Nonlinear Index Research Articles

Cardiovascular responses as predictors of mortality in children with acute brain injury.

Investigate the utility of cardiovascular responses such as heart rate (HR), blood pressure (BP), and heart rate variability (HRV) in the prognosis of children with acute acquired brain injury (ABI). Children under 18 years with severe acute acquired brain injury (ABI) who survived at least 12 h after PICU admission were included in a prospective observational cohort in a tertiary academic PICU. Physiological variables, neurological data, laboratory tests (chemistry and hematology), and medications were recorded within 12 h of admission. Linear and nonlinear HRV indices, CT scans, PICU scores, and survival rates were evaluated. Seventy-two children, median age 10.7 years (IQR 4.1-13.6), were eligible for the study; 28 (38.9%) were diagnosed with brain death (BD). Tachycardia, SBP and MBP < 5th percentile, and MBP and DBP> 99th percentile were significantly associated with mortality. Poincaré SD1/SD2 was significantly associated with mortality after adjusting for age, sex and ongoing medication. Tachycardia, systolic hypotension and median hypo and hypertension were associated to mortality in children with severe ABI. While further validation through larger, multicenter studies is necessary, the Poincaré SD1/SD2 ratio has shown promise as a prognostic tool for predicting mortality in children with severe ABI. This study explores cardiovascular changes, including heart rate and blood pressure, and linear/nonlinear HRV measures using ECG at 1000 Hz, and compare them with other prognostic factors like brain tomography and PICU scores. Tachycardia, hypo/hypertension in the early hours after admission are linked to early mortality in children with severe traumatic and non-traumatic brain injury. Linear/non-linear measures of HRV were also related to survival. Higher HRV values indicating better survival chances. We identified Poincaré SD1/SD2 ratio as a promising tool for predicting mortality in children with severe ABI.

Influences of Attentional Focus on Across- and Within-Sentence Variability in Adults Who Do and Do Not Stutter.

Research has found an advantage to maintaining an external attentional focus while speaking as an increase in accuracy and a decrease in across-sentence variability has been found when producing oral-motor and speech tasks. What is not clear is how attention affects articulatory variability both across and within sentences, or how attention affects articulatory control in speakers who stutter. The purpose of this study was to investigate the effects of an internal versus external attention focus on articulatory variability at the sentence level. This study used linear (spatial-temporal index [STI]) and nonlinear (recurrence quantification analysis [RQA]) indices to measure lip aperture variability in 10 adults who stutter (AWS) and 15 adults who do not stutter (ANS) while they repeated sentences under an internal versus external attentional focus, virtual reality task (withVR.app; retrieved December 2023 from https://therapy.withvr.app). Four RQA measures were used to calculate within sentence variability including percent recurrence, percent determinism (%DET), stability (MAXLINE), and stationarity (TREND). Sentence duration measures were also obtained. AWS' movement durations were significantly longer than those of the ANS across conditions, and the AWS were more affected by the attentional focus shifts as their speech rate significantly increased when speaking with an external focus. AWS' speech patterns were also significantly more deterministic (%DET) and stable (MAXLINE) across attentional focus conditions compared to those of the ANS. Both groups showed an effect from attentional shifts as they exhibited less variability (i.e., more consistent) across sentences (STI) and less determinism (%DET) and stability (MAXLINE) within sentences when repeating sentences under an external attentional focus. STI values were not significantly different between the AWS and ANS for the internal or external attentional focus tasks. There were no significant main effects for group or condition for TREND; however, a main effect for sentence type was found. Results suggest that AWS use a more restrictive and less flexible approach to movement and that an external focus fosters more flexibility and thus responsiveness to external factors.

Heart rate variability and insomnia in depressed patients with breast cancer

ObjectivesDepression is associated with unhealthy autonomic regulation. However, whether patients with breast cancer (BC) with different degrees of depression can be identified from linear and non-linear dynamics in the autonomic...

