Oscillations of Thick Accretion Discs Around Black Holes - II

We present a numerical study of the global modes of oscillation of thick accretion discs around black holes. We have previously studied the case of constant distributions of specific angular momentum. In this second paper, we investigate (i) how the size of the disc affects the oscillation eigenfrequencies, and (ii) the effect of power-law distributions of angular momentum on the oscillations. In particular, we compare the oscillations of the disc with the epicyclic eigenfrequencies of a test particle with different angular momentum distributions orbiting around the central object. We find that there is a frequency shift away from the epicyclic eigenfrequency of the test particle to lower values as the size of the tori is increased. We have also studied the response of a thick accretion disc to a localized external perturbation using non constant specific angular momentum distributions within the disc. We find that in this case it is also possible (as reported previously for constant angular momentum distributions) to efficiently excite internal modes of oscillation. In fact we show here that the local perturbations excite global oscillations (acoustic p modes) closely related to the epicyclic oscillations of test particles. Our results are particularly relevant in the context of low mass X-ray binaries and microquasars, and the high frequency Quasi-Periodic Oscillations (QPOs) observed in them. Our computations make use of a Smooth Particle Hydrodynamics (SPH) code in azimuthal symmetry, and use a gravitational potential that mimics the effects of strong gravity.Comment: 10 pages, 8 figures, accepted for publication as a paper in the Monthly Notices of the Royal Astronomical Societ

Oscillations of Thick Accretion Discs Around Black Holes

We present a numerical study of the response of a thick accretion disc to a localized, external perturbation with the aim of exciting internal modes of oscillation. We find that the perturbations efficiently excite global modes recently identified as acoustic p--modes, and closely related to the epicyclic oscillations of test particles. The two strongest modes occur at eigenfrequencies which are in a 3:2 ratio. We have assumed a constant specific angular momentum distribution within the disc. Our models are in principle scale--free and can be used to simulate accretion tori around stellar or super massive black holes.Comment: 4 pages, 4 figures, accepted for publication as a letter in the Monthly Notices of the Royal Astronomical Societ

Estudio sobre aspectos evolutivos de la DIC (Dependencia e independencia de campo) en un grupo de jóvenes y de ancianos

Se ha realizado un estudio sobre los estilos cognitivos en dos cohortes evolutivas: un grupo joven y otro de ancianos, aplicando el GEFT con dos objetivos: - Constatar las modificaciones que sufre el estilo cognitivo en estos dos períodos del ciclo vital.- Analizar las diferencias intersexuales en ambos períodos. Las conclusiones coinciden con los estudios de COMALLI (1965), SCHAWARTZ y KARP (1967), etc., al comprobar que el estilo cognitivo evoluciona desde una independencia de campo en los grupos jóvenes, hacia una dependencia de campo claramente manifiesta en la senectud. Las diferencias intersexuales no son significativas en ninguno de los dos grupos analizados, aunqtte se encuentran de alguna manera más acentuadas en la tercera edad.Study about evolutive aspects of FDI in youth-old age. A study has been realized about cognitive styles in two evolutive cuts: youth-old age, by applying the GEFT with two objectives:- To verify the modificatios that cognitive sytle undergoes through these life span periods. - To analize intersexual differences in each one of these cohorts. The conclusions coincide with the studies of COMALLI (1965), SCHAWARTZ and KARP (1967), etc., by confirming that style changes from a FI in the youth groups towards a very clear FD in the old age group. Sexual differences aren't significatives in none of the groups, though they are more accentuate in the old age one

Time-dependent attractors for non-autonomous nonlocal reaction-diffusion equations

In this paper, the existence and uniqueness of weak and strong solutions for a non-autonomous nonlocal reaction-diffusion equation is proved. Next, the existence of minimal pullback attractors in the L2 -norm in the frameworks of universes of fixed bounded sets and those given by a tempered growth condition, and some relationships between them are established. Finally, we prove the existence of minimal pullback attractors in the H1-norm and study relationships among these new families and those given previously in the L2 - context. The results are also new in the autonomous framework in order to ensure the existence of global compact attractors, as a particular case.Ministerio de Economía y CompetitividadFondo Europeo de Desarrollo RegionalJunta de Andalucí

Robustness of time-dependent attractors in H1-norm for nonlocal problems

In this paper, the existence of regular pullback attractors as well as their upper semicontinuous behaviour in H1-norm are analysed for a parameterized family of non-autonomous nonlocal reaction-diffusion equations without uniqueness, improving previous results [Nonlinear Dyn. 84 (2016), 35–50].Ministerio de Economía y CompetitividadFondo Europeo de Desarrollo RegionalJunta de Andalucí

Tolerancia digestiva en el recién nacido prematuro.

