51,607 research outputs found
Parsec-scale structures and diffuse bands in a translucent interstellar medium at z 0.079
We present a detailed study of the QSO-galaxy pair [SDSS J163956.35+112758.7
(zq = 0.993) and SDSS J163956.38+112802.1 (zg = 0.079)] based on observations
carried out using the Giant Meterwave Radio Telescope (GMRT), the Very Large
Baseline Array (VLBA), the Sloan Digital Sky Survey (SDSS) and the ESO New
Technology Telescope (NTT). We show that the interstellar medium of the galaxy
probed by the QSO line of sight has near-solar metallicity (12+log(O/H) =
8.47+/-0.25) and dust extinction (E(B-V) 0.83+/-0.11) typical of what is
usually seen in translucent clouds. We report the detection of absorption in
the \lambda 6284 diffuse interstellar band (DIB) with a rest equivalent width
of 1.45+/-0.20\AA. Our GMRT spectrum shows a strong 21-cm absorption at the
redshift of the galaxy with an integrated optical depth of 15.70+/-0.13 km/s.
Follow-up VLBA observations show that the background radio source is resolved
into three components with a maximum projected separation of 89 pc at the
redshift of the galaxy. One of these components is too weak to provide useful
HI 21-cm absorption information. The integrated HI optical depth towards the
other two components are higher than that measured in our GMRT spectrum and
differ by a factor 2. By comparing the GMRT and VLBA spectra we show the
presence of structures in the 21-cm optical depth on parsec scales. We discuss
the implications of such structures for the spin-temperature measurements in
high-z damped Lyman-alpha systems. The analysis presented here suggests that
this QSO-galaxy pair is an ideal target for studying the DIBs and molecular
species using future observations in optical and radio wavebands.Comment: 10 pages, 8 figures, 2 tables, accepted for publication in MNRA
Effect of dopants on thermal stability and self-diffusion in iron nitride thin films
We studied the effect of dopants (Al, Ti, Zr) on the thermal stability of
iron nitride thin films prepared using a dc magnetron sputtering technique.
Structure and magnetic characterization of deposited samples reveal that the
thermal stability together with soft magnetic properties of iron nitride thin
films get significantly improved with doping. To understand the observed
results, detailed Fe and N self-diffusion measurements were performed. It was
observed that N self-diffusion gets suppressed with Al doping whereas Ti or Zr
doping results in somewhat faster N diffusion. On the other hand Fe
self-diffusion seems to get suppressed with any dopant of which heat of nitride
formation is significantly smaller than that of iron nitride. Importantly, it
was observed that N self-diffusion plays only a trivial role, as compared to Fe
self-diffusion, in affecting the thermal stability of iron nitride thin films.
Based on the obtained results effect of dopants on self-diffusion process is
discussed.Comment: 10 pages, 9 fig
Evaporative segregation in 80 percent Ni-20 percent Cr and 60 percent Fe-40 percent Ni alloys
The phenomenon of evaporative segregation in binary alloys has been investigated through a study of some experimental evaporation data relating to the Ni-Cr and Ni-Fr systems. In normal evaporation it is assumed that (1) the evaporating alloy is always homogeneous, (2) the vapor is instantly removed, and (3) the alloy follows Raoult's law. The solutions of the evaporation equations for the two most important cases are presented and experimental data are analyzed with these equations. The difference between observed and calculated values of evaporation constants lies within one order of magnitude. This is surprising because of the major assumptions stated above. Experimental results have shown that the evaporation time and final solute concentration are logarithmically related, further supporting our evaporation equations. It is further shown that neglecting the nonlogarithmic term in these evaporation equations may introduce considerable errors in the analysis
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The Effect of Ru substitution for Ni on the superconductivity in MgCNi3-xRux
The superconductor MgCNi3 has been chemically doped by partial substitution
of Ru for Ni in the solid solution MgCNi3-xRux for 0<x<0.5. Magnetic and
specific heat measurements show that the Sommerfeld parameter (gamma_exp) and
TC decrease immediately on Ru substitution, but that a TC above 2K is
maintained even for a relatively large decrease in gamma_exp. Ferromagnetism is
not observed to develop through Ru substitution, and the normal state magnetic
susceptibility is suppressed.Comment: 18 pages, 13 figure
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