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Sample records for earth ion conduction

  1. Stability and oxide ion conductivity in rare-earth aluminium cuspidines

    SciTech Connect

    Martin-Sedeno, M.C.; Marrero-Lopez, D.; Losilla, E.R.; Bruque, S.; Nunez, P.; Aranda, M.A.G. . E-mail: g_aranda@uma.es

    2006-11-15

    RE{sub 4}(Al{sub 2-}{sub x}Ge{sub x}O{sub 7+}{sub x}{sub /2}{open_square}{sub 1-}{sub x}{sub /2})O{sub 2} (RE=Gd{sup 3+} and Nd{sup 3+}) oxy-cuspidine series have been prepared by ceramic method (RE=Gd{sup 3+}) and freeze-dried precursor method (RE=Nd{sup 3+}). The compositional ranges and the high temperature stability have been determined for both series. Gadolinium aluminium cuspidines are stable at very high temperatures but the analogous neodymium compounds are only stable below 1273 K. Joint Rietveld analyses of neutron powder diffraction (NPD) and laboratory X-ray powder diffraction (LXRPD) have been carried out for Nd{sub 4}(Al{sub 2}O{sub 7}{open_square}{sub 1})O{sub 2} and Nd{sub 4}(Al{sub 1.5}Ge{sub 0.5}O{sub 7.25}{open_square}{sub 0.75})O{sub 2} compositions. Furthermore, Rietveld refinement of synchrotron X-ray powder diffraction (SXRPD) data were carried out for Gd{sub 4}(Al{sub 1.0}Ge{sub 1.0}O{sub 7.5}{open_square}{sub 0.5})O{sub 2} composition. The refinements have confirmed the known structural features of the cuspidine framework. These cuspidines series are oxide ion conductors with negligible electronic contribution as determined from impedance spectroscopy at variable oxygen partial pressures. The enhancement in the overall oxide conductivity along the two oxy-cuspidine series is two orders of magnitude. Typical ionic conductivity values for doped samples are around 4x10{sup -5} S cm{sup -1} at 973 K. - Graphical abstract: The attached figure shows the changes in the oxygen distribution of oxy-cuspidines determined by neutron powder diffraction. These oxo-salts are e ion conductors with negligible electronic contribution.

  2. Oxygen ion conducting materials

    DOEpatents

    Vaughey, John; Krumpelt, Michael; Wang, Xiaoping; Carter, J. David

    2005-07-12

    An oxygen ion conducting ceramic oxide that has applications in industry including fuel cells, oxygen pumps, oxygen sensors, and separation membranes. The material is based on the idea that substituting a dopant into the host perovskite lattice of (La,Sr)MnO.sub.3 that prefers a coordination number lower than 6 will induce oxygen ion vacancies to form in the lattice. Because the oxygen ion conductivity of (La,Sr)MnO.sub.3 is low over a very large temperature range, the material exhibits a high overpotential when used. The inclusion of oxygen vacancies into the lattice by doping the material has been found to maintain the desirable properties of (La,Sr)MnO.sub.3, while significantly decreasing the experimentally observed overpotential.

  3. Oxygen ion conducting materials

    DOEpatents

    Carter, J. David; Wang, Xiaoping; Vaughey, John; Krumpelt, Michael

    2004-11-23

    An oxygen ion conducting ceramic oxide that has applications in industry including fuel cells, oxygen pumps, oxygen sensors, and separation membranes. The material is based on the idea that substituting a dopant into the host perovskite lattice of (La,Sr)MnO.sub.3 that prefers a coordination number lower than 6 will induce oxygen ion vacancies to form in the lattice. Because the oxygen ion conductivity of (La,Sr)MnO.sub.3 is low over a very large temperature range, the material exhibits a high overpotential when used. The inclusion of oxygen vacancies into the lattice by doping the material has been found to maintain the desirable properties of (La,Sr)MnO.sub.3, while significantly decreasing the experimentally observed overpotential.

  4. Oxygen ion conducting materials

    DOEpatents

    Vaughey, John; Krumpelt, Michael; Wang, Xiaoping; Carter, J. David

    2003-01-01

    An oxygen ion conducting ceramic oxide that has applications in industry including fuel cells, oxygen pumps, oxygen sensors, and separation membranes. The material is based on the idea that substituting a dopant into the host perovskite lattice of (La,Sr)MnO.sub.3 that prefers a coordination number lower than 6 will induce oxygen ion vacancies to form in the lattice. Because the oxygen ion conductivity of (La,Sr)MnO.sub.3 is low over a very large temperature range, the material exhibits a high overpotential when used. The inclusion of oxygen vacancies into the lattice by doping the material has been found to maintain the desirable properties of (La,Sr)MnO.sub.3, while significantly decreasing the experimentally observed overpotential.

  5. Lithium ion conducting electrolytes

    SciTech Connect

    Angell, C.A.; Liu, C.; Xu, K.; Skotheim, T.A.

    1999-10-05

    The present invention relates generally to highly conductive alkali-metal ion non-crystalline electrolyte systems, and more particularly to novel and unique molten (liquid), rubbery, and solid electrolyte systems which are especially well suited for use with high current density electrolytic cells such as primary and secondary batteries.

  6. Lithium ion conducting electrolytes

    DOEpatents

    Angell, Charles Austen; Liu, Changle; Xu, Kang; Skotheim, Terje A.

    1999-01-01

    The present invention relates generally to highly conductive alkali-metal ion non-crystalline electrolyte systems, and more particularly to novel and unique molten (liquid), rubbery, and solid electrolyte systems which are especially well suited for use with high current density electrolytic cells such as primary and secondary batteries.

  7. Ion-conducting membranes

    DOEpatents

    Masel, Richard L.; Chen, Qingmei; Liu, Zengcai; Kutz, Robert

    2016-06-21

    An ion conducting polymeric composition mixture comprises a copolymer of styrene and vinylbenzyl-R.sub.s. R.sub.s is selected from the group consisting of imidazoliums and pyridiniums. The composition contains 10%-90% by weight of vinylbenzyl-R.sub.s. The composition can further comprise a polyolefin comprising substituted polyolefins, a polymer comprising cyclic amine groups, a polymer comprising at least one of a phenylene group and a phenyl group, a polyamide, and/or the reaction product of a constituent having two carbon-carbon double bonds. The composition can be in the form of a membrane. In a preferred embodiment, the membrane is a Helper Membrane that increases the faradaic efficiency of an electrochemical cell into which the membrane is incorporated, and also allows product formation at lower voltages than in cells without the Helper Membrane.

  8. Lithium ion conducting electrolytes

    DOEpatents

    Angell, C. Austen; Liu, Changle

    1996-01-01

    A liquid, predominantly lithium-conducting, ionic electrolyte having exceptionally high conductivity at temperatures of 100.degree. C. or lower, including room temperature, and comprising the lithium salts selected from the group consisting of the thiocyanate, iodide, bromide, chloride, perchlorate, acetate, tetrafluoroborate, perfluoromethane sulfonate, perfluoromethane sulfonamide, tetrahaloaluminate, and heptahaloaluminate salts of lithium, with or without a magnesium-salt selected from the group consisting of the perchlorate and acetate salts of magnesium. Certain of the latter embodiments may also contain molecular additives from the group of acetonitrile (CH.sub.3 CN) succinnonitrile (CH.sub.2 CN).sub.2, and tetraglyme (CH.sub.3 --O--CH.sub.2 --CH.sub.2 --O--).sub.2 (or like solvents) solvated to a Mg.sup.+2 cation to lower the freezing point of the electrolyte below room temperature. Other particularly useful embodiments contain up to about 40, but preferably not more than about 25, mol percent of a long chain polyether polymer dissolved in the lithium salts to provide an elastic or rubbery solid electrolyte of high ambient temperature conductivity and exceptional 100.degree. C. conductivity. Another embodiment contains up to about but not more than 10 mol percent of a molecular solvent such as acetone.

  9. Lithium ion conducting electrolytes

    DOEpatents

    Angell, C.A.; Liu, C.

    1996-04-09

    A liquid, predominantly lithium-conducting, ionic electrolyte is described having exceptionally high conductivity at temperatures of 100 C or lower, including room temperature, and comprising the lithium salts selected from the group consisting of the thiocyanate, iodide, bromide, chloride, perchlorate, acetate, tetrafluoroborate, perfluoromethane sulfonate, perfluoromethane sulfonamide, tetrahaloaluminate, and heptahaloaluminate salts of lithium, with or without a magnesium-salt selected from the group consisting of the perchlorate and acetate salts of magnesium. Certain of the latter embodiments may also contain molecular additives from the group of acetonitrile (CH{sub 3}CN), succinnonitrile (CH{sub 2}CN){sub 2}, and tetraglyme (CH{sub 3}--O--CH{sub 2}--CH{sub 2}--O--){sub 2} (or like solvents) solvated to a Mg{sup +2} cation to lower the freezing point of the electrolyte below room temperature. Other particularly useful embodiments contain up to about 40, but preferably not more than about 25, mol percent of a long chain polyether polymer dissolved in the lithium salts to provide an elastic or rubbery solid electrolyte of high ambient temperature conductivity and exceptional 100 C conductivity. Another embodiment contains up to about but not more than 10 mol percent of a molecular solvent such as acetone. 2 figs.

  10. Thin film ion conducting coating

    DOEpatents

    Goldner, Ronald B.; Haas, Terry; Wong, Kwok-Keung; Seward, George

    1989-01-01

    Durable thin film ion conducting coatings are formed on a transparent glass substrate by the controlled deposition of the mixed oxides of lithium:tantalum or lithium:niobium. The coatings provide durable ion transport sources for thin film solid state storage batteries and electrochromic energy conservation devices.

  11. Instability of some divalent rare earth ions and photochromic effect

    NASA Astrophysics Data System (ADS)

    Egranov, A. V.; Sizova, T. Yu.; Shendrik, R. Yu.; Smirnova, N. A.

    2016-03-01

    It was shown that the divalent rare earth ions (La, Ce, Gd, Tb, Lu, and Y) in cubic sites in alkaline earth fluorides are unstable with respect to electron autodetachment since its d1(eg) ground state is located in the conduction band which is consistent with the general tendency of these ions in various compounds. The localization of doubly degenerate d1(eg) level in the conduction band creates a configuration instability around the divalent rare earth ion that leading to the formation of anion vacancy in the nearest neighborhood, as was reported in the previous paper [A. Egranov, T. Sizova, Configurational instability at the excited impurity ions in alkaline earth fluorites, J. Phys. Chem. Solids 74 (2013) 530-534]. Thus, the formation of the stable divalent ions as La, Ce, Gd, Tb, Lu, and Y (PC+ centers) in CaF2 and SrF2 crystals during x-ray irradiation occurs via the formation of charged anion vacancies near divalent ions (Re2+va), which lower the ground state of the divalent ion relative to the conductivity band. Photochromic effect occurs under thermally or optically stimulated electron transition from the divalent rare earth ion to the neighboring anion vacancy and reverse under ultraviolet light irradiation. It is shown that the optical absorption of the PC+ centers due to d → d and d → f transitions of the divalent rare-earth ion.

  12. Fluorine-ion conductivity of different technological forms of solid electrolytes R 1- y M y F3- y (LaF3 Type ) ( M = Ca, Sr, Ba; R Are Rare Earth Elements)

    NASA Astrophysics Data System (ADS)

    Sorokin, N. I.; Sobolev, B. P.

    2016-05-01

    We have investigated the conductivity of some representatives of different technological forms of fluoride-conducting solid electrolytes R 1- y M y F3- y ( M = Ca, Sr, Ba; R are rare earth elements) with an LaF3 structure: single crystals, cold- and hot-pressing ceramics based on a charge prepared in different ways (mechanochemical synthesis, solid-phase synthesis, and fragmentation of single crystals), polycrystalline alloys, etc. It is shown (by impedance spectroscopy), that different technological forms of identical chemical composition ( R, M, y) exhibit different electrical characteristics. The maximum conductivity is observed for the single-crystal form of R 1- y M y F3- y tysonite phases, which provides (in contrast to other technological forms) the formation of true volume ion-conducting characteristics.

  13. Lithium ion conducting ionic electrolytes

    DOEpatents

    Angell, C.A.; Xu, K.; Liu, C.

    1996-01-16

    A liquid, predominantly lithium-conducting, ionic electrolyte is described which has exceptionally high conductivity at temperatures of 100 C or lower, including room temperature. It comprises molten lithium salts or salt mixtures in which a small amount of an anionic polymer lithium salt is dissolved to stabilize the liquid against recrystallization. Further, a liquid ionic electrolyte which has been rubberized by addition of an extra proportion of anionic polymer, and which has good chemical and electrochemical stability, is described. This presents an attractive alternative to conventional salt-in-polymer electrolytes which are not cationic conductors. 4 figs.

  14. Lithium ion conducting ionic electrolytes

    DOEpatents

    Angell, C. Austen; Xu, Kang; Liu, Changle

    1996-01-01

    A liquid, predominantly lithium-conducting, ionic electrolyte is described which has exceptionally high conductivity at temperatures of 100.degree. C. or lower, including room temperature. It comprises molten lithium salts or salt mixtures in which a small amount of an anionic polymer lithium salt is dissolved to stabilize the liquid against recrystallization. Further, a liquid ionic electrolyte which has been rubberized by addition of an extra proportion of anionic polymer, and which has good chemical and electrochemical stability, is described. This presents an attractive alternative to conventional salt-in-polymer electrolytes which are not cationic conductors.

  15. VLF waves at satellite altitude to investigate Earth electrical conductivity

    NASA Astrophysics Data System (ADS)

    Leye, P. O.; Tarits, P.

    2015-03-01

    At and near the Earth surface, electromagnetic (EM) fields radiated from VLF transmitters are commonly used in geological exploration to determine the shallow Earth conductivity structure. Onboard satellites such as DEMETER, the electric and magnetic sensors detect the VLF signal in altitude. While we know for surface measurement that the VLF EM field recorded at some distance from the transmitter is a function of the ground conductivity, we do not know how this relationship changes when the field is measured at satellite altitude. Here we study the electromagnetic field radiated by a vertical electric dipole located on the Earth surface in the VLF range and measured at satellite altitude in a free space. We investigate the EM field as function of distance from the source, the height above the Earth surface, and the electrical conductivity of the Earth. The mathematical solution in altitude has more severe numerical complications than the well-known solutions at or near the Earth surface. We test most of the solutions developed for the latter case and found that direct summation was best at several hundred kilometers above the Earth. The numerical modeling of the EM field in altitude shows that the field remains a function of Earth conductivity. The dependence weakens with altitude and distance from the transmitter. It remains more important for the electric radial component.

  16. Effect of Ion Content on Conductivity and Morphology of Single-Ion Conducting Ionomers

    NASA Astrophysics Data System (ADS)

    Wang, Jing-Han Helen; Colby, Ralph H.

    2013-03-01

    Ionomers based on short poly(ethylene oxide) side chains and sodium sulfonated styrene are synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization, to systematically study the effect of ion content and counterion species on ionic conductivity. Glass transition temperature increases gradually as ions are incorporated at low ion content then sharply as the ion content reaches 1:4 ions to ether oxygen (EO) ratio. Dielectric relaxation spectroscopy is used to measure the conductivity, dielectric constant and segmental relaxations in these ionomers. The ionomer with 1:80 ions to EO ratio shows highest room temperature conductivity that results from the best combination of number density of simultaneously conducting ions and their mobility, assessed by an electrode polarization model. The micro-phase separation that is anticipated in the ionomers with higher ion contents is probed by x-ray scattering. Sodium counterions are mostly trapped in ionic aggregates while larger counterions, such as tetramethylammonium, exhibit higher conductivity and conducting ion concentration.

  17. Ion Channel Probes for Scanning Ion Conductance Microscopy

    PubMed Central

    2015-01-01

    The sensitivity and selectivity of ion channels provide an appealing opportunity for sensor development. Here, we describe ion channel probes (ICPs), which consist of multiple ion channels reconstituted into lipid bilayers suspended across the opening of perflourinated glass micropipets. When incorporated with a scanning ion conductance microscope (SICM), ICPs displayed a distance-dependent current response that depended on the number of ion channels in the membrane. With distance-dependent current as feedback, probes were translated laterally, to demonstrate the possibility of imaging with ICPs. The ICP platform yields several potential advantages for SICM that will enable exciting opportunities for incorporation of chemical information into imaging and for high-resolution imaging. PMID:25425190

  18. Tuning Ion Conducting Pathways Using Holographic Polymerization

    NASA Astrophysics Data System (ADS)

    Smith, Derrick; Li, Christopher; Dong, Bin; Bunning, Timothy

    2012-02-01

    While much research has demonstrated repeatable characteristics of electrolyte membranes, the fundamentals behind the interactions during ionic diffusion in solid polymer electrolyte membranes for battery applications are not well understood, specifically the role of nanostructures, which hold the key to improving performance of energy storage devices such as fuel cells and Lithium ion batteries. The challenges in fabricating highly controlled model systems are largely responsible for the interdependent ambiguities between nanostructures and the corresponding ion conducting behavior. In this work, Holographic Polymer Electrolyte Membranes (hPEM) volume gratings comprised of alternating layers of crosslinked polymer resin and lithium ion salt were fabricated using holographic polymerization with an average d-spacing of approximately 200 nm. These one-dimensional confinement structures were used to quantitatively study the anisotropic ionic conductivity between the directions of in-plane and normal to the layers, and the unique ion conducting behavior was correlated with nanoscale phase separation. These volume gratings also offer an exciting route to fabricate multifunctional gratings for optic and sensing applications.

  19. Ion conducting organic/inorganic hybrid polymers

    NASA Technical Reports Server (NTRS)

    Meador, Maryann B. (Inventor); Kinder, James D. (Inventor)

    2010-01-01

    This invention relates to a series of organic/inorganic hybrid polymers that are easy to fabricate into dimensionally stable films with good ion-conductivity over a wide range of temperatures for use in a variety of applications. The polymers are prepared by the reaction of amines, preferably diamines and mixtures thereof with monoamines with epoxy-functionalized alkoxysilanes. The products of the reaction are polymerized by hydrolysis of the alkoxysilane groups to produce an organic-containing silica network. Suitable functionality introduced into the amine and alkoxysilane groups produce solid polymeric membranes which conduct ions for use in fuel cells, high-performance solid state batteries, chemical sensors, electrochemical capacitors, electro-chromic windows or displays, analog memory devices and the like.

  20. Single Nanopore Investigations with Ion Conductance Microscopy

    PubMed Central

    Chen, Chiao-Chen; Zhou, Yi; Baker, Lane A.

    2011-01-01

    A three-electrode scanning ion conductance microscope (SICM) was used to investigate the local current-voltage properties of a single nanopore. In this experimental configuration, the response measured is a function of changes in the resistances involved in the pathways of ion migration. Single nanopore membranes utilized in this study were prepared with an epoxy painting procedure to isolate a single nanopore from a track-etch multi-pore membrane. Current-voltage responses measured with the SICM probe in the vicinity of a single nanopore were investigated in detail and agreed well with equivalent circuit models proposed in this study. With this modified SICM, the current-voltage responses characterized for the case of a single cylindrical pore and a single conical pore exhibit distinct conductance properties that originate from the geometry of nanopores. PMID:21923184

  1. Highly sensitive determination of hydrazine ion by ion-exclusion chromatography with ion-exchange enhancement of conductivity detection.

    PubMed

    Mori, Masanobu; Tanaka, Kazuhiko; Xu, Qun; Ikedo, Mikaru; Taoda, Hiroshi; Hu, Wenzhi

    2004-06-11

    An ion-exclusion chromatography method with ion-exchange enhancement of conductivity was developed for the selective separation and sensitive determination of hydrazine ion from alkali/alkaline earth metal cations and ammonium ion. Hydrazine ion was separated by ion-exclusion/penetration effect from other cations on a weakly basic anion-exchange column in the OH- form (TSKgel DEAE-5PW). Moreover, two different ion-exchange resin columns were inserted between the separating column and conductimetric detector in order to improve the sensitivity of hydrazine ion. The first enhancement column packed with a strongly basic anion-exchange resin in the SO4(2-) form (TSKgel SAX) for hydrazine ion can convert from N2H5OH to (N2H5)2SO4. Moreover, the second enhancement column packed with a strongly acidic cation-change resin in the H+ form (TSKgel SCX) can convert to H2SO4. As a result, the sensitivity of hydrazine ion using two conductivity enhancement columns could be 26.8-times greater than using the separating column alone. This method was effectiveness also for the enhancement of ammonium ion (6.1-times) and sodium ion (1.2-times). The calibration graph of hydrazine ion detected as H2SO4 was linear over the concentration range of 0.001-100 ppm (r2 = 0.9988). The detection limit of hydrazine ion in this system was 0.64 ppb. Therefore, hydrazine ion in real boiler water sample could be accurately determined, avoiding the interference of other cations. PMID:15250415

  2. Conductance of Ion Channels - Theory vs. Experiment

    NASA Technical Reports Server (NTRS)

    Pohorille, Andrew; Wilson, Michael; Mijajlovic, Milan

    2013-01-01

    Transmembrane ion channels mediate a number of essential physiological processes in a cell ranging from regulating osmotic pressure to transmission of neural signals. Kinetics and selectivity of ion transport is of critical importance to a cell and, not surprisingly, it is a subject of numerous experimental and theoretical studies. In this presentation we will analyze in detail computer simulations of two simple channels from fungi - antiamoebin and trichotoxin. Each of these channels is made of an alpha-helical bundle of small, nongenomically synthesized peptides containing a number of rare amino acids and exhibits strong antimicrobial activity. We will focus on calculating ionic conductance defined as the ratio of ionic current through the channel to applied voltage. From molecular dynamics simulations, conductance can be calculated in at least two ways, each involving different approximations. Specifically, the current, given as the number of charges transferred through the channel per unit of time, can be obtained from the number of events in which ions cross the channel during the simulation. This method works well for large currents (high conductance values and/or applied voltages). If the number of crossing events is small, reliable estimates of current are difficult to achieve. Alternatively, conductance can be estimated assuming that ion transport can be well approximated as diffusion in the external potential given by the free energy profile. Then, the current can be calculated by solving the one-dimensional diffusion equation in this external potential and applied voltage (the generalized Nernst-Planck equation). To do so three ingredients are needed: the free energy profile, the position-dependent diffusion coefficient and the diffusive flux of ions into the channel. All these quantities can be obtained from molecular dynamics simulations. An important advantage of this method is that it can be used equally well to estimating large and small currents

  3. Cuprous Ion Conducting Montmorillonite- Polypyrrole Nanocomposites

    NASA Astrophysics Data System (ADS)

    Krishantha, D. M. M.; Rajapakse, R. M. G.; Tennakoon, D. T. B.; Bandara, W. M. A. T.; Thilakarathna, P. N. L.

    2006-06-01

    Solid state polymer-Silicate nanocomposite based on Polypyrrole-Cu+-montmorilonite were prepared and electrical properties were investigated. In this preparation, Na-montmorillonite (Na+-MMT) was purified by repeated washing with distilled water and the intergallery cations were exchanged for Cu(II). The cupric ions exchanged-MMT(Cu(II)-- MMT) was again exposed to pyrrole in aqueous acidic solution to yield polypyrrole-Cu+-MMT nanocomposite. DC polarization test and AC impedance measurement reveal that the materials are mixed conductors. The ionic conductivity is due to the motion of cuprous ions which is facilitated by microstructure of polypyrrrole present in the intergalleries. An electrochemical cell was fabricated using the materials which can be represented by Cu(s)/ Cu+-PPY-MMT/Cu2SO4 (s)/Na2SO4(S)-Na2S2O8(s)/ and gave a 1.00 V. The cell is rechargeable.

  4. Conductivity and Correlations in Fe at Earth Core Conditions

    NASA Astrophysics Data System (ADS)

    Cohen, R. E.; Zhang, Peng; Haule, Kristjan

    We have computed electrical conductivity in iron at Earth core conditions self-consistently within many-body theory using DFT/DMFT. We find that electron correlations are important even in the generation of Earth's magnetic field. Earth's magnetic field was believed to arise from thermal convection of molten iron alloy in Earth's outer core, but density functional theory (DFT) calculations suggested that the conductivity of iron is too high to support thermal convection, so that new geodynamo models were being developed. The DFT computations for resistivity were based on the scattering of electrons off of atomic vibrations, or electron-phonon (e-p) scattering. We applied self-consistent density functional theory plus dynamical mean-field theory (DFT+DMFT) to iron and found that at high temperatures electron-electron (e-e) scattering is comparable to the e-p scattering, bringing theory into agreement with experiments and solving the transport problem in Earth's core, consistent with the conventional thermal geodynamo [Peng, Cohen, and Haule, Nature 517, 605, 2015]. How electron correlations change with pressure, and how this affects material properties, will be discussed. This work is supported by the US National Science Foundation and the ERC Advanced grant ToMCaT.

  5. Ion-Conducting Organic/Inorganic Polymers

    NASA Technical Reports Server (NTRS)

    Kinder, James D.; Meador, Mary Ann B.

    2007-01-01

    Ion-conducting polymers that are hybrids of organic and inorganic moieties and that are suitable for forming into solid-electrolyte membranes have been invented in an effort to improve upon the polymeric materials that have been used previously for such membranes. Examples of the prior materials include perfluorosulfonic acid-based formulations, polybenzimidazoles, sulfonated polyetherketone, sulfonated naphthalenic polyimides, and polyethylene oxide (PEO)-based formulations. Relative to the prior materials, the polymers of the present invention offer greater dimensional stability, greater ease of formation into mechanically resilient films, and acceptably high ionic conductivities over wider temperature ranges. Devices in which films made of these ion-conducting organic/inorganic polymers could be used include fuel cells, lithium batteries, chemical sensors, electrochemical capacitors, electrochromic windows and display devices, and analog memory devices. The synthesis of a polymer of this type (see Figure 1) starts with a reaction between an epoxide-functionalized alkoxysilane and a diamine. The product of this reaction is polymerized by hydrolysis and condensation of the alkoxysilane group, producing a molecular network that contains both organic and inorganic (silica) links. The silica in the network contributes to the ionic conductivity and to the desired thermal and mechanical properties. Examples of other diamines that have been used in the reaction sequence of Figure 1 are shown in Figure 2. One can use any of these diamines or any combination of them in proportions chosen to impart desired properties to the finished product. Alternatively or in addition, one could similarly vary the functionality of the alkoxysilane to obtain desired properties. The variety of available alkoxysilanes and diamines thus affords flexibility to optimize the organic/inorganic polymer for a given application.

  6. Persistent ion beam induced conductivity in zinc oxide nanowires

    SciTech Connect

    Johannes, Andreas; Niepelt, Raphael; Gnauck, Martin; Ronning, Carsten

    2011-12-19

    We report persistently increased conduction in ZnO nanowires irradiated by ion beam with various ion energies and species. This effect is shown to be related to the already known persistent photo conduction in ZnO and dubbed persistent ion beam induced conduction. Both effects show similar excitation efficiency, decay rates, and chemical sensitivity. Persistent ion beam induced conduction will potentially allow countable (i.e., single dopant) implantation in ZnO nanostructures and other materials showing persistent photo conduction.

  7. Thermal Expansion and Thermal Conductivity of Rare Earth Silicates

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Lee, Kang N.; Bansal, Narottam P.

    2006-01-01

    Rare earth silicates are considered promising candidate materials for environmental barrier coatings applications at elevated temperature for ceramic matrix composites. High temperature thermophysical properties are of great importance for coating system design and development. In this study, the thermal expansion and thermal conductivity of hot-pressed rare earth silicate materials were characterized at temperatures up to 1400 C. The effects of specimen porosity, composition and microstructure on the properties were also investigated. The materials processing and testing issues affecting the measurements will also be discussed.

  8. Scanning Ion Conductance Microscopy of Live Keratinocytes

    NASA Astrophysics Data System (ADS)

    Hegde, V.; Mason, A.; Saliev, T.; Smith, F. J. D.; McLean, W. H. I.; Campbell, P. A.

    2012-07-01

    Scanning ion conductance microscopy (SICM) is perhaps the least well known technique from the scanning probe microscopy (SPM) family of instruments. As with its more familiar counterpart, atomic force microscopy (AFM), the technique provides high-resolution topographic imaging, with the caveat that target structures must be immersed in a conducting solution so that a controllable ion current may be utilised as the basis for feedback. In operation, this non-contact characteristic of SICM makes it ideal for the study of delicate structures, such as live cells. Moreover, the intrinsic architecture of the instrument, incorporating as it does, a scanned micropipette, lends itself to combination approaches with complementary techniques such as patch-clamp electrophysiology: SICM therefore boasts the capability for both structural and functional imaging. For the present observations, an ICnano S system (Ionscope Ltd., Melbourn, UK) operating in 'hopping mode' was used, with the objective of assessing the instrument's utility for imaging live keratinocytes under physiological buffers. In scans employing cultured HaCaT cells (spontaneously immortalised, human keratinocytes), we compared the qualitative differences of live cells imaged with SICM and AFM, and also with their respective counterparts after chemical fixation in 4% paraformaldehyde. Characteristic surface microvilli were particularly prominent in live cell imaging by SICM. Moreover, time lapse SICM imaging on live cells revealed that changes in the pattern of microvilli could be tracked over time. By comparison, AFM imaging on live cells, even at very low contact forces (

  9. Angular Approach Scanning Ion Conductance Microscopy.

    PubMed

    Shevchuk, Andrew; Tokar, Sergiy; Gopal, Sahana; Sanchez-Alonso, Jose L; Tarasov, Andrei I; Vélez-Ortega, A Catalina; Chiappini, Ciro; Rorsman, Patrik; Stevens, Molly M; Gorelik, Julia; Frolenkov, Gregory I; Klenerman, David; Korchev, Yuri E

    2016-05-24

    Scanning ion conductance microscopy (SICM) is a super-resolution live imaging technique that uses a glass nanopipette as an imaging probe to produce three-dimensional (3D) images of cell surface. SICM can be used to analyze cell morphology at nanoscale, follow membrane dynamics, precisely position an imaging nanopipette close to a structure of interest, and use it to obtain ion channel recordings or locally apply stimuli or drugs. Practical implementations of these SICM advantages, however, are often complicated due to the limitations of currently available SICM systems that inherited their design from other scanning probe microscopes in which the scan assembly is placed right above the specimen. Such arrangement makes the setting of optimal illumination necessary for phase contrast or the use of high magnification upright optics difficult. Here, we describe the designs that allow mounting SICM scan head on a standard patch-clamp micromanipulator and imaging the sample at an adjustable approach angle. This angle could be as shallow as the approach angle of a patch-clamp pipette between a water immersion objective and the specimen. Using this angular approach SICM, we obtained topographical images of cells grown on nontransparent nanoneedle arrays, of islets of Langerhans, and of hippocampal neurons under upright optical microscope. We also imaged previously inaccessible areas of cells such as the side surfaces of the hair cell stereocilia and the intercalated disks of isolated cardiac myocytes, and performed targeted patch-clamp recordings from the latter. Thus, our new, to our knowledge, angular approach SICM allows imaging of living cells on nontransparent substrates and a seamless integration with most patch-clamp setups on either inverted or upright microscopes, which would facilitate research in cell biophysics and physiology. PMID:27224490

  10. Solid lithium ion conducting electrolytes and methods of preparation

    SciTech Connect

    Narula, Chaitanya K.; Daniel, Claus

    2015-11-19

    A composition comprised of nanoparticles of lithium ion conducting solid oxide material, wherein the solid oxide material is comprised of lithium ions, and at least one type of metal ion selected from pentavalent metal ions and trivalent lanthanide metal ions. Solution methods useful for synthesizing these solid oxide materials, as well as precursor solutions and components thereof, are also described. The solid oxide materials are incorporated as electrolytes into lithium ion batteries.

  11. Solid lithium ion conducting electrolytes and methods of preparation

    DOEpatents

    Narula, Chaitanya K; Daniel, Claus

    2013-05-28

    A composition comprised of nanoparticles of lithium ion conducting solid oxide material, wherein the solid oxide material is comprised of lithium ions, and at least one type of metal ion selected from pentavalent metal ions and trivalent lanthanide metal ions. Solution methods useful for synthesizing these solid oxide materials, as well as precursor solutions and components thereof, are also described. The solid oxide materials are incorporated as electrolytes into lithium ion batteries.

  12. Testing Conducted for Lithium-Ion Cell and Battery Verification

    NASA Technical Reports Server (NTRS)

    Reid, Concha M.; Miller, Thomas B.; Manzo, Michelle A.

    2004-01-01

    The NASA Glenn Research Center has been conducting in-house testing in support of NASA's Lithium-Ion Cell Verification Test Program, which is evaluating the performance of lithium-ion cells and batteries for NASA mission operations. The test program is supported by NASA's Office of Aerospace Technology under the NASA Aerospace Flight Battery Systems Program, which serves to bridge the gap between the development of technology advances and the realization of these advances into mission applications. During fiscal year 2003, much of the in-house testing effort focused on the evaluation of a flight battery originally intended for use on the Mars Surveyor Program 2001 Lander. Results of this testing will be compared with the results for similar batteries being tested at the Jet Propulsion Laboratory, the Air Force Research Laboratory, and the Naval Research Laboratory. Ultimately, this work will be used to validate lithium-ion battery technology for future space missions. The Mars Surveyor Program 2001 Lander battery was characterized at several different voltages and temperatures before life-cycle testing was begun. During characterization, the battery displayed excellent capacity and efficiency characteristics across a range of temperatures and charge/discharge conditions. Currently, the battery is undergoing lifecycle testing at 0 C and 40-percent depth of discharge under low-Earth-orbit (LEO) conditions.

  13. Scanning ion conductance microscopy of living cells.

    PubMed Central

    Korchev, Y E; Bashford, C L; Milovanovic, M; Vodyanoy, I; Lab, M J

    1997-01-01

    Currently there is a great interest in using scanning probe microscopy to study living cells. However, in most cases the contact the probe makes with the soft surface of the cell deforms or damages it. Here we report a scanning ion conductance microscope specially developed for imaging living cells. A key feature of the instrument is its scanning algorithm, which maintains the working distance between the probe and the sample such that they do not make direct physical contact with each other. Numerical simulation of the probe/sample interaction, which closely matches the experimental observations, provides the optimum working distance. The microscope scans highly convoluted surface structures without damaging them and reveals the true topography of cell surfaces. The images resemble those produced by scanning electron microscopy, with the significant difference that the cells remain viable and active. The instrument can monitor small-scale dynamics of cell surfaces as well as whole-cell movement. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 PMID:9251784

  14. Energetics of ion conduction through the K+ channel

    NASA Astrophysics Data System (ADS)

    Bernèche, Simon; Roux, Benoît

    2001-11-01

    K+ channels are transmembrane proteins that are essential for the transmission of nerve impulses. The ability of these proteins to conduct K+ ions at levels near the limit of diffusion is traditionally described in terms of concerted mechanisms in which ion-channel attraction and ion-ion repulsion have compensating effects, as several ions are moving simultaneously in single file through the narrow pore. The efficiency of such a mechanism, however, relies on a delicate energy balance-the strong ion-channel attraction must be perfectly counterbalanced by the electrostatic ion-ion repulsion. To elucidate the mechanism of ion conduction at the atomic level, we performed molecular dynamics free energy simulations on the basis of the X-ray structure of the KcsA K+ channel. Here we find that ion conduction involves transitions between two main states, with two and three K+ ions occupying the selectivity filter, respectively; this process is reminiscent of the `knock-on' mechanism proposed by Hodgkin and Keynes in 1955. The largest free energy barrier is on the order of 2-3kcalmol-1, implying that the process of ion conduction is limited by diffusion. Ion-ion repulsion, although essential for rapid conduction, is shown to act only at very short distances. The calculations show also that the rapidly conducting pore is selective.

  15. Engineering closed optical transitions in rare-earth ion crystals

    NASA Astrophysics Data System (ADS)

    Bartholomew, John G.; Ahlefeldt, Rose L.; Sellars, Matthew J.

    2016-01-01

    We propose a protocol to preserve the spin state of rare-earth ions when they are optically cycled. This technique uses large magnetic fields to increase the probability of an optically excited ion returning to its initial spin state. This Zeeman enhanced cyclicity is shown to be applicable to non-Kramers ions in various crystals irrespective of the site symmetry. The specific example of Pr3 +:Y2SiO5 is investigated to demonstrate that the protocol can create closed optical transitions even where the point group symmetry of the site is C1. In this example, the predicted cyclicity exceeds 104. This high level of cyclicity extends the usefulness of rare-earth ion crystals for applications in quantum and classical information processing. We explore the use of this technique to enable single-ion, spin-state optical readout and the creation of ensemble-based spectral features that are robust against optical cycling.

  16. Observations of molecular ions in the earth's magnetosphere

    NASA Technical Reports Server (NTRS)

    Craven, P. D.; Chappell, C. R.; Kakani, L.; Olsen, R. C.

    1985-01-01

    The retarding ion mass spectrometer on Dynamics Explorer 1 operating over the polar cap during a large magnetic storm has measured fluxes of up to 10 to the 6th ions/sq cm s of the molecular ions N2(+), NO(+), and O2(+). These ions were measured beginning low in the satellite orbit (1.1 earth radii) and extending to about 3 earth radii geocentric altitude. Near perigee, the ions have a rammed distribution indicating a cold Maxwellian plasma (1000-2000 K). The molecular ions gradually shift to a field-aligned distribution at the higher alitudes. An upward flow of 5-10 km/s is found in these field-aligned measurements. The density of the molecular ions is on the order of 2/cu cm at all altitudes, and the energy of the ions generally increases as the satellite moves sunward across the southern polar cap. Kinetic energies of at least 20 eV were found at 2.5 earth-radii geocentric distance.

  17. Radiation from lightning return strokes over a finitely conducting earth

    NASA Technical Reports Server (NTRS)

    Le Vine, D. M.; Gesell, L.; Kao, Michael

    1986-01-01

    The effects of the conductivity of the earth on radiation from lightning return strokes are examined theoretically using a piecewise linear transmission line model for the return stroke. First, calculations are made of the electric field radiated during the return stroke, and then this electric field is used to compute the response of conventional AM radio receivers and electric field change systems during the return stroke. The calculations apply to the entire transient waveform (they are not restricted to the initial portions of the return stroke) and yield fast field changes and RF radiation in agreement with measurements made during real lightning. This research was motivated by measurements indicating that a time delay exists between the time of arrival of the fast electric field change and the RF radiation from first return strokes. The time delay is on the order of 20 microsec for frequencies in the HF-UHF range for lightning in Florida. The time delay is obtained theoretically in this paper. It occurs when both the effects of attenuation due to conductivity of the earth, and the finite velocity of propagation of the current pulse up the return stroke channel, are taken into account in the model.

  18. Thermal conductivity of earth materials at high temperatures.

    NASA Technical Reports Server (NTRS)

    Schatz, J. F.; Simmons, G.

    1972-01-01

    The total thermal conductivity (lattice plus radiative) of several important earth materials is measured in the temperature range from 500 to 1900 K. A new technique is used in which a CO2 laser generates a low-frequency temperature wave at one face of a small disk-shaped sample, and an infrared detector views the opposite face to detect the phase of the emerging radiation. Phase data at several frequencies yield the simultaneous determination of the thermal diffusivity and the mean extinction coefficient of the material. The lattice, radiative, and total thermal conductivities are then calculated. Results for single-crystal and polycrystalline forsterite-rich olivines and an enstatite indicate that, even in relatively pure large-grained material, the radiative conductivity does not increase rapidly with temperature. The predicted maximum total thermal conductivity at a depth of 400 km in an olivine mantle is 0.020 cal/cm/sec/deg C, which is less than twice the surface value.

  19. Energetic ion acceleration during magnetic reconnection in the Earth's magnetotail

    NASA Astrophysics Data System (ADS)

    Imada, Shinsuke; Hirai, Mariko; Hoshino, Masahiro

    2015-12-01

    In this paper, we present a comprehensive study of the energetic ion acceleration during magnetic reconnection in the Earth's magnetosphere using the Geotail data. A clear example of the energetic ion acceleration up to 1 MeV around an X-type neutral line is shown. We find that the energetic ions are localized at far downstream of reconnection outflow. The time variation of energetic ion and electron is almost the same. We observe ˜100 keV ions over the entire observation period. We study ten events in which the Geotail satellite observed in the vicinity of diffusion region in order to understand the reconnection characteristics that determine the energetic ion acceleration efficiency. We find that the reconnection electric field, total amount of reduced magnetic energy, reconnection rate, satellite location in the Earth's magnetosphere (both X GSM and Y GSM) show high correlation with energetic ion acceleration efficiency. Also, ion temperature, electron temperature, ion/electron temperature ratio, current sheet thickness, and electric field normal to the neutral sheet show low correlation. We do not find any correlation with absolute value of outflow velocity and current density parallel to magnetic field. The energetic ion acceleration efficiency is well correlated with large-scale parameters (e.g., total amount of reduced magnetic energy and satellite location), whereas the energetic electron acceleration efficiency is correlated with small-scale parameters (e.g., current sheet thickness and electric field normal to the neutral sheet). We conclude that the spatial size of magnetic reconnection is important for energetic ion acceleration in the Earth's magnetotail.

  20. Earth's polar cap ionization patches lead to ion upflow

    NASA Astrophysics Data System (ADS)

    Zhang, Q. H.; Zong, Q.; Lockwood, M. M.; Liang, J.; Zhang, B.; Moen, J. I.; Zhang, S.; Zhang, Y.; Ruohoniemi, J. M.; Thomas, E. G.; Liu, R.; Dunlop, M. W.; Yang, H. G.; Hu, H.; Liu, Y.; Lester, M.

    2014-12-01

    The Earth constantly losses matter through ions escaping from the polar ionosphere. This makes the ionosphere as an important source of plasma for the magnetosphere and could modulate atmospheric isotope abundances on geological timescales, depending on what fraction of the upflowing ions subsequently return to the ionosphere and what fraction are ejected into interplanetary space. It has been proposed that the magnetosphere is dynamically modulated by the presence of the ionospheric ions, particularly heavy ions O+, during magnetic substorms and storms. The origin and formation mechanism of ionospheric ion upflow is, however, poorly understood, particularly under disturbed space weather conditions. We report simultaneous direct observations of ion upflow and a patch of ionization at the center of the polar cap region during a geomagnetic storm. Our observations indicate enhanced fluxes of upwelling O+ ions originate from the patch and were accelerated by the enhanced ambipolar electric field. This enhancement is caused by soft electron precipitations. Polar cap patches therefore provide an important source of upwelling ions for accelerations mechanisms at greater altitudes which can eject the ions. These observations give new insight into the processes of ionosphere-magnetosphere coupling and the potential loss of terrestrial water dissociation products into space which, although extremely slow in the case of Earth, may be significant for other planets and moons.

  1. Thermal and electrical conductivity of iron at Earth's core conditions.

    PubMed

    Pozzo, Monica; Davies, Chris; Gubbins, David; Alfè, Dario

    2012-05-17

    The Earth acts as a gigantic heat engine driven by the decay of radiogenic isotopes and slow cooling, which gives rise to plate tectonics, volcanoes and mountain building. Another key product is the geomagnetic field, generated in the liquid iron core by a dynamo running on heat released by cooling and freezing (as the solid inner core grows), and on chemical convection (due to light elements expelled from the liquid on freezing). The power supplied to the geodynamo, measured by the heat flux across the core-mantle boundary (CMB), places constraints on Earth's evolution. Estimates of CMB heat flux depend on properties of iron mixtures under the extreme pressure and temperature conditions in the core, most critically on the thermal and electrical conductivities. These quantities remain poorly known because of inherent experimental and theoretical difficulties. Here we use density functional theory to compute these conductivities in liquid iron mixtures at core conditions from first principles--unlike previous estimates, which relied on extrapolations. The mixtures of iron, oxygen, sulphur and silicon are taken from earlier work and fit the seismologically determined core density and inner-core boundary density jump. We find both conductivities to be two to three times higher than estimates in current use. The changes are so large that core thermal histories and power requirements need to be reassessed. New estimates indicate that the adiabatic heat flux is 15 to 16 terawatts at the CMB, higher than present estimates of CMB heat flux based on mantle convection; the top of the core must be thermally stratified and any convection in the upper core must be driven by chemical convection against the adverse thermal buoyancy or lateral variations in CMB heat flow. Power for the geodynamo is greatly restricted, and future models of mantle evolution will need to incorporate a high CMB heat flux and explain the recent formation of the inner core. PMID:22495307

  2. Water in the Earth's Mantle: Mineral-specific IR Absorption Coefficients and Radiative Thermal Conductivities

    NASA Astrophysics Data System (ADS)

    Thomas, S. M.

    2015-12-01

    Minor and trace element chemistry, phase relations, rheology, thermal structure and the role of volatiles and their abundance in the deep Earth mantle are still far from fully explored, but fundamental to understanding the processes involved in Earth formation and evolution. Theory and high pressure experiments imply a significant water storage capacity of nominally anhydrous minerals, such as majoritic garnet, olivine, wadsleyite and ringwoodite, composing the Earth's upper mantle and transition zone to a depth of 660 km. Studying the effect of water incorporation on chemical and physical mineral properties is of importance, because the presence of trace amounts of water, incorporated as OH through charge-coupled chemical substitutions into such nominally anhydrous high-pressure silicates, notably influences phase relations, melting behavior, conductivity, elasticity, viscosity and rheology. Knowledge of absolute water contents in nominally anhydrous minerals is essential for modeling the Earth's interior water cycle. One of the most common and sensitive tools for water quantification is IR spectroscopy for which mineral-specific absorption coefficients are required. Such calibration constants can be derived from hydrogen concentrations determined by independent techniques, such as secondary ion mass spectrometry, Raman spectroscopy or proton-proton(pp)-scattering. Here, analytical advances and mineral-specific IR absorption coefficients for the quantification of H2O in major phases of the Earth's mantle will be discussed. Furthermore, new data from optical absorption measurements in resistively heated diamond-anvil cells at high pressures and temperatures up to 1000 K will be presented. Experiments were performed on synthetic single-crystals of olivine, ringwoodite, majoritic garnet, and Al-bearing phase D with varying iron, aluminum and OH contents to calculate radiative thermal conductivities and study their contribution to heat transfer in the Earth's interior

  3. Evaluation of the Influence of Beam Ions Exhausted from Ion Thrusters on Earth's Environment and Communication

    NASA Astrophysics Data System (ADS)

    Yamagiwa, Yoshiki; Kumatani, Yasuhiro; Miyamoto, Shigehiro; Otsu, Hirotaka

    The influence of exhausted beam ions from ion thrusters on Earth's environment and communication was analyzed by the detailed modeling of the exhausted ions' and electrons' motion and the energy exchange process between the exhausted ions and the circumferential particles. The analytical results showed that the density distribution of plasma components near the earth will change locally by the energy input of exhausted ions trapped by the geomagnetic field if the large scale operation of ion thrusters is performed, but its influence on earth's environment will be small compared with that by the natural phenomena such a magnetic storm. However, the influence on GPS communication will be large and the electrical charge of spacecraft will be progressed.

  4. Cooling history of Earth's core with high thermal conductivity

    NASA Astrophysics Data System (ADS)

    Davies, Christopher J.

    2015-10-01

    Thermal evolution models of Earth's core constrain the power available to the geodynamo process that generates the geomagnetic field, the evolution of the solid inner core and the thermal history of the overlying mantle. Recent upward revision of the thermal conductivity of liquid iron mixtures by a factor of 2-3 has drastically reduced the estimated power available to generate the present-day geomagnetic field. Moreover, this high conductivity increases the amount of heat that is conducted out of the core down the adiabatic gradient, bringing it into line with the highest estimates of present-day core-mantle boundary heat flow. These issues raise problems with the standard scenario of core cooling in which the core has remained completely well-mixed and relatively cool for the past 3.5 Ga. This paper presents cooling histories for Earth's core spanning the last 3.5 Ga to constrain the thermodynamic conditions corresponding to marginal dynamo evolution, i.e. where the ohmic dissipation remains just positive over time. The radial variation of core properties is represented by polynomials, which gives good agreement with radial profiles derived from seismological and mineralogical data and allows the governing energy and entropy equations to be solved analytically. Time-dependent evolution of liquid and solid light element concentrations, the melting curve, and gravitational energy are calculated for an Fe-O-S-Si model of core chemistry. A suite of cooling histories are presented by varying the inner core boundary density jump, thermal conductivity and amount of radiogenic heat production in the core. All models where the core remains superadiabatic predict an inner core age of ≲ 600Myr , about two times younger than estimates based on old (lower) thermal conductivity estimates, and core temperatures that exceed present estimates of the lower mantle solidus prior to the last 0.5-1.5 Ga. Allowing the top of the core to become strongly subadiabatic in recent times

  5. Ion Concentration- and Voltage-Dependent Push and Pull Mechanisms of Potassium Channel Ion Conduction

    PubMed Central

    Kasahara, Kota; Shirota, Matsuyuki; Kinoshita, Kengo

    2016-01-01

    The mechanism of ion conduction by potassium channels is one of the central issues in physiology. In particular, it is still unclear how the ion concentration and the membrane voltage drive ion conduction. We have investigated the dynamics of the ion conduction processes in the Kv1.2 pore domain, by molecular dynamics (MD) simulations with several different voltages and ion concentrations. By focusing on the detailed ion movements through the pore including selectivity filter (SF) and cavity, we found two major conduction mechanisms, called the III-IV-III and III-II-III mechanisms, and the balance between the ion concentration and the voltage determines the mechanism preference. In the III-IV-III mechanism, the outermost ion in the pore is pushed out by a new ion coming from the intracellular fluid, and four-ion states were transiently observed. In the III-II-III mechanism, the outermost ion is pulled out first, without pushing by incoming ions. Increases in the ion concentration and voltage accelerated ion conductions, but their mechanisms were different. The increase in the ion concentrations facilitated the III-IV-III conductions, while the higher voltages increased the III-II-III conductions, indicating that the pore domain of potassium channels permeates ions by using two different driving forces: a push by intracellular ions and a pull by voltage. PMID:26950215

  6. Ion Concentration- and Voltage-Dependent Push and Pull Mechanisms of Potassium Channel Ion Conduction.

    PubMed

    Kasahara, Kota; Shirota, Matsuyuki; Kinoshita, Kengo

    2016-01-01

    The mechanism of ion conduction by potassium channels is one of the central issues in physiology. In particular, it is still unclear how the ion concentration and the membrane voltage drive ion conduction. We have investigated the dynamics of the ion conduction processes in the Kv1.2 pore domain, by molecular dynamics (MD) simulations with several different voltages and ion concentrations. By focusing on the detailed ion movements through the pore including selectivity filter (SF) and cavity, we found two major conduction mechanisms, called the III-IV-III and III-II-III mechanisms, and the balance between the ion concentration and the voltage determines the mechanism preference. In the III-IV-III mechanism, the outermost ion in the pore is pushed out by a new ion coming from the intracellular fluid, and four-ion states were transiently observed. In the III-II-III mechanism, the outermost ion is pulled out first, without pushing by incoming ions. Increases in the ion concentration and voltage accelerated ion conductions, but their mechanisms were different. The increase in the ion concentrations facilitated the III-IV-III conductions, while the higher voltages increased the III-II-III conductions, indicating that the pore domain of potassium channels permeates ions by using two different driving forces: a push by intracellular ions and a pull by voltage. PMID:26950215

  7. Cold ions in the hot plasma sheet of Earth's magnetotail.

    PubMed

    Seki, Kanako; Hirahara, Masafumi; Hoshino, Masahiro; Terasawa, Toshio; Elphic, Richard C; Saito, Yoshifumi; Mukai, Toshifumi; Hayakawa, Hajime; Kojima, Hirotsugu; Matsumoto, Hiroshi

    2003-04-10

    Most visible matter in the Universe exists as plasma. How this plasma is heated, and especially how the initial non-equilibrium plasma distributions relax to thermal equilibrium (as predicted by Maxwell-Boltzman statistics), is a fundamental question in studies of astrophysical and laboratory plasmas. Astrophysical plasmas are often so tenuous that binary collisions can be ignored, and it is not clear how thermal equilibrium develops for these 'collisionless' plasmas. One example of a collisionless plasma is the Earth's plasma sheet, where thermalized hot plasma with ion temperatures of about 5 x 10(7) K has been observed. Here we report direct observations of a plasma distribution function during a solar eclipse, revealing cold ions in the Earth's plasma sheet in coexistence with thermalized hot ions. This cold component cannot be detected by plasma sensors on satellites that are positively charged in sunlight, but our observations in the Earth's shadow show that the density of the cold ions is comparable to that of hot ions. This high density is difficult to explain within existing theories, as it requires a mechanism that permits half of the source plasma to remain cold upon entry into the hot turbulent plasma sheet. PMID:12686993

  8. Iterative electromagnetic Born inversion applied to earth conductivity imaging

    SciTech Connect

    Alumbaugh, D.L.

    1993-08-01

    This thesis investigates the use of a fast imaging technique to deduce the spatial conductivity distribution in the earth from low frequency (< 1 MHz), cross well electromagnetic (EM) measurements. The theory embodied in this work is the extension of previous strategies and is based on the Born series approximation to solve both the forward and inverse problem. Nonlinear integral equations are employed to derive the series expansion which accounts for the scattered magnetic fields that are generated by inhomogeneities embedded in either a homogenous or a layered earth. A sinusoidally oscillating, vertically oriented magnetic dipole is employed as a source, and it is assumed that the scattering bodies are azimuthally symmetric about the source dipole axis. The use of this model geometry reduces the 3-D vector problem to a more manageable 2-D scalar form. The validity of the cross well EM method is tested by applying the imaging scheme to two sets of field data. Images of the data collected at the Devine, Texas test site show excellent correlation with the well logs. Unfortunately there is a drift error present in the data that limits the accuracy of the results. A more complete set of data collected at the Richmond field station in Richmond, California demonstrates that cross well EM can be successfully employed to monitor the position of an injected mass of salt water. Both the data and the resulting images clearly indicate the plume migrates toward the north-northwest. The plausibility of these conclusions is verified by applying the imaging code to synthetic data generated by a 3-D sheet model.

  9. Defect association mediated ionic conductivity of rare earth doped nanoceria: Dependency on ionic radius

    NASA Astrophysics Data System (ADS)

    Anirban, Sk.; Sinha, A.; Bandyopadhyay, S.; Dutta, A.

    2016-05-01

    Rare earth doped nanoceria Ce0.9RE0.1O1.95 (RE = Pr, Nd, Eu and Gd) were prepared through citrate auto-ignition method. The single phase cubic fluorite structure with space group Fm3 ¯m of the compositions were confirmed from Rietveld analysis of XRD data. The particle size of the compositions were in the range 49.77 nm to 66.20 nm. An ionic radius dependent lattice parameter variation was found. The DC conductivity of each composition was evaluated using Random Barrier Model. The conductivity decreased and activation energy increased with increasing ionic radius from Gd to Pr doping due to the size mismatch with host ions and formation of stable defect associate. The formation of different defect associates and their correlation with ionic conductivity has been discussed.

  10. Diffuse ions produced by electromagnetic ion beam instabilities. [in earth's bow shock

    NASA Technical Reports Server (NTRS)

    Winske, D.; Leroy, M. M.

    1984-01-01

    The evolution of the electromagnetic ion beam instability driven by the reflected ion component backstreaming away from the earth's bow shock into the foreshock region is studied by means of computer simulation. The linear and quasi-linear stages of the instability are found to be in good agreement with known results for the resonant mode propagating parallel to the beam along the magnetic field and with theory developed in this paper for the nonresonant mode, which propagates antiparallel to the beam direction. The quasi-linear stage, which produces large amplitude delta B approximately B, sinusoidal transverse waves and 'intermediate' ion distributions, is terminated by a nonlinear phase in which strongly nonlinear, compressive waves and 'diffuse' ion distributions are produced. Additional processes by which the diffuse ions are accelerated to observed high energies are not addressed. The results are discussed in terms of the ion distributions and hydromagnetic waves observed in the foreshock of the earth's bow shock and of interplanetary shocks.

  11. Spherical harmonic analysis of earth's conductive heat flow

    NASA Astrophysics Data System (ADS)

    Hamza, V. M.; Cardoso, R. R.; Ponte Neto, C. F.

    2008-04-01

    A reappraisal of the international heat flow database has been carried out and the corrected data set was employed in spherical harmonic analysis of the conductive component of global heat flow. Procedures used prior to harmonic analysis include analysis of the heat flow data and determination of representative mean values for a set of discretized area elements of the surface of the earth. Estimated heat flow values were assigned to area elements for which experimental data are not available. However, no corrections were made to account for the hypothetical effects of regional-scale convection heat transfer in areas of oceanic crust. New sets of coefficients for 12° spherical harmonic expansion were calculated on the basis of the revised and homogenized data set. Maps derived on the basis of these coefficients reveal several new features in the global heat flow distribution. The magnitudes of heat flow anomalies of the ocean ridge segments are found to have mean values of less than 150 mW/m2. Also, the mean global heat flow values for the raw and binned data are found to fall in the range of 56-67 mW/m2, down by nearly 25% compared to the previous estimate of 1993, but similar to earlier assessments based on raw data alone. To improve the spatial resolution of the heat flow anomalies, the spherical harmonic expansions have been extended to higher degrees. Maps derived using coefficients for 36° harmonic expansion have allowed identification of new features in regional heat flow fields of several oceanic and continental segments. For example, lateral extensions of heat flow anomalies of active spreading centers have been outlined with better resolution than was possible in earlier studies. Also, the characteristics of heat flow variations in oceanic crust away from ridge systems are found to be typical of conductive cooling of the lithosphere, there being little need to invoke the hypothesis of unconfined hydrothermal circulation on regional scales. Calculations

  12. Oxygen ion-conducting dense ceramic

    DOEpatents

    Balachandran, Uthamalingam; Kleefisch, Mark S.; Kobylinski, Thaddeus P.; Morissette, Sherry L.; Pei, Shiyou

    1998-01-01

    Preparation, structure, and properties of mixed metal oxide compositions and their uses are described. Mixed metal oxide compositions of the invention have stratified crystalline structure identifiable by means of powder X-ray diffraction patterns. In the form of dense ceramic membranes, the present compositions demonstrate an ability to separate oxygen selectively from a gaseous mixture containing oxygen and one or more other volatile components by means of ionic conductivities.

  13. Origins of energetic ions in the Earth's magnetosheath

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This final report describes activities under NASA contract NAS5-31213 to Lockheed Missiles and Space Company. The report covers the entire contract period from 8 May 1991 to 7 Jun. 1994. This is a contract under the NASA Guest Investigator Program for the analysis and interpretation of the combined scientific data from the Hot Plasma Composition Experiment (HPCE) and the Charge Energy Mass (CHEM) spectrometer on the AMPTE/Charge Composition Explorer (CCE) spacecraft. These combined data sets have been used to survey the energetic ion environment in the earth's magnetosheath to determine the origins and relative strengths of the energetic ion populations found there.

  14. Effect of volcanic debris on stratospheric ion conductivity

    NASA Technical Reports Server (NTRS)

    Somayajulu, Y. V.; Garg, S. C.; John, T.; Zalpuri, K. S.

    1989-01-01

    The reduction is reported of stratospheric ion conductivities in the altitude range of 20 to 27 km attributable to the aerosols injected into the stratosphere by the eruption of volcano Nevado Del Ruiz on November 13, 1985. Three balloon experiments were conducted from Hyderabad, India (17.5 N, 78.6 E) carrying a Langmuir probe payload for measuring stratospheric ion conductivities. The first flight took place about 9 months before the volcanic eruption, the second 3 weeks after the eruption and the third about a year later. Lidar observations from Japan, Hawaii and Europe reported detection of aerosol layers in the 18 to 25 km altitude range attributable to the Nevado Del Ruiz volcanic eruption. A comparison of the conductivity profiles shows that the reduction of ion conductivities is: 57.3 percent at 20 km and 31 percent at 25 km. A year after the eruption, conductivities at all heights tended to recover.

  15. Direct measurement of ion mobility in a conducting polymer.

    PubMed

    Stavrinidou, Eleni; Leleux, Pierre; Rajaona, Harizo; Khodagholy, Dion; Rivnay, Jonathan; Lindau, Manfred; Sanaur, Sébastien; Malliaras, George G

    2013-08-27

    Using planar junctions between the conducting polymer PEDOT:PSS and various electrolytes, it is possible to inject common ions and directly observe their transit through the film. The 1D geometry of the experiment allows a straightforward estimate of the ion drift mobilities. PMID:23784809

  16. Thin film method of conducting lithium-ions

    DOEpatents

    Zhang, J.G.; Benson, D.K.; Tracy, C.E.

    1998-11-10

    The present invention relates to the composition of a solid lithium-ion electrolyte based on the Li{sub 2}O-CeO{sub 2}-SiO{sub 2} system having good transparent characteristics and high ion conductivity suitable for uses in lithium batteries, electrochromic devices and other electrochemical applications. 12 figs.

  17. Thin film method of conducting lithium-ions

    DOEpatents

    Zhang, Ji-Guang; Benson, David K.; Tracy, C. Edwin

    1998-11-10

    The present invention relates to the composition of a solid lithium-ion electrolyte based on the Li.sub.2 O--CeO.sub.2 --SiO.sub.2 system having good transparent characteristics and high ion conductivity suitable for uses in lithium batteries, electrochromic devices and other electrochemical applications.

  18. Oxygen ion-conducting dense ceramic

    DOEpatents

    Balachandran, Uthamalingam; Kleefisch, Mark S.; Kobylinski, Thaddeus P.; Morissette, Sherry L.; Pei, Shiyou

    1996-01-01

    Preparation, structure, and properties of mixed metal oxide compositions containing at least strontium, cobalt, iron and oxygen are described. The crystalline mixed metal oxide compositions of this invention have, for example, structure represented by Sr.sub..alpha. (Fe.sub.1-x Co.sub.x).sub..alpha.+.beta. O.sub..delta. where x is a number in a range from 0.01 to about 1, .alpha. is a number in a range from about 1 to about 4, .beta. is a number in a range upward from 0 to about 20, and .delta. is a number which renders the compound charge neutral, and wherein the composition has a non-perovskite structure. Use of the mixed metal oxides in dense ceramic membranes which exhibit oxygen ionic conductivity and selective oxygen separation, are described as well as their use in separation of oxygen from an oxygen-containing gaseous mixture.

  19. Oxygen ion-conducting dense ceramic

    DOEpatents

    Balachandran, Uthamalingam; Kleefisch, Mark S.; Kobylinski, Thaddeus P.; Morissette, Sherry L.; Pei, Shiyou

    1997-01-01

    Preparation, structure, and properties of mixed metal oxide compositions containing at least strontium, cobalt, iron and oxygen are described. The crystalline mixed metal oxide compositions of this invention have, for example, structure represented by Sr.sub..alpha. (Fe.sub.1-x Co.sub.x).sub..alpha.+.beta. O.sub..delta. where x is a number in a range from 0.01 to about 1, .alpha. is a number in a range from about 1 to about 4, .beta. is a number in a range upward from 0 to about 20, and .delta. is a number which renders the compound charge neutral, and wherein the composition has a non-perovskite structure. Use of the mixed metal oxides in dense ceramic membranes which exhibit oxygen ionic conductivity and selective oxygen separation, are described as well as their use in separation of oxygen from an oxygen-containing gaseous mixture.

  20. Ion-/proton-conducting apparatus and method

    DOEpatents

    Yates, Matthew; Liu, Dongxia

    2011-05-17

    A c-axis-oriented HAP thin film synthesized by seeded growth on a palladium hydrogen membrane substrate. An exemplary synthetic process includes electrochemical seeding on the substrate, and secondary and tertiary hydrothermal treatments under conditions that favor growth along c-axes and a-axes in sequence. By adjusting corresponding synthetic conditions, an HAP this film can be grown to a controllable thickness with a dense coverage on the underlying substrate. The thin films have relatively high proton conductivity under hydrogen atmosphere and high temperature conditions. The c-axis oriented films may be integrated into fuel cells for application in the intermediate temperature range of 200-600.degree. C. The electrochemical-hydrothermal deposition technique may be applied to create other oriented crystal materials having optimized properties, useful for separations and catalysis as well as electronic and electrochemical applications, electrochemical membrane reactors, and in chemical sensors.

  1. Ion/proton-conducting apparatus and method

    DOEpatents

    Yates, Matthew; Xue, Wei

    2014-12-23

    A c-axis-oriented HAP thin film synthesized by seeded growth on a palladium hydrogen membrane substrate. An exemplary synthetic process includes electrochemical seeding on the substrate, and secondary and tertiary hydrothermal treatments under conditions that favor growth along c-axes and a-axes in sequence. By adjusting corresponding synthetic conditions, an HAP this film can be grown to a controllable thickness with a dense coverage on the underlying substrate. The thin films have relatively high proton conductivity under hydrogen atmosphere and high temperature conditions. The c-axis oriented films may be integrated into fuel cells for application in the intermediate temperature range of 200-600.degree. C. The electrochemical-hydrothermal deposition technique may be applied to create other oriented crystal materials having optimized properties, useful for separations and catalysis as well as electronic and electrochemical applications, electrochemical membrane reactors, and in chemical sensors. Additional high-density and gas-tight HAP film compositions may be deposited using a two-step deposition method that includes an electrochemical deposition method followed by a hydrothermal deposition method. The two-step method uses a single hydrothermal deposition solution composition. The method may be used to deposit HAP films including but not limited to at least doped HAP films, and more particularly including carbonated HAP films. In addition, the high-density and gas-tight HAP films may be used in proton exchange membrane fuel cells.

  2. Radiated and conducted EMI from a 30-cm ion thruster

    NASA Technical Reports Server (NTRS)

    Whittlesey, A. C.; Peer, W.

    1981-01-01

    In order to properly assess the interaction of a spacecraft with the EMI environment produced by an ion thruster, the EMI environment was characterized. Therefore, radiated and conducted emissions were measured from a 30-cm mercury ion thruster. The ion thruster beam current varied from zero to 2.0 amperes and the emissions were measured from 5 KHz to 200 MHz. Several different types of antennas were used to obtain the measurements. The various measurements that were made included: magnetic field due to neutralizer/beam current loop; radiated electric fields of thruster and plume; and conducted emissions on arc discharge, neutralizer keeper and magnetic baffle lines.

  3. Ion acoustic solitons in Earth's upward current region

    SciTech Connect

    Main, D. S.; Scholz, C.; Newman, D. L.; Ergun, R. E.

    2012-07-15

    The formation and evolution of ion acoustic solitons in Earth's auroral upward current region are studied using one- and two-dimensional (2D) electrostatic particle-in-cell simulations. The one-dimensional simulations are confined to processes that occur in the auroral cavity and include four plasma populations: hot electrons, H{sup +} and O{sup +} anti-earthward ion beams, and a hot H{sup +} background population. Ion acoustic solitons are found to form for auroral-cavity ion beams consistent with acceleration through double-layer (DL) potentials measured by FAST. A simplified one-dimensional model simulation is then presented in order to isolate the mechanisms that lead to the formation of the ion acoustic soliton. Results of a two-dimensional simulation, which include both the ionosphere and the auroral cavity, separated by a low-altitude DL, are then presented in order to confirm that the soliton forms in a more realistic 2D geometry. The 2D simulation is initialized with a U-shaped potential structure that mimics the inferred shape of the low altitude transition region based on observations. In this simulation, a soliton localized perpendicular to the geomagnetic field is observed to form and reside next to the DL. Finally, the 2D simulation results are compared with FAST data and it is found that certain aspects of the data can be explained by assuming the presence of an ion acoustic soliton.

  4. Conducting Ni nanoparticles in an ion-modified polymer

    SciTech Connect

    Sze, J.Y.; Tay, B.K.; Pakes, C.I.; Jamieson, D.N.; Prawer, S.

    2005-09-15

    Conductive-atomic force microscopy has been used to perform nanoscale current imaging of Ni-ion-implanted polythylene terephthlate films. A reduction in bulk sheet resistivity, as the Ni dose is increased, is found to be accompanied by an evolution in local conductivity from a spatially homogeneous insulator to an interconnected network of conducting Ni crystallites. The crystallites have a mean dimension of 12.3 nm, confirmed by x-ray-diffraction analysis.

  5. Effect of Lithium Ion Concentration of a Single-Ion-Conducting Block Copolymer Electrolyte on the Morphology-Conductivity Relationship

    NASA Astrophysics Data System (ADS)

    Rojas, Adriana A.; Inceoglu, Sebnem; Mackay, Nikolaus G.; Devaux, Didier; Stone, Greg; Balsara, Nitash

    2015-03-01

    Single-ion-conducting electrolytes are desirable for lithium metal batteries because they enable the sole conduction of lithium ions, the reacting species in lithium batteries; hence, they avert detrimental battery limitations due to salt concentration gradients. A single-ion-conducting block copolymer electrolyte, poly(ethylene oxide)-b-polystyrenesulfonyllithium (trifluoromethyl sulfonyl) imide (PEO-b-PSLiTFSI), was characterized in-situ and ex-situ for its ionic conductivity and morphology using AC impedance spectroscopy and small angle x-ray scattering, respectively. This work is the first to elucidate the relationship between the two properties in a single-ion block copolymer electrolyte. The transference number for the copolymers was determined to be greater than or equal to 0.87, indicating that to a good approximation, the block copolymers are single-ion conducting electrolytes. It was found that increasing the molecular weight of the PSLiTFSI block led to an increase in the extent of block copolymer block-mixing and a change in the conductivity profile from discontinuous to continuous. These effects can be attributed to the disruption of PEO crystallization, which was shown to drive microphase separation. Joint Center for Energy Storage Research, Lawrence Berkeley National Laboratory.

  6. Enhanced Salt Removal by Unipolar Ion Conduction in Ion Concentration Polarization Desalination

    NASA Astrophysics Data System (ADS)

    Kwak, Rhokyun; Pham, Van Sang; Kim, Bumjoo; Chen, Lan; Han, Jongyoon

    2016-05-01

    Chloride ion, the majority salt in nature, is ∼52% faster than sodium ion (DNa+ = 1.33, DCl‑ = 2.03[10‑9m2s‑1]). Yet, current electrochemical desalination technologies (e.g. electrodialysis) rely on bipolar ion conduction, removing one pair of the cation and the anion simultaneously. Here, we demonstrate that novel ion concentration polarization desalination can enhance salt removal under a given current by implementing unipolar ion conduction: conducting only cations (or anions) with the unipolar ion exchange membrane stack. Combining theoretical analysis, experiment, and numerical modeling, we elucidate that this enhanced salt removal can shift current utilization (ratio between desalted ions and ions conducted through electrodes) and corresponding energy efficiency by the factor ∼(D‑ ‑ D+)/(D‑ + D+). Specifically for desalting NaCl, this enhancement of unipolar cation conduction saves power consumption by ∼50% in overlimiting regime, compared with conventional electrodialysis. Recognizing and utilizing differences between unipolar and bipolar ion conductions have significant implications not only on electromembrane desalination, but also energy harvesting applications (e.g. reverse electrodialysis).

  7. Enhanced Salt Removal by Unipolar Ion Conduction in Ion Concentration Polarization Desalination.

    PubMed

    Kwak, Rhokyun; Pham, Van Sang; Kim, Bumjoo; Chen, Lan; Han, Jongyoon

    2016-01-01

    Chloride ion, the majority salt in nature, is ∼52% faster than sodium ion (DNa+ = 1.33, DCl- = 2.03[10(-9)m(2)s(-1)]). Yet, current electrochemical desalination technologies (e.g. electrodialysis) rely on bipolar ion conduction, removing one pair of the cation and the anion simultaneously. Here, we demonstrate that novel ion concentration polarization desalination can enhance salt removal under a given current by implementing unipolar ion conduction: conducting only cations (or anions) with the unipolar ion exchange membrane stack. Combining theoretical analysis, experiment, and numerical modeling, we elucidate that this enhanced salt removal can shift current utilization (ratio between desalted ions and ions conducted through electrodes) and corresponding energy efficiency by the factor ∼(D- - D+)/(D- + D+). Specifically for desalting NaCl, this enhancement of unipolar cation conduction saves power consumption by ∼50% in overlimiting regime, compared with conventional electrodialysis. Recognizing and utilizing differences between unipolar and bipolar ion conductions have significant implications not only on electromembrane desalination, but also energy harvesting applications (e.g. reverse electrodialysis). PMID:27158057

  8. Enhanced Salt Removal by Unipolar Ion Conduction in Ion Concentration Polarization Desalination

    PubMed Central

    Kwak, Rhokyun; Pham, Van Sang; Kim, Bumjoo; Chen, Lan; Han, Jongyoon

    2016-01-01

    Chloride ion, the majority salt in nature, is ∼52% faster than sodium ion (DNa+ = 1.33, DCl− = 2.03[10−9m2s−1]). Yet, current electrochemical desalination technologies (e.g. electrodialysis) rely on bipolar ion conduction, removing one pair of the cation and the anion simultaneously. Here, we demonstrate that novel ion concentration polarization desalination can enhance salt removal under a given current by implementing unipolar ion conduction: conducting only cations (or anions) with the unipolar ion exchange membrane stack. Combining theoretical analysis, experiment, and numerical modeling, we elucidate that this enhanced salt removal can shift current utilization (ratio between desalted ions and ions conducted through electrodes) and corresponding energy efficiency by the factor ∼(D− − D+)/(D− + D+). Specifically for desalting NaCl, this enhancement of unipolar cation conduction saves power consumption by ∼50% in overlimiting regime, compared with conventional electrodialysis. Recognizing and utilizing differences between unipolar and bipolar ion conductions have significant implications not only on electromembrane desalination, but also energy harvesting applications (e.g. reverse electrodialysis). PMID:27158057

  9. Ionomer Design Principles for Single Ion-Conducting Energy Materials

    NASA Astrophysics Data System (ADS)

    Colby, Ralph; Liang, Siwei; Liu, Wenjuan; Hyeok Choi, U.; Runt, James; Shiau, Huai-Suen; Janik, Michael

    2012-02-01

    Single-ion conducting ionomers with low glass transition temperature, high dielectric constant and containing bulky ions with diffuse charge, are needed for polymer membranes that transport small counterions. Overarching design principles emerging from quantum chemistry calculations suggest that diffuse charge can be attained from simple considerations of atomic electronegativity. For lithium or sodium batteries, perfluorinated tetraphenyl borate ionomers with solvating polar comonomers are proposed. For fluoride or hydroxide batteries and for iodide transporting solar cells, tetra-alkyl phosphonium ionomers with anion receptors are proposed. First attempts to construct such ionomers to test these ideas will be discussed, with results from dielectric spectroscopy to measure conductivity, dielectric constant and number density of simultaneously conducting ions.

