Performance of Recycled Polylactic Acid/Amorphous Polyhydroxyalkanoate Blends.

Blends of polylactic acid (PLA) with amorphous polyhydroxyalkanoate (aPHA) are less brittle than neat PLA, thus enabling their use as biodegradable packaging. This work investigated the impact of recycling on the properties of neat PLA and PLA/aPHA blends with 90 and 75 wt. % PLA. After the materials were subjected to five heat histories in a single-screw extruder, the mechanical, rheological, and thermal properties were measured. All recycled compounds with 100% PLA and 75% PLA had similar decomposition behavior, whereas the decomposition temperatures for the blends with 90% PLA decreased with each additional heat cycle. The glass transition and melting temperatures were not impacted by reprocessing, but the crystallinity increased with more heat cycles. The complex viscosity of the reprocessed PLA and PLA/aPHA blends was much lower than for the neat PLA and increasing the number of heat cycles produced smaller reductions in the complex viscosity of 100% PLA and the blend with 90% PLA; no change in complex viscosity was observed for blends with 75% PLA exposed to 2 to 5 heat cycles. The tensile properties were not affected by reprocessing, whereas the impact strength for the 75% PLA blend decreased with reprocessing. These properties suggest that users will be able to incorporate scrap into the neat resin for thermoformed packaging.

Observations on the Representation of Asians in Surgical Training and Leadership.

INTRODUCTION: Diversity in medicine has a positive effect on outcomes, especially for Asian patients. We sought to evaluate representation of Asians across entry and leadership levels in surgical training. METHODS: Publicly accessible population data from 2018 to 2023 were collected from the US Census Bureau, the Association of American Medical Colleges, and the American Board of Surgery (ABS). Frequencies based on self-identified Asian status were identified, and proportions were calculated. RESULTS: The US census showed Asians constituted 4.9% of the US population in 2018 versus 6% in 2023. The proportion of Asian medical students rose from 21.6% to 24.8%; however, Asian surgical residency applicants remained constant at 20%. ABS certifications of Asians have increased from 13.7% to 18.5%. ABS examiners increased from 15.7% to 17.1%. CONCLUSIONS: In 5 years, Asians have made numeric gains in medical school and surgical training. However, Asian representation lags at Board examiner levels compared to the medical student population. The ABS has made recent efforts at transparency around examiner and examinee characteristics. A pillar of ensuring a well-trained surgical workforce to serve the public is to mandate that all surgical trainees and graduates undergo fair examinations, and are fairly assessed on their qualifications. Observed progress should further invigorate all surgical applicants, residents and leadership to take an even more active role in making surgery more diverse and welcoming to all, by including careful analyses of diversity at all levels.

A Look at Demographics and Transition to Virtual Assessments: An Analysis of Bias in the American Board of Surgery General Surgery Certifying Exams.

OBJECTIVE: The goals of this study were (1) to assess if examiner ratings in the American Board of Surgery (ABS) General Surgery Cetifying Exam (CE) are biased based on the gender, race, and ethnicity of the candidate or the examiners, and (2) if the format of delivering of the exams, in-person or virtual, affects how examiners rate candidates. DESIGN: We included every candidate-examiner combination for first time takers of the general surgery oral exam. Total scores and pass/fail outcomes based on the 4 scores given by examiners to candidates were analyzed using multilevel models, with candidates as random effects. Explanatory variables included the gender, race, and ethnicity of candidates and examiners, and the format of the exam (in-person or virtual). Candidates' first attempt scores on the ABS General Surgery Qualifying Exam (QE) were also included in the models to control for the baseline knowledge of the candidate. Three sets of models were evaluated for each demographic variable (gender, race, ethnicity) due to missingness in data. p-values and coefficients of determination R2 were used to quantify the statistical and practical significance of the model coefficients (an existent relationship between the explored variables on CE scores was considered statistically and practically significant if the p-value was lower than 0.01 and R2 higher than 1%). PARTICIPANTS: All first-time takers of the American Board of Surgery General Surgery Certifying Exam from 2016 to 2022 that had demographic data, and the examiners that participated in those exams. RESULTS: The number of candidates/examiners for the 3 sets of models was 8665/514 (gender), 5906/465 (race), and 4678/295 (ethnicity). The demographic variables, format of the exam, or their interactions were not found to significantly relate to examiner-candidate ratings or pass/fail outcomes. The only variable that was significantly related to CE scores was candidates' QE scores, which was added to the models as a measure of candidates' initial knowledge; this held for all models for total scores (F[1,8659] = 1069.89, p-value < 0.01, R2 = 5% [gender models], F(1,5696.3) = 589.13, p-value < 0.01, R2 = 5% [race models], F(1,4459.5) = 278.33, p-value < 0.01, R2 = 5% [ethnicity models]), and pass/fail outcomes (CI = 1.61-1.73, p-value < 0.01, R2 = 3% [gender models], CI = 1.67-1.85, p-value < 0.01, R2 = 3% [race models], CI = 2.17-2.90, p-value < 0.01, R2 = 3% [ethnicity models]). CONCLUSIONS: This study shows that there is not a relationship between candidate and examiner gender, race, or ethnicity, and exam outcomes based on statistical models looking at examiner-candidate ratings and pass/fail outcomes. In addition, the delivery of the certifying exam in a virtual format appears to have no statistical impact on outcomes compared to in-person delivery. This suggests that the ABS is performing well in both demographic bias and virtual space.

