New Mass Estimates for Massive Binary Systems: A Probabilistic Approach Using Polarimetric Radiative Transfer

Understanding the evolution of massive binary stars requires accurate estimates of their masses. This understanding is critically important because massive star evolution can potentially lead to gravitational-wave sources such as binary black holes or neutron stars. For Wolf-Rayet (WR) stars with optically thick stellar winds, their masses can only be determined with accurate inclination angle estimates from binary systems which have spectroscopic Msini measurements. Orbitally phased polarization signals can encode the inclination angle of binary systems, where the WR winds act as scattering regions. We investigated four Wolf-Rayet + O star binary systems, WR 42, WR 79, WR 127, and WR 153, with publicly available phased polarization data to estimate their masses. To avoid the biases present in analytic models of polarization while retaining computational expediency, we used a Monte Carlo radiative-transfer model accurately emulated by a neural network. We used the emulated model to investigate the posterior distribution of the parameters of our four systems. Our mass estimates calculated from the estimated inclination angles put strong constraints on existing mass estimates for three of the systems, and disagree with the existing mass estimates for WR 153. We recommend a concerted effort to obtain polarization observations that can be used to estimate the masses of WR binary systems and increase our understanding of their evolutionary paths

The first dynamical mass determination of a nitrogen-rich Wolf-Rayet star using a combined visual and spectroscopic orbit

This is the author accepted manuscript. The final version is available from IOP Publishing via the DOI in this recordWe present the first visual orbit for the nitrogen-rich Wolf-Rayet binary, WR 133 (WN5o + O9I), based on observations made with the CHARA Array and the MIRC-X combiner. This orbit represents the first visual orbit for a WN star and only the third Wolf-Rayet star with a visual orbit. The orbit has a period of 112.8 days, a moderate eccentricity of 0.36, and a separation of a = 0.79 mas on the sky. We combine the visual orbit with an SB2 orbit and Gaia parallax to find that the derived masses of the component stars are MWR = 9.3 ±1.6M⊙ and MO = 22.6 ±3.2M⊙, with the large errors owing to the nearly face-on geometry of the system combined with errors in the spectroscopic parameters. We also derive an orbital parallax that is identical to the Gaia-determined distance. We present a preliminary spectral analysis and atmosphere models of the component stars, and find the mass-loss rate in agreement with polarization variability and our orbit. However, the derived masses are low compared to the spectral types and spectral model. Given the close binary nature, we suspect that WR 133 should have formed through binary interactions, and represents an ideal target for testing evolutionary models given its membership in the cluster NGC 6871.National Science FoundationNOAO community access programEuropean Union Horizon 2020European Research Council (ERC)Science and Technology Facilities Council (STFC)NAS

Acute readmission following deep brain stimulation surgery for Parkinson\u27s disease: A nationwide analysis

INTRODUCTION: Deep brain stimulation (DBS) surgery is an efficacious, underutilized treatment for Parkinson\u27s disease (PD). Studies of DBS post-operative outcomes are often restricted to data from a single center and consider DBS in isolation. National estimates of DBS readmission and post-operative outcomes are needed, as are comparisons to commonly performed surgeries. METHODS: This study used datasets from the 2013 and 2014 Nationwide Readmissions Database (NRD). Our sample was restricted to PD patients discharged alive after hospitalization for DBS surgery. Descriptive analyses examined patient, clinical, hospital and index hospitalization characteristics. The all-cause, non-elective 30-day readmission rate after DBS was calculated, and logistic regression models were built to examine factors associated with readmission. Readmission rates for the most common surgical procedures were calculated and compared to DBS. RESULTS: There were 6058 DBS surgeries for PD in our sample, most often involving a male aged 65 and older, who lived in a high socioeconomic status zip code. DBS patients had an average of four comorbidities. With respect to outcomes, the majority of patients were discharged home (95.3%). Non-elective readmission was rare (4.9%), and was associated with socioeconomic status, comorbidity burden, and teaching hospital status. Much higher acute, non-elective readmission rates were observed for common procedures such as upper gastrointestinal endoscopy (16.2%), colonoscopy (14.0%), and cardiac defibrillator and pacemaker procedures (11.1%). CONCLUSION: Short-term hospitalization outcomes after DBS are generally favorable. Socioeconomic disparities in DBS use persist. Additional efforts may be needed to improve provider referrals for and patient access to DBS

Rho-guanine nucleotide exchange factors during development: Force is nothing without control

The development of multicellular organisms is associated with extensive rearrangements of tissues and cell sheets. The driving force for these rearrangements is generated mostly by the actin cytoskeleton. In order to permit the reproducible development of a specific body plan, dynamic reorganization of the actin cytoskeleton must be precisely coordinated in space and time. GTP-exchange factors that activate small GTPases of the Rho family play an important role in this process. Here we review the role of this class of cytoskeletal regulators during important developmental processes such as epithelial morphogenesis, cytokinesis, cell migration, cell polarity, neuronal growth cone extension and phagocytosis in different model systems