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Sample records for arbitrary ionic charge

  1. Dielectric function of a collisional plasma for arbitrary ionic charge.

    PubMed

    Nersisyan, H B; Veysman, M E; Andreev, N E; Matevosyan, H H

    2014-03-01

    A simple model for the dielectric function of a completely ionized plasma with an arbitrary ionic charge that is valid for long-wavelength high-frequency perturbations is derived using an approximate solution of a linearized Fokker-Planck kinetic equation for electrons with a Landau collision integral. The model accounts for both the electron-ion collisions and the collisions of the subthermal (cold) electrons with thermal ones. The relative contribution of the latter collisions to the dielectric function is treated phenomenologically, introducing some parameter ϰ that is chosen in such a way as to get a well-known expression for stationary electric conductivity in the low-frequency region and fulfill the requirement of a vanishing contribution of electron-electron collisions in the high-frequency region. This procedure ensures the applicability of our model in a wide range of plasma parameters as well as the frequency of the electromagnetic radiation. Unlike the interpolation formula proposed earlier by Brantov et al. [Brantov et al., JETP 106, 983 (2008)], our model fulfills the Kramers-Kronig relations and permits a generalization for the cases of degenerate and strongly coupled plasmas. With this in mind, a generalization of the well-known Lee-More model [Y. T. Lee and R. M. More, Phys. Fluids 27, 1273 (1984)] for stationary conductivity and its extension to dynamical conductivity [O. F. Kostenko and N. E. Andreev, GSI Annual Report No. GSI-2008-2, 2008 (unpublished), p. 44] is proposed for the case of plasmas with arbitrary ionic charge.

  2. Extending the applicability of the Goldschmidt tolerance factor to arbitrary ionic compounds

    PubMed Central

    Sato, Toyoto; Takagi, Shigeyuki; Deledda, Stefano; Hauback, Bjørn C.; Orimo, Shin-ichi

    2016-01-01

    Crystal structure determination is essential for characterizing materials and their properties, and can be facilitated by various tools and indicators. For instance, the Goldschmidt tolerance factor (T) for perovskite compounds is acknowledged for evaluating crystal structures in terms of the ionic packing. However, its applicability is limited to perovskite compounds. Here, we report on extending the applicability of T to ionic compounds with arbitrary ionic arrangements and compositions. By focussing on the occupancy of constituent spherical ions in the crystal structure, we define the ionic filling fraction (IFF), which is obtained from the volumes of crystal structure and constituent ions. Ionic compounds, including perovskites, are arranged linearly by the IFF, providing consistent results with T. The linearity guides towards finding suitable unit cell and composition, thus tackling the main obstacle for determining new crystal structures. We demonstrate the utility of the IFF by solving the structure of three hydrides with new crystal structures. PMID:27032978

  3. Diffuse charge dynamics in ionic thermoelectrochemical systems

    NASA Astrophysics Data System (ADS)

    Stout, Robert F.; Khair, Aditya S.

    2017-08-01

    Thermoelectrics are increasingly being studied as promising electrical generators in the ongoing search for alternative energy sources. In particular, recent experimental work has examined thermoelectric materials containing ionic charge carriers; however, the majority of mathematical modeling has been focused on their steady-state behavior. Here, we determine the time scales over which the diffuse charge dynamics in ionic thermoelectrochemical systems occur by analyzing the simplest model thermoelectric cell: a binary electrolyte between two parallel, blocking electrodes. We consider the application of a temperature gradient across the device while the electrodes remain electrically isolated from each other. This results in a net voltage, called the thermovoltage, via the Seebeck effect. At the same time, the Soret effect results in migration of the ions toward the cold electrode. The charge dynamics are described mathematically by the Poisson-Nernst-Planck equations for dilute solutions, in which the ion flux is driven by electromigration, Brownian diffusion, and thermal diffusion under a temperature gradient. The temperature evolves according to the heat equation. This nonlinear set of equations is linearized in the (experimentally relevant) limit of a "weak" temperature gradient. From this, we show that the time scale on which the thermovoltage develops is the Debye time, 1 /D κ2 , where D is the Brownian diffusion coefficient of both ion species, and κ-1 is the Debye length. However, the concentration gradient due to the Soret effect develops on the bulk diffusion time, L2/D , where L is the distance between the electrodes. For thin diffuse layers, which is the condition under which most real devices operate, the Debye time is orders of magnitude less than the diffusion time. Therefore, rather surprisingly, the majority of ion motion occurs after the steady thermovoltage has developed. Moreover, the dynamics are independent of the thermal diffusion

  4. Brownian dynamics determine universality of charge transport in ionic liquids

    SciTech Connect

    Sangoro, Joshua R; Iacob, Ciprian; Mierzwa, Michal; Paluch, Marian; Kremer, Friedrich

    2012-01-01

    Broadband dielectric spectroscopy is employed to investigate charge transport in a variety of glass-forming ionic liquids over wide frequency, temperature and pressure ranges. Using a combination of Einstein, Einstein-Smoluchowski, and Langevin relations, the observed universal scaling of charge transport in ionic liquids is traced back to the dominant role of Brownian dynamics.

  5. Charge dynamics in ionic polymer metal composites

    NASA Astrophysics Data System (ADS)

    Porfiri, Maurizio

    2008-11-01

    In this paper, we study the charge dynamics in ionic polymer metal composites (IPMCs) in response to a voltage difference applied across their electrodes. We use the Poisson-Nernst-Planck equations to model the time evolution of the electric potential and the concentration of mobile counterions. We present an analytical solution of the nonlinear initial-boundary value problem by using matched asymptotic expansions. We determine the charge and electric potential distributions as functions of time in the whole IPMC region. We show that in the bulk polymer region the IPMC is approximately electroneutral; in contrast, charge distribution boundary layers arise at the polymer-electrode interfaces. Prominent charge depletion and enrichment at the polymer-electrode interface are present even at moderately low input-voltage levels. We use the proposed analytical solution to derive a physics-based circuit model of IPMCs. The equivalent circuit comprises a linear resistor in series connection with a nonlinear capacitor. We derive closed-form expressions for the resistance and the capacitance by conducting a qualitative phase-plane analysis of the inner approximation of the asymptotic expansion. The circuit conductivity is independent of the IPMC dielectric constant and is proportional to the ion diffusivity; whereas, the capacitance is proportional to the square root of the dielectric constant and is independent of the diffusivity. The conductivity depends on the polymer thickness, while the capacitance is independent of it. The capacitance nonlinearity is extremely pronounced, and dramatic capacitance reduction is observed for moderately low voltage levels. We validate the proposed analytical solution along with the derived circuit model through extensive comparisons with finite element results available in the technical literature.

  6. Transport-Induced Inversion of Screening Ionic Charges in Nanochannels.

    PubMed

    Zhu, Xin; Guo, Lingzi; Ni, Sheng; Zhang, Xingye; Liu, Yang

    2016-12-15

    This work reveals a counterintuitive but basic process of ionic screening in nanofluidic channels. Steady-state numerical simulations and mathematical analysis show that, under significant longitudinal ionic transport, the screening ionic charges can be locally inverted in the channels: their charge sign becomes the same as that of the channel surface charges. The process is identified to originate from the coupling of ionic electro-diffusion transport and junction two-dimensional electrostatics. This finding may expand our understanding of ionic screening and electrical double layers in nanochannels. Furthermore, the charge inversion process results in a body-force torque on channel fluids, which is a possible mechanism for vortex generation in the channels and their nonlinear current-voltage characteristics.

  7. Ionic charge accumulation at microscopic interfaces in filled composites

    SciTech Connect

    Zhu Yutao; Wang Xinheng; Xie Hengkun; Liu Yaonan

    1996-12-31

    In this paper the charge accumulation process at microscopic interfaces in insulating materials filled with inorganic fillers is analyzed by using a unit model. Dynamic equations of interfacial ionic charge accumulation are proposed by the authors. The charge accumulation and its regulations are proved by TSC test results obtained on silica filled EPDM samples.

  8. Voltage charging enhances ionic conductivity in gold nanotube membranes.

    PubMed

    Gao, Peng; Martin, Charles R

    2014-08-26

    Ionically conductive membranes are used in many electrochemical processes and devices, including batteries, fuel cells, and electrolyzers. In all such applications, it is advantageous to use membranes with high ionic conductivity because membrane resistance causes a voltage loss suffered by the cell. We describe here a method for enhancing ionic conductivity in membranes containing small diameter (4 nm) gold nanotubes. This entails making the gold nanotube membrane the working electrode in an electrochemical cell and applying a voltage to the membrane. We show here that voltage charging in this way can increase membrane ionic conductivity by over an order of magnitude. When expressed in terms of the ionic conductivity of the electrolyte, κ, within an individual voltage-charged tube, the most negative applied voltage yielded a κ comparable to that of 1 M aqueous KCl, over 2 orders of magnitude higher than κ of the 0.01 M KCl solution contacting the membrane.

  9. Lattice models of ionic systems with charge asymmetry

    NASA Astrophysics Data System (ADS)

    Artyomov, Maxim N.; Kobelev, Vladimir; Kolomeisky, Anatoly B.

    2003-04-01

    The thermodynamics of a charge-asymmetric lattice gas of positive ions carrying charge q and negative ions with charge -zq is investigated using Debye-Hückel theory. Explicit analytic and numerical calculations, which take into account the formation of neutral and charged clusters and cluster solvation by the residual ions, are performed for z=2, 3, and 4. As charge asymmetry increases, the predicted critical point shifts to lower temperatures and higher densities. This trend agrees well with the results from recent Monte Carlo simulations for continuum charge-asymmetric hard-sphere ionic fluids and with the corresponding predictions from continuum Debye-Hückel theory.

  10. Heliumlike and lithiumlike ionic sequences: Critical charges

    NASA Astrophysics Data System (ADS)

    Guevara, N. L.; Turbiner, A. V.

    2011-12-01

    In nonrelativistic quantum mechanics we study the Coulomb systems of infinitely massive center of charge Z and two-three electrons: (Z,e,e) and (Z,e,e,e). It is shown that in both cases the total energy curve in Z is smooth, without any visible irregularities. Thus, for both systems the physical integer charges Z=1,2,... do not play a distinguished role as would be associated with charge quantization. By definition, a critical charge Zcr is a charge which separates a domain of the existence of bound states from a domain of unbound ones (continuum). For both systems the critical charges are found, Zcr,2e=0.910850 and Zcr,3e=2.0090, respectively. Based on numerical analysis, the Puiseux expansion in fractional powers of (Z-Zcr) is constructed for both systems. Our results indicate the existence of a square-root branch point singularity at Zcr with exponent 3/2. A connection between the critical charge and the radius of convergence of 1/Z expansion is briefly discussed.

  11. Charge inversion of divalent ionic solutions in silica channels

    NASA Astrophysics Data System (ADS)

    Lorenz, Christian D.; Travesset, Alex

    2007-06-01

    Recent experiments [F. H. J. van der Heyden , Phys. Rev. Lett. 96, 224502 (2006)] of streaming currents in silica nanochannels with divalent ions report charge inversion, i.e., interfacial charges attracting counterions in excess of their own nominal charge, in conflict with existing theoretical and simulation results. We reveal the mechanism of charge inversion by using all-atomic molecular dynamics simulations. Our results show excellent agreement with experiments, both qualitatively and quantitatively. We further discuss the implications of our study for the general problem of ionic correlations in solutions as well as in regards to the properties of silica-water interfaces.

  12. Charge Transport and Glassy Dynamics in Ionic Liquids

    SciTech Connect

    Sangoro, Joshua R; Kremer, Friedrich

    2012-01-01

    Ionic liquids (ILs) exhibit unique features such as low melting points, low vapor pressures, wide liquidus temperature ranges, high thermal stability, high ionic conductivity, and wide electrochemical windows. As a result, they show promise for use in variety of applications: as reaction media, in batteries and supercapacitors, in solar and fuel cells, for electrochemical deposition of metals and semiconductors, for protein extraction and crystallization, and many others. Because of the ease with which they can be supercooled, ionic liquids offer new opportunities to investigate long-standing questions regarding the nature of the dynamic glass transition and its possible link to charge transport. Despite the significant steps achieved from experimental and theoretical studies, no generally accepted quantitative theory of dynamic glass transition to date has been capable of reproducing all the experimentally observed features. In this Account, we discuss recent studies of the interplay between charge transport and glassy dynamics in ionic liquids as investigated by a combination of several experimental techniques including broadband dielectric spectroscopy, pulsed field gradient nuclear magnetic resonance, dynamic mechanical spectroscopy, and differential scanning calorimetry. Based on EinsteinSmoluchowski relations, we use dielectric spectra of ionic liquids to determine diffusion coefficients in quantitative agreement with independent pulsed field gradient nuclear magnetic resonance measurements, but spanning a broader range of more than 10 orders of magnitude. This approach provides a novel opportunity to determine the electrical mobility and effective number density of charge carriers as well as their types of thermal activation from the measured dc conductivity separately. We also unravel the origin of the remarkable universality of charge transport in different classes of glass-forming ionic liquids.

  13. Charge correlations in multicomponent ionic crystalline membranes

    NASA Astrophysics Data System (ADS)

    Thomas, Creighton; Olvera de La Cruz, Monica

    2012-02-01

    We investigate the dissociation state of a polyelectrolyte membrane with charged head groups in solution. This state depends on the salt concentration and pH of the solution, but spatial correlations also highly influence it. Spatial correlations are typically neglected in these systems, as they are difficult to treat analytically, but they can qualitatively alter the results. We numerically incorporate charge correlations on both flat and curved membranes by simulating a multicomponent system on a fluctuating network with electrostatic interactions, using the replica exchange Monte Carlo approach. The salt-induced screening effects are modeled within the Debye-Huckel theory. For weak enough screening, we find a strong suppression of dissociation regardless of pH, and the membrane may exhibit a reentrant structural phase transition as pH is varied.

  14. Charge transport in gapless electron-hole systems with arbitrary band dispersion

    NASA Astrophysics Data System (ADS)

    Das Sarma, S.; Hwang, E. H.

    2015-05-01

    Using the semiclassical Boltzmann transport theory, we analytically consider dc charge transport in gapless electron-hole (both chiral and nonchiral) systems in the presence of resistive scattering due to static disorder arising from random quenched impurities in the background. We obtain the dependence of the Boltzmann conductivity on carrier density and temperature for arbitrary band dispersion in arbitrary dimensionality assuming long-range (˜1 /r ) Coulomb disorder and zero-range white-noise disorder [˜δ (r ) ]. We establish that the temperature and the density dependence of the Boltzmann conductivity manifests scaling behaviors determining, respectively, the intrinsic semimetallic or the extrinsic metallic property of the gapless system. Our results apply equally well to both chiral and nonchiral gapless systems, and provide a qualitative understanding of the dependence of the Boltzmann conductivity on the band dispersion in arbitrary dimensionality.

  15. Modern ab initio valence bond theory calculations reveal charge shift bonding in protic ionic liquids.

    PubMed

    Patil, Amol Baliram; Bhanage, Bhalchandra Mahadeo

    2016-06-21

    The nature of bonding interactions between the cation and the anion of an ionic liquid is at the heart of understanding ionic liquid properties. A particularly interesting case is a special class of ionic liquids known as protic ionic liquids. The extent of proton transfer in protic ionic liquids has been observed to vary according to the interacting species. Back proton transfer renders protic ionic liquids volatile and to be considered as inferior ionic liquids. We try to address this issue by employing modern ab initio valence bond theory calculations. The results indicate that the bonding in the cation and the anion of a prototypical ionic liquid, ethylammonium nitrate, is fundamentally different. It is neither characteristic of covalent/polar covalent bonding nor ionic bonding but rather charge shift bonding as a resonance hybrid of two competing ionic molecular electronic structure configurations. An investigation of other analogous protic ionic liquids reveals that this charge shift bonding seems to be a typical characteristic of protic ionic liquids while the ionic solid analogue compound ammonium nitrate has less charge shift bonding character as compared to protic ionic liquids. Further the extent of charge shift bonding character has been found to be congruent with the trends in many physicochemical properties such as melting point, conductivity, viscosity, and ionicity of the studied ionic liquids indicating that percentage charge shift character may serve as a key descriptor for large scale computational screening of ionic liquids with desired properties.

  16. Charges, currents, and potentials in ionic channels of one conformation.

    PubMed Central

    Chen, D; Eisenberg, R

    1993-01-01

    Flux through an open ionic channel is analyzed with Poisson-Nernst-Planck (PNP) theory. The channel protein is described as an unchanging but nonuniform distribution of permanent charge, the charge distribution observed (in principle) in x-ray diffraction. Appropriate boundary conditions are derived and presented in some generality. Three kinds of charge are present: (a) permanent charge on the atoms of the protein, the charge independent of the electric field; (b) free or mobile charge, carried by ions in the pore as they flux through the channel; and (c) induced (sometimes called polarization) charge, in the pore and protein, created by the electric field, zero when the electric field is zero. The permanent charge produces an offset in potential, a built-in Donnan potential at both ends of the channel pore. The system is completely solved for bathing solutions of two ions. Graphs describe the distribution of potential, concentration, free (i.e., mobile) and induced charge, and the potential energy associated with the concentration of charge, as well as the unidirectional flux as a function of concentration of ions in the bath, for a distribution of permanent charge that is uniform. The model shows surprising complexity, exhibiting some (but not all) of the properties usually attributed to single filing and exchange diffusion. The complexity arises because the arrangement of free and induced charge, and thus of potential and potential energy, varies, sometimes substantially, as conditions change, even though the channel structure and conformation (of permanent charge) is strictly constant. Energy barriers and wells, and the concomitant binding sites and binding phenomena, are outputs of the PNP theory: they are computed, not assumed. They vary in size and location as experimental conditions change, while the conformation of permanent charge remains constant, thus giving the model much of its interesting behavior. PMID:7686784

  17. Breaking the paradigm: Record quindecim charged magnetic ionic liquids

    DOE PAGES

    Prodius, D.; Smetana, V.; Steinberg, S.; ...

    2016-12-08

    A family of bis(trifluoromethanesulfonyl)amide-based ionic liquids of composition [RE5(C2H5-C3H3N2-CH2COO)16(H2O)8](Tf2N)15 (RE = Er, Ho, Tm; C3H3N2 ≡ imidazolium moiety) featuring the cationic, record quindecim {15+} charged pentanuclear rare earth (RE)-containing ion [RE5(C2H5-C3H3N2-CH2COO)16(H2O)8]15+ has been synthesized and characterized. In addition, due to the presence of rare earth ions, these ionic liquids show a response to magnetic fields with the highest effective magnetic moment observed so far for an ionic liquid and are rare examples of ionic liquids showing luminescence in the near-infrared. As a result, these ionic liquids also were successfully employed in a three-component synthesis of 2-pyrrolo-3'-yloxindole with an extremely lowmore » (<0.035 mol%) catalyst loading rate.« less

  18. Breaking the paradigm: Record quindecim charged magnetic ionic liquids

    SciTech Connect

    Prodius, D.; Smetana, V.; Steinberg, S.; Wilk-Kozubek, M.; Mudryk, Y.; Pecharsky, V. K.; Mudring, A. -V.

    2016-12-08

    A family of bis(trifluoromethanesulfonyl)amide-based ionic liquids of composition [RE5(C2H5-C3H3N2-CH2COO)16(H2O)8](Tf2N)15 (RE = Er, Ho, Tm; C3H3N2 ≡ imidazolium moiety) featuring the cationic, record quindecim {15+} charged pentanuclear rare earth (RE)-containing ion [RE5(C2H5-C3H3N2-CH2COO)16(H2O)8]15+ has been synthesized and characterized. In addition, due to the presence of rare earth ions, these ionic liquids show a response to magnetic fields with the highest effective magnetic moment observed so far for an ionic liquid and are rare examples of ionic liquids showing luminescence in the near-infrared. As a result, these ionic liquids also were successfully employed in a three-component synthesis of 2-pyrrolo-3'-yloxindole with an extremely low (<0.035 mol%) catalyst loading rate.

  19. Influence of ionic charges on the bilayers of lamellar phases.

    PubMed

    Zou, Aihua; Hoffmann, Heinz; Freiberger, Norbert; Glatter, Otto

    2007-03-13

    The influence of ionic charges on the mesophases in the ternary system of C(12-16)E(6) (LA 070), ethylhexylglycerid (EHG), and water was studied. The charge was introduced by adding the ionic surfactant SDS (sodium dodecyl sulfate). The single lamellar phase (5 wt % LA 070 and 240 mM EHG in water) yields a bluish homogeneous solution. With the addition of SDS, the samples become more and more clear. Rheology measurements indicate that increased charge density increases the storage modulus G', and the lamellar phases show typical behavior of a viscoelastic fluid with a yield stress at higher SDS concentration. SAXS measurements show that the interlamellar distance D decreases with SDS concentration. The addition of ionic surfactants suppresses the Helfrich undulations, flattens the bilayers, and decreases interbilayer spacing due to electrostatic repulsions of the ionic surfactant head groups. Furthermore, the L(alpha) phase transforms into vesicle phases as the SDS concentration is increased. Second, it is shown that with added NaCl electrolyte the phase with charged surfactant behaves again in the same way as the initial uncharged system. The addition of salt screens the electrostatic interaction, which leads to a higher flexibility of the bilayers and a decrease of the storage modulus G'. Theoretical calculations show that the shear moduli of the L(alpha) phases are much smaller than the osmotic pressure of the systems. Several models are proposed for the explanation of the shear moduli. The model due to Lekkerkerker for the electric contribution of the bending constant of the bilayer seems to yield good results for the transition to vesicles.

  20. Criticality in charge-asymmetric hard-sphere ionic fluids.

    PubMed

    Aqua, Jean-Noël; Banerjee, Shubho; Fisher, Michael E

    2005-10-01

    Phase separation and criticality are analyzed in z:1 charge-asymmetric ionic fluids of equisized hard spheres by generalizing the Debye-Hückel approach combined with ionic association, cluster solvation by charged ions, and hard-core interactions, following lines developed by Fisher and Levin for the 1:1 case (i.e., the restricted primitive model). Explicit analytical calculations for 2:1 and 3:1 systems account for ionic association into dimers, trimers, and tetramers and subsequent multipolar cluster solvation. The reduced critical temperatures, Tc* (normalized by z), decrease with charge asymmetry, while the critical densities increase rapidly with . The results compare favorably with simulations and represent a distinct improvement over all current theories such as the mean spherical approximation, symmetric Poisson-Boltzmann theory, etc. For z not equal to 1, the interphase Galvani (or absolute electrostatic) potential difference, Deltaphi(T), between coexisting liquid and vapor phases is calculated and found to vanish as absolute value (T-Tc) beta when T-->Tc-with, since our approximations are classical, beta = (1/2). Above Tc, the compressibility maxima and so-called k-inflection loci (which aid the fast and accurate determination of the critical parameters) are found to exhibit a strong z dependence.

  1. Electromechanical modeling of charge sensing in ionic polymers

    NASA Astrophysics Data System (ADS)

    Farinholt, Kevin M.; Leo, Donald J.

    2003-08-01

    A model for charge sensing due to imposed deformation in ionic polymer materials is presented. The basic concept of this model is that mechanical deformation induces charge at the surface of the polymer and produces a measureable discharge of current as the material is deformed. This discharge of current occurs when a short-circuit electrical boundary condition is applied across the material electrodes. An expression for charge density, electric field and electric potential under short-circuit conditions is developed from the electrostatic field equations. The solution for charge density is coupled with the mechanical deformation through a proportionality constant. Expressions for induced charge and current flow are then derived from the equations for electric displacement at the surface of the material. Experimental results support the basic form of the model and also demonstrate that the geometric scaling predicted in the model agrees with measured data. Analysis of the length scale predicted by the model produces qualitative agreement with previously published results but also points to the need for a greater understanding of the interfacial mechanics in the ionic polymer transducers.

  2. Spatial inhomogeneities in ionic liquids, charged proteins, and charge stabilized colloids from collective variables theory.

    PubMed

    Patsahan, O; Ciach, A

    2012-09-01

    Effects of size and charge asymmetry between oppositely charged ions or particles on spatial inhomogeneities are studied for a large range of charge and size ratios. We perform a stability analysis of the primitive model of ionic systems with respect to periodic ordering using the collective variables-based theory. We extend previous studies [Ciach et al., Phys. Rev. E 75, 051505 (2007)] in several ways. First, we employ a nonlocal approximation for the reference hard-sphere fluid which leads to the Percus-Yevick pair direct correlation functions for the uniform case. Second, we use the Weeks-Chandler-Anderson regularization scheme for the Coulomb potential inside the hard core. We determine the relevant order parameter connected with the periodic ordering and analyze the character of the dominant fluctuations along the λ lines. We show that the above-mentioned modifications produce large quantitative and partly qualitative changes in the phase diagrams obtained previously. We discuss possible scenarios of the periodic ordering for the whole range of size and charge ratios of the two ionic species, covering electrolytes, ionic liquids, charged globular proteins or nanoparticles in aqueous solutions, and charge-stabilized colloids.

  3. An iterative, fast, linear-scaling method for computing induced charges on arbitrary dielectric boundaries.

    PubMed

    Tyagi, Sandeep; Süzen, Mehmet; Sega, Marcello; Barbosa, Marcia; Kantorovich, Sofia S; Holm, Christian

    2010-04-21

    Simulating coarse-grained models of charged soft-condensed matter systems in presence of dielectric discontinuities between different media requires an efficient calculation of polarization effects. This is almost always the case if implicit solvent models are used near interfaces or large macromolecules. We present a fast and accurate method (ICC( small star, filled)) that allows to simulate the presence of an arbitrary number of interfaces of arbitrary shape, each characterized by a different dielectric permittivity in one-, two-, and three-dimensional periodic boundary conditions. The scaling behavior and accuracy of the underlying electrostatic algorithms allow to choose the most appropriate scheme for the system under investigation in terms of precision and computational speed. Due to these characteristics the method is particularly suited to include nonplanar dielectric boundaries in coarse-grained molecular dynamics simulations.

  4. Generalized charged Nariai solutions in arbitrary even dimensions with multiple magnetic charges

    NASA Astrophysics Data System (ADS)

    Batista, Carlos

    2016-12-01

    Higher-dimensional solutions for Einstein-Maxwell equations that generalize the charged Nariai spacetime are obtained. The solutions presented here are made from the direct product of several 2-spaces of constant curvature. These solutions turn out to have many magnetic charges, contrary to the usual higher-dimensional generalization of the Nariai spacetime, which has no magnetic charge at all. These solutions are then used to generate black hole metrics. Finally, it is analyzed how these generalized Nariai solutions are modified in more general theories of gravity.

  5. Electric birefringence anomaly of solutions of ionically charged anisometric particles.

    PubMed

    Hoffmann, H; Gräbner, Dieter

    2015-02-01

    The term "electric birefringence anomaly" is known as the electric birefringence (EB) signal that occurs in solutions of ionically charged anisometric particles in a narrow concentration region. The signal is of opposite sign to the normal birefringence that occurs below and above this narrow concentration region. The normal electric birefringence signals in the dilute and more concentrated regions are due to the orientation of the particles in the direction of the applied electric field. The origin for the anomalous signal was not completely understood until now. The article summarises previous results in which the anomalous results had been observed but not well understood. It shows that the birefringence anomaly occurs in systems as diverse as micellar solutions, polyelectrolytes, solutions of clays, viruses and fibres. In all these systems the anomaly signals are present at the concentration when the length of the colloidal particles including the thickness of the electric double layer are about the same as the mean distance between the colloidal particles. Under these conditions the electric double layers of the particles overlap along the main axis of the particles but not in the direction across the particles. As a consequence of this situation a dipole is built up across the particles by the migration of the counter-ions of the particles in the electric field and this dipole leads to an orientation of the particles perpendicular to the electric field. The anomalous signal can usually be observed simultaneously with the normal signal. The amplitude of the anomalous signal can be larger than the amplitude of the normal signal. As a consequence the total birefringence changes its sign in the anomalous concentration region. The anomaly signal of the clays can also be explained by a fluctuating dipole around the particles, which is due to the fact that the centre of the ionic charges of the particles does not fall on the centre of the ionic charge of the counter

  6. Poynting flux in the neighbourhood of a point charge in arbitrary motion and radiative power losses

    NASA Astrophysics Data System (ADS)

    Singal, Ashok K.

    2016-07-01

    We examine the electromagnetic fields in the neighbourhood of a ‘point charge’ in arbitrary motion and thereby determine the Poynting flux across a spherical surface of vanishingly small radius surrounding the charge. We show that the radiative power losses from a point charge turn out to be proportional to the scalar product of the instantaneous velocity and the first time-derivative of the acceleration of the charge. This may seem to be discordant with the familiar Larmor formula where the instantaneous power radiated from a charge is proportional to the square of acceleration. However, it seems that the root cause of the discrepancy actually lies in Larmor’s formula, which is derived using the acceleration fields but without due consideration for the Poynting flux associated with the velocity-dependent self-fields ‘co-moving’ with the charge. Further, while deriving Larmor’s formula, one equates the Poynting flux through a surface at some later time to the radiation loss by the enclosed charge at the retarded time. Poynting’s theorem, on the other hand, relates the outgoing radiation flux from a closed surface to the rate of energy decrease within the enclosed volume, all calculated for the same given instant only. Here we explicitly show the absence of any Poynting flux in the neighbourhood of an instantly stationary point charge, implying no radiative losses from such a charge, which is in complete conformity with energy conservation. We further show how Larmor’s formula is still able to serve our purpose in the vast majority of cases. It is further shown that Larmor’s formula in general violates momentum conservation and, in the case of synchrotron radiation, leads to a potentially incorrect conclusion about the pitch angle changes of the radiating charges, and that only the radiation reaction formula yields a correct result, consistent with special relativity.

  7. Conserved Killing charges of quadratic curvature gravity theories in arbitrary backgrounds

    SciTech Connect

    Devecioglu, Deniz Olgu; Sarioglu, Oezguer

    2011-01-15

    We extend the Abbott-Deser-Tekin procedure of defining conserved quantities of asymptotically constant-curvature spacetimes, and give an analogous expression for the conserved charges of geometries that are solutions of quadratic curvature gravity models in generic D dimensions and that have arbitrary asymptotes possessing at least one Killing isometry. We show that the resulting charge expression correctly reduces to its counterpart when the background is taken to be a space of constant curvature and, moreover, is background gauge invariant. As applications, we compute and comment on the energies of two specific examples: the three-dimensional Lifshitz black hole and a five-dimensional companion of the first, whose energy has never been calculated before.

  8. Retreating behavior of a charged ionic liquid droplet in a dielectric liquid under electric field

    NASA Astrophysics Data System (ADS)

    Ahn, Myung Mo; Im, Do Jin; Kang, In Seok

    2013-11-01

    Ionic liquids show great promise as excellent solvents or catalysts in energy and biological fields due to their unique chemical and physical properties. The ionic liquid droplets in microfluidic systems can also be used as a potential platform for chemical biological reactions. In order to control electrically the ionic liquid droplets in a microfluidic device, the charging characteristics of ionic liquid droplets need to be understood. In this work, the charging characteristics of various ionic liquids are investigated by using the parallel plate electrodes system. Under normal situation, a charged droplet shows bouncing motion between electrodes continuously. However, for some special ionic liquids, interesting retreating behavior of charged ionic liquid droplet has been observed. This retreating behavior of ionic liquid droplet has been analyzed experimentally by the image analysis and the electrometer signal analysis. Based on the hypothesis of charge leakage of the retreating ionic liquid droplets, FT-IR spectroscopy analysis has also been performed. The retreating behavior of ionic liquid droplet is discussed from the intermolecular point of view according to the species of ionic liquids. This research was supported by grant No. 2013R1A1A2011956 funded by the Ministry of Science, ICT and Future Planning (MSIP) and by grant No. 2013R1A1A2010483 funded by the Ministry of Education, Science and Technology (MEST) through the NRF.

  9. Ionic strength independence of charge distributions in solvation of biomolecules

    NASA Astrophysics Data System (ADS)

    Virtanen, J. J.; Sosnick, T. R.; Freed, K. F.

    2014-12-01

    Electrostatic forces enormously impact the structure, interactions, and function of biomolecules. We perform all-atom molecular dynamics simulations for 5 proteins and 5 RNAs to determine the dependence on ionic strength of the ion and water charge distributions surrounding the biomolecules, as well as the contributions of ions to the electrostatic free energy of interaction between the biomolecule and the surrounding salt solution (for a total of 40 different biomolecule/solvent combinations). Although water provides the dominant contribution to the charge density distribution and to the electrostatic potential even in 1M NaCl solutions, the contributions of water molecules and of ions to the total electrostatic interaction free energy with the solvated biomolecule are comparable. The electrostatic biomolecule/solvent interaction energies and the total charge distribution exhibit a remarkable insensitivity to salt concentrations over a huge range of salt concentrations (20 mM to 1M NaCl). The electrostatic potentials near the biomolecule's surface obtained from the MD simulations differ markedly, as expected, from the potentials predicted by continuum dielectric models, even though the total electrostatic interaction free energies are within 11% of each other.

  10. Ionic strength independence of charge distributions in solvation of biomolecules

    SciTech Connect

    Virtanen, J. J.; Sosnick, T. R.; Freed, K. F.

    2014-12-14

    Electrostatic forces enormously impact the structure, interactions, and function of biomolecules. We perform all-atom molecular dynamics simulations for 5 proteins and 5 RNAs to determine the dependence on ionic strength of the ion and water charge distributions surrounding the biomolecules, as well as the contributions of ions to the electrostatic free energy of interaction between the biomolecule and the surrounding salt solution (for a total of 40 different biomolecule/solvent combinations). Although water provides the dominant contribution to the charge density distribution and to the electrostatic potential even in 1M NaCl solutions, the contributions of water molecules and of ions to the total electrostatic interaction free energy with the solvated biomolecule are comparable. The electrostatic biomolecule/solvent interaction energies and the total charge distribution exhibit a remarkable insensitivity to salt concentrations over a huge range of salt concentrations (20 mM to 1M NaCl). The electrostatic potentials near the biomolecule's surface obtained from the MD simulations differ markedly, as expected, from the potentials predicted by continuum dielectric models, even though the total electrostatic interaction free energies are within 11% of each other.

  11. Magnetohydrodynamic effects on a charged colloidal sphere with arbitrary double-layer thickness

    NASA Astrophysics Data System (ADS)

    Hsieh, Tzu H.; Keh, Huan J.

    2010-10-01

    An analytical study is presented for the magnetohydrodynamic (MHD) effects on a translating and rotating colloidal sphere in an arbitrary electrolyte solution prescribed with a general flow field and a uniform magnetic field at a steady state. The electric double layer surrounding the charged particle may have an arbitrary thickness relative to the particle radius. Through the use of a simple perturbation method, the Stokes equations modified with an electric force term, including the Lorentz force contribution, are dealt by using a generalized reciprocal theorem. Using the equilibrium double-layer potential distribution from solving the linearized Poisson-Boltzmann equation, we obtain closed-form formulas for the translational and angular velocities of the spherical particle induced by the MHD effects to the leading order. It is found that the MHD effects on the particle movement associated with the translation and rotation of the particle and the ambient fluid are monotonically increasing functions of κa, where κ is the Debye screening parameter and a is the particle radius. Any pure rotational Stokes flow of the electrolyte solution in the presence of the magnetic field exerts no MHD effect on the particle directly in the case of a very thick double layer (κa →0). The MHD effect caused by the pure straining flow of the electrolyte solution can drive the particle to rotate, but it makes no contribution to the translation of the particle.

  12. Magnetohydrodynamic effects on a charged colloidal sphere with arbitrary double-layer thickness.

    PubMed

    Hsieh, Tzu H; Keh, Huan J

    2010-10-07

    An analytical study is presented for the magnetohydrodynamic (MHD) effects on a translating and rotating colloidal sphere in an arbitrary electrolyte solution prescribed with a general flow field and a uniform magnetic field at a steady state. The electric double layer surrounding the charged particle may have an arbitrary thickness relative to the particle radius. Through the use of a simple perturbation method, the Stokes equations modified with an electric force term, including the Lorentz force contribution, are dealt by using a generalized reciprocal theorem. Using the equilibrium double-layer potential distribution from solving the linearized Poisson-Boltzmann equation, we obtain closed-form formulas for the translational and angular velocities of the spherical particle induced by the MHD effects to the leading order. It is found that the MHD effects on the particle movement associated with the translation and rotation of the particle and the ambient fluid are monotonically increasing functions of κa, where κ is the Debye screening parameter and a is the particle radius. Any pure rotational Stokes flow of the electrolyte solution in the presence of the magnetic field exerts no MHD effect on the particle directly in the case of a very thick double layer (κa→0). The MHD effect caused by the pure straining flow of the electrolyte solution can drive the particle to rotate, but it makes no contribution to the translation of the particle.

  13. Charge detector for the measurement of ionic solutes.

    PubMed

    Yang, Bingcheng; Chen, Yongjing; Mori, Masanobu; Ohira, Shin-Ichi; Azad, Abul K; Dasgupta, Purnendu K; Srinivasan, Kannan

    2010-02-01

    We describe a flow-through ionic charge detector in the form of a three-compartmented system. A central water channel is separated from two outer channels bearing water (or a dilute electrolyte) by a cation-exchange membrane (CEM) and an anion-exchange membrane (AEM). Independent fluid input/output ports address all channels. One platinum electrode is put in each outer channel. When the AEM-side electrode is positive with respect to the CEM-side electrode and voltage (approximately 1-10 V) is applied, the observed background current is from the transport of H(+)/OH(-) through the CEM/AEM to the negative/positive electrodes, respectively. The H(+) and OH(-) are generated by the ionization of water, in part aided by the electric field. If an electrolyte (X(+)Y(-)) is injected in to the central channel, X(+) and Y(-) migrate through the CEM and AEM to the negative and positive electrodes, respectively, and generate a current pulse. The integrated area of the current signal (coulombs) elicited by this electrolyte injection is dependent on a number of variables, the most important being the central channel residence time and the applied voltage (V(app)); these govern the transport of the injected electrolyte to/through the membranes. Other parameters include electrode placement, fluid composition, and outer channel flow rates. For strong electrolytes, depending on the operating conditions, the current peak area (hereinafter called the measured charge signal, Q(m)) can both be less or more than the charge represented by the electrolyte injected (Q(i)). Q(m) is less than Q(i) if transport to/through the membranes is subquantitative. Q(m) can be greater than Q(i) at higher V(app). At constant V(app) more voltage is dropped across the membranes as the central channel becomes more conductive and water dissociation at the membrane surface is enhanced. Effectively, the membranes experience a greater applied voltage as the central channel becomes more conductive. The resulting

  14. Scalable Graphene-Based Membranes for Ionic Sieving with Ultrahigh Charge Selectivity.

    PubMed

    Hong, Seunghyun; Constans, Charlotte; Surmani Martins, Marcos Vinicius; Seow, Yong Chin; Guevara Carrió, Juan Alfredo; Garaj, Slaven

    2017-02-08

    Nanostructured graphene-oxide (GO) laminate membranes, exhibiting ultrahigh water flux, are excellent candidates for next generation nanofiltration and desalination membranes, provided the ionic rejection could be further increased without compromising the water flux. Using microscopic drift-diffusion experiments, we demonstrated the ultrahigh charge selectivity for GO membranes, with more than order of magnitude difference in the permeabilities of cationic and anionic species of equivalent hydration radii. Measuring diffusion of a wide range of ions of different size and charge, we were able to clearly disentangle different physical mechanisms contributing to the ionic sieving in GO membranes: electrostatic repulsion between ions and charged chemical groups; and the compression of the ionic hydration shell within the membrane's nanochannels, following the activated behavior. The charge-selectivity allows us to rationally design membranes with increased ionic rejection and opens up the field of ion exchange and electrodialysis to the GO membranes.

  15. Apparent Ionic Charge in Electrolyte and Polyelectrolyte Solutions

    ERIC Educational Resources Information Center

    Magdelenat, H.; And Others

    1978-01-01

    Compares average displacements of charged particles under thermal motion alone with those obtained by the action of an external electric field to develop a concept of "apparent charge" to approximate actual structural charge in an electrolyte solution. (SL)

  16. Determination of the Ionic Charge States of SEPs Using the University of Chicago IMP-8 Instrument

    NASA Astrophysics Data System (ADS)

    Dietrich, W.

    We use a new method to calculate the mean ionization charge state of solar energetic particles (SEPs) observed with the University of Chicago Cosmic Ray Nuclear Composition experiment on the IMP-8 satellite. The method, using the time to maximum flux, is demonstrated for several gradual SEP events, including the events on 29 September 1989, 19 October 1989, 24 October 1989, and 6 November 1997. Mean ionic charge states are deduced for heavy ions with energies in the range ~10- 500 MeV/nucleon. The ionic charge determination is made only during the onset of the SEP events. These mean charge states agree well with previous measurements for SEP events both at low energy (~0.5-4 MeV/nucleon reported by ISEE-3) and at higher energies (~200-500 MeV/nucleon reported by LDEF). The mean ionic charge states are then used to determine an average temperature and source region for these particles.

  17. Using FT-IR spectroscopy to measure charge organization in ionic liquids.

    PubMed

    Burba, Christopher M; Janzen, Jonathan; Butson, Eric D; Coltrain, Gage L

    2013-07-25

    A major goal in the field of ionic liquids is correlating transport property trends with the underlying liquid structure of the compounds, such as the degree of charge organization among the constituent ions. Traditional techniques for experimentally assessing charge organization are specialized and not readily available for routine measurements. This represents a significant roadblock in elucidating these correlations. We use a combination of transmission and polarized-ATR infrared spectroscopy to measure the degree of charge organization for ionic liquids. The technique is illustrated with a family of 1-alkyl-3-methylimidazolium trifluoromethanesulfonate ionic liquids at 30 °C. As expected, the amount of charge organization decreases as the alkyl side chain is lengthened, highlighting the important role of short-range repulsive interactions in defining quasilattice structure. Inherent limitations of the method are identified and discussed. The quantitative measurements of charge organization are then correlated with trends in the transport properties of the compounds to highlight the relationship between charge and momentum transport and the underlying liquid structure. Most research laboratories possess infrared spectrometers capable of conducting these measurements; thus, the proposed method may represent a cost-effective solution for routinely measuring charge organization in ionic liquids.

  18. Using FT-IR Spectroscopy to Measure Charge Organization in Ionic Liquids

    PubMed Central

    Burba, Christopher M.; Janzen, Jonathan; Butson, Eric D.; Coltrain, Gage L.

    2013-01-01

    A major goal in the field of ionic liquids is correlating transport property trends with the underlying liquid structure of the compounds, such as the degree of charge organization among the constituent ions. Traditional techniques for experimentally assessing charge organization are specialized and not readily available for routine measurements. This represents a significant roadblock in elucidating these correlations. We use a combination of transmission and polarized-ATR infrared spectroscopy to measure the degree of charge organization for ionic liquids. The technique is illustrated with a family of 1-alkyl-3-methylimidazolium trifluoromethansulfonate ionic liquids at 30°C. As expected, the amount of charge organization decreases as the alkyl side chain is lengthened, highlighting the important role of short-range repulsive interactions in defining quasilattice structure. Inherent limitations of the method are identified and discussed. The quantitative measurements of charge organization are then correlated with trends in the transport properties of the compounds to highlight the relationship between charge and momentum transport and the underlying liquid structure. Most research laboratories possess infrared spectrometers capable of conducting these measurements, thus, the proposed method may represent a cost-effective solution for routinely measuring charge organization in ionic liquids. PMID:23781877

  19. New method of calculating the wakefields of a point charge in a waveguide of arbitrary cross section

    NASA Astrophysics Data System (ADS)

    Baturin, S. S.; Kanareykin, A. D.

    2016-05-01

    A new method for calculating the Cherenkov wakefield acting on a point charged particle passing through a longitudinally homogeneous structure lined with layer(s) of an arbitrary retarding (dielectric, resistive, or corrugated) material has been developed. In this paper we present a rigorous derivation of the expressions for the fields that are valid at the cross section of the particle on the basis of a conformal mapping method. This new formalism allows reduction of the loss factor calculation to a simple derivation of a conformal mapping function from the arbitrary cross section onto a circular disc. We generalize these results to the case of a bunch with an arbitrary transverse distribution by deriving a two-dimensional Green function at the cross section of the particle. Consequently, for the first time analytical expressions for the transverse distributions of the electric field Ez for the most commonly used cylindrical, planar and elliptical cross section geometries are found. The proposed approach significantly decreases simulation time and opens new possibilities in optimizing wakefield effects resulting from short charged particle bunches for FEL and Linear Collider applications.

  20. Charge transport and structural dynamics in ultra-thin films of polymerized ionic liquids

    NASA Astrophysics Data System (ADS)

    Heres, Maximilian; Cosby, Tyler; Berdzinski, Stefan; Strehmel, Veronica; Benson, Roberto; Sangoro, Joshua

    Ion conduction and structural dynamics in a series of ultra-thin films of imidazolium based polymerized ionic liquids are investigated using broadband dielectric spectroscopy, atomic force microscopy, and ellipsometry. No alteration in the characteristic charge transport rate is observed between bulk sample and films as thin as 12nm. These results are discussed within the recent approaches proposed to explain the confinement effects on structural dynamics in polymers and low molecular weight ionic liquids. NSF DRM Polymers Program.

  1. Charge Transport and Dynamics in Confined Ammonium and Phosphonium-based Ionic Liquids

    NASA Astrophysics Data System (ADS)

    Harris, Matthew; Cosby, Tyler; Tsunashima, Katsuhiko; Sangoro, Joshua

    Charge transport and structural dynamics in a homologous series of ammonium and phosphonium ionic liquids confined in silica nanopores are investigated by broadband dielectric spectroscopy and Fourier transform infrared spectroscopy. The impact of the central atom of the cation on the physicochemical properties as well as the interplay between confinement effects and pore-wall interactions through silica surface silanization are investigated. The results are discussed within the framework of current understanding of confinement effects in ionic liquid systems, especially in comparison to imidazolium-based ionic liquids.

  2. Charge Transport and Dynamics in Confined Phosphonium-based Ionic Liquids

    NASA Astrophysics Data System (ADS)

    Cosby, Tyler; Tsunashima, Katsuhiko; Sangoro, Joshua

    Charge transport and structural dynamics in a homologous series of phosphonium-based ionic liquids confined in silica nanopores are investigated by broadband dielectric spectroscopy and Fourier transform infrared spectroscopy. The impact of alkyl chain length and hydrophobic aggregation on the physicochemical properties as well as the interplay between confinement effects and pore-wall interactions through silica surface silanization are investigated. The results are discussed within the framework of current understanding of confinement effects in ionic liquid systems, especially in comparison to imidazolium-based ionic liquids. NSF DMR Polymers Program.

  3. Ionic charging by local imbalance at interfaces in hybrid lead halide perovskites

    NASA Astrophysics Data System (ADS)

    Almora, Osbel; Guerrero, Antonio; Garcia-Belmonte, GermÃ

    2016-01-01

    Identification of specific operating mechanisms becomes particularly challenging when mixed ionic-electronic conductors are used in optoelectronic devices. Ionic effects in perovskite solar cells are believed to distort operation curves and possess serious doubts about their long term stability. Current hysteresis and switchable photovoltaic characteristics have been connected to the kinetics of ion migration. However, the nature of the specific ionic mechanism (or mechanisms) able to explain the operation distortions is still poorly understood. It is observed here that the local rearrangement of ions at the electrode interfaces gives rise to commonly observed capacitive effects. Charging transients in response to step voltage stimuli using thick CH3NH3PbI3 samples show two main polarization processes and reveal the structure of the ionic double-layer at the interface with the non-reacting contacts. It is observed that ionic charging, with a typical response time of 10 s, is a local effect confined in the vicinity of the electrode, which entails absence of net mobile ionic concentration (space-charge) in the material bulk.

  4. Ionic charging by local imbalance at interfaces in hybrid lead halide perovskites

    SciTech Connect

    Almora, Osbel; Guerrero, Antonio; Garcia-Belmonte, Germà

    2016-01-25

    Identification of specific operating mechanisms becomes particularly challenging when mixed ionic-electronic conductors are used in optoelectronic devices. Ionic effects in perovskite solar cells are believed to distort operation curves and possess serious doubts about their long term stability. Current hysteresis and switchable photovoltaic characteristics have been connected to the kinetics of ion migration. However, the nature of the specific ionic mechanism (or mechanisms) able to explain the operation distortions is still poorly understood. It is observed here that the local rearrangement of ions at the electrode interfaces gives rise to commonly observed capacitive effects. Charging transients in response to step voltage stimuli using thick CH{sub 3}NH{sub 3}PbI{sub 3} samples show two main polarization processes and reveal the structure of the ionic double-layer at the interface with the non-reacting contacts. It is observed that ionic charging, with a typical response time of 10 s, is a local effect confined in the vicinity of the electrode, which entails absence of net mobile ionic concentration (space-charge) in the material bulk.

  5. Charging of ionic liquid surfaces under X-ray irradiation: the measurement of absolute binding energies by XPS.

    PubMed

    Villar-Garcia, Ignacio J; Smith, Emily F; Taylor, Alasdair W; Qiu, Fulian; Lovelock, Kevin R J; Jones, Robert G; Licence, Peter

    2011-02-21

    Ionic liquid surfaces can become electrically charged during X-ray photoelectron spectroscopy experiments, due to the flux of photoelectrons leaving the surface. This causes a shift in the measured binding energies of X-ray photoelectron peaks that depends on the magnitude of the surface charging. Consequently, a charge correction method is required for ionic liquids. Here we demonstrate the nature and extent of surface charging in ionic liquids and model it using chronopotentiometry. We report the X-ray photoelectron spectra for a range of imidazolium based ionic liquids and investigate the use of long alkyl chains (C(n)H(2n+1), n ≥ 8) and the imidazolium nitrogen, both of which are part of the ionic liquid chemical structure, as internal references for charge correction. Accurate and reproducible binding energies are obtained which allow comparisons to be made across ionic liquid-based systems.

  6. Ionic liquid based lithium battery electrolytes: charge carriers and interactions derived by density functional theory calculations.

    PubMed

    Angenendt, Knut; Johansson, Patrik

    2011-06-23

    The solvation of lithium salts in ionic liquids (ILs) leads to the creation of a lithium ion carrying species quite different from those found in traditional nonaqueous lithium battery electrolytes. The most striking differences are that these species are composed only of ions and in general negatively charged. In many IL-based electrolytes, the dominant species are triplets, and the charge, stability, and size of the triplets have a large impact on the total ion conductivity, the lithium ion mobility, and also the lithium ion delivery at the electrode. As an inherent advantage, the triplets can be altered by selecting lithium salts and ionic liquids with different anions. Thus, within certain limits, the lithium ion carrying species can even be tailored toward distinct important properties for battery application. Here, we show by DFT calculations that the resulting charge carrying species from combinations of ionic liquids and lithium salts and also some resulting electrolyte properties can be predicted.

  7. Ionic charge state measurements during He(+)-rich solar particle events

    NASA Technical Reports Server (NTRS)

    Hovestadt, D.; Klecker, B.; Scholer, M.; Gloeckler, G.

    1984-01-01

    Ionic charge state measurements of carbon, oxygen, and iron in He(+)-rich energetic particle events are presented. The data have been obtained with the Max-Planck-Institut/University of Maryland sensor system on the ISEE 3 spacecraft. The ionic charge states cannot be explained in terms of a model in which the coronal temperature determines a charge equilibrium which is subsequently frozen-in nor in terms of charge exchange during transition through coronal matter after acceleration. It is concluded that the acceleration and probably also the injection process is biased against particles with high mass-to-charge ratios. The plasma injected into the acceleration process must consist of material of cold (not greater than 8.5 x 10 to the 4th K) as well as hot (2.5 x 10 to the 6th K) origin. The cold material must be more abundant than the hot material.

  8. NMR Study of Ion Dynamics and Charge Storage in Ionic Liquid Supercapacitors

    PubMed Central

    2015-01-01

    Ionic liquids are emerging as promising new electrolytes for supercapacitors. While their higher operating voltages allow the storage of more energy than organic electrolytes, they cannot currently compete in terms of power performance. More fundamental studies of the mechanism and dynamics of charge storage are required to facilitate the development and application of these materials. Here we demonstrate the application of nuclear magnetic resonance spectroscopy to study the structure and dynamics of ionic liquids confined in porous carbon electrodes. The measurements reveal that ionic liquids spontaneously wet the carbon micropores in the absence of any applied potential and that on application of a potential supercapacitor charging takes place by adsorption of counterions and desorption of co-ions from the pores. We find that adsorption and desorption of anions surprisingly plays a more dominant role than that of the cations. Having elucidated the charging mechanism, we go on to study the factors that affect the rate of ionic diffusion in the carbon micropores in an effort to understand supercapacitor charging dynamics. We show that the line shape of the resonance arising from adsorbed ions is a sensitive probe of their effective diffusion rate, which is found to depend on the ionic liquid studied, as well as the presence of any solvent additives. Taken as whole, our NMR measurements allow us to rationalize the power performances of different electrolytes in supercapacitors. PMID:25973552

  9. NMR Study of Ion Dynamics and Charge Storage in Ionic Liquid Supercapacitors.

    PubMed

    Forse, Alexander C; Griffin, John M; Merlet, Céline; Bayley, Paul M; Wang, Hao; Simon, Patrice; Grey, Clare P

    2015-06-10

    Ionic liquids are emerging as promising new electrolytes for supercapacitors. While their higher operating voltages allow the storage of more energy than organic electrolytes, they cannot currently compete in terms of power performance. More fundamental studies of the mechanism and dynamics of charge storage are required to facilitate the development and application of these materials. Here we demonstrate the application of nuclear magnetic resonance spectroscopy to study the structure and dynamics of ionic liquids confined in porous carbon electrodes. The measurements reveal that ionic liquids spontaneously wet the carbon micropores in the absence of any applied potential and that on application of a potential supercapacitor charging takes place by adsorption of counterions and desorption of co-ions from the pores. We find that adsorption and desorption of anions surprisingly plays a more dominant role than that of the cations. Having elucidated the charging mechanism, we go on to study the factors that affect the rate of ionic diffusion in the carbon micropores in an effort to understand supercapacitor charging dynamics. We show that the line shape of the resonance arising from adsorbed ions is a sensitive probe of their effective diffusion rate, which is found to depend on the ionic liquid studied, as well as the presence of any solvent additives. Taken as whole, our NMR measurements allow us to rationalize the power performances of different electrolytes in supercapacitors.

  10. Ionic charge distributions of energetic particles from solar flares

    NASA Technical Reports Server (NTRS)

    Mullan, D. J.; Waldron, W. L.

    1986-01-01

    The effects which solar flare X-rays have on the charge states of solar cosmic rays is determined quantitatively. Rather than to characterize the charge distribution by temperature alone, it is proposed that the X-ray flux at the acceleration site also is used. The effects of flare X-rays are modeled mathematically.

  11. Self-Amplified Surface Charging and Partitioning of Ionic Liquids in Nanopores

    NASA Astrophysics Data System (ADS)

    Neal, Justin N.; Van Aken, K. L.; Gogotsi, Y.; Wesolowski, David J.; Wu, Jianzhong

    2017-09-01

    We study ion partitioning and self-charging of nanoporous electrodes with room-temperature ionic liquids using a classical density-functional theory that accounts for molecular-excluded volume effects and electrostatic correlations. Nanopores of zero electrical potential are predicted to favor adsorption of small ions even without specific surface attraction, and the imbalanced distributions of cations and anions inside the pore induces a net surface charge that promotes further enrichment of small ions. The self-amplified ion partitioning is most significant when the nanopore and the ionic species are of comparable dimension.

  12. Tuning transport selectivity of ionic species by phosphoric acid gradient in positively charged nanochannel membranes.

    PubMed

    Yang, Meng; Yang, Xiaohai; Wang, Kemin; Wang, Qing; Fan, Xin; Liu, Wei; Liu, Xizhen; Liu, Jianbo; Huang, Jin

    2015-02-03

    The transport of ionic species through a nanochannel plays important roles in fundamental research and practical applications of the nanofluidic device. Here, we demonstrated that ionic transport selectivity of a positively charged nanochannel membrane can be tuned under a phosphoric acid gradient. When phosphoric acid solution and analyte solution were connected by the positively charged nanochannel membrane, the faster-moving analyte through the positively charged nanochannel membrane was the positively charged dye (methylviologen, MV(2+)) instead of the negatively charged dye (1,5-naphthalene disulfonate, NDS(2-)). In other words, a reversed ion selectivity of the nanochannel membranes can be found. It can be explained as a result of the combination of diffusion, induced electroosmosis, and induced electrophoresis. In addition, the influencing factors of transport selectivity, including concentration of phosphoric acid, penetration time, and volume of feed solution, were also investigated. The results showed that the transport selectivity can further be tuned by adjusting these factors. As a method of tuning ionic transport selectivity by establishing phosphoric acid gradient, it will be conducive to improving the separation of ionic species.

  13. The structure of pH dependent block copolymer micelles: charge and ionic strength dependence

    SciTech Connect

    Pople, John A

    2002-08-06

    We characterize the structures of various polyelectrolyte block copolymer micelles in dilute aqueous solution as a function of pH and ionic strength. The block copolymers carry a common core block 2-(diethylamino) ethyl methacrylate (DEAEMA) and one of three coronal blocks: 2-(dimethylamino) ethyl methacrylate (DMAEMA), polyethylene oxide (PEO), and DMAEMA whose side-chain amine groups are selectively quaternized with benzyl chloride (Q-DMAEMA). The PEO-DEAEMA, DMAEMA-DEAEMA, and Q-DMAEMA-DEAEMA copolymers form micelles with electrostatically neutral, weakly charged, and highly charged coronae, respectively. We adjust the fractional charge a on the DEAEMA and DMAEMA blocks by adjusting the solution pH. For DMAEMA-DEAEMA micelles increasing the fractional charge a swells the micelle corona while decreasing the aggregation number due to electrostatic repulsions. The decrease in aggregation number is also observed with increasing a for the PEO-DEAEMA and Q-DMAEMA-DEAEMA micelles, due to electrostatic repulsions between the hydrophobic DEAEMA blocks. Increasing the ionic strength causes the DMAEMA-DEAEMA micelle corona to shrink as the salt screens electrostatic repulsions within the corona. In all three copolymers increases in the ionic strength causes the micelle aggregation number to increase by screening the electrostatic repulsions between chains. Trends in the corona thickness with varying fractional charge and ionic strength are compared with a number of theoretical models providing additional insight into the micelle structure.

  14. Charge-assisted halogen bonding: donor-acceptor complexes with variable ionicity.

    PubMed

    Lieffrig, Julien; Jeannin, Olivier; Frąckowiak, Arkadiusz; Olejniczak, Iwona; Świetlik, Roman; Dahaoui, Slimane; Aubert, Emmanuel; Espinosa, Enrique; Auban-Senzier, Pascale; Fourmigué, Marc

    2013-10-25

    Charge-assisted halogen bonding is unambiguously revealed from structural and electronic investigations of a series of isostructural charge-transfer complexes derived from iodinated tetrathiafulvalene and tetracyanoquinodimethane derivatives, (EDT-TTFI2)2(TCNQF(n)), n=0-2, which exhibit variable degrees of ionicity. The iodinated tetrathiafulvalene derivative, EDT-TTFI2, associates with tetracyanoquinodimethane (TCNQ) and its derivatives of increasing reduction potential (TCNQF, TCNQF2) through highly directional C-I⋅⋅⋅N≡C halogen-bond interactions. With the less oxidizing TCNQ acceptor, a neutral and insulating charge-transfer complex is isolated whereas with the more oxidizing TCNQF2 acceptor, an ionic, highly conducting charge-transfer salt is found, both of 2:1 stoichiometry and isostructural with the intermediate TCNQF complex, in which a neutral-ionic conversion takes place upon cooling. A correlation between the degree of charge transfer and the C-I⋅⋅⋅N≡C halogen-bond strength is established from the comparison of the structures of the three isostructural complexes at temperatures from 300 to 20 K, thus demonstrating the importance of electrostatics in the halogen-bonding interaction. The neutral-ionic conversion in (EDT-TTFI2)2(TCNQF) is further investigated through the temperature dependence of its magnetic susceptibility and the stretching modes of the C≡N groups. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Orientational ordering of ionic liquids near a charged mica surface.

    PubMed

    Payal, Rajdeep Singh; Balasubramanian, Sundaram

    2012-05-14

    The self-assembly of ions in room-temperature ionic liquids adsorbed on a mica surface is studied using molecular dynamics simulations. Four liquids from the 1-methyl,n-alkylimidazolium bis(trifluoromethylsulfonyl)imide ([C(n)mim][NTf(2)]) family are investigated, where n ranges between 2 and 8. Cations with ethyl or butyl groups are found to orient with the hydrocarbon tails lying parallel to the surface, while the hexyl and octyl tails of cations are observed to be oriented perpendicular to it. The crossover in the orientational preference matches recent observations of surface forces of these liquids.

  16. A comparative study of room temperature ionic liquids and their organic solvent mixtures near charged electrodes

    NASA Astrophysics Data System (ADS)

    Vatamanu, Jenel; Vatamanu, Mihaela; Borodin, Oleg; Bedrov, Dmitry

    2016-11-01

    The structural properties of electrolytes consisting of solutions of ionic liquids in a polar solvent at charged electrode surfaces are investigated using classical atomistic simulations. The studied electrolytes consisted of tetraethylammonium tetrafluoroborate (NEt4-BF4), 1-ethyl-3-methylimidazolium tetrafluoroborate (c2mim-BF4) and 1-octyl-3-methylimidazolium tetrafluoroborate (c8mim-BF4) salts dissolved in acetonitrile solvent. We discuss the influence of electrolyte concentration, chemical structure of the ionic salt, temperature, conducting versus semiconducting nature of the electrode, electrode geometry and surface roughness on the electric double layer structure and capacitance and compare these properties with those obtained for pure room temperature ionic liquids. We show that electrolytes consisting of solutions of ions can behave quite differently from pure ionic liquid electrolytes.

  17. Electrophoresis of a particle at an arbitrary surface potential and double layer thickness: importance of nonuniformly charged conditions.

    PubMed

    Hsu, Jyh-Ping; Huang, Hsiao-Ting; Yeh, Li-Hsien; Tseng, Shiojenn

    2012-02-07

    Recent advances in material science and technology yield not only various kinds of nano- and sub-micro-scaled particles but also particles of various charged conditions such as Janus particles. The characterization of these particles can be challenging because conventional electrophoresis theory is usually based on drastic assumptions that are unable to realistically describe the actual situation. In this study, the influence of the nonuniform charged conditions on the surface of a particle at an arbitrary level of surface potential and double layer thickness on its electrophoretic behavior is investigated for the first time in the literature taking account of the effect of double-layer polarization. Several important results are observed. For instance, for the same averaged surface potential, the mobility of a nonuniformly charged particle is generally smaller than that of a uniformly charged particle, and the difference between the two depends upon the thickness of double layer. This implies that using the conventional electrophoresis theory may result in appreciable deviation, which can be on the order of ca. 20%. In addition, the nonuniform surface charge can yield double vortex in the vicinity of a particle by breaking the symmetric of the flow field, which has potential applications in mixing and/or regulating the medium confined in a submicrometer-sized space, where conventional mixing devices are inapplicable.

  18. Charged-particle transport in gases in electric and magnetic fields crossed at arbitrary angles: Multiterm solution of Boltzmann's equation.

    PubMed

    White, R D; Ness, K F; Robson, R E; Li, B

    1999-08-01

    A multiterm solution of the Boltzmann equation has been developed and used to calculate transport coefficients of charged-particle swarms in gases under the influence of electric and magnetic fields crossed at arbitrary angles psi. The hierarchy resulting from a spherical harmonic decomposition of the Boltzmann equation in the hydrodynamic regime [Ness, Phys. Rev. A 47, 327 (1993)] is solved numerically by representing the speed dependence of the phase-space distribution function in terms of an expansion in Sonine polynomials about a weighted sum of Maxwellian distributions at different temperatures. Results are given for charged-particle swarms in certain model gases over a range of psi and field strengths. The variation of the transport coefficients with psi is addressed using physical arguments. The errors associated with the two-term approximation and inadequacies of Legendre polynomial expansions are highlighted.

  19. Ionic Behavior in Highly Concentrated Aqueous Solutions Nanoconfined between Discretely Charged Silicon Surfaces.

    PubMed

    Qiu, Yinghua; Ma, Jian; Chen, Yunfei

    2016-05-17

    Through molecular dynamics simulations considering thermal vibration of surface atoms, ionic behaviors in concentrated NaCl solutions confined between discretely charged silicon surfaces have been investigated. The electric double layer structure was found to be sensitive to the density and distribution of surface charges. Due to the discreteness of the surface charge, a slight charge inversion appeared which depended on the surface charge density, bulk concentration, and confinement. In the nanoconfined NaCl solutions concentrated from 0.2 to 4.0 M, the locations of accumulation layers for Na(+) and Cl(-) ions remained stable, but their peak values increased. The higher the concentration was, the more obvious the charge inversion appeared. In 4.0 M NaCl solution, Na(+) and Cl(-) ions show obvious alternating layered distributions which may correspond to the solidification found in experiments. By changing surface separation, the confinement had a large effect on the ionic distribution. As both surfaces approached each other, many ions and water molecules were squeezed out of the confined space. Two adjacent layers in ion or water distribution profiles can be forced closer to each other and merge together. From ionic hydration analysis, the coordination number of Na(+) ions in highly confined space was much lower than that in the bulk.

  20. Possible emittance growth induced by nonlinear space charge fields for arbitrary particle distributions

    NASA Astrophysics Data System (ADS)

    Kikuchi, Takashi; Horioka, Kazuhiko

    2016-06-01

    A procedure to obtain a ratio of beam radii at final and initial states in arbitrary particle distributions is proposed, and is applied to the estimation of possible emittance growth for Gaussian and thermal equilibrium distributions. The ratios are estimated for Gaussian and thermal equilibrium distributions as a function of tune depression. The possible emittance growth as a function of tune depression and nonlinear field energy factor is also estimated with and without a constant radius ratio approximation. It is confirmed that the possible emittance growths are almost the same in comparison to the cases with and without the constant radius ratio approximation at each distribution.

  1. Coherent Synchrotron Radiation and Space Charge for a 1-D Bunch on an Arbitrary Planar Orbit

    SciTech Connect

    Warnock, R.L.; /SLAC

    2008-01-08

    Realistic modeling of coherent synchrotron radiation (CSR) and the space charge force in single-pass systems and rings usually requires at least a two-dimensional (2-D) description of the charge/current density of the bunch. Since that leads to costly computations, one often resorts to a 1-D model of the bunch for first explorations. This paper provides several improvements to previous 1-D theories, eliminating unnecessary approximations and physical restrictions.

  2. Crystalline polymorphism induced by charge regulation in ionic membranes.

    PubMed

    Leung, Cheuk-Yui; Palmer, Liam C; Kewalramani, Sumit; Qiao, Baofu; Stupp, Samuel I; Olvera de la Cruz, Monica; Bedzyk, Michael J

    2013-10-08

    The crystallization of molecules with polar and hydrophobic groups, such as ionic amphiphiles and proteins, is of paramount importance in biology and biotechnology. By coassembling dilysine (+2) and carboxylate (-1) amphiphiles of various tail lengths into bilayer membranes at different pH values, we show that the 2D crystallization process in amphiphile membranes can be controlled by modifying the competition of long-range and short-range interactions among the polar and the hydrophobic groups. The pH and the hydrophobic tail length modify the intermolecular packing and the symmetry of their crystalline phase. For hydrophobic tail lengths of 14 carbons (C14), we observe the coassembly into crystalline bilayers with hexagonal molecular ordering via in situ small- and wide-angle X-ray scattering. As the tail length increases, the hexagonal lattice spacing decreases due to an increase in van der Waals interactions, as demonstrated by atomistic molecular dynamics simulations. For C16 and C18 we observe a reentrant crystalline phase transition sequence, hexagonal-rectangular-C-rectangular-P-rectangular-C-hexagonal, as the solution pH is increased from 3 to 10.5. The stability of the rectangular phases, which maximize tail packing, increases with increasing tail length. As a result, for very long tails (C22), the possibility of observing packing symmetries other than rectangular-C phases diminishes. Our work demonstrates that it is possible to systematically exchange chemical and mechanical energy by changing the solution pH value within a range of physiological conditions at room temperature in bilayers of molecules with ionizable groups.

