During transcription initiation,RNA polymerase binds tightly to the promoter DNA defining the start of transcription,transcribes comparatively slowly,and frequently releases short transcripts(3-8 nucleotides)in a proc...During transcription initiation,RNA polymerase binds tightly to the promoter DNA defining the start of transcription,transcribes comparatively slowly,and frequently releases short transcripts(3-8 nucleotides)in a process called abortive cycling.Transitioning to elongation,the second phase of transcription,the polymerase dissociates from the promoter while RNA synthesis continues.Elongation is characterized by higher rates of transcription and tight binding to the RNA transcript.The RNA polymerase from enterophage T7 (T7 RNAP) has been used as a model to understand the mechanism of transcription in general,and the transition from initiation to elongation specifically.This single-subunit enzyme undergoes dramatic conformational changes during this transition to support the changing requirements of nucleic acid interactions while continuously maintaining polymerase function.Crystal structures,available of multiple stages of the initiation complex and of the elongation complex,combined with biochemical and biophysical data,offer molecular detail of the transition.Some of the crystal structures contain a variant of T7 RNAP where proline 266 is substituted by leucine.This variant shows less abortive products and altered timing of transition,and is a valuable tool to study these processes.The structural transitions from early to late initiation are well understood and are consistent with solution data.The timing of events and the structural intermediates in the transition from late initiation to elongation are less well understood,but the available data allows one to formulate testable models of the transition to guide further research.展开更多
The interaction of the heavy charged particles, of energy higher than a few MeV/amu with semiconductor single crystals can lead to the structural modification of their physical properties and participate at the creati...The interaction of the heavy charged particles, of energy higher than a few MeV/amu with semiconductor single crystals can lead to the structural modification of their physical properties and participate at the creation of the defects which are called latent tracks. Several models were tested for explaining the track formation in semiconductors irradiated with swift heavy ions, one of them is the thermal spike model. This work shows that the experimental data obtained in semiconductors, in our case in InP irradiated with swift heavy ions can be described on the basis of the thermal spike model. The experimental results obtained on InP have allowed the parameters of this model to be understood. The only free parameter is the electron-phonon coupling constant g which is unknown in InP This model allows the evolution of track radii to be found as a function of electronic stopping power （dE/dx）e for different beam energies. For InP a good agreement is observed between calculated track radii and experimental ones on one hand, and on the other hand between calculated and experimental threshold value of electronic stopping power. This allows determining the electron-phonon coupling value for InP to be equal 0.9 × 10%11 Wcm-3K-land the （dE/dx）e threshold for latent track formation in InP equal 27 ＋ 3 keV/nm for ion energies ranging from 0.4-10 MeV/amu.展开更多
Several methods of mutation detection, such as single-strand conformation polymorphism (SSCP), tandem SSCP/heteroduplex analysis and SNaPshot analysis were developed using homemade kit on AB1 310 genetic analyzer, and...Several methods of mutation detection, such as single-strand conformation polymorphism (SSCP), tandem SSCP/heteroduplex analysis and SNaPshot analysis were developed using homemade kit on AB1 310 genetic analyzer, and were successfully applied to mutation detection of 31 colorectal tumor samples. The sieving capability of homemade kit and commercial kit were compared, results demonstrate that homemade kit has higher resolution and shorter analysis time. In clinical tumor samples, 26% K-ras (exon 1) and 24% p53 (exons 7–8) were found to have mutations, and all mutations were single point variations. A majority of mutations occurred in one gene, only 1 tumor contained alterations in the two genes, which indicates that development of colorectal cancer lies on alternate pathways, and may correlate with different gene mutations Keywords single nucleotide polymorphism (SNP) - single-strand conformation polymorphism (SSCP) - heteroduplex analysis (HA) - SNaPshot - linear polyacrylamide (LPA) - polydimethylacrylamide (PDMA)展开更多
