Ion Profiles Research Articles

Rate coefficients for the reactions of CO[formula omitted] with O: Lessons from MAVEN at Mars

In the lower ionosphere of Mars, the relative density distributions of the major ions CO 2 + , O 2 + , and O + are largely determined by three reactions, including the two channels of the reaction of CO 2 + with O, which yield either O 2 + (R1) or O + (R2), and the reaction of O + with CO 2 , which yields solely O 2 + (R3). There have been only two measurements of the rate coefficients for reactions (R1) and (R2) in the last 50 years, and they are very different (Fehsenfeld et al., 1970; Tenewitz et al., 2018). Although we have carried out a fairly thorough exploration of parameter space in our quest to fit the density profiles of the major ions and O atoms as measured by instruments on the MAVEN spacecraft, we report here only a small fraction of that exploration. In this investigation, we have used the atmosphere of Mars as a laboratory to distinguish between the two sets of rate coefficients. We find that the best fits to the O 2 + , CO 2 + , and O + densities are for the three models in which the Fehsenfeld et al. rate coefficients are adopted, each of which has its advantages. We conclude that the favored O density profile is 1 . 5 ± 0 . 5 times the measured profile, and that the rate coefficients measured 50 years ago are much better than those recently measured at explaining the density profiles of O 2 + , CO 2 + , and O + in the Martian ionosphere as we know it. • There have been only two measured rate constants for the important reactions of CO 2 + + O. • We have used the thermosphere/ionosphere of Mars as a laboratory to distinguish them. • An alternative Te profile is constructed and the O density profiles are scaled by small factors. • We adopt the electron densities measured by the MAVEN LPW and binned as for the ions. • Full 1-D models show that the 50-year old rate coefficients yield better ion density distributions.

Interphase boundary layer-dominated strain mechanisms in Cu+ implanted Zr-Nb nanoscale multilayers

Sputter-deposited Zr/Nb nanoscale metallic multilayers with a periodicity of 27 (thin) and 96 nm (thick) were subjected to Cu+implantation with low and high fluences and then studied using various experimental techniques in combination with DFT calculations. After Cu+ implantation, the thinner multilayer exhibited a tensile strain along c-axis in Nb layers and a compressive strain in Zr layers, while the thicker multilayer showed a compressive strain in both layers. The strain is higher in the thin multilayer and increases for higher fluences. We developed a mathematical method for the fundamental understanding of the deformation mechanisms in metallic multilayers subjected to radiation damage. In the model, the cumulative strain within a layer is described as the combination of two contributions coming from the interfacial region and the inner region of the layers. The semi-analytical model predicts that the interfacial strain is dominant and extends over a certain region around the interface. Predictions are well supported by ab-initio calculations which show that in the vicinity of the interface and in the Zr side, vacancies and interstitials (low energy barriers) exhibit high mobility compared to the Nb side, thus resulting in a high recombination rate. As a consequence, less strain occurs in the Zr side of the interface compared to the Nb side. The density and distribution of various types of defects along the ion profile (low and high damaged regions) are obtained by combining DFT results and the predictions of the model.

Upgrading the Scanning Two-Dimensional Ionization Profile Monitor in Beam Transport Lines

The scanning two-dimensional ionization profile monitor (IPM) has been upgraded for the beam diagnostics in beam transport lines. The main parts of the monitor are an extractor, a scanner, and two analyzers with a slit at which residual-gas ionization products collected from a beam path as long as 50 mm arrive. The current amplifier based on microchannel plates and a current collector are placed in sequence behind the slit in order to increase the IPM sensitivity under high-vacuum conditions (n × 10−6 Pa). Two-dimensional beam profiles are obtained by scanning. A special electronic unit containing high-voltage supplies and collector-current meters has been created for the scanning and IPM control. Three upgraded IPMs have been placed between the accelerator and the physical facilities in each beamline of the DC-280 FLNR JINR cyclotron. Data processing and simultaneous display of experimental results from several IPMs are carried out by a program developed in the LabVIEW design environment. The minimum current of the 40Ar ion beam with the energy of 5 MeV/nucleon at which the monitor is still operable is estimated to be several tens of picoamperes. The reliability of the upgraded IPM has been demonstrated by its operation.

