Polar Ion Research Articles

Oxygen evolution and corrosion behavior of Pb-CeO2 anodes in sulfuric acid solution

Pb-CeO2 composite anodes with different CeO2 contents were prepared by a powder metallurgy method. For comparison, pure Pb and Pb-Ag (0.8 wt%) anodes were also prepared as references by melt casting. The oxygen evolution and corrosion behaviors of the anodes were evaluated by performing measurements of galvanostatic polarizations, Tafel curves, anodic polarization curves, mass increments, and ion concentrations. The morphologies and phase compositions of the anode oxidation layers after polarization were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The results showed that as the content of CeO2 increased, the stabilized potential of the composite anodes gradually decreased; the Pb-CeO2 (>1.5 wt%) composite anode exhibited lower stabilized potential and higher electrocatalytic activity than the Pb-Ag anode during galvanostatic polarization. The Pb-CeO2 (>0.5 wt%) composite anode showed better corrosion resistance than the pure Pb and Pb-Ag (0.8 wt%) anode. The increase in CeO2 content improves the compactness and thickness of the oxide layer formed on the anode surface, but excess CeO2 leads to high porosity of the anode, thus deteriorating the performance. The Pb-CeO2 (2.5 wt%) anode showed comprehensively improved electrochemical performance and corrosion resistance.

Injection of Polarized Protons and Light Ions in the Nuclotron Superconducting Synchrotron

A source of polarized deuterons and protons (SPI) has been created as part of the experimental program on accelerated polarized beams at the Nuclotron superconducting synchrotron. The electrostatic accelerating tube has been replaced by an accelerator with spatially homogeneous quadrupole focusing (RFQ linac), and the power-supply system of the ion sources has been also replaced to work with the source of polarized ions on the preinjector of the LU-20 linear accelerator. This article presents the results of 52–54 experiments on the acceleration of polarized protons and light ions in the Nuclotron.

Investigation of the Eightwise Switching Mechanism and Its Suppression in SrTiO3 Modulated by Humidity and Interchanged Top and Bottom Platinum and LaNiO3 Electrode Contacts

AbstractMemristive devices are hardware components for applications in neuromorphic computing, memories, and logic computation. This work contributes to the ongoing debate on the switching mechanism of eightwise polarity in SrTiO3‐based resistive switches. Specifically the effect of atmospheric humidity on the materials defect chemistry and switching properties is considered. Asymmetric devices are designed by exchanging the top and bottom positions of Pt and LaNiO3 electrodes allowing for a separate analysis of the top and the bottom metal‐oxide interfaces. Under dry atmospheres the switching hysteresis is enhanced with a top Pt contact and suppressed with a bottom Pt contact. It is argued that the buried position and dense microstructure of the bottom platinum impedes an oxygen vacancy driven switching mechanism. Under humid atmospheres eightwise switching occurs in both devices suggesting the presence of two switching mechanisms within the same eightwise switching polarity, namely, oxygen vacancy and hydroxide ion enabled switching. The findings help develop strategies to suppress eightwise switching by burying the active metal‐oxide interface and ensuring dense electrode microstructures. Suppression of switching mechanisms relying on exchange with the environment is desirable for technological implementation of resistive switches and for strategies in stacking of memristive devices for memory and for neuromorphic hardware.

Management of Crystallization Kinetics for Efficient and Stable Low-Dimensional Ruddlesden-Popper (LDRP) Lead-Free Perovskite Solar Cells.

Low‐dimensional Ruddlesden–Popper (LDRP) lead‐free perovskite has great potential due to its improved stability and oriented crystal growth, which is mainly attributed to the effective control of crystallization kinetics. However, the crystallization kinetics of LDRP lead‐free perovskite films are highly limited by Lewis theory. Here, the management of the crystallization kinetics of LDRP tin (Sn) perovskite films jointly controlled by Lewis adducts and the ion exchange process using a mixture of polar aprotic solvent dimethyl sulfoxide (DMSO) and ion liquid solvent methylammonium acetate (MAAc) (the process named as “L‐I”) is demonstrated. Homogeneous nucleated LDRP Sn perovskite films with average grain size close to 9 µm are achieved. Both low electron and hole defect density with a magnitude of 1016, high carrier mobility, and excellent electrical performance are obtained. As a result, the LDRP Sn perovskite solar cell (PSC) with power conversion efficiency (PCE) of 4.03% is achieved using a simple one‐step method without antisolvents, which is one of the best LDRP Sn PSCs. Most importantly, the PSC exhibits excellent stability with no degradation in PCE after 94 d in a nitrogen atmosphere owing to the high‐quality film and the inhibition of the oxidation of Sn2+.

