Spins of the supermassive black hole in M87: new constraints from TeV observations

The rapid TeV $\gamma-$ray variability detected in the well-known nearby radio galaxy M87 implies an extremely compact emission region (5-10 Schwarzschild radii) near the horizon of the supermassive black hole in the galactic center. TeV photons are affected by dilution due to interaction with the radiation field of the advection-dominated accretion flow (ADAF) around the black hole, and can thus be used to probe the innermost regions around the black hole. We calculate the optical depth of the ADAF radiation field to the TeV photons and find it strongly depends on the spin of the black hole. We find that transparent radii of 10 TeV photons are of $5R_{\rm S}$ and $13R_{\rm S}$ for the maximally rotating and non-rotating black holes, respectively. With the observations, the calculated transparent radii strongly suggest the black hole is spinning fast in the galaxy. TeV photons could be used as a powerful diagnostic for estimating black hole spins in galaxies in the future.Comment: 4 pages, 4 figures. to appear in ApJ

Hypertensive Cardiomyopathy: Diagnostic Approach and Clinical Differentiation from Hypertrophic Cardiomyopathy

Hypertensive Cardiomyopathy (HTN-CM) is a structural cardiac disorder generally accompanied by concentric or eccentric Left Ventricular Hypertrophy (LVH) associated with diastolic or/and systolic dysfunction in patients with persistent systemic hypertension. It occurs in the absence of other cardiac diseases capable of causing myocardial hypertrophy or cardiac dysfunction. Long standing arterial hypertension (HTN) leads to structural and functional myocardial abnormalities resulting in myocardial ischemia, fibrosis, and hypertrophy. HTN-CM is predominantly a disease of impaired relaxation rather than impaired contractility, although subtle myocardial systolic abnormalities could be detected recently by Global Longitudinal Systolic Strain (GLS) Speckle Tracking Echocardiography (STE). Importantly, the accompanying LVH is itself a risk factor for mortality and morbidity and is considered an independent predictor for Sudden Cardiac Death (SCD). Therefore, early detection of LVH development in patients with Hypertensive Hypertrophic Cardiomyopathy (HTN-CM) is crucial for optimal treatment. In addition to pathological findings, echocardiography and cardiac magnetic resonance imaging are ideal tools for the diagnosis of HTN-CM and can differentiate it from Hypertrophic Cardiomyopathy (HCM). Timely diagnosis of this condition and utilization of appropriate treatment are required to improve morbidity and mortality in hypertensive patients. This review presents an overview of utilization of multidisciplinary imaging modalities approach for proper diagnosis of HTN-CM and its differentiation from HCM. Relevant article highlighted key points in differentiation of HTN-CM from HCM and the effects of hypertension on cardiac hypertrophy and heart failure development are discussed in clinical case study

Probing the central black hole in M87 with gamma-rays

Recent high-sensitivity observation of the nearby radio galaxy M87 have provided important insights into the central engine that drives the large-scale outflows seen in radio, optical and X-rays. This review summarizes the observational status achieved in the high energy (HE;<100 GeV) and very high energy (VHE; >100 GeV) gamma-ray domains, and discusses the theoretical progress in understanding the physical origin of this emission and its relation to the activity of the central black hole.Comment: Invited compact review to be published in Modern Physics Letters A; 19 pages, 4 figure

Sub-clinical Detection of Left Ventricular Myocardial Dysfunction in Valvular Heart Diseases: A State-of-the-Art Review in a Speckle Tracking Echocardiography and Myocardial Performance

