Hydromagnetic Stability of a Slim Disk in a Stationary Geometry

The magnetorotational instability originates from the elastic coupling of fluid elements in orbit around a gravitational well. Since inertial accelerations play a fundamental dynamical role in the process, one may expect substantial modifications by strong gravity in the case of accretion on to a black hole. In this paper, we develop a fully covariant, Lagrangian displacement vector field formalism with the aim of addressing these issues for a disk embedded in a stationary geometry with negligible radial flow. This construction enables a transparent connection between particle dynamics and the ensuing dispersion relation for MHD wave modes. The MRI--in its incompressible variant-- is found to operate virtually unabated down to the marginally stable orbit; the putative inner boundary of standard accretion disk theory. To get a qualitative feel for the dynamical evolution of the flow below $r_{\rm ms}$, we assume a mildly advective accretion flow such that the angular velocity profile departs slowly from circular geodesic flow. This exercise suggests that the turbulent eddies will occur at spatial scales approaching the radial distance while tracking the surfaces of null angular velocity gradients. The implied field topology, namely large-scale horizontal field domains, should yield strong mass segregation at the displacement nodes of the non-linear modes when radiation stress dominates the local disk structure (an expectation supported by quasi-linear arguments and by the non-linear behavior of the MRI in a non-relativistic setting). Under this circumstance, baryon-poor flux in horizontal field domains will be subject to radial buoyancy and to the Parker instability, thereby promoting the growth of poloidal field.Comment: submitted to M.N.R.A.S. (3/29/02), 14 pages, 2 figures v2 accepted paper: clarified text and added discussion on radial flow effects. Added reference

Menopausia, el inicio del envejecimiento de las mujeres chilenas. Un estudio cualitativo

Indexación: Scopus.Objective. To develop the meaning of menopause of a group of post-menopausal women and their relationship with aging. Methods. Qualitative descriptive study on 15 Chilean women that completed a taped face-to-face in depth interview that were interpreted according to Krippendorff. Results. A qualitative content analysis revealed the presence of two themes: (a) Cessation of women's reproductive stage and (b) a life transition to aging. Conclusion. Women perceived their menopause as the beginning of aging focusing on the end of fertility and the social connotation that this new role implies. Feeling old 10 years before the customary beginning of old age is an important starting point to be incorporated in women's health education.http://ref.scielo.org/x7bfh