Three dimensional（3D） bioprinting, which involves depositing bioinks（mixed biomaterials） layer by layer to form computer-aided designs, is an ideal method for fabricating complex 3D biological structures. However,...Three dimensional（3D） bioprinting, which involves depositing bioinks（mixed biomaterials） layer by layer to form computer-aided designs, is an ideal method for fabricating complex 3D biological structures. However, it remains challenging to prepare biomaterials with micro-nanostructures that accurately mimic the nanostructural features of natural tissues. A novel nanotechnological tool, electrospinning, permits the processing and modification of proper nanoscale biomaterials to enhance neural cell adhesion, migration, proliferation, differentiation, and subsequent nerve regeneration. The composite scaffold was prepared by combining 3D bioprinting with subsequent electrochemical deposition of polypyrrole and electrospinning of silk fibroin to form a composite polypyrrole/silk fibroin scaffold. Fourier transform infrared spectroscopy was used to analyze scaffold composition. The surface morphology of the scaffold was observed by light microscopy and scanning electron microscopy. A digital multimeter was used to measure the resistivity of prepared scaffolds. Light microscopy was applied to observe the surface morphology of scaffolds immersed in water or Dulbecco＇s Modified Eagle＇s Medium at 37℃ for 30 days to assess stability. Results showed characteristic peaks of polypyrrole and silk fibroin in the synthesized conductive polypyrrole/silk fibroin scaffold, as well as the structure of the electrospun nanofiber layer on the surface. The electrical conductivity was 1 × 10^-5–1 × 10^-3 S/cm, while stability was 66.67%. A 3-（4,5-dimethyl-2-thiazolyl）-2,5-diphenyl-2-H-tetrazolium bromide assay was employed to measure scaffold cytotoxicity in vitro. Fluorescence microscopy was used to observe Ed U-labeled Schwann cells to quantify cell proliferation. Immunohistochemistry was utilized to detect S100β immunoreactivity, while scanning electron microscopy was applied to observe the morphology of adherent Schwann cells. Results demonstrated that the polypyrrole/silk fibroin scaffold was not cytotoxic and did not affect Schwann cell proliferation. Moreover, filopodia formed on the scaffold and Schwann cells were regularly arranged. Our findings verified that the composite polypyrrole/silk fibroin scaffold has good biocompatibility and may be a suitable material for neural tissue engineering.展开更多
Summary:In late December 2019,COVID-19 was firstly recognized in Wuhan,China and spread rapidly to all of the provinces of China.The West Campus of Wuhan Union Hospital,the designated hospital to admit and treat the s...Summary:In late December 2019,COVID-19 was firstly recognized in Wuhan,China and spread rapidly to all of the provinces of China.The West Campus of Wuhan Union Hospital,the designated hospital to admit and treat the severe and critically ill COVID-19 cases,has treated a large number of such patients with great success and obtained lots of valuable experiences based on the Chinese guideline(V7.0).To standardize and share the treatment procedures of severe and critically ill cases,Wuhan Union Hospital has established a working group and formulated an operational recommendation,including the monitoring,early warning indicators,and several treatment principles for severe and critically ill cases.The treatment experiences may provide some constructive suggestions for treating the severe and critically ill COVID-19 cases all over the world.展开更多
α-Hederagenin(H),derived from Hedera nepalensis var.sinensis,is a pentacyclic oleane-type triterpenoid that exhibits clear cytotoxicity to different tumor cell lines.In this study,a series of novel C-28 derivatives o...α-Hederagenin(H),derived from Hedera nepalensis var.sinensis,is a pentacyclic oleane-type triterpenoid that exhibits clear cytotoxicity to different tumor cell lines.In this study,a series of novel C-28 derivatives of hederagenin(H) were designed and synthesized in attempt to develop potent tumor resistance reverse activities agents.Previous research showed that H6 displayed robust reverse activity for paclitaxel resistance in KBV cells.Importantly,Co-treatment of paclitaxel with H6 significantly reduced the tumor weight to 42%.Pleasingly,H6 enhanced the efficacy of paclitaxel against KBV cancer cell-derived xenograft tumors in nude mice.Mechanism studies had found that H6 activated permeability glycoprotein(P-gp) ATPase,reduced intracellular ATP levels and inhibited efflux of P-gp substrates,thus enhancing the antitumor activity of paclitaxel on KBV cells.Molecular docking analysis of homology P-gp and H6 then conducted using the Surflex-Dock module.H6 showed a high binding affinity docking score with a total score of 5.4148,much higher than that of H(0.1414).The nov.el C-28 derivatives of H was synthesized from H6 via three-step reaction.The reversal activity of all synthesized H derivatives were tested using the MTT assay.The results showed that the derivatives of nitrogen groups at C-28 displayed same even potent activity than parent compound H6.In addition,its underlying mechanism of action and in vivo activity are in explore.展开更多
