Universal features of electron-phonon interactions in atomic wires

The effect of electron-phonon interactions in the conductance through metallic atomic wires is theoretically analyzed. The proposed model allows to consider an atomic size region electrically and mechanically coupled to bulk electrodes. We show that under rather general conditions the features due to electron-phonon coupling are described by universal functions of the system transmission coefficients. It is predicted that the reduction of the conductance due to electron-phonon coupling which is observed close to perfect transmission should evolve into an enhancement at low transmission. This crossover can be understood in a transparent way as arising from the competition between elastic and inelastic processes.Comment: 5 pages, 5 figure

Constraining the expansion history of the universe from the red shift evolution of cosmic shear

We present a quantitative analysis of the constraints on the total equation of state parameter that can be obtained from measuring the red shift evolution of the cosmic shear. We compare the constraints that can be obtained from measurements of the spin two angular multipole moments of the cosmic shear to those resulting from the two dimensional and three dimensional power spectra of the cosmic shear. We find that if the multipole moments of the cosmic shear are measured accurately enough for a few red shifts the constraints on the dark energy equation of state parameter improve significantly compared to those that can be obtained from other measurements.Comment: 17 pages, 4 figure

Elliptical motions of stars in close binary systems

Motions of stars in close binary systems with a conservative mass exchange are examined. It is shown that Paczynski-Huang model widely used now for obtaining the semi-major axis variation of a relative stars orbit is incorrect, because it brings about large mistakes. A new model suitable for elliptical orbits of stars is proposed. Both of reactive and attractive forces between stars and a substance of the flowing jet are taken into account. A possibility of a mass exchange at presence of accretion disk is considere

Apego como marco teórico para entender los trastornos de personalidad: Consideraciones psicoterapéuticas, neurocientíficas y de desarrollo

In this paper we propose that John Bowlby\u27s attachment theory provides a theoretically coherent, empirically based, and clinically useful model for understanding personality pathology. This theoretical framework brings parsimony and breadth to the conceptualization of the etiology, maintenance, and treatment of personality disorders (PDs). Attachment theory can explain both the intrapersonal and interpersonal difficulties common in those with PDs and is consistent with findings from studies across multiple domains of knowledge, including evolutionary biology, ethology/comparative psychology, developmental psychology, experimental social-personality psychology, and neuroscience.PDs are characterized by significant interpersonal challenges. Recently, these challenges have been hypothesized to stem from underlying maladaptive attachment schemas. Our goal is to outline and elaborate on attachment theory as a foundation for the etiology and pathology of PDs and to highlight the implications of this theory for treatment. We begin with a brief review of attachment, describing its conceptualization and assessment in both children and adults in order to examine PD development. This theoretical foundation is supported by a body of empirical research, from which we present findings from neurobiological and developmental literatures linking attachment and PDs. We then examine the role of attachment in the psychotherapy process and in treatment outcome. Further, we outline research reporting changes in attachment patterns as a result of treatment. Finally, we summarize the implications of attachment theory for understanding PDs and present possible directions for future research.En este trabajo proponemos que la teoría de apego de John Bowlby ofrece un modelo teoréticamente coherente, empíricamente basado y clínicamente útil para entender la patología de personalidad. Este marco teorético trae parquedad y anchura a la conceptualización de la etiología, mantenimiento y tratamiento de trastornos de personalidad. La teoría de apego puede explicar las dificultades tanto intrapersonales como interpersonales comunes a las personas con trastornos de personalidad y es consistente con los descubrimientos de estudios de varios dominios del saber, incluyendo biología evolutiva, etiología/psicología comparada, psicología de desarrollo, psicología de personalidad y psicología social-personalidad experimental, y neurociencia. Trastornos de personalidad son caracterizados por los retos interpersonales significativos. Últimamente, se han hecho hipótesis que estos retos son el resultado de esquemas de apego mal adaptivos. Nuestro objetivo es explicar y elaborar la teoría de apego como la base para la etiología y patología de trastornos de personalidad y acentuar las implicaciones de esta teoría para el tratamiento. Empezamos con un pequeño análisis del apego, describiendo sus conceptualizaciones y evaluación tanto en niños como adultos para examinar el desarrollo de trastornos de personalidad. Este fundamento teórico está apoyado por la investigación empírica, de la que presentamos resultados de la literatura neurobiológica y de desarrollo relacionados con el apego y los trastornos de personalidad. Luego investigamos el papel que tiene el apego en los procesos de psicoterapia y en los resultados del tratamiento. Finalmente, resumimos las implicaciones de la teoría de apego para entender trastornos de personalidad y presentamos unas posibles direcciones para las futuras investigaciones

Microscopic origin of the conducting channels in metallic atomic-size contacts

We present a theoretical approach which allows to determine the number and orbital character of the conducting channels in metallic atomic contacts. We show how the conducting channels arise from the atomic orbitals having a significant contribution to the bands around the Fermi level. Our theory predicts that the number of conducting channels with non negligible transmission is 3 for Al and 5 for Nb one-atom contacts, in agreement with recent experiments. These results are shown to be robust with respect to disorder. The experimental values of the channels transmissions lie within the calculated distributions.Comment: 11 pages, 4 ps-figures. Submitted to Phys. Rev. Let