Nanoscale mullite powder were synthesized via Sol-gel-SCFD and middle temperature treatment by using AIP( aluminum-isopropoxde) and TEOS ( tetraethyl orthosili-cate) as starting materials. Both of the binary aerogel o...Nanoscale mullite powder were synthesized via Sol-gel-SCFD and middle temperature treatment by using AIP( aluminum-isopropoxde) and TEOS ( tetraethyl orthosili-cate) as starting materials. Both of the binary aerogel of alumina-silica and calcined nanoscale materials were investigated by using TG-DSC ( thermogravimetry-differentialscanning calorimeter) , TEM( transmission electron microscope) , XRD(X-Ray diffractometer ) and specific surfacearea and porosimetry. TG-DSC indicated the removal of most of the volatiles, i.e. 15.98% up to about 700℃ ,and in the DSC curve , existence of two exothermic peak atabout 445℃ and 1015℃ may be due to the crystallizationof Si-O-Al-O in diphasic gels and mullitization and a small endothermic peak at about 805℃ indicated the decomposition of structural water molecules . On the colligation of the results of TG-DSC, XRD and TEM, the beginning temperature of mullitization in Al2O3-SiO2 aerogel system can be confirmed at about 1015℃. XRD results also showed the formation of mullite at the range 1100-1200℃. TEM and surface area and porosimetry results showed that the nanosized mullite were calcinated at 1100and 1200℃ exhibited size 30 nm and 50 nm, specific surface area 138.91 m2/g and 95.81 m2/g.展开更多
Dear Editor CRISPR from Prevotella and Francisella 1 （Cpfl） is an emerging RNA-guided endonuclease system that relies on thymidine-rich protospacer adjacent motif （PAM） for DNA targeting （Zetsche et al., 2015）. ...Dear Editor CRISPR from Prevotella and Francisella 1 （Cpfl） is an emerging RNA-guided endonuclease system that relies on thymidine-rich protospacer adjacent motif （PAM） for DNA targeting （Zetsche et al., 2015）. CRISPR-Cpfl has unique features that could be advantageous over the CRISPR-Cas9 system. For example, Cpfl requires only a 42 nt crRNA, while Cas9 uses 100 nt gRNA. While Cas9 generates blunt ends of DNA breaks, the Cpfl cleavage results in 5＇ overhangs distal from the protospacer, which may improve efficiency for NHEJ-based gene insertion. Interestingly, Cpfl proteins also have RNase activity （Fonfara et al., 2016）, which was utilized to process crRNA arrays for multiplexed genome editing in both mammalian systems and plants （Wang et al., 2017; Zetsche et al., 2017）.展开更多
基金This work was supported by the project of Wuhan Science & Technology(20011007088)and Hubei province project of key problem tackling(2001AA101B07)
文摘Nanoscale mullite powder were synthesized via Sol-gel-SCFD and middle temperature treatment by using AIP( aluminum-isopropoxde) and TEOS ( tetraethyl orthosili-cate) as starting materials. Both of the binary aerogel of alumina-silica and calcined nanoscale materials were investigated by using TG-DSC ( thermogravimetry-differentialscanning calorimeter) , TEM( transmission electron microscope) , XRD(X-Ray diffractometer ) and specific surfacearea and porosimetry. TG-DSC indicated the removal of most of the volatiles, i.e. 15.98% up to about 700℃ ,and in the DSC curve , existence of two exothermic peak atabout 445℃ and 1015℃ may be due to the crystallizationof Si-O-Al-O in diphasic gels and mullitization and a small endothermic peak at about 805℃ indicated the decomposition of structural water molecules . On the colligation of the results of TG-DSC, XRD and TEM, the beginning temperature of mullitization in Al2O3-SiO2 aerogel system can be confirmed at about 1015℃. XRD results also showed the formation of mullite at the range 1100-1200℃. TEM and surface area and porosimetry results showed that the nanosized mullite were calcinated at 1100and 1200℃ exhibited size 30 nm and 50 nm, specific surface area 138.91 m2/g and 95.81 m2/g.
文摘Dear Editor CRISPR from Prevotella and Francisella 1 （Cpfl） is an emerging RNA-guided endonuclease system that relies on thymidine-rich protospacer adjacent motif （PAM） for DNA targeting （Zetsche et al., 2015）. CRISPR-Cpfl has unique features that could be advantageous over the CRISPR-Cas9 system. For example, Cpfl requires only a 42 nt crRNA, while Cas9 uses 100 nt gRNA. While Cas9 generates blunt ends of DNA breaks, the Cpfl cleavage results in 5＇ overhangs distal from the protospacer, which may improve efficiency for NHEJ-based gene insertion. Interestingly, Cpfl proteins also have RNase activity （Fonfara et al., 2016）, which was utilized to process crRNA arrays for multiplexed genome editing in both mammalian systems and plants （Wang et al., 2017; Zetsche et al., 2017）.
