Dimensional Dependence of the Hydrodynamics of Core-Collapse Supernovae

The multidimensional character of the hydrodynamics in core-collapse supernova (CCSN) cores is a key facilitator of explosions. Unfortunately, much of this work has necessarily been performed assuming axisymmetry and it remains unclear whether or not this compromises those results. In this work, we present analyses of simplified two- and three-dimensional CCSN models with the goal of comparing the multidimensional hydrodynamics in setups that differ only in dimension. Not surprisingly, we find many differences between 2D and 3D models. While some differences are subtle and perhaps not crucial to understanding the explosion mechanism, others are quite dramatic and make interpreting 2D CCSN models problematic. In particular, we find that imposing axisymmetry artificially produces excess power at the largest spatial scales, power that has been deemed critical in the success of previous explosion models and has been attributed solely to the standing accretion shock instability. Nevertheless, our 3D models, which have an order of magnitude less power on large scales compared to 2D models, explode earlier. Since we see explosions earlier in 3D than in 2D, the vigorous sloshing associated with the large scale power in 2D models is either not critical in any dimension or the explosion mechanism operates differently in 2D and 3D. Possibly related to the earlier explosions in 3D, we find that about 25% of the accreted material spends more time in the gain region in 3D than in 2D, being exposed to more integrated heating and reaching higher peak entropies, an effect we associate with the differing characters of turbulence in 2D and 3D. Finally, we discuss a simple model for the runaway growth of buoyant bubbles that is able to quantitatively account for the growth of the shock radius and predicts a critical luminosity relation.Comment: Submitted to the Astrophysical Journa

PHM Triage Curriculum Enhances Residents’ Skills and Comfort of Leading Triage Calls

Background: Though hospital triage is typically considered a role of pediatric hospitalists, these skills are important for residents to learn for any pediatric subspeciality. Additionally, many of these skills are addressed in the Accreditation Council for Graduate Medical Education’s (ACGME) Pediatric Milestones and the American Board of Pediatrics’ (ABP) Entrustable Professional Activities (EPA) as competencies expected of residency graduates. Currently, the pediatric residents at our medium-sized midwestern program do not participate in hospital triage, leaving this as a large gap in their education. Objective: To evaluate how a Pediatric Hospital Medicine (PHM) Triage Curriculum enhances pediatric residents’ knowledge, skills, and attitudes pertaining to hospital triage. Methods: After developing learning goals and objectives, we implemented a 2-week rotation for third- or fourth-year pediatric residents to lead supervised hospital triage phone calls. Asynchronous self-study materials included a triage guide and handoff checklist, and learning occurred through the Experiential Learning Cycle with explicit self-reflection and instructional guidance from the supervising attending. The curriculum was evaluated through a case study-mixed methods explanatory sequential design with 1. A quantitative retrospective post-pre survey assessing self-perceived knowledge and skills, and 2. A qualitative post-rotation interview. Results to date have been reviewed with descriptive statistics and a general qualitative approach. Results: 12 residents have completed the rotation with a 10/12 (83%) response rate. 10/10 (100%) residents agreed or strongly agreed that it is important to learn skills of triage hospital medicine and stated that they are comfortable leading triage calls much more or somewhat more than before. Themes identified in the qualitative interview include increased comfort in leading triage calls; improved assessment of patients over the phone to determine disposition and level of care; improved patient care; and applicability to all their future careers. Conclusions: All residents had perceived improvements in knowledge and skills pertaining to triage medicine after completing the rotation, and they recognized the utility of these skills for their future careers. We will continue to address the logistical and systemic barriers to resident and faculty engagement in the curriculum.https://digitalcommons.unmc.edu/chri_forum/1052/thumbnail.jp

Induced Rotation in 3D Simulations of Core Collapse Supernovae: Implications for Pulsar Spins

