The Magnetospheric Multiscale spacecraft encountered an electron diffusion region (EDR) in a symmetric reconnection in the Earth's magnetotail. The EDR contained a guide field of about 2 nT, which ...was 13% of the magnetic field in the inflow region, and its thickness was about 2 local electron inertial lengths. Intense energy dissipation, a super-Alfvénic electron jet, electron nongyrotropy, and crescent-shaped electron velocity distributions were observed in association with this EDR. These features are similar to those of the EDRs in asymmetric reconnection at the dayside magnetopause. Electrons gained about 50% of their energy from the immediate upstream to the EDR. Crescent electron distributions were seen at the boundary of the EDR, while highly curved magnetic field lines inside the EDR may have gyrotropized the electrons. The EDR was characterized by a parallel current that was carried by antiparallel drifting electrons that were probably accelerated by a parallel electric field along the guide field. These results reveal the essential electron physics of the EDR and provide a significant example of an EDR in symmetric reconnection with a weak guide field.
We report on the observations of an electron vortex magnetic hole corresponding to a new type of coherent structure in the turbulent magnetosheath plasma using the Magnetospheric Multiscale mission ...data. The magnetic hole is characterized by a magnetic depression, a density peak, a total electron temperature increase (with a parallel temperature decrease but a perpendicular temperature increase), and strong currents carried by the electrons. The current has a dip in the core region and a peak in the outer region of the magnetic hole. The estimated size of the magnetic hole is about 0.23 i (∼30 e) in the quasi-circular cross-section perpendicular to its axis, where i and e are respectively the proton and electron gyroradius. There are no clear enhancements seen in high-energy electron fluxes. However, there is an enhancement in the perpendicular electron fluxes at 90° pitch angle inside the magnetic hole, implying that the electrons are trapped within it. The variations of the electron velocity components Vem and Ven suggest that an electron vortex is formed by trapping electrons inside the magnetic hole in the cross-section in the M-N plane. These observations demonstrate the existence of a new type of coherent structures behaving as an electron vortex magnetic hole in turbulent space plasmas as predicted by recent kinetic simulations.
Transport of high-current relativistic electron beams in dense plasmas is of interest in many areas of research. However, so far the mechanism of such beam-plasma interaction is still not well ...understood due to the appearance of small time- and space-scale effects. Here we identify a new regime of electron beam transport in solid-density plasma, where kinetic effects that develop on small time and space scales play a dominant role. Our three-dimensional particle-in-cell simulations show that in this regime the electron beam can evolve into layered short microelectron bunches when collisions are relatively weak. The phenomenon is attributed to a secondary instability, on the space- and timescales of the electron skin depth (tens of nanometers) and few femtoseconds of strong electrostatic modulation of the microelectron current filaments formed by Weibel-like instability of the original electron beam. Analytical analysis on the amplitude, scale length, and excitation condition of the self-generated electrostatic fields is clearly validated by the simulations.
To describe the experience of endovascular treatment (EVT) of acute ischaemic stroke caused by isolated internal carotid artery (ICA) occlusion, with emphasis on treatment strategies, outcomes, and ...prognostic factors.
A retrospective examination was performed of 66 consecutive patients with acute moderate-to-severe stroke who underwent EVT for isolated ICA occlusion from July 2016 to June 2021. The modified thrombolysis in cerebral ischaemia (mTICI) score was used to evaluate reperfusion outcomes. A multivariate analysis was performed to identify risk factors associated with poor 90-day outcome (modified Rankin Scale mRS 3–6).
The National Institutes of Health Stroke Scale (NIHSS) median score of the 66 patients at admission was 15. Twelve patients (18.2%) showed thrombus migration to the M1 segment or proximal M2 during EVT and underwent additional intracranial thrombectomy. Successful reperfusion (mTICI 2b–3) was achieved in 60 patients (90.9%) and complete reperfusion (mTICI 3) in 42 (63.6%). A poor functional outcome was seen in 27 patients (40.9%). The rate of 90-day mortality was 9.1% (6/66). Higher NIHSS scores and a lower Alberta Stroke Program Early CT Score (ASPECTS) were independently associated with poor outcomes. Complete reperfusion was the only treatment factor with a significant predictive value (adjusted odds ratio OR 0.03; 95% CI = 0.01 to 0.25; p=0.001).
Endovascular therapy is safe and effective in patients with acute ischaemic stroke due to isolated ICA occlusion. Prevention of thrombus migration and complete reperfusion should be the aim of EVT.
•Thrombus migration is common during thrombectomy for isolated ICA occlusion.•Complete reperfusion should be the aim of thrombectomy for isolated ICA occlusion.•Addition of data helps guide treatment for isolated ICA occlusion.
Well-coated single-walled carbon nanotube (SWNT) with polyaniline (PANI) composite electrodes with good uniformity for electrochemical capacitors are prepared by the polymerization of aniline ...containing well-dissolved SWNTs. The capacitance properties are investigated with cyclic voltammetry, charge–discharge tests and ac impedance spectroscopy. The composite electrode shows much higher specific capacitance, better power characteristics and is more promising for application in capacitor than pure PANI electrode. The effect and role of SWNT in the composite electrode are also discussed in detail.
