To investigate the risk of thoracoabdominal injuries in six-year-old child occupants in a reclined seating posture during frontal collisions, and provide a reference for developing child restraint systems (CRS).

Three validated biomechanical models of six-year-old child occupants in different seating postures with detailed anatomical structures were used. The acceleration curve from a sport utility vehicle crash test was applied to analyze the effects of seating posture on thoracic motion trajectory, chest acceleration, thoracoabdominal compression, viscous criterion (VC) of the chest and abdomen, internal organ strain, and spinal stress.

Thoracic motion trajectories varied in the Z-direction under three seating postures. As the upper torso angle increased, thoracoabdominal kinematic injury parameters showed an upward trend. The thoracic and abdominal VC under 120° and 135° posture increased by 67% and 113%, 10.7% and 25% compared with that under 105° standard sitting posture. The risk of thoracic internal organ injury was inversely related to the seating angle, while the risk of abdominal internal organ injury was positively related to the seating angle. The primary spinal injury mechanism was compression-flexion.

CRS protection evaluation should comprehensively consider thoracoabdominal kinematic parameters, internal organ biomechanics, and spinal injury risk. These findings have important implications for CRS development in intelligent driving systems and occupant protection strategy formulation.

To investigate stress distributions of the knee joint at 0 and 15^th day after anterior cruciate ligament reconstruction (ACLR) under a compressive force through the axis of the femoral shaft onto the proximal femur.

A three-dimensional (3D) finite element model of the human knee joint incorporating viscoelastic material properties was developed. The one-dimensional (1D) Prony series viscoelastic constitutive model parameters for articular cartilage, menisci, ligaments, and anterior cruciate ligament (ACL) grafts were determined by fitting experimental creep curves. The viscoelastic parameters of ACL grafts at 15^th day after ACLR surgery were extrapolated. Finite element simulations were then performed to analyze the von Mises stress distributions in knee ligaments, ACL grafts, articular cartilage, and menisci under 1.5 kN vertical downward compressive load applied to the femur, with loading durations of 1 second and 600 seconds.

At 15^th day after ACLR surgery, the initial relaxation modulus and equilibrium modulus of human ACL grafts remained elevated compared to native ACL tissues, resulting in a significantly higher stress concentration within the grafts relative to healthy ACL. Despite the compromised mechanical properties of the grafts after ACLR surgery, the vertical downward compressive force applied to the femur under both short-term (1 s) and prolonged (600 s) loading durations, exhibited a minimal biomechanical impact on articular cartilage and meniscal structures.

Following ACLR, vertical compressive loads during weight-bearing rehabilitation exercises such as standing demonstrate minimal impact on articular cartilage and meniscus, while promoting fibrous regeneration of the graft. This renders such exercises a prudent early-stage rehabilitation strategy. Graft preparation requires balanced consideration of elastic and viscous properties, with grafts exhibiting higher relaxation modulus and viscosity coefficient than healthy ACL proving more effective in maintaining early postoperative knee stability.

To investigate the therapeutic effects of copper-doped barium titanate (BaCuTiO₄) piezoelectric materials combined with low-intensity pulsed ultrasound (LIPUS) to activate their piezoelectric-catalytic synergistic effect for treating implant-associated infections.

BaCuTiO₄ coatings were synthesized on the surface of Ti-6Al-4V substrates using a hydrothermal method, and their surface morphology was characterized by scanning electron microscopy. The piezoelectric characteristics of the coatings were analyzed using a piezoresponse force microscope. An in vitro biofilm model of methicillin-resistant staphylococcus aureus (MRSA) was used, with barium titanate (BaTiO₃) coatings serving as the control group. Under LIPUS intervention (1.0 W/cm², 1 MHz, 10 min), the bacterial viability was assessed using colony counting to evaluate the antibacterial performance of the BaCuTiO₄ coatings. Confocal microscopy was used to observe biofilm viability in different groups, assessing the biofilm removal capability of the coatings. Reactive oxygen species (ROS) generation in each group was detected using Rhodamine b as a probe to evaluate the catalytic efficiency of the coatings in generating ROS.

Copper doping significantly reduced the piezoelectric coefficient of the coating (from 17.7 pm/V to 7.8 pm/V), bringing its piezoelectric performance closer to the requirements of natural bone tissues. Under LIPUS activation, the BaCuTiO₄ coatings increased the generation efficiency of reactive oxygen species by 67.5% and effectively disrupted and removed biofilms formed by MRSA, achieving an antibacterial rate of 90.5%.

The BaCuTiO₄ coatings achieve efficient antibacterial and biofilmclearing functions through a piezoelectric-catalytic synergistic mechanism. Their piezoelectric properties are well-matched with natural bone tissues, promoting implant osseointegration.

To study the hemodynamic characteristics of autologous arteriovenous fistula (AVF) and provide a theoretical basis for reducing its stenosis rate.

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.

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.

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.

To investigate the protective effect of cerebrospinal fluid (CSF) on the spinal cord in patients with scoliosis and evaluate its buffering effect during gravitational traction surgery and in daily life, so as to provide a theoretical guidance for surgical planning and postoperative rehabilitation of scoliosis.

A three-dimensional coupled spinal cord-CSF finite element model was established to simulate the biomechanical responses of the spine under two scenarios: gravitational traction surgery and daily life. Comparative analyses were conducted for conditions with and without CSF, and the buffering effect of CSF was quantitatively assessed.

During simulated gravitational traction surgery, CSF significantly reduced the stress and deformation of the spinal cord, with the stress in spinal cord white and gray matter decreasing by 65%-90% and deformation decreasing by 70%-95%. In the daily life scenario, CSF provided greater protective effects in lateral flexion and anterior-posterior flexion directions, with stress reductions of 60%-85%. However, in torsion, the buffering effect of CSF was relatively weaker, with stress reductions of only 10%-25%.

CSF significantly reduces spinal cord stress and deformation during gravitational traction surgery and in daily life, reducing the risk of injury.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.