Entire loosening stage monitoring of bolted joints via nonlinear electro-mechanical impedance spectroscopy

This article proposes a nonlinear electro-mechanical impedance spectroscopy (NEMIS) methodology for the entire loosening stage monitoring of bolted joints. Unlike the conventional electro-mechanical impedance spectroscopy (EMIS) implemented in the frequency domain, NEMIS utilizes a temporal interrogating signal to procure the developed nonlinear impedance spectrum. It can harness the structural resonance information akin to the conventional EMIS, while concurrently capturing the contact acoustic nonlinearity (CAN) features with only one solitary Piezoelectric Wafer Active Sensor (PWAS). To elucidate the underlying principles of NEMIS, a comparative analysis juxtaposing the conventional EMIS, nonlinear ultrasonic techniques, and the proposed NEMIS was conducted. Subsequently, a reduced-order analytical model was established to simulate the rough contact interfaces of the bolted joints under various looseness states. Parametric studies were carried out to demonstrate the resonance deviation and nonlinear features resulting from the bolt looseness. Ultimately, the experimental implementation of NEMIS for the entire loosening stage monitoring of the bolted joint was performed compared with the conventional EMIS method. It was proved that NEMIS could detect both the incipient bolt loosening at an embryo stage and severe loosening of the bolted joint at the terminal period, integrating the continuous monitoring capability of conventional EMIS and the sensitivity of nonlinear ultrasonic methodology. The quantification on the severity of bolt loosening was accomplished via both linear and nonlinear damage indices, exhibiting a consistent trend with the gradations of bolt looseness. The article culminates in a summary, concluding remarks, and suggestions for future work.

Weighted squared envelope nonlinear Gini index and its application to rotating machinery condition monitoring

Abstract Sparsity measures are effective tools for rotating machinery condition monitoring. However, under complex operating conditions, existing sparsity measures often exhibit significant fluctuations, making it difficult to accurately detect early faults and monotonically represent the degradation processes. To tackle these challenges, a novel health indicator named the weighted squared envelope nonlinear Gini index is proposed in this paper. Firstly, by introducing a nonlinearly increasing weight sequence inspired by the sigmoid function and the quadratic function-based quasi-arithmetic mean, a novel sparsity measure, the nonlinear Gini index, is developed based on the ratio of different quasi-arithmetic means framework. Building upon this foundation, the weighted squared envelope nonlinear Gini index is further constructed for condition monitoring by incorporating the weighted squared envelope into the nonlinear Gini index. When applied to two bearing run-to-failure datasets, the proposed health indicator shows improved sensitivity to early fault features and is able to depict the degradation processes monotonically, demonstrating notable advantages in condition monitoring.

Study of Solvent Dependent on Third-Order Nonlinear Optical and Thermo-Optic Coefficient of Malachite Green Dye.

This study reveals the solvent dependent third-order nonlinear optical (NLO) features of malachite green (MG) dye using Z-scan technique. MG dye is dissolved in polar solvents, including DMF, DMSO, ethanol, acetone, methanol, and 1-propanol. The study employs the Z-scan instrument, using a continuous wave (CW) laser as the excitation source, operating at a wavelength of 650nm. The closed aperture (CA) and open aperture (OA) Z-scan techniques are used to assess the nonlinear indices of refraction (n2) and nonlinear coefficient of absorption (β) of MG dye. MG dye demonstrates both saturable absorption (SA) and reverse saturable absorption (RSA) in the OA Z-scan results, due to negative and positive NLO absorption coefficients. MG dye proves a self-defocusing NLO refractive index while operating under low-power conditions. The third-order NLO susceptibility (χ3) of MG dye in various liquids are calculated to be the order of 10-6 esu. Multilinear regression fit is applied here to investigate the various intermolecular interactions between the solute and solvent. MG dye exhibited large thermo-optic coefficient of the order of 10- 3 K- 1 is observed. The results give important new information about the characteristics of MG dye and indicate potential sources of material for NLO applications in future.

Analysis of the Nonlinear Complex Response of Cracked Blades at Variable Rotational Speeds

The operation of an aero-engine involves various non-stationary processes of acceleration and deceleration, with rotational speed varying in response to changing working conditions to meet different power requirements. To investigate the nonlinear dynamic behaviour of cracked blades under variable rotational speed conditions, this study constructed a rotating blade model with edge-penetrating cracks and proposes a component modal synthesis method that accounts for time-varying rotational speed. The nonlinear response behaviours of cracked blades were examined under three distinct operating conditions: spinless, steady speed, and non-constant speed. The findings indicated a competitive relationship between the effects of rotational speed fluctuations and unbalanced excitation on crack nonlinearity. Variations in rotational speed dominated when rotational speed perturbation was minimal; conversely, aerodynamic forces dominated when the effects of rotational speed were pronounced. An increase in rotational speed perturbation enhanced the super-harmonic nonlinearity induced by cracks, elevated the nonlinear damage index (NDI), and accentuated the crack breathing effect. As the perturbation coefficient increased, the super-harmonic nonlinearity of the crack intensified, resulting in a more complex vibration form and phase diagram.

