Objective To explore the correlation between single-leg standing posture control and ankle plantar flexor muscle stability,so as to provide a new theoretical basis for improving the ability of human posture control.Methods A total of 20 healthy male college students were randomly selected as the experimental subjects.The iBalance tester and training system was used to test the trajectory data of the center of pressure(COP)of the foot standing on one leg.The CON-TREX MJ multi-joint isokinetic test and training system was used to test the moment amplitude data during the contraction of ankle plantar flexor muscles.Univariate repeated measures variance analysis was used to analyze the standard deviation data of ankle plantar flexor moment amplitude between groups.The Pearson correlation coefficient was used to study the correlation.Results The greater the intensity of the muscle stabilization task performed by the ankle plantar flexor muscle,the greater the standard deviation of the moment amplitude.The C90 area was positively correlated with the coefficient of variation(CV)of the 10％maximum voluntary contraction(MVC)moment of ankleplantar flexor muscle(r=0.761,P＜0.05)during single-leg standing without interference.The C90 area was positively correlated with the CV(r=0.632,P＜0.05)of the 30％MVC moment of ankle plantar flexor muscle during single-leg standing.When the proprioception was interfered during single-leg standing,the C90 area was positively correlated with the CV(r=0.583,P＜0.05)of the 20％MVC moment amplitude of ankleplantar flexor muscle.Conclusions With the increasing difficulty of muscle strength stabilization performed by the ankle plantar flexor muscles,muscle stability decreases.There is a positive correlation between ankle plantar flexor strength stability and single-leg standing posture control.Compared with the case without interference,under visual and proprioceptive interference,an additional information input is reduced or disturbed,and it is more difficult to maintain body balance,and the ankle plantar flexor muscle needs a higher muscle stability in the force mode to participate in the posture control of the human body during single-leg standing.

Objective To address the limitations of conventional physics-informed neural network(PINN)in handling hemodynamic boundary constraints,an improved hard boundary-constrained PINN(HBC-PINN)framework was proposed to achieve precise prediction of blood flow fields within stenotic arteries.Methods An idealized stenosed vessel geometry model was established and computational fluid dynamic simulation was performed to obtain a validation dataset.Appropriate boundary dependent trial functions were designed according to the hard constraint method to embed the flow boundary conditions into the network output.Thus,an HBC-PINN model with the hard boundary constraint method was constructed to predict the velocity field and pressure field of stenosed blood flow.Meanwhile,an original PINN model with the soft constraint method was also built for comparison.By evaluating the accuracy of the two models on the validation dataset,the capability of the HBC-PINN model to simulate hemodynamics without using any labeled data for training was verified.Results The effectiveness of the HBC-PINN method in predicting hemodynamic parameters in stenosed blood flow tasks was validated.The relative L2 errors of the flow velocity and pressure predicted by the HBC-PINN in two different stenosis scenarios were both lower than 0.5％,representing an improvement of over 48.8％in accuracy compared to the original PINN model.Additionally,the prediction accuracy of the transverse velocity also increased by more than 35.4％.Conclusions Implementing hard constraints on boundary conditions in the PINN modeling process can effectively improve the prediction accuracy of hemodynamic parameters and the efficiency of model solving.

Objective To explore the impact of vision impairment(VI)on the gait of hemiplegic patients,assess their walking ability and fall risks,and provide a basis for developing effective rehabilitation strategies.Methods Thirty hemiplegic patients were enrolled and stratified by the severity of visual acuity impairment into three groups(unimpaired,mildly impaired,and severely impaired).The gait data of patients under uncorrected vision were collected using the Qualisys motion capture system and the Kistler three-dimensional force platform,and the balance ability of patients was assessed simultaneously.Subsequently,the gait and assessment data were statistically analyzed to compare inter-group differences.Results Compared with the visually unimpaired group,significant differences in step length,symmetry,and walking speed were observed in hemiplegic patients of the mild visual impairment group and severe visual impairment group.As VI increased,gait abnormalities became more pronounced,with a longer double-limb support phase,a longer swing phase of the affected limb,and a shorter single-limb support phase of the affected limb in the gait cycle.Compared with the visually unimpaired group,significant differences in center of pressure(COP)and COP symmetry were found between the mild visual impairment group and severe visual impairment group,with gait abnormalities intensifying.The Berg balance scale(BBS)scores showed that there was a significant difference between the visually unimpaired group and severe visual impairment group,indicating that the group with visual impairment had poorer balance ability.Conclusions VI has a significant negative impact on the gait and walking ability of hemiplegic patients.This study emphasizes the importance of focusing on the impact of VI in the rehabilitation of hemiplegic patients,with regular vision assessments and personalized interventions being conducted,which are of great significance in enhancing patients' walking quality.

