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

Light bending scenario for accreting black holes in X-ray polarimetry

We discuss a model of an X-ray illuminating source above an accretion disk of a rotating black hole. Within the so called lamp-post scheme we compute the expected (observed) polarization properties of the radiation reaching an observer. We explore the dependencies on model parameters, employing Monte Carlo radiation transfer computations of the X-ray reflection on the accretion disk and taking general relativity effects into account. In particular, we discuss the role of the black hole spin, of the observer viewing angle, and of the primary X-ray source distance from the black hole. We give several examples of the resulting polarization degree for two types of exemplary objects - active galactic nuclei and Galactic black holes. In order to assess potential observability of the polarization features, we assume the sensitivity of the proposed New Hard X-ray Mission (NHXM). We examine the energy range from several keV to ~50 keV, so the iron-line complex and the Compton hump are included in our model spectra. We find the resultant polarization degree to increase at the higher end of the studied energy band, i.e. at >~20 keV. Thus, the best results for polarimetry of reflection spectra should be achieved at the Compton hump energy region. We also obtain higher polarization degree for large spin values of the black hole, small heights of the primary source, and low inclination angles of the observer.Comment: 17 pages, 14 figures, accepted in Ap

Modeling the X-ray fractional variability spectrum of Active Galactic Nuclei using multiple flares

Using Monte-Carlo simulations of X-ray flare distributions across the accretion disk of active galactic nuclei (AGN), we obtain modeling results for the energy-dependent fractional variability amplitude. Referring to previous results of this model, we illustrate the relation between the shape of the point-to-point fractional variability spectrum, F_pp, and the time-integrated spectral energy distribution, F_E. The results confirm that the spectral shape and variability of the iron Kalpha line are dominated by the flares closest to the disk center.Comment: 2 pages, 1 figure, conference proceedings of the AGN meeting held in October 2006 in Xi'an, China. To appear in "The Central Engine of Active Galactic Nuclei", ed. L. C. Ho and J.-M. Wang (San Francisco: ASP

Constraining global parameters of accreting black holes by modeling magnetic flares

We present modeling results for the reprocessed radiation expected from magnetic flares above AGN accretion disks. Relativistic corrections for the orbital motion of the flare and for the curved space-time in the vicinity of the black hole are taken into account. We investigate the local emission spectra, as seen in a frame co-orbiting with the disk, and the observed spectra at infinity. We investigate long-term flares at different orbital phases and short-term flares for various global parameters of the accreting black hole. Particular emphasis is put on the relation between the iron Kalpha line and the Compton hump as these two features can be simultaneously observed by the Suzaku satellite and later by Simbol-X.Comment: 4 pages, 1 figure, 1 table, proceedings for a poster at the international conference "The Extreme Universe in the Suzaku Era" held in Kyoto, Japan, December 4-8, 200

On the origin of the broad, relativistic iron line of MCG-6-30-15 observed by XMM-Newton

The relativistic iron line profile recently observed by XMM-Newton in the spectrum of the Seyfert 1 galaxy MCG--6-30-15 (Wilms et al., 2001) is discussed in the framework of the lamp-post model. It is shown that the steep disc emissivity, the large line equivalent width and the amount of Compton reflection can be self- consistently reproduced in this scenario

Polarization signatures of strong gravity in AGN accretion discs

The effects of strong gravity on the polarization of the Compton reflection from an X-ray illuminated accretion disc are studied. The gravitational field of a rotating black hole influences Stokes parameters of the radiation along the propagation to a distant observer. Assuming the lamp-post model, the degree and the angle of polarization are examined as functions of the observer's inclination angle, of the height of the primary source and of the inner radius of the disc emitting region. It is shown that polarimetry can provide essential information on the properties of black holes sources, and it is argued that time variation of the polarization angle is a strong signature of general relativity effects. The expected polarization degree and angle should be detectable by new generation polarimeters, like the one planned for the Xeus mission.Comment: Accepted for publication in MNRAS; 6 pages, 3 figure