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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]

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]

Recent observations and particle‐tracing models have revealed a counterintuitive difference between the behaviors of magnetospheric protons and oxygen ions when they encounter the magnetopause. The oxygen ions usually meander around the magnetopause without a full escape to the magnetosheath, whereas the protons can more easily stream across the magnetopause despite their smaller gyroradii. Here, we analytically identify the mechanisms that cause this species dependence. As magnetospheric ions drift toward the magnetopause, the grazing angle of their magnetopause encounter is constrained within a narrow range near 0°, with its maximum being proportional to the square root of the ion gyroradius. It is the grazing angle that largely determines the follow‐up ion motion. The ions with larger grazing angles would meander around the magnetopause, whereas the meandering motion for ions with smaller grazing angles could be easily disrupted to enable their escape even if the normal magnetic field is very weak. Plain Language Summary: The Earth's magnetic field is constrained by the interplanetary field within a finite region named the magnetosphere. The boundary of this region, the magnetopause, separates the magnetospheric plasma from the cooler and denser population in the shocked solar wind. Some of the magnetospheric particles, however, can still penetrate the magnetopause and escape into the interplanetary space. One may expect that heavy ions, like singly charged oxygen ions, are more likely to escape than protons due to their larger gyroradii; however, the opposite trend has been identified in spacecraft observations. This counterintuitive feature, although reproduced in a particle‐tracing model, has not yet been fully understood. Here, we analyze the particle trajectories to identify the mechanism underlying the species dependence of the ion escape. When magnetospheric ions encounter the magnetopause, their grazing angles are constrained within a narrow range near 0°, with the maximum angle depending positively on ion gyroradius. We find that the ions with larger grazing angles would meander around the magnetopause without a full escape, whereas the meandering motion for those with smaller angles could be more easily disrupted by a weak normal magnetic field to enable their field‐aligned escape. Key Points: Despite their smaller gyroradii, protons are found more likely to escape from the magnetosphere than oxygen ionsA mechanism leading to the counterintuitive species dependence is analytically identified based on a simple modelThe model also explains the bifurcated gyrophase bunching of the oxygen ions observed in the magnetosheath [ABSTRACT FROM AUTHOR]

The present study reports a gas‐phase photoelectrochemical (GPEC) system in which photoanode and photocathode materials are coated on each side with a pellet of the oxygen‐ion conductor yttria‐stabilized zirconia (YSZ), where light irradiation is feasible on both sides. As a model gas‐phase reaction, we chose dry reforming of methane (DRM), which converts greenhouse gases into valuable syngas. Consequently, the stoichiometric DRM reaction proceeded in our GPEC system, indicating that the oxygen ions in a YSZ pellet act as mediators to link the redox reactions. It was also noted that UV light irradiation on the anodic side was more effective than that on the cathodic side, suggesting that the photogenerated holes in the anodic YSZ side activate methane molecules, while photogenerated electrons are injected into Rh nanoparticles to cause carbon dioxide reduction in the cathodic side. Our GPEC system converts greenhouse gases into valuable syngas by light irradiation. [ABSTRACT FROM AUTHOR]

The D‐shaped ion velocity distribution generated by the time‐of‐flight (ToF) effect can be considered as an important characteristic of reconnection exhausts in the magnetopause and magnetotail reconnection processes. In this study, we reported the D‐shaped velocity distribution of O+ ions produced by the ToF effect in the magnetotail reconnection exhaust based on the observations from the Cluster spacecraft. The observed cutoff velocity of O+ ions is smaller than that of H+ ions at the same time, which is different from the previous theoretical prediction. We suggested that the difference between the two cutoff velocities is probably due to O+ ions having a larger reconnection diffusion region than H+ ions. We also demonstrated a remote‐sensing method to estimate the spatial scale ratio between the O+ and H+ diffusion regions and the distance from the observation site to the center of the magnetotail reconnection region. Plain Language Summary: The reconnection processes at the Earth's magnetopause and magnetotail can convert the magnetic energy into the kinetic energy of the plasma, thus producing high‐speed reconnection exhausts. The exhausting ions usually show a D‐shaped velocity distribution caused by the time‐of‐flight effect. Previous works usually focused only on exhausting protons from the reconnection site, while O+ ions could also be abundant during geomagnetic active times. In this study, we analyzed a reconnection event to investigate the behaviors of O+ and H+ ions in the magnetotail reconnection exhaust region using the observations from the Cluster spacecraft. It is suggested that different behaviors of H+ and O+ ions are probably due to O+ ions having a larger reconnection diffusion region than H+ ions. In addition, we proposed a remote‐sensing method to estimate the spatial scale ratio between the O+ and H+ diffusion regions and the distance from the observation site to the center of the magnetotail reconnection region. Key Points: The time‐of‐flight effect of O+ ions in magnetotail reconnection exhaust was observed by the Cluster spacecraftThe observed cutoff velocity of O+ is smaller than that of H+, indicating that O+ may have a larger diffusion region than H+A remote‐sensing method to estimate the spatial scale ratio between O+ and H+ diffusion regions is introduced [ABSTRACT FROM AUTHOR]

