Conduction velocities along longitudinal (vL) and transverse (vT) fiber axes were determined in isolated porcine hearts from subepicardial activation patterns that were produced by local stimulation ...and measured with a multiterminal electrode. In some of the experiments extracellular K+ (K+o) and transmembrane potentials were recorded. During normal perfusion vL and vT were (cm/sec) 50.08 +/- 2.13, (SE) and 21.08 +/- 0.97. After 3 to 5 min of global ischemia, vL and vT decreased to approximately 30 and 13 cm/sec. Before the occurrence of total inexcitability propagation became time dependent 2: 1 block developed and centrifugal spread from the stimulus site was partially blocked at short intervals and was normal at long intervals. This suggested that slowed conduction was dependent on spatial nonuniformities of recovery from excitability. Slowing of conduction during ischemia was not explained by accumulation of K+o alone, because vL and vT at a given K+o were lower during ischemia than during perfusion with elevated K+. In hearts perfused at 20 mM K+o "slow responses" were produced by addition of epinephrine (2.5 X 10(-5)M). Resting membrane potentials of slow responses were significantly lower than of depressed action potentials during ischemia. The values vL and vT of slow responses (10 and 5 cm/sec) were much lower than the lowest values during ischemia (20 and 10 cm/sec). This indicates that slow conduction in ischemia is associated with depressed action potentials initiated by a partially inactivated rapid Na+ inward current. The time dependence of nonuniform propagation and the relatively high conduction velocities explain two major characteristics of reentrant tachycardias in acute ischemia: the large diameters of reentrant circuits and the beat-to-beat changes in localization of conduction block.
We show that the X-ray line flux of the Mn Kα line at 5.9 keV from the decay of ...Fe is a promising diagnostic to distinguish between Type Ia supernova (SN Ia) explosion models. Using radiation ...transport calculations, we compute the line flux for two three-dimensional explosion models: a near-Chandrasekhar mass delayed detonation and a violent merger of two (1.1 and 0.9 M...) white dwarfs. Both models are based on solar metallicity zero-age main-sequence progenitors. Due to explosive nuclear burning at higher density, the delayed-detonation model synthesizes ~3.5 times more radioactive ...Fe than the merger model. As a result, we find that the peak Mn K... line flux of the delayed-detonation model exceeds that of the merger model by a factor of ~4.5. Since in both models the 5.9-keV X-ray flux peaks five to six years after the explosion, a single measurement of the X-ray line emission at this time can place a constraint on the explosion physics that is complementary to those derived from earlier phase optical spectra or light curves. We perform detector simulations of current and future X-ray telescopes to investigate the possibilities of detecting the X-ray line at 5.9 keV. Of the currently existing telescopes, XMM-Newton/pn is the best instrument for close (~1-2 Mpc), non-background limited SNe Ia because of its large effective area. Due to its low instrumental background, Chandra/ACIS is currently the best choice for SNe Ia at distances above ~2 Mpc. For the delayed-detonation scenario, a line detection is feasible with Chandra up to ~3 Mpc for an exposure time of 10... s. We find that it should be possible with currently existing X-ray instruments (with exposure times ...5 x 10... s) to detect both of our models at sufficiently high S/N to distinguish between them for hypothetical events within the Local Group. The prospects for detection will be better with future missions. For example, the proposed Athena/X-IFU instrument could detect our delayed-detonation model out to a distance of ~5 Mpc. This would make it possible to study future events occurring during its operational life at distances comparable to those of the recent supernovae SN 2011fe (~6.4 Mpc) and SN 2014J (~3.5 Mpc). (ProQuest: ... denotes formulae/symbols omitted.)
We investigate the nature and classification of PMN J1603-4904, a bright radio source close to the Galactic plane, which is associated with one of the brightest hard-spectrum gamma -ray sources ...detected by Fermi/LAT. It has previously been classified as a low-peaked BL Lac object based on its broadband emission and the absence of optical emission lines. Optical measurements, however, suffer strongly from extinction and the absence of pronounced short-time gamma -ray variability over years of monitoring is unusual for a blazar. In this paper, we are combining new and archival multiwavelength data of PMN J1603-4904 in order to reconsider the classification and nature of this unusual gamma -ray source. The TANAMI VLBI data and the shape of the broadband SED challenge the current blazar classification of one of the brightest gamma -ray sources in the sky. PMN J1603-4904 seems to be either a highly peculiar BLLac object or a misaligned jet source. In the latter case, the intriguing VLBI structure opens room for a possible classification of PMN J1603-4904 as a gamma -ray bright CSO.
