Optimising Time-Frequency Distributions: A Surface Metrology Approach

Time-frequency signal processing offers a significant advantage over temporal or frequency-only methods, but representations require optimisation for a given signal. Standard practice includes choosing the appropriate time-frequency distribution and fine-tuning its parameters, usually via visual inspection and various measures-the most commonly used ones are based on the Rényi entropies or energy concentration by Stanković. However, a discrepancy between the observed representation quality and reported numerical value may arise when the filter kernel has greater adaptability. Herein, a performance measure derived from the Abbot-Firestone curve similar to the volume parameters in surface metrology is proposed as the objective function to be minimised by the proposed minimalistic differential evolution variant that is parameter-free and uses a population of five members. Tests were conducted on two synthetic signals of different frequency modulations and one real-life signal. The multiform tiltable exponential kernel was optimised according to the Rényi entropy, Stanković's energy concentration and the proposed measure. The resulting distributions were mutually evaluated using the same measures and visual inspection. The optimiser demonstrated a reliable convergence for all considered measures and signals, while the proposed measure showed consistent alignment of reported numerical values and visual assessments.

Treatment of Chiari Malformation and Concomitant Paediatric Scoliosis Long-Term Follow-Up in One Major Referral Centre in the UK

OBJECTIVE

Paediatric scoliosis (PS) and Chiari malformation type 1 (CM-1) have been reported to be associated with each other. Scoliosis curvature is a common finding among patients operated for CM-1, and curve development has been related to it. We report a cohort of PS and CM-1 patients managed with posterior fossa and upper cervical decompression (PFUCD) by a single surgeon, with an average of two years of follow-up.

METHODS

We present a retrospective cohort in a single referral centre for patients with CM-1 and PS.

RESULTS

From 2011 to 2018, we identified fifteen patients with CM-1 and PS; eleven underwent PFUCD, ten had symptomatic CM-1, and one had asymptomatic CM-1 but showed curve progression. The remaining four CM-1 patients were asymptomatic and were hence treated conservatively. The average follow-up post-PFUCD was 26.2 months. Scoliosis surgery was performed in seven cases; six patients underwent PFUCD prior to the scoliosis correction. One scoliosis case underwent surgery in the presence of mild CM-1 treated conservatively. The remaining four cases were scheduled for scoliosis correction surgery, while three were managed conservatively, with one case lost to follow-up. The average time between PFUCD and scoliosis surgery was 11 months. None of the cases had intraoperative neuromonitoring alerts or perioperative neurological complications.

CONCLUSION

CM-1 with concomitant scoliosis can be found. Symptomatic CM-1 might require surgery, but as we discovered, PFUCD had negligible effect on curve progression and the future need for scoliosis surgery.

Do Preoperative Supine Radiographs Predict Postoperative Residual Lumbar Curvatures in Adolescent Idiopathic Scoliosis? A Retrospective Cohort Study

STUDY DESIGN

Retrospective comparative study.

OBJECTIVES

This study compares supine vs bending flexibility radiographs and evaluates their ability to predict residual postoperative lumbar curvature after selective thoracic fusion for Lenke 1 and 2 curves across different lumbar modifiers (A, B, and C) in adolescent idiopathic scoliosis (AIS).

METHODS

This was a retrospective review of AIS Lenke 1 and 2 patients who underwent posterior fusion. All patients had preoperative flexibility radiographs including side-bending and supine posteroanterior (PA) films, in addition to pre- and post-operative standing PA and lateral radiographs. We used SurgiMap 2.0 software for all radiographic measurements. Pearson correlations and linear regression models were developed in SAS.

RESULTS

A total of 86 patients were included mean age 14.9 years and follow-up 72.3 months. Preoperative supine lumbar Cobb angle and preoperative side-bending Cobb angles had similar, positive correlations with postoperative lumbar Cobb angle, r = .55 (P < .001) and r = .54 (P < .001), respectively. Three regression models were built to predict postoperative lumbar Cobb angles from preoperative information: Model S (R2 = .39) uses preoperative supine lumbar curve; Model B (R2 = .44) uses preoperative side-bending lumbar curve; Model SB (R2 = .49) uses both preoperative supine and side-bending lumbar curves. Model S and B performed just as well as Model SB.

