Showing papers on "Ion published in 1971"
TL;DR: It is suggested that the ability of the alkaline earth cations to shift the conductance-voltage curves of a nerve along the voltage axis by 20–26 mv for a 10-fold increase in concentration may be due to essentially a screening rather than a binding phenomenon.
Abstract: Phospholipid bilayer membranes were bathed in a decimolar solution of monovalent ions, and the conductance produced by neutral carriers of these monovalent cations and anions was used to assess the electric potential at the surface of the membrane. When the bilayers were formed from a neutral lipid, phosphatidylethanolamine, the addition of alkaline earth cations produced no detectable surface potential, indicating that little or no binding occurs to the polar head group with these ions. When the bilayers were formed from a negatively charged lipid, phosphatidylserine, the addition of Sr and Ba decreased the magnitude of the surface potential as predicted by the theory of the diffuse double layer. In particular, the potential decreased 27 mv for a 10-fold increase in concentration in the millimolar-decimolar range. A 10-fold increase in the Ca or Mg concentration also produced a 27 mv decrease in potential in this region, which was again due to screening, but it was necessary to invoke some specific binding to account for the observation that these cations were effective at a lower concentration than Ba or Sr. It is suggested that the ability of the alkaline earth cations to shift the conductance-voltage curves of a nerve along the voltage axis by 20–26 mv for a 10-fold increase in concentration may be due to essentially a screening rather than a binding phenomenon.
600 citations
TL;DR: Voltage clamp currents from medium sized ganglion cells of Helix pomatia have a fast transient outward current component in addition to the usually observed inward and outward currents.
Abstract: Voltage clamp currents from medium sized ganglion cells of Helix pomatia have a fast transient outward current component in addition to the usually observed inward and outward currents. This component is inactivated at normal resting potential. The current, which is carried by K+ ions, may surpass leakage currents by a factor of 100 after inactivation has been removed by hyperpolarizing conditioning pulses. Its kinetics are similar to those of the inward current, except that it has a longer time constant of inactivation. It has a threshold close to resting potential. This additional component is also present in giant cells, where however, it is less prominent. Pacemaker activity is controlled by this current. It was found that inward currents have a slow inactivating process in addition to a fast, Hodgkin-Huxley type inactivation. The time constants of the slow process are similar to those of slow outward current inactivation.
429 citations
TL;DR: Triatomic hydrogen positive ion surface crossing effects in chemical reactions based on potential energy surfaces calculation using diatomics-in-molecules approach were investigated in this paper, where the potential energy surface calculation was carried out using a graph-based approach.
Abstract: Triatomic hydrogen positive ion surface crossing effects in chemical reactions based on potential energy surfaces calculation using diatomics-in- molecules approach
384 citations
378 citations
367 citations
TL;DR: The tracks formed in nuclear emulsion by energetic heavy ions are made up of grains sensitized by the passage of a single ion.
Abstract: The tracks formed in nuclear emulsion by energetic heavy ions are made up of grains sensitized by the passage of a single ion. Cells may also be inactivated by the passage of a single ion, in a mode called ion-kill. Emulsion tracks pass from the grain-count regime, where the tracks is a sequence of isolated grains, to the track-width regime, where the track is fully closed and has a cross-sectional area larger than that of an emulsion grain, with increasing values of $z^{2}/\beta ^{2}$ for the charged particle causing the track. The measured value of the inactivation cross section for human kidney cells increases in a similar way. The response of cells is not the same as emulsion grains, because cells may also be inactivated by a gamma-kill mode, involving the cumulative effect of overlapping delta rays from several ions, in addition to the ion-kill mode present in both emulsion and cells. These considerations lead to the equations $P=\sigma /\sigma _{0}=[1-e^{-z^{2}/\kappa ...
321 citations
TL;DR: In this paper, a simple collision model involving only the primary ion and a single isolated surface atom is proposed to identify surface impurity atoms, which can be used for characterizing thin films.
299 citations
TL;DR: Evidence is presented that the transport of lipid-soluble ions through bilayer membranes occurs in three distinct steps: adsorption to the membranesolution interface; passage over an activation barrier to the opposite interface; and desorption into the aqueous solution.
Abstract: Evidence is presented that the transport of lipid-soluble ions through bilayer membranes occurs in three distinct steps: (1) adsorption to the membranesolution interface; (2) passage over an activation barrier to the opposite interface; and (3) desorption into the aqueous solution Support for this mechanism comes from a consideration of the potential energy of the ion, which has a minimum in the interface The formal analysis of the model shows that the rate constants of the individual transport steps can be determined from the relaxation of the electric current after a sudden change in the voltage Such relaxation experiments have been carried out with dipicrylamine and tetraphenylborate as permeable ions In both cases the rate-determining step is the jump from the adsorption site into the aqueous phase Furthermore, it has been found that with increasing ion concentration the membrane conductance goes through a maximum In accordance with the model recently developed by L J Bruner, this behavior is explained by a saturation of the interface, which leads to a blocking of the conductance at high concentrations
294 citations
TL;DR: In this article, the conditions under which an oxide surface in aqueous solution will obey the Nernst equation with respect to H+/OH as potential-determining ions are investigated and a modified form of the NE is derived.