  10. Coherent optical ultrasound detection with rare-earth ion dopants.

    PubMed

    Tay, Jian Wei; Ledingham, Patrick M; Longdell, Jevon J

    2010-08-10

    We describe theoretical and experimental demonstration for optical detection of ultrasound using a spectral hole engraved in cryogenically cooled rare-earth ion-doped solids. Our method utilizes the dispersion effects due to the spectral hole to perform phase-to-amplitude modulation conversion. Like previous approaches using spectral holes, it has the advantage of detection with large étendue. The method also has the benefit that high sensitivity can be obtained with moderate absorption contrast for the spectral holes. PMID:20697433

  11. Solid electrolytes for fluoride ion batteries: ionic conductivity in polycrystalline tysonite-type fluorides.

    PubMed

    Rongeat, Carine; Reddy, M Anji; Witter, Raiker; Fichtner, Maximilian

    2014-02-12

    Batteries based on a fluoride shuttle (fluoride ion battery, FIB) can theoretically provide high energy densities and can thus be considered as an interesting alternative to Li-ion batteries. Large improvements are still needed regarding their actual performance, in particular for the ionic conductivity of the solid electrolyte. At the current state of the art, two types of fluoride families can be considered for electrolyte applications: alkaline-earth fluorides having a fluorite-type structure and rare-earth fluorides having a tysonite-type structure. As regard to the latter, high ionic conductivities have been reported for doped LaF3 single crystals. However, polycrystalline materials would be easier to implement in a FIB due to practical reasons in the cell manufacturing. Hence, we have analyzed in detail the ionic conductivity of La(1-y)Ba(y)F(3-y) (0 ≤ y ≤ 0.15) solid solutions prepared by ball milling. The combination of DC and AC conductivity analyses provides a better understanding of the conduction mechanism in tysonite-type fluorides with a blocking effect of the grain boundaries. Heat treatment of the electrolyte material was performed and leads to an improvement of the ionic conductivity. This confirms the detrimental effect of grain boundaries and opens new route for the development of solid electrolytes for FIB with high ionic conductivities. PMID:24444763

  12. Conducting ion tracks generated by charge-selected swift heavy ions

    NASA Astrophysics Data System (ADS)

    Gupta, Srashti; Gehrke, H. G.; Krauser, J.; Trautmann, C.; Severin, D.; Bender, M.; Rothard, H.; Hofsäss, H.

    2016-08-01

    Conducting ion tracks in tetrahedral amorphous carbon (ta-C) thin films were generated by irradiation with swift heavy ions of well-defined charge state. The conductivity of tracks and the surface topography of the films, showing characteristic hillocks at each track position, were investigated using conductive atomic force microscopy measurements. The dependence of track conductivity and hillock size on the charge state of the ions was studied using 4.6 MeV/u Pb ions of charge state 53+, 56+ and 60+ provided by GANIL, as well as 4.8 MeV/u Bi and Au ions of charge state from 50+ to 61+ and 4.2 MeV/u 238U ions in equilibrium charge state provided by UNILAC of GSI. For the charge state selection at GSI, an additional stripper-foil system was installed at the M-branch that now allows routine irradiations with ions of selected charge states. The conductivity of tracks in ta-C increases significantly when the charge state increases from 51+ to 60+. However, the conductivity of individual tracks on the same sample still shows large variations, indicating that tracks formed in ta-C are either inhomogeneous or the conductivity is limited by the interface between ion track and Si substrate.

  13. Conduction Mechanisms and Structure of Ionomeric Single-Ion Conductors

    SciTech Connect

    Colby, Ralph H.; Maranas, Janna K; Mueller, Karl T; Runt, James; Winey, Karen I

    2015-03-05

    Our team has designed using DFT (Gaussian) and synthesized low glass transition temperature single-ion conductors that are either polyanions that conduct small cations Li, Na, Cs or polycations that conduct small anions F, OH, Br. We utilize a wide range of complimentary experimental materials charactization tools to understand ion transport; differential scanning calorimetry, dielectric relaxation spectroscopy, infrared spectroscopy, nuclear magnetic resonance spectroscopy, linear viscoelasticity, X-ray scattering and molecular dynamics simulations. The glass transition temperature Tg needs to be as low as possible to facilitate ion transport, so the nonionic parts of the polymer need to be polar, flexible and have strong solvation interactions with the ions. The lowest Tg we have managed for polyanions conducting Li is -60 C. In contrast, polysiloxanes with PEO side chains and tetrabutylphosphonium cationic side groups have Tg ~ -75C that barely increases with ion content, as anticipated by DFT. A survey of all polyanions in the literature suggests that Tg < -80C is needed to achieve the 10-4 S/cm conductivity needed for battery separators.

  14. Magnetic properties of oxide glasses containing iron and rare-earth ions

    NASA Astrophysics Data System (ADS)

    Akamatsu, Hirofumi; Kawabata, Jun; Fujita, Koji; Murai, Shunsuke; Tanaka, Katsuhisa

    2011-10-01

    Measurements of fundamental magnetic properties including not only dc and ac susceptibilities but also magnetic aging effects have been performed for aluminoborate glasses with high concentrations of iron and rare-earth R3+ ions (R=Sm, Gd, and Tb) in order to give an insight into the magnetic structures and interactions in amorphous oxides containing both 3d transition metal and 4f rare-earth ions, which manifest magnetic interactions that differ from each other. We demonstrate that the antiferromagnetic interactions between iron and rare-earth ions as well as those between iron ions play a significant role for their magnetic properties, while those between rare-earth ions are of little importance. Most of the rare-earth ions remain paramagnetic even below the spin-freezing temperatures under the strong molecular field caused by the spin-glass freezing of the iron ions, as in the case of rare-earth garnet ferrites.

  15. Nanoscale ion sequestration to determine the polarity selectivity of ion conductance in carriers and channels.

    PubMed

    Cranfield, Charles G; Bettler, Taren; Cornell, Bruce

    2015-01-01

    The nanoscale spacing between a tethered lipid bilayer membrane (tBLM) and its supporting gold electrode can be utilized to determine the polarity selectivity of the conduction of ion channels and ion carriers embedded in a membrane. The technique relies upon a bias voltage sequestering or eliminating ions, of a particular polarity, into or out of the aqueous electrolyte region between the gold electrode and the tethered membrane. A demonstration is given, using ac swept frequency impedance spectrometry, of the bias polarity dependence of the ionophore conductance of gramicidin A, a cationic selective channel, and valinomycin, a potassium ion selective carrier. We further use pulsed amperometry to show that the intrinsic voltage dependence of the ion conduction is actually selective of the polarity of the transported ion and not simply of the direction of the ionic current flow. PMID:25474616

  16. Electrical studies on silver based fast ion conducting glassy materials

    NASA Astrophysics Data System (ADS)

    Rao, B. Appa; Kumar, E. Ramesh; Kumari, K. Rajani; Bhikshamaiah, G.

    2014-04-01

    Among all the available fast ion conductors, silver based glasses exhibit high conductivity. Further, glasses containing silver iodide enhances fast ion conducting behavior at room temperature. Glasses of various compositions of silver based fast ion conductors in the AgI-Ag2O-[(1-x)B2O3-xTeO2] (x=0 to1 mol% in steps of 0.2) glassy system have been prepared by melt quenching method. The glassy nature of the compounds has been confirmed by X-ray diffraction. The electrical conductivity (AC) measurements have been carried out in the frequency range of 1 KHz-3MHz by Impedance Analyzer in the temperature range 303-423K. The DC conductivity measurements were also carried out in the temperature range 300-523K. From both AC and DC conductivity studies, it is found that the conductivity increases and activation energy decreases with increasing the concentration of TeO2 as well as with temperature. The conductivity of the present glass system is found to be of the order of 10-2 S/cm at room temperature. The ionic transport number of these glasses is found to be 0.999 indicating that these glasses can be used as electrolyte in batteries.

  17. Electrical studies on silver based fast ion conducting glassy materials

    SciTech Connect

    Rao, B. Appa Kumar, E. Ramesh Kumari, K. Rajani Bhikshamaiah, G.

    2014-04-24

    Among all the available fast ion conductors, silver based glasses exhibit high conductivity. Further, glasses containing silver iodide enhances fast ion conducting behavior at room temperature. Glasses of various compositions of silver based fast ion conductors in the AgI−Ag{sub 2}O−[(1−x)B{sub 2}O{sub 3}−xTeO{sub 2}] (x=0 to1 mol% in steps of 0.2) glassy system have been prepared by melt quenching method. The glassy nature of the compounds has been confirmed by X-ray diffraction. The electrical conductivity (AC) measurements have been carried out in the frequency range of 1 KHz–3MHz by Impedance Analyzer in the temperature range 303–423K. The DC conductivity measurements were also carried out in the temperature range 300–523K. From both AC and DC conductivity studies, it is found that the conductivity increases and activation energy decreases with increasing the concentration of TeO{sub 2} as well as with temperature. The conductivity of the present glass system is found to be of the order of 10{sup −2} S/cm at room temperature. The ionic transport number of these glasses is found to be 0.999 indicating that these glasses can be used as electrolyte in batteries.

  18. Magnetism of perovskite cobaltites with Kramers rare-earth ions

    SciTech Connect

    Jirák, Z. Hejtmánek, J.; Knížek, K.; Novák, P.; Šantavá, E.; Fujishiro, H.

    2014-05-07

    The band-gap insulators RECoO{sub 3} (RE = Nd{sup 3+}, Sm{sup 3+}, and Dy{sup 3+}) with Co{sup 3+} ions stabilized in the non-magnetic low-spin state have been investigated by specific heat measurements. The experiments evidence an antiferromagnetic ordering of the rare earths with Néel temperature of T{sub N} = 1.25, 1.50, and 3.60 K for NdCoO{sub 3}, SmCoO{sub 3}, and DyCoO{sub 3}, respectively. With increasing external field, the lambda peak in specific heat, indicative of the transition, shifts to lower temperatures and vanishes for field of about 3 T. Starting from this point, a broader Schottky peak is formed, centered in 1 K range, and its position is moved to higher temperatures proportionally to applied field. The origin of the peak is in Zeeman splitting of the ground Kramers doublet, and the gradual shift with field defines effective g-factors for the rare-earth pseudospins in studied compounds. The results obtained are confronted with the calculations of crystal field splitting of the rare-earth multiplets.

  19. Sulfur control in ion-conducting membrane systems

    DOEpatents

    Stein, VanEric Edward; Richards, Robin Edward; Brengel, David Douglas; Carolan, Michael Francis

    2003-08-05

    A method for controlling the sulfur dioxide partial pressure in a pressurized, heated, oxygen-containing gas mixture which is contacted with an ion-conducting metallic oxide membrane which permeates oxygen ions. The sulfur dioxide partial pressure in the oxygen-depleted non-permeate gas from the membrane module is maintained below a critical sulfur dioxide partial pressure, p.sub.SO2 *, to protect the membrane material from reacting with sulfur dioxide and reducing the oxygen flux of the membrane. Each ion-conducting metallic oxide material has a characteristic critical sulfur dioxide partial pressure which is useful in determining the required level of sulfur removal from the feed gas and/or from the fuel gas used in a direct-fired feed gas heater.

  20. Ion conduction in crystalline superionic solids and its applications

    NASA Astrophysics Data System (ADS)

    Chandra, Angesh

    2014-06-01

    Superionic solids an area of multidisciplinary research activity, incorporates to study the physical, chemical and technological aspects of rapid ion movements within the bulk of the special class of ionic materials. It is an emerging area of materials science, as these solids show tremendous technological scopes to develop wide variety of solid state electrochemical devices such as batteries, fuel cells, supercapacitors, sensors, electrochromic displays (ECDs), memories, etc. These devices have wide range of applicabilities viz. power sources for IC microchips to transport vehicles, novel sensors for controlling atmospheric pollution, new kind of memories for computers, smart windows/display panels, etc. The field grew with a rapid pace since then, especially with regards to designing new materials as well as to explore their device potentialities. Amongst the known superionic solids, fast Ag+ ion conducting crystalline solid electrolytes are attracted special attention due to their relatively higher room temperature conductivity as well as ease of materials handling/synthesis. Ion conduction in these electrolytes is very much interesting part of today. In the present review article, the ion conducting phenomenon and some device applications of crystalline/polycrystalline superionic solid electrolytes have been reviewed in brief. Synthesis and characterization tools have also been discussed in the present review article.

  1. Ion Current Rectification, Limiting and Overlimiting Conductances in Nanopores

    PubMed Central

    van Oeffelen, Liesbeth; Van Roy, Willem; Idrissi, Hosni; Charlier, Daniel; Lagae, Liesbet; Borghs, Gustaaf

    2015-01-01

    Previous reports on Poisson-Nernst-Planck (PNP) simulations of solid-state nanopores have focused on steady state behaviour under simplified boundary conditions. These are Neumann boundary conditions for the voltage at the pore walls, and in some cases also Donnan equilibrium boundary conditions for concentrations and voltages at both entrances of the nanopore. In this paper, we report time-dependent and steady state PNP simulations under less restrictive boundary conditions, including Neumann boundary conditions applied throughout the membrane relatively far away from the nanopore. We simulated ion currents through cylindrical and conical nanopores with several surface charge configurations, studying the spatial and temporal dependence of the currents contributed by each ion species. This revealed that, due to slow co-diffusion of oppositely charged ions, steady state is generally not reached in simulations or in practice. Furthermore, it is shown that ion concentration polarization is responsible for the observed limiting conductances and ion current rectification in nanopores with asymmetric surface charges or shapes. Hence, after more than a decade of collective research attempting to understand the nature of ion current rectification in solid-state nanopores, a relatively intuitive model is retrieved. Moreover, we measured and simulated current-voltage characteristics of rectifying silicon nitride nanopores presenting overlimiting conductances. The similarity between measurement and simulation shows that overlimiting conductances can result from the increased conductance of the electric double-layer at the membrane surface at the depletion side due to voltage-induced polarization charges. The MATLAB source code of the simulation software is available via the website http://micr.vub.ac.be. PMID:25978328

  2. Origins of energetic ions in the Earth's magnetosheath

    NASA Technical Reports Server (NTRS)

    Fuselter, S. A.; Shelley, E. G.; Klumpar, D. M.

    1992-01-01

    The analysis and interpretation of the combined scientific data from the Hot Plasma Composition Experiment (HPCE) and the Charge Energy Mass (CHEM) spectrometer on the Active Mesospheric Particle Tracer Experiment (AMPTE) Charge Composition Explorer (CCE) spacecraft are discussed. These combined data sets have and will be used to survey the energetic ion environment in the Earth's magnetosheath to determine the origins and relative strengths of the energetic ion populations found there. A computer code was developed to analyze and interpret the data sets. The focus of the first year was on the determination of the contribution of leaked magnetospheric protons to the total energetic proton population. Emphasis was placed on intervals when the AMPTE spacecraft was in the plasma depletion layer because it was argued that in this region, only the leaked population contributes to the energetic ion population. Manipulation of the CHEM data and comparison of the CHEM and HPCE data over their common energy range near the magnetopause also contributed directly to a second study of that region.

  3. Ion-Conducting Polymer Films as Chemical Sensors

    SciTech Connect

    Hughes, R.C.; Patel, S.V.; Pfeifer, K.B.; Yelton, W.G.

    1999-05-03

    Solid Polymer Electrolytes (SPE) are widely used in batteries and fuel cells because of the high ionic conductivity that can be achieved at room temperature. The ions are usually Li or protons, although other ions can be shown to conduct in these polymer films. There has been very little work on using these films as chemical sensors. We have found that thin films of polymers like polyethyleneoxide (PEO) are very sensitive to low concentrations of volatile organic compounds (VOCS) like common solvents. We will present impedance spectroscopy of PEO films in the frequency range 0.01 Hz to 1 MHz for different concentrations of VOCS. We find that the measurement frequency is important for distinguishing ionic conductivity from the double layer capacitance and parasitic capacitances.

  4. Polymerized ionic liquid diblock copolymers: impact of water/ion clustering on ion conductivity.

    PubMed

    Nykaza, Jacob R; Ye, Yuesheng; Nelson, Rachel L; Jackson, Aaron C; Beyer, Frederick L; Davis, Eric M; Page, Kirt; Sharick, Sharon; Winey, Karen I; Elabd, Yossef A

    2016-01-28

    Herein, we examine the synergistic impact of both ion clustering and block copolymer morphology on ion conductivity in two polymerized ionic liquid (PIL) diblock copolymers with similar chemistries but different side alkyl spacer chain lengths (ethyl versus undecyl). When saturated in liquid water, water/ion clusters were observed only in the PIL block copolymer with longer alkyl side chains (undecyl) as evidenced by both small-angle neutron scattering and intermediate-angle X-ray scattering, i.e., water/ion clusters form within the PIL microdomain under these conditions. The resulting bromide ion conductivity in the undecyl sample was higher than the ethyl sample (14.0 mS cm(-1)versus 6.1 mS cm(-1) at 50 °C in liquid water) even though both samples had the same block copolymer morphology (lamellar) and the undecyl sample had a lower ion exchange capacity (0.9 meq g(-1)versus 1.4 meq g(-1)). No water/ion clusters were observed in either sample under high humidity or dry conditions. The resulting ion conductivity in the undecyl sample with lamellar morphology was significantly higher in the liquid water saturated state compared to the high humidity state (14.0 mS cm(-1)versus 4.2 mS cm(-1)), whereas there was no difference in ion conductivity in the ethyl sample when comparing these two states. These results show that small chemical changes to ion-containing block copolymers can induce water/ion clusters within block copolymer microdomains and this can subsequently have a significant effect on ion transport. PMID:26575014

  5. Anisotropic Lithium Ion Conductivity in Single-Ion Diblock Copolymer Electrolyte Thin Films.

    PubMed

    Aissou, Karim; Mumtaz, Muhammad; Usluer, Özlem; Pécastaings, Gilles; Portale, Giuseppe; Fleury, Guillaume; Cloutet, Eric; Hadziioannou, Georges

    2016-02-01

    Well-defined single-ion diblock copolymers consisting of a Li-ion conductive poly(styrenesulfonyllithium(trifluoromethylsulfonyl)imide) (PSLiTFSI) block associated with a glassy polystyrene (PS) block have been synthesized via reversible addition fragmentation chain transfer polymerization. Conductivity anisotropy ratio up to 1000 has been achieved from PS-b-PSLiTFSI thin films by comparing Li-ion conductivities of out-of-plane (aligned) and in-plane (antialigned) cylinder morphologies at 40 °C. Blending of PS-b-PSLiTFSI thin films with poly(ethylene oxide) homopolymer (hPEO) enables a substantial improvement of Li-ion transport within aligned cylindrical domains, since hPEO, preferentially located in PSLiTFSI domains, is an excellent lithium-solvating material. Results are also compared with unblended and blended PSLiTFSI homopolymer (hPSLiTFSI) homologues, which reveals that ionic conductivity is improved when thin films are nanostructured. PMID:26618916

  6. The Transport of Solar Ions Through the Earth's Magnetosphere

    NASA Technical Reports Server (NTRS)

    Lennartsson, O. W.

    1999-01-01

    This report covers the initial phase of an investigation that was originally selected by NASA Headquarters for funding by a grant but was later transferred to NASA GSFC for continued funding under a new and separate contract. The principal objective of the investigation, led by Dr. O.W. Lennartsson, is to extract information about the solar origin plasma in Earth's magnetosphere, specifically about the entry and transport of this plasma, using energetic (10 eV/e to 18 keV/e) ion composition data from the Lockheed Plasma Composition Experiment on the NASA/ESA International Sun-Earth Explorer One (ISEE 1) satellite. These data were acquired many years ago, from November 1977 through March of 1982, but, because of subsequent failures of similar experiments on several other spacecraft, they are still the only substantial ion composition data available from Earth's magnetotail, beyond 10 R(sub E), in the critically important sub-kev to keV energy range. All of the Lockheed data now exist in a compacted scientific format, suitable for large-scale statistical investigations, which has been archived both at Lockheed Martin in Palo Alto and at the National Space Science Data Center (NSSDC) in Greenbelt. The completion of the archiving, by processing the remaining half of the data, was made possible by separate funding through a temporary NASA program for data restoration and was given priority over the data analysis by a no-cost extension of the subject grant. By chance, the period of performance coincided with an international study of source and loss processes of magnetospheric plasma, sponsored by the International Space Science Institute (ISSI) in Bern, Switzerland, for which Dr. Lennartsson was invited to serve as one of 12 co-chairs. This study meshed well with the continued analysis of the NASA/Lockheed ISEE ion composition data and provided a natural forum for a broader discussion of the results from this unique experiment. What follows is arranged, for the most

  7. A simple model for the formation of 'reflected', 'intermediate', and 'diffuse' ion distributions upstream of earth's bow shock

    NASA Technical Reports Server (NTRS)

    Lee, M. A.; Skadron, G.

    1985-01-01

    Detailed energetic ion and low-frequency wave experiments on ISEE 1, 2, and 3, have established correlations between the types of ion populations and waves observed to exist in the earth's foreshock region. The present calculation has the objective to quantitatively test the picture obtained for the earth's foreshock region. An analysis is conducted of the coupled spatial and temporal evolution of upstream protons and hydromagnetic waves by means of a simple model in which the protons are represented by counterstreaming beams which resonate with hydromagnetic waves, exciting the outward propagating modes and damping the inward propagating modes at a single wave number.

  8. Proposal for laser cooling of rare-earth ions

    NASA Astrophysics Data System (ADS)

    Lepers, Maxence; Hong, Ye; Wyart, Jean-François; Dulieu, Olivier

    2016-01-01

    The efficiency of laser cooling relies on the existence of an almost closed optical-transition cycle in the energy spectrum of the considered species. In this respect, rare-earth elements exhibit many transitions which are likely to induce noticeable leaks from the cooling cycle. In this work, to determine whether laser cooling of singly ionized erbium Er+ is feasible, we have performed accurate electronic-structure calculations of energies and spontaneous-emission Einstein coefficients of Er+, using a combination of ab initio and least-squares-fitting techniques. We identify five weak closed transitions suitable for laser cooling, the broadest of which is in the kilohertz range. For the strongest transitions, by simulating the cascade dynamics of spontaneous emission, we show that repumping is necessary, and we discuss possible repumping schemes. We expect our detailed study on Er+ to give good insight into the laser cooling of neighboring ions such as Dy+.

  9. Conductive Polymeric Binder for Lithium-Ion Battery Anode

    NASA Astrophysics Data System (ADS)

    Gao, Tianxiang

    Tin (Sn) has a high-specific capacity (993 mAhg-1) as an anode material for Li-ion batteries. To overcome the poor cycling performance issue caused by its large volume expansion and pulverization during the charging and discharging process, many researchers put efforts into it. Most of the strategies are through nanostructured material design and introducing conductive polymer binders that serve as matrix of the active material in anode. This thesis aims for developing a novel method for preparing the anode to improve the capacity retention rate. This would require the anode to have high electrical conductivity, high ionic conductivity, and good mechanical properties, especially elasticity. Here the incorporation of a conducting polymer and a conductive hydrogel in Sn-based anodes using a one-step electrochemical deposition via a 3-electrode cell method is reported: the Sn particles and conductive component can be electrochemically synthesized and simultaneously deposited into a hybrid thin film onto the working electrode directly forming the anode. A well-defined three dimensional network structure consisting of Sn nanoparticles coated by conducting polymers is achieved. Such a conductive polymer-hydrogel network has multiple advantageous features: meshporous polymeric structure can offer the pathway for lithium ion transfer between the anode and electrolyte; the continuous electrically conductive polypyrrole network, with the electrostatic interaction with elastic, porous hydrogel, poly (2-acrylamido-2-methyl-1-propanesulfonic acid-co-acrylonitrile) (PAMPS) as both the crosslinker and doping anion for polypyrrole (PPy) can decrease the volume expansion by creating porous scaffold and softening the system itself. Furthermore, by increasing the amount of PAMPS and creating an interval can improve the cycling performance, resulting in improved capacity retention about 80% after 20 cycles, compared with only 54% of that of the control sample without PAMPS. The cycle

  10. Energetics of Multi-Ion Conduction Pathways in Potassium Ion Channels

    PubMed Central

    2013-01-01

    Potassium ion channels form pores in cell membranes, allowing potassium ions through while preventing the passage of sodium ions. Despite numerous high-resolution structures, it is not yet possible to relate their structure to their single molecule function other than at a qualitative level. Over the past decade, there has been a concerted effort using molecular dynamics to capture the thermodynamics and kinetics of conduction by calculating potentials of mean force (PMF). These can be used, in conjunction with the electro-diffusion theory, to predict the conductance of a specific ion channel. Here, we calculate seven independent PMFs, thereby studying the differences between two potassium ion channels, the effect of the CHARMM CMAP forcefield correction, and the sensitivity and reproducibility of the method. Thermodynamically stable ion–water configurations of the selectivity filter can be identified from all the free energy landscapes, but the heights of the kinetic barriers for potassium ions to move through the selectivity filter are, in nearly all cases, too high to predict conductances in line with experiment. This implies it is not currently feasible to predict the conductance of potassium ion channels, but other simpler channels may be more tractable. PMID:24353479

  11. Rod/Coil Block Copolyimides for Ion-Conducting Membranes

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Kinder, James D.

    2003-01-01

    Rod/coil block copolyimides that exhibit high levels of ionic conduction can be made into diverse products, including dimensionally stable solid electrolyte membranes that function well over wide temperature ranges in fuel cells and in lithium-ion electrochemical cells. These rod/coil block copolyimides were invented to overcome the limitations of polymers now used to make such membranes. They could also be useful in other electrochemical and perhaps some optical applications, as described below. The membranes of amorphous polyethylene oxide (PEO) now used in lithium-ion cells have acceptably large ionic conductivities only at temperatures above 60 C, precluding use in what would otherwise be many potential applications at lower temperatures. PEO is difficult to process, and, except at the highest molecular weights it is not very dimensionally stable. It would be desirable to operate fuel cells at temperatures above 80 C to take advantage of better kinetics of redox reactions and to reduce contamination of catalysts. Unfortunately, proton-conduction performance of a typical perfluorosulfonic polymer membrane now used as a solid electrolyte in a fuel cell decreases with increasing temperature above 80 C because of loss of water from within the membrane. The loss of water has been attributed to the hydrophobic nature of the polymer backbone. In addition, perfluorosulfonic polymers are expensive and are not sufficiently stable for long-term use. Rod/coil block copolyimides are so named because each molecule of such a polymer comprises short polyimide rod segments alternating with flexible polyether coil segments (see figure). The rods and coils can be linear, branched, or mixtures of linear and branched. A unique feature of these polymers is that the rods and coils are highly incompatible, giving rise to a phase separation with a high degree of ordering that creates nanoscale channels in which ions can travel freely. The conduction of ions can occur in the coil phase

  12. Precious metal catalysts with oxygen-ion conducting support

    SciTech Connect

    Ganguli, P.S.; Sundaresan, S.

    1993-08-03

    A three-way supported catalyst is described for treatment of combustion gas emissions from mobile or stationary sources, comprising: an oxygen-ion conducting support material having surface area at least about 20 m[sup 2]/gm, and two active metals selected from the group consisting of (1) platinum and rhodium and (2) palladium and rhodium dispersed on the support material in overall amount of about 0.01-2.2 wt. % of the catalyst.

  13. Ionic conductivity of alkaline (Li 2O, Na 2O) and alkaline-earth (BaO) borates in crystallization (vitrification) region

    NASA Astrophysics Data System (ADS)

    Solntsev, V. P.; Davydov, A. V.

    2011-11-01

    In this paper we report the existence of abnormal behavior of electric properties of alkaline (Li 2O,Na 2O) and alkaline-earth (BaO) borate in the melt—a crystal (glass) transition region. Results of measurement of conductivity in the mentioned interval evidence the existence of a strong variation of electric properties depending on the concentration of alkaline and alkaline-earth ions. The reasons of such behavior are discussed.

  14. Electronically conductive polymer binder for lithium-ion battery electrode

    SciTech Connect

    Liu, Gao; Xun, Shidi; Battaglia, Vincent S; Zheng, Honghe

    2014-10-07

    A family of carboxylic acid group containing fluorene/fluorenon copolymers is disclosed as binders of silicon particles in the fabrication of negative electrodes for use with lithium ion batteries. These binders enable the use of silicon as an electrode material as they significantly improve the cycle-ability of silicon by preventing electrode degradation over time. In particular, these polymers, which become conductive on first charge, bind to the silicon particles of the electrode, are flexible so as to better accommodate the expansion and contraction of the electrode during charge/discharge, and being conductive promote the flow battery current.

  15. Mixed oxygen ion/electron-conducting ceramics for oxygen separation

    SciTech Connect

    Stevenson, J.W.; Armstrong, T.R.; Armstrong, B.L.

    1996-08-01

    Mixed oxygen ion and electron-conducting ceramics are unique materials that can passively separate high purity oxygen from air. Oxygen ions move through a fully dense ceramic in response to an oxygen concentration gradient, charge-compensated by an electron flux in the opposite direction. Compositions in the system La{sub 1{minus}x}M{sub x}Co{sub 1{minus}y{minus}z}Fe{sub y}N{sub z}O{sub 3{minus}{delta}}, perovskites where M=Sr, Ca, and Ba, and N=Mn, Ni, Cu, Ti, and Al, have been prepared and their electrical, oxygen permeation, oxygen vacancy equilibria, and catalytic properties evaluated. Tubular forms, disks, and asymmetric membrane structures, a thin dense layer on a porous support of the same composition, have been fabricated for testing purposes. In an oxygen partial gradient, the passive oxygen flux through fully dense structures was highly dependent on composition. An increase in oxygen permeation with increased temperature is attributed to both enhanced oxygen vacancy mobility and higher vacancy populations. Highly acceptor-doped compositions resulted in oxygen ion mobilities more than an order of magnitude higher than yttria-stabilized zirconia. The mixed conducting ceramics have been utilized in a membrane reactor configuration to upgrade methane to ethane and ethylene. Conditions were established to balance selectivity and throughput in a catalytic membrane reactor constructed from mixed conducting ceramics.

  16. Collective Diffusion Model for Ion Conduction through Microscopic Channels

    PubMed Central

    Liu, Yingting; Zhu, Fangqiang

    2013-01-01

    Ion conduction through microscopic channels is of central importance in both biology and nanotechnology. To better understand the current-voltage (I-V) dependence of ion channels, here we describe and prove a collective diffusion model that quantitatively relates the spontaneous ion permeation at equilibrium to the stationary ionic fluxes driven by small voltages. The model makes it possible to determine the channel conductance in the linear I-V range from equilibrium simulations without the application of a voltage. To validate the theory, we perform molecular-dynamics simulations on two channels—a conical-shaped nanopore and the transmembrane pore of an α-hemolysin—under both equilibrium and nonequilibrium conditions. The simulations reveal substantial couplings between the motions of cations and anions, which are effectively captured by the collective coordinate in the model. Although the two channels exhibit very different linear ranges in the I-V curves, in both cases the channel conductance at small voltages is in reasonable agreement with the prediction from the equilibrium simulation. The simulations also suggest that channel charges, rather than geometric asymmetry, play a more prominent role in current rectification. PMID:23442858

  17. Spin Crossover and Thermal Conductivity in the Earth's Lower Mantle

    NASA Astrophysics Data System (ADS)

    Goncharov, A. F.

    2008-12-01

    Changes in the electronic structure of iron at high pressures toward a spin-paired state in ferropericlase and silicate perovskite may directly influence the thermal conductivity of the lower mantle. The pressure dependence of optical absorption in ferropericlase, Mg(1-x)FexO (x=0.06-0.25), and silicate perovskite, Mg0.9Fe0.1SiO3, has been determined in the IR through UV regions up to 133 GPa. Whereas (Mg,Fe)O exhibits a strong pressure dependence of absorption and spectral changes associated with the high-spin (HS) to low-spin (LS) transition of Fe2+ (Goncharov et al., Science 312, 1205 (2006)), the pressure dependence of optical absorption in (Mg,Fe)SiO3 is relatively weak. We observe a moderate increase in absorption with pressure for (Mg,Fe)SiO3 in the visible and infrared spectral range due to a red-shift of absorption in ultraviolet, however the crystal-field transitions of Fe2+ become weaker with pressure and disappear above 50 GPa as a result of the HS-LS transition in (Mg,Fe)SiO3. The results on silicate perovskite show that optical absorption in the visible and near infrared spectral range is dominated by O- Fe3+ charge transfer and Fe3+- Fe2+ intervalence transitions, whereas a contribution from the Fe2+ crystal-field transitions is substantially smaller. The temperature dependence of the optical absorption of (Mg,Fe)O measured up to 65 GPa and 800 K is moderate below 30 GPa and weak above 30 GPa. The estimated total pressure dependent radiative conductivity (in approximation of a large grain size) is lower than expected from the pressure extrapolation of the ambient and low-pressure data. A new method has been developed to measure thermal diffusivity of mantle materials at high P-T using time-resolved radiometry combined with a pulsed-IR source. Here, the technique is tested on MgO to 32 GPa and Mg0.9Fe0.1SiO3 perovskite synthesized at 125 GPa. I thank B. Haugen, S. D. Jacobsen, V. V. Struzhkin, P. Beck, J. Montoya, J. Badro, D. Antonangeli, S

  18. Comparative study of ion conducting pathways in borate glasses

    SciTech Connect

    Hall, Andreas; Swenson, Jan; Adams, Stefan

    2006-11-01

    The conduction pathways in metal-halide doped silver, lithium, and sodium diborate glasses have been examined by bond valence analysis of reverse Monte Carlo (RMC) produced structural models of the glasses. Although all glass compositions have basically the same short-range structure of the boron-oxygen network, it is evident that the intermediate-range structure is strongly dependent on the type of mobile ion. The topography of the pathways and the coordination of the pathway sites differ distinctly between the three glass systems. The mobile silver ions in the AgI-doped glass tend to be mainly iodine-coordinated and travel in homogeneously distributed pathways located in salt-rich channels of the borate network. In the NaCl-doped glass, there is an inhomogeneous spatial distribution of pathways that reflects the inhomogeneous introduction of salt ions into the glass. However, since the salt clusters are not connected, no long-range conduction pathways are formed without including also oxygen-rich regions. The pathways in the LiCl-doped glass are slightly more evenly distributed compared to the NaCl-doped glass (but not as ordered as in the AgI-doped glass), and the regions of mainly oxygen-coordinated pathway sites are of higher importance for the long-range migration. In order to more accurately investigate how these differences in the intermediate-range order of the glasses affect the ionic conductivity, we have compared the realistic structure models to more or less randomized structures. An important conclusion from this comparison is that we find no evidence that a pronounced intermediate-range order in the atomic structure or in the network of conduction pathways, as in the AgI-doped glass, is beneficial for the dc conductivity.

  19. Scanning Ion Conductance Microscopy for Studying Biological Samples

    PubMed Central

    Happel, Patrick; Thatenhorst, Denis; Dietzel, Irmgard D.

    2012-01-01

    Scanning ion conductance microscopy (SICM) is a scanning probe technique that utilizes the increase in access resistance that occurs if an electrolyte filled glass micro-pipette is approached towards a poorly conducting surface. Since an increase in resistance can be monitored before the physical contact between scanning probe tip and sample, this technique is particularly useful to investigate the topography of delicate samples such as living cells. SICM has shown its potential in various applications such as high resolution and long-time imaging of living cells or the determination of local changes in cellular volume. Furthermore, SICM has been combined with various techniques such as fluorescence microscopy or patch clamping to reveal localized information about proteins or protein functions. This review details the various advantages and pitfalls of SICM and provides an overview of the recent developments and applications of SICM in biological imaging. Furthermore, we show that in principle, a combination of SICM and ion selective micro-electrodes enables one to monitor the local ion activity surrounding a living cell. PMID:23202197

  20. Ion acceleration to supra-thermal energies in the near-Earth magnetotail

    NASA Astrophysics Data System (ADS)

    Elena, Kronberg

    2016-07-01

    We here present an analysis of ion composition measurements by the RAPID instruments onboard Cluster. We discuss the evidence for an acceleration of ions to energies above 100 keV in the near-Earth current sheet, in the vicinity of a possible near-Earth neutral line, and we investigate the physical details of such an acceleration. We present observations of tailward bulk flows in the near-Earth tail associated with plasmoid-like magnetic structures. These flows are superimposed by low-frequency magnetic and electric field fluctuations. Observations and modelling show that resonant interactions between ions and low-frequency electromagnetic fluctuations facilitate the ion energization inside plasmoids.

  1. Mobile ion distribution and anharmonic thermal motion in fast ion conducting Cu/sub 2/S

    SciTech Connect

    Cava, R.J.; Reidinger, F.; Wuensch, B.J.

    1981-01-01

    A unique model was determined for the mobile copper ion disorder in hexagonal Cu/sub 2/S between 120/sup 0/ and 325/sup 0/C via single crystal neutron diffraction. The copper ions partially occupy two sets of three-coordinated sites within the HCP sulfur array and display anharmonic thermal motion. The results suggest that the conductivity is two dimensional in nature.

  2. Simulating imaging with the scanning ion-conductance microscope.

    PubMed

    Adenle, Omolabake; Fitzgerald, William

    2005-01-01

    The Scanning Ion-Conductance Microscope (SICM) is a member of the family of Scanned Probe Microscopes (SPM). Examples include the Scanning Electrochemical Microscope (SECM) and Atomic Force Microscope (AFM). SICM uses the ion-concentration field at the tip of a micropipette filled with an electrolyte solution as a probe to generate images of sample topography. As with other members of the SPM family, the probe geometry determines the observed image. This paper presents mathematical models for simulating the SICM in its different operating modes with the intent of creating a framework within which the effect of probe-geometry can be studied. We validate our model by comparing simulated approach-curves with empirical data. Finally, we show simulated images of a Gaussian-bump substrate under the different operating modes of the SICM. PMID:17280955

  3. Temporal evolution of helix hydration in a light-gated ion channel correlates with ion conductance

    PubMed Central

    Lórenz-Fonfría, Víctor A.; Bamann, Christian; Resler, Tom; Schlesinger, Ramona; Bamberg, Ernst; Heberle, Joachim

    2015-01-01

    The discovery of channelrhodopsins introduced a new class of light-gated ion channels, which when genetically encoded in host cells resulted in the development of optogenetics. Channelrhodopsin-2 from Chlamydomonas reinhardtii, CrChR2, is the most widely used optogenetic tool in neuroscience. To explore the connection between the gating mechanism and the influx and efflux of water molecules in CrChR2, we have integrated light-induced time-resolved infrared spectroscopy and electrophysiology. Cross-correlation analysis revealed that ion conductance tallies with peptide backbone amide I vibrational changes at 1,665(−) and 1,648(+) cm−1. These two bands report on the hydration of transmembrane α-helices as concluded from vibrational coupling experiments. Lifetime distribution analysis shows that water influx proceeded in two temporally separated steps with time constants of 10 μs (30%) and 200 μs (70%), the latter phase concurrent with the start of ion conductance. Water efflux and the cessation of the ion conductance are synchronized as well, with a time constant of 10 ms. The temporal correlation between ion conductance and hydration of helices holds for fast (E123T) and slow (D156E) variants of CrChR2, strengthening its functional significance. PMID:26460012

  4. Phase modulation mode of scanning ion conductance microscopy

    SciTech Connect

    Li, Peng; Zhang, Changlin; Liu, Lianqing E-mail: gli@engr.pitt.edu; Wang, Yuechao; Yang, Yang; Li, Guangyong E-mail: gli@engr.pitt.edu

    2014-08-04

    This Letter reports a phase modulation (PM) mode of scanning ion conductance microscopy. In this mode, an AC current is directly generated by an AC voltage between the electrodes. The portion of the AC current in phase with the AC voltage, which is the current through the resistance path, is modulated by the tip-sample distance. It can be used as the input of feedback control to drive the scanner in Z direction. The PM mode, taking the advantages of both DC mode and traditional AC mode, is less prone to electronic noise and DC drift but maintains high scanning speed. The effectiveness of the PM mode has been proven by experiments.

  5. Proposal for laser cooling of rare-earth ions

    NASA Astrophysics Data System (ADS)

    Dulieu, Olivier; Hong, Ye; Wyart, Jean-François; Lepers, Maxence

    2016-05-01

    The efficiency of laser cooling relies on the existence of an almost closed optical-transition cycle in the energy spectrum of the considered species. In this respect, rare-earth elements exhibit many transitions which are likely to induce noticeable leaks from the cooling cycle. In this work, to determine whether laser cooling of singly ionized erbium Er+ is feasible, we have performed accurate electronic-structure calculations of energies and spontaneous-emission Einstein coefficients of Er+, using a combination of ab initio and least-squares-fitting techniques. We identify five weak closed transitions suitable for laser cooling, the broadest of which is in the kilohertz range. For the strongest transitions, by simulating the cascade dynamics of spontaneous emission, we show that repumping is necessary, and we discuss possible repumping schemes.We expect our detailed study on Er+ to give good insight into the laser cooling of neighboring ions such as Dy+. Supported by ``Agence Nationale de la Recherche'' (ANR), under the project COPOMOL (Contract No. ANR-13-IS04-0004-01).

  6. Electronically conductive polymer binder for lithium-ion battery electrode

    SciTech Connect

    Liu, Gao; Battaglia, Vincent S.; Park, Sang -Jae

    2015-10-06

    A family of carboxylic acid groups containing fluorene/fluorenon copolymers is disclosed as binders of silicon particles in the fabrication of negative electrodes for use with lithium ion batteries. Triethyleneoxide side chains provide improved adhesion to materials such as, graphite, silicon, silicon alloy, tin, tin alloy. These binders enable the use of silicon as an electrode material as they significantly improve the cycle-ability of silicon by preventing electrode degradation over time. In particular, these polymers, which become conductive on first charge, bind to the silicon particles of the electrode, are flexible so as to better accommodate the expansion and contraction of the electrode during charge/discharge, and being conductive promote the flow battery current.

  7. Electronically conductive polymer binder for lithium-ion battery electrode

    SciTech Connect

    Liu, Gao; Xun, Shidi; Battaglia, Vincent S.; Zheng, Honghe; Wu, Mingyan

    2015-07-07

    A family of carboxylic acid groups containing fluorene/fluorenon copolymers is disclosed as binders of silicon particles in the fabrication of negative electrodes for use with lithium ion batteries. Triethyleneoxide side chains provide improved adhesion to materials such as, graphite, silicon, silicon alloy, tin, tin alloy. These binders enable the use of silicon as an electrode material as they significantly improve the cycle-ability of silicon by preventing electrode degradation over time. In particular, these polymers, which become conductive on first charge, bind to the silicon particles of the electrode, are flexible so as to better accommodate the expansion and contraction of the electrode during charge/discharge, and being conductive promote the flow battery current.

  8. Defect Chemistry, Oxygen Ion Conduction, and Proton Conduction of Oxides with Brownmillerite and Related Structures.

    NASA Astrophysics Data System (ADS)

    Zhang, Guobin

    This dissertation presents a study on defect structure, oxygen ion conductivity, proton conductivity, electronic conductivity, and high temperature equilibrium redox properties of brownmillerite related oxides with general formula A _{rm n}B _{rm n}O_ {rm 3n-1} (n = 2 to infty ). A defect chemistry model is proposed for the brownmillerite oxides with high oxygen ion conductivity. Ba_2 In_2O_5 was chosen as the model material and its electrical conductivity and transport properties have been studied in detail. The oxygen ion conduction above the order-disorder temperature, T_{rm d} ~ 925^circC, and a mixed ionic-electronic conduction below T _{rm d}, was studied by conductivity and EMF measurements as a function of temperature and oxygen activity. The main defects are intrinsic anion Frenkel defects below T_{rm d}, and above T_{rm d} the oxide can be treated as acceptor doped perovskite with extrinsic oxygen vacancies. Charge compensation involves only ionic defects over the whole P(O_2 ) range used in this study. The formation and mobility enthalpies of the Frenkel defects, the redox enthalpies, and the band gap have been obtained for this oxide. A similar study has been done for other compositions in Ba _{rm n}In _2Zr_{rm n-2} O_{rm 3n-1} system. The proposed model is in good agreement with the experimental results. Evidence for protonic conduction was also found in these materials, especially at low temperatures. Three regions of protonic conduction in the Arrhenius plot have been observed and analyzed. The proton formation and mobility enthalpies have been obtained. The observed proton conductivity transition at the oxygen order-disorder transition temperature directly confirms the proton formation mechanism by incorporation of H_2O molecules into oxygen vacancies. A defect chemistry study was also conducted for the brownmillerite oxides with high electronic conductivity with Ca_2(Al_{ rm x}Fe_{rm 2-x})O_5 chosen as the model system. The main defects are

  9. Swift heavy ion irradiation reduces porous silicon thermal conductivity

    NASA Astrophysics Data System (ADS)

    Massoud, M.; Canut, B.; Newby, P.; Frechette, L.; Chapuis, P. O.; Bluet, J. M.

    2014-12-01

    While the electrical conductivity of semiconductors can be easily changed over order of magnitudes (8 in silicon) by playing on the doping, the thermal conductivity (TC) control is a challenging issue. Nevertheless, numerous applications require TC control in Si down to 1 W m-1 K-1. Among them, there are thermal insulation requirements in MEMS, thermal management issues in 3D packaging or TC reduction for thermoelectric applications. Towards this end, the formation of nanoporous Si by electrochemical anodisation is efficient. Nevertheless, in this case the material is too fragile for MEMS application or even to withstand CMOS technological processes. In this work, we show that ion irradiation in the electronic regime is efficient for reducing TC in meso-porous Si (PSi), which is more mechanically robust than the nanoporous PSi. We have studied three different mass to energy ratios (238U at 110 MeV and 130Xe at 91 MeV and 29 MeV) with fluences ranging from 1012 cm-2 to 7 × 1013 cm-2. The sample properties, after irradiation, have been measured by infrared spectroscopy, Raman spectroscopy and scanning electron microscopy. The TC has been measured using scanning thermal microscopy. Although, bulk Si is insensitive to ion interaction in the electronic regime, we have observed the amorphisation of the PSi resulting in a TC reduction even for the low dose and energy. For the highest irradiation dose a very important reduction factor of four was obtained.

  10. Upper mantle electrical conductivity for seven subcontinental regions of the Earth

    USGS Publications Warehouse

    Campbell, W.H.; Schiffmacher, E.R.

    1988-01-01

    Spherical harmonic analysis coefficients of the external and internal parts of the quiet-day geomagnetic field variations (Sq) separated for the 7 continental regions of the observatories have been used to determine conductivity profiles to depths of about 600 km by the Schmucker equivalent substitute conductor method. The profiles give evidence of increases in conductivity between about 150 and 350 km depth, then a general increase in conductivity thereafter. For South America we found a high conductivity at shallow depths. The European profile showed a highly conducting layer near 125 km. At the greater depths, Europe, Australia and South America had the lowest values of conductivity. North America and east Asia had intermediate values whereas the African and central Asian profiles both showed the conductivities rising rapidly beyond 450 km depth. The regional differences indicate that there may be considerable lateral heterogeneity of electrical conductivity in the Earth's upper mantle. -Authors

  11. Earth Conductivity Estimation from Through-the-Earth Measurements of 94 Coal Mines Using Different Electromagnetic Models

    PubMed Central

    Yan, Lincan; Waynert, Joseph; Sunderman, Carl

    2015-01-01

    Through-the-Earth (TTE) communication systems require minimal infrastructure to operate. Hence, they are assumed to be more survivable and more conventional than other underground mine communications systems. This survivability is a major advantage for TTE systems. In 2006, Congress passed the Mine Improvement and New Emergency Response Act (MINER Act), which requires all underground coal mines to install wireless communications systems. The intent behind this mandate is for trapped miners to be able to communicate with surface personnel after a major accident-hence, the interest in TTE communications. To determine the likelihood of establishing a TTE communication link, it would be ideal to be able to predict the apparent conductivity of the overburden above underground mines. In this paper, all 94 mine TTE measurement data collected by Bureau of Mines in the 1970s and early 1980s, are analyzed for the first time to determine the apparent conductivity of the overburden based on three different models: a homogenous half-space model, a thin sheet model, and an attenuation factor or Q-factor model. A statistical formula is proposed to estimate the apparent earth conductivity for a specific mine based on the TTE modeling results given the mine depth and signal frequency. PMID:26213457

  12. Developments in suppressor technology for inorganic ion analysis by ion chromatography using conductivity detection.

    PubMed

    Hadda, Paul R; Jackson, Peter E; Shaw, Matthew J

    2003-06-01

    A review is presented detailing the development and use of suppression devices for the conductimetric detection of inorganic ions by ion chromatography (IC). An overview of the general response equation for conductivity detection is also given. Topics of discussion include the role and function of suppressors, the development of early suppressors including packed column and membrane devices from 1975 to 1990 and the subsequent progression towards present day commercially available suppressors and recent innovations. Post-suppression devices for signal enhancement are also discussed. PMID:12877197

  13. The heavy ion diffusion region in magnetic reconnection in the Earth's magnetotail

    NASA Astrophysics Data System (ADS)

    Liu, Y. H.; Mouikis, C. G.; Kistler, L. M.; Wang, S.; Roytershteyn, V.; Karimabadi, H.

    2015-05-01

    While the plasma in the Earth's magnetotail predominantly consists of protons and electrons, there are times when a significant amount of oxygen is present. When magnetic reconnection occurs, the behavior of these heavy ions can be significantly different from that of the protons, due to their larger gyroradius. In this study, we investigate the heavy ion distribution functions in the reconnection ion diffusion region from a 2.5D three-species particle-in-cell numerical simulation and compare those with Cluster observations from the near-Earth magnetotail. From the simulation results, we find that the heavy ions are demagnetized and accelerated in a larger diffusion region, the heavy ion diffusion region. The ion velocity distribution functions show that, inside the heavy ion diffusion region, heavy ions appear as counterstreaming beams along z in the GSM x-z plane, while drifting in y, carrying cross-tail current. We compare this result with Cluster observations in the vicinity of reconnection regions in the near-Earth magnetotail and find that the simulation predictions are consistent with the observed ion distribution functions in the ion diffusion region, as well as the inflow, exhaust, and separatrix regions. Based on the simulation and observation results, the presence of a multiscale diffusion region model, for O+ abundant reconnection events in the Earth's magnetotail, is demonstrated. A test particle simulation shows that in the diffusion region, the H+ gains energy mainly through Ex, while the O+ energy gain comes equally from Ex and Ey.

  14. Scanning ion conductance microscopy studies of amyloid fibrils at nanoscale

    NASA Astrophysics Data System (ADS)

    Zhang, Shuai; Cho, Sang-Joon; Busuttil, Katerina; Wang, Chen; Besenbacher, Flemming; Dong, Mingdong

    2012-05-01

    Atomic force microscopy (AFM) has developed to become a very versatile nano-scale technique to reveal the three-dimensional (3D) morphology of amyloid aggregates under physiological conditions. However, the imaging principle of AFM is based on measuring the `force' between a sharp tip and a given nanostructure, which may cause mechanical deformation of relatively soft objects. To avoid the deformation, scanning ion conductance microscopy (SICM) is an alternative scanning probe microscopy technique, operating with alternating current mode. Here we can indeed reveal the 3D morphology of amyloid fibrils and it is capable of exploring proteins with nanoscale resolution. Compared with conventional AFM, we show that SICM can provide precise height measurements of amyloid protein aggregates, a feature that enables us to obtain unique insight into the detailed nucleation and growth mechanisms behind amyloid self-assembly.

  15. Double micropipettes configuration method of scanning ion conductance microscopy.

    PubMed

    Zhuang, Jian; Li, Zeqing; Jiao, Yangbohan

    2016-07-01

    In this paper, a new double micropipettes configuration mode of scanning ion conductance microscopy (SICM) is presented to better overcome ionic current drift and further improve the performance of SICM, which is based on a balance bridge circuit. The article verifies the feasibility of this new configuration mode from theoretical and experimental analyses, respectively, and compares the quality of scanning images in the conventional single micropipette configuration mode and the new double micropipettes configuration mode. The experimental results show that the double micropipettes configuration mode of SICM has better effect on restraining ionic current drift and better performance of imaging. Therefore, this article not only proposes a new direction of overcoming the ionic current drift but also develops a new method of SICM stable imaging. PMID:27475561

  16. Double micropipettes configuration method of scanning ion conductance microscopy

    NASA Astrophysics Data System (ADS)

    Zhuang, Jian; Li, Zeqing; Jiao, Yangbohan

    2016-07-01

    In this paper, a new double micropipettes configuration mode of scanning ion conductance microscopy (SICM) is presented to better overcome ionic current drift and further improve the performance of SICM, which is based on a balance bridge circuit. The article verifies the feasibility of this new configuration mode from theoretical and experimental analyses, respectively, and compares the quality of scanning images in the conventional single micropipette configuration mode and the new double micropipettes configuration mode. The experimental results show that the double micropipettes configuration mode of SICM has better effect on restraining ionic current drift and better performance of imaging. Therefore, this article not only proposes a new direction of overcoming the ionic current drift but also develops a new method of SICM stable imaging.

  17. Cd and Hg ions stimulate cell membrane potassium conductance

    SciTech Connect

    Jungwirth, A.; Paulmichl, M.; Lang, F. )

    1989-02-09

    Intracellular microelectrodes have been applied to study the effect of cadmium (Cd) and mercury (Hg) ions on cultured renal epitheloid Madin Darby Canine Kidney (MDCK) cells. Within 10 seconds Cd and within 50 seconds Hg hyperpolarize the cell membrane from - 53 {plus minus} 1 mV to - 68 {plus minus} 1 mV and - 67 {plus minus} 1 mV, resp., increase the potassium selectivity of the cell membrane (tk) from 0.33 {plus minus} 0.02 to 0.64 {plus minus} 0.03 and 0.77 {plus minus} 0.02, resp., and reduce the apparent cell membrane resistance from 40 {plus minus} 2 MOhm to 27 {plus minus} 2 MOhm and 22 {plus minus} 2 MOhm, resp.. Thus, both, Cd and Hg hyperpolarize the cell membrane by enhancement of the potassium conductance. The concentration required to elicit half maximal hyperpolarization is some 400 nmol/1 for either, Cd or Hg. Barium (1 mmol/1) depolarizes the cell membrane to - 34 {plus minus} 1 mV and virtually abolishes tk in the absence of Cd and Hg. In the presence of barium Cd leads to a transient, Hg to a sustained reappearance of tk and hyperpolarization. Thus, the Cd induced potassium conductance is blocked by barium with delay, the Hg induced potassium conductance is insensitive to barium. Quinidine (1 mmol/1) depolarizes the cell membrane to - 3 {plus minus}1 mV and abolishes the effect of both, Cd and Hg. In the nominal absence of extracellular calcium Cd leads to transient, Hg to sustained increase of tk and hyperpolarization of the cell membrane. In conclusion, both, CD and Hg at the low concentrations encountered during Cd and Hg intoxication enhance potassium conductance of MDCK cell membranes. However, the channels activated apparently differ.

  18. On the origins of energetic ions in the earth's dayside magnetosheath

    NASA Technical Reports Server (NTRS)

    Fuselier, S. A.; Klumpar, D. M.; Shelley, E. G.

    1991-01-01

    Energetic ion events in the earth's dayside subsolar magnetosheath (0900 - 1300 Local Time) are surveyed using data from the AMPTE/CCE Hot Plasma Composition Experiment. Ion species carrying the signature of their origin O(+) and energetic He(2+) are used to distinguish between magnetospheric and solar wind origins for the energetic ion events. The results of this survey indicate that the majority of energetic (10-17 keV/e) H(+) and He(2+) ions observed in the dayside magnetosheath are accelerated from the solar wind population. The energetic He(2+) to H(+) density ratio in the magnetosheath is consistent with that predicted from first-order Fermi acceleration of solar wind ions in the turbulent regions upstream and downstream from the earth's quasi-parallel bow shock. The simultaneous occurrence of both energetic He(2+) and magnetospheric O(+) indicates that, on occasion, both Fermi acceleration of solar wind ions and leakage of magnetospheric ions occurs in the dayside magnetosheath.

  19. Ion-exchangeable, electronically conducting layered perovskite oxyfluorides.

    PubMed

    Kobayashi, Yoji; Tian, Mingliang; Eguchi, Miharu; Mallouk, Thomas E

    2009-07-22

    Cation-exchangeable d(0) layered perovskites are amenable to intercalation, exfoliation, and a variety of topochemical reactions, but they lack the interesting electronic and magnetic functionalities of mixed-valent perovskites. Conversely, electronically and magnetically interesting layered perovskites lack scope in terms of interlayer chemistry. To bridge this gap, the insulating, cation-exchangeable layered perovskites RbLaNb(2)O(7), KCa(2)Nb(3)O(10), and NaYTiO(4) were reacted with poly(tetrafluoroethylene) under inert atmosphere conditions to yield layer perovskites in which some of the oxygen is substituted by fluorine. In the fluorinated materials, the B-site cations are reduced to a mixed-valent state without introducing oxygen vacancies into the anion sublattice. The resulting electronically conducting solids can be exposed to air and water and even ion-exchanged in acid without oxidation of the B-site cations. Electronic transport measurements on the air-stable RbLaNb(2)O(6)F reveal room-temperature conductivity (2-7 x 10(2) ohms x cm) via a variable-range hopping mechanism, which is not substantially changed after aqueous proton exchange to H(1-x)Rb(x)LaNb(2)O(6)F (x approximately = 0.2). PMID:19548670

  20. Tetraarylborate polymer networks as single-ion conducting solid electrolytes

    DOE PAGESBeta

    Van Humbeck, Jeffrey F.; Aubrey, Michael L.; Alsbaiee, Alaaeddin; Ameloot, Rob; Coates, Geoffrey W.; Dichtel, William R.; Long, Jeffrey R.

    2015-06-23

    A new family of solid polymer electrolytes based upon anionic tetrakis(phenyl)borate tetrahedral nodes and linear bis-alkyne linkers is reported. Sonogashira polymerizations using tetrakis(4-iodophenyl)borate, tetrakis(4-iodo-2,3,5,6-tetrafluorophenyl)borate and tetrakis(4-bromo-2,3,5,6-tetrafluorophenyl)borate delivered highly cross-linked polymer networks with both 1,4-diethynylbeznene and a tri(ethylene glycol) substituted derivative. Promising initial conductivity metrics have been observed, including high room temperature conductivities (up to 2.7 × 10-4 S cm-1), moderate activation energies (0.25–0.28 eV), and high lithium ion transport numbers (up to tLi+ = 0.93). Initial investigations into the effects of important materials parameters such as bulk morphology, porosity, fluorination, and other chemical modification, provide starting design parameters for furthermore » development of this new class of solid electrolytes.« less

  1. Tetraarylborate polymer networks as single-ion conducting solid electrolytes

    SciTech Connect

    Van Humbeck, Jeffrey F.; Aubrey, Michael L.; Alsbaiee, Alaaeddin; Ameloot, Rob; Coates, Geoffrey W.; Dichtel, William R.; Long, Jeffrey R.

    2015-06-23

    A new family of solid polymer electrolytes based upon anionic tetrakis(phenyl)borate tetrahedral nodes and linear bis-alkyne linkers is reported. Sonogashira polymerizations using tetrakis(4-iodophenyl)borate, tetrakis(4-iodo-2,3,5,6-tetrafluorophenyl)borate and tetrakis(4-bromo-2,3,5,6-tetrafluorophenyl)borate delivered highly cross-linked polymer networks with both 1,4-diethynylbeznene and a tri(ethylene glycol) substituted derivative. Promising initial conductivity metrics have been observed, including high room temperature conductivities (up to 2.7 × 10-4 S cm-1), moderate activation energies (0.25–0.28 eV), and high lithium ion transport numbers (up to tLi+ = 0.93). Initial investigations into the effects of important materials parameters such as bulk morphology, porosity, fluorination, and other chemical modification, provide starting design parameters for further development of this new class of solid electrolytes.

  2. METHOD OF SEPARATING RARE EARTHS BY ION EXCHANGE

    DOEpatents

    Spedding, F.H.; Powell, J.E.

    1960-10-18

    A process is given for separating yttrium and rare earth values having atomic numbers of from 57 through 60 and 68 through 71 from an aqueous solution whose pH value can range from 1 to 9. All rare earths and yttrium are first adsorbed on a cation exchange resin, and they are then eluted with a solution of N-hydroxyethylethylenediaminetriacetic acid (HEDTA) in the order of decreasing atomic number, yttrium behaving like element 61; the effluents are collected in fractions. The HEDTA is recovered by elution with ammonia solution and the resin is regenerated with sulfuric acid. Rare earths are precipitated from the various effluents with oxalic acid, and each supernatant is passed over cation exchange resin for adsorption of HEDTA and nonprecipitated rare earths: the oxalic acid is not retained by the resin.

  3. Compilation of 3D global conductivity model of the Earth for space weather applications

    NASA Astrophysics Data System (ADS)

    Alekseev, Dmitry; Kuvshinov, Alexey; Palshin, Nikolay

    2015-07-01

    We have compiled a global three-dimensional (3D) conductivity model of the Earth with an ultimate goal to be used for realistic simulation of geomagnetically induced currents (GIC), posing a potential threat to man-made electric systems. Bearing in mind the intrinsic frequency range of the most intense disturbances (magnetospheric substorms) with typical periods ranging from a few minutes to a few hours, the compiled 3D model represents the structure in depth range of 0-100 km, including seawater, sediments, earth crust, and partly the lithosphere/asthenosphere. More explicitly, the model consists of a series of spherical layers, whose vertical and lateral boundaries are established based on available data. To compile a model, global maps of bathymetry, sediment thickness, and upper and lower crust thicknesses as well as lithosphere thickness are utilized. All maps are re-interpolated on a common grid of 0.25×0.25 degree lateral spacing. Once the geometry of different structures is specified, each element of the structure is assigned either a certain conductivity value or conductivity versus depth distribution, according to available laboratory data and conversion laws. A numerical formalism developed for compilation of the model, allows for its further refinement by incorporation of regional 3D conductivity distributions inferred from the real electromagnetic data. So far we included into our model four regional conductivity models, available from recent publications, namely, surface conductance model of Russia, and 3D conductivity models of Fennoscandia, Australia, and northwest of the United States.

  4. Amplitude Modulation Mode of Scanning Ion Conductance Microscopy.

    PubMed

    Li, Peng; Liu, Lianqing; Yang, Yang; Zhou, Lei; Wang, Dong; Wang, Yuechao; Li, Guangyong

    2015-08-01

    Live-cell imaging at the nanoscale resolution is a hot research topic in the field of life sciences for the direct observation of cellular biological activity. Scanning ion conductance microscopy (SICM) is one of the few effective imaging tools for live-cell imaging at the nanoscale resolution. However, there are various problems in existing scanning modes. The hopping and AC modes suffer from low speed, whereas the DC mode is prone to instability because of the DC drift and external electrical interference. In this article, we propose an amplitude modulation (AM) mode of SICM, which employs an AC voltage to enhance the stability and improve the scanning speed. In this AM mode, we introduce a capacitance compensation method to eliminate capacitance effect and use the amplitude of the AC current component to control the tip movement. Experimental results on polydimethylsiloxane samples verify the validity of the AM mode and demonstrate an improved performance of both speed and stability of this new mode. PMID:25759185

  5. Scanning Ion Conductance Microscopy for living cell membrane potential measurement

    NASA Astrophysics Data System (ADS)

    Panday, Namuna

    Recently, the existence of multiple micro-domains of extracellular potential around individual cells have been revealed by voltage reporter dye using fluorescence microscopy. One hypothesis is that these long lasting potential patterns play a vital role in regulating important cell activities such as embryonic patterning, regenerative repair and reduction of cancerous disorganization. We used multifunctional Scanning Ion Conductance Microscopy (SICM) to study these extracellular potential patterns of single cell with higher spatial resolution. To validate this novel technique, we compared the extracellular potential distribution on the fixed HeLa cell surface and Polydimethylsiloxane (PDMS) surface and found significant difference. We then measured the extracellular potential distributions of living melanocytes and melanoma cells and found both the mean magnitude and spatial variation of extracellular potential of the melanoma cells are bigger than those of melanocytes. As compared to the voltage reporter dye based fluorescence microscope method, SICM can achieve quantitative potential measurements of non-labeled living cell membranes with higher spatial resolution.

  6. A study of the formation and dynamics of the Earth's plasma sheet using ion composition data

    NASA Technical Reports Server (NTRS)

    Lennartsson, O. W.

    1994-01-01

    Over two years of data from the Lockheed Plasma Composition Experiment on the ISEE 1 spacecraft, covering ion energies between 100 eV/e and about 16 keV/e, have been analyzed in an attempt to extract new information about three geophysical issues: (1) solar wind penetration of the Earth's magnetic tail; (2) relationship between plasma sheet and tail lobe ion composition; and (3) possible effects of heavy terrestrial ions on plasma sheet stability.

  7. Method for determining thermal conductivity and thermal capacity per unit volume of earth in situ

    DOEpatents

    Poppendiek, Heinz F.

    1982-01-01

    A method for determining the thermal conductivity of the earth in situ is based upon a cylindrical probe (10) having a thermopile (16) for measuring the temperature gradient between sets of thermocouple junctions (18 and 20) of the probe after it has been positioned in a borehole and has reached thermal equilibrium with its surroundings, and having means (14) for heating one set of thermocouple junctions (20) of the probe at a constant rate while the temperature gradient of the probe is recorded as a rise in temperature over several hours (more than about 3 hours). A fluid annulus thermally couples the probe to the surrounding earth. The recorded temperature curves are related to the earth's thermal conductivity, k.sub..infin., and to the thermal capacity per unit volume, (.gamma.c.sub.p).sub..infin., by comparison with calculated curves using estimates of k.sub..infin. and (.gamma.c.sub.p).sub..infin. in an equation which relates these parameters to a rise in the earth's temperature for a known and constant heating rate.

  8. Equilibrium selectivity alone does not create K+-selective ion conduction in K+ channels

    NASA Astrophysics Data System (ADS)

    Liu, Shian; Lockless, Steve W.

    2013-11-01

    Potassium (K+) channels are selective for K+ over Na+ ions during their transport across membranes. We and others have previously shown that tetrameric K+ channels are primarily occupied by K+ ions in their selectivity filters under physiological conditions, demonstrating the channel’s intrinsic equilibrium preference for K+ ions. Based on this observation, we hypothesize that the preference for K+ ions over Na+ ions in the filter determines its selectivity during ion conduction. Here, we ask whether non-selective cation channels, which share an overall structure and similar individual ion-binding sites with K+ channels, have an ion preference at equilibrium. The variants of the non-selective Bacillus cereus NaK cation channel we examine are all selective for K+ over Na+ ions at equilibrium. Thus, the detailed architecture of the K+ channel selectivity filter, and not only its equilibrium ion preference, is fundamental to the generation of selectivity during ion conduction.

  9. A multiscale study of ion heating in Earth's magnetotail

    NASA Astrophysics Data System (ADS)

    Lapenta, Giovanni; Ashour-Abdalla, Maha; Walker, Raymond J.; El Alaoui, Mostafa

    2016-01-01

    Ion heating during a substorm on 15 February 2008, starting at 0348 UT, is studied with a new approach recently described in Ashour-Abdalla et al. (2015). The general conditions of the magnetotail are obtained from a global magnetohydrodynamic (MHD) model and are used to drive a full kinetic particle-in-cell (PIC) simulation of a 3-D region of the tail. Within the kinetic box, the ions, the electrons, and the fields evolve self-consistently. The large scales are captured by the MHD model and the small scales by the PIC model based on the MHD state. This approach is used to study ion heating. Different heating mechanisms were analyzed by examining the velocity distributions at different locations. In the x direction heating occurs as the reconnection-generated ion jet interacts with the environment in which it propagates. The heating is found mostly in the separatrices and increases downstream of the reconnection region. In the y direction the heating is less intense and is found near the dipolarization fronts. It occurs as ions become magnetized and gyrotropize the distribution function. In addition, ions can be heated in the y direction by the reconnection electric field near the reconnection site. In the z direction the ions are heated by the formation of beams moving along z between the separatrices.

  10. Increasing ion sorption and desorption rates of conductive electrodes

    SciTech Connect

    DePaoli, David William; Kiggans, Jr., James O; Tsouris, Costas; Bourcier, William; Campbell, Robert; Mayes, Richard T

    2014-12-30

    An electrolyte system includes a reactor having a pair of electrodes that may sorb ions from an electrolyte. The electrolyte system also includes at least one power supply in electrical communication with the reactor. The at least one power supply may supply a DC signal and an AC signal to the pair of electrodes during sorption of the ions. In addition, the power supply may supply only the AC signal to the pair of electrodes during desorption of the ions.

  11. Role of finite ionospheric conductivity on toroidal field line oscillations in the Earth's magnetosphere -- Analytic solutions

    NASA Astrophysics Data System (ADS)

    Bulusu, Jayashree; Sinha, A. K.; Vichare, Geeta

    2016-06-01

    An analytic solution has been formulated to study the role of ionospheric conductivity on toroidal field line oscillations in the Earth's magnetosphere. The effect of ionospheric conductivity is addressed in two limits, viz, (a) when conductance of Alfvén wave is much different from ionospheric Pedersen conductance and (b) when conductance of Alfvén wave is close to the ionospheric Pedersen conductance. In the former case, the damping is not significant and standing wave structures are formed. However, in the latter case, the damping is significant leading to mode translation. Conventionally, "rigid-end" and "free-end" cases refer to eigenstructures for infinitely large and vanishingly small limit of ionospheric conductivity, respectively. The present work shows that when the Pedersen conductance overshoots (undershoots) the Alfvén wave conductance, a free-end (rigid-end) mode gets transformed to rigid-end (free-end) mode with an increase (decrease) in harmonic number. This transformation takes place within a small interval of ionospheric Pedersen conductance around Alfvén wave conductance, beyond which the effect of conductivity on eigenstructures of field line oscillations is small. This regime of conductivity limit (the difference between upper and lower limits of the interval) decreases with increase in harmonic number. Present paper evaluates the damping effect for density index other than the standard density index m = 6, using perturbation technique. It is found that for a small departure from m = 6, both mode frequency and damping rate become a function of Pedersen conductivity.

  12. EXPERIMENTAL EFFECTS OF CONDUCTIVITY AND MAJOR IONS ON STREAM PERIPHYTON - abstract

    EPA Science Inventory

    Our study examined if specific conductivities comprised of different ions associated with resource extraction affected stream periphyton assemblages, which are important sources of primary production. Sixteen artificial streams were dosed with two ion recipes intended to mimic so...

  13. Detection of singly ionized energetic lunar pick-up ions upstream of earth's bow shock

    NASA Technical Reports Server (NTRS)

    Hilchenbach, M.; Hovestadt, D.; Klecker, B.; Moebius, E.

    1992-01-01

    Singly ionized suprathermal ions upstream of the earth's bow shock have been detected by using the time-of-flight spectrometer SULEICA on the AMPTE/IRM satellite. The data were collected between August and December 1985. The flux of the ions in the mass range between 23 and 37 amu is highly anisotropic towards the earth. The ions are observed with a period of about 29 days around new moon (+/- 3 days). The correlation of the energy of the ions with the solar wind speed and the interplanetary magnetic field orientation indicates the relation to the pick-up process. We conclude that the source of these pick-up ions is the moon. We argue that due to the impinging solar wind, atoms are sputtered off the lunar surface, ionized in the sputtering process or by ensuing photoionization and picked up by the solar wind.

  14. An Update on the Lithium-Ion Cell Low-Earth-Orbit Verification Test Program

    NASA Technical Reports Server (NTRS)

    Reid, Concha M.; Manzo, Michelle A.; Miller, Thomas B.; McKissock, Barbara I.; Bennett, William

    2007-01-01

    A Lithium-Ion Cell Low-Earth-Orbit Verification Test Program is being conducted by NASA Glenn Research Center to assess the performance of lithium-ion (Li-ion) cells over a wide range of low-Earth-orbit (LEO) conditions. The data generated will be used to build an empirical model for Li-ion batteries. The goal of the modeling will be to develop a tool to predict the performance and cycle life of Li-ion batteries operating at a specified set of mission conditions. Using this tool, mission planners will be able to design operation points of the battery system while factoring in mission requirements and the expected life and performance of the batteries. Test conditions for the program were selected via a statistical design of experiments to span a range of feasible operational conditions for LEO aerospace applications. The variables under evaluation are temperature, depth-of-discharge (DOD), and end-of-charge voltage (EOCV). The baseline matrix was formed by generating combinations from a set of three values for each variable. Temperature values are 10 C, 20 C and 30 C. Depth-of-discharge values are 20%, 30% and 40%. EOCV values are 3.85 V, 3.95 V, and 4.05 V. Test conditions for individual cells may vary slightly from the baseline test matrix depending upon the cell manufacturer s recommended operating conditions. Cells from each vendor are being evaluated at each of ten sets of test conditions. Cells from four cell manufacturers are undergoing life cycle tests. Life cycling on the first sets of cells began in September 2004. These cells consist of Saft 40 ampere-hour (Ah) cells and Lith ion 30 Ah cells. These cells have achieved over 10,000 cycles each, equivalent to about 20 months in LEO. In the past year, the test program has expanded to include the evaluation of Mine Safety Appliances (MSA) 50 Ah cells and ABSL battery modules. The MSA cells will begin life cycling in October 2006. The ABSL battery modules consist of commercial Sony hard carbon 18650 lithium-ion

  15. Energization of Ions in near-Earth current sheet disruptions

    NASA Technical Reports Server (NTRS)

    Taktakishvili, A.; Lopez, R. E.; Goodrich, C. C.

