Expulsion Of Ions Research Articles

Toward Modeling the Structure of Electrolytes at Charged Mineral Interfaces Using Classical Density Functional Theory.

The organization of water molecules and ions between charged mineral surfaces determines the stability of colloidal suspensions and the strength of phase-separated particulate gels. In this article, we assemble a density functional that measures the free energy due to the interaction of water molecules and ions in electric double layers. The model accounts for the finite size of the particles using fundamental measure theory, hydrogen-bonding between water molecules using Wertheim's statistical association theory, long-range dispersion interactions using Barker and Henderson's high-temperature expansion, electrostatic correlations using a functionalized mean-spherical approximation, and Coulomb forces through the Poisson equation. These contributions are shown to produce highly correlated structures, aptly rendering the layering of counterions and co-ions at highly charged surfaces and permitting the solvation of ions and surfaces to be measured by a combination of short-range associations and long-ranged attractions. The model is tested in a planar geometry near soft, charged surfaces to reproduce the structure of water near graphene and mica. For mica surfaces, explicitly representing the density of the outer oxygen layer of the exposed silica tetrahedra allows water molecules to hydrogen-bond to the solid. When electrostatic interactions are included, water molecules assume a hybrid character, being accounted for implicitly in the dielectric constant but explicitly otherwise. The disjoining pressure between approaching like-charged surfaces is calculated, demonstrating the model's ability to probe pressure oscillations that arise during the expulsion of ions and water layers from the interfacial gap and predict strong interattractive stresses that form at narrow interfacial spacing when the surface charge is overscreened. This interattractive stress arises not due to in-plane correlations under strong electrostatic coupling but due to the out-of-plane structuring of associating ions and water molecules.

Mechanisms of Systemic Osmoregulation in Insects.

Water is essential to life. Terrestrial insects lose water by evaporation from the body surface and respiratory surfaces, as well as in the excretory products, posing a challenge made more acute by their high surface-to-volume ratio. These losses must be kept to a minimum and be offset by water gained from other sources. By contrast, insects such as the blood-sucking bug Rhodnius prolixus consume up to 10 times their body weight in a single blood meal, necessitating rapid expulsion of excess water and ions. How do insects manage their ion and water budgets? A century of study has revealed a great deal about the organ systems that insects use to maintain their ion and water balance and their regulation. Traditionally, a taxonomically wide range of species were studied, whereas more recent research has focused on model organisms to leverage the power of the molecular genetic approach. Key advances in new technologies have become available for a wider range of species in the past decade. We document how these approaches have already begun to inform our understanding of the diversity and conservation of insect systemic osmoregulation. We advocate that these technologies be combined with traditional approaches to study a broader range of nonmodel species to gain a comprehensive overview of the mechanism underpinning systemic osmoregulation in the most species-rich group of animals on earth, the insects.

Synthesis, characterization, and application of hydroxyapatite grafted over pristine charcoal /activated charcoal for removal of pb2+ ions from aqueous solution

Hydroxyapatite (HAP) is one of the major components found in bones and teeth and has outstanding biocompatibility. Hydroxyapatite is a possible sorbent for heavy metals in contaminated water attributable to its high adsorption capabilities and solubility of water very low. However, pure hydroxyapatite is very difficult to use because it exists in the form of white power and also is too much costly. The above difficulties were overcome by the synthesis and characterization of hydroxyapatite grafted over Pristine charcoal/ activated charcoal for the expulsion of lead ions from aqueous solutions by the simple hydrothermal process at different temperatures like 120 °C and 150 °C. The result reveals that rod-like HAP nanocrystals with a range of 22––62 nm, are impregnated over charcoal. Characterization of synthesized hydroxyapatite samples by using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), and Energy-dispersive X-ray spectroscopy (EDX) methods. To investigate adsorbent for removal of Pb2+ from an aqueous solution of Pb (NO3)2, and to vary the adsorbent dosage to evaluate its influence on the adsorption efficiency. The observed that synthesis of HT-CH at 120 °C gives the best result, UV Analysis for the calculation of equilibrium sorption capacity of HT-CH120 and HT-ACH120 on the adsorption of Pb2+ ion is carried out by Lambert-Beer law. The equilibrium sorption capacity of HT-CH120 is 76.13 mg/gm while the equilibrium sorption capacity of HT-ACH120 is 15.8 mg/gm.

