Search results for "connectivity"
showing 10 items of 246 documents
Pre- and post-ictal brain activity characterization using combined source decomposition and connectivity estimation in epileptic children
2019
In this research, the study of functional connectivity between sources of electroencephalogram (EEG) activity assessed for different classes (well before seizure, preictal and post-ictal) was performed. EEG recordings were acquired from 12 subjects with focal epilepsy. Then, ten common spatial patterns (CSP) were obtained for EEG segments describing 95% of Riemannian distance between pairs of classes, followed by estimation of multivariate autoregressive (MVAR) models’ coefficients. The MVAR models were further used to extract coherence as a functional connectivity measures. Our results show that the coherence between CSP sources differs between baseline and pre-ictal segments: it has the l…
Multivariate Frequency Domain Analysis of Causal Interactions in Physiological Time Series
2011
A common way of obtaining information about a physiological system is to measure one or more signals from the system, consider their temporal evolution in the form of numerical time series, and obtain quantitative indexes through the application of time series analysis techniques. While historical approaches to time series analysis were addressed to the study of single signals, recent advances have made it possible to study collectively the behavior of several signals measured simultaneously from the considered system. In fact, multivariate (MV) time series analysis is nowadays extensively used to characterize interdependencies among multiple signals collected from dynamical physiological s…
Clustering-Based Algorithm for Connectivity Maintenance in Vehicular Ad-Hoc Networks
2014
International audience; Among recent advances in wireless communication technologies' field, Vehicular Ad-hoc Networks (VANETs) have drawn the attention of both academic and industry researchers due to their potential applications including driving safety, entertainment, emergency applications, and content sharing. VANET networks are characterized by their high mobile topology changes. Clustering is one of the control schemes used to make this global topology less dynamic. It allows the formation of dynamic virtual backbone used to organize the medium access, to support quality of service and to simplify routing. Mainly, nodes are organized into clusters with at least one cluster head (CH) …
Data Backup Dilemma
2016
When the Great East Japan Earthquake struck in 2011, several municipalities lost their residential data including backup. Since none of them had ever considered the total loss of data, data backup policy had been paid little attention. In many cases, the backup tapes were simply stored inside the server room, just beside the server rack. Following the calamity, the Japanese national government tried to introduce a data backup system to municipalities using the cloud. The purpose was to secure the safekeeping of backup data. However, municipalities were reluctant to go along with this since overcoming the loss of network connectivity during an earthquake remained foremost in their minds. The…
Disconnected Graph Layout and the Polyomino Packing Approach
2002
Conference name: GD: International Symposium on Graph Drawing 9th International Symposium Date of Conference: 23–26 September 2001 We review existing algorithms and present a new approach for layout of disconnected graphs. The new approach is based on polyomino representation of components as opposed to rectangles. The parameters of our algorithm and their influence on the drawings produced as well as a variation of the algorithm for multiple pages are discussed. We also analyze our algorithm both theoretically and experimentally and compare it with the existing ones. The new approach produces much more compact and uniform drawings than previous methods. © Springer-Verlag Berlin Heidelberg …
Functional Connectivity of Nucleus Accumbens and Medial Prefrontal Cortex With Other Brain Regions During Early-Abstinence Is Associated With Alcohol…
2021
Background: Alcohol dependence (AD) is a chronic recurrent brain disease that causes a heavy disease burden worldwide, partly due to high relapse rates after detoxification. Verified biomarkers are not available for AD and its relapse, although the nucleus accumbens (NAc) and medial prefrontal cortex (mPFC) may play important roles in the mechanism of addiction. This study investigated AD- and relapse-associated functional connectivity (FC) of the NAc and mPFC with other brain regions during early abstinence.Methods: Sixty-eight hospitalized early-abstinence AD male patients and 68 age- and education-matched healthy controls (HCs) underwent resting-functional magnetic resonance imaging (r-f…
Paysage & [et] infrastructures de transport : modélisation des impacts des infrastructures sur les réseaux écologiques
2013
The development of linear infrastructures leads to the fragmentation and the artificialisation of the landscape across scales. Landscape fragmentation is a spatial process that is accompanied by a progressive decrease of the connectivity between the elements needed to conduct ecological processes. Thus, maintaining a good level of connectivity between natural habitats, compatible with human activities, has become a major issue for the preservation of biodiversity.By mobilizing methods from graph theory and landscape ecology, the thesis seeks to demonstrate the value of landscape graphs to model ecological networks and analyze impacts of transportation infrastructures at regional scale.The m…
Left but not right temporal involvement in opaque idiom comprehension: a repetitive transcranial magnetic stimulation study
2004
Abstract It has been suggested that figurative language, which includes idioms, is controlled by the right hemisphere. We tested the right hemisphere hypothesis by using repetitive transcranial magnetic stimulation (rTMS) to transiently disrupt the function of the frontal and temporal areas of the right versus left hemisphere in a group of normal participants involved in a task of opaque idiom versus literal sentence comprehension. Forty opaque, nonambiguous idioms were selected. Fifteen young healthy participants underwent rTMS in two sessions. The experiment was run in five blocks, corresponding to the four stimulated scalp positions (left frontal and temporal and right frontal and tempor…
Effect of Topological Structure and Coupling Strength in Weighted Multiplex Networks
2018
Algebraic connectivity (second smallest eigenvalue of the supra-Laplacian matrix of the underlying multilayer network) and inter-layer coupling strength play an important role in the diffusion processes on the multiplex networks. In this work, we study the effect of inter-layer coupling strength, topological structure on algebraic connectivity in weighted multiplex networks. The results show a remarkable transition in the value of algebraic connectivity from classical cases where the inter-layer coupling strength is homogeneous. We investigate various topological structures in multiplex networks using configuration model, the Barabasi-Albert model (BA) and empirical data-set of multiplex ne…
On complete metric spaces containing the Sierpinski curve
1998
It is proved that a complete metric space topologically contains the Sierpiński universal plane curve if and only if it has a subset with so-called bypass property, i.e. it has a subset K K containing an arc such that for each a ∈ K a\in K and for each open arc A ⊂ K A\subset K with a ∈ A a\in A , there exists an arbitrary small arc in K ∖ { a } K\setminus \{a\} joining the two components of A ∖ { a } A\setminus \{a\} .