Breathers in oscillator chains with Hertzian interactions

We prove nonexistence of breathers (spatially localized and time-periodic oscillations) for a class of Fermi-Pasta-Ulam lattices representing an uncompressed chain of beads interacting via Hertz's contact forces. We then consider the setting in which an additional on-site potential is present, motivated by the Newton's cradle under the effect of gravity. Using both direct numerical computations and a simplified asymptotic model of the oscillator chain, the so-called discrete p-Schr\"odinger (DpS) equation, we show the existence of discrete breathers and study their spectral properties and mobility. Due to the fully nonlinear character of Hertzian interactions, breathers are found to be much more localized than in classical nonlinear lattices and their motion occurs with less dispersion. In addition, we study numerically the excitation of a traveling breather after an impact at one end of a semi-infinite chain. This case is well described by the DpS equation when local oscillations are faster than binary collisions, a situation occuring e.g. in chains of stiff cantilevers decorated by spherical beads. When a hard anharmonic part is added to the local potential, a new type of traveling breather emerges, showing spontaneous direction-reversing in a spatially homogeneous system. Finally, the interaction of a moving breather with a point defect is also considered in the cradle system. Almost total breather reflections are observed at sufficiently high defect sizes, suggesting potential applications of such systems as shock wave reflectors

Motion of discrete solitons assisted by nonlinearity management

We demonstrate that periodic modulation of the nonlinearity coefficient in the discrete nonlinear Schr\"{o}dinger (DNLS) equation can strongly facilitate creation of traveling solitons in the lattice. We predict this possibility in an analytical form, and test it in direct simulations. Systematic simulations reveal several generic dynamical regimes, depending on the amplitude and frequency of the time modulation, and on initial thrust which sets the soliton in motion. These regimes include irregular motion, regular motion of a decaying soliton, and regular motion of a stable one. The motion may occur in both the straight and reverse directions, relative to the initial thrust. In the case of stable motion, extremely long simulations in a lattice with periodic boundary conditions demonstrate that the soliton keeps moving as long as we can monitor without any visible loss. Velocities of moving stable solitons are in good agreement with the analytical prediction, which is based on requiring a resonance between the ac drive and motion of the soliton through the periodic potential. All the generic dynamical regimes are mapped in the model's parameter space. Collisions between moving stable solitons are briefly investigated too, with a conclusion that two different outcomes are possible: elastic bounce, or bounce with mass transfer from one soliton to the other. The model can be realized experimentally in a Bose-Einstein condensate trapped in a deep optical lattice

Assessment of coercive persuasion: the Scale of Detection of Coercive Persuasion in Group Contexts (EDPC)

Comunicación presentada en las Jornadas Internacionales ICSA 2017 sobre Dinámicas sectarias y radicalizaciónCoercive persuasion refers to the control and manipulation developed by abusive groups, through different aggressive strategies that influence changes in the environment of its members, distorting cognition, altering emotions and generating significant psychosocial damage. It is a subtle, gradual and powerful force that affects around 500,000 Spanish victims of cultic groups (Cuevas & Perlado, 2011; Cuevas, 2012). Attaining power is one of the main goals of these groups, being the control and exploitation of the individual a part of the process. This derives to individuals giving up their own goals, freedom, material possessions, family and social networks, health or even life itself (Rodríguez-Carballeira, Saldaña, Almendros, Martin-Peña, Escartín, & Porrúa-Garcia, 2015). Such strategies are often implemented in a planned, graduate way and using deceit, difficulting that people who targeted are able to detect their evident aggressiveness and the generated damage. If there is an obvious shortage of instruments measuring psychological abuse in different fields (partner violence, harassment, bullying, etc.), the development of tools to assess the presence of such strategies in group contexts is even more scarce (Almendros, Gámez-Guadix, Carrobles & Rodríguez Carballeira, 2011). One of those assessment tools, the Interview for Detection of Coercive Persuasion (Cuevas & Canto, 2006) contains a wide range of coercive and abusive practises taking place within manipulative group. It has been applied in Spain in the forensic field in prosecutions of abusive groups (Dharma Tradición, Casa Yoga, Miguelianos, Revelance, etc.). The main objective of this recently validated tool (Cuevas, 2016) was to identify and provide evidences of the systematic application of coercive persuasion techniques on victims of abusive groups (Cuevas, 2012, 2016). Deriving from this instrument, sharing objectives, a new scale of 40 items and validated in Spanish population: the Scale of Detection of Coercive Persuasion in Group Contexts, or EDPC (Cuevas, 2016 ). To validate the EDPC, a Spanish sample of 134 people who identified themselves as having been abused or having been overly controlled by a group was selected. To assess criterion validity of the instrument, other different instruments (BSI MOS-SSS, RSE, SLEQ, ICP and EDS) were used. The group psychological abuse scale GPA (Chambers, Langone, Dole, & Grice, 1994), Spanish modified version (Almendros et al.,2004; Almendros et al., 2009) was used to assess the convergent validity of the instrument. The EDPC showed appropriate psychometric properties. In respect to reliability, the standardized Cronbach alpha coefficient reached a value of 0.97. The exploratory factorial analysis indicated the presence of a factor (coercive persuasion), establishing the suitability of a one-dimensional model. This scale aims to be useful in clinical and forensic fields, in order to assess the control and manipulation exercised in group contexts. Using it could be relevant to provide evidences of coercive groups practises, helping at trying to determinate the relationship between damage on the victims and the specific actions taken by groups or individuals who perform the abusive behaviors.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Breathers in inhomogeneous nonlinear lattices: an analysis via centre manifold reduction

