75 research outputs found
Microquasars: summary and outlook
Microquasars are compact objects (stellar-mass black holes and neutron stars)
that mimic, on a smaller scale, many of the phenomena seen in quasars. Their
discovery provided new insights into the physics of relativistic jets observed
elsewhere in the universe, and in particular, the accretion-jet coupling in
black holes. Microquasars are opening new horizons for the understanding of
ultraluminous X-ray sources observed in external galaxies, gamma-ray bursts of
long duration, and the origin of stellar black holes and neutron stars.
Microquasars are one of the best laboratories to probe General Relativity in
the limit of the strongest gravitational fields, and as such, have become an
area of topical interest for both high energy physics and astrophysics. At
present, back hole astrophysics exhibits historical and epistemological
similarities with the origins of stellar astrophysics in the last century.Comment: 14 pages, 7 figures, To appear in Belloni, T. (ed.): The Jet Paradigm
- From Microquasars to Quasars, Lect. Notes Phys. 794 (2009
An overview of jets and outflows in stellar mass black holes
In this book chapter, we will briefly review the current empirical
understanding of the relation between accretion state and and outflows in
accreting stellar mass black holes. The focus will be on the empirical
connections between X-ray states and relativistic (`radio') jets, although we
are now also able to draw accretion disc winds into the picture in a systematic
way. We will furthermore consider the latest attempts to measure/order jet
power, and to compare it to other (potentially) measurable quantities, most
importantly black hole spin.Comment: Accepted for publication in Space Science Reviews. Also to appear in
the Space Sciences Series of ISSI - The Physics of Accretion on to Black
Holes (Springer Publisher
Black Hole Spin via Continuum Fitting and the Role of Spin in Powering Transient Jets
The spins of ten stellar black holes have been measured using the
continuum-fitting method. These black holes are located in two distinct classes
of X-ray binary systems, one that is persistently X-ray bright and another that
is transient. Both the persistent and transient black holes remain for long
periods in a state where their spectra are dominated by a thermal accretion
disk component. The spin of a black hole of known mass and distance can be
measured by fitting this thermal continuum spectrum to the thin-disk model of
Novikov and Thorne; the key fit parameter is the radius of the inner edge of
the black hole's accretion disk. Strong observational and theoretical evidence
links the inner-disk radius to the radius of the innermost stable circular
orbit, which is trivially related to the dimensionless spin parameter a_* of
the black hole (|a_*| < 1). The ten spins that have so far been measured by
this continuum-fitting method range widely from a_* \approx 0 to a_* > 0.95.
The robustness of the method is demonstrated by the dozens or hundreds of
independent and consistent measurements of spin that have been obtained for
several black holes, and through careful consideration of many sources of
systematic error. Among the results discussed is a dichotomy between the
transient and persistent black holes; the latter have higher spins and larger
masses. Also discussed is recently discovered evidence in the transient sources
for a correlation between the power of ballistic jets and black hole spin.Comment: 30 pages. Accepted for publication in Space Science Reviews. Also to
appear in hard cover in the Space Sciences Series of ISSI "The Physics of
Accretion onto Black Holes" (Springer Publisher). Changes to Sections 5.2,
6.1 and 7.4. Section 7.4 responds to Russell et al. 2013 (MNRAS, 431, 405)
who find no evidence for a correlation between the power of ballistic jets
and black hole spi
A randomized controlled trial of nonoperative treatment versus open reduction and internal fixation for stable, displaced, partial articular fractures of the radial head: The RAMBO trial
