Initial Curve Research Articles

S7A-07 SESSION 7A: SAGITTAL SYNOSTOSIS AN UPDATE ON THE OUTCOMES OF SPRING-ASSISTED SURGERY FOR SAGITTAL CRANIOSYNOSTOSIS

Introduction: Spring-assisted surgery (SAS) is an efficacious means for correcting scaphocephaly due to sagittal craniosynostosis. Early intervention for sagittal craniosynostosis using spring-assisted surgery (SAS) is an alternative to calvarial vault remodeling. SAS is performed for patients younger than 6 months of age, and it requires two operations: one for spring placement and a second for spring removal. The long-term safety and efficacy of this technique continue to be reviewed as this technique gains greater acceptance. The nuances of optimizing outcome will also be reviewed. Methods: We performed a retrospective examination of the electronic medical record for all patients treated with SAS for isolated sagittal synostosis at our institution with at least 1 year of follow up (N=179). Cephalic index (CI) was calculated from CT scans, laser Doppler scans, and 3DMD stereophotogammetry. Perioperative data was collected on OR time, blood loss, transfusion rates, and hospital stay, and complications were also collected. Results: There were 179 patients who underwent SAS from 2001 to February 2018. The mean gestationally-corrected age at spring placement and spring removal were 4.4 months and 9.4 months, respectively. Operative time for spring placement was 44.9 minutes, and for spring removal was 26.8 minutes. The mean hospital length of stay for spring placement was 35 hours, and for spring removal was 7.6 hours. One patient required a blood transfusion for the initial placement operation and none for the removal procedure. Mean CI prior to SAS was 70. This improved to 75 after spring placement (p<0.001) and was 74.0 at 1 year after spring placement. This has been maintained with a mean of 75.7 at 12 years post op. Major complications, defined as those requiring a return to the operating room to address spring malposition, exposure, or infection, occurred at a rate of 6.1% with the majority of these occurring during the initial learning curve of the procedure. Conclusion: SAS for isolated craniosynostosis continues to have consistent correction of CI that is maintained over time and a favorable complication profile, as shown by this updated analysis. Outcomes are optimized by earlier placement, accurate positioning in relation to the coronal and lambdoid sutures, and accurate force selection based on type of scaphocephaly and patient profile. The spring removal procedure can be done safely as an outpatient. Finally, after the initial learning curve, the endoscopic approach mirrors the outcomes of the open spring placement.

Use of a Novel Computerized Drill for Pedicle Screw Insertion in the Thoracic and Lumbar Spine: A Cadaveric Study.

A variety of techniques have been utilized to improve the accuracy of pedicle screw instrumentation. Recently, a novel handheld computerized drill system, IntelliSense Drill Technology, has been used in orthopedic trauma to improve drilling accuracy and reduce radiation and iatrogenic injury. The specialized drill technology detects changes in cortical density to prevent inadvertent cortical violation. The aim of this study is to assess the ability of this system to identify pedicle trajectories in the thoracic and lumbar spine compared to a standard freehand technique. Two spine surgeons, including 1 senior-level and 1 junior-level attending drilled pedicle screw tracts using a freehand technique and computerized drill technology in 4 cadaveric spines from T2 to S1. A total of 134 pedicle screws were placed, including 70 by the senior surgeon and 64 by the junior surgeon. Cortical violations were assessed using computed tomography after instrumenting each pedicle tract, and procedure time for insertion of pedicle screws was recorded. A total of 15 (22.4%) and 12 (18.2%) pedicle violations were noted using the freehand and computerized drill technique, respectively (P = .767). Perforations using the computerized drill decreased from 31.1% in the first attempt to 5.9% in the second attempt (P = .027). Mean drill time per pedicle using the freehand and computerized drill techniques were comparable (12.2 ± 8.4 versus 12.1 ± 13.2, P = .871), and both surgeons had an improvement in procedure time using the computerized drill (surgeon 1: 12.3 ± 13.7-5.7 ± 3.8 [SD], P = .059; surgeon 2: 20.3 ± 20.0-10.4 ± 5.6 [SD], P = .063). We demonstrate the use of a novel drill technology for placement of pedicle screws in the thoracic and lumbar spine. After an initial learning curve, this technology is comparable to use of a freehand technique by both a senior-level and a junior-level attending surgeon in a cadaveric model. Further investigation is needed to identify the clinical role of this technology in spine surgery.