Ultrasound Promoted Expulsion of Lead Ions from Wastewater using Ionic Liquid Modified Aluminium Isopropoxide

In the present investigation Methyltrioctylammonium Chloride modified Aluminium isopropoxide was prepared under ultrasonicator. The IL-Aluminium isopropoxide was characterized using FTIR and X-ray diffractometer (XRD). The Prepared IL-Aluminium isopropoxide was tested for the adsorption of Pb2+ from aqueous solution and isotherms were determined. The Pb2+ adsorption performance of the prepared samples was studied by Atomic Adsorption Spectroscopy (AAS) method. Adsorption of Pb2+ on the chemically modified Aluminium isopropoxide was correlated well with the Langmuir model. Correlation coefficients (R2) of Langmuir adsorption isotherms was 0.9994. Efficient synthesis strategy and high adsorption efficiency of IL-Aluminium isopropoxide showed a best ability to remove Pb2+ metal ions from water.

On the interactions between three fireballs in low-temperature plasma* *To the memory of Noah Hershkowitz, a great plasma physicist and magnanimous human. His passing leaves a gap in the hearts of his colleagues and friends that can hardly be filled. His contributions to experimental plasma physics, in particular to the physics of complex space charge structures, such as double layers,

Extensive experimental investigations have been carried out on the interaction between three plasma fireballs in low-temperature plasma. The particle dynamics within the plasma space charge formations and the exchange between them have been investigated. Cold Langmuir probe measurements were taken showing the influence of the fireballs on the background plasma parameters. The current oscillations show specific frequencies for the dynamic states of the fireballs, where periodic expulsion and backflow of ions occur near the surrounding double layer. Interaction maxima or resonance phenomena are revealed at specific distances between the electrodes.

Expulsion of Hydroxide Ions from Methyl Hydration Shells.

The affinity of hydroxide ions for methyl hydration shells is assessed using a combined experimental and theoretical analysis of tert-butyl alcohol (TBA) dissolved in pure water and aqueous NaOH and NaI. The experimental results are obtained using Raman multivariate curve resolution (Raman-MCR) and a new three-component total least squares (Raman-TLS) spectral decomposition strategy used to highlight vibrational perturbations resulting from interactions between TBA and aqueous ions. The experiments are interpreted and extended with the aid of effective fragment potential molecular dynamics (EFP-MD) simulations, as well as Kirkwood-Buff calculations and octanol/water partition measurements, to relate TBA-ion distribution functions to TBA solubility changes. The combined experimental and simulation results reveal that methyl group hydration shells more strongly expel hydroxide than iodide anions, whose populations near the methyl groups of TBA are predicted to be correlated with sodium counterion localization near the TBA hydroxyl group.

Dynamics of channel formation and self-focusing of q-Gaussian laser pulse

Dynamics of low-density channel formed by the radial expulsion of electrons and ions due to the ponderomotive force of the q-Gaussian laser is investigated. Under perturbation approximation, an expression for channel density is derived in order to analyze the depletion of density inside the channel. WKB approximation is employed to study the propagation of q-Gaussian laser in the self-formed channel. For realizing better channeling and self-focusing of laser, laser and plasma parameters are optimized. The effect of q-parameter on the channel formation and spot size has been graphically presented and discussed.

Removal of phosphate ions from wastewater by treated hydrogel based on chitosan

Chitosan/ Gelatin/2-(Dimethylamino) ethyl methacrylate (Cs/Gltn/PDMAEMA) hydrogel was synthesized by gamma irradiation for the expulsion of phosphate ions from wastewater. Chemical adjustment of the hydrogel with thiourea was performed to introduce thiol groups Cs/Gltn/PDMAEMA-treated. More over trapping of SiO2 into the hydrogel matrix to acquire Cs/Gltn/PDMAEMA/SiO2 composite. It was found that the gelation increases with increasing PDMAEMA content in the hydrogel. The maximum gelation performed at an equal ratio of Cs/Gltn at a radiation dose of 15 kGy. The adsorption capacities of the prepared systems towards phosphate ions were investigated. It was obtained that the maximum removal is achieved at pH 6 through 180 min. However, the removal percent decreases with increasing phosphate ions concentration and temperature. The ability of the prepared adsorbents towards phosphate ions removal are ascending ordered in the sequence of Cs/Gltn/PDMAEMA hydrogel, Cs/Gltn/PDMAEMA-treated , and Cs/Gltn/PDMAEMA/SiO2 composite. The pseudo-second-order equation fits well the adsorption kinetics. The adsorption isotherm follows the Freundlich model higher than the Langmuir model

Helium-induced electronic transitions in photo-excited Ba+-Hen exciplexes.