The effect of shot peening (SP) on microstructure and hardness of ultrafine-grained (UFG) low-alloy steel was investigated. With increasing shot-peening time from 0.5 to 1.5 h, grain size of UFG low-alloy steel decrea...The effect of shot peening (SP) on microstructure and hardness of ultrafine-grained (UFG) low-alloy steel was investigated. With increasing shot-peening time from 0.5 to 1.5 h, grain size of UFG low-alloy steel decreases from 400 to 280 nm at surface whilst that of the layer with a depth of 160μm decreases from (230 ± 15) to (75 ± 5) nm. Interestingly, nanoindentation shows that hardness increases linearly with increasing the SP duration, reaching a value as high as (7.10 ± 0.1) GPa at the depth of 160 μm after the SP duration of 1.5 h. The thickness of the SP treated layer is measured as^300 μm. The Hall-Petch (H-P) relationship was established for the hardening layer. Correspondingly, abrasion resistance should be ~51% higher than that of as-prepared UFG low-alloy steel. As shown in SP processing, grain refinement is the key factor responsible for the strengthening of the studied steel.展开更多
Background and Aims:There are no comparative studies on the efficacy of hepatic resection(HR)and CyberKnife stereotactic body radiation therapy(CK-SBRT)plus transhepatic arterial chemotherapy embolization(TACE)in the ...Background and Aims:There are no comparative studies on the efficacy of hepatic resection(HR)and CyberKnife stereotactic body radiation therapy(CK-SBRT)plus transhepatic arterial chemotherapy embolization(TACE)in the treatment of large hepatocellular carcinoma(HCC).Therefore,this study aimed to compare the efficacy of HR and CKSBRT+TACE in large HCC.Methods:A total of one hundred and sixteen patients were selected from November 2011 to December 2016.Among them,50 were allocated to the CKSBRT+TACE group and 66 were allocated to the HR group.The Kaplan-Meier method was applied to calculate overall survival(OS)and progression-free survival(PFS)rates.Propensity score matching was performed to control for baseline differences between the groups.Results:Thirtysix paired patients were selected from the CK-SBRT+TACE and HR groups.After propensity score matching,the 1-,2-and 3-year OS rates were 83.3%,77.8%and 66.7%in the HR group and 80.6%,72.2%and 52.8%in the CKSBRT+TACE group,respectively.The 1-,2-and 3-year PFS rates were 71.6%,57.3%and 42.3%in the HR group and 66.1%,45.8%and 39.3%in the CK-SBRT+TACE group,respectively(OS:p=0.143;PFS:p=0.445).Both a high platelet count and low alpha-fetoprotein value were revealed as influencing factors in improving OS and PFS.Conclusions:CK-SBRT+TACE brought local effects that were similar to those of HR in HCC patients with a large and single lesion.Moreover,the liver injury occurrence rate was acceptable in both groups.展开更多
For the existing problems of walking chair robot such as simple function,lower bearing capacity and not walking in complex environment,a novel varistructured quadruped / biped human-carrying walking chair robot is pro...For the existing problems of walking chair robot such as simple function,lower bearing capacity and not walking in complex environment,a novel varistructured quadruped / biped human-carrying walking chair robot is proposed.The proposed robot could be used as biped and quadruped walking chair robots.Considering the conversion of the walking chair robot from the quadruped to the biped or vice versa,6-UPS and 2-UPS＋UP（U,P and S are universal joint,the prismatic pair,and sphere joint,respectively） parallel mechanisms are selected as the leg mechanism of the biped walking robot and quadruped walking robot,respectively.Combining the screw theory and theory of mechanism,the degrees of freedom of the leg mechanism and the body mechanism in diferent motion states are computed so as to meet the requirements of mechanism design.The motion characteristics of the 2-UPS＋UP parallel mechanism which is the key part of the walking chair robot are analyzed.Then,the workspace of the moving platform is drawn and the efect of the structural parameters on the workspace volume is studied.Finally,it is found that the volume of the workspace of the moving platform is bigger when the side length ratio and the vertex angle ratio of the fxed platform and the moving platform which are isosceles triangles are close to 1.This study provides a theoretical foundation for the prototype development.展开更多
