Heteroclinic synchronization: Ultrasubharmonic locking

According to the traditional view of synchronization, a weak periodic input is able to lock a nonlinear oscillator at a frequency close to that of the input (1∶1 zone). If the forcing increases, it is possible to achieve synchronization at subharmonic bands also. Using a competitive dynamical system we show the inverse phenomenon: with a weak signal the 1∶1 zone is narrow, but the synchronization of ultrasubharmonics is dominant. In the system’s phase space, there exists a heteroclinic contour in the autonomous regime, which is the image of sequential dynamics. Under the action of a weak periodic forcing, in the vicinity of the contour a stable limit cycle with long period appears. This results in the locking of very low-frequency oscillations with the finite frequency of the forcing. We hypothesize that this phenomenon can be the origin for the synchronization of slow and fast brain rhythms.This work was supported by National Institute of Neurological Disorders and Stroke Grant No. 7R01-NS-38022, National Science Foundation Grant No. EIA-0130708, Spanish MEC BFI2003-07276, and Fundación BBVA

Transient cognitive dynamics, metastability, and decision making

Transient Cognitive Dynamics, Metastability, and Decision Making. Rabinovich et al. PLoS Computational Biology. 2008. 4(5) doi:10.1371/journal.pcbi.1000072The idea that cognitive activity can be understood using nonlinear dynamics has been intensively discussed at length for the last 15 years. One of the popular points of view is that metastable states play a key role in the execution of cognitive functions. Experimental and modeling studies suggest that most of these functions are the result of transient activity of large-scale brain networks in the presence of noise. Such transients may consist of a sequential switching between different metastable cognitive states. The main problem faced when using dynamical theory to describe transient cognitive processes is the fundamental contradiction between reproducibility and flexibility of transient behavior. In this paper, we propose a theoretical description of transient cognitive dynamics based on the interaction of functionally dependent metastable cognitive states. The mathematical image of such transient activity is a stable heteroclinic channel, i.e., a set of trajectories in the vicinity of a heteroclinic skeleton that consists of saddles and unstable separatrices that connect their surroundings. We suggest a basic mathematical model, a strongly dissipative dynamical system, and formulate the conditions for the robustness and reproducibility of cognitive transients that satisfy the competing requirements for stability and flexibility. Based on this approach, we describe here an effective solution for the problem of sequential decision making, represented as a fixed time game: a player takes sequential actions in a changing noisy environment so as to maximize a cumulative reward. As we predict and verify in computer simulations, noise plays an important role in optimizing the gain.This work was supported by ONR N00014-07-1-0741. PV acknowledges support from Spanish BFU2006-07902/BFI and CAM S-SEM-0255-2006

Origin of coherent structures in a discrete chaotic medium

Using as an example a large lattice of locally interacting Hindmarsh-Rose chaotic neurons, we disclose the origin of ordered structures in a discrete nonequilibrium medium with fast and slow chaotic oscillations. The origin of the ordering mechanism is related to the appearance of a periodic average dynamics in the group of chaotic neurons whose individual slow activity is significantly synchronized by the group mean field. Introducing the concept of a "coarse grain" as a cluster of neuron elements with periodic averaged behavior allows consideration of the dynamics of a medium composed of these clusters. A study of this medium reveals spatially ordered patterns in the periodic and slow dynamics of the coarse grains that are controlled by the average intensity of the fast chaotic pulsation

Plug-Ins para el paquete R Commander de R: una aplicación al cálculo de probabilidades

R is a prestigious software for the analysis of statistical data, and R Commander is a graphical interface of R that provides menus and facilitates its use among the non-specialized public. In this work, it was analyzed the menu options offered by R Commander for the probabilities calculation in models of random variables, and built a plug-in to improve these options for students and users who are not familiar with the properties of the variables. The programming of the plug-ins requires the Tcl / Tk programming language, which can be used through the tcltk and tcltk2 of R libraries.R es un prestigioso software para el análisis de datos estadísticos, y R Commander es una interfaz gráfica de R que proporciona menús y facilita su uso entre el público no especializado. En este trabajo se analizaron las opciones de menú que ofrece R Commander para el cálculo de probabilidades en modelos de variables aleatorias, y se construye un plug-in para mejorar dichas opciones de cara a estudiantes y usuarios que no estén familiarizados con las propiedades de las probabilidades. La programación de los plug-ins precisa del lenguaje de programación Tcl/Tk, que se puede utilizar a través de las librerías tcltk y tcltk2 de R