Purpose: The main advantages of charged particle radiotherapy compared to conventional X-ray external beam radiotherapy are a better tumor conformality coupled with the capability of treating deep-seated radio-resistant tumors. This work investigates the possibility to use oxygen beams for hadron therapy, as an alternative to carbon ions. Materials and Methods: Oxygen ions have the advantage of a higher relative biological effectiveness (RBE) and better conformality to the tumor target. This work describes the mixed radiation field produced by an oxygen beam in water and compares it to the one produced by a therapeutic carbon ion beam. The study has been performed using Geant4 simulations. The dose is calculated for incident carbon ions with energies of 162 MeV/u and 290 MeV/u, and oxygen ions with energies of 192 MeV/u and 245 MeV/u, and hence that the range of the primary oxygen ions projectiles in water was located at the same depth as the carbon ions. Results: The results show that the benefits of oxygen ions are more pronounced when using lower energies because of a slightly higher peak-to-entrance ratio, which allows either providing higher dose in tumor target or reducing it in the surrounding healthy tissues. It is observed that, per incident particle, oxygen ions deliver higher doses than carbon ions. Conclusions: This result coupled with the higher RBE shows that it may be possible to use a lower fluence of oxygen ions to achieve the same therapeutic dose in the patient as that obtained with carbon ion therapy. [ABSTRACT FROM AUTHOR]

The relationship between dispersive Alfvén waves (DAWs), magnetospheric activity, and O+ ion outflow/energy density is examined using measurements from the Van Allen Probes. We show that correlated DAW activity and O+ outflow/energization is a characteristic feature of the inner magnetosphere during active conditions and during storms persists for several hours over large L‐shell and azimuthal ranges of the plasma sheet. Though enhanced during substorm and storm active periods, these correlated features are most intense during geomagnetic storms. Comparisons show a linear relationship between DAW electric (and magnetic) field energy density and outflowing O+ energy. Statistical measurements from a large number of storms also reveal a linear relationship between DAW energy density and gross enhancements in energetic O+ energy densities. These observations support the notion that DAWs play an important role in the energization of O+ ions into and within the inner magnetosphere. Plain Language Summary: Geomagnetic storms are major disturbances in the Earth's magnetosphere, during which the particle content and pressure in the magnetosphere increase considerably. Much of the pressure increase is due to singly charged oxygen ions that come from the ionosphere. How this happens is not clear. Analyzing satellite observations, we found evidence suggesting that a particular type of low‐frequency electromagnetic wave called a dispersive Alfvén wave may be playing a key role. These waves are found to be more prevalent and intense in the magnetosphere during storms. Oxygen ion energies are shown to increase with increasing intensities of these waves. The oxygen ion contribution to pressure also increases in association with intensified wave activity. These observations support the notion that the waves energize and heat oxygen ions into and within the magnetosphere over extended periods of time, which leads to significant magnetospheric pressure increases. Key Points: Dispersive Alfven wave energy density is enhanced during substorms and geomagnetic stormsOxygen ion outflow energy and energy density are correlated with dispersive Alfven wave energy densityObservations support modeling that dispersive Alfven waves enhance oxygen ion energy density in the inner magnetosphere [ABSTRACT FROM AUTHOR]

Enlargement of memory window through forming compliance current was demonstrated in Gd:SiO2 resistive random access memory (RRAM) with a gadolinium (Gd) electrode. Lower forming compliance current for Gd:SiO2 RRAM with a Gd electrode results in larger memory window as compared with the RRAM with a Pt electrode. Through analyses on the current conduction mechanism, we demonstrate that a lower forming compliance current leads to a thinner conductive filament forming and less oxygen ions penetrating into Gd electrode, which caused higher on current and lower off current. Furthermore, a possible resistive switching model was proposed to explain the effect of Gd electrode on RRAM device. [ABSTRACT FROM AUTHOR]