CONCLUSION

Either supine or side-bending radiographs alone may be used to estimate mean residual postoperative lumbar curvature after selective posterior thoracic fusion, but little is to be gained by taking both supine and side-bending radiographs.

Prenatal gender-customized head circumference nomograms result in reclassification of microcephaly and macrocephaly

BACKGROUND

Local and worldwide prenatal charts for estimated fetal weight and postnatal charts for head circumference are gender specific. However, prenatal head circumference nomograms are not gender customized.

OBJECTIVE

This study aimed to create gender-customized curves to assess between-gender head circumference differences and to study the clinical significance of using such gender-customized curves.

STUDY DESIGN

A single-center retrospective study was conducted between June 2012 and December 2020. Prenatal head circumference measurements were obtained from routine estimated fetal weight ultrasound scans. Postnatal head circumference measurement at birth and gender were retrieved from computerized neonatal files. Head circumference curves were created, and the normal range was defined for the male and female subpopulations. After applying gender-specific curves, we analyzed the outcome of cases classified as microcephaly and macrocephaly according to non-gender-customized curves, which were reclassified as normal according to gender-specific curves. For these cases, clinical information and postnatal long-term outcomes were retrieved from patients' medical records.

RESULTS

The cohort included 11,404 participants (6000 males and 5404 females). The curve for male head circumference was significantly higher than the female curve for all gestational weeks (P<.0001). Applying gender customized curves resulted in fewer cases of male fetuses defined as 2 standard deviations above the normal range and female fetuses defined as 2 standard deviations below of the normal range. Cases reclassified as normal head circumference after the application of gender-customized curves were not related to increased adverse postnatal outcomes. The rate of neurocognitive phenotypes was not higher than the expected rate in both male and female cohorts. Polyhydramnios and gestational diabetes mellitus were more common in the normalized male cohort, whereas oligohydramnios, fetal growth restriction, and cesarean delivery were more common in the normalized female cohort.

CONCLUSION

Prenatal gender-customized curves for head circumference can reduce the overdiagnosis of microcephaly in females and macrocephaly in males. According to our results, gender-customized curves did not affect the clinical yield of prenatal measurements. Therefore, we suggest that gender-specific curves be used to avoid unnecessary workup and parental anxiety.

High-Performance Curved Piezoelectric Single-Crystal Composites via 3D-Printing-Assisted Dice and Insert Technology for Underwater Acoustic Transducer Applications

Piezoelectric single-crystal composites (PSCCs) have been studied and applied because of their improved resolution and power source level performance in underwater acoustic transducer applications relative to traditional piezoelectric ceramic composites (PCCs). Currently, the methods to fabricate curved PSCCs are mostly derived from PCCs, including molding with flexible backing, molding with heating, and molding with the casting rubber method. Unfortunately, the methods mentioned above are not suitable for preparing curved PSCCs for underwater acoustic transducer applications because of their brittleness, the large anisotropy of piezoelectric single crystals, and the high thickness (>2 mm) of PSCCs for achieving the low operating frequency (<700 kHz). In the present work, we proposed a preparation method, 3D-printing-assisted dice and insert technology, and successfully prepared curved PSCCs with high performance. Although the PSCCs have a low volume fraction of single crystals in this work (∼33%), a high thickness electromechanical factor k_t of 86% and a large piezoelectric coefficient d₃₃ of 1550 pC/N were achieved in the curved 1-3 PSCCs, which are superior to other reported PSCCs and PCCs with nearly the same volume fraction of single crystals and piezoelectric ceramics. This work presents a paradigm for fabricating curved PSCCs for underwater acoustic transducers, and this method shows the potential for large-area, special-shaped PSCCs, which are key materials for next-generation underwater acoustic transducers.