    1995-01-01

    In this study we examine observations made by AMPTE/CCE of energetic ion bursts during seven substorm periods when the satellite was located near the neutral sheet, and CCE observed the disruption cross-tail current in situ. We compare ion observations to analytic calculations of particle acceleration. We find that the acceleration region size, which we assume to be essentially the current disruption region, to be on the order of 1 R(sub E). Events exhibiting weak acceleration had either relatively small acceleration regions (apparently associated with pseudobreakup activity on the ground) or relatively small changes in the local magnetic field (suggesting that the magnitude of the local current disruption region was limited). These results add additional support for the view that the particle bursts observed during turbulent current sheet disruptions are due to inductive acceleration of ions.

  16. The electromagnetic ion beam instability upstream of the earth's bow shock

    NASA Technical Reports Server (NTRS)

    Gary, S. P.; Gosling, J. T.; Forslund, D. W.

    1981-01-01

    The linear theory of the electromagnetic ion beam instability for arbitrary angles of propagation has been studied. The parameters considered in the theory are typical of the solar wind upstream of the earth's bow shock when a 'reflected' proton beam is present. Maximum growth occurs for propagation parallel to the ambient magnetic field B, but this instability also displays significant growth at wave-vectors oblique to B. Oblique, unstable modes seem to be the likely source of the compressive magnetic fluctuations recently observed in conjunction with the 'diffuse' ion population. An energetic ion beam does not directly give rise to linear growth of either ion acoustic or whistler mode instabilities.

  17. Rare earth ion doped non linear laser crystals

    NASA Astrophysics Data System (ADS)

    Jaque, D.; Romero, J. J.; Ramirez, M. O.; Garcia, J. A. S.; de Las Heras, C.; Bausa, L. E.; Sole, J. G.

    2003-01-01

    We show how non linear crystals activated with Yb3+ or Nd3+ ions can be used to develop diode pumped solid state lasers emitting in the visible region of the electromagnetic spectrum. For this purpose we have selected relevant examples of systems investigated in our laboratory.

  18. Quantum CPF gates between rare earth ions through measurement

    NASA Astrophysics Data System (ADS)

    Xiao, Yun-Feng; Han, Zheng-Fu; Yang, Yong; Guo, Guang-Can

    2004-09-01

    We propose a method to realize quantum controlled phase flip (CPF) through interaction between a single-photon pulse and two microsphere cavities with a single three-level ion respectively and final photonic measurement. Our CPF gates are scalable with extremely high fidelity and low error rate, and are more applicable based on current laboratory cavity-QED technology.

  19. Multispacecraft observations of diffuse ions upstream of Earth's bow shock

    NASA Astrophysics Data System (ADS)

    Kis, A.; Scholer, M.; Klecker, B.; Moebius, E.; Lucek, E.; Reme, H.

    We present observations of upstream ions at times of large separation distance between the Cluster spacecraft (~5000 km). On 18 February, 2003, during particulary quiet interplanetary conditions, the Cluster spacecraft were moving inbound through the foreshock region, where for more than 12 hours they simultaneously observed a continuous presence of a diffuse ion population. Using the HIA and CODIF sensors of the CIS plasma instrument onboard SC-1 and -3, we were able to directly measure the upstream ion density gradients in the energy range 10-32 keV in several energy bands. During this time period, the spacecraft distance from the bow shock parallel to the local magnetic field varies considerably (between 0 and 15 Re). The distance to the bow shock has been determined by using upstream magnetic field and plasma parameters and a bow shock model. We find up to 10 Re from the bow shock an exponential decrease of the upstream ion density, with an e-folding distance increasing from 3.1 to 5.6 Re at energies from 10 keV to 32 keV, respectively. From the e-folding distance the parallel diffusion coefficient and its energy dependence can be determined. At distances more than 10 Re the gradient is close to zero.

  20. Transport toward earth of ions sputtered from the moon's surface by the solar wind

    NASA Astrophysics Data System (ADS)

    Cladis, J. B.; Francis, W. E.; Vondrak, R. R.

    1994-01-01

    The transport of typical ions from the surface of the Moon to the vicinity of Earth was calculated using a test particle approach. It was assumed that the ions were sputtered from the surface by the solar wind, with fluxes in the range determined experimentally by Elphic et al. (1991), and were accelerated initially to 10 eV by the potential of the Moon on its sunlit side. Si(+) and Ca(+) ions were selected for this transport analysis because their masses are within two prominent ion mass groups that have high sputtering yields. In the solar wind the ion trajectories were traced in the following superimposed fields: (1) a steady magnetic field B0 at an angle of 45 deg to the solar wind velocity VSW, (2) the motional electric field Ezero = -V(sub SW x B0, and (3) turbulent magnetic and electric fields generated by hydromagnetic waves with a k-space power spectrum of absolute value of k-5/3 propagating along both directions of the magnetic field B0. Interactions with Earth's bow shock and magnetosphere were included. Case histories of the ions were recorded in the XGSM, YGSM plane and in various planes perpendicular to the E0 x B0 drift direction of the ions between the Moon and Earth. The number density, energy and angular distributions, and directional and omnidirectional fluxes of the ions were constructed from the case histories. It was found that the diffusion of the ions increases rapidly as the amplitude of the turbulence delta Brms increases beyond the value 0.04 B0. Recent measurements of lunar ions upstream of the bow shock by Hilchenbach et al. (1992) generally confirm the predicted behavior of the ions.

  1. Spin-orbit thermal entanglement in a rare-earth-metal ion: Susceptibility witness

    NASA Astrophysics Data System (ADS)

    Duarte, O. S.; Castro, C. S.; Reis, M. S.

    2013-07-01

    In the present work, we explore the thermal entanglement between spin and orbital angular momentum in a rare-earth ion. A witness, based on the magnetic susceptibility and capable of revealing entanglement between these two angular momenta of different nature, is introduced. We found entanglement temperatures of 322 K for promethium and 715 K for samarium. These high temperatures make interesting the use of rare-earth in applications of quantum-information processes at room temperature.

  2. Observations of nonadiabatic acceleration of ions in Earth`s magnetotail

    SciTech Connect

    Frank, L.A.; Paterson, W.R.; Kivelson, M.G.

    1994-08-01

    The authors present observations of the three-dimensional velocity distributions of protons in the energy range 20 eV to 52 keV at locations within and near the current sheet of Earth`s magnetotail at geocentric radial distances 35 to 87 R{sub E}. These measurements were acquired on December 8, 1990, with a set of electrostatic analyzers on board the Galileo spacecraft during its approach to Earth in order to obtain one of its gravitational assists to Jupiter. It is found that the velocity distributions are inadequately described as quasi-Maxwellian distributions such as those found in the central plasma sheet at positions nearer to Earth. Instead the proton velocity distributions can be categorized into two major types. The first type is the `lima bean` shaped distribution with high-speed bulk flows and high temperatures that are similar to those found nearer to Earth in the plasma sheet boundary layer. The second type consists of colder protons with considerably lesser bulk flow speeds. Examples of velocity distributions are given for the plasma mantle, a region near the magnetic neutral line, positions earthward and tailward of the neutral line, and the plasma sheet boundary layer. At positions near the neutral line, only complex velocity distributions consisting of the colder protons are found, whereas both of the above types of distributions are found in and near the current sheet at earthward and tailward locations. Bulk flows are directed generally earthward and tailward at positions earthward and tailward of the neutral line, respectively. Only the high-speed, hot distribution is present in the plasma sheet boundary layer. The observations are interpreted in terms of the nonadiabatic acceleration of protons that flow into the current sheet from the plasma mantle. For this interpretation the hot, {open_quotes}lima bean{close_quotes} shaped distributions are associated with meandering, or Speiser, orbits in the current sheet. 31 refs., 13 figs.

  3. Maximization of the rate of chloride conduction in the CFTR channel pore by ion-ion interactions.

    PubMed

    Gong, Xiandi; Linsdell, Paul

    2004-06-01

    Multi-ion pore behaviour has been identified in many Cl(-) channel types but its biophysical significance is uncertain. Here, we show that mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel that disrupt anion-anion interactions within the pore are associated with drastically reduced single channel conductance. These results are consistent with models suggesting that rapid Cl(-) permeation in CFTR results from repulsive ion-ion interactions between Cl(-) ions bound concurrently inside the pore. Naturally occurring mutations that disrupt these interactions can result in cystic fibrosis. PMID:15130785

  4. Trivalent rare-earth ions as photon down-shifter for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Steudel, Franziska; Loos, Sebastian; Ahrens, Bernd; Schweizer, Stefan

    2014-05-01

    Rare-earth doped borate glasses are investigated for their potential as photon down-shifting cover glass for CdTe solar cells. Note, that CdTe solar cells have a poor response in the ultraviolet and blue spectral range due to absorption in the CdS buffer layer having a band gap of 2.4 eV. The following trivalent rare-earth ions are analyzed in detail: Sm3+, Eu3+, and Tb3+. These ions provide strong absorption bands in the ultraviolet / blue spectral range and an intense emission in the red (Sm3+ and Eu3+) or green (Tb3+) spectral range. The gain in short-circuit current density of a CdTe solar cell is calculated for different rare-earth ion concentrations. The calculations are based on the rare-earth's absorption coefficients as well as their photoluminescence (PL) quantum efficiency. For Sm3+, the PL quantum efficiency depends significantly on the doping concentration. Finally, the potential of double-doped borate glasses, i.e. glasses doped with two different rare-earth ions, is investigated.

  5. Sensitivity of the interpretation of the experimental ion thermal diffusivity to the determination of the ion conductive heat flux

    SciTech Connect

    Stacey, W. M.

    2014-04-15

    A moments equation formalism for the interpretation of the experimental ion thermal diffusivity from experimental data is used to determine the radial ion thermal conduction flux that must be used to interpret the measured data. It is shown that the total ion energy flux must be corrected for thermal and rotational energy convection, for the work done by the flowing plasma against the pressure and viscosity, and for ion orbit loss of particles and energy, and expressions are presented for these corrections. Each of these factors is shown to have a significant effect on the interpreted ion thermal diffusivity in a representative DIII-D [J. Luxon, Nucl. Fusion 42, 614 (2002)] discharge.

  6. Luminescent instabilities in dense rare earth ion systems

    NASA Astrophysics Data System (ADS)

    Kuditcher, Amos

    1999-11-01

    This thesis reports experiments and theory on intrinsic mirrorless bistability in the luminescence of ytterbium- doped crystals and glasses. The main results are the observation of intrinsically bistable luminescence at room temperature and chromatic switching at low temperature, reported here for the first time. The nonlinear dynamics responsible for these optical phenomena are shown to arise from ion-ion interactions controlled by the application of resonant electromagnetic fields. On the theoretical side, the classical Lorentz local field correction is shown to be the lowest order term of radiation-driven correlation contributions to local polarization which arise from inter-ion coherences and cooperative relaxation and frequency shifts beyond the dynamic shift are predicted. The nonlinear Maxwell-Bloch equations are extended to describe energy transfer between different species of ions predicting bistability in excited state populations which then emit bistable luminescence as a consequence, and an intensity dependent transfer rate is predicted. Diffusive excitation migration in space is also explored as a possible mechanism for generating multiple instabilities, but is not predicted to give rise to hysteresis loops by itself. On the experimental side, original observations of intrinsic optical switching and hysteresis are reported in the luminescence of Yb:CsCdBr 3 and Yb, Tm:glass. Evidence of cross-coupling between different impurities is also presented, together with spectroscopic details of intrinsic chromatic switching between different luminescent transitions of the acceptor species in Yb, Er:CsCdBr3 excited at the infrared Yb resonance wavelength. Conclusive spectroscopic evidence that excludes thermal effects as responsible for low temperature intrinsic switching is also presented. Room temperature intrinsic optical switching and hysteresis are reported for the first time in bulk Yb,Tm:glass samples. Switching, hysteresis, and clamping of laser output

  7. Ion distributions in the Earth's foreshock upstream from the bow shock

    NASA Technical Reports Server (NTRS)

    Fuselier, S. A.

    1995-01-01

    A variety of suprathermal and energetic ion distributions are found upstream from shocks. Some distributions, such as field-aligned beams, are generated directly at the shock either through reflection processes or through leakage from the hotter downstream region. Other distributions, such as intermediate distributions, evolve from these parent distributions through wave-particle interactions. This paper reviews our current understanding of the creation and evolution of suprathermal distributions at shocks. Examples of suprathermal ion distributions are taken from observations at the Earth's bow shock. Particular emphasis is placed on the creation of field-aligned beams and specularly reflected ion distributions and on the evolution of these distributions in the Earth's ion foreshock. However, the results from this heavily studied region are applicable to interplanetary shocks, bow shocks at other planets, and comets.

  8. Two-temperature models of old supernova remnants with ion and electron thermal conduction

    NASA Technical Reports Server (NTRS)

    Cui, Wei; Cox, Donald P.

    1992-01-01

    To investigate the potential effects thermal conduction may have on the evolution of old supernova remnants, we present the results of 1D (spherically symmetric) numerical simulations of a remnant in a homogeneous interstellar medium for four different cases: (1) without thermal conduction; (2) with both electron and ion thermal conduction assuming equal temperatures; (3) with electron thermal conduction only, following electron and ion temperatures separately; and (4) with both electron and ion thermal conduction following separate temperatures. We followed the entire evolution until the completion of the remnant bubble collapse. Our most significant result is that in remnant evolution studies concerned principally with either the shell or bubble evolution at late times, reasonable results are obtained with single-temperature models. When the electron and ion temperatures are followed separately, however, ion thermal conduction cannot safely be ignored.

  9. Continental growth on Early Earth: Crustal electrical conductivity models of the Barberton Greenstone Belt, South Africa

    NASA Astrophysics Data System (ADS)

    Weckmann, U.; Kutter, S.; De Wit, M.

    2014-12-01

    The Barberton Greenstone Belt (BGB, South Africa) is one of the few Archean remnants where the tectonic evolution of the Early Earth can be studied. The first formation of the crust is a controversially discussed topic among geoscientists. Tectonics on the Early Earth might have been similar to the plate movement and their driving forces that we observe today. However, regarding that some fundamental conditions like the thermal setting were considerably different at this time other processes like vertical mass transport might have played the governing role in tectonics. Therefore contrasting evolutionary models of the BGB exist, mainly based on a number of geological and petrological studies. However, there is only little information on its deeper architecture. For a better understanding of past processes and the character of the tectonic regime which led to the formation of the BGB, magnetotelluric (MT) surveys were carried out as a part of the German-South African Inkaba yeAfrica research initiative. At approximately 200 MT sites aligned along six profiles (approx. 80 to 110 km length) data was collected during two field experiments in 2009 and 2010. The MT method images the electrical conductivity of rocks and is particularly sensitive to imprints of tectonic processes resulting in persistent mineralization e.g. along shear planes. Against the surrounding of significantly conductive geological units like the Phanerozoic Transvaal cover, the rocks of the BGB are generally characterized by high electrical resistivities. Particularly plutons such as the Dalmein Pluton can be traced deeply into the crust. Contrary, faults of the BGB appear as zones of high conductivity down to a depth of 5 to 10 km. We will present 3D inversion results indicating an extension of the plutons of the western BGB beneath the Transvaal cover and a sharp conductivity contrast of the BGB compared to the eastern batholiths. We will discuss existing models of the evolution of the BGB in view

  10. Ion funnel with extended mass range and reduced conductance limit aperture

    DOEpatents

    Tolmachev, Aleksey V.; Smith, Richard D.

    2008-04-01

    An improved ion funnel design is disclosed that decreases the axial RF (parasite) fields at the ion funnel exit. This is achieved by addition of one or more compensation electrodes after the conductance limit electrode. Various RF voltage profiles may be applied to the various electrodes minimizing the parasite axial potential wells. The smallest RF aperture that serves as the conductance limiting electrode is further reduced over standard designs. Overall, the ion funnel improves transmission ranges of both low m/z and high m/z ions, reducing RF activation of ions and decreasing the gas load to subsequent differential pumping stages.

  11. Ultrafine Na-4-mica: uptake of alkali and alkaline earth metal cations by ion exchange.

    PubMed

    Kodama, Tatsuya; Ueda, Masahito; Nakamuro, Yumiko; Shimizu, Ken-ichi; Komarneni, Sridhar

    2004-06-01

    The cation exchange properties of alkali and alkaline earth metal cations at room temperature were investigated on an ultrafine, highly charged Na-4-mica (with the ideal mica composition Na4Mg6Al4Si4O20F4.xH2O). Ultrafine mica crystallites of 200 nm in size led to faster Sr2+ uptake kinetics in comparison to larger mica crystallites. The alkali metal ion (K+, Cs+, and Li+) exchange uptake was rapid, and complete exchange occurred within 30 min. For the alkaline earth metal ions Ba2+, Ca2+, and Mg2+, however, the exchange uptake required lengthy periods from 3 days to 4 weeks to be completed, similar to its Sr uptake, as previously reported. Kinetic models of the modified Freundlich and parabolic diffusion were examined for the experimental data on the Ba2+, Ca2+, and Mg2+ uptakes. The modified Freundlich model described well the Ba2+ ion uptake kinetics as well as that for the Sr2+ ion, while for the Ca2+ and Mg2+ ions the parabolic diffusion model showed better fitting. The alkali and alkaline earth ion exchange isotherms were also determined in comparison to the Sr2+ exchange isotherm. The thermodynamic equilibria for these cations were compared by using Kielland plots evaluated from the isotherms. PMID:15984251

  12. ION AND TEMPERATURE DEPENDENCE OF ELECTRICAL CONDUCTANCE FOR NATURAL WATERS

    EPA Science Inventory

    Four empirical equations describing the temperature dependence of electrical conductance of aqueous solutions are compared for the case of single electrolytes. The best method uses a modified Walden product where the log of the ratio between the conductances at two temperatures i...

  13. Formation of ion acoustic solitary waves upstream of the earth's bow shock. [in solar wind

    NASA Technical Reports Server (NTRS)

    Pangia, M. J.; Lee, N. C.; Parks, G. K.

    1985-01-01

    The turbulent plasma development of Lee and Parks is applied to the solar wind approaching the earth's bow shock region. The ponderomotive force contribution is due to ion acoustic waves propagating in the direction of the ambient magnetic field. In this case, the envelope of the ion acoustic wave is shown to satisfy the cubic Schroedinger equation. Modulational instabilities exist for waves in the solar wind, thereby predicting the generation of solitary waves. This analysis further identifies that the ion acoustic waves which exhibit this instability have short wavelengths.

  14. An experimental test of the electromagnetic ion cyclotron instability within the earth's magnetosphere

    NASA Technical Reports Server (NTRS)

    Mauk, B. H.; Mcpherron, R. L.

    1980-01-01

    Examples of propagating electromagnetic Alfven/ion cyclotron waves in plasma particle and magnetic field data observed by the ATS-6 geostationary satellite are discussed. These waves were viewed mainly near the afternoon and dusk regions of the earth's magnetosphere with normalized frequencies in the 0.05 to 0.5 range. Two wave events were analyzed: both appeared coincidentally with the encounter of cool plasma populations which joined the hot populations already present. An electromagnetic ion cyclotron instability was proposed as the wave generation mechanism; this theory was tested by evaluating the linear growth integrals under the measured anisotropic hot ion distribution.

  15. Optical spectra of triply-charged rare-earth ions in polycrystalline corundum

    NASA Astrophysics Data System (ADS)

    Kaplyanskiĭ, A. A.; Kulinkin, A. B.; Kutsenko, A. B.; Feofilov, S. P.; Zakharchenya, R. I.; Vasilevskaya, T. N.

    1998-08-01

    Solid samples of polycrystalline corundum α-Al2O3 activated by triply-charged rare-earth ions RE3+ (R=Eu3+, Er3+, Pr3+) were synthesized by the sol-gel technology. Characteristic narrow-line optical absorption and luminescence spectra produced by intraconfigurational 4 f-4 f transitions in RE3+ ions have been measured. RE3+ ions have been established to form one dominant type of optical centers in the corundum matrix, and the energy diagram of Eu3+ and Er3+ Stark levels in corundum has been determined.

  16. Behaviour of Paramagnetic Light Rare Earth Ions in LRE-123 Superconductors

    NASA Astrophysics Data System (ADS)

    Jirsa, M.; Rameš, M.; Muralidhar, M.; Volochová, D.; Diko, P.

    The slightly curved paramagnetic background (due to Brillouin dependence) of the paramagnetic light rare earth ions in 123 superconductors mixes below Tc with reversible magnetization, which hinders evaluation of the associated thermodynamic characteristics. We propose a method how to determine the effective number of magnetons per ion, the principal parameter of the Brillouin function course, even in materials with pores, with unknown or varying density and/or the local composition. The method was tested on various types of compounds containing Gd ions, like pure Gd-211, tetragonal Gd-123, (Y,Gd)-123, and (Nd,Eu,Gd)- 123 and on orthorhombic (oxygenated) Gd-123 and (Nd,Eu,Gd)-123.

  17. Performance and Comparison of Lithium-Ion Batteries Under Low-Earth-Orbit Mission Profiles

    NASA Technical Reports Server (NTRS)

    Reid, Concha M.; Smart, Marshall C.; Bugga, Ratnakumar V.; Manzo, Michelle A.; Miller, Thomas B.; Gitzendanner, Rob

    2007-01-01

    The performance of two 28 V, 25 Ah lithium-ion batteries is being evaluated under low-Earth-orbit mission profiles for satellite and orbiter applications. The batteries are undergoing life testing and have achieved over 12,000 cycles to 40 percent depth-of-discharge.

  18. Investigations of hyperfine and isotope structures in optical spectra of crystals with rare-earth ions

    NASA Astrophysics Data System (ADS)

    Popova, M. N.

    2015-10-01

    This is a review of works on hyperfine and isotope structures in the spectra of rare-earth ions in crystals that have been performed at the Laboratory of Fourier Spectroscopy of the Institute for Spectroscopy, Russian Academy of Sciences. The applicability of these studies to the development of optical quantum memory is discussed.

  19. Investigation of thermophysical characteristics of SrMoO4 crystals, nominally pure and doped with rare earth ions

    NASA Astrophysics Data System (ADS)

    Popov, P. A.; Skrobov, S. A.; Matovnikov, A. V.; Ivleva, L. I.; Dunaeva, E. E.; Shekhovtsov, A. N.; Kosmyna, M. B.

    2015-11-01

    Thermophysical characteristics of SrMoO4 crystals (grown by the Czochralski method from intrinsic melts), nominally pure and doped with rare earth ions, have been investigated. The temperature and concentration dependences of the thermal conductivity are obtained for SrMoO4 samples containing Nd3+ (0.28, 0.56, 0.84, and 1.33 at %), Pr3+ (0.01 and 0.41 at %), Ho3+ (0.01 and 0.06 at %), and Ho3+ (0.13 at %) + Tm3+ (0.13 at %) in a temperature range of 50-300 K. The thermal conductivities are measured in the directions parallel and/or perpendicular to the crystal optical axis. The thermal conductivity of nominally pure SrMoO4 at 300 K in the direction perpendicular to the c axis has been found to be 4.2 W/(m K). The introduction of impurities of rare earth metals reduces the thermal conductivity of SrMoO4 crystals. The anisotropy of the thermal conductivity is weak. The measured molar specific heat C P ( T) of a nominally pure SrMoO4 crystal is 116.2 J/(mol K) at 300 K. The temperature dependence of the phonon mean free path l( T) in a SrMoO4 crystal is calculated for the temperature range of 80-300 K based on experimental data.

  20. Structure and ionic diffusion of alkaline-earth ions in mixed cation glasses

    SciTech Connect

    Konstantinou, Konstantinos; Sushko, Petr; Duffy, Dorothy M.

    2015-08-15

    A series of mixed cation silicate glasses of the composition A2O – 2MO – 4SiO2, with A=Li,Na,K and M=Ca,Sr,Ba has been investigated by means of molecular dynamics simulations in order to understand the effect of the nature of the cations on the mobility of the alkaline-earth ions within the glass network. The size of the alkaline-earth cation was found to affect the inter-atomic distances, the coordination number distributions and the bond angle distributions , whereas the medium-range order was almost unaffected by the type of the cation. All the alkaline-earth cations contribute to lower vibrational frequencies but it is observed that that there is a shift to smaller frequencies and the vibrational density of states distribution gets narrower as the size of the alkaline-earth increases. The results from our modeling for the ionic diffusion of the alkaline-earth cations are in a qualitative agreement with the experimental observations in that there is a distinct correlation between the activation energy for diffusion of alkaline earth-ions and the cation radii ratio. An asymmetrical linear behavior in the diffusion activation energy with increasing size difference is observed. The results can be described on the basis of a theoretical model that relates the diffusion activation energy to the electrostatic interactions of the cations with the oxygens and the elastic deformation of the silicate network.

  1. Preparation and properties of electrically conducting ceramics based on indium oxide-rare earth oxides-hafnium oxides

    SciTech Connect

    Marchant, D.D.; Bates, J.L.

    1983-09-01

    Electrically conducting refractory oxides based on adding indium oxide to rare earth-stabilized hafnium oxide are being studied for use in magnetohydrodynamic (MHD) generators, fuel cells, and thermoelectric generators. The use of indium oxide generally increases the electrical conductivity. The results of measurements of the electrical conductivity and data on corrosion resistance in molten salts are presented.

  2. Conductivity study and fourier transform infrared (FTIR) characterization of methyl cellulose solid polymer electrolyte with sodium iodide conducting ion

    SciTech Connect

    Abiddin, Jamal Farghali Bin Zainal; Ahmad, Azizah Hanom

    2015-08-28

    Sodium ion (Na{sup +}) based solid polymer electrolyte (SPE) has been prepared using solution cast technique with distilled water as solvent and Methylcellulose (MC) as a polymer host. Methylcellulose polymer was chosen as the polymer host due to the abundance of lone pair electrons in the carbonyl and C-O-C constituents, which in turn provide multiple hopping sites for the Na{sup +} conducting ions. Variable compositions of sodium iodide (NaI) salt were prepared to investigate the optimum MC-NaI weight ratio. Results from Electrical Impedance Spectroscopy (EIS) technique show that pure methylcellulose has a low conductivity of 3.61 × 10{sup −11} S/cm.The conductivity increases as NaI content increases up to optimum NaIcomposition of 40 wt%, which yields an average conductivity of 2.70 × 10{sup −5} S/cm.

  3. Observation of Photon Echoes From Evanescently Coupled Rare-Earth Ions in a Planar Waveguide

    NASA Astrophysics Data System (ADS)

    Marzban, Sara; Bartholomew, John G.; Madden, Stephen; Vu, Khu; Sellars, Matthew J.

    2015-07-01

    We report the measurement of the inhomogeneous linewidth, homogeneous linewidth, and spin-state lifetime of Pr3 + ions in a novel waveguide architecture. The TeO2 slab waveguide deposited on a bulk Pr3 +∶Y2SiO5 crystal allows the 3H4↔1D2 transition of Pr3 + ions to be probed by the optical evanescent field that extends into the substrate. The 2-GHz inhomogeneous linewidth, the optical coherence time of 70 ±5 μ s , and the spin-state lifetime of 9.8 ±0.3 s indicate that the properties of ions interacting with the waveguide mode are consistent with those of bulk ions. This result establishes the foundation for large, integrated, and high performance rare-earth-ion quantum systems based on a waveguide platform.

  4. Observational evidence on the origin of ions upstream of the earth's bow shock

    NASA Technical Reports Server (NTRS)

    Thomsen, M. F.; Gosling, J. T.; Schwartz, S. J.

    1983-01-01

    The kinematic formalism described by Schwartz et al. (1983) is used to quantitatively compare the zeroth order predicted energies for four different source hypotheses for ions detected upstream of the earth's bow shock with previously published observations of upstream field-aligned beams and gyrating ion events. Specular reflection of a fraction of the incident solar wind is found to be the most credible explanation of gyrating ion events observed upstream of shocks ranging from quasi-parallel to nearly perpendicular. The recent hypothesis that field-aligned beams are the result of leakage from the magnetosheath of ions which were originally specularly reflected at quasi-perpendicular portions of the shock provides good agreement with observed energies of many field-aligned beams. Only magnetic moment conserving reflection of solar wind ions is capable of accounting for two very energetic beam events.

  5. Observation of Photon Echoes From Evanescently Coupled Rare-Earth Ions in a Planar Waveguide.

    PubMed

    Marzban, Sara; Bartholomew, John G; Madden, Stephen; Vu, Khu; Sellars, Matthew J

    2015-07-01

    We report the measurement of the inhomogeneous linewidth, homogeneous linewidth, and spin-state lifetime of Pr3+ ions in a novel waveguide architecture. The TeO2 slab waveguide deposited on a bulk Pr3+∶Y2SiO5 crystal allows the 3H4↔1D2 transition of Pr3+ ions to be probed by the optical evanescent field that extends into the substrate. The 2-GHz inhomogeneous linewidth, the optical coherence time of 70±5  μs, and the spin-state lifetime of 9.8±0.3  s indicate that the properties of ions interacting with the waveguide mode are consistent with those of bulk ions. This result establishes the foundation for large, integrated, and high performance rare-earth-ion quantum systems based on a waveguide platform. PMID:26182097

  6. Coupling of a locally implanted rare-earth ion ensemble to a superconducting micro-resonator

    SciTech Connect

    Wisby, I. Tzalenchuk, A. Ya.; Graaf, S. E. de; Adamyan, A.; Kubatkin, S. E.; Gwilliam, R.; Meeson, P. J.; Lindström, T.

    2014-09-08

    We demonstrate the coupling of rare-earth ions locally implanted in a substrate (Gd{sup 3+} in Al{sub 2}O{sub 3}) to a superconducting NbN lumped-element micro-resonator. The hybrid device is fabricated by a controlled ion implantation of rare-earth ions in well-defined micron-sized areas, aligned to lithographically defined micro-resonators. The technique does not degrade the internal quality factor of the resonators which remain above 10{sup 5}. Using microwave absorption spectroscopy, we observe electron-spin resonances in good agreement with numerical modelling and extract corresponding coupling rates of the order of 1 MHz and spin linewidths of 50–65 MHz.

  7. Ab initio calculations on the positive ions of the alkaline-earth oxides, fluorides, and hydroxides

    NASA Technical Reports Server (NTRS)

    Partridge, H.; Langhoff, S. R.; Bauschlicher, C. W., Jr.

    1986-01-01

    Theoretical dissociation energies are presented for the alkaline-earth fluoride, hydroxide, and oxide positive ions that are considered to be accurate to 0.1-0.2 eV. The r(e) for the positive ions are found to be consistently shorter than the corresponding neutrals by 0.07 + or -0.02 A. The bonding in the ground states is demonstrated to be of predominantly M + 2 X - character. The a 3 Pi and A 1 Pi are found to lie considerably above the X 1 Sigma + ground states of the alkaline-earth fluoride and hydroxide positive ions. The overall agreement of the theoretical ionization potentials with the available experimental appearance potentials is satisfactory; these values should represent the most accurate and consistent set available.

  8. Negative Dielectric Constant Material Based on Ion Conducting Materials

    NASA Technical Reports Server (NTRS)

    Gordon, Keith L. (Inventor); Kang, Jin Ho (Inventor); Park, Cheol (Inventor); Lillehei, Peter T. (Inventor); Harrison, Joycelyn S. (Inventor)

    2014-01-01

    Metamaterials or artificial negative index materials (NIMs) have generated great attention due to their unique and exotic electromagnetic properties. One exemplary negative dielectric constant material, which is an essential key for creating the NIMs, was developed by doping ions into a polymer, a protonated poly(benzimidazole) (PBI). The doped PBI showed a negative dielectric constant at megahertz (MHz) frequencies due to its reduced plasma frequency and an induction effect. The magnitude of the negative dielectric constant and the resonance frequency were tunable by doping concentration. The highly doped PBI showed larger absolute magnitude of negative dielectric constant at just above its resonance frequency than the less doped PBI.

  9. Proton Incorporation and Protonic Conduction in Rare Earth Substituted Barium Cerate Ceramics.

    NASA Astrophysics Data System (ADS)

    Buchanan, Richard M.

    Perovskite-type oxides, particularly rare-earth -substituted barium cerates, are generally recognized as potentially important high-temperature proton conductors. However, considerable literature debate exists regarding such vital issues as the effect of various substituents on proton conduction, details of the proton transport mechanism, and the role of grain boundaries. In this work, conductivity measurements (via impedance spectroscopy) unequivocally indicate protonic conduction in Nd-, Gd-, and Yb-substituted BaCeO_3 , as shown by decreased conductivity following dehydration and by a large hydrogen/deuterium isotope effect. However, combined TGA/conductivity measurements, performed from 100-900^circC, show a pronounced, distinctive oxygen partial pressure dependence in only the Nd-substituted samples. The traditional defect chemistry model explains these trends only when the uncommon Nd(IV) oxidation state is included. A model of the relevant electronic band structure is presented, and the rationale for the existence of Nd(IV) in BaCeO_3 is discussed, including ionization potentials and ionic radii. In calculating the low energy proton diffusion path, the inclusion of partial covalency in static lattice simulations yields results more consistent with experiment. Long -range proton transport requires three separate steps: inter -oxygen hopping, and two distinct hydroxyl reorientations. The previously observed reverse correlation of activation energy with lattice parameter suggests reorientation as rate-limiting. The non-classical isotope effect and other experimental anomalies are resolvable by semi-classical models, although proton tunneling appears to be insignificant. An observed drop in activation energy near 300^circ C supports the concept of a low collision energy exchange. XPS indicates a continuous Ba-rich grain boundary phase in these materials. Thin films grown by solid-source MOCVD have bulk protonic conductivity comparable to ceramics, but, as

  10. Ionic conductivity of binary fluorides of potassium and rare earth elements

    NASA Astrophysics Data System (ADS)

    Sorokin, N. I.

    2016-01-01

    The ionic conductivity s of KYF4 and K2 RF5 single crystals ( R = Gd, Ho, Er) and KNdF4 and K2 RF5 ceramic samples ( R = Dy, Er) has been studied in the temperature range of 340-500°C. A comparative analysis of the σ values for these objects has been performed. Binary fluorides of potassium and rare earth elements were synthesized by the hydrothermal method (temperature 480°C, pressure 100-150 MPa) in the R 2O3-KF-H2O systems. The σ values of tetraf luorides are 3 × 10-5 S/cm (KYF4 single crystal) and 3 × 10-6 S/cm (KNdF4 ceramics) at 435°C. A K2ErF5 single crystal with σ = 1.2 × 10-4 S/cm at 435°C has the maximum value of ionic conductivity among pentafluorides. The anisotropy of ionic transport was found in K2HoF5 single crystals, σ∥ c /σ⊥ c = 2.5, where σ∥ c and σ⊥ c are, respectively, the conductivities along the crystallographic c axis and in the perpendicular direction.

  11. Formation of conductive polymers using nitrosyl ion as an oxidizing agent

    DOEpatents

    Choi, Kyoung-Shin; Jung, Yongju; Singh, Nikhilendra

    2016-06-07

    A method of forming a conductive polymer deposit on a substrate is disclosed. The method may include the steps of preparing a composition comprising monomers of the conductive polymer and a nitrosyl precursor, contacting the substrate with the composition so as to allow formation of nitrosyl ion on the exterior surface of the substrate, and allowing the monomer to polymerize into the conductive polymer, wherein the polymerization is initiated by the nitrosyl ion and the conductive polymer is deposited on the exterior surface of the substrate. The conductive polymer may be polypyrrole.

  12. Neoclassical ion thermal conductivity modified by finite banana effects in a tokamak plasma

    SciTech Connect

    Chang, C.S.

    1997-06-01

    A finite-banana-width correction to the neoclassical ion thermal conductivity is obtained in a tokamak plasma under the conventional assumption that the particle flow parallel to magnetic-field lines dominates the trapped particle{close_quote}s orbital dynamics. It is found that the finite-banana-width effect makes ion thermal conductivity itself be a function of radial plasma density gradient and magnetic shear. Negative radial gradients in plasma density and/or safety factor can reduce the neoclassical ion thermal conductivity when the banana width is a significant fraction of the gradient scale length. {copyright} {ital 1997 American Institute of Physics.}

  13. Large-scale, nonsubtractive patterning of transparent conducting oxides by ion bombardment

    SciTech Connect

    Sosa, Norma E.; Chen, Christopher; Liu Jun; Marks, Tobin J.; Hersam, Mark C.

    2011-07-11

    While significant progress has been achieved in the fabrication and performance of transparent electronic devices, substantially less research effort has been devoted to transparent interconnects, despite their critical importance for transparent integrated circuitry. Here, we exploit the crystal disorder induced by Ar{sup +} ion bombardment to achieve efficient fabrication of electrically conductive patterns on indium oxide surfaces. The resulting ion-induced patterns are characterized by conductive atomic force microscopy, secondary ion mass spectrometry, and four-point charge transport measurements. Massively parallel patterning is demonstrated over square centimeter areas with a patterned electrical conductivity of {approx}10{sup 4} S cm{sup -1}.

  14. Molecular mobility, morphology, and ion conduction in ionomers for electroactive devices

    NASA Astrophysics Data System (ADS)

    Tudryn, Gregory J.

    A sequential study of ion-containing polymers capable of ion solvation with varied ion content, dielectric constant, and counterions is presented in this dissertation in order to compare ion transport properties in ionomers with various ionic interactions. Structure-property relationships in these ion containing polymers are defined using x-ray scattering, rheology and dielectric spectroscopy, enabling the quantification of ion transport dynamics. Poly(ethylene oxide), (PEO) based ionomers are investigated in order to probe the relation between ion conduction and segmental relaxation, and copolymers of PEO and Poly(tetramethylene oxide), (PTMO) further develop an understanding of the trade-off between ion solvation and segmental dynamics. Ionomers with ionic liquid counterions probe diffuse charge interactions and steric effects on ion transport, and incorporation of ionic liquids into ionomer membranes such as Nafion provides desirable thermal and ion conducting properties which extend the use of such membranes for electroactive devices. PEO ionomers exhibit a strong relation between ionic conductivity and segmental dynamics, providing insight that the glass transition temperature, Tg, dominates the ion conduction mechanism. Increasing temperature induces aggregation of ionic groups as evidenced by the static dielectric constant and X-ray scattering as a function of temperature, revealing the contribution of ionic dipoles in the measured dielectric constant. The trade-off between ion solvation and fast polymer segmental dynamics are quantified in copolymer ionomers of PEO and lower Tg PTMO. While conducting ion content remains nearly unchanged, conductivity is lowered upon incorporation of PTMO, because the vast majority of the PTMO microphase separates from the PEO-rich microdomain that remains continuous and contributes most of the ion conduction. Dielectric constants and X-ray scattering show consistent changes with temperature that suggest a cascading

  15. Earth

    NASA Technical Reports Server (NTRS)

    Carr, M. H.

    1984-01-01

    The following aspects of the planet Earth are discussed: plate tectonics, the interior of the planet, the formation of the Earth, and the evolution of the atmosphere and hydrosphere. The Earth's crust, mantle, and core are examined along with the bulk composition of the planet.

  16. Ion Conduction in Polymerized Ionic Liquids with Different Pendant Groups

    SciTech Connect

    Fan, Fei; Wang, Yangyang; Hong, Tao; Heres, Maximilian F; Saito, Tomonori; Sokolov, Alexei P

    2015-01-01

    Polymerized ionic liquids (PolyILs) are promising candidates for energy storage and electrochemical devices applications. Understanding their ionic transport mechanism is the key for designing highly conductive PolyILs. By using broadband dielectric spectroscopy (BDS), rheology, and differential scanning calorimetry (DSC), a systematic study has been carried out to provide a better understanding of the ionic transport mechanism in PolyILs with different pendant groups. The variation of pendant groups results in different dielectric, mechanical, and thermal properties of these PolyILs. The Walden plot analysis shows that the data points for all these PolyILs fall above the ideal Walden line, and the deviation from the ideal line increases upon approaching the glass transition temperature (Tg). The conductivity for these PolyILs at their Tgs are much higher than the usually reported value 10 15 S/cm for polymer electrolytes, in which the ionic transport is closely coupled to the segmental dynamics. These results indicate a decoupling of ionic conductivity from the segmental relaxation in these materials. The degree of decoupling increases with the increase of the fragility of polymer segmental relaxation. We relate this observation to a decrease in polymer packing efficiency with an increase in fragility.

  17. Ion Conduction in Polymerized Ionic Liquids with Different Pendant Groups

    DOE PAGESBeta

    Fan, Fei; Wang, Yangyang; Hong, Tao; Heres, Maximilian F; Saito, Tomonori; Sokolov, Alexei P

    2015-01-01

    Polymerized ionic liquids (PolyILs) are promising candidates for energy storage and electrochemical devices applications. Understanding their ionic transport mechanism is the key for designing highly conductive PolyILs. By using broadband dielectric spectroscopy (BDS), rheology, and differential scanning calorimetry (DSC), a systematic study has been carried out to provide a better understanding of the ionic transport mechanism in PolyILs with different pendant groups. The variation of pendant groups results in different dielectric, mechanical, and thermal properties of these PolyILs. The Walden plot analysis shows that the data points for all these PolyILs fall above the ideal Walden line, and the deviationmore » from the ideal line increases upon approaching the glass transition temperature (Tg). The conductivity for these PolyILs at their Tgs are much higher than the usually reported value 10 15 S/cm for polymer electrolytes, in which the ionic transport is closely coupled to the segmental dynamics. These results indicate a decoupling of ionic conductivity from the segmental relaxation in these materials. The degree of decoupling increases with the increase of the fragility of polymer segmental relaxation. We relate this observation to a decrease in polymer packing efficiency with an increase in fragility.« less

  18. Ion velocity distributions in the vicinity of the current sheet in Earth's distant magnetotail

    NASA Technical Reports Server (NTRS)

    Frank, L. A.; Paterson, W. R.; Ackerson, K. L.; Kokubun, S.; Kivelson, M. G.; Yamamoto, T.; Fairfield, D. H.

    1994-01-01

    Observations of the three-dimensional velocity distributions of positive ions and electrons have been recently gained for the first time in Earth's distant magnetotail with the Galileo and Geotail spacecraft. For this brief discussion of these exciting results the focus is on the overall character of the ion velocity distributions during substorm activity. The ion velocity distributions within and near the magnetotail current sheet are not accurately described as convecting, isotropic Maxwellians. The observed velocity distributions are characterized by at least two robust types. The first type is similar to the 'lima bean'-shaped velocity distributions that are expected from the nonadiabatic acceleration of ions which execute Speiser-type trajectories in the current sheet. The second distribution is associated with the presence of cold ion beams that presumably also arise from the acceleration of plasma mantle ions in the electric and weak magnetic fields in the current sheet. The ion velocity distributions in a magnetic field structure that is similar to that for plasmoids are also examined. Again the velocity distributions are not Maxwellian but are indicative of nonadiabatic acceleration. An example of the pressure tensor within the plasmoid-like event is also presented because it is anticipated that the off-diagonal elements are important in a description of magnetotail dynamics. Thus our concept of magnetotail dynamics must advance from the present assumption of co-moving electron and ion Maxwellian distributions into reformulations in terms of global kinematical models and nonadiabatic particle motion.

  19. Broadband conductivity spectra of fast-ion-conducting silver selenite glasses: Dependence on power law and scaling

    NASA Astrophysics Data System (ADS)

    Deb, B.; Bhattacharya, S.; Ghosh, A.

    2011-11-01

    In this letter we have studied broadband conductivity spectra (10 Hz-3 GHz) of fast-ion-conducting silver selenite glasses of compositions xAgI-(1-x)(yAg2O-(1-y)SeO2). We have observed that the conductivity spectra below 10 MHz are characterized by a power law with exponent less than unity, while the conductivity spectra in the high-frequency range (above 10 MHz) have been adequately explained in the framework of the unified site relaxation model with exponent greater than unity. The scaling of the conductivity spectra indicates that the time-temperature superposition principle is valid in the low-frequency regime, but not in the high-frequency regime.

  20. Selective Measurement of Calcium and Sodium Ion Conductance Using Sub-Micropipette Probes with Ion Filters

    NASA Astrophysics Data System (ADS)

    Deng, Xiao Long; Takami, Tomohide; Son, Jong Wan; Kawai, Tomoji; Park, Bae Ho

    2012-02-01

    Selective ion currents in aqueous calcium chloride and sodium chloride solutions with concentrations of up to 1.0 M were observed with sub-micropipettes in which poly(vinyl chloride) (PVC) films containing ionophores selectively filtered cations. Calcium bis[4-(1,1,3,3-tetramethylbutyl)phenyl] phosphate (HDOPP-Ca) and bis[(12-crown-4)methyl]-2-dodecyl-2-methylmalonate [bis(12-crown-4)] were used as the ionophores to filter calcium and sodium ions, respectively. The selective ion current was observed using a low-current detection system developed from scanning tunneling microscopy. The approximate linear relationship between the ion concentration and ion current suggests that the sub-micropipette probe can be used to detect the intracellular local concentration of a specific ion up to 1.0 M.

  1. Estimation of Heavy Ion Densities From Linearly Polarized EMIC Waves At Earth

    SciTech Connect

    Kim, Eun-Hwa; Johnson, Jay R.; Lee, Dong-Hun

    2014-02-24

    Linearly polarized EMIC waves are expected to concentrate at the location where their wave frequency satisfies the ion-ion hybrid (IIH) resonance condition as the result of a mode conversion process. In this letter, we evaluate absorption coefficients at the IIH resonance in the Earth geosynchronous orbit for variable concentrations of helium and azimuthal and field-aligned wave numbers in dipole magnetic field. Although wave absorption occurs for a wide range of heavy ion concentration, it only occurs for a limited range of azimuthal and field-aligned wave numbers such that the IIH resonance frequency is close to, but not exactly the same as the crossover frequency. Our results suggest that, at L = 6.6, linearly polarized EMIC waves can be generated via mode conversion from the compressional waves near the crossover frequency. Consequently, the heavy ion concentration ratio can be estimated from observations of externally generated EMIC waves that have polarization.

  2. Nonthermal ions and associated magnetic field behavior at a quasi-parallel earth's bow shock

    NASA Technical Reports Server (NTRS)

    Wilkinson, W. P.; Pardaens, A. K.; Schwartz, S. J.; Burgess, D.; Luehr, H.; Kessel, R. L.; Dunlop, M.; Farrugia, C. J.

    1993-01-01

    Attention is given to ion and magnetic field measurements at the earth's bow shock from the AMPTE-UKS and -IRM spacecraft, which were examined in high time resolution during a 45-min interval when the field remained closely aligned with the model bow shock normal. Dense ion beams were detected almost exclusively in the midst of short-duration periods of turbulent magnetic field wave activity. Many examples of propagation at large elevation angles relative to the ecliptic plane, which is inconsistent with reflection in the standard model shock configuration, were discovered. The associated waves are elliptically polarized and are preferentially left-handed in the observer's frame of reference, but are less confined to the maximum variance plane than other previously studied foreshock waves. The association of the wave activity with the ion beams suggests that the former may be triggered by an ion-driven instability, and possible candidates are discussed.

  3. Sulfonated polyaniline, a conducting polymer electrode for ion transfer batteries

    SciTech Connect

    Barbero, C.; Miras, M.C.; Koetz, R.; Haas, O.

    1994-12-31

    Sulfonated polyaniline (SPAN) was synthesized by sulfonation of polyaniline base with f6ming sulfuric acid. The polymer films were characterized by XPS, FFIR and UV-vis-NIR. XPS in combination with FTIR shows that the preparation procedure leads to a ca. 47% sulfonation of an otherwise unchanged polyaniline backbone. Electrodes modified with SPAN films exhibited two redox steps in aqueous as well as in nonaqueous electrolytes. Probe Beam Deflection and Quartz Crystal Microbalance were used to study the ion exchange mechanism. Protons are predominantly expelled during the first and second oxidation steps in acidic aqueous solution, accompanied by a counterflux of solvent. In nonaqueous electrolyte, expulsion of cations seems to be the dominant flux during SPAN oxidation, while solvent counterflux plays a significant role. The specific charge of SPAN films was found to be ca. 37 Ah/kg in aqueous solution (only first redox process used) and ca. 68 Ah/kg in nonaqueous media (both redox processes). Based on their experimental results, an estimation for a practical SPAN/Li battery would have 50% more specific energy than a PANI/Li one.

  4. Effect of low energy oxygen ion beam irradiation on ionic conductivity of solid polymer electrolyte

    SciTech Connect

    Manjunatha, H. Kumaraswamy, G. N.; Damle, R.

    2014-04-24

    Over the past three decades, solid polymer electrolytes (SPEs) have drawn significant attention of researchers due to their prospective commercial applications in high energy-density batteries, electrochemical sensors and super-capacitors. The optimum conductivity required for such applications is about 10{sup −2} – 10{sup −4} S/cm, which is hard to achieve in these systems. It is known that the increase in the concentration of salt in the host polymer results in a continuous increase in the ionic conductivity. However, there is a critical concentration of the salt beyond which the conductivity decreases due to formation of ion pairs with no net charge. In the present study, an attempt is made to identify the concentration at which ion pair formation occurs in PEO: RbBr. We have attempted to modify microstructure of the host polymer matrix by low energy ion (Oxygen ion, O{sup +1} with energy 100 keV) irradiation. Ionic conductivity measurements in these systems were carried out using Impedance Spectroscopy before and after irradiation to different fluencies of the oxygen ion. It is observed that the conductivity increases by one order in magnitude. The increase in ionic conductivity may be attributed to the enhanced segmental motion of the polymer chains. The study reveals the importance of ion irradiation as an effective tool to enhance conductivity in SPEs.

  5. Correlation of ion-ion interaction with electrical conductivity in solid state polymeric separator for energy storage applications

    NASA Astrophysics Data System (ADS)

    Sharma, Parul Kumar; Sadiq, M.; Bhatt, Chandni; Sharma, A. L.

    2016-05-01

    In the present study, we report innovative study on the prepared high quality solid state free standing thin polymeric separator. In prepared free standing polymeric separator, polymer (PEO) has been used as host matrix; appropriate bulky anion salt (LiPF6) as conducting species and Nano ceramic filler (BaTiO3) is used to enrich the mechanical and thermal stability of separator used for the device applications. The Fourier Transform Infra-Red (FTIR) result has been analysed properly of the prepared materials to look the microscopic interaction among polymer-ion, ion-ion and polymer-ion-clay interaction. Electrical conductivity results has been recorded using the impedance spectroscopy results which gives the estimated value of the order of ˜10-3 Scm-1 of the nano ceramic doped polymeric separator which is desirable for energy storage application. A fine correlation has been established between the obtained results by this two analysis.

  6. Novel Ordered Crown Ether-Containing Polyimides for Ion Conduction

    NASA Technical Reports Server (NTRS)

    Irvin, Jennifer A.; Stasko, Daniel; Fallis, Stephen; Guenthner, Andrew J.; Webber, Cynthia; Blackwell, John; Chvalun, Sergei N.

    2003-01-01

    We report the synthesis and characterization of thermally-stable polyimides for use as battery and fuel cell electrolyte membranes. Dianhydrides used were 1,4,5,8- naphthalenetetracarboxylic dianhydride and/or 4,4'-(hexafluoroisopropylidene)diphthalic anhydride. Diamines used were anti-4,4-diaminodibenzo-l8-crown-6, 4,4'- diaminodibenzo-24-crown-8, 2,2-bis(4-aminophenyl)hexafluoropropane, and/or 2,5- diaminobenzenesulfonic acid. The polymers were characterized using electrochemical impedance spectroscopy (EIS), thermal analysis and X-ray diffraction. Polymers containing the hexafluoroisopropylidene (HFIP) group were soluble in common organic solvents, while polymers without the HFIP group were very poorly soluble. Sulfonation yields polymers that are sparingly soluble in aqueous base and/or methanol. Degree of sulfonation, determined by titration, was between one and three sulfonate groups per repeat unit. Proton conductivity was determined as a function of water content, with a maximum conductivity of l x 10(exp -2) per centimeter when fully hydrated. Crown ether-containing polymers exhibit a high degree of order that may be indicative of crown ether channel formation, which may facilitate Li(+) transport for use in battery membranes.

  7. Field-aligned ion beams upstream of the earth's bow shock Evidence for a magnetosheath source

    NASA Technical Reports Server (NTRS)

    Thomsen, M. F.; Gosling, J. T.; Bame, S. J.; Feldman, W. C.; Paschmann, G.; Sckopke, N.

    1983-01-01

    High time resolution ISEE-1 and -2 observations of upstream field-aligned ion beams at several crossings of the earth's bow shock indicate that some beams are due to high energy magnetosheath particles leaking through the shock into the upstream region. The distribution immediately downstream of these oblique shocks consists of a 'core' of directly transmitted, slightly heated ions, plus a crescent-shaped, high-velocity distribution, centered roughly on the magnetic field in the direction toward the upstream region, with a fairly well defined low velocity cutoff.

  8. Source Distributions of Substorm Ions Observed in the Near-Earth Magnetotail

    NASA Technical Reports Server (NTRS)

    Ashour-Abdalla, M.; El-Alaoui, M.; Peroomian, V.; Walker, R. J.; Raeder, J.; Frank, L. A.; Paterson, W. R.

    1999-01-01

    This study employs Geotail plasma observations and numerical modeling to determine sources of the ions observed in the near-Earth magnetotail near midnight during a substorm. The growth phase has the low-latitude boundary layer as its most important source of ions at Geotail, but during the expansion phase the plasma mantle is dominant. The mantle distribution shows evidence of two distinct entry mechanisms: entry through a high latitude reconnection region resulting in an accelerated component, and entry through open field lines traditionally identified with the mantle source. The two entry mechanisms are separated in time, with the high-latitude reconnection region disappearing prior to substorm onset.

  9. Isotope fractionation in surface ionization ion source of alkaline-earth iodides

    SciTech Connect

    Suzuki, T.; Kanzaki, C.; Nomura, M.; Fujii, Y.

    2012-02-15

    The relationship between the isotope fractionation of alkaline-earth elements in the surface ionization ion source and the evaporation filament current, i.e., filament temperature, was studied. It was confirmed that the isotope fractionation depends on the evaporation filament temperature; the isotope fractionation in the case of higher temperature of filament becomes larger. The ionization and evaporation process in the surface ionization ion source was discussed, and it was concluded that the isotope fractionation is suppressed by setting at the lower temperature of evaporation filament because the dissociations are inhibited on the evaporation filament.

  10. ION AND MOLECULE SENSORS USING MOLECULAR RECOGNITION IN LUMINESCENT, CONDUCTIVE POLYMERS

    EPA Science Inventory

    This program integrates three individual, highly interactive projects that will use molecular recognition strategies to develop sensor technology based on luminescent, conductive polymers that contain sites for binding specific molecules or ions in the presence of related molecul...

  11. Ion-conducting ceramic apparatus, method, fabrication, and applications

    DOEpatents

    Yates, Matthew; Liu, Dongxia

    2012-03-06

    A c-axis-oriented HAP thin film synthesized by seeded growth on a palladium hydrogen membrane substrate. An exemplary synthetic process includes electrochemical seeding on the substrate, and secondary and tertiary hydrothermal treatments under conditions that favor growth along c-axes and a-axes in sequence. By adjusting corresponding synthetic conditions, an HAP this film can be grown to a controllable thickness with a dense coverage on the underlying substrate. The thin films have relatively high proton conductivity under hydrogen atmosphere and high temperature conditions. The c-axis oriented films may be integrated into fuel cells for application in the intermediate temperature range of 200-600.degree. C. The electrochemical-hydrothermal deposition technique may be applied to create other oriented crystal materials having optimized properties, useful for separations and catalysis as well as electronic and electrochemical applications, electrochemical membrane reactors, and in chemical sensors.

  12. Proton Ion Conducting Polymer Electrolyte Pan: NH4PF6

    NASA Astrophysics Data System (ADS)

    Sikkanthar, S.; Karthikeyan, S.; Rajeswari, N.; Selvasekarapandian, S.; Sanjeeviraja, C.

    2013-07-01

    Polymer electrolytes are an important class of materials and have been used in high energy batteries, fuel cells, gas sensors, display devices etc. PAN based polymer electrolyte films doped with ammonium hexafluorophosphate (NH4PF6) has been prepared by the solution casting method. The prepared films have been investigated by different techniques such as XRD, FTIR and AC Impedance spectroscopy. XRD studies reveal the amorphous nature of the polymer blend-salt complexes. The FTIR analysis confirms the complex formation of the polymer with salt. From the AC Impedance spectroscopy, the maximum proton conductivity at room temperature has been found to be 3.98×10-4 S cm-1 for 20 mol% salt doped electrolyte.

  13. Multi-Ion Mechanism for Ion Permeation and Block in the Cystic Fibrosis Transmembrane Conductance Regulator Chloride Channel

    PubMed Central

    Linsdell, Paul; Tabcharani, Joseph A.; Hanrahan, John W.

    1997-01-01

    The mechanism of Cl− ion permeation through single cystic fibrosis transmembrane conductance regulator (CFTR) channels was studied using the channel-blocking ion gluconate. High concentrations of intracellular gluconate ions cause a rapid, voltage-dependent block of CFTR Cl− channels by binding to a site ∼40% of the way through the transmembrane electric field. The affinity of gluconate block was influenced by both intracellular and extracellular Cl− concentration. Increasing extracellular Cl− concentration reduced intracellular gluconate affinity, suggesting that a repulsive interaction occurs between Cl− and gluconate ions within the channel pore, an effect that would require the pore to be capable of holding more than one ion simultaneously. This effect of extracellular Cl− is not shared by extracellular gluconate ions, suggesting that gluconate is unable to enter the pore from the outside. Increasing the intracellular Cl− concentration also reduced the affinity of intracellular gluconate block, consistent with competition between intracellular Cl− and gluconate ions for a common binding site in the pore. Based on this evidence that CFTR is a multi-ion pore, we have analyzed Cl− permeation and gluconate block using discrete-state models with multiple occupancy. Both two- and three-site models were able to reproduce all of the experimental data with similar accuracy, including the dependence of blocker affinity on external Cl− (but not gluconate) ions and the dependence of channel conductance on Cl− concentration. The three-site model was also able to predict block by internal and external thiocyanate (SCN−) ions and anomalous mole fraction behavior seen in Cl−/SCN− mixtures. PMID:9379169

  14. Multi-Ion mechanism for ion permeation and block in the cystic fibrosis transmembrane conductance regulator chloride channel.

    PubMed

    Linsdell, P; Tabcharani, J A; Hanrahan, J W

    1997-10-01

    The mechanism of Cl ion permeation through single cystic fibrosis transmembrane conductance regulator (CFTR) channels was studied using the channel-blocking ion gluconate. High concentrations of intracellular gluconate ions cause a rapid, voltage-dependent block of CFTR Cl channels by binding to a site approximately 40% of the way through the transmembrane electric field. The affinity of gluconate block was influenced by both intracellular and extracellular Cl concentration. Increasing extracellular Cl concentration reduced intracellular gluconate affinity, suggesting that a repulsive interaction occurs between Cl and gluconate ions within the channel pore, an effect that would require the pore to be capable of holding more than one ion simultaneously. This effect of extracellular Cl is not shared by extracellular gluconate ions, suggesting that gluconate is unable to enter the pore from the outside. Increasing the intracellular Cl concentration also reduced the affinity of intracellular gluconate block, consistent with competition between intracellular Cl and gluconate ions for a common binding site in the pore. Based on this evidence that CFTR is a multi-ion pore, we have analyzed Cl permeation and gluconate block using discrete-state models with multiple occupancy. Both two- and three-site models were able to reproduce all of the experimental data with similar accuracy, including the dependence of blocker affinity on external Cl (but not gluconate) ions and the dependence of channel conductance on Cl concentration. The three-site model was also able to predict block by internal and external thiocyanate (SCN) ions and anomalous mole fraction behavior seen in Cl/SCN mixtures. PMID:9379169

  15. Mixed Barrier Model for the Mixed Glass Former Effect in Ion Conducting Glasses

    NASA Astrophysics Data System (ADS)

    Schuch, Michael; Müller, Christian R.; Maass, Philipp; Martin, Steve W.

    2009-04-01

    Mixing two types of glass formers in ion conducting glasses can be exploited to lower conductivity activation energy and thereby increasing the ionic conductivity, a phenomenon known as the mixed glass former effect (MGFE). We develop a model for this MGFE, where activation barriers for individual ion jumps get lowered in inhomogeneous environments containing both types of network forming units. Fits of the model to experimental data allow one to estimate the strength of the barrier reduction, and they indicate a spatial clustering of the two types of network formers. The model predicts a time-temperature superposition of conductivity spectra onto a common master curve independent of the mixing ratio.

  16. Ion mobility imaging and contrast mechanism of apparent conductivity in MREIT.

    PubMed

    Oh, Tong In; Kim, Young Tae; Minhas, Atul; Seo, Jin Keun; Kwon, Oh In; Woo, Eung Je

    2011-04-01

    Magnetic resonance electrical impedance tomography (MREIT) aims to produce high-resolution cross-sectional images of conductivity distribution inside the human body. Injected current into an imaging object induces a distribution of internal magnetic flux density, which is measured by using an MRI scanner. We can reconstruct a conductivity image based on its relation with the measured magnetic flux density. In this paper, we explain the contrast mechanism in MREIT by performing and analyzing a series of numerical simulations and imaging experiments. We built a stable conductivity phantom including a hollow insulating cylinder with holes. Filling both inside and outside the hollow cylinder with the same saline, we controlled ion mobilities to create a conductivity contrast without being affected by the ion diffusion process. From numerical simulations and imaging experiments, we found that slopes of induced magnetic flux densities change with hole diameters and therefore conductivity contrasts. Associating the hole diameter with apparent conductivity of the region inside the hollow cylinder with holes, we could experimentally validate the contrast mechanism in MREIT. Interpreting reconstructed apparent conductivity images of the phantom as ion mobility images, we discuss the meaning of the apparent conductivity seen by a certain probing method. In designing MREIT imaging experiments, the ion mobility imaging method using the proposed stable conductivity phantom will enable us to estimate a distinguishable conductivity contrast for a given set of imaging parameters. PMID:21411866

  17. Ion engine propelled Earth-Mars cycler with nuclear thermal propelled transfer vehicle, volume 2

    NASA Technical Reports Server (NTRS)

    Meyer, Rudolf X.; Baker, Myles; Melko, Joseph

    1994-01-01

    The goal of this project was to perform a preliminary design of a long term, reusable transportation system between earth and Mars which would be capable of providing both artificial gravity and shelter from solar flare radiation. The heart of this system was assumed to be a Cycler spacecraft propelled by an ion propulsion system. The crew transfer vehicle was designed to be propelled by a nuclear-thermal propulsion system. Several Mars transportation system architectures and their associated space vehicles were designed.

  18. Multicomponent analysis of mixed rare-earth metal ion solutions by the electronic tongue sensor system

    SciTech Connect

    Legin, A.; Kirsanov, D.; Rudnitskaya, A.; Rovny, S.; Logunov, M.

    2007-07-01

    Novel electrochemical sensors based on well-known extracting agents are developed. Sensors have shown high sensitivity towards a variety of rear earth metal ions in acidic media at pH=2. Multi-sensor system (electronic tongue) comprising newly developed sensors was successfully applied for the analysis of binary and ternary mixtures of Ce{sup 3+}, Nd{sup 3+}, Sm{sup 3+} and Gd{sup 3+} cations in different combinations. (authors)

  19. Neutral atomic oxygen beam produced by ion charge exchange for Low Earth Orbital (LEO) simulation

    NASA Technical Reports Server (NTRS)

    Banks, Bruce; Rutledge, Sharon; Brdar, Marko; Olen, Carl; Stidham, Curt

    1987-01-01

    A low energy neutral atomic oxygen beam system was designed and is currently being assembled at the Lewis Research Center. The system utilizes a 15 cm diameter Kaufman ion source to produce positive oxygen ions which are charge exchange neutralized to produce low energy (variable from 5 to 150 eV) oxygen atoms at a flux simulating real time low Earth orbital conditions. An electromagnet is used to direct only the singly charged oxygen ions from the ion source into the charge exchange cell. A retarding potential grid is used to slow down the oxygen ions to desired energies prior to their charge exchange. Cryogenically cooled diatomic oxygen gas in the charge exchange cell is then used to transfer charge to the oxygen ions to produce a neutral atomic oxygen beam. Remaining non-charge exchanged oxygen ions are then swept from the beam by electromagnetic or electrostatic deflection depending upon the desired experiment configuration. The resulting neutral oxygen beam of 5 to 10 cm in diameter impinges upon target materials within a sample holder fixture that can also provide for simultaneous heating and UV exposure during the atomic oxygen bombardment.

  20. Femtosecond Laser-Induced Upconversion Luminescence in Rare-Earth Ions by Nonresonant Multiphoton Absorption.

    PubMed

    Yao, Yunhua; Xu, Cheng; Zheng, Ye; Yang, Chengshuai; Liu, Pei; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong; Zhang, Shian

    2016-07-21

    The upconversion luminescence of rare-earth ions has attracted considerable interest because of its important applications in photoelectric conversion, color display, laser device, multiplexed biolabeling, and security printing. Previous studies mainly explored the upconversion luminescence generation through excited state absorption, energy transfer upconversion, and photon avalanche under the continuous wave laser excitation. Here, we focus on the upconversion luminescence generation through a nonresonant multiphoton absorption by using the intense femtosecond pulsed laser excitation and study the upconversion luminescence intensity control by varying the femtosecond laser phase and polarization. We show that the upconversion luminescence of rare-earth ions under the intense femtosecond laser field excitation is easy to be obtained due to the nonresonant multiphoton absorption through the nonlinear interaction between light and matter, which is not available by the continuous wave laser excitation in previous works. We also show that the upconversion luminescence intensity can be effectively controlled by varying the femtosecond pulsed laser phase and polarization, which can open a new technological opportunity to generate and control the upconversion luminescence of rare-earth ions and also can be further extended to the relevant application areas. PMID:27367751

  1. Optical detection of a single rare-earth ion in a crystal

    PubMed Central

    Kolesov, R.; Xia, K.; Reuter, R.; Stöhr, R.; Zappe, A.; Meijer, J.; Hemmer, P.R.; Wrachtrup, J.

    2012-01-01

    Rare-earth-doped laser materials show strong prospects for quantum information storage and processing, as well as for biological imaging, due to their high-Q 4f↔4f optical transitions. However, the inability to optically detect single rare-earth dopants has prevented these materials from reaching their full potential. Here we detect a single photostable Pr3+ ion in yttrium aluminium garnet nanocrystals with high contrast photon antibunching by using optical upconversion of the excited state population of the 4f↔4f optical transition into ultraviolet fluorescence. We also demonstrate on-demand creation of Pr3+ ions in a bulk yttrium aluminium garnet crystal by patterned ion implantation. Finally, we show generation of local nanophotonic structures and cell death due to photochemical effects caused by upconverted ultraviolet fluorescence of praseodymium-doped yttrium aluminium garnet in the surrounding environment. Our study demonstrates versatile use of rare-earth atomic-size ultraviolet emitters for nanoengineering and biotechnological applications. PMID:22929786

  2. Optical detection of a single rare-earth ion in a crystal

    NASA Astrophysics Data System (ADS)

    Kolesov, R.; Xia, K.; Reuter, R.; Stöhr, R.; Zappe, A.; Meijer, J.; Hemmer, P. R.; Wrachtrup, J.

    2012-08-01

    Rare-earth-doped laser materials show strong prospects for quantum information storage and processing, as well as for biological imaging, due to their high-Q 4f↔4f optical transitions. However, the inability to optically detect single rare-earth dopants has prevented these materials from reaching their full potential. Here we detect a single photostable Pr3+ ion in yttrium aluminium garnet nanocrystals with high contrast photon antibunching by using optical upconversion of the excited state population of the 4f↔4f optical transition into ultraviolet fluorescence. We also demonstrate on-demand creation of Pr3+ ions in a bulk yttrium aluminium garnet crystal by patterned ion implantation. Finally, we show generation of local nanophotonic structures and cell death due to photochemical effects caused by upconverted ultraviolet fluorescence of praseodymium-doped yttrium aluminium garnet in the surrounding environment. Our study demonstrates versatile use of rare-earth atomic-size ultraviolet emitters for nanoengineering and biotechnological applications.

  3. Laser polarization and phase control of up-conversion fluorescence in rare-earth ions

    PubMed Central

    Yao, Yunhua; Zhang, Shian; Zhang, Hui; Ding, Jingxin; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong

    2014-01-01

    We theoretically and experimentally demonstrate the up-conversion fluorescence control via resonance-mediated two-photon absorption in rare-earth ions by varying both the laser polarization and phase. We show that both the laser polarization and phase can control the up-conversion fluorescence, and the up-conversion fluorescence intensity is decreased when the laser polarization changes from linear through elliptical to circular. We also show that the laser polarization will affect the control efficiency of the up-conversion fluorescence by varying the laser phase, and the circular polarization will reduce the control efficiency. Furthermore, we suggest that the control efficiency by varying the laser polarization and the effect of the laser polarization on the control efficiency by varying the laser phase can be artificially manipulated by controlling the laser spectral bandwidth. This optical control method opens a new opportunity to control the up-conversion fluorescence of rare-earth ions, which may have significant impact on the related applications of rare-earth ions. PMID:25465401

  4. Solid Phase Luminescence of Several Rare Earth Ions on Ion-Exchange Films

    NASA Technical Reports Server (NTRS)

    Tanner, Stephen P.; Street, Kenneth W., Jr.

    1999-01-01

    The development and characterization of a novel ion-exchange film for solid-phase fluorometry and phosphorimetry is reported. This new cation-exchange material is suitable for spectroscopic applications in the ultraviolet and visible regions. It is advantageous because it, as a single entity, is easily recovered from solution and mounted in the spectrofluorometers. After preconcentration on the film, the luminescence intensity of lanthanide ions is several orders of magnitude greater than that of the corresponding solution, depending on the volume of solution and the amount of film. This procedure allows emission spectral measurements and determination of lanthanide ions at solution concentrations of < 5 (micro)g/L. The film may be stored for subsequent reuse or as a permanent record of the analysis. The major drawback to the use of the film is slow uptake of analyte due to diffusion limitations.

  5. Ion conduction in the KcsA potassium channel analyzed with a minimal kinetic model.

    PubMed

    Mafé, Salvador; Pellicer, Julio

    2005-02-01

    We use a model by Nelson to study the current-voltage and conductance-concentration curves of bacterial potassium channel KcsA without assuming rapid ion translocation. Ion association to the channel filter is rate controlling at low concentrations, but dissociation and transport in the filter can limit conduction at high concentration for ions other than K+. The absolute values of the effective rate constants are tentative but the relative changes in these constants needed to qualitatively explain the experiments should be of significance. PMID:15783362

  6. Correlation between cation conduction and ionic morphology in a PEO-based single ion conductor

    NASA Astrophysics Data System (ADS)

    Lin, Kan-Ju; Maranas, Janna

    2011-03-01

    We use molecular dynamics simulation to study ion transport and backbone mobility of a PEO-based single ion conductor. Ion mobility depends on the chemical structure and the local environment of the ions, which consequently impact ionic conductivity. We characterize the aggregation state of the ions, and assess the role of ion complexes in ionomer dynamics. In addition to solvated cations and pairs, higher order ion clusters are found. Most of the ion clusters are in string-like structure and cross-link two or more different ionomer chains through ionic binding. Ionic crosslinks decrease mobility at the ionic co-monomer; hence the mobility of the adjacent PEO segment is influenced. Na ions show slow mobility when they are inside large clusters. The hopping timescale for Na varies from 20 ns to 200. A correlation is found between Na mobility and the number of hops from one coordination site to another. Besides ether oxygens, Na ions in the ionomer also use the anion and the edge of the cluster as hopping sites. The string-like structure of clusters provide less stable sites at the two ends thus ions are more mobile in those regions. We observed Grotthus like mechanism in our ionomer, in which the positive charge migrates within the string-like cluster without the cations actually moving.

  7. Bombardment induced ion transport - part IV: ionic conductivity of ultra-thin polyelectrolyte multilayer films.

    PubMed

    Wesp, Veronika; Hermann, Matthias; Schäfer, Martin; Hühn, Jonas; Parak, Wolfgang J; Weitzel, Karl-Michael

    2016-02-14

    The dependence of the ionic conductance of ultra-thin polyelectrolyte multilayer (PEM) films on the temperature and the number of bilayers has been investigated by the recently developed low energy bombardment induced ion transport (BIIT) method. To this end multilayers of alternating poly(sodium 4-styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) layers were deposited on a metal electrode and subsequently bombarded by a low energy potassium ion beam. Ions are transported through the film according to the laws of electro-diffusion towards a grounded backside electrode. They are neutralized at the interface between the polymer film and the metal electrode. The detected neutralization current scales linearly with the acceleration potential of the ion beam indicating Ohmic behavior for the (PAH/PSS)x multilayer, where x denotes the number of bilayers. The conductance exhibits a non-monotonic dependence on the number of bilayers, x. For 2 ≤ x ≤ 8 the conductance increases non-linearly with the number of bilayers. For x ≥ 8 the conductance decreases with increasing number of bilayers. The variation of the conductance is rationalized by a model accounting for the structure dependence of the conductivity. The thinnest sample for which the conductance has been measured is the single bilayer reflecting properties dominated by the interface. The activation energy for the ion transport is 0.49 eV. PMID:26411996

  8. Oxygen ion implantation induced microstructural changes and electrical conductivity in Bakelite RPC detector material

    NASA Astrophysics Data System (ADS)

    Kumar, K. V. Aneesh; Ranganathaiah, C.; Kumarswamy, G. N.; Ravikumar, H. B.

