Stable, metastable and unstable states in the mean-field RFIM at T=0

We compute the probability of finding metastable states at a given field in the mean-field random field Ising model at T=0. Remarkably, this probability is finite in the thermodynamic limit, even on the so-called ``unstable'' branch of the magnetization curve. This implies that the branch is reachable when the magnetization is controlled instead of the magnetic field, in contrast with the situation in the pure system.Comment: 10 pages, 3 figure

Prominent effect of soil network heterogeneity on microbial invasion

Using a network representation for real soil samples and mathematical models for microbial spread, we show that the structural heterogeneity of the soil habitat may have a very significant influence on the size of microbial invasions of the soil pore space. In particular, neglecting the soil structural heterogeneity may lead to a substantial underestimation of microbial invasion. Such effects are explained in terms of a crucial interplay between heterogeneity in microbial spread and heterogeneity in the topology of soil networks. The main influence of network topology on invasion is linked to the existence of long channels in soil networks that may act as bridges for transmission of microorganisms between distant parts of soil

Flow Path Resistance in Heterogeneous Porous Media Recast into a Graph-Theory Problem

Acknowledgment is made to the U.S. NSF (EAR-1847689) and the Donors of the American Chemical Society Petroleum Research Fund (59864-DNI9) for partial support of this research. The authors also thank Drs Matthias Willmann, Jefrey Hyman and Markus Holzner for assistance with numerical simulations and insightful discussionsPeer reviewedPublisher PD

Emergence of log-normal type distributions in avalanche processes in living systems : a network model

Funding We acknowledge financial support from the Agence Nationale de la Recherche (ANR grant number ANR-18-CE45-0012-01) and from the French Research Minister (MESRI) for SP. PhD funding. Acknowledgments We are very grateful for the participants of the second ISINP meeting at Lake Como for stimulating exchanges about our talk. We are thanful to P. Argoul, A. Guillet, E. Hartè, L. Delmarre for fruitful discussions. SP wishes to thank T. Matteuzzi for his inspiring considerations. We are indebted to Erika Polizzi for her graphical help.Peer reviewedPublisher PD

Spanning avalanches in the three-dimensional Gaussian Random Field Ising Model with metastable dynamics: field dependence and geometrical properties

Spanning avalanches in the 3D Gaussian Random Field Ising Model (3D-GRFIM) with metastable dynamics at T=0 have been studied. Statistical analysis of the field values for which avalanches occur has enabled a Finite-Size Scaling (FSS) study of the avalanche density to be performed. Furthermore, direct measurement of the geometrical properties of the avalanches has confirmed an earlier hypothesis that several kinds of spanning avalanches with two different fractal dimensions coexist at the critical point. We finally compare the phase diagram of the 3D-GRFIM with metastable dynamics with the same model in equilibrium at T=0.Comment: 16 pages, 17 figure

Complexity and anisotropy in host morphology make populations safer against epidemic outbreaks

One of the challenges in epidemiology is to account for the complex morphological structure of hosts such as plant roots, crop fields, farms, cells, animal habitats and social networks, when the transmission of infection occurs between contiguous hosts. Morphological complexity brings an inherent heterogeneity in populations and affects the dynamics of pathogen spread in such systems. We have analysed the influence of realistically complex host morphology on the threshold for invasion and epidemic outbreak in an SIR (susceptible-infected-recovered) epidemiological model. We show that disorder expressed in the host morphology and anisotropy reduces the probability of epidemic outbreak and thus makes the system more resistant to epidemic outbreaks. We obtain general analytical estimates for minimally safe bounds for an invasion threshold and then illustrate their validity by considering an example of host data for branching hosts (salamander retinal ganglion cells). Several spatial arrangements of hosts with different degrees of heterogeneity have been considered in order to analyse separately the role of shape complexity and anisotropy in the host population. The estimates for invasion threshold are linked to morphological characteristics of the hosts that can be used for determining the threshold for invasion in practical applications.Comment: 21 pages, 8 figure

Modelling avalanches in martensites

Solids subject to continuous changes of temperature or mechanical load often exhibit discontinuous avalanche-like responses. For instance, avalanche dynamics have been observed during plastic deformation, fracture, domain switching in ferroic materials or martensitic transformations. The statistical analysis of avalanches reveals a very complex scenario with a distinctive lack of characteristic scales. Much effort has been devoted in the last decades to understand the origin and ubiquity of scale-free behaviour in solids and many other systems. This chapter reviews some efforts to understand the characteristics of avalanches in martensites through mathematical modelling.Comment: Chapter in the book "Avalanches in Functional Materials and Geophysics", edited by E. K. H. Salje, A. Saxena, and A. Planes. The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-319-45612-6_

Beneficios del Uso de Herramientas Participativas para Apoyar el Aprendizaje Curricular de los Estudiantes: 4 Estudios de Caso

This work is part of a project financed by the Spanish Ministry for Economy and competitiveness and the European Regional Development Fund (FEDER) in which researchers from four Spanish universities accompany four Primary schools to problematize, change and improve their curricular practices. This work considers if the own participation in these democratic and inclusive processes enhances the student’s willingness to learning through IAP's own tools. It is a multiple case study, articulated through 4 cases. The study was carried out in schools in the following Spanish regions: Murcia (C1), Valencia (C2), Madrid (C3) and the Basque Country (C4). The selected schools were immersed in a participatory action research process. After a brief presentation of the process, the participatory tools used ondifferent occasions by teachers, students, families and social agents, within the participatory action research process, are presented. From this triangulation of tools and participants, the positive impact of the use of these qualitative and participatory tools in the teaching-learning processes of the students is observed. The results focus on satisfaction with the PAR methodology and how it promotes the learning of curricular content.Este trabajo forma parte de un proyecto financiado por el Ministerio español de Economía y Competitividad y el Fondo Europeo de Desarrollo Regional (FEDER) en el que investigadores de cuatro universidades españolas acompañan a cuatro escuelas de Primaria a problematizar, cambiar y mejorar sus prácticas curriculares. Se plantea si la propia participación en los procesos democráticos e inclusivos mejora la disposición del alumnado al aprendizaje a través de herramientas propias de IAP. Se trata de un estudio de caso múltiple articulado a través de 4 casos. El estudio ha sido realizado en centros escolares de las siguientes regiones españolas: Murcia (C1), Valencia (C2), Madrid (C3) y País Vasco (C4). Las escuelas seleccionadas estaban inmersas en un proceso de investigación acción participativa. Tras una breve presentación del proceso se presentan las herramientas participativas utilizadas en diferentes ocasionespor el profesorado, el alumnado, las familias y los agentes sociales, dentro del proceso de investigación acción participativa. A partir de esta triangulación de herramientas y participantes, se observa el impacto positivo del uso de estas herramientas cualitativas y participativas en los procesos de enseñanza-aprendizaje del alumnado. Los resultados se centran en la satisfacción con la metodología IAP y como esta fomenta el aprendizaje de contenidos curriculares