bluuebunny/crossref_metadata_2025_split huggingface dataset:
Divergence dating using mixed effects clock modelling: An application to HIV-1
Authors: Bletsa Magda , Suchard Marc A , Ji Xiang , Gryseels Sophie , Vrancken Bram , Baele Guy , Worobey Michael , Lemey Philippe 
Published: August 2019

AbstractThe need to estimate divergence times in evolutionary histories in the presence of various sources of substitution rate variation has stimulated a rich development of relaxed molecular clock models. Viral evolutionary studies frequently adopt an uncorrelated clock model as a generic relaxed molecular clock process, but this may impose considerable estimation bias if discrete rate variation exists among clades or lineages. For HIV-1 group M, rate variation among subtypes has been shown to result in inconsistencies in time to the most recent common ancestor estimation. Although this calls into question the adequacy of available molecular dating methods, no solution to this problem has been offered so far. Here, we investigate the use of mixed effects molecular clock models, which combine both fixed and random effects in the evolutionary rate, to estimate divergence times. Using simulation, we demonstrate that this model outperforms existing molecular clock models in a Bayesian framework for estimating time-measured phylogenies in the presence of mixed sources of rate variation, while also maintaining good performance in simpler scenarios. By analysing a comprehensive HIV-1 group M complete genome data set we confirm considerable rate variation among subtypes that is not adequately modelled by uncorrelated relaxed clock models. The mixed effects clock model can accommodate this rate variation and results in a time to the most recent common ancestor of HIV-1 group M of 1920 (1915–25), which is only slightly earlier than the uncorrelated relaxed clock estimate for the same data set. The use of complete genome data appears to have a more profound impact than the molecular clock model because it reduces the credible intervals by 50 per cent relative to similar estimates based on short envelope gene sequences.
Subjective Age at Work: Feeling Younger or Older Than One’s Actual Age Predicts Perceived Control and Motivation at Work
Authors: Shane Jacob , Hamm Jeremy , Heckhausen Jutta 
Published: August 2019

Abstract
Using a life-span theoretical perspective, the present study examined how subjective age relates to perceived control and motivational investment in the work domain. Data from the Midlife in the United States National Study of Health and Well-Being (MIDUS I, II, and III; 1995–2013; n = 2,395) were analyzed using parallel process growth curve modeling. Our analyses used a mediation framework and focused on how changes in subjective age relate to changes in work-specific perceived control and motivational investment over time. Results suggested that feeling progressively younger than one’s actual age predicted increased levels of perceived control over and motivational investment in one’s work situation, as mediated by domain-general perceived control capacity and selective primary control striving, respectively. Results are discussed within the motivational theory of life-span development, specifically, how subjective age operates as a secondary control strategy that enhances or diminishes motivational investment and perceived control in work during midlife.
The Consequences of Structural Racism on MCAT Scores and Medical School Admissions: The Past Is Prologue
Authors: Lucey Catherine Reinis , Saguil Aaron 
Published: August 2019

Those in medical education have a responsibility to prepare a physician workforce that can serve increasingly diverse communities, encourage healthy changes in patients, and advocate for the social changes needed to advance the health of all. The authors of this Perspective discuss many of the likely causes of the observed differences in mean Medical College Admission Test (MCAT) scores between students from groups well represented in medicine and those from groups underrepresented in medicine. The lower mean MCAT scores of underrepresented groups can present challenges to diversifying the physician workforce if medical schools only admit those applicants with the highest MCAT scores. The authors review the psychometric literature, which showed no evidence of bias in the exam, and note that the differences in mean MCAT scores between racial and ethnic groups are similar to those in other measures of academic achievement and performance on high-stakes tests.
The authors then describe the ways in which structural racism in the United States has contributed to differences in achievement for underrepresented students compared with well-represented students. These differences are not due to differences in aptitude but to differences in opportunities. The authors describe the widespread consequences of structural racism on economic success, educational opportunity, and bias in the educational environment. They close with 3 recommendations for medical schools that may mitigate the consequences of structural racism while maintaining academic standards and admitting students likely to succeed. Adopting these recommendations may help the medical profession build the diverse physician workforce needed to serve communities today.
Investigating Group Differences in Examinees’ Preparation for and Performance on the New MCAT Exam
Authors: Girotti Jorge A. , Chanatry Julie A. , Clinchot Daniel M. , McClure Stephanie C. , Swan Sein Aubrie , Walker Ian W. , Searcy Cynthia A. 
Published: August 2019

