential usefulness of these systems as biomarkers. This review aims to contribute to a better understanding of these systems, as well as an improved patient profile. Furthermore, a deep knowledge of these complex systems would also allow proposing new lines of research for the development of new therapeutic tools as a promising start for new approaches to this disease. Copyright © 2018 Sociedad Española de Arteriosclerosis. Publicado por Elsevier España, S.L.U. All rights reserved.

  9. Acute systolic heart failure and uncontrolled hypertension: what is the missing link?

    Science.gov (United States)

    Meseeha, Marcelle G; Sattur, Sudhakar

    2016-09-01

    Pheochromocytoma is a rare tumor in adults, with an estimated annual incidence of 0.8 per 100,000 persons. Cardiomyopathy is an uncommon presentation of such a rare disease. Serious cardiovascular complications of these tumors are related to potent effects of secreted catecholamines. The mechanism of pheochromocytoma-related cardiomyopathy is not well understood but it is likely due to the effect of excess catecholamines and their oxidation products which have been found to have a direct toxic effect on the myocardium. We describe below a case of a 70-year old female with uncontrolled hypertension and new onset acute systolic heart failure, who on further evaluation was noted to have pheochromocytoma-related cardiomyopathy. Pheochromocytoma should be strongly considered in the differential diagnosis of non-ischemic cardiomyopathy for a patient with elevated blood pressures relative to severity of cardiac dysfunction.

  10. An investigation of link quality assessment for mobile multi-hop and multi-rate wireless networks

    NARCIS (Netherlands)

    Zhou, J.; Jacobsson, M.; Onur, E.; Niemegeers, I.

    2011-01-01

    Wireless ad hoc networks will be an important component in future communication systems. The performance of wireless ad hoc networks can be improved by link quality-aware applications. Wireless link quality is dynamic in nature, especially in mobile scenarios. Therefore, accurate and fast packet

  11. Potential of commercial microwave link network derived rainfall for river runoff simulations

    Science.gov (United States)

    Smiatek, Gerhard; Keis, Felix; Chwala, Christian; Fersch, Benjamin; Kunstmann, Harald

    2017-03-01

    Commercial microwave link networks allow for the quantification of path integrated precipitation because the attenuation by hydrometeors correlates with rainfall between transmitter and receiver stations. The networks, operated and maintained by cellphone companies, thereby provide completely new and country wide precipitation measurements. As the density of traditional precipitation station networks worldwide is significantly decreasing, microwave link derived precipitation estimates receive increasing attention not only by hydrologists but also by meteorological and hydrological services. We investigate the potential of microwave derived precipitation estimates for streamflow prediction and water balance analyses, exemplarily shown for an orographically complex region in the German Alps (River Ammer). We investigate the additional value of link derived rainfall estimations combined with station observations compared to station and weather radar derived values. Our river runoff simulation system employs a distributed hydrological model at 100 × 100 m grid resolution. We analyze the potential of microwave link derived precipitation estimates for two episodes of 30 days with typically moderate river flow and an episode of extreme flooding. The simulation results indicate the potential of this novel precipitation monitoring method: a significant improvement in hydrograph reproduction has been achieved in the extreme flooding period that was characterized by a large number of local strong precipitation events. The present rainfall monitoring gauges alone were not able to correctly capture these events.

  12. Towards a whole-network risk assessment for railway bridge failures caused by scour during flood events

    Directory of Open Access Journals (Sweden)

    Lamb Rob

    2016-01-01

    Full Text Available Localised erosion (scour during flood flow conditions can lead to costly damage or catastrophic failure of bridges, and in some cases loss of life or significant disruption to transport networks. Here, we take a broad scale view to assess risk associated with bridge scour during flood events over an entire infrastructure network, illustrating the analysis with data from the British railways. There have been 54 recorded events since 1846 in which scour led to the failure of railway bridges in Britain. These events tended to occur during periods of extremely high river flow, although there is uncertainty about the precise conditions under which failures occur, which motivates a probabilistic analysis of the failure events. We show how data from the historical bridge failures, combined with hydrological analysis, have been used to construct fragility curves that quantify the conditional probability of bridge failure as a function of river flow, accompanied by estimates of the associated uncertainty. The new fragility analysis is tested using flood events simulated from a national, spatial joint probability model for extremes in river flows. The combined models appear robust in comparison with historical observations of the expected number of bridge failures in a flood event, and provide an empirical basis for further broad-scale network risk analysis.

  13. Cascaded optical fiber link using the Internet network for remote clocks comparison

    CERN Document Server

    Chiodo, Nicola; Stefani, Fabio; Wiotte, Fabrice; Camisard, Emilie; Chardonnet, Christian; Santarelli, Giorgio; Amy-Klein, Anne; Pottie, Paul-Eric; Lopez, Olivier

    2015-01-01

    We report a cascaded optical link of 1100 km for ultra-stable frequency distribution over an Internet fiber network. The link is composed of four spans for which the propagation noise is actively compensated. The robustness and the performance of the link are ensured by five fully automated optoelectronic stations, two of them at the link ends, and three deployed on the field and connecting the spans. This device coherently regenerates the optical signal with the heterodyne optical phase locking of a low-noise laser diode. Optical detection of the beat-note signals for the laser lock and the link noise compensation are obtained with stable and low-noise fibered optical interferometer. We show 3.5 days of continuous operation of the noise-compensated 4-span cascaded link leading to fractional frequency instability of 4x10-16 at 1-s measurement time and 1x10-19 at 2000 s. This cascaded link was extended to 1480-km with the same performance. This work is a significant step towards a sustainable wide area ultra-s...

  14. Linked to innovation : Shaping an innovative climate through network intentionality and educators' social network position

    NARCIS (Netherlands)

    Moolenaar, Nienke M.; Daly, Alan J.; Cornelissen, Frank; Liou, Yi Hwa; Caillier, Stacey; Riordan, Rob; Wilson, Kelly; Cohen, N. Andrew

    2014-01-01

    This study investigates whether educators' cognitive and structural social capital is associated with perceptions of innovative climate in charter schools. We explore a new concept to assess educators' cognitive social capital, namely network intentionality, meaning the extent to which an educator

  15. Linked to innovation: Shaping an innovative climate through network intentionality and educators’ social network position

    NARCIS (Netherlands)

    Moolenaar, Nienke; Daly, Alan J.; Daly, A.J.; Cornelissen, Frank; Liou, Yi-Hwa; Caillier, Stacey; Riordan, Rob; Wilson, Kelly; Cohen, N. Andrew

    2014-01-01

    This study investigates whether educators’ cognitive and structural social capital is associated with perceptions of innovative climate in charter schools. We explore a new concept to assess educators’ cognitive social capital, namely network intentionality, meaning the extent to which an educator

  16. Case study of the development of a SANDF tactical data link network enabling capability [Journal article

    CSIR Research Space (South Africa)

    Smith

    2011-11-01

    Full Text Available stream_source_info Smith_2011_ABSTARCT ONLY.pdf.txt stream_content_type text/plain stream_size 5823 Content-Encoding ISO-8859-1 stream_name Smith_2011_ABSTARCT ONLY.pdf.txt Content-Type text/plain; charset=ISO-8859... SANDF TACTICAL DATA LINK NETWORK ENABLING CAPABILITY Corn? J. Smith and Jacobus P. Venter * Abstract. In the scope of Tactical Data Links (TDL), the South African National Defence Force (SANDF) started the journey to establish a national TDL...

  17. Linked Heritage: a collaborative terminology management platform for a network of multilingual thesauri and controlled vocabularies

    Directory of Open Access Journals (Sweden)

    Marie-Veronique Leroi

    2013-01-01

    Full Text Available Terminology and multilingualism have been one of the main focuses of the Athena Project. Linked Heritage as a legacy of this project also deals with terminology and bring theory to practice applying the recommendations given in the Athena Project. Linked Heritage as a direct follow-up of these recommendations on terminology and multilingualism is currently working on the development of a Terminology Management Platform (TMP. This platform will allow any cultural institution to register, SKOSify and manage its terminology in a collaborative way. This Terminology Management Platform will provide a network of multilingual and cross-domain terminologies.

  18. Escape routes, weak links, and desynchronization in fluctuation-driven networks.

    Science.gov (United States)

    Schäfer, Benjamin; Matthiae, Moritz; Zhang, Xiaozhu; Rohden, Martin; Timme, Marc; Witthaut, Dirk

    2017-06-01

    Shifting our electricity generation from fossil fuel to renewable energy sources introduces large fluctuations to the power system. Here, we demonstrate how increased fluctuations, reduced damping, and reduced intertia may undermine the dynamical robustness of power grid networks. Focusing on fundamental noise models, we derive analytic insights into which factors limit the dynamic robustness and how fluctuations may induce a system escape from an operating state. Moreover, we identify weak links in the grid that make it particularly vulnerable to fluctuations. These results thereby not only contribute to a theoretical understanding of how fluctuations act on distributed network dynamics, they may also help designing future renewable energy systems to be more robust.

  19. Modeling radio link performance in UMTS W-CDMA network simulations

    DEFF Research Database (Denmark)

    Klingenbrunn, Thomas; Mogensen, Preben Elgaard

    2000-01-01

    This article presents a method to model the W-CDMA radio receiver performance, which is usable in network simulation tools for third generation mobile cellular systems. The method represents a technique to combine link level simulations with network level simulations. The method is derived from [1......], which defines a stochastic mapping function from a Signal-to-Interference Ratio into a Bit-Error-Rate for a TDMA system. However, in order to work in a W-CDMA based system, the fact that the Multiple-Access Interference in downlink consists of both Gaussian inter-cell interference and orthogonal intra...

  20. Degree distribution and assortativity in line graphs of complex networks

    NARCIS (Netherlands)

    Wang, X.; Trajanovski, S.; Kooij, R.E.; Mieghem, P. van

    2016-01-01

    Topological characteristics of links of complex networks influence the dynamical processes executed on networks triggered by links, such as cascading failures triggered by links in power grids and epidemic spread due to link infection. The line graph transforms links in the original graph into

  1. The Heart Failure Overweight/Obesity Survival Paradox: The Missing Sex Link.

    Science.gov (United States)

    Vest, Amanda R; Wu, Yuping; Hachamovitch, Rory; Young, James B; Cho, Leslie

    2015-11-01

    This study sought to determine whether body mass index (BMI) has a differential impact on survival for females versus males with advanced systolic heart failure (HF). Females have a survival advantage in HF, the mechanisms of which are unclear. There is also a proposed "obesity survival paradox" in which excess adiposity promotes HF survival. We reviewed 3,811 patients with left ventricular ejection fraction ≤40% who had undergone cardiopulmonary exercise testing between 1995 and 2011. The endpoint was all-cause mortality. Multivariable analysis was performed using a Cox proportional hazards model. Because of the nonlinearity of BMI, a restricted cubic spline was used. An interaction term was added to investigate the impact of BMI on mortality by sex. The unadjusted data demonstrated an overall obesity survival paradox in HF. This survival paradox disappeared for males after adjustment for potential confounders, with overweight and obese males showing higher adjusted mortality hazard ratios compared with normal weight males. Conversely, females in the overweight BMI range (25.0 to 29.9 kg/m(2)) had the lowest adjusted mortality (hazard ratio: 0.84; 95% confidence interval: 0.77 to 0.93; p = 0.0005 compared with normal weight females) with a nadir in mortality hazard just below BMI 30 kg/m(2). The multivariable model supported a differential impact of BMI on mortality in males versus females (p for interaction obesity survival paradox disappeared after adjustment for confounders. Overweight and obese males had higher adjusted mortality than normal weight males, whereas a BMI in the overweight range was associated with a significant survival benefit in females. Copyright © 2015 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  2. Failure to deactivate the default mode network indicates a possible endophenotype of autism

    Directory of Open Access Journals (Sweden)

    Spencer Michael D

    2012-12-01

    Full Text Available Abstract Background Reduced activity during cognitively demanding tasks has been reported in the default mode network in typically developing controls and individuals with autism. However, no study has investigated the default mode network (DMN in first-degree relatives of those with autism (such as siblings and it is not known whether atypical activation of the DMN is specific to autism or whether it is also present in unaffected relatives. Here we use functional magnetic resonance imaging to investigate the pattern of task-related deactivation during completion of a visual search task, the Embedded Figures Task, in teenagers with autism, their unaffected siblings and typically developing controls. Findings We identified striking reductions in deactivation during the Embedded Figures Task in unaffected siblings compared to controls in brain regions corresponding to the default mode network. Adolescents with autism and their unaffected siblings similarly failed to deactivate regions, including posterior cingulate and bilateral inferior parietal cortex. Conclusions This suggests that a failure to deactivate these regions is a functional endophenotype of autism, related to familial risk for the condition shared between individuals with autism and their siblings.

  3. Using LinkedIn in the Marketing Classroom: Exploratory Insights and Recommendations for Teaching Social Media/Networking

    Science.gov (United States)

    McCorkle, Denny E.; McCorkle, Yuhua Li

    2012-01-01

    With the rapid growth of social networking and media comes their consideration for use in the marketing classroom. Social networking skills are becoming essential for personal branding (e.g., networking, self-marketing) and corporate/product branding (e.g., marketing communication). This paper addresses the use of LinkedIn (i.e., an online…

  4. An Energy-Efficient Link with Adaptive Transmit Power Control for Long Range Networks

    DEFF Research Database (Denmark)

    Blaszczyk, Tomasz; Lynggaard, Per

    2016-01-01

    — A considerable amount of research is carried out to develop a reliable smart sensor system with high energy efficiency for battery operated wireless IoT devices in the agriculture sector. However, only a limited amount of research has covered automatic transmission power adjustment schemes...... and algorithms which are essential for deployment of wireless IoT nodes. This paper presents an adaptive link algorithm for farm applications with emphasis on power adjustment for long range communication networks....

  5. An Energy-Efficient Link with Adaptive Transmit Power Control for Long Range Networks

    DEFF Research Database (Denmark)

    Lynggaard, P.; Blaszczyk, Tomasz

    2016-01-01

    A considerable amount of research is carried out to develop a reliable smart sensor system with high energy efficiency for battery operated wireless IoT devices in the agriculture sector. However, only a limited amount of research has covered automatic transmission power adjustment schemes...... and algorithms which are essential for deployment of wireless IoT nodes. This paper presents an adaptive link algorithm for farm applications with emphasis on power adjustment for long range communication networks....

  6. Is CoV(t)-based Modeling Sufficient for Traffic Characterization in Network Links ?

    OpenAIRE

    Noirie, Ludovic; Post, Georg

    2008-01-01

    http://euronf.enst.fr/archive/164/EuroNFDeliverableDSEA641.pdf; International audience; For performance evaluation and dimensioning of packet-based networks, engineers need simple, efficient and realistic traffic models. The traffic volume on a packet link, observed at different time scales t, has previously been modeled as a stationary stochastic process based on the Coefficient of Variation CoV(t). In this paper we try to supply the missing information about the shape of the distribution fu...

  7. Impact of Radio Link Unreliability on the Connectivity of Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Gorce Jean-Marie

    2007-01-01

    Full Text Available Many works have been devoted to connectivity of ad hoc networks. This is an important feature for wireless sensor networks (WSNs to provide the nodes with the capability of communicating with one or several sinks. In most of these works, radio links are assumed ideal, that is, with no transmission errors. To fulfil this assumption, the reception threshold should be high enough to guarantee that radio links have a low transmission error probability. As a consequence, all unreliable links are dismissed. This approach is suboptimal concerning energy consumption because unreliable links should permit to reduce either the transmission power or the number of active nodes. The aim of this paper is to quantify the contribution of unreliable long hops to an increase of the connectivity of WSNs. In our model, each node is assumed to be connected to each other node in a probabilistic manner. Such a network is modeled as a complete random graph, that is, all edges exist. The instantaneous node degree is then defined as the number of simultaneous valid single-hop receptions of the same message, and finally the mean node degree is computed analytically in both AWGN and block-fading channels. We show the impact on connectivity of two MACs and routing parameters. The first one is the energy detection level such as the one used in carrier sense mechanisms. The second one is the reliability threshold used by the routing layer to select stable links only. Both analytic and simulation results show that using opportunistic protocols is challenging.

  8. On Efficient Link Recommendation in Social Networks Using Actor-Fact Matrices

    Directory of Open Access Journals (Sweden)

    Michał Ciesielczyk

    2015-01-01

    Full Text Available Link recommendation is a popular research subject in the field of social network analysis and mining. Often, the main emphasis is put on the development of new recommendation algorithms, semantic enhancements to existing solutions, design of new similarity measures, and so forth. However, relatively little scientific attention has been paid to the impact that various data representation models have on the performance of recommendation algorithms. And by performance we do not mean the time or memory efficiency of algorithms, but the precision and recall of recommender systems. Our recent findings unanimously show that the choice of network representation model has an important and measurable impact on the quality of recommendations. In this paper we argue that the computation quality of link recommendation algorithms depends significantly on the social network representation and we advocate the use of actor-fact matrix as the best alternative. We verify our findings using several state-of-the-art link recommendation algorithms, such as SVD, RSVD, and RRI using both single-relation and multirelation dataset.

  9. Social Networking Sites: Guidelines For Creating New Business Opportunities Through Facebook, Twitter And LinkedIn

    Directory of Open Access Journals (Sweden)

    Rodica Maria Savulescu

    2013-05-01

    Full Text Available The world is swiftly evolving. We now face the challenge of adapting the business sector to the increasingly dynamic transformation brought about by Web 2.0 technologies and social networks in particular. The extensive use of social networking sites (SNSs such as Facebook, Twitter and LinkedIn has spawned questions regarding the possibility of using such new platforms in order to generate more business revenue.While it is demonstrated that social networking can be profitable for companies and their brands in terms of exposure, brand awareness and actual sales, it can also prove detrimental if not managed correctly. At the same time, SNSs can affect every aspects of the business environment, like product development, marketing communication or the process of recruiting. This article explores the characteristics of social media and their impact on business and proposes several guidelines for companies that decide to employ SNSs in their activity.

  10. Lateralized Resting-State Functional Brain Network Organization Changes in Heart Failure.

    Directory of Open Access Journals (Sweden)

    Bumhee Park

    Full Text Available Heart failure (HF patients show brain injury in autonomic, affective, and cognitive sites, which can change resting-state functional connectivity (FC, potentially altering overall functional brain network organization. However, the status of such connectivity or functional organization is unknown in HF. Determination of that status was the aim here, and we examined region-to-region FC and brain network topological properties across the whole-brain in 27 HF patients compared to 53 controls with resting-state functional MRI procedures. Decreased FC in HF appeared between the caudate and cerebellar regions, olfactory and cerebellar sites, vermis and medial frontal regions, and precentral gyri and cerebellar areas. However, increased FC emerged between the middle frontal gyrus and sensorimotor areas, superior parietal gyrus and orbito/medial frontal regions, inferior temporal gyrus and lingual gyrus/cerebellar lobe/pallidum, fusiform gyrus and superior orbitofrontal gyrus and cerebellar sites, and within vermis and cerebellar areas; these connections were largely in the right hemisphere (p<0.005; 10,000 permutations. The topology of functional integration and specialized characteristics in HF are significantly changed in regions showing altered FC, an outcome which would interfere with brain network organization (p<0.05; 10,000 permutations. Brain dysfunction in HF extends to resting conditions, and autonomic, cognitive, and affective deficits may stem from altered FC and brain network organization that may contribute to higher morbidity and mortality in the condition. Our findings likely result from the prominent axonal and nuclear structural changes reported earlier in HF; protecting neural tissue may improve FC integrity, and thus, increase quality of life and reduce morbidity and mortality.

  11. Linking Climate Risk, Policy Networks and Adaptation Planning in Public Lands

    Science.gov (United States)

    Lubell, M.; Schwartz, M.; Peters, C.

    2014-12-01

    Federal public land management agencies in the United States have engaged a variety of planning efforts to address climate adaptation. A major goal of these efforts is to build policy networks that enable land managers to access information and expertise needed for responding to local climate risks. This paper investigates whether the perceived and modeled climate risk faced by different land managers is leading to larger networks or more participating in climate adaptation. In theory, the benefits of climate planning networks are larger when land managers are facing more potential changes. The basic hypothesis is tested with a survey of public land managers from hundreds of local and regional public lands management units in the Southwestern United States, as well as other stakeholders involved with climate adaptation planning. All survey respondents report their perceptions of climate risk along a variety of dimensions, as well as their participation in climate adaptation planning and information sharing networks. For a subset of respondents, we have spatially explicity GIS data about their location, which will be linked with downscaled climate model data. With the focus on climate change, the analysis is a subset of the overall idea of linking social and ecological systems.

  12. Colony Failure Linked to Low Sperm Viability in Honey Bee (Apis mellifera Queens and an Exploration of Potential Causative Factors.

    Directory of Open Access Journals (Sweden)

    Jeffery S Pettis

    Full Text Available Queen health is closely linked to colony performance in honey bees as a single queen is normally responsible for all egg laying and brood production within the colony. In the U. S. in recent years, queens have been failing at a high rate; with 50% or greater of queens replaced in colonies within 6 months when historically a queen might live one to two years. This high rate of queen failure coincides with the high mortality rates of colonies in the US, some years with >50% of colonies dying. In the current study, surveys of sperm viability in US queens were made to determine if sperm viability plays a role in queen or colony failure. Wide variation was observed in sperm viability from four sets of queens removed from colonies that beekeepers rated as in good health (n = 12; average viability = 92%, were replacing as part of normal management (n = 28; 57%, or where rated as failing (n = 18 and 19; 54% and 55%. Two additional paired set of queens showed a statistically significant difference in viability between colonies rated by the beekeeper as failing or in good health from the same apiaries. Queens removed from colonies rated in good health averaged high viability (ca. 85% while those rated as failing or in poor health had significantly lower viability (ca. 50%. Thus low sperm viability was indicative of, or linked to, colony performance. To explore the source of low sperm viability, six commercial queen breeders were surveyed and wide variation in viability (range 60-90% was documented between breeders. This variability could originate from the drones the queens mate with or temperature extremes that queens are exposed to during shipment. The role of shipping temperature as a possible explanation for low sperm viability was explored. We documented that during shipment queens are exposed to temperature spikes ( 40°C and these spikes can kill 50% or more of the sperm stored in queen spermathecae in live queens. Clearly low sperm viability is

  13. Colony Failure Linked to Low Sperm Viability in Honey Bee (Apis mellifera) Queens and an Exploration of Potential Causative Factors.

    Science.gov (United States)

    Pettis, Jeffery S; Rice, Nathan; Joselow, Katie; vanEngelsdorp, Dennis; Chaimanee, Veeranan

    2016-01-01

    Queen health is closely linked to colony performance in honey bees as a single queen is normally responsible for all egg laying and brood production within the colony. In the U. S. in recent years, queens have been failing at a high rate; with 50% or greater of queens replaced in colonies within 6 months when historically a queen might live one to two years. This high rate of queen failure coincides with the high mortality rates of colonies in the US, some years with >50% of colonies dying. In the current study, surveys of sperm viability in US queens were made to determine if sperm viability plays a role in queen or colony failure. Wide variation was observed in sperm viability from four sets of queens removed from colonies that beekeepers rated as in good health (n = 12; average viability = 92%), were replacing as part of normal management (n = 28; 57%), or where rated as failing (n = 18 and 19; 54% and 55%). Two additional paired set of queens showed a statistically significant difference in viability between colonies rated by the beekeeper as failing or in good health from the same apiaries. Queens removed from colonies rated in good health averaged high viability (ca. 85%) while those rated as failing or in poor health had significantly lower viability (ca. 50%). Thus low sperm viability was indicative of, or linked to, colony performance. To explore the source of low sperm viability, six commercial queen breeders were surveyed and wide variation in viability (range 60-90%) was documented between breeders. This variability could originate from the drones the queens mate with or temperature extremes that queens are exposed to during shipment. The role of shipping temperature as a possible explanation for low sperm viability was explored. We documented that during shipment queens are exposed to temperature spikes ( 40°C) and these spikes can kill 50% or more of the sperm stored in queen spermathecae in live queens. Clearly low sperm viability is linked to

  14. Risk and Resilience Analysis of Complex Network Systems Considering Cascading Failure and Recovery Strategy Based on Coupled Map Lattices

    Directory of Open Access Journals (Sweden)

    Fuchun Ren

    2015-01-01

    Full Text Available Risk and resilience are important and challenging issues in complex network systems since a single failure may trigger a whole collapse of the systems due to cascading effect. New theories, models, and methods are urgently demanded to deal with this challenge. In this paper, a coupled map lattices (CML based approach is adopted to analyze the risk of cascading process in Watts-Strogatz (WS small-world network and Barabási and Albert (BA scale-free network, respectively. Then, to achieve an effective and robust system and provide guidance in countering the cascading failure, a modified CML model with recovery strategy factor is proposed. Numerical simulations are put forward based on small-world CML and scale-free CML. The simulation results reveal that appropriate recovery strategies would significantly improve the resilience of networks.

  15. A network physiology approach to the assessment of the link between sinoatrial and ventricular cardiac controls.

    Science.gov (United States)

    Porta, Alberto; Bari, Vlasta; De Maria, Beatrice; Baumert, Mathias

    2017-06-27

    A network physiology approach to evaluate the strength of the directed interactions among cardiac controls at sinoatrial and ventricular levels and respiration (R) is proposed. The network is composed of three nodes (i.e. sinoatrial and ventricular cardiac controls and R) and their activity is exemplified by the variability of heart period (HP), the variability of the duration of the electrical activity of the heart approximated as the temporal distance between Q-wave onset and T-wave end or apex (i.e. QTe or QTa) and thoracic movements respectively. Model-based transfer entropy provided the estimate of the strength of the causal link from the source to the destination conditioned on the remaining node activity. The interactions were monitored in 15 healthy subjects aged from 24 to 54 years (9 males). Increasing levels of sympathetic activity were induced by graded head-up tilt with table inclination of 0, 15, 30, 45, 60, 75°. We found that: (i) the strength of the causal link from HP to QTe gradually decreases with tilt table angle, while that in the reverse direction is weak, even though significant, and constant; (ii) the action of R on HP is stronger than that from R to QTe; (iii) the strength of the relation from R to HP is weakly related to tilt table inclination, while that from R to QTe does not depend on it; (iv) while QTe cannot affect R, a weak causal dependence of R on HP is detected; (v) the network computed over QTa is qualitatively similar to that over QTe, even though the strength of the causal relations might be different. The proposed network physiology approach provides a comprehensive picture of the directed links among relevant cardiac regulatory mechanisms and their evolution with sympathetic tone usable to identify pathological conditions.

  16. Promoting wired links in wireless mesh networks: an efficient engineering solution.

    Science.gov (United States)

    Barekatain, Behrang; Raahemifar, Kaamran; Ariza Quintana, Alfonso; Triviño Cabrera, Alicia

    2015-01-01

    Wireless Mesh Networks (WMNs) cannot completely guarantee good performance of traffic sources such as video streaming. To improve the network performance, this study proposes an efficient engineering solution named Wireless-to-Ethernet-Mesh-Portal-Passageway (WEMPP) that allows effective use of wired communication in WMNs. WEMPP permits transmitting data through wired and stable paths even when the destination is in the same network as the source (Intra-traffic). Tested with four popular routing protocols (Optimized Link State Routing or OLSR as a proactive protocol, Dynamic MANET On-demand or DYMO as a reactive protocol, DYMO with spanning tree ability and HWMP), WEMPP considerably decreases the end-to-end delay, jitter, contentions and interferences on nodes, even when the network size or density varies. WEMPP is also cost-effective and increases the network throughput. Moreover, in contrast to solutions proposed by previous studies, WEMPP is easily implemented by modifying the firmware of the actual Ethernet hardware without altering the routing protocols and/or the functionality of the IP/MAC/Upper layers. In fact, there is no need for modifying the functionalities of other mesh components in order to work with WEMPPs. The results of this study show that WEMPP significantly increases the performance of all routing protocols, thus leading to better video quality on nodes.

  17. Promoting wired links in wireless mesh networks: an efficient engineering solution.

    Directory of Open Access Journals (Sweden)

    Behrang Barekatain

    Full Text Available Wireless Mesh Networks (WMNs cannot completely guarantee good performance of traffic sources such as video streaming. To improve the network performance, this study proposes an efficient engineering solution named Wireless-to-Ethernet-Mesh-Portal-Passageway (WEMPP that allows effective use of wired communication in WMNs. WEMPP permits transmitting data through wired and stable paths even when the destination is in the same network as the source (Intra-traffic. Tested with four popular routing protocols (Optimized Link State Routing or OLSR as a proactive protocol, Dynamic MANET On-demand or DYMO as a reactive protocol, DYMO with spanning tree ability and HWMP, WEMPP considerably decreases the end-to-end delay, jitter, contentions and interferences on nodes, even when the network size or density varies. WEMPP is also cost-effective and increases the network throughput. Moreover, in contrast to solutions proposed by previous studies, WEMPP is easily implemented by modifying the firmware of the actual Ethernet hardware without altering the routing protocols and/or the functionality of the IP/MAC/Upper layers. In fact, there is no need for modifying the functionalities of other mesh components in order to work with WEMPPs. The results of this study show that WEMPP significantly increases the performance of all routing protocols, thus leading to better video quality on nodes.