Heavy ion and proton induced single event upsets in 3D SRAM

Abstract Three-dimensional (3D) memory has considerable application prospects to improve the memory storages to satisfy the highly integrated circuits, while the radiation effects for the 3D memory are complicated due to its multiple sensitive layers. In this paper, heavy ions and protons are used to investigate the radiation sensitivity of an advanced 3D Static Random Access Memory (SRAM). The single-event upsets (SEU) on different layers are distinguished and discussed. The track profile of heavy ions and its impacts on diverse layers are calculated and verified by the Monte Carlo simulation. Direct ionization induced SEU merely exists in the irradiation of protons with high Linear Energy Transfer (LET), which is about 2–3 magnitude order larger than that caused by nuclear reaction. The ultrahigh-energy heavy ions can induce higher SEU cross sections than the ions with medium energy and barely enough range. Moreover, the ultrahigh-energy heavy ions are suitable to be used to evaluate the radiation sensitivity of 3D SRAM with intact packages, if the actual LET values are extracted effectively. The experimental results are essential and supportive for the future application of 3D memory in space electronic systems.

Macroscopic surface charges from microscopic simulations.

Attaining accurate average structural properties in a molecular simulation should be considered a prerequisite if one aims to elicit meaningful insights into a system's behavior. For charged surfaces in contact with an electrolyte solution, an obvious example is the density profile of ions along the direction normal to the surface. Here, we demonstrate that, in the slab geometry typically used in simulations, imposing an electric displacement field D determines the integrated surface charge density of adsorbed ions at charged interfaces. This allows us to obtain macroscopic surface charge densities irrespective of the slab thickness used in our simulations. We also show that the commonly used Yeh-Berkowitz method and the "mirrored slab" geometry both impose vanishing integrated surface charge densities. We present results both for relatively simple rocksalt (1 1 1) interfaces and the more complex case of kaolinite's basal faces in contact with an aqueous electrolyte solution.

Quasi-linear heat transport induced by ITG turbulence in the presence of impurities

The impurity effects on turbulent transport induced by ion temperature gradient (ITG) turbulence are numerically studied in tokamak plasmas, using a gyrokinetic quasi-linear model. The characteristics of the instability and heat fluxes in the presence of impurity ions are investigated for a broad parameter regime, including temperature and density gradients of main and impurity ions, concentration, charge and mass numbers of impurity ions, magnetic shear as well as wave vector spectrum. The heat fluxes are demonstrated to depend not only on the saturation amplitude of the instability but also on the phase shift between and . The peaking factor of temperature/density profile, defined as the ratio of major radius to gradient scale length when the total turbulent heat flux equals zero, is fitted with linear/quadratic functions. In addition, the contributions from diagonal and off-diagonal terms to heat fluxes are identified in detail, i.e. the main ion heat diffusion are proved to be dominated by off-diagonal (diagonal) terms for regions of weak (strong) ITG. In general, steep temperature gradients of main ions as well as hollow density profiles of impurity ions significantly enhance instability and heat fluxes. However, it is interesting to find that the effect of impurity ions with positive density gradient may transit from the enhancement to reduction of the quasi-linear heat flux of main ions in regions of steep ITG, corresponding to transport barriers (e.g. pedestal of H-mode and I-mode plasmas). Both strong and weak positive magnetic shear decrease heat transport.

Scaling Risk Assessment in Nanofiltration of Mine Waters.

Nanofiltration can be applied for the treatment of mine waters. One of the main problems is the risk of crystallization of sparingly soluble salts on the membrane surface (scaling). In this work, a series of batch-mode nanofiltration experiments of the mine waters was performed in a dead-end Sterlitech® HP 4750X Stirred Cell. Based on the laboratory results, the concentration profiles of individual ions along the membrane length in a single-pass industrial-scale nanofiltration (NF) unit was calculated, assuming the tanks-in-series flow model inside the membrane module. These calculations also propose a method for estimating the maximum achievable recovery before the occurrence of the calcium sulfate dihydrate scaling in a single-pass NF 40″ length spiral wound module, simultaneously allowing metastable supersaturation of calcium sulfate dihydrate. The performance of three membrane types (NF270, NFX, NFDL) has been evaluated for the nanofiltration of mine water.