    2016-05-01

    In order to explore the structural modification induced electrical conductivity, samples of Bakelite Resistive Plate Chamber (RPC) detector materials were exposed to 100 keV Oxygen ion in the fluences of 1012, 1013, 1014 and 1015 ions/cm2. Ion implantation induced microstructural changes have been studied using Positron Annihilation Lifetime Spectroscopy (PALS) and X-Ray Diffraction (XRD) techniques. Positron lifetime parameters viz., o-Ps lifetime and its intensity shows the deposition of high energy interior track and chain scission leads to the formation of radicals, secondary ions and electrons at lower ion implantation fluences (1012 to1014 ions/cm2) followed by cross-linking at 1015 ions/cm2 fluence due to the radical reactions. The reduction in electrical conductivity of Bakelite detector material is correlated to the conducting pathways and cross-links in the polymer matrix. The appropriate implantation energy and fluence of Oxygen ion on polymer based Bakelite RPC detector material may reduce the leakage current, improves the efficiency, time resolution and thereby rectify the aging crisis of the RPC detectors.

  9. Electrolytic process to produce sodium hypochlorite using sodium ion conductive ceramic membranes

    SciTech Connect

    Balagopal, Shekar; Malhotra, Vinod; Pendleton, Justin; Reid, Kathy Jo

    2012-09-18

    An electrochemical process for the production of sodium hypochlorite is disclosed. The process may potentially be used to produce sodium hypochlorite from seawater or low purity un-softened or NaCl-based salt solutions. The process utilizes a sodium ion conductive ceramic membrane, such as membranes based on NASICON-type materials, in an electrolytic cell. In the process, water is reduced at a cathode to form hydroxyl ions and hydrogen gas. Chloride ions from a sodium chloride solution are oxidized in the anolyte compartment to produce chlorine gas which reacts with water to produce hypochlorous and hydrochloric acid. Sodium ions are transported from the anolyte compartment to the catholyte compartment across the sodium ion conductive ceramic membrane. Sodium hydroxide is transported from the catholyte compartment to the anolyte compartment to produce sodium hypochlorite within the anolyte compartment.

  10. Evidence for solar wind origin of energetic heavy ions in the earth's radiation belt

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    Analysis of data from our energetic ion composition experiment on ISEE-1 has revealed the presence of substantial fluxes of carbon, oxygen, and heavier ions above 400 keV/nucleon at L values between approximately 2.5 and 4 earth radii. The measured C/O ratio varies systematically from 1.3 at 450 keV/nucleon to 4.1 at 1.3 MeV/nucleon, and no iron is observed above 200 keV/nucleon. These results provide strong evidence for a solar wind origin for energetic ions in the outer radiation belt. The absence of iron and the increase of the carbon-to-oxygen ratio with energy suggest that the condition for the validity of the first adiabatic invariant may have a strong influence on the trapping of these particles.

  11. Ion conics and counterstreaming electrons generated by lower hybrid waves in the earth's magnetosphere

    NASA Technical Reports Server (NTRS)

    Chang, Tom; Crew, Geoffrey B.; Retterrer, John M.; Jasperse, John R.

    1989-01-01

    The exotic phenomenon of energetic ion-conic and counterstreaming electron formation by lower hybrid waves along discrete auroral field lines in the earth magnetosphere is considered. Mean-particle calculations, plasma simulations, and analytical treatments of the acceleration processes are described. It is shown that, in the primary auroral electron-beam region, lower hybrid waves could be an efficient mechanism for the transverse heating of H (+) and O(+) ions of ionospheric origin, as well as for the field-aligned heating of the ambient electrons leading to coincident counterstreaming electron distributions. For O(+) ions to be energized by such a wave-particle interaction process, however, some sort of preheating mechanism is required.

  12. Kinetic theory for the ion humps at the foot of the Earth's bow shock

    NASA Astrophysics Data System (ADS)

    Jovanović, D.; Krasnoselskikh, V. V.

    2009-10-01

    The nonlinear kinetic theory is presented for the ion acoustic perturbations at the foot of the Earth's quasiperpendicular bow shock, that is characterized by weakly magnetized electrons and unmagnetized ions. The streaming ions, due to the reflection of the solar wind ions from the shock, provide the free energy source for the linear instability of the acoustic wave. In the fully nonlinear regime, a coherent localized solution is found in the form of a stationary ion hump, which is traveling with the velocity close to the phase velocity of the linear mode. The structure is supported by the nonlinearities coming from the increased population of the resonant beam ions, trapped in the self-consistent potential. As their size in the direction perpendicular to the local magnetic field is somewhat smaller that the electron Larmor radius and much larger that the Debye length, their spatial properties are determined by the effects of the magnetic field on weakly magnetized electrons. These coherent structures provide a theoretical explanation for the bipolar electric pulses, observed upstream of the shock by Polar and Cluster satellite missions.

  13. Investigation of the Transport of Solar Ions Through the Earth's Magnetosphere

    NASA Technical Reports Server (NTRS)

    Lennartsson, O. W.; Evans, David (Technical Monitor)

    2000-01-01

    The objective of this study has been to infer, by statistical means, the most probable mode of entry of solar wind plasma into Earth's magnetotail, using a particular set of archived data from the Lockheed Plasma Composition Experiment on the International Sun-Earth Explorer One (ISEE-1) satellite, jointly sponsored by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) in the 1970's and 80's. Despite their considerable age, the Lockheed ISEE-1 data are still, at the time of this report, the only substantial ion composition data in the sub-keV to keV energy range available from the magnetotail beyond 9 R(sub E), because of various technical problems with ion mass spectrometers on later missions, and are therefore a unique source of information about the mixing of solar and terrestrial origin plasmas in the tail, within the ISEE-1 apogee of almost 23 R(sub E). The entire set of archived data used in this study, covering the 4.5 years of operation of the instrument and comprising not only tail measurements but also data from the inner magnetosphere as well as data from outside the magnetopause, is now available to the public via the WorldWideWeb at the address: http://cis.spasci.com/ISEE_ions The fundamental assumption of this and other studies of magnetosphere ion composition is that He++ and O+ ions are virtually certain "tags" of solar and terrestrial origins, respectively. This is an assumption with strong theoretical basis and it is corroborated by observational evidence, including the often substantial differences between the velocity distribution functions of those two species. The H+ ions can have a dual origin, in principle, but the close resemblance in the ISEE-1 data between the dynamics of H+ and He++ ions indicates a predominantly solar origin of the H+ ions in the tail, at least. By the same token, the usually minor He+ ions are probably almost entirely of terrestrial origin, because of their similarity to the O

  14. In Situ Study of Strain-Dependent Ion Conductivity of Stretchable Polyethylene Oxide Electrolyte

    PubMed Central

    Kelly, Taylor; Ghadi, Bahar Moradi; Berg, Sean; Ardebili, Haleh

    2016-01-01

    There is a strong need in developing stretchable batteries that can accommodate stretchable or irregularly shaped applications including medical implants, wearable devices and stretchable electronics. Stretchable solid polymer electrolytes are ideal candidates for creating fully stretchable lithium ion batteries mainly due to their mechanical and electrochemical stability, thin-film manufacturability and enhanced safety. However, the characteristics of ion conductivity of polymer electrolytes during tensile deformation are not well understood. Here, we investigate the effects of tensile strain on the ion conductivity of thin-film polyethylene oxide (PEO) through an in situ study. The results of this investigation demonstrate that both in-plane and through-plane ion conductivities of PEO undergo steady and linear growths with respect to the tensile strain. The coefficients of strain-dependent ion conductivity enhancement (CSDICE) for in-plane and through-plane conduction were found to be 28.5 and 27.2, respectively. Tensile stress-strain curves and polarization light microscopy (PLM) of the polymer electrolyte film reveal critical insights on the microstructural transformation of stretched PEO and the potential consequences on ionic conductivity. PMID:26831948

  15. In Situ Study of Strain-Dependent Ion Conductivity of Stretchable Polyethylene Oxide Electrolyte

    NASA Astrophysics Data System (ADS)

    Kelly, Taylor; Ghadi, Bahar Moradi; Berg, Sean; Ardebili, Haleh

    2016-02-01

    There is a strong need in developing stretchable batteries that can accommodate stretchable or irregularly shaped applications including medical implants, wearable devices and stretchable electronics. Stretchable solid polymer electrolytes are ideal candidates for creating fully stretchable lithium ion batteries mainly due to their mechanical and electrochemical stability, thin-film manufacturability and enhanced safety. However, the characteristics of ion conductivity of polymer electrolytes during tensile deformation are not well understood. Here, we investigate the effects of tensile strain on the ion conductivity of thin-film polyethylene oxide (PEO) through an in situ study. The results of this investigation demonstrate that both in-plane and through-plane ion conductivities of PEO undergo steady and linear growths with respect to the tensile strain. The coefficients of strain-dependent ion conductivity enhancement (CSDICE) for in-plane and through-plane conduction were found to be 28.5 and 27.2, respectively. Tensile stress-strain curves and polarization light microscopy (PLM) of the polymer electrolyte film reveal critical insights on the microstructural transformation of stretched PEO and the potential consequences on ionic conductivity.

  16. High charge state carbon and oxygen ions in Earth's equatorial quasi-trapping region

    NASA Technical Reports Server (NTRS)

    Christon, S. P.; Hamilton, D. C.; Gloeckler, G.; Eastmann, T. E.

    1994-01-01

    Observations of energetic (1.5 - 300 keV/e) medium-to-high charge state (+3 less than or equal to Q less than or equal to +7) solar wind origin C and O ions made in the quasi-trapping region (QTR) of Earth's magnetosphere are compared to ion trajectories calculated in model equatorial magnetospheric magnetic and electric fields. These comparisons indicate that solar wind ions entering the QTR on the nightside as an energetic component of the plasma sheet exit the region on the dayside, experiencing little or no charge exchange on the way. Measurements made by the CHarge Energy Mass (CHEM) ion spectrometer on board the Active Magnetospheric Particle Tracer Explorer/Charge Composition Explorer (AMPTE/CCE) spacecraft at 7 less than L less than 9 from September 1984 to January 1989 are the source of the new results contained herein: quantitative long-term determination of number densities, average energies, energy spectra, local time distributions, and their variation with geomagnetic disturbance level as indexed by Kp. Solar wind primaries (ions with charge states unchanged) and their secondaries (ions with generally lower charge states produced from primaries in the magnetosphere via charge exchange)are observed throughout the QTR and have distinctly different local time variations that persist over the entire 4-year analysis interval. During Kp larger than or equal to 3 deg intervals, primary ion (e.g., O(+6)) densities exhibit a pronounced predawn maximum with average energy minimum and a broad near-local-noon density minimum with average energy maximum. Secondary ion (e.g., O(+5)) densities do not have an identifiable predawn peak, rather they have a broad dayside maximum peaked in local morning and a nightside minimum. During Kp less than or equal to 2(-) intervals, primary ion density peaks are less intense, broader in local time extent, and centered near midnight, while secondary ion density local time variations diminish. The long-time-interval baseline helps

  17. Electrical conduction in alkali borate glasses; a unique dependence on the concentration of modifier ions

    NASA Astrophysics Data System (ADS)

    Doweidar, H.; Moustafa, Y. M.; El-Damrawi, G. M.; Ramadan, R. M.

    2008-01-01

    The electrical conduction of Li2O-B2O3, Na2O-B2O3 and K2O-B2O3 glasses seems, at first sight, to be dominated by the activation energy. Regardless of the size of the alkali ion, there is a unique dependence of conductivity, at a certain temperature, on the alkali-alkali distance and thus on N (the number of ions per cm3). The linear dependence of logσ on N-3/2 for all types of alkali ions reveals that N is the basic parameter that determines the conductivity at a certain temperature. A derived semi-empirical relation can be used to calculate the conductivity as a function of N and temperature.

  18. Energy Transfer in Rare Earth Ion Clusters and Fluorescence from Rare Earth Doped LANTHANUM(1.85)STRONTIUM(0.15)COPPER -OXYGEN(4) Superconductors.

    NASA Astrophysics Data System (ADS)

    Tissue, Brian Max

    1988-12-01

    Laser spectroscopy of rare earth ions in solids was used to study mechanisms of non-resonant energy transfer within rare earth clusters, and to detect insulating, impurity phases in rare earth doped La_{1.85 }Sr_{0.15}CuO _4 superconductors. The mechanisms of phonon-assisted, non-resonant energy transfer were studied in well-defined dimer sites in Er^{3+ }:SrF_2 and Pr ^{3+}:CaF_2. Application of a magnetic field to Er^{3+} :SrF_2 greatly increased the energy transfer rate. The magnetic field dependence in Er^{3+}:SrF _2 indicates that the mechanism of non-resonant energy transfer is a two-phonon, resonant process (Orbach process). Application of a magnetic field to Pr ^{3+}:CaF_2 had no effect on the energy transfer rate because no significant Zeeman splittings occurred. The temperature dependence of the energy transfer rate in Pr^{3+ }:CaF_2 showed the mechanism to be a one-phonon-assisted process at low temperatures and predominantly an Orbach process above 10 K. In the second part of this thesis, laser spectroscopy of a Eu ^{3+} probe ion is developed to detect impurity phases in La_{1.85 }Sr_{0.15}CuO _4 superconductors. Two impurity phases were found in polycrystalline La_ {1.85}Sr_{0.15} CuO_4: unreacted La _2O_3 starting material, and a La-silicate phase, which formed from contamination during sintering. The spectroscopic technique was found to be more than 100 times more sensitive than powder x -ray diffraction to detect minor impurity phases. In preparing the superconductors, several studies were made on the effect of Pr^{3+}, Eu ^{3+}, Bi^{3+ }, and fluorine dopants on the superconducting properties of La_{1.85}Sr _{0.15}CuO_4 and La_2Cuo_4 . Pr^{3+}, Eu ^{3+}, Bi^ {3+}, and F_2 doping all decreased the superconductivity in La_ {1.85}Sr^{0.15} CuO_4. Treating semi-conducting La_2CuO_4 in F_2 gas converted it to a superconductor with an onset T_{rm c} of 30-35 K.

  19. Nuclear Spin Lattice Relaxation and Conductivity Studies of the Non-Arrhenius Conductivity Behavior in Lithium Fast Ion Conducting Sulfide Glasses

    SciTech Connect

    Benjamin Michael Meyer

    2003-05-31

    As time progresses, the world is using up more of the planet's natural resources. Without technological advances, the day will eventually arrive when these natural resources will no longer be sufficient to supply all of the energy needs. As a result, society is seeing a push for the development of alternative fuel sources such as wind power, solar power, fuel cells, and etc. These pursuits are even occurring in the state of Iowa with increasing social pressure to incorporate larger percentages of ethanol in gasoline. Consumers are increasingly demanding that energy sources be more powerful, more durable, and, ultimately, more cost efficient. Fast Ionic Conducting (FIC) glasses are a material that offers great potential for the development of new batteries and/or fuel cells to help inspire the energy density of battery power supplies. This dissertation probes the mechanisms by which ions conduct in these glasses. A variety of different experimental techniques give a better understanding of the interesting materials science taking place within these systems. This dissertation discusses Nuclear Magnetic Resonance (NMR) techniques performed on FIC glasses over the past few years. These NMR results have been complimented with other measurement techniques, primarily impedance spectroscopy, to develop models that describe the mechanisms by which ionic conduction takes place and the dependence of the ion dynamics on the local structure of the glass. The aim of these measurements was to probe the cause of a non-Arrhenius behavior of the conductivity which has been seen at high temperatures in the silver thio-borosilicate glasses. One aspect that will be addressed is if this behavior is unique to silver containing fast ion conducting glasses. more specifically, this study will determine if a non-Arrhenius correlation time, {tau}, can be observed in the Nuclear Spin Lattice Relaxation (NSLR) measurements. If so, then can this behavior be modeled with a new single distribution

  20. Ionomer Design, Synthesis and Characterization for Ion-Conducting Energy Materials

    NASA Astrophysics Data System (ADS)

    Colby, Ralph H.

    2013-03-01

    For ionic actuators and battery separators, it is vital to utilize single-ion conductors that avoid the detrimental polarization of other ions; the commonly studied dual-ion conductors simply will not be used in the next generation of materials for these applications. Ab initio quantum chemistry calculations at 0 K in vacuum characterize ion interactions and ion solvation by various functional groups, allowing identification of constituents with weak interactions to be incorporated in ionomers for facile ion transport. Simple ideas for estimating the ion interactions and solvation at practical temperatures and dielectric constants are presented that indicate the rank ordering observed at 0 K in vacuum should be preserved. Hence, such ab initio calculations are useful for screening the plethora of combinations of polymer-ion, counterion and polar functional groups, to decide which are worthy of synthesis for new ionomers. Single-ion conducting ionomers are synthesized based on these calculations, with low glass transition temperatures (facile dynamics) to prepare ion-conducting membranes for ionic actuators and battery separators. Characterization by X-ray scattering, dielectric spectroscopy, NMR and linear viscoelasticity collectively develop a coherent picture of ionic aggregation and both counterion and polymer dynamics. Examples are shown of how ab initio calculations can be used to understand experimental observations of dielectric constant, glass transition temperature and conductivity of polymerized ionic liquids with counterions being either lithium, sodium, fluoride, hydroxide (for batteries) or bulky ionic liquids (for ionic actuators). This work was supported by the Department of Energy under Grant BES-DE-FG02-07ER46409.

  1. Molecular Dynamics Simulation of the Antiamoebin Ion Channel: Linking Structure and Conductance

    NASA Technical Reports Server (NTRS)

    Wilson, Michael A.; Wei, Chenyu; Bjelkmar, Paer; Wallace, B. A.; Pohorille, Andrew

    2011-01-01

    Molecular dynamics simulations were carried out in order to ascertain which of the potential multimeric forms of the transmembrane peptaibol channel, antiamoebin, is consistant with its measured conductance. Estimates of the conductance obtained through counting ions that cross the channel and by solving the Nernst-Planck equation yield consistent results, indicating that the motion of ions inside the channel can be satisfactorily described as diffusive.The calculated conductance of octameric channels is markedly higher than the conductance measured in single channel recordings, whereas the tetramer appears to be non-conducting. The conductance of the hexamer was estimated to be 115+/-34 pS and 74+/-20 pS, at 150 mV and 75 mV, respectively, in satisfactory agreement with the value of 90 pS measured at 75 mV. On this basis we propose that the antiamoebin channel consists of six monomers. Its pore is large enough to accommodate K(+) and Cl(-) with their first solvation shells intact. The free energy barrier encountered by K(+) is only 2.2 kcal/mol whereas Cl(-) encounters a substantially higher barrier of nearly 5 kcal/mol. This difference makes the channel selective for cations. Ion crossing events are shown to be uncorrelated and follow Poisson statistics. keywords: ion channels, peptaibols, channel conductance, molecular dynamics

  2. Space weathering of near-Earth and main belt silicate-rich asteroids: observations and ion irradiation experiments

    NASA Astrophysics Data System (ADS)

    Marchi, S.; Brunetto, R.; Magrin, S.; Lazzarin, M.; Gandolfi, D.

    2005-12-01

    In this paper we report the results of a comparison between ion irradiation experiments (N^+, Ar^+, Ar++) on silicates, a large spectral data set of silicate-rich (S-type) asteroids, and ordinary chondrite meteorites (OCs). Ion irradiation experiments - conducted on Fe-poor olivine, Fe-poor orthopyroxene, bulk silicate-rich rocks and one OC - have been monitored by means of reflectance spectroscopy (0.3-2.5 μm). All these experiments produce reddening and darkening of reflectance spectra. The observational data consist of a set of visible and near-infrared (0.4-2.4 μm) spectra of S-type asteroids, that belong to main belt (MBAs) and near-Earth (NEOs) populations. By analyzing the spectra of OCs, MBAs, and NEOs, we find a similar mineralogy between most asteroids and meteorites, but different distributions of spectral slopes. We interpret these findings in the frame of space weathering induced by solar wind ion irradiation.

  3. Inorganic backbone ionomers: Design and dielectric response of single-ion conducting polymers

    NASA Astrophysics Data System (ADS)

    Bartels, Joshua

    Ion-conducting polymers were studied primarily through the use of dielectric spectroscopy. The conclusions drawn from ion conduction models of the dielectric data are corroborated by additional independent experiments, including x-ray scattering, calorimetry, prism coupling, and DFT calculations. The broad concern of this dissertation is to understand and clarify a path forward in ion conducting polymer research. This is achieved by considering low-Tg ionomers and the advantages imparted by siloxane and phosphazene backbones. The most successful dielectric spectroscopy model for the materials studied is the electrode polarization model (EP), whereas other models, such as the Dyre random barrier model, fail to describe the experimental results. Seven nonionic ether oxygen (EO) containing polymers were studied in order to observe the effect that backbone chemistry has on dipole motion. Conventional carboncarbon backbone EO-containing polymers show no distinct advantage over similar EO-pendant polysiloxane or polyphosphazene systems. The mobility and effective backbone Tg imparted by the inorganic backbones are comparable. A short EO pendant results in a lower static dielectric constant due to restricted motion of dipoles close to the chain. The flexibility and chemical versatility of inorganic backbone polymers motivates further study of two ionomer systems. A polypohosphazene iodide conducting system was characterized by dielectric spectroscopy and x-ray scattering. Two end "tail" functionalization of the ammonium ion were used, a tail with two EOs and an alkyl tail of six carbons. This functional group plays an important role in ion dynamics and can wrap around the ion and self-solvate when EOs are present. The iodide-ammonium ionomers are observed to have unusually large high-frequency dielectric constants due to atomic polarization of ions. The strength of the atomic polarization scales with ion content. The aggregation state of ions is able to be determined from

  4. Fast ion conductivity in strained defect-fluorite structure created by ion tracks in Gd2Ti2O7

    PubMed Central

    Aidhy, Dilpuneet S.; Sachan, Ritesh; Zarkadoula, Eva; Pakarinen, Olli; Chisholm, Matthew F.; Zhang, Yanwen; Weber, William J.

    2015-01-01

    The structure and ion-conducting properties of the defect-fluorite ring structure formed around amorphous ion-tracks by swift heavy ion irradiation of Gd2Ti2O7 pyrochlore are investigated. High angle annular dark field imaging complemented with ion-track molecular dynamics simulations show that the atoms in the ring structure are disordered, and have relatively larger cation-cation interspacing than in the bulk pyrochlore, illustrating the presence of tensile strain in the ring region. Density functional theory calculations show that the non-equilibrium defect-fluorite structure can be stabilized by tensile strain. The pyrochlore to defect-fluorite structure transformation in the ring region is predicted to be induced by recrystallization during a melt-quench process and stabilized by tensile strain. Static pair-potential calculations show that planar tensile strain lowers oxygen vacancy migration barriers in pyrochlores, in agreement with recent studies on fluorite and perovskite materials. In view of these results, it is suggested that strain engineering could be simultaneously used to stabilize the defect-fluorite structure and gain control over its high ion-conducting properties. PMID:26555848

  5. Fast ion conductivity in strained defect-fluorite structure created by ion tracks in Gd2Ti2O7

    DOE PAGESBeta

    Aidhy, Dilpuneet S.; Sachan, Ritesh; Zarkadoula, Eva; Pakarinen, Olli; Chisholm, Matthew F.; Zhang, Yanwen; Weber, William J.

    2015-11-10

    The structure and ion-conducting properties of the defect-fluorite ring structure formed around amorphous ion-tracks by swift heavy ion irradiation of Gd2Ti2O7 pyrochlore are investigated. High angle annular dark field imaging complemented with ion-track molecular dynamics simulations show that the atoms in the ring structure are disordered, and have relatively larger cation-cation interspacing than in the bulk pyrochlore, illustrating the presence of tensile strain in the ring region. Density functional theory calculations show that the non-equilibrium defect-fluorite structure can be stabilized by tensile strain. The pyrochlore to defect-fluorite structure transformation in the ring region is predicted to be induced by recrystallizationmore » during a melt-quench process and stabilized by tensile strain. Static pair-potential calculations show that planar tensile strain lowers oxygen vacancy migration barriers in pyrochlores, in agreement with recent studies on fluorite and perovskite materials. Lastly, in view of these results, it is suggested that strain engineering could be simultaneously used to stabilize the defect-fluorite structure and gain control over its high ion-conducting properties.« less

  6. Energy density of ionospheric and solar wind origin ions in the near-Earth magnetotail during substorms

    NASA Technical Reports Server (NTRS)

    Daglis, Loannis A.; Livi, Stefano; Sarris, Emmanuel T.; Wilken, Berend

    1994-01-01

    Comprehensive energy density studies provide an important measure of the participation of various sources in energization processes and have been relatively rare in the literature. We present a statistical study of the energy density of the near-Earth magnetotail major ions (H(+), O(+), He(++), He(+)) during substorm expansion phase and discuss its implications for the solar wind/magnetosphere/ionosphere coupling. Our aim is to examine the relation between auroral activity and the particle energization during substorms through the correlation between the AE indices and the energy density of the major magnetospheric ions. The data we used here were collected by the charge-energy-mass (CHEM) spectrometer on board the Active Magnetospheric Particle Trace Explorer (AMPTE)/Charge Composition Explorer (CCE) satellite in the near-equatorial nightside magnetosphere, at geocentric distances approximately 7 to 9 R(sub E). CHEM provided the opportunity to conduct the first statistical study of energy density in the near-Earth magnetotail with multispecies particle data extending into the higher energy range (greater than or equal to 20 keV/E). the use of 1-min AE indices in this study should be emphasized, as the use (in previous statistical studies) of the (3-hour) Kp index or of long-time averages of AE indices essentially smoothed out all the information on substorms. Most distinct feature of our study is the excellent correlation of O(+) energy density with the AE index, in contrast with the remarkably poor He(++) energy density - AE index correlation. Furthermore, we examined the relation of the ion energy density to the electrojet activity during substorm growth phase. The O(+) energy density is strongly correlated with the pre-onset AU index, that is the eastward electrojet intensity, which represents the growth phase current system. Our investigation shows that the near-Earth magnetotail is increasingly fed with energetic ionospheric ions during periods of enhanced

  7. Bioinspired Protein Channel-Based Scanning Ion Conductance Microscopy (Bio-SICM) for Simultaneous Conductance and Specific Molecular Imaging.

    PubMed

    Macazo, Florika C; White, Ryan J

    2016-03-01

    The utility of stochastic single-molecule detection using protein nanopores has found widespread application in bioanalytical sensing as a result of the inherent signal amplification of the resistive pulse method. Integration of protein nanopores with high-resolution scanning ion conductance microscopy (SICM) extends the utility of SICM by enabling selective chemical imaging of specific target molecules, while simultaneously providing topographical information about the net ion flux through a pore under a concentration gradient. In this study, we describe the development of a bioinspired scanning ion conductance microscopy (bio-SICM) approach that couples the imaging ability of SICM with the sensitivity and chemical selectivity of protein channels to perform simultaneous pore imaging and specific molecule mapping. To establish the framework of the bio-SICM platform, we utilize the well-studied protein channel α-hemolysin (αHL) to map the presence of β-cyclodextrin (βCD) at a substrate pore opening. We demonstrate concurrent pore and specific molecule imaging by raster scanning an αHL-based probe over a glass membrane containing a single 25-μm-diameter glass pore while recording the lateral positions of the probe and channel activity via ionic current. We use the average channel current to create a conductance image and the raw current-time traces to determine spatial localization of βCD. With further optimization, we believe that the bio-SICM platform will provide a powerful analytical methodology that is generalizable, and thus offers significant utility in a myriad of bioanalytical applications. PMID:26848947

  8. GYROSURFING ACCELERATION OF IONS IN FRONT OF EARTH's QUASI-PARALLEL BOW SHOCK

    SciTech Connect

    Kis, Arpad; Lemperger, Istvan; Wesztergom, Viktor; Agapitov, Oleksiy; Krasnoselskikh, Vladimir; Dandouras, Iannis E-mail: Kis.Arpad@csfk.mta.hu

    2013-07-01

    It is well known that shocks in space plasmas can accelerate particles to high energies. However, many details of the shock acceleration mechanism are still unknown. A critical element of shock acceleration is the injection problem; i.e., the presence of the so called seed particle population that is needed for the acceleration to work efficiently. In our case study, we present for the first time observational evidence of gyroresonant surfing acceleration in front of Earth's quasi-parallel bow shock resulting in the appearance of the long-suspected seed particle population. For our analysis, we use simultaneous multi-spacecraft measurements provided by the Cluster spacecraft ion (CIS), magnetic (FGM), and electric field and wave instrument (EFW) during a time period of large inter-spacecraft separation distance. The spacecraft were moving toward the bow shock and were situated in the foreshock region. The results show that the gyroresonance surfing acceleration takes place as a consequence of interaction between circularly polarized monochromatic (or quasi-monochromatic) transversal electromagnetic plasma waves and short large amplitude magnetic structures (SLAMSs). The magnetic mirror force of the SLAMS provides the resonant conditions for the ions trapped by the waves and results in the acceleration of ions. Since wave packets with circular polarization and different kinds of magnetic structures are very commonly observed in front of Earth's quasi-parallel bow shock, the gyroresonant surfing acceleration proves to be an important particle injection mechanism. We also show that seed ions are accelerated directly from the solar wind ion population.

  9. Gyrosurfing Acceleration of Ions in Front of Earth's Quasi-parallel Bow Shock

    NASA Astrophysics Data System (ADS)

    Kis, Arpad; Agapitov, Oleksiy; Krasnoselskikh, Vladimir; Khotyaintsev, Yuri V.; Dandouras, Iannis; Lemperger, Istvan; Wesztergom, Viktor

    2013-07-01

    It is well known that shocks in space plasmas can accelerate particles to high energies. However, many details of the shock acceleration mechanism are still unknown. A critical element of shock acceleration is the injection problem; i.e., the presence of the so called seed particle population that is needed for the acceleration to work efficiently. In our case study, we present for the first time observational evidence of gyroresonant surfing acceleration in front of Earth's quasi-parallel bow shock resulting in the appearance of the long-suspected seed particle population. For our analysis, we use simultaneous multi-spacecraft measurements provided by the Cluster spacecraft ion (CIS), magnetic (FGM), and electric field and wave instrument (EFW) during a time period of large inter-spacecraft separation distance. The spacecraft were moving toward the bow shock and were situated in the foreshock region. The results show that the gyroresonance surfing acceleration takes place as a consequence of interaction between circularly polarized monochromatic (or quasi-monochromatic) transversal electromagnetic plasma waves and short large amplitude magnetic structures (SLAMSs). The magnetic mirror force of the SLAMS provides the resonant conditions for the ions trapped by the waves and results in the acceleration of ions. Since wave packets with circular polarization and different kinds of magnetic structures are very commonly observed in front of Earth's quasi-parallel bow shock, the gyroresonant surfing acceleration proves to be an important particle injection mechanism. We also show that seed ions are accelerated directly from the solar wind ion population.

  10. Investigations into the Influence of Heavy Ions on EMIC Wave Propagation in the Earth's Magnetosphere

    NASA Astrophysics Data System (ADS)

    Keller, S.; Kim, E. H.; Johnson, J.

    2015-12-01

    Geomagnetic pulsations in the Pc1 frequency range (0.2 to 5.0 Hz), which are known as electromagnetic ion cyclotron (EMIC) waves, are often observed at magnetically conjugate locations by spacecraft in the equatorial magnetosphere and ground-based stations. One difficulty in linking the propagation of detected radiation between these regions is the presence of stop bands near the heavy ion cyclotron resonance locations. Recent full wave calculations (Kim and Johnson, Full wave modeling of EMIC waves in the Earth's magnetosphere, 2015 AGU fall meeting) demonstrate how EMIC waves propagate to higher magnetic latitudes in an electron-proton-He+ plasma. However, while the heavy ion concentration can be large during the solar maximum and geomagnetic storms, they adopted a 5% He+ plasma. In this study, we explore the roles of heavy ion (He+ and O+) concentrations on the levels of EMIC wave energy that reach lower altitudes using a two-dimensional, finite element, full wave model. The Poynting flux and polarization of the emissions are used to monitor the propagation and absorption of wave energy, as well as mode coupling between left- and right-hand circularly polarized modes. Due to the increase in heavy ion populations in the magnetosphere, the consequences that geomagnetic storms have on EMIC wave propagation are also discussed.

  11. Shapes of Energetic Ion Spectra in Saturn's Magnetosphere Compared with those at Earth and Jupiter

    NASA Astrophysics Data System (ADS)

    Hamilton, D. C.; Mitchell, D. G.; Krimigis, S. M.

    2013-12-01

    Saturn's magnetosphere contains suprathermal and energetic ions that originate from a number of plasma sources including Enceladus, Titan, Saturn's atmosphere and ionosphere and the solar wind, with internal sources dominating. Although different species originate at different locations, transport processes and acceleration during or after transport distribute the energetic ions throughout the magnetosphere out to the magnetopause. In principle, the shapes of the energy spectra of these ions contain information on acceleration processes. However, because outside of about 9 RS long-term average spectra of all species are quite good power laws, it is difficult to pick one energy parameter (e.g., energy/charge or energy/nucleon) as better organizing the spectra by, for example, maintaining constant abundance ratios from low to high energies. Inside of 9 RS there are energy-dependent losses that alter the spectra but aren't directly related to acceleration. Here, using data from the Cassini/CHEMS sensor, we investigate ion spectra over the energy per charge range 3-220 keV/e in more detail with better resolution in both space and time, looking for evidence of spectral differences among species based on charge (e.g., O+ vs. O++) or plasma source (e.g., O+ (Enceladus) vs. He++ (solar wind)). We will compare Saturn's ion spectra with those from the magnetospheres of Earth and Jupiter and discuss implications for acceleration processes.

  12. Color-tunable heat-resistant polyaryletherketones co-coordinated with various rare earth ions

    NASA Astrophysics Data System (ADS)

    Liu, Dan; Shi, Qirong; Wang, Zhonggang

    2012-09-01

    Europium (Eu3+) and terbium (Tb3+) ions coordinated with 1,10-phenantroline (Phen), N,N-dimethylformamide (DMF) and carboxyl-containing polyaryletherketone (PEK) represent new luminescent materials (PEK-Eux3+Tb1-x3+-Phens, x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1). The results of FTIR, elemental analysis and XRD confirm that the coordination reaction indeed occurs and the rare earth ions are homogeneously dispersed in the PEK matrix. The polyarylethertone rare earth complexes exhibit high glass transition temperature and good thermal stability because of their wholly aromatic structures. The luminescence measurements indicate that the relative emission intensities of Tb3+ to Eu3+ ions depend on their ratio in the system, and the color of PEK-Eux3+Tb1-x3+-Phens under UV excitation can be tuned by changing the x value. The materials thus prepared show promising potential in the full color large area display field.

  13. Numerical simulations of the optical gain of crystalline fiber doped by rare earth and transition ion

    NASA Astrophysics Data System (ADS)

    Daoui, A. K.; Boubir, B.; Adouane, A.; Demagh, N.; Ghoumazi, M.

    2015-02-01

    A fiber laser is a laser whose gain medium is a doped fiber, although lasers whose cavity is made wholly of fibers have also been called fiber lasers. The gain media in a fiber laser is usually fiber doped with rare-earth ions, such as erbium (Er), neodymium (Nd), ytterbium (Yb), thulium (Tm), or praseodymium (Pr), which is doped into the core of the optical fiber, similar to those used to transmit telecommunications signals. Fiber lasers find many applications in materials processing, including cutting, welding, drilling, and marking metal. To maximize their market penetration, it is necessary to increase their output power. In this work, we present a detailed study based on the numerical simulation using MATLAB, of one of the principal characteristics of a fiber laser doped with rare earth ions and transition ion. The gain depends on several parameters such as the length of the doped fiber, the density, the pump power, noise, etc.). The used program resolves the state equations in this context together with those governing the light propagation phenomena. The developed code can also be used to study the dynamic operating modes of a doped fiber laser.

  14. Lithium-Ion Batteries Being Evaluated for Low-Earth-Orbit Applications

    NASA Technical Reports Server (NTRS)

    McKissock, Barbara I.

    2005-01-01

    The performance characteristics and long-term cycle life of aerospace lithium-ion (Li-ion) batteries in low-Earth-orbit applications are being investigated. A statistically designed test using Li-ion cells from various manufacturers began in September 2004 to study the effects of temperature, end-of-charge voltage, and depth-of-discharge operating conditions on the cycle life and performance of these cells. Performance degradation with cycling is being evaluated, and performance characteristics and failure modes are being modeled statistically. As technology improvements are incorporated into aerospace Li-ion cells, these new designs can be added to the test to evaluate the effect of the design changes on performance and life. Cells from Lithion and Saft have achieved over 2000 cycles under 10 different test condition combinations and are being evaluated. Cells from Mine Safety Appliances (MSA) and modules made up of commercial-off-the-shelf 18650 Li-ion cells connected in series/parallel combinations are scheduled to be added in the summer of 2005. The test conditions include temperatures of 10, 20, and 30 C, end-of-charge voltages of 3.85, 3.95, and 4.05 V, and depth-of-discharges from 20 to 40 percent. The low-Earth-orbit regime consists of a 55 min charge, at a constant-current rate that is 110 percent of the current required to fully recharge the cells in 55 min until the charge voltage limit is reached, and then at a constant voltage for the remaining charge time. Cells are discharged for 35 min at the current required for their particular depth-of-discharge condition. Cells are being evaluated in four-cell series strings with charge voltage limits being applied to individual cells by the use of charge-control units designed and produced at the NASA Glenn Research Center. These charge-control units clamp the individual cell voltages as each cell reaches its end-of-charge voltage limit, and they bypass the excess current from that cell, while allowing the full

  15. Comparative study of ion cyclotron waves at Mars, Venus and Earth

    NASA Astrophysics Data System (ADS)

    Wei, H. Y.; Russell, C. T.; Zhang, T. L.; Blanco-Cano, X.

    2011-08-01

    Ion cyclotron waves are generated in the solar wind when it picks up freshly ionized planetary exospheric ions. These waves grow from the free energy of the highly anisotropic distribution of fresh pickup ions, and are observed in the spacecraft frame with left-handed polarization and a wave frequency near the ion's gyrofrequency. At Mars and Venus and in the Earth's polar cusp, the solar wind directly interacts with the planetary exospheres. Ion cyclotron waves with many similar properties are observed in these diverse plasma environments. The ion cyclotron waves at Mars indicate its hydrogen exosphere to be extensive and asymmetric in the direction of the interplanetary electric field. The production of fast neutrals plays an important role in forming an extended exosphere in the shape and size observed. At Venus, the region of exospheric proton cyclotron wave production may be restricted to the magnetosheath. The waves observed in the solar wind at Venus appear to be largely produced by the solar-wind-Venus interaction, with some waves at higher frequencies formed near the Sun and carried outward by the solar wind to Venus. These waves have some similarity to the expected properties of exospherically produced proton pickup waves but are characterized by magnetic connection to the bow shock or by a lack of correlation with local solar wind properties respectively. Any confusion of solar derived waves with exospherically derived ion pickup waves is not an issue at Mars because the solar-produced waves are generally at much higher frequencies than the local pickup waves and the solar waves should be mostly absorbed when convected to Mars distance as the proton cyclotron frequency in the plasma frame approaches the frequency of the solar-produced waves. In the Earth's polar cusp, the wave properties of ion cyclotron waves are quite variable. Spatial gradients in the magnetic field may cause this variation as the background field changes between the regions in which

  16. The MT inversion for conductivity anisotropy and EDA precursor, stress field and deformation band in the Earth's deep crust

    NASA Astrophysics Data System (ADS)

    Lin, Chang-You; Yang, Chang-Fu; Wu, Yu-Xia; Chen, Jun-Ying

    1996-08-01

    The conductivity anisotropy behaviour is described for certain environment in the Earth’s crust and the MT inversion method for a layered symmetrically anisotropic model is presented. The inversion interpretations of the anisotropic model from the observational data are helpful to identify the earthquake precusors as indicated by the deep conductivity anisotropic variations, and also provide some useful information to investigate the stress states and deformation bands in the deep crust of the Earth.

  17. Determination of electron and ion thermal conductivities by analysis of Alcator-A profile data

    NASA Astrophysics Data System (ADS)

    Liewer, P. C.; Pfeiffer, W.; Waltz, R. E.

    1983-02-01

    Profile data from the Alcator-A tokamak are analyzed using the onetwo transport code to study thermal conductivities and power balance. It is found that the observed central ion temperatures can be explained by assuming an ion thermal conductivity equal to the neoclassical value as calculated recently by Bolton and Ware. For low density, n¯=1×1014 cm-3, the possible anomaly in the ion conductivity is small: ±30% of the Bolton-Ware value. The anomalous electron thermal conductivity as deduced from the profile data is = ≂2.5(±1.5)×1017 cm-1 sec-1. The power balance study shows that at low densities, electron energy losses from radiation and thermal conduction are equally important, and both are larger than the exchanges loss to the ions. At higher densities, n¯≥2×1014 cm-3, electron energy losses by thermal conduction and exchange are equally important, and both are larger than the radiation loss. Convective losses, as calculated from measured particle confinement times, are negligible for all densities analyzed.

  18. Fast calculation of the sensitivity matrix for responses to the Earth's conductivity: General strategy and examples

    NASA Astrophysics Data System (ADS)

    Pankratov, O. V.; Kuvshinov, A. V.

    2010-09-01

    Modern electromagnetic studies of the Earth deal with three-dimensional data sets and their inversion in the class of three-dimensional models. Due to the large scale of the 3D inverse problem, it is usually solved using gradient-type iteration techniques. These techniques require repeated calculations of the gradient of the penalty function (i.e., the sum of the misfit and the regularization term) with respect to the model parameters that describe the spatial distribution of conductivity. Since there are generally no analytical tools for calculating the misfit gradient, its computation requires the application of some numerical techniques. Unfortunately, it is impossible to perform mass calculations of the misfit gradient even using modern computing if one applies conventional numerical differentiation. In reality, in this case the number of calls of the forward problem is proportional to the number of the sought parameters, which is very large in case of a 3D inversion. However, there is a much more efficient method for calculation of the misfit gradient, namely, the adjoint-field technique. At present, this technique is widely used in the numerical schemes of the 3D inversion of electromagnetic and other data. With this technique we can calculate the misfit gradient with the same computational burden as that required for the solution of a single additional forward problem. Although this technique is widely used, we failed to find any comprehensive description of this technique in the literature that would allow one to apply this approach for any particular scheme of sounding, profiling, or transillumination as easily as a general formula is applied for a given case. In the present paper, we obtain general formulas for the quick calculation of the derivatives of the frequency-domain responses and the derivatives of the misfit function with respect to the variations in conductivity. We also show how the derived general formulas are transformed into particular

  19. Kinetic modeling of ion conduction in KcsA potassium channel.

    PubMed

    Mafé, Salvador; Pellicer, Julio; Cervera, Javier

    2005-05-22

    KcsA constitutes a potassium channel of known structure that shows both high conduction rates and selectivity among monovalent cations. A kinetic model for ion conduction through this channel that assumes rapid ion transport within the filter has recently been presented by Nelson. In a recent, brief communication, we used the model to provide preliminary explanations to the experimental current-voltage J-V and conductance-concentration g-S curves obtained for a series of monovalent ions (K(+),Tl(+), and Rb(+)). We did not assume rapid ion transport in the calculations, since ion transport within the selectivity filter could be rate limiting for ions other than native K(+). This previous work is now significantly extended to the following experimental problems. First, the outward rectification of the J-V curves in K(+) symmetrical solutions is analyzed using a generalized kinetic model. Second, the J-V and g-S curves for NH(4) (+) are obtained and compared with those of other ions (the NH(4) (+) J-V curve is qualitatively different from those of Rb(+) and Tl(+)). Third, the effects of Na(+) block on K(+) and Rb(+) currents through single KcsA channels are studied and the different blocking behavior is related to the values of the translocation rate constants characteristic of ion transport within the filter. Finally, the significantly decreased K(+) conductance caused by mutation of the wild-type channel is also explained in terms of this rate constant. In order to keep the number of model parameters to a minimum, we do not allow the electrical distance (an empirical parameter of kinetic models that controls the exponential voltage dependence of the dissociation rate) to vary with the ionic species. Without introducing the relatively high number of adjustable parameters of more comprehensive site-based models, we show that ion association to the filter is rate controlling at low concentrations, but ion dissociation from the filter and ion transport within the filter

  20. Influence of other rare earth ions on the optical refrigeration efficiency in Yb:YLF crystals.

    PubMed

    Di Lieto, Alberto; Sottile, Alberto; Volpi, Azzurra; Zhang, Zhonghan; Seletskiy, Denis V; Tonelli, Mauro

    2014-11-17

    We investigated the effect of rare earth impurities on the cooling efficiency of Yb³⁺:LiYF₄ (Yb:YLF). The refrigeration performance of two single crystals, doped with 5%-at. Yb and with identical history but with different amount of contaminations, have been compared by measuring the cooling efficiency curves. Spectroscopic and elemental analyses of the samples have been carried out to identify the contaminants, to quantify their concentrations and to understand their effect on the cooling efficiencies. A model of energy transfer processes between Yb and other rare earth ions is suggested, identifying Erbium and Holmium as elements that produce a detrimental effect on the cooling performance. PMID:25402099

  1. Macroscopic ion acceleration associated with the formation of the ring current in the earth's magnetosphere

    NASA Technical Reports Server (NTRS)

    Mauk, B. H.; Meng, C.-I.

    1986-01-01

    As an illustration of the operation of macroscopic ion acceleration processes within the earth's magnetosphere, the paper reviews processes thought to be associated with the formation of the earth's ring-current populations. Arguing that the process of global, quasi-curl-free convection cannot explain particle characteristics observed in the middle (geosynchronous) to outer regions, it is concluded that the transport and energization of the seed populations that give rise to the ring-current populations come about in two distinct stages involving distinct processes. Near and outside the geostationary region, the energization and transport are always associated with highly impulsive and relatively localized processes driven by inductive electric fields. The subsequent adiabatic earthward transport is driven principally by enhanced, curl-free global convection fields.

  2. Determining the static dielectric permittivity of ion conducting materials when obscured by electrode polarization

    NASA Astrophysics Data System (ADS)

    Grâsjö, Johan; Welch, Ken; Strømme, Maria

    2008-09-01

    A method is derived for the determination of the static dielectric permittivity of ion conducting materials when this parameter is obscured by electrode polarization in as-recorded low frequency dielectric spectra. The method requires permittivity measurements at two different electrode separations, and is applicable when the electric fields created by charge separation near the electrode surfaces do not induce nonlinear effects in the frequency region where electrode polarization begins to affect the dielectric response. The performance of the method is illustrated by the analysis of an ion conducting cellulose gel biosynthesized by the Acetobacter. xylinum bacterium. The method opens up possibilities to obtain more detailed information about dynamic processes in ion conducting materials from dielectric spectroscopy.

  3. Characteristics and Mechanisms in Ion-Conducting Polymer Films as Chemical Sensors

    SciTech Connect

    HUGHES,ROBERT C.; YELTON,WILLIAM G.; PFEIFER,KENT B.; PATEL,SANJAY V.

    2000-07-12

    Solid Polymer Electrolytes (SPE) are widely used in batteries and fuel cells because of the high ionic conductivity that can be achieved at room temperature. The ions are usually Li or protons, although other ions can be shown to conduct in these polymer films. There has been very little published work on SPE films used as chemical sensors. The authors have found that thin films of polymers like polyethylene oxide (PEO) are very sensitive to low concentrations of volatile organic compounds (VOCs) such as common solvents. Evidence of a new sensing mechanism involving the percolation of ions through narrow channels of amorphous polymer is presented. They present impedance spectroscopy of PEO films in the frequency range 0.0001 Hz to 1 MHz for different concentrations of VOCs and relative humidity. They find that the measurement frequency is important for distinguishing ionic conductivity from the double layer capacitance and the parasitic capacitance.

  4. Fabrication of ion conductive tin oxide-phosphate amorphous thin films by atomic layer deposition

    SciTech Connect

    Park, Suk Won; Jang, Dong Young; Kim, Jun Woo; Shim, Joon Hyung

    2015-07-15

    This work reports the atomic layer deposition (ALD) of tin oxide-phosphate films using tetrakis(dimethylamino)tin and trimethyl phosphate as precursors. The growth rates were 1.23–1.84 Å/cycle depending upon the deposition temperature and precursor combination. The ionic conductivity of the ALD tin oxide-phosphate films was evaluated by cross-plane impedance measurements in the temperature range of 50–300 °C under atmospheric air, with the highest conductivity measured as 1.92 × 10{sup −5} S cm{sup −1} at 300 °C. Furthermore, high-resolution x-ray photoelectron spectroscopy exhibited two O1s peaks that were classified as two subpeaks of hydroxyl ions and oxygen ions, revealing that the quantity of hydroxyl ions in the ALD tin oxide-phosphate films influences their ionic conductivity.

  5. Energetic optimization of ion conduction rate by the K+ selectivity filter

    NASA Astrophysics Data System (ADS)

    Morais-Cabral, João H.; Zhou, Yufeng; MacKinnon, Roderick

    2001-11-01

    The K+ selectivity filter catalyses the dehydration, transfer and rehydration of a K+ ion in about ten nanoseconds. This physical process is central to the production of electrical signals in biology. Here we show how nearly diffusion-limited rates are achieved, by analysing ion conduction and the corresponding crystallographic ion distribution in the selectivity filter of the KcsA K+ channel. Measurements with K+ and its slightly larger analogue, Rb+, lead us to conclude that the selectivity filter usually contains two K+ ions separated by one water molecule. The two ions move in a concerted fashion between two configurations, K+-water-K+-water (1,3 configuration) and water-K+-water-K+ (2,4 configuration), until a third ion enters, displacing the ion on the opposite side of the queue. For K+, the energy difference between the 1,3 and 2,4 configurations is close to zero, the condition of maximum conduction rate. The energetic balance between these configurations is a clear example of evolutionary optimization of protein function.

  6. Previously hidden low-energy ions: a better map of near-Earth space and the terrestrial mass balance

    NASA Astrophysics Data System (ADS)

    André, Mats

    2015-12-01

    This is a review of the mass balance of planet Earth, intended also for scientists not usually working with space physics or geophysics. The discussion includes both outflow of ions and neutrals from the ionosphere and upper atmosphere, and the inflow of meteoroids and larger objects. The focus is on ions with energies less than tens of eV originating from the ionosphere. Positive low-energy ions are complicated to detect onboard sunlit spacecraft at higher altitudes, which often become positively charged to several tens of volts. We have invented a technique to observe low-energy ions based on the detection of the wake behind a charged spacecraft in a supersonic ion flow. We find that low-energy ions usually dominate the ion density and the outward flux in large volumes in the magnetosphere. The global outflow is of the order of 1026 ions s-1. This is a significant fraction of the total number outflow of particles from Earth, and changes plasma processes in near-Earth space. We compare order of magnitude estimates of the mass outflow and inflow for planet Earth and find that they are similar, at around 1 kg s-1 (30 000 ton yr-1). We briefly discuss atmospheric and ionospheric outflow from other planets and the connection to evolution of extraterrestrial life.

  7. Mixed ion/electron-conductive protective soft nanomatter-based conformal surface modification of lithium-ion battery cathode materials

    NASA Astrophysics Data System (ADS)

    Park, Jang-Hoon; Kim, Ju-Myung; Lee, Chang Kee; Lee, Sang-Young

    2014-10-01

    Understanding and control of interfacial phenomena between electrode material and liquid electrolytes are of major scientific importance for boosting development of high-performance lithium ion batteries with reliable electrochemical/safety attributes. Here, as an innovative surface engineering approach to address the interfacial issues, a new concept of mixed ion/electron-conductive soft nanomatter-based conformal surface modification of the cathode material is presented. The soft nanomatter is comprised of an electron conductive carbonaceous (C) substance embedded in an ion conductive polyimide (PI) nanothin compliant film. In addition to its structural uniqueness, the newly proposed surface modification benefits from a simple fabrication process. The PI/carbon soft nanomatter is directly synthesized on LiCoO2 surface via one-pot thermal treatment of polyamic acid (=PI precursor) and sucrose (=carbon source) mixture, where the LiCoO2 powders are chosen as a model system to explore the feasibility of this surface engineering strategy. The resulting PI/carbon coating layer facilitates electronic conduction and also suppresses unwanted side reactions arising from the cathode material-liquid electrolyte interface. These synergistic coating effects of the multifunctional PI/carbon soft nanomatter significantly improve high-voltage cell performance and also mitigate interfacial exothermic reaction between cathode material and liquid electrolyte.

  8. Preparation and structure of carbonated calcium hydroxyapatite substituted with heavy rare earth ions

    SciTech Connect

    Yasukawa, Akemi; Kandori, Kazuhiko; Tanaka, Hidekazu; Gotoh, Keiko

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer LnCaHap solid solution particles were prepared using five types of heavy rare earth ions by a precipitation method. Black-Right-Pointing-Pointer The length and the crystallinity of the LnCaHap particles first increased and then decreased with increasing Ln{sup 3+} contents. Black-Right-Pointing-Pointer A series of YCaHap solid solution particles formed with Y/(Y + Ca) = 0-0.10 were investigated using various methods in detail. -- Abstract: Calcium hydroxyapatite (CaHap) particles substituted five types of heavy rare earth ions (Ln: Y{sup 3+}, Gd{sup 3+}, Dy{sup 3+}, Er{sup 3+} and Yb{sup 3+}) were synthesized using a precipitation method and characterized using various means. These Ln ions strongly affected the crystal phases and the structures of the products. With increasing Ln/(Ln + Ca) in the starting solution ([X{sub Ln}]), the length and the crystallinity of the particles first increased and then decreased. The rare earth metal-calcium hydroxyapatite (LnCaHap) solid solution particles were obtained at [X{sub Y}] {<=} 0.10 for substituting Y system and at [X{sub Ln}] {<=} 0.01-0.03 for substituting the other Ln systems. LnPO{sub 4} was mixed with LnCaHap at higher [X{sub Ln}] for all Ln systems. A series of yttrium-calcium hydroxyapatite (YCaHap) solid solutions with [X{sub Y}] = 0-0.10 were investigated using XRD, TEM, ICP-AES, IR and TG-DTA in detail.

  9. Synthesis, characterization, luminescence and electrical conductivity of the metal ions (M) doped KAl0.33W1.67O6

    NASA Astrophysics Data System (ADS)

    Ravi, G.; Kumar, K. Sravan; Guje, Ravinder; Sreenu, K.; Prasad, G.; Vithal, M.

    2016-01-01

    Metal ions (M) (M=Ag+, Cu2+, Sm3+ and Eu3+) doped KAl0.33W1.67O6 are obtained at room temperature by ion exchange method. These materials are characterized by powder X-Ray diffraction (XRD), and UV-visible DRS. All these materials are crystallized in a cubic lattice with Fd 3 bar m space group. The dependence of photoluminescence properties of Sm3+ and Eu3+ in KAl0.33W1.67O6 lattice is examined with reference to rare earth ion concentration. The AC conductivity measurements of Ag+ and Cu2+ doped KAl0.33W1.67O6 are carried out in the temperature range 30-450 °C. The variation of conductivity with frequency and temperature is explained.

  10. Stochastic Growth of Ion Cyclotron And Mirror Waves In Earth's Magnetosheath

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.; Grubits, K. A.

    2001-01-01

    Electromagnetic ion cyclotron and mirror waves in Earth's magnetosheath are bursty, have widely variable fields, and are unexpectedly persistent, properties difficult to reconcile with uniform secular growth. Here it is shown for specific periods that stochastic growth theory (SGT) quantitatively accounts for the functional form of the wave statistics and qualitatively explains the wave properties. The wave statistics are inconsistent with uniform secular growth or self-organized criticality, but nonlinear processes sometimes play a role at high fields. The results show SGT's relevance near marginal stability and suggest that it is widely relevant to space and astrophysical plasmas.

  11. Raman Spectroscopic Characterization of Rare Earth Ions Doped Bismuth-Based Glasses

    SciTech Connect

    Pop, L.; Culea, E.; Bosca, M.; Culea, M.

    2007-04-23

    The xReO(1-x)[3Bi2O3{center_dot}PbO] glass systems with diferent rare earth ions (ReO = CeO2, Tb4O7) have been prepared and examined with the aim of determining their structural characteristics. Raman sprectroscopy and density measurements were used to characterize the samples. Raman spectroscopy data permitted to identify some of the structural units that built up the lead bismuthate vitreous network. Density data were used to calculate the Poisson's ratio in terms of the Makishima-Mackenzie model.

  12. Ion Pair in Extreme Aqueous Environments, Molecular-Based and Electric Conductance Approaches

    SciTech Connect

    Chialvo, Ariel A; Gruszkiewicz, Miroslaw {Mirek} S; Simonson, J Michael {Mike}; Palmer, Donald; Cole, David R

    2009-01-01

    We determine by molecular-based simulation the density profiles of the Na+!Cl! ion-pair association constant in steam environments along three supercritical isotherms to interrogate the behavior of ion speciation in dilute aqueous solutions at extreme conditions. Moreover, we describe a new ultra-sensitive flow-through electric conductance apparatus designed to bridge the gap between the currently lowest steam-density conditions at which we are experimentally able to attain electric conductance measurements and the theoretically-reachable zero-density limit. Finally, we highlight important modeling challenges encountered near the zero-density limit and discuss ways to overcome them.

  13. Lithium ion conductive behavior of TiO2 nanotube/ionic liquid matrices

    PubMed Central

    2014-01-01

    A series of TiO2 nanotube (TNT)/ionic liquid matrices were prepared, and their lithium ion conductive properties were studied. SEM images implied that ionic liquid was dispersed on the whole surface of TNT. Addition of TNT to ionic liquid (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (BMImTFSA)) resulted in significant increase of ionic conductivity. Furthermore, lithium transference number was also largely enhanced due to the interaction of anion with TNT. Vogel-Fulcher-Tammann parameter showed higher carrier ion number for TNT/BMImTFSA in comparison with BMImTFSA. PMID:25313300

  14. Local structure around rare-earth ions in B2O3 glass at high pressure

    NASA Astrophysics Data System (ADS)

    Funabiki, Fuji; Matsuishi, Satoru; Hosono, Hideo

    2013-06-01

    Melt quenching of B2O3 with less than 25 mol. % rare-earth oxide (RE2O3) at ambient pressure results in a milky white glass because of liquid-liquid phase separation into B2O3 and RE2O3.3B2O phases. In contrast, we have found that melt quenching under GPa-order pressure realizes a transparent RE-doped B2O3 glass. This study investigates the local structure around the RE ions in the B2O3 glass prepared at 3 GPa using optical measurements and electron-spin-echo envelope modulation spectroscopy. It is shown that the RE-rich microparticles disappear and the RE ions are isolated from each other in a highly symmetric crystal field formed by triangular and tetrahedral boron units. This result is consistent with that extrapolated from the data for RE-doped sodium borate glasses.

  15. Generation of electromagnetic ion cyclotron waves in the near-Earth magnetotail during dipolarization: Two-dimensional global hybrid simulation

    NASA Astrophysics Data System (ADS)

    Guo, Zhifang; Wu, Mingyu; Du, Aimin

    2016-04-01

    We employ two-dimensional global hybrid simulations to study the generation, propagation, and polarization of electromagnetic ion cyclotron (EMIC) waves in the near-Earth magnetotail (around x = - 10 R E ) during dipolarization. In our simulation, EMIC waves with left-hand polarized signals originate in the low-latitude magnetotail as a result of the ion temperature anisotropy which is due to ion heating by Alfvén waves. Subsequently, EMIC waves can propagate along the ambient magnetic field toward high-latitudes. Our work provides one possible mechanism for the generation of EMIC waves observed in the near-Earth magnetotail.

  16. A Study on Removal of Rare Earth Elements from U.S. Coal Byproducts by Ion Exchange

    NASA Astrophysics Data System (ADS)

    Rozelle, Peter L.; Khadilkar, Aditi B.; Pulati, Nuerxida; Soundarrajan, Nari; Klima, Mark S.; Mosser, Morgan M.; Miller, Charles E.; Pisupati, Sarma V.

    2016-03-01

    Rare earth elements are known to occur in low concentrations in U.S. coals and coal byproducts. These low concentrations may make rare earth element recovery from these materials unattractive, using only physical separation techniques. However, given the significant production of rare earths through ion exchange extraction in China, two U.S. coal byproducts were examined for ion extraction, using ammonium sulfate, an ionic liquid, and a deep eutectic solvent as lixiviants. Extraction of rare earth elements in each case produced high recoveries of rare earth elements to the solution. This suggests that in at least the cases of the materials examined, U.S. coal byproducts may be technically suitable as REE ores. More work is required to establish economic suitability.

  17. Statistical analysis of diffuse ion events upstream of the Earth's bow shock

    NASA Technical Reports Server (NTRS)

    Trattner, K. J.; Mobius, E.; Scholer, M.; Klecker, B.; Hilchenbach, M.; Luehr, H.

    1994-01-01

    A statistical study of diffuse energetic ion events and their related waves upstream of the Earth's bow shock was performed using data from the Active Magnetospheric Particle Tracer Explorers/Ion Release Module (AMPTE/IRM) satellite over two 5-month periods in 1984 and 1985. The data set was used to test the assumption in the self-consistent model of the upstream wave and particle populations by Lee (1982) that the particle acceleration through hydromagnetic waves and the wave generation are directly coupled. The comparison between the observed wave power and the wave power predicted on the observed energetic particle energy density and solar wind parameters results in a high correlation coefficient of about 0.89. The intensity of diffuse ions falls off approximately exponentially with the distance upstream from the bow shock parallel to the magnetic field with e-folding distances which vary from approximately 3.3 R(sub E) to approximately 11.7 R(sub E) over the energy range from 10 keV/e to 67.3 keV/e for both protons and alpha particles. After normalizing the upstream particle densities to zero bow shock distance by using these exponential variations, a good correlation (0.7) of the density of the diffuse ions with the solar wind density was found. This supports the suggestion that the solar wind is the source of the diffuse ions. Furthermore, the spectral slope of the diffuse ions correlates well with the solar wind velocity component in the direction of the interplanetary magnetic field (0.68 and 0.66 for protons and alpha particles) which concurs with the notion that the solar wind plays an important role in the acceleration of the upstream particles.

  18. Investigation of thermal diffusivity dependence on temperature in a group of optical single crystals doped with rare earth ions

    NASA Astrophysics Data System (ADS)

    Trefon-Radziejewska, D.; Bodzenta, J.

    2015-07-01

    The group of YAG, YVO4 and GdCOB single crystals was examined to determine the thermal diffusivity as a function of temperature in range from 30 °C to 300 °C. Further investigations concerned on analysis of the influence of dopants on these dependencies. The experimental setup based on thermal wave method with mirage detection was used. The samples represented different crystallographic systems such as cubic (YAG) tetragonal (YVO4) and monoclinic (GdCOB). The anisotropy of thermal conductivity of investigated samples was taken into account in the investigations. The crystals were doped with calcium ions, rare earth ions such as ytterbium, neodymium, and thulium, and also with transition metal vanadium. The results confirmed that influence of doping on the thermal diffusivity of investigated materials strongly depends on temperature. In general the thermal diffusivity decreases with increasing of sample temperature from 30 °C to 300 °C, however the drop in thermal diffusivity is the highest for pure single crystals. Doping is another factor reducing the heat transport in single crystals. Introduction of dopant ions into a crystal lattice leads to a significant decrease in the thermal diffusivity at lower temperatures in comparison with pure crystals. However, the influence of dopants becomes less pronounced with increasing temperature, and in case of weakly doped crystals it becomes negligible at higher temperatures. The interpretation of thermal diffusivity dependence on temperature for single crystals was based on the Debye model of lattice thermal conductivity of solids. The results allowed to conclude that the decrease of thermal diffusivity with temperature and increasing concentration of impurities is caused by shortening of the phonons mean free path due to phonon-phonon and phonon-point defect scatterings.

  19. Mapping the earth conductivity-depth structure of African geomagnetic equatorial anomaly regions using solar quiet current variations

    NASA Astrophysics Data System (ADS)

    Ugbor, D. O.; Okeke, F. N.; Yumoto, K.

    2016-04-01

    The solar quiet day ionospheric (Sq) current variations observed in Abuja, Bangui and Addis Ababa were used to delineate the mantle conductivity-depth structure along the equatorial African regions. Spherical harmonic analysis (SHA) was employed in separating the internal and external field contributions to the Sq variations. For each of the paired external and internal coefficients of the SHA, we used transfer function to compute the conductivity-depth profile for the region. Strikingly, we observed increased electrical conductivity values in the Earth layers and deep depth penetration. The calculated average electrical conductivity values in Addis Ababa and Abuja are 0.087 Sm-1 and 0.104 Sm-1 at depths of 93 km and 121 km respectively. These values suddenly rose to 0.235 Sm-1 and 0.222 Sm-1 at depths of 440 km and 427 km respectively. In Bangui, the calculated average values are 0.092 Sm-1, 0.144 Sm-1, 0.312 Sm-1 and 0.466 Sm-1 at 96 km, 300 km, 834 km and 1228 km depths respectively. At the greatest depths of penetration of 1412 km, 1385 km and 1278 km in Addis Ababa, Abuja and Bangui, the electrical conductivity attained the highest values of 0.415 Sm-1, 0.467 Sm-1 and 0.515 Sm-1 respectively. Two most Earth conductive layers were discovered in the magnetic equatorial zone. These layers lie between the depth of about 100 and 400 km within the upper mantle and beyond 1200 km in the lower mantle. It can be inferred that the closer one goes towards the Earth magnetic equator; the deeper the Sq current can penetrate the Earth's interior.

  20. Indirect determination of cyanide compounds by ion chromatography with conductivity measurement

    SciTech Connect

    Nonomura, M.

    1987-09-01

    Ion chromatography (IC) is a suitable analytical technique for the determination of anions. The cyanide is not detected by the conductivity detector of the ion chromatograph due to its low dissolution constant (pK = 9.2). This paper describes an IC procedure for the determination of free cyanide and metal cyanide complexes that uses a conductivity detector. It is based on the oxidation of cyanide ion by sodium hypochlorite to cyanate ion (pK = 3.66). Therefore, cyanide ion can now be measured indirectly by the conductivity detector. In this procedure, optimum operating conditions were examined. In addition, the interferences from anions and reducing agents were investigated. The method was applied to the determination of metal cyanide complexes. The coefficients of variation (%) for CN/sup -/ (1.05 mg/L), Zn(CN)/sub 4//sup 2 -/ (CN/sup -/, 0.80 mg/L), and Ni(CN)/sub 4//sup 2 -/ (CN/sup -/, 0.96 mg/L) were 1.1%, 1.5%, and 0.5%, respectively. The proposed method proved to be useful for the determination of cyanide compounds in natural water and waste water.

  1. Conductance and Ion Selectivity of a Mesoscopic Protein Nanopore Probed with Cysteine Scanning Mutagenesis

    PubMed Central

    Merzlyak, Petr G.; Capistrano, Maria-Fatima P.; Valeva, Angela; Kasianowicz, John J.; Krasilnikov, Oleg V.

    2005-01-01

    Nanometer-scale proteinaceous pores are the basis of ion and macromolecular transport in cells and organelles. Recent studies suggest that ion channels and synthetic nanopores may prove useful in biotechnological applications. To better understand the structure-function relationship of nanopores, we are studying the ion-conducting properties of channels formed by wild-type and genetically engineered versions of Staphylococcus aureus α-hemolysin (αHL) reconstituted into planar lipid bilayer membranes. Specifically, we measured the ion selectivities and current-voltage relationships of channels formed with 24 different αHL point cysteine mutants before and after derivatizing the cysteines with positively and negatively charged sulfhydryl-specific reagents. Novel negative charges convert the selectivity of the channel from weakly anionic to strongly cationic, and new positive charges increase the anionic selectivity. However, the extent of these changes depends on the channel radius at the position of the novel charge (predominately affects ion selectivity) or on the location of these charges along the longitudinal axis of the channel (mainly alters the conductance-voltage curve). The results suggest that the net charge of the pore wall is responsible for cation-anion selectivity of the αHL channel and that the charge at the pore entrances is the main factor that determines the shape of the conductance-voltage curves. PMID:16085767

  2. Suppressing gate errors through extra ions coupled to a cavity in frequency-domain quantum computation using rare-earth-ion-doped crystal

    NASA Astrophysics Data System (ADS)

    Nakamura, Satoshi; Goto, Hayato; Kujiraoka, Mamiko; Ichimura, Kouichi; Quantum Computer Team

    The rare-earth-ion-doped crystals, such as Pr3+: Y2SiO5, are promising materials for scalable quantum computers, because the crystals contain a large number of ions which have long coherence time. The frequency-domain quantum computation (FDQC) enables us to employ individual ions coupled to a common cavity mode as qubits by identifying with their transition frequencies. In the FDQC, operation lights with detuning interact with transitions which are not intended to operate, because ions are irradiated regardless of their positions. This crosstalk causes serious errors of the quantum gates in the FDQC. When ``resonance conditions'' between eigenenergies of the whole system and transition-frequency differences among ions are satisfied, the gate errors increase. Ions for qubits must have transitions avoiding the conditions for high-fidelity gate. However, when a large number of ions are employed as qubits, it is difficult to avoid the conditions because of many combinations of eigenenergies and transitions. We propose new implementation using extra ions to control the resonance conditions, and show the effect of the extra ions by a numerical simulation. Our implementation is useful to realize a scalable quantum computer using rare-earth-ion-doped crystal based on the FDQC.

  3. Ion beam irradiation as a tool to improve the ionic conductivity in solid polymer electrolyte systems

    NASA Astrophysics Data System (ADS)

    Manjunatha, H.; Damle, R.; Kumaraswamy, G. N.

    2016-05-01

    Solid polymer electrolytes (SPEs) have potential applications in solid state electronic and energy devices. The optimum conductivity of SPEs required for such applications is about 10-1 - 10-3 Scm-1, which is hard to achieve in these systems. It is observed that ionic conductivity of SPEs continuously increase with increasing concentration of inorganic salt in the host polymer. However, there is a critical concentration of the salt beyond which the conductivity of SPEs decreases due to the formation of ion pairs. In the present study, solid polymer thin films based on poly (ethylene oxide) (PEO) complexed with NaBr salt with different concentrations have been prepared and the concentration at which ion pair formation occurs in PEOxNaBr is identified. The microstructure of the SPE with highest ionic conductivity is modified by irradiating it with low energy O+1 ion (100 keV) of different fluencies. It is observed that the ionic conductivity of irradiated SPEs increases by one order in magnitude. The increase in ionic conductivity may be attributed to the enhanced segmental motion of the polymer chains due to radiation induced micro structural modification.

  4. Properties and the origin of Almost Monoenergetic Ion (AMI) beams observed near the Earth's bow shock

    NASA Astrophysics Data System (ADS)

    Lutsenko, V. N.; Gavrilova, E. A.

    2011-08-01

    Beams of Almost Monoenergetic Ions (AMI) in the energy range from 20 to 800 keV were discovered in the DOK-2 experiment (Interball project) in the magnetosheath and upstream of the Earth's bow shock. This work summarizes the analysis results of ~730 AMI events registered in 1995-2000. Statistics of AMI properties, their nature and origin are considered. The analysis of a large array of new data confirmed our earlier suggested ideas on the AMI nature, origin, and their acceleration model. These ideas were further developed and refined. According to this model, AMI are a result of solar wind ions acceleration in small regions with a potential electric field arising due to disruptions of the bow shock current sheet filaments. It has been found that the reason of the current filaments disruptions in most cases was the Hot Flow Anomaly phenomenon (HFA) caused by an interaction of a tangential discontinuity in the solar wind with the Earth's bow shock. It is shown that the study of AMI can provide new information on large-scale properties and dynamics of the bow shock current sheet.

  5. Atomic Scale Picture of the Ion Conduction Mechanism in Tetrahedral Network of Lanthanum Barium Gallate

    SciTech Connect

    Jalarvo, Niina H; Gourdon, Olivier; Bi, Zhonghe; Gout, Delphine J; Ohl, Michael E; Paranthaman, Mariappan Parans

    2013-01-01

    Combined experimental study of impedance spectroscopy, neutron powder diffraction and quasielastic neutron scattering was performed to shed light into the atomic scale ion migration processes in proton and oxide ion conductor; La0.8Ba1.2GaO3.9 . This material consist of tetrahedral GaO4 units, which are rather flexible and rocking motion of these units promotes the ionic migration process. The oxide ion (vacancy) conduction takes place on channels along c axis, involving a single elementary step, which occurs between adjacent tetrahedron (inter-tetrahedron jump). The proton conduction mechanism consists of intra-tetrahedron and inter-tetrahedron elementary processes. The intra-tetrahedron proton transport is the rate-limiting process, with activation energy of 0.44 eV. The rocking motion of the GaO4 tetrahedron aids the inter-tetrahedral proton transport, which has the activation energy of 0.068 eV.

  6. Li Ion Conducting Polymer Gel Electrolytes Based on Ionic Liquid/PVDF-HFP Blends

    PubMed Central

    Ye, Hui; Huang, Jian; Xu, Jun John; Khalfan, Amish; Greenbaum, Steve G.