Abstract: The conditions under which an oxide surface in aqueous solution will obey the Nernst equation with respect to H+/OH– as potential-determining ions are investigated and a modified form of the Nernst equation is derived. This is combined with a model of the inner part of the double layer involving adsorption of both anions and cations of a supporting uni-univalent electrolyte and a discreteness-of-charge correction in their adsorption isotherms. Theoretical total differential capacities at the interface are compared with experimental data for TiO2 and SiO2.
290 citations
TL;DR: The ionic conductivity of the solid electrolyte NaAl11O17 has been measured from − 150 to + 820°C using a novel nonpolarizing solid electrode, reversible to sodium ions as mentioned in this paper.
Abstract: The ionic conductivity of the solid electrolyte NaAl11O17 has been measured from − 150 to + 820°C using a novel nonpolarizing solid electrode, reversible to sodium ions. The resistivity at 25°C was found to be 72 Ω‐cm, the lowest value reported for any ionically conducting oxide ceramic. The enthalpy of motion is 3.79 kcal/mole, and the transport of sodium ions takes place by an interstitialcy mechanism.
288 citations
TL;DR: In this article, the competitive adsorption of phosphate + arsenate and phosphate + selenite on goethite and gibbsite has been measured and described by a Langmuir-type exchange equation.
Abstract: The competitive adsorption of phosphate + arsenate and phosphate + selenite on goethite and gibbsite has been measured. The oxide surface contains sites common to both anions on which competitive adsorption takes place and sites on which only one or the other anion is able to adsorb. The maximum amount of anions adsorbed from a mixture is approximately equal to the sum of the maximum adsorption for each anion in the absence of competition. The number of sites at which competition takes place is almost equal to the number of sites available to the anion with the lower adsorption in the absence of a competitor. Competition is described by a Langmuir-type exchange equation.
TL;DR: Upper Martian atmosphere UV emission spectrum observation noting carbon dioxide photoionization, ion fluorescent scattering and photon/electron dissociative excitation as discussed by the authors, showing that carbon dioxide photos are photoionized.
Abstract: Upper Martian atmosphere UV emission spectrum observation noting carbon dioxide photoionization, ion fluorescent scattering and photon/electron dissociative excitation
TL;DR: Electrophysiological and electron-microscopic studies were made of the effect of lanthanum ions on frog neuromuscular junctions, finding that with continued La-treatment, the frequency of miniature end-plate potentials subsides slowly until they are no longer detectable at most end-plates.
Abstract: 1. Electrophysiological and electron-microscopic studies were made of the effect of lanthanum ions on frog neuromuscular junctions. 2. In the presence of 1 mM La$^{2+}$, nerve impulses continued to invade the nerve terminals but ceased to release transmitter. 3. Lanthanum caused a rapid and large increase in the frequency of miniature end-plate potentials; presumably because La activates the mechanism of transmitter release without the usual prerequisite of presynaptic membrane depolarization. At 4 degrees C, La caused a 10 000-fold, or even larger increase in the rate of leakage of transmitter quanta. Such high rate of transmitter release was not accompanied by obvious changes in electron-microscopic structure of the nerve terminals. 4. With continued La-treatment, the frequency of miniature end-plate potentials subsides slowly until they are no longer detectable at most end-plates. During this period the number of synaptic vesicles is reduced until practically all the endings become completely depleted of synaptic vesicles. In contrast, coated vesicles and membrane-bound tubes and cysternae become more numerous.
TL;DR: A computer treatment is developed for determining the conformations of flexible molecules, such as nucleotides, in aqueous solution.
Abstract: A computer treatment is developed for determining the conformations of flexible molecules, such as nucleotides, in aqueous solution.
TL;DR: In this article, the electronic relaxation in solutions of solvated Fe3+, Mn2+ and Cr3+ is controlled by modulation of the quadratic zero field splitting interaction caused by collisions of the hydrated complex with bulk solvent molecules.