It has been suggested that the observed rotation periods of radio pulsars might be induced by a non-axisymmetric spiral-mode instability in the turbulent region behind the stalled supernova bounce shock, even if the progenitor core was not initially rotating. In this paper, using the three-dimensional AMR code CASTRO with a realistic progenitor and equation of state and a simple neutrino heating and cooling scheme, we present a numerical study of the evolution in 3D of the rotational profile of a supernova core from collapse, through bounce and shock stagnation, to delayed explosion. By the end of our simulation ($\sim$420 ms after core bounce), we do not witness significant spin up of the proto-neutron star core left behind. However, we do see the development before explosion of strong differential rotation in the turbulent gain region between the core and stalled shock. Shells in this region acquire high spin rates that reach $\sim$$150\,$ Hz, but this region contains too little mass and angular momentum to translate, even if left behind, into rapid rotation for the full neutron star. We find also that much of the induced angular momentum is likely to be ejected in the explosion, and moreover that even if the optimal amount of induced angular momentum is retained in the core, the resulting spin period is likely to be quite modest. Nevertheless, induced periods of seconds are possible.Comment: Accepted to the Astrophysical Journa

Comparison of Third Year Medical Student Wellness Before and During the SARS-CoV2 Pandemic

Introduction Depression and suicidal ideation have a higher prevalence in medical students when compared to other age-matched populations.1,2 The SARS-CoV2 pandemic has further threatened medical trainee well-being with increased stress and risk of mental illness.3,4 Objective To compare medical student well-being at a single institution before and during the SARS-CoV2 pandemic. Methods Third year medical students at a single institution voluntarily completed a survey during pediatric clerkship orientation as part of an ongoing, non-pandemic longitudinal wellness study. The survey instrument includes basic demographic information, the validated World Health Organization (WHO) (FIVE) Well-Being Index (WHO-5), and questions about physical activity. Data from mid-academic year students rotating on the pediatric clerkship in the 2019-2020 (two cohorts, pre-pandemic) and 2020-21 (three cohorts, during pandemic) academic years were compared across compositive survey scores and sub-question scores. Results Study participation was 81% pre-pandemic (n=34) and 59% during the pandemic (n=39) with no statistically significant differences in age or gender. Mean WHO-5 well-being scores trended up from the pre-pandemic to pandemic groups without reaching statistical significance (16.3 vs 17.5, p=0.13). The mean individual survey question on feeling fresh and rested significantly improved from pre-pandemic to pandemic groups (2.74 vs 3.23, p\u3c0.05). Remaining question mean scores were similar or trended toward improved well-being from pre-pandemic to pandemic groups; cheerful/good spirits (3.62 vs 3.82, p=0.15), calm/relaxed (3.32 vs 3.33, p=0.48), active/vigorous (3.18 vs 3.31, p=0.28), and interest in daily life (3.41 vs 3.79, p=0.08). Based on using the composite WHO-5 survey as a validated tool to screen for depression, there was a trend towards less students screening positive for depression in the pandemic group (26.5% pre-pandemic vs 10.5% pandemic, p=0.07). Discussion From our small sample of third year medical students at a single institution, we find that well-being is stable when comparing matched groups across academic years before and during the SARS-CoV2 pandemic. Interestingly, survey subsection data demonstrates improved subjective feelings of being rested in the pandemic group and suggests lower rates of depression based on screening cutoffs (WHO-5). We suspect this may be related to changes in the educational environment such as transitioning from the clinical environment to virtual rotations, or time away from rotations entirely which may have allowed for increased personal wellness time. Focus groups and further investigation are necessary to identify which factors are altering levels of student well-being. References Dyrbye LN, Thomas MR, Shanafelt TD. Systematic review of depression, anxiety, and other indicators of psychological distress among U.S. and Canadian medical students. Acad Med J Assoc Am Med Coll. 2006;81(4):354-373. doi:10.1097/00001888-200604000-00009 Rotenstein LS, Ramos MA, Torre M, et al. Prevalence of Depression, Depressive Symptoms, and Suicidal Ideation Among Medical Students: A Systematic Review and Meta-Analysis. JAMA. 2016;316(21):2214-2236. doi:10.1001/jama.2016.17324 Kannampallil TG, Goss CW, Evanoff BA, Strickland JR, McAlister RP, Duncan J. Exposure to COVID-19 patients increases physician trainee stress and burnout. PLOS ONE. 2020;15(8):e0237301. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0237301. Accessed Oct 5, 2020. doi: 10.1371/journal.pone.0237301. Wu S, Li Z, Li Z, et al. The mental state and risk factors of chinese medical staff and medical students in early stages of the COVID-19 epidemic. Compr Psychiatry. 2020;102:152202. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7437442/. Accessed Oct 21, 2020. doi: 10.1016/j.comppsych.2020.152202.https://digitalcommons.unmc.edu/chri_forum/1019/thumbnail.jp