Empirical study of sensor observation services server instances

The number of Sensor Observation Service (SOS) instances available online has been increasing in the last few years. The SOS specification standardises interfaces and data formats for exchanging sensor-related in-formation between information providers and consumers. SOS in conjunction with other specifications in the Sensor Web Enablement initiative, at-tempts to realise the Sensor Web vision, a worldwide system where sensor networks of any kind are interconnected. In this paper we present an empirical study of actual instances of servers implementing SOS. The study focuses mostly in which parts of the specification are more frequently included in real implementations, and how exchanged messages follows the structure defined by XML Schema files. Our findings can be of practical use when implementing servers and clients based on the SOS specification, as they can be optimized for common scenarios.Comment: 25 pages, 11 tables, 6 figure

Examining urban polarization in five Spanish historic cities through online datasets and onsite perceptions

At present, the planning and management of historic districts are faced with the challenge of striking a balance between the needs of residents and seasonal pressures from visitors. These socially bustling sites could also benefit from the data cross-referencing of cultural and social patterns in order to identify areas for improvement. This research analyses geo-referenced online datasets and data from social media applications, subsequently contrasting these with onsite data from in-person interviews. These specific variables highlight parallels and conflicts between districts designated World Heritage areas in five Spanish cities. The study provides a quantitative analysis of hotspots and coldspots within the built environment. This is followed by an examination of these two types of areas using qualitative data linked to the three most challenging issues: housing and the built environment; basic services; and cultural services. When analysing the future of historic districts three major challenges to management highlighted in the results should be considered. Firstly, even in socially active districts, imbalances and dysfunctional areas are highlighted by both online data and onsite perceptions. Secondly, the study of the dynamics of districts for observing how stakeholders adapt to this social, economic, and mobilityrelated polarization. Thirdly, while the study acknowledges the changes to the consumption of culture, there is still potential for improvement in hosting alternative or countercultural movements.Funding for open access charge: CRUE-Universitat Jaume

New species and new records of Lygistorrhina Skuse from Mexico (Diptera: Lygistorrhinidae)

Lygistorrhina (Probolaeus) acahuizotla sp. nov., is described and illustrated based on adults from the locality of Acahuizotla in the state of Guerrero, Mexico. The species is related to Lygistorrhina (Probolaeus) alexi Huerta & Ibáñez-Bernal. The male is distinguished mainly from other congeneric species by the presence of a pair of preapical setae on the mediotergite, pale-yellow fore coxa, with brown pigmentation medially, and “U-shaped” tegmen. New records of Lygistorrhina (Probolaeus) alexi Huerta & Ibáñez-Bernal from Tecpan de Galeana, in the state of Guerrero and from Biology Station of Chamela, in the state of Jalisco, both in west Mexico, are added. A key to the species of Lygistorrhina from Mexico is provided.Lygistorrhina (Probolaeus) acahuizotla sp. nov., es descrita e ilustrada basada en adultos procedentes de la localidad de Acahuizotla, en el estado de Guerrero, México. Esta especie está relacionada a Lygistorrhina (Probolaeus) alexi Huerta & Ibáñez-Bernal. El macho se distingue principalmente de otras especies congenéres por la presencia de un par de sedas preapicales en el mediotergito, coxa anterior pálida amarilla con pigmentación parda medialmente y tegmen en forma de “U”. Nuevos registros de Lygistorrhina (Probolaeus) alexi Huerta & Ibáñez-Bernal de Tecpan de Galeana, para el estado de Guerrero y para la Estación Biológica de Chamela, en el estado de Jalisco, ambos registros son incluidos al occidente de México. Se proporciona una clave para las especies de Lygistorrhina de México

