Using genomic in situ hybridization with genomic DNA, high-order chromatin fibers were successfully exhibited under a light microscope through the cell cycle in barley, rice, maize and field bean. From the interphase ...Using genomic in situ hybridization with genomic DNA, high-order chromatin fibers were successfully exhibited under a light microscope through the cell cycle in barley, rice, maize and field bean. From the interphase to prophase and metaphase of mitosis, the fibers were basically similar. Each was estimated to be around 200 nm in diameter, but the strength of signals was not the same along the fiber length. Through the cell cycle a series of dynamic distribution changes occurred in the fibers. In the interphase, they were unraveled. At the early prophase they were arranged with parallel and mirror symmetry. During late-prophase and metaphase, the fibers were bundled and became different visible chromosomes. The parallel coiling and mirror symmetry structures were visible clearly until the metaphase. In anaphase they disappeared. During telophase, in peripheral regions of congregated chromosome group, borderlines of the chromosomes disappeared and the fibers were unraveled. This demonstrated that mitotic chromosomes are assembled and organized by parallel and adjacent coiling of the fibers and the fibers should be the highest order structure for DNA coiling.展开更多
We report the generation of passively tunable high peak signal-to-noise ratio harmonic mode-locked （HML） all- normal-dispersion Yb-doped fiber laser with a single birefringent filter in a ring cavity configuration. ...We report the generation of passively tunable high peak signal-to-noise ratio harmonic mode-locked （HML） all- normal-dispersion Yb-doped fiber laser with a single birefringent filter in a ring cavity configuration. The highest fourth harmonic of the fundamental mode-locked frequency at a repetition rate of 88 MHz is obtained. The pulses are compressed to 627fs by using an external grating-pair compressor. For the fourth HML output, the peak signal-to-noise ratio of the rf is 73dB and the average power is as high as 110mW with the pump power of 500mW. Soliton bunches which contain multipulses are also observed in the weak mode-locked regime of the HML, and the separation between interpulses in a dissipative soliton bunch can be controlled by adjustment of the waveplates and spectral filter in the cavity：展开更多
We construct a system of magnetic tweezers and apply it to study the interaction between histones and DNA. The condensation of DNA by purified histones at low ionic strengths is directly monitored by recording the len...We construct a system of magnetic tweezers and apply it to study the interaction between histones and DNA. The condensation of DNA by purified histones at low ionic strengths is directly monitored by recording the length of the DNA as a function of elapsed time. It is found that DNA condensates in a dynamic manner. The binding of hist, ones to DNA is energetically favoured, but the ten,sion applied on DNA tends to unravel the DNA-histone complex, The competition between the two processes determiners the rate of the DNA condensation.展开更多
A kind of tapered segmented cladding fiber(T-SCF)with large mode area(LMA)is proposed,and the mode and amplification characteristics of T-SCFs with concave,linear,and convex tapered structures are investigated based o...A kind of tapered segmented cladding fiber(T-SCF)with large mode area(LMA)is proposed,and the mode and amplification characteristics of T-SCFs with concave,linear,and convex tapered structures are investigated based on finite-element method(FEM)and few-mode steady-state rate equation.Simulation results indicate that the concave tapered structure can introduce high loss for high-order modes(HOMs)that is advantageous to achieve single-mode operation,whereas the convex tapered structure provides large effective mode area that can help to mitigate nonlinear effects.Meanwhile,the small-to-large amplification scheme shows further advantages on stripping off HOMs,and the large-to-small amplification scheme decreases the heat load density induced by the high-power pump.Moreover,singlemode propagation performance,effective mode area,and heat load density of the T-SCF are superior to those of tapered step index fiber(T-SIF).These theoretical model and numerical results can provide instructive suggestions for designing high-power fiber lasers and amplifiers.展开更多
Background:The use of image analysis to understand the structure of chromosome and chromatin is critical to the study of genetic evolution and diversification.Furthermore,a detailed chromosome map and the structure of...Background:The use of image analysis to understand the structure of chromosome and chromatin is critical to the study of genetic evolution and diversification.Furthermore,a detailed chromosome map and the structure of chromatin in the nucleus may contribute to the plant breeding and the study of fundamental biology and genetics in organisms.Results:In plants with a fully annotated genome project,such as the Leguminosae species,the integration of genetic information,including DNA sequence data,a linkage map,and the cytological quantitative chromosome map could further improve their genetic value.The numerical parameters of chromocenters in 3D can provide useful genetic information for phylogenetic studies of plant diversity and heterochromatic markers whose epigenetic changes may explain the developmental and environmental changes in the plant genome.Extended DNA fibers combined with fluorescence in situ hybridization revealed the highest spatial resolution of the obtained genome structure.Moreover,image analysis at the nano-scale level using a helium ion microscope revealed the surface structure of chromatin,which consists of chromatin fibers compacted into plant chromosomes.Conclusions:The studies described in this review sought to measure and evaluate chromosome and chromatin using the image analysis method,which may reduce measurement time and improve resolution.Further,we discussed the development of an effective image analysis to evaluate the structure of chromosome and chromatin.An effective application study of cell biology and the genetics of plants using image analysis methods is expected to be a major propeller in the development of new applications.展开更多
基金Supported by the National Natural Science Foundation of China(39870423 and 30670736)China Postdoctoral Science Foundation(2003034496).
