Although a number of finite element (FE) adult cervical spine models have been developed to understand the injury mechanisms of the neck in automotive related crash scenarios, there have been fewer efforts to develop a child neck model. In this study, a 10-year-old ligamentous cervical spine FE model was developed for application in the improvement of pediatric safety related to motor vehicle crashes. The model geometry was obtained from medical scans and meshed using a multi-block approach. Appropriate properties based on review of literature in conjunction with scaling were assigned to different parts of the model. Child tensile force–deformation data in three segments, Occipital-C2 (C0–C2), C4–C5 and C6–C7, were used to validate the cervical spine model and predict failure forces and displacements. Design of computer experiments was performed to determine failure properties for intervertebral discs and ligaments needed to set up the FE model. The model-predicted ultimate displacements and forces were within the experimental range. The cervical spine FE model was validated in flexion and extension against the child experimental data in three segments, C0–C2, C4–C5 and C6–C7. Other model predictions were found to be consistent with the experimental responses scaled from adult data. The whole cervical spine model was also validated in tension, flexion and extension against the child experimental data. This study provided methods for developing a child ligamentous cervical spine FE model and to predict soft tissue failures in tension.

Under an appropriate exposure dose, AgNPs provide positive impacts on rice tillering, yield, grain metabolite profile, and soil bacteria.

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Objective To explore the high-risk factors of augmented vertebra recompression after percutaneous vertebral augmentation (PVA) in the treatment of osteoporotic vertebral compression fracture (OVCF) and analyze the correlation between these factors and augmented vertebra recompression after PVA. Methods A retrospective analysis was conducted on 353 patients who received PVA for a single-segment osteoporotic vertebral compression fracture from January 2017 to December 2018 in our department according to the inclusion criteria. All cases meeting the inclusion and exclusion criteria were divided into two groups: 82 patients in the recompression group and 175 patients in the non-compression group. The following covariates were reviewed: age, gender, body mass index (BMI), injured vertebral segment, bone mineral density (BMD) during follow-up, intravertebral cleft (IVC) before operation, selection of surgical methods, unilateral or bilateral puncture, volume of bone cement injected, postoperative leakage of bone cement, distribution of bone cement, contact between the bone cement and the upper or lower endplates, and anterior height of injured vertebrae before operation, after surgery, and at the last follow-up. Univariate analysis was performed on these factors, and the statistically significant factors were substituted into the logistic regression model to analyze their correlation with the augmented vertebra recompression after PVA. Results A total of 257 patients from 353 patients were included in this study. The follow-up time was 12–24 months, with an average of 13.5 ± 0.9 months. All the operations were successfully completed, and the pain of patients was relieved obviously after PVA. Univariate analysis showed that in the early stage after PVA, the augmented vertebra recompression was correlated with BMD, surgical methods, volume of bone cement injected, preoperative IVC, contact between bone cement and the upper or lower endplates, and recovery of anterior column height. The difference was statistically significant (P < 0.05). Among them, multiple factors logistic regression elucidated that more injected cement (P < 0.001, OR = 0.558) and high BMD (P = 0.028, OR = 0.583) were negatively correlated with the augmented vertebra recompression after PVA, which meant protective factors (B < 0). Preoperative IVC (P < 0.001, OR = 3.252) and bone cement not in contact with upper or lower endplates (P = 0.006, OR = 2.504) were risk factors for the augmented vertebra recompression after PVA. The augmented vertebra recompression after PVP was significantly less than that of PKP (P = 0.007, OR = 0.337). Conclusions The augmented vertebra recompression after PVA is due to the interaction of various factors, such as surgical methods, volume of bone cement injected, osteoporosis, preoperative IVC, and whether the bone cement is in contact with the upper or lower endplates.

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Piezoelectric thin rings are periodically introduced and placed on a base plate along the radial direction, forming a onedimensional thin circular plate of piezoelectric radial phononic crystals (CPPRPC). Based on flexural wave equation of thin circular plate and the transfer matrix method, the behavior of flexural waves propagating in CPPRPC is analyzed theoretically and numerically, especially in the band gaps. The transmission curves of CPPRPC and homogeneousmaterial plate are calculated for comparison. Afterwards finite element simulations are carried out to verify the theoretical results. Furthermore, the effects of the length ratio, thickness ratio, period number and control gain on the flexural wave band gap are discussed in detail. Our results show that there are band gaps of flexural wave in CPPRPC. Structural parameters and outer active control gain have important influences on the band gaps. In particular, low and broad band gaps can be obtained effectively by varying outer active control gain.

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