1,524 research outputs found

    Evolution of inclined planets in three-dimensional radiative discs

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    While planets in the solar system only have a low inclination with respect to the ecliptic there is mounting evidence that in extrasolar systems the inclination can be very high, at least for close-in planets. One process to alter the inclination of a planet is through planet-disc interactions. Recent simulations considering radiative transport have shown that the evolution of migration and eccentricity can strongly depend on the thermodynamic state of the disc. We extend previous studies to investigate the planet-disc interactions of fixed and moving planets on inclined and eccentric orbits. We also analyse the effect of the disc's thermodynamic properties on the orbital evolution of embedded planets in detail. The protoplanetary disc is modelled as a viscous gas where the internally produced dissipation is transported by radiation. For locally isothermal discs, we confirm previous results and find inclination damping and inward migration for planetary cores. For low inclinations i < 2 H/r, the damping is exponential, while di/dt is proportional to i^-2 for larger i. For radiative discs, the planetary migration is very limited, as long as their inclination exceeds a certain threshold. If the inclination is damped below this threshold, planetary cores with a mass up to approximately 33 Earth masses start to migrate outwards, while larger cores migrate inwards right from the start. The inclination is damped for all analysed planet masses. In a viscous disc an initial inclination of embedded planets will be damped for all planet masses. This damping occurs on timescales that are shorter than the migration time. If the inclination lies beneath a certain threshold, the outward migration in radiative discs is not handicapped. Outward migration is strongest for circular and non-inclined orbits

    A decidable policy language for history-based transaction monitoring

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    Online trading invariably involves dealings between strangers, so it is important for one party to be able to judge objectively the trustworthiness of the other. In such a setting, the decision to trust a user may sensibly be based on that user's past behaviour. We introduce a specification language based on linear temporal logic for expressing a policy for categorising the behaviour patterns of a user depending on its transaction history. We also present an algorithm for checking whether the transaction history obeys the stated policy. To be useful in a real setting, such a language should allow one to express realistic policies which may involve parameter quantification and quantitative or statistical patterns. We introduce several extensions of linear temporal logic to cater for such needs: a restricted form of universal and existential quantification; arbitrary computable functions and relations in the term language; and a "counting" quantifier for counting how many times a formula holds in the past. We then show that model checking a transaction history against a policy, which we call the history-based transaction monitoring problem, is PSPACE-complete in the size of the policy formula and the length of the history. The problem becomes decidable in polynomial time when the policies are fixed. We also consider the problem of transaction monitoring in the case where not all the parameters of actions are observable. We formulate two such "partial observability" monitoring problems, and show their decidability under certain restrictions

    High-Resolution Spectroscopy of FUors

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    High-resolution spectroscopy was obtained of the FUors FU Ori and V1057 Cyg between 1995 and 2002 with SOFIN at NOT and with HIRES at Keck I. During those years FU Ori remained about 1 mag. (in B) below its 1938-39 maximum brightness, but V1057 Cyg (B ~ 10.5 at peak in 1970-71) faded from about 13.5 to 14.9 and then recovered slightly. Their photospheric spectra resemble a rotating G0 Ib supergiant, with v_eq sin i = 70 km/s for FU Ori and 55 km/s for V1057 Cyg. As V1057 Cyg faded, P Cyg structure in Halpha and the IR CaII lines strengthened and a complex shortward-displaced shell spectrum increased in strength, disappeared in 1999, and reappeared in 2001. Night-to-night changes in the wind structure of FU Ori show evidence of sporadic infall. The strength of P Cyg absorption varied cyclically with a period of 14.8 days, with phase stability maintained over 3 seasons, and is believed to be the rotation period. The structure of the photospheric lines also varies cyclically, but with a period of 3.54 days. A similar variation may be present in V1057 Cyg. As V1057 Cyg has faded, the emission lines of a pre-existing low-excitation chromosphere have emerged, so we believe the `line doubling' in V1057 Cyg is produced by these central emission cores in the absorption lines, not by orbital motion in an inclined Keplerian disk. No dependence of v_eq sin i on wavelength or excitation potential was detected in either star, again contrary to expectation for a self-luminous accretion disk. Nor are critical lines in the near infrared accounted for by synthetic disk spectra. A rapidly rotating star near the edge of stability (Larson 1980), can better explain these observations. FUor eruptions may not be a property of ordinary TTS, but may be confined to a special subspecies of rapid rotators having powerful quasi-permanent winds.Comment: 41 pages (including 32 figures and 9 tables); ApJ, in press; author affiliation, figs. 3 and 9 correcte

