Serendipitous discovery of a dying Giant Radio Galaxy associated with NGC 1534, using the Murchison Widefield Array

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.Recent observations with the Murchison Widefield Array at 185~MHz have serendipitously unveiled a heretofore unknown giant and relatively nearby ($z = 0.0178$) radio galaxy associated with NGC\,1534. The diffuse emission presented here is the first indication that NGC\,1534 is one of a rare class of objects (along with NGC\,5128 and NGC\,612) in which a galaxy with a prominent dust lane hosts radio emission on scales of $\sim$700\,kpc. We present details of the radio emission along with a detailed comparison with other radio galaxies with disks. NGC1534 is the lowest surface brightness radio galaxy known with an estimated scaled 1.4-GHz surface brightness of just 0.2\,mJy\,arcmin$^{-2}$. The radio lobes have one of the steepest spectral indices yet observed: $\alpha=-2.1\pm0.1$, and the core to lobe luminosity ratio is $Peer reviewe

Overcoming real-world obstacles in 21 cm power spectrum estimation: A method demonstration and results from early Murchison Widefield Array data

We present techniques for bridging the gap between idealized inverse covariance weighted quadratic estimation of 21 cm power spectra and the real-world challenges presented universally by interferometric observation. By carefully evaluating various estimators and adapting our techniques for large but incomplete data sets, we develop a robust power spectrum estimation framework that preserves the so-called "Epoch of Reionization (EoR) window" and keeps track of estimator errors and covariances. We apply our method to observations from the 32-tile prototype of the Murchinson Widefield Array to demonstrate the importance of a judicious analysis technique. Lastly, we apply our method to investigate the dependence of the clean EoR window on frequency—especially the frequency dependence of the so-called “wedge" feature—and establish upper limits on the power spectrum from z ¼ 6.2 to z ¼ 11:7. Our lowest limit is ?ðkÞ < 0.3 Kelvin at 95% confidence at a comoving scale k ¼ 0.046 Mpc-1 and z ¼ 9.5

Modifying Ligand-Induced and Constitutive Signaling of the Human 5-HT4 Receptor

G protein–coupled receptors (GPCRs) signal through a limited number of G-protein pathways and play crucial roles in many biological processes. Studies of their in vivo functions have been hampered by the molecular and functional diversity of GPCRs and the paucity of ligands with specific signaling effects. To better compare the effects of activating different G-protein signaling pathways through ligand-induced or constitutive signaling, we developed a new series of RASSLs (receptors activated solely by synthetic ligands) that activate different G-protein signaling pathways. These RASSLs are based on the human 5-HT4b receptor, a GPCR with high constitutive Gs signaling and strong ligand-induced G-protein activation of the Gs and Gs/q pathways. The first receptor in this series, 5-HT4-D100A or Rs1 (RASSL serotonin 1), is not activated by its endogenous agonist, serotonin, but is selectively activated by the small synthetic molecules GR113808, GR125487, and RO110-0235. All agonists potently induced Gs signaling, but only a few (e.g., zacopride) also induced signaling via the Gq pathway. Zacopride-induced Gq signaling was enhanced by replacing the C-terminus of Rs1 with the C-terminus of the human 5-HT2C receptor. Additional point mutations (D66A and D66N) blocked constitutive Gs signaling and lowered ligand-induced Gq signaling. Replacing the third intracellular loop of Rs1 with that of human 5-HT1A conferred ligand-mediated Gi signaling. This Gi-coupled RASSL, Rs1.3, exhibited no measurable signaling to the Gs or Gq pathway. These findings show that the signaling repertoire of Rs1 can be expanded and controlled by receptor engineering and drug selection

Study of redshifted H I from the epoch of reionization with drift scan

The detection of the Epoch of Reionization (EoR) in the redshifted 21-cm line is a challenging task. Here we formulate the detection of the EoR signal using the drift scan strategy. This method potentially has better instrumental stability as compared to the case where a single patch of sky is tracked. We demonstrate that the correlation time between measured visibilities could extend up to 1-2 hr for an interferometer array such as the Murchison Widefield Array (MWA), which has a wide primary beam. We estimate the EoR power based on cross-correlation of visibilities across time and show that the drift scan strategy is capable of the detection of the EoR signal with comparable/better signal-to-noise as compared to the tracking case. We also estimate the visibility correlation for a set of bright point sources and argue that the statistical inhomogeneity of bright point sources might allow their separation from the EoR signal

The Murchison Widefield Array: The Square Kilometre Array Precursor at Low Radio Frequencies

The Murchison Widefield Array (MWA) is one of three Square Kilometre Array Precursor telescopes and is located at the Murchison Radio-astronomy Observatory in the Murchison Shire of the mid-west of Western Australia, a location chosen for its extremely low levels of radio frequency interference. The MWA operates at low radio frequencies, 80–300 MHz, with a processed bandwidth of 30.72 MHz for both linear polarisations, and consists of 128 aperture arrays (known as tiles) distributed over a ~3-km diameter area. Novel hybrid hardware/software correlation and a real-time imaging and calibration systems comprise the MWA signal processing backend. In this paper, the as-built MWA is described both at a system and sub-system level, the expected performance of the array is presented, and the science goals of the instrument are summarised

The Indian Pulsar Timing Array Data Release 2: I. Dataset and Timing Analysis

The Indian Pulsar Timing Array (InPTA) employs unique features of the upgraded Giant Metrewave Radio Telescope (uGMRT) to monitor dozens of the International Pulsar Timing Array (IPTA) millisecond pulsars (MSPs), simultaneously in the 300-500 MHz and the 1260-1460 MHz bands. This dual-band approach ensures that any frequency-dependent delays are accurately characterized, significantly improving the timing precision for pulsar observations, which is crucial for pulsar timing arrays. We present details of InPTA's second data release that involves 7 yrs of data on 27 IPTA MSPs. This includes sub-banded Times of Arrival (ToAs), Dispersion Measures (DM), and initial timing ephemerides for our MSPs. A part of this dataset, originally released in InPTA's first data release, is being incorporated into IPTA's third data release which is expected to detect and characterize nanohertz gravitational waves in the coming years. The entire dataset is reprocessed in this second data release providing some of the highest precision DM estimates so far and interesting solar wind related DM variations in some pulsars. This is likely to characterize the noise introduced by the dynamic inter-stellar ionised medium much better than the previous release thereby increasing sensitivity to any future gravitational wave search

THEORETICAL CONCEPT OF JOB SATISFACTION - A STUDY

Job satisfaction is one of the important factors that have drawn attention of the organization as well as academicians. In view of the rising competition as a result of globalisation, managers have placed great importance on the construct of job satisfaction. This may be due to the findings of many studies that job satisfaction is a significant determinant of organizational commitment. Highly satisfied employees will exert extra effort and contribute positively to the effectiveness and efficiency of their organizations. Job satisfaction will lead to better performance and the employees will be more committed towards their organization. Hence, this study is focused to consolidate the theoretical concept about job satisfaction.</jats:p

The use of ultrasound-guided wire localisation in orthopaedics

The use of ultrasound-guided wire localisation of lesions is not well described in the orthopaedic literature. We describe a case of an impalpable schwannoma of the femoral nerve and another of sacroiliitis with an associated pelvic abscess. In both, surgical localisation was difficult. Peri-operative ultrasound-guided wire localisation was used to guide surgery and minimise tissue damage, thereby optimising the results and recovery of the patient. </jats:p