  3. Dynamic Charge Storage in Ionic Liquids-Filled Nanopores: Insight from a Computational Cyclic Voltammetry Study.

    PubMed

    He, Yadong; Huang, Jingsong; Sumpter, Bobby G; Kornyshev, Alexei A; Qiao, Rui

    2015-01-02

    Understanding the dynamic charge storage in nanoporous electrodes with room-temperature ionic liquid electrolytes is essential for optimizing them to achieve supercapacitors with high energy and power densities. Herein, we report coarse-grained molecular dynamics simulations of the cyclic voltammetry of supercapacitors featuring subnanometer pores and model ionic liquids. We show that the cyclic charging and discharging of nanopores are governed by the interplay between the external field-driven ion transport and the sloshing dynamics of ions inside of the pore. The ion occupancy along the pore length depends strongly on the scan rate and varies cyclically during charging/discharging. Unlike that at equilibrium conditions or low scan rates, charge storage at high scan rates is dominated by counterions while the contribution by co-ions is marginal or negative. These observations help explain the perm-selective charge storage observed experimentally. We clarify the mechanisms underlying these dynamic phenomena and quantify their effects on the efficiency of the dynamic charge storage in nanopores.

  4. Multiply charged ionic crystals for nuclear laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Campbell, Corey J.; Steele, Adam V.; Churchill, Layne R.; Depalatis, Michael V.; Naylor, Dave E.; Matsukevich, Dzmitry N.; Chapman, Michael S.; Kuzmich, Alex

    2009-05-01

    Coherent excitation of the electronic states of atoms and molecules with lasers is at the heart of modern spectroscopy and metrology. To extend these techniques to nuclear states would be a tremendous advance. However, the typical excitation energies for nuclear matter are in the keV to MeV energy range, where coherent radiation sources are lacking. In the remarkable case of the ^229Th nucleus, the energy splitting of the ground state doublet is only several eV ^1, which may be within the reach of coherent table-top UV lasers. We have produced laser-cooled crystals of the more abundant ^232Th^3+ in an rf Paul trap. This is the first time that a multiply charged ion has been laser cooled. Our work opens an avenue for excitation of the nuclear transition in a trapped, cold ^229Th^3+ ion. Laser excitation of nuclear states would establish a new bridge between atomic and nuclear physics, with the promise of new levels of metrological precision. ^1 Kroger, L. A. & Reich, C. W. Features of Low-Energy Level Scheme of Th-229 as Observed in Alpha-Decay of U-233. Nucl Phys A 259, 29 (1976).

  5. Effect of surface bilayer charges on the magnetic field around ionic channels

    NASA Astrophysics Data System (ADS)

    Gomes Soares, Marília Amável; Cortez, Celia Martins; Oliveira Cruz, Frederico Alan de; Silva, Dilson

    2017-01-01

    In this work, we present a physic-mathematical model for representing the ion transport through membrane channels, in special Na+ and K+-channels, and discuss the influence of surface bilayer charges on the magnetic field behavior around the ionic current. The model was composed of a set of equations, including: a nonlinear differential Poisson-Boltzmann equation which usually allows to estimate the surface potentials and electric potential profile across membrane; equations for the ionic flux through channel and the ionic current density based on Armstrong's model for Na+ and K+ permeability and other Physics concepts; and a magnetic field expression derived from the classical Ampère equation. Results from computational simulations using the finite element method suggest that the ionic permeability is strongly dependent of surface bilayer charges, the current density through a K+-channel is very less sensible to temperature changes than the current density through a Na+- channel, active Na+-channels do not directly interfere with the K+-channels around, and vice-versa, since the magnetic perturbation generated by an active channel is of short-range.

  6. A multi-physical model for charge and mass transport in a flexible ionic polymer sensor

    NASA Astrophysics Data System (ADS)

    Zhu, Zicai; Asaka, Kinji; Takagi, Kentaro; Aabloo, Alvo; Horiuchi, Tetsuya

    2016-04-01

    An ionic polymer material can generate electrical potential and function as a bio-sensor under a non-uniform deformation. Ionic polymer-metal composite (IPMC) is a typical flexible ionic polymer sensor material. A multi-physical sensing model is presented at first based on the same physical equations in the physical model for IPMC actuator we obtained before. Under an applied bending deformation, water and cation migrate to the direction of outside electrode immediately. Redistribution of cations causes an electrical potential difference between two electrodes. The cation migration is strongly restrained by the generated electrical potential. And the migrated cations will move back to the inner electrode under the concentration diffusion effect and lead to a relaxation of electrical potential. In the whole sensing process, transport and redistribution of charge and mass are revealed along the thickness direction by numerical analysis. The sensing process is a revised physical process of the actuation, however, the transport properties are quite different from those of the later. And the effective dielectric constant of IPMC, which is related to the morphology of the electrode-ionic polymer interface, is proved to have little relation with the sensing amplitude. All the conclusions are significant for ionic polymer sensing material design.

  7. The mean ionic charges of N, Ne, MG, SI and S in solar energetic particle events

    NASA Technical Reports Server (NTRS)

    Luhn, A.; Hovestadt, D.; Klecker, B.; Scholer, M.; Gloeckler, G.; Ipavich, F. M.; Galvin, A. B.; Fan, C. Y.; Fisk, L. A.

    1985-01-01

    The mean ionic charges of nitrogen, neon, magnesium, silicon, and sulfur in solar flare particle events were determined for 12 flares during the time interval from September 1978 to September 1979. The observations were carried out with the MPI/UoMd ULEZEQ Sensor on the ISEE-3 satellite comparing the results with mean charge states established in a hot coronal plasma under equilibrium conditions, different temperatures for different elements are discussed. These range from approx. 2 million K to 7 million K in a single flare. From flare to flare the variation in temperature for each element is less than the variation between different ion species.

  8. Rate limiting activity of charge transfer during lithiation from ionic liquids

    NASA Astrophysics Data System (ADS)

    Rodrigues, Marco-Tulio F.; Lin, Xinrong; Gullapalli, Hemtej; Grinstaff, Mark W.; Ajayan, Pulickel M.

    2016-10-01

    Given the increased use of room temperature ionic liquid electrolytes in Li-ion batteries, due to their non-flammability and negligible volatility, this study evaluates the lithiation kinetics to understand and improve the rate performance of Li-ion batteries. Lithium titanate spinel is used as a model electrode and the electrolyte is composed of LiTFSI and TFSI-coordinated alkoxy-modified phosphonium ionic liquid. Based on the analysis of activation energies for each process, we report that the charge-transfer reaction at the electrode/electrolyte interface is the rate-limiting step for cell operation. This finding is further supported by the observation that a 50-fold decrease in charge-transfer resistance at higher temperatures leads to a significant performance improvement over that of a traditional organic electrolyte at room temperature. Charge-transfer resistance and electrolyte wetting on the electrode surface are critical processes for optimal battery performance, and such processes need to be included when designing new ionic liquids in order to exceed the power density obtained with the use of current carbonate-based electrolytes.

  9. Controlled Clustering in Binary Charged Colloids by Adsorption of Ionic Surfactants.

    PubMed

    Nakamura, Yuki; Okachi, Manami; Toyotama, Akiko; Okuzono, Tohru; Yamanaka, Junpei

    2015-12-15

    We report on the controlled clustering of oppositely charged colloidal particles by the adsorption of ionic surfactants, which tunes charge numbers Z of particles. In particular, we studied the heteroclustering of submicron-sized polystyrene (PS) and silica particles, both of which are negatively charged, in the presence of cetylpyridinium chloride (CPC), a cationic surfactant. The surfactant concentration Csurf was selected below the critical micelle concentration. As CPC molecules were adsorbed, Z values of the PS and silica particles decreased, inverting to positive when Csurf exceeded the isoelectric point Ciep. Hydrophobic PS particles exhibited much lower Ciep than hydrophilic silica particles. At Csurf valuess between their Ciep values, the particles were oppositely charged, and clustering was enabled. To explain the clustering behavior, we investigated adsorption isotherms of the CPC and screened-Coulomb-type pair potential. Expected applications of the present findings are the control of colloidal associations and construction of various particle types into heterogeneous colloidal clusters.

  10. New Estimates of Inferred Ionic Charge States for Solar Energetic Particle Events with ACE and STEREO

    NASA Astrophysics Data System (ADS)

    Labrador, A. W.; Sollitt, L. S.; Cohen, C. M.; Cummings, A. C.; Leske, R. A.; Mason, G. M.; Mewaldt, R. A.; Stone, E.; von Rosenvinge, T. T.; Wiedenbeck, M. E.

    2012-12-01

    Solar energetic particle (SEP) mean ionic charge states can depend on source temperatures and populations (e.g. seed populations) and conditions during acceleration and transport such as stripping. Multi-spacecraft observations of charge states from widely separated spacecraft may reveal evidence for seed populations that vary with longitude. In this presentation, we report new estimates of inferred high energy ionic charge states using the Sollitt et al. (2008) method that fits SEP energy-dependent decay times for SEP event elements to derive mean charge states. In the method, intensity decay times during SEP events are fitted for each element for various energies, and then the energy dependence of the decay times is fitted for each element. Finally, charge-to-mass ratios relative to that of a calibration element (carbon in this case) are obtained, and when Q(C)=5.9 is assumed for calibration, mean charge states for other elements can be inferred. Previously, ACE/SIS and ACE/ULEIS data were applied to three SEP events (Nov. 6, 1997; Nov. 4, 2001; Apr. 21, 2002) with this method, and last year, we reported new results for the Dec. 6, 2006 SEP event compatible with SAMPEX/MAST results. Additional work continues to generalize and extend the software to use publicly available online data from ACE and the two STEREO spacecraft. Energy ranges are those covered by the instruments on ACE (e.g. reference element C at <.1 MeV/nuc from ULEIS to ~64 MeV/nuc from SIS) and on STEREO (e.g. C at 3.2 - 33 MeV/nuc from LET). Initial candidate SEP events for multi-spacecraft charge state estimates are those of Mar. 8, 2011, Mar. 21, 2011, Jan. 24, 2012, and Mar. 4, 2012. Results from events observed by single spacecraft may also be reported.

  11. Dynamics of Charged Species in Ionic-Neutral Block Copolymer and Surfactant Complexes

    DOE PAGES

    Borreguero, Jose M.; Pincus, Philip A.; Sumpter, Bobby G.; ...

    2017-06-21

    Structure–property relationships of ionic block copolymer (BCP) surfactant complexes are critical toward the progress of favorable engineering design of efficient charge-transport materials. In this paper, molecular dynamics simulations are used to understand the dynamics of charged-neutral BCP and surfactant complexes. The dynamics are examined for two different systems: charged-neutral double-hydrophilic and hydrophobic–hydrophilic block copolymers with oppositely charged surfactant moieties. The dynamics of the surfactant head, tails, and charges are studied for five different BCP volume fractions. We observe that the dynamics of the different species solely depend on the balance between electrostatic and entropic interactions between the charged species andmore » the neutral monomers. The favorable hydrophobic–hydrophobic interactions and the unfavorable hydrophobic–hydrophilic interactions determine the mobilities of the monomers. The dynamical properties of the charge species influence complex formation. Structural relaxations exhibit length-scale dependent behavior, with slower relaxation at the radius of gyration length-scale and faster relaxation at the segmental length-scale, consistent with previous results. The dynamical analysis correlates ion-exchange kinetics to the self-assembly behavior of the complexes.« less

  12. Cation-cation clusters in ionic liquids: Cooperative hydrogen bonding overcomes like-charge repulsion.

    PubMed

    Knorr, Anne; Ludwig, Ralf

    2015-12-02

    Direct spectroscopic evidence for H-bonding between like-charged ions is reported for the ionic liquid, 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate. New infrared bands in the OH frequency range appear at low temperatures indicating the formation of H-bonded cation-cation clusters similar to those known for water and alcohols. Supported by DFT calculations, these vibrational bands can be assigned to attractive interaction between the hydroxyl groups of the cations. The repulsive Coulomb interaction is overcome by cooperative hydrogen bonding between ions of like charge. The transition energy from purely cation-anion interacting configurations to those including cation-cation H-bonds is determined to be 3-4 kJmol(-1). The experimental findings and DFT calculations strongly support the concept of anti-electrostatic hydrogen bonds (AEHBs) as recently suggested by Weinhold and Klein. The like-charge configurations are kinetically stabilized with decreasing temperatures.

  13. Conformations of polyelectrolyte macromolecules with different charge density in solutions of different ionic strengths

    NASA Astrophysics Data System (ADS)

    Dommes, O. A.; Okatova, O. V.; Pavlov, G. M.

    2016-11-01

    Studies of charged polymer chains are interesting in both fundamental and applied aspects. Especially, polyelectrolytes attract huge attention of researchers due to their ability to form interpolymer complexes with synthetic and biopolymers. The study was carried out on the fractions of hydrophilic copolymers of N-methyl-N-vinyl acetamide and N-methyl-N-vinyl amine hydrochloride of different degrees of polymerization and of different charge density using methods of molecular hydrodynamics. Hydrodynamic and conformational characteristics as well as molar masses of isolated molecules were estimated. In addition, the intrinsic viscosity of fractions was studied at the extreme ionic strengths - in distilled water (∼10-6M) and in 6M NaCl. Scaling relations for intrinsic viscosity, sedimentation and translational diffusion coefficients with molar mass were obtained. Conformational behavior of macromolecules with different linear charge density was compared.

  14. Effect of cation symmetry on the organization of ionic liquids near a charged mica surface.

    PubMed

    Payal, Rajdeep Singh; Balasubramanian, Sundaram

    2014-07-16

    Atomistic molecular dynamics simulations have been carried out to understand the effect of the symmetry of cations on the microscopic organization of ionic liquids near a charged mica surface. Ionic liquids with a 1,3-alkylimidazolium ([C(n)C(m)im](+)) cation and a bis(trifluoromethylsulfonyl)imide ([NTf2](-)) anion were investigated. Apart from symmetry, the length of the alkyl group attached to the cation is found to crucially determine the ion structure near the solid surface. In the first adsorbed layer, the ring planes of cations with shorter alkyl groups (less than four carbon atoms) are oriented either parallel or perpendicular to the surface. However, cations with longer alkyl tails are exclusively observed to have their ring planes parallel to the mica surface. The alkyl groups too show a similar dependence of their orientation on the tail length. Further, symmetric cations with alkyl groups of intermediate length are more highly structured at the interface than their asymmetric counterparts.

  15. Optical spin-to-orbital angular momentum conversion in ultra-thin metasurfaces with arbitrary topological charges

    SciTech Connect

    Bouchard, Frédéric; De Leon, Israel; Schulz, Sebastian A.; Upham, Jeremy; Karimi, Ebrahim; Boyd, Robert W.

    2014-09-08

    Orbital angular momentum associated with the helical phase-front of optical beams provides an unbounded “space” for both classical and quantum communications. Among the different approaches to generate and manipulate orbital angular momentum states of light, coupling between spin and orbital angular momentum allows a faster manipulation of orbital angular momentum states because it depends on manipulating the polarisation state of light, which is simpler and generally faster than manipulating conventional orbital angular momentum generators. In this work, we design and fabricate an ultra-thin spin-to-orbital angular momentum converter, based on plasmonic nano-antennas and operating in the visible wavelength range that is capable of converting spin to an arbitrary value of orbital angular momentum ℓ. The nano-antennas are arranged in an array with a well-defined geometry in the transverse plane of the beam, possessing a specific integer or half-integer topological charge q. When a circularly polarised light beam traverses this metasurface, the output beam polarisation switches handedness and the orbital angular momentum changes in value by ℓ=±2qℏ per photon. We experimentally demonstrate ℓ values ranging from ±1 to ±25 with conversion efficiencies of 8.6% ± 0.4%. Our ultra-thin devices are integratable and thus suitable for applications in quantum communications, quantum computations, and nano-scale sensing.

  16. Theory of Frequency-Dependent Polarization of General Planar Electrodes with Zeta Potentials of Arbitrary Magnitude in Ionic Media.

    PubMed

    Scott; Paul; Kaler

    2000-10-15

    Electrode polarization effects have long aggravated the efforts of low frequency analysis, particularly those investigations carried out on biological material or in highly conductive media. Beginning from elementary equations of electrostatics and hydrodynamics, a comprehensive model is devised to account for the screening of a general planar electrode by an ionic double layer. The surface geometry of the planar electrode is left unspecified to include any type of micromachined array. Building on the previous work by DeLacey and White (1982, J. Chem. Soc. Faraday Trans. 2 78, 457) using a variational theorem, we extend their numerical results with compact analytic solutions, analogous to the Debye-Hückel potential for dc systems, but applicable now to dynamic ac experiments. The variational approach generates functions that are not restricted by perturbation expansions or numerical convergence, representing optimal approximations to the exact solutions. Copyright 2000 Academic Press.

  17. Electrical charging effects on the sliding friction of a model nano-confined ionic liquid.

    PubMed

    Capozza, R; Benassi, A; Vanossi, A; Tosatti, E

    2015-10-14

    Recent measurements suggest the possibility to exploit ionic liquids (ILs) as smart lubricants for nano-contacts, tuning their tribological and rheological properties by charging the sliding interfaces. Following our earlier theoretical study of charging effects on nanoscale confinement and squeezout of a model IL, we present here molecular dynamics simulations of the frictional and lubrication properties of that model under charging conditions. First, we describe the case when two equally charged plates slide while being held together to a confinement distance of a few molecular layers. The shear sliding stress is found to rise strongly and discontinuously as the number of IL layers decreases stepwise. However, the shear stress shows, within each given number of layers, only a weak dependence upon the precise value of the normal load, a result in agreement with data extracted from recent experiments. We subsequently describe the case of opposite charging of the sliding plates and follow the shear stress when the charging is slowly and adiabatically reversed in the course of time, under fixed load. Despite the fixed load, the number and structure of the confined IL layers change with changing charge, and that in turn drives strong friction variations. The latter involves first of all charging-induced freezing of the IL film, followed by a discharging-induced melting, both made possible by the nanoscale confinement. Another mechanism for charging-induced frictional changes is a shift of the plane of maximum shear from mid-film to the plate-film interface, and vice versa. While these occurrences and results invariably depend upon the parameters of the model IL and upon its specific interaction with the plates, the present study helps identifying a variety of possible behavior, obtained under very simple assumptions, while connecting it to an underlying equilibrium thermodynamics picture.

  18. Electrical charging effects on the sliding friction of a model nano-confined ionic liquid

    NASA Astrophysics Data System (ADS)

    Capozza, R.; Benassi, A.; Vanossi, A.; Tosatti, E.

    2015-10-01

    Recent measurements suggest the possibility to exploit ionic liquids (ILs) as smart lubricants for nano-contacts, tuning their tribological and rheological properties by charging the sliding interfaces. Following our earlier theoretical study of charging effects on nanoscale confinement and squeezout of a model IL, we present here molecular dynamics simulations of the frictional and lubrication properties of that model under charging conditions. First, we describe the case when two equally charged plates slide while being held together to a confinement distance of a few molecular layers. The shear sliding stress is found to rise strongly and discontinuously as the number of IL layers decreases stepwise. However, the shear stress shows, within each given number of layers, only a weak dependence upon the precise value of the normal load, a result in agreement with data extracted from recent experiments. We subsequently describe the case of opposite charging of the sliding plates and follow the shear stress when the charging is slowly and adiabatically reversed in the course of time, under fixed load. Despite the fixed load, the number and structure of the confined IL layers change with changing charge, and that in turn drives strong friction variations. The latter involves first of all charging-induced freezing of the IL film, followed by a discharging-induced melting, both made possible by the nanoscale confinement. Another mechanism for charging-induced frictional changes is a shift of the plane of maximum shear from mid-film to the plate-film interface, and vice versa. While these occurrences and results invariably depend upon the parameters of the model IL and upon its specific interaction with the plates, the present study helps identifying a variety of possible behavior, obtained under very simple assumptions, while connecting it to an underlying equilibrium thermodynamics picture.

  19. Electrical charging effects on the sliding friction of a model nano-confined ionic liquid

    SciTech Connect

    Capozza, R.; Vanossi, A.; Benassi, A.; Tosatti, E.

    2015-10-14

    Recent measurements suggest the possibility to exploit ionic liquids (ILs) as smart lubricants for nano-contacts, tuning their tribological and rheological properties by charging the sliding interfaces. Following our earlier theoretical study of charging effects on nanoscale confinement and squeezout of a model IL, we present here molecular dynamics simulations of the frictional and lubrication properties of that model under charging conditions. First, we describe the case when two equally charged plates slide while being held together to a confinement distance of a few molecular layers. The shear sliding stress is found to rise strongly and discontinuously as the number of IL layers decreases stepwise. However, the shear stress shows, within each given number of layers, only a weak dependence upon the precise value of the normal load, a result in agreement with data extracted from recent experiments. We subsequently describe the case of opposite charging of the sliding plates and follow the shear stress when the charging is slowly and adiabatically reversed in the course of time, under fixed load. Despite the fixed load, the number and structure of the confined IL layers change with changing charge, and that in turn drives strong friction variations. The latter involves first of all charging-induced freezing of the IL film, followed by a discharging-induced melting, both made possible by the nanoscale confinement. Another mechanism for charging-induced frictional changes is a shift of the plane of maximum shear from mid-film to the plate-film interface, and vice versa. While these occurrences and results invariably depend upon the parameters of the model IL and upon its specific interaction with the plates, the present study helps identifying a variety of possible behavior, obtained under very simple assumptions, while connecting it to an underlying equilibrium thermodynamics picture.

  20. Ionic Charge Transfer Complex Induced Visible Light Harvesting and Photocharge Generation in Perovskite.

    PubMed

    Ng, Tsz-Wai; Thachoth Chandran, Hrisheekesh; Chan, Chiu-Yee; Lo, Ming-Fai; Lee, Chun-Sing

    2015-09-16

    Organometal trihalide perovskite has recently emerged as a new class of promising material for high efficiency solar cells applications. While excess ions in perovskites are recently getting a great deal of attention, there is so far no clear understanding on both their formation and relating ions interaction to the photocharge generation in perovskite. Herein, we showed that tremendous ions indeed form during the initial stage of perovskite formation when the organic methylammonium halide (MAXa, Xa=Br and I) meets the inorganic PbXb2 (Xb=Cl, Br, I). The strong charge exchanges between the Pb2+ cations and Xa- anions result in formation of ionic charge transfer complexes (iCTC). MAXa parties induce empty valence electronic states within the forbidden bandgap of PbXb2. The strong surface dipole provide sufficient driving force for sub-bandgap electron transition with energy identical to the optical bandgap of forming perovskites. Evidences from XPS/UPS and photoluminescence studies showed that the light absorption, exciton dissociation, and photocharge generation of the perovskites are closely related to the strong ionic charge transfer interactions between Pb2+ and Xa- ions in the perovskite lattices. Our results shed light on mechanisms of light harvesting and subsequent free carrier generation in perovskites.

  1. Electrostatics in ionic solution : work and energy, charge regulation, and in homogeneous surfaces

    NASA Astrophysics Data System (ADS)

    Boon, N. J. H.

    2012-01-01

    This thesis concerns the electrostatic properties of charged objects that are immersed into an ionic solvent, for example water with dissolved salt. Typically, the ions inside such a solvent form layers of countercharge close to the charged objects, causing `screening' of the charges. By employing Density Functional Theory (DFT) one is able integrate out the degrees of freedom of the ions and find relations that describe the effective electrostatic properties of the charged objects. One finds that for a large parameter regime the electrostatic potential everywhere in the solvent should satisfy the well established Poisson-Boltzmann equation. We study the electrostatic capacity of porous electrodes in salt water, and derive a method to reversibly extract electric energy from salinity gradients that occur for example at an estuary where sea- and river water meet. However, in the main part of this thesis we consider charged colloidal particles, and study the effect of internal porosity as well as heterogeneities in the surface-charge density (patchy particles) on colloid-colloid interactions. In a far-field analysis we derive equations that describe these interactions for particles with nonvanishing multipole moments, for example `Janus' colloids with a strong dipole component. If such particles locally have a high surface charge density, then the nonlinear dependence of the counterion density on the local charge density leads to a generalisation of charge renormalisation from purely monopolar to dipolar, quadrupolar, etc., including `mode couplings'. In a more detailed approach, which turns out to be important for colloidal particles at smaller distances from each other, we consider the chemical processes that lead to surface charge, and specify a parameter regime in which charging can be described by a single `chargeability' parameter. As we show in this thesis, the phase diagrams we obtain within this regime have many similarities with a `constant surface potential

  2. Spectroscopic Evidence for Clusters of Like-Charged Ions in Ionic Liquids Stabilized by Cooperative Hydrogen Bonding.

    PubMed

    Knorr, Anne; Stange, Peter; Fumino, Koichi; Weinhold, Frank; Ludwig, Ralf

    2016-02-16

    Direct spectroscopic evidence for hydrogen-bonded clusters of like-charged ions is reported for ionic liquids. The measured infrared O-H vibrational bands of the hydroxyethyl groups in the cations can be assigned to the dispersion-corrected DFT calculated frequencies of linear and cyclic clusters. Compensating the like-charge Coulomb repulsion, these cationic clusters can range up to cyclic tetramers resembling molecular clusters of water and alcohols. These ionic clusters are mainly present at low temperature and show strong cooperative effects in hydrogen bonding. DFT-D3 calculations of the pure multiply charged clusters suggest that the attractive hydrogen bonds can compete with repulsive Coulomb forces.

  3. Ionic charge transport between blockages: Sodium cation conduction in freshly excised bulk brain tissue

    SciTech Connect

    Emin, David; Akhtari, Massoud; Ellingson, B. M.; Mathern, G. W.

    2015-08-15

    We analyze the transient-dc and frequency-dependent electrical conductivities between blocking electrodes. We extend this analysis to measurements of ions’ transport in freshly excised bulk samples of human brain tissue whose complex cellular structure produces blockages. The associated ionic charge-carrier density and diffusivity are consistent with local values for sodium cations determined non-invasively in brain tissue by MRI (NMR) and diffusion-MRI (spin-echo NMR). The characteristic separation between blockages, about 450 microns, is very much shorter than that found for sodium-doped gel proxies for brain tissue, >1 cm.

  4. The entrance system laboratory prototype for an advanced mass and ionic charge composition experiment.

    PubMed

    Allegrini, F; Desai, M I; Livi, R; Livi, S; McComas, D J; Randol, B

    2009-10-01

    Electrostatic analyzers (ESA) have been used extensively for the characterization of plasmas in a variety of space environments. They vary in shape, geometry, and size and are adapted to the specific particle population to be measured and the configuration of the spacecraft. Their main function is to select the energy per charge of the particles within a passband. An energy-per-charge range larger than that of the passband can be sampled by varying the voltage difference between the ESA electrodes. The voltage sweep takes time and reduces the duty cycle for a particular energy-per-charge passband. Our design approach for an advanced mass and ionic charge composition experiment (AMICCE) has a novel electrostatic analyzer that essentially serves as a spectrograph and selects ions simultaneously over a broad range of energy-per-charge (E/q). Only three voltage settings are required to cover the entire range from approximately 10 to 270 keV/q, thus dramatically increasing the product of the geometric factor times the duty cycle when compared with other instruments. In this paper, we describe the AMICCE concept with particular emphasis on the prototype of the entrance system (ESA and collimator), which we designed, developed, and tested. We also present comparisons of the laboratory results with electrostatic simulations.

  5. Protein diffusion through charged nanopores with different radii at low ionic strength.

    PubMed

    Stroeve, Pieter; Rahman, Masoud; Naidu, Lekkala Dev; Chu, Gilbert; Mahmoudi, Morteza; Ramirez, Patricio; Mafe, Salvador

    2014-10-21

    The diffusion of two similar molecular weight proteins, bovine serum albumin (BSA) and bovine haemoglobin (BHb), through nanoporous charged membranes with a wide range of pore radii is studied at low ionic strength. The effects of the solution pH and the membrane pore diameter on the pore permeability allow quantifying the electrostatic interaction between the charged pore and the protein. Because of the large screening Debye length, both surface and bulk diffusion occur simultaneously. By increasing the pore diameter, the permeability tends to the bulk self-diffusion coefficient for each protein. By decreasing the pore diameter, the charges on the pore surface electrostatically hinder the transport even at the isoelectric point of the protein. Surprisingly, even at pore sizes 100 times larger than the protein, the electrostatic hindrance still plays a major role in the transport. The experimental data are qualitatively explained using a two-region model for the membrane pore and approximated equations for the pH dependence of the protein and pore charges. The experimental and theoretical results should be useful for designing protein separation processes based on nanoporous charged membranes.

  6. Ionic charge states of N, Ne, Mg, Si and S in solar energetic particle events

    NASA Technical Reports Server (NTRS)

    Luhn, A.; Klecker, B.; Hovestadt, D.; Scholer, M.; Gloeckler, G.; Ipavich, F. M.; Fan, C. Y.; Fisk, L. A.

    1984-01-01

    The mean ionic charges and source-region temperatures of flare-accelerated N, Ne, Mg, Si and S in three large solar-energetic-particle events during 1978-1979 are determined from ISEE-3 observations, extending the findings of Hovestadt et al. (1981) and Gloeckler et al. (1981) for C, He, O, and Fe. The results are presented in tables and graphs, and the charge states are shown to correspond to different source temperatures even in the same flare, assuming equilibration in the hot plasma. The electron temperatures range from 2 x 10 to the 6th K for C, N, O, Si, and S, 4 x 10 to the 6th K for Ne and Fe, and 7 x 10 to the 6th K for Mg. The possibility that these temperature inconsistencies reflect different stages in the approach to equilibrium is considered.

  7. Determination of Surface Charge of Titanium Dioxide (Anatase) at High Ionic Strength

    NASA Astrophysics Data System (ADS)

    Schoonen, M. A.; Strongin, D. R.

    2014-12-01

    Charge development on mineral surfaces is an important control on the fate of minor and trace elements in a wide range of environments, including in possible radioactive waste repositories. Formation waters have often a high ionic strength. In this study, we determined the zeta potential (ζ) of anatase in potassium chloride solutions with concentrations up to 3M (25°C). The zeta potential is the potential at the hydrodynamic shear plane. In this study, we made use of the electro-acoustic effect. This effect is based on the development of a measureable potential/current when the electrical double layer outside the shearplane is separated from a charged particle through rapid oscillation induced by a sound wave. The advantage of this type of measurement is that the particles are not subjected to a high electric field (common to typical zeta potential measurements), which leads to electrode reactions and a shift of solution pH. Measurements were collected by subtracting the ion vibration current (IVI) due to the presence of potassium and chloride ions from the CVI. The correction is necessary for measurements in solutions with I > 0.25 M. This subtraction was done at each of the measurement conditions by centrifuging the slurrly, measuring the IVI of the supernatant, reconstituting the slurry, and then measuring CVI of the slurry. Subtraction of IVI at each condition is critical because IVI changes with pH and accounts for most of raw signal. The results show that the anatase isoelectric point shifts from a pH ~6.5 to a value of ~4.5 at 1M KCl. At ionic strength in excess of 1 M KCl, the surface appears to be slightly negatively charged accross the pH range accessible by this technique (pH 2.5-10). The loss of an isoelectric point suggests that KCl is no longer an indifferent electrolyte at 1 M KCl and higher. The results are in disagreement with earlier measurements in which anatase was shown to have a positive charge at high ionic strength across the pH scale. The

  8. β-Lactoglobulin (BLG) binding to highly charged cationic polymer-grafted magnetic nanoparticles: effect of ionic strength.

    PubMed

    Qin, Li; Xu, Yisheng; Han, Haoya; Liu, Miaomiao; Chen, Kaimin; Wang, Siyi; Wang, Jie; Xu, Jun; Li, Li; Guo, Xuhong

    2015-12-15

    Poly(2-(methacryloyloxy)ethyltrimethyl ammonium chloride) (PMATAC) modified magnetic nanoparticles (NPs) with a high zeta potential of ca. 50mV were synthesized by atom transfer radical polymerization (ATRP). The prepared NPs consist of a magnetic core around 13nm and a PMATAC shell around 20nm attached on the surface of magnetic nanoparticles. Thermodynamic binding parameters between β-lactoglobulin and these polycationic NPs were investigated at different ionic strengths by high-resolution turbidimetry, dynamic light scattering (DLS), and isothermal titration calorimetry (ITC). Both turbidity and ITC show that binding affinities for BLG display a non-monotonic ionic strength dependence trend and a maximum appears at ionic strength of 50mM. Such observation should arise from the coeffects of protein charge anisotropy visualized by DelPhi electrostatic modeling and the strong electrostatic repulsion among highly charged NPs at a variety of ionic strengths.

  9. Estimation of acidity constants, ionic mobilities and charges of antimicrobial peptides by capillary electrophoresis.

    PubMed

    Tůmová, Tereza; Monincová, Lenka; Čeřovský, Václav; Kašička, Václav

    2016-12-01

    Capillary electrophoresis (CE) was employed for the determination of thermodynamic acidity constants (pKa ) and actual ionic mobilities of polycationic antimicrobial peptides (AMPs). The effective electrophoretic mobilities of AMPs were measured by CE in a series of the background electrolytes within a wide pH range (2.00-12.25), at constant ionic strength (25 mM) and ambient temperature, using polybrene coated fused silica capillaries to suppress sorption of cationic AMPs to the capillary wall. Eventually, Haarhoff-Van der Linde peak fitting function was used for the determination of correct migration times of some AMPs peaks that were distorted by electromigration dispersion. The measured effective mobilities were corrected to 25°C. Mixed acidity constants, pKa,i mix , and actual ionic mobilities, mi , of AMPs were determined by the nonlinear regression analysis of pH dependence of their effective mobilities. The pKa,i mix values were recalculated to thermodynamic pKa s using the Debye-Hückel theory. Thermodynamic pKa of imidazolium group of histidine residues was found to be in the range 3.72-4.98, pKa of α-NH3(+) group was in the range 6.14-6.93, and pKa of ε-NH3(+) group of lysine spanned the interval 7.26-9.84, depending on the particular amino acid sequence of the AMPs. Actual ionic mobilities of AMPs with positive charges from one to six elementary units achieved values (9.8 - 36.5) × 10(-9) m(2) V(-1) s(-1) . © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Benchmark calculations of nonconservative charged-particle swarms in dc electric and magnetic fields crossed at arbitrary angles.

    PubMed

    Dujko, S; White, R D; Petrović, Z Lj; Robson, R E

    2010-04-01

    A multiterm solution of the Boltzmann equation has been developed and used to calculate transport coefficients of charged-particle swarms in gases under the influence of electric and magnetic fields crossed at arbitrary angles when nonconservative collisions are present. The hierarchy resulting from a spherical-harmonic decomposition of the Boltzmann equation in the hydrodynamic regime is solved numerically by representing the speed dependence of the phase-space distribution function in terms of an expansion in Sonine polynomials about a Maxwellian velocity distribution at an internally determined temperature. Results are given for electron swarms in certain collisional models for ionization and attachment over a range of angles between the fields and field strengths. The implicit and explicit effects of ionization and attachment on the electron-transport coefficients are considered using physical arguments. It is found that the difference between the two sets of transport coefficients, bulk and flux, resulting from the explicit effects of nonconservative collisions, can be controlled either by the variation in the magnetic field strengths or by the angles between the fields. In addition, it is shown that the phenomena of ionization cooling and/or attachment cooling/heating previously reported for dc electric fields carry over directly to the crossed electric and magnetic fields. The results of the Boltzmann equation analysis are compared with those obtained by a Monte Carlo simulation technique. The comparison confirms the theoretical basis and numerical integrity of the moment method for solving the Boltzmann equation and gives a set of well-established data that can be used to test future codes and plasma models.

  11. Constraints on CME Evolution from in situ Observations of Ionic Charge States

    NASA Technical Reports Server (NTRS)

    Gruesbeck, Jacob R.; Lepri, Susan T.; Zurbuchen, Thomas H.; Antiochos, Spiro K.

    2010-01-01

    We present a novel procedure for deriving the physical properties of Coronal Mass Ejections (CMES) in the corona. Our methodology uses in-situ measurements of ionic charge states of C, O, Si and Fe in the heliosphere and interprets them in the context of a model for the early evolution of ICME plasma, between 2 - 5 R-solar. We find that the data can be fit only by an evolution that consists of an initial heating of the plasma, followed by an expansion that ultimately results in cooling. The heating profile is consistent with a compression of coronal plasma due to flare reconnect ion jets and an expansion cooling due to the ejection, as expected from the standard CME/flare model. The observed frozen-in ionic charge states reflect this time-history and, therefore, provide important constraints for the heating and expansion time-scales, as well as the maximum temperature the CME plasma is heated to during its eruption. Furthermore, our analysis places severe limits on the possible density of CME plasma in the corona. We discuss the implications of our results for CME models and for future analysis of ICME plasma composition.

  12. Influence of Solute Charge and Pyrrolidinium Ionic Liquid Alkyl Chain Length on Probe Rotational Reorientation Dynamics

    SciTech Connect

    Guo, Jianchang; Mahurin, Shannon Mark; Baker, Gary A; Hillesheim, Patrick C; Dai, Sheng; Shaw, Robert W

    2014-01-01

    In recent years, the effect of molecular charge on the rotational dynamics of probe solutes in room temperature ionic liquids (RTILs) has been a subject of growing interest. For the purpose of extending our understanding of charged solute behavior within RTILs, we have studied the rotational dynamics of three illustrative xanthene fluorescent probes within a series of N-alkylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([Cnmpyr][Tf2N]) RTILs with different n-alkyl chain lengths (n = 3, 4, 6, 8, or 10) using time-resolved fluorescence anisotropy decay. The rotational dynamics of the neutral probe rhodamine B dye lies between the stick and slip boundary conditions due to the influence of specific hydrogen bonding interactions. The rotation of the negatively-charged sulforhodamine 640 is slower than that of its positively-charged counterpart rhodamine 6G. An analysis based upon Stokes-Einstein-Debye hydrodynamics indicates that SR640 adheres to stick boundary conditions due to specific interactions, whereas the faster rotation of R6G is attributed to weaker electrostatic interactions. No dependence of the rotational dynamics on the solvent alkyl chain length was observed for any of the three dyes, suggesting that the specific interactions between dyes and RTILs are independent of this solvent parameter.

  13. Communication: Modeling of concentration dependent water diffusivity in ionic solutions: Role of intermolecular charge transfer.

    PubMed

    Yao, Yi; Berkowitz, Max L; Kanai, Yosuke

    2015-12-28

    The translational diffusivity of water in solutions of alkali halide salts depends on the identity of ions, exhibiting dramatically different behavior even in solutions of similar salts of NaCl and KCl. The water diffusion coefficient decreases as the salt concentration increases in NaCl. Yet, in KCl solution, it slightly increases and remains above bulk value as salt concentration increases. Previous classical molecular dynamics simulations have failed to describe this important behavior even when polarizable models were used. Here, we show that inclusion of dynamical charge transfer among water molecules produces results in a quantitative agreement with experiments. Our results indicate that the concentration-dependent diffusivity reflects the importance of many-body effects among the water molecules in aqueous ionic solutions. Comparison with quantum mechanical calculations shows that a heterogeneous and extended distribution of charges on water molecules around the ions due to ion-water and also water-water charge transfer plays a very important role in controlling water diffusivity. Explicit inclusion of the charge transfer allows us to model accurately the difference in the concentration-dependent water diffusivity between Na(+) and K(+) ions in simulations, and it is likely to impact modeling of a wide range of systems for medical and technological applications.

  14. Communication: Modeling of concentration dependent water diffusivity in ionic solutions: Role of intermolecular charge transfer

    SciTech Connect

    Yao, Yi; Berkowitz, Max L. E-mail: ykanai@unc.edu; Kanai, Yosuke E-mail: ykanai@unc.edu

    2015-12-28

    The translational diffusivity of water in solutions of alkali halide salts depends on the identity of ions, exhibiting dramatically different behavior even in solutions of similar salts of NaCl and KCl. The water diffusion coefficient decreases as the salt concentration increases in NaCl. Yet, in KCl solution, it slightly increases and remains above bulk value as salt concentration increases. Previous classical molecular dynamics simulations have failed to describe this important behavior even when polarizable models were used. Here, we show that inclusion of dynamical charge transfer among water molecules produces results in a quantitative agreement with experiments. Our results indicate that the concentration-dependent diffusivity reflects the importance of many-body effects among the water molecules in aqueous ionic solutions. Comparison with quantum mechanical calculations shows that a heterogeneous and extended distribution of charges on water molecules around the ions due to ion-water and also water-water charge transfer plays a very important role in controlling water diffusivity. Explicit inclusion of the charge transfer allows us to model accurately the difference in the concentration-dependent water diffusivity between Na{sup +} and K{sup +} ions in simulations, and it is likely to impact modeling of a wide range of systems for medical and technological applications.

  15. Communication: Modeling of concentration dependent water diffusivity in ionic solutions: Role of intermolecular charge transfer

    NASA Astrophysics Data System (ADS)

    Yao, Yi; Berkowitz, Max L.; Kanai, Yosuke

    2015-12-01

    The translational diffusivity of water in solutions of alkali halide salts depends on the identity of ions, exhibiting dramatically different behavior even in solutions of similar salts of NaCl and KCl. The water diffusion coefficient decreases as the salt concentration increases in NaCl. Yet, in KCl solution, it slightly increases and remains above bulk value as salt concentration increases. Previous classical molecular dynamics simulations have failed to describe this important behavior even when polarizable models were used. Here, we show that inclusion of dynamical charge transfer among water molecules produces results in a quantitative agreement with experiments. Our results indicate that the concentration-dependent diffusivity reflects the importance of many-body effects among the water molecules in aqueous ionic solutions. Comparison with quantum mechanical calculations shows that a heterogeneous and extended distribution of charges on water molecules around the ions due to ion-water and also water-water charge transfer plays a very important role in controlling water diffusivity. Explicit inclusion of the charge transfer allows us to model accurately the difference in the concentration-dependent water diffusivity between Na+ and K+ ions in simulations, and it is likely to impact modeling of a wide range of systems for medical and technological applications.

  16. Stabilization of enzymes in ionic liquids via modification of enzyme charge.

    PubMed

    Nordwald, Erik M; Kaar, Joel L

    2013-09-01

    Due to the propensity of ionic liquids (ILs) to inactivate enzymes, the development of strategies to improve enzyme utility in these solvents is critical to fully exploit ILs for biocatalysis. We have developed a strategy to broadly improve enzyme utility in ILs based on elucidating the effect of charge modifications on the function of enzymes in IL environments. Results of stability studies in aqueous-IL mixtures indicated a clear connection between the ratio of enzyme-containing positive-to-negative sites and enzyme stability in ILs. Stability studies of the effect of [BMIM][Cl] and [EMIM][EtSO4 ] on chymotrypsin specifically found an optimum ratio of positively-charged amine-to-negatively-charged acid groups (0.39). At this ratio, the half-life of chymotrypsin was increased 1.6- and 4.3-fold relative to wild-type chymotrypsin in [BMIM][Cl] and [EMIM][EtSO4 ], respectively. The half-lives of lipase and papain were similarly increased as much as 4.0 and 2.4-fold, respectively, in [BMIM][Cl] by modifying the ratio of positive-to-negative sites of each enzyme. More generally, the results of stability studies found that modifications that reduce the ratio of enzyme-containing positive-to-negative sites improve enzyme stability in ILs. Understanding the impact of charge modification on enzyme stability in ILs may ultimately be exploited to rationally engineer enzymes for improved function in IL environments.

  17. Estimation of the ionic charge of non-metallic species into an electrical discharge through a web application

    NASA Astrophysics Data System (ADS)

    Pérez Gutiérrez, B. R.; Vera-Rivera, F. H.; Niño, E. D. V.

    2016-08-01

    Estimate the ionic charge generated in electrical discharges will allow us to know more accurately the concentration of ions implanted on the surfaces of nonmetallic solids. For this reason, in this research a web application was developed to allow us to calculate the ionic charge generated in an electrical discharge from the experimental parameters established in an ion implantation process performed in the JUPITER (Joint Universal Plasma and Ion Technologies Experimental Reactor) reactor. The estimated value of the ionic charge will be determined from data acquired on an oscilloscope, during startup and shutdown of electrical discharge, which will then be analyzed and processed. The study will provide best developments with regard to the application of ion implantation in various industrial sectors.

  18. Time-dependent density functional theory for the charging kinetics of electric double layer containing room-temperature ionic liquids

    SciTech Connect

    Lian, Cheng; Zhao, Shuangliang; Liu, Honglai; Wu, Jianzhong

    2016-11-29

    Understanding the charging kinetics of electric double layers is of fundamental importance for the design and development of novel electrochemical devices such as supercapacitors and field-effect transistors. In this paper, we study the dynamic behavior of room-temperature ionic liquids using a classical time-dependent density functional theory that accounts for the molecular excluded volume effects, the electrostatic correlations, and the dispersion forces. While the conventional models predict a monotonic increase of the surface charge with time upon application of an electrode voltage, our results show that dispersion between ions results in a non-monotonic increase of the surface charge with the duration of charging. Finally and furthermore, we investigate the effects of van der Waals attraction between electrode/ionic-liquid interactions on the charging processes.

  19. Time-dependent density functional theory for the charging kinetics of electric double layer containing room-temperature ionic liquids

    DOE PAGES

    Lian, Cheng; Univ. of California, Riverside, CA; Zhao, Shuangliang; ...

    2016-11-29

    Understanding the charging kinetics of electric double layers is of fundamental importance for the design and development of novel electrochemical devices such as supercapacitors and field-effect transistors. In this paper, we study the dynamic behavior of room-temperature ionic liquids using a classical time-dependent density functional theory that accounts for the molecular excluded volume effects, the electrostatic correlations, and the dispersion forces. While the conventional models predict a monotonic increase of the surface charge with time upon application of an electrode voltage, our results show that dispersion between ions results in a non-monotonic increase of the surface charge with the durationmore » of charging. Finally and furthermore, we investigate the effects of van der Waals attraction between electrode/ionic-liquid interactions on the charging processes.« less

  20. Dynamics of electrical double layer formation in room-temperature ionic liquids under constant-current charging conditions

    SciTech Connect

    Jiang, Xikai; Huang, Jingsong; Zhao, Hui; Sumpter, Bobby G; Qiao, Rui

    2014-01-01

    We report detailed simulation results on the formation dynamics of an electrical double layer (EDL) inside an electrochemical cell featuring room-temperature ionic liquids (RTILs) enclosed between two planar electrodes. Under relatively small charging currents, the evolution of cell potential during charging can be suitably predicted by the Landau-Ginzburg-type continuum model proposed recently (M. Z. Bazant, B. D. Storey, and A. A. Kornyshev, Phys. Rev. Lett., 106, 046102, 2011). Under very large charging currents, the cell potential shows pronounced oscillation during the initial stage of charging, a feature not captured by the continuum model. Such oscillation originates from the sequential growth of the ionic space charge layers near the electrode surface, allowing the evolution of EDLs in RTILs with time, an atomistic process difficult to visualize experimentally, to be studied by analyzing the cell potential under constant current charging conditions. While the continuum model cannot predict the potential oscillation under such far-from-equilibrium charging conditions, it can nevertheless qualitatively capture the growth of cell potential during the later stage of charging. Improving the continuum model by introducing frequency-dependent dielectric constant and density-dependent ion diffusion coefficients may help to further extend the applicability of the model. Keywords: ionic

  1. Nanomechanics of layer-by-layer polyelectrolyte complexes: a manifestation of ionic cross-links and fixed charges.

    PubMed

    Han, Biao; Chery, Daphney R; Yin, Jie; Lu, X Lucas; Lee, Daeyeon; Han, Lin

    2016-01-28

    This study investigates the roles of two distinct features of ionically cross-linked polyelectrolyte networks - ionic cross-links and fixed charges - in determining their nanomechanical properties. The layer-by-layer assembled poly(allylamine hydrochloride)/poly(acrylic acid) (PAH/PAA) network is used as the model material. The densities of ionic cross-links and fixed charges are modulated through solution pH and ionic strength (IS), and the swelling ratio, elastic and viscoelastic properties are quantified via an array of atomic force microscopy (AFM)-based nanomechanical tools. The roles of ionic cross-links are underscored by the distinctive elastic and viscoelastic nanomechanical characters observed here. First, as ionic cross-links are highly sensitive to solution conditions, the instantaneous modulus, E0, exhibits orders-of-magnitude changes upon pH- and IS-governed swelling, distinctive from the rubber elasticity prediction based on permanent covalent cross-links. Second, ionic cross-links can break and self-re-form, and this mechanism dominates force relaxation of PAH/PAA under a constant indentation depth. In most states, the degree of relaxation is >90%, independent of ionic cross-link density. The importance of fixed charges is highlighted by the unexpectedly more elastic nature of the network despite low ionic cross-link density at pH 2.0, IS 0.01 M. Here, the complex is a net charged, loosely cross-linked, where the degree of relaxation is attenuated to ≈50% due to increased elastic contribution arising from fixed charge-induced Donnan osmotic pressure. In addition, this study develops a new method for quantifying the thickness of highly swollen polymer hydrogel films. It also underscores important technical considerations when performing nanomechanical tests on highly rate-dependent polymer hydrogel networks. These results provide new insights into the nanomechanical characters of ionic polyelectrolyte complexes, and lay the ground for further

  2. Nature of hydrogen bonding in charged hydrogen-bonded complexes and imidazolium-based ionic liquids.

    PubMed

    Izgorodina, Ekaterina I; MacFarlane, Douglas R

    2011-12-15

    The nature of hydrogen bonding was compared in neutral complexes and negatively charged complexes consisting of either the HF molecule or the halide anion (fluoride and chloride) and the C-H bond in the methane molecule with a varying degree of fluorination (such as CH(4), CH(2)F(2), and CHF(3)). Both linear (C(3v) symmetry) and nonlinear (C(2v) symmetry) hydrogen-bonded complexes were studied. Symmetry-adapted perturbation theory was used to decompose interaction energies into fundamental components such as Coulomb, repulsion, induction and dispersion to analyze the interplay among these forces in stabilizing hydrogen bonding. In the linear charged complexes, both Coulomb attraction and induction significantly contributed to the stabilization of hydrogen bonding. In the nonlinear charged complexes, mainly Coulomb attraction contributed to the HB complex stabilization, with the inductive forces playing a less important role. Contrary to the neutral complexes, dispersion forces played only a marginal role in the charged complexes. Interplay between the fundamental forces was also investigated in the ion pairs of the imidazolium-based ionic liquid, [C(2)mim]Cl, that were categorized as either (1) typical ion-ion interaction, with the anion interacting from above or below the imidazolium plane; or (2) hydrogen-bonding interaction, with the anion interacting with the C2-H bond of the imidazolium cation. Both types of interactions were found to induce similar charge transfers, and the analysis of the energetic components revealed only a slight difference in the ion pairs studied: (1) both interactions were electrostatically driven, between 86% and 88% of the overall attractive energy, with the electrostatic component being slightly lower in the hydrogen-bonded ion pairs by ~8 kJ mol(-1); and (2) dispersion forces were found to be stronger in the typical ion-ion interactions by ~15 kJ mol(-1) and could be possible only due to the fact that the anion was able to move

  3. Charge ordering and scattering pre-peaks in ionic liquids and alcohols.

    PubMed

    Perera, Aurélien

    2017-01-04

    The structural properties of ionic liquids and alcohols are viewed under the charge ordering process as a common basis to explain the peculiarity of their radiation scattering properties, namely the presence, or absence, of a scattering pre-peak. Through the analysis of models, it is shown that the presence, or absence, of a radiation scattering pre-peak is principally related to the symmetry breaking, or not, of the global charge order, induced by the peculiarities of the molecular shapes. This symmetry breaking is achieved, in practice, by the emergence of specific types of clusters, which manifests how the global charge order has changed into a local form. Various atom-atom correlations witness the symmetry breaking induced by this re organization, and this is manifested into a pre-peak in the structure factor. This approach explains why associated liquids such as water do not show a scattering pre-peak. It also explains under which conditions core-soft models can mimic associating liquids.

  4. Size and shape of charged micelles of ionic surfactants in aqueous salt solutions.

    PubMed

    Ikeda, S; Ozeki, S; Hayashi, S

    1980-06-01

    Light-scattering has been measured on aqueous NaCl solutions of dodecyldimethylammonium chloride and sodium dodecyl sulfate. From molecular weight determination it is confirmed that spherical micelles are formed at low NaCl concentrations, but at high NaCl concentrations the small micelles formed at the critical micelle concentration further associate to form large rod-like micelles with increasing micelle concentration. The reduction of repulsion between charged groups induces the sphere-rod transition of micelle shape. The dependence of molecular weight on ionic strength can be expressed by double logarithmic relations, which are dependent on the micelle shape. While dodecyldimethylammonium chloride dissolves even in 4.00 M NaCl, sodium dodecyl sulfate solutions exhibit some XXX in angular dissymmetry at NaCl concentrations higher than 0.50 M at low temperatures.

  5. Ionic screening of charged impurities in electrolytically gated graphene: A partially linearized Poisson-Boltzmann model.

    PubMed

    Sharma, P; Mišković, Z L

    2015-10-07

    We present a model describing the electrostatic interactions across a structure that consists of a single layer of graphene with large area, lying above an oxide substrate of finite thickness, with its surface exposed to a thick layer of liquid electrolyte containing salt ions. Our goal is to analyze the co-operative screening of the potential fluctuation in a doped graphene due to randomness in the positions of fixed charged impurities in the oxide by the charge carriers in graphene and by the mobile ions in the diffuse layer of the electrolyte. In order to account for a possibly large potential drop in the diffuse later that may arise in an electrolytically gated graphene, we use a partially linearized Poisson-Boltzmann (PB) model of the electrolyte, in which we solve a fully nonlinear PB equation for the surface average of the potential in one dimension, whereas the lateral fluctuations of the potential in graphene are tackled by linearizing the PB equation about the average potential. In this way, we are able to describe the regime of equilibrium doping of graphene to large densities for arbitrary values of the ion concentration without restrictions to the potential drop in the electrolyte. We evaluate the electrostatic Green's function for the partially linearized PB model, which is used to express the screening contributions of the graphene layer and the nearby electrolyte by means of an effective dielectric function. We find that, while the screened potential of a single charged impurity at large in-graphene distances exhibits a strong dependence on the ion concentration in the electrolyte and on the doping density in graphene, in the case of a spatially correlated two-dimensional ensemble of impurities, this dependence is largely suppressed in the autocovariance of the fluctuating potential.

  6. Dynamics of electrical double layer formation in room-temperature ionic liquids under constant-current charging conditions.

    PubMed

    Jiang, Xikai; Huang, Jingsong; Zhao, Hui; Sumpter, Bobby G; Qiao, Rui

    2014-07-16

    We report detailed simulation results on the formation dynamics of an electrical double layer (EDL) inside an electrochemical cell featuring room-temperature ionic liquids (RTILs) enclosed between two planar electrodes. Under relatively small charging currents, the evolution of cell potential from molecular dynamics (MD) simulations during charging can be suitably predicted by the Landau-Ginzburg-type continuum model proposed recently (Bazant et al 2011 Phys. Rev. Lett. 106 046102). Under very large charging currents, the cell potential from MD simulations shows pronounced oscillation during the initial stage of charging, a feature not captured by the continuum model. Such oscillation originates from the sequential growth of the ionic space charge layers near the electrode surface. This allows the evolution of EDLs in RTILs with time, an atomistic process difficult to visualize experimentally, to be studied by analyzing the cell potential under constant-current charging conditions. While the continuum model cannot predict the potential oscillation under such far-from-equilibrium charging conditions, it can nevertheless qualitatively capture the growth of cell potential during the later stage of charging. Improving the continuum model by introducing frequency-dependent dielectric constant and density-dependent ion diffusion coefficients may help to further extend the applicability of the model. The evolution of ion density profiles is also compared between the MD and the continuum model, showing good agreement.

  7. Liquid-liquid phase separation of a monoclonal antibody at low ionic strength: Influence of anion charge and concentration.

    PubMed

    Reiche, Katharina; Hartl, Josef; Blume, Alfred; Garidel, Patrick

    2017-01-01

    Liquid-liquid phase separation (LLPS) of a monoclonal antibody solution was investigated at low ionic strength in the presence of oligovalent anions, such as citrate, trimellitate, pyromellitate and mellitate. Phase separation was observed at the isoelectric point of the antibody at pH8.7 as well as in more acidic pH regions in the presence of the tested oligovalent ions. This can be attributed to charge neutralization via binding of the oligovalent anions to the positively charged antibody. The influence of the anion concentration on liquid-liquid phase separation with respect to the net charge of the antibody was examined. Similarities to the formation of a complex coacervate were shown to apply. These findings enable us to understand the usage of excipients to rationally induce or avoid liquid-liquid phase separation at low ionic strength. Furthermore we present a method to directly examine the competition of different ions for the solvation shell, called buffer equilibration.

  8. Daylight-driven photocatalytic degradation of ionic dyes with negatively surface-charged In2S3 nanoflowers: dye charge-dependent roles of reactive species

    NASA Astrophysics Data System (ADS)

    Ge, Suxiang; Cai, Lejuan; Li, Dapeng; Fa, Wenjun; Zhang, Yange; Zheng, Zhi

    2015-12-01

    Even though dye degradation is a successful application of semiconductor photocatalysis, the roles of reactive species in dye degradation have not received adequate attention. In this study, we systematically investigated the degradation of two cationic dyes (rhodamine B and methylene blue) and two anionic dyes (methyl orange and orange G) over negatively surface-charged In2S3 nanoflowers synthesized at 80 °C under indoor daylight lamp irradiation. It is notable to find In2S3 nanoflowers were more stable in anionic dyes degradation compared to that in cationic dyes removal. The active species trapping experiments indicated photogenerated electrons were mainly responsible for cationic dyes degradation, but holes were more important in anionic dyes degradation. A surface-charge-dependent role of reactive species in ionic dye degradation was proposed for revealing such interesting phenomenon. This study would provide a new insight for preparing highly efficient daylight-driven photocatalyst for ionic dyes degradation.

  9. Effect of surface charge density and electro-osmotic flow on ionic current in a bipolar nanopore fluidic diode

    NASA Astrophysics Data System (ADS)

    Pal Singh, Kunwar; Kumar, Manoj

    2011-10-01

    We have simulated bipolar nanopore fluidic diodes for different values of surface charge densities, electrolyte concentrations, and thickness of transition zone. Nanopore enrichment leads to increased nanopore conductivity with the surface charge density at low electrolyte concentrations. Potential drop across the nanopore and electric field inside the nanopore decreases. Forward current and ionic current rectification peaks for a specific value of surface charge density. Even though the electro-osmotic current component remains small as compared to other components, its non-inclusion in the modeling leads to serious errors in the solutions. Significant ion current rectification can be obtained even if transition zone between oppositely charged zones is not narrow. The effect of the surface charge is screened by counterions at higher electrolyte concentrations, which leads to reduced electrolyte polarization and a decrease in the ion current rectification.

  10. Remarkable enhancement of charge carrier mobility of conjugated polymer field-effect transistors upon incorporating an ionic additive.

    PubMed

    Luo, Hewei; Yu, Chenmin; Liu, Zitong; Zhang, Guanxin; Geng, Hua; Yi, Yuanping; Broch, Katharina; Hu, Yuanyuan; Sadhanala, Aditya; Jiang, Lang; Qi, Penglin; Cai, Zhengxu; Sirringhaus, Henning; Zhang, Deqing

    2016-05-01

    Organic semiconductors with high charge carrier mobilities are crucial for flexible electronic applications. Apart from designing new conjugated frameworks, different strategies have been explored to increase charge carrier mobilities. We report a new and simple approach to enhancing the charge carrier mobility of DPP-thieno[3,2-b]thiophene-conjugated polymer by incorporating an ionic additive, tetramethylammonium iodide, without extra treatments into the polymer. The resulting thin films exhibit a very high hole mobility, which is higher by a factor of 24 than that of thin films without the ionic additive under the same conditions. On the basis of spectroscopic grazing incidence wide-angle x-ray scattering and atomic force microscopy studies as well as theoretical calculations, the remarkable enhancement of charge mobility upon addition of tetramethylammonium iodide is attributed primarily to an inhibition of the torsion of the alkyl side chains by the presence of the ionic species, facilitating a more ordered lamellar packing of the alkyl side chains and interchain π-π interactions.

  11. Remarkable enhancement of charge carrier mobility of conjugated polymer field-effect transistors upon incorporating an ionic additive

    PubMed Central

    Luo, Hewei; Yu, Chenmin; Liu, Zitong; Zhang, Guanxin; Geng, Hua; Yi, Yuanping; Broch, Katharina; Hu, Yuanyuan; Sadhanala, Aditya; Jiang, Lang; Qi, Penglin; Cai, Zhengxu; Sirringhaus, Henning; Zhang, Deqing

    2016-01-01

    Organic semiconductors with high charge carrier mobilities are crucial for flexible electronic applications. Apart from designing new conjugated frameworks, different strategies have been explored to increase charge carrier mobilities. We report a new and simple approach to enhancing the charge carrier mobility of DPP-thieno[3,2-b]thiophene–conjugated polymer by incorporating an ionic additive, tetramethylammonium iodide, without extra treatments into the polymer. The resulting thin films exhibit a very high hole mobility, which is higher by a factor of 24 than that of thin films without the ionic additive under the same conditions. On the basis of spectroscopic grazing incidence wide-angle x-ray scattering and atomic force microscopy studies as well as theoretical calculations, the remarkable enhancement of charge mobility upon addition of tetramethylammonium iodide is attributed primarily to an inhibition of the torsion of the alkyl side chains by the presence of the ionic species, facilitating a more ordered lamellar packing of the alkyl side chains and interchain π-π interactions. PMID:27386541

  12. The Ionic Charge of Solar Energetic Particles with Energies of 0.3-70 MeV per Nucleon

    NASA Astrophysics Data System (ADS)

    Oetliker, M.; Klecker, B.; Hovestadt, D.; Mason, G. M.; Mazur, J. E.; Leske, R. A.; Mewaldt, R. A.; Blake, J. B.; Looper, M. D.

    1997-03-01

    With the three particle sensors Low Energy Ion Composition Analyzer (LICA), Heavy Ion Large Area Proportional Counter Telescope (HILT), and Mass Spectrometer Telescope (MAST) on board the polar-orbiting Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) satellite, the ionic charge of solar energetic particles (SEP) was measured over a wide energy range from 0.3 to 70 MeV per nucleon. For each sensor, the evaluation was performed separately. The results obtained with LICA (0.3-10 MeV per nucleon) and MAST (15-70 MeV per nucleon) were published earlier by Mason et al. and Leske et al., respectively. In this work we present the results of the HILT sensor (7-50 MeV per nucleon) and discuss the combined results of the three instruments. With HILT, the mean ionic charge of SEP was measured for carbon, nitrogen, oxygen, neon, magnesium, silicon, sulfur, argon, calcium, and iron in the energy range 7-50 MeV per nucleon during two consecutive large SEP events in 1992 October-November. The mean ionic charge was inferred from the rigidity-dependent geomagnetic flux cutoff. The coronal temperatures deduced from the mean ionic charges are well in accordance with the value of ~2 × 106 K except for neon and magnesium, as previously reported. The data measured with the three sensors, LICA, HILT, and MAST, agree well and are in accordance with data previously measured at energies below 3 MeV per nucleon (Luhn et al.), except for iron, where we observed a significant energy dependence of the mean charge over the energy range 0.3-70 MeV per nucleon.

  13. Reorientational dynamics of charged and neutral solutes in 1-alkyl-3-methylimidazoilum bis(trifluoromethylsulfonyl)imide ionic liquids: Realization of ionic component of hydrogen bond

    NASA Astrophysics Data System (ADS)

    Sahu, Prabhat Kumar; Sarkar, Moloy

    2016-05-01

    Role of electrostatic interaction on rotational relaxation dynamics of two charged solutes, sodium 8-methoxypyrene-1,3,6-trisulfonate (MPTS), 1-pyrenesulfonic acid sodium salt (1-PSA) and neutral perylene has been studied in two structurally similar but chemically distinguishable imidazolium-based ionic liquids (ILs). Analysis of the results reveals that rotational relaxation of MPTS is significantly hindered even in the IL where acidic C2-H of the imidazolium moiety is replaced by the methyl group. Moreover, rotational relaxation of neutral perylene is found to be faster than mononegative 1-PSA which is again observed to be faster than that of tri-negative MPTS in the same ILs.

  14. Thermodynamics, electrostatics, and ionic current in nanochannels grafted with pH-responsive end-charged polyelectrolyte brushes.

    PubMed

    Chen, Guang; Das, Siddhartha

    2017-03-01

    In this paper, we study the thermodynamics, electrostatics, and an external electric field driven ionic current in a pH-responsive, end-charged polyelectrolyte (PE) brush grafted nanochannel. By employing a mean field theory, we unravel a highly nonintuitive interplay of pH and electrolyte salt concentration in dictating the height of the end-charged PE brush. Larger pH or weak hydrogen ion concentration leads to maximum ionization of the charge-producing group-as a consequence, the resulting the electric double layer (EDL) energy get maximized causing a maximum deviation of the brush height from the value (d0 ) of the uncharged brush. This deviation may result in enhancement or lowering of the brush height as compared to d0 depending on whether the PE end locates lower or higher than h/2 (h is the nanochannel half height) and the salt concentration. Subsequently, we use this combined PE-brush-configuration-EDL-electrostatics framework to compute the ionic current in the nanochannel. We witness that the ionic current for smaller pH is much larger despite the corresponding magnitude of the EDL electrostatic potential being much smaller-this stems from the presence of a much larger concentration of H+ ions at small pH and the fact that H+ ions have very large mobilities. In fact, this ionic current shows a steep variation with pH that can be useful in exploring new designs for applications involving quantification and characterization of ionic current in PE-brush-grafted nanochannels. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Observation of Charge Inversion of an Ionic Liquid at the Solid Salt-Liquid Interface by Sum Frequency Generation Spectroscopy.

    PubMed

    Peñalber, Chariz Y; Baldelli, Steven

    2012-04-05

    Sum frequency generation (SFG) vibrational spectroscopy of the ionic liquid, 1-butyl-3-methylimidazolium dicyanamide [BMIM][DCA], in contact with two different solid salt surfaces, BaF2(111) single crystal and solid NaCl{100}, are discussed in this Letter. This investigation describes the nature of an ionic liquid-(solid) salt interface using SFG, contributing a new understanding to the molecular-level interactions involved in salts, which are conceptually similar compounds (of purely ionic character) but of different physical properties (liquid versus solid at room temperature). Results show the presence of [BMIM](+) at the NaCl{100} surface and [DCA](-) at the BaF2(111) surface. [BMIM](+) cations adhere closely via Coulombic interactions to the negatively charged NaCl{100} surface, while [DCA](-) anions subsequently have a strong electrostatic affinity to the positively charged BaF2(111) surface. Ions of the ionic liquid adsorb to the solid salt surface to form a Helmholtz-like electric double layer.

  16. Ionic Covalent Organic Frameworks: Design of a Charged Interface Aligned on 1D Channel Walls and Its Unusual Electrostatic Functions.

    PubMed

    Huang, Ning; Wang, Ping; Addicoat, Matthew A; Heine, Thomas; Jiang, Donglin

    2017-04-24

    Covalent organic frameworks (COFs) have emerged as a tailor-made platform for designing layered two-dimensional polymers. However, most of them are obtained as neutral porous materials. Here, we report the construction of ionic crystalline porous COFs with positively charged walls that enable the creation of well aligned yet spatially confined ionic interface. The unconventional reversed AA-stacking mode alternately orientates the cationic centers to both sides of the walls; the ionic interface endows COFs with unusual electrostatic functions. Because all of the walls are decorated with electric dipoles, the uptake of CO2 is enhanced by three fold compared to the neutral analog. By virtue of sufficient open space between cations, the ionic interface exhibits exceptional accessibility, efficiency, and selectivity in ion exchange to trap anionic pollutants. These findings suggest that construction of the ionic interface of COFs offers a new way to structural and functional designs. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Evolutionary Optimization of a Charge Transfer Ionic Potential Model for Ta/Ta-Oxide Heterointerfaces

    DOE PAGES

    Sasikumar, Kiran; Narayanan, Badri; Cherukara, Mathew; ...

    2017-03-19

    Heterostructures of tantalum and its oxide are of tremendous technological interest for a myriad of technological applications, including electronics, thermal management, catalysis and biochemistry. In particular, local oxygen stoichiometry variation in TaOx memristors comprising of thermodynamically stable metallic (Ta) and insulating oxide (Ta2O5) have been shown to result in fast switching on the subnanosecond timescale over a billion cycles. This rapid switching opens up the potential for advanced functional platforms such as stateful logic operations and neuromorphic computation. Despite its broad importance, an atomistic scale understanding of oxygen stoichiometry variation across Ta/TaOx heterointerfaces, such as during early stages of oxidationmore » and oxide growth, is not well understood. This is mainly due to the lack of a unified interatomic potential model for tantalum oxides that can accurately describe metallic (Ta), ionic (TaOx) as well as mixed (Ta/TaOx interfaces) bonding environments simultaneously. To address this challenge, we introduce a Charge Transfer Ionic Potential (CTIP) model for Ta/Ta-oxide system by training against lattice parameters, cohesive energies, equations of state (EOS), elastic properties, and surface energies of the various experimentally observed Ta2O5 polymorphs (hexagonal, orthorhombic and monoclinic) obtained from density functional theory (DFT) calculations. The best CTIP parameters are determined by employing a global optimization scheme driven by genetic algorithms followed by local Simplex optimization. Our newly developed CTIP potential accurately predicts structure, thermodynamics, energetic ordering of polymorphs, as well as elastic and surface properties of both Ta and Ta2O5, in excellent agreement with DFT calculations and experiments. We employ our newly parameterized CTIP potential to investigate the early stages of oxidation and atomic scale mechanisms associated with oxide growth on Ta surface at various

  18. Influence of ionic strength and beta2-glycoprotein I concentration on agglutination of like-charged phospholipid membranes.

