Sarcoidosis is a multisystem, granulomatous disorder of unknown etiology, most often presenting between the ages of 20 and 40 and in African Americans. The objective of this work was to examine ...racial differences in sarcoidosis risk and heterogeneity in risk among families, and to test for evidence of genetic inheritance in selected sarcoidosis families. First, all newly diagnosed cases occurring between 1990 and 1994 among members of the Health Alliance Plan health maintenance organization in Detroit, Michigan were identified. Annual incidence, in number of new cases per 100,000, was highest in 30-39 year old African American females (107). Overall, African Americans had about a threefold higher age adjusted annual incidence (36.5) compared with Caucasians (11.3). Next, heterogeneity in familial risk of sarcoidosis was examined in 3,395 siblings and parents of 558 index cases (361 African American, 197 Caucasian) diagnosed at Henry Ford Hospital between 1965 and 1994. Using the age-, race- and sex-specific cumulative incidence of sarcoidosis in the sample, a statistically significant heterogeneity of familial risk (p $<$ 0.001) was found. Index cases (n = 69) from high risk families were more likely African American (Odds ratio (OR) = 3.24; 95% confidence interval (CI) = 1.71-6.14) and had an offspring or second degree relative affected (OR = 6.21; 95% CI = 2.86-13.45). A segregation analysis was performed on 56 African American families comprised of 698 individuals ascertained through a sarcoidosis case with at least one additional affected first degree relative. In analyses without an ascertainment correction, Mendelian inheritance was rejected. The best fitting model included a non-transmitted environmental factor with a common sibling environmental component and higher risk in females than males. The inference about etiology for sarcoidosis was similar whether the incidence of disease within the family sample or in the population were used to estimate disease prevalence in these 56 families. In conclusion, in this patient population sarcoidosis is three times more common in African Americans compared with Caucasians and significant heterogeneity of risk exists among families. In a sample of African American families, evidence exists for the disease distribution being dependent on both shared and individual-specific environmental factors rather than a Mendelian major factor.
The observed profile of spectral lines from a relativistic accretion disk can
constrain parameters such as the disk geometry and the rotation of the central
black hole. The formation of the spectral ...line in a disk generally has been
modeled with simple assumptions such as local isotropy of emission. Here we
consider line formation in the presence of velocity gradients induced by the
differential flow in the disk. In this case the emission can have anisotropy in
the form of an azimuthal dependence relative to the local principle axes of
shear. Since the physical conditions in a disk are uncertain in detail, we
investigate this effect with simple parameterized models based on Sobolev
theory to highlight the overall character of the changes in the line profile.
We find that velocity gradients generally cause a relative increase of flux in
the red wing, hence the inner radius of the disk would be underestimated if the
effect were not taken into consideration. If the inner radius is used as a
signature of black hole rotation, as when the disk is not emissive within the
marginally stable circular orbit, then the inferred rotation would be
overestimated in cases where the emissivity of the disk has fairly shallow
fall-off with radius. If the disk were emissive even within the marginally
stable orbit, then the local azimuthal anisotropy of emission produces features
in the line profile which distinguish rotating from nonrotating black holes.
The observed profile of spectral lines from a relativistic accretion disk can constrain parameters such as the disk geometry and the rotation of the central black hole. The formation of the spectral ...line in a disk generally has been modeled with simple assumptions such as local isotropy of emission. Here we consider line formation in the presence of velocity gradients induced by the differential flow in the disk. In this case the emission can have anisotropy in the form of an azimuthal dependence relative to the local principle axes of shear. Since the physical conditions in a disk are uncertain in detail, we investigate this effect with simple parameterized models based on Sobolev theory to highlight the overall character of the changes in the line profile. We find that velocity gradients generally cause a relative increase of flux in the red wing, hence the inner radius of the disk would be underestimated if the effect were not taken into consideration. If the inner radius is used as a signature of black hole rotation, as when the disk is not emissive within the marginally stable circular orbit, then the inferred rotation would be overestimated in cases where the emissivity of the disk has fairly shallow fall-off with radius. If the disk were emissive even within the marginally stable orbit, then the local azimuthal anisotropy of emission produces features in the line profile which distinguish rotating from nonrotating black holes.
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