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]

LiF-NaF-KF melt is used to investigate the feasibility of using electrochemical methods to characterize and remove trace amounts of oxygen ions. Electrochemical methods including cyclic voltammograms and chronoamperometry are applied to characterize the oxidation processes of the trace oxygen ions in LiF-NaF-KF melt. The results show that the anodic peak currents vs. the square roots of scan rates is linearity passing through the origin, indicating the oxidation of oxygen ions is controlled by ions diffusion process. The dependency of the anodic peak currents vs. the concentrations of oxygen ions is also linearity when the concentration is no more than 1200 ppm. So the anodic peak current can be used to determine the oxygen ions content in the melt online. The peak currents of oxygen ions oxidation are gradually reduced after 3 h, 8 h and 20 h constant-potential electrolysis. Oxygen ions concentration is reduced to 200 ppm in LiF-NaF-KF melt after 20 h constant-potential electrolysis. [ABSTRACT FROM AUTHOR]

Cyclic voltammetry was applied to characterize oxidation processes of oxygen ions and fluoride ions on a graphite electrode in LiF-NdF 3 -Nd 2 O 3 melt. The effects of the concentration of Nd 2 O 3 , temperature, electrode area on the oxidation of oxygen ions and critical potential have been discussed. Oxidation processes of oxygen ions include adsorption and gas evolution of oxidation products, which is proved by the the smooth and fluctuant cyclic voltammograms. During adsorption process, both the peak current density and the peak potential of oxidation of oxygen ions increase with the increase of Nd 2 O 3 concentration. The peak current density of oxidation of oxygen ions displays a linearity within 2.5wt% Nd 2 O 3 in the melt. The kinetics of the oxidation of oxygen ions is controlled by both electrochemical reaction step and mass transfer. During gas evolution, the oxidation process of oxygen ions is controlled by electrochemical reaction step. Oxidation of flouride ions starts from the critical potential. The critical potential by reverse scan is independent of the electrode area, but depends on electrode area by positive scan. Increasing temperature causes significantly increased the adsoprtion current density for oxidation of oxygen ions. At 950 °C, after the critical potential relatively big current peaks involving formaiton of perflouride compounds occurs after the cirtical potential. [ABSTRACT FROM AUTHOR]

Abstract: We report on the synthesis of nanostructured Ag4O4 by thermal evaporation of silver films followed by oxidation with beams of oxygen ions with different kinetic energy in the 50–300eV range. This method, which combines simplicity and versatility, allows to control the oxide structural properties, and in particular to obtain Ag4O4 thin films characterized by different nanoscale morphologies and crystalline structure, depending on the pristine silver layer morphology and on the energy of the oxygen ions. Monoclinic and tetragonal Ag4O4 phases, or a mixture of the two, can be obtained. The nanoscale porosity of the material makes it interesting for applications where surface mediated Ag ion release plays a crucial role. [Copyright &y& Elsevier]

Abstract: We measured the double-to-single ionization ratios R of Helium bombarded by C q+ and O q+ ions (q =1∼3). The velocity of the projectile varies from v Bohr to 4 v Bohr, the energy varies from 25keV/amu to 500keV/amu. The value of R increases rapidly with the collision velocity and reaches the maximum when the velocity is about 2 or 3 v Bohr, then it decreases slowly for the higher velocity. A simple model is presented to estimate the value R varying with the collision velocity. The results calculated by the model are in agreement with the experimental data basically. [Copyright &y& Elsevier]

Abstract: L x-ray production cross sections have been measured for thin solid targets (∼50μg/cm2) of 57La, 58Ce, 60Nd and 62Sm for 35–60MeV C4+ and O5+ ions. There is an increase in these cross sections with the increasing projectile energy and the ratio of its atomic number to the atomic number of the target nucleus (Z 1/Z 2). The measured L x-ray production cross sections have been compared with the predicted values of the first Born approximation (FBA) and of the ECPSSR theory that accounts for the projectile energy loss and Coulomb deflection and the perturbed stationary-state and relativistic nature of the L-shell. For C4+ ions, there is a reasonable agreement with the ECPSSR predicted values for the higher Z elements (Nd and Sm), while for the lower Z elements (La and Ce), the FBA is in a better accord with the data. For O5+ ions, the FBA gives a better agreement for all the elements than the ECPSSR theory. [Copyright &y& Elsevier]