How Does the Sequence of the American Board of Surgery Examinations Impact Pass/Fail Outcomes?

OBJECTIVE: Historically, the American Board of Surgery required surgeons to pass the qualifying examination (QE) before taking the certifying examination (CE). However, in the 2020-2021 academic year, with mitigating circumstances related to COVID-19, the ABS removed this sequencing requirement to facilitate the certification process for those candidates who were negatively impacted by a QE delivery failure. This decoupling of the traditional order of exam delivery has provided a natural comparator to the traditional route and an analysis of the impact of examination sequencing on candidate performance. METHODS: All candidates who applied for the canceled July 2020 QE were allowed to take the CE before passing the QE. The sample was then reduced to include only first-time candidates to ensure comparable groups for performance outcomes. Logistic regression was used to analyze the relationship between the order of taking the QE and the CE, controlling for other examination performance, international medical graduate status, and gender. RESULTS: Only first-time candidates who took both examinations were compared (n=947). Examination sequence was not a significant predictor of QE pass/fail outcomes, OR=0.54; 95% CI, 0.19-1.61, P =0.26. However, examination sequence was a significant predictor of CE pass/fail outcomes, OR=2.54; 95% CI, 1.46-4.68, P =0.002. CONCLUSIONS: This important study suggests that preparation for the QE increases the probability of passing the CE and provides evidence that knowledge may be foundational for clinical judgment. The ABS will consider these findings for examination sequencing moving forward.

Tandem Hydroperoxyl-Alkylperoxyl Radical Quenching by an Engineered Nanoporous Cerium Oxide Nanoparticle Macrostructure (NCeONP): Toward Efficient Solid-State Autoxidation Inhibitors.

The use of nanomaterials as inhibitors of the autoxidation of organic materials is attracting tremendous interest in petrochemistry, food storage, and biomedical applications. Metal oxide materials and CeO2 in particular represent one of the most investigated inorganic materials with promising radical trapping and antioxidant abilities. However, despite the importance, examples of the CeO2 material's ability to retard the autoxidation of organic substrates are still lacking, together with a plausible chemical mechanism for radical trapping. Herein, we report the synthesis of a new CeO2-derived nanoporous material (NCeONP) with excellent autoxidation inhibiting properties due to its ability to catalyze the cross-dismutation of alkyl peroxyl (ROO•) and hydroperoxyl (HOO•) radicals, generated in the system by the addition of the pro-aromatic hydrocarbon γ-terpinene. The antioxidant ability of NCeONP is superior to that of other nanosized metal oxides, including TiO2, ZnO, ZrO2, and pristine CeO2 nanoparticles. Studies of the reaction with a sacrificial reductant allowed us to propose a mechanism of inhibition consisting of H atom transfer from HOO• to the metal oxides (MOx + HOO• → MOx-H• + O2), followed by the release of the H atom to an ROO• radical (MOx-H• + ROO• → MOx + ROOH). Besides identifying NCeONP as a promising material for developing effective antioxidants, our study provides the first evidence of a radical mechanism that can be exploited to develop novel solid-state autoxidation inhibitors.

