During geomagnetic disturbances, electric fields induced in the Earth and in power systems, pipelines and submarine cables can interfere with the operation of these systems. Calculations for submarine cables are compl...During geomagnetic disturbances, electric fields induced in the Earth and in power systems, pipelines and submarine cables can interfere with the operation of these systems. Calculations for submarine cables are complicated by the need to consider not just the induction directly into the cable but also the earth potentials produced at the coast at each end of the cable. To determine the coast potentials, we present a new model of the ocean and earth conductivity structure that spans the whole length of a cable from one coast to another. Calculations are based on the generalised thin sheet approach introduced by Ranganayaki and Madden but converted to a transmission line model that can be solved using standard circuit theory techniques. It is shown how the transmission line model can be used to calculate the earth potential profile from one side of an ocean or sea to the other. Example calculations are presented for a shallow sea, a shallow ocean, and a deep ocean that are simplified approximations to the North Sea, Tasman Sea and Pacific Ocean and show that the peak potentials occur at the coast. An examination is also made of how the width of a shallow sea and the width of the continental shelf affect these coast potentials. The modelling technique and example results provide a guide for more detailed modelling of geomagnetic induction along the routes of specific submarine cables.展开更多
Lysine-specific demethylase 4A(KDM4A)catalyzes demethylation of histone lysine residues,which regulates chromatin state and transcription.In drosophila and mice,KDM4A plays an important role in multiple biological pro...Lysine-specific demethylase 4A(KDM4A)catalyzes demethylation of histone lysine residues,which regulates chromatin state and transcription.In drosophila and mice,KDM4A plays an important role in multiple biological processes including development,aging,metabolism,and immunity,however the functions of KDM4A in fish are still unclear.There are two copies of the kdm4a gene in zebrafish,namely kdm4aa and kdm4ab,kdm4aa was edited using CRISPR/Cas9 technology in the present study,then homozygous kdm4aa mutants(kdm4aa^(-/-))were obtained,and loss of kdm4aa was confirmed by sequencing and increased H3K9me3.Whole-mount in situ hybridization showed that kdm4aa is widely expressed during the embryonic development of zebrafish.Compared with WT zebrafish,kdm4aa^(-/-)zebrafish showed no significant difference in gamete formation and fertilization,but the survival rate of kdm4aa^(-/-)embryos dramatically reduced to 21%at 26 hpf.Further observation showed that about 80%of survived kdm4aa^(-/-)zebrafish experienced disruption in stripe formation,and 10%of survived kdm4aa^(-/-)zebrafish underwent vertebral malformation.Alizarin red S staining demonstrated the abnormal spinal development in kdm4aa^(-/-)zebrafish.These results indicated that kdm4aa is required for normal embryonic development of zebrafish,loss of kdm4aa function leads to decreased survival during the early stages of zebrafish development and morphological variation in adult zebrafish.展开更多
An ion flux dropout near the dipolarization front(DF) at around XGSM=-11 REin the Earth's plasma sheet was observed by Time History of Events and Macroscale Interaction during substorms(THEMIS) on March31, 2009. T...An ion flux dropout near the dipolarization front(DF) at around XGSM=-11 REin the Earth's plasma sheet was observed by Time History of Events and Macroscale Interaction during substorms(THEMIS) on March31, 2009. The ion differential energy fluxes at energies from 450 e V to 150 ke V measured by the ESA and SST instruments from THC began to decrease about 2 s before the detection of the DF and reached a local minimum 6 s later. Then, the ion fluxes gradually increased to form a dropout around the DF. The spatial extent of the dropout was about 4,000 km. For energies above 20 ke V, the ion fluxes after the dropout are greater than those before it,contrary to the fluxes at energies below 20 ke V. The associated ion density variation indicates that the ion flux dropout coincides with the ion density dropout. Taking advantage of multipoint observations, THD, THC, and THE detected the same DF consecutively. Only THC detected an obvious ion flux dropout; THD observed an indistinct one about 2 s before THC; no high-energy(E [ 30 ke V) ion flux dropout was observed by THE. Our study suggests that the ion flux dropout may evolve withthe earthward-propagating DF, and its properties can depend on locations relative to the DF.展开更多
文摘During geomagnetic disturbances, electric fields induced in the Earth and in power systems, pipelines and submarine cables can interfere with the operation of these systems. Calculations for submarine cables are complicated by the need to consider not just the induction directly into the cable but also the earth potentials produced at the coast at each end of the cable. To determine the coast potentials, we present a new model of the ocean and earth conductivity structure that spans the whole length of a cable from one coast to another. Calculations are based on the generalised thin sheet approach introduced by Ranganayaki and Madden but converted to a transmission line model that can be solved using standard circuit theory techniques. It is shown how the transmission line model can be used to calculate the earth potential profile from one side of an ocean or sea to the other. Example calculations are presented for a shallow sea, a shallow ocean, and a deep ocean that are simplified approximations to the North Sea, Tasman Sea and Pacific Ocean and show that the peak potentials occur at the coast. An examination is also made of how the width of a shallow sea and the width of the continental shelf affect these coast potentials. The modelling technique and example results provide a guide for more detailed modelling of geomagnetic induction along the routes of specific submarine cables.