    Analysis of cerebrospinal fluid from cattle with central nervous system disorders after storage for 24 hours with autologous serum

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    BACKGROUND: We compared the changes in cell morphology, total and differential cell counts between cerebrospinal fluid (CSF) samples analyzed within an hour of collection (fresh sample) and after the addition of autologous serum and storage for 24 h (stored sample) in 27 cattle with central nervous system disorders. RESULTS: There was a positive linear correlation between total and differential cell counts in the fresh and the stored samples. Cell morphology was preserved in all stored samples, except for increased vacuolization of mononuclear cells and cleaved nuclei of some small mononuclear cells. In the stored CSF samples, the total nucleated cell count and monocyte percentage were decreased (P = 0.01; P = 0.03), while the lymphocyte percentage was increased (P = 0.04). Mononuclear pleocytosis diagnosed in 20 fresh samples was cytologically confirmed in 12 of the 20 stored samples. In the remaining eight stored samples, the number of total nucleated cells was within the normal range. Neutrophilic pleocytosis was confirmed in all seven stored samples. The overall agreement rate between cytologic interpretation of the fresh and the stored CSF samples was 70 % (100 % for neutrophilic pleocytosis and 60 % for mononuclear pleocytosis). CONCLUSIONS: Adding 11 % of autologous serum to CSF samples might allow delayed analysis with a good agreement rate for CSF cytological interpretation. Caution is nonetheless warranted, as animal age, anamnesis, and neurological presentation need to be considered when interpreting stored CSF without pleocytosis. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12917-015-0502-x) contains supplementary material, which is available to authorized users

    Integración entre servicios de salud y comunidad. Evaluación cualitativa de servicios de primer nivel de atención de la ciudad de Corrientes

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    La integración entre el equipo de salud y su comunidad de referencia es una de las condiciones operativas, y conceptuales, de la Atención Primaria de la Salud. Con el fin de evaluarla, se realizó una investigación en las Salas de Atención Primaria de la Salud de la Ciudad de Corrientes. Se utilizó un método exploratorio orientado desde una perspectiva interpretativa-cualitativa. 30 alumnos de la Carrera de Medicina de la Universidad Nacional del Nordeste fueron capacitados a tal efecto. Se realizaron observaciones in situ y entrevistas semi-estructuradas al personal de salud y a usuarios de las salas. Se realizó un análisis de contenido, esquematizado en un sistema de categorías preestablecidas y enriquecido con subcategorias inducidas a partir del análisis de la información. Como facilitadores para la integración, se encontró por parte del personal del equipo: conocimiento de los problemas de la zona, residencia en el barrio, buena accesibilidad a la atención y respuesta adecuada a la demanda; y por parte de la población: predisposición a participar. Como barreras para la integración: diferencias de conceptos respecto al rol del primer nivel de atención entre equipo de salud y comunidad y escasa integración de algunos profesionales. Se concluyó con que existen factores favorecedores importantes que habría que aprovechar y potenciar; en tanto, habría que trabajar sobre las barreras, comenzando por el rol fundamental que para esto tiene el equipo de salud. La mejor identificación de categorías que ha permitido este trabajo propicia la realización de estudios de mayor profundidad

    Measurements of polarized photo-pion production on longitudinally polarized HD and Implications for Convergence of the GDH Integral

