The general meshless local Petrov-Galerkin (MLPG) weak forms of the displacement and trac- tion boundary integral equations (BIEs) are presented for solids undergoing small deformations. Using the directly der...The general meshless local Petrov-Galerkin (MLPG) weak forms of the displacement and trac- tion boundary integral equations (BIEs) are presented for solids undergoing small deformations. Using the directly derived non-hyper-singular integral equations for displacement gradients, simple and straight- forward derivations of weakly singular traction BIEs for solids undergoing small deformations are also pre- sented. As a framework for meshless approaches, the MLPG weak forms provide the most general basis for the numerical solution of the non-hyper-singular displacement and traction BIEs. By employing the various types of test functions, several types of MLPG/BIEs are formulated. Numerical examples show that the pre- sent methods are very promising, especially for solving the elastic problems in which the singularities in dis- placements, strains, and stresses are of primary concern.展开更多
Th boundary integral equation (BIE) of displacement derivatives isput at a disadvan- tage for the difficulty involved in the evaluationof the hypersingular integrals. In this paper, the op- erators δ_ijand ε_ij are ...Th boundary integral equation (BIE) of displacement derivatives isput at a disadvan- tage for the difficulty involved in the evaluationof the hypersingular integrals. In this paper, the op- erators δ_ijand ε_ij are used to ac to the derivative BIE. The boundarydisplacements tractions and displacement derivatives are transformedinto a set of new boundary tensors as boundary variables. A new BIEformulation termed natural boundary integral equation (NBIE) isobtained. The NBIE is applied to solving two-dimensional elasticityproblems. In the NBIE only the strongly singular inte- grals arecontained. The Cauchy principal value integrals occurring in the NBIEare evaluated. A combination of the NBIE and displacement BIE can beused to directly calculate the boundary stress- es. The numericalresults of several examples demonstrate the accuracy of the NBIE.展开更多
Objective:To determine the active components of Eupolyphaga sinensis Walker(Tu Bie Chong)and explore the mechanisms underlying its fracture-healing ability.Methods: A modified Einhorn method was used to develop a rat ...Objective:To determine the active components of Eupolyphaga sinensis Walker(Tu Bie Chong)and explore the mechanisms underlying its fracture-healing ability.Methods: A modified Einhorn method was used to develop a rat tibial fracture model.Progression of bone healing was assessed using radiological methods.Safranin O/fast green and CD31 immunohistochemical staining were performed to evaluate the growth of bone cells and angiogenesis at the fracture site.Methylthiazoletetrazolium blue and wound healing assays were used to analyze cell viability and migration.The Transwell assay was used to explore the invasion capacity of the cells.Tubule formation assays were used to assess the angiogenesis capacity of human vascular endothelial cells(HUVECs).qRT-PCR was used to evaluate the changes in gene transcription levels.Results: Tu Bie Chong fraction 3(TF3)significantly shortened the fracture healing time in model rats.X-ray results showed that on day 14,fracture healing in the TF3 treatment group was significantly better than that in the control group(P=.0086).Tissue staining showed that cartilage growth and the number of H-shaped blood vessels at the fracture site of the TF3 treatment group were better than those of the control group.In vitro,TF3 significantly promoted the proliferation and wound healing of MC3T3-E1s and HUVECs(all P<.01).Transwell assays showed that TF3 promoted the migration of HUVECs,but inhibited the migration of MC3T3-E1 cells.Tubule formation experiments confirmed that TF3 markedly promoted the ability of vascular endothelial cells to form microtubules.Gene expression analysis revealed that TF3 significantly promoted the expression of VEGFA,SPOCD1,NGF,and NGFR in HUVECs.In MC3T3-E1 cells,the transcript levels of RUNX2 and COL2A1 were significantly elevated following TF3 treatment.Conclusion: TF3 promotes fracture healing by promoting bone regeneration associated with the RUNX2 pathway and angiogenesis associated with the VEGFA pathway.展开更多
Microfold (M) cells are a kind of intestinal epithelial cell in the follicle-associated epithelium (FAE) of Peyer’s patches. They can transport antigens and microorganisms to lymphoid tissues. Bovine spongiform encep...Microfold (M) cells are a kind of intestinal epithelial cell in the follicle-associated epithelium (FAE) of Peyer’s patches. They can transport antigens and microorganisms to lymphoid tissues. Bovine spongiform encephalopathy (BSE) is a fatal neurodegenerative disorder in cattle. It is linked to variant Creutzfeldt-Jakob disease in humans. Although it is thought that M cells transport the BSE agent, the exact mechanism by which it crosses the intestinal barrier is not clear. We have bovine intestinal epithelial cell line (BIE cells), which can differentiate into the M cell type in vitro after stimulation, and which is able to transport the BSE agent. We show here that M cells are able to incorporate large numbers of PrP coated magnetic particles into