    2009-01-01

    Ionic liquids thermodynamically compatible with Li metal are very promising for applications to rechargeable lithium batteries. 1-methyl-3-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (P13TFSI) is screened out as a particularly promising ionic liquid in this study. Dimensionally stable, elastic, flexible, nonvolatile polymer gel electrolytes (PGEs) with high electrochemical stabilities, high ionic conductivities and other desirable properties have been synthesized by dissolving Li imide salt (LiTFSI) in P13TFSI ionic liquid and then mixing the electrolyte solution with poly(vinylidene-co-hexafluoropropylene) (PVDF-HFP) copolymer. Adding small amounts of ethylene carbonate to the polymer gel electrolytes dramatically improves the ionic conductivity, net Li ion transport concentration, and Li ion transport kinetics of these electrolytes. They are thus favorable and offer good prospects in the application to rechargeable Li batteries including open systems like Li/air batteries, as well as more “conventional” rechargeable lithium and lithium ion batteries. PMID:20354587

  7. Computational studies of solid-state alkali conduction in rechargeable alkali-ion batteries

    DOE PAGESBeta

    Deng, Zhi; Mo, Yifei; Ong, Shyue Ping

    2016-03-25

    The facile conduction of alkali ions in a crystal host is of crucial importance in rechargeable alkali-ion batteries, the dominant form of energy storage today. In this review, we provide a comprehensive survey of computational approaches to study solid-state alkali diffusion. We demonstrate how these methods have provided useful insights into the design of materials that form the main components of a rechargeable alkali-ion battery, namely the electrodes, superionic conductor solid electrolytes and interfaces. We will also provide a perspective on future challenges and directions. Here, the scope of this review includes the monovalent lithium- and sodium-ion chemistries that aremore » currently of the most commercial interest.« less

  8. Mesocosm Community Response Sensitivities to Specific Conductivity Comprised of Different Major Ions

    EPA Science Inventory

    Traditional toxicity test assays have been used to evaluate the relative sensitivity to different major ion mixtures as a proxy for understanding what the response of aquatic species growing in their natural environment would be during exposure to specific conductivity stress ema...

  9. The role of tortuosity on ion conduction in block copolymer electrolyte thin films

    NASA Astrophysics Data System (ADS)

    Kambe, Yu; Arges, Christopher G.; Nealey, Paul F.

    This talk discusses the role of grain tortuosity on ion conductivity in block copolymer electrolyte (BCE) thin films. In particular, we studied lamellae forming BCEs with both domains oriented perpendicular to the substrate surface and connected directly from one electrode to another - i.e., tortuosity of one. The BCE is composed of ion-conducting, poly(2-vinyl n-methylpyridinium) blocks and non-ionic polystyrene blocks. Prior to creating the BCE, the pristine block copolymer, poly(styrene- b-2-vinyl pyridine), was directly self-assembled (DSA) on topographical or chemical patterns via graphoepitaxy and chemoepitaxy. A chemical vapor infiltration reaction modified the P2VP block into positively charged, fixed quaternary ammonium groups paired with mobile counteranions. The graphoepitaxy process utilized topographical interdigitated gold nanoelectrodes (100s of nanometers spacing between electrodes) created via e-beam lithography. Alternatively, chemical patterns had gold electrodes incorporated into them with 10s to 100s of microns spacing using conventional optical lithography. The interdigitated gold electrodes enabled in-plane ion conductivity measurements of the DSA BCEs to study the role of grain tortuosity on ion conductivity. U.S. Department of Energy Office of Science: Contract No. DE-AC02-06CH11357.

  10. Amorphization and reduction of thermal conductivity in porous silicon by irradiation with swift heavy ions

    SciTech Connect

    Newby, Pascal J.; Canut, Bruno; Bluet, Jean-Marie; Lysenko, Vladimir; Gomes, Severine; Isaiev, Mykola; Burbelo, Roman; Chantrenne, Patrice; Frechette, Luc G.

    2013-07-07

    In this article, we demonstrate that the thermal conductivity of nanostructured porous silicon is reduced by amorphization and also that this amorphous phase in porous silicon can be created by swift (high-energy) heavy ion irradiation. Porous silicon samples with 41%-75% porosity are irradiated with 110 MeV uranium ions at six different fluences. Structural characterisation by micro-Raman spectroscopy and SEM imaging show that swift heavy ion irradiation causes the creation of an amorphous phase in porous Si but without suppressing its porous structure. We demonstrate that the amorphization of porous silicon is caused by electronic-regime interactions, which is the first time such an effect is obtained in crystalline silicon with single-ion species. Furthermore, the impact on the thermal conductivity of porous silicon is studied by micro-Raman spectroscopy and scanning thermal microscopy. The creation of an amorphous phase in porous silicon leads to a reduction of its thermal conductivity, up to a factor of 3 compared to the non-irradiated sample. Therefore, this technique could be used to enhance the thermal insulation properties of porous Si. Finally, we show that this treatment can be combined with pre-oxidation at 300 Degree-Sign C, which is known to lower the thermal conductivity of porous Si, in order to obtain an even greater reduction.

  11. Nanoslit design for ion conductivity gradient enhanced dielectrophoresis for ultrafast biomarker enrichment in physiological media.

    PubMed

    Rohani, Ali; Varhue, Walter; Liao, Kuo-Tang; Chou, Chia-Fu; Swami, Nathan S

    2016-05-01

    Selective and rapid enrichment of biomolecules is of great interest for biomarker discovery, protein crystallization, and in biosensing for speeding assay kinetics and reducing signal interferences. The current state of the art is based on DC electrokinetics, wherein localized ion depletion at the microchannel to nanochannel interface is used to enhance electric fields, and the resulting biomarker electromigration is balanced against electro-osmosis in the microchannel to cause high degrees of biomarker enrichment. However, biomarker enrichment is not selective, and the levels fall off within physiological media of high conductivity, due to a reduction in ion concentration polarization and electro-osmosis effects. Herein, we present a methodology for coupling AC electrokinetics with ion concentration polarization effects in nanoslits under DC fields, for enabling ultrafast biomarker enrichment in physiological media. Using AC fields at the critical frequency necessary for negative dielectrophoresis of the biomarker of interest, along with a critical offset DC field to create proximal ion accumulation and depletion regions along the perm-selective region inside a nanoslit, we enhance the localized field and field gradient to enable biomarker enrichment over a wide spatial extent along the nanoslit length. While enrichment under DC electrokinetics relies solely on ion depletion to enhance fields, this AC electrokinetic mechanism utilizes ion depletion as well as ion accumulation regions to enhance the field and its gradient. Hence, biomarker enrichment continues to be substantial in spite of the steady drop in nanostructure perm-selectivity within physiological media. PMID:27462378

  12. The magnetospheric disturbance ring current as a source for probing the deep earth electrical conductivity

    USGS Publications Warehouse

    Campbell, W.H.

    1990-01-01

    Two current rings have been observed in the equatorial plane of the earth at times of high geomagnetic activity. An eastward current exists between about 2 and 3.5 earth radii (Re) distant, and a larger, more variable companion current exists between about 4 and 9 Re. These current regions are loaded during geomagnetic substorms. They decay, almost exponentially, after the cessation of the particle influx that attends the solar wind disturbance. This review focuses upon characteristics needed for intelligent use of the ring current as a source for induction probing of the earth's mantle. Considerable difficulties are found with the assumption that Dst is a ring-current index. ?? 1990 Birkha??user Verlag.

  13. Stellar wind interaction and pick-up ion escape of the Kepler-11 "super-Earths"

    NASA Astrophysics Data System (ADS)

    Kislyakova, K. G.; Johnstone, C. P.; Odert, P.; Erkaev, N. V.; Lammer, H.; Lüftinger, T.; Holmström, M.; Khodachenko, M. L.; Güdel, M.

    2014-02-01

    Aims: We study the interactions between stellar winds and the extended hydrogen-dominated upper atmospheres of planets. We estimate the resulting escape of planetary pick-up ions from the five "super-Earths" in the compact Kepler-11 system and compare the escape rates with the efficiency of the thermal escape of neutral hydrogen atoms. Methods: Assuming the stellar wind of Kepler-11 is similar to the solar wind, we use a polytropic 1D hydrodynamic wind model to estimate the wind properties at the planetary orbits. We apply a direct simulation Monte Carlo model to model the hydrogen coronae and the stellar wind plasma interaction around Kepler-11b-f within a realistic expected heating efficiency range of 15-40%. The same model is used to estimate the ion pick-up escape from the XUV heated and hydrodynamically extended upper atmospheres of Kepler-11b-f. From the interaction model, we study the influence of possible magnetic moments, calculate the charge exchange and photoionization production rates of planetary ions, and estimate the loss rates of pick-up H+ ions for all five planets. We compare the results between the five "super-Earths" and the thermal escape rates of the neutral planetary hydrogen atoms. Results: Our results show that a huge neutral hydrogen corona is formed around the planet for all Kepler-11b-f exoplanets. The non-symmetric form of the corona changes from planet to planet and is defined mostly by radiation pressure and gravitational effects. Non-thermal escape rates of pick-up ionized hydrogen atoms for Kepler-11 "super-Earths" vary between ~6.4 × 1030 s-1 and ~4.1 × 1031 s-1, depending on the planet's orbital location and assumed heating efficiency. These values correspond to non-thermal mass loss rates of ~1.07 × 107 g s-1 and ~6.8 × 107 g s-1 respectively, which is a few percent of the thermal escape rates.

  14. Stellar wind interaction and pick-up ion escape of the Kepler-11 "super-Earths"

    NASA Astrophysics Data System (ADS)

    Kislyakova, Kristina; Johnstone, Colin; Odert, Petra; Erkaev, Nikolai; Lammer, Helmut; Lüftinger, Theresa; Holmstöm, Mats; Khodachenko, Maxim; Güdel, Manuel

    2014-05-01

    We present the results of modeling of the interactions between stellar wind and the extended hydrogen-dominated upper atmospheres of planets and estimate the resulting escape of planetary pick-up ions from the 5 «super-Earths» in the compact Kepler-11 system. We compare the escape rates with the efficiency of the thermal escape of neutral hydrogen atoms. Assuming the stellar wind of Kepler-11 is similar to the solar wind, we used a polytropic 1D hydrodynamic wind model to estimate the wind properties at the planetary orbits. We applied a Direct Simulation Monte Carlo Model to model the hydrogen coronae and the stellar wind plasma interaction around Kepler-11b-f planets within a realistic expected heating efficiency range of 15-40%. The same model was used to estimate the ion pick-up escape from the XUV heated and hydrodynamically extended upper atmospheres of Kepler-11b-f. Modeling clarifies the influence of possible magnetic moments on escape processes and allows to estimate the charge exchange and photoionization production rates of planetary ions as well as the loss rates of pick-up H+ ions for all five planets. This study presents also the comparison of the results between the five 'super-Earths' and in a more general sense also with the thermal escape rates of the neutral planetary hydrogen atoms. Our results show that for all Kepler-11b-f exoplanets, a huge neutral hydrogen corona is formed around the planet. The non-symmetric form of the corona changes from planet to planet and is defined mostly by radiation pressure, charge-exchange and gravitational effects. According to our estimates, nonthermal escape rates of pick-up ionized hydrogen atoms for Kepler-11 «super-Earths» vary between ~ 6.4 × 1030 s-1 and ~ 4.1 × 1031 s-1 depending on the planet's orbital location and assumed heating efficiency. These values correspond to non-thermal mass loss rates of ~ 1.07 × 107 g·s-1 and ~ 6.8 × 107 g·s-1 respectively, which is a few percent of the thermal

  15. Bond-length distributions for ions bonded to oxygen: alkali and alkaline-earth metals

    PubMed Central

    Gagné, Olivier Charles; Hawthorne, Frank Christopher

    2016-01-01

    Bond-length distributions have been examined for 55 configurations of alkali-metal ions and 29 configurations of alkaline-earth-metal ions bonded to oxygen, for 4859 coordination polyhedra and 38 594 bond distances (alkali metals), and for 3038 coordination polyhedra and 24 487 bond distances (alkaline-earth metals). Bond lengths generally show a positively skewed Gaussian distribution that originates from the variation in Born repulsion and Coulomb attraction as a function of interatomic distance. The skewness and kurtosis of these distributions generally decrease with increasing coordination number of the central cation, a result of decreasing Born repulsion with increasing coordination number. We confirm the following minimum coordination numbers: [3]Li+, [3]Na+, [4]K+, [4]Rb+, [6]Cs+, [3]Be2+, [4]Mg2+, [6]Ca2+, [6]Sr2+ and [6]Ba2+, but note that some reported examples are the result of extensive dynamic and/or positional short-range disorder and are not ordered arrangements. Some distributions of bond lengths are distinctly multi-modal. This is commonly due to the occurrence of large numbers of structure refinements of a particular structure type in which a particular cation is always present, leading to an over-representation of a specific range of bond lengths. Outliers in the distributions of mean bond lengths are often associated with anomalous values of atomic displacement of the constituent cations and/or anions. For a sample of [6]Na+, the ratio U eq(Na)/U eq(bonded anions) is partially correlated with 〈[6]Na+—O2−〉 (R 2 = 0.57), suggesting that the mean bond length is correlated with vibrational/displacement characteristics of the constituent ions for a fixed coordination number. Mean bond lengths also show a weak correlation with bond-length distortion from the mean value in general, although some coordination numbers show the widest variation in mean bond length for zero distortion, e.g. Li+ in [4]- and [6]-coordination, Na+ in [4]- and [6

  16. Bond-length distributions for ions bonded to oxygen: alkali and alkaline-earth metals.

    PubMed

    Gagné, Olivier Charles; Hawthorne, Frank Christopher

    2016-08-01

    Bond-length distributions have been examined for 55 configurations of alkali-metal ions and 29 configurations of alkaline-earth-metal ions bonded to oxygen, for 4859 coordination polyhedra and 38 594 bond distances (alkali metals), and for 3038 coordination polyhedra and 24 487 bond distances (alkaline-earth metals). Bond lengths generally show a positively skewed Gaussian distribution that originates from the variation in Born repulsion and Coulomb attraction as a function of interatomic distance. The skewness and kurtosis of these distributions generally decrease with increasing coordination number of the central cation, a result of decreasing Born repulsion with increasing coordination number. We confirm the following minimum coordination numbers: ([3])Li(+), ([3])Na(+), ([4])K(+), ([4])Rb(+), ([6])Cs(+), ([3])Be(2+), ([4])Mg(2+), ([6])Ca(2+), ([6])Sr(2+) and ([6])Ba(2+), but note that some reported examples are the result of extensive dynamic and/or positional short-range disorder and are not ordered arrangements. Some distributions of bond lengths are distinctly multi-modal. This is commonly due to the occurrence of large numbers of structure refinements of a particular structure type in which a particular cation is always present, leading to an over-representation of a specific range of bond lengths. Outliers in the distributions of mean bond lengths are often associated with anomalous values of atomic displacement of the constituent cations and/or anions. For a sample of ([6])Na(+), the ratio Ueq(Na)/Ueq(bonded anions) is partially correlated with 〈([6])Na(+)-O(2-)〉 (R(2) = 0.57), suggesting that the mean bond length is correlated with vibrational/displacement characteristics of the constituent ions for a fixed coordination number. Mean bond lengths also show a weak correlation with bond-length distortion from the mean value in general, although some coordination numbers show the widest variation in mean bond length for zero distortion, e.g. Li(+) in

  17. A simple model for multi-ion permeation. Single-vacancy conduction in a simple pore model.

    PubMed Central

    Schumaker, M F; MacKinnon, R

    1990-01-01

    Recent experimental evidence suggests that certain membrane channels operate in a nearly ion-saturated state. We therefore consider a "single-vacancy" model of ion permeation: if a channel has n conducting sites, it will contain either n or n-1 ions. Simple analytical expressions for the current, conductance, and reversal potential under bi-ionic conditions are derived. The results are compared with those of single ion models and recent experiments on Ca2(+)-activated K+ channels. PMID:1701102

  18. Ion Acceleration at Earth, Saturn and Jupiter and its Global Impact on Magnetospheric Structure

    NASA Astrophysics Data System (ADS)

    Brandt, Pontus

    2016-07-01

    The ion plasma pressures at Earth, Saturn and Jupiter are significant players in the electrodynamic force-balance that governs the structure and dynamics of these magnetospheres. There are many similarities between the physical mechanisms that are thought to heat the ion plasma to temperatures that even exceed those of the solar corona. In this presentation we compare the ion acceleration mechanisms at the three planetary magnetospheres and discuss their global impacts on magnetopsheric structure. At Earth, bursty-bulk flows, or "bubbles", have been shown to accelerate protons and O+ to high energies by the earthward moving magnetic dipolarization fronts. O+ ions display a more non-adiabatic energization in response to these fronts than protons do as they are energized and transported in to the ring-current region where they reach energies of several 100's keV. We present both in-situ measurements from the NASA Van Allen Probes Mission and global Energetic Neutral (ENA) images from the High-Energy Neutral Atom (HENA) Camera on board the IMAGE Mission, that illustrate these processes. The global impact on the magnetospheric structure is explored by comparing the empirical magnetic field model TS07d for given driving conditions with global plasma pressure distributions derived from the HENA images. At Saturn, quasi-periodic energization events, or large-scale injections, occur beyond about 9 RS around the post-midnight sector, clearly shown by the Ion and Neutral Atom Camera (INCA) on board the Cassini mission. In contrast to Earth, the corotational drift dominates even the energetic ion distributions. The large-scale injections display similar dipolarization front features can be found and there are indications that like at Earth the O+ responds more non-adiabatically than protons do. However, at Saturn there are also differences in that there appears to be energization events deep in the inner magnetosphere (6-9 RS) preferentially occurring in the pre

  19. Synthesis of rock-salt type lithium borohydride and its peculiar Li+ ion conduction properties

    NASA Astrophysics Data System (ADS)

    Miyazaki, R.; Maekawa, H.; Takamura, H.

    2014-05-01

    The high energy density and excellent cycle performance of lithium ion batteries makes them superior to all other secondary batteries and explains why they are widely used in portable devices. However, because organic liquid electrolytes have a higher operating voltage than aqueous solution, they are used in lithium ion batteries. This comes with the risk of fire due to their flammability. Solid electrolytes are being investigated to find an alternative to organic liquid. However, the nature of the solid-solid point contact at the interface between the electrolyte and electrode or between the electrolyte grains is such that high power density has proven difficult to attain. We develop a new method for the fabrication of a solid electrolyte using LiBH4, known for its super Li+ ion conduction without any grain boundary contribution. The modifications to the conduction pathway achieved by stabilizing the high pressure form of this material provided a new structure with some LiBH4, more suitable to the high rate condition. We synthesized the H.P. form of LiBH4 under ambient pressure by doping LiBH4 with the KI lattice by sintering. The formation of a KI - LiBH4 solid solution was confirmed both macroscopically and microscopically. The obtained sample was shown to be a pure Li+ conductor despite its small Li+ content. This conduction mechanism, where the light doping cation played a major role in ion conduction, was termed the "Parasitic Conduction Mechanism." This mechanism made it possible to synthesize a new ion conductor and is expected to have enormous potential in the search for new battery materials.

  20. Ionic Conduction in Lithium Ion Battery Composite Electrode Governs Cross-sectional Reaction Distribution

    PubMed Central

    Orikasa, Yuki; Gogyo, Yuma; Yamashige, Hisao; Katayama, Misaki; Chen, Kezheng; Mori, Takuya; Yamamoto, Kentaro; Masese, Titus; Inada, Yasuhiro; Ohta, Toshiaki; Siroma, Zyun; Kato, Shiro; Kinoshita, Hajime; Arai, Hajime; Ogumi, Zempachi; Uchimoto, Yoshiharu

    2016-01-01

    Composite electrodes containing active materials, carbon and binder are widely used in lithium-ion batteries. Since the electrode reaction occurs preferentially in regions with lower resistance, reaction distribution can be happened within composite electrodes. We investigate the relationship between the reaction distribution with depth direction and electronic/ionic conductivity in composite electrodes with changing electrode porosities. Two dimensional X-ray absorption spectroscopy shows that the reaction distribution is happened in lower porosity electrodes. Our developed 6-probe method can measure electronic/ionic conductivity in composite electrodes. The ionic conductivity is decreased for lower porosity electrodes, which governs the reaction distribution of composite electrodes and their performances. PMID:27193448

  1. Ionic Conduction in Lithium Ion Battery Composite Electrode Governs Cross-sectional Reaction Distribution

    NASA Astrophysics Data System (ADS)

    Orikasa, Yuki; Gogyo, Yuma; Yamashige, Hisao; Katayama, Misaki; Chen, Kezheng; Mori, Takuya; Yamamoto, Kentaro; Masese, Titus; Inada, Yasuhiro; Ohta, Toshiaki; Siroma, Zyun; Kato, Shiro; Kinoshita, Hajime; Arai, Hajime; Ogumi, Zempachi; Uchimoto, Yoshiharu

    2016-05-01

    Composite electrodes containing active materials, carbon and binder are widely used in lithium-ion batteries. Since the electrode reaction occurs preferentially in regions with lower resistance, reaction distribution can be happened within composite electrodes. We investigate the relationship between the reaction distribution with depth direction and electronic/ionic conductivity in composite electrodes with changing electrode porosities. Two dimensional X-ray absorption spectroscopy shows that the reaction distribution is happened in lower porosity electrodes. Our developed 6-probe method can measure electronic/ionic conductivity in composite electrodes. The ionic conductivity is decreased for lower porosity electrodes, which governs the reaction distribution of composite electrodes and their performances.

  2. Ionic Conduction in Lithium Ion Battery Composite Electrode Governs Cross-sectional Reaction Distribution.

    PubMed

    Orikasa, Yuki; Gogyo, Yuma; Yamashige, Hisao; Katayama, Misaki; Chen, Kezheng; Mori, Takuya; Yamamoto, Kentaro; Masese, Titus; Inada, Yasuhiro; Ohta, Toshiaki; Siroma, Zyun; Kato, Shiro; Kinoshita, Hajime; Arai, Hajime; Ogumi, Zempachi; Uchimoto, Yoshiharu

    2016-01-01

    Composite electrodes containing active materials, carbon and binder are widely used in lithium-ion batteries. Since the electrode reaction occurs preferentially in regions with lower resistance, reaction distribution can be happened within composite electrodes. We investigate the relationship between the reaction distribution with depth direction and electronic/ionic conductivity in composite electrodes with changing electrode porosities. Two dimensional X-ray absorption spectroscopy shows that the reaction distribution is happened in lower porosity electrodes. Our developed 6-probe method can measure electronic/ionic conductivity in composite electrodes. The ionic conductivity is decreased for lower porosity electrodes, which governs the reaction distribution of composite electrodes and their performances. PMID:27193448

  3. Molecular Dynamics Simulation of the Antiamoebin Ion Channel: Linking Structure and Conductance

    PubMed Central

    Wilson, Michael A.; Wei, Chenyu; Bjelkmar, Pär; Wallace, B.A.; Pohorille, Andrew

    2011-01-01

    Molecular-dynamics simulations were carried out to ascertain which of the potential multimeric forms of the transmembrane peptaibol channel, antiamoebin, is consistent with its measured conductance. Estimates of the conductance obtained through counting ions that cross the channel and by solving the Nernst-Planck equation yield consistent results, indicating that the motion of ions inside the channel can be satisfactorily described as diffusive. The calculated conductance of octameric channels is markedly higher than the conductance measured in single channel recordings, whereas the tetramer appears to be nonconducting. The conductance of the hexamer was estimated to be 115 ± 34 pS and 74 ± 20 pS, at 150 mV and 75 mV, respectively, in satisfactory agreement with the value of 90 pS measured at 75 mV. On this basis, we propose that the antiamoebin channel consists of six monomers. Its pore is large enough to accommodate K+ and Cl− with their first solvation shells intact. The free energy barrier encountered by K+ is only 2.2 kcal/mol whereas Cl− encounters a substantially higher barrier of nearly 5 kcal/mol. This difference makes the channel selective for cations. Ion crossing events are shown to be uncorrelated and follow Poisson statistics. PMID:21575573

  4. Toward a System-Based Approach to Electromagnetic Ion Cyclotron Waves in Earth's Magnetosphere

    NASA Astrophysics Data System (ADS)

    Gamayunov, K. V.; Engebretson, M. J.; Rassoul, H.

    2015-12-01

    We consider a nonlinear wave energy cascade from the low frequency range into the higher frequency domain of electromagnetic ion cyclotron (EMIC) wave generation as a possible source of seed fluctuations for EMIC wave growth due to the ion cyclotron instability in Earth's magnetosphere. The theoretical analysis shows that energy cascade from the Pc 4-5 frequency range (2-22 mHz) into the range of Pc 1-2 pulsations (0.1-5 Hz) is able to supply the level of seed fluctuations that guarantees growth of EMIC waves up to an observable level during one pass through the near equatorial region where the ion cyclotron instability takes place. We also analyze magnetic field data from the Polar and Van Allen Probes spacecraft to test this nonlinear mechanism. We restrict our analysis to magnetic spectra only. We do not analyze the third-order moment for total energy of the magnetic and velocity fluctuations, but judge whether a nonlinear energy cascade is present or whether it is not by only analyzing the appearance of power-law distributions in the low frequency part of the magnetic field spectra. While the power-law spectrum alone does not guarantee that a nonlinear cascade is present, the power-law distribution is a strong indication of the possible development of a nonlinear cascade. Our data analysis shows that a nonlinear energy cascade is indeed observed in both the outer and inner magnetosphere, and EMIC waves are growing from this nonthermal background. All the analyzed data are in good agreement with the theoretical model presented in this study. Overall, the results of this study support a nonlinear energy cascade in Earth's magnetosphere as a mechanism which is responsible for supplying seed fluctuating energy in the higher frequency domain where EMIC waves grow due to the ion cyclotron instability. Keywords: nonlinear energy cascade, ultra low frequency waves, electromagnetic ion cyclotron waves, seed fluctuationsAcknowledgments: This paper is based upon work

  5. Use of contactless conductivity detection for non-invasive characterisation of monolithic stationary-phase coatings for application in capillary ion chromatography.

    PubMed

    Gillespie, Eoin; Connolly, Damian; Macka, Miroslav; Nesterenko, Pavel N; Paull, Brett

    2007-12-01

    A capacitively-coupled contactless conductivity detector (C4D) has been utilised as an on-capillary detector within a capillary ion chromatograph, incorporating a reversed-phase monolithic silica capillary column semi-permanently modified with a suitable ionic surfactant. The monolithic capillary column (150 x 0.1 mm i.d.) was modified using sodium dioctyl sulfosuccinate (DOSS), an anionic surfactant, for the separation of small inorganic and organic cations. With the use of the on-capillary conductivity detector, the longitudinal homogeneity and temporal stability of the coating were investigated. The approach allowed a detailed non-invasive observation of the nature of the ion-exchange coating over time, and an example of an application of the technique to produce a longitudinal stationary-phase charge gradient is shown. An investigation of the basis of the measured on-capillary conductivity was carried out with a counter ion study, clearly showing the on-capillary detection technique could also distinguish between chemical forms of the immobilised ion exchanger. The above method was used to produce a stable and homogeneously-modified monolithic ion-exchange capillary column, for application to the separation of inorganic alkaline earth cations and amino acids. PMID:18318285

  6. Discovery of ions with nuclear charge Z greater than or equal to 9 stability trapped in the earth's radiation belts

    NASA Technical Reports Server (NTRS)

    Spjeldvik, W. N.; Fritz, T. A.

    1981-01-01

    Observations of MeV heavy ions obtained by Explorer 45 in an equatorial earth orbit during a 7 month period in 1972 are presented, including data from four major magnetic storms. The spacecraft contained a heavy ion detector telescope and heavy ion discriminator electronics. Heavy ions were distinguished from protons and electrons, and He ions and ions heavier than F were recorded on separate data channels. The L equals 2.25 to L equals 4 zones were probed, and it was found that the relative enhancement in heavy ion fluxes in the radiation belts over the prestorm ion flux intensities tends to increase with increasing ion mass and/or increasing ion energy in the MeV range. The radial profiles of ions with nucleon number greater than nine peak at L equals 2.9, and MeV ions in this class decay on time scales from 23 days at L equals 3.25 to 55 days at L equals 2.25. Indirect evidence indicated a solar source for the very heavy ions in the magnetosphere.

  7. Sol-gel derived hybrid materials doped with rare earth metal ions

    NASA Astrophysics Data System (ADS)

    Zelazowska, E.; Rysiakiewicz-Pasek, E.; Borczuch-Laczka, M.; Cholewa-Kowalska, K.

    2011-10-01

    Sol-gel derived organic-inorganic hybrid materials doped with rare earth metal ions (Pr 3+) and small amounts of lithium ions (˜0.1-0.2 wt.%) were produced from the tetraethyl orthosilicate (TEOS), AlCl 3·6H 2O (about 10 mol%), ethyl methacrylate, butyl methacrylate and some other organic additions (ca. 35-40 wt.% of organics in the fresh gels) to obtain hybrid organic-inorganic hosts. The gel and hybrid materials obtained were aged at room temperature for three weeks, then heated in an electric drier for 3 h at temperature of 125 °C and investigated for morphology, structure and luminescence properties by X-ray diffraction (XRD), scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM/EDS), Fourier transform infrared spectroscopy (FTIR), 29Si and 27Al MAS nuclear magnetic resonance and fluorescence spectroscopy. An influence of the organic additions and inorganic dopants on microstructure of the materials obtained and their luminescence properties has been examined. Under excitation with UV radiation in a range of ˜210-350 nm, the sharp and relatively intense luminescence emission lines due to 3P 0 → 3H 4 (blue) and 3P 0 → 3F 3 (red) transitions of Pr 3+ ions were observed in the luminescence spectra of gel and hybrid materials of SA-series.

  8. Population gratings in saturable optical fibers with randomly oriented rare-earth ions

    NASA Astrophysics Data System (ADS)

    Stepanov, S.; Martinez, L. M.; Hernandez, E. H.; Agruzov, P.; Shamray, A.

    2015-07-01

    Formation of the dynamic population gratings in optical fibers with randomly oriented rare-earth ions is analyzed with a special interest to the grating component for readout with the orthogonal light polarization. It is shown that as compared with a simple model case of the collinearly oriented dipole-like centers their random orientation leads to approximately 2-times growth of the effective saturation power P sat when it is estimated from the incident power dependence of the fiber absorption or from that of the fluorescence intensity. An optimal incident power, for which the maximum of the dynamic population grating amplitude for collinear light polarization is observed, also follows this change in P sat, while formation of the grating for orthogonal polarization needs essentially higher light power. The reduced anisotropy of the active centers, which is in charge of the experimentally observed weakening of the polarization hole burning (PHB) and of the fluorescence polarization, compensates in some way the effect of random ion orientation. The ratio between the maximum conventional (i.e. for the interacting waves collinear polarizations) two-wave mixing (TWM) amplitude and the initial not saturable fiber optical density proves to be, however, nearly the same as in the model case of collinearly oriented dipoles. The ratio between the PHB effect and the amplitude of the anisotropic grating, which is responsible for TWM of the orthogonally polarized waves, is also not influenced significantly by the reduced anisotropy of ions.

  9. Ion Conduction and Polymer Dynamics of Poly(2-vinylpyridine) - Lithium Perchlorate Mixtures

    NASA Astrophysics Data System (ADS)

    Atorngitjawat, Pornpen; Runt, James

    2008-03-01

    Ion conduction and polymer dynamics of single phase mixtures of poly(2-vinylpyridine) (P2VPy) with 0.1 to 10 mol% lithium perchlorate (LiClO4) were investigated using broadband dielectric spectroscopy. Interpretation of the relaxation behavior was assisted by findings from wide-angle and small-angle X-ray scattering experiments, and other techniques. Five dielectric relaxations were observed: a local β process in the glassy state, a segmental relaxation, a slow segmental process, an ion-mode relaxation, and electrode polarization. The local P2VPy relaxation was strongly suppressed with increasing LiClO4 content arising from the formation of transient crosslinks, which lead to a subsequent decrease in the number of free pyridine groups, and/or a reduction in the local free volume in the presence of LiClO4. Ion conduction at low LiClO4 concentrations (< 10 mol%) is governed by the diffusion of anions through the matrix, which is strongly coupled with the segmental relaxation. At relatively high LiClO4 concentration (10 mol%), partial decoupling between ion motion and the segmental relaxation was observed, leading to increased conductivity.

  10. Bulk mixed ion electron conduction in amorphous gallium oxide causes memristive behaviour.

    PubMed

    Aoki, Yoshitaka; Wiemann, Carsten; Feyer, Vitaliy; Kim, Hong-Seok; Schneider, Claus Michael; Ill-Yoo, Han; Martin, Manfred

    2014-01-01

    In thin films of mixed ionic electronic conductors sandwiched by two ion-blocking electrodes, the homogeneous migration of ions and their polarization will modify the electronic carrier distribution across the conductor, thereby enabling homogeneous resistive switching. Here we report non-filamentary memristive switching based on the bulk oxide ion conductivity of amorphous GaOx (x~1.1) thin films. We directly observe reversible enrichment and depletion of oxygen ions at the blocking electrodes responding to the bias polarity by using photoemission and transmission electron microscopies, thus proving that oxygen ion mobility at room temperature causes memristive behaviour. The shape of the hysteresis I-V curves is tunable by the bias history, ranging from narrow counter figure-eight loops to wide hysteresis, triangle loops as found in the mathematically derived memristor model. This dynamical behaviour can be attributed to the coupled ion drift and diffusion motion and the oxygen concentration profile acting as a state function of the memristor. PMID:24632885

  11. Building non-tortuous ion-conduction pathways using self-assembled block copolymers

    NASA Astrophysics Data System (ADS)

    Kim, Onnuri; Park, Moon Jeong

    Ion-containing polymers with self-assembled morphologies are becoming important ingredients of a wide range of electrochemical devices such as lithium-ion batteries, fuel cells and electroactive actuators. Although several studies have reported the relationship between morphologies and ion transport properties of such polymers, the most of quantitative analysis have been limited to two-dimensional morphologies as they occupy a large window of the phase diagrams. In present study, we investigated the effects of morphology on the ion transport efficiency with a focus on three-dimensional symmetry. A range of three-dimensional self-assembled morphologies, i.e., ill-defined cubic, orthorhombic network (O70) , and face-centered cubic phases (fcc) were achieved for a single sulfonated block copolymer upon the addition of non-stoichiometric ionic liquids. The type of three-dimensional lattice was found out to play a crucial role in determining the ion transport properties of composite membranes, where the most efficient ion-conduction was demonstrated for fcc phases with lowest tortuosity of 1 over orthorhombic networks phases (tortuosity:1.5). This intriguing result suggests a new avenue to designing polymer electrolytes with improved transport properties.

  12. Negative oxygen ion formation in reactive magnetron sputtering processes for transparent conductive oxides

    SciTech Connect

    Welzel, Thomas; Ellmer, Klaus

    2012-11-15

    Reactive d.c. magnetron sputtering in Ar/O{sub 2} gas mixtures has been investigated with energy-resolved mass spectrometry. Different metal targets (Mg, Ti, Zn, In, InSn, and Sn), which are of importance for transparent conductive oxide thin film deposition, have been used to study the formation of negative ions, mainly high-energetic O{sup -}, which are supposed to induce radiation damage in thin films. Besides their energy distribution, the ions have been particularly investigated with respect to their intensity in comparison of the different target materials. To realize the comparability, various calibration factors had to be introduced. After their application, major differences in the negative ion production have been observed for the target materials. The intensity, especially of O{sup -}, differs by about two orders of magnitude. It is shown that this difference results almost exclusively from ions that gain their energy in the target sheath. Those may gain additional energy from the sputtering process or reflection at the target. Low-energetic negative ions are, however, less affected by changes of the target material. The results concerning O{sup -} formation are discussed in term of the sputtering rate from the target and are compared to models for negative ion formation.

  13. Bulk mixed ion electron conduction in amorphous gallium oxide causes memristive behaviour

    NASA Astrophysics Data System (ADS)

    Aoki, Yoshitaka; Wiemann, Carsten; Feyer, Vitaliy; Kim, Hong-Seok; Schneider, Claus Michael; Ill-Yoo, Han; Martin, Manfred

    2014-03-01

    In thin films of mixed ionic electronic conductors sandwiched by two ion-blocking electrodes, the homogeneous migration of ions and their polarization will modify the electronic carrier distribution across the conductor, thereby enabling homogeneous resistive switching. Here we report non-filamentary memristive switching based on the bulk oxide ion conductivity of amorphous GaOx (x~1.1) thin films. We directly observe reversible enrichment and depletion of oxygen ions at the blocking electrodes responding to the bias polarity by using photoemission and transmission electron microscopies, thus proving that oxygen ion mobility at room temperature causes memristive behaviour. The shape of the hysteresis I-V curves is tunable by the bias history, ranging from narrow counter figure-eight loops to wide hysteresis, triangle loops as found in the mathematically derived memristor model. This dynamical behaviour can be attributed to the coupled ion drift and diffusion motion and the oxygen concentration profile acting as a state function of the memristor.

  14. The Thermal Conductivity of the Earth's Lower Mantle and Implications for Heat Flow at the Core-Mantle Boundary

    NASA Astrophysics Data System (ADS)

    Rainey, Emma Sojourner Gage

    The thermal conductivity of the Earth's lowermost mantle controls the rate of heat flow across the core-mantle boundary, and is thus a critical parameter for determining the core and mantle thermal state and evolution. This parameter and its dependence on pressure, temperature, and composition are poorly known, in part due to the inherent difficulties in determining thermal conductivities at the high pressures and temperatures (135 GPa and 3800 K) that occur at the base of the mantle. In this dissertation I estimate the thermal conductivity of the lower mantle using measurements of the thermal conductivity of MgO and (Mg,Fe)SiO3 perovskite made at high pressure and high temperature in the laser-heated diamond anvil cell. Using three-dimensional heat flow modeling, I demonstrate that the steady-state temperature distributions that form during laser heating experiments in the diamond anvil cell depend on the sample thermal conductivity as well as the experimental geometry. Relative thermal conductivity can be determined by comparing measured temperature vs. laser power curves with a numerical model. I use this technique to determine the pressure-dependence of thermal conductivity of MgO and (Mg,Fe)SiO3 perovskite, and then I extrapolate absolute measurements of thermal conductivity taken near ambient pressure to lower mantle conditions. I also estimate the contribution of radiation to heat transfer in the lower mantle. My resulting value for the thermal conductivity of the lowermost mantle is approximately 6 W/m·K, lower than the commonly assumed value of 10 W/m·K. When combined with estimates for the lower mantle boundary layer temperature gradient, the total core-mantle boundary heat flow is roughly 7 TW. This heat flow implies a slow growth rate for the Earth's inner core.

  15. A mechanical nanogate based on a carbon nanotube for reversible control of ion conduction

    NASA Astrophysics Data System (ADS)

    He, Zhongjin; Corry, Ben; Lu, Xiaohua; Zhou, Jian

    2014-03-01

    Control of mass transport through nanochannels is of critical importance in many nanoscale devices and nanofiltration membranes. The gates in biological channels, which control the transport of substances across cell membranes, can provide inspiration for this purpose. Gates in many biological channels are formed by a constriction ringed with hydrophobic residues which can prevent ion conduction even when they are not completely physically occluded. In this work, we use molecular dynamics simulations to design a nanogate inspired by this hydrophobic gating mechanism. Deforming a carbon nanotube (12,12) with an external force can form a hydrophobic constriction in the centre of the tube that controls ion conduction. The simulation results show that increasing the magnitude of the applied force narrows the constriction and lowers the fluxes of K+ and Cl- found under an electric field. With the exerted force larger than 5 nN, the constriction blocks the conduction of K+ and Cl- due to partial dehydration while allowing for a noticeable water flux. Ion conduction can revert back to the unperturbed level upon force retraction, suggesting the reversibility of the nanogate. The force can be exerted by available experimental facilities, such as atomic force microscope (AFM) tips. It is found that partial dehydration in a continuous water-filled hydrophobic constriction is enough to close the channel, while full dewetting is not necessarily required. This mechanically deformed nanogate has many potential applications, such as a valve in nanofluidic systems to reversibly control ion conduction and a high-performance nanomachine for desalination and water treatment.Control of mass transport through nanochannels is of critical importance in many nanoscale devices and nanofiltration membranes. The gates in biological channels, which control the transport of substances across cell membranes, can provide inspiration for this purpose. Gates in many biological channels are formed

  16. A mechanical nanogate based on a carbon nanotube for reversible control of ion conduction.

    PubMed

    He, Zhongjin; Corry, Ben; Lu, Xiaohua; Zhou, Jian

    2014-04-01

    Control of mass transport through nanochannels is of critical importance in many nanoscale devices and nanofiltration membranes. The gates in biological channels, which control the transport of substances across cell membranes, can provide inspiration for this purpose. Gates in many biological channels are formed by a constriction ringed with hydrophobic residues which can prevent ion conduction even when they are not completely physically occluded. In this work, we use molecular dynamics simulations to design a nanogate inspired by this hydrophobic gating mechanism. Deforming a carbon nanotube (12,12) with an external force can form a hydrophobic constriction in the centre of the tube that controls ion conduction. The simulation results show that increasing the magnitude of the applied force narrows the constriction and lowers the fluxes of K(+) and Cl(-) found under an electric field. With the exerted force larger than 5 nN, the constriction blocks the conduction of K(+) and Cl(-) due to partial dehydration while allowing for a noticeable water flux. Ion conduction can revert back to the unperturbed level upon force retraction, suggesting the reversibility of the nanogate. The force can be exerted by available experimental facilities, such as atomic force microscope (AFM) tips. It is found that partial dehydration in a continuous water-filled hydrophobic constriction is enough to close the channel, while full dewetting is not necessarily required. This mechanically deformed nanogate has many potential applications, such as a valve in nanofluidic systems to reversibly control ion conduction and a high-performance nanomachine for desalination and water treatment. PMID:24566473

  17. Radiative properties of few F- and Cl- like alkali and alkaline-earth metal ions

    NASA Astrophysics Data System (ADS)

    Nandy, D. K.; Singh, Sukhjit; Sahoo, B. K.

    2015-09-01

    We present high-accuracy calculations of radiative properties such as oscillator strengths and transition probabilities, of the allowed ns 2S1/2 → np 2P1/2, 3/2 transitions and of the forbidden np 2P1/2 → np 2P3/2 transitions in the F- and Cl-like alkali and alkaline-earth ions with the ground state principal quantum number n of the respective ion. For this purpose, we have employed the Dirac-Fock, relativistic second-order many-body perturbation theory and an all-order perturbative relativistic method in the coupled-cluster (CC) theory framework. To test the validity of these methods for giving accurate results, we first evaluated the ionization potentials in the creation processes of these ions and compare them with their experimental values listed in the National Institute of Science and Technology data base. Moreover, both the allowed and forbidden transition amplitudes are estimated using the above three methods and a comparative analysis is made to follow-up the electron correlation trends in order to demonstrate the need of using a sophisticated method like the CC theory for their precise determination. For astrophysical use, we provide the most precise values of the transition properties by combining the experimental energies, which suppresses uncertainties from the calculated energies, using the transition amplitudes from the CC method. These data will be useful in the abundance analysis of the considered ions in the astronomical objects and for the diagnostic processes of astrophysical plasmas.

  18. Electrolytic method to make alkali alcoholates using ion conducting alkali electrolyte/separator

    DOEpatents

    Joshi, Ashok V.; Balagopal, Shekar; Pendelton, Justin

    2011-12-13

    Alkali alcoholates, also called alkali alkoxides, are produced from alkali metal salt solutions and alcohol using a three-compartment electrolytic cell. The electrolytic cell includes an anolyte compartment configured with an anode, a buffer compartment, and a catholyte compartment configured with a cathode. An alkali ion conducting solid electrolyte configured to selectively transport alkali ions is positioned between the anolyte compartment and the buffer compartment. An alkali ion permeable separator is positioned between the buffer compartment and the catholyte compartment. The catholyte solution may include an alkali alcoholate and alcohol. The anolyte solution may include at least one alkali salt. The buffer compartment solution may include a soluble alkali salt and an alkali alcoholate in alcohol.

  19. Cross sections for deeply inelastic transfer reactions induced by heavy ions in rare-earth targets

    NASA Astrophysics Data System (ADS)

    Rivet, M. F.; Bimbot, R.; Gardès, D.; Fleury, A.; Hubert, F.; Llabador, Y.

    1982-04-01

    Cross sections have been measured for deeply inelastic transfer reactions leading to the production of several radio-nuclides. Rare-earth targets were used and the projectiles were Ar, Cr, Fe and Cu ions. The reactions studied corresponded to transfers of two to nine protons and variable numbers of neutrons. The results obtained were used to study the evolution of some characteristics of these reactions, such as integrated cross sections and widths of the isotopic distributions, versus incident mass and transferred mass. These results confirm that mass transfer is driven by the potential energy of the composite system. The decrease of cross sections for increasing charge transfer may be quantitatively explained by assuming thermodynamical equilibrium of the mass asymmetry degree of freedom.

  20. On atmospheric loss of oxygen ions from earth through magnetospheric processes.

    PubMed

    Seki, K; Elphic, R C; Hirahara, M; Terasawa, T; Mukai, T

    2001-03-01

    In Earth's environment, the observed polar outflow rate for O(+) ions, the main source of oxygen above gravitational escape energy, corresponds to the loss of approximately 18% of the present-day atmospheric oxygen over 3 billion years. However, part of this apparent loss can actually be returned to the atmosphere. Examining loss rates of four escape routes with high-altitude spacecraft observations, we show that the total oxygen loss rate inferred from current knowledge is about one order of magnitude smaller than the polar O(+) outflow rate. This disagreement suggests that there may be a substantial return flux from the magnetosphere to the low-latitude ionosphere. Then the net oxygen loss over 3 billion years drops to approximately 2% of the current atmospheric oxygen content. PMID:11239148

  1. Influence of rare earth ions on microstructural and optical properties of ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Riyajuddin, Sk.; Naseem, Swaleha; Khan, Wasi; Ahmad, Shabbir; Faizan, M.; Naqvi, A. H.

    2016-05-01

    Pure and 3% rare earth ions (Nd3+ & Gd3+) doped ZnO samples were synthesized by sol-gel method, followed by annealing at temperature 450°C for 2hr. The samples were characterized by XRD, FTIR and UV-visible spectroscopy. XRD result confirmed single phase nature of all samples with crystalline structure. The average crystallite size of the doped samples found to be decreases as caculated using Debye-Scherrer's formula. FTIR spectra indicate absorption band centered at 464 cm-1 which is attributed to Zn-O lattice vibration. It confirms the formaton of compounds. UV-visible spectroscopy was used to study the optical properties and band gap of the synthesised materials using Tauc's relation.

  2. Birefringence and polarization rotator induced by electromagnetically induced transparency in rare earth ion-doped crystals

    NASA Astrophysics Data System (ADS)

    Li, Zhixiang; Liu, Jianji; Yu, Ping; Zhang, Guoquan

    2016-05-01

    The birefringence induced by the electromagnetically induced transparency effect in a {Pr}^{3+}:{Y}_2 {SiO}_5 crystal was studied by using a balanced polarimeter technique. The results show that it is possible to control the polarization state of the output probe beam by adjusting the experimental conditions. Particularly, the coherently prepared {Pr}^{3+}:{Y}_2 {SiO}_5 crystal can serve as a polarization rotator for a linearly polarized input probe beam at the two-photon resonant condition. Such coherent control on the polarization of light should be useful for polarization-based classical and quantum information processing such as all-optical switching, polarization preserving light pulse memory and polarization qubits based on rare earth ion-doped solids.

  3. Modification of phonon processes in nanostructured rare-earth-ion-doped crystals

    NASA Astrophysics Data System (ADS)

    Lutz, Thomas; Veissier, Lucile; Thiel, Charles W.; Cone, Rufus L.; Barclay, Paul E.; Tittel, Wolfgang

    2016-07-01

    Nano-structuring impurity-doped crystals affects the phonon density of states and thereby modifies the atomic dynamics induced by interaction with phonons. We propose the use of nano-structured materials in the form of powders or phononic bandgap crystals to enable or improve persistent spectral hole burning and coherence for inhomogeneously broadened absorption lines in rare-earth-ion-doped crystals. This is crucial for applications such as ultra-precise radio-frequency spectrum analyzers and optical quantum memories. As an example, we discuss how phonon engineering can enable spectral hole burning in erbium-doped materials operating in the convenient telecommunication band and present simulations for density of states of nano-sized powders and phononic crystals for the case of Y2SiO5 , a widely used material in current quantum memory research.

  4. [Improvement of anti-stokes energy transfer between rare earth ions--2. Numerical calculation and analysis].

    PubMed

    Chen, Xiao-bo; Wang, Ce; Kang, Dong-guo; Sawanobori, Naruhito; Wang, Shui-feng; Li, Yong-liang; Wang, Ping

    2010-08-01

    The dynamics of all levels were calculated numerically in the present article for Er(0.5)Yb(3):FOV oxyfluoride nanophase vitroceramics. The population dynamical processes were analyzed carefully. It was found for the first time that traditional phonon-assisted energy transfer theory of rare earth ion energy transfer can not well explain the observed experimental calibrated results, as it does not take into account the difference between Stokes and anti-Stokes process. A coefficient, the improved factor of the intensity ratio of Stokes to anti-Stokes process in quantum Raman theory compared to classical Raman theory, was introduced for the first time to successfully describe the anti-Stokes energy transfer. The theoretical improvement results are coincident with experiments very well. This improvement is very significant and indispensable when the photonics of nanomaterials is probed. PMID:20939297

  5. Formation and dynamics of "waterproof" photoluminescent complexes of rare earth ions in crowded environment.

    PubMed

    Ignatova, Tetyana; Blades, Michael; Duque, Juan G; Doorn, Stephen K; Biaggio, Ivan; Rotkin, Slava V

    2014-12-28

    Understanding behavior of rare-earth ions (REI) in crowded environments is crucial for several nano- and bio-technological applications. Evolution of REI photoluminescence (PL) in small compartments inside a silica hydrogel, mimic to a soft matter bio-environment, has been studied and explained within a solvation model. The model uncovered the origin of high PL efficiency to be the formation of REI complexes, surrounded by bile salt (DOC) molecules. Comparative study of these REI-DOC complexes in bulk water solution and those enclosed inside the hydrogel revealed a strong correlation between an up to 5×-longer lifetime of REIs and appearance of the DOC ordered phase, further confirmed by dynamics of REI solvation shells, REI diffusion experiments and morphological characterization of microstructure of the hydrogel. PMID:25379879

  6. Coherent phase control of resonance-mediated two-photon absorption in rare-earth ions

    SciTech Connect

    Zhang, Shian Lu, Chenhui; Jia, Tianqing; Sun, Zhenrong; Qiu, Jianrong

    2013-11-04

    We theoretically and experimentally demonstrate the quantum coherent control of the resonance-mediated two-photon absorption in rare-earth ions by the phase-shaped femtosecond laser pulse. Our theoretical results show that the resonance-mediated two-photon absorption can be effectively controlled, but the control efficiency depends on the laser repetition rate in real experiment due to the long lifetime and the short decoherence time of the excited state, and the larger laser repetition rate yields the lower control efficiency. These theoretical results are experimentally confirmed in glass sample doped with Er{sup 3+} by utilizing the femtosecond lasers with low repetition rate of 1 kHz and high repetition rate of 80 MHz.

  7. Improving the intensity and efficiency of compressed echo in rare-earth-ion-doped crystal

    NASA Astrophysics Data System (ADS)

    Xiu-Rong, Ma; Yu-Qing, Liang; Song, Wang; Shuang-Gen, Zhang; Yun-Long, Shan

    2016-07-01

    We investigate the intensity and efficiency of a compressed echo, which is important in arbitrary waveform generation (AWG). A new model of compressed echo is proposed based on the optical Bloch equations, which exposes much more detailed parameters than the conventional model, such as the time delay of the chirp lasers, the nature of the rare-earth-ion-doped crystal, etc. According to the novel model of compressed echo, we find that reducing the time delay of the chirp lasers and scanning the lasers around the center frequency of the inhomogeneously broadened spectrum, while utilizing a crystal with larger coherence time and excitation lifetime can improve the compressed echo’s intensity and efficiency. The theoretical analysis is validated by numerical simulations. Project supported by Special Funds for Scientific and Technological Innovation Projects in Tianjin, China (Grant No. 10FDZDGX00400) and the Tianjin Research Program of Application Foundation and Advanced Technology, China (Grant No. 15JCQNJC01100).

  8. Combining molecular dynamics and an electrodiffusion model to calculate ion channel conductance.

    PubMed

    Wilson, Michael A; Nguyen, Thuy Hien; Pohorille, Andrew

    2014-12-14

    Establishing the relation between the structures and functions of protein ion channels, which are protein assemblies that facilitate transmembrane ion transport through water-filled pores, is at the forefront of biological and medical sciences. A reliable way to determine whether our understanding of this relation is satisfactory is to reproduce the measured ionic conductance over a broad range of applied voltages. This can be done in molecular dynamics simulations by way of applying an external electric field to the system and counting the number of ions that traverse the channel per unit time. Since this approach is computationally very expensive we develop a markedly more efficient alternative in which molecular dynamics is combined with an electrodiffusion equation. This alternative approach applies if steady-state ion transport through channels can be described with sufficient accuracy by the one-dimensional diffusion equation in the potential given by the free energy profile and applied voltage. The theory refers only to line densities of ions in the channel and, therefore, avoids ambiguities related to determining the surface area of the channel near its endpoints or other procedures connecting the line and bulk ion densities. We apply the theory to a simple, model system based on the trichotoxin channel. We test the assumptions of the electrodiffusion equation, and determine the precision and consistency of the calculated conductance. We demonstrate that it is possible to calculate current/voltage dependence and accurately reconstruct the underlying (equilibrium) free energy profile, all from molecular dynamics simulations at a single voltage. The approach developed here applies to other channels that satisfy the conditions of the electrodiffusion equation. PMID:25494790

  9. Combining molecular dynamics and an electrodiffusion model to calculate ion channel conductance

    NASA Astrophysics Data System (ADS)

    Wilson, Michael A.; Nguyen, Thuy Hien; Pohorille, Andrew

    2014-12-01

    Establishing the relation between the structures and functions of protein ion channels, which are protein assemblies that facilitate transmembrane ion transport through water-filled pores, is at the forefront of biological and medical sciences. A reliable way to determine whether our understanding of this relation is satisfactory is to reproduce the measured ionic conductance over a broad range of applied voltages. This can be done in molecular dynamics simulations by way of applying an external electric field to the system and counting the number of ions that traverse the channel per unit time. Since this approach is computationally very expensive we develop a markedly more efficient alternative in which molecular dynamics is combined with an electrodiffusion equation. This alternative approach applies if steady-state ion transport through channels can be described with sufficient accuracy by the one-dimensional diffusion equation in the potential given by the free energy profile and applied voltage. The theory refers only to line densities of ions in the channel and, therefore, avoids ambiguities related to determining the surface area of the channel near its endpoints or other procedures connecting the line and bulk ion densities. We apply the theory to a simple, model system based on the trichotoxin channel. We test the assumptions of the electrodiffusion equation, and determine the precision and consistency of the calculated conductance. We demonstrate that it is possible to calculate current/voltage dependence and accurately reconstruct the underlying (equilibrium) free energy profile, all from molecular dynamics simulations at a single voltage. The approach developed here applies to other channels that satisfy the conditions of the electrodiffusion equation.

  10. Single Lithium-Ion Conducting Polymer Electrolytes Based on a Super-Delocalized Polyanion.

    PubMed

    Ma, Qiang; Zhang, Heng; Zhou, Chongwang; Zheng, Liping; Cheng, Pengfei; Nie, Jin; Feng, Wenfang; Hu, Yong-Sheng; Li, Hong; Huang, Xuejie; Chen, Liquan; Armand, Michel; Zhou, Zhibin

    2016-02-12

    A novel single lithium-ion (Li-ion) conducting polymer electrolyte is presented that is composed of the lithium salt of a polyanion, poly[(4-styrenesulfonyl)(trifluoromethyl(S-trifluoromethylsulfonylimino)sulfonyl)imide] (PSsTFSI(-)), and high-molecular-weight poly(ethylene oxide) (PEO). The neat LiPSsTFSI ionomer displays a low glass-transition temperature (44.3 °C; that is, strongly plasticizing effect). The complex of LiPSsTFSI/PEO exhibits a high Li-ion transference number (tLi (+) =0.91) and is thermally stable up to 300 °C. Meanwhile, it exhibits a Li-ion conductivity as high as 1.35×10(-4)  S cm(-1) at 90 °C, which is comparable to that for the classic ambipolar LiTFSI/PEO SPEs at the same temperature. These outstanding properties of the LiPSsTFSI/PEO blended polymer electrolyte would make it promising as solid polymer electrolytes for Li batteries. PMID:26840215

  11. Electrically conductive polyimide film containing gold (III) ions, composition, and process of making

    NASA Technical Reports Server (NTRS)

    Caplan, Maggie L. (Inventor); Stoakley, Diane M. (Inventor); St. Clair, Anne K. (Inventor)

    1996-01-01

    An electrically conductive, thermooxidatively stable poltimide, especially a film thereof, is prepared from an intimate admixture of a particular polyimide and gold (III) ions, in an amount sufficient to provide between 17 and 21 percent by weight of gold (III) ions, based on the weight of electrically conductive, thermooxidatively stable polyimide. The particular polyimide is prepared from a polyamic acid which has been synthesized from a dianhydride/diamine combination selected from the group consisting of 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 2,2-bis[4-(4 -aminophenoxy)phenyl]hexafluoropropane; 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 4,4'-oxydianiline; 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride and 4,4'-oxydianiline; and 3,3'4,4'-benzophenonetetracarboxylic dianhydride and 2,2-bis(3-aminophenyl)hexafluoropropane.

  12. Determination of anionic surfactants during wastewater recycling process by ion pair chromatography with suppressed conductivity detection

    NASA Technical Reports Server (NTRS)

    Levine, L. H.; Judkins, J. E.; Garland, J. L.; Sager, J. C. (Principal Investigator)

    2000-01-01

    A direct approach utilizing ion pairing reversed-phase chromatography coupled with suppressed conductivity detection was developed to monitor biodegradation of anionic surfactants during wastewater recycling through hydroponic plant growth systems and fixed-film bioreactors. Samples of hydroponic nutrient solution and bioreactor effluent with high concentrations (up to 120 mS electrical conductance) of inorganic ions can be analyzed without pretreatment or interference. The presence of non-ionic surfactants did not significantly affect the analysis. Dynamic linear ranges for tested surfactants [Igepon TC-42, ammonium lauryl sulfate, sodium laureth sulfate and sodium alkyl (C10-C16) ether sulfate] were 2 to approximately 500, 1 to approximately 500, 2.5 to approximately 550 and 3.0 to approximately 630 microg/ml, respectively.

  13. Ion conductivity of the bacterial translocation channel SecYEG engaged in translocation.

    PubMed

    Knyazev, Denis G; Winter, Lukas; Bauer, Benedikt W; Siligan, Christine; Pohl, Peter

    2014-08-29

    While engaged in protein transport, the bacterial translocon SecYEG must maintain the membrane barrier to small ions. The preservation of the proton motif force was attributed to (i) cation exclusion, (ii) engulfment of the nascent chain by the hydrophobic pore ring, and (iii) a half-helix partly plugging the channel. In contrast, we show here that preservation of the proton motif force is due to a voltage-driven conformational change. Preprotein or signal peptide binding to the purified and reconstituted SecYEG results in large cation and anion conductivities only when the membrane potential is small. Physiological values of membrane potential close the activated channel. This voltage-dependent closure is not dependent on the presence of the plug domain and is not affected by mutation of 3 of the 6 constriction residues to glycines. Cellular ion homeostasis is not challenged by the small remaining leak conductance. PMID:25016015

  14. Ion conductance of the Ca(2+)-activated maxi-K+ channel from the embryonic rat brain.

    PubMed

    Mienville, J M; Clay, J R

    1997-01-01

    By using single-channel recording techniques, we measured the conductance (gK) of the Ca(2+)-activated Maxi-K+ channel from the embryonic rat brain, and examined its dependence on K+ ions present in equimolar concentrations on both sides of the membrane patch. With ionic strength maintained constant by substitution of N-methyl-D-glucamine for K+, gK has a sigmoidal dependence upon [K+]. This result has been obscured in previous work by variations in ionic strength, which has a marked effect on single-channel conductance, especially in the limit for which this variable approaches zero. The gK versus [K+] relationship is described, theoretically, by a three-barrier, two-binding-site model in which the barrier that an ion must cross to leave the channel is decreased as [K+] is increased. PMID:8994603

  15. Ion Conductivity of the Bacterial Translocation Channel SecYEG Engaged in Translocation*

    PubMed Central

    Knyazev, Denis G.; Winter, Lukas; Bauer, Benedikt W.; Siligan, Christine; Pohl, Peter

    2014-01-01

    While engaged in protein transport, the bacterial translocon SecYEG must maintain the membrane barrier to small ions. The preservation of the proton motif force was attributed to (i) cation exclusion, (ii) engulfment of the nascent chain by the hydrophobic pore ring, and (iii) a half-helix partly plugging the channel. In contrast, we show here that preservation of the proton motif force is due to a voltage-driven conformational change. Preprotein or signal peptide binding to the purified and reconstituted SecYEG results in large cation and anion conductivities only when the membrane potential is small. Physiological values of membrane potential close the activated channel. This voltage-dependent closure is not dependent on the presence of the plug domain and is not affected by mutation of 3 of the 6 constriction residues to glycines. Cellular ion homeostasis is not challenged by the small remaining leak conductance. PMID:25016015

  16. Determination of surfactant sodium lauryl ether sulfate by ion pairing chromatography with suppressed conductivity detection

    SciTech Connect

    Ye, M.Y.; Walkup, R.G.; Hill, K.D. )

    1994-01-01

    A method for the determination of the anionic Steol CS-330 surfactant is described. CS-330 is a complex mixture of oligomers due to the various sizes of fatty alcohols and the number of moles of the ethoxylation. The main component of CS-330 is sodium lauryl ether sulfate (SLES). Since a SLES molecule has a hydrophilic sulfate head and a hydrophobic alkyl ethoxyl tail, it is very difficult to separate these molecules with conventional reverse phase chromatography or ion exchange chromatography. This work uses ion pairing chromatography with suppressed conductivity detection. The separation of oligomers in CS-330 is achieved. SLES does not have UV-absorbing chromophores, therefore an optical detector is not very sensitive. Suppressed conductivity detection technique significantly increases sensitivity and a quantitation limit of 56.60 ppm is achieved.

  17. Decoupling ion conductivity and fluid permeation through optimizing hydrophilic channel morphology

    NASA Astrophysics Data System (ADS)

    Chu, Peter Po-Jen; Fang, Yu-Shin; Tseng, Yu-Chen

    2016-05-01

    Approaches to improve membrane ion conductivity usually leads to higher degree of swelling, more serious fuel cross-over and often sacrificed membrane mechanical strength. Preserving all three main membrane properties is a tough challenge in searching high ion conducting fuel cell membrane. The long standing dilemma is resolved by decoupling ion conduction and fluid permeation property by creating optimized channel morphology using external electric field poling. Success of this approach is demonstrated in the proton conducting membrane composed of poly(ether sulfones) (PES) and sulfonated poly(ether ether ketone) (sPEEK, degree of sulfonation=50%) composites prepared under electric field poling condition. The external field enhanced the aromatic chain ordering from both sPEEK and PES and improved the miscibility. This induced interaction is conducive to the formation of more densely packed amorphous domains that eventually leads to preferentially ordered hydrophilic proton conducting channels having a average dimension (3 nm) smaller than that in generic sPEEK or Nafion. The narrower but more ordered channel displayed much lower methanol permeability (3.17×10-7 cm2/s), and lower swelling ratio (31.20%), while the conductivity (~10-1 S/cm) is higher than that of Nafion, or sPEEK at higher (64%) degree of sulfonation. The composite is chemically stable and highly durable with improved membrane mechanical strength. Nearly 50% increase of DMFC power output is observed using this membrane, and the best power density is recorded at 155 mA/cm2 (80 °C, 1M Methanol).

  18. In situ observations of ion scale current sheet and associated electron heating in Earth's magnetosheath turbulence

    NASA Astrophysics Data System (ADS)

    Chasapis, Alexandros; Retinò, Alessandro; Sahraoui, Fouad; Greco, Antonella; Vaivads, Andris; Sundkvist, David; Canu, Patrick

    2014-05-01

    Magnetic reconnection occurs in thin current sheets that form in turbulent plasmas. Numerical simulations indicate that turbulent reconnection contributes to the dissipation of magnetic field energy and results in particle heating and non-thermal acceleration. Yet in situ measurements are required to determine its importance as a dissipation mechanism at those scales. The Earth's magnetosheath downstream of the quasi-parallel shock is a turbulent near-Earth environment that offers a privileged environment for such a study. Here we present a study of the properties of thin current sheets by using Cluster data. We studied the distribution of the current sheets as a function of their magnetic shear angle, the PVI index and the electron heating. The properties of the observed current sheets were different for high shear (θ > 90 degrees) and low shear current sheets (θ < 90 degrees). These high-shear current sheets account for about ˜ 20% of the total and have an average thickness comparable to the ion inertial length. Enhancement of electron temperature within these current sheets suggest that they are important for local electron heating and energy dissipation.

  19. Effect of rare earth ions on the properties of glycine phosphite single crystals

    NASA Astrophysics Data System (ADS)

    Senthilkumar, K.; Moorthy Babu, S.; Kumar, Binay; Bhagavannarayana, G.

    2013-01-01

    Optically transparent glycine phosphite (GPI) single crystals doped with rare earth metal ions (Ce, Nd and La) were grown from aqueous solution by employing the solvent evaporation and slow cooling methods. Co-ordination of dopants with GPI was confirmed by X-ray fluorescence spectroscopic analysis. Single crystal X-ray diffraction analysis was carried out to determine the lattice parameters and to analyze the structural morphology of GPI with dopants, which indicates that cell parameters of doped crystals were significantly varied with pure GPI. Crystalline perfection of doped GPI crystals was determined by high resolution X-ray diffraction analysis by means of full width at half maximum values. Influence of the dopants on the optical properties of the material was determined. Paraelectric to ferroelectric transition temperature (Tc) of doped GPI crystals were identified using differential scanning calorimetric measurements. Piezoelectric charge coefficient d33 was measured for pure and doped GPI crystals. Hysteresis (P-E) loop was traced for ferroelectric b-axis and (100) plane of pure and doped GPI crystals with different biasing field and ferroelectric parameters were calculated. Mechanical stability of crystals was determined by Vickers microhardness measurements; elastic stiffness constant 'C11' and yield strength 'σy' were calculated from hardness values. Mechanical and ferroelectric properties of doped crystals were improved with doping of rare earth metals.

  20. Giant magnetostrain based on strong single ion anisotropy of rare earth materials

    NASA Astrophysics Data System (ADS)

    Doerr, M.; Raasch, S.; Rotter, M.; Frontzek, M.; Meyer, D. C.; Leisegang, T.; Zschintzsch, M.; Svoboda, P.; Loewenhaupt, M.

    2008-05-01

    The volume, shape and microstructure of solids can be influenced by magnetic fields. Much effort is focused on magnetic shape memory (MSM) materials. Recently, the MSM effect has been discovered to occur also in the paramagnetic state, e.g. in RCu2 compounds (R = rare earth). RMSM materials distinguish themselves from conventional MSM materials by the new origin of the magnetoic anisotropy: the strong rare-earth single ion anisotropy. Due to the pseudo-hexagonal symmetry of RCu2, three orientational variants exists, each of them rotated by about 60 deg with respect to the others. Switching these variants by an external field results in a change of the macroscopic shape. The strain is in the order of one percent (= Giant MagnetoStrain). The variant's fraction remains unchanged when ramping down the field. The virgin state can be recovered by heating or by a perpendicularly directed field. We present temperature and field dependent measurements of magnetostrain and magentization at the model substance Tb0.5Dy0.5Cu2. The macroscopic characterization of the sample is complemented by a detailed microscopic analysis done by elastic neutron scattering. Although the GMS effect of RCu2 was worked out at single crystals, the principle of this magneto-mechanical coupling phenomenon is also useful for polycrystalline or microscaled applications. The existence of this structural irreversibility shows the potential to construct field controlled actuators or switches.

  1. Hybrid quantum nanophotonic devices for coupling to rare-earth ions

    NASA Astrophysics Data System (ADS)

    Miyazono, Evan; Hartz, Alex; Zhong, Tian; Faraon, Andrei

    2015-03-01

    With an assortment of narrow line-width transitions spanning the visible and IR spectrum and long spin coherence times, rare-earth doped crystals are the leading material system for solid-state quantum memories. Integrating these materials in an on-chip optical platform would create opportunities for highly integrated light-matter interfaces for quantum communication and quantum computing. Nano-photonic resonators with high quality factors and small mode volumes are required for efficient on-chip coupling to the small dipole moment of rare-earth ion transitions. However, direct fabrication of optical cavities in these crystals with current nanofabrication techniques is difficult and unparallelized, as either exotic etch chemistries or physical milling processes are required. We fabricated hybrid devices by mechanically transferring a nanoscale membrane of gallium arsenide (GaAs) onto a neodymium-doped yttrium silicon oxide (Y2SiO5) crystal and then using electron beam lithography and standard III-V dry etching to pattern nanobeam photonic crystal cavities and ring resonator cavities, a technique that is easily adapted to other frequency ranges for arbitrary dopants in any rare earth host system. Single crystalline GaAs was chosen for its low loss and high refractive index at the transition wavelength. We demonstrated the potential to evanescently couple between the cavity field and the 883 nm 4I9/2- 4F3/2 transition of nearby neodymium impurities in the host crystal by examining transmission spectra through a waveguide coupled to the resonator with a custom-built confocal microscope. The prospects and requirements for using this system for scalable quantum networks are discussed.

  2. Preparation and ion conductivity of composite films AgI-ZnO

    NASA Astrophysics Data System (ADS)

    Fateev, Sergey S.; Tveryanovich, Yu S.; Tomaev, V. V.; Fokina, Svetlana V.

    2015-05-01

    It has been proven that with laser deposition silver iodide retains its chemical composition and structure. A film has been produced with the help of laser deposition, consisting of finely divided crystals of ZnO and AgI. Its structure has been reviewed using X-Ray phase analysis, and its electric conductivity has been reviewed using impedance measurement. Special attention has been given to the effect of phase interaction on ion transport.

  3. Spatial frequency method and apparatus for investigating earth conductivity with high vertical resolution by induction techniques

    SciTech Connect

    Barber, T.D.

    1989-06-06

    This patent describes an induction sonde for measuring a characteristic of an earth formation traversed by a borehole comprising: a support member; transmitter means secured to the support member for transmitting an electromagnetic induction signal into the formation about the sonde; and receiver means secured to the support member a preselected distance from the transmitter means for receiving induction signals from the formation thereby determining the vertical response as a function of depth, the preselected distance being selected to provided a sonde with no zeros in the spatial frequency response in the frequency range of interest, the spatial frequency response being the Fourier transform of the vertical response.

  4. Surface Plasmon Resonance Sensing Detection of Mercury and Lead Ions Based on Conducting Polymer Composite

    PubMed Central

    Abdi, Mahnaz M.; Abdullah, Luqman Chuah; Sadrolhosseini, Amir R.; Mat Yunus, Wan Mahmood; Moksin, Mohd Maarof; Tahir, Paridah Md.

    2011-01-01

    A new sensing area for a sensor based on surface plasmon resonance (SPR) was fabricated to detect trace amounts of mercury and lead ions. The gold surface used for SPR measurements were modified with polypyrrole-chitosan (PPy-CHI) conducting polymer composite. The polymer layer was deposited on the gold surface by electrodeposition. This optical sensor was used for monitoring toxic metal ions with and without sensitivity enhancement by chitosan in water samples. The higher amounts of resonance angle unit (ΔRU) were obtained for PPy-CHI film due to a specific binding of chitosan with Pb2+ and Hg2+ ions. The Pb2+ ion bind to the polymer films most strongly, and the sensor was more sensitive to Pb2+ compared to Hg2+. The concentrations of ions in the parts per million range produced the changes in the SPR angle minimum in the region of 0.03 to 0.07. Data analysis was done by Matlab software using Fresnel formula for multilayer system. PMID:21931763

  5. Conductive carbon filled polymeric electrodes: novel ion optical elements for time-of-flight mass spectrometers.

    PubMed

    Appel, Matthew F; van der Veer, Wytze E; Benter, Thorsten

    2002-10-01

    A new technique employing conductive polymeric electrodes for the generation of linear electric fields is proposed and validated. A hollow cylinder comprised of DuPont's Vespel SP-22, a polymer loaded with conductive carbon particles, is used to enhance the performance of a hybrid reflectron compared to a conventional dual stage gridless reflectron composed of discrete metal ring electrodes. Both devices have comparable physical dimensions and nearly identical ion optical properties. Instrumental resolution measurements are used to validate this novel design. PMID:12387322

  6. Ion-Electron-Conducting Polymer Composites: Promising Electromagnetic Interference Shielding Material.

    PubMed

    Vyas, Manoj Kumar; Chandra, Amita

    2016-07-20

    Polymer nanocomposites consisting of poly(vinylidenefluoride-co-hexafluoropropylene) PVdF-HFP, inorganic salt (LiBF4), organic salt (EMIMBF4), multiwalled carbon nanotubes (MWCNTs), and Fe3O4 nanoparticles were prepared as electromagnetic shield material. Improvement in conductivity and dielectric property due to the introduction of EMIMBF4, LiBF4, and MWCNTs was confirmed by complex impedance spectroscopy. The highest conductivity obtained is ∼1.86 mS/cm. This is attributed to the high ionic conductivity of the ionic liquids and the formation of a connecting network by the MWCNTs facilitating electron conduction. The total electromagnetic interference (EMI) shielding effectiveness has a major contribution to it due to absorption. Although the total shielding effectiveness in the Ku band (12.4-18 GHz) of pure ion-conducting system was found to be ∼19 dB and that for the polymer composites which are mixed (ion + electron) conductors is ∼46 dB, the contributions due to absorption are ∼16 and ∼42 dB, respectively. PMID:27351810

  7. Use of Ionic Liquids in Rod-Coil Block Copolyimides for Improved Lithium Ion Conduction

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Tigelaar, Dean M.; Chapin, Kara; Bennett, William R.

