escape rate
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Author(s):  
Jiayin Pan

Abstract Let M be an open n-manifold of nonnegative Ricci curvature and let p ∈ M {p\in M} . We show that if ( M , p ) {(M,p)} has escape rate less than some positive constant ϵ ⁢ ( n ) {\epsilon(n)} , that is, minimal representing geodesic loops of π 1 ⁢ ( M , p ) {\pi_{1}(M,p)} escape from any bounded balls at a small linear rate with respect to their lengths, then π 1 ⁢ ( M , p ) {\pi_{1}(M,p)} is virtually abelian. This generalizes the author’s previous work [J. Pan, On the escape rate of geodesic loops in an open manifold with nonnegative Ricci curvature, Geom. Topol. 25 2021, 2, 1059–1085], where the zero escape rate is considered.


2021 ◽  
Author(s):  
Lei Wang ◽  
Can Huang ◽  
Yasong Ge ◽  
A. M. Du ◽  
Rongsheng Wang ◽  
...  

Abstract How ion escape from the near-Mars space is one of the biggest puzzles for understanding the atmospheric evolution of Mars. Ions in the plasma wake region continuously escape from the unmagnetized planet. Although the average ion escape rate in the wake region is relatively low, observations also have revealed the presence of events that contribute bursty and enhanced ion escape fluxes. Boundary instabilities and magnetic reconnection are suggested to be the candidate mechanisms. However, there is a lack of evaluation of ion escape caused by reconnection and comparison of the two mechanisms under a similar plasma environment. Here, we show an exciting reconnection event in the Martian wake. Two types of flux ropes are observed during the event. One was generated by reconnection, while others were produced by dayside boundary instability and convected to tail. The escape rate of oxygen ions in the reconnection region was estimated to be about 53–72% of the total tailward escape. Furthermore, the escape flux in the flux rope produced by reconnection was over twice that caused by dayside instabilities.


2021 ◽  
Author(s):  
Francisco González-Galindo ◽  
Jean-Yves Chaufray ◽  
Franck Lefèvre ◽  
Franck Montmessin ◽  
Margaux Vals ◽  
...  

<p>The thermal escape of hydrogen from Mars is recognized as one of the major drivers of the long-term climatic evolution of the planet. Recent works have shown that, contrary to what was previously believed, water is not trapped in the lower atmosphere of Mars. Instead, it can be transported to the middle/upper atmosphere, producing layers of supersaturated water (Fedorova et al., 2018, 2021). Upper atmospheric water can then be converted to hydrogen by photolysis or chemical reactions with ions, boosting the rate of hydrogen escape (Chaffin et al., 2017; Stone et al., 2020). Strong seasonal variations in the escape rate, and significant increases of both the water abundance in the mesosphere and the hydrogen escape rate during dust storms, evidence the strong coupling between the hydrogen escape and the water cycle (Chaffin et al., 2014; Fedorova et al., 2018, 2020). A global model able to simulate all the processes related to water, from the ice sublimation to the transport to the upper atmosphere and its atmospheric escape, is needed in order to help interpreting the observations. This model can also be used to explore also the water cycle and hydrogen escape on past Mars conditions characterized by different orbital parameters, allowing for a better estimation of the accumulated escape rate.</p> <p>Previous simulations with the LMD-Mars Global Climate Model (LMD-MGCM), and their comparison with observational results by SPICAM/Mars Express showed that the simulated escape rate was underestimated, in particular during the second half of the Martian year (Chaufray et al., 2021). However, those simulations did not take into account the microphysical processes producing water supersaturation, and thus underestimated the role of water transport in the escape rate. In addition, the model did not include the photochemistry of water-derived ions, which can play an important role in converting water into hydrogen (Stone et al., 2020).</p> <p>New simulations with an improved version of the LMD-MGCM have been produced that overcome those previous limitations. The water cloud microphysics has now been fully considered in the simulations, using the model by Navarro et al. (2014). The photochemical model has been updated to include water-derived ions (H2O+, H3O+, OH+). Also, the deuterium fractionation model has been improved (Rossi et al., 2021), and deuterated species have been included in the photochemical model. While this last modification is not expected to modify the hydrogen escape rate, the inclusion of deuterated species can provide important diagnostics on the hydrogen escape and its accumulation over Mars history.</p> <p>In this presentation we will show the results of the improved version of the LMD-MGCM, comparing with available observations. The focus will be on the predicted hydrogen escape rate, and how it is affected by the inclusion of different physical processes. We find that including the possibility of water supersaturation increases the Hydrogen escape rate in more than one order of magnitude at most seasons, taking the simulated rate to better agreement with SPICAM observations during the second half of the year. This confirms previous observational results indicating the importance of water supersaturation (Fedorova et al. 2020). We also find that the inclusion of water-derived ions in the photochemistry also increases the escape rate, in particular during the first part of the year. We will also compare the predicted water abundance in the mesosphere with Mars Express and ExoMars TGO observations, and the abundances of water-derived ions with NGIMS/MAVEN measurements.</p> <p>References:</p> <p>Chaffin, M. et al., Unexpected variability of Martian hydrogen escape, Geophysical Research Letters, Volume 41, pp. 314-320 (2014)</p> <p>Chaffin, M. et al., Elevated atmospheric escape of atomic hydrogen from Mars induced by high-altitude water, Nature Geoscience, 10, pp. 174-178 (2017)</p> <p>Fedorova, A. et al., Water vapor in the middle atmosphere of Mars during the 2007 global dust storm, Icarus, 300, pp. 440-457 (2018)</p> <p>Fedorova, A. et al., Stormy water on Mars: The distribution and saturation of atmospheric water during the dusty season, Science, 367, pp. 297-300 (2020)</p> <p>Fedorova, A. et al., Multi-Annual Monitoring of the Water Vapor Vertical Distribution on Mars by SPICAM on Mars Express, Journal of Geophysical Research: Planets, 126, e06616 (2021)</p> <p>Navarro, T. et al., Global climate modeling of the Martian water cycle with improved microphysics and radiatively active water ice clouds, Journal of Geophysical Research: Planets, 119, pp. 1479-1495 (2014)</p> <p>Rossi, L. et al., The Effect of the Martian 2018 Global Dust Storm on HDO as Predicted by a Mars Global Climate Model, Geophysical Research Letters, 48, e90962 (2021)</p> <p>Stone, S. et al., Hydrogen escape from Mars is driven by seasonal and dust storm transport of water,Science, 370, pp. 824-831 (2020)</p>


