We present an analysis of optical spectra for 29 DAO white dwarfs. First, we present our new up-to-date model atmosphere grids computed without the assumption of local thermodynamic equilibrium in which we have included carbon, nitrogen, and oxygen at solar abundances. We demonstrate that the addition of these metals in the model atmospheres is essential in overcoming the Balmer-line problem, which manifests itself as an inability to fit all the Balmer lines simultaneously with consistent atmospheric parameters. We then present the spectroscopic analysis of our sample of DAO white dwarfs for which we determine the effective temperature, surface gravity, and helium abundance. We also present 18 hot DA white dwarfs that also suffer from the Balmer-line problem. We analyze these stars with models analogous to those for the DAO white dwarfs save for the presence of helium. Systematic differences between our newly determined atmospheric parameters with respect to previous determinations are explored. Far-ultraviolet spectra from the FUSE archive are then examined to demonstrate that there exists a correlation between higher metallic abundances and instances of the Balmer-line problem. The implications of these findings for all hot, hydrogen-rich white dwarfs are discussed. Specifically, the possible evolutionary scenario for DAO white dwarfs is revised and post-extreme horizontal branch evolution is no longer needed to explain the evolution for the majority of the DAO stars. Finally, we discuss how the presence of metals might drive a weak stellar wind which in turn could explain the presence of helium in DAO white dwarfs.
The aim of the study was to define criteria for left ventricular pacing in dilated cardiomyopathy (DCM) using an echocardiographic evaluation of interventricular electromechanical delay (IMD) and a correlation of IMD to QRS duration. Standard 12-lead ECG and echocardiography with pulsed Doppler tissue imaging (DTI) were recorded in 35 DCM patients (mean age 58 +/- 11 years) with QRS duration from narrow (80 ms) to broad (222 ms) patterns. The timefor left ventricular activation was evaluated from the onset of QRS to the onset of aortic flow (Q-Ao) by standard pulsed Doppler (SP) or to the onset of mitral annulus systolic wave (Q-Mit) (DTI). The time for right ventricular activation was determinedfrom the onset of QRS to the onset of pulmonary flow (Q-Pulm) (SP) or to the onset of tricuspid annulus systolic wave (Q-Tri) (DTI). (Q-Ao)-(Q-Pulm) and (Q-Mit)-(Q-Tri) determined IMD for each method, respectively. QRS width and IMD showed correlation coefficients of r = 0.86 ([Q-Ao]-[Q-Pulm]) and r = 0.82 ([Q-Mit]-[Q-Tri]) (P < or = 0.001 ). Mean IMD of 77 +/- 15 ms (SP) and 88 +/- 26 ms (DTI) were noted for QRS width above 150 ms. Left ventricle delayed activation was positively correlated to QRS widening with both methods, (r = 0.90, [Q-Ao]), (r = 0.83, [Q-Mit]) (P < or = 0.001). In conclusion, QRS duration is a good marker of an interventricular mechanical asynchrony. According to IMD correction, left ventricular pacing may be mainly proposed to symptomatic DCM patients with QRS duration > 150 ms.
This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies.
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