Continuous Tracking of Foot Strike Pattern during a Maximal 800-Meter Run

(1) Background: Research into foot strike patterns (FSP) has increased due to its potential influence on performance and injury reduction. The purpose of this study was to evaluate changes in FSP throughout a maximal 800-m run using a conformable inertial measurement unit attached to the foot; (2) Methods: Twenty-one subjects (14 female, 7 male; 23.86 ± 4.25 y) completed a maximal 800-m run while foot strike characteristics were continually assessed. Two measures were assessed across 100-m intervals: the percentage of rearfoot strikes (FSP_%RF), and foot strike angle (FSA). The level of significance was set to p ≤ 0.05; (3) Results: There were no differences in FSP_%RF throughout the run. Significant differences were seen between curve and straight intervals for FSA_AVE (F [1, 20] = 18.663, p < 0.001, η_p² = 0.483); (4) Conclusions: Participants displayed decreased FSA, likely indicating increased plantarflexion, on the curve compared to straight intervals. The analyses of continuous variables, such as FSA, allow for the detection of subtle changes in foot strike characteristics, which is not possible with discrete classifiers, such as FSP_%RF.

Measuring the intensity of conflicts in conservation

Conflicts between the interests of biodiversity conservation and other human activities pose a major threat to natural ecosystems and human well-being, yet few methods exist to quantify their intensity and model their dynamics. We develop a categorization of conflict intensity based on the curve of conflict, a model originally used to track the escalation and deescalation of armed conflicts. Our categorization assigns six intensity levels reflecting the discourse and actions of stakeholders involved in a given conflict, from coexistence or collaboration to physical violence. Using a range of case studies, we demonstrate the value of our approach in quantifying conflict trends, estimating transition probabilities between conflict stages, and modeling conflict intensity as a function of relevant covariates. By taking an evidence-based approach to quantifying stakeholder behavior, the proposed framework allows for a better understanding of the drivers of conservation conflict development across a diverse range of socioecological scenarios.

Coronavirus disease 2019-The principles of the curve, explained simply

In the setting of the coronavirus disease 2019 pandemic, the concept of the disease curve has become ubiquitous in medicine and across society. Nevertheless, even among medical specialists, there are common misconception about the curve and how it affects population outcomes. This article provides a simple review of the various population dynamics at play. Principles such as the area under the curve and the threshold of capacity are discussed and simply conceptualized. Understanding the fundamental characteristics of a problem can allow us to see it with more clarity. By the end of the article, the reader will gain an effortless a sense of insight on this topic.

Kinematic modifications of the lower limb during the acceleration phase of bend sprinting

A decrease in speed when sprinting on the bend compared with the straight has been attributed to kinetic, kinematic and spatiotemporal modifications. Although maximal speed is dependent on an athlete's ability to accelerate, there is limited research investigating the acceleration phase of bend sprinting. This study used a lower limb and trunk marker set with 15 optoelectronic cameras to examine kinematic and spatiotemporal variables of the lower limb during sprinting on the bend and straight. Nine sprinters completed up to six 30 m maximal effort trials in bend (radius 36.5 m, lane one) and straight conditions. An increase in body lateral lean at touchdown resulted in a number of asymmetric kinematic modifications. Whilst the left limb demonstrated a greater peak hip adduction, peak hip internal rotation and peak ankle eversion on the bend compared with the straight, the right limb was characterised by an increase in peak hip abduction. These results demonstrate that kinematic modifications start early in the race and likely accumulate, resulting in greater modifications at maximal speed. It is recommended that strength and conditioning programmes target the hip, ankle and foot in the non-sagittal planes. In addition, sprint training should prioritise specificity by occurring on the bend.

Measurement of bend sprinting kinematics with three-dimensional motion capture: a test-retest reliability study

Sprint velocity decreases on the bend when compared with the straight, therefore understanding technique during bend sprinting could have important implications for aiding race performance. Few bend sprinting studies have used optoelectronic cameras to investigate kinematic variables. Limited published evidence regarding the reliability of marker sets in conditions representative of elite bend sprinting makes model selection difficult. Therefore, a test-retest protocol was conducted to establish the reliability and minimum detectable difference of a lower limb and trunk marker set during bend sprinting (radius: 36.5 m). Six participants completed five, 60 m trials at maximum effort, with data collected at 38-45 m. This was repeated 2-7 days later. Spatio-temporal (e.g., contact time) and kinematic variables (e.g., peak joint angles) were evaluated. Intra-class correlation coefficients (ICC) were used to determine the between- and within-day reliability. Between-day reliability (ICC 3, k) was fair to excellent for all variables. Compared to between-day, within-day reliability demonstrated stronger agreement for the majority of variables. Thus, same-day data collection is preferable. It has been established that the marker set is reliable for future use. In addition, the minimal detectable difference was calculated which serves as useful reference for future research in bend sprinting.

