Slightly generalized Generalized Contagion: Unifying simple models of biological and social spreading

We motivate and explore the basic features of generalized contagion, a model mechanism that unifies fundamental models of biological and social contagion. Generalized contagion builds on the elementary observation that spreading and contagion of all kinds involve some form of system memory. We discuss the three main classes of systems that generalized contagion affords, resembling: simple biological contagion; critical mass contagion of social phenomena; and an intermediate, and explosive, vanishing critical mass contagion. We also present a simple explanation of the global spreading condition in the context of a small seed of infected individuals.Comment: 8 pages, 5 figures; chapter to appear in "Spreading Dynamics in Social Systems"; Eds. Sune Lehmann and Yong-Yeol Ahn, Springer Natur

On finite monoids of cellular automata.

For any group G and set A, a cellular automaton over G and A is a transformation τ:AG→AGτ:AG→AG defined via a finite neighbourhood S⊆GS⊆G (called a memory set of ττ) and a local function μ:AS→Aμ:AS→A. In this paper, we assume that G and A are both finite and study various algebraic properties of the finite monoid CA(G,A)CA(G,A) consisting of all cellular automata over G and A. Let ICA(G;A)ICA(G;A) be the group of invertible cellular automata over G and A. In the first part, using information on the conjugacy classes of subgroups of G, we give a detailed description of the structure of ICA(G;A)ICA(G;A) in terms of direct and wreath products. In the second part, we study generating sets of CA(G;A)CA(G;A). In particular, we prove that CA(G,A)CA(G,A) cannot be generated by cellular automata with small memory set, and, when G is finite abelian, we determine the minimal size of a set V⊆CA(G;A)V⊆CA(G;A) such that CA(G;A)=⟨ICA(G;A)∪V⟩CA(G;A)=⟨ICA(G;A)∪V⟩

PELIGROSIDAD A LOS MOVIMIENTOS DE LADERA EN LA VERTIENTE MERIDIONAL DE SIERRA NEVADA (GRANADA) A PARTIR DE LA ESTIMACIÓN MULTI-TÉCNICA DE LA ACTIVIDAD

El presente trabajo aborda la cartografía de la susceptibilidad y la peligrosidad a los movimientos de ladera, en un ambiente montañoso, con información limitada sobre su actividad. El análisis y validación de la susceptibilidad se realizada mediante un modelo elaborado a partir del ModelBuilder™ de ArcGIS basado en el Método de la Matriz en un SIG. Dicho modelo necesita una cartografía previa de los movimientos, un MDE y un análisis discriminante de los factores determinantes de la estabilidad. Los datos del análisis reflejan que el 15% de la zona estudiada muestra una susceptibilidad a los movimientos de moderada a muy alta que, a su vez, coincide con lugares donde se encuentran la mayoría de las infraestructuras públicas de la región. Además, los valores registrados en la validación mediante el grado de ajuste están por encima del 83% para las zonas de susceptibilidad alta y muy alta. Estas zonas que presentan un mayor grado de susceptibilidad y, por tanto, una mayor exposición potencial al riesgo, son las seleccionadas para el análisis detallado de la peligrosidad. El principal problema, que, por otra parte, suele ser generalizado en este tipo de áreas para la estimación de la frecuencia con la que se suceden movimientos de ladera, es la falta de información sobre su ocurrencia. Por tanto, y con el objetivo de obtener la mayor información posible, los datos relativos a la actividad de los movimientos se extraen de diversas fuentes y técnicas, de forma que interactivamente solventen sus correspondientes limitaciones. Estos datos se extraen de una documentación previa, tanto en prensa como bibliografía específica, donde se presentan trabajos sobre DInSAR, fotogrametría aérea y LIDAR, y TLS. Además, se realiza de forma específica un análisis dendrogeomorfológico de árboles en movimientos de ladera y se revisa la ortofotografía aérea histórica de la zona de estudio. Posteriormente, con los datos de actividad, se realiza un análisis de los factores desencadenantes, que refleja que los movimientos de ladera están relacionados con episodios de precipitaciones intensas y prolongadas, y no tanto con la actividad sísmica del área. Por último, de forma indirecta, se estima la peligrosidad de la zona de estudio a los movimientos de ladera, asociando los resultados obtenidos de actividad con los factores desencadenantes; esto es, con periodos de precipitaciones intensas. Así, se establece un periodo de retorno que se extrapola a toda el área, con la asunción de que los grandes deslizamientos se generan o reactivan, conjuntamente con movimientos superficiales, tras periodos lluviosos intensos y prolongados, y que las lluvias torrenciales generan movimientos de ladera superficiales tipo flujo y desprendimientos. Los resultados obtenidos indican que la frecuencia con la que se generan los movimientos es de 5 años para los flujos superficiales y desprendimientos (F=0,2), y de 18 años para los deslizamientos y movimientos complejos (F=0,06). La zona, en términos generales, presenta determinados sectores con susceptibilidad moderada a muy alta, sin embargo la peligrosidad a los movimientos de ladera es de moderada a muy baja. En términos de probabilidad temporal, los flujos y desprendimientos son los movimientos con mayor peligrosidad

