1,006 research outputs found
Adaptive networks: coevolution of disease and topology
Adaptive networks have been recently introduced in the context of disease
propagation on complex networks. They account for the mutual interaction
between the network topology and the states of the nodes. Until now, existing
models have been analyzed using low-complexity analytic formalisms, revealing
nevertheless some novel dynamical features. However, current methods have
failed to reproduce with accuracy the simultaneous time evolution of the
disease and the underlying network topology. In the framework of the adaptive
SIS model of Gross et al. [Phys. Rev. Lett. 96, 208701 (2006)], we introduce an
improved compartmental formalism able to handle this coevolutionary task
successfully. With this approach, we analyze the interplay and outcomes of both
dynamical elements, process and structure, on adaptive networks featuring
different degree distributions at the initial stage.Comment: 11 pages, 8 figures, 1 appendix. To be published in Physical Review
Exact solution of bond percolation on small arbitrary graphs
We introduce a set of iterative equations that exactly solves the size
distribution of components on small arbitrary graphs after the random removal
of edges. We also demonstrate how these equations can be used to predict the
distribution of the node partitions (i.e., the constrained distribution of the
size of each component) in undirected graphs. Besides opening the way to the
theoretical prediction of percolation on arbitrary graphs of large but finite
size, we show how our results find application in graph theory, epidemiology,
percolation and fragmentation theory.Comment: 5 pages and 3 figure
Modeling the dynamical interaction between epidemics on overlay networks
Epidemics seldom occur as isolated phenomena. Typically, two or more viral
agents spread within the same host population and may interact dynamically with
each other. We present a general model where two viral agents interact via an
immunity mechanism as they propagate simultaneously on two networks connecting
the same set of nodes. Exploiting a correspondence between the propagation
dynamics and a dynamical process performing progressive network generation, we
develop an analytic approach that accurately captures the dynamical interaction
between epidemics on overlay networks. The formalism allows for overlay
networks with arbitrary joint degree distribution and overlap. To illustrate
the versatility of our approach, we consider a hypothetical delayed
intervention scenario in which an immunizing agent is disseminated in a host
population to hinder the propagation of an undesirable agent (e.g. the spread
of preventive information in the context of an emerging infectious disease).Comment: Accepted for publication in Phys. Rev. E. 15 pages, 7 figure
Comportement du béton de chanvre en compression simple et cisaillement
International audience Dans la littérature, la plupart des mélanges chaux/chanvre étudiés montrent un comportement fragile et une très faible résistance mécanique. Les formulations sont généralement riches en liant et légèrement compactées. Jusqu'à présent, ce matériau n'est pas considéré comme un matériau porteur et est principalement utilisé comme isolant de remplissage, combiné avec des composants de structure en bois, en béton ou en maçonnerie. Le présent travail est une étude expérimentale du comportement du béton de chanvre à la compression et au cisaillement, afin d'évaluer la capacité porteuse et au contreventement de ce matériau bio-sourcé, tout en assurant de bonnes qualités d'isolation thermique. Deux séries de tests sont effectuées. Le premier est un test de compression uniaxiale dans chaque direction pour caractériser l'anisotropie mécanique du matériau. Le second permet de caractériser le comportement au cisaillement de différentes configurations de la composition. Les expériences réalisées montrent une ductilité élevée de ce matériau en cisaillement, ce qui confirme les résultats de la littérature sur les structures de paroi. Ces résultats sont très prometteurs, notamment pour des applications parasismiques.</p
Understanding the Behavior of Sulfidic Colloids in the Presence of Metals
Riverton, Wyoming was host to a former uranium and vanadium ore processing plant, which operated from 1958 to 1963. The milling operations at the site contaminated the surface and shallow groundwater. The area became a Department of Energy (DOE) legacy site, where the U.S. Nuclear Regulatory Commission approved the DOE’s natural flushing compliance strategy. Up until the flooding in 2010, the natural flushing compliance strategy was going underway as expected. Sampling after the flood revealed a significant increase in contaminant concentration.
