Energetic electron precipitation from Earth's outer radiation belt heats the upper atmosphere and alters its chemical properties. The precipitating flux intensity, typically modelled using inputs ...from high-altitude, equatorial spacecraft, dictates the radiation belt's energy contribution to the atmosphere and the strength of space-atmosphere coupling. The classical quasi-linear theory of electron precipitation through moderately fast diffusive interactions with plasma waves predicts that precipitating electron fluxes cannot exceed fluxes of electrons trapped in the radiation belt, setting an apparent upper limit for electron precipitation. Here we show from low-altitude satellite observations, that ~100 keV electron precipitation rates often exceed this apparent upper limit. We demonstrate that such superfast precipitation is caused by nonlinear electron interactions with intense plasma waves, which have not been previously incorporated in radiation belt models. The high occurrence rate of superfast precipitation suggests that it is important for modelling both radiation belt fluxes and space-atmosphere coupling.
The Exploration of energization and Radiation in Geospace (ERG) project explores the acceleration, transport, and loss of relativistic electrons in the radiation belts and the dynamics for geospace ...storms. This project consists of three research teams for satellite observation, ground-based network observation, and integrated data analysis/simulation. This synergetic approach is essential for obtaining a comprehensive understanding of the relativistic electron generation/loss processes of the radiation belts as well as geospace storms through cross-energy/cross-regional couplings, in which different plasma/particle populations and regions are strongly coupled with each other. This paper gives an overview of the ERG project and presents the initial results from the ERG (Arase) satellite.
The in situ measurement of charged particles plays a key role in understanding space plasma physics. Velocity distribution functions of ions and electrons have been acquired with electrostatic ...analyzers onboard spacecraft. Since conventional energy analyzers (e.g., top-hat electrostatic analyzers) have essentially a two-dimensional field of view, the solid angle coverage is achieved with the aid of spacecraft spin motion or with additional entrance deflection systems in front of the electrostatic analyzer. In the latter case, however, the full angular scan is realized only in the lower energy range (typically only up to 5–15 keV/e), due to the limitation of the electric field applied to the deflector. Here we propose a novel deflection system for extending the energy coverage up to tens of keV. This is especially useful for plasma observations in situations where the anisotropy of the energetic part (> 10 keV) of charged particles plays an essential role in plasma dynamics and hence is of significant interest.
Graphical Abstract
Accuracy validation of gait analysis using pose estimation with artificial intelligence (AI) remains inadequate, particularly in objective assessments of absolute error and similarity of waveform ...patterns. This study aimed to clarify objective measures for absolute error and waveform pattern similarity in gait analysis using pose estimation AI (OpenPose). Additionally, we investigated the feasibility of simultaneous measuring both lower limbs using a single camera from one side. We compared motion analysis data from pose estimation AI using video footage that was synchronized with a three-dimensional motion analysis device. The comparisons involved mean absolute error (MAE) and the coefficient of multiple correlation (CMC) to compare the waveform pattern similarity. The MAE ranged from 2.3 to 3.1° on the camera side and from 3.1 to 4.1° on the opposite side, with slightly higher accuracy on the camera side. Moreover, the CMC ranged from 0.936 to 0.994 on the camera side and from 0.890 to 0.988 on the opposite side, indicating a "very good to excellent" waveform similarity. Gait analysis using a single camera revealed that the precision on both sides was sufficiently robust for clinical evaluation, while measurement accuracy was slightly superior on the camera side.
The ERG Science Center Miyoshi, Yoshizumi; Hori, Tomoaki; Shoji, Masafumi ...
Earth, planets and space,
06/2018, Volume:
70, Issue:
1
Journal Article
Peer reviewed
Open access
The Exploration of energization and Radiation in Geospace (ERG) Science Center serves as a hub of the ERG project, providing data files in a common format and developing the space physics environment ...data analysis software and plug-ins for data analysis. The Science Center also develops observation plans for the ERG (Arase) satellite according to the science strategy of the project. Conjugate observations with other satellites and ground-based observations are also planned. These tasks contribute to the ERG project by achieving quick analysis and well-organized conjugate ERG satellite and ground-based observations.
•The ability to cease motion was compared between older and younger adults using.•A rapid stopping task was used to compare both groups.•Both the reaction stopping times were longer in the older ...group.•The braking time was significantly longer in older adults.•With advancing age, motor control declines during initiation and termination phases.