In 2015, the Medical College Admission Test (MCAT) was redesigned to better assess the concepts and reasoning skills students need to be ready for the medical school curriculum. During the new exam’s design and rollout, careful attention was paid to the opportunities examinees had to learn the new content and their access to free and low-cost preparation resources. The design committee aimed to mitigate possible unintended effects of the redesign, specifically increasing historical mean group differences in MCAT scores for examinees from lower socioeconomic status (SES) backgrounds and races/ethnicities underrepresented in medicine compared with those from higher SES backgrounds and races/ethnicities not underrepresented in medicine.
In this article, the authors describe the characteristics and scores of examinees who took the new MCAT exam in 2017 and compare those trends with historical ones from 2013, presenting evidence that the diversity and performance of examinees has remained stable even with the exam’s redesign. They also describe the use of free and low-cost MCAT preparation resources and MCAT preparation courses for examinees from higher and lower SES backgrounds and who are enrolled in undergraduate institutions with more and fewer resources, showing that examinees from lower SES backgrounds and who attend institutions with fewer resources use many free and low-cost test preparation resources at lower rates than their peers. The authors conclude with a description of the next phase of this research: to gather qualitative and quantitative data about the preparation strategies, barriers, and needs of all examinees, but especially those from lower SES and underrepresented racial/ethnic backgrounds.
The Validity of Scores From the New MCAT Exam in Predicting Student Performance: Results From a Multisite Study
Authors: Busche Kevin , Elks Martha L. , Hanson Joshua T. , Jackson-Williams Loretta , Manuel R. Stephen , Parsons Wanda L. , Wofsy David , Yuan Kun 
Published: August 2019

Purpose
The new Medical College Admission Test (MCAT) was introduced in April 2015. This report presents findings from the first study of the validity of scores from the new MCAT exam in predicting student performance in the first year of medical school (M1).

Method
The authors analyzed data from the national population of 2016 matriculants with scores from the new MCAT exam (N = 7,970) and the sample of 2016 matriculants (N = 955) from 16 medical schools who volunteered to participate in the validity research. They examined correlations of students’ MCAT total scores and total undergraduate grade point averages (UGPAs), alone and together, with their summative performance in M1, and the success rate of students with different MCAT scores in their on-time progression to the second year of medical school (M2). They assessed whether MCAT scores provided comparable prediction of performance in M1 by students’ race/ethnicity, socioeconomic background, and gender.

Results
Correlations of MCAT scores with summative performance in M1 ranged from medium to large. Although MCAT scores and UGPAs provided similar prediction of performance in M1, using both metrics provided better prediction than either alone. Additionally, students with a wide range of MCAT scores progressed to M2 on time. Finally, MCAT scores provided comparable prediction of performance in M1 for students from different sociodemographic backgrounds.

Conclusions
This study provides early evidence that scores from the new MCAT exam predict student performance in M1. Future research will examine the validity of MCAT scores in predicting performance in later years.
Learning Challenges, Teaching Strategies, and Cognitive Load: Insights From the Experience of Seasoned Endoscopy Teachers
Authors: Sewell Justin L. , Bowen Judith L. , Cate Olle ten , O’Sullivan Patricia S. , Shah Brijen , Boscardin Christy K. 
Published: August 2019

Purpose
Learners of medical procedures must develop, refine, and apply schemas for both cognitive and psychomotor constructs, which may strain working memory capacity. Procedures with limitations in visual and tactile information may add risk of cognitive overload. The authors sought to elucidate how experienced procedural teachers perceived learners’ challenges and their own teaching strategies in the exemplar setting of gastrointestinal endoscopy.

