10,053 research outputs found
Simple chamber facilitates chemiluminescent detection of bacteria
Test chamber enables rapid estimation of bacteria in a test sample through the reaction of luminol and an oxidant with the cytochrome C portion of certain species of bacteria. Intensity of the light emitted in the reaction is a function of the specific bacteria in the test sample
Driving extreme variability: The evolving corona and evidence for jet launching in Markarian 335
Variations in the X-ray emission from the narrow line Seyfert 1 galaxy,
Markarian 335 (Mrk 335), are studied on both long and short timescales through
observations made between 2006 and 2013 with XMM-Newton, Suzaku and NuSTAR.
Changes in the geometry and energetics of the corona that give rise to this
variability are inferred through measurements of the relativistically blurred
reflection seen from the accretion disc. On long timescales, we find that
during the high flux epochs the corona has expanded, covering the inner regions
of the accretion disc out to a radius of 26(-7,+10)rg. The corona contracts to
within 12rg and 5rg in the intermediate and low flux epochs, respectively.
While the earlier high flux observation made in 2006 is consistent with a
corona extending over the inner part of the accretion disc, a later high flux
observation that year revealed that the X-ray source had become collimated into
a vertically-extended jet-like corona and suggested relativistic motion of
material upward. On short timescales, we find that an X-ray flare during a low
flux epoch in 2013 corresponded to a reconfiguration from a slightly extended
corona to one much more compact, within just 2~3rg of the black hole. There is
evidence that during the flare itself, the spectrum softened and the corona
became collimated and slightly extended vertically as if a jet-launching event
was aborted. Understanding the evolution of the X-ray emitting corona may
reveal the underlying mechanism by which the luminous X-ray sources in AGN are
powered.Comment: 21 pages, 9 figures. Accepted for publication in MNRA
Description and field test of an in situ coliform monitoring system
A prototype in situ system for monitoring the levels of fecal coliforms in shallow water bodies was developed and evaluated. This system was based on the known relationship between the concentration of the coliform bacteria and the amount of hydrogen they produce during growth in a complex organic media. The prototype system consists of a sampler platform, which sits on the bottom; a surface buoy, which transmits sampler-generated data; and a shore station, which receives, displays the data, and controls the sampler. The concept of remote monitoring of fecal coliform concentrations by utilizing a system based on the electrochemical method was verified during the evaluation of the prototype
Multimegawatt thermionic reactor systems for space applications
Design features and performance characteristics of thermionic reactor systems for space application
Six-coordinate organotin(IV) complexes formed using the Kläui ligands; [CpCo{P(OR′)2O}3]SnR3 − nCln
The complexes [CpCo{P(OR′)2O}3]SnR3 − nCln [R′ = Me, Et; R = Ph, Me] are readily prepared from the corresponding organotin chloride and the sodium salt of the Kläui ligands. The X-ray crystal structures of the full series are reported for R = Ph, n = 0-3, and these show that they are all six-coordinate, including the Ph3Sn derivative which is the first example of a SnC3O3 coordination sphere. 1H, 13C, 31P and 119Sn NMR spectra are reported, and interpreted in terms of significant second-order effects and fluxional processes
Probing the geometry and motion of AGN coronae through accretion disc emissivity profiles
To gain a better understanding of the inner disc region that comprises active
galactic nuclei it is necessary to understand the pattern in which the disc is
illuminated (the emissivity profile) by X-rays emitted from the continuum
source above the black hole (corona). The differences in the emissivity
profiles produced by various corona geometries are explored via general
relativistic ray tracing simulations. Through the analysis of various
parameters of the geometries simulated it is found that emissivity profiles
produced by point source and extended geometries such as cylindrical slabs and
spheroidal coronae placed on the accretion disc are distinguishable. Profiles
produced by point source and conical geometries are not significantly
different, requiring an analysis of reflection fraction to differentiate the
two geometries. Beamed point and beamed conical sources are also simulated in
an effort to model jet-like coronae, though the differences here are most
evident in the reflection fraction. For a point source we determine an
approximation for the measured reflection fraction with the source height and
velocity. Simulating spectra from the emissivity profiles produced by the
various geometries produce distinguishable differences. Overall spectral
differences between the geometries do not exceed 15 per cent in the most
extreme cases. It is found that emissivity profiles can be useful in
distinguishing point source and extended geometries given high quality spectral
data of extreme, bright sources over long exposure times. In combination with
reflection fraction, timing, and spectral analysis we may use emissivity
profiles to discern the geometry of the X-ray source.Comment: 15 pages, 12 figures. Accepted for publication in MNRA
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