2,623 research outputs found
Variable line profiles due to non-axisymmetric patterns in an accretion disc around a rotating black hole
We have explored spectral line profiles due to spiral patterns in accretion
discs around black holes. A parametrization was employed for the shape and
emissivity of spiral waves, which can be produced by non-axisymmetric
perturbations affecting the disc density and ionization structure. The effects
of the light-travel time, energy shift, and gravitational focusing near to a
rotating black hole were taken into account. A high-resolution ray-tracing code
was used to follow the time variations of the synthetic line profile. A variety
of expected spectral features were examined and the scheme applied to a broad
iron line observed in MCG-6-30-15.Comment: 11 pages (LaTeX), 7 figures (EPS); PASJ accepte
Emission Line Profiles from Self-Gravitating Thin Disks
We have constructed general relativistic models of a stationary, axially
symmnetric, Keplerian thin disk around a rotating black hole. We computed
profiles of a spectral line, emitted in the inner region of the disk. In our
models we have taken into account also the self-gravity of the disk. The aim of
this work is to study gravitational effects on the line profiles in connection
with the X-ray features observed in spectra of active galactic nuclei. In some
cases, the calculated profiles are clearly affected by the disk gravity but
relativistic dragging effects are found to be negligible.Comment: 26 pages, 8 figures, uuencoded postscript file, to appear in The
Astrophysical Journal, Part I. Printed version available upon request from
the author
Frame-dragging effects on magnetic fields near a rotating black hole
We discuss the role of general relativity frame dragging acting on magnetic
field lines near a rotating (Kerr) black hole. Near ergosphere the magnetic
structure becomes strongly influenced and magnetic null points can develop. We
consider aligned magnetic fields as well as fields inclined with respect to the
rotation axis, and the two cases are shown to behave in profoundly different
ways. Further, we construct surfaces of equal values of local electric and
magnetic intensities, which have not yet been discussed in the full generality
of a boosted rotating black hole.Comment: to appear in the proceedings of "The Central Kiloparsec in Galactic
Nuclei (AHAR 2011)", Journal of Physics: Conference Series (JPCS), IOP
Publishin
Experimental study of skull bones reconstruction with the use of autografts and hydroxyapatitical gel
Introduction. To conduct reconstructive surgical interventions at pathological processes of skull base bone, defects of the temporal bone and dura mater, is especially complicated with the appearance of liquorrhea. This necessitates the improvement of operative technique and the use of new plastic materials. Objective: to study the features of meninges and skull bone defects plastic using autobone, fascia and HAP gel based on clinical observation, and macroscopic and microscopic experimental studies. Materials and methods: 36 mature nonlinear rats of both sexes up to 6 months old, weighing 190-250 g were divided into 2 groups. In the 1st (experimental) group there were 18 animals and autofragments of fascia and tibia with the addition of GAP gel were used for implantation; and in the 2nd group (comparison, n=18) the same plastic material without gel was used. The introduction of implant was carried out under general anesthesia in a standardized defect of skull frontal bones. The method of clinical observation, stereoscopic, common histological examination after staining with hematoxylin-eosin was applied. Results: The introduction of bone’s and fascia autografts into skull defect and dura mater provides the structural function of the damage tightly closing, preventing or stopping of liquorrhea, besides fascia contributes to vascularization of tissues in the healing zone. Additional administration of HAP ge, provides pronounced adhesion to bone tissue, gaps filling in the graft bed, creates a microenvironment for metabolism in the zone, shows a positive effect on osteogenesis, promotes calcification and bone reconstruction in the area of the defect. The results obtained also indicate the peculiarities of reparative processes in the bones of the skull, expressed in the dependence of bone repair and / or the development of fibrous tissue in the defect area and the density of adherence of the bone to the mother tissue, which is accompanied by improved bone restructuring under tight contact of the mother bone with the implanted material and the prevalence of fibrous tissue in case of their violation. This data confirm the effectiveness and promise HAPG use along with autofascia and autobone to close the defects of the meninges and skull bones and are important for improving reconstructive-restorative surgical interventions