intracellular vesicles, which we collected. The results of 2-DE show a specific protein associated with the PrP-coated particles, compared with non-coated particles. This protein was identified as aldolase A, a glycolytic pathway enzyme, using LC-MS/MS analysis. Aldolase A was synthesized and secreted by BIE cells, and increased during M cell differentiation. In the villi of the bovine intestine, aldolase A was detected on the surface of the epithelium and in the mucus droplet of goblet cells. In the FAE of bovine jejunal and ileal Peyer’s patches, aldolase A was localized on the surface and the apical part of the M cells. The binding of rbPrP to aldolase A was clearly detected and inhibited by pre-treatment of anti-aldolase A antibody. Aldolase A was co-stained with incorporated PrPSc in M-BIE cells. These results suggest that bovine M cells and goblet cells synthesize aldolase A, and that aldolase A may have the ability to bind PrP and associate with PrP in cellular vesicles. Therefore, aldolase A-positive M cells may play a key role in the invasion of BSE into the body.展开更多
The objective of this paper is to develop a dynamic slip model for a shear crack under constant stress drop. This crack problem is formulated by a traction boundary integral equation （BIE） in the frequency domain an...The objective of this paper is to develop a dynamic slip model for a shear crack under constant stress drop. This crack problem is formulated by a traction boundary integral equation （BIE） in the frequency domain and then solved by the hyper-singular boundary element method as well as the regularization technique proposed in this paper. Based on the spectral integral form of the kernel function, the unbounded term can be isolated and extracted from the hyper-singular kernel function by using the method of subtracted and added back in wave number domain. Finally, based on the inverse transformation from the frequency domain to the time domain, the time histories of crack opening displacement under constant stress drop can be determined. Three rupture models （simultaneous rupture model, symmetric bilaterally-propagating model and unilaterally propagating model） with specified time histories of stress drop are considered in this paper. Even though these three models will cause the same final slip shapes because of the same constant stress drop, the associated slip time functions differ significantly from each other during the rupture process.展开更多
The low-order polynomial-distributed eigenstrain formulation of the boundary integral equation （BIE） and the corresponding definition of the Eshelby tensors are proposed for the elliptical inhomogeneities in two-dim...The low-order polynomial-distributed eigenstrain formulation of the boundary integral equation （BIE） and the corresponding definition of the Eshelby tensors are proposed for the elliptical inhomogeneities in two-dimensional elastic media. Taking the results of the traditional subdomain boundary element method （BEM） as the control, the effectiveness of the present algorithm is verified for the elastic media with a single elliptical inhomogeneity. With the present computational model and algorithm, significant improvements are achieved in terms of the efficiency as compared with the traditional BEM and the accuracy as compared with the constant eigenstrain formulation of the BIE.展开更多
文摘The general meshless local Petrov-Galerkin (MLPG) weak forms of the displacement and trac- tion boundary integral equations (BIEs) are presented for solids undergoing small deformations. Using the directly derived non-hyper-singular integral equations for displacement gradients, simple and straight- forward derivations of weakly singular traction BIEs for solids undergoing small deformations are also pre- sented. As a framework for meshless approaches, the MLPG weak forms provide the most general basis for the numerical solution of the non-hyper-singular displacement and traction BIEs. By employing the various types of test functions, several types of MLPG/BIEs are formulated. Numerical examples show that the pre- sent methods are very promising, especially for solving the elastic problems in which the singularities in dis- placements, strains, and stresses are of primary concern.
文摘Th boundary integral equation (BIE) of displacement derivatives isput at a disadvan- tage for the difficulty involved in the evaluationof the hypersingular integrals. In this paper, the op- erators δ_ijand ε_ij are used to ac to the derivative BIE. The boundarydisplacements tractions and displacement derivatives are transformedinto a set of new boundary tensors as boundary variables. A new BIEformulation termed natural boundary integral equation (NBIE) isobtained. The NBIE is applied to solving two-dimensional elasticityproblems. In the NBIE only the strongly singular inte- grals arecontained. The Cauchy principal value integrals occurring in the NBIEare evaluated. A combination of the NBIE and displacement BIE can beused to directly calculate the boundary stress- es. The numericalresults of several examples demonstrate the accuracy of the NBIE.
基金supported by“the Fundamental Research Funds for the Central Universities”(2020-JYB-ZDGG-054)“Beijing university of Chinese medicine XINAO Award Fund”(2019)Beijing University of Chinese Medicine Scientific Research and Development Fund(2170072220002).