Association Between American Board of Surgery Initial Certification and Medical Malpractice Payments.

OBJECTIVE: To measure associations between surgeons' examination performance and obtaining American Board of Surgery certification with the likelihood of having medical malpractice payments. BACKGROUND: Further research is needed to establish a broader understanding of the association of board certification and patient and practice outcomes. METHODS: Retrospective analysis using propensity score-matched surgeons who attempted to obtain American Board of Surgery certification. Surgeons who completed residency between 2000 and 2019 (n=910) and attempted to become certified were categorized as certified or failing to obtain certification. In addition, groups were categorized as either passing or failing their first attempt on the qualifying and certifying examinations. Malpractice payment reports were dichotomized for surgeons who either had a payment report or not. RESULTS: The hazard rate (HR) of malpractice payment reports was significantly greater for surgeons who attempted and failed to obtain certification [HR=1.87; 95% confidence interval (CI), 1.28-2.74] than for surgeons who were certified. Moreover, surgeons who failed either the qualifying (HR=1.64; 95% CI, 1.14-2.37) or certifying examination (HR=1.72; 95% CI, 1.14-2.60) had significantly higher malpractice payment HRs than those who passed the examinations on their first attempt. CONCLUSIONS: Failing to obtain board certification was associated with a higher rate of medical malpractice payments. In addition, failing examinations in the certification examination process on the first attempt was also associated with higher rates of medical malpractice payments. This study provides further evidence that board certification is linked to potential indicators for patient outcomes and practice quality.

Impact of Melt Processing Conditions on the Degradation of Polylactic Acid.

To reduce the degradation of polylactic acid (PLA) during processing, which reduces the molecular weight of PLA and its properties, prior studies have recommended low processing temperatures. In contrast, this work investigated the impact of four factors affecting shear heating (extruder type, screw configuration, screw speed, and feed rate) on the degradation of PLA. The polylactic acid was processed using a quad screw extruder (QSE) and a comparable twin screw extruder (TSE), two screw configurations, higher screw speeds, and several feed rates. The processed PLA was characterized by its rheological, thermal, and material composition properties. In both screw configurations, the QSE (which has a greater free volume) produced 3-4 °C increases in melt temperature when the screw speed was increased from 400 rpm to 1000 rpm, whereas the temperature rise was 24-25 °C in the TSE. PLA processed at low screw speeds, however, exhibited greater reductions in molecular weight-i.e., 9% in the QSE and 7% in the TSE. Screw configurations with fewer kneading blocks, and higher feed rates in the QSE, reduced degradation of PLA. At lower processing temperatures, it was found that an increase in melt temperature and shear rate did not significantly contribute to the degradation of PLA. Reducing the residence time during processing minimized the degradation of PLA in a molten state.

The Impact of Reprocessing with a Quad Screw Extruder on the Degradation of Polypropylene.

During mechanical recycling, polypropylene typically is reprocessed using a single- or twin-screw extruder. The degradation of polypropylene during this reprocessing reduces the polymer's molecular weight and, consequently, limits the performance of the recycled resin. This work investigated the impact of a quad screw extruder (QSE), which has greater free volume, on the reprocessing of an impact copolymer polypropylene. To mimic the recycling process, the polypropylene was subjected to three processing cycles using a QSE and a comparable twin-screw extruder (TSE) operated at three screw speeds. The reprocessed materials were characterized for their rheological, morphological, and mechanical properties. For both extruders, increasing the number of reprocessing cycles and the screw speed resulted in higher melt flow indices, decreases in zero-shear viscosity, and shifting of the crossover points for the storage and loss moduli, which indicate reductions in the molecular weight and narrowing of the molecular weight distribution of the polypropylene. The QSE exhibited greater reductions in molecular weight compared to the TSE, probably due to the higher stresses associated with the three intermeshing points along its screws. Reprocessing caused a significant reductions in the Izod impact strength of the reprocessed polypropylene, which correlated with reductions in the particle size and particle size distribution of the dispersed rubbery phase in the polypropylene during reprocessing.

