385 research outputs found

    The Hamiltonian tube of a cotangent-lifted action

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    The Marle-Guillemin-Sternberg (MGS) form is local model for a neighborhood of an orbit of a Hamiltonian Lie group action on a symplectic manifold. One of the main features of the MGS form is that it puts simultaneously in normal form the existing symplectic structure and momentum map. The main drawback of the MGS form is that it does not have an explicit expression. We will obtain a MGS form for cotangent-lifted actions on cotangent bundles that, in addition to its defining features, respects the additional fibered structure present. This model generalizes previous results obtained by T. Schmah for orbits with fully-isotropic momentum. In addition, our construction is explicit up to the integration of a differential equation on G. This equation can be easily solved for the groups SO(3) or SL(2), thus giving explicit symplectic coordinates for arbitrary canonical actions of these groups on any cotangent bundle.Peer ReviewedPostprint (author's final draft

    Is there a rationale and role for long-acting anticholinergic bronchodilators in asthma?

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    The authors acknowledge the medical writing assistance received from Sam Yarwood, PhD, of Complete HealthVizion, in the form of literature searches and preparation and revision of the draft manuscript.Peer reviewedPublisher PD

    Nuevas propuestas en el ámbito de los Algoritmos Genéticos Distribuidos para la Extracción de Reglas Clasificación

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    Esta investigación parte de la combinación de los modelos genéticos distribuidos con los modelos de genéticos aprendizaje de reglas para conseguir un modelo de aprendizaje distribuido escalable y flexible frente a conjuntos de datos no balanceados. Se ha desarrollado un nuevo algoritmo denominado EDGAR (Effícient Distributed Genetic Algorithm for Rule Extraction). Este Algoritmo genera clasificadores basados en reglas de alta calidad en precisión y tamaño . EDGAR combina la distribución de datos con modelos genéticos distribuidos para resolver problemas de alta cardinalidad y clases no balanceadas con resultados competitivos en el ámbito de los algoritmos genéticos de aprendizaje supervisado para la clasificación. Se han desarrollado mejoras especificas que permite el tratamiento directo de los conjuntos de datos con desbalanceo de clases y atributos numéricos continuos.This research it is based on the combination of distributed genetic models with the genetic algorithms for rule learning in order to produce a distributed learning model flexible and scalable in the scenery of imbalanced datasets. A new algorithm has been developed named EDGAR (Efficient Distributed Genetic Algorithm for Rule Extraction). This algorithm produces high quality rule classifiers in accuracy and size. EDGAR combines data distribution with genetic distributed models in order to solve high dimensional data problems and imbalanced data problems with competitive results in the context of supervised genetic algorithm for classification . New techniques has been developed allowing this proposal to handle directl

    Self-regulation in family foster children

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    This poster presents research on foster children’s capacities for self-regulation and its relation to adversity history. Children in family foster care are a vulnerable population due to their experiences of maltreatment and separation from primary caregivers. Research has shown high rates of behavioral problems and impulsivity in these children, as well as other difficulties such as poor academic adjustment. Recent theory and research advances suggest some of these problems are due to deficits in self-regulatory capacities, such as executive functions or emotion regulation. Early adversity in key developmental stages, like that suffered by many foster children, can undermine the normative development of these capacities and, consequently, their psychosocial adjustment. This study explores this topic in a sample of foster children between 4 and 8 years old who were living in non-relative foster families for at least six months in Southern Spain. We used the Behavior Rating Inventory of Executive Function (BRIEF; Gioia, Isquith, Guy, & Kenworthy, 2000), a widely used parent-reported questionnaire, to assess self-regulation in the foster children. The BRIEF was answered by the primary foster caregiver during a home visit. The information regarding adverse events and trajectory in the child protection services was obtained through case records in collaboration with caseworkers. The results of this study show us information about the capacities of self-regulation of children in family foster care. Due to the centrality of self-regulation in development and the fact that it remains responsive to well-designed interventions beyond early childhood, interventions for foster children and families should consider targeting this dimension to improve their outcomes

    Foster children’s attachment representations: the role of type of maltreatment and the relationship with birth family

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    Children in foster care are at risk of developing insecure and disorganized attachment, which is problematic for establishing new relationships in foster families. However, most previous studies have focused on attachment behaviors in young children rather than on attachment representations. We compared foster children’s attachment representations with those of a community group, analyzing also the contribution made by different factors to foster children’s attachment representations. We assessed the attachment representations of 109 children aged between 4 and 9 years (51 children in non-kin foster care and 58 community children) in southern Spain, using a narrative story stem measure. Case records information were collected for adversity and child protection variables. Foster children had fewer security and more avoidance indicators than their community counterparts, with those who had suffered more severe maltreatment scoring lower for security and higher for disorganization. Exposure to physical and emotional abuse and birth parents’ opposition to the foster placement predicted more disorganized attachment representations. Interventions with foster children should consider their heterogeneity in terms of attachment outcomes, and foster caregivers of abused children may need guidance in order to provide therapeutic caregiving.Spanish Ministry of Economy, Industry and Competitiveness and the European Regional Development Fund SEJ2006-12216; PSI2010-19287; PSI2015-67757-

    Overcoming the Challenge of Producing Large and Flat Nanocellular Polymers: A Study with PMMA

