Objective To re-estimate price elasticity of different income groups’ demand for cigarette in terms of the lastest national tobacco consumption data and provide policy-makers with evidence to make decision on public policy of tobacco control. Methods A total of 16 056 adults of different income were surveyed in 27 provinces in 2002 and the data analyzed by using two-part model (logistic and log-linear model). Results We found that the demand elasticities were -0.589, -0.234, -0.017 and 0.247 for the poor group, low income group, middle income group and high income group, respectively. Conclusions Increasing tobacco tax will result in decreasing more cigarette consumption of lower income groups than higher groups, bearing more taxation of higher income groups than lower income groups, therefore tobacco taxation is not regressive.
Due to lack of the practical technique to measure the biomechanical properties of the ocular cornea in vivo, clinical ophthalmologists have some difficulties in understanding the deformation mechanism of the cornea under the action of physiological intraocular pressures. Using Young's theory analysis of the corneal deformation during applanation tonometry, the relation between the elasticity moduli of the cornea and the applanated corneal area and the measured and true intraocular pressures can be obtained. A new applanation technique has been developed for measuring the biomechanical properties of the ocular cornea tissue in vivo, which can simultaneously acquire the data of the applanation area and displacement of the corneal deformation as well as the exerted applanation force on the cornea. Experimental results on a rabbit's eyeball demonstrated that the present technique could be used to measure the elasticity moduli and creep properties of the ocular cornea nondestructively in vivo.
ObjectiveTo explore the effectiveness difference between titanium elastic intramedullary nail internal fixation and bone plate internal fixation in the treatment of adult Galeazzi fracture.MethodsNinety-seven patients of Galeazzi fracture according with the selection criteria were divided into 2 groups by prospective cohort study, who were admitted between January 2012 and November 2015. In the patients, 59 were treated with open reduction and bone plate internal fixation (plate group), and 38 with titanium elastic intramedullary nail internal fixation (minimally invasive group). There was no significant difference in the gender, age, cause of injury, fracture site, type of fracture, and time from injury to operation between 2 groups (P>0.05). The operation time, intraoperative blood loss, fracture healing time, and complications were recorded and compared between 2 groups, and the forearm function was evaluated by Anderson score.ResultsAll the patients were followed up 12-23 months (mean, 17 months). The operation time, intraoperative blood loss, fracture healing time of minimally invasive group were significantly less than those in plate group (P<0.05). There were 1 case of fracture nonunion, 1 case of wound infection in plate group, and 1 case of nail tail slight infection in minimally invasive group, which were all cured after the corresponding treatment. The remaining patients had good fracture healing, and no vascular injury, internal fixation failure, deep infection, or other complications occurred. According to Anderson score at 12 months after operation, the forearm function results were excellent in 46 cases, good in 12 cases, and poor in 1 case, with an excellent and good rate of 98.3% in plate group; and the results were excellent in 26 cases, good in 11 cases, and poor in 1 case, with an excellent and good rate of 97.4% in minimally invasive group; showing no significant difference (χ2=0.10, P=0.75).ConclusionMinimally invasive fixation with titanium elastic nail has such advantages as small damage, quick recovery, no skin scarring, etc. As long as the correct indication is selected, minimally invasive titanium intramedullary nail internal fixation of Galeazzi fractures can also get good effectiveness.
The mechanical behavior modeling of human soft biological tissues is a key issue for a large number of medical applications, such as surgery simulation, surgery planning, diagnosis, etc. To develop a biomechanical model of human soft tissues under large deformation for surgery simulation, the adaptive quasi-linear viscoelastic (AQLV) model was proposed and applied in human forearm soft tissues by indentation tests. An incremental ramp-and-hold test was carried out to calibrate the model parameters. To verify the predictive ability of the AQLV model, the incremental ramp-and-hold test, a single large amplitude ramp-and-hold test and a sinusoidal cyclic test at large strain amplitude were adopted in this study. Results showed that the AQLV model could predict the test results under the three kinds of load conditions. It is concluded that the AQLV model is feasible to describe the nonlinear viscoelastic properties of in vivo soft tissues under large deformation. It is promising that this model can be selected as one of the soft tissues models in the software design for surgery simulation or diagnosis.
Mitral valve disease is one of the most popular heart valve diseases. Precise positioning and displaying of the valve characteristics is necessary for the minimally invasive mitral valve repairing procedures. This paper presents a multi-resolution elastic registration method to compute the deformation functions constructed from cubic B-splines in three dimensional ultrasound images, in which the objective functional to be optimized was generated by maximum likelihood method based on the probabilistic distribution of the ultrasound speckle noise. The algorithm was then applied to register the mitral valve voxels. Numerical results proved the effectiveness of the algorithm.