Analysis of symmetries in models of multi-strain infections

In mathematical studies of the dynamics of multi-strain diseases caused by antigenically diverse pathogens, there is a substantial interest in analytical insights. Using the example of a generic model of multi-strain diseases with cross-immunity between strains, we show that a significant understanding of the stability of steady states and possible dynamical behaviours can be achieved when the symmetry of interactions between strains is taken into account. Techniques of equivariant bifurcation theory allow one to identify the type of possible symmetry-breaking Hopf bifurcation, as well as to classify different periodic solutions in terms of their spatial and temporal symmetries. The approach is also illustrated on other models of multi-strain diseases, where the same methodology provides a systematic understanding of bifurcation scenarios and periodic behaviours. The results of the analysis are quite generic, and have wider implications for understanding the dynamics of a large class of models of multi-strain diseases

Localization of gravity on a de Sitter thick braneworld without scalar fields

In this work we present a simple thick braneworld model that is generated by an intriguing interplay between a 5D cosmological constant with a de Sitter metric induced in the 3-brane without the inclusion of scalar fields. We show that 4D gravity is localized on this brane, provide analytic expressions for the massive Kaluza-Klein (KK) fluctuation modes and also show that the spectrum of metric excitations displays a mass gap. We finally present the corrections to Newton's law due to these massive modes. This model has no naked singularities along the fifth dimension despite the existence of a mass gap in the graviton spectrum as it happens in thick branes with 4D Poincare symmetry, providing a simple model with very good features: the curvature is completely smooth along the fifth dimension, it localizes 4D gravity and the spectrum of gravity fluctuations presents a mass gap, a fact that rules out the existence of phenomenologically dangerous ultralight KK excitations in the model. We finally present our solution as a limit of scalar thick branes.Comment: 11 pages in latex, no figures, title and abstract changed, a new section and some references adde

Diets containing sea cucumber (Isostichopus badionotus) meals are hypocholesterolemic in young rats

Peer reviewedPublisher PD

Determining the neurotransmitter concentration profile at active synapses

Establishing the temporal and concentration profiles of neurotransmitters during synaptic release is an essential step towards understanding the basic properties of inter-neuronal communication in the central nervous system. A variety of ingenious attempts has been made to gain insights into this process, but the general inaccessibility of central synapses, intrinsic limitations of the techniques used, and natural variety of different synaptic environments have hindered a comprehensive description of this fundamental phenomenon. Here, we describe a number of experimental and theoretical findings that has been instrumental for advancing our knowledge of various features of neurotransmitter release, as well as newly developed tools that could overcome some limits of traditional pharmacological approaches and bring new impetus to the description of the complex mechanisms of synaptic transmission

Modular reorganization of the global network of gene regulatory interactions during perinatal human brain development.

BACKGROUND During early development of the nervous system, gene expression patterns are known to vary widely depending on the specific developmental trajectories of different structures. Observable changes in gene expression profiles throughout development are determined by an underlying network of precise regulatory interactions between individual genes. Elucidating the organizing principles that shape this gene regulatory network is one of the central goals of developmental biology. Whether the developmental programme is the result of a dynamic driven by a fixed architecture of regulatory interactions, or alternatively, the result of waves of regulatory reorganization is not known. RESULTS Here we contrast these two alternative models by examining existing expression data derived from the developing human brain in prenatal and postnatal stages. We reveal a sharp change in gene expression profiles at birth across brain areas. This sharp division between foetal and postnatal profiles is not the result of pronounced changes in level of expression of existing gene networks. Instead we demonstrate that the perinatal transition is marked by the widespread regulatory rearrangement within and across existing gene clusters, leading to the emergence of new functional groups. This rearrangement is itself organized into discrete blocks of genes, each targeted by a distinct set of transcriptional regulators and associated to specific biological functions. CONCLUSIONS Our results provide evidence of an acute modular reorganization of the regulatory architecture of the brain transcriptome occurring at birth, reflecting the reassembly of new functional associations required for the normal transition from prenatal to postnatal brain development

Measurements of neutrino oscillation in appearance and disappearance channels by the T2K experiment with 6.6 x 10(20) protons on target

111 pages, 45 figures, submitted to Physical Review D. Minor revisions to text following referee comments111 pages, 45 figures, submitted to Physical Review D. Minor revisions to text following referee comments111 pages, 45 figures, submitted to Physical Review D. Minor revisions to text following referee commentsWe thank the J-PARC staff for superb accelerator performance and the CERN NA61/SHINE Collaboration for providing valuable particle production data. We acknowledge the support of MEXT, Japan; NSERC, NRC, and CFI, Canada; CEA and CNRS/IN2P3, France; DFG, Germany; INFN, Italy; National Science Centre (NCN), Poland; RSF, RFBR and MES, Russia; MINECO and ERDF funds, Spain; SNSF and SER, Switzerland; STFC, UK; and the U. S. Deparment of Energy, USA. We also thank CERN for the UA1/NOMAD magnet, DESY for the HERA-B magnet mover system, NII for SINET4, the WestGrid and SciNet consortia in Compute Canada, GridPP, UK, and the Emerald High Performance Computing facility in the Centre for Innovation, UK. In addition, participation of individual researchers and institutions has been further supported by funds from ERC (FP7), EU; JSPS, Japan; Royal Society, UK; and DOE Early Career program, USA