CMOS-compatible RF/microwave devices,such as filters and amplifiers,have been widely used in wireless communication systems.However,secondary-electron emission phenomena often occur in RF/microwave devices based on si...CMOS-compatible RF/microwave devices,such as filters and amplifiers,have been widely used in wireless communication systems.However,secondary-electron emission phenomena often occur in RF/microwave devices based on silicon(Si)wafers,especially in the high-frequency range.In this paper,we have studied the major factors that influence the secondary-electron yield(SEY)in commercial Si wafers with different doping concentrations.We show that the SEY is suppressed as the doping concentration increases,corresponding to a relatively short effective escape depthλ.Meanwhile,the reduced narrow band gap is beneficial in suppressing the SEY,in which the absence of a shallow energy band below the conduction band will easily capture electrons,as revealed by first-principles calculations.Thus,the new physical mechanism combined with the effective escape depth and band gap can provide useful guidance for the design of integrated RF/microwave devices based on Si wafers.展开更多
Alfalfa(Medicago sativa L.)is a nutritious forage crop with wide ecological adaptability.The molecular breeding of alfalfa is restricted by its heterozygous tetraploid genome and the difficult genetic manipulation pro...Alfalfa(Medicago sativa L.)is a nutritious forage crop with wide ecological adaptability.The molecular breeding of alfalfa is restricted by its heterozygous tetraploid genome and the difficult genetic manipulation process.Under time and resource constraints,we applied a more convenient approach.We investigated two MtGA3ox genes,MtGA3ox1 and MtGA3ox2,of Medicago truncatula,a diploid legume model species,finding that MtGA3ox1 plays a major role in GA-regulated plant architecture.Mutation of neither gene affected nitrogenase activity.These results suggest that MtGA3ox1 can be used in semidwarf and prostrate alfalfa breeding.Based on the M.truncatula MtGA3ox1 sequence,MsGA3ox1 was cloned from alfalfa,and two knockout targets were designed.An efficient CRISPR/Cas9-based genome editing protocol was used to generate msga3ox1 mutants in alfalfa.We obtained three lines that carried mutations in all four alleles in the T0 generation.Fifteen clonal plants were vegetatively propagated from each transgenic line using shoot cuttings.The plant height and internode length of msga3ox1 null mutants were significantly decreased.The number of total lateral branches,leaf/stem ratio and crude protein content of aerial plant parts of msga3ox1 mutants were significantly increased.Thus,we obtained semi-dwarf and prostrate alfalfa by gene editing.展开更多
Alfalfa(Medicago sativa)is one of the most important forage crops in the world;however,its molecular genetics and breeding research are hindered due to the lack of a high-quality reference genome.Here,we report a de n...Alfalfa(Medicago sativa)is one of the most important forage crops in the world;however,its molecular genetics and breeding research are hindered due to the lack of a high-quality reference genome.Here,we report a de novo assembled 816-Mb high-quality,chromosome-level haploid genome sequence for‘Zhongmu No.1’alfalfa,a heterozygous autotetraploid.The contig N50 is 3.92 Mb,and 49165 genes are annotated in the genome.The alfalfa genome is estimated to have diverged from M.truncatula approximately 8 million years ago.Genomic population analysis of 162 alfalfa accessions revealed high genetic diversity,weak population structure,and extensive gene flow from wild to cultivated alfalfa.Genome-wide association studies identified many candidate genes associated with important agronomic traits.Furthermore,we showed that MsFTa2,a Flowering Locus T homolog,whose expression is upregulated in salt-resistant germplasms,may be associated with fall dormancy and salt resistance.Taken together,these genomic resources will facilitate alfalfa genetic research and agronomic improvement.展开更多
基金Project supported by the Administration of Science,Technology and Industry of National Defense of China (Grant No.HTKJ2021KL504001)the National Natural Science Foundation of China (Grant Nos.12004297 and 12174364)+3 种基金the China Postdoctoral Science Foundation (Grant No.2022M712507)the Fundamental Research Funds for the Central Universities (Grant No.xzy01202003)the National 111 Project of China (Grant No.B14040)the support from the Instrument Analysis Center of Xi’an Jiaotong University。
文摘CMOS-compatible RF/microwave devices,such as filters and amplifiers,have been widely used in wireless communication systems.However,secondary-electron emission phenomena often occur in RF/microwave devices based on silicon(Si)wafers,especially in the high-frequency range.In this paper,we have studied the major factors that influence the secondary-electron yield(SEY)in commercial Si wafers with different doping concentrations.We show that the SEY is suppressed as the doping concentration increases,corresponding to a relatively short effective escape depthλ.Meanwhile,the reduced narrow band gap is beneficial in suppressing the SEY,in which the absence of a shallow energy band below the conduction band will easily capture electrons,as revealed by first-principles calculations.Thus,the new physical mechanism combined with the effective escape depth and band gap can provide useful guidance for the design of integrated RF/microwave devices based on Si wafers.
基金supported by the Agricultural Variety Improvement Project of Shandong Province(2019LZGC010)the National Key Research and Development Program of China(2019YFD1002701).
文摘Alfalfa(Medicago sativa L.)is a nutritious forage crop with wide ecological adaptability.The molecular breeding of alfalfa is restricted by its heterozygous tetraploid genome and the difficult genetic manipulation process.Under time and resource constraints,we applied a more convenient approach.We investigated two MtGA3ox genes,MtGA3ox1 and MtGA3ox2,of Medicago truncatula,a diploid legume model species,finding that MtGA3ox1 plays a major role in GA-regulated plant architecture.Mutation of neither gene affected nitrogenase activity.These results suggest that MtGA3ox1 can be used in semidwarf and prostrate alfalfa breeding.Based on the M.truncatula MtGA3ox1 sequence,MsGA3ox1 was cloned from alfalfa,and two knockout targets were designed.An efficient CRISPR/Cas9-based genome editing protocol was used to generate msga3ox1 mutants in alfalfa.We obtained three lines that carried mutations in all four alleles in the T0 generation.Fifteen clonal plants were vegetatively propagated from each transgenic line using shoot cuttings.The plant height and internode length of msga3ox1 null mutants were significantly decreased.The number of total lateral branches,leaf/stem ratio and crude protein content of aerial plant parts of msga3ox1 mutants were significantly increased.Thus,we obtained semi-dwarf and prostrate alfalfa by gene editing.
基金supported by the National Key Research&Development Program of China(2019YFD1002701)Agricultural Variety Improvemnt Project of Shandong Province(2019LZGC010)the Project for Extramural Scientists of the State Key Laboratory for Agrobiotech no logy(2020SKLAB6-15,2011SKLAB01-1).
文摘Alfalfa(Medicago sativa)is one of the most important forage crops in the world;however,its molecular genetics and breeding research are hindered due to the lack of a high-quality reference genome.Here,we report a de novo assembled 816-Mb high-quality,chromosome-level haploid genome sequence for‘Zhongmu No.1’alfalfa,a heterozygous autotetraploid.The contig N50 is 3.92 Mb,and 49165 genes are annotated in the genome.The alfalfa genome is estimated to have diverged from M.truncatula approximately 8 million years ago.Genomic population analysis of 162 alfalfa accessions revealed high genetic diversity,weak population structure,and extensive gene flow from wild to cultivated alfalfa.Genome-wide association studies identified many candidate genes associated with important agronomic traits.Furthermore,we showed that MsFTa2,a Flowering Locus T homolog,whose expression is upregulated in salt-resistant germplasms,may be associated with fall dormancy and salt resistance.Taken together,these genomic resources will facilitate alfalfa genetic research and agronomic improvement.