Dwindling Surface Cooling of a Rotating Jovian Planet Leads to a Convection Zone that Grows to a Finite Depth

Recent measurements of Jupiter's gravitational field (by Juno) and seismology of Saturn's rings (by Cassini) strongly suggest that both planets have a stably-stratified core that still possesses a primordial gradient in the concentration of heavy elements. The existence of such a "diffusely" stratified core has been a surprise as it was long expected that the Jovian planets should be fully convective and hence fully mixed. A vigorous zone of convection, driven by surface cooling, forms at the surface and deepens through entrainment of fluid from underneath. In fact, it was believed that this convection zone should grow so rapidly that the entire planet would be consumed in less than a million years. Here we suggest that two processes, acting in concert, present a solution to this puzzle. All of the giant planets are rapidly rotating and have a cooling rate that declines with time. Both of these effects reduce the rate of fluid entrainment into the convection zone. Through the use of an analytic prescription of entrainment in giant planets, we demonstrate that these two effects, rotation and dwindling surface cooling, result in a convection zone which initially grows but eventually stalls. The depth to which the convective interface asymptotes depends on the rotation rate and on the stratification of the stable interior. Conversely, in a nonrotating planet, or in a planet that maintains a higher level of cooling than current models suggest, the convection zone deepens forever, eventually spanning the entire planet.Comment: 7 pages, 2 figures, accepted for publication by Astrophysical Journal Letter

Rotation reduces convective mixing in Jupiter and other gas giants

Recent measurements of Jupiter's gravitational moments by the Juno spacecraft and seismology of Saturn's rings suggest that the primordial composition gradients in the deep interior of these planets have persisted since their formation. One possible explanation is the presence of a double-diffusive staircase below the planet's outer convection zone, which inhibits mixing across the deeper layers. However, hydrodynamic simulations have shown that these staircases are not long-lasting and can be disrupted by overshooting convection. In this paper we suggests that planetary rotation could be another factor for the longevity of primordial composition gradients. Using rotational mixing-length theory and 3D hydrodynamic simulations, we demonstrate that rotation significantly reduces both the convective velocity and the mixing of primordial composition gradients. In particular, for Jovian conditions at $t\sim10^{8}~\mathrm{yrs}$ after formation, rotation reduces the convective velocity by a factor of 6, and in turn, the kinetic energy flux available for mixing gets reduced by a factor of $6^3\sim 200$. This leads to an entrainment timescale that is more than two orders of magnitude longer than without rotation. We encourage future hydrodynamic models of Jupiter and other gas giants to include rapid rotation, because the decrease in the mixing efficiency could explain why Jupiter and Saturn are not fully mixed.Comment: Accepted for publication in the Astrophysical Journal Letter

A Novel Approach to Resonant Absorption of the Fast MHD Eigenmodes of a Coronal Arcade

The arched eld lines forming coronal arcades are often observed to undulate as magne- tohydrodynamic (MHD) waves propagate both across and along the magnetic eld. These waves are most likely a combination of resonantly coupled fast magnetoacoustic waves and Alfv\' en waves. The coupling results in resonant absorption of the fast waves, converting fast wave energy into Alfv\' en waves. The fast eigenmodes of the arcade have proven difficult to compute or derive analytically, largely because of the mathematical complexity that the coupling introduces. When a traditional spectral decomposition is employed, the discrete spectrum associated with the fast eigenmodes is often subsumed into the continuous Alfv \'en spectrum. Thus fast eigenmodes, become collective modes or quasi-modes. Here we present a spectral decomposition that treats the eigenmodes as having real frequencies but complex wavenumbers. Using this procedure we derive dispersion relations, spatial damping rates, and eigenfunctions for the resonant, fast eigenmodes of the arcade. We demonstrate that resonant absorption introduces a fast mode that would not exist otherwise. This new mode is heavily damped by resonant absorption, only travelling a few wavelengths before losing most of its energy