The possibility for helium-induced electronic transitions in a photo-excited atom is investigated using Ba+ excited to the 6p 2P state as a prototypical example. A diabatization scheme has been designed to obtain the necessary potential energy surfaces and couplings for complexes of Ba+ with an arbitrary number of helium atoms. It involves computing new He-Ba+ electronic wave functions and expanding them in determinants of the non-interacting complex. The 6p 2P ← 6s 2S photodissociation spectrum of He⋯Ba+ calculated with this model shows very weak coupling for a single He atom. However, several electronic relaxation mechanisms are identified, which could potentially explain the expulsion of barium ions from helium nanodroplets observed experimentally upon Ba+ photoexcitation. For instance, an avoided crossing in the ring-shaped He7Ba+ structure is shown to provide an efficient pathway for fine structure relaxation. Symmetry breaking by either helium density fluctuations or vibrations can also induce efficient relaxation in these systems, e.g., bending vibrations in the linear He2Ba+ excimer. The identified relaxation mechanisms can provide insight into helium-induced non-adiabatic transitions observed in other systems.

Study of channel formation and relativistic ultra-short laser pulse propagation in helium plasma

In this study, plasma channel formation in pure He plasma (ionization electron density 0.01–0.1nc) interacting with ultra-short relativistic laser pulses (50 fs, >1019 W cm−2) was observed and analyzed. By appropriately selecting the laser pulse and gas backing pressure of the gas jet, a clear density channel longer than 300 μm and wider than 25 μm was achieved in less than 1.5 ps following the passage of the laser pulse, with a radial electron density gradient of ~1023 cm−4 at the channel walls. Numerical simulations for studying the affects of the plasma density, kinetic motion of electrons and ions, and nonlinear laser propagation on the plasma channel formation were carried out, which reproduced the experimental features. These density channels were mainly driven by the radial expulsion of plasma ions, with strong continuous laser self-focusing acting to improve the channeling efficiency. These channels can guide the propagation of ultra-intense laser pulses and supply several advanced applications in high-energy physics, including fast-ignition inertial confinement fusion, plasma-based particle accelerations, and sources of radiation.

The CASTOR-K Code, Recent Developments and Applications

The CASTOR-K code is a hybrid magnetohydrodynamic (MHD)-drift kinetic code developed for the study of MHD modes in the presence of energetic ion populations. It allows a fast assessment of the linear stability of the modes, as well as an accurate calculation of damping due to thermal species (Landau damping). These capabilities make the code an invaluable tool for parametric studies and data analysis. In recent years, CASTOR-K has been mostly used to analyze JET data, including the identification of mechanisms involved in the expulsion of energetic ions from the plasma. However, in order to prepare the code to be used for a wider range of tokamaks including ITER, the code is being subject to a series of important improvements. These improvements aim not only to introduce new physics in the code but also to make it capable of exchanging data with other codes through its integration in modelling infrastructures. In this paper a description of the CASTOR-K code is presented, as well as a summary of the most important results obtained with this code and a description of the new improvements being implemented.

Entrapment of elusive guests within metal-seamed nanocapsules.

Anions play a crucial role in locking alkali metals on the interior of metal-organic capsules that contain structural water gates. This role is further evidenced when stitching-up the capsule seam, resulting in either expulsion or trapping of cesium ions depending on the anion employed.

Entrapment of Elusive Guests within Metal‐Seamed Nanocapsules

AbstractAnions play a crucial role in locking alkali metals on the interior of metal–organic capsules that contain structural water gates. This role is further evidenced when stitching‐up the capsule seam, resulting in either expulsion or trapping of cesium ions depending on the anion employed.

