On Matter Coupling in 5D Kaluza-Klein Model

We analyze some unphysical features of the geodesic approach to matter coupling in a compactified Kaluza-Klein scenario, like the q/m puzzle and the huge massive modes. We propose a new approach, based on Papapetrou multipole expansion, that provides a new equation for the motion of a test particle. We show how this equation provides right couplings and does not generate huge massive modes.Comment: 4 pages, to appear in Proceedings of the II Stueckelberg Workshop - Int. J. Mod. Phys.

Universality of transport properties of ultra-thin oxide films

We report low-temperature measurements of current-voltage characteristics for highly conductive Nb/Al-AlOx-Nb junctions with thicknesses of the Al interlayer ranging from 40 to 150 nm and ultra-thin barriers formed by diffusive oxidation of the Al surface. In the superconducting state these devices have revealed a strong subgap current leakage. Analyzing Cooper-pair and quasiparticle currents across the devices, we conclude that the strong suppression of the subgap resistance comparing with conventional tunnel junctions originates from a universal bimodal distribution of transparencies across the Al-oxide barrier proposed earlier by Schep and Bauer. We suggest a simple physical explanation of its source in the nanometer-thick oxide films relating it to strong local barrier-height fluctuations which are generated by oxygen vacancies in thin aluminum oxide tunnel barriers formed by thermal oxidation.Comment: revised text and a new figur

The law of intellectual property of 1933 : projects and parliamentary debates on copyrights in Argentina

El 26 de Septiembre de 1933, durante la presidencia de Agustín P. Justo, se sancionó en la Argentina la ley de propiedad artística e intelectual N° 11.723. El proyecto fue presentado al Congreso Nacional por el diputado Roberto Noble y su estudio recayó sobre una Comisión Especial designada por el poder Ejecutivo Nacional que fue presidida por el senador Matías Sánchez Sorondo. El objetivo de este artículo consiste en analizar las diferentes posturas que los bloques partidarios esgrimieron sobre la sanción de la ley de derechos autorales en el Congreso de la Nación y que versaron principalmente sobre el rol del Estado frente a la propiedad intelectual, la situación de los productores culturales y los mecanismos de circulación de sus obras en el plano local. Las fuentes seleccionadas para llevar a cabo este estudio han sido los Diarios de Sesiones de la Cámara de Diputados y Senadores del Congreso Nacional y diversos estatutos legales referentes a los derechos de autor en la Argentina. La hipótesis del artículo sostiene que a través de la sanción de la ley 11.723 el Estado argentino comenzó a perfilar nuevas modalidades de intervención en el campo cultural. En ese contexto, senadores y diputados de diferentes bloques partidarios coincidieron en que el Estado debía asumir nuevas atribuciones. Con ese fin, la ley de propiedad intelectual de 1933 estableció la creación de la Comisión Nacional de Cultura y el Registro de la Propiedad IntelectualThe 26th September 1933, during the presidency of Agustín P. Justo, the Law of artistic and intellectual property N ° 11.723 was sanctioned in Argentina. The bill was introduced to the National Congress by the deputy Roberto Noble and its revision was assigned to a Special Commission designated by the National Executive and chaired by the senator Matías Sánchez Sorondo. The aim of this article is to analyze the different party blocks positions during the debate for the sanction of the copyright law in the National Congress, which focused mainly on the role of the State as regards intellectual property, the situation of cultural producers and the circulation mechanisms of works of art at the local level. The privileged sources to carry out this study have been the Diaries of Sessions of the Chamber of Deputies and Senators of the National Congress and several legal statutes referring to the rights of author in Argentina. The article hypothesis is that through the sanction of that law, the Argentine State began to outline new modalities of intervention in the cultural field. In that context, senators and congress representatives from different party blocks agreed on the fact that the state should assume new powers. With that aim, the intellectual property law of 1933 established the creation of the national commission of culture and the registry of intellectual property.Fil: Lacquaniti, Leandro Gustavo. Universidad de Buenos Aire

Control of reaching movements by muscle synergy combinations

Controlling the movement of the arm to achieve a goal, such as reaching for an object, is challenging because it requires coordinating many muscles acting on many joints. The central nervous system (CNS) might simplify the control of reaching by directly mapping initial states and goals into muscle activations through the combination of muscle synergies, coordinated recruitment of groups of muscles with specific activation profiles. Here we review recent results from the analysis of reaching muscle patterns supporting such a control strategy. Muscle patterns for point-to-point movements can be reconstructed by the combination of a small number of time-varying muscle synergies, modulated in amplitude and timing according to movement directions and speeds. Moreover, the modulation and superposition of the synergies identified from point-to-point movements captures the muscle patterns underlying multi-phasic movements, such as reaching through a via-point or to a target whose location changes after movement initiation. Thus, the sequencing of time-varying muscle synergies might implement an intermittent controller which would allow the construction of complex movements from simple building blocks

Mapping Muscles Activation to Force Perception during Unloading

It has been largely proved that while judging a force humans mainly rely on the motor commands produced to interact with that force (i.e., sense of effort). Despite of a large bulk of previous investigations interested in understanding the contributions of the descending and ascending signals in force perception, very few attempts have been made to link a measure of neural output (i.e., EMG) to the psychophysical performance. Indeed, the amount of correlation between EMG activity and perceptual decisions can be interpreted as an estimate of the contribution of central signals involved in the sensation of force. In this study we investigated this correlation by measuring the muscular activity of eight arm muscles while participants performed a quasi-isometric force detection task. Here we showed a method to quantitatively describe muscular activity ("muscle-metric function") that was directly comparable to the description of the participants' psychophysical decisions about the stimulus force. We observed that under our experimental conditions, muscle-metric absolute thresholds and the shape of the muscle-metric curves were closely related to those provided by the psychophysics. In fact a global measure of the muscles considered was able to predict approximately 60% of the perceptual decisions total variance. Moreover the inter-subjects differences in psychophysical sensitivity showed high correlation with both participants' muscles sensitivity and participants' joint torques. Overall, our findings gave insights into both the role played by the corticospinal motor commands while performing a force detection task and the influence of the gravitational muscular torque on the estimation of vertical forces