Mostrando recursos 61 - 80 de 104.426

  1. Large-N pion scattering at finite temperature: The f(0)(500) and chiral restoration

    Cortés, Santiago; Gómez Nicola, Ángel; Morales, John
    We consider the O(N + 1)/O(N) nonlinear sigma model for large N as an effective theory for low-energy QCD at finite temperature T, in the chiral limit. At T = 0 this formulation provides a good description of scattering data in the scalar channel and dynamically generates the f_(0)(500) pole, the pole position lying within experimental determinations. Previous T = 0 results with this model are updated using newer analysis of pion scattering data. We calculate the pion scattering amplitude at finite T and show that it exactly satisfies thermal unitarity, which had been assumed but not formally proven in...

  2. Large-n pion scattering, finite-temperature effects and the relationship of the f(0)(500) with chiral symmetry restoration

    Cortés, Santiago; Gómez Nicola, Ángel; Morales, John
    In this work, we review how the mass and the width of the f(0)(500) pole behave in a regime where temperature is below the critical chiral transition value. This is attained by considering a large-N O(N +1)/O(N) invariant Nonlinear Sigma Model (NLSM) such that we can study the dynamical generation of an f(0)(500) resonance. Introducing thermal effects via the imaginary time formalism allows us to study the behavior of the pole and relate it to chiral restoration.

  3. Permanent magnetism, magnetic anisotropy, and hysteresis of thiol-capped gold nanoparticles

    Crespo del Arco, Patricia; Litran, R.; Rojas, T. C.; Multigner, M.; De la Fuente, J. M.; Sánchez López, J. C.; Garcia, M. A.; Hernando, A.; Penadés, S.; Fernández, A.
    We report on the experimental observation of magnetic hysteresis up to room temperature in thiol-capped Au nanoparticles with 1.4 nm size. The coercive field ranges from 860 Oe at 5 K to 250 Oe at 300 K. It is estimated that the Au atoms exhibit a magnetic moment of mu=0.036mu(B). However, Au nanoparticles with similar size but stabilized by means of a surfactant, i.e., weak interaction between protective molecules and Au surface atoms, are diamagnetic, as bulk Au samples are. The apparent ferromagnetism is consequently associated with 5d localized holes generated through Au-S bonds. These holes give rise to localized...

  4. Erratum: Permanent magnetism, magnetic anisotropy, and hysteresis of thiol-capped gold nanoparticles (vol 93, art no 087204, 2004)

    Crespo del Arco, Patricia; Litran, R.; Multigner, M.; De la Fuente, J. M.; Sánchez-López, J. C.; García, M. A.; Hernando Grande, Antonio; Penadés, S.; Fernández, A.

  5. Metallic magnetic nanoparticles

    Hernando Grande, Antonio; Crespo del Arco, Patricia; García, M. A.
    In this paper, we reviewed some relevant aspects of the magnetic properties of metallic nanoparticles with small size ( below 4 nm), covering the size effects in nanoparticles of magnetic materials, as well as the appearance of magnetism at the nanoscale in materials that are nonferromagnetic in bulk. These results are distributed along the text that has been organized around three important items: fundamental magnetic properties, different fabrication procedures, and characterization techniques. A general introduction and some experimental results recently obtained in Pd and Au nanoparticles have also been included. Finally, the more promising applications of magnetic nanoparticles in biomedicine...

  6. Surface plasmon resonance of capped Au nanoparticles

    García, M. A.; De la Venta, J; Crespo del Arco, Patricia; LLopis,, J.; Penadés, S.; Fernández, A.; Hernando Grande, Antonio
    In this Rapid Communication we show the relationship between surface plasmon resonance damping and the intensity of surface bonding for capped Au nanoparticles, (NPs). Up to now the influence of capping has been included as a phenomenological modification of the scattering constant. It is indicated here that the effective NP size is the parameter mainly affected by surface bonding. Experimental results in different Au-thiol NPs are shown to be in excellent agreement with the expression we propose for damping. Moreover, according to our model the resonance profile gives a deep insight of the interface bonding strength.

