1,524 research outputs found
Evolution of inclined planets in three-dimensional radiative discs
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
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
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
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
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
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
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
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
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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