Space-charge effects in ionization beam profile monitors

Ionization profile monitors (IPMs) are widely used in particle accelerators for fast evaluation of parameters of high energy beams. Due to the space-charge effects and several other physical reasons, as well as due to instrumental effects, the measured IPM profiles differ from the those of the beams. Empirical mathematical models are commonly used for reconstruction of the profiles. Here we present proper correction algorithm based on the space-charge dynamics of the secondaries in IPMs. We also demonstrate efficiency of the beam size reconstruction from experimentally measured profiles and discuss practical aspects limiting the IPM accuracy.

Stability of nanobubbles in different salts solutions

The stability of nanobubbles in electrolyte solutions under different ion valence values was studied using deionized water, NaCl, Na 2 SO 4 , Na 3 PO 4 , CaCl 2, and FeCl 3 . Nanobubbles were generated using hydrodynamic cavitation, and bubbles were tested for size and zeta potential. All the samples were stable for one week with no significant deviation in either bubble size or zeta potential values. The variation of size and zeta potential among six samples can be attributed to the solution properties and was mainly dependent on solution pH and the cation valency. The ion profiles revealed that the cation concentration at the bubble surface was higher than that of bulk, confirming that the bubbles were negatively charged for neutral and high pH values ( ≥ 4 ) under low valency cation adsorption. The high valency cations have the potential to neutralize or completely reverse the bubble charge. Anions or co-ions have minimal effect on the surface potential or the surface charge. The calculated internal pressures of bubble were unrealistically high, suggesting that the surface tension should be lower than that of water for nanobubble solutions. The interaction energy profile shows no significant energy barrier that overcomes the attractive van der Waals forces for all the solutions, except NaCl which had a 1.87 × 10 −20 J barrier at a 5 nm separation distance. However, with the recorded stable bubbles, the calculation of the attractive van der Waals forces produced unrealistic values indicating that the Hamaker constant used for the calculation may not be valid at the nanobubble gas-liquid interface. This revealed that nanobubbles should contain exceptional interfacial properties that need to be carefully investigated and evaluated.

Design, characterization and performance evaluation of few-mode EDFA system with propagation up to six modes

Modal gain equalized system for six mode-erbium doped fiber amplifier (6M-EDFA) is designed and analyzed. For the ease in calculation an appropriate pump combination of linearly polarized LP01, LP31 and LP21 modes required for reduction in differential mode gain (DMGλ) is mathematically obtained from extended Giles model. An optimized centre depressed erbium ion profile is also obtained separately. The optimum simplified unidirectional pump combination at 980 nm is then used to excite centre depressed erbium ion profile to achieve considerable reduction in DMGλ. The mathematical analysis is further corroborated with simulation results. The 6M-EDFA system designed provided a minimum DMGλ of 4.41 dB in six mode group and DMGλ of 1.37 dB in five mode group. At smaller values of pump power, a mean gain of about 24.364 dB is achieved at 1550 nm and at lower input signal power of -7 dBm per mode. Gain spectrum is observed to be completely flat over C band for all six modes. Further investigation on evolution of amplified spontaneous emission (ASE) is reported for 6M-EDFA for the first time with new performance metric namely ASE ratio to indicate the deviation of noise between six modes. The ASE ratio of about 2.387 is obtained indicating that the designed system is reasonably immune to noise effects. The influence of non ideal high concentration effects is also investigated on the designed system. The DMGλ values are observed to monotonically increase with length and concentration and decrease with wavelength and input signal powers.

Electronic structure calculations in electrolyte solutions: Methods for neutralization of extended charged interfaces.

Density functional theory (DFT) is often used for simulating extended materials such as infinite crystals or surfaces, under periodic boundary conditions (PBCs). In such calculations, when the simulation cell has non-zero charge, electrical neutrality has to be imposed, and this is often done via a uniform background charge of opposite sign ("jellium"). This artificial neutralization does not occur in reality, where a different mechanism is followed as in the example of a charged electrode in electrolyte solution, where the surrounding electrolyte screens the local charge at the interface. The neutralizing effect of the surrounding electrolyte can be incorporated within a hybrid quantum-continuum model based on a modified Poisson-Boltzmann equation, where the concentrations of electrolyte ions are modified to achieve electroneutrality. Among the infinite possible ways of modifying the electrolyte charge, we propose here a physically optimal solution, which minimizes the deviation of concentrations of electrolyte ions from those in open boundary conditions (OBCs). This principle of correspondence of PBCs with OBCs leads to the correct concentration profiles of electrolyte ions, and electroneutrality within the simulation cell and in the bulk electrolyte is maintained simultaneously, as observed in experiments. This approach, which we call the Neutralization by Electrolyte Concentration Shift (NECS), is implemented in our electrolyte model in the Order-N Electronic Total Energy Package (ONETEP) linear-scaling DFT code, which makes use of a bespoke highly parallel Poisson-Boltzmann solver, DL_MG. We further propose another neutralization scheme ("accessible jellium"), which is a simplification of NECS. We demonstrate and compare the different neutralization schemes on several examples.