  18. Ophthalmology on social networking sites: an observational study of Facebook, Twitter, and LinkedIn

    Directory of Open Access Journals (Sweden)

    Micieli JA

    2015-02-01

    Full Text Available Jonathan A Micieli,1 Edmund Tsui2 1Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, ON, Canada; 2Department of Surgery, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA Background: The use of social media in ophthalmology remains largely unknown. Our aim was to evaluate the extent and involvement of ophthalmology journals, professional associations, trade publications, and patient advocacy and fundraising groups on social networking sites. Methods: An archived list of 107 ophthalmology journals from SCImago, trade publications, professional ophthalmology associations, and patient advocacy organizations were searched for their presence on Facebook, Twitter, and LinkedIn. Activity and popularity of each account was quantified by using the number of “likes” on Facebook, the number of followers on Twitter, and members on LinkedIn. Results: Of the 107 journals ranked by SCImago, 21.5% were present on Facebook and 18.7% were present on Twitter. Journal of Community Eye Health was the most popular on Facebook and JAMA Ophthalmology was most popular on Twitter. Among the 133 members of the International Council of Ophthalmology, 17.3% were present on Facebook, 12.8% were present on Twitter, and 7.5% were present on LinkedIn. The most popular on Facebook was the International Council of Ophthalmology, and the American Academy of Ophthalmology was most popular on Twitter and LinkedIn. Patient advocacy organizations were more popular on all sites compared with journals, professional association, and trade publications. Among the top ten most popular pages in each category, patient advocacy groups were most active followed by trade publications, professional associations, and journals. Conclusion: Patient advocacy groups lead the way in social networking followed by professional organizations and journals. Although some journals use social media, most have yet to engage its full potential and maximize the number of

  19. Risk and Resilience Analysis of Complex Network Systems Considering Cascading Failure and Recovery Strategy Based on Coupled Map Lattices

    OpenAIRE

    Fuchun Ren; Tingdi Zhao; Hongli Wang

    2015-01-01

    Risk and resilience are important and challenging issues in complex network systems since a single failure may trigger a whole collapse of the systems due to cascading effect. New theories, models, and methods are urgently demanded to deal with this challenge. In this paper, a coupled map lattices (CML) based approach is adopted to analyze the risk of cascading process in Watts-Strogatz (WS) small-world network and Barabási and Albert (BA) scale-free network, respectively. Then, to achieve an...

  20. From link-prediction in brain connectomes and protein interactomes to the local-community-paradigm in complex networks.

    KAUST Repository

    Cannistraci, C.V.

    2013-04-08

    Growth and remodelling impact the network topology of complex systems, yet a general theory explaining how new links arise between existing nodes has been lacking, and little is known about the topological properties that facilitate link-prediction. Here we investigate the extent to which the connectivity evolution of a network might be predicted by mere topological features. We show how a link/community-based strategy triggers substantial prediction improvements because it accounts for the singular topology of several real networks organised in multiple local communities - a tendency here named local-community-paradigm (LCP). We observe that LCP networks are mainly formed by weak interactions and characterise heterogeneous and dynamic systems that use self-organisation as a major adaptation strategy. These systems seem designed for global delivery of information and processing via multiple local modules. Conversely, non-LCP networks have steady architectures formed by strong interactions, and seem designed for systems in which information/energy storage is crucial.

  1. From link-prediction in brain connectomes and protein interactomes to the local-community-paradigm in complex networks.

    Science.gov (United States)

    Cannistraci, Carlo Vittorio; Alanis-Lobato, Gregorio; Ravasi, Timothy

    2013-01-01

    Growth and remodelling impact the network topology of complex systems, yet a general theory explaining how new links arise between existing nodes has been lacking, and little is known about the topological properties that facilitate link-prediction. Here we investigate the extent to which the connectivity evolution of a network might be predicted by mere topological features. We show how a link/community-based strategy triggers substantial prediction improvements because it accounts for the singular topology of several real networks organised in multiple local communities - a tendency here named local-community-paradigm (LCP). We observe that LCP networks are mainly formed by weak interactions and characterise heterogeneous and dynamic systems that use self-organisation as a major adaptation strategy. These systems seem designed for global delivery of information and processing via multiple local modules. Conversely, non-LCP networks have steady architectures formed by strong interactions, and seem designed for systems in which information/energy storage is crucial.

  2. Energy - photovoltaic: network-linked systems. 5. ed.; Energie - Photovoltaik: Netzgekoppelte Anlagen

    Energy Technology Data Exchange (ETDEWEB)

    Lutz, H.P.

    2000-09-01

    The new brochure called ''Photovoltaics - network-linked systems'' published by the Energy Information Center (IE) of the state of Baden-Wuerttemberg gives a comprehensive general view at the various aspects of photovoltaics. How a network-linked photovoltaics systems is built and how it functions, which quality criteria exist.. all this information is given to potential operators of systems, planners and installers. The question of rentability is also discussed, pointing at avoidable expenditures during installation. For future operators, a project is carried out virtually, starting from the designing stage over agreements with the energy supplier up to the licencing procedures and insurance matters. Tax issued are also taken into consideration. Various incentives and support methods are discussed. Other subjects are the integration of network-linked photovoltaics systems into the power supply - also under the new conditions of the liberalized power market. [German] Einen umfassenden Ueberblick ueber die verschiedenen Aspekte der Photovoltaik bietet die neue Broschuere 'Photovoltaik - netzgekoppelte Anlagen', die das Informationszentrum Energie (IE) des Landesgewerbeamts Baden-Wuerttemberg herausgegeben hat. Wie eine netzgekoppelte Photovoltaik-Anlage aufgebaut ist und funktioniert, welche Kriterien fuer Qualitaet es gibt - darueber koennen sich potentielle Betreiber von Anlagen, Planer und Installateure informieren. Es wird auch die Frage der Rentabilitaet diskutiert und auf vermeidbaren Installationsaufwand hingewiesen. Fuer kuenftige Anlagenbetreiber wird die Realisierung eines Projektes durchgespielt - von der Auslegung der Anlage ueber die Abstimmung mit dem Energieversorger bis hin zu Genehmigungs- und Versicherungsfragen. Zudem werden steuerrechtliche Aspekte beruecksichtigt sowie verschiedene Foerderverfahren diskutiert. Weitere Themen sind die Integration netzgekoppelter Photovoltaik-Anlagen in die Stromversorgung - auch

  3. Artificial Neural Network Algorithm for Condition Monitoring of DC-link Capacitors Based on Capacitance Estimation

    DEFF Research Database (Denmark)

    Soliman, Hammam Abdelaal Hammam; Wang, Huai; Gadalla, Brwene Salah Abdelkarim

    2015-01-01

    challenges. A capacitance estimation method based on Artificial Neural Network (ANN) algorithm is therefore proposed in this paper. The implemented ANN estimated the capacitance of the DC-link capacitor in a back-toback converter. Analysis of the error of the capacitance estimation is also given......In power electronic converters, reliability of DC-link capacitors is one of the critical issues. The estimation of their health status as an application of condition monitoring have been an attractive subject for industrial field and hence for the academic research filed as well. More reliable...... solutions are required to be adopted by the industry applications in which usage of extra hardware, increased cost, and low estimation accuracy are the main challenges. Therefore, development of new condition monitoring methods based on software solutions could be the new era that covers the aforementioned...

  4. MyGeneFriends: A Social Network Linking Genes, Genetic Diseases, and Researchers.

    Science.gov (United States)

    Allot, Alexis; Chennen, Kirsley; Nevers, Yannis; Poidevin, Laetitia; Kress, Arnaud; Ripp, Raymond; Thompson, Julie Dawn; Poch, Olivier; Lecompte, Odile

    2017-06-16

    The constant and massive increase of biological data offers unprecedented opportunities to decipher the function and evolution of genes and their roles in human diseases. However, the multiplicity of sources and flow of data mean that efficient access to useful information and knowledge production has become a major challenge. This challenge can be addressed by taking inspiration from Web 2.0 and particularly social networks, which are at the forefront of big data exploration and human-data interaction. MyGeneFriends is a Web platform inspired by social networks, devoted to genetic disease analysis, and organized around three types of proactive agents: genes, humans, and genetic diseases. The aim of this study was to improve exploration and exploitation of biological, postgenomic era big data. MyGeneFriends leverages conventions popularized by top social networks (Facebook, LinkedIn, etc), such as networks of friends, profile pages, friendship recommendations, affinity scores, news feeds, content recommendation, and data visualization. MyGeneFriends provides simple and intuitive interactions with data through evaluation and visualization of connections (friendships) between genes, humans, and diseases. The platform suggests new friends and publications and allows agents to follow the activity of their friends. It dynamically personalizes information depending on the user's specific interests and provides an efficient way to share information with collaborators. Furthermore, the user's behavior itself generates new information that constitutes an added value integrated in the network, which can be used to discover new connections between biological agents. We have developed MyGeneFriends, a Web platform leveraging conventions from popular social networks to redefine the relationship between humans and biological big data and improve human processing of biomedical data. MyGeneFriends is available at lbgi.fr/mygenefriends.

  5. Cross-Linked Liquid Crystalline Systems From Rigid Polymer Networks to Elastomers

    CERN Document Server

    Broer, Dirk

    2011-01-01

    With rapidly expanding interest in liquid crystalline polymers and elastomers among the liquid crystal community, researchers are currently exploring the wide range of possible application areas for these unique materials, including optical elements on displays, tunable lasers, strain gauges, micro-structures, and artificial muscles. Written by respected scientists from academia and industry around the world, who are not only active in the field but also well-known in more traditional areas of research, "Cross-Linked Liquid Crystalline Systems: From Rigid Polymer Networks to Elastomers&qu

  6. Weak Links: Stabilizers of Complex Systems from Proteins to Social Networks

    Science.gov (United States)

    Csermely, Peter

    Why do women stabilize our societies? Why can we enjoy and understand Shakespeare? Why are fruitflies uniform? Why do omnivorous eating habits aid our survival? Why is Mona Lisa's smile beautiful? -- Is there any answer to these questions? This book shows that the statement: "weak links stabilize complex systems" holds the answers to all of the surprising questions above. The author (recipientof several distinguished science communication prizes) uses weak (low affinity, low probability) interactions as a thread to introduce a vast varietyof networks from proteins to ecosystems.

  7. Game-Theoretic Optimal Power-Link Quality Topology Control in Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Evangelos D. SPYROU

    2017-05-01

    Full Text Available One of the most significant problems in Wireless Sensor Network (WSN deployment is the generation of topologies that maximize transmission reliability and guarantee network connectivity while also maximizing the network’s lifetime. Transmission power settings have a large impact on the aforementioned factors. Increasing transmission power to provide coverage is the intuitive solution yet with it may come with lower packet reception and shorter network lifetime. However, decreasing the transmission power may result in the network being disconnected. To balance these trade-offs we propose a discrete strategy game-theoretic solution, which we call TopGame that aims to maximize the reliability between nodes while using the most appropriate level of transmission power that guarantees connectivity. In this paper, we provide the conditions for the convergence of our algorithm to a pure Nash equilibrium as well as experimental results. Here we show, using the Indriya WSN testbed, that TopGame is more energy-efficient and approaches a similar packet reception ratio with the current closest state of the art protocol ART. Finally, we provide a methodology for further optimization of our work using an indicator function to distinguish between satisfactory and poor links.

  8. Linking Supply Chain Network Complexity to Interdependence and Risk-Assessment: Scale Development and Empirical Investigation

    Directory of Open Access Journals (Sweden)

    Samyadip Chakraborty

    2015-12-01

    Full Text Available Concepts like supply chain network complexity, interdependence and risk assessment have been prominently discussed directly and indirectly in management literature over past decades and plenty of frameworks and conceptual prescriptive research works have been published contributing towards building the body of knowledge. However previous studies often lacked quantification of the findings. Consequently, the need for suitable scales becomes prominent for measuring those constructs to empirically support the conceptualized relationships. This paper expands the understanding of supply chain network complexity (SCNC and also highlights its implications on interdependence (ID between the actors and risk assessment (RAS in transaction relationships. In doing so, SCNC and RAS are operationalized to understand how SCNC affects interdependence and risk assessment between the actors in the supply chain network. The contribution of this study lies in developing and validating multi-item scales for these constructs and empirically establishing the hypothesized relationships in the Indian context based on firm data collected using survey–based questionnaire. The methodology followed included structural equation modeling. The study findings indicate that SCNC had significant relationship with interdependence, which in turn significantly affected risk assessment. This study carries both academic and managerial implications and provides an empirically supported framework linking network complexity with the two key variables (ID and RAS, playing crucial roles in managerial decision making. This study contributes to the body of knowledge and aims at guiding managers in better understanding transaction relationships.

  9. A contractile actomyosin network linked to adherens junctions by Canoe/afadin helps drive convergent extension

    Science.gov (United States)

    Sawyer, Jessica K.; Choi, Wangsun; Jung, Kuo-Chen; He, Li; Harris, Nathan J.; Peifer, Mark

    2011-01-01

    Integrating individual cell movements to create tissue-level shape change is essential to building an animal. We explored mechanisms of adherens junction (AJ):cytoskeleton linkage and roles of the linkage regulator Canoe/afadin during Drosophila germband extension (GBE), a convergent-extension process elongating the body axis. We found surprising parallels between GBE and a quite different morphogenetic movement, mesoderm apical constriction. Germband cells have an apical actomyosin network undergoing cyclical contractions. These coincide with a novel cell shape change—cell extension along the anterior–posterior (AP) axis. In Canoe's absence, GBE is disrupted. The apical actomyosin network detaches from AJs at AP cell borders, reducing coordination of actomyosin contractility and cell shape change. Normal GBE requires planar polarization of AJs and the cytoskeleton. Canoe loss subtly enhances AJ planar polarity and dramatically increases planar polarity of the apical polarity proteins Bazooka/Par3 and atypical protein kinase C. Changes in Bazooka localization parallel retraction of the actomyosin network. Globally reducing AJ function does not mimic Canoe loss, but many effects are replicated by global actin disruption. Strong dose-sensitive genetic interactions between canoe and bazooka are consistent with them affecting a common process. We propose a model in which an actomyosin network linked at AP AJs by Canoe and coupled to apical polarity proteins regulates convergent extension. PMID:21613546

  10. Listening to Whispers of Ripple: Linking Wallets and Deanonymizing Transactions in the Ripple Network

    Directory of Open Access Journals (Sweden)

    Moreno-Sanchez Pedro

    2016-10-01

    Full Text Available The decentralized I owe you (IOU transaction network Ripple is gaining prominence as a fast, low-cost and efficient method for performing same and cross-currency payments. Ripple keeps track of IOU credit its users have granted to their business partners or friends, and settles transactions between two connected Ripple wallets by appropriately changing credit values on the connecting paths. Similar to cryptocurrencies such as Bitcoin, while the ownership of the wallets is implicitly pseudonymous in Ripple, IOU credit links and transaction flows between wallets are publicly available in an online ledger. In this paper, we present the first thorough study that analyzes this globally visible log and characterizes the privacy issues with the current Ripple network. In particular, we define two novel heuristics and perform heuristic clustering to group wallets based on observations on the Ripple network graph. We then propose reidentification mechanisms to deanonymize the operators of those clusters and show how to reconstruct the financial activities of deanonymized Ripple wallets. Our analysis motivates the need for better privacy-preserving payment mechanisms for Ripple and characterizes the privacy challenges faced by the emerging credit networks.

  11. Ophthalmology on social networking sites: an observational study of Facebook, Twitter, and LinkedIn.

    Science.gov (United States)

    Micieli, Jonathan A; Tsui, Edmund

    2015-01-01

    The use of social media in ophthalmology remains largely unknown. Our aim was to evaluate the extent and involvement of ophthalmology journals, professional associations, trade publications, and patient advocacy and fundraising groups on social networking sites. An archived list of 107 ophthalmology journals from SCImago, trade publications, professional ophthalmology associations, and patient advocacy organizations were searched for their presence on Facebook, Twitter, and LinkedIn. Activity and popularity of each account was quantified by using the number of "likes" on Facebook, the number of followers on Twitter, and members on LinkedIn. Of the 107 journals ranked by SCImago, 21.5% were present on Facebook and 18.7% were present on Twitter. Journal of Community Eye Health was the most popular on Facebook and JAMA Ophthalmology was most popular on Twitter. Among the 133 members of the International Council of Ophthalmology, 17.3% were present on Facebook, 12.8% were present on Twitter, and 7.5% were present on LinkedIn. The most popular on Facebook was the International Council of Ophthalmology, and the American Academy of Ophthalmology was most popular on Twitter and LinkedIn. Patient advocacy organizations were more popular on all sites compared with journals, professional association, and trade publications. Among the top ten most popular pages in each category, patient advocacy groups were most active followed by trade publications, professional associations, and journals. Patient advocacy groups lead the way in social networking followed by professional organizations and journals. Although some journals use social media, most have yet to engage its full potential and maximize the number of potential interested individuals.

  12. Surveillance and Protection-Based Approach for Link Failures over Fiber-to the-Home (FTTH with Combination of ACS and SANTAD

    Directory of Open Access Journals (Sweden)

    Aswir Premadi

    2009-05-01

    Full Text Available This paper introduces an in-service transmission surveillance and protection-based approach for fiber failures/faults over fiber-to-the-home passive optical network (FTTH-PON with an excellent combination of Access Control System (ACS and Smart Access Network Testing, Analyzing and Database (SANTAD. Our hardware design works on a standard local area network (LAN using a specially designed hardware interfaced with a microcontroller integrated Ethernet to monitor the status of optical signals flow and provide the restoration against fiber failures/faults in FTTH-PON. We also introduce the centralized management and access control program by means of SANTAD. ACS is used to control the troubleshooting mechanism carried out by SANTAD. This design will be implemented at central office (CO for distant monitoring and remote controlling each optical fiber line’s status as well as for detecting any failures/faults that occurs in the network system downwardly from CO towards multiple optical network units (ONUs. The scope of this discussion only highlighted on the monitoring and controlling instead of the restoration scheme.

  13. Usage of link-level performance indicators for HSDPA network-level simulations in E-UMTS

    NARCIS (Netherlands)

    Brouwer, Frank; de Bruin, I.C.C.; Silva, João Carlos; Souto, Nuno; Cercas, Francisco; Correia, Américo

    2004-01-01

    The paper describes integration of HSDPA (high-speed downlink packet access) link-level simulation results into network-level simulations for enhanced UMTS. The link-level simulations model all physical layer features depicted in the 3GPP standards. These include: generation of transport blocks;

  14. Imbalanced functional link between executive control network and reward network explain the online-game seeking behaviors in Internet gaming disorder.

    Science.gov (United States)

    Dong, Guangheng; Lin, Xiao; Hu, Yanbo; Xie, Chunming; Du, Xiaoxia

    2015-03-17

    Literatures have shown that Internet gaming disorder (IGD) subjects show impaired executive control and enhanced reward sensitivities than healthy controls. However, how these two networks jointly affect the valuation process and drive IGD subjects' online-game-seeking behaviors remains unknown. Thirty-five IGD and 36 healthy controls underwent a resting-states scan in the MRI scanner. Functional connectivity (FC) was examined within control and reward network seeds regions, respectively. Nucleus accumbens (NAcc) was selected as the node to find the interactions between these two networks. IGD subjects show decreased FC in the executive control network and increased FC in the reward network when comparing with the healthy controls. When examining the correlations between the NAcc and the executive control/reward networks, the link between the NAcc - executive control network is negatively related with the link between NAcc - reward network. The changes (decrease/increase) in IGD subjects' brain synchrony in control/reward networks suggest the inefficient/overly processing within neural circuitry underlying these processes. The inverse proportion between control network and reward network in IGD suggest that impairments in executive control lead to inefficient inhibition of enhanced cravings to excessive online game playing. This might shed light on the mechanistic understanding of IGD.

  15. A unique microRNA profile in end-stage heart failure indicates alterations in specific cardiovascular signaling networks.

    Directory of Open Access Journals (Sweden)

    Sathyamangla V Naga Prasad

    Full Text Available It is well established that the gene expression patterns are substantially altered in cardiac hypertrophy and heart failure, however, less is known about the reasons behind such global differences. MicroRNAs (miRNAs are short non-coding RNAs that can target multiple molecules to regulate wide array of proteins in diverse pathways. The goal of the study was to profile alterations in miRNA expression using end-stage human heart failure samples with an aim to build signaling network pathways using predicted targets for the altered miRNA and to determine nodal molecules regulating individual networks. Profiling of miRNAs using custom designed microarray and validation with an independent set of samples identified eight miRNAs that are altered in human heart failure including one novel miRNA yet to be implicated in cardiac pathology. To gain an unbiased perspective on global regulation by top eight altered miRNAs, functional relationship of predicted targets for these eight miRNAs were examined by network analysis. Ingenuity Pathways Analysis network algorithm was used to build global signaling networks based on the targets of altered miRNAs which allowed us to identify participating networks and nodal molecules that could contribute to cardiac pathophysiology. Majority of the nodal molecules identified in our analysis are targets of altered miRNAs and known regulators of cardiovascular signaling. Cardio-genomics heart failure gene expression public data base was used to analyze trends in expression pattern for target nodal molecules and indeed changes in expression of nodal molecules inversely correlated to miRNA alterations. We have used NF kappa B network as an example to show that targeting other molecules in the network could alter the nodal NF kappa B despite not being a miRNA target suggesting an integrated network response. Thus, using network analysis we show that altering key functional target proteins may regulate expression of the myriad

  16. Logical Link Control and Channel Scheduling for Multichannel Underwater Sensor Networks

    Directory of Open Access Journals (Sweden)

    Jun Li

    2012-08-01

    Full Text Available With recent developments in terrestrial wireless networks and advances in acoustic communications, multichannel technologies have been proposed to be used in underwater networks to increase data transmission rate over bandwidth-limited underwater channels. Due to high bit error rates in underwater networks, an efficient error control technique is critical in the logical link control (LLC sublayer to establish reliable data communications over intrinsically unreliable underwater channels. In this paper, we propose a novel protocol stack architecture featuring cross-layer design of LLC sublayer and more efficient packetto- channel scheduling for multichannel underwater sensor networks. In the proposed stack architecture, a selective-repeat automatic repeat request (SR-ARQ based error control protocol is combined with a dynamic channel scheduling policy at the LLC sublayer. The dynamic channel scheduling policy uses the channel state information provided via cross-layer design. It is demonstrated that the proposed protocol stack architecture leads to more efficient transmission of multiple packets over parallel channels. Simulation studies are conducted to evaluate the packet delay performance of the proposed cross-layer protocol stack architecture with two different scheduling policies: the proposed dynamic channel scheduling and a static channel scheduling. Simulation results show that the dynamic channel scheduling used in the cross-layer protocol stack outperforms the static channel scheduling. It is observed that, when the dynamic channel scheduling is used, the number of parallel channels has only an insignificant impact on the average packet delay. This confirms that underwater sensor networks will benefit from the use of multichannel communications.

  17. Analisis Performansi Perutingan Link State Menggunakan Algoritma Djikstra Pada Platform Software Defined Network (SDN

    Directory of Open Access Journals (Sweden)

    Abu Riza Sudiyatmoko

    2016-05-01

    Full Text Available Software Defined Network (SDN merupakan paradigma baru dalam sistem jaringan. Konsep dasar yang diusung oleh SDN adalah pemisahan antara layer control dan forward dalam perangkat yang berbeda. Konsep inilah yang menjadi perbedaan anatar SDN dan jaringan konvensional. Selain itu SDN memberikan konsep network topology virtualisation dan memungkinkan administrator untuk melakukan customize pada control plane. Dengan diterapkannya protokol OpenFlow pada SDN maka terdapat peluang untuk menerapkan perutingan flow based pada jaringan SDN dalam pendistribusian data dari source sampai ke destination. Link state IS-IS merupakan protokol routing yang menggunakan algoritma djikstra untuk menentukan jalur terbaik dalam pendistribusian paket. Dalam penelitian ini dilakukan analisis terhadap implementasi Link State IS-IS pada paltform SDN dengan menggunakan arsitektur RouteFlow. Parameter yang digunakan adalah  throughput, delay, jitter dan packet loss serta performansi perangkat controller. Hasil pengujian pada kondisi overload yaitu dengan background traffic 125 Mb nilai packet loss mencapai 1,23%, nilai throughput 47,6 Mbp/s dan jitter 2.012 ms. Nilai delay terbesar adalah pada topology 11 switch 11 host yaitu berkisar diangka 553 ms. Sedangkan performansi perangkat controller  dengan konsumsi memory pada saat menjalankan mengontrol jaringan berkisar diantara 25,638%  sampai  39,04%

  18. Numerical Modeling of Force-Stiffness Response of Cross-Linked Actin Networks Using Tensegrity Systems

    Directory of Open Access Journals (Sweden)

    Xian Xu

    2015-01-01

    Full Text Available A three-dimensional tensegrity structure is used as a computational model for cross-linked actin networks. The postbuckling behavior of the members under compression is considered and the constitutive relation of the postbuckling members is modeled as a second-order polynomial. A numerical scheme incorporating the equivalent constitution of the postbuckling members is used to predict the structural response of the tensegrity model under compression loads. The numerical simulation shows that the stiffness of the tensegrity structure nonlinearly increases before member buckling and abruptly decreases to a lower level as soon as members buckle. This result qualitatively mimics the experimentally observed stiffness to compression stress response of cross-linked actin networks. In order to take member length variety into account, a large number of simulations with the length of buckling members varying in the given range are also carried out. It is found that the mean response of the simulations using different buckling member length exhibits more resemblance to the experimental observation.

  19. Closed-loop healthcare monitoring in a collaborative heart failure network.

    Science.gov (United States)

    Modre-Osprian, Robert; Pölzl, Gerhard; Von Der Heidt, Andreas; Kastner, Peter

    2014-01-01

    Heart failure (HF) is a growing public health problem. The management of HF is usually multi-disciplinary and should comprise the cooperation of all groups of individuals involved in the care like clinicians, cardiologists, general practitioners, internists, nurses, relatives and patients. There is an ongoing debate with regard to monitoring and the optimal level and intensity of care for which kind of patients. Based on our experience with the recently established HF network HerzMobil Tirol, we developed a concept how to combine mHealth-based telemonitoring and disease management programs. The collaborative HF management concept timely and efficiently closes the feedback loop between patients and care providers and allows for continuity of care. The aim is to gradually adjust intensity of care according to the patients' level of disease severity and risk of readmission after hospital discharge along the overall trajectory of illness. Next steps will be to investigate how to define shared decision making, rights, duties, responsibilities and liabilities of the individual stakeholders as well as to analyze business models for reimbursement.

  20. Unique MicroRNA Profile in End-stage Heart Failure Indicates Alterations in Specific Cardiovascular Signaling Networks*

    OpenAIRE

    Naga Prasad, Sathyamangla V.; Duan, Zhong-Hui; Gupta, Manveen K.; Surampudi, Venkata Suresh K.; Volinia, Stefano; Calin, George A.; Liu, Chang-Gong; Kotwal, Ashwin; Moravec, Christine S.; Starling, Randall C.; Perez, Dianne M.; Sen, Subha; Wu, Qingyu; Plow, Edward F.; Croce, Carlo M.

    2009-01-01

    It is well established that gene expression patterns are substantially altered in cardiac hypertrophy and heart failure, but the reasons for such differences are not clear. MicroRNAs (miRNAs) are short noncoding RNAs that provide a novel mechanism for gene regulation. The goal of this study was to comprehensively test for alterations in miRNA expression using human heart failure samples with an aim to build signaling pathway networks using predicted targets for the miRNAs and to identify noda...

  1. Equipment Management for Sensor Networks: Linking Physical Infrastructure and Actions to Observational Data

    Science.gov (United States)

    Jones, A. S.; Horsburgh, J. S.; Matos, M.; Caraballo, J.

    2015-12-01

    Networks conducting long term monitoring using in situ sensors need the functionality to track physical equipment as well as deployments, calibrations, and other actions related to site and equipment maintenance. The observational data being generated by sensors are enhanced if direct linkages to equipment details and actions can be made. This type of information is typically recorded in field notebooks or in static files, which are rarely linked to observations in a way that could be used to interpret results. However, the record of field activities is often relevant to analysis or post-processing of the observational data. We have developed an underlying database schema and deployed a web interface for recording and retrieving information on physical infrastructure and related actions for observational networks. The database schema for equipment was designed as an extension to the Observations Data Model 2 (ODM2), a community-developed information model for spatially discrete, feature based earth observations. The core entities of ODM2 describe location, observed variable, and timing of observations, and the equipment extension contains entities to provide additional metadata specific to the inventory of physical infrastructure and associated actions. The schema is implemented in a relational database system for storage and management with an associated web interface. We designed the web-based tools for technicians to enter and query information on the physical equipment and actions such as site visits, equipment deployments, maintenance, and calibrations. These tools were implemented for the iUTAH (innovative Urban Transitions and Aridregion Hydrosustainability) ecohydrologic observatory, and we anticipate that they will be useful for similar large-scale monitoring networks desiring to link observing infrastructure to observational data to increase the quality of sensor-based data products.