Ultrasound Imaging of Nonlinear Media Response Using a Pressure-Dependent Nonlinearity Index

It has been shown that within the range of acoustic pressures used in ultrasound imaging, waveforms are distorted during propagation in tissue due to the physically nonlinear behavior of the tissue. This distortion leads to changes in the spectrum of the received ultrasound echoes, causing the transfer of signal energy from the fundamental frequency to higher harmonics. Interestingly, adipose tissue exhibits up to 50 % stronger nonlinear behavior compared to other soft tissues. The tissue nonlinearity parameter B/A is typically measured ex vivo using an ultrasound method in transmission mode, which requires extensive receiving systems. Currently, there is no improved ultrasound method for measuring the B/A nonlinearity parameter in vivo, which could be used in assessing the degree of fatty liver disease. We propose a new, simple approach to estimating nonlinear tissue properties. The proposed method involves transmitting ultrasound waves at significantly different acoustic pressures, recording echoes only in the fundamental frequency band at various depths, and introducing a nonlinearity index (NLI) based on specific echo amplitude ratios. The NLI at a given depth is calculated using the ratio of two dimensionless parameters. The first parameter is a predetermined constant obtained by dividing the total echo values from transmitting a signal at higher sound pressure by those from a signal at lower sound pressure, summed over a small tissue sample volume located near the transducer. The second parameter is calculated at a fixed distance from the transducer, determined by dividing the total echo values from transmitting a signal at higher sound pressure by those from a signal at lower pressure, summed over a small tissue volume of the tissue at that distance from the transducer. The reliability of the proposed measurements for assessing tissue nonlinearity has been substantiated through experimental confirmation of the existing correlations between the values of NLI and B/A in water, sunflower oil, and animal liver tissue samples with oil-enriched regions. The NLI was more than 15 % higher in sunflower oil than in water. The NLI in bovine liver sample below the area with injected oil (mimicking “steatosis”) was more than 35 % higher than in regions without oil. This method represents a promising modality for the nonlinear characterization of tissue regions in vivo, particularly for diagnosing fatty liver disease.

Using nonlinear dynamics analysis to evaluate time response of cupping therapy with different intervention timings on reducing muscle fatigue.

Cupping therapy has been indicated effective in reducing muscle fatigue after 24h based on the spectral analyses of surface electromyography (sEMG). However, there is no sufficient evidence showing changes of sEMG nonlinear indexes at more time points after cupping therapy. Furthermore, it is unclear whether the intervention timings of cupping therapy affect the recovery from muscle fatigue. The purpose of this study was to use the sEMG nonlinear analysis to assess the difference of time response of cupping therapy between different intervention timings after muscle fatigue. This randomized controlled trial recruited 26 healthy volunteers. Cupping therapy (-300mmHg pressure for 5min by the 45mm-diameter cup) was applied before (i.e., pre-condition) or after (i.e., post-condition) muscle fatigue induced by performing repeated biceps curls at 75% of the 10 repetitions of maximum (RM) on the non-dominant upper extremity. Subjects were randomly allocated to the pre-condition group or the post-condition group. The sEMG signals during the maximal voluntary isometric contractions (MVC) of the biceps were recorded at four time points (i.e., baseline; post 1: immediate after cupping-fatigue/fatigue-cupping interventions; post 2: 3h after cupping-fatigue/fatigue-cupping interventions; post 3: 6h after cupping-fatigue/fatigue-cupping interventions). Two nonlinear sEMG indexes (sample entropy, SampEn; and percent determinism based on recurrence quantification analysis, %DET) were used to evaluate the recovery from exercise-introduced muscle fatigue. The Friedman test followed by the Nemenyi test and the Mann-Whitney U test were applied in statistics. The SampEn and %DET change rate did not show any significant differences at four time points in the pre-condition group. However, there were significant delayed effects instead of immediate effects on improving muscle fatigue in the post-condition group (SampEn change rate: baseline 0.0000 ± 0.0000 vs. post 2 0.1105 ± 0.2253, p < 0.05; baseline 0.0000 ± 0.0000 vs. post 3 0.0627 ± 0.4665, p < 0.05; post 1-0.0321 ± 0.2668 vs. post 3 0.0627 ± 0.4665, p < 0.05; and %DET change rate: baseline 0.0000 ± 0.0000 vs. post 2-0.1240 ± 0.1357, p < 0.01; baseline 0.0000 ± 0.0000 vs. post 3 0.0704 ± 0.6495, p < 0.05; post 1 0.0700 ± 0.3819 vs. post 3 0.0704 ± 0.6495, p < 0.05). Moreover, the SampEn change rate of the post-condition group (0.1105 ± 0.2253) was significantly higher than that of the pre-condition group (0.0006 ± 0.0634, p < 0.05) at the post 2 time point. No more significant between-groups difference was found in this study. This is the first study demonstrating that both the pre-condition and post-condition of cupping therapy are useful for reducing muscle fatigue. The post-condition cupping therapy can e ffectively alleviate exercise-induced muscle fatigue and there is a significant delayed effect, especially 3h after the interventions. Although the pre-condition cupping therapy can not significantly enhance muscle manifestations, it can recover muscles into a non-fatigued state.

