Initial Curve Research Articles

The Study of the Relaxation Properties of Recycled Polypropylene Filled with Galvanic Waste

The article shows the influence of the content of galvanic waste with different chemical composition on the physico-mechanical properties of thermoplastic composite material. In this study, samples of a secondary polypropylene filled with 15 wt.% galvanic waste with high content of iron and chromium were analysed. For a detailed evaluation of the mechanical behavior of filled recycled polypropylene, stress relaxation of the samples was tested in a wide temperature range from 20 to 120 degrees Celsius. According to the results of the study a generalized relaxation curve was developed in a special computer program by a parallel shift of initial curve of the stress relaxation along the axis of log(t).

A review and validation of overall survival extrapolation in health technology assessments of cancer immunotherapy by the National Institute for Health and Care Excellence: how did the initial best estimate compare to trial data subsequently made available?

Background: Validation of overall survival (OS) extrapolations of immune-checkpoint inhibitors (ICIs) during the National Institute for Health and Care Excellence (NICE) Single Technology Assessment (STA) process is limited due to data still maturing at the time of submission. Inaccurate extrapolation may lead to inappropriate decision-making. The availability of more mature trial data facilitates a retrospective analysis of the plausibility and validity of initial extrapolations. This study compares these extrapolations to subsequently available longer-term data.Methods: A systematic search of completed NICE appraisals of ICIs from March 2000 to December 2017 was performed. A targeted search was also undertaken to procure published OS data from the pivotal clinical trials for each identified STA made available post-submission to NICE. Initial Kaplan-Meier curves and associated extrapolations from NICE documentation were extracted to compare the accuracy of OS projections versus the most mature data.Results: The review identified 11 STAs, of which 10 provided OS data upon submission to NICE. The extrapolations undertaken considered parametric or piecewise survival models. Additional data cut-offs provided a mean of 18 months of OS beyond the end of the original data. Initial extrapolations typically under-estimated OS from the most mature data cut-off by 0.4–2.7%, depending on the choice of assessment method and use of the manufacturer- or ERG-preferred extrapolation.Conclusion: Long-term extrapolation of OS is required for NICE STAs based on initial immature OS data. The results of this study demonstrate that the initial OS extrapolations employed by manufacturers and ERGs generally predicted OS reasonably well when compared to more mature data (when available), although on average they appeared to underestimate OS. This review and validation shows that, while the choice of OS extrapolation is uncertain, the methods adopted are generally aligned with later-published follow-up data and appear appropriate for informing HTA decisions.

Equiareal Shape-from-Template

This paper studies the 3D reconstruction of a deformable surface from a single image and a reference surface, known as the template. This problem is known as Shape-from-Template and has been recently shown to be well-posed for isometric deformations, for which the surface bends without altering geodesics. This paper studies the case of equiareal deformations. They are elastic deformations where the local area is preserved and thus include isometry as a special case. Elastic deformations have been studied before in Shape-from-Template, yet no theoretical results were given on the existence or uniqueness of solutions. The equiareal model is much more widely applicable than isometry. This paper brings Monge’s theory, widely used for studying the solutions of nonlinear first-order PDEs, to the field of 3D reconstruction. It uses this theory to establish a theoretical framework for equiareal Shape-from-Template and answers the important question of whether it is possible to reconstruct a surface exactly with a much weaker prior than isometry. We prove that equiareal Shape-from-Template has a maximum of two local solutions sufficiently near an initial curve that lies on the surface. In addition, we propose an analytical reconstruction algorithm that can recover the multiple solutions. Our algorithm uses standard numerical tools for ODEs. We use the perspective camera model and give reconstruction results with both synthetic and real examples.

