Objective:To compare the changes in fracture displacement under different vertical loadings between the 2 different internal fixation modalities for vertically unstable femoral neck fractures of Pauwels type Ⅲ by a mechanical study and a finite element analysis.Methods:Twelve biomimic bones were transversely dissected from 10 cm below the lesser trochanter of the femur to create femoral neck fracture models with a Pauwels angle of 70° using a swing saw. The models were equally divided into 2 groups ( n=6): group A was fixed with 3 cannulated screws after fracture reduction (scheme A), and group B with 3 cannulated screws plus a self-designed anteromedial support plate after fracture reduction (scheme B). Continuous vertical force was applied using a mechanical testing machine. Changes in displacement were recorded and load-displacement curves were plotted. One volunteer (female, 28 years old, 168 cm in height and 65 kg in weight) was selected for finite element analysis of her CT images of both lower limbs to examine the maximum displacement and the maximum Mises stress in scheme A and scheme B respectively. Results:In groups A and B respectively: All the 6 biomimic mimetic bones had similar load and displacement curves, and similar fracture displacements (Dx) at different loading points (N X); the curves of 6 biomimic bones were highly fitted with S-shaped curve equation (the r-square value was close to 1). At the initial loading stage (0 N0.05). When the load was 100 N

Objective To investigate the effect of ventilation with different tidal volumes on respiratory mechanics and haemodynamics in children with severe pneumonia.Methods A total of 104 children with severe pneumonia were divided into the control group and the observation group using a random number table method,with 52 cases in each group.Both groups underwent mechanical ventilation treatment.The control group was treated with conventional tidal volume of 10-12 mL/kg,while the observation group was given a low tidal volume of 6-8 mL/kg.The respiratory mechanics indicators,hemodynamic indicators and inflammatory factor indicators before and after treatment were compared between the two groups.Results After treatment,the airway resistance(AR)and airway closing pressure(AOP)were lower in the observation group than those of the control group(P＜0.05),and pulmonary dynamic compliance(Cdyn)was higher in the observation group than that of the control group(P＜0.05).There were no significant differences in heart rate(HR),mean arterial pressure(MAP)and central venous pressure(CVP)after treatment between the two groups(P＜0.05).After treatment,the levels of interleukin(IL)-6,IL-8 and tumor necrosis factor-α(TNF-α)were all lower in the observation group than those in the control group(P＜0.05).Conclusion Small tidal volume mechanical ventilation is effective in improving the respiratory mechanics of children with severe pneumonia without causing large fluctuations in their hemodynamics.At the same time,it can reduce the level of inflammatory factors in the organism.

Objective To investigate the effect of ventilation with different tidal volumes on respiratory mechanics and haemodynamics in children with severe pneumonia.Methods A total of 104 children with severe pneumonia were divided into the control group and the observation group using a random number table method,with 52 cases in each group.Both groups underwent mechanical ventilation treatment.The control group was treated with conventional tidal volume of 10-12 mL/kg,while the observation group was given a low tidal volume of 6-8 mL/kg.The respiratory mechanics indicators,hemodynamic indicators and inflammatory factor indicators before and after treatment were compared between the two groups.Results After treatment,the airway resistance(AR)and airway closing pressure(AOP)were lower in the observation group than those of the control group(P＜0.05),and pulmonary dynamic compliance(Cdyn)was higher in the observation group than that of the control group(P＜0.05).There were no significant differences in heart rate(HR),mean arterial pressure(MAP)and central venous pressure(CVP)after treatment between the two groups(P＜0.05).After treatment,the levels of interleukin(IL)-6,IL-8 and tumor necrosis factor-α(TNF-α)were all lower in the observation group than those in the control group(P＜0.05).Conclusion Small tidal volume mechanical ventilation is effective in improving the respiratory mechanics of children with severe pneumonia without causing large fluctuations in their hemodynamics.At the same time,it can reduce the level of inflammatory factors in the organism.

Objective:To compare the changes in fracture displacement under different vertical loadings between the 2 different internal fixation modalities for vertically unstable femoral neck fractures of Pauwels type Ⅲ by a mechanical study and a finite element analysis.Methods:Twelve biomimic bones were transversely dissected from 10 cm below the lesser trochanter of the femur to create femoral neck fracture models with a Pauwels angle of 70° using a swing saw. The models were equally divided into 2 groups ( n=6): group A was fixed with 3 cannulated screws after fracture reduction (scheme A), and group B with 3 cannulated screws plus a self-designed anteromedial support plate after fracture reduction (scheme B). Continuous vertical force was applied using a mechanical testing machine. Changes in displacement were recorded and load-displacement curves were plotted. One volunteer (female, 28 years old, 168 cm in height and 65 kg in weight) was selected for finite element analysis of her CT images of both lower limbs to examine the maximum displacement and the maximum Mises stress in scheme A and scheme B respectively. Results:In groups A and B respectively: All the 6 biomimic mimetic bones had similar load and displacement curves, and similar fracture displacements (Dx) at different loading points (N X); the curves of 6 biomimic bones were highly fitted with S-shaped curve equation (the r-square value was close to 1). At the initial loading stage (0 N0.05). When the load was 100 N