The vascular surgery in-training examination predicts performance on qualifying examination.

OBJECTIVE: Vascular surgery trainees participate in the vascular surgery in-training examination (VSITE) during each year of their training. Although the VSITE was developed as a low-stakes, formative examination, performance on that examination might correlate with the pass rates for the Vascular Surgery Board written qualifying examination (VQE) and oral certifying examination (VCE) and might, therefore, guide both trainees and program directors. The present study was designed to examine the ability of the VSITE to predict trainees' performance on the VQE and VCE. METHODS: All first-time candidates of the Vascular Surgery Board VQE and VCE were analyzed from 2016 to 2020, including those from both the integrated and independent training pathways. VSITE scores from the final year of training were associated with the VQE scores and the probability of passing the VQE and VCE both. Linear and logistic regression models were used to determine the ability of VSITE results to predict the VQE scores and the probability of passing each board examination. RESULTS: VSITE scores available for the 559 candidates (69.3% male; 30.7% female) who had completed the VQE and 369 candidates (66.7% male; 33.3% female) who had completed both the VQE and the VCE. The linear regression model results for the final year of training showed that the VSITE scores explained 34% of the variance in the VQE scores (29% for the integrated and 37% for the independent trainees). Logistic regression demonstrated that the final year VSITE scores were a significant predictor of passing the VQE for both integrated and independent trainees (P < .001). A VSITE score of 500 during the final year of training predicted a VQE passing probability of >90% for each group of candidates. The probability of passing the VQE decreased to 73% for candidates from integrated programs, 61% for candidates from independent programs, and 64% for the whole cohort when the score was 400. The VSITE scores were a significant predictor of passing the VCE only for the candidates from independent programs (odds ratio, 1.01; 95% confidence interval, 1.00-1.02; P < .01), for whom a VSITE score of 400 correlated with an 82% probability of passing the VCE. CONCLUSIONS: VSITE performance is predictive of passing the VQE for trainees from both integrated and independent training paradigms. Vascular surgery trainees and training programs should optimize their preparation and educational efforts to maximize performance on the VSITE during their final year of training to improve the likelihood of passing the VQE. Further analysis of the predictive value of VSITE scores during the earlier years of training might allow the board certification examinations to be administered earlier in the final year of training.

Implementation of the Vascular Surgery Board virtual certifying examination.

OBJECTIVE: The onset of the COVID-19 (coronavirus disease 2019) pandemic mandated postponement of the in-person Vascular Surgery Board 2020 certifying examination (CE). Vascular surgery virtual CEs (VVCEs) were developed for the scheduled 2020 CEs (rescheduled to January 2021) and 2021 CEs (rescheduled to July 2021) to avoid postponing the certification testing. In the present study, we have reported the development, implementation, and outcomes of the first two VVCEs. METHODS: The VVCE was similar to the in-person format (three 30-minutes sessions, two examiners, four questions) but required a proctor and a host. In contrast to the general surgery VCEs, the VVCE also incorporated images. The candidates and examiners were instructed on the format, and technology checks were performed before the VVCE. The candidates were given the opportunity to invalidate their examination for technology-related reasons immediately after the examination. Postexamination surveys were administered to all the participants. RESULTS: The VVCEs were completed by 356 of 357 candidates (99.7%). The pass rates for the January 2021 and July 2021 examinations were 97.6% (first time, 99.4%; retake, 70%) and 94.7% (first time, 94.6%; retake, 100%), respectively. The pass rates were not significantly different from the 2019 in-person CE (χ2 = 2.30; P = .13; and χ2 = 0.01; P = .91, for the January 2021 and July 2021 examinations, respectively). None of the candidates had invalidated their examination. The candidates (162 of 356; 46%), examiners (64 of 118; 54%), proctors (25 of 27; 93%), and hosts (8 of 9; 89%) completing the survey were very satisfied with the examination (Likert score 4 or 5: candidates, 92.6%; noncandidates, 96.9%) and found the technology domains (Zoom, audio, video, viewing images) to be very good (Likert score 4 or 5), with candidate and other responder scores of 73% to 84% and >94%, respectively. Significantly more of the candidates had favored a future VVCE compared with the examiners (87% vs 32%; χ2 = 67.1; P < .001). The free text responses from all responders had commented favorably on the organization and implementation of the examination. However, some candidates had expressed concerns about image sizes, and some examiners had expressed concern about the time constraints for the question format. The candidates appreciated the convenience of an at-home examination, especially the avoidance of travel costs. CONCLUSIONS: The two Vascular Surgery Board VCEs were shown to be psychometrically sound and were overwhelmingly successful, demonstrating that image-based virtual examinations are feasible and could become the standard for the future.

