Initial Curve Research Articles

Curvature flow with driving force on fixed boundary points

In this paper, we consider the curvature flow with driving force on fixed boundary points in the plane. We give a general local existence and uniqueness result of this problem with \(C^2\) initial curve. For a special family of initial curves, we classify the solutions into three categories. Moreover, in each category, the asymptotic behavior is given.

On Curvature Flow with Driving Force Starting as Singular Initial Curve in the Plane

We consider a family of axisymmetric curves evolving by its curvature with driving force in the plane. However, the initial curve is oriented singularly at origin. We investigate this problem by level set method and give some criteria to judge whether the interface evolution is fattening or not. In the end, we can classify the solutions into three categories and provide the asymptotic behavior in each category. Our main tools in this paper are level set method and intersection number principle.

Growing Rods Are an Effective Fusionless Method of Controlling Early-Onset Scoliosis Associated With Neurofibromatosis Type 1 (NF1): A Multicenter Retrospective Case Series.

Spinal deformities associated with neurofibromatosis type 1 (NF1) often have an early onset. These curves frequently develop dysplastic features. Rapid progression is common, and is often difficult to control with casting or bracing. Spinal fusion at a young age can potentially interfere with chest and trunk growth. Growing rods (GRs) have been used in early-onset scoliosis (EOS) effectively. The purpose of this study was to evaluate GR use in NF1. Retrospective data collection was performed from a multicenter EOS database with additional patients from our own institute. Each patient had a genetic diagnosis of NF1 and was treated with GR. Results were compared with reported results of GR in EOS in the literature. Fourteen patients from 5 centers underwent a total of 71 procedures with an average follow-up of 54 months. Mean age at surgery was 6.8 years. Means of initial and final curves were 74 and 36 degrees, respectively (51% correction). Spine grew at an average of 39 mm (11.2 mm per year). Implant-related complications were the most common (8/14, 57%), including failure of proximal construct (5/14), rod breakage (2/14), and prominent implants (1/14). There was no significant difference between screws and hooks as proximal anchors (Fischer test). Two patients had deep infection that needed debridement. This retrospective pooled data study is the first report on the treatment of early-onset NF1 scoliosis with GRs. The use of GRs in these patients effectively controls the spinal deformity and facilitates growth of the spine. The complications were no greater than those seen in other conditions causing EOS. Failure of proximal anchors was found to be the most common complication. Level IV-retrospective case series.

Prospective evaluation of vesicourethral anastomosis outcomes in robotic radical prostatectomy during early experience in a university hospital

ABSTRACTPurpose:Robotic assisted radical prostatectomy (RARP) presents challenges for the surgeon, especially during the initial learning curve. We aimed to evaluate early and mid-term functional outcomes and complications related to vesicourethral anastomosis (VUA), in patients who underwent RARP, during the initial experience in an academic hospital. We also assessed possible predictors of postoperative incontinence and compared these results with the literature.Materials and Methods:We prospectively collected data from consecutive patients that underwent RARP. Patients with at least 6 months of follow-up were included in the analysis for the following outcomes: time to complete VUA, continence and complications related to anastomosis. Nerve-sparing status, age, BMI, EBL, pathological tumor staging, and prostate size were evaluated as possible factors predicting early and midterm continence. Results were compared with current literature.Results:Data from 60 patients was assessed. Mean time to complete VUA was 34 minutes, and console time was 247 minutes. Continence in 6 months was 90%. Incidence of urinary leakage was 3.3%, no patients developed bladder neck contracture or postoperative urinary retention. On multivariate analysis, age and pathological staging was associated to 3-month continence status.Conclusion:Our data show that, during early experience with RARP in a public university hospital, it is possible to achieve good results regarding continence and other outcomes related to VUA. We also found that age and pathological staging was associated to early continence status.