We consider an infinite chain of particles linearly coupled to their nearest neighbours and subject to an anharmonic local potential. The chain is assumed weakly inhomogeneous. We look for small amplitude discrete breathers. The problem is reformulated as a nonautonomous recurrence in a space of time-periodic functions, where the dynamics is considered along the discrete spatial coordinate. We show that small amplitude oscillations are determined by finite-dimensional nonautonomous mappings, whose dimension depends on the solutions frequency. We consider the case of two-dimensional reduced mappings, which occurs for frequencies close to the edges of the phonon band. For an homogeneous chain, the reduced map is autonomous and reversible, and bifurcations of reversible homoclinics or heteroclinic solutions are found for appropriate parameter values. These orbits correspond respectively to discrete breathers, or dark breathers superposed on a spatially extended standing wave. Breather existence is shown in some cases for any value of the coupling constant, which generalizes an existence result obtained by MacKay and Aubry at small coupling. For an inhomogeneous chain the study of the nonautonomous reduced map is in general far more involved. For the principal part of the reduced recurrence, using the assumption of weak inhomogeneity, we show that homoclinics to 0 exist when the image of the unstable manifold under a linear transformation intersects the stable manifold. This provides a geometrical understanding of tangent bifurcations of discrete breathers. The case of a mass impurity is studied in detail, and our geometrical analysis is successfully compared with direct numerical simulations

Vortex solutions of the defocusing discrete nonlinear Schrödinger equation

International audienceWe consider the existence, stability and dynamical evolution of dark vortex states in the two‐dimensional defocusing DNLS equation, a model of interest both to atomic physics and to nonlinear optics. Our considerations are chiefly based on initializing such vortex configurations at the anti‐continuum limit of zero coupling between adjacent sites, and continuing them to finite values of the coupling. Discrete defocusing vortices become unstable past a critical coupling strength and, subsequently feature a cascade of alternating stabilization‐destabilization windows for any finite lattice

