Bardeen-Petterson effect and the disk structure of the Seyfert galaxy NGC 1068

VLBA high spatial resolution observations of the disk structure of the active galactic nucleus NGC 1068 has recently revealed that the kinematics and geometry of this AGN is well characterized by an outer disk of H2O maser emission having a compact milliarcsecond (parsec) scale structure, which is encircling a thin rotating inner disk surrounding a ~10^7 M_\sun compact mass, likely a black hole. A curious feature in this source is the occurrence of a misalignment between the inner and outer parts of the disk, with the galaxy's radio jet being orthogonal to the inner disk. We interpret this peculiar configuration as due to the Bardeen-Petterson effect, a general relativistic effect that warps an initially inclined (to the black hole equator) viscous disk, and drives the angular momentum vector of its inner part into alignment with the rotating black hole spin. We estimate the time-scale for both angular momenta to get aligned as a function the spin parameter of the Kerr black hole. We also reproduce the shape of the parsec and kiloparsec scale jets, assuming a model in which the jet is precessing with a period and aperture angle that decrease exponentially with time, as expected from the Bardeen-Petterson effect.Comment: 12 pages, 3 figures, accepted for publication in The Astrophysical Journa

Observational evidence of spin-induced precession in active galactic nuclei

We show that it is possible to explain the physical origin of jet precession in active galactic nuclei (AGNs) through the misalignment between the rotation axes of the accretion disk and of the Kerr black hole. We apply this scenario to quasars, Seyfert galaxies and also to the Galactic Center black hole Sgr A*, for which signatures of either jet or disk precession have been found. The formalism adopted is parameterized by the ratio of the precession period to the black hole mass and can be used to put constraints to the physical properties of the accretion disk as well as to the black hole spin in those systems.Comment: 10 pages, 1 figure, accepted for publication in ApJ Letter

Simulating nearly edge-on sloshing in the galaxy cluster Abell 2199

Off-axis collisions between galaxy clusters may induce the phenomenon of sloshing, causing dense gas to be dragged from the cool core of a cluster, resulting in a spiral of enhanced X-ray emission. Abell 2199 displays signatures of sloshing in its core and it is possible that the orbital plane of the collision is seen nearly edge-on. We aim to evaluate whether the features of Abell 2199 can be explained by a sloshing spiral seen under a large inclination angle. To address this, we perform tailored hydrodynamical $N$-body simulations of a non-frontal collision with a galaxy group of $M_{200}=1.6\times10^{13}\,{\rm M_{\odot}}$. We obtain a suitable scenario in which the group passed by the main cluster core 0.8 Gyr ago, with a pericentric separation of 292 kpc. Good agreement is obtained from the temperature maps as well as the residuals from a $\beta$-model fit to the simulated X-ray emission. We find that under an inclination of $i=70^{\circ}$ the simulation results remain consistent with the observations.Comment: 13 pages, 14 figures, accepted for publication in MNRAS; replaced Fig.

Quebra de dormência em diásporos de teca (Tectona grandis L.f.).

Tectona grandis L.f. é uma essência florestal exótica de importância econômica e social para o Brasil. As mudas dessa espécie são produzidas através de diásporos constituídos dos frutos com endocarpo e mesocarpo rígidos. O objetivo do presente trabalho foi avaliar o efeito de métodos de quebra de dormência na germinação das sementes desta espécie. Para superar a dormência do endocarpo e mesocarpo, os diásporos de teca foram submetidos à imersão em água quente, imersão em ácido sulfúrico (33,5%) e imersão em água corrente. Os diásporos foram distribuídos em substrato constituído de areia, e o teste de germinação foi realizado em câmara de germinação com temperatura de 30 ºC, sob luz branca durante oito horas por dia. As avaliações foram feitas diariamente, durante 60 dias. O método de imersão dos diásporos em ácido sulfúrico por três minutos, foi o tratamento mais eficiente, apresentando 73% das sementes germinadas

Fitting Isochrones to Open Cluster photometric data: A new global optimization tool

We present a new technique to fit color-magnitude diagrams of open clusters based on the Cross-Entropy global optimization algorithm. The method uses theoretical isochrones available in the literature and maximizes a weighted likelihood function based on distances measured in the color-magnitude space. The weights are obtained through a non parametric technique that takes into account the star distance to the observed center of the cluster, observed magnitude uncertainties, the stellar density profile of the cluster among others. The parameters determined simultaneously are distance, reddening, age and metallicity. The method takes binary fraction into account and uses a Monte-Carlo approach to obtain uncertainties on the determined parameters for the cluster by running the fitting algorithm many times with a re-sampled data set through a bootstrapping procedure. We present results for 9 well studied open clusters, based on 15 distinct data sets, and show that the results are consistent with previous studies. The method is shown to be reliable and free of the subjectivity of most previous visual isochrone fitting techniques.Comment: 19 pages, 25 figures, accepted for publication in Astronomy&Astrophysic

Safe and stable generation of induced pluripotent stem cells using doggybone DNA vectors

The application of induced pluripotent stem cells (iPSCs) in advanced therapies is increasing at pace, but concerns remain over their clinical safety profile. We report the first-ever application of doggybone DNA (dbDNA) vectors to generate human iPSCs. dbDNA vectors are closed-capped linear double-stranded DNA gene expression cassettes that contain no bacterial DNA and are amplified by a chemically defined, current good manufacturing practice (cGMP)-compliant methodology. We achieved comparable iPSC reprogramming efficiencies using transiently expressing dbDNA vectors with the same iPSC reprogramming coding sequences as the state-of-the-art OriP/EBNA1 episomal vectors but, crucially, in the absence of p53 shRNA repression. Moreover, persistent expression of EBNA1 from bacterially derived episomes resulted in stimulation of the interferon response, elevated DNA damage, and increased spontaneous differentiation. These cellular activities were diminished or absent in dbDNA-iPSCs, resulting in lines with a greater stability and safety potential for cell therapy

Current Status of Simulations

As the title suggests, the purpose of this chapter is to review the current status of numerical simulations of black hole accretion disks. This chapter focuses exclusively on global simulations of the accretion process within a few tens of gravitational radii of the black hole. Most of the simulations discussed are performed using general relativistic magnetohydrodynamic (MHD) schemes, although some mention is made of Newtonian radiation MHD simulations and smoothed particle hydrodynamics. The goal is to convey some of the exciting work that has been going on in the past few years and provide some speculation on future directions.Comment: 15 pages, 14 figures, to appear in the proceedings of the ISSI-Bern workshop on "The Physics of Accretion onto Black Holes" (8-12 October 2012