Relationship between perceived and actual quality of data checking
Data quality is critical to reaching correct research conclusions. Researchers attempt to ensure that they have accurate data by checking the data after it has been entered. Previous research has demonstrated that some methods of data checking are better than others, but not all researchers use the best methods. Perhaps researchers continue to use less optimal data checking methods because they mistakenly believe that they are highly accurate. The purpose of this study was to examine the relationship between perceived data quality and actual data quality. A total of 29 participants completed this study. Participants checked that letters and numbers had been entered correctly into the computer using one of three randomly assigned data checking methods. Afterwards, they rated the quality of their data checking method. The sample correlations between perceived and actual data quality were small to moderate and confidence intervals for the population correlations did not include high values. We conclude that the relationship between actual and perceived data quality is not high
The upper kHz QPO: a gravitationally lensed vertical oscillation
We show that a luminous torus in the Schwarzschild metric oscillating along
its own axis gives rise to a periodically varying flux of radiation, even
though the source of radiation is steady and perfectly axisymmetric. This
implies that the simplest oscillation mode in an accretion flow, axisymmetric
up-and-down motion at the meridional epicyclic frequency, may be directly
observable when it occurs in the inner parts of accretion flow around neutron
stars and black holes. The high-frequency modulations of the X-ray flux
observed in low-mass X-ray binaries at two frequencies (twin kHz QPOs) could
then be a signature of strong gravity both because radial and meridional
oscillations have different frequencies in non-Newtonian gravity, and because
strong gravitational deflection of light rays causes the flux of radiation to
be modulated at the higher frequency.Comment: 8 p., 4 fig
Signatures of X-ray reverberation in the power spectra of AGN
We compute fully relativistic disc response functions in the case of the
"lamp-post" geometry using the full observed reflection spectrum for various
X-ray source heights, disc inclination, and spin values of the central black
hole. Since the observed PSD is equal to the product of the intrinsic power
spectrum with the "transfer function" (i.e. the Fourier transform of the disc
response function), we are able to predict the observed PSDs in the case of
X-ray illumination of the inner disc. The observed PSD should show a prominent
dip at high frequencies and an oscillatory behaviour, with a decreasing
amplitude, at higher frequencies. The reverberation "echo" features should be
more prominent in energy bands where the reflection component is more
pronounced. The frequency of the dip is independent of energy, and it is mainly
determined by the black hole mass and the X-ray source height. The amplitude of
the dip increases with increasing black hole spin and inclination angle, as
long as the height of the "lamp" is smaller than ~10 gravitational radii. The
detection of the X-ray reverberation signals in the PSDs can provide further
evidence for X-ray illumination of the inner disc in AGN. Our results are
largely independent of the assumed geometry of the disc-corona system, as long
as it does not change with time, and the disc response function is
characterized by a sharp rise, a "plateau", and a decline at longer times.
Irrespective of the geometry, the frequency of the main dip should decrease
with increasing "mean time" of the response function, and the amplitude of the
dip should increase with increasing reflection fraction.Comment: Astronomy and Astrophysics accepte
The influence of electrostatic interactions on the detection of heme-globin complexes in ESI-MS
AbstractThe heme-globin complexes of hemoglobin and myoglobin are investigated in positive-ion mode and negative-ion mode using a nano-ESI source coupled to a quadrupole ion trap MS and an orthogonal time-of-flight MS. The extent of dissociation of these noncovalent complexes upon collisional activation and thus their gas-phase stability is strongly dependent on the polarity of the ESI-MS experiment as well as on the charge of the prosthetic group (ferri-heme [Fe3+-heme]+ vs. ferro-heme [Fe2+-heme]±0). The results clearly point to the important role of electrostatic interactions on the gas phase stability of noncovalent complexes and therefore the ion signals observed in ESI-MS experiments
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