Laser powder bed fusion(L-PBF)of Mg alloys has provided tremendous opportunities for customized production of aeronautical and medical parts.Layer thickness(LT)is of great significance to the L-PBF process but has not...Laser powder bed fusion(L-PBF)of Mg alloys has provided tremendous opportunities for customized production of aeronautical and medical parts.Layer thickness(LT)is of great significance to the L-PBF process but has not been studied for Mg alloys.In this study,WE43 Mg alloy bulk cubes,porous scaffolds,and thin walls with layer thicknesses of 10,20,30,and 40μm were fabricated.The required laser energy input increased with increasing layer thickness and was different for the bulk cubes and porous scaffolds.Porosity tended to occur at the connection joints in porous scaffolds for LT40 and could be eliminated by reducing the laser energy input.For thin wall parts,a large overhang angle or a small wall thickness resulted in porosity when a large layer thicknesses was used,and the porosity disappeared by reducing the layer thickness or laser energy input.A deeper keyhole penetration was found in all occasions with porosity,explaining the influence of layer thickness,geometrical structure,and laser energy input on the porosity.All the samples achieved a high fusion quality with a relative density of over 99.5%using the optimized laser energy input.The increased layer thickness resulted to more precipitation phases,finer grain sizes and decreased grain texture.With the similar high fusion quality,the tensile strength and elongation of bulk samples were significantly improved from 257 MPa and 1.41%with the 10μm layer to 287 MPa and 15.12%with the 40μm layer,in accordance with the microstructural change.The effect of layer thickness on the compressive properties of porous scaffolds was limited.However,the corrosion rate of bulk samples accelerated with increasing the layer thickness,mainly attributed to the increased number of precipitation phases.展开更多
Laser powder bed fusion(L-PBF)has been employed to additively manufacture WE43 magnesium(Mg)alloy biodegradable implants,but WE43 L-PBF samples exhibit excessively rapid corrosion.In this work,dense WE43 L-PBF samples...Laser powder bed fusion(L-PBF)has been employed to additively manufacture WE43 magnesium(Mg)alloy biodegradable implants,but WE43 L-PBF samples exhibit excessively rapid corrosion.In this work,dense WE43 L-PBF samples were built with the relativity density reaching 99.9%.High temperature oxidation was performed on the L-PBF samples in circulating air via various heating temperatures and holding durations.The oxidation and diffusion at the elevated temperature generated a gradient structure composed of an oxide layer at the surface,a transition layer in the middle and the matrix.The oxide layer consisted of rare earth(RE)oxides,and became dense and thick with increasing the holding duration.The matrix was composed ofα-Mg,RE oxides and Mg_(24)RE_(5) precipitates.The precipitates almost disappeared in the transition layer.Enhanced passivation effect was observed in the samples treated by a suitable high temperature oxidation.The original L-PBF samples lost 40%weight after 3-day immersion in Hank’s solution,and broke into fragments after 7-day immersion.The casted and solution treated samples lost roughly half of the weight after 28-day immersion.The high temperature oxidation samples,which were heated at 525℃ for 8 h,kept the structural integrity,and lost only 6.88%weight after 28-day immersion.The substantially improved corrosion resistance was contributed to the gradient structure at the surface.On one hand,the outmost dense layer of RE oxides isolated the corrosive medium;on the other hand,the transition layer considerably inhibited the corrosion owing to the lack of precipitates.Overall,high temperature oxidation provides an efficient,economic and safe approach to inhibit the corrosion of WE43 L-PBF samples,and has promising prospects for future clinical applications.展开更多