    2007-01-01

    Solvent-free, solid polymer electrolytes (SPE) have the potential to improve safety, increase design flexibility and enhance performance of rechargeable lithium batteries. Solution based electrolytes are flammable and typically incompatible with lithium metal anodes, limiting energy density. We have previously demonstrated use of polyimide rod coil block copolymers doped with lithium salts as electrolytes for lithium polymer batteries. The polyimide rod blocks provide dimensional stability while the polyethylene oxide (PEO) coil portions conduct ions. Phase separation of the rods and coils in these highly branched polymers provide channels with an order of magnitude improvement in lithium conduction over polyethylene oxide itself at room temperature. In addition, the polymers have been demonstrated in coin cells to be compatible with lithium metal. For practical use at room temperature and below, however, at least an order of magnitude improvement in ion conduction is still required. The addition of nonvolatile, room temperature ionic liquids has been shown to improve the ionic conductivity of high molecular weight PEO. Herein we describe use of these molten salts to improve ionic conductivity in the rod-coil block copolymers.

  8. Effect of swift heavy O7+ ion radiations on conductivity of lithium based polymer blend electrolyte

    NASA Astrophysics Data System (ADS)

    Joge, Prajakta; Kanchan, D. K.; Sharma, Poonam; Jayswal, Manish; Avasthi, D. K.

    2014-07-01

    In the present work, effect of swift heavy O7+ ion of 80 MeV of different fluences, on conductivity of [PVA(47.5)-PEO(47.5)-LiCF3SO3(5)]-EC(8) polymeric films has been investigated using ac impedance spectroscopy. The power law exponent n, hopping frequency ωh and activation energies for conduction Eac and relaxation Ear, have been investigated for different fluences. The DSC measurements are carried out in order to investigate the variations in the degree of crystallinity and thermal parameters (Tm) of the blend specimen prior and after irradiation. The Fourier Transform Infrared (FT-IR) measurements are carried out in order to investigate the changes in the vibrational modes of molecules upon irradiation. The FT-IR measurements corroborate the formation of amorphous phase in the blend matrix after irradiation. The conductivity is found to be optimum at the fluence of 1×1012 ions/cm2. The enhancement and the improvement in the electrolytic properties of PVA-PEO blend upon O7+ ion irradiation have been observed.

  9. Conduction mechanisms in ion-irradiated InGaAs layers

    SciTech Connect

    Joulaud, L.; Mangeney, J.; Chimot, N.; Crozat, P.; Fishman, G.; Bourgoin, J.C.

    2005-03-15

    The electrical and optical properties of H{sup +}- and Au{sup +}-irradiated InGaAs layers were studied using Hall-effect, van der Pauw, and relaxation-time measurements. Comparing the different results allows us to obtain information on the nature of the defects created by these two irradiations. Proton irradiation introduces donor-acceptor paired defects. Gold-ion irradiation creates neutral defect clusters and ionized point defects. The carrier mobilities in all of the irradiated materials are degraded, decreasing with increasing irradiation dose. A scattering model taking into account the paired defects is developed and the mobility evolution calculated from this model agrees with the experimental data of both annealed and unannealed samples. The photocurrent spectra reveal a metallic conduction in the band gap in the case of light-ion irradiation, while such type of conduction does not appear for heavy-ion irradiation. This metallic conduction is a consequence of band tailing induced by shallow defects and vanishes when the material is annealed at 400 deg. C. The proton irradiation-induced defects appear to be related to the EL-2-like defects.

  10. Ion-conduction mechanisms in NaSICON-type membranes for energy storage and utilization

    SciTech Connect

    McDaniel, Anthony H.; Ihlefeld, Jon F.; Bartelt, Norman Charles

    2015-10-01

    Next generation metal-ion conducting membranes are key to developing energy storage and utilization technologies like batteries and fuel ce lls. Sodium super-ionic conductors (aka NaSICON) are a class of compounds with AM 1 M 2 (PO 4 ) 3 stoichiometry where the choice of "A" and "M" cation varies widely. This report, which de scribes substitutional derivatives of NZP (NaZr 2 P 3 O 12 ), summarizes the accomplishments of a Laboratory D irected Research and Development (LDRD) project to analyze transport mec hanisms using a combination of in situ studies of structure, composition, and bonding, com bined with first principles theory and modeling. We developed an experimental platform and applied methods, such as synchrotron- based X-ray spectroscopies, to probe the electronic structure of compositionally well-controlled NaSICON films while in operation ( i.e ., conducting Na ions exposed to oxygen or water va por atmospheres). First principles theory and modeling were used to interpret the experimental observations and develop an enhanced understanding of atomistic processes that give rise to, and affect, ion conduction.

  11. Reduced Graphene Oxide Films with Ultrahigh Conductivity as Li-Ion Battery Current Collectors.

    PubMed

    Chen, Yanan; Fu, Kun; Zhu, Shuze; Luo, Wei; Wang, Yanbin; Li, Yiju; Hitz, Emily; Yao, Yonggang; Dai, Jiaqi; Wan, Jiayu; Danner, Valencia A; Li, Teng; Hu, Liangbing

    2016-06-01

    Solution processed, highly conductive films are extremely attractive for a range of electronic devices, especially for printed macroelectronics. For example, replacing heavy, metal-based current collectors with thin, light, flexible, and highly conductive films will further improve the energy density of such devices. Films with two-dimensional building blocks, such as graphene or reduced graphene oxide (RGO) nanosheets, are particularly promising due to their low percolation threshold with a high aspect ratio, excellent flexibility, and low cost. However, the electrical conductivity of these films is low, typically less than 1000 S/cm. In this work, we for the first time report a RGO film with an electrical conductivity of up to 3112 S/cm. We achieve high conductivity in RGO films through an electrical current-induced annealing process at high temperature of up to 2750 K in less than 1 min of anneal time. We studied in detail the unique Joule heating process at ultrahigh temperature. Through a combination of experimental and computational studies, we investigated the fundamental mechanism behind the formation of a highly conductive three-dimensional structure composed of well-connected RGO layers. The highly conductive RGO film with high direct current conductivity, low thickness (∼4 μm) and low sheet resistance (0.8 Ω/sq.) was used as a lightweight current collector in Li-ion batteries. PMID:27148884

  12. Sol-gel-derived hybrid materials multi-doped with rare-earth metal ions

    NASA Astrophysics Data System (ADS)

    Zelazowska, E.; Rysiakiewicz-Pasek, E.; Borczuch-Laczka, M.; Cholewa-Kowalska, K.

    2012-06-01

    Four different hybrid organic-inorganic materials based on TiO2-SiO2 matrices with organic additives and doped with rare-earth metal ions (III) from the group of europium, cerium, terbium, neodymium, dysprosium and samarium, were synthesized by sol-gel method. Tetraethyl orthosilicate, titanium (IV) isopropoxide and organic compounds, such as butyl acrylate, butyl methacrylate, ethyl acetoacetate, ethylene glycol dimethacrylate, ethyl acetate, propylene carbonate, organic solvents and certain inorganic salts were used in the synthesis. The inorganic part of the sols, which were used in the synthesis of all the hybrid materials, was prepared separately and then the organic parts were added. The materials obtained were aged for three weeks at room temperature and then heated in an electric oven for three hours at temperatures of 80 °C-150 °C. Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM/EDX); X-ray diffraction (XRD); Fourier transform infrared spectroscopy (KBr technique); 29Si magic-angle spinning nuclear magnetic resonance; and fluorescence spectroscopy were used for the examination of morphology, microstructure and luminescence properties, respectively. Photoluminescence properties with relatively intense narrow emission lines of Tb, Eu, Dy, Nd, Sm respectively to the RE-ions doping, were observed for all the hybrid materials.

  13. Visible WGM emissions from rare earth ion doped ZnO microspheres

    NASA Astrophysics Data System (ADS)

    K, Fabitha; Rao, M. S. Ramachandra

    ZnO is known to be an ideal candidate for short wavelength range opto-electronic device applications due to its wide and direct bandgap (3.37 eV) and high excitonic binding energy (60 meV). Apart from the UV emission at ~380 nm (free exciton emission) ZnO also possesses a broad emission band centered at ~530 nm which is expected to be originated from the oxygen vacancy (Vo) defects. In rare earth (RE) ion doped ZnO, emissions originate from the 4f levels of RE ions will be obtained in addition to the characteristic emissions of ZnO. Small micro/nanostructures made of ZnO with high crystalline quality show unique characteristics in light emission, especially in lasing applications. A micro/ nanostructured ZnO crystal generally has a wurtzite structure with a natural hexagonal cross section, which serves as a WGM lasing micro cavity owing to its high reflective index (~2). However, there exists a potential optical loss at corners of hexagons; therefore, an isotropic structure like spheres may be a better candidate to achieve efficient light confinement. In our work, highly smooth micro spheres with different diameters were grown. Raman spectroscopy measurements confirm the hexagonal wurtzite structure of ZnO, SEM and AFM studies shows the smooth surfaced spheres. WGM lasing characteristics of ZnO spheres have been investigated using optical pumping with 488 nm laser in a micro-PL system. Details of the results will be presented.

  14. A new model of Earth's radial conductivity structure derived from over 10 yr of satellite and observatory magnetic data

    NASA Astrophysics Data System (ADS)

    Püthe, Christoph; Kuvshinov, Alexey; Khan, Amir; Olsen, Nils

    2015-12-01

    We present a new model of the radial (1-D) conductivity structure of Earth's mantle. This model is derived from more than 10 yr of magnetic measurements from the satellites Ørsted, CHAMP, SAC-C and the Swarm trio as well as the global network of geomagnetic observatories. After removal of core and crustal field as predicted by a recent field model, we fit the magnetic data with spherical harmonic coefficients describing ring current activity and associated induction effects and estimate global C-responses at periods between 1.5 and 150 d. The C-responses are corrected for 3-D effects due to induction in the oceans and inverted for a 1-D model of mantle conductivity using both probabilistic and deterministic methods. Very similar results are obtained, consisting of a highly resistive upper mantle, an increase in conductivity in and beneath the transition zone and a conductive lower mantle. Analysis of the Hessian of the cost function reveals that the data are most sensitive to structures at depths between 800 and 1200 km, in agreement with the results obtained from the probabilistic approach. Preliminary interpretation of the inverted conductivity structure based on laboratory-based conductivity profiles shows that the recovered structure in the lower mantle either requires higher temperatures or the presence of material of high conductivity related to ponding of carbonate melts below the transition zone.

  15. The electrical conductivity of the Earth's upper mantle as estimated from satellite measured magnetic field variations. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Didwall, E. M.

    1981-01-01

    Low latitude magnetic field variations (magnetic storms) caused by large fluctuations in the equatorial ring current were derived from magnetic field magnitude data obtained by OGO 2, 4, and 6 satellites over an almost 5 year period. Analysis procedures consisted of (1) separating the disturbance field into internal and external parts relative to the surface of the Earth; (2) estimating the response function which related to the internally generated magnetic field variations to the external variations due to the ring current; and (3) interpreting the estimated response function using theoretical response functions for known conductivity profiles. Special consideration is given to possible ocean effects. A temperature profile is proposed using conductivity temperature data for single crystal olivine. The resulting temperature profile is reasonable for depths below 150-200 km, but is too high for shallower depths. Apparently, conductivity is not controlled solely by olivine at shallow depths.

  16. Adjoint sensitivity method for the downward continuation of the Earth's geomagnetic field through an electrically conducting mantle

    NASA Astrophysics Data System (ADS)

    Hagedoorn, J. M.; Martinec, Z.

    2012-12-01

    Recent models of the Earth's geomagnetic field at the core-mantle boundary (CMB) are based on satellite measurements and/or observatory data, which are mostly harmonically downward continued to the CMB. One aim of the upcoming satellite mission Swarm is to determine the three-dimensional distribution of electric conductivity of the Earth's mantle. On this background, we developed an adjoint sensitivity downward continuation approach that is capable to consider three-dimensional electric conductivity distributions. Martinec (Geophys. J. Int., 136, 1999) developed a time-domain spectral-finite element approach for the forward modelling of vector electromagnetic induction data as measured on ground-based magnetic observatory or by satellites. We design a new method to compute the sensitivity of the magnetic induction data to a magnetic field prescribed at the core-mantle boundary, which we term the adjoint sensitivity method. The forward and adjoint initial boundary-value problems, both solved in the time domain, are identical, except for the specification of prescribed boundary conditions. The respective boundary-value data are the measured X magnetic component for the forward method and the difference between the measured and predicted Z magnetic component for the adjoint method. The squares of the differences in Z magnetic component summed up over the time of observation and all spatial positions of observations determine the misfit. Then the sensitivities of observed data, i.e. the partial derivatives of the misfit with respect to the parameters characterizing the magnetic field at the core-mantle boundary, are obtained by the surface integral over the core-mantle boundary of the product of the adjoint solution multiplied by the time-dependent functions describing the time variability of magnetic field at the core-mantle boundary, and integrated over the time of observation. The time variability of boundary data is represented in terms of locally supported B

  17. Rare-earth-ion-doped waveguide lasers on a silicon chip

    NASA Astrophysics Data System (ADS)

    Pollnau, Markus

    2015-03-01

    Rare-earth-ion-doped materials are of high interest as amplifiers and lasers in integrated optics. Their longer excited-state lifetimes and the weaker refractive-index change accompanied with rare-earth-ion excitation compared to electron-hole pairs in III-V semiconductors provide spatially and temporally stable optical gain, allowing for high-speed amplification and narrow-linewidth lasers. Amorphous Al2O3 deposited onto thermally oxidized silicon wafers offers the advantage of integration with silicon photonics and electronics. Layer deposition by RF reactive co-sputtering and micro-structuring by chlorine-based reactive-ion etching provide low-loss channel waveguides. With erbium doping, we improved the gain to 2 dB/cm at 1533 nm and a gain bandwidth of 80 nm. The gain is limited by migration-accelerated energy-transfer upconversion and a fast quenching process. Since stimulated emission is even faster than this quenching process, lasers are only affected in terms of their threshold, allowing us to demonstrate diode-pumped micro-ring, distributed-feedback (DFB), and distributed-Bragg-reflector (DBR) lasers in Al2O3:Er3+ and Al2O3:Yb3+ on a silicon chip. Surface-relief Bragg gratings were patterned by laser-interference lithography. Monolithic DFB and DBR cavities with Q-factors of 1.35×106 were realized. In an Er-doped DFB laser, single-longitudinal-mode operation at 1545 nm was achieved with a linewidth of 1.7 kHz, corresponding to a laser Q-factor of 1.14×1011. Yb-doped DFB and DBR lasers were demonstrated at 1020 nm with output powers of 55 mW and a slope efficiency of 67% versus launched pump power. A dual-phaseshift, dual-wavelength laser was achieved and a stable microwave signal at ~15 GHz was created via the heterodyne photo-detection of the two laser wavelengths.

  18. Ion conduction and conformational flexibility of a bacterial voltage-gated sodium channel.

    PubMed

    Boiteux, Céline; Vorobyov, Igor; Allen, Toby W

    2014-03-01

    Voltage-gated Na(+) channels play an essential role in electrical signaling in the nervous system and are key pharmacological targets for a range of disorders. The recent solution of X-ray structures for the bacterial channel NavAb has provided an opportunity to study functional mechanisms at the atomic level. This channel's selectivity filter exhibits an EEEE ring sequence, characteristic of mammalian Ca(2+), not Na(+), channels. This raises the fundamentally important question: just what makes a Na(+) channel conduct Na(+) ions? Here we explore ion permeation on multimicrosecond timescales using the purpose-built Anton supercomputer. We isolate the likely protonation states of the EEEE ring and observe a striking flexibility of the filter that demonstrates the necessity for extended simulations to study conduction in this channel. We construct free energy maps to reveal complex multi-ion conduction via knock-on and "pass-by" mechanisms, involving concerted ion and glutamate side chain movements. Simulations in mixed ionic solutions reveal relative energetics for Na(+), K(+), and Ca(2+) within the pore that are consistent with the modest selectivity seen experimentally. We have observed conformational changes in the pore domain leading to asymmetrical collapses of the activation gate, similar to proposed inactivated structures of NavAb, with helix bending involving conserved residues that are critical for slow inactivation. These structural changes are shown to regulate access to fenestrations suggested to be pathways for lipophilic drugs and provide deeper insight into the molecular mechanisms connecting drug activity and slow inactivation. PMID:24550503

  19. Effects of near-Earth stochastic acceleration and reflections of magnetotail ions on the formation of auroral arcs

    NASA Technical Reports Server (NTRS)

    Ashour-Abdalla, Maha; Zelenyi, L. M.; Bosqued, Jean-Michael; Peroomian, V.; Wang, Z.; Schriver, D.; Richard, R.

    1992-01-01

    Findings obtained from global kinetic simulations of magnetotail plasma are discussed. A region of strongly nonadiabatic ion acceleration (known as the 'wall' region) exists in the near earth tail and demarcates two very different regimes of ion motion: adiabatic and quasi-adiabatic. After convection through the wall, ion distributions rapidly become isotropized and thermalized. A strong enhancement of the cross tail current occurs on the tailward side of the wall. Comparison of numerical and adiabatic pressure profiles indicates that nonadiabatic processes operating in this region may contribute significantly to a pressure balance relief in the course of quasi-steady magnetospheric convection.

  20. Influence of sulphate ion on the electrical conductivity of lithium -boro-phosphate glasses

    NASA Astrophysics Data System (ADS)

    Narayana Reddy, C.; Chakradhar, R. P. S.

    2009-07-01

    The effect of Li2SO4 on the electrical conductivity of Li2O- B2O3- P2O5 glass system prepared by melt quenching technique has been studied. Frequency and temperature dependent conductivity measurements have been carried out in the frequency range of 10 Hz to 10 MHz and a temperature range of 523 K-603 K respectively. Conductivity in these glasses is governed by the incorporation of lithium salt in the macromolecular structure. It exhibits Arrhenius behavior over the entire temperature range. Addition of Li2SO4 expands the glass network. Consequently the conductivity increases while activation energy decreases. Impedance spectra of these glasses show a single semicircle indicating one type of conduction. The nature of conductivity behavior observed can be explained using Almond-West type power law with a single exponent σ (ω) = σ (0) + A ωs. The power law exponent (s) decreases with temperature. Scaling behavior has also been carried out using the reduced plots of conductivity with frequency, which suggests the ion transport mechanism remains unaffected by temperature and composition.

  1. Gallium ion implantation greatly reduces thermal conductivity and enhances electronic one of ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Xia, Minggang; Cheng, Zhaofang; Han, Jinyun; Zheng, Minrui; Sow, Chorng-Haur; Thong, John T. L.; Zhang, Shengli; Li, Baowen

    2014-05-01

    The electrical and thermal conductivities are measured for individual zinc oxide (ZnO) nanowires with and without gallium ion (Ga+) implantation at room temperature. Our results show that Ga+ implantation enhances electrical conductivity by one order of magnitude from 1.01 × 103 Ω-1m-1 to 1.46 × 104 Ω-1m-1 and reduces its thermal conductivity by one order of magnitude from 12.7 Wm-1K-1 to 1.22 Wm-1K-1 for ZnO nanowires of 100 nm in diameter. The measured thermal conductivities are in good agreement with those in theoretical simulation. The increase of electrical conductivity origins in electron donor doping by Ga+ implantation and the decrease of thermal conductivity is due to the longitudinal and transverse acoustic phonons scattering by Ga+ point scattering. For pristine ZnO nanowires, the thermal conductivity decreases only two times when its diameter reduces from 100 nm to 46 nm. Therefore, Ga+-implantation may be a more effective method than diameter reduction in improving thermoelectric performance.

  2. Production of high resistivity water by electrodialysis. Influence of ion-exchange textiles as conducting spacers

    SciTech Connect

    Laktionov, E.; Dejean, E.; Sandeaux, J.; Sandeaux, R.; Gavach, C.; Pourcelly, G.

    1999-01-01

    Production of high resistivity water was investigated by electrodialysis (ED) using either inert or conducting spacers. Ion-exchange textiles were used as conducting spacers. Experiments were performed on a preindustrial scale with a pilot consisting of nine two-compartment cells, each membrane having an effective area of 176 cm{sup 2}. Three configurations of the ED stack were investigated for the dilution compartment: EDIT-(2) with a 2-mm thick ion-exchange textile, and ED-(2) or ED-(0.4), with a 0.4-mm thick inert spacer inserted between 2 or 0.4 mm thick dilution compartments, respectively. The textile induces a moderate increase in the pressure drop between the inlet and outlet of the stack. The performances of the different processes were compared under various experimental conditions of pH, nitrogen bubbling throughout the feed solution, flow rate, and current density. The results show that for an inlet conductivity of 10--15 {micro}S/cm, a flow rate of 2.2 {times} 10{sup {minus}5} m{sup 3}/s, and an applied voltage of 80 V, an outlet conductivity of 0.4 {micro}S/cm was obtained with the EDIT process, while no value lower than 5 {micro}S/cm was obtained with the ED process using both stacks.

  3. Conduction Mechanisms of Chloride Ions in ClC-Type Channels

    PubMed Central

    Corry, Ben; O'Mara, Megan; Chung, Shin-Ho

    2004-01-01

    The conduction properties of ClC-0 and ClC-1 chloride channels are examined using electrostatic calculations and three-dimensional Brownian dynamics simulations. We create an open-state configuration of the prokaryotic ClC Cl− channel using its known crystallographic structure as a basis. Two residues that are occluding the channel are slowly pushed outward with molecular dynamics to create a continuous ion-conducting path with the minimum radius of 2.5 Å. Then, retaining the same pore shape, the prokaryotic ClC channel is converted to either ClC-0 or ClC-1 by replacing all the nonconserved dipole-containing and charged amino acid residues. Employing open-state ClC-0 and ClC-1 channel models, current-voltage curves consistent with experimental measurements are obtained. We find that conduction in these pores involves three ions. We locate the binding sites, as well as pinpointing the rate-limiting steps in conduction, and make testable predictions about how the single channel current across ClC-0 and ClC-1 will vary as the ionic concentrations are increased. Finally, we demonstrate that a ClC-0 homology model created from an alternative sequence alignment fails to replicate any of the experimental observations. PMID:14747320

  4. Nanoclay and swift heavy ions induced piezoelectric and conducting nanochannel based polymeric membrane for fuel cell

    NASA Astrophysics Data System (ADS)

    Jana, Karun Kumar; Srivastava, Anshuman; Parkash, Om; Avasthi, Devesh K.; Rana, Dipak; Shahi, Vinod K.; Maiti, Pralay

    2016-01-01

    Through nanochannels are fabricated in poly(vinylidene fluoride-co-hexafluoro propylene) films by bombarding swift heavy ions (SHI) of energy 80 MeV and thereby creating latent tracks in the ion passage followed by chemical etching of the amorphous track. The dimension of the nanochannel is varied from 34 to 65 nm using different fluences and by dispersing organically modified nanoclay in polymer matrix. The nanochannels are grafted with polystyrene using the free radicals caused by SHI irradiation followed by their sulfonation. Nanoclay nucleates piezoelectric β-phase in copolymer whose extent gets enhanced after irradiation, grafting and sulfonation leading to a better material. The efficiency of functionalized nanochannel conduction is studied through dc conductivity of the bulk film in the semiconducting range against the insulating nature of the pristine copolymer. Current-voltage (I-V) characteristic of the membrane exhibits strong fluence dependency and shows superior conduction in functionalized nanohybrid. Proton conductivity of the functionalized nanohybrid is 6.2 × 10-2 S cm-1, while methanol permeability drastically reduces indicating higher values of the selective parameter of the developed membrane as compared to Nafion. Membrane electrode assembly studies of functionalized nanohybrid show 0.63 V as open circuit voltage leading to power density of 30.8 mW/cm2, considerably higher than the functionalized copolymer.

  5. Dawn-dusk asymmetry in ion pitch-angle anisotropy in the near-Earth magnetosphere and tail plasma sheet

    NASA Astrophysics Data System (ADS)

    Wang, C.; Zaharia, S. G.; Lyons, L. R.; Angelopoulos, V.

    2012-12-01

    We found a strong dawn-dusk asymmetry in ion pitch-angle anisotropy from spatial distributions statistically determined using THEMIS observations. The asymmetry varies significantly with ion energies and is a result of different processes. The anisotropy of ions below several hundreds eV in the tail plasma sheet (beyond X = 10 Re) and the near-Earth magnetosphere (inside r = 10 Re) is dominantly negative (relatively higher particle fluxes near 0 and 180 degree pitch-angle) and is more strongly negative in the post-midnight sector than the pre-midnight sector. The negative anisotropy is likely caused by field-aligned ionosphere outflow and the post-midnight enhancement is correlated with stronger electron precipitation energy fluxes that create stronger outflow. For ions between 1 to 10 keV in the near-Earth magnetosphere, anisotropy is found to be strongly positive (relatively higher fluxes near 90 degree pitch-angle) in the morning sector while near isotropic in the evening sector. Comparing the fluxes within the region of the positive anisotropy with other MLTs suggests that the positive anisotropy is caused by field-aligned ions not being able to drift as earthward as 90 degree ions. For ions of 10 keV and above, magnetic drift shell splitting results in strongly positive anisotropy on the dayside, while additional magnetopause shadowing causes strongly negative anisotropy in the post-midnight sector.

  6. Compliant glass–polymer hybrid single ion-conducting electrolytes for lithium batteries

    PubMed Central

    Villaluenga, Irune; Wujcik, Kevin H.; Tong, Wei; Devaux, Didier; Wong, Dominica H. C.; DeSimone, Joseph M.; Balsara, Nitash P.

    2016-01-01

    Despite high ionic conductivities, current inorganic solid electrolytes cannot be used in lithium batteries because of a lack of compliance and adhesion to active particles in battery electrodes as they are discharged and charged. We have successfully developed a compliant, nonflammable, hybrid single ion-conducting electrolyte comprising inorganic sulfide glass particles covalently bonded to a perfluoropolyether polymer. The hybrid with 23 wt% perfluoropolyether exhibits low shear modulus relative to neat glass electrolytes, ionic conductivity of 10−4 S/cm at room temperature, a cation transference number close to unity, and an electrochemical stability window up to 5 V relative to Li+/Li. X-ray absorption spectroscopy indicates that the hybrid electrolyte limits lithium polysulfide dissolution and is, thus, ideally suited for Li-S cells. Our work opens a previously unidentified route for developing compliant solid electrolytes that will address the challenges of lithium batteries. PMID:26699512

  7. Electron conductivity in GeTe and GeSe upon ion implantation of Bi

    SciTech Connect

    Fedorenko, Ya. G.

    2015-12-15

    This paper presents results on ion implantation of bismuth in GeTe and GeSe films. The conductivity and the thermopower of amorphous chalcogenide films are investigated. Electron conductivity in the films is attained at the Bi implantation doses higher than (1.5–2) × 10{sup 16} cm{sup −2}. In conjunction with the structural modification in the films as revealed Raman spectroscopy, the results suggest the structural re-arrangement of the amorphous network occurs via weakening the bonds of a lower energy. The onset of electron conductivity is hindered by a stronger bond in an alloy. In GeTe, this is the Ge-Ge bond.

  8. Image formation, resolution, and height measurement in scanning ion conductance microscopy

    SciTech Connect

    Rheinlaender, Johannes; Schaeffer, Tilman E.

    2009-05-01

    Scanning ion conductance microscopy (SICM) is an emerging tool for the noncontact investigation of biological samples such as live cells. It uses an ion current through the opening of a tapered nanopipette filled with an electrolyte for topography measurements. Despite its successful application to numerous systems no systematic investigation of the image formation process has yet been performed. Here, we use finite element modeling to investigate how the scanning ion conductance microscope images small particles on a planar surface, providing a fundamental characterization of the imaging process. We find that a small particle appears with a height that is only a fraction of its actual height. This has significant consequences for the quantitative interpretation of SICM images. Furthermore, small and low particles are imaged as rings in certain cases. This can cause small, closely spaced particles to appear with a lateral orientation that is rotated by 90 deg. Considering both real space and spatial frequency space we find that a reasonable and useful definition of lateral resolution of SICM is the smallest distance at which two small particles can clearly be resolved from each other in an image. We find that this resolution is approximately equal to three times the inner radius of the pipette tip opening.

  9. Cytosolic Ca(2+) Signals Enhance the Vacuolar Ion Conductivity of Bulging Arabidopsis Root Hair Cells.

    PubMed

    Wang, Yi; Dindas, Julian; Rienmüller, Florian; Krebs, Melanie; Waadt, Rainer; Schumacher, Karin; Wu, Wei-Hua; Hedrich, Rainer; Roelfsema, M Rob G

    2015-11-01

    Plant cell expansion depends on the uptake of solutes across the plasma membrane and their storage within the vacuole. In contrast to the well-studied plasma membrane, little is known about the regulation of ion transport at the vacuolar membrane. We therefore established an experimental approach to study vacuolar ion transport in intact Arabidopsis root cells, with multi-barreled microelectrodes. The subcellular position of electrodes was detected by imaging current-injected fluorescent dyes. Comparison of measurements with electrodes in the cytosol and vacuole revealed an average vacuolar membrane potential of -31 mV. Voltage clamp recordings of single vacuoles resolved the activity of voltage-independent and slowly deactivating channels. In bulging root hairs that express the Ca(2+) sensor R-GECO1, rapid elevation of the cytosolic Ca(2+) concentration was observed, after impalement with microelectrodes, or injection of the Ca(2+) chelator BAPTA. Elevation of the cytosolic Ca(2+) level stimulated the activity of voltage-independent channels in the vacuolar membrane. Likewise, the vacuolar ion conductance was enhanced during a sudden increase of the cytosolic Ca(2+) level in cells injected with fluorescent Ca(2+) indicator FURA-2. These data thus show that cytosolic Ca(2+) signals can rapidly activate vacuolar ion channels, which may prevent rupture of the vacuolar membrane, when facing mechanical forces. PMID:26232520

  10. Enhanced diffusive ion scattering in front of the Earth's quasi-parallel bow shock: a case study

    NASA Astrophysics Data System (ADS)

    Kis, Arpad; Scholer, Manfred; Klecker, Berndt; Lucek, Elisabeth; Dandouras, Iannis; Lemperger, István; Wesztergom, Viktor; Novák, Attila; Szalai, Sándor

    2014-05-01

    In our study we report on observations of energetic ions upstream of the Earth's quasi-parallel bow shock by Cluster at times of large inter-spacecraft separation distance. For the analysis we use the ion data provided by the CIS-HIA in the 10-32 keV energy range and the magnetic data recorded by the FGM instrument. We determine the spatial gradient of partial energetic ion densities at various distances from the bow shock. The gradient in all energy channels decreases exponentially with distance and the e-folding distance of the gradients depends approximately linearly on energy but there is a significant difference in their values obtained at the observed three upstream ion events. We demonstrate for the first time that under specific interplanetary conditions the mechanism of the diffuse ion scattering can change significantly and results in an anomalous diffusive process charactized by an unusually small e-folding distance.

  11. Coordination and ion-ion interactions of chromium centers in alkaline earth zinc borate glasses probed by electron paramagnetic resonance and optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Sumalatha, B.; Omkaram, I.; Rajavardana Rao, T.; Linga Raju, Ch

    2013-05-01

    Electron paramagnetic resonance (EPR), optical absorption and FT-IR studies have been carried out on chromium ions incorporated in alkaline earth zinc borate glasses. The EPR spectra exhibit two resonance signals with effective g values at g ≈ 1.99 and ≈1.97. The resonance signal at g ≈ 1.99 is attributed to the contribution from both the exchange coupled Cr3+-Cr3+ ion pairs and the isolated Cr3+ ions and the resonance signal at g ≈ 1.97 is due to Cr5+ ions. The paramagnetic susceptibility (χ) was calculated from the EPR data at various (123-303 K) temperatures and the Curie temperature (θp) was calculated from the 1/χ-T graph. The optical absorption spectra exhibit three bands at ˜360 nm, ˜440 nm and a broad band at ˜615 nm characteristic of Cr3+ ions in an octahedral symmetry. From the observed band positions, the crystal-field splitting parameter Dq and the Racah parameters (B and C) have been evaluated. From the ultraviolet edges, the optical band gap energies (Eopt) and Urbach energy (ΔE) are calculated. The theoretical optical basicity (Λth) of these glasses has also been evaluated. Chromium ions doped alkaline earth zinc borate glasses show BO3 and BO4 structural units in the FT-IR studies.

  12. Optical properties and size distribution of the nanocolloids made of rare-earth ion-doped NaYF4

    NASA Astrophysics Data System (ADS)

    Patel, Darayas N.; Lewis, Ashley; Wright, Donald M.; Lewis, Danielle; Valentine, Rueben; Valentine, Maucus; Wessley, Dennis; Sarkisov, Sergey; Darwish, Abdalla M.

    2015-03-01

    In this paper we investigate optical properties and size distribution of the nano-colloids made of trivalent rare-earth ion doped fluorides: holmium and ytterbium, thulium and ytterbium, and erbium and ytterbium co-doped NaYF4. These materials were synthesized by using simple co-precipitation synthetic method. The initially prepared micro-crystals had very weak or no visible upconversion fluorescence signals when being pumped with a 980-nm laser. The fluorescence intensity significantly increased after the crystals were annealed at a temperature of 400°C - 600°C undergoing the transition from cubic alpha to hexagonal beta phase of the fluoride host. Nano-colloids of the crystals were made in polar solvents using the laser ablation and ball milling methods. Size analyses of the prepared nano-colloids were conducted using a dynamic light scatterometer and atomic force microscope. The nano-colloids were filled in holey PCFs and their fluorescent properties were studied and the feasibility of new a type of fiber amplifier/laser was evaluated.

  13. Development of high capacity, high rate lithium ion batteries utilizing metal fiber conductive additives

    NASA Astrophysics Data System (ADS)

    Ahn, Soonho; Kim, Youngduk; Kim, Kyung Joon; Kim, Tae Hyung; Lee, Hyungkeun; Kim, Myung H.

    As lithium ion cells dominate the battery market, the performance improvement is an utmost concern among developers and researchers. Conductive additives are routinely employed to enhance electrode conductivity and capacity. Carbon particulates—graphite or carbon black powders—are conventional and popular choices as conductive fillers. However, percolation requirements of particles demand significant volumetric content of impalpable, and thereby high area conductive fillers. As might be expected, the electrode active surface area escalates unnecessarily, resulting in overall increase in reaction with electrolytes and organic solvents. The increased reactions usually manifest as an irreversible loss of anode capacity, gradual oxidation and consumption of electrolyte on the cathode—which causes capacity decline during cycling—and an increased threat to battery safety by gas evolution and exothermic solvent oxidation. In this work we have utilized high aspect ratio, flexible, micronic metal fibers as low active area and high conductivity additives. The metal fibers appear well dispersed within the electrode and to satisfy percolation requirements very efficiently at very low volumetric content compared to conventional carbon-based conductive additives. Results from 18650-type cells indicate significant enhancements in electrode capacity and high rate capability while the irreversible capacity loss is negligible.

  14. Defect Physics and Ionic conduction in Solid Electrolyte Interphase for Lithium Ion Batteries

    NASA Astrophysics Data System (ADS)

    Pan, Jie; Cheng, Yang-Tse; Qi, Yue

    The ionic conduction through the solid electrolyte interphase (SEI) is important to the rate capability of the battery. The origin of ionic conduction in the SEI is defect formation and transport. In this study, we developed a theoretical method based on density functional theory to calculate the ionic conductivity in LiF, an important SEI component, in contact with electrode materials. Seventeen native defects with their relevant charge states were investigated to determine the dominant defects on various electrodes. The contacted electrode serves as a Li reservoir with adjustable Li chemical potential (μLi) for defect formation. The formation energy and diffusion barrier of defects were mapped to ionic conductivity by the Nernst-Einstein relationship. The main defect is Schottky pair in the intrinsic region and Li ion vacancy in the p-type region. The ionic conductivity is calculated to be approximately 10-31 S/cm when LiF is in contact with an anode but it can increase to 10-12 S/cm on a cathode. Comparing with other SEI components, the ionic conductivity is very low in LiF if it is coated on an anode surface. However, due to the low concentration of electronic carriers, LiF can act as a good passivation layer on the electrode and prevent further electrolyte decomposition. This work is supported by Department of Energy and National Science Foundation.

  15. Spatial distributions of ion pitch angle anisotropy in the near-Earth magnetosphere and tail plasma sheet

    NASA Astrophysics Data System (ADS)

    Wang, Chih-Ping; Zaharia, Sorin G.; Lyons, Larry R.; Angelopoulos, Vassilis

    2013-01-01

    We have quantified anisotropy of ion pitch angle distributions observed by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft and determined statistically how anisotropy varies with particle energy, as well as spatial distributions and dependences on geomagnetic activity. In the tail plasma sheet, ions from a few keV to a few tens of keV are mostly isotropic. The locations and energy ranges for these isotropic ions and their changes with Dst are consistent with ions being isotropized by current sheet scattering predicted using empirical magnetic field models. Ions of a few hundreds of keV in the tail have cigar-shaped or unidirectional pitch angle distribution (PAD) and are likely a result of Speiser motion. The majority of ions in the near-Earth magnetosphere are expected to conserve their first and second adiabatic invariants as they move with pitch angle dependent drift. This gives drift shell splitting, which plays an important role in generating pancake-shaped PAD observed from ~1 keV up to hundreds of keV. The magnetic local time of the pancake PAD rotates with increasing energy. Loss of near 90° ions due to magnetopause shadowing can further explain the butterfly-shaped PAD observed at the postmidnight sector at energies above 30 keV. For ions below a few hundreds of eV in the tail plasma sheet and the near-Earth magnetosphere, their PAD is dominantly bidirectional, which is likely due to ionosphere outflow. High-energy ions on the dayside become less anisotropic during higher AE, when pitch angle scattering by electromagnetic ion cyclotron waves may play an important role.

  16. Use of scanning ion conductance microscopy to guide and redirect neuronal growth cones.

    PubMed

    Pellegrino, Mario; Orsini, Paolo; De Gregorio, Francesca

    2009-07-01

    Scanning ion conductance microscopy has been applied to neuronal growth cones of the leech either to image or to stimulate them. Growth cone advance was recorded in non-contact mode using a 2% ion current decrease criterion for pipette-membrane distance control. We demonstrate effective growth cone remodelling using a 5% criterion (near-scanning). Recurrent line near-scanning aligned growth cone processes along the scan line. The new membrane protrusions, marked by DiI, started a few minutes after scanning onset and progressively grew in thickness. Using scanning patterns suitable for connecting distinct growth cones, new links were consistently developed. Although the underlying mechanism is still a matter for investigation, a mechanical perturbation produced by the moving probe appeared to induce the process formation. Thanks to its deterministic and interactive features, this novel approach to guiding growth cones is a promising way to develop networks of identified neurons as well as link them with artificial structures. PMID:19447298

  17. Distinguishing two contributions to the nearly constant loss in ion-conducting glasses.

    PubMed

    Sidebottom, D L; Murray-Krezan, C M

    2002-11-01

    In an effort to understand the origins of the nearly constant loss in disordered materials, we report dielectric studies of a series of sodium germanate glasses, (Na2O)(x)(GeO2)(1-x) for x=0, 0.003, 0.01, 0.03, and 0.1 at temperatures between 85 and 700 K. Analysis of the conductivity scaling for these glasses demonstrates the existence of two contributions in the near constant loss; one due to mobile cations that conforms to the same scaling properties found for ion hopping at high temperatures and the other due to the glass network which dominates at low temperatures and low ion densities. PMID:12443129

  18. Polynuclear Silver(I) Triazole Complexes: Ion Conduction and Nanowire Formation in the Mesophase.

    PubMed

    Su, Padi Y S; Hsu, S J; Tseng, Jing C W; Hsu, Hsiu-Fu; Wang, Wen-Jwu; Lin, Ivan J B

    2016-01-01

    Examples of polynuclear metallomesogens are few. Herein,1,2,4-triazole ligands were used to prepare mono- and polynuclear silver(I) triazole metallomesogens. Besides showing an SmA phase in the mesophase, two interesting properties were observed. First, higher ion conductivity is always found for the polynuclear complexes than for the mononuclear complexes with the same anion, an observation contrary to the knowledge that migration of a monomeric cation should be faster than that of a polymeric cation. Second, thermolysis of the polynuclear silver(I) triazole complexes in the assembled mesophase yielded Ag nanowires, in an excellent demonstration of the assembled nature of the polynuclear silver(I) ions in the thermolysis process. PMID:26602494

  19. Facile and Nonradiation Pretreated Membrane as a High Conductive Separator for Li-Ion Batteries.

    PubMed

    Li, Bao; Li, Yongjun; Dai, Dongmei; Chang, Kun; Tang, Hongwei; Chang, Zhaorong; Wang, Chunru; Yuan, Xiao-Zi; Wang, Haijiang

    2015-09-16

    Polyolefin membranes are widely used as separators in commercialized Li-ion batteries. They have less polarized surfaces compared with polarized molecules of electrolyte, leading to a poor wetting state for separators. Radiation pretreatments are often adopted to solve such a problem. Unfortunately, they can only activate several nanometers deep from the surface, which limits the performance improvement. Here we report a facile and scalable method to polarize polyolefin membranes via a chemical oxidation route. On the surfaces of pretreated membrane, layers of poly(ethylene oxide) and poly(acrylic acid) can easily be coated, thus resulting in a high Li-ion conductivity of the membrane. Assembled with this decorated separator in button cells, both high-voltage (Li1.2Mn0.54Co0.13Ni0.13O2) and moderate-voltage (LiFePO4) cathode materials show better electrochemical performances than those assembled with pristine polyolefin separators. PMID:26320596

  20. Altered ion channel conductance and ionic selectivity induced by large imposed membrane potential pulse.

    PubMed Central

    Chen, W; Lee, R C

    1994-01-01

    The effects of large magnitude transmembrane potential pulses on voltage-gated Na and K channel behavior in frog skeletal muscle membrane were studied using a modified double vaseline-gap voltage clamp. The effects of electroconformational damage to ionic channels were separated from damage to lipid bilayer (electroporation). A 4 ms transmembrane potential pulse of -600 mV resulted in a reduction of both Na and K channel conductivities. The supraphysiologic pulses also reduced ionic selectivity of the K channels against Na+ ions, resulting in a depolarization of the membrane resting potential. However, TTX and TEA binding effects were unaltered. The kinetics of spontaneous reversal of the electroconformational damage of channel proteins was found to be dependent on the magnitude of imposed membrane potential pulse. These results suggest that muscle and nerve dysfunction after electrical shock may be in part caused by electroconformational damage to voltage-gated ion channels. PMID:7948676

  1. Oxide-ion and proton conducting electrolyte materials for clean energy applications: structural and mechanistic features.

    PubMed

    Malavasi, Lorenzo; Fisher, Craig A J; Islam, M Saiful

    2010-11-01

    This critical review presents an overview of the various classes of oxide materials exhibiting fast oxide-ion or proton conductivity for use as solid electrolytes in clean energy applications such as solid oxide fuel cells. Emphasis is placed on the relationship between structural and mechanistic features of the crystalline materials and their ion conduction properties. After describing well-established classes such as fluorite- and perovskite-based oxides, new materials and structure-types are presented. These include a variety of molybdate, gallate, apatite silicate/germanate and niobate systems, many of which contain flexible structural networks, and exhibit different defect properties and transport mechanisms to the conventional materials. It is concluded that the rich chemistry of these important systems provides diverse possibilities for developing superior ionic conductors for use as solid electrolytes in fuel cells and related applications. In most cases, a greater atomic-level understanding of the structures, defects and conduction mechanisms is achieved through a combination of experimental and computational techniques (217 references). PMID:20848015

  2. Development of Chemically and Thermally Robust Lithium Fast Ion Conducting Chalcogenide Glasses

    NASA Technical Reports Server (NTRS)

    Martin, Steve W.; Hagedorn, Norman (Technical Monitor)

    2002-01-01

    In this project, a new research thrust into the development of an entirely new class of FIC glasses has begun that may lead to a new set of optimized thin-film lithium ion conducting materials. New chemically robust FIC glasses are being prepared that are expected to exhibit unusually high chemical and electrochemical stability. New thermally robust FIC glasses are being prepared that exhibit softening points in excess of 500 C which will dramatically expand the usable operating temperature range of batteries, fuel-cells, and sensors using such electrolytes. Glasses are being explored in the general compositional series xLi2S+ yGa2S3 + (1-x-y)GeS2. Li2S is added as the source of the conductive lithium ions. GeS2 is the base glass-forming phase and the trivalent sulfides, Ga2S3, is added to increase the "refractoniness" of the glass, that is to significantly increase the softening point of the glass as well as its chemical stability. By optimizing the composition of the glass, new glasses and glass-ceramic FIC materials have been prepared with softening points in excess of 500 C and conductivities above 10(exp -3)/Ohm cm at room temperature. These latter attributes are currently not available in any FIC glasses to date.

  3. 1,2,3-Triazolium-Based Epoxy-Amine Networks: Ion-Conducting Polymer Electrolytes.

    PubMed

    Ly Nguyen, Thi Khanh; Obadia, Mona Marie; Serghei, Anatoli; Livi, Sébastien; Duchet-Rumeau, Jannick; Drockenmuller, Eric

    2016-07-01

    A diepoxy-functionalized 1,2,3-triazolium ionic liquid is synthesized in three steps and used in combination with a poly(propylene glycol) diamine to obtain ion-conducting epoxy-amine networks (EANs). The curing kinetics are followed by Fourier transform infrared spectroscopy, while the physical, mechanical, and ion-conducting properties of the resulting networks are studied by swelling experiments, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical thermal analysis, and broadband dielectric spectroscopy. The curing kinetics and thermomechanical properties of this system are relatively similar to those of conventional DGEBA- (bisphenol A diglycidyl ether)-based EANs with low glass transition temperature (Tg = -44 and -52 °C, respectively) characteristic of rubbery polymer networks. The anhydrous ionic conductivity of the pure network at 30 °C reaches a remarkably high value of 2 × 10(-7) S cm(-1) that could be further increased to 10(-6) S cm(-1) by the addition of 10 wt% LiTFSI. PMID:26924313

  4. Can anisotropic conductivity in the lower ionosphere and in the Earth's crust be studied by Schumann resonance transients?

    NASA Astrophysics Data System (ADS)

    Ludván, Brigitta; Bór, József; Steinbach, Péter; Novák, Attila; Sátori, Gabriella

    2015-04-01

    Schumann resonance transients (SRTs) are extremely low frequency (ELF, 3-3000 Hz) wave packets of high amplitude electromagnetic (EM) waves produced by intense lightning discharges worldwide. Near the lower end of the ELF band, frequencies are close to the lowest spherical eigenfrequencies of the closed EM waveguide formed by the surface of the Earth and the lower ionosphere. Therefore, these waves suffer little attenuation during their propagation and can be detected globally at any point on Earth. SRTs detected both in the vertical electric and in the horizontal magnetic components of the atmospheric EM field at the Széchenyi István Geophysical Observatory (NCK, 16.7 E, 47.6 N) on 1st and 2nd August, 2012 have been analyzed. Azimuths of their parent lightning discharges were calculated from the horizontal components of the corresponding Poynting vector. Parent lightning strokes of the considered SRTs (342 and 245 events on the first and on the second day, respectively) have been identified in the records of the World Wide Lightning Location Network (WWLLN) using the detection times of the events in the two datasets. It was found that the azimuths of the sources at NCK station deduced from ELF records systematically differ from source azimuths calculated using WWLLN provided lightning locations. The difference between the corresponding azimuth values from the two methods shows the same pattern on both examined days when it is plotted as function of the WWLLN data based source azimuth. The symmetry of this pattern agrees well with the symmetry of the conductivity variations of the Earth's crust determined by independent magnetotelluric methods at NCK station. The differences have similar diurnal variation, too, on the two days with the largest difference occurring near midnight, local time. Our results agree well with findings of Füllekrug and Sukhorukov (GRL, 1999) and support the idea that the azimuthal dependence of source azimuth differences can be related

  5. Stabilized finite element methods to simulate the conductances of ion channels

    NASA Astrophysics Data System (ADS)

    Tu, Bin; Xie, Yan; Zhang, Linbo; Lu, Benzhuo

    2015-03-01

    We have previously developed a finite element simulator, ichannel, to simulate ion transport through three-dimensional ion channel systems via solving the Poisson-Nernst-Planck equations (PNP) and Size-modified Poisson-Nernst-Planck equations (SMPNP), and succeeded in simulating some ion channel systems. However, the iterative solution between the coupled Poisson equation and the Nernst-Planck equations has difficulty converging for some large systems. One reason we found is that the NP equations are advection-dominated diffusion equations, which causes troubles in the usual FE solution. The stabilized schemes have been applied to compute fluids flow in various research fields. However, they have not been studied in the simulation of ion transport through three-dimensional models based on experimentally determined ion channel structures. In this paper, two stabilized techniques, the SUPG and the Pseudo Residual-Free Bubble function (PRFB) are introduced to enhance the numerical robustness and convergence performance of the finite element algorithm in ichannel. The conductances of the voltage dependent anion channel (VDAC) and the anthrax toxin protective antigen pore (PA) are simulated to validate the stabilization techniques. Those two stabilized schemes give reasonable results for the two proteins, with decent agreement with both experimental data and Brownian dynamics (BD) simulations. For a variety of numerical tests, it is found that the simulator effectively avoids previous numerical instability after introducing the stabilization methods. Comparison based on our test data set between the two stabilized schemes indicates both SUPG and PRFB have similar performance (the latter is slightly more accurate and stable), while SUPG is relatively more convenient to implement.

  6. Luminescent properties of rare earth ions in one-dimensional oxide nanowires.

    PubMed

    Song, Hongwei; Yu, Lixin; Yang, LinMei; Lu, Shaozhe

    2005-09-01

    Rare-earth doped one-dimensional oxide nanowires including LaPO4, La2O3, and Gd2O3 were synthesized by the hydrothermal method. Their luminescent properties including local environments, electronic transitions, energy transfer, and frequency up-conversion luminescence processes were systematically studied. In LaPO4:Eu and La2O3:Eu nanowires, different symmetry sites of Eu3+ ions were identified, which obviously differed from those of the corresponding micrometer-sized particles. This was attributed to crystal field degeneration in the fringe along the length axis. In LaPO4:Eu nanowires, the electronic transition rate of 5D1-sigmaJ7FJ increased approximately 2 times over that of the zero-dimensional nanoparticles and micrometer-sized particles, which was related to the variation of dipole field induced by shape anisotropy. Considering the nonradiative relaxations, meanwhile, the luminescent quantum efficiency for 5D1-sigmaJ7FJ transitions of Eu3+ in nanowires increased 100% over that in nanoparticles and 20% over that in micrometer particles. In Gd2O3:Eu3+, LaPO4:Ce3+, and LaPO4:Tb3+ nanowires and micrometer-sized particles, the electronic transition rate of rare earths had only a little variation. In LaPO4:Ce3+/Tb3+ nanowires, the energy transfer rate of Ce3+--> Tb3+ decreased 3 times compared to that in micrometer rods. Despite this, the brightness for the 5D4-7F5 green emissions of Tb3+ increased several times due to decreased energy transfer from the excited states higher than 5D4 to some defect levels. In Gd2O3:Er3+/Yb3+ nanocrystals, as the shape varied from nanopapers to nanowires, the relative intensity of up-conversion luminescence of 2H(11/2)/4S(3/2)-4I(15/2) and 4F(9/2)-4I(15/2) to the infrared down-conversion luminescence of 4I(13/2)-4I(15/2) increased remarkably, indicating efficient up-conversion luminescence. Our present results indicate that rare-earth-doped oxide nanowires is a type of new and efficient phosphors. PMID:16193968

  7. Ion conduction in substates of the batrachotoxin-modified Na+ channel from toad skeletal muscle.

    PubMed Central

    Naranjo, D; Latorre, R

    1993-01-01

    Batrachotoxin-modified Na+ channels from toad muscle were inserted into planar lipid bilayers composed of neutral phospholipids. Single-channel conductances were measured for [Na+] ranging between 0.4 mM and 3 M. When membrane preparations were made in the absence of protease inhibitors, two open conductance states were identified: a fully open state (16.6 pS in 200 mM symmetrical NaCl) and a substate that was 71% of the full conductance. The substate was predominant at [Na+] > 65 mM, whereas the presence of the fully open state was predominant at [Na+] < 15 mM. Addition of protease inhibitors during membrane preparation stabilized the fully open state over the full range of [Na+] studied. In symmetrical Na+ solutions and in biionic conditions, the ratio of amplitudes remained constant and the two open states exhibited the same permeability ratios of PLi/PNa and PCs/PNa. The current-voltage relations for both states showed inward rectification only at [Na+] < 10 mM, suggesting the presence of asymmetric negative charge densities at both channel entrances, with higher charge density in the external side. An energy barrier profile that includes double ion occupancy and asymmetric charge densities at the channel entrances was required to fit the conductance-[Na+] relations and to account for the rectification seen at low [Na+]. Energy barrier profiles differing only in the energy peaks can give account of the differences between both conductance states. Estimation of the surface charge density at the channel entrances is very dependent on the ion occupancy used and the range of [Na+] tested. Independent evidence for the existence of a charged external vestibule was obtained at low external [Na+] by identical reduction of the outward current induced by micromolar additions of Mg2+ and Ba2+. PMID:8388264

  8. Estimating the power law distribution of Earth electrical conductivity from low-frequency, controlled-source electromagnetic data

    NASA Astrophysics Data System (ADS)

    Beskardes, G. D.; Weiss, C. J.; Everett, M. E.

    2013-12-01

    Electromagnetic methods of geophysical exploration are a reflection of the spatio-temporal variability in ground conductivity, a macroscopic physical property that is a function of lithology, pore-scale surface chemistry, fracture networks, and the presence and distribution of fluids and partial melts. As such, the bulk electrical properties of some representative elementary volume within the subsurface derive from the macroscopic effect of charge buildup and current pathways across a range of length scales within. Quantifying this relationship between multiscale electrical properties and the observed geophysical data is a critical step toward meaningful geologic interpretation. Previously we presented evidence of near-surface electromagnetic data whose small scale fluctuations are both repeatable and fractally distributed -- an observation that supports the notion of a spatially hierarchical Earth. Bounded by the end member cases from homogenized isotropic and anisotropic media, we present numerical modeling results from textured and spatially-correlated, stochastic geologic media, demonstrating that the electromagnetic response is a power law distribution similar to that seen in the earlier observational data, rather than a smooth response polluted with Gaussian noise as is commonly assumed. Furthermore, we show that such power law behavior is dependent on correlation length within the medium and that the power law distribution of Earth conductivity can be estimated from that of the observed electromagnetic data.

  9. Iron-silica interaction at extreme conditions and the electrically conducting layer at the base of Earth's mantle.

    PubMed

    Dubrovinsky, L; Dubrovinskaia, N; Langenhorst, F; Dobson, D; Rubie, D; Gessmann, C; Abrikosov, I A; Johansson, B; Baykov, V I; Vitos, L; Le Bihan, T; Crichton, W A; Dmitriev, V; Weber, H-P

    2003-03-01

    The boundary between the Earth's metallic core and its silicate mantle is characterized by strong lateral heterogeneity and sharp changes in density, seismic wave velocities, electrical conductivity and chemical composition. To investigate the composition and properties of the lowermost mantle, an understanding of the chemical reactions that take place between liquid iron and the complex Mg-Fe-Si-Al-oxides of the Earth's lower mantle is first required. Here we present a study of the interaction between iron and silica (SiO2) in electrically and laser-heated diamond anvil cells. In a multianvil apparatus at pressures up to 140 GPa and temperatures over 3,800 K we simulate conditions down to the core-mantle boundary. At high temperature and pressures below 40 GPa, iron and silica react to form iron oxide and an iron-silicon alloy, with up to 5 wt% silicon. At pressures of 85-140 GPa, however, iron and SiO2 do not react and iron-silicon alloys dissociate into almost pure iron and a CsCl-structured (B2) FeSi compound. Our experiments suggest that a metallic silicon-rich B2 phase, produced at the core-mantle boundary (owing to reactions between iron and silicate), could accumulate at the boundary between the mantle and core and explain the anomalously high electrical conductivity of this region. PMID:12621431

  10. Impurity trapped exciton states related to rare earth ions in crystals under high hydrostatic pressure

    SciTech Connect

    Grinberg, M. Mahlik, S.

    2013-01-15

    Emission related to rare earth ions in solids takes place usually due to 4f{sup n} {yields} 4f{sup n} and 4f{sup n-1}5d{sup 1} {yields} 4f{sup n} internal transitions. In the case of band to band excitation the effective energy transfer from the host to optically active impurity is required. Among other processes one of the possibilities is capturing of the electron at excited state and hole at the ground state of impurity. Localization of electron or hole at the dopand site creates a long range Coulomb potential that attracts the second carrier which then occupies the localized Rydberg-like states. Such a system can be considered as impurity trapped exciton. Usually impurity trapped exciton is a short living phenomenon which decays non-radiatively leaving the impurity ion in the excited state. However, in several compounds doped with Eu{sup 2+} the impurity trapped exciton states become stable and contribute to the radiative processes though anomalous luminescence that appears apart of the 4f{sup 7} {yields} 4f{sup 7} and 4f{sup 7}5d{sup 1} {yields} 5f{sup 7} emission. In this contribution pressure effect on energies of the 4f{sup n-1}5d{sup 1}{yields}5f{sup n} transitions in Ln doped oxides and fluorides as well as influence of pressure on the energy of impurity trapped exciton states is discussed. The latest results on high pressure investigations of luminescence related to Pr{sup 3+}, and Eu{sup 2+} in different lattices are reviewed.

  11. Molecular Dynamics Study of Gramicidin A in Lipid Bilayer: Electrostatic Map and Ion Conduction

    NASA Astrophysics Data System (ADS)

    Saito, Hiroaki; Iwayama, Masashi; Kawaguchi, Kazutomo; Mizukami, Taku; Miyakawa, Takeshi; Takasu, Masako; Nagao, Hidemi

    The electrostatic potential (ESP) of gramicidin A (GA) in the DMPC lipid bilayers with/without an external uniform electrostatic field was investigated by molecular dynamics (MD) simulation. We found that the ESP profile with an external electrostatic field became step shape. The water and polar groups of the lipid and GA are rearranged in order to restore a flat ESP in the water bulk and GA channel interior. The reorientation of the polar head group enhances the ESP difference between each hydration regions of the membrane, and this should yield an increase of ion conductance through the GA channel.

  12. Second harmonic detection in the electrochemical strain microscopy of Ag-ion conducting glass

    SciTech Connect

    Yang, Sangmo; Okatan, Mahmut Baris; Paranthaman, Mariappan Parans; Jesse, Stephen; Noh, Tae Won; Kalinin, Sergei V.

    2014-11-14

    The first and second harmonic electromechanical responses and their cross-correlation in Ag-ion conducting glass were investigated using band-excitation electrochemical strain microscopy (ESM). Consecutive ESM images with increasing magnitudes of the applied AC voltage allowed observation of not only reversible surface displacement but also irreversible silver nanoparticle formation above a certain threshold voltage. The second harmonic ESM response was anticorrelated with the first harmonic response in many local regions. Furthermore, the nucleation sites of silver nanoparticles were closely related to the anti-correlated regions, specifically, with low second harmonic and high first harmonic ESM responses. The possible origins of the second harmonic ESM response are discussed.

  13. Influence of dry mixing and distribution of conductive additives in cathodes for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Bauer, Werner; Nötzel, Dorit; Wenzel, Valentin; Nirschl, Hermann

    2015-08-01

    Conductive additives, like carbon black or graphite, are essential components of lithium ion batteries due to the limited electrical conductivity of most electrode materials. However, there is still a lack of knowledge about the optimized distribution of these materials within the electrode. A dry mixing process is used in order to prepare a conductive coating by depositing carbon black on the surface of Li(Ni1/3Mn1/3Co1/3)O2 (NMC) cathode particles. It is demonstrated that this - from a theoretically point of view - favorable distribution does not allow the preparation of working electrodes without taking into account the role of the binder. After adding an organic binder to the slurry, the polymer deposits on top of the carbon shell during drying and inhibits the conductive contact between the particles. This can be avoided by a fraction of distributed carbon particles which are associated with the binder phase providing conductive paths through the isolating organic material. It is shown that carbon black and graphite are principally fulfilling this task, but both materials are leading to varying processing behavior and electrode properties.

  14. A novel method for structure-based prediction of ion channel conductance properties.

    PubMed Central

    Smart, O S; Breed, J; Smith, G R; Sansom, M S

    1997-01-01

    A rapid and easy-to-use method of predicting the conductance of an ion channel from its three-dimensional structure is presented. The method combines the pore dimensions of the channel as measured in the HOLE program with an Ohmic model of conductance. An empirically based correction factor is then applied. The method yielded good results for six experimental channel structures (none of which were included in the training set) with predictions accurate to within an average factor of 1.62 to the true values. The predictive r2 was equal to 0.90, which is indicative of a good predictive ability. The procedure is used to validate model structures of alamethicin and phospholamban. Two genuine predictions for the conductance of channels with known structure but without reported conductances are given. A modification of the procedure that calculates the expected results for the effect of the addition of nonelectrolyte polymers on conductance is set out. Results for a cholera toxin B-subunit crystal structure agree well with the measured values. The difficulty in interpreting such studies is discussed, with the conclusion that measurements on channels of known structure are required. Images FIGURE 1 FIGURE 3 FIGURE 4 FIGURE 6 FIGURE 10 PMID:9138559

  15. Analysis of inorganic nitrogen and related anions in high salinity water using ion chromatography with tandem UV and conductivity detectors.

    PubMed

    Wilson, Brian; Gandhi, Jay; Zhang, Chunlong Carl

    2011-09-01

    Over 97% of the Earth's water is high salinity water in the form of gulfs, oceans, and salt lakes. There is an increasing concern for the quality of water in bays, gulfs, oceans, and other natural waters. These waters are affected by many different sources of contamination. The sources are, but not limited to, groundwater run-off of nitrogen containing fertilizer, pesticides, cleaning agents, solid wastes, industrial waters, and many more. The final destinations of these contaminants are rivers, lakes, and bayous that eventually will lead to bays, gulfs, and oceans. Many industries depend on the quality of these waters, such as the fishing industry. In addition to wild marine life, there are large aquariums and fish and shrimp farms that are required to know the quality of the water. However, the ability of these industries to monitor their processes is limited. Most analytical methods do not apply to the analysis of high salinity waters. They are dependent on wet chemistry techniques, spectrophotometers, and flow analyzers. These methods do not have the accuracy, precision, and sensitivity when compared to ion chromatography (IC). Since the inception of IC, it has become a standard practice for determining the content of many different water samples. Many IC methods are limited in the range of analytes that can be detected, as well as the numerous sample sources of which the methods are applicable. The main focus of current IC methods does not include high salinity waters. This research demonstrates an ion chromatographic method that has the ability to determine low level concentrations of inorganic nitrogen and related anions (nitrite-N, nitrate-N, phosphorous-P, sulfate, bromide, chloride, sulfide, fluoride, ammonia, calcium, and magnesium) in a single run using a combination of UV and conductivity detectors. This method is applicable to various waters, and uses both freshwater and high salinity water samples. PMID:21859532

  16. Quantitative parameters for the sequestering capacity of polyacrylates towards alkaline earth metal ions.

    PubMed

    De Stefano, Concetta; Gianguzza, Antonio; Piazzese, Daniela; Sammartano, Silvio

    2003-10-17

    The complex formation constants of polyacrylic (PAA) ligands (1.4ions were determined in different ionic media at different ionic strengths, 0earth metal complexes is discussed in the light of sequestering effects in natural waters. PMID:18969177

  17. Synthesis and structure of some nano-sized rare-earth metal ions doped potassium hexacyanoferrates

    NASA Astrophysics Data System (ADS)

    Narayan, Himanshu; Alemu, Hailemichael; Nketsa, Pusetso F.; Manatha, Toka J.; Madhavi Thakurdesai, And

    2015-05-01

    Rare-earth ions doped potassium hexacyanoferrates (KR-HCF); with the general formula KRFe(CN)6 · 3H2 O [with, R≡Y, Gd and Yb] nanoparticles were synthesized through precipitation. Characterization was done through particle-size analyzer, scanning electron microscopy (SEM), Fourier Transform infra-red (FTIR) and Raman spectroscopy, and powder X-ray diffraction (XRD). The XRD data was analyzed on FullProf Software Suite program and the unit-cell structure and lattice parameters of KR-HCF samples were determined from scratch and refined further. All the three KR-HCF nanoparticles seem to crystallize in the orthorhombic primitive PMMM space-group. Reasonably good agreement was found with the previously reported lattice constants of KGd-HCF and KYb-HCF orthorhombic single-crystals, except that they assume different space-groups. The observed dissimilarity of space-groups may be attributed to the different time scales involved in the synthesis process. Moreover, the crystal structure of KYFe(CN)6 · 3H2 O nanoparticles is being reported for the very first time.

  18. In situ stress observation in oxide films and how tensile stress influences oxygen ion conduction

    PubMed Central

    Fluri, Aline; Pergolesi, Daniele; Roddatis, Vladimir; Wokaun, Alexander; Lippert, Thomas

    2016-01-01

    Many properties of materials can be changed by varying the interatomic distances in the crystal lattice by applying stress. Ideal model systems for investigations are heteroepitaxial thin films where lattice distortions can be induced by the crystallographic mismatch with the substrate. Here we describe an in situ simultaneous diagnostic of growth mode and stress during pulsed laser deposition of oxide thin films. The stress state and evolution up to the relaxation onset are monitored during the growth of oxygen ion conducting Ce0.85Sm0.15O2-δ thin films via optical wafer curvature measurements. Increasing tensile stress lowers the activation energy for charge transport and a thorough characterization of stress and morphology allows quantifying this effect using samples with the conductive properties of single crystals. The combined in situ application of optical deflectometry and electron diffraction provides an invaluable tool for strain engineering in Materials Science to fabricate novel devices with intriguing functionalities. PMID:26912416

  19. In situ stress observation in oxide films and how tensile stress influences oxygen ion conduction

    NASA Astrophysics Data System (ADS)

    Fluri, Aline; Pergolesi, Daniele; Roddatis, Vladimir; Wokaun, Alexander; Lippert, Thomas

    2016-02-01

    Many properties of materials can be changed by varying the interatomic distances in the crystal lattice by applying stress. Ideal model systems for investigations are heteroepitaxial thin films where lattice distortions can be induced by the crystallographic mismatch with the substrate. Here we describe an in situ simultaneous diagnostic of growth mode and stress during pulsed laser deposition of oxide thin films. The stress state and evolution up to the relaxation onset are monitored during the growth of oxygen ion conducting Ce0.85Sm0.15O2-δ thin films via optical wafer curvature measurements. Increasing tensile stress lowers the activation energy for charge transport and a thorough characterization of stress and morphology allows quantifying this effect using samples with the conductive properties of single crystals. The combined in situ application of optical deflectometry and electron diffraction provides an invaluable tool for strain engineering in Materials Science to fabricate novel devices with intriguing functionalities.

  20. In situ stress observation in oxide films and how tensile stress influences oxygen ion conduction.

    PubMed

    Fluri, Aline; Pergolesi, Daniele; Roddatis, Vladimir; Wokaun, Alexander; Lippert, Thomas

    2016-01-01

    Many properties of materials can be changed by varying the interatomic distances in the crystal lattice by applying stress. Ideal model systems for investigations are heteroepitaxial thin films where lattice distortions can be induced by the crystallographic mismatch with the substrate. Here we describe an in situ simultaneous diagnostic of growth mode and stress during pulsed laser deposition of oxide thin films. The stress state and evolution up to the relaxation onset are monitored during the growth of oxygen ion conducting Ce0.85Sm0.15O2-δ thin films via optical wafer curvature measurements. Increasing tensile stress lowers the activation energy for charge transport and a thorough characterization of stress and morphology allows quantifying this effect using samples with the conductive properties of single crystals. The combined in situ application of optical deflectometry and electron diffraction provides an invaluable tool for strain engineering in Materials Science to fabricate novel devices with intriguing functionalities. PMID:26912416

  1. A new model of Earth's radial conductivity structure derived from over 10 years of satellite and observatory magnetic data

    NASA Astrophysics Data System (ADS)

    Püthe, Christoph; Kuvshinov, Alexey; Olsen, Nils; Khan, Amir

    2015-04-01

    We present a new model of the radial (1-D) conductivity structure of Earth's mantle. This model was derived from more than ten years of magnetic measurements taken by the satellites Ørsted, CHAMP, SAC-C and the Swarm trio as well as the global network of geomagnetic observatories. After removal of core and crustal field as predicted by a recent field model we fit the data with spherical harmonic coefficients describing ring current activity and associated induction effects, and estimate global C-responses at periods between 1.5 days and 150 days. An iterative approach is used to correct the estimated C-responses for 3-D effects arising from induction in a heterogeneous surface shell that takes into account the distribution of oceans and continents. We invert the corrected C-responses for a 1-D model of mantle conductivity using both probabilistic and deterministic methods. The different methods yield very similar results, consisting of a highly resistive upper mantle, a conductive lower mantle, and an increase in conductivity in and beneath the transition zone. Analysis of the Hessian of the cost function reveals that the data are most sensitive to structures at depths between 700 km and 1200 km, in agreement with the results obtained from the probabilistic approach. The recovered models feature a marked kink in this well-resolved depth range.

  2. High index contrast potassium double tungstate waveguides towards efficient rare-earth ion amplification on-chip

    NASA Astrophysics Data System (ADS)

    Sefunc, Mustafa Akin; Segerink, Frans; Garcia-Blanco, Sonia

    2015-02-01

    Rare-earth ion doped KY(WO4)2 amplifiers are proposed to be a good candidate for many future applications by benefiting from the excellent gain characteristics of rare-earth ions, namely high bit rate amplification (earth ions were conventionally fabricated on layers overgrown onto undopedKY(WO4)2 substrates. Such amplifiers exhibit a refractive index contrast between the doped and undoped layer of typically <0.02, leading to large devices not suited for the high degree of integration required in photonic applications. Furthermore, the large mode diameter in the waveguide core requires high pump input powers to fully invert the material. In this study, we experimentally demonstrate high index contrast waveguides in crystalline KY(WO4)2, compatible with the integration onto passive photonic platforms. Firstly, a layer of KY(WO4)2 is transferred onto a silicon dioxide substrate using bonding with UV curable optical adhesive. A subsequent polishing step permits precise control of the transferred layer thickness, which defines the height of the waveguides. Small-footprint (in the order of few microns) high index contrast waveguides were patterned using focused ion beam milling. When doped with rare-earth ions, for instance, Er3+ or Yb3+, such high contrast waveguides will lead to very efficient amplifiers, in which the active material can be efficiently pumped by a confined mode with very good overlap with the signal mode. Consequently, lower pump power will be required to obtain same amount of gain from the amplifier leading to power efficient devices.

  3. Electrical conducting bis(oxalato)platinate complex with direct connection of CuII ions.

    PubMed

    Yamamoto, Chihiro; Nishikawa, Hiroyuki; Nihei, Masayuki; Shiga, Takuya; Hedo, Masato; Uwatoko, Yoshiya; Sawa, Hiroshi; Kitagawa, Hiroshi; Taguchi, Yasujiro; Iwasa, Yoshihiro; Oshio, Hiroki

    2006-12-11

    Reactions of K1.62[Pt(ox)2].2H2O and [Cu(bpy)(H2O)3](NO3)2 yielded partially oxidized one-dimensional (1D) bis(oxalato)platinates of [Cu(bpy)(H2O)n]6[Pt(ox)2]7.7H2O (n = 2, 3, or 4) (1) and [Cu(bpy)(H2O)n]8[Pt(ox)2]10.8H2O (n = 3 or 4) (2). The average oxidation numbers of the platinum ions in 1 and 2 are +2.29 and +2.40, respectively. Complexes 1 and 2 crystallize in the triclinic P and monoclinic C2/c space groups, respectively, and the [Pt(ox)2]n- anions are stacked along the crystallographic b axis with 7-fold periodicity for 1 and 10-fold periodicity for 2. In 1, an oxalato ligand in the platinum chain directly coordinates to a paramagnetic [Cu(bpy)(H2O)3]2+ ion, whereas no such direct coordination was observed for 2. The electrical conductivity of 2 at room temperature along the platinum chain is approximately 3 orders of magnitude smaller (sigma||= 1.3 x 10(-3) S cm(-1)) than that of 1 (sigma|| = 0.9-0.5 S cm(-1)), and the activation energies of 1 and 2 are 29 and 67 meV, respectively. The longest inter-platinum distances in 1 and 2 are 2.762 and 3.0082 A, respectively, and this is responsible for the lower electrical conductivity of 2. An X-ray oscillation photograph taken along the b axis of 1 reveals the 7-fold periodicity in the 1D chain, consistent with the period of the Peierls distortion estimated from the degree of partial oxidation. The semiconducting state of 1 can therefore be regarded as a commensurate Peierls state. The magnetoresistance of 1 at ambient pressure indicates no interaction between conduction electrons in the platinum chain and local spins of the paramagnetic CuII ions. Application of hydrostatic pressures of up to 3 GPa enhances electrical conduction, as is often seen as the usual pressure effect on the electrical conductivity, which is due to enhanced orbital (Pt-5dz2) overlap by pressure application. PMID:17140235

  4. Maskless Lithography and in situ Visualization of Conductivity of Graphene using Helium Ion Microscopy

    SciTech Connect

    Iberi, Vighter O.; Vlassiouk, Ivan V.; Zhang, X. -G.; Matola, Brad R.; Linn, Allison R.; Joy, David Charles; Adam Justin Rondinone

    2015-07-07

    The remarkable mechanical and electronic properties of graphene make it an ideal candidate for next generation nanoelectronics. With the recent development of commercial-level single-crystal graphene layers, the potential for manufacturing household graphene-based devices has improved, but significant challenges still remain with regards to patterning the graphene into devices. In the case of graphene supported on a substrate, traditional nanofabrication techniques such as e-beam lithography (EBL) are often used in fabricating graphene nanoribbons but the multi-step processes they require can result in contamination of the graphene with resists and solvents. In this letter, we report the utility of scanning helium ion lithography for fabricating functional graphene nanoconductors that are supported directly on a silicon dioxide layer, and we measure the minimum feature size achievable due to limitations imposed by thermal fluctuations and ion scattering during the milling process. Further we demonstrate that ion beams, due to their positive charging nature, may be used to observe and test the conductivity of graphene-based nanoelectronic devices in situ.

