The Galactic Center

In the past decade high resolution measurements in the infrared employing adaptive optics imaging on 10m telescopes have allowed determining the three dimensional orbits stars within ten light hours of the compact radio source at the center of the Milky Way. These observations show the presence of a three million solar mass black hole in Sagittarius A* beyond any reasonable doubt. The Galactic Center thus constitutes the best astrophysical evidence for the existence of black holes which have long been postulated, and is also an ideal `lab' for studying the physics in the vicinity of such an object. Remarkably, young massive stars are present there and probably have formed in the innermost stellar cusp. Variable infrared and X-ray emission from Sagittarius A* are a new probe of the physical processes and space-time curvature just outside the event horizon.Comment: Write up of the talk at IAU Symposium No. 238 (21-25 August 2006, Prague), to appear in Proceedings of "Black Holes: from Stars to Galaxies" (Cambridge University Press), p. 17

Why Does the Importance of Education for Health Differ across the United States?

The positive association between educational attainment and adult health (“the gradient”) is stronger in some areas of the United States than in others. Explanations for the geographic pattern have not been rigorously investigated. Grounded in a contextual and life-course perspective, the aim of this study is to assess childhood circumstances (e.g., childhood health, compulsory schooling laws) and adult circumstances (e.g., wealth, lifestyles, economic policies) as potential explanations. Using data on U.S.-born adults aged 50 to 59 years at baseline (n = 13,095) and followed for up to 16 years across the 1998 to 2014 waves of the Health and Retirement Study, the authors examined how and why educational gradients in morbidity, functioning, and mortality vary across nine U.S. regions. The findings indicate that the gradient is stronger in some areas than others partly because of geographic differences in childhood socioeconomic conditions and health, but mostly because of geographic differences in adult circumstances such as wealth, lifestyles, and economic and tobacco policies

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

Why Does the Importance of Education for Health Differ across the United States?

The positive association between educational attainment and adult health (“the gradient”) is stronger in some areas of the United States than in others. Explanations for the geographic pattern have not been rigorously investigated. Grounded in a contextual and life-course perspective, the aim of this study is to assess childhood circumstances (e.g., childhood health, compulsory schooling laws) and adult circumstances (e.g., wealth, lifestyles, economic policies) as potential explanations. Using data on U.S.-born adults aged 50 to 59 years at baseline (n = 13,095) and followed for up to 16 years across the 1998 to 2014 waves of the Health and Retirement Study, the authors examined how and why educational gradients in morbidity, functioning, and mortality vary across nine U.S. regions. The findings indicate that the gradient is stronger in some areas than others partly because of geographic differences in childhood socioeconomic conditions and health, but mostly because of geographic differences in adult circumstances such as wealth, lifestyles, and economic and tobacco policies

Iron lines from transient and persisting hot spots on AGN accretion disks

[abridged] We model the X-ray reprocessing from a strong co-rotating flare above an accretion disk in active galactic nuclei. We explore the horizontal structure and evolution of the underlying hot spot. To obtain the spectral evolution seen by a distant observer, we apply a general relativity ray-tracing technique. We concentrate on the energy band around the iron K-line, where the relativistic effects are most pronounced. Persistent flares lasting for a significant fraction of the orbital time scale and short, transient flares are considered. In our time-resolved analysis, the spectra recorded by a distant observer depend on the position of the flare/spot with respect to the central black hole. If the flare duration significantly exceeds the light travel time across the spot, then the spot horizontal stratification is unimportant. On the other hand, if the flare duration is comparable to the light travel time across the spot radius, the lightcurves exhibit a typical asymmetry in their time profiles. The sequence of dynamical spectra proceeds from more strongly to less strongly ionized re-emission. At all locations within the spot the spectral intensity increases towards edge-on emission angles, revealing the limb brightening effect. Future X-ray observatories with significantly larger effective collecting areas will enable to spectroscopically map out the azimuthal irradiation structure of the accretion disk and to localize persistent flares. If the hot spot is not located too close to the marginally stable orbit of the black hole, it will be possible to probe the reflecting medium via the sub-structure of the iron K-line. Indications for transient flares will only be obtained from analyzing the observed lightcurves on the gravitational time scale of the accreting supermassive black hole.Comment: 15 pages, 8 figures, accepted by Astronomy & Astrophysic