General relativistic radiative transfer: formulation and emission from structured tori around black holes

We construct a general relativistic radiative transfer (RT) formulation, applicable to particles with or without mass in astrophysical settings. Derived from first principles, the formulation is manifestly covariant. Absorption and emission, as well as relativistic, geometrical and optical depth effects are treated self-consistently. The RT formulation can handle 3D geometrical settings and structured objects with variations and gradients in the optical depths across the objects and along the line-of-sight. The presence of mass causes the intensity variation along the particle bundle ray to be reduced by an aberration factor. We apply the formulation and demonstrate RT calculations for emission from accretion tori around rotating black holes, considering two cases: idealised optically thick tori that have a sharply defined emission boundary surface, and structured tori that allow variations in the absorption coefficient and emissivity within the tori. Intensity images and emission spectra of these tori are calculated. Geometrical effects, such as lensing-induced self-occulation and multiple-image contribution are far more significant in accretion tori than geometrically thin accretion disks. Optically thin accretion tori emission line profiles are distinguishable from the profiles of lines from optically thick accretion tori and optically thick geometrically thin accretion disks. Line profiles of optically thin accretion tori have a weaker dependence on viewing inclination angle than those of the optically thick accretion tori or accretion disks, especially at high viewing inclination angles. Limb effects are present in accretion tori with finite optical depths. Finally, in accretion flows onto relativistic compact objects, gravitationally induced line resonance can occur. This resonance occurs easily in 3D flows, but not in 2D flows, such as a thin accretion disk around a black hole.Comment: 13 pages, 10 figures, Accepted for publication in Astronomy and Astrophysic

Gravitating discs around black holes

Fluid discs and tori around black holes are discussed within different approaches and with the emphasis on the role of disc gravity. First reviewed are the prospects of investigating the gravitational field of a black hole--disc system by analytical solutions of stationary, axially symmetric Einstein's equations. Then, more detailed considerations are focused to middle and outer parts of extended disc-like configurations where relativistic effects are small and the Newtonian description is adequate. Within general relativity, only a static case has been analysed in detail. Results are often very inspiring, however, simplifying assumptions must be imposed: ad hoc profiles of the disc density are commonly assumed and the effects of frame-dragging and completely lacking. Astrophysical discs (e.g. accretion discs in active galactic nuclei) typically extend far beyond the relativistic domain and are fairly diluted. However, self-gravity is still essential for their structure and evolution, as well as for their radiation emission and the impact on the environment around. For example, a nuclear star cluster in a galactic centre may bear various imprints of mutual star--disc interactions, which can be recognised in observational properties, such as the relation between the central mass and stellar velocity dispersion.Comment: Accepted for publication in CQG; high-resolution figures will be available from http://www.iop.org/EJ/journal/CQ

Differentiation between athlete's heart and dilated cardiomyopathy in athletic individuals.

OBJECTIVE: Distinguishing early dilated cardiomyopathy (DCM) from physiological left ventricular (LV) dilatation with LV ejection fraction 11% from baseline to peak exercise compared with 23% of patients with DCM (p63% in 92% grey-zone athletes compared with 17% patients with DCM (p11% from baseline to peak exercise or achieve a peak LV ejection fraction >63% had sensitivity of 77% and 83%, respectively, and specificity of 96% and 92%, respectively, for predicting DCM. CONCLUSION: Comprehensive assessment using a cascade of routine investigations revealed that exercise stress echocardiography has the greatest discriminatory value in differentiating between grey-zone athletes and asymptomatic patients with DCM. Our findings require validation in larger studies

Black hole spin: theory and observation

In the standard paradigm, astrophysical black holes can be described solely by their mass and angular momentum - commonly referred to as `spin' - resulting from the process of their birth and subsequent growth via accretion. Whilst the mass has a standard Newtonian interpretation, the spin does not, with the effect of non-zero spin leaving an indelible imprint on the space-time closest to the black hole. As a consequence of relativistic frame-dragging, particle orbits are affected both in terms of stability and precession, which impacts on the emission characteristics of accreting black holes both stellar mass in black hole binaries (BHBs) and supermassive in active galactic nuclei (AGN). Over the last 30 years, techniques have been developed that take into account these changes to estimate the spin which can then be used to understand the birth and growth of black holes and potentially the powering of powerful jets. In this chapter we provide a broad overview of both the theoretical effects of spin, the means by which it can be estimated and the results of ongoing campaigns.Comment: 55 pages, 5 figures. Published in: "Astrophysics of Black Holes - From fundamental aspects to latest developments", Ed. Cosimo Bambi, Springer: Astrophysics and Space Science Library. Additional corrections mad