  7. Magnetic and microstructural analysis of palladium nanoparticles with different capping systems

    Litrán, R.; Sampedro, B.; Rojas,, T. C.; Multigner, M.; Sánchez López, J. C.; Crespo del Arco, Patricia; López Cartes, C.; García, M. A.; Hernando Grande, Antonio; Fernández, A.
    Palladium nanoparticles capped with different protective systems in a size range between 1.2 and 2.4 nm have been obtained by varying the preparation chemical method. Magnetization curves for all the samples show hysteresis loops, evidencing a ferromagnetic or a permanent magnetism in the nanoparticles. The microstructure of the nanoparticles has been analyzed by x-ray absorption and transmission electron microscopy. The nature of the magnetic behavior found for all these Pd nanoparticles (NPs) is different depending on their sizes and structural features and is explained on the basis of two different suggested mechanisms. The particles protected by means of a surfactant...

  8. Origin of orbital ferromagnetism and giant magnetic anisotropy at the nanoscale

    Hernando Grande, Antonio; Crespo del Arco, Patricia; Garcia, M.A.
    The origin of orbital magnetism recently observed in different nanostructured films and particles is discussed as a consequence of spin-orbit coupling. It is shown that contact potentials induced at the thin film surface by broken symmetries, as domain boundaries in self-assembled monolayers, lead to orbital states that in some cases are of large radius. The component of the angular momentum normal to the surface can reach very high values that decrease the total energy by decreasing spin-orbit interaction energy. Intraorbital ferromagnetic spin correlations induce orbital momenta alignment. The estimated values of the magnetic moments per atom are in good agreement...

  9. Erratum: Origin of orbital ferromagnetism and giant magnetic anisotropy at the nanoscale (vol 96, pg 057206, 2006)

    Hernando Grande, Antonio; Crespo del Arco, Patricia; Garcia, M. A.

  10. Depoimento de Renata Fragoso Máximo


    Iniciação no futebol e futsal; Futsal na rua; Prática de voleibol; Incentivo da família; Futsal na escola; Educação Física na Escola; Experiências significativas no esporte; Trajetória no futsal; Clubes e as competições; Inserção no futsal universitário com a Universidade Federal do Rio Grande do Sul (UFRGS); Motivação no futsal universitário; Experiência no futsal universitário; O significado da prática esportiva dentro do time da UFRGS; Outras facetas com o futsal e o futebol.

  11. Depoimento de Laura Giovana dos Santos Andrade


    Inserção na modalidade; Futsal ensino fundamental, Competições no ensino médio; Participação de campeonatos/torneios na escola; Educação Física na escola; Participação no voleibol; Inserção no futsal universitário com a Universidade Federal do Rio Grande do Sul (UFRGS); Apoio da família; Motivação. O significado da prática esportiva dentro do futsal universitário; Meninos e Meninas no futebol; Experiência no esporte.

  12. Depoimento de Rafaela Rocha Giozza


    Inserção no esporte; Incentivo familiar; Aulas de Educação Física; Formação esportiva; Dificuldades na prática esportiva do futsal; Significados relacionados com a prática esportiva do futsal; Mulheres e futsal; Feminilidade; Valores adquiridos com a prática do futsal; Motivação para prática de futsal.

  13. Escala Piers-Harris children’s self-concept scale: Uma versão com repostas de um a seis

    Veiga, Feliciano; Domingues, Dora
    É apresentada a adaptação da Piers-Harris Children’s Self-Concept Scale, uma versão com repostas de 1 (discordo totalmente) a 6 (concordo totalmente) da escala americana, revista e publicada em versão reduzida, PHCSCS-2 (Piers & Hertzberg, 2002) e da sua adaptação portuguesa (Veiga, 2006). São apresentadas as propriedades psicométricas desta nova versão (PHCSCS V1-6), em que os coeficientes de fidelidade encontrados se mostraram adequados. Os resultados de análises realizadas permitem continuar a falar em seis fatores — comportamento, estatuto intelectual e escolar, atributos e aparência física, ansiedade, popularidade e satisfação - -felicidade —, com uma distribuição dos itens coerente com a versão PHCSCS-2. Relativamente à validade externa, considerou-se a relação...