Purpose of the state-of-the-art review: Left ventricular (LV) global longitudinal strain (GLS) is recently recognized as a more sensitive measure of LV myocardial systolic function compared with LV ejection fraction (LVEF). In addition, left ventricular GLS , myocardial performance index (MPI) and maximum rate of LV pressure rise during isovolumetric contraction (LV dP/dtmax) are more reproducible than traditional assessment of LV systolic function by two dimensional echocardiography (2DE) LVEF. These underutilized techniques can detect preclinical myocardial dysfunction in patients who are at risk of LV failure in valvular-induced heart disease . Current guidelines for diagnosis and treatment of valvular heart disease (VHD) include LVEF as one of the parameters to take into consideration in the clinical decision-making. However, a large body of evidence has shown that left ventricular GLS, MPI and LV dP/dtmax have been classically considered as a sensitive marker of LV contractility and inotropic state. In turn GLS and myocardial performance may be a better prognosticator than LVEF in aortic and mitral valve heart diseases. This timely state-of-the-art review, appraised the evidence and role of GLS, MPI and dP/dT as clinical tools in patients with aortic and mitral valve disease. Recent findings: Left ventricular GLS has been shown to be prognostic in low-flow, low-gradient severe aortic stenosis with preserved LVEF. The role of left ventricular GLS, Tei index (MPI) and maximum rate of LV pressure rise (LV dP/dtmax) in patients with aortic regurgitation and mitral valve diseases (regurgitation and stenosis) is less well established. Summary: Echocardiography is considered the primary non-invasive imaging tool for valvular heart disease assessment and the cornerstone method in diagnosing and evaluating the morphology and severity of aortic and mitral valve diseases. Currently, diagnostic-cardiac catheterization is no more recommended except in very rare cases when echocardiographic image quality is suboptimal, non-diagnostic and when the results of 2DE are discrepant with clinical data. Once clinical decision-making is based on the 2DE and three dimensional echocardiographic in assessment of the severity of mitral and aortic valve diseases, it is crucial that standards should be adopted to maintain accuracy and consistency across echocardiographic laboratories. This illustrative review article assesses left ventricular systolic function (LVEF) employing two and/or three dimensional echocardiography in comparison to GLS, MPI and LV dP/dtmax, especially applied for aortic valve (AV) and mitral valve (MV) diseases. It is noteworthy that this document only provides echocardiographic standards rather than making recommendations for clinical management. Conclusion: It is concluded that GLS, MPI and maximum rate of LV pressure rise during isovolumetric contraction (LV dP/dtmax) are recommended and more so, they should be increasingly used to identify subclinical LV myocardial dysfunction in patients with mitral and aortic valve heart diseases, to identify optimal timing for surgery and prognosticate outcomes after surgery

Linear Accelerating Superluminal Motion Model

Accelerating superluminal motions were detected recently by multi-epoch Very Long Baseline Interferometry (VLBI) observations. Here, a Linear Accelerating Superluminal Motion (LASM) model is proposed to interpret the observed phenomena. The model provides a direct and accurate way to estimate the viewing angle of a relativistic jet. It also predicts that both Doppler boosting and deboosting effects may take place in an accelerating forward jet. The LASM model is applied to the data of the quasar 3C 273, and the initial velocity, acceleration and viewing angle of its three components are derived through model fits. The variations of the viewing angle suggest that a supermassive black hole binary system may exist in the center of 3C273. The gap between the inner and outer jet in some radio loud AGNs my be explained in terms of Doppler deboosting effects when the components accelerate to ultra-relativistic speed.Comment: 12 Pages, 3 Figues, 1 Table, Accepted for Publication by ApJ Lette

Accretion onto the Supermassive Black Hole in M87

Chandra X-ray observations of the giant elliptical galaxy M87 resolve the thermal state of the hot interstellar medium into the accretion (Bondi) radius of its central 3 10^9 Msun black hole. We measure the X-ray gas temperature and density profiles and calculate the Bondi accretion rate, Mdot_Bondi \sim 0.1 Msun/yr. The X-ray luminosity of the active nucleus of M87 observed with Chandra is L_{x, 0.5-7 \keV} \sim 7 \times 10^{40}erg/s. This value is much less than the predicted nuclear luminosity, L_{Bondi} \sim 5 \times 10^{44} erg/s, for accretion at the Bondi rate with a canonical accretion radiative efficiency of 10%. If the black hole in M87 accretes at this rate it must do so at a much lower radiative efficiency than the canonical value. The multiwavelength spectrum of the nucleus is consistent with that predicted by an advection-dominated flow. However, as is likely, the X-ray nucleus is dominated by jet emission then the properties of flow must be modified, possibly by outflows. We show that the overall energetics of the system are just consistent with the predicted Bondi nuclear power. This suggests that either most of the accretion energy is released in the relativistic jet or that the central engine of M87 undergoes on-off activity cycles. We show that, at present, the energy dumped into the ISM by the jet may reduce the accretion rate onto the black hole by a factor \propto (v_j/c_s)^{-2}, where v_j is the jet velocity and c_s the ISM sound speed, and that this is sufficient to account for the low nuclear luminosity.Comment: emulateapj.sty, revised version, accepted by Ap

X-ray Spectral Survey of WGACAT Quasars, II: Optical and Radio Properties of Quasars with Low Energy X-ray Cut-offs

We have selected quasars with X-ray colors suggestive of a low energy cut-off, from the ROSAT PSPC pointed archive. We examine the radio and optical properties of these 13 quasars. Five out of the seven quasars with good optical spectra show associated optical absorption lines, with two having high delta-v candidate systems. Two other cut-off quasars show reddening associated with the quasar. We conclude that absorption is highly likely to be the cause of the X-ray cut-offs, and that the absorbing material associated with the quasars, not intervening along the line-of-sight. The suggestion that Gigahertz Peaked Sources are associated with X-ray cut-offs remains unclear with this expanded sample.Comment: 17 pages, LaTeX, including 2 Tables and 1 figure. Ap.J. in pres

New Insight in the Assessment of Left Ventricular Function in Paradoxical Low Flow Aortic Stenosis Patients with Normal Left Ventricular Ejection Fraction: A Mini-Review