Objective To investigate the dynamic balance ability of healthy young adults under different obstacle-crossing strategies,thereby providing a theoretical basis for fall prevention training and public facility design.Methods Twenty healthy young adults participated in the experiment using F-scan plantar pressure analysis insoles.The subjects were required to cross three obstacles with different combinations of height and width.With their dominant foot serving as the leading foot and the non-dominant foot as the trailing foot,the subjects performed both lateral and forward crossing maneuvers,and their plantar pressure data were collected.Results Different crossing strategies significantly affected the adjustment speed of the leading foot's center of pressure in the medial-lateral direction(COP_ML),the area of the 95％confidence circle,ML amplitude,and anterior-posterior(AP)amplitude(P＜0.05).These strategies also significantly impacted the trailing foot's COP_ML adjustment speed,the area of the 95％confidence circle,and the range between the maximum and minimum swings(P＜0.05).For the leading foot,during lateral and forward crossing,the balance parameter values under different heights and widths were statistically significant(P＜0.05),increasing as the height and width increased.For the trailing foot,during forward crossing,the balance parameter values under different heights were statistically significant(P＜0.05),increasing with height,while during lateral crossing,the differences in balance parameter values were not statistically significant(P＞0.05).Conclusions Healthy young adults demonstrate better balance ability with the leading foot during forward obstacle crossing,which aligns with the movement habits of the dominant foot and daily activity patterns.The trailing foot exhibits a more stable plantar pressure distribution during lateral obstacle crossing,likely due to a larger contact area and more even center of gravity distribution.

Objective The sample entropy(SEn)was used to explore standing balance ability and balance control characteristics of the human body under different time scales,in order to reveal the influence of different support conditions and standing tasks on balance control mechanisms.Methods Twenty-two young adults(11 males,11 females)performed standing tasks on hard and soft support surfaces using both legs,the left leg,and the right leg.Each task lasted 30 seconds.Center of pressure(COP)data in the anterior-posterior(AP)and medial-lateral(ML)directions were collected,and sample entropy(SEn),entropic half-life(EnHL),and entropy change rate were calculated.Results When males stood on their left leg on a soft support surface,significant differences in EnHL were observed in both the AP and ML directions(P＜0.05).Significant differences in EnHL in the AP direction were also found for both males and females standing on their right leg on a soft support surface(P＜0.05).Under all standing conditions,EnHL values for both males and females exceeded 100 ms.During one-legged standing on a soft support surface,males exhibited significantly higher SEn values in both the AP and ML directions compared to females(P＜0.05).During double-legged standing on a hard support surface,males showed an entropy change rate of-0.005,indicating a backward movement trend and fewer posture adjustments.Additionally,during double-legged standing on a soft support surface,the time to reach EnHL in the ML direction was 194 ms for males and 192 ms for females,while females had a shorter EnHL time in the AP direction(168 ms).Changes in the support surface had a minor impact on EnHL.Conclusions Reduced proprioception may lead to variations in balance control strategies between genders and limbs.Males tended to adjust forward,whereas females tended to adjust backward.Gender did not significantly affect the stability of balance control during double-leg standing.Males may require more intervention and adjustment to maintain balance under specific disruptive conditions.

Objective To analyze the effects and differences of two veno-arterial extracorporeal membrane oxygenation(VA-ECMO)cannulation methods and subsequent left ventricular unloading on cardiac function and hemodynamics.Methods The lumped parameter model(LPM)of VA-ECMO integrated with the cardiovascular system in the MATLAB/Simulink environment was extended to simulate and analyze the changes in ventricular function and blood flow in the heart failure patient model under central VA-ECMO or peripheral VA-ECMO support.The effects of using arterial vasodilators or a left atrial drainage cannula on left ventricular function under central VA-ECMO support at a pump flow rate of 3 L/min were compared.Results Under central VA-ECMO or peripheral VA-ECMO support,left ventricular pressure and volume increased,and stroke volume and ventricular work decreased.Both arterial vasodilators and the left atrial drainage cannula could reduce left ventricular pressure and volume.Arterial vasodilators additionally increased stroke volume and improved left ventricular ejection fraction from 11.6％to 19.5％.Conclusions Both VA-ECMO cannulation methods provide effective circulatory support in the heart failure patient model,with similar effects on ventricular function.Under central VA-ECMO support,arterial vasodilators can improve left ventricular function more effectively than the left atrial drainage cannula.