Method
The authors interviewed 22 experienced endoscopy teachers in the United States, Canada, and the Netherlands between May 2016 and March 2019 and performed thematic analysis using template analysis method. Interviews addressed learner challenges and teaching strategies from the teacher participants’ perspectives. Cognitive load theory informed data interpretation and analysis.

Results
Participants described taking steps to “diagnose” trainee ability and identify struggling trainees. They described learning challenges related to trainees (performance over mastery goal orientation, low self-efficacy, lack of awareness), tasks (psychomotor challenges, mental model development, tactile understanding), teachers (teacher–trainee relationship, inadequate teaching, teaching variability), and settings (internal/external distractions, systems issues). Participants described employing strategies that could match intrinsic load to learners’ levels (teaching along developmental continuum, motor instruction, technical assistance/takeover), minimize extraneous load (optimize environment, systems solutions, emotional support, define expectations), and optimize germane load (promote mastery, teach schemas, stop and focus).

Conclusions
Participants provided insight into possible challenges while learning complex medical procedures with limitations in sensory channels, as well as teaching strategies that may address these challenges at individual and systems levels. Using cognitive load theory, the authors provide recommendations for procedural teachers.
The Decline in Community Preceptor Teaching Activity: Exploring the Perspectives of Pediatricians Who No Longer Teach Medical Students
Authors: Paul Caroline R. , Vercio Chad , Tenney-Soeiro Rebecca , Peltier Chris , Ryan Michael S. , Van Opstal Elizabeth R. , Alerte Anton , Christy Cynthia , Kantor Julie L. , Mills William A. , Patterson Patricia B. , Petershack Jean , Wai Andrew , Beck Dallaghan Gary L. 
Published: August 2019

Purpose
Difficulty in recruiting and retaining community preceptors for medical student education has been described in the literature. Yet little, if any, information is known about community outpatient preceptors who have stopped or decreased teaching time with students. This study aimed to examine these preceptors’ perspectives about this phenomenon.

Method
Using a phenomenology framework, this multi-institutional qualitative study used semistructured interviews with community pediatric preceptors who had stopped or reduced teaching time with medical students. Interviews were conducted between October 2017 and January 2018 and transcribed verbatim. Interviews explored factors for engaging in teaching, or decreasing or ceasing teaching, that would enable future teaching. An initial code book was developed and refined as data were analyzed to generate themes.

Results
Twenty-seven community pediatricians affiliated with 10 institutions participated. Thirty-seven codes resulted in 4 organizing themes: evolution of health care, personal barriers, educational system, and ideal situations to recruit and retain preceptors, each with subthemes.

Conclusions
From the viewpoints of physicians who had decreased or stopped teaching students, this study more deeply explores previously described reasons contributing to the decline of community preceptors, adds newly described barriers, and offers strategies to help counter this phenomenon based on preceptors’ perceptions. These findings appear to be manifestations of deeper issues including the professional identify of clinical educators. Understanding the barriers and strategies and how they relate to preceptors themselves should better inform education leaders to more effectively halt the decline of community precepting and enhance the clinical precepting environment for medical students.
Surgery for Unilateral Sacral Fractures: Are the Indications Clear?
Authors: Vallier Heather A. , Lowe Jason A. , Agel Julie , Mullis Brian H. , Jones Clifford B. , Teague David , Kempton Laurence , Miller Anna N. , Spitler Clay A. , Kubiak Erik , Routt Milton L. Chip. , Leighton Ross , Morshed Saam , Tornetta Paul 
Published: August 2019

Objectives:
To evaluate unilateral sacral fractures and compare those treated operatively versus nonoperatively to determine indications for surgery.