BACKGROUND:Due to the lack of mechanical stimulation generated by functional loading,alveolar bone atrophy and bone loss in the missing area prevents the effective embedding of dental implants.Therefore,it is necessary to implant bone meal during implantation to compensate for the lack of alveolar bone height on the stability of the implant. OBJECTIVE:To derive the optimal time point for second-stage restorations from a biomechanical perspective by means of finite element analysis,thereby providing a biomechanical basis for selecting the correct time point for second-stage restoration to shorten the clinical course of dental implantation. METHODS:Three-dimensional finite element models of the maxilla were developed for normal,16-deficient with conventional implant surgery(model B)and 16-deficient with internal maxillary sinus lift(model A).Model A was filled with hydroxyapatite bone powder between the mucosa and the maxillary sinus floor,and Model B and the normal maxillary bone model did not require bone grafting.The healing time of bone grafting was set at 3-9 months postoperatively,and a force of 200 N was applied to the adjacent teeth at 3-5 months postoperatively,and directly to the implant at 6-9 months,simulating the load applied to the implant in the second stage of restoration.Biomechanical analysis of the three models was performed with the aid of the implants and the surrounding hard and soft tissues. RESULTS AND CONCLUSION:The stress on Model A and Model B was around 103 MPa and 95 MPa respectively when the force was directly loaded onto the implant.Bone grafting increased the stress values on the implant,while not doing bone grafting reduced the stress on the implant and the whole system.As the strength of the bone powder increased,the stress values on the alveolar bone decreased.When the healing time was up to 6-9 months postoperatively,the stress values were ranked as follows:normal model

Objective:To analyze the electroencephalogram (EEG) features of patients with Alzheimer’s disease (AD) and mild cognitive impairment (MCI), and to combine the characteristics for classification and prediction.Methods:One hundred and thirty-five patients attending the Department of Neurology at the General Hospital of Tianjin Medical University were enrolled, including 34 patients with AD, 67 patients with MCI, and 34 healthy control (HC). The electroencephalogram signals of these patients in the resting state were collected and preprocessed. Relative power spectral density features and sample entropy features on a multi-band scale were extracted to compare the whole-brain differences in electroencephalogram features among the 3 groups of subjects, and then subdivided into brain regions and individual leads for in-depth analysis. The above two features were fused to classify and predict AD, MCI, and HC by support vector machine (SVM).Results:The frontal regions had higher δ relative power spectral densities than the other regions, and the occipital and temporal regions showed relatively lower distributions. θ-Band relative power spectral densities had a more even distribution of sizes across brain regions. α-Band relative power spectral densities were concentrated in the occipital lobe, while β-band relative power spectral densities were mainly concentrated in the parietal and temporal lobes. Except for the central lobe, the δ-band relative power spectral densities of the AD group were higher than those of the MCI group ( P < 0.05) and HC group ( P < 0.01) in all brain regions and the whole brain. θ-band relative power spectral densities of the AD group were higher than those of the MCI gourp ( P < 0.001) and HC group ( P < 0.001) in the whole brain and in all brain regions. α-Band relative power spectral densities of the AD group were lower than those of the other groups only in the temporal lobe (all P < 0.05). The relative power spectral density of the β-band in the AD group was higher than that of the other groups in the whole brain and in all brain regions ( P < 0.05, 0.01, 0.001). The difference in the relative power spectral density of the δ-band in the C3 lead in the central lobe of the AD and HC groups was statistically significant ( P < 0.05). The relative power spectral density of the γ-band in the temporal lobe was higher than that in the other regions of the AD group, the MCI group, and the HC group. The relative power spectral density of the γ-band in the T3 lead in the AD group was significantly lower than that in the T4 lead. The average entropy of samples in the whole brain and in each brain region was lower than that in the HC group in the AD and MCI groups (all P < 0.05). The entropy of the samples at lead C3 in the AD group was lower than that in the MCI group ( P < 0.05). The differences between the relative power spectral density, sample entropy, and the actual data classification evaluation indexes (accuracy rate, precision rate, recall rate, and F1 score) that fused the two features, and the rearranged data were all statistically significant (all P < 0.001). When the relative power spectral density feature and the sample entropy feature were fused in the classification features, the best classification prediction was achieved, with an accuracy rate of 80%, a precision rate of 78%, a recall rate of 78%, and the F1 score of 79%. Conclusions:Relative power spectral density and sample entropy analysis can reveal the abnormalities of electroencephalogram activities of AD and MCI patients from different perspectives (linear and nonlinear), and the combination of these two features in classification prediction can improve the classification effect.