Magnetic and Dielectric Properties of Y3−x Sm x Fe5O12 (x = 0.0 to 3.0)

Single-phase polycrystalline samples of Y3−x Sm x Fe5O12 (x = 0.0–3.0) were prepared by using a solid-state reaction method. The lattice constant is found to increase from 12.372 A for x = 0.0 to 12.524 A for $x = 3.0$ . The substitution of Sm3+ at Y3+ site is confirmed from the red shift of Raman F2g mode. Magnetization loops measured at room temperature and the analysis of initial magnetization curves show that saturation magnetization value decreases with an increase in Sm concentration due to the possible antiferromagnetic interaction. On the other hand, temperature variation of magnetization plots shows that all the samples exhibit ferrimagnetic transition with transition temperature in the range of 550 K for x = 0.0 to 573 K for $x = 3.0$ . The dielectric constant increases upon Sm substitution, and the analysis of impedance and dielectric spectra shows the contribution of both grains and grain boundaries.

Does Previous Laparoscopic Experience Influence Basic Robotic Surgical Skills?

Studies addressing the effect of laparoscopic experience on robotic skills have produced conflicting results. This study aimed to compare simulated robotic surgical tasks using the virtual reality simulator dV-Trainer between laparoscopically experienced surgeons and first-year surgical residents. A cross-sectional study. Participants completed 4 trials of the following tasks on the dV-Trainer: Peg Board 2, Ring and Rail 1, and Suture Sponge 1. Performance was recorded using a computerized built-in scoring algorithm. Scores and metrics were compared between groups 1 and 2 and between the first and subsequent trials. Hospital de Clínicas, Porto Alegre, Brazil, a tertiary care teaching hospital. Twenty laparoscopically experienced surgeons (group 1) and 20 first-year surgical residents (group 2). All participants completed the study. The overall scores for Peg Board 2 (738.04 ± 267.83 vs 730.39 ± 225.31; p = 0.57), Ring and Rail 1 (919.03 ± 242.69 vs 965.84 ± 222.96; p = 0.13), and Suture Sponge 1 (563.62 ± 185.50 vs 560.99 ± 152.71; p = 0.67) did not differ significantly between groups 1 and 2. Group 1 had better results for master workspace range in Peg Board 2 and Ring and Rail 1. Group 2 had higher scores for economy of motion in Peg Board 2 and Ring and Rail 1 and for excessive instrument force in Ring and Rail 1. In both groups, the overall scores in the third and fourth trials were significantly higher than those in the first trial. There are no significant differences in the performance of simulated robotic surgical tasks between laparoscopically experienced surgeons and laparoscopically naïve surgical residents. Some slight differences were observed in specific metrics, but these differences were not sufficient to change the final results. We may assume that laparoscopic experience should not be an essential step in the initial learning curve of robotic surgery.

Salient object segmentation based on active contouring.

Traditional saliency detection algorithms lack object semantic character, and the segmentation algorithms cannot highlight the saliency of the segmentation regions. In order to compensate for the defects of these two algorithms, the salient object segmentation model, which is a novel combination of two algorithms, is established in this paper. With the help of a priori knowledge of image boundary background traits, the K-means++ algorithm is used to cluster the pixels for each region; in line with the sensitivity of the human eye to color and with its attention mechanism, the joint probability distribution of the regional contrast ratio and spatial saliency is established. The selection of the salient area is based on the probabilities, for which the region boundary is taken as the initial curve, and the level-set algorithm is used to perform the salient object segmentation of the image. The curve convergence condition is established according to the confidence level for the segmented region, thus avoiding over-convergence of the segmentation curve. With this method, the salient region boundary is adjacent to the object contour, so the curve evolution time is shorter, and compared with the traditional Li algorithm, the proposed algorithm has higher segmentation evaluation scores, with the additional benefit of emphasizing the importance of the object.