Statistical filtering of useful concrete creep data from imperfect laboratory tests

The reporting and evaluation of creep tests of concrete is complicated by the fact that creep is significant even for the shortest observable load durations. Compared to the strain after 0.1 s load duration, the strain at 2 h duration is typically 53% greater. Most experimenters have for decades been unaware of this fact. Consequently, the reported creep curves require correction by a time shift, which ranges from 0 to 2 h. This further implies a vertical shift of entire creep curve, important for all times up to structure lifetime. To filter out the errors, it is argued that, within an initial period during which the advance of hydration is negligible, which is normally about 1 day, the initial basic creep must follow a power law of the time. Creep test data from the literature are used to prove it. Corrections by time and deformation shifts are determined by minimization of the sum of squared deviations of the power law from the creep test data. For a fixed exponent n and time shift s, the optimization is reduced to linear regressions of two kinds, depending on whether the data are given in terms of either the compliance function or the creep coefficient. For both, the linear regression parameters depend nonlinearly on the chosen values of n and s. To avoid nonlinear optimization, which need not converge to the correct result, a set of many discrete values of n and s within their realistic ranges is selected and the (n, s) combination minimizing the objective function is obtained by a search. Enforcing a power law form of the initial creep curve is found to lead to better data fits. The optimum exponent n for the entire database is around 0.3, applicable to the time period cca (10 s, 1 day). After that, the exponent transits to about 0.1, and prior to that it is about 0.08. After filtering out the errors, the corrected database will allow better calibration of the general creep prediction model such as B3 or B4.

Detecting Method of Hardened Depth in Surface-Hardened Steel by Magnetic Field on Steel

Detecting Method of Hardened Depth in Surface-Hardened Steel by Magnetic Field on Steel

Outcomes and Resource Utilization in Robotic Mitral Valve Repair: Beyond the Learning Curve

BackgroundAfter the initial learning curve associated with mastering a robotic procedure, there is a plateau where operative time and complication rates stabilize. Our objective was to evaluate one surgeon's experience with robotic mitral valve repairs (MVRep) beyond the learning curve and to compare its effectiveness against the traditional open approach. MethodsData from Ronald Reagan University of California, Los Angeles Medical Center was prospectively collected from January 2008 to March 2016 to identify adult patients undergoing robotic MVRep. Operative times, complication rates, and cost for robotic versus open MVRep were compared using multivariate regressions, adjusting for comorbidities and previous cardiac surgeries. ResultsDuring the study period, 175 robotic (41%) and 259 open (59%) MVRep cases were performed at our institution. As the surgeon performed more robotic operations, there was a decrease in room time (554-410 min, P < 0.001), surgery time (405-271 min, P < 0.001), and cross-clamp times (179-93 min, P < 0.001). After application of a multivariate regression model, robotic MVRep was associated with lower odds of complications (odds ratio = 0.42, P = 0.001), shorter length of stay (β = −2.51, P < 0.001), and a reduction of 11% in direct (P = 0.003) and 24% in room costs (P < 0.001), but a 51% increase in surgery cost (P < 0.001). ConclusionsAs the surgeon gained experience with robotic MVRep, operative times decreased in a steady manner. Robotic MVRep had comparable outcomes to open MVRep and lower overall cost. The observed difference in costs is likely related to shorter length of stay and lower room cost with the robotic approach.

Effects of Hot-Pressing Temperature on the Magnetic Properties of Hot-Pressed Nanocrystalline Nd–Fe–B Magnets

Bulk nanocrystalline Nd–Fe–B magnets are prepared by the hot-pressing method at different temperatures of 450 °C–650 °C. The initial magnetization curve changes from a single-phase magnetization for the magnets prepared below 600 °C to a two-phase magnetization for the magnets prepared at 650 °C. The Henkel plot is also measured to investigate the exchange coupling interaction, and the results show that two positive peaks occur on the $\delta \text{M}$ curve for the magnet prepared at 650 °C. Scanning electron microscopy results show that the (Pr, Nd)-rich phase is aggregated along the gaps of the ribbons at 650 °C, and the (Pr, Nd)-rich phase behaves magnetically soft property. The inhomogeneous microstructure caused by the aggregation of (Pr, Nd)-rich phase with the temperature increase leads to the change in magnetization behaviors.