  2. Regional Attenuation Correction of Weather Radar Using a Distributed Microwave-Links Network

    Directory of Open Access Journals (Sweden)

    Yang Xue

    2017-01-01

    Full Text Available The complex temporal-spatial variation of raindrop size distribution will affect the precision of precipitation quantitative estimates (QPE produced from radar data, making it difficult to correct echo attenuation. Given the fact that microwave links can obtain the total path attenuation accurately, we introduce the concept of regional attenuation correction using a multiple-microwave-links network based on the tomographic reconstruction of attenuation coefficients. Derived from the radar-based equation, the effect of rainfall distribution on the propagation of radar and microwave link signals was analyzed. This article focuses on modeling of the tomographic reconstruction of attenuation coefficients and regional attenuation correction algorithms. Finally, a numerical simulation of regional attenuation correction was performed to verify the algorithms employed here. The results demonstrate that the correction coefficient (0.9175 falls between the corrected and initial field of radar reflectivity factor (root mean square error, 2.3476 dBz; average deviation, 0.0113 dBz. Compared with uncorrected data, the accuracy of the corrected radar reflectivity factor was improved by 26.12%, and the corrected rainfall intensity distribution was improved by 51.85% validating the region attenuation correction algorithm. This method can correct the regional attenuation of weather radar echo effectively and efficiently; it can be widely used for the radar attenuation correction and the promotion of quantitative precipitation estimation by weather radar.

  3. A new measure based on degree distribution that links information theory and network graph analysis.

    Science.gov (United States)

    Hadley, Michael W; McGranaghan, Matt F; Willey, Aaron; Liew, Chun Wai; Reynolds, Elaine R

    2012-06-24

    Detailed connection maps of human and nonhuman brains are being generated with new technologies, and graph metrics have been instrumental in understanding the general organizational features of these structures. Neural networks appear to have small world properties: they have clustered regions, while maintaining integrative features such as short average pathlengths. We captured the structural characteristics of clustered networks with short average pathlengths through our own variable, System Difference (SD), which is computationally simple and calculable for larger graph systems. SD is a Jaccardian measure generated by averaging all of the differences in the connection patterns between any two nodes of a system. We calculated SD over large random samples of matrices and found that high SD matrices have a low average pathlength and a larger number of clustered structures. SD is a measure of degree distribution with high SD matrices maximizing entropic properties. Phi (Φ), an information theory metric that assesses a system's capacity to integrate information, correlated well with SD - with SD explaining over 90% of the variance in systems above 11 nodes (tested for 4 to 13 nodes). However, newer versions of Φ do not correlate well with the SD metric. The new network measure, SD, provides a link between high entropic structures and degree distributions as related to small world properties.

  4. Automated and comprehensive link engineering supporting branched, ring, and mesh network topologies

    Science.gov (United States)

    Farina, J.; Khomchenko, D.; Yevseyenko, D.; Meester, J.; Richter, A.

    2016-02-01

    Link design, while relatively easy in the past, can become quite cumbersome with complex channel plans and equipment configurations. The task of designing optical transport systems and selecting equipment is often performed by an applications or sales engineer using simple tools, such as custom Excel spreadsheets. Eventually, every individual has their own version of the spreadsheet as well as their own methodology for building the network. This approach becomes unmanageable very quickly and leads to mistakes, bending of the engineering rules and installations that do not perform as expected. We demonstrate a comprehensive planning environment, which offers an efficient approach to unify, control and expedite the design process by controlling libraries of equipment and engineering methodologies, automating the process and providing the analysis tools necessary to predict system performance throughout the system and for all channels. In addition to the placement of EDFAs and DCEs, performance analysis metrics are provided at every step of the way. Metrics that can be tracked include power, CD and OSNR, SPM, XPM, FWM and SBS. Automated routine steps assist in design aspects such as equalization, padding and gain setting for EDFAs, the placement of ROADMs and transceivers, and creating regeneration points. DWDM networks consisting of a large number of nodes and repeater huts, interconnected in linear, branched, mesh and ring network topologies, can be designed much faster when compared with conventional design methods. Using flexible templates for all major optical components, our technology-agnostic planning approach supports the constant advances in optical communications.

  5. A new measure based on degree distribution that links information theory and network graph analysis

    Science.gov (United States)

    2012-01-01

    Background Detailed connection maps of human and nonhuman brains are being generated with new technologies, and graph metrics have been instrumental in understanding the general organizational features of these structures. Neural networks appear to have small world properties: they have clustered regions, while maintaining integrative features such as short average pathlengths. Results We captured the structural characteristics of clustered networks with short average pathlengths through our own variable, System Difference (SD), which is computationally simple and calculable for larger graph systems. SD is a Jaccardian measure generated by averaging all of the differences in the connection patterns between any two nodes of a system. We calculated SD over large random samples of matrices and found that high SD matrices have a low average pathlength and a larger number of clustered structures. SD is a measure of degree distribution with high SD matrices maximizing entropic properties. Phi (Φ), an information theory metric that assesses a system’s capacity to integrate information, correlated well with SD - with SD explaining over 90% of the variance in systems above 11 nodes (tested for 4 to 13 nodes). However, newer versions of Φ do not correlate well with the SD metric. Conclusions The new network measure, SD, provides a link between high entropic structures and degree distributions as related to small world properties. PMID:22726594

  6. Three linked nomograms for predicting biochemical failure in prostate cancer treated with radiotherapy plus androgen deprivation therapy.

    Science.gov (United States)

    López-Torrecilla, Jose; Boladeras, Anna; Cabeza, María Angeles; Zapatero, Almudena; Jove, Josep; Esteban, Luis M; Henriquez, Ivan; Casaña, Manuel; González-San Segundo, Carmen; Gómez-Caamaño, Antonio; Mengual, Jose Luis; Hervás, Asunción; Muñoz, Julia Luisa; Sanz, Gerardo

    2015-10-01

    Nomograms were established to predict biochemical recurrence (BCR) after radiotherapy (RT) with a low weight of the characteristic variables of RT and androgen deprivation therapy (ADT). Our aim is to provide a new stratified tool for predicting BCR at 4 and 7 years in patients treated using RT with radical intent. A retrospective, nonrandomized analysis was performed on 5044 prostate cancer (PCa) patients with median age 70 years, who received RT-with or without ADT-between November 1992 and May 2007. Median follow-up was 5.5 years. BCR was defined as a rise in serum prostate-specific antigen (PSA) of 2 ng/ml over the post-treatment PSA nadir. Univariate association between predictor variables and BCR was assessed by the log-rank test, and three linked nomograms were created for multivariate prognosis of BCR-free survival. Each nomogram corresponds to a category of the Gleason score-either 6,7, or 8-10-and all of them were created from a single proportional hazards regression model stratified also by months of ADT (0, 1-6, 7-12, 13-24, 25-36, 36-60). The performance of this model was analyzed by calibration, discrimination, and clinical utility. Initial PSA, clinical stage, and RT dose were significant variables (p Cancer Network (NCCN) risk groups. For each Gleason score category, the nomogram provides information on the benefit of adding ADT to a specific RT dose.

  7. Linking in with LinkedIn[R]: Three Exercises That Enhance Professional Social Networking and Career Building

    Science.gov (United States)

    Gerard, Joseph G.

    2012-01-01

    Getting students to network with one another can be one of the biggest challenges in college courses, despite being a highly important function of higher education. Networking can, in fact, lead to that first job or to professional advancement, and technology can improve the success of individual and institutional efforts. This article describes…

  8. Processes entangling interactions in communities: forbidden links are more important than abundance in a hummingbird–plant network

    Science.gov (United States)

    Vizentin-Bugoni, Jeferson; Maruyama, Pietro Kiyoshi; Sazima, Marlies

    2014-01-01

    Understanding the relative importance of multiple processes on structuring species interactions within communities is one of the major challenges in ecology. Here, we evaluated the relative importance of species abundance and forbidden links in structuring a hummingbird–plant interaction network from the Atlantic rainforest in Brazil. Our results show that models incorporating phenological overlapping and morphological matches were more accurate in predicting the observed interactions than models considering species abundance. This means that forbidden links, by imposing constraints on species interactions, play a greater role than species abundance in structuring the ecological network. We also show that using the frequency of interaction as a proxy for species abundance and network metrics to describe the detailed network structure might lead to biased conclusions regarding mechanisms generating network structure. Together, our findings suggest that species abundance can be a less important driver of species interactions in communities than previously thought. PMID:24552835

  9. Cascading failures and the emergence of cooperation in evolutionary-game based models of social and economical networks.

    Science.gov (United States)

    Wang, Wen-Xu; Lai, Ying-Cheng; Armbruster, Dieter

    2011-09-01

    We study catastrophic behaviors in large networked systems in the paradigm of evolutionary games by incorporating a realistic "death" or "bankruptcy" mechanism. We find that a cascading bankruptcy process can arise when defection strategies exist and individuals are vulnerable to deficit. Strikingly, we observe that, after the catastrophic cascading process terminates, cooperators are the sole survivors, regardless of the game types and of the connection patterns among individuals as determined by the topology of the underlying network. It is necessary that individuals cooperate with each other to survive the catastrophic failures. Cooperation thus becomes the optimal strategy and absolutely outperforms defection in the game evolution with respect to the "death" mechanism. Our results can be useful for understanding large-scale catastrophe in real-world systems and in particular, they may yield insights into significant social and economical phenomena such as large-scale failures of financial institutions and corporations during an economic recession.

  10. A Spatio-Temporal exploratory analysis of pipe-failure incidents in the Water Distribution Network of Limassol, Cyprus

    OpenAIRE

    Gagatsis, Anastasios

    2011-01-01

    This paper presents the first attempt to the use of Geographic Information Systems technology in the Water Distribution Networks of Cyprus. A variety of exploratory, statistical and visualization techniques were used in order to identify patterns in the degradation of the WDN of Limassol. The distribution of pipe-failure incidents was studied at the level of District Metered Areas (DMA) boundary classifications and at the location level using point-pattern analysis methodologies. A modified v...

  11. Decreased creatine kinase is linked to diastolic dysfunction in rats with right heart failure induced by pulmonary artery hypertension

    NARCIS (Netherlands)

    Fowler, E.D.; Benoist, D.; Drinkhill, M.J.; Stones, R.; Helmes, M.H.B.; Wüst, R.C.I.; Stienen, G.J.M.; Steele, D.S.; White, E.

    2015-01-01

    Our objective was to investigate the role of creatine kinase in the contractile dysfunction of right ventricular failure caused by pulmonary artery hypertension. Pulmonary artery hypertension and right ventricular failure were induced in rats by monocrotaline and compared to saline-injected control

  12. Predicting network instabilities in mobile directional wireless networks

    Science.gov (United States)

    Coleman, David M.; Milner, Stuart D.; Davis, Christopher C.

    2013-09-01

    We have been investigating the dynamics of molecular systems as analogies for directional wireless networks. This has provided significant insight into reconfigurations of mobile wireless networks using directional point-to-point links (e.g. free-space optics or radio frequency). In this effort, we conceptualize the network as a giant molecule comprised of atoms that exert forces (attraction and repulsion) that stretch and relax the corresponding links. We monitor second-order variations of a potential energy function to gain an improved understanding of the large dimensionality of the optimized reconfiguration for network topology management. Ultimately, we envision this approach will allow for the prediction of two distinct events: 1) localized link failures and 2) catastrophic network events such as a partition. Our results show the detection of localized link failures and the availability for resource allocation more than one minute ahead of the failure (due to known events such as range and antenna blockage) with <80% accuracy.

  13. Adaptive link selection algorithms for distributed estimation

    Science.gov (United States)

    Xu, Songcen; de Lamare, Rodrigo C.; Poor, H. Vincent

    2015-12-01

    This paper presents adaptive link selection algorithms for distributed estimation and considers their application to wireless sensor networks and smart grids. In particular, exhaustive search-based least mean squares (LMS) / recursive least squares (RLS) link selection algorithms and sparsity-inspired LMS / RLS link selection algorithms that can exploit the topology of networks with poor-quality links are considered. The proposed link selection algorithms are then analyzed in terms of their stability, steady-state, and tracking performance and computational complexity. In comparison with the existing centralized or distributed estimation strategies, the key features of the proposed algorithms are as follows: (1) more accurate estimates and faster convergence speed can be obtained and (2) the network is equipped with the ability of link selection that can circumvent link failures and improve the estimation performance. The performance of the proposed algorithms for distributed estimation is illustrated via simulations in applications of wireless sensor networks and smart grids.

  14. GABAB receptor deficiency causes failure of neuronal homeostasis in hippocampal networks.

    Science.gov (United States)

    Vertkin, Irena; Styr, Boaz; Slomowitz, Edden; Ofir, Nir; Shapira, Ilana; Berner, David; Fedorova, Tatiana; Laviv, Tal; Barak-Broner, Noa; Greitzer-Antes, Dafna; Gassmann, Martin; Bettler, Bernhard; Lotan, Ilana; Slutsky, Inna

    2015-06-23

    Stabilization of neuronal activity by homeostatic control systems is fundamental for proper functioning of neural circuits. Failure in neuronal homeostasis has been hypothesized to underlie common pathophysiological mechanisms in a variety of brain disorders. However, the key molecules regulating homeostasis in central mammalian neural circuits remain obscure. Here, we show that selective inactivation of GABAB, but not GABA(A), receptors impairs firing rate homeostasis by disrupting synaptic homeostatic plasticity in hippocampal networks. Pharmacological GABA(B) receptor (GABA(B)R) blockade or genetic deletion of the GB(1a) receptor subunit disrupts homeostatic regulation of synaptic vesicle release. GABA(B)Rs mediate adaptive presynaptic enhancement to neuronal inactivity by two principle mechanisms: First, neuronal silencing promotes syntaxin-1 switch from a closed to an open conformation to accelerate soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex assembly, and second, it boosts spike-evoked presynaptic calcium flux. In both cases, neuronal inactivity removes tonic block imposed by the presynaptic, GB(1a)-containing receptors on syntaxin-1 opening and calcium entry to enhance probability of vesicle fusion. We identified the GB(1a) intracellular domain essential for the presynaptic homeostatic response by tuning intermolecular interactions among the receptor, syntaxin-1, and the Ca(V)2.2 channel. The presynaptic adaptations were accompanied by scaling of excitatory quantal amplitude via the postsynaptic, GB(1b)-containing receptors. Thus, GABA(B)Rs sense chronic perturbations in GABA levels and transduce it to homeostatic changes in synaptic strength. Our results reveal a novel role for GABA(B)R as a key regulator of population firing stability and propose that disruption of homeostatic synaptic plasticity may underlie seizure's persistence in the absence of functional GABA(B)Rs.

  15. Design of robust dependent networks against flow-based cascading failures

    NARCIS (Netherlands)

    Ouboter, T.M.; Worm, D.T.H.; Kooij, R.E.; Wang, H.

    2014-01-01

    In this paper we propose strategies to increase the robustness of a communication network which depends on the proper functioning of an electricity network. The strategies involve selecting nodes of the communication network and removing their dependency on the electricity network. Compared to

  16. Structure and stability of online chat networks built on emotion-carrying links

    Science.gov (United States)

    Gligorijević, Vladimir; Skowron, Marcin; Tadić, Bosiljka

    2013-02-01

    High-resolution data of online chats are studied as a physical system in the laboratory in order to quantify collective behavior of users. Our analysis reveals strong regularities characteristic of natural systems with additional features. In particular, we find self-organized dynamics with long-range correlations in user actions and persistent associations among users that have the properties of a social network. Furthermore, the evolution of the graph and its architecture with specific k-core structure are shown to be related with the type and the emotion arousal of exchanged messages. Partitioning of the graph by deletion of the links which carry high arousal messages exhibits critical fluctuations at the percolation threshold.

  17. Condition Monitoring for DC-link Capacitors Based on Artificial Neural Network Algorithm

    DEFF Research Database (Denmark)

    Soliman, Hammam Abdelaal Hammam; Wang, Huai; Gadalla, Brwene Salah Abdelkarim

    2015-01-01

    hardware will reduce the cost, and therefore could be more promising for industry applications. A condition monitoring method based on Artificial Neural Network (ANN) algorithm is therefore proposed in this paper. The implementation of the ANN to the DC-link capacitor condition monitoring in a back......In power electronic systems, capacitor is one of the reliability critical components . Recently, the condition monitoring of capacitors to estimate their health status have been attracted by the academic research. Industry applications require more reliable power electronics products...... with preventive maintenance. However, the existing capacitor condition monitoring methods suffer from either increased hardware cost or low estimation accuracy, being the challenges to be adopted in industry applications. New development in condition monitoring technology with software solutions without extra...

  18. Classical to quantum optical network link for orbital angular momentum-carrying light.

    Science.gov (United States)

    Zhou, Zhi-Yuan; Li, Yan; Ding, Dong-Sheng; Zhang, Wei; Shi, Shuai; Shi, Bao-Sen

    2015-07-13

    Using orbital angular momentum (OAM) conservation in second-order nonlinear interaction processes, we create a classical to quantum optical network link in the OAM degrees of freedom of light via sum frequency generation, followed by spontaneous parametric down-conversion. Coherent OAM-carrying beams at 1550 nm are up-converted to 525.5-nm OAM-carrying beams in the first crystal, and are used to pump a second crystal to generate non-degenerate OAM entangled photon pairs at 795 nm and 1550 nm. By switching the OAM carried by the classical part, OAM correlation in the quantum part is shifted. High-level OAM entanglements in two-dimensional subspaces are verified.

  19. Cross-Layer Explicit Link Status Notification to Improve TCP Performance in Wireless Networks

    Directory of Open Access Journals (Sweden)

    Yun Ji-Hoon

    2009-01-01

    Full Text Available To alleviate the performance degradation of conventional TCP in wireless networks, many schemes have been proposed so far. One category of such schemes is the Explicit Loss Notification (ELN scheme in which TCP senders are notified of wireless losses so as to avoid congestion control against those losses. Thus the key design factor of the ELN scheme is how to detect wireless losses accurately and rapidly. This paper proposes a new ELN scheme, in which wireless losses are detected by monitoring the operation of the wireless link layer. By exploiting such cross-layer design, the proposed scheme can detect wireless losses without additional transmission over the wireless link and thus achieves accurate detection with minimum delay. The proposed scheme additionally sends new information, that is, Explicit Retransmission Start Notification, in order to prevent spurious timeouts of the TCP senders. Furthermore, in order to handle packet reordering and avoid successive shrinking of a congestion window due to multiple packet drops, a new TCP modification is proposed. Through intensive simulations, it is demonstrated that the proposed scheme outperforms the other ELN schemes, and yields the throughput performance of more than 400% of TCP-Reno and 150% of Snoop in the considered environments.

  20. Ultra-Reliable Link Adaptation for Downlink MISO Transmission in 5G Cellular Networks

    Directory of Open Access Journals (Sweden)

    Udesh Oruthota

    2016-03-01

    Full Text Available This paper discusses robust link adaptation for a downlink precoded multiple input single output system, for guaranteeing ultra-reliable (99.999% transmissions to mobile users (e.g., slowly moving machines in a factory served by a small cell network. The proposed technique compensates the effect of inaccurate channel state information (CSI caused by user mobility, as well as the variation of precoders in the interfering cells. Both of these impairments translate into instability of the received signal-to-noise plus interference ratios (SINRs, and may lead to CSI mispredictions and potentially erroneous transmissions. We show that, by knowing the statistics of the propagation channels and the precoders variations, it is possible to compute a backoff that guarantees robust link adaptation. The backoff value is based on the statistics of realized SINR, and is consequently used to adapt the transmissions according to current channel state. Theoretical analysis accompanied by simulation results show that the proposed approach is suitable for attaining 5G ultra-reliability targets in realistic settings.

  1. Adaptive Predistortions Based on Neural Networks Associated with Levenberg-Marquardt Algorithm for Satellite Down Links

    Directory of Open Access Journals (Sweden)

    Roviras Daniel

    2008-01-01

    Full Text Available Abstract This paper presents adaptive predistortion techniques based on a feed-forward neural network (NN to linearize power amplifiers such as those used in satellite communications. Indeed, it presents the suitable NN structures which give the best performances for three satellite down links. The first link is a stationary memoryless travelling wave tube amplifier (TWTA, the second one is a nonstationary memoryless TWT amplifier while the third is an amplifier with memory modeled by a memoryless amplifier followed by a linear filter. Equally important, it puts forward the studies concerning the application of different NN training algorithms in order to determine the most prefermant for adaptive predistortions. This comparison examined through computer simulation for 64 carriers and 16-QAM OFDM system, with a Saleh's TWT amplifier, is based on some quality measure (mean square error, the required training time to reach a particular quality level, and computation complexity. The chosen adaptive predistortions (NN structures associated with an adaptive algorithm have a low complexity, fast convergence, and best performance.

  2. Adaptive Predistortions Based on Neural Networks Associated with Levenberg-Marquardt Algorithm for Satellite Down Links

    Directory of Open Access Journals (Sweden)

    Daniel Roviras

    2008-08-01

    Full Text Available This paper presents adaptive predistortion techniques based on a feed-forward neural network (NN to linearize power amplifiers such as those used in satellite communications. Indeed, it presents the suitable NN structures which give the best performances for three satellite down links. The first link is a stationary memoryless travelling wave tube amplifier (TWTA, the second one is a nonstationary memoryless TWT amplifier while the third is an amplifier with memory modeled by a memoryless amplifier followed by a linear filter. Equally important, it puts forward the studies concerning the application of different NN training algorithms in order to determine the most prefermant for adaptive predistortions. This comparison examined through computer simulation for 64 carriers and 16-QAM OFDM system, with a Saleh's TWT amplifier, is based on some quality measure (mean square error, the required training time to reach a particular quality level, and computation complexity. The chosen adaptive predistortions (NN structures associated with an adaptive algorithm have a low complexity, fast convergence, and best performance.

  3. Real time data acquisition of commercial microwave link networks for hydrometeorological applications

    Science.gov (United States)

    Chwala, C.; Keis, F.; Kunstmann, H.

    2015-11-01

    The usage of data from commercial microwave link (CML) networks for scientific purposes is becoming increasingly popular, in particular for rain rate estimation. However, data acquisition and availability is still a crucial problem and limits research possibilities. To overcome this issue, we have developed an open source data acquisition system based on the Simple Network Management Protocol (SNMP). It is able to record transmitted- and received signal levels of a large number of CMLs simultaneously with a temporal resolution of up to one second. We operate this system at Ericsson Germany, acquiring data from 450 CMLs with minutely real time transfer to our data base. Our data acquisition system is not limited to a particular CML hardware model or manufacturer, though. We demonstrate this by running the same system for CMLs of a different manufacturer, operated by an alpine skiing resort in Germany. There, the data acquisition is running simultaneously for four CMLs with a temporal resolution of one second. We present an overview of our system, describe the details of the necessary SNMP requests and show results from its operational application.

  4. Real-time data acquisition of commercial microwave link networks for hydrometeorological applications

    Science.gov (United States)

    Chwala, Christian; Keis, Felix; Kunstmann, Harald

    2016-03-01

    The usage of data from commercial microwave link (CML) networks for scientific purposes is becoming increasingly popular, in particular for rain rate estimation. However, data acquisition and availability is still a crucial problem and limits research possibilities. To overcome this issue, we have developed an open-source data acquisition system based on the Simple Network Management Protocol (SNMP). It is able to record transmitted and received signal levels of a large number of CMLs simultaneously with a temporal resolution of up to 1 s. We operate this system at Ericsson Germany, acquiring data from 450 CMLs with minutely real-time transfer to our database. Our data acquisition system is not limited to a particular CML hardware model or manufacturer, though. We demonstrate this by running the same system for CMLs of a different manufacturer, operated by an alpine ski resort in Germany. There, the data acquisition is running simultaneously for four CMLs with a temporal resolution of 1 s. We present an overview of our system, describe the details of the necessary SNMP requests and show results from its operational application.

  5. Application of network properties and signal strength to identify face-to-face links in an electronic dataset

    CERN Document Server

    Sekara, Vedran

    2014-01-01

    Understanding how people interact and socialize is important in many contexts, from disease control to urban planning. Datasets that capture this specific aspect of human life have increased in size and availability over the last few years. We have yet to understand, however, to what extent such electronic datasets may serve as a valid proxy for real life face-to-face interactions. For an observational dataset, gathered by mobile phones, we attack the problem of identifying transient and non-important links, as well as how to highlight important interactions. Using the Bluetooth signal strength parameter to distinguish between observations, we demonstrate that weak links, compared to strong links, have a lower probability of being observed at later times, while such links--on average--also have lower link-weights and a lower probability of sharing an online friendship. Further, the role of link-strength is investigated in relation to social network properties.

  6. Linking Network Activity to Synaptic Plasticity during Sleep: Hypotheses and Recent Data.

    Science.gov (United States)

    Puentes-Mestril, Carlos; Aton, Sara J

    2017-01-01

    Research findings over the past two decades have supported a link between sleep states and synaptic plasticity. Numerous mechanistic hypotheses have been put forth to explain this relationship. For example, multiple studies have shown structural alterations to synapses (including changes in synaptic volume, spine density, and receptor composition) indicative of synaptic weakening after a period of sleep. Direct measures of neuronal activity and synaptic strength support the idea that a period of sleep can reduce synaptic strength. This has led to the synaptic homeostasis hypothesis (SHY), which asserts that during slow wave sleep, synapses are downscaled throughout the brain to counteract net strengthening of network synapses during waking experience (e.g., during learning). However, neither the cellular mechanisms mediating these synaptic changes, nor the sleep-dependent activity changes driving those cellular events are well-defined. Here we discuss potential cellular and network dynamic mechanisms which could underlie reductions in synaptic strength during sleep. We also discuss recent findings demonstrating circuit-specific synaptic strengthening (rather than weakening) during sleep. Based on these data, we explore the hypothetical role of sleep-associated network activity patterns in driving synaptic strengthening. We propose an alternative to SHY-namely that depending on experience during prior wake, a variety of plasticity mechanisms may operate in the brain during sleep. We conclude that either synaptic strengthening or synaptic weakening can occur across sleep, depending on changes to specific neural circuits (such as gene expression and protein translation) induced by experiences in wake. Clarifying the mechanisms underlying these different forms of sleep-dependent plasticity will significantly advance our understanding of how sleep benefits various cognitive functions.

  7. Generate networks with power-law and exponential-law distributed degrees: with applications in link prediction of tumor pathways

    Directory of Open Access Journals (Sweden)

    WenJun Zhang

    2016-03-01

    Full Text Available In present study I proposed a method for generating biological networks based on power-law (p(x=x^(-a and exponential-law (p(x=e^(-ax distribution functions. Given the parameter of power-law or exponential-law distribution function, a, the algorithm generates an expected frequency distribution according to the given parameter, thereafter creates an adjacency matrix in which (practical frequency distribution of node degrees matches the expected frequency distribution. The results showed that power-law distribution function performs much better than exponential-law distribution function in generating networks. Using the revised algorithm, tumor related networks (pathways are simulated and predicted. The results prove that the algorithm is overall effective in predicting network links (14.6%-21.2%of correctly predicted links against 0.1%-3.4% of that for random assignments. Matlab codes of the algorithms are given also.

  8. A national internet-linked based database for pediatric interstitial lung diseases: the French network

    Directory of Open Access Journals (Sweden)

    Nathan Nadia

    2012-06-01

    Full Text Available Abstract Background Interstitial lung diseases (ILDs in children represent a heterogeneous group of rare respiratory disorders that affect the lung parenchyma. After the launch of the French Reference Centre for Rare Lung Diseases (RespiRare®, we created a national network and a web-linked database to collect data on pediatric ILD. Methods Since 2008, the database has been set up in all RespiRare® centres. After patient's parents' oral consent is obtained, physicians enter the data of children with ILD: identity, social data and environmental data; specific aetiological diagnosis of the ILD if known, genetics, patient visits to the centre, and all medical examinations and tests done for the diagnosis and/or during follow up. Each participating centre has a free access to his own patients' data only, and cross-centre studies require mutual agreement. Physicians may use the system as a daily aid for patient care through a web-linked medical file, backed on this database. Results Data was collected for 205 cases of ILD. The M/F sex ratio was 0.9. Median age at diagnosis was 1.5 years old [0–16.9]. A specific aetiology was identified in 149 (72.7% patients while 56 (27.3% cases remain undiagnosed. Surfactant deficiencies and alveolar proteinosis, haemosiderosis, and sarcoidosis represent almost half of the diagnoses. Median length of follow-up is 2.9 years [0–17.2]. Conclusions We introduce here the French network and the largest national database in pediatric ILDs. The diagnosis spectrum and the estimated incidence are consistent with other European databases. An important challenge will be to reduce the proportion of unclassified ILDs by a standardized diagnosis work-up. This database is a great opportunity to improve patient care and disease pathogenesis knowledge. A European network including physicians and European foundations is now emerging with the initial aim of devising a simplified European database/register as a first step to

  9. Importance of RIFLE (Risk, Injury, Failure, Loss, and End-Stage Renal Failure) and AKIN (Acute Kidney Injury Network) in Hemodialysis Initiation and Intensive Care Unit Mortality.

    Science.gov (United States)

    Kara, Iskender; Yildirim, Fatma; Kayacan, Esra; Bilaloğlu, Burcu; Turkoglu, Melda; Aygencel, Gülbin

    2017-07-01

    Our study evaluated the differences between early and late hemodialysis (HD) initiation in the intensive care unit (ICU) according to the RIFLE (Risk, Injury, Failure, Loss, and End-stage renal failure) and AKIN (Acute Kidney Injury Network) classifications. On the assumption that early initiation of HD in critical patients according to the RIFLE and AKIN criteria decreases mortality, we retrospectively evaluated the medical records of 68 patients in our medical ICU and divided the patients into 2 groups: Those undergoing HD in no risk, risk, or injury stage according to RIFLE and in stage 0, I, or II according to AKIN were defined as early HD and those in failure stage according to RIFLE and in stage III according to AKIN were defined as late HD. The median age of the patients was 66.5 years, and 56.5% were male. HD was started in 25% and 39.7% of the patients in the early stage in the RIFLE and AKIN classification, respectively. According to RIFLE, HD was started in 61.5% of the surviving patients in the early stage; this rate was 16.4% in the deceased patients (P=0.001). HD was commenced in 69.2% of the surviving patients in AKIN stages 0, I, and II and in 32.7% of the deceased patients (P=0.026). Sepsis (61.5% vs. 94.5%; P=0.001) and mechanical ventilation (30.8% vs. 87.3%; P<0.001) during HD increased ICU mortality, whereas HD initiation in the early stages according to RIFLE decreased ICU mortality (61.5% vs. 16.4%; P=0.001). In conclusion, in critically ill patients, HD initiation in the early stages according to the RIFLE classification decreased our ICU mortality.