Author(s):  
Yanjun Zhou ◽  
Cangtao Yin

Tunneling corrections on Kramers escape rates with power-law distribution in three damping systems are obtained separately based on flux over population theory by introducing the tunneling correction into flux. Two common barriers (Eckart barrier and parabolic barrier) are used to calculate tunneling corrections. We take the relevant parameters from the [Formula: see text] reaction to further study how the tunneling correction affects the escape rates in three damping cases. It shows that the tunneling correction has great impact on escape rate in low damping and overdamped systems, but has little impact in low-to-intermediate damping (LID) system. Heretofore, we extend our previous work to a wider range of application areas.


2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Youssef Chahid ◽  
Nienke M. G. Rorije ◽  
Soufian el Boujoufi ◽  
Ron A. A. Mathôt ◽  
Liffert Vogt ◽  
...  

Abstract Background Increased vascular permeability is an early sign of vascular damage and can be measured with the transcapillary escape rate of albumin (TERalb). Although TERalb has a multi-exponential kinetic model, most published TERalb data are based on mono-exponential kinetic models with variation in blood sampling schemes. Aim of this posthoc study was to evaluate the influence of variation in blood sampling schemes and the impact of mono- or bi-exponential analyses on the calculation of TERalb. Study participants were part of a cross-over intervention study protocol, investigating effects of sodium loading on blood pressure, endothelial surface layer and microcirculation. Multiple blood samples were drawn between 3 and 60 min after injection of radioactive iodide labeled human serum albumin (rHSA). Results In total 27 male participants with 54 measurements were included. For all participants the maximum serum radioactivity was reached within 20 min, while 85% of the participants had their maximum serum activity within 10 min. The TERalb calculated with the subsequently chosen T20–60 min reference scheme (6.19 ± 0.49%/h) was significantly lower compared to the TERalb of the T3–60 min, T5–60 min, and Tmax – 60 min schemes. There was no significant difference between the T20–60 min reference scheme and the T10–60 min and T15–60 min schemes. Bi-exponential kinetic modeling did not result in significant different observations compared to the mono-exponential kinetic analysis. Conclusions As there is variation in the timing of the maximum serum radioactivity of rHSA, blood sampling schemes starting before 10 min after administration of rHSA will result in a significant overestimation of TERalb. In addition, variation in kinetic modeling did not result in significant changes in TERalb. Therefore, we emphasize the need to standardize TERalb and for practical and logistical reasons advocate the use of a mono-exponential model with blood sampling starting 20 min after rHSA administration.


2021 ◽  
Author(s):  
Youssef Chahid ◽  
Nienke Rorije ◽  
Soufian el Boujoufi ◽  
Ron Mathôt ◽  
Liffert Vogt ◽  
...  

Abstract Background Increased vascular permeability is an early sign of vascular damage and can be measured with the transcapillary escape rate of albumin (TERalb). Although TERalb has a multi-exponential kinetic model, most published TERalb data are based on mono-exponential kinetic models with variation in blood sampling schemes. Aim of this posthoc study was to evaluate the influence of variation in blood sampling schemes and the impact of mono- or bi-exponential analyses on the calculation of TERalb. Study participants were part of a cross-over intervention study protocol, investigating effects of sodium loading on blood pressure, endothelial surface layer and microcirculation. Multiple blood samples were drawn between 3 and 60 minutes after injection of radioactive iodide labeled human serum albumin (rHSA). Results In total 27 male participants with 54 measurements were included. For all participants the maximum serum radioactivity was reached within 20 minutes, while 85% of the participants had their maximum serum activity within 10 min. The TERalb calculated with the subsequently chosen T20 – 60 min reference scheme (6.19 ± 0.49%/h) was significantly lower compared to the TERalb of the T3 – 60 min, T5 – 60 min, and Tmax – 60 min schemes. There was no significant difference between the T20 – 60 min reference scheme and the T10 – 60 min and T15 – 60 min schemes. Bi-exponential kinetic modeling did not result in significant different observations compared to the mono-exponential kinetic analysis.Conclusions As there is variation in the timing of the maximum serum radioactivity of rHSA, blood sampling schemes starting before 10 minutes after administration of rHSA will result in a significant overestimation of TERalb. In addition, variation in kinetic modeling did not result in significant changes in TERalb. Therefore, we emphasize the need to standardize TERalb and for practical and logistical reasons advocate the use of a mono-exponential model with blood sampling starting 20 minutes after rHSA administration.


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