One Hundred Fifteen Cases of Pure Laparoscopic Living Donor Right Hepatectomy at a Single Center.

The pure laparoscopic approach to donor hepatectomy is being taken more often. However, few centers perform pure laparoscopic donor right hepatectomy (PLDRH) because it requires a high level of surgical skill. Studies reporting initial outcomes of PLDRH may prompt further implementation of the technique and help reduce initial learning curves at other transplant centers. This study reports performance of PLDRH at a single center with extensive experience of adult living donor liver transplantation. Data from 115 donors (and recipients) who underwent PLDRH between November 2015 and June 2017 were analyzed retrospectively. Subgroup analysis was performed to compare outcomes between the initial (November 2015 to October 2016) and more recent (November 2016 to June 2017) periods. During the initial period, 3 (2.6%) donors experienced complications greater than grade III on the Clavien-Dindo scale. By contrast, no donors developed complications during the recent period. The operative time (293.6 minutes vs 344.4 minutes; P < 0.001) and hospital stay (7.3 days vs 8.3 days; P = 0.002) were significantly shorter during the more recent period. Also, Δhemoglobin (Hb)%, calculated as ΔHb% = [(preoperative Hb - postoperative Hb)/preoperative Hb] × 100 (14.9% vs 17.5%; P = 0.042), and Δaspartate aminotransferase (AST)%, calculated as ΔAST% = [(peak AST - preoperative AST)/preoperative AST] × 100 (1048.9% vs 1316.6%; P = 0.009), were significantly lower during the recent period. Pure laparoscopic donor right hepatectomy is both feasible and safe when performed at a center experienced in adult living donor liver transplantation. Performance of about 60 PLDRHs over 1 year is sufficient to standardize the procedure.

Optimization of Casting in Early-onset Scoliosis

Early-onset scoliosis is a spine deformity that presents before the age of 3 years. When compared with age-matched controls, children with the condition are known to be at risk for significant morbidity and mortality. Although many works support the use of casting for this condition, the key technical factors to optimize the outcomes of casting are not clear. This work was designed to evaluate the role of frequency of radiographic imaging and over the shoulder straps in the outcomes of casting. Two surgeons at 2 centers followed nearly identical protocols for applying casts for early-onset scoliosis. At center A, the surgeon hoped to improve outcomes by obtaining radiographs after each cast and by reinforcing the cast with shoulder straps. At center B, the surgeon did not use shoulder straps and limited radiographs to once every 6 months. Children were included if they were 3 years or below of age and had a curve of ≥50 degrees at the time of the first cast and had a minimum of 3 years of follow-up. Center was used as a variable in a multivariable regression that also included: age at first cast, initial curve magnitude, and presence of a syrinx or genetic syndrome with the outcome of curve resolution. There were 40 children at center A, 9 of whom experienced resolution of their scoliosis. There were 36 children at center B, and 11 demonstrated scoliosis resolution. At center A, 2 of 10 children with a syrinx or genetic syndrome demonstrated curve resolution while 7 of 30 without these comorbidities did. At center B 3 of 10 children with a syrinx or genetic syndrome had curve resolution while 8 of 26 children without these comorbidities did. The children in group A demonstrated results very similar to the children of group B. Thus, the extra burden of shoulder straps and frequent radiographs are unnecessary. Level III.

Cumulative Sum Analysis of the Learning Curve for Modified Retroperitoneoscopic Living-Donor Nephrectomy

Objectives: To introduce our modified retroperitoneoscopic living-donor nephrectomy (RPLDN) techniques and estimate the learning curve. Methods: We retrospectively evaluated 121 consecutive donors who underwent modified RPLDN performed by a single surgeon. While the surgeon controlled the renal vessels, one hand was inserted through an abdominal incision for assistance. The kidney was manually retrieved through the abdominal incision. The learning curve was evaluated using the cumulative sum (CUSUM) method, which was a graphical method showing changes in individual surgical performance. Results: The mean operating time and warm ischemic time (WIT) were 129.4 min and 154.5 s, respectively. The mean estimated blood loss (EBL) was 44.4 mL. Regarding intraoperative complications, no open conversions or blood transfusions were required. The CUSUM learning curve included the following 3 unique phases: phase 1 (the initial 32 cases), representing the initial learning curve; phase 2 (the middle 38 cases), representing expert competence; and phase 3 (the final 51 cases), representing mastery. Conclusions: Our modified method has the advantages of a short operating time, an optimized WIT, a low EBL, and acceptable complication rates. The surgeon completed the initial learning phase of RPLDN after 32 cases and could effectively perform RPLDN after 70 cases.