    PubMed

    Perutková, Šárka; Frank-Bertoncelj, Mojca; Rozman, Blaž; Kralj-Iglič, Veronika; Iglič, Aleš

    2013-11-01

    The effect of ionic strength on adhesion between negatively charged giant unilamellar vesicles induced by beta2-glycoprotein I (β2-GPI) was studied experimentally and theoretically. Measuring the effective angle of contact between adhering vesicles indicated that the strength of adhesion between vesicles decreases with increasing ionic strength, and increases with concentration of β2-GPI. In the theoretical part we focused on the study of the average orientation of β2-GPI near the charged membrane and its role in mediating the attractive interactions between the vesicles. β2-GPI proteins were modelled as rods with internal distribution of electric charge. The predictions of Monte Carlo simulations show orthogonal orientation of some of the membrane attached β2-GPI in narrow gap between two vesicles. On the contrary, at larger distances between vesicles the proteins are parallelly attached to the membrane surface. A local minimum of the free energy corresponding to β2-GPI-mediated adhesion of two neighbouring vesicles was predicted. The strength of adhesion was confirmed to decrease at high ionic strength.

  19. Ionic protein-lipid interaction at the plasma membrane: what can the charge do?

    PubMed

    Li, Lunyi; Shi, Xiaoshan; Guo, Xingdong; Li, Hua; Xu, Chenqi

    2014-03-01

    Phospholipids are the major components of cell membranes, but they have functional roles beyond forming lipid bilayers. In particular, acidic phospholipids form microdomains in the plasma membrane and can ionically interact with proteins via polybasic sequences, which can have functional consequences for the protein. The list of proteins regulated by ionic protein-lipid interaction has been quickly expanding, and now includes membrane proteins, cytoplasmic soluble proteins, and viral proteins. Here we review how acidic phospholipids in the plasma membrane regulate protein structure and function via ionic interactions, and how Ca(2+) regulates ionic protein-lipid interactions via direct and indirect mechanisms.

  20. The effect of various quantum mechanically derived partial atomic charges on the bulk properties of chloride-based ionic liquids

    NASA Astrophysics Data System (ADS)

    Zolghadr, Amin Reza; Ghatee, Mohammad Hadi; Moosavi, Fatemeh

    2016-08-01

    Partial atomic charges using various quantum mechanical calculations for [Cnmim]Cl (n = 1, 4) ionic liquids (ILs) are obtained and used for development of molecular dynamics simulation (MD) force fields. The isolated ion pairs are optimized using HF, B3LYP, and MP2 methods for electronic structure with 6-311++G(d,p) basis set. Partial atomic charges are assigned to the atomic center with CHELPG and NBO methods. The effect of these sets of partial charges on the static and dynamic properties of ILs is evaluated by performing a series of MD simulations and comparing the essential thermodynamic properties with the available experimental data and available molecular dynamics simulation results. In contrast to the general trends reported for ionic liquids with BF4, PF6, and iodide anions (in which restrained electrostatic potential (RESP) charges are preferred), partial charges derived by B3LYP-NBO method are relatively good in prediction of the structural, dynamical, and thermodynamic energetic properties of the chloride based ILs.

  1. Ionic charge, radius, and potential control root/soil concentration ratios of fifty cationic elements in the organic horizon of a beech (Fagus sylvatica) forest podzol.

    PubMed

    Tyler, Germund

    2004-08-15

    The root/organic soil concentration ratio; R/S) of 50 cationic mineral elements was related to their ionic properties, including ionic radius (r), ionic charge (z), and ionic potential (z/r or z2/r). The materials studied were ectomycorrhizal beech (Fagus sylvatica L.) roots and their almost purely organic soil substrate, the O-horizon (mor; raw humus) of a Podzol in South Sweden, developed in a site which has been untouched by forestry or other mechanical disturbance since at least 50 years and located in an area with no local sources of pollution. Elements determined by ICP-AES were aluminium, barium, calcium, iron, potassium, magnesium, manganese, sodium and strontium. Determined by ICP-MS were silver, beryllium, bismuth, cadmium, cerium, cobalt, chromium, caesium, copper, dysprosium, erbium, europium, gallium, gadolinium, hafnium, mercury, holmium, indium, lanthanum, lithium, lutetium, niobium, neodymium, nickel, lead, praseodymium, rubidium, scandium, samarium, tin, terbium, thorium, titanium, thallium, thulium, uranium, vanadium, yttrium, ytterbium, zinc and zirconium. The R/S ratios were most clearly related to the ionic potential of the cationic elements studied, which accounted for approximately 60% of the variability in R/S among elements. The ionic charge of an element was more important than the ionic radius. Elements with high ionic charge had low R/S ratios and vice versa. No clear differences in R/S between essential and non-essential plant nutrients were observed, especially when ions of similar charge were compared.

  2. Effect of dense plasmas on exchange-energy shifts in highly charged ions: An alternative approach for arbitrary perturbation potentials

    SciTech Connect

    Rosmej, F.; Bennadji, K.; Lisitsa, V. S.

    2011-09-15

    An alternative method of calculation of dense plasma effects on exchange-energy shifts {Delta}E{sub x} of highly charged ions is proposed which results in closed expressions for any plasma or perturbation potential. The method is based on a perturbation theory expansion for the inner atomic potential produced by charged plasma particles employing the Coulomb Green function method. This approach allows us to obtain analytic expressions and scaling laws with respect to the electron temperature T, density n{sub e}, and nuclear charge Z. To demonstrate the power of the present method, two specific models were considered in detail: the ion sphere model (ISM) and the Debye screening model (DSM). We demonstrate that analytical expressions can be obtained even for the finite temperature ISM. Calculations have been carried out for the singlet 1s2p{sup 1} P{sub 1} and triplet 1s2p{sup 3} P{sub 1} configurations of He-like ions with charge Z that can be observed in dense plasmas via the He-like resonance and intercombination lines. Finally we discuss recently available purely numerical calculations and experimental data.

  3. Mechanistic Studies of Charge Injection from Metallic Electrodes into Organic Semiconductors Mediated by Ionic Functionalities: Final Report

    SciTech Connect

    Nguyen, Thuc-Quyen; Bazan, Guillermo; Mikhailovsky, Alexander

    2014-04-15

    Metal-organic semiconductor interfaces are important because of their ubiquitous role in determining the performance of modern electronics such as organic light emitting diodes (OLEDs), fuel cells, batteries, field effect transistors (FETs), and organic solar cells. Interfaces between metal electrodes required for external wiring to the device and underlying organic structures directly affect the charge carrier injection/collection efficiency in organic-based electronic devices primarily due to the mismatch between energy levels in the metal and organic semiconductor. Environmentally stable and cost-effective electrode materials, such as aluminum and gold typically exhibit high potential barriers for charge carriers injection into organic devices leading to increased operational voltages in OLEDs and FETs and reduced charge extraction in photovoltaic devices. This leads to increased power consumption by the device, reduced overall efficiency, and decreased operational lifetime. These factors represent a significant obstacle for development of next generation of cheap and energy-efficient components based on organic semiconductors. It has been noticed that introduction of organic materials with conjugated backbone and ionic pendant groups known as conjugated poly- and oligoelectrolytes (CPEs and COEs), enables one to reduce the potential barriers at the metal-organic interface and achieve more efficient operation of a device, however exact mechanisms of the phenomenon have not been understood. The goal of this project was to delineate the function of organic semiconductors with ionic groups as electron injection layers. The research incorporated a multidisciplinary approach that encompassed the creation of new materials, novel processing techniques, examination of fundamental electronic properties and the incorporation of the resulting knowledgebase into development of novel organic electronic devices with increased efficiency, environmental stability, and reduced

  4. Nanocomposite semi-solid redox ionic liquid electrolytes with enhanced charge-transport capabilities for dye-sensitized solar cells.

    PubMed

    Rutkowska, Iwona A; Marszalek, Magdalena; Orlowska, Justyna; Ozimek, Weronika; Zakeeruddin, Shaik M; Kulesza, Pawel J; Grätzel, Michael

    2015-08-10

    The ability of Pt nanostructures to induce the splitting of the II bond in iodine (triiodide) molecules is explored here to enhance electron transfer in the iodine/iodide redox couple. Following the dispersal of Pt nanoparticles at 2 % (weight) level, charge transport was accelerated in triiodide/iodide-containing 1,3-dialkylimidazolium room-temperature ionic liquid. If both Pt nanoparticles and multi-walled carbon nanotubes were introduced into the ionic-liquid-based system, a solid-type (nonfluid) electrolyte was obtained. By using solid-state voltammetric (both sandwich-type and microelectrode-based) methodology, the apparent diffusion coefficients for charge transport increased to approximately 1×10(-6)  cm(2)  s(-1) upon the incorporation of the carbon-nanotube-supported iodine-modified Pt nanostructures. A dye-sensitized solar cell comprising TiO2 covered with a heteroleptic Ru(II) -type sensitizer (dye) and the semisolid triiodide/iodide ionic liquid electrolyte admixed with carbon-nanotube-supported Pt nanostructures yielded somewhat higher power conversion efficiencies (up to 7.9 % under standard reporting conditions) than those of the analogous Pt-free system. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Direct determination of the ionic charge distribution of helium and iron in He-3-rich solar energetic particle events

    NASA Technical Reports Server (NTRS)

    Klecker, B.; Hovestadt, D.; Scholer, M.; Gloeckler, G.; Ipavich, F. M.; Fan, C. Y.; Fisk, L. A.

    1984-01-01

    The first direct measurement of the ionic charge distribution of the helium isotopes and of iron in (He-3)-Fe-rich solar energetic particle events is reported. No significant contribution of singly ionized helium to the events is found. The two-sigma upper limits for the He-3(+)/He-3(2+) and He-4(+)/He-4(2+) ratios are 0.02 and 0.03, respectively. The mean charge state of iron found by averaging five (He-3)-Fe-rich solar energetic particle events is 19 + or -2, significantly larger than the iron charge state for energetic solar particles in normal composition events. These results appear to favor the resonant heating model proposed by Fisk (1978). It is concluded that temperatures in the source region exceed 5 million K in the events under study.

  6. Charge-Shift Corrected Electronegativities and the Effect of Bond Polarity and Substituents on Covalent-Ionic Resonance Energy.

    PubMed

    James, Andrew M; Laconsay, Croix J; Galbraith, John Morrison

    2017-07-13

    Bond dissociation energies and resonance energies for HnA-BHm molecules (A, B = H, C, N, O, F, Cl, Li, and Na) have been determined in order to re-evaluate the concept of electronegativity in the context of modern valence bond theory. Following Pauling's original scheme and using the rigorous definition of the covalent-ionic resonance energy provided by the breathing orbital valence bond method, we have derived a charge-shift corrected electronegativity scale for H, C, N, O, F, Cl, Li, and Na. Atomic charge shift character is defined using a similar approach resulting in values of 0.42, 1.06, 1.43, 1.62, 1.64, 1.44, 0.46, and 0.34 for H, C, N, O, F, Cl, Li, and Na, respectively. The charge-shift corrected electronegativity values presented herein follow the same general trends as Pauling's original values with the exception of Li having a smaller value than Na (1.57 and 1.91 for Li and Na respectively). The resonance energy is then broken down into components derived from the atomic charge shift character and polarization effects. It is then shown that most of the resonance energy in the charge-shift bonds H-F, H3C-F, and Li-CH3 and borderline charge-shift H-OH is associated with polarity rather than the intrinsic atomic charge-shift character of the bonding species. This suggests a rebranding of these bonds as "polar charge-shift" rather than simply "charge-shift". Lastly, using a similar breakdown method, it is shown that the small effect the substituents -CH3, -NH2, -OH, and -F have on the resonance energy (<10%) is mostly due to changes in the charge-shift character of the bonding atom.

  7. Dynamics and relaxation of charge carriers in poly(methylmethacrylate)-based polymer electrolytes embedded with ionic liquid

    NASA Astrophysics Data System (ADS)

    Pal, P.; Ghosh, A.

    2015-12-01

    In the present paper, we have studied dynamics and relaxation of the charge carriers in polymethylmethacrylate-lithium bis(trifluoromethane sulfonyl)imide polymer electrolytes embedded with 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquid. We have analyzed the frequency dependent conductivity spectra using the random free-energy barrier model coupled with the contribution of electrode polarization in the low frequency region. The temperature dependence of ionic conductivity, and relaxation time obtained from the analysis of the spectra exhibits Vogel-Tammann-Fulcher type behavior. The Barton-Nakajima-Namikawa relation is consistent with the results obtained from the random free-energy barrier model. The scaling of ac conductivity spectra has been performed to understand the effect of temperature as well as the composition on the relaxation mechanism. The analysis of the ac conductivity also clearly indicates the existence of a nearly constant loss phenomenon at low temperatures or at high frequencies.

  8. Polymeric Ionic Networks with High Charge Density: Solid-like Electrolytes in Lithium Metal Batteries

    DOE PAGES

    Zhang, Pengfei; Li, Mingtao; Jiang, Xueguang; ...

    2015-11-02

    Polymerized ionic networks (PINs) with six ion pairs per repeating unit are synthesized by nucleophilic-substitution-mediated polymerization or radical polymerization of monomers bearing six 1-vinylimidazolium cations. PIN-based solid-like electrolytes show good ionic conductivities (up to 5.32 × 10-3 S cm-1 at 22 °C), wide electrochemical stability windows (up to 5.6 V), and good interfacial compatibility with the electrodes.

  9. Polymeric Ionic Networks with High Charge Density: Solid-like Electrolytes in Lithium Metal Batteries

    SciTech Connect

    Zhang, Pengfei; Li, Mingtao; Jiang, Xueguang; Fang, Youxing; Veith, Gabriel M.; Sun, Xiao-Guang; Dai, Sheng

    2015-11-02

    Polymerized ionic networks (PINs) with six ion pairs per repeating unit are synthesized by nucleophilic-substitution-mediated polymerization or radical polymerization of monomers bearing six 1-vinylimidazolium cations. PIN-based solid-like electrolytes show good ionic conductivities (up to 5.32 × 10-3 S cm-1 at 22 °C), wide electrochemical stability windows (up to 5.6 V), and good interfacial compatibility with the electrodes.

  10. Charge regulation in ionic solutions: thermal fluctuations and Kirkwood-Schumaker interactions.

    PubMed

    Adžić, Nataša; Podgornik, Rudolf

    2015-02-01

    We study the behavior of two macroions with dissociable charge groups, regulated by local variables such as pH and electrostatic potential, immersed in a monovalent salt solution, considering cases where the net charge can either change sign or remain of the same sign depending on these local parameters. The charge regulation in both cases is described by the proper free-energy function for each of the macroions, while the coupling between the charges is evaluated on the approximate Debye-Hückel level. The charge correlation functions and the ensuing charge fluctuation forces are calculated analytically and numerically. Strong attraction between like-charged macroions is found close to the point of zero charge, specifically due to asymmetric, anticorrelated charge fluctuations of the macroion charges. The general theory is then implemented for a system of two proteinlike macroions, generalizing the form and magnitude of the Kirkwood-Schumaker interaction.

  11. Conformal weights of charged Rényi entropy twist operators for free scalar fields in arbitrary dimensions

    NASA Astrophysics Data System (ADS)

    Dowker, J. S.

    2016-04-01

    I compute the conformal weights of the twist operators of free scalar fields for charged Rényi entropy in both odd and even dimensions. Explicit expressions can be found, in odd dimensions as a function of the chemical potential in the absence of a conical singularity and thence by images for all integer coverings. This method, developed some time ago, is equivalent, in results, to the replica technique. A review is given. The same method applies for even dimensions but a general form is more immediately available. For no chemical potential, the closed form in the covering order is written in an alternative way related to old trigonometric sums. Some derivatives are obtained. An analytical proof is given of a conjecture made by Bueno, Myers and Witczak-Krempa regarding the relation between the conformal weights and a corner coefficient (a universal quantity) in the Rényi entropy.

  12. Effective charges of ionic liquid determined self-consistently through combination of molecular dynamics simulation and density-functional theory.

    PubMed

    Ishizuka, Ryosuke; Matubayasi, Nobuyuki

    2017-07-18

    A self-consistent scheme combining the molecular dynamics (MD) simulation and density functional theory (DFT) was recently proposed to incorporate the effects of the charge transfer and polarization of ions into non-poralizable force fields of ionic liquids for improved description of energetics and dynamics. The purpose of the present work is to analyze the detailed setups of the MD/DFT scheme by focusing on how the basis set, exchange-correlation (XC) functional, charge-fitting method or force field for the intramolecular and Lennard-Jones interactions affects the MD/DFT results of 1,3-dimethylimidazolium bis(trifluoromethylsulfonyl) imide ( [C1mim][NTf2]) and 1-ethyl-3-methylimidazolium glycinate ( [C2mim][Gly]). It was found that the double-zeta valence polarized or larger size of basis set is required for the convergence of the effective charge of the ion. The choice of the XC functional was further not influential as far as the generalized gradient approximation is used. The charge-fitting method and force field govern the accuracy of the MD/DFT scheme, on the other hand. We examined the charge-fitting methods of Blöchl, the iterative Hirshfeld (Hirshfeld-I), and REPEAT in combination with Lopes et al.'s force field and general AMBER force field. There is no single combination of charge fitting and force field that provides good agreements with the experiments, while the MD/DFT scheme reduces the effective charges of the ions and leads to better description of energetics and dynamics compared to the original force field with unit charges. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  13. Like-charge attraction of molecular cations in water: subtle balance between interionic interactions and ionic solvation effect.

    PubMed

    Inagaki, Taichi; Aono, Shinji; Nakano, Hiroshi; Yamamoto, Takeshi

    2014-05-22

    Despite strong electrostatic repulsion, like-charged ions in aqueous solution can effectively attract each other via ion-water interactions. In this paper we investigate such an effective interaction of like-charged ions in water by using the 3D-RISM-SCF method (i.e., electronic structure theory combined with three-dimensional integral equation theory for molecular solvents). Free energy profiles are calculated at the CCSD(T) level for a series of molecular ions including guanidinium (Gdm(+)), alkyl-substituted ammonium, and aromatic amine cations. Polarizable continuum model (PCM) and mean-field QM/MM free energy calculations are also performed for comparison. The results show that the stability of like-charged ion pairs in aqueous solution is determined by a very subtle balance between interionic interactions (including dispersion and π-stacking interactions) and ionic solvation/hydrophobic effects and that the Gdm(+) ion has a rather favorable character for like-charge association among all the cations studied. Furthermore, we investigate the like-charge pairing in Arg-Ala-Arg and Lys-Ala-Lys tripeptides in water and show that the Arg-Arg pair has a contact free-energy minimum of about -6 kcal/mol. This result indicates that arginine pairing observed on protein surfaces and interfaces is stabilized considerably by solvation effects.

  14. High flux, positively charged loose nanofiltration membrane by blending with poly (ionic liquid) brushes grafted silica spheres.

    PubMed

    Yu, Liang; Zhang, Yatao; Wang, Yuanming; Zhang, Haoqin; Liu, Jindun

    2015-04-28

    Silica spheres modified by poly (ionic liquid) brushes, a novel positively charged nanomaterial is prepared by atom transfer radical polymerization (ATRP). A high flux positively charged loose nanofiltration membrane is fabricated via "blending-phase inversion" method. The morphology structures, hydrophilicity, thermal and mechanical properties, permeation performance of these membranes are investigated in detail. The results reveal that the hybrid membranes have enhanced surface hydrophilicity, water permeability, thermal stability, and mechanical properties. Characterization of membrane separation properties shows that the hybrid membranes possess higher salt permeability and relatively higher rejection for reactive dyes, which may open opportunities for the recycling of reactive dyes wastewater. Moreover, such hybrid membranes have an outstanding operational stability and salts concentration showed little effect on the separation properties.

  15. Quantitative prediction of physical properties of imidazolium based room temperature ionic liquids through determination of condensed phase site charges: a refined force field.

    PubMed

    Mondal, Anirban; Balasubramanian, Sundaram

    2014-03-27

    Quantitative prediction of physical properties of room temperature ionic liquids through nonpolarizable force field based molecular dynamics simulations is a challenging task. The challenge lies in the fact that mean ion charges in the condensed phase can be less than unity due to polarization and charge transfer effects whose magnitude cannot be fully captured through quantum chemical calculations conducted in the gas phase. The present work employed the density-derived electrostatic and chemical (DDEC/c3) charge partitioning method to calculate site charges of ions using electronic charge densities obtained from periodic density functional theory (DFT) calculations of their crystalline phases. The total ion charges obtained thus range between -0.6e for chloride and -0.8e for the PF6 ion. The mean value of the ion charges obtained from DFT calculations of an ionic liquid closely matches that obtained from the corresponding crystal thus confirming the suitability of using crystal site charges in simulations of liquids. These partial charges were deployed within the well-established force field developed by Lopes et al., and consequently, parameters of its nonbonded and torsional interactions were refined to ensure that they reproduced quantum potential energy scans for ion pairs in the gas phase. The refined force field was employed in simulations of seven ionic liquids with six different anions. Nearly quantitative agreement with experimental measurements was obtained for the density, surface tension, enthalpy of vaporization, and ion diffusion coefficients.

  16. Nonlinear space charge dynamics in mixed ionic-electronic conductors: Resistive switching and ferroelectric-like hysteresis of electromechanical response

    NASA Astrophysics Data System (ADS)

    Morozovska, Anna N.; Eliseev, Eugene A.; Varenyk, Olexandr V.; Kim, Yunseok; Strelcov, Evgheni; Tselev, Alexander; Morozovsky, Nicholas V.; Kalinin, Sergei V.

    2014-08-01

    We performed self-consistent modelling of nonlinear electrotransport and electromechanical response of thin films of mixed ionic-electronic conductors (MIEC) allowing for steric effects of mobile charged defects (ions, protons, or vacancies), electron degeneration, and Vegard stresses. We establish correlations between the features of the nonlinear space-charge dynamics, current-voltage, and bending-voltage curves for different types of the film electrodes. A pronounced ferroelectric-like hysteresis of the bending-voltage loops and current maxima on the double hysteresis current-voltage loops appear for the electron-transport electrodes. The double hysteresis loop with pronounced humps indicates a memristor-type resistive switching. The switching occurs due to the strong nonlinear coupling between the electronic and ionic subsystems. A sharp meta-stable maximum of the electron density appears near one open electrode and moves to another one during the periodic change of applied voltage. Our results can explain the nonlinear nature and correlation of electrical and mechanical memory effects in thin MIEC films. The analytical expression proving that the electrically induced bending of MIEC films can be detected by interferometric methods is derived.

  17. Nonlinear space charge dynamics in mixed ionic-electronic conductors: Resistive switching and ferroelectric-like hysteresis of electromechanical response

    SciTech Connect

    Morozovska, Anna N.; Morozovsky, Nicholas V.; Eliseev, Eugene A.; Varenyk, Olexandr V.; Kim, Yunseok; Strelcov, Evgheni; Tselev, Alexander; Kalinin, Sergei V.

    2014-08-14

    We performed self-consistent modelling of nonlinear electrotransport and electromechanical response of thin films of mixed ionic-electronic conductors (MIEC) allowing for steric effects of mobile charged defects (ions, protons, or vacancies), electron degeneration, and Vegard stresses. We establish correlations between the features of the nonlinear space-charge dynamics, current-voltage, and bending-voltage curves for different types of the film electrodes. A pronounced ferroelectric-like hysteresis of the bending-voltage loops and current maxima on the double hysteresis current-voltage loops appear for the electron-transport electrodes. The double hysteresis loop with pronounced humps indicates a memristor-type resistive switching. The switching occurs due to the strong nonlinear coupling between the electronic and ionic subsystems. A sharp meta-stable maximum of the electron density appears near one open electrode and moves to another one during the periodic change of applied voltage. Our results can explain the nonlinear nature and correlation of electrical and mechanical memory effects in thin MIEC films. The analytical expression proving that the electrically induced bending of MIEC films can be detected by interferometric methods is derived.

  18. Ionic Blocks

    ERIC Educational Resources Information Center

    Sevcik, Richard S.; Gamble, Rex; Martinez, Elizabet; Schultz, Linda D.; Alexander, Susan V.

    2008-01-01

    "Ionic Blocks" is a teaching tool designed to help middle school students visualize the concepts of ions, ionic compounds, and stoichiometry. It can also assist high school students in reviewing their subject mastery. Three dimensional blocks are used to represent cations and anions, with color indicating charge (positive or negative) and size…

  19. Ionic Blocks

    ERIC Educational Resources Information Center

    Sevcik, Richard S.; Gamble, Rex; Martinez, Elizabet; Schultz, Linda D.; Alexander, Susan V.

    2008-01-01

    "Ionic Blocks" is a teaching tool designed to help middle school students visualize the concepts of ions, ionic compounds, and stoichiometry. It can also assist high school students in reviewing their subject mastery. Three dimensional blocks are used to represent cations and anions, with color indicating charge (positive or negative) and size…

  20. Charged plate in asymmetric electrolytes: One-loop renormalization of surface charge density and Debye length due to ionic correlations.

    PubMed

    Ding, Mingnan; Lu, Bing-Sui; Xing, Xiangjun

    2016-10-01

    Self-consistent field theory (SCFT) is used to study the mean potential near a charged plate inside a m:-n electrolyte. A perturbation series is developed in terms of g=4πκb, where band1/κ are Bjerrum length and bare Debye length, respectively. To the zeroth order, we obtain the nonlinear Poisson-Boltzmann theory. For asymmetric electrolytes (m≠n), the first order (one-loop) correction to mean potential contains a secular term, which indicates the breakdown of the regular perturbation method. Using a renormalizaton group transformation, we remove the secular term and obtain a globally well-behaved one-loop approximation with a renormalized Debye length and a renormalized surface charge density. Furthermore, we find that if the counterions are multivalent, the surface charge density is renormalized substantially downwards and may undergo a change of sign, if the bare surface charge density is sufficiently large. Our results agrees with large MC simulation even when the density of electrolytes is relatively high.

  1. Charged plate in asymmetric electrolytes: One-loop renormalization of surface charge density and Debye length due to ionic correlations

    NASA Astrophysics Data System (ADS)

    Ding, Mingnan; Lu, Bing-Sui; Xing, Xiangjun

    2016-10-01

    Self-consistent field theory (SCFT) is used to study the mean potential near a charged plate inside a m :-n electrolyte. A perturbation series is developed in terms of g =4 π κ b , where b a n d 1 /κ are Bjerrum length and bare Debye length, respectively. To the zeroth order, we obtain the nonlinear Poisson-Boltzmann theory. For asymmetric electrolytes (m ≠n ), the first order (one-loop) correction to mean potential contains a secular term, which indicates the breakdown of the regular perturbation method. Using a renormalizaton group transformation, we remove the secular term and obtain a globally well-behaved one-loop approximation with a renormalized Debye length and a renormalized surface charge density. Furthermore, we find that if the counterions are multivalent, the surface charge density is renormalized substantially downwards and may undergo a change of sign, if the bare surface charge density is sufficiently large. Our results agrees with large MC simulation even when the density of electrolytes is relatively high.

  2. Tuning extreme ultraviolet emission for optimum coupling with multilayer mirrors for future lithography through control of ionic charge states

    SciTech Connect

    Ohashi, Hayato Higashiguchi, Takeshi Suzuki, Yuhei; Kawasaki, Masato; Li, Bowen; Dunne, Padraig; O'Sullivan, Gerry; Kanehara, Tatsuhiko; Aida, Yuya; Nakamura, Nobuyuki; Torii, Shuichi; Makimura, Tetsuya; Jiang, Weihua

    2014-01-21

    We report on the identification of the optimum plasma conditions for a laser-produced plasma source for efficient coupling with multilayer mirrors at 6.x nm for beyond extreme ultraviolet lithography. A small shift to lower energies of the peak emission for Nd:YAG laser-produced gadolinium plasmas was observed with increasing laser power density. Charge-defined emission spectra were observed in electron beam ion trap (EBIT) studies and the charge states responsible identified by use of the flexible atomic code (FAC). The EBIT spectra displayed a larger systematic shift of the peak wavelength of intense emission at 6.x nm to longer wavelengths with increasing ionic charge. This combination of spectra enabled the key ion stage to be confirmed as Gd{sup 18+}, over a range of laser power densities, with contributions from Gd{sup 17+} and Gd{sup 19+} responsible for the slight shift to longer wavelengths in the laser-plasma spectra. The FAC calculation also identified the origin of observed out-of-band emission and the charge states responsible.

  3. Gradual improvements of charge carrier mobility at ionic liquid/rubrene single crystal interfaces

    NASA Astrophysics Data System (ADS)

    Yokota, Yasuyuki; Hara, Hisaya; Morino, Yusuke; Bando, Ken-ichi; Ono, Sakurako; Imanishi, Akihito; Okada, Yugo; Matsui, Hiroyuki; Uemura, Takafumi; Takeya, Jun; Fukui, Ken-ichi

    2016-02-01

    We report evolution of electric characteristics of an electric double layer field-effect transistor based on the ionic liquid/rubrene single crystal interfaces. In contrast to usual devices, the field effect mobility was found to gradually increase with time for a day, followed by minor long-term fluctuations. Although the details of the evolution were somewhat device dependent, the final values of the mobility turned out to be 3-4 times larger irrespective of the initial values. These observations are explained by the evolution of the flat interface by defect-induced spontaneous dissolution of rubrene molecules at the ionic liquid/rubrene single crystal interfaces, revealed by frequency modulation atomic force microscopy.

  4. Ionic Strength, Surface Charge, and Packing Density Effects on the Properties of Peptide Self-Assembled Monolayers.

    PubMed

    Leo, Norman; Liu, Juan; Archbold, Ian; Tang, Yongan; Zeng, Xiangqun

    2017-02-28

    The various environmental parameters of packing density, ionic strength, and solution charge were examined for their effects on the properties of the immobilized peptide mimotope CH19 (CGSGSGSQLGPYELWELSH) that binds with the therapeutic antibody Trastuzumab (Herceptin) on a gold substrate. The immobilization of CH19 onto gold was examined with a quartz crystal microbalance (QCM). The QCM data showed the presence of intermolecular interactions resulting in the increase of viscoelastic properties of the peptide self-assembled monolayer (SAM). The CH19 SAM was diluted with CS7 (CGSGSGS) to decrease the packing density as CH19/CS7. The packing density and ionic strength parameters were evaluated by atomic force microscopy (AFM), ellipsometry, and QCM. AFM and ellipsometry showed a distinct conformational difference between CH19 and CH19/CS7, indicating a relationship between packing density and conformational state of the immobilized peptide. The CH19 SAM thickness was 40 Å with a rough topology, while the CH19/CS7 SAM thickness was 20 Å with a smooth topology. The affinity studies showed that the affinity of CH19 and CH19/CS7 to Trastuzumab were both on the order of 10(7) M(-1) in undiluted PBS buffer, while the dilution of the buffer by 1000× increased both SAMs affinities to Trastuzumab to the order of 10(15) M(-2) and changed the binding behavior from noncooperative to cooperative binding. This indicated that ionic strength had a more pronounced effect on binding properties of the CH19 SAM than packing density. Electrochemical impedance spectroscopy (EIS) was conducted on the CH19/CS7 SAM, which showed an increase in impedance after each EIS measurement cycle. Cyclic voltammetry on the CH19/CS7 SAM decreased impedance to near initial values. The impact of the packing density, buffer ionic strength, and local charge perturbation of the peptide SAM properties was interpreted based on the titratable sites in CH19 that could participate in the proton transfer and

  5. Charge ordering induces a smectic phase in oblate ionic liquid crystals.

    PubMed

    Ganzenmüller, G C; Patey, G N

    2010-09-24

    We report a computer simulation study of an electroneutral mixture of oppositely charged oblate ellipsoids of revolution with aspect ratio A=1/3. In contrast with hard or soft repulsive ellipsoids, which are purely nematic, this system exhibits a smectic-A phase in which charges of equal sign are counterintuitively packed in layers perpendicular to the nematic director.

  6. Ionic fluids containing both strongly and weakly interacting ions of the same charge have unique ionic and chemical environments as a function of ion concentration.

    PubMed

    Wang, Hui; Kelley, Steven P; Brantley, Jimmy W; Chatel, Gregory; Shamshina, Julia; Pereira, Jorge F B; Debbeti, Varun; Myerson, Allan S; Rogers, Robin D

    2015-04-07

    Liquid multi-ion systems made by combining two or more salts can exhibit charge ordering and interactions not found in the parent salts, leading to new sets of properties. This is investigated herein by examining a liquid comprised of a single cation, 1-ethyl-3-methylimidazolium ([C2mim](+)), and two anions with different properties, acetate ([OAc](-)) and bis(trifluoromethylsulfonyl)imide ([NTf2](-)). NMR and IR spectroscopy indicate that the electrostatic interactions are quite different from those in either [C2mim][OAc] or [C2mim][NTf2]. This is attributed to the ability of [OAc](-) to form complexes with the [C2mim](+) ions at greater than 1:1 stoichiometries by drawing [C2mim](+) ions away from the less basic [NTf2](-) ions. Solubility studies with molecular solvents (ethyl acetate, water) and pharmaceuticals (ibuprofen, diphenhydramine) show nonlinear trends as a function of ion content, which suggests that solubility can be tuned through changes in the ionic compositions.

  7. Self-Consistent Determination of Atomic Charges of Ionic Liquid through a Combination of Molecular Dynamics Simulation and Density Functional Theory.

    PubMed

    Ishizuka, Ryosuke; Matubayasi, Nobuyuki

    2016-02-09

    A self-consistent scheme is developed to determine the atomic partial charges of ionic liquid. Molecular dynamics (MD) simulation was conducted to sample a set of ion configurations, and these configurations were subject to density functional theory (DFT) calculations to determine the partial charges. The charges were then averaged and used as inputs for the subsequent MD simulation, and MD and DFT calculations were repeated until the MD results are not altered any more. We applied this scheme to 1,3-dimethylimidazolium bis(trifluoromethylsulfonyl) imide ([C1mim][NTf2]) and investigated its structure and dynamics as a function of temperature. At convergence, the average ionic charges were ±0.84 e at 350 K due to charge transfer among ions, where e is the elementary charge, while the reduced ionic charges do not affect strongly the density of [C1mim][NTf2] and radial distribution function. Instead, major effects are found on the energetics and dynamics, with improvements of the overestimated heat of vaporization and the too slow motions of ions observed in MD simulations using commonly used force fields.

  8. Positively charged imidazolium-based ionic liquid-protected silver nanoparticles: a promising disinfectant in root canal treatment.

    PubMed

    Abbaszadegan, A; Nabavizadeh, M; Gholami, A; Aleyasin, Z S; Dorostkar, S; Saliminasab, M; Ghasemi, Y; Hemmateenejad, B; Sharghi, H

    2015-08-01

    To synthesize and characterize silver nanoparticles (Ag NPs) with different surface charges in order to evaluate their cytotoxicity and antibacterial activity in the absence and presence of dentine compared with NaOCl and CHX. Ag NPs with positive, negative and neutral surface charges were synthesized and characterized. The first phase of the experiment determined the minimum inhibitory concentrations (MICs) of NPs against planktonic E. faecalis and compared them with that of NaOCl and CHX. The second phase tested the elimination of E. faecalis at different contact times (5, 20 and 60 min and 4 and 24 h), and the role of dentine in their inactivation was assessed. In the third phase, the most effective Ag NP solution was selected for cytocompatibility assessment. An MTT-based cytotoxicity assay was used to evaluate the cytotoxicity of the selected NP solution in different concentrations on L929 fibroblasts compared to that of 2.5% NaOCl and 0.2% CHX. Student's t-test and repeated measures manova approach were used for statistical analyses. The characterization revealed synthesis of colloidal NPs in the size range of 5-10 nm in diameter. The results indicated that Ag NP with a positive surface charge had the smallest MIC against planktonic E. faecalis, and it was active in very lower concentrations compared to NaOCl, CHX and the other tested AgNPs. Positive-charged Ag NPs at 5.7 × 10(-10)  mol L(-1) completely prevented the growth of E. faecalis after 5 min of contact time, a finding comparable to 0.025% NaOCl. Dentine powder had variable inhibitory effects on all tested materials after 1 h incubation period, but after 24 h, NaOCl and the positive-charged Ag NPs were not inhibited by dentine at any concentration used. CHX was the most and the positively charged Ag NP solution was the least toxic solutions to L929 fibroblasts (P < 0.001). Ag NP surface charge was important in bactericidal efficacy against E. faecalis. The positively charged

  9. Model of photo-induced neutral-ionic phase transition in organic charge-transfer salts

    NASA Astrophysics Data System (ADS)

    Yartsev, V. M.

    1998-01-01

    One-dimensional donor-acceptor mixed chains are modeled by a periodic DADA tetramer. Electron coupling to intramolecular vibrations are taken into account explicitly. Generalized adiabatic potentials are calculated for the cases of regular and dimerized stacks which are characteristic, respectively, of quasi-neutral (N) and quasi-ionic (I) phases of a tetrathiafulvalene-chloranil compound. A sharp difference in life-times of photo-induced I-states in the N-phase and N-states in the I-phase is discussed within the periodic DADA tetramer model.

  10. Results from the Heavy Ions In Space (HIIS) experiment on the ionic charge state of solar energetic particles

    NASA Technical Reports Server (NTRS)

    Tylka, Allan J.; Boberg, Paul R.; Adams, James H., Jr.; Beahm, Lorraine P.; Kleis, Thomas

    1995-01-01

    It has long been known that low-energy solar energetic particles (SEP's) are partially-ionized. For example, in large, so-called 'gradual' solar energetic particle events, at approximately 1 MeV/nucleon the measured mean ionic charge state, Q, of Fe ions is 14.1 +/- 0.2, corresponding to a plasma temperature of approximately 2 MK in the coronal or solar-wind source material. Recent studies, which have greatly clarified the origin of solar energetic particles and their relation to solar flares, suggest that ions in these SEP events are accelerated not at a flare site, but by shocks propagating through relatively low-density regions in the interplanetary medium. As a result, the partially-ionized states observed at low energies are expected to continue to higher energies. However, up to now there have been no high-energy measurements of ionic charge states to confirm this notion. We report here HIIS observations of Fe-group ions at 50-600 MeV/nucleon, at energies and fluences which cannot be explained by fully-ionized galactic cosmic rays, even in the presence of severe geomagnetic cutoff suppression. Above approximately 200 MeV/nucleon, all features of our data -- fluence, energy spectrum, elemental composition, and arrival directions -- can be explained by the large SEP events of October 1989, provided that the mean ionic charge state at these high energies is comparable to the measured value at approximately 1 MeV/nucleon. By comparing the HIIS observations with measurements in interplanetary space in October 1989, we determine the mean ionic charge state of SEP Fe ions at approximately 200-600 MeV/nucleon to be Q = 13.4 plus or minus 1.0, in good agreement with the observed value at approximately 1 MeV/nucleon. The source of the ions below approximately 200 MeV/nucleon is not yet clear. Partially-ionized ions are less effectively deflected by the Earth's magnetic field than fully-ionized cosmic rays and therefore have greatly enhanced access to low-Earth orbit

  11. Importance of Ion Packing on the Dynamics of Ionic Liquids during Micropore Charging

    SciTech Connect

    He, Yadong; Qiao, Rui; Vatamanu, Jenel; Borodin, Oleg; Bedrov, Dmitry; Huang, Jingsong; Sumpter, Bobby G.

    2015-12-07

    In molecular simulations of the diffusion of EMIM+ and TESI- ions in slit-shaped micropores under conditions similar to those during charging show that in pores that accommodate only a single layer of ions, ions diffuse increasingly faster as the pore becomes charged (with diffusion coefficients even reaching similar to 5 x 10-9 m2/s), unless the pore becomes very highly charged. In pores wide enough to fit more than one layer of ions, ion diffusion is slower than in the bulk and changes modestly as the pore becomes charged. Moreover, analysis of these results revealed that the fast (or slow) diffusion of ions inside a micropore during charging is correlated most strongly with the dense (or loose) ion packing inside the pore. Finally, the molecular details of the ions and the precise width of the pores modify these trends weakly, except when the pore is so narrow that the ion conformation relaxation is strongly constrained by the pore walls.

  12. Importance of Ion Packing on the Dynamics of Ionic Liquids during Micropore Charging

    DOE PAGES

    He, Yadong; Qiao, Rui; Vatamanu, Jenel; ...

    2015-12-07

    In molecular simulations of the diffusion of EMIM+ and TESI- ions in slit-shaped micropores under conditions similar to those during charging show that in pores that accommodate only a single layer of ions, ions diffuse increasingly faster as the pore becomes charged (with diffusion coefficients even reaching similar to 5 x 10-9 m2/s), unless the pore becomes very highly charged. In pores wide enough to fit more than one layer of ions, ion diffusion is slower than in the bulk and changes modestly as the pore becomes charged. Moreover, analysis of these results revealed that the fast (or slow) diffusionmore » of ions inside a micropore during charging is correlated most strongly with the dense (or loose) ion packing inside the pore. Finally, the molecular details of the ions and the precise width of the pores modify these trends weakly, except when the pore is so narrow that the ion conformation relaxation is strongly constrained by the pore walls.« less

  13. A wave-function based approach for polarizable charge model: Systematic comparison of polarization effects on protic, aprotic, and ionic liquids.

    PubMed

    Nakano, Hiroshi; Yamamoto, Takeshi; Kato, Shigeki

    2010-01-28

    We first describe a wave-function based formalism of polarizable charge model by starting from the Hartree product ansatz for the total wave function and making the second-order expansion of individual molecular energies with the use of partial charge operators. The resulting model is shown to be formally equivalent to the charge response kernel model that starts from the linear-response approximation to partial charges, and also closely related to a family of fluctuating charge models that are based on the electronegativity equalization principle. We then apply the above model to a systematic comparison of polarization effects on qualitatively different liquids, namely, protic solvents (water and methanol), an aprotic polar solvent (acetonitrile), and imidazolium-based ionic liquids. Electronic polarization is known to decelerate molecular motions in conventional solvents while it accelerates them in ionic liquids. To obtain more insights into these phenomena, we consider an effective decomposition of total polarization energy into molecular contributions, and show that their statistical distribution is well-correlated with the acceleration/deceleration of molecular motions. In addition, we perform effective nonpolarizable simulations based on mean polarized charges, and compare them with fully polarizable simulations. The result shows that the former can reproduce structural properties of conventional solvents rather accurately, while they fail qualitatively to reproduce acceleration of molecular motions in ionic liquids.

  14. Potential sputtering of ionic species from rare gas solids by multiply charged ion impact

    NASA Astrophysics Data System (ADS)

    Fukai, K.; Fujita, S.; Tachibana, T.; Koizumi, T.; Hirayama, T.

    2010-03-01

    The interaction of low-energy multiply charged Arq + (q <= 7) ions with a solid Ne surface is experimentally studied. Desorption of very large cluster ions Nen + (n > 100) is observed. The size distribution of smaller (n = 1-3) cluster ions depends strongly on the charge state of the incident ion, whereas that of larger (n > 7) cluster ions exhibits no dependence on the charge state, indicating that desorption of large cluster ions is due to kinetic sputtering. The potential sputtering yield is estimated by analyzing the size distribution of the desorbed cluster ions. The results suggest that the ion desorption mechanism, which is known as desorption induced by electronic transitions, can also be applied to explain the present results.

  15. Impact of Environmental Conditions (pH, Ionic Strength, And Electrolyte Type) On The Surface Charge And Aggregation Of Silver Nanoparticles Suspensions

    EPA Science Inventory

    The impact of capping agents and environmental conditions (pH, ionic strength, and background electrolytes) on surface charge and aggregation potential of silver nanoparticles (AgNPs) suspensions were investigated. Capping agents are chemicals used in the synthesis of nanopartic...

  16. Impact of Environmental Conditions (pH, Ionic Strength, And Electrolyte Type) On The Surface Charge And Aggregation Of Silver Nanoparticles Suspensions

    EPA Science Inventory

    The impact of capping agents and environmental conditions (pH, ionic strength, and background electrolytes) on surface charge and aggregation potential of silver nanoparticles (AgNPs) suspensions were investigated. Capping agents are chemicals used in the synthesis of nanopartic...

  17. Separation of carbon dioxide from nitrogen or methane by supported ionic liquid membranes (SILMs): influence of the cation charge of the ionic liquid.

    PubMed

    Hojniak, Sandra D; Khan, Asim Laeeq; Hollóczki, Oldamur; Kirchner, Barbara; Vankelecom, Ivo F J; Dehaen, Wim; Binnemans, Koen

    2013-12-05

    Supported ionic liquid membranes (SILMs) are promising tools for the separation of carbon dioxide from other gases. In this paper, new imidazolium, pyrrolidinium, piperidinium, and morpholinium ionic liquids with a triethylene glycol side chain and tosylate anions, as well as their symmetrical dicationic analogues, have been synthesized and incorporated into SILMs. The selectivities for CO2/N2 and CO2/CH4 separations have been measured. The selectivities exhibited by the dicationic ionic liquids are up to two times higher than the values of the corresponding monocationic ionic liquids. Quantum chemical calculations have been used to investigate the difference in the interaction of carbon dioxide with monocationic and dicationic ionic liquids. The reason for the increased gas separation selectivity of the dicationic ionic liquids is two-fold: (1) a decrease in permeance of nitrogen and methane through the ionic liquid layer, presumably due to their less favorable interactions with the gases, while the permeance of carbon dioxide is reduced much less; (2) an increase in the number of interaction sites for the interactions with the quadrupolar carbon dioxide molecules in the dicationic ionic liquids, compared to the monocationic analogues.

  18. A counter-charge layer in generalized solvents framework for electrical double layers in neat and hybrid ionic liquid electrolytes

    SciTech Connect

    Huang, Jingsong; Feng, Guang; Sumpter, Bobby G; Qiao, Rui; Meunier, Vincent

    2011-01-01

    Room-temperature ionic liquids (RTILs) have received significant attention as electrolytes due to a number of attractive properties such as their wide electrochemical windows. Since electrical double layers (EDLs) are the cornerstone for the applications of RTILs in electrochemical systems such as supercapacitors, it is important to develop an understanding of the structure capacitance relationships for these systems. Here we present a theoretical framework termed counter-charge layer in generalized solvents (CGS) for describing the structure and capacitance of the EDLs in neat RTILs and in RTILs mixed with different mass fractions of organic solvents. Within this framework, an EDL is made up of a counter-charge layer exactly balancing the electrode charge, and of polarized generalized solvents (in the form of layers of ion pairs, each of which has a zero net charge but has a dipole moment the ion pairs thus can be considered as a generalized solvent) consisting of all RTILs inside the system except the counter-ions in the counter-charge layer, together with solvent molecules if present. Several key features of the EDLs that originate from the strong ion ion correlation in RTILs, e.g., overscreening of electrode charge and alternating layering of counter-ions and co-ions, are explicitly incorporated into this framework. We show that the dielectric screening in EDLs is governed predominately by the polarization of generalized solvents (or ion pairs) in the EDL, and the capacitance of an EDL can be related to its microstructure with few a priori assumptions or simplifications. We use this framework to understand two interesting phenomena observed in molecular dynamics simulations of EDLs in a neat IL of 1-butyl-3- methylimidazolium tetrafluoroborate ([BMIM][BF4]) and in a mixture of [BMIM][BF4] and acetonitrile (ACN): (1) the capacitance of the EDLs in the [BMIM][BF4]/ACN mixture increases only slightly when the mass fraction of ACN in the mixture increases from zero

  19. Charging and aggregation of latex particles in aqueous solutions of ionic liquids: towards an extended Hofmeister series.

    PubMed

    Oncsik, Tamas; Desert, Anthony; Trefalt, Gregor; Borkovec, Michal; Szilagyi, Istvan

    2016-03-14

    The effect of ionic liquid (IL) constituents and other monovalent salts on the stability of polystyrene latex particles was studied by electrophoresis and light scattering in dilute aqueous suspensions. The surface charge and the aggregation rate were both sensitive to the type of ion leading to different critical coagulation concentration (CCC) values. Systematic variation of the type of IL cation and anion allows us to place these ions within the Hofmeister series. We find that the dicyanoamide anion should be placed between iodide and thiocyanate, while all 1-alkyl-3-methylimidazolium cations can be positioned to the left of the tetramethylammonium and ammonium ions. The hydrophobicity of the 1-butyl-1-methylpyrrolidinium (BMPL(+)) ion is intermediate between 1-ethyl-3-methylimidazolium (EMIM(+)) and 1-butyl-3-methylimidazolium (BMIM(+)). With increasing alkyl chain length, the 1-alkyl-3-methylimidazolium cations adsorb on the latex particles very strongly, and 1-hexyl-3-methylimidazolium (HMIM(+)) and 1-octyl-3-methylimidazolium (OMIM(+)) lead to pronounced charge reversal and to an intermediate restabilization region.

  20. Experimental evidence of high pressure decoupling between charge transport and structural dynamics in a protic ionic glass-former.

    PubMed

    Wojnarowska, Z; Rams-Baron, M; Knapik-Kowalczuk, J; Połatyńska, A; Pochylski, M; Gapinski, J; Patkowski, A; Wlodarczyk, P; Paluch, M

    2017-08-01

    In this paper the relaxation dynamics of ionic glass-former acebutolol hydrochloride (ACB-HCl) is studied as a function of temperature and pressure by using dynamic light scattering and broadband dielectric spectroscopy. These unique experimental data provide the first direct evidence that the decoupling between the charge transport and structural relaxation exists in proton conductors over a wide T-P thermodynamic space, with the time scale of structural relaxation being constant at the liquid-glass transition (τα = 1000 s). We demonstrate that the enhanced proton transport, being a combination of intermolecular H(+) hopping between cation and anion as well as tautomerization process within amide moiety of ACB molecule, results in a breakdown of the Stokes-Einstein relation at ambient and elevated pressure with the fractional exponent k being pressure dependent. The dT g /dP coefficient, stretching exponent βKWW and dynamic modulus E a /ΔV (#) were found to be the same regardless of the relaxation processes studied. This is in contrast to the apparent activation volume parameter that is different when charge transport and structural dynamics are considered. These experimental results together with theoretical considerations create new ideas to design efficient proton conductors for potential electrochemical applications.

  1. Trace Element Partitioning under Crustal and Uppermost Mantle Conditions: The Influences of Ionic Radius, Cation Charge, Pressure, and Temperature

    NASA Astrophysics Data System (ADS)

    Wood, B. J.; Blundy, J. D.

    2003-12-01

    The controls on partitioning of trace elements between crystals and silicate melts were initially the subject of crystal-chemical, rather than petrogenetic interest. Goldschmidt (1937) systematized his observations of elemental concentrations in minerals as a means of understanding and predicting element behavior during crystallization from liquids or gases. Thus, he proposed his three "rules" of element partitioning, which may be summarized as follows: (i) Any two ions of the same charge and very similar ionic radius have essentially the same crystal-liquid partition coefficient (D=[i]xtl/[i]liq, where [i] refers to the concentration of element i). (ii) If there is a small difference of ionic radius, the smaller ion enters the crystal preferentially, e.g., DMg2+>DFe2+, DK+>DRb+>DCs+. (iii) For ions of similar radius but different charges, the ion with the higher charge enters the crystal preferentially, i.e., DSc3+>DMg2+>DLi+, DCa2+>DNa+, and DBa2+>DK+. These principles were taught to generations of students and, as we will show below, under certain circumstances, retain a degree of validity. They are neither, however, universally correct nor do they have any quantitative applicability. The aim of this chapter is to summarize the ways in which Goldschmidt's work has been amplified through a combination of theory and experimental measurement in order to quantify crystal-liquid partitioning behavior.Since the development of accurate methods of determining element concentration at the ppm level, the trace-element contents of igneous rocks have frequently been used to model their chemical evolution. These studies use estimated crystal-liquid partition coefficients together with solutions for the differential equations describing, e.g., fractional crystallization or fractional melting (Schilling and Winchester, 1967; Gast, 1968; Shaw, 1970) to model evolution of the melt during precipitation or dissolution of the crystalline phases. Generally, because of lack of data

  2. When Like Charged Ions Attract in Ionic Liquids: Controlling the Formation of Cationic Clusters by the Interaction Strength of the Counterions.

    PubMed

    Strate, Anne; Niemann, Thomas; Michalik, Dirk; Ludwig, Ralf

    2017-01-09

    The properties of ionic liquids are described by a subtle balance between Coulomb interaction, hydrogen bonding, and dispersion forces. We show that lowering the attractive Coulomb interaction by choosing weakly coordinating anions leads to the formation of cationic clusters. These clusters of like-charged ions are stabilized by cooperative hydrogen bonding and controlled by the interaction potential of the anion. IR and NMR spectroscopy combined with computational methods are used to detect and characterize these unusual, counter-intuitively formed clusters. They can be only observed for weakly coordinating anions. When cationic clusters are formed, cyclic tetramers are particularly stable. Therein, cooperative hydrogen-bond attraction can compete with like-charge repulsion. We present a simple but effective spectroscopic scale for the possibility of like-charge attraction in ionic liquids, based on IR and NMR signatures.

  3. Characterization of electrical conduction and nature of charge carriers in mixed and ionic conductors

    NASA Astrophysics Data System (ADS)

    Geffroy, Pierre-Marie; Pons, Aénor; Béchade, Emilie; Masson, Olivier; Fouletier, Jacques

    2017-08-01

    The characterization of proton conduction leads to controversial data, often resulting from misinterpretation of the experimental measurements. All methods require the detection of minute variations in the hydrogen concentration in a flowing gas. Such analysis in a gas containing water vapor is a challenge. We propose a new setup allowing the measurement of P(O2), P(H2) and P(H2O). Two methods for determination of the transport numbers are used, i.e., the permeation and Faradaic efficiency methods. Two cases are considered in this study, i.e., a mixed conductor (mostly electronic conductor), i.e., palladium, and a purely ionic conductor, i.e., La9.6(SiO4)6O2.4 oxyapatite, which is an anionic conductor, though protonic conduction has been assumed in recent studies. This study clearly shows that La9.6(SiO4)6O2.4 oxyapatite is a pure anionic conductor, without contribution from protonic conduction, under usual conditions (1 atm., 475-615 °C).

  4. Surface charge of polymer particles in water: the role of ionic end-groups.

    PubMed

    Roger, Kevin; Eissa, Mohammed; Elaissari, Abdelhamid; Cabane, Bernard

    2013-09-10

    Polymer particles, containing macromolecules made by the polymerization of nonionic monomers, can be ionized in water thanks to the end-groups of the macromolecules. We show that poly(methylmethacrylate) particles with ionic end-groups can acquire colloidal properties such as dispersion metastability and electrokinetic mobility. We demonstrate that the variation of these colloidal properties according to solution pH is uniquely determined by the chemical nature of the end-groups and therefore by the nature of the initiator used in the polymerization reaction. We compare polymer dispersions in which the polymer particles were made by different processes (e.g., surfactant-free emulsion polymerization or precipitation of the macromolecules induced by solvent shifting). For each colloidal dispersion, we determine the number of end-groups that are actually located at the surfaces of the particles, and we show that this number is a trace of the process by which the macromolecules were self-assembled into colloidal particles. We propose that it is possible to recover mechanistic details of this self-assembly process through measurements of the distribution of end-groups within the particles.

  5. The Rates of Interexchange of Ions Across Fixed Charge Membranes in Bi-Ionic Systems

    PubMed Central

    Gottlieb, Melvin H.

    1968-01-01

    This paper examines the applicability of the Nernst-Planck approach in treating the relationship between the initial rates at which critical ions interexchange across permselective membranes in bi-ionic systems and the rates of self-exchange of these ions across the same membranes. Data are presented for five species of univalent cations with two types of cation permeable membranes, a polystyrene sulfonic acid-collodion matrix membrane, and an oxidized collodion membrane; five species of univalent anions were studied with a protamine-collodion matrix anion permeable membrane. Except with systems involving H+ ion, the experimentally found relationships between the rates of interexchange and the rates of self-exchange were in agreement, in most cases within ±5%, with the values calculated from an expression in which interaction between the critical ions in the membrane is not taken into account. In systems with H+ ion, the experimental rates of interexchange were from 27% to 40% less than calculated values. PMID:5713451

  6. An ionic charge-transfer dyad prepared cost-effectively from a tetrathiafulvalene carboxylate anion and a TMPyP cation.

    PubMed

    Xue, Li-Jun; Huo, Peng; Li, Yan-Hong; Hou, Jin-Le; Zhu, Qin-Yu; Dai, Jie

    2016-01-28

    Great progress has been made in combining a TTF moiety with a porphyrin unit by covalent bonds, but only a few examples were reported in which TTF and porphyrin assembled by noncovalent interactions. In contrast to the energy- and time-consuming synthetic procedures for the covalent system, the assembly of a non-covalent ionic system would be a cost-effective way to construct donor-acceptor ensembles. Herein a new type of ionic TTF-porphyrin dyad is obtained. A methylated tetra(4-pyridyl) porphyrin (5,10,15,20-tetrakis-(N-methyl-4-pyridyl)-porphyrin, TMPyP) is selected as the cation, and TTF-bicarboxylate (L(1)) or TTF-tetracarboxylate (L(2)) is used as the anion. Crystal structures of two TTF-TMPyP ionic D-A compounds, TMPyP-(HL(1))4·3H2O (1) and TMPyP-(H2L(2))2·5H2O (2), were characterized by single-crystal X-ray diffraction. The strong ionic interaction enhances the charge-transfer between the regular mixed-stacking donors and acceptors, which are investigated comprehensively by spectral, electrochemical and theoretical studies. The variation in properties between L(1) and L(2) is of great advantage to understand the influence factors for charge-transfer. The charge-transfer properties can be modulated not only by the nature of the donor or the acceptor, but also the cation-anion ratio in the salt, which shows great flexibility of the D-A ionic dyad in the design and preparation of new charge-transfer systems.

  7. Solar Wind Sputtering of Lunar Soil Analogs: The Effect of Ionic Charge and Mass

    NASA Technical Reports Server (NTRS)

    Hijazi, H.; Bannister, M. E.; Meyer, F. W.; Rouleau, C. M.; Barghouty, A. F.; Rickman, D. L.; Hijazi, H.

    2014-01-01

    In this contribution we report sput-tering measurements of anorthite, an analog material representative of the lunar highlands, by singly and multicharged ions representative of the solar wind. The ions investigated include protons, as well as singly and multicharged Ar ions (as proxies for the heavier solar wind constituents), in the charge state range +1 to +9, and had a fixed solar-wind-relevant impact velocity of approximately 310 km/s or 500 eV/ amu. The goal of the measurements was to determine the sputtering contribution of the heavy, multicharged minority solar wind constituents in comparison to that due to the dominant H+ fraction.

  8. The ionic charge of Copper-64 complexes conjugated to an engineered antibody effects biodistribution

    DOE PAGES

    Dearling, Jason L. J.; Smith, Suzanne V.; Paterson, Brett M.; ...

    2015-04-15

    The development of biomolecules as imaging probes requires radiolabeling methods that do not significantly influence their biodistribution. Sarcophagine (Sar) chelators form extremely stable complexes with copper, and are therefore a promising option for labeling proteins with ⁶⁴Cu. However, initial studies using the first-generation sarcophagine bifunctional chelator SarAr to label the engineered antibody fragment ch14.18-ΔCH2 (MW 120 kDa) with ⁶⁴Cu showed high tracer retention in the kidneys,(>38% injected dose per gram (ID/g) 48 h post-injection), presumably because the high local positive charge on the CuII-SarAr moiety resulted in increased binding of the labeled protein to the negatively charged basal cells ofmore » the glomerulus. To test this hypothesis, ch14.18-ΔCH2 was conjugated with a series of Sar derivatives of decreasing positive charge and three commonly used macrocyclic polyaza polycarboxylate (PAC) BFCs. The immunoconjugates were labeled with ⁶⁴Cu and injected into mice, and PET/CT images were obtained at 24 and 48 h post injection (p.i.). At 48 h p.i., ex vivo biodistribution was carried out. In addition, to demonstrate the potential of metastasis detection using ⁶⁴Cu-labeled ch14.18-ΔCH2, a preclinical imaging study of intrahepatic neuroblastoma tumors was performed carried out. Reducing the positive charge on the Sar chelators decreased kidney uptake of Cu-labeled ch14.18-ΔCH2 by more than 6-fold, from >45 ID/g to <6% ID/g, while the uptake in most other tissues, including liver, was relatively unchanged. However, despite this dramatic decrease, the renal uptake of the PAC BFCs was generally lower than that of the Sar derivatives, as was the liver uptake. Uptake of ⁶⁴Cu-labeled ch14.18-ΔCH2 in neuroblastoma hepatic metastases was detected using PET.« less

  9. The ionic charge of Copper-64 complexes conjugated to an engineered antibody effects biodistribution

    SciTech Connect

    Dearling, Jason L. J.; Smith, Suzanne V.; Paterson, Brett M.; Akurathi, Vamisidhar; Betanzos-Lara, Soledad; Treves, S. Ted; Voss, Stephan D.; White, Jonathan M.; Huston, James S.; Donnelly, Paul S.; Packard, Alan B.

    2015-04-15

    The development of biomolecules as imaging probes requires radiolabeling methods that do not significantly influence their biodistribution. Sarcophagine (Sar) chelators form extremely stable complexes with copper, and are therefore a promising option for labeling proteins with ⁶⁴Cu. However, initial studies using the first-generation sarcophagine bifunctional chelator SarAr to label the engineered antibody fragment ch14.18-ΔCH2 (MW 120 kDa) with ⁶⁴Cu showed high tracer retention in the kidneys,(>38% injected dose per gram (ID/g) 48 h post-injection), presumably because the high local positive charge on the CuII-SarAr moiety resulted in increased binding of the labeled protein to the negatively charged basal cells of the glomerulus. To test this hypothesis, ch14.18-ΔCH2 was conjugated with a series of Sar derivatives of decreasing positive charge and three commonly used macrocyclic polyaza polycarboxylate (PAC) BFCs. The immunoconjugates were labeled with ⁶⁴Cu and injected into mice, and PET/CT images were obtained at 24 and 48 h post injection (p.i.). At 48 h p.i., ex vivo biodistribution was carried out. In addition, to demonstrate the potential of metastasis detection using ⁶⁴Cu-labeled ch14.18-ΔCH2, a preclinical imaging study of intrahepatic neuroblastoma tumors was performed carried out. Reducing the positive charge on the Sar chelators decreased kidney uptake of Cu-labeled ch14.18-ΔCH2 by more than 6-fold, from >45 ID/g to <6% ID/g, while the uptake in most other tissues, including liver, was relatively unchanged. However, despite this dramatic decrease, the renal uptake of the PAC BFCs was generally lower than that of the Sar derivatives, as was the liver uptake. Uptake of ⁶⁴Cu-labeled ch14.18-ΔCH2 in neuroblastoma hepatic metastases was detected using PET.

  10. Charge Fluctuations and Boundary Conditions of Biological Ion Channels: Effect on the Ionic Transition Rate

    SciTech Connect

    Tindjong, R.; McClintock, P. V. E.; Luchinsky, D. G.; Kaufman, I.; Eisenberg, R. S.

    2009-04-23

    A self-consistent solution is derived for the Poisson-Nernst-Planck (PNP) equation, valid both inside a biological ion channel and in the adjacent bulk fluid. An iterative procedure is used to match the two solutions together at the channel mouth. Charge fluctuations at the mouth are modeled as shot noise flipping the height of the potential barrier at the selectivity site. The resultant estimates of the conductivity of the ion channel are in good agreement with Gramicidin experimental measurements and they reproduce the observed current saturation with increasing concentration.

  11. First-Principles United Atom Force Field for the Ionic Liquid BMIM(+)BF4(-): An Alternative to Charge Scaling.

    PubMed

    Son, Chang Yun; McDaniel, Jesse G; Schmidt, J R; Cui, Qiang; Yethiraj, Arun

    2016-04-14

    Molecular dynamics study of ionic liquids (ILs) is a challenging task. While accurate fully polarizable atomistic models exist, they are computationally too demanding for routine use. Most nonpolarizable atomistic models predict diffusion constants that are much lower than experiment. Scaled charge atomistic models are cost-effective and give good results for single component ILs but are in qualitative error for the phase behavior of mixtures, due to inaccurate prediction of the IL cohesive energy. In this work, we present an alternative approach for developing computationally efficient models that importantly preserves both the correct dynamics and cohesive energy of the IL. Employing a "top-down" approach, a hierarchy of coarse-grained models for BMIM(+)BF4(-) are developed by systematically varying the polarization/atomic resolution of the distinct functional groups. Parametrization is based on symmetry-adapted perturbation theory (SAPT) calculations involving the homomolecular species; all cross interactions are obtained from mixing rules, and there are no adjustable parameters. We find that enhanced dynamics from a united-atom description counteracts the effect of reduced polarization, enabling computationally efficient models that exhibit quantitative agreement with experiment for both static and dynamic properties. We give explicit suggestions for reduced-description models that are computationally more efficient, more accurate, and more fundamentally sound than existing nonpolarizable atomistic models.

  12. Light scattering studies on solutions of charged rod-like fd-virus at very low ionic strength

    NASA Astrophysics Data System (ADS)

    Schulz, Susanne F.; Maier, Erich E.; Weber, R.

    1989-01-01

    Light scattering experiments are reported on semidilute, aqueous solutions of rod-like fd-virus (length L=880 nm, molecular weight 16.4×106 dalton) near the overlap concentration c*=1 particle/length3. In solutions of very low ionic strength, a liquid-like structure with a significant intensity maximum of the elastically scattered light is observed. The structure is caused by the electrostatic interaction of the charged rods. It vanishes, when enough salt is added so that the interaction potential is screened on the interparticle distance. The scattering vector qmax of the maximum scales with the fd concentration as c1/2. The experimental values for qmaxL fit very well to Monto Carlo simulations if the concentration is scaled to c*. Dynamic light scattering of the fd solutions reflects the influence of the static structure factor in the same way as observed for interacting spherical macromolecules: The first cumulant of the field correlation function divided by the square of the scattering vector shows a behavior reciprocal to that of the static structure factor.

  13. Synthesis of p -and n-type Gels Doped with Ionic Charge Carriers

    NASA Astrophysics Data System (ADS)

    Alveroglu, E.; Yilmaz, Y.

    2010-03-01

    In this study, we synthesized the new kinds of semiconducting polymeric gels having negative ( n-type) and positive ( p-type) counter ions as charge carriers. The polyacrylamide gel was doped with pyranine (8-hydroxypyrene-1,3,6-trisulfonic acid, trisodium salt), having {text{SO}}3^{ - } ions as side groups and Na+ as counter ions, so-called p-type semiconducting gel. The doping process was performed during the polymerization where the pyranine binds to the polymer strands over OH group chemically via radical addition. In a similar way, N-isopropylacrylamide (NIPA) gel was doped with methacrylamidopropyltrimethyl ammonium chloride (MAPTAC), having Cl- as counter ions, so-called n-type semiconducting gel. Here MAPTAC was embedded by copolymerization within the polymer network (NIPA). These semiconducting gels can show different electrical properties by changing the concentration of the doping agents, swelling ratio etc. We have shown that the pn junction, formed by combining p-type and n-type gels together in close contact, rectifies the current similar to the conventional Si and Ge diodes.

  14. Rotational Diffusion of Charged and Nondipolar Solutes in Ionic Liquid-Organic Solvent Mixtures: Evidence for Stronger Specific Solute-Solvent Interactions in Presence of Organic Solvent.

    PubMed

    Prabhu, Sugosh R; Dutt, G B

    2015-08-20

    Rotational diffusion of a charged solute, rhodamine 110 (R110), and a nondipolar solute, 2,5-dimethyl-1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DMDPP), has been investigated in ionic liquids, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Tf2N]) and 1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([BMIM][FAP]), with 0.8 mole fraction of dibenzyl ether (DBE). This study has been undertaken to find out how specific interactions between the solute and the ionic liquid are affected upon dilution with a nondipolar solvent. It has been observed that at a given viscosity (η) and temperature (T), the reorientation times of R110 increase by 40-60% in the ionic liquid-organic solvent mixtures compared to ones in the corresponding neat ionic liquids. In the case of DMDPP, the influence of DBE is less pronounced, and its reorientation times increase by 25-50% at a given η/T. The addition of DBE weakens the numerous interactions prevailing between the cations and the anions of the ionic liquids, which results in stronger specific interactions between the solutes and the constituent ions, consequently leading to slower rotation of the solutes.

