For high-precision pulsar timing analysis and low-frequency gravitational wave detection,it is essential to accurately determine pulsar pulse times of arrival(ToAs)and associated uncertainties.To measure the ToAs and ...For high-precision pulsar timing analysis and low-frequency gravitational wave detection,it is essential to accurately determine pulsar pulse times of arrival(ToAs)and associated uncertainties.To measure the ToAs and their uncertainties,various cross-correlation-based techniques can be employed.We develop methodologies to investigate the impact of the template-matching method,profile shape,signal-to-noise ratio of both template and observation on ToA uncertainties.These methodologies are then applied to data from the International Pulsar Timing Array.We demonstrate that the Fourier domain Markov chain Monte Carlo method is generally superior to other methods,while the Gaussian interpolation shift method outperforms other methods in certain cases,such as profiles with large duty cycles or smooth profiles without sharp features.However,it is important to note that our study focuses solely on ToA uncertainty,and the optimal method for determining both ToA and ToA uncertainty may differ.展开更多
Purpose The purpose of this investigation was to examine the acute effects of low-load unilateral submaximal leg extension muscle actions with and without blood flow restriction(BFR)on maximal voluntary isometric cont...Purpose The purpose of this investigation was to examine the acute effects of low-load unilateral submaximal leg extension muscle actions with and without blood flow restriction(BFR)on maximal voluntary isometric contraction(MVIC)torque,electromyographic(EMG)amplitude(AMP)and EMG mean power frequency(MPF).Methods Twelve(mean±SD;23±4 years)men performed 75 submaximal(1×30,3×15)unilateral leg extension muscle actions with or without BFR.Before and immediately after the 75 reps,ultrasound measures and MVIC muscle actions were performed,and surface EMG was simultaneously assessed from the vastus lateralis.BFR was applied at 60%of total arterial occlusion.Separate repeated measures ANOVA’s,and Bonferroni corrected t-tests were performed to examine MVIC,EMG AMP,and EMG MPF.An alpha of P<0.05 was considered statistically significant for all comparisons.Results There was no significant(P=0.077)interaction or main effect for Condition(P=0.442)for EMG AMP.There was,however,an interaction(P=0.014)for EMG MPF(posttest BFR decrease>posttest non-BFR decrease).There was a main effect for Time,collapsed across Condition,for MVIC torque(P<0.001;(mean±SD;294.9±20.1 N·m to 138.6±12.2 N·m),but no main effect for Time for EMG AMP.Conclusion The findings of the present study indicated there were similar fatigue-induced decreases in MVIC torque and mode-specific decreases in EMG mean power frequency between the BFR and non-BFR conditions,but no changes in EMG amplitude.The decrease in MVIC torque may be due,in part,to the fatigue-induced buildup of metabolic byproducts that adversely affects excitation-contraction coupling and force output.展开更多
Annual variations of interstellar scintillation can be modelled to constrain parameters of the ionized interstellar medium.If a pulsar is in a binary system,then investigating the orbital parameters is possible throug...Annual variations of interstellar scintillation can be modelled to constrain parameters of the ionized interstellar medium.If a pulsar is in a binary system,then investigating the orbital parameters is possible through analysis of the orbital variation of scintillation.In observations carried out from 2011 to 2020 by the European Pulsar Timing Array radio telescopes,PSRs J0613-0200and J0636+5128 show strong annual variations in their scintillation velocity,while the former additionally exhibits an orbital fluctuation.Bayesian theory and Markov-chain-Monte-Carlo methods are used to interpret these periodic variations.We assume a thin and anisotropic scattering screen model,and discuss the mildly and extremely anisotropic scattering cases.PSR J0613-0200is best described by mildly anisotropic scattering,while PSR J0636+5128 exhibits extremely anisotropic scattering.We measure the distance,velocity,and degree of anisotropy of the scattering screen for our two pulsars,finding that scattering screen distances from Earth for PSRs J0613-0200 and J0636+5128 are 316_(-20)^(+28)pc and 262_(-38)^(+96)pc,respectively.The positions of these scattering screens are coincident with the shell of the Local Bubble towards both pulsars.These associations add to the growing evidence of the Local Bubble shell as a dominant region of scattering along many sightlines.展开更多
基金support by the Deutsche Forschungsgemeinschaft(DFG)through the Heisenberg program(Project No.433075039)。
文摘For high-precision pulsar timing analysis and low-frequency gravitational wave detection,it is essential to accurately determine pulsar pulse times of arrival(ToAs)and associated uncertainties.To measure the ToAs and their uncertainties,various cross-correlation-based techniques can be employed.We develop methodologies to investigate the impact of the template-matching method,profile shape,signal-to-noise ratio of both template and observation on ToA uncertainties.These methodologies are then applied to data from the International Pulsar Timing Array.We demonstrate that the Fourier domain Markov chain Monte Carlo method is generally superior to other methods,while the Gaussian interpolation shift method outperforms other methods in certain cases,such as profiles with large duty cycles or smooth profiles without sharp features.However,it is important to note that our study focuses solely on ToA uncertainty,and the optimal method for determining both ToA and ToA uncertainty may differ.