FeCoCrNiMox composite powders were prepared using the mechanical alloying technique and made into high-entropy alloy(HEA)coatings with the face-centered cubic phase using plasma spraying to address the element segrega...FeCoCrNiMox composite powders were prepared using the mechanical alloying technique and made into high-entropy alloy(HEA)coatings with the face-centered cubic phase using plasma spraying to address the element segregation problem in HEAs and pre-pare uniform HEA coatings.Scanning electron microscopy,transmission electron microscopy,and X-ray diffractometry were employed to characterize these coatings’microstructure and phase composition.The hardness,elastic modulus,and fracture toughness of coatings were tested,and the corrosion resistance was analyzed in simulated seawater.Results show that the hardness of the coating is HV0.1606.15,the modulus of elasticity is 128.42 GPa,and the fracture toughness is 43.98 MPa·m^(1/2).The corrosion potential of the coating in 3.5wt%NaCl solution is-0.49 V,and the corrosion current density is 1.2×10^(−6)A/cm^(2).The electrochemical system comprises three parts:the electrolyte,the adsorption and metallic oxide films produced during immersion,and the FeCoNiCrMo HEA coating.Over in-creasingly long periods,the corrosion reaction rate increases first and then decreases,the corrosion product film comprising metal oxides reaches a dynamic balance between formation and dissolution,and the internal reaction of the coating declines.展开更多
目的研究p53凋亡刺激蛋白(apoptosis-stimulating protein of p53, ASPP)家族成员在结直肠癌(colorectal cancer, CRC)组织中的表达及其与临床病理特征的关系。方法采用免疫组织化学方法和免疫荧光染色方法检测115例CRC组织中ASPP蛋白...目的研究p53凋亡刺激蛋白(apoptosis-stimulating protein of p53, ASPP)家族成员在结直肠癌(colorectal cancer, CRC)组织中的表达及其与临床病理特征的关系。方法采用免疫组织化学方法和免疫荧光染色方法检测115例CRC组织中ASPP蛋白家族成员(ASPP1、ASPP2、iASPP)的表达,并应用统计学方法检验ASPP的表达与CRC临床病理特征之间的关系。结果 ASPP1在115例CRC组织中均无表达,ASPP2的表达率为91.3%(105/115),iASPP的表达率为22.6%(26/115)。ASPP2的表达在≥50岁与<50岁组患者间差异具有统计学意义(P<0.01);0+Ⅰ期CRC中的表达与Ⅲ期相比,差异具有统计学意义(P<0.05);浸润深度上,Tis+T1组与T3组相比,差异具有统计学意义(P<0.01);淋巴结转移分组,N0与N2组间差异具有统计学意义(P<0.01)。iASPP在淋巴结转移分组N0组与N1组相比,差异具有统计学意义(P<0.05)。ASPP2和iASPP的表达与CRC的其他临床病理特征均无相关性。结论 ASPP家族成员在CRC组织中的表达存在差异;ASPP2可用于判断CRC患者的预后。展开更多
Wistar rats were intragastrical y perfused with Chinese medicines used for tonifying the kidney. These included 0.180 g/mL of Herba Epimedi （Epimedium）, Semen Cuscutae （Dodder Seed）, or Herba Cistanches （Desertli...Wistar rats were intragastrical y perfused with Chinese medicines used for tonifying the kidney. These included 0.180 g/mL of Herba Epimedi （Epimedium）, Semen Cuscutae （Dodder Seed）, or Herba Cistanches （Desertliving Cistanche）, 0.04 mg/mL monoamine oxidase-B inhibitor selegiline, or distil ed water for 14 consecutive days to prepare drug-containing serum or blank serum. MES23.5 cells in the logarithmic phase were cultured in media supplemented with 15%drug-containing serum for 24 hours, fol owed by incubation in culture solution containing 100μmol/L H2O2 for 3 hours. 3-（4,5-Dimethylthiazol-2-yl）-2,5-diphenyltetrazolium bromide （MTT） and flow tometry results showed that al drug-containing serums improved the survival rate of H 2 O 2-injured MES23.5 cells, inhibited pro-apoptotic FasL and caspase-3 expression, promoted anti-apoptotic Bcl-2 expression. However, drug-containing serums had little influence on Fas expression in H 2 O 2-injured MES23.5 cells. Enzyme-linked immunosorbent assay results showed that serum containing Herba Cistanches or Herba Epimedi increased the expression of nerve growth factor, brain-derived neurotrophic factor, and glial cellline-derived neurotrophic factor in injured MES23.5 cells;serum containing Semen Cuscutae only increased brain-derived neurotrophic factor expres-sion; while expression of the above neurotrophic factors remained the same in cells treated with serum containing selegiline. These findings indicate that Chinese medicines used to tonify the kid-ney can protect nerve cells by regulating the expression of apoptosis-related factors and neuro-trophic factors in MES23.5 cells.展开更多
基金funded by the National Key Research and Development Program of China(2018YFE0104200)National Natural Science Foundation of China(51875310,52175274,82172065)Tsinghua Precision Medicine Foundation.
