804 research outputs found
Modeling the Emission from Turbulent Relativistic Jets in Active Galactic Nuclei
We present a numerical model developed to calculate observed fluxes of
relativistic jets in active galactic nuclei. The observed flux of each
turbulent eddy is dependent upon its variable Doppler boosting factor, computed
as a function of the relativistic sum of the individual eddy and bulk jet
velocities and our viewing angle to the jet. The total observed flux is found
by integrating the radiation from the eddies over the turbulent spectrum. We
consider jets that contain turbulent eddies that have either standard
Kolmogorov or recently derived relativistic turbulence spectra. We also account
for the time delays in receiving the emission of the eddies due to their
different simulated positions in the jet, as well as due to the varying beaming
directions as they turn over. We examine these theoretical light curves and
compute power spectral densities (PSDs) for a range of viewing angles, bulk
velocities of the jet, and turbulent velocities. These PSD slopes depend
significantly on the turbulent velocity and are essentially independent of
viewing angle and bulk velocity. The flux variations produced in the
simulations for realistic values of the parameters tested are consistent with
the types of variations observed in radio-loud AGN as, for example, recently
measured with the Kepler satellite, as long as the turbulent velocities are not
too high.Comment: 18 pages, 6 figures; v3: in press at J Astrophys Astro
The Fanaroff-Riley Transition and the Optical Luminosity of the Host Elliptical Galaxy
We show that a model for radio source dynamics we had earlier proposed can
readily reproduce the relationship between the radio power division separating
the two Fanaroff-Riley classes of extragalactic radio sources and the optical
luminosity of the host galaxy, as found by Owen and Ledlow (1994). In our
scenario, when less powerful jets eventually slow down to the point that the
advance of the working surface (i.e., hotspot) becomes subsonic with respect to
the external gas, the jet's collimation is severely weakened. This criterion
distinguishes the powerful and well collimated FR II sources from the weaker
sources producing the less collimated FR I type morphologies.Comment: 6 pages, 1 figure; typo corrected; refs updated; now published in A&
Clinical application of high throughput molecular screening techniques for pharmacogenomics.
Genetic analysis is one of the fastest-growing areas of clinical diagnostics. Fortunately, as our knowledge of clinically relevant genetic variants rapidly expands, so does our ability to detect these variants in patient samples. Increasing demand for genetic information may necessitate the use of high throughput diagnostic methods as part of clinically validated testing. Here we provide a general overview of our current and near-future abilities to perform large-scale genetic testing in the clinical laboratory. First we review in detail molecular methods used for high throughput mutation detection, including techniques able to monitor thousands of genetic variants for a single patient or to genotype a single genetic variant for thousands of patients simultaneously. These methods are analyzed in the context of pharmacogenomic testing in the clinical laboratories, with a focus on tests that are currently validated as well as those that hold strong promise for widespread clinical application in the near future. We further discuss the unique economic and clinical challenges posed by pharmacogenomic markers. Our ability to detect genetic variants frequently outstrips our ability to accurately interpret them in a clinical context, carrying implications both for test development and introduction into patient management algorithms. These complexities must be taken into account prior to the introduction of any pharmacogenomic biomarker into routine clinical testing
Testing Models of the Individual and Cosmological Evolutions of Powerful Radio Galaxies
We seek to develop an essentially analytical model for the evolution of
Fanaroff-Riley Class II radio galaxies as they age individually and as their
numbers vary with cosmological epoch. Such modeling is required in order to
probe in more detail the impact of radio galaxies on the growth of structures
in the universe, which appears likely to have been quite significant at z > 1.
In this first paper of a series we compare three rather sophisticated
analytical models for the evolution of linear size and lobe power of FR II
radio galaxies, those of Kaiser, Dennett-Thorpe & Alexander (1997), Blundell,
Rawlings & Willott (1999), and Manolakou & Kirk (2002). We perform
multi-dimensional Monte Carlo simulations in order to compare the predictions
of each model for radio powers, sizes, redshifts and spectral indices with
data. The observational samples used here are the low frequency radio surveys,
3CRR, 6CE and 7CRS, which are flux-limited and complete. We search for and
describe the best parameters for each model, after doing statistical tests on
them. We find that no existing model can give acceptable fits to all the
properties of the surveys considered, although the Kaiser, Dennett-Thorpe &
Alexander (1997) model gives better overall results than do the Manolakou &
Kirk (2002) or Blundell, Rawlings & Willott (1999) models for most of the tests
we performed. We suggest ways in which these models may be improved.Comment: 26 pages, 5 figures; substantially improved version, with additional
statistical tests; to appear in MNRA
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