Energetic ion losses caused by magnetohydrodynamic activity resonant and non-resonant with energetic ions in Large Helical Device

Experiments to reveal energetic ion dynamics associated with magnetohydrodynamic activity are ongoing in the Large Helical Device (LHD). Interactions between beam-driven toroidal Alfvén eigenmodes (TAEs) and energetic ions have been investigated. Energetic ion losses induced by beam-driven burst TAEs have been observed using a scintillator-based lost fast-ion probe (SLIP) in neutral beam-heated high β plasmas. The loss flux of co-going beam ions increases as the TAE amplitude increases. In addition to this, the expulsion of beam ions associated with edge-localized modes (ELMs) has been also recognized in LHD. The SLIP has indicated that beam ions having co-going and barely co-going orbits are affected by ELMs. The relation between ELM amplitude and ELM-induced loss has a dispersed structure. To understand the energetic ion loss process, a numerical simulation based on an orbit-following model, DELTA5D, that incorporates magnetic fluctuations is performed. The calculation result shows that energetic ions confined in the interior region are lost due to TAE instability, with a diffusive process characterizing their loss. For the ELM, energetic ions existing near the confinement/loss boundary are lost through a convective process. We found that the ELM-induced loss flux measured by SLIP changes with the ELM phase. This relation between the ELM amplitude and measured ELM-induced loss results in a more dispersed loss structure.

Evaluating the Corrosion Behaviour of PVD Al-Based Coatings By Characterising the Relaxation Time of the Open Circuit Potential in AC-DC-AC cyclic tests

A recently developed AC-DC-AC cyclic test method is used for the first time to evaluate the corrosion behaviour of PVD Al-based coatings. The technique can induce relatively rapid coating degradation as the cathodic reactions at the coating/metal interface produce OH- ions and H2 gas. The AC-DC-AC cyclic test steps involve characterising the coating properties using electrochemical impedance spectroscopy (EIS), a DC cathodic potential step (this is applied for given period of time to induce the electrochemical reactions that cause coating damage) and a potential relaxation stage (when the open circuit potential (Eoc) is monitored over a given time for the coating to reach a stable Eoc condition). This relaxation time defines when cathodic reactions stop and the processes such as electrolyte/ion travel from the coating, pore formation, corrosion reactions and double layer stabilisation that were accelerated (by DC polarisation) reach the steady state. The analysis of Eoc during AC-DC-AC cyclic test involves the regression of an expression describing the potential relaxation which includes two summed terms attributed to i) the end of cathodic reaction and ii) to expulsion of electrolyte ions from the coating. The new AC-DC-AC test technique provides a rapid evaluation of corrosion degradation behaviour of PVD AlCr(Ti) coatings in a shorter time (≤ 24hrs) than traditional EIS and SST tests (days or weeks). The influence of applied DC was determined by subjecting constant voltages of -2V -4V, and -8V to the PVD Al-based coating relative to the stable Eoc value.

Expulsion of Ions from Hydrophobic Hydration Shells

Raman spectroscopy is combined with multivariate curve resolution to quantify interactions between ions and molecular hydrophobic groups in water. The molecular solutes in this study all have similar structures, with a trimethyl hydrophobic domain and a polar or charged headgroup. Our results imply that aqueous sodium and fluoride ions are strongly expelled from the first hydration shells of the hydrophobic (methyl) groups, while iodide ions are found to enter the hydrophobic hydration shell, to an extent that depends on the methyl group partial charge. However, our quantitative estimates of the corresponding ion binding equilibrium constants indicate that the iodide concentration in the first hydrophobic hydration shell is generally lower than that in the surrounding bulk water, and so an iodide ion cannot be viewed as having a true affinity for the molecular hydrophobic interface, but rather is less strongly expelled from such an interface than fluoride.

The Nucleotide, Inhibitor, and Cation Binding Sites of P‐type II ATPases

P-type ATPases constitute a ubiquitous superfamily of cation transport enzymes, responsible for carrying out actions of paramount importance in biology such as ion transport and expulsion of toxic ions from cells. The harmonized toggling of gates in the extra- and intracellular domains explain the phenomenon of specific cation binding in selective physiological states. A quantitative understanding of the fundamental aspects of ion transport mechanism and regulation of P-type ATPases requires detailed knowledge of thermodynamical, structural, and functional properties. Computational studies have made significant contributions to our understanding of biological ion pumps. Various 3D structures of Ca(2+) -ATPase between E1 and E2 transition states have given a impetus to the theorists to work on the Na(+) K(+) - and H(+) K(+) -ATPase to address important questions about their function. The current review delineates the importance of cation, nucleotide, and inhibitor binding domains, with a focus on the therapeutic potential and biological relevance of the three P-type II ATPases. This will give an insight into the ion selectivity and their conduction across the transmembrane helices of P-type II ATPases, which may pave the way to a range of fundamental questions about the mechanism and aid in the efforts of structure- and analog-based drug design.