  10. Activation and Inhibition of Sodium-Hydrogen Exchanger Is a Mechanism That Links the Pathophysiology and Treatment of Diabetes Mellitus With That of Heart Failure.

    Science.gov (United States)

    Packer, Milton

    2017-10-17

    The mechanisms underlying the progression of diabetes mellitus and heart failure are closely intertwined, such that worsening of one condition is frequently accompanied by worsening of the other; the degree of clinical acceleration is marked when the 2 coexist. Activation of the sodium-hydrogen exchanger in the heart and vasculature (NHE1 isoform) and the kidneys (NHE3 isoform) may serve as a common mechanism that links both disorders and may underlie their interplay. Insulin insensitivity and adipokine abnormalities (the hallmarks of type 2 diabetes mellitus) are characteristic features of heart failure; conversely, neurohormonal systems activated in heart failure (norepinephrine, angiotensin II, aldosterone, and neprilysin) impair insulin sensitivity and contribute to microvascular disease in diabetes mellitus. Each of these neurohormonal derangements may act through increased activity of both NHE1 and NHE3. Drugs used to treat diabetes mellitus may favorably affect the pathophysiological mechanisms of heart failure by inhibiting either or both NHE isoforms, and drugs used to treat heart failure may have beneficial effects on glucose tolerance and the complications of diabetes mellitus by interfering with the actions of NHE1 and NHE3. The efficacy of NHE inhibitors on the risk of cardiovascular events may be enhanced when heart failure and glucose intolerance coexist and may be attenuated when drugs with NHE inhibitory actions are given concomitantly. Therefore, the sodium-hydrogen exchanger may play a central role in the interplay of diabetes mellitus and heart failure, contribute to the physiological and clinical progression of both diseases, and explain certain drug-drug and drug-disease interactions that have been reported in large-scale randomized clinical trials. © 2017 American Heart Association, Inc.

  11. 75 FR 26180 - Effects on Broadband Communications Networks of Damage To or Failure of Network Equipment or...

    Science.gov (United States)

    2010-05-11

    ... networks for voice, video, data, and other communications services, the reliability and survivability of... rely on broadband communications networks to supply voice, video, and data service to fixed and mobile... survivability to three broad classes of harm: (1) Physical damage (whether due to malevolent acts, accidents, or...

  12. Species abundance, not diet breadth, drives the persistence of the most linked pollinators as plant-pollinator networks disassemble.

    Science.gov (United States)

    Winfree, Rachael; Williams, Neal M; Dushoff, Jonathan; Kremen, Claire

    2014-05-01

    Theoretical and simulation studies predict that the order of species loss from mutualist networks with respect to how linked species are to other species within the network will determine the rate at which networks collapse. However, the empirical order of species loss with respect to linkage has rarely been investigated. Furthermore, a species' linkage is a composite of its diet breadth and its abundance, yet the relative importance of these two factors in determining species loss order is poorly known. Here we explore the order of pollinator species loss in two contrasting study systems undergoing land-use intensification, using >20,000 pollinator specimens. We found that a pollinator species' linkage, as measured independently within plant-pollinator networks, positively predicted its persistence at human-disturbed sites in three of four analyses. The strongest predictor of persistence in all analyses was pollinator species abundance. In contrast, diet breadth poorly predicted persistence. Overall, our results suggest that community disassembly order buffers plant-pollinator networks against environmental change by retaining the highly linked species that make a disproportionate contribution to network robustness. Furthermore, these highly linked species likely persist because they are also the most common species, not because they are dietary generalists.

  13. The Inverse Contagion Problem (ICP) vs.. Predicting site contagion in real time, when network links are not observable

    Science.gov (United States)

    Mushkin, I.; Solomon, S.

    2017-10-01

    We study the inverse contagion problem (ICP). As opposed to the direct contagion problem, in which the network structure is known and the question is when each node will be contaminated, in the inverse problem the links of the network are unknown but a sequence of contagion histories (the times when each node was contaminated) is observed. We consider two versions of the ICP: The strong problem (SICP), which is the reconstruction of the network and has been studied before, and the weak problem (WICP), which requires "only" the prediction (at each time step) of the nodes that will be contaminated at the next time step (this is often the real life situation in which a contagion is observed and predictions are made in real time). Moreover, our focus is on analyzing the increasing accuracy of the solution, as a function of the number of contagion histories already observed. For simplicity, we discuss the simplest (deterministic and synchronous) contagion dynamics and the simplest solution algorithm, which we have applied to different network types. The main result of this paper is that the complex problem of the convergence of the ICP for a network can be reduced to an individual property of pairs of nodes: the "false link difficulty". By definition, given a pair of unlinked nodes i and j, the difficulty of the false link (i,j) is the probability that in a random contagion history, the nodes i and j are not contaminated at the same time step (or at consecutive time steps). In other words, the "false link difficulty" of a non-existing network link is the probability that the observations during a random contagion history would not rule out that link. This probability is relatively straightforward to calculate, and in most instances relies only on the relative positions of the two nodes (i,j) and not on the entire network structure. We have observed the distribution of false link difficulty for various network types, estimated it theoretically and confronted it

  14. Three linked nomograms for predicting biochemical failure in prostate cancer treated with radiotherapy plus androgen deprivation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Torrecilla, Jose [Hospital General Universitario, Servicio Oncologia Radioterapica- ERESA, Valencia (Spain); Boladeras, Anna [Institut Catala d' Oncologia, S.Oncologia Radioterapica, Hospitalet (Spain); Angeles Cabeza, Maria [Hospital Universitario Doce de Octubre, S.Oncologia Radioterapica, Madrid (Spain); Zapatero, Almudena [Hospital Universitario de la Princesa, S.Oncologia Radioterapica, Madrid (Spain); Jove, Josep [Institut Catala d' Oncologia, S.Oncologia Radioterapica, Badalona (Spain); Esteban, Luis M. [Universidad de Zaragoza, Escuela Universitaria Politecnica de La Almunia, Zaragoza (Spain); Henriquez, Ivan [Hospital Universitari Sant Joan de Reus, S.Oncologia Radioterapica, Reus (Spain); Casana, Manuel; Mengual, Jose Luis [Fundacion Instituto Valenciano de Oncologia, S.Oncologia Radioterapica, Valencia (Spain); Gonzalez-San Segundo, Carmen [Hospital Universitario Gregorio Maranon, S.Oncologia Radioterapica, Madrid (Spain); Gomez-Caamano, Antonio [Hospital Clinico Universitario de Santiago, S.Oncologia Radioterapica, Santiago de Compostela (Spain); Hervas, Asuncion [Hospital Universitario Ramon y Cajal, S.Oncologia Radioterapica, Madrid (Spain); Munoz, Julia Luisa [Hospital Infanta Cristina, S.Oncologia Radioterapica, Badajoz (Spain); Sanz, Gerardo [Universidad de Zaragoza, Departamento de Metodos Estadisticos, Zaragoza (Spain)

    2015-10-15

    Nomograms were established to predict biochemical recurrence (BCR) after radiotherapy (RT) with a low weight of the characteristic variables of RT and androgen deprivation therapy (ADT). Our aim is to provide a new stratified tool for predicting BCR at 4 and 7 years in patients treated using RT with radical intent. A retrospective, nonrandomized analysis was performed on 5044 prostate cancer (PCa) patients with median age 70 years, who received RT - with or without ADT - between November 1992 and May 2007. Median follow-up was 5.5 years. BCR was defined as a rise in serum prostate-specific antigen (PSA) of 2 ng/ml over the post-treatment PSA nadir. Univariate association between predictor variables and BCR was assessed by the log-rank test, and three linked nomograms were created for multivariate prognosis of BCR-free survival. Each nomogram corresponds to a category of the Gleason score - either 6,7, or 8-10 - and all of them were created from a single proportional hazards regression model stratified also by months of ADT (0, 1-6, 7-12, 13-24, 25-36, 36-60). The performance of this model was analyzed by calibration, discrimination, and clinical utility. Initial PSA, clinical stage, and RT dose were significant variables (p < 0.01). The model showed a good calibration. The concordance probability was 0.779, improving those obtained with other nomograms (0.587, 0.571, 0.554) in the database. Survival curves showed best clinical utility in a comparison with National Comprehensive Cancer Network (NCCN) risk groups. For each Gleason score category, the nomogram provides information on the benefit of adding ADT to a specific RT dose. (orig.) [German] Es wurden Nomogramme etabliert, um ein biochemisches Rezidiv (BCR) nach einer Strahlentherapie (RT) vorhersagen zu koennen und den Einfluss der charakteristischen Variablen der RT und der Androgendeprivationstherapie (ADT) dabei moeglichst gering zu halten. Unser Ziel ist es, ein neues stratifiziertes Instrument

  15. The Impact of a Power Electronics Converter in Phase Failure Work on the Power System Network

    Directory of Open Access Journals (Sweden)

    Dariusz Zieliński

    2016-09-01

    Full Text Available The paper presents the impact of phase failure work on power converters. The study includes a three-level NPC inverter (Neutral Point Clamped, controlled by Voltage Oriented Control (VOC. The NPC converter integrates renewable energy sources with the power grid. The article includes a discussion about the causes of phase failure work and an analysis of the converter’s failure and its impact on the power grid. The simulations were performed in MATLAB/Simulink. The study also includes the concept of an integrated protection for IGBTs, controlled by the DSP microprocessor system.

  16. The effect of destination linked feature selection in real-time network intrusion detection

    CSIR Research Space (South Africa)

    Mzila, P

    2013-07-01

    Full Text Available techniques in the network intrusion detection system (NIDS) is the feature selection technique. The ability of NIDS to accurately identify intrusion from the network traffic relies heavily on feature selection, which describes the pattern of the network...

  17. Prediction of Cascading Collapse Occurrence due to the Effect of Hidden Failure of a Protection System using Artificial Neural Network

    Directory of Open Access Journals (Sweden)

    Nor Hazwani Idris

    2017-06-01

    Full Text Available Transmission line act as a medium of transportation for electrical energy from a power station to the consumer. There are many factors that could cause the cascading collapse such as instability of voltage and frequency, the change of environment and weather, the software and operator error and also the failure in protection system. Protection system plays an important function in maintaining the stability and reliability of the power grid. Hidden failures in relay protection systems are the primary factors for triggering the cascading collapse. This paper presents an Artificial Neural Network (ANN model for prediction of cascading collapse occurrence due to the effect of hidden failure of protection system. The ANN model has been developed through the normalized training and testing data process with optimum number of hidden layer, the momentum rate and the learning rate. The ANN model employs probability of hidden failure, random number of line limit power flow and exposed line as its input while trip index of cascading collapse occurrence as its output. IEEE 14 bus system is used in this study to illustrate the proposed approach. The performance of the results is analysed in terms of its Mean Square Error (MSE and Correlation Coefficient (R. The results show the ANN model produce reliable prediction of cascading collapse occurrence.

  18. Beyond Failure: Potentially Mitigating Failed Author Searches in the Online Library Catalog through the Use of Linked Data

    Science.gov (United States)

    Moulaison, Heather Lea; Stanley, Susan Nicole

    2013-01-01

    Linked data stores house vetted content that can supplement the information available through online library catalogs, potentially mitigating failed author searches if information about the author exists in linked data formats. In this case study, a total of 689 failed author index queries from a large Midwestern academic library's online library…

  19. Defective support network: a major obstacle to coping for patients with heart failure: a qualitative study

    Directory of Open Access Journals (Sweden)

    Parvin Mangolian Shahrbabaki

    2016-04-01

    Full Text Available Background: Heart failure as a chronic disease poses many challenges for a patient in his or her everyday life. Support in various aspects of life positively affects coping strategies and influences the well-being and health outcomes of heart failure patients. Inadequate support may lead to a worsening of symptoms, increased hospital readmissions, psychological disorders, and a reduced quality of life. Objective: This study explored obstacles to coping related to support for heart failure patients as viewed by the patients themselves and their family members and caregivers. Design: This qualitative study was conducted using content analysis. The 20 Iranian participants included 11 patients with heart failure, three cardiologists, three nurses, and three family members of heart failure patients selected through purposive sampling. Data were collected through semi-structured interviews and analyzed using the Lundman and Graneheim qualitative content analysis method. Results: During data analysis, ‘defective support network’ developed as the main theme along with four other categories of ‘inadequate family performance’, ‘inadequate support by the healthcare team’, ‘distorted societal social support’, and ‘inadequate welfare support’. Conclusion: The findings of the current study can assist health authorities and planners in identifying the needs of patients with heart failure so as to focus and plan on facilitating their coping as much as possible by obviating the existing obstacles.

  20. Coupled dynamics of node and link states in complex networks: a model for language competition

    Science.gov (United States)

    Carro, Adrián; Toral, Raúl; San Miguel, Maxi

    2016-11-01

    Inspired by language competition processes, we present a model of coupled evolution of node and link states. In particular, we focus on the interplay between the use of a language and the preference or attitude of the speakers towards it, which we model, respectively, as a property of the interactions between speakers (a link state) and as a property of the speakers themselves (a node state). Furthermore, we restrict our attention to the case of two socially equivalent languages and to socially inspired network topologies based on a mechanism of triadic closure. As opposed to most of the previous literature, where language extinction is an inevitable outcome of the dynamics, we find a broad range of possible asymptotic configurations, which we classify as: frozen extinction states, frozen coexistence states, and dynamically trapped coexistence states. Moreover, metastable coexistence states with very long survival times and displaying a non-trivial dynamics are found to be abundant. Interestingly, a system size scaling analysis shows, on the one hand, that the probability of language extinction vanishes exponentially for increasing system sizes and, on the other hand, that the time scale of survival of the non-trivial dynamical metastable states increases linearly with the size of the system. Thus, non-trivial dynamical coexistence is the only possible outcome for large enough systems. Finally, we show how this coexistence is characterized by one of the languages becoming clearly predominant while the other one becomes increasingly confined to ‘ghetto-like’ structures: small groups of bilingual speakers arranged in triangles, with a strong preference for the minority language, and using it for their intra-group interactions while they switch to the predominant language for communications with the rest of the population.

  1. Beyond neutral and forbidden links: morphological matches and the assembly of mutualistic hawkmoth-plant networks.

    Science.gov (United States)

    Sazatornil, Federico D; Moré, Marcela; Benitez-Vieyra, Santiago; Cocucci, Andrea A; Kitching, Ian J; Schlumpberger, Boris O; Oliveira, Paulo E; Sazima, Marlies; Amorim, Felipe W

    2016-11-01

    A major challenge in evolutionary ecology is to understand how co-evolutionary processes shape patterns of interactions between species at community level. Pollination of flowers with long corolla tubes by long-tongued hawkmoths has been invoked as a showcase model of co-evolution. Recently, optimal foraging models have predicted that there might be a close association between mouthparts' length and the corolla depth of the visited flowers, thus favouring trait convergence and specialization at community level. Here, we assessed whether hawkmoths more frequently pollinate plants with floral tube lengths similar to their proboscis lengths (morphological match hypothesis) against abundance-based processes (neutral hypothesis) and ecological trait mismatches constraints (forbidden links hypothesis), and how these processes structure hawkmoth-plant mutualistic networks from five communities in four biogeographical regions of South America. We found convergence in morphological traits across the five communities and that the distribution of morphological differences between hawkmoths and plants is consistent with expectations under the morphological match hypothesis in three of the five communities. In the two remaining communities, which are ecotones between two distinct biogeographical areas, interactions are better predicted by the neutral hypothesis. Our findings are consistent with the idea that diffuse co-evolution drives the evolution of extremely long proboscises and flower tubes, and highlight the importance of morphological traits, beyond the forbidden links hypothesis, in structuring interactions between mutualistic partners, revealing that the role of niche-based processes can be much more complex than previously known. © 2016 The Authors. Journal of Animal Ecology © 2016 British Ecological Society.

  2. A temperature-responsive network links cell shape and virulence traits in a primary fungal pathogen.

    Directory of Open Access Journals (Sweden)

    Sinem Beyhan

    2013-07-01

    Full Text Available Survival at host temperature is a critical trait for pathogenic microbes of humans. Thermally dimorphic fungal pathogens, including Histoplasma capsulatum, are soil fungi that undergo dramatic changes in cell shape and virulence gene expression in response to host temperature. How these organisms link changes in temperature to both morphologic development and expression of virulence traits is unknown. Here we elucidate a temperature-responsive transcriptional network in H. capsulatum, which switches from a filamentous form in the environment to a pathogenic yeast form at body temperature. The circuit is driven by three highly conserved factors, Ryp1, Ryp2, and Ryp3, that are required for yeast-phase growth at 37°C. Ryp factors belong to distinct families of proteins that control developmental transitions in fungi: Ryp1 is a member of the WOPR family of transcription factors, and Ryp2 and Ryp3 are both members of the Velvet family of proteins whose molecular function is unknown. Here we provide the first evidence that these WOPR and Velvet proteins interact, and that Velvet proteins associate with DNA to drive gene expression. Using genome-wide chromatin immunoprecipitation studies, we determine that Ryp1, Ryp2, and Ryp3 associate with a large common set of genomic loci that includes known virulence genes, indicating that the Ryp factors directly control genes required for pathogenicity in addition to their role in regulating cell morphology. We further dissect the Ryp regulatory circuit by determining that a fourth transcription factor, which we name Ryp4, is required for yeast-phase growth and gene expression, associates with DNA, and displays interdependent regulation with Ryp1, Ryp2, and Ryp3. Finally, we define cis-acting motifs that recruit the Ryp factors to their interwoven network of temperature-responsive target genes. Taken together, our results reveal a positive feedback circuit that directs a broad transcriptional switch between

  3. Two and a half years of country-wide rainfall maps using radio links from commercial cellular telecommunication networks

    NARCIS (Netherlands)

    Overeem, A.; Leijnse, H.; Uijlenhoet, R.

    2016-01-01

    Although rainfall estimation employing microwave links from cellular telecommunication networks is recognized as a new promising measurement technique, its potential for long-term large-scale operational rainfall monitoring remains to be demonstrated. This study contributes to this endeavor by

  4. An Interference-Aware Traffic-Priority-Based Link Scheduling Algorithm for Interference Mitigation in Multiple Wireless Body Area Networks

    Directory of Open Access Journals (Sweden)

    Thien T. T. Le

    2016-12-01

    Full Text Available Currently, wireless body area networks (WBANs are effectively used for health monitoring services. However, in cases where WBANs are densely deployed, interference among WBANs can cause serious degradation of network performance and reliability. Inter-WBAN interference can be reduced by scheduling the communication links of interfering WBANs. In this paper, we propose an interference-aware traffic-priority-based link scheduling (ITLS algorithm to overcome inter-WBAN interference in densely deployed WBANs. First, we model a network with multiple WBANs as an interference graph where node-level interference and traffic priority are taken into account. Second, we formulate link scheduling for multiple WBANs as an optimization model where the objective is to maximize the throughput of the entire network while ensuring the traffic priority of sensor nodes. Finally, we propose the ITLS algorithm for multiple WBANs on the basis of the optimization model. High spatial reuse is also achieved in the proposed ITLS algorithm. The proposed ITLS achieves high spatial reuse while considering traffic priority, packet length, and the number of interfered sensor nodes. Our simulation results show that the proposed ITLS significantly increases spatial reuse and network throughput with lower delay by mitigating inter-WBAN interference.

  5. An interpretation of neural networks as inference engines with application to transformer failure diagnosis

    Energy Technology Data Exchange (ETDEWEB)

    Castro, Adriana R. Garcez; Miranda, Vladimiro [Instituto de Engenharia de Sistemas e Computadores do Porto, INESC Porto (Portugal)

    2005-12-01

    An artificial neural network concept has been developed for transformer fault diagnosis using dissolved gas-in-oil analysis (DGA). A new methodology for mapping the neural network into a rule-based inference system is described. This mapping makes explicit the knowledge implicitly captured by the neural network during the learning stage, by transforming it into a Fuzzy Inference System. Some studies are reported, illustrating the good results obtained. (author)

  6. A Novel Topology Link-Controlling Approach for Active Defense of a Node in a Network

    Directory of Open Access Journals (Sweden)

    Jun Li

    2017-03-01

    Full Text Available With the rapid development of virtual machine technology and cloud computing, distributed denial of service (DDoS attacks, or some peak traffic, poses a great threat to the security of the network. In this paper, a novel topology link control technique and mitigation attacks in real-time environments is proposed. Firstly, a non-invasive method of deploying virtual sensors in the nodes is built, which uses the resource manager of each monitored node as a sensor. Secondly, a general topology-controlling approach of resisting the tolerant invasion is proposed. In the proposed approach, a prediction model is constructed by using copula functions for predicting the peak of a resource through another resource. The result of prediction determines whether or not to initiate the active defense. Finally, a minority game with incomplete strategy is employed to suppress attack flows and improve the permeability of the normal flows. The simulation results show that the proposed approach is very effective in protecting nodes.

  7. A Novel Topology Link-Controlling Approach for Active Defense of a Node in a Network.

    Science.gov (United States)

    Li, Jun; Hu, HanPing; Ke, Qiao; Xiong, Naixue

    2017-03-09

    With the rapid development of virtual machine technology and cloud computing, distributed denial of service (DDoS) attacks, or some peak traffic, poses a great threat to the security of the network. In this paper, a novel topology link control technique and mitigation attacks in real-time environments is proposed. Firstly, a non-invasive method of deploying virtual sensors in the nodes is built, which uses the resource manager of each monitored node as a sensor. Secondly, a general topology-controlling approach of resisting the tolerant invasion is proposed. In the proposed approach, a prediction model is constructed by using copula functions for predicting the peak of a resource through another resource. The result of prediction determines whether or not to initiate the active defense. Finally, a minority game with incomplete strategy is employed to suppress attack flows and improve the permeability of the normal flows. The simulation results show that the proposed approach is very effective in protecting nodes.

  8. Linking macroecology and community ecology: refining predictions of species distributions using biotic interaction networks.

    Science.gov (United States)

    Staniczenko, Phillip P A; Sivasubramaniam, Prabu; Suttle, K Blake; Pearson, Richard G

    2017-06-01

    Macroecological models for predicting species distributions usually only include abiotic environmental conditions as explanatory variables, despite knowledge from community ecology that all species are linked to other species through biotic interactions. This disconnect is largely due to the different spatial scales considered by the two sub-disciplines: macroecologists study patterns at large extents and coarse resolutions, while community ecologists focus on small extents and fine resolutions. A general framework for including biotic interactions in macroecological models would help bridge this divide, as it would allow for rigorous testing of the role that biotic interactions play in determining species ranges. Here, we present an approach that combines species distribution models with Bayesian networks, which enables the direct and indirect effects of biotic interactions to be modelled as propagating conditional dependencies among species' presences. We show that including biotic interactions in distribution models for species from a California grassland community results in better range predictions across the western USA. This new approach will be important for improving estimates of species distributions and their dynamics under environmental change. © 2017 The Authors. Ecology Letters published by CNRS and John Wiley & Sons Ltd.

  9. Active Noise Control Using a Functional Link Artificial Neural Network with the Simultaneous Perturbation Learning Rule

    Directory of Open Access Journals (Sweden)

    Ya-li Zhou

    2009-01-01

    Full Text Available In practical active noise control (ANC systems, the primary path and the secondary path may be nonlinear and time-varying. It has been reported that the linear techniques used to control such ANC systems exhibit degradation in performance. In addition, the actuators of an ANC system very often have nonminimum-phase response. A linear controller under such situations yields poor performance. A novel functional link artificial neural network (FLANN-based simultaneous perturbation stochastic approximation (SPSA algorithm, which functions as a nonlinear mode-free (MF controller, is proposed in this paper. Computer simulations have been carried out to demonstrate that the proposed algorithm outperforms the standard filtered-x least mean square (FXLMS algorithm, and performs better than the recently proposed filtered-s least mean square (FSLMS algorithm when the secondary path is time-varying. This observation implies that the SPSA-based MF controller can eliminate the need of the modeling of the secondary path for the ANC system.

  10. A simple structure wavelet transform circuit employing function link neural networks and SI filters

    Science.gov (United States)

    Mu, Li; Yigang, He

    2016-12-01

    Signal processing by means of analog circuits offers advantages from a power consumption viewpoint. Implementing wavelet transform (WT) using analog circuits is of great interest when low-power consumption becomes an important issue. In this article, a novel simple structure WT circuit in analog domain is presented by employing functional link neural network (FLNN) and switched-current (SI) filters. First, the wavelet base is approximated using FLNN algorithms for giving a filter transfer function that is suitable for simple structure WT circuit implementation. Next, the WT circuit is constructed with the wavelet filter bank, whose impulse response is the approximated wavelet and its dilations. The filter design that follows is based on a follow-the-leader feedback (FLF) structure with multiple output bilinear SI integrators and current mirrors as the main building blocks. SI filter is well suited for this application since the dilation constant across different scales of the transform can be precisely implemented and controlled by the clock frequency of the circuit with the same system architecture. Finally, to illustrate the design procedure, a seventh-order FLNN-approximated Gaussian wavelet is implemented as an example. Simulations have successfully verified that the designed simple structure WT circuit has low sensitivity, low-power consumption and litter effect to the imperfections.

  11. Structures and properties of PAX linked regulatory networks architecting and pacing the emergence of neuronal diversity.

    Science.gov (United States)

    Curto, Gloria G; Gard, Chris; Ribes, Vanessa

    2015-08-01

    Over the past two decades, Pax proteins have received a lot of attention from researchers working on the generation and assembly of neural circuits during vertebrate development. Through tissue or cell based phenotypic analyses, or more recently using genome-wide approaches, they have highlighted the pleiotropic functions of Pax proteins during neurogenesis. This review discusses the wide range of molecular and cellular mechanisms by which these transcription factors control in time and space the number and identity of neurons produced during development. We first focus on the position of Pax proteins within gene regulatory networks that generate patterns of cellular differentiation within the central nervous system. Next, the architecture of Pax-linked regulatory loops that provide a tempo of differentiation to progenitor cells is presented. Finally, we examine the molecular foundations providing a "multitasking" property to Pax proteins. Amongst the Pax factors that are expressed within the developing nervous system, Pax6 is the most extensively studied and thus holds a dominant position in this article. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Network films of conducting polymer-linked polyoxometalate-modified gold nanoparticles: Preparation and electrochemical characterization

    Energy Technology Data Exchange (ETDEWEB)

    Ernst, Andrzej Z. [Department of Chemistry, University of Warsaw, Pasteura 1, PL-02-093 Warsaw (Poland); Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056 (United States); Zoladek, Sylwia [Department of Chemistry, University of Warsaw, Pasteura 1, PL-02-093 Warsaw (Poland); Wiaderek, Kamila [Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056 (United States); Cox, James A. [Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056 (United States)], E-mail: coxja@muohio.edu; Kolary-Zurowska, Aneta; Miecznikowski, Krzysztof [Department of Chemistry, University of Warsaw, Pasteura 1, PL-02-093 Warsaw (Poland); Kulesza, Pawel J. [Department of Chemistry, University of Warsaw, Pasteura 1, PL-02-093 Warsaw (Poland)], E-mail: pkulesza@chem.uw.edu.pl

    2008-04-20

    The ability of Keggin-type phosphododecamolybdate (PMo{sub 12}O{sub 40}{sup 3-}, PMo{sub 12}) to undergo chemisorption on solid surfaces (including gold) is explored here to convert (by ligand place-exchange and phase transfer to aqueous solution) the alkanothiolate-modified Au nanoparticles of controlled size (prepared in toluene) into a stable colloidal solution of PMo{sub 12}-protected gold nanoparticles, PMo{sub 12}-AuNPs, the sizes of which are ca. 4-5 nm as determined by transmission electron microscopy. By dip-coating, PMo{sub 12}-AuNPs were assembled on carbon electrode substrates. The step-by-step assembly, by which alternate exposures to the solutions of PMo{sub 12}-AuNPs and either anilinium cations or pyrrole monomers, was utilized to grow in controlled manner hybrid network films in which the negatively charged PMo{sub 12}-AuNP deposits were linked, or electrostatically attracted, by ultra-thin, positively charged conducting polymer (polyaniline or polypyrrole) structures. The three-dimensionally distributed PMo{sub 12}-AuNPs immobilized within the polypyrrole-based composite film exhibited some electrocatalytic reactivity towards reduction of hydrogen peroxide.