New updated models need to be developed to help understand the situation at Riverton, for which this laboratory experiment is conducted. We want to understand the behavior of sulfidic colloids in the groundwater to the presence of metals. At the lab of Stanford’s Green Earth Sciences Building, samples of Riverton groundwater solution and 0.1 M NaCl water solution were place under different parameters. These parameters were: different Ferrihydrite and Sulfur ratios (0.05, 0.1, 0.5, and 2), the duration of agitation (3h, 9h, 24h, 48h, 3d, 5d, 10d, and 14d), and the metals used (Uranium, Zinc, Copper, Nickel, and Molybdenum). The generation of sulfidic colloids is closely monitored throughout the progression of the experiment, which will give insight to their behavior
Water column gradients beneath the summer ice of a High Arctic freshwater lake as indicators of sensitivity to climate change
Ice cover persists throughout summer over many lakes at extreme polar latitudes but is likely to become increasingly rare with ongoing climate change. Here we addressed the question of how summer ice-cover affects the underlying water column of Ward Hunt Lake, a freshwater lake in the Canadian High Arctic, with attention to its vertical gradients in limnological properties that would be disrupted by ice loss. Profiling in the deepest part of the lake under thick mid-summer ice revealed a high degree of vertical structure, with gradients in temperature, conductivity and dissolved gases. Dissolved oxygen, nitrous oxide, carbon dioxide and methane rose with depth to concentrations well above air-equilibrium, with oxygen values at >150% saturation in a mid water column layer of potential convective mixing. Fatty acid signatures of the seston also varied with depth. Benthic microbial mats were the dominant phototrophs, growing under a dim green light regime controlled by the ice cover, water itself and weakly colored dissolved organic matter that was mostly autochthonous in origin. In this and other polar lakes, future loss of mid-summer ice will completely change many water column properties and benthic light conditions, resulting in a markedly different ecosystem regime
Creación de un entorno virtual en Houdini con animaciones y simulaciones controladas por audio
El proyecto trata sobre la creación de un entorno virtual en el que se van a producir
animaciones y simulaciones 3D, haciendo uso del software de Houdini, y de la creación
de una canción en Cakewalk que controle el funcionamiento de los efectos.
Una parte importante del proyecto se basa en mostrar la eficacia de producir dichas
animaciones y simulaciones disponiendo del archivo original de la música, ya que con
este archivo se podrÃan exportar diferentes pistas, instrumentos o sonidos de la propia
canción producida.
Poder optar a obtener archivos separados por grupos de instrumentos o sonidos es
una gran ventaja, porque posibilita gestionar el procesamiento del audio dentro de
Houdini y su resultado estético final. Esto se debe a que en una canción, no todos los
sonidos e instrumentos tienen la misma intensidad. Clasificarlos por grupos en función
de su rango dinámico y aplicarlos en diferentes animaciones mediante un proceso de
gestión del audio facilita que el resultado pueda ajustarse de manera mucho más
precisa. Además, esta práctica mejora el resultado final, ya que se facilita la distinción
de los diferentes instrumentos y sonidos de manera visual.
Finalmente, en este proyecto se propone crear un vÃdeo final de alta calidad como
resultado de la ejecución de los efectos y la música en el que se va a enseñar el
aspecto que podrÃa tener un entorno virtual con elementos que reaccionan al audi
Propagation dynamics on networks featuring complex topologies
Analytical description of propagation phenomena on random networks has
flourished in recent years, yet more complex systems have mainly been studied
through numerical means. In this paper, a mean-field description is used to
coherently couple the dynamics of the network elements (nodes, vertices,
individuals...) on the one hand and their recurrent topological patterns
(subgraphs, groups...) on the other hand. In a SIS model of epidemic spread on
social networks with community structure, this approach yields a set of ODEs
for the time evolution of the system, as well as analytical solutions for the
epidemic threshold and equilibria. The results obtained are in good agreement
with numerical simulations and reproduce random networks behavior in the
appropriate limits which highlights the influence of topology on the processes.
Finally, it is demonstrated that our model predicts higher epidemic thresholds
for clustered structures than for equivalent random topologies in the case of
networks with zero degree correlation.Comment: 10 pages, 5 figures, 1 Appendix. Published in Phys. Rev. E (mistakes
in the PRE version are corrected here
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