  15. Charged local anesthetics block ionic conduction in the sheep cardiac sarcoplasmic reticulum calcium release channel.

    PubMed Central

    Tinker, A; Williams, A J

    1993-01-01

    We have examined the effect of the charged local anesthetics QX314, QX222, and Procaine on monovalent cation conduction in the Ca2+ release channel of the sheep cardiac sarcoplasmic reticulum. All three blockers only affect cation conductance when present at the cytoplasmic face of the channel. QX222 and Procaine act as voltage-dependent blockers. With 500 Hz filtering, this is manifest as a relatively smooth reduction in single-channel current amplitude most prominent at positive holding potentials. Quantitative analysis gives an effective valence of approximately 0.9 for both ions and Kb(0)s of 9.2 and 15.8 mM for QX222 and Procaine, respectively. Analysis of the concentration dependence of block suggests that QX222 is binding to a single site with a Km of 491 microM at a holding potential of 60 mV. The use of amplitude distribution analysis, with the data filtered at 1 to 2 kHz, reveals that the voltage and concentration dependence of QX222 block occurs largely because of changes in the blocker on rate. The addition of QX314 has a different effect, leading to the production of a substate with an amplitude of approximately one-third that of the control. The substate's occurrence is dependent on holding potential and QX314 concentration. Quantitative analysis reveals that the effect is highly voltage dependent, with a valence of approximately 1.5 caused by approximately equal changes in the on and off rates. Kinetic analysis of the concentration dependence of the substate occurrence reveals positive cooperativity with at least two QX314s binding to the conduction pathway, and this is largely accounted for by changes in the on rate. A paradoxical increase in the off rate at high positive holding potentials and with increasing QX314 concentration at 80 mV suggests the existence of a further QX314-dependent reaction that is both voltage and concentration dependent. The substate block is interpreted physically as a form of partial occlusion in the vestibule of the

  16. Design of an electrolyte composition for stable and rapid charging-discharging of a graphite negative electrode in a bis(fluorosulfonyl)imide-based ionic liquid

    NASA Astrophysics Data System (ADS)

    Matsui, Yukiko; Yamagata, Masaki; Murakami, Satoshi; Saito, Yasuteru; Higashizaki, Tetsuya; Ishiko, Eriko; Kono, Michiyuki; Ishikawa, Masashi

    2015-04-01

    We evaluate the effects of lithium salt on the charge-discharge performance of a graphite negative electrode in 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMImFSI) ionic liquid-based electrolytes. Although the graphite negative electrode exhibits good cyclability and rate capability in both 0.43 mol dm-3 LiFSI/EMImFSI and LiTFSI/EMImFSI (TFSI- = bis(trifluoromethylsulfonyl)imide) at room temperature, only the LiFSI/EMImFSI system enables the graphite electrode to be operated with sufficient discharge capacity at the low temperature of 0 °C, even though there is no noticeable difference in ionic conductivity, compared with LiTFSI/EMImFSI. Furthermore, a clear difference in the low-temperature behaviors of the two cells composed of EMImFSI with a high-concentration of lithium salts is observed. Additionally, charge-discharge operation of the graphite electrode at C-rate of over 5.0 can be achieved using of the high-concentration LiFSI/EMImFSI electrolyte. Considering the low-temperature characteristics in both high-concentration electrolytes, the stable and rapid charge-discharge operation in the high-concentration LiFSI/EMImFSI is presumably attributed to a suitable electrode/electrolyte interface with low resistivity. These results suggest that optimization of the electrolyte composition can realize safe and high-performance lithium-ion batteries that utilize ionic liquid-based electrolytes.

  17. On the physical origin of the cation-anion intermediate bond in ionic liquids Part I. Placing a (weak) hydrogen bond between two charges.

    PubMed

    Lehmann, Sebastian B C; Roatsch, Martin; Schöppke, Matthias; Kirchner, Barbara

    2010-07-21

    The intermediate bond forces in ionic liquids are investigated from static quantum chemical calculations at various methods and two basis sets. The experimentally observed red-shift of the donor-proton bond stretching frequency due to a bond elongation is confirmed by all methods. Comparing Hartree-Fock to second-order Møller-Plesset perturbation theory, the Hartree-Fock method gives in many cases an erroneous description of the geometries. Furthermore, the Hartree-Fock interaction energies can deviate up to 60 kJ mol(-1) from Møller-Plesset perturbation theory indicating the importance of dispersion interaction. While the usual trends of decreasing stability or interaction energies with increasing ion sizes are found, the geometries involving hydrogen atoms do not change this order of total interaction energies. Therefore, the hydrogen bond is not the most important interaction for ion pairs with regard to the total interaction energy. On the other hand, the different established analysis methods give rise to hydrogen bonding in several ion pairs. Charge analysis reveals the hydrogen-bonding character of the ion pair and shows, depending on the type of ions combined and further on the type of conformers considered, that a hydrogen bond can be present. The possibility of hydrogen bonding is also shown by an analysis of the frontier orbitals. Calculating potential energy surfaces and observing from this the change in the donor proton bond indicates that regular hydrogen bonds are possible in ion pairs of ionic liquids. Thereby, the maximum of bond elongation exceeds the one of a usual hydrogen bond by far. The more salt-like hydrogen-bonded ion pair [NH(4)][BF(4)] exhibits a steeper maximum than the more ionic liquid like ion pair [EtNH(3)][BF(4)]. The fact that imidazolium-based ionic liquids as [Emim][Cl] can display two faces, hydrogen bonding and purely ionic bonding, points to a disturbing rather than stabilizing role of hydrogen bonding on the interaction of

  18. Ionic Structure at Dielectric Interfaces

    NASA Astrophysics Data System (ADS)

    Jing, Yufei

    The behavior of ions in liquids confined between macromolecules determines the outcome of many nanoscale assembly processes in synthetic and biological materials such as colloidal dispersions, emulsions, hydrogels, DNA, cell membranes, and proteins. Theoretically, the macromolecule-liquid boundary is often modeled as a dielectric interface and an important quantity of interest is the ionic structure in a liquid confined between two such interfaces. The knowledge gleaned from the study of ionic structure in such models can be useful in several industrial applications, such as biosensors, lithium-ion batteries double-layer supercapacitors for energy storage and seawater desalination. Electrostatics plays a critical role in the development of such functional materials. Many of the functions of these materials, result from charge and composition heterogeneities. There are great challenges in solving electrostatics problems in heterogeneous media with arbitrary shapes because electrostatic interactions remains unknown but depend on the particular density of charge distributions. Charged molecules in heterogeneous media affect the media's dielectric response and hence the interaction between the charges is unknown since it depends on the media and on the geometrical properties of the interfaces. To determine the properties of heterogeneous systems including crucial effects neglected in classical mean field models such as the hard core of the ions, the dielectric mismatch and interfaces with arbitrary shapes. The effect of hard core interactions accounts properly for short range interactions and the effect of local dielectric heterogeneities in the presence of ions and/or charged molecules for long-range interactions are both analyzed via an energy variational principle that enables to update charges and the medium's response in the same simulation time step. In particular, we compute the ionic structure in a model system of electrolyte confined by two planar dielectric

  19. Charge-tagged N-heterocyclic carbenes (NHC): Direct transfer from ionic liquid solutions and long-lived nature in the gas phase

    NASA Astrophysics Data System (ADS)

    Rodrigues, Thyago S.; Lesage, Denis; da Silva, Wender A.; Cole, Richard B.; Ebeling, Günter; Dupont, Jaïrton; de Oliveira, Heibbe C. B.; Eberlin, Marcos N.; Neto, Brenno A. D.

    2017-06-01

    Negatively charge-tagged N-heterocyclic carbenes have been formed in solution via deprotonation of imidazolium ions bearing acid side groups and transferred to the gas phase via ESI(-)-MS. The structure of the putative and apparently stable gaseous carbenes formed in such conditions were then probed via reactions with carbon dioxide using a triple quadrupole mass spectrometer particularly optimized for ion/molecule reactions of ESI-generated ions. Complete conversion to imidazolium carboxylates was achieved, which seems to demonstrate the efficiency of the transfer, the gas-phase stability, and the long-lived nature of these unprecedented charge-tagged carbenes and their predominance in the ionic population. Comprehensive studies on the intrinsic reactivity of N-heterocyclic carbenes with silent charge tags are therefore possible. [Figure not available: see fulltext.

  20. Crystallization of binary ionic mixtures in dense stellar plasmas

    NASA Astrophysics Data System (ADS)

    Segretain, L.; Chabrier, G.

    1993-04-01

    The crystallization diagrams of arbitrary dense binary ionic mixtures are examined within the framework of the density-functional theory of freezing. The behaviour of the phase diagram is shown to depend strongly on the charge ratio in the mixture. As the charge ratio Z1/Z2 is lowered, the phase diagram evolves from a spindle shape into an azeotropic phase diagram and finally into a eutectic phase diagram. This has import ant consequences on the crystallization of trace elements in White Dwarfs, and on the subsequent gravitational energy release, leading to a substantial modification of the cooling history of these stars.

  1. A force field for guanidinium-based ionic liquids that utilizes the electron charge distribution of the actual liquid: a molecular simulation study.

    PubMed

    Klähn, Marco; Seduraman, Abirami; Wu, Ping

    2008-09-04

    We propose a new all-atom force field for guanidinium-based ionic liquids (GILs) which is based on the charge distribution in the actual liquid. It comprises all cations that can be built by attaching alkyl chains of variable length to an acyclic or cyclic guanidinium compound and that are paired with nitrate or perchlorate anions. We based the parametrization of the force field on liquid-phase charge distributions to improve the prediction of energetic and dynamic properties of GILs. The impact of electron charge transfer and polarization on various properties of GILs is systematically assessed. A significant average electron charge transfer between -0.12 and -0.06 e from anions to the central guanidinium group of the cations and a strong polarization of acyclic cations are observed by applying a combined quantum mechanical/molecular mechanical (QM/MM) approach. Molecular dynamics simulations of GILs are performed, utilizing the proposed force field. Derived structures approach the accuracy of QM/MM structures, and a previously reported crystal structure remains stable throughout the simulations. Mass densities are reproduced with a deviation of only 1.4% from experimental data. The calculated melting point of a GIL crystal deviates only 8% from the measured value. Self-diffusion coefficients of various GILs are reported, and a comparison with a diffusion coefficient derived from experimental data indicates that the values are within a reasonable range. We observe that the melting point of a GIL crystal was lowered up to 60 K and that diffusion coefficients are substantially increased by a factor of up to 3.5 upon consideration of charge transfer and polarization. The results demonstrate that liquid-phase partial charges are capable of improving the quality of ionic liquid force fields substantially and that their utilization led to a model that can be applied to predict structural, energetic, and dynamic properties of GILs.

  2. Charge carrier dynamics and relaxation in (polyethylene oxide-lithium-salt)-based polymer electrolyte containing 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide as ionic liquid.

    PubMed

    Karmakar, A; Ghosh, A

    2011-11-01

    In this paper we report the dynamics of charge carriers and relaxation in polymer electrolytes based on polyethylene oxide (PEO), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPTFSI) ionic liquid prepared by solution cast technique. It has been observed that the incorporation of BMPTFSI into PEO-LiTFSI electrolyte is an effective way for increasing the amorphous phase to a large extent. It has also been observed that both the glass transition and melting temperatures decrease with the increase of BMPTFSI concentration. The ionic conductivity of these polymer electrolytes increases with the increase of BMPTFSI concentration. The highest ionic conductivity obtained at 25 °C is ~3×10(-4) S cm(-1) for the electrolyte containing 60 wt % BMPTFSI and ethylene oxide (EO)/Li ratio of 20. The temperature dependence of the dc conductivity and the hopping frequency show Vogel-Tamman-Fulcher type behavior indicating a strong coupling between the ionic and the polymer chain segmental motions. The frequency dependence of the ac conductivity exhibits a power law with an exponent n which decreases with the increase of temperature. The scaling of the ac conductivity indicates that relaxation dynamics of charge carriers follows a common mechanism for all temperatures and BMPTFSI concentrations. We have also presented the electric modulus data which have been analyzed in the framework of a Havriliak-Negami equation and the shape parameters obtained by the analysis show slight temperature dependence, but change sharply with BMPTFSI concentration. The stretched exponent β obtained from Kohlrausch-Williams-Watts fit to the modulus data is much lower than unity signifying that the relaxation is highly nonexponential. The decay function obtained from analysis of experimental modulus data is highly asymmetric with time.

  3. Charge carrier dynamics and relaxation in (polyethylene oxide-lithium-salt)-based polymer electrolyte containing 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide as ionic liquid

    NASA Astrophysics Data System (ADS)

    Karmakar, A.; Ghosh, A.

    2011-11-01

    In this paper we report the dynamics of charge carriers and relaxation in polymer electrolytes based on polyethylene oxide (PEO), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPTFSI) ionic liquid prepared by solution cast technique. It has been observed that the incorporation of BMPTFSI into PEO-LiTFSI electrolyte is an effective way for increasing the amorphous phase to a large extent. It has also been observed that both the glass transition and melting temperatures decrease with the increase of BMPTFSI concentration. The ionic conductivity of these polymer electrolytes increases with the increase of BMPTFSI concentration. The highest ionic conductivity obtained at 25 °C is ˜3×10-4 S cm-1 for the electrolyte containing 60 wt % BMPTFSI and ethylene oxide (EO)/Li ratio of 20. The temperature dependence of the dc conductivity and the hopping frequency show Vogel-Tamman-Fulcher type behavior indicating a strong coupling between the ionic and the polymer chain segmental motions. The frequency dependence of the ac conductivity exhibits a power law with an exponent n which decreases with the increase of temperature. The scaling of the ac conductivity indicates that relaxation dynamics of charge carriers follows a common mechanism for all temperatures and BMPTFSI concentrations. We have also presented the electric modulus data which have been analyzed in the framework of a Havriliak-Negami equation and the shape parameters obtained by the analysis show slight temperature dependence, but change sharply with BMPTFSI concentration. The stretched exponent β obtained from Kohlrausch-Williams-Watts fit to the modulus data is much lower than unity signifying that the relaxation is highly nonexponential. The decay function obtained from analysis of experimental modulus data is highly asymmetric with time.

  4. A Self-Consistent Charge-Embedding Methodology for ab initio Qantum Chemical Custer Modeling of Ionic Solids and Surfaces: Application to the (001) Surface of Hematite

    SciTech Connect

    Batista, Enrique; Friesner, Richard A.

    2002-07-16

    To ab initio simulate an ionic crystal using a cluster of atoms, one must surround that cluster with point charges. These point charges add the effect of the electrostatic potential of the rest of the crystal on the electronic structure of the quantum cluster. The value of the point charges has to be chosen to reproduce the crystal field in the region of the cluster. In this work, a method to compute the necessary point charges is presented. The algorithm to choose the point charges is an extension of the one presented by Derenzo et al. [J. Chem. Phys. 2000, 112, 2074]. The method consists of a self-consistent loop, fitting in each iteration the value of the point charges to reproduce the electrostatic field, calculated from the quantum simulation, in the region of the cluster. This method was then applied to the study of the (001) basal surface of hematite, R-Fe2O3. As the cluster size is systematically increased, it is shown that to fully converge the electrostatic effect on the electronic structure of the cluster, clusters of the order of 60 atoms are necessary. As a convergence parameter for the cluster to the bulk behavior, we used the ionization energy of the cluster. In the limit of an infinite cluster, we obtained the work function of hematite to be 5.6 eV.

  5. Numerical study of density functional theory with mean spherical approximation for ionic condensation in highly charged confined electrolytes

    NASA Astrophysics Data System (ADS)

    Joubaud, R.; Bernard, O.; Delville, A.; Ern, A.; Rotenberg, B.; Turq, P.

    2014-06-01

    We investigate numerically a density functional theory (DFT) for strongly confined ionic solutions in the canonical ensemble by comparing predictions of ionic concentration profiles and pressure for the double-layer configuration to those obtained with Monte Carlo (MC) simulations and the simpler Poisson-Boltzmann (PB) approach. The DFT consists of a bulk (ion-ion) and an ion-solid part. The bulk part includes nonideal terms accounting for long-range electrostatic and short-range steric correlations between ions and is evaluated with the mean spherical approximation and the local density approximation. The ion-solid part treats the ion-solid interactions at the mean-field level through the solution of a Poisson problem. The main findings are that ionic concentration profiles are generally better described by PB than by DFT, although DFT captures the nonmonotone co-ion profile missed by PB. Instead, DFT yields more accurate pressure predictions than PB, showing in particular that nonideal effects are important to describe highly confined ionic solutions. Finally, we present a numerical methodology capable of handling nonconvex minimization problems so as to explore DFT predictions when the reduced temperature falls below the critical temperature.

  6. Lithium-modulated conduction band edge shifts and charge-transfer dynamics in dye-sensitized solar cells based on a dicyanamide ionic liquid.

    PubMed

    Bai, Yu; Zhang, Jing; Wang, Yinghui; Zhang, Min; Wang, Peng

    2011-04-19

    Lithium ions are known for their potent function in modulating the energy alignment at the oxide semiconductor/dye/electrolyte interface in dye-sensitized solar cells (DSCs), offering the opportunity to control the associated multichannel charge-transfer dynamics. Herein, by optimizing the lithium iodide content in 1-ethyl-3-methylimidazolium dicyanamide-based ionic liquid electrolytes, we present a solvent-free DSC displaying an impressive 8.4% efficiency at 100 mW cm(-2) AM1.5G conditions. We further scrutinize the origins of evident impacts of lithium ions upon current density-voltage characteristics as well as photocurrent action spectra of DSCs based thereon. It is found that, along with a gradual increase of the lithium content in ionic liquid electrolytes, a consecutive diminishment of the open-circuit photovoltage arises, primarily owing to a noticeable downward movement of the titania conduction band edge. The conduction band edge displacement away from vacuum also assists the formation of a more favorable energy offset at the titania/dye interface, and thereby leads to a faster electron injection rate and a higher exciton dissociation yield as implied by transient emission measurements. We also notice that the adverse influence of the titania conduction band edge downward shift arising from lithium addition upon photovoltage is partly compensated by a concomitant suppression of the triiodide involving interfacial charge recombination. © 2011 American Chemical Society

  7. The correlation of the properties of pyrrolidinium-based ionic liquid electrolytes with the discharge-charge performances of rechargeable Li-O2 batteries

    NASA Astrophysics Data System (ADS)

    Li, Yu; Zhang, Zhonglin; Duan, Donghong; Sun, Yanbo; Wei, Guoqiang; Hao, Xiaogang; Liu, Shibin; Han, Yunxia; Meng, Weijuan

    2016-10-01

    Pyrrolidinium-based ionic liquids (ILs), such as PYR13TFSI, PYR14TFSI, and PYR1(2O1)TFSI, exhibit high thermal and electrochemical stability with wide electrochemical windows as electrolytes for application to rechargeable Li-O2 batteries. In this work, several fundamental properties of three ILs are measured: the ionic conductivity, oxygen solubility, and oxygen diffusion coefficient. The oxygen electro-reduction kinetics is characterized using cyclic voltammetry. The performances of Li-O2 batteries with these IL electrolytes are also investigated using electrochemical impedance spectroscopy and galvanostatic discharge-charge tests. The results demonstrate that the PYR1(2O1)TFSI electrolyte battery has a higher first-discharge voltage than the PYR13TFSI electrolyte and PYR14TFSI electrolyte batteries. Both PYR13TFSI- and PYR1(2O1)TFSI-based batteries exhibit higher first-discharge capacities and better cycling stabilities than the PYR14TFSI-based battery for 30 cycles. A theoretical analysis of the experimental results shows that the diffusion coefficient and solubility of oxygen in the electrolyte remarkably affect the discharge capacity and cycling stability of the batteries. Particularly, the oxygen diffusion coefficient of the IL electrolyte can effectively facilitate the electrochemical oxygen electro-reduction reaction and oxygen concentration distribution in the catalyst layers of air electrodes. The oxygen diffusion coefficient and oxygen solubility improvements of IL electrolytes can enhance the discharge-charge performances of Li-O2 batteries.

  8. Ion transport with charge-protected and non-charge-protected cations in alcohol-based electrolytes using the compensated Arrhenius formalism. Part I: ionic conductivity and the static dielectric constant.

    PubMed

    Petrowsky, Matt; Fleshman, Allison; Frech, Roger

    2012-05-17

    The temperature dependence of ionic conductivity and the static dielectric constant is examined for 0.30 m TbaTf- or LiTf-1-alcohol solutions. Above ambient temperature, the conductivity increases with temperature to a greater extent in electrolytes whose salt has a charge-protected cation. Below ambient temperature, the dielectric constant changes only slightly with temperature in electrolytes whose salt has a cation that is not charge-protected. The compensated Arrhenius formalism is used to describe the temperature-dependent conductivity in terms of the contributions from both the exponential prefactor σo and Boltzmann factor exp(-Ea/RT). This analysis explains why the conductivity decreases with increasing temperature above 65 °C for the LiTf-dodecanol electrolyte. At higher temperatures, the decrease in the exponential prefactor is greater than the increase in the Boltzmann factor.

  9. Ion transport with charge-protected and non-charge-protected cations using the compensated Arrhenius formalism. Part 2. Relationship between ionic conductivity and diffusion.

    PubMed

    Petrowsky, Matt; Fleshman, Allison; Bopege, Dharshani N; Frech, Roger

    2012-08-09

    Temperature-dependent ionic conductivities and cation/anion self-diffusion coefficients are measured for four electrolyte families: TbaTf-linear primary alcohols, LiTf-linear primary alcohols, TbaTf-n-alkyl acetates, and LiTf-n-alkyl acetates. The Nernst-Einstein equation does not adequately describe the data. Instead, the compensated Arrhenius formalism is applied to both conductivity and diffusion data. General trends based on temperature and alkyl chain length are observed when conductivity is plotted against cation or anion diffusion coefficient, but there is no clear pattern to the data. However, plotting conductivity exponential prefactors against those for diffusion results in four distinct curves, one each for the alcohol and acetate families described above. Furthermore, the TbaTf-alcohol and TbaTf-acetate data are "in line" with each other. The conductivity prefactors for the LiTf-alcohol data are smaller than those for the TbaTf data. The LiTf-acetate data have the lowest conductivity prefactors. This trend in prefactors mirrors the observed trend in degree of ionic association for these electrolytes.

  10. Statistical mechanics of dust charging in a multi-ion plasma with negative and positive ionic species

    SciTech Connect

    Mishra, S. K.; Misra, Shikha

    2015-02-15

    On the basis of statistical mechanics and charging kinetics, the charge distribution over uniform size spherical dust particles in a multi-ion plasma comprising of multiple charged negative and positive ions is investigated. Two specific situations where the complex plasma is viz., (i) dark (no emission from dust) and (ii) irradiated by laser light (causing photoemission from dust) have been taken into account. The analytical formulation includes the population balance equation for the charged dust particles along with number and energy balance of the complex plasma constituents. The departure of the results for multi-ion plasma from that in case of usual singly charged positive ion plasma is graphically illustrated and discussed. In contrast to electron-ion plasma, significant number of particles is seen to acquire opposite charge in case of pure positive-negative ion plasma, even in the absence of electron emission from the dust grains. The effects of various plasma parameters viz., number density, particle size, and work function of dust on charge distribution have also been examined.

  11. Modulation of the metarhodopsin I/metarhodopsin II equilibrium of bovine rhodopsin by ionic strength--evidence for a surface-charge effect.

    PubMed

    Delange, F; Merkx, M; Bovee-Geurts, P H; Pistorius, A M; Degrip, W J

    1997-01-15

    The effects of ionic strength on formation and decay of metarhodopsin II (MII), the active photointermediate of bovine rhodopsin, were studied in the native membrane environment by means of ultraviolet/ visible and Fourier-transform infrared (FTIR) spectroscopy. By increasing the concentration of KCl in the range from hypotonic to 4 M, the apparent pKa of the metarhodopsin I(MI)/MII equilibrium is shifted by approximately pH three, in favor of the MII intermediate. In addition, the apparent rate of MII formation is enhanced by an increase in ionic strength (about twofold in the presence of 2 M KCl). MIII decay is independent of the salt concentration. Attenuated-total-reflectance/FTIR data show that the high-salt conditions have no effect on the rigidity of the membrane matrix and do not induce structural changes in the intermediates themselves. Different salts were tested for their ability to shift the MI/MII equilibrium; however, no clear ion dependence was observed. We interpret these results as an indication for direct involvement of the cytosolic surface charge in the regulation of the photochemical activity of bovine rhodopsin.

  12. Dipolar self-consistent field theory for ionic liquids between charged plates: Effects of dielectric contrast between cation and anion under external electrostatic fields

    NASA Astrophysics Data System (ADS)

    Nakamura, Issei

    We develop a new dipolar self-consistent field theory (DSCFT) for both incompressible and compressible ionic liquids under external electrostatic fields. Our theory accounts for the difference between the dipole moments and the molecular volumes of the cation and anion, and the double layer caused by the strong association of the ions with the electrodes. To date, few theoretical studies have considered the dielectric contrast between the cation and anion. Thus, our study focuses on the effect of the dielectric inhomogeneity on the ion distribution and the capacitance. Our theory shows that the capacitance changes with the applied voltage in agreement with experimental observations. Importantly, the dielectric contrast and the difference in molecular volumes between the cation and anion have equal effects on the magnitude of the capacitance. We also consider compressible ionic liquids by developing a hybrid of DSCFT combined with Monte Carlo simulations. We then demonstrate that the hard-core nature of the ions causes oscillations in the density profile and dielectric value near the charged plates. Accordingly, the dielectric constants derived from the classical theories of Onsager and Kirkwood are shown to be gross approximations of the true situation in nanochannels. National Natural Science Foundation of China (21474112).

  13. Response of an environment-sensitive intramolecular charge transfer probe towards solubilization of liposome membranes by a non-ionic detergent: association and dissociation kinetics.

    PubMed

    Paul, Bijan Kumar; Guchhait, Nikhil

    2012-10-01

    The present report describes an endeavor to follow the solubilization of DMPC and DMPG liposome membranes by a non-ionic detergent Triton X-100 on the lexicon of environment-sensitive intramolecular charge transfer (ICT) photophysics of an extrinsic molecular probe 5-(4-dimethylamino-phenyl)-penta-2, 4-dienoic acid methyl ester (DPDAME). The prospective applicability of the probe to function as a reporter for detergent-sequestered solubilization of liposome membranes is argued on the basis of comparison of the spectral properties of the probe in various environments. Fluorescence anisotropy study delineates the degree of motional restriction imposed on the probe in different microheterogeneous assemblies. The kinetics of association of the probe with the liposome membranes and the dissociation kinetics of TX-100-sequestered solubilization process of the liposomes have been monitored by the stopped-flow fluorescence technique and the results are rationalized in relevance to fluorescence anisotropy study.

  14. Response of an environment-sensitive intramolecular charge transfer probe towards solubilization of liposome membranes by a non-ionic detergent: Association and dissociation kinetics

    NASA Astrophysics Data System (ADS)

    Paul, Bijan Kumar; Guchhait, Nikhil

    2012-10-01

    The present report describes an endeavor to follow the solubilization of DMPC and DMPG liposome membranes by a non-ionic detergent Triton X-100 on the lexicon of environment-sensitive intramolecular charge transfer (ICT) photophysics of an extrinsic molecular probe 5-(4-dimethylamino-phenyl)-penta-2, 4-dienoic acid methyl ester (DPDAME). The prospective applicability of the probe to function as a reporter for detergent-sequestered solubilization of liposome membranes is argued on the basis of comparison of the spectral properties of the probe in various environments. Fluorescence anisotropy study delineates the degree of motional restriction imposed on the probe in different microheterogeneous assemblies. The kinetics of association of the probe with the liposome membranes and the dissociation kinetics of TX-100-sequestered solubilization process of the liposomes have been monitored by the stopped-flow fluorescence technique and the results are rationalized in relevance to fluorescence anisotropy study.

  15. Comment on ``Model of ionic charge states of impulsive solar energetic particles in solar flares'' by M. Dolores Rodríguez-Frías, Luis del Peral, and Jorge Pérez-Peraza

    NASA Astrophysics Data System (ADS)

    Kovaltsov, Gennadi A.; Kartavykh, Yulia Y.; Kocharov, Leon; Ostryakov, Valery M.; Torsti, Jarmo

    2002-10-01

    Attention is drawn to the fact that the numerical code ESCAPE by [2001] is in conflict with other models of charge-changing processes in solar corona, including the most reliable model by [1992]. We find in the >0.1 MeV nucleon-1 energy range a tendency of the ESCAPE code to overestimate the ionic charge of iron. This implies an underestimation of the density × acceleration-time product in the ion acceleration region in solar corona.

  16. Arbitrary Metrics in Psychology

    ERIC Educational Resources Information Center

    Blanton, Hart; Jaccard, James

    2006-01-01

    Many psychological tests have arbitrary metrics but are appropriate for testing psychological theories. Metric arbitrariness is a concern, however, when researchers wish to draw inferences about the true, absolute standing of a group or individual on the latent psychological dimension being measured. The authors illustrate this in the context of 2…

  17. Arbitrary Metrics in Psychology

    ERIC Educational Resources Information Center

    Blanton, Hart; Jaccard, James

    2006-01-01

    Many psychological tests have arbitrary metrics but are appropriate for testing psychological theories. Metric arbitrariness is a concern, however, when researchers wish to draw inferences about the true, absolute standing of a group or individual on the latent psychological dimension being measured. The authors illustrate this in the context of 2…

  18. Modeling of ionic liquids

    NASA Astrophysics Data System (ADS)

    Tatlipinar, Hasan

    2017-02-01

    Ionic liquids are very important entry to industry and technology. Because of their unique properties they may classified as a new class of materials. IL usually classified as a high temperature ionic liquids (HTIL) and room temperature ionic liquids (RTIL). HTIL are molten salts. There are many research studies on molten salts such as recycling, new energy sources, rare elements mining. RTIL recently become very important in daily life industry because of their "green chemistry" properties. As a simple view ionic liquids consist of one positively charged and one negatively charged components. Because of their Coulombic or dispersive interactions the local structure of ionic liquids emerges. In this presentation the local structural properties of the HTIL are discussed via correlation functions and integral equation theories. RTIL are much more difficult to do modeling, but still general consideration for the modeling of the HTIL is valid also for the RTIL.

  19. Positively and Negatively Charged Ionic Modifications to Cellulose Assessed as Cotton-Based Protease-Lowering and Haemostatic Wound Agents

    USDA-ARS?s Scientific Manuscript database

    Recent developments in cellulose wound dressings targeted to different stages of wound healing have been based on structural and charge modifications that function to modulate events in the complex inflammatory and hemostatic phases of wound healing. Hemostasis and inflammation comprise two overlapp...

  20. Interatomic potentials for ionic systems with density functional accuracy based on charge densities obtained by a neural network

    NASA Astrophysics Data System (ADS)

    Ghasemi, S. Alireza; Hofstetter, Albert; Saha, Santanu; Goedecker, Stefan

    2015-07-01

    Based on an analysis of the short-range chemical environment of each atom in a system, standard machine-learning-based approaches to the construction of interatomic potentials aim at determining directly the central quantity, which is the total energy. This prevents, for instance, an accurate description of the energetics of systems in which long-range charge transfer or ionization is important. We propose therefore not to target directly with machine-learning methods the total energy but an intermediate physical quantity, namely, the charge density, which then in turn allows us to determine the total energy. By allowing the electronic charge to distribute itself in an optimal way over the system, we can describe not only neutral but also ionized systems with unprecedented accuracy. We demonstrate the power of our approach for both neutral and ionized NaCl clusters where charge redistribution plays a decisive role for the energetics. We are able to obtain chemical accuracy, i.e., errors of less than a millihartree per atom compared to the reference density functional results for a huge data set of configurations with large structural variety. The introduction of physically motivated quantities which are determined by the short-range atomic environment via a neural network also leads to an increased stability of the machine-learning process and transferability of the potential.

  1. Ionic Surfactant Binding to pH-Responsive Polyelectrolyte Brush-Grafted Nanoparticles in Suspension and on Charged Surfaces.

    PubMed

    Riley, John K; An, Junxue; Tilton, Robert D

    2015-12-29

    The interactions between silica nanoparticles grafted with a brush of cationic poly(2-(dimethylamino) ethyl methacrylate) (SiO2-g-PDMAEMA) and anionic surfactant sodium dodecyl sulfate (SDS) is investigated by dynamic light scattering, electrophoretic mobility, quartz crystal microbalance with dissipation, ellipsometry, and atomic force microscopy. SiO2-g-PDMAEMA exhibits pH-dependent charge and size properties which enable the SDS binding to be probed over a range of electrostatic conditions and brush conformations. SDS monomers bind irreversibly to SiO2-g-PDMAEMA at low surfactant concentrations (∼10(-4) M) while exhibiting a pH-dependent threshold above which cooperative, partially reversible SDS binding occurs. At pH 5, SDS binding induces collapse of the highly charged and swollen brush as observed in the bulk by DLS and on surfaces by QCM-D. Similar experiments at pH 9 suggest that SDS binds to the periphery of the weakly charged and deswollen brush and produces SiO2-g-PDMAEMA/SDS complexes with a net negative charge. SiO2-g-PDMAEMA brush collapse and charge neutralization is further confirmed by colloidal probe AFM measurements, where reduced electrosteric repulsions and bridging adhesion are attributed to effects of the bound SDS. Additionally, sequential adsorption schemes with SDS and SiO2-g-PDMAEMA are used to enhance deposition relative to SiO2-g-PDMAEMA direct adsorption on silica. This work shows that the polyelectrolyte brush configuration responds in a more dramatic fashion to SDS than to pH-induced changes in ionization, and this can be exploited to manipulate the structure of adsorbed layers and the corresponding forces of compression and friction between opposing surfaces.

  2. Effects of compatibility of polymer binders with solvate ionic liquid electrolytes on discharge and charge reactions of lithium-sulfur batteries

    NASA Astrophysics Data System (ADS)

    Nakazawa, Toshitada; Ikoma, Ai; Kido, Ryosuke; Ueno, Kazuhide; Dokko, Kaoru; Watanabe, Masayoshi

    2016-03-01

    Electrochemical reactions in Li-S cells with a solvate ionic liquid (SIL) electrolyte composed of tetraglyme (G4) and Li[TFSA] (TFSA: bis(trifluoromethanesulfonyl)amide) are studied. The sulfur cathode (S cathode) comprises sulfur, carbon powder, and a polymer binder. Poly(ethylene oxide) (PEO) and poly(vinyl alcohol) (PVA-x) with different degrees of saponification (x%) are used as binders to prepare the composite cathodes. For the Li-S cell containing PEO binder, lithium polysulfides (Li2Sm, 2 ≤ m ≤ 8), reaction intermediates of the S cathode, dissolve into the electrolyte, and Li2Sm acts as a redox shuttle in the Li-S cell. In contrast, in the Li-S cell with PVA-x binder, the dissolution of Li2Sm is suppressed, leading to high columbic efficiencies during charge-discharge cycles. The compatibility of the PVA-x binder with the SIL electrolyte changes depending on the degree of saponification. Decreasing the degree of saponification leads to increased electrolyte uptake by the PVA-x binder, increasing the charge and discharge capacities of Li-S cell. The rate capability of Li-S cell is also enhanced by the partial swelling of the PVA-x binder. The enhanced performance of Li-S cell containing PVA-x is attributed to the lowering of resistance of Li+ ion transport in the composite cathode.

  3. Effect of a pyrrolidinium zwitterion on charge/discharge cycle properties of Li/LiCoO2 and graphite/Li cells containing an ionic liquid electrolyte

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Seitaro; Yoshizawa-Fujita, Masahiro; Takeoka, Yuko; Rikukawa, Masahiro

    2016-11-01

    Ionic liquids (ILs) containing zwitterions have been studied as electrolytes for lithium-ion batteries (LIBs). The effects of addition of a pyrrolidinium zwitterion in an IL electrolyte on the thermal and electrochemical stability and charge/discharge properties of Li/LiCoO2 and graphite/Li cells were investigated. The thermal decomposition temperature of the IL electrolyte composed of N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)amide ([P13][FSA])/lithium bis(trifluoromethylsulfonyl)amide (LiTFSA) with 3-(1-butylpyrrolidinium)propane-1-sulfonate (Bpyps) as the zwitterionic additive, the thermal decomposition temperature was about 300 °C. The electrochemical window of [P13][FSA]/LiTFSA/Bpyps was 0-+5.4 V vs. Li/Li+, which was almost identical to that of [P13][FSA]/LiTFSA. Li|electrolyte|LiCoO2 cells containing the IL/Bpyps electrolyte system exhibited high capacities in the cut-off voltage range of 3.0-4.6 V, even after 50 cycles. The increase in the interfacial resistance between the electrolyte and cathode with cycling was suppressed. In the cyclic voltammograms of cells employing a graphite electrode, the intercalation/deintercalation of lithium ions were observed in the range of 0 and + 0.4 V vs. Li/Li+. Further, graphite|electrolyte|Li cells containing [P13][FSA]/LiTFSA/Bpyps exhibited stable charge/discharge cycle behaviour over 50 cycles.

  4. The nuclear and ionic charge distribution particle experiments on the ISEE-1 and ISEE-C spacecraft

    NASA Technical Reports Server (NTRS)

    Hovestadt, D.; Klecker, B.; Scholer, M.; Arbinger, H.; Gloeckler, G.; Ipavich, F. M.; Cain, J.; Fan, C. Y.; Fisk, L. A.; Ogallagher, J. J.

    1978-01-01

    The ISEE-1 and ISEE-C instruments are designed to measure the elemental abundances, charge state composition, energy spectra, and angular distributions of energetic ions in the energy range 2 keV/charge to 80 MeV/nucleon and electrons between 75 and 1300 keV. The instrument consists of three sensor systems: (1) ULECA which is an electrostatic deflection system with rectangular solid-state detectors for the 3-560 keV/charge range; (2) ULEWATT which is a double dE/dX vs E thin-window flowthrough proportional counter/solid-state detector telescope for the 0.2-80 MeV/nucleon (Fe) range; and (3) ULEZEQ which is a combination of an electrostatic deflection analyzer and a thin-window dE/dX vs E system with thin-window proportional counter and position-sensitive solid-state detector. The applications of the instruments to solar and interplanetary phenomena and to magnetospheric acceleration and trapped particles are discussed.

  5. Ionic Specificity in pH Regulated Charged Interfaces: Fe[superscript 3+]versus La[superscript 3+

    SciTech Connect

    Wang, Wenjie; Park, Rebecca Y.; Meyer, David H.; Travesset, Alex; Vaknin, David

    2012-03-26

    We determine the distribution of two trivalent ions Fe{sup 3+} and La{sup 3+} next to two different amphiphilic charged interfaces as ions or complexes, consisting of the phosphate lipid dihexadecyl phosphate (DHDP) and the fatty acid arachidic acid (AA). These amphiphiles provide a wide range of pK{sub a} values, from 2.1 (DHDP) to 5.1 (AA), thus allowing manipulation of the surface charge over extremely low pH (pH {approx}1 or larger), and the two ions provide two limiting cases of specificity for the amphiphiles. We find that La{sup 3+} distribution is mostly sensitive to the surface charge, whereas the Fe{sup 3+} binding depends on its character in the solution and is highly specific, as indicated by the crucial role played by iron complexes (Fe(OH){sub 3} or Fe(OH){sup 2+}) forming covalent bonds even for an uncharged interface. The implications of the results to other ions and/or amphiphilic interfaces are also discussed.

  6. Charge heterogeneity profiling of monoclonal antibodies using low ionic strength ion-exchange chromatography and well-controlled pH gradients on monolithic columns.

    PubMed

    Talebi, Mohammad; Nordborg, Anna; Gaspar, Andras; Lacher, Nathan A; Wang, Qian; He, Xiaoping Z; Haddad, Paul R; Hilder, Emily F

    2013-11-22

    In this work, the suitability of employing shallow pH gradients generated using single component buffer systems as eluents through cation-exchange (CEX) monolithic columns is demonstrated for the high-resolution separation of monoclonal antibody (mAb) charge variants in three different biopharmaceuticals. A useful selection of small molecule buffer species is described that can be used within very narrow pH ranges (typically 1 pH unit) defined by their buffer capacity for producing controlled and smooth pH profiles when used together with porous polymer monoliths. Using very low ionic strength eluents also enabled direct coupling with electrospray ionisation mass spectrometry. The results obtained by the developed pH gradient approach for the separation of closely related antibody species appear to be consistent with those obtained by imaged capillary isoelectric focusing (iCE) in terms of both resolution and separation profile. Both determinants of resolution, i.e., peak compression and peak separation contribute to the gains in resolution, evidently through the Donnan potential effect, which is increased by decreasing the eluent concentration, and also through the way electrostatic charges are distributed on the protein surface. Retention mechanisms based on the trends observed in retention of proteins at pH values higher than the electrophoretic pI are also discussed using applicable theories. Employing monolithic ion-exchangers is shown to enable fast method development, short analysis time, and high sample throughput owing to the accelerated mass transport of the monolithic media. The possibility of short analysis time, typically less than 15 min, and high sample throughput is extremely useful in the assessment of charge-based changes to the mAb products, such as during manufacturing or storage.

  7. Modulation of cellulase activity by charged lipid bilayers with different acyl chain properties for efficient hydrolysis of ionic liquid-pretreated cellulose.

    PubMed

    Mihono, Kai; Ohtsu, Takeshi; Ohtani, Mai; Yoshimoto, Makoto; Kamimura, Akio

    2016-10-01

    The stability of cellulase activity in the presence of ionic liquids (ILs) is critical for the enzymatic hydrolysis of insoluble cellulose pretreated with ILs. In this work, cellulase was incorporated in the liposomes composed of negatively charged 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG) and zwitterionic phosphatidylcholines (PCs) with different length and degree of unsaturation of the acyl chains. The liposomal cellulase-catalyzed reaction was performed at 45°C in the acetate buffer solution (pH 4.8) with 2.0g/L CC31 as cellulosic substrate. The crystallinity of CC31 was reduced by treating with 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) at 120°C for 30min. The liposomal cellulase continuously catalyzed hydrolysis of the pretreated CC31 for 48h producing glucose in the presence of 15wt% [Bmim]Cl. The charged lipid membranes were interactive with [Bmim](+), as elucidated by the [Bmim]Cl-induced alterations in fluorescence polarization of the membrane-embedded 1,6-diphenyl-1,3,5-hexatriene (DPH) molecules. The charged membranes offered the microenvironment where inhibitory effects of [Bmim]Cl on the cellulase activity was relieved. The maximum glucose productivity GP of 10.8 mmol-glucose/(hmol-lipid) was obtained at the reaction time of 48h with the cellulase incorporated in the liposomes ([lipid]=5.0mM) composed of 50mol% POPG and 1,2-dilauroyl-sn-glycero-3-phosohocholine (DLPC) with relatively short and saturated acyl chains. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Charging Properties of Cassiterite (alpha-SnO2) Surfaces in NaCl and RbCl Ionic Media.

    SciTech Connect

    Rosenqvist, Jorgen K; Machesky, Michael L.; Vlcek, Lukas; Wesolowski, David J

    2009-09-01

    The acid-base properties of cassiterite ({alpha}-SnO{sub 2}) surfaces at 10-50 C were studied using potentiometric titrations of powder suspensions in aqueous NaCl and RbCl media. The proton sorption isotherms exhibited common intersection points in the pH range of 4.0-4.5 under all conditions, and the magnitude of charging was similar but not identical in NaCl and RbCl. The hydrogen bonding configuration at the oxide-water interface, obtained from classical molecular dynamics (MD) simulations, was analyzed in detail, and the results were explicitly incorporated in calculations of protonation constants for the reactive surface sites using the revised MUSIC model. The calculations indicated that the terminal SnOH{sub 2} group is more acidic than the bridging Sn{sub 2}OH group, with protonation constants (log K{sub H}) of 3.60 and 5.13 at 25 C, respectively. This is contrary to the situation on the isostructural {alpha}-TiO{sub 2} (rutile), apparently because of the difference in electronegativity between Ti and Sn. MD simulations and speciation calculations indicated considerable differences in the speciation of Na{sup +} and Rb{sup +}, despite the similarities in overall charging. Adsorbed sodium ions are almost exclusively found in bidentate surface complexes, whereas adsorbed rubidium ions form comparable numbers of bidentate and tetradentate complexes. Also, the distribution of adsorbed Na{sup +} between the different complexes shows a considerable dependence on the surface charge density (pH), whereas the distribution of adsorbed Rb{sup +} is almost independent of pH. A surface complexation model (SCM) capable of accurately describing both the measured surface charge and the MD-predicted speciation of adsorbed Na{sup +}/Rb{sup +} was formulated. According to the SCM, the deprotonated terminal group (SnOH{sup -0.40}) and the protonated bridging group (Sn{sub 2}OH{sup +0.36}) dominate the surface speciation over the entire pH range of this study (2.7-10). The

  9. Charging Properties of Cassiterite (alpha-SnO2) surfaces in NaCl and RbCl Ionic Media.

    SciTech Connect

    Rosenqvist, Jorgen K; Machesky, Michael L.; Vlcek, Lukas; Wesolowski, David J

    2009-09-01

    The acid-base properties of cassiterite (alpha-SnO2) surfaces at 10-50 degrees C were studied using potentiometric titrations of powder suspensions in aqueous NaCl and RbCl media. The proton sorption isotherms exhibited common intersection points in the pH range of 4.0-4.5 under all conditions, and the magnitude of charging was similar but not identical in NaCl and RbCl. The hydrogen bonding configuration at the oxide-water interface, obtained from classical molecular dynamics (MD) simulations, was analyzed in detail, and the results were explicitly incorporated in calculations of protonation constants for the reactive surface sites using the revised MUSIC model. The calculations indicated that the terminal SnOH2 group is more acidic than the bridging Sn2OH group, with protonation constants (log KH) of 3.60 and 5.13 at 25 degrees C, respectively. This is contrary to the situation on the isostructural alpha-TiO2 (rutile), apparently because of the difference in electronegativity between Ti and Sn. MD simulations and speciation calculations indicated considerable differences in the speciation of Na+ and Rb+, despite the similarities in overall charging. Adsorbed sodium ions are almost exclusively found in bidentate surface complexes, whereas adsorbed rubidium ions form comparable numbers of bidentate and tetradentate complexes. Also, the distribution of adsorbed Na+ between the different complexes shows a considerable dependence on the surface charge density (pH), whereas the distribution of adsorbed Rb+ is almost independent of pH. A surface complexation model (SCM) capable of accurately describing both the measured surface charge and the MD-predicted speciation of adsorbed Na+/Rb+ was formulated. According to the SCM, the deprotonated terminal group (SnOH(-0.40)) and the protonated bridging group (Sn2OH+0.36) dominate the surface speciation over the entire pH range of this study (2.7-10). The complexation of medium cations increases significantly with increasing

  10. Imidazolium Ionic Liquid Functionalized Carbon Nanotubes for Improved Interfacial Charge Transfer and Simultaneous Determination of Dihydroxybenzene Isomers.

    PubMed

    Wei, Huan; Wu, Xiao-Shuai; Wen, Guo-Yun; Qiao, Yan

    2016-05-14

    In this paper; an imidazolium ionic liquid (IL) is used to functionalize multi-walled carbon nanotubes (MWNTs) by covalent bonding on the MWNT surface. The functionalization not only provides a hydrophilic surface for ion accessibility but also prevents the aggregation of MWNTs. The IL-functionalized MWNTs were then applied for the electrochemical determination of the dihydroxybenzene isomers hydroquinone (HQ); catechol (CC); and resorcinol (RC), exhibiting excellent recognition ability towards the three compounds. The linear calibration ranges for HQ; CC and RC are 0.9-150 μM; 0.9-150 μM and 1.9-145 μM and the detection limits are found to be 0.15 μM for HQ; 0.10 μM for CC and 0.38 μM for RC based on S/N of 3. The proposed electrochemical sensor was also found to be useful for the determination of the dihydroxybenzene isomers in Yellow River water with reliable recovery.

  11. Arbitrary Waveform Generator.

    DTIC Science & Technology

    This report describes a system for storing an arbitrary waveform on non-volatile random access memory ( NVRAM ) device and generating an analog signal...using the NVRAM device. A central processing unit is used to synthesize an arbitrary waveform and create a digital representation of the waveform and...transfer the digital representation to a microprocessor which, in turn, writes the digital data into an NVRAM device which has been mapped into a

  12. A scaled-ionic-charge simulation model that reproduces enhanced and suppressed water diffusion in aqueous salt solutions.

    PubMed

    Kann, Z R; Skinner, J L

    2014-09-14

    Non-polarizable models for ions and water quantitatively and qualitatively misrepresent the salt concentration dependence of water diffusion in electrolyte solutions. In particular, experiment shows that the water diffusion coefficient increases in the presence of salts of low charge density (e.g., CsI), whereas the results of simulations with non-polarizable models show a decrease of the water diffusion coefficient in all alkali halide solutions. We present a simple charge-scaling method based on the ratio of the solvent dielectric constants from simulation and experiment. Using an ion model that was developed independently of a solvent, i.e., in the crystalline solid, this method improves the water diffusion trends across a range of water models. When used with a good-quality water model, e.g., TIP4P/2005 or E3B, this method recovers the qualitative behaviour of the water diffusion trends. The model and method used were also shown to give good results for other structural and dynamic properties including solution density, radial distribution functions, and ion diffusion coefficients.

  13. A synchrotron x-ray diffraction and hard x-ray photoelectron spectroscopy study of Zn negative electrodes at different charge and discharge states of Zn/MnO2 batteries using an ionic liquid-based gel polymer electrolyte

    NASA Astrophysics Data System (ADS)

    Abad, José; Santos, Florencio; Tafur, Juan P.; Urbina, Antonio; Román, Elisa; González-Martínez, J. F.; Rubio-Zuazo, J.; Castro, G. R.; Fernández Romero, Antonio J.

    2017-09-01

    Zn/MnO2 batteries including an ionic liquid-based gel polymer electrolyte (IL-GPE) have been discharged or discharged and then recharged reaching different states of charge. The Zn electrodes used in these Zn/MnO2 batteries are studied by HAXPES and synchrotron XRD techniques. Besides, HAXPES measurements are compared with the results obtained by a conventional XPS. Formation of Zn(OH)2 and ZnO is found in intermediate states of charge during charging and discharging. However, only ZnO is observed in the anode when a full discharging was carried out. Conversely, an entire charging process produces a complete reduction of all Zn2+ species to metallic Zn. In addition, various techniques have confirmed the entrance of Triflate anions and NMP solvent molecules in the electrode, accompanying the Zn2+ cations movement during the charging.

  14. Electrochemical Film Formation on Magnesium Metal in an Ionic Liquid That Dissolves Metal Triflate and Its Application to an Active Material with Anion Charge Carrier.

    PubMed

    Shiga, Tohru; Kato, Yuichi; Inoue, Masae

    2016-11-16

    Irregular metallic growth at the anode during recharging of batteries can seriously influence the safety of batteries. To address this problem, we have attempted to design active anode materials with anion charge carriers and recently observed the formation and dissolution of an electrochemical film by triflate anions (CF3SO3(-)) at the surface of magnesium in an ionic liquid (IL) electrolyte of Mg(CF3SO3)2, which represents a rare anode material. The effect of heterogeneous cations on film formation was examined in this work. In an IL that dissolves NaCF3SO3, sodium ions with a lower reduction potential than Mg(2+)/Mg would not be expected to assist film formation. However, to our surprise, we discovered that some sodium ions are involved in film formation. The sodium ions are believed to act as a cross-linking point for the formation of a film network, which resulted in fairly good reversibility for film formation. In a Ce(CF3SO3)3-IL electrolyte, an electrochemically formed film free of Ce(3+) was obtained. The trivalent cerium cations were deactivated and transformed to an oxide on Mg metal. However, the reversibility of film formation in the Ce(CF3SO3)3 system did not meet the expected level. By coupling the film formation and dissolution behavior with a V2O5 cathode, a rechargeable battery was fabricated with dual ion transport species of Na(+) or Ce(3+) for the cathode and CF3SO3(-) for the anode. The unique battery with NaCF3SO3 is demonstrated to exhibit good discharge/charge performance with long-term cyclability.

  15. Spatial profiles of electron density, electron temperature, average ionic charge, and EUV emission of laser-produced Sn plasmas for EUV lithography

    NASA Astrophysics Data System (ADS)

    Sato, Yuta; Tomita, Kentaro; Tsukiyama, Syoichi; Eguchi, Toshiaki; Uchino, Kiichiro; Kouge, Kouichiro; Tomuro, Hiroaki; Yanagida, Tatsuya; Wada, Yasunori; Kunishima, Masahito; Kodama, Takeshi; Mizoguchi, Hakaru

    2017-03-01

    Spatial profiles of the electron density (n e), electron temperature (T e), and average ionic charge (Z) of laser-produced Sn plasmas for EUV lithography, whose conversion efficiency (CE) is sufficiently high for practical use, were measured using a collective Thomson scattering (TS) technique. For plasma production, Sn droplets of 26 µm diameter were used as a fuel. First, a picosecond-pulsed laser was used to expand a Sn target. Next, a CO2 laser was used to generate plasmas. By changing the injection timing of the picosecond and CO2 lasers, three different types of plasmas were generated. The CEs of the three types of plasmas differed, and ranged from 2.8 to 4.0%. Regarding the different plasma conditions, the spatial profiles of n e, T e, and Z clearly differed. However, under all plasma conditions, intense EUV was only observed at a sufficiently high T e (> 25 eV) and in an adequate n e range [1024–(2 × 1025) m‑3]. These plasma parameters lie in the efficient-EUV light source range, as predicted by simulations.

  16. Charge-storage performance of Li/LiFePO4 cells with additive-incorporated ionic liquid electrolytes at various temperatures

    NASA Astrophysics Data System (ADS)

    Wongittharom, Nithinai; Wang, Chueh-Han; Wang, Yi-Chen; Fey, George Ting-Kuo; Li, Hui-Ying; Wu, Tzi-Yi; Lee, Tai-Chou; Chang, Jeng-Kuei

    2014-08-01

    Butylmethylpyrrolidinium bis(trifluoromethanesulfonyl)imide (BMP-TFSI) ionic liquid (IL) with LiTFSI solute is used as a base electrolyte for Li/LiFePO4 cells. Three kinds of electrolyte additive, namely vinylene carbonate (VC), gamma-butyrolactone (γ-BL), and propylene carbonate (PC), with various concentrations are introduced. The thermal stability, flammability, and electrochemical properties of the electrolytes are investigated. At 25 °C, the additives (γ-BL is found to be the most effective) can significantly improve the capacity, high-rate performance, and cyclability of the cells. With an increase in temperature to 50 °C, the benefits of the additives gradually become insignificant. At 75 °C, the additives even have adverse effects. At such an elevated temperature, in the plain IL electrolyte (without additives), a LiFePO4 capacity of 152 mAh g-1 is found at 0.1 C. 77% of this capacity can be retained when the rate is increased to 3 C. These values are superior to those found for the additive-incorporated IL and conventional organic electrolytes. Moreover, negligible capacity loss is measured after 100 charge-discharge cycles at 75 °C in the plain IL electrolyte.

  17. Novel Energy Sources -Material Architecture and Charge Transport in Solid State Ionic Materials for Rechargeable Li ion Batteries

    SciTech Connect

    Katiyar, Ram S; Gómez, M; Majumder, S B; Morell, G; Tomar, M S; Smotkin, E; Bhattacharya, P; Ishikawa, Y

    2009-01-19

    Since its introduction in the consumer market at the beginning of 1990s by Sony Corporation ‘Li-ion rechargeable battery’ and ‘LiCoO2 cathode’ is an inseparable couple for highly reliable practical applications. However, a separation is inevitable as Li-ion rechargeable battery industry demand more and more from this well serving cathode. Spinel-type lithium manganate (e.g., LiMn2O4), lithium-based layered oxide materials (e.g., LiNiO2) and lithium-based olivine-type compounds (e.g., LiFePO4) are nowadays being extensively studied for application as alternate cathode materials in Li-ion rechargeable batteries. Primary goal of this project was the advancement of Li-ion rechargeable battery to meet the future demands of the energy sector. Major part of the research emphasized on the investigation of electrodes and solid electrolyte materials for improving the charge transport properties in Li-ion rechargeable batteries. Theoretical computational methods were used to select electrodes and electrolyte material with enhanced structural and physical properties. The effect of nano-particles on enhancing the battery performance was also examined. Satisfactory progress has been made in the bulk form and our efforts on realizing micro-battery based on thin films is close to give dividend and work is progressing well in this direction.

  18. Structural and vibrational spectroscopic studies on charge transfer and ionic hydrogen bonding interactions of melaminium benzoate dihydrate.

    PubMed

    Kanagathara, N; Marchewka, M K; Drozd, M; Gunasekaran, S; Rajakumar, P R; Anbalagan, G

    2015-06-15

    Single crystals of melaminium benzoate dihydrate (MBDH) have been grown from aqueous solution by the slow solvent evaporation method at room temperature. Crystalline nature of the grown crystal has been confirmed by X-ray powder diffraction studies. The optimized geometry, frequency and intensity of the vibrational bands of MBDH were obtained by the Hartree-Fock and density functional theory using B3LYP/cam-B3LYP with 6-311++G(d,p) basis set. The harmonic vibrational frequencies were calculated and the scaled values have been compared with the experimental FT-IR and FT-Raman spectral values. The obtained vibrational wavenumbers and optimized geometric parameters are found to be in good agreement with the experimental data. UV-Visible spectrum was recorded in the region 200-400 nm and the electronic properties, HOMO-LUMO energies and other related electronic parameters are calculated. The isotropic chemical shifts computed by (1)H and (13)C NMR analysis also show good agreement with experimental observation. Natural bond orbital (NBO) analysis has been performed on MBDH compound to analyze the stability of the molecule arising from hyperconjugative interactions and charge delocalization. Molecular electrostatic potential surface (MEP) has also been performed by DFT/cam-B3LYP method with 6-311++G(d,p) basis set. Differential scanning calorimetric measurements performed on the powder sample indicate the phase transition point approximately at 368 and 358K for heating and cooling, respectively. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. A scale of metal ion binding strengths correlating with ionic charge, Pauling electronegativity, toxicity, and other physiological effects.

    PubMed

    Kinraide, Thomas B; Yermiyahu, Uri

    2007-09-01

    Equilibrium constants for binding to plant plasma membranes have been reported for several metal ions, based upon adsorption studies and zeta-potential measurements. LogK values for the ions are these: Al(3+), 4.30; La(3+), 3.34; Cu(2+), 2.60; Ca(2+) and Mg(2+), 1.48; Na(+) and K(+), 0 M(-1). These values correlate well with logK values for ion binding to many organic and inorganic ligands. LogK values for metal ion binding to 12 ligands were normalized and averaged to produce a scale for the binding of 49 ions. The scale correlates well with the values presented above (R(2)=0.998) and with ion binding to cell walls and other biomass. The scale is closely related to the charge (Z) and Pauling electronegativity (PE) of 48 ions (all but Hg(2+)); R(2)=0.969 for the equation (Scale values)=-1.68+Z(1.22+0.444PE). Minimum rhizotoxicity of metal ions appears to be determined by binding strengths: log a(PM,M)=1.60-2.41exp[0.238(Scale values)] determines the value of ion activities at the plasma membrane surface (a(PM,M)) that will ensure inhibition of root elongation. Additional toxicity appears to be related to softness, accounting for the great toxicity of Ag(+), for example. These binding-strength values correlate with additional physiological effects and are suitable for the computation of cell-surface electrical potentials.

  20. Arbitrary order permanent Cartesian multipolar electrostatic interactions

    NASA Astrophysics Data System (ADS)

    Boateng, H. A.; Todorov, I. T.

    2015-01-01

    Recently, there has been a concerted effort to implement advanced classical potential energy surfaces by adding higher order multipoles to fixed point charge electrostatics in a bid to increase the accuracy of simulations of condensed phase systems. One major hurdle is the unwieldy nature of the expressions which in part has limited developers mostly to including only dipoles and quadrupoles. In this paper, we present a generalization of the Cartesian formulation of electrostatic multipolar interactions that enables the specification of an arbitrary order of multipoles. Specifically, we derive formulas for arbitrary order implementation of the particle mesh Ewald method and give a closed form formula for the stress tensor in the reciprocal space. In addition, we provide recurrence relations for common electrostatic potentials employed in molecular simulations, which allows for the generalization to arbitrary order and guarantees a computational cost that scales as O(p3) for Cartesian multipole interactions of order p.

  1. Arbitrary Metrics Redux

    ERIC Educational Resources Information Center

    Blanton, Hart; Jaccard, James

    2006-01-01

    Reducing the arbitrariness of a metric is distinct from the pursuit of validity, rational zero points, data transformations, standardization, and the types of statistical procedures one uses to analyze interval-level versus ordinal-level data. A variety of theoretical, methodological, and statistical tools can assist researchers who wish to make…

  2. Measuring the effect of ion-induced drift-gas polarization on the electrical mobilities of multiply-charged ionic liquid nanodrops in air.

    PubMed

    Fernández-García, Juan; Fernández de la Mora, Juan

    2013-12-01

    The electrical mobilities of multiply-charged nanodrops of the ionic liquid 1-ethyl, 3-methylimidazolium dicyanamide (EMI-N[CN]2) were accurately measured in air at 20 °C for mass-selected clusters of composition [EMI-N[CN]2] n [EMI(+)] z , with 2 ≤ n ≤ 369 and 1 ≤ z ≤ 10. We confirm prior reports that the mobility Z of a globular ion of mass m is given approximately by the modified Stokes-Millikan law for spheres, Z  =  Z SM,mod (d m   +  d g , z, m), where d m   =  (6m/πρ)(1/3) is the nanodrop mass-diameter based on the density ρ of the liquid (corrected for the capillary compression and electrostatic deformation of the nanodrop), and d g is an effective air molecule diameter. There is however a measurable (up to 7%) and systematic z-dependent departure of Z from Z SM,mod . As theoretically expected at small ε (*) , this effect is accurately described by a simple correction factor of the form Z/Z SM,mod   =  δ(1  -  βε (*)), where kTε (*) is the potential energy due to the ion-induced dipole (polarization) attraction between a perfectly-conducting charged nanodrop and a polarized neutral gas-molecule at a distance (d m   +  d g )/2 from its center. An excellent fit of this model to hundreds of data points is found for d g ≈ 0.26 nm, β ≈ 0.36, and δ ≈ 0.954. Accounting for the effect of polarization decreases d g considerably with respect to values inferred from earlier nanodrop measurements that ignored this effect. In addition, and in spite of ambiguities in the mobility calibration scale, the measured constant δ smaller than unity increases Millikan's drag enhancement factor from the accepted value ξ m ≈ 1.36 to the new value ξ ≈ ξ m /δ ≈ 1.42  ± 0.03.

  3. Measuring the Effect of Ion-Induced Drift-Gas Polarization on the Electrical Mobilities of Multiply-Charged Ionic Liquid Nanodrops in Air

    NASA Astrophysics Data System (ADS)

    Fernández-García, Juan; Fernández de la Mora, Juan

    2013-12-01

    The electrical mobilities of multiply-charged nanodrops of the ionic liquid 1-ethyl, 3-methylimidazolium dicyanamide (EMI-N[CN]2) were accurately measured in air at 20 °C for mass-selected clusters of composition [EMI-N[CN]2] n [EMI+] z , with 2 ≤ n ≤ 369 and 1 ≤ z ≤ 10. We confirm prior reports that the mobility Z of a globular ion of mass m is given approximately by the modified Stokes-Millikan law for spheres, Z = Z SM, mod ( d m + d g , z, m), where d m = (6 m/ πρ)1/3 is the nanodrop mass-diameter based on the density ρ of the liquid (corrected for the capillary compression and electrostatic deformation of the nanodrop), and d g is an effective air molecule diameter. There is however a measurable (up to 7 %) and systematic z-dependent departure of Z from Z SM,mod . As theoretically expected at small ɛ * , this effect is accurately described by a simple correction factor of the form Z/ Z SM, mod = δ(1 - βɛ *), where kTɛ * is the potential energy due to the ion-induced dipole ( polarization) attraction between a perfectly-conducting charged nanodrop and a polarized neutral gas-molecule at a distance ( d m + d g )/2 from its center. An excellent fit of this model to hundreds of data points is found for d g ≈ 0.26 nm, β ≈ 0.36, and δ ≈ 0.954. Accounting for the effect of polarization decreases d g considerably with respect to values inferred from earlier nanodrop measurements that ignored this effect. In addition, and in spite of ambiguities in the mobility calibration scale, the measured constant δ smaller than unity increases Millikan's drag enhancement factor from the accepted value ξ m ≈ 1.36 to the new value ξ ≈ ξ m / δ ≈ 1.42 ± 0.03.

  4. Ionic liquids, electrolyte solutions including the ionic liquids, and energy storage devices including the ionic liquids

    DOEpatents

    Gering, Kevin L.; Harrup, Mason K.; Rollins, Harry W.

    2015-12-08

    An ionic liquid including a phosphazene compound that has a plurality of phosphorus-nitrogen units and at least one pendant group bonded to each phosphorus atom of the plurality of phosphorus-nitrogen units. One pendant group of the at least one pendant group comprises a positively charged pendant group. Additional embodiments of ionic liquids are disclosed, as are electrolyte solutions and energy storage devices including the embodiments of the ionic liquid.

  5. A novel measuring method for arbitrary optical vortex by three spiral spectra

    NASA Astrophysics Data System (ADS)

    Ni, Bo; Guo, Lana; Yue, Chengfeng; Tang, Zhilie

    2017-02-01

    In this letter, the topological charge of non-integer vortices determined by three arbitrary spiral spectra is theoretically demonstrated for the first time. Based on the conclusion, a novel method to measure non-integer vortices is presented. This method is applicable not only to arbitrary non-integer vortex but also to arbitrary integer vortex.

  6. Arbitrary waveform generator

    NASA Astrophysics Data System (ADS)

    Griffin, Maurice; Sugawara, Glen

    1995-02-01

    A system for storing an arbitrary waveform on nonvolatile random access memory (NVRAM) device and generating an analog signal using the NVRAM device is described. A central processing unit is used to synthesize an arbitrary waveform and create a digital representation of the waveform and transfer the digital representation to a microprocessor which, in turn, writes the digital data into an NVRAM device which has been mapped into a portion of the microprocessor address space. The NVRAM device is removed from address space and placed into an independent waveform generation unit. In the waveform generation unit, an address clock provides an address timing signal and a cycle clock provides a transmit signal. Both signals are applied to an address generator. When both signals are present, the address generator generates and transmits to the NVRAM device a new address for each cycle of the address timing signal. In response to each new address generated, the NVRAM devices provides a digital output which is applied to a digital to analog converter. The converter produces a continuous analog output which is smoothed by a filter to produce the arbitrary waveform.

  7. Ionic Strength Sensing in Living Cells.

    PubMed

    Liu, Boqun; Poolman, Bert; Boersma, Arnold J

    2017-09-06

    Knowledge of the ionic strength in cells is required to understand the in vivo biochemistry of the charged biomacromolecules. Here, we present the first sensors to determine the ionic strength in living cells, by designing protein probes based on Förster resonance energy transfer (FRET). These probes allow observation of spatiotemporal changes in the ionic strength on the single-cell level.

  8. Electrode screening by ionic liquids.

    PubMed

    Lynden-Bell, R M; Frolov, A I; Fedorov, M V

    2012-02-28

    In this work we are concerned with the short-range screening provided by the ionic liquid dimethylimidazolium chloride near a charged wall. We study the free energy profiles (or potentials of mean force) for charged and neutral solutes as a function of distance from a charged wall. Four different wall charge densities are used in addition to a wall with zero charge. The highest magnitude of the charge densities is ±1 e nm(-2) which is close to the maximum limit of charge densities accessible in experiments, while the intermediate charges ±0.5 e nm(-2) are in the range of densities typically used in most of the experimental studies. Positively and negatively charged solutes of approximately the size of a BF ion and a Cl(-) ion are used as probes. We find that the ionic liquid provides excellent electrostatic screening at a distance of 1-2 nm. The free energy profiles show minima which are due to layering in the ionic liquid near the electrodes. This indicates that the solute ions tend to displace ionic liquid ions in the layers when approaching the electrode. The important role of non-electrostatic forces is demonstrated by the oscillations in the free energy profiles of uncharged solutes as a function of distance from the wall.