The objective of this study was to determine the visco-hyperelastic constitutive law of brain tissue under dynamic impacts. A method combined by finite element simulations and optimization algorithm was employed for the determination of material variables. Firstly, finite element simulations of brain tissue dynamic uniaxial tension, with a maximum stretch rate of 1.3 and strain rates of 30 s–1 and 90 s–1, were developed referring to experimental data. Then, fitting errors between the engineering stress-strain curves predicted by simulations and experimental average curves were assigned as objective functions, and the multi-objective genetic algorithm was employed for the optimation solution. The results demonstrate that the brain tissue finite element models assigned with the novel obtained visco-hyperelastic material law could predict the brain tissue’s dynamic mechanical characteristic well at different loading rates. Meanwhile, the novel material law could also be applied in the human head finite element models for the improvement of the biofidelity under dynamic impact loadings.
There are two main types of fluid in bone tissue: blood and interstitial fluid. The metabolism of cells mainly relies on the microenvironment of the interstitial fluid. Researches of osteonal fluid seepage behavior based on the microstructure of bone tissue have become a hot point. The aim of the present research work is to assess the effect of blood pressure oscillation on the osteonal interstitial fluid seepage behavior. We established finite element osteon models for a hollow and that considering blood pressure oscillation, respectively, with COMSOL Multiphysics software in order to compare their fluid flow behavior under the axial loading. The results predicted that the interstitial fluid pressure field was enlarged considering the blood pressure oscillation, while the velocity filed changed little. Specifically, the increase of blood pressure oscillatory amplitude could result in the increase of osteonal interstitial fluid pressure, while the blood pressure oscillatory frequency had limited effects on the osteonal pore fluid pressure. Moreover, the blood pressure oscillatory amplitude and frequency had no effect on the osteonal interstitial fluid velocity. The finite element model can be used for the study of the poroelastic behaviors of the osteon under non-axisymmetric loads and microcracks, and can also be a new way to study the mechanism of bone mechanotransduction and electromechanotransduction.
Objective To investigate the elasticity of demand for health care services in China, and to provide suggestions for further studies. Methods Databases including PubMed, The Cochrane Library (Issue 10, 2015), EMbase, CNKI, VIP and WanFang Data were searched from inception to December 2015 to collect studies about price elasticity or income elasticity of demand for health care services. Literatures were screened and related information was independently extracted by two reviewers. Then qualitative approaches were applied to describe the elasticity. Results A total of 31 studies were included. Estimates of the own-price elasticity of demand for health care services ranged from –2.520 to 2.944 in 25 studies; 2 studies estimated cross-price elasticity between outpatient and inpatient service and one study estimated cross-price elasticity between different levels of inpatient services and all estimates were positive; Estimates of the income elasticity ranged from –0.020 to 2.480 in 28 studies. Demand for inpatient services was more income sensitive than the demand for outpatient services and urban citizens were more sensitive to income than their rural counterparts. Conclusion Health service is insensitive to price and belongs to necessity; inpatient service and outpatient service are substitutes for each other and different levels of inpatient services are substitutes for each other; government are supposed to tackle with the unbalanced increase of the demand of outpatient and inpatient services along with the increase of income to guide rational health-seeking behaviors.
ObjectiveTo identify risk factors for severe elastic recoil after percutaneous transluminal angioplasty (PTA) in the femoropopliteal artery disease based on intravascular ultrasound (IVUS) imaging and to develop a risk prediction model. MethodsA retrospective analysis was conducted on the clinical data from the patients with femoropopliteal artery disease treated at the First Affiliated Hospital of Chongqing Medical University from September 2020 to February 2022. Based on the IVUS images, a multivariate logistic regression analysis was conducted to identify the risk factors for severe elastic recoil in the patients with femoropopliteal artery disease after PTA. A nomogram prediction model was established to predict the occurrence of severe elastic recoil, and the area under receiver operating characteristic curve (AUC) was used to evaluate its ability to distinguish the occurrence of severe elastic recoil, which was validated using a calibration curve. ResultsA total of 34 patients with femoropopliteal artery disease who received PTA treatment were enrolled. Of the 803 vessel slices were analyzed, 451 (56.16%) demonstrated severe elastic recoil on IVUS imaging. The multivariate logistic regression analysis showed that the increased plaque burden, luminal eccentric index, external elastic membrane remodeling index, and the external elastic membrane-balloon area ratio were the risk factors for the occurrence of severe elastic recoil (P＜0.05). The AUC of the nomogram prediction model based on these risk factors exhibited moderate discrimination [AUC (95%CI)=0.775 (0.732, 0.818)]. The predicted probability of the nomogram model for severe elastic recoil was in a good agreement with the actual probability (P=0.862). ConclusionThe severe elastic recoil prediction model developed in this study, based on IVUS imaging data, can effectively identify high-risk factors for severe elastic recoil after PTA in patients with femoropopliteal artery disease, demonstrating a moderate predictive discrimination capability.
This study was aimed to compare the mechanical characteristics under different physiological load conditions with three-dimensional finite element model of rigid fixation and elastic fixation in the lumbar. We observed the stress distribution characteristics of a sample of healthy male volunteer modeling under vertical, flexion and extension torque situation. The outcomes showed that there existed 4-6 times pressure on the connecting rod of rigid fixation compared with the elastic fixations under different loads, and the stress peak and area of force on elastic fixation were much higher than that of the rigid fixations. The elastic fixation has more biomechanical advantages than rigid fixation in promoting interbody lumbar fusion after surgery.