Poly(phenylacetylene) Amines: A General Route to Water-Soluble Helical Polyamines

Poly(phenylacetylene)s bearing prim- and sec-amine groups are barely known because of their poisoning activity toward the polymerization catalyst. Herein, we prepare 11 different amino polymers in high yields by direct polymerization of their corresponding ammonium salts in water using [Rh(cod)2]+BF4– as catalyst. They are stable, water-soluble, and show a helical structure that responds to external stimuli (polarity, pH, and metal ions) acting on the pendants. The location of the amino group in the pendant is shown to be critical for the helical response to protonation.

Estimating the Kinetic Energy Budget of the Polar Wind Outflow

AbstractIonospheric outflow from the polar cap through the polar wind plays an important role in the evolution of the atmosphere and magnetospheric dynamics. Both solar illumination and solar wind energy input are known to be energy sources of the polar wind. However, observational studies of the energy transfer from these two energy sources to the polar wind are difficult. Because of their low energy, polar wind ions are invisible to regular ion detectors onboard a positively charged spacecraft. Using a new technique that indirectly measures these low‐energy ions, we are able to estimate the energy budget of the polar wind. Our results show that solar illumination provides about 107 W of the kinetic energy of the polar wind, in addition to the energy transferred from the solar wind with a maximum rate of about 108 W. The energy transfer efficiency of solar illumination to the kinetic energy of the polar wind is about 6 to 7 orders of magnitude lower than that of the solar wind. Moreover, daily and seasonal changes in the orientation of the geomagnetic dipole axis control solar illumination over the polar cap, modulating both energies of the polar wind and energy transfer efficiencies from the two energy sources.

Exploration of a Composite Index to Describe Magnetospheric Activity: Reduction of the Magnetospheric State Vector to a Single Scalar

AbstractGeomagnetic activity is usually gauged by a single time‐dependent geomagnetic index. One drawback is that an individual geomagnetic index measures only one aspect of the activity in the Earth's magnetosphere. Here we construct a time‐dependent 11‐element magnetospheric state vector E for Earth that consists of measures of high‐latitude currents, polar cap current, magnetospheric convection, plasma pressure, ion and electron precipitation rates, the intensity of substorm‐injected electrons, and the elapsed time since the last substorm onset. At the same time we construct an eight‐element time‐dependent solar‐wind state vector S from the measured properties of the solar wind at Earth. In this S → E picture a time‐dependent “magnetospheric‐activity index” E(1) is created from a weighted sum of the 11 variables in the magnetospheric state vector, with the weights chosen by the vector correlation properties between the magnetospheric state vector E and the solar wind state vector S. The properties and advantages of this E(1) index are examined for the years 1991–2007. Comparing fits made on different subsets of the data demonstrates the robustness of the definition of E(1); tests using out‐of‐sample data demonstrate the accuracy of solar wind predictions of E(1). The advantages of the composite index E(1) include a more direct association with the solar wind, linearity, high predictability, and versatility with respect to (a) storm‐versus‐quiet intervals, (b) solar maximum versus solar minimum, and (c) the various types of solar wind plasma. Defining magnetospheric storms with the composite index E(1) is explored, and categorizing magnetospheric storms using the magnetospheric state vector E is considered.

Polar Ion Temperature Variations During the 22 January 2012 Magnetic Storm

AbstractWe study the 22 January 2012 magnetic storm, during which some localized neutral density (DN) increases developed, and its polar ion temperature (Ti) variations in terms of the earthward Poynting flux (S||) deposited into the coupled ionosphere‐thermosphere system. We investigate the storm's nature, some flow channel events that are the ionospheric signatures of flux transfer events triggered by magnetic reconnections, and the resultant thermospheric responses. We utilize solar and interplanetary magnetic field data and multi‐instrument topside ionospheric and thermospheric measurements. Results reveal the presence of antisunward propagating solar wind Alfven waves during the various storm phases triggering flux transfer events/flow channel events and launching atmospheric gravity waves whose Ti signatures appeared as episodic Ti variations. Various scenarios demonstrate the direct correlation between S|| and DN and the irregular Ti responses within/above flow channels that we explain in terms of frictional heating (Tfrc). We identify Ti responses during various flow channel events as (1) direct/intermittent and (2) opposite, with S|| and DN reflecting the respective underlying flow channel development at the time of detection as (1) early stage when Tfrc was high due to the still large velocity differences between ions and neutrals and as (2) late stage when Tfrc ceased since ions and neutrals moved together. Ti oscillations are observed to be originating from polar or auroral flow channels and propagating across the polar cap toward the equator. We conclude that antisunward solar wind Alfven waves had a significant impact on Ti variability during this storm by modulating magnetic reconnection and launching atmospheric gravity waves.