  13. Weak Links The Universal Key to the Stability of Networks and Complex Systems

    CERN Document Server

    Csermely, Peter

    2009-01-01

    How can our societies be stabilized in a crisis? Why can we enjoy and understand Shakespeare? Why are fruitflies uniform? How do omnivorous eating habits aid our survival? What makes the Mona Lisa’s smile beautiful? How do women keep our social structures intact? – Could there possibly be a single answer to all these questions? This book shows that the statement: "weak links stabilize complex systems" provides the key to understanding each of these intriguing puzzles, and many others too. The author (recipient of several distinguished science communication prizes) uses weak (low affinity, low probability) interactions as a thread to introduce a vast variety of networks from proteins to economics and ecosystems. Many people, from Nobel Laureates to high-school students have helped to make the book understandable to all interested readers. This unique book and the ideas it develops will have a significant impact on many, seemingly diverse, fields of study. A very personal, engaging, and unique book that wil...

  14. Linking Biosynthetic Gene Clusters to their Metabolites via Pathway-Targeted Molecular Networking

    Science.gov (United States)

    Trautman, Eric P.; Crawford, Jason M.

    2016-01-01

    The connection of microbial biosynthetic gene clusters to the small molecule metabolites they encode is central to the discovery and characterization of new metabolic pathways with ecological and pharmacological potential. With increasing microbial genome sequence information being deposited into publicly available databases, it is clear that microbes have the coding capacity for many more biologically active small molecules than previously realized. Of increasing interest are the small molecules encoded by the human microbiome, as these metabolites likely mediate a variety of currently uncharacterized human-microbe interactions that influence health and disease. In this mini-review, we describe the ongoing biosynthetic, structural, and functional characterizations of the genotoxic colibactin pathway in gut bacteria as a thematic example of linking biosynthetic gene clusters to their metabolites. We also highlight other natural products that are produced through analogous biosynthetic logic and comment on some current disconnects between bioinformatics predictions and experimental structural characterizations. Lastly, we describe the use of pathway-targeted molecular networking as a tool to characterize secondary metabolic pathways within complex metabolomes and to aid in downstream metabolite structural elucidation efforts. PMID:26456470

  15. Reversible mechano-memory in sheared cross-linked actin networks

    Science.gov (United States)

    Majumdar, Sayantan; Gardel, Margaret L.

    2015-03-01

    Is it possible to control the shear modulus of a material mechanically? We reconstitute a network of actin filaments cross-linked with Filamin A and show that the system has remarkable property to respond under shear in a deformation history dependent manner. When a large shear stress pulse is applied to the system, the system remembers the direction of deformation long after the stress pulse is removed. For the next loading cycle, shear response of the system becomes anisotropic; if the applied pulse direction is same as the previous one, the system behaves like a viscoelastic solid but a transient liquefaction is observed if the pulse direction is reversed. Imaging and normal force measurements under shear suggest that this anisotropic response comes from stretching and bending dominated deformation directions induced by the large shear deformation giving rise to a direction dependent mechano-memory. The long time scale over which the memory effect persists has relevance in various deformations in cellular and multicellular systems. S.M. acknowledges support from a Kadanoff-Rice Post Doctoral fellowship from MRSEC, University of Chicago.

  16. Prognostic impact of in-hospital hyperglycemia in hospitalized patients with acute heart failure: Results of the IN-HF (Italian Network on Heart Failure) Outcome registry.

    Science.gov (United States)

    Targher, Giovanni; Dauriz, Marco; Tavazzi, Luigi; Temporelli, Pier Luigi; Lucci, Donata; Urso, Renato; Lecchi, Gabriella; Bellanti, Giancarlo; Merlo, Marco; Rossi, Andrea; Maggioni, Aldo P

    2016-01-15

    Although diabetes mellitus is frequently associated with heart failure (HF), the association between elevated admission glucose levels and adverse outcomes has not been well established in hospitalized patients with acute HF. We prospectively evaluated in-hospital mortality, post-discharge 1-year mortality and 1-year re-hospitalization rates in the Italian Network on Heart Failure (IN-HF) Outcome registry cohort of 1776 patients hospitalized with acute HF and stratified by their admission glucose levels (i.e., known diabetes, newly diagnosed hyperglycemia, no diabetes). Compared with those without diabetes (n = 586), patients with either known diabetes (n = 749) (unadjusted-odds ratio [OR] 1.64, 95%CI 0.99–2.70) or newly diagnosed hyperglycemia (n = 441) (unadjusted-OR 2.34, 95%CI 1.39–3.94) had higher in-hospital mortality, but comparable post-discharge 1-year mortality rates. After adjustment for age, sex, systolic blood pressure, estimated glomerular filtration rate, left ventricular ejection fraction, HF etiology and HF worsening/de novo presentation, the results remained unchanged in patients with known diabetes (adjusted-OR 1.86, 95%CI 1.01–3.42), while achieved borderline significance in those with newly diagnosed hyperglycemia (adjusted-OR 1.81, 95%CI 0.95–3.45). One-year re-hospitalization rates were lower in patients with newly diagnosed hyperglycemia (adjusted-hazard ratio 0.74, 95%CI 0.56–0.96) than in other groups. Elevated admission blood glucose levels are associated with poorer in-hospital survival outcomes in patients with acute HF, especially in those with previously known diabetes. This finding further highlights the importance of tight glycemic control during hospital stay and address the need of dedicated intervention studies to identify customized clinical protocols to improve in-hospital survival of these high-risk patients.

  17. HerzMobil Tirol network: rationale for and design of a collaborative heart failure disease management program in Austria.

    Science.gov (United States)

    Von der Heidt, Andreas; Ammenwerth, Elske; Bauer, Karl; Fetz, Bettina; Fluckinger, Thomas; Gassner, Andrea; Grander, Willhelm; Gritsch, Walter; Haffner, Immaculata; Henle-Talirz, Gudrun; Hoschek, Stefan; Huter, Stephan; Kastner, Peter; Krestan, Susanne; Kufner, Peter; Modre-Osprian, Robert; Noebl, Josef; Radi, Momen; Raffeiner, Clemens; Welte, Stefan; Wiseman, Andreas; Poelzl, Gerhard

    2014-11-01

    Heart failure (HF) is approaching epidemic proportions worldwide and is the leading cause of hospitalization in the elderly population. High rates of readmission contribute substantially to excessive health care costs and highlight the fragmented nature of care available to HF patients. Disease management programs (DMPs) have been implemented to improve health outcomes, patient satisfaction, and quality of life, and to reduce health care costs. Telemonitoring systems appear to be effective in the vulnerable phase after discharge from hospital to prevent early readmissions. DMPs that emphasize comprehensive patient education and guideline-adjusted therapy have shown great promise to result in beneficial long-term effects. It can be speculated that combining core elements of the aforementioned programs may substantially improve long-term cost-effectiveness of patient management.We introduce a collaborative post-discharge HF disease management program (HerzMobil Tirol network) that incorporates physician-controlled telemonitoring and nurse-led care in a multidisciplinary network approach.

  18. Commutation failure at restart of an inverter

    Energy Technology Data Exchange (ETDEWEB)

    Bruntt, M.

    1997-12-31

    The sensitivity of commutation failures for an HVDC inverter due to AC voltage magnitude reduction and AC voltage distortion depends on the specific HVDC main circuit design and on the HVDC control system. There are ways to improve the immunity towards commutation failures, but they can never be completely avoided. This report deals with commutation failures at restart of an inverter, and does not consider the initial commutation failure. If the AC system after the fault is capable of absorbing the power from the restarting HVDC link without disturbing the AC voltage significantly, the HVDC link is back to normal operation after typically 50 to 200 ms after the fault is cleared. The stability of the connected AC systems is not seriously affected by this limited time period with lack or excess of power. This report deals with the idea of finding an indicator for the second commutation failure during restart. The process of commutation failures and furthermore commutation failures during restart are characterized. A network which is considered to be general is analysed to find indication of commutation failure during restart. Different potential indictors are examined. The effect of changing the general control parameters during the restart to help the recovery in critical situations is also examined. The analysis do, however, not give the answer to which parameters are the best to change because this question need to be answered for each specific case. Finally a specific network is analysed to find an indicator of a second commutation failure. (EG)

  19. Decreased creatine kinase is linked to diastolic dysfunction in rats with right heart failure induced by pulmonary artery hypertension.

    Science.gov (United States)

    Fowler, Ewan D; Benoist, David; Drinkhill, Mark J; Stones, Rachel; Helmes, Michiel; Wüst, Rob C I; Stienen, Ger J M; Steele, Derek S; White, Ed

    2015-09-01

    Our objective was to investigate the role of creatine kinase in the contractile dysfunction of right ventricular failure caused by pulmonary artery hypertension. Pulmonary artery hypertension and right ventricular failure were induced in rats by monocrotaline and compared to saline-injected control animals. In vivo right ventricular diastolic pressure-volume relationships were measured in anesthetized animals; diastolic force-length relationships in single enzymatically dissociated myocytes and myocardial creatine kinase levels by Western blot. We observed diastolic dysfunction in right ventricular failure indicated by significantly steeper diastolic pressure-volume relationships in vivo and diastolic force-length relationships in single myocytes. There was a significant reduction in creatine kinase protein expression in failing right ventricle. Dysfunction also manifested as a shorter diastolic sarcomere length in failing myocytes. This was associated with a Ca(2+)-independent mechanism that was sensitive to cross-bridge cycling inhibition. In saponin-skinned failing myocytes, addition of exogenous creatine kinase significantly lengthened sarcomeres, while in intact healthy myocytes, inhibition of creatine kinase significantly shortened sarcomeres. Creatine kinase inhibition also changed the relatively flat contraction amplitude-stimulation frequency relationship of healthy myocytes into a steeply negative, failing phenotype. Decreased creatine kinase expression leads to diastolic dysfunction. We propose that this is via local reduction in ATP:ADP ratio and thus to Ca(2+)-independent force production and diastolic sarcomere shortening. Creatine kinase inhibition also mimics a definitive characteristic of heart failure, the inability to respond to increased demand. Novel therapies for pulmonary artery hypertension are needed. Our data suggest that cardiac energetics would be a potential ventricular therapeutic target. Copyright © 2015. Published by Elsevier Ltd.

  20. Robustness of weighted networks

    Science.gov (United States)

    Bellingeri, Michele; Cassi, Davide

    2018-01-01

    Complex network response to node loss is a central question in different fields of network science because node failure can cause the fragmentation of the network, thus compromising the system functioning. Previous studies considered binary networks where the intensity (weight) of the links is not accounted for, i.e. a link is either present or absent. However, in real-world networks the weights of connections, and thus their importance for network functioning, can be widely different. Here, we analyzed the response of real-world and model networks to node loss accounting for link intensity and the weighted structure of the network. We used both classic binary node properties and network functioning measure, introduced a weighted rank for node importance (node strength), and used a measure for network functioning that accounts for the weight of the links (weighted efficiency). We find that: (i) the efficiency of the attack strategies changed using binary or weighted network functioning measures, both for real-world or model networks; (ii) in some cases, removing nodes according to weighted rank produced the highest damage when functioning was measured by the weighted efficiency; (iii) adopting weighted measure for the network damage changed the efficacy of the attack strategy with respect the binary analyses. Our results show that if the weighted structure of complex networks is not taken into account, this may produce misleading models to forecast the system response to node failure, i.e. consider binary links may not unveil the real damage induced in the system. Last, once weighted measures are introduced, in order to discover the best attack strategy, it is important to analyze the network response to node loss using nodes rank accounting the intensity of the links to the node.

  1. The effect of link-based topological changes and recoveries on the robustness of cooperation on scale-free networks

    Science.gov (United States)

    Wang, Shuai; Liu, Jing

    2016-07-01

    The emergence of cooperation is one of the key metaphors behind many social disciplines and phenomena. Existing studies show that intentional attacks on nodes damage the robustness of cooperation distinctly, and the heterogeneity among nodes promotes the emergence of cooperation. However, the impact of link-based attacks and the connectivity of networks on the cooperative mechanism is still unclear. In this paper, we focus on the effect of edge removal on the emergence of cooperation together with the connectivity of networks. The results show that malicious attacks evaluated by edge-degree are efficient to invade cooperators, and heterogeneous networks tend to perform poorly when attacks arise. Furthermore, we analyze the performance of several recovering strategies, and conclude that the connectivity is crucial to the recovery of functionality of whole networks.

  2. Feature network models for proximity data : statistical inference, model selection, network representations and links with related models

    NARCIS (Netherlands)

    Frank, Laurence Emmanuelle

    2006-01-01

    Feature Network Models (FNM) are graphical structures that represent proximity data in a discrete space with the use of features. A statistical inference theory is introduced, based on the additivity properties of networks and the linear regression framework. Considering features as predictor

  3. A methodology for linking 2D overland flow models with the sewer network model SWMM 5.1 based on dynamic link libraries.

    Science.gov (United States)

    Leandro, Jorge; Martins, Ricardo

    2016-01-01

    Pluvial flooding in urban areas is characterized by a gradually varying inundation process caused by surcharge of the sewer manholes. Therefore urban flood models need to simulate the interaction between the sewer network and the overland flow in order to accurately predict the flood inundation extents. In this work we present a methodology for linking 2D overland flow models with the storm sewer model SWMM 5. SWMM 5 is a well-known free open-source code originally developed in 1971. The latest major release saw its structure re-written in C ++ allowing it to be compiled as a command line executable or through a series of calls made to function inside a dynamic link library (DLL). The methodology developed herein is written inside the same DLL in C + +, and is able to simulate the bi-directional interaction between both models during simulation. Validation is done in a real case study with an existing urban flood coupled model. The novelty herein is that the new methodology can be added to SWMM without the need for editing SWMM's original code. Furthermore, it is directly applicable to other coupled overland flow models aiming to use SWMM 5 as the sewer network model.

  4. Enhancement of Localization Accuracy in Cellular Networks via Cooperative AdHoc Links

    DEFF Research Database (Denmark)

    Lhomme, Edouard; Frattasi, Simone; Figueiras, Joao

    2006-01-01

    Positioning information enables new applications for cellular phones, personal communication systems, and specialized mobile radios. The network heterogeneity emerging in the fourth generation (4G) of mobile networks can be utilized for enhancements of the location estimation accuracy...

  5. Early Detection Of Failure Mechanisms In Resilient Biostructures: A Network Flow Study

    Science.gov (United States)

    2017-10-01

    the flow network algorithm. This in- house written algorithm extracts the connectivity information from the numerical model ; weights (Von-Mises...cartilage of the rostrum, a model of the rostrum was constructed without the lattice architecture . Figure 23 shows the computational model of the...pressure on the rostrum without the lattice architecture A flow network model of the homogenous rostrum displayed in Figure 23 is constructed from the

  6. Ventral and Dorsal Striatum Networks in Obesity: Link to Food Craving and Weight Gain.

    Science.gov (United States)

    Contreras-Rodríguez, Oren; Martín-Pérez, Cristina; Vilar-López, Raquel; Verdejo-Garcia, Antonio

    2017-05-01

    The food addiction model proposes that obesity overlaps with addiction in terms of neurobiological alterations in the striatum and related clinical manifestations (i.e., craving and persistence of unhealthy habits). Therefore, we aimed to examine the functional connectivity of the striatum in excess-weight versus normal-weight subjects and to determine the extent of the association between striatum connectivity and individual differences in food craving and changes in body mass index (BMI). Forty-two excess-weight participants (BMI > 25) and 39 normal-weight participants enrolled in the study. Functional connectivity in the ventral and dorsal striatum was indicated by seed-based analyses on resting-state data. Food craving was indicated with subjective ratings of visual cues of high-calorie food. Changes in BMI between baseline and 12 weeks follow-up were assessed in 28 excess-weight participants. Measures of connectivity in the ventral striatum and dorsal striatum were compared between groups and correlated with craving and BMI change. Participants with excess weight displayed increased functional connectivity between the ventral striatum and the medial prefrontal and parietal cortices and between the dorsal striatum and the somatosensory cortex. Dorsal striatum connectivity correlated with food craving and predicted BMI gains. Obesity is linked to alterations in the functional connectivity of dorsal striatal networks relevant to food craving and weight gain. These neural alterations are associated with habit learning and thus compatible with the food addiction model of obesity. Copyright © 2016 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

  7. Exposing the role of exposure : Identifying and evaluating critical links in public transport networks

    NARCIS (Netherlands)

    Cats, O.; Yap, M.; Van Oort, N.

    2015-01-01

    Network vulnerability depends on the probability that adverse events occur and on the impacts of such disruptions on network functionality. Most studies on transport network vulnerability have only analysed vulnerability in terms of the reduction in performance indicators given that a disruption

  8. Body Image and Dieting Failure in College Men and Women: Examining Links between Depression and Eating Problems.

    Science.gov (United States)

    Koenig, Linda J.; Wasserman, Erika L.

    1995-01-01

    Explored whether the links of depression, eating problems, and body image that apply to women also apply to men. A study of 234 male and female college students showed depression was higher in those with negative body image for both men and women. Depression accounted for significant variability in eating problems only in women. (GR)

  9. Artificial Neural Network based DC-link Capacitance Estimation in a Diode-bridge Front-end Inverter System

    DEFF Research Database (Denmark)

    Soliman, Hammam Abdelaal Hammam; Abdelsalam, Ibrahim; Wang, Huai

    2017-01-01

    , a proposed software condition monitoring methodology based on Artificial Neural Network (ANN) algorithm is presented. Matlab software is used to train and generate the proposed ANN. The proposed methodology estimates the capacitance of the DC-link capacitor in a three phase front-end diode bridge AC......In modern design of power electronic converters, reliability of DC-link capacitors is an essential aspect to be considered. The industrial field have been attracted to the monitoring of their health condition and the estimation of their ageing process status. The existing condition monitoring...

  10. Capacitance Estimation for DC-link Capacitors in a Back-to-Back Converter Based on Artificial Neural Network Algorithm

    DEFF Research Database (Denmark)

    Soliman, Hammam Abdelaal Hammam; Wang, Huai; Blaabjerg, Frede

    2016-01-01

    of the aforementioned challenges and shortcomings. In this paper, a pure software condition monitoring method based on Artificial Neural Network (ANN) algorithm is proposed. The implemented ANN estimates the capacitance of the dc-link capacitor in a back-to-back converter. The error analysis of the estimated results......The reliability of dc-link capacitors in power electronic converters is one of the critical aspects to be considered in modern power converter design. The observation of their ageing process and the estimation of their health status have been an attractive subject for the industrial field and hence...

  11. ERCC6L2 Mutations Link a Distinct Bone-Marrow-Failure Syndrome to DNA Repair and Mitochondrial Function

    OpenAIRE

    Tummala, Hemanth; Kirwan, Michael; Walne, Amanda J.; Hossain, Upal; Jackson, Nicholas; Pondarre, Corinne; Plagnol, Vincent; Vulliamy, Tom; Dokal, Inderjeet

    2014-01-01

    Exome sequencing was performed in three index cases with bone marrow failure and neurological dysfunction and whose parents are first-degree cousins. Homozygous truncating mutations were identified in ERCC6L2 in two of the individuals. Both of these mutations affect the subcellular localization and stability of ERCC6L2. We show here that knockdown of ERCC6L2 in human A549 cells significantly reduced their viability upon exposure to the DNA-damaging agents mitomycin C and Irofulven, but not et...

  12. Analysis of serum inflammatory mediators identifies unique dynamic networks associated with death and spontaneous survival in pediatric acute liver failure.

    Science.gov (United States)

    Azhar, Nabil; Ziraldo, Cordelia; Barclay, Derek; Rudnick, David A; Squires, Robert H; Vodovotz, Yoram

    2013-01-01

    Tools to predict death or spontaneous survival are necessary to inform liver transplantation (LTx) decisions in pediatric acute liver failure (PALF), but such tools are not available. Recent data suggest that immune/inflammatory dysregulation occurs in the setting of acute liver failure. We hypothesized that specific, dynamic, and measurable patterns of immune/inflammatory dysregulation will correlate with outcomes in PALF. We assayed 26 inflammatory mediators on stored serum samples obtained from a convenience sample of 49 children in the PALF study group (PALFSG) collected within 7 days after enrollment. Outcomes were assessed within 21 days of enrollment consisting of spontaneous survivors, non-survivors, and LTx recipients. Data were subjected to statistical analysis, patient-specific Principal Component Analysis (PCA), and Dynamic Bayesian Network (DBN) inference. Raw inflammatory mediator levels assessed over time did not distinguish among PALF outcomes. However, DBN analysis did reveal distinct interferon-gamma-related networks that distinguished spontaneous survivors from those who died. The network identified in LTx patients pre-transplant was more like that seen in spontaneous survivors than in those who died, a finding supported by PCA. The application of DBN analysis of inflammatory mediators in this small patient sample appears to differentiate survivors from non-survivors in PALF. Patterns associated with LTx pre-transplant were more like those seen in spontaneous survivors than in those who died. DBN-based analyses might lead to a better prediction of outcome in PALF, and could also have more general utility in other complex diseases with an inflammatory etiology.

  13. Analysis of serum inflammatory mediators identifies unique dynamic networks associated with death and spontaneous survival in pediatric acute liver failure.

    Directory of Open Access Journals (Sweden)

    Nabil Azhar

    Full Text Available Tools to predict death or spontaneous survival are necessary to inform liver transplantation (LTx decisions in pediatric acute liver failure (PALF, but such tools are not available. Recent data suggest that immune/inflammatory dysregulation occurs in the setting of acute liver failure. We hypothesized that specific, dynamic, and measurable patterns of immune/inflammatory dysregulation will correlate with outcomes in PALF.We assayed 26 inflammatory mediators on stored serum samples obtained from a convenience sample of 49 children in the PALF study group (PALFSG collected within 7 days after enrollment. Outcomes were assessed within 21 days of enrollment consisting of spontaneous survivors, non-survivors, and LTx recipients. Data were subjected to statistical analysis, patient-specific Principal Component Analysis (PCA, and Dynamic Bayesian Network (DBN inference.Raw inflammatory mediator levels assessed over time did not distinguish among PALF outcomes. However, DBN analysis did reveal distinct interferon-gamma-related networks that distinguished spontaneous survivors from those who died. The network identified in LTx patients pre-transplant was more like that seen in spontaneous survivors than in those who died, a finding supported by PCA.The application of DBN analysis of inflammatory mediators in this small patient sample appears to differentiate survivors from non-survivors in PALF. Patterns associated with LTx pre-transplant were more like those seen in spontaneous survivors than in those who died. DBN-based analyses might lead to a better prediction of outcome in PALF, and could also have more general utility in other complex diseases with an inflammatory etiology.

  14. Linking Simulation with Formal Verification and Modeling of Wireless Sensor Network in TLA+

    Science.gov (United States)

    Martyna, Jerzy

    In this paper, we present the results of the simulation of a wireless sensor network based on the flooding technique and SPIN protocols. The wireless sensor network was specified and verified by means of the TLA+ specification language [1]. For a model of wireless sensor network built this way simulation was carried with the help of specially constructed software tools. The obtained results allow us to predict the behaviour of the wireless sensor network in various topologies and spatial densities. Visualization of the output data enable precise examination of some phenomenas in wireless sensor networks, such as a hidden terminal, etc.

  15. Link-Layer and Network-Layer Performance of an Undersea Acoustic Network at Fleet Battle Experiment-India

    National Research Council Canada - National Science Library

    Hartfield, Grant

    2003-01-01

    .... Many factors constrain or impair undersea acoustic communications. Analysis of a sample portion of the data reveals insights about the overall throughput, latency, and reliability of the Seaweb network...

  16. Application of the network robustness index to identifying critical road-network links in Chittenden County, Vermont.

    Science.gov (United States)

    2010-06-01

    The purpose of this project is to conduct a pilot application of the Network : Robustness Index (NRI) for the Chittenden County Regional Transportation Model. : Using the results, improvements to the method to increase its effectiveness for more : wi...

  17. ERCC6L2 mutations link a distinct bone-marrow-failure syndrome to DNA repair and mitochondrial function.

    Science.gov (United States)

    Tummala, Hemanth; Kirwan, Michael; Walne, Amanda J; Hossain, Upal; Jackson, Nicholas; Pondarre, Corinne; Plagnol, Vincent; Vulliamy, Tom; Dokal, Inderjeet

    2014-02-06

    Exome sequencing was performed in three index cases with bone marrow failure and neurological dysfunction and whose parents are first-degree cousins. Homozygous truncating mutations were identified in ERCC6L2 in two of the individuals. Both of these mutations affect the subcellular localization and stability of ERCC6L2. We show here that knockdown of ERCC6L2 in human A549 cells significantly reduced their viability upon exposure to the DNA-damaging agents mitomycin C and Irofulven, but not etoposide and camptothecin, suggesting a role in nucleotide excision repair. ERCC6L2-knockdown cells also displayed H2AX phosphorylation, which significantly increased upon genotoxic stress, suggesting an early DNA-damage response. Intriguingly, ERCC6L2 was seen to translocate to the mitochondria and the nucleus in response to DNA damage, and ERCC6L2 knockdown induced intracellular reactive oxygen species (ROS). Treatment with the ROS scavenger N-acetyl cysteine attenuated the Irofulven-induced cytotoxicity in ERCC6L2-knockdown cells and abolished ERCCGL2 traffic to the mitochondria and nucleus in response to this DNA-damaging agent. Collectively, these observations identify a distinct bone-marrow-failure syndrome due to mutations in ERCC6L2, a gene implicated in DNA repair and mitochondrial function. Copyright © 2014 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.

  18. Rainfall monitoring based on microwave links from cellular telecommunication networks: First results from a West African test bed

    Science.gov (United States)

    Doumounia, Ali; Gosset, Marielle; Cazenave, Frederic; Kacou, Modeste; Zougmore, François

    2014-08-01

    Rainfall monitoring based on commercial terrestrial microwave links is tested for the first time in Burkina Faso, in Sahelian West Africa. In collaboration with one national cellular phone operator, Telecel Faso, the attenuation on a 29 km long microwave link operating at 7 GHz was monitored at 1 s time rate for the monsoon season 2012. The time series of attenuation is transformed into rain rates and compared with rain gauge data. The method is successful in quantifying rainfall: 95% of the rainy days are detected. The correlation with the daily rain gauge series is 0.8, and the season bias is 6%. The correlation at the 5 min time step within each event is also high. These results demonstrate the potential interest of exploiting national and regional wireless telecommunication networks for monitoring rainfall in Africa, where operational rain gauge networks are degrading and the hydrometeorological risk increasing.

  19. Multi-Hop Link Capacity of Multi-Route Multi-Hop MRC Diversity for a Virtual Cellular Network

    Science.gov (United States)

    Daou, Imane; Kudoh, Eisuke; Adachi, Fumiyuki

    In virtual cellular network (VCN), proposed for high-speed mobile communications, the signal transmitted from a mobile terminal is received by some wireless ports distributed in each virtual cell and relayed to the central port that acts as a gateway to the core network. In this paper, we apply the multi-route MHMRC diversity in order to decrease the transmit power and increase the multi-hop link capacity. The transmit power, the interference power and the link capacity are evaluated for DS-CDMA multi-hop VCN by computer simulation. The multi-route MHMRC diversity can be applied to not only DS-CDMA but also other access schemes (i. e. MC-CDMA, OFDM, etc.).

  20. Anchoring behavior, orientational order, and reorientation dynamics of nematic liquid crystal droplets dispersed in cross-linked polymer networks.

    Science.gov (United States)

    Roussel, Frédérick; Fung, Bing M

    2003-04-01

    The orientational ordering and the electro-optical properties of nematic liquid crystal (LC) droplets confined to cross-linked polymer networks are investigated as a function of the anchoring conditions at the polymer-liquid crystal interface. Normal alignment (homeotropic) or parallel alignment (planar) inside LC droplets was controlled by using acrylate polymers with appropriate side chains. Drastic changes in the reorientation dynamics of the confined nematic liquid crystal phase are observed, as well as in the orientational ordering of the phase-separated LC which was investigated by 13C-NMR (nuclear magnetic resonance) spectroscopy. The cross-link density of the polymer network also affects the orientational ordering and the electro-optical properties of the confined LC phase. Faster switching times and higher-order parameters were found for samples with LC droplets exhibiting planar anchoring.

  1. Project configured supply networks: Governance of delivery and failures in operations

    DEFF Research Database (Denmark)

    Koch, Christian

    2008-01-01

      Supply networks in complex B2B- construction deliver knowledge, materials, components, subsystems, competences, workforce and management. The delivery network and its governance forms are partly permanent, partly project specific. Integration upstream varies by project, constituting a range...... as theoretical frame. The case study is a Danish architectural, engineering and construction supply network for one building project. The governance forms found were; internal integration and hierarchy, SCM-efforts, subsystem deliveries, and contracting per project. There was a very uneven upstream integration......; Three engineering design areas were integrated with production and even the client. The architectural design is the most 'clear-cut' singular, whereas the supplies of pre-cast concrete core, elevator and kitchen were integrated knowledge, material, workforce and management subsystem deliveries. 160...

  2. VCSEL-based gigabit IR-UWB link for converged communication and sensing applications in optical metro-access networks

    DEFF Research Database (Denmark)

    Pham, Tien Thang; Gibbon, Timothy Braidwood; Tafur Monroy, Idelfonso

    2012-01-01

    We report on experimental demonstration of an impulse radio ultrawideband (IR-UWB) based converged communication and sensing system. A 1550-nm VCSEL-generated IR-UWB signal is used for 2-Gbps wireless data distribution over 800-m and 50-km single mode fiber links which present short-range in...... application, paving the way forward for the development and deployment of converged UWB VCSEL-based technologies in access and in-building networks of the future....

  3. Effects of network morphology on the failure stress of highly porous media

    NARCIS (Netherlands)

    Chung, J.W; de Hosson, J.T.M.