Growth-Friendly Spine Surgery in Escobar Syndrome.

The aims of this study were to characterize the spinal deformity of patients with Escobar syndrome, describe results of growth-friendly treatments, and compare these results with those of an idiopathic early-onset scoliosis (EOS) cohort to determine whether the axial stiffness in Escobar syndrome limited correction. We used 2 multicenter databases to review the records of 8 patients with EOS associated with Escobar syndrome who had at least 2-year follow-up after initiation of growth-friendly treatment from 1990 to 2016. An idiopathic EOS cohort of 16 patients matched for age at surgery (±1 y), postoperative follow-up (±1 y), and initial curve magnitude (±10 degrees) was identified. A randomized 1:2 matching algorithm was applied (α=0.05). In the Escobar group, spinal deformity involved 7 to 13 vertebrae and ranged from no vertebral anomalies in 3 patients to multiple segmentation defects in 6 patients. Mean age at first surgery was 5 years (range, 1.4 to 7.8 y) with a mean follow-up of 7.5 years (range, 4.0 to 10 y). Mean major curve improved from 76 degrees at initial presentation, to 43 degrees at first instrumentation, to 37 degrees at final follow-up (both P<0.001). Mean pelvic obliquity improved from 16 degrees (range, 5 to 31 degrees) preoperatively to 4 degrees (range, 0 to 8 degrees) at final follow-up (P=0.005). There were no differences in the mean percentage of major curve correction between the idiopathic EOS and Escobar groups at the immediate postoperative visit (P=0.743) or final follow-up (P=0.511). There were no differences between the cohorts in T1-S1 height at initial presentation (P=0.129) or in growth per month (P=0.211). Multiple congenital fusions and spinal curve deformity are common in Escobar syndrome. Despite large areas of congenital fusion, growth-friendly constructs facilitate spinal growth and improve curve correction. These results are comparable to those in idiopathic EOS. Level III-case-control study.

An Adjoint Technique for Estimation of Interstation Phase and Group Dispersion from Ambient Noise Cross Correlations

AbstractA method of extracting group and phase velocity dispersions jointly for Love‐ and Rayleigh‐wave observations is presented. This method uses a spectral element representation of a path average Earth model parameterized with density, shear‐wave velocity, radial anisotropy, and VP/VS ratio. An initial dispersion curve is automatically estimated using a heuristic approach to prevent misidentification of the phase. A second step then more accurately fits the observed noise correlation function (NCF) between interstation pairs in the frequency domain. For good quality cross correlations with reasonable signal‐to‐noise ratio, we are able to very accurately fit the spectrum of NCFs and hence obtain reliable estimates of both phase and group velocity jointly for Love and Rayleigh surface waves. In addition, we also show how uncertainties can be estimated with linearized approximations from the Jacobians and subsequently used in tomographic inversions.

Learning curve analysis of transvaginal natural orifice transluminal endoscopic hysterectomy

BackgroundNo data are available to assess the learning curve for transvaginal natural orifice transluminal endoscopic hysterectomy for non-prolapsed uteri in benign gynecologic diseases. The lack of exposure to transvaginal natural orifice transluminal endoscopic hysterectomy during training, in addition to a poorly defined learning curve, further deters interested physicians from applying this technique to daily practice. The aim of this study was to evaluate the learning curve and perioperative outcome of transvaginal natural orifice transluminal endoscopic hysterectomy by an experienced endoscopist.MethodsA total of 240 cases of transvaginal natural orifice transluminal endoscopic hysterectomies with or without adnexectomy for various benign gynecologic diseases were included. Demographic data and various perioperative parameters were reviewed from the prospectively collected database. Operative time was set as a surrogate marker for surgical competency. The learning curve was evaluated using the cumulative sum method.ResultsThe overall mean operative time (OT) was 76.5 min ± 22.4. Four unique phases of the learning curve were derived using cumulative sum analysis: the mean OT of phase I (the initial learning curve of 20 cases) was 86.3 ± 23.7 min, phase II (acquisition of competence of 80 cases) was 71.0 ± 21.4 min, phase III (proficiency and plateau of 80 cases) was 76.0 ± 20.4 min, and phase IV (post-learning in which more challenging cases were managed) was 81.3 ± 23.6 min. No major complications were encountered. One case in phase III converted to laparoscopy due to difficulty in performing anterior colpotomy.ConclusionOur data demonstrated four distinct phases of the learning curve of transvaginal natural orifice transluminal endoscopic hysterectomy. In a well-trained endoscopist, surgical competence in transvaginal natural orifice transluminal endoscopic hysterectomy can be reached after 20 cases.