Optical and optoelectrical characterizations of Cu2ZnSn3S8: A potential nominee for optoelectronic and photovoltaic applications

A successful trial has been accomplished in synthesizing a stable phase of Cu2ZnSn3S8 (CZTS8). The deposited thin films have been obtained by utilizing the chemical bath deposition (CBD) process. Basic characterizations have been applied to check the formation of our new stable material. The formed CZTS8 films disclose the amorphous nature as presented in the x-ray diffraction (XRD) patterns. Also, an enhancement in film morphology has been obtained by expanding the film thickness. Moreover, optoelectrical and linear/nonlinear optical features have been studied for the as-deposited films. Our material has interesting characteristics to be a promising window sheet for thin film solar cells. It reveals a tendency to be an n-type semiconductor material. Further, it shows high optical absorption as well as high optical conductivity. Moreover, it has a direct optical transition, and its energy gap is varied in the range (3.89 eV - 3.94 eV). Additionally, the dispersion and optoelectrical indices were affected by the variation in both film thickness and film roughness. Furthermore, the nonlinear optical indices χ(1),χ(3) and n2 were improved via the increase in film thickness. A satisfactory correlation has been performed between all of the evaluated parameters. The main goal of this study has been achieved by obtaining n-type material by increasing the Tin and Sulfur contents in the CZTS8 as compared with the known p-type material (Cu2ZnSnS4) CZTS4. The revealed findings acknowledge that CZTS8 could be a promising nominee for either optoelectronic or photovoltaic applications.

Optical properties of transition metals complex films derived from hydrazone oxime for optoelectronic devices

Hydrazone incorporating oxime nucleus and its Ni2+, Mn2+, Zn2+ and UO22+ metallic chelates have been prepared and completely characterized by different spectral, theoretical, and analytical techniques including NMR, FT-IR, mass, and EAS spectroscopy. The finding denoted that the Hydrazone ligand bonded as a dibasic tridentate chelator via deprotonated oximato nitrogen, enol carbonyl oxygen and hydrazono azomethine nitrogen atoms resultant in octahedral geometry for Ni2+, Mn2+, Zn2+ and UO22+. Theoretical studies by DFT/B3LYP/LANLDZ together with dipole moment, geometrical optimization, energetic parameters, and energy gap (HOMO–LUMO) were employed to support the geometrical structure of the synthetics. Additionally, these complexes were prepared in the form of thin film onto cleaned glass substrate by spin-coating technique. The values of the optical band gap (Eg) and film index of refraction (n) have been determined by many different methods. It was found that the hydrazone-oxime (OBBH2) film has the highest value of Eg (eV) where the UOBB complex film has the smallest value of Eg (2.56 eV). The latter is very close to the Eg value of ZnSe (2.58 eV). The refractive index changes with wavelengths show normal dispersion which is well discussed in terms of Sellmeier's dispersion model. Also, the nonlinear optical parameters viz. the first (χ(1)) and third (χ(3)) orders of nonlinear optical susceptibilities and the non-linear index of refraction (n2) have been studied. The complex dielectric constant (ε⌣=εr+iεi)), conductivity (σ⌣=σr+iσi), sheet resistance (Rs), and thermal have been investigated over the whole spectral range. According to the results of χ(1), χ(3) and n2 the complex films under study are candidates to be used in optical switching gadgets, optical modulators, and optical signal processing.

