On the formation of low-mass black holes in massive binary stars

Recently (Brown \& Bethe 1994) it was suggested that most stars with main sequence mass in the range of about $18 - 30 M_{\odot}$ explode, returning matter to the Galaxy, and then go into low-mass ($\geq 1.5 M_{\odot}$) black holes. Even more massive main-sequence stars would, presumably, chiefly g o into high-mass ($\sim 10 M_{\odot}$) black holes. The Brown-Bethe estimates gave approximately $5 \times {10}^{8}$ low-mass black holes in the Galaxy. A pressing question, which we attempt to answer here, is why, with the possible exception of the compact objects in SN1987A and 4U\,1700--37, none of these have been seen. We address this question in three parts. Firstly, black holes are generally ``seen'' only in binaries, by the accretion of matter from a companion star. High mass black holes are capable of accreting more matter than low-mass black holes, so there is a selection effect favoring them. This, in itself, would not be sufficient to show why low-mass black holes have not been seen, since neutron stars (of nearly the same mass) are seen in abundance. Secondly, and this is our main point, the primary star in a binary ---the first star to evolve--- loses its hydrogen envelope by transfer of matter to the secondary and loss into space, and the resulting ``naked'' helium star evolves differently than a helium core, which is at least initially covered by the hydrogen envelope in a massive main-sequence star. We show that primary stars in binaries can end up as neutron stars even if their initial mass substantially exceeds the mass limit for neutron star formation from single stars ($\sim 18 M_{\odot}$). An example is 4U\,1223--62, in which we suggest that the initial primary mass exceeded $35 M_{\odot}$, yet X-ray pulsationsComment: uuencoded compressed postscript. The preprint is also available at http://www.ast.cam.ac.uk/preprint/PrePrint.htm

Gender Identity and Pronoun Usage in Standardized Patient Encounters

The standardized documentation clinicians use to record evaluations of a patient are called Subjective, Objective, Assessment, and Plan (SOAP) notes. Consistent pronoun documentation and usage in these notes is especially important for affirming transgender and gender non-conforming patients as this population experiences significant health disparities linked to medical mistrust. A sample of SOAP notes (n=286) was taken from standardized patient encounters at the University of Louisville School of Medicine in 2017 (n=137) and 2018 (n=149). There were five case iterations of the standardized patient based on gender identity. The notes were coded using the software Dedoose for the following themes: pronouns clearly established, consistent pronoun usage, no pronoun usage, and disregard for established pronouns. Pronouns were clearly established in only 27.27% of the notes (n=78/286). Non-cisgender patients were more likely to have pronouns that were clearly established (41% vs 5%). Consistent pronoun usage was most often observed among the notes of cisgender patients. Inconsistent pronoun usage and disregard for established pronouns was observed most often for genderqueer patients (16%, n=14). Complete absence of pronoun use occurred in the notes of trans women (7%, n=3), genderqueer patients (8%, n=7), and cisgender women (3%, n=2) patients. These notes demonstrate a lack of rigor in recording pronouns accurately and consistently for patients, which can be profoundly detrimental to non-cisgender patient care. These discrepancies can be remedied by including training about gender-affirming care and interacting with non-cisgender patients in the clinical skills curriculum

Gender Identity and Pronoun Usage in Standardized Patient Encounters

One of the most common documentation frameworks clinicians use for patient evaluations are Subjective, Objective, Assessment, and Plan, (SOAP) notes. The clinician will usually record medical, family, social, etc. history as “subjective” information. Temperature, blood pressure, lab work, etc. would be considered “objective” information. An evaluation of the patient’s health and possible medical issues would be considered the “assessment,” and their intentions for current and future treatment would be the “plan” within these notes. Trainees often write SOAP notes after completing a standardized patient (SP) encounter—an educational practice used in medical schools to simulate real-world physician-patient interactions in order to develop and assess clinical reasoning skills. A standardized patient is employed to act as a patient, memorizing and reciting previously delineated information provided by medical educators

Comparing Medical Student Nonverbal Behavior With Cisgender And Transgender Standardized Patients