Environmental DNA analysis confirms extant populations of the cryptic Irwin’s turtle within its historical range

Background Approximately 50% of freshwater turtles worldwide are currently threatened by habitat loss, rural development and altered stream flows. Paradoxically, reptiles are understudied organisms, with many species lacking basic geographic distribution and abundance data. The iconic Irwin’s turtle, Elseya irwini, belongs to a unique group of Australian endemic freshwater turtles capable of cloacal respiration. Water resource development, increased presence of saltwater crocodiles and its cryptic behaviour, have made sampling for Irwin’s turtle in parts of its range problematic, resulting in no confirmed detections across much of its known range for > 25 years. Here, we used environmental DNA (eDNA) analysis for E. irwini detection along its historical and contemporary distribution in the Burdekin, Bowen and Broken River catchments and tributaries. Five replicate water samples were collected at 37 sites across those three river catchments. Environmental DNA was extracted using a glycogen-aided precipitation method and screened for the presence of E. irwini through an eDNA assay targeting a 127 base pair-long fragment of the NADH dehydrogenase 4 (ND4) mitochondrial gene. Results Elseya irwini eDNA was detected at sites within its historic distribution in the lower Burdekin River, where the species had not been formally recorded for > 25 years, indicating the species still inhabits the lower Burdekin area. We also found higher levels of E. iriwni eDNA within its contemporary distribution in the Bowen and Broken Rivers, matching the prevailing scientific view that these areas host larger populations of E. irwini. Conclusions This study constitutes the first scientific evidence of E. irwini presence in the lower Burdekin since the original type specimens were collected as part of its formal description, shortly after the construction of the Burdekin Falls Dam. From the higher percentage of positive detections in the upper reaches of the Broken River (Urannah Creek), we conclude that this area constitutes the core habitat area for the species. Our field protocol comprises a user-friendly, time-effective sampling method. Finally, due to safety risks associated with traditional turtle sampling methods in the Burdekin River (e.g., estuarine crocodiles) we propose eDNA sampling as the most pragmatic detection method available for E. irwini

Thematic Analysis of Third-Year Medical Student Reflections on Social Determinants of Health During Their Pediatric Clerkship: Emergent Themes and Topic Interconnectedness

Background. Social determinants of health (SDOH), as defined by the World Health Organization, are the “non-medical factors that influence health outcomes… the conditions in which people are born, grow, work, live, and age, and the wider set of forces and systems shaping the conditions of daily life.” Studies have estimated that SDOH account for 30-55% of health outcomes. Understanding the impact of SDOH can be integrated into medical education in different formats, here we explore student reflections. Methods. In the 2021-2022 academic year, third-year medical students at a midwestern medical school submitted discussion board reflections on their experiences with SDOH during their 8-week pediatric clerkship. We analyzed de-identified posts to look for emergent themes that showcase the experiences and perceptions of medical students as they care for patients and learn about the socio-environmental factors in the community. Initial coding was built on a preliminary codebook drafted based on the medical school’s SDOH curriculum. Utilizing a grounded theory approach, we added new codes as novel topics and themes emerged. We then examined the relationships between the codes and SDOH categories outlined in the US Department of Health and Human Services Healthy People 2030 objectives. Results. Ninety-seven student discussion posts were analyzed. Our preliminary results demonstrate the two most common themes, social support and communication, together represented approximately 50% of all student responses. With the addition of the next two most frequently discussed topics, healthcare access and diet/nutrition, this set of themes comprises over 75% of student responses. Student responses also demonstrated the interconnectedness of SDOH categories through frequent overlap of categories during coding and analysis. Conclusion. Our study demonstrates the most common SDOH themes students identified during the pediatric clerkship involve social support, communication, access to care, and diet/nutrition. We found a multifactorial, connected nature of those themes as they impact patient health. This study validates the need for explicit education on SDOH topics during medical school so that future physicians are well-equipped to intervene or accommodate these factors throughout their careers. Future directions include comparing our results to preexisting social and educational frameworks and future cohort comparisons as curriculum evolves.https://digitalcommons.unmc.edu/chri_forum/1065/thumbnail.jp

