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Using data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, we explore the plasma properties of Martian magnetotail current sheets (CS), to further understand the solar wind interaction with Mars and ion escape. There are some CS exhibit energetic oxygen ions that show narrow beam structures in the energy spectrum, which primarily occurs in the hemisphere where the solar wind electric field (Esw) is directed away from the planet. On average, these CS have a higher escaping flux than that of the CS without energetic oxygen ion beams, suggesting different roles in ion escape. The CS with energetic oxygen ion beams exhibits different proton and electron properties to the CS without energetic oxygen ion beams, indicating their different origins. Our analysis suggests that the CS with energetic oxygen ion beams may result from the interaction between the penetrated solar wind and localized oxygen ion plumes. Plain Language Summary: Ion escape into space, driven by solar wind interactions with Mars, plays a pivotal role in the evolution of the Martian atmosphere. An important escape channel of planetary oxygen ions is the current sheet in the nightside magnetotail. Yet, our existing understanding of plasma characteristics within this magnetic structure remains quite limited. Based on the MAVEN observations, we find the current sheets can be categorized into two distinct types according to the energy distribution patterns of oxygen ions: one is with the appearance of energetic oxygen ions with narrow beam structure, the other one is not. On average, the current sheets with energetic oxygen ion beams have a higher escaping flux than those without, suggesting different roles in ion escape. Furthermore, the two types of current sheets exhibit markedly distinct plasma properties, indicating that they have different origins. Here we suggest that the current sheet with energetic oxygen ion beams arise from the interaction between the penetrated solar wind and localized oxygen ion plumes. Key Points: Martian magnetotail current sheets occasionally exhibit energetic oxygen ions that show beam structures in the energy spectrumThe current sheets with energetic oxygen ion beam usually have a higher escaping flux than those withoutPlasma properties in current sheets differ significantly differences between those with and without energetic oxygen ion beams [ABSTRACT FROM AUTHOR]

Abstract Using data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, we explore the plasma properties of Martian magnetotail current sheets (CS), to further understand the solar wind interaction with Mars and ion escape. There are some CS exhibit energetic oxygen ions that show narrow beam structures in the energy spectrum, which primarily occurs in the hemisphere where the solar wind electric field (Esw) is directed away from the planet. On average, these CS have a higher escaping flux than that of the CS without energetic oxygen ion beams, suggesting different roles in ion escape. The CS with energetic oxygen ion beams exhibits different proton and electron properties to the CS without energetic oxygen ion beams, indicating their different origins. Our analysis suggests that the CS with energetic oxygen ion beams may result from the interaction between the penetrated solar wind and localized oxygen ion plumes.

Large-scale inverted-V channels of upflowing oxygen ions are frequently identified in data collected by Cluster, at all local times, near the open-closed field line boundary over Earth’s high-latitude ionosphere-occur with downward propagating MHD Alfvén waves which have cascaded into kinetic regimes of plasma. The transverse acceleration of the oxygen ions in the center of these structures is interpreted as the integrated energization by these waves along the channels. Also observed within the channels are upward parallel electric fields, a key characteristic of kinetic Alfvén waves, which may contribute not only to lifting the ions but also to precipitating aurora electrons that might initiate ion upflow in the ionosphere below. Statistics on five-year observations of Cluster show that the channels typically form during geomagnetic perturbations, particularly when solar-wind dynamic pressure is high or highly fluctuated. Near the open-closed field line boundary, the stronger the wave power, the higher the upward oxygen flux and the higher the beam energy, indicating that these waves provide a simple but efficient way to drive oxygen upflows.

Atmospheric oxygen is produced and consumed by life on Earth, and the ozone layer protects life on Earth from harmful solar UV radiation. The research on oxygen in the Earth system is of interest to many different geoscientific communities, from paleoclimatology to aeronomy. I provide a brief overview of the research activities and their motivations. In situ measurements and remote sensing of atmospheric oxygen are described. The global evolution, distribution, and trends of atmospheric oxygen are discussed.