The Origin of Observed Magnetic Variability for a Sol on Mars From InSight

AbstractDay‐night variations in the magnetic field at Mars have been previously observed at satellite altitudes. The InSight Fluxgate Magnetometer (IFG) has provided the first evidence for diurnal magnetic field variations at the martian surface. IFG data show diurnal variations with typical peak amplitudes of 20–40nT in the early morning to midmorning; the amplitude of the magnetic field varies over the first 389 sols of the mission and peaks between sols 50 and 100. Temperature variations, solar array currents, and lander activities all generate magnetic fields. Particularly, the first two of these also produce signals with clear diurnal variations. We first assess the IFG data calibration and conclude that temperature and solar array currents have only minimal effects on the variability we observe in the final calibrated magnetic field data. We use satellite magnetic field data and a Mars global circulation model to make predictions for the temporal evolution of wind‐driven fields in the ionosphere. Such fields vary due to seasonal changes in the ionization profile and the winds, and in the altitude range of the dynamo region, that is, the region in which electric currents can be produced. We find that the amplitude and seasonal variability of the surface magnetic fields are generally consistent with those predicted from wind‐driven currents. Moreover, a regional dust storm in the vicinity of the InSight landing site, which started around sol 45, might be responsible for the higher magnetic field amplitudes observed in the IFG data in the early part of the mission.

Analytical Study for Fractional Order Mathematical Model of Concentration of Ca2+ in Astrocytes Cell with a Composite Fractional Derivative

In this paper, we have studied the concentration profile of Cytosolic calcium ion (Ca[Formula: see text] with the aid of fractional calculus. A mathematical model has been considered to examine the influence of fractional advection diffusion equation (cross flow) for the calcium profile. A closed form solution of the fractional advection diffusion equation, arising in study of diffusion of cytosolic calcium in astocytes cell, has been obtained by using Sumudu transform techniques. Graphs for the calcium concentration profiles have been simulated for certain values of the parameters to examine the various effects on concentrations of Cytosolic calcium ion.

Functionalized Single-atom Thickness Boron Nitride Membrane for Separation of Arsenite Ion from Water: A Molecular Dynamics Simulation Study

In this research, the performance of functionalized boron nitride nanosheet (BNNS) as a nanostructure membrane with single-atom thickness for the separation of arsenite ions from aqueous solution was examined by molecular dynamics simulation method. The simulated system included a functionalized BNNS placed in an ionic solution containing sodium arsenite, while the external pressures were applied to the system. For the high-water permeability and full ions rejection, the pore of BNNS was functionalized by passivizing pore edge atoms with F and H atoms. Then hydrostatic pressures in the range of 5-100 MPa was applied to the system. During the molecular dynamics simulations, water molecules and arsenite ions were monitored, and some analyses such as water flux, the density profile of water and ion, hydrogen bonds, and radial distribution function were obtained. Results showed that functionalized BNNS was able to conduct water molecules with high permeability through its pore, whereas ions were not able to pass through the pore.