Correlation properties of heart rate variability for exercise prescription during prolonged running at constant speeds: A randomized cross-over trial.

The study explores the validity of the nonlinear index alpha 1 of detrended fluctuation analysis (DFAa1) of heart rate (HR) variability for exercise prescription in prolonged constant load running bouts of different intensities. 21 trained endurance athletes (9w and 12m) performed a ramp test for ventilatory threshold (vVT1 and vVT2) and DFAa1-based (vDFAa1-1 at 0.75 and vDFAa1-2 at 0.5) running speed detection as well as two 20-min running bouts at vDFAa1-1 and vDFAa1-2 (20-vDFAa1-1 and 20-vDFAa1-2), in which HR, oxygen consumption (VO2), respiratory frequency (RF), DFAa1, and blood lactate concentration [La-] were assessed. 20-vDFAa1-2 could not be finished by all participants (finisher group (FG), n=15 versus exhaustion group (EG), n=6). Despite similar mean external loads of vDFAa1-1 (10.6±1.9km/h) and vDFAa1-2 (13.1±2.4km/h) for all participants compared to vVT1 (10.8±1.7km/h) and vVT2 (13.2±1.9km/h), considerable differences were present for 20-vDFAa1-2 in EG (15.2±2.4km/h). 20-vDFAa1-1 and 20-DFAa1-2 yielded significant differences in FG for HR (76.2±5.7 vs. 86.4±5.9 %HRPEAK), VO2 (62.1±5.0 vs. 77.5±8.6 %VO2PEAK), RF (40.6±11.3 vs. 46.1±9.8bpm), DFA-a1 (0.86±0.23 vs. 0.60±0.15), and [La-] (1.41±0.45 vs. 3.34±2.24mmol/L). Regarding alterations during 20-vDFAa1-1, all parameters showed small changes for all participants, while during 20-vDFAa1-2 RF and DFAa1 showed substantial alterations in FG (RF: 15.6% and DFAa1: -12.8%) and more pronounced in EG (RF: 20.1% and DFAa1: -35.9%). DFAa1-based exercise prescription from incremental testing could be useful for most participants in prolonged running bouts, at least in the moderate to heavy intensity domain. In addition, an individually different increased risk of overloading may occur in the heavy to severe exercise domains and should be further elucidated in the light of durability and decoupling assessment.

Integration of Open Metal Sites in an Amino-Functionalized Sm(III)-Organic Framework toward Enhanced Third-Order Nonlinear Optical Property.

A variety of new inorganic and organic materials have emerged to advance laser technologies and optical engineering. A rational design approach can contribute significantly to fabricating nonlinear optically active metal-organic frameworks (MOFs) by considering the underlying structure-property linkage. Here, it has been embarked on a study of novel samarium(III) MOF, ([Sm2(ata)3(DMF)4]·DMF (ata2-: 2-aminoterephthalate), abbreviated as NH2-Sm-MUM-4) with enhanced nonlinear optical (NLO) properties. The crystal structure of this MOF represents a 6-connected framework with a pcu topology and distinctive characteristics, including open metal sites, free amine groups, and great stability, making it suitable for third-order NLO activity. The nonlinear index of refraction (n2) revealed the self-focusing impacts of NH2-Sm-MUM-4 at different incident intensities. The highest value of n2 and β related to 10 mw power of incident intensity are 5.15 cm2/W and 2.65 cm/W, respectively. As far as the authors know, this is the first study examining the potential systematic structural-property associations in Sm-MOFs considering improved third-order NLO properties.

Nonlinear Electrophoresis of Microparticles in Shear Thinning Fluids.

The nonlinear electric field dependence of particle electrophoresis has been demonstrated to occur in Newtonian fluids for highly charged particles under large electric fields. It has also been predicted to arise from the rheological effects of non-Newtonian fluids even at small electric fields. We present in this work an experimental verification of nonlinear electrophoresis in shear thinning xanthan gum solutions through a straight rectangular microchannel. The addition of polymer into a Newtonian buffer solution is found to change the electric field dependence from linear to superlinear for electroosmotic, electrokinetic, and electrophoretic velocities. The nonlinear index of each of these electrokinetic phenomena increases with the increasing polymer or buffer concentration, among which electrophoresis exhibits the strongest nonlinearity. Both these observed trends are captured by a dimensionless electrokinetic shear thinning number that depends on the power-law index of fluid viscosity and the Debye length.

