4 research outputs found
Correlated multiplexity and connectivity of multiplex random networks
Nodes in a complex networked system often engage in more than one type of
interactions among them; they form a multiplex network with multiple types of
links. In real-world complex systems, a node's degree for one type of links and
that for the other are not randomly distributed but correlated, which we term
correlated multiplexity. In this paper we study a simple model of multiplex
random networks and demonstrate that the correlated multiplexity can
drastically affect the properties of giant component in the network.
Specifically, when the degrees of a node for different interactions in a duplex
Erdos-Renyi network are maximally correlated, the network contains the giant
component for any nonzero link densities. In contrast, when the degrees of a
node are maximally anti-correlated, the emergence of giant component is
significantly delayed, yet the entire network becomes connected into a single
component at a finite link density. We also discuss the mixing patterns and the
cases with imperfect correlated multiplexity.Comment: Revised version, 12 pages, 6 figure
Suppressing cascades of load in interdependent networks
Understanding how interdependence among systems affects cascading behaviors
is increasingly important across many fields of science and
engineering.Inspired by cascades of load shedding in coupled electric grids and
other infrastructure, we study the Bak-Tang-Wiesenfeld sandpile model on
modular random graphs and on graphs based on actual, interdependent power
grids. Starting from two isolated networks, adding some connectivity between
them is beneficial, for it suppresses the largest cascades in each system. Too
much interconnectivity, however, becomes detrimental for two reasons. First,
interconnections open pathways for neighboring networks to inflict large
cascades. Second, as in real infrastructure, new interconnections increase
capacity and total possible load, which fuels even larger cascades. Using a
multitype branching process and simulations we show these effects and estimate
the optimal level of interconnectivity that balances their tradeoffs. Such
equilibria could allow, for example, power grid owners to minimize the largest
cascades in their grid. We also show that asymmetric capacity among
interdependent networks affects the optimal connectivity that each prefers and
may lead to an arms race for greater capacity. Our multitype branching process
framework provides building blocks for better prediction of cascading processes
on modular random graphs and on multi-type networks in general.Comment: Accepted to PNAS Plus. Author summary: 2 pages, 1 figure. Main paper:
13 pages, 7 figures. Supporting information: 7 pages, 10 figure
Transcriptome Profiling of Citrus Fruit Response to Huanglongbing Disease
Huanglongbing (HLB) or “citrus greening” is the most destructive citrus disease worldwide. In this work, we studied host responses of citrus to infection with Candidatus Liberibacter asiaticus (CaLas) using next-generation sequencing technologies. A deep mRNA profile was obtained from peel of healthy and HLB-affected fruit. It was followed by pathway and protein-protein network analysis and quantitative real time PCR analysis of highly regulated genes. We identified differentially regulated pathways and constructed networks that provide a deep insight into the metabolism of affected fruit. Data mining revealed that HLB enhanced transcription of genes involved in the light reactions of photosynthesis and in ATP synthesis. Activation of protein degradation and misfolding processes were observed at the transcriptomic level. Transcripts for heat shock proteins were down-regulated at all disease stages, resulting in further protein misfolding. HLB strongly affected pathways involved in source-sink communication, including sucrose and starch metabolism and hormone synthesis and signaling. Transcription of several genes involved in the synthesis and signal transduction of cytokinins and gibberellins was repressed while that of genes involved in ethylene pathways was induced. CaLas infection triggered a response via both the salicylic acid and jasmonic acid pathways and increased the transcript abundance of several members of the WRKY family of transcription factors. Findings focused on the fruit provide valuable insight to understanding the mechanisms of the HLB-induced fruit disorder and eventually developing methods based on small molecule applications to mitigate its devastating effects on fruit production