Plesiosaurs (Diapsida, sauropterygia) from Late Cretaceous (Late Campanian- Early maastrichtian) marginal marine environments from north Patagonia

Fil: O`Gorman, Jose Patricio. División Paleontología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin

Superposition of a static perfect fluid and a radial elecric field

We obtain a two-parameter set of solutions, which represents a spherically symmetric space-time with a superposition of a neutral fluid and an electric field. The electromagnetic four-potential of this Einstein-Maxwell space-time is taken in the form A=(q/n)(r^n)dt, when n=/0 and A=q*ln(r)dt, when n=0 (where q and n are arbitrary constants)Comment: 12 pages, RevTeX, no figure

Dynamic gating in the nucleus accumbens: Behavioral state-dependent synchrony with the prefrontal cortex and hippocampus

Contextual and sensory information, goals, and the motor plan to achieve them are integrated in the nucleus accumbens (NA). Although this integration needs flexibility to operate in a variety of environments, models of NA function rarely consider changing behavioral states. Here, intracellular recordings in anesthetized rats revealed rapid changes in the synchronization between NA up states and prefrontal cortical (PFC) local field potentials (LFPs). The synchronization of the NA with the PFC and ventral hippocampus also varied over time in awake rats, depending on the behavioral state of the animal: NA LFPs followed hippocampal theta rhythms during spatial exploration, but not during an operant task when they were instead synchronized with slower PFC rhythms. These data indicate that the ability of the NA to follow cortical inputs can rapidly change, allowing for a mechanism that could select an optimal response for a given behavioral condition

Thin-disk models in an Integrable Weyl-Dirac theory

We construct a class of static, axially symmetric solutions representing razor-thin disks of matter in an Integrable Weyl-Dirac theory proposed in Found. Phys. 29, 1303 (1999). The main differences between these solutions and the corresponding general relativistic one are analyzed, focusing on the behavior of physical observables (rotation curves of test particles, density and pressure profiles). We consider the case in which test particles move on Weyl geodesics. The same rotation curve can be obtained from many different solutions of the Weyl-Dirac theory, although some of these solutions present strong qualitative differences with respect to the usual general relativistic model (such as the appearance a ring-like density profile). In particular, for typical galactic parameters all rotation curves of the Weyl-Dirac model present Keplerian fall-off. As a consequence, we conclude that a more thorough analysis of the problem requires the determination of the gauge function $\beta$ on galactic scales, as well as restrictions on the test-particle behavior under the action of the additional fields introduced by this theory.Comment: 18 pages, 3 figures; accepted in General Relativity and Gravitatio

Regularity and chaos in the nuclear masses

Shell effects in atomic nuclei are a quantum mechanical manifestation of the single--particle motion of the nucleons. They are directly related to the structure and fluctuations of the single--particle spectrum. Our understanding of these fluctuations and of their connections with the regular or chaotic nature of the nucleonic motion has greatly increased in the last decades. In the first part of these lectures these advances, based on random matrix theories and semiclassical methods, are briefly reviewed. Their consequences on the thermodynamic properties of Fermi gases and, in particular, on the masses of atomic nuclei are then presented. The structure and importance of shell effects in the nuclear masses with regular and chaotic nucleonic motion are analyzed theoretically, and the results are compared to experimental data. We clearly display experimental evidence of both types of motionComment: 40 pages, 10 figures, Lectures delivered at the VIII Hispalensis International Summer School, Sevilla, Spain, June 2003 (to appear in Lecture Notes in Physics, Springer--Verlag, Eds. J. M. Arias and M. Lozano

The Memory of the National and the National as Memory

This essay seeks to illuminate a different, more encompassing kind of transition than that from dictatorship to post-dictatorship (and its attendant forms of memory of military brutal force and human rights abuses) often privileged by studies of political violence and social memory. The focus is twofold: first, to describe a transition from the world of the social to that of the post-social, i.e. a transition from a welfare state-centered form of the nation to its neoliberal competitive state counterpart; and secondly, to analyze its attendant memory dynamics. The double articulation of collective memory under neoliberalism, the deep and recurring violence it has involved at both the social and the individual level, and its self-articulation as a social memory apparatus are apparent in two Chilean films exploring the logic (Pablo Larraín’s Tony Manero) and the history (Patricio Guzmán’s Nostalgia de la luz) of the implementation of this neoliberal memory apparatus in Chile. Este trabajo intenta iluminar una transición más amplia que aquella entre dictadura y post-dictadura ( y sus correspondientes formas de memoria sobre la violencia militar o los abusos a los derechos humanos) que suele ser el objeto de estudio de los trabajos sobre violencia política y memoria social. Mi interés es doble: primero, describir una transición del mundo social al post-social (es decir, una transición desde una forma de estado-nación centrada en el estado de bienestar a su contraparte neoliberal y competitiva; y en segundo lugar, analizar sus correspondientes formas de memoria. La doble articulación de la memoria colectiva bajo el neoliberalismo, la profunda y recurrente violencia presente, tanto a nivel social como a nivel individual, y su autoarticulación como un aparato de la memoria social son evidentes en las dos películas chilenas Tony Manero de Pablo Larraín y Nostalgia de la luz de Patricio Guzmán que exploran la lógica y la historia de la implementación de este aparato de la memoria neoliberal en Chile

El cancionero latinoamericano y su lamento a la minería

1 archivo PDF (5 páginas). tyvlxliiBreve recorrido por el cancionero latinoamericano, que ha plasmado en sus letras las andanzas y quebrantos de los mineros, en el socavón o a cielo abierto. Destacan intérpretes que en su momento fueron parte del llamado Nuevo Canto Latinoamericano. ABSTRACT: A brief tour of the Latin American songbook, which has resulted in its Iyrics and breaks the adventures of miners in the tunnel or open sky. Interpreters emphasize that once were part of the Latin American New Song called. PALABRAS CLAVE: Óscar Chávez. Los Calchakis. Vrctor Manuel. Patricio Manns. Jorge Cafrune. Atahualpa Yupanki. Horacio Guarany. Víctor Jara. Quelentaro. Norteños 4 de Palau. Savia Andina. Alí Primera. Isabel y Ángel Parra. Mercedes Sosa. Jorge Salemo. Daniel Viglietti. KEYWORDS: Óscar Chávez. Los Calchakis. Víctor Manuel. Patricio Manns. Jorge Cafrune. Atahualpa Yupanki. Horacio Guarany. Víctor Jara. Quelentaro. Norteños 4 de Palau. Savia Andina. Alí Primera. Isabel y Ángel Parra. Mercedes Sosa. Jorge Salemo. Daniel Viglietti