Comprehensive linear and nonlinear heart rate variability normative data in children.

The autonomic nervous system (ANS) is critical in regulating involuntary bodily functions, including heart rate. Heart rate variability (HRV) reflects the complex interplay between the ANS and humoral factors, making it a valuable noninvasive tool for assessing autonomic function. While HRV has been extensively studied in adults, normative data for HRV in children, primarily based on long-term rhythm recordings, are limited. This study aimed to establish comprehensive normative data for HRV in children. In this retrospective study, we examined 24-h Holter monitors of children aged 1day to 18years, divided into six age groups, at Nemours Children's Health in Orlando, Florida, spanning the years 2013-2023. HRV analysis encompassed time-domain, frequency-domain, and nonlinear indices. Holter data for a total of 247 patients in six age groups were included. An age-related uptrend was observed in all time- and frequency-domain variables except the normalized unit of low-frequency power. Entropy analysis revealed contradictory results among different entropy techniques. Sample and approximate entropy analyses were consistent and showed less complexity and more predictability of HRV with decreasing heart rate, while Shannon entropy analysis showed the opposite. Fractal detrended fluctuation analysis exhibited significant decreases across the age groups, suggestive of diminishing self-similarity of HRV patterns. Control of heart rate and HRV is a highly complex process and requires further study for a better understanding. It seems that no single parameter can fully elucidate the entire process. A combination of time-domain, frequency-domain, and nonlinear indices may be necessary to explain HRV behavior in the growing body.

Recurrence quantification analysis of uterine vectormyometriogram reveals differences between normal-weight and overweight parturient women

Objective.This study aims to use recurrence quantification analysis (RQA) of uterine vectormyometriogram (VMG) created from the slow wave (SW) and high wave (HW) bands of electrohysterogram (EHG) signals and assess the directionality of the EHG activity (horizontal orX, vertical orY) in normal-weight (NW) and overweight (OW) women during the first stage of labor.Approach. The study involved 41 parturient women (NW = 21 and OW = 20) during the first stage of labor, all of whom were attended at the Gynecology and Obstetrics Hospital of the Maternal and Child Institute of the State of Mexico in Toluca, Mexico. Twenty-minute EHG signals were analyzed in horizontal and vertical directions. Linear and nonlinear indices such as dominant frequency (Dom), Sample Entropy (SampEn), and RQA measures of VMG were computed for SW and HW bands.Main results. Significant differences in SampEn and Dom were observed in the SW band between NW and OW in bothXandYdirections, indicating more regular dynamics of electrical uterine activity and a higher Dom in NW parturient women compared to OW women. Additionally, the RQA indices calculated from the VMG of SW were consistent and revealed that NW women exhibit more regular dynamics compared to OW women.Significance. The study demonstrates that RQA of VMG signals and EHG directionality differentiate uterine activity between NW and OW women during the first stage of labor. These findings suggest that the uterine vector may become more periodic, predictable, and stable in NW women compared to OW women. This highlights the importance of tailored clinical strategies for managing labor in OW women to improve maternal and infant outcomes.

Tapered photonic crystal fiber based on artificial intelligence-design for pulse compression

In this study, we employ a deep neural network(DNN) to achieve rapid prediction of dispersion and effective mode area in Pb-silicate photonic crystal fiber. Subsequently, this prediction model is used to drive a particle swarm optimization(PSO) algorithm to design tapered Pb-silicate photonic crystal fibers for pulse compression. The designed fibers exhibit an increasing nonlinear index profile, enabling self-similar pulse compression(SSPC) of pulses at a wavelength of 2μm. In compliance with fundamental soliton conditions, a 0.566 m tapered PCF achieves notable pulse compression. It reduces the initial pulse width of 1.76 ps to 52 fs, achieving a remarkable compression factor of 33.92, while maintaining a quality factor of 1.01 and less than 5.4% pedestal energy. In scenarios where fundamental soliton conditions are not met, a 1.74 m tapered PCF also achieves significant compression. It compresses a pulse with a width of 1.76 ps and a peak power of 1 kW to a pulse width of 13.7 fs and a peak power of 24.82 kW, resulting in a compression factor of 129. The proposed approach overcomes the empirical reliance inherent in manual design and significantly reduces computational demands, enabling the design of pulse compression fiber tapers tailored to input pulse shapes.