文摘Laser powder bed fusion(L-PBF)of Mg alloys has provided tremendous opportunities for customized production of aeronautical and medical parts.Layer thickness(LT)is of great significance to the L-PBF process but has not been studied for Mg alloys.In this study,WE43 Mg alloy bulk cubes,porous scaffolds,and thin walls with layer thicknesses of 10,20,30,and 40μm were fabricated.The required laser energy input increased with increasing layer thickness and was different for the bulk cubes and porous scaffolds.Porosity tended to occur at the connection joints in porous scaffolds for LT40 and could be eliminated by reducing the laser energy input.For thin wall parts,a large overhang angle or a small wall thickness resulted in porosity when a large layer thicknesses was used,and the porosity disappeared by reducing the layer thickness or laser energy input.A deeper keyhole penetration was found in all occasions with porosity,explaining the influence of layer thickness,geometrical structure,and laser energy input on the porosity.All the samples achieved a high fusion quality with a relative density of over 99.5%using the optimized laser energy input.The increased layer thickness resulted to more precipitation phases,finer grain sizes and decreased grain texture.With the similar high fusion quality,the tensile strength and elongation of bulk samples were significantly improved from 257 MPa and 1.41%with the 10μm layer to 287 MPa and 15.12%with the 40μm layer,in accordance with the microstructural change.The effect of layer thickness on the compressive properties of porous scaffolds was limited.However,the corrosion rate of bulk samples accelerated with increasing the layer thickness,mainly attributed to the increased number of precipitation phases.
基金funded by the National Key Research and Development Program of China (2018YFE0104200)National Natural Science Foundation of China (51875310, 52175274, 82172065)Tsinghua Precision Medicine Foundation
文摘Laser powder bed fusion(L-PBF)has been employed to additively manufacture WE43 magnesium(Mg)alloy biodegradable implants,but WE43 L-PBF samples exhibit excessively rapid corrosion.In this work,dense WE43 L-PBF samples were built with the relativity density reaching 99.9%.High temperature oxidation was performed on the L-PBF samples in circulating air via various heating temperatures and holding durations.The oxidation and diffusion at the elevated temperature generated a gradient structure composed of an oxide layer at the surface,a transition layer in the middle and the matrix.The oxide layer consisted of rare earth(RE)oxides,and became dense and thick with increasing the holding duration.The matrix was composed ofα-Mg,RE oxides and Mg_(24)RE_(5) precipitates.The precipitates almost disappeared in the transition layer.Enhanced passivation effect was observed in the samples treated by a suitable high temperature oxidation.The original L-PBF samples lost 40%weight after 3-day immersion in Hank’s solution,and broke into fragments after 7-day immersion.The casted and solution treated samples lost roughly half of the weight after 28-day immersion.The high temperature oxidation samples,which were heated at 525℃ for 8 h,kept the structural integrity,and lost only 6.88%weight after 28-day immersion.The substantially improved corrosion resistance was contributed to the gradient structure at the surface.On one hand,the outmost dense layer of RE oxides isolated the corrosive medium;on the other hand,the transition layer considerably inhibited the corrosion owing to the lack of precipitates.Overall,high temperature oxidation provides an efficient,economic and safe approach to inhibit the corrosion of WE43 L-PBF samples,and has promising prospects for future clinical applications.
基金supported by the National Natural Natural Science Foundation of China(No.52271055)the Natural Science Foundation of Hebei Province,China(No.E2024202154).