Quality Improvement in Laparoscopic Donor Nephrectomy by Self-Imposed Proctored Preceptorship Model

Initiation of an advanced laparoscopic surgery program requires skill and proper training. Despite description of multiple surgical training modules, an ideal method for training of surgeons for advanced laparoscopic procedures is lacking. We propose an abbreviated self-imposed proctored preceptorship training model as the optimum training method for training skilled laparoscopic surgeons in advanced laparoscopic procedures like laparoscopic donor nephrectomy. The laparoscopic donor nephrectomy program was started at the Institute using preceptorship-proctorship model. One hundred left laparoscopic donor nephrectomies were performed over the course of 2 years. Outcomes in terms of performance related (Surgeon) outcomes in the form of learning curve and patient outcomes in terms of donor outcomes and recipient results and were studied. Learning curve was calculated using the moving average method and calculation of mean operative time of every five consecutive cases. Mean operative time for laparoscopic donor nephrectomy was 108.1 ± 26.5 min, the warm ischemia time averaged at 3.5 ± 1.3 min and the mean blood loss was 130.1 ± 54.9 ml. Moving average analysis revealed that approximately 20 LDN cases were needed to complete the learning phase. According to the mean operative time of every five consecutive cases, learning phase of LDN was completed between 26 and 30 cases. We believe that the abbreviated self-imposed proctored preceptorship model of training is an optimum model for starting a new advanced laparoscopic surgery program and can help surgeons to overcome the initial learning curve.

Clinical Outcomes of Collagenase Injections During a Surgeon’s Initial Learning Phase

Purpose Collagenase Clostridium histolyticum (CCH) has increasingly been used to treat Dupuytren contracture since its Food and Drug Administration approval in 2010. One concern among practitioners is the learning curve of this new technique. This study characterizes success and complication rates for surgeons with no prior experience with CCH treatment. Methods We recruited 10 hand and upper-extremity surgeons for this study. Retrospective clinical records were reviewed for the first 10 CCH injections by each surgeon. Preinjection, postmanipulation, and 30- to 90-day follow-up measurements were recorded, along with any complications. Finally, provider opinions regarding CCH for Dupuytren contracture were collected. Results There were 100 CCH injections in 100 fingers: 42 with isolated metacarpophalangeal contractures, 24 with isolated proximal interphalangeal contractures, and 34 with both metacarpophalangeal and proximal interphalangeal contractures. At 30- to 90-day follow-up, 61.4% of primary joints demonstrated improvement of contracture to within 0° to 5° degrees from full extension, 85.2% showed greater than 50% reduction in contracture, and 12 patients were lost to follow-up. Trend analysis suggested a flat initial learning curve. Complications occurred in 33 cases and included skin tears (31) and lymphadenopathy (4). No tendon ruptures were observed. All surgeons were either satisfied or extremely satisfied with CCH and continued using it in their practices. Conclusions Clinical results achieved from practitioners' early injections mirrored success and surgeon satisfaction rates previously reported in the literature. However, complication rates were higher than those in initial clinical trials but similar to later studies that used local anesthesia during manipulation. Trends in clinical outcomes among the first 10 injections suggest an initially flat learning curve for CCH. Practitioners' opinions of CCH remained favorable after early use. Type of study/level of evidence Therapeutic III.