Background: The choice between operative or nonoperative treatment is questioned for partial articular fractures of the radial head that have at least 2 millimeters of articular step-off on at least one radiograph (defined as displaced), but less than 2 millimeter of gap between the fragments (defined as stable) and that are not associated with an elbow dislocation, interosseous ligament injury, or other fractures. These kinds of fractures are often classified as Mason type-2 fractures. Retrospective comparative studies suggest that operative treatment might be better than nonoperative treatment, but the long-term results of nonoperative treatment are very good. Most experts agree that problems like reduced range of motion, painful crepitation, nonunion or bony ankylosis are infrequent with both nonoperative and operative treatment of an isolated displaced partial articular fracture of the radial head, but determining which patients will have problems is difficult. A prospective, randomized comparison would help minimize bias and determine the balance between operative and nonoperative risks and benefits. Methods/Design. The RAMBO trial (Radial Head - Amsterdam - Amphia - Boston - Others) is an international prospective, randomized, multicenter trial. The primary objective of this study is to compare patient related outcome defined by the 'Disabilities of Arm, Shoulder and Hand (DASH) score' twelve months after injury between operative and nonoperative treated patients. Adult patients with partial articular fractures of the radial head that comprise at least 1/3rd of the articular surface, have ≥ 2 millimeters of articular step-off but less than 2 millimeter of gap between the fragments will be enrolled. Secondary outcome measures will be the Mayo Elbow Performance Index (MEPI), the Oxford Elbow Score (OES), pain intensity through the 'Numeric Rating Scale', range of motion (flexion arc and rotational arc), radiographic appearance of the fracture (heterotopic ossification, radiocapitellar and ulnohumeral arthrosis, fracture healing, and signs of implant loosening or breakage) and adverse events (infection, nerve injury, secondary interventions) after one year. Discussion. The successful completion of this trial will provide evidence on the best treatment for stable, displaced, partial articular fractures of the radial head. Trial registration. The trial is registered at the Dutch Trial Register: NTR3413
'Disc-jet' coupling in black hole X-ray binaries and active galactic nuclei
In this chapter I will review the status of our phenomenological
understanding of the relation between accretion and outflows in accreting black
hole systems. This understanding arises primarily from observing the relation
between X-ray and longer wavelength (infrared, radio) emission. The view is
necessarily a biased one, beginning with observations of X-ray binary systems,
and attempting to see if they match with the general observational properties
of active galactic nuclei.Comment: 28 pages, 15 figures, To appear in Belloni, T. (ed.): The Jet
Paradigm - From Microquasars to Quasars, Lect. Notes Phys. 794 (2009
Atividade alelopática de folhas e pseudofrutos de Hovenia dulcis Thunb. (Rhamnaceae) sobre a germinação de Lactuca sativa L. (Asteraceae)
Using numerical classification of profiles based on Vis-NIR spectra to distinguish soils from the Piracicaba Region, Brazil
Análise de componentes principais de atributos físicos, químicos e mineralógicos de solos do bioma cerrado
Exploiting a Dual-Fluorescence Process in Fluorene-Dibenzothiophene-S,S-dioxide Co-Polymers to Give Efficient Single Polymer LEDs with Broadened Emission.
A description of the synthesis of random (9,9-dioctylfluorene-2,7-diyl)-dibenzothiophene-S,S-dioxide-3,7-diyl) co-polymers (p(F-S)x) by palladium- catalyzed Suzuki cross-coupling polymerization where the feed ration of the latter is varied from 2 to 30 mol % (i.e., x=2-30) is given. Polymer light emitting devices are fabricated with the configuration indium tin oxide/poly(3,4-ethylenediocythiophene):poly(styrenesulfonic acid)/p(F-S)x/Ba/Al. The device external quantum efficiency increased as the ration of the S co-monomer was increased, up to a maximum of 1.3% at 100 mA cm(-2) for p(F-S)30 and a brightness of 3 770 cd m(-2) (at 10V). The S units impart improved electron injection, more balanced mobilities, and markedly improved device performance compared to poly(9,9-dioctylflouorene) under similar conditions. These co-polymers display broad emission, observed as greenish-white light, which arises from dual fluorescence, viz. both local excited states and charge transfer states. Utilizing dual emission can reduce problems associated with Forster energy transfer from high-energy to-low energy excited states
The use of mice in diabetes research:The impact of physiological characteristics, choice of model and husbandry practices
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