16,523 research outputs found
Charged particle sources for implantation and surface reactions Final report
High temperature ion source developed for implantation and surface reactions of Ar, Pb, and Ga ion
AXJ1749+684: a narrow emission-line galaxy with a flat X-ray spectrum
We report the serendipitous detection of an X-ray source, AXJ1749+684, with
the ASCA Gas Imaging Spectrometer. AXJ1749+684 is identified with a
LINER/starburst-type spiral galaxy KUG 1750+683A at a redshift z = 0.05. It has
a hard X-ray spectrum, consistent with that of the X-ray background (XRB) in
the 1-10 keV band. Despite the optical classification, the X-ray luminosity
cannot be explained by starburst activity. Combined with spatial variations in
the optical emission line ratios, this suggests the presence of an obscured
Seyfert nucleus embedded within a starforming galaxy. Similar behaviour could
explain the ambiguous properties of the faint narrow-line X-ray galaxies
(NLXGs) emerging from deep X-ray surveys.Comment: MNRAS Letters in press, 6 pages, 7 figures in MNRAS LaTex styl
Universal trapping scaling on the unstable manifold for a collisionless electrostatic mode
An amplitude equation for an unstable mode in a collisionless plasma is
derived from the dynamics on the two-dimensional unstable manifold of the
equilibrium. The mode amplitude decouples from the phase due to the
spatial homogeneity of the equilibrium, and the resulting one-dimensional
dynamics is analyzed using an expansion in . As the linear growth rate
vanishes, the expansion coefficients diverge; a rescaling
of the mode amplitude absorbs these
singularities and reveals that the mode electric field exhibits trapping
scaling as . The dynamics for
depends only on the phase where is the derivative of the dielectric as
.Comment: 11 pages (Latex/RevTex), 2 figures available in hard copy from the
Author ([email protected]); paper accepted by Physical Review
Letter
The Distance to the Vela Supernova Remnant
We have obtained high resolution Ca II and Na I absorption line spectra
toward 68 OB stars in the direction of the Vela Supernova Remnant. The stars
lie at distances of 190 -- 2800 pc as determined by Hipparcos and spectroscopic
parallax estimations. The presence of high velocity absorption attributable to
the remnant along some of the sight lines constrains the remnant distance to
250+/-30 pc. This distance is consistent with several recent investigations
that suggest that the canonical remnant distance of 500 pc is too large.Comment: To be published in The Astrophysical Journal Letters Figure 1 y-axis
labels correcte
The Utilization of Dissolved Free Amino Acids by Estuarine Microorganisms
The importance of bacteria in the cycling of carbon in the Pamlico River estuary was studied by measuring the rates of uptake of organic compounds. Our methods allowed analysis with the Michaelis-Menten kinetics equations, and both the rates of uptake of dissolved free amino acids (DFAA) and glucose as well as the percentage of carbon subsequently respired as CO2 were determined. In addition, the concentrations of the amino acids in the water were determined using ion exchange chromatography. Other tests included measurements of primary productivity and of the effects of the other amino acids in the water upon the uptake of one amino acid. (...
The Effect Of Pitting Corrosion On The Position Of Aircraft Structural Failures
Corrosion has been shown over the last decade to significantly reduce the structural integrity of aircraft as they age. Previous work at DSTO has shown that pitting and exfoliation corrosion are particularly deleterious to aircraft structural integrity. In addition to reducing fatigue endurance, pitting also increases the surface area of the component over which fatigue failures can occur. This paper reports the results of a Monte-Carlo model of this phenomenon, which has been labelled 'corrosion criticality'. This model concentrates on the effect of the pit spatial density and position on the endurance of a fatigue coupon designed to mimic a simple aircraft component. The study's results show that pitting increases the area of the coupon over which failures can occur
X-ray spectroscopy of the broad line radio galaxy 3C111
We present an ASCA observation of the broad line radio galaxy 3C111. The
X-ray spectrum is well described by a model consisting of a
photoelectrically-absorbed power-law form. The inferred absorbing column
density is significantly greater than expected on the basis of 21-cm
measurements of Galactic HI. Whilst this may be due intrinsic absorption from a
circumnuclear torus or highly warped accretion disk, inhomogeneities and
molecular gas within the foreground giant molecular cloud may also be
responsible for some of this excess absorption. We also claim a marginal
detection of a broad iron Ka line which is well explained as being a
fluorescent line originating from the central regions of a
radiatively-efficient accretion disk. This line appears weak in comparison to
those found in (radio-quiet) Seyfert nuclei. We briefly discuss the
implications of this fact.Comment: 7 pages including 2 postscript figures. Accepted for publication in
MNRA
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