Escala de evaluación de persuasión coercitiva en contextos grupales

Introducción: La persuasión coercitiva puede emplearse con distintos fines: explotación económica, control o poder, satisfacción sexual, etc. Se trataría de una forma de influencia social extrema, que puede causar importantes daños psicosociales: trastornos o lesiones psicológicas, daño moral, alteración de la capacidad volitiva, afectación de las redes socio-familiares, pérdidas materiales, intensificar problemas de salud preexistentes, o incluso la pérdida de la misma vida (Rodríguez-Carballeira, Saldaña, Almendros, Martín-Peña, Escartín y Porrúa-García, 2015). Uno de los escasos instrumentos validados, la Entrevista de Persuasión Coercitiva (Cuevas, 2016), recoge una amplia gama de coerciones y abusos desarrollados en contextos grupales manipulativos. En España se ha aplicado en procesos forenses relacionados con victimización de grupos abusivos. Su principal objetivo es identificar y constatar si se han aplicado técnicas de persuasión coercitiva sobre la víctima evaluada, relacionándolas con los consecuentes daños psicológicos. A partir de ésta derivaron los ítems de la Escala de Detección de Persuasión Coercitiva en Contextos Grupales (EDPC). Método: Método 1. Participantes: 134 españoles, autoidentificados como víctimas de abuso psicológico grupal. 69 varones (51,5%) y 65 mujeres (48,5%). Edad media de 48,85 años (DT = 11,91). 2. Instrumentos para la validación: Cuestionario sociodemográfico, Información sobre experiencias grupales, Información tras la salida del grupo Escala de abuso psicológico grupal (GPA, Chambers Langone, Dole y Grice, 1994) Medical Outcomes Study Support Survey (MOS-SSS, Sherbourne y Stewart, 1991) Stressful Life Event Questionnaire (SLQ, Roohafza, Ramezani, Sadeghi, Shanam, Zolfagari y Sarafzadegan, 2011) Escala de Autoestima (RSE, Rosenberg, 1965) Brief Symptoms Inventory (BSI, Derogatis, 1975) Inventario de Cogniciones Postraumáticas (ICP, Foa, Ehlers, Clark, Toliln y Orsillo, 1999) Escala de Deseabilidad Social (SDS, Crowne y Marlon, 1960) . 3. Procedimiento Base de datos Proquest, accesible a través de internet. Invitaciones para participar dirigidas a ex miembros de grupos manipulativos. A través de asociaciones, profesionales y foros especializados, difusión en medios de comunicación , etc. del 23/07/15—30/09/2015. 4. Plan de Ánálisis Se examinan las características psicométricas de la escala: pruebas paramétricas y no paramétricas para evaluar diferencias grupales, análisis descriptivo de los ítems, consistencia interna y su estructura, a través de análisis factorial. Resultados: Resultados Sus propiedades psicométricas han sido adecuadas. FIABILIDAD: coeficiente alfa de Cronbach estandarizado = 0,97. ANÁLISIS FACTORIAL: presencia de un factor (persuasión coercitiva), estableciendo la idoneidad de un modelo unidimensional. VALIDEZ CONVERGENTE: las correlaciones entre la EDPC y la GPA son muy elevadas y significativas (p<0,01), especialmente con respecto a la escala global (r = 0,77**), constatando una elevada validez convergente. VALIDEZ DE CRITERIO: correlaciones significativas de las puntuaciones EDPC con diferentes instrumentos de ajuste, constatando una adecuada validez de criterio: EDPC– SLEQ: r = 0,37 **; EDPC– ICP: r = 0,30 **; EDC– IpBSI (paranoia): r = 0,19 *; EDCP-MOS-SSS: r = - 0,19 * Conclusiones: Nos encontramos con una nuevo instrumento, la Escala de Evaluación de Persuasión Coercitiva en Contextos grupales –EDPC-, con 40 ítems, que ha sido validado en población española, con adecuadas propiedades psicomé- tricas. Valora la manipulación y el control ejercidos en contextos grupales. Utilizar este tipo de herramientas resulta relevante para la identificación de relaciones grupales abusivas. Además, su uso en contextos forenses puede contribuir a constatar la responsabilidad de los grupos coercitivos; un soporte para relacionar determinados daños en las víctimas con la aplicación sostenida de comportamientos abusivos en contextos grupales.Dentro del ámbito del abuso psicológico hallamos la acción de los grupos manipulativos, habitualmente identificados, aunque no necesariamente, como organizaciones con derivas sectarias. Estos grupos se caracterizan por la aplicación sistemática de una serie de estrategias persuasivas de tipo coercitivo. Se trata de técnicas, comportamientos, actitudes, etc. que vulneran la libertad de las personas que las reciben, explotándolas y sometiéndolas y que por lo tanto, también quedan encuadradas dentro del abuso psicológico. Esta distinción resulta de extremada relevancia y de interés social, por lo que necesitamos poder identificarlas, evaluando la intensidad de la persuasión coercitiva aplicada, así como diferenciarlas de otras formas de presión psicológica socialmente tolerables. A partir de la Entrevista de Persuasión Coercitiva (Cuevas, 2016; Cuevas y Canto, 2006), se seleccionó una amplia gama de coerciones y abusos desarrollados en contextos grupales manipulativos, elaborando un instrumento en formato escala, de 40 ítems en su versión final, que se valida en población española: la Escala de Detección de Persuasión Coercitiva en Contextos Grupales -EDPC-.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Carbon materials for the electrooxidation of nucleobases, nucleosides and nucleotides toward cytosine methylation detection: a review

