Biodegradable wires,able to provide load-bearing support for various biomedical applications,are the novel trends in current biomaterial research.A thin 99.92%Mg wire with a diameter of 250μm was prepared via direct ...Biodegradable wires,able to provide load-bearing support for various biomedical applications,are the novel trends in current biomaterial research.A thin 99.92%Mg wire with a diameter of 250μm was prepared via direct extrusion with an extreme reduction ratio of 1:576.The total imposed strain in a single processing step was 6.36.Extrusion was carried out at elevated temperatures in the range from 230 to 310℃and with various ram speeds ranging from^0.2 to^0.5 mm/s.The resulting wires show very good mechanical properties which vary with extrusion parameters.Maximum true tensile stress at room temperature reaches^228 MPa and ductility reaches^13%.The proposed single-step direct extrusion can be an effective method for the production of Mg wires in sufficient quantities for bioapplications.The fractographic analysis revealed that failure of the wires may be closely connected with inclusions(e.g.,Mg O particles).The results are essential for determining the optimal processing conditions of hot extrusion for thin Mg wire.The smaller grain size,as the outcome of the lower extrusion temperature,is identified as the main parameter affecting the tensile properties of the wires.展开更多
The Ti-35Nb-2Zr-0.3O(mass fraction,%)alloy was melted under a high-purity argon atmosphere in a high vacuumnon-consumable arc melting furnace,followed by cold deformation.The effects of cold deformation process on mic...The Ti-35Nb-2Zr-0.3O(mass fraction,%)alloy was melted under a high-purity argon atmosphere in a high vacuumnon-consumable arc melting furnace,followed by cold deformation.The effects of cold deformation process on microstructure andmechanical properties were investigated using the OM,XRD,TEM,Vicker hardness tester and universal material testing machine.Results indicated that the alloy showed multiple plastic deformation mechanisms,including stress-inducedα'martensite(SIMα')transformation,dislocation slipping and deformation twins.With the increase of cold deformation reduction,the tensile strength andhardness increased owing to the increase of dislocation density and grain refinement,and the elastic modulus slightly increasedowing to the increase of SIMα'phase.The90%cold deformed alloy exhibited a great potential to become a new candidate forbiomedical applications since it possessed low elastic modulus(56.2GPa),high tensile strength(1260MPa)and highstrength-to-modulus ratio(22.4×10-3),which are superior than those of Ti-6Al-4V alloy.展开更多
Herbs of activating blood circulation to remove blood stasis (ABCRBS) are a category of over 10% in the modern Chinese Pharmacopoeia. A new borderline discipline, biomechanopharmacology, is shaping by the efforts of a...Herbs of activating blood circulation to remove blood stasis (ABCRBS) are a category of over 10% in the modern Chinese Pharmacopoeia. A new borderline discipline, biomechanopharmacology, is shaping by the efforts of applying biomechanics in pharmacological studies of ABCRBS herbs. Biomechanics is involved in modeling of blood stasis syndrome (BSS) with mechanical force induced injury and model evaluation by shear stress monitoring for blood coagulation. Investigations showed that tetramethylpyrazine (TMP) contained in Ligusticum chuanxiong Hort and diallyl trisulfide (DT) extracted from garlic demonstrated inhibiting characteristics on vWF mediated platelet activation and thrombus formation occurring under high shear rates. The effect of TMP on shear-induced platelet aggregation might be due to inhibition of calcium channel activity since it showed significant inhibition on intracellular level of calcium demonstrated by laser confocal microscope. The combined effects of TMP and shear stress on rat cerebral microvascular endothelial cell (rCMEC) were investigated by various doses of TMP incorporated with different levels of shear stress generated by a rotational cone-plate rheometer. The results indicated that apoptosis of rCMECs could be restrained by a combination of medial level of shear stress with a suitable dose of TMP. To study the influences of shear stress, pressure and TMP on angiogenesis of vascular endothelial cell, cultured rCMEC was pretreated in a flow chamber with independent adjustment for levels of shear stress and pressure, and then 3D cultured on Matrigel. The results indicate that combined effects of shear stress, pressure and TMP may influence angiogenesis significantly. We believe that research on interactions among blood shear stress, secretion of endothelial cell, and pharmacodynamics will be an interesting area of biomechanopharmacology. Herbs of ABCRBS and their extracts for protecting endothelial cells to maintain their normal functions are expected.展开更多
基金Financial support of the Czech Technical University in Prague in the frame of the project SGS18/191/OHK4/3T/14financial support of the European Regional Development Fund (project CZ.02.1.01/0.0/0.0/16-019/0000778)
文摘Biodegradable wires,able to provide load-bearing support for various biomedical applications,are the novel trends in current biomaterial research.A thin 99.92%Mg wire with a diameter of 250μm was prepared via direct extrusion with an extreme reduction ratio of 1:576.The total imposed strain in a single processing step was 6.36.Extrusion was carried out at elevated temperatures in the range from 230 to 310℃and with various ram speeds ranging from^0.2 to^0.5 mm/s.The resulting wires show very good mechanical properties which vary with extrusion parameters.Maximum true tensile stress at room temperature reaches^228 MPa and ductility reaches^13%.The proposed single-step direct extrusion can be an effective method for the production of Mg wires in sufficient quantities for bioapplications.The fractographic analysis revealed that failure of the wires may be closely connected with inclusions(e.g.,Mg O particles).The results are essential for determining the optimal processing conditions of hot extrusion for thin Mg wire.The smaller grain size,as the outcome of the lower extrusion temperature,is identified as the main parameter affecting the tensile properties of the wires.