Selective Molecular Transport in Thermoresponsive Polymer Membranes: Role of Nanoscale Hydration and Fluctuations

For a wide range of modern soft functional materials the selective transport of sub-nanometer-sized molecules (`penetrants') through a stimuli-responsive polymeric membrane is key to the desired function. In this study, we investigate the diffusion properties of penetrants ranging from non-polar to polar molecules and ions in a matrix of collapsed Poly(N-isopropylacrylamide) (PNIPAM) polymers in water by means of extensive molecular dynamics simulations. We find that the water distributes heterogeneously in fractal-like cluster structures embedded in the nanometer-sized voids of the polymer matrix. The nano-clustered water acts as an important player in the penetrant diffusion, which proceeds via a hopping mechanism through `wet' transition states: the penetrants hop from one void to another via transient water channels opened by rare but decisive polymer fluctuations. The diffusivities of the studied penetrants extend over almost five orders of magnitude and thus enable a formulation of an analytical scaling relation with a clear non-Stokesian, exponential dependence of the diffusion coefficient on the penetrant's radius for the uncharged penetrants. Charged penetrants (ions) behave differently as they get captured in large isolated water clusters. Finally, we find large energetic activation barriers for hopping, which significantly depend on the hydration state and thereby challenge available transport theories.

Role of the Occluding Septate Junction Protein Mesh in Epithelial Integrity and Ion Transport in the Drosophila Renal Tubules

Background/objectiveEpithelial occluding junctions are specialized cell‐cell junctions that establish and maintain cell polarity and control paracellular ion, solute and water transport. Tight junctions are the occluding junctions in the epithelia of vertebrates, whereas the epithelia of invertebrates possess septate junctions (SJs). Molecular and genetic analysis of Drosophila SJs have identified a number of transmembrane as well as cytoplasmic scaffolding proteins expressed in a tissue‐specific manner. However, many questions about the role of these proteins in SJ assembly, maintenance and function remain open. Recently, an integral protein, Mesh, has been identified within the SJs of Drosophila midgut and renal tubule epithelia, and shown to be required for the barrier function of the midgut. Here, we report, for the first time, examination of the role of Mesh in adult fly renal tubules, whose function in the maintenance of internal homeostasis relies on regulated transepithelial ion and water secretion/absorption.Methodsmesh knockdown in the fly tubules was achieved using the GAL4‐UAS system. Expression and localization of Mesh and a scaffolding SJ protein, Discs large (Dlg), in control and mutant tubules were determined using confocal microscopy and available antibodies. Transepithelial fluid and K+ transport in the main segment of the control and mesh knockdown tubules were measured using the Ramsay assay and a K+‐specific electrode.ResultsAdult fly renal tubules consist of four major morphologically and functionally distinct segments and have two cell types, the larger principal cells and smaller intercalated stellate cells. We found that developmental mesh knockdown in the tubule principal cells was associated with enlarged initial and main segments of the adult fly tubule and reduced septate junctional localization of a scaffolding protein, Dlg, especially in the enlarged initial segment. In addition, the main segment transepithelial fluid and K+ transport in isotonic condition was abolished in mesh knockdown tubules compared to the control groups.Conclusions and significanceThese data suggest that the SJ protein Mesh is required for SJ assembly, epithelial integrity and ion transport in the fly renal tubule epithelium. Since the Mesh mammalian homolog, Susd2, is also highly expressed in the mouse renal epithelium with unknown function, these studies pave the way for further characterization of the Mesh/Susd2 family of proteins in both invertebrates and vertebrates.Support or Funding InformationThis project was supported by NIH/NIDDK to ARRThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Supramolecular nanodots derived from citric acid and beta-amines with high quantum yield and sensitive photoluminescence

Herein, we reported the characterization of a highly fluorescent and sensitive amorphous nanodots synthesized by hydrothermal treatment of citric acid in the presence of various β-amines below 200 °C. Five-membered ring fused 2-pyridone compounds are effectively produced in the condensation reaction, and serve as the main building blocks to self-assemble into supramolecular nanodots under hydrogen bonding. The 2-pyridone compounds are not the sole blue species, but effectively enhance the photoluminescence quantum yield of citric acid derived nanodots. Compared with the excitation-independent emission in dilute solution, the dense nanodots exhibit red-shifted, suppressed and unexpected excitation-dependent emission. Moreover, the supramolecular nanodots have high sensitivity in various ambient conditions, such as pH, solvent polarity and metal ions.