  14. Cultura física y liderazgo

    Morales Rincón, Camilo Andrés
    Physical culture is based on movement and corporeality but is not limited to, through its various components such as recreation, sports and physical education and those resulting flows are also routed to the integral formation of being, developing and strengthening capacities and skills in different areas of adjustment. We will focus on leadership and how physical processes from culture to different agents we strengthen and develop this skill.

  15. Beneficios y riesgos asociados en la actividad física para la salud

    Pérez Muñoz, Salvador; Domínguez Muñoz, Rafael; Sánchez Muñoz, Antonio; Rodríguez Cayetano, Alberto
    In the following article outlines that physical activity is beneficial for health, but the first step was to determine what activity is beneficial for health. And finally, highlights the benefits and risks to physical activity, from a triple perspective preventive, rehabilitative and wellness.

  16. Factores físicos, socio­económicos y psicológicos que inciden en la deserción deportiva en la escuela superior politécnica de Chimborazo

    Chávez Hernández, Jaime Patricio; Calero Morales, Santiago; Savedra Valdiviezo, Ower Armando
    In the transition from high school to higher education elite athletes decide to put sports activities aside. This research objective is to determine the influence of socioeconomic, psychological and physical factors in the students´ sport dropout at Escuela Superior Politécnica de Chimborazo. This is a correlational type research with an essentially quantitative approach and the survey technique is used. A questionnaire to 179 former athletes, 69 athletes and eight coaches was applied to analyze various factors. The results, applying the Mann­Whitney U test with a margin of error of 0,05, show that socioeconomic factor with an asymptotic significance 0.006 influence...

  17. La evaluación de las habilidades motrices en la clase de Educación Física desde una perspectiva integral

    Herrera Mena, Hugo; Espinoza Moreno, Luis Alfredo; Valle Salazar, Javier Guillermo; Maqueira Caraballo, Giceya; Pérez Iribar, Giorvi
    The research presented is described, within the field work of the evaluation in physical education, as a peculiar way to comprehend the reality of school children learning from a concept in such a way as to educate them on it. Based on scientific methods and framed in the primary school "García Moreno", of the canton Riobamba, province Chimborazo in Ecuador, provides actions from the personal component of the teaching­learning process and the context conditions that guide the evaluation aimed at cognitive domains, affective, physical and driving partner that develops this subject from the motor skills. This allowed to prepare teachers...

  18. El discurso antirracista de un antropólogo indigenista: Juan Comas Camps

    Gómez Izquierdo, Jorge
    Formador de generaciones de antropólogos físicos en México, Juan Comas Camps también fue profesor de instituciones de enseñanza e investigador emérito por la UNAM. Republicano español refugiado, editor de varias revistas, compilador, historiador, polemista, excomunista, activista del antirracismo internacional y científico nacionalista comprometido con el indigenismo del Estado revolucionario. Llega a México en 1939, época en que el auge de la antropología responde a la exigencia de mejoramiento de las condiciones de vida de las masas indígenas y en que su incorporación a la nación requiere de la participación del antropólogo social.

  19. Los procesos del racismo

    Knauth, Lothar
    A primera vista, la palabra raza parece ser inocua, sobre todo en español. De manera figurativa puede significar cualquier categoría de personas o animales relacionados con ciertas características que los definen, como “una raza de aventureros”. De hecho, se trata en el fondo de un concepto de identidad, pero también de distinción y discriminación que se asocia fácilmente con características físicas, de facciones y tez.

  20. La Integración Escolar y la asimilación de la diferencia

    Hernando Freile, Alvaro
    En este artículo se presentan algunas de las contradicciones y paradojas que encontramos en la acción del sistema educativo a la hora de asumir sus responsabilidades en el campo de la integración. Población inmigrante, discapacitados, alumnado con necesidades educativas especiales, alumnado en situación de fracaso escolar por cuestiones socioeconómicas, alumnado diverso, al fin y al cabo, cuenta con un conjunto de recursos reglados y una serie de programas específicos para ser atendidos. ¿Pero es esta atención suficiente para garantizar la igualdad de oportunidades? El autor realiza un acercamiento intuitivo al concepto de Integración Escolar partiendo de ideas y creencias, enlazándolas en preguntas y,...

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