  9. How arbitrary is language?

    PubMed Central

    Monaghan, Padraic; Shillcock, Richard C.; Christiansen, Morten H.; Kirby, Simon

    2014-01-01

    It is a long established convention that the relationship between sounds and meanings of words is essentially arbitrary—typically the sound of a word gives no hint of its meaning. However, there are numerous reported instances of systematic sound–meaning mappings in language, and this systematicity has been claimed to be important for early language development. In a large-scale corpus analysis of English, we show that sound–meaning mappings are more systematic than would be expected by chance. Furthermore, this systematicity is more pronounced for words involved in the early stages of language acquisition and reduces in later vocabulary development. We propose that the vocabulary is structured to enable systematicity in early language learning to promote language acquisition, while also incorporating arbitrariness for later language in order to facilitate communicative expressivity and efficiency. PMID:25092667

  10. Spectral methods on arbitrary grids

    NASA Technical Reports Server (NTRS)

    Carpenter, Mark H.; Gottlieb, David

    1995-01-01

    Stable and spectrally accurate numerical methods are constructed on arbitrary grids for partial differential equations. These new methods are equivalent to conventional spectral methods but do not rely on specific grid distributions. Specifically, we show how to implement Legendre Galerkin, Legendre collocation, and Laguerre Galerkin methodology on arbitrary grids.

  11. Understanding of the Effects of Ionic Strength on the Bimolecular Rate Constant between Structurally Identified Redox Enzymes and Charged Substrates Using Numerical Simulations on the Basis of the Poisson-Boltzmann Equation.

    PubMed

    Sugimoto, Yu; Kitazumi, Yuki; Shirai, Osamu; Yamamoto, Masahiro; Kano, Kenji

    2016-03-31

    To understand electrostatic interactions in biomolecules, the bimolecular rate constants (k) between redox enzymes and charged substrates (in this study, redox mediators in the electrode reaction) were evaluated at various ionic strengths (I) for the mediated bioelectrocatalytic reaction. The k value between bilirubin oxidase (BOD) and positively charged mediators increased with I, while that between BOD and negatively charged mediators decreased with I. The opposite trend was observed for the reaction of glucose oxidase (GOD). In the case of noncharged mediators, the k value was independent of I for both BOD and GOD. These results reflect the electrostatic interactions between the enzymes and the mediators. Furthermore, we estimated k/k° (k° being the thermodynamic rate constant) by numerical simulation (finite element method) based on the Poisson-Boltzmann (PB) equation. By considering the charges of individual atoms involved in the amino acids around the substrate binding sites in the enzymes, the simulated k/k° values well reproduced the experimental data. In conclusion, k/k° can be predicted by PB-based simulation as long as the crystal structure of the enzyme and the substrate binding site are known.

  12. Characterizing the surface charge of synthetic nanomembranes by the streaming potential method

    PubMed Central

    Datta, Subhra; Conlisk, A. T.; Kanani, Dharmesh M.; Zydney, Andrew L.; Fissell, William H.; Roy, Shuvo

    2010-01-01

    The inference of the surface charge of polyethylene glycol (PEG)-coated and uncoated silicon membranes with nanoscale pore sizes from streaming potential measurements in the presence of finite electric double layer (EDL) effects is studied theoretically and experimentally. The developed theoretical model for inferring the pore wall surface charge density from streaming potential measurements is applicable to arbitrary pore cross-sectional shapes and accounts for the effect of finite salt concentration on the ionic mobilities and the thickness of the deposited layer of PEG. Theoretical interpretation of the streaming potential data collected from silicon membranes having nanoscale pore sizes, with/without pore wall surface modification with PEG, indicates that finite electric double layer (EDL) effects in the pore-confined electrolyte significantly affect the interpretation of the membrane charge and that surface modification with PEG leads to a reduction in the pore wall surface charge density. The theoretical model is also used to study the relative significance of the following uniquely nanoscale factors affecting the interpretation of streaming potential in moderate to strongly charged pores: altered net charge convection by applied pressure differentials, surface-charge effects on ionic conduction, and electroosmotic convection of charges. PMID:20462592

  13. Characterizing the surface charge of synthetic nanomembranes by the streaming potential method.

    PubMed

    Datta, Subhra; Conlisk, A T; Kanani, Dharmesh M; Zydney, Andrew L; Fissell, William H; Roy, Shuvo

    2010-08-01

    The inference of the surface charge of polyethylene glycol (PEG)-coated and uncoated silicon membranes with nanoscale pore sizes from streaming potential measurements in the presence of finite electric double layer (EDL) effects is studied theoretically and experimentally. The developed theoretical model for inferring the pore wall surface charge density from streaming potential measurements is applicable to arbitrary pore cross-sectional shapes and accounts for the effect of finite salt concentration on the ionic mobilities and the thickness of the deposited layer of PEG. Theoretical interpretation of the streaming potential data collected from silicon membranes having nanoscale pore sizes, with/without pore wall surface modification with PEG, indicates that finite electric double layer (EDL) effects in the pore-confined electrolyte significantly affect the interpretation of the membrane charge and that surface modification with PEG leads to a reduction in the pore wall surface charge density. The theoretical model is also used to study the relative significance of the following uniquely nanoscale factors affecting the interpretation of streaming potential in moderate to strongly charged pores: altered net charge convection by applied pressure differentials, surface-charge effects on ionic conduction, and electroosmotic convection of charges. Copyright (c) 2010 Elsevier Inc. All rights reserved.

  14. Modeling electrokinetics in ionic liquids.

    PubMed

    Wang, Chao; Bao, Jie; Pan, Wenxiao; Sun, Xin

    2017-03-17

    Using direct numerical simulations, we provide a thorough study regarding the electrokinetics of ionic liquids. In particular, modified Poisson-Nernst-Planck (MPNP) equations are solved to capture the crowding and overscreening effects characteristic of an ionic liquid. For modeling electrokinetic flows in an ionic liquid, the MPNP equations are coupled with Navier-Stokes equations to study the coupling of ion transport, hydrodynamics, and electrostatic forces. Specifically, we consider the ion transport between two parallel charged surfaces, charging dynamics in a nanopore, capacitance of electric double-layer capacitors, electro-osmotic flow in a nanochannel, electroconvective instability on a plane ion-selective surface, and electroconvective flow on a curved ion-selective surface. We also discuss how crowding and overscreening and their interplay affect the electrokinetic behaviors of ionic liquids in these application problems. This article is protected by copyright. All rights reserved.

  15. Thermodynamics and micro heterogeneity of ionic liquids.

    PubMed

    Gomes, Margarida F Costa; Lopes, J N Canongia; Padua, A A H

    2010-01-01

    The high degree of organisation in the fluid phase of room-temperature ionic liquids has major consequences on their macroscopic properties, namely on their behaviour as solvents. This nanoscale self-organisation is the result of an interplay between two types of interaction in the liquid phase - Coulomb and van der Waals - that eventually leads to the formation of medium-range structures and the recognition of some ionic liquids as composed of a high-charge density, cohesive network permeated by low-charge density regions.In this chapter, the structure of the ionic liquids will be explored and some of their consequences to the properties of ionic liquids analyzed.

  16. Hydrogen bonding in ionic liquids.

    PubMed

    Hunt, Patricia A; Ashworth, Claire R; Matthews, Richard P

    2015-03-07

    Ionic liquids (IL) and hydrogen bonding (H-bonding) are two diverse fields for which there is a developing recognition of significant overlap. Doubly ionic H-bonds occur when a H-bond forms between a cation and anion, and are a key feature of ILs. Doubly ionic H-bonds represent a wide area of H-bonding which has yet to be fully recognised, characterised or explored. H-bonds in ILs (both protic and aprotic) are bifurcated and chelating, and unlike many molecular liquids a significant variety of distinct H-bonds are formed between different types and numbers of donor and acceptor sites within a given IL. Traditional more neutral H-bonds can also be formed in functionalised ILs, adding a further level of complexity. Ab initio computed parameters; association energies, partial charges, density descriptors as encompassed by the QTAIM methodology (ρBCP), qualitative molecular orbital theory and NBO analysis provide established and robust mechanisms for understanding and interpreting traditional neutral and ionic H-bonds. In this review the applicability and extension of these parameters to describe and quantify the doubly ionic H-bond has been explored. Estimating the H-bonding energy is difficult because at a fundamental level the H-bond and ionic interaction are coupled. The NBO and QTAIM methodologies, unlike the total energy, are local descriptors and therefore can be used to directly compare neutral, ionic and doubly ionic H-bonds. The charged nature of the ions influences the ionic characteristics of the H-bond and vice versa, in addition the close association of the ions leads to enhanced orbital overlap and covalent contributions. The charge on the ions raises the energy of the Ylp and lowers the energy of the X-H σ* NBOs resulting in greater charge transfer, strengthening the H-bond. Using this range of parameters and comparing doubly ionic H-bonds to more traditional neutral and ionic H-bonds it is clear that doubly ionic H-bonds cover the full range of weak

  17. Ionic Channels in Thunderclouds

    NASA Astrophysics Data System (ADS)

    Losseva, T. V.; Fomenko, A. S.; Nemtchinov, I. V.

    2007-12-01

    We proceed to study the formation and propagation of ionic channels in thunderclouds in the framework of the model of the corona discharge wave propagation (Fomenko A.S., Losseva T.V., Nemtchinov I.V. The corona discharge waves in thunderclouds and formation of ionic channels // 2004 Fall Meeting. EOS Trans. AGU. 2004. V. 85. ¹ 47. Suppl. Abstract AE23A-0835.). In this model we proposed a hypothesis that the structure of a thundercloud becomes nonuniform due to corona discharge on the drops and ice particles and formation of ionic channels with higher conductivity than the surrounding air. When the onset strength of corona discharge becomes smaller than the electric field strength the corona discharge increases concentrations of ions in a small part of the cloud (a hot spot). An additional charge at opposite ends of the hot spot forms due to polarization process. The increased electric field initiates corona discharge in other parts of the cloud on ice particles and water drops with smaller sizes. The corona discharge front moves as a wave with the velocity of the order of ion drift and formes a highly conductive channel. We model this non-stationary problem with Poisson equation which is solved simultaneously with a simplified set of kinetic equations for ions, small charged particles and electrons (at high electric fields), including ionization due to electronic impact, attachment and formation of positive ions. By applying 3D numerical simulations we obtain the parameters of formed ionic channels with respect to onset electric fields both from large particles (in hot spot) and from small particles (surrounding hot spot), microscopic currents from particles with different sizes and the external electric field in the cloud. The interaction of ionic channels is also investigated. This work was supported by Russian Foundation of Basic Research (Project No 07-05-00998-à).

  18. A Simple Arbitrary Solid Slicer

    SciTech Connect

    Yao, J

    2005-06-23

    The intersection of a given plane and an arbitrary (possibly non-convex, with multiple connectivities) meshed solid is exactly expressed by a set of planar cross-sections. A rule for marching on the edges of an arbitrary polyhedron is set for obtaining the topology of the cross-section. The method neither seeks triangulation of the surface mesh nor utilizes look-up tables, therefore it has optimal efficiency.

  19. First principles approach to ionicity of fragments

    NASA Astrophysics Data System (ADS)

    Pilania, Ghanshyam; Liu, Xiang-Yang; Valone, Steven M.

    2015-02-01

    We develop a first principles approach towards the ionicity of fragments. In contrast to the bond ionicity, the fragment ionicity refers to an electronic property of the constituents of a larger system, which may vary from a single atom to a functional group or a unit cell to a crystal. The fragment ionicity is quantitatively defined in terms of the coefficients of contributing charge states in a superposition of valence configurations of the system. Utilizing the constrained density functional theory-based computations, a practical method to compute the fragment ionicity from valence electron charge densities, suitably decomposed according to the Fragment Hamiltonian (FH) model prescription for those electron densities, is presented for the first time. The adopted approach is illustrated using BeO, MgO and CaO diatomic molecules as simple examples. The results are compared and discussed with respect to the bond ionicity scales of Phillips and Pauling.

  20. Mass-imbalanced ionic Hubbard chain

    NASA Astrophysics Data System (ADS)

    Sekania, Michael; Baeriswyl, Dionys; Jibuti, Luka; Japaridze, George I.

    2017-07-01

    A repulsive Hubbard model with both spin-asymmetric hopping (t↑≠t↓ ) and a staggered potential (of strength Δ ) is studied in one dimension. The model is a compound of the mass-imbalanced (t↑≠t↓ ,Δ =0 ) and ionic (t↑=t↓ ,Δ >0 ) Hubbard models, and may be realized by cold atoms in engineered optical lattices. We use mostly mean-field theory to determine the phases and phase transitions in the ground state for a half-filled band (one particle per site). We find that a period-two modulation of the particle (or charge) density and an alternating spin density coexist for arbitrary Hubbard interaction strength, U ≥0 . The amplitude of the charge modulation is largest at U =0 , decreases with increasing U and tends to zero for U →∞ . The amplitude for spin alternation increases with U and tends to saturation for U →∞ . Charge order dominates below a value Uc, whereas magnetic order dominates above. The mean-field Hamiltonian has two gap parameters, Δ↑ and Δ↓, which have to be determined self-consistently. For U Uc they have different signs, and for U =Uc one gap parameter jumps from a positive to a negative value. The weakly first-order phase transition at Uc can be interpreted in terms of an avoided criticality (or metallicity). The system is reluctant to restore a symmetry that has been broken explicitly.

  1. Effect of microwave radiation on surface charge, surface sites and ionic state of iron, and the activity of crocidolite asbestos fibres

    NASA Astrophysics Data System (ADS)

    Gulumian, M.; Pollak, H.

    1998-12-01

    Surface charge, surface sites, and the content of ferrous ions of crocidolite asbestos fibres are some of the properties which are considered to play a role in determining their activity in biological systems. Any treatment which changes these properties may therefore change their activity and subsequently increase or decrease their toxicity in biological surroundings. Surfaces of crocidolite fibres are shown to be negatively charged. In the present study, microwave radiation at 300°C was able to increase the number of positive charges within the bulk of the crocidolite fibres. In the presence of atmospheric oxygen, this increase could simultaneously reduce the hydroxyl groups on the surface of the fibres. The increase in positive charge was monitored by: (i) Mössbauer spectroscopy, where a change in the oxidation state of iron from ferrous to ferric was observed, (ii) visual microscopic observations of the irradiated fibres where there was an increase in their aggregation, and (iii) the difficulty to suspend these radiated fibres in solution. A decrease in the number of the surface hydroxyl groups on the other hand, was monitored by infrared spectroscopy. The reduction in the activity of the radiated crocidolite fibres was investigated by studying their ability to peroxidize lipids. Results have shown that changes in their surface charge, surface site and a reduction of the content of ferrous ions produce a concomitant decrease in their ability to initiate lipid peroxidation.

  2. Ionic conductors for solid oxide fuel cells

    DOEpatents

    Krumpelt, Michael; Bloom, Ira D.; Pullockaran, Jose D.; Myles, Kevin M.

    1993-01-01

    An electrolyte that operates at temperatures ranging from 600.degree. C. to 800.degree. C. is provided. The electrolyte conducts charge ionically as well as electronically. The ionic conductors include molecular framework structures having planes or channels large enough to transport oxides or hydrated protons and having net-positive or net-negative charges. Representative molecular framework structures include substituted aluminum phosphates, orthosilicates, silicoaluminates, cordierites, apatites, sodalites, and hollandites.

  3. Ionic conductors for solid oxide fuel cells

    SciTech Connect

    Krumpelt, M.; Bloom, I.D.; Pullockaran, J.D.; Myles, K.M.

    1991-12-31

    An electrolyte that operates at temperatures ranging from 600{degree}C to 800{degree}C is discussed. The electrolyte conducts charge ionically as well as electronically. The ionic conductors include molecular framework structures having planes or channels large enough to transport oxides or hydrated protons and having net-positive or net-negative charges. Representative molecular framework structures include substituted aluminum phosphates, orthosilicates, silicoaluminates, cordierites, apatites, sodalites, and hollandites.

  4. Additive polarizabilities in ionic liquids.

    PubMed

    Bernardes, Carlos E S; Shimizu, Karina; Lopes, José Nuno Canongia; Marquetand, Philipp; Heid, Esther; Steinhauser, Othmar; Schröder, Christian

    2016-01-21

    An extended designed regression analysis of experimental data on density and refractive indices of several classes of ionic liquids yielded statistically averaged atomic volumes and polarizabilities of the constituting atoms. These values can be used to predict the molecular volume and polarizability of an unknown ionic liquid as well as its mass density and refractive index. Our approach does not need information on the molecular structure of the ionic liquid, but it turned out that the discrimination of the hybridization state of the carbons improved the overall result. Our results are not only compared to experimental data but also to quantum-chemical calculations. Furthermore, fractional charges of ionic liquid ions and their relation to polarizability are discussed.

  5. Arbitrary shape surface Fresnel diffraction.

    PubMed

    Shimobaba, Tomoyoshi; Masuda, Nobuyuki; Ito, Tomoyoshi

    2012-04-09

    Fresnel diffraction calculation on an arbitrary shape surface is proposed. This method is capable of calculating Fresnel diffraction from a source surface with an arbitrary shape to a planar destination surface. Although such calculation can be readily calculated by the direct integral of a diffraction calculation, the calculation cost is proportional to O(N²) in one dimensional or O(N⁴) in two dimensional cases, where N is the number of sampling points. However, the calculation cost of the proposed method is O(N log N) in one dimensional or O(N² log N) in two dimensional cases using non-uniform fast Fourier transform.

  6. Representing Arbitrary Boosts for Undergraduates.

    ERIC Educational Resources Information Center

    Frahm, Charles P.

    1979-01-01

    Presented is a derivation for the matrix representation of an arbitrary boost, a Lorentz transformation without rotation, suitable for undergraduate students with modest backgrounds in mathematics and relativity. The derivation uses standard vector and matrix techniques along with the well-known form for a special Lorentz transformation. (BT)

  7. Macrocyclic lanthanide complexes as artificial nucleases and ribonucleases: effects of pH, metal ionic radii, number of coordinated water molecules, charge, and concentrations of the metal complexes.

    PubMed

    Chang, C Allen; Wu, Bo Hong; Kuan, Bu Yuan

    2005-09-19

    We have been interested in the design, synthesis, and characterization of artificial nucleases and ribonucleases by employing macrocyclic lanthanide complexes because their high thermodynamic stability, low kinetic lability, high coordination number, and charge density (Lewis acidity) allow more design flexibility and stability. In this paper, we report the study of the use of the europium(III) complex, EuDO2A+ (DO2A is 1,7-dicarboxymethyl-1,4,7,10-tetraazacyclododecane) and other lanthanide complexes (i.e., LaDO2A+, YbDO2A+, EuK21DA+, EuEDDA+, and EuHEDTA where K21DA is 1,7-diaza-4,10,13-trioxacyclopentadecane-N,N'-diacetic acid, EDDA is ethylenediamine-N,N'-diacetic acid, and HEDTA is N-hydroxyethyl-ethylenediamine-N,N',N'-triacetic acid), as potential catalysts for the hydrolysis of the phosphodiester bond of BNPP (sodium bis(4-nitrophenyl)-phosphate). For the pH range 7.0-11.0 studied, EuDO2A+ promotes BNPP hydrolysis with the quickest rates among LaDO2A+, EuDO2A+, and YbDO2A+. This indicates that charge density is not the only factor affecting the reaction rates. Among the four complexes, EuDO2A+, EuK21DA+, EuEDDA+, and EuHEDTA, with their respective number of inner-sphere coordinated water molecules three, two, five, and three, EuEDDA+, with the greatest number of inner-sphere coordinated water molecules and a positive charge, promotes BNPP hydrolysis more efficiently at pH below 8.4, and the observed rate trend is EuEDDA+ > EuDO2A+ > EuK21DA+ > EuHEDTA. At pH > 8.4, the EuEDDA+ solution becomes misty and precipitates form. At pH 11.0, the hydrolysis rate of BNPP in the presence of EuDO2A+ is 100 times faster than that of EuHEDTA, presumably because the positively charged EuDO2A+ is more favorable for binding with the negatively charged phosphodiester compounds. The logarithmic hydrolysis constants (pKh) were determined, and are reported in the parentheses, by fitting the kinetic k(obs) data vs pH for EuDO2A+ (8.4), LaDO2A+ (8.4), YbDO2A+ (9.4), EuK21DA+ (7

  8. Long range electrostatic forces in ionic liquids.

    PubMed

    Gebbie, Matthew A; Smith, Alexander M; Dobbs, Howard A; Lee, Alpha A; Warr, Gregory G; Banquy, Xavier; Valtiner, Markus; Rutland, Mark W; Israelachvili, Jacob N; Perkin, Susan; Atkin, Rob

    2017-01-19

    Ionic liquids are pure salts that are liquid under ambient conditions. As liquids composed solely of ions, the scientific consensus has been that ionic liquids have exceedingly high ionic strengths and thus very short Debye screening lengths. However, several recent experiments from laboratories around the world have reported data for the approach of two surfaces separated by ionic liquids which revealed remarkable long range forces that appear to be electrostatic in origin. Evidence has accumulated demonstrating long range surface forces for several different combinations of ionic liquids and electrically charged surfaces, as well as for concentrated mixtures of inorganic salts in solvent. The original interpretation of these forces, that ionic liquids could be envisioned as "dilute electrolytes," was controversial, and the origin of long range forces in ionic liquids remains the subject of discussion. Here we seek to collate and examine the evidence for long range surface forces in ionic liquids, identify key outstanding questions, and explore possible mechanisms underlying the origin of these long range forces. Long range surface forces in ionic liquids and other highly concentrated electrolytes hold diverse implications from designing ionic liquids for energy storage applications to rationalizing electrostatic correlations in biological self-assembly.

  9. Arbitrary bending plasmonic light waves.

    PubMed

    Epstein, Itai; Arie, Ady

    2014-01-17

    We demonstrate the generation of self-accelerating surface plasmon beams along arbitrary caustic curvatures. These plasmonic beams are excited by free-space beams through a two-dimensional binary plasmonic phase mask, which provides the missing momentum between the two beams in the direction of propagation and sets the required phase for the plasmonic beam in the transverse direction. We examine the cases of paraxial and nonparaxial curvatures and show that this highly versatile scheme can be designed to produce arbitrary plasmonic self-accelerating beams. Several different plasmonic beams, which accelerate along polynomial and exponential trajectories, are demonstrated both numerically and experimentally, with a direct measurement of the plasmonic light intensity using a near-field scanning optical microscope.

  10. Perturbative gadgets at arbitrary orders

    NASA Astrophysics Data System (ADS)

    Jordan, Stephen P.; Farhi, Edward

    2008-06-01

    Adiabatic quantum algorithms are often most easily formulated using many-body interactions. However, experimentally available interactions are generally two-body. In 2004, Kempe, Kitaev, and Regev introduced perturbative gadgets, by which arbitrary three-body effective interactions can be obtained using Hamiltonians consisting only of two-body interactions. These three-body effective interactions arise from the third order in perturbation theory. Since their introduction, perturbative gadgets have become a standard tool in the theory of quantum computation. Here we construct generalized gadgets so that one can directly obtain arbitrary k -body effective interactions from two-body Hamiltonians. These effective interactions arise from the k th order in perturbation theory.

  11. Mass action in ionic solutions

    NASA Astrophysics Data System (ADS)

    Eisenberg, Bob

    2011-07-01

    The law of mass action describes reactants as simple ideal fluids of concentrations of uncharged noninteracting particles. Ionic solutions contain interacting charged particles and are not ideal. Interactions of reactants can then be mistaken for complexities in chemical reactions or enzymatic catalysts. The variational theory of complex fluids describes flowing mixtures like biological solutions. When a component is added, the theory derives-by mathematics alone-a new set of differential equations that automatically captures all interactions. A variational theory of ionic solutions (as complex fluids) provides computable description of ions in solutions and proteins. Numerical inefficiencies have delayed experimental verification.

  12. Photonic Arbitrary Waveform Generation Technology

    DTIC Science & Technology

    2006-06-01

    filters or ring resonator based technologies [26-29]. Key aspects of the filter technology are the flatness of the filter channel, the crosstalk...photodetectors would also be warranted. 28 References [1] K. Nosu, “ Advanced coherent lightwave technologies ,” IEEE Commun. Magn,, vol. 26...AFRL-SN-RS-TR-2006-208 Final Technical Report June 2006 PHOTONIC ARBITRARY WAVEFORM GENERATION TECHNOLOGY University of

  13. Ionic crystals

    SciTech Connect

    Mahan, G.D.

    1985-03-01

    The theme of the second Petra School of Physics was the optical properties of solids. The author's lectures will discuss the theory of ionic crystals such as the alkali halides. The general topics will include a discussion of: the local electric fields, multipole polarizability, core level spectra, and electron energy levels. The subject of alkali halides is today regarded as unfashionable. They were quite popular years ago, but fashions and fancies in science have moved elsewhere. One should not think they are well understood. The author's impression of this field is that activity stopped, not because the problems were solved, but rather because the workers got tired of not being able to solve them. For example, we still do not have a good theory of crystal structure, since microscopic forces are not well characterized. One concludes that other quantities which depend upon forces, such as the elastic constants, are also not well understood, although theories of them are published all of the time. As another example, we still do not have a good theory of bonding. Here there are two camps: one which regards the bonding as ionic, while the other advocates significant amounts of covalency. Recently we have shown that both the elastic constants, and the amount of covalent bonding, depend significantly upon the higher multipole polarizabilities. In summary, the subject of ionic crystals is a field where there are still many unresolved issues awaiting good research. 21 refs., 5 figs., 4 tabs.

  14. Charge Compensation in RE3+ (RE = Eu, Gd) and M+ (M = Li, Na, K) Co-Doped Alkaline Earth Nanofluorides Obtained by Microwave Reaction with Reactive Ionic Liquids Leading to Improved Optical Properties

    SciTech Connect

    Lorbeer, C; Behrends, F; Cybinska, J; Eckert, H; Mudring, Anja -V

    2014-01-01

    Alkaline earth fluorides are extraordinarily promising host matrices for phosphor materials with regard to rare earth doping. In particular, quantum cutting materials, which might considerably enhance the efficiency of mercury-free fluorescent lamps or SC solar cells, are often based on rare earth containing crystalline fluorides such as NaGdF4, GdF3 or LaF3. Substituting most of the precious rare earth ions and simultaneously retaining the efficiency of the phosphor is a major goal. Alkaline earth fluoride nanoparticles doped with trivalent lanthanide ions (which are required for the quantum cutting phenomenon) were prepared via a microwave assisted method in ionic liquids. As doping trivalent ions into a host with divalent cations requires charge compensation, this effect was thoroughly studied by powder X-ray and electron diffraction, luminescence spectroscopy and 23Na, 139La and 19F solid state NMR spectroscopy. Monovalent alkali ions were codoped with the trivalent lanthanide ions to relieve stress and achieve a better crystallinity and higher quantum cutting abilities of the prepared material. 19F-magic angle spinning (MAS)-NMR-spectra, assisted by 19F{23Na} rotational echo double resonance (REDOR) studies, reveal distinct local fluoride environments, the populations of which are discussed in relation to spatial distribution and clustering models. In the co-doped samples, fluoride species having both Na+ and La3+ ions within their coordination sphere can be identified and quantified. This interplay of mono- and trivalent ions in the CaF2 lattice appears to be an efficient charge compensation mechanism that allows for improved performance characteristics of such co-doped phosphor materials.

  15. Multistability, ionic doping, and charge dynamics in electrosynthesized polypyrrole, polymer-nanoparticle blend nonvolatile memory, and fixed p-i-n junction polymer light-emitting electrochemical cells

    NASA Astrophysics Data System (ADS)

    Simon, Daniel Theodore

    A variety of factors make semiconducting polymers a fascinating alternative for both device development and new areas of fundamental research. Among these are solution processability, low cost, flexibility, and the strong dependence of conduction on the presence of charge compensating ions. With the lack of a complete fundamental understanding of the materials, and the growing demand for novel solutions to semiconductor device design, research in the field can take many, often multifaceted, routes. Due to ion-mediated conduction and versatility of fabrication, conducting polymers can provide a route to the study of neural signaling. In the first of three research topics presented, junctions of polypyrrole electropolymenzed on microelectrode arrays are demonstrated. Indi vidual junctions, when synthesized in a three-electrode configuration, exhibit current switching behavior analogous to neural weighting. Junctions copolymerized with thiophene exhibit current rectification and the nonlinear current-voltage behavior requisite for complex neural systems. Applications to larger networks, and eventual use in analysis of signaling, are discussed. In the second research topic, nonvolatile resistive memory consisting of gold nanoparticles embedded in a polymer film is examined using admittance spectroscopy. The frequency dependence of the devices indicates space-charge-limited transport in the high-conductivity "on" state, and similar transport in the lower-conductivity "off' state. Furthermore, a larger do capacitance of the on state indicates that a greater amount of filling of midgap trap levels introduced by the nanoparticles increases conductivity, leading to the memory effect. Implications on the question as to whether or not the on state is the result of percolation pathways is discussed. The third and final research topic is a presentation of enhanced efficiency of polymer light-emitting electrochemical cells (LECs) by means of forming a doping self

  16. Strong and weak adsorptions of polyelectrolyte chains onto oppositely charged spheres

    NASA Astrophysics Data System (ADS)

    Cherstvy, Andrey; Winkler, Roland

    2007-03-01

    We investigate the complexation of long thin polyelectrolyte chains with the oppositely charged sphere. In the limit of strong adsorption, when strongly charged polyelectrolyte chains adapt definite wrapped conformations on the sphere surface (solenoidal, tennis-ball-like, etc.), we analytically solve the linear Poisson-Boltzmann equation and calculate the electrostatic potential and energy of the complex. We discuss some biological applications of the obtained results, including those for DNA wrapping in the nucleosome core particles and for aggregate formation of DNA with oppositely charged nano-spheres studied in vitro. For weak adsorption, when a flexible weakly charged polyelectrolyte chain is localized next to the sphere in solution, we solve the Edwards equation for the chain conformations in the Hulth'en potential. The latter is used as an approximation for the screened Debye-H"uckel potential of the sphere. For arbitrary sphere radius, we predict the critical conditions for polyelectrolyte adsorption as a coupling between critical sphere and polyelectrolyte charge densities, sphere radius, temperature, and ionic strength in solution. We find that the critical charge density of the sphere exhibits a distinctively different dependence on the Debye screening length than for polyelectrolyte adsorption onto a flat surface. We compare our findings with experimental measurements on complex formation of various polyelectrolytes (DNA, PSS, AMPS, etc.) with oppositely charged colloidal particles and cationic micelles, where similar universal scaling relations for the sphere charge density have been revealed.

  17. Equientangled bases in arbitrary dimensions

    SciTech Connect

    Karimipour, V.; Memarzadeh, L.

    2006-01-15

    For the space of two identical systems of arbitrary dimensions, we introduce a continuous family of bases with the following properties: (i) the bases are orthonormal (ii) in each basis, all the states have the same values of entanglement, and (iii) they continuously interpolate between the product basis and the maximally entangled basis. The states thus constructed may find applications in many areas related to the quantum information science including quantum cryptography, optimal Bell tests, and the investigation of the enhancement of channel capacity due to entanglement.

  18. Maximal cuts in arbitrary dimension

    NASA Astrophysics Data System (ADS)

    Bosma, Jorrit; Sogaard, Mads; Zhang, Yang

    2017-08-01

    We develop a systematic procedure for computing maximal unitarity cuts of multiloop Feynman integrals in arbitrary dimension. Our approach is based on the Baikov representation in which the structure of the cuts is particularly simple. We examine several planar and nonplanar integral topologies and demonstrate that the maximal cut inherits IBPs and dimension shift identities satisfied by the uncut integral. Furthermore, for the examples we calculated, we find that the maximal cut functions from different allowed regions, form the Wronskian matrix of the differential equations on the maximal cut.

  19. Modeling electrokinetics in ionic liquids: General

    DOE PAGES

    Wang, Chao; Bao, Jie; Pan, Wenxiao; ...

    2017-04-01

    Using direct numerical simulations, we provide a thorough study regarding the electrokinetics of ionic liquids. In particular, modified Poisson–Nernst–Planck equations are solved to capture the crowding and overscreening effects characteristic of an ionic liquid. For modeling electrokinetic flows in an ionic liquid, the modified Poisson-Nernst-Planck equations are coupled with Navier–Stokes equations to study the coupling of ion transport, hydrodynamics, and electrostatic forces. Specifically, we consider the ion transport between two parallel charged surfaces, charging dynamics in a nanopore, capacitance of electric double-layer capacitors, electroosmotic flow in a nanochannel, electroconvective instability on a plane ion-selective surface, and electroconvective flow on amore » curved ionselective surface. Lastly, we also discuss how crowding and overscreening and their interplay affect the electrokinetic behaviors of ionic liquids in these application problems.« less

  20. Depolarization of water in protic ionic liquids.

    PubMed

    Zahn, Stefan; Wendler, Katharina; Delle Site, Luigi; Kirchner, Barbara

    2011-09-07

    A mixture of the protic ionic liquid mono-methylammonium nitrate with 1.6 wt% water was investigated from Car-Parrinello molecular dynamics simulations. In contrast to imidazolium-based ionic liquids, the cation possesses strong directional hydrogen bonds to water and all hydrogen bonds in the mixture have a comparable strength. This results in a good incorporation of water into the hydrogen bond network of mono-methylammonium nitrate and a tetrahedral hydrogen bond coordination of water. Hence, one might expect a larger dipole moment of water in the investigated mixture compared to neat water due to the good hydrogen bond network incorporation and the charged vicinity of water in the protic ionic liquid. However, the opposite is observed pointing to strong electrostatic screening in protic ionic liquids. Additionally, the influence of water on the properties of the protic ionic liquid is discussed.

  1. Theoretical investigation of the ionic selectivity of polyelectrolyte multilayer membranes in nanofiltration.

    PubMed

    Dirir, Yonis Ibrahim; Hanafi, Yamina; Ghoufi, Aziz; Szymczyk, Anthony

    2015-01-13

    Polyelectrolyte multilayer membranes have proven to be promising materials for ion nanofiltration. In this work, we implement a continuum mesoscopic transport model developed in previous works (Szymczyk, A.; Zhu, H.; Balannec, B. Langmuir 2010, 26, 1214; Szymczyk, A.; Zhu, H.; Balannec, B. J. Phys. Chem. B 2010, 114, 10143) to investigate the pressure-driven transport of electrolyte mixtures through this kind of membrane. The model accounts for an inhomogeneous distribution of the fixed charge through an arbitrary number of polyelectrolyte bilayers. We show that accounting for the multiple bipolar charge distribution resulting from the layer-by-layer assembly of polyelectrolytes with opposite charge is responsible for the increase in the Na(+)/Mg(2+) selectivity reported experimentally with respect to conventional nanofiltration membranes. The model also allows the rationalizing of the seemingly contradictory experimental results reported in the literature (i.e., the increase or decrease in the selectivity with the number of bilayers or the existence of an optimum number of bilayers). It is shown, however, that the nonmonotonous variation of the ionic selectivity does not originate from the multibipolar distribution of the fixed charge through polyelectrolyte multilayer membranes but from the existence of an optimum skin layer thickness.

  2. Phase Behavior of Ionic Microgels

    NASA Astrophysics Data System (ADS)

    Gottwald, D.; Likos, C. N.; Kahl, G.; Löwen, H.

    2004-02-01

    We employ effective interaction potentials between spherical polyelectrolyte microgels in order to investigate theoretically the structure, thermodynamics, and phase behavior of ionic microgel solutions. Combining a genetic algorithm with accurate free energy calculations we are able to perform an unrestricted search of candidate crystal structures. Hexagonal, body-centered orthogonal, and trigonal crystals are found to be stable at high concentrations and charges of the microgels, accompanied by reentrant melting behavior and fluid-fcc-bcc transitions below the overlap concentration.

  3. Phase behavior of ionic microgels.

    PubMed

    Gottwald, D; Likos, C N; Kahl, G; Löwen, H

    2004-02-13

    We employ effective interaction potentials between spherical polyelectrolyte microgels in order to investigate theoretically the structure, thermodynamics, and phase behavior of ionic microgel solutions. Combining a genetic algorithm with accurate free energy calculations we are able to perform an unrestricted search of candidate crystal structures. Hexagonal, body-centered orthogonal, and trigonal crystals are found to be stable at high concentrations and charges of the microgels, accompanied by reentrant melting behavior and fluid-fcc-bcc transitions below the overlap concentration.

  4. Exact solution of the one-dimensional Hubbard model with arbitrary boundary magnetic fields

    NASA Astrophysics Data System (ADS)

    Li, Yuan-Yuan; Cao, Junpeng; Yang, Wen-Li; Shi, Kangjie; Wang, Yupeng

    2014-02-01

    The one-dimensional Hubbard model with arbitrary boundary magnetic fields is solved exactly via the Bethe ansatz methods. With the coordinate Bethe ansatz in the charge sector, the second eigenvalue problem associated with the spin sector is constructed. It is shown that the second eigenvalue problem can be transformed into that of the inhomogeneous XXX spin chain with arbitrary boundary fields which can be solved via the off-diagonal Bethe ansatz method.

  5. On catalysis by ionic liquids.

    PubMed

    Chakraborti, Asit K; Roy, Sudipta Raha

    2009-05-27

    A molecular level mechanism of catalysis by an ionic liquid (IL) is proposed as an "electrophile nucleophile dual activation" through a "relay of cooperative hydrogen bonds and charge-charge interactions". Spectroscopic ((1)H NMR and IR) studies were used to probe the involvement of the C-2 hydrogen and the AcO(-) anion of [bmim][OAc] in the catalysis for O-t-Boc formation. Ion fishing by MALDI-TOF-TOF MS and MS-MS established the hydrogen bonded clusters.

  6. Influence of resonant charge exchange on the viscosity of partially ionized plasma in a magnetic field

    SciTech Connect

    Zhdanov, V. M. Stepanenko, A. A.

    2013-12-15

    The influence of resonant charge exchange for ion-atom interaction on the viscosity of partially ionized plasma embedded in the magnetic field is investigated. The general system of equations used to derive the viscosity coefficients for an arbitrary plasma component in the 21-moment approximation of Grad’s method is presented. The expressions for the coefficients of total and partial viscosities of a multicomponent partially ionized plasma in the magnetic field are obtained. As an example, the coefficients of the parallel and transverse viscosities for the ionic and neutral components of the partially ionized hydrogen plasma are calculated. It is shown that the account for resonant charge exchange can lead to a substantial change of the parallel and transverse viscosity of the plasma components in the region of low degrees of ionization on the order of 0.1.

  7. Decay behavior of screened electrostatic surface forces in ionic liquids: the vital role of non-local electrostatics.

    PubMed

    Kjellander, Roland

    2016-07-28

    Screened electrostatic surface forces, also called double layer forces, between surfaces in ionic liquids can, depending on the circumstances, decay in an exponentially damped, oscillatory manner or in a plain exponential way (the latter as in dilute electrolyte solutions where ion-ion correlations are very weak). The occurrence of both of these behaviors in dense ionic liquids, where ion-ion correlations are very strong, is analyzed in the current work using exact statistical mechanics formulated in a manner that is physically transparent. A vital ingredient in understanding the decay behaviors is the fact that electrostatics in dense electrolytes have a non-local nature caused by the strong correlations. It is shown that the effects of non-locality can be elucidated by a remarkably simple, general expression for the decay parameter κ that replaces the classical expression for the inverse Debye length κDH of the Debye-Hückel (DH) and non-linear Poisson-Boltzmann approximations. This exact expression is valid for both the plain exponential and the oscillatory cases. It shows how strong correlations can give rise to plain exponential decay with a long decay length. Such a decay can arise from anion-cation associations of various kinds, for instance transient ion pairing or association caused by many-body correlations; ion pairing is a possibility but not a necessity for this to occur. Theoretical analysis is done for systems consisting of ions with an arbitrary shape and internal charge density and immersed planar walls with arbitrary internal charge distribution and any short-range ion-surface interaction. The screened electrostatic surface force between two walls is at large separations proportional to the product of effective surface charge densities of each wall. For the oscillatory case, each wall contributes with a phase shift to the oscillations of the interaction.

  8. Arbitrary Inequality in Reputation Systems

    NASA Astrophysics Data System (ADS)

    Frey, Vincenz; van de Rijt, Arnout

    2016-12-01

    Trust is an essential condition for exchange. Large societies must substitute the trust traditionally provided through kinship and sanctions in small groups to make exchange possible. The rise of internet-supported reputation systems has been celebrated for providing trust at a global scale, enabling the massive volumes of transactions between distant strangers that are characteristic of modern human societies. Here we problematize an overlooked side-effect of reputation systems: Equally trustworthy individuals may realize highly unequal exchange volumes. We report the results of a laboratory experiment that shows emergent differentiation between ex ante equivalent individuals when information on performance in past exchanges is shared. This arbitrary inequality results from cumulative advantage in the reputation-building process: Random initial distinctions grow as parties of good repute are chosen over those lacking a reputation. We conjecture that reputation systems produce artificial concentration in a wide range of markets and leave superior but untried exchange alternatives unexploited.

  9. Arbitrary Inequality in Reputation Systems

    PubMed Central

    Frey, Vincenz; van de Rijt, Arnout

    2016-01-01

    Trust is an essential condition for exchange. Large societies must substitute the trust traditionally provided through kinship and sanctions in small groups to make exchange possible. The rise of internet-supported reputation systems has been celebrated for providing trust at a global scale, enabling the massive volumes of transactions between distant strangers that are characteristic of modern human societies. Here we problematize an overlooked side-effect of reputation systems: Equally trustworthy individuals may realize highly unequal exchange volumes. We report the results of a laboratory experiment that shows emergent differentiation between ex ante equivalent individuals when information on performance in past exchanges is shared. This arbitrary inequality results from cumulative advantage in the reputation-building process: Random initial distinctions grow as parties of good repute are chosen over those lacking a reputation. We conjecture that reputation systems produce artificial concentration in a wide range of markets and leave superior but untried exchange alternatives unexploited. PMID:27995957

  10. Arbitrary Inequality in Reputation Systems.

    PubMed

    Frey, Vincenz; van de Rijt, Arnout

    2016-12-20

    Trust is an essential condition for exchange. Large societies must substitute the trust traditionally provided through kinship and sanctions in small groups to make exchange possible. The rise of internet-supported reputation systems has been celebrated for providing trust at a global scale, enabling the massive volumes of transactions between distant strangers that are characteristic of modern human societies. Here we problematize an overlooked side-effect of reputation systems: Equally trustworthy individuals may realize highly unequal exchange volumes. We report the results of a laboratory experiment that shows emergent differentiation between ex ante equivalent individuals when information on performance in past exchanges is shared. This arbitrary inequality results from cumulative advantage in the reputation-building process: Random initial distinctions grow as parties of good repute are chosen over those lacking a reputation. We conjecture that reputation systems produce artificial concentration in a wide range of markets and leave superior but untried exchange alternatives unexploited.

  11. Generalization of the electronic susceptibility for arbitrary molecular geometries.

    PubMed

    Scherrer, Arne; Dreßler, Christian; Ahlert, Paul; Sebastiani, Daniel

    2016-04-14

    We generalize the explicit representation of the electronic susceptibility χ[R](r, r') for arbitrary molecular geometries R. The electronic susceptibility is a response function that yields the response of the molecular electronic charge density at linear order to an arbitrary external perturbation. We address the dependence of this response function on the molecular geometry. The explicit representation of the molecular geometry dependence is achieved by means of a Taylor expansion in the nuclear coordinates. Our approach relies on a recently developed low-rank representation of the response function χ[R](r, r') which allows a highly condensed storage of the expansion and an efficient application within dynamical chemical environments. We illustrate the performance and accuracy of our scheme by computing the vibrationally induced variations of the response function of a water molecule and its resulting Raman spectrum.

  12. Method and apparatus using an active ionic liquid for algae biofuel harvest and extraction

    SciTech Connect

    Salvo, Roberto Di; Reich, Alton; Dykes, Jr., H. Waite H.; Teixeira, Rodrigo

    2012-11-06

    The invention relates to use of an active ionic liquid to dissolve algae cell walls. The ionic liquid is used to, in an energy efficient manner, dissolve and/or lyse an algae cell walls, which releases algae constituents used in the creation of energy, fuel, and/or cosmetic components. The ionic liquids include ionic salts having multiple charge centers, low, very low, and ultra low melting point ionic liquids, and combinations of ionic liquids. An algae treatment system is described, which processes wet algae in a lysing reactor, separates out algae constituent products, and optionally recovers the ionic liquid in an energy efficient manner.

  13. Ionic Liquids Database- (ILThermo)

    National Institute of Standards and Technology Data Gateway

    SRD 147 Ionic Liquids Database- (ILThermo) (Web, free access)   IUPAC Ionic Liquids Database, ILThermo, is a free web research tool that allows users worldwide to access an up-to-date data collection from the publications on experimental investigations of thermodynamic, and transport properties of ionic liquids as well as binary and ternary mixtures containing ionic liquids.

  14. Thermotropic Ionic Liquid Crystals

    PubMed Central

    Axenov, Kirill V.; Laschat, Sabine

    2011-01-01

    The last five years’ achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed. PMID:28879986

  15. Unravelling nanoconfined films of ionic liquids

    SciTech Connect

    Lee, Alpha A.; Vella, Dominic; Goriely, Alain; Perkin, Susan

    2014-09-07

    The confinement of an ionic liquid between charged solid surfaces is treated using an exactly solvable 1D Coulomb gas model. The theory highlights the importance of two dimensionless parameters: the fugacity of the ionic liquid, and the electrostatic interaction energy of ions at closest approach, in determining how the disjoining pressure exerted on the walls depends on the geometrical confinement. Our theory reveals that thermodynamic fluctuations play a vital role in the “squeezing out” of charged layers as the confinement is increased. The model shows good qualitative agreement with previous experimental data, with all parameters independently estimated without fitting.

  16. Sandia's Arbitrary Waveform MEMO Actuator

    SciTech Connect

    Brian Sosnowchik, Mark Jenkins

    2003-08-07

    SAMA is a multichannel, arbitrary waveform generator program for driving microelectromechanical systems (MEMS). It allows the user to piece together twelve available wave parts, thereby permitting the user to create practically any waveform, or upload a previously constructed signal. The waveforms (bundled together as a signal) may simultaneously be output through four different channels to actuate MEMS devices, and the number of output channels may be increased depending on the DAQ card or instrument utilized. Additionally, real-time changes may be made to the frequency and amplitude. The signal may be paused temporarily. The waveform may be saved to file for future uploading. Recent work for this version has focused on modifications that will allow loading previously generated arbitrary waveforms, independent channel waveform amplification, adding a pause function, separating the "modify waveform: and "end program" functions, and simplifying the user interface by adding test blocks with statements to help the user program and output the desired signals. The program was developed in an effort to alleviate some of the limitations of Micro Driver. For example, Micro Driver will not allow the user to select a segment of a sine wave, but rather the user is limited to choosing either a whole or half sine wave pattern. It therefore becomes quite difficult ot construct partial sine wave patterns out of a "ramp" waveparts for several reasons. First, one must determine on paper how many data points each ramp will cover, and what the slopes of these ramps will be. Second, from what was observed, Micro Driver has difficulty processing more than six distinct waveparts during sequencing. The program will allow the user to input the various waves into the desired sequence; however, it will not allow the user to compile them (by clicking "ok" and returning to the main screen). Third, should the user decide that they want to increase the amplitute of the output signal, they must

  17. Nonlinear capacitance and electrochemical response of ionic liquid-ionic polymers

    NASA Astrophysics Data System (ADS)

    Davidson, Jacob D.; Goulbourne, N. C.

    2011-04-01

    In this paper we present a physics-based model for the electrochemical response of ionic liquid-ionic polymer transducers (IPTs) and show how the mobile ionic liquid ions influence the charging characteristics and actuation performance of a device. It is assumed that a certain fraction of the ionic liquid ions exist as "free," making for a total of 3 mobile ions. This leads to predictions of distinctly different charging characteristics for ionic liquid versus water-based IPTs, since for the latter there is only a single mobile ion. The large ionic liquid ions are modeled by including steric effects in a set of modified Nernst-Planck/Poisson equations, and the resulting system of equations is solved using the method of matched asymptotic expansions (MAE). The inclusion of steric effects allows for a realistic description of boundary layer composition near actuator operating voltages (~1 V). Analytical expressions for the charge transferred and differential capacitance are derived as a function of the fraction of free ionic liquid ions, influence of steric effects in formation of the electric double layer, and applied voltage. It is shown that the presence of free ionic liquid ions tends to increase the overall amount of charge transferred, and also leads to a nonmonotonic capacitance-voltage curve. We suggest that these results could be used to experimentally identify the extent of free ionic liquid ion movement and to test the validity of the assumptions made in the underlying theory. A comparison with numerical results shows that while the MAE solution procedure gives valid results for capacitance and charge transferred, it cannot predict the dynamic response due to the presence of multiple time scales in the current decay. This is in contrast to previous results in analyzing water-based IPTs, where the MAE solution is in good agreement with numerical results at all times and applied voltages due to the presence of only a single mobile ion. By examining the

  18. Optical arbitrary waveform characterization using linear spectrograms.

    PubMed

    Jiang, Zhi; Leaird, Daniel E; Long, Christopher M; Boppart, Stephen A; Weiner, Andrew M

    2010-08-01

    We demonstrate the first application of linear spectrogram methods based on electro-optic phase modulation to characterize optical arbitrary waveforms generated under spectral line-by-line control. This approach offers both superior sensitivity and self-referencing capability for retrieval of periodic high repetition rate optical arbitrary waveforms.

  19. Mean-Field Description of Ionic Size Effects with Non-Uniform Ionic Sizes: A Numerical Approach

    PubMed Central

    Zhou, Shenggao; Wang, Zhongming; Li, Bo

    2013-01-01

    Ionic size effects are significant in many biological systems. Mean-field descriptions of such effects can be efficient but also challenging. When ionic sizes are different, explicit formulas in such descriptions are not available for the dependence of the ionic concentrations on the electrostatic potential, i.e., there is no explicit, Boltzmann type distributions. This work begins with a variational formulation of the continuum electrostatics of an ionic solution with such non-uniform ionic sizes as well as multiple ionic valences. An augmented Lagrange multiplier method is then developed and implemented to numerically solve the underlying constrained optimization problem. The method is shown to be accurate and efficient, and is applied to ionic systems with non-uniform ionic sizes such as the sodium chloride solution. Extensive numerical tests demonstrate that the mean-field model and numerical method capture qualitatively some significant ionic size effects, particularly those for multivalent ionic solutions, such as the stratification of multivalent counterions near a charged surface. The ionic valence-to-volume ratio is found to be the key physical parameter in the stratification of concentrations. All these are not well described by the classical Poisson–Boltzmann theory, or the generalized Poisson–Boltzmann theory that treats uniform ionic sizes. Finally, various issues such as the close packing, limitation of the continuum model, and generalization of this work to molecular solvation are discussed. PMID:21929014

  20. Calculation of Electric Filed Formed by Electrodes of Arbitrary Complexity

    NASA Astrophysics Data System (ADS)

    Chorniy, Anton; Nemchenko, Konstantin

    2002-08-01

    We propose the generalized methodics utilising capacity coefficient matrix for numerical calculation of electric fields. This methodics allows to calculate the potential and strength of electric field created by electrodes of arbitrary forms. As initial conditions either potentials or charges of definite electrodes are used. The methodics uses the integral form of Maxwell equations allowing to avoid consideration of boundary conditions and summation of errors while solving numerically the differential equations. Thus, the offered methodics can be applied for the systems with no symmetry. As an example, we have used this methodics to calculate the electric fields inside an ion diod consisting of a big number of electrodes of various sizes and forms.

  1. Two-body quantum propagation in arbitrary potentials

    NASA Astrophysics Data System (ADS)

    Grasselli, Federico; Bertoni, Andrea; Goldoni, Guido

    2016-08-01

    We have implemented a unitary, numerically exact, Fourier split step method, based on a proper Suzuki-Trotter factorization of the quantum evolution operator, to propagate a two-body complex in arbitrary external potential landscapes taking into account exactly the internal structure. We have simulated spatially indirect Wannier-Mott excitons - optically excited electron-hole pairs with the two charges confined to different layers of a semiconductor heterostructure with prototypical 1D and 2D potentials emphasizing the effects of the internal dynamics and the insufficiency of mean-field methods in this context.

  2. Modeling the effects of pH and ionic strength on swelling of polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Drozdov, A. D.; deClaville Christiansen, J.

    2015-03-01

    A model is developed for the elastic response of a polyelectrolyte gel under unconstrained and constrained swelling in a water bath with an arbitrary pH, where a monovalent salt is dissolved. A gel is treated as a three-phase medium consisting of an equivalent polymer network, solvent (water), and solute (mobile ions). Transport of solvent and solute is thought of as their diffusion through the network accelerated by an electric field formed by mobile and fixed ions and accompanied by chemical reactions (self-ionization of water molecules, dissociation of functional groups attached to polymer chains, and formation of ion pairs between bound charges and mobile counter-ions). Constitutive equations are derived by means of the free energy imbalance inequality for an arbitrary three-dimensional deformation with finite strains. Adjustable parameters in the governing relations are found by fitting equilibrium swelling diagrams on several hydrogels. The effects of pH, ionic strength of solution, and constraints on equilibrium water uptake are studied numerically.

  3. Continuum description of ionic and dielectric shielding for molecular-dynamics simulations of proteins in solution.

    PubMed

    Egwolf, Bernhard; Tavan, Paul

    2004-01-22

    We extend our continuum description of solvent dielectrics in molecular-dynamics (MD) simulations, which has provided an efficient and accurate solution of the Poisson equation, to ionic solvents as described by the linearized Poisson-Boltzmann (LPB) equation. We start with the formulation of a general theory for the electrostatics of an arbitrarily shaped molecular system, which consists of partially charged atoms and is embedded in a LPB continuum. This theory represents the reaction field induced by the continuum in terms of charge and dipole densities localized within the molecular system. Because these densities cannot be calculated analytically for systems of arbitrary shape, we introduce an atom-based discretization and a set of carefully designed approximations. This allows us to represent the densities by charges and dipoles located at the atoms. Coupled systems of linear equations determine these multipoles and can be rapidly solved by iteration during a MD simulation. The multipoles yield the reaction field forces and energies. Finally, we scrutinize the quality of our approach by comparisons with an analytical solution restricted to perfectly spherical systems and with results of a finite difference method.

  4. Charge-ordering transitions without charge differentiation

    NASA Astrophysics Data System (ADS)

    Quan, Yundi; Pardo, Victor; Pickett, Warren

    2013-03-01

    The distorted perovskite nickelate system RNiO3 (R=rare earth except La) undergoes a metal-insulator transition (MIT) at a temperature that varies smoothly with the R ionic radius. This MIT is accompanied by structural transition which leads to two inequivalent Ni sites in the cell, and has been explained by charge ordering (CO): charge is transferred between the Ni1 and Ni2 sites in a long-range ordered fashion. Experimental data on core binding energies, ionic radii, and Mossbauer shifts are interpreted in terms of Ni cation charges of 3 +/- δ with, for example, δ ~ 0.3 for YNiO3. Making use of first principles DFT results and a new approach not invoking integration of the charge density, we find[2] that the Ni 3 d occupation is identical (to high accuracy) for the two Ni sites. We also present results for other compounds (La2VCuO6, YNiO3, CaFeO3, AgNiO2, V4O7), all of which have distinct ``charge states'' that have identical 3 d occupation. This quantitative procedure will be discussed and some implications will be outlined. DOE Grant No. DE-FG02-04ER46111 and Ramon y Cajal Program

  5. Perylenediimide-surfactant complexes: thermotropic liquid-crystalline materials via ionic self-assembly.

    PubMed

    Guan, Ying; Zakrevskyy, Yuriy; Stumpe, Joachim; Antonietti, Markus; Faul, Charl F J

    2003-04-07

    In this communication we present the facile preparation and characterisation of thermotropic liquid-crystalline materials from the ionic self-assembly of a charged perylenediimide derivative and oppositely charged surfactants.

  6. Ionic electrostatic excitations along biological membranes

    NASA Astrophysics Data System (ADS)

    Moradi, Afshin

    2011-02-01

    A theoretical analysis of ionic electrostatic excitations of a charged biological membrane is presented within the framework of the fluid theory for surface ions inside and outside the cell, in conjunction with the Poisson's equation. General expressions of dispersion relations are obtained for electrostatic oscillations of intrinsic cellular with different shapes and symmetries.

  7. Vaporisation of a dicationic ionic liquid.

    PubMed

    Lovelock, Kevin R J; Deyko, Alexey; Corfield, Jo-Anne; Gooden, Peter N; Licence, Peter; Jones, Robert G

    2009-02-02

    Highest heat of vaporization yet: The dicationic ionic liquid [C(3)(C(1)Im)(2)][Tf(2)N](2) evaporates as a neutral ion triplet. These neutral ion triplets can then be ionised to form singly and doubly charged ions. The mass spectrum exhibits the dication attached to one remaining anion, and the naked dication itself (see picture).

  8. Solvation and Reaction in Ionic Liquids

    SciTech Connect

    Maroncelli, Mark

    2010-10-15

    The long-range goal of our DOE-sponsored research is to obtain a fundamental understanding of solvation effects on photo-induced charge transfer and related processes. Much of the focus during the past funding period has been on studies of ionic liquids and on characterizing various reactions with which to probe the nature of this interesting new solvent medium.

  9. Acidic Ionic Liquids.

    PubMed

    Amarasekara, Ananda S

    2016-05-25

    Ionic liquid with acidic properties is an important branch in the wide ionic liquid field and the aim of this article is to cover all aspects of these acidic ionic liquids, especially focusing on the developments in the last four years. The structural diversity and synthesis of acidic ionic liquids are discussed in the introduction sections of this review. In addition, an unambiguous classification system for various types of acidic ionic liquids is presented in the introduction. The physical properties including acidity, thermo-physical properties, ionic conductivity, spectroscopy, and computational studies on acidic ionic liquids are covered in the next sections. The final section provides a comprehensive review on applications of acidic ionic liquids in a wide array of fields including catalysis, CO2 fixation, ionogel, electrolyte, fuel-cell, membrane, biomass processing, biodiesel synthesis, desulfurization of gasoline/diesel, metal processing, and metal electrodeposition.

  10. Double layers and double wells in arbitrary degenerate plasmas

    NASA Astrophysics Data System (ADS)

    Akbari-Moghanjoughi, M.

    2016-06-01

    Using the generalized hydrodynamic model, the possibility of variety of large amplitude nonlinear excitations is examined in electron-ion plasma with arbitrary electron degeneracy considering also the ion temperature effect. A new energy-density relation is proposed for plasmas with arbitrary electron degeneracy which reduces to the classical Boltzmann and quantum Thomas-Fermi counterparts in the extreme limits. The pseudopotential method is employed to find the criteria for existence of nonlinear structures such as solitons, periodic nonlinear structures, and double-layers for different cases of adiabatic and isothermal ion fluids for a whole range of normalized electron chemical potential, η0, ranging from dilute classical to completely degenerate electron fluids. It is observed that there is a Mach-speed gap in which no large amplitude localized or periodic nonlinear excitations can propagate in the plasma under consideration. It is further revealed that the plasma under investigation supports propagation of double-wells and double-layers the chemical potential and Mach number ranges of which are studied in terms of other plasma parameters. The Mach number criteria for nonlinear waves are shown to significantly differ for cases of classical with η0 < 0 and quantum with η0 > 0 regimes. It is also shown that the localized structure propagation criteria possess significant dissimilarities for plasmas with adiabatic and isothermal ions. Current research may be generalized to study the nonlinear structures in plasma containing positrons, multiple ions with different charge states, and charged dust grains.

  11. Double layers and double wells in arbitrary degenerate plasmas

    SciTech Connect

    Akbari-Moghanjoughi, M.

    2016-06-15

    Using the generalized hydrodynamic model, the possibility of variety of large amplitude nonlinear excitations is examined in electron-ion plasma with arbitrary electron degeneracy considering also the ion temperature effect. A new energy-density relation is proposed for plasmas with arbitrary electron degeneracy which reduces to the classical Boltzmann and quantum Thomas-Fermi counterparts in the extreme limits. The pseudopotential method is employed to find the criteria for existence of nonlinear structures such as solitons, periodic nonlinear structures, and double-layers for different cases of adiabatic and isothermal ion fluids for a whole range of normalized electron chemical potential, η{sub 0}, ranging from dilute classical to completely degenerate electron fluids. It is observed that there is a Mach-speed gap in which no large amplitude localized or periodic nonlinear excitations can propagate in the plasma under consideration. It is further revealed that the plasma under investigation supports propagation of double-wells and double-layers the chemical potential and Mach number ranges of which are studied in terms of other plasma parameters. The Mach number criteria for nonlinear waves are shown to significantly differ for cases of classical with η{sub 0} < 0 and quantum with η{sub 0} > 0 regimes. It is also shown that the localized structure propagation criteria possess significant dissimilarities for plasmas with adiabatic and isothermal ions. Current research may be generalized to study the nonlinear structures in plasma containing positrons, multiple ions with different charge states, and charged dust grains.

  12. On the stability of IrCl6(3-) and other triply charged anions: solvent stabilization versus ionic fragmentation and electron detachment for the IrCl6(3-).(H2O)n n = 0-10 microsolvated clusters.

    PubMed

    Boxford, William E; Dessent, Caroline E H

    2005-07-07

    The intrinsic gas-phase stability of the IrCl(6)(3-) trianion and its microsolvated clusters, IrCl(6)(3-).(H(2)O)(n) n = 1-10, have been investigated using density functional theory (DFT) calculations. Although IrCl(6)(3-) is known to exist as a stable complex ion in bulk solutions, our calculations indicate that the bare trianion is metastable with respect to decay via both electron detachment and ionic fragmentation. To estimate the lifetime of IrCl(6)(3-), we have computed the electron tunneling probability using an adaption of the Wentzel-Kramer-Brillouin theory and predict that the trianion will decay spontaneously via electron tunneling on a time scale of 2.4 x 10(-13) s. The global minimum structure for IrCl(6)(3-).H(2)O was found to contain a bifurcated hydrogen bond, whereas for IrCl(6)(3-).(H(2)O)(2), two low energy minima were identified; one involving two bifurcated water-ion hydrogen bonds and a second combining a bifurcated hydrogen bond with a water-water hydrogen bond. Clusters based on each of these structural motifs were obtained for all of the n = 3-10 systems, and the effect of solvation on the possible decay pathways was explored. The calculations reveal that solvation stabilizes IrCl(6)(3-) with respect to both electron detachment decay and ionic fragmentation, with the magnitude of the repulsive Coulomb barrier for ionic fragmentation increasing smoothly with sequential solvation. This study is the first to compare the propensity for electron detachment versus ionic fragmentation decay for a sequentially solvated triply charged anion.

  13. Ionic liquids behave as dilute electrolyte solutions

    PubMed Central

    Gebbie, Matthew A.; Valtiner, Markus; Banquy, Xavier; Fox, Eric T.; Henderson, Wesley A.; Israelachvili, Jacob N.

    2013-01-01

    We combine direct surface force measurements with thermodynamic arguments to demonstrate that pure ionic liquids are expected to behave as dilute weak electrolyte solutions, with typical effective dissociated ion concentrations of less than 0.1% at room temperature. We performed equilibrium force–distance measurements across the common ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][NTf2]) using a surface forces apparatus with in situ electrochemical control and quantitatively modeled these measurements using the van der Waals and electrostatic double-layer forces of the Derjaguin–Landau–Verwey–Overbeek theory with an additive repulsive steric (entropic) ion–surface binding force. Our results indicate that ionic liquids screen charged surfaces through the formation of both bound (Stern) and diffuse electric double layers, where the diffuse double layer is comprised of effectively dissociated ionic liquid ions. Additionally, we used the energetics of thermally dissociating ions in a dielectric medium to quantitatively predict the equilibrium for the effective dissociation reaction of [C4mim][NTf2] ions, in excellent agreement with the measured Debye length. Our results clearly demonstrate that, outside of the bound double layer, most of the ions in [C4mim][NTf2] are not effectively dissociated and thus do not contribute to electrostatic screening. We also provide a general, molecular-scale framework for designing ionic liquids with significantly increased dissociated charge densities via judiciously balancing ion pair interactions with bulk dielectric properties. Our results clear up several inconsistencies that have hampered scientific progress in this important area and guide the rational design of unique, high–free-ion density ionic liquids and ionic liquid blends. PMID:23716690

  14. Ionic liquids behave as dilute electrolyte solutions.

    PubMed

    Gebbie, Matthew A; Valtiner, Markus; Banquy, Xavier; Fox, Eric T; Henderson, Wesley A; Israelachvili, Jacob N

    2013-06-11

    We combine direct surface force measurements with thermodynamic arguments to demonstrate that pure ionic liquids are expected to behave as dilute weak electrolyte solutions, with typical effective dissociated ion concentrations of less than 0.1% at room temperature. We performed equilibrium force-distance measurements across the common ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][NTf2]) using a surface forces apparatus with in situ electrochemical control and quantitatively modeled these measurements using the van der Waals and electrostatic double-layer forces of the Derjaguin-Landau-Verwey-Overbeek theory with an additive repulsive steric (entropic) ion-surface binding force. Our results indicate that ionic liquids screen charged surfaces through the formation of both bound (Stern) and diffuse electric double layers, where the diffuse double layer is comprised of effectively dissociated ionic liquid ions. Additionally, we used the energetics of thermally dissociating ions in a dielectric medium to quantitatively predict the equilibrium for the effective dissociation reaction of [C4mim][NTf2] ions, in excellent agreement with the measured Debye length. Our results clearly demonstrate that, outside of the bound double layer, most of the ions in [C4mim][NTf2] are not effectively dissociated and thus do not contribute to electrostatic screening. We also provide a general, molecular-scale framework for designing ionic liquids with significantly increased dissociated charge densities via judiciously balancing ion pair interactions with bulk dielectric properties. Our results clear up several inconsistencies that have hampered scientific progress in this important area and guide the rational design of unique, high-free-ion density ionic liquids and ionic liquid blends.

  15. Charge Transport in Nonaqueous Liquid Electrolytes: A Paradigm Shift

    DTIC Science & Technology

    2015-05-18

    SECURITY CLASSIFICATION OF: We studied the temperature-dependence of mass and charge transport ( ionic conductivity, self-diffusion, fluidity, and...Shift Report Title We studied the temperature-dependence of mass and charge transport ( ionic conductivity, self-diffusion, fluidity, and dielectric...and their electrolytes over a wide range of salt concentrations (including ionic liquids!). We also developed a molecular-level picture of mass

  16. Dynamics of Ion Transport in Ionic Liquids.

    PubMed

    Lee, Alpha A; Kondrat, Svyatoslav; Vella, Dominic; Goriely, Alain

    2015-09-04

    A gap in understanding the link between continuum theories of ion transport in ionic liquids and the underlying microscopic dynamics has hindered the development of frameworks for transport phenomena in these concentrated electrolytes. Here, we construct a continuum theory for ion transport in ionic liquids by coarse graining a simple exclusion process of interacting particles on a lattice. The resulting dynamical equations can be written as a gradient flow with a mobility matrix that vanishes at high densities. This form of the mobility matrix gives rise to a charging behavior that is different to the one known for electrolytic solutions, but which agrees qualitatively with the phenomenology observed in experiments and simulations.

  17. Studying Ionic Channels as Physical Systems

    NASA Astrophysics Data System (ADS)

    Eisenberg, Bob

    2000-03-01

    Ionic channels are proteins with holes down their middle that act as gatekeepers for cells by controlling flow of ions across otherwise insulating membranes. Ionic channels are a large class of proteins of great biological/clinical importance, investigated in hundreds of laboratories every day. The techniques of molecular biology allow channel proteins to be studied easily one molecule at a time, with knowledge and control of the location of charges of the protein in several favorable cases. Once open, channels have simple unchanging structure. Ionic channels are a biological system of considerable importance that can be studied as a physical system of known structure. The natural function of channels is to pass current, driven by gradients of concentration and electrical potential across the membrane. Ions diffuse in electric fields created by the protein and neighboring charges. A simple mean field theory of electrostatics and electrodiffusion using Poisson and Nernst-Planck (diffusion) equations fits a wide range of data from many channel types, provided the protein is described as a distribution of fixed charge, not as a fixed profile of potential or as rate constants. These PNP equations can be generalized to deal with chemical specificity and selectivity. Some ionic channels preferentially conduct a particular type of ion (e.g., Ca) even in the presence of large excess of other ions. If ions and charges of the active site of the channel are described as spheres, using the mean spherical approximation of physical chemistry, the excluded volume of the ions and active site account quantitatively for the excess free energy and thus selectivity of the channel. The PNP equations are nearly the Poisson drift diffusion equations of semiconductor physics. They are a nonequilibrium and highly nonlinear system, easily solved by Gummel iteration, that describe (with one set of parameters) a variety of different physical devices. They also describe ionic channels.