Influences of surface polarity and Pd ion implantation on the wettability of Al-12Si(-2 Mg)/SiC systems

N-type 6H-SiC (0001) single crystals were implanted with 20 keV Pd ions at three doses of 5 × 1015, 5 × 1016 and 5 × 1017 ions/cm2 at room temperature. The wetting of SiC single crystal by molten Al-12Si and Al-12Si-2Mg were performed by using the sessile drop method in a high vacuum at 1323 K. The influences of surface polarity and Pd ion implantation on the wettability of Al-12Si(-2 Mg)/SiC systems were investigated. The experimental results showed that the equilibrium contact angles of molten Al-12Si and Al-12Si-2Mg on the C-terminated SiC were respectively lower than those on the Si-terminated SiC, which can be related to the formation of Al4C3 at the interface. The wettability of Al-12Si/C(Si)-terminated SiC systems was improved with the 2 wt% Mg addition due to the decrease of the solid-liquid surface energy (σSL) originated from the enhancement of interfacial interactions. Moreover, the equilibrium contact angles of Al-12Si/C(Si)-terminated SiC systems decreased more or less with the Pd implantation dose increasing, while those of Al-12Si-2Mg/C(Si)-terminated SiC systems gradually increased, which can be mainly attributed to the variation of interfacial interactions of Al-12Si(-Mg)/SiC systems.

Crosslink between calcium and sodium signalling.

What is the topic of this review? This paper overviews the links between Ca2+ and Na+ signalling in various types of cells. What advances does it highlight? This paper highlights the general importance of ionic signalling and overviews the molecular mechanisms linking Na+ and Ca2+ dynamics. In particular, the narrative focuses on the molecular physiology of plasmalemmal and mitochondrial Na+ -Ca2+ exchangers and plasmalemmal transient receptor potential channels. Functional consequences of Ca2+ and Na+ signalling for co-ordination of neuronal activity with astroglial homeostatic pathways fundamental for synaptic transmission are discussed. Transmembrane ionic gradients, which are an indispensable feature of life, are used for generation of cytosolic ionic signals that regulate a host of cellular functions. Intracellular signalling mediated by Ca2+ and Na+ is tightly linked through several molecular pathways that generate Ca2+ and Na+ fluxes and are in turn regulated by both ions. Transient receptor potential (TRP) channels bridge endoplasmic reticulum Ca2+ release with generation of Na+ and Ca2+ currents. The plasmalemmal Na+ -Ca2+ exchanger (NCX) flickers between forward and reverse mode to co-ordinate the influx and efflux of both ions with membrane polarization and cytosolic ion concentrations. The mitochondrial calcium uniporter channel (MCU) and mitochondrial Na+ -Ca2+ exchanger (NCLX) mediate Ca2+ entry into and release from this organelle and couple cytosolic Ca2+ and Na+ fluctuations with cellular energetics. Cellular Ca2+ and Na+ signalling controls numerous functional responses and, in the CNS, provides for fast regulation of astroglial homeostatic cascades that are crucial for maintenance of synaptic transmission.

The influence of the electron correlations on dynamic of two-electron charge exchange between ions and polar molecules

Introduction. In the theory of electron capture the exchange interactions at large internuclear distances R between projectile and target particles are the most important ones, since they are associated with the largest cross sections. However, their accurate calculation in the asymptotic region of large R by standard ab initio techniques still requires significant computational effort. In the case of two-electron exchange interaction the situation is much complicated due to necessity of the usage of analytic approximation for the two-electron wave function which must have correct asymptotic (at large R ) behavior in whole configuration space of the electronic coordinates. This requirements can be satisfied by using the method of surface integrals and the Green’s function formalism. The present studies devoted to construction of asymptotically correct two-electronic wave function and two-electronic exchange interaction of the system which consist of the atomic ion and polar molecule. Purpose. To construct a closed analytical expression for two-electron exchange interaction potential, which defines the charge-exchange processes between the polar molecule and multicharged ion. Results . Within the framework of a semiclassical approach and approximation of a coulomb-dipole potential the closed analytical expression of the two-electron exchange interaction responsible for two-step mechanism of charge-exchange between the polar molecule and multicharged ion has been obtained. Conclusion . We have constructed the semiclassical representation for two-electron wave function of the quasimolecular system which consist of polar molecule and atomic ion for large separation R between heavy particles. Using obtained results a closed analytical form (in terms of full elliptic integrals) of the leading asymptotic term of exponentially small two-electron exchange interaction between the polar molecule and atomic ion has been obtained. The derived expression for exchange interaction can be used for study of the two-electron transfer processes in collision of polar molecules with atomic ions.