Flame stabilization is the key to extending scramjets to hypersonic speeds;accordingly,this topic has attracted much attention in theoretical research and engineering design.This study performed large eddy simulations...Flame stabilization is the key to extending scramjets to hypersonic speeds;accordingly,this topic has attracted much attention in theoretical research and engineering design.This study performed large eddy simulations(LESs)of lifted hydrogen jet combustion in a stepped-wall combustor,focusing on the flame stabilization mechanisms,especially for the autoignition effect.An assumed probability density function(PDF)approach was used to close the subgrid chemical reaction source.The reliability of the solver was confirmed by comparing the LES results with experimental data and published simulated results.The hydrogen jet and the incoming stream were first mixed by entraining large-scale vortices in the shear layer,and stable combustion in the near-wall region was achieved downstream of the flame induction region.The autoignition cascade is a transition of fuel-rich flame to stoichiometric ratio flame that plays a role in forming the flame base,which subsequently causes downstream flame stabilization.Three cases with different jet total temperatures are compared,and the results show that the increase in the total temperature reduces the lift-off distance of the flame.In the highest total temperature case,an excessively large scalar dissipation rate inhibits the autoignition cascade,resulting in a fuel-rich low-temperature flame.展开更多
In this work, high-pressure phase behavior of LiPN2 within 0-300 GPa was studied by using an unbiased structure searching method in combination with first-principles calculations. Three pressure- induced phase transit...In this work, high-pressure phase behavior of LiPN2 within 0-300 GPa was studied by using an unbiased structure searching method in combination with first-principles calculations. Three pressure- induced phase transitions were predicted, as tI16 →hR4 →cF64 → oP8 at 44, 136, and 259 GPa, respectively. The six-fold coordination environments were found for all high-pressure polymorphs, which are substantially different from the four-fold coordination environments observed in the tI16 structure. The hR4 and cF64 structures consist of close-packed PN6 and LiN6 octahedra connected by edge-sharing, whereas the oP8 structure is built up from edge- and face-sharing PN6 and LiN6 octahedra with N lying in the center of the trigonal prisms. The electronic structure analysis reveals that LiPN2 is a semiconductor within the pressure range studied and P-N and Li-N bonds are covalent and ionic, respectively. The results obtained are expected to provide insight and guidance for future experiments on LiPN2 and other alkali metal nitridophosphates.展开更多
基金supported by the National Natural Science Foundation of China,No.81671823,81701835a grant from the National Key Research and Development Program of China,No.2016YFC1101603a grant from the Natural Science Research Program of Nantong of China,No.MS12016056
文摘Three dimensional（3D） bioprinting, which involves depositing bioinks（mixed biomaterials） layer by layer to form computer-aided designs, is an ideal method for fabricating complex 3D biological structures. However, it remains challenging to prepare biomaterials with micro-nanostructures that accurately mimic the nanostructural features of natural tissues. A novel nanotechnological tool, electrospinning, permits the processing and modification of proper nanoscale biomaterials to enhance neural cell adhesion, migration, proliferation, differentiation, and subsequent nerve regeneration. The composite scaffold was prepared by combining 3D bioprinting with subsequent electrochemical deposition of polypyrrole and electrospinning of silk fibroin to form a composite polypyrrole/silk fibroin scaffold. Fourier transform infrared spectroscopy was used to analyze scaffold composition. The surface morphology of the scaffold was observed by light microscopy and scanning electron microscopy. A digital multimeter was used to measure the resistivity of prepared scaffolds. Light microscopy was applied to observe the surface morphology of scaffolds immersed in water or Dulbecco＇s Modified Eagle＇s Medium at 37℃ for 30 days to assess stability. Results showed characteristic peaks of polypyrrole and silk fibroin in the synthesized conductive polypyrrole/silk fibroin scaffold, as well as the structure of the electrospun nanofiber layer on the surface. The electrical conductivity was 1 × 10^-5–1 × 10^-3 S/cm, while stability was 66.67%. A 3-（4,5-dimethyl-2-thiazolyl）-2,5-diphenyl-2-H-tetrazolium bromide assay was employed to measure scaffold cytotoxicity in vitro. Fluorescence microscopy was used to observe Ed U-labeled Schwann cells to quantify cell proliferation. Immunohistochemistry was utilized to detect S100β immunoreactivity, while scanning electron microscopy was applied to observe the morphology of adherent Schwann cells. Results demonstrated that the polypyrrole/silk fibroin scaffold was not cytotoxic and did not affect Schwann cell proliferation. Moreover, filopodia formed on the scaffold and Schwann cells were regularly arranged. Our findings verified that the composite polypyrrole/silk fibroin scaffold has good biocompatibility and may be a suitable material for neural tissue engineering.