    2002-01-01

    In this study four types of morphologies are generated to illustrate the importance of the details of the network structure in relation to its mechanical strength while keeping the density fixed. By varying the disorder parameter in a dynamical system of weakly interacting void-volume spheres, it is

  4. Symmetric Link Key Management for Secure Neighbor Discovery in a Decentralized Wireless Sensor Network

    Science.gov (United States)

    2017-09-01

    KEY MANAGEMENT FOR SECURE NEIGHBOR DISCOVERY IN A DECENTRALIZED WIRELESS SENSOR NETWORK by Kelvin T. Chew September 2017 Thesis Advisor...lightweight security protocol is necessary to prevent unauthorized nodes from accessing network data and resources. In this thesis, we focus on the management ... MANAGEMENT FOR SECURE NEIGHBOR DISCOVERY IN A DECENTRALIZED WIRELESS SENSOR NETWORK Kelvin T. Chew Captain, United States Marine Corps B.S

  5. VCP-dependent muscle degeneration is linked to defects in a dynamic tubular lysosomal network in vivo.

    Science.gov (United States)

    Johnson, Alyssa E; Shu, Huidy; Hauswirth, Anna G; Tong, Amy; Davis, Graeme W

    2015-07-13

    Lysosomes are classically viewed as vesicular structures to which cargos are delivered for degradation. Here, we identify a network of dynamic, tubular lysosomes that extends throughout Drosophila muscle, in vivo. Live imaging reveals that autophagosomes merge with tubular lysosomes and that lysosomal membranes undergo extension, retraction, fusion and fission. The dynamics and integrity of this tubular lysosomal network requires VCP, an AAA-ATPase that, when mutated, causes degenerative diseases of muscle, bone and neurons. We show that human VCP rescues the defects caused by loss of Drosophila VCP and overexpression of disease relevant VCP transgenes dismantles tubular lysosomes, linking tubular lysosome dysfunction to human VCP-related diseases. Finally, disruption of tubular lysosomes correlates with impaired autophagosome-lysosome fusion, increased cytoplasmic poly-ubiquitin aggregates, lipofuscin material, damaged mitochondria and impaired muscle function. We propose that VCP sustains sarcoplasmic proteostasis, in part, by controlling the integrity of a dynamic tubular lysosomal network.

  6. Linking social and pathogen transmission networks using microbial genetics in giraffe (Giraffa camelopardalis)

    National Research Council Canada - National Science Library

    VanderWaal, Kimberly L; Atwill, Edward R; Isbell, Lynne. A; McCowan, Brenda; Altizer, Sonia

    2014-01-01

    Although network analysis has drawn considerable attention as a promising tool for disease ecology, empirical research has been hindered by limitations in detecting the occurrence of pathogen transmission...

  7. Marine Spatial Planning in a Transboundary Context: Linking Baja California with California's Network of Marine Protected Areas

    Directory of Open Access Journals (Sweden)

    Nur Arafeh-Dalmau

    2017-05-01

    Full Text Available It is acknowledged that an effective path to globally protect marine ecosystems is through the establishment of eco-regional scale networks of MPAs spanning across national frontiers. In this work we aimed to plan for regionally feasible networks of MPAs that can be ecologically linked with an existing one in a transboundary context. We illustrate our exercise in the Ensenadian eco-region, a shared marine ecosystem between the south of California, United States of America (USA, and the north of Baja California, Mexico; where conservation actions differ across the border. In the USA, California recently established a network of MPAs through the Marine Life Protection Act (MLPA, while in Mexico: Baja California lacks a network of MPAs or a marine spatial planning effort to establish it. We generated four different scenarios with Marxan by integrating different ecological, social, and management considerations (habitat representation, opportunity costs, habitat condition, and enforcement costs. To do so, we characterized and collected biophysical and socio-economic information for Baja California and developed novel approaches to quantify and incorporate some of these considerations. We were able to design feasible networks of MPAs in Baja California that are ecologically linked with California's network (met between 78.5 and 84.4% of the MLPA guidelines and that would represent a low cost for fishers and aquaculture investors. We found that when multiple considerations are integrated more priority areas for conservation emerge. For our region, human distribution presents a strong gradient from north to south and resulted to be an important factor for the spatial arrangement of the priority areas. This work shows how, despite the constraints of a data-poor area, the available conservation principles, mapping, and planning tools can still be used to generate spatial conservation plans in a transboundary context.

  8. The rationale for an acute heart failure syndromes clinical trials network.

    Science.gov (United States)

    Collins, Sean P; Levy, Phillip D; Lindsell, Christopher J; Pang, Peter S; Storrow, Alan B; Miller, Chadwick D; Naftilan, Allen J; Thohan, Vinay; Abraham, William T; Hiestand, Brian; Filippatos, Gerasimos; Diercks, Deborah B; Hollander, Judd; Nowak, Richard; Peacock, W Frank; Gheorghiade, Mihai

    2009-08-01

    Clinical trials involving novel therapies treating acute heart failure syndromes (AHFS) have shown limited success with regard to both efficacy and safety. As a direct result, outcomes have changed little over time and AHFS remains a disease process associated with largely no change in hospitalization rates (80%), hospital length of stay (median 4.5 days), and in-hospital (4-7%) and 60-day mortality (10%). Despite extensive emergency department (ED) involvement during the initial phase of AHFS management, clinical trials have enrolled patients after the ED phase of management, up to 48 hours after initial therapy, long after many patients have experienced significant beneficial effects of standard therapy. As standard therapy has provided symptomatic improvement in up to 70% of patients in these trials, it is not surprising that investigational agents started after 24 to 48 hours of standard therapy have shown limited clinical efficacy when compared with standard therapy. The ability to screen, enroll, and randomize in the emergency setting is fundamental. The unique environment, the ethical complexities of enrollment in emergency-based research, and the need for rapid and standardized study-compliant care represent key challenges to active recruitment in AHFS studies. Specifically, the ability to identify and enroll a large cohort of AHFS patients early (academic physicians with experience in clinical trials and acute management of heart failure who together can surmount this barrier and provide a framework for conducting early trials in AHFS.

  9. Reef-fish larval dispersal patterns validate no-take marine reserve network connectivity that links human communities

    KAUST Repository

    Abesamis, Rene A.

    2017-03-24

    Networks of no-take marine reserves (NTMRs) are a widely advocated strategy for managing coral reefs. However, uncertainty about the strength of population connectivity between individual reefs and NTMRs through larval dispersal remains a major obstacle to effective network design. In this study, larval dispersal among NTMRs and fishing grounds in the Philippines was inferred by conducting genetic parentage analysis on a coral-reef fish (Chaetodon vagabundus). Adult and juvenile fish were sampled intensively in an area encompassing approximately 90 km of coastline. Thirty-seven true parent-offspring pairs were accepted after screening 1978 juveniles against 1387 adults. The data showed all types of dispersal connections that may occur in NTMR networks, with assignments suggesting connectivity among NTMRs and fishing grounds (n = 35) far outnumbering those indicating self-recruitment (n = 2). Critically, half (51%) of the inferred occurrences of larval dispersal linked reefs managed by separate, independent municipalities and constituent villages, emphasising the need for nested collaborative management arrangements across management units to sustain NTMR networks. Larval dispersal appeared to be influenced by wind-driven seasonal reversals in the direction of surface currents. The best-fit larval dispersal kernel estimated from the parentage data predicted that 50% of larvae originating from a population would attempt to settle within 33 km, and 95% within 83 km. Mean larval dispersal distance was estimated to be 36.5 km. These results suggest that creating a network of closely spaced (less than a few tens of km apart) NTMRs can enhance recruitment for protected and fished populations throughout the NTMR network. The findings underscore major challenges for regional coral-reef management initiatives that must be addressed with priority: (1) strengthening management of NTMR networks across political or customary boundaries; and (2) achieving adequate population

  10. Reef-fish larval dispersal patterns validate no-take marine reserve network connectivity that links human communities

    Science.gov (United States)

    Abesamis, Rene A.; Saenz-Agudelo, Pablo; Berumen, Michael L.; Bode, Michael; Jadloc, Claro Renato L.; Solera, Leilani A.; Villanoy, Cesar L.; Bernardo, Lawrence Patrick C.; Alcala, Angel C.; Russ, Garry R.

    2017-09-01

    Networks of no-take marine reserves (NTMRs) are a widely advocated strategy for managing coral reefs. However, uncertainty about the strength of population connectivity between individual reefs and NTMRs through larval dispersal remains a major obstacle to effective network design. In this study, larval dispersal among NTMRs and fishing grounds in the Philippines was inferred by conducting genetic parentage analysis on a coral-reef fish ( Chaetodon vagabundus). Adult and juvenile fish were sampled intensively in an area encompassing approximately 90 km of coastline. Thirty-seven true parent-offspring pairs were accepted after screening 1978 juveniles against 1387 adults. The data showed all types of dispersal connections that may occur in NTMR networks, with assignments suggesting connectivity among NTMRs and fishing grounds ( n = 35) far outnumbering those indicating self-recruitment ( n = 2). Critically, half (51%) of the inferred occurrences of larval dispersal linked reefs managed by separate, independent municipalities and constituent villages, emphasising the need for nested collaborative management arrangements across management units to sustain NTMR networks. Larval dispersal appeared to be influenced by wind-driven seasonal reversals in the direction of surface currents. The best-fit larval dispersal kernel estimated from the parentage data predicted that 50% of larvae originating from a population would attempt to settle within 33 km, and 95% within 83 km. Mean larval dispersal distance was estimated to be 36.5 km. These results suggest that creating a network of closely spaced (less than a few tens of km apart) NTMRs can enhance recruitment for protected and fished populations throughout the NTMR network. The findings underscore major challenges for regional coral-reef management initiatives that must be addressed with priority: (1) strengthening management of NTMR networks across political or customary boundaries; and (2) achieving adequate population

  11. Animal models to study links between cardiovascular disease and renal failure and their relevance to human pathology

    Directory of Open Access Journals (Sweden)

    Tim David Hewitson

    2015-09-01

    Full Text Available The close association between cardiovascular pathology and renal dysfunction are well documented and significant. Patients with conventional risk factors for cardiovascular disease like diabetes and hypertension also suffer renal dysfunction. This is unsurprising if the kidney is simply regarded as a ‘modified blood vessel’ and thus traditional risk factors will affect both systems. Consistent with this, it is relatively easy to comprehend how patients with either sudden or gradual cardiac and or vascular compromise have changes in both renal haemodynamic and regulatory systems. However, patients with pure or primary renal dysfunction, also have metabolic changes (e.g. oxidant stress, inflammation, nitric oxide or endocrine changes that affect the cardiovascular system. Thus cardiovascular and renal systems are intimately, bidirectionally and inextricably linked. Whilst we understand several of these links, some of the mechanisms for these connections remain incompletely explained. Animal models of cardiovascular and renal disease allow us to explore such mechanisms, and more importantly, potential therapeutic strategies. In this article we review various experimental models used, and examine critically how representative they are of the human condition

  12. Link and route availability for Inter-working multi-hop wireless networks

    CSIR Research Space (South Africa)

    Salami, O

    2009-09-01

    Full Text Available In inter-working multi-hop wireless networks, establishing resilient connectivity between source-destination node pairs is a major issue. The issue of connectivity in multi-hop wireless networks have been studied. However, these analyses focused...

  13. Scale-space measures for graph topology link protein network architecture to function

    NARCIS (Netherlands)

    Hulsman, M.; Dimitrakopoulos, C.; De Ridder, J.

    2014-01-01

    MOTIVATION: The network architecture of physical protein interactions is an important determinant for the molecular functions that are carried out within each cell. To study this relation, the network architecture can be characterized by graph topological characteristics such as shortest paths and

  14. Knitted Patterns or Contagious Hotspots?: Linking Views on Knowledge and Organizational Networked Learning

    Science.gov (United States)

    Cornelissen, Frank; de Jong, Tjip; Kessels, Joseph

    2012-01-01

    Purpose: This paper aims to propose a framework which connects perspectives on knowledge and learning to various approaches of social networks studies. The purpose is twofold: providing input for the discourse in organizational studies about the way different views on knowledge and networks drive design choices and activities of researchers,…

  15. W. C. U. MicroNet: A State Network Linking Secondary Science and Math Classrooms.

    Science.gov (United States)

    Perry, Linda J.

    1984-01-01

    Western Carolina University (W.C.U.) MicroNet is designed to improve mathematics and science teaching by forming a support network for teachers. Describes: (1) the W. C. U. MicroNet system; (2) advantages of the network for students, teachers, and the university; (3) successes and problems; and (4) future endeavors. (JN)

  16. Linked to Innovation: Shaping an Innovative Climate through Network Intentionality and Educators' Social Network Position

    Science.gov (United States)

    Moolenaar, Nienke M.; Daly, Alan J.; Cornelissen, Frank; Liou, Yi-Hwa; Caillier, Stacey; Riordan, Rob; Wilson, Kelly; Cohen, N. Andrew

    2014-01-01

    This study investigates whether educators' cognitive and structural social capital is associated with perceptions of innovative climate in charter schools. We explore a new concept to assess educators' cognitive social capital, namely network intentionality, meaning the extent to which an educator is intentional in connecting and…

  17. Secured Message Transmission in Mobile AD HOC Networks through Identification and Removal of Byzantine Failures

    OpenAIRE

    V Anitha; Akilandeswari, Dr. J.

    2011-01-01

    The emerging need for mobile ad hoc networks and secured data transmission phase is of crucial importance depending upon the environments like military. In this paper, a new way to improve the reliability of message transmission is presented. In the open collaborative MANET environment, any node can maliciously or selfishly disrupt and deny communication of other nodes. Dynamic changing topology makes it hard to determine the adversary nodes that affect the communication in MANET. An SMT prot...

  18. Small human sperm vacuoles observed under high magnification are pocket-like nuclear concavities linked to chromatin condensation failure.

    Science.gov (United States)

    Boitrelle, F; Albert, M; Petit, J-M; Ferfouri, F; Wainer, R; Bergere, M; Bailly, M; Vialard, F; Selva, J

    2013-08-01

    Since an embryo's ability to grow to the blastocyst stage and implant can be improved by selection of a normal spermatozoon with a vacuole-free head, this study set out to determine the nature of small sperm vacuoles observed under high magnification (>×6300). For 15 infertile men with various sperm profiles, high-magnification microscopy was used to select motile, morphometrically normal spermatozoa with no vacuoles (n=450) or more than two small vacuoles (each of which occupied less than 4% of the head's area; n=450). Spermatozoa acrosome reaction status and degree of chromatin condensation were analysed. Three-dimensional deconvolution microscopy was used to accurately image the nucleus and acrosome at all depths in all spermatozoa. In all 450 spermatozoa with small vacuoles, the latter were seen to be abnormal, DNA-free nuclear concavities. Spermatozoa with small vacuoles were significantly more likely than vacuole-free spermatozoa to have noncondensed chromatin (39.8% versus 9.3%, respectively; Pvacuoles observed under high magnification are pocket-like nuclear concavities related to failure of chromatin condensation. Copyright © 2013 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

  19. Identifying potential functional impact of mutations and polymorphisms: Linking heart failure, increased risk of arrhythmias and sudden cardiac death.

    Directory of Open Access Journals (Sweden)

    BENOIT eJAGU

    2013-09-01

    Full Text Available Researchers and clinicians have discovered several important concepts regarding the mechanisms responsible for increased risk of arrhythmias, heart failure and sudden cardiac death. One major step in defining the molecular basis of normal and abnormal cardiac electrical behaviour has been the identification of single mutations that greatly increase the risk for arrhythmias and sudden cardiac death by changing channel-gating characteristics. Indeed, mutations in several genes encoding ion channels, such as SCN5A, which encodes the major cardiac Na+ channel, have emerged as the basis for a variety of inherited cardiac arrhythmias such as long QT syndrome, Brugada syndrome, progressive cardiac conduction disorder, sinus node dysfunction or sudden infant death syndrome. In addition, genes encoding ion channel accessory proteins, like anchoring or chaperone proteins, which modify the expression, the regulation of endocytosis and the degradation of ion channel α-subunits have also been reported as susceptibility genes for arrhythmic syndromes. The regulation of ion channel protein expression also depends on a fine-tuned balance among different other mechanisms, such as gene transcription, RNA processing, post-transcriptional control of gene expression by miRNA, protein synthesis, assembly and post-translational modification and trafficking.

  20. Selective removal of heavy metal ions by disulfide linked polymer networks

    DEFF Research Database (Denmark)

    Ko, Dongah; Sung Lee, Joo; Patel, Hasmukh A.

    2017-01-01

    a moderate surface area, it demonstrated cadmium removal efficiency equivalent to highly porous activated carbon while it showed 16 times faster sorption kinetics compared to activated carbon, owing to the high affinity of cadmium towards disulfide and thiol functionality in the polymer network. The metal...... sorption mechanism on polymer network was studied by sorption kinetics, effect of pH, and metal complexation. We observed that the metal ions―copper, cadmium, and zinc showed high binding affinity in polymer network, even in the presence of competing cations like calcium in water....

  1. Intestinal congestion and right ventricular dysfunction: a link with appetite loss, inflammation, and cachexia in chronic heart failure.

    Science.gov (United States)

    Valentova, Miroslava; von Haehling, Stephan; Bauditz, Juergen; Doehner, Wolfram; Ebner, Nicole; Bekfani, Tarek; Elsner, Sebastian; Sliziuk, Veronika; Scherbakov, Nadja; Murín, Ján; Anker, Stefan D; Sandek, Anja

    2016-06-01

    Mechanisms leading to cachexia in heart failure (HF) are not fully understood. We evaluated signs of intestinal congestion in patients with chronic HF and their relationship with cachexia. Of the 165 prospectively enrolled outpatients with left ventricular ejection fraction ≤40%, 29 (18%) were cachectic. Among echocardiographic parameters, the combination of right ventricular dysfunction and elevated right atrial pressure (RAP) provided the best discrimination between cachectic and non-cachectic patients [area under the curve 0.892, 95% confidence interval (CI): 0.832-0.936]. Cachectic patients, compared with non-cachectic, had higher prevalence of postprandial fullness, appetite loss, and abdominal discomfort. Abdominal ultrasound showed a larger bowel wall thickness (BWT) in the entire colon and terminal ileum in cachectic than in non-cachectic patients. Bowel wall thickness correlated positively with gastrointestinal symptoms, high-sensitivity C-reactive protein, RAP, and truncal fat-free mass, the latter serving as a marker of the fluid content. Logistic regression analysis showed that BWT was associated with cachexia, even after adjusting for cardiac function, inflammation, and stages of HF (odds ratio 1.4, 95% CI: 1.0-1.8; P-value = 0.03). Among the cardiac parameters, only RAP remained significantly associated with cachexia after multivariable adjustment. Cardiac cachexia was associated with intestinal congestion irrespective of HF stage and cardiac function. Gastrointestinal discomfort, appetite loss, and pro-inflammatory activation provide probable mechanisms, by which intestinal congestion may trigger cardiac cachexia. However, our results are preliminary and larger studies are needed to clarify the intrinsic nature of this relationship. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.

  2. Self-reinforcement and protein sustained delivery of hyaluronan hydrogel by tailoring a dually cross-linked network

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Chunhong; Xu, Guoguang; Wang, Xinghui [Department of Materials Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Tu, Mei; Zeng, Rong; Rong, Jianhua [Department of Materials Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China); Zhao, Jianhao, E-mail: jhzhao@jnu.edu.cn [Department of Materials Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China)

    2015-01-01

    A series of self-reinforcing hyaluronan hydrogels were developed to improve mechanical properties and protein sustained delivery thanks to a dually cross-linked network. Hyaluronan gel particles (HGPs, 1–5 μm in diameter) with different cross-linking densities, i.e. HGPs-1.5, HGPs-3 and HGPs-15, were prepared in an inverse emulsion system and used as the reinforcing phase after glycidyl methacrylation, while glycidyl methacrylated hyaluronan with a substitution degree of 45.2% was synthesized as the matrix phase. These two phases were cross-linked under ultraviolet irradiation to form self-reinforcing hyaluronan hydrogels (srHAs) that showed typical cross-linked structure of HGPs connecting the matrix phase by cross-section observation. In comparison to hyaluronan bulk gels and their blends with HGPs, srHAs distinctly enhanced the mechanical properties and BSA long-term sustained delivery, especially srHA-1.5 showed the highest compressive modulus of 220 ± 15 kPa and the slowest BSA delivery (67% release at 14 d). The 3T3 fibroblast cell culture showed that all the srHAs had no cytotoxicity. - Highlights: • New self-reinforcing HA hydrogels with a dually cross-linked network were developed. • Self-reinforcing HA hydrogels greatly enhanced the mechanical properties. • Self-reinforcing HA hydrogels prolonged the sustained delivery of BSA. • The self-reinforcing mechanism and BSA diffusion mechanism were discussed. • Self-reinforcing HA hydrogels had no cytotoxicity to 3T3 fibroblast cells.

  3. Observation of Skin-to-Skin Contact and Analysis of Factors Linked to Failure to Breastfeed Within 2 Hours After Birth.

    Science.gov (United States)

    Robiquet, Perrine; Zamiara, Pierre-Emmanuel; Rakza, Thameur; Deruelle, Philippe; Mestdagh, Béatrice; Blondel, Géraldine; Turck, Dominique; Subtil, Damien

    2016-04-01

    Successful breastfeeding at birth seems to be associated with skin-to-skin contact between mother and newborn and newborn suckling, both within the first 2 hours of life. In practice, knowledge about the number and cause of interruptions of this contact has to be increased. To measure the actual time of skin-to-skin contact in the first 2 hours after birth, study the events that occur during this period, and search for factors linked to failure to breastfeed. Thirty women wishing to breastfeed gave their consent for us to observe and analyze the first 2 hours of the baby's life during skin-to-skin contact. Mean total duration of skin-to-skin contact for the 30 newborns during the first 2 hours was 90.4 ± 25.0 minutes; 17 (56.7%) were interrupted at least twice during this time, mainly for neonatal care. The first interruption took place before the first breastfeed in 60% of cases. Mean time before the first breastfeed was 44.6 ± 21.1 minutes. Seven infants did not breastfeed in the first 2 hours (23.3%). The factors linked to this failure were nulliparity, lower umbilical arterial pH at birth, and early interruptions in skin-to-skin contact. Among them, only early interruptions of skin-to-skin contact appear to be modifiable. In the first 2 hours of life, early interruptions of skin-to-skin contact should be discouraged as they reduce the chances of early breastfeed.

  4. Uncertain links in host–parasite networks: lessons for parasite transmission in a multi-host system

    Science.gov (United States)

    2017-01-01

    For many parasites, the full set of hosts that are susceptible to infection is not known, and this could lead to a bias in estimates of transmission. We used counts of individual adult parasites from historical parasitology studies in southern Africa to map a bipartite network of the nematode parasites of herbivore hosts that occur in Botswana. Bipartite networks are used in community ecology to represent interactions across trophic levels. We used a Bayesian hierarchical model to predict the full set of host–parasite interactions from existing data on parasitic gastrointestinal nematodes of wild and domestic ungulates given assumptions about the distribution of parasite counts within hosts, while accounting for the relative uncertainty of less sampled species. We used network metrics to assess the difference between the observed and predicted networks, and to explore the connections between hosts via their shared parasites using a host–host unipartite network projected from the bipartite network. The model predicts a large number of missing links and identifies red hartebeest, giraffe and steenbok as the hosts that have the most uncertainty in parasite diversity. Further, the unipartite network reveals clusters of herbivores that have a high degree of parasite sharing, and these clusters correspond closely with phylogenetic distance rather than with the wild/domestic boundary. These results provide a basis for predicting the risk of cross-species transmission of nematode parasites in areas where livestock and wildlife share grazing land. This article is part of the themed issue ‘Opening the black box: re-examining the ecology and evolution of parasite transmission’. PMID:28289262

  5. The Analysis of a Link Between a Remote Local Area Network and Its Server Resources

    National Research Council Canada - National Science Library

    Beaver, Theresa

    2005-01-01

    ... paramount. One way to provide this support is to create a Local Area Network (LAN) in which the workstations are positioned at the deployed location while the servers are maintained at a Main Operating Base (MOB...

  6. Cat Swarm Optimization Based Functional Link Artificial Neural Network Filter for Gaussian Noise Removal from Computed Tomography Images

    Directory of Open Access Journals (Sweden)

    M. Kumar

    2016-01-01

    Full Text Available Gaussian noise is one of the dominant noises, which degrades the quality of acquired Computed Tomography (CT image data. It creates difficulties in pathological identification or diagnosis of any disease. Gaussian noise elimination is desirable to improve the clarity of a CT image for clinical, diagnostic, and postprocessing applications. This paper proposes an evolutionary nonlinear adaptive filter approach, using Cat Swarm Functional Link Artificial Neural Network (CS-FLANN to remove the unwanted noise. The structure of the proposed filter is based on the Functional Link Artificial Neural Network (FLANN and the Cat Swarm Optimization (CSO is utilized for the selection of optimum weight of the neural network filter. The applied filter has been compared with the existing linear filters, like the mean filter and the adaptive Wiener filter. The performance indices, such as peak signal to noise ratio (PSNR, have been computed for the quantitative analysis of the proposed filter. The experimental evaluation established the superiority of the proposed filtering technique over existing methods.

  7. Reducing Latency in Internet Access Links with Mechanisms in Endpoints and within the Network

    OpenAIRE

    Khademi, Naeem

    2015-01-01

    Excessive and unpredictable end-to-end latency is a major problem for today’s Internet performance, affecting a range of applications from real-time multimedia to web traffic. This is mainly attributed to the interaction between the TCP congestion control mechanism and the unmanaged large buffers deployed across the Internet. This dissertation investigates transport and link layer solutions to solve the Internet’s latency problem on the access links. These solutions operate on the sender side...

  8. Building Capacity for Earthquake Monitoring: Linking Regional Networks with the Global Community

    Science.gov (United States)

    Willemann, R. J.; Lerner-Lam, A.

    2006-12-01

    Installing or upgrading a seismic monitoring network is often among the mitigation efforts after earthquake disasters, and this is happening in response to the events both in Sumatra during December 2004 and in Pakistan during October 2005. These networks can yield improved hazard assessment, more resilient buildings where they are most needed, and emergency relief directed more quickly to the worst hit areas after the next large earthquake. Several commercial organizations are well prepared for the fleeting opportunity to provide the instruments that comprise a seismic network, including sensors, data loggers, telemetry stations, and the computers and software required for the network center. But seismic monitoring requires more than hardware and software, no matter how advanced. A well-trained staff is required to select appropriate and mutually compatible components, install and maintain telemetered stations, manage and archive data, and perform the analyses that actually yield the intended benefits. Monitoring is more effective when network operators cooperate with a larger community through free and open exchange of data, sharing information about working practices, and international collaboration in research. As an academic consortium, a facility operator and a founding member of the International Federation of Digital Seismographic Networks, IRIS has access to a broad range of expertise with the skills that are required to help design, install, and operate a seismic network and earthquake analysis center, and stimulate the core training for the professional teams required to establish and maintain these facilities. But delivering expertise quickly when and where it is unexpectedly in demand requires advance planning and coordination in order to respond to the needs of organizations that are building a seismic network, either with tight time constraints imposed by the budget cycles of aid agencies following a disastrous earthquake, or as part of more informed

  9. A failure of suppression within the default mode network in depressed adolescents with compulsive internet game play.

    Science.gov (United States)

    Han, Doug Hyun; Kim, Sun Mi; Bae, Sujin; Renshaw, Perry F; Anderson, Jeffrey S

    2016-04-01

    Individuals who are chronic, compulsive video game players experience an elevated incidence of major depression. Excessive or problematic game play can interact with depression clinically, and may magnify impulsive behavior associated with video gaming. Functional brain imaging was performed during a Wisconsin Card Sorting Test (WCST) task in 42 healthy control and 95 volunteers seeking treatment for compulsive video game playing, including 60 participants without major depression (pure internet gaming disorder, pure IGD) and 35 participants comorbid with major depression (IGD+MDD). In response to the WCST in contrast to fixation, activation was observed in canonical brain attentional networks including bilateral intraparietal sulcus, frontal eye fields, and middle temporal cortical regions as well as dorsolateral prefrontal, inferior parietal and anterior insula, anterior cingulate cortex in all participants. For WCST>Fixation contrasts, the IGD+MDD group exhibited greater relative activation within the left hippocampus, compared to healthy control participants. For WCST>Fixation contrasts, the IGD+MDD group exhibited greater relative activation within the left hippocampus and the right parahippocampal gyrus immediately posterior to the hippocampus, compared to the pure IGD group. In cohorts of individuals with a history of compulsive internet game play, individuals with depression showed failure to suppress default mode network activity during an attentionally demanding task, compared to individuals without depression, including comparison groups with and without a history of compulsive video gaming. This reduced suppression of the brain regions within the default mode network may be a consequence of depressive neurophysiology or represent a predisposition for depression within compulsive game players. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Collagen cross-linking but not collagen amount associates with elevated filling pressures in hypertensive patients with stage C heart failure: potential role of lysyl oxidase.