Improved analytical methods for the determination of the degree of methylation of DNA are of vital relevance, as they may enable the detection of certain diseases, such as carcinomas and infertility, in the early stages of development. Among the analytical methods for the detection and quantification of epigenetic modifications in DNA, electroanalytical platforms are emerging as potential feasible tools for clinical purposes. This review describes the fundamentals of the electrochemical responses of nucleobases, nucleosides, nucleotides and DNA in general from the pioneering studies at mercury electrodes to the most recent studies during the last two decades. Concerning these latter studies, we will exclusively focus on carbonaceous electrodes such as carbon, graphite, glassy carbon, boron-doped diamond, carbon nanofibers, carbon nanotubes and graphene. This review will also provide an overview of the feasibility of the development of electrochemical sensors for the simultaneous determination and quantification of naturally occurring DNA bases and nucleotides as well as the methylation of cytosine in DNA using carbon materials.The authors give thanks to the University of Alicante for funding and collaboration in this review. This work has also been financially supported by the MICINN-FEDER (Spain) through the projects CTQ2013-48280-C3-3 R and CTQ2013-44083-P

The cluster initial mass function of the M82 disk Super Star Clusters

The presence of a population of a large number ($\sim$400) of almost coeval (100--300 Myr) super star clusters (SSCs) in the disk of M82 offers an opportunity to construct the Cluster Initial Mass Function (CIMF) from the observed present-day Cluster Mass Function (CMF). We carry out the dynamical and photometric evolution of the CMF assuming the clusters move in circular orbits under the gravitational potential of the host galaxy using the semi-analytical simulation code EMACSS. We explore power-law and log-normal functions for the CIMFs, and populate the clusters in the disk assuming uniform, power-law, and exponential radial distribution functions. We find that the observed CMF is best produced by a CIMF that is power-law in form with an index of 1.8, for a power-law radial distribution function. More importantly, we establish that the observed turn-over in the present-day CMF is the result of observational incompleteness rather than due to dynamically induced effects, or an intrinsically log-normal CIMF, as was proposed for the fossil starburst region B of this galaxy. Our simulations naturally reproduce the mass-radius relation observed for a sub-sample of M82 SSCs.Comment: 17 pages, 11 figures, accepted to be published on MNRA

Competitividad en Pymes bajo un esquema de trabajo en red y diferenciación del producto. Caso comedores urbanos de Food Trucks en Ciudad Juárez, Chihuahua, México

A pesquisa, mostra o modelo de negócio de venda de comida feita na hora de um veículo que pode ser mobilizada para si ou motor também conhecido como Food Truks (FT), sob a tendência das instalações ou estacionamento de vários destes, na mesma praça comercial a oferta de alimentação gourmet. O trabalho demonstra a importância da cooperação e relação entre estas pequenas e médias empresas (PME) em Ciudad Juárez, Chihuahua (CJS) e sua tendência para a rede abrigo de um regime de colaboração. Depois de se referir a alguma base teórica para a competitividade e redes, os resultados preliminares em que destaca as relações que surgem entre empresas e partes interessadas, mostrando as principais considerações para o trabalho sob este modelo de rede são apresentados, bem como os aspectos da apresentação, qualidade e produtos de imagem, tais como factores de diferenciação para a obtenção de melhorias competitivas. Além disso, uma série de recomendações a considerar a região como uma unidade de análise são desenvolvidas