Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici(Pst), is an airborne disease. In China, it frequently develops initially in central Shaanxi and southwestern Gansu, and from there, inoculum spreads to ...Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici(Pst), is an airborne disease. In China, it frequently develops initially in central Shaanxi and southwestern Gansu, and from there, inoculum spreads to the eastern wheat production regions. Field investigations have suggested that Pst could spread from the west to the east within central Shaanxi andthat Gansu could serve as the inoculum source for central Shaanxi, but there is no direct evidence for this hypothetical dispersal route. In the current study, 321 Pst isolates collected from central Shaanxi and Gansu in the 2019–2020 and2020–2021 winter wheat cropping seasons were genotyped using 23 pairs of KASP-SNP markers. The dispersion among subpopulations was analyzed using several approaches, and overall, the populations were found to exhibit high levels of genetic diversity. There was little genetic divergence(0.05>FST>0) within central Shaanxi. However, significant gene flow(Nm>4) driven by wind-oriented dispersal from west(Baoji) to east(Weinan) occurred. There was also gene flow among the 4 Gansu subpopulations of Tianshui, Longnan, Pingliang, and Qingyang. Migration of the pathogen occurred between central Shaanxi and Gansu. Migration from Gansu to central Shaanxi was major compared with that from central Shaanxi to Gansu that was minor. Genetic variation occurred among isolates, instead of among subpopulations and within isolates. Linkage disequilibrium revealed that there was strong genetic recombination in the subpopulations from Gansu and central Shaanxi. Therefore, the present study provides molecular evidence that Pst spread from west to east in central Shaanxi and showed that Gansu(especially Longnan and Tianshui) was one of the major origins of the pathogen inoculum of wheat stripe rust in central Shaanxi. The results revealed the west-to-east transmission route of wheat stripe rust in central Shaanxi, being used to guide integrated management of the disease.展开更多
Optical fiber acceleration seismometer as an important instrument can offer high sensitivity, anti-jamming and non-touched advantage which has an extensive application field. Its signal processing ability will decide ...Optical fiber acceleration seismometer as an important instrument can offer high sensitivity, anti-jamming and non-touched advantage which has an extensive application field. Its signal processing ability will decide whole system’s performance to some extent because it will affect directly the factors such as resolving power, precision and dynamic range. The signal processing is usually realized by analog circuits which was more inferior in stability, flexibility and anti-jamming to digital processing system. A digital processing system of optical fiber acceleration seismometer has been designed based on the embedded system design scheme. Synthetic-heterodyne demodulation has been studied, and signal processing has been realized. The double processors of ARM and DSP are employed to implement respectively the system control and signal processing, and to provide the output interfaces such as LCD, DAC and Ethernet interface. This system can vary with the measured signal in real time and linearly, and its work frequency bandwidth is between 10Hz and 1kHz. The system has better anti-jamming ability and can work normally when the SNR is 40dB.展开更多
The exploration of the appropriate red phosphor with good luminescence properties is an important issue in the development of current white light-emitting diode(WLED) devices. Transition metal Mn-doped compounds are f...The exploration of the appropriate red phosphor with good luminescence properties is an important issue in the development of current white light-emitting diode(WLED) devices. Transition metal Mn-doped compounds are fascinating luminescent materials. Herein, we performed a systematic theoretical study of the microstructure and optical properties of K_2TiF_6:Mn^(4+) using the CALYPSO structure search method in combination with first-principles calculations. We uncovered a novel structure of K_2TiF_6:Mn^(4+) with space group P-3m1 symmetry, where the impurity Mn_(4+) ions are accurately located at the center of the MnF_6 octahedra. Based on our developed complete energy matrix diagonalization(CEMD)method, we calculated transition lines for ~2E_g →~4A_2,~4A_2→~4T_2, and^4A_2→T2at 642 nm, 471 nm, and 352 nm,respectively, which are in good agreement with the available experimental data. More remarkably, we also found another transition(~4A_2→~2T_2) that lies at 380 nm, which should be a promising candidate for laser action.展开更多
High pressure is an effective method to induce structural and electronic changes,creating novel high-pressure structures with excellent physical and chemical properties.Herein,we investigate the structural phase trans...High pressure is an effective method to induce structural and electronic changes,creating novel high-pressure structures with excellent physical and chemical properties.Herein,we investigate the structural phase transition of hafnium dihydrogen(HfH2)in a pressure range of 0 GPa-500 GPa through the first-principles calculations and the crystal structure analysis by particle swarm optimization(CALYPSO)code.The high-pressure phase transition sequence of HfH2is I4/mmm→Cmma→P-3m1 and the two phase transition pressure points are 220.21 GPa and 359.18 GPa,respectively.A newly trigonal P-3m1 structure with 10-fold coordination first appears as an energy superior structure under high pressure.These three structures are all metallic with the internal ionic bonding of Hf and H atoms.Moreover,the superconducting transition temperature(Tc)values of Cmma at 300 GPa and P-3m1 at 500 GPa are 3.439 K and 19.737 K,respectively.Interestingly,the superconducting transition temperature of the P-3m1 structure presents an upward trend with the pressure rising,which can be attributed to the increase of electron-phonon coupling caused by the enhanced Hf-d electronic density of states at Fermi level under high pressure.展开更多