Filtration efficiency and loading characteristics of PM2.5 through commercial electret filter media

Abstract Atmospheric PM2.5 pollution has been attracting much public attention for decades because of its adverse health effects. China and other Asian countries are frequently exposed to high PM2.5 concentrations, and filtration techniques through HVAC systems and indoor air cleaners are often used to mitigate PM2.5 in indoor environments, e.g. commercial and residential buildings, schools, and hospitals. Electret filter media provide lower pressure resistance and are frequently used in air purification systems. However, existing test standards, e.g. ASHRAE 52.2-2012, only challenge filters with particles larger than 300 nm which makes it impossible to assess filter performance at the most penetrating particle size (MPPS) since the inherent MPPS of electret media is smaller than 100 nm. In this study for investigating the performance of the electret filter media against PM2.5, the filter media were first challenged with monodisperse particles of 3–500 nm (the majority of PM2.5 number concentration resides in this range) at face velocities of 0.05, 0.25 and 0.5 m s−1 to obtain initial efficiency curves. Then the time-dependent efficiencies during the loading process were investigated using polydisperse NaCl particles which mimicked the size distribution of typical atmospheric PM2.5. Additionally, the effects of fiber charge and particle charge on initial efficiency and loading characteristics were evaluated by intentionally removing the fiber charges and charging the particles bipolarly (neutralized) or unipolarly. Results showed that the effects of fiber and particle charges on initial efficiency enhancement depended on particle sizes. The polarization force enhanced the collection of particles larger than ∼20 nm particles, the image force enhanced the collection of particles smaller than ∼100 nm, and the Columbic force enhanced the collection of particles smaller than ∼300 nm. Charging the particles unipolarly can slow down the reduction of electrical efficiency during loading and enhance the minimum efficiency by 10–30% for 50–500 nm particles, compared to that of bipolarly charged particles. A model using an electric degradation parameter and mechanical collection efficiency raising factor was applied to explain the performance of electret media in loading processes.

Cloud Computing for MATLAB and R Users

Cloud based computing has tremendous potential for academia in general and researchers in particular. The ability to store, read and manipulate large data sets is increasingly important to be on the cutting edge of research. While most researchers have extensive programming skills, they generally are not computer scientists. A number of cloud based, virtual work spaces have been developed which can bring enormous computing advantages over any desktop or laptop. However, the instructions to get up and running in the cloud are often overwhelming, and require a significant investment of time. There is an initial steep learning curve associated with developing a high performance computing environment that several times becomes an obstacle that prevents many to benefit the most from using the cloud. This paper seeks to demystify the process and get the reader up and running very quickly. Once this initial process is over and the reader is proficient on these issues, performing computational chores that would take days on a desktop can be done in minutes. We next show the way the readers can implement their research using two well-known computer programs, MATLAB and R.

Crystal and magnetic properties of 57Fe doped MnAs for magnetic refrigeration application

The Mn1−x 57Fe x As (x = 0.001, 0.003, 0.005) compounds for magnetic refrigeration application were synthesized by using a solid-vapor reaction method. We have investigated the crystallographic and magnetic properties of Mn1−x 57Fe x As (x = 0.001, 0.003, 0.005) samples by using x-ray diffractometer (XRD), vibrating sample magnetometer (VSM), superconducting quantum interference device (SQUID), and Mossbauer spectrometer. The XRD patterns, revealed that all samples exhibited hexagonal space group P63/mmc below Curie temperature (T C ), while above T C they belong to the orthorhombic space group Pnma. The temperature-dependent magnetization curves under 200 Oe between 4.2 and 320 K showed a large hysteresis in the magnetization as a function of the temperature. To analyze the meagnetocaloric effect, the value of magnetic entropy (−ΔS M ) was calculated from the isothermal initial curves up to 5 T at various temperatures. Mossbauer spectra of Mn0.997 57Fe0.003As sample were taken at various temperatures ranging from 4.2 to 315 K.

How Is Pulmonary Function and Exercise Tolerance Affected in Patients With AIS Who Have Undergone Spinal Fusion?

