Magnetic Activity in Thick Accretion Disks and Associated Observable Phenomena: II. Flux Storage

In paper I, we have studied the conditions under which flux tubes are expelled from adiabatic thick accretion disks. In the present paper, we explore a few other models of thick disks, where flux tubes could be stored. We show that flux tubes with sufficiently weak fields are not expelled out if they move adiabatically inside an isothermal disk; they continue to oscillate around mean equipotential surfaces inside the disk. If the field in the flux tube is amplified due to the shear, they are eventually expelled away. We explore a `toy' model also, where the entropy increase outwards from the center of the thick disk and find a similar behavior. Flux storage in the disk, as in the case of the sun, in general, enhances the possibility of sustained magnetic activity formation of coronae in the chimney region. The existence of coronae on the disk surface may explain the short-time variability in the spectra of Blazars and the emission of energetic particles from AGNs and Quasars. It may also supply matter to the cosmic jets through magnetized winds.Comment: LaTeX, 27 pages, Astrophysical Journal (In press), March 20th Issu

Advances in imaging for atrial fibrillation ablation.

Over the last fifteen years, our understanding of the pathophysiology of atrial fibrillation (AF) has paved the way for ablation to be utilized as an effective treatment option. With the aim of gaining more detailed anatomical representation, advances have been made using various imaging modalities, both before and during the ablation procedure, in planning and execution. Options have flourished from procedural fluoroscopy, electroanatomic mapping systems, preprocedural computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, and combinations of these technologies. Exciting work is underway in an effort to allow the electrophysiologist to assess scar formation in real time. One advantage would be to lessen the learning curve for what are very complex procedures. The hope of these developments is to improve the likelihood of a successful ablation procedure and to allow more patients access to this treatment

Knowledge of Pharmacology of Analgesics Among Nurses in a Tertiary Centre

Objectives: To evaluate the knowledge of nurses about the analgesics they administer in our hospital. Methodology: A total of 102 nurses completed the questionnaire which included 20 multiple choice questions based on the dosage forms, mechanism of action, route of administration, adverse effects of the commonly administered analgesics, the nurses’ educational qualifications and their working experience. Frequency, percentage, mean, Kruskal Wallis test and Mann Whitneys test were used to analyse data. Answers were given a score out of 20(100%). Results: The sample comprised of 17(16.6%) senior staff nurses, 38(37%) junior staff nurses and 47(46%) student nurses. Of the staff, 10.8 % were BSc and MSc nurses, 43.1 were GNM staff. The mean knowledge score of BSc & MSc staff was 12.18, GNM staff was 11.7 and of student nurses was 13.38. None of the groups scored more than 15, suggesting their knowledge was inadequate. There was a correlation between knowledge and experience in the staff nurses. Conclusion: The result of this study suggests that the knowledge of pharmacology of analgesics among nurses is inadequate, and thus supports the need for supplementary pharmacology education for nurses in clinical settings, focusing on common drugs they administer and help prevent medical errors

Long-Term Measurements of Sunspot Magnetic Tilt Angles

Tilt angles of close to 30,600 sunspots are determined using Mount Wilson daily averaged magnetograms taken from 1974 to 2012, and MDI/SoHO magnetograms taken from 1996 to 2010. Within a cycle, more than 90% of sunspots have a normal polarity alignment along the east-west direction following Hale's law. The median tilts increase with increasing latitude (Joy's law) at a rate of ~0.5 degree per degree of latitude. Tilt angles of spots appear largely invariant with respect to time at a given latitude, but they decrease by ~0.9degree per year on average, a trend which largely reflects Joy's law following the butterfly diagram. We find an asymmetry between the hemispheres in the mean tilt angles. On average, the tilts are greater in the southern than in the northern hemisphere for all latitude zones, and the differences increase with increasing latitude.Comment: 29 pages, 13 figures, to appear on ApJ, October 20, 2012 website: http://www2.ess.ucla.edu/~jingli/ApJ201210

Explaining the decline in the auction rate securities market

Auction rate securities are an example of a relatively obscure financial market instrument that has been caught up in the recent negative sentiment affecting the financial markets. This article examines these securities and sheds some light on recent events.Auctions ; Securities ; Financial markets

A possible explanation of the Maunder minimum from a flux transport dynamo model

We propose that the poloidal field at the end of the last sunspot cycle before the Maunder minimum fell to a very low value due to fluctuations in the Babcock--Leighton process. With this assumption, a flux transport dynamo model is able to explain various aspects of the historical records of the Maunder minimum remarkably well on choosing the parameters of the model suitably to give the correct growth time

Two-step Emergence of the Magnetic Flux Sheet from the Solar Convection Zone

We perform two-dimensional MHD simulations on the solar flux emergence. We set the initial magnetic flux sheet at z=-20,000 km in the convection zone. The flux sheet rises through the convective layer due to the Parker instability, however, decelerates beneath the photosphere because the plasma on the flux sheet piles up owing to the convectively stable photosphere above. Meanwhile, the flux sheet becomes locally unstable to the Parker instability within the photosphere, and the further evolution to the corona occurs (two-step emergence model). We carry out a parameter survey to investigate the condition for this two-step model. We find that magnetic fluxes which form active regions are likely to have undergone the two-step emergence. The condition for the two-step emergence is 10^21 - 10^22 Mx with 10^4 G at z=-20,000 km in the convection zone.Comment: 41 pages, 15 figures, 1 table, Accepted for publication in Ap

A theoretical model of torsional oscillations from a flux transport dynamo model

Assuming that the torsional oscillation is driven by the Lorentz force of the magnetic field associated with the sunspot cycle, we use a flux transport dynamo to model it and explain its initiation at a high latitude before the beginning of the sunspot cycle.Comment: 3 pages, 2 figures. proceedings of IAU symposium 273, Physics of Sun and star spots, Ventura, California 22-26 August 201

The physics of twisted magnetic tubes rising in a stratified medium: two dimensional results

The physics of a twisted magnetic flux tube rising in a stratified medium is studied using a numerical MHD code. The problem considered is fully compressible (no Boussinesq approximation), includes ohmic resistivity, and is two dimensional, i.e., there is no variation of the variables in the direction of the tube axis. We study a high plasma beta case with small ratio of radius to external pressure scaleheight. The results obtained can therefore be of relevance to understand the transport of magnetic flux across the solar convection zone.Comment: To be published in ApJ, Vol. 492, Jan 10th, 1998; 25 pages, 16 figures. NEW VERSION: THE PREVIOUS ONE DIDN'T PRINT CORRECTLY. The style file overrulehere.sty is include