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Selective precipitation and non-isothermal crystallization kinetics of britholite from low grade REE-bearing slag
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作者 Zhuang Ma Zengwu Zhao +1 位作者 xingqi guo Wentao guo 《Journal of Rare Earths》 SCIE EI CAS CSCD 2023年第11期1812-1818,I0006,共8页
In order to improve the recovery rate of rare earth,the effect of P_(2)O_(5) and cooling rate on the selective precipitation of CaO-SiO_(2)-TiO_(2)-P_(2)O_(5)-Nb_(2)O_(5)-CeO_(2)-CaF_(2) slag system was explored using... In order to improve the recovery rate of rare earth,the effect of P_(2)O_(5) and cooling rate on the selective precipitation of CaO-SiO_(2)-TiO_(2)-P_(2)O_(5)-Nb_(2)O_(5)-CeO_(2)-CaF_(2) slag system was explored using X-ray powder diffraction,a scanning electron microscope,an electron probe micro-analyzer and a confocal laser scanning microscope.The apatite(Ca_(2.02)Ce_(7.98)Si_(6.00)O_(26.00))is tiny and difficult to be separated from the slag without P_(2)O_(5).When the addition of P_(2)O_(5) is 6 wt%-10 wt%,the cerium and phosphorus are found to be enriched in britholite(Ca_(5-x)Ce_(x)[(SiO_(4))_(x)(PO_(4))_(3-x)]F)phase while x is negatively correlated with P_(2)O_(5) content in the slag.The influence of P_(2)O_(5) and cooling rate on the non-isothermal crystallization kinetics was also investigated.For the cooling rate between 5 and 40℃/min,continuous cooling transformation diagram of britholite was constructed when the P205 content is between 6 wt%-10 wt%.The modified Avrami model was applied to determine the crystallization mode of slag with 10 wt%P_(2)O_(5).It is shown that the crystallization mode is diffusion-controlled with constant nucleation rate and one-dimensional growth.In consideration of quantity and volume of crystals,the reasonable cooling rate is between 10and 30℃/min. 展开更多
关键词 P_(2)O_(5) CRYSTALLIZATION Kinetics Low grade REE-bearing slag Rare earths
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Isolation of a strong matrix attachment region (MAR) and identification of its function in vitro and in vivo 被引量:2
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作者 Kewei Zhang Jianmei Wang +4 位作者 guodong Yang xingqi guo Fujiang Wen Decai Cui Chengchao Zheng 《Chinese Science Bulletin》 SCIE EI CAS 2002年第23期1999-2005,共7页
Inclusion of MARs in transgene cassettes enhances their expression and reduces position-effect variations in the transgenic host. Four new MARs (TM2, TM3, AM1 and AM2) were isolated from tobacco and Arabidopsis by PCR... Inclusion of MARs in transgene cassettes enhances their expression and reduces position-effect variations in the transgenic host. Four new MARs (TM2, TM3, AM1 and AM2) were isolated from tobacco and Arabidopsis by PCR method. The nuclei isolated from suspension-cultured cells of rice were used to prepare nuclear matrix. With a characterized MAR (TM1) as a positive control, the Matrix-MAR interactions were tested by an in vitro binding assay to identify the DNA sequences as MARs and their binding strength to nuclear matrix in vitro was compared. The results showed that TM2 and TM3 had stronger binding strength than TM1. To determine the functions of the four new MARs in vivo, binary vectors pBI121 carrying a uidA GUS reporter gene were modified with direct repeat MARs inserted on both sides of the reporter gene cassette and were transferred into tobaccos via Agrobacterium-mediated transformation procedure. Quantitative GUS assays of the transgenic tobaccos showed that when flanking a GUS reporter gene 展开更多
关键词 MAR ISOLATION nuclear matrix in VITRO binding ASSAY Β-GLUCURONIDASE foreign gene EXPRESSION high efficient EXPRESSION vector construction.
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