Shorter Anesthesia Time and Improved Initial Curve Correction with an Alternative Risser Casting Technique

Shorter Anesthesia Time and Improved Initial Curve Correction with an Alternative Risser Casting Technique

Study on Hysteresis Model of Welding Material in Unstiffened Welded Joints of Steel Tubular Truss Structure

The weld form of intersecting joints in a steel tubular truss structure changes with the various intersecting curves. As the key role of joints in energy dissipation and seismic resistance, the weld is easy to damage, as a result the constitutive behavior of the weld is different from that of the base metal. In order to define the cumulative damage characteristic and study the constitutive behavior of welded metal with the influence of damage accumulation, low-cycle fatigue tests were carried out to evaluate overall response characteristics and to quantify variation of cyclic stress amplitude, unloading stiffness and energy dissipation capacity. The results show that the cyclic softening behavior of welding materials is apparent, however, the steel shows hardening behavior with the increase of cyclic cycles, while the cyclic stress amplitude, unloading stiffness, and energy dissipation capacity of the welding materials degenerate gradually. Based on the Ramberg–Osgood model and introducing the damage variable D, a hysteretic model of welding material with the effect of damage accumulation was established, including an initial loading curve, cyclic stress-strain curve, and hysteretic curve model. Further, the evolution equation of D was also built. The parameters reflecting the damage degradation were fitted by the test data, and the simulation results of the model were proved to be in good agreement with the test results.

The robotic-assisted pancreaticoduodenectomy with vascular reconstruction: our personal experience

Introduction: Firstly described in 2003, the widespread of robotic pancreaticoduodenectomy (PD) is still slow. The complexity of the procedure, the higher cost of this technology and the lack of a specific training confined this procedure to high-selected centres. We investigated the perioperative outcomes of our first 50 robotic PD including our initial experience with resection and reconstruction of superior mesenteric/portal vein (PD-SMV/PV) in order to evaluate the safety and feasibility of this approach. Methods: We performed a retrospective analysis from January 2012 to April 2017 of our prospectively maintained database on robotic pancreatic surgery. Results: A total of 50 patients during the time period evaluated underwent to robotic PD. We performed 45 robotic PD and 5 robotic PD-SMV/PV. The overall operative time was 425 min (290–550), with a reduction over the course of learning curve, while the median blood loss was 170 ml (30–700). We observed a low conversion rate 5/50 (10%) and an acceptable overall postoperative morbidity rate of 12/50 (24%). The pancreatic fistula rate was 8/50 (16 %), but only 3 (6%) clinically significant. We achieved a R0 resection rate in 46/50 (92%) of patients with a mean lymph nodes retrieved of 20.5 (17–25). The reoperation rate for all series was low 6/50 (12%) as well as the 90-day mortality rate 3/50 (6%). Conclusions: Despite our initial learning curve, the robotic approach seems to be safe and effective giving some potential advantages in terms of estimated blood loss and conversion rate, preserving a good oncologic adequacy.

Irreversible permeability and DC losses relationship for selected soft magnetic materials

The paper presents the relations for the irreversible permeability at initial magnetization curve, derived and verified for selected soft magnetic materials (FeSi and NiFe steel sheets, compacted and sintered NiFe powder, non-sintered warm compacted Fe powder and Fe-phenolphormaldehyde resin composites). The derivation was based on the Steinmetz law for DC energy losses. Verification of the relations was performed by the comparison of experimental and calculated dependences of the irreversible permeability versus magnetic induction, where the empirical functions in the relations were found. For NiFe steel sheet and all composites the functions were allowed to be taken as constants with a good accuracy. The relations were so proposed for each of the selected soft magnetic materials within the induction ranges covering the ranges of validity of the Steinmetz law.

