Nanocrystalline E and η electron compounds and supersaturated solid solution of the Cu-Sn system have been prepared by mechanical alloying of elemental Cu and Sn powders. The atomie alloying and microstructure of the...Nanocrystalline E and η electron compounds and supersaturated solid solution of the Cu-Sn system have been prepared by mechanical alloying of elemental Cu and Sn powders. The atomie alloying and microstructure of the resultant alloys have been investigated by XRD, DSC and 119Sn Mossbauer spectroscopy. A little amount of SnO2 was detected by Mossbauer spectroscopy, although no trace of diffiaction peaks occurred in the XRD pattern. Thus the spectra for all the milled samples should be fitted using two quadrupole-splitting doublets: one corre sponding to SnO2, the other corresponding to the resultant alloys. The composition dependence of the hyperfine parameters has been eXtensively discussed and explained well with respect to oxidation, sudece effect resulting from grain refinement, coordination environment asymmetry and distortion caused or/and induced by mechanical alloying.展开更多
Among over 170 different types of chemical modifications on RNA nucleobases identified so far,RNA methylation is the major type of epitranscriptomic modifications existing on almost all types of RNAs,and has been demo...Among over 170 different types of chemical modifications on RNA nucleobases identified so far,RNA methylation is the major type of epitranscriptomic modifications existing on almost all types of RNAs,and has been demonstrated to participate in the entire process of RNA metabolism,including transcription,pre-mRNA alternative splicing and maturation,mRNA nucleus export,mRNA degradation and stabilization,mRNA translation.Attributing to the development of high-throughput detection technologies and the identification of both dynamic regulators and recognition proteins,mechanisms of RNA methylation modification in regulating the normal development of the organism as well as various disease occurrence and developmental abnormalities upon RNA methylation dysregulation have become increasingly clear.Here,we particularly focus on three types of RNA methylations:N^(6)-methylcytosine(m^(6)A),5-methylcytosine(m^(5)C),and N^(7)-methyladenosine(m^(7)G).We summarize the elements related to their dynamic installment and removal,specific binding proteins,and the development of high-throughput detection technologies.Then,for a comprehensive understanding of their biological significance,we also overview the latest knowledge on the underlying mechanisms and key roles of these three mRNA methylation modifications in gametogenesis,embryonic development,immune system development,as well as disease and tumor progression.展开更多
The ther m al deco m position mechanism of a m m oniu m thiotungstate of the size of 63 ～75 μmin H2 has been investigated by D T A and X R D methods . The ther m al deco m position activationenergies and the ord...The ther m al deco m position mechanism of a m m oniu m thiotungstate of the size of 63 ～75 μmin H2 has been investigated by D T A and X R D methods . The ther m al deco m position activationenergies and the orders of a m m oniu m thiotu ngstate were calculated by means of Kissinger , Freem an Carroll and Coast Redfern m ethods . It w as also obtained that therm al deco m posi tion is cond ucted according to four reaction equations :( N H4) 2 W S4· H2 O(s) ( N H4) 2 W S4(s) + H2 O(g) W S2(s) + 2 N H3(g) + H2(g) + 2 S(s) + H2 O(g) W S2(s) + 2 N H3(g) + 2 H2 S(g) + H2 O(g) W S2(s) + W(s) + 2 N H3(g) + 2 H2 S(g) + H2 O(g) .展开更多
Synthesis of a m m oniu m alu min u m carbonate hydroxide ( A A C H) w as investigated usinga m m oniu m alu min u m sulfate and a m moniu m hydro carbonate as the starting m aterials . Itw as found that A A C Hca...Synthesis of a m m oniu m alu min u m carbonate hydroxide ( A A C H) w as investigated usinga m m oniu m alu min u m sulfate and a m moniu m hydro carbonate as the starting m aterials . Itw as found that A A C Hcan be synthesized by adding a m m oniu m alu m inu m sulfate solution torapidly stirred a m moniu m hydro - carbonate solution at a tem perature of 30 ℃. A A C Hcantransfor m to α Al2 O3 co m pletely by calcining at 1100 ℃ for 1 hour , and the obtained po w ders , with a particle size of 100 n m , can be sintered to 98 99 % relative density at 1500 ℃for 2 hours .展开更多
文摘Nanocrystalline E and η electron compounds and supersaturated solid solution of the Cu-Sn system have been prepared by mechanical alloying of elemental Cu and Sn powders. The atomie alloying and microstructure of the resultant alloys have been investigated by XRD, DSC and 119Sn Mossbauer spectroscopy. A little amount of SnO2 was detected by Mossbauer spectroscopy, although no trace of diffiaction peaks occurred in the XRD pattern. Thus the spectra for all the milled samples should be fitted using two quadrupole-splitting doublets: one corre sponding to SnO2, the other corresponding to the resultant alloys. The composition dependence of the hyperfine parameters has been eXtensively discussed and explained well with respect to oxidation, sudece effect resulting from grain refinement, coordination environment asymmetry and distortion caused or/and induced by mechanical alloying.
基金supported by the National Natural Science Foundation of China(32121001,32201213)。
文摘Among over 170 different types of chemical modifications on RNA nucleobases identified so far,RNA methylation is the major type of epitranscriptomic modifications existing on almost all types of RNAs,and has been demonstrated to participate in the entire process of RNA metabolism,including transcription,pre-mRNA alternative splicing and maturation,mRNA nucleus export,mRNA degradation and stabilization,mRNA translation.Attributing to the development of high-throughput detection technologies and the identification of both dynamic regulators and recognition proteins,mechanisms of RNA methylation modification in regulating the normal development of the organism as well as various disease occurrence and developmental abnormalities upon RNA methylation dysregulation have become increasingly clear.Here,we particularly focus on three types of RNA methylations:N^(6)-methylcytosine(m^(6)A),5-methylcytosine(m^(5)C),and N^(7)-methyladenosine(m^(7)G).We summarize the elements related to their dynamic installment and removal,specific binding proteins,and the development of high-throughput detection technologies.Then,for a comprehensive understanding of their biological significance,we also overview the latest knowledge on the underlying mechanisms and key roles of these three mRNA methylation modifications in gametogenesis,embryonic development,immune system development,as well as disease and tumor progression.
文摘The ther m al deco m position mechanism of a m m oniu m thiotungstate of the size of 63 ～75 μmin H2 has been investigated by D T A and X R D methods . The ther m al deco m position activationenergies and the orders of a m m oniu m thiotu ngstate were calculated by means of Kissinger , Freem an Carroll and Coast Redfern m ethods . It w as also obtained that therm al deco m posi tion is cond ucted according to four reaction equations :( N H4) 2 W S4· H2 O(s) ( N H4) 2 W S4(s) + H2 O(g) W S2(s) + 2 N H3(g) + H2(g) + 2 S(s) + H2 O(g) W S2(s) + 2 N H3(g) + 2 H2 S(g) + H2 O(g) W S2(s) + W(s) + 2 N H3(g) + 2 H2 S(g) + H2 O(g) .
文摘Synthesis of a m m oniu m alu min u m carbonate hydroxide ( A A C H) w as investigated usinga m m oniu m alu min u m sulfate and a m moniu m hydro carbonate as the starting m aterials . Itw as found that A A C Hcan be synthesized by adding a m m oniu m alu m inu m sulfate solution torapidly stirred a m moniu m hydro - carbonate solution at a tem perature of 30 ℃. A A C Hcantransfor m to α Al2 O3 co m pletely by calcining at 1100 ℃ for 1 hour , and the obtained po w ders , with a particle size of 100 n m , can be sintered to 98 99 % relative density at 1500 ℃for 2 hours .