The influence of drag-reducing superhydrophobic(SHPo)surface on turbulent boundary layer(TBL)is investigated.A large area of the SHPo surface(about 10δ99 in the streamwise and 5δ99 in the spanwise)is fabricated to f...The influence of drag-reducing superhydrophobic(SHPo)surface on turbulent boundary layer(TBL)is investigated.A large area of the SHPo surface(about 10δ99 in the streamwise and 5δ99 in the spanwise)is fabricated to fully evolve the coherent structures in the TBL.A comparative experiment is carried out by time-resolved particle image velocimetry on a smooth surface and the SHPo surface at Re_(τ)=528.Velocity profiles with high spatial resolution are obtained by the single-pixel resolution ensemble correlation method.The reduction of the streamwise velocity gradient is observed in the near-wall region of y<0.05δ99 on the SHPo surface.By comparing the turbulence statistics,it is discovered that the Reynolds shear stress is reduced by 15.7%,and the turbulent kinetic energy is reduced by 12.3%on the SHPo surface.The coherent structures are investigated by the snapshot proper orthogonal decomposition(POD)and conditional average method.The intensity of Q_(2)/Q_(4)events on the SHPo surface has declined by 16.1%and 12.7%,respectively.The number of clockwise spanwise vortices is substantially reduced by 47%.Through spatial two-point correlation analysis,the streamwise and wall-normal direction scales of the coherent structures on the SHPo surface are suppressed.展开更多
Thermally grown amorphous SiO2 （a-SiOz） films were implanted at room temperature （RT） with 100 keV C-ions to 5.0× 10^17 ions/cm2. These samples were irradiated at RT with 853 MeV Pb-ions to 1.0x 1012 and 5.0&...Thermally grown amorphous SiO2 （a-SiOz） films were implanted at room temperature （RT） with 100 keV C-ions to 5.0× 10^17 ions/cm2. These samples were irradiated at RT with 853 MeV Pb-ions to 1.0x 1012 and 5.0× 10^12 ions/cm2. Then the samples were investigated using Transmission Electron Microscopy （TEM） at RT. Significant microstructure modifications were observed in C-doped a-SiO2/Si samples after high energy Pb-ion irradiations, and the formation of new structures depended strongly on the Pb-ion irradiation fluences. For example, tracks in high density were observed in a 1.0× 10^12 Pb/cm2 irradiated and C-doped sample. Additionally, the length of tracks grows, and a large number of 8H-SiC nanocrystals can be seen in the film when irradiation fluence is increased to 5.0× 10^12 Pb/cm2. Possible modification processes of C-doped a-SiO2 under swift heavy ion irradiations are briefly discussed.展开更多
文摘During transcription initiation,RNA polymerase binds tightly to the promoter DNA defining the start of transcription,transcribes comparatively slowly,and frequently releases short transcripts(3-8 nucleotides)in a process called abortive cycling.Transitioning to elongation,the second phase of transcription,the polymerase dissociates from the promoter while RNA synthesis continues.Elongation is characterized by higher rates of transcription and tight binding to the RNA transcript.The RNA polymerase from enterophage T7 (T7 RNAP) has been used as a model to understand the mechanism of transcription in general,and the transition from initiation to elongation specifically.This single-subunit enzyme undergoes dramatic conformational changes during this transition to support the changing requirements of nucleic acid interactions while continuously maintaining polymerase function.Crystal structures,available of multiple stages of the initiation complex and of the elongation complex,combined with biochemical and biophysical data,offer molecular detail of the transition.Some of the crystal structures contain a variant of T7 RNAP where proline 266 is substituted by leucine.This variant shows less abortive products and altered timing of transition,and is a valuable tool to study these processes.The structural transitions from early to late initiation are well understood and are consistent with solution data.The timing of events and the structural intermediates in the transition from late initiation to elongation are less well understood,but the available data allows one to formulate testable models of the transition to guide further research.
文摘基于奇偶空间的"快照"RAIM算法利用冗余GPS卫星,可以一步检测系统的较大偏差故障,但对中等的累积型故障不具备检测能力。利用多元累积和检测冗余方程的奇偶残差向量,得到了一种新的RAIM算法——多元累积RAIM(Multivariate Cumulative RAIM,MC-RAIM),并将平均运行长度(Average Run Length,ARL)作为该算法性能判决的指标,根据Markov链的状态转移矩阵计算不同维数、窗口参数和报警门限下的ARL,通过仿真实验证明该算法对于GPS系统的中等累积型故障具有检测能力,弥补了原有RAIM算法的缺陷。
文摘The interaction of the heavy charged particles, of energy higher than a few MeV/amu with semiconductor single crystals can lead to the structural modification of their physical properties and participate at the creation of the defects which are called latent tracks. Several models were tested for explaining the track formation in semiconductors irradiated with swift heavy ions, one of them is the thermal spike model. This work shows that the experimental data obtained in semiconductors, in our case in InP irradiated with swift heavy ions can be described on the basis of the thermal spike model. The experimental results obtained on InP have allowed the parameters of this model to be understood. The only free parameter is the electron-phonon coupling constant g which is unknown in InP This model allows the evolution of track radii to be found as a function of electronic stopping power （dE/dx）e for different beam energies. For InP a good agreement is observed between calculated track radii and experimental ones on one hand, and on the other hand between calculated and experimental threshold value of electronic stopping power. This allows determining the electron-phonon coupling value for InP to be equal 0.9 × 10%11 Wcm-3K-land the （dE/dx）e threshold for latent track formation in InP equal 27 ＋ 3 keV/nm for ion energies ranging from 0.4-10 MeV/amu.