A Revised Orbital Ephemeris for HAT-P-9b

We present here three transit observations of HAT-P-9b taken on 14 February 2010, 18 February 2010, and 05 April 2010 UT from the University of Arizona's 1.55 meter Kuiper telescope on Mt. Bigelow. Our transit light curves were obtained in the I filter for all our observations, and underwent the same reduction process. All three of our transits deviated significantly (approximately 24 minutes earlier) from the ephemeris of Shporer et al. (2008). However, due to the large time span between our observed transits and those of Shporer et al. (2008), a 6.5 second (2 sigma) shift downwards in orbital period from the value of Shporer et al. (2008) is sufficient to explain all available transit data. We find a new period of 3.922814 +/- 0.000002 days for HAT-P-9b with no evidence for significant nonlinearities in the transit period.Comment: 10 pages, 3 figure

A Complete Catalog of Swift GRB Spectra and Durations: Demise of a Physical Origin for Pre-Swift High-Energy Correlations

We calculate durations and spectral paramaters for 218 Swift bursts detected by the BAT instrument between and including GRBs 041220 and 070509, including 77 events with measured redshifts. Incorporating prior knowledge into the spectral fits, we are able to measure the characteristic $\nu F_{\nu}$ spectral peak energy $E_{\rm pk,obs}$ and the isotropic equivalent energy $E_{\rm iso}$ (1--$10^4$ keV) for all events. This complete and rather extensive catalog, analyzed with a unified methodology, allows us to address the persistence and origin of high-energy correlations suggested in pre-Swift observations. We find that the $E_{\rm pk,obs}$-$E_{\rm iso}$ correlation is present in the Swift sample; however, the best-fit powerlaw relation is inconsistent with the best-fit pre-Swift relation at >5 sigma significance. Moreover, it has a factor >~ 2 larger intrinsic scatter, after accounting for large errors on $E_{\rm pk,obs}$. A large fraction of the Swift events are hard and subluminous relative to (and inconsistent with) the pre-Swift relation, in agreement with indications from BATSE GRBs without redshift. Moreover, we determine an experimental threshold for the BAT detector and show how the $E_{\rm pk,obs}$--$E_{\rm iso}$ correlation arises artificially due to partial correlation with the threshold. We show that pre-Swift correlations found by Amati et al.(2002), Yonetoku et al. (2004), Firmani et al.(2006) (and independently by others) are likely unrelated to the physical properties of GRBs and are likely useless for tests of cosmology. Also, an explanation of these correlations in terms of a detector threshold provides a natural and quantitative explanation for why short-duration GRBs and events at low redshift tend to be outliers to the correlations.Comment: 25 pages, 9 figures, 2 tables, Accepted to Ap

NIMBUS: The Near-Infrared Multi-Band Ultraprecise Spectroimager for SOFIA

We present a new and innovative near-infrared multi-band ultraprecise spectroimager (NIMBUS) for SOFIA. This design is capable of characterizing a large sample of extrasolar planet atmospheres by measuring elemental and molecular abundances during primary transit and occultation. This wide-field spectroimager would also provide new insights into Trans-Neptunian Objects (TNO), Solar System occultations, brown dwarf atmospheres, carbon chemistry in globular clusters, chemical gradients in nearby galaxies, and galaxy photometric redshifts. NIMBUS would be the premier ultraprecise spectroimager by taking advantage of the SOFIA observatory and state of the art infrared technologies. This optical design splits the beam into eight separate spectral bandpasses, centered around key molecular bands from 1 to 4 microns. Each spectral channel has a wide field of view for simultaneous observations of a reference star that can decorrelate time-variable atmospheric and optical assembly effects, allowing the instrument to achieve ultraprecise calibration for imaging and photometry for a wide variety of astrophysical sources. NIMBUS produces the same data products as a low-resolution integral field spectrograph over a large spectral bandpass, but this design obviates many of the problems that preclude high-precision measurements with traditional slit and integral field spectrographs. This instrument concept is currently not funded for development.Comment: 14 pages, 9 figures, SPIE Astronomical Telescopes and Instrumentation 201