Abstract: Electronic relaxation in solutions of solvated Fe3+, Mn2+ (S=5/2) and Cr3+ (S=3/2) is controlled by modulation of the quadratic zero field splitting interaction. The modulation is caused by collisions of the hydrated complex with bulk solvent molecules. Theoretical expressions are derived for the electronic transversal and longitudinal relaxation times T 2e and T 1e and are used to interpret the E.S.R. data of these ions. The analysis yields results for the zero field splitting constants and for the mean lifetime between collisions. The latter are found to be in the range 4–9 × 10-12 s. The nuclear relaxation rate of the solvent nuclei are affected by the dipole-dipole and scalar interaction with the unpaired electrons of the paramagnetic ions. The usual equations for nuclear relaxation due to these interactions are modified to take into account the existence of several T 1e s and T 2e s. These equations are used to analyse proton relaxation data in aqueous solutions of Cr3+, Fe3+ and Mn2+. The E.S.R. and...
TL;DR: The concentrations of H(+) ions in the dayside region of the plasmasphere, measured from March 1968 through February 1969 by the Lockheed light-ion mass spectrometer aboard the OGO 5 satellite, are presented and analyzed in this paper.
Abstract: The concentrations of H(+) ions in the dayside region of the plasmasphere, measured from March 1968 through February 1969 by the Lockheed light-ion mass spectrometer aboard the OGO 5 satellite, are presented and analyzed. The position of the plasmapause on the dayside appears to be determined by the level of magnetic activity present during the previous corotation of the dayside sector through the formative nightside region. Observations of the buildup of H(+) density versus local time following magnetic storms indicate that H(+) ions flow from the dayside ionosphere into the plasmasphere and plasma trough. Plasmapause density profiles in the afternoon-dusk sector show the effects of the dayside filling from the ionosphere. In addition, several of the dayside profiles display a steep drop in the H(+) density of about a factor of 10 inside the plasmapause position.
TL;DR: In this paper, the vibrational excitation of N2 molecules by resonance scattering of electrons of 2-3 eV is calculated with a compound state model, that is on the assumption that the mechanism is e+N2 to N2-to N2+e'.
Abstract: The vibrational excitation of N2 molecules by resonance scattering of electrons of 2-3 eV is calculated with a compound state model, that is on the assumption that the mechanism is e+N2 to N2- to N2+e'. The complex electronic energy of the N2- ion is treated parametrically, the essential new point being that Gamma /h(cross), the autoionization rate, varies with the separation of the nuclei. The variation comes from the dependence of the angular momentum barrier on the energy of the emitted electron. Good agreement is obtained with the experimental energy dependence of cross sections with reasonable values of the parameters. Calculations have also been done to illustrate the transition to the impulse limit as Gamma is increased, and to the compound molecule limit as Gamma is reduced.
TL;DR: In this article, the surface of the Cu target becomes covered with microscopic cones, which give the target a velvet-like black appearance when the cones are closely spaced, and the result of dense cone coverage is a lower sputtering yield and more oblique ejection of sputtered material.
Abstract: When a Cu surface is sputtered by ion bombardment under the condition that Mo atoms arrive at the Cu surface during sputtering an unexpected phenomenon can arise: The surface of the Cu target becomes covered with microscopic cones. The cone density increases with increasing flux density of arriving Mo atoms. When the cones are closely spaced they give the target a velvet‐like black appearance. The result of dense cone coverage is a lower sputtering yield and a more oblique ejection of sputtered material. The cone tops seem to consist of Mo nuclei which are constantly replenished via surface migration and protect the underlying Cu from being sputtered.
TL;DR: A Gaussian basis set consisting of 12s-type, 6p-type and 4d-type functions has been optimized for the third row atoms, together with a 9s, 5p, 3d set for the corresponding dipositive ion as mentioned in this paper.
Abstract: A Gaussian basis set consisting of 12s-type, 6p-type and 4d-type functions has been optimized for the third row atoms, together with a 9s, 5p, 3d set for the corresponding dipositive ion. The applicability of these atomic sets for molecular calculation is discussed.
TL;DR: In this article, the hypernetted chain integral equation is used to calculate the ion-ion pair correlation functions and the thermodynamic properties of models for aqueous alkali halides.
Abstract: The hypernetted‐chain integral equation is used to calculate the ion–ion pair correlation functions and the thermodynamic properties of models for aqueous alkali halides based on an ion–ion pair potential function having four terms: the usual Coulomb term, a core repulsion term of order r−9, a well‐known dielectric repulsion term of order r−4, and a “Gurney” term to represent the effect of the overlap of the structure‐modified regions, “cospheres,” about the ions when the ions come close together. The only parameter in the potential which is adjusted to fit excess free energy data for solutions is the coefficient Aij of the Gurney term for the interaction of ions of species i and j. This is scaled so it represents the molar free energy change of water displaced from the cospheres when they overlap. The corresponding entropy change Sij and volume change Vij are adjusted to fit, respectively, heat of dilution and apparent molal volume data. Some thermodynamic problems in this fitting process, due to the und...
