69,967 research outputs found
The Classification of Extragalactic X-ray Jets
The overall classification of X-ray jets has clung to that prevalent in the
radio: FRI vs. FRII (including quasars). Indeed, the common perception is that
X-ray emission from FRI's is synchrotron emission whereas that from FRII's may
be IC/CMB and/or synchrotron. Now that we have a sizable collection of sources
with detected X-ray emission from jets and hotspots, it seems that a more
unbiased study of these objects could yield additional insights on jets and
their X-ray emission. The current contribution is a first step in the process
of analyzing all of the relevant parameters for each detected component for the
sources collected in the XJET website. This initial effort involves measuring
the ratio of X-ray to radio fluxes and evaluating correlations with other jet
parameters. For single zone synchrotron X-ray emission, we anticipate that
larger values of fx/fr should correlate inversely with the average magnetic
field strength (if the acceleration process is limited by loss time equals
acceleration time). Beamed IC/CMB X-rays should produce larger values of fx/fr
for smaller values of the angle between the jet direction and the line of sight
but will also be affected by the low frequency radio spectral index.Comment: 4 pages; to appear in the conference proceedings: "X-Ray Astronomy
2009: Present Status, Multiwavelength Approach and Future Perspectives";
Bologna, Italy, September 2009, Editors: A. Comastri, M. Cappi, L. Angelini,
2010 AIP (in press
X-ray Emission from the Radio Jet in 3C 120
We report the discovery of X-ray emission from a radio knot at a projected
distance of 25" from the nucleus of the Seyfert galaxy, 3C 120. The data were
obtained with the ROSAT High Resolution Imager (HRI). Optical upper limits for
the knot preclude a simple power law extension of the radio spectrum and we
calculate some of the physical parameters for thermal bremsstrahlung and
synchrotron self-Compton models. We conclude that no simple model is consistent
with the data but if the knot contains small regions with flat spectra, these
could produce the observed X-rays (via synchrotron emission) without being
detected at other wavebands.Comment: 6 pages latex plus 3 ps/eps figures. Uses 10pt.sty and
emulateapj.sty. Accepted for publication in the ApJ (6 Jan 99
Development of CO2 laser Doppler instrumentation for detection of clear air turbulence, volume 2: Appendices
Analyses of the mounting and mount support systems of the clear air turbulence transmitters verify that satisfactory shock and vibration isolation are attained. The mount support structure conforms to flight crash safety requirements with high margins of safety. Restraint cables reinforce the mounts in the critical loaded forward direction limiting maximum forward system deflection to 1 1/4 inches
Electron Energy Distributions at Relativistic Shock Sites: Observational Constraints from the Cygnus A Hotspots
We report new detections of the hotspots in Cygnus A at 4.5 and 8.0 microns
with the Spitzer Space Telescope. Together with detailed published radio
observations and synchrotron self-Compton modeling of previous X-ray
detections, we reconstruct the underlying electron energy spectra of the two
brightest hotspots (A and D). The low-energy portion of the electron
distributions have flat power-law slopes (s~1.5) up to the break energy which
corresponds almost exactly to the mass ratio between protons and electrons; we
argue that these features are most likely intrinsic rather than due to
absorption effects. Beyond the break, the electron spectra continue to higher
energies with very steep slopes s>3. Thus, there is no evidence for the
`canonical' s=2 slope expected in 1st order Fermi-type shocks within the whole
observable electron energy range. We discuss the significance of these
observations and the insight offered into high-energy particle acceleration
processes in mildly relativistic shocks.Comment: 5 pages, 3 figures, in Extragalactic Jets: Theory and Observation
from Radio to Gamma Ray, Eds. T. A. Rector and D. S. De Youn
Mesoscale assessments of cloud and rainfall over the British Isles
There are no author-identified significant results in this report
An evaluation of the effects of stacking sequence and thickness on the fatigue life of quasi-isotropic graphite/epoxy laminates
Notched and unnotched geometries at 16, 32, and 64-ply thicknesses of a 90/45/0-45 (ns) laminate and a 45/0/-45/90 (ns) laminate were tested in compression-compression fatigue. The fatigue life and the initiation, type, and progression of damage were determined. Interlaminar stresses generated at straight, free edges of axially loaded laminates were used to interpret the test results. The fatigue lives of the notched specimens did not appear to be a strong function of laminate stacking sequence or specimen thickness. The stress concentration at the hole dominated over the interlaminar stresses at the straight free edge. The unnotched specimens of the 90/45/0/-45 (ns) laminate with tensile interlaminar normal stresses delaminated more readily than did the 45/0/-45/90 (ns) laminate with compressive interlaminar normal stress. The life of the 16-ply unnotched specimens was lower than the 32- and 64-ply specimens. Delaminations were located at the interface where the maximum shear stress occurred regardless of the sense or magnitude of the interlaminar normal stress. An antibuckling fixture was effective in preventing out-of-plane motion without overconstraining the specimen
Fracture behavior of thick, laminated graphite/epoxy composites
The effect of laminate thickness on the fracture behavior of laminated graphite epoxy (T300/5208) composites was studied. The predominantly experimental research program included the study of the 0/+ or - 45/90 sub ns and 0/90 sub ns laminates with thickness of 8, 32, 64, 96 and 120 plies and the 0/+ or - 45 sub ns laminate with thickness of 6, 30, 60, 90 and 120 plies. The research concentrated on the measurement of fracture toughness utilizing the center-cracked tension, compact tension and three point bend specimen configurations. The development of subcritical damage at the crack tip was studied nondestructively using enhanced X-ray radiography and destructively using the laminate deply technique. The test results showed fracture toughness to be a function of laminate thickness. The fracture toughness of the 0 + or - 45/90 sub ns and 0/90 sub ns laminates decreased with increasing thickness and asymptotically approached lower bound values of 30 ksi square root of in. (1043 MPa square root of mm and 25 ksi square root of in (869 MPa square root of mm respectively. In contrast to the other two laminates, the fracture toughness of the 0/+ or - 45 sub ns laminate increased sharply with increasing thickness but reached an upper plateau value of 40 ksi square root of in (1390 MPa square root of mm) at 30 plies. Fracture toughness was independent of crack size for both thin and thick laminates for all three laminate types except for the 0/90 sub 2s laminate which spilt extensively. The center cracked tension, three point bend and compact tension specimens gave comparable results
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