For older adults, falls often occur when transitioning from motion to a complete stop, as the motor control required during this phase is very complex and challenging. The purpose of this study was to clarify the effect of aging on the motor control required to terminate motion. Twenty-five healthy older adults (aged >65 years) and 25 healthy young adults (20–23 years) performed a rapid stopping task while standing on a force plate. The rapid stopping task was conducted by analyzing center of pressure (COP) on the force plate during a visually guided tracking experiment. To assess the ability to terminate motion, we measured the velocity waveform for the COP, along with the reaction, propulsion, braking, and total movement times. Both the reaction and movement times of the older-adult group were significantly longer than those of the younger-adult group (all, p < 0.05). There was no significant difference between the groups in regard to the initial backward propulsion time; however, in the subsequent sequence of backward braking, forward propulsion, and backward braking, all times were longer in the older-adult group than in the younger-adult group (p < 0.05). Our results show that the series of time delays shown by older adults when initiating and terminating motion is due to not only delayed reactions but also delayed stopping. Furthermore, our findings suggest that older adults have not only a diminished propulsion ability but also a diminished braking ability.
The effects of changes in the anterior-posterior center of pressure (AP-COP) position on the lower limb joint moments during double-leg squatting remain unclear. The purpose of this study was to ...determine the effects of AP-COP positional changes on the hip, knee, and ankle extensor moments during double-leg squatting. Sixteen male participants (22.1 ± 1.5 years) performed double-leg squatting under two conditions (anterior and posterior COP conditions) with visual feedback on their COP positions. Kinematics and kinetics were analyzed using a three-dimensional motion analysis system and force plates. The hip, knee and ankle flexion angles and extensor moments at peak vertical ground reaction force were compared between the two conditions using paired t tests. The COP position was 53.5 ± 2.4% of the foot length, starting from the heel, under the anterior condition and 44.4 ± 2.1% under the posterior condition (
< 0.001). The knee extensor moment was significantly smaller under the anterior than the posterior COP condition (
= 0.003, 95% confidence interval (CI) -0.087 to -0.021 Nm/kg/m), while the ankle extensor moment significantly larger under the anterior COP condition than under the posterior COP condition (
< 0.001, 95% CI 0.113 to 0.147 Nm/kg/m). There was no significant difference in hip extensor moment (
= 0.431). The ankle dorsiflexion angle was significantly larger under the anterior than the posterior COP condition (
= 0.003, 95% CI 0.6 to 2.6°), while there was no difference in trunk, hip, or knee flexion angle. The present results indicate that changes in the AP-COP position mainly affect the ankle and knee extensor moments during double-leg squatting, while the effect on the lower limb joint and trunk flexion angles was limited. Visual feedback on the AP-COP position could be useful for modifying the ankle and knee extensor moments during double-leg squatting.
Plasmaspheric hiss waves play an important role in electron precipitation, leading to the formation of slot region in the Earth's radiation belt. Previous studies indicate that the electron density ...and the background magnetic field strength are responsible for the intensity of whistler‐mode waves and resultant electron precipitation. Nevertheless, no direct evidence of the strong pitch angle scattering of energetic electrons by hiss waves inside the plasmasphere has been obtained due to the small loss cone near the magnetic equator, where the scattering occurs. Furthermore, the density and magnetic field structures have not been investigated simultaneously and on the same magnetic field lines as the hiss wave enhancement and electron precipitation. With high angular resolution data of ∼10–100 keV electron flux obtained by the Medium‐Energy Particle experiments‐electron analyzer onboard the Exploration of energization and Radiation in Geospace satellite, we identified two events of the strong electron precipitation. A detailed examination revealed that the precipitation occurs in association with the amplitude enhancement of hiss waves. Moreover, strong scattering occurs simultaneously with electron density enhancements, while the magnetic field strength hardly correlates with the wave intensity. Our direct observations indicate that the electron density and its spatial structure (gradient) are crucial to electron precipitation. The observations also indicate that strong scattering leading to substantial loss cone filling occurs up to the magnetic latitude of ∼15° for the events.
Key Points
In situ observations directly show that the strong scattering of energetic electrons occurs during plasmaspheric hiss waves enhancement
The hiss wave enhancements and electron precipitation are correlated with electron density increase but not with magnetic field intensity
Density enhancement may be important for the whistler‐mode wave enhancement and resultant electron precipitation
Highlights • We examine the effect of aging on vertical postural control in the upright stance. • Elderly and young groups were compared performing voluntary COP shift tasks. • Postural strategy in ...the elderly: center of mass lowered during backward COP shift. • Influence of aging on vertical postural control is demonstrated.
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