    Science.gov (United States)

    López, Begoña; Querejeta, Ramón; González, Arantxa; Larman, Mariano; Díez, Javier

    2012-09-01

    We investigated whether the quality of myocardial collagen associates with elevated left-sided filling pressures in 38 hypertensive patients with stage C chronic heart failure. Filling pressures were assessed invasively measuring pulmonary capillary wedge pressure. Left ventricular chamber stiffness constant was calculated from the deceleration time of the early mitral filling wave. The fraction of myocardial volume occupied by total collagen tissue and collagen type I fibers was assessed histomorphologically. The degree of collagen cross-linking (CCL), which determines the formation of insoluble stiff collagen, was assessed by colorimetric and enzymatic procedures. The expression of lysyl oxidase (LOX), which regulates CCL, was assessed by Western blot. Compared with patients with normal pulmonary capillary wedge pressure (≤12 mm Hg; n=16), patients with elevated pulmonary capillary wedge pressure (>12 mm Hg; n=22) exhibited increases of left ventricular chamber stiffness constant, fraction of myocardial volume occupied by total collagen tissue, fraction of myocardial volume occupied by collagen type I fibers, CCL, insoluble stiff collagen, and LOX. Pulmonary capillary wedge pressure was correlated with left ventricular chamber stiffness constant (r=0.639; Pcollagen (r=0.474; Pcollagen tissue or fraction of myocardial volume occupied by collagen type I fibers. In addition, CCL was correlated with insoluble stiff collagen (r=0.612; Pcollagen (ie, degree of cross-linking) that associates with elevated filling pressures. It is suggested that LOX-mediated excessive CCL facilitates the increase in left ventricular stiffness with the resulting elevation of filling pressures in these patients.

  11. X-chromosome terminal deletion in a female with premature ovarian failure: Haploinsufficiency of X-linked genes as a possible explanation

    Directory of Open Access Journals (Sweden)

    Melo Joana B

    2010-07-01

    Full Text Available Abstract Background Premature ovarian failure (POF has repeatedly been associated to X-chromosome deletions. FMR1 gene premutation allele's carrier women have an increased risk for POF. We intent to determine the cause of POF in a 29 year old female, evaluating both of these situations. Methods Concomitant analysis of FMR1 gene CGG repeat number and karyotype revealed an X-chromosome terminal deletion. Fluorescence in situ further characterized the breakpoint. A methylation assay for FMR1 gene allowed to determine its methylation status, and hence, the methylation status of the normal X-chromosome. Results We report a POF patient with a 46,X,del(X(q26 karyotype and with skewed X-chromosome inactivation of the structural abnormal X-chromosome. Conclusions Despite the hemizygosity of FMR1 gene, the patient does not present Fragile X syndrome features, since the normal X-chromosome is not subject to methylation. The described deletion supports the hypothesis that haploinsufficiency of X-linked genes can be on the basis of POF, and special attention should be paid to X-linked genes in region Xq28 since they escape inactivation and might have a role in this disorder. A full clinical and cytogenetic characterization of all POF cases is important to highlight a pattern and help to understand which genes are crucial for normal ovarian development.

  12. X-chromosome terminal deletion in a female with premature ovarian failure: Haploinsufficiency of X-linked genes as a possible explanation.

    Science.gov (United States)

    Ferreira, Susana I; Matoso, Eunice; Pinto, Marta; Almeida, Joana; Liehr, Thomas; Melo, Joana B; Carreira, Isabel M

    2010-07-20

    Premature ovarian failure (POF) has repeatedly been associated to X-chromosome deletions. FMR1 gene premutation allele's carrier women have an increased risk for POF. We intent to determine the cause of POF in a 29 year old female, evaluating both of these situations. Concomitant analysis of FMR1 gene CGG repeat number and karyotype revealed an X-chromosome terminal deletion. Fluorescence in situ further characterized the breakpoint. A methylation assay for FMR1 gene allowed to determine its methylation status, and hence, the methylation status of the normal X-chromosome. We report a POF patient with a 46,X,del(X)(q26) karyotype and with skewed X-chromosome inactivation of the structural abnormal X-chromosome. Despite the hemizygosity of FMR1 gene, the patient does not present Fragile X syndrome features, since the normal X-chromosome is not subject to methylation. The described deletion supports the hypothesis that haploinsufficiency of X-linked genes can be on the basis of POF, and special attention should be paid to X-linked genes in region Xq28 since they escape inactivation and might have a role in this disorder. A full clinical and cytogenetic characterization of all POF cases is important to highlight a pattern and help to understand which genes are crucial for normal ovarian development.

  13. Regional neuronal network failure and cognition in late-onset sporadic Alzheimer disease.

    Science.gov (United States)

    Carter, S F; Embleton, K V; Anton-Rodriguez, J M; Burns, A; Ralph, M A L; Herholz, K

    2014-06-01

    The severe cognitive deficits in Alzheimer disease are associated with structural lesions in gray and white matter in addition to changes in synaptic function. The current investigation studied the breakdown of the structure and function in regional networks involving the Papez circuit and extended neocortical association areas. Cortical volumetric and diffusion tensor imaging (3T MR imaging), positron-emission tomography with (18)F fluorodeoxyglucose on a high-resolution research tomograph, and comprehensive neuropsychological assessments were performed in patients with late-onset sporadic Alzheimer disease, those with mild cognitive impairment, and elderly healthy controls. Atrophy of the medial temporal lobes was the strongest and most consistent abnormality in patients with mild cognitive impairment and Alzheimer disease. Atrophy in the temporal, frontal, and parietal regions was most strongly related to episodic memory deficits, while deficits in semantic cognition were also strongly related to reductions of glucose metabolism in the posterior cingulate cortex and temporoparietal regions. Changes in fractional anisotropy within white matter tracts, particularly in the left cingulum bundle, uncinate fasciculus, superior longitudinal fasciculus, and inferior fronto-occipital fasciculus, were significantly associated with the cognitive deficits in multiple regression analyses. Posterior cingulate and orbitofrontal metabolic deficits appeared to be related to microstructural changes in projecting white matter tracts. Many lesioned network components within the Papez circuit and extended neocortical association areas were significantly associated with cognitive dysfunction in both mild cognitive impairment and late-onset sporadic Alzheimer disease. Hippocampal atrophy was the most prominent lesion, with associated impairment of the uncinate and cingulum white matter microstructures and hippocampal and posterior cingulate metabolic impairment. © 2014 by American

  14. Face Patch Resting State Networks Link Face Processing to Social Cognition.

    Directory of Open Access Journals (Sweden)

    Caspar M Schwiedrzik

    Full Text Available Faces transmit a wealth of social information. How this information is exchanged between face-processing centers and brain areas supporting social cognition remains largely unclear. Here we identify these routes using resting state functional magnetic resonance imaging in macaque monkeys. We find that face areas functionally connect to specific regions within frontal, temporal, and parietal cortices, as well as subcortical structures supporting emotive, mnemonic, and cognitive functions. This establishes the existence of an extended face-recognition system in the macaque. Furthermore, the face patch resting state networks and the default mode network in monkeys show a pattern of overlap akin to that between the social brain and the default mode network in humans: this overlap specifically includes the posterior superior temporal sulcus, medial parietal, and dorsomedial prefrontal cortex, areas supporting high-level social cognition in humans. Together, these results reveal the embedding of face areas into larger brain networks and suggest that the resting state networks of the face patch system offer a new, easily accessible venue into the functional organization of the social brain and into the evolution of possibly uniquely human social skills.

  15. Exploitation of complex network topology for link prediction in biological interactomes

    KAUST Repository

    Alanis Lobato, Gregorio

    2014-06-01

    The network representation of the interactions between proteins and genes allows for a holistic perspective of the complex machinery underlying the living cell. However, the large number of interacting entities within the cell makes network construction a daunting and arduous task, prone to errors and missing information. Fortunately, the structure of biological networks is not different from that of other complex systems, such as social networks, the world-wide web or power grids, for which growth models have been proposed to better understand their structure and function. This means that we can design tools based on these models in order to exploit the topology of biological interactomes with the aim to construct more complete and reliable maps of the cell. In this work, we propose three novel and powerful approaches for the prediction of interactions in biological networks and conclude that it is possible to mine the topology of these complex system representations and produce reliable and biologically meaningful information that enriches the datasets to which we have access today.

  16. Face Patch Resting State Networks Link Face Processing to Social Cognition

    Science.gov (United States)

    Schwiedrzik, Caspar M.; Zarco, Wilbert; Everling, Stefan; Freiwald, Winrich A.

    2015-01-01

    Faces transmit a wealth of social information. How this information is exchanged between face-processing centers and brain areas supporting social cognition remains largely unclear. Here we identify these routes using resting state functional magnetic resonance imaging in macaque monkeys. We find that face areas functionally connect to specific regions within frontal, temporal, and parietal cortices, as well as subcortical structures supporting emotive, mnemonic, and cognitive functions. This establishes the existence of an extended face-recognition system in the macaque. Furthermore, the face patch resting state networks and the default mode network in monkeys show a pattern of overlap akin to that between the social brain and the default mode network in humans: this overlap specifically includes the posterior superior temporal sulcus, medial parietal, and dorsomedial prefrontal cortex, areas supporting high-level social cognition in humans. Together, these results reveal the embedding of face areas into larger brain networks and suggest that the resting state networks of the face patch system offer a new, easily accessible venue into the functional organization of the social brain and into the evolution of possibly uniquely human social skills. PMID:26348613

  17. Face Patch Resting State Networks Link Face Processing to Social Cognition.

    Science.gov (United States)

    Schwiedrzik, Caspar M; Zarco, Wilbert; Everling, Stefan; Freiwald, Winrich A

    2015-01-01

    Faces transmit a wealth of social information. How this information is exchanged between face-processing centers and brain areas supporting social cognition remains largely unclear. Here we identify these routes using resting state functional magnetic resonance imaging in macaque monkeys. We find that face areas functionally connect to specific regions within frontal, temporal, and parietal cortices, as well as subcortical structures supporting emotive, mnemonic, and cognitive functions. This establishes the existence of an extended face-recognition system in the macaque. Furthermore, the face patch resting state networks and the default mode network in monkeys show a pattern of overlap akin to that between the social brain and the default mode network in humans: this overlap specifically includes the posterior superior temporal sulcus, medial parietal, and dorsomedial prefrontal cortex, areas supporting high-level social cognition in humans. Together, these results reveal the embedding of face areas into larger brain networks and suggest that the resting state networks of the face patch system offer a new, easily accessible venue into the functional organization of the social brain and into the evolution of possibly uniquely human social skills.

  18. Determination of oil well production performance using artificial neural network (ANN linked to the particle swarm optimization (PSO tool

    Directory of Open Access Journals (Sweden)

    Mohammad Ali Ahmadi

    2015-06-01

    In this work, novel and rigorous methods based on two different types of intelligent approaches including the artificial neural network (ANN linked to the particle swarm optimization (PSO tool are developed to precisely forecast the productivity of horizontal wells under pseudo-steady-state conditions. It was found that there is very good match between the modeling output and the real data taken from the literature, so that a very low average absolute error percentage is attained (e.g., <0.82%. The developed techniques can be also incorporated in the numerical reservoir simulation packages for the purpose of accuracy improvement as well as better parametric sensitivity analysis.

  19. Stress reduction in phase-separated, cross-linked networks: influence of phase structure and kinetics of reaction.

    Science.gov (United States)

    Szczepanski, Caroline R; Stansbury, Jeffrey W

    2014-10-05

    A mechanism for polymerization shrinkage and stress reduction was developed for heterogeneous networks formed via ambient, photo-initiated polymerization-induced phase separation (PIPS). The material system used consists of a bulk homopolymer matrix of triethylene glycol dimethacrylate (TEGDMA) modified with one of three non-reactive, linear prepolymers (poly-methyl, ethyl and butyl methacrylate). At higher prepolymer loading levels (10-20 wt%) an enhanced reduction in both shrinkage and polymerization stress is observed. The onset of gelation in these materials is delayed to a higher degree of methacrylate conversion (~15-25%), providing more time for phase structure evolution by thermodynamically driven monomer diffusion between immiscible phases prior to network macro-gelation. The resulting phase structure was probed by introducing a fluorescently tagged prepolymer into the matrix. The phase structure evolves from a dispersion of prepolymer at low loading levels to a fully co-continuous heterogeneous network at higher loadings. The bulk modulus in phase separated networks is equivalent or greater than that of poly(TEGDMA), despite a reduced polymerization rate and cross-link density in the prepolymer-rich domains.

  20. Linking experiment and theory for three-dimensional networked binary metal nanoparticle–triblock terpolymer superstructures

    KAUST Repository

    Li, Zihui

    2014-02-21

    © 2014 Macmillan Publishers Limited. Controlling superstructure of binary nanoparticle mixtures in three dimensions from self-assembly opens enormous opportunities for the design of materials with unique properties. Here we report on how the intimate coupling of synthesis, in-depth electron tomographic characterization and theory enables exquisite control of superstructure in highly ordered porous three-dimensional continuous networks from single and binary mixtures of metal nanoparticles with a triblock terpolymer. Poly(isoprene-block-styrene-block-(N,N-dimethylamino)ethyl methacrylate) is synthesized and used as structure-directing agent for ligand-stabilized platinum and gold nanoparticles. Quantitative analysis provides insights into short-and long-range nanoparticle-nanoparticle correlations, and local and global contributions to structural chirality in the networks. Results provide synthesis criteria for next-generation mesoporous network superstructures from binary nanoparticle mixtures for potential applications in areas including catalysis.

  1. Interlocking editorship. A network analysis of the links between economic journals

    CERN Document Server

    Baccini, Alberto; 10.1007/s11192-009-0053-7

    2011-01-01

    The exploratory analysis developed in this paper relies on the hypothesis that each editor possesses some power in the definition of the editorial policy of her journal. Consequently if the same scholar sits on the board of editors of two journals, those journals could have some common elements in their editorial policies. The proximity of the editorial policies of two scientific journals can be assessed by the number of common editors sitting on their boards. A database of all editors of ECONLIT journals is used. The structure of the network generated by interlocking editorship is explored by applying the instruments of network analysis. Evidences have been found of a compact network containing different components. This is interpreted as the result of a plurality of perspectives about the appropriate methods for the investigation of problems and the construction of theories within the domain of economics.

  2. Analysis of Single-Mode Fiber Link Performance for Attenuation in Long-Haul Optical Networks

    Science.gov (United States)

    Kaur, Karamjit; Singh, Hardeep

    2017-06-01

    In the past decades, optical fiber has been widely used in communication system owing to low transmission losses, large information carrying capacity, small size, immunity to electrical interference and increased signal security. Focusing on increasing the network transmission capacity, control on the quality of transmission was the field that withdraws attention of research community. For this reason, fiber losses and their compensation remain the important design issue. In the present work, an effort is put in to design a system capable of doing error analysis of system for power losses taking place in the presence of attenuation effect. Attenuation is one of the important phenomena that determine the maximum possible distance between a transmitter and receiver or quantity and position of amplifiers and repeaters in optical networks. The mathematical model equations are obtained representing variation trends of bit error rate BER and Q-value with varying attenuation, which has been verified by different wavelength sources and network conditions.

  3. Scandinavian links

    DEFF Research Database (Denmark)

    Matthiessen, Christian Wichmann; Knowles, Richard D.

    2014-01-01

    The European Round Table of Industrialists identified in the 1980ies 14 missing links in the transportation network of the continent. Three of them were found around the Danish island of Zealand. One link is within the nation, the other two are between nations. One link connects heavy economic....... They concentrate traffic flows and create strong transport corridors. They are the basis of new regional development regimes. “Ferries connect systems, fixed links unite systems”....

  4. Linking plant specialization to dependence in interactions for seed set in pollination networks.

    Science.gov (United States)

    Tur, Cristina; Castro-Urgal, Rocío; Traveset, Anna

    2013-01-01

    Studies on pollination networks have provided valuable information on the number, frequency, distribution and identity of interactions between plants and pollinators. However, little is still known on the functional effect of these interactions on plant reproductive success. Information on the extent to which plants depend on such interactions will help to make more realistic predictions of the potential impacts of disturbances on plant-pollinator networks. Plant functional dependence on pollinators (all interactions pooled) can be estimated by comparing seed set with and without pollinators (i.e. bagging flowers to exclude them). Our main goal in this study was thus to determine whether plant dependence on current insect interactions is related to plant specialization in a pollination network. We studied two networks from different communities, one in a coastal dune and one in a mountain. For ca. 30% of plant species in each community, we obtained the following specialization measures: (i) linkage level (number of interactions), (ii) diversity of interactions, and (iii) closeness centrality (a measure of how much a species is connected to other plants via shared pollinators). Phylogenetically controlled regression analyses revealed that, for the largest and most diverse coastal community, plants highly dependent on pollinators were the most generalists showing the highest number and diversity of interactions as well as occupying central positions in the network. The mountain community, by contrast, did not show such functional relationship, what might be attributable to their lower flower-resource heterogeneity and diversity of interactions. We conclude that plants with a wide array of pollinator interactions tend to be those that are more strongly dependent upon them for seed production and thus might be those more functionally vulnerable to the loss of network interaction, although these outcomes might be context-dependent.

  5. Linking plant specialization to dependence in interactions for seed set in pollination networks.

    Directory of Open Access Journals (Sweden)

    Cristina Tur

    Full Text Available Studies on pollination networks have provided valuable information on the number, frequency, distribution and identity of interactions between plants and pollinators. However, little is still known on the functional effect of these interactions on plant reproductive success. Information on the extent to which plants depend on such interactions will help to make more realistic predictions of the potential impacts of disturbances on plant-pollinator networks. Plant functional dependence on pollinators (all interactions pooled can be estimated by comparing seed set with and without pollinators (i.e. bagging flowers to exclude them. Our main goal in this study was thus to determine whether plant dependence on current insect interactions is related to plant specialization in a pollination network. We studied two networks from different communities, one in a coastal dune and one in a mountain. For ca. 30% of plant species in each community, we obtained the following specialization measures: (i linkage level (number of interactions, (ii diversity of interactions, and (iii closeness centrality (a measure of how much a species is connected to other plants via shared pollinators. Phylogenetically controlled regression analyses revealed that, for the largest and most diverse coastal community, plants highly dependent on pollinators were the most generalists showing the highest number and diversity of interactions as well as occupying central positions in the network. The mountain community, by contrast, did not show such functional relationship, what might be attributable to their lower flower-resource heterogeneity and diversity of interactions. We conclude that plants with a wide array of pollinator interactions tend to be those that are more strongly dependent upon them for seed production and thus might be those more functionally vulnerable to the loss of network interaction, although these outcomes might be context-dependent.

  6. Using LTE Networks for UAV Command and Control Link: A Rural-Area Coverage Analysis

    DEFF Research Database (Denmark)

    Nguyen, Huan Cong; Amorim, Rafhael Medeiros de; Wigard, Jeroen

    2017-01-01

    In this paper we investigate the ability of Long-Term Evolution (LTE) network to provide coverage for Unmanned Aerial Vehicles (UAVs) in a rural area, in particular for the Command and Control (C2) downlink. The study takes into consideration the dependency of the large-scale path loss on the hei......In this paper we investigate the ability of Long-Term Evolution (LTE) network to provide coverage for Unmanned Aerial Vehicles (UAVs) in a rural area, in particular for the Command and Control (C2) downlink. The study takes into consideration the dependency of the large-scale path loss...

  7. On the Delay Characteristics for Point-to-Point links using Random Linear Network Coding with On-the-fly Coding Capabilities

    DEFF Research Database (Denmark)

    Tömösközi, Máté; Fitzek, Frank; Roetter, Daniel Enrique Lucani

    2014-01-01

    . This metric captures the elapsed time between (network) encoding RTP packets and completely decoding the packets in-order on the receiver side. Our solutions are implemented and evaluated on a point-to-point link between a Raspberry Pi device and a network (de)coding enabled software running on a regular PC...

  8. 1.25 Gbit/s bidirectional link in an access network employing a reconfigurable optical add/drop multiplexer and a reflective semiconductor optical amplifier

    NARCIS (Netherlands)

    Urban, P.J.; de Laat, M.M.; Klein, E.J.; Koonen, A.M.J.; Khoe, G.D.; de Waardt, H.; Marciniak, M.; Jaworski, M.; Zdabiwicz, M.

    2008-01-01

    In this paper, we demonstrate symmetrical bidirectional transmission of 1.25 Gbit/s wavelength channels in an access network link employing centralized light generation, colourless optical network unit (ONU) and a reconfigurable optical add/drop multiplexer (ROADM). The architecture of ONU is based

  9. Energy-Efficient Link-Layer Jamming Attacks against Wireless Sensor Network MAC Protocols

    NARCIS (Netherlands)

    Law, Y.W.; van Hoesel, L.F.W.; Doumen, J.M.; Hartel, Pieter H.; Havinga, Paul J.M.; Atluri, V.; Samarati, P.; Ning, P.; Du, W.

    2005-01-01

    A typical wireless sensor node has little protection against radio jamming. The situation becomes worse if energy efficient jamming can be achieved by exploiting knowledge of the data link layer. Encrypting the packets may help prevent the jammer from taking actions based on the content of the

  10. Case study: development of a SANDF tactical data link network enabling capability

    CSIR Research Space (South Africa)

    Smith, CJ

    2011-11-01

    Full Text Available appropriately named Link-ZA. This paper expands on the implementation evolution and challenges of the standard over the last 10 years and provides a generic TDL Capability Model with a strategy for establishing interoperability between different implementations...

  11. A molecular characterization of hyper-cross-linked hybrid polyPOSS-imide networks

    NARCIS (Netherlands)

    Neyertz, Sylvie; Brown, David; Raaijmakers, Michiel; Benes, Nieck Edwin

    2016-01-01

    Hybrid hyper-cross-linked membranes based on inorganic polyhedral oligomeric silsesquioxanes (POSS) covalently bonded with organic imides have been shown to maintain remarkable molecular sieving abilities and gas separation performances up to 300 C. These films are obtained through the interfacial

  12. Escape routes, weak links, and desynchronization in fluctuation-driven networks

    DEFF Research Database (Denmark)

    Schäfer, Benjamin; Matthiae, Moritz; Zhang, Xiaozhu

    2017-01-01

    on fundamental noise models, we derive analytic insights into which factors limit the dynamic robustness and how fluctuations may induce a system escape from an operating state. Moreover, we identify weak links in the grid that make it particularly vulnerable to fluctuations. These results thereby not only...

  13. A Linked and Open Dataset from a Network of Learning Repositories on Organic Agriculture

    Science.gov (United States)

    Rajabi, Enayat; Sanchez-Alonso, Salvador; Sicilia, Miguel-Angel; Manouselis, Nikos

    2017-01-01

    Exposing eLearning objects on the Web of Data leads to sharing and reusing of educational resources and improves the interoperability of data on the Web. Furthermore, it enriches e-learning content, as it is connected to other valuable resources using the Linked Data principles. This paper describes a study performed on the Organic.Edunet…

  14. Network signatures link hepatic effects of anti-diabetic interventions with systemic disease parameters

    NARCIS (Netherlands)

    Kelder, T.; Verschuren, L.; Ommen, B. van; Gool, A.J. van; Radonjic, M.

    2014-01-01

    Background: Multifactorial diseases such as type 2 diabetes mellitus (T2DM), are driven by a complex network of interconnected mechanisms that translate to a diverse range of complications at the physiological level. To optimally treat T2DM, pharmacological interventions should, ideally, target key

  15. Children in Protective Services: The Missing Educational Link for Children in Kinship Networks.

    Science.gov (United States)

    Rittner, Barbara; Sacks, Arlene

    1995-01-01

    Explores how school social workers and children's protective services (CPS) can collaborate to improve the social and educational functioning of maltreated children living in kinship networks. A collaboration model between school social workers and CPS is suggested using provisions of the Individuals with Disabilities Act. (JPS)

  16. Linking biodiversity to mutualistic networks – woody species and ectomycorrhizal fungi

    Directory of Open Access Journals (Sweden)

    Ecaterina Fodor

    2013-05-01

    Full Text Available Mutualistic interactions are currently mapped by bipartite networkswith particular architecture and properties. The mycorrhizae connectthe trees and permit them to share resources, therefore relaxing thecompetition. Ectomycorrhizal macrofungi associated with woody species(Quercus robur, Q. cerris, Q. petraea, Tilia tomentosa, Carpinus betulus, Corylus avellana, and Q. pubescens growing in a temperate, broadleaved mixed forest, from a hilly area near the city of Cluj–Napoca, central Romania were included in a bipartite mutualistic network. Community structure was investigated using several network metrics, modularity and nestedness algorithms in conjunction with C-score index cluster analysis and nonmetric multidimensional scaling (the Kulczynski similarity was index used as most appropriate metric selected by minimal stress criterion. The results indicate that the network presents high asymmetry (hosts are outnumbered by mycobionts at a great extent, high connectance, low modularity, andhigh nestedness, competition playing a secondary role in community assemblage (non significant difference between simulated and observed Cscore.The nestedness pattern is non-random and is comparable to previouslypublished results for other similar interactions containing plants. Inthe proposed network, woody species function exclusively as generalists. Modularity analysis is a finer tool were identifying species roles than centrality measures, however, the two types of algorithms permit the separation of species according to their roles as for example connectors (generalist species and ultraperipheral species (specialists. Supergeneralist woody species function as hubs for the diverse ectomycorrhizal community while supergeneralistectomycorrhizal fungi glue the hubs into a coherent aggregate.

  17. Beyond the edge: Linking agricultural landscapes, stream networks, and best management practices

    Science.gov (United States)

    Kreiling, Rebecca M.; Thoms, Martin C.; Richardson, William B.

    2018-01-01

    Despite much research and investment into understanding and managing nutrients across agricultural landscapes, nutrient runoff to freshwater ecosystems is still a major concern. We argue there is currently a disconnect between the management of watershed surfaces (agricultural landscape) and river networks (riverine landscape). These landscapes are commonly managed separately, but there is limited cohesiveness between agricultural landscape-focused research and river science, despite similar end goals. Interdisciplinary research into stream networks that drain agricultural landscapes is expanding but is fraught with problems. Conceptual frameworks are useful tools to order phenomena, reveal patterns and processes, and in interdisciplinary river science, enable the joining of multiple areas of understanding into a single conceptual–empirical structure. We present a framework for the interdisciplinary study and management of agricultural and riverine landscapes. The framework includes components of an ecosystems approach to the study of catchment–stream networks, resilience thinking, and strategic adaptive management. Application of the framework is illustrated through a study of the Fox Basin in Wisconsin, USA. To fully realize the goal of nutrient reduction in the basin, we suggest that greater emphasis is needed on where best management practices (BMPs) are used within the spatial context of the combined watershed–stream network system, including BMPs within the river channel. Targeted placement of BMPs throughout the riverine landscape would increase the overall buffering capacity of the system to nutrient runoff and thus its resilience to current and future disturbances.

  18. Fibril growth kinetics link buffer conditions and topology of 3D collagen I networks.

    Science.gov (United States)

    Kalbitzer, Liv; Pompe, Tilo

    2018-02-01

    Three-dimensional fibrillar networks reconstituted from collagen I are widely used as biomimetic scaffolds for in vitro and in vivo cell studies. Various physicochemical parameters of buffer conditions for in vitro fibril formation are well known, including pH-value, ion concentrations and temperature. However, there is a lack of a detailed understanding of reconstituting well-defined 3D network topologies, which is required to mimic specific properties of the native extracellular matrix. We screened a wide range of relevant physicochemical buffer conditions and characterized the topology of the reconstituted 3D networks in terms of mean pore size and fibril diameter. A congruent analysis of fibril formation kinetics by turbidimetry revealed the adjustment of the lateral growth phase of fibrils by buffer conditions to be key in the determination of pore size and fibril diameter of the networks. Although the kinetics of nucleation and linear growth phase were affected by buffer conditions as well, network topology was independent of those two growth phases. Overall, the results of our study provide necessary insights into how to engineer 3D collagen matrices with an independent control over topology parameters, in order to mimic in vivo tissues in in vitro experiments and tissue engineering applications. The study reports a comprehensive analysis of physicochemical conditions of buffer solutions to reconstitute defined 3D collagen I matrices. By a combined analysis of network topology, i.e., pore size and fibril diameter, and the kinetics of fibril formation we can reveal the dependence of 3D network topology on buffer conditions, such as pH-value, phosphate concentration and sodium chloride content. With those results we are now able to provide engineering strategies to independently tune the topology parameters of widely used 3D collagen scaffolds based on the buffer conditions. By that, we enable the straightforward mimicking of extracellular matrices of in vivo

  19. Linking biodiversity to mutualistic networks – woody species and ectomycorrhizal fungi

    Directory of Open Access Journals (Sweden)

    Ecaterina Fodor

    2013-07-01

    Full Text Available Mutualistic interactions are currently mapped by bipartite networks with particular architecture and properties. The mycorrhizae connect the trees and permit them to share resources, therefore relaxing the competition. Ectomycorrhizal macrofungi associated with woody species (Quercus robur, Q. cerris, Q. petraea, Tilia tomentosa, Carpinus betulus, Corylus avellana, and Q. pubescens growing in a temperate, broadleaved mixed forest, from a hilly area near the city of Cluj–Napoca, central Romania were included in a bipartite mutualistic network. Community structure was investigated using several network metrics, modularity and nestedness algorithms in conjunction with C-score index cluster analysis and nonmetric multidimensional scaling (the Kulczynski similarity was index used as most appropriate metric selected by minimal stress criterion. The results indicate that the network presents high asymmetry (hosts are outnumbered by mycobionts at a great extent, high connectance, low modularity, and high nestedness, competition playing a secondary role in community assemblage (non significant difference between simulated and observed C-score. The nestedness pattern is non-random and is comparable to previously published results for other similar interactions containing plants. In the proposed network, woody species function exclusively as generalists. Modularity analysis is a finer tool were identifying species roles than centrality measures, however, the two types of algorithms permit the separation of species according to their roles as for example connectors (generalist species and ultraperipheral species (specialists. Supergeneralist woody species function as hubs for the diverse ectomycorrhizal community while supergeneralist ectomycorrhizal fungi glue the hubs into a coherent aggregate. 

