The influence of loading path, intermediate principal stress and weak layers on the deformation property and failure characteristics of soft-hard interbedded rock mass is initially discussed in this study. First, the laboratory experiments of multiaxial compression failure are carried out to soft-hard interbedded rock samples of Jinping. Three failure modes of rock samples caused by different distribution forms of weak layers under uniaxial compression and deformation property and failure characteristics of rock samples in different loading paths under biaxial compression are analyzed. Then, considering the property of strain softening, numerical models are established based on the elastic-brittle-plastic constitutive relation. The effect of weak layer dip angle, quantity, distribution form, and volume ratio on strength characteristics is further investigated. The results reveal that the failure mode of Jinping soft-hard interbedded rock samples generally follows the pattern of multi-fracture splitting under uniaxial compression, and the pattern of tension-shear damage under biaxial compression. The intermediate principal stress is positively correlated with the vertical failure loading. The number of weak layers has no significant effect on the “U” type strength characteristics of samples. However, as the number of weak layers increases, there is a tendency for the minimum of vertical failure loading to move forward in the direction of smaller dip.
To explore the optimal implantation strategy of tissue-engineered liver (TEL) constructed based on decellularized spleen matrix (DSM) in rats.DSM was prepared by freeze-thawing and perfusion with sodium dodecyl sulfate (SDS) of the spleen of healthy SD rats. Primary rat hepatocytes isolated using modified Seglen 2-step perfusion method were implanted into the DSM to construct the TEL. The advantages and disadvantages were evaluated of 4 transplant strategies of the TEL, namely ectopic vascular anastomosis, liver cross-section suture transplantation, intrahepatic insertion and mesenteric transplantation.The planting rate of hepatocytes in the DSM was (74.5∓7.7)%. HE staining and scanning electron microscopy showed satisfactory cell status, and immunofluorescence staining confirmed the normal expression of ALB and G6Pc in the cells. For TEL implantation, ectopic vascular anastomosis was difficult and resulted in a mortality rate of 33.3% perioperatively and massive thrombus formation in the matrix within 6 h. Hepatic cross-section suture failed to rapidly establish sufficient blood supply, and no viable graft was observed 3 days after the operation. With intrahepatic insertion method, the hepatocytes in the DSM could survive as long as 14 days. Mesenteric transplantation resulted in a hepatocyte survival rate of (38.3+7.1)% at 14 days after implantation.TEL constructed based on DSM can perform liver-specific functions with a good cytological bioactivity. Mesenteric transplantation of the TEL, which is simple, safe and effective, is currently the optimal transplantation strategy.
This paper aims to apply a virtual boundary element method (VBEM) to solve the inverse problems of three-dimensional heat conduction in orthotropic media. This method avoids the singular integrations in the conventional bound... | Find, read and cite all the research you need on Tech Science Press
According to the characteristics of geotechnical and underground engineering structures, the variational principle employing modified Reissner functional into which independent rotation field has been introduced. The rotation field is interpolated by true rotation at each node. The rational type of incompatible fields of 4-node element is discussed. The incompatible displacement functions being suitable for arbitrary quadrilateral element are denoted. An internal parameter type incompatible element with rotational degrees of freedom is established and the numerical computation formulae are developed. The element of this paper is proved to pass the patch test. The compatibility with beam elements with rotation freedoms can be easily made. From the computational examination questions as well as the underground tunnel engineering example, it is shown that the numerical results by using the computation model of this paper have good accuracy. A perfect numerical method is developed for analyses and computations of geotechnical and underground engineering structures.
This paper investigates the influence of heterogeneity on mechanical and acoustic emission (AE) behaviours of stratified rock specimens under uniaxial compression using a digital image processing (DIP)-based finite difference method (FDM). In the DIP, a developed image segmentation algorithm based on seeded region growing (SRG) is proposed to fully acquire the mesostructure of stratified rock specimens, instead of the traditional threshold value method. To sufficiently capture the heterogeneity of stratified rock, Weibull statistical manner is adopted to describe mechanical properties of each material component. Three schemes are adopted to study the effect of heterogeneity with different homogeneity index and different mesostructure under two compression loading conditions. The results show that heterogeneity has a great influence on the mechanical and AE behaviours of stratified rock. As the homogeneity of material components increases, the peak strength and brittleness of rocks increase, and the macro elastic modulus improves as well. Simultaneously, the AE modes change from swarm shock to main shock. Under the same component content, the macro-property is better while the component distribution is concentrative relatively, especially to the property of strength. For the coupling effect of mesostructure and heterogeneity arising from material components, mesostructure is considered to cause the visible increase of AE counts. And the numerical results agree well with the previously numerical results and experimental data.
