Two Dimensional Clustering of Gamma-Ray Bursts using durations and hardness

Gamma-Ray Bursts (GRBs) have been conventionally bifurcated into two distinct categories: ``short'' and ``long'' with durations less than and greater than two seconds respectively. However, there is a lot of literature (although with conflicting results) regarding the existence of a third intermediate class. To investigate this issue, we extend a recent study (arXiv:1612.08235) on classification of GRBs to two dimensions by incorporating the GRB hardness in addition to the observed durations. We carry out this unified analysis on GRB datasets from four detectors, viz. BATSE, RHESSI, Swift (observed and intrinsic frame), and Fermi-GBM. We consider the duration and hardness features in log-scale for each of these datasets and determine the best-fit parameters using Gaussian Mixture Model. This is followed by information theoretic criterion (AIC and BIC) to determine if a three-component fit is favored compared to a two-component one or vice-versa. For BATSE, we find that both AIC and BIC show preference for three components with decisive significance. For Fermi and RHESSI, both AIC and BIC show preference for two components, although the significance is marginal from AIC, but decisive using BIC. For Swift dataset in both the observed and rest frame, we find that three components are favored according to AIC with decisive significance, and two are preferred with BIC with marginal to strong significance.Comment: 13 pages, 10 figures. This is an extension of arXiv:1612.08235 to two-dimension

Life Extension of Aircraft Components - An IAF Perspective

Due to escalating cost of aircraft and feasibility for upgrading existing fleet with advance technology insertions at comparatively lesser cost, a trend is observed world over to extend the life of aircraft. IAF is no exception to this.Since OEMs have started demanding exhorbitant fees for giving life extension technology of their aircraft, a number of life extension projects have been undertaken by IAF with the help of various R&D, Public Sector, academic,certification and inspection agencies. These studies have highlighted the need to carry out basic and applied research for life extension of various aircraft components like airframe structures, aeroengine, undercarriage, canopies /perspex and rotables. A core group formed at the instance of IAF has identified these proposals under a project code named `Project LIFEX'. It is the perception of IAF that adequate expertise is available within the country to meet all her life extension requirements

Cosmic Neutrino Bound on the Dark Matter Annihilation Rate in the Late Universe

How large can the dark matter self-annihilation rate in the late universe be? This rate depends on (rho_DM/m_chi)^2 , where rho_DM/m_chi is the number density of dark matter, and the annihilation cross section is averaged over the velocity distribution. Since the clustering of dark matter is known, this amounts to asking how large the annihilation cross section can be. Kaplinghat, Knox, and Turner proposed that a very large annihilation cross section could turn a halo cusp into a core, improving agreement between simulations and observations; Hui showed that unitarity prohibits this for large dark matter masses. We show that if the annihilation products are Standard Model particles, even just neutrinos, the consequent fluxes are ruled out by orders of magnitude, even at small masses. Equivalently, to invoke such large annihilation cross sections, one must now require that essentially no Standard Model particles are produced.Comment: 4 pages, 2 figures; to appear in the proceedings of the TeV Particle Astrophysics II Workshop, Madison, Wisconsin, 28-31 Aug 200

Checking the validity of truncating the cumulant hierarchy description of a small system

We analyze the behavior of the first few cumulant in an array with a small number of coupled identical particles. Desai and Zwanzig (J. Stat. Phys., {\bf 19}, 1 (1978), p. 1) studied noisy arrays of nonlinear units with global coupling and derived an infinite hierarchy of differential equations for the cumulant moments. They focused on the behavior of infinite size systems using a strategy based on truncating the hierarchy. In this work we explore the reliability of such an approach to describe systems with a small number of elements. We carry out an extensive numerical analysis of the truncated hierarchy as well as numerical simulations of the full set of Langevin equations governing the dynamics. We find that the results provided by the truncated hierarchy for finite systems are at variance with those of the Langevin simulations for large regions of parameter space. The truncation of the hierarchy leads to a dependence on initial conditions and to the coexistence of states which are not consistent with the theoretical expectations based on the multidimensional linear Fokker-Planck equation for finite arrays

An evaluation of the technique of use of metered dose inhaler administration in bronchial asthma children

Background: Inadequate understanding and performance of drug administration using metered-dose inhaler (MDI) in paediatric population affects therapeutic outcome. Hence, this study aimed to evaluate the impact of two educational interventional methods for usage of MDI in paediatric patients of bronchial asthma.Methods: This prospective, interventional study was done in paediatric asthma patients who were prescribed drugs with (MDI) with/without spacer at outpatient department of pediatrics. Patients were divided in group A (video) or group B (leaflet) as per random table method and method to use MDI was assessed by using checklist as per WHO guide to good prescribing at baseline. Investigator taught the technique by a video (group A) and leaflet (group B) to the selected population. Patients were followed up after 15 days and assessed for use of MDI using the same checklist. Data were analysed by using paired and unpaired ‘t’-test.Results: A total of 100 pediatric asthma patients were included in study group A (50) and group B (50). The average no. of steps (WHO checklist) followed was significantly improved at post intervention in both group A (with spacer, p<0.0001) as well as B (without spacer, p<0.05). Although average no. of steps followed were more in group A, no significant difference was found between two groups after intervention.Conclusions: As video is an audio-visual method of demonstration, and hence help us memorise the step of inhalational technique in pediatric patients. Repeated demonstration/education to patients/caregivers may improve the method of MDI usage

