20,936 research outputs found
The radio spectra of reddened 2MASS QSOs: evidence for young radio jets
Multifrequency radio continuum observations (1.4-22 GHz) of a sample of
reddened QSOs are presented. We find a high incidence (13/16) of radio spectral
properties, such as low frequency turnovers, high frequency spectral breaks or
steep power-law slopes, similar to those observed in powerful compact steep
spectrum (CSS) and gigahertz-peaked spectrum (GPS) sources. The radio data are
consistent with relatively young radio jets with synchotron ages <1e6-1e7yr.
This calculation is limited by the lack of high resolution (milli-arcsec) radio
observations. For the one source in the sample that such data are available a
much younger radio age is determined, <2e3yr, similar to those of GPS/CSS
sources. These findings are consistent with claims that reddened QSOs are young
systems captured at the first stages of the growth of their supermassive black
holes. It also suggests that expanding radio lobes may be an important feedback
mode at the early stages of the evolution of AGN.Comment: 9 pages, to appear in MNRA
Asymptotic decay of pair correlations in a Yukawa fluid
We analyse the asymptotic decay of the total correlation
function, , for a fluid composed of particles interacting via a (point)
Yukawa pair potential. Such a potential provides a simple model for dusty
plasmas. The asymptotic decay is determined by the poles of the liquid
structure factor in the complex plane. We use the hypernetted-chain closure to
the Ornstein-Zernike equation to determine the line in the phase diagram,
well-removed from the freezing transition line, where crossover occurs in the
ultimate decay of , from monotonic to damped oscillatory. We show: i)
crossover takes place via the same mechanism (coalescence of imaginary poles)
as in the classical one-component plasma and in other models of Coulomb fluids
and ii) leading-order pole contributions provide an accurate description of
at intermediate distances as well as at long range.Comment: 5 pages, 3 figure
Adaptation of NASA technology for the optimization of orthopedic knee implants
The NASA technology originally developed for the optimization of composite structures (engine blades) is adapted and applied to the optimization of orthopedic knee implants. A method is developed enabling the tailoring of the implant for optimal interaction with the environment of the tibia. The shape of the implant components are optimized, such that the stresses in the bone are favorably controlled to minimize bone degradation and prevent failures. A pilot tailoring system is developed and the feasibility of the concept is elevated. The optimization system is expected to provide the means for improving knee prosthesis and individual implant tailoring for each patient
Double Entry Accounts for Farmers
The purpose of keeping accounts is to give the farmer or other business man definite and detailed financial information on his business to help him in forming his business policy for the future. Since the information desired varies with the man who is to use it, the type of books kept must vary to correspond. Therefore, this circular does not attempt to set forth any one system, but rather, to explain the general principles which underlie all systems of double entry accounting in order that the person who is to use the accounts may adapt them to his own particular need
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