Tesis ( Nutrición y Dietética)La finalidad de realizar esta investigación fue identificar el perfil epidemiológico y clínico del recién nacido prematuro desde un enfoque nutricional y conocer la prevalencia de los aspectos involucrados en la aparición intolerancia alimentaria y su asociación significativa. Para tal efecto se realizó un estudio de tipo relacional con un diseño no experimental, retrospectivo transeccional y descriptivo con el total de recién nacidos prematuros que cumplían con los criterios de inclusión y que fueron hospitalizados en la unidad de Neonatología de la clínica Indisa el año dos mil seis. Los resultados arrojaron que el género más prevalente fue el sexo masculino y la clasificación nutricional adecuado para la edad gestacional. En esta población el sexo masculino y el tipo de alimentación láctea a base de fórmula exclusiva o mixta presentaron asociación significativa con la aparición de intolerancia alimentaria, los signos de mtolerancia alimentaria más prevalentes fueron la distensión abdominal y los residuos gástricos. Con todo esto la hipótesis que plantea que los recién nacidos prematuros alimentados con leche materna ya sea exclusiva o mixta presenta mejor tolerancia alimentaria versus los alimentados exclusivamente a base de fórmula queda aceptada y se plantea la necesidad de fomentar y apoyar a las madres de los recién nacidos prematuros para la extracción y utilización de la leche materna

A search for radio pulsars and fast transients in M31 using the WSRT

We present the results of the most sensitive and comprehensive survey yet undertaken for radio pulsars and fast transients in the Andromeda galaxy (M31) and its satellites, using the Westerbork Synthesis Radio Telescope (WSRT) at a central frequency of 328 MHz. We used the WSRT in a special configuration called 8gr8 (eight-grate) mode, which provides a large instantaneous field-of-view, about 5 square degrees per pointing, with good sensitivity, long dwell times (up to 8 hours per pointing), and good spatial resolution (a few arc minutes) for locating sources. We have searched for both periodicities and single pulses in our data, aiming to detect bright, persistent radio pulsars and rotating radio transients (RRATs) of either Galactic or extragalactic origin. Our searches did not reveal any confirmed periodic signals or bright single bursts from (potentially) cosmological distances. However, we do report the detection of several single pulse events, some repeating at the same dispersion measure, which could potentially originate from neutron stars in M31. One in particular was seen multiple times, including a burst of six pulses in 2000 seconds, at a dispersion measure of 54.7 pc cm^-3, which potentially places the origin of this source outside of our Galaxy. Our results are compared to a range of hypothetical populations of pulsars and RRATs in M31 and allow us to constrain the luminosity function of pulsars in M31. They also show that, unless the pulsar population in M31 is much dimmer than in our Galaxy, there is no need to invoke any violation of the inverse square law of the distance for pulsar fluxes.Comment: 18 pages, 14 figures, 8 tables. Accepted for publication in the main journal of MNRA

Forced Oscillations in Fluid Tori and Quasi-Periodic Oscillations

The kilo-Hertz Quasi--Periodic Oscillations in X-ray binaries could originate within the accretion flow, and be a signature of non--linear fluid oscillations and mode coupling in strong gravity. The possibility to decipher these systems will impact our knowledge of fundamental parameters such as the neutron star mass, radius, and spin. Thus they offer the possibility to constrain the nuclear equation of state and the rotation parameter of stellar--mass black holes. We review the general properties of these oscillations from a hydrodynamical point of view, when the accretion flow is subject to external perturbations and summarize recent results.Comment: Astronomische Nachrichten, in pres