文摘FeCoCrNiMox composite powders were prepared using the mechanical alloying technique and made into high-entropy alloy(HEA)coatings with the face-centered cubic phase using plasma spraying to address the element segregation problem in HEAs and pre-pare uniform HEA coatings.Scanning electron microscopy,transmission electron microscopy,and X-ray diffractometry were employed to characterize these coatings’microstructure and phase composition.The hardness,elastic modulus,and fracture toughness of coatings were tested,and the corrosion resistance was analyzed in simulated seawater.Results show that the hardness of the coating is HV0.1606.15,the modulus of elasticity is 128.42 GPa,and the fracture toughness is 43.98 MPa·m^(1/2).The corrosion potential of the coating in 3.5wt%NaCl solution is-0.49 V,and the corrosion current density is 1.2×10^(−6)A/cm^(2).The electrochemical system comprises three parts:the electrolyte,the adsorption and metallic oxide films produced during immersion,and the FeCoNiCrMo HEA coating.Over in-creasingly long periods,the corrosion reaction rate increases first and then decreases,the corrosion product film comprising metal oxides reaches a dynamic balance between formation and dissolution,and the internal reaction of the coating declines.
文摘目的研究p53凋亡刺激蛋白(apoptosis-stimulating protein of p53, ASPP)家族成员在结直肠癌(colorectal cancer, CRC)组织中的表达及其与临床病理特征的关系。方法采用免疫组织化学方法和免疫荧光染色方法检测115例CRC组织中ASPP蛋白家族成员(ASPP1、ASPP2、iASPP)的表达,并应用统计学方法检验ASPP的表达与CRC临床病理特征之间的关系。结果 ASPP1在115例CRC组织中均无表达,ASPP2的表达率为91.3%(105/115),iASPP的表达率为22.6%(26/115)。ASPP2的表达在≥50岁与<50岁组患者间差异具有统计学意义(P<0.01);0+Ⅰ期CRC中的表达与Ⅲ期相比,差异具有统计学意义(P<0.05);浸润深度上,Tis+T1组与T3组相比,差异具有统计学意义(P<0.01);淋巴结转移分组,N0与N2组间差异具有统计学意义(P<0.01)。iASPP在淋巴结转移分组N0组与N1组相比,差异具有统计学意义(P<0.05)。ASPP2和iASPP的表达与CRC的其他临床病理特征均无相关性。结论 ASPP家族成员在CRC组织中的表达存在差异;ASPP2可用于判断CRC患者的预后。
基金supported by the Developmental Fund of Chen Keji Integrative Medicine,No.CKJ2010025the Key Foundation of Society Development in Fujian Province,No.2013Y0059
文摘Wistar rats were intragastrical y perfused with Chinese medicines used for tonifying the kidney. These included 0.180 g/mL of Herba Epimedi （Epimedium）, Semen Cuscutae （Dodder Seed）, or Herba Cistanches （Desertliving Cistanche）, 0.04 mg/mL monoamine oxidase-B inhibitor selegiline, or distil ed water for 14 consecutive days to prepare drug-containing serum or blank serum. MES23.5 cells in the logarithmic phase were cultured in media supplemented with 15%drug-containing serum for 24 hours, fol owed by incubation in culture solution containing 100μmol/L H2O2 for 3 hours. 3-（4,5-Dimethylthiazol-2-yl）-2,5-diphenyltetrazolium bromide （MTT） and flow tometry results showed that al drug-containing serums improved the survival rate of H 2 O 2-injured MES23.5 cells, inhibited pro-apoptotic FasL and caspase-3 expression, promoted anti-apoptotic Bcl-2 expression. However, drug-containing serums had little influence on Fas expression in H 2 O 2-injured MES23.5 cells. Enzyme-linked immunosorbent assay results showed that serum containing Herba Cistanches or Herba Epimedi increased the expression of nerve growth factor, brain-derived neurotrophic factor, and glial cellline-derived neurotrophic factor in injured MES23.5 cells;serum containing Semen Cuscutae only increased brain-derived neurotrophic factor expres-sion; while expression of the above neurotrophic factors remained the same in cells treated with serum containing selegiline. These findings indicate that Chinese medicines used to tonify the kid-ney can protect nerve cells by regulating the expression of apoptosis-related factors and neuro-trophic factors in MES23.5 cells.