Design:
Prospective, multicenter, observational study.

Setting:
Sixteen trauma centers.

Patients/Participants:
Skeletally mature patients with pelvic ring injury and unilateral zone 1 or 2 sacral fractures and without anteroposterior compression injuries.

Main Outcome Measurements:
Injury plain anteroposterior, inlet, and outlet radiographs and computed tomography scans of the pelvis were evaluated for fracture displacement.

Results:
Three hundred thirty-three patients with unilateral sacral fractures and a mean age of 41 years with a mean Injury Severity Score of 15 were included. Ninety-two percent sustained lateral compression injuries, and 63% of all fractures were in zone 1. Thirty-three percent of patients were treated operatively, including all without lateral compression patterns. Operative patients were more likely to have zone 2 fractures (54%) and to have posterior cortical displacement (29% vs. 6.2%), both with P < 0.001. Over 60% of all patients had no posterior displacement. Mean rotational displacements comparing the injured side versus the intact side were no different for patients treated operatively compared with those treated nonoperatively.

Conclusions:
Most unilateral sacral fractures are minimally or nondisplaced. Many patients with radiographically similar fractures were treated operatively and nonoperatively by different surgeons. This suggests an opportunity to develop consistent indications for treatment.

Level of Evidence:
Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.
Treating the Orthopaedic Trauma Knowledge Gap: Quantification of Orthopaedic Resident Knowledge Gaps and Validation of a Multimodal Course to Address the Deficiencies
Authors: Graves Matt L. , Paryavi Ebrahim , Hung Leroy , Reilly Mark C. , Guy Pierre , O'Toole Robert V. 
Published: August 2019

Objectives:
To determine whether knowledge-based deficiencies are adequately addressed at the AO North America Basic Principles of Fracture Management course.

Design:
Pretest, posttest.

Setting:
Eighteen national trauma courses.

Participants:
Two thousand one hundred forty-nine learners.

Intervention:
Pre- and postcourse 20-item tests of basic fracture knowledge, including 14 trauma topics.

Main Outcome Measures:
Deficiencies were defined as <60% correct answers on the precourse test. Postcourse knowledge gaps were defined as <75% correct responses.

Results:
Deficiencies were noted in 7 of the 14 topics on the precourse test. All topics with deficiencies on the precourse test were shown to have statistically significant improvement in postcourse test scores. All topics without deficiencies were shown to have statistically significant improvement in postcourse test scores. The average overall precourse test score was 63% (95% confidence interval, 61%–65%), and the average overall postcourse test score was 81% (95% confidence interval, 79%–83%). The pretest to posttest difference was statistically significant (P < 0.05). The control questions, covering material that was not discussed in the course, did not have statistically significant improvement in scores.

Conclusions:
Residents are entering residency programs with limited knowledge of fracture care, and significant gaps remain at the junior level at the time of course participation, suggesting that supplemental fracture courses play an important role in resident education. Validation of short-term learning is possible through a pretest and posttest technique, and it can guide design changes, as opposed to relying on satisfaction surveys alone.
Practice Patterns for Management of Pediatric Femur Fractures in Low- and Middle-Income Countries
Authors: Curran Patrick F. , Albright Patrick , Ibrahim John M. , Ali Syed H. , Shearer David W. , Sabatini Coleen S. 
Published: August 2019

Background:
Femoral shaft fractures in children are common in low and middle income countries. In high-income countries, patient age, fracture pattern, associated injuries, child/family socioeconomic status, and surgeon preference dictate fracture management. There is limited literature on treatment patterns for pediatric femur fractures in resource-limited settings. This study surveys surgeons from low (LIC), lower-middle (LMIC), and upper-middle income (UMIC) countries regarding treatment patterns for pediatric femur fractures.

