49 research outputs found
Radio emission and jets from microquasars
To some extent, all Galactic binary systems hosting a compact object are
potential `microquasars', so much as all galactic nuclei may have been quasars,
once upon a time. The necessary ingredients for a compact object of stellar
mass to qualify as a microquasar seem to be: accretion, rotation and magnetic
field. The presence of a black hole may help, but is not strictly required,
since neutron star X-ray binaries and dwarf novae can be powerful jet sources
as well. The above issues are broadly discussed throughout this Chapter, with a
a rather trivial question in mind: why do we care? In other words: are jets a
negligible phenomenon in terms of accretion power, or do they contribute
significantly to dissipating gravitational potential energy? How do they
influence their surroundings? The latter point is especially relevant in a
broader context, as there is mounting evidence that outflows powered by
super-massive black holes in external galaxies may play a crucial role in
regulating the evolution of cosmic structures. Microquasars can also be thought
of as a form of quasars for the impatient: what makes them appealing, despite
their low number statistics with respect to quasars, are the fast variability
time-scales. In the first approximation, the physics of the jet-accretion
coupling in the innermost regions should be set by the mass/size of the
accretor: stellar mass objects vary on 10^5-10^8 times shorter time-scales,
making it possible to study variable accretion modes and related ejection
phenomena over average Ph.D. time-scales. [Abridged]Comment: 28 pages, 13 figures, To appear in Belloni, T. (ed.): The Jet
Paradigm - From Microquasars to Quasars, Lect. Notes Phys. 794 (2009
Supermassive Black Hole Binaries: The Search Continues
Gravitationally bound supermassive black hole binaries (SBHBs) are thought to
be a natural product of galactic mergers and growth of the large scale
structure in the universe. They however remain observationally elusive, thus
raising a question about characteristic observational signatures associated
with these systems. In this conference proceeding I discuss current theoretical
understanding and latest advances and prospects in observational searches for
SBHBs.Comment: 17 pages, 4 figures. To appear in the Proceedings of 2014 Sant Cugat
Forum on Astrophysics. Astrophysics and Space Science Proceedings, ed.
C.Sopuerta (Berlin: Springer-Verlag
Evaluating the effects of pelleting Deoxynivalenol-contaminated dried distillers grains with solubles in the presence of sodium metabisulfite on analyzed DON levels
Deoxynivalenol (DON), also known as vomitoxin, was prevalent in the 2009 U.S.
corn crop and subsequently present in dried distillers grains with solubles (DDGS), in
which DON levels are about 3 times higher than the original corn source. One method
shown to reduce DON levels was by increasing moisture and temperature when sodium
bisulfite was added to DON-contaminated corn (Young et al., 19874). Therefore, a pilot
study aimed first to replicate these results by placing DON-contaminated DDGS in an
autoclave (60 min at 250°F) in the presence of sodium metabisulfite (SMB). The study
used 6 treatments: (1) control, (2) 0.5% SMB, (3) 1.0% SMB, (4) 2.5% SMB, (5) 5.0%
SMB, and (6) 5.0% SMB with 100 mL/kg water added to evaluate the role of water.
After drying, samples were analyzed at North Dakota State University Veterinary Diagnostic Laboratory (NDSU; Fargo, ND). Autoclaving reduced DON levels (R2 = 0.99)
with increasing SMB, justifying a follow-up study that aimed to assess whether SMB has
the same detoxifying effects on corn DDGS in a commercial pellet mill.
For this study, batches of 450 lb DDGS were prepared from DDGS with a known
DON concentration (23.4 ppm). The pellet mill was set to a production rate of 1,000
lb/h so retention rate and conditioning temperature could be altered within each batch.
Within each batch, 4 samples were collected at conditioning temperatures of 150 and
180°F and retention times of 30 and 60 sec within each temperature. Samples were
sent to NDSU for full mycotoxin analysis. No differences (P > 0.15) were found in
conditioning temperature or retention time on total DON, DON, or acetyl-DON;
however, pelleting DDGS reduced (quadratic; P < 0.01) DON and total DON as SMB
increased. Based on these results, the reduction in DON and total DON levels appear
to plateau somewhere between SMB levels of 2.5 and 5.0%. These results imply that
pelleting in combination with SMB may allow pork producers to utilize DON-contaminated DDGS more effectively, but additional research is required to determine the
effect of pelleting SMB in DON-contaminated diets on growth performance of pigs
Inherited missense variants that affect GFI1B function do not necessarily cause bleeding diatheses
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