基金supported by the National Key R&D Program of China (2021YFD1401000)the National Natural Science Foundation of China (32072358 and 32272507)the Natural Science Basic Research Plan in Shaanxi Province, China (2020JZ-15)。
文摘Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici(Pst), is an airborne disease. In China, it frequently develops initially in central Shaanxi and southwestern Gansu, and from there, inoculum spreads to the eastern wheat production regions. Field investigations have suggested that Pst could spread from the west to the east within central Shaanxi andthat Gansu could serve as the inoculum source for central Shaanxi, but there is no direct evidence for this hypothetical dispersal route. In the current study, 321 Pst isolates collected from central Shaanxi and Gansu in the 2019–2020 and2020–2021 winter wheat cropping seasons were genotyped using 23 pairs of KASP-SNP markers. The dispersion among subpopulations was analyzed using several approaches, and overall, the populations were found to exhibit high levels of genetic diversity. There was little genetic divergence(0.05>FST>0) within central Shaanxi. However, significant gene flow(Nm>4) driven by wind-oriented dispersal from west(Baoji) to east(Weinan) occurred. There was also gene flow among the 4 Gansu subpopulations of Tianshui, Longnan, Pingliang, and Qingyang. Migration of the pathogen occurred between central Shaanxi and Gansu. Migration from Gansu to central Shaanxi was major compared with that from central Shaanxi to Gansu that was minor. Genetic variation occurred among isolates, instead of among subpopulations and within isolates. Linkage disequilibrium revealed that there was strong genetic recombination in the subpopulations from Gansu and central Shaanxi. Therefore, the present study provides molecular evidence that Pst spread from west to east in central Shaanxi and showed that Gansu(especially Longnan and Tianshui) was one of the major origins of the pathogen inoculum of wheat stripe rust in central Shaanxi. The results revealed the west-to-east transmission route of wheat stripe rust in central Shaanxi, being used to guide integrated management of the disease.
文摘Optical fiber acceleration seismometer as an important instrument can offer high sensitivity, anti-jamming and non-touched advantage which has an extensive application field. Its signal processing ability will decide whole system’s performance to some extent because it will affect directly the factors such as resolving power, precision and dynamic range. The signal processing is usually realized by analog circuits which was more inferior in stability, flexibility and anti-jamming to digital processing system. A digital processing system of optical fiber acceleration seismometer has been designed based on the embedded system design scheme. Synthetic-heterodyne demodulation has been studied, and signal processing has been realized. The double processors of ARM and DSP are employed to implement respectively the system control and signal processing, and to provide the output interfaces such as LCD, DAC and Ethernet interface. This system can vary with the measured signal in real time and linearly, and its work frequency bandwidth is between 10Hz and 1kHz. The system has better anti-jamming ability and can work normally when the SNR is 40dB.
基金Project supported by the National Natural Science Foundation of China(Grant No.11574220)Fundamental Research Funds for the Central Universities,China(Grant No.SWU118055)+1 种基金the Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund(the second phase)China
文摘The exploration of the appropriate red phosphor with good luminescence properties is an important issue in the development of current white light-emitting diode(WLED) devices. Transition metal Mn-doped compounds are fascinating luminescent materials. Herein, we performed a systematic theoretical study of the microstructure and optical properties of K_2TiF_6:Mn^(4+) using the CALYPSO structure search method in combination with first-principles calculations. We uncovered a novel structure of K_2TiF_6:Mn^(4+) with space group P-3m1 symmetry, where the impurity Mn_(4+) ions are accurately located at the center of the MnF_6 octahedra. Based on our developed complete energy matrix diagonalization(CEMD)method, we calculated transition lines for ~2E_g →~4A_2,~4A_2→~4T_2, and^4A_2→T2at 642 nm, 471 nm, and 352 nm,respectively, which are in good agreement with the available experimental data. More remarkably, we also found another transition(~4A_2→~2T_2) that lies at 380 nm, which should be a promising candidate for laser action.
基金the National Natural Science Foundation of China(Grant Nos.11804031 and 11904297)the Scientific Research Project of Education Department of Hubei Province,China(Grant No.Q20191301)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.SWUKT22049)the Chongqing Talent Plan for Young Top Notch Talents,China(Grant No.202005007)。
文摘High pressure is an effective method to induce structural and electronic changes,creating novel high-pressure structures with excellent physical and chemical properties.Herein,we investigate the structural phase transition of hafnium dihydrogen(HfH2)in a pressure range of 0 GPa-500 GPa through the first-principles calculations and the crystal structure analysis by particle swarm optimization(CALYPSO)code.The high-pressure phase transition sequence of HfH2is I4/mmm→Cmma→P-3m1 and the two phase transition pressure points are 220.21 GPa and 359.18 GPa,respectively.A newly trigonal P-3m1 structure with 10-fold coordination first appears as an energy superior structure under high pressure.These three structures are all metallic with the internal ionic bonding of Hf and H atoms.Moreover,the superconducting transition temperature(Tc)values of Cmma at 300 GPa and P-3m1 at 500 GPa are 3.439 K and 19.737 K,respectively.Interestingly,the superconducting transition temperature of the P-3m1 structure presents an upward trend with the pressure rising,which can be attributed to the increase of electron-phonon coupling caused by the enhanced Hf-d electronic density of states at Fermi level under high pressure.
