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

Distorted cyclotron line profile in Cep X-4 as observed by NuSTAR

We present spectral analysis of NuSTAR and Swift observations of Cep X-4 during its outburst in 2014. We observed the source once during the peak of the outburst and once during the decay, finding good agreement in the spectral shape between the observations. We describe the continuum using a powerlaw with a Fermi-Dirac cutoff at high energies. Cep X-4 has a very strong cyclotron resonant scattering feature (CRSF) around 30 keV. A simple absorption-like line with a Gaussian optical depth or a pseudo-Lorentzian profile both fail to describe the shape of the CRSF accurately, leaving significant deviations at the red side of the line. We characterize this asymmetry with a second absorption feature around 19 keV. The line energy of the CRSF, which is not influenced by the addition of this feature, shows a small but significant positive luminosity dependence. With luminosities between (1-6)e36 erg/s, Cep X-4 is below the theoretical limit where such a correlation is expected. This behavior is similar to Vela X-1 and we discuss parallels between the two systems.Comment: 6 pages, 4 figure, accepted for publication in ApJ letter

Elderly day care centers: Recommendations for improvement

Indexación: Scopus.Introduction: Chile has become a country that continues to grow at an accelerated pace. One of the key pieces of the Comprehensive Policy for Positive Aging for Chile is the development of Day Centers for the Elderly (CDPM) directed elderly at the foot of the dependency. Objective: To know the perception of a group of PMs, their caregivers and professionals of their participation in the CDPM with the purpose of designing recommendations to improve this new type of geriatric service established in the country. Methodology: Qualitative descriptive study performed in 30 participants through 4 focus groups: 2 in elderly (n=12), 1 with caregivers (n=8) and 1 with center professionals (n=10). Results: Two main comprehensive categories were identified: 1) Perception of benefits for elderly: improvement of functionality, increase of well-being and insertion of the social mayor, 2) Recommendations for improvement of CDPM: Criteria for inclusive income, flexibility and diversity in activities stipulated and Improvements in egress. Conclusions: The elderly, their caregivers and the professionals who attend them are consistent in pointing out that elderly assistance to this type of service reports benefits in its functionality, well-being and social insertion. This study contributes to broadening the understanding of results in the uses of CDPM by reporting an experience in a particular social context. © 2018 Spanish Publishers Associate. All rights reserved.Introduction: Chile has become a country that continues to grow at an accelerated pace. One of the key pieces of the Comprehensive Policy for Positive Aging for Chile is the development of Day Centers for the Elderly (CDPM) directed elderly at the foot of the dependency. Objective: To know the perception of a group of PMs, their caregivers and professionals of their participation in the CDPM with the purpose of designing recommendations to improve this new type of geriatric service established in the country. Methodology: Qualitative descriptive study performed in 30 participants through 4 focus groups: 2 in elderly (n=12), 1 with caregivers (n=8) and 1 with center professionals (n=10). Results: Two main comprehensive categories were identified: 1) Perception of benefits for elderly: improvement of functionality, increase of well-being and insertion of the social mayor, 2) Recommendations for improvement of CDPM: Criteria for inclusive income, flexibility and diversity in activities stipulated and Improvements in egress. Conclusions: The elderly, their caregivers and the professionals who attend them are consistent in pointing out that elderly assistance to this type of service reports benefits in its functionality, well-being and social insertion. This study contributes to broadening the understanding of results in the uses of CDPM by reporting an experience in a particular social context.http://www.gerokomos.com/wp-content/uploads/2018/03/29-1-2018-009.pd

How to reduce the number of rating scale items without predictability loss?

Rating scales are used to elicit data about qualitative entities (e.g., research collaboration). This study presents an innovative method for reducing the number of rating scale items without the predictability loss. The "area under the receiver operator curve method" (AUC ROC) is used. The presented method has reduced the number of rating scale items (variables) to 28.57\% (from 21 to 6) making over 70\% of collected data unnecessary. Results have been verified by two methods of analysis: Graded Response Model (GRM) and Confirmatory Factor Analysis (CFA). GRM revealed that the new method differentiates observations of high and middle scores. CFA proved that the reliability of the rating scale has not deteriorated by the scale item reduction. Both statistical analysis evidenced usefulness of the AUC ROC reduction method.Comment: 14 pages, 5 figure

Estimating numerical error in neural network simulations on Graphics Processing Units

Abstract. We present our view of the main physical ingredients determining the evolution of neutron star magnetic fields. This includes the basic properties of neutron star matter, possible scenarios for the origin of the magnetic field, constraints and mechanisms for its evolution, and a discussion of our recent work on the Hall drift

The Central American agricultural sector in the run-up to negotiations for the EAA with the European Union: potential conflicts and scenarios

The present study aims to describe the current context, identify the potential points of conflict and determine some of the possible scenarios within the setting and as a result of the negotiation of an Economic Association Agreement (EAA) between the European Union (EU) and Central America (CA), in the specific case of the farming sector. The study is structured around the following set of specific objectives: - Describe the relations between the European Union and Central America in terms of agriculture. - Identify the main interests of the EU and CA farming sectors in the negotiations for an Economic Association Agreement. - Identify potential ‘winning’ and ‘losing’ products in Central American agricultural as a result of this economic association agreement