Abstract: We present a method of polar cusp identification using high charge state heavy ions. There is reason to think that these ions would constitute shocked solar wind ions such as doubly charged helium ions, He2+, and multiply charged oxygen ions, O(3−8)+, that appear to have relatively easy access to one or both of the polar cusps essentially at all times. The observations made with the ISTP/POLAR spacecraft were mostly obtained during geomagnetically non-storm times in April 2001 when the spacecraft orbit allowed northern cusp encounters with low trajectory angle between the spacecraft velocity vector and the overall cusp magnetic field orientation. We also show one extended cusp crossing during the modest magnetic storm of April 22, 2001 (with D st ∼−103 nT). It is found that during the study period, 1–10keV high charge state ions are present in the cusp region at virtually all times, during storm or quiet. We also found that what appears to be the interior of the northern polar magnetic cusp region can be rather turbulent both in the local magnetic field direction and in the energetic charged particle kinetic flow characteristics. There is some evidence for temporally varying turbulent acceleration processes, either within the cusp domain itself or in the surrounding magnetosphere. In terms of the present ion observations, there is little to distinguish the dayside low latitude boundary layer (LB) ion signatures from those of the interior of the polar cusp region (high charge state ions, abundant 1–10keV ion fluxes). [Copyright &y& Elsevier]

High-brightness negative ion beams, especially O- beams, from a compact gaseous plasma source are studied to evaluate the suitability for high-resolution SIMS. Ion-optical calculations are made using the beam parameters from the new source. Results suggest that sub-100 nm spot with O- beam current of 10 pA is achievable. Beam focusing, the resulting beam current distributions at the target and the expected instrumental performance are discussed. [Copyright &y& Elsevier]

A simple model to describe rate changes during the reversible electrochemical promotion of supported metal catalysts has been formulated. Polarisation of the interface between the ion-conducting support and the metal modifies the electron extraction potential of the metal as a result of the spillover of ionic oxygen species. By considering a simple reaction mechanism that involves a charged transition state and accounting for the effect of long-range electrostatic interactions, it is possible to express reaction rates as a function of applied overpotential. It is shown that under certain conditions reaction rates are predicted to increase on application of both negative and positive overpotentials, in agreement with some experimental studies (e.g. Refs. [Catal. Today 11 (1992) 303; J. Catal. 159 (1996) 189]), as a result of electron donation and acceptance from both the metal catalyst and the surface O/O2− redox couple. [Copyright &y& Elsevier]

The improvement of the electrical properties of silicon oxynitride layers formed by nitridation of silicon dioxide layers using the electron impact plasma method has been achieved by a platinum (Pt) method which includes the Pt deposition on the oxynitride layers followed by heat treatment at 300 °C in an oxygen atmosphere. A leakage current density and the density of oxide fixed positive charges induced by the plasma treatment are markedly decreased by the Pt treatment. Although the thickness of the oxynitride layers is not changed and the nitrogen concentration is decreased by the Pt treatment, the dielectric constant increases after the Pt treatment probably due to the elimination of defect states. It is concluded that the improvement of the electrical characteristics results from the injection of oxygen ions (O−), produced by the catalytic activities of Pt, into the oxynitride layers, and the elimination of defect states by a reaction with the O− ions. [Copyright &y& Elsevier]

Measurements of XPS survey, core levels (N 1s, O 1s, Pb 4f, I 3d), and valence band (VB) spectra of CH3NH3PbI3 (MAPbI3) hybrid perovskite prepared on different substrates (glass, indium tin oxide (ITO), and TiO2) aged under different light-soaking conditions at room temperature are presented. The results reveal that the photochemical stability of MAPbI3 depends on the type of substrate and gradually decreases when glass is replaced by ITO and TiO2. Also, the degradation upon exposure to visible light is accompanied by the formation of MAI, PbI2, and Pb0 products as shown by XPS core levels spectra. According to XPS O 1s and VB spectra measurements, this degradation process is superimposed on the partial oxidation of lead atoms in ITO/MAPbI3 and TiO2/MAPbI3, for which Pb–O bonds are formed due to the diffusion of the oxygen ions from the substrates. This unexpected interaction leads to additional photochemical degradation. [ABSTRACT FROM AUTHOR]