Infantile Idiopathic Scoliosis: Factors Affecting EDF Casting Success

Study DesignIRB-approved retrospective single cohort study. ObjectivesTo review our ten-year history with EDF (Elongation Derotation Flexion) casting in patients with infantile idiopathic scoliosis (IIS) to better understand which factors predict successful outcomes. Summary of Background DataNumerous studies have demonstrated the efficacy of EDF casting in the treatment of progressive infantile idiopathic scoliosis. But none have reproduced the success of Mehta’s even with early intervention. MethodsPatients with IIS treated with EDF casting with a minimum 24-month follow-up were included. Radiographs and clinical records were reviewed. Age, sex, and curve type were documented. Precast, traction, in cast, in brace, and final Cobb angles were measured and recorded. Outcomes were defined by Cobb angle at final follow-up out of cast or brace. Patients were considered cured if the final Cobb angle was <10°, palliated at 10°–45°, and failed if they required surgical treatment. ResultsSixty-three patients with IIS were reviewed. Thirty-two were excluded for incomplete records or insufficient follow-up, leaving 31 patients. No patients progressed to surgical intervention during the study. Patients with a Cobb angle >10° in the final cast were 7.3 times more likely to fall into the palliative range at the most recent follow-up than if their Cobb angle was 10° or less even when adjusted for age. Earlier age at onset of casting (14.9 vs. 21.1 months) was not statistically significant (p=.073). Magnitude of initial curvature, flexibility, initial correction, sex, and curve type were also not found to be significant. ConclusionEDF casting is a valid treatment option for IIS with a high cure rate. Major Cobb angle at the end of casting is most predictive of outcome. Cobb angles >10° at the end of casting had a 7.3 times greater risk of falling into the palliated category versus Cobb angles less than or equal to 10° even when adjusted for age. Initial curve magnitude, curve flexibility, sex, and curve type were not predictive. Level of EvidenceLevel IV.

Probabilistic strength based matrix crack evolution model in multi-directional composite laminates under fatigue loading

A model to predict the matrix crack evolution in multi-directional (MD) polymer matrix composite laminates under in-plane fatigue loading is presented in the current work. Unlike matrix crack evolution under static loading, the matrix cracks in off-axis plies do not form tunneling cracks under fatigue loading; rather, they initiate and grow with increasing load cycles. A probabilistic strength based criterion for matrix crack initiation in off-axis plies based on a Weibull distribution for in situ ply strength variation has been used. An oblique co-ordinate based shear lag analysis has been used to estimate the stresses in the cracked laminate. Smith Watson Topper (SWT) parameter has been used to model the number of cycles to initiate the first matrix crack, and log-normal probability distribution has been used to handle the scatter in crack initiation life. The matrix crack growth rate has been modeled using Paris law based on mixed mode effective stress intensity factor. Using the crack initiation curve and strength degradation based on Palmgren-Miner damage rule, new crack initiation has been simulated. Few parameters needed for the threshold stress intensity and saturation crack spacing have been identified from a reference stress data of cross-ply laminate. The crack density evolution has been simulated for cross-ply and MD-laminates under various constant amplitude in-plane fatigue stress levels. The matrix crack density evolution and its stiffness degradation predictions with the number of cycles have been compared with existing experimental values. A good correlation is found to exist between the experimental data and predictions for both cross-ply and MD-laminates.

