16,279 research outputs found
Quantitative Analysis of Hydrogenated DLC Films by Visible Raman Spectroscopy
The correlations between properties of hydrogenated diamond like carbon films
and their Raman spectra have been investigated. The films are prepared by
plasma deposition technique, keeping different hydrogen to methane ratio during
the growth process. The hydrogen concentration, sp content, hardness and
optical Tauc gap of the materials have been estimated from a detail analysis of
their Raman spectra. We have also measured the same parameters of the films by
using other commonly used techniques, like sp content in films by x-ray
photoelectron spectroscopy, their Tauc gap by ellipsometric measurements and
hardness by micro-hardness testing. The reasons for the mismatch between the
characteristics of the films, as obtained by Raman measurements and by the
above mentioned techniques, have been discussed. We emphasize on the importance
of the visible Raman spectroscopy in reliably predicting the above key
properties of DLC films.Comment: 19 pages, 8 figure
User's Guide for ERB 7 SEFDT. Volume 1: User's Guide. Volume 2: Quality Control Report, Year 1
The Nimbus-7 ERB SEFDT Data User's Guide is presented. The guide consists of four subsections which describe: (1) the scope of the data User's Guide; (2) the background on Nimbus-7 Spacecraft and the ERB experiment; (3) the SEFDT data product and processing scenario; and (4) other related products and documents
Classical Electron Model with Negative Energy Density in Einstein-Cartan Theory of Gravitation
Experimental result regarding the maximum limit of the radius of the electron
\sim 10^{-16} cm and a few of the theoretical works suggest that the
gravitational mass which is a priori a positive quantity in Newtonian mechanics
may become negative in general theory of relativity. It is argued that such a
negative gravitational mass and hence negative energy density also can be
obtained with a better physical interpretation in the framework of
Einstein-Cartan theory.Comment: 12 Latex pages, added refs and conclusion
Counter-rotating Accretion Disks
We consider accretion disks consisting of counter-rotating gaseous components
with an intervening shear layer. Configurations of this type may arise from the
accretion of newly supplied counter-rotating gas onto an existing co-rotating
gas disk. For simplicity we consider the case where the gas well above the disk
midplane is rotating with angular rate and that well below has the
same properties but is rotating with rate . Using the Shakura-Sunyaev
alpha turbulence model, we find self-similar solutions where a thin (relative
to the full disk thickness) equatorial layer accretes very rapidly, essentially
at free-fall speed. As a result the accretion speed is much larger than it
would be for an alpha disk rotating in one direction. Counter-rotating
accretion disks may be a transient stage in the formation of counter-rotating
galaxies and in the accretion of matter onto compact objects.Comment: 7 pages, 3 figures, aas2pp4.sty, submitted to Ap
Properties of nonaqueous electrolytes Quarterly report, 20 Sep. - 19 Dec. 1966
Vapor phase chromatographic analysis of dimethyl formamide, and physical properties of electrolytes containing lithium chloride and/or aluminum chlorid
Planetary Nebulae with Ultra-Violet Imaging Telescope (UVIT): Far Ultra-violet halo around the Bow Tie nebula (NGC 40)
Context. NGC 40 is a planetary nebula with diffuse X-ray emission, suggesting
an interaction of the high speed wind from WC8 central star (CS) with the
nebula. It shows strong Civ 1550 {\AA} emission that cannot be explained by
thermal processes alone. We present here the first map of this nebula in C IV
emission, using broad band filters on the UVIT.
Aims. To map the hot C IV emitting gas and its correspondence with soft X-ray
(0.3-8 keV) emitting regions, in order to study the shock interaction with the
nebula and the ISM. This also illustrates the potential of UVIT for nebular
studies.
Methods. Morphological study of images of the nebula obtained at an angular
resolution of about 1.3" in four UVIT filter bands that include C IV 1550 {\AA}
and C II] 2326 {\AA} lines and UV continuum. Comparisons with X-ray, optical,
and IR images from literature.
Results. The C II] 2326 {\AA} images show the core of the nebula with two
lobes on either side of CS similar to [N II]. The C IV emission in the core
shows similar morphology and extant as that of diffuse X-ray emission
concentrated in nebular condensations. A surprising UVIT discovery is the
presence of a large faint FUV halo in FUV Filter with {\lambda}eff of 1608
{\AA}. The UV halo is not present in any other UV filter. FUV halo is most
likely due to UV fluorescence emission from the Lyman bands of H2 molecules.
Unlike the optical and IR halo, FUV halo trails predominantly towards
south-east side of the nebular core, opposite to the CS's proper motion
direction.
Conclusions. Morphological similarity of C IV 1550 {\AA} and X-ray emission
in the core suggests that it results mostly from interaction of strong CS wind
with the nebula. The FUV halo in NGC 40 highlights the existence of H2
molecules extensively in the regions even beyond the optical and IR halos.Comment: 4 pages, 5 figures, accepted for publication as a letter in Astronomy
& Astrophysic
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