We show that the X-ray line flux of the Mn K alpha line at 5.9 keV from the decay of ...Fe is a promising diagnostic to distinguish between Type Ia supernova (SN Ia) explosion models. Using radiation ...transport calculations, we compute the line flux for two three-dimensional explosion models: a near-Chandrasekhar mass delayed detonation and a violent merger of two (1.1 and 0.9 M...) white dwarfs. Both models are based on solar metallicity zero-age main-sequence progenitors. Due to explosive nuclear burning at higher density, the delayed-detonation model synthesizes ~3.5 times more radioactive ...Fe than the merger model. As a result, we find that the peak Mn K... line flux of the delayed-detonation model exceeds that of the merger model by a factor of ~4.5. Since in both models the 5.9-keV X-ray flux peaks five to six years after the explosion, a single measurement of the X-ray line emission at this time can place a constraint on the explosion physics that is complementary to those derived from earlier phase optical spectra or light curves. We perform detector simulations of current and future X-ray telescopes to investigate the possibilities of detecting the X-ray line at 5.9 keV. Of the currently existing telescopes, XMM-Newton/pn is the best instrument for close (~1-2 Mpc), non-background limited SNe Ia because of its large effective area. Due to its low instrumental background, Chandra/ACIS is currently the best choice for SNe Ia at distances above ~2 Mpc. For the delayed-detonation scenario, a line detection is feasible with Chandra up to ~3 Mpc for an exposure time of 10... s. We find that it should be possible with currently existing X-ray instruments (with exposure times ...5 x 10... s) to detect both of our models at sufficiently high S/N to distinguish between them for hypothetical events within the Local Group. The prospects for detection will be better with future missions. For example, the proposed Athena/X-IFU instrument could detect our delayed-detonation model out to a distance of ~5 Mpc. This would make it possible to study future events occurring during its operational life at distances comparable to those of the recent supernovae SN 2011fe (~6.4 Mpc) and SN 2014J (~3.5 Mpc). (ProQuest: ... denotes formulae/symbols omitted.)
LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental ...physics. The Japan Aerospace Exploration Agency (JAXA) selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with an expected launch in the late 2020s using JAXA’s H3 rocket. LiteBIRD is planned to orbit the Sun–Earth Lagrangian point L2, where it will map the cosmic microwave background polarization over the entire sky for three years, with three telescopes in 15 frequency bands between 34 and 448 GHz, to achieve an unprecedented total sensitivity of $2.2\, \mu$K-arcmin, with a typical angular resolution of 0.5° at 100 GHz. The primary scientific objective of LiteBIRD is to search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. We provide an overview of the LiteBIRD project, including scientific objectives, mission and system requirements, operation concept, spacecraft and payload module design, expected scientific outcomes, potential design extensions, and synergies with other projects.
We report on the first detection of a quasi-simultaneous radio-X-ray flare of Cygnus X-1. The detection was made on 2005 April 16 with pointed observations by the RXTE and the Ryle telescope, during ...a phase where the black hole candidate was close to a transition from its soft state to its hard state. The radio flare lagged the X-rays by similar to 7 minutes, peaking at 3:20 hr barycentric time (TDB 2,453,476.63864). We discuss this lag in the context of models explaining such flaring events as the ejection of electron bubbles emitting synchrotron radiation.
MXB 0656-072 is an accreting X-ray pulsar with a Be star companion, showing notable emission in Hα. In October 2003 this system exhibited a large and extended X-ray outburst.
RXTE observations during ...this outburst indicated a pulse period of 160.4
s and a cyclotron resonance scattering feature in the spectrum at ∼32
keV. This paper presents pulse profile analysis and phase-resolved X-ray spectroscopy of
RXTE observations during this outburst.
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