Thermal conductivity of high- T c superconductors

This paper reviews existing data on the thermal conductivity of high- T c superconductors. Included are discussions of pristine polycrystalline high- T c ceramics, single crystal specimens, and high- T c materials structurally modified by substitution or by radiation damage. The thermal conductivity of high- T c superconductors is compared with that of conventional superconductors, and dramatic differences are found between the two families. Mechanisms of thermal conductivity applicable to high- T c perovskites are discussed and implications for theories of high- T c superconductivity are noted.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45121/1/10948_2004_Article_BF00617463.pd

An adaptive denoising method dedicated to human cardiac MR-DTI

International audienc

Six-month outcomes of a high intensity exercise programme in young patients with hypertrophic cardiomyopathy : the SAFE-HCM trial

Background: Moderate intensity exercise training in older patients with hypertrophic cardiomyopathy (HCM) can improve functional capacity, without significant harm. However, younger patients are attracted to high intensity training (HIT) regimes. The SAFE-HCM study demonstrated that an individually tailored, HIT programme in young patients with HCM was feasible, and provided both health and psychological benefits, without an increase in the burden of arrhythmia. Purpose: To assess whether observed benefits of a HIT programme in young patients with HCM are sustained at 6 months. Methods: Eighty patients with HCM (45.7y+/-8.6) underwent baseline clinical and psychological assessment. Individuals were randomised to a 12-week HIT programme (n = 40) or usual care (n = 40). Baseline evaluation was repeated at 12 weeks (T12). Feasibility, safety, health and psychological benefits were assessed. At 12-weeks individuals were encouraged to continue with the frequency and intensity of physical activity (PA) achieved at the end of the cardiac rehabilitation programme. Participants in the exercise arm were invited to follow-up at 6 months (T6m). Results: The majority (83%) of participants completed the 12-week study. At T12 there was no significant difference between groups in the composite arrhythmia safety outcome (p = 0.99). The indices of exercise capacity were significantly improved in the exercise compared to the control group; peak VO2 (+3.7ml/kg/min [CI 1.1,6.3], p = 0.006), VO2/kg at anaerobic threshold (VO2/kgAT) (+2.44ml/kg/min [CI 0.6,4.2], p = 0.009), time to AT (+115s [CI 54.3,175.9], p < 0.001) and exercise time (max ET) (+108s [CI 33.7,182.2], p = 0.005). The exercise group also demonstrated greater reduction in systolic BP (-7.3mmHg [CI -11.7,-2.8], p = 0.002), BMI (-0.8kg/m2 [CI-1.1,-0.4], p < 0.001), anxiety (-2.6 [CI-3.6,-1.6], p= <0.001) and depression (-1.1 [CI -2.0,-0.2], p = 0.015) scores. At T6m patient reported exercise adherence was comparable to baseline PA in 33/34 of the exercise group attending for follow up. Most exercise gains dissipated with the exception of time to AT (p = 0.002), max ET (p = 0.003), VO2/kgAT (p = 0.04) and anxiety score (p < 0.001) (Figure 1). There were no sustained episodes of atrial or ventricular arrhythmias. The incidence of NSVT did not differ between time points (p = 0.09). Conclusion: A 12-week HIT programme in young patients with HCM offers considerable gains in fitness and psychological outcomes, with no increase in arrhythmic burden. At T6m exercise levels as well as most physiological adaptations and health benefits returned to baseline, as seen in other studies when formal participation in an exercise programme comes to an end. This highlights the importance of the implementation of strategies to encourage ongoing engagement in PA. Potential solutions include identification of barriers to exercise, as well as adoption of novel tele-rehabilitation approaches