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters

BACKGROUND CONTEXT Minimally invasive oblique lateral lumbar interbody fusion (MIS-OLIF) using a tubular retractor and pre-psoas approach has recently been gaining popularity because of its potential for minimizing para-spinal muscle damage and reducing recovery time. However, the published literature has not characterized the surgeon's learning curve with the technically demanding technique of a minimally invasive oblique lateral lumbar interbody fusion (MIS-OLIF). PURPOSE The purpose of this study is to define and analyze the learning curve for MIS-OLIF with a single spine surgeon's experience based on intra- and perioperative parameters. STUDY DESIGN/SETTING This study is retrospective analysis of single surgeon's consecutive case series in a single institution. PATIENT SAMPLE Fifty-seven consecutive patients with single or multilevel degenerative lumbar diseases who were treated by MIS-OLIF were included in the study. Surgeries were performed using oblique pre-psoas approach with a tubular retractor, and a cage was inserted using an orthogonal maneuver by a single surgeon. The corresponding segments were fixed with additional percutaneous pedicle screws. MIS-OLIF without posterior decompression was performed in 33 cases and MIS-OLIF plus posterior decompression was performed in 24 cases. OUTCOME MEASURES Corrected operative time per level, operative blood loss, postoperative drainage, transfusion rate, and ambulation recovery time were measured. Intraoperative and postoperative complication incidences were also identified. Clinical results were assessed using the visual analogue scale (VAS). METHODS The learning curve was assessed using a logarithmic curve-fit regression analysis. In the single-level OLIF group (n=21), 12 patients were defined as the “early” group (among the first 30 cases of the series), and the subsequent 9 cases were defined as the “late” group for comparison. RESULTS Corrected operative time gradually decreased as the series progressed, and an asymptote was reached after about 30 cases. Average VAS scores for lower back pain and radiating pain also significantly decreased from an average of 6.9-3.8 and 7.6-2.5, respectively. In the single-level OLIF series, operative time was significantly shorter in the late group (99±54 minutes) than the early group (141±21 minutes) and blood loss during the operation was significantly reduced in the late group (482±269 mL) compared with the early group (542±157 mL). Ambulation recovery time and VAS scores for back and leg pain did not differ between the two groups. There were two cases of retroperitoneal hematoma in the early second group requiring revision surgeries CONCLUSIONS The MIS-OLIF is a technically difficult procedure to the practicing spine surgeon with regard to unfamiliar retroperitoneal approach. Although it is not easy to master this minimally invasive technique, operative time and blood loss improved with the surgeon's experience. After the initial learning curve, this technique could be an effective and reliable option for the surgical treatment of lumbar degenerative disease. Further studies are warranted to delineate the methods to minimize the complications associated with the learning curve.

P3873Introduction of leadless transcatheter intracardiac pacing: assessing the initial learning curve

P3873Introduction of leadless transcatheter intracardiac pacing: assessing the initial learning curve

The Effect of Laser Energy on the Initial Plasma Characteristics of Laser-Triggered Vacuum Switch

With the development of pulsed-power technology, more and more applications require high-voltage and heavy-current pulse switches. Laser-triggered vacuum switch combines laser technology, vacuum switch technology, and three-electrode trigger switch technology, and has the advantages of heavy current capability, good isolation from the main circuit, and short delay time. In this paper, the 1-D thermal conduction model was developed to analyze the influence of laser energy on the velocity of initial plasma. The relationship between the ablation area and the laser energy was derived. The theoretical analysis can be verified by the relationship between the trigger delay time and laser energy and the initial plasma microcurrent curve in the experiments.

On the importance of magnetic material characterization for the design of particle accelerator magnets

In this paper, the importance of magnetic material measurements in the framework of the design of magnets for particle accelerator is discussed. In particular, five samples of different ferromagnetic materials are analyzed experimentally and compared with literature results. These materials have been (or will be) used for producing yokes for several normal-conductor magnets at CERN, such as REX-ISOLDE main dipole, ELENA dipole and quadrupole, and SESAME dipole. The comparison with literature shows several disagreements. The main one of them is analyzed in detail in a case study based on finite elements simulation of a quadrupole magnet installed in CERN. This analysis shows that a good knowledge of the yoke initial magnetization curve is important to guarantee a given level of magnet performance, especially concerning its field quality.