Effects of the second virial coefficient on the adiabatic lapse rate of dry atmospheres

We study the effect of the second virial coefficient on the adiabatic lapse rate of a dry atmosphere. To this end, we compute the corresponding adiabatic curves, the internal energy, and the heat capacity, among other thermodynamic parameters. We apply these results to Earth, Mars, Venus, Titan, and the exoplanet G1 851d, considering three physically relevant virial coefficients in each case: the hard-sphere, van der Waals, and the square-well potential. These examples illustrate under which atmospheric conditions the effect of the second virial coefficient is relevant. Taking the latter into account yields corrections towards the experimental values of the lapse rates of Venus and Titan in some instances.Comment: 12 pages, 8 figures. Comments are welcom

Variedades econométricas en la agricultura cubana

El objetivo fundamental de este estudio es obtener cierto número de resultados empíricos sobre el sector agropecuario cubano, con énfasis en su subsector exportador. Estos resultados deberán validar —o refutar— determinadas hipótesis que hemos formulado a partir del conocimiento y estudio tanto de la agricultura cubana como del papel de este importante sector en el desarrollo económico de cualquier país. Otra importante motivación de este trabajo fue la experimentación con metodologías econométricas que hemos visto aplicadas al caso de otros países y que en el medio cubano resultan novedosas y no están ampliamente difundidas. De modo que otra pretensión no menos importante de este trabajo, es que sirva de referencia metodológica para los que deseen mejorar los esfuerzos de investigación sobre la economía cuban

A Vector Non-abelian Chern-Simons Duality

Abelian Chern-Simons gauge theory is known to possess a `$S$-self-dual' action where its coupling constant $k$ is inverted {\it i.e.} $k \leftrightarrow {1 \over k}$. Here a vector non-abelian duality is found in the pure non-abelian Chern-Simons action at the classical level. The dimensional reduction of the dual Chern-Simons action to two-dimensions constitutes a dual Wess-Zumino-Witten action already given in the literature.Comment: 14+1 pages, LaTeX file, no figures, version to appear in Phys. Rev

Angular emission properties of a layer of rare-earth based nanophosphors embedded in one-dimensional photonic crystal coatings

The angular properties of light emitted from rare-earth based nanophosphors embedded in optical resonators built in one-dimensional photonic crystal coatings are herein investigated. Strong directional dependence of the photoluminescence spectra is found. Abrupt angular variations of the enhancement caused by the photonic structure and the extraction power are observed, in good agreement with calculated polar emission patterns. Our results confirm that the optical cavity favors the extraction of different wavelengths at different angles and that integration of nanophosphors within photonic crystals provides control over the directional emission properties that could be put into practice in phosphorescent displays.Ministerio de Ciencia e Innovación MAT2008- 02166, CSD2007-00007Junta de Andalucía FQM3579, FQM524

A microscopic model for a class of mixed-spin quantum antiferromagnets

We propose a microscopic model that describes the magnetic behavior of the mixed-spin quantum systems R$_2$BaNiO$_5$ (R= magnetic rare earth). An evaluation of the properties of this model by Quantum Monte Carlo simulations shows remarkable good agreement with the experimental data and provides new insight into the physics of mixed-spin quantum magnets.Comment: revised version to be published in Phys. Rev.

Changes in the Papez Circuit in early stages of Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of demenMa. Neuronal and synapMc losses occur iniMally and predominantly in the medial temporal lobe structures including hippocampus, amygdala and thalamus, structures that belong to the Papez circuit. The integrity of the connecMons amongst them is essenMal for episodic memory, which is specifically impaired in AD. For this reason we have invesMgated the degeneraMon paRern of subcorMcal structures and its relaMon to early stages of AD, i.e. Mild CogniMve Impairment (MCI), both in the amnesic and mulMdomain types using structural magneMc resonance imaging (using a 3T GE scanner) and VBM‐DARTEL