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Irwin J.A.,Queens University | Brar R.S.,University of Ontario Institute of Technology | Saikia D.J.,University of Pune | Saikia D.J.,Cotton College State University | Henriksen R.N.,Queens University
Monthly Notices of the Royal Astronomical Society | Year: 2013

We present the first maps of NGC 3044 and NGC 4157 at λ 450 μm and λ 850 μm from the JamesClerk Maxwell Telescope as well as the first maps at 617 MHzfrom the Giant Metrewave Radio Telescope. High-latitude emission has been detected in both the radio continuum and sub-mm for NGC 3044 and in the radio continuum for NGC 4157, including several new features. For NGC 3044, in addition, we find 617MHz emission extending to the north of the major axis, beginning at the far ends of the major axis. One of these low-intensity features, more than 10 kpc from the major axis, has apparently associated emission at λ 20 cm and may be a result of in-disc activity related to star formation. The dust spectrum at longwavelengths required fittingwith a two-temperaturemodel for both galaxies, implying the presence of cold dust (Tc = 9.5K for NGC 3044 and Tc = 15.3K for NGC4157).Dustmasses areMd = 1.6 × 108Mȯ andMd = 2.1 × 107Mȯ forNGC3044 and NGC 4157, respectively, and are dominated by the cold component. There is a clear correlation between the 617MHz and λ 850 μmemission in the two galaxies. In the case of NGC 3044 for which the λ 850 μm data are strongly dominated by cold dust, this implies a relation between the non-thermal synchrotron emission and cold dust. The 617MHz component represents an integration of massive star formation over the past 107-8 yr and the λ 850 μm emission represents heating from the diffuse interstellar radiation field (ISRF). The 617 MHz-λ 850 μm correlation improves when a smoothing kernel is applied to the λ 850 μm data to account for differences between the cosmic ray (CR) electron diffusion scale and the mean free path of an ISRF photon to dust. The best-fitting relation is L617MHz ∞ L850μm 2.1±0.2 for NGC 3044. If variations in the cold dust emissivity are dominated by variations in dust density, and the synchrotron emission depends on magnetic field strength (a function of gas density) as well as CR electron generation (a function ofmassive star formation rate and therefore density via the Schmidt law) then the expected correlation for NGC 3044 is L617MHz ∞ L850μm 2.2, in agreement with the observed correlation. © 2013 The Authors. Source


Deka R.K.,Gauhati University | Paul A.,Cotton College State University | Chaliha A.,Biswanath College
Ain Shams Engineering Journal | Year: 2015

This paper describes a one dimensional unsteady natural convection flow past an infinite vertical cylinder with heat and mass transfer under the effect of constant heat flux at the surface of the cylinder. Closed form solutions of the dimensionless unsteady linear governing boundary layer equations are obtained in terms of Bessel functions and modified Bessel functions by Laplace transform method. The numerical values of velocity, temperature and concentration profiles are obtained for different values of the physical parameters namely, thermal Grashof number, mass Grashof number, Prandtl number, Schmidt number and time and presented in graphs. Also, skin friction and Sherwood number are shown graphically and discussed. It is observed that the velocity and temperature increase unboundedly with time, while the concentration approaches steady state at larger times. © 2015 Faculty of Engineering, Ain Shams University. Source


Mao M.Y.,University of Tasmania | Mao M.Y.,CSIRO | Sharp R.,Australian National University | Norris R.P.,CSIRO | And 12 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

The Australia Telescope Large Area Survey (ATLAS) has surveyed 7 square degrees of sky around the Chandra Deep Field South and the European Large Area ISO Survey-South 1 fields at 1.4GHz. ATLAS aims to reach a uniform sensitivity of 10 ̌Jybeam -1 rms over the entire region with first data release currently reaching ∼ 30 ̌Jybeam -1 rms. Here we present 466 new spectroscopic redshifts for radio sources in ATLAS as part of our optical follow-up programme. Of the 466 radio sources with new spectroscopic redshifts, 142 have star-forming optical spectra, 282 show evidence for active galactic nuclei (AGN) in their optical spectra, 10 have stellar spectra and 32 have spectra revealing redshifts, but with insufficient features to classify. We compare our spectroscopic classifications with two mid-infrared diagnostics and find them to be in broad agreement. We also construct the radio luminosity function for star-forming galaxies to z = 0.5 and for AGN to z = 0.8. The radio luminosity function for star-forming galaxies appears to be in good agreement with previous studies. The radio luminosity function for AGN appears higher than previous studies of the local AGN radio luminosity function. We explore the possibility of evolution, cosmic variance and classification techniques affecting the AGN radio luminosity function. ATLAS is a pathfinder for the forthcoming Evolution Map of the Universe (EMU) survey and the data presented in this paper will be used to guide EMU's survey design and early science papers. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS. Source


Dixit A.S.,North - Eastern Hill University | Singh N.S.,Cotton College State University
Journal of Photochemistry and Photobiology B: Biology | Year: 2016

Seasonality in daily locomotor activity pattern was investigated in the subtropical tree sparrow by exposing a group of birds to natural day lengths (NDL) for 30 days and another group to 12L/12D for 14 days followed by transfer to constant dim light (LLdim) for another 15 days in four different seasons of the year. Serum testosterone levels were also measured during different seasons. Sparrows, under NDL, exhibited distinct circadian rhythmicity in their locomotor activity with almost similar general pattern in different seasons that restricted mainly to the light hours. However, they showed season-dependent differences in the characteristics of circadian locomotor activity rhythm. Birds, when exposed to 12L/12D, showed entrainment of their locomotor activity rhythm with the activity confined mainly during the light phase. Though, tau (τ) under free run conditions did not show any significant difference, the activity period varied significantly in different seasons. The highest level of testosterone was recorded in the spring season that corresponded with the maximum locomotor activity in spring months. The seasonality in daily locomotor activity correlates with the seasonal changes in testosterone levels suggesting the influence of gonadal steroids on endogenous circadian system which is indicative of adaptation of tree sparrow to local photoperiodic conditions. © 2016 Elsevier B.V. All rights reserved. Source


Deka R.K.,Gauhati University | Paul A.,Cotton College State University | Kalit N.,Board of Secondary Education
Frontiers in Heat and Mass Transfer | Year: 2015

A theoretical study of thermal radiation effects on unsteady MHD natural convection flow of an electrically conducting fluid past a vertical plate with variable temperature is considered. It is supposed that the temperature of the plate decays exponentially with time. Exact solutions to the nondimensionalised coupled linear partial differential equations representing the flow problem are obtained using Laplace transform technique. Effects of different physical parameters involved in the temperature and velocity profiles are investigated, shown graphically and discussed. Skin friction and Nusselt number are also derived and their variations with respect to the parameters are investigated. © 2015, Global Digital Central. All rights reserved. Source

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