Cloud cover plays a pivotal role in assessing observational conditions for astronomical site-testing.Except for the fraction of observing time,its fragmentation also wields a significant influence on the quality of ni...Cloud cover plays a pivotal role in assessing observational conditions for astronomical site-testing.Except for the fraction of observing time,its fragmentation also wields a significant influence on the quality of nighttime sky clarity.In this article,we introduce the functionΓ∈[0,1],designed to comprehensively capture both the fraction of available observing time and its continuity.Leveraging in situ measurement data gathered at the Muztagh-Ata site between 2017 and 2021,we showcase the effectiveness of our approach.The statistical result illustrates that the Muztagh-Ata site affords approximately 122 nights that were absolutely clear and 205 very good nights annually,corresponding toΓ≥0.9 andΓ≥0.36 respectively.展开更多
Axon regeneration of central neurons is a complex process that is tightly regulated by multiple extrinsic and intrinsic factors.The expression levels of distinct genes are changed after central neural system(CNS)injur...Axon regeneration of central neurons is a complex process that is tightly regulated by multiple extrinsic and intrinsic factors.The expression levels of distinct genes are changed after central neural system(CNS)injury and affect axon regeneration.A previous study identified dusp2 as an upregulated gene in zebrafish with spinal cord injury.Here,we found that dual specificity phosphatase 2(DUSP2)is a negative regulator of axon regeneration of the Mauthner cell(M-cell).DUSP2 is a phosphatase that mediates the dephosphorylation of JNK.In this study,we knocked out dusp2 by CRISPR/Cas9 and found that M-cell axons of dusp2(-/-)zebrafish had a better regeneration at the early stage after birth(within 8 days after birth),while those of dusp2^(+/-)zebrafish did not.Overexpression of DUSP2 in Tg(Tol 056)zebrafish by single-cell electroporation retarded the regeneration of M-cell axons.Western blotting results showed that DUSP2 knockout slightly increased the levels of phosphorylated JNK.These findings suggest that knocking out DUSP2 promoted the regeneration of zebrafish M-cell axons,possibly through enhancing JNK phosphorylation.展开更多
The caesium atomic fountain clock is a primary frequency standard.During its operation,a Majorana transition frequency shift will occur once a magnetic field at some special locations along the atomic trajectory is si...The caesium atomic fountain clock is a primary frequency standard.During its operation,a Majorana transition frequency shift will occur once a magnetic field at some special locations along the atomic trajectory is singular.In this study,by developing a physical model,we analyzed the magnetic field requirements for atomic adiabatic transition and calculated the influence of the Majorana atomic transition on the atomic state via a quantum method.Based on the simulation results for the magnetic field in the fountain clock,we applied the Monte Carlo method to simulate the relationship between the Majorana transition frequency shift and the magnetic field at the entrance of the magnetic shielding,as well as the initial atomic population.Measurement of the Majorana transition frequency shift was realized by state-selecting asymmetrically populated atoms.The relationship between the Majorana transition frequency shift and the axial magnetic field at the entrance of the magnetic shielding was obtained.The measured results were essentially consistent with the calculated results.Thus,the magnetic field at the entrance of the magnetic shielding was configured,and the Majorana transition frequency shift of the fountain clock was calculated to be 4.57×10^(-18).展开更多
KIC 10417986 is a short orbital period(0.0737 day)ellipsoidal variable star with aδSct andγDor hybrid pulsation component discovered by Kepler.The ground-based spectroscopic observations were carried out in the wint...KIC 10417986 is a short orbital period(0.0737 day)ellipsoidal variable star with aδSct andγDor hybrid pulsation component discovered by Kepler.The ground-based spectroscopic observations were carried out in the winters of 2020 and 2021 to investigate the binary nature of this star.We derive the orbital parameters using the rvfit code with a result of K_(1)=29.7±1.5 km s^(-1),γ=-18.7±1.7 km s^(-1),and confirm an orbital period of 0.84495 day instead of the result given by Kepler.The atmospheric parameters of the primary are determined by the synthetic spectral fitting technique with the estimated values of T_(eff)=7411±187 K,log g=4.2±0.3 dex,[M/H]=0.08±0.09 dex and vsini=52±11 km s^(-1).KIC 10417986 is a circular orbit binary system.From the single-lined nature and mass function of the star,the derived orbital inclination is 26°±6°,and the mass of the secondary is 0.52_(-0.09)^(+0.18)M_(⊙),which should be a late-K to early-M type star.Fourteen frequencies are extracted from Kepler light curves,of which six independent frequencies in the high-frequency region are identified as the p-mode pulsations ofδSct star,and one independent frequency in the low-frequency region(f_(2)=1.3033 cd^(-1))is probably the rotational frequency due to the starspots rather than the ellipsoidal effect.展开更多