文摘Objective:To determine the active components of Eupolyphaga sinensis Walker(Tu Bie Chong)and explore the mechanisms underlying its fracture-healing ability.Methods: A modified Einhorn method was used to develop a rat tibial fracture model.Progression of bone healing was assessed using radiological methods.Safranin O/fast green and CD31 immunohistochemical staining were performed to evaluate the growth of bone cells and angiogenesis at the fracture site.Methylthiazoletetrazolium blue and wound healing assays were used to analyze cell viability and migration.The Transwell assay was used to explore the invasion capacity of the cells.Tubule formation assays were used to assess the angiogenesis capacity of human vascular endothelial cells(HUVECs).qRT-PCR was used to evaluate the changes in gene transcription levels.Results: Tu Bie Chong fraction 3(TF3)significantly shortened the fracture healing time in model rats.X-ray results showed that on day 14,fracture healing in the TF3 treatment group was significantly better than that in the control group(P=.0086).Tissue staining showed that cartilage growth and the number of H-shaped blood vessels at the fracture site of the TF3 treatment group were better than those of the control group.In vitro,TF3 significantly promoted the proliferation and wound healing of MC3T3-E1s and HUVECs(all P<.01).Transwell assays showed that TF3 promoted the migration of HUVECs,but inhibited the migration of MC3T3-E1 cells.Tubule formation experiments confirmed that TF3 markedly promoted the ability of vascular endothelial cells to form microtubules.Gene expression analysis revealed that TF3 significantly promoted the expression of VEGFA,SPOCD1,NGF,and NGFR in HUVECs.In MC3T3-E1 cells,the transcript levels of RUNX2 and COL2A1 were significantly elevated following TF3 treatment.Conclusion: TF3 promotes fracture healing by promoting bone regeneration associated with the RUNX2 pathway and angiogenesis associated with the VEGFA pathway.
文摘Microfold (M) cells are a kind of intestinal epithelial cell in the follicle-associated epithelium (FAE) of Peyer’s patches. They can transport antigens and microorganisms to lymphoid tissues. Bovine spongiform encephalopathy (BSE) is a fatal neurodegenerative disorder in cattle. It is linked to variant Creutzfeldt-Jakob disease in humans. Although it is thought that M cells transport the BSE agent, the exact mechanism by which it crosses the intestinal barrier is not clear. We have bovine intestinal epithelial cell line (BIE cells), which can differentiate into the M cell type in vitro after stimulation, and which is able to transport the BSE agent. We show here that M cells are able to incorporate large numbers of PrP coated magnetic particles into intracellular vesicles, which we collected. The results of 2-DE show a specific protein associated with the PrP-coated particles, compared with non-coated particles. This protein was identified as aldolase A, a glycolytic pathway enzyme, using LC-MS/MS analysis. Aldolase A was synthesized and secreted by BIE cells, and increased during M cell differentiation. In the villi of the bovine intestine, aldolase A was detected on the surface of the epithelium and in the mucus droplet of goblet cells. In the FAE of bovine jejunal and ileal Peyer’s patches, aldolase A was localized on the surface and the apical part of the M cells. The binding of rbPrP to aldolase A was clearly detected and inhibited by pre-treatment of anti-aldolase A antibody. Aldolase A was co-stained with incorporated PrPSc in M-BIE cells. These results suggest that bovine M cells and goblet cells synthesize aldolase A, and that aldolase A may have the ability to bind PrP and associate with PrP in cellular vesicles. Therefore, aldolase A-positive M cells may play a key role in the invasion of BSE into the body.
文摘The objective of this paper is to develop a dynamic slip model for a shear crack under constant stress drop. This crack problem is formulated by a traction boundary integral equation （BIE） in the frequency domain and then solved by the hyper-singular boundary element method as well as the regularization technique proposed in this paper. Based on the spectral integral form of the kernel function, the unbounded term can be isolated and extracted from the hyper-singular kernel function by using the method of subtracted and added back in wave number domain. Finally, based on the inverse transformation from the frequency domain to the time domain, the time histories of crack opening displacement under constant stress drop can be determined. Three rupture models （simultaneous rupture model, symmetric bilaterally-propagating model and unilaterally propagating model） with specified time histories of stress drop are considered in this paper. Even though these three models will cause the same final slip shapes because of the same constant stress drop, the associated slip time functions differ significantly from each other during the rupture process.
基金supported by the National Natural Science Foundation of China(No.10972131)the Graduate Innovation Foundation of Shanghai University(No.SHUCX102351)
文摘The low-order polynomial-distributed eigenstrain formulation of the boundary integral equation （BIE） and the corresponding definition of the Eshelby tensors are proposed for the elliptical inhomogeneities in two-dimensional elastic media. Taking the results of the traditional subdomain boundary element method （BEM） as the control, the effectiveness of the present algorithm is verified for the elastic media with a single elliptical inhomogeneity. With the present computational model and algorithm, significant improvements are achieved in terms of the efficiency as compared with the traditional BEM and the accuracy as compared with the constant eigenstrain formulation of the BIE.
