838 research outputs found
A Review of Research on the Kentucky River Ecosystem: Biota and Human Impacts
This report provides information about the water conditions in the Kentucky River Basin, through collection of previous studies
Excess sub-millimetre emission from GRS 1915+105
We present the first detections of the black hole X-ray binary GRS 1915+105
at sub-millimetre wavelengths. We clearly detect the source at 350 GHz on two
epochs, with significant variability over the 24 hr between epochs.
Quasi-simultaneous radio monitoring indicates an approximately flat spectrum
from 2 - 350 GHz, although there is marginal evidence for a minimum in the
spectrum between 15 - 350 GHz. The flat spectrum and correlated variability
imply that the sub-mm emission arises from the same synchrotron source as the
radio emission. This source is likely to be a quasi-steady partially
self-absorbed jet, in which case these sub-mm observations probe significantly
closer to the base of the jet than do radio observations and may be used in
future as a valuable diagnostic of the disc:jet connection in this source.Comment: 5 pages, 3 figures, accepted for publication in MNRA
Synthesis of neutral nickel catalysts for ethylene polymerization – the influence of ligand size on catalyst stability
A facile synthesis of nickel salicylaldimine complexes with labile dissociating ligands is described. In addition to producing highly active ethylene polymerization catalysts, important insights into the effect of ligand size on catalyst stability and information on the mechanism of polymerization are provided
Cygnus X-3 in outburst : quenched radio emission, radiation losses and variable local opacity
We present multiwavelength observations of Cygnus X-3 during an extended
outburst in 1994 February - March. Intensive radio monitoring at 13.3, 3.6 &
2.0 cm is complemented by observations at (sub)millimetre and infrared
wavelengths, which find Cyg X-3 to be unusually bright and variable, and
include the first reported detection of the source at 0.45 mm. We report the
first confirmation of quenched radio emission prior to radio flaring
independent of observations at Green Bank. The observations reveal evidence for
wavelength-dependent radiation losses and gradually decreasing opacity in the
environment of the radio jet. We find that the radiation losses are likely to
be predominantly inverse Compton losses experienced by the radio-emitting
electrons in the strong radiation field of a luminous companion to the compact
object. We interpret the decreasing opacity during the flare sequence as
resulting from a decreasing proportion of thermal electrons entrained in the
jet, reflecting a decreasing density in the region of jet formation. We
present, drawing in part on the work of other authors, a model based upon
mass-transfer rate instability predicting gamma-ray, X-ray, infrared and radio
trends during a radio flaring sequence.Comment: LaTeX, 11 pages, 6 figures. Submitted to MNRA
Insights into the Deactivation of Neutral Nickel Ethylene Polymerization Catalysts in the Presence of Functionalized Olefins
A study on the products of reaction between a neutral nickel(II) olefin polymerization catalyst and methyl acrylate is presented. A deactivation mechanism involving hydrogen transfer from substrate to catalyst is suggested
Adhesion Between Surfaces Separated by Molecularly Thin Perfluoropolyether Films
The relationship between the adhesion of surfaces separated by a molecularly thin liquid film and the surface energy of the film was investigated. AFM-based force–distance curves were measured on a series of carbon surfaces coated with hydroxyl-terminated perfluoropolyether (PFPE) films. The surface energy of the PFPE films was varied by altering either the total film thickness or the bonding ratio of the film by changing the concentration of the PFPE film in the solution and/or the pull-rate during dip-coating. A linear relationship between adhesion force and surface energy was observed. Adhesion was found to vanish at non-zero values of surface energy. The experimental results indicate that the adhesive force between macroscopic bodies separated by molecularly thin liquid films is linearly proportional to the excess surface energy of the film
MERLIN observations of relativistic ejections from GRS 1915+105
We present high resolution MERLIN radio images of multiple relativistic
ejections from GRS 1915+105 in 1997 October / November. The observations were
made at a time of complex radio behaviour, corresponding to multiple
optically-thin outbursts and several days of rapid radio flux oscillations. The
radio imaging resolved four major ejection events from the system. As
previously reported from earlier VLA observations of the source, we observe
apparent superluminal motions resulting from intrinsically relativistic motions
of the ejecta. However, our measured proper motions are significantly greater
than those observed on larger angular scales with the VLA. Under the assumption
of an intrinsically symmetric ejection, we can place an upper limit on the
distance to GRS 1915+105 of 11.2 +/- 0.8 kpc. Solutions for the velocities
unambiguously require a higher intrinsic speed by about 0.1c than that derived
from the earlier VLA observations, whilst the angle to the line-of-sight is not
found to be significantly different. At a distance of 11 kpc, we obtain
solutions of v = 0.98 (-0.05,+0.02)c and theta = 66 +/- 2 degrees. The jet also
appears to be curved on a scale which corresponds to a period of around 7 days.
We observe significant evolution of the linear polarisation of the approaching
component, with large rotations in position angle and a general decrease in
fractional polarisation. The power input into the formation of the jet is very
large, >10^38 erg/s at 11 kpc for a pair plasma. If the plasma contains a cold
proton for each electron, then the mass outflow rate, >10^18 g/sec is
comparable to inflow rates previously derived from X-ray spectral fits.Comment: 14 pages, 7 figures. Accepted for publication in MNRA
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