Steering Control in a Low-Cost Driving Simulator: A Case for the Role of Virtual Vehicle Cab

OBJECTIVE

The aim of this study was to investigate steering control in a low-cost driving simulator with and without a virtual vehicle cab.

BACKGROUND

In low-cost simulators, the lack of a vehicle cab denies driver access to vehicle width, which could affect steering control, insofar as locomotor adjustments are known to be based on action-scaled visual judgments of the environment.

METHOD

Two experiments were conducted in which steering control with and without a virtual vehicle cab was investigated in a within-subject design, using cornering and straight-lane-keeping tasks.

RESULTS

Driving around curves without vehicle cab information made drivers deviate more from the lane center toward the inner edge in right (virtual cab = 4 ± 19 cm; no cab = 42 ± 28 cm; at the apex of the curve, p < .001) but not in left curves. More lateral deviation from the lane center toward the edge line was also found in driving without the virtual cab on straight roads (virtual cab = 21 ± 28 cm; no cab = 36 ± 27 cm; p < .001), whereas driving stability and presence ratings were not affected. In both experiments, the greater lateral deviation in the no-cab condition led to significantly more time driving off the lane.

CONCLUSION

The findings strongly suggest that without cab information, participants underestimate the distance to the right edge of the car (in contrast to the left edge) and thus vehicle width. This produces considerable differences in the steering trajectory.

APPLICATION

Providing a virtual vehicle cab must be encouraged for more effectively capturing drivers' steering control in low-cost simulators.

Risk factors for motorcycle loss-of-control crashes

OBJECTIVE

The present article identifies and assesses the effect of critical factors on the risk of motorcycle loss-of-control (LOC) crashes.

METHOD

Data come from a French project on road crashes, which include all fatal road crashes and a random sample of 1/20th of nonfatal crashes in France in 2011, based on police reports. A case-control study was carried out on a sample of 903 crashes for 444 LOC motorcycle riders (case) and 470 non-LOC and nonresponsible motorcycle riders (control). The sample was weighted due to the randomization of nonfatal crashes. Missing values were imputed using multiple imputation.

RESULTS

Road alignment and surface conditions, human factors, and motorcycle type played important roles in motorcycle LOC crashes. Riding in a curve was associated with a 3-fold greater risk of losing control of motorcycle than riding in a straight line. Poor road adhesion significantly increased the risk of losing control; the risk increased more than 20-fold when deteriorated road adhesion was encountered unexpectedly, due to loose gravel, ice, oil, bumps, road marking, metal plates, etc. For motorcyclists, riding with a positive blood alcohol concentration (over or equal to the legal limit of 0.5 g/L) was very dangerous, often resulting in losing control. The risk of LOC crash varied for different types of motorcycle: Riders of roadsters and sports bikes were more likely to have an LOC crash greater than that of riders of basic or touring motorcycles. In addition, LOC risk increased with speed; a model using the square of the traveling speed showed better fit than one using speed itself.

CONCLUSION

The LOC crash factors related to riders, vehicles, and road infrastructure identified here were expected but were rarely identified and taken simultaneously into account in previous studies. They could be targeted by countermeasures to improve motorcyclist safety.