Study DesignProspectively enrolled AIS patients who underwent spinal fusion, with 2 year follow-up. ObjectivesTo evaluate the cardiovascular fitness and activity level in patients with AIS pre– and post–spinal fusion and to determine if initial curve magnitude or pulmonary function is predictive of exercise capacity. Summary of Background DataResearchers have tried to link pulmonary function testing (PFT) to exercise capacity; the results are mixed. Some report no improvement in PFTs or aerobic activity after surgical correction, and PFT measures were not predictive of exercise capacity. Conflicting results have shown Vo2max results to fall within normal range in AIS patients while PFTs show minimal impairment. MethodsAIS patients underwent PFT and oxygen consumption (VO2) testing during a submaximal graded exercise test (GXT) pre– and post–spinal fusion. Vo2max was predicted in those patients who completed the test to 85% of maximal heart rate. Pre- to postoperative changes were assessed and then compared to age-matched control subjects. Correlations between Vo2max and curve severity, pulmonary function, and activity level were assessed. ResultsThirty-seven patients participated. Vo2max was predicted in 23 patients pre- and postoperation. There was a significant reduction in Vo2max postfusion (39.5 ± 6.5 mL/kg/min vs 42.1 ± 8.1 mL/kg/min, p = .033); however, compared with controls (40.5 ± 6.5 mL/kg/min), all data were within the normal range (p > .05). AIS patients reporting high activity had significantly greater Vo2max than those reporting low activity both pre and postoperatively, but this difference only met statistical significance preop (p < .05). Curve magnitude and PFT measures were not found to correlate with Vo2max (p > .05). ConclusionsVo2max in patients with AIS is within normal range both pre- and postfusion. Pulmonary limitations are accommodated for with a slightly increased breathing rate and a slightly reduced overall workload. Activity level rather than curve severity affects Vo2max outcomes following fusion in AIS.

Metal-Organic Framework Template Derived Porous CoSe2 Nanosheet Arrays for Energy Conversion and Storage.

Porous CoSe2 on carbon cloth is prepared from a cobalt-based metal organic framework template with etching and selenization reaction, which has both a larger specific surface area and outstanding electrical conductivity. As the catalyst for oxygen evolution reaction, the porous CoSe2 achieves a lower onset potential of 1.48 V versus the reversible hydrogen electrode (RHE) and a small potential of 1.52 V (vs RHE) at an anodic current density of 10 mA cm-2. Especially, the linear sweep voltammogram curve of the porous CoSe2 is in consist with the initial curve after durability test for 24 h. When tested as an electrode for supercapacitor, it can deliver a specific capacitance of 713.9 F g-1 at current density of 1 mA cm-2 and exhibit excellent cycling stability in that a capacitance retention of 92.4% can be maintained after 5000 charge-discharge cycles at 5 mA cm-2. Our work presents a novel strategy for construction of electrochemical electrode.

Thoracoscopic Esophageal Atresia Repair in Pakistan: Early Learning Curve

Background: Esophageal atresia is rare congenital anomaly, which is traditionally repaired by open thoracotomy. Thoracoscopic esophageal atresia repair has evolved as an effective and safe technique.Material and Methods: This is a retrospective review of 11 cases of esophageal atresia (type C), between June 2015 to May 2016. The objective of study is to describe our initial learning curve of thoracoscopic esophageal atresia repair.Results: Out of 11 patients, initial 4 underwent video assisted technique through single incision of 2 cm to visualize the exact video-scopic anatomy and to do few steps if possible. In last 7 cases, steps were completed with both ends mobilization and intracorporeally single layer interrupted stitching of esophagus. Complications encountered in 3 patients like esophageal leak in one managed conservatively, stenosis and reflux in one patient each.Conclusion: Thoracoscopic esophageal atresia repair is challenging and demanding surgery. Every surgeon has a learning curve before successful thoracoscopic repair which requires skills and learning under supervision of experienced surgeons.