The terrestrial ring current, flowing near the equator at the altitude of 2 RE～7 RE, is one of the most significant electric current systems of the Earth's magnetosphere. Energetic ions (~1 keV to hundreds of keV), such as protons and oxygen ions, are thought to be the main carriers of the ring current. The enhancement of ring current during geomagnetic storms is widely regarded as the main reason for the geomagnetic field disturbance. After the storm main phase, it usually takes several days (i.e., storm recovery phase) for the ring current to return to the original level of quiet times. In this paper, we present some recent studies concerning the relative contributions of different particle species, especially oxygen ions, to the ring current and the loss mechanism of the ring current during the magnetic storm recovery phase. Partial pressures of different species increase significantly at high auroral electrojet levels with hydrogen pressure being dominant inside the plasmasphere. The pressures of the heavy ions and electrons increase outside the plasmapause and develop a strong dawn-dusk asymmetry with ion pressures peaking at dusk and electron pressures peaking at dawn. In addition, ring current hydrogen with energies ranging from 50 keV up to several hundred keV is the dominant component of plasma pressure during both quiet and active times, while helium contribution is generally small. Oxygen with 10 keV < E < 50 keV and electrons with 0.1 keV < E < 40 keV become increasingly important during active times contributing more than 25% and 20% on the nightside, respectively. O+ ions' contribution to ring current is strongly connected geomagnetic activity. During large storms when sym-H0.8) and occasionally even larger than 1 when L < 3. Compared with the situation without much O+ ions contributing to the ring current, the O+ pressure and total plasma pressure are much larger when O+ ions are involved and the pressure peak moves to low L shells as sym-H decreases. Besides, the probability without much O+ is zero at most L shells when sym-H is less than −60 nT. These observational features suggest that O+ ions play an important role in the ring current during geomagnetic active times and no storm events exist without O+ ions being present. On the other hand, during relatively quiet conditions, the higher the probability, the lower of the value R. The strong correlation indicates that O+ ions are always absent during quiet times. During storm recovery phase, the observed lifetimes of H+ and O+ ions in general increase with L shell and the lifetimes of H+ ions are shorter than that of O+ ions when E < ~50 keV while the situation is reversed when E > ~50 keV, which is consistent with theory prediction. Furthermore, the observed lifetimes are in general consistent with model predictions of charge exchange lifetime, which confirms that charge exchange is a dominant loss mechanism of ring current ions during storm recovery phase.

The influence of high-linear energy transfer (LET) particle radiation on the functionalities of mesenchymal stromal cells (MSCs) is largely unknown. Here, we analyzed the effects of proton (1H), helium (4He), carbon (12C) and oxygen (16O) ions on human bone marrow-MSCs. Cell cycle distribution and apoptosis induction were examined by flow cytometry, and DNA damage was quantified using γH2AX immunofluorescence and Western blots. Relative biological effectiveness values of MSCs amounted to 1.0-1.1 for 1H, 1.7-2.3 for 4He, 2.9-3.4 for 12C and 2.6-3.3 for 16O. Particle radiation did not alter the MSCs' characteristic surface marker pattern, and MSCs maintained their multi-lineage differentiation capabilities. Apoptosis rates ranged low for all radiation modalities. At 24 h after irradiation, particle radiation-induced ATM and CHK2 phosphorylation as well as γH2AX foci numbers returned to baseline levels. The resistance of human MSCs to high-LET irradiation suggests that MSCs remain functional after exposure to moderate doses of particle radiation as seen in normal tissues after particle radiotherapy or during manned space flights. In the future, in vivo models focusing on long-term consequences of particle irradiation on the bone marrow niche and MSCs are needed. [ABSTRACT FROM AUTHOR]

Objective. To study the secondary neutrons generated by primary oxygen beams for cancer treatment and compare the results to those from primary protons, helium, and carbon ions. This information can provide useful insight into the positioning of neutron detectors in phantom for future experimental dose assessments. Approach. Mono-energetic oxygen beams and spread-out Bragg peaks were simulated using the Monte Carlo particle transport codes FLUktuierende KAskade , tool for particle simulation, and Monte Carlo N-Particle, with energies within the therapeutic range. The energy and angular distribution of the secondary neutrons were quantified. Main results. The secondary neutron spectra generated by primary oxygen beams present the same qualitative trend as for other primary ions. The energy distributions resemble continuous spectra with one peak in the thermal/epithermal region, and one other peak in the fast/relativistic region, with the most probable energy ranging from 94 up to 277 MeV and maximum energies exceeding 500 MeV. The angular distribution of the secondary neutrons is mainly downstream-directed for the fast/relativistic energies, whereas the thermal/epithermal neutrons present a more isotropic propagation. When comparing the four different primary ions, there is a significant increase in the most probable energy as well as the number of secondary neutrons per primary particle when increasing the mass of the primaries. Significance. Most previous studies have only presented results of secondary neutrons generated by primary proton beams. In this work, secondary neutrons generated by primary oxygen beams are presented, and the obtained energy and angular spectra are added as supplementary material. Furthermore, a comparison of the secondary neutron generation by the different primary ions is given, which can be used as the starting point for future studies on treatment plan comparison and secondary neutron dose optimisation. The distal penumbra after the maximum dose deposition appears to be a suitable location for in-phantom dose assessments., (© 2024 Institute of Physics and Engineering in Medicine.)