Objective To design and verify an implantable dialysis port that enables the central venous catheter to no longer be placed on the body surface,and to study the effect of the central venous catheter's structural design on its performance.Methods The feasibility of the dialysis port was verified by flow and pressure experiments.Four representative catheter structures were analyzed by finite element method.The recirculation rate,flow rate-pressure ratio and proportion of indwelling particles were recorded,and performance differences were analyzed.An experimental platform was built to verify the simulation conclusion,and the fluid flow direction of the arteriovenous cavity was quantified by the salinity measurement method.Results The dialysis port could reach the flow requirement of 300 mL/min under the 45 kPa pressure.The recirculation rate of the measured central venous catheter was between 10.7％and 23.5％,and the residual value of heparin was between 2.3％and 2.8％.The performance of the catheter with bundle mouth,positive position and side hole structure was better.Conclusions The implantable dialysis port can potentially cooperate with central venous catheters to establish a new vascular access approach.The structure of the central venous catheter should adopt the design of bundle mouth,positive position and side hole,which has better recirculation rate and heparin locking performance with low flow rate-pressure ratio.This study provides a theoretical and experimental basis for structural design and clinical selection of the central venous catheter.

Objective To achieve non-invasive and precise prediction of mean arterial pressure(MAP)based on a fully convolutional neural network(FCNN).Methods A high-precision blood pressure data acquisition system compliant with international metrological standards was used in conjunction with the'gold standard'auscultation method to collect blood pressure and pulse waveform data from patients.True MAP values were derived via Gaussian fitting of pulse waveform data,constructing a traceable dataset.The FCNN was applied to this dataset to develop a novel MAP prediction method.Additionally,the predictive accuracy of the FCNN was compared with linear regression and conventional empirical formulas.Results The mean squared errors(MSE)for MAP prediction using the FCNN,linear regression,and empirical formulas were 19.76,21.40,and 30.97,respectively.The coefficients of determination(R2)were 0.90,0.89,and 0.84,and the prediction accuracies were 0.90,0.89,and 0.85,respectively.Conclusions By using systolic blood pressure,diastolic blood pressure,age,and arm circumference as input parameters,the FCNN-based MAP prediction method significantly reduces the bias of empirical formulas.This approach not only improves the accuracy of hemodynamic boundary condition acquisition but also contributes to refining the metrological traceability system of non-invasive blood pressure measurement.

Objective To study the hemodynamic characteristics of autologous arteriovenous fistula(AVF)and provide a theoretical basis for reducing its stenosis rate.Methods Bidirectional fluid-structure interaction(FSI)simulations were conducted on a modified AVF model.Flow field and wall shear stress(WSS)distributions in the internal fistula at different periods and angles in a cardiac cycle were analyzed for retrograde flow(confluence)and anterograde flow(shunt)modes in models with varying anastomosis angles.Results Under confluence modes,the WSS＜1 Pa area in the 60° anastomosis angle model was the smallest(7.027 mm2),while the 45°,60°,and 90° models showed no significant differences in eddy current size and intensity.Under shunt modes,the 45° anastomosis angle model had the smallest WSS＜1 Pa area(9.079 mm2),but the 60° model exhibited the lowest eddy current intensity and distribution area.In addition,the difference in the WSS＜1 Pa area between the 60° and 45° models was only 2.661 mm2.Conclusions Under both confluence and shunt flow modes,establishing an AVF with 60° anastomosis angle is conducive to reducing the risk of vascular stenosis in arteriovenous fistula.

Objective To investigate the feasibility of parallel capillary bundle arrays for physiomimetic impedance modeling and establish a parametric quantification framework,thereby providing a customizable impedance characterization methodology for diverse in-vitro mock circulation researches.Methods Based on the parallel flow resistance and Poiseuille equation,a tube resistance element with multiple parallel-aligned capillary glass tubes was designed and fabricated.The resistance values of the capillary-bundle and a ball valve were measured through constant flow experiments analogous to electrical resistance measurement method.Moreover,a simple lumped-parameter mock circulation loop was constructed and the pressure and flow rate for each node of the loop were measured under different input flow waveforms.An 0D-Windkessel model corresponding to the experiment was developed.The impedance and compliance were adjusted to match the simulated and experimental pressure and flow waveforms.The accuracy of the capillary bundle impedance in pulsatile experiments was verified by using the computational resistance values.Results The constant-flow impedance calibration experiments revealed that the capillary bundle impedance remained unaffected by flow rate variations over a wide flow range.When the capillary bundle impedance was integrated into the pulsatile circulatory system and the same impedance value obtained from the constant-flow calibration was applied in the computational model,the resulting pressure and flow waveforms showed good agreement with those measured in the pulsatile experiments.However,when the ball valves with nominally identical impedance values were inserted in the pulsatile system,the calculated impedance exhibited a two-fold difference,and significant discrepancies were observed between the simulated and experimental terminal flow waveforms.Conclusions The capillary bundle impedance maintains a constant value regardless of flow rate variations.Once the calibrated resistance value is determined through constant flow experiments,it can be directly applied to pulsatile systems.This approach can provide quantitative pulsatile flow conditions for testing various medical devices.