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Hypervelocity impacts play a significant role in the evolution of asteroids, causing material to be ejected and partially reaccreted. However, the dynamics and evolution of ejected material in a binary asteroid system have never been observed directly. Observations of Double Asteroid Redirection Test (DART) impact on asteroid Dimorphos have revealed features on a scale of thousands of kilometers, including curved ejecta streams and a tail bifurcation originating from the Didymos system. Here we show that these features result naturally from the dynamical interaction of the ejecta with the binary system and solar radiation pressure. These mechanisms may be used to constrain the orbit of a secondary body, or to investigate the binary nature of an asteroid. Also, they may reveal breakup or fission events in active asteroids, and help determine the asteroid’s properties following an impact event. In the case of DART, our findings suggest that Dimorphos is a very weak, rubble-pile asteroid, with an ejecta mass estimated to be in the range of (1.1-5.5)×10 7  kg. Double Asteroid Redirection Test (DART) mission’s impact on asteroid Dimorphos has led to various impact related features. Here, the authors show that those features result naturally from the dynamical interaction of the ejecta with the binary system and solar radiation pressure.

Kinetic deflection is a planetary defense technique delivering spacecraft momentum to a small body to deviate its course from Earth. The deflection efficiency depends on the impactor and target. Among them, the contribution of global curvature was poorly understood. The ejecta plume created by NASA’s Double Asteroid Redirection Test impact on its target asteroid, Dimorphos, exhibited an elliptical shape almost aligned along its north-south direction. Here, we identify that this elliptical ejecta plume resulted from the target’s curvature, reducing the momentum transfer to 44 ± 10% along the orbit track compared to an equivalent impact on a flat target. We also find lower kinetic deflection of impacts on smaller near-Earth objects due to higher curvature. A solution to mitigate low deflection efficiency is to apply multiple low-energy impactors rather than a single high-energy impactor. Rapid reconnaissance to acquire a target’s properties before deflection enables determining the proper locations and timing of impacts. Double Asteroid Redirection Test (DART) mission impact on asteroid Dimophos resulted in an elliptical ejecta plume. Here, the authors show that this elliptical ejecta is due to the curvature of the asteroid and makes kinetic momentum transfer less efficient.

In this work, we investigate trajectories that require thrust to maintain periodic structure in the circular restricted three-body problem (CR3BP). We produce bounds in position and velocity space for the energy-constrained reachable set of initial conditions. Our trajectories are energy-optimal and analyzed via linear analysis. We provide validation for our technique and analyze the cost of deviating in various directions to the reference. For our given reference, we find that it is relatively expensive to decrease perilune distance for orbits in the Earth-Moon system.

With the successful impact of the NASA DART spacecraft in the Didymos-Dimorphos binary asteroid system, we provide an initial analysis of the post-impact perturbed binary asteroid dynamics. To compare our simulation results with observations, we introduce a set of \"observable elements\" calculated using only the physical separation of the binary asteroid, rather than traditional Keplerian elements. Using numerical methods that treat the fully spin-orbit-coupled dynamics, we estimate the system's mass and the impact-induced changes in orbital velocity, semimajor axis, and eccentricity. We find that the changes to the mutual orbit depend strongly on the separation distance between Didymos and Dimorphos at the time of impact. If Dimorphos enters a tumbling state after the impact, this may be observable through changes in the system's eccentricity and orbit period. We also find that any DART-induced reshaping of Dimorphos would generally reduce the required change in orbital velocity to achieve the measured post-impact orbit period and will be assessed by the ESA Hera mission in 2027.

