50 research outputs found
PSR B0329+54: Statistics of Substructure Discovered within the Scattering Disk on RadioAstron Baselines of up to 235,000 km
We discovered fine-scale structure within the scattering disk of PSR B0329+54
in observations with the RadioAstron ground-space radio interferometer. Here,
we describe this phenomenon, characterize it with averages and correlation
functions, and interpret it as the result of decorrelation of the
impulse-response function of interstellar scattering between the
widely-separated antennas. This instrument included the 10-m Space Radio
Telescope, the 110-m Green Bank Telescope, the 14x25-m Westerbork Synthesis
Radio Telescope, and the 64-m Kalyazin Radio Telescope. The observations were
performed at 324 MHz, on baselines of up to 235,000 km in November 2012 and
January 2014. In the delay domain, on long baselines the interferometric
visibility consists of many discrete spikes within a limited range of delays.
On short baselines it consists of a sharp spike surrounded by lower spikes. The
average envelope of correlations of the visibility function show two
exponential scales, with characteristic delays of and , indicating the presence of two scales of
scattering in the interstellar medium. These two scales are present in the
pulse-broadening function. The longer scale contains 0.38 times the scattered
power of the shorter one. We suggest that the longer tail arises from
highly-scattered paths, possibly from anisotropic scattering or from
substructure at large angles.Comment: 15 pages, 6 figures, 3 tables; accepted by Astrophysical journa
Thermodynamic Assessment of the Cu-Pt System
A CALPHAD assessment of the Cu-Pt system has been carried out. Two and four sublattice models were applied to describe the Gibbs free energies of ordered phases where the contribution of SRO is taken explicitly into account through the reciprocal parameters. The disordered fcc A1 and liquid phases were treated as substitutional solutions. A consistent set of parameters for the phases in the Cu-Pt system as obtained, and those parameters can satisfactorily reproduce the experimental phase equilibria and thermodynamic properties, such as enthalpies, activity of Cu, and long-range order parameters