A new physical interpretation of optical and infrared variability in quasars

Changing-look quasars are a recently identified class of active galaxies in which the strong UV continuum and/or broad optical hydrogen emission lines associated with unobscured quasars either appear or disappear on timescales of months to years. The physical processes responsible for this behaviour are still debated, but changes in the black hole accretion rate or accretion disk structure appear more likely than changes in obscuration. Here we report on four epochs of spectroscopy of SDSS J110057.70-005304.5, a quasar at a redshift of $z=0.378$ whose UV continuum and broad hydrogen emission lines have faded, and then returned over the past $\approx$20 years. The change in this quasar was initially identified in the infrared, and an archival spectrum from 2010 shows an intermediate phase of the transition during which the flux below rest-frame $\approx$3400\AA\ has decreased by close to an order of magnitude. This combination is unique compared to previously published examples of changing-look quasars, and is best explained by dramatic changes in the innermost regions of the accretion disk. The optical continuum has been rising since mid-2016, leading to a prediction of a rise in hydrogen emission line flux in the next year. Increases in the infrared flux are beginning to follow, delayed by a $\sim$3 year observed timescale. If our model is confirmed, the physics of changing-look quasars are governed by processes at the innermost stable circular orbit (ISCO) around the black hole, and the structure of the innermost disk. The easily identifiable and monitored changing-look quasars would then provide a new probe and laboratory of the nuclear central engine.Comment: 13 pages, 4 figures, 3 tables. Published in MNRAS. All code and data links on GitHub, https://github.com/d80b2t/WISE_L

Myocardial mechanics in young adult patients with diabetes mellitus: Effects altered load, inotropic state and dynamic exercise

AbstractThe disease entity “diabetic cardiomyopathy” has been extensively described in young patients with diabetes in the absence of ischemic, hypertensive or valvular heart disease. The most convincing data have been a 30% to 40% incidence of decreased radionuclide angiographic left ventricular ejection fraction response to dynamic exercise. In the current study, the hypothesis was tested that this abnormal ejection fraction response was due to alterations in ventricular loading conditions or cardiac autonomic innervation (extrinsic factors), or both, rather than to abnormalities in intrinsic ventricular systolic fiber function (contractility).Twenty normotensive patients with diabetes (mean age 30 ± 5 years, mean duration 15 ± 6 years) and 20 age-matched normal subjects were studied. All patients with diabetes had a normal treadmill exercise tolerance test without evidence of myocardial ischemia. By radionuclide angiography, all normal subjects increased ejection fraction with exercise (62 ± 4% to 69 ± 6%; p < 0.001). In contrast, 11(55%) of 20 patients with diabetes maintained or increased ejection fraction with exercise (group 1; 62 ± 4% to 69 ± 6%; p < 0.001) and 9 (45%) of 20 showed an exercise-induced decrease (group 2; 73 ± 4% to 66 ± 6%; p < 0.001). No difference in the incidence of microangiopathy, as noted by funduscopic examination, was present between the diabetic groups. Despite the abnormal ejection fraction response to exercise in the group 2 patients with diabetes, all patients with diabetes had a nor response to afterload manipulation, normal baseline ventricular contractility as assessed by load- and heart rate-independent end-systolic indexes and normal contractile reserve as assessed with dobutamine challenge.Autonomic dysfunction did not explain the disparate results between the group 2 patients' radionuclide angiographic data and their load-independent tests of ventricular contractility and reserve. In addition, the high ejection fraction at rest in group 2 patients (73±4% versus 62 ± 4% for normal subjects; p < 0.001) was not related to the abnormal tests of autonomic function. Thus, when left ventricular systolic performance was assessed by load- and rate-independent indexes, there was no evidence for cardiomyopathy in young adult patients with diabetes who have normal blood nressure and no ischemie heart disease

Unemployment Risk and Wage Differentials

Workers in less secure jobs are often paid less than identical-looking workers in more secure jobs. We show that this lack of compensating differentials for unemployment risk can arise in equilibrium when all workers are identical, and firms differ, but do so only in offered job security (the probability that the worker is not sent into unemployment). In a setting where workers search on and off the job, wages paid increase with job security for at least all firms in the risky tail of the distribution of firm-level unemployment risk. As a result, unemployment spells become persistent for low-wage and unemployed workers, a seeming pattern of ‘unemployment scarring’, that is created entirely by firm heterogeneity alone. Higher in the wage distribution, workers can take wage cuts to move to more stable employment

Real-Time 3-Dimensional Transesophageal Echocardiography in the Evaluation of Post-Operative Mitral Annuloplasty Ring and Prosthetic Valve Dehiscence

ObjectivesThis study sought to assess the use of real-time (RT) 3-dimensional (3D) transthoracic and transesophageal echocardiography (TEE) in the evaluation of post-operative mitral valve dehiscence.BackgroundMitral valve replacement or repair may be complicated by post-operative dehiscence of the valve or annuloplasty ring resulting in clinically significant mitral regurgitation or hemolysis. Diagnosis is generally performed using 2-dimensional transthoracic echocardiography and TEE. Recently, an RT 3D TEE probe has been developed to produce high-quality real-time images.MethodsWe used RT 3D TEE to evaluate mitral regurgitation after mitral valve repair or replacement as a result of mitral ring dehiscence. We studied the additional information and diagnostic utility provided by RT 3D TEE.ResultsEighteen patients were studied (8 patients after repair and 10 after replacement). Real-time 3D TEE allowed accurate evaluation of the pathology, including definition of the type of ring or prosthesis used; description of the site, size, shape, and area of the dehisced segment; and clear definition of the origin of the mitral regurgitation.ConclusionsIn mitral valve dehiscence, RT 3D TEE provides additional information about the exact anatomic characteristics of the dehiscence that can be used to help in planning the most appropriate corrective intervention