  18. Image method for Coulomb energy for many-body system of charged dielectric spheres

    NASA Astrophysics Data System (ADS)

    Qin, Jian; de Pablo, Juan; Freed, Karl

    2015-03-01

    Ion polarization is important for understanding ion solvation and the stability of ion clusters in polymeric materials which typically exhibit a low and spatially inhomogeneous dielectric permittivity. The simplest approach for modeling ion polarization involves treating the ions as charged spheres with an internal dielectric permittivity differing from that of the medium. The surface polarization contribution to the electrostatic energy for a system of such dielectric spheres can be evaluated perturbatively. We derived closed-form expressions for this energy as a function of the positions of an arbitrary number of polarized surfaces. Our approach is a generalization of the image method for conducting spheres. Using this approach, we calculated the polarization corrections to the cohesion energy for ion clusters and for densely packed ionic crystals. The method can be readily adapted for investigating ion polarization effects in both Monte Carlo and molecular dynamics simulations.

  19. Functional ionic liquids for enhancement of Li-ion transfer: the effect of cation structure on the charge-discharge performance of the Li4Ti5O12 electrode.

    PubMed

    Shimizu, Masahiro; Usui, Hiroyuki; Sakaguchi, Hiroki

    2016-02-21

    As the development of high energy-density Li-ion batteries moves ahead, ensuring safety of the batteries has become increasingly important. Among the unique physicochemical properties of ionic liquids, thermal stability can be one of the answers to the challenge. The use of ionic liquids, however, causes critical issues concerning the kinetics of Li-ion transfer at the electrode-electrolyte interface. In the present study, ionic liquids consisting of 1-((2-methoxyethoxy)methyl)-1-methylpiperidinium (PP1MEM) or 1-hexyl-1-methylpiperidinium (PP16) and bis(trifluoromethanesulfonyl)amide (TFSA) were applied to an electrolyte for Li-ion batteries, and we investigated the effect of cation structure on interfacial Li-ion transfer using Li4Ti5O12 as a model electrode by means of Raman spectroscopy and electrochemical impedance spectroscopy. It was found that the ether functional group in the PP1MEM cation has the meaningful function; the cation structure reduces the electrostatic interaction between the Li ion and TFSA anions in an ionic liquid electrolyte. The solvation number of the TFSA anion per Li ion consequently became smaller than that in PP16-TFSA, and the lower solvation number in PP1MEM-TFSA allowed the facile Li-ion diffusion in the electrolyte bulk rather than the interfacial Li-ion transfer and significantly improved the rate performance. The results offer the prospect of utilization of PP1MEM-TFSA as an electrolyte solvent. The knowledge obtained from this study contributes to the development of next-generation Li-ion batteries having both high energy density and high safety.

  20. Chromatin Ionic Atmosphere Analyzed by a Mesoscale Electrostatic Approach

    PubMed Central

    Gan, Hin Hark; Schlick, Tamar

    2010-01-01

    Characterizing the ionic distribution around chromatin is important for understanding the electrostatic forces governing chromatin structure and function. Here we develop an electrostatic model to handle multivalent ions and compute the ionic distribution around a mesoscale chromatin model as a function of conformation, number of nucleosome cores, and ionic strength and species using Poisson-Boltzmann theory. This approach enables us to visualize and measure the complex patterns of counterion condensation around chromatin by examining ionic densities, free energies, shielding charges, and correlations of shielding charges around the nucleosome core and various oligonucleosome conformations. We show that: counterions, especially divalent cations, predominantly condense around the nucleosomal and linker DNA, unburied regions of histone tails, and exposed chromatin surfaces; ionic screening is sensitively influenced by local and global conformations, with a wide ranging net nucleosome core screening charge (56–100e); and screening charge correlations reveal conformational flexibility and interactions among chromatin subunits, especially between the histone tails and parental nucleosome cores. These results provide complementary and detailed views of ionic effects on chromatin structure for modest computational resources. The electrostatic model developed here is applicable to other coarse-grained macromolecular complexes. PMID:20959100

  1. Charge renormalization in planar and spherical charged lipidic aqueous interfaces.

    PubMed

    Bordi, Federico; Cametti, Cesare; Sennato, Simona; Paoli, Beatrice; Marianecci, Carlotta

    2006-03-16

    The charge renormalization in planar and spherical charged lipidic aqueous interfaces has been investigated by means of thermodynamic and electrokinetic measurements. We analyzed the behavior of mixed DOTAP/DOPE monolayers at the air-electrolyte solution interface and DOTAP/DOPE liposomes 100 nm in size dispersed in an aqueous phase of varying ionic strength. For the two systems, we have compared the "effective" surface charge derived from the measurements of surface potential and zeta-potential to the "bare" charge based on the stoichiometry of the lipid mixture investigated. The results confirm that a strong charge renormalization occurs, whose strength depends on the geometry of the mesoscopic system. The dependence of the "effective" charge on the "bare" charge is discussed in light of an analytical approximation based on the Poisson-Boltzmann equation recently proposed.

  2. Arbitrary segments of absolute negative mobility

    NASA Astrophysics Data System (ADS)

    Chen, Ruyin; Nie, Linru; Chen, Chongyang; Wang, Chaojie

    2017-01-01

    In previous research work, investigators have reported only one or two segments of absolute negative mobility (ANM) in a periodic potential. In fact, many segments of ANM also occur in the system considered here. We investigate transport of an inertial particle in a gating ratchet periodic potential subjected to a constant bias force. Our numerical results show that its mean velocity can decrease with the bias force increasing, i.e. ANM phenomenon. Furthermore, the ANM can take place arbitrary segments, even up to more than thirty. Intrinsic physical mechanism and conditions for arbitrary segments of ANM to occur are discussed in detail.

  3. Understanding the polarity of ionic liquids.

    PubMed

    Ab Rani, M A; Brant, A; Crowhurst, L; Dolan, A; Lui, M; Hassan, N H; Hallett, J P; Hunt, P A; Niedermeyer, H; Perez-Arlandis, J M; Schrems, M; Welton, T; Wilding, R

    2011-10-06

    The polarities of a wide range of ionic liquids have been determined using the Kamlet-Taft empirical polarity scales α, β and π*, with the dye set Reichardt's Dye, N,N-diethyl-4-nitroaniline and 4-nitroaniline. These have been compared to measurements of these parameters with different dye sets and to different polarity scales. The results emphasise the importance of recognising the role that the nature of the solute plays in determining these scales. It is particularly noted that polarity scales based upon charged solutes can give very different values for the polarity of ionic liquids compared to those based upon neutral probes. Finally, the effects of commonplace impurities in ionic liquids are reported.

  4. Interfacial biocatalysis on charged and immobilized substrates: the roles of enzyme and substrate surface charge.

    PubMed

    Feller, Bob E; Kellis, James T; Cascão-Pereira, Luis G; Robertson, Channing R; Frank, Curtis W

    2011-01-04

    An enzyme charge ladder was used to examine the role of electrostatic interactions involved in biocatalysis at the solid-liquid interface. The reactive substrate consisted of an immobilized bovine serum albumin (BSA) multilayer prepared using a layer-by-layer technique. The zeta potential of the BSA substrate and each enzyme variant was measured to determine the absolute charge in solution. Enzyme adsorption and the rate of substrate surface hydrolysis were monitored for the enzyme charge ladder series to provide information regarding the strength of the enzyme-substrate interaction and the rate of interfacial biocatalysis. First, each variant of the charge ladder was examined at pH 8 for various solution ionic strengths. We found that for positively charged variants the adsorption increased with the magnitude of the charge until the surface became saturated. For higher ionic strength solutions, a greater positive enzyme charge was required to induce adsorption. Interestingly, the maximum catalytic rate was not achieved at enzyme saturation but at an invariable intermediate level of adsorption for each ionic strength value. Furthermore, the maximum achievable reaction rate for the charge ladder was larger for higher ionic strength values. We propose that diffusion plays an important role in interfacial biocatalysis, and for strong enzyme-substrate interaction, the rate of diffusion is reduced, leading to a decrease in the overall reaction rate. We investigated the effect of substrate charge by varying the solution pH from 6.1 to 8.7 and by examining multiple ionic strength values for each pH. The same intermediate level of adsorption was found to maximize the overall reaction rate. However, the ionic strength response of the maximum achievable rate was clearly dependent on the pH of the experiment. We propose that this observation is not a direct effect of pH but is caused by the change in substrate surface charge induced by changing the pH. To prove this

  5. Falcon: automated optimization method for arbitrary assessment criteria

    DOEpatents

    Yang, Tser-Yuan; Moses, Edward I.; Hartmann-Siantar, Christine

    2001-01-01

    FALCON is a method for automatic multivariable optimization for arbitrary assessment criteria that can be applied to numerous fields where outcome simulation is combined with optimization and assessment criteria. A specific implementation of FALCON is for automatic radiation therapy treatment planning. In this application, FALCON implements dose calculations into the planning process and optimizes available beam delivery modifier parameters to determine the treatment plan that best meets clinical decision-making criteria. FALCON is described in the context of the optimization of external-beam radiation therapy and intensity modulated radiation therapy (IMRT), but the concepts could also be applied to internal (brachytherapy) radiotherapy. The radiation beams could consist of photons or any charged or uncharged particles. The concept of optimizing source distributions can be applied to complex radiography (e.g. flash x-ray or proton) to improve the imaging capabilities of facilities proposed for science-based stockpile stewardship.

  6. Capacity of arbitrary-order orbital angular momentum multiplexing system

    NASA Astrophysics Data System (ADS)

    Zhao, Yaqin; Zhong, Xin; Ren, Guanghui; He, Shengyang; Wu, Zhilu

    2017-03-01

    Arbitrary-order orbital angular momentum multiplexing (AOAMM) systems utilize OAM modes with both integer and fractional topological charges which are non-orthogonal. In this paper, the transmission matrix and the capacity per unit bandwidth, i.e., the spectral efficiency (SE) of an AOAMM system is derived based on the spatial cross correlations of the OAM submodes under different aperture conditions. The results show that in limited apertures, the SEs of AOAMM systems increase dramatically as the interval of two adjacent OAM submodes decreases by losing orthogonality. AOAMM systems are effective choices for satisfying the explosive growth of the communication requirements. This paper provides insight into the selection of spatially multiplexing approaches and the design of interference mitigation techniques for AOAMM systems with increased SEs.

  7. Nonlocal electrostatics in ionic liquids: The key to an understanding of the screening decay length and screened interactions.

    PubMed

    Kjellander, Roland

    2016-09-28

    Screened electrostatic interactions in ionic liquids are investigated by means of exact statistical mechanical analysis combined with physical arguments that enhance the transparency and conceptual accessibility of the analysis and results. The constituent ions and immersed particles in the liquid can have arbitrary shapes and any internal charge distributions. The decay of the screened electrostatic potential and the free energy of interaction in ionic liquids can be exponentially damped oscillatory (like in molten simple salts) as well as plain exponential and long-ranged (like in dilute electrolyte solutions). Both behaviors are in agreement with the exact statistical mechanical analysis and reasons for their appearances are investigated. Exact but surprisingly simple expressions for the decay parameter κ of the screened electrostatics are obtained, which replace the classical expression for the Debye-Hückel parameter κDH (the reciprocal Debye length). The expressions are applicable both for cases with plain exponential and oscillatory behaviors. The key importance of nonlocal electrostatics is thereby demonstrated explicitly. Dielectric properties of ionic liquids and other electrolytes are investigated, in particular the static dielectric function ϵ̃(k) and some effective relative permittivities (Er(eff) and Er(∗)), which take roles that the dielectric constant εr has for polar liquids consisting of electroneutral molecules. The dielectric constant in the latter case, which is the limit of ϵ̃(k) when the wave number k → 0, can be expressed solely in terms of dipolar features of the molecules. In contrast to this, the effective dielectric permittivities of ionic liquids have contributions also from quadrupolar, octupolar, and higher multipolar features of the constituent ions. The "dielectric constant" of electrolytes does not exist since ϵ̃(k)→∞ when k → 0, a well-known effect of perfect screening. The effective relative permittivities, Er

  8. Nonlocal electrostatics in ionic liquids: The key to an understanding of the screening decay length and screened interactions

    NASA Astrophysics Data System (ADS)

    Kjellander, Roland

    2016-09-01

    Screened electrostatic interactions in ionic liquids are investigated by means of exact statistical mechanical analysis combined with physical arguments that enhance the transparency and conceptual accessibility of the analysis and results. The constituent ions and immersed particles in the liquid can have arbitrary shapes and any internal charge distributions. The decay of the screened electrostatic potential and the free energy of interaction in ionic liquids can be exponentially damped oscillatory (like in molten simple salts) as well as plain exponential and long-ranged (like in dilute electrolyte solutions). Both behaviors are in agreement with the exact statistical mechanical analysis and reasons for their appearances are investigated. Exact but surprisingly simple expressions for the decay parameter κ of the screened electrostatics are obtained, which replace the classical expression for the Debye-Hückel parameter κDH (the reciprocal Debye length). The expressions are applicable both for cases with plain exponential and oscillatory behaviors. The key importance of nonlocal electrostatics is thereby demonstrated explicitly. Dielectric properties of ionic liquids and other electrolytes are investigated, in particular the static dielectric function ɛ ˜ ( k ) and some effective relative permittivities ( Er eff and Er ∗ ), which take roles that the dielectric constant ɛr has for polar liquids consisting of electroneutral molecules. The dielectric constant in the latter case, which is the limit of ɛ ˜ ( k ) when the wave number k → 0, can be expressed solely in terms of dipolar features of the molecules. In contrast to this, the effective dielectric permittivities of ionic liquids have contributions also from quadrupolar, octupolar, and higher multipolar features of the constituent ions. The "dielectric constant" of electrolytes does not exist since ɛ ˜ ( k ) → ∞ when k → 0, a well-known effect of perfect screening. The effective relative

  9. Arbitrary order transfer maps for RF cavities

    SciTech Connect

    van Zeijts, J.

    1995-12-31

    Current modeling of transfer maps for superconducting RF cavities at CEBAF includes only linear effects. Here we extend the transfer mapping modeling capability to include arbitrary order field information generated from the MAFIA field data. We include coupler kicks, normal and skew quadrupole focussing and higher order effects.

  10. Light storage with light of arbitrary polarization

    SciTech Connect

    Gao Hong; Rosenberry, Mark; Batelaan, Herman

    2003-05-01

    We have demonstrated the phase coherence of stored light in Rb vapor with a completely optical technique. Combining this technique with polarization measurements provides strong evidence that arbitrary polarizations can be stored. The fidelity obtained exceeds 95% for all polarizations. We view the capability to store polarizations as a first step towards building a quantum memory in such a system.

  11. Structure-morphology-property relationships in polymerized ionic liquids

    NASA Astrophysics Data System (ADS)

    Sangoro, Joshua; Heres, Maximilian; Minutolo, Joseph; Shamblin, Jacob; Lang, Maik; Berdzinski, Stefan; Strehmel, Veronika; Paddison, Stephen

    2015-03-01

    Charge transport and structural dynamics in systematic series of polymerized ammonium- and imidazolium- based ionic liquids are investigated by broadband dielectric spectroscopy, temperature-modulated differential scanning calorimetry, and x-ray as well neutron scattering techniques. Detailed analysis reveal strong decoupling of these processes in the polymerized ionic liquids, implying failure of the classical theories in describing charge transport and molecular dynamics in these systems. In addition, a strong correlation is observed between the ionic conductivity at the respective calorimetric glass transition temperatures and the morphologies revealed by the scattering experiments. In this talk, a physical explanation of the origin of the observed decoupling of ionic conductivity from structural dynamics will be proposed.

  12. A quantitative approach to ionic adsorption

    NASA Astrophysics Data System (ADS)

    Gollisch, H.; Fritsche, L.

    1980-02-01

    Binding properties of multi-atomic systems with ionic bonds are calculated by using a recently developed method based on the density functional formalism. The charge density is obtained from a superposition of the respective atomic densities where the charge transfer between these atoms is chosen such that the total energy attains a minimum. The kinetic energy of the electrons can to a very good approximation be calculated by means of a modified Thomas-Fermi-v. Weizsäcker expression. The molecules NaCl and NaW and a NaW 4 cluster have been treated as model systems for ionic interaction. Moreover, we have computed the binding properties of a Na atom adsorbed on a W(100) surface. This particular problem is the primary subject of the present study. The calculations yield binding energies, binding distances, vibrational frequencies, and induced dipole moments.

  13. Radicals in ionic liquids.

    PubMed

    Strehmel, Veronika

    2012-05-14

    Stable radicals and recombination of photogenerated lophyl radicals are investigated in ionic liquids. The 2,2,6,6-tetramethylpiperidine-1-yloxyl derivatives contain various substituents at the 4-position to the nitroxyl group, including hydrogen-bond-forming or ionic substituents that undergo additional interactions with the individual ions of the ionic liquids. Some of these spin probes contain similar ions to ionic liquids to avoid counter-ion exchange with the ionic liquid. Depending on the ionic liquid anion, the Stokes-Einstein theory or the Spernol-Gierer-Wirtz theory can be applied to describe the temperature dependence of the average rotational correlation time of the spin probe in the ionic liquids. Furthermore, the spin probes give information about the micropolarity of the ionic liquids. In this context the substituent at the 4-position to the nitroxyl group plays a significant role. Covalent bonding of a spin probe to the imidazolium ion results in bulky spin probes that are strongly immobilized in the ionic liquid. Furthermore, lophyl radical recombination in the dark, which is chosen to understand the dynamics of bimolecular reactions in ionic liquids, shows a slow process at longer timescale and a rise time at a shorter timescale. Although various reactions may contribute to the slower process during lophyl radical recombination, it follows a second-order kinetics that does not clearly show solvent viscosity dependence. However, the rise time, which may be attributed to radical pair formation, increases with increasing solvent viscosity. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Mesoscale studies of ionic closed membranes with polyhedral geometries

    NASA Astrophysics Data System (ADS)

    Olvera de la Cruz, Monica

    2016-06-01

    Large crystalline molecular shells buckle spontaneously into icosahedra while multicomponent shells buckle into various polyhedra. Continuum elastic theory explains the buckling of closed shells with one elastic component into icosahedra. A generalized elastic model, on the other hand, describes the spontaneous buckling of inhomogeneous shells into regular and irregular polyhedra. By co-assembling water-insoluble anionic (-1) amphiphiles with cationic (3+) amphiphiles, we realized ionic vesicles. Results revealed that surface crystalline domains and the unusual shell shapes observed arise from the competition of ionic correlations with charge-regulation. We explain here the mechanism by which these ionic membranes generate a mechanically heterogeneous vesicle.

  15. Mesoscale studies of ionic closed membranes with polyhedral geometries

    DOE PAGES

    Olvera de la Cruz, Monica

    2016-06-01

    Large crystalline molecular shells buckle spontaneously into icosahedra while multicomponent shells buckle into various polyhedra. Continuum elastic theory explains the buckling of closed shells with one elastic component into icosahedra. A generalized elastic model, on the other hand, describes the spontaneous buckling of inhomogeneous shells into regular and irregular polyhedra. By coassembling water-insoluble anionic (–1) amphiphiles with cationic (3+) amphiphiles, we realized ionic vesicles. Results revealed that surface crystalline domains and the unusual shell shapes observed arise from the competition of ionic correlations with charge-regulation. We explain here the mechanism by which these ionic membranes generate a mechanically heterogeneous vesicle.

  16. Exploring the location and orientation of 4-( N, N-dimethylamino) cinnamaldehyde in anionic, cationic and non-ionic micelles

    NASA Astrophysics Data System (ADS)

    Panja, Subhasis; Chowdhury, Papia; Chakravorti, Sankar

    2003-01-01

    This Letter reports probing of non-ionic, anionic and cationic micelles utilizing different dual emission properties of 4-( N, N-dimethylamino) cinnamaldehyde. Twisted intramolecular charge transfer (TICT) band is more enhanced and blue shifted in non-ionic micelle than those are in ionic micelles. In non-ionic micelle, the molecule enters in the core region whereas, in ionic micelles, it is anchored in the interfacial region with different orientations. Micellar-water interface electric field in ionic micelles was found to have profound effect on TICT decay time. Interestingly, inorganic salt-counterion binding helps the acceptor moiety to enter into the core region in anionic micelle.

  17. Interaction between heterogeneously charged surfaces: Surface patches and charge modulation

    NASA Astrophysics Data System (ADS)

    Ben-Yaakov, Dan; Andelman, David; Diamant, Haim

    2013-02-01

    When solid surfaces are immersed in aqueous solutions, some of their charges can dissociate and leave behind charged patches on the surface. Although the charges are distributed heterogeneously on the surface, most of the theoretical models treat them as homogeneous. For overall non-neutral surfaces, the assumption of surface charge homogeneity is rather reasonable since the leading terms of two such interacting surfaces depend on the nonzero average charge. However, for overall neutral surfaces the nature of the surface charge distribution is crucial in determining the intersurface interaction. In the present work we study the interaction between two charged surfaces across an aqueous solution for several charge distributions. The analysis is preformed within the framework of the linearized Poisson-Boltzmann theory. For periodic charge distributions the interaction is found to be repulsive at small separations, unless the two surface distributions are completely out-of-phase with respect to each other. For quenched random charge distributions we find that due to the presence of the ionic solution in between the surfaces, the intersurface repulsion dominates over the attraction in the linear regime of the Poisson-Boltzmann theory. The effect of quenched charge heterogeneity is found to be particularly substantial in the case of large charged domains.

  18. Polar interface phonons in ionic toroidal systems.

    PubMed

    Nguyen, N D; Evrard, R; Stroscio, Michael A

    2016-09-01

    We use the dielectric continuum model to obtain the polar (Fuchs-Kliewer like) interface vibration modes of toroids made of ionic materials either embedded in a different material or in vacuum, with applications to nanotoroids specially in mind. We report the frequencies of these modes and describe the electric potential they produce. We establish the quantum-mechanical Hamiltonian appropriate for their interaction with electric charges. This Hamiltonian can be used to describe the effect of this interaction on different types of charged particles either inside or outside the torus.

  19. Polar interface phonons in ionic toroidal systems

    NASA Astrophysics Data System (ADS)

    Nguyen, N. D.; Evrard, R.; Stroscio, Michael A.

    2016-09-01

    We use the dielectric continuum model to obtain the polar (Fuchs-Kliewer like) interface vibration modes of toroids made of ionic materials either embedded in a different material or in vacuum, with applications to nanotoroids specially in mind. We report the frequencies of these modes and describe the electric potential they produce. We establish the quantum-mechanical Hamiltonian appropriate for their interaction with electric charges. This Hamiltonian can be used to describe the effect of this interaction on different types of charged particles either inside or outside the torus.

  20. The Interactions between Imidazolium-Based Ionic Liquids and Stable Nitroxide Radical Species: A Theoretical Study.

    PubMed

    Zhang, Shaoze; Wang, Guimin; Lu, Yunxiang; Zhu, Weiliang; Peng, Changjun; Liu, Honglai

    2016-08-04

    In this work, the interactions between imidazolium-based ionic liquids and some stable radicals based on 2,2,6,6-tetramethylpiperidine-1-yloxyl (TEMPO) have been systematically investigated using density functional theory calculations at the level of M06-2x. Several different substitutions, such as hydrogen bonding formation substituent (OH) and ionic substituents (N(CH3)3(+) and OSO3(-)), are presented at the 4-position of the spin probe, which leads to additional hydrogen bonds or ionic interactions between these substitutions and ionic liquids. The interactions in the systems of the radicals containing ionic substitutions with ionic liquids are predicted much stronger than those in the systems of neutral radicals, resulting in a significant reduction of the mobility of ionic radicals in ionic liquids. To further understand the nature of these interactions, the natural bond order, atoms in molecules, noncovalent interaction index, electron density difference, energy decomposition analysis, and charge decomposition analysis schemes were employed. The additional ionic interactions between ionic radicals and counterions in ionic liquids are dominantly contributed from the electrostatic term, while the orbital interaction plays a major role in other interactions. The results reported herein are important to understand radical processes in ionic liquids and will be very useful in the design of task-specific ionic liquids to make the processes more efficient.

  1. Structure, ionic conductivity and mobile carrier density in fast ionic conducting chalcogenide glasses

    SciTech Connect

    Yao, Wenlong

    2006-01-01

    This thesis consists of six sections. The first section gives the basic research background on the ionic conduction mechanism in glass, polarization in the glass, and the method of determining the mobile carrier density in glass. The proposed work is also included in this section. The second section is a paper that characterizes the structure of MI + M2S + (0.1 Ga2S3 + 0.9 GeS2) (M = Li, Na, K and Cs) glasses using Raman and IR spectroscopy. Since the ionic radius plays an important role in determining the ionic conductivity in glasses, the glass forming range for the addition of different alkalis into the basic glass forming system 0.1 Ga2S3 + 0.9 GeS2 was studied. The study found that the change of the alkali radius for the same nominal composition causes significant structure change to the glasses. The third section is a paper that investigates the ionic conductivity of MI + M2S + (0.1Ga2S3 + 0.9 GeS2) (M = Li, Na, K and Cs) glasses system. Corresponding to the compositional changes in these fast ionic conducting glasses, the ionic conductivity shows changes due to the induced structural changes. The ionic radius effect on the ionic conductivity in these glasses was investigated. The fourth section is a paper that examines the mobile carrier density based upon the measurements of space charge polarization. For the first time, the charge carrier number density in fast ionic conducting chalcogenide glasses was determined. The experimental impedance data were fitted using equivalent circuits and the obtained parameters were used to determine the mobile carrier density. The influence of mobile carrier density and mobility on the ionic conductivity was separated. The fifth section is a paper that studies the structures of low-alkali-content Na2S + B2S3 (x ≤ 0.2) glasses by neutron and synchrotron x-ray diffraction

  2. Potential of Zero Charge and Its Temperature Derivative for Au(111) Electrode|Alkanethiol SAM|1.0 M Aqueous Electrolyte Solution Interfaces: Impact of Electrolyte Solution Ionic Strength and Its Effect on the Structure of the Modified Electrode|Electrolyte Solution Interface

    DOE PAGES

    Smalley, John F.

    2017-04-06

    In this study, we demonstrate how small and rapid temperature perturbations (produced by the indirect laser-induced temperature jump (ILIT) technique) of solid metal electrode|electrolyte solution interfaces may be used to determine the potential of zero (total) charge (Epzc) and its temperature derivativemore » $$\\left(\\frac{dEpzc}{dT}\\right)$$ of Au(111) electrode surfaces modified by alkanethiol self-assembled monolayers in contact with high ionic strength (i.e., 1.0 M) aqueous electrolyte solutions. The Epzc’s measured for two different types of SAMs (made from either HS(CH2)n-1CH3 (5 ≤ n ≤ 12, Epzc = -(0.99 ± 0.12) V vs SSCE) or HS(CH2)nOH (3 ≤ n ≤ 16, Epzc = (0.46 ± 0.22) V vs SSCE)) are considerably different than those measured previously at much lower electrolyte solution ionic strengths. For mixed monolayers made from both HS(CH2)n-1CH3 and HS(CH2)nFc (where Fc refers to ferrocene), the difference in Epzc decreases as a function of the surface concentration of the Fc moiety (i.e., [Fc]), and it completely disappears at a surprisingly small [Fc] (~4.0 × 10–11 mol cm–2). These observations for the Au(111)|hydrophobic (neat and mixed) SAM|aqueous electrolyte solution interfaces, along with the surface potentials (gSml(dip)) evaluated for the contacting electrolyte solution surfaces of these interfaces, are consistent with a structure for the water molecule components of these surfaces where there is a net orientation of the dipoles of these molecules. Accordingly, the negative (oxygen) ends of these molecules point toward the SAM surface. The positive values of gSml(dip) evaluated for hydrophilic SAM (e.g., made from HS(CH2)nOH)|aqueous electrolyte solution interfaces) also indicate that the structure of these interfaces is similar to that of the hydrophobic interfaces. However, gSml(dip) decreases with increasing ionic strength for the hydrophilic interfaces, while it increases with increasing ionic strength for the hydrophobic

  3. Fraunhofer diffraction by arbitrary-shaped obstacles.

    PubMed

    Malinka, Aleksey V; Zege, Eleonora P

    2009-08-01

    We consider Fraunhofer diffraction by an ensemble of large arbitrary-shaped screens that are randomly oriented in the plane of a wavefront and have edges of arbitrary shape. It is shown that far outside the main diffraction peak the differential scattering cross section behaves asymptotically as theta(-3), where theta is the diffraction angle. Moreover, the differential scattering cross section depends only on the length of the contours bordering the screens and does not depend on the shape of the obstacles. As both strictly forward and total diffraction cross sections are specified by obstacle area only, the differential cross section of size-distributed obstacles is expected to be nearly independent of obstacle shape over the entire region of the diffraction angles.

  4. General Potential Theory of Arbitrary Wing Sections

    NASA Technical Reports Server (NTRS)

    Theodorsen, T.; Garrick, I. E.

    1979-01-01

    The problem of determining the two dimensional potential flow around wing sections of any shape is examined. The problem is condensed into the compact form of an integral equation capable of yielding numerical solutions by a direct process. An attempt is made to analyze and coordinate the results of earlier studies relating to properties of wing sections. The existing approximate theory of thin wing sections and the Joukowski theory with its numerous generalizations are reduced to special cases of the general theory of arbitrary sections, permitting a clearer perspective of the entire field. The method which permits the determination of the velocity at any point of an arbitrary section and the associated lift and moments is described. The method is also discussed in terms for developing new shapes of preassigned aerodynamical properties.

  5. Unsteady aerodynamic modeling for arbitrary motions

    NASA Technical Reports Server (NTRS)

    Edwards, J. W.; Ashley, H.; Breakwell, J. V.

    1977-01-01

    A study is presented on the unsteady aerodynamic loads due to arbitrary motions of a thin wing and their adaptation for the calculation of response and true stability of aeroelastic modes. In an Appendix, the use of Laplace transform techniques and the generalized Theodorsen function for two-dimensional incompressible flow is reviewed. New applications of the same approach are shown also to yield airloads valid for quite general small motions. Numerical results are given for the two-dimensional supersonic case. Previously proposed approximate methods, starting from simple harmonic unsteady theory, are evaluated by comparison with exact results obtained by the present approach. The Laplace inversion integral is employed to separate the loads into 'rational' and 'nonrational' parts, of which only the former are involved in aeroelastic stability of the wing. Among other suggestions for further work, it is explained how existing aerodynamic computer programs may be adapted in a fairly straightforward fashion to deal with arbitrary transients.

  6. The arbitrariness and normativity of social conventions.

    PubMed

    Al-Amoudi, Ismael; Latsis, John

    2014-06-01

    This paper investigates a puzzling feature of social conventions: the fact that they are both arbitrary and normative. We examine how this tension is addressed in sociological accounts of conventional phenomena. Traditional approaches tend to generate either synchronic accounts that fail to consider the arbitrariness of conventions, or diachronic accounts that miss central aspects of their normativity. As a remedy, we propose a processual conception that considers conventions as both the outcome and material cause of much human activity. This conceptualization, which borrows from the économie des conventions as well as critical realism, provides a novel perspective on how conventions are nested and defined, and on how they are established, maintained and challenged.

  7. Potential flow about arbitrary biplane wing sections

    NASA Technical Reports Server (NTRS)

    Garrick, I E

    1937-01-01

    A rigorous treatment is given of the problem of determining the two-dimensional potential flow around arbitrary biplane cellules. The analysis involves the use of elliptic functions and is sufficiently general to include the effects of such elements as the section shapes, the chord ratio, gap, stagger, and decalage, which elements may be specified arbitrarily. The flow problem is resolved by making use of the methods of conformal representation. Thus the solution of the problem of transforming conformally two arbitrary contours into two circles is expressed by a pair of simultaneous integral equations, for which a method of numerical solution is outlined. As an example of the numerical process, the pressure distribution over certain arrangements of the NACA 4412 airfoil in biplane combinations is presented and compared with the monoplane pressure distribution.

  8. Quantum Fidelity for Arbitrary Gaussian States.

    PubMed

    Banchi, Leonardo; Braunstein, Samuel L; Pirandola, Stefano

    2015-12-31

    We derive a computable analytical formula for the quantum fidelity between two arbitrary multimode Gaussian states which is simply expressed in terms of their first- and second-order statistical moments. We also show how such a formula can be written in terms of symplectic invariants and used to derive closed forms for a variety of basic quantities and tools, such as the Bures metric, the quantum Fisher information, and various fidelity-based bounds. Our result can be used to extend the study of continuous-variable protocols, such as quantum teleportation and cloning, beyond the current one-mode or two-mode analyses, and paves the way to solve general problems in quantum metrology and quantum hypothesis testing with arbitrary multimode Gaussian resources.

  9. Quantum Fidelity for Arbitrary Gaussian States

    NASA Astrophysics Data System (ADS)

    Banchi, Leonardo; Braunstein, Samuel L.; Pirandola, Stefano

    2015-12-01

    We derive a computable analytical formula for the quantum fidelity between two arbitrary multimode Gaussian states which is simply expressed in terms of their first- and second-order statistical moments. We also show how such a formula can be written in terms of symplectic invariants and used to derive closed forms for a variety of basic quantities and tools, such as the Bures metric, the quantum Fisher information, and various fidelity-based bounds. Our result can be used to extend the study of continuous-variable protocols, such as quantum teleportation and cloning, beyond the current one-mode or two-mode analyses, and paves the way to solve general problems in quantum metrology and quantum hypothesis testing with arbitrary multimode Gaussian resources.

  10. Ionic liquid tunes microemulsion curvature.

    PubMed

    Liu, Liping; Bauduin, Pierre; Zemb, Thomas; Eastoe, Julian; Hao, Jingcheng

    2009-02-17

    Middle-phase microemulsions formed from cationic dioctadecyldimethylammonium chloride (DODMAC), anionic sodium dodecylsulfate (SDS), n-butanol, and n-heptane were studied. An ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), was employed as the electrolyte in the aqueous media instead of inorganic salts usually used in microemulsion formulation. Studies have been carried out as a function of the concentrations of [bmim][BF4], n-butanol, total surfactant (cDODMAC+SDS), and temperature on the phase behavior and the ultralow interfacial tensions in which the anionic component is present in excess in the catanionic film. Ultralow interfacial tension measurements confirmed the formation of middle-phase microemulsions and the necessary conditions for stabilizing middle-phase microemulsions. Electrical conductivity, small-angle X-ray scattering (SAXS), and small-angle neutron scattering (SANS) experiments were also performed, indicating that the typical heptane domain size has an average radius of 360 A and the ionic liquid induces softening of the charged catanionic film. Most interestingly, the IL concentration (cIL) is shown to act as an effective interfacial curvature-control parameter, representing a new approach to tuning the formulation of microemulsions and emulsions. The results expand the potential uses of ILs but also point to the design of new ILs that may achieve superefficient control over interfacial and self-assembly systems.

  11. Evaluation of permanently charged electrofibrous filters

    SciTech Connect

    Biermann, A.H.; Lum, B.Y.; Bergman, W.

    1982-10-18

    These studies showed that loading the permanently charged filters with captured aerosols will lead to a neutralization of the filter charge. The transfer from the captured aerosol to the fiber surface and the subsequent neutralization of fiber charge. The increased efficiency is due to the additional mechanical capture by the particle deposits. The minimum efficiency obtained during the loading of solid aerosols is determined by the aerosol charge, with highly charged aerosols producing a lower minimum. Permanently charged filters lose their fiber charge when exposed to organic solvents or ionic water solutions. The fiber charge neutralization was minimized by coating the charged fibers with a polymer. Several different coating techniques were examined. Unfortunately, preventing the neutralization of fiber charge is not sufficient to prevent a deterioration of filter efficiency.

  12. Probabilistically teleporting arbitrary two-qubit states

    NASA Astrophysics Data System (ADS)

    Choudhury, Binayak S.; Dhara, Arpan

    2016-12-01

    In this paper we make use of two non-maximally entangled three-qubit channels for probabilistically teleporting arbitrary two particle states from a sender to a receiver. We also calculate the success probability of the teleportation. In the protocol we use two measurements of which one is a POVM and the other is a projective measurement. The POVM provides the protocol with operational advantage.

  13. Distinguishing Proteins From Arbitrary Amino Acid Sequences

    PubMed Central

    Yau, Stephen S.-T.; Mao, Wei-Guang; Benson, Max; He, Rong Lucy

    2015-01-01

    What kinds of amino acid sequences could possibly be protein sequences? From all existing databases that we can find, known proteins are only a small fraction of all possible combinations of amino acids. Beginning with Sanger's first detailed determination of a protein sequence in 1952, previous studies have focused on describing the structure of existing protein sequences in order to construct the protein universe. No one, however, has developed a criteria for determining whether an arbitrary amino acid sequence can be a protein. Here we show that when the collection of arbitrary amino acid sequences is viewed in an appropriate geometric context, the protein sequences cluster together. This leads to a new computational test, described here, that has proved to be remarkably accurate at determining whether an arbitrary amino acid sequence can be a protein. Even more, if the results of this test indicate that the sequence can be a protein, and it is indeed a protein sequence, then its identity as a protein sequence is uniquely defined. We anticipate our computational test will be useful for those who are attempting to complete the job of discovering all proteins, or constructing the protein universe. PMID:25609314

  14. Ionic liquids in tribology.

    PubMed

    Minami, Ichiro

    2009-06-24

    Current research on room-temperature ionic liquids as lubricants is described. Ionic liquids possess excellent properties such as non-volatility, non-flammability, and thermo-oxidative stability. The potential use of ionic liquids as lubricants was first proposed in 2001 and approximately 70 articles pertaining to fundamental research on ionic liquids have been published through May 2009. A large majority of the cations examined in this area are derived from 1,3-dialkylimidazolium, with a higher alkyl group on the imidazolium cation being beneficial for good lubrication, while it reduces the thermo-oxidative stability. Hydrophobic anions provide both good lubricity and significant thermo-oxidative stability. The anions decompose through a tribochemical reaction to generate metal fluoride on the rubbed surface. Additive technology to improve lubricity is also explained. An introduction to tribology as an interdisciplinary field of lubrication is also provided.

  15. Non-classical diffusion in ionic liquids.

    PubMed

    Taylor, Alasdair W; Licence, Peter; Abbott, Andrew P

    2011-06-07

    In this study the diffusion coefficient of neutral and cationic ferrocenyl-derivatives have been characterised in a range of 1-alkyl-3-methylimidazolium ionic liquids of the general form [C(n)C(1)Im](+)[X](-). The electrochemistry of ferrocene, 1-ferrocenylmethylimidazole (FcC(1)Im), 1-ferrocenylmethylimidazolium bis(trifluoromethanesulfonyl)imide ([FcC(1)C(1)Im][Tf(2)N]) and N,N,N,N-trimethylferrocenyl-methylammonium bis(trifluoromethanesulfonyl)imide ([FcC(1)NMe(3)][Tf(2)N]), in 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C(2)C(1)Im][Tf(2)N]) was investigated. It was shown that the diffusion coefficients of each were not significantly affected by the presence and location of a positive charge on the ferrocenyl-derivative, suggesting that coulombic solvent-solute interactions did not hinder motion of these species in ionic liquids. The diffusion coefficients for [FcC(1)C(1)Im][Tf(2)N] in five [C(n)C(1)Im][X] ionic liquids were determined as a function of temperature and the data shown to disobey the Stokes-Einstein equation. This observation is consistent with the fact that ionic liquids are glass formers, systems in which non-Stokesian behaviour is well documented. Measured diffusion coefficient data was used to determine correlation length in the ionic liquid and was found to correlate with the average size of holes, or voids, within the ionic liquid. This interpretation suggests that a model by which a migrating species can jump between voids or holes within the liquid is highly appropriate and is consistent with the observed behaviour measured across a range of temperatures.

  16. Applications of ionic liquids.

    PubMed

    Patel, Divia Dinesh; Lee, Jong-Min

    2012-06-01

    Ionic liquids have recently gained popularity in the scientific community owing to their special properties and characteristics. One of the reasons why ionic liquids have been termed "green solvents" is due to their negligible vapour pressure. Their use in electrochemical, biological and metal extraction applications is discussed. Wide research has been carried out for their use in batteries, solar panels, fuel cells, drug deliveries and biomass pretreatments. This work aims to consolidate the various findings from previous works in these areas.

  17. High H- ionic conductivity in barium hydride

    NASA Astrophysics Data System (ADS)

    Verbraeken, Maarten C.; Cheung, Chaksum; Suard, Emmanuelle; Irvine, John T. S.

    2015-01-01

    With hydrogen being seen as a key renewable energy vector, the search for materials exhibiting fast hydrogen transport becomes ever more important. Not only do hydrogen storage materials require high mobility of hydrogen in the solid state, but the efficiency of electrochemical devices is also largely determined by fast ionic transport. Although the heavy alkaline-earth hydrides are of limited interest for their hydrogen storage potential, owing to low gravimetric densities, their ionic nature may prove useful in new electrochemical applications, especially as an ionically conducting electrolyte material. Here we show that barium hydride shows fast pure ionic transport of hydride ions (H-) in the high-temperature, high-symmetry phase. Although some conductivity studies have been reported on related materials previously, the nature of the charge carriers has not been determined. BaH2 gives rise to hydride ion conductivity of 0.2 S cm-1 at 630 °C. This is an order of magnitude larger than that of state-of-the-art proton-conducting perovskites or oxide ion conductors at this temperature. These results suggest that the alkaline-earth hydrides form an important new family of materials, with potential use in a number of applications, such as separation membranes, electrochemical reactors and so on.

  18. Micro-ionics: next generation power sources.

    PubMed

    Tuller, Harry L; Litzelman, Scott J; Jung, Woochul

    2009-05-07

    The desire for ever smarter systems-on-a-chip and plug-free portable electronics with longer operating times between recharge has stimulated growing interest in micro-ionic systems. The use of thin film and photolithographic processing techniques, commonly at temperatures considerably below those utilized in conventional ceramics processing methods, leads to ionic or mixed ionic-electronic materials with nanosized dimensions. The implications for nanosized grains on the conductivity of thin film solid oxide electrolytes are examined. Grain boundary engineering, as a means of controlling and ultimately enhancing transport along and across grain boundaries, becomes essential given that such boundaries often dominate the transport properties of such nano-dimensioned materials. Heterogeneous doping by selective in-diffusion along grain boundaries was introduced as a potentially powerful means of achieving this. This is coupled with the modeling of space charge distributions at such boundaries, taking into account possible dopant segregation to the boundaries. The use of lithographic methods for generating geometrically well defined structures is used to illustrate how one can achieve a much improved understanding of electrode processes in SOFC structures. Indeed, the more idealized structures achievable by application of microelectronic processing provide a marvelous opportunity to uncover the science underlying the technology of micro- and ultimately macro-ionics.

  19. Clausius entropy for arbitrary bifurcate null surfaces

    NASA Astrophysics Data System (ADS)

    Baccetti, Valentina; Visser, Matt

    2014-02-01

    Jacobson’s thermodynamic derivation of the Einstein equations was originally applied only to local Rindler horizons. But at least some parts of that construction can usefully be extended to give meaningful results for arbitrary bifurcate null surfaces. As presaged in Jacobson’s original article, this more general construction sharply brings into focus the questions: is entropy objectively ‘real’? Or is entropy in some sense subjective and observer-dependent? These innocent questions open a Pandora’s box of often inconclusive debate. A consensus opinion, though certainly not universally held, seems to be that Clausius entropy (thermodynamic entropy, defined via a Clausius relation {\\rm{d}}S = \\unicode{x111} Q/T) should be objectively real, but that the ontological status of statistical entropy (Shannon or von Neumann entropy) is much more ambiguous, and much more likely to be observer-dependent. This question is particularly pressing when it comes to understanding Bekenstein entropy (black hole entropy). To perhaps further add to the confusion, we shall argue that even the Clausius entropy can often be observer-dependent. In the current article we shall conclusively demonstrate that one can meaningfully assign a notion of Clausius entropy to arbitrary bifurcate null surfaces—effectively defining a ‘virtual Clausius entropy’ for arbitrary ‘virtual (local) causal horizons’. As an application, we see that we can implement a version of the generalized second law (GSL) for this virtual Clausius entropy. This version of GSL can be related to certain (nonstandard) integral variants of the null energy condition. Because the concepts involved are rather subtle, we take some effort in being careful and explicit in developing our framework. In future work we will apply this construction to generalize Jacobson’s derivation of the Einstein equations.

  20. Blur invariants constructed from arbitrary moments.

    PubMed

    Kautsky, Jaroslav; Flusser, Jan

    2011-12-01

    This paper deals with moment invariants with respect to image blurring. It is mainly a reaction to the works of Zhang and Chen , recently published in these Transactions. We present a general method on how to construct blur invariants from arbitrary moments and show that it is no longer necessary to separately derive the invariants for each polynomial basis. We show how to discard dependent terms in blur invariants definition and discuss a proper implementation of the invariants in orthogonal bases using recurrent relations. An example for Legendre moments is given. © 2011 IEEE

  1. Hybrid benchmarking of arbitrary quantum gates

    NASA Astrophysics Data System (ADS)

    Chasseur, Tobias; Reich, Daniel M.; Koch, Christiane P.; Wilhelm, Frank K.

    2017-06-01

    We present a protocol for interleaved randomized benchmarking of arbitrary quantum gates using Monte Carlo sampling of quantum states. It is generally applicable, including non-Clifford gates while preserving key advantages of randomized benchmarking such as error amplification as well as independence from state preparation and measurement errors. This property is crucial for implementations in many contemporary systems. Although the protocol scales exponentially in the number of qubits, it is superior to direct Monte Carlo sampling of the average gate fidelity in both the total number of experiments by orders of magnitude and savings in classical preprocessing, that are exponential.

  2. Metamaterial electromagnetic concentrators with arbitrary geometries.

    PubMed

    Yang, Jingjing; Huang, Ming; Yang, Chengfu; Xiao, Zhe; Peng, Jinhui

    2009-10-26

    The electromagnetic concentrators play an important role in the harnessing of light in solar cells or similar devices, where high field intensities are required. The material parameters for two-dimensional (2D) metamaterial-assisted electromagnetic concentrators with arbitrary geometries are derived based on transformation-optical approach. Enhancements in field intensities of the 2D concentrator have been shown by full-wave simulation. All theoretical and numerical results validate the material parameters for the 2D concentrator with irregular cross section we developed.

  3. Approach of arbitrary clipping in volume rendering

    NASA Astrophysics Data System (ADS)

    Lin, Lan; Li, Lijun; Zhou, Jianzhong; Jiang, Qing

    2005-11-01

    This paper proposes a new clipping method that is capable of using arbitrary geometries in volume rendering. With the assistance of pre-computed outer contour mesh, the method adopts Constructive Solid Geometry (CSG) for clipping, and uses 3D texture for the rendering of clipping surface. The outer contour mesh defines the boundary of the volume data, and improves the efficiency of clipping and rendering. Furthermore, CSG-based clipping method protects the topology of geometries. This method computes the texture coordinate in vertex shader to implement the 3D texture mapping, and achieves high frame rates based on the powerful programming graphics hardware.

  4. Confined systems within arbitrary enclosed surfaces

    NASA Astrophysics Data System (ADS)

    Burrows, B. L.; Cohen, M.

    2016-06-01

    A new model of electronic confinement in atoms and molecules is presented. This is based on the electronic flux J which is assumed to vanish on some notional bounding surface of arbitrary shape. J is necessarily calculated using an approximate wave-function, whose parameters are chosen to satisfy the required surface conditions. This model embraces the results of all previous calculations for which the wave-functions or their derivatives vanish on conveniently shaped surfaces, but now extends the theory to more general surfaces. Examples include one-centre hydrogen-like atoms, the valence state of Li and the two centre molecular systems {{{H}}}2+ and {{HeH}}++.

  5. Gaussian Quadrature Formulae for Arbitrary Positive Measures

    PubMed Central

    Fernandes, Andrew D.; Atchley, William R.

    2007-01-01

    We present computational methods and subroutines to compute Gaussian quadrature integration formulas for arbitrary positive measures. For expensive integrands that can be factored into well-known forms, Gaussian quadrature schemes allow for efficient evaluation of high-accuracy and -precision numerical integrals, especially compared to general ad hoc schemes. In addition, for certain well-known density measures (the normal, gamma, log-normal, Student’s t, inverse-gamma, beta, and Fisher’s F) we present exact formulae for computing the respective quadrature scheme. PMID:19455218

  6. Adding control to arbitrary unknown quantum operations

    PubMed Central

    Zhou, Xiao-Qi; Ralph, Timothy C.; Kalasuwan, Pruet; Zhang, Mian; Peruzzo, Alberto; Lanyon, Benjamin P.; O'Brien, Jeremy L.

    2011-01-01

    Although quantum computers promise significant advantages, the complexity of quantum algorithms remains a major technological obstacle. We have developed and demonstrated an architecture-independent technique that simplifies adding control qubits to arbitrary quantum operations—a requirement in many quantum algorithms, simulations and metrology. The technique, which is independent of how the operation is done, does not require knowledge of what the operation is, and largely separates the problems of how to implement a quantum operation in the laboratory and how to add a control. Here, we demonstrate an entanglement-based version in a photonic system, realizing a range of different two-qubit gates with high fidelity. PMID:21811242

  7. Fixed Junction Photovoltaic Devices Based On Polymerizable Ionic Liquids

    NASA Astrophysics Data System (ADS)

    Limanek, Austin; Leger, Janelle, , Dr.

    Recently, polymer-based photovoltaic devices (PPVs) have received significant attention as a possible affordable, large area and flexible solar energy technology. In particular, research on chemically fixed p-i-n junctions in polymer photovoltaic devices has shown promising results. These devices are composed of ionic monomers in a polymer matrix sandwiched between two electrodes. When a potential is applied, the ionic monomers migrate towards their corresponding electrodes, enabling electrochemical doping of the polymer. This leads to the formation of bonds between the polymer and ionic monomers, resulting in the formation of a chemically fixed p-i-n junction. However, early devices suffered from long charging times and low overall response. This has been attributed to the low phase compatibility between the ionic monomers and the polymer. It has been shown for light-emitting electrochemical cells, replacing the ionic monomers with polymerizable ionic liquids (PILs) mitigates these challenges. We will present the use of PILs as the dopant in fixed junction PPV devices. Preliminary devices demonstrate significantly improved performance, decreased charging times, and high open circuit voltages. This research supported by the National Science Foundation DMR-1057209.

  8. Long-range electrostatic screening in ionic liquids.

    PubMed

    Gebbie, Matthew A; Dobbs, Howard A; Valtiner, Markus; Israelachvili, Jacob N

    2015-06-16

    Electrolyte solutions with high concentrations of ions are prevalent in biological systems and energy storage technologies. Nevertheless, the high interaction free energy and long-range nature of electrostatic interactions makes the development of a general conceptual picture of concentrated electrolytes a significant challenge. In this work, we study ionic liquids, single-component liquids composed solely of ions, in an attempt to provide a novel perspective on electrostatic screening in very high concentration (nonideal) electrolytes. We use temperature-dependent surface force measurements to demonstrate that the long-range, exponentially decaying diffuse double-layer forces observed across ionic liquids exhibit a pronounced temperature dependence: Increasing the temperature decreases the measured exponential (Debye) decay length, implying an increase in the thermally driven effective free-ion concentration in the bulk ionic liquids. We use our quantitative results to propose a general model of long-range electrostatic screening in ionic liquids, where thermally activated charge fluctuations, either free ions or correlated domains (quasiparticles), take on the role of ions in traditional dilute electrolyte solutions. This picture represents a crucial step toward resolving several inconsistencies surrounding electrostatic screening and charge transport in ionic liquids that have impeded progress within the interdisciplinary ionic liquids community. More broadly, our work provides a previously unidentified way of envisioning highly concentrated electrolytes, with implications for diverse areas of inquiry, ranging from designing electrochemical devices to rationalizing electrostatic interactions in biological systems.

  9. Long-range electrostatic screening in ionic liquids

    PubMed Central

    Gebbie, Matthew A.; Dobbs, Howard A.; Valtiner, Markus; Israelachvili, Jacob N.

    2015-01-01

    Electrolyte solutions with high concentrations of ions are prevalent in biological systems and energy storage technologies. Nevertheless, the high interaction free energy and long-range nature of electrostatic interactions makes the development of a general conceptual picture of concentrated electrolytes a significant challenge. In this work, we study ionic liquids, single-component liquids composed solely of ions, in an attempt to provide a novel perspective on electrostatic screening in very high concentration (nonideal) electrolytes. We use temperature-dependent surface force measurements to demonstrate that the long-range, exponentially decaying diffuse double-layer forces observed across ionic liquids exhibit a pronounced temperature dependence: Increasing the temperature decreases the measured exponential (Debye) decay length, implying an increase in the thermally driven effective free-ion concentration in the bulk ionic liquids. We use our quantitative results to propose a general model of long-range electrostatic screening in ionic liquids, where thermally activated charge fluctuations, either free ions or correlated domains (quasiparticles), take on the role of ions in traditional dilute electrolyte solutions. This picture represents a crucial step toward resolving several inconsistencies surrounding electrostatic screening and charge transport in ionic liquids that have impeded progress within the interdisciplinary ionic liquids community. More broadly, our work provides a previously unidentified way of envisioning highly concentrated electrolytes, with implications for diverse areas of inquiry, ranging from designing electrochemical devices to rationalizing electrostatic interactions in biological systems. PMID:26040001

  10. Are Ionic Liquids Chemically Stable?

    PubMed

    Wang, Binshen; Qin, Li; Mu, Tiancheng; Xue, Zhimin; Gao, Guohua

    2017-02-27

    Ionic liquids have attracted a great deal of interest in recent years, illustrated by their applications in a variety of areas involved with chemistry, physics, biology, and engineering. Usually, the stabilities of ionic liquids are highlighted as one of their outstanding advantages. However, are ionic liquids really stable in all cases? This review covers the chemical stabilities of ionic liquids. It focuses on the reactivity of the most popular imidazolium ionic liquids at structural positions, including C2 position, N1 and N3 positions, and C4 and C5 positions, and decomposition on the imidazolium ring. Additionally, we discuss decomposition of quaternary ammonium and phosphonium ionic liquids and hydrolysis and nucleophilic reactions of anions of ionic liquids. The review aims to arouse caution on potential decomposition of ionic liquids and provides a guide for better utilization of ionic liquids.

  11. Interactions in ion pairs of protic ionic liquids: comparison with aprotic ionic liquids.

    PubMed

    Tsuzuki, Seiji; Shinoda, Wataru; Miran, Md Shah; Kinoshita, Hiroshi; Yasuda, Tomohiro; Watanabe, Masayoshi

    2013-11-07

    The stabilization energies for the formation (E(form)) of 11 ion pairs of protic and aprotic ionic liquids were studied by MP2/6-311G** level ab initio calculations to elucidate the difference between the interactions of ions in protic ionic liquids and those in aprotic ionic liquids. The interactions in the ion pairs of protic ionic liquids (diethylmethylammonium [dema] and dimethylpropylammonium [dmpa] based ionic liquids) are stronger than those of aprotic ionic liquids (ethyltrimethylammonium [etma] based ionic liquids). The E(form) for the [dema][CF3SO3] and [dmpa][CF3SO3] complexes (-95.6 and -96.4 kcal/mol, respectively) are significantly larger (more negative) than that for the [etma][CF3SO3] complex (-81.0 kcal/mol). The same trend was observed for the calculations of ion pairs of the three cations with the Cl(-), BF4(-), TFSA(-) anions. The anion has contact with the N-H bond of the dema(+) or dmpa(+) cations in the most stable geometries of the dema(+) and dmpa(+) complexes. The optimized geometries, in which the anions locate on the counter side of the cations, are 11.0-18.0 kcal/mol less stable, which shows that the interactions in the ions pairs of protic ionic liquids have strong directionality. The E(form) for the less stable geometries for the dema(+) and dmpa(+) complexes are close to those for the most stable etma(+) complexes. The electrostatic interaction, which is the major source of the attraction in the ion pairs, is responsible for the directionality of the interactions and determining the magnitude of the interaction energy. Molecular dynamic simulations of the [dema][TFSA] and [dmpa][TFSA] ionic liquids show that the N-H bonds of the cations have contact with the negatively charged (oxygen and nitrogen) atoms of TFSA(-) anion, while the strong directionality of the interactions was not suggested from the simulation of the [etma][CF3SO3] ionic liquid.

  12. Interactions in ion pairs of protic ionic liquids: Comparison with aprotic ionic liquids

    SciTech Connect

    Tsuzuki, Seiji; Shinoda, Wataru; Miran, Md. Shah; Kinoshita, Hiroshi; Yasuda, Tomohiro; Watanabe, Masayoshi

    2013-11-07

    The stabilization energies for the formation (E{sub form}) of 11 ion pairs of protic and aprotic ionic liquids were studied by MP2/6-311G{sup **} level ab initio calculations to elucidate the difference between the interactions of ions in protic ionic liquids and those in aprotic ionic liquids. The interactions in the ion pairs of protic ionic liquids (diethylmethylammonium [dema] and dimethylpropylammonium [dmpa] based ionic liquids) are stronger than those of aprotic ionic liquids (ethyltrimethylammonium [etma] based ionic liquids). The E{sub form} for the [dema][CF{sub 3}SO{sub 3}] and [dmpa][CF{sub 3}SO{sub 3}] complexes (−95.6 and −96.4 kcal/mol, respectively) are significantly larger (more negative) than that for the [etma][CF{sub 3}SO{sub 3}] complex (−81.0 kcal/mol). The same trend was observed for the calculations of ion pairs of the three cations with the Cl{sup −}, BF{sub 4}{sup −}, TFSA{sup −} anions. The anion has contact with the N–H bond of the dema{sup +} or dmpa{sup +} cations in the most stable geometries of the dema{sup +} and dmpa{sup +} complexes. The optimized geometries, in which the anions locate on the counter side of the cations, are 11.0–18.0 kcal/mol less stable, which shows that the interactions in the ions pairs of protic ionic liquids have strong directionality. The E{sub form} for the less stable geometries for the dema{sup +} and dmpa{sup +} complexes are close to those for the most stable etma{sup +} complexes. The electrostatic interaction, which is the major source of the attraction in the ion pairs, is responsible for the directionality of the interactions and determining the magnitude of the interaction energy. Molecular dynamic simulations of the [dema][TFSA] and [dmpa][TFSA] ionic liquids show that the N–H bonds of the cations have contact with the negatively charged (oxygen and nitrogen) atoms of TFSA{sup −} anion, while the strong directionality of the interactions was not suggested from the simulation

  13. Radiation from an Accelerated Point Charge and Non-Inertial Observers

    ERIC Educational Resources Information Center

    Leonov, A. B.

    2012-01-01

    It is known that observers comoving with a uniformly accelerated point charge detect the electromagnetic field of a charge as a static electric field. We show that one can find a similar family of observers, which detect the field of a charge as a static electric field, in the general case of arbitrary point-charge motion. We find the velocities…

  14. Radiation from an Accelerated Point Charge and Non-Inertial Observers

    ERIC Educational Resources Information Center

    Leonov, A. B.

    2012-01-01

    It is known that observers comoving with a uniformly accelerated point charge detect the electromagnetic field of a charge as a static electric field. We show that one can find a similar family of observers, which detect the field of a charge as a static electric field, in the general case of arbitrary point-charge motion. We find the velocities…

  15. Ionic Adsorption and Desorption of CNT Nanoropes

    PubMed Central

    Shang, Jun-Jun; Yang, Qing-Sheng; Yan, Xiao-Hui; He, Xiao-Qiao; Liew, Kim-Meow

    2016-01-01

    A nanorope is comprised of several carbon nanotubes (CNTs) with different chiralities. A molecular dynamic model is built to investigate the ionic adsorption and desorption of the CNT nanoropes. The charge distribution on the nanorope is obtained by using a modified gradient method based on classical electrostatic theory. The electrostatic interactions among charged carbon atoms are calculated by using the Coulomb law. It was found here that the charged nanorope can adsorb heavy metal ions, and the adsorption and desorption can be realized by controlling the strength of applied electric field. The distance between the ions and the nanorope as well as the amount of ions have an effect on the adsorption capacity of the nanorope. The desorption process takes less time than that of adsorption. The study indicates that the CNT nanorope can be used as a core element of devices for sewage treatment. PMID:28335306

  16. Ionic Adsorption and Desorption of CNT Nanoropes.

    PubMed

    Shang, Jun-Jun; Yang, Qing-Sheng; Yan, Xiao-Hui; He, Xiao-Qiao; Liew, Kim-Meow

    2016-09-28

    A nanorope is comprised of several carbon nanotubes (CNTs) with different chiralities. A molecular dynamic model is built to investigate the ionic adsorption and desorption of the CNT nanoropes. The charge distribution on the nanorope is obtained by using a modified gradient method based on classical electrostatic theory. The electrostatic interactions among charged carbon atoms are calculated by using the Coulomb law. It was found here that the charged nanorope can adsorb heavy metal ions, and the adsorption and desorption can be realized by controlling the strength of applied electric field. The distance between the ions and the nanorope as well as the amount of ions have an effect on the adsorption capacity of the nanorope. The desorption process takes less time than that of adsorption. The study indicates that the CNT nanorope can be used as a core element of devices for sewage treatment.

  17. Geometrical critical phenomena on a random surface of arbitrary genus

    NASA Astrophysics Data System (ADS)

    Duplantier, Bertrand; Kostov, Ivan K.

    1990-08-01

    The statistical mechanics of self-avoiding walks (SAW) or of the O( n)-loop model on a two-dimensional random surface are shown to be exactly solvable. The partition functions of SAW and surface configurations (possibly in the presence of vacuum loops) are calculated by planar diagram enumeration techniques. Two critical regimes are found: a dense phase where the infinite walks and loops fill the infinite surface, the non-filled part staying finite, and a dilute phase where the infinite surface singularity on the one hand, and walk and loop singularities on the other, merge together. The configuration critical exponents of self-avoiding networks of any fixed topology G, on a surface with arbitrary genus H, are calculated as universal functions of G and H. For self-avoiding walks, the exponents are built from an infinite set of basic conformal dimensions associated with central charges c = -2 (dense phase) and c = 0 (dilute phase). The conformal spectrum ΔL, L ⩾ 1 associated with L-leg star polymers is calculated exactly, for c = -2 and c = 0. This is generalized to the set of L-line "watermelon" exponents ΔL of the O( n) model on a random surface. The results are in perfect agreement with the conformal theory of Knizhnik, Polyakov and Zamolodchikov describing matter fields coupled to 2D quantum gravity. The infinite series of dimensions ΔL dressed by gravity calculated here, together with the corresponding SAW conformal dimensions ΔL(0) in the plane, known independently from Coulomb-gas techniques, match the KPZ relation Δ - Δ (0) = {Δ(1 - Δ)}/{κ}, where c = {1 - 6(1 - κ) 2}/{k}. This provides a cross check of Coulomb-gas techniques, the KPZ conformal theory of matter fields with 2D quantum gravity and the universality of random lattices. The divergences of the partition functions of self-avoiding networks on the random surface, possibly in the presence of vacuum loops, are shown to satisfy a factorization theorem over the vertices of the network. This

  18. Neutron scattering from charged polymer lattices

    SciTech Connect

    Hayter, J.B.

    1987-12-02

    Aqueous suspensions of charged polymer latex particles exhibit several forms of ordered structure, the particular form depending on the size, number density and charge of the latex particles, and on the ionic strength of the aqueous medium. At low ionic strength, the inter-particle potential may become sufficiently long-ranged to generate crystalline order, which usually shows bcc symmetry at low density and becomes fcc above about 3% volume fraction of latex in the system. As the ionic strength increases, the crystalline structure melts, and ordered liquid structures develop. This paper reviews some of the recent small-angle neutron scattering experiments on polymer latex suspensions, in the light of new theoretical methods which permit in situ analysis of the particle size and charge. The discussion also encompasses new experimental methods for studying latex structures under dynamic shear conditions.

  19. Arbitrary Order Hierarchical Bases for Computational Electromagnetics

    SciTech Connect

    Rieben, R N; White, D; Rodrigue, G

    2002-12-20

    We present a clear and general method for constructing hierarchical vector bases of arbitrary polynomial degree for use in the finite element solution of Maxwell's equations. Hierarchical bases enable p-refinement methods, where elements in a mesh can have different degrees of approximation, to be easily implemented. This can prove to be quite useful as sections of a computational domain can be selectively refined in order to achieve a greater error tolerance without the cost of refining the entire domain. While there are hierarchical formulations of vector finite elements in publication (e.g. [1]), they are defined for tetrahedral elements only, and are not generalized for arbitrary polynomial degree. Recently, Hiptmair, motivated by the theory of exterior algebra and differential forms presented a unified mathematical framework for the construction of conforming finite element spaces [2]. In [2], both 1-form (also called H(curl)) and 2-form (also called H(div)) conforming finite element spaces and the definition of their degrees of freedom are presented. These degrees of freedom are weighted integrals where the weighting function determines the character of the bases, i.e. interpolatory, hierarchical, etc.

  20. Search times with arbitrary detection constraints

    NASA Astrophysics Data System (ADS)

    Campos, Daniel; Bartumeus, Frederic; Méndez, Vicenç

    2013-08-01

    Random encounters in space are central to describing diffusion-limited reactions, animal foraging, search processes, and many other situations in nature. These encounters, however, are often constrained by the capacity of the searcher to detect and/or recognize its target. This can be due to limited binding and perception abilities of the searcher or hiding and avoiding mechanisms used by the target. Hence detection failure upon passage over the target location turns the process into an n-passage problem, with n being random. Here we provide a general description of this detection problem for arbitrary dimensions and arbitrary detection constraints. The mean detection time (MDT) for a random searcher embedded in a sea of homogeneously distributed targets is obtained as a function of the target density ρ, the size domain L, and the effective detection distance a. While the scaling with ρ and L is found to be universal and equivalent to that found for the corresponding first-passage problem, the scaling of the MDT on a depends on the specific detection mechanism considered.

  1. Correlation Imaging with Arbitrary Sampling Trajectories

    PubMed Central

    Li, Yu

    2014-01-01

    The presented work aims to develop a generalized linear approach to image reconstruction with arbitrary sampling trajectories for high-speed MRI. This approach is based on a previously developed image reconstruction framework, "correlation imaging" (1). In the presented work, correlation imaging with arbitrary sampling trajectories is implemented in a multi-dimensional hybrid space that is formed from the physical sampling space and a virtually defined space. By introducing an undersampling trajectory with both uniformity and randomness in the hybrid space, correlation imaging may take advantage of multiple image reconstruction mechanisms including coil sensitivity encoding, data sparsity and information sharing. This hybrid-space implementation is demonstrated in multi-slice 2D imaging, multi-scan imaging, and radial dynamic imaging. Since more information is used in image reconstruction, it is found that hybrid-space correlation imaging outperforms several conventional techniques. The presented approach will benefit clinical MRI by enabling correlation imaging to be used to accelerate multi-scan clinical protocols that need different sampling trajectories in different scans. PMID:24629517

  2. Ionic liquid-assisted electrospray ionization of polysaccharides.

    PubMed

    Chang, Yu-Ling; Lee, Yuan-Chun; Yang, Wen-Bin; Chen, Chung-Hsuan

    2011-04-01

    In this work, we give the report of significant detection sensitivity improvement of electrospray ionization (ESI) mass spectra of polysaccharides by adding various ionic liquid compounds into samples. Mass spectra obtained were greatly simplified and appeared to be similar to spectra from matrix-assisted laser desorption/ionization due to the narrow charge number distribution. Mass spectra of polysaccharides with the attachment of either anion or cation of ionic liquid compounds were observed. No protonated or deprotonated polysaccharide ions were detected when ionic liquid compounds were added into samples. Little alkali-attached polysaccharide ions were observed. Ionic liquid-assisted ESI (ILA-ESI) mass spectrometry has significantly improved the detection sensitivity of large neutral polysaccharide compounds. Copyright © 2011 John Wiley & Sons, Ltd.

  3. Facilitated Ion Transport in Smectic Ordered Ionic Liquid Crystals

    SciTech Connect

    Lee, Jin Hong; Han, Kee Sung; Lee, Je Seung; Lee, Albert S.; Park, Seo Kyung; Hong, Sung Yun; Lee, Jong-Chan; Mueller, Karl T.; Hong, Soon Man; Koo, Chong Min

    2016-09-08

    We investigated a novel ionic mixture of an imidazolium-based room temperature IL containing ethylene oxide functionalized phosphite anion and a lithium salt that self-assembles into a smectic-ordered IL crystal. The two key features in this work are the unique origin of the smectic order of the ionic mixtures and the facilitated ion transport behavior in the smectic ordered IL crystal. In fact, the IL crystals are self-assembled through Coulombic interactions between ion species, not through the hydrophilic-phobic interactions between charged ion heads and hydrophobic long alkyl pendants or the steric interaction between mesogenic moieties. Furthermore, the smectic order in the IL crystal ionogel facilitates exceptional and remarkable ionic transport. Large ionic conductivity, viscoelastic robustness, and additional electrochemical stability of the IL crystal ionogels provide promising opportunities for future electrochemical applications.