Bend sprinting performance: new insights into the effect of running lane

Athletes in inner lanes may be disadvantaged during athletic sprint races containing a bend portion because of the tightness of the bend. We empirically investigated the veracity of modelled estimates of this disadvantage and the effect of running lane on selected kinematic variables. Three-dimensional video analysis was conducted on nine male athletes in lanes 8, 5 and 2 of the bend of an outdoor track (radii: 45.10, 41.41 and 37.72 m, respectively). There was over 2% (p < 0.05) reduction in mean race velocity from lane 8 (left step 9.56 ± 0.43 m/s, right step: 9.49 ± 0.41 m/s) to lane 5 (left step: 9.36 ± 0.51 m/s, right step: 9.30 ± 0.51 m/s), with only slight further reductions from lane 5 to lane 2 (left step: 9.34 ± 0.61 m/s, right step: 9.30 ± 0.63 m/s). Race velocity decreased mainly because of reductions in step frequency as radius decreased. These unique data demonstrate the extent of the disadvantage of inner lane allocation during competition may be greater than previously suspected. Variations in race velocity changes might indicate some athletes are better able to accommodate running at tighter radii than others, which should have implications for athletes' training.

Physical assessment and reference growth curves for children with 46, XY disorders of sex development

IMPORTANCE

Impaired growth is an important factor in patients with disorders of sex development (DSD).

OBJECTIVE

To profile the growth of children with 46, XY DSD.

METHODS

We compared heights between 46, XY DSD children and normal boys and obtained growth curves for DSD using the λ-median coefficient of variation method. The study subjects were categorized into groups with good response and poor response to the human chorionic gonadotrophin (HCG) test according to testosterone levels and were compared height standard deviation scores (HtSDS) with normal boys.

RESULTS

A total of 571 children with noncongenital adrenal hyperplasia (CAH) 46, XY DSD were enrolled in this study. The overall HtSDS for the DSD subjects were -0.031 ± 1.202. The HtSDS of DSD boys were lower than those for normal boys among multiple age groups since early infancy. In children aged ≥12 years, the HtSDS values were significantly lower than the normal reference values for boys of the same age in both the good and poor response groups (P = .025 and P = .003, respectively).The HtSDS in the poor response group was generally lower than the normal reference value (P = .017). The average HtSDS values in the poor response groups were lower than those in the good response groups across multiple age groups.

INTERPRETATION

Growth retardation was evident in boys with non-CAH 46,XY DSD in early childhood and puberty. The level of growth retardation was related to testosterone level. DSD-specific growth curves can improve our understanding of growth dynamics and minimize the scope for bias in the assessment of growth in these children.

Automatic extraction of 3D anatomical feature curves of hip bone models reconstructed from CT images

3D anatomical feature curves (AFC) on bone models reconstructed from CT/MRI images are important in some fields, such as preoperative planning, intra-operative navigation, patient-specific prosthesis design, etc. Interactive extraction of feature curves on patient-specific bone models is time-consuming, has low repeatability and accuracy. This paper presents a computer graphics method to automatically extract AFC from 3D hip bone models reconstructed from CT images. A DCSS (direct curvature scale space)-based technique is firstly used to extract anatomical feature points (AFP) in every contour, using anatomical structure information as prior knowledge so that AFP are extracted and only extracted. Then, corresponding AFP are linked in different contours and AFC is generated. AFC obtained by our method were compared with those interactively extracted by three surgeons, which showed that our method is feasible (Dice coefficient: 0.94; Average symmetric surface distance: 3.97 mm). The method was also applied to identify anatomical landmarks, which showed that our method is superior to the curvature-based methods that fail to identify landmark regions or have too many redundant regions, which results in failures to subsequently label landmark regions using pre-defined spatial adjacency matrices.

Force production during maximal effort bend sprinting: Theory vs reality

This study investigated whether the "constant limb force" hypothesis can be applied to bend sprinting on an athletics track and to understand how force production influences performance on the bend compared with the straight. Force and three-dimensional video analyses were conducted on seven competitive athletes during maximal effort sprinting on the bend (radius 37.72 m) and straight. Left step mean peak vertical and resultant force decreased significantly by 0.37 body weight (BW) and 0.21 BW, respectively, on the bend compared with the straight. Right step force production was not compromised in the same way, and some athletes demonstrated substantial increases in these variables on the bend. More inward impulse during left (39.9 ± 6.5 Ns) than right foot contact (24.7 ± 5.8 Ns) resulted in 1.6° more turning during the left step on the bend. There was a 2.3% decrease in velocity from straight to bend for both steps. The constant limb force hypothesis is not entirely valid for maximal effort sprinting on the bend. Also, the force requirements of bend sprinting are considerably different to straight-line sprinting and are asymmetrical in nature. Overall, bend-specific strength and technique training may improve performance during this portion of 200- and 400-m races.