Evaluation of multisite performance of SWAT model in the Gomti River Basin, India

The basin was calibrated through monthly discharge for the period (2002–2008) including 2 years as warm-up (2000–2001), after that model was validated on 5 years of hydrometeorological datasets (2009–2013) at two gauge sites located at Neemsar (upstream gauge) and Lucknow (downstream gauge). It is found that the most sensitive parameter for moisture condition II (CN2) was initial curve number. The p-factor and r-factor were obtained in calibration period at Neemsar 0.73 and 0.58 while at Lucknow values are 0.79 and 0.51, whereas in validation period values are 0.61, 0.45 and 1.22, 0.75, respectively. Three statistical parameters have been used to evaluate the SWAT model performance such as Coefficient of Determination (R2), Nash–Sutcliff efficiency (NSE), percent bias (PBIAS). The NSE and R2 values were observed as 0.85, 0.84 and 0.87, 0.86, respectively, in the time of calibration period and values is 0.76, 0.76 and 0.79, 0.83, respectively, in the time of validation period at two above said gauging stations. The PBIAS values during calibration and validation period are − 13.3, − 14.7 and − 4.0, − 15.7, respectively, at the same gauge site which indicates good model performance result.

Experimental study on dynamic deformation properties of muck soil under low frequency cyclic loading

A series of dynamic triaxial tests were performed to investigate the dynamic deformation properties of the muck soil, in the Pearl River Delta region of Shenzhen, China, under different consolidation ratios, loading frequencies and cyclic stress with SPAX-2000 triaxial testing system. The results showed that the initial stress-strain hysteresis curve of the muck soil under the low-frequency cyclic loading developed rapidly and the curve shape changes from sparse to tight and to slightly sparse. The cumulative plastic strain of muck soil increased nonlinearly with the dynamic stress amplitude, and there was a critical dynamic stress. As the dynamic stress amplitude reached its critical value, the strain increased sharply and the soil microstructure was destroyed. There was a frequency threshold between 0.25 Hz and 0.5 Hz, and the cumulative plastic strain development mode was from stable model to over-destructive model. The stiffness of the muck decreased gradually, and the plastic deformation increased as the number of cycles increased. Therefore, the lower the loading frequency developed, the greater the plastic deformation would be. The dynamic elastic modulus decreased as the plastic deformation increased, while the dynamic elastic modulus increased as the consolidation stress increased. Moreover, the empirical formulas of dynamic elastic modulus and plastic strain index were established with the consolidation stress ratio as the parameter, and the validity was verified by experimental data.

Effect of grain boundary on magnetization behaviors in 2:17 type SmCo magnet

Abstract The effect of grain boundary area on the magnetization behaviors in Sm25Co48Fe20Cu5Zr2 magnet was investigated. Grain boundary area with deficiency of Cu and incomplete cellular microstructure was clearly observed. In-situ Kerr observation revealed that the magnetization reversals firstly occurred in the grain boundary areas and then propagated into the interiors of grain. The grain boundary areas with weakened pinning force of magnetic domain walls could undermine the coercivity and induce inferior squareness of the magnet. The investigation using Fresnel LTEM demonstrated that the grain boundary area was magnetized more easily than the grain interior, which agreed with the multi-stage phenomenon of the initial magnetization curve of the magnet.

Magnetic Properties of Polycrystalline Compounds Cu0.64Mn0.86[Fe(CN)6]·7.2H2O and Cu0.84Mn0.66[Fe(CN)6]·7.1H2O

In this work, polycrystalline powder samples of Cu0.64Mn0.86[Fe(CN)6]·7.2H2O and Cu0.84Mn0.66[Fe(CN)6]·7.1 H2O have been synthesized by a coprecipitation method. The lattice parameter a is 10.053(8) A and 10.083 A for Cu0.64Mn0.86[Fe(CN)6]·7.2H2O and Cu0.84Mn0.66[Fe(CN)6]·7.1H2O, respectively. When the temperature reaches to 5 K, the magnetization is 7.262 emu/g and 0.142 emu/g for Cu0.64Mn0.86[Fe(CN)6]·7.2H2O and Cu0.84Mn0.66[Fe(CN)6]·7.1H2O, respectively. The coercive field and the remanent magnetization of Cu0.64Mn0.86[Fe(CN)6]·7.2H2O are 1204 Oe and 0.382 μB/fu, respectively. The coercive field and the remanent magnetization of Cu0.84Mn0.66[Fe(CN)6]·7.1H2O are 833 Oe and 0.681 μB/fu, respectively. In the initial magnetization curve, under the external magnetic field of 7 T, the magnetization of Cu0.64Mn0.86[Fe(CN)6]·7.2H2O and Cu0.84Mn0.66[Fe(CN)6]·7.1H2O is 2.13 μB/fu and 2.44 μB/fu, respectively. The difference between the calculated magnetic moment and the theoretical magnetic moment is quite large, which may be due to spin frustration.