基金supported by The NASA Planetary Science Division,under the Solar System Exploration Research Virtual Institute Cooperative Agreement(NNH16ZDA001N)program titled“Radiation Effects on Volatiles and Exploration of Asteroids and Lunar Surfaces(REVEALS)”related to crew safety and human space exploration.
文摘Purpose The purpose of this investigation was to examine the acute effects of low-load unilateral submaximal leg extension muscle actions with and without blood flow restriction(BFR)on maximal voluntary isometric contraction(MVIC)torque,electromyographic(EMG)amplitude(AMP)and EMG mean power frequency(MPF).Methods Twelve(mean±SD;23±4 years)men performed 75 submaximal(1×30,3×15)unilateral leg extension muscle actions with or without BFR.Before and immediately after the 75 reps,ultrasound measures and MVIC muscle actions were performed,and surface EMG was simultaneously assessed from the vastus lateralis.BFR was applied at 60%of total arterial occlusion.Separate repeated measures ANOVA’s,and Bonferroni corrected t-tests were performed to examine MVIC,EMG AMP,and EMG MPF.An alpha of P<0.05 was considered statistically significant for all comparisons.Results There was no significant(P=0.077)interaction or main effect for Condition(P=0.442)for EMG AMP.There was,however,an interaction(P=0.014)for EMG MPF(posttest BFR decrease>posttest non-BFR decrease).There was a main effect for Time,collapsed across Condition,for MVIC torque(P<0.001;(mean±SD;294.9±20.1 N·m to 138.6±12.2 N·m),but no main effect for Time for EMG AMP.Conclusion The findings of the present study indicated there were similar fatigue-induced decreases in MVIC torque and mode-specific decreases in EMG mean power frequency between the BFR and non-BFR conditions,but no changes in EMG amplitude.The decrease in MVIC torque may be due,in part,to the fatigue-induced buildup of metabolic byproducts that adversely affects excitation-contraction coupling and force output.
基金supported by the National Natural Science Foundation of China(Grant No.12003047)the Major Science and Technology Program of Xinjiang Uygur Autonomous Region(Grant No.2022A03013-2)+2 种基金the Natural Science Foundation of Xinjiang Uygur Autonomous Region(Grant No.2022D01D85)support by the Deutsche Forschungsgemeinschaft(DFG)through the Heisenberg programme(Project No.433075039)financial support from“Programme National de Cosmologie et Galaxies”(PNCG)of CNRS/INSU,France。
文摘Annual variations of interstellar scintillation can be modelled to constrain parameters of the ionized interstellar medium.If a pulsar is in a binary system,then investigating the orbital parameters is possible through analysis of the orbital variation of scintillation.In observations carried out from 2011 to 2020 by the European Pulsar Timing Array radio telescopes,PSRs J0613-0200and J0636+5128 show strong annual variations in their scintillation velocity,while the former additionally exhibits an orbital fluctuation.Bayesian theory and Markov-chain-Monte-Carlo methods are used to interpret these periodic variations.We assume a thin and anisotropic scattering screen model,and discuss the mildly and extremely anisotropic scattering cases.PSR J0613-0200is best described by mildly anisotropic scattering,while PSR J0636+5128 exhibits extremely anisotropic scattering.We measure the distance,velocity,and degree of anisotropy of the scattering screen for our two pulsars,finding that scattering screen distances from Earth for PSRs J0613-0200 and J0636+5128 are 316_(-20)^(+28)pc and 262_(-38)^(+96)pc,respectively.The positions of these scattering screens are coincident with the shell of the Local Bubble towards both pulsars.These associations add to the growing evidence of the Local Bubble shell as a dominant region of scattering along many sightlines.