Effects of the Schroth exercise on idiopathic scoliosis: a meta-analysis.

The purpose of this study was to examine the effects of the Schroth exercise on idiopathic scoliosis. The overall effect size was analyzed in 15 primary studies and a subgroup analysis of the standardized mean differences of effect sizes from 15 primary studies was also conducted. We used PUBMED, MEDLINE, NDSL, EMBASE, and Web of Science. The key terms used in these searches were "Schroth," "scoliosis-specific exercise," "scoliosis," and "idiopathic scoliosis." Cobb's angle, asymmetry, angle of trunk rotation (ATR), strength of back extensor, strength of trunk flexor, quality of life (QOL), balance, chest expansion, and pulmonary function were coded as outcome measures for computing effect sizes. Potential moderating variables of the Schroth exercise included: 1) pre-intervention severity of the scoliosis; 2) duration; and 3) specific types of Schroth exercise. The overall effect size of the Schroth exercise is high (g=0.724). In addition, Schroth exercise may be more beneficial for scoliosis patients who have a 10 to 30° Cobb's angle than for those with a greater than 30° Cobb's angle. Patients should practice the exercise for at least one month to have a better effect. Thus, therapists should consider patients' initial curve status and exercise duration before prescribing the Schroth exercise program. Core muscle strength was most influenced, and structural deformity also changed after the Schroth exercise. In sum, the Schroth exercise is a recommended treatment method for scoliosis patients.

The influence of previous robotic experience in the initial learning curve of laparoscopic radical prostatectomy.

ABSTRACTIntroduction:This study analyzed the impact of the experience with Robotic-Assisted Laparoscopic Prostatectomy (RALP) on the initial experience with Laparoscopic Radical Prostatectomy (LRP) by examining perioperative results and early outcomes of 110 patients. LRPs were performed by two ro-botic fellowship trained surgeons with daily practice in RALP.Patients and Methods:110 LRP were performed to treat aleatory selected patients. The patients were divided into 4 groups for prospective analyses. A transperitoneal approach that simulates the RALP technique was used.Results:The median operative time was 163 minutes (110-240), and this time significantly decreased through case 40, when the time plateaued (p=0.0007). The median blood loss was 250mL. No patients required blood transfusion. There were no life-threatening complications or deaths. Minor complications were uniformly distributed along the series (P=0.6401). The overall positive surgical margins (PSM) rate was 28.2% (20% in pT2 and 43.6% in pT3). PSM was in the prostate apex in 61.3% of cases. At the 12-month follow-up, 88% of men were continent (0-1 pad).Conclusions:The present study shows that there are multiple learning curves for LRP. The shallowest learning curve was seen for the operative time. Surgeons transitioning between the RALP and LRP techniques were considered competent based on the low perioperative complication rate, absence of major complications, and lack of blood transfusions. This study shows that a learning curve still exists and that there are factors that must be considered by surgeons transitioning between the two techniques.

Influence of NiO Nanoparticles on Magnetic Properties of Neodymium Doped Tellurite Glasses

Series of glass samples with composition (72.5-x)TeO2-15MgO-10Na2O-2.5Nd2O3-xNiO where 1.0 ≤ x ≤ 2.5 mol% are prepared using melt quenching method. The glasses are characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The XRD spectra confirmed the amorphous nature of prepared glasses. TEM images manifest the existence of NiO NPs which are homogeneously distributed in the glass matrix. The magnetization M(H) curve reveals that the glass displays an anomalous hysteresis behavior at room temperature. It is observed that M(H) is dependent on the NiO content. The initial curve of magnetization lies positively as a function of the magnetic field under 1000 H (O.e).

