Microscopic phase-field simulation of atomic site occupation in ordering process of NiAl_9Fe_6 alloy

The process of γ(fcc)→γ(fcc)+γ'(L12)phase transformation was simulated by using microscopic phase-field method for the low supersaturation NiAl9Fe6 alloy.It is found that in the γ' phase,the ordering degree of Al atoms is obviously higher than that of Fe atoms,and the ordering of Al atoms precedes their clustering,while the case of Fe atoms is opposite.The α site is mainly occupied by Ni atoms,while the β site is occupied in common by Al,Fe and Ni atoms.At order-disorder interphase boundary,the ordering degree of Al atoms is higher than that of Fe atoms,and at the β site,the Fe atomic site occupation probabilities vary from high to low during ordering;the Al atomic site occupation probabilities are similar to those of Fe atoms,but their values are much higher than those of Fe atoms;Ni atoms are opposite to both of them.Meanwhile,during the ordering transformation,γ' phase is always a complex Ni3(AlFeNi)single-phase,and it is precipitated by the non-classical nucleation and growth style.Finally,in the alloy system,the volume of γ' ordered phase is less than that of γ phase,and the volume ratio of order to disorder is about 77%.

双歧杆菌对过敏性哮喘儿童DC成熟及其分泌细胞因子的影响

目的研究青春型双歧杆菌对过敏性哮喘儿童外周血单个核细胞(PBMC)来源的树突状细胞(DC)表达CD86和HLA-DR及其分泌IL-1βI、L-6I、L-10、IL-12、IL-23和IFN-γ的影响。方法从15名过敏性哮喘儿童和15名非哮喘儿童的外周血单个核细胞诱导生成未成熟DC,分别加入青春型双歧杆菌或脂多糖(LPS)后继续培养DC 2天,①每天于倒置显微镜下观察DC形态;②用流式细胞仪检测各组DC表面CD86和HLA-DR的分子表达;③用ELISA方法检测培养上清中IL-1βI、L-6I、L-10、IL-12I、L-23和IFN-γ的水平。结果①DC经双歧杆菌和LPS分组处理后第2天,于倒置显微镜下观察到双歧杆菌组和LPS组的DC突起均较空白组明显,具有突起的细胞数量较空白组增多,而双歧杆菌组与LPS组比较,LPS组有突起的细胞数量明显增多,提示DC过度生长。②双歧杆菌刺激后,哮喘儿童DC表面CD86表达明显增高,HLA-DR表达无明显变化,非哮喘儿童CD86和HLA-DR表达均无明显变化;LPS刺激可明显增加哮喘儿童和非哮喘儿童CD86和HLA-DR的表达。③双歧杆菌刺激哮喘儿童DC分泌IL-12、IFN-γI、L-1β及IL-6水平增高,刺激非哮喘儿童DC分泌IL-12I、L-10I、L-1β及IL-23水平增高。结论①过敏性哮喘儿童DC表面CD86的表达可能存在缺陷,双歧杆菌能适度上调其表达,在DC的成熟过程中可能起调节作用。②双歧杆菌能刺激过敏性哮喘儿童DC分泌IL-12和IFN-γ,从而改变Th2优势分化,纠正Th1/Th2失衡。③过敏性哮喘儿童DC分泌IL-10可能存在缺陷,从而影响免疫耐受的形成。④双歧杆菌可能通过刺激哮喘儿童DC分泌IL-1β及IL-6增高,达到促进Th17细胞分化的作用。