基金Project(20133069014)supported by the National Aerospace Science Foundation of China
文摘The Ti-35Nb-2Zr-0.3O(mass fraction,%)alloy was melted under a high-purity argon atmosphere in a high vacuumnon-consumable arc melting furnace,followed by cold deformation.The effects of cold deformation process on microstructure andmechanical properties were investigated using the OM,XRD,TEM,Vicker hardness tester and universal material testing machine.Results indicated that the alloy showed multiple plastic deformation mechanisms,including stress-inducedα'martensite(SIMα')transformation,dislocation slipping and deformation twins.With the increase of cold deformation reduction,the tensile strength andhardness increased owing to the increase of dislocation density and grain refinement,and the elastic modulus slightly increasedowing to the increase of SIMα'phase.The90%cold deformed alloy exhibited a great potential to become a new candidate forbiomedical applications since it possessed low elastic modulus(56.2GPa),high tensile strength(1260MPa)and highstrength-to-modulus ratio(22.4×10-3),which are superior than those of Ti-6Al-4V alloy.
基金The project is supported by NSFC(90209055,10272116).The authors are in—debted to Bin Li,Ligong Jiao,Dong Han,Zhigang Ouyang,Ruomei Qi,Yun You and Wen Li for their contributions tO the experimental researches
文摘Herbs of activating blood circulation to remove blood stasis (ABCRBS) are a category of over 10% in the modern Chinese Pharmacopoeia. A new borderline discipline, biomechanopharmacology, is shaping by the efforts of applying biomechanics in pharmacological studies of ABCRBS herbs. Biomechanics is involved in modeling of blood stasis syndrome (BSS) with mechanical force induced injury and model evaluation by shear stress monitoring for blood coagulation. Investigations showed that tetramethylpyrazine (TMP) contained in Ligusticum chuanxiong Hort and diallyl trisulfide (DT) extracted from garlic demonstrated inhibiting characteristics on vWF mediated platelet activation and thrombus formation occurring under high shear rates. The effect of TMP on shear-induced platelet aggregation might be due to inhibition of calcium channel activity since it showed significant inhibition on intracellular level of calcium demonstrated by laser confocal microscope. The combined effects of TMP and shear stress on rat cerebral microvascular endothelial cell (rCMEC) were investigated by various doses of TMP incorporated with different levels of shear stress generated by a rotational cone-plate rheometer. The results indicated that apoptosis of rCMECs could be restrained by a combination of medial level of shear stress with a suitable dose of TMP. To study the influences of shear stress, pressure and TMP on angiogenesis of vascular endothelial cell, cultured rCMEC was pretreated in a flow chamber with independent adjustment for levels of shear stress and pressure, and then 3D cultured on Matrigel. The results indicate that combined effects of shear stress, pressure and TMP may influence angiogenesis significantly. We believe that research on interactions among blood shear stress, secretion of endothelial cell, and pharmacodynamics will be an interesting area of biomechanopharmacology. Herbs of ABCRBS and their extracts for protecting endothelial cells to maintain their normal functions are expected.