  5. Strong electrolyte continuum theory solution for equilibrium profiles, diffusion limitation, and conductance in charged ion channels.

    PubMed Central

    Levitt, D G

    1985-01-01

    The solution for the ion flux through a membrane channel that incorporates the electrolyte nature of the aqueous solution is a difficult theoretical problem that, until now, has not been properly formulated. The difficulty arises from the complicated electrostatic problem presented by a high dielectric aqueous channel piercing a low dielectric lipid membrane. The problem is greatly simplified by assuming that the ratio of the dielectric constant of the water to that of the lipid is infinite. It is shown that this is a good approximation for most channels of biological interest. This assumption allows one to derive simple analytical expressions for the Born image potential and the potential from a fixed charge in the channel, and it leads to a differential equation for the potential from the background electrolyte. This leads to a rigorous solution for the ion flux or the equilibrium potential based on a combination of the Nernst-Planck equation and strong electrolyte theory (i.e., Gouy-Chapman or Debye-Huckel). This approach is illustrated by solving the system of equations for the specific case of a large channel containing fixed negative charges. The following characteristics of this channels are discussed: anion and mono- and divalent cation conductance, saturation of current with increasing concentration, current-voltage relationship, influence of location and valence of fixed charge, and interaction between ions. The qualitative behavior of this channel is similar to that of the acetylcholine receptor channel. PMID:2410048

  6. Effect of mixed transition metal ions on DC conductivity in lithium bismuth borate glasses

    SciTech Connect

    Khasa, S.; Yadav, Arti Dahiya, M. S.; Seema,; Ashima; Agarwal, A.

    2015-06-24

    The DC conductivities of glasses having composition x(2NiO·V{sub 2}O{sub 5})·(30-x)Li{sub 2}O·20Bi{sub 2}O{sub 3}·50B{sub 2}O{sub 3} (with x=0, 2, 5, 7 and 10, i.e. NVLBB glasses) and glass samples having composition 7NiO·23 Li{sub 2}O·20Bi{sub 2}O{sub 3}·50B{sub 2}O{sub 3} and 7V{sub 2}O{sub 5}·23Li{sub 2}O·20Bi{sub 2}O{sub 3}·50B{sub 2}O{sub 3} (NLBB and VLBB respectively) are investigated as a function of temperature. Conductivity for glasses containing higher percentage of lithium ions is predominantly ionic and in glasses containing higher percentage of transition metal (TM) ions is predominantly electronic. The observed increase in conductivity with x and peak-like behavior at x=7 in NVLBB glasses due to competitive transport of small polaron contributing to a significant structural change in NVLBB glasses. Variation of molar volume and density was also observed with x. In NVLBB glasses, as x increases density increases except a slight decrease at x=7. Also density increases in NLBB whereas in case of VLBB it decreases in comparison to NVLBB1 glass composition. Mott’s small polaron hopping (SPH) model has been applied to analyze the high temperature conductivity data and activation energy.

  7. Design of ternary alkaline-earth metal Sn(II) oxides with potential good p-type conductivity

    DOE PAGESBeta

    Du, Mao -Hua; Singh, David J.; Zhang, Lijun; Li, Yuwei; Xu, Qiaoling; Ma, Yanming; Zheng, Weitao

    2016-04-19

    Oxides with good p-type conductivity have been long sought after to achieve high performance all-oxide optoelectronic devices. Divalent Sn(II) based oxides are promising candidates because of their rather dispersive upper valence bands caused by the Sn-5s/O-2p anti-bonding hybridization. There are so far few known Sn(II) oxides being p-type conductive suitable for device applications. Here, we present via first-principles global optimization structure searches a material design study for a hitherto unexplored Sn(II)-based system, ternary alkaline-earth metal Sn(II) oxides in the stoichiometry of MSn2O3 (M = Mg, Ca, Sr, Ba). We identify two stable compounds of SrSn2O3 and BaSn2O3, which can bemore » stabilized by Sn-rich conditions in phase stability diagrams. Their structures follow the Zintl behaviour and consist of basic structural motifs of SnO3 tetrahedra. Unexpectedly they show distinct electronic properties with band gaps ranging from 1.90 (BaSn2O3) to 3.15 (SrSn2O3) eV, and hole effective masses ranging from 0.87 (BaSn2O3) to above 6.0 (SrSn2O3) m0. Further exploration of metastable phases indicates a wide tunability of electronic properties controlled by the details of the bonding between the basic structural motifs. Lastly, this suggests further exploration of alkaline-earth metal Sn(II) oxides for potential applications requiring good p-type conductivity such as transparent conductors and photovoltaic absorbers.« less

  8. Trivalent aluminum ion conducting characteristics in Al{sub 2}(WO{sub 4}){sub 3} single crystals

    SciTech Connect

    Imanaka, N.; Tamura, S.; Hiraiwa, M.; Adachi, G.; Dabkowska, H.; Dabkowski, A.; Greedan, J.E.

    1998-09-01

    Single crystals of the trivalent Al{sup 3+} ion conductor Al{sub 2}(WO{sub 4}){sub 3} were grown by the Czochralski (CZ) method. The ionic conductivity in the a-, b-, and c-axis directions was determined and Al{sup 3+} ion conduction in the direction of the b-axis was concluded to be the most suitable pathway for ion migration in the tungstate grains. The ionic conductivities in the a- and c-axis directions were 0.3 and 10{sup {minus}2} times lower than the conductivity in the b-axis. Consistent with this observation, the lowest activation energy (E{sub a}) for Al{sup 3+} ion migration was obtained for the b-axis direction. The E{sub a} of the conductivity in the direction of the c-axis was almost comparable to that of the polycrystalline samples and the E{sub a} of the Al{sup 3+} ionic conduction in the grains of this material was explicitly verified to be controlled by the Al{sup 3+} ionic migration in the c-axis direction. The Al{sup 3+} ion conductivity of the polycrystalline sample was higher in the higher temperature region, indicating that the conductivity in the grain boundaries enhances the total Al{sup 3+} ion conductivity to a considerable extent. From the oxygen pressure dependencies of the electrical conductivity and the polarization behavior, the single crystals were demonstrated to be pure Al{sup 3+} ionic conductors showing an anisotropic ion conducting behavior.

  9. Alternative configuration scheme for signal amplification with scanning ion conductance microscopy

    NASA Astrophysics Data System (ADS)

    Kim, Joonhui; Kim, Seong-Oh; Cho, Nam-Joon

    2015-02-01

    Scanning Ion Conductance Microscopy (SICM) is an emerging nanotechnology tool to investigate the morphology and charge transport properties of nanomaterials, including soft matter. SICM uses an electrolyte filled nanopipette as a scanning probe and detects current changes based on the distance between the nanopipette apex and the target sample in an electrolyte solution. In conventional SICM, the pipette sensor is excited by applying voltage as it raster scans near the surface. There have been attempts to improve upon raster scanning because it can induce collisions between the pipette sidewalls and target sample, especially for soft, dynamic materials (e.g., biological cells). Recently, Novak et al. demonstrated that hopping probe ion conductance microscopy (HPICM) with an adaptive scan method can improve the image quality obtained by SICM for such materials. However, HPICM is inherently slower than conventional raster scanning. In order to optimize both image quality and scanning speed, we report the development of an alternative configuration scheme for SICM signal amplification that is based on applying current to the nanopipette. This scheme overcomes traditional challenges associated with low bandwidth requirements of conventional SICM. Using our alternative scheme, we demonstrate successful imaging of L929 fibroblast cells and discuss the capabilities of this instrument configuration for future applications.

  10. Ion Conductance of the Stem of the Anthrax Toxin Channel during Lethal Factor Translocation

    PubMed Central

    Schiffmiller, Aviva; Finkelstein, Alan

    2014-01-01

    The tripartite anthrax toxin consists of protective antigen (PA), lethal factor (LF), and edema factor (EF). PA63 (the 63 kDa, C-terminal part of PA) forms heptameric channels in cell membranes that allow for the transport of LF and EF into the cytosol. These channels are mushroom-shaped, with a ring of seven phenylalanine residues (known as the phenylalanine clamp) lining the junction between the cap and stem. It is known that when LF is translocated through the channel, the phenylalanine clamp creates a seal that causes an essentially complete block of conduction. In order to examine ion conductance in the stem of the channel, we used Venus yellow fluorescent protein (YFP) as a molecular stopper to trap LFN (the 30 kDa, 263-residue N-terminal segment of LF), and various truncated constructs of LFN, in mutant channels in which the phenylalanine clamp residues were mutated to alanines. Here we present evidence that ion movement occurs within the channel stem (but is stopped, of course, at the phenylalanine clamp) during protein translocation. Furthermore, we also propose that the lower region of the stem plays an important role in securing peptide chains during translocation. PMID:24996036

  11. Conductive Polymer-Coated VS4 Submicrospheres As Advanced Electrode Materials in Lithium-Ion Batteries.

    PubMed

    Zhou, Yanli; Li, Yanlu; Yang, Jing; Tian, Jian; Xu, Huayun; Yang, Jian; Fan, Weiliu

    2016-07-27

    VS4 as an electrode material in lithium-ion batteries holds intriguing features like high content of sulfur and one-dimensional structure, inspiring the exploration in this field. Herein, VS4 submicrospheres have been synthesized via a simple solvothermal reaction. However, they quickly degrade upon cycling as an anode material in lithium-ion batteries. So, three conductive polymers, polythiophene (PEDOT), polypyrrole (PPY), and polyaniline (PANI), are coated on the surface to improve the electron conductivity, suppress the diffusion of polysulfides, and modify the interface between electrode/electrolyte. PANI is the best in the polymers. It improves the Coulombic efficiency to 86% for the first cycle and keeps the specific capacity at 755 mAh g(-1) after 50 cycles, higher than the cases of naked VS4 (100 mAh g(-1)), VS4@PEDOT (318 mAh g(-1)), and VS4@PPY (448 mAh g(-1)). The good performances could be attributed to the improved charge-transfer kinetics and the strong interaction between PANI and VS4 supported by theoretical simulation. The discharge voltage ∼2.0 V makes them promising cathode materials. PMID:27377263

  12. Scanning ion conductance microscopy (SICM): from measuring cell mechanical properties to guiding neuron growth

    NASA Astrophysics Data System (ADS)

    Pellegrino, Mario; Orsini, Paolo; Pellegrini, Monica; Tognoni, Elisabetta; Ascoli, Cesare; Baschieri, Paolo; Dinelli, Franco

    2013-04-01

    Scanning ion conductance microscopy (SICM) is a type of scanning probe microscopy based on the continuous measurement of an ion current flowing through a pipette filled with an electrolyte solution, while the pipette apex approaches a non-conductive sample. This technique can be operated in environmental conditions such as those of cell cultures and does not require a direct contact between probe and sample. It is therefore particularly suitable for the investigation of living specimens. SICM was initially proposed as an instrument that could obtain topographic 3D images with high resolution. Later, simple modifications have been devised to apply a mechanical stimulus to the specimen via a solution flux coming out from the pipette aperture. This modified setup has been employed to measure cell membrane elasticity and to guide the growth cones of neurons for tens of micrometers, by means of repeated non-contact scanning. Both these applications require an accurate measurement of the mechanical forces acting on the cell surface, which can be obtained by combining SICM, Atomic force microscopy (AFM) and inverted optical microscopy in the same apparatus. In this configuration, a SICM pipette is approached to an AFM cantilever while monitoring the cantilever deflection as a function of the pressure applied to the pipette and the relative distance. In addition, the pipette aperture can be imaged in situ by exploiting the AFM operation, so that all the experimental parameters can be effectively controlled in the investigation of pressure effects on living cells.

  13. Lithium-Ion-Conducting Electrolytes: From an Ionic Liquid to the Polymer Membrane

    PubMed Central

    Fernicola, A.; Weise, F. C.; Greenbaum, S. G.; Kagimoto, J.; Scrosati, B.; Soleto, A.

    2009-01-01

    This work concerns the design, the synthesis, and the characterization of the N-butyl-N-ethylpiperidinium N,N-bis(trifluoromethane)sulfonimide (PP24TFSI) ionic liquid (IL). To impart Li-ion transport, a suitable amount of lithium N,N-bis-(trifluoromethane)sulfonimide (LiTFSI) is added to the IL. The Li–IL mixture displays ionic conductivity values on the order of 10−4 S cm−1 and an electrochemical stability window in the range of 1.8–4.5 V vs Li+/Li. The voltammetric analysis demonstrates that the cathodic decomposition gives rise to a passivating layer on the surface of the working electrode, which kinetically extends the stability of the Li/IL interface as confirmed by electrochemical impedance spectroscopy measurements. The LiTFSI–PP24TFSI mixture is incorporated in a poly(vinylidene fluoride-co-hexafluoropropylene) matrix to form various electrolyte membranes with different LiTFSI–PP24TFSI contents. The ionic conductivity of all the membranes resembles that of the LiTFSI–IL mixture, suggesting an ionic transport mechanism similar to that of the liquid component. NMR measurements demonstrate a reduction in the mobility of all ions following the addition of LiTFSI to the PP24TFSI IL and when incorporating the mixture into the membrane. Finally, an unexpected but potentially significant enhancement in Li transference number is observed in passing from the liquid to the membrane electrolyte system. PMID:20354582

  14. Insulated Conducting Cantilevered Nanotips and Two-Chamber Recording System for High Resolution Ion Sensing AFM

    PubMed Central

    Meckes, Brian; Arce, Fernando Teran; Connelly, Laura S.; Lal, Ratnesh

    2014-01-01

    Biological membranes contain ion channels, which are nanoscale pores allowing controlled ionic transport and mediating key biological functions underlying normal/abnormal living. Synthetic membranes with defined pores are being developed to control various processes, including filtration of pollutants, charge transport for energy storage, and separation of fluids and molecules. Although ionic transport (currents) can be measured with single channel resolution, imaging their structure and ionic currents simultaneously is difficult. Atomic force microscopy enables high resolution imaging of nanoscale structures and can be modified to measure ionic currents simultaneously. Moreover, the ionic currents can also be used to image structures. A simple method for fabricating conducting AFM cantilevers to image pore structures at high resolution is reported. Tungsten microwires with nanoscale tips are insulated except at the apex. This allows simultaneous imaging via cantilever deflections in normal AFM force feedback mode as well as measuring localized ionic currents. These novel probes measure ionic currents as small as picoampere while providing nanoscale spatial resolution surface topography and is suitable for measuring ionic currents and conductance of biological ion channels. PMID:24663394

  15. Alternative configuration scheme for signal amplification with scanning ion conductance microscopy.

    PubMed

    Kim, Joonhui; Kim, Seong-Oh; Cho, Nam-Joon

    2015-02-01

    Scanning Ion Conductance Microscopy (SICM) is an emerging nanotechnology tool to investigate the morphology and charge transport properties of nanomaterials, including soft matter. SICM uses an electrolyte filled nanopipette as a scanning probe and detects current changes based on the distance between the nanopipette apex and the target sample in an electrolyte solution. In conventional SICM, the pipette sensor is excited by applying voltage as it raster scans near the surface. There have been attempts to improve upon raster scanning because it can induce collisions between the pipette sidewalls and target sample, especially for soft, dynamic materials (e.g., biological cells). Recently, Novak et al. demonstrated that hopping probe ion conductance microscopy (HPICM) with an adaptive scan method can improve the image quality obtained by SICM for such materials. However, HPICM is inherently slower than conventional raster scanning. In order to optimize both image quality and scanning speed, we report the development of an alternative configuration scheme for SICM signal amplification that is based on applying current to the nanopipette. This scheme overcomes traditional challenges associated with low bandwidth requirements of conventional SICM. Using our alternative scheme, we demonstrate successful imaging of L929 fibroblast cells and discuss the capabilities of this instrument configuration for future applications. PMID:25725851

  16. Electrodiffusion of ions approaching the mouth of a conducting membrane channel.

    PubMed Central

    Peskoff, A; Bers, D M

    1988-01-01

    The movement of ions in the aqueous medium as they approach the mouth (radius a) of a conducting membrane channel is analyzed. Starting with the Nernst-Planck and Poisson equations, we derive a nonlinear integrodifferential equation for the electric potential, phi(r), a less than or equal to r less than infinity. The formulation allows deviations from charge neutrality and dependence of phi(r) on ion flux. A numerical solution is obtained by converting the equation to an integral equation that is solved by an iterative method for an assumed mouth potential, combined with a shooting method to adjust the mouth potential until the numerical solution agrees with an asymptotic expansion of the potential at r-a much greater than lambda (lambda = Debye length). Approximate analytic solutions are obtained by assuming charge neutrality (Läuger, 1976) and by linearizing. The linear approximation agrees with the exact solution under most physiological conditions, but the charge-neutrality solution is only valid for r much greater than lambda and thus cannot be used unless a much greater than lambda. Families of curves of ion flux vs. potential drop across the electrolyte, phi(infinity)-phi (a), and of permeant ion density at the channel mouth, n1(a), vs. flux are obtained for different values of a/lambda and S = a d phi/dr(a). If a much greater than lambda and S = O, the maximum flux (which is approached when n1(a)----0) is reduced by 50% compared to the value predicted by the charge-neutrality solution. Access resistance is shown to be a factor a/[2 (a + lambda)] times the published formula (Hille, 1968), which was derived without including deviations from charge neutrality and ion density gradients and hence does not apply when there is no counter-ion current. The results are applied to an idealized diffusion-limited channel with symmetric electrolytes. For S = O, the current/voltage curves saturate at a value dependent on a/lambda; for S greater than O, they increase

  17. In vitro exposure to Escherichia coli decreases ion conductance in the jejunal epithelium of broiler chickens.

    PubMed

    Awad, Wageha A; Hess, Claudia; Khayal, Basel; Aschenbach, Jörg R; Hess, Michael

    2014-01-01

    Escherichia coli (E. coli) infections are very widespread in poultry. However, little is known about the interaction between the intestinal epithelium and E. coli in chickens. Therefore, the effects of avian non-pathogenic and avian pathogenic Escherichia coli (APEC) on the intestinal function of broiler chickens were investigated by measuring the electrogenic ion transport across the isolated jejunal mucosa. In addition, the intestinal epithelial responses to cholera toxin, histamine and carbamoylcholine (carbachol) were evaluated following an E. coli exposure. Jejunal tissues from 5-week-old broilers were exposed to 6×10(8) CFU/mL of either avian non-pathogenic E. coli IMT11322 (Ont:H16) or avian pathogenic E. coli IMT4529 (O24:H4) in Ussing chambers and electrophysiological variables were monitored for 1 h. After incubation with E. coli for 1 h, either cholera toxin (1 mg/L), histamine (100 μM) or carbachol (100 μM) were added to the incubation medium. Both strains of avian E. coli (non-pathogenic and pathogenic) reduced epithelial ion conductance (Gt) and short-circuit current (Isc). The decrease in ion conductance after exposure to avian pathogenic E. coli was, at least, partly reversed by the histamine or carbachol treatment. Serosal histamine application produced no significant changes in the Isc in any tissues. Only the uninfected control tissues responded significantly to carbachol with an increase of Isc, while the response to carbachol was blunted to non-significant values in infected tissues. Together, these data may explain why chickens rarely respond to intestinal infections with overt secretory diarrhea. Instead, the immediate response to intestinal E. coli infections appears to be a tightening of the epithelial barrier. PMID:24637645

  18. In Vitro Exposure to Escherichia coli Decreases Ion Conductance in the Jejunal Epithelium of Broiler Chickens

    PubMed Central

    Awad, Wageha A.; Hess, Claudia; Khayal, Basel; Aschenbach, Jörg R.; Hess, Michael

    2014-01-01

    Escherichia coli (E. coli) infections are very widespread in poultry. However, little is known about the interaction between the intestinal epithelium and E. coli in chickens. Therefore, the effects of avian non-pathogenic and avian pathogenic Escherichia coli (APEC) on the intestinal function of broiler chickens were investigated by measuring the electrogenic ion transport across the isolated jejunal mucosa. In addition, the intestinal epithelial responses to cholera toxin, histamine and carbamoylcholine (carbachol) were evaluated following an E. coli exposure. Jejunal tissues from 5-week-old broilers were exposed to 6×108 CFU/mL of either avian non-pathogenic E. coli IMT11322 (Ont:H16) or avian pathogenic E. coli IMT4529 (O24:H4) in Ussing chambers and electrophysiological variables were monitored for 1 h. After incubation with E. coli for 1 h, either cholera toxin (1 mg/L), histamine (100 μM) or carbachol (100 μM) were added to the incubation medium. Both strains of avian E. coli (non-pathogenic and pathogenic) reduced epithelial ion conductance (Gt) and short-circuit current (Isc). The decrease in ion conductance after exposure to avian pathogenic E. coli was, at least, partly reversed by the histamine or carbachol treatment. Serosal histamine application produced no significant changes in the Isc in any tissues. Only the uninfected control tissues responded significantly to carbachol with an increase of Isc, while the response to carbachol was blunted to non-significant values in infected tissues. Together, these data may explain why chickens rarely respond to intestinal infections with overt secretory diarrhea. Instead, the immediate response to intestinal E. coli infections appears to be a tightening of the epithelial barrier. PMID:24637645

  19. Ion Torrent sequencing for conducting genome-wide scans for mutation mapping analysis.

    PubMed

    Damerla, Rama Rao; Chatterjee, Bishwanath; Li, You; Francis, Richard J B; Fatakia, Sarosh N; Lo, Cecilia W

    2014-04-01

    Mutation mapping in mice can be readily accomplished by genome wide segregation analysis of polymorphic DNA markers. In this study, we showed the efficacy of Ion Torrent next generation sequencing for conducting genome-wide scans to map and identify a mutation causing congenital heart disease in a mouse mutant, Bishu, recovered from a mouse mutagenesis screen. The Bishu mutant line generated in a C57BL/6J (B6) background was intercrossed with another inbred strain, C57BL/10J (B10), and the resulting B6/B10 hybrid offspring were intercrossed to generate mutants used for the mapping analysis. For each mutant sample, a panel of 123 B6/B10 polymorphic SNPs distributed throughout the mouse genome was PCR amplified, bar coded, and then pooled to generate a single library used for Ion Torrent sequencing. Sequencing carried out using the 314 chip yielded >600,000 usable reads. These were aligned and mapped using a custom bioinformatics pipeline. Each SNP was sequenced to a depth >500×, allowing accurate automated calling of the B6/B10 genotypes. This analysis mapped the mutation in Bishu to an interval on the proximal region of mouse chromosome 4. This was confirmed by parallel capillary sequencing of the 123 polymorphic SNPs. Further analysis of genes in the map interval identified a splicing mutation in Dnaic1(c.204+1G>A), an intermediate chain dynein, as the disease causing mutation in Bishu. Overall, our experience shows Ion Torrent amplicon sequencing is high throughput and cost effective for conducting genome-wide mapping analysis and is easily scalable for other high volume genotyping analyses. PMID:24306492

  20. The role of cystic fibrosis transmembrane conductance regulator phenylalanine 508 side chain in ion channel gating.

    PubMed

    Cui, Liying; Aleksandrov, Luba; Hou, Yue-Xian; Gentzsch, Martina; Chen, Jey-Hsin; Riordan, John R; Aleksandrov, Andrei A

    2006-04-15

    Cystic fibrosis transmembrane conductance regulator (CFTR) is an ion channel employing the ABC transporter structural motif. Deletion of a single residue (Phe508) in the first nucleotide-binding domain (NBD1), which occurs in most patients with cystic fibrosis, impairs both maturation and function of the protein. However, substitution of the Phe508 with small uncharged amino acids, including cysteine, is permissive for maturation. To explore the possible role of the phenylalanine aromatic side chain in channel gating we introduced a cysteine at this position in cysless CFTR, enabling its selective chemical modification by sulfhydryl reagents. Both cysless and wild-type CFTR ion channels have identical mean open times when activated by different nucleotide ligands. Moreover, both channels could be locked in an open state by introducing an ATPase inhibiting mutation (E1371S). However, the introduction of a single cysteine (F508C) prevented the cysless E1371S channel from maintaining the permanently open state, allowing closing to occur. Chemical modification of cysless E1371S/F508C by sulfhydryl reagents was used to probe the role of the side chain in ion channel function. Specifically, benzyl-methanethiosulphonate modification of this variant restored the gating behaviour to that of cysless E1371S containing the wild-type phenylalanine at position 508. This provides the first direct evidence that a specific interaction of the Phe508 aromatic side chain plays a role in determining the residency time in the closed state. Thus, despite the fact that this aromatic side chain is not essential for CFTR folding, it is important in the ion channel function. PMID:16484308

  1. The role of cystic fibrosis transmembrane conductance regulator phenylalanine 508 side chain in ion channel gating

    PubMed Central

    Cui, Liying; Aleksandrov, Luba; Hou, Yue-Xian; Gentzsch, Martina; Chen, Jey-Hsin; Riordan, John R; Aleksandrov, Andrei A

    2006-01-01

    Cystic fibrosis transmembrane conductance regulator (CFTR) is an ion channel employing the ABC transporter structural motif. Deletion of a single residue (Phe508) in the first nucleotide-binding domain (NBD1), which occurs in most patients with cystic fibrosis, impairs both maturation and function of the protein. However, substitution of the Phe508 with small uncharged amino acids, including cysteine, is permissive for maturation. To explore the possible role of the phenylalanine aromatic side chain in channel gating we introduced a cysteine at this position in cysless CFTR, enabling its selective chemical modification by sulfhydryl reagents. Both cysless and wild-type CFTR ion channels have identical mean open times when activated by different nucleotide ligands. Moreover, both channels could be locked in an open state by introducing an ATPase inhibiting mutation (E1371S). However, the introduction of a single cysteine (F508C) prevented the cysless E1371S channel from maintaining the permanently open state, allowing closing to occur. Chemical modification of cysless E1371S/F508C by sulfhydryl reagents was used to probe the role of the side chain in ion channel function. Specifically, benzyl-methanethiosulphonate modification of this variant restored the gating behaviour to that of cysless E1371S containing the wild-type phenylalanine at position 508. This provides the first direct evidence that a specific interaction of the Phe508 aromatic side chain plays a role in determining the residency time in the closed state. Thus, despite the fact that this aromatic side chain is not essential for CFTR folding, it is important in the ion channel function. PMID:16484308

  2. Mechanism for proton conduction of the M(2) ion channel of influenza A virus.

    PubMed

    Mould, J A; Li, H C; Dudlak, C S; Lear, J D; Pekosz, A; Lamb, R A; Pinto, L H

    2000-03-24

    The M(2) integral membrane protein of influenza A virus forms a proton-selective ion channel. We investigated the mechanism for proton transport of the M(2) protein in Xenopus oocytes using a two-electrode voltage clamp and in CV-1 cells using the whole cell patch clamp technique. Membrane currents were recorded while manipulating the external solution to alter either the total or free proton concentration or the solvent itself. Membrane conductance decreased by approximately 50% when D(2)O replaced H(2)O as the solvent. From this, we conclude that hydrogen ions do not pass through M(2) as hydronium ions, but instead must interact with titratable groups that line the pore of the channel. M(2) currents measured in solutions of low buffer concentration (<15 mM in oocytes and <0.15 mM in CV-1 cells) were smaller than those studied in solutions of high buffer concentration. Furthermore, the reversal voltage measured in low buffer was shifted to a more negative voltage than in high buffer. Also, at a given pH, M(2) current amplitude in 15 mM buffer decreased when pH-pK(a) was increased by changing the buffer pK(a). Collectively, these results demonstrate that M(2) currents can be limited by external buffer capacity. The data presented in this study were also used to estimate the maximum single channel current of the M(2) ion channel, which was calculated to be on the order of 1-10 fA. PMID:10722698

  3. Luminescent activation of planar optical waveguides in LiNbO 3 with rare earth ions Ln 3+ - a review

    NASA Astrophysics Data System (ADS)

    Tsonev, Lyubomir

    2008-02-01

    Based on the publications during the period 1990-2006, an attempt is made to summarize some of the important tendencies in integrated optics as well as the different techniques for activating lithium niobate by doping it with rare earth (lanthanide) ions. Luminescence properties of lanthanide ions in lithium niobate and in other hosts are reviewed in relation with their application in active thin film optical devices. The technological problems reported by different authors are commented. The possibilities for producing active waveguiding devices in lithium niobate only by low-temperature processes are discussed.

  4. Robust quantum gates and a bus architecture for quantum computing with rare-earth-ion-doped crystals

    SciTech Connect

    Wesenberg, Janus; Moelmer, Klaus

    2003-07-01

    We present a composite pulse controlled phase gate which, together with a bus architecture, improves the feasibility of a recent quantum computing proposal based on rare-earth-ion-doped crystals. The proposed gate operation is tolerant to variations between ions of coupling strengths, pulse lengths, and frequency shifts. In the absence of decoherence effects, it achieves worst case fidelities above 0.999 with relative variations in coupling strength as high as 10% and frequency shifts up to several percent of the resonant Rabi frequency of the laser used to implement the gate. We outline an experiment to demonstrate the creation and detection of maximally entangled states in the system.

  5. The ionic transport mechanism and coupling between the ion conduction and segmental relaxation processes of PEO20-LiCF3SO3 based ion conducting polymer clay composites.

    PubMed

    Dam, Tapabrata; Jena, Sidhartha S; Pradhan, Dillip K

    2016-07-20

    A series of ion conducting polymer-clay composites has been prepared using a solution casting technique. Relaxation dynamics and the ionic transport mechanism are systematically studied employing broadband dielectric spectroscopy over a wide frequency and temperature range. Among different phenomenological and theoretical models for ion conduction in disordered ionic conductors, conductivity isotherm spectra are analysed using the modified Almond-West and random free energy barrier model. Conductivity scaling suggests that the ionic transport mechanism is independent of temperature, and a similar inference is also obtained using scaled electrical modulus spectra. DC conductivity along with conductivity and segmental relaxation time following the Vogel-Tammann-Fulcher relationship suggests coupling between the ionic transport and segmental relaxation processes. Electrical modulus and dielectric formalism are used to understand the conductivity and segmental relaxation processes, respectively. The presence of first and second universality in the ionic transport mechanism is discussed using the real part of conductivity spectra and dielectric loss spectra. The crossover between the first and second universality is explained using the Kramer-Krönig approach. The ion diffusion coefficient is investigated using Ratner's classical approach in combination with the modified Stokes-Einstein relationship to correlate the coupled nature of the ion conduction mechanism and polymer segmental motion. PMID:27399598

  6. Increasing the intensity of protonated secondary ions in time-of-flight secondary ion mass spectrometry using a proton-conducting ionic liquid, diethylmethylammonium trifluoromethanesulfonate

    NASA Astrophysics Data System (ADS)

    Fujiwara, Yukio; Saito, Naoaki

    2015-07-01

    To increase the secondary ion intensities of organic molecules, room-temperature ionic liquids were investigated in two time-of-flight secondary ion mass spectrometry (TOF-SIMS) experiments. First, ionic liquids as well as glycerol were tested as liquid matrices of arginine. The secondary ion intensity of protonated arginine was increased 200-fold by using a proton-conducting ionic liquid, diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]). The matrix effect of [dema][TfO] was higher than that of glycerol, which is a typical matrix in SIMS. Next, ionic liquids were tested as primary ion beams. The number of protonated secondary ions of arginine was significantly increased by using a primary ion beam of [dema][TfO].

  7. Effect of Rare Earth Ions on the Properties of Composites Composed of Ethylene Vinyl Acetate Copolymer and Layered Double Hydroxides

    PubMed Central

    Wang, Lili; Li, Bin; Zhao, Xiaohong; Chen, Chunxia; Cao, Jingjing

    2012-01-01

    Background The study on the rare earth (RE)-doped layered double hydroxides (LDHs) has received considerable attention due to their potential applications in catalysts. However, the use of RE-doped LDHs as polymer halogen-free flame retardants was seldom investigated. Furthermore, the effect of rare earth elements on the hydrophobicity of LDHs materials and the compatibility of LDHs/polymer composite has seldom been reported. Methodology/Principal Findings The stearate sodium surface modified Ni-containing LDHs and RE-doped Ni-containing LDHs were rapidly synthesized by a coprecipitation method coupled with the microwave hydrothermal treatment. The influences of trace amounts of rare earth ions La, Ce and Nd on the amount of water molecules, the crystallinity, the morphology, the hydrophobicity of modified Ni-containing LDHs and the adsorption of modifier in the surface of LDHs were investigated by TGA, XRD, TEM, contact angle and IR, respectively. Moreover, the effects of the rare earth ions on the interfacial compatibility, the flame retardancy and the mechanical properties of ethylene vinyl acetate copolymer (EVA)/LDHs composites were also explored in detail. Conclusions/Significance S-Ni0.1MgAl-La displayed more uniform dispersion and better interfacial compatibility in EVA matrix compared with other LDHs. Furthermore, the S-Ni0.1MgAl-La/EVA composite showed the best fire retardancy and mechanical properties in all composites. PMID:22693627

  8. Novel rare earth ions-doped oxyfluoride nano-composite with efficient upconversion white-light emission

    SciTech Connect

    Chen Daqin; Wang Yuansheng Yu Yunlong; Huang Ping; Weng Fangyi

    2008-10-15

    Transparent SiO{sub 2}-Al{sub 2}O{sub 3}-NaF-YF{sub 3} bulk nano-composites triply doped with Ho{sup 3+}, Tm{sup 3+} and Yb{sup 3+} were fabricated by melt-quenching and subsequent heating. X-ray diffraction and transmission electron microscopy measurements demonstrated the homogeneous precipitation of the {beta}-YF{sub 3} crystals with mean size of 20 nm among the glass matrix, and rare earth ions were found to partition into these nano-crystals. Under single 976 nm laser excitation, intense red, green and blue upconversion emissions were simultaneously observed owing to the successive energy transfer from Yb{sup 3+} to Ho{sup 3+} or Tm{sup 3+}. Various colors of luminescence, including bright perfect white light, can be easily tuned by adjusting the concentrations of the rare earth ions in the material. The overall energy efficiency of the white-light upconversion was estimated to be about 0.2%. - Graphical abstract: Under single 976 nm laser excitation, intense red, green and blue upconversion emissions were simultaneously observed owing to the successive energy transfer from Yb{sup 3+} to Ho{sup 3+} or Tm{sup 3+}. Various colors of luminescence, including bright perfect white light with CIE-X=0.351 and CIE-Y=0.306, can be easily tuned by adjusting the concentrations of the rare earth ions in the transparent oxyfluoride glass ceramics.

  9. Development of High Conductivity Lithium-Ion Electrolytes for Low Temperature Cell Applications

    NASA Technical Reports Server (NTRS)

    Smart, M. C.; Ratnakumar, B. V.; Surampudi, S.

    1998-01-01

    NASA has continued interest in developing power sources which are capable of operating at low temperatures (-20 C and below) to enable future missions, such as the Mars Rover and Lander. Thus, under a program sponsored by the Mars Exploration Program, we have been involved in developing Li-ion batteries with improved low temperature performance. To accomplish this task, the focus of the research has been upon the development of advanced electrolyte systems with improved low temperature properties. This had led to the identification of a carbonate-based electrolyte, consisting of 1.0 M LiPF6 in EC + DEC + DMC (33:33:34), which has been shown to have excellent performance at -20 C in Li-ion AA-size prototype cells. Other groups are also actively engaged in developing electrolytes which can result in improved low temperature performance of Li-ion cells, including Polystor, Yardney, and Covalent. In addition to developing cells capable of operation at -20 C, there is continued interest in systems which can successfully operate at even lower temperatures (less than -30 C) and at high discharge rates (greater than C/2). Thus, we are currently focusing upon developing advanced electrolytes which are highly conductive at low temperatures and will result in cells capable of operation at -40 C. One approach to improve the low temperature conductivity of ethylene carbonate-based electrolytes involves adding co-solvents which will decrease the viscosity and extend the liquid range. Candidate solvent additives include formates, acetates, cyclic and aliphatic ethers, lactones, as well as other carbonates. Using this approach, we have prepared a number of electrolytes which contain methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), ethyl proprionate (EP), and 1,2-dimethoxyethane (DME), some of which have been characterized and reported. Other groups have also reported electrolytes based on mixtures of carbonates and acetates. In the present study, electrolytes which

  10. Direct Imaging of Nanoscale Conductance Evolution in Ion-Gel-Gated Oxide Transistors.

    PubMed

    Ren, Yuan; Yuan, Hongtao; Wu, Xiaoyu; Chen, Zhuoyu; Iwasa, Yoshihiro; Cui, Yi; Hwang, Harold Y; Lai, Keji

    2015-07-01

    Electrostatic modification of functional materials by electrolytic gating has demonstrated a remarkably wide range of density modulation, a condition crucial for developing novel electronic phases in systems ranging from complex oxides to layered chalcogenides. Yet little is known microscopically when carriers are modulated in electrolyte-gated electric double-layer transistors (EDLTs) due to the technical challenge of imaging the buried electrolyte-semiconductor interface. Here, we demonstrate the real-space mapping of the channel conductance in ZnO EDLTs using a cryogenic microwave impedance microscope. A spin-coated ionic gel layer with typical thicknesses below 50 nm allows us to perform high resolution (on the order of 100 nm) subsurface imaging, while maintaining the capability of inducing the metal-insulator transition under a gate bias. The microwave images vividly show the spatial evolution of channel conductance and its local fluctuations through the transition as well as the uneven conductance distribution established by a large source-drain bias. The unique combination of ultrathin ion-gel gating and microwave imaging offers a new opportunity to study the local transport and mesoscopic electronic properties in EDLTs. PMID:26061780

  11. Incorporation of conductive polymer into soft carbon electrodes for lithium ion capacitors

    NASA Astrophysics Data System (ADS)

    Lim, Young-Geun; Park, Min-Sik; Kim, Ki Jae; Jung, Kyu-Sung; Kim, Jung Ho; Shahabuddin, Mohammed; Byun, Dongjin; Yu, Ji-Sang

    2015-12-01

    The positive effects of incorporating electrically conductive poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT-PSS) into the negative electrode (NE) of a lithium ion capacitor (LIC) is investigated. The binding material of the NE, styrene-butadiene rubber (SBR), is partially substituted by conductive PEDOT-PSS. The soft carbon NE with 1.0 wt% PEDOT-PSS exhibits enhanced capacity retention of 64% at a current density of 5 C by lowering its electrical and electrochemical charge transfer resistance. The rate capability increased with increasing amounts of PEDOT-PSS, with no variation in the Li+ diffusivity. This improved electrochemical performance of the NE is also reflected in the LIC full-cell configuration. An LIC employing a 1.0 wt% PEDOT-PSS NE delivers 6.6 F at a high current density of 100 C, which is higher than the 6.0 F measured for the LIC with a bare NE. Moreover, the LIC with the 1.0 wt% PEDOT-PSS NE retains 85% of its initial capacitance even after 5000 cycles. These results are mainly attributed to the favourable electrical network formed by the incorporation of PEDOT-PSS into the NE. Thus, we believe that the incorporation of conductive PEDOT-PSS is a viable approach for obtaining high-power LICs.

  12. Enhancement of Li+ ion conductivity in solid polymer electrolytes using surface tailored porous silica nanofillers

    NASA Astrophysics Data System (ADS)

    Mohanta, Jagdeep; Singh, Udai P.; Panda, Subhendu K.; Si, Satyabrata

    2016-09-01

    The current study represents the design and synthesis of polyethylene oxide (PEO)-based solid polymer electrolytes by solvent casting approach using surface tailored porous silica as nanofillers. The surface tailoring of porous silica nanostructure is achieved through silanization chemistry using 3-glycidyloxypropyl trimethoxysilane in which silane part get anchored to the silica surface whereas epoxy group get stellated from the silica surface. Surface tailoring of silica with epoxy group increases the room temperature electrochemical performances of the resulting polymer electrolytes. Ammonical hydrolysis of organosilicate precursor is used for both silica preparation and their surface tailoring. The composite solid polymer electrolyte films are prepared by solution mixing of PEO with lithium salt in presence of silica nanofillers and cast into film by solvent drying, which are then characterized by impedance measurement for conductivity study and wide angle x-ray diffraction for change in polymer crystallinity. Room temperature impedance measurement reveals Li+ ion conductivity in the order of 10‑4 S cm‑1, which is correlated to the decrease in PEO crystallinity. The enhancement of conductivity is further observed to be dependent on the amount of silica as well as on their surface characteristics.

  13. Thermal conductivity and nanocrystalline structure of platinum deposited by focused ion beam

    NASA Astrophysics Data System (ADS)

    Alaie, Seyedhamidreza; Goettler, Drew F.; Jiang, Ying-Bing; Abbas, Khawar; Ghasemi Baboly, Mohammadhosein; Anjum, D. H.; Chaieb, S.; Leseman, Zayd C.

    2015-02-01

    Pt deposited by focused ion beam (FIB) is a common material used for attachment of nanosamples, repair of integrated circuits, and synthesis of nanostructures. Despite its common use little information is available on its thermal properties. In this work, Pt deposited by FIB is characterized thermally, structurally, and chemically. Its thermal conductivity is found to be substantially lower than the bulk value of Pt, 7.2 W m-1 K-1 versus 71.6 W m-1 K-1 at room temperature. The low thermal conductivity is attributed to the nanostructure of the material and its chemical composition. Pt deposited by FIB is shown, via aberration corrected TEM, to be a segregated mix of nanocrystalline Pt and amorphous C with Ga and O impurities. Ga impurities mainly reside in the Pt while O is homogeneously distributed throughout. The Ga impurity, small grain size of the Pt, and the amorphous carbon between grains are the cause for the low thermal conductivity of this material. Since Pt deposited by FIB is a common material for affixing samples, this information can be used to assess systematic errors in thermal characterization of different nanosamples. This application is also demonstrated by thermal characterization of two carbon nanofibers and a correction using the reported thermal properties of the Pt deposited by FIB.

  14. Ion and molecule sensors using molecular recognition in luminescent, conductive polymers. FY 1997 year-end progress report

    SciTech Connect

    Wasielewski, M.R.

    1997-01-01

    'The purpose of this project is to use molecular recognition strategies to develop sensor technology based on luminescent, conductive polymers that contain sites for binding specific molecules or ions in the presence of related molecules or ions. Selective binding of a particular molecule or ion of interest to these polymers will result in a large change in their luminescence and/or conductivity, which can be used to both qualitatively and quantitatively sense the presence of the bound molecules or ions. The main thrusts and accomplishments in the first year of this project involve developing polymer syntheses that yield conjugated polymers to which a wide variety of ligands for metal ion binding can be readily incorporated.'

  15. Full 3-D TLM simulations of the Earth-ionosphere cavity: Effect of conductivity on the Schumann resonances

    NASA Astrophysics Data System (ADS)

    Toledo-Redondo, S.; Salinas, A.; Fornieles, J.; Portí, J.; Lichtenegger, H. I. M.

    2016-06-01

    Schumann resonances can be found in planetary atmospheres, inside the cavity formed by the conducting surface of the planet and the lower ionosphere. They are a powerful tool to investigate both the electric processes that occur in the atmosphere and the characteristics of the surface and the lower ionosphere. Results from a full 3-D model of the Earth-ionosphere electromagnetic cavity based on the Transmission-Line Modeling (TLM) method are presented. A Cartesian scheme with homogeneous cell size of 10 km is used to minimize numerical dispersion present in spherical schemes. Time and frequency domain results have been obtained to study the resonance phenomenon. The effect of conductivity on the Schumann resonances in the cavity is investigated by means of numerical simulations, studying the transition from resonant to nonresonant response and setting the conductivity limit for the resonances to develop inside the cavity. It is found that the transition from resonant to nonresonant behavior occurs for conductivity values above roughly 10-9 S/m. For large losses in the cavity, the resonances are damped, but, in addition, the peak frequencies change according to the local distance to the source and with the particular electromagnetic field component. These spatial variations present steep variations around each mode's nodal position, covering distances around 1/4 of the mode wavelength, the higher modes being more sensitive to this effect than the lower ones. The dependence of the measured frequency on the distance to the source and particular component of the electric field offers information on the source generating these resonances.

  16. Self-Depolarization Studies on Some Fast Ag+ Ion Conducting Glasses

    NASA Astrophysics Data System (ADS)

    Agrawal, R. C.; Verma, M. L.; Bhatt, A.

    2002-12-01

    A novel technique based on the dc polarization method is being reported to study polarization/self-depolarization phenomenon in some fast Ag+ ion conducting glass systems viz.: 0.8[0.75AgI: 0.25AgCl]: 0.2[Ag2O: MoO3] & 0.7[0.75AgI: 0.25AgCl]: 0.3[Ag2O: WO3]. These superionic glasses were prepared recently in the present laboratory using an alternate host: "a quenched [0.75AgI: 0.25AgCl] mixed system/solid solution" in place of the traditional host AgI. An extensive investigation on ion transport behavior of these systems has been done which appeared elsewhere in the literature. In the present study, the sample pallet, placed in between two blocking (graphite) electrodes, was initially polarized with the help of an external d. c. potential (~ 0.5 V) for sufficient long time ensuring that the system attained the state of complete polarization. This resulted into a build up of a potential gradient across the two faces of the sample pallet, which can be measured instantly on removal of the external dc potential. This has been be referred to as an 'Instant Peak Potential (Vp)'. The magnitude of 'Vp' gives the quantitative information regarding the number of mobile Ag+ ions present in the system at a given temperature. 'Vp' measurements were carried out extensively on the sample pallets of different thickness as a function of time and temperature. The log Vp - 1/T variations for these systems were found to be almost analogous to log n - 1/T plots, reported earlier.

  17. Investigations on the phase equilibria of some hydride ion conducting electrolyte systems and their application for hydrogen monitoring in sodium coolant

    NASA Astrophysics Data System (ADS)

    Joseph, Kitheri; Sujatha, K.; Nagaraj, S.; Mahendran, K. H.; Sridharan, R.; Periaswami, G.; Gnanasekaran, T.

    2005-09-01

    Electrochemical meters for measuring hydrogen levels in liquid sodium need thermodynamically stable hydride ion conducting electrolytes. In order to identify electrolytes that have high hydride ion conductivity, phase diagram of systems consisting of low melting compounds such as CaCl 2-LiCl, SrBr 2-LiBr, SrBr 2-SrHBr and CaBr 2-CaHBr were investigated by differential scanning calorimetry and their phase diagrams established. Using these information and supplementary information on effects of addition of alkaline earth hydride to these systems, potential electrolytes were tested for their use in electrochemical meters. Meters were constructed using electrolytes with (i) 22mol%SrCl 2-12.2mol%CaCl 2-54.5mol%LiCl-11.3mol%CaHCl, (ii) 70mol%LiCl-16mol%CaHCl-14mol%CaCl 2 and (iii) 40mol%CaHBr-60mol%CaBr 2 compositions. Output of meters that had Li ions in liquid phase electrolyte showed non-linearity at low hydrogen levels. Output of meters using CaBr 2-40mol%CaHBr solid showed linearity in the concentration range of 50-250 ppb in sodium.

  18. Inorganic Solid-State Electrolytes for Lithium Batteries: Mechanisms and Properties Governing Ion Conduction.

    PubMed

    Bachman, John Christopher; Muy, Sokseiha; Grimaud, Alexis; Chang, Hao-Hsun; Pour, Nir; Lux, Simon F; Paschos, Odysseas; Maglia, Filippo; Lupart, Saskia; Lamp, Peter; Giordano, Livia; Shao-Horn, Yang

    2016-01-13

    This Review is focused on ion-transport mechanisms and fundamental properties of solid-state electrolytes to be used in electrochemical energy-storage systems. Properties of the migrating species significantly affecting diffusion, including the valency and ionic radius, are discussed. The natures of the ligand and metal composing the skeleton of the host framework are analyzed and shown to have large impacts on the performance of solid-state electrolytes. A comprehensive identification of the candidate migrating species and structures is carried out. Not only the bulk properties of the conductors are explored, but the concept of tuning the conductivity through interfacial effects-specifically controlling grain boundaries and strain at the interfaces-is introduced. High-frequency dielectric constants and frequencies of low-energy optical phonons are shown as examples of properties that correlate with activation energy across many classes of ionic conductors. Experimental studies and theoretical results are discussed in parallel to give a pathway for further improvement of solid-state electrolytes. Through this discussion, the present Review aims to provide insight into the physical parameters affecting the diffusion process, to allow for more efficient and target-oriented research on improving solid-state ion conductors. PMID:26713396

  19. Maskless Lithography and in situ Visualization of Conductivity of Graphene using Helium Ion Microscopy

    DOE PAGESBeta

    Iberi, Vighter O.; Vlassiouk, Ivan V.; Zhang, X. -G.; Matola, Brad R.; Linn, Allison R.; Joy, David Charles; Adam Justin Rondinone

    2015-07-07

    The remarkable mechanical and electronic properties of graphene make it an ideal candidate for next generation nanoelectronics. With the recent development of commercial-level single-crystal graphene layers, the potential for manufacturing household graphene-based devices has improved, but significant challenges still remain with regards to patterning the graphene into devices. In the case of graphene supported on a substrate, traditional nanofabrication techniques such as e-beam lithography (EBL) are often used in fabricating graphene nanoribbons but the multi-step processes they require can result in contamination of the graphene with resists and solvents. In this letter, we report the utility of scanning helium ionmore » lithography for fabricating functional graphene nanoconductors that are supported directly on a silicon dioxide layer, and we measure the minimum feature size achievable due to limitations imposed by thermal fluctuations and ion scattering during the milling process. Further we demonstrate that ion beams, due to their positive charging nature, may be used to observe and test the conductivity of graphene-based nanoelectronic devices in situ.« less

  20. Local electroporation of a single cell using a scanning ion conductance microscope

    NASA Astrophysics Data System (ADS)

    Iwata, Futoshi; Yamazaki, Koji; Ishizaki, Kimihiro; Ushiki, Tatuo

    2014-03-01

    We developed a novel electroporation technique for molecular delivery into a single cell. A nanopipette, a thermally pulled glass capillary, is prepared as to act as a pair of tiny electrodes for single-cell electroporation. An Ag/AgCl wire is inserted into the nanopipette, and the outside edge of the nanopipette is coated by Ag sputtering. Electric pulses are applied between the outside and inside electrodes to form a local electric field at the edge of the nanopipette. To position the pipette edge in the vicinity of the cell membrane, we control the probe-surface distance using a scanning ion conductance microscope (SICM). The SICM technique achieves non-contact approach of the nanopipette edge on the cell membrane, which allows low-invasive electroporation of a single cell. As a demonstration of this technique, a fluorescent molecule of propidium iodide was successfully delivered into a single HeLa cell.

  1. High rate lithium-sulfur battery enabled by sandwiched single ion conducting polymer electrolyte

    NASA Astrophysics Data System (ADS)

    Sun, Yubao; Li, Gai; Lai, Yuanchu; Zeng, Danli; Cheng, Hansong

    2016-02-01

    Lithium-sulfur batteries are highly promising for electric energy storage with high energy density, abundant resources and low cost. However, the battery technologies have often suffered from a short cycle life and poor rate stability arising from the well-known “polysulfide shuttle” effect. Here, we report a novel cell design by sandwiching a sp3 boron based single ion conducting polymer electrolyte film between two carbon films to fabricate a composite separator for lithium-sulfur batteries. The dense negative charges uniformly distributed in the electrolyte membrane inherently prohibit transport of polysulfide anions formed in the cathode inside the polymer matrix and effectively blocks polysulfide shuttling. A battery assembled with the composite separator exhibits a remarkably long cycle life at high charge/discharge rates.

  2. Second harmonic detection in the electrochemical strain microscopy of Ag-ion conducting glass

    DOE PAGESBeta

    Yang, Sangmo; Okatan, Mahmut Baris; Paranthaman, Mariappan Parans; Jesse, Stephen; Noh, Tae Won; Kalinin, Sergei V.

    2014-11-14

    The first and second harmonic electromechanical responses and their cross-correlation in Ag-ion conducting glass were investigated using band-excitation electrochemical strain microscopy (ESM). Consecutive ESM images with increasing magnitudes of the applied AC voltage allowed observation of not only reversible surface displacement but also irreversible silver nanoparticle formation above a certain threshold voltage. The second harmonic ESM response was anticorrelated with the first harmonic response in many local regions. Furthermore, the nucleation sites of silver nanoparticles were closely related to the anti-correlated regions, specifically, with low second harmonic and high first harmonic ESM responses. The possible origins of the second harmonicmore » ESM response are discussed.« less

  3. Simultaneous Scanning Ion Conductance Microscopy and Atomic Force Microscopy with Microchanneled Cantilevers.

    PubMed

    Ossola, Dario; Dorwling-Carter, Livie; Dermutz, Harald; Behr, Pascal; Vörös, János; Zambelli, Tomaso

    2015-12-01

    We combined scanning ion conductance microscopy (SICM) and atomic force microscopy (AFM) into a single tool using AFM cantilevers with an embedded microchannel flowing into the nanosized aperture at the apex of the hollow pyramid. An electrode was positioned in the AFM fluidic circuit connected to a second electrode in the bath. We could thus simultaneously measure the ionic current and the cantilever bending (in optical beam deflection mode). First, we quantitatively compared the SICM and AFM contact points on the approach curves. Second, we estimated where the probe in SICM mode touches the sample during scanning on a calibration grid and applied the finding to image a network of neurites on a Petri dish. Finally, we assessed the feasibility of a double controller using both the ionic current and the deflection as input signals of the piezofeedback. The experimental data were rationalized in the framework of finite elements simulations. PMID:26684144

  4. Simultaneous Scanning Ion Conductance Microscopy and Atomic Force Microscopy with Microchanneled Cantilevers

    NASA Astrophysics Data System (ADS)

    Ossola, Dario; Dorwling-Carter, Livie; Dermutz, Harald; Behr, Pascal; Vörös, János; Zambelli, Tomaso

    2015-12-01

    We combined scanning ion conductance microscopy (SICM) and atomic force microscopy (AFM) into a single tool using AFM cantilevers with an embedded microchannel flowing into the nanosized aperture at the apex of the hollow pyramid. An electrode was positioned in the AFM fluidic circuit connected to a second electrode in the bath. We could thus simultaneously measure the ionic current and the cantilever bending (in optical beam deflection mode). First, we quantitatively compared the SICM and AFM contact points on the approach curves. Second, we estimated where the probe in SICM mode touches the sample during scanning on a calibration grid and applied the finding to image a network of neurites on a Petri dish. Finally, we assessed the feasibility of a double controller using both the ionic current and the deflection as input signals of the piezofeedback. The experimental data were rationalized in the framework of finite elements simulations.

  5. p-type conduction in Zn-ion implanted InN films

    NASA Astrophysics Data System (ADS)

    Xie, W. M.; Y Xie, Q.; Zhu, H. P.; Wang, W.; Cai, H. L.; Zhang, F. M.; Wu, X. S.

    2015-06-01

    We report p-type conductivity in wurtzite indium nitride (InN) experimentally and theoretically. The as-deposited InN films are implanted with various doses of Zn ions. The Hall coefficient is positive for samples with doses of 2.5 ~ 10   ×   1014 ions cm-2 at low temperature and turns negative as the temperature increases. This notable sign change of the Hall coefficient confirms the existence of mobile holes in Zn-implanted InN. Moreover, first principle calculations indicate that Zn may be a more stable p-type dopant in InN than that of Mg and Ba because of its low ionization energy.

  6. Development of potassium ion conducting hollow glass fibers. [potassium sulfur battery

    NASA Technical Reports Server (NTRS)

    Tsang, F. Y.

    1974-01-01

    Potassium ion conducting glasses, chemically resistant to potassium, potassium sulfide and sulfur, were made and their possible utility as the membrane material for a potassium/sulfur battery was evaluated. At least one satisfactory candidate was found. It possesses an electrical resistance which makes it usable as a membrane in the form of a fine hollow fiber. It's chemical and electrochemical resistances are excellent. The other aspects of the possible potassium sulfur battery utilizing such fine hollow fibers, including the header (or tube sheet) and a cathode current collector were studied. Several cathode materials were found to be satisfactory. None of the tube sheet materials studied possessed all the desired properties. Multi-fiber cells had very limited life-time due to physical failure of fibers at the fiber/tube sheet junctions.

  7. High rate lithium-sulfur battery enabled by sandwiched single ion conducting polymer electrolyte.

    PubMed

    Sun, Yubao; Li, Gai; Lai, Yuanchu; Zeng, Danli; Cheng, Hansong

    2016-01-01

    Lithium-sulfur batteries are highly promising for electric energy storage with high energy density, abundant resources and low cost. However, the battery technologies have often suffered from a short cycle life and poor rate stability arising from the well-known "polysulfide shuttle" effect. Here, we report a novel cell design by sandwiching a sp(3) boron based single ion conducting polymer electrolyte film between two carbon films to fabricate a composite separator for lithium-sulfur batteries. The dense negative charges uniformly distributed in the electrolyte membrane inherently prohibit transport of polysulfide anions formed in the cathode inside the polymer matrix and effectively blocks polysulfide shuttling. A battery assembled with the composite separator exhibits a remarkably long cycle life at high charge/discharge rates. PMID:26898772

  8. High rate lithium-sulfur battery enabled by sandwiched single ion conducting polymer electrolyte

    PubMed Central

    Sun, Yubao; Li, Gai; Lai, Yuanchu; Zeng, Danli; Cheng, Hansong

    2016-01-01

    Lithium-sulfur batteries are highly promising for electric energy storage with high energy density, abundant resources and low cost. However, the battery technologies have often suffered from a short cycle life and poor rate stability arising from the well-known “polysulfide shuttle” effect. Here, we report a novel cell design by sandwiching a sp3 boron based single ion conducting polymer electrolyte film between two carbon films to fabricate a composite separator for lithium-sulfur batteries. The dense negative charges uniformly distributed in the electrolyte membrane inherently prohibit transport of polysulfide anions formed in the cathode inside the polymer matrix and effectively blocks polysulfide shuttling. A battery assembled with the composite separator exhibits a remarkably long cycle life at high charge/discharge rates. PMID:26898772

  9. Block copolymer with simultaneous electric and ionic conduction for use in lithium ion batteries

    DOEpatents

    Javier, Anna Esmeralda K; Balsara, Nitash Pervez; Patel, Shrayesh Naran; Hallinan, Jr., Daniel T

    2013-10-08

    Redox reactions that occur at the electrodes of batteries require transport of both ions and electrons to the active centers. Reported is the synthesis of a block copolymer that exhibits simultaneous electronic and ionic conduction. A combination of Grignard metathesis polymerization and click reaction was used successively to synthesize the block copolymer containing regioregular poly(3-hexylthiophene) (P3HT) and poly(ethylene oxide) (PEO) segments. The P3HT-PEO/LiTFSI mixture was then used to make a lithium battery cathode with LiFePO.sub.4 as the only other component. All-solid lithium batteries of the cathode described above, a solid electrolyte and a lithium foil as the anode showed capacities within experimental error of the theoretical capacity of the battery. The ability of P3HT-PEO to serve all of the transport and binding functions required in a lithium battery electrode is thus demonstrated.

  10. Theory for charge states of energetic oxygen ions in the earth's radiation belts

    NASA Technical Reports Server (NTRS)

    Spjeldvik, W. N.; Fritz, T. A.

    1978-01-01

    Fluxes of geomagnetically trapped energetic oxygen ions have been studied in detail. Ion distributions in radial locations below the geostationary orbit, energy spectra between 1 keV and 100 MeV, and the distribution over charge states have been computed for equatorially mirroring ions. Both ionospheric and solar wind oxygen ion sources have been considered, and it is found that the charge state distributions in the interior of the radiation belts are largely independent of the charge state characteristics of the sources. In the MeV range, oxygen ions prove to be a more sensitive probe for radiation belt dynamics than helium ions and protons.

  11. Simultaneous Interfacial Reactivity and Topography Mapping with Scanning Ion Conductance Microscopy.

    PubMed

    Momotenko, Dmitry; McKelvey, Kim; Kang, Minkyung; Meloni, Gabriel N; Unwin, Patrick R

    2016-03-01

    Scanning ion conductance microscopy (SICM) is a powerful technique for imaging the topography of a wide range of materials and interfaces. In this report, we develop the use and scope of SICM, showing how it can be used for mapping spatial distributions of ionic fluxes due to (electro)chemical reactions occurring at interfaces. The basic idea is that there is a change of ion conductance inside a nanopipet probe when it approaches an active site, where the ionic composition is different to that in bulk solution, and this can be sensed via the current flow in the nanopipet with an applied bias. Careful tuning of the tip potential allows the current response to be sensitive to either topography or activity, if desired. Furthermore, the use of a distance modulation SICM scheme allows reasonably faithful probe positioning using the resulting ac response, irrespective of whether there is a reaction at the interface that changes the local ionic composition. Both strategies (distance modulation or tuned bias) allow simultaneous topography-activity mapping with a single channel probe. The application of SICM reaction imaging is demonstrated on several examples, including voltammetric mapping of electrocatalytic reactions on electrodes and high-speed electrochemical imaging at rates approaching 4 s per image frame. These two distinct approaches provide movies of electrochemical current as a function of potential with hundreds of frames (images) of surface reactivity, to reveal a wealth of spatially resolved information on potential- (and time) dependent electrochemical phenomena. The experimental studies are supported by detailed finite element method modeling that places the technique on a quantitative footing. PMID:26798938

  12. Simulation of the low earth orbital atomic oxygen interaction with materials by means of an oxygen ion beam

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; Rutledge, Sharon K.; Paulsen, Phillip E.; Steuber, Thomas J.

    1989-01-01

    Atomic oxygen is the predominant species in low-Earth orbit between the altitudes of 180 and 650 km. These highly reactive atoms are a result of photodissociation of diatomic oxygen molecules from solar photons having a wavelength less than or equal to 2430A. Spacecraft in low-Earth orbit collide with atomic oxygen in the 3P ground state at impact energies of approximately 4.2 to 4.5 eV. As a consequence, organic materials previously used for high altitude geosynchronous spacecraft are severely oxidized in the low-Earth orbital environment. The evaluation of materials durability to atomic oxygen requires ground simulation of this environment to cost effectively screen materials for durability. Directed broad beam oxygen sources are necessary to evaluate potential spacecraft materials performance before and after exposure to the simulated low-Earth orbital environment. This paper presents a description of a low energy, broad oxygen ion beam source used to simulate the low-Earth orbital atomic oxygen environment. The results of materials interaction with this beam and comparison with actual in-space tests of the same meterials will be discussed. Resulting surface morphologies appear to closely replicate those observed in space tests.

  13. Increase of ionic conductivity in the microporous lithosilicate RUB-29 by Na-ion exchange processes

    NASA Astrophysics Data System (ADS)

    Park, S.-H.; Senyshyn, A.; Paulmann, C.

    2007-12-01

    The ionic conductivity in the zeolite-like lithosilicate RUB-29 (Cs 14Li 24[Li 18Si 72O 172]·14H 2O [S.-H. Park, J.B. Parise, H. Gies, H. Liu, C.P. Grey, B.H. Toby, J. Am. Chem. Soc. 122 (2000) 11023-11024]) increases via simple ion-exchange processes, in particular when Na cations replace a part of Cs + and Li + of the material. The resulting ionic conductivity value of 3.2×10 -3 S cm -1 at 885 K is about two orders higher than that for the original material [S.-H. Park, J.B. Parise, M.E. Franke, T. Seydel, C. Paulmann, Micropor. Mesopor. Mater., in print ( doi:10.1016/j.micromeso.2007.03.040 available online since April 19, 2007)]. The structural basis of a Na +-exchanged RUB-29 sample (Na-RUB-29) at 673 K could be elucidated by means of neutron powder diffraction. Rietveld refinements confirmed the replacement of Na + for both parts of Cs and Li cations, agreeing with idealized cell content, Na 8Cs 8Li 40Si 72O 172. As a result of the incorporation of Na + in large pores, the number of Li + vacancies in dense Li 2O-layers of the structure could increase. This can be one of the main reasons for the improved conductivity in Na-RUB-29. In addition, mobile Na cations may also contribute to the conductivity in Na-RUB-29 as continuous scattering length densities were found around the sites for Na in difference Fourier map.

  14. Developments in the Field of Conducting and Non-conducting Polymer Based Potentiometric Membrane Sensors for Ions Over the Past Decade

    PubMed Central

    Faridbod, Farnoush; Ganjali, Mohammad Reza; Dinarvand, Rassoul; Norouzi, Parviz

    2008-01-01

    Many research studies have been conducted on the use of conjugated polymers in the construction of chemical sensors including potentiometric, conductometric and amperometric sensors or biosensors over the last decade. The induction of conductivity on conjugated polymers by treating them with suitable oxidizing agents won Heeger, MacDiarmid and Shirakawa the 2000 Nobel Prize in Chemistry. Common conjugated polymers are poly(acetylene)s, poly(pyrrole)s, poly(thiophene)s, poly(terthiophene)s, poly(aniline)s, poly(fluorine)s, poly(3-alkylthiophene)s, polytetrathiafulvalenes, poly-napthalenes, poly(p-phenylene sulfide), poly(p-phenylenevinylene)s, poly(3,4-ethylene-dioxythiophene), polyparaphenylene, polyazulene, polyparaphenylene sulfide, poly-carbazole and polydiaminonaphthalene. More than 60 sensors for inorganic cations and anions with different characteristics based on conducting polymers have been reported. There have also been reports on the application of non-conducting polymers (nCPs), i.e. PVC, in the construction of potentiometric membrane sensors for determination of more than 60 inorganic cations and anions. However, the leakage of ionophores from the membranes based on these polymers leads to relatively lower life times. In this article, we try to give an overview of Solid-Contact ISE (SCISE), Single-Piece ISE (SPISE), Conducting Polymer (CP)-Based, and also non-conducting polymer PVC-based ISEs for various ions which their difference is in the way of the polymer used with selective\\ membrane. In SCISEs and SPISEs, the plasticized PVC containing the ionophore and ionic additives govern the selectivity behavior of the electrode and the conducting polymer is responsible of ion-to-electron transducer. However, in CPISEs, the conducting polymer layer is doped with a suitable ionophore which enhances the ion selectivity of the CP while its redox response has to be suppressed.

  15. All-Optical Preparation of Coherent Dark States of a Single Rare Earth Ion Spin in a Crystal

    NASA Astrophysics Data System (ADS)

    Xia, Kangwei; Kolesov, Roman; Wang, Ya; Siyushev, Petr; Reuter, Rolf; Kornher, Thomas; Kukharchyk, Nadezhda; Wieck, Andreas D.; Villa, Bruno; Yang, Sen; Wrachtrup, Jörg

    2015-08-01

    All-optical addressing and coherent control of single solid-state based quantum bits is a key tool for fast and precise control of ground-state spin qubits. So far, all-optical addressing of qubits was demonstrated only in a very few systems, such as color centers and quantum dots. Here, we perform high-resolution spectroscopic of native and implanted single rare earth ions in solid, namely, a cerium ion in yttrium aluminum garnet (YAG) crystal. We find narrow and spectrally stable optical transitions between the spin sublevels of the ground and excited optical states. Utilizing these transitions we demonstrate the generation of a coherent dark state in electron spin sublevels of a single Ce3 + ion in YAG by coherent population trapping.

  16. Conductivity through Polymer Electrolytes and Its Implications in Lithium-Ion Batteries: Real-World Application of Periodic Trends

    ERIC Educational Resources Information Center

    Compton, Owen C.; Egan, Martin; Kanakaraj, Rupa; Higgins, Thomas B.; Nguyen, SonBinh T.

    2012-01-01

    Periodic conductivity trends are placed in the scope of lithium-ion batteries, where increases in the ionic radii of salt components affect the conductivity of a poly(ethyleneoxide)-based polymer electrolyte. Numerous electrolytes containing varying concentrations and types of metal salts are prepared and evaluated in either one or two laboratory…

  17. Deceleration of the solar wind upstream from the earth's bow shock and the origin of diffuse upstream ions

    NASA Technical Reports Server (NTRS)

    Bame, S. J.; Asbridge, J. R.; Feldman, W. C.; Gosling, J. T.; Paschmann, G.; Skopke, N.

    1980-01-01

    Observations with the Los Alamos Scientific Laboratory/Max-Planck-Institut crossed-fan solar wind ion experiment on ISEE I reveal that the solar wind is decelerated and deflected away from the direction of the earth's bow shock as it enters that portion of the upstream region populated by diffuse bow shock ions and long-period (10-60 s) waves. Typically, the average directed velocity vector changes by 7-10 km/s as it enters the wave region. At times, average speed changes as large as 25-40 km/s are observed. Superposed upon these changes in average flow speed are large amplitude (+ or - 15) fluctuations in flow speed associated with the waves themselves. The observations suggest that the solar wind deceleration is the result of momentum transfer from reflected bow shock ions to the wind via the long-period waves as the reflected ion beams go unstable. The broad angular distributions of the diffuse ions thus appear to be produced as a consequence of the disruption of reflected ion beams.

  18. Opiates inhibit ion conductances elicited by cell swelling and cAMP in cultured cells.

    PubMed

    Callaghan, R; Riordan, J R

    1995-10-15

    The effect of several opiate compounds on I- efflux was investigated in cultured cell lines. I- efflux was evoked by two distinct stimuli, namely cell swelling and elevation of cellular cAMP levels by prostaglandin E2. Cells expressing the multidrug resistance P-glycoprotein were found to have increased I- efflux in response to hypo-osmotic challenge. This increased I- efflux in P-glycoprotein containing cells was reduced to levels found in parental cells by the opiates morphine, pentazocine and naloxone. Addition of prostaglandin E2 to T84 cells resulted in elevated cellular cAMP levels and a significant I- efflux. This cAMP stimulated efflux was also inhibited by several opiates. None of the opiates was able to alter cAMP levels or protein kinase A mediated phosphorylation of immunoprecipitated cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel in T84 cells. The ability of opiates to alter ion conductances is discussed in relation to the anti-diarrheal effects of these compounds. PMID:8566169

  19. Solvent extraction of rare-earth ions based on functionalized ionic liquids

    SciTech Connect

    Sun, Xiaoqi; Dai, Sheng; Luo, Huimin

    2012-01-01

    We herein report the achievement of enhanced extractabilities and selectivities for separation of rare earth elements based on functionalized ionic liquids. This work highlights the potential of developing a comprehensive ionic liquid-based extraction strategy for rare earth elements using ionic liquids as both extractant and diluent.

  20. Spectroscopic and Lasing Properties of Rare-Earth Ion Based Laser Materials

    NASA Astrophysics Data System (ADS)

    Petrin, Roger Ronald

    Scope and method of study. The spectroscopic and lasing properties of several rare-earth based laser materials were investigated. The dynamics of energy transfer in Tm,Ho:YAG were studied using time-resolved spectroscopy. The results were used in a rate equation based computer simulation of laser operation. Absorption, fluorescence, and fluorescence excitation spectroscopy were used to investigate the origin of blue emission in Nd:YAG, Nd:GSGG, and Nd:ZBAN. Alexandrite laser pumped lasing properties of Nd:ZBAN were also studied. The effects of a pump wavelength dependent loss mechanism were examined using a rate equation based computer simulation of the Nd:ZBAN laser system. Findings and conclusions. Evidence for energy migration in the rm Tm^{3+} ^3H_4 multiplet was found. A mechanism producing green emission involving excited state absorption of pump photons from the Ho^ {3+} metastable state was also identified. Rate parameters for the relevant energy transfer processes for Tm,Ho:YAG were determined through spectroscopic measurements. Using the spectroscopically determined rate parameters and no fitting parameters, computer simulations of laser operation were able to reproduce the relaxation oscillations and the time delay between the pump and lasing output previously observed experimentally. The origin of the blue emission observed in Nd:YAG and Nd:GSGG was identified as the ^2P_{3/2} multiplet. An excited state absorption process involving a pump photon and an ion excited to the ^4F_ {5/2}, ^2H_{9/2} multiplets was found to populate the ^2P _{3/2} multiplet. Similar processes were also identified in the Nd:ZBAN system and the first laser operation of this material in bulk form was reported. Computer simulations indicated that only in materials with slow non-radiative decay processes and in systems with high peak power pump sources would excited state absorption of pump photons from levels above the metastable state be an important loss mechanism in Nd^{3

  1. Modeling Li-ion conductivity in LiLa(PO3)4 powder

    NASA Astrophysics Data System (ADS)

    Mounir, Ferhi; Karima, Horchani-Naifer; Khaled, Ben Saad; Mokhtar, Férid

    2012-07-01

    Polycrystalline powder and single-crystal of LiLa(PO3)4 are synthesized by solid state reaction and flux technique, respectively. A morphological description of the obtained product was made based on scanning electron microscopy micrographs. The obtained powder was characterized by X-ray powder diffraction, FTIR and Raman spectroscopies. Ionic conductivity of the LiLa(PO3)4 powder was measured and evaluated over a temperature range from 553 to 913 K. Single crystals of LiLa(PO3)4 are characterized by single-crystal X-ray diffraction. The LiLa(PO3)4 structure was found to be isotypic with LiNd(PO3)4. It crystallizes in the monoclinic system with space group C2/c and cell parameters: a=16.635(6) Å, b=7.130(3) Å, c=9.913(3) Å, β=126.37(4)°, V=946.72(6) Å3 and Z=4. The LiLa(PO3)4 structure was described as an alternation between spiraling chains (PO3)n and (La3+, Li+) cations along the b direction. The small Li+ ions, coordinated to four oxygen atoms, were located in the large connected cavities created between the LaO8 polyhedra and the polyphosphate chains. The jumping of Li+ through tunnels of the crystalline network was investigated using complex impedance spectroscopy. The close value of the activation energies calculated through the analysis of conductivity data and loss spectra indicate that the transport in the investigated system is through hopping mechanism. The correlation between ionic conductivity of LiLa(PO3)4 and its crystallographic structure was investigated and the most probably transport pathway model was determined.

