356 research outputs found

    Wide QRS Tachycardia with Atrioventricular Dissociation and an HV Interval of 60 msec

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73193/1/j.1540-8167.1997.tb00814.x.pd

    Extending the limits of globule detection -- ISOPHOT Serendipity Survey Observations of interstellar clouds

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    A faint I170=4I_{\rm 170}=4 MJysr1^{-1} bipolar globule was discovered with the ISOPHOT 170 μ\mum Serendipity Survey (ISOSS). ISOSS J 20246+6541 is a cold (Td14.5T_{\rm d}\approx 14.5 K) FIR source without an IRAS pointsource counterpart. In the Digitized Sky Survey B band it is seen as a 3\arcmin size bipolar nebulosity with an average excess surface brightness of 26\approx 26 mag/\square \arcsec . The CO column density distribution determined by multi-isotopic, multi-level CO measurements with the IRAM-30m telescope agrees well with the optical appearance. An average hydrogen column density of 1021\approx 10^{21}cm2^{-2} was derived from both the FIR and CO data. Using a kinematic distance estimate of 400 pc the NLTE modelling of the CO, HCO+^+, and CS measurements gives a peak density of 104\approx 10^4cm3^{-3}. The multiwavelength data characterise ISOSS 20246+6541 as a representative of a class of globules which has not been discovered so far due to their small angular size and low 100μ\mu m brightness. A significant overabundance of 13^{13}CO is found X(13CO)150×X(C18O)X(^{13}CO) \ge 150\times X(C^{18}O). This is likely due to isotope selective chemical processes.Comment: 5 pages, 3 figure

    Radiofrequency Ablation of Idiopathic Left Anterior Fascicular Tachycardia

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71580/1/j.1540-8167.1995.tb00389.x.pd

    Effect of Dust Extinction on Estimating Star Formation Rate of Galaxies: Lyman Continuum Extinction

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    We re-examine the effect of Lyman continuum (λ912\lambda \leq 912 \AA) extinction (LCE) by dust in H {\sc ii} regions in detail and discuss how it affects the estimation of the global star formation rate (SFR) of galaxies. To clarify the first issue, we establish two independent methods for estimating a parameter of LCE (ff), which is defined as the fraction of Lyman continuum photons contributing to hydrogen ionization in an H {\sc ii} region. One of those methods determines ff from the set of Lyman continuum flux, electron density and metallicity. In the framework of this method, as the metallicity and/or the Lyman photon flux increase, ff is found to decrease. The other method determines ff from the ratio of infrared flux to Lyman continuum flux. Importantly, we show that f \la 0.5 via both methods in many H {\sc ii} regions of the Galaxy. Thus, it establishes that dust in such H {\sc ii} regions absorbs significant amount of Lyman continuum photons directly. To examine the second issue, we approximate ff to a function of only the dust-to-gas mass ratio (i.e., metallicity), assuming a parameter fit for the Galactic H {\sc ii} regions. We find that a characteristic f^\hat{f}, which is defined as ff averaged over a galaxy-wide scale, is 0.3 for the nearby spiral galaxies. This relatively small f^\hat{f} indicates that a typical increment factor due to LCE for estimating the global SFR (1/f^1/\hat{f}) is large (3\sim 3) for the nearby spiral galaxies. Therefore, we conclude that the effect of LCE is not negligible relative to other uncertainties of estimating the SFR of galaxies.Comment: 18 papges, 11 figures, accepted by Ap
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