Influence of solvent polarization and non-uniform ion size on electrostatic properties between charged surfaces in an electrolyte solution

In this paper, we study electrostatic properties between two similar or oppositely charged surfaces immersed in an electrolyte solution by using the mean-field approach accounting for solvent polarization and non-uniform size effects. Applying a free energy formalism accounting for unequal ion sizes and orientational ordering of water dipoles, we derive coupled and self-consistent equations to calculate electrostatic properties between charged surfaces. Electrostatic properties for similarly charged surfaces depend on the counterion size but not on the coion size. Moreover, electrostatic potential and osmotic pressure between similarly charged surfaces are found to be increased with increasing counterion size. On the other hand, the corresponding ones between oppositely charged surfaces are related to both sizes of positive and negative ions. For oppositely charged surfaces, the electrostatic potential, number density of solvent molecules, and relative permittivity of an electrolyte having unequal ion sizes are not symmetric about the centerline between the charged surfaces. For either case, the consideration of solvent polarization results in a decrease in the electrostatic potential and the osmotic pressure compared to the case without the effect.

Dust ion acoustic waves in four component magnetized dusty plasma with effect of slow rotation and superthermal electrons

Dust ion acoustic waves are investigated in four component magneto-rotating dusty plasma comprising opposite polarity dust grains, ions, and nonthermal electrons using the concept of one fluid and two fluid models. The Zakharov-Kuznetsov equation is derived using the reductive perturbation technique to study the nonlinear solitary wave structures. The numerical results show that the superthermality of electrons affects both amplitude and width of the solitary waves while the rotational frequency has a small impression on the width. It is shown that the solitary wave changes its potential from positive to negative at a critical value of the superthermal parameter. It is also observed that the inertial role of dust grains flourishes the effect of rotational frequency and also changes the critical value of the superthermal parameter where the positive/negative potential solitary waves exist.

Dicarboxylic acids analyzed by time-of-flight secondary ions mass spectrometry. Part III: Pentanedioic acid

Time-of-flight secondary ion mass spectrometry was carried out to analyze a commercially available butanedioic acid (succinic acid) powder. Positive and negative polarity ion spectra were obtained using a 25 keV Bi3+ ion beam rastered over areas of 50 × 50 μm2. The main observed fragments were the protonated molecule [M+H]+ at 119 Da and the deprotonated molecule [M-H]− at 117 Da with their respective oligomers.

Dicarboxylic acids analyzed by time-of-flight secondary ions mass spectrometry. Part IV: Hexanedioic acid

Time-of-flight secondary ion mass spectrometry was carried out to analyze a commercially available hexanedioic acid (adipic acid) powder. Positive and negative polarity ion spectra were obtained using a 25 keV Bi3+ ion beam rastered over areas of 50 × 50 μm2. The main observed fragments were the protonated molecule [M+H]+ at 105 Da and the deprotonated molecule [M-H]− at 103 Da with their respective oligomers.

Dicarboxylic acids analyzed by time-of-flight secondary ions mass spectrometry. Part VI: Oxanedioic acid

Time-of-flight secondary ion mass spectrometry was carried out to analyze a commercially available octanedioic acid (suberic acid) powder. Positive and negative polarity ion spectra were obtained using a 25 keV Bi3+ ion beam rastered over areas of 50 × 50 μm2. The main observed fragments were the protonated molecule [M+H]+ at 105 Da and the deprotonated molecule [M-H]− at 103 Da with their respective oligomers.

Dicarboxylic acids analyzed by time-of-flight secondary ions mass spectrometry. Part V: Heptanedioic acid

Time-of-flight secondary ion mass spectrometry was carried out to analyze a commercially available heptanedioic acid (pimelic acid) powder. Positive and negative polarity ion spectra were obtained using a 25 keV Bi3+ ion beam rastered over areas of 50 × 50 μm2. The main observed fragments were the protonated molecule [M+H]+ at 105 u and the deprotonated molecule [M-H]− at 103 Da with their respective oligomers.