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    Although nanocellular polymers are interesting materials with improved properties in comparison with conventional or microcellular polymers, the production of large and flat parts of those materials is still challenging. Herein, gas dissolution foaming process is used to produce large and flat nanocellular polymethylmethacrylate samples. In order to do that, the foaming step is performed in a hot press. The methodology is optimized to produce flat samples with dimensions of 100 × 100 × 6 mm3, relative densities in the range 0.25–0.55 and cell sizes around 250 nm. Additionally, foaming parameters are modified to study their influence on the final cellular structure, and the materials produced in this paper are compared with samples produced by using a most conventional approach in which foaming step is conducted in a thermal bath. Results obtained show that an increment in the foaming temperature leads to a reduction in relative density and an increase of cell nucleation density. Moreover, differences in the final cellular structure for materials produced by both foaming routes are studied, proving that although there exist some differences, the mechanisms governing the nucleation and growing are the same in both processes, leading to the production of homogeneous materials with very similar cellular structures

    A closed-form formula for the RBF-based approximation of the Laplace-Beltrami operator

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    In this paper we present a method that uses radial basis functions to approximatethe Laplace&-Beltrami operator that allows to solve numerically diffusion (and reaction&-diffusion) equations on smooth, closed surfaces embedded in R3. The novelty of the methodis in a closed-form formula for the Laplace&-Beltrami operator derived in the paper, whichinvolve the normal vector and the curvature at a set of points on the surface of interest.An advantage of the proposed method is that it does not rely on the explicit knowledgeof the surface, which can be simply defined by a set of scattered nodes. In that case, thesurface is represented by a level set function from which we can compute the needed normalvectors and the curvature. The formula for the Laplace&-Beltrami operator is exact for radialbasis functions and it also depends on the first and second derivatives of these functionsat the scattered nodes that define the surface. We analyze the converge of the method andwe present numerical simulations that show its performance. We include an application thatarises in cardiology.This work has been supported by Spanish MICINN Grant FIS2016-77892-R. We thank the anonymous reviewer for his or her careful reading of our manuscript and his or her many insightful comments and suggestions

    Caregiver ratings of executive functions among foster children in middle childhood: Associations with early adversity and school adjustment

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    Children in foster care often present difficulties related to executive functions, such as poor school adjustment and impulsivity. Despite their importance, few studies have analyzed executive functions in foster children, especially beyond preschool age. This study sought to analyze the executive functions of a sample of 43 Spanish foster children aged between five and nine years (M = 7.51, SD = 1.29), using a caregiver-reported questionnaire. We also explored the relationship between executive functions, early adversity variables, and teacher-reported school adjustment. Results indicate that participants experienced more executive function-related difficulties than the measure's standardization sample in almost all areas, particularly in behavioral regulation, although they were found to have ageappropriate executive function levels in some areas, such as monitoring and organization of materials. Prenatal substance exposure was associated with poorer planning/organization skills, whereas other early adversity variables showed no statistically significant associations with executive functions. A higher level of difficulty in inhibitory control and other areas were associated with poorer school adjustment as reported by teachers. The results of our study point to an important presence of executive function difficulties in foster children in middle childhood, a finding which highlights the need for early intervention efforts targeting these skills among this population

    Differential associations of threat and deprivation with emotion understanding in maltreated children in foster care

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    Children in foster care are a remarkably heterogeneous group regarding their adaptation, and disrupted emotion understanding is one of the processes that may lead to differential outcomes in them. Previous research has found different effects for abused and for neglected children in emotion recognition. However, very few studies have analysed more complex forms of emotion understanding in maltreated children while considering different adversity dimensions. The present study analysed associations between threat and deprivation exposure and different facets of emotion understanding in a sample of maltreated children in foster care. The sample comprised 51 children from 4 to 9 years old (M = 7.07, SD = 1.63) in nonkin foster care in Spain. We used the Test of Emotional Comprehension to measure emotion understanding and maltreatment reports to measure exposure to threat and deprivation. Threat exposure predicted enhanced external emotion understanding after controlling for age, vocabulary, and deprivation, particularly understanding emotions based on desires. Deprivation predicted worse external emotion understanding. Our findings reinforce the limits of cumulative risks models for understanding foster children's developmental outcomes and the value of assessing separately adversity dimensions when possible, given the variable relations of threat and deprivation exposure with social cognitive development

    Caracterización de las áreas urbanas gallegas en función de los flujos de movilidad obligada

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    La realidad territorial en los municipios gallegos evolucionó a ritmos dispares, afectados por dinámicas muy diferentes en cada uno de los casos. Los problemas en la aplicación de la normativa urbanística y de los instrumentos técnicos para la gestión del suelo gestaron unos ámbitos urbanos desconectados de su realidad metropolitana. Las áreas de influencia en las ciudades de Galicia presentan modelos complejos, adaptados a las dificultades que les privaron de una gestión prudente y coherente de los nuevos territorios urbanos. En la evaluación de la nueva realidad urbana, de sus condiciones y características, la movilidad residencial y la recurrente diaria es un elemento de primer rango de análisis. La escala adquirida por el proceso de urbanización es fruto de estos comportamientos en lo referente a la movilidad. Esta se ha intensificado en los últimos años y muestra de modo claro cuáles son las dinámicas funcionales reales, necesitadas de una nueva y urgente organización y gobernanza territoriales.Territorial reality in Galician municipalities evolved to different rhythms, affected by very different dynamics in each one of the cases. The problems in the application of the town-planning and technical instruments for land management provoked the disconnection between cities and their metropolitan nature. Areas of influence in Galician cities present complex models, adapted to the difficulties which deprived them from a prudent and coherent management of the new urban territories. In the assessment of the new urban reality, its conditions and characteristics, residential mobility is a key issue of analysis. The scale of the process of urbanization is a result of these behaviours with regard to mobility. In fact, mobility has intensified in the last years and clearly shows real functional dynamics, needing a new and urgent territorial organization and governance
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