  4. Robust and versatile ionic liquid microarrays achieved by microcontact printing

    NASA Astrophysics Data System (ADS)

    Gunawan, Christian A.; Ge, Mengchen; Zhao, Chuan

    2014-04-01

    Lab-on-a-chip and miniaturized systems have gained significant popularity motivated by marked differences in material performance at the micro-to-nano-scale realm. However, to fully exploit micro-to-nano-scale chemistry, solvent volatility and lack of reproducibility need to be overcome. Here, we combine the non-volatile and versatile nature of ionic liquids with microcontact printing in an attempt to establish a facile protocol for high throughput fabrication of open microreactors and microfluidics. The micropatterned ionic liquid droplets have been demonstrated as electrochemical cells and reactors for microfabrication of metals and charge transfer complexes, substrates for immobilization of proteins and as membrane-free high-performance amperometric gas sensor arrays. The results suggest that miniaturized ionic liquid systems can be used to solve the problems of solvent volatility and slow mass transport in viscous ionic liquids in lab-on-a-chip devices, thus providing a versatile platform for a diverse number of applications.

  5. A pressure sensitive ionic gel FET for tactile sensing

    NASA Astrophysics Data System (ADS)

    Yamada, S.; Sato, T.; Toshiyoshi, H.

    2017-06-01

    Field-effect-transistor (FET) is combined with an ionic gel to realize a pressure sensitive ionic-gel field-effect-transistor (PSG-FET) of high sensitivity and low operational voltage. The ionic gels form a layer of charge accumulation in a nanometric scale called the electrical double layer (EDL) on each electrode upon voltage application and exhibit quite high capacitance. The source-drain current through the ZnO channel increases from the initial 44 nA (without pressure) to 783 μA (with pressure, 7 kPa), yielding an ON/OFF contrast as large as 1.7 × 104, due to EDLs, which is interpreted as a pressure sensitivity of 2.2 × 103 kPa-1. Judging from the drain current and the gate voltage properties, the threshold voltage is calculated to be 2.8 V owing the large capacitance created by the ionic gel.

  6. Electrostatic attraction between ionic reverse micelles with dielectric discontinuity

    NASA Astrophysics Data System (ADS)

    Chen, Peilong

    2002-11-01

    We have calculated the thermally-averaged electrostatic attractive potential between two spherical ionic reverse micelles in a medium of a different dielectric constant. Specifically the attractions between the charge density fluctuations in one micelle and interface polarizations on the other are computed. For water-in-oil microemulsions, we find that these contributions completely overwhelm those from correlated fluctuations in charge densities between two micelles.

  7. Molecular solutes in ionic liquids: a structural perspective.

    PubMed

    Pádua, Agílio A H; Costa Gomes, Margarida F; Canongia Lopes, José N A

    2007-11-01

    Understanding physicochemical properties of ionic liquids is important for their rational use in extractions, reactions, and other applications. Ionic liquids are not simple fluids: their ions are generally asymetric, flexible, with delocalized electrostatic charges, and available in a wide variety. It is difficult to capture their subtle properties with models that are too simplistic. Molecular simulation using atomistic force fields, which describe structures and interactions in detail, is an excellent tool to gain insights into their liquid-state organization, how they solvate different compounds, and what molecular factors determine their properties. The identification of certain ionic liquids as self-organized phases, with aggregated nonpolar and charged domains, provides a new way to interpret the solvation and structure of their mixtures. Many advances are the result of a successful interplay between experiment and modeling, possible in this field where none of the two methodologies had a previous advance.

  8. Pink noise of ionic conductance through single artificial nanopores revisited.

    PubMed

    Tasserit, C; Koutsioubas, A; Lairez, D; Zalczer, G; Clochard, M-C

    2010-12-31

    We report voltage-clamp measurements through single conical nanopore obtained by chemical etching of a single ion track in polyimide film. Special attention is paid to the pink noise of the ionic current (i.e., 1/f noise) measured with different filling liquids. The relative pink-noise amplitude is almost independent of concentration and pH for KCl solutions, but varies strongly using ionic liquids. In particular, we show that depending on the ionic liquid, the transport of charge carriers is strongly facilitated (low noise and higher conductivity than in the bulk) or jammed. These results show that the origin of the pink noise can be ascribed neither to fluctuations of the pore geometry nor to the pore wall charges, but rather to a cooperative effect on ions motion in confined geometry.

  9. Pink Noise of Ionic Conductance through Single Artificial Nanopores Revisited

    NASA Astrophysics Data System (ADS)

    Tasserit, C.; Koutsioubas, A.; Lairez, D.; Zalczer, G.; Clochard, M.-C.

    2010-12-01

    We report voltage-clamp measurements through single conical nanopore obtained by chemical etching of a single ion track in polyimide film. Special attention is paid to the pink noise of the ionic current (i.e., 1/f noise) measured with different filling liquids. The relative pink-noise amplitude is almost independent of concentration and pH for KCl solutions, but varies strongly using ionic liquids. In particular, we show that depending on the ionic liquid, the transport of charge carriers is strongly facilitated (low noise and higher conductivity than in the bulk) or jammed. These results show that the origin of the pink noise can be ascribed neither to fluctuations of the pore geometry nor to the pore wall charges, but rather to a cooperative effect on ions motion in confined geometry.

  10. Ion association at discretely-charged dielectric interfaces: Giant charge inversion

    NASA Astrophysics Data System (ADS)

    Wang, Zhi-Yong; Wu, Jianzhong

    2017-07-01

    Giant charge reversal has been identified for the first time by Monte Carlo simulation for a discretely charged surface in contact with a trivalent electrolyte solution. It takes place regardless of the surface charge density under study and the monovalent salt. In stark contrast to earlier predictions based on the 2-dimensional Wigner crystal model to describe strong correlation of counterions at the macroion surface, we find that giant charge reversal reflects an intricate interplay of ionic volume effects, electrostatic correlations, surface charge heterogeneity, and the dielectric response of the confined fluids. While the novel phenomenon is yet to be confirmed with experiment, the simulation results appear in excellent agreement with a wide range of existing observations in the subregime of charge inversion. Our findings may have far-reaching implications to understanding complex electrochemical phenomena entailing ionic fluids under dielectric confinements.

  11. Stretchable, transparent, ionic conductors.

    PubMed

    Keplinger, Christoph; Sun, Jeong-Yun; Foo, Choon Chiang; Rothemund, Philipp; Whitesides, George M; Suo, Zhigang

    2013-08-30

    Existing stretchable, transparent conductors are mostly electronic conductors. They limit the performance of interconnects, sensors, and actuators as components of stretchable electronics and soft machines. We describe a class of devices enabled by ionic conductors that are highly stretchable, fully transparent to light of all colors, and capable of operation at frequencies beyond 10 kilohertz and voltages above 10 kilovolts. We demonstrate a transparent actuator that can generate large strains and a transparent loudspeaker that produces sound over the entire audible range. The electromechanical transduction is achieved without electrochemical reaction. The ionic conductors have higher resistivity than many electronic conductors; however, when large stretchability and high transmittance are required, the ionic conductors have lower sheet resistance than all existing electronic conductors.

  12. Lewis Acidic Ionic Liquids.

    PubMed

    Brown, Lucy C; Hogg, James M; Swadźba-Kwaśny, Małgorzata

    2017-08-21

    Until very recently, the term Lewis acidic ionic liquids (ILs) was nearly synonymous with halometallate ILs, with a strong focus on chloroaluminate(III) systems. The first part of this review covers the historical context in which these were developed, speciation of a range of halometallate ionic liquids, attempts to quantify their Lewis acidity, and selected recent applications: in industrial alkylation processes, in supported systems (SILPs/SCILLs) and in inorganic synthesis. In the last decade, interesting alternatives to halometallate ILs have emerged, which can be divided into two sub-sections: (1) liquid coordination complexes (LCCs), still based on halometallate species, but less expensive and more diverse than halometallate ionic liquids, and (2) ILs with main-group Lewis acidic cations. The two following sections cover these new liquid Lewis acids, also highlighting speciation studies, Lewis acidity measurements, and applications.

  13. Molecular dynamics study of screening at ionic surfaces

    NASA Astrophysics Data System (ADS)

    Desai, T. G.

    2007-10-01

    Molecular dynamics simulations of NaCl fluid are used to understand the behavior of ionic fluid to screen the field generated by charges on the ionic crystal surfaces in absence of any external electric field. The NaCl fluid in the strongly coupled regime (corresponding to the melt) in contact with the charged octopolar (111) NaCl surface shows that the spatial correlations decay in an oscillatory manner, with a screening length λQ given by the envelope of the damped oscillations. By contrast to the Debye-Huckel theory, in the strongly coupled regime, λQ increases with increasing coupling strength (also seen in bulk ionic simulations). The NaCl fluid confined between neutral (100) NaCl surfaces also shows weak oscillatory charge decay near the surface. Similar oscillatory exponential decay was seen when the NaCl fluid was confined between two analytically smooth neutral walls. The origin of these oscillations was due to the difference in ion sizes. NaCl fluid confined between neutral octopolar (110) and dipolar (110) surface show stronger density oscillations than (100) surface but comparatively very weak charge oscillations. This paper shows that the strength of the charges on the crystal surfaces is enough to induce a characteristic spatial distribution of charges in the contacting fluid and the extent of distribution depends on the type of surface.

  14. Molecular Dynamics Study of Screening at Ionic Surfaces

    SciTech Connect

    T.G. Desai

    2007-10-01

    Molecular-dynamics simulations of NaCl fluid are used to understand the behavior of ionic fluid to screen the field generated by charges on the ionic crystal surfaces in absence of any external electric field. The NaCl fluid in the strongly-coupled regime (corresponding to the melt) in contact with the charged octopolar (111) NaCl surface shows that the spatial correlations decay in an oscillatory manner, with a screening length, ?Q, given by the envelope of the damped oscillations. By contrast to the Debye-Huckel theory, in the strongly-coupled regime, ?Q increases with increasing coupling strength (also seen in bulk ionic simulations). The NaCl fluid confined between neutral (100) NaCl surfaces also shows weak oscillatory charge decay near the surface. Similar oscillatory exponential decay was seen when the NaCl fluid was confined between two analytically smooth neutral walls. The origin of these oscillations was due to the difference in ion sizes. NaCl fluid confined between neutral octopolar (110) and dipolar (110) surface show stronger density oscillations than (100) surface but omparatively very weak charge oscillations. This paper shows that the strength of the charges on the crystal surfaces is enough to induce a characteristic spatial distribution of charges in the contacting fluid and the extent of distribution depends on the type of surface.

  15. Polymerizable ionic liquid crystals.

    PubMed

    Jazkewitsch, Olga; Ritter, Helmut

    2009-09-17

    Polymerizable vinylimidazolium ionic liquids (ILs) that contain mesogenic coumarin and biphenyl units, respectively, have been synthesized. The N-alkylation of N-vinylimidazole with bromoalkylated mesogenic units 7-(6-bromohexyloxy)coumarin (1) and 4,4'-bis(6-bromohexyloxy)biphenyl (2) was then carried out. The thermal behavior of the obtained ILs 3 and 4 was investigated by differential scanning calorimetry and polarizing optical microscopy. These measurements showed that the attached mesogenic units induce the self-assembly of ILs and, therefore, the occurrence of liquid crystalline phases. Subsequently, the ionic liquid crystals (ILCs) 3 and 4 were polymerized by a free-radical mechanism.

  16. Optimization of ionic conductivity in doped ceria

    PubMed Central

    Andersson, David A.; Simak, Sergei I.; Skorodumova, Natalia V.; Abrikosov, Igor A.; Johansson, Börje

    2006-01-01

    Oxides with the cubic fluorite structure, e.g., ceria (CeO2), are known to be good solid electrolytes when they are doped with cations of lower valence than the host cations. The high ionic conductivity of doped ceria makes it an attractive electrolyte for solid oxide fuel cells, whose prospects as an environmentally friendly power source are very promising. In these electrolytes, the current is carried by oxygen ions that are transported by oxygen vacancies, present to compensate for the lower charge of the dopant cations. Ionic conductivity in ceria is closely related to oxygen-vacancy formation and migration properties. A clear physical picture of the connection between the choice of a dopant and the improvement of ionic conductivity in ceria is still lacking. Here we present a quantum-mechanical first-principles study of the influence of different trivalent impurities on these properties. Our results reveal a remarkable correspondence between vacancy properties at the atomic level and the macroscopic ionic conductivity. The key parameters comprise migration barriers for bulk diffusion and vacancy–dopant interactions, represented by association (binding) energies of vacancy–dopant clusters. The interactions can be divided into repulsive elastic and attractive electronic parts. In the optimal electrolyte, these parts should balance. This finding offers a simple and clear way to narrow the search for superior dopants and combinations of dopants. The ideal dopant should have an effective atomic number between 61 (Pm) and 62 (Sm), and we elaborate that combinations of Nd/Sm and Pr/Gd show enhanced ionic conductivity, as compared with that for each element separately. PMID:16478802

  17. Ionic liquids in chemical engineering.

    PubMed

    Werner, Sebastian; Haumann, Marco; Wasserscheid, Peter

    2010-01-01

    The development of engineering applications with ionic liquids stretches back to the mid-1990s when the first examples of continuous catalytic processes using ionic liquids and the first studies of ionic liquid-based extractions were published. Ever since, the use of ionic liquids has seen tremendous progress in many fields of chemistry and engineering, and the first commercial applications have been reported. The main driver for ionic liquid engineering applications is to make practical use of their unique property profiles, which are the result of a complex interplay of coulombic, hydrogen bonding and van der Waals interactions. Remarkably, many ionic liquid properties can be tuned in a wide range by structural modifications at their cation and anion. This review highlights specific examples of ionic liquid applications in catalysis and in separation technologies. Additionally, the application of ionic liquids as working fluids in process machines is introduced.

  18. Streptococcus mutans and Streptococcus intermedius adhesion to fibronectin films are oppositely influenced by ionic strength.

    PubMed

    Busscher, Henk J; van de Belt-Gritter, Betsy; Dijkstra, Rene J B; Norde, Willem; van der Mei, Henny C

    2008-10-07

    Bacterial adhesion to protein-coated surfaces is mediated by an interplay of specific and nonspecific interactions. Although nonspecific interactions are ubiquitously present, little is known about the physicochemical mechanisms of specific interactions. The aim of this paper is to determine the influence of ionic strength on the adhesion of two streptococcal strains to fibronectin films. Streptococcus mutans LT11 and Streptococcus intermedius NCTC11324 both possess antigen I/II with the ability to bind fibronectin from solution, but S. intermedius binds approximately 20x less fibronectin than does the S. mutans strain under identical conditions. Both strains as well as fibronectin films are negatively charged in low ionic strength phosphate buffered saline (PBS, 10x diluted), but bacteria appear uncharged in high ionic strength PBS. Physicochemical modeling on the basis of overall cell surface properties (cell surface hydrophobicity and zeta potentials) demonstrates that both strains should favor adhesion to fibronectin films in a high ionic strength environment as compared to in a low ionic strength environment, where electrostatic repulsion between equally charged surfaces is dominant. Adhesion of S. intermedius to fibronectin films in a parallel plate flow chamber was completely in line with this modeling, while in addition atomic force microscopy (AFM) indicated stronger adhesion forces upon retraction between fibronectin-coated tips and the cell surfaces in high ionic strength PBS than in low ionic strength PBS. Thus, the dependence of the interaction on ionic strength is dominated by the overall negative charge on the interacting surfaces. Adhesion of S. mutans to fibronectin films, however, was completely at odds with theoretical modeling, and the strain adhered best in low ionic strength PBS. Moreover, AFM indicated weaker repulsive forces upon approach between fibronectin-coated tips and the cell surfaces in low ionic strength PBS than in high ionic

  19. Ion trajectory simulation for electrode configurations with arbitrary geometries.

    PubMed

    Wu, Guangxiang; Cooks, R Graham; Ouyang, Zheng; Yu, Meng; Chappell, William J; Plass, Wolfgang R

    2006-09-01

    A multi-particle ion trajectory simulation program ITSIM 6.0 is described, which is capable of ion trajectory simulations for electrode configurations with arbitrary geometries. The electrode structures are input from a 3D drawing program AutoCAD and the electric field is calculated using a 3D field solver COMSOL. The program CreatePot acts as interface between the field solver and ITSIM 6.0. It converts the calculated electric field into a field array file readable by ITSIM 6.0 and ion trajectories are calculated by solving Newton's equation using Runge-Kutta integration methods. The accuracy of the field calculation is discussed for the ideal quadrupole ion trap in terms of applied mesh density. Electric fields of several different types of devices with 3D geometry are simulated, including ion transport through an ion optical system as a function of pressure. Ion spatial distributions, including the storage of positively charged ions only and simultaneous storage of positively/negatively charged ions in commercial linear ion traps with various geometries, are investigated using different trapping modes. Inelastic collisions and collision induced dissociation modeled using RRKM theory are studied, with emphasis on the fragmentation of n-butylbenzene inside an ideal quadrupole ion trap. The mass spectrum of 1,3-dichlorobenzene is simulated for the rectilinear ion trap device and good agreement is observed between the simulated and the experimental mass spectra. Collisional cooling using helium at different pressures is found to affect mass resolution in the rectilinear ion trap.

  20. A multiprojection noncontact fluorescence tomography setup for imaging arbitrary geometries

    NASA Astrophysics Data System (ADS)

    Meyer, H.; Garofalakis, A.; Zacharakis, G.; Economou, E. N.; Mamalaki, C.; Kioussis, D.; Ntziachristos, V.; Ripoll, J.

    2005-04-01

    Optical imaging and tomography in tissues can facilitate the quantitative study of several important chromophores and fluorophores in-vivo. Due to this fact, there has been great interest in developing imaging systems offering quantitative information on the location and concentration of chromophores and fluorescent probes. However, most imaging systems currently used in research make use of fiber technology for delivery and detection, which restricts the size of the photon collecting arrays leading to insufficient spatial sampling and field of view. To enable large data sets and full 360o angular measurements, we developed a novel imaging system that enables 3D imaging of fluorescent signals in bodies of arbitrary shapes in a non-contact geometry in combination with a 3D surface reconstruction algorithm. The system consists of a rotating subject holder and a lens coupled Charge Coupled Device (CCD) camera in combination with a fiber coupled laser scanning device. An Argon ion laser is used as the source and different filters are used for the detection of various fluorophores or fluorescing proteins. With this new setup a large measurements dataset can be achieved while the use of inversion models give a high capacity for quantitative 3D reconstruction of fluorochrome distributions as well as high spatial resolution. The system is currently being tested in the observation of the distribution of Green Fluorescent Protein (GFP) expressing T-lymphocytes in order to study the function of the immune system in a murine model.

  1. Fluctuations of induced charge in ionization detectors

    SciTech Connect

    Samedov, V. V.

    2016-12-15

    Fluctuations of charge induced by charge carriers on the detector electrodes make a significant contribution to the energy resolution of ionization detectors, namely, semiconductor detectors and gas and liquid ionization chambers. These fluctuations are determined by the capture of charge carriers, as they drift in the bulk of the detector under the action of an electric field, by traps. In this study, we give a correct mathematical description of charge induction on electrodes of an ionization detector for an arbitrary electric field distribution in the detector with consideration of charge carrier capture by traps. The characteristic function obtained in this study yields the general expression for the distribution function of the charge induced on the detector electrodes. The formulas obtained in this study are useful for analysis of the influence of charge carrier transport on energy resolution of ionization detectors.

  2. Cloning quantum entanglement in arbitrary dimensions

    SciTech Connect

    Karpov, E.; Navez, P.; Cerf, N.J.

    2005-10-15

    We have found a quantum cloning machine that optimally duplicates the entanglement of a pair of d-dimensional quantum systems prepared in an arbitrary isotropic state. It maximizes the entanglement of formation contained in the two copies of any maximally entangled input state, while preserving the separability of unentangled input states. Moreover, it cannot increase the entanglement of formation of isotropic states. For large d, the entanglement of formation of each clone tends to one-half the entanglement of the input state, which corresponds to a classical behavior. Finally, we investigate a local entanglement cloner, which yields entangled clones with one-fourth the input entanglement in the large-d limit.

  3. Fast polar decomposition of an arbitrary matrix

    NASA Technical Reports Server (NTRS)

    Higham, Nicholas J.; Schreiber, Robert S.

    1988-01-01

    The polar decomposition of an m x n matrix A of full rank, where m is greater than or equal to n, can be computed using a quadratically convergent algorithm. The algorithm is based on a Newton iteration involving a matrix inverse. With the use of a preliminary complete orthogonal decomposition the algorithm can be extended to arbitrary A. How to use the algorithm to compute the positive semi-definite square root of a Hermitian positive semi-definite matrix is described. A hybrid algorithm which adaptively switches from the matrix inversion based iteration to a matrix multiplication based iteration due to Kovarik, and to Bjorck and Bowie is formulated. The decision when to switch is made using a condition estimator. This matrix multiplication rich algorithm is shown to be more efficient on machines for which matrix multiplication can be executed 1.5 times faster than matrix inversion.

  4. Aerodynamic shape optimization of arbitrary hypersonic vehicles

    NASA Technical Reports Server (NTRS)

    Dulikravich, George S.; Sheffer, Scott G.

    1991-01-01

    A new method was developed to optimize, in terms of aerodynamic wave drag minimization, arbitrary (nonaxisymmetric) hypersonic vehicles in modified Newtonian flow, while maintaining the initial volume and length of the vehicle. This new method uses either a surface fitted Fourier series to represent the vehicle's geometry or an independent point motion algorithm. In either case, the coefficients of the Fourier series or the spatial locations of the points defining each cross section were varied and a numerical optimization algorithm based on a quasi-Newton gradient search concept was used to determine the new optimal configuration. Results indicate a significant decrease in aerodynamic wave drag for simple and complex geometries at relatively low CPU costs. In the case of a cone, the results agreed well with known analytical optimum ogive shapes. The procedure is capable of accepting more complex flow field analysis codes.

  5. Driving atoms with light of arbitrary statistics

    NASA Astrophysics Data System (ADS)

    Gardiner, C. W.; Parkins, A. S.

    1994-08-01

    The main objective of this article was to integrate the work of Kolobov and Sokolov, Gardiner, and Carmichael concerning the possibility of a kind of 'modular quantum optics' in which nonclassical light beams could be generated and then used as inputs to other quantum systems. In addition, to extend this consolidated study to include the feasibilities of multiple input and output into each system; longer chains of systems, each driving the next; and arbitrary quantum white noise inputs into the atoms. Thus, the coupled-systems approach was developed to the extent that its full practical use can be manifested. Included in the investigation were single and two-mode squeezed light, antibunched light of two different kinds, and highly nonclassical light from atom-cavity systems. One problem may be anticipated from realistic systems and that is the size of the matrices which may ensue.

  6. Generalized sheath criterion for arbitrary degenerate plasmas

    NASA Astrophysics Data System (ADS)

    Akbari-Moghanjoughi, M.

    2017-01-01

    In this research, we study the generalized sheath criterion for plasmas with an arbitrary degree of electron degeneracy and temperature, ranging from the classical dilute regime to the fully degenerate quantum plasmas. The latter may be relevant to warm dense matter and/or laboratory high energy density matter or even astrophysical stellar plasmas. The hydrostatic one dimensional model is used to establish the generalized Bohm's criterion for sheath entrance ion speed limits, and the small amplitude theory of the sheath problem, which accurately describes the sheath parameters for lower ion acoustic Mach numbers, is developed. Our results indicate that the sheath characteristic parameters such as electrostatic potential and density profiles, as well as the wall potential and the sheath length, are significantly affected by plasma parameters such as the ion and electron temperature and number densities in the plasma region. In particular, there are fundamental differences between sheath structures of the dilute classical plasmas and those of dense quantum ones.

  7. Solving stochastic inflation for arbitrary potentials

    SciTech Connect

    Martin, Jerome; Musso, Marcello

    2006-02-15

    A perturbative method for solving the Langevin equation of inflationary cosmology in the presence of backreaction is presented. In the Gaussian approximation, the method permits an explicit calculation of the probability distribution of the inflaton field for an arbitrary potential, with or without the volume effects taken into account. The perturbative method is then applied to various concrete models, namely, large field, small field, hybrid, and running mass inflation. New results on the stochastic behavior of the inflaton field in those models are obtained. In particular, it is confirmed that the stochastic effects can be important in new inflation while it is demonstrated they are negligible in (vacuum dominated) hybrid inflation. The case of stochastic running mass inflation is discussed in some details and it is argued that quantum effects blur the distinction between the four classical versions of this model. It is also shown that the self-reproducing regime is likely to be important in this case.

  8. Quantum sensing with arbitrary frequency resolution

    NASA Astrophysics Data System (ADS)

    Boss, J. M.; Cujia, K. S.; Zopes, J.; Degen, C. L.

    2017-05-01

    Quantum sensing takes advantage of well-controlled quantum systems for performing measurements with high sensitivity and precision. We have implemented a concept for quantum sensing with arbitrary frequency resolution, independent of the qubit probe and limited only by the stability of an external synchronization clock. Our concept makes use of quantum lock-in detection to continuously probe a signal of interest. Using the electronic spin of a single nitrogen-vacancy center in diamond, we demonstrate detection of oscillating magnetic fields with a frequency resolution of 70 microhertz over a megahertz bandwidth. The continuous sampling further guarantees an enhanced sensitivity, reaching a signal-to-noise ratio in excess of 104 for a 170-nanotesla test signal measured during a 1-hour interval. Our technique has applications in magnetic resonance spectroscopy, quantum simulation, and sensitive signal detection.

  9. A classical density functional theory for interfacial layering of ionic liquids

    SciTech Connect

    Wu, Jianzhong; Jiang, Tao; Jiang, Deen; Jin, Zhehui; Henderson, Douglous

    2011-01-01

    Ionic liquids have attracted much recent theoretical interest for broad applications as environmentally-friendly solvents in separation and electrochemical processes. Because of the intrinsic complexity of organic ions and strong electrostatic correlations, the electrochemical properties of ionic liquids often defy the descriptions of conventional mean-field methods including the venerable, and over-used, Gouy-Chapman-Stern (GCS) theory. Classical density functional theory (DFT) has proven to be useful in previous studies of the electrostatic properties of aqueous electrolytes but until recently it has not been applied to ionic liquids. Here we report predictions from the DFT on the interfacial properties of ionic liquids near neutral or charged surfaces. By considering the molecular size, topology, and electrostatic correlations, we have examined major factors responsible for the unique features of electric-double layers of ionic-liquid including formation of long-range and alternating structures of cations and anions at charged surfaces.

  10. Fun with Ionic Compounds

    ERIC Educational Resources Information Center

    Logerwell, Mollianne G.; Sterling, Donna R.

    2007-01-01

    Ionic bonding is a fundamental topic in high school chemistry, yet it continues to be a concept that students struggle to understand. Even if they understand atomic structure and ion formation, it can be difficult for students to visualize how ions fit together to form compounds. This article describes several engaging activities that help…

  11. Fun with Ionic Compounds

    ERIC Educational Resources Information Center

    Logerwell, Mollianne G.; Sterling, Donna R.

    2007-01-01

    Ionic bonding is a fundamental topic in high school chemistry, yet it continues to be a concept that students struggle to understand. Even if they understand atomic structure and ion formation, it can be difficult for students to visualize how ions fit together to form compounds. This article describes several engaging activities that help…

  12. Synthesis of ionic liquids

    DOEpatents

    Dai, Sheng; Luo, Huimin

    2011-11-01

    Ionic compounds which are liquids at room temperature are formed by the method of mixing a neutral organic ligand with the salt of a metal cation and its conjugate anion. The liquids are hydrophobic, conductive and stable and have uses as solvents and in electrochemical devices.

  13. Synthesis of ionic liquids

    DOEpatents

    Dai, Sheng [Knoxville, TN; Luo, Huimin [Knoxville, TN

    2008-09-09

    Ionic compounds which are liquids at room temperature are formed by the method of mixing a neutral organic liqand with the salt of a metal cation and its conjugate anion. The liquids are hydrophobic, conductive and stable and have uses as solvents and in electrochemical devices.

  14. Ion momentum and energy transfer rates for charge exchange collisions

    NASA Technical Reports Server (NTRS)

    Horwitz, J.; Banks, P. M.

    1973-01-01

    The rates of momentum and energy transfer have been obtained for charge exchange collisions between ion and neutral gases having arbitrary Maxwellian temperatures and bulk transport velocities. The results are directly applicable to the F-region of the ionosphere where 0+ - 0 charge is the dominant mechanism affecting ion momentum and energy transfer.

  15. Periodic ground state for the charged massive Schwinger model

    SciTech Connect

    Nagy, S.; Sailer, K.; Polonyi, J.

    2004-11-15

    It is shown that the charged massive Schwinger model supports a periodic vacuum structure for arbitrary charge density, similar to the common crystalline layout known in solid state physics. The dynamical origin of the inhomogeneity is identified in the framework of the bosonized model and in terms of the original fermionic variables.

  16. Pycnonuclear reaction rates for binary ionic mixtures

    NASA Technical Reports Server (NTRS)

    Ichimaru, S.; Ogata, S.; Van Horn, H. M.

    1992-01-01

    Through a combination of compositional scaling arguments and examinations of Monte Carlo simulation results for the interparticle separations in binary-ionic mixture (BIM) solids, we have derived parameterized expressions for the BIM pycnonuclear rates as generalizations of those in one-component solids obtained previously by Salpeter and Van Horn and by Ogata et al. We have thereby discovered a catalyzing effect of the heavier elements, which enhances the rates of reactions among the lighter elements when the charge ratio exceeds a critical value of approximately 2.3.

  17. Pycnonuclear reaction rates for binary ionic mixtures

    NASA Technical Reports Server (NTRS)

    Ichimaru, S.; Ogata, S.; Van Horn, H. M.

    1992-01-01

    Through a combination of compositional scaling arguments and examinations of Monte Carlo simulation results for the interparticle separations in binary-ionic mixture (BIM) solids, we have derived parameterized expressions for the BIM pycnonuclear rates as generalizations of those in one-component solids obtained previously by Salpeter and Van Horn and by Ogata et al. We have thereby discovered a catalyzing effect of the heavier elements, which enhances the rates of reactions among the lighter elements when the charge ratio exceeds a critical value of approximately 2.3.

  18. Electrotunable lubricity with ionic liquids: the influence of nanoscale roughness.

    PubMed

    David, Alessio; Fajardo, Oscar Y; Kornyshev, Alexei A; Urbakh, Michael; Bresme, Fernando

    2017-07-01

    The properties of ionic liquids can be modified by applying an external electrostatic potential, providing a route to control their performance in nanolubrication applications. Most computational studies to date have focused on the investigation of smooth surfaces. Real surfaces are generally inhomogeneous and feature roughness of different length scales. We report here a study of the possible effects that surface roughness may have on electrotunable lubricity with ionic liquids, performed here by means of non-equilibrium molecular dynamics simulations. In order to advance our understanding of the interplay of friction and substrate structure we investigate coarse grained models of ionic liquids confined in model surfaces with nanometer roughness. The friction is shown to depend on the roughness of the substrate and the direction of shear. For the investigated systems, the friction coefficient is found to increase with roughness. These results are in contrast with previous studies, where roughness induced reduction of friction was reported, and they highlight the strong sensitivity of the friction process to the structure of the surfaces. The friction force features a maximum at a specific surface charge density. This behaviour is reminiscent of the one reported in ionic liquids confined by flat surfaces, showing the generality of this physical effect in confined ionic liquids. We find that an increase of the substrate-liquid dispersion interactions shifts the maximum to lower surface charges. This effect opens a route to control electrotunable friction phenomena by tuning both the electrostatic potential and the composition of the confining surfaces.

  19. Ionic colloidal crystals: Ordered, multicomponent structures via controlled heterocoagulation.

    PubMed

    Maskaly, Garry R; García, R Edwin; Carter, W Craig; Chiang, Yet-Ming

    2006-01-01

    We propose a new type of ordered colloid, the "ionic colloidal crystal" (ICC), which is stabilized by attractive electrostatic interactions analogous to those in atomic ionic materials. The rapid self-organization of colloids via this method should result in a diversity of orderings that are analogous to ionic compounds. Most of these complex structures would be difficult to produce by other methods. We use a Madelung summation approach to evaluate the conditions where ICC's are thermodynamically stable. Using this model, we compare the relative electrostatic energies of various structures showing that the regions of ICC stability are determined by two dimensionless parameters representing charge balance and the spatial extent of the electrostatic interactions. Parallels and distinctions between ICC's and classical ionic crystals are discussed. Monte Carlo simulations are utilized to examine the glass transition and melting temperatures, between which crystallization can occur, of a model system having the rocksalt structure. These tools allow us to make a first-order prediction of the experimentally accessible regions of surface charge, particle size, ionic strength, and temperature where ICC formation is probable.

  20. Charge Renormalization and Charge Oscillation in Asymmetric Primitive Model of Electrolytes

    NASA Astrophysics Data System (ADS)

    Ding, Mingnan; Liang, Yihao; Lu, Bing-Sui; Xing, Xiangjun

    2016-12-01

    Debye charging method is generalized to study the linear response properties of the asymmetric primitive model for electrolytes. Analytic results are obtained for the effective charge distributions of constituent ions inside the electrolyte, from which all static linear response properties of the system follow. It is found that, as the ion density increases, both the screening length and the dielectric constant receive substantial renormalization due to ionic correlations. Furthermore, the valence of larger ion is substantially renormalized upward by ionic correlations, while those of smaller ions remain approximately the same. For sufficiently high density, the system exhibits charge oscillations. The threshold ion density for charge oscillation is much lower than the corresponding values for symmetric electrolytes. Our results agree well with large-scale Monte Carlo simulations, and find good agreement in general, except for the case of small ion sizes (d = 4 Å) near the charge oscillation threshold.

  1. Superradiance instability of small rotating AdS black holes in arbitrary dimensions

    NASA Astrophysics Data System (ADS)

    Delice, Ã.-zgür; Durǧut, Türküler

    2015-07-01

    We investigate the stability of D dimensional singly rotating Myers-Perry-AdS black holes under superradiance against scalar field perturbations. It is well known that small four dimensional rotating or charged Anti-de Sitter (AdS) black holes are unstable against superradiance instability of a scalar field. Recent works extended the existence of this instability to five dimensional rotating charged AdS black holes or static charged AdS black holes in arbitrary dimensions. In this paper we analytically prove that rotating small AdS black holes in arbitrary dimensions also shows superradiance instability irrespective of the value of the (positive) angular momentum quantum number. To do this we solve the Klein-Gordon equation in the slow rotation, low frequency limit. By using the asymptotic matching technique, we are able to calculate the real and imaginary parts of the correction terms to the frequency of the scalar field due to the presence of the black hole, confirming the presence of superradiance instability. We see that, unlike in the case of static AdS black holes, the analytical method is valid for rotating AdS black holes for any value of angular momentum number and spacetime dimensions. For comparison we derive the corresponding correction terms for Myers-Perry black holes in the black hole bomb formalism in the Appendix and see that the results are in agreement.

  2. Ionic electroactive hybrid transducers

    NASA Astrophysics Data System (ADS)

    Akle, Barbar J.; Bennett, Matthew D.; Leo, Donald J.

    2005-05-01

    Ionic electroactive actuators have received considerable attention in the past ten years. Ionic electroactive polymers, sometimes referred to as artificial muscles, have the ability to generate large bending strain and moderate stress at low applied voltages. Typical types of ionic electroactive polymer transducers include ionic polymers, conducting polymers, and carbon nanotubes. Preliminary research combining multiple types of materials proved to enhance certain transduction properties such as speed of response, maximum strain, or quasi-static actuation. Recently it was demonstrated that ionomer-ionic liquid transducers can operate in air for long periods of time (>250,000 cycles) and showed potential to reduce or eliminate the back-relaxation issue associated with ionomeric polymers. In addition, ionic liquids have higher electrical stability window than those operated with water as the solvent thereby increasing the maximum strain that the actuator can produce. In this work, a new technique developed for plating metal particulates on the surface of ionomeric materials is applied to the development of hybrid transducers that incorporate carbon nanotubes and conducting polymers as electrode materials. The new plating technique, named the direct assembly process, consists of mixing a conducting powder with an ionomer solution. This technique has demonstrated improved response time and strain output as compared to previous methods. Furthermore, the direct assembly process is less costly to implement than traditional impregnation-reduction methods due to less dependence on reducing agents, it requires less time, and is easier to implement than other processes. Electrodes applied using this new technique of mixing RuO2 (surface area 45~65m2/g) particles and Nafion dispersion provided 5x the displacement and 10x the force compared to a transducer made with conventional methods. Furthermore, the study illustrated that the response speed of the transducer is optimized

  3. Repulsion between Oppositely Charged Planar Macroions

    PubMed Central

    Jho, YongSeok; Brown, Frank L. H.; Kim, MahnWon; Pincus, Philip A.

    2013-01-01

    The repulsive interaction between oppositely charged macroions is investigated using Grand Canonical Monte Carlo simulations of an unrestricted primitive model, including the effect of inhomogeneous surface charge and its density, the depth of surface charge, the cation size, and the dielectric permittivity of solvent and macroions, and their contrast. The origin of the repulsion is a combination of osmotic pressure and ionic screening resulting from excess salt between the macroions. The excess charge over-reduces the electrostatic attraction between macroions and raises the entropic repulsion. The magnitude of the repulsion increases when the dielectric constant of the solvent is lowered (below that of water) and/or the surface charge density is increased, in good agreement with experiment. Smaller size of surface charge and the cation, their discreteness and mobility are other factors that enhance the repulsion and charge inversion phenomenons. PMID:23940518

  4. Ionic Block Copolymers for Anion Exchange Membranes

    NASA Astrophysics Data System (ADS)

    Tsai, Tsung-Han; Herbst, Dan; Giffin, Guinevere A.; di Noto, Vito; Witten, Tom; Coughlin, E. Bryan

    2013-03-01

    Anion exchange membrane (AEM) fuel cells have regained interest because it allows the use of non-noble metal catalysts. Until now, most of the studies on AEM were based on random polyelectrolytes. In this work, Poly(vinylbenzyltrimethylammonium bromide)-b- (methylbutylene) ([PVBTMA][Br]-b-PMB) was studied by SAXS, TEM and dielectric spectroscopy to understand the fundamental structure-conductivity relationship of ion transport mechanisms within well-ordered block copolymers. The ionic conductivity and the formation of order structure were dependent on the casting solvent. Higher ion exchange capacity (IEC) of the membranes showed higher conductivity at as IEC values below 1.8mmol/g, as above this, the ionic conductivity decreases due to more water uptake leading to dilution of charge density. The humidity dependence of morphology exhibited the shifting of d-spacing to higher value and the alteration in higher characteristic peak of SAXS plot as the humidity increase from the dry to wet state. This phenomenon can be further explained by a newly developed polymer brush theory. Three ionic conduction pathways with different conduction mechanism within the membranes can be confirmed by broadband electric spectroscopy. US Army MURI (W911NF1010520)

  5. Osmotic Pressure in Ionic Microgel Dispersions

    NASA Astrophysics Data System (ADS)

    Denton, Alan R.; Tang, Qiyun

    2015-03-01

    Microgels are microscopic gel particles, typically 10-1000 nm in size, that are swollen by a solvent. Hollow microgels (microcapsules) can encapsulate cargo, such as dye molecules or drugs, in their solvent-filled cavities. Their sensitive response to environmental conditions (e.g., temperature, pH) and influence on flow properties suit microgels to widespread applications in the chemical, pharmaceutical, food, and consumer care industries. When dispersed in water, polyelectrolyte gels become charged through dissociation of counterions. The electrostatic contribution to the osmotic pressure inside and outside of ionic microgels influences particle swelling and bulk materials properties, including thermodynamic, structural, optical, and rheological properties. Within the primitive and cell models of polyelectrolyte solutions, we derive an exact statistical mechanical formula for the contribution of mobile microions to the osmotic pressure within ionic microgels. Using Poisson-Boltzmann theory, we validate this result by explicitly calculating ion distributions across the surface of an ionic microgel and the electrostatic contribution to the osmotic pressure. Within a coarse-grained one-component model, we further chart the limits of the cell model for salty dispersions. This work was supported by the National Science Foundation under Grant No. DMR-1106331.

  6. Observation of highly decoupled conductivity in protic ionic conductors.

    PubMed

    Wojnarowska, Zaneta; Wang, Yangyang; Paluch, Krzysztof J; Sokolov, Alexei P; Paluch, Marian

    2014-05-21

    Ionic liquids (ILs) are key materials for the development of a wide range of emerging technologies. Protic ionic liquids, an important class of ILs, have long been envisioned as promising anhydrous electrolytes for fuel cells. It is well known that in comparison to all other cations, protons exhibit abnormally high conductivity in water. Such superprotonic dynamics was expected in protic ionic conductors as well. However, many years of extensive studies led to the disappointing conclusion that this is not the case and most protic ionic liquids display subionic behavior. Therefore, the relatively low conductivity seems to be the main obstacle for the application of protic ionic liquids in fuel cells. Using dielectric spectroscopy, herein we report the observation of highly decoupled conductivity in a newly synthesized protic ionic conductor. We show that its proton transport is strongly decoupled from the structural relaxation, in terms of both temperature dependence and characteristic rates. This finding offers a fresh look on the charge transport mechanism in PILs and also provides new ideas for design of anhydrous materials with exceptionally high proton conductivity.

  7. Morphology-induced low temperature conductivity in ionic liquids

    NASA Astrophysics Data System (ADS)

    Erbas, Aykut; Olvera de La Cruz, Monica; Olvera de la Cruz Team

    Ionic liquids exhibit nano-scale liquid crystalline order depending on the polymeric details of salt molecules. The resulting morphology and temperature behavior are key factors in determining the room temperature conductivity of ionic liquids. Here we discuss the phase behavior and related ionic conductivities of dry ionic liquids with volume fractions close to unity by using extensive molecular dynamics simulations. Temperature dependence, effective persistence length of tails, and excluded volume symmetry of amphiphilic ionic liquid molecules are investigated in large scale systems with short and long-range electrostatics. Our results suggest that by adjusting stiffness of the amphiphilic molecules and excluded volume interactions, lamellar or interconnected 3D phases can be obtained. Resulting phases have significant effects on the conductive properties. If there is no excluded volume asymmetry along the molecules, mostly lamellar phases with anisotropic conductivities emerge. If the excluded volume interactions become asymmetric, lamellar phases are replaced by interconnected phases consist of charged groups. Within temperature ranges that morphological phases are observed, conductivities exhibit low-temperature maxima in accord with experiments of ionic liquid-based liquid Center of Bio-inspried Energy Center (CBES).

  8. Comparing two tetraalkylammonium ionic liquids. I. Liquid phase structure

    NASA Astrophysics Data System (ADS)

    Lima, Thamires A.; Paschoal, Vitor H.; Faria, Luiz F. O.; Ribeiro, Mauro C. C.; Giles, Carlos

    2016-06-01

    X-ray scattering experiments at room temperature were performed for the ionic liquids n-butyl-trimethylammonium bis(trifluoromethanesulfonyl)imide, [N1114][NTf2], and methyl-tributylammonium bis(trifluoromethanesulfonyl)imide, [N1444][NTf2]. The peak in the diffraction data characteristic of charge ordering in [N1444][NTf2] is shifted to longer distances in comparison to [N1114][NTf2], but the peak characteristic of short-range correlations is shifted in [N1444][NTf2] to shorter distances. Molecular dynamics (MD) simulations were performed for these ionic liquids using force fields available from the literature, although with new sets of partial charges for [N1114]+ and [N1444]+ proposed in this work. The shifting of charge and adjacency peaks to opposite directions in these ionic liquids was found in the static structure factor, S(k), calculated by MD simulations. Despite differences in cation sizes, the MD simulations unravel that anions are allowed as close to [N1444]+ as to [N1114]+ because anions are located in between the angle formed by the butyl chains. The more asymmetric molecular structure of the [N1114]+ cation implies differences in partial structure factors calculated for atoms belonging to polar or non-polar parts of [N1114][NTf2], whereas polar and non-polar structure factors are essentially the same in [N1444][NTf2]. Results of this work shed light on controversies in the literature on the liquid structure of tetraalkylammonium based ionic liquids.

  9. Comparing two tetraalkylammonium ionic liquids. I. Liquid phase structure.

    PubMed

    Lima, Thamires A; Paschoal, Vitor H; Faria, Luiz F O; Ribeiro, Mauro C C; Giles, Carlos

    2016-06-14

    X-ray scattering experiments at room temperature were performed for the ionic liquids n-butyl-trimethylammonium bis(trifluoromethanesulfonyl)imide, [N1114][NTf2], and methyl-tributylammonium bis(trifluoromethanesulfonyl)imide, [N1444][NTf2]. The peak in the diffraction data characteristic of charge ordering in [N1444][NTf2] is shifted to longer distances in comparison to [N1114][NTf2], but the peak characteristic of short-range correlations is shifted in [N1444][NTf2] to shorter distances. Molecular dynamics (MD) simulations were performed for these ionic liquids using force fields available from the literature, although with new sets of partial charges for [N1114](+) and [N1444](+) proposed in this work. The shifting of charge and adjacency peaks to opposite directions in these ionic liquids was found in the static structure factor, S(k), calculated by MD simulations. Despite differences in cation sizes, the MD simulations unravel that anions are allowed as close to [N1444](+) as to [N1114](+) because anions are located in between the angle formed by the butyl chains. The more asymmetric molecular structure of the [N1114](+) cation implies differences in partial structure factors calculated for atoms belonging to polar or non-polar parts of [N1114][NTf2], whereas polar and non-polar structure factors are essentially the same in [N1444][NTf2]. Results of this work shed light on controversies in the literature on the liquid structure of tetraalkylammonium based ionic liquids.

  10. Thermoelectric Power in Bilayer Graphene Device with Ionic Liquid Gating.

    PubMed

    Chien, Yung-Yu; Yuan, Hongtao; Wang, Chang-Ran; Lee, Wei-Li

    2016-02-08

    The quest for materials showing large thermoelectric power has long been one of the important subjects in material science and technology. Such materials have great potential for thermoelectric cooling and also high figure of merit ZT thermoelectric applications. We have fabricated bilayer graphene devices with ionic-liquid gating in order to tune its band gap via application of a perpendicular electric field on a bilayer graphene. By keeping the Fermi level at charge neutral point during the cool-down, we found that the charge puddles effect can be greatly reduced and thus largely improve the transport properties at low T in graphene-based devices using ionic liquid gating. At (Vig, Vbg) = (-1 V, +23 V), a band gap of about 36.6 ± 3 meV forms, and a nearly 40% enhancement of thermoelectric power at T = 120 K is clearly observed. Our works demonstrate the feasibility of band gap tuning in a bilayer graphene using ionic liquid gating. We also remark on the significant influence of the charge puddles effect in ionic-liquid-based devices.

  11. Thermoelectric Power in Bilayer Graphene Device with Ionic Liquid Gating

    PubMed Central

    Chien, Yung-Yu; Yuan, Hongtao; Wang, Chang-Ran; Lee, Wei-Li

    2016-01-01

    The quest for materials showing large thermoelectric power has long been one of the important subjects in material science and technology. Such materials have great potential for thermoelectric cooling and also high figure of merit ZT thermoelectric applications. We have fabricated bilayer graphene devices with ionic-liquid gating in order to tune its band gap via application of a perpendicular electric field on a bilayer graphene. By keeping the Fermi level at charge neutral point during the cool-down, we found that the charge puddles effect can be greatly reduced and thus largely improve the transport properties at low T in graphene-based devices using ionic liquid gating. At (Vig, Vbg) = (−1 V, +23 V), a band gap of about 36.6 ± 3 meV forms, and a nearly 40% enhancement of thermoelectric power at T = 120 K is clearly observed. Our works demonstrate the feasibility of band gap tuning in a bilayer graphene using ionic liquid gating. We also remark on the significant influence of the charge puddles effect in ionic-liquid-based devices. PMID:26852799

  12. Thermoelectric Power in Bilayer Graphene Device with Ionic Liquid Gating

    NASA Astrophysics Data System (ADS)

    Chien, Yung-Yu; Yuan, Hongtao; Wang, Chang-Ran; Lee, Wei-Li

    2016-02-01

    The quest for materials showing large thermoelectric power has long been one of the important subjects in material science and technology. Such materials have great potential for thermoelectric cooling and also high figure of merit ZT thermoelectric applications. We have fabricated bilayer graphene devices with ionic-liquid gating in order to tune its band gap via application of a perpendicular electric field on a bilayer graphene. By keeping the Fermi level at charge neutral point during the cool-down, we found that the charge puddles effect can be greatly reduced and thus largely improve the transport properties at low T in graphene-based devices using ionic liquid gating. At (Vig, Vbg) = (‑1 V, +23 V), a band gap of about 36.6 ± 3 meV forms, and a nearly 40% enhancement of thermoelectric power at T = 120 K is clearly observed. Our works demonstrate the feasibility of band gap tuning in a bilayer graphene using ionic liquid gating. We also remark on the significant influence of the charge puddles effect in ionic-liquid-based devices.

  13. Counterion condensation and ionic conductivity

    NASA Astrophysics Data System (ADS)

    Penafiel, L. Miguel; Litovitz, Theodore A.

    1992-02-01

    The occurrence of counterion condensation is demonstrated through measurements of the incremental ionic conductivity of pH buffered Na polyacrylate solutions. pH values were selected to allow variation of the charge density parameter ξ in the range between 0.4 and 2.8, that is, across ξ=1, the theoretical critical level for counterion condensation. The results show two regions where the incremental conductivity, ΔσP, varies differently with ξ. For ξ<1.3, ΔσP remains relatively constant. A sharp drop in ΔσP is observed between ξ=1.3 and ξ=1.7 corresponding to the onset of counterion condensation. It is suggested that this discontinuity reflects a drastic change in the polyion mobility caused by a structural rearrangement of the macromolecule. For ξ≳1.7, ΔσP decreases with approximately constant slope. This latter behavior agrees qualitatively but not quantitatively with the prediction of the counterion condensation model.

  14. Port-based teleportation in arbitrary dimension.

    PubMed

    Studziński, Michał; Strelchuk, Sergii; Mozrzymas, Marek; Horodecki, Michał

    2017-09-07

    Port-based teleportation (PBT), introduced in 2008, is a type of quantum teleportation protocol which transmits the state to the receiver without requiring any corrections on the receiver's side. Evaluating the performance of PBT was computationally intractable and previous attempts succeeded only with small systems. We study PBT protocols and fully characterize their performance for arbitrary dimensions and number of ports. We develop new mathematical tools to study the symmetries of the measurement operators that arise in these protocols and belong to the algebra of partially transposed permutation operators. First, we develop the representation theory of the mentioned algebra which provides an elegant way of understanding the properties of subsystems of a large system with general symmetries. In particular, we introduce the theory of the partially reduced irreducible representations which we use to obtain a simpler representation of the algebra of partially transposed permutation operators and thus explicitly determine the properties of any port-based teleportation scheme for fixed dimension in polynomial time.

  15. Arbitrary-resolution global sensitivity kernels

    NASA Astrophysics Data System (ADS)

    Nissen-Meyer, T.; Fournier, A.; Dahlen, F.

    2007-12-01

    Extracting observables out of any part of a seismogram (e.g. including diffracted phases such as Pdiff) necessitates the knowledge of 3-D time-space wavefields for the Green functions that form the backbone of Fréchet sensitivity kernels. While known for a while, this idea is still computationally intractable in 3-D, facing major simulation and storage issues when high-frequency wavefields are considered at the global scale. We recently developed a new "collapsed-dimension" spectral-element method that solves the 3-D system of elastodynamic equations in a 2-D space, based on exploring symmetry considerations of the seismic-wave radiation patterns. We will present the technical background on the computation of waveform kernels, various examples of time- and frequency-dependent sensitivity kernels and subsequently extracted time-window kernels (e.g. banana- doughnuts). Given the computationally light-weighted 2-D nature, we will explore some crucial parameters such as excitation type, source time functions, frequency, azimuth, discontinuity locations, and phase type, i.e. an a priori view into how, when, and where seismograms carry 3-D Earth signature. A once-and-for-all database of 2-D waveforms for various source depths shall then serve as a complete set of global time-space sensitivity for a given spherically symmetric background model, thereby allowing for tomographic inversions with arbitrary frequencies, observables, and phases.

  16. Fast approximate surface evolution in arbitrary dimension

    PubMed Central

    Malcolm, James; Rathi, Yogesh; Yezzi, Anthony; Tannenbaum, Allen

    2013-01-01

    The level set method is a popular technique used in medical image segmentation; however, the numerics involved make its use cumbersome. This paper proposes an approximate level set scheme that removes much of the computational burden while maintaining accuracy. Abandoning a floating point representation for the signed distance function, we use integral values to represent the signed distance function. For the cases of 2D and 3D, we detail rules governing the evolution and maintenance of these three regions. Arbitrary energies can be implemented in the framework. This scheme has several desirable properties: computations are only performed along the zero level set; the approximate distance function requires only a few simple integer comparisons for maintenance; smoothness regularization involves only a few integer calculations and may be handled apart from the energy itself; the zero level set is represented exactly removing the need for interpolation off the interface; and evolutions proceed on the order of milliseconds per iteration on conventional uniprocessor workstations. To highlight its accuracy, flexibility and speed, we demonstrate the technique on intensity-based segmentations under various statistical metrics. Results for 3D imagery show the technique is fast even for image volumes. PMID:24392194

  17. Solving Nonlinear Euler Equations with Arbitrary Accuracy

    NASA Technical Reports Server (NTRS)

    Dyson, Rodger W.

    2005-01-01

    A computer program that efficiently solves the time-dependent, nonlinear Euler equations in two dimensions to an arbitrarily high order of accuracy has been developed. The program implements a modified form of a prior arbitrary- accuracy simulation algorithm that is a member of the class of algorithms known in the art as modified expansion solution approximation (MESA) schemes. Whereas millions of lines of code were needed to implement the prior MESA algorithm, it is possible to implement the present MESA algorithm by use of one or a few pages of Fortran code, the exact amount depending on the specific application. The ability to solve the Euler equations to arbitrarily high accuracy is especially beneficial in simulations of aeroacoustic effects in settings in which fully nonlinear behavior is expected - for example, at stagnation points of fan blades, where linearizing assumptions break down. At these locations, it is necessary to solve the full nonlinear Euler equations, and inasmuch as the acoustical energy is of the order of 4 to 5 orders of magnitude below that of the mean flow, it is necessary to achieve an overall fractional error of less than 10-6 in order to faithfully simulate entropy, vortical, and acoustical waves.

  18. Heterotic string in an arbitrary background field

    NASA Astrophysics Data System (ADS)

    Sen, Ashoke

    1985-10-01

    An expression for the light-cone gauge action for the first-quantized heterotic string in the presence of arbitrary background gauge, gravitational, and antisymmetric tensor fields is derived. The result is a two-dimensional local field theory with N=1/2 supersymmetry. The constraints imposed on the background fields in order to make this theory one-loop finite are derived. These constraints are identical to the equations of motion for the massless fields at the linearized level. Finally, it is shown that if there is no background antisymmetric tensor field, and if the gauge connection is set equal to the spin connection, the effective action is that of an N=1 supersymmetric nonlinear and N=2 supersymmetric Georgi-Glashow models the occurrence of the fermion fractionization is the necessity; the ignorance of it results in the inconsistency in the perturbative calculation of the mass splittings among the members of the supermultiplets. The notable feature of our result is that the degeneracy due to the Jackiw-Rebbi zero mode is not independent of the one required by the supersymmetry, suggesting a nontrivial structure in embedding the topology of Higgs fields into supersymmetric gauge theories.

  19. Understanding rigid body motion in arbitrary dimensions

    NASA Astrophysics Data System (ADS)

    Leyvraz, Francois

    2015-05-01

    Why would anyone wish to generalize the already unappetizing subject of rigid body motion to an arbitrary number of dimensions? At first sight, the subject seems to be both repellent and superfluous. The author will try to argue that an approach involving no specific three-dimensional constructs is actually easier to grasp than the traditional approach and might thus be generally useful to understand rigid body motion both in three dimensions and in the general case. Specific differences between the viewpoint suggested here and the usual one include the following: here angular velocities are systematically treated as antisymmetric matrices, a symmetric tensor I quite different from the moment of inertia tensor plays a central role, whereas the latter is shown to be a far more complex object, namely a tensor of rank four. A straightforward way to define it is given. The Euler equation is derived and the use of Noether’s theorem to obtain conserved quantities is illustrated. Finally the equations of motion for a heavy top as well as for two bodies linked by a spherical joint are derived to display the simplicity and the power of the method.

  20. Polyphosphonium-based bipolar membranes for rectification of ionic currents.

    PubMed

    Gabrielsson, Erik O; Berggren, Magnus

    2013-01-01

    Bipolar membranes (BMs) have interesting applications within the field of bioelectronics, as they may be used to create non-linear ionic components (e.g., ion diodes and transistors), thereby extending the functionality of, otherwise linear, electrophoretic drug delivery devices. However, BM based diodes suffer from a number of limitations, such as narrow voltage operation range and/or high hysteresis. In this work, we circumvent these problems by using a novel polyphosphonium-based BM, which is shown to exhibit improved diode characteristics. We believe that this new type of BM diode will be useful for creating complex addressable ionic circuits for delivery of charged biomolecules.

  1. Toward complementary ionic circuits: the npn ion bipolar junction transistor.

    PubMed

    Tybrandt, Klas; Gabrielsson, Erik O; Berggren, Magnus

    2011-07-06

    Many biomolecules are charged and may therefore be transported with ionic currents. As a step toward addressable ionic delivery circuits, we report on the development of a npn ion bipolar junction transistor (npn-IBJT) as an active control element of anionic currents in general, and specifically, demonstrate actively modulated delivery of the neurotransmitter glutamic acid. The functional materials of this transistor are ion exchange layers and conjugated polymers. The npn-IBJT shows stable transistor characteristics over extensive time of operation and ion current switch times below 10 s. Our results promise complementary chemical circuits similar to the electronic equivalence, which has proven invaluable in conventional electronic applications.

  2. ELECTRICAL REGULATING APPARATUS INCLUDING AN IONIC CURRENT REGULATOR

    DOEpatents

    Brackney, H.W.

    1958-08-12

    An apparatus is described for regulating the operation of an electromagmetic charged particle separator lt consists of an electrical circuit for innproving the regulation of the accelerating voltage of a calutron when the ionic current regulator control means is disconnected. The novel circuit arrangement connects the input of the ionic current regulator to a voltage divider. in association with a second voltage regulatora to furnish an accelerating voltage output which remains constant at a mean value instead of zero as has been the practice.

  3. Super ionic conductive glass

    DOEpatents

    Susman, S.; Volin, K.J.

    Described is an ionically conducting glass for use as a solid electrolyte in a power or secondary cell containing an alkali metal-containing anode and a cathode separated by an alkali metal ion conducting glass having an ionic transference number of unity and the general formula: A/sub 1 + x/D/sub 2-x/3/Si/sub x/P/sub 3 - x/O/sub 12 - 2x/3/, wherein A is a network modifier for the glass and is an alkali metal of the anode, D is an intermediate for the glass and is selected from the class consisting of Zr, Ti, Ge, Al, Sb, Be, and Zn and X is in the range of from 2.25 to 3.0. Of the alkali metals, Na and Li are preferred and of the intermediate, Zr, Ti and Ge are preferred.

  4. Super ionic conductive glass

    DOEpatents

    Susman, Sherman; Volin, Kenneth J.

    1984-01-01

    An ionically conducting glass for use as a solid electrolyte in a power or secondary cell containing an alkali metal-containing anode and a cathode separated by an alkali metal ion conducting glass having an ionic transference number of unity and the general formula: A.sub.1+x D.sub.2-x/3 Si.sub.x P.sub.3-x O.sub.12-2x/3, wherein A is a network modifier for the glass and is an alkali metal of the anode, D is an intermediate for the glass and is selected from the class consisting of Zr, Ti, Ge, Al, Sb, Be, and Zn and X is in the range of from 2.25 to 3.0. Of the alkali metals, Na and Li are preferred and of the intermediate, Zr, Ti and Ge are preferred.

  5. Thermodynamic estimation: Ionic materials

    SciTech Connect

    Glasser, Leslie

    2013-10-15

    Thermodynamics establishes equilibrium relations among thermodynamic parameters (“properties”) and delineates the effects of variation of the thermodynamic functions (typically temperature and pressure) on those parameters. However, classical thermodynamics does not provide values for the necessary thermodynamic properties, which must be established by extra-thermodynamic means such as experiment, theoretical calculation, or empirical estimation. While many values may be found in the numerous collected tables in the literature, these are necessarily incomplete because either the experimental measurements have not been made or the materials may be hypothetical. The current paper presents a number of simple and relible estimation methods for thermodynamic properties, principally for ionic materials. The results may also be used as a check for obvious errors in published values. The estimation methods described are typically based on addition of properties of individual ions, or sums of properties of neutral ion groups (such as “double” salts, in the Simple Salt Approximation), or based upon correlations such as with formula unit volumes (Volume-Based Thermodynamics). - Graphical abstract: Thermodynamic properties of ionic materials may be readily estimated by summation of the properties of individual ions, by summation of the properties of ‘double salts’, and by correlation with formula volume. Such estimates may fill gaps in the literature, and may also be used as checks of published values. This simplicity arises from exploitation of the fact that repulsive energy terms are of short range and very similar across materials, while coulombic interactions provide a very large component of the attractive energy in ionic systems. Display Omitted - Highlights: • Estimation methods for thermodynamic properties of ionic materials are introduced. • Methods are based on summation of single ions, multiple salts, and correlations. • Heat capacity, entropy

  6. Simulation method of spatial laser field for arbitrary distance optical transmission with carbon nanotube

    NASA Astrophysics Data System (ADS)

    Wang, Jianmin; Bai, Rumeng; Zhou, Ye; Zhao, Guang

    2017-06-01

    In this paper, an arbitrary distance optical transmission simulation method for free-space optical communication system is presented. Based on this method, direct point-to-point performance tests between two optical terminals can be realized in the laboratory, and the test results are equivalent to those on-orbit. A theoretical analysis of this method is presented in this paper. Verification experiments showed that there is a good linearity between the incoming power density and output photocurrent of the carbon nanotube (CNT); the relative power difference between the CNT and the charge-coupled device (CCD) camera is 4.75%, which can be ignored compared with the link redundancy.

  7. Vibrational Spectroscopy of Ionic Liquids.

    PubMed

    Paschoal, Vitor H; Faria, Luiz F O; Ribeiro, Mauro C C

    2017-01-04

    Vibrational spectroscopy has continued use as a powerful tool to characterize ionic liquids since the literature on room temperature molten salts experienced the rapid increase in number of publications in the 1990's. In the past years, infrared (IR) and Raman spectroscopies have provided insights on ionic interactions and the resulting liquid structure in ionic liquids. A large body of information is now available concerning vibrational spectra of ionic liquids made of many different combinations of anions and cations, but reviews on this literature are scarce. This review is an attempt at filling this gap. Some basic care needed while recording IR or Raman spectra of ionic liquids is explained. We have reviewed the conceptual basis of theoretical frameworks which have been used to interpret vibrational spectra of ionic liquids, helping the reader to distinguish the scope of application of different methods of calculation. Vibrational frequencies observed in IR and Raman spectra of ionic liquids based on different anions and cations are discussed and eventual disagreements between different sources are critically reviewed. The aim is that the reader can use this information while assigning vibrational spectra of an ionic liquid containing another particular combination of anions and cations. Different applications of IR and Raman spectroscopies are given for both pure ionic liquids and solutions. Further issues addressed in this review are the intermolecular vibrations that are more directly probed by the low-frequency range of IR and Raman spectra and the applications of vibrational spectroscopy in studying phase transitions of ionic liquids.

  8. Electrotunable Lubricity with Ionic Liquid Nanoscale Films

    PubMed Central

    Fajardo, O. Y.; Bresme, F.; Kornyshev, A. A.; Urbakh, M.

    2015-01-01

    One of the main challenges in tribology is finding the way for an in situ control of friction without changing the lubricant. One of the ways for such control is via the application of electric fields. In this respect a promising new class of lubricants is ionic liquids, which are solvent-free electrolytes, and their properties should be most strongly affected by applied voltage. Based on a minimal physical model, our study elucidates the connection between the voltage effect on the structure of the ionic liquid layers and their lubricating properties. It reveals two mechanisms of variation of the friction force with the surface charge density, consistent with recent AFM measurements, namely via the (i) charge effect on normal and in-plane ordering in the film and (ii) swapping between anion and cation layers at the surfaces. We formulate conditions that would warrant low friction coefficients and prevent wear by resisting “squeezing-out” of the liquid under compression. These results give a background for controllable variation of friction. PMID:25572127

  9. Quantifying the effect of ionic screening with protein-decorated graphene transistors.

    PubMed

    Ping, Jinglei; Xi, Jin; Saven, Jeffery G; Liu, Renyu; Johnson, A T Charlie

    2017-03-15

    Liquid-based applications of biomolecule-decorated field-effect transistors (FETs) range from biosensors to in vivo implants. A critical scientific challenge is to develop a quantitative understanding of the gating effect of charged biomolecules in ionic solution and how this influences the readout of the FETs. To address this issue, we fabricated protein-decorated graphene FETs and measured their electrical properties, specifically the shift in Dirac voltage, in solutions of varying ionic strength. We found excellent quantitative agreement with a model that accounts for both the graphene polarization charge and ionic screening of ions adsorbed on the graphene as well as charged amino acids associated with the immobilized protein. The technique and analysis presented here directly couple the charging status of bound biomolecules to readout of liquid-phase FETs fabricated with graphene or other two-dimensional materials.

  10. Electrochemical properties of the double layer of an ionic liquid using a dimer model electrolyte and density functional theory.

    PubMed

    Henderson, Douglas; Wu, Jianzhong

    2012-03-01

    Most theoretical studies of the properties of an electrolyte, including an ionic liquid, treat the electrolyte as a mixture of charged hard spheres in a solvent modeled as a dielectric continuum. However, ionic liquids generally consist of nonspherical ions that are not dissolved in a solvent. A simple extension of the primitivel model of electrolytes is to represent an ionic liquid as a mixture of charged hard spheres (negative monovalent ions in our case) and nonspherical ions consisting of a dimer of two touching hard spheres, one of which is charged (monovalent and positive in our case) and the other is neutral. This simple model has been used previously by Federov et al. and by ourselves. Here, we use the classical density functional theory to study the interfacial properties of the model ionic liquid over a range of electrode charges and two electrolyte concentrations. For simplicity, all of the spheres have the same diameter. In contrast to the simulations of Federov and Kornyshev, we find that a plot of the differential capacitance of the dimer electrolyte versus the surface potential typically exhibits only a single hump. Also, differing from the studies of Lamperski et al. for a spherical electrolyte, which showed a decline of the maximal differential capacitance as the ionic concentration decreases, the maximum of the differential capacitance of the dimer electrolyte increases slightly with decreasing ionic concentration. Our theoretical results show other unexpected effects of the geometry of ionic species on the electrochemical properties of the electric double layer of an ionic liquid.

  11. Multiplicative asset exchange with arbitrary return distributions

    NASA Astrophysics Data System (ADS)

    Moukarzel, Cristian F.

    2011-08-01

    The conservative wealth exchange process derived from trade interactions is modeled as a multiplicative stochastic transference of value, where each interaction multiplies the wealth of the poorest of the two intervening agents by a random gain η = 1 + κ, with κ a random return. Analyzing the kinetic equation for the wealth distribution P(w, t), general properties are derived for arbitrary return distributions π(κ). If the geometrical average of the gain is larger than one, i.e. if langlnηrangπ > 0, in the long time limit a nontrivial equilibrium wealth distribution P(w) is attained. Whenever langlnηrangπ < 0, on the other hand, wealth condensation occurs, meaning that a single agent gets the whole wealth in the long run. This concentration phenomenon happens even if the average return langκrangπ of the poor agent is positive. In the stable phase, P(w) behaves as w(T - 1) for w\\to 0 , and we find T exactly. This exponent is nonzero in the stable phase but goes to zero on approach to the condensation interface. The exact wealth distribution can be obtained analytically for the particular case of Kelly betting, and it turns out to be an exponential P(w) = e - w. We show, however, that our model is never reversible, no matter what π(κ) is. In the condensing phase, the wealth of an agent with relative rank x is found to be w(x, t) ~ extlanglnηrangπ for finite times t. The wealth distribution is consequently P(w) ~ 1/w for finite times, while all wealth ends up in the hands of the richest agent for large times. Numerical simulations are carried out and found to satisfactorily compare with the above-mentioned analytical results.