An Approach to Estimate Wetting Path of Soil–Water Retention Curve from Drying Path

The Soil–Water Retention Curve (SWRC) is an important part of any constitutive relationship for unsaturated soils. The SWRC is a hysteretic curve, and geotechnical problems such as unsaturated slope stability analysis can lead to different results based on each branches. Although the majority of SWRC models can just predict the initial drying curve, the wetting path in many practical projects is critical and in fact occurs. In this research, an approach is presented to estimate the wetting path of genetic-based model as a sample of accurate models using initial drying. For this purpose, based on Feng and Fredlund (in: Proceedings of the 52nd Canadian geotechnical conference, Regina, Sask, 1999) hysteresis model of SWRC and using more than 180 soil samples, which are results from pressure plate tests carried out on clay, silty clay, sandy loam and loam, statistical values are suggested for the gravimetric water content difference of main drying and wetting curves at various suctions. The results show acceptable accuracy of the method.

Endoscopic anterior component separation: a novel technical approach.

Open anterior release of the external oblique fascia to enable midline closure of large abdominal wall defects is associated with relevant morbidity due to extensive subcutaneous dissection. Using endoscopic techniques, wound complications can be minimized. However, identification of the correct entry point (e.g. for balloon trocar insertion) can be challenging especially in adipose patients. We therefore present a technical modification facilitating the entire procedure. A novel technique for endoscopic anterior component separation using a trocar system allowing blunt and sharp dissection under direct vision is described. This brief communication also contains our initial experience and learning curve with this novel approach. Endoscopic release of the external oblique fascia was successfully performed 29 times in a total of 15 patients. Body mass index accounted for 30.8kg/m2 (median; range 21.6-42.5). Transverse width of midline defect accounted for 7cm (median; range 4-12). Subsequent hernia repair was successfully done using sublay mesh reinforcement (n=13) or a laparoscopic intraperitoneal onlay mesh procedure (n=2) with midline closure in all cases. One hematoma was seen at site of release managed conservatively. Using a trocar system allowing blunt and sharp dissection under direct vision may be a viable option for the endoscopic anterior component separation.

Non-linear soil modelling by correction of the hysteretic damping using a modified Iwan model together with Masing rules

Even at this time, there is no universal mathematical model that can adequately describe the actual behaviour of cyclically loaded soils but rather thoughtful attempts were made to describe the appropriate behaviour for a well-defined soil type. The overestimation of damping ratio at large strain can result when the hysteretic damping is calculated using the unloading–reloading stress–strain hysteresis loop obtained by the second Masing rules. In this paper, a method is proposed to overcome the encountered problem of overestimation of hysteretic damping by including a factor modulus to correct the hysteretic damping in order to have a good agreement between numerical and experimental results. By this method, the initial hyperbolic backbone curve is segmented by a series of linear elements and the Masing rules are associated with the Iwan model. For low shear strains (γ ≤ 3.10−2), a corrector factor λ1 (rather than the reduction factor) will be in the interval (1 ≤ λ1 ≤ 7) and in the interval (0.4 ≤ λ1 ≤ 1.0) for the other cases (γ > 3.10−2), in such way that the obtained results will be in good agreement with experimental ones.

Ferromagnetism in Fe-doped BaTiO3 Ceramics

Polycrystalline samples of BaTi1−xFexO3 (x = 0.00–0.30) are prepared by solid-state reaction method and their structural and magnetic properties are studied. Detailed investigation of XRD patterns reveal the coexistence of tetragonal (space group P4mm) and hexagonal phases (space group P6 3/mmc) for x ≥ 0.1. Magnetic measurements reveal room-temperature ferromagnetism in x = 0.15–0.3 samples, and their ferromagnetic transition temperature increases from 397 K for x = 0.15 to 464 K for x = 0.3. The initial magnetization curves for x = 0.15–0.3 are analyzed in terms of bound magnetic polaron (BMP) model. The analysis of susceptibility data in the paramagnetic region by Curie-Weiss law confirms the ferromagnetic transition for x ≥ 0.15 and the effective magnetic moment systematically increases with increase in Fe concentration.