文摘Several methods of mutation detection, such as single-strand conformation polymorphism (SSCP), tandem SSCP/heteroduplex analysis and SNaPshot analysis were developed using homemade kit on AB1 310 genetic analyzer, and were successfully applied to mutation detection of 31 colorectal tumor samples. The sieving capability of homemade kit and commercial kit were compared, results demonstrate that homemade kit has higher resolution and shorter analysis time. In clinical tumor samples, 26% K-ras (exon 1) and 24% p53 (exons 7–8) were found to have mutations, and all mutations were single point variations. A majority of mutations occurred in one gene, only 1 tumor contained alterations in the two genes, which indicates that development of colorectal cancer lies on alternate pathways, and may correlate with different gene mutations Keywords single nucleotide polymorphism (SNP) - single-strand conformation polymorphism (SSCP) - heteroduplex analysis (HA) - SNaPshot - linear polyacrylamide (LPA) - polydimethylacrylamide (PDMA)
基金the National Natural Science Foundation of China(Grant Nos.11732010,11972251,11872272,11902218,and 12172242)the Ministry of Industry and Information Technology(Grant No.[2019]360).
文摘The influence of drag-reducing superhydrophobic(SHPo)surface on turbulent boundary layer(TBL)is investigated.A large area of the SHPo surface(about 10δ99 in the streamwise and 5δ99 in the spanwise)is fabricated to fully evolve the coherent structures in the TBL.A comparative experiment is carried out by time-resolved particle image velocimetry on a smooth surface and the SHPo surface at Re_(τ)=528.Velocity profiles with high spatial resolution are obtained by the single-pixel resolution ensemble correlation method.The reduction of the streamwise velocity gradient is observed in the near-wall region of y<0.05δ99 on the SHPo surface.By comparing the turbulence statistics,it is discovered that the Reynolds shear stress is reduced by 15.7%,and the turbulent kinetic energy is reduced by 12.3%on the SHPo surface.The coherent structures are investigated by the snapshot proper orthogonal decomposition(POD)and conditional average method.The intensity of Q_(2)/Q_(4)events on the SHPo surface has declined by 16.1%and 12.7%,respectively.The number of clockwise spanwise vortices is substantially reduced by 47%.Through spatial two-point correlation analysis,the streamwise and wall-normal direction scales of the coherent structures on the SHPo surface are suppressed.
基金supported by the National Natural Science Foundation of China (Grant No.10475102)the Scientific Research Foundation of Heze University,China (Grant No.XY09WL02)the Heze University Doctoral Foundation (Grant No.XY10BS02)
文摘Thermally grown amorphous SiO2 （a-SiOz） films were implanted at room temperature （RT） with 100 keV C-ions to 5.0× 10^17 ions/cm2. These samples were irradiated at RT with 853 MeV Pb-ions to 1.0x 1012 and 5.0× 10^12 ions/cm2. Then the samples were investigated using Transmission Electron Microscopy （TEM） at RT. Significant microstructure modifications were observed in C-doped a-SiO2/Si samples after high energy Pb-ion irradiations, and the formation of new structures depended strongly on the Pb-ion irradiation fluences. For example, tracks in high density were observed in a 1.0× 10^12 Pb/cm2 irradiated and C-doped sample. Additionally, the length of tracks grows, and a large number of 8H-SiC nanocrystals can be seen in the film when irradiation fluence is increased to 5.0× 10^12 Pb/cm2. Possible modification processes of C-doped a-SiO2 under swift heavy ion irradiations are briefly discussed.