基金This research was supported in part by National Natural Science Foundation of China，supported by Research Funds of China Space Medical Engineering，supported by State Key Laboratory of Space Medicine Fundamentals and Applications, China Astronaut Research and Training Centre
基金The work was supported by COVID-19 Emergency Scientific Research Project of Science and Technology Department,Hubei Province(No.2020FCA041).
文摘Summary:In late December 2019,COVID-19 was firstly recognized in Wuhan,China and spread rapidly to all of the provinces of China.The West Campus of Wuhan Union Hospital,the designated hospital to admit and treat the severe and critically ill COVID-19 cases,has treated a large number of such patients with great success and obtained lots of valuable experiences based on the Chinese guideline(V7.0).To standardize and share the treatment procedures of severe and critically ill cases,Wuhan Union Hospital has established a working group and formulated an operational recommendation,including the monitoring,early warning indicators,and several treatment principles for severe and critically ill cases.The treatment experiences may provide some constructive suggestions for treating the severe and critically ill COVID-19 cases all over the world.
基金supported by State Key Laboratory of Drug Research(SIMM1705KF-07)
文摘α-Hederagenin(H),derived from Hedera nepalensis var.sinensis,is a pentacyclic oleane-type triterpenoid that exhibits clear cytotoxicity to different tumor cell lines.In this study,a series of novel C-28 derivatives of hederagenin(H) were designed and synthesized in attempt to develop potent tumor resistance reverse activities agents.Previous research showed that H6 displayed robust reverse activity for paclitaxel resistance in KBV cells.Importantly,Co-treatment of paclitaxel with H6 significantly reduced the tumor weight to 42%.Pleasingly,H6 enhanced the efficacy of paclitaxel against KBV cancer cell-derived xenograft tumors in nude mice.Mechanism studies had found that H6 activated permeability glycoprotein(P-gp) ATPase,reduced intracellular ATP levels and inhibited efflux of P-gp substrates,thus enhancing the antitumor activity of paclitaxel on KBV cells.Molecular docking analysis of homology P-gp and H6 then conducted using the Surflex-Dock module.H6 showed a high binding affinity docking score with a total score of 5.4148,much higher than that of H(0.1414).The nov.el C-28 derivatives of H was synthesized from H6 via three-step reaction.The reversal activity of all synthesized H derivatives were tested using the MTT assay.The results showed that the derivatives of nitrogen groups at C-28 displayed same even potent activity than parent compound H6.In addition,its underlying mechanism of action and in vivo activity are in explore.
基金NSAF (Grant No. U1430132)the National Natural Science Foundation of China (NSFC)(Grant No. 51574079)the Science and Technology Research Project of Education Department of Liaoning Province (L20150177).
文摘The effect of shot peening (SP) on microstructure and hardness of ultrafine-grained (UFG) low-alloy steel was investigated. With increasing shot-peening time from 0.5 to 1.5 h, grain size of UFG low-alloy steel decreases from 400 to 280 nm at surface whilst that of the layer with a depth of 160μm decreases from (230 ± 15) to (75 ± 5) nm. Interestingly, nanoindentation shows that hardness increases linearly with increasing the SP duration, reaching a value as high as (7.10 ± 0.1) GPa at the depth of 160 μm after the SP duration of 1.5 h. The thickness of the SP treated layer is measured as^300 μm. The Hall-Petch (H-P) relationship was established for the hardening layer. Correspondingly, abrasion resistance should be ~51% higher than that of as-prepared UFG low-alloy steel. As shown in SP processing, grain refinement is the key factor responsible for the strengthening of the studied steel.
基金This study protocol was supported by a grant from the Beijing Municipal Science and Technology Commission Fund(Z171100001017181).
文摘Background and Aims:There are no comparative studies on the efficacy of hepatic resection(HR)and CyberKnife stereotactic body radiation therapy(CK-SBRT)plus transhepatic arterial chemotherapy embolization(TACE)in the treatment of large hepatocellular carcinoma(HCC).Therefore,this study aimed to compare the efficacy of HR and CKSBRT+TACE in large HCC.Methods:A total of one hundred and sixteen patients were selected from November 2011 to December 2016.Among them,50 were allocated to the CKSBRT+TACE group and 66 were allocated to the HR group.The Kaplan-Meier method was applied to calculate overall survival(OS)and progression-free survival(PFS)rates.Propensity score matching was performed to control for baseline differences between the groups.Results:Thirtysix paired patients were selected from the CK-SBRT+TACE and HR groups.After propensity score matching,the 1-,2-and 3-year OS rates were 83.3%,77.8%and 66.7%in the HR group and 80.6%,72.2%and 52.8%in the CKSBRT+TACE group,respectively.The 1-,2-and 3-year PFS rates were 71.6%,57.3%and 42.3%in the HR group and 66.1%,45.8%and 39.3%in the CK-SBRT+TACE group,respectively(OS:p=0.143;PFS:p=0.445).Both a high platelet count and low alpha-fetoprotein value were revealed as influencing factors in improving OS and PFS.Conclusions:CK-SBRT+TACE brought local effects that were similar to those of HR in HCC patients with a large and single lesion.Moreover,the liver injury occurrence rate was acceptable in both groups.
