Communities as Well Separated Subgraphs With Cohesive Cores: Identification of Core-Periphery Structures in Link Communities

Communities in networks are commonly considered as highly cohesive subgraphs which are well separated from the rest of the network. However, cohesion and separation often cannot be maximized at the same time, which is why a compromise is sought by some methods. When a compromise is not suitable for the problem to be solved it might be advantageous to separate the two criteria. In this paper, we explore such an approach by defining communities as well separated subgraphs which can have one or more cohesive cores surrounded by peripheries. We apply this idea to link communities and present an algorithm for constructing hierarchical core-periphery structures in link communities and first test results.Comment: 12 pages, 2 figures, submitted version of a paper accepted for the 7th International Conference on Complex Networks and Their Applications, December 11-13, 2018, Cambridge, UK; revised version at http://141.20.126.227/~qm/papers

Influence of wiring cost on the large-scale architecture of human cortical connectivity

In the past two decades some fundamental properties of cortical connectivity have been discovered: small-world structure, pronounced hierarchical and modular organisation, and strong core and rich-club structures. A common assumption when interpreting results of this kind is that the observed structural properties are present to enable the brain's function. However, the brain is also embedded into the limited space of the skull and its wiring has associated developmental and metabolic costs. These basic physical and economic aspects place separate, often conflicting, constraints on the brain's connectivity, which must be characterized in order to understand the true relationship between brain structure and function. To address this challenge, here we ask which, and to what extent, aspects of the structural organisation of the brain are conserved if we preserve specific spatial and topological properties of the brain but otherwise randomise its connectivity. We perform a comparative analysis of a connectivity map of the cortical connectome both on high- and low-resolutions utilising three different types of surrogate networks: spatially unconstrained (‘random’), connection length preserving (‘spatial’), and connection length optimised (‘reduced’) surrogates. We find that unconstrained randomisation markedly diminishes all investigated architectural properties of cortical connectivity. By contrast, spatial and reduced surrogates largely preserve most properties and, interestingly, often more so in the reduced surrogates. Specifically, our results suggest that the cortical network is less tightly integrated than its spatial constraints would allow, but more strongly segregated than its spatial constraints would necessitate. We additionally find that hierarchical organisation and rich-club structure of the cortical connectivity are largely preserved in spatial and reduced surrogates and hence may be partially attributable to cortical wiring constraints. In contrast, the high modularity and strong s-core of the high-resolution cortical network are significantly stronger than in the surrogates, underlining their potential functional relevance in the brain

Wiederauffindung von wiederverwendbaren Software-Dokumenten: Repraesentationsmethoden und Suchverfahren

Available from TIB Hannover: RR 8166(95-01) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBayerische Forschungsstiftung, Muenchen (Germany)DEGerman

Plasma placental RNA allelic ratio permits noninvasive prenatal chromosomal aneuploidy detection

Current methods for prenatal diagnosis of chromosomal aneuploidies involve the invasive sampling of fetal materials using procedures such as amniocentesis or chorionic villus sampling and constitute a finite risk to the fetus. Here, we outline a strategy for fetal chromosome dosage assessment that can be performed noninvasively through analysis of placental expressed mRNA in maternal plasma. We achieved noninvasive prenatal diagnosis of fetal trisomy 21 by determining the ratio between alleles of a single-nucleotide polymorphism (SNP) in PLAC4 mRNA, which is transcribed from chromosome 21 and expressed by the placenta, in maternal plasma. PLAC4 mRNA in maternal plasma was fetal derived and cleared after delivery. The allelic ratios in maternal plasma correlated with those in the placenta. Fetal trisomy 21 was detected noninvasively in 90% of cases and excluded in 96.5% of control