BACKGROUND It is essential for medical students to effectively communicate with patients of all gender identities. Nonverbal behaviors such as eye contact and nodding are key communication skills. Evaluating nonverbal behavior is one way to assess the quality of patient care, and examining providers’ behaviors while working with cisgender and transgender patients can identify potential biases linked to patient identity. METHODS To evaluate nonverbal behavior, we analyzed video-recorded training sessions with medical students interviewing standardized patients who identified as cisgender or transgender women. All students identified as cisgender men or cisgender women. Ten nonverbal behaviors were rated from 1-7 using adapted nonverbal communication scales. We also observed whether nonverbal cues were perceived to detract from the encounter. RESULTS Average scores for nonverbal behaviors were similar between students working with cisgender and transgender patients. Nodding frequency showed the largest difference between cisgender (m=5.65) and transgender (m=4.93) patients. When considering student gender identity, men had lower facial expressivity and smiling frequency scores on average but higher scores for unnecessary silence compared to women across encounters. Detracting behaviors that negatively impacted the patient encounters were most likely to be self-touching/unpurposive movements (41%) and unnecessary silences (26%). DISCUSSION The consistency in nonverbal behavior during encounters with cisgender and transgender patients is encouraging. It is possible that LGBTQ health training in medical education contributed to this outcome; however, differences in verbal communication could be more important to health disparities for transgender patients. Additional practice with unpurposive movements and unnecessary silences could improve nonverbal communication skills.https://ir.library.louisville.edu/uars/1056/thumbnail.jp

Extinction and Distance to Anomalous X-ray Pulsars from X-ray Scattering Halos

We analyze the X-ray scattering halos around three Galactic Anomalous X-ray Pulsars (AXPs) in order to constrain the distance and the optical extinction of each source. We obtain surface brightness distributions from EPIC-pn data obtained with XMM-Newton, compare the profiles of different sources, and fit them with a model based on the standard theory of X-ray scattering by dust grains, both for a uniform distribution of dust along the line of sight, and for dust distributions constrained by previous measurements. Somewhat surprisingly, we find that for all three sources, the uniform distribution reproduces the observed surface brightness as well as or better than the distributions that are informed by previous constraints. Nevertheless, the inferred total dust columns are robust, and serve to confirm that previous measurements based on interstellar edges in high-resolution X-ray spectra and on modelling of broad-band X-ray spectra were reliable. Specifically, we find Av ~= 4, 6, and 8 mag for 4U 0142+61, 1E 1048.1-5937, and 1RXS J170849.0-400910, respectively. For 1E 1048.1-5937, this is well in excess of the extinction expected towards a HI bubble along the line of sight, thus casting further doubt on the suggested association with the source.Comment: 8 pages, 6 figure

Effect of humidity on nitric acid uptake to mineral dust aerosol particles

International audienceThis study presents the first laboratory observation of HNO3 uptake by airborne mineral dust particles. The model aerosols were generated by dry dispersion of Arizona Test Dust (ATD), SiO2, and by nebulizing a saturated solution of calcium carbonate. The uptake of 13N-labeled gaseous nitric acid was observed in a flow reactor on the 0.2?2 s reaction time scale at room temperature and atmospheric pressure. The amount of nitric acid appearing in the aerosol phase at the end of the flow tube was found to be a linear function of the aerosol surface area. SiO2 particles did not show any significant uptake, while the CaCO3 aerosol was found to be more reactive than ATD. Due to the smaller uncertainty associated with the reactive surface area in the case of suspended particles as compared to bulk powder samples, we believe that we provide an improved estimate of the rate of uptake of HNO3 to mineral dust. The fact that the rate of uptake was smaller at a concentration of 1012 than at 1011 was indicative of a complex uptake mechanism. The uptake coefficient averaged over the first 2 s of reaction time at a concentration of 1012 molecules cm-3 was found to increase with increasing relative humidity, from 0.022±0.007 at 12% RH to 0.113±0.017 at 73% RH , which was attributed to an increasing degree of solvation of the more basic minerals. The extended processing of the dust by higher concentrations of HNO3 at 85% RH led to a water soluble coating on the particles and enhanced their hygroscopicity

Mid-infrared PAH and H2 emission as a probe of physical conditions in extreme PDRs

Mid-infrared (IR) observations of polycyclic aromatic hydrocarbons (PAHs) and molecular hydrogen emission are a potentially powerful tool to derive physical properties of dense environments irradiated by intense UV fields. We present new, spatially resolved, \emph{Spitzer} mid-IR spectroscopy of the high UV-field and dense photodissocation region (PDR) around Monoceros R2, the closest ultracompact \hII region, revealing the spatial structure of ionized gas, PAHs and H$_2$ emissions. Using a PDR model and PAH emission feature fitting algorithm, we build a comprehensive picture of the physical conditions prevailing in the region. We show that the combination of the measurement of PAH ionization fraction and of the ratio between the H$_2$ 0-0 S(3) and S(2) line intensities, respectively at 9.7 and 12.3 $\mu$m, allows to derive the fundamental parameters driving the PDR: temperature, density and UV radiation field when they fall in the ranges $T = 250-1500$K, $n_H=10^4-10^6$cm$^{-3}$, $G_0=10^3-10^5$ respectively. These mid-IR spectral tracers thus provide a tool to probe the similar but unresolved UV-illuminated surface of protoplanetary disks or the nuclei of starburst galaxies.Comment: Accepted for publication in ApJ Letter