Automatic tree parameter extraction by a Mobile LiDAR System in an urban context

e0196004In an urban context, tree data are used in city planning, in locating hazardous trees and in environmental monitoring. This study focuses on developing an innovative methodology to automatically estimate the most relevant individual structural parameters of urban trees sampled by a Mobile LiDAR System at city level. These parameters include the Diameter at Breast Height (DBH), which was estimated by circle fitting of the points belonging to different height bins using RANSAC. In the case of non-circular trees, DBH is calculated by the maximum distance between extreme points. Tree sizes were extracted through a connectivity analysis. Crown Base Height, defined as the length until the bottom of the live crown, was calculated by voxelization techniques. For estimating Canopy Volume, procedures of mesh generation and α-shape methods were implemented. Also, tree location coordinates were obtained by means of Principal Component Analysis. The workflow has been validated on 29 trees of different species sampling a stretch of road 750 m long in Delft (The Netherlands) and tested on a larger dataset containing 58 individual trees. The validation was done against field measurements. DBH parameter had a correlation R2 value of 0.92 for the height bin of 20 cm which provided the best results. Moreover, the influence of the number of points used for DBH estimation, considering different height bins, was investigated. The assessment of the other inventory parameters yield correlation coefficients higher than 0.91. The quality of the results confirms the feasibility of the proposed methodology, providing scalability to a comprehensive analysis of urban treesS

Consumo colaborativo. Análisis, estudio de casos de éxito y buenas prácticas

Se pretende estudiar en este Trabajo Fin de Máster la influencia en la sociedad de un fenómeno de actualidad como es el consumo colaborativo. Para ello se han fijado dos objetivos relacionados entre sí. Por un lado profundizar en este nuevo movimiento desde todas sus aristas bajo un punto de vista teórico para conseguir una visión independiente de cada una de ellas así como una visión de conjunto que las relacione. De este modo, a nivel teórico, analizaremos conceptos tan importantes como son los factores claves para su aparición, la creación y modificación de nuevos mercados, sus modelos de negocio, los marketplaces P2P, los riesgos a los que se enfrenta y la financiación de estas iniciativas. Por otro lado, aplicaremos este conocimiento en una segunda parte práctica. Para ello, utilizando como metodología científica el estudio de casos, se analizan una serie de casos de éxito de los más significativos de este movimiento poniendo el foco en el panorama español. Por último extraeremos del análisis unas buenas prácticas que le puedan ser de utilidad a una ‘startup’ en sus primeros pasos. ABSTRACT I intend to study in this research the influence in the society of a new movement, the so called Collaborative Consumption – a form of consumption where people share goods and services. Two related objectives have been set in this context. On the one hand it will be necessary to deep into this new movement from different perspectives under a theoretical point of view to get an independent view of each one as well as an overview that relates all of them. To accomplish this, it will be necessary to discuss important concepts such as the key factors for its occurrence, the creation and modification of new markets, business models, the P2P marketplaces, the risks it faces and the funding part of these initiatives. On the other hand, we will apply this knowledge in a second practical part using the case study as scientific methodology. A series of case studies, the most significant of this movement, will be analyzed focusing on the Spanish landscape. Finally, we will derive from the analysis a set of best practices that could be helpful to a start-up in its first steps