  20. From nurture to network: examining links between perceptions of parenting received in childhood and social bonds in adulthood.

    Science.gov (United States)

    Parker, G B; Barrett, E A; Hickie, I B

    1992-07-01

    The authors' goal was to consider the extent to which key characteristics of their parents influence children's later socialization in terms of social networks and intimate relationships and thus to examine whether there is evidence of such continuity. The authors reviewed the pertinent literature and then examined studies using a measure of key dimensions of the parenting received in childhood (the Parental Bonding Instrument) as well as measures of adult social networks. The literature review revealed evidence of links (more evident in women) between perceptions of having received uncaring parenting and deficiencies in diffuse social bonds, which could reflect a causal process, a general response bias, or methodological limitations. By contrast, studies using the Parental Bonding Instrument and a specific measure of adult intimate bonds failed to find links between perceptions of parenting received in childhood and the quality of current intimate relationships unless there was extreme deprivation of parental care; in that case, the current intimate relationship was more likely to be rated as uncaring. These findings refine the view that early socialization experiences shape and dictate interpersonal relationships in adulthood. Any deficiencies in parent-child relationships, except, perhaps, gross parental deprivation, appear capable of modification by a range of experiences (particularly subsequent interpersonal relationships).

  1. The quality of hospital work environments and missed nursing care is linked to heart failure readmissions: a cross-sectional study of US hospitals.

    Science.gov (United States)

    Carthon, J Margo Brooks; Lasater, Karen B; Sloane, Douglas M; Kutney-Lee, Ann

    2015-04-01

    Threats to quality and patient safety may exist when necessary nursing care is omitted. Empirical research is needed to determine how missed nursing care is associated with patient outcomes. The aim of this study was to examine the relationship between missed nursing care and hospital readmissions. Cross-sectional examination, using three linked data sources-(1) nurse survey, (2) patient discharge data from three states (California, New Jersey and Pennsylvania) and (3) administrative hospital data- from 2005 to 2006. We explored the incidence of 30-day readmission for 160 930 patients with heart failure in 419 acute care hospitals in the USA. Logistic regression was used to assess the effect of missed care on the odds of readmission, adjusting for patient and hospital characteristics. The most frequently missed nursing care activities across all hospitals in our sample included talking to and comforting patients (42.0%), developing and updating care plans (35.8%) and educating patients and families (31.5%). For 4 of the 10 studied care activities, each 10 percentage-point increase in the number of nurses reporting having missed the activity was associated with an increase in the odds of readmission by 2-8% after adjusting for patient and hospital characteristics. However, missed nursing care was no longer a significant predictor of readmission once adjusting for the nurse work environment, except in the case of the delivery of treatments and procedures (OR 1.08, 95% CI 1.02 to 1.14). Missed care is an independent predictor of heart failure readmissions. However, once adjusting for the quality of the nurse work environment, this relationship is attenuated. Improvements in nurses' working conditions may be one strategy to reduce care omissions and improve patient outcomes. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  2. Biomine: predicting links between biological entities using network models of heterogeneous databases

    Directory of Open Access Journals (Sweden)

    Eronen Lauri

    2012-06-01

    Full Text Available Abstract Background Biological databases contain large amounts of data concerning the functions and associations of genes and proteins. Integration of data from several such databases into a single repository can aid the discovery of previously unknown connections spanning multiple types of relationships and databases. Results Biomine is a system that integrates cross-references from several biological databases into a graph model with multiple types of edges, such as protein interactions, gene-disease associations and gene ontology annotations. Edges are weighted based on their type, reliability, and informativeness. We present Biomine and evaluate its performance in link prediction, where the goal is to predict pairs of nodes that will be connected in the future, based on current data. In particular, we formulate protein interaction prediction and disease gene prioritization tasks as instances of link prediction. The predictions are based on a proximity measure computed on the integrated graph. We consider and experiment with several such measures, and perform a parameter optimization procedure where different edge types are weighted to optimize link prediction accuracy. We also propose a novel method for disease-gene prioritization, defined as finding a subset of candidate genes that cluster together in the graph. We experimentally evaluate Biomine by predicting future annotations in the source databases and prioritizing lists of putative disease genes. Conclusions The experimental results show that Biomine has strong potential for predicting links when a set of selected candidate links is available. The predictions obtained using the entire Biomine dataset are shown to clearly outperform ones obtained using any single source of data alone, when different types of links are suitably weighted. In the gene prioritization task, an established reference set of disease-associated genes is useful, but the results show that under favorable

  3. Diastolic tissue Doppler indexes correlate with the degree of collagen expression and cross-linking in heart failure and normal ejection fraction.

    Science.gov (United States)

    Kasner, Mario; Westermann, Dirk; Lopez, Begoña; Gaub, Regina; Escher, Felicitas; Kühl, Uwe; Schultheiss, Heinz-Peter; Tschöpe, Carsten

    2011-02-22

    We attempted to correlate echocardiographic analysis of diastolic function with changes of myocardial collagen in middle-aged patients with heart failure (HF) despite normal ejection fraction (EF). Increased collagen deposition may contribute to the deterioration of the left ventricular compliance and diastolic dysfunction in HF. We investigated 41 patients (median age 50 years [interquartile range: 41 to 57 years]) with normal EF (median 62% [interquartile range: 56% to 70%]) whose endomyocardial biopsies were taken previously. Assessment of diastolic function was performed by mitral-flow and tissue Doppler measurements. Sirius red and immunohistologic staining was performed to determine collagen volume fraction (CVF) and cross-linking, collagen types I and III expression, and lysyl-oxidase (LOX) expression. Expression of collagen messenger ribonucleic acid was determined by real-time polymerase chain reaction. Twenty-six patients with HFNEF with diastolic dysfunction showed a significant increase in total collagen and collagen I expression compared with that of 15 controls. This was accompanied with enhanced collagen cross-linking and LOX overexpression in HFNEF. Among all flow Doppler, only deceleration time of E was associated with CVF (R = 0.43), whereas tissue Doppler parameters correlated with CVF, collagen I at the protein and mRNA levels (E' [R = -0.58, -0.60, -0.45]; E'/A' [R = -0.32, -0.36, -0.31]), and left ventricular filling index (E/E' [R = 0.72, 0.68, 0.63]), respectively. No correlation with collagen III was found. The degree of collagen cross-linking and LOX expression was related to E' (R = -0.55 and -0.60) and E/E' (R = 0.72 and 0.71), respectively, but not to flow Doppler. Collagen overexpression correlated with reduced exercise capacity. Patients with HFNEF showed increased content of myocardial collagen type I, enhanced collagen cross-linking, and LOX expression, which were associated with impaired diastolic tissue Doppler parameters

  4. Exploring the Link between Genetic Relatedness r and Social Contact Structure k in Animal Social Networks.

    Science.gov (United States)

    Wolf, Jochen B W; Traulsen, Arne; James, Richard

    2011-01-01

    Our understanding of how cooperation can arise in a population of selfish individuals has been greatly advanced by theory. More than one approach has been used to explore the effect of population structure. Inclusive fitness theory uses genetic relatedness r to express the role of population structure. Evolutionary graph theory models the evolution of cooperation on network structures and focuses on the number of interacting partners k as a quantity of interest. Here we use empirical data from a hierarchically structured animal contact network to examine the interplay between independent, measurable proxies for these key parameters. We find strong inverse correlations between estimates of r and k over three levels of social organization, suggesting that genetic relatedness and social contact structure capture similar structural information in a real population.

  5. Beyond the Edge: Linking Agricultural Landscapes, Stream Networks, and Best Management Practices.

    Science.gov (United States)

    Kreiling, R M; Thoms, M C; Richardson, W B

    2018-01-01

    Despite much research and investment into understanding and managing nutrients across agricultural landscapes, nutrient runoff to freshwater ecosystems is still a major concern. We argue there is currently a disconnect between the management of watershed surfaces (agricultural landscape) and river networks (riverine landscape). These landscapes are commonly managed separately, but there is limited cohesiveness between agricultural landscape-focused research and river science, despite similar end goals. Interdisciplinary research into stream networks that drain agricultural landscapes is expanding but is fraught with problems. Conceptual frameworks are useful tools to order phenomena, reveal patterns and processes, and in interdisciplinary river science, enable the joining of multiple areas of understanding into a single conceptual-empirical structure. We present a framework for the interdisciplinary study and management of agricultural and riverine landscapes. The framework includes components of an ecosystems approach to the study of catchment-stream networks, resilience thinking, and strategic adaptive management. Application of the framework is illustrated through a study of the Fox Basin in Wisconsin, USA. To fully realize the goal of nutrient reduction in the basin, we suggest that greater emphasis is needed on where best management practices (BMPs) are used within the spatial context of the combined watershed-stream network system, including BMPs within the river channel. Targeted placement of BMPs throughout the riverine landscape would increase the overall buffering capacity of the system to nutrient runoff and thus its resilience to current and future disturbances. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  6. Task-linked Diurnal Brain Network Reorganization in Older Adults: A Graph Theoretical Approach.

    Science.gov (United States)

    Anderson, John A E; Sarraf, Saman; Amer, Tarek; Bellana, Buddhika; Man, Vincent; Campbell, Karen L; Hasher, Lynn; Grady, Cheryl L

    2017-03-01

    Testing older adults in the morning generally improves behavioral performance relative to afternoon testing. Morning testing is also associated with brain activity similar to that of young adults. Here, we used graph theory to explore how time of day (TOD) affects the organization of brain networks in older adults across rest and task states. We used nodes from the automated anatomical labeling atlas to construct participant-specific correlation matrices of fMRI data obtained during 1-back tasks with interference and rest. We computed pairwise group differences for key graph metrics, including small-worldness and modularity. We found that older adults tested in the morning and young adults did not differ on any graph metric. Both of these groups differed from older adults tested in the afternoon during the tasks-but not rest. Specifically, the latter group had lower modularity and small-worldness (indices of more efficient network organization). Across all groups, higher modularity and small-worldness strongly correlated with reduced distractibility on an implicit priming task. Increasingly, TOD is seen as important for interpreting and reproducing neuroimaging results. Our study emphasizes how TOD affects brain network organization and executive control in older adults.

  7. Fast Prediction of HCCI Combustion with an Artificial Neural Network Linked to a Fluid Mechanics Code

    Energy Technology Data Exchange (ETDEWEB)

    Aceves, S M; Flowers, D L; Chen, J; Babaimopoulos, A

    2006-08-29

    We have developed an artificial neural network (ANN) based combustion model and have integrated it into a fluid mechanics code (KIVA3V) to produce a new analysis tool (titled KIVA3V-ANN) that can yield accurate HCCI predictions at very low computational cost. The neural network predicts ignition delay as a function of operating parameters (temperature, pressure, equivalence ratio and residual gas fraction). KIVA3V-ANN keeps track of the time history of the ignition delay during the engine cycle to evaluate the ignition integral and predict ignition for each computational cell. After a cell ignites, chemistry becomes active, and a two-step chemical kinetic mechanism predicts composition and heat generation in the ignited cells. KIVA3V-ANN has been validated by comparison with isooctane HCCI experiments in two different engines. The neural network provides reasonable predictions for HCCI combustion and emissions that, although typically not as good as obtained with the more physically representative multi-zone model, are obtained at a much reduced computational cost. KIVA3V-ANN can perform reasonably accurate HCCI calculations while requiring only 10% more computational effort than a motored KIVA3V run. It is therefore considered a valuable tool for evaluation of engine maps or other performance analysis tasks requiring multiple individual runs.

  8. Default network connectivity is linked to memory status in multiple sclerosis.

    Science.gov (United States)

    Leavitt, Victoria M; Paxton, Jessica; Sumowski, James F

    2014-10-01

    Memory impairment affects 50% of multiple sclerosis (MS) patients. Altered resting-state functional connectivity (FC) has been observed in the default network (DN) of MS patients. No study to date has examined the association of DN FC to its behavioral concomitant, memory. The approach of the present study represents a methodological shift allowing straightforward interpretation of FC alterations in MS, as it presupposes specificity of a network to its paired cognitive function. We examined FC from fMRI collected during rest in the DN of 43 MS patients with and without memory-impairment. Memory-intact patients showed increased DN FC relative to memory-impaired patients. There were no regions of higher FC in memory-impaired patients. DN FC was positively correlated with memory function, such that higher FC was associated with better memory performance. Results were unchanged after controlling for cognitive efficiency, supporting specificity of the DN to memory and not cognitive status more generally. These findings support DN FC as a marker of memory function in MS patients that can be targeted by future treatment interventions. Pairing a functional network with its behavioral concomitant represents a straightforward method for interpreting FC alterations in patients with MS.

  9. Systems Nutrigenomics Reveals Brain Gene Networks Linking Metabolic and Brain Disorders

    Directory of Open Access Journals (Sweden)

    Qingying Meng

    2016-05-01

    Full Text Available Nutrition plays a significant role in the increasing prevalence of metabolic and brain disorders. Here we employ systems nutrigenomics to scrutinize the genomic bases of nutrient–host interaction underlying disease predisposition or therapeutic potential. We conducted transcriptome and epigenome sequencing of hypothalamus (metabolic control and hippocampus (cognitive processing from a rodent model of fructose consumption, and identified significant reprogramming of DNA methylation, transcript abundance, alternative splicing, and gene networks governing cell metabolism, cell communication, inflammation, and neuronal signaling. These signals converged with genetic causal risks of metabolic, neurological, and psychiatric disorders revealed in humans. Gene network modeling uncovered the extracellular matrix genes Bgn and Fmod as main orchestrators of the effects of fructose, as validated using two knockout mouse models. We further demonstrate that an omega-3 fatty acid, DHA, reverses the genomic and network perturbations elicited by fructose, providing molecular support for nutritional interventions to counteract diet-induced metabolic and brain disorders. Our integrative approach complementing rodent and human studies supports the applicability of nutrigenomics principles to predict disease susceptibility and to guide personalized medicine.

  10. A Social Network Analysis of the Financial Links Backing Health and Fitness Apps.

    Science.gov (United States)

    Grundy, Quinn; Held, Fabian; Bero, Lisa

    2017-11-01

    To identify the major stakeholders in mobile health app development and to describe their financial relationships using social network analysis. We conducted a structured content analysis of a purposive sample of prominent health and fitness apps available in November 2015 in the United States, Canada, and Australia. We conducted a social network analysis of apps' developers, investors, other funding sources, and content advisors to describe the financial relationships underpinning health app development. Prominent health and fitness apps are largely developed by private companies based in North America, with an average of 4.7 (SD = 5.5) financial relations, including founders, external investors, acquiring companies, and commercial partnerships. Network analysis revealed a core of 41 sampled apps connected to 415 other entities by 466 financial relations. This core largely comprised apps published by major technology, pharmaceutical, and fashion corporations. About one third of apps named advisors, many of whom had commercial affiliations. Public health needs to extend its scrutiny and advocacy beyond the health messages contained within apps to understanding commercial influences on health and, when necessary, challenging them.

  11. Systems Nutrigenomics Reveals Brain Gene Networks Linking Metabolic and Brain Disorders.

    Science.gov (United States)

    Meng, Qingying; Ying, Zhe; Noble, Emily; Zhao, Yuqi; Agrawal, Rahul; Mikhail, Andrew; Zhuang, Yumei; Tyagi, Ethika; Zhang, Qing; Lee, Jae-Hyung; Morselli, Marco; Orozco, Luz; Guo, Weilong; Kilts, Tina M; Zhu, Jun; Zhang, Bin; Pellegrini, Matteo; Xiao, Xinshu; Young, Marian F; Gomez-Pinilla, Fernando; Yang, Xia

    2016-05-01

    Nutrition plays a significant role in the increasing prevalence of metabolic and brain disorders. Here we employ systems nutrigenomics to scrutinize the genomic bases of nutrient-host interaction underlying disease predisposition or therapeutic potential. We conducted transcriptome and epigenome sequencing of hypothalamus (metabolic control) and hippocampus (cognitive processing) from a rodent model of fructose consumption, and identified significant reprogramming of DNA methylation, transcript abundance, alternative splicing, and gene networks governing cell metabolism, cell communication, inflammation, and neuronal signaling. These signals converged with genetic causal risks of metabolic, neurological, and psychiatric disorders revealed in humans. Gene network modeling uncovered the extracellular matrix genes Bgn and Fmod as main orchestrators of the effects of fructose, as validated using two knockout mouse models. We further demonstrate that an omega-3 fatty acid, DHA, reverses the genomic and network perturbations elicited by fructose, providing molecular support for nutritional interventions to counteract diet-induced metabolic and brain disorders. Our integrative approach complementing rodent and human studies supports the applicability of nutrigenomics principles to predict disease susceptibility and to guide personalized medicine. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  12. Effects of cross-linking molecular weights in a hyaluronic acid-poly(ethylene oxide) hydrogel network on its properties

    Energy Technology Data Exchange (ETDEWEB)

    Noh, Insup [Department of Chemical Engineering, Seoul National University of Technology, 172 Gongnung-dong, Nowon-gu, Seoul 139-743 (Korea, Republic of); Kim, Gun-Woo [Department of Chemical Engineering, Seoul National University of Technology, 172 Gongnung-dong, Nowon-gu, Seoul 139-743 (Korea, Republic of); Choi, Yoon-Jeong [Department of Chemical Engineering, Seoul National University of Technology, 172 Gongnung-dong, Nowon-gu, Seoul 139-743 (Korea, Republic of); Kim, Mi-Sook [Department of Chemical Engineering, Seoul National University of Technology, 172 Gongnung-dong, Nowon-gu, Seoul 139-743 (Korea, Republic of); Park, Yongdoo [Korea Artificial Organ Center, Korea University, Seoul 136-705 (Korea, Republic of); Lee, Kyu-Back [Korea Artificial Organ Center, Korea University, Seoul 136-705 (Korea, Republic of); Kim, In-Sook [Dental Research Institute, Seoul National University, Seoul 110-749 (Korea, Republic of); Hwang, Soon-Jung [Dental Research Institute, Seoul National University, Seoul 110-749 (Korea, Republic of); Tae, Giyoong [Department of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of)

    2006-09-15

    We examined the effects of cross-linking molecular weights on the properties of a hyaluronic acid (HA)-poly(ethylene oxide) (PEO) hydrogel. Swelling behaviors, mechanical strength and rheological behaviors of the HA-PEO hydrogel were evaluated by employing different cross-linking molecular weights (100 kDa and 1.63 mDa) of the HAs in the hydrogel networks. The low molecular weight of HA was obtained in advance by treating high molecular weight HA with a hydrogen chloride solution. Methacrylation of HA was obtained by grafting aminopropylmethacrylate to its caroboxylic acid functional groups. While reduction of the HA molecular weights was confirmed by gel permeation chromatography, the degree of methacrylate grafting to the HA was measured by {sup 1}H-nuclear magnetic resonance. Synthesis of the HA-PEO hydrogel was successfully achieved via the Michael-type addition reaction between the methacrylate arm groups in the HA and the six thiol groups in PEO. The hydrogel formation was not dependent upon the HA molecular weights and its gelation behaviors were markedly different. Compared to the properties of the high molecular weight HA-based PEO one, the low molecular weight HA-based hydrogel induced quicker hydrogelation, as observed from the behaviors of the elastic and viscous modulus. Furthermore, the low molecular weight HA-based hydrogel demonstrated stronger mechanical properties as measured with a texture analyzer, lower water absorption as measured with a microbalance and smaller pore sizes on its surface and cross section as observed with scanning electron microscopy. The information about the effects of the cross-linking molecular weights of the gel network on the properties of the HA-based PEO hydrogel may lead to better design of hydrogels, especially in tissue engineering applications.

  13. Accuracy of interpretation of full-length pediatric echocardiograms transmitted over an integrated services digital network telemedicine link.

    Science.gov (United States)

    Cotton, John L; Gallaher, Keith J; Henry, G William

    2002-09-01

    Transmission of echocardiograms via telemedicine links has allowed remote hospitals direct access to pediatric cardiology subspecialty care. This study assessed the accuracy of echocardiogram interpretation across an integrated services digital network (ISDN) telemedicine link. Telemedicine systems were installed between Cape Fear Valley Medical Center neonatal intensive care unit and University of North Carolina Hospitals. One board-certified pediatric cardiologist interpreted 105 full-length echocardiograms that were videotaped and then transmitted over the system. Six months later, the same cardiologist reinterpreted the 105 original videotape studies from the off-site hospital and results were compared with the interpretations of the transmitted data. Interpretation of transmitted echocardiograms did not differ significantly from the original studies for diagnosis, evaluation of left ventricular function, valve function evaluation, and the presence of a ductus arteriosus. Minor differences in qualitative parameters were seen. Transmission of full-length echocardiograms over the ISDN telemedicine link is comparable to videotape review. There was no loss of significant clinical information, and the minor discrepancies noted did not impact management decisions.

  14. A UV-Induced Genetic Network Links the RSC Complex to Nucleotide Excision Repair and Shows Dose-Dependent Rewiring

    Directory of Open Access Journals (Sweden)

    Rohith Srivas

    2013-12-01

    Full Text Available Efficient repair of UV-induced DNA damage requires the precise coordination of nucleotide excision repair (NER with numerous other biological processes. To map this crosstalk, we generated a differential genetic interaction map centered on quantitative growth measurements of >45,000 double mutants before and after different doses of UV radiation. Integration of genetic data with physical interaction networks identified a global map of 89 UV-induced functional interactions among 62 protein complexes, including a number of links between the RSC complex and several NER factors. We show that RSC is recruited to both silenced and transcribed loci following UV damage where it facilitates efficient repair by promoting nucleosome remodeling. Finally, a comparison of the response to high versus low levels of UV shows that the degree of genetic rewiring correlates with dose of UV and reveals a network of dose-specific interactions. This study makes available a large resource of UV-induced interactions, and it illustrates a methodology for identifying dose-dependent interactions based on quantitative shifts in genetic networks.

  15. A novel mutation in the AVPR2 gene (222delA) associated with X-linked nephrogenic diabetes insipidus in a boy with growth failure.

    Science.gov (United States)

    Abaci, Ayhan; Wood, Kent; Demir, Korcan; Büyükgebiz, Atilla; Böber, Ece; Kopp, Peter

    2010-01-01

    To study the case of a 2 10/12-year-old boy who had growth failure and delayed bone maturation. We reviewed the history, which revealed that he had had polyuria, polydipsia, lack of weight gain, and frequent vomiting since the age of 5 months. On physical examination, his height was 86 cm (-1.93 standard deviation [SD]), his weight 10.5 kg (-2.67 SD), and he had motor and mental retardation. His maternal great-grandfather also had polyuria and polydipsia (but not diabetes mellitus), suggesting X-linked nephrogenic diabetes insipidus as the underlying cause. The patient underwent a water deprivation-desmopressin test. The coding region of the AVPR2 gene was amplified by polymerase chain reaction and submitted to direct sequence analysis. The water deprivation test confirmed the diagnosis of diabetes insipidus, and administration of desmopressin did not diminish his water secretion. Direct sequencing of the AVPR2 gene revealed a novel deletion of adenine at position 222 (222delA) in exon 2. This mutation is predicted to lead to a frameshift beginning at amino acid 75 and a premature stop codon at position 115 (FS75>115X). His height and weight, as well as his motor skills, improved after initiation of therapy with hydrochlorothiazide and amiloride. Growth delay can be associated with diabetes insipidus. The X-linked nephrogenic diabetes insipidus in this boy is caused by a novel mutation in the AVPR2 gene that is predicted to truncate the receptor protein.

  16. Sismos a l'Ecole : a Seismic Educational Network (FRANCE) linked with Research

    Science.gov (United States)

    Berenguer, J.; Le Puth, J.; Courboulex, F.; Zodmi, B.; Boneff, M.

    2007-12-01

    Ahead of the quick evolution of our society, in which scientific information has to be accurately understood by a great majority, the promotion of a responsible behaviour coming from educated and trained citizens has become a priority. One of the roles of school is to enable children to understand sciences, these same sciences that were long ago the prerogative of scientific laboratories. The educational network SISMOS à l\\'"Ecole is an example of a project structured on the knowledge of seismic risks through a scientific and technological approach. It develops a teaching method leading to an approach towards the knowledge of natural disasters. The original and innovating feature of this educational network is to enable students to set up a seismograph in their school. The recorded signals - coming from a regional or a worldwide seismic activity - feed an on- line database, which is in fact a real research centre for seismic resources as well as a starting point for educational and scientific activities. The network, that numbers about thirty stations set up in France, in its overseas departments and territories, and in a couple of French schools abroad, is based upon an experience initiated in the French Riviera ten years ago or so. The achievement of the program has from then on gone beyond the simple purpose of conveying seismic data that research and monitoring centres could have recorded. Thanks to the use of scientific measures, students become involved and get into complex notions revolving around geophysics and geosciences. Developing simple tools, setting up concrete experiments combined with an investigate reasoning makes it easier to build up a quality scientific culture as well as an education of citizens to risks.

  17. Adaptation of irrigation networks to climate change: Linking robust design and stakeholder contribution

    Energy Technology Data Exchange (ETDEWEB)

    Granados, A.; Martín-Carrasco, F.J.; García de Jalón, S.; Iglesias, A.

    2015-07-01

    Agriculture is a particularly sensitive sector to the potential impacts of climate change. Thus, irrigation infrastructure is required to be robust to cope with these potential threats. The objective of this research is designing more robust irrigation networks, considering cost and stakeholder contribution. To that end, the investigation was addressed in three phases: a sensitivity analysis to understand the effectiveness of the distinct variables, a cost-effectiveness analysis assessing their efficiency, and a global study of the most efficient variables to provide an insight into their function. The sensitivity analysis indicates that the networks oversized by means of the coefficient of utilisation or the factor of safety, behave better than those oversized via the continuous specific discharge; moreover, the degree of freedom has been shown ineffective. The cost-effectiveness analysis shows that the coefficient of utilisation and the factor of safety are the most efficient variables, as they introduced safety margin oversizing fewer network elements and to a lesser extent than the continuous specific discharge. It also shows that stakeholder contribution, conveyed as a reduction of the degree of freedom, plays an important role in the network’s adaptive capacity to change. The global study of these variables reveals the subtlety of the coefficient of utilisation, which is the variable that better reproduces the farmer behaviour during demand increase scenarios. In conclusion, the results identify the coefficient of utilisation as the variable which provides the safest margins and reveal the importance of stakeholder contribution in absorb the demand increase in a better manner. (Author)

  18. Microvoid formation and strain hardening in highly cross-linked polymer networks.

    Science.gov (United States)

    Mukherji, Debashish; Abrams, Cameron F

    2008-11-01

    Using molecular dynamics simulations of a generic model, we observe strain hardening in highly cross-linked polymer glasses under tensile deformation. We show that formation of microvoids, without bond breaking, constitutes the microscopic origins of strain hardening. A well-defined functional form is observed for the void size distribution that is consistent with voids in dense equilibrium Lennard-Jones particle packings, independent of strain. Microvoid-based strain hardening is not observed in a separate model with tetrahedral bond angle constraints, indicating that flexible cross-linkers are the key factor in the development of strain hardening behavior.

  19. Evaluation of a discrete 4-PAM optical link for future automotive networks

    OpenAIRE

    Soenen, Wouter; Vaernewyck, Renato; Bauwelinck, Johan

    2012-01-01

    A comparative study is presented between NRZ and 4-PAM to investigate the feasibility of Gigabit transmission in automotive optical networks. The system utilizes a SI-PCS fiber and an 850 nm VCSEL as transmitter. Laser driver and receiver are realized with discrete transistors at board level. Eye diagram measurements reveal that 4-PAM outperforms NRZ using 1m and 6m of fiber. Bitrates of 2 Gb/s are achieved at a BER ≤ 100000. Covering longer distances shows that SI-PCS introduces severe dispe...

  20. An Energy-Efficient Link Layer Protocol for Reliable Transmission over Wireless Networks

    Directory of Open Access Journals (Sweden)

    Iqbal Adnan

    2009-01-01

    Full Text Available In multihop wireless networks, hop-by-hop reliability is generally achieved through positive acknowledgments at the MAC layer. However, positive acknowledgments introduce significant energy inefficiencies on battery-constrained devices. This inefficiency becomes particularly significant on high error rate channels. We propose to reduce the energy consumption during retransmissions using a novel protocol that localizes bit-errors at the MAC layer. The proposed protocol, referred to as Selective Retransmission using Virtual Fragmentation (SRVF, requires simple modifications to the positive-ACK-based reliability mechanism but provides substantial improvements in energy efficiency. The main premise of the protocol is to localize bit-errors by performing partial checksums on disjoint parts or virtual fragments of a packet. In case of error, only the corrupted virtual fragments are retransmitted. We develop stochastic models of the Simple Positive-ACK-based reliability, the previously-proposed Packet Length Optimization (PLO protocol, and the SRVF protocol operating over an arbitrary-order Markov wireless channel. Our analytical models show that SRVF provides significant theoretical improvements in energy efficiency over existing protocols. We then use bit-error traces collected over different real networks to empirically compare the proposed and existing protocols. These experimental results further substantiate that SRVF provides considerably better energy efficiency than Simple Positive-ACK and Packet Length Optimization protocols.