TL;DR: In this paper, the energy of the gaseous ions of the lanthanides and actinides was estimated for the lowest spectroscopic level of the configurations involving 4f, 5d, 6p, and 6s electrons for lanthanide ions and 5f, 6d, 7p and 7s electron for actinide ions.
Abstract: Methods are described for estimating energies of the electronic configurations of the gaseous ions of the lanthanides and actinides. Energies are tabulated for the lowest spectroscopic level of the configurations involving 4f, 5d, 6p, and 6s electrons for the lanthanide ions and 5f, 6d, 7p, and 7s electrons for the actinide ions. Some additional values are listed to be added to the previous tabulation for neutral atoms.
TL;DR: A toroidal plasma heated by an energetic neutral beam (thus consisting of an energetic ion component and a lower-energy bulk plasma) can produce net thermonuclear power under conditions far less restrictive than Lawson's criterion.
Abstract: A toroidal plasma heated by an energetic neutral beam (thus consisting of an energetic ion component and a lower-energy bulk plasma) can produce net thermonuclear power under conditions far less restrictive than Lawson's criterion.
TL;DR: In this paper, a model for the surface structure of rutile is proposed, based on infra-red studies of a crystalline sample prepared by the combustion of Ti(iso-PrO)4.
Abstract: A model for the surface structure of rutile is proposed, based on infra-red studies of a crystalline rutile sample prepared by the combustion of Ti(iso-PrO)4. It is suggested that the exterior surfaces of the rutile crystals correspond to three low index crystal planes—namely the (100), (101) and (110). Of these the first two are capable of adsorbing molecular water as ligand coordinated to Ti4+ surface ions, whereas the (110) crystal face adsorbs water dissociatively leading to the presence of equal quantities of two types of OH– ions. One of these types is associated with a surface Ti4+ ion which is five coordinate with respect to lattice oxide ions whereas the other type is bound to a surface Ti4+ ion which is only four fold oxide ion coordinate. It is possible to rationalize the observed thermal dehydroxylation and dehydration properties of the oxide and also account for its pyridine adsorption properties.
TL;DR: In this paper, the influence of a molecule's dipole moment on its ability to capture an electron into a stable bound state is examined, and it is proved that, in the fixed-nuclei approximation, a value greater than 1·625 Debye for the Dipole moment suffices to guarantee the existence of a discrete spectrum of negative ion states.
Abstract: The influence of a molecule's dipole moment on its ability to capture an electron into a stable bound state is examined. It is proved that, in the fixednuclei approximation, a value greater than 1·625 Debye for the dipole moment suffices to guarantee the existence of a discrete spectrum of negative ion states. Implications for Hartree-Fock calculations of negative ions are discussed. The interaction of electronic, vibrational and rotational motions in negative dipolar ions is studied, and conclusions are drawn for real molecules.
TL;DR: The limits of very slow and very fast sheath growth in a low-pressure plasma can be described by Child's law and the ion matrix model, respectively as mentioned in this paper, and it is shown that the range between these two extremes can be treated analytically by transforming the equations to the sheath edge frame of reference.
Abstract: The limits of very slow and very fast sheath growth in a low‐pressure plasma can be described by Child's law and the ion matrix model, respectively. It is shown that if the sheath edge grows with constant speed, the range between these two extremes can be treated analytically by transforming the equations to the sheath edge frame of reference. This provides a continuous transition between the two extremes which reduces to Child's law for very slow growth and to the ion matrix model for very fast growth. The theoretical expression for sheath thickness calculated from the continuous transition model is found to be in good agreement with experimental results.
TL;DR: In this article, the pulse-height vs energy response of a surface-barrier detector was measured for the ions He, C, O, Al, S, Ni, Cu, Ag, 31 MeV, and U, 26 MeV.
TL;DR: In this paper, a fast and very sensitive technique has been developed to determine the extent of ionic contamination of oxides in MOS capacitors, based on the measurement of the displacement current response to a slow linear ramp voltage at elevated temperatures.
Abstract: A fast, simple and very sensitive technique has been developed to determine the extent of ionic contamination of oxides in MOS capacitors. The method is capable of detecting better than 109 mobile ions/cm2 and is based on the measurement of the displacement current response to a slow linear ramp voltage at elevated temperatures. This yields an ionic displacement current peak whose area is proportional to the total mobile ionic space charge. The method is expected to be very useful for routine process and quality control applications. This technique has been used to study positive mobile charge behavior in silicon dioxide. The voltage dependence of the ionic displacement current indicates that trapping of ions occurs at the metal‐oxide interface and that ionic transport from the metal to the silicon interface is controlled by trap emission. Ion transport from the silicon to the metal interface is characterized by a single, bulk‐limited transport mechanism below 300°C with an activation energy that appears concentration dependent. Above 300°C an additional transport mechanism is observed which is slow in comparison to the primary transport mechanism.