35 research outputs found
Jointly setting upper limits on multiple components of an anisotropic stochastic gravitational-wave background
With the increasing sensitivities of the gravitational wave (GW) detectors
and more detectors joining the international network, the chances of detection
of a stochastic GW background (SGWB) are progressively increasing. Different
astrophysical and cosmological processes are likely to give rise to backgrounds
with distinct spectral signatures and distributions on the sky. The observed
SGWB will therefore be a superposition of these components. Hence, one of the
first questions that will come up after the first detection of a SGWB will
likely be about identifying the dominant components and their distributions on
the sky. Both these questions were addressed separately in the literature,
namely, how to separate components of isotropic backgrounds and how to probe
the anisotropy of a single component. Here, we address the question of how to
separate distinct anisotropic backgrounds with (sufficiently) different
spectral shapes. We first obtain the combined Fisher information matrix from
folded data using an efficient analysis pipeline PyStoch, which incorporates
covariances between pixels and spectral indices. This is necessary for
estimating the detection statistic and setting upper limits. However, based on
a recent study, we ignore the pixel-to-pixel noise covariance that does not
have a significant effect on the results at the present sensitivity levels of
the detectors. We show that the joint analysis accurately separates and
estimates backgrounds with different spectral shapes and different sky
distributions with no major bias. This does come at the cost of increased
variance. Thus making the joint upper limits safer, though less strict than the
individual analysis. We finally set joint upper limits on the multicomponent
anisotropic background using Advanced LIGO data taken up to the first half of
the third observing run.Comment: 14 pages, 10 figures, 2 table
Bayesian parameter estimation for targeted anisotropic gravitational-wave background
Extended sources of the stochastic gravitational backgrounds have been conventionally searched on the spherical harmonics bases. The analysis during the previous observing runs by the ground-based gravitational-wave detectors, such as LIGO and Virgo, have yielded the constraints on the angular power spectrum Cℓ, yet it lacks the capability of estimating other parameters such as a spectral index. In this paper, we introduce an alternative Bayesian formalism to search for such stochastic signals with a particular distribution of anisotropies on the sky. This approach provides a Bayesian posterior of model parameters and also enables selection tests among different signal models. While the conventional analysis fixes the highest angular scale a priori, here we show a more systematic and quantitative way to determine the cutoff scale based on a Bayes factor, which depends on the amplitude and the angular scale of observed signals. Also, we analyze the third observing runs of LIGO and Virgo for the population of millisecond pulsars and obtain the 95% constraints of the signal amplitude, ϵ<2.7×10-8PGC2018-094773-B-C32, CEX2020-001007-
Targeted search for the stochastic gravitational-wave background from the galactic millisecond pulsar population
The millisecond pulsars, old-recycled objects spinning with high frequency
(kHz) sustaining the deformation from their spherical shape, may
emit gravitational-waves (GW). These are one of the potential candidates
contributing to the anisotropic stochastic gravitational-wave background (SGWB)
observable in the ground-based GW detectors. Here, we present the results from
a likelihood-based targeted search for the SGWB due to millisecond pulsars in
the Milky Way, by analyzing the data from the first three observing runs of
Advanced LIGO and Advanced Virgo detector. We assume that the shape of SGWB
power spectra and the sky distribution is known a priori from the population
synthesis model. The information of the ensemble source properties, i.e., the
in-band number of pulsars, and the averaged ellipticity,
is encoded in the maximum likelihood statistic. We do not find
significant evidence for the SGWB signal from the considered source population.