Effects of low salinity media on growth, condition, and gill ion transporter expression in juvenile Gulf killifish, Fundulus grandis

The Gulf killifish, Fundulus grandis, is a euryhaline teleost which has important ecological roles in the brackish-water marshes of its native range as well as commercial value as live bait for saltwater anglers. Effects of osmoregulation on growth, survival, and body condition at 0.5, 5.0, 8.0 and 12.0‰ salinity were studied in F. grandis juveniles during a 12-week trial. Relative expression of genes encoding the ion transport proteins Na+/K+-ATPase (NKA), Na+/K+/2Cl− cotransporter(NKCC1), and cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel was analyzed. At 0.5‰, F. grandis showed depressed growth, body condition, and survival relative to higher salinities. NKA relative expression was elevated at 7days post-transfer but decreased at later time points in fish held at 0.5‰ while other salinities produced no such increase. NKCC1, the isoform associated with expulsion of ions in saltwater, was downregulated from week 1 to week 3 at 0.5‰ while CFTR relative expression produced no significant results across time or salinity. Our results suggest that Gulf killifish have physiological difficulties with osmoregulation at a salinity of 0.5‰ and that this leads to reduced growth performance and survival while salinities in the 5.0–12.0‰ are adequate for normal function.

Electron-rich sheath dynamics. I. Transient currents and sheath-plasma instabilities

The evolution of an electron-rich sheath on a plane electrode has been investigated experimentally. A rapidly rising voltage is applied to a plane gridded electrode in a weakly ionized, low temperature, and field-free discharge plasma. Transient currents during the transition from ion-rich to electron-rich sheath are explained including the current closure. Time-resolved current-voltage characteristics of the electrode are presented. The time scale for the formation of an electron-rich sheath is determined by the ion dynamics and takes about an ion plasma period. When the ions have been expelled from the sheath a high-frequency sheath-plasma instability grows. The electric field contracts into the electron-rich sheath which implies that the potential outside the sheath drops. It occurs abruptly and creates a large current pulse on the electrode which is not a conduction but a displacement current. The expulsion of ions from the vicinity of the electrode lowers the electron density, electrode current, and the frequency of the sheath-plasma oscillations. Electron energization in the sheath creates ionization which reduces the space charge density, hence sheath electric field. The sheath-plasma instability is weakened or vanishes. The ionization rate decreases, and the sheath electric field recovers. A relaxation instability with repeated current transients can arise which is presented in a companion paper. Only for voltages below the ionization potential a quiescent electron rich-sheath is observed.

Aqua Ions–Graphene Interfacial and Confinement Behavior: Insights from Isobaric–Isothermal Molecular Dynamics

We carry out a systematic microstructural characterization of the solid-fluid interface (SFI) of water and simple metal chloride aqueous solutions in contact with a free-standing plate or with two such plates separated by an interplate distance 0 ≤ h (Å) ≤ 30 at ambient conditions via isothermal-isobaric molecular dynamics. With this characterization, we target the interrogation of the system in search for answers to fundamental questions regarding the structure of the "external" and "internal" (confined) SFIs, the effect of the differential hydration behavior among species, and its link to species expulsion from confinement. For water at ambient conditions, we found that the structure of the "external" SFIs is independent of the interplate distance h in the range 0 ≤ h (Å) ≤ 30, that is, the absence of wall-mediated correlation effects between "external" and "internal" SFIs, and that for h < 9 Å the slit-pores dewet. Moreover, we observed a selective expulsion of ions caused by the differential hydration between the anion and the cations with a consequent charging of the slit-pore. All these observations were interpreted in terms of the axial profiles for precisely defined order parameters, including tetrahedral configuration, hydrogen bonding, and species coordination numbers.