Objective To establish a finite element model of the T2-L5 thoracolumbar spine and verify its validity,to provide numerical model support for exploring the dynamic response characteristics and injury mechanism under spinal impact loads.Methods A three-dimensional(3D)finite element model of the T2-L5 thoracolumbar spine was established based on CT scanning data.The load-rotation angle curve of the T12-L1 segment under different moments(flexion,extension,rotation,and lateral bending conditions)was calculated and compared with the data reported in the literature.Free-fall loads at different heights were applied to the finite element models of the T2-6,T7-11,and T12-L5 spine.The peak axial force and bending moment were obtained by finite element simulation analysis and compared with data reported in the literature.Results The maximum rotation angle of the T12-L1 finite element model was-2.24°-1.55° under moments in different directions,which was in good agreement with the literature data.The peak axial force of T2-6,T7-11,and T12-L5 spine finite element models subjected to different free-fall loads was 1.7-5.3 kN,1.3-5.5 kN,and 1.3-7.5 kN respectively,which were within the error range reported in the literature.Stress nephograms of the spine and intervertebral discs showed that the vertebral body was first stressed from the outer edge.The intervertebral disc was subjected to the main load by the nucleus pulposus,consistent with the actual spinal injury mechanism.Conclusions The T2-L5 spine model established in this study can correctly simulate the biomechanical behavioral characteristics of the spine under different working conditions,and the analysis results are effective.

Postzygotic mutations are acquired in normal tissues throughout an individual's lifetime and hold clues for identifying mutagenic factors.Here,we investigated postzygotic mutation spectra of healthy individuals using optimized ultra-deep exome sequencing of the time-series samples from the same volunteer as well as the samples from different individuals.In blood,sperm,and muscle cells,we resolved three common types of mutational signatures.Signatures A and B represent clock-like mutational processes,and the polymorphisms of epigenetic regulation genes influence the pro-portion of signature B in mutation profiles.Notably,signature C,characterized by C＞T transitions at GpCpN sites,tends to be a feature of diverse normal tissues.Mutations of this type are likely to occur early during embryonic development,supported by their relatively high allelic frequencies,presence in multiple tissues,and decrease in occurrence with age.Almost none of the public datasets for tumors feature this signature,except for 19.6％of samples of clear cell renal cell carcinoma with increased activation of the hypoxia-inducible factor 1(HIF-1)signaling pathway.Moreover,the accumulation of signature C in the mutation profile was accelerated in a human embryonic stem cell line with drug-induced activation of HIF-1α.Thus,embryonic hypoxia may explain this novel signature across multiple normal tissues.Our study suggests that hypoxic condition in an early stage of embryonic development is a crucial factor inducing C＞T transitions at GpCpN sites;and indi-viduals'genetic background may also influence their postzygotic mutation profiles.

OBJECTIVETo construct a three-dimensional finite element model of the upper airway and adjacent structure of an obstructive sleep apnea hypopnea syndrome (OSAHS) patient for biomechanical analysis. And to study the influence of glossopharyngeum of an OSAHS patient with three-dimensional finite element model during titrated mandible advancement.

METHODSDICOM format image information of an OSAHS patient's upper airway was obtained by thin-section CT scanning and digital image processing were utilized to construct a three-dimensional finite element model by Mimics 10.0, Imageware 10.0 and Ansys software. The changes and the law of glossopharyngeum were observed by biomechanics and morphology after loading with titrated mandible advancement.

RESULTSA three-dimensional finite element model of the adjacent upper airway structure of OSAHS was established successfully. After loading, the transverse diameter of epiglottis tip of glossopharyngeum increased significantly, although the sagittal diameter decreased correspondingly. The principal stress was mainly distributed in anterior wall of the upper airway. The location of principal stress concentration did not change significantly with the increasing of distance. The stress of glossopharyngeum increased during titrated mandible advancement.

CONCLUSIONA more precise three-dimensional finite model of upper airway and adjacent structure of an OSAHS patient is established and improved efficiency by Mimics, Imageware and Ansys software. The glossopharyngeum of finite element model of OSAHS is analyzed by titrated mandible advancement and can effectively show the relationship between mandible advancement and the glossopharyngeum.