Search results for "Connectivity"
showing 10 items of 246 documents
Impacts écologiques des formes d'urbanisation : modélisations urbaines et paysagères
2015
The global increase of urbanization during the past decades have induced a progressive artificialization of natural environments. The building of transport infrastructures and new housings causes a landscape fragmentation in an irreversible way and a strong decrease of the connectivity of ecological habitats. Maintaining the functionality of ecological networks is becoming a major goal of sustainable urban planning policies. With a special focus on urban evolutions in the horizon 2030 in the urban area of Besançon in eastern France (residential development and road traffic evolutions), this thesis aims to assess the potential impact of urban forms on landscape connectivity of animal species…
Decremental 2- and 3-connectivity on planar graphs
1996
We study the problem of maintaining the 2-edge-, 2-vertex-, and 3-edge-connected components of a dynamic planar graph subject to edge deletions. The 2-edge-connected components can be maintained in a total ofO(n logn) time under any sequence of at mostO(n) deletions. This givesO(logn) amortized time per deletion. The 2-vertex- and 3-edge-connected components can be maintained in a total ofO(n log2n) time. This givesO(log2n) amortized time per deletion. The space required by all our data structures isO(n). All our time bounds improve previous bounds.
Multivariate EEG spectral analysis evidences the functional link between motor and visual cortex during integrative sensorimotor tasks
2012
The identification of the networks connecting brain areas and the understanding of their role in executing complex tasks is a crucial issue in cognitive neuroscience. In this study, specific visuomotor tasks were devised to reveal the functional network underlying the cooperation process between visual and motor regions. Electroencephalography (EEG) data were recorded from twelve healthy subjects during a combined visuomotor task, which integrated precise grip motor commands with sensory visual feedback (VM). This condition was compared with control tasks involving pure motor action (M), pure visual perception (V) and visuomotor performance without feedback (V + M). Multivariate parametric …
Técnicas de análisis de posproceso en resonancia magnetica parael estudio de la conectividad cerebral
2011
Brain connectivity is a key concept for understanding brain function. Current methods to detect and quantify different types of connectivity with neuroimaging techniques are fundamental for understanding the pathophysiology of many neurologic and psychiatric disorders. This article aims to present a critical review of the magnetic resonance imaging techniques used to measure brain connectivity within the context of the Human Connectome Project. We review techniques used to measure: a) structural connectivity b) functional connectivity (main component analysis, independent component analysis, seed voxel, meta-analysis), and c) effective connectivity (psychophysiological interactions, causal …
The role of soils in regulation and provision of blue and green water
2021
The United Nations Sustainable Development Goal 6 aims for clean water and sanitation for all by 2030, through eight subgoals dealing with four themes: (i) water quantity and availability, (ii) water quality, (iii) finding sustainable solutions and (iv) policy and governance. In this opinion paper, we assess how soils and associated land and water management can help achieve this goal, considering soils at two scales: local soil health and healthy landscapes. The merging of these two viewpoints shows the interlinked importance of the two scales. Soil health reflects the capacity of a soil to provide ecosystem services at a specific location, taking into account local climate and soil condit…
Connectivity in hydrology and sediment dynamics
2020
Connectivity has emerged as a significant conceptual framework for understanding the transfer of surface water and sediment through landscapes. The concept has been widely adopted in the field of catchment hydrology but has also been valuable to investigate rates of soil erosion by water and sediment export across landscapes. To study connectivity, we gathered a group of scientists that worked on synthesizing and consolidating all theories and aspects of connectivity research. Within the EU-funded ESSEM COST Action CONNECTEUR (ES1306), five working groups were established: (a) theory, (b) measuring, (c) modelling, (d) indices, and (e) society. One of the outputs of this COST Action is this …
Expanding genetic graphs' potential to analyse ecological connectivity: assessment of graphs construction methods
2019
International audience; Dispersal movements are often constrained in human-shaped landscapes, thereby threatening species survival. Landscape genetics approaches are commonly used to analyse ecological connectivity because genetic data well reflect dispersal capacities. When species occupy discrete habitat patches, graph-theoretic methods are a particularly relevant approach to study dispersal-driven gene flow. The links of a genetic graph can be weighted using different genetic distances between populations (nodes). Similarly, graph pruning (link set selection) can rely on different criteria. However, despite growing interest in genetic graphs, the influence of these parameters remains mos…
A multispecies approach for modeling the ecological impact of urban development using landscape graphs
2013
International audience; Managing urban sprawl is become a major concern in the field of landscape ecology, since the land use changes involved by urban development may affect the ability of wildlife species to move across the landscape. In order to compare the ecological impact of several urban patterns, we aim at combining two complementary approaches: 1) Simulations of residential development from an initial land use map, using morphological rules of urban development (i.e. fractal vs non fractal) and accessibility constraints; 2) Models of ecological networks applied to a given natural habitat, using a landscape graphs-based approach. As landscape graphs are built according to the moving…
Graphab: A software dedicated to the modelling of landscape networks
2016
International audience; Land cover changes resulting from urban sprawl, transport network intensification and agricultural changes contribute to fragment wildlife habitats and may lead to question viability of animal and plant populations. Landscape ecologists have shown that populations living in fragmented habitats are forced to adopt specific dynamics (patchy populations or metapopulations) making them highly dependent on fluxes between their habitat patches. Landscape connectivity may be defined as the functional response of a given species in terms of movement and individual fluxes to the potential links between habitat patches provided by the landscape structure.Many methods are used …
Assessing habitat connectivity of the lesser horseshoe bat using graph theory to explain its distribution
2011
The lesser horseshoe bat, Rhinolophus hipposideros was formerly widespread and quite common in north-western Europe, but has undergone a dramatic decline from the 1960s. The main hypothesis for this decline is a change of habitat quality. Recent works have stressed the importance of good connection between roosts and foraging areas by tree lines and well-structured hedgerows. Thus, landscape connectivity is assumed to be a key-factor for population sustainability. The present study is based on a case study in Franche-Comté (France). Its purpose is to model the distribution of the lesser horseshoe bat and to characterize the functional connectivity of its habitat. Graph theory is used effici…