Paradoxical valvular aortic stenosis (VAS) is a challenging area of clinical cardiology for the practitioners. It involves a small aortic valve area, low flow rate and mean pressure gradient although there is normal left ventricular ejection fraction. The aim of this study was to assess left ventricular (LV) dysfunction in a symptomatic severe aortic valve stenosis which is of crucial importance in identifying patients at risk of heart failure, postoperative complications and increased mortality. There are new insights which are involved in assessment of LV myocardial function including global longitudinal strain (GLS) by two-dimensional speckle tracking echocardiography (2D STE), myocardial performance index (MPI) and maximum rate of LV pressure rise (+dP/dt) during isovolumetric contraction time of the LV. This information can provide both diagnostic and prognostic information in addition to standard echocardiographic and clinical parameters. However, a profound understanding of the complex interaction between loading conditions, chamber geometry and contractility is necessary for the correct interpretation of myocardial deformation in order to draw appropriate conclusions in patients with aortic valve disease. This mini review is related to new and novel insights into the assessment of left ventricular function (LVF) in paradoxical low flow aortic stenosis patients with normal left ventricular ejection fraction (LVEF)

Prediction of Preclinical Myocardial Dysfunction among Obese Diabetics with Preserved Ejection Fraction Using Tissue Doppler Imaging and Speckle Tracking Echocardiography

Background. Obesity and type 2 diabetes mellitus (T2DM) are two interrelated and preventable disorders. However, they are responsible for significant global mortality from cardiovascular diseases (CVDs). Clinical studies have demonstrated that global longitudinal strain (GLS) using speckle tracking echocardiography (STE), can assess myocardial function accurately in apparently, healthy patients with diabetes and obesity in the settings of acute and chronic ischemia and suspected cardiomyopathy without heart failure. No such studies have been published to date regarding subclinical detection of cardiac dysfunction among obese patients with T2DM. This study aims to investigate the role of STE in the early pre-clinical diagnosis of impairment of diastolic and systolic dysfunction in obese patients with T2DM. This study also investigated whether it is possible to detect early pre-clinical impairment of diastolic and systolic dysfunction in obese T2DM patients, via Tissue Doppler Imaging (TDI), maximum rate of left ventricular pressure development (peak dP/dt) and GLS using STE for comparison. Subjects and Methods. After clearance from the review board of Dibba- Hospital, Alfujairah, UAE, all the available records of patients with the diagnosis of obesity and diabetes were examined. The study included 214 patients presenting with obesity in conjunction with diabetes and 93 age-matched healthy control subjects. STE was performed among all the patients and subjects along with Tissue Doppler Imaging (TDI). This study assessed maximal rate of pressure rise during ventricular contraction (peak dP/dt) and global longitudinal strain (GLS) using STE methods. Transthoracic echocardiography, myocardial Doppler-derived systolic (sm), early diastolic velocity (em) and GLS were also obtained, among all the subjects. Results. The results show that cardiac functions via conventional echocardiography (CE) were similar in the 2 groups. Using TDI and conventional mitral Doppler flow, obese subjects with diabetes showed an evidence of diastolic function abnormalities in the form of lower Ea velocity (9.5 ± 2.9 vs. 18.4 ± 3.5 cm/s, p < 0.0001), an increased Aa velocity (16.5 ± 2.4 vs. 14.1 ± 2.2 cm/s p < 0.05), higher left ventricular filling pressure (E/Ea = 12 ± 4.4 vs 8±3.1), p 35) (n = 26) had reduced LV systolic and diastolic function compared with healthy controls. Regarding, systolic function indices, the findings revealed lower average longitudinal peak systolic strain, sm and reduced em, although, LV ejection fraction remained normal (56.48% ± 8.81). Among subjects with severe obesity (n = 26), the findings reveal that global longitudinal presystolic strain (GLPSS) is highly correlated with maximum rate of pressure development of LV (dp/dt), although the LVEF remained normal, in comparison to systolic strain and dp/dt. (.5% ±1.4 vs -19.54% ± 4.5; p < 0.001), in the age-matched healthy subjects. However, the frequency/grade of DCM detected by STE, among patients having obesity with T2DM, correlated closely with the degree of obesity, metabolic abnormalities and clustering of other major risk factors, especially high blood pressure. The findings also revealed that chest pain due to coronary heart disease (CAD), dyspnea and DCM were more common among female patients compared to men. Conclusion. The results indicate that patients having obesity with T2DM should be advised to undertake early TDI and STE for early diagnosis of decreased cardiac diastolic and systolic dysfunctions and cardiomyopathy, which is likely to be missed by conventional echocardiography. Significant differences in regional and global strain were also identified between the severely obese diabetic (BMI ≥ 35), (GLPSS (-13) patients compared to less obese subjects