Background Medical and lifestyle management are crucial for Alzheimer's disease (AD). Cerebral blood flow (CBF), vital for brain health, is reduced in AD, and influenced by modifiable risk factors. Method The PREVENTION study is an ongoing randomized clinical trial (McEwen, 2021). Forty‐eight participants with biomarker evidence of amyloidosis had completed the study at the time of the analysis (Table 1). The control arm received recommendations and medical management for a year; the active arm additionally received coaching, exercise training, and supplementation. We examined the effects of the 1) the intervention and 2) adherence on diabetic risk (QUICKI) and post‐trial CBF measured using ASL MRI. Adherence was measured using the clinician rating scale (CRS), which uses a scale of 1‐7 (Kemp, 1998). We hypothesized that those in 1) the active arm and 2) with higher intervention adherence would have improved post‐trial QUICKI and CBF, particularly in regions previously shown to be influenced by physical activity, insulin sensitivity, and cardiovascular risk and relevant to AD (Hoscheidt, 2017; Kapasouri, 2022; Hafdi, 2022; Moore, 2015; Yang, 2023; Chen, 2011). Absolute CBF was estimated using MRI‐Cloud. Post‐trial CBF was analyzed using a linear model, accounting for baseline CBF, adherence, age, and education. Adherence was treated as a continuous measure. Change in QUICKI was analyzed using mixed effects general linear models, including treatment group, adherence, time, and the interactions between time and treatment group and time and adherence as independent variables, controlling for age. Adherence was a categorical measure, based on a cutoff score ≤ 4 (occasional reluctance) (Kemp, 1996). Result Treatment arms did not differ in any demographic measures at baseline or CRS. The active arm (n = 18) showed significantly greater post‐trial CBF in regions related to cardiovascular, diabetic, and AD risk, compared to control (n = 20) (Figure 1; Table 2). Higher adherence scores were associated with greater improvement in regional CBF (Figure 2) and QUICKI F(1,55) = 6.19, p = 0.02). Conclusion In this small sample, we found evidence that a multi‐domain intervention focused on medical management, exercise, and a carbohydrate‐restricted diet improved diabetic risk and CBF in patients with AD.

Medical and lifestyle management are crucial for Alzheimer's disease (AD). Cerebral blood flow (CBF), vital for brain health, is reduced in AD, and influenced by modifiable risk factors. The PREVENTION study is an ongoing randomized clinical trial (McEwen, 2021). Forty-eight participants with biomarker evidence of amyloidosis had completed the study at the time of the analysis (Table 1). The control arm received recommendations and medical management for a year; the active arm additionally received coaching, exercise training, and supplementation. We examined the effects of the 1) the intervention and 2) adherence on diabetic risk (QUICKI) and post-trial CBF measured using ASL MRI. Adherence was measured using the clinician rating scale (CRS), which uses a scale of 1-7 (Kemp, 1998). We hypothesized that those in 1) the active arm and 2) with higher intervention adherence would have improved post-trial QUICKI and CBF, particularly in regions previously shown to be influenced by physical activity, insulin sensitivity, and cardiovascular risk and relevant to AD (Hoscheidt, 2017; Kapasouri, 2022; Hafdi, 2022; Moore, 2015; Yang, 2023; Chen, 2011). Absolute CBF was estimated using MRI-Cloud. Post-trial CBF was analyzed using a linear model, accounting for baseline CBF, adherence, age, and education. Adherence was treated as a continuous measure. Change in QUICKI was analyzed using mixed effects general linear models, including treatment group, adherence, time, and the interactions between time and treatment group and time and adherence as independent variables, controlling for age. Adherence was a categorical measure, based on a cutoff score ≤ 4 (occasional reluctance) (Kemp, 1996). Treatment arms did not differ in any demographic measures at baseline or CRS. The active arm (n = 18) showed significantly greater post-trial CBF in regions related to cardiovascular, diabetic, and AD risk, compared to control (n = 20) (Figure 1; Table 2). Higher adherence scores were associated with greater improvement in regional CBF (Figure 2) and QUICKI F(1,55) = 6.19, p = 0.02). In this small sample, we found evidence that a multi-domain intervention focused on medical management, exercise, and a carbohydrate-restricted diet improved diabetic risk and CBF in patients with AD.