Методика интерпретации электромагнитных зондирований в геоэлектрических условиях юга Сибирской платформы (электрофациальный анализ)

The article considers advanced approaches to interpreting electromagnetic data i.e. near-field transient electromagnetic sounding (TEM) that provide prompt information on the area under study. The electric facies analysis is an innovative technique of electromagnetic survey in which at the stage of the qualitative analysis of the electromagnetic survey data, the initial curves are integrated into the GeoDepth Paradigm seismic processing package by means of specialized software. As a result of the study, electric facies for the main geoelectric complexes have been mapped in the Stratimagic environment. The maps are based on the stratigraphic marks obtained by the seismic survey. The comparison of the electric facies maps and longitudinal conductivity maps shows the anomalous field match which confirms the method correctness. The electric facies classes are thereafter compared with the test data on the deep-hole wells located in the studied area. The electric facies analysis significantly increases the level and enhanced the informational content of the qualitative analysis of the TEM data. The integration of the electromagnetic data in seismic software packages facilitates integration at all stages of the geophysical data interpretation, thus increasing the validity of the complex predictive parameter and the reliability of mapping for the promising oil-and-gas sites.

Identification of Magnetization Characteristics of Material From Measured Inductance Data

This paper introduces a novel identification method of the magnetization properties of the core material for an inductor from measured inductance data. The proposed method allows us to obtain the magnetic hysteresis characteristics without a special measurement instrument for material $B - H$ properties. The proposed method determines the parameters included in the distribution function for the Preisach model from the measured $L - I$ characteristics. It is shown that the identified initial magnetization curve and the minor loops are in good agreement with the original $B - H$ curves. The uniqueness for the identification problem is numerically verified.

Application of the Brooks-Corey model in the conditions of lower cretaceous deposits in terrigenous reservoirs of Western Siberia

The paper deals with the issues of determining Brooks-Corey model parameters in the approximation of capillary curves under the conditions of productive strata of Western Siberia. It was emphasized that in the conditions of reservoirs of Western Siberia, there are close correlations between current water saturation of capillary curves at fixed values of capillary pressure and reservoir properties (absolute permeability, residual water saturation). Using these correlations, the approximation model parameters (initial capillary pressure and capillary curve steepness) were accurately assessed.

Different inflow control methods in cirrhotic patients undergoing laparoscopic liver resection

In the last decade, laparoscopic liver resection (LLR) has been adopted increasingly worldwide (1,2). This observed trend is promising despite the initial significant learning curve required for LLR (3-5). Even with today’s technological advances such as high definition 3-dimension visualization, improved energy devices and ultrasonic dissectors, hepatobiliary surgeons are still faced with challenges when performing liver resection on cirrhotic livers. This is because cirrhotic patients require not only extensive pre-operative planning and optimization, but also challenging post-operative care (6,7). Intra-operatively, the mobilization and transection of a hard-nodular cirrhotic liver is arduous and regardless of the technique employed, intra-operative vascular control is critical due to the direct impact intra-operative blood loss has on post-operative recovery and long-term oncological outcomes (8).

Experienced operators achieve superior patency and wound complication rates with endoscopic great saphenous vein harvest compared with open harvest in lower extremity bypasses