Systematic Bias in Helioseismic Measurements of Meridional Circulation Arising from Nonlocal Averaging Kernels

Meridional circulation in the solar convection zone plays a profound role in regulating the interior dynamics of the Sun and its magnetism. While it is well accepted that meridional flows move from the equator towards the poles at the Sun's surface, helioseismic observations have yet to provide a definitive answer for the depth at which those flows return to the equator, or the number of circulation cells in depth. In this work, we investigate whether the discrepancies regarding the nature of the return flow are intrinsic to how helioseismic observations are made. We examine the seismic signature of possible meridional flow profiles by convolving time-distance averaging kernels with the mean flows obtained from 3-D hydrodynamic simulations of the solar convection zone. At mid and high latitudes, we find that weak flow structures in the deeper regions of the convection zone can be strongly obscured by signal from the much stronger surface flows. This contamination is the result of extended side lobes in the averaging kernels and generates a spurious equatorward signal of 2--3 m s$^{-1}$ at those latitudes, and at $\approx 70~\mathrm{Mm}$ depth. At low latitudes, however, the flows in the simulations tend to be stronger and multiple cells across the shell depth can produce a sufficiently strong seismic signal to survive the convolution process. The signal associated with the deep equatorward return flow in the Sun is expected to be weak and in the same sense as the contamination from the surface. Hence, the return flow needs to exceed $\sim 2$--$3~ \mathrm{m~s^{-1}}$ in magnitude for reported detections to be considered significant.Comment: Submitted to AAS Journal

Association between an anesthesia department development program for junior faculty and long-term production of publications: A longitudinal cohort study

An important mission of academic medical departments is to further the scholarship and education of its junior faculty. In 2013, Hindman et al. described the design and initial outcomes of a faculty development program for junior faculty at the University of Iowa Department of Anesthesia. In the current study, we reassessed whether the program increased the production of publications long-term. We included all department faculty, years before joining the department, and years after leaving the department, to control for the effects of simply being current faculty in the department, benefiting from its resources, and having had progressively more experience working. The population studied was the faculty for any period between January 2006 and December 2022. The dependent variable was the count of publications in Scopus each year with the faculty member's Scopus identifier, 1996 through 2022. The two-year faculty development program included non-clinical time, two mentors, defined mentorship plan, didactic program, and financial support for clinical and/or laboratory studies. Statistical analyses were with logistic and Poisson random effect models for panel data, with standard errors estimated using jackknife resampling. Among the 128 distinct faculty in the department from 2006 through 2022, the 10% with the most publications per year accounted for 54% of the total annual publications. The two-year program was completed by 41% (53/128). Completion of the faculty development program was associated with a 17% absolute increase in the predicted marginal probability of one or more publications per year, from 25% to 41%. The 95% confidence interval for the 17% absolute increase was 9% to 24% (P < .0001). The predictive marginal effect of completing the program was 1.7 more publications per year per faculty (95% confidence interval 1.1 to 2.4, P < .0001). The estimate was also 1.7 more publications per year while limiting consideration to the 108 faculty who joined the department after 1996 and including as an independent variable the count of publications the year before joining the department. A faculty development program for junior faculty can reliably increase the production of publications in an anesthesiology department by at least one per year. However, there is considerable heterogeneity in publication production among faculty. •Earlier study described design and initial outcomes of a development program for junior faculty.•Publications per year examined of all faculty at the department, in program or not, 2006–2022.•The 10% faculty with most publications per year accounted for 54% of total annual publications.•Development program had 17% absolute increase probability of ≥1 publications per year.•Predictive marginal effect of completing program was 1.7 more publications per year per faculty

Overall anesthesia department quality of clinical supervision of trainees over a year evaluated using mixed effects models