Heart Rate Variability in Military Pilots During Flight: A Scoping Review.

Piloting an aircraft is a complex multitasking activity that involves managing information in a nonautomatic way and generates a high workload (psychological, cognitive, and physical) for the pilot. The excess of these demands can result in decreased performance and may impair flight safety. Heart rate variability (HRV) has been used in recent studies as a method to investigate operator's workload in complex environments. This measure can assess the stress and recovery ability of the autonomic nervous system. However, a better understanding of flight influence on the pilot's autonomic modulation is necessary. Therefore, this scoping review aims to systematically map the studies related to changes in the autonomic modulation in military pilots during flight, in order to characterize their workload at different times and flight profiles. A literature search was conducted using MEDLINE (by PubMed), SCOPUS, and LILACS databases. Recent records (2002-2022) that analyzed HRV in military pilots during flight were included. Meanwhile, studies in which piloting activity was not performed were excluded. The study was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline extension for Scoping Reviews and the Updated Methodological Guidance for the Conduct of Scoping Reviews. A total of 298 records were obtained, of which 19 were included in the scoping review. The studies analyzed flights performed in high- and low-performance aircrafts, helicopters, and flight simulators, using time domain, frequency domain, and nonlinear HRV indices. Real and simulated flights produced significant autonomic changes. Some flights elicited autonomic nervous system responses that persisted up to 5 h after landing. During real flight, the most sensitive indices for identifying variations in pilot workload were root mean square of successive differences between normal heartbeats, standard deviation of interbeat interval of normal sinus beat (SDNN), ratio of low-frequency to high-frequency power, and Poincaré plot standard deviation perpendicular to the line of identity (SD1), whereas the interbeat interval (RR), SDNN, SD1, and Poincaré plot standard deviation along the line of identity (SD2) were the most sensitive indices when comparing segments of simulated flight with different levels of difficulty. This scoping review provided insight into the influence of flight on autonomic modulation in military pilots. Some key themes were highlighted: Increased sympathetic activity during flight, sensibility of different domains of HRV to flight demands, and autonomic changes during recovery time. Future research efforts may allow us to enhance the understanding of pilot's workload limits and to elucidate the optimal postflight recovery time.

Bolt-loosening Fault Diagnosis in Rotor Systems with Nonlinear Vibration Transmissibility Function-based Features and Indexes

Bolt-loosening Fault Diagnosis in Rotor Systems with Nonlinear Vibration Transmissibility Function-based Features and Indexes

Neuromuscular conditions in post-stroke ankle-foot dysfunction reflected by surface electromyography

BackgroundRating scales and linear indices of surface electromyography (sEMG) cannot quantify all neuromuscular conditions associated with ankle-foot dysfunction in hemiplegic patients. This study aimed to reveal potential neuromuscular conditions of ankle-foot dysfunction in hemiplegic patients by nonlinear network indices of sEMG.MethodsFourteen male patients with hemiplegia and 10 age- and sex-matched healthy male adults were recruited and tested in static standing position. The characteristics of the root mean square (RMS), median frequency (MF), and three nonlinear indices, the clustering coefficient (C), the average shortest path length (L), and the degree centrality (DC), of eight groups of muscles in bilateral calves were observed.ResultsCompared to those of the control group, the RMS of the medial gastrocnemius (MG), flexor digitorum longus (FDL), and extensor digitorum longus (EDL) on the affected side were significantly lower (P < 0.05), and the RMS of the tibial anterior (TA) and EDL on the unaffected side were significantly higher (P < 0.05). The MF of the EDL on the affected side was significantly higher than that on the control side (P < 0.05). The C of the unaffected side was significantly higher than that of the control group, whereas the L was lower (P < 0.05). Compared to those of the control group, the DC of the TA, EDL, and soleus (SOL) on the unaffected sides were higher (P < 0.05), and the DC of the MG on the affected sides was lower (P < 0.05).ConclusionThe change trends and clinical significance of these three network indices, including C, L, and DC, are not in line with those of the traditional linear indices, the RMS and the MF. The C and L may reflect the degree of synchronous activation of muscles during a certain motor task. The DC might be able to quantitatively assess the degree of muscle involvement and reflect the degree of involvement of a single muscle. Linear and nonlinear indices may reveal more neuromuscular conditions in hemiplegic ankle-foot dysfunction from different aspects.Trial registrationChiCTR2100055090.