This article presents a case study of the stability of the south anchorage of Taizhou Yangtze River Bridge in China. The gravity anchorage was embedded in soil and designed according to the current code of China. The code-based stability assessment is based on two-dimensional (2D) analyses under the assumption of plane strain conditions. Two typical failure modes of sliding and overturning are considered separately. The 2D plane strain model assumes the size of a structure in one dimension is significantly larger than the sizes in the other two dimensions. It is, thus, unsuitable for gravity anchorage because its sizes are similar in all three dimensions. Additionally, the effect of surrounding soil is ignored apart from the base friction in the anti-sliding stability assumption leading to the conservative design. Therefore, a three-dimensional model is more appropriate. Three-dimensional finite element model combined with strength reduction method is used to analyse the stability of anchorage. Reduced-scale model tests are used to calibrate the numerical model. The results show that the code-based design is indeed too conservative. The effects of stiffness and strength of the surrounding soil on the stability of anchorage are investigated through parametric studies to facilitate the economical design of gravity anchorage.
To assess the impact of pile driving on adjacent submarine pipelines during the reconstruction of a pier berth, the local damage model of submarine pipelines is established to explore the safety thresholds of the particle peak velocity and horizontal displacement. The results are analyzed and adjusted by the existing standards and the corresponding literatures. Then, a three-dimensional numerical model is presented to assess the feasibility of the construction of piles by the obtained safety limits, in which the nonlinear behavior of the soil and stress–seepage coupling analysis are considered. After the construction, the safety of submarine pipelines is rechecked by the measured value of the particle peak velocity and horizontal displacement. Meanwhile, the propagation law of vibration, the horizontal displacement of underground soil, and the pore pressure during pile driving are explored. The results indicate that the construction of piles of 2# mooring pier did not cause damage to adjacent submarine pipelines. However, the construction of piles of 1# mooring pier which is nearer may cause damage to submarine pipelines.
Objective
To investigate the clinical features of myeloperoxidase antineutrophil cytoplasmic antibody (MPO-ANCA) associated hypertrophic pachymeningitis (HP).
Methods
Clinical data of 4 casesdiagnosed with MPO-ANCA vasculitis complicated with HP in our hospital were analyzed retrospectively and the related literaturewere reviewed.
Results
Four male patients with an age range from 44 to 66 years were diagnosed with ANCA-associated HP. The main clinical manifestations included headache and with- various degree ofmultiple cranial paralysis. During active phase of the disease, all patients showed perinu- clear(p)-ANCA positive, elevated levels of inflammatory biomarkers and titers of MPO-ANCA, whereas renal function, cytoplasmic (c)-ANCA and protease 3 (PR3)-ANCA were negative. Contrast-enhanced cranial ma- gnetic resonance imaging (MRI) scan showed obviously thickened dura mater and sinusitis or mass in paranasal sinus. Four patients were sensitive to glucocorticoid. Three patients had a relapse during glucocorti- coid tapering and were undercontrol when the dosage of glucocorticoid was increased and immunosuppressive agents were added. Levels of inflammatory biomarkers, titers of MPO-ANCA and p-ANCA recovered to normal, and the dural thickness on MRI was reduced in the remission stage.
Conclusion
MPO-ANCA associated HP is a type of central nervous system involvement in ANCA associated vasculitis (AAV). It involves the upper respiratory tract more frequently, and less frequently progresses to systemic AAV. This should be taken into consideration when middle-aged and elderly patients presented with headache and multiple cranial neuropathies. Enhanced MRI is the preferred examination for diagnosis, and dural biopsy should be done when necessary.
Key words:
Myeloperoxidase; Antineutrophil cytoplasmic antibody; Pachymeningitis, hypertrophic; Granuloma; Vasulitis
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