Energetic particle transport and loss induced by helically-trapped energetic-ion-driven resistive interchange modes in the Large Helical Device

In this work, energetic-ion confinement and loss due to energetic-ion driven magnetohydrodynamic modes are studied using comprehensive neutron diagnostics and orbit-following numerical simulations for the Large Helical Device (LHD). The neutron flux monitor is employed in order to obtain global confinement of energetic ions and two installed vertical neutron cameras (VNCs) viewing different poloidal cross-sections are utilized in order to measure the radial profile of energetic ions. A strong helically-trapped energetic-ion-driven resistive interchange mode (EIC) excited in relatively low-density plasma terminated high-temperature state in LHD. Changes in the neutron emission profile due to the EIC excitation are clearly visualized by the VNCs. The reduction in the neutron signal for the helical ripple valley increases with EIC amplitude, which reaches approximately 50%. In addition to the EIC experiment, orbit-following simulations using the DELTA5D code with EIC fluctuations were performed to assess the energetic-ion transport and loss. Two-dimensional temporal evolution results show that the neutron emissivity at the helical ripple decreases significantly due to the EIC. The rapid reduction in neutron emissivity shows that the helically-trapped beam ions immediately escape from the plasma. The reduction in the VNC signals for the helical ripple valley and the total neutron emission rate increase with increasing EIC amplitude, as observed in the experiment. Calculated line-integrated neutron emission results show that the profile measured by VNC1 has one peak, whereas the profile measured by VNC2 has two peaks, as observed in the experiment. Although the neutron emission profile for VNC2 has a relatively wide peak compared with the experimental results, the significant decrease in neutron signal corresponding to the helical ripple valley was successfully reproduced.

Project AMIGA: The Circumgalactic Medium of Andromeda*

Abstract Project AMIGA (Absorption Maps In the Gas of Andromeda) is a survey of the circumgalactic medium (CGM) of Andromeda (M31, ≃ 300 kpc) along 43 QSO sightlines at impact parameters 25 ≤ R ≤ 569 kpc (25 at R ≲ ). We use ultraviolet absorption measurements of Si ii, Si iii, Si iv, C ii, and C iv from the Hubble Space Telescope/Cosmic Origins Spectrograph and O vi from the Far Ultraviolet Spectroscopic Explorer to provide an unparalleled look at how the physical conditions and metals are distributed in the CGM of M31. We find that Si iii and O vi have a covering factor near unity for R ≲ 1.2 and ≲1.9 , respectively, demonstrating that M31 has a very extended ∼104–105.5 K ionized CGM. The metal and baryon masses of the 104–105.5 K CGM gas within are ≳108 and ≳4 × 1010 (Z/0.3 Z ⊙)−1 M ⊙, respectively. There is not much azimuthal variation in the column densities or kinematics, but there is with R. The CGM gas at R ≲ 0.5 is more dynamic and has more complicated, multiphase structures than at larger radii, perhaps a result of more direct impact of galactic feedback in the inner regions of the CGM. Several absorbers are projected spatially and kinematically close to M31 dwarf satellites, but we show that those are unlikely to give rise to the observed absorption. Cosmological zoom simulations of ∼L* galaxies have O vi extending well beyond as observed for M31 but do not reproduce well the radial column density profiles of the lower ions. However, some similar trends are also observed, such as the lower ions showing a larger dispersion in column density and stronger dependence on R than higher ions. Based on our findings, it is likely that the Milky Way has a ∼104–105.5 K CGM as extended as for M31 and their CGM (especially the warm–hot gas probed by O vi) are overlapping.

Respiratory Muscle Strengths and Their Association with Lean Mass and Handgrip Strengths in Older Institutionalized Individuals.

The study of reduced respiratory muscle strengths in relation to the loss of muscular function associated with ageing is of great interest in the study of sarcopenia in older institutionalized individuals. The present study assesses the association between respiratory muscle parameters and skeletal mass content and strength, and analyzes associations with blood cell counts and biochemical parameters related to protein, lipid, glucose and ion profiles. A multicenter cross-sectional study was performed among patients institutionalized in nursing homes. The respiratory muscle function was evaluated by peak expiratory flow, maximal respiratory pressures and spirometry parameters, and skeletal mass function and lean mass content with handgrip strength, walking speed and bioimpedance, respectively. The prevalence of reduced respiratory muscle strength in the sample ranged from 37.9% to 80.7%. Peak expiratory flow significantly (p < 0.05) correlated to handgrip strength and gait speed, as well as maximal inspiratory pressure (p < 0.01). Maximal expiratory pressure significantly (p < 0.01) correlated to handgrip strength. No correlation was obtained with muscle mass in any of parameters related to reduced respiratory muscle strength. The most significant associations within the blood biochemical parameters were observed for some protein and lipid biomarkers e.g., glutamate-oxaloacetate transaminase (GOT), urea, triglycerides and cholesterol. Respiratory function muscle parameters, peak expiratory flow and maximal respiratory pressures were correlated with reduced strength and functional impairment but not with lean mass content. We identified for the first time a relationship between peak expiratory flow (PEF) values and GOT and urea concentrations in blood which deserves future investigations in order to manage these parameters as a possible biomarkers of reduced respiratory muscle strength.