Espacios de medidas vectoriales

RESUMEN Los preliminares sobre funciones, operadores y medidas se centran en exhibir la integral de Bochner como herramienta para definir los espacios de funciones de Lebesgue-Bochner, de operadores de Dinculeanu, p-sumantes y p-sumantes positivos, o la de los operadores cono absolutamente sumantes. La dualidad de los espacios de Lebesgue-Bochner se resuelve dando entrada a las medidas vectoriales y a los conceptos de p-variación y p-semivariación. La propiedad de Radon-Nikodým guarda equivalencia con el teorema de Riesz en contexto también vectorial. La noción de tipo y cotipo de Rademacher se introduce para resolver en la parte final de la memoria el cálculo de estos valores para una familia de espacios de funciones vectoriales. Los espacios de funciones de Banach son los verdaderos protagonistas de la memoria, pues van a parametrizar la gran familia de espacios de medidas vectoriales. Los espacios invariantes por reordenamiento proporcionan un contexto apropiado en el que detenerse. Los espacios de funciones vectoriales de Banach, también llamados espacios de Köthe-Bochner, serán protagonistas como dominios de los operadores lineales y continuos que vienen representados por las medidas vectoriales objeto de nuestro estudio. En el capítulo segundo se introduce el concepto de E-variación, donde E representa el espacio de funciones de Banach, y se define el espacio de medidas de E-variación finita. La E-semivariación que se define a continuación consiste en la traslación al campo de las medidas de la situación de los operadores lineales y continuos con dominio en un espacio de funciones de Banach. El espacio de medidas VE(X) representa al de los operadores lineales y continuos con ciertas limitaciones. Aparecen de manera sistemática la nueva clase de Dinculeanu y la clásica de los operadores cono absolutamente sumantes y se obtiene una nueva caracterización de la propiedad de Radon-Nikodým para E con norma absolutamente continua. La abstracción máxima se tiene al considerar la E[X; Y;Z]-semivariación, pues engloba todos los casos previos. Si se restringe la familia de espacios de funciones de Banach a aquellos que satisfacen la propiedad (J) se comprueba la expresión equivalente de la E-variación definida por Gretsky y Uhl. La (E;∞)-variación viene motivada de forma similar a la que define a los espacios de Lebesgue, así se recuperan los espacios de medidas de M(E)-variación acotada. Como aplicación del desarrollo de la teoría a los espacios invariantes por reordenamiento se presenta la familia de los espacios de medidas vectoriales de Lorentz Vpq(X). Otros espacios de medidas vectoriales que se ajustan a este apartado son los de Orlicz. Los corolarios que se enumeran son ya conocidos y aparecen en las referencias citadas. En el capítulo cuarto se presenta la familia de espacios de Musielak-Orlicz (también llamados de Orlicz generalizados, parametrizados por una función M). Por contener como casos concretos a todos los espacios de Lebesgue y Orlicz, y por tener miembros que no satisfacen la propiedad (J), estos espacios representan, en cierto modo, los límites de la E-variación que se definía en el capítulo anterior. La teoría obtenida hasta entonces es aplicable a parte de la familia de espacios de Musielak-Orlicz. Se destaca un espacio concreto para comprobar cómo la hipótesis de la propiedad (J) es imprescindible en una definición de E-variación como la de Gretsky y Uhl. El ejemplo utilizado es un espacio de la clase de espacios de Nakano (con función M de tipo potencial). Se finaliza esta memoria caracterizando el tipo y el cotipo de Rademacher para los espacios de sucesiones de Nakano vectoriales afinando resultados previos. ____________________________________________________________________________________________________Preliminary chapter is focused on function, operator and measure spaces. Duality and Radon-Nikodým property are examined in Lebesgue-Bochner function spaces. Banach funciton spaces are the true main characters of this memoir, within which rearrangement invariant spaces deserve special attention. Vector-valued Banach function spaces, also called Köthe-Bochner spaces, play an important role in the last step. The concepts of E-variation and E-semivariation are introduced in chapter 2, where E is a Banach function space. They are used to help representing the space of continuous linear operatos under some limitations. A new characterization of Radon-Nikodým property is shown for spaces E with absolute coninuous norm. When restricting to spaces satisfying property (J) it is shown that the E-variation coincides with the one given by Gretsky and Uhl. Measure spaces related to Lorentz and Orlicz spaces are defined and studied. In chapter four, Musielak-Orlicz function spaces (also called generalized Orlicz spaces, parametrized by a function M). One space in this family is used to prove that property (J) is essential in variation by Gretsky and Uhl. Nakano sequence spaces (with potential function M) are investigated through the study of their Rademacher type and cotype