基金from Shanghai Agriculture Applied Technology Development Program,China(Grant No.G20190102)National Natural Science Foundation of China(Grant No.81770165 to BH)Shanghai Municipal Education Commission(Project for Gaofeng Discipline of Fishery).
文摘Lysine-specific demethylase 4A(KDM4A)catalyzes demethylation of histone lysine residues,which regulates chromatin state and transcription.In drosophila and mice,KDM4A plays an important role in multiple biological processes including development,aging,metabolism,and immunity,however the functions of KDM4A in fish are still unclear.There are two copies of the kdm4a gene in zebrafish,namely kdm4aa and kdm4ab,kdm4aa was edited using CRISPR/Cas9 technology in the present study,then homozygous kdm4aa mutants(kdm4aa^(-/-))were obtained,and loss of kdm4aa was confirmed by sequencing and increased H3K9me3.Whole-mount in situ hybridization showed that kdm4aa is widely expressed during the embryonic development of zebrafish.Compared with WT zebrafish,kdm4aa^(-/-)zebrafish showed no significant difference in gamete formation and fertilization,but the survival rate of kdm4aa^(-/-)embryos dramatically reduced to 21%at 26 hpf.Further observation showed that about 80%of survived kdm4aa^(-/-)zebrafish experienced disruption in stripe formation,and 10%of survived kdm4aa^(-/-)zebrafish underwent vertebral malformation.Alizarin red S staining demonstrated the abnormal spinal development in kdm4aa^(-/-)zebrafish.These results indicated that kdm4aa is required for normal embryonic development of zebrafish,loss of kdm4aa function leads to decreased survival during the early stages of zebrafish development and morphological variation in adult zebrafish.
基金supported by the National Natural Science Foundation of China(40774081)Ministry of Science and Technology of China(2011CB811404)the Specialized Research Fund for State Key Laboratories
文摘An ion flux dropout near the dipolarization front(DF) at around XGSM=-11 REin the Earth's plasma sheet was observed by Time History of Events and Macroscale Interaction during substorms(THEMIS) on March31, 2009. The ion differential energy fluxes at energies from 450 e V to 150 ke V measured by the ESA and SST instruments from THC began to decrease about 2 s before the detection of the DF and reached a local minimum 6 s later. Then, the ion fluxes gradually increased to form a dropout around the DF. The spatial extent of the dropout was about 4,000 km. For energies above 20 ke V, the ion fluxes after the dropout are greater than those before it,contrary to the fluxes at energies below 20 ke V. The associated ion density variation indicates that the ion flux dropout coincides with the ion density dropout. Taking advantage of multipoint observations, THD, THC, and THE detected the same DF consecutively. Only THC detected an obvious ion flux dropout; THD observed an indistinct one about 2 s before THC; no high-energy(E [ 30 ke V) ion flux dropout was observed by THE. Our study suggests that the ion flux dropout may evolve withthe earthward-propagating DF, and its properties can depend on locations relative to the DF.