Theoretical prediction of radiation-enhanced diffusion behavior in nickel under self-ion irradiation

The enhanced diffusion in materials under irradiation plays an important role in the long-term microstructural evolution. In this work, the self-ion irradiation in nickel was used as a model system to study the effect of radiation-enhanced diffusion on the implanted ion profiles. Initially, the depth profiles of vacancies and implanted ions for nickel self-ion irradiation with ion energies up to 15 MeV were computed by the high-efficiency Monte Carlo code IM3D (Irradiation of Materials in 3D). The results are in good agreement with those predicted by SRIM (Stopping and Range of Ions in Matter). Then, diffusion coefficients as functions of temperature and damage rate were obtained, and the depth-dependent diffusion coefficients at various temperatures and damage rates were also illustrated. For this purpose, we used a temperature-dependent effective sink concentration for nickel, which was estimated from the available experimental investigations on the damage structures of irradiated nickel. At length, case studies on the time evolution of implanted ion profiles under the condition of nickel self-irradiation were performed and discussed based on Fick’s second law. The results help to understand the fundamental diffusion properties in ion irradiation, especially under higher-dose irradiation.

Triacylglycerols and Fatty Acid Compositions of Cucumber, Tomato, Pumpkin, and Carrot Seed Oils by Ultra-Performance Convergence Chromatography Combined with Quadrupole Time-of-Flight Mass Spectrometry.

The triacylglycerol (TAG) compositions of cucumber, tomato, pumpkin, and carrot seed oils were analyzed using ultra-performance convergence chromatography (UPC2) combined with quadrupole time-of-flight mass spectrometry (Q-TOF MS). A total of 36, 42, 39, and 27 different TAGs were characterized based on their Q-TOF MS accurate molecular weight and MS2 fragment ion profiles in the cucumber, tomato, pumpkin, and carrot seed oils, respectively. Generally, different vegetable seed oils had different TAGs compositions. Among the identified fatty acids, linoleic acid was the most abundant fatty acid in cucumber, tomato, and pumpkin seed oils and the second most abundant in carrot seed oil with relative concentrations of 54.48, 48.69, 45.10, and 15.92 g/100 g total fatty acids, respectively. Oleic acid has the highest concentration in carrot seed oil and the second highest in cucumber, tomato, and pumpkin seed oils, with relative concentrations of 78.97, 18.57, 27.16, and 33.39 g/100 g total fatty acids, respectively. The chemical compositions of TAGs and fatty acids could promote understanding about the chemical profiles of certain vegetable seed oils, thus improving the potential ability to select appropriate oils with specific functions and a high nutritional value and then develop functional foods in the future.

Chitosan-Sugarcane Bagasse Microspheres as Fertilizer Delivery: On/Off Water Availability System

Enhanced efficiency fertilizer is a sustainable alternative to increase agricultural productivity. In this regard, the nutrient coating or encapsulation is one of the alternatives to improve the effectiveness of the fertilizer. Several matrices can be used, but predominantly the biodegradable ones, which have no environmental impacts. Chitosan has favorable characteristics, as biodegradation and harmless impacts on the soil, to use as a holder for fertilizers. In this work, microspheres of chitosan and sugarcane bagasse were prepared by the inversion phase method followed by potassium nitrate (KNO3) fertilizer sorption. The structural, morphological and thermal properties were evaluated by Fourier transformed infrared, (FTIR), X-ray diffractometry (XDR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) before and after release evaluation. The release profile of fertilizer ions was assessed in water and soil. The matrices served only as support for KNO3 and no chemical interaction was observed. KNO3 releasing behavior reached a plateau after one hour of test for all samples. The release process generated cavities on the surface of microspheres since these spaces were previously fulfilled with fertilizer as observed by SEM. However, in the soil, the materials were dependent on the amount of water available and we observed a diffusion process for the nutrient release.