Caesium atomic fountain clock is a primary frequency standard,which realizes the duration of second.Its performance is mostly dominated by the frequency accuracy,and the C-field induced second-order Zeeman frequency s...Caesium atomic fountain clock is a primary frequency standard,which realizes the duration of second.Its performance is mostly dominated by the frequency accuracy,and the C-field induced second-order Zeeman frequency shift is the major effect,which limits the accuracy improvement.By applying a high-precision current supply and high-performance magnetic shieldings,the C-field stability has been improved significantly.In order to achieve a uniform C-field,this paper proposes a doubly wound C-field solenoid,which compensates the radial magnetic field along the atomic flight region generated by the lead-out single wire and improves the accuracy evaluation of second-order Zeeman frequency shift.Based on the stable and uniform C-field,we launch the selected atoms to different heights and record the magnetically sensitive Ramsey transition|F=3,mF=-1→|F=4,mF=-1 central frequency,obtaining this frequency shift as 131.03×10^(-15)and constructing the C-field profile(σ=0.15 n T).Meanwhile,during normal operation,we lock NTSC-F2 to the central frequency of the magnetically sensitive Ramsey transition|F=3,mF=-1→|F=4,mF=-1 fringe for ten consecutive days and record this frequency fluctuation in time domain.The first evaluation of second-order Zeeman frequency shift uncertainty is 0.10×10^(-15).The total deviation of the frequency fluctuation on the clock transition induced by the C-field instability is less than 2.6×10^(-17).Compared with NTSC-F1,NTSC-F2,there appears a significant improvement.展开更多
基金supported by the Chinese Academy of Science(CAS)“Light of West China”Program(No.2022_XBQNXZ_014)the Joint Research Fund in Astronomy under a cooperative agreement between the National Natural Science Foundation of China(NSFC),the Chinese Academy of Sciences(CAS)(grant No.U2031209)+1 种基金the Xinjiang Natural Science Foundation(grant No.2022D01A357)the National Natural Science Foundation of China(NSFC,grant No.11873081)。
文摘Cloud cover plays a pivotal role in assessing observational conditions for astronomical site-testing.Except for the fraction of observing time,its fragmentation also wields a significant influence on the quality of nighttime sky clarity.In this article,we introduce the functionΓ∈[0,1],designed to comprehensively capture both the fraction of available observing time and its continuity.Leveraging in situ measurement data gathered at the Muztagh-Ata site between 2017 and 2021,we showcase the effectiveness of our approach.The statistical result illustrates that the Muztagh-Ata site affords approximately 122 nights that were absolutely clear and 205 very good nights annually,corresponding toΓ≥0.9 andΓ≥0.36 respectively.
基金granted by the National Natural Science Foundation of China,No.82071357Ministry of Science and Technology of China,No.2019YFA0405600(both to BH).
文摘Axon regeneration of central neurons is a complex process that is tightly regulated by multiple extrinsic and intrinsic factors.The expression levels of distinct genes are changed after central neural system(CNS)injury and affect axon regeneration.A previous study identified dusp2 as an upregulated gene in zebrafish with spinal cord injury.Here,we found that dual specificity phosphatase 2(DUSP2)is a negative regulator of axon regeneration of the Mauthner cell(M-cell).DUSP2 is a phosphatase that mediates the dephosphorylation of JNK.In this study,we knocked out dusp2 by CRISPR/Cas9 and found that M-cell axons of dusp2(-/-)zebrafish had a better regeneration at the early stage after birth(within 8 days after birth),while those of dusp2^(+/-)zebrafish did not.Overexpression of DUSP2 in Tg(Tol 056)zebrafish by single-cell electroporation retarded the regeneration of M-cell axons.Western blotting results showed that DUSP2 knockout slightly increased the levels of phosphorylated JNK.These findings suggest that knocking out DUSP2 promoted the regeneration of zebrafish M-cell axons,possibly through enhancing JNK phosphorylation.
