Transition from homogeneous to inhomogeneous limit cycles : Effect of local filtering in coupled oscillators

10 pages, 8 FigsPeer reviewedPublisher PD

Hyperon bulk viscosity in the presence of antikaon condensate

We investigate the hyperon bulk viscosity due to the non-leptonic process $n + p \rightleftharpoons p + \Lambda$ in $K^-$ condensed matter and its effect on the r-mode instability in neutron stars. We find that the hyperon bulk viscosity coefficient in the presence of antikaon condensate is suppressed compared with the case without the condensate. The suppressed hyperon bulk viscosity in the superconducting phase is still an efficient mechanism to damp the r-mode instability in neutron stars.Comment: AASTeX; 21 pages including 5 figures; change in the title and replaced by the revised versio

Effect of hyperon-hyperon interaction on bulk viscosity and r-mode instability in neutron stars

We investigate the effect of hyperon matter including hyperon-hyperon interaction on bulk viscosity. Equations of state are constructed within the framework of a relativistic field theoretical model where baryon-baryon interaction is mediated by the exchange of scalar and vector mesons. Hyperon-hyperon interaction is also taken into account by the exchange of two strange mesons. This interaction results in a smaller maximum mass neutron star compared with the case without the interaction. The coefficient of bulk viscosity due to the non-leptonic weak process is determined by these equations of state. The interacting hyperon matter reduces the bulk viscosity coefficient in a neutron star interior compared with the no interaction case. The r-mode instability is more effectively suppressed in hyperon-hyperon interaction case than that without the interaction.Comment: 25 pages, 10 figures; two new figures added and results and discussion section revised; final version to appear in PR

Probing dense matter in neutron stars with axial w-modes

We study the problem of extracting information about composition and equation of state of dense matter in neutron star interior using axial w-modes. We determine complex frequencies of axial w-modes for a set of equations of state involving hyperons as well as Bose-Einstein condensates of antikaons adopting the continued fraction method. Hyperons and antikaon condensates result in softer equations of state leading to higher frequencies of first axial w-modes than that of nuclear matter case, whereas the opposite happens in case of damping times. The presence of condensates may lead to the appearance of a new stable branch of superdense stars beyond the neutron star branch called the third family. The existence of same mass compact stars in both branches are known as neutron star twins. Further investigation of twins reveal that first axial w-mode frequencies of superdense stars in the third family are higher than those of the corresponding twins in the neutron star branch.Comment: LaTeX; 23 pages including two tables and 11 figure

Medication errors reported in a tertiary care private hospital in Eastern India: a three years experience

Background: Medication errors (MEs) can cause significant harm to patients. The MEs identified through reporting processes currently report only a fraction of the actual number of MEs. Data about MEs is limited in India, especially from eastern and north-eastern parts of India. The objective of this study was to analyse the various types of Medication errors reported in a tertiary care private hospital in Eastern India. The aim was to determine the various factors associated with these errors and steps to be taken to reduce the MEs in this healthcare setup.Methods: We carried out a prospective passive surveillance study over the course of 3 years (2016-2018) on 50,822 admitted patients after obtaining approval from the Institutional Ethics Committee. A detailed root-cause analysis was performed for every reported error by a team of healthcare quality professionals and clinical pharmacists along with a clinical pharmacologist followed by appropriate preventive and corrective actions.Results: In our study, a total number of 88 medication errors were reported from a sample size of 50,822 (0.0017%). 61 of the reported MEs were administration errors (69.3%). Higher preponderance of medication errors was seen in male patients (53.1%) in comparison to female patients (46.9%).Conclusions: In this study gross under-reporting of MEs were observed which is in line with previously published studies in India. The reasons reported for gross under-reporting can function as an effective tool to ensure improved reporting of MEs and implementation of mitigation strategies

Bulk viscosity and r-modes of neutron stars

The bulk viscosity due to the non-leptonic process involving hyperons in $K^-$ condensed matter is discussed here. We find that the bulk viscosity is modified in a superconducting phase. Further, we demonstrate how the exotic bulk viscosity coefficient influences $r$-modes of neutron stars which might be sources of detectable gravitational waves.Comment: 4 page, 2 figures; presented in the Quark Matter 2008 held in Jaipur, India from 4-10 February, 2008; to be published in J. Phys.

Exotica in rotating compact stars

The determination of mass and radius of a single neutron star EXO 0748-676 has been reported recently. Also, the estimate of radius from the measurement of moment of inertia of pulsar A in double pulsar system PSR J0737-3039 would be possible in near future. Here we construct models of static and uniformly rotating neutron stars involving exotic matter and compare our theoretical calculations with the recent findings from observations to probe dense matter in neutron stars.Comment: 8 pages, 3 figures Plenary talk at the 5th International Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPAQGP), Kolkata, India, 8-12 February, 200

Multi-Objective Differential Evolution for Automatic Clustering with Application to Micro-Array Data Analysis

This paper applies the Differential Evolution (DE) algorithm to the task of automatic fuzzy clustering in a Multi-objective Optimization (MO) framework. It compares the performances of two multi-objective variants of DE over the fuzzy clustering problem, where two conflicting fuzzy validity indices are simultaneously optimized. The resultant Pareto optimal set of solutions from each algorithm consists of a number of non-dominated solutions, from which the user can choose the most promising ones according to the problem specifications. A real-coded representation of the search variables, accommodating variable number of cluster centers, is used for DE. The performances of the multi-objective DE-variants have also been contrasted to that of two most well-known schemes of MO clustering, namely the Non Dominated Sorting Genetic Algorithm (NSGA II) and Multi-Objective Clustering with an unknown number of Clusters K (MOCK). Experimental results using six artificial and four real life datasets of varying range of complexities indicate that DE holds immense promise as a candidate algorithm for devising MO clustering schemes