ObjectivePrior studies have suggested improved wound complication rates but decreased primary patency in lower extremity bypasses performed with endoscopic vein harvest (EVH) vs open vein harvest (OVH). We hypothesize that the inferior patency reflects the initial learning curve for EVH and that improved patency can be achieved with experience. MethodsThis was a single-institution review of 113 patients with critical limb ischemia who underwent infrainguinal bypass with a continuous segment of great saphenous vein harvested endoscopically (n = 49) or through a single open incision (n = 64) from 2012 to 2017. EVH was performed by surgeons with >5 years' experience with this technique. Operative outcomes, patency, complications, and readmission rates were compared between the harvest methods. EVH data were also compared with our prior reported series of our initial experience with this technique to determine the effects of experience on outcomes. ResultsThere were no significant differences in patient demographics, medications, operative indications, or inflow/outflow vessels between the two groups. Mean operative time was 322 minutes and median hospital length of stay was 6 days for OVH, and was 340 minutes and 5 days for EVH, which was not significant. Harvest-related wound complications were more frequent with OVH (28% vs 2%, P < .001). Primary patency at 1 and 3 years was 65% and 58% for OVH, and 79% and 71% for EVH, respectively (P = .18), assisted primary patency was 77% and 74% for OVH and 94% and 89% for EVH, respectively (P = .05), and secondary patency was 82% and 79% for OVH and 95% and 95% for EVH, respectively (P = .03). The 30-day readmission rates were similar between OVH (20%) and EVH (12%, P = .26), but 90-day readmissions were more frequent in the OVH group (34% vs 14%, P = .018). Compared with our earlier series of EVH, the current cohort had significantly improved 3-year primary (71% vs 42%, P = .012), primary assisted patency (89 vs 66%, P = .034), and secondary patency (95% vs 66%, P = .003). ConclusionsWith experience, lower extremity bypass using EVH can result in improved patency compared with OVH and initial EVH use, while also resulting in fewer wound complications and readmissions, with comparable operative times and hospital length of stay. This technique should be more widely adopted by vascular surgeons as a primary method of vein harvest.

Analytic reconstruction of a two-dimensional velocity field from an observed diffusive scalar

Inverting an evolving diffusive scalar field to reconstruct the underlying velocity field is an underdetermined problem. Here we show, however, that for two-dimensional incompressible flows, this inverse problem can still be uniquely solved if high-resolution tracer measurements, as well as velocity measurements along a curve transverse to the instantaneous scalar contours, are available. Such measurements enable solving a system of partial differential equations for the velocity components by the method of characteristics. If the value of the scalar diffusivity is known, then knowledge of just one velocity component along a transverse initial curve is sufficient. These conclusions extend to the shallow-water equations and to flows with spatially dependent diffusivity. We illustrate our results on velocity reconstruction from tracer fields for planar Navier–Stokes flows and for a barotropic ocean circulation model. We also discuss the use of the proposed velocity reconstruction in oceanographic applications to extend localized velocity measurements to larger spatial domains with the help of remotely sensed scalar fields.

Development of imjSCORE for early prediction of response to nivolumab among patients with advanced cancer.

e14169 Background: Cross-sectional Imaging (CI) plays an essential role in early assessment of patients on immune checkpoint inhibitors (ICIs), yet often remains inconclusive in the setting of advanced disease, prior cancer treatment, toxicity, and cancer unrelated findings. Best timing of scans is also uncertain and may affect interpretation. We propose here a robust, reproducible imjScore based on measurable tumor response on the first two re-staging scans and their ratios that may predict treatment impact. Our approach incorporates the prognostic aspect of early imaging, time lag of ICIs effect, and alternative measures of treatment impact. Methods: Retrospective review of CI studies was performed in 92 patients with advanced stage solid tumors treated with Nivolumab during 6/2015-8/2018 at Boston Medical Center utilizing standard clinical protocols. Time on therapy (TOTx) was used as a surrogate marker of therapy impact. Modified imRECIST score utilizing Σ of 4 discrete cancer lesions at baseline (&lt; 1 month before Nivolumab), 1st, and 2nd CI since initiation of Nivolumab were adjusted for TOTx. Our imjSCORE averages "predicted days on therapy" calculated from best fit function of tumor change/day [%] at each time point vs. TOTx and ratios between 1st and 2nd scan. Results: Median TOTx was 70 days (range from 1 to 1029). Differences in imRECIST scores derived from two early restaging CI studies adjusted for TOTx were able to identify with high statistical significance two groups of "SHORT" vs "LONG" sojourn on Nivolumab based on Median of 70 days. Early progression curve was associated with shorter benefit of Nivolumab; subset with pseudo-progression curve showed still significantly shorter sojourn on Nivolumab compared to initial regression or stable score curves (P &lt; .002). Conclusions: The development of imjScore may differentiate with high likelihood patients with short versus long sojourn on Nivolumab. Our CI-based evaluation using the imjSCORE suggests a clear benefit from early imaging with a response curve and standardized point analysis of the 1st and 2nd post-treatment scans. If validated with other ICIs, this scoring tool may allow early prediction of ICIs treatment response and clinical outcome. Further correlation of imjSCORE with clinical biomarkers may be useful to build predictive nomograms of "short" versus "long" treatment impact.

