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135 results on '"Tandon, S.N."'

3. RECOVERY OF CR(III) FROM TANNERY SPENT CHROME LIQUOR FOR REUSE

Author

Khwaja, A.R., Singh, Rashmi, and Tandon, S.N.

Subjects
Chromium -- Usage, Tanning -- Environmental aspects, Chemistry, Technical -- Research, Engineering and manufacturing industries, Environmental issues
Abstract

This paper embodies details on the extraction behavior of Cr(III) along with A1(III), Fe(III), Mg(II), Mn(II), Co(II), Ni(II), and Cu(II) from hydrochloric acid media employing the Cyanex 301-toluene system. All of these metals, except Cr(III), Mg(II), and Mn(II), are extracted into the organic phase. This property of the extractant has been used to separate Cr(III) from the binary mixtures. The partition data have been extended onto spent chrome liquor, and this waste has been treated in such a manner so that it becomes suitable for use in trivalent plating baths. The hydrolytic stability and recycling capacity has been reported. Because the concentration of Cr(III) in the waste is much lower than that required for chromium depositions in Cr(III) plating baths, a concentration step using MgO as a precipitating agent has been appended. To summarize, this paper envisages a new approach to tannery waste management that focuses on treating spent chrome liquors using a solvent extraction technique in such a manner that the waste becomes suitable for use in trivalent plating baths. This would not only help abate pollution but also recover the metal in a pure form.

Published
2000

8. UVIT observations of the star-forming ring in NGC 7252: Evidence of possible AGN feedback suppressing central star formation

Author

George, K., primary, Joseph, P., additional, Mondal, C., additional, Devaraj, A., additional, Subramaniam, A., additional, Stalin, C. S., additional, Côté, P., additional, Ghosh, S. K., additional, Hutchings, J. B., additional, Mohan, R., additional, Postma, J., additional, Sankarasubramanian, K., additional, Sreekumar, P., additional, and Tandon, S.N., additional

Published
2018
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9. UVIT observations of the star-forming ring in NGC7252: Evidence of possible AGN feedback suppressing central star formation.

Author

George, K., Joseph, P., Mondal, C., Devaraj, A., Subramaniam, A., Stalin, C. S., Côté, P., Ghosh, S. K., Hutchings, J. B., Mohan, R., Postma, J., Sankarasubramanian, K., Sreekumar, P., and Tandon, S.N.

Subjects
ULTRAVIOLET telescopes, STAR formation, STAR observations, ACTIVE galactic nuclei, STARBURSTS
Abstract

Context. Some post-merger galaxies are known to undergo a starburst phase that quickly depletes the gas reservoir and turns it into a red-sequence galaxy, though the details are still unclear. Aims. Here we explore the pattern of recent star formation in the central region of the post-merger galaxy NGC7252 using highresolution ultraviolet (UV) images from the UVIT on ASTROSAT. Methods. The UVIT images with 1.2 and 1.4 arcsec resolution in the FUV and NUV are used to construct a FUV-NUV colour map of the central region. Results. The FUV-NUV pixel colour map for this canonical post-merger galaxy reveals a blue circumnuclear ring of diameter ~1000 (3.2 kpc) with bluer patches located over the ring. Based on a comparison to single stellar population models, we show that the ring is comprised of stellar populations with ages ≲300 Myr, with embedded star-forming clumps of younger age (≲150Myr). Conclusions. The suppressed star formation in the central region, along with the recent finding of a large amount of ionised gas, leads us to speculate that this ring may be connected to past feedback from a central super-massive black hole that has ionised the hydrogen gas in the central ~400 ~1:3 kpc. [ABSTRACT FROM AUTHOR]

Published
2018
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26. Imaging polarimetry of some selected dark clouds

Author

Sen, A.K., Gupta, Ranjan, Ramaprakash, A.N., and Tandon, S.N.

Abstract

A set of eight Bok Globules CB3, CB25, CB39, CB52, CB54, CB58, CB62 and CB246 were observed polarimetrically in white light, using our Imaging Polarimeter (IMPOL), from the 1.2 m IR telescope at Mount Abu, India. The observations were carried out on different nights during the period December 1997 and April 1998. The CCD images obtained from the instrument (IMPOL) were analyzed, to produce polarization map of the Bok Globules. The stars in the field, which are mostly background to the cloud show typically 2% of linear polarization. Clouds which are less dynamic (having $^{12} CO$ line widths $\Delta V < 2.5$ km s$^{-1}$ ), in general show slightly better alignment of polarization vectors with the projected direction of galactic plane. On the other hand the more dynamic group of clouds, has the polarization vectors more scattered and poorly aligned with the projected direction of the galactic plane. However one of the clouds observed CB58 does not follow this trend very well.

Published
2000

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