文摘Using genomic in situ hybridization with genomic DNA, high-order chromatin fibers were successfully exhibited under a light microscope through the cell cycle in barley, rice, maize and field bean. From the interphase to prophase and metaphase of mitosis, the fibers were basically similar. Each was estimated to be around 200 nm in diameter, but the strength of signals was not the same along the fiber length. Through the cell cycle a series of dynamic distribution changes occurred in the fibers. In the interphase, they were unraveled. At the early prophase they were arranged with parallel and mirror symmetry. During late-prophase and metaphase, the fibers were bundled and became different visible chromosomes. The parallel coiling and mirror symmetry structures were visible clearly until the metaphase. In anaphase they disappeared. During telophase, in peripheral regions of congregated chromosome group, borderlines of the chromosomes disappeared and the fibers were unraveled. This demonstrated that mitotic chromosomes are assembled and organized by parallel and adjacent coiling of the fibers and the fibers should be the highest order structure for DNA coiling.
基金Supported by the National Key Technology R&D Program of the Ministry of Science and Technology under Grant No2012BAC23B03the National Key Basic Research Program of China under Grant No 2013CB922401the National Natural Science Foundation of China under Grants No 11474002
文摘We report the generation of passively tunable high peak signal-to-noise ratio harmonic mode-locked （HML） all- normal-dispersion Yb-doped fiber laser with a single birefringent filter in a ring cavity configuration. The highest fourth harmonic of the fundamental mode-locked frequency at a repetition rate of 88 MHz is obtained. The pulses are compressed to 627fs by using an external grating-pair compressor. For the fourth HML output, the peak signal-to-noise ratio of the rf is 73dB and the average power is as high as 110mW with the pump power of 500mW. Soliton bunches which contain multipulses are also observed in the weak mode-locked regime of the HML, and the separation between interpulses in a dissipative soliton bunch can be controlled by adjustment of the waveplates and spectral filter in the cavity：
基金Supported by the National Natural Science Foundation of China under Grant No 10334100. The authors acknowledge the help of Professor .J. Yan of the National University of Singapore in setting up the instrument.
文摘We construct a system of magnetic tweezers and apply it to study the interaction between histones and DNA. The condensation of DNA by purified histones at low ionic strengths is directly monitored by recording the length of the DNA as a function of elapsed time. It is found that DNA condensates in a dynamic manner. The binding of hist, ones to DNA is energetically favoured, but the ten,sion applied on DNA tends to unravel the DNA-histone complex, The competition between the two processes determiners the rate of the DNA condensation.
基金the National Key R&D Program of China(No.2020YFB1805802)National Natural Science Foundation of China(Nos.62005012 and 61827817)+1 种基金State Key Laboratory of Rail Traffic Control and Safety(No.RCS2019ZZ007)Beijing Jiaotong University,and Shandong Province Higher Educational Science and Technology Program(No.J18KA368).
文摘A kind of tapered segmented cladding fiber(T-SCF)with large mode area(LMA)is proposed,and the mode and amplification characteristics of T-SCFs with concave,linear,and convex tapered structures are investigated based on finite-element method(FEM)and few-mode steady-state rate equation.Simulation results indicate that the concave tapered structure can introduce high loss for high-order modes(HOMs)that is advantageous to achieve single-mode operation,whereas the convex tapered structure provides large effective mode area that can help to mitigate nonlinear effects.Meanwhile,the small-to-large amplification scheme shows further advantages on stripping off HOMs,and the large-to-small amplification scheme decreases the heat load density induced by the high-power pump.Moreover,singlemode propagation performance,effective mode area,and heat load density of the T-SCF are superior to those of tapered step index fiber(T-SIF).These theoretical model and numerical results can provide instructive suggestions for designing high-power fiber lasers and amplifiers.
基金This work was supported by“e-ASIA Joint Research Program”,“Development of nano-visualization for structural analyses of genetic materials and early infection process for further innovation of functional bio-nanotechnology”from SICORP,and the Mobility Plus Project(No.JPJSBP 120203507)(to NO)This work was also supported by“The 51st Research Grants in the Natural Sciences”from The Mitsubishi Foundation and Nanotechnology Platform of MEXT(No.JPMXP09F20OS0004)(to NO)。
文摘Background:The use of image analysis to understand the structure of chromosome and chromatin is critical to the study of genetic evolution and diversification.Furthermore,a detailed chromosome map and the structure of chromatin in the nucleus may contribute to the plant breeding and the study of fundamental biology and genetics in organisms.Results:In plants with a fully annotated genome project,such as the Leguminosae species,the integration of genetic information,including DNA sequence data,a linkage map,and the cytological quantitative chromosome map could further improve their genetic value.The numerical parameters of chromocenters in 3D can provide useful genetic information for phylogenetic studies of plant diversity and heterochromatic markers whose epigenetic changes may explain the developmental and environmental changes in the plant genome.Extended DNA fibers combined with fluorescence in situ hybridization revealed the highest spatial resolution of the obtained genome structure.Moreover,image analysis at the nano-scale level using a helium ion microscope revealed the surface structure of chromatin,which consists of chromatin fibers compacted into plant chromosomes.Conclusions:The studies described in this review sought to measure and evaluate chromosome and chromatin using the image analysis method,which may reduce measurement time and improve resolution.Further,we discussed the development of an effective image analysis to evaluate the structure of chromosome and chromatin.An effective application study of cell biology and the genetics of plants using image analysis methods is expected to be a major propeller in the development of new applications.