The proximal thoracic curve in adolescent idiopathic scoliosis: surgical strategy and management outcomes

There is no consensus on the definition of a structural proximal thoracic curve (PTC) and the indications for fusion. As such, we assessed a single institute's experience in the management of large PTCs (>35 degrees) in patients with adolescent idiopathic scoliosis (AIS) who were either fused or not fused. A retrospective radiographic analyses of 30 consecutive AIS patients with double thoracic curves who underwent PSF with a minimum of 2 years' follow-up were included for review. The patients were divided into two groups: group 1 (n = 15 patients) with fusion extended up to T2 or T3 and group 2 (n = 15) with fusion limited to T5 or below. Shoulder balance was assessed according to clavicular angle, first-rib difference, and radiographic shoulder height difference (SHD). PTCs were defined based on a Cobb angle of >35, the presence of apical rotation, and a positive T1 tilt. The decision to fuse the PTC was based on curve magnitude only, with those between 35 and 45 degrees undergoing a selective fusion of the main thoracic curve (MTC), with both curves fused if the PTC was more than 45 degrees. In group 1, there were eight females and seven males. Their ages ranged between 12 and 33 years, with a mean of 16.2 ± 5.5 years. Postoperatively, the mean PTC correction was 45.6%, which statistically differed from preoperative status (p = 0.001). No statistical difference was noted in T1 tilt and the first-rib difference from preoperative to postoperative follow-up (p > 0.05). However, the clavicular angle and SHD were increased significantly at the immediate postoperative interval (p < 0.05) but demonstrated no significant changes between the initial and the last follow-up values (p > 0.05). Group 2 consisted of one male and 14 females. The mean age was 16.4 ± 4 years (range: 11 to 28 years). The mean spontaneous PTC correction was 28.3% and remained essentially unchanged at the end of the follow-up. The improvement in the curve from preoperative status was highly statistically significant (p = 0.001). All radiographic shoulder parameters exhibited a significant increase in the immediate postoperative period and at last follow-up, and shoulder balance improvement was not noted on follow-up. Although both groups were not statistically similar with regards to the preoperative PTC, AVR, apical vertebral translation, and shoulder parameters, no significant difference could be found in PTC or shoulder parameters between both groups at last follow-up (p > 0.05). Our study illustrates important observations that should be considered in defining the PTC for fusion consideration. Spontaneous correction of the PTC occurs in structural curves greater than 35 degrees and less than 45 degrees, and this correction is maintained over time. Despite that correction, radiographic shoulder parameters are expected to slightly increase. Nonfusion strategy may be appropriate for PTCs between 35 and 45 degrees. After fusion of both the MTC and the PTC, the radiographic shoulder parameters did not significantly differ. Preoperative radiographic shoulder parameters are not predictive of postoperative shoulder imbalance.

Exact confidence interval estimation for the difference in diagnostic accuracy with three ordinal diagnostic groups

In the cases with three ordinal diagnostic groups, the important measures of diagnostic accuracy are the volume under surface (VUS) and the partial volume under surface (PVUS) which are the extended forms of the area under curve (AUC) and the partial area under curve (PAUC). This article addresses confidence interval estimation of the difference in paired VUS s and the difference in paired PVUS s. To focus especially on studies with small to moderate sample sizes, we propose an approach based on the concepts of generalized inference. A Monte Carlo study demonstrates that the proposed approach generally can provide confidence intervals with reasonable coverage probabilities even at small sample sizes. The proposed approach is compared to a parametric bootstrap approach and a large sample approach through simulation. Finally, the proposed approach is illustrated via an application to a data set of blood test results of anemia patients.