Effect of Protein Adsorption on Air Plastron Behavior of a Superhydrophobic Surface.

Protein fouling on critical biointerfaces causes significant public health and clinical ramifications. Multiple strategies, including superhydrophobic (SHP) surfaces and coatings, have been explored to mitigate protein adsorption on solid surfaces. SHP materials with underwater air plastron (AP) layers hold great promise by physically reducing the contact area between a substrate and protein molecules. However, sustaining AP stability or lifetime is crucial in determining the durability and long-term applications of SHP materials. This work investigated the effect of protein on the AP stability using model SHP substrates, which were prepared from a mixture of silica nanoparticles and epoxy. The AP stability was determined using a submersion test with real-time visualization. The results showed that AP stability was significantly weakened by protein solutions compared to water, which could be attributed to the surface tension of protein solutions and protein adsorption on SHP substrates. The results were further examined to reveal the correlation between protein fouling and accelerated AP dissipation on SHP materials by confocal fluorescent imaging, surface energy measurement, and surface robustness modeling of the Cassie-Baxter to Wenzel transition. The study reveals fundamental protein adsorption mechanisms on SHP materials, which could guide future SHP material design to better mitigate protein fouling on critical biointerfaces.

Outcomes of the First Virtual General Surgery Certifying Exam of the American Board of Surgery.

OBJECTIVE: To Study the Outcomes of the First Virtual General Surgery Certifying Exam of the American Board of Surgery. SUMMARY OF BACKGROUND DATA: The ABS General Surgery CE is normally an in-person oral examination. Due to the COVID-19 outbreak, the ABS was required to reschedule these. After 2 small pilots, the CE's October administration represented the first large-scale remote virtual exam. The purpose of this report is to compare the outcomes of this virtual and the previous in-person CEs. METHODS: CE candidates were asked to provide feedback on their experience via a survey. The passing rate was compared to the 1025 candidates who took the 2019-2020 in-person CEs. RESULTS: Of the 308 candidates who registered for the virtual CE, 306 completed the exam (99.4%) and 188 completed the survey (61.4%). The majority had a very positive experience. They rated the virtual CE as very good/excellent in security (90%), ease of exam platform (77%), audio quality (71%), video quality (69%), and overall satisfaction (86%). Notably, when asked their preference, 78% preferred the virtual exam. There were no differences in the passing rates between the virtual or in-person exams. CONCLUSIONS: The first virtual CE by the ABS was completed using available internet technology. There was high satisfaction, with the majority preferring the virtual platform. Compared to past in-person CEs, there was no difference in outcomes as measured by passing rates. These data suggest that expansion of the virtual CE may be desirable.

Evaluating Superhydrophobic Surfaces under External Pressures using Quartz Crystal Microbalance.

The performance of hydrophobic surfaces under hydraulic pressures is critical to a wide range of practical applications such as drag reduction of seaboard vessels and design of microfluidic devices. This research focuses on the evaluation of drag reduction and velocity slip of hydrophobic surfaces and coatings under external hydrostatic pressures using an acoustic wave device (i.e., quartz crystal microbalance, QCM). The correlation between the resonant frequency shift of a QCM device and drag reduction of hydrophobic surface coated on the QCM was theoretically developed and the model was validated by comparing the measurement results of the drag reduction of an epoxy-based superhydrophobic coating with those measured by a rheometer. The QCM device was further employed to study the wetting state transition and drag reduction of water on a micropillar array based superhydrophobic surface under elevated hydrostatic pressures. It was found that the transition from Cassie to Wenzel states occurred at a critical hydrostatic pressure which was indicated by a sudden frequency drop of the QCM device. In addition, the effective heights of the meniscus at the liquid/air interface increased with the external pressure before the transition took place. The drag reduction induced by the micropillar surface decreased with the increasing hydrostatic pressures. It was demonstrated that the developed QCM based technology provides a low cost, simple, and reliable tool for evaluating hydrophobic performance of various surfaces under external hydrostatic pressures.

