河钢集团有限公司开发了利用钢液中形成TiOx−MgO−CaO细小粒子改善焊接粗晶热影响区韧性的ITFFP技术(Improve the toughness of HAZ by forming TiOx−MgO−CaO fine particles in steel),成功试制生产出大线能量焊接用30 mm厚度规格(H30)...河钢集团有限公司开发了利用钢液中形成TiOx−MgO−CaO细小粒子改善焊接粗晶热影响区韧性的ITFFP技术(Improve the toughness of HAZ by forming TiOx−MgO−CaO fine particles in steel),成功试制生产出大线能量焊接用30 mm厚度规格(H30)和60 mm厚度规格(H60)EH420海洋工程用钢.母材力学性能试验结果表明,H30和H60试制钢屈服强度分别达到461 MPa和534 MPa,抗拉强度分别达到570 MPa和628 MPa,延伸率分别为26%和24.5%,满足EH420海洋工程用钢国家标准要求.采用Gleeble-3800型热模拟试验机对试制钢进行了200 kJ·cm−1条件下热模拟试验,并对焊接热影响区中的显微组织和−40℃冲击韧性进行了分析和测试.结果表明,试制钢中形成的CaO(−MgO)−Al2O3−TiOx−MnS夹杂物可以有效地诱导针状铁素体析出,显著提高钢材的冲击韧性.另外,利用气电立焊设备对H30和H60试制钢分别进行了焊接线能量为247 kJ·cm−1和224 kJ·cm−1的实焊试验,结果显示,H30试制钢焊接接头表面和根部焊缝处−40℃冲击吸收功值≥74 J,焊接热影响区≥115 J,H60试制钢焊接接头表面和根部焊缝处−40℃冲击吸收功值≥91 J,焊接热影响区≥75 J,焊接接头的冲击性能远高于国家标准值42 J.展开更多
The operation mechanism of single cross slip multiplication(SCSM)is investigated by studying the response of one dislocation loop expanding in face-centered-cubic(FCC)single crystal using three-dimensional discrete di...The operation mechanism of single cross slip multiplication(SCSM)is investigated by studying the response of one dislocation loop expanding in face-centered-cubic(FCC)single crystal using three-dimensional discrete dislocation dynamic(3D-DDD)simulation.The results show that SCSM can trigger highly correlated dislocation generation in a short time,which may shed some light on understanding the large strain burst observed experimentally.Furthermore,we find that there is a critical stress and material size for the operation of SCSM,which agrees with that required to trigger large strain burst in the compression tests of FCC micropillars.展开更多
Background Infantile spasms is a severe epileptic encephalopathy, which is refractory to conventional antiepileptic drugs. Adrenocorticotropic hormone （ACTH） has been the major therapy for infantile spasms; however,...Background Infantile spasms is a severe epileptic encephalopathy, which is refractory to conventional antiepileptic drugs. Adrenocorticotropic hormone （ACTH） has been the major therapy for infantile spasms; however, ACTH therapy is ineffective for some patients. The variations in the receptor genes can contribute to antiepileptic drug resistance. This study was to elucidate the possible associations between the variations of the MC2R gene and ACTH responsiveness in patients with infantile spasms. Methods We screened for variations in the promoter and coding region of the MC2R gene in 91 Chinese patients with infantile spasms and 94 controls, using PCR and a direct sequencing method. The frequencies of the genotypes, alleles and reconstructed haplotypes were analyzed in the cases and controls. The association between ACTH responsiveness and genetic variations of the MC2R gene was also assessed. Results Four single nucleotide polymorphisms （SNPs） were identified in the MC2R promoter, one of which was a novel specimen at position-2 from the transcription start site ATT, -2T〉C. Three SNPs （rs1893220, rs2186944 and -2T〉C） showed a significant difference between the cases and controls （P 〈0.05 for all）. The frequency of the common TCCT haplotype carrying four-SNP major alleles was significantly lower in the cases （39%） than in the controls （60%） （P=-0.00003）. The homozygous carriers of the TCCT haplotype had a much lower relative risk than the non-carriers （RR=O.42, 95%C/ 0.26-0.70, P=-0.0001）. ACTH responsiveness was strongly associated with the TCCT haplotype （P=-0.000082）. Compared with non-carriers of the TCCT haplotype, the homozygous and heterozygous carriers were more responsive to ACTH therapy （P=0.0002; P=-0.0003, respectively）. Conclusions Our results indicated that the TCCT haplotype in the MC2R promoter is strongly associated with the responsiveness of the ACTH therapy performed on patients with infantile spasms. The polymorphisms of the MC2R promoter might be one important factor that influences the efficacy of ACTH therapy on infantile spasms.展开更多
