Cooling rate is a key factor that can drastically affect the phase transformation and thermal stress of duplex stainless steels. Therefore, in this research, different sand moulds were used to explore the influence of...Cooling rate is a key factor that can drastically affect the phase transformation and thermal stress of duplex stainless steels. Therefore, in this research, different sand moulds were used to explore the influence of cooling rate on the solidification of the 2304 duplex stainless steel (DSS). The macro and micro structures of the 2304 DSS were investigated. Small equiaxed grains are obtained in chromite sand mould sample with a lower pouring temperature and a higher cooling rate, whereas coarse columnar and equiaxed grains are found in silica sand and refractory powder mould samples. The size of austenite phase is significantly increased with decreasing cooling rate, while the ferrite phase content ranging from 51.6% to 53.9% does not change obviously. In addition, the linear contraction of the 2304 DSS decreases from 2.34% to 1.09% when the mean cooling rate above 1,173 K increases from 0.99 K·s-1 to 3.66 K·s-1.展开更多
OBJECTIVE:To investigate the effects of acupotomy on the subchondral bone absorption and mechanical properties in rabbits with knee osteoarthritis(KOA).METHODS:The rabbits were divided into blank control,model,acupoto...OBJECTIVE:To investigate the effects of acupotomy on the subchondral bone absorption and mechanical properties in rabbits with knee osteoarthritis(KOA).METHODS:The rabbits were divided into blank control,model,acupotomy and electroacupuncture(EA)groups,with 12 rabbits in each.Modified Videman's method was used to prepare KOA model.The acupotomy and EA group were given indicated intervention for 3 weeks.The behavior of rabbits in each group was recorded.Subsequently,cartilage–subchondral bone units were obtained and morphological changes were observed by optical microscope and micro computed tomography.Compression test was used to detect the mechanical properties of subchondral bone,Western blot and real-time polymerase chain reaction(RT-PCR)were applied to detect the expression of bone morphogenetic protein 2-Smad1(BMP2-Smad1)pathway in subchondral bone.RESULTS:Compared with the control group,rabbits in the KOA group showed lameness,knee pain,and cartilage degradation;the subchondral bone showed active resorption,the mechanical properties decreased significantly and the BMP2-Smad1 pathway downregulated significantly.Both acupotomy and EA intervention could increase the thickness of trabecular bone(Tb.Th),the bone volume fraction(BV/TV)and the thickness of subchondral bone plate,reduce the separation of trabecular bone(Tb.Sp),improve the maximum load and elastic modulus of subchondral bone,and effectively delay cartilage degeneration in KOA rabbits.This process may be achieved through upregulation the related proteins of BMP2-Smad1 pathway.The maximum load and elastic modulus of subchondral bone in the acupotomy group were slightly better than those in the EA group.CONCLUSIONS:Acupotomy could effectively protect cartilage by inhibiting abnormal bone resorption and improving mechanical properties of subchondral bone thorough the related proteins of BMP2-Smad1 pathway in KOA rabbits.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 50904044)
文摘Cooling rate is a key factor that can drastically affect the phase transformation and thermal stress of duplex stainless steels. Therefore, in this research, different sand moulds were used to explore the influence of cooling rate on the solidification of the 2304 duplex stainless steel (DSS). The macro and micro structures of the 2304 DSS were investigated. Small equiaxed grains are obtained in chromite sand mould sample with a lower pouring temperature and a higher cooling rate, whereas coarse columnar and equiaxed grains are found in silica sand and refractory powder mould samples. The size of austenite phase is significantly increased with decreasing cooling rate, while the ferrite phase content ranging from 51.6% to 53.9% does not change obviously. In addition, the linear contraction of the 2304 DSS decreases from 2.34% to 1.09% when the mean cooling rate above 1,173 K increases from 0.99 K·s-1 to 3.66 K·s-1.
基金Longitudinal Research Development Fund of Beijing University of Chinese Medicine:to Investigate the Effect of Acupotomy on Subchondral Bone Remodeling in Knee Osteoarthritis Based on BMP2-Smad1 Pathway(2020-ZXFZJJ-031)National Natural Science Foundation of China:to Investigate the Mechanism of Acupotomy"Regulating Tendon and Treating Bone"in the Treatment of KOA based on the Vascularization of Hypoxic Cartilage Mediated by HIF-1α/VEGF Pathway(82074523)。
文摘OBJECTIVE:To investigate the effects of acupotomy on the subchondral bone absorption and mechanical properties in rabbits with knee osteoarthritis(KOA).METHODS:The rabbits were divided into blank control,model,acupotomy and electroacupuncture(EA)groups,with 12 rabbits in each.Modified Videman's method was used to prepare KOA model.The acupotomy and EA group were given indicated intervention for 3 weeks.The behavior of rabbits in each group was recorded.Subsequently,cartilage–subchondral bone units were obtained and morphological changes were observed by optical microscope and micro computed tomography.Compression test was used to detect the mechanical properties of subchondral bone,Western blot and real-time polymerase chain reaction(RT-PCR)were applied to detect the expression of bone morphogenetic protein 2-Smad1(BMP2-Smad1)pathway in subchondral bone.RESULTS:Compared with the control group,rabbits in the KOA group showed lameness,knee pain,and cartilage degradation;the subchondral bone showed active resorption,the mechanical properties decreased significantly and the BMP2-Smad1 pathway downregulated significantly.Both acupotomy and EA intervention could increase the thickness of trabecular bone(Tb.Th),the bone volume fraction(BV/TV)and the thickness of subchondral bone plate,reduce the separation of trabecular bone(Tb.Sp),improve the maximum load and elastic modulus of subchondral bone,and effectively delay cartilage degeneration in KOA rabbits.This process may be achieved through upregulation the related proteins of BMP2-Smad1 pathway.The maximum load and elastic modulus of subchondral bone in the acupotomy group were slightly better than those in the EA group.CONCLUSIONS:Acupotomy could effectively protect cartilage by inhibiting abnormal bone resorption and improving mechanical properties of subchondral bone thorough the related proteins of BMP2-Smad1 pathway in KOA rabbits.