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    We report new measurements of inclusive pion production from frozen-spin HD for polarized photon beams covering the Delta(1232) resonance. These provide data simultaneously on both H and D with nearly complete angular distributions of the spin-difference cross sections entering the Gerasimov-Drell-Hearn (GDH) sum rule. Recent results from Mainz and Bonn exceed the GDH prediction for the proton by 22 microbarns, suggesting as yet unmeasured high-energy components. Our pi0 data reveal a different angular dependence than assumed in Mainz analyses and integrate to a value that is 18 microbarns lower, suggesting a more rapid convergence. Our results for deuterium are somewhat lower than published data, considerably more precise and generally lower than available calculations.Comment: 4 pages, 4 figures. Submitted for publication in Physical Review Letter

    Evolución de la demanda ambulatoria del sector público de la Ciudad de Corrientes en el período 1991-2013

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    La estrategia de atención primaria de la salud (APS) promueve fuertemente el rol del primer nivel de atención (PNA) como puerta de entrada al sistema; siendo su utilización un indicador de importancia que tiene dentro del sistema. A fin de evaluar la tendencia y distribución de demanda ambulatoria del subsector público en la ciudad de Corrientes (CCtes.), se analizaron las consultas externas del período 1991-2013 según los Anuarios de Estadísticas de la Provincia. Se utilizaron datos censales y proyecciones de población. Se evaluó la tendencia de utilización mediante el número de consultas en ambos niveles y tasas poblacionales. En el período la población de la CCtes. creció un 81,20 %; en tanto, el incremento de las consultas fue del 51,66 %: un 99,27 % las hospitalarias y 21,55 % las del PNA. En el primer trienio del período las consultas fueron superiores en el PNA. Luego la relación se invirtió y sólo volvió a superar el PNA al hospital en dos oportunidades: en el año 1998 y el período 2004-2007. Finalmente, se observa una recuperación en los últimos cuatro años observados. Las tasas provinciales pasaron de 3,5 a 5,0 consultas/habitantes/año; en tanto en la CCtes. pasó de 5,0 a 5,2 consultas/habitantes/año. Se concluye que en la CCtes., según las tasas, la utilización no ha variado y que el PNA no ha ocupado un lugar de relevancia en la atención ambulatoria.

    Type III migration in a low viscosity disc

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    We study the type III migration of a Saturn mass planet in low viscosity discs. The planet is found to experience cyclic episodes of rapid decay in orbital radius, each amounting to a few Hill radii. We find this to be due to the scattering of large- scale vortices present in the disc. The origin and role of vortices in the context of type III migration is explored. It is shown through numerical simulations and semi- analytical modelling that spiral shocks induced by a sufficiently massive planet will extend close to the planet orbital radius. The production of vortensity across shock tips results in thin high vortensity rings with a characteristic width of the local scale height. For planets with masses equal to and above that of Saturn, the rings are co-orbital features extending the entire azimuth. Linear stability analysis show there exists unstable modes that are localised about local vortensity minima which coincide with gap edges. Simulations show that vortices are non-linear a outcome. We used hydrodynamic simulations to examine vortex-planet interactions. Their effect is present in discs with kinematic viscosity less than about an order of magnitude smaller than the typically adopted value of \nu = 10^{-5}\Omega_pr_p(0)^2, where r_p(0) and \Omega_p are the initial orbital radius and angular velocity of the planet respectively. We find that the magnitude of viscosity affects the nature of type III migration but not the extent of the orbital decay. The role of vortices as a function of initial disc mass is also explored and it is found that the amount of orbital decay during one episode of vortex-planet interaction is independent of initial disc mass. We incorporate the concept of the co-orbital mass deficit in the analysis of our results and link it to the presence of vortices at gap edges.Comment: 20 pages, 20 figures, accepted for publication in MNRA

    Conditional generation of N-photon entangled states of light

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    We propose a scheme for conditional generation of two-mode N-photon path-entangled states of traveling light field. These states may find applications in quantum optical lithography and they may be used to improve the sensitivity of interferometric measurements. Our method requires only single-photon sources, linear optics (beam splitters and phase shifters), and photodetectors with single photon sensitivity.Comment: 4 pages, 2 figures, RevTeX
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