Characterization of Stereolithography Printed Soft Tooling for Micro Injection Molding.

The use of microfeature-enabled devices, such as microfluidic platforms and anti-fouling surfaces, has grown in both potential and application in recent years. Injection molding is an attractive method of manufacturing these devices due to its excellent process throughput and commodity-priced raw materials. Still, the manufacture of micro-structured tooling remains a slow and expensive endeavor. This work investigated the feasibility of utilizing additive manufacturing, specifically a Digital Light Processing (DLP)-based inverted stereolithography process, to produce thermoset polymer-based tooling for micro injection molding. Inserts were created with an array of 100-µm wide micro-features, having different heights and thus aspect ratios. These inserts were molded with high flow polypropylene to investigate print process resolution capabilities, channel replication abilities, and insert wear and longevity. Samples were characterized using contact profilometry as well as optical and scanning electron microscopies. Overall, the inserts exhibited a maximum lifetime of 78 molding cycles and failed by cracking of the entire insert. Damage was observed for the higher aspect ratio features but not the lower aspect ratio features. The effect of the tool material on mold temperature distribution was modeled to analyze the impact of processing and mold design.

Fabrication of Flexible Polymer Molds for Polymer Microstructuring by Roll-to-Roll Hot Embossing.

Roll-to-roll hot embossing could revolutionize the manufacturing of multifunctional polymer films with the ability to process large area at a high rate with reduced cost. The continuous hot embossing of the films, however, has been hindered due to the lack of durable and flexible molds, which can replicate micro and nanofeatures with reliability over several embossing cycles. In this work, we demonstrate for the first time the fabrication of a flexible polymer (polyimide) mold from the commercially available sheet by a maskless photolithography approach combined with inductively coupled plasma etching and its potential application to the roll-to-roll hot embossing process. The flexible polyimide mold consisted of holes with controlled dimensions: diameter: 14 µm, spacing: 16.5 µm, and depth: 6.8 µm. The reliability of flexible polyimide mold was tested and implemented by embossing micron-sized features on a commercial thermoplastic polymer, polyamide, and thermoplastic elastomer (TPE) sheet. The polyimide mold replicated micron-sized features on polymer substrates (polyamide and TPE) with excellent fidelity and was durable even after numerous embossing cycles.

Numerical evaluation and experimental validation of cross-flow microfiltration device design.

This research presents a comprehensive analysis of the design and validation of a cross-flow microfiltration device for separation of microspheres based on size. Simulation results showed that pillar size, pillar shape, incorporation of back-flow preventers, and rounding of pillar layouts affected flow patterns in a cross-flow microfiltration device. Simulation results suggest that larger pillar sizes reduce filtration capacity by decreasing the density of microfiltration gaps in the device. Therefore, 10 µm rather than 20 µm diameter pillars were incorporated in the device. Fluid flow was not greatly affected when comparing circular, octagonal, and hexagonal pillars. However, side-channel fluid velocities decreased when using triangular and square pillars. The lengths of back-flow prevention walls were optimized to completely prevent back flow without inhibiting filtration ability. A trade-off was observed in the designs of the pillar layouts; while rounding the pillars layout in the channels bends eliminated stagnation areas, the design also decreased side-channel fluid velocity compared to the right-angle layout. Experimental separation efficiency was tested using polydimethylsiloxane (PDMS) and silicon microfluidic devices with microspheres simulating white and red blood cells. Efficiencies for separation of small microspheres to the side channels ranged from 73 to 75%. The silicon devices retained the large microspheres in the main channel with efficiencies between 95 and 100%, but these efficiencies were lower with PDMS devices and were affected by sphere concentration. Additionally, PDMS devices resulted in greater agglomeration of spheres when compared to silicon devices. PDMS devices, however, were easier and less expensive to fabricate.