文摘河钢集团有限公司开发了利用钢液中形成TiOx−MgO−CaO细小粒子改善焊接粗晶热影响区韧性的ITFFP技术(Improve the toughness of HAZ by forming TiOx−MgO−CaO fine particles in steel),成功试制生产出大线能量焊接用30 mm厚度规格(H30)和60 mm厚度规格(H60)EH420海洋工程用钢.母材力学性能试验结果表明,H30和H60试制钢屈服强度分别达到461 MPa和534 MPa,抗拉强度分别达到570 MPa和628 MPa,延伸率分别为26%和24.5%,满足EH420海洋工程用钢国家标准要求.采用Gleeble-3800型热模拟试验机对试制钢进行了200 kJ·cm−1条件下热模拟试验,并对焊接热影响区中的显微组织和−40℃冲击韧性进行了分析和测试.结果表明,试制钢中形成的CaO(−MgO)−Al2O3−TiOx−MnS夹杂物可以有效地诱导针状铁素体析出,显著提高钢材的冲击韧性.另外,利用气电立焊设备对H30和H60试制钢分别进行了焊接线能量为247 kJ·cm−1和224 kJ·cm−1的实焊试验,结果显示,H30试制钢焊接接头表面和根部焊缝处−40℃冲击吸收功值≥74 J,焊接热影响区≥115 J,H60试制钢焊接接头表面和根部焊缝处−40℃冲击吸收功值≥91 J,焊接热影响区≥75 J,焊接接头的冲击性能远高于国家标准值42 J.
基金the National Natural Science Foundation of China under Grant No 11132006the National Basic Research Program of China under Grant No 2010CB631005.
文摘The operation mechanism of single cross slip multiplication(SCSM)is investigated by studying the response of one dislocation loop expanding in face-centered-cubic(FCC)single crystal using three-dimensional discrete dislocation dynamic(3D-DDD)simulation.The results show that SCSM can trigger highly correlated dislocation generation in a short time,which may shed some light on understanding the large strain burst observed experimentally.Furthermore,we find that there is a critical stress and material size for the operation of SCSM,which agrees with that required to trigger large strain burst in the compression tests of FCC micropillars.
基金This study was supported by the grants from the National Natural Science Foundation of China （No. 30770747）, the Beijing Municipal Natural Science Foundation （No. 7081002, No. 7042024） and the Capital Development Foundation of Beijing （No. 2003-2007）.
文摘Background Infantile spasms is a severe epileptic encephalopathy, which is refractory to conventional antiepileptic drugs. Adrenocorticotropic hormone （ACTH） has been the major therapy for infantile spasms; however, ACTH therapy is ineffective for some patients. The variations in the receptor genes can contribute to antiepileptic drug resistance. This study was to elucidate the possible associations between the variations of the MC2R gene and ACTH responsiveness in patients with infantile spasms. Methods We screened for variations in the promoter and coding region of the MC2R gene in 91 Chinese patients with infantile spasms and 94 controls, using PCR and a direct sequencing method. The frequencies of the genotypes, alleles and reconstructed haplotypes were analyzed in the cases and controls. The association between ACTH responsiveness and genetic variations of the MC2R gene was also assessed. Results Four single nucleotide polymorphisms （SNPs） were identified in the MC2R promoter, one of which was a novel specimen at position-2 from the transcription start site ATT, -2T〉C. Three SNPs （rs1893220, rs2186944 and -2T〉C） showed a significant difference between the cases and controls （P 〈0.05 for all）. The frequency of the common TCCT haplotype carrying four-SNP major alleles was significantly lower in the cases （39%） than in the controls （60%） （P=-0.00003）. The homozygous carriers of the TCCT haplotype had a much lower relative risk than the non-carriers （RR=O.42, 95%C/ 0.26-0.70, P=-0.0001）. ACTH responsiveness was strongly associated with the TCCT haplotype （P=-0.000082）. Compared with non-carriers of the TCCT haplotype, the homozygous and heterozygous carriers were more responsive to ACTH therapy （P=0.0002; P=-0.0003, respectively）. Conclusions Our results indicated that the TCCT haplotype in the MC2R promoter is strongly associated with the responsiveness of the ACTH therapy performed on patients with infantile spasms. The polymorphisms of the MC2R promoter might be one important factor that influences the efficacy of ACTH therapy on infantile spasms.