An intensive monitoring of adverse drug reactions in pediatric hospitalized patients of a tertiary care hospital

Background: Children are at a higher risk of therapeutic failure due to major difference in pharmacokinetic, pharmacodynamics of drugs, off-label use and divergence of their illness from adult. The safety of drugs used in adult patients cannot be extrapolated to a pediatric age group. Hence, this study aimed to evaluate the incidence and overall pattern of adverse drug reactions in pediatric patients hospitalized in pediatric wards at a tertiary care hospital in India.Methods: Pediatric patients up to 12 years hospitalized in two randomly selected pediatric units were enrolled and followed up daily till discharge. Detailed information of patients and ADRs (adverse drug reactions) if any were recorded from case records. ADRs were assessed for incidence, onset, duration, management, outcome, causality, severity, preventability, seriousness and risk factors. Appropriateness of drug treatment in patients with ADRs was analyzed using Phadke’s criteria. Data was analyzed using student’s t test, ANOVA and Chi square test.Results: A total of 700 patients were enrolled (mean age 3.95±0.12 years). A total of 66 ADRs observed in 58 patients. Intravenous (70.4%) being most common route for ADRs. The incidence of ADRs was 8.28%. Majority of ADRs occurred within 1 day, commonly affected skin and appendages followed by (28.78%), GI (25.75%) ADRs were frequently associated with antimicrobials (69.38%) and vaccines and sera (12.24%). Majority of reactions were mild (56%%), non-serious (77.2%), not preventable (95.4%), recovered completely at discharge (83.33%) and had possible (77.2%) causal association with suspect drug. Age group 0-3 years and prescription of ≥5 drugs were risk factors for occurrence of ADRs. Semi rational drug therapy was observed in 65.5% patients.Conclusions: Clinicians should be vigilant regarding occurrence of ADRs in pediatrics especially during the first week of hospitalization. Risk factors like 0-3 years of age and multiple drugs should be taken into consideration during treatment of these patients to help minimize adverse drug reactions

Quark Mass Matrices with Four and Five Texture Zeroes, and the CKM Matrix, in terms of Mass Eigenvalues

Using the triangular matrix techniques of Kuo et al and Chiu et al for the four and five texture zero cases, with vanishing (11) elements for U and D matrices, it is shown, from the general eigenvalue equations and hierarchy conditions, that the quark mass matrices, and the CKM matrix can be expressed (except for the phases) entirely in terms of quark masses. The matrix structures are then quite simple and transparent. We confirm their results for the five texture zero case but find, upon closer examination of all the CKM elements which our results provide, that six of their nine patterns for the four texture zero case are not compatible with experiments. In total, only one five-texture zero and three four-texture zero patterns are allowed.Comment: 15 pages, 3 table

Variational Inference as an alternative to MCMC for parameter estimation and model selection

Most applications of Bayesian Inference for parameter estimation and model selection in astrophysics involve the use of Monte Carlo techniques such as Markov Chain Monte Carlo (MCMC) and nested sampling. However, they are time consuming and their convergence to posterior is difficult to determine. In this work, we introduce variational inference (VI) as an alternative to solve astrophysics problems, and demonstrate its usefullness for parameter estimation and model selection. Variational inference converts the inference problem into an optimization problem by approximating the posterior from a known family of distributions and using Kullback-Leibler divergence to characterize the difference. It takes advantage of fast optimization techniques, which make it ideal to deal with large datasets and makes it trivial to parallelize. We derive a new approximate evidence estimation based on variational posterior and importance sampling technique called posterior weighted importance sampling for evidence (PWISE), which is useful to perform Bayesian model selection. As a proof of principle, we apply variational inference to five different problems in astrophysics, where Monte Carlo techniques were previously used. These include assessment of significance of annual modulation in the COSINE-100 dark matter experiment, measuring exoplanet orbital parameters from radial velocity data, tests of periodicities in measurements of Newton's constant $G$, assessing the significance of a turnover in the spectral lag data of GRB 160625B and estimating the mass of a galaxy cluster using weak gravitational lensing. We find that variational inference is much faster than MCMC and nested sampling techniques for most of these problems while providing competitive results. All our analysis codes have been made publicly available.Comment: 15 pages, 3 figures. Added one more example and introduced and applied a new metric for calculating Bayesian evidence in Variational Inferenc