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

Effects of low-dose doxycycline and bisphosphonate clodronate on alveolar bone loss and gingival levels of matrix metalloproteinase-9 and interleukin-1 ß in rats with diabetes: A histomorphometric and immunohistochemical study

Background: Bisphosphonates (BPs) and low-dose doxycycline (LDD) have been shown to inhibit bone resorption and to improve the levels of proinflammatory mediators and destructive enzymes in gingival tissues, respectively. The purpose of this study is to evaluate the effect of mono and combined BP clodronate and LDD therapies in reducing gingival levels of matrix metalloproteinase-9 (MMP-9), interleukin-1ß (IL-1ß), and alveolar bone loss in rats with diabetes. Methods: Fifty adult Wistar rats were divided into five study groups as follows: 1) group 1 = diabetes control; 2) group 2 = diabetes + periodontitis; 3) group 3 = diabetes + periodontitis + LDD; 4) group 4 = diabetes + periodontitis + clodronate; and 5) group 5 = diabetes + periodontitis + LDD + clodronate. LDD and clodronate were given as a single agent or as combination therapy during the 7 days of the post-experimental periodontitis period. On day 7, the rats were sacrificed, the mobility of the tooth was recorded, and block biopsies were removed. The gingival tissues were analyzed histologically and immunohistochemically for expression of MMP-9 and IL-1ß. Alveolar bone loss was evaluated morphometrically under a light microscope. Data analysis was performed statistically by Kruskal-Wallis and post hoc Tukey and Spearman correlation tests. Results: Alveolar bone loss was significantly greater in groups 2 through 5 than group 1 (P 0.05). Animals with periodontitis (group 2) expressed significantly higher levels of MMP-9 and IL-1ß compared with those without periodontitis (group 1) (P <0.05). MMP-9 expression was significantly lower in group 3 than groups 1, 2, and 5 (P <0.05). IL-1ß expression was significantly lower in the groups 1, 3, 4, and 5 than 2 (P <0.01) but was not significantly different among groups 1, 3, 4, and 5. Positive correlations were found between alveolar bone loss and density of inflammation (? = 0.319, P = 0.021) and between MMP-9 and IL-1ß (? = 0.418, P = 0.002), respectively. Conclusion: Our findings suggest that ligature-induced periodontitis in animals with diabetes results in significantly higher levels of MMP-9 and IL-1ß expression in gingiva. The use of mono and combined clodronate and LDD administrations may significantly reduce levels of MMP-9 and IL-1ß expression. However, drug administration did not affect alveolar bone levels during the study period