基金Project supported by the National Natural Science Foundation of China(Nos.11522222,11925207,and 11472305)the Scientific Research Plan of National University of Defense Technology in 2019(No.ZK19-02)the Postgraduate Scientific Research Innovation Project of Hunan Province(Nos.CX20200008 and CX20200084),China。
基金supported by National Natural Science Foundation of China (No. 61075099) FP7-PEOPLE-2012-IRSES:Marie Curie Action "International Research Staf Exchange Scheme" (No. 318902)
文摘For the existing problems of walking chair robot such as simple function,lower bearing capacity and not walking in complex environment,a novel varistructured quadruped / biped human-carrying walking chair robot is proposed.The proposed robot could be used as biped and quadruped walking chair robots.Considering the conversion of the walking chair robot from the quadruped to the biped or vice versa,6-UPS and 2-UPS＋UP（U,P and S are universal joint,the prismatic pair,and sphere joint,respectively） parallel mechanisms are selected as the leg mechanism of the biped walking robot and quadruped walking robot,respectively.Combining the screw theory and theory of mechanism,the degrees of freedom of the leg mechanism and the body mechanism in diferent motion states are computed so as to meet the requirements of mechanism design.The motion characteristics of the 2-UPS＋UP parallel mechanism which is the key part of the walking chair robot are analyzed.Then,the workspace of the moving platform is drawn and the efect of the structural parameters on the workspace volume is studied.Finally,it is found that the volume of the workspace of the moving platform is bigger when the side length ratio and the vertex angle ratio of the fxed platform and the moving platform which are isosceles triangles are close to 1.This study provides a theoretical foundation for the prototype development.
基金National Natural Science Foundation of China(Nos.91741205 and 11522222)。
文摘Flame stabilization is the key to extending scramjets to hypersonic speeds;accordingly,this topic has attracted much attention in theoretical research and engineering design.This study performed large eddy simulations(LESs)of lifted hydrogen jet combustion in a stepped-wall combustor,focusing on the flame stabilization mechanisms,especially for the autoignition effect.An assumed probability density function(PDF)approach was used to close the subgrid chemical reaction source.The reliability of the solver was confirmed by comparing the LES results with experimental data and published simulated results.The hydrogen jet and the incoming stream were first mixed by entraining large-scale vortices in the shear layer,and stable combustion in the near-wall region was achieved downstream of the flame induction region.The autoignition cascade is a transition of fuel-rich flame to stoichiometric ratio flame that plays a role in forming the flame base,which subsequently causes downstream flame stabilization.Three cases with different jet total temperatures are compared,and the results show that the increase in the total temperature reduces the lift-off distance of the flame.In the highest total temperature case,an excessively large scalar dissipation rate inhibits the autoignition cascade,resulting in a fuel-rich low-temperature flame.
基金The authors acknowledge funding support from the National Natural Science Foundation of China （GrantNos. 11474128 and 11534003）, Science Challenge Project （Grant No. TZ2016001）, National Key Research and Development Pro- gram of China （Grant Nos. 2016YFB0201200, 2016YFB0201201, and 2016YFB0201204）, and Program for JLU Science and Tech- nology Innovative Research Team. Parts of the calculations were performed in the high-performance computing center of Jilin Uni- versity.
文摘In this work, high-pressure phase behavior of LiPN2 within 0-300 GPa was studied by using an unbiased structure searching method in combination with first-principles calculations. Three pressure- induced phase transitions were predicted, as tI16 →hR4 →cF64 → oP8 at 44, 136, and 259 GPa, respectively. The six-fold coordination environments were found for all high-pressure polymorphs, which are substantially different from the four-fold coordination environments observed in the tI16 structure. The hR4 and cF64 structures consist of close-packed PN6 and LiN6 octahedra connected by edge-sharing, whereas the oP8 structure is built up from edge- and face-sharing PN6 and LiN6 octahedra with N lying in the center of the trigonal prisms. The electronic structure analysis reveals that LiPN2 is a semiconductor within the pressure range studied and P-N and Li-N bonds are covalent and ionic, respectively. The results obtained are expected to provide insight and guidance for future experiments on LiPN2 and other alkali metal nitridophosphates.