  2. Development of Mixed Ion-Electron Conducting Metal Oxides for Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Kan, Wang Hay

    A solid oxide fuel cell (SOFC) is an energy conversion device, which directly converts chemical fuels (e.g., H2, C xHy) into electricity and heat with high efficiency up to 90%. The by-product of CO2 can be safely sequestrated or subsequently chemically transformed back into fuels (e.g., CO, CH 4) by electrolysis using renewable energy sources such as solar and wind. The state-of-the-art Ni-YSZ anode is de-activated in the presence of ppm level of H2S and forming coke in hydrocarbons. Currently, mixed ion and electron conductors (MIECs) are considered as alternatives for Ni-YSZ in SOFCs. The key goal of the research was to develop mixed ion-electron conducting metal oxides based on B-site disordered perovskite-type Ba(Ca,Nb)1-x MxO3-delta (M = Mn, Fe, Co), the B-site 1:1 ordered perovskite-type (M = Mn, Fe, Co) and the Sr2PbO4-type Sr2Ce1-xPrxO4 for SOFCs. Ba2(Ca,Nb)2-xMxO6-delta was chemically stable in 30 ppm levels of H2S at 600 °C for 24 h and in pure CO2 at 800 °C for 24 h. The thermal expansion coefficients (TEC) of the as-prepared ordered perovskites was found to be comparable to Zr0.84Y0.16O1.92 (YSZ). The near-surface concentration of Fe2+ in Ba2Ca 0.67Fe0.33NbO6-delta was found to be about 3 times higher than that in the bulk sample. The electrochemical performance of Ba2Ca0.67M0.33NbO6-delta was assessed by ac impedance spectroscopy using a YSZ supported half-cell. The area specific polarization resistance (ASR) of all samples was found to decrease with increasing temperature. The ASR for H2 gas oxidation can be correlated to the higher concentration of low valence Fe2+ species near-surface (nano-scale). BaCa0.335M0.165Nb0.5O3-delta crystallizes in the B-site disordered primitive perovskite (space group Pm-3m) at 900 °C in air, which can be converted into the B-site 1:2 ordered perovskite (space group P-3m1) at 1200 °C and the B-site 1:1 ordered double perovskite phase (space group Fm-3m ) at 1300 °C. The chemical stability of the perovskites in CO

  3. EPR and optical absorption studies of Cu{sup 2+} ions in alkaline earth alumino borate glasses

    SciTech Connect

    Ramesh Kumar, V.; Rao, J.L. . E-mail: jlrao46@yahoo.co.in; Gopal, N.O.

    2005-08-11

    Electron paramagnetic resonance (EPR) and optical absorption spectra of Cu{sup 2+} ions in alkaline earth alumino borate glasses doped with different concentrations of CuO have been studied. The EPR spectra of all the glasses exhibit the resonance signals, characteristic of Cu{sup 2+} ions present in axially elongated octahedral sites. The number of spins participating in the resonance has been calculated as a function of temperature for calcium alumino borate (CaAB) glass doped with 0.1 mol% of CuO. From the EPR data, the paramagnetic susceptibility ({chi}) was calculated at different temperatures (T) and from the 1/{chi}-T graph, the Curie temperature of the glass has been evaluated. The optical absorption spectra of all the glasses show a single broad band, which has been assigned to the {sup 2}B{sub 1g} {yields} {sup 2}B{sub 2g} transition of the Cu{sup 2+} ions. The variation in the intensity of optical absorption with the ionic radius of the alkaline earth ion has been explained based on the Coulombic forces. By correlating the EPR and optical absorption spectral data, the nature of the in-plane {sigma} bonding between Cu{sup 2+} ion and the ligands is estimated. From the fundamental ultraviolet absorption edges of the glasses, the optical energy gap (E {sub opt}) and the Urbach energy ({delta}E) are evaluated. The variation in E {sub opt} and {delta}E is explained based on the number of defect centers in the glass.

  4. Three interesting coordination compounds based on metalloligand and alkaline-earth ions: Syntheses, structures, thermal behaviors and magnetic property

    NASA Astrophysics Data System (ADS)

    Zhou, Qiang; Qian, Jun; Zhang, Chi

    2016-09-01

    Based on metalloligand LCu ([Cu(2,4-pydca)2]2-, 2,4-pydca2- = pyridine-2,4-dicarboxylate) and alkaline-earth ions (Ca2+, Sr2+, and Ba2+), three interesting coordination compounds, [Ca(H2O)7][LCu·H2O]·H2O (1), {Sr[LCu·H2O]·4H2O}n (2), and {Ba[LCu·H2O]·8H2O}n (3), have been synthesized and well-characterized by elemental analysis, infrared spectroscopy, thermogravimetric and single-crystal X-ray diffraction analysis. X-ray crystallographic studies reveal that 1 features a discrete 0D coordination compound, while 2 and 3 exhibit the 2D network and 1D chain structures, respectively. Compound 2 is constructed from {LCu}2 dimers connected with {Sr2} units, which is fabricated by two Sr2+ ions bridged via two μ2-O bridges, while compound 3 is formed by 1D {Ba}n chain linked with metalloligands LCu and exhibits an interesting sandwich like chain structure. It is noted that the coordination numbers of alkaline-earth ions are in positive correlation with their radiuses. Moreover, the magnetic property of compound 2 has been studied.

  5. Efficient automatic screening for Li ion conductive inorganic oxides with bond valence pathway models and percolation algorithm

    NASA Astrophysics Data System (ADS)

    Nakayama, Masanobu; Kimura, Mayumi; Jalem, Randy; Kasuga, Toshihiro

    2016-01-01

    Fast ion conductive solid oxide electrolytes are urgently needed because of the development of batteries, fuel cells, and sensors. Ab initio density functional theory can predict ionic conductivities with high accuracy, although it often requires large computational resources and time. In this paper, we use empirical bond valence relations [Adams et al., Phys. Status Solidi A 208, 1746 (2011)] and a percolation algorithm for fast, efficient, fully automated evaluation of migration energies for Li ion conduction in 14 olivine-type LiMXO4 compounds. The results showed a high correlation coefficient with the ab initio density functional theory (DFT) approach, indicating that our method could be attractive for identifying fast ion conductors in databases of numerous candidates.

  6. Determination of the interaction parameters of ions from a rarefied plasma flow with electrically conducting surfaces using thermoanemometric probes

    SciTech Connect

    Shuvalov, V.A.; Gubin, V.V.; Kostenko, V.S.; Reznichenko, N.P.

    1985-05-01

    A method is proposed for measuring a combination of parameters associated with the interaction of ions from a rarefied plasma with electrically conducting surfaces using thermoanemometric probes. Results of measurements of the ion-electron secondary emission coefficients and of the accommodation coefficients for the energy and the normal and tangential momenta of inert gas and molecular nitrogen ions on the surfaces of commercial materials are presented. Empirical approximations are given for the dependences of the energy and normal momentum accommodation coefficients on the orientation of the probe-target with respect to the velocity vector of the flow.

  7. Local time occurrence frequency of energetic ions in the earth's magnetosheath

    NASA Technical Reports Server (NTRS)

    Fuselier, S. A.; Hill, P.; Baumjohann, W.; Gosling, J. T.

    1993-01-01

    The occurrence frequency of energetic ions in the energy range from 8 to 40 keV/e as a function of local time in the magnetosheath is presented. Energetic ions are observed in the magnetosheath with a minimum probability of 25 percent for all local times. The occurrence frequency for the energetic ions is higher on the dawnside than on the duskside but shows a relative maximum postnoon in the local time range from 12 to 15 hours. The postnoon relative maximum is attributed to a magnetospheric source for the energetic ions while the dawn-dusk asymmetry is attributed to a quasi-parallel bow shock source.

  8. Low-conductance HCN1 ion channels augment the frequency response of rod and cone photoreceptors.

    PubMed

    Barrow, Andrew J; Wu, Samuel M

    2009-05-01

    Hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channels are expressed in several tissues throughout the body, including the heart, the CNS, and the retina. HCN channels are found in many neurons in the retina, but their most established role is in generating the hyperpolarization-activated current, I(h), in photoreceptors. This current makes the light response of rod and cone photoreceptors more transient, an effect similar to that of a high-pass filter. A unique property of HCN channels is their small single-channel current, which is below the thermal noise threshold of measuring electronics. We use nonstationary fluctuation analysis (NSFA) in the intact retina to estimate the conductance of single HCN channels, revealing a conductance of approximately 650 fS in both rod and cone photoreceptors. We also analyze the properties of HCN channels in salamander rods and cones, from the biophysical to the functional level, showing that HCN1 is the predominant isoform in both cells, and demonstrate how HCN1 channels speed up the light response of both rods and cones under distinct adaptational conditions. We show that in rods and cones, HCN channels increase the natural frequency response of single cells by modifying the photocurrent input, which is limited in its frequency response by the speed of a molecular signaling cascade. In doing so, HCN channels form the first of several systems in the retina that augment the speed of the visual response, allowing an animal to perceive visual stimuli that change more quickly than the underlying photocurrent. PMID:19420251

  9. Characterization of tip size and geometry of the pipettes used in scanning ion conductance microscopy.

    PubMed

    Tognoni, Elisabetta; Baschieri, Paolo; Ascoli, Cesare; Pellegrini, Monica; Pellegrino, Mario

    2016-04-01

    Scanning ion-conductance microscopy (SICM) belongs to the family of scanning-probe microscopies. The spatial resolution of these techniques is limited by the size of the probe. In SICM the probe is a pipette, obtained by heating and pulling a glass capillary tubing. The size of the pipette tip is therefore an important parameter in SICM experiments. However, the characterization of the tip is not a consolidated routine in SICM experimental practice. In addition, potential and limitations of the different methods available for this characterization may not be known to all users. We present an overview of different methods for characterizing size and geometry of the pipette tip, with the aim of collecting and facilitating the use of several pieces of information appeared in the literature in a wide interval of time under different disciplines. In fact, several methods that have been developed for pipettes used in cell physiology can be also fruitfully employed in the characterization of the SICM probes. The overview includes imaging techniques, such as scanning electron microscopy and atomic Force microscopy, and indirect methods, which measure some physical parameter related to the size of the pipette. Examples of these parameters are the electrical resistance of the pipette filled with a saline solution and the surface tension at the pipette tip. We discuss advantages and drawbacks of the methods, which may be helpful in answering a wide range of experimental questions. PMID:26826619

  10. Comparison of Atomic Force Microscopy and Scanning Ion Conductance Microscopy for Live Cell Imaging.

    PubMed

    Seifert, Jan; Rheinlaender, Johannes; Novak, Pavel; Korchev, Yuri E; Schäffer, Tilman E

    2015-06-23

    Atomic force microscopy (AFM) and scanning ion conductance microscopy (SICM) are excellent and commonly used techniques for imaging the topography of living cells with high resolution. We present a direct comparison of AFM and SICM for imaging microvilli, which are small features on the surface of living cells, and for imaging the shape of whole cells. The imaging quality on microvilli increased significantly after cell fixation for AFM, whereas for SICM it remained constant. The apparent shape of whole cells in the case of AFM depended on the imaging force, which deformed the cell. In the case of SICM, cell deformations were avoided, owing to the contact-free imaging mechanism. We estimated that the lateral resolution on living cells is limited by the cell's elastic modulus for AFM, while it is not for SICM. By long-term, time-lapse imaging of microvilli dynamics, we showed that the imaging quality decreased with time for AFM, while it remained constant for SICM. PMID:26011471

  11. An alternative mechanism of clathrin-coated pit closure revealed by ion conductance microscopy

    PubMed Central

    Novak, Pavel; Taylor, Marcus; Diakonov, Ivan A.; Ziyadeh-Isleem, Azza; Bitoun, Marc; Guicheney, Pascale; Lab, Max J.; Gorelik, Julia; Merrifield, Christien J.; Klenerman, David

    2012-01-01

    Current knowledge of the structural changes taking place during clathrin-mediated endocytosis is largely based on electron microscopy images of fixed preparations and x-ray crystallography data of purified proteins. In this paper, we describe a study of clathrin-coated pit dynamics in living cells using ion conductance microscopy to directly image the changes in pit shape, combined with simultaneous confocal microscopy to follow molecule-specific fluorescence. We find that 70% of pits closed with the formation of a protrusion that grew on one side of the pit, covered the entire pit, and then disappeared together with pit-associated clathrin–enhanced green fluorescent protein (EGFP) and actin-binding protein–EGFP (Abp1-EGFP) fluorescence. This was in contrast to conventionally closing pits that closed and cleaved from flat membrane sheets and lacked accompanying Abp1-EGFP fluorescence. Scission of both types of pits was found to be dynamin-2 dependent. This technique now enables direct spatial and temporal correlation between functional molecule-specific fluorescence and structural information to follow key biological processes at cell surfaces. PMID:22564416

  12. Scanning Ion Conductance Microscopic Study for Cellular Uptake of Cationic Conjugated Polymer Nanoparticles.

    PubMed

    Shan, Yuping; Panday, Namuna; Myoung, Yong; Twomey, Megan; Wang, Xuewen; Li, Wenzhi; Celik, Emrah; Moy, Vincent; Wang, Hongda; Moon, Joong Ho; He, Jin

    2016-04-01

    Positively charged conjugated polymer nanoparticles (CPNs) are emerging biomaterials exhibiting high levels of cellular entry. High rate of cellular entry efficiency is believed that the amphiphilic CPNs interact efficiently with the negatively charged hydrophobic cellular membranes. For the first time, the cell surface morphological changes of human cervical cancer cells treated with CPNs using a scanning probe microscopy technique, scanning ion conductance microscopy (SICM) are imaged. After 1 h of CPN incubation, distinct changes are observed in cell surface morphology such as interconnected protrusions and pits with sub-micrometer sizes, which are not observed from cells treated with positively charged polyethyleneimine (PEI) under the same treatment conditions. The change on cell surface morphology is quantified by surface roughness ratio, which is increased as CPN concentration increases, while the ratio first increases and then decreases as the incubation time increases. These results suggest that cells respond actively toward CPN with both positive charges on the side chain and the hydrophobicity from rigid aromatic backbone, which leads to subsequent endocytosis. In conclusion, it is demonstrated that SICM is a suitable imaging technique to reveal the dynamic alternations on the cell surface morphology at the early stage of nanoparticles endocytosis with high resolution. PMID:26757346

  13. Implementation of an optimal stomatal conductance scheme in the Australian Community Climate Earth Systems Simulator (ACCESS1.3b)

    NASA Astrophysics Data System (ADS)

    Kala, J.; De Kauwe, M. G.; Pitman, A. J.; Lorenz, R.; Medlyn, B. E.; Wang, Y.-P.; Lin, Y.-S.; Abramowitz, G.

    2015-12-01

    We implement a new stomatal conductance scheme, based on the optimality approach, within the Community Atmosphere Biosphere Land Exchange (CABLEv2.0.1) land surface model. Coupled land-atmosphere simulations are then performed using CABLEv2.0.1 within the Australian Community Climate and Earth Systems Simulator (ACCESSv1.3b) with prescribed sea surface temperatures. As in most land surface models, the default stomatal conductance scheme only accounts for differences in model parameters in relation to the photosynthetic pathway but not in relation to plant functional types. The new scheme allows model parameters to vary by plant functional type, based on a global synthesis of observations of stomatal conductance under different climate regimes over a wide range of species. We show that the new scheme reduces the latent heat flux from the land surface over the boreal forests during the Northern Hemisphere summer by 0.5-1.0 mm day-1. This leads to warmer daily maximum and minimum temperatures by up to 1.0 °C and warmer extreme maximum temperatures by up to 1.5 °C. These changes generally improve the climate model's climatology of warm extremes and improve existing biases by 10-20 %. The bias in minimum temperatures is however degraded but, overall, this is outweighed by the improvement in maximum temperatures as there is a net improvement in the diurnal temperature range in this region. In other regions such as parts of South and North America where ACCESSv1.3b has known large positive biases in both maximum and minimum temperatures (~ 5 to 10 °C), the new scheme degrades this bias by up to 1 °C. We conclude that, although several large biases remain in ACCESSv1.3b for temperature extremes, the improvements in the global climate model over large parts of the boreal forests during the Northern Hemisphere summer which result from the new stomatal scheme, constrained by a global synthesis of experimental data, provide a valuable advance in the long-term development

  14. Model oxygen ions distributions in the Earth{close_quote}s magnetosphere for different pitch-angles

    SciTech Connect

    Beliaev, A.A.; Koroteyeva, E.G.; Panasyuk, M.I.

    1996-07-01

    Results of calculations of energetic, spatial and charge distributions of oxygen ions in the Earth{close_quote}s radiation belts are present. The model of oxygen radiation belts for various pitch angles is suggested. Model is based on the solution of stationary Fokker-Planck equation for particles{close_quote} diffusion due to magnetic and electric field fluctuations and accounts for particles losses due to Coulomb interactions and charge exchange. Particles{close_quote} distributions are studied as function of fluctuations{close_quote} power indices and source spectra (both solar and ionospheric) on the magnetosphere boundary. Comparison is made with experimental data. {copyright} {ital 1996 American Institute of Physics.}

  15. A new silver ion conducting SbI3-Ag4P2O7 nanocomposite solid electrolyte

    NASA Astrophysics Data System (ADS)

    Suthanthiraraj, S. Austin; Sarumathi, R.

    2013-12-01

    This paper presents an investigation on a new series of silver ion conducting nanocomposite materials of silver pyrophosphate-based solid electrolytes with various amounts of antimony iodide. The detailed electrical conductivity studies carried out by impedance spectroscopic analysis in the frequency range from 20 Hz to 1 MHz have shown that silver ionic conductivity attains a maximum value of 4.1 × 10-4 S cm-1 at room temperature for the typical composition having 60 mol% of SbI3. Powder samples characterized by X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetric analysis and silver ionic transport studies were identified to indicate the existence of AgI, in addition to certain new phases in all the different compositions of the system. The conduction channel for Ag+ ions across phosphate network was found to get expanded by the presence of iodide ion. The formation of P-O-M (M=Sb3+) within the crystal structure is also favoured, where Sb3+ ions may serve as ionic cross-links between non-bridging oxygen of different phosphate groups. The field emission scanning electron microscopic investigations of their microstructures have suggested the presence of nanocomposites, leading to the observed electrical conductivity data coupled with many interesting features closely related to the particle size and practical application as solid electrolyte for the fabrication of solid-state battery at ambient conditions.

  16. Electrical conduction of ion tracks in tetrahedral amorphous carbon: temperature, field and doping dependence and comparison with matrix data

    NASA Astrophysics Data System (ADS)

    Krauser, J.; Gehrke, H.-G.; Hofsäss, H.; Amani, J.; Trautmann, C.; Weidinger, A.

    2015-12-01

    This paper gives an extended overview of the electrical properties of ion tracks in hydrogen-free tetrahedral amorphous carbon (ta-C) with a sp3 bond fraction of about 80%. The films were grown by mass selected ion beam deposition of 100 eV 12C+ ions. The ion tracks are generated by irradiation of ta-C films with uranium ions of 1 GeV kinetic energy. Along the ion path a conversion from diamond-like (sp3) carbon to graphite-like (sp2) carbon takes place. Topography and current measurements of individual ion tracks were performed by atomic force microscopy at ambient temperature. The temperature dependence of the electric conductivity was studied between 15 and 390 K by means of 0.28 mm2 large contact pads averaging over about 107 tracks. For each sample and at each temperature the conductivity as a function of the applied electrical field (non-ohmic behaviour) was measured separately and the data were extrapolated to field zero. In this way, the zero-field conductivity was determined independent from the field dependence. In spite of large differences in the absolute values, the temperature dependence of the zero-field conductivities is found to be very similar in shape for all samples. The conductivities follow a {T}-{1/4} law up to temperatures slightly below room temperature. At higher temperatures a transport mechanism based on over-barrier hopping dominates with an activation energy of about 220 meV for tracks and 260 meV for the ta-C matrix. The field dependence measurements show that the deviation of the I-V characteristics from ohmic behaviour decreases with increasing zero-field conductivity. We also tested Cu-doped ta-C samples and found that they conduct significantly better than pure ta-C. However, the doping also increases the zero-field conductivity resulting in a weaker contrast between the track and matrix. The data are interpreted within the so-called ‘barrier model’ where the electrons are assumed to move fairly freely in well-conducting sp2

  17. Uniform surface modification of diatomaceous earth with amorphous manganese oxide and its adsorption characteristics for lead ions

    NASA Astrophysics Data System (ADS)

    Li, Song; Li, Duanyang; Su, Fei; Ren, Yuping; Qin, Gaowu

    2014-10-01

    A novel method to produce composite sorbent material compromising porous diatomaceous earth (DE) and surface functionalized amorphous MnO2 is reported. Via a simple in situ redox reaction over the carbonized DE powders, a uniform layer of amorphous MnO2 was anchored onto the DE surface. The hybrid adsorbent was characterized by X-ray diffraction, scanning electron microscopy, and infrared spectroscopy. The batch method has been employed to investigate the effects of surface coating on adsorption performance of DE. According to the equilibrium studies, the adsorption capacity of DE for adsorbing lead ions after MnO2 modification increased more than six times. And the adsorption of Pb2+ on the MnO2 surface is based on ion-exchange mechanism. The developed strategy presents a novel opportunity to prepare composite adsorbent materials by integrating nanocrystals with porous matrix.

  18. Physical and optical absorption studies of Fe3+ - ions doped lithium borate glasses containing certain alkaline earths

    NASA Astrophysics Data System (ADS)

    Bhogi, Ashok; Kumar, R. Vijaya; Kistaiah, P.

    2016-05-01

    Iron ion doped lithium borate glasses with the composition 15RO-25Li2O-59B2O3-1Fe2O3 (where R= Ca, Sr and Ba) have been prepared by the conventional melt quenching technique and characterized to investigate the physical and optical properties using XRD, density, molar volume and UV-Visible spectroscopy. The optical absorption spectra exhibit a band at around 460 nm which is assigned to 6A1g(S) → 4Eg (G) of Fe3+ ions with distorted octahedral symmetry. From ultraviolet absorption edges, the optical band gap and Urbach energies have been evaluated. The effect of alkaline earths on these properties is discussed.

  19. Mass Spectrometric Observation of Doubly Charged Alkaline-Earth Argon Ions.

    PubMed

    Hattendorf, Bodo; Gusmini, Bianca; Dorta, Ladina; Houk, Robert S; Günther, Detlef

    2016-09-01

    Doubly charged diatomic ions MAr(2+) where M=Mg, Ca, Sr or Ba have been observed by mass spectrometry with an inductively coupled plasma ion source. Abundance ratios are quite high, 0.1 % for MgAr(2+) , 0.4 % for CaAr(2+) , 0.2 % for SrAr(2+) and 0.1 % for BaAr(2+) relative to the corresponding doubly charged atomic ions M(2+) . It is assumed that these molecular ions are formed through reactions of the doubly charged metal ions with neutral argon atoms within the ion source. Bond dissociation energies (D0 ) were calculated and agree well with previously published values. The abundance ratios MAr(+) /M(+) and MAr(2+) /M(2+) generally follow the predicted bond dissociation energies with the exception of MgAr(2+) . Mg(2+) should form the strongest bond with Ar [D0 (MgAr(2+) )=124 to 130 kJ mol(-1) ] but its relative abundance is similar to that of the weakest bound BaAr(2+) (D0 =34 to 42 kJ mol(-1) ). The relative abundances of the various MAr(2+) ions are higher than those expected from an argon plasma at T=6000 K, indicating that collisions during ion extraction reduce the abundance of the MAr(2+) ions relative to the composition in the source. The corresponding singly charged MAr(+) ions are also observed but occur at about three orders of magnitude lower intensity than MAr(2+) . PMID:27252087

  20. Alkali metal, alkaline earth metal, and ammonium ion selectivities of dibenzo-16-crown-5 compounds with functional side arms in ion-selective electrodes

    SciTech Connect

    Ohki, Akira; Lu, J.P.; Huang, X.; Bartsch, R.A. )

    1994-12-01

    Potentiometric selectivities of 11 dibenzo-16-crown-5 compounds for alkali metal, alkaline earth metal, and ammonium ions have been determined in solvent polymeric membrane electrodes. The ionophores bear one or two pendent groups on the central carbon of the three-carbon bridge in the polyether ring. Side-arm variation includes OCH[sub 3], OCH[sub 2]CH[sub 2]OCH[sub 3], OCH[sub 2]CO[sub 2]C[sub 2]H[sub 5], OCH[sub 2]C(O)N(C[sub 2]H[sub 5])[sub 2], and OCH[sub 2]C(O)N(C[sub 5]H[sub 11])[sub 2] units. Attachment of a propyl group to the ring carbon that bears an extended, oxygen-containing side arm increases the selectivity for Na[sup +] relative to larger alkali metal and alkaline earth metal cations. For a given side arm, a linear relationship is obtained when the enhancement in Na[sup +] selectivity produced by attachment of a geminal propyl group is plotted against the diameter of the interference ion. Potentiometric responses of the dibenzo-16-crown-5 compounds are rationalized in terms of the crown ether ring size and the oxygen basicity, conformational positioning, and rigidity of the side arm. 22 refs., 3 figs., 2 tabs.

  1. Chirped dissipative ion-cyclotron solitons in the Earth's low-altitude ionospheric plasma with two ion species

    SciTech Connect

    Kovaleva, I. Kh.

    2013-03-15

    Conditions for the excitation of small-scale nonlinear ion-cyclotron gradient-drift dissipative structures in cold ionospheric plasma are considered. The solution for the wave electric field in this structure in the form of a chirped soliton satisfying the equation of the Ginzburg-Landau type is derived in the electrostatic approach. The dissipative structure as a whole represents the chirped soliton accompanied by the comoving quasineutral plasma hump. The possibility of the excitation of two modes of this type (the high- and low-frequency ones) in plasma containing light and heavy ion impurities is considered. The role of electromagnetic corrections and the possible contribution introduced by these structures to the transport processes in the ionosphere are discussed.

  2. Mesoscale Origin of the Enhanced Cycling-Stability of the Si-Conductive Polymer Anode for Li-ion Batteries

    SciTech Connect

    Gu, Meng; Xiao, Xingcheng; Liu, Gao; Thevuthasan, Suntharampillai; Baer, Donald R.; Zhang, Jiguang; Liu, Jun; Browning, Nigel D.; Wang, Chong M.

    2014-01-14

    Electrode used in lithium-ion battery is invariably a composite of multifunctional components. The performance of the electrode is controlled by the interactive function of all components at mesoscale. Fundamental understanding of mesoscale phenomenon sets the basis for innovative designing of new materials. Here we report the achievement and origin of a significant performance enhancement of electrode for lithium ion batteries based on Si nanoparticles wrapped with conductive polymer. This new material is in marked contrast with conventional material, which exhibit fast capacity fade. In-situ TEM unveils that the enhanced cycling stability of the conductive polymer-Si composite is associated with mesoscale concordant function of Si nanoparticles and the conductive polymer. Reversible accommodation of the volume changes of Si by the conductive polymer allows good electrical contact between all the particles during the cycling process. In contrast, the failure of the conventional Si-electrode is probed to be the inadequate electrical contact.

  3. Energy transfer kinetics in oxy-fluoride glass and glass-ceramics doped with rare-earth ions

    SciTech Connect

    Sontakke, Atul D.; Annapurna, K.

    2012-07-01

    An investigation of donor-acceptor energy transfer kinetics in dual rare earths doped precursor oxy-fluoride glass and its glass-ceramics containing NaYF{sub 4} nano-crystals is reported here, using three different donor-acceptor ion combinations such as Nd-Yb, Yb-Dy, and Nd-Dy. The precipitation of NaYF{sub 4} nano-crystals in host glass matrix under controlled post heat treatment of precursor oxy-fluoride glasses has been confirmed from XRD, FESEM, and transmission electron microscope (TEM) analysis. Further, the incorporation of dopant ions inside fluoride nano-crystals has been established through optical absorption and TEM-EDX analysis. The noticed decreasing trend in donor to acceptor energy transfer efficiency from precursor glass to glass-ceramics in all three combinations have been explained based on the structural rearrangements that occurred during the heat treatment process. The reduced coupling phonon energy for the dopant ions due to fluoride environment and its influence on the overall phonon assisted contribution in energy transfer process has been illustrated. Additionally, realization of a correlated distribution of dopant ions causing clustering inside nano-crystals has also been reported.

  4. Some Rare Earth Elements Analysis by Microwave Plasma Torch Coupled with the Linear Ion Trap Mass Spectrometry

    PubMed Central

    Xiong, Xiaohong; Jiang, Tao; Qi, Wenhao; Zuo, Jun; Yang, Meiling; Fei, Qiang; Xiao, Saijin; Yu, Aimin; Zhu, Zhiqiang; Chen, Huanwen

    2015-01-01

    A sensitive mass spectrometric analysis method based on the microwave plasma technique is developed for the fast detection of trace rare earth elements (REEs) in aqueous solution. The plasma was produced from a microwave plasma torch (MPT) under atmospheric pressure and was used as ambient ion source of a linear ion trap mass spectrometer (LTQ). Water samples were directly pneumatically nebulized to flow into the plasma through the central tube of MPT. For some REEs, the generated composite ions were detected in both positive and negative ion modes and further characterized in tandem mass spectrometry. Under the optimized conditions, the limit of detection (LOD) was at the level 0.1 ng/mL using MS2 procedure in negative mode. A single REE analysis can be completed within 2~3 minutes with the relative standard deviation ranging between 2.4% and 21.2% (six repeated measurements) for the 5 experimental runs. Moreover, the recovery rates of these REEs are between the range of 97.6%–122.1%. Two real samples have also been analyzed, including well and orange juice. These experimental data demonstrated that this method is a useful tool for the field analysis of REEs in water and can be used as an alternative supplement of ICP-MS. PMID:26421013

  5. Some Rare Earth Elements Analysis by Microwave Plasma Torch Coupled with the Linear Ion Trap Mass Spectrometry.

    PubMed

    Xiong, Xiaohong; Jiang, Tao; Qi, Wenhao; Zuo, Jun; Yang, Meiling; Fei, Qiang; Xiao, Saijin; Yu, Aimin; Zhu, Zhiqiang; Chen, Huanwen

    2015-01-01

    A sensitive mass spectrometric analysis method based on the microwave plasma technique is developed for the fast detection of trace rare earth elements (REEs) in aqueous solution. The plasma was produced from a microwave plasma torch (MPT) under atmospheric pressure and was used as ambient ion source of a linear ion trap mass spectrometer (LTQ). Water samples were directly pneumatically nebulized to flow into the plasma through the central tube of MPT. For some REEs, the generated composite ions were detected in both positive and negative ion modes and further characterized in tandem mass spectrometry. Under the optimized conditions, the limit of detection (LOD) was at the level 0.1 ng/mL using MS(2) procedure in negative mode. A single REE analysis can be completed within 2~3 minutes with the relative standard deviation ranging between 2.4% and 21.2% (six repeated measurements) for the 5 experimental runs. Moreover, the recovery rates of these REEs are between the range of 97.6%-122.1%. Two real samples have also been analyzed, including well and orange juice. These experimental data demonstrated that this method is a useful tool for the field analysis of REEs in water and can be used as an alternative supplement of ICP-MS. PMID:26421013

  6. Low Temperature Life-Cycle Testing of a Lithium-Ion Battery for Low-Earth-Orbiting Spacecraft

    NASA Technical Reports Server (NTRS)

    Reid, Concha

    2006-01-01

    A flight-qualified, lithium-ion (Li-ion) battery developed for the Mars Surveyor Program 2001 Landeris undergoing life-testing at low temperature under a low-Earth-orbit (LEO) profile to assess its capability to provide long term energy storage for aerospace missions. NASA has embarked upon an ambitious course to return humans to the moon by 2015-2020 in preparation for robotic and human exploration of Mars and robotic exploration of the moons of outer planets. Li-ion batteries are excellent candidates to provide power and energy storage for multiple aspects of these missions due to their high specific energy, high energy density, and excellent low temperature performance. Laboratory testing of Li-ion technology is necessary in order to assess lifetime, characterize multi-cell battery-level performance under aerospace conditions, and to gauge safety aspects of the technology. Life-cycle testing provides an opportunity to examine battery-level performance and the dynamics of individual cells in the stack over the entire life of the battery. Data generated through this testing will be critical to establish confidence in the technology for its widespread use in manned and unmanned missions.

  7. Conductivity degradation of polyvinylidene fluoride composite binder during cycling: Measurements and simulations for lithium-ion batteries

    DOE PAGESBeta

    Grillet, Anne M.; Humplik, Thomas; Stirrup, Emily K.; Roberts, Scott A.; Barringer, David A.; Snyder, Chelsea M.; Janvrin, Madison R.; Apblett, Christopher A.

    2016-07-02

    The polymer-composite binder used in lithium-ion battery electrodes must both hold the electrodes together and augment their electrical conductivity while subjected to mechanical stresses caused by active material volume changes due to lithiation and delithiation. We have discovered that cyclic mechanical stresses cause significant degradation in the binder electrical conductivity. After just 160 mechanical cycles, the conductivity of polyvinylidene fluoride (PVDF):carbon black binder dropped between 45–75%. This degradation in binder conductivity has been shown to be quite general, occurring over a range of carbon black concentrations, with and without absorbed electrolyte solvent and for different polymer manufacturers. Mechanical cycling ofmore » lithium cobalt oxide (LiCoO2) cathodes caused a similar degradation, reducing the effective electrical conductivity by 30–40%. Mesoscale simulations on a reconstructed experimental cathode geometry predicted the binder conductivity degradation will have a proportional impact on cathode electrical conductivity, in qualitative agreement with the experimental measurements. Lastly, ohmic resistance measurements were made on complete batteries. Direct comparisons between electrochemical cycling and mechanical cycling show consistent trends in the conductivity decline. This evidence supports a new mechanism for performance decline of rechargeable lithium-ion batteries during operation – electrochemically-induced mechanical stresses that degrade binder conductivity, increasing the internal resistance of the battery with cycling.« less

  8. Flexible, solid-state, ion-conducting membrane with 3D garnet nanofiber networks for lithium batteries.

    PubMed

    Fu, Kun Kelvin; Gong, Yunhui; Dai, Jiaqi; Gong, Amy; Han, Xiaogang; Yao, Yonggang; Wang, Chengwei; Wang, Yibo; Chen, Yanan; Yan, Chaoyi; Li, Yiju; Wachsman, Eric D; Hu, Liangbing

    2016-06-28

    Beyond state-of-the-art lithium-ion battery (LIB) technology with metallic lithium anodes to replace conventional ion intercalation anode materials is highly desirable because of lithium's highest specific capacity (3,860 mA/g) and lowest negative electrochemical potential (∼3.040 V vs. the standard hydrogen electrode). In this work, we report for the first time, to our knowledge, a 3D lithium-ion-conducting ceramic network based on garnet-type Li6.4La3Zr2Al0.2O12 (LLZO) lithium-ion conductor to provide continuous Li(+) transfer channels in a polyethylene oxide (PEO)-based composite. This composite structure further provides structural reinforcement to enhance the mechanical properties of the polymer matrix. The flexible solid-state electrolyte composite membrane exhibited an ionic conductivity of 2.5 × 10(-4) S/cm at room temperature. The membrane can effectively block dendrites in a symmetric Li | electrolyte | Li cell during repeated lithium stripping/plating at room temperature, with a current density of 0.2 mA/cm(2) for around 500 h and a current density of 0.5 mA/cm(2) for over 300 h. These results provide an all solid ion-conducting membrane that can be applied to flexible LIBs and other electrochemical energy storage systems, such as lithium-sulfur batteries. PMID:27307440

  9. Magnesiothermically reduced diatomaceous earth as a porous silicon anode material for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Shen, Lanyao; Guo, Xianwei; Fang, Xiangpeng; Wang, Zhaoxiang; Chen, Liquan

    2012-09-01

    Three-dimensional porous silicon has been prepared by magnesiothermically reducing diatomaceous earth. BET surface area analysis shows that the specific surface area of the obtained porous silicon is about 96 m2 g-1, much higher than that of the diatomaceous earth (6 m2 g-1). The silicon products after HCl immersion have a porous structure similar to that of the diatomaceous earth, with pore sizes around 200 nm. Galvanostatic cycling tests show that the initial charge and discharge capacities of the porous silicon are 1321 mAh g-1 and 1818 mAh g-1, respectively. A reversible capacity of 633 mAh g-1 is retained after 30 cycles.

  10. Rietveld neutron powder profile analysis and electrical conductivity of the fast silver-ion conductor (LaO)AgS

    SciTech Connect

    Wilmer, D.; Wuensch, B. J.; Jorgensen, J. D.

    1999-11-18

    Lanthanum silver oxysulfide, (LaO)AgS, exhibits a predominantly ionic conductivity of 10{sup {minus}3} to 10{sup {minus}1} S/cm between 300 K and 770 K. The tetragonal structure consists of alternating (LaO) and (AgS) sheets, their sequence being O-La-S-Ag-S-La-O. The structure suggests that ionic transport arises from migration of silver ions within the AgS layers analogous to sodium ion transport in Na-{beta}-alumina. Neutron powder diffraction data measured at five temperatures between 300 K and 770 K are analyzed using the Rietveld method to determine the distribution and thermal vibration parameters of the mobile silver ions. The structural investigation is accompanied by measurements of the total conductivity in the same temperature range in order to resolve severe discrepancies in the literature data.

  11. Earth's ion upflow associated with polar cap patches: Global and in situ observations

    NASA Astrophysics Data System (ADS)

    Zhang, Qing-He; Zong, Qiu-Gang; Lockwood, Michael; Heelis, Roderick A.; Hairston, Marc; Liang, Jun; McCrea, Ian; Zhang, Bei-Chen; Moen, Jøran; Zhang, Shun-Rong; Zhang, Yong-Liang; Ruohoniemi, J. Michael; Lester, Mark; Thomas, Evan G.; Liu, Rui-Yuan; Dunlop, Malcolm W.; Liu, Yong C.-M.; Ma, Yu-Zhang

    2016-03-01

    We report simultaneous global monitoring of a patch of ionization and in situ observation of ion upflow at the center of the polar cap region during a geomagnetic storm. Our observations indicate strong fluxes of upwelling O+ ions originating from frictional heating produced by rapid antisunward flow of the plasma patch. The statistical results from the crossings of the central polar cap region by Defense Meteorological Satellite Program F16-F18 from 2010 to 2013 confirm that the field-aligned flow can turn upward when rapid antisunward flows appear, with consequent significant frictional heating of the ions, which overcomes the gravity effect. We suggest that such rapidly moving patches can provide an important source of upwelling ions in a region where downward flows are usually expected. These observations give new insight into the processes of ionosphere-magnetosphere coupling.

  12. Determination of equilibrium constants of alkaline earth metal ion chelates with Dowex A-1 chelating resin.

    PubMed

    Harju, L; Krook, T

    1995-03-01

    A complexation chemistry model is applied to chelating ion-exchange systems and a method is presented for the determination of equilibrium constants for metal ion chelates with these resins. Protonation constants for the iminodiacetic based chelating resin Dowex A-1 were determined from potentiometric pH-data. Equilibrium constants were determined for 1:1 beryllium, magnesium, calcium, strontium and barium chelates with the resin in a wide pH range by measuring the concentrations of respective metal ions in the aqueous phase with direct current plasma atomic emission spectrometry (DCP-AES). A batch technique was used for the equilibrium experiments. At pH below 7 protonated 1:1 species were also found to be formed with the resin. From the obtained equilibrium constants, theoretical distribution coefficients were calculated as function of pH for respective metal ion resin system. PMID:18966248

  13. Potentiometric CO2 Sensor Using Li+ Ion Conducting Li3PO4 Thin Film Electrolyte

    PubMed Central

    Noh, Whyo Sub; Satyanarayana, L.; Park, Jin Seong

    2005-01-01

    Li+ ion conducting Li3PO4 thin film electrolytes with thickness 300nm, 650nm and 1.2μm were deposited on Al2O3 substrate at room temperature by thermal evaporation method. Reference and sensing electrodes were printed on Au interfaces by conventional screen printing technique. The overall dimension of the sensor was 3 × 3 mm and of electrodes were 1 × 1.5 mm each. The fabricated solid state potentiometric CO2 sensors of type: CO2, O2, Au, Li2TiO3-TiO2| Li3PO4 |Li2CO3, Au, CO2, O2 have been investigated for CO2 sensing properties. The electromotive force (emf) and Δemf/dec values of the sensors are dependent on the thickness of the electrolyte film. 1.2μm thickness deposited sensor has shown good sensing behavior than the sensors with less thickness. The Δemf values of the sensor are linearly increased up to 460°C operating temperature and became stable above 460°C. Between 460-500°C temperatures region the sensor has reached an equilibrium state and the experimentally obtained Δemf values are about 80% of the theoretically calculated values. A Nernst's slope of -61mV/decade has been obtained between 250 to 5000 ppm of CO2 concentration at 500°C temperature. The sensor is suitable for ease of mass production in view of its miniaturization and cost effectiveness after some further improvement.

  14. Visualization of Live Cochlear Stereocilia at a Nanoscale Resolution Using Hopping Probe Ion Conductance Microscopy.

    PubMed

    Vélez-Ortega, A Catalina; Frolenkov, Gregory I

    2016-01-01

    The mechanosensory apparatus that detects sound-induced vibrations in the cochlea is located on the apex of the auditory sensory hair cells and it is made up of actin-filled projections, called stereocilia. In young rodents, stereocilia bundles of auditory hair cells consist of 3-4 rows of stereocilia of decreasing height and varying thickness. Morphological studies of the auditory stereocilia bundles in live hair cells have been challenging because the diameter of each stereocilium is near or below the resolution limit of optical microscopy. In theory, scanning probe microscopy techniques, such as atomic force microscopy, could visualize the surface of a living cell at a nanoscale resolution. However, their implementations for hair cell imaging have been largely unsuccessful because the probe usually damages the bundle and disrupts the bundle cohesiveness during imaging. We overcome these limitations by using hopping probe ion conductance microscopy (HPICM), a non-contact scanning probe technique that is ideally suited for the imaging of live cells with a complex topography. Organ of Corti explants are placed in a physiological solution and then a glass nanopipette-which is connected to a 3D-positioning piezoelectric system and to a patch clamp amplifier-is used to scan the surface of the live hair cells at nanometer resolution without ever touching the cell surface.Here, we provide a detailed protocol for the imaging of mouse or rat stereocilia bundles in live auditory hair cells using HPICM. We provide information about the fabrication of the nanopipettes, the calibration of the HPICM setup, the parameters we have optimized for the imaging of live stereocilia bundles and, lastly, a few basic image post-processing manipulations. PMID:27259929

  15. Relative abundance of heavy ions in the inner zone of the radiation belts of the earth

    SciTech Connect

    Panasyuk, M.I.

    1986-03-01

    The energy dependences of the relative abundances of energetic (E > 1 MeV/nucleon) H, He, and O ions in the radiation belts are analyzed on the basis of experimental results obtained from measurement of their spectral characteristics on several satellites: Molniya-2, Kosmos-900, Prognoz-5, Explorer-45, ISEE-1, and OV1-19. It is shown that the formation of the energy dependence of He/H and O/H can be explained with a model providing for ion diffusion into the interior of the radiation belts with Coulomb losses taken into account under thecondition that the total-energy spectra at the boundary are more rigid for the heavy ions and are determined by such parameters of the quiet solar wind as the relative concentrations of the individual ion components and their charge states. It is shown that the fluxes of O and Fe ions with E > 1 MeV/nucleon measured on the orbital stations Salyut-6 and Skylab have an energy dependence of the relative abundances not inconsistent with above-noted mechanism for the formation of energetic ions of the inner radiation belt.

  16. Use of weak acids to determine the bulk diffusion limitation of H+ ion conductance through the gramicidin channel.

    PubMed Central

    Decker, E R; Levitt, D G

    1988-01-01

    The addition of 2 M formic acid at pH 3.75 increased the single channel H+ ion conductance of gramicidin channels 12-fold at 200 mV. Other weak acids (acetic, lactic, oxalic) produce a similar, but smaller increase. Formic acid (and other weak acids) also blocks the K+ conductance at pH 3.75, but not at pH 6.0 when the anion form predominates. This increased H+ conductance and K+ block can be explained by formic acid (HF) binding to the mouth of the gramicidin channel (Km = 1 M) and providing a source of H+ ions. A kinetic model is derived, based on the equilibrium binding of formic acid to the channel mouth, that quantitatively predicts the conductance for different mixtures of H+, K+, and formic acid. The binding of the neutral formic acid to the mouth of the gramicidin channel is directly supported by the observation that a neutral molecule with a similar structure, formamide (and malonamide and acrylamide), blocks the K+ conductance at pH 6.0. The H+ conductance in the presence of formic acid provides a lower bound for the intrinsic conductance of the gramicidin channel when there is no diffusion limitation at the channel mouth. The 12-fold increase in conductance produced by formic acid suggests that greater than 90% of the total resistance to H+ results from diffusion limitation in the bulk solution. PMID:2449253

  17. Multispacecraft Observations of Few-MeV SEP Ion Event Onsets Near Earth

    NASA Astrophysics Data System (ADS)

    Eastman, T. E.; Christon, S. P.; Decker, R. B.; Roelof, E. C.

    2003-12-01

    Few-MeV-energy SEP proton flux onsets observed in interplanetary space near Earth are used to investigate the effectiveness of a single spacecraft stationed at the sunward L1 libration point ( ˜230 Re) to provide complete early warning information about Solar Energetic Particle (SEP) events. Knowledge of the behavior and distribution of few-MeV-energy protons at onset aids development of asset protection, predictive capabilities, and understanding of magnetospheric disturbances related to SEP appearance at Earth. Widely separated spacecraft, ACE near L1 and GOES-8, Geotail, and IMP-8 nearer to Earth ( ˜6.6-44 Re), provided simultaneous SEP observations from late 1997 to the present. A number of cases of spatial-temporal intensity variations between L1 and nearer-Earth observations are presented. Cases presented demonstrate large-scale transport characteristics both consistent and inconsistent with simple outward radial propagation (i.e., convection with the solar wind) of a locally planar feature over the ˜230 Re ( ˜0.01 AU) maximum separation distance.

  18. Communications via the radio artificial earth satellite: Design of the tracking diagram and features for conducting QSO

    NASA Technical Reports Server (NTRS)

    Dobrozhanskiy, V.; Rybkin, V.

    1980-01-01

    A detailed examination is made of the operation of a transmitting artifical Earth satellite. A tracking diagram for the satellite is constructed. The zone of radio visibility can be determined based on the techniques proposed.

  19. Synthesis of rock-salt type lithium borohydride and its peculiar Li{sup +} ion conduction properties

    SciTech Connect

    Miyazaki, R.; Maekawa, H.; Takamura, H.

    2014-05-01

    The high energy density and excellent cycle performance of lithium ion batteries makes them superior to all other secondary batteries and explains why they are widely used in portable devices. However, because organic liquid electrolytes have a higher operating voltage than aqueous solution, they are used in lithium ion batteries. This comes with the risk of fire due to their flammability. Solid electrolytes are being investigated to find an alternative to organic liquid. However, the nature of the solid-solid point contact at the interface between the electrolyte and electrode or between the electrolyte grains is such that high power density has proven difficult to attain. We develop a new method for the fabrication of a solid electrolyte using LiBH{sub 4,} known for its super Li{sup +} ion conduction without any grain boundary contribution. The modifications to the conduction pathway achieved by stabilizing the high pressure form of this material provided a new structure with some LiBH{sub 4}, more suitable to the high rate condition. We synthesized the H.P. form of LiBH{sub 4} under ambient pressure by doping LiBH{sub 4} with the KI lattice by sintering. The formation of a KI - LiBH{sub 4} solid solution was confirmed both macroscopically and microscopically. The obtained sample was shown to be a pure Li{sup +} conductor despite its small Li{sup +} content. This conduction mechanism, where the light doping cation played a major role in ion conduction, was termed the “Parasitic Conduction Mechanism.” This mechanism made it possible to synthesize a new ion conductor and is expected to have enormous potential in the search for new battery materials.

  20. Low Temperature Life-cycle Testing of a Lithium-ion Battery for Low-earth-orbiting Spacecraft

    NASA Technical Reports Server (NTRS)

    Reid, Concha

    2004-01-01

    A flight-qualified, lithium-ion (Li-ion) battery developed for the Mars Surveyor Program 2001 lander is undergoing life-testing at low temperature under a low-Earth-orbit (LEO) profile to assess its capability to provide long term energy storage for aerospace missions. NASA has embarked upon an ambitious course to return humans to the moon by 2015-2020 in preparation for robotic and human exploration of Mars and robotic exploration of the moons of outer planets. Li-ion batteries are excellent candidates to provide power and energy storage for multiple aspects of these missions due to their low specific energy, low energy density, and excellent low temperature performance. Laboratory testing of Li-ion technology is necessary in order to assess lifetime, characterize multi-cell battery-level performance under aerospace conditions, and to gauge safety aspects of the technology. Life-cycle testing provides an opportunity to examine battery-level performance and the dynamics of individual cells in the stack over the entire life of the battery. Data generated through this testing will be critical to establish confidence in the technology for its widespread use in manned and unmanned mission. This paper discusses the performance of the 28 volt, 25 ampere-hour battery through 6000 LEO cycles, which corresponds to one year on LEO orbit. Testing is being performed at 0 C and 40% depth-of-discharge. Individual cell behaviors and their effect on the performance of the battery are described. Capacity, impedance, energy efficiency and end-of-discharge voltage at 1000 cycle intervals are reported. Results from this life-testing will help contribute to the database on battery-level performance of aerospace Li-ion batteries and low temperature cycling under LEO conditions.

  1. 7Li NMR spectroscopy and ion conduction mechanism in mesoporous silica (SBA-15) composite poly(ethylene oxide) electrolyte

    NASA Astrophysics Data System (ADS)

    Reddy, M. Jaipal; Chu, Peter P.

    A composite of mesoporous silica (SBA-15) with a polyethylene oxide (PEO) polymer electrolyte is examined for use in various electrochemical devices. Incorporation of SBA-15 in a PEO:LiClO 4 polymer electrolyte facilitates salt dissociation, enhances ion conductivity, and improves miscibility between organic and inorganic moieties. Optimized conductivity is found at 10 wt.% SBA-15 composition, above this concentration the conductivity is reduced due to aggregation of a SBA-15:Li rich phase. Heating above melt temperature of PEO allows more of the polymer segments to interact with SBA-15. This results in a greater degree of disorder upon cooling, and the ion conductivity is enhanced. A 7Li MAS NMR study reveals three types of lithium-ion coordination. Two major types of conduction mechanism can be identified: one through conventional amorphous PEO; a second via hopping in a sequential manner by replacing the nearby vacancies ('holes') on the surface (both interior and exterior) of the SBA-15 channels.

  2. Conducting polymer-skinned electroactive materials of lithium-ion batteries: ready for monocomponent electrodes without additional binders and conductive agents.

    PubMed

    Kim, Ju-Myung; Park, Han-Saem; Park, Jang-Hoon; Kim, Tae-Hee; Song, Hyun-Kon; Lee, Sang-Young

    2014-08-13

    Rapid growth of mobile and even wearable electronics is in pursuit of high-energy-density lithium-ion batteries. One simple and facile way to achieve this goal is the elimination of nonelectroactive components of electrodes such as binders and conductive agents. Here, we present a new concept of monocomponent electrodes comprising solely electroactive materials that are wrapped with an insignificant amount (less than 0.4 wt %) of conducting polymer (PEDOT:PSS or poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate)). The PEDOT:PSS as an ultraskinny surface layer on electroactive materials (LiCoO2 (LCO) powders are chosen as a model system to explore feasibility of this new concept) successfully acts as a kind of binder as well as mixed (both electrically and ionically) conductive film, playing a key role in enabling the monocomponent electrode. The electric conductivity of the monocomponent LCO cathode is controlled by simply varying the PSS content and also the structural conformation (benzoid-favoring coil structure and quinoid-favoring linear or extended coil structure) of PEDOT in the PEDOT:PSS skin. Notably, a substantial increase in the mass-loading density of the LCO cathode is realized with the PEDOT:PSS skin without sacrificing electronic/ionic transport pathways. We envisage that the PEDOT:PSS-skinned electrode strategy opens a scalable and versatile route for making practically meaningful binder-/conductive agent-free (monocomponent) electrodes. PMID:24988178

  3. Ion acceleration at CME-driven shocks near the Earth and the Sun

    SciTech Connect

    Desai, Mihir; Dayeh, Maher; Ebert, Robert; Smith, Charles; Mason, Glenn; Li, G.

    2012-11-20

    We compare the behavior of heavy ion spectra during an Energetic Storm Particle (ESP) event that exhibited clear evidence of wave excitation with that observed during an intense, large gradual Solar Energetic Particle (SEP) event in which the associated <0.2 MeV/nucleon ions are delayed >12 hr. We interpret that the ESP event is an example of the first-order Fermi acceleration process where enhancements in the magnetic field power spectral densities around local ion cyclotron frequency {nu}{sub pc} indicate the presence of Alfven waves excited by accelerated protons streaming away from the in-situ interplanetary shock. The softening or unfolding of the CNO energy spectrum below {approx}200 keV/nucleon and the systematic organization of the Fe and O spectral roll-overs with the E/q ratio during the ESP event are likely due to M/Q-dependent trapping and scattering of the heavy ions by the proton-excited waves. Based on striking similarities in the spectral behavior observed upstream of both, the ESP and the SEP event, we suggest that coupling between proton-generated Alfven waves and energetic ions is also operating at the distant CME shock during the large, gradual SEP event, thereby providing us with a new, powerful tool to remotely probe the roles of shock geometries and wave-particle interactions at near-Sun CME-driven shocks.

  4. Ceramic separators based on Li+-conducting inorganic electrolyte for high-performance lithium-ion batteries with enhanced safety

    NASA Astrophysics Data System (ADS)

    Jung, Yun-Chae; Kim, Seul-Ki; Kim, Moon-Sung; Lee, Jeong-Hye; Han, Man-Seok; Kim, Duck-Hyun; Shin, Woo-Cheol; Ue, Makoto; Kim, Dong-Won

    2015-10-01

    Flexible ceramic separators based on Li+-conducting lithium lanthanum zirconium oxide are prepared as thin films and directly applied onto negative electrode to produce a separator-electrode assembly with good interfacial adhesion and low interfacial resistances. The ceramic separators show an excellent thermal stability and high ionic conductivity as compared to conventional polypropylene separator. The lithium-ion batteries assembled with graphite negative electrode, Li+-conducting ceramic separator and LiCoO2 positive electrode exhibit good cycling performance in terms of discharge capacity, capacity retention and rate capability. It is also demonstrated that the use of a ceramic separator can greatly improve safety over cells employing a polypropylene separator, which is highly desirable for lithium-ion batteries with enhanced safety.

  5. Toward practical application of functional conductive polymer binder for a high-energy lithium-ion battery design.

    PubMed

    Zhao, Hui; Wang, Zhihui; Lu, Peng; Jiang, Meng; Shi, Feifei; Song, Xiangyun; Zheng, Ziyan; Zhou, Xin; Fu, Yanbao; Abdelbast, Guerfi; Xiao, Xingcheng; Liu, Zhi; Battaglia, Vincent S; Zaghib, Karim; Liu, Gao

    2014-11-12

    Silicon alloys have the highest specific capacity when used as anode material for lithium-ion batteries; however, the drastic volume change inherent in their use causes formidable challenges toward achieving stable cycling performance. Large quantities of binders and conductive additives are typically necessary to maintain good cell performance. In this report, only 2% (by weight) functional conductive polymer binder without any conductive additives was successfully used with a micron-size silicon monoxide (SiO) anode material, demonstrating stable and high gravimetric capacity (>1000 mAh/g) for ∼500 cycles and more than 90% capacity retention. Prelithiation of this anode using stabilized lithium metal powder (SLMP) improves the first cycle Coulombic efficiency of a SiO/NMC full cell from ∼48% to ∼90%. The combination enables good capacity retention of more than 80% after 100 cycles at C/3 in a lithium-ion full cell. PMID:25314674

  6. Ion probe determinations of the rare earth concentrations of individual meteoritic phosphate grains

    NASA Technical Reports Server (NTRS)

    Crozaz, G.; Zinner, E.

    1985-01-01

    A new ion probe method for quantitative measurements of the concentrations of all the REE down to the ppm level in 5-20 micron spots is presented. The first application of the method is the determination of REE abundances in meteoritic phosphates. Results are shown to be in good agreement with previous INAA and ion probe determinations. The merrillites in the St. Severin amphoterite are richer in REE than the apatites (the enrichment factors, for various REE, range from 2.3 to 14.2) in contradiction with the results of Ebihara and Honda (1983). Provided good standards for other mineral phases are found or implanted marker ion techniques are used, the method should find a wide range of applications for the study of both terrestrial and extraterrestrial crystals at the microscopic level.

  7. Preparation of composite polymer electrolytes by electron beam-induced grafting: Proton- and lithium ion-conducting membranes

    NASA Astrophysics Data System (ADS)

    Nasef, M. M.; Saidi, H.; Dahlan, K. Z. M.

    2007-12-01

    Two classes of composite polymer electrolyte membranes, one conducting lithium ions (Li +) and the other conducting protons (H +) were prepared using simultaneous electron beam-induced grafting. Porous poly(vinylidene fluoride) (PVDF) films were impregnated with styrene and subjected to electron beam (EB) irradiation to obtain polystyrene (PS) filled PVDF precursor films that were subsequently treated with either chlorosulfonic acid/1,1,2,2-tetrachloroethane mixture to obtain H +-conducting composite membranes or LiPH 6/EC/DEC liquid electrolyte to obtain Li +-conducting composite membranes. The properties of the obtained membranes were evaluated using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and AC impedance measurements. The obtained membranes were found to achieve grafting content up to 46% with superior Li +-conductivity of 1.91 × 10 -3 S/cm and H +-conductivity of 5.95 × 10 -2 S/cm. The results of this work show that simultaneous radiation-induced grafting with EB is a promising method to prepare high quality ion-conducting membranes for possible use in fuel cells and lithium batteries.

  8. Flexible and Conducting Metal-Fabric Composites Using the Flame Spray Process for the Production of Li-Ion Batteries

    NASA Astrophysics Data System (ADS)

    Voyer, Joel

    2013-06-01

    The wire flame spray process was used to produce electrically conductive and flexible Al coatings onto diverse textile fabrics. The investigation studied the influence of the spraying parameters and fabric materials on the electrical conductivity of the metal-fabric composites. Furthermore, this study showed that the production of flexible Li-ion batteries having good electrical properties based on the use of such flame-sprayed aluminium cathode current collectors is viable. Results show that a coating quantity threshold of about 20 mg/cm2 exists to obtain a sufficient electrical surface conductivity for a commercial use of the produced metal-fabric composites. An excellent electrical surface conductivity of the composites (about 500 SA) could be achieved through an adequate optimization of the spraying parameters. This conductivity increase enabled a reduction of the coating quantity and thus the flexibility of the fabric materials is better conserved, rendering the use of such composites for flexible batteries even more interesting. This study showed that the production of electrically conductive and flexible metal-fabric composites having sufficient electrical conductivity for the manufacture of flexible Li ions batteries is possible. This new method of producing such batteries represents an alternative to other chemically based processes which are hazardous to the environment because of their chemical nature.

  9. Laser-induced grating spectroscopy of rare earth ions in solids

    SciTech Connect

    French, V.A.

    1992-01-01

    The characteristics of energy transfer and migration processes important in the optical dynamics of Tm,Ho:YAG and Tm:YAG laser crystals were investigated using both time-resolved fluorescence spectroscopy and laser-induced grating spectroscopy. Four-wave mixing techniques were used to produce permanent laser-induced refractive index gratings in Eu-doped silicate glasses. The effects on the characteristics of these permanent gratings produced by changing the divalent modifier ions of the glass host are reported. Efficient long-range energy migration was found to take place in the [sup 3]F[sub 4] level of the Tm ions, which enhances the energy transfer to Ho ions. The parameters describing excitation migration were determined experimentally and used to calculate an overall Tm-Ho energy transfer rate. This was found to be in close agreement with the rate determined by the results of fluorescence spectral dynamics measurements. Theoretical estimates were made of the fundamental ion-ion interaction rates responsible for each of the physical processes investigated here and the results were all found to be in close agreement with the experimentally determined values. The author extends previous investigations on the Eu-doped silicate glasses by describing the variation of the four-wave-mixing signal intensity of a series of glasses with different divalent alkaline network modifier ions. The temperature dependence of the signal from one of the samples was measured and a theoretical explanation for the change in the refractive index associated with the double-minimum potential well model is developed.

  10. Counter-ion Dependent, Longitudinal Unzipping of Multi-Walled Carbon Nanotubes to Highly Conductive and Transparent Graphene Nanoribbons

    PubMed Central

    Shinde, Dhanraj B.; Majumder, Mainak; Pillai, Vijayamohanan K.

    2014-01-01

    Here we report for the first time, a simple hydrothermal approach for the bulk production of highly conductive and transparent graphene nanoribbons (GNRs) using several counter ions from K2SO4, KNO3, KOH and H2SO4 in aqueous media, where, selective intercalation followed by exfoliation gives highly conducting GNRs with over 80% yield. In these experiments, sulfate and nitrate ions act as a co-intercalant along with potassium ions resulting into exfoliation of multi-walled carbon nanotubes (MWCNTs) in an effective manner. The striking similarity of experimental results in KOH and H2SO4 that demonstrates partially damaged MWCNTs, implies that no individual K+, SO42− ion plays a key role in unwrapping of MWCNTs, rather this process is largely effective in the presence of both cations and anions working in a cooperative manner. The GNRs can be used for preparing conductive 16 kΩsq−1, transparent (82%) and flexible thin films using low cost fabrication method. PMID:24621526

  11. Extraction Separation of Rare-Earth Ions via Competitive Ligand Complexations between Aqueous and Ionic-Liquid Phases

    SciTech Connect

    Luo, Huimin; Sun, Xiaoqi; Bell, Jason R; Dai, Sheng

    2011-01-01

    The extraction separation of rare earth elements is the most challenging separation processes in hydrometallurgy and advanced nuclear fuel cycles. The TALSPEAK process (Trivalent Actinide Lanthanide Separations by Phosphorus-reagent Extraction from Aqueous Komplexes) is a prime example of these separation processes. The objective of this paper is to explore the use of ionic liquids (ILs) for the TALSPEAK-like process, to further enhance its extraction efficiencies for lanthanides, and to investigate the potential of using this modified TALSPEAK process for separation of lanthanides among themselves. Eight imidazolium ILs ([Cnmim][NTf2] and [Cnmim][BETI], n=4,6,8,10) and one pyrrolidinium IL ([C4mPy][NTf2]) were investigated as diluents using di(2-ethylhexyl)phosphoric acid (HDEHP) as an extractant for separation of lanthanide ions from aqueous solutions of 50 mM glycolic acid or citric acid and 5 mM diethylenetriamine pentaacetic acid (DTPA). The extraction efficiencies were studied in comparison with diisopropylbenzene (DIPB), an organic solvent used as diluent for the conventional TALSPEAK extraction system. Excellent extraction efficiencies and selectivities were found for a number of lanthanide ions using HDEHP as an extractant in these ILs. The effects of different alkyl chain lengths in the cations of ILs and anions on extraction efficiencies and selectivities of lanthanide ions are also presented in this paper.

  12. Energetic heavy ions observed upstream of the Earth's bow shock by the STEP/EPACT instrument on WIND

    NASA Astrophysics Data System (ADS)

    Mason, G. M.; Mazur, J. E.; von Rosenvinge, T. T.

    The Supra-Thermal through Energetic Particle (STEP) subsystem of the EPACT experiment on the WIND spacecraft observed numerous short duration heavy ion enhancements during the ˜9 month period Nov. 1994-Sept. 1995. These enhancements were most frequent and intense when WIND was close to the magnetosphere, but were often observed also during the period when the spacecraft was >100 RE upstream. The events occur in association with high speed solar wind streams that are signatures of corotating interaction regions (CIRs). A typical event observed on January 31, 1995 when WIND was 195 RE upstream showed strong field aligned anisotropies and rapid time variations. Heavy ion abundances near 45 keV/nucleon (nuc) were He:C:O:Fe = 86 : 1.46 : ≡1 ∶ 0.12, similar to those observed at higher energies in CIRs, and distinctly different from magnetospheric ring current abundances measured on the AMPTE spacecraft. We suggest that the CIRs provide the seed population for these heavy ion events, that are then further accelerated in association with the Earth's bow shock.

  13. The calculation of electron chemical potential and ion charge state and their influence on plasma conductivity in electrical explosion of metal wire

    SciTech Connect

    Shi, Zongqian; Wang, Kun; Li, Yao; Shi, Yuanjie; Wu, Jian; Jia, Shenli

    2014-03-15

    The electron chemical potential and ion charge state (average ion charge and ion distribution) are important parameters in calculating plasma conductivity in electrical explosion of metal wire. In this paper, the calculating method of electron chemical potential and ion charge state is discussed at first. For the calculation of electron chemical potential, the ideal free electron gas model and Thomas-Fermi model are compared and analyzed in terms of the coupling constant of plasma. The Thomas-Fermi ionization model, which is used to calculate ion charge state, is compared with the method based on Saha equation. Furthermore, the influence of electron degenerated energy levels and ion excited states in Saha equation on the ion charge state is also analyzed. Then the influence of different calculating methods of electron chemical potential and ion charge state on plasma conductivity is discussed by applying them in the Lee-More conductivity model.

  14. Ion slip effect on a steady flow through a circular pipe of a dusty conducting Oldroyd 8-constant fluid

    NASA Astrophysics Data System (ADS)

    Attia, H. A.; Abdeen, M. A. M.; Elbarawy, M. T. M. M.

    2014-09-01

    In this paper, a steady magnetohydrodynamic (MHD) flow of a dusty incompressible electrically conducting Oldroyd 8-constant fluid through a circular pipe is examined with considering the ion slip effect. A constant pressure gradient in the axial direction and an external uniform magnetic field in the perpendicular direction are applied. A numerical solution is obtained for the governing nonlinear momentum equations by using finite differences. The effect of the ion slip, the non-Newtonian fluid characteristics, and the particle-phase viscosity on the velocity, volumetric flow rates, and skin friction coefficients of both the fluid and particle phases is reported.

  15. Multiscale Dynamics in Soft-Matter Systems: Enzyme Catalysis, Sec-Facilitated Protein Translocation, and Ion-Conduction in Polymers

    NASA Astrophysics Data System (ADS)

    Miller, Thomas

    Nature exhibits dynamics that span extraordinary ranges of space and time. In some cases, these dynamical hierarchies are well separated, simplifying their understanding and description. But chemistry and biology are replete with examples of dynamically coupled scales. In this talk, we will discuss the use of high-performance computing and new simulation methods that enable the inclusion of nuclear quantum effects, such as zero point energy and tunneling, in the reaction dynamics of enzymes, as well as coarse-graining strategies to enable minute-timescale simulations of protein targeting to cell membranes and ion-conduction in polymer electrolytes for lithium-ion battery applications.

  16. A mechanically robust and highly ion-conductive polymer-blend coating for high-power and long-life lithium-ion battery anodes.

    PubMed

    Li, Fu-Sheng; Wu, Yu-Shiang; Chou, Jackey; Winter, Martin; Wu, Nae-Lih

    2015-01-01

    A mechanically robust and ion-conductive polymeric coating containing two polymers, polyethylene glycol tert-octylphenyl ether and poly(allyl amine), with four tailored functional groups is developed for graphite and graphite-Si composite anodes. The coating, acting as an artificial solid electrolyte interphase, leads to remarkable enhancement in capacity reversibility and cycling stability, as well as a high-rate performance of the studied anodes. PMID:25377527

  17. Epitaxial growth and lithium ion conductivity of lithium-oxide garnet for an all solid-state battery electrolyte.

    PubMed

    Kim, Sangryun; Hirayama, Masaaki; Taminato, Sou; Kanno, Ryoji

    2013-09-28

    Epitaxial thin films of Al-doped Li7La3Zr2O12 (LLZO) with a cubic garnet-type structure were successfully synthesized using pulsed laser deposition to investigate the lithium ion conduction in grains. Two orientations of the films were obtained depending on the Gd3Ga5O12 (GGG) substrate orientation, LLZO(001)/GGG(001) and LLZO(111)/GGG(111). The ionic conductivities in the grains of the (001) and (111) films were 2.5 × 10(-6) and 1.0 × 10(-5) S cm(-1) at 298 K, respectively, which were lower than those of polycrystalline LLZO of over 10(-4) S cm(-1). X-ray reflectometry and inductively coupled plasma mass spectrometry revealed a large amount of Al(3+) of over 0.6 moles substituted for Li(+). These results indicate that the Al(3+) substitution in the LLZO lattice decreases the number of movable lithium ions and blocks the three-dimensional lithium migration pathway. The lattice mismatch between the film and the substrate induced the lattice distortion of the LLZO, resulting in different conductivities between the (001) and (111) films. The epitaxial-film model system directly clarified a substantial impact of the Al substitution and the lattice distortion on the lithium ion conductivity in the LLZO. PMID:23877300

  18. Effect of ion irradiation on the thermal conductivity of UO2 and U3O8 epitaxial layers

    NASA Astrophysics Data System (ADS)

    Weisensee, Patricia B.; Feser, Joseph P.; Cahill, David G.

    2013-11-01

    The effect of 2 MeV Ar+-ion irradiation on the thermal conductivity of epitaxial layers of UO2 and U3O8 was studied with time-domain thermoreflectance (TDTR) at temperatures between 323 and 658 K. The thermal conductivity of unirradiated UO2 is 10.2 W m-1 K-1 at 323 K and scales with temperature like 1/T. Upon irradiation with doses >0.7 × 1015 Ar+ cm-2, the thermal conductivity decreases to a nearly constant value <4 W m-1 K. By comparing the data to an analytic model, we report the point-scattering strength of irradiation induced defects in UO2. Unirradiated U3O8 has a thermal conductivity of 1.6 W m-1 K-1 at 333 K. Low and medium doses of Ar-ion irradiation decrease the thermal conductivity of U3O8 to <1.0 W m-1 K-1. Unexpectedly, it is found that higher doses of Ar+ irradiation increased the conductivity of U3O8 to ˜2.0 W m-1 K-1.

  19. Ion transport study in polymer-nanocomposite films by dielectric spectroscopy and conductivity scaling

    NASA Astrophysics Data System (ADS)

    Tripathi, Namrata; Thakur, Awalendra K.; Shukla, Archana; Marx, David T.

    2015-07-01

    The dielectric and conductivity response of polymer nanocomposite electrolytes (films of PMMA4LiClO4 dispersed with nano-CeO2 powder) have been investigated. The dielectric behavior was analyzed via the dielectric permittivity (ε‧) and dissipation factor (tan δ) of the samples. The analysis has shown the presence of space charge polarization at lower frequencies. The real part of ac conductivity spectra of materials obeys the Jonscher power law. Parameters such as dc conductivity, hopping rate, activation energies and the concentration of charge carriers were determined from conductivity data using the Almond West formalism. It is observed that the higher ionic conductivity at higher temperature is due to increased thermally-activated hopping rates accompanied by a significant increase in carrier concentration. The contribution of carrier concentration to the total conductivity is also confirmed from activation energy of migration conduction and from Summerfield scaling. The ac conductivity results are also well correlated with TEM results.

  20. Electrical conductivity model of Al-bearing bridgmanite with implications for the electrical structure of the Earth's lower mantle

    NASA Astrophysics Data System (ADS)

    Yoshino, Takashi; Kamada, Seiji; Zhao, Chengcheng; Ohtani, Eiji; Hirao, Naohisa

    2016-01-01

    Electrical conductivity measurements of bridgmanite with various Al contents and a constant Mg# of 90 were performed at temperatures ranging from room temperature up to 2000 K at pressures of 26-28 GPa in a Kawai-type multianvil apparatus by impedance spectroscopy analysis. The incorporation of Al into bridgmanite raises its electrical conductivity significantly, but it is a small conductivity variation with respect to the quantity of Al. Synchrotron Mössbauer spectroscopy of recovered samples showed significant amounts of ferric iron in aluminous bridgmanite. The mobility of the charge carriers in bridgmanite was calculated based on the conductivity and the Fe3+/ΣFe ratio. The relationship between the logarithm of the electrical conductivity and the reciprocal temperature is consistent with Fe2+-Fe3+ electron hopping (small polarons) as the dominant conduction mechanism at low temperatures (<1400 K) and ionic conduction at higher temperatures (>1600 K). By taking various conduction mechanisms into account, we develop an electrical conductivity model for aluminous bridgmanite as a function of the Al and Fe contents. The small polaron conduction model indicates that the electrical conductivity of aluminous bridgmanite has a maximum at around 0.06 Al atoms per formula unit, and any further increase in the Al content in bridgmanite reduces the conductivity. In contrast, the ionic conduction model indicates that the electrical conductivity simply increases with increasing Al content. The resulting conductivity of Al-bearing bridgmanite first increases up to 0.06 Al atoms per formula unit and then remains constant or increases with increasing Al content at higher temperatures. The increase in conductivity observed in the uppermost part of the lower mantle by electromagnetic studies can be explained by the gradual decomposition of majorite garnet. The deeper lower mantle conductivity would be controlled by small polaron conduction because of the large positive