Secondary flux ropes are suggested to play important roles in energy dissipation and particle acceleration during magnetic reconnection. However, their generation mechanism is not fully understood. ...In this Letter, we present the first direct evidence that a secondary flux rope was generated due to the evolution of an electron vortex, which was driven by the electron Kelvin-Helmholtz instability in an ion diffusion region as observed by the Magnetospheric Multiscale mission. The subion scale (less than the ion inertial length) flux rope was embedded within the electron vortex, which contained a secondary electron diffusion region at the trailing edge of the flux rope. We propose that intense electron shear flow produced by reconnection generated the electron Kelvin-Helmholtz vortex, which induced a secondary reconnection in the exhaust of the primary X line and then led to the formation of the flux rope. This result strongly suggests that secondary electron Kelvin-Helmholtz instability is important for reconnection dynamics.
Abstract The spatiotemporal optical vortex (STOV) laser pulse, characterized by containing a space-time dependent spiral phase structure and intrinsic transverse orbital angular momentum (OAM), has ...been of much recent research interest for basic physics as well as potential applications in optical communication and manipulation, as well as the attosecond sciences. Here we consider electron acceleration and generation of attosecond hard x-rays by irradiating a thin foil with intense STOV laser pulse. It is found that the affected foil electrons can be trapped and acquire transverse OAM, or synchrotron-like motion, from the STOV, as well as accelerated forward by the transverse and enhanced axial laser electric fields to form a tiny energetic bunch at the front of the laser pulse and emit short ( ∼ 400 attosecond) high-flux ( > 10 9 photons per pulse) hard (100–1000 keV) x rays.
Energetic electrons have frequently been observed in small‐scale flux ropes. However, whether these energetic electrons were energized directly within the flux rope or not is unknown. In this paper, ...we present concrete evidence provided by the Magnetospheric Multiscale mission that a secondary flux rope provided strong acceleration for electrons expelled by the reconnection X line. We find that the energetic electron fluxes inside the ion‐scale flux rope were larger than those outside the flux rope. Electrons were adiabatically accelerated by betatron and Fermi mechanisms inside the flux rope. The highest energy electrons (>100 keV) were produced by betatron acceleration, whereas Fermi acceleration was unable to accelerate the electrons to high energy probably due to the finite distance of the acceleration region along the field‐aligned direction. These results confirm the essential role of ion‐scale flux ropes in producing energetic electrons.
Key Points
First quantitative evidence for adiabatic electron acceleration within ion‐scale flux rope
The most energetic electrons were produced by betatron acceleration inside the flux rope
This paper proposes a dynamic programming model to explore the optimal stockpiling path for China's strategic petroleum reserve before 2020. The optimal oil acquisition sizes in 2008–2020 under ...different scenarios are estimated. The effects of oil price, risks and elasticity value on inventory size are further investigated. It is found that the optimal stockpile acquisition strategies are mainly determined by oil price and total inventory costs. While oil supply disruption is not considered, China's optimal stockpile acquisition rate increases from 19.2 to 52million barrels from 2008 to 2020. If an oil supply disruption occurs, the oil acquisition rate will be reduced significantly. However, it may not be a good strategy to interrupt oil reserve activities in order to minimize the total costs for the entire planning period.
► A dynamic programming model for explore the optimal path of China's strategic petroleum reserve till 2020. ► China's optimal acquisition sizes increase from 19.2 to 52million barrels. ► Sensitivity analysis of optimal stockpile size under different disruption conditions and elasticity values.
Contamination of drinking water by per- and polyfluoroalkyl substances (PFASs) emitted from manufacturing plants, fire-fighting foams, and urban waste streams has received considerable attention due ...to concerns over toxicity and environmental persistence; however, PFASs in ambient air remain poorly understood, especially in the United States (US). We measured PFAS concentrations in ambient fine particulate matter (PM
2.5
) at 5 locations across North Carolina over a 1 year period in 2019. Thirty-four PFASs, including perfluoroalkyl carboxylic, perfluoroalkane sulfonic, perfluoroalkyl ether carboxylic and sulfonic acids were analyzed by UHPLC/ESI-MS/MS. Quarterly averaged concentrations ranged from <0.004-14.1 pg m
−3
. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) ranged from <0.18 to 14.1 pg m
−3
, comparable to previous PM
2.5
measurements from Canada and Europe (<0.02-3.5 pg m
−3
). Concentrations above 1 pg m
−3
were observed in July-September at Charlotte (14.1 pg m
−3
, PFOA), Wilmington (4.75 pg m
−3
, PFOS), and Research Triangle Park (1.37 pg m
−3
, PFOS). Notably, PM
2.5
has a short atmospheric lifetime (<2 weeks), and thus, the presence of PFOS in these samples raises questions about their sources, since PFOS production was phased out in the US ∼20 years ago. This is the first US study to provide insights into ambient PFAS concentrations in PM
2.5
.
Quarterly PFOS concentrations (pg m
−3
) in ambient PM
2.5
in North Carolina, US. Highest concentrations were measured during July-September.
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