Earlier studies of supervision in anesthesiology focused on how to evaluate the quality of individual anesthesiologist's clinical supervision of trainees. What is unknown is how to evaluate clinical supervision collectively, as provided by the department's faculty anesthesiologists. This information can be a metric that departments report annually or use to evaluate the effect of programs on the quality of clinical supervision over time. This retrospective cohort study used all 48,788 evaluations of the 115 faculty anesthesiologists using the De Oliveira Filho supervision scale completed by 202 residents and fellows over nine academic years at one department. The distributions of mean scores among raters had marked negative skewness and were inconsistent with normal distributions. Consequently, accurate confidence intervals were impracticably wide, and their interpretation suggested lack of validity. In contrast, the logits of the proportions of scores equaling the maximum possible value, calculated for each rater, followed distributions sufficiently close to normal for statistically reliable use in random effects modeling. Parameters and confidence intervals were estimated using the intercept only random effects models, and then inverses computed to convert results from the logit scale to proportions. That approach is analogous to random effect meta-analysis of proportional incidence (or prevalence). Departments that chose to use semi-annual or annual surveys of trainees regarding supervision quality, and report those raw counts, will have far lower estimates of supervision quality versus when calculated accurately using daily evaluations of individual anesthesiologists. Random effects meta-analysis of percentage incidences of maximum scores is a suitable statistical approach to analyze the daily supervision scores of individual anesthesiologists to evaluate the overall quality of clinical supervision provided to the trainees by the department over a year. •Goal is to evaluate overall anesthesia departmental clinical supervision annually.•Retrospective cohort study performed, with 48,788 evaluations by 202 residents and fellows.•Mean scores markedly negatively skewed making accurate confidence intervals very wide.•Random effects meta-analysis of proportional incidence of quality supervision can be used.•Random effects meta-analysis weights each rater individually, decreasing institutional bias

Sex-Specific Intubation Biomechanics: Intubation Forces Are Greater in Male Than in Female Patients, Independent of Body Weight

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Binomial entropy of anesthesiologists’ ratings of nurse anesthetists’ clinical performance explains information loss when adjusting evaluations for rater leniency

Managers and clinical directors have the ethical and administrative responsibility, and professional duty, to identify clinicians who are performing significantly better or worse than their peers. At the University of Iowa, faculty anesthesiologists (raters) working with Certified Registered Nurse Anesthetists (ratees) evaluate their clinical performance daily using a valid and reliable work habits scale. Because the evaluations are used for ongoing professional practice evaluation and performance reviews, rater bias should be reduced. However, adjustment for rater bias (leniency) causes many raters’ evaluations to have little influence on ranking of ratees. The retrospective cohort study was from a large teaching hospital. Functionally, ratings are binary: the value is 1 when all six items in the scale are scored at the maximum performance, and 0, otherwise (i.e., any item less than maximum). The 40,027 ratings over 5.8 years were sorted by rater in descending sequence of date. The Shannon information content of the ratings was quantified using binomial entropy. The most recent 6359 ratings from 2020 were analyzed using mixed effects logistic regression, with each rater as a fixed effect and ratees as random effects. Using all 74 raters, the Spearman correlation coefficient between the precisions of the raters’ coefficients in the logistic regression and the corresponding binomial entropy was 0.997 (99% confidence interval [CI] 0.992 to 0.999). Excluding the 33 raters who provided all ratings being 1’s or 0’s, the remaining 41 raters’ Spearman correlation was 0.985 (99% confidence interval 0.965 to 0.997). Those 41 raters had median binomial entropies that were 76% of the normalized maximum entropy (99% CI 62% to 86%), while the other 33 raters’ entropy was 0%. When the same rater gave the same rating >10 times in a row, there was a median of 23 more identical ratings in the run (99% CI 21 to 26, N=535). Most loss of information originates from raters who provide all ratees with the largest possible score for all items and from raters who never provide ratings with the maximum score. There should be educative feedback to raters who consistently rate all ratees the same, both for departments with quantitative evaluations using a reliable scale and departments using qualitative evaluations