The effect of testing and feedback on the forgetting curves for radiograph interpretation skills

Objectives: Forgetting curves plot skill decay over time. After exposure to a simulation-based radiograph interpretation learning system, we determined the rate of learning decay and how this was impacted by testing (with and without feedback). Further, we examined the association of initial learning parameters on the forgetting curve.Methods: This was a multicenter, four-arm randomized control trial. Medical trainees completed 80 elbow radiographs and a 20-case post-test. Group 1 had no testing until 12 months; Groups 2–4 had testing every 2 months until 12 months. At 6 months, Group 3 testing was feedback-enhanced, while Group 4 had feedback-enhanced testing at 2, 6, and 10 months.Results: There were 106 participants (n = 42 Group 1; n = 22 Groups 2 and 3; n = 20 Group 4). Group 1 showed an –8.1% learning decay at 12-months relative to other groups. In Groups 2, 3, and 4, there was no significant learning decay (+0.8%), and there were no differences in skill decay between these groups. Initial score and learning curve slope were predictive of retained skill.Conclusions: Learning decay was mitigated by exposure to 20 test cases (with and without feedback) every two months. Initial learning parameters predicted learning retention and may inform refresher education scheduling.

Improving Reversibility of Anionic Redox Reaction of NaVO3 By Metal Doping for Sodium-Ion Batteries

Traditionally, positive electrode materials in lithium/sodium-ion batteries (LIBs/NIBs) undergo charge and discharge through redox reaction of the transition metal (TM) within the structure. As a result, the number of electron transfer is limited by the available valence states of the TM. Recently, there is an increased interest in solid-state anionic redox reaction (ARR) in positive electrode materials that compensates the charge transfer by the oxygen atoms. ARR can potentially increase the capacity of the active material with the additional charge-transfer site. It can also open the door to more transition-metal compounds that are originally thought to be inactive. Our previous work has shown that NaVO3 (NVO) can undergo anionic redox reaction while the oxidation state of V remains 5+ between 1.5 and 4.9 V vs. Na/Na+.[1] It can give a capacity of more than 100 mAh g-1, though its capacity fades with cycling. Here, we aim at improving the stability and capacity of the material by incorporating other transition metals into the structure to utilize both the anionic and cationic redox reactions. As a start, we synthesized a single phase Na1.3Co0.1V0.9O3 (NCVO) with Co2+ doping by a typical solid-state method. Both NVO and NCVO materials were first discharged to 1.2 V to investigate the amount of V5+/4+ redox reaction that is available in the material and then charged to 4.7 V. Figure 1a shows the first and second charge-discharge curve of the two materials. Interestingly, the incorporation of Co into the structure reduces the activity of V5+/4+ during initial discharge, with a smaller capacity of 38 mAh g-1 for NCVO as opposed to 94 mAh g-1 for NVO to 1.2 V. Though, the amount of charge and discharge capacities during 2nd cycle are the same, suggesting changes in reaction mechanism of the material with Co2+ addition. The available capacity of about 180 mAh g-1 is higher than that can be obtained from Co and V redox reactions alone, so part of the capacity comes from oxygen redox reaction. Figure 1b shows the cycle performance of NCVO and it gives good stability. In addition, NCVO can delivers better rate performance with a discharge capacity of 130 mAh g-1 at 50 mA g-1. Further works with techniques such as ex-situ XRD, XPS and GITT to characterize the material and understand the reaction mechanism are underway. More results on the effect of the metal dopant will be presented at the meeting. [1] J. Zhang, B. Su, A. Kitajou, M. Fujita, Y. Cui, M. Oda, W. Zhou, P. H.-L. Sit, D. Y. W. Yu, J. Power Sources 400, 377 (2018). Figure 1. (a) Initial discharge and second charge-discharge curves of NVO and NCVO electrodes at 10 mA g−1 between 1.2 and 4.7 V vs. Na/Na+; (b) Cycle performance of NCVO between 1.2 and 4.7 V. Figure 1