  12. Arbitrary Shape Deformation in CFD Design

    NASA Technical Reports Server (NTRS)

    Landon, Mark; Perry, Ernest

    2014-01-01

    Sculptor(R) is a commercially available software tool, based on an Arbitrary Shape Design (ASD), which allows the user to perform shape optimization for computational fluid dynamics (CFD) design. The developed software tool provides important advances in the state-of-the-art of automatic CFD shape deformations and optimization software. CFD is an analysis tool that is used by engineering designers to help gain a greater understanding of the fluid flow phenomena involved in the components being designed. The next step in the engineering design process is to then modify, the design to improve the components' performance. This step has traditionally been performed manually via trial and error. Two major problems that have, in the past, hindered the development of an automated CFD shape optimization are (1) inadequate shape parameterization algorithms, and (2) inadequate algorithms for CFD grid modification. The ASD that has been developed as part of the Sculptor(R) software tool is a major advancement in solving these two issues. First, the ASD allows the CFD designer to freely create his own shape parameters, thereby eliminating the restriction of only being able to use the CAD model parameters. Then, the software performs a smooth volumetric deformation, which eliminates the extremely costly process of having to remesh the grid for every shape change (which is how this process had previously been achieved). Sculptor(R) can be used to optimize shapes for aerodynamic and structural design of spacecraft, aircraft, watercraft, ducts, and other objects that affect and are affected by flows of fluids and heat. Sculptor(R) makes it possible to perform, in real time, a design change that would manually take hours or days if remeshing were needed.

  13. Lattice summations for spread out particles: Applications to neutral and charged systems

    NASA Astrophysics Data System (ADS)

    Heyes, D. M.; Brańka, A. C.

    2013-01-01

    This work is concerned with the lattice energy of periodic assemblies of mass and charge distributions of the form, exp (-αp2), where α is an adjustable positive variable and {p} is the vector from the lattice site or average position. The energy of interaction between two distributions is the density-weighted integral of the interactions between the volume elements of each distribution. Reciprocal space lattice summation formulas derived for particles represented by gaussian smeared-out density distributions are applied to the gaussian potential and a bounded version of the soft-sphere potential for a range of exponents. Two types of spatial broadening are considered, continuous or physical broadening (PB) and broadening resulting from the time average of point particle positions, so-called "time" broadening (TB). For neutral mass distributions a reciprocal space lattice summation formula is derived which is applied to the bounded soft-sphere potential. For the charged systems, the methodology described in Heyes [J. Chem. Phys. 74, 1924 (1981), 10.1063/1.441285] is used, which for the PB case gives the Ewald-like formulas derived by Gingrich and Wilson [Chem. Phys. Lett. 500, 178 (2010), 10.1016/j.cplett.2010.10.010] using a different method. Another expression for the lattice energy of the spread out charge distributions is derived which is cast entirely in terms of a summation over the reciprocal lattice vectors, without the arbitrary charge spreading function used in the Ewald method. The effects of charge spreading on a generalized definition of the Madelung constant (M) for a selection of crystal lattices are shown to be insignificant for route mean square displacements up to values typical of melting of an ionic crystal. When the length scale of the charge distribution becomes comparable to or greater than the mean inter particle spacing, however, the effects of charge broadening on the lattice energy are shown to be significant. In the PB case, M → 0

  14. Lattice summations for spread out particles: applications to neutral and charged systems.

    PubMed

    Heyes, D M; Brańka, A C

    2013-01-21

    This work is concerned with the lattice energy of periodic assemblies of mass and charge distributions of the form, exp (-αp(2)), where α is an adjustable positive variable and p(̱) is the vector from the lattice site or average position. The energy of interaction between two distributions is the density-weighted integral of the interactions between the volume elements of each distribution. Reciprocal space lattice summation formulas derived for particles represented by gaussian smeared-out density distributions are applied to the gaussian potential and a bounded version of the soft-sphere potential for a range of exponents. Two types of spatial broadening are considered, continuous or physical broadening (PB) and broadening resulting from the time average of point particle positions, so-called "time" broadening (TB). For neutral mass distributions a reciprocal space lattice summation formula is derived which is applied to the bounded soft-sphere potential. For the charged systems, the methodology described in Heyes [J. Chem. Phys. 74, 1924 (1981)] is used, which for the PB case gives the Ewald-like formulas derived by Gingrich and Wilson [Chem. Phys. Lett. 500, 178 (2010)] using a different method. Another expression for the lattice energy of the spread out charge distributions is derived which is cast entirely in terms of a summation over the reciprocal lattice vectors, without the arbitrary charge spreading function used in the Ewald method. The effects of charge spreading on a generalized definition of the Madelung constant (M) for a selection of crystal lattices are shown to be insignificant for route mean square displacements up to values typical of melting of an ionic crystal. When the length scale of the charge distribution becomes comparable to or greater than the mean inter particle spacing, however, the effects of charge broadening on the lattice energy are shown to be significant. In the PB case, M → 0 for the uniform charge density or α → 0

  15. Viscoelastic Nanomechanics of Ionically Cross-linked Polyelectrolyte Networks

    NASA Astrophysics Data System (ADS)

    Han, Biao; Lee, Daeyeon; Han, Lin

    2015-03-01

    Understanding the mechanics of ionic polyelectrolyte networks is critical for applications where nm-to-um mechanics is the key to success. This study aims to reveal the roles of ionic cross-links and fixed charges in the viscoelasticity of layer-by-layer poly(allylamine hydrochloride)/poly(acrylic acid) microfilms, PAH/PAA, a complex held by pH-sensitive amine-carboxyl links. AFM-nanoindentation and force relaxation (tip R =12.5um) was performed at ionic strength(IS) =0.01-1.0M, pH =5.5-2.0 (pKa of PAA =2.3). When pH changes from 5.5 to 2.0, the films swell for 4x from densely linked, net neutral state to loosely linked, positively charged one. A >100x reduction in indentation modulus was observed at all IS, suggesting the dominance of decrease in cross-link density. In most states, more than 90% force relaxation was observed, where cross-link breaking/reformation likely dominates viscoelasticity. However, at pH =2.5 and IS =0.01M, when electrical double layer repulsion is important (Debye length =3nm), relaxation was about 60%, highlighting the contribution of fixed charges. In summary, this study revealed unique viscoelastic behaviors of PAH/PAA due to the pH- and IS-dependent cross-link and charge densities.

  16. Understanding the impact of the central atom on the ionic liquid behavior: Phosphonium vs ammonium cations

    SciTech Connect

    Carvalho, Pedro J.; Ventura, Sónia P. M.; Batista, Marta L. S.; Schröder, Bernd; Coutinho, João A. P.; Gonçalves, Fernando; Esperança, José; Mutelet, Fabrice

    2014-02-14

    The influence of the cation's central atom in the behavior of pairs of ammonium- and phosphonium-based ionic liquids was investigated through the measurement of densities, viscosities, melting temperatures, activity coefficients at infinite dilution, refractive indices, and toxicity against Vibrio fischeri. All the properties investigated are affected by the cation's central atom nature, with ammonium-based ionic liquids presenting higher densities, viscosities, melting temperatures, and enthalpies. Activity coefficients at infinite dilution show the ammonium-based ionic liquids to present slightly higher infinite dilution activity coefficients for non-polar solvents, becoming slightly lower for polar solvents, suggesting that the ammonium-based ionic liquids present somewhat higher polarities. In good agreement these compounds present lower toxicities than the phosphonium congeners. To explain this behavior quantum chemical gas phase DFT calculations were performed on isolated ion pairs at the BP-TZVP level of theory. Electronic density results were used to derive electrostatic potentials of the identified minimum conformers. Electrostatic potential-derived CHelpG and Natural Population Analysis charges show the P atom of the tetraalkylphosphonium-based ionic liquids cation to be more positively charged than the N atom in the tetraalkylammonium-based analogous IL cation, and a noticeable charge delocalization occurring in the tetraalkylammonium cation, when compared with the respective phosphonium congener. It is argued that this charge delocalization is responsible for the enhanced polarity observed on the ammonium based ionic liquids explaining the changes in the thermophysical properties observed.

  17. Understanding the impact of the central atom on the ionic liquid behavior: phosphonium vs ammonium cations.

    PubMed

    Carvalho, Pedro J; Ventura, Sónia P M; Batista, Marta L S; Schröder, Bernd; Gonçalves, Fernando; Esperança, José; Mutelet, Fabrice; Coutinho, João A P

    2014-02-14

    The influence of the cation's central atom in the behavior of pairs of ammonium- and phosphonium-based ionic liquids was investigated through the measurement of densities, viscosities, melting temperatures, activity coefficients at infinite dilution, refractive indices, and toxicity against Vibrio fischeri. All the properties investigated are affected by the cation's central atom nature, with ammonium-based ionic liquids presenting higher densities, viscosities, melting temperatures, and enthalpies. Activity coefficients at infinite dilution show the ammonium-based ionic liquids to present slightly higher infinite dilution activity coefficients for non-polar solvents, becoming slightly lower for polar solvents, suggesting that the ammonium-based ionic liquids present somewhat higher polarities. In good agreement these compounds present lower toxicities than the phosphonium congeners. To explain this behavior quantum chemical gas phase DFT calculations were performed on isolated ion pairs at the BP-TZVP level of theory. Electronic density results were used to derive electrostatic potentials of the identified minimum conformers. Electrostatic potential-derived CHelpG and Natural Population Analysis charges show the P atom of the tetraalkylphosphonium-based ionic liquids cation to be more positively charged than the N atom in the tetraalkylammonium-based analogous IL cation, and a noticeable charge delocalization occurring in the tetraalkylammonium cation, when compared with the respective phosphonium congener. It is argued that this charge delocalization is responsible for the enhanced polarity observed on the ammonium based ionic liquids explaining the changes in the thermophysical properties observed.

  18. Graphene-ionic liquid composites

    DOEpatents

    Aksay, Ilhan A.; Korkut, Sibel; Pope, Michael; Punckt, Christian

    2016-11-01

    Method of making a graphene-ionic liquid composite. The composite can be used to make elec-trodes for energy storage devices, such as batteries and supercapacitors. Dis-closed and claimed herein is method of making a graphene-ionic liquid com-posite, comprising combining a graphene source with at least one ionic liquid and heating the combination at a temperature of at least about 130 .degree. C.

  19. Design of Energetic Ionic Liquids

    DTIC Science & Technology

    2009-05-12

    effectiveness of the FMO method in both providing accurate results and reducing computational requirements, timings were performed for the ionic liquid ...Technical Paper 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Design of Energetic Ionic Liquids 5b. GRANT NUMBER 5c...Design of Energetic Ionic Liquids challenge project is to address several key technical issues and challenges associated with the characterization

  20. Photoionization in micelles: Addition of charged electron acceptors

    NASA Astrophysics Data System (ADS)

    Stenland, Chris; Kevan, Larry

    The relative photoyield of the electron donor N, N, N', N'-tetramethylbenzidine (TMB), solubilized in sodium and lithium dodecyl sulfate micelles with added charged electron acceptors was investigated. It was attempted to control the acceptor distance from a charged micellar interface by differently charged acceptors, cationic dimethyl viologen and anionic ferricyanide. However, back electron transfer from both cationic and anionic acceptors was found to be efficient. Thus simple electrostatic arguments for control of the photoyield do not seem applicable. Salt effects associated with the added ionic acceptors which partially neutralize the ionic micellar interface are suggested to be an important factor.

  1. Electrolytes between dielectric charged surfaces: Simulations and theory

    SciTech Connect

    Santos, Alexandre P. dos Levin, Yan

    2015-05-21

    We present a simulation method to study electrolyte solutions in a dielectric slab geometry using a modified 3D Ewald summation. The method is fast and easy to implement, allowing us to rapidly resum an infinite series of image charges. In the weak coupling limit, we also develop a mean-field theory which allows us to predict the ionic distribution between the dielectric charged plates. The agreement between both approaches, theoretical and simulational, is very good, validating both methods. Examples of ionic density profiles in the strong electrostatic coupling limit are also presented. Finally, we explore the confinement of charge asymmetric electrolytes between neutral surfaces.

  2. New exact solution for the exterior gravitational field of a charged spinning mass

    SciTech Connect

    Chamorro, A. ); Manko, V.S. ); Denisova, T.E. )

    1991-11-15

    An exact asymptotically flat solution of the Einstein-Maxwell equations describing the exterior gravitational field of a charged rotating axisymmetric mass possessing an arbitrary set of multipole moments is presented explicitly.

  3. Charge fluctuations in nanoscale capacitors.

    PubMed

    Limmer, David T; Merlet, Céline; Salanne, Mathieu; Chandler, David; Madden, Paul A; van Roij, René; Rotenberg, Benjamin

    2013-09-06

    The fluctuations of the charge on an electrode contain information on the microscopic correlations within the adjacent fluid and their effect on the electronic properties of the interface. We investigate these fluctuations using molecular dynamics simulations in a constant-potential ensemble with histogram reweighting techniques. This approach offers, in particular, an efficient, accurate, and physically insightful route to the differential capacitance that is broadly applicable. We demonstrate these methods with three different capacitors: pure water between platinum electrodes and a pure as well as a solvent-based organic electrolyte each between graphite electrodes. The total charge distributions with the pure solvent and solvent-based electrolytes are remarkably Gaussian, while in the pure ionic liquid the total charge distribution displays distinct non-Gaussian features, suggesting significant potential-driven changes in the organization of the interfacial fluid.

  4. Charge Fluctuations in Nanoscale Capacitors

    NASA Astrophysics Data System (ADS)

    Limmer, David T.; Merlet, Céline; Salanne, Mathieu; Chandler, David; Madden, Paul A.; van Roij, René; Rotenberg, Benjamin

    2013-09-01

    The fluctuations of the charge on an electrode contain information on the microscopic correlations within the adjacent fluid and their effect on the electronic properties of the interface. We investigate these fluctuations using molecular dynamics simulations in a constant-potential ensemble with histogram reweighting techniques. This approach offers, in particular, an efficient, accurate, and physically insightful route to the differential capacitance that is broadly applicable. We demonstrate these methods with three different capacitors: pure water between platinum electrodes and a pure as well as a solvent-based organic electrolyte each between graphite electrodes. The total charge distributions with the pure solvent and solvent-based electrolytes are remarkably Gaussian, while in the pure ionic liquid the total charge distribution displays distinct non-Gaussian features, suggesting significant potential-driven changes in the organization of the interfacial fluid.

  5. Aggregation and Charge Behavior of Metallic and Nonmetallic Nanoparticles in the Presence of Competing Similarly-Charged Inorganic Ions

    EPA Science Inventory

    The influence of competing, similarly charged, inorganic ions on the size and charge behavior of suspended titanium-dioxide (nTiO2), silver (nAg) and fullerene (nC60) nanoparticles (NPs) was investigated. Under pH and ionic conditions similar to natural water bodies, Ca2+ induced...

  6. Aggregation and Charge Behavior of Metallic and Nonmetallic Nanoparticles in the Presence of Competing Similarly-Charged Inorganic Ions

    EPA Science Inventory

    The influence of competing, similarly charged, inorganic ions on the size and charge behavior of suspended titanium-dioxide (nTiO2), silver (nAg) and fullerene (nC60) nanoparticles (NPs) was investigated. Under pH and ionic conditions similar to natural water bodies, Ca2+ induced...

  7. Ionic size effects on the Poisson-Boltzmann theory

    NASA Astrophysics Data System (ADS)

    Colla, Thiago; Nunes Lopes, Lucas; dos Santos, Alexandre P.

    2017-07-01

    In this paper, we develop a simple theory to study the effects of ionic size on ionic distributions around a charged spherical particle. We include a correction to the regular Poisson-Boltzmann equation in order to take into account the size of ions in a mean-field regime. The results are compared with Monte Carlo simulations and a density functional theory based on the fundamental measure approach and a second-order bulk expansion which accounts for electrostatic correlations. The agreement is very good even for multivalent ions. Our results show that the theory can be applied with very good accuracy in the description of ions with highly effective ionic radii and low concentration, interacting with a colloid or a nanoparticle in an electrolyte solution.

  8. Arbitrary amplitude electrostatic wave propagation in a magnetized dense plasma containing helium ions and degenerate electrons

    NASA Astrophysics Data System (ADS)

    Mahmood, S.; Sadiq, Safeer; Haque, Q.; Ali, Munazza Z.

    2016-06-01

    The obliquely propagating arbitrary amplitude electrostatic wave is studied in a dense magnetized plasma having singly and doubly charged helium ions with nonrelativistic and ultrarelativistic degenerate electrons pressures. The Fermi temperature for ultrarelativistic degenerate electrons described by N. M. Vernet [(Cambridge University Press, Cambridge, 2007), p. 57] is used to define ion acoustic speed in ultra-dense plasmas. The pseudo-potential approach is used to solve the fully nonlinear set of dynamic equations for obliquely propagating electrostatic waves in a dense magnetized plasma containing helium ions. The upper and lower Mach number ranges for the existence of electrostatic solitons are found which depends on the obliqueness of the wave propagation with respect to applied magnetic field and charge number of the helium ions. It is found that only compressive (hump) soliton structures are formed in all the cases and only subsonic solitons are formed for a singly charged helium ions plasma case with nonrelativistic degenerate electrons. Both subsonic and supersonic soliton hump structures are formed for doubly charged helium ions with nonrelativistic degenerate electrons and ultrarelativistic degenerate electrons plasma case containing singly as well as doubly charged helium ions. The effect of propagation direction on the soliton amplitude and width of the electrostatic waves is also presented. The numerical plots are also shown for illustration using dense plasma parameters of a compact star (white dwarf) from literature.

  9. Arbitrary amplitude electrostatic wave propagation in a magnetized dense plasma containing helium ions and degenerate electrons

    SciTech Connect

    Mahmood, S. Sadiq, Safeer; Haque, Q.; Ali, Munazza Z.

    2016-06-15

    The obliquely propagating arbitrary amplitude electrostatic wave is studied in a dense magnetized plasma having singly and doubly charged helium ions with nonrelativistic and ultrarelativistic degenerate electrons pressures. The Fermi temperature for ultrarelativistic degenerate electrons described by N. M. Vernet [(Cambridge University Press, Cambridge, 2007), p. 57] is used to define ion acoustic speed in ultra-dense plasmas. The pseudo-potential approach is used to solve the fully nonlinear set of dynamic equations for obliquely propagating electrostatic waves in a dense magnetized plasma containing helium ions. The upper and lower Mach number ranges for the existence of electrostatic solitons are found which depends on the obliqueness of the wave propagation with respect to applied magnetic field and charge number of the helium ions. It is found that only compressive (hump) soliton structures are formed in all the cases and only subsonic solitons are formed for a singly charged helium ions plasma case with nonrelativistic degenerate electrons. Both subsonic and supersonic soliton hump structures are formed for doubly charged helium ions with nonrelativistic degenerate electrons and ultrarelativistic degenerate electrons plasma case containing singly as well as doubly charged helium ions. The effect of propagation direction on the soliton amplitude and width of the electrostatic waves is also presented. The numerical plots are also shown for illustration using dense plasma parameters of a compact star (white dwarf) from literature.

  10. [Theoretical investigation of the saturation correction for ionization chambers irradiated with pulsed beams of arbitrary pulse length].

    PubMed

    Karsch, Leonhard; Pawelke, Jörg

    2014-09-01

    In ionization chambers, not all released charge is collected due to the recombination of charge carriers. This effect is taken into account by the saturation correction factor kS. A physical description of the correction factor has been established for pulsed radiation. However, it is only accurate when the pulse length is short compared with the collection time of the ionization chamber. In this paper we develop a description of the saturation correction for radiation pulses of arbitrary length. For this, a system of partial differential equations is solved iteratively. The numerical solutions are verified experimentally for a Roos ionization chamber (PTW TM34001) exposed to a pulsed electron beam. The results of this iterative procedure describe the experimental data well. The calculations are also possible for beam structures which are experimentally hard to get and thereby contribute to a better understanding and correct description of the saturation correction at arbitrary pulse length. Among other things the pulse length dependent distributions of the charge carriers in the ionization chamber is calculated, inclusive of the transition to the conditions prevailing in the case of continuous irradiation. Furthermore is shown that the formula for kS established by Hochhäuser and Balk is applicable even at arbitrary pulse length, if pulse duration dependent effective values are used for the parameters a and p. These effective values have been determined for the Roos chamber at pulse lengths up to 300 μs.

  11. Electrostatic correlations on the ionic selectivity of cylindrical membrane nanopores.

    PubMed

    Buyukdagli, Sahin; Ala-Nissila, T

    2014-02-14

    We characterize the role of electrostatic fluctuations on the charge selectivity of cylindrical nanopores confining electrolyte mixtures. To this end, we develop an extended one-loop theory that can account for correlation effects induced by the surface charge, nanoconfinement of the electrolyte, and interfacial polarization charges associated with the low permittivity membrane. We validate the quantitative accuracy of the theory by comparisons with previously obtained Monte-Carlo simulation data from the literature, and scrutinize in detail the underlying forces driving the ionic selectivity of the nanopore. In the biologically relevant case of electrolytes with divalent cations such as CaCl2 in negatively charged nanopores, electrostatic correlations associated with the dense counterion layer in the channel result in an increase of the pore coion density with the surface charge. This peculiarity analogous to the charge inversion phenomenon remains intact for dielectrically inhomogeneous pores, which indicates that the effect should be observable in nanofiltration membranes or DNA-blocked nanopores characterized by a low membrane permittivity. Our results show that a quantitatively accurate consideration of correlation effects is necessary to determine the ionic selectivity of nanopores in the presence of electrolytes with multivalent counterions.

  12. Electrostatic correlations on the ionic selectivity of cylindrical membrane nanopores

    NASA Astrophysics Data System (ADS)

    Buyukdagli, Sahin; Ala-Nissila, T.

    2014-02-01

    We characterize the role of electrostatic fluctuations on the charge selectivity of cylindrical nanopores confining electrolyte mixtures. To this end, we develop an extended one-loop theory that can account for correlation effects induced by the surface charge, nanoconfinement of the electrolyte, and interfacial polarization charges associated with the low permittivity membrane. We validate the quantitative accuracy of the theory by comparisons with previously obtained Monte-Carlo simulation data from the literature, and scrutinize in detail the underlying forces driving the ionic selectivity of the nanopore. In the biologically relevant case of electrolytes with divalent cations such as CaCl2 in negatively charged nanopores, electrostatic correlations associated with the dense counterion layer in the channel result in an increase of the pore coion density with the surface charge. This peculiarity analogous to the charge inversion phenomenon remains intact for dielectrically inhomogeneous pores, which indicates that the effect should be observable in nanofiltration membranes or DNA-blocked nanopores characterized by a low membrane permittivity. Our results show that a quantitatively accurate consideration of correlation effects is necessary to determine the ionic selectivity of nanopores in the presence of electrolytes with multivalent counterions.

  13. Ionic liquids in bioanalysis.

    PubMed

    Kailasa, Suresh Kumar; Rawat, Karuna A; Wu, Hui-Fen

    2015-01-01

    Ionic liquids (ILs) are entirely composed of ions and they possess fascinating properties, including low volatility, tunable viscosity, miscibility and electrolytic conductivity, which make them promising alternatives to traditional organic solvents used in sample preparation. The recent surge in the number of publications clearly indicates an increasing interest of the analytical and bioanalytical community toward these exciting and unique solvents. This article highlights the recent advances in the use of ILs as extraction solvents, as materials for separation and preconcentration in chromatographic techniques, and as matrices in mass spectrometric techniques for bioassays in biocomplex samples. We also briefly discuss the potential applications of ILs in biocatalysis.

  14. Microwave beam power transmission at an arbitrary range

    NASA Technical Reports Server (NTRS)

    Pinero, L. R.; Christian, J. L., Jr.; Acosta, R. J.

    1992-01-01

    The power transfer efficiency between two circular apertures at an arbitrary range is obtained numerically. The apertures can have generally different sizes and arbitrary taper illuminations. The effects of distance and taper illumination on the transmission efficiency are investigated for equal size apertures. The result shows that microwave beam power is more effective at close ranges, namely distances less than 2D(exp 2)/lambda. Also shown was the power transfer efficiency increase with taper illumination for close range distances. A computer program was developed for calculating the power transfer efficiency at an arbitrary range.

  15. Conformal array design on arbitrary polygon surface with transformation optics

    SciTech Connect

    Deng, Li Hong, Weijun Zhu, Jianfeng; Peng, Biao; Li, Shufang; Wu, Yongle

    2016-06-15

    A transformation-optics based method to design a conformal antenna array on an arbitrary polygon surface is proposed and demonstrated in this paper. This conformal antenna array can be adjusted to behave equivalently as a uniformly spaced linear array by applying an appropriate transformation medium. An typical example of general arbitrary polygon conformal arrays, not limited to circular array, is presented, verifying the proposed approach. In summary, the novel arbitrary polygon surface conformal array can be utilized in array synthesis and beam-forming, maintaining all benefits of linear array.

  16. Solving Einstein's Equation Numerically on Manifolds with Arbitrary Topologie

    NASA Astrophysics Data System (ADS)

    Lindblom, Lee

    2017-01-01

    This talk will summarize some of the numerical methods we have developed for solving Einstein's equation numerically on manifolds with arbitrary spatial topologies. These methods include the use of multi-cube representations of arbitrary manifolds, a convenient new way to specify the differential structure on multi-cube representations, and a new fully covariant first-order symmetric hyperbolic representation of Einstein's equation. Progress on the problem of constructing the ``reference metrics'' (which are an essential element of our numerical method) for arbitrary manifolds will be described, and numerical results will be presented for some example simulations.

  17. Charging machine

    DOEpatents

    Medlin, John B.

    1976-05-25

    A charging machine for loading fuel slugs into the process tubes of a nuclear reactor includes a tubular housing connected to the process tube, a charging trough connected to the other end of the tubular housing, a device for loading the charging trough with a group of fuel slugs, means for equalizing the coolant pressure in the charging trough with the pressure in the process tubes, means for pushing the group of fuel slugs into the process tube and a latch and a seal engaging the last object in the group of fuel slugs to prevent the fuel slugs from being ejected from the process tube when the pusher is removed and to prevent pressure liquid from entering the charging machine.

  18. Nanoporous membranes with electrochemically switchable, chemically stabilized ionic selectivity.

    PubMed

    Small, Leo J; Wheeler, David R; Spoerke, Erik D

    2015-10-28

    Nanopore size, shape, and surface charge all play important roles in regulating ionic transport through nanoporous membranes. The ability to control these parameters in situ provides a means to create ion transport systems tunable in real time. Here, we present a new strategy to address this challenge, utilizing three unique electrochemically switchable chemistries to manipulate the terminal functional group and control the resulting surface charge throughout ensembles of gold plated nanopores in ion-tracked polycarbonate membranes 3 cm(2) in area. We demonstrate the diazonium mediated surface functionalization with (1) nitrophenyl chemistry, (2) quinone chemistry, and (3) previously unreported trimethyl lock chemistry. Unlike other works, these chemistries are chemically stabilized, eliminating the need for a continuously applied gate voltage to maintain a given state and retain ionic selectivity. The effect of surface functionalization and nanopore geometry on selective ion transport through these functionalized membranes is characterized in aqueous solutions of sodium chloride at pH = 5.7. The nitrophenyl surface allows for ionic selectivity to be irreversibly switched in situ from cation-selective to anion-selective upon reduction to an aminophenyl surface. The quinone-terminated surface enables reversible changes between no ionic selectivity and a slight cationic selectivity. Alternatively, the trimethyl lock allows ionic selectivity to be reversibly switched by up to a factor of 8, approaching ideal selectivity, as a carboxylic acid group is electrochemically revealed or hidden. By varying the pore shape from cylindrical to conical, it is demonstrated that a controllable directionality can be imparted to the ionic selectivity. Combining control of nanopore geometry with stable, switchable chemistries facilitates superior control of molecular transport across the membrane, enabling tunable ion transport systems.

  19. Proton charge extensions

    NASA Astrophysics Data System (ADS)

    Stryker, Jesse R.; Miller, Gerald A.

    2016-01-01

    We examine how corrections to S -state energy levels En S in hydrogenic atoms due to the finite proton size are affected by moments of the proton charge distribution. The corrections to En S are computed moment by moment. The results demonstrate that the next-to-leading order term in the expansion is of order rp/aB times the size of the leading order term. Our analysis thus dispels any concern that the larger relative size of this term for muonic hydrogen versus electronic hydrogen might account for the current discrepancy of proton radius measurements extracted from the two systems. Furthermore, the next-to-leading order term in powers of rp/aB that we derive from a dipole proton form factor is proportional to , rather than , as would be expected from the scalar nature of the form factor. The dependence of the finite-size correction on and higher odd-power moments is shown to be a general result for any spherically symmetric proton charge distribution. A method for computing the moment expansion of the finite-size correction to arbitrary order is introduced and the results are tabulated for principal quantum numbers up to n =7 .

  20. In silico rational design of ionic liquids for the exfoliation and dispersion of boron nitride nanosheets.

    PubMed

    García, Gregorio; Atilhan, Mert; Aparicio, Santiago

    2016-01-14

    A requirement for exploiting most of the unique properties of boron-nitride (BN) nanosheets is their isolation from the bulk material. A rational design of task-specific ionic liquids (ILs) through DFT simulations is reported in this work. The applied computational protocol allowed the screening of large IL families, which was carried out bearing in mind the achievement of strong π-π stacking between the anions and BN nanosheets as well as a negative charge transfer from the anion to the surface. The selected ionic liquids yielded strong interaction energies with BN nanosheets and high charge transfer values, while the main features of the ionic liquid are not affected in the presence of nanosheets. DFT simulations provided a detailed picture of the interaction mechanism and useful structure-property relationships in the search of a new ionic liquid for BN exfoliation.

  1. The equilibrium structure of lithium salt solutions in ether-functionalized ammonium ionic liquids.

    PubMed

    Figueiredo, Pedro Henrique; Siqueira, Leonardo J A; Ribeiro, Mauro C C

    2012-10-11

    Molecular dynamics simulations have been performed for ionic liquids based on a ternary mixture of lithium and ammonium cations and a common anion, bis(trifluoromethylsulfonyl)imide, [Tf(2)N](-). We address structural changes resulting from adding Li(+) in ionic liquids with increasing length of an ether-functionalized chain in the ammonium cation. The calculation of static structure factors reveals the lithium effect on charge ordering and intermediate range order in comparison with the neat ionic liquids. The charge ordering is modified in the lithium solution because the coordination of [Tf(2)N](-) toward Li(+) is much stronger than ammonium cations. Intermediate range order is observed in neat ionic liquids based on ammonium cations with a long chain, but in the lithium solutions, there is also a nonhomogenous distribution of Li(+) cations. The presence of Li(+) enhances interactions between the ammonium cations due to correlations between the oxygen atom of the ether chain and the nitrogen atom of another ammonium cation.

  2. Atmospheric Pressure Method and Apparatus for Removal of Organic Matter with Atomic and Ionic Oxygen

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A. (Inventor); Rutledge, Sharon K. (Inventor)

    1996-01-01

    A gas stream containing ionic and atomic oxygen in inert gas is used to remove organic matter from a substrate. The gas stream is formed by flowing a mixture of gaseous oxygen in an inert gas such as helium at atmospheric pressure past a high voltage, current limited, direct current arc which contacts the gas mixture and forms the ionic and atomic oxygen. The arc is curved at the cathode end and the ionic oxygen formed by the arc nearer to the anode end of the arc is accelerated in a direction towards the cathode by virtue of its charge. The relatively high mass to charge ratio of the ionic oxygen enables at least some of it to escape the arc before contacting the cathode and it is directed onto the substrate. This is useful for cleaning delicate substrates such as fine and historically important paintings and delicate equipment and the like.

  3. Atmospheric Pressure Method and Apparatus for Removal of Organic Matter with Atomic and Ionic Oxygen

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A. (Inventor); Rutledge, Sharon K. (Inventor)

    1997-01-01

    A gas stream containing ionic and atomic oxygen in inert gas is used to remove organic matter from a substrate. The gas stream is formed by flowing a mixture of gaseous oxygen in an inert gas such as helium at atmospheric pressure past a high voltage, current limited, direct current arc which contacts the gas mixture and forms the ionic and atomic oxygen. The arc is curved at the cathode end and the ionic oxygen formed by the arc nearer to the anode end of the arc is accelerated in a direction towards the cathode by virtue of its charge. The relatively high mass to charge ratio of the ionic oxygen enables at least some of it to escape the arc before contacting the cathode and it is directed onto the substrate. This is useful for cleaning delicate substrates such as fine and historically important paintings and delicate equipment and the like.

  4. Structural investigation of room-temperature ionic liquids and high-temperature ionic melts using triplet correlation functions

    NASA Astrophysics Data System (ADS)

    Dhabal, Debdas; Gupta, Aditya; Kashyap, Hemant K.

    2017-03-01

    We use means of molecular dynamics simulation to understand the local structural arrangements in three trihexyltetradecylphosphonium (P6,6,6 ,14 +) based room-temperature ionic liquids (RTILs) by using triplet correlation functions (TCFs) along with pair correlation functions (PCFs) and X-ray scattering structure functions (S(q)s). The anions in these RTILs are either spherically symmetric but with different effective sizes (bromide (Br-) and tetrafluoroborate (BF4-)) or angular such as dicyanamide (DCA-). The simulated PCFs, S(q)s, and TCFs of the three RTILs have been compared with three high-temperature ionic melts (HTIMs); NaBr, NaCl, and NaF. In general, the pair correlation function gives angle-averaged probability as a function of inter-particle distance whereas the TCFs associated with equilateral and isosceles triangle configurations can be used to delineate angle-resolved information of liquids structure within nearest solvation shells. For the three ionic liquids studied, a very careful examination of co-ionic and counter-ionic TCFs associated with the equilateral triangular configuration within the nearest solvation shells of the ions reveals that co-ions (cat-cat-cat and an-an-an) favor close-packed local arrangement, but with lower probability for the DCA- RTIL. Co-ionic and counter-ionic TCFs obtained for HTIMs are found to be similar to that of RTILs with spherical anions. The TCFs associated with the isosceles triangle configuration signify that the ionic liquid with Br- anions tends to exhibit larger anion-cation-anion angle than that in the other two RTILs. Moreover, diffused counter-ionic angular correlations are observed in the DCA- system. We also observed angle-dependent charge ordering in all the three RTILs although its extent is enhanced for RTILs with spherical anions, very similar to what we find for NaBr, NaCl, and NaF melts. This study suggests that the presence of charge ordering is a generic feature of both the RTILs and HTIMs.

  5. Pyrrolidinium ionic liquid crystals.

    PubMed

    Goossens, Karel; Lava, Kathleen; Nockemann, Peter; Van Hecke, Kristof; Van Meervelt, Luc; Driesen, Kris; Görller-Walrand, Christiane; Binnemans, Koen; Cardinaels, Thomas

    2009-01-01

    N-alkyl-N-methylpyrrolidinium cations have been used for the design of ionic liquid crystals, including a new type of uranium-containing metallomesogen. Pyrrolidinium salts with bromide, bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, hexafluorophosphate, thiocyanate, tetrakis(2- thenoyltrifluoroacetonato)europate(III) and tetrabromouranyl counteranions were prepared. For the bromide salts and tetrabromouranyl compounds, the chain length of the alkyl group C(n)H(2n+1) was varied from eight to twenty carbon atoms (n = 8, 10-20). The compounds show rich mesomorphic behaviour: highly ordered smectic phases (the crystal smectic E phase and the uncommon crystal smectic T phase), smectic A phases, and hexagonal columnar phases were observed, depending on chain length and anion. This work gives better insight into the nature and formation of the crystal smectic T phase, and the molecular requirements for the appearance of this highly ordered phase. This uncommon tetragonal mesophase is thoroughly discussed on the basis of detailed powder X-ray diffraction experiments and in relation to the existing literature. Structural models are proposed for self-assembly of the molecules within the smectic layers. In addition, the photophysical properties of the compounds containing a metal complex anion were investigated. For the uranium-containing mesogens, luminescence can be induced by dissolving them in an ionic liquid matrix. The europium-containing compound shows intense red photoluminescence with high colour purity.

  6. Diff-invariant kinetic terms in arbitrary dimensions

    NASA Astrophysics Data System (ADS)

    Barbero G., J. Fernando; Villaseñor, Eduardo J.

    2002-06-01

    We study the physical content of quadratic diff-invariant Lagrangians in arbitrary dimensions by using covariant symplectic techniques. This paper extends previous results in dimension four. We discuss the difference between the even and odd dimensional cases.

  7. Component analysis of a mixed beam generated by vacuum electrospray of an ionic liquid

    SciTech Connect

    Fujiwara, Yukio; Saito, Naoaki; Nonaka, Hidehiko; Ichimura, Shingo

    2012-03-15

    Vacuum electrospray of a quaternary ammonium ionic liquid, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl) amide (DEME-TFSA), was investigated to develop a primary ion source for secondary ion mass spectrometry (SIMS). Since the ionic liquid contains many methyl and ethyl groups as well as protons, its beam is expected to efficiently produce protonated molecules for SIMS analysis of organic materials. Experimental results showed that the beam consisted of charged particles of m/z about 1000 and charged droplets of m/z > 10{sup 5}. The current components of both the charged particles and droplets changed with the applied voltage and the flow rate of the ionic liquid. With decreasing flow rate, the current component of the charged droplets increased, whereas that of the charged particles decreased. The m/z values of the charged droplets diminished with decreasing flow rate and increasing capillary voltage. In addition to masses and charge numbers, the numbers of the charged droplets and the charged particles were estimated.

  8. The coagulation rate of charged aerosols in ionized gases

    SciTech Connect

    Matsoukas, T.

    1997-03-15

    The charging of aerosols occurs by natural or artificial means in many systems, for example, in electrostatic precipitators and radioactive ionizers, in flames and glow discharges, in ambient air, and in outer space. The author obtains analytical expressions for the coagulation rate of aerosols in ionized gases taking into account the statistical distribution of the aerosol charge due to the random nature the charging process. Depending on the asymmetry of the ionic environment, the charge distribution may be bipolar (symmetric charging) or unipolar (highly asymmetric charging). In symmetric charging the attraction between opposite charges is almost exactly counterbalanced by repulsion between like charges and the net effect is a slight increase in the overall coagulation rate. In asymmetric charging all particles carry charges of the same polarity, interparticle interactions are repulsive, and the rate of coagulation decreases. However, the effect of the charge distribution in these systems is to increase the rate of coagulation above the rate that would be obtained if all particles carried the mean charge. This increase is substantial for larger particles in highly asymmetric ionic environments.

  9. Shockwave Absorption using Network-forming Ionic glass

    NASA Astrophysics Data System (ADS)

    Lee, Jaejun; Yang, Ke; Moore, Jeffrey; Sottos, Nancy; MURI SWED Collaboration

    2015-06-01

    Network-forming ionic glasses composed of di-ammonium cations and citrate anions exhibit significant potential for dissipation of shock wave energy. The long alkyl side chains in the di-ammonium cation form a soft matrix, while the negatively charged heads of anions segregate into hard nanophase domains. Similar to polyurea, which has microphase separation of soft and hard domains, we hypothesize that shock wave dissipation of the ionic glass occurs by bond breaking in the hard domains and/or pressure-induced phase transition. By employing size-tunable alkyl side chains in the cations, we examine the effect of the relative soft domain size on energy dissipation. A series of thin film (ca. 50 μm) ionic glass specimens are subjected to laser-induced compressive stress waves and the transmitted response measured interferometrically. Structural changes of the ionic glass due to shock wave impact are characterized by x-ray diffraction. When compared directly to polyurea films of identical thickness and geometry, the ionic glass showed superior shock-wave mitigating performance. ONR MURI program.

  10. Task-specific ionic liquid for solubilizing metal oxides.

    PubMed

    Nockemann, Peter; Thijs, Ben; Pittois, Stijn; Thoen, Jan; Glorieux, Christ; Van Hecke, Kristof; Van Meervelt, Luc; Kirchner, Barbara; Binnemans, Koen

    2006-10-26

    Protonated betaine bis(trifluoromethylsulfonyl)imide is an ionic liquid with the ability to dissolve large quantities of metal oxides. This metal-solubilizing power is selective. Soluble are oxides of the trivalent rare earths, uranium(VI) oxide, zinc(II) oxide, cadmium(II) oxide, mercury(II) oxide, nickel(II) oxide, copper(II) oxide, palladium(II) oxide, lead(II) oxide, manganese(II) oxide, and silver(I) oxide. Insoluble or very poorly soluble are iron(III), manganese(IV), and cobalt oxides, as well as aluminum oxide and silicon dioxide. The metals can be stripped from the ionic liquid by treatment of the ionic liquid with an acidic aqueous solution. After transfer of the metal ions to the aqueous phase, the ionic liquid can be recycled for reuse. Betainium bis(trifluoromethylsulfonyl)imide forms one phase with water at high temperatures, whereas phase separation occurs below 55.5 degrees C (temperature switch behavior). The mixtures of the ionic liquid with water also show a pH-dependent phase behavior: two phases occur at low pH, whereas one phase is present under neutral or alkaline conditions. The structures, the energetics, and the charge distribution of the betaine cation and the bis(trifluoromethylsulfonyl)imide anion, as well as the cation-anion pairs, were studied by density functional theory calculations.

  11. An imidazolium based ionic liquid electrolyte for lithium batteries

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Kwang; Matic, Aleksandar; Ahn, Jou-Hyeon; Jacobsson, Per

    An electrolyte for lithium batteries based on the ionic liquid 3-methy-1-propylimidazolium bis(trifluoromethysulfony)imide (PMIMTFSI) complexed with lithium bis(trifluoromethysulfony)imide (LiTFSI) at a molar ratio of 1:1 has been investigated. The electrolyte shows a high ionic conductivity (∼1.2 × 10 -3 S cm -1) at room temperature. Over the whole investigated temperature range the ionic conductivity is more than one order of magnitude higher than for an analogue electrolyte based on N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide (Py 14TFSI) complexed with LiTFSI and used here as a benchmark. Raman results indicate furthermore that the degree of lithium coordinated TFSI is slightly lower in the electrolyte based on PMIMTFSI and thus that the Li + charge carriers should be higher than in electrolytes based on Py 14TFSI. An ionic liquid gel electrolyte membrane was obtained by soaking a fibrous fully interconnected membrane, made of electrospun P(VdF-HFP), in the electrolyte. The gel electrolyte was cycled in Li/ionic liquid polymer electrolyte/Li cells over 15 days and in Li/LiFePO 4 cells demonstrating good interfacial stability and highly stable discharge capacities with a retention of >96% after 50 cycles (∼146 mAh g -1).

  12. Variation of ionic conductivity in a plastic-crystalline mixture.

    PubMed

    Reuter, D; Geiß, C; Lunkenheimer, P; Loidl, A

    2017-09-14

    Ionically conducting plastic crystals (PCs) are possible candidates for solid-state electrolytes in energy-storage devices. Interestingly, the admixture of larger molecules to the most prominent molecular PC electrolyte, succinonitrile, was shown to drastically enhance its ionic conductivity. Therefore, binary mixtures seem to be a promising way to tune the conductivity of such solid-state electrolytes. However, to elucidate the general mechanisms of ionic charge transport in plastic crystals and the influence of mixing, a much broader database is needed. In the present work, we investigate mixtures of two well-known plastic-crystalline systems, cyclohexanol and cyclooctanol, to which 1 mol. % of Li ions were added. Applying differential scanning calorimetry and dielectric spectroscopy, we present a thorough investigation of the phase behavior and the ionic and dipolar dynamics of this system. All mixtures reveal plastic-crystalline phases with corresponding orientational glass-transitions. Moreover, their conductivity seems to be dominated by the "revolving-door" mechanism, implying a close coupling between the ionic translational and the molecular reorientational dynamics of the surrounding plastic-crystalline matrix. In contrast to succinonitrile-based mixtures, there is no strong variation of this coupling with the mixing ratio.

  13. Correlating morphology to dc conductivity in polymerized ionic liquids

    NASA Astrophysics Data System (ADS)

    Iacob, Ciprian; Matusmoto, Atsushi; Inoue, Tadashi; Runt, James

    Polymerized ionic liquids (PILs) combine the attractive mechanical characteristics of polymers and unique physico-chemical properties of low molecular weight ionic liquids in the same material. PILs have shown remarkable advantages when employed in electrochemical devices such as dye-sensitized solar cells and lithium batteries, among others. Understanding their ionic transport mechanism is the key for designing highly conductive PILs. In the current study, the correlation between morphology and charge transport in two homologous series of PILs with systematic variation of the alkyl chain length and anions is investigated using broadband dielectric spectroscopy, rheology, differential scanning calorimetry and X-ray scattering. As the alkyl chain length increases, the backbone-to-backbone separation increases, and dc-conductivity consequently decreases. The cations dominate structural dynamics since they are attached to the polymer chains, while the anions are smaller and more mobile ionic species thereby controlling the ionic conductivity. Further interpretation of decoupling of dc conductivity from the segmental relaxation enabled the correlation between polymer morphology and dc conductivity. Supported by the National Science Foundation, Polymers Program.

  14. Variation of ionic conductivity in a plastic-crystalline mixture

    NASA Astrophysics Data System (ADS)

    Reuter, D.; Geiß, C.; Lunkenheimer, P.; Loidl, A.

    2017-09-01

    Ionically conducting plastic crystals (PCs) are possible candidates for solid-state electrolytes in energy-storage devices. Interestingly, the admixture of larger molecules to the most prominent molecular PC electrolyte, succinonitrile, was shown to drastically enhance its ionic conductivity. Therefore, binary mixtures seem to be a promising way to tune the conductivity of such solid-state electrolytes. However, to elucidate the general mechanisms of ionic charge transport in plastic crystals and the influence of mixing, a much broader database is needed. In the present work, we investigate mixtures of two well-known plastic-crystalline systems, cyclohexanol and cyclooctanol, to which 1 mol. % of Li ions were added. Applying differential scanning calorimetry and dielectric spectroscopy, we present a thorough investigation of the phase behavior and the ionic and dipolar dynamics of this system. All mixtures reveal plastic-crystalline phases with corresponding orientational glass-transitions. Moreover, their conductivity seems to be dominated by the "revolving-door" mechanism, implying a close coupling between the ionic translational and the molecular reorientational dynamics of the surrounding plastic-crystalline matrix. In contrast to succinonitrile-based mixtures, there is no strong variation of this coupling with the mixing ratio.

  15. Electrochemical and thermal properties of graphite electrodes with imidazolium- and piperidinium-based ionic liquids

    NASA Astrophysics Data System (ADS)

    Profatilova, Irina A.; Choi, Nam-Soon; Roh, Sae Weon; Kim, Sung Soo

    The electrochemical and thermal properties of graphite electrodes with electrolytes containing 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMITFSI) and N-methyl, N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (MPPpTFSI) ionic liquids are investigated. The ionic liquids undergo extensive reductive decomposition on a graphite electrode during the first charge. The effect of a fluoroethylene carbonate (FEC) additive on the reductive decomposition of the ionic liquids is examined by electrochemical, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis. Thermal reactions between a lithiated graphite electrode and an ionic liquid-containing electrolyte are investigated with differential scanning calorimetry (DSC). The introduction of an ionic liquid can effectively reduce the exothermic heat evolution from the thermal reactions between a lithiated graphite electrode and an electrolyte.

  16. Fast dynamic holographic recording based on conductive ionic metal-alkanoate liquid crystals and smectic glasses.

    PubMed

    Klimusheva, G; Bugaychuk, S; Garbovskiy, Yu; Kolesnyk, O; Mirnaya, T; Ishchenko, A

    2006-01-15

    Recordings of dynamic holograms with microsecond relaxation times under the action of nanosecond laser pulses are obtained in composites on the base of a novel class of liquid crystals (LCs) in ionic metal-alkanoates. Holographic parameters and relaxation characteristics are measured for doped lyotropic ionic LC, for sandwichlike cells (consisting of a dye layer and a layer of the lyotropic ionic LC), and for colored ionic smectic glasses. The structure of the materials is investigated by use of the small-angle x-ray technique. The mechanism of resonance nonlinearity in photosensitive centers and mechanisms of the grating erasure connected with a charge transport in the ionic conductive LC matrix are discussed.

  17. Symmetry Breaking in Chiral Ionic Liquids Evidenced by Vibrational Optical Activity.

    PubMed

    Oulevey, Patric; Luber, Sandra; Varnholt, Birte; Bürgi, Thomas

    2016-09-19

    Ionic liquids (ILs) are receiving increasing interest for their use in synthetic laboratories and industry. Being composed of charged entities, they show a complex and widely unexplored dynamic behavior. Chiral ionic liquids (CILs) have a high potential as solvents for use in asymmetric synthesis. Chiroptical methods, owing to their sensitivity towards molecular conformation, offer unique possibilities to study the structure of these chiral ionic liquids. Raman optical activity proved particularly useful to study ionic liquids composed of amino acids and the achiral 1-ethyl-3-methylimidazolium counterion. We could substantiate, supported by selected theoretical methods, that the achiral counterion adopts an overall chiral conformation in the presence of chiral amino acid ions. These findings suggest that in the design of chiral ionic liquids for asymmetric synthesis, the structure of the achiral counter ion also has to be carefully considered.

  18. Closed description of arbitrariness in resolving quantum master equation

    NASA Astrophysics Data System (ADS)

    Batalin, Igor A.; Lavrov, Peter M.

    2016-07-01

    In the most general case of the Delta exact operator valued generators constructed of an arbitrary Fermion operator, we present a closed solution for the transformed master action in terms of the original master action in the closed form of the corresponding path integral. We show in detail how that path integral reduces to the known result in the case of being the Delta exact generators constructed of an arbitrary Fermion function.

  19. RF arbitrary waveform generation using tunable planar lightwave circuits

    NASA Astrophysics Data System (ADS)

    Samadi, P.; Chen, L. R.; Callender, C.; Dumais, P.; Jacob, S.; Celo, D.

    2011-07-01

    We demonstrate photonically-assisted generation of RF arbitrary waveforms using planar lightwave circuits (PLCs) fabricated on silica-on-silicon. We exploit thermo-optic effects in silica in order to tune the response of the PLC and hence reconfigure the generated waveform. We demonstrate the generation of pulse trains at 40 GHz and 80 GHz with flat-top, Gaussian, and apodized profiles. These results demonstrate the potential for RF arbitrary waveform generation using chip-scale photonic solutions.

  20. Skin effect with arbitrary specularity in Maxwellian plasma

    SciTech Connect

    Latyshev, A. V.; Yushkanov, A. A.

    2010-11-15

    The problem of the skin effect with arbitrary specularity in Maxwellian plasma with specular-diffuse boundary conditions is solved. A new analytical method is developed that makes it possible to obtain a solution up to an arbitrary degree of accuracy. The method is based on the idea of symmetric continuation of not only the electric field, but also electron distribution function. The solution is obtained in a form of von Neumann series.

  1. Computation of Casimir interactions between arbitrary three-dimensional objects with arbitrary material properties

    SciTech Connect

    Reid, M. T. Homer; White, Jacob; Johnson, Steven G.

    2011-07-15

    We extend a recently introduced method for computing Casimir forces between arbitrarily shaped metallic objects [M. T. H. Reid et al., Phys. Rev. Lett. 103 040401 (2009)] to allow treatment of objects with arbitrary material properties, including imperfect conductors, dielectrics, and magnetic materials. Our original method considered electric currents on the surfaces of the interacting objects; the extended method considers both electric and magnetic surface current distributions, and obtains the Casimir energy of a configuration of objects in terms of the interactions of these effective surface currents. Using this new technique, we present the first predictions of Casimir interactions in several experimentally relevant geometries that would be difficult to treat with any existing method. In particular, we investigate Casimir interactions between dielectric nanodisks embedded in a dielectric fluid; we identify the threshold surface-surface separation at which finite-size effects become relevant, and we map the rotational energy landscape of bound nanoparticle diclusters.

  2. Synthesis, characterization and applications of ionic supramolecular assemblies

    NASA Astrophysics Data System (ADS)

    Lin, Xinrong

    Supramolecular ionic assemblies not only provide alternatives to conventional polymers, but also introduce unique and interesting functions for the design of "smart" polymeric assemblies for use in a number of fields due to their programmable and reversible properties. Research in the area has led to an understanding of the connection between molecular contributions and macroscopic properties, as well as a range of applications from material processing/manufacuturing to energy transfer and storage. To this end, we have developed a library of charged building blocks based on ionic liquids to create functional supramolecular ionic assemblies. The polymeric ionic assemblies prepared from a di-phosphonium and poly (acrylic acid) were first studied and found to have the potential to be utilized as "smart" materials due to their ability to reversibly respond to stimuli such as temperature and pressure. With the interest of elucidating the molecular contributions to the bulk macroscopic material properties, six supramolecular assemblies were sequentially characterized in terms of thermal, rheological and X-ray studies. The effect of side alkyl chain was found to dramatically change the material properties. A second type of supramolecular assembly was investigated based on a poly-phosphonium ionic liquid, which was complexed with a number of carboxylic acids. The material properties were easily manipulated from a sticky fiber to a brittle solid by changing the composition of the carboxylic acid. A crosslinked supramolecular assembly combining ionic interactions and weak covalent bonds, specifically disulfide bonds, was next designed and characterized. The network properties could be switched between "on and off" using mild conditions. The polymeric ionic networks and their building block ionic liquids are also of interest as safe electrolytes in energy storage devices due to their non-flammability, non-volatility, etc. We have identified one ionic liquid with superior

  3. Synthesis and properties of dicationic ionic liquids containing a siloxane structural moiety

    NASA Astrophysics Data System (ADS)

    Glukhov, L. M.; Krasovskiy, V. G.; Chernikova, E. A.; Kapustin, G. I.; Kustov, L. M.; Koroteev, A. A.

    2015-12-01

    Five new ionic liquids formed by doubly charged cations containing a siloxane moiety and bis(trifluoromethylsulfonyl) imide anion are synthesized and characterized. Their thermal stability is studied by means of TGA; melting points (glass transition temperatures) and densities are measured. The temperature dependences of kinematic viscosity of the obtained ionic liquids are presented along with their approximations by the Vogel-Tammann-Fulcher equation.

  4. Mesoscale studies of ionic closed membranes with polyhedral geometries

    DTIC Science & Technology

    2016-07-25

    the unusual shell shapes observed arise from the competition of ionic correla- tions with charge-regulation. We explain here the mechanism by which...structures are expected only in specific regions of the parameter space of the two-component system (R, YA, κAYB, κB). Shape competition between the elastic...are required. Therefore, faceting effects are expected to occur for a narrow range of shell sizes where the shape- competition is consistent with the

  5. Ionic Liquids in Electro-active Devices (ILED)

    DTIC Science & Technology

    2013-12-12

    charge location on structure at the nanoscale and the correlation of structure with membrane performance. Novel families of electromechanical transducers...Carl L. Willis, Karen I. Winey. Structure–property relationship in sulfonated pentablock copolymers, Journal of Membrane Science, (03 2012): 169. doi...aromatic and sulfonated ionomer for high elastic modulus ionic polymer membrane micro-actuators, Smart Materials and Structures, (05 2012): 0. doi

  6. Raman study of the pressure-induced neutral-to-ionic transition in tetrathiafulvalene chloranil

    NASA Astrophysics Data System (ADS)

    Hanfland, M.; Brillante, A.; Girlando, A.; Syassen, K.

    1988-07-01

    The pressure-induced phase transition from a neutral regular stack to an ionic dimerized stack (NR-ID) in the tetrathiafulvalene chloranil charge-transfer crystal has been studied by Raman spectroscopy. An accurate estimate of the change of ionicity during the phase transition is obtained from calculations of mode frequencies which are based on the trimer (NR phase) and dimer (ID phase) models of the electron-molecular-vibration interaction. The possibility of the formation of ionic dimers embedded in neutral chains as precursors of the phase change is discussed.

  7. Synthesis and Properties of Highly Dispersed Ionic Silica–Poly(ethylene oxide) Nanohybrids

    PubMed Central

    2013-01-01

    We report an ionic hybrid based on silica nanoparticles as the anion and amine-terminated poly(ethylene oxide) (PEO) as a cation. The charge on the nanoparticle anion is carried by the surface hydroxyls. SAXS and TEM reveal an exceptional degree of dispersion of the silica in the polymer and high degree of order in both thin film and bulk forms. In addition to better dispersion, the ionic hybrid shows improved flow characteristics compared to silica/PEO mixtures in which the ionic interactions are absent. PMID:23351113

  8. The moment sum-rules for ionic liquids at criticality

    NASA Astrophysics Data System (ADS)

    Fantoni, Riccardo

    2017-07-01

    We discuss the first three well known moment charge-charge sum-rules for a general ionic liquid. For the special symmetric case of the Restricted Primitive Model, Das, Kim, and Fisher (2011) has recently discovered, through Monte Carlo simulations, that the Stillinger-Lovett or second-moment sum-rule fails at criticality. We critically discuss a possible explanation for this unexpected behavior. On the other hand the fourth-moment sum-rule turns out to be able to account for the results of the simulations at criticality.

  9. CADDIS Volume 2. Sources, Stressors and Responses: Ionic Strength

    EPA Pesticide Factsheets

    Introduction to the ionic strength module, when to list ionic strength as a candidate cause, ways to measure ionic strength, simple and detailed conceptual diagrams for ionic strength, ionic strength module references and literature reviews.

  10. Engineered Ionic Gates for Ion Conduction Based on Sodium and Potassium Activated Nanochannels.

    PubMed

    Liu, Qian; Xiao, Kai; Wen, Liping; Lu, Heng; Liu, Yahui; Kong, Xiang-Yu; Xie, Ganhua; Zhang, Zhen; Bo, Zhishan; Jiang, Lei

    2015-09-23

    In living systems, ion conduction plays a major role in numerous cellular processes and can be controlled by biological ion channels in response to specific environmental stimuli. This article describes biomimetic ionic gates for ion conduction based on sodium and potassium activated nanochannels. The Na(+) activated ionic gate and K(+) activated ionic gate were developed by immobilizing the alkali metal cation-responsive functional molecules, 4'-aminobenzo-15-crown-5 and 4'-aminobenzo-18-crown-6, respectively, onto the conical polyimide nanochannels. When the ionic gate was in the presence of the specific alkali metal cation, positively charged complexes formed between the crown ether and the alkali metal cation. On the basis of the resulting changes in surface charge, wettability and effective pore size, the nanochannel can achieve reversible switching. The switching behaviors of the two complexes differed due to the differences in binding strength between the two complexes. The Na(+) activated ionic gate is able to open and close to control the ion conduction through the nanochannel, and the K(+) activated ionic gate enables selective cation and anion conduction through the nanochannel. The Na(+) and K(+) activated ionic gates show great promise for use in clinical medicine, biosensors and drug delivery based on their high sensitivity and selectivity of being activated, and good stability.

  11. Dielectric spectroscopy of ionic microgel suspensions.

    PubMed

    Mohanty, P S; Nöjd, S; Bergman, M J; Nägele, G; Arrese-Igor, S; Alegria, A; Roa, R; Schurtenberger, P; Dhont, J K G

    2016-12-06

    The determination of the net charge and size of microgel particles as a function of their concentration, as well as the degree of association of ions to the microgel backbone, has been pursued in earlier studies mainly by scattering and rheology. These methods suffer from contributions due to inter-particle interactions that interfere with the characterization of single-particle properties. Here we introduce dielectric spectroscopy as an alternative experimental method to characterize microgel systems. The advantage of dielectric spectroscopy over other experimental methods is that the polarization due to mobile charges within a microgel particle is only weakly affected by inter-particle interactions. Apart from electrode polarization effects, experimental spectra on PNIPAM-co-AA [poly(N-isopropylacrylamide-co-acrylic acid)] ionic microgel particles suspended in de-ionized water exhibit three well-separated relaxation modes, which are due to the polarization of the mobile charges within the microgel particles, the diffuse double layer around the particles, and the polymer backbone. Expressions for the full frequency dependence of the electrode-polarization contribution to the measured dielectric response are derived, and a theory is proposed for the polarization resulting from the mobile charges within the microgel. Relaxation of the diffuse double layer is modeled within the realm of a cell model. The net charge and the size of the microgel particles are found to be strongly varying with concentration. A very small value of the diffusion coefficient of ions within the microgel is found, due to a large degree of chemical association of protons to the polymer backbone.

  12. Arbitrary amplitude electro-acoustic solitary waves in an adiabatic dusty plasma

    NASA Astrophysics Data System (ADS)

    Tanjia, Fatema; Mamun, A. A.

    2008-12-01

    The properties of different types of electro-acoustic (namely ion-acoustic (IA), dust ion-acoustic (DIA), and dust-acoustic (DA)) solitary waves (SWs) in an adiabatic dusty plasma (containing negatively charged cold dust, adiabatic hot ions and inertia-less adiabatic hot electrons) are investigated by the pseudo-potential approach. The combined effects of the adiabatic electrons and ions, and negatively charged dust on the basic properties (critical Mach number, amplitude and width) of the arbitrary amplitude electro-acoustic SWs are systematically and explicitly examined. It is found that the combined effects of the adiabatic electrons and ions, and negatively charged dust significantly modify the basic properties (critical Mach number, amplitude and width) of the SWs. It is also found that due to the effect of the adiabaticity of electrons, the negative DIA SWs (which are found to exist in a dusty plasma containing isothermal electrons, cold ions and negatively charged static dust) disappear, i.e. due to the effect of adiabatic electrons, one cannot have negative DIA SWs for any possible set of dusty plasma parameters.

  13. Electrodeposition in Ionic Liquids.

    PubMed

    Zhang, Qinqin; Wang, Qian; Zhang, Suojiang; Lu, Xingmei; Zhang, Xiangping

    2016-02-03

    Due to their attractive physico-chemical properties, ionic liquids (ILs) are increasingly used as deposition electrolytes. This review summarizes recent advances in electrodeposition in ILs and focuses on its similarities and differences with that in aqueous solutions. The electrodeposition in ILs is divided into direct and template-assisted deposition. We detail the direct deposition of metals, alloys and semiconductors in five types of ILs, including halometallate ILs, air- and water-stable ILs, deep eutectic solvents (DESs), ILs with metal-containing cations, and protic ILs. Template-assisted deposition of nanostructures and macroporous structures in ILs is also presented. The effects of modulating factors such as deposition conditions (current density, current density mode, deposition time, temperature) and electrolyte components (cation, anion, metal salts, additives, water content) on the morphology, compositions, microstructures and properties of the prepared materials are highlighted.

  14. Ionic liquids as surfactants

    NASA Astrophysics Data System (ADS)

    Smirnova, N. A.; Safonova, E. A.

    2010-10-01

    Problems of self-assembling in systems containing ionic liquids (ILs) are discussed. Main attention is paid to micellization in aqueous solutions of dialkylimidazolium ILs and their mixtures with classical surfactants. Literature data are reviewed, the results obtained by the authors and co-workers are presented. Thermodynamic aspects of the studies and problems of molecular-thermodynamic modeling receive special emphasis. It is shown that the aggregation behavior of dialkylimidazolium ILs is close to that of alkyltrimethylammonium salts (cationic surfactants) though ILs have a higher ability to self-organize, especially as it concerns long-range ordering. Some aspects of ILs applications are outlined where their common features with classical surfactants and definite specificity are of value.

  15. Charge Spreading in Deep Eutectic Solvents.

    PubMed

    Zahn, Stefan; Kirchner, Barbara; Mollenhauer, Doreen

    2016-11-04

    Ab initio molecular dynamic simulations reveal significantly reduced ion charges in several choline-based deep eutectic solvents, which are cheap and eco-friendly alternatives to ionic liquids. Increasing hydrogen bond strength between the anion and the organic compound enhances charge spreading from the anion to the organic compound while the positive charge is stronger located at the cation. Nonetheless, the negative charge transferred from chloride to urea in choline chloride urea mixtures is negligible. Thus, it seems questionable if charge delocalization occurring through hydrogen bonding between the halide anion and the organic compound is responsible for the deep eutectic melting point. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Fluctuation of surface charge in membrane pores.

    PubMed Central

    Bashford, C Lindsay; Alder, Glenn M; Pasternak, Charles A

    2002-01-01

    Surface charge in track-etched polyethylene terephthalate (PET) membranes with narrow pores has been probed with a fluorescent cationic dye (3,3'-diethyloxacarbocyanine iodide (diO-C2-(3))) using confocal microscopy. Staining of negatively charged PET membranes with diO-C2-(3) is a useful measure of surface charge for the following reasons: 1) the dye inhibits K(+) currents through the pores and reduces their selectivity for cations; 2) it inhibits [3H]-choline+ transport and promotes 36Cl- transport across the membrane in a pH- and ionic-strength-dependent fashion; and 3) staining of pores by diO-C2-(3) is reduced by low pH and by the presence of divalent cations such as Ca2+ and Zn2+. Measurement of the time dependence of cyanine staining of pores shows fluctuations of fluorescence intensity that occur on the same time scale as do fluctuations of ionic current in such pores. These data support our earlier proposal that fluctuations in ionic current across pores in synthetic and biological membranes reflect fluctuations in the surface charge of the pore walls in addition to molecular changes in pore proteins. PMID:11916860

  17. Sensitivity of Superfolder GFP to Ionic Agents

    PubMed Central

    Stepanenko, Olesya V.; Stepanenko, Olga V.; Kuznetsova, Irina M.; Verkhusha, Vladislav V.; Turoverov, Konstantin K.

    2014-01-01

    Superfolder variant of the green fluorescent protein (sfGFP) became a favorite probe for examination of the unfolding–refolding processes of fluorescent proteins with beta-barrel structure owing to its reversible unfolding in comparison with other fluorescent proteins. Its benefit is the proper folding even in fusion constructions with poorly folded polypeptides. We noticed that guanidine thiocyanate affects not only the structure of protein but its chromophore directly. Therefore we studied the influence of ionic denaturants and salts including guanidine thiocyanate, guanidine hydrochloride, sodium chloride and sodium thiocyanate on spectral features of sfGFP. It was shown that moderate amounts of the studied agents do not disrupt sfGFP structure but provoke pronounced alteration of its spectral characteristics. Changes in absorption and CD spectra in visible spectral range indicate the specific binding of SCN− and Cl− anions in the sfGFP chromophore vicinity. The anion binding results in the redistribution of sfGFP molecules with neutral and anionic chromophores. This also hinders the proton transfer in the chromophore excited state, considerably decreasing the fluorescence intensity of sfGFP. Our results indicate that when ionic denaturants are used in the studies of fluorescent protein folding their effect on fluorophore charge state should be taken into account. PMID:25347822

  18. Applications of ionic liquids in electrochemical sensors.

    PubMed

    Wei, Di; Ivaska, Ari

    2008-01-28

    Ionic liquids (ILs) are molten salts with the melting point close to or below room temperature. They are composed of two asymmetrical ions of opposite charges that only loosely fit together (usually bulky organic cations and smaller anions). The good solvating properties, high conductivity, non-volatility, low toxicity, large electrochemical window (i.e. the electrochemical potential range over which the electrolyte is neither reduced nor oxidized on electrodes) and good electrochemical stability, make ILs suitable for many applications. Recently, novel ion selective sensors, gas sensors and biosensors based on ILs have been developed. IL gels were found to have good biocompatibility with enzymes, proteins and even living cells. Besides a brief discussion of the properties of ILs and their general applications based on these properties, this review focuses on the application of ILs in electroanalytical sensors.

  19. Ionic solutions of two-dimensional materials

    NASA Astrophysics Data System (ADS)

    Cullen, Patrick L.; Cox, Kathleen M.; Bin Subhan, Mohammed K.; Picco, Loren; Payton, Oliver D.; Buckley, David J.; Miller, Thomas S.; Hodge, Stephen A.; Skipper, Neal T.; Tileli, Vasiliki; Howard, Christopher A.

    2017-03-01

    Strategies for forming liquid dispersions of nanomaterials typically focus on retarding reaggregation, for example via surface modification, as opposed to promoting the thermodynamically driven dissolution common for molecule-sized species. Here we demonstrate the true dissolution of a wide range of important 2D nanomaterials by forming layered material salts that spontaneously dissolve in polar solvents yielding ionic solutions. The benign dissolution advantageously maintains the morphology of the starting material, is stable against reaggregation and can achieve solutions containing exclusively individualized monolayers. Importantly, the charge on the anionic nanosheet solutes is reversible, enables targeted deposition over large areas via electroplating and can initiate novel self-assembly upon drying. Our findings thus reveal a unique solution-like behaviour for 2D materials that enables their scalable production and controlled manipulation.

  20. Ionic composition of the earth's radiation belts

    NASA Technical Reports Server (NTRS)

    Spjeldvik, W. N.

    1983-01-01

    Several different ion species have been positively identified in the earth's radiation belts. Besides protons, there are substantial fluxes of helium, carbon and oxygen ions, and there are measurable quantities of even heavier ions. European, American and Soviet space experimenters have reported ion composition measurements over wide ranges of energies: at tens of keV (ring-current energies) and below, and at hundreds of keV and above. There is still a gap in the energy coverage from several tens to several hundreds of keV where little observational data are available. In this review emphasis is placed on the radiation belt ionic structure above 100 keV. Both quiet time conditions and geomagnetic storm periods are considered, and comparison of the available space observations is made with theoretical analysis of geomagnetically trapped ion spatial, energy and charge state distributions.