The best Bayesian upper limit with confidence for the parameters are
and , which is
comparable to the bounds on mean ellipticity with the GW observations of the
individual pulsars. Finally, we show that for the plausible case of
, with the one year of observations, the one-sigma sensitivity
on might reach and for the
second-generation detector network having A+ sensitivity and third-generation
detector network respectively.Comment: 13 pages, 3 figures, 1 tabl
Community prevalence of methicillin and vancomycin resistant Staphylococcus aureus in and around Bangalore, southern India
Thyroid Cytology in India: Contemporary Review and Meta-analysis
Fine-needle aspiration cytology (FNAC) is a screening test for triaging thyroid nodules, aiding in subsequent clinical management. However, the advantages have been overshadowed by the multiplicity of reporting systems and a wide range of nomenclature used. The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) was formulated in 2007, to give the world a uniform thyroid cytology reporting system, facilitating easy interpretation by the clinicians. Here, we review the status of thyroid FNAC in India in terms of various reporting systems used including a meta-analysis of the previously published data. An extensive literature search was performed using internet search engines. The reports with detailed classification system used in thyroid cytology were included. The meta-analysis of published data was compared with the implied risk of malignancy by TBSRTC. More than 50 studies were retrieved and evaluated. TBSRTC is currently the most widely used reporting system with different studies showing good efficacy and interobserver concordance. Ancillary techniques have, as of now, limited applicability and acceptability in thyroid cytology in India. Twenty-eight published articles met the criteria for inclusion in the meta-analysis. When compared with TBSRTC recommendations, the meta-analysis showed a higher risk of malignancy for categories I and III. Thyroid FNAC is practiced all over India. TBSRTC has found widespread acceptance, with most institutions using this system for routine thyroid cytology reporting. However, reasons for a high malignancy risk for categories I and III need to be looked into. Various possible contributing factors are discussed in the review
Dyeing of silk with Procion HE dyes
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effect of various dyeing parameters on exhaustion and fixation of bifunctional
monochlorotriazine dyes (Procion HE dyes) on silk has been studied. Factorial
design has been used to obtain the optimum conditions of dyeing. Maximum
exhaustion has been obtained with 110 g/L sodium chloride and 3 g/L sodium
carbonate. Temperature in the range 60-80°C has no influence on exhaustion.
Improvement in mechanical properties of dyed silk suggests the formation of
crosslinks in the fibre by these dyes.</span
Upper limits on persistent gravitational waves using folded data and the full covariance matrix from Advanced LIGOs first two observing runs
The stochastic gravitational wave background (SGWB) created by astrophysical
sources in the nearby universe is likely to be anisotropic. Upper limits on
SGWB anisotropy have been produced for all major data taking runs by the
ground-based laser interferometric detectors. However, due to the challenges
involved in numerically inverting the pixel-to-pixel noise covariance matrix,
which is necessary for setting upper limits, the searches accounted for angular
correlations in the map by using the spherical harmonic basis, where
regularization was relatively easier. This approach is better suited though for
extended sources.Moreover, the upper limit maps produced in the two different
bases are seemingly different. While the upper limits may be consistent within
statistical errors, it was important to check whether the results would remain
consistent if the full noise covariance matrix was used in the pixel basis.
Here, we use the full pixel-to-pixel Fisher information matrix to create upper
limit maps of SGWB anisotropy. We first perform an unmodeled search for
persistent, directional gravitational wave sources using folded data from the
first (O1) and second (O2) observing runs of Advanced LIGO and show that the
results are consistent with the upper limits published by the LIGO-Virgo
Collaboration (LVC). We then explore various ways to account for the
pixel-to-pixel Fisher information matrix using singular value decomposition and
Bayesian regularization schemes. We also account for the bias arising from
regularization in the likelihood. We do not find evidence for any SGWB signal
in the data, consistent with the LVC results and, though the upper limits
differ significantly. Through an injection study we show that they are all
valid upper limits, that is, the upper limit in a pixel is less than the
injected signal strength in less than of the pixels.Comment: 17 pages, 7 figure
A Mild and Environmentally benign Synthesis of Benzimidazoles: Relevance to the pectin hetero Polysaccharide as a Catalyst
Abstract We have developed a green procedure by using benzaldehyde and o-phenylene diamine as the model substrate, hetero polysaccharide pectin as a catalyst and water as a solvent. The generality and scope of this protocol was determined by synthesizing various derivatives of benzimidazole in good to excellent yield through this environment friendly, time and energy saving, green method
Targeted search for the stochastic gravitational-wave background from the galactic millisecond pulsar population
The millisecond pulsars, old-recycled objects spinning with high frequency (kHz) sustaining the deformation from their spherical shape, may emit gravitational-waves (GW). These are one of the potential candidates contributing to the anisotropic stochastic gravitational-wave background (SGWB) observable in the ground-based GW detectors. Here, we present the results from a likelihood-based targeted search for the SGWB due to millisecond pulsars in the Milky Way, by analyzing the data from the first three observing runs of Advanced LIGO and Advanced Virgo detector. We assume that the shape of SGWB power spectra and the sky distribution is known a priori from the population synthesis model. The information of the ensemble source properties, i.e., the in-band number of pulsars, and the averaged ellipticity, is encoded in the maximum likelihood statistic. We do not find significant evidence for the SGWB signal from the considered source population. The best Bayesian upper limit with confidence for the parameters are and , which is comparable to the bounds on mean ellipticity with the GW observations of the individual pulsars. Finally, we show that for the plausible case of , with the one year of observations, the one-sigma sensitivity on might reach and for the second-generation detector network having A+ sensitivity and third-generation detector network respectively