12CO and 13CO J=3-2 observations toward N11 in the Large Magellanic Cloud

After 30 Doradus, N11 is the second largest and brightest nebula in the LMC. This large nebula has several OB associations with bright nebulae at its surroundings. N11 was previously mapped at the lowest rotational transitions of $^{12}$CO (J=1--0 and 2--1), and in some particular regions pointings of the $^{13}$CO J=1--0 and 2--1 lines were also performed. Using ASTE we mapped the whole extension of the N11 nebula in the $^{12}$CO J=3--2 line, and three sub-regions in the $^{13}$CO J=3--2 line. The regions mapped in the $^{13}$CO J=3--2 were selected based on that they may be exposed to the radiation at different ways: a region lying over the nebula related to the OB association LH10 (N11B), another one that it is associated with the southern part of the nebula related to the OB association LH13 (N11D), and finally a farther area at the southwest without any embedded OB association (N11I). We found that the morphology of the molecular clouds lying in each region shows some signatures that could be explained by the expansion of the nebulae and the action of the radiation. Fragmentation generated in a molecular shell due to the expansion of the N11 nebula is suggested. The integrated line ratios $^{12}$CO/$^{13}$CO show evidences of selective photodissociation of the $^{13}$CO, and probably other mechanisms such as chemical fractionation. The CO contribution to the continuum at 870 $\mu$m was directly derived. The distribution of the integrated line ratios $^{12}$CO J=3--2/2--1 show hints of stellar feedback in N11B and N11D. The ratio between the virial and LTE mass (M$_{\rm vir}$/M$_{\rm LTE}$) is higher than unity in all analyzed molecular clumps, which suggests that the clumps are not gravitationally bounded and may be supported by external pressure. A non-LTE analysis suggests that we are mapping gas with densities about a few 10$^{3}$ cm$^{-3}$.Comment: Accepted to be published in A&A. Figures were degrade

Contemporary absurdity and the role of design as a strategic possibility of social welfare from symbolic production

Los objetos hipertecnológicos han propiciado aparentes estados de soberanía en los usuarios sobre tales dispositivos, no obstante, resulta evidente que la electricidad, la red inalámbrica, el contexto temporal y espacial, entre otros, mantienen a los sujetos vinculados a la realidad cotidiana. Pese a ello el sujeto suele tener una parcela de la consciencia en el dispositivo virtual y otra en la cotidianeidad que, de acuerdo con su propia historia, le remite los referentes para significar los contenidos de dicho dispositivo. Así, el sujeto se desplaza por instantes entre uno y otro lado o en ambos al mismo tiempo. Esto es, se integran los contenidos de los dos lados y se convierten en la consciencia que se deconstruye de manera permanente ya no solo con la experiencia de vida sino con esta y la integración de los nuevos contenidos mediáticosLa sociedad contemporánea observa condiciones particulares de deterioro advertidas en las conductas patológicas sociales generadas por los medios masivos de comunicación, anteriormente por la imagen radiada televisada y recientemente por los contenidos y plataformas digitales mediadas por la Web. Estos perjuicios sociales que tienen como origen la imagen deben no solo ser subsanados para evitar acrecentar las evidentes patologías sociales generadas sino incluso hacer uso de los propios medios que las forman para contrarrestarlas a través del diseño como coadyuvante del bienestar social. El estulto definido por Foucault, sugiere una profunda subjetivización del sujeto posmoderno mermado en sus facultades cognitivas por las representaciones formales hipermediáticas visuales cuyas consecuencias tienden a ser desastrosas. Es necesario subrayar que el diseño abarca una parte importante de la cultura no solo como cultura material sino particularmente simbólica. Por ello es menester que las áreas del diseño ostenten propiedades axiológicas no solo estéticas sino principalmente éticas. Así, el objetivo de este trabajo es la problematización de dicho estulto y la posibilidad de paliarlo desde el diseño en sus manifestaciones simbólicas visuales. Para ello se caracteriza la postura de Foucault en torno al término “estulto social”, se extrapolan los principios hacia la sociedad de hoy caracterizada por los medios digitales del ciberespacio; para posteriormente argumentar el papel del diseño como visualidad en estos medios hipertecnificados. Finalmente se proponen argumentos sobre la posibilidad de volver a la ética del bienestar al diseño. Metodológicamente se trata de la exploración de textos vinculados con los problemas mediáticos de la sociedad de hoy, y la producción simbólica desde la imagen en los medios tecnológicos, para proponer principios éticos para mejorar los contenidos del diseño visual