基金Project supported by the National Natural Science Foundation of China(Grant No.12173044)Research and Development Project of Scientific Research Instruments and Equipment of Chinese Academy of Sciences(Grant No.YJKYYQ20200020)+1 种基金Large Research Infrastructures Improvement Funds of Chinese Academy of Sciences(Grant No.DSS-WXGZ-2020-0005)Chinese Academy of Sciences for Western Young Scholars(Grant Nos.XAB2018A06,XAB2019A07,and XAB2018B16)。
文摘The caesium atomic fountain clock is a primary frequency standard.During its operation,a Majorana transition frequency shift will occur once a magnetic field at some special locations along the atomic trajectory is singular.In this study,by developing a physical model,we analyzed the magnetic field requirements for atomic adiabatic transition and calculated the influence of the Majorana atomic transition on the atomic state via a quantum method.Based on the simulation results for the magnetic field in the fountain clock,we applied the Monte Carlo method to simulate the relationship between the Majorana transition frequency shift and the magnetic field at the entrance of the magnetic shielding,as well as the initial atomic population.Measurement of the Majorana transition frequency shift was realized by state-selecting asymmetrically populated atoms.The relationship between the Majorana transition frequency shift and the axial magnetic field at the entrance of the magnetic shielding was obtained.The measured results were essentially consistent with the calculated results.Thus,the magnetic field at the entrance of the magnetic shielding was configured,and the Majorana transition frequency shift of the fountain clock was calculated to be 4.57×10^(-18).
基金support from the National Natural Science Foundation of China(NSFC,Grant Nos.11403088,11873081,U2031209,11833002,12090040,12090042 and 12003020)partially supported by the Open Project Program of the Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences。
文摘KIC 10417986 is a short orbital period(0.0737 day)ellipsoidal variable star with aδSct andγDor hybrid pulsation component discovered by Kepler.The ground-based spectroscopic observations were carried out in the winters of 2020 and 2021 to investigate the binary nature of this star.We derive the orbital parameters using the rvfit code with a result of K_(1)=29.7±1.5 km s^(-1),γ=-18.7±1.7 km s^(-1),and confirm an orbital period of 0.84495 day instead of the result given by Kepler.The atmospheric parameters of the primary are determined by the synthetic spectral fitting technique with the estimated values of T_(eff)=7411±187 K,log g=4.2±0.3 dex,[M/H]=0.08±0.09 dex and vsini=52±11 km s^(-1).KIC 10417986 is a circular orbit binary system.From the single-lined nature and mass function of the star,the derived orbital inclination is 26°±6°,and the mass of the secondary is 0.52_(-0.09)^(+0.18)M_(⊙),which should be a late-K to early-M type star.Fourteen frequencies are extracted from Kepler light curves,of which six independent frequencies in the high-frequency region are identified as the p-mode pulsations ofδSct star,and one independent frequency in the low-frequency region(f_(2)=1.3033 cd^(-1))is probably the rotational frequency due to the starspots rather than the ellipsoidal effect.
基金the National Key R&D Program of China(Grant No.2016YFF0200202)the Maintenance and Reformation Program for the Major Science and Technology Fundamental Devices of the Chinese Academy of Sciences(Grant No.DSS-WXGZ-2020-0005)the Foundation for Western Young Scholars,China(Grant No.XAB2018A06)。
文摘Caesium atomic fountain clock is a primary frequency standard,which realizes the duration of second.Its performance is mostly dominated by the frequency accuracy,and the C-field induced second-order Zeeman frequency shift is the major effect,which limits the accuracy improvement.By applying a high-precision current supply and high-performance magnetic shieldings,the C-field stability has been improved significantly.In order to achieve a uniform C-field,this paper proposes a doubly wound C-field solenoid,which compensates the radial magnetic field along the atomic flight region generated by the lead-out single wire and improves the accuracy evaluation of second-order Zeeman frequency shift.Based on the stable and uniform C-field,we launch the selected atoms to different heights and record the magnetically sensitive Ramsey transition|F=3,mF=-1→|F=4,mF=-1 central frequency,obtaining this frequency shift as 131.03×10^(-15)and constructing the C-field profile(σ=0.15 n T).Meanwhile,during normal operation,we lock NTSC-F2 to the central frequency of the magnetically sensitive Ramsey transition|F=3,mF=-1→|F=4,mF=-1 fringe for ten consecutive days and record this frequency fluctuation in time domain.The first evaluation of second-order Zeeman frequency shift uncertainty is 0.10×10^(-15).The total deviation of the frequency fluctuation on the clock transition induced by the C-field instability is less than 2.6×10^(-17).Compared with NTSC-F1,NTSC-F2,there appears a significant improvement.