Methods:
Surgeons completed an electronic survey reporting surgeon demographics and treatment preference for pediatric femur fractures. Treatment preferences and indications for treatment were separated into 4 groups: infant (0 to 6 mo); toddler (7 mo to 4 y); child (5 to 12 y); adolescent (12 to 17 y). The survey was available in English, Spanish, and French. Analysis was completed with t test and χ2 test for continuous and categorical variables, respectively, and weighted Pearson correlation (P<0.05).

Results:
Survey respondents consisted of 413 surgeons from 83 countries (20 LIC, 33 LMIC, 30 UMIC). The majority of respondents were fellowship trained (83%) most commonly in pediatrics (26%) and trauma (43%). Most treated >10 pediatric femur fractures per year (68%). Respondents reported treating infant femur fractures nonoperatively using Pavlik harness (19%), spica cast (60%), or traction with delayed spica cast (14%). Decreasing socioeconomic status was associated with higher nonoperative treatment rate in toddlers, children, and adolescents. Respondents commonly utilize bed rest and traction for child femur fractures in LICs (63%) and LMICs (65%) compared with UMICs (35%) (UMIC vs. LMIC P<0.001; UMIC vs. LIC P<0.001). Surgeries in children more commonly involve open reduction with internal fixation (UMIC 19%, LMIC 33%, LIC 40%; P<0.05 between UMIC-LMIC and UMIC-LIC).

Conclusion:
This is one of the largest surveys describing treatment patterns for pediatric femur fractures in low and middle income countries. Differences are evident including lower operative treatment rate in younger children and lower intramedullary fixation rates in older children. Future studies should investigate the value of treatment options in resource-limited settings.

Level of Evidence:
Level II—prospective comparative study.
Operating Room Intervention Rates After Orthopaedic Resident-reduced Pediatric Both-Bone Forearm Fractures Relative to the Academic Calendar
Authors: Wu John C. , Daley Erika , Koueiter Denise M. , Lilly Ryan , Vara Alexander D. , Settecerri Jeffrey J. 
Published: August 2019

Background:
The purpose of this study was to evaluate the operating room (OR) intervention rates and quality of fracture reductions for pediatric diaphyseal both-bone forearm fractures performed by orthopaedic residents relative to the academic year. OR intervention was defined as any procedure performed in the OR, including closed reduction and casting, and was used to identify fractures that required secondary intervention after initial closed reduction performed by an orthopaedic resident in the emergency department.

Methods:
A retrospective analysis identified pediatric patients presenting at our institution with both-bone forearm fractures from July 2010 to June 2016. Emergency-room sedation time, highest experience of orthopaedic resident documented to be present at the time of sedation (in postgraduate months), and frequencies of OR intervention were obtained by chart review. Fracture characteristics were determined by radiographic review. Immediate postreduction radiographs were used to measure cast indices, and adequacy of reduction was determined by postreduction angulation and translation.

Results:
During the time period studied, 470 both-bone forearm reductions under sedation were performed by an orthopaedic resident at our institution. Of these, 41 fractures (41 patients) required 42 OR interventions (40 involved surgical fixation and 2 were repeat closed reductions). The academic year was divided into quartiles. The April to June quartile had the highest overall percentage of OR intervention (10.6%), followed by July to September (8.6%); however, there was no significant difference between quartiles in the percentages of reductions that needed OR intervention (P=0.553). There was also no correlation between the experience level of the resident performing the reduction (based on postgraduate months) and the frequency of OR intervention (P=0.244). The anteroposterior (AP) and lateral reduction grades did not vary based on quarters (P=0.584; 0.353). The ability to obtain adequate reduction and the rate of unacceptable cast index were also not significantly different between quarters (P=0.347 and 0.465).

Conclusions:
We found no significant difference in rates of OR intervention or the quality of reduction for pediatric both-bone diaphyseal forearm fractures treated by orthopaedic residents relative to the academic year.

Level of Evidence:
Level III—comparative cohort study.