Purpose: Astronauts on missions beyond low Earth orbit will be exposed to galactic cosmic radiation, and there is concern about potential adverse cardiovascular effects. Most of the research to identify cardiovascular risk of space radiation has been performed in rodent models. To aid in the translation of research results to humans, the current study identified long-term effects of high-energy charged particle irradiation on cardiovascular function and structure in a larger non-rodent animal model., Materials and Methods: At the age of 12 months, male New Zealand white rabbits were exposed to whole-body protons (250 MeV) or oxygen ions ( 16 O, 600 MeV/n) at a dose of 0 or 0.5 Gy and were followed for 12 months after irradiation. Ultrasonography was used to measure in vivo cardiac function and blood flow parameters at 10- and 12-months post-irradiation. At 12 months after irradiation, blood cell counts and blood chemistry values were assessed, and cardiac tissue and aorta were collected for histological as well as molecular and biochemical analyses. Plasma was used for metabolomic analysis and to quantify common markers of cardiac injury., Results: A small but significant decrease in the percentage of circulating lymphocytes and an increase in neutrophil percentage was seen 12 months after 0.5 Gy protons, while 16 O exposure resulted in an increase in monocyte percentage. Markers of cardiac injury, cardiac troponin I (cTnI) and N-Terminal pro-B-type Natriuretic Peptide were modestly increased in the proton group, and cTnI was also increased after 16 O. On the other hand, metabolomics on plasma at 12 months revealed no changes. Both types of irradiation demonstrated alterations in cardiac mitochondrial morphology and an increase in left ventricular protein levels of inflammatory cell marker CD68. However, changes in cardiac function were only mild., Conclusion: Low dose charged particle irradiation caused mild long-term changes in inflammatory markers, cardiac function, and structure in the rabbit heart, in line with previous studies in mouse and rat models., Competing Interests: Declaration of Competing Interest The authors report no conflicts of interest., (Copyright © 2023 The Committee on Space Research (COSPAR). Published by Elsevier B.V. All rights reserved.)

A Ti/VO x /ITO memristor prepared at room temperature presents low switching voltages (set/reset voltages ~ −6 mV/190 mV) as well as good resistive switching characteristics including acceptable ON/OFF ratio (~ 10) and long data retention (>104 s). Such ultralow switching voltages mainly result from appropriate interface engineering combined with rational material design. Due to Ti's high oxygen-gettering capability, its contact with VO x leads to formation of a TiO x interlayer with numerous oxygen vacancies (V O 2+) near the interface even at room temperature. This interfacial V O 2+ facilitates oxygen ions (O2-) migration by enlarging the available free space and weakening the local oxygen-cation bonds, thus resulting in the low switching voltages. Moreover, the graded O2- distribution in the TiO x interlayer induces a built-in electric field (E built-in), which has the same direction to the external electric field generated by the set voltage. This E built-in accelerates the O2- migration and thus leads to the ultralow set voltage. The resistive switching mechanism is revealed to be based on formation and collapse of the Schottky barrier caused by the O2- drift in the TiO x interlayer. The Boolean logic functions including 'NOT', 'AND', 'OR', 'NAND' and 'NOR' are demoed by using a single memristor, showing a great potential for in-memory computing. • The memristor with a Ti/VOx/ITO configuration presents an ultralow set voltage (−6 mV) and a low reset voltage (190 mV). • The resistive switching mechanism is revealed to be mainly based on formation and collapse of the Schottky barrier. • The Boolean logic functions are demoed by using a single memristor, showing a great potential for in-memory computing. [ABSTRACT FROM AUTHOR]