212 research outputs found

    Stroke Prevention With Left Atrial Appendage Closure in Patients With Atrial Fibrillation and Prior Intracranial Hemorrhage

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    BACKGROUND Oral anticoagulation (OAC) is deemed a relative contraindication after intracranial hemorrhage (ICH) if the cause cannot be eliminated and the risk of recurrence is high. That leaves atrial fibrillation (AF) patients at high risk of thromboembolic events. Endovascular left atrial appendage closure (LAAC) can be an alternative to OAC for patients requiring stroke prevention. METHODS We performed a retrospective single-centre analysis of 138 consecutive ICH patients with nonvalvular AF and high stroke risk who underwent LAAC between 2010 and 2022 at Vancouver General Hospital. We report the baseline characteristics, procedural results, and follow-up data, comparing the observed stroke/transient ischemic attack (TIA) rate with the predicted event rate based on their CHA2_{2}DS2_{2}-VASc scores. RESULTS The average age was 76.1 ± 8.5 years; the mean CHA2_{2}DS2_{2}-VASc score was 4.4 ± 1.5; and the mean HAS-BLED score was 3.7 ± 0.9. The procedural success rate was 98.6%, and the complication rate was 3.6% with no periprocedural death, stroke, or TIA. The antithrombotic regimen post-LAAC consisted of short-term dual antiplatelet therapy (1-6 months) followed by aspirin alone for a minimum of 6 months in 86.2%. At mean follow-up of 14.7 ± 13.7 months, 9 deaths (6.5%, 7 cardiovascular, 2 noncardiovascular), 2 strokes (1.4%), and 1 TIA (0.7%) had occurred. The annualized observed stroke/TIA rate was 1.8%, which was lower than the adjusted predicted stroke rate of 7.0% (95% confidence interval: 4.8%-9.2%). Two patients (1.5%) suffered another ICH (both on aspirin monotherapy). One device-related thrombus (0.7%) was confirmed and treated with OAC without sequelae. CONCLUSION Endovascular LAAC is a feasible alternative to OAC for stroke prevention in patients with nonvalvular AF and prior ICH

    In the Shadow of the Transiting Disk: Imaging epsilon Aurigae in Eclipse

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    Eclipses of the single-line spectroscopic binary star, epsilon Aurigae, provide an opportunity to study the poorly-defined companion. We used the MIRC beam combiner on the CHARA array to create interferometric images during eclipse ingress. Our results demonstrate that the eclipsing body is a dark disk that is opaque and tilted, and therefore exclude alternative models for the system. These data constrain the geometry and masses of the components, providing evidence that the F-star is not a massive supergiant star.Comment: As submitted to Nature. Published in Nature April 8, 2010

    Spectroscopy, MOST Photometry, and Interferometry of MWC 314: Is it an LBV or an interacting binary?

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    MWC 314 is a bright candidate luminous blue variable that resides in a fairly close binary system, with an orbital period of 60.753±\pm0.003 d. We observed MWC 314 with a combination of optical spectroscopy, broad-band ground- and space-based photometry, as well as with long baseline, near-infrared interferometry. We have revised the single-lined spectroscopic orbit and explored the photometric variability. The orbital light curve displays two minima each orbit that can be partially explained in terms of the tidal distortion of the primary that occurs around the time of periastron. The emission lines in the system are often double-peaked and stationary in their kinematics, indicative of a circumbinary disc. We find that the stellar wind or circumbinary disc is partially resolved in the K\prime-band with the longest baselines of the CHARA Array. From this analysis, we provide a simple, qualitative model in an attempt to explain the observations. From the assumption of Roche Lobe overflow and tidal synchronisation at periastron, we estimate the component masses to be M1 5\approx 5 M_\odot and M215\approx 15 M_\odot, which indicates a mass of the LBV that is extremely low. In addition to the orbital modulation, we discovered two pulsational modes with the MOST satellite. These modes are easily supported by a low-mass hydrogen-poor star, but cannot be easily supported by a star with the parameters of an LBV. The combination of these results provides evidence that the primary star was likely never a normal LBV, but rather is the product of binary interactions. As such, this system presents opportunities for studying mass-transfer and binary evolution with many observational techniques.Comment: 26 pages, 7 figures, 5 tables, 2 appendices with 7 additional tables and 2 additional figures. Accepted for publication in MNRA

    Low-temperature Ferromagnetism in a Weakly Doped Hubbard Magnet

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    In the framework of the diagrammatic method with self-consistent field, the maximum on the temperature dependence of the susceptibility of a weakly doped narrow-band Hubbard magnet below the Curie temperature TC is predicted. By numerical calculations, it is proved that it appears at small hole concentrations nh. In this case, the temperature dependence of the magnetization M(T) has a typical Fermi-like shape with the point of inflection at a temperature Tinf . The approximate solution of the system of equations for the mean spin and the chemical potential gives the Schottky susceptibility typical of a two-level system with a gap of order of nh(1 - nh)W, where W is the bandwidth. This behavior reflects the existence of two subbands with up- and down-spins. It may be observed experimentally in the surface layers of oxide metal nanoparticles with narrow bands and a weak oxygen nonstoichiometry.У межах теорiї ефективного самоузгодженого поля для слабко легованого хаббардовського магнетика передбачено появу низькотемпературного максимуму типу Шотткi на кривiй сприйнятливостi. Показано, що дану аномалiю зумовлено конкуренцiєю кiнематичних i теплових взаємодiй колективiзованих електронiв. Оцiнка величини молярної сприйнятливостi дозволяє зробити висновок про можливу реалiзацiю зазначеного явища в поверхневих шарах металооксидних наночастинок iз вузькими зонами

    Gene expression profiling during the embryo-to-larva transition in the giant red sea urchin Mesocentrotus franciscanus

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    © 2017 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. In echinoderms, major morphological transitions during early development are attributed to different genetic interactions and changes in global expression patterns that shape the regulatory program for the specification of embryonic territories. In order more thoroughly to understand these biological and molecular processes, we examined the transcriptome structure and expression profiles during the embryo-to-larva transition of a keystone species, the giant red sea urchin Mesocentrotus franciscanus. Using a de novo assembly approach, we obtained 176,885 transcripts from which 60,439 (34%) had significant alignments to known proteins. From these transcripts, ~80% were functionally annotated allowing the identification of ~2,600 functional, structural, and regulatory genes involved in developmental process. Analysis of expression profiles between gastrula and pluteus stages of M. franciscanus revealed 791 differentially expressed genes with 251 GO overrepresented terms. For gastrula, up-regulated GO terms were mainly linked to cell differentiation and signal transduction involved in cell cycle checkpoints. In the pluteus stage, major GO terms were associated with phosphoprotein phosphatase activity, muscle contraction, and olfactory behavior, among others. Our evolutionary comparative analysis revealed that several of these genes and functional pathways are highly conserved among echinoids, holothuroids, and ophiuroids.Link_to_subscribed_fulltex

    The GJ 436 System: Directly Determined Astrophysical Parameters of an M-Dwarf and Implications for the Transiting Hot Neptune

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    The late-type dwarf GJ 436 is known to host a transiting Neptune-mass planet in a 2.6-day orbit. We present results of our interferometric measurements to directly determine the stellar diameter (R=0.455±0.018RR_{\star} = 0.455 \pm 0.018 R_{\odot}) and effective temperature (TEFF=3416±54T_{\rm EFF} = 3416 \pm 54 K). We combine our stellar parameters with literature time-series data, which allows us to calculate physical and orbital system parameters, including GJ 436's stellar mass (M=0.5070.062+0.071MM_{\star} = 0.507^{+ 0.071}_{- 0.062} M_{\odot}) and density (ρ=5.370.27+0.30ρ\rho_* = 5.37^{+ 0.30}_{- 0.27} \rho_\odot), planetary radius (Rp=0.3690.015+0.015RJupiterR_{p} = 0.369^{+ 0.015}_{- 0.015} R_{Jupiter}), planetary mass (Mp=0.0780.008+0.007MJupiterM_{p} = 0.078^{+ 0.007}_{- 0.008} M_{Jupiter}), implying a mean planetary density of ρp=1.550.10+0.12ρJupiter\rho_{p} = 1.55^{+ 0.12}_{- 0.10} \rho_{Jupiter}. These values are generally in good agreement with previous literature estimates based on assumed stellar mass and photometric light curve fitting. Finally, we examine the expected phase curves of the hot Neptune GJ 436b, based on various assumptions concerning the efficiency of energy redistribution in the planetary atmosphere, and find that it could be constrained with {\it Spitzer